Adding upstream version 3.45.1.upstream/3.45.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

158 files changed, 238621 insertions, 0 deletions

diff --git a/src/alter.c b/src/alter.c
new file mode 100644
index 0000000..ec45e14
--- /dev/null
+++ b/src/alter.c
@@ -0,0 +1,2306 @@
+/*
+** 2005 February 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that used to generate VDBE code
+** that implements the ALTER TABLE command.
+*/
+#include "sqliteInt.h"
+
+/*
+** The code in this file only exists if we are not omitting the
+** ALTER TABLE logic from the build.
+*/
+#ifndef SQLITE_OMIT_ALTERTABLE
+
+/*
+** Parameter zName is the name of a table that is about to be altered
+** (either with ALTER TABLE ... RENAME TO or ALTER TABLE ... ADD COLUMN).
+** If the table is a system table, this function leaves an error message
+** in pParse->zErr (system tables may not be altered) and returns non-zero.
+**
+** Or, if zName is not a system table, zero is returned.
+*/
+static int isAlterableTable(Parse *pParse, Table *pTab){
+  if( 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7)
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+   || (pTab->tabFlags & TF_Eponymous)!=0
+   || ( (pTab->tabFlags & TF_Shadow)!=0
+        && sqlite3ReadOnlyShadowTables(pParse->db)
+   )
+#endif
+  ){
+    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Generate code to verify that the schemas of database zDb and, if
+** bTemp is not true, database "temp", can still be parsed. This is
+** called at the end of the generation of an ALTER TABLE ... RENAME ...
+** statement to ensure that the operation has not rendered any schema
+** objects unusable.
+*/
+static void renameTestSchema(
+  Parse *pParse,                  /* Parse context */
+  const char *zDb,                /* Name of db to verify schema of */
+  int bTemp,                      /* True if this is the temp db */
+  const char *zWhen,              /* "when" part of error message */
+  int bNoDQS                      /* Do not allow DQS in the schema */
+){
+  pParse->colNamesSet = 1;
+  sqlite3NestedParse(pParse,
+      "SELECT 1 "
+      "FROM \"%w\"." LEGACY_SCHEMA_TABLE " "
+      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
+      " AND sql NOT LIKE 'create virtual%%'"
+      " AND sqlite_rename_test(%Q, sql, type, name, %d, %Q, %d)=NULL ",
+      zDb,
+      zDb, bTemp, zWhen, bNoDQS
+  );
+
+  if( bTemp==0 ){
+    sqlite3NestedParse(pParse,
+        "SELECT 1 "
+        "FROM temp." LEGACY_SCHEMA_TABLE " "
+        "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
+        " AND sql NOT LIKE 'create virtual%%'"
+        " AND sqlite_rename_test(%Q, sql, type, name, 1, %Q, %d)=NULL ",
+        zDb, zWhen, bNoDQS
+    );
+  }
+}
+
+/*
+** Generate VM code to replace any double-quoted strings (but not double-quoted
+** identifiers) within the "sql" column of the sqlite_schema table in
+** database zDb with their single-quoted equivalents. If argument bTemp is
+** not true, similarly update all SQL statements in the sqlite_schema table
+** of the temp db.
+*/
+static void renameFixQuotes(Parse *pParse, const char *zDb, int bTemp){
+  sqlite3NestedParse(pParse,
+      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE
+      " SET sql = sqlite_rename_quotefix(%Q, sql)"
+      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
+      " AND sql NOT LIKE 'create virtual%%'" , zDb, zDb
+  );
+  if( bTemp==0 ){
+    sqlite3NestedParse(pParse,
+      "UPDATE temp." LEGACY_SCHEMA_TABLE
+      " SET sql = sqlite_rename_quotefix('temp', sql)"
+      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
+      " AND sql NOT LIKE 'create virtual%%'"
+    );
+  }
+}
+
+/*
+** Generate code to reload the schema for database iDb. And, if iDb!=1, for
+** the temp database as well.
+*/
+static void renameReloadSchema(Parse *pParse, int iDb, u16 p5){
+  Vdbe *v = pParse->pVdbe;
+  if( v ){
+    sqlite3ChangeCookie(pParse, iDb);
+    sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iDb, 0, p5);
+    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, 1, 0, p5);
+  }
+}
+
+/*
+** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy"
+** command.
+*/
+void sqlite3AlterRenameTable(
+  Parse *pParse,            /* Parser context. */
+  SrcList *pSrc,            /* The table to rename. */
+  Token *pName              /* The new table name. */
+){
+  int iDb;                  /* Database that contains the table */
+  char *zDb;                /* Name of database iDb */
+  Table *pTab;              /* Table being renamed */
+  char *zName = 0;          /* NULL-terminated version of pName */
+  sqlite3 *db = pParse->db; /* Database connection */
+  int nTabName;             /* Number of UTF-8 characters in zTabName */
+  const char *zTabName;     /* Original name of the table */
+  Vdbe *v;
+  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
+
+  if( NEVER(db->mallocFailed) ) goto exit_rename_table;
+  assert( pSrc->nSrc==1 );
+  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
+
+  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
+  if( !pTab ) goto exit_rename_table;
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  zDb = db->aDb[iDb].zDbSName;
+
+  /* Get a NULL terminated version of the new table name. */
+  zName = sqlite3NameFromToken(db, pName);
+  if( !zName ) goto exit_rename_table;
+
+  /* Check that a table or index named 'zName' does not already exist
+  ** in database iDb. If so, this is an error.
+  */
+  if( sqlite3FindTable(db, zName, zDb)
+   || sqlite3FindIndex(db, zName, zDb)
+   || sqlite3IsShadowTableOf(db, pTab, zName)
+  ){
+    sqlite3ErrorMsg(pParse,
+        "there is already another table or index with this name: %s", zName);
+    goto exit_rename_table;
+  }
+
+  /* Make sure it is not a system table being altered, or a reserved name
+  ** that the table is being renamed to.
+  */
+  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ){
+    goto exit_rename_table;
+  }
+  if( SQLITE_OK!=sqlite3CheckObjectName(pParse,zName,"table",zName) ){
+    goto exit_rename_table;
+  }
+
+#ifndef SQLITE_OMIT_VIEW
+  if( IsView(pTab) ){
+    sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);
+    goto exit_rename_table;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Invoke the authorization callback. */
+  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
+    goto exit_rename_table;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto exit_rename_table;
+  }
+  if( IsVirtual(pTab) ){
+    pVTab = sqlite3GetVTable(db, pTab);
+    if( pVTab->pVtab->pModule->xRename==0 ){
+      pVTab = 0;
+    }
+  }
+#endif
+
+  /* Begin a transaction for database iDb. Then modify the schema cookie
+  ** (since the ALTER TABLE modifies the schema). Call sqlite3MayAbort(),
+  ** as the scalar functions (e.g. sqlite_rename_table()) invoked by the
+  ** nested SQL may raise an exception.  */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ){
+    goto exit_rename_table;
+  }
+  sqlite3MayAbort(pParse);
+
+  /* figure out how many UTF-8 characters are in zName */
+  zTabName = pTab->zName;
+  nTabName = sqlite3Utf8CharLen(zTabName, -1);
+
+  /* Rewrite all CREATE TABLE, INDEX, TRIGGER or VIEW statements in
+  ** the schema to use the new table name.  */
+  sqlite3NestedParse(pParse,
+      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
+      "sql = sqlite_rename_table(%Q, type, name, sql, %Q, %Q, %d) "
+      "WHERE (type!='index' OR tbl_name=%Q COLLATE nocase)"
+      "AND   name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
+      , zDb, zDb, zTabName, zName, (iDb==1), zTabName
+  );
+
+  /* Update the tbl_name and name columns of the sqlite_schema table
+  ** as required.  */
+  sqlite3NestedParse(pParse,
+      "UPDATE %Q." LEGACY_SCHEMA_TABLE " SET "
+          "tbl_name = %Q, "
+          "name = CASE "
+            "WHEN type='table' THEN %Q "
+            "WHEN name LIKE 'sqliteX_autoindex%%' ESCAPE 'X' "
+            "     AND type='index' THEN "
+             "'sqlite_autoindex_' || %Q || substr(name,%d+18) "
+            "ELSE name END "
+      "WHERE tbl_name=%Q COLLATE nocase AND "
+          "(type='table' OR type='index' OR type='trigger');",
+      zDb,
+      zName, zName, zName,
+      nTabName, zTabName
+  );
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  /* If the sqlite_sequence table exists in this database, then update
+  ** it with the new table name.
+  */
+  if( sqlite3FindTable(db, "sqlite_sequence", zDb) ){
+    sqlite3NestedParse(pParse,
+        "UPDATE \"%w\".sqlite_sequence set name = %Q WHERE name = %Q",
+        zDb, zName, pTab->zName);
+  }
+#endif
+
+  /* If the table being renamed is not itself part of the temp database,
+  ** edit view and trigger definitions within the temp database
+  ** as required.  */
+  if( iDb!=1 ){
+    sqlite3NestedParse(pParse,
+        "UPDATE sqlite_temp_schema SET "
+            "sql = sqlite_rename_table(%Q, type, name, sql, %Q, %Q, 1), "
+            "tbl_name = "
+              "CASE WHEN tbl_name=%Q COLLATE nocase AND "
+              "  sqlite_rename_test(%Q, sql, type, name, 1, 'after rename', 0) "
+              "THEN %Q ELSE tbl_name END "
+            "WHERE type IN ('view', 'trigger')"
+        , zDb, zTabName, zName, zTabName, zDb, zName);
+  }
+
+  /* If this is a virtual table, invoke the xRename() function if
+  ** one is defined. The xRename() callback will modify the names
+  ** of any resources used by the v-table implementation (including other
+  ** SQLite tables) that are identified by the name of the virtual table.
+  */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( pVTab ){
+    int i = ++pParse->nMem;
+    sqlite3VdbeLoadString(v, i, zName);
+    sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pVTab, P4_VTAB);
+  }
+#endif
+
+  renameReloadSchema(pParse, iDb, INITFLAG_AlterRename);
+  renameTestSchema(pParse, zDb, iDb==1, "after rename", 0);
+
+exit_rename_table:
+  sqlite3SrcListDelete(db, pSrc);
+  sqlite3DbFree(db, zName);
+}
+
+/*
+** Write code that will raise an error if the table described by
+** zDb and zTab is not empty.
+*/
+static void sqlite3ErrorIfNotEmpty(
+  Parse *pParse,        /* Parsing context */
+  const char *zDb,      /* Schema holding the table */
+  const char *zTab,     /* Table to check for empty */
+  const char *zErr      /* Error message text */
+){
+  sqlite3NestedParse(pParse,
+     "SELECT raise(ABORT,%Q) FROM \"%w\".\"%w\"",
+     zErr, zDb, zTab
+  );
+}
+
+/*
+** This function is called after an "ALTER TABLE ... ADD" statement
+** has been parsed. Argument pColDef contains the text of the new
+** column definition.
+**
+** The Table structure pParse->pNewTable was extended to include
+** the new column during parsing.
+*/
+void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
+  Table *pNew;              /* Copy of pParse->pNewTable */
+  Table *pTab;              /* Table being altered */
+  int iDb;                  /* Database number */
+  const char *zDb;          /* Database name */
+  const char *zTab;         /* Table name */
+  char *zCol;               /* Null-terminated column definition */
+  Column *pCol;             /* The new column */
+  Expr *pDflt;              /* Default value for the new column */
+  sqlite3 *db;              /* The database connection; */
+  Vdbe *v;                  /* The prepared statement under construction */
+  int r1;                   /* Temporary registers */
+
+  db = pParse->db;
+  assert( db->pParse==pParse );
+  if( pParse->nErr ) return;
+  assert( db->mallocFailed==0 );
+  pNew = pParse->pNewTable;
+  assert( pNew );
+
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  iDb = sqlite3SchemaToIndex(db, pNew->pSchema);
+  zDb = db->aDb[iDb].zDbSName;
+  zTab = &pNew->zName[16];  /* Skip the "sqlite_altertab_" prefix on the name */
+  pCol = &pNew->aCol[pNew->nCol-1];
+  pDflt = sqlite3ColumnExpr(pNew, pCol);
+  pTab = sqlite3FindTable(db, zTab, zDb);
+  assert( pTab );
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Invoke the authorization callback. */
+  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
+    return;
+  }
+#endif
+
+
+  /* Check that the new column is not specified as PRIMARY KEY or UNIQUE.
+  ** If there is a NOT NULL constraint, then the default value for the
+  ** column must not be NULL.
+  */
+  if( pCol->colFlags & COLFLAG_PRIMKEY ){
+    sqlite3ErrorMsg(pParse, "Cannot add a PRIMARY KEY column");
+    return;
+  }
+  if( pNew->pIndex ){
+    sqlite3ErrorMsg(pParse,
+         "Cannot add a UNIQUE column");
+    return;
+  }
+  if( (pCol->colFlags & COLFLAG_GENERATED)==0 ){
+    /* If the default value for the new column was specified with a
+    ** literal NULL, then set pDflt to 0. This simplifies checking
+    ** for an SQL NULL default below.
+    */
+    assert( pDflt==0 || pDflt->op==TK_SPAN );
+    if( pDflt && pDflt->pLeft->op==TK_NULL ){
+      pDflt = 0;
+    }
+    assert( IsOrdinaryTable(pNew) );
+    if( (db->flags&SQLITE_ForeignKeys) && pNew->u.tab.pFKey && pDflt ){
+      sqlite3ErrorIfNotEmpty(pParse, zDb, zTab,
+          "Cannot add a REFERENCES column with non-NULL default value");
+    }
+    if( pCol->notNull && !pDflt ){
+      sqlite3ErrorIfNotEmpty(pParse, zDb, zTab,
+          "Cannot add a NOT NULL column with default value NULL");
+    }
+
+
+    /* Ensure the default expression is something that sqlite3ValueFromExpr()
+    ** can handle (i.e. not CURRENT_TIME etc.)
+    */
+    if( pDflt ){
+      sqlite3_value *pVal = 0;
+      int rc;
+      rc = sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_BLOB, &pVal);
+      assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+      if( rc!=SQLITE_OK ){
+        assert( db->mallocFailed == 1 );
+        return;
+      }
+      if( !pVal ){
+        sqlite3ErrorIfNotEmpty(pParse, zDb, zTab,
+           "Cannot add a column with non-constant default");
+      }
+      sqlite3ValueFree(pVal);
+    }
+  }else if( pCol->colFlags & COLFLAG_STORED ){
+    sqlite3ErrorIfNotEmpty(pParse, zDb, zTab, "cannot add a STORED column");
+  }
+
+
+  /* Modify the CREATE TABLE statement. */
+  zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);
+  if( zCol ){
+    char *zEnd = &zCol[pColDef->n-1];
+    while( zEnd>zCol && (*zEnd==';' || sqlite3Isspace(*zEnd)) ){
+      *zEnd-- = '\0';
+    }
+    /* substr() operations on characters, but addColOffset is in bytes. So we
+    ** have to use printf() to translate between these units: */
+    assert( IsOrdinaryTable(pTab) );
+    assert( IsOrdinaryTable(pNew) );
+    sqlite3NestedParse(pParse,
+        "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
+          "sql = printf('%%.%ds, ',sql) || %Q"
+          " || substr(sql,1+length(printf('%%.%ds',sql))) "
+        "WHERE type = 'table' AND name = %Q",
+      zDb, pNew->u.tab.addColOffset, zCol, pNew->u.tab.addColOffset,
+      zTab
+    );
+    sqlite3DbFree(db, zCol);
+  }
+
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    /* Make sure the schema version is at least 3.  But do not upgrade
+    ** from less than 3 to 4, as that will corrupt any preexisting DESC
+    ** index.
+    */
+    r1 = sqlite3GetTempReg(pParse);
+    sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, r1, BTREE_FILE_FORMAT);
+    sqlite3VdbeUsesBtree(v, iDb);
+    sqlite3VdbeAddOp2(v, OP_AddImm, r1, -2);
+    sqlite3VdbeAddOp2(v, OP_IfPos, r1, sqlite3VdbeCurrentAddr(v)+2);
+    VdbeCoverage(v);
+    sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, 3);
+    sqlite3ReleaseTempReg(pParse, r1);
+
+    /* Reload the table definition */
+    renameReloadSchema(pParse, iDb, INITFLAG_AlterAdd);
+
+    /* Verify that constraints are still satisfied */
+    if( pNew->pCheck!=0
+     || (pCol->notNull && (pCol->colFlags & COLFLAG_GENERATED)!=0)
+     || (pTab->tabFlags & TF_Strict)!=0
+    ){
+      sqlite3NestedParse(pParse,
+        "SELECT CASE WHEN quick_check GLOB 'CHECK*'"
+        " THEN raise(ABORT,'CHECK constraint failed')"
+        " WHEN quick_check GLOB 'non-* value in*'"
+        " THEN raise(ABORT,'type mismatch on DEFAULT')"
+        " ELSE raise(ABORT,'NOT NULL constraint failed')"
+        " END"
+        "  FROM pragma_quick_check(%Q,%Q)"
+        " WHERE quick_check GLOB 'CHECK*'"
+        " OR quick_check GLOB 'NULL*'"
+        " OR quick_check GLOB 'non-* value in*'",
+        zTab, zDb
+      );
+    }
+  }
+}
+
+/*
+** This function is called by the parser after the table-name in
+** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument
+** pSrc is the full-name of the table being altered.
+**
+** This routine makes a (partial) copy of the Table structure
+** for the table being altered and sets Parse.pNewTable to point
+** to it. Routines called by the parser as the column definition
+** is parsed (i.e. sqlite3AddColumn()) add the new Column data to
+** the copy. The copy of the Table structure is deleted by tokenize.c
+** after parsing is finished.
+**
+** Routine sqlite3AlterFinishAddColumn() will be called to complete
+** coding the "ALTER TABLE ... ADD" statement.
+*/
+void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){
+  Table *pNew;
+  Table *pTab;
+  int iDb;
+  int i;
+  int nAlloc;
+  sqlite3 *db = pParse->db;
+
+  /* Look up the table being altered. */
+  assert( pParse->pNewTable==0 );
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  if( db->mallocFailed ) goto exit_begin_add_column;
+  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
+  if( !pTab ) goto exit_begin_add_column;
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTab) ){
+    sqlite3ErrorMsg(pParse, "virtual tables may not be altered");
+    goto exit_begin_add_column;
+  }
+#endif
+
+  /* Make sure this is not an attempt to ALTER a view. */
+  if( IsView(pTab) ){
+    sqlite3ErrorMsg(pParse, "Cannot add a column to a view");
+    goto exit_begin_add_column;
+  }
+  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ){
+    goto exit_begin_add_column;
+  }
+
+  sqlite3MayAbort(pParse);
+  assert( IsOrdinaryTable(pTab) );
+  assert( pTab->u.tab.addColOffset>0 );
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+
+  /* Put a copy of the Table struct in Parse.pNewTable for the
+  ** sqlite3AddColumn() function and friends to modify.  But modify
+  ** the name by adding an "sqlite_altertab_" prefix.  By adding this
+  ** prefix, we insure that the name will not collide with an existing
+  ** table because user table are not allowed to have the "sqlite_"
+  ** prefix on their name.
+  */
+  pNew = (Table*)sqlite3DbMallocZero(db, sizeof(Table));
+  if( !pNew ) goto exit_begin_add_column;
+  pParse->pNewTable = pNew;
+  pNew->nTabRef = 1;
+  pNew->nCol = pTab->nCol;
+  assert( pNew->nCol>0 );
+  nAlloc = (((pNew->nCol-1)/8)*8)+8;
+  assert( nAlloc>=pNew->nCol && nAlloc%8==0 && nAlloc-pNew->nCol<8 );
+  pNew->aCol = (Column*)sqlite3DbMallocZero(db, sizeof(Column)*nAlloc);
+  pNew->zName = sqlite3MPrintf(db, "sqlite_altertab_%s", pTab->zName);
+  if( !pNew->aCol || !pNew->zName ){
+    assert( db->mallocFailed );
+    goto exit_begin_add_column;
+  }
+  memcpy(pNew->aCol, pTab->aCol, sizeof(Column)*pNew->nCol);
+  for(i=0; i<pNew->nCol; i++){
+    Column *pCol = &pNew->aCol[i];
+    pCol->zCnName = sqlite3DbStrDup(db, pCol->zCnName);
+    pCol->hName = sqlite3StrIHash(pCol->zCnName);
+  }
+  assert( IsOrdinaryTable(pNew) );
+  pNew->u.tab.pDfltList = sqlite3ExprListDup(db, pTab->u.tab.pDfltList, 0);
+  pNew->pSchema = db->aDb[iDb].pSchema;
+  pNew->u.tab.addColOffset = pTab->u.tab.addColOffset;
+  assert( pNew->nTabRef==1 );
+
+exit_begin_add_column:
+  sqlite3SrcListDelete(db, pSrc);
+  return;
+}
+
+/*
+** Parameter pTab is the subject of an ALTER TABLE ... RENAME COLUMN
+** command. This function checks if the table is a view or virtual
+** table (columns of views or virtual tables may not be renamed). If so,
+** it loads an error message into pParse and returns non-zero.
+**
+** Or, if pTab is not a view or virtual table, zero is returned.
+*/
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+static int isRealTable(Parse *pParse, Table *pTab, int bDrop){
+  const char *zType = 0;
+#ifndef SQLITE_OMIT_VIEW
+  if( IsView(pTab) ){
+    zType = "view";
+  }
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTab) ){
+    zType = "virtual table";
+  }
+#endif
+  if( zType ){
+    sqlite3ErrorMsg(pParse, "cannot %s %s \"%s\"",
+        (bDrop ? "drop column from" : "rename columns of"),
+        zType, pTab->zName
+    );
+    return 1;
+  }
+  return 0;
+}
+#else /* !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE) */
+# define isRealTable(x,y,z) (0)
+#endif
+
+/*
+** Handles the following parser reduction:
+**
+**  cmd ::= ALTER TABLE pSrc RENAME COLUMN pOld TO pNew
+*/
+void sqlite3AlterRenameColumn(
+  Parse *pParse,                  /* Parsing context */
+  SrcList *pSrc,                  /* Table being altered.  pSrc->nSrc==1 */
+  Token *pOld,                    /* Name of column being changed */
+  Token *pNew                     /* New column name */
+){
+  sqlite3 *db = pParse->db;       /* Database connection */
+  Table *pTab;                    /* Table being updated */
+  int iCol;                       /* Index of column being renamed */
+  char *zOld = 0;                 /* Old column name */
+  char *zNew = 0;                 /* New column name */
+  const char *zDb;                /* Name of schema containing the table */
+  int iSchema;                    /* Index of the schema */
+  int bQuote;                     /* True to quote the new name */
+
+  /* Locate the table to be altered */
+  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
+  if( !pTab ) goto exit_rename_column;
+
+  /* Cannot alter a system table */
+  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ) goto exit_rename_column;
+  if( SQLITE_OK!=isRealTable(pParse, pTab, 0) ) goto exit_rename_column;
+
+  /* Which schema holds the table to be altered */ 
+  iSchema = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iSchema>=0 );
+  zDb = db->aDb[iSchema].zDbSName;
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Invoke the authorization callback. */
+  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
+    goto exit_rename_column;
+  }
+#endif
+
+  /* Make sure the old name really is a column name in the table to be
+  ** altered.  Set iCol to be the index of the column being renamed */
+  zOld = sqlite3NameFromToken(db, pOld);
+  if( !zOld ) goto exit_rename_column;
+  for(iCol=0; iCol<pTab->nCol; iCol++){
+    if( 0==sqlite3StrICmp(pTab->aCol[iCol].zCnName, zOld) ) break;
+  }
+  if( iCol==pTab->nCol ){
+    sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pOld);
+    goto exit_rename_column;
+  }
+
+  /* Ensure the schema contains no double-quoted strings */
+  renameTestSchema(pParse, zDb, iSchema==1, "", 0);
+  renameFixQuotes(pParse, zDb, iSchema==1);
+
+  /* Do the rename operation using a recursive UPDATE statement that
+  ** uses the sqlite_rename_column() SQL function to compute the new
+  ** CREATE statement text for the sqlite_schema table.
+  */
+  sqlite3MayAbort(pParse);
+  zNew = sqlite3NameFromToken(db, pNew);
+  if( !zNew ) goto exit_rename_column;
+  assert( pNew->n>0 );
+  bQuote = sqlite3Isquote(pNew->z[0]);
+  sqlite3NestedParse(pParse,
+      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
+      "sql = sqlite_rename_column(sql, type, name, %Q, %Q, %d, %Q, %d, %d) "
+      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X' "
+      " AND (type != 'index' OR tbl_name = %Q)",
+      zDb,
+      zDb, pTab->zName, iCol, zNew, bQuote, iSchema==1,
+      pTab->zName
+  );
+
+  sqlite3NestedParse(pParse,
+      "UPDATE temp." LEGACY_SCHEMA_TABLE " SET "
+      "sql = sqlite_rename_column(sql, type, name, %Q, %Q, %d, %Q, %d, 1) "
+      "WHERE type IN ('trigger', 'view')",
+      zDb, pTab->zName, iCol, zNew, bQuote
+  );
+
+  /* Drop and reload the database schema. */
+  renameReloadSchema(pParse, iSchema, INITFLAG_AlterRename);
+  renameTestSchema(pParse, zDb, iSchema==1, "after rename", 1);
+
+ exit_rename_column:
+  sqlite3SrcListDelete(db, pSrc);
+  sqlite3DbFree(db, zOld);
+  sqlite3DbFree(db, zNew);
+  return;
+}
+
+/*
+** Each RenameToken object maps an element of the parse tree into
+** the token that generated that element.  The parse tree element
+** might be one of:
+**
+**     *  A pointer to an Expr that represents an ID
+**     *  The name of a table column in Column.zName
+**
+** A list of RenameToken objects can be constructed during parsing.
+** Each new object is created by sqlite3RenameTokenMap().
+** As the parse tree is transformed, the sqlite3RenameTokenRemap()
+** routine is used to keep the mapping current.
+**
+** After the parse finishes, renameTokenFind() routine can be used
+** to look up the actual token value that created some element in
+** the parse tree.
+*/
+struct RenameToken {
+  const void *p;         /* Parse tree element created by token t */
+  Token t;               /* The token that created parse tree element p */
+  RenameToken *pNext;    /* Next is a list of all RenameToken objects */
+};
+
+/*
+** The context of an ALTER TABLE RENAME COLUMN operation that gets passed
+** down into the Walker.
+*/
+typedef struct RenameCtx RenameCtx;
+struct RenameCtx {
+  RenameToken *pList;             /* List of tokens to overwrite */
+  int nList;                      /* Number of tokens in pList */
+  int iCol;                       /* Index of column being renamed */
+  Table *pTab;                    /* Table being ALTERed */
+  const char *zOld;               /* Old column name */
+};
+
+#ifdef SQLITE_DEBUG
+/*
+** This function is only for debugging. It performs two tasks:
+**
+**   1. Checks that pointer pPtr does not already appear in the
+**      rename-token list.
+**
+**   2. Dereferences each pointer in the rename-token list.
+**
+** The second is most effective when debugging under valgrind or
+** address-sanitizer or similar. If any of these pointers no longer
+** point to valid objects, an exception is raised by the memory-checking
+** tool.
+**
+** The point of this is to prevent comparisons of invalid pointer values.
+** Even though this always seems to work, it is undefined according to the
+** C standard. Example of undefined comparison:
+**
+**     sqlite3_free(x);
+**     if( x==y ) ...
+**
+** Technically, as x no longer points into a valid object or to the byte
+** following a valid object, it may not be used in comparison operations.
+*/
+static void renameTokenCheckAll(Parse *pParse, const void *pPtr){
+  assert( pParse==pParse->db->pParse );
+  assert( pParse->db->mallocFailed==0 || pParse->nErr!=0 );
+  if( pParse->nErr==0 ){
+    const RenameToken *p;
+    u32 i = 1;
+    for(p=pParse->pRename; p; p=p->pNext){
+      if( p->p ){
+        assert( p->p!=pPtr );
+        i += *(u8*)(p->p) | 1;
+      }
+    }
+    assert( i>0 );
+  }
+}
+#else
+# define renameTokenCheckAll(x,y)
+#endif
+
+/*
+** Remember that the parser tree element pPtr was created using
+** the token pToken.
+**
+** In other words, construct a new RenameToken object and add it
+** to the list of RenameToken objects currently being built up
+** in pParse->pRename.
+**
+** The pPtr argument is returned so that this routine can be used
+** with tail recursion in tokenExpr() routine, for a small performance
+** improvement.
+*/
+const void *sqlite3RenameTokenMap(
+  Parse *pParse,
+  const void *pPtr,
+  const Token *pToken
+){
+  RenameToken *pNew;
+  assert( pPtr || pParse->db->mallocFailed );
+  renameTokenCheckAll(pParse, pPtr);
+  if( ALWAYS(pParse->eParseMode!=PARSE_MODE_UNMAP) ){
+    pNew = sqlite3DbMallocZero(pParse->db, sizeof(RenameToken));
+    if( pNew ){
+      pNew->p = pPtr;
+      pNew->t = *pToken;
+      pNew->pNext = pParse->pRename;
+      pParse->pRename = pNew;
+    }
+  }
+
+  return pPtr;
+}
+
+/*
+** It is assumed that there is already a RenameToken object associated
+** with parse tree element pFrom. This function remaps the associated token
+** to parse tree element pTo.
+*/
+void sqlite3RenameTokenRemap(Parse *pParse, const void *pTo, const void *pFrom){
+  RenameToken *p;
+  renameTokenCheckAll(pParse, pTo);
+  for(p=pParse->pRename; p; p=p->pNext){
+    if( p->p==pFrom ){
+      p->p = pTo;
+      break;
+    }
+  }
+}
+
+/*
+** Walker callback used by sqlite3RenameExprUnmap().
+*/
+static int renameUnmapExprCb(Walker *pWalker, Expr *pExpr){
+  Parse *pParse = pWalker->pParse;
+  sqlite3RenameTokenRemap(pParse, 0, (const void*)pExpr);
+  if( ExprUseYTab(pExpr) ){
+    sqlite3RenameTokenRemap(pParse, 0, (const void*)&pExpr->y.pTab);
+  }
+  return WRC_Continue;
+}
+
+/*
+** Iterate through the Select objects that are part of WITH clauses attached
+** to select statement pSelect.
+*/
+static void renameWalkWith(Walker *pWalker, Select *pSelect){
+  With *pWith = pSelect->pWith;
+  if( pWith ){
+    Parse *pParse = pWalker->pParse;
+    int i;
+    With *pCopy = 0;
+    assert( pWith->nCte>0 );
+    if( (pWith->a[0].pSelect->selFlags & SF_Expanded)==0 ){
+      /* Push a copy of the With object onto the with-stack. We use a copy
+      ** here as the original will be expanded and resolved (flags SF_Expanded
+      ** and SF_Resolved) below. And the parser code that uses the with-stack
+      ** fails if the Select objects on it have already been expanded and
+      ** resolved.  */
+      pCopy = sqlite3WithDup(pParse->db, pWith);
+      pCopy = sqlite3WithPush(pParse, pCopy, 1);
+    }
+    for(i=0; i<pWith->nCte; i++){
+      Select *p = pWith->a[i].pSelect;
+      NameContext sNC;
+      memset(&sNC, 0, sizeof(sNC));
+      sNC.pParse = pParse;
+      if( pCopy ) sqlite3SelectPrep(sNC.pParse, p, &sNC);
+      if( sNC.pParse->db->mallocFailed ) return;
+      sqlite3WalkSelect(pWalker, p);
+      sqlite3RenameExprlistUnmap(pParse, pWith->a[i].pCols);
+    }
+    if( pCopy && pParse->pWith==pCopy ){
+      pParse->pWith = pCopy->pOuter;
+    }
+  }
+}
+
+/*
+** Unmap all tokens in the IdList object passed as the second argument.
+*/
+static void unmapColumnIdlistNames(
+  Parse *pParse,
+  const IdList *pIdList
+){
+  int ii;
+  assert( pIdList!=0 );
+  for(ii=0; ii<pIdList->nId; ii++){
+    sqlite3RenameTokenRemap(pParse, 0, (const void*)pIdList->a[ii].zName);
+  }
+}
+
+/*
+** Walker callback used by sqlite3RenameExprUnmap().
+*/
+static int renameUnmapSelectCb(Walker *pWalker, Select *p){
+  Parse *pParse = pWalker->pParse;
+  int i;
+  if( pParse->nErr ) return WRC_Abort;
+  testcase( p->selFlags & SF_View );
+  testcase( p->selFlags & SF_CopyCte );
+  if( p->selFlags & (SF_View|SF_CopyCte) ){
+    return WRC_Prune;
+  }
+  if( ALWAYS(p->pEList) ){
+    ExprList *pList = p->pEList;
+    for(i=0; i<pList->nExpr; i++){
+      if( pList->a[i].zEName && pList->a[i].fg.eEName==ENAME_NAME ){
+        sqlite3RenameTokenRemap(pParse, 0, (void*)pList->a[i].zEName);
+      }
+    }
+  }
+  if( ALWAYS(p->pSrc) ){  /* Every Select as a SrcList, even if it is empty */
+    SrcList *pSrc = p->pSrc;
+    for(i=0; i<pSrc->nSrc; i++){
+      sqlite3RenameTokenRemap(pParse, 0, (void*)pSrc->a[i].zName);
+      if( pSrc->a[i].fg.isUsing==0 ){
+        sqlite3WalkExpr(pWalker, pSrc->a[i].u3.pOn);
+      }else{
+        unmapColumnIdlistNames(pParse, pSrc->a[i].u3.pUsing);
+      }
+    }
+  }
+
+  renameWalkWith(pWalker, p);
+  return WRC_Continue;
+}
+
+/*
+** Remove all nodes that are part of expression pExpr from the rename list.
+*/
+void sqlite3RenameExprUnmap(Parse *pParse, Expr *pExpr){
+  u8 eMode = pParse->eParseMode;
+  Walker sWalker;
+  memset(&sWalker, 0, sizeof(Walker));
+  sWalker.pParse = pParse;
+  sWalker.xExprCallback = renameUnmapExprCb;
+  sWalker.xSelectCallback = renameUnmapSelectCb;
+  pParse->eParseMode = PARSE_MODE_UNMAP;
+  sqlite3WalkExpr(&sWalker, pExpr);
+  pParse->eParseMode = eMode;
+}
+
+/*
+** Remove all nodes that are part of expression-list pEList from the
+** rename list.
+*/
+void sqlite3RenameExprlistUnmap(Parse *pParse, ExprList *pEList){
+  if( pEList ){
+    int i;
+    Walker sWalker;
+    memset(&sWalker, 0, sizeof(Walker));
+    sWalker.pParse = pParse;
+    sWalker.xExprCallback = renameUnmapExprCb;
+    sqlite3WalkExprList(&sWalker, pEList);
+    for(i=0; i<pEList->nExpr; i++){
+      if( ALWAYS(pEList->a[i].fg.eEName==ENAME_NAME) ){
+        sqlite3RenameTokenRemap(pParse, 0, (void*)pEList->a[i].zEName);
+      }
+    }
+  }
+}
+
+/*
+** Free the list of RenameToken objects given in the second argument
+*/
+static void renameTokenFree(sqlite3 *db, RenameToken *pToken){
+  RenameToken *pNext;
+  RenameToken *p;
+  for(p=pToken; p; p=pNext){
+    pNext = p->pNext;
+    sqlite3DbFree(db, p);
+  }
+}
+
+/*
+** Search the Parse object passed as the first argument for a RenameToken
+** object associated with parse tree element pPtr. If found, return a pointer
+** to it. Otherwise, return NULL.
+**
+** If the second argument passed to this function is not NULL and a matching
+** RenameToken object is found, remove it from the Parse object and add it to
+** the list maintained by the RenameCtx object.
+*/
+static RenameToken *renameTokenFind(
+  Parse *pParse,
+  struct RenameCtx *pCtx,
+  const void *pPtr
+){
+  RenameToken **pp;
+  if( NEVER(pPtr==0) ){
+    return 0;
+  }
+  for(pp=&pParse->pRename; (*pp); pp=&(*pp)->pNext){
+    if( (*pp)->p==pPtr ){
+      RenameToken *pToken = *pp;
+      if( pCtx ){
+        *pp = pToken->pNext;
+        pToken->pNext = pCtx->pList;
+        pCtx->pList = pToken;
+        pCtx->nList++;
+      }
+      return pToken;
+    }
+  }
+  return 0;
+}
+
+/*
+** This is a Walker select callback. It does nothing. It is only required
+** because without a dummy callback, sqlite3WalkExpr() and similar do not
+** descend into sub-select statements.
+*/
+static int renameColumnSelectCb(Walker *pWalker, Select *p){
+  if( p->selFlags & (SF_View|SF_CopyCte) ){
+    testcase( p->selFlags & SF_View );
+    testcase( p->selFlags & SF_CopyCte );
+    return WRC_Prune;
+  }
+  renameWalkWith(pWalker, p);
+  return WRC_Continue;
+}
+
+/*
+** This is a Walker expression callback.
+**
+** For every TK_COLUMN node in the expression tree, search to see
+** if the column being references is the column being renamed by an
+** ALTER TABLE statement.  If it is, then attach its associated
+** RenameToken object to the list of RenameToken objects being
+** constructed in RenameCtx object at pWalker->u.pRename.
+*/
+static int renameColumnExprCb(Walker *pWalker, Expr *pExpr){
+  RenameCtx *p = pWalker->u.pRename;
+  if( pExpr->op==TK_TRIGGER
+   && pExpr->iColumn==p->iCol
+   && pWalker->pParse->pTriggerTab==p->pTab
+  ){
+    renameTokenFind(pWalker->pParse, p, (void*)pExpr);
+  }else if( pExpr->op==TK_COLUMN
+   && pExpr->iColumn==p->iCol
+   && ALWAYS(ExprUseYTab(pExpr))
+   && p->pTab==pExpr->y.pTab
+  ){
+    renameTokenFind(pWalker->pParse, p, (void*)pExpr);
+  }
+  return WRC_Continue;
+}
+
+/*
+** The RenameCtx contains a list of tokens that reference a column that
+** is being renamed by an ALTER TABLE statement.  Return the "last"
+** RenameToken in the RenameCtx and remove that RenameToken from the
+** RenameContext.  "Last" means the last RenameToken encountered when
+** the input SQL is parsed from left to right.  Repeated calls to this routine
+** return all column name tokens in the order that they are encountered
+** in the SQL statement.
+*/
+static RenameToken *renameColumnTokenNext(RenameCtx *pCtx){
+  RenameToken *pBest = pCtx->pList;
+  RenameToken *pToken;
+  RenameToken **pp;
+
+  for(pToken=pBest->pNext; pToken; pToken=pToken->pNext){
+    if( pToken->t.z>pBest->t.z ) pBest = pToken;
+  }
+  for(pp=&pCtx->pList; *pp!=pBest; pp=&(*pp)->pNext);
+  *pp = pBest->pNext;
+
+  return pBest;
+}
+
+/*
+** An error occurred while parsing or otherwise processing a database
+** object (either pParse->pNewTable, pNewIndex or pNewTrigger) as part of an
+** ALTER TABLE RENAME COLUMN program. The error message emitted by the
+** sub-routine is currently stored in pParse->zErrMsg. This function
+** adds context to the error message and then stores it in pCtx.
+*/
+static void renameColumnParseError(
+  sqlite3_context *pCtx,
+  const char *zWhen,
+  sqlite3_value *pType,
+  sqlite3_value *pObject,
+  Parse *pParse
+){
+  const char *zT = (const char*)sqlite3_value_text(pType);
+  const char *zN = (const char*)sqlite3_value_text(pObject);
+  char *zErr;
+
+  zErr = sqlite3MPrintf(pParse->db, "error in %s %s%s%s: %s",
+      zT, zN, (zWhen[0] ? " " : ""), zWhen,
+      pParse->zErrMsg
+  );
+  sqlite3_result_error(pCtx, zErr, -1);
+  sqlite3DbFree(pParse->db, zErr);
+}
+
+/*
+** For each name in the the expression-list pEList (i.e. each
+** pEList->a[i].zName) that matches the string in zOld, extract the
+** corresponding rename-token from Parse object pParse and add it
+** to the RenameCtx pCtx.
+*/
+static void renameColumnElistNames(
+  Parse *pParse,
+  RenameCtx *pCtx,
+  const ExprList *pEList,
+  const char *zOld
+){
+  if( pEList ){
+    int i;
+    for(i=0; i<pEList->nExpr; i++){
+      const char *zName = pEList->a[i].zEName;
+      if( ALWAYS(pEList->a[i].fg.eEName==ENAME_NAME)
+       && ALWAYS(zName!=0)
+       && 0==sqlite3_stricmp(zName, zOld)
+      ){
+        renameTokenFind(pParse, pCtx, (const void*)zName);
+      }
+    }
+  }
+}
+
+/*
+** For each name in the the id-list pIdList (i.e. each pIdList->a[i].zName)
+** that matches the string in zOld, extract the corresponding rename-token
+** from Parse object pParse and add it to the RenameCtx pCtx.
+*/
+static void renameColumnIdlistNames(
+  Parse *pParse,
+  RenameCtx *pCtx,
+  const IdList *pIdList,
+  const char *zOld
+){
+  if( pIdList ){
+    int i;
+    for(i=0; i<pIdList->nId; i++){
+      const char *zName = pIdList->a[i].zName;
+      if( 0==sqlite3_stricmp(zName, zOld) ){
+        renameTokenFind(pParse, pCtx, (const void*)zName);
+      }
+    }
+  }
+}
+
+
+/*
+** Parse the SQL statement zSql using Parse object (*p). The Parse object
+** is initialized by this function before it is used.
+*/
+static int renameParseSql(
+  Parse *p,                       /* Memory to use for Parse object */
+  const char *zDb,                /* Name of schema SQL belongs to */
+  sqlite3 *db,                    /* Database handle */
+  const char *zSql,               /* SQL to parse */
+  int bTemp                       /* True if SQL is from temp schema */
+){
+  int rc;
+
+  sqlite3ParseObjectInit(p, db);
+  if( zSql==0 ){
+    return SQLITE_NOMEM;
+  }
+  if( sqlite3StrNICmp(zSql,"CREATE ",7)!=0 ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  db->init.iDb = bTemp ? 1 : sqlite3FindDbName(db, zDb);
+  p->eParseMode = PARSE_MODE_RENAME;
+  p->db = db;
+  p->nQueryLoop = 1;
+  rc = sqlite3RunParser(p, zSql);
+  if( db->mallocFailed ) rc = SQLITE_NOMEM;
+  if( rc==SQLITE_OK
+   && NEVER(p->pNewTable==0 && p->pNewIndex==0 && p->pNewTrigger==0)
+  ){
+    rc = SQLITE_CORRUPT_BKPT;
+  }
+
+#ifdef SQLITE_DEBUG
+  /* Ensure that all mappings in the Parse.pRename list really do map to
+  ** a part of the input string.  */
+  if( rc==SQLITE_OK ){
+    int nSql = sqlite3Strlen30(zSql);
+    RenameToken *pToken;
+    for(pToken=p->pRename; pToken; pToken=pToken->pNext){
+      assert( pToken->t.z>=zSql && &pToken->t.z[pToken->t.n]<=&zSql[nSql] );
+    }
+  }
+#endif
+
+  db->init.iDb = 0;
+  return rc;
+}
+
+/*
+** This function edits SQL statement zSql, replacing each token identified
+** by the linked list pRename with the text of zNew. If argument bQuote is
+** true, then zNew is always quoted first. If no error occurs, the result
+** is loaded into context object pCtx as the result.
+**
+** Or, if an error occurs (i.e. an OOM condition), an error is left in
+** pCtx and an SQLite error code returned.
+*/
+static int renameEditSql(
+  sqlite3_context *pCtx,          /* Return result here */
+  RenameCtx *pRename,             /* Rename context */
+  const char *zSql,               /* SQL statement to edit */
+  const char *zNew,               /* New token text */
+  int bQuote                      /* True to always quote token */
+){
+  i64 nNew = sqlite3Strlen30(zNew);
+  i64 nSql = sqlite3Strlen30(zSql);
+  sqlite3 *db = sqlite3_context_db_handle(pCtx);
+  int rc = SQLITE_OK;
+  char *zQuot = 0;
+  char *zOut;
+  i64 nQuot = 0;
+  char *zBuf1 = 0;
+  char *zBuf2 = 0;
+
+  if( zNew ){
+    /* Set zQuot to point to a buffer containing a quoted copy of the
+    ** identifier zNew. If the corresponding identifier in the original
+    ** ALTER TABLE statement was quoted (bQuote==1), then set zNew to
+    ** point to zQuot so that all substitutions are made using the
+    ** quoted version of the new column name.  */
+    zQuot = sqlite3MPrintf(db, "\"%w\" ", zNew);
+    if( zQuot==0 ){
+      return SQLITE_NOMEM;
+    }else{
+      nQuot = sqlite3Strlen30(zQuot)-1;
+    }
+
+    assert( nQuot>=nNew );
+    zOut = sqlite3DbMallocZero(db, nSql + pRename->nList*nQuot + 1);
+  }else{
+    zOut = (char*)sqlite3DbMallocZero(db, (nSql*2+1) * 3);
+    if( zOut ){
+      zBuf1 = &zOut[nSql*2+1];
+      zBuf2 = &zOut[nSql*4+2];
+    }
+  }
+
+  /* At this point pRename->pList contains a list of RenameToken objects
+  ** corresponding to all tokens in the input SQL that must be replaced
+  ** with the new column name, or with single-quoted versions of themselves.
+  ** All that remains is to construct and return the edited SQL string. */
+  if( zOut ){
+    int nOut = nSql;
+    memcpy(zOut, zSql, nSql);
+    while( pRename->pList ){
+      int iOff;                   /* Offset of token to replace in zOut */
+      u32 nReplace;
+      const char *zReplace;
+      RenameToken *pBest = renameColumnTokenNext(pRename);
+
+      if( zNew ){
+        if( bQuote==0 && sqlite3IsIdChar(*pBest->t.z) ){
+          nReplace = nNew;
+          zReplace = zNew;
+        }else{
+          nReplace = nQuot;
+          zReplace = zQuot;
+          if( pBest->t.z[pBest->t.n]=='"' ) nReplace++;
+        }
+      }else{
+        /* Dequote the double-quoted token. Then requote it again, this time
+        ** using single quotes. If the character immediately following the
+        ** original token within the input SQL was a single quote ('), then
+        ** add another space after the new, single-quoted version of the
+        ** token. This is so that (SELECT "string"'alias') maps to
+        ** (SELECT 'string' 'alias'), and not (SELECT 'string''alias').  */
+        memcpy(zBuf1, pBest->t.z, pBest->t.n);
+        zBuf1[pBest->t.n] = 0;
+        sqlite3Dequote(zBuf1);
+        sqlite3_snprintf(nSql*2, zBuf2, "%Q%s", zBuf1,
+            pBest->t.z[pBest->t.n]=='\'' ? " " : ""
+        );
+        zReplace = zBuf2;
+        nReplace = sqlite3Strlen30(zReplace);
+      }
+
+      iOff = pBest->t.z - zSql;
+      if( pBest->t.n!=nReplace ){
+        memmove(&zOut[iOff + nReplace], &zOut[iOff + pBest->t.n],
+            nOut - (iOff + pBest->t.n)
+        );
+        nOut += nReplace - pBest->t.n;
+        zOut[nOut] = '\0';
+      }
+      memcpy(&zOut[iOff], zReplace, nReplace);
+      sqlite3DbFree(db, pBest);
+    }
+
+    sqlite3_result_text(pCtx, zOut, -1, SQLITE_TRANSIENT);
+    sqlite3DbFree(db, zOut);
+  }else{
+    rc = SQLITE_NOMEM;
+  }
+
+  sqlite3_free(zQuot);
+  return rc;
+}
+
+/*
+** Set all pEList->a[].fg.eEName fields in the expression-list to val.
+*/
+static void renameSetENames(ExprList *pEList, int val){
+  if( pEList ){
+    int i;
+    for(i=0; i<pEList->nExpr; i++){
+      assert( val==ENAME_NAME || pEList->a[i].fg.eEName==ENAME_NAME );
+      pEList->a[i].fg.eEName = val;
+    }
+  }
+}
+
+/*
+** Resolve all symbols in the trigger at pParse->pNewTrigger, assuming
+** it was read from the schema of database zDb. Return SQLITE_OK if
+** successful. Otherwise, return an SQLite error code and leave an error
+** message in the Parse object.
+*/
+static int renameResolveTrigger(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  Trigger *pNew = pParse->pNewTrigger;
+  TriggerStep *pStep;
+  NameContext sNC;
+  int rc = SQLITE_OK;
+
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = pParse;
+  assert( pNew->pTabSchema );
+  pParse->pTriggerTab = sqlite3FindTable(db, pNew->table,
+      db->aDb[sqlite3SchemaToIndex(db, pNew->pTabSchema)].zDbSName
+  );
+  pParse->eTriggerOp = pNew->op;
+  /* ALWAYS() because if the table of the trigger does not exist, the
+  ** error would have been hit before this point */
+  if( ALWAYS(pParse->pTriggerTab) ){
+    rc = sqlite3ViewGetColumnNames(pParse, pParse->pTriggerTab);
+  }
+
+  /* Resolve symbols in WHEN clause */
+  if( rc==SQLITE_OK && pNew->pWhen ){
+    rc = sqlite3ResolveExprNames(&sNC, pNew->pWhen);
+  }
+
+  for(pStep=pNew->step_list; rc==SQLITE_OK && pStep; pStep=pStep->pNext){
+    if( pStep->pSelect ){
+      sqlite3SelectPrep(pParse, pStep->pSelect, &sNC);
+      if( pParse->nErr ) rc = pParse->rc;
+    }
+    if( rc==SQLITE_OK && pStep->zTarget ){
+      SrcList *pSrc = sqlite3TriggerStepSrc(pParse, pStep);
+      if( pSrc ){
+        Select *pSel = sqlite3SelectNew(
+            pParse, pStep->pExprList, pSrc, 0, 0, 0, 0, 0, 0
+        );
+        if( pSel==0 ){
+          pStep->pExprList = 0;
+          pSrc = 0;
+          rc = SQLITE_NOMEM;
+        }else{
+          /* pStep->pExprList contains an expression-list used for an UPDATE
+          ** statement. So the a[].zEName values are the RHS of the
+          ** "<col> = <expr>" clauses of the UPDATE statement. So, before
+          ** running SelectPrep(), change all the eEName values in
+          ** pStep->pExprList to ENAME_SPAN (from their current value of
+          ** ENAME_NAME). This is to prevent any ids in ON() clauses that are
+          ** part of pSrc from being incorrectly resolved against the
+          ** a[].zEName values as if they were column aliases.  */
+          renameSetENames(pStep->pExprList, ENAME_SPAN);
+          sqlite3SelectPrep(pParse, pSel, 0);
+          renameSetENames(pStep->pExprList, ENAME_NAME);
+          rc = pParse->nErr ? SQLITE_ERROR : SQLITE_OK;
+          assert( pStep->pExprList==0 || pStep->pExprList==pSel->pEList );
+          assert( pSrc==pSel->pSrc );
+          if( pStep->pExprList ) pSel->pEList = 0;
+          pSel->pSrc = 0;
+          sqlite3SelectDelete(db, pSel);
+        }
+        if( pStep->pFrom ){
+          int i;
+          for(i=0; i<pStep->pFrom->nSrc && rc==SQLITE_OK; i++){
+            SrcItem *p = &pStep->pFrom->a[i];
+            if( p->pSelect ){
+              sqlite3SelectPrep(pParse, p->pSelect, 0);
+            }
+          }
+        }
+
+        if(  db->mallocFailed ){
+          rc = SQLITE_NOMEM;
+        }
+        sNC.pSrcList = pSrc;
+        if( rc==SQLITE_OK && pStep->pWhere ){
+          rc = sqlite3ResolveExprNames(&sNC, pStep->pWhere);
+        }
+        if( rc==SQLITE_OK ){
+          rc = sqlite3ResolveExprListNames(&sNC, pStep->pExprList);
+        }
+        assert( !pStep->pUpsert || (!pStep->pWhere && !pStep->pExprList) );
+        if( pStep->pUpsert && rc==SQLITE_OK ){
+          Upsert *pUpsert = pStep->pUpsert;
+          pUpsert->pUpsertSrc = pSrc;
+          sNC.uNC.pUpsert = pUpsert;
+          sNC.ncFlags = NC_UUpsert;
+          rc = sqlite3ResolveExprListNames(&sNC, pUpsert->pUpsertTarget);
+          if( rc==SQLITE_OK ){
+            ExprList *pUpsertSet = pUpsert->pUpsertSet;
+            rc = sqlite3ResolveExprListNames(&sNC, pUpsertSet);
+          }
+          if( rc==SQLITE_OK ){
+            rc = sqlite3ResolveExprNames(&sNC, pUpsert->pUpsertWhere);
+          }
+          if( rc==SQLITE_OK ){
+            rc = sqlite3ResolveExprNames(&sNC, pUpsert->pUpsertTargetWhere);
+          }
+          sNC.ncFlags = 0;
+        }
+        sNC.pSrcList = 0;
+        sqlite3SrcListDelete(db, pSrc);
+      }else{
+        rc = SQLITE_NOMEM;
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Invoke sqlite3WalkExpr() or sqlite3WalkSelect() on all Select or Expr
+** objects that are part of the trigger passed as the second argument.
+*/
+static void renameWalkTrigger(Walker *pWalker, Trigger *pTrigger){
+  TriggerStep *pStep;
+
+  /* Find tokens to edit in WHEN clause */
+  sqlite3WalkExpr(pWalker, pTrigger->pWhen);
+
+  /* Find tokens to edit in trigger steps */
+  for(pStep=pTrigger->step_list; pStep; pStep=pStep->pNext){
+    sqlite3WalkSelect(pWalker, pStep->pSelect);
+    sqlite3WalkExpr(pWalker, pStep->pWhere);
+    sqlite3WalkExprList(pWalker, pStep->pExprList);
+    if( pStep->pUpsert ){
+      Upsert *pUpsert = pStep->pUpsert;
+      sqlite3WalkExprList(pWalker, pUpsert->pUpsertTarget);
+      sqlite3WalkExprList(pWalker, pUpsert->pUpsertSet);
+      sqlite3WalkExpr(pWalker, pUpsert->pUpsertWhere);
+      sqlite3WalkExpr(pWalker, pUpsert->pUpsertTargetWhere);
+    }
+    if( pStep->pFrom ){
+      int i;
+      for(i=0; i<pStep->pFrom->nSrc; i++){
+        sqlite3WalkSelect(pWalker, pStep->pFrom->a[i].pSelect);
+      }
+    }
+  }
+}
+
+/*
+** Free the contents of Parse object (*pParse). Do not free the memory
+** occupied by the Parse object itself.
+*/
+static void renameParseCleanup(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  Index *pIdx;
+  if( pParse->pVdbe ){
+    sqlite3VdbeFinalize(pParse->pVdbe);
+  }
+  sqlite3DeleteTable(db, pParse->pNewTable);
+  while( (pIdx = pParse->pNewIndex)!=0 ){
+    pParse->pNewIndex = pIdx->pNext;
+    sqlite3FreeIndex(db, pIdx);
+  }
+  sqlite3DeleteTrigger(db, pParse->pNewTrigger);
+  sqlite3DbFree(db, pParse->zErrMsg);
+  renameTokenFree(db, pParse->pRename);
+  sqlite3ParseObjectReset(pParse);
+}
+
+/*
+** SQL function:
+**
+**     sqlite_rename_column(SQL,TYPE,OBJ,DB,TABLE,COL,NEWNAME,QUOTE,TEMP)
+**
+**   0. zSql:     SQL statement to rewrite
+**   1. type:     Type of object ("table", "view" etc.)
+**   2. object:   Name of object
+**   3. Database: Database name (e.g. "main")
+**   4. Table:    Table name
+**   5. iCol:     Index of column to rename
+**   6. zNew:     New column name
+**   7. bQuote:   Non-zero if the new column name should be quoted.
+**   8. bTemp:    True if zSql comes from temp schema
+**
+** Do a column rename operation on the CREATE statement given in zSql.
+** The iCol-th column (left-most is 0) of table zTable is renamed from zCol
+** into zNew.  The name should be quoted if bQuote is true.
+**
+** This function is used internally by the ALTER TABLE RENAME COLUMN command.
+** It is only accessible to SQL created using sqlite3NestedParse().  It is
+** not reachable from ordinary SQL passed into sqlite3_prepare() unless the
+** SQLITE_TESTCTRL_INTERNAL_FUNCTIONS test setting is enabled.
+*/
+static void renameColumnFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  RenameCtx sCtx;
+  const char *zSql = (const char*)sqlite3_value_text(argv[0]);
+  const char *zDb = (const char*)sqlite3_value_text(argv[3]);
+  const char *zTable = (const char*)sqlite3_value_text(argv[4]);
+  int iCol = sqlite3_value_int(argv[5]);
+  const char *zNew = (const char*)sqlite3_value_text(argv[6]);
+  int bQuote = sqlite3_value_int(argv[7]);
+  int bTemp = sqlite3_value_int(argv[8]);
+  const char *zOld;
+  int rc;
+  Parse sParse;
+  Walker sWalker;
+  Index *pIdx;
+  int i;
+  Table *pTab;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  sqlite3_xauth xAuth = db->xAuth;
+#endif
+
+  UNUSED_PARAMETER(NotUsed);
+  if( zSql==0 ) return;
+  if( zTable==0 ) return;
+  if( zNew==0 ) return;
+  if( iCol<0 ) return;
+  sqlite3BtreeEnterAll(db);
+  pTab = sqlite3FindTable(db, zTable, zDb);
+  if( pTab==0 || iCol>=pTab->nCol ){
+    sqlite3BtreeLeaveAll(db);
+    return;
+  }
+  zOld = pTab->aCol[iCol].zCnName;
+  memset(&sCtx, 0, sizeof(sCtx));
+  sCtx.iCol = ((iCol==pTab->iPKey) ? -1 : iCol);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  db->xAuth = 0;
+#endif
+  rc = renameParseSql(&sParse, zDb, db, zSql, bTemp);
+
+  /* Find tokens that need to be replaced. */
+  memset(&sWalker, 0, sizeof(Walker));
+  sWalker.pParse = &sParse;
+  sWalker.xExprCallback = renameColumnExprCb;
+  sWalker.xSelectCallback = renameColumnSelectCb;
+  sWalker.u.pRename = &sCtx;
+
+  sCtx.pTab = pTab;
+  if( rc!=SQLITE_OK ) goto renameColumnFunc_done;
+  if( sParse.pNewTable ){
+    if( IsView(sParse.pNewTable) ){
+      Select *pSelect = sParse.pNewTable->u.view.pSelect;
+      pSelect->selFlags &= ~SF_View;
+      sParse.rc = SQLITE_OK;
+      sqlite3SelectPrep(&sParse, pSelect, 0);
+      rc = (db->mallocFailed ? SQLITE_NOMEM : sParse.rc);
+      if( rc==SQLITE_OK ){
+        sqlite3WalkSelect(&sWalker, pSelect);
+      }
+      if( rc!=SQLITE_OK ) goto renameColumnFunc_done;
+    }else if( IsOrdinaryTable(sParse.pNewTable) ){
+      /* A regular table */
+      int bFKOnly = sqlite3_stricmp(zTable, sParse.pNewTable->zName);
+      FKey *pFKey;
+      sCtx.pTab = sParse.pNewTable;
+      if( bFKOnly==0 ){
+        if( iCol<sParse.pNewTable->nCol ){
+          renameTokenFind(
+              &sParse, &sCtx, (void*)sParse.pNewTable->aCol[iCol].zCnName
+          );
+        }
+        if( sCtx.iCol<0 ){
+          renameTokenFind(&sParse, &sCtx, (void*)&sParse.pNewTable->iPKey);
+        }
+        sqlite3WalkExprList(&sWalker, sParse.pNewTable->pCheck);
+        for(pIdx=sParse.pNewTable->pIndex; pIdx; pIdx=pIdx->pNext){
+          sqlite3WalkExprList(&sWalker, pIdx->aColExpr);
+        }
+        for(pIdx=sParse.pNewIndex; pIdx; pIdx=pIdx->pNext){
+          sqlite3WalkExprList(&sWalker, pIdx->aColExpr);
+        }
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+        for(i=0; i<sParse.pNewTable->nCol; i++){
+          Expr *pExpr = sqlite3ColumnExpr(sParse.pNewTable,
+                                                  &sParse.pNewTable->aCol[i]);
+          sqlite3WalkExpr(&sWalker, pExpr);
+        }
+#endif
+      }
+
+      assert( IsOrdinaryTable(sParse.pNewTable) );
+      for(pFKey=sParse.pNewTable->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
+        for(i=0; i<pFKey->nCol; i++){
+          if( bFKOnly==0 && pFKey->aCol[i].iFrom==iCol ){
+            renameTokenFind(&sParse, &sCtx, (void*)&pFKey->aCol[i]);
+          }
+          if( 0==sqlite3_stricmp(pFKey->zTo, zTable)
+           && 0==sqlite3_stricmp(pFKey->aCol[i].zCol, zOld)
+          ){
+            renameTokenFind(&sParse, &sCtx, (void*)pFKey->aCol[i].zCol);
+          }
+        }
+      }
+    }
+  }else if( sParse.pNewIndex ){
+    sqlite3WalkExprList(&sWalker, sParse.pNewIndex->aColExpr);
+    sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
+  }else{
+    /* A trigger */
+    TriggerStep *pStep;
+    rc = renameResolveTrigger(&sParse);
+    if( rc!=SQLITE_OK ) goto renameColumnFunc_done;
+
+    for(pStep=sParse.pNewTrigger->step_list; pStep; pStep=pStep->pNext){
+      if( pStep->zTarget ){
+        Table *pTarget = sqlite3LocateTable(&sParse, 0, pStep->zTarget, zDb);
+        if( pTarget==pTab ){
+          if( pStep->pUpsert ){
+            ExprList *pUpsertSet = pStep->pUpsert->pUpsertSet;
+            renameColumnElistNames(&sParse, &sCtx, pUpsertSet, zOld);
+          }
+          renameColumnIdlistNames(&sParse, &sCtx, pStep->pIdList, zOld);
+          renameColumnElistNames(&sParse, &sCtx, pStep->pExprList, zOld);
+        }
+      }
+    }
+
+
+    /* Find tokens to edit in UPDATE OF clause */
+    if( sParse.pTriggerTab==pTab ){
+      renameColumnIdlistNames(&sParse, &sCtx,sParse.pNewTrigger->pColumns,zOld);
+    }
+
+    /* Find tokens to edit in various expressions and selects */
+    renameWalkTrigger(&sWalker, sParse.pNewTrigger);
+  }
+
+  assert( rc==SQLITE_OK );
+  rc = renameEditSql(context, &sCtx, zSql, zNew, bQuote);
+
+renameColumnFunc_done:
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_ERROR && sqlite3WritableSchema(db) ){
+      sqlite3_result_value(context, argv[0]);
+    }else if( sParse.zErrMsg ){
+      renameColumnParseError(context, "", argv[1], argv[2], &sParse);
+    }else{
+      sqlite3_result_error_code(context, rc);
+    }
+  }
+
+  renameParseCleanup(&sParse);
+  renameTokenFree(db, sCtx.pList);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  db->xAuth = xAuth;
+#endif
+  sqlite3BtreeLeaveAll(db);
+}
+
+/*
+** Walker expression callback used by "RENAME TABLE".
+*/
+static int renameTableExprCb(Walker *pWalker, Expr *pExpr){
+  RenameCtx *p = pWalker->u.pRename;
+  if( pExpr->op==TK_COLUMN
+   && ALWAYS(ExprUseYTab(pExpr))
+   && p->pTab==pExpr->y.pTab
+  ){
+    renameTokenFind(pWalker->pParse, p, (void*)&pExpr->y.pTab);
+  }
+  return WRC_Continue;
+}
+
+/*
+** Walker select callback used by "RENAME TABLE".
+*/
+static int renameTableSelectCb(Walker *pWalker, Select *pSelect){
+  int i;
+  RenameCtx *p = pWalker->u.pRename;
+  SrcList *pSrc = pSelect->pSrc;
+  if( pSelect->selFlags & (SF_View|SF_CopyCte) ){
+    testcase( pSelect->selFlags & SF_View );
+    testcase( pSelect->selFlags & SF_CopyCte );
+    return WRC_Prune;
+  }
+  if( NEVER(pSrc==0) ){
+    assert( pWalker->pParse->db->mallocFailed );
+    return WRC_Abort;
+  }
+  for(i=0; i<pSrc->nSrc; i++){
+    SrcItem *pItem = &pSrc->a[i];
+    if( pItem->pTab==p->pTab ){
+      renameTokenFind(pWalker->pParse, p, pItem->zName);
+    }
+  }
+  renameWalkWith(pWalker, pSelect);
+
+  return WRC_Continue;
+}
+
+
+/*
+** This C function implements an SQL user function that is used by SQL code
+** generated by the ALTER TABLE ... RENAME command to modify the definition
+** of any foreign key constraints that use the table being renamed as the
+** parent table. It is passed three arguments:
+**
+**   0: The database containing the table being renamed.
+**   1. type:     Type of object ("table", "view" etc.)
+**   2. object:   Name of object
+**   3: The complete text of the schema statement being modified,
+**   4: The old name of the table being renamed, and
+**   5: The new name of the table being renamed.
+**   6: True if the schema statement comes from the temp db.
+**
+** It returns the new schema statement. For example:
+**
+** sqlite_rename_table('main', 'CREATE TABLE t1(a REFERENCES t2)','t2','t3',0)
+**       -> 'CREATE TABLE t1(a REFERENCES t3)'
+*/
+static void renameTableFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  const char *zDb = (const char*)sqlite3_value_text(argv[0]);
+  const char *zInput = (const char*)sqlite3_value_text(argv[3]);
+  const char *zOld = (const char*)sqlite3_value_text(argv[4]);
+  const char *zNew = (const char*)sqlite3_value_text(argv[5]);
+  int bTemp = sqlite3_value_int(argv[6]);
+  UNUSED_PARAMETER(NotUsed);
+
+  if( zInput && zOld && zNew ){
+    Parse sParse;
+    int rc;
+    int bQuote = 1;
+    RenameCtx sCtx;
+    Walker sWalker;
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    sqlite3_xauth xAuth = db->xAuth;
+    db->xAuth = 0;
+#endif
+
+    sqlite3BtreeEnterAll(db);
+
+    memset(&sCtx, 0, sizeof(RenameCtx));
+    sCtx.pTab = sqlite3FindTable(db, zOld, zDb);
+    memset(&sWalker, 0, sizeof(Walker));
+    sWalker.pParse = &sParse;
+    sWalker.xExprCallback = renameTableExprCb;
+    sWalker.xSelectCallback = renameTableSelectCb;
+    sWalker.u.pRename = &sCtx;
+
+    rc = renameParseSql(&sParse, zDb, db, zInput, bTemp);
+
+    if( rc==SQLITE_OK ){
+      int isLegacy = (db->flags & SQLITE_LegacyAlter);
+      if( sParse.pNewTable ){
+        Table *pTab = sParse.pNewTable;
+
+        if( IsView(pTab) ){
+          if( isLegacy==0 ){
+            Select *pSelect = pTab->u.view.pSelect;
+            NameContext sNC;
+            memset(&sNC, 0, sizeof(sNC));
+            sNC.pParse = &sParse;
+
+            assert( pSelect->selFlags & SF_View );
+            pSelect->selFlags &= ~SF_View;
+            sqlite3SelectPrep(&sParse, pTab->u.view.pSelect, &sNC);
+            if( sParse.nErr ){
+              rc = sParse.rc;
+            }else{
+              sqlite3WalkSelect(&sWalker, pTab->u.view.pSelect);
+            }
+          }
+        }else{
+          /* Modify any FK definitions to point to the new table. */
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+          if( (isLegacy==0 || (db->flags & SQLITE_ForeignKeys))
+           && !IsVirtual(pTab)
+          ){
+            FKey *pFKey;
+            assert( IsOrdinaryTable(pTab) );
+            for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
+              if( sqlite3_stricmp(pFKey->zTo, zOld)==0 ){
+                renameTokenFind(&sParse, &sCtx, (void*)pFKey->zTo);
+              }
+            }
+          }
+#endif
+
+          /* If this is the table being altered, fix any table refs in CHECK
+          ** expressions. Also update the name that appears right after the
+          ** "CREATE [VIRTUAL] TABLE" bit. */
+          if( sqlite3_stricmp(zOld, pTab->zName)==0 ){
+            sCtx.pTab = pTab;
+            if( isLegacy==0 ){
+              sqlite3WalkExprList(&sWalker, pTab->pCheck);
+            }
+            renameTokenFind(&sParse, &sCtx, pTab->zName);
+          }
+        }
+      }
+
+      else if( sParse.pNewIndex ){
+        renameTokenFind(&sParse, &sCtx, sParse.pNewIndex->zName);
+        if( isLegacy==0 ){
+          sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
+        }
+      }
+
+#ifndef SQLITE_OMIT_TRIGGER
+      else{
+        Trigger *pTrigger = sParse.pNewTrigger;
+        TriggerStep *pStep;
+        if( 0==sqlite3_stricmp(sParse.pNewTrigger->table, zOld)
+            && sCtx.pTab->pSchema==pTrigger->pTabSchema
+          ){
+          renameTokenFind(&sParse, &sCtx, sParse.pNewTrigger->table);
+        }
+
+        if( isLegacy==0 ){
+          rc = renameResolveTrigger(&sParse);
+          if( rc==SQLITE_OK ){
+            renameWalkTrigger(&sWalker, pTrigger);
+            for(pStep=pTrigger->step_list; pStep; pStep=pStep->pNext){
+              if( pStep->zTarget && 0==sqlite3_stricmp(pStep->zTarget, zOld) ){
+                renameTokenFind(&sParse, &sCtx, pStep->zTarget);
+              }
+              if( pStep->pFrom ){
+                int i;
+                for(i=0; i<pStep->pFrom->nSrc; i++){
+                  SrcItem *pItem = &pStep->pFrom->a[i];
+                  if( 0==sqlite3_stricmp(pItem->zName, zOld) ){
+                    renameTokenFind(&sParse, &sCtx, pItem->zName);
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+#endif
+    }
+
+    if( rc==SQLITE_OK ){
+      rc = renameEditSql(context, &sCtx, zInput, zNew, bQuote);
+    }
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_ERROR && sqlite3WritableSchema(db) ){
+        sqlite3_result_value(context, argv[3]);
+      }else if( sParse.zErrMsg ){
+        renameColumnParseError(context, "", argv[1], argv[2], &sParse);
+      }else{
+        sqlite3_result_error_code(context, rc);
+      }
+    }
+
+    renameParseCleanup(&sParse);
+    renameTokenFree(db, sCtx.pList);
+    sqlite3BtreeLeaveAll(db);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    db->xAuth = xAuth;
+#endif
+  }
+
+  return;
+}
+
+static int renameQuotefixExprCb(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_STRING && (pExpr->flags & EP_DblQuoted) ){
+    renameTokenFind(pWalker->pParse, pWalker->u.pRename, (const void*)pExpr);
+  }
+  return WRC_Continue;
+}
+
+/* SQL function: sqlite_rename_quotefix(DB,SQL)
+**
+** Rewrite the DDL statement "SQL" so that any string literals that use
+** double-quotes use single quotes instead.
+**
+** Two arguments must be passed:
+**
+**   0: Database name ("main", "temp" etc.).
+**   1: SQL statement to edit.
+**
+** The returned value is the modified SQL statement. For example, given
+** the database schema:
+**
+**   CREATE TABLE t1(a, b, c);
+**
+**   SELECT sqlite_rename_quotefix('main',
+**       'CREATE VIEW v1 AS SELECT "a", "string" FROM t1'
+**   );
+**
+** returns the string:
+**
+**   CREATE VIEW v1 AS SELECT "a", 'string' FROM t1
+**
+** If there is a error in the input SQL, then raise an error, except
+** if PRAGMA writable_schema=ON, then just return the input string
+** unmodified following an error.
+*/
+static void renameQuotefixFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  char const *zDb = (const char*)sqlite3_value_text(argv[0]);
+  char const *zInput = (const char*)sqlite3_value_text(argv[1]);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  sqlite3_xauth xAuth = db->xAuth;
+  db->xAuth = 0;
+#endif
+
+  sqlite3BtreeEnterAll(db);
+
+  UNUSED_PARAMETER(NotUsed);
+  if( zDb && zInput ){
+    int rc;
+    Parse sParse;
+    rc = renameParseSql(&sParse, zDb, db, zInput, 0);
+
+    if( rc==SQLITE_OK ){
+      RenameCtx sCtx;
+      Walker sWalker;
+
+      /* Walker to find tokens that need to be replaced. */
+      memset(&sCtx, 0, sizeof(RenameCtx));
+      memset(&sWalker, 0, sizeof(Walker));
+      sWalker.pParse = &sParse;
+      sWalker.xExprCallback = renameQuotefixExprCb;
+      sWalker.xSelectCallback = renameColumnSelectCb;
+      sWalker.u.pRename = &sCtx;
+
+      if( sParse.pNewTable ){
+        if( IsView(sParse.pNewTable) ){
+          Select *pSelect = sParse.pNewTable->u.view.pSelect;
+          pSelect->selFlags &= ~SF_View;
+          sParse.rc = SQLITE_OK;
+          sqlite3SelectPrep(&sParse, pSelect, 0);
+          rc = (db->mallocFailed ? SQLITE_NOMEM : sParse.rc);
+          if( rc==SQLITE_OK ){
+            sqlite3WalkSelect(&sWalker, pSelect);
+          }
+        }else{
+          int i;
+          sqlite3WalkExprList(&sWalker, sParse.pNewTable->pCheck);
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+          for(i=0; i<sParse.pNewTable->nCol; i++){
+            sqlite3WalkExpr(&sWalker,
+               sqlite3ColumnExpr(sParse.pNewTable,
+                                         &sParse.pNewTable->aCol[i]));
+          }
+#endif /* SQLITE_OMIT_GENERATED_COLUMNS */
+        }
+      }else if( sParse.pNewIndex ){
+        sqlite3WalkExprList(&sWalker, sParse.pNewIndex->aColExpr);
+        sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
+      }else{
+#ifndef SQLITE_OMIT_TRIGGER
+        rc = renameResolveTrigger(&sParse);
+        if( rc==SQLITE_OK ){
+          renameWalkTrigger(&sWalker, sParse.pNewTrigger);
+        }
+#endif /* SQLITE_OMIT_TRIGGER */
+      }
+
+      if( rc==SQLITE_OK ){
+        rc = renameEditSql(context, &sCtx, zInput, 0, 0);
+      }
+      renameTokenFree(db, sCtx.pList);
+    }
+    if( rc!=SQLITE_OK ){
+      if( sqlite3WritableSchema(db) && rc==SQLITE_ERROR ){
+        sqlite3_result_value(context, argv[1]);
+      }else{
+        sqlite3_result_error_code(context, rc);
+      }
+    }
+    renameParseCleanup(&sParse);
+  }
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  db->xAuth = xAuth;
+#endif
+
+  sqlite3BtreeLeaveAll(db);
+}
+
+/* Function:  sqlite_rename_test(DB,SQL,TYPE,NAME,ISTEMP,WHEN,DQS)
+**
+** An SQL user function that checks that there are no parse or symbol
+** resolution problems in a CREATE TRIGGER|TABLE|VIEW|INDEX statement.
+** After an ALTER TABLE .. RENAME operation is performed and the schema
+** reloaded, this function is called on each SQL statement in the schema
+** to ensure that it is still usable.
+**
+**   0: Database name ("main", "temp" etc.).
+**   1: SQL statement.
+**   2: Object type ("view", "table", "trigger" or "index").
+**   3: Object name.
+**   4: True if object is from temp schema.
+**   5: "when" part of error message.
+**   6: True to disable the DQS quirk when parsing SQL.
+**
+** The return value is computed as follows:
+**
+**   A. If an error is seen and not in PRAGMA writable_schema=ON mode,
+**      then raise the error.
+**   B. Else if a trigger is created and the the table that the trigger is
+**      attached to is in database zDb, then return 1.
+**   C. Otherwise return NULL.
+*/
+static void renameTableTest(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  char const *zDb = (const char*)sqlite3_value_text(argv[0]);
+  char const *zInput = (const char*)sqlite3_value_text(argv[1]);
+  int bTemp = sqlite3_value_int(argv[4]);
+  int isLegacy = (db->flags & SQLITE_LegacyAlter);
+  char const *zWhen = (const char*)sqlite3_value_text(argv[5]);
+  int bNoDQS = sqlite3_value_int(argv[6]);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  sqlite3_xauth xAuth = db->xAuth;
+  db->xAuth = 0;
+#endif
+
+  UNUSED_PARAMETER(NotUsed);
+
+  if( zDb && zInput ){
+    int rc;
+    Parse sParse;
+    int flags = db->flags;
+    if( bNoDQS ) db->flags &= ~(SQLITE_DqsDML|SQLITE_DqsDDL);
+    rc = renameParseSql(&sParse, zDb, db, zInput, bTemp);
+    db->flags |= (flags & (SQLITE_DqsDML|SQLITE_DqsDDL));
+    if( rc==SQLITE_OK ){
+      if( isLegacy==0 && sParse.pNewTable && IsView(sParse.pNewTable) ){
+        NameContext sNC;
+        memset(&sNC, 0, sizeof(sNC));
+        sNC.pParse = &sParse;
+        sqlite3SelectPrep(&sParse, sParse.pNewTable->u.view.pSelect, &sNC);
+        if( sParse.nErr ) rc = sParse.rc;
+      }
+
+      else if( sParse.pNewTrigger ){
+        if( isLegacy==0 ){
+          rc = renameResolveTrigger(&sParse);
+        }
+        if( rc==SQLITE_OK ){
+          int i1 = sqlite3SchemaToIndex(db, sParse.pNewTrigger->pTabSchema);
+          int i2 = sqlite3FindDbName(db, zDb);
+          if( i1==i2 ){
+            /* Handle output case B */
+            sqlite3_result_int(context, 1);
+          }
+        }
+      }
+    }
+
+    if( rc!=SQLITE_OK && zWhen && !sqlite3WritableSchema(db) ){
+      /* Output case A */
+      renameColumnParseError(context, zWhen, argv[2], argv[3],&sParse);
+    }
+    renameParseCleanup(&sParse);
+  }
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  db->xAuth = xAuth;
+#endif
+}
+
+/*
+** The implementation of internal UDF sqlite_drop_column().
+**
+** Arguments:
+**
+**  argv[0]: An integer - the index of the schema containing the table
+**  argv[1]: CREATE TABLE statement to modify.
+**  argv[2]: An integer - the index of the column to remove.
+**
+** The value returned is a string containing the CREATE TABLE statement
+** with column argv[2] removed.
+*/
+static void dropColumnFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  int iSchema = sqlite3_value_int(argv[0]);
+  const char *zSql = (const char*)sqlite3_value_text(argv[1]);
+  int iCol = sqlite3_value_int(argv[2]);
+  const char *zDb = db->aDb[iSchema].zDbSName;
+  int rc;
+  Parse sParse;
+  RenameToken *pCol;
+  Table *pTab;
+  const char *zEnd;
+  char *zNew = 0;
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  sqlite3_xauth xAuth = db->xAuth;
+  db->xAuth = 0;
+#endif
+
+  UNUSED_PARAMETER(NotUsed);
+  rc = renameParseSql(&sParse, zDb, db, zSql, iSchema==1);
+  if( rc!=SQLITE_OK ) goto drop_column_done;
+  pTab = sParse.pNewTable;
+  if( pTab==0 || pTab->nCol==1 || iCol>=pTab->nCol ){
+    /* This can happen if the sqlite_schema table is corrupt */
+    rc = SQLITE_CORRUPT_BKPT;
+    goto drop_column_done;
+  }
+
+  pCol = renameTokenFind(&sParse, 0, (void*)pTab->aCol[iCol].zCnName);
+  if( iCol<pTab->nCol-1 ){
+    RenameToken *pEnd;
+    pEnd = renameTokenFind(&sParse, 0, (void*)pTab->aCol[iCol+1].zCnName);
+    zEnd = (const char*)pEnd->t.z;
+  }else{
+    assert( IsOrdinaryTable(pTab) );
+    zEnd = (const char*)&zSql[pTab->u.tab.addColOffset];
+    while( ALWAYS(pCol->t.z[0]!=0) && pCol->t.z[0]!=',' ) pCol->t.z--;
+  }
+
+  zNew = sqlite3MPrintf(db, "%.*s%s", pCol->t.z-zSql, zSql, zEnd);
+  sqlite3_result_text(context, zNew, -1, SQLITE_TRANSIENT);
+  sqlite3_free(zNew);
+
+drop_column_done:
+  renameParseCleanup(&sParse);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  db->xAuth = xAuth;
+#endif
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(context, rc);
+  }
+}
+
+/*
+** This function is called by the parser upon parsing an
+**
+**     ALTER TABLE pSrc DROP COLUMN pName
+**
+** statement. Argument pSrc contains the possibly qualified name of the
+** table being edited, and token pName the name of the column to drop.
+*/
+void sqlite3AlterDropColumn(Parse *pParse, SrcList *pSrc, const Token *pName){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  Table *pTab;                    /* Table to modify */
+  int iDb;                        /* Index of db containing pTab in aDb[] */
+  const char *zDb;                /* Database containing pTab ("main" etc.) */
+  char *zCol = 0;                 /* Name of column to drop */
+  int iCol;                       /* Index of column zCol in pTab->aCol[] */
+
+  /* Look up the table being altered. */
+  assert( pParse->pNewTable==0 );
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  if( NEVER(db->mallocFailed) ) goto exit_drop_column;
+  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
+  if( !pTab ) goto exit_drop_column;
+
+  /* Make sure this is not an attempt to ALTER a view, virtual table or
+  ** system table. */
+  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ) goto exit_drop_column;
+  if( SQLITE_OK!=isRealTable(pParse, pTab, 1) ) goto exit_drop_column;
+
+  /* Find the index of the column being dropped. */
+  zCol = sqlite3NameFromToken(db, pName);
+  if( zCol==0 ){
+    assert( db->mallocFailed );
+    goto exit_drop_column;
+  }
+  iCol = sqlite3ColumnIndex(pTab, zCol);
+  if( iCol<0 ){
+    sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pName);
+    goto exit_drop_column;
+  }
+
+  /* Do not allow the user to drop a PRIMARY KEY column or a column
+  ** constrained by a UNIQUE constraint.  */
+  if( pTab->aCol[iCol].colFlags & (COLFLAG_PRIMKEY|COLFLAG_UNIQUE) ){
+    sqlite3ErrorMsg(pParse, "cannot drop %s column: \"%s\"",
+        (pTab->aCol[iCol].colFlags&COLFLAG_PRIMKEY) ? "PRIMARY KEY" : "UNIQUE",
+        zCol
+    );
+    goto exit_drop_column;
+  }
+
+  /* Do not allow the number of columns to go to zero */
+  if( pTab->nCol<=1 ){
+    sqlite3ErrorMsg(pParse, "cannot drop column \"%s\": no other columns exist",zCol);
+    goto exit_drop_column;
+  }
+
+  /* Edit the sqlite_schema table */
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb>=0 );
+  zDb = db->aDb[iDb].zDbSName;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Invoke the authorization callback. */
+  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, zCol) ){
+    goto exit_drop_column;
+  }
+#endif
+  renameTestSchema(pParse, zDb, iDb==1, "", 0);
+  renameFixQuotes(pParse, zDb, iDb==1);
+  sqlite3NestedParse(pParse,
+      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
+      "sql = sqlite_drop_column(%d, sql, %d) "
+      "WHERE (type=='table' AND tbl_name=%Q COLLATE nocase)"
+      , zDb, iDb, iCol, pTab->zName
+  );
+
+  /* Drop and reload the database schema. */
+  renameReloadSchema(pParse, iDb, INITFLAG_AlterDrop);
+  renameTestSchema(pParse, zDb, iDb==1, "after drop column", 1);
+
+  /* Edit rows of table on disk */
+  if( pParse->nErr==0 && (pTab->aCol[iCol].colFlags & COLFLAG_VIRTUAL)==0 ){
+    int i;
+    int addr;
+    int reg;
+    int regRec;
+    Index *pPk = 0;
+    int nField = 0;               /* Number of non-virtual columns after drop */
+    int iCur;
+    Vdbe *v = sqlite3GetVdbe(pParse);
+    iCur = pParse->nTab++;
+    sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite);
+    addr = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
+    reg = ++pParse->nMem;
+    if( HasRowid(pTab) ){
+      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, reg);
+      pParse->nMem += pTab->nCol;
+    }else{
+      pPk = sqlite3PrimaryKeyIndex(pTab);
+      pParse->nMem += pPk->nColumn;
+      for(i=0; i<pPk->nKeyCol; i++){
+        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, reg+i+1);
+      }
+      nField = pPk->nKeyCol;
+    }
+    regRec = ++pParse->nMem;
+    for(i=0; i<pTab->nCol; i++){
+      if( i!=iCol && (pTab->aCol[i].colFlags & COLFLAG_VIRTUAL)==0 ){
+        int regOut;
+        if( pPk ){
+          int iPos = sqlite3TableColumnToIndex(pPk, i);
+          int iColPos = sqlite3TableColumnToIndex(pPk, iCol);
+          if( iPos<pPk->nKeyCol ) continue;
+          regOut = reg+1+iPos-(iPos>iColPos);
+        }else{
+          regOut = reg+1+nField;
+        }
+        if( i==pTab->iPKey ){
+          sqlite3VdbeAddOp2(v, OP_Null, 0, regOut);
+        }else{
+          sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, i, regOut);
+        }
+        nField++;
+      }
+    }
+    if( nField==0 ){
+      /* dbsqlfuzz 5f09e7bcc78b4954d06bf9f2400d7715f48d1fef */
+      pParse->nMem++;
+      sqlite3VdbeAddOp2(v, OP_Null, 0, reg+1);
+      nField = 1;
+    }
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, reg+1, nField, regRec);
+    if( pPk ){
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iCur, regRec, reg+1, pPk->nKeyCol);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_Insert, iCur, regRec, reg);
+    }
+    sqlite3VdbeChangeP5(v, OPFLAG_SAVEPOSITION);
+
+    sqlite3VdbeAddOp2(v, OP_Next, iCur, addr+1); VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addr);
+  }
+
+exit_drop_column:
+  sqlite3DbFree(db, zCol);
+  sqlite3SrcListDelete(db, pSrc);
+}
+
+/*
+** Register built-in functions used to help implement ALTER TABLE
+*/
+void sqlite3AlterFunctions(void){
+  static FuncDef aAlterTableFuncs[] = {
+    INTERNAL_FUNCTION(sqlite_rename_column,  9, renameColumnFunc),
+    INTERNAL_FUNCTION(sqlite_rename_table,   7, renameTableFunc),
+    INTERNAL_FUNCTION(sqlite_rename_test,    7, renameTableTest),
+    INTERNAL_FUNCTION(sqlite_drop_column,    3, dropColumnFunc),
+    INTERNAL_FUNCTION(sqlite_rename_quotefix,2, renameQuotefixFunc),
+  };
+  sqlite3InsertBuiltinFuncs(aAlterTableFuncs, ArraySize(aAlterTableFuncs));
+}
+#endif  /* SQLITE_ALTER_TABLE */
diff --git a/src/analyze.c b/src/analyze.c
new file mode 100644
index 0000000..59e3d98
--- /dev/null
+++ b/src/analyze.c
@@ -0,0 +1,2004 @@
+/*
+** 2005-07-08
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code associated with the ANALYZE command.
+**
+** The ANALYZE command gather statistics about the content of tables
+** and indices.  These statistics are made available to the query planner
+** to help it make better decisions about how to perform queries.
+**
+** The following system tables are or have been supported:
+**
+**    CREATE TABLE sqlite_stat1(tbl, idx, stat);
+**    CREATE TABLE sqlite_stat2(tbl, idx, sampleno, sample);
+**    CREATE TABLE sqlite_stat3(tbl, idx, nEq, nLt, nDLt, sample);
+**    CREATE TABLE sqlite_stat4(tbl, idx, nEq, nLt, nDLt, sample);
+**
+** Additional tables might be added in future releases of SQLite.
+** The sqlite_stat2 table is not created or used unless the SQLite version
+** is between 3.6.18 and 3.7.8, inclusive, and unless SQLite is compiled
+** with SQLITE_ENABLE_STAT2.  The sqlite_stat2 table is deprecated.
+** The sqlite_stat2 table is superseded by sqlite_stat3, which is only
+** created and used by SQLite versions 3.7.9 through 3.29.0 when
+** SQLITE_ENABLE_STAT3 defined.  The functionality of sqlite_stat3
+** is a superset of sqlite_stat2 and is also now deprecated.  The
+** sqlite_stat4 is an enhanced version of sqlite_stat3 and is only 
+** available when compiled with SQLITE_ENABLE_STAT4 and in SQLite
+** versions 3.8.1 and later.  STAT4 is the only variant that is still
+** supported.
+**
+** For most applications, sqlite_stat1 provides all the statistics required
+** for the query planner to make good choices.
+**
+** Format of sqlite_stat1:
+**
+** There is normally one row per index, with the index identified by the
+** name in the idx column.  The tbl column is the name of the table to
+** which the index belongs.  In each such row, the stat column will be
+** a string consisting of a list of integers.  The first integer in this
+** list is the number of rows in the index.  (This is the same as the
+** number of rows in the table, except for partial indices.)  The second
+** integer is the average number of rows in the index that have the same
+** value in the first column of the index.  The third integer is the average
+** number of rows in the index that have the same value for the first two
+** columns.  The N-th integer (for N>1) is the average number of rows in 
+** the index which have the same value for the first N-1 columns.  For
+** a K-column index, there will be K+1 integers in the stat column.  If
+** the index is unique, then the last integer will be 1.
+**
+** The list of integers in the stat column can optionally be followed
+** by the keyword "unordered".  The "unordered" keyword, if it is present,
+** must be separated from the last integer by a single space.  If the
+** "unordered" keyword is present, then the query planner assumes that
+** the index is unordered and will not use the index for a range query.
+** 
+** If the sqlite_stat1.idx column is NULL, then the sqlite_stat1.stat
+** column contains a single integer which is the (estimated) number of
+** rows in the table identified by sqlite_stat1.tbl.
+**
+** Format of sqlite_stat2:
+**
+** The sqlite_stat2 is only created and is only used if SQLite is compiled
+** with SQLITE_ENABLE_STAT2 and if the SQLite version number is between
+** 3.6.18 and 3.7.8.  The "stat2" table contains additional information
+** about the distribution of keys within an index.  The index is identified by
+** the "idx" column and the "tbl" column is the name of the table to which
+** the index belongs.  There are usually 10 rows in the sqlite_stat2
+** table for each index.
+**
+** The sqlite_stat2 entries for an index that have sampleno between 0 and 9
+** inclusive are samples of the left-most key value in the index taken at
+** evenly spaced points along the index.  Let the number of samples be S
+** (10 in the standard build) and let C be the number of rows in the index.
+** Then the sampled rows are given by:
+**
+**     rownumber = (i*C*2 + C)/(S*2)
+**
+** For i between 0 and S-1.  Conceptually, the index space is divided into
+** S uniform buckets and the samples are the middle row from each bucket.
+**
+** The format for sqlite_stat2 is recorded here for legacy reference.  This
+** version of SQLite does not support sqlite_stat2.  It neither reads nor
+** writes the sqlite_stat2 table.  This version of SQLite only supports
+** sqlite_stat3.
+**
+** Format for sqlite_stat3:
+**
+** The sqlite_stat3 format is a subset of sqlite_stat4.  Hence, the
+** sqlite_stat4 format will be described first.  Further information
+** about sqlite_stat3 follows the sqlite_stat4 description.
+**
+** Format for sqlite_stat4:
+**
+** As with sqlite_stat2, the sqlite_stat4 table contains histogram data
+** to aid the query planner in choosing good indices based on the values
+** that indexed columns are compared against in the WHERE clauses of
+** queries.
+**
+** The sqlite_stat4 table contains multiple entries for each index.
+** The idx column names the index and the tbl column is the table of the
+** index.  If the idx and tbl columns are the same, then the sample is
+** of the INTEGER PRIMARY KEY.  The sample column is a blob which is the
+** binary encoding of a key from the index.  The nEq column is a
+** list of integers.  The first integer is the approximate number
+** of entries in the index whose left-most column exactly matches
+** the left-most column of the sample.  The second integer in nEq
+** is the approximate number of entries in the index where the
+** first two columns match the first two columns of the sample.
+** And so forth.  nLt is another list of integers that show the approximate
+** number of entries that are strictly less than the sample.  The first
+** integer in nLt contains the number of entries in the index where the
+** left-most column is less than the left-most column of the sample.
+** The K-th integer in the nLt entry is the number of index entries 
+** where the first K columns are less than the first K columns of the
+** sample.  The nDLt column is like nLt except that it contains the 
+** number of distinct entries in the index that are less than the
+** sample.
+**
+** There can be an arbitrary number of sqlite_stat4 entries per index.
+** The ANALYZE command will typically generate sqlite_stat4 tables
+** that contain between 10 and 40 samples which are distributed across
+** the key space, though not uniformly, and which include samples with
+** large nEq values.
+**
+** Format for sqlite_stat3 redux:
+**
+** The sqlite_stat3 table is like sqlite_stat4 except that it only
+** looks at the left-most column of the index.  The sqlite_stat3.sample
+** column contains the actual value of the left-most column instead
+** of a blob encoding of the complete index key as is found in
+** sqlite_stat4.sample.  The nEq, nLt, and nDLt entries of sqlite_stat3
+** all contain just a single integer which is the same as the first
+** integer in the equivalent columns in sqlite_stat4.
+*/
+#ifndef SQLITE_OMIT_ANALYZE
+#include "sqliteInt.h"
+
+#if defined(SQLITE_ENABLE_STAT4)
+# define IsStat4     1
+#else
+# define IsStat4     0
+# undef SQLITE_STAT4_SAMPLES
+# define SQLITE_STAT4_SAMPLES 1
+#endif
+
+/*
+** This routine generates code that opens the sqlite_statN tables.
+** The sqlite_stat1 table is always relevant.  sqlite_stat2 is now
+** obsolete.  sqlite_stat3 and sqlite_stat4 are only opened when
+** appropriate compile-time options are provided.
+**
+** If the sqlite_statN tables do not previously exist, it is created.
+**
+** Argument zWhere may be a pointer to a buffer containing a table name,
+** or it may be a NULL pointer. If it is not NULL, then all entries in
+** the sqlite_statN tables associated with the named table are deleted.
+** If zWhere==0, then code is generated to delete all stat table entries.
+*/
+static void openStatTable(
+  Parse *pParse,          /* Parsing context */
+  int iDb,                /* The database we are looking in */
+  int iStatCur,           /* Open the sqlite_stat1 table on this cursor */
+  const char *zWhere,     /* Delete entries for this table or index */
+  const char *zWhereType  /* Either "tbl" or "idx" */
+){
+  static const struct {
+    const char *zName;
+    const char *zCols;
+  } aTable[] = {
+    { "sqlite_stat1", "tbl,idx,stat" },
+#if defined(SQLITE_ENABLE_STAT4)
+    { "sqlite_stat4", "tbl,idx,neq,nlt,ndlt,sample" },
+#else
+    { "sqlite_stat4", 0 },
+#endif
+    { "sqlite_stat3", 0 },
+  };
+  int i;
+  sqlite3 *db = pParse->db;
+  Db *pDb;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  u32 aRoot[ArraySize(aTable)];
+  u8 aCreateTbl[ArraySize(aTable)];
+#ifdef SQLITE_ENABLE_STAT4
+  const int nToOpen = OptimizationEnabled(db,SQLITE_Stat4) ? 2 : 1;
+#else
+  const int nToOpen = 1;
+#endif
+
+  if( v==0 ) return;
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  assert( sqlite3VdbeDb(v)==db );
+  pDb = &db->aDb[iDb];
+
+  /* Create new statistic tables if they do not exist, or clear them
+  ** if they do already exist.
+  */
+  for(i=0; i<ArraySize(aTable); i++){
+    const char *zTab = aTable[i].zName;
+    Table *pStat;
+    aCreateTbl[i] = 0;
+    if( (pStat = sqlite3FindTable(db, zTab, pDb->zDbSName))==0 ){
+      if( i<nToOpen ){
+        /* The sqlite_statN table does not exist. Create it. Note that a 
+        ** side-effect of the CREATE TABLE statement is to leave the rootpage 
+        ** of the new table in register pParse->regRoot. This is important 
+        ** because the OpenWrite opcode below will be needing it. */
+        sqlite3NestedParse(pParse,
+            "CREATE TABLE %Q.%s(%s)", pDb->zDbSName, zTab, aTable[i].zCols
+        );
+        aRoot[i] = (u32)pParse->regRoot;
+        aCreateTbl[i] = OPFLAG_P2ISREG;
+      }
+    }else{
+      /* The table already exists. If zWhere is not NULL, delete all entries 
+      ** associated with the table zWhere. If zWhere is NULL, delete the
+      ** entire contents of the table. */
+      aRoot[i] = pStat->tnum;
+      sqlite3TableLock(pParse, iDb, aRoot[i], 1, zTab);
+      if( zWhere ){
+        sqlite3NestedParse(pParse,
+           "DELETE FROM %Q.%s WHERE %s=%Q",
+           pDb->zDbSName, zTab, zWhereType, zWhere
+        );
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+      }else if( db->xPreUpdateCallback ){
+        sqlite3NestedParse(pParse, "DELETE FROM %Q.%s", pDb->zDbSName, zTab);
+#endif
+      }else{
+        /* The sqlite_stat[134] table already exists.  Delete all rows. */
+        sqlite3VdbeAddOp2(v, OP_Clear, (int)aRoot[i], iDb);
+      }
+    }
+  }
+
+  /* Open the sqlite_stat[134] tables for writing. */
+  for(i=0; i<nToOpen; i++){
+    assert( i<ArraySize(aTable) );
+    sqlite3VdbeAddOp4Int(v, OP_OpenWrite, iStatCur+i, (int)aRoot[i], iDb, 3);
+    sqlite3VdbeChangeP5(v, aCreateTbl[i]);
+    VdbeComment((v, aTable[i].zName));
+  }
+}
+
+/*
+** Recommended number of samples for sqlite_stat4
+*/
+#ifndef SQLITE_STAT4_SAMPLES
+# define SQLITE_STAT4_SAMPLES 24
+#endif
+
+/*
+** Three SQL functions - stat_init(), stat_push(), and stat_get() -
+** share an instance of the following structure to hold their state
+** information.
+*/
+typedef struct StatAccum StatAccum;
+typedef struct StatSample StatSample;
+struct StatSample {
+  tRowcnt *anDLt;                 /* sqlite_stat4.nDLt */
+#ifdef SQLITE_ENABLE_STAT4
+  tRowcnt *anEq;                  /* sqlite_stat4.nEq */
+  tRowcnt *anLt;                  /* sqlite_stat4.nLt */
+  union {
+    i64 iRowid;                     /* Rowid in main table of the key */
+    u8 *aRowid;                     /* Key for WITHOUT ROWID tables */
+  } u;
+  u32 nRowid;                     /* Sizeof aRowid[] */
+  u8 isPSample;                   /* True if a periodic sample */
+  int iCol;                       /* If !isPSample, the reason for inclusion */
+  u32 iHash;                      /* Tiebreaker hash */
+#endif
+};                                                    
+struct StatAccum {
+  sqlite3 *db;              /* Database connection, for malloc() */
+  tRowcnt nEst;             /* Estimated number of rows */
+  tRowcnt nRow;             /* Number of rows visited so far */
+  int nLimit;               /* Analysis row-scan limit */
+  int nCol;                 /* Number of columns in index + pk/rowid */
+  int nKeyCol;              /* Number of index columns w/o the pk/rowid */
+  u8 nSkipAhead;            /* Number of times of skip-ahead */
+  StatSample current;       /* Current row as a StatSample */
+#ifdef SQLITE_ENABLE_STAT4
+  tRowcnt nPSample;         /* How often to do a periodic sample */
+  int mxSample;             /* Maximum number of samples to accumulate */
+  u32 iPrn;                 /* Pseudo-random number used for sampling */
+  StatSample *aBest;        /* Array of nCol best samples */
+  int iMin;                 /* Index in a[] of entry with minimum score */
+  int nSample;              /* Current number of samples */
+  int nMaxEqZero;           /* Max leading 0 in anEq[] for any a[] entry */
+  int iGet;                 /* Index of current sample accessed by stat_get() */
+  StatSample *a;            /* Array of mxSample StatSample objects */
+#endif
+};
+
+/* Reclaim memory used by a StatSample
+*/
+#ifdef SQLITE_ENABLE_STAT4
+static void sampleClear(sqlite3 *db, StatSample *p){
+  assert( db!=0 );
+  if( p->nRowid ){
+    sqlite3DbFree(db, p->u.aRowid);
+    p->nRowid = 0;
+  }
+}
+#endif
+
+/* Initialize the BLOB value of a ROWID
+*/
+#ifdef SQLITE_ENABLE_STAT4
+static void sampleSetRowid(sqlite3 *db, StatSample *p, int n, const u8 *pData){
+  assert( db!=0 );
+  if( p->nRowid ) sqlite3DbFree(db, p->u.aRowid);
+  p->u.aRowid = sqlite3DbMallocRawNN(db, n);
+  if( p->u.aRowid ){
+    p->nRowid = n;
+    memcpy(p->u.aRowid, pData, n);
+  }else{
+    p->nRowid = 0;
+  }
+}
+#endif
+
+/* Initialize the INTEGER value of a ROWID.
+*/
+#ifdef SQLITE_ENABLE_STAT4
+static void sampleSetRowidInt64(sqlite3 *db, StatSample *p, i64 iRowid){
+  assert( db!=0 );
+  if( p->nRowid ) sqlite3DbFree(db, p->u.aRowid);
+  p->nRowid = 0;
+  p->u.iRowid = iRowid;
+}
+#endif
+
+
+/*
+** Copy the contents of object (*pFrom) into (*pTo).
+*/
+#ifdef SQLITE_ENABLE_STAT4
+static void sampleCopy(StatAccum *p, StatSample *pTo, StatSample *pFrom){
+  pTo->isPSample = pFrom->isPSample;
+  pTo->iCol = pFrom->iCol;
+  pTo->iHash = pFrom->iHash;
+  memcpy(pTo->anEq, pFrom->anEq, sizeof(tRowcnt)*p->nCol);
+  memcpy(pTo->anLt, pFrom->anLt, sizeof(tRowcnt)*p->nCol);
+  memcpy(pTo->anDLt, pFrom->anDLt, sizeof(tRowcnt)*p->nCol);
+  if( pFrom->nRowid ){
+    sampleSetRowid(p->db, pTo, pFrom->nRowid, pFrom->u.aRowid);
+  }else{
+    sampleSetRowidInt64(p->db, pTo, pFrom->u.iRowid);
+  }
+}
+#endif
+
+/*
+** Reclaim all memory of a StatAccum structure.
+*/
+static void statAccumDestructor(void *pOld){
+  StatAccum *p = (StatAccum*)pOld;
+#ifdef SQLITE_ENABLE_STAT4
+  if( p->mxSample ){
+    int i;
+    for(i=0; i<p->nCol; i++) sampleClear(p->db, p->aBest+i);
+    for(i=0; i<p->mxSample; i++) sampleClear(p->db, p->a+i);
+    sampleClear(p->db, &p->current);
+  }
+#endif
+  sqlite3DbFree(p->db, p);
+}
+
+/*
+** Implementation of the stat_init(N,K,C,L) SQL function. The four parameters
+** are:
+**     N:    The number of columns in the index including the rowid/pk (note 1)
+**     K:    The number of columns in the index excluding the rowid/pk.
+**     C:    Estimated number of rows in the index
+**     L:    A limit on the number of rows to scan, or 0 for no-limit 
+**
+** Note 1:  In the special case of the covering index that implements a
+** WITHOUT ROWID table, N is the number of PRIMARY KEY columns, not the
+** total number of columns in the table.
+**
+** For indexes on ordinary rowid tables, N==K+1.  But for indexes on
+** WITHOUT ROWID tables, N=K+P where P is the number of columns in the
+** PRIMARY KEY of the table.  The covering index that implements the
+** original WITHOUT ROWID table as N==K as a special case.
+**
+** This routine allocates the StatAccum object in heap memory. The return 
+** value is a pointer to the StatAccum object.  The datatype of the
+** return value is BLOB, but it is really just a pointer to the StatAccum
+** object.
+*/
+static void statInit(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  StatAccum *p;
+  int nCol;                       /* Number of columns in index being sampled */
+  int nKeyCol;                    /* Number of key columns */
+  int nColUp;                     /* nCol rounded up for alignment */
+  int n;                          /* Bytes of space to allocate */
+  sqlite3 *db = sqlite3_context_db_handle(context);   /* Database connection */
+#ifdef SQLITE_ENABLE_STAT4
+  /* Maximum number of samples.  0 if STAT4 data is not collected */
+  int mxSample = OptimizationEnabled(db,SQLITE_Stat4) ?SQLITE_STAT4_SAMPLES :0;
+#endif
+
+  /* Decode the three function arguments */
+  UNUSED_PARAMETER(argc);
+  nCol = sqlite3_value_int(argv[0]);
+  assert( nCol>0 );
+  nColUp = sizeof(tRowcnt)<8 ? (nCol+1)&~1 : nCol;
+  nKeyCol = sqlite3_value_int(argv[1]);
+  assert( nKeyCol<=nCol );
+  assert( nKeyCol>0 );
+
+  /* Allocate the space required for the StatAccum object */
+  n = sizeof(*p) 
+    + sizeof(tRowcnt)*nColUp;                    /* StatAccum.anDLt */
+#ifdef SQLITE_ENABLE_STAT4
+  n += sizeof(tRowcnt)*nColUp;                   /* StatAccum.anEq */
+  if( mxSample ){
+    n += sizeof(tRowcnt)*nColUp                  /* StatAccum.anLt */
+      + sizeof(StatSample)*(nCol+mxSample)       /* StatAccum.aBest[], a[] */
+      + sizeof(tRowcnt)*3*nColUp*(nCol+mxSample);
+  }
+#endif
+  p = sqlite3DbMallocZero(db, n);
+  if( p==0 ){
+    sqlite3_result_error_nomem(context);
+    return;
+  }
+
+  p->db = db;
+  p->nEst = sqlite3_value_int64(argv[2]);
+  p->nRow = 0;
+  p->nLimit = sqlite3_value_int64(argv[3]);
+  p->nCol = nCol;
+  p->nKeyCol = nKeyCol;
+  p->nSkipAhead = 0;
+  p->current.anDLt = (tRowcnt*)&p[1];
+
+#ifdef SQLITE_ENABLE_STAT4
+  p->current.anEq = &p->current.anDLt[nColUp];
+  p->mxSample = p->nLimit==0 ? mxSample : 0;
+  if( mxSample ){
+    u8 *pSpace;                     /* Allocated space not yet assigned */
+    int i;                          /* Used to iterate through p->aSample[] */
+
+    p->iGet = -1;
+    p->nPSample = (tRowcnt)(p->nEst/(mxSample/3+1) + 1);
+    p->current.anLt = &p->current.anEq[nColUp];
+    p->iPrn = 0x689e962d*(u32)nCol ^ 0xd0944565*(u32)sqlite3_value_int(argv[2]);
+  
+    /* Set up the StatAccum.a[] and aBest[] arrays */
+    p->a = (struct StatSample*)&p->current.anLt[nColUp];
+    p->aBest = &p->a[mxSample];
+    pSpace = (u8*)(&p->a[mxSample+nCol]);
+    for(i=0; i<(mxSample+nCol); i++){
+      p->a[i].anEq = (tRowcnt *)pSpace; pSpace += (sizeof(tRowcnt) * nColUp);
+      p->a[i].anLt = (tRowcnt *)pSpace; pSpace += (sizeof(tRowcnt) * nColUp);
+      p->a[i].anDLt = (tRowcnt *)pSpace; pSpace += (sizeof(tRowcnt) * nColUp);
+    }
+    assert( (pSpace - (u8*)p)==n );
+  
+    for(i=0; i<nCol; i++){
+      p->aBest[i].iCol = i;
+    }
+  }
+#endif
+
+  /* Return a pointer to the allocated object to the caller.  Note that
+  ** only the pointer (the 2nd parameter) matters.  The size of the object
+  ** (given by the 3rd parameter) is never used and can be any positive
+  ** value. */
+  sqlite3_result_blob(context, p, sizeof(*p), statAccumDestructor);
+}
+static const FuncDef statInitFuncdef = {
+  4,               /* nArg */
+  SQLITE_UTF8,     /* funcFlags */
+  0,               /* pUserData */
+  0,               /* pNext */
+  statInit,        /* xSFunc */
+  0,               /* xFinalize */
+  0, 0,            /* xValue, xInverse */
+  "stat_init",     /* zName */
+  {0}
+};
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** pNew and pOld are both candidate non-periodic samples selected for 
+** the same column (pNew->iCol==pOld->iCol). Ignoring this column and 
+** considering only any trailing columns and the sample hash value, this
+** function returns true if sample pNew is to be preferred over pOld.
+** In other words, if we assume that the cardinalities of the selected
+** column for pNew and pOld are equal, is pNew to be preferred over pOld.
+**
+** This function assumes that for each argument sample, the contents of
+** the anEq[] array from pSample->anEq[pSample->iCol+1] onwards are valid. 
+*/
+static int sampleIsBetterPost(
+  StatAccum *pAccum, 
+  StatSample *pNew, 
+  StatSample *pOld
+){
+  int nCol = pAccum->nCol;
+  int i;
+  assert( pNew->iCol==pOld->iCol );
+  for(i=pNew->iCol+1; i<nCol; i++){
+    if( pNew->anEq[i]>pOld->anEq[i] ) return 1;
+    if( pNew->anEq[i]<pOld->anEq[i] ) return 0;
+  }
+  if( pNew->iHash>pOld->iHash ) return 1;
+  return 0;
+}
+#endif
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Return true if pNew is to be preferred over pOld.
+**
+** This function assumes that for each argument sample, the contents of
+** the anEq[] array from pSample->anEq[pSample->iCol] onwards are valid. 
+*/
+static int sampleIsBetter(
+  StatAccum *pAccum, 
+  StatSample *pNew, 
+  StatSample *pOld
+){
+  tRowcnt nEqNew = pNew->anEq[pNew->iCol];
+  tRowcnt nEqOld = pOld->anEq[pOld->iCol];
+
+  assert( pOld->isPSample==0 && pNew->isPSample==0 );
+  assert( IsStat4 || (pNew->iCol==0 && pOld->iCol==0) );
+
+  if( (nEqNew>nEqOld) ) return 1;
+  if( nEqNew==nEqOld ){
+    if( pNew->iCol<pOld->iCol ) return 1;
+    return (pNew->iCol==pOld->iCol && sampleIsBetterPost(pAccum, pNew, pOld));
+  }
+  return 0;
+}
+
+/*
+** Copy the contents of sample *pNew into the p->a[] array. If necessary,
+** remove the least desirable sample from p->a[] to make room.
+*/
+static void sampleInsert(StatAccum *p, StatSample *pNew, int nEqZero){
+  StatSample *pSample = 0;
+  int i;
+
+  assert( IsStat4 || nEqZero==0 );
+
+  /* StatAccum.nMaxEqZero is set to the maximum number of leading 0
+  ** values in the anEq[] array of any sample in StatAccum.a[]. In
+  ** other words, if nMaxEqZero is n, then it is guaranteed that there
+  ** are no samples with StatSample.anEq[m]==0 for (m>=n). */
+  if( nEqZero>p->nMaxEqZero ){
+    p->nMaxEqZero = nEqZero;
+  }
+  if( pNew->isPSample==0 ){
+    StatSample *pUpgrade = 0;
+    assert( pNew->anEq[pNew->iCol]>0 );
+
+    /* This sample is being added because the prefix that ends in column 
+    ** iCol occurs many times in the table. However, if we have already
+    ** added a sample that shares this prefix, there is no need to add
+    ** this one. Instead, upgrade the priority of the highest priority
+    ** existing sample that shares this prefix.  */
+    for(i=p->nSample-1; i>=0; i--){
+      StatSample *pOld = &p->a[i];
+      if( pOld->anEq[pNew->iCol]==0 ){
+        if( pOld->isPSample ) return;
+        assert( pOld->iCol>pNew->iCol );
+        assert( sampleIsBetter(p, pNew, pOld) );
+        if( pUpgrade==0 || sampleIsBetter(p, pOld, pUpgrade) ){
+          pUpgrade = pOld;
+        }
+      }
+    }
+    if( pUpgrade ){
+      pUpgrade->iCol = pNew->iCol;
+      pUpgrade->anEq[pUpgrade->iCol] = pNew->anEq[pUpgrade->iCol];
+      goto find_new_min;
+    }
+  }
+
+  /* If necessary, remove sample iMin to make room for the new sample. */
+  if( p->nSample>=p->mxSample ){
+    StatSample *pMin = &p->a[p->iMin];
+    tRowcnt *anEq = pMin->anEq;
+    tRowcnt *anLt = pMin->anLt;
+    tRowcnt *anDLt = pMin->anDLt;
+    sampleClear(p->db, pMin);
+    memmove(pMin, &pMin[1], sizeof(p->a[0])*(p->nSample-p->iMin-1));
+    pSample = &p->a[p->nSample-1];
+    pSample->nRowid = 0;
+    pSample->anEq = anEq;
+    pSample->anDLt = anDLt;
+    pSample->anLt = anLt;
+    p->nSample = p->mxSample-1;
+  }
+
+  /* The "rows less-than" for the rowid column must be greater than that
+  ** for the last sample in the p->a[] array. Otherwise, the samples would
+  ** be out of order. */
+  assert( p->nSample==0 
+       || pNew->anLt[p->nCol-1] > p->a[p->nSample-1].anLt[p->nCol-1] );
+
+  /* Insert the new sample */
+  pSample = &p->a[p->nSample];
+  sampleCopy(p, pSample, pNew);
+  p->nSample++;
+
+  /* Zero the first nEqZero entries in the anEq[] array. */
+  memset(pSample->anEq, 0, sizeof(tRowcnt)*nEqZero);
+
+find_new_min:
+  if( p->nSample>=p->mxSample ){
+    int iMin = -1;
+    for(i=0; i<p->mxSample; i++){
+      if( p->a[i].isPSample ) continue;
+      if( iMin<0 || sampleIsBetter(p, &p->a[iMin], &p->a[i]) ){
+        iMin = i;
+      }
+    }
+    assert( iMin>=0 );
+    p->iMin = iMin;
+  }
+}
+#endif /* SQLITE_ENABLE_STAT4 */
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Field iChng of the index being scanned has changed. So at this point
+** p->current contains a sample that reflects the previous row of the
+** index. The value of anEq[iChng] and subsequent anEq[] elements are
+** correct at this point.
+*/
+static void samplePushPrevious(StatAccum *p, int iChng){
+  int i;
+
+  /* Check if any samples from the aBest[] array should be pushed
+  ** into IndexSample.a[] at this point.  */
+  for(i=(p->nCol-2); i>=iChng; i--){
+    StatSample *pBest = &p->aBest[i];
+    pBest->anEq[i] = p->current.anEq[i];
+    if( p->nSample<p->mxSample || sampleIsBetter(p, pBest, &p->a[p->iMin]) ){
+      sampleInsert(p, pBest, i);
+    }
+  }
+
+  /* Check that no sample contains an anEq[] entry with an index of
+  ** p->nMaxEqZero or greater set to zero. */
+  for(i=p->nSample-1; i>=0; i--){
+    int j;
+    for(j=p->nMaxEqZero; j<p->nCol; j++) assert( p->a[i].anEq[j]>0 );
+  }
+
+  /* Update the anEq[] fields of any samples already collected. */
+  if( iChng<p->nMaxEqZero ){
+    for(i=p->nSample-1; i>=0; i--){
+      int j;
+      for(j=iChng; j<p->nCol; j++){
+        if( p->a[i].anEq[j]==0 ) p->a[i].anEq[j] = p->current.anEq[j];
+      }
+    }
+    p->nMaxEqZero = iChng;
+  }
+}
+#endif /* SQLITE_ENABLE_STAT4 */
+
+/*
+** Implementation of the stat_push SQL function:  stat_push(P,C,R)
+** Arguments:
+**
+**    P     Pointer to the StatAccum object created by stat_init()
+**    C     Index of left-most column to differ from previous row
+**    R     Rowid for the current row.  Might be a key record for
+**          WITHOUT ROWID tables.
+**
+** The purpose of this routine is to collect statistical data and/or
+** samples from the index being analyzed into the StatAccum object.
+** The stat_get() SQL function will be used afterwards to
+** retrieve the information gathered.
+**
+** This SQL function usually returns NULL, but might return an integer
+** if it wants the byte-code to do special processing.
+**
+** The R parameter is only used for STAT4
+*/
+static void statPush(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+
+  /* The three function arguments */
+  StatAccum *p = (StatAccum*)sqlite3_value_blob(argv[0]);
+  int iChng = sqlite3_value_int(argv[1]);
+
+  UNUSED_PARAMETER( argc );
+  UNUSED_PARAMETER( context );
+  assert( p->nCol>0 );
+  assert( iChng<p->nCol );
+
+  if( p->nRow==0 ){
+    /* This is the first call to this function. Do initialization. */
+#ifdef SQLITE_ENABLE_STAT4
+    for(i=0; i<p->nCol; i++) p->current.anEq[i] = 1;
+#endif
+  }else{
+    /* Second and subsequent calls get processed here */
+#ifdef SQLITE_ENABLE_STAT4
+    if( p->mxSample ) samplePushPrevious(p, iChng);
+#endif
+
+    /* Update anDLt[], anLt[] and anEq[] to reflect the values that apply
+    ** to the current row of the index. */
+#ifdef SQLITE_ENABLE_STAT4
+    for(i=0; i<iChng; i++){
+      p->current.anEq[i]++;
+    }
+#endif
+    for(i=iChng; i<p->nCol; i++){
+      p->current.anDLt[i]++;
+#ifdef SQLITE_ENABLE_STAT4
+      if( p->mxSample ) p->current.anLt[i] += p->current.anEq[i];
+      p->current.anEq[i] = 1;
+#endif
+    }
+  }
+
+  p->nRow++;
+#ifdef SQLITE_ENABLE_STAT4
+  if( p->mxSample ){
+    tRowcnt nLt;
+    if( sqlite3_value_type(argv[2])==SQLITE_INTEGER ){
+      sampleSetRowidInt64(p->db, &p->current, sqlite3_value_int64(argv[2]));
+    }else{
+      sampleSetRowid(p->db, &p->current, sqlite3_value_bytes(argv[2]),
+                                         sqlite3_value_blob(argv[2]));
+    }
+    p->current.iHash = p->iPrn = p->iPrn*1103515245 + 12345;
+
+    nLt = p->current.anLt[p->nCol-1];
+    /* Check if this is to be a periodic sample. If so, add it. */
+    if( (nLt/p->nPSample)!=(nLt+1)/p->nPSample ){
+      p->current.isPSample = 1;
+      p->current.iCol = 0;
+      sampleInsert(p, &p->current, p->nCol-1);
+      p->current.isPSample = 0;
+    }
+
+    /* Update the aBest[] array. */
+    for(i=0; i<(p->nCol-1); i++){
+      p->current.iCol = i;
+      if( i>=iChng || sampleIsBetterPost(p, &p->current, &p->aBest[i]) ){
+        sampleCopy(p, &p->aBest[i], &p->current);
+      }
+    }
+  }else
+#endif
+  if( p->nLimit && p->nRow>(tRowcnt)p->nLimit*(p->nSkipAhead+1) ){
+    p->nSkipAhead++;
+    sqlite3_result_int(context, p->current.anDLt[0]>0);
+  }
+}
+
+static const FuncDef statPushFuncdef = {
+  2+IsStat4,       /* nArg */
+  SQLITE_UTF8,     /* funcFlags */
+  0,               /* pUserData */
+  0,               /* pNext */
+  statPush,        /* xSFunc */
+  0,               /* xFinalize */
+  0, 0,            /* xValue, xInverse */
+  "stat_push",     /* zName */
+  {0}
+};
+
+#define STAT_GET_STAT1 0          /* "stat" column of stat1 table */
+#define STAT_GET_ROWID 1          /* "rowid" column of stat[34] entry */
+#define STAT_GET_NEQ   2          /* "neq" column of stat[34] entry */
+#define STAT_GET_NLT   3          /* "nlt" column of stat[34] entry */
+#define STAT_GET_NDLT  4          /* "ndlt" column of stat[34] entry */
+
+/*
+** Implementation of the stat_get(P,J) SQL function.  This routine is
+** used to query statistical information that has been gathered into
+** the StatAccum object by prior calls to stat_push().  The P parameter
+** has type BLOB but it is really just a pointer to the StatAccum object.
+** The content to returned is determined by the parameter J
+** which is one of the STAT_GET_xxxx values defined above.
+**
+** The stat_get(P,J) function is not available to generic SQL.  It is
+** inserted as part of a manually constructed bytecode program.  (See
+** the callStatGet() routine below.)  It is guaranteed that the P
+** parameter will always be a pointer to a StatAccum object, never a
+** NULL.
+**
+** If STAT4 is not enabled, then J is always
+** STAT_GET_STAT1 and is hence omitted and this routine becomes
+** a one-parameter function, stat_get(P), that always returns the
+** stat1 table entry information.
+*/
+static void statGet(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  StatAccum *p = (StatAccum*)sqlite3_value_blob(argv[0]);
+#ifdef SQLITE_ENABLE_STAT4
+  /* STAT4 has a parameter on this routine. */
+  int eCall = sqlite3_value_int(argv[1]);
+  assert( argc==2 );
+  assert( eCall==STAT_GET_STAT1 || eCall==STAT_GET_NEQ 
+       || eCall==STAT_GET_ROWID || eCall==STAT_GET_NLT
+       || eCall==STAT_GET_NDLT 
+  );
+  assert( eCall==STAT_GET_STAT1 || p->mxSample );
+  if( eCall==STAT_GET_STAT1 )
+#else
+  assert( argc==1 );
+#endif
+  {
+    /* Return the value to store in the "stat" column of the sqlite_stat1
+    ** table for this index.
+    **
+    ** The value is a string composed of a list of integers describing 
+    ** the index. The first integer in the list is the total number of 
+    ** entries in the index. There is one additional integer in the list 
+    ** for each indexed column. This additional integer is an estimate of
+    ** the number of rows matched by a equality query on the index using
+    ** a key with the corresponding number of fields. In other words,
+    ** if the index is on columns (a,b) and the sqlite_stat1 value is 
+    ** "100 10 2", then SQLite estimates that:
+    **
+    **   * the index contains 100 rows,
+    **   * "WHERE a=?" matches 10 rows, and
+    **   * "WHERE a=? AND b=?" matches 2 rows.
+    **
+    ** If D is the count of distinct values and K is the total number of 
+    ** rows, then each estimate is usually computed as:
+    **
+    **        I = (K+D-1)/D
+    **
+    ** In other words, I is K/D rounded up to the next whole integer.
+    ** However, if I is between 1.0 and 1.1 (in other words if I is
+    ** close to 1.0 but just a little larger) then do not round up but
+    ** instead keep the I value at 1.0.
+    */
+    sqlite3_str sStat;   /* Text of the constructed "stat" line */
+    int i;               /* Loop counter */
+
+    sqlite3StrAccumInit(&sStat, 0, 0, 0, (p->nKeyCol+1)*100);
+    sqlite3_str_appendf(&sStat, "%llu", 
+        p->nSkipAhead ? (u64)p->nEst : (u64)p->nRow);
+    for(i=0; i<p->nKeyCol; i++){
+      u64 nDistinct = p->current.anDLt[i] + 1;
+      u64 iVal = (p->nRow + nDistinct - 1) / nDistinct;
+      if( iVal==2 && p->nRow*10 <= nDistinct*11 ) iVal = 1;
+      sqlite3_str_appendf(&sStat, " %llu", iVal);
+#ifdef SQLITE_ENABLE_STAT4
+      assert( p->current.anEq[i] );
+#endif
+    }
+    sqlite3ResultStrAccum(context, &sStat);
+  }
+#ifdef SQLITE_ENABLE_STAT4
+  else if( eCall==STAT_GET_ROWID ){
+    if( p->iGet<0 ){
+      samplePushPrevious(p, 0);
+      p->iGet = 0;
+    }
+    if( p->iGet<p->nSample ){
+      StatSample *pS = p->a + p->iGet;
+      if( pS->nRowid==0 ){
+        sqlite3_result_int64(context, pS->u.iRowid);
+      }else{
+        sqlite3_result_blob(context, pS->u.aRowid, pS->nRowid,
+                            SQLITE_TRANSIENT);
+      }
+    }
+  }else{
+    tRowcnt *aCnt = 0;
+    sqlite3_str sStat;
+    int i;
+
+    assert( p->iGet<p->nSample );
+    switch( eCall ){
+      case STAT_GET_NEQ:  aCnt = p->a[p->iGet].anEq; break;
+      case STAT_GET_NLT:  aCnt = p->a[p->iGet].anLt; break;
+      default: {
+        aCnt = p->a[p->iGet].anDLt; 
+        p->iGet++;
+        break;
+      }
+    }
+    sqlite3StrAccumInit(&sStat, 0, 0, 0, p->nCol*100);
+    for(i=0; i<p->nCol; i++){
+      sqlite3_str_appendf(&sStat, "%llu ", (u64)aCnt[i]);
+    }
+    if( sStat.nChar ) sStat.nChar--;
+    sqlite3ResultStrAccum(context, &sStat);
+  }
+#endif /* SQLITE_ENABLE_STAT4 */
+#ifndef SQLITE_DEBUG
+  UNUSED_PARAMETER( argc );
+#endif
+}
+static const FuncDef statGetFuncdef = {
+  1+IsStat4,       /* nArg */
+  SQLITE_UTF8,     /* funcFlags */
+  0,               /* pUserData */
+  0,               /* pNext */
+  statGet,         /* xSFunc */
+  0,               /* xFinalize */
+  0, 0,            /* xValue, xInverse */
+  "stat_get",      /* zName */
+  {0}
+};
+
+static void callStatGet(Parse *pParse, int regStat, int iParam, int regOut){
+#ifdef SQLITE_ENABLE_STAT4
+  sqlite3VdbeAddOp2(pParse->pVdbe, OP_Integer, iParam, regStat+1);
+#elif SQLITE_DEBUG
+  assert( iParam==STAT_GET_STAT1 );
+#else
+  UNUSED_PARAMETER( iParam );
+#endif
+  assert( regOut!=regStat && regOut!=regStat+1 );
+  sqlite3VdbeAddFunctionCall(pParse, 0, regStat, regOut, 1+IsStat4,
+                             &statGetFuncdef, 0);
+}
+
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+/* Add a comment to the most recent VDBE opcode that is the name
+** of the k-th column of the pIdx index.
+*/
+static void analyzeVdbeCommentIndexWithColumnName(
+  Vdbe *v,         /* Prepared statement under construction */
+  Index *pIdx,     /* Index whose column is being loaded */
+  int k            /* Which column index */
+){
+  int i;           /* Index of column in the table */
+  assert( k>=0 && k<pIdx->nColumn );
+  i = pIdx->aiColumn[k];
+  if( NEVER(i==XN_ROWID) ){
+    VdbeComment((v,"%s.rowid",pIdx->zName));
+  }else if( i==XN_EXPR ){
+    assert( pIdx->bHasExpr );
+    VdbeComment((v,"%s.expr(%d)",pIdx->zName, k));
+  }else{
+    VdbeComment((v,"%s.%s", pIdx->zName, pIdx->pTable->aCol[i].zCnName));
+  }
+}
+#else
+# define analyzeVdbeCommentIndexWithColumnName(a,b,c)
+#endif /* SQLITE_DEBUG */
+
+/*
+** Generate code to do an analysis of all indices associated with
+** a single table.
+*/
+static void analyzeOneTable(
+  Parse *pParse,   /* Parser context */
+  Table *pTab,     /* Table whose indices are to be analyzed */
+  Index *pOnlyIdx, /* If not NULL, only analyze this one index */
+  int iStatCur,    /* Index of VdbeCursor that writes the sqlite_stat1 table */
+  int iMem,        /* Available memory locations begin here */
+  int iTab         /* Next available cursor */
+){
+  sqlite3 *db = pParse->db;    /* Database handle */
+  Index *pIdx;                 /* An index to being analyzed */
+  int iIdxCur;                 /* Cursor open on index being analyzed */
+  int iTabCur;                 /* Table cursor */
+  Vdbe *v;                     /* The virtual machine being built up */
+  int i;                       /* Loop counter */
+  int jZeroRows = -1;          /* Jump from here if number of rows is zero */
+  int iDb;                     /* Index of database containing pTab */
+  u8 needTableCnt = 1;         /* True to count the table */
+  int regNewRowid = iMem++;    /* Rowid for the inserted record */
+  int regStat = iMem++;        /* Register to hold StatAccum object */
+  int regChng = iMem++;        /* Index of changed index field */
+  int regRowid = iMem++;       /* Rowid argument passed to stat_push() */
+  int regTemp = iMem++;        /* Temporary use register */
+  int regTemp2 = iMem++;       /* Second temporary use register */
+  int regTabname = iMem++;     /* Register containing table name */
+  int regIdxname = iMem++;     /* Register containing index name */
+  int regStat1 = iMem++;       /* Value for the stat column of sqlite_stat1 */
+  int regPrev = iMem;          /* MUST BE LAST (see below) */
+#ifdef SQLITE_ENABLE_STAT4
+  int doOnce = 1;              /* Flag for a one-time computation */
+#endif
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  Table *pStat1 = 0;
+#endif
+
+  sqlite3TouchRegister(pParse, iMem);
+  assert( sqlite3NoTempsInRange(pParse, regNewRowid, iMem) );
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 || NEVER(pTab==0) ){
+    return;
+  }
+  if( !IsOrdinaryTable(pTab) ){
+    /* Do not gather statistics on views or virtual tables */
+    return;
+  }
+  if( sqlite3_strlike("sqlite\\_%", pTab->zName, '\\')==0 ){
+    /* Do not gather statistics on system tables */
+    return;
+  }
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb>=0 );
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( sqlite3AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,
+      db->aDb[iDb].zDbSName ) ){
+    return;
+  }
+#endif
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  if( db->xPreUpdateCallback ){
+    pStat1 = (Table*)sqlite3DbMallocZero(db, sizeof(Table) + 13);
+    if( pStat1==0 ) return;
+    pStat1->zName = (char*)&pStat1[1];
+    memcpy(pStat1->zName, "sqlite_stat1", 13);
+    pStat1->nCol = 3;
+    pStat1->iPKey = -1;
+    sqlite3VdbeAddOp4(pParse->pVdbe, OP_Noop, 0, 0, 0,(char*)pStat1,P4_DYNAMIC);
+  }
+#endif
+
+  /* Establish a read-lock on the table at the shared-cache level. 
+  ** Open a read-only cursor on the table. Also allocate a cursor number
+  ** to use for scanning indexes (iIdxCur). No index cursor is opened at
+  ** this time though.  */
+  sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+  iTabCur = iTab++;
+  iIdxCur = iTab++;
+  pParse->nTab = MAX(pParse->nTab, iTab);
+  sqlite3OpenTable(pParse, iTabCur, iDb, pTab, OP_OpenRead);
+  sqlite3VdbeLoadString(v, regTabname, pTab->zName);
+
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    int nCol;                     /* Number of columns in pIdx. "N" */
+    int addrRewind;               /* Address of "OP_Rewind iIdxCur" */
+    int addrNextRow;              /* Address of "next_row:" */
+    const char *zIdxName;         /* Name of the index */
+    int nColTest;                 /* Number of columns to test for changes */
+
+    if( pOnlyIdx && pOnlyIdx!=pIdx ) continue;
+    if( pIdx->pPartIdxWhere==0 ) needTableCnt = 0;
+    if( !HasRowid(pTab) && IsPrimaryKeyIndex(pIdx) ){
+      nCol = pIdx->nKeyCol;
+      zIdxName = pTab->zName;
+      nColTest = nCol - 1;
+    }else{
+      nCol = pIdx->nColumn;
+      zIdxName = pIdx->zName;
+      nColTest = pIdx->uniqNotNull ? pIdx->nKeyCol-1 : nCol-1;
+    }
+
+    /* Populate the register containing the index name. */
+    sqlite3VdbeLoadString(v, regIdxname, zIdxName);
+    VdbeComment((v, "Analysis for %s.%s", pTab->zName, zIdxName));
+
+    /*
+    ** Pseudo-code for loop that calls stat_push():
+    **
+    **   Rewind csr
+    **   if eof(csr) goto end_of_scan;
+    **   regChng = 0
+    **   goto chng_addr_0;
+    **
+    **  next_row:
+    **   regChng = 0
+    **   if( idx(0) != regPrev(0) ) goto chng_addr_0
+    **   regChng = 1
+    **   if( idx(1) != regPrev(1) ) goto chng_addr_1
+    **   ...
+    **   regChng = N
+    **   goto chng_addr_N
+    **
+    **  chng_addr_0:
+    **   regPrev(0) = idx(0)
+    **  chng_addr_1:
+    **   regPrev(1) = idx(1)
+    **  ...
+    **
+    **  endDistinctTest:
+    **   regRowid = idx(rowid)
+    **   stat_push(P, regChng, regRowid)
+    **   Next csr
+    **   if !eof(csr) goto next_row;
+    **
+    **  end_of_scan:
+    */
+
+    /* Make sure there are enough memory cells allocated to accommodate 
+    ** the regPrev array and a trailing rowid (the rowid slot is required
+    ** when building a record to insert into the sample column of 
+    ** the sqlite_stat4 table.  */
+    sqlite3TouchRegister(pParse, regPrev+nColTest);
+
+    /* Open a read-only cursor on the index being analyzed. */
+    assert( iDb==sqlite3SchemaToIndex(db, pIdx->pSchema) );
+    sqlite3VdbeAddOp3(v, OP_OpenRead, iIdxCur, pIdx->tnum, iDb);
+    sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
+    VdbeComment((v, "%s", pIdx->zName));
+
+    /* Invoke the stat_init() function. The arguments are:
+    ** 
+    **    (1) the number of columns in the index including the rowid
+    **        (or for a WITHOUT ROWID table, the number of PK columns),
+    **    (2) the number of columns in the key without the rowid/pk
+    **    (3) estimated number of rows in the index,
+    */
+    sqlite3VdbeAddOp2(v, OP_Integer, nCol, regStat+1);
+    assert( regRowid==regStat+2 );
+    sqlite3VdbeAddOp2(v, OP_Integer, pIdx->nKeyCol, regRowid);
+#ifdef SQLITE_ENABLE_STAT4
+    if( OptimizationEnabled(db, SQLITE_Stat4) ){
+      sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regTemp);
+      addrRewind = sqlite3VdbeAddOp1(v, OP_Rewind, iIdxCur);
+      VdbeCoverage(v);
+    }else
+#endif
+    {
+      addrRewind = sqlite3VdbeAddOp1(v, OP_Rewind, iIdxCur);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_Count, iIdxCur, regTemp, 1);
+    }
+    assert( regTemp2==regStat+4 );
+    sqlite3VdbeAddOp2(v, OP_Integer, db->nAnalysisLimit, regTemp2);
+    sqlite3VdbeAddFunctionCall(pParse, 0, regStat+1, regStat, 4,
+                               &statInitFuncdef, 0);
+
+    /* Implementation of the following:
+    **
+    **   Rewind csr
+    **   if eof(csr) goto end_of_scan;
+    **   regChng = 0
+    **   goto next_push_0;
+    **
+    */
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regChng);
+    addrNextRow = sqlite3VdbeCurrentAddr(v);
+
+    if( nColTest>0 ){
+      int endDistinctTest = sqlite3VdbeMakeLabel(pParse);
+      int *aGotoChng;               /* Array of jump instruction addresses */
+      aGotoChng = sqlite3DbMallocRawNN(db, sizeof(int)*nColTest);
+      if( aGotoChng==0 ) continue;
+
+      /*
+      **  next_row:
+      **   regChng = 0
+      **   if( idx(0) != regPrev(0) ) goto chng_addr_0
+      **   regChng = 1
+      **   if( idx(1) != regPrev(1) ) goto chng_addr_1
+      **   ...
+      **   regChng = N
+      **   goto endDistinctTest
+      */
+      sqlite3VdbeAddOp0(v, OP_Goto);
+      addrNextRow = sqlite3VdbeCurrentAddr(v);
+      if( nColTest==1 && pIdx->nKeyCol==1 && IsUniqueIndex(pIdx) ){
+        /* For a single-column UNIQUE index, once we have found a non-NULL
+        ** row, we know that all the rest will be distinct, so skip 
+        ** subsequent distinctness tests. */
+        sqlite3VdbeAddOp2(v, OP_NotNull, regPrev, endDistinctTest);
+        VdbeCoverage(v);
+      }
+      for(i=0; i<nColTest; i++){
+        char *pColl = (char*)sqlite3LocateCollSeq(pParse, pIdx->azColl[i]);
+        sqlite3VdbeAddOp2(v, OP_Integer, i, regChng);
+        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regTemp);
+        analyzeVdbeCommentIndexWithColumnName(v,pIdx,i);
+        aGotoChng[i] = 
+        sqlite3VdbeAddOp4(v, OP_Ne, regTemp, 0, regPrev+i, pColl, P4_COLLSEQ);
+        sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
+        VdbeCoverage(v);
+      }
+      sqlite3VdbeAddOp2(v, OP_Integer, nColTest, regChng);
+      sqlite3VdbeGoto(v, endDistinctTest);
+  
+  
+      /*
+      **  chng_addr_0:
+      **   regPrev(0) = idx(0)
+      **  chng_addr_1:
+      **   regPrev(1) = idx(1)
+      **  ...
+      */
+      sqlite3VdbeJumpHere(v, addrNextRow-1);
+      for(i=0; i<nColTest; i++){
+        sqlite3VdbeJumpHere(v, aGotoChng[i]);
+        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regPrev+i);
+        analyzeVdbeCommentIndexWithColumnName(v,pIdx,i);
+      }
+      sqlite3VdbeResolveLabel(v, endDistinctTest);
+      sqlite3DbFree(db, aGotoChng);
+    }
+  
+    /*
+    **  chng_addr_N:
+    **   regRowid = idx(rowid)            // STAT4 only
+    **   stat_push(P, regChng, regRowid)  // 3rd parameter STAT4 only
+    **   Next csr
+    **   if !eof(csr) goto next_row;
+    */
+#ifdef SQLITE_ENABLE_STAT4
+    if( OptimizationEnabled(db, SQLITE_Stat4) ){
+      assert( regRowid==(regStat+2) );
+      if( HasRowid(pTab) ){
+        sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, regRowid);
+      }else{
+        Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
+        int j, k, regKey;
+        regKey = sqlite3GetTempRange(pParse, pPk->nKeyCol);
+        for(j=0; j<pPk->nKeyCol; j++){
+          k = sqlite3TableColumnToIndex(pIdx, pPk->aiColumn[j]);
+          assert( k>=0 && k<pIdx->nColumn );
+          sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, regKey+j);
+          analyzeVdbeCommentIndexWithColumnName(v,pIdx,k);
+        }
+        sqlite3VdbeAddOp3(v, OP_MakeRecord, regKey, pPk->nKeyCol, regRowid);
+        sqlite3ReleaseTempRange(pParse, regKey, pPk->nKeyCol);
+      }
+    }
+#endif
+    assert( regChng==(regStat+1) );
+    {
+      sqlite3VdbeAddFunctionCall(pParse, 1, regStat, regTemp, 2+IsStat4,
+                                 &statPushFuncdef, 0);
+      if( db->nAnalysisLimit ){
+        int j1, j2, j3;
+        j1 = sqlite3VdbeAddOp1(v, OP_IsNull, regTemp); VdbeCoverage(v);
+        j2 = sqlite3VdbeAddOp1(v, OP_If, regTemp); VdbeCoverage(v);
+        j3 = sqlite3VdbeAddOp4Int(v, OP_SeekGT, iIdxCur, 0, regPrev, 1);
+        VdbeCoverage(v);
+        sqlite3VdbeJumpHere(v, j1);
+        sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
+        sqlite3VdbeJumpHere(v, j2);
+        sqlite3VdbeJumpHere(v, j3);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
+      }
+    }
+
+    /* Add the entry to the stat1 table. */
+    callStatGet(pParse, regStat, STAT_GET_STAT1, regStat1);
+    assert( "BBB"[0]==SQLITE_AFF_TEXT );
+    sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regTemp, "BBB", 0);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
+    sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regTemp, regNewRowid);
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+    sqlite3VdbeChangeP4(v, -1, (char*)pStat1, P4_TABLE);
+#endif
+    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+
+    /* Add the entries to the stat4 table. */
+#ifdef SQLITE_ENABLE_STAT4
+    if( OptimizationEnabled(db, SQLITE_Stat4) && db->nAnalysisLimit==0 ){
+      int regEq = regStat1;
+      int regLt = regStat1+1;
+      int regDLt = regStat1+2;
+      int regSample = regStat1+3;
+      int regCol = regStat1+4;
+      int regSampleRowid = regCol + nCol;
+      int addrNext;
+      int addrIsNull;
+      u8 seekOp = HasRowid(pTab) ? OP_NotExists : OP_NotFound;
+
+      if( doOnce ){
+        int mxCol = nCol;
+        Index *pX;
+
+        /* Compute the maximum number of columns in any index */
+        for(pX=pTab->pIndex; pX; pX=pX->pNext){
+          int nColX;                     /* Number of columns in pX */
+          if( !HasRowid(pTab) && IsPrimaryKeyIndex(pX) ){
+            nColX = pX->nKeyCol;
+          }else{
+            nColX = pX->nColumn;
+          }
+          if( nColX>mxCol ) mxCol = nColX;
+        }
+
+        /* Allocate space to compute results for the largest index */
+        sqlite3TouchRegister(pParse, regCol+mxCol);
+        doOnce = 0;
+#ifdef SQLITE_DEBUG
+        /* Verify that the call to sqlite3ClearTempRegCache() below
+        ** really is needed.
+        ** https://sqlite.org/forum/forumpost/83cb4a95a0 (2023-03-25)
+        */
+        testcase( !sqlite3NoTempsInRange(pParse, regEq, regCol+mxCol) );
+#endif
+        sqlite3ClearTempRegCache(pParse);  /* tag-20230325-1 */
+        assert( sqlite3NoTempsInRange(pParse, regEq, regCol+mxCol) );
+      }
+      assert( sqlite3NoTempsInRange(pParse, regEq, regCol+nCol) );
+
+      addrNext = sqlite3VdbeCurrentAddr(v);
+      callStatGet(pParse, regStat, STAT_GET_ROWID, regSampleRowid);
+      addrIsNull = sqlite3VdbeAddOp1(v, OP_IsNull, regSampleRowid);
+      VdbeCoverage(v);
+      callStatGet(pParse, regStat, STAT_GET_NEQ, regEq);
+      callStatGet(pParse, regStat, STAT_GET_NLT, regLt);
+      callStatGet(pParse, regStat, STAT_GET_NDLT, regDLt);
+      sqlite3VdbeAddOp4Int(v, seekOp, iTabCur, addrNext, regSampleRowid, 0);
+      VdbeCoverage(v);
+      for(i=0; i<nCol; i++){
+        sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iTabCur, i, regCol+i);
+      }
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regCol, nCol, regSample);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regTabname, 6, regTemp);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur+1, regNewRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, iStatCur+1, regTemp, regNewRowid);
+      sqlite3VdbeAddOp2(v, OP_Goto, 1, addrNext); /* P1==1 for end-of-loop */
+      sqlite3VdbeJumpHere(v, addrIsNull);
+    }
+#endif /* SQLITE_ENABLE_STAT4 */
+
+    /* End of analysis */
+    sqlite3VdbeJumpHere(v, addrRewind);
+  }
+
+
+  /* Create a single sqlite_stat1 entry containing NULL as the index
+  ** name and the row count as the content.
+  */
+  if( pOnlyIdx==0 && needTableCnt ){
+    VdbeComment((v, "%s", pTab->zName));
+    sqlite3VdbeAddOp2(v, OP_Count, iTabCur, regStat1);
+    jZeroRows = sqlite3VdbeAddOp1(v, OP_IfNot, regStat1); VdbeCoverage(v);
+    sqlite3VdbeAddOp2(v, OP_Null, 0, regIdxname);
+    assert( "BBB"[0]==SQLITE_AFF_TEXT );
+    sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regTemp, "BBB", 0);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
+    sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regTemp, regNewRowid);
+    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+    sqlite3VdbeChangeP4(v, -1, (char*)pStat1, P4_TABLE);
+#endif
+    sqlite3VdbeJumpHere(v, jZeroRows);
+  }
+}
+
+
+/*
+** Generate code that will cause the most recent index analysis to
+** be loaded into internal hash tables where is can be used.
+*/
+static void loadAnalysis(Parse *pParse, int iDb){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3VdbeAddOp1(v, OP_LoadAnalysis, iDb);
+  }
+}
+
+/*
+** Generate code that will do an analysis of an entire database
+*/
+static void analyzeDatabase(Parse *pParse, int iDb){
+  sqlite3 *db = pParse->db;
+  Schema *pSchema = db->aDb[iDb].pSchema;    /* Schema of database iDb */
+  HashElem *k;
+  int iStatCur;
+  int iMem;
+  int iTab;
+
+  sqlite3BeginWriteOperation(pParse, 0, iDb);
+  iStatCur = pParse->nTab;
+  pParse->nTab += 3;
+  openStatTable(pParse, iDb, iStatCur, 0, 0);
+  iMem = pParse->nMem+1;
+  iTab = pParse->nTab;
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
+    Table *pTab = (Table*)sqliteHashData(k);
+    analyzeOneTable(pParse, pTab, 0, iStatCur, iMem, iTab);
+#ifdef SQLITE_ENABLE_STAT4
+    iMem = sqlite3FirstAvailableRegister(pParse, iMem);
+#else
+    assert( iMem==sqlite3FirstAvailableRegister(pParse,iMem) );
+#endif
+  }
+  loadAnalysis(pParse, iDb);
+}
+
+/*
+** Generate code that will do an analysis of a single table in
+** a database.  If pOnlyIdx is not NULL then it is a single index
+** in pTab that should be analyzed.
+*/
+static void analyzeTable(Parse *pParse, Table *pTab, Index *pOnlyIdx){
+  int iDb;
+  int iStatCur;
+
+  assert( pTab!=0 );
+  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  sqlite3BeginWriteOperation(pParse, 0, iDb);
+  iStatCur = pParse->nTab;
+  pParse->nTab += 3;
+  if( pOnlyIdx ){
+    openStatTable(pParse, iDb, iStatCur, pOnlyIdx->zName, "idx");
+  }else{
+    openStatTable(pParse, iDb, iStatCur, pTab->zName, "tbl");
+  }
+  analyzeOneTable(pParse, pTab, pOnlyIdx, iStatCur,pParse->nMem+1,pParse->nTab);
+  loadAnalysis(pParse, iDb);
+}
+
+/*
+** Generate code for the ANALYZE command.  The parser calls this routine
+** when it recognizes an ANALYZE command.
+**
+**        ANALYZE                            -- 1
+**        ANALYZE  <database>                -- 2
+**        ANALYZE  ?<database>.?<tablename>  -- 3
+**
+** Form 1 causes all indices in all attached databases to be analyzed.
+** Form 2 analyzes all indices the single database named.
+** Form 3 analyzes all indices associated with the named table.
+*/
+void sqlite3Analyze(Parse *pParse, Token *pName1, Token *pName2){
+  sqlite3 *db = pParse->db;
+  int iDb;
+  int i;
+  char *z, *zDb;
+  Table *pTab;
+  Index *pIdx;
+  Token *pTableName;
+  Vdbe *v;
+
+  /* Read the database schema. If an error occurs, leave an error message
+  ** and code in pParse and return NULL. */
+  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    return;
+  }
+
+  assert( pName2!=0 || pName1==0 );
+  if( pName1==0 ){
+    /* Form 1:  Analyze everything */
+    for(i=0; i<db->nDb; i++){
+      if( i==1 ) continue;  /* Do not analyze the TEMP database */
+      analyzeDatabase(pParse, i);
+    }
+  }else if( pName2->n==0 && (iDb = sqlite3FindDb(db, pName1))>=0 ){
+    /* Analyze the schema named as the argument */
+    analyzeDatabase(pParse, iDb);
+  }else{
+    /* Form 3: Analyze the table or index named as an argument */
+    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pTableName);
+    if( iDb>=0 ){
+      zDb = pName2->n ? db->aDb[iDb].zDbSName : 0;
+      z = sqlite3NameFromToken(db, pTableName);
+      if( z ){
+        if( (pIdx = sqlite3FindIndex(db, z, zDb))!=0 ){
+          analyzeTable(pParse, pIdx->pTable, pIdx);
+        }else if( (pTab = sqlite3LocateTable(pParse, 0, z, zDb))!=0 ){
+          analyzeTable(pParse, pTab, 0);
+        }
+        sqlite3DbFree(db, z);
+      }
+    }
+  }
+  if( db->nSqlExec==0 && (v = sqlite3GetVdbe(pParse))!=0 ){
+    sqlite3VdbeAddOp0(v, OP_Expire);
+  }
+}
+
+/*
+** Used to pass information from the analyzer reader through to the
+** callback routine.
+*/
+typedef struct analysisInfo analysisInfo;
+struct analysisInfo {
+  sqlite3 *db;
+  const char *zDatabase;
+};
+
+/*
+** The first argument points to a nul-terminated string containing a
+** list of space separated integers. Read the first nOut of these into
+** the array aOut[].
+*/
+static void decodeIntArray(
+  char *zIntArray,       /* String containing int array to decode */
+  int nOut,              /* Number of slots in aOut[] */
+  tRowcnt *aOut,         /* Store integers here */
+  LogEst *aLog,          /* Or, if aOut==0, here */
+  Index *pIndex          /* Handle extra flags for this index, if not NULL */
+){
+  char *z = zIntArray;
+  int c;
+  int i;
+  tRowcnt v;
+
+#ifdef SQLITE_ENABLE_STAT4
+  if( z==0 ) z = "";
+#else
+  assert( z!=0 );
+#endif
+  for(i=0; *z && i<nOut; i++){
+    v = 0;
+    while( (c=z[0])>='0' && c<='9' ){
+      v = v*10 + c - '0';
+      z++;
+    }
+#ifdef SQLITE_ENABLE_STAT4
+    if( aOut ) aOut[i] = v;
+    if( aLog ) aLog[i] = sqlite3LogEst(v);
+#else
+    assert( aOut==0 );
+    UNUSED_PARAMETER(aOut);
+    assert( aLog!=0 );
+    aLog[i] = sqlite3LogEst(v);
+#endif
+    if( *z==' ' ) z++;
+  }
+#ifndef SQLITE_ENABLE_STAT4
+  assert( pIndex!=0 ); {
+#else
+  if( pIndex ){
+#endif
+    pIndex->bUnordered = 0;
+    pIndex->noSkipScan = 0;
+    while( z[0] ){
+      if( sqlite3_strglob("unordered*", z)==0 ){
+        pIndex->bUnordered = 1;
+      }else if( sqlite3_strglob("sz=[0-9]*", z)==0 ){
+        int sz = sqlite3Atoi(z+3);
+        if( sz<2 ) sz = 2;
+        pIndex->szIdxRow = sqlite3LogEst(sz);
+      }else if( sqlite3_strglob("noskipscan*", z)==0 ){
+        pIndex->noSkipScan = 1;
+      }
+#ifdef SQLITE_ENABLE_COSTMULT
+      else if( sqlite3_strglob("costmult=[0-9]*",z)==0 ){
+        pIndex->pTable->costMult = sqlite3LogEst(sqlite3Atoi(z+9));
+      }
+#endif
+      while( z[0]!=0 && z[0]!=' ' ) z++;
+      while( z[0]==' ' ) z++;
+    }
+
+    /* Set the bLowQual flag if the peak number of rows obtained
+    ** from a full equality match is so large that a full table scan
+    ** seems likely to be faster than using the index.
+    */
+    if( aLog[0] > 66              /* Index has more than 100 rows */
+     && aLog[0] <= aLog[nOut-1]   /* And only a single value seen */
+    ){
+      pIndex->bLowQual = 1;
+    }
+  }
+}
+
+/*
+** This callback is invoked once for each index when reading the
+** sqlite_stat1 table.  
+**
+**     argv[0] = name of the table
+**     argv[1] = name of the index (might be NULL)
+**     argv[2] = results of analysis - on integer for each column
+**
+** Entries for which argv[1]==NULL simply record the number of rows in
+** the table.
+*/
+static int analysisLoader(void *pData, int argc, char **argv, char **NotUsed){
+  analysisInfo *pInfo = (analysisInfo*)pData;
+  Index *pIndex;
+  Table *pTable;
+  const char *z;
+
+  assert( argc==3 );
+  UNUSED_PARAMETER2(NotUsed, argc);
+
+  if( argv==0 || argv[0]==0 || argv[2]==0 ){
+    return 0;
+  }
+  pTable = sqlite3FindTable(pInfo->db, argv[0], pInfo->zDatabase);
+  if( pTable==0 ){
+    return 0;
+  }
+  if( argv[1]==0 ){
+    pIndex = 0;
+  }else if( sqlite3_stricmp(argv[0],argv[1])==0 ){
+    pIndex = sqlite3PrimaryKeyIndex(pTable);
+  }else{
+    pIndex = sqlite3FindIndex(pInfo->db, argv[1], pInfo->zDatabase);
+  }
+  z = argv[2];
+
+  if( pIndex ){
+    tRowcnt *aiRowEst = 0;
+    int nCol = pIndex->nKeyCol+1;
+#ifdef SQLITE_ENABLE_STAT4
+    /* Index.aiRowEst may already be set here if there are duplicate 
+    ** sqlite_stat1 entries for this index. In that case just clobber
+    ** the old data with the new instead of allocating a new array.  */
+    if( pIndex->aiRowEst==0 ){
+      pIndex->aiRowEst = (tRowcnt*)sqlite3MallocZero(sizeof(tRowcnt) * nCol);
+      if( pIndex->aiRowEst==0 ) sqlite3OomFault(pInfo->db);
+    }
+    aiRowEst = pIndex->aiRowEst;
+#endif
+    pIndex->bUnordered = 0;
+    decodeIntArray((char*)z, nCol, aiRowEst, pIndex->aiRowLogEst, pIndex);
+    pIndex->hasStat1 = 1;
+    if( pIndex->pPartIdxWhere==0 ){
+      pTable->nRowLogEst = pIndex->aiRowLogEst[0];
+      pTable->tabFlags |= TF_HasStat1;
+    }
+  }else{
+    Index fakeIdx;
+    fakeIdx.szIdxRow = pTable->szTabRow;
+#ifdef SQLITE_ENABLE_COSTMULT
+    fakeIdx.pTable = pTable;
+#endif
+    decodeIntArray((char*)z, 1, 0, &pTable->nRowLogEst, &fakeIdx);
+    pTable->szTabRow = fakeIdx.szIdxRow;
+    pTable->tabFlags |= TF_HasStat1;
+  }
+
+  return 0;
+}
+
+/*
+** If the Index.aSample variable is not NULL, delete the aSample[] array
+** and its contents.
+*/
+void sqlite3DeleteIndexSamples(sqlite3 *db, Index *pIdx){
+  assert( db!=0 );
+  assert( pIdx!=0 );
+#ifdef SQLITE_ENABLE_STAT4
+  if( pIdx->aSample ){
+    int j;
+    for(j=0; j<pIdx->nSample; j++){
+      IndexSample *p = &pIdx->aSample[j];
+      sqlite3DbFree(db, p->p);
+    }
+    sqlite3DbFree(db, pIdx->aSample);
+  }
+  if( db->pnBytesFreed==0 ){
+    pIdx->nSample = 0;
+    pIdx->aSample = 0;
+  }
+#else
+  UNUSED_PARAMETER(db);
+  UNUSED_PARAMETER(pIdx);
+#endif /* SQLITE_ENABLE_STAT4 */
+}
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Populate the pIdx->aAvgEq[] array based on the samples currently
+** stored in pIdx->aSample[]. 
+*/
+static void initAvgEq(Index *pIdx){
+  if( pIdx ){
+    IndexSample *aSample = pIdx->aSample;
+    IndexSample *pFinal = &aSample[pIdx->nSample-1];
+    int iCol;
+    int nCol = 1;
+    if( pIdx->nSampleCol>1 ){
+      /* If this is stat4 data, then calculate aAvgEq[] values for all
+      ** sample columns except the last. The last is always set to 1, as
+      ** once the trailing PK fields are considered all index keys are
+      ** unique.  */
+      nCol = pIdx->nSampleCol-1;
+      pIdx->aAvgEq[nCol] = 1;
+    }
+    for(iCol=0; iCol<nCol; iCol++){
+      int nSample = pIdx->nSample;
+      int i;                    /* Used to iterate through samples */
+      tRowcnt sumEq = 0;        /* Sum of the nEq values */
+      tRowcnt avgEq = 0;
+      tRowcnt nRow;             /* Number of rows in index */
+      i64 nSum100 = 0;          /* Number of terms contributing to sumEq */
+      i64 nDist100;             /* Number of distinct values in index */
+
+      if( !pIdx->aiRowEst || iCol>=pIdx->nKeyCol || pIdx->aiRowEst[iCol+1]==0 ){
+        nRow = pFinal->anLt[iCol];
+        nDist100 = (i64)100 * pFinal->anDLt[iCol];
+        nSample--;
+      }else{
+        nRow = pIdx->aiRowEst[0];
+        nDist100 = ((i64)100 * pIdx->aiRowEst[0]) / pIdx->aiRowEst[iCol+1];
+      }
+      pIdx->nRowEst0 = nRow;
+
+      /* Set nSum to the number of distinct (iCol+1) field prefixes that
+      ** occur in the stat4 table for this index. Set sumEq to the sum of 
+      ** the nEq values for column iCol for the same set (adding the value 
+      ** only once where there exist duplicate prefixes).  */
+      for(i=0; i<nSample; i++){
+        if( i==(pIdx->nSample-1)
+         || aSample[i].anDLt[iCol]!=aSample[i+1].anDLt[iCol] 
+        ){
+          sumEq += aSample[i].anEq[iCol];
+          nSum100 += 100;
+        }
+      }
+
+      if( nDist100>nSum100 && sumEq<nRow ){
+        avgEq = ((i64)100 * (nRow - sumEq))/(nDist100 - nSum100);
+      }
+      if( avgEq==0 ) avgEq = 1;
+      pIdx->aAvgEq[iCol] = avgEq;
+    }
+  }
+}
+
+/*
+** Look up an index by name.  Or, if the name of a WITHOUT ROWID table
+** is supplied instead, find the PRIMARY KEY index for that table.
+*/
+static Index *findIndexOrPrimaryKey(
+  sqlite3 *db,
+  const char *zName,
+  const char *zDb
+){
+  Index *pIdx = sqlite3FindIndex(db, zName, zDb);
+  if( pIdx==0 ){
+    Table *pTab = sqlite3FindTable(db, zName, zDb);
+    if( pTab && !HasRowid(pTab) ) pIdx = sqlite3PrimaryKeyIndex(pTab);
+  }
+  return pIdx;
+}
+
+/*
+** Load the content from either the sqlite_stat4
+** into the relevant Index.aSample[] arrays.
+**
+** Arguments zSql1 and zSql2 must point to SQL statements that return
+** data equivalent to the following:
+**
+**    zSql1: SELECT idx,count(*) FROM %Q.sqlite_stat4 GROUP BY idx
+**    zSql2: SELECT idx,neq,nlt,ndlt,sample FROM %Q.sqlite_stat4
+**
+** where %Q is replaced with the database name before the SQL is executed.
+*/
+static int loadStatTbl(
+  sqlite3 *db,                  /* Database handle */
+  const char *zSql1,            /* SQL statement 1 (see above) */
+  const char *zSql2,            /* SQL statement 2 (see above) */
+  const char *zDb               /* Database name (e.g. "main") */
+){
+  int rc;                       /* Result codes from subroutines */
+  sqlite3_stmt *pStmt = 0;      /* An SQL statement being run */
+  char *zSql;                   /* Text of the SQL statement */
+  Index *pPrevIdx = 0;          /* Previous index in the loop */
+  IndexSample *pSample;         /* A slot in pIdx->aSample[] */
+
+  assert( db->lookaside.bDisable );
+  zSql = sqlite3MPrintf(db, zSql1, zDb);
+  if( !zSql ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3DbFree(db, zSql);
+  if( rc ) return rc;
+
+  while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    int nIdxCol = 1;              /* Number of columns in stat4 records */
+
+    char *zIndex;   /* Index name */
+    Index *pIdx;    /* Pointer to the index object */
+    int nSample;    /* Number of samples */
+    int nByte;      /* Bytes of space required */
+    int i;          /* Bytes of space required */
+    tRowcnt *pSpace;
+
+    zIndex = (char *)sqlite3_column_text(pStmt, 0);
+    if( zIndex==0 ) continue;
+    nSample = sqlite3_column_int(pStmt, 1);
+    pIdx = findIndexOrPrimaryKey(db, zIndex, zDb);
+    assert( pIdx==0 || pIdx->nSample==0 );
+    if( pIdx==0 ) continue;
+    if( pIdx->aSample!=0 ){
+      /* The same index appears in sqlite_stat4 under multiple names */
+      continue;
+    }
+    assert( !HasRowid(pIdx->pTable) || pIdx->nColumn==pIdx->nKeyCol+1 );
+    if( !HasRowid(pIdx->pTable) && IsPrimaryKeyIndex(pIdx) ){
+      nIdxCol = pIdx->nKeyCol;
+    }else{
+      nIdxCol = pIdx->nColumn;
+    }
+    pIdx->nSampleCol = nIdxCol;
+    pIdx->mxSample = nSample;
+    nByte = sizeof(IndexSample) * nSample;
+    nByte += sizeof(tRowcnt) * nIdxCol * 3 * nSample;
+    nByte += nIdxCol * sizeof(tRowcnt);     /* Space for Index.aAvgEq[] */
+
+    pIdx->aSample = sqlite3DbMallocZero(db, nByte);
+    if( pIdx->aSample==0 ){
+      sqlite3_finalize(pStmt);
+      return SQLITE_NOMEM_BKPT;
+    }
+    pSpace = (tRowcnt*)&pIdx->aSample[nSample];
+    pIdx->aAvgEq = pSpace; pSpace += nIdxCol;
+    pIdx->pTable->tabFlags |= TF_HasStat4;
+    for(i=0; i<nSample; i++){
+      pIdx->aSample[i].anEq = pSpace; pSpace += nIdxCol;
+      pIdx->aSample[i].anLt = pSpace; pSpace += nIdxCol;
+      pIdx->aSample[i].anDLt = pSpace; pSpace += nIdxCol;
+    }
+    assert( ((u8*)pSpace)-nByte==(u8*)(pIdx->aSample) );
+  }
+  rc = sqlite3_finalize(pStmt);
+  if( rc ) return rc;
+
+  zSql = sqlite3MPrintf(db, zSql2, zDb);
+  if( !zSql ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3DbFree(db, zSql);
+  if( rc ) return rc;
+
+  while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    char *zIndex;                 /* Index name */
+    Index *pIdx;                  /* Pointer to the index object */
+    int nCol = 1;                 /* Number of columns in index */
+
+    zIndex = (char *)sqlite3_column_text(pStmt, 0);
+    if( zIndex==0 ) continue;
+    pIdx = findIndexOrPrimaryKey(db, zIndex, zDb);
+    if( pIdx==0 ) continue;
+    if( pIdx->nSample>=pIdx->mxSample ){
+      /* Too many slots used because the same index appears in
+      ** sqlite_stat4 using multiple names */
+      continue;
+    }
+    /* This next condition is true if data has already been loaded from 
+    ** the sqlite_stat4 table. */
+    nCol = pIdx->nSampleCol;
+    if( pIdx!=pPrevIdx ){
+      initAvgEq(pPrevIdx);
+      pPrevIdx = pIdx;
+    }
+    pSample = &pIdx->aSample[pIdx->nSample];
+    decodeIntArray((char*)sqlite3_column_text(pStmt,1),nCol,pSample->anEq,0,0);
+    decodeIntArray((char*)sqlite3_column_text(pStmt,2),nCol,pSample->anLt,0,0);
+    decodeIntArray((char*)sqlite3_column_text(pStmt,3),nCol,pSample->anDLt,0,0);
+
+    /* Take a copy of the sample. Add 8 extra 0x00 bytes the end of the buffer.
+    ** This is in case the sample record is corrupted. In that case, the
+    ** sqlite3VdbeRecordCompare() may read up to two varints past the
+    ** end of the allocated buffer before it realizes it is dealing with
+    ** a corrupt record.  Or it might try to read a large integer from the
+    ** buffer.  In any case, eight 0x00 bytes prevents this from causing
+    ** a buffer overread.  */
+    pSample->n = sqlite3_column_bytes(pStmt, 4);
+    pSample->p = sqlite3DbMallocZero(db, pSample->n + 8);
+    if( pSample->p==0 ){
+      sqlite3_finalize(pStmt);
+      return SQLITE_NOMEM_BKPT;
+    }
+    if( pSample->n ){
+      memcpy(pSample->p, sqlite3_column_blob(pStmt, 4), pSample->n);
+    }
+    pIdx->nSample++;
+  }
+  rc = sqlite3_finalize(pStmt);
+  if( rc==SQLITE_OK ) initAvgEq(pPrevIdx);
+  return rc;
+}
+
+/*
+** Load content from the sqlite_stat4 table into 
+** the Index.aSample[] arrays of all indices.
+*/
+static int loadStat4(sqlite3 *db, const char *zDb){
+  int rc = SQLITE_OK;             /* Result codes from subroutines */
+  const Table *pStat4;
+
+  assert( db->lookaside.bDisable );
+  if( OptimizationEnabled(db, SQLITE_Stat4)
+   && (pStat4 = sqlite3FindTable(db, "sqlite_stat4", zDb))!=0
+   && IsOrdinaryTable(pStat4)
+  ){
+    rc = loadStatTbl(db,
+      "SELECT idx,count(*) FROM %Q.sqlite_stat4 GROUP BY idx COLLATE nocase", 
+      "SELECT idx,neq,nlt,ndlt,sample FROM %Q.sqlite_stat4",
+      zDb
+    );
+  }
+  return rc;
+}
+#endif /* SQLITE_ENABLE_STAT4 */
+
+/*
+** Load the content of the sqlite_stat1 and sqlite_stat4 tables. The
+** contents of sqlite_stat1 are used to populate the Index.aiRowEst[]
+** arrays. The contents of sqlite_stat4 are used to populate the
+** Index.aSample[] arrays.
+**
+** If the sqlite_stat1 table is not present in the database, SQLITE_ERROR
+** is returned. In this case, even if SQLITE_ENABLE_STAT4 was defined 
+** during compilation and the sqlite_stat4 table is present, no data is 
+** read from it.
+**
+** If SQLITE_ENABLE_STAT4 was defined during compilation and the 
+** sqlite_stat4 table is not present in the database, SQLITE_ERROR is
+** returned. However, in this case, data is read from the sqlite_stat1
+** table (if it is present) before returning.
+**
+** If an OOM error occurs, this function always sets db->mallocFailed.
+** This means if the caller does not care about other errors, the return
+** code may be ignored.
+*/
+int sqlite3AnalysisLoad(sqlite3 *db, int iDb){
+  analysisInfo sInfo;
+  HashElem *i;
+  char *zSql;
+  int rc = SQLITE_OK;
+  Schema *pSchema = db->aDb[iDb].pSchema;
+  const Table *pStat1;
+
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( db->aDb[iDb].pBt!=0 );
+
+  /* Clear any prior statistics */
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  for(i=sqliteHashFirst(&pSchema->tblHash); i; i=sqliteHashNext(i)){
+    Table *pTab = sqliteHashData(i);
+    pTab->tabFlags &= ~TF_HasStat1;
+  }
+  for(i=sqliteHashFirst(&pSchema->idxHash); i; i=sqliteHashNext(i)){
+    Index *pIdx = sqliteHashData(i);
+    pIdx->hasStat1 = 0;
+#ifdef SQLITE_ENABLE_STAT4
+    sqlite3DeleteIndexSamples(db, pIdx);
+    pIdx->aSample = 0;
+#endif
+  }
+
+  /* Load new statistics out of the sqlite_stat1 table */
+  sInfo.db = db;
+  sInfo.zDatabase = db->aDb[iDb].zDbSName;
+  if( (pStat1 = sqlite3FindTable(db, "sqlite_stat1", sInfo.zDatabase))
+   && IsOrdinaryTable(pStat1)
+  ){
+    zSql = sqlite3MPrintf(db, 
+        "SELECT tbl,idx,stat FROM %Q.sqlite_stat1", sInfo.zDatabase);
+    if( zSql==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+    }else{
+      rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
+      sqlite3DbFree(db, zSql);
+    }
+  }
+
+  /* Set appropriate defaults on all indexes not in the sqlite_stat1 table */
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  for(i=sqliteHashFirst(&pSchema->idxHash); i; i=sqliteHashNext(i)){
+    Index *pIdx = sqliteHashData(i);
+    if( !pIdx->hasStat1 ) sqlite3DefaultRowEst(pIdx);
+  }
+
+  /* Load the statistics from the sqlite_stat4 table. */
+#ifdef SQLITE_ENABLE_STAT4
+  if( rc==SQLITE_OK ){
+    DisableLookaside;
+    rc = loadStat4(db, sInfo.zDatabase);
+    EnableLookaside;
+  }
+  for(i=sqliteHashFirst(&pSchema->idxHash); i; i=sqliteHashNext(i)){
+    Index *pIdx = sqliteHashData(i);
+    sqlite3_free(pIdx->aiRowEst);
+    pIdx->aiRowEst = 0;
+  }
+#endif
+
+  if( rc==SQLITE_NOMEM ){
+    sqlite3OomFault(db);
+  }
+  return rc;
+}
+
+
+#endif /* SQLITE_OMIT_ANALYZE */
diff --git a/src/attach.c b/src/attach.c
new file mode 100644
index 0000000..4a6a25b
--- /dev/null
+++ b/src/attach.c
@@ -0,0 +1,617 @@
+/*
+** 2003 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the ATTACH and DETACH commands.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_ATTACH
+/*
+** Resolve an expression that was part of an ATTACH or DETACH statement. This
+** is slightly different from resolving a normal SQL expression, because simple
+** identifiers are treated as strings, not possible column names or aliases.
+**
+** i.e. if the parser sees:
+**
+**     ATTACH DATABASE abc AS def
+**
+** it treats the two expressions as literal strings 'abc' and 'def' instead of
+** looking for columns of the same name.
+**
+** This only applies to the root node of pExpr, so the statement:
+**
+**     ATTACH DATABASE abc||def AS 'db2'
+**
+** will fail because neither abc or def can be resolved.
+*/
+static int resolveAttachExpr(NameContext *pName, Expr *pExpr)
+{
+  int rc = SQLITE_OK;
+  if( pExpr ){
+    if( pExpr->op!=TK_ID ){
+      rc = sqlite3ResolveExprNames(pName, pExpr);
+    }else{
+      pExpr->op = TK_STRING;
+    }
+  }
+  return rc;
+}
+
+/*
+** Return true if zName points to a name that may be used to refer to
+** database iDb attached to handle db.
+*/
+int sqlite3DbIsNamed(sqlite3 *db, int iDb, const char *zName){
+  return (
+      sqlite3StrICmp(db->aDb[iDb].zDbSName, zName)==0
+   || (iDb==0 && sqlite3StrICmp("main", zName)==0)
+  );
+}
+
+/*
+** An SQL user-function registered to do the work of an ATTACH statement. The
+** three arguments to the function come directly from an attach statement:
+**
+**     ATTACH DATABASE x AS y KEY z
+**
+**     SELECT sqlite_attach(x, y, z)
+**
+** If the optional "KEY z" syntax is omitted, an SQL NULL is passed as the
+** third argument.
+**
+** If the db->init.reopenMemdb flags is set, then instead of attaching a
+** new database, close the database on db->init.iDb and reopen it as an
+** empty MemDB.
+*/
+static void attachFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  int i;
+  int rc = 0;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  const char *zName;
+  const char *zFile;
+  char *zPath = 0;
+  char *zErr = 0;
+  unsigned int flags;
+  Db *aNew;                 /* New array of Db pointers */
+  Db *pNew = 0;             /* Db object for the newly attached database */
+  char *zErrDyn = 0;
+  sqlite3_vfs *pVfs;
+
+  UNUSED_PARAMETER(NotUsed);
+  zFile = (const char *)sqlite3_value_text(argv[0]);
+  zName = (const char *)sqlite3_value_text(argv[1]);
+  if( zFile==0 ) zFile = "";
+  if( zName==0 ) zName = "";
+
+#ifndef SQLITE_OMIT_DESERIALIZE
+# define REOPEN_AS_MEMDB(db)  (db->init.reopenMemdb)
+#else
+# define REOPEN_AS_MEMDB(db)  (0)
+#endif
+
+  if( REOPEN_AS_MEMDB(db) ){
+    /* This is not a real ATTACH.  Instead, this routine is being called
+    ** from sqlite3_deserialize() to close database db->init.iDb and
+    ** reopen it as a MemDB */
+    Btree *pNewBt = 0;
+    pVfs = sqlite3_vfs_find("memdb");
+    if( pVfs==0 ) return;
+    rc = sqlite3BtreeOpen(pVfs, "x\0", db, &pNewBt, 0, SQLITE_OPEN_MAIN_DB);
+    if( rc==SQLITE_OK ){
+      Schema *pNewSchema = sqlite3SchemaGet(db, pNewBt);
+      if( pNewSchema ){
+        /* Both the Btree and the new Schema were allocated successfully.
+        ** Close the old db and update the aDb[] slot with the new memdb
+        ** values.  */
+        pNew = &db->aDb[db->init.iDb];
+        if( ALWAYS(pNew->pBt) ) sqlite3BtreeClose(pNew->pBt);
+        pNew->pBt = pNewBt;
+        pNew->pSchema = pNewSchema;
+      }else{
+        sqlite3BtreeClose(pNewBt);
+        rc = SQLITE_NOMEM;
+      }
+    }
+    if( rc ) goto attach_error;
+  }else{
+    /* This is a real ATTACH
+    **
+    ** Check for the following errors:
+    **
+    **     * Too many attached databases,
+    **     * Transaction currently open
+    **     * Specified database name already being used.
+    */
+    if( db->nDb>=db->aLimit[SQLITE_LIMIT_ATTACHED]+2 ){
+      zErrDyn = sqlite3MPrintf(db, "too many attached databases - max %d", 
+        db->aLimit[SQLITE_LIMIT_ATTACHED]
+      );
+      goto attach_error;
+    }
+    for(i=0; i<db->nDb; i++){
+      assert( zName );
+      if( sqlite3DbIsNamed(db, i, zName) ){
+        zErrDyn = sqlite3MPrintf(db, "database %s is already in use", zName);
+        goto attach_error;
+      }
+    }
+  
+    /* Allocate the new entry in the db->aDb[] array and initialize the schema
+    ** hash tables.
+    */
+    if( db->aDb==db->aDbStatic ){
+      aNew = sqlite3DbMallocRawNN(db, sizeof(db->aDb[0])*3 );
+      if( aNew==0 ) return;
+      memcpy(aNew, db->aDb, sizeof(db->aDb[0])*2);
+    }else{
+      aNew = sqlite3DbRealloc(db, db->aDb, sizeof(db->aDb[0])*(db->nDb+1) );
+      if( aNew==0 ) return;
+    }
+    db->aDb = aNew;
+    pNew = &db->aDb[db->nDb];
+    memset(pNew, 0, sizeof(*pNew));
+  
+    /* Open the database file. If the btree is successfully opened, use
+    ** it to obtain the database schema. At this point the schema may
+    ** or may not be initialized.
+    */
+    flags = db->openFlags;
+    rc = sqlite3ParseUri(db->pVfs->zName, zFile, &flags, &pVfs, &zPath, &zErr);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_NOMEM ) sqlite3OomFault(db);
+      sqlite3_result_error(context, zErr, -1);
+      sqlite3_free(zErr);
+      return;
+    }
+    assert( pVfs );
+    flags |= SQLITE_OPEN_MAIN_DB;
+    rc = sqlite3BtreeOpen(pVfs, zPath, db, &pNew->pBt, 0, flags);
+    db->nDb++;
+    pNew->zDbSName = sqlite3DbStrDup(db, zName);
+  }
+  db->noSharedCache = 0;
+  if( rc==SQLITE_CONSTRAINT ){
+    rc = SQLITE_ERROR;
+    zErrDyn = sqlite3MPrintf(db, "database is already attached");
+  }else if( rc==SQLITE_OK ){
+    Pager *pPager;
+    pNew->pSchema = sqlite3SchemaGet(db, pNew->pBt);
+    if( !pNew->pSchema ){
+      rc = SQLITE_NOMEM_BKPT;
+    }else if( pNew->pSchema->file_format && pNew->pSchema->enc!=ENC(db) ){
+      zErrDyn = sqlite3MPrintf(db, 
+        "attached databases must use the same text encoding as main database");
+      rc = SQLITE_ERROR;
+    }
+    sqlite3BtreeEnter(pNew->pBt);
+    pPager = sqlite3BtreePager(pNew->pBt);
+    sqlite3PagerLockingMode(pPager, db->dfltLockMode);
+    sqlite3BtreeSecureDelete(pNew->pBt,
+                             sqlite3BtreeSecureDelete(db->aDb[0].pBt,-1) );
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+    sqlite3BtreeSetPagerFlags(pNew->pBt,
+                      PAGER_SYNCHRONOUS_FULL | (db->flags & PAGER_FLAGS_MASK));
+#endif
+    sqlite3BtreeLeave(pNew->pBt);
+  }
+  pNew->safety_level = SQLITE_DEFAULT_SYNCHRONOUS+1;
+  if( rc==SQLITE_OK && pNew->zDbSName==0 ){
+    rc = SQLITE_NOMEM_BKPT;
+  }
+  sqlite3_free_filename( zPath );
+
+  /* If the file was opened successfully, read the schema for the new database.
+  ** If this fails, or if opening the file failed, then close the file and 
+  ** remove the entry from the db->aDb[] array. i.e. put everything back the
+  ** way we found it.
+  */
+  if( rc==SQLITE_OK ){
+    sqlite3BtreeEnterAll(db);
+    db->init.iDb = 0;
+    db->mDbFlags &= ~(DBFLAG_SchemaKnownOk);
+    if( !REOPEN_AS_MEMDB(db) ){
+      rc = sqlite3Init(db, &zErrDyn);
+    }
+    sqlite3BtreeLeaveAll(db);
+    assert( zErrDyn==0 || rc!=SQLITE_OK );
+  }
+#ifdef SQLITE_USER_AUTHENTICATION
+  if( rc==SQLITE_OK && !REOPEN_AS_MEMDB(db) ){
+    u8 newAuth = 0;
+    rc = sqlite3UserAuthCheckLogin(db, zName, &newAuth);
+    if( newAuth<db->auth.authLevel ){
+      rc = SQLITE_AUTH_USER;
+    }
+  }
+#endif
+  if( rc ){
+    if( ALWAYS(!REOPEN_AS_MEMDB(db)) ){
+      int iDb = db->nDb - 1;
+      assert( iDb>=2 );
+      if( db->aDb[iDb].pBt ){
+        sqlite3BtreeClose(db->aDb[iDb].pBt);
+        db->aDb[iDb].pBt = 0;
+        db->aDb[iDb].pSchema = 0;
+      }
+      sqlite3ResetAllSchemasOfConnection(db);
+      db->nDb = iDb;
+      if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
+        sqlite3OomFault(db);
+        sqlite3DbFree(db, zErrDyn);
+        zErrDyn = sqlite3MPrintf(db, "out of memory");
+      }else if( zErrDyn==0 ){
+        zErrDyn = sqlite3MPrintf(db, "unable to open database: %s", zFile);
+      }
+    }
+    goto attach_error;
+  }
+  
+  return;
+
+attach_error:
+  /* Return an error if we get here */
+  if( zErrDyn ){
+    sqlite3_result_error(context, zErrDyn, -1);
+    sqlite3DbFree(db, zErrDyn);
+  }
+  if( rc ) sqlite3_result_error_code(context, rc);
+}
+
+/*
+** An SQL user-function registered to do the work of an DETACH statement. The
+** three arguments to the function come directly from a detach statement:
+**
+**     DETACH DATABASE x
+**
+**     SELECT sqlite_detach(x)
+*/
+static void detachFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  const char *zName = (const char *)sqlite3_value_text(argv[0]);
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  int i;
+  Db *pDb = 0;
+  HashElem *pEntry;
+  char zErr[128];
+
+  UNUSED_PARAMETER(NotUsed);
+
+  if( zName==0 ) zName = "";
+  for(i=0; i<db->nDb; i++){
+    pDb = &db->aDb[i];
+    if( pDb->pBt==0 ) continue;
+    if( sqlite3DbIsNamed(db, i, zName) ) break;
+  }
+
+  if( i>=db->nDb ){
+    sqlite3_snprintf(sizeof(zErr),zErr, "no such database: %s", zName);
+    goto detach_error;
+  }
+  if( i<2 ){
+    sqlite3_snprintf(sizeof(zErr),zErr, "cannot detach database %s", zName);
+    goto detach_error;
+  }
+  if( sqlite3BtreeTxnState(pDb->pBt)!=SQLITE_TXN_NONE
+   || sqlite3BtreeIsInBackup(pDb->pBt)
+  ){
+    sqlite3_snprintf(sizeof(zErr),zErr, "database %s is locked", zName);
+    goto detach_error;
+  }
+
+  /* If any TEMP triggers reference the schema being detached, move those
+  ** triggers to reference the TEMP schema itself. */
+  assert( db->aDb[1].pSchema );
+  pEntry = sqliteHashFirst(&db->aDb[1].pSchema->trigHash);
+  while( pEntry ){
+    Trigger *pTrig = (Trigger*)sqliteHashData(pEntry);
+    if( pTrig->pTabSchema==pDb->pSchema ){
+      pTrig->pTabSchema = pTrig->pSchema;
+    }
+    pEntry = sqliteHashNext(pEntry);
+  }
+
+  sqlite3BtreeClose(pDb->pBt);
+  pDb->pBt = 0;
+  pDb->pSchema = 0;
+  sqlite3CollapseDatabaseArray(db);
+  return;
+
+detach_error:
+  sqlite3_result_error(context, zErr, -1);
+}
+
+/*
+** This procedure generates VDBE code for a single invocation of either the
+** sqlite_detach() or sqlite_attach() SQL user functions.
+*/
+static void codeAttach(
+  Parse *pParse,       /* The parser context */
+  int type,            /* Either SQLITE_ATTACH or SQLITE_DETACH */
+  FuncDef const *pFunc,/* FuncDef wrapper for detachFunc() or attachFunc() */
+  Expr *pAuthArg,      /* Expression to pass to authorization callback */
+  Expr *pFilename,     /* Name of database file */
+  Expr *pDbname,       /* Name of the database to use internally */
+  Expr *pKey           /* Database key for encryption extension */
+){
+  int rc;
+  NameContext sName;
+  Vdbe *v;
+  sqlite3* db = pParse->db;
+  int regArgs;
+
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ) goto attach_end;
+
+  if( pParse->nErr ) goto attach_end;
+  memset(&sName, 0, sizeof(NameContext));
+  sName.pParse = pParse;
+
+  if( 
+      SQLITE_OK!=resolveAttachExpr(&sName, pFilename) ||
+      SQLITE_OK!=resolveAttachExpr(&sName, pDbname) ||
+      SQLITE_OK!=resolveAttachExpr(&sName, pKey)
+  ){
+    goto attach_end;
+  }
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( ALWAYS(pAuthArg) ){
+    char *zAuthArg;
+    if( pAuthArg->op==TK_STRING ){
+      assert( !ExprHasProperty(pAuthArg, EP_IntValue) );
+      zAuthArg = pAuthArg->u.zToken;
+    }else{
+      zAuthArg = 0;
+    }
+    rc = sqlite3AuthCheck(pParse, type, zAuthArg, 0, 0);
+    if(rc!=SQLITE_OK ){
+      goto attach_end;
+    }
+  }
+#endif /* SQLITE_OMIT_AUTHORIZATION */
+
+
+  v = sqlite3GetVdbe(pParse);
+  regArgs = sqlite3GetTempRange(pParse, 4);
+  sqlite3ExprCode(pParse, pFilename, regArgs);
+  sqlite3ExprCode(pParse, pDbname, regArgs+1);
+  sqlite3ExprCode(pParse, pKey, regArgs+2);
+
+  assert( v || db->mallocFailed );
+  if( v ){
+    sqlite3VdbeAddFunctionCall(pParse, 0, regArgs+3-pFunc->nArg, regArgs+3,
+                               pFunc->nArg, pFunc, 0);
+    /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this
+    ** statement only). For DETACH, set it to false (expire all existing
+    ** statements).
+    */
+    sqlite3VdbeAddOp1(v, OP_Expire, (type==SQLITE_ATTACH));
+  }
+  
+attach_end:
+  sqlite3ExprDelete(db, pFilename);
+  sqlite3ExprDelete(db, pDbname);
+  sqlite3ExprDelete(db, pKey);
+}
+
+/*
+** Called by the parser to compile a DETACH statement.
+**
+**     DETACH pDbname
+*/
+void sqlite3Detach(Parse *pParse, Expr *pDbname){
+  static const FuncDef detach_func = {
+    1,                /* nArg */
+    SQLITE_UTF8,      /* funcFlags */
+    0,                /* pUserData */
+    0,                /* pNext */
+    detachFunc,       /* xSFunc */
+    0,                /* xFinalize */
+    0, 0,             /* xValue, xInverse */
+    "sqlite_detach",  /* zName */
+    {0}
+  };
+  codeAttach(pParse, SQLITE_DETACH, &detach_func, pDbname, 0, 0, pDbname);
+}
+
+/*
+** Called by the parser to compile an ATTACH statement.
+**
+**     ATTACH p AS pDbname KEY pKey
+*/
+void sqlite3Attach(Parse *pParse, Expr *p, Expr *pDbname, Expr *pKey){
+  static const FuncDef attach_func = {
+    3,                /* nArg */
+    SQLITE_UTF8,      /* funcFlags */
+    0,                /* pUserData */
+    0,                /* pNext */
+    attachFunc,       /* xSFunc */
+    0,                /* xFinalize */
+    0, 0,             /* xValue, xInverse */
+    "sqlite_attach",  /* zName */
+    {0}
+  };
+  codeAttach(pParse, SQLITE_ATTACH, &attach_func, p, p, pDbname, pKey);
+}
+#endif /* SQLITE_OMIT_ATTACH */
+
+/*
+** Expression callback used by sqlite3FixAAAA() routines.
+*/
+static int fixExprCb(Walker *p, Expr *pExpr){
+  DbFixer *pFix = p->u.pFix;
+  if( !pFix->bTemp ) ExprSetProperty(pExpr, EP_FromDDL);
+  if( pExpr->op==TK_VARIABLE ){
+    if( pFix->pParse->db->init.busy ){
+      pExpr->op = TK_NULL;
+    }else{
+      sqlite3ErrorMsg(pFix->pParse, "%s cannot use variables", pFix->zType);
+      return WRC_Abort;
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Select callback used by sqlite3FixAAAA() routines.
+*/
+static int fixSelectCb(Walker *p, Select *pSelect){
+  DbFixer *pFix = p->u.pFix;
+  int i;
+  SrcItem *pItem;
+  sqlite3 *db = pFix->pParse->db;
+  int iDb = sqlite3FindDbName(db, pFix->zDb);
+  SrcList *pList = pSelect->pSrc;
+
+  if( NEVER(pList==0) ) return WRC_Continue;
+  for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){
+    if( pFix->bTemp==0 ){
+      if( pItem->zDatabase ){
+        if( iDb!=sqlite3FindDbName(db, pItem->zDatabase) ){
+          sqlite3ErrorMsg(pFix->pParse,
+              "%s %T cannot reference objects in database %s",
+              pFix->zType, pFix->pName, pItem->zDatabase);
+          return WRC_Abort;
+        }
+        sqlite3DbFree(db, pItem->zDatabase);
+        pItem->zDatabase = 0;
+        pItem->fg.notCte = 1;
+      }
+      pItem->pSchema = pFix->pSchema;
+      pItem->fg.fromDDL = 1;
+    }
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER)
+    if( pList->a[i].fg.isUsing==0
+     && sqlite3WalkExpr(&pFix->w, pList->a[i].u3.pOn)
+    ){
+      return WRC_Abort;
+    }
+#endif
+  }
+  if( pSelect->pWith ){
+    for(i=0; i<pSelect->pWith->nCte; i++){
+      if( sqlite3WalkSelect(p, pSelect->pWith->a[i].pSelect) ){
+        return WRC_Abort;
+      }
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Initialize a DbFixer structure.  This routine must be called prior
+** to passing the structure to one of the sqliteFixAAAA() routines below.
+*/
+void sqlite3FixInit(
+  DbFixer *pFix,      /* The fixer to be initialized */
+  Parse *pParse,      /* Error messages will be written here */
+  int iDb,            /* This is the database that must be used */
+  const char *zType,  /* "view", "trigger", or "index" */
+  const Token *pName  /* Name of the view, trigger, or index */
+){
+  sqlite3 *db = pParse->db;
+  assert( db->nDb>iDb );
+  pFix->pParse = pParse;
+  pFix->zDb = db->aDb[iDb].zDbSName;
+  pFix->pSchema = db->aDb[iDb].pSchema;
+  pFix->zType = zType;
+  pFix->pName = pName;
+  pFix->bTemp = (iDb==1);
+  pFix->w.pParse = pParse;
+  pFix->w.xExprCallback = fixExprCb;
+  pFix->w.xSelectCallback = fixSelectCb;
+  pFix->w.xSelectCallback2 = sqlite3WalkWinDefnDummyCallback;
+  pFix->w.walkerDepth = 0;
+  pFix->w.eCode = 0;
+  pFix->w.u.pFix = pFix;
+}
+
+/*
+** The following set of routines walk through the parse tree and assign
+** a specific database to all table references where the database name
+** was left unspecified in the original SQL statement.  The pFix structure
+** must have been initialized by a prior call to sqlite3FixInit().
+**
+** These routines are used to make sure that an index, trigger, or
+** view in one database does not refer to objects in a different database.
+** (Exception: indices, triggers, and views in the TEMP database are
+** allowed to refer to anything.)  If a reference is explicitly made
+** to an object in a different database, an error message is added to
+** pParse->zErrMsg and these routines return non-zero.  If everything
+** checks out, these routines return 0.
+*/
+int sqlite3FixSrcList(
+  DbFixer *pFix,       /* Context of the fixation */
+  SrcList *pList       /* The Source list to check and modify */
+){
+  int res = 0;
+  if( pList ){
+    Select s; 
+    memset(&s, 0, sizeof(s));
+    s.pSrc = pList;
+    res = sqlite3WalkSelect(&pFix->w, &s);
+  }
+  return res;
+}
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER)
+int sqlite3FixSelect(
+  DbFixer *pFix,       /* Context of the fixation */
+  Select *pSelect      /* The SELECT statement to be fixed to one database */
+){
+  return sqlite3WalkSelect(&pFix->w, pSelect);
+}
+int sqlite3FixExpr(
+  DbFixer *pFix,     /* Context of the fixation */
+  Expr *pExpr        /* The expression to be fixed to one database */
+){
+  return sqlite3WalkExpr(&pFix->w, pExpr);
+}
+#endif
+
+#ifndef SQLITE_OMIT_TRIGGER
+int sqlite3FixTriggerStep(
+  DbFixer *pFix,     /* Context of the fixation */
+  TriggerStep *pStep /* The trigger step be fixed to one database */
+){
+  while( pStep ){
+    if( sqlite3WalkSelect(&pFix->w, pStep->pSelect)
+     || sqlite3WalkExpr(&pFix->w, pStep->pWhere) 
+     || sqlite3WalkExprList(&pFix->w, pStep->pExprList)
+     || sqlite3FixSrcList(pFix, pStep->pFrom)
+    ){
+      return 1;
+    }
+#ifndef SQLITE_OMIT_UPSERT
+    {
+      Upsert *pUp;
+      for(pUp=pStep->pUpsert; pUp; pUp=pUp->pNextUpsert){
+        if( sqlite3WalkExprList(&pFix->w, pUp->pUpsertTarget)
+         || sqlite3WalkExpr(&pFix->w, pUp->pUpsertTargetWhere)
+         || sqlite3WalkExprList(&pFix->w, pUp->pUpsertSet)
+         || sqlite3WalkExpr(&pFix->w, pUp->pUpsertWhere)
+        ){
+          return 1;
+        }
+      }
+    }
+#endif
+    pStep = pStep->pNext;
+  }
+
+  return 0;
+}
+#endif
diff --git a/src/auth.c b/src/auth.c
new file mode 100644
index 0000000..fa6c82d
--- /dev/null
+++ b/src/auth.c
@@ -0,0 +1,268 @@
+/*
+** 2003 January 11
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the sqlite3_set_authorizer()
+** API.  This facility is an optional feature of the library.  Embedded
+** systems that do not need this facility may omit it by recompiling
+** the library with -DSQLITE_OMIT_AUTHORIZATION=1
+*/
+#include "sqliteInt.h"
+
+/*
+** All of the code in this file may be omitted by defining a single
+** macro.
+*/
+#ifndef SQLITE_OMIT_AUTHORIZATION
+
+/*
+** Set or clear the access authorization function.
+**
+** The access authorization function is be called during the compilation
+** phase to verify that the user has read and/or write access permission on
+** various fields of the database.  The first argument to the auth function
+** is a copy of the 3rd argument to this routine.  The second argument
+** to the auth function is one of these constants:
+**
+**       SQLITE_CREATE_INDEX
+**       SQLITE_CREATE_TABLE
+**       SQLITE_CREATE_TEMP_INDEX
+**       SQLITE_CREATE_TEMP_TABLE
+**       SQLITE_CREATE_TEMP_TRIGGER
+**       SQLITE_CREATE_TEMP_VIEW
+**       SQLITE_CREATE_TRIGGER
+**       SQLITE_CREATE_VIEW
+**       SQLITE_DELETE
+**       SQLITE_DROP_INDEX
+**       SQLITE_DROP_TABLE
+**       SQLITE_DROP_TEMP_INDEX
+**       SQLITE_DROP_TEMP_TABLE
+**       SQLITE_DROP_TEMP_TRIGGER
+**       SQLITE_DROP_TEMP_VIEW
+**       SQLITE_DROP_TRIGGER
+**       SQLITE_DROP_VIEW
+**       SQLITE_INSERT
+**       SQLITE_PRAGMA
+**       SQLITE_READ
+**       SQLITE_SELECT
+**       SQLITE_TRANSACTION
+**       SQLITE_UPDATE
+**
+** The third and fourth arguments to the auth function are the name of
+** the table and the column that are being accessed.  The auth function
+** should return either SQLITE_OK, SQLITE_DENY, or SQLITE_IGNORE.  If
+** SQLITE_OK is returned, it means that access is allowed.  SQLITE_DENY
+** means that the SQL statement will never-run - the sqlite3_exec() call
+** will return with an error.  SQLITE_IGNORE means that the SQL statement
+** should run but attempts to read the specified column will return NULL
+** and attempts to write the column will be ignored.
+**
+** Setting the auth function to NULL disables this hook.  The default
+** setting of the auth function is NULL.
+*/
+int sqlite3_set_authorizer(
+  sqlite3 *db,
+  int (*xAuth)(void*,int,const char*,const char*,const char*,const char*),
+  void *pArg
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  db->xAuth = (sqlite3_xauth)xAuth;
+  db->pAuthArg = pArg;
+  if( db->xAuth ) sqlite3ExpirePreparedStatements(db, 1);
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+/*
+** Write an error message into pParse->zErrMsg that explains that the
+** user-supplied authorization function returned an illegal value.
+*/
+static void sqliteAuthBadReturnCode(Parse *pParse){
+  sqlite3ErrorMsg(pParse, "authorizer malfunction");
+  pParse->rc = SQLITE_ERROR;
+}
+
+/*
+** Invoke the authorization callback for permission to read column zCol from
+** table zTab in database zDb. This function assumes that an authorization
+** callback has been registered (i.e. that sqlite3.xAuth is not NULL).
+**
+** If SQLITE_IGNORE is returned and pExpr is not NULL, then pExpr is changed
+** to an SQL NULL expression. Otherwise, if pExpr is NULL, then SQLITE_IGNORE
+** is treated as SQLITE_DENY. In this case an error is left in pParse.
+*/
+int sqlite3AuthReadCol(
+  Parse *pParse,                  /* The parser context */
+  const char *zTab,               /* Table name */
+  const char *zCol,               /* Column name */
+  int iDb                         /* Index of containing database. */
+){
+  sqlite3 *db = pParse->db;          /* Database handle */
+  char *zDb = db->aDb[iDb].zDbSName; /* Schema name of attached database */
+  int rc;                            /* Auth callback return code */
+
+  if( db->init.busy ) return SQLITE_OK;
+  rc = db->xAuth(db->pAuthArg, SQLITE_READ, zTab,zCol,zDb,pParse->zAuthContext
+#ifdef SQLITE_USER_AUTHENTICATION
+                 ,db->auth.zAuthUser
+#endif
+                );
+  if( rc==SQLITE_DENY ){
+    char *z = sqlite3_mprintf("%s.%s", zTab, zCol);
+    if( db->nDb>2 || iDb!=0 ) z = sqlite3_mprintf("%s.%z", zDb, z);
+    sqlite3ErrorMsg(pParse, "access to %z is prohibited", z);
+    pParse->rc = SQLITE_AUTH;
+  }else if( rc!=SQLITE_IGNORE && rc!=SQLITE_OK ){
+    sqliteAuthBadReturnCode(pParse);
+  }
+  return rc;
+}
+
+/*
+** The pExpr should be a TK_COLUMN expression.  The table referred to
+** is in pTabList or else it is the NEW or OLD table of a trigger.  
+** Check to see if it is OK to read this particular column.
+**
+** If the auth function returns SQLITE_IGNORE, change the TK_COLUMN 
+** instruction into a TK_NULL.  If the auth function returns SQLITE_DENY,
+** then generate an error.
+*/
+void sqlite3AuthRead(
+  Parse *pParse,        /* The parser context */
+  Expr *pExpr,          /* The expression to check authorization on */
+  Schema *pSchema,      /* The schema of the expression */
+  SrcList *pTabList     /* All table that pExpr might refer to */
+){
+  Table *pTab = 0;      /* The table being read */
+  const char *zCol;     /* Name of the column of the table */
+  int iSrc;             /* Index in pTabList->a[] of table being read */
+  int iDb;              /* The index of the database the expression refers to */
+  int iCol;             /* Index of column in table */
+
+  assert( pExpr->op==TK_COLUMN || pExpr->op==TK_TRIGGER );
+  assert( !IN_RENAME_OBJECT );
+  assert( pParse->db->xAuth!=0 );
+  iDb = sqlite3SchemaToIndex(pParse->db, pSchema);
+  if( iDb<0 ){
+    /* An attempt to read a column out of a subquery or other
+    ** temporary table. */
+    return;
+  }
+
+  if( pExpr->op==TK_TRIGGER ){
+    pTab = pParse->pTriggerTab;
+  }else{
+    assert( pTabList );
+    for(iSrc=0; iSrc<pTabList->nSrc; iSrc++){
+      if( pExpr->iTable==pTabList->a[iSrc].iCursor ){
+        pTab = pTabList->a[iSrc].pTab;
+        break;
+      }
+    }
+  }
+  iCol = pExpr->iColumn;
+  if( pTab==0 ) return;
+
+  if( iCol>=0 ){
+    assert( iCol<pTab->nCol );
+    zCol = pTab->aCol[iCol].zCnName;
+  }else if( pTab->iPKey>=0 ){
+    assert( pTab->iPKey<pTab->nCol );
+    zCol = pTab->aCol[pTab->iPKey].zCnName;
+  }else{
+    zCol = "ROWID";
+  }
+  assert( iDb>=0 && iDb<pParse->db->nDb );
+  if( SQLITE_IGNORE==sqlite3AuthReadCol(pParse, pTab->zName, zCol, iDb) ){
+    pExpr->op = TK_NULL;
+  }
+}
+
+/*
+** Do an authorization check using the code and arguments given.  Return
+** either SQLITE_OK (zero) or SQLITE_IGNORE or SQLITE_DENY.  If SQLITE_DENY
+** is returned, then the error count and error message in pParse are
+** modified appropriately.
+*/
+int sqlite3AuthCheck(
+  Parse *pParse,
+  int code,
+  const char *zArg1,
+  const char *zArg2,
+  const char *zArg3
+){
+  sqlite3 *db = pParse->db;
+  int rc;
+
+  /* Don't do any authorization checks if the database is initializing
+  ** or if the parser is being invoked from within sqlite3_declare_vtab.
+  */
+  assert( !IN_RENAME_OBJECT || db->xAuth==0 );
+  if( db->xAuth==0 || db->init.busy || IN_SPECIAL_PARSE ){
+    return SQLITE_OK;
+  }
+
+  /* EVIDENCE-OF: R-43249-19882 The third through sixth parameters to the
+  ** callback are either NULL pointers or zero-terminated strings that
+  ** contain additional details about the action to be authorized.
+  **
+  ** The following testcase() macros show that any of the 3rd through 6th
+  ** parameters can be either NULL or a string. */
+  testcase( zArg1==0 );
+  testcase( zArg2==0 );
+  testcase( zArg3==0 );
+  testcase( pParse->zAuthContext==0 );
+
+  rc = db->xAuth(db->pAuthArg, code, zArg1, zArg2, zArg3, pParse->zAuthContext
+#ifdef SQLITE_USER_AUTHENTICATION
+                 ,db->auth.zAuthUser
+#endif
+                );
+  if( rc==SQLITE_DENY ){
+    sqlite3ErrorMsg(pParse, "not authorized");
+    pParse->rc = SQLITE_AUTH;
+  }else if( rc!=SQLITE_OK && rc!=SQLITE_IGNORE ){
+    rc = SQLITE_DENY;
+    sqliteAuthBadReturnCode(pParse);
+  }
+  return rc;
+}
+
+/*
+** Push an authorization context.  After this routine is called, the
+** zArg3 argument to authorization callbacks will be zContext until
+** popped.  Or if pParse==0, this routine is a no-op.
+*/
+void sqlite3AuthContextPush(
+  Parse *pParse,
+  AuthContext *pContext, 
+  const char *zContext
+){
+  assert( pParse );
+  pContext->pParse = pParse;
+  pContext->zAuthContext = pParse->zAuthContext;
+  pParse->zAuthContext = zContext;
+}
+
+/*
+** Pop an authorization context that was previously pushed
+** by sqlite3AuthContextPush
+*/
+void sqlite3AuthContextPop(AuthContext *pContext){
+  if( pContext->pParse ){
+    pContext->pParse->zAuthContext = pContext->zAuthContext;
+    pContext->pParse = 0;
+  }
+}
+
+#endif /* SQLITE_OMIT_AUTHORIZATION */
diff --git a/src/backup.c b/src/backup.c
new file mode 100644
index 0000000..22615d1
--- /dev/null
+++ b/src/backup.c
@@ -0,0 +1,767 @@
+/*
+** 2009 January 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the implementation of the sqlite3_backup_XXX() 
+** API functions and the related features.
+*/
+#include "sqliteInt.h"
+#include "btreeInt.h"
+
+/*
+** Structure allocated for each backup operation.
+*/
+struct sqlite3_backup {
+  sqlite3* pDestDb;        /* Destination database handle */
+  Btree *pDest;            /* Destination b-tree file */
+  u32 iDestSchema;         /* Original schema cookie in destination */
+  int bDestLocked;         /* True once a write-transaction is open on pDest */
+
+  Pgno iNext;              /* Page number of the next source page to copy */
+  sqlite3* pSrcDb;         /* Source database handle */
+  Btree *pSrc;             /* Source b-tree file */
+
+  int rc;                  /* Backup process error code */
+
+  /* These two variables are set by every call to backup_step(). They are
+  ** read by calls to backup_remaining() and backup_pagecount().
+  */
+  Pgno nRemaining;         /* Number of pages left to copy */
+  Pgno nPagecount;         /* Total number of pages to copy */
+
+  int isAttached;          /* True once backup has been registered with pager */
+  sqlite3_backup *pNext;   /* Next backup associated with source pager */
+};
+
+/*
+** THREAD SAFETY NOTES:
+**
+**   Once it has been created using backup_init(), a single sqlite3_backup
+**   structure may be accessed via two groups of thread-safe entry points:
+**
+**     * Via the sqlite3_backup_XXX() API function backup_step() and 
+**       backup_finish(). Both these functions obtain the source database
+**       handle mutex and the mutex associated with the source BtShared 
+**       structure, in that order.
+**
+**     * Via the BackupUpdate() and BackupRestart() functions, which are
+**       invoked by the pager layer to report various state changes in
+**       the page cache associated with the source database. The mutex
+**       associated with the source database BtShared structure will always 
+**       be held when either of these functions are invoked.
+**
+**   The other sqlite3_backup_XXX() API functions, backup_remaining() and
+**   backup_pagecount() are not thread-safe functions. If they are called
+**   while some other thread is calling backup_step() or backup_finish(),
+**   the values returned may be invalid. There is no way for a call to
+**   BackupUpdate() or BackupRestart() to interfere with backup_remaining()
+**   or backup_pagecount().
+**
+**   Depending on the SQLite configuration, the database handles and/or
+**   the Btree objects may have their own mutexes that require locking.
+**   Non-sharable Btrees (in-memory databases for example), do not have
+**   associated mutexes.
+*/
+
+/*
+** Return a pointer corresponding to database zDb (i.e. "main", "temp")
+** in connection handle pDb. If such a database cannot be found, return
+** a NULL pointer and write an error message to pErrorDb.
+**
+** If the "temp" database is requested, it may need to be opened by this 
+** function. If an error occurs while doing so, return 0 and write an 
+** error message to pErrorDb.
+*/
+static Btree *findBtree(sqlite3 *pErrorDb, sqlite3 *pDb, const char *zDb){
+  int i = sqlite3FindDbName(pDb, zDb);
+
+  if( i==1 ){
+    Parse sParse;
+    int rc = 0;
+    sqlite3ParseObjectInit(&sParse,pDb);
+    if( sqlite3OpenTempDatabase(&sParse) ){
+      sqlite3ErrorWithMsg(pErrorDb, sParse.rc, "%s", sParse.zErrMsg);
+      rc = SQLITE_ERROR;
+    }
+    sqlite3DbFree(pErrorDb, sParse.zErrMsg);
+    sqlite3ParseObjectReset(&sParse);
+    if( rc ){
+      return 0;
+    }
+  }
+
+  if( i<0 ){
+    sqlite3ErrorWithMsg(pErrorDb, SQLITE_ERROR, "unknown database %s", zDb);
+    return 0;
+  }
+
+  return pDb->aDb[i].pBt;
+}
+
+/*
+** Attempt to set the page size of the destination to match the page size
+** of the source.
+*/
+static int setDestPgsz(sqlite3_backup *p){
+  int rc;
+  rc = sqlite3BtreeSetPageSize(p->pDest,sqlite3BtreeGetPageSize(p->pSrc),0,0);
+  return rc;
+}
+
+/*
+** Check that there is no open read-transaction on the b-tree passed as the
+** second argument. If there is not, return SQLITE_OK. Otherwise, if there
+** is an open read-transaction, return SQLITE_ERROR and leave an error 
+** message in database handle db.
+*/
+static int checkReadTransaction(sqlite3 *db, Btree *p){
+  if( sqlite3BtreeTxnState(p)!=SQLITE_TXN_NONE ){
+    sqlite3ErrorWithMsg(db, SQLITE_ERROR, "destination database is in use");
+    return SQLITE_ERROR;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Create an sqlite3_backup process to copy the contents of zSrcDb from
+** connection handle pSrcDb to zDestDb in pDestDb. If successful, return
+** a pointer to the new sqlite3_backup object.
+**
+** If an error occurs, NULL is returned and an error code and error message
+** stored in database handle pDestDb.
+*/
+sqlite3_backup *sqlite3_backup_init(
+  sqlite3* pDestDb,                     /* Database to write to */
+  const char *zDestDb,                  /* Name of database within pDestDb */
+  sqlite3* pSrcDb,                      /* Database connection to read from */
+  const char *zSrcDb                    /* Name of database within pSrcDb */
+){
+  sqlite3_backup *p;                    /* Value to return */
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(pSrcDb)||!sqlite3SafetyCheckOk(pDestDb) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+
+  /* Lock the source database handle. The destination database
+  ** handle is not locked in this routine, but it is locked in
+  ** sqlite3_backup_step(). The user is required to ensure that no
+  ** other thread accesses the destination handle for the duration
+  ** of the backup operation.  Any attempt to use the destination
+  ** database connection while a backup is in progress may cause
+  ** a malfunction or a deadlock.
+  */
+  sqlite3_mutex_enter(pSrcDb->mutex);
+  sqlite3_mutex_enter(pDestDb->mutex);
+
+  if( pSrcDb==pDestDb ){
+    sqlite3ErrorWithMsg(
+        pDestDb, SQLITE_ERROR, "source and destination must be distinct"
+    );
+    p = 0;
+  }else {
+    /* Allocate space for a new sqlite3_backup object...
+    ** EVIDENCE-OF: R-64852-21591 The sqlite3_backup object is created by a
+    ** call to sqlite3_backup_init() and is destroyed by a call to
+    ** sqlite3_backup_finish(). */
+    p = (sqlite3_backup *)sqlite3MallocZero(sizeof(sqlite3_backup));
+    if( !p ){
+      sqlite3Error(pDestDb, SQLITE_NOMEM_BKPT);
+    }
+  }
+
+  /* If the allocation succeeded, populate the new object. */
+  if( p ){
+    p->pSrc = findBtree(pDestDb, pSrcDb, zSrcDb);
+    p->pDest = findBtree(pDestDb, pDestDb, zDestDb);
+    p->pDestDb = pDestDb;
+    p->pSrcDb = pSrcDb;
+    p->iNext = 1;
+    p->isAttached = 0;
+
+    if( 0==p->pSrc || 0==p->pDest 
+     || checkReadTransaction(pDestDb, p->pDest)!=SQLITE_OK 
+     ){
+      /* One (or both) of the named databases did not exist or an OOM
+      ** error was hit. Or there is a transaction open on the destination
+      ** database. The error has already been written into the pDestDb 
+      ** handle. All that is left to do here is free the sqlite3_backup 
+      ** structure.  */
+      sqlite3_free(p);
+      p = 0;
+    }
+  }
+  if( p ){
+    p->pSrc->nBackup++;
+  }
+
+  sqlite3_mutex_leave(pDestDb->mutex);
+  sqlite3_mutex_leave(pSrcDb->mutex);
+  return p;
+}
+
+/*
+** Argument rc is an SQLite error code. Return true if this error is 
+** considered fatal if encountered during a backup operation. All errors
+** are considered fatal except for SQLITE_BUSY and SQLITE_LOCKED.
+*/
+static int isFatalError(int rc){
+  return (rc!=SQLITE_OK && rc!=SQLITE_BUSY && ALWAYS(rc!=SQLITE_LOCKED));
+}
+
+/*
+** Parameter zSrcData points to a buffer containing the data for 
+** page iSrcPg from the source database. Copy this data into the 
+** destination database.
+*/
+static int backupOnePage(
+  sqlite3_backup *p,              /* Backup handle */
+  Pgno iSrcPg,                    /* Source database page to backup */
+  const u8 *zSrcData,             /* Source database page data */
+  int bUpdate                     /* True for an update, false otherwise */
+){
+  Pager * const pDestPager = sqlite3BtreePager(p->pDest);
+  const int nSrcPgsz = sqlite3BtreeGetPageSize(p->pSrc);
+  int nDestPgsz = sqlite3BtreeGetPageSize(p->pDest);
+  const int nCopy = MIN(nSrcPgsz, nDestPgsz);
+  const i64 iEnd = (i64)iSrcPg*(i64)nSrcPgsz;
+  int rc = SQLITE_OK;
+  i64 iOff;
+
+  assert( sqlite3BtreeGetReserveNoMutex(p->pSrc)>=0 );
+  assert( p->bDestLocked );
+  assert( !isFatalError(p->rc) );
+  assert( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) );
+  assert( zSrcData );
+  assert( nSrcPgsz==nDestPgsz || sqlite3PagerIsMemdb(pDestPager)==0 );
+
+  /* This loop runs once for each destination page spanned by the source 
+  ** page. For each iteration, variable iOff is set to the byte offset
+  ** of the destination page.
+  */
+  for(iOff=iEnd-(i64)nSrcPgsz; rc==SQLITE_OK && iOff<iEnd; iOff+=nDestPgsz){
+    DbPage *pDestPg = 0;
+    Pgno iDest = (Pgno)(iOff/nDestPgsz)+1;
+    if( iDest==PENDING_BYTE_PAGE(p->pDest->pBt) ) continue;
+    if( SQLITE_OK==(rc = sqlite3PagerGet(pDestPager, iDest, &pDestPg, 0))
+     && SQLITE_OK==(rc = sqlite3PagerWrite(pDestPg))
+    ){
+      const u8 *zIn = &zSrcData[iOff%nSrcPgsz];
+      u8 *zDestData = sqlite3PagerGetData(pDestPg);
+      u8 *zOut = &zDestData[iOff%nDestPgsz];
+
+      /* Copy the data from the source page into the destination page.
+      ** Then clear the Btree layer MemPage.isInit flag. Both this module
+      ** and the pager code use this trick (clearing the first byte
+      ** of the page 'extra' space to invalidate the Btree layers
+      ** cached parse of the page). MemPage.isInit is marked 
+      ** "MUST BE FIRST" for this purpose.
+      */
+      memcpy(zOut, zIn, nCopy);
+      ((u8 *)sqlite3PagerGetExtra(pDestPg))[0] = 0;
+      if( iOff==0 && bUpdate==0 ){
+        sqlite3Put4byte(&zOut[28], sqlite3BtreeLastPage(p->pSrc));
+      }
+    }
+    sqlite3PagerUnref(pDestPg);
+  }
+
+  return rc;
+}
+
+/*
+** If pFile is currently larger than iSize bytes, then truncate it to
+** exactly iSize bytes. If pFile is not larger than iSize bytes, then
+** this function is a no-op.
+**
+** Return SQLITE_OK if everything is successful, or an SQLite error 
+** code if an error occurs.
+*/
+static int backupTruncateFile(sqlite3_file *pFile, i64 iSize){
+  i64 iCurrent;
+  int rc = sqlite3OsFileSize(pFile, &iCurrent);
+  if( rc==SQLITE_OK && iCurrent>iSize ){
+    rc = sqlite3OsTruncate(pFile, iSize);
+  }
+  return rc;
+}
+
+/*
+** Register this backup object with the associated source pager for
+** callbacks when pages are changed or the cache invalidated.
+*/
+static void attachBackupObject(sqlite3_backup *p){
+  sqlite3_backup **pp;
+  assert( sqlite3BtreeHoldsMutex(p->pSrc) );
+  pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
+  p->pNext = *pp;
+  *pp = p;
+  p->isAttached = 1;
+}
+
+/*
+** Copy nPage pages from the source b-tree to the destination.
+*/
+int sqlite3_backup_step(sqlite3_backup *p, int nPage){
+  int rc;
+  int destMode;       /* Destination journal mode */
+  int pgszSrc = 0;    /* Source page size */
+  int pgszDest = 0;   /* Destination page size */
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(p->pSrcDb->mutex);
+  sqlite3BtreeEnter(p->pSrc);
+  if( p->pDestDb ){
+    sqlite3_mutex_enter(p->pDestDb->mutex);
+  }
+
+  rc = p->rc;
+  if( !isFatalError(rc) ){
+    Pager * const pSrcPager = sqlite3BtreePager(p->pSrc);     /* Source pager */
+    Pager * const pDestPager = sqlite3BtreePager(p->pDest);   /* Dest pager */
+    int ii;                            /* Iterator variable */
+    int nSrcPage = -1;                 /* Size of source db in pages */
+    int bCloseTrans = 0;               /* True if src db requires unlocking */
+
+    /* If the source pager is currently in a write-transaction, return
+    ** SQLITE_BUSY immediately.
+    */
+    if( p->pDestDb && p->pSrc->pBt->inTransaction==TRANS_WRITE ){
+      rc = SQLITE_BUSY;
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* If there is no open read-transaction on the source database, open
+    ** one now. If a transaction is opened here, then it will be closed
+    ** before this function exits.
+    */
+    if( rc==SQLITE_OK && SQLITE_TXN_NONE==sqlite3BtreeTxnState(p->pSrc) ){
+      rc = sqlite3BtreeBeginTrans(p->pSrc, 0, 0);
+      bCloseTrans = 1;
+    }
+
+    /* If the destination database has not yet been locked (i.e. if this
+    ** is the first call to backup_step() for the current backup operation),
+    ** try to set its page size to the same as the source database. This
+    ** is especially important on ZipVFS systems, as in that case it is
+    ** not possible to create a database file that uses one page size by
+    ** writing to it with another.  */
+    if( p->bDestLocked==0 && rc==SQLITE_OK && setDestPgsz(p)==SQLITE_NOMEM ){
+      rc = SQLITE_NOMEM;
+    }
+
+    /* Lock the destination database, if it is not locked already. */
+    if( SQLITE_OK==rc && p->bDestLocked==0
+     && SQLITE_OK==(rc = sqlite3BtreeBeginTrans(p->pDest, 2,
+                                                (int*)&p->iDestSchema)) 
+    ){
+      p->bDestLocked = 1;
+    }
+
+    /* Do not allow backup if the destination database is in WAL mode
+    ** and the page sizes are different between source and destination */
+    pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
+    pgszDest = sqlite3BtreeGetPageSize(p->pDest);
+    destMode = sqlite3PagerGetJournalMode(sqlite3BtreePager(p->pDest));
+    if( SQLITE_OK==rc 
+     && (destMode==PAGER_JOURNALMODE_WAL || sqlite3PagerIsMemdb(pDestPager))
+     && pgszSrc!=pgszDest 
+    ){
+      rc = SQLITE_READONLY;
+    }
+  
+    /* Now that there is a read-lock on the source database, query the
+    ** source pager for the number of pages in the database.
+    */
+    nSrcPage = (int)sqlite3BtreeLastPage(p->pSrc);
+    assert( nSrcPage>=0 );
+    for(ii=0; (nPage<0 || ii<nPage) && p->iNext<=(Pgno)nSrcPage && !rc; ii++){
+      const Pgno iSrcPg = p->iNext;                 /* Source page number */
+      if( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) ){
+        DbPage *pSrcPg;                             /* Source page object */
+        rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg,PAGER_GET_READONLY);
+        if( rc==SQLITE_OK ){
+          rc = backupOnePage(p, iSrcPg, sqlite3PagerGetData(pSrcPg), 0);
+          sqlite3PagerUnref(pSrcPg);
+        }
+      }
+      p->iNext++;
+    }
+    if( rc==SQLITE_OK ){
+      p->nPagecount = nSrcPage;
+      p->nRemaining = nSrcPage+1-p->iNext;
+      if( p->iNext>(Pgno)nSrcPage ){
+        rc = SQLITE_DONE;
+      }else if( !p->isAttached ){
+        attachBackupObject(p);
+      }
+    }
+  
+    /* Update the schema version field in the destination database. This
+    ** is to make sure that the schema-version really does change in
+    ** the case where the source and destination databases have the
+    ** same schema version.
+    */
+    if( rc==SQLITE_DONE ){
+      if( nSrcPage==0 ){
+        rc = sqlite3BtreeNewDb(p->pDest);
+        nSrcPage = 1;
+      }
+      if( rc==SQLITE_OK || rc==SQLITE_DONE ){
+        rc = sqlite3BtreeUpdateMeta(p->pDest,1,p->iDestSchema+1);
+      }
+      if( rc==SQLITE_OK ){
+        if( p->pDestDb ){
+          sqlite3ResetAllSchemasOfConnection(p->pDestDb);
+        }
+        if( destMode==PAGER_JOURNALMODE_WAL ){
+          rc = sqlite3BtreeSetVersion(p->pDest, 2);
+        }
+      }
+      if( rc==SQLITE_OK ){
+        int nDestTruncate;
+        /* Set nDestTruncate to the final number of pages in the destination
+        ** database. The complication here is that the destination page
+        ** size may be different to the source page size. 
+        **
+        ** If the source page size is smaller than the destination page size, 
+        ** round up. In this case the call to sqlite3OsTruncate() below will
+        ** fix the size of the file. However it is important to call
+        ** sqlite3PagerTruncateImage() here so that any pages in the 
+        ** destination file that lie beyond the nDestTruncate page mark are
+        ** journalled by PagerCommitPhaseOne() before they are destroyed
+        ** by the file truncation.
+        */
+        assert( pgszSrc==sqlite3BtreeGetPageSize(p->pSrc) );
+        assert( pgszDest==sqlite3BtreeGetPageSize(p->pDest) );
+        if( pgszSrc<pgszDest ){
+          int ratio = pgszDest/pgszSrc;
+          nDestTruncate = (nSrcPage+ratio-1)/ratio;
+          if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
+            nDestTruncate--;
+          }
+        }else{
+          nDestTruncate = nSrcPage * (pgszSrc/pgszDest);
+        }
+        assert( nDestTruncate>0 );
+
+        if( pgszSrc<pgszDest ){
+          /* If the source page-size is smaller than the destination page-size,
+          ** two extra things may need to happen:
+          **
+          **   * The destination may need to be truncated, and
+          **
+          **   * Data stored on the pages immediately following the 
+          **     pending-byte page in the source database may need to be
+          **     copied into the destination database.
+          */
+          const i64 iSize = (i64)pgszSrc * (i64)nSrcPage;
+          sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);
+          Pgno iPg;
+          int nDstPage;
+          i64 iOff;
+          i64 iEnd;
+
+          assert( pFile );
+          assert( nDestTruncate==0 
+              || (i64)nDestTruncate*(i64)pgszDest >= iSize || (
+                nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
+             && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+pgszDest
+          ));
+
+          /* This block ensures that all data required to recreate the original
+          ** database has been stored in the journal for pDestPager and the
+          ** journal synced to disk. So at this point we may safely modify
+          ** the database file in any way, knowing that if a power failure
+          ** occurs, the original database will be reconstructed from the 
+          ** journal file.  */
+          sqlite3PagerPagecount(pDestPager, &nDstPage);
+          for(iPg=nDestTruncate; rc==SQLITE_OK && iPg<=(Pgno)nDstPage; iPg++){
+            if( iPg!=PENDING_BYTE_PAGE(p->pDest->pBt) ){
+              DbPage *pPg;
+              rc = sqlite3PagerGet(pDestPager, iPg, &pPg, 0);
+              if( rc==SQLITE_OK ){
+                rc = sqlite3PagerWrite(pPg);
+                sqlite3PagerUnref(pPg);
+              }
+            }
+          }
+          if( rc==SQLITE_OK ){
+            rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1);
+          }
+
+          /* Write the extra pages and truncate the database file as required */
+          iEnd = MIN(PENDING_BYTE + pgszDest, iSize);
+          for(
+            iOff=PENDING_BYTE+pgszSrc; 
+            rc==SQLITE_OK && iOff<iEnd; 
+            iOff+=pgszSrc
+          ){
+            PgHdr *pSrcPg = 0;
+            const Pgno iSrcPg = (Pgno)((iOff/pgszSrc)+1);
+            rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg, 0);
+            if( rc==SQLITE_OK ){
+              u8 *zData = sqlite3PagerGetData(pSrcPg);
+              rc = sqlite3OsWrite(pFile, zData, pgszSrc, iOff);
+            }
+            sqlite3PagerUnref(pSrcPg);
+          }
+          if( rc==SQLITE_OK ){
+            rc = backupTruncateFile(pFile, iSize);
+          }
+
+          /* Sync the database file to disk. */
+          if( rc==SQLITE_OK ){
+            rc = sqlite3PagerSync(pDestPager, 0);
+          }
+        }else{
+          sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
+          rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 0);
+        }
+    
+        /* Finish committing the transaction to the destination database. */
+        if( SQLITE_OK==rc
+         && SQLITE_OK==(rc = sqlite3BtreeCommitPhaseTwo(p->pDest, 0))
+        ){
+          rc = SQLITE_DONE;
+        }
+      }
+    }
+  
+    /* If bCloseTrans is true, then this function opened a read transaction
+    ** on the source database. Close the read transaction here. There is
+    ** no need to check the return values of the btree methods here, as
+    ** "committing" a read-only transaction cannot fail.
+    */
+    if( bCloseTrans ){
+      TESTONLY( int rc2 );
+      TESTONLY( rc2  = ) sqlite3BtreeCommitPhaseOne(p->pSrc, 0);
+      TESTONLY( rc2 |= ) sqlite3BtreeCommitPhaseTwo(p->pSrc, 0);
+      assert( rc2==SQLITE_OK );
+    }
+  
+    if( rc==SQLITE_IOERR_NOMEM ){
+      rc = SQLITE_NOMEM_BKPT;
+    }
+    p->rc = rc;
+  }
+  if( p->pDestDb ){
+    sqlite3_mutex_leave(p->pDestDb->mutex);
+  }
+  sqlite3BtreeLeave(p->pSrc);
+  sqlite3_mutex_leave(p->pSrcDb->mutex);
+  return rc;
+}
+
+/*
+** Release all resources associated with an sqlite3_backup* handle.
+*/
+int sqlite3_backup_finish(sqlite3_backup *p){
+  sqlite3_backup **pp;                 /* Ptr to head of pagers backup list */
+  sqlite3 *pSrcDb;                     /* Source database connection */
+  int rc;                              /* Value to return */
+
+  /* Enter the mutexes */
+  if( p==0 ) return SQLITE_OK;
+  pSrcDb = p->pSrcDb;
+  sqlite3_mutex_enter(pSrcDb->mutex);
+  sqlite3BtreeEnter(p->pSrc);
+  if( p->pDestDb ){
+    sqlite3_mutex_enter(p->pDestDb->mutex);
+  }
+
+  /* Detach this backup from the source pager. */
+  if( p->pDestDb ){
+    p->pSrc->nBackup--;
+  }
+  if( p->isAttached ){
+    pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
+    assert( pp!=0 );
+    while( *pp!=p ){
+      pp = &(*pp)->pNext;
+      assert( pp!=0 );
+    }
+    *pp = p->pNext;
+  }
+
+  /* If a transaction is still open on the Btree, roll it back. */
+  sqlite3BtreeRollback(p->pDest, SQLITE_OK, 0);
+
+  /* Set the error code of the destination database handle. */
+  rc = (p->rc==SQLITE_DONE) ? SQLITE_OK : p->rc;
+  if( p->pDestDb ){
+    sqlite3Error(p->pDestDb, rc);
+
+    /* Exit the mutexes and free the backup context structure. */
+    sqlite3LeaveMutexAndCloseZombie(p->pDestDb);
+  }
+  sqlite3BtreeLeave(p->pSrc);
+  if( p->pDestDb ){
+    /* EVIDENCE-OF: R-64852-21591 The sqlite3_backup object is created by a
+    ** call to sqlite3_backup_init() and is destroyed by a call to
+    ** sqlite3_backup_finish(). */
+    sqlite3_free(p);
+  }
+  sqlite3LeaveMutexAndCloseZombie(pSrcDb);
+  return rc;
+}
+
+/*
+** Return the number of pages still to be backed up as of the most recent
+** call to sqlite3_backup_step().
+*/
+int sqlite3_backup_remaining(sqlite3_backup *p){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return p->nRemaining;
+}
+
+/*
+** Return the total number of pages in the source database as of the most 
+** recent call to sqlite3_backup_step().
+*/
+int sqlite3_backup_pagecount(sqlite3_backup *p){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return p->nPagecount;
+}
+
+/*
+** This function is called after the contents of page iPage of the
+** source database have been modified. If page iPage has already been 
+** copied into the destination database, then the data written to the
+** destination is now invalidated. The destination copy of iPage needs
+** to be updated with the new data before the backup operation is
+** complete.
+**
+** It is assumed that the mutex associated with the BtShared object
+** corresponding to the source database is held when this function is
+** called.
+*/
+static SQLITE_NOINLINE void backupUpdate(
+  sqlite3_backup *p,
+  Pgno iPage,
+  const u8 *aData
+){
+  assert( p!=0 );
+  do{
+    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
+    if( !isFatalError(p->rc) && iPage<p->iNext ){
+      /* The backup process p has already copied page iPage. But now it
+      ** has been modified by a transaction on the source pager. Copy
+      ** the new data into the backup.
+      */
+      int rc;
+      assert( p->pDestDb );
+      sqlite3_mutex_enter(p->pDestDb->mutex);
+      rc = backupOnePage(p, iPage, aData, 1);
+      sqlite3_mutex_leave(p->pDestDb->mutex);
+      assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
+      if( rc!=SQLITE_OK ){
+        p->rc = rc;
+      }
+    }
+  }while( (p = p->pNext)!=0 );
+}
+void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
+  if( pBackup ) backupUpdate(pBackup, iPage, aData);
+}
+
+/*
+** Restart the backup process. This is called when the pager layer
+** detects that the database has been modified by an external database
+** connection. In this case there is no way of knowing which of the
+** pages that have been copied into the destination database are still 
+** valid and which are not, so the entire process needs to be restarted.
+**
+** It is assumed that the mutex associated with the BtShared object
+** corresponding to the source database is held when this function is
+** called.
+*/
+void sqlite3BackupRestart(sqlite3_backup *pBackup){
+  sqlite3_backup *p;                   /* Iterator variable */
+  for(p=pBackup; p; p=p->pNext){
+    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
+    p->iNext = 1;
+  }
+}
+
+#ifndef SQLITE_OMIT_VACUUM
+/*
+** Copy the complete content of pBtFrom into pBtTo.  A transaction
+** must be active for both files.
+**
+** The size of file pTo may be reduced by this operation. If anything 
+** goes wrong, the transaction on pTo is rolled back. If successful, the 
+** transaction is committed before returning.
+*/
+int sqlite3BtreeCopyFile(Btree *pTo, Btree *pFrom){
+  int rc;
+  sqlite3_file *pFd;              /* File descriptor for database pTo */
+  sqlite3_backup b;
+  sqlite3BtreeEnter(pTo);
+  sqlite3BtreeEnter(pFrom);
+
+  assert( sqlite3BtreeTxnState(pTo)==SQLITE_TXN_WRITE );
+  pFd = sqlite3PagerFile(sqlite3BtreePager(pTo));
+  if( pFd->pMethods ){
+    i64 nByte = sqlite3BtreeGetPageSize(pFrom)*(i64)sqlite3BtreeLastPage(pFrom);
+    rc = sqlite3OsFileControl(pFd, SQLITE_FCNTL_OVERWRITE, &nByte);
+    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+    if( rc ) goto copy_finished;
+  }
+
+  /* Set up an sqlite3_backup object. sqlite3_backup.pDestDb must be set
+  ** to 0. This is used by the implementations of sqlite3_backup_step()
+  ** and sqlite3_backup_finish() to detect that they are being called
+  ** from this function, not directly by the user.
+  */
+  memset(&b, 0, sizeof(b));
+  b.pSrcDb = pFrom->db;
+  b.pSrc = pFrom;
+  b.pDest = pTo;
+  b.iNext = 1;
+
+  /* 0x7FFFFFFF is the hard limit for the number of pages in a database
+  ** file. By passing this as the number of pages to copy to
+  ** sqlite3_backup_step(), we can guarantee that the copy finishes 
+  ** within a single call (unless an error occurs). The assert() statement
+  ** checks this assumption - (p->rc) should be set to either SQLITE_DONE 
+  ** or an error code.  */
+  sqlite3_backup_step(&b, 0x7FFFFFFF);
+  assert( b.rc!=SQLITE_OK );
+
+  rc = sqlite3_backup_finish(&b);
+  if( rc==SQLITE_OK ){
+    pTo->pBt->btsFlags &= ~BTS_PAGESIZE_FIXED;
+  }else{
+    sqlite3PagerClearCache(sqlite3BtreePager(b.pDest));
+  }
+
+  assert( sqlite3BtreeTxnState(pTo)!=SQLITE_TXN_WRITE );
+copy_finished:
+  sqlite3BtreeLeave(pFrom);
+  sqlite3BtreeLeave(pTo);
+  return rc;
+}
+#endif /* SQLITE_OMIT_VACUUM */
diff --git a/src/bitvec.c b/src/bitvec.c
new file mode 100644
index 0000000..13f87d5
--- /dev/null
+++ b/src/bitvec.c
@@ -0,0 +1,411 @@
+/*
+** 2008 February 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements an object that represents a fixed-length
+** bitmap.  Bits are numbered starting with 1.
+**
+** A bitmap is used to record which pages of a database file have been
+** journalled during a transaction, or which pages have the "dont-write"
+** property.  Usually only a few pages are meet either condition.
+** So the bitmap is usually sparse and has low cardinality.
+** But sometimes (for example when during a DROP of a large table) most
+** or all of the pages in a database can get journalled.  In those cases,
+** the bitmap becomes dense with high cardinality.  The algorithm needs
+** to handle both cases well.
+**
+** The size of the bitmap is fixed when the object is created.
+**
+** All bits are clear when the bitmap is created.  Individual bits
+** may be set or cleared one at a time.
+**
+** Test operations are about 100 times more common that set operations.
+** Clear operations are exceedingly rare.  There are usually between
+** 5 and 500 set operations per Bitvec object, though the number of sets can
+** sometimes grow into tens of thousands or larger.  The size of the
+** Bitvec object is the number of pages in the database file at the
+** start of a transaction, and is thus usually less than a few thousand,
+** but can be as large as 2 billion for a really big database.
+*/
+#include "sqliteInt.h"
+
+/* Size of the Bitvec structure in bytes. */
+#define BITVEC_SZ        512
+
+/* Round the union size down to the nearest pointer boundary, since that's how
+** it will be aligned within the Bitvec struct. */
+#define BITVEC_USIZE \
+    (((BITVEC_SZ-(3*sizeof(u32)))/sizeof(Bitvec*))*sizeof(Bitvec*))
+
+/* Type of the array "element" for the bitmap representation.
+** Should be a power of 2, and ideally, evenly divide into BITVEC_USIZE.
+** Setting this to the "natural word" size of your CPU may improve
+** performance. */
+#define BITVEC_TELEM     u8
+/* Size, in bits, of the bitmap element. */
+#define BITVEC_SZELEM    8
+/* Number of elements in a bitmap array. */
+#define BITVEC_NELEM     (BITVEC_USIZE/sizeof(BITVEC_TELEM))
+/* Number of bits in the bitmap array. */
+#define BITVEC_NBIT      (BITVEC_NELEM*BITVEC_SZELEM)
+
+/* Number of u32 values in hash table. */
+#define BITVEC_NINT      (BITVEC_USIZE/sizeof(u32))
+/* Maximum number of entries in hash table before
+** sub-dividing and re-hashing. */
+#define BITVEC_MXHASH    (BITVEC_NINT/2)
+/* Hashing function for the aHash representation.
+** Empirical testing showed that the *37 multiplier
+** (an arbitrary prime)in the hash function provided
+** no fewer collisions than the no-op *1. */
+#define BITVEC_HASH(X)   (((X)*1)%BITVEC_NINT)
+
+#define BITVEC_NPTR      (BITVEC_USIZE/sizeof(Bitvec *))
+
+
+/*
+** A bitmap is an instance of the following structure.
+**
+** This bitmap records the existence of zero or more bits
+** with values between 1 and iSize, inclusive.
+**
+** There are three possible representations of the bitmap.
+** If iSize<=BITVEC_NBIT, then Bitvec.u.aBitmap[] is a straight
+** bitmap.  The least significant bit is bit 1.
+**
+** If iSize>BITVEC_NBIT and iDivisor==0 then Bitvec.u.aHash[] is
+** a hash table that will hold up to BITVEC_MXHASH distinct values.
+**
+** Otherwise, the value i is redirected into one of BITVEC_NPTR
+** sub-bitmaps pointed to by Bitvec.u.apSub[].  Each subbitmap
+** handles up to iDivisor separate values of i.  apSub[0] holds
+** values between 1 and iDivisor.  apSub[1] holds values between
+** iDivisor+1 and 2*iDivisor.  apSub[N] holds values between
+** N*iDivisor+1 and (N+1)*iDivisor.  Each subbitmap is normalized
+** to hold deal with values between 1 and iDivisor.
+*/
+struct Bitvec {
+  u32 iSize;      /* Maximum bit index.  Max iSize is 4,294,967,296. */
+  u32 nSet;       /* Number of bits that are set - only valid for aHash
+                  ** element.  Max is BITVEC_NINT.  For BITVEC_SZ of 512,
+                  ** this would be 125. */
+  u32 iDivisor;   /* Number of bits handled by each apSub[] entry. */
+                  /* Should >=0 for apSub element. */
+                  /* Max iDivisor is max(u32) / BITVEC_NPTR + 1.  */
+                  /* For a BITVEC_SZ of 512, this would be 34,359,739. */
+  union {
+    BITVEC_TELEM aBitmap[BITVEC_NELEM];    /* Bitmap representation */
+    u32 aHash[BITVEC_NINT];      /* Hash table representation */
+    Bitvec *apSub[BITVEC_NPTR];  /* Recursive representation */
+  } u;
+};
+
+/*
+** Create a new bitmap object able to handle bits between 0 and iSize,
+** inclusive.  Return a pointer to the new object.  Return NULL if
+** malloc fails.
+*/
+Bitvec *sqlite3BitvecCreate(u32 iSize){
+  Bitvec *p;
+  assert( sizeof(*p)==BITVEC_SZ );
+  p = sqlite3MallocZero( sizeof(*p) );
+  if( p ){
+    p->iSize = iSize;
+  }
+  return p;
+}
+
+/*
+** Check to see if the i-th bit is set.  Return true or false.
+** If p is NULL (if the bitmap has not been created) or if
+** i is out of range, then return false.
+*/
+int sqlite3BitvecTestNotNull(Bitvec *p, u32 i){
+  assert( p!=0 );
+  i--;
+  if( i>=p->iSize ) return 0;
+  while( p->iDivisor ){
+    u32 bin = i/p->iDivisor;
+    i = i%p->iDivisor;
+    p = p->u.apSub[bin];
+    if (!p) {
+      return 0;
+    }
+  }
+  if( p->iSize<=BITVEC_NBIT ){
+    return (p->u.aBitmap[i/BITVEC_SZELEM] & (1<<(i&(BITVEC_SZELEM-1))))!=0;
+  } else{
+    u32 h = BITVEC_HASH(i++);
+    while( p->u.aHash[h] ){
+      if( p->u.aHash[h]==i ) return 1;
+      h = (h+1) % BITVEC_NINT;
+    }
+    return 0;
+  }
+}
+int sqlite3BitvecTest(Bitvec *p, u32 i){
+  return p!=0 && sqlite3BitvecTestNotNull(p,i);
+}
+
+/*
+** Set the i-th bit.  Return 0 on success and an error code if
+** anything goes wrong.
+**
+** This routine might cause sub-bitmaps to be allocated.  Failing
+** to get the memory needed to hold the sub-bitmap is the only
+** that can go wrong with an insert, assuming p and i are valid.
+**
+** The calling function must ensure that p is a valid Bitvec object
+** and that the value for "i" is within range of the Bitvec object.
+** Otherwise the behavior is undefined.
+*/
+int sqlite3BitvecSet(Bitvec *p, u32 i){
+  u32 h;
+  if( p==0 ) return SQLITE_OK;
+  assert( i>0 );
+  assert( i<=p->iSize );
+  i--;
+  while((p->iSize > BITVEC_NBIT) && p->iDivisor) {
+    u32 bin = i/p->iDivisor;
+    i = i%p->iDivisor;
+    if( p->u.apSub[bin]==0 ){
+      p->u.apSub[bin] = sqlite3BitvecCreate( p->iDivisor );
+      if( p->u.apSub[bin]==0 ) return SQLITE_NOMEM_BKPT;
+    }
+    p = p->u.apSub[bin];
+  }
+  if( p->iSize<=BITVEC_NBIT ){
+    p->u.aBitmap[i/BITVEC_SZELEM] |= 1 << (i&(BITVEC_SZELEM-1));
+    return SQLITE_OK;
+  }
+  h = BITVEC_HASH(i++);
+  /* if there wasn't a hash collision, and this doesn't */
+  /* completely fill the hash, then just add it without */
+  /* worrying about sub-dividing and re-hashing. */
+  if( !p->u.aHash[h] ){
+    if (p->nSet<(BITVEC_NINT-1)) {
+      goto bitvec_set_end;
+    } else {
+      goto bitvec_set_rehash;
+    }
+  }
+  /* there was a collision, check to see if it's already */
+  /* in hash, if not, try to find a spot for it */
+  do {
+    if( p->u.aHash[h]==i ) return SQLITE_OK;
+    h++;
+    if( h>=BITVEC_NINT ) h = 0;
+  } while( p->u.aHash[h] );
+  /* we didn't find it in the hash.  h points to the first */
+  /* available free spot. check to see if this is going to */
+  /* make our hash too "full".  */
+bitvec_set_rehash:
+  if( p->nSet>=BITVEC_MXHASH ){
+    unsigned int j;
+    int rc;
+    u32 *aiValues = sqlite3StackAllocRaw(0, sizeof(p->u.aHash));
+    if( aiValues==0 ){
+      return SQLITE_NOMEM_BKPT;
+    }else{
+      memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
+      memset(p->u.apSub, 0, sizeof(p->u.apSub));
+      p->iDivisor = (p->iSize + BITVEC_NPTR - 1)/BITVEC_NPTR;
+      rc = sqlite3BitvecSet(p, i);
+      for(j=0; j<BITVEC_NINT; j++){
+        if( aiValues[j] ) rc |= sqlite3BitvecSet(p, aiValues[j]);
+      }
+      sqlite3StackFree(0, aiValues);
+      return rc;
+    }
+  }
+bitvec_set_end:
+  p->nSet++;
+  p->u.aHash[h] = i;
+  return SQLITE_OK;
+}
+
+/*
+** Clear the i-th bit.
+**
+** pBuf must be a pointer to at least BITVEC_SZ bytes of temporary storage
+** that BitvecClear can use to rebuilt its hash table.
+*/
+void sqlite3BitvecClear(Bitvec *p, u32 i, void *pBuf){
+  if( p==0 ) return;
+  assert( i>0 );
+  i--;
+  while( p->iDivisor ){
+    u32 bin = i/p->iDivisor;
+    i = i%p->iDivisor;
+    p = p->u.apSub[bin];
+    if (!p) {
+      return;
+    }
+  }
+  if( p->iSize<=BITVEC_NBIT ){
+    p->u.aBitmap[i/BITVEC_SZELEM] &= ~(1 << (i&(BITVEC_SZELEM-1)));
+  }else{
+    unsigned int j;
+    u32 *aiValues = pBuf;
+    memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
+    memset(p->u.aHash, 0, sizeof(p->u.aHash));
+    p->nSet = 0;
+    for(j=0; j<BITVEC_NINT; j++){
+      if( aiValues[j] && aiValues[j]!=(i+1) ){
+        u32 h = BITVEC_HASH(aiValues[j]-1);
+        p->nSet++;
+        while( p->u.aHash[h] ){
+          h++;
+          if( h>=BITVEC_NINT ) h = 0;
+        }
+        p->u.aHash[h] = aiValues[j];
+      }
+    }
+  }
+}
+
+/*
+** Destroy a bitmap object.  Reclaim all memory used.
+*/
+void sqlite3BitvecDestroy(Bitvec *p){
+  if( p==0 ) return;
+  if( p->iDivisor ){
+    unsigned int i;
+    for(i=0; i<BITVEC_NPTR; i++){
+      sqlite3BitvecDestroy(p->u.apSub[i]);
+    }
+  }
+  sqlite3_free(p);
+}
+
+/*
+** Return the value of the iSize parameter specified when Bitvec *p
+** was created.
+*/
+u32 sqlite3BitvecSize(Bitvec *p){
+  return p->iSize;
+}
+
+#ifndef SQLITE_UNTESTABLE
+/*
+** Let V[] be an array of unsigned characters sufficient to hold
+** up to N bits.  Let I be an integer between 0 and N.  0<=I<N.
+** Then the following macros can be used to set, clear, or test
+** individual bits within V.
+*/
+#define SETBIT(V,I)      V[I>>3] |= (1<<(I&7))
+#define CLEARBIT(V,I)    V[I>>3] &= ~(1<<(I&7))
+#define TESTBIT(V,I)     (V[I>>3]&(1<<(I&7)))!=0
+
+/*
+** This routine runs an extensive test of the Bitvec code.
+**
+** The input is an array of integers that acts as a program
+** to test the Bitvec.  The integers are opcodes followed
+** by 0, 1, or 3 operands, depending on the opcode.  Another
+** opcode follows immediately after the last operand.
+**
+** There are 6 opcodes numbered from 0 through 5.  0 is the
+** "halt" opcode and causes the test to end.
+**
+**    0          Halt and return the number of errors
+**    1 N S X    Set N bits beginning with S and incrementing by X
+**    2 N S X    Clear N bits beginning with S and incrementing by X
+**    3 N        Set N randomly chosen bits
+**    4 N        Clear N randomly chosen bits
+**    5 N S X    Set N bits from S increment X in array only, not in bitvec
+**
+** The opcodes 1 through 4 perform set and clear operations are performed
+** on both a Bitvec object and on a linear array of bits obtained from malloc.
+** Opcode 5 works on the linear array only, not on the Bitvec.
+** Opcode 5 is used to deliberately induce a fault in order to
+** confirm that error detection works.
+**
+** At the conclusion of the test the linear array is compared
+** against the Bitvec object.  If there are any differences,
+** an error is returned.  If they are the same, zero is returned.
+**
+** If a memory allocation error occurs, return -1.
+*/
+int sqlite3BitvecBuiltinTest(int sz, int *aOp){
+  Bitvec *pBitvec = 0;
+  unsigned char *pV = 0;
+  int rc = -1;
+  int i, nx, pc, op;
+  void *pTmpSpace;
+
+  /* Allocate the Bitvec to be tested and a linear array of
+  ** bits to act as the reference */
+  pBitvec = sqlite3BitvecCreate( sz );
+  pV = sqlite3MallocZero( (sz+7)/8 + 1 );
+  pTmpSpace = sqlite3_malloc64(BITVEC_SZ);
+  if( pBitvec==0 || pV==0 || pTmpSpace==0  ) goto bitvec_end;
+
+  /* NULL pBitvec tests */
+  sqlite3BitvecSet(0, 1);
+  sqlite3BitvecClear(0, 1, pTmpSpace);
+
+  /* Run the program */
+  pc = i = 0;
+  while( (op = aOp[pc])!=0 ){
+    switch( op ){
+      case 1:
+      case 2:
+      case 5: {
+        nx = 4;
+        i = aOp[pc+2] - 1;
+        aOp[pc+2] += aOp[pc+3];
+        break;
+      }
+      case 3:
+      case 4:
+      default: {
+        nx = 2;
+        sqlite3_randomness(sizeof(i), &i);
+        break;
+      }
+    }
+    if( (--aOp[pc+1]) > 0 ) nx = 0;
+    pc += nx;
+    i = (i & 0x7fffffff)%sz;
+    if( (op & 1)!=0 ){
+      SETBIT(pV, (i+1));
+      if( op!=5 ){
+        if( sqlite3BitvecSet(pBitvec, i+1) ) goto bitvec_end;
+      }
+    }else{
+      CLEARBIT(pV, (i+1));
+      sqlite3BitvecClear(pBitvec, i+1, pTmpSpace);
+    }
+  }
+
+  /* Test to make sure the linear array exactly matches the
+  ** Bitvec object.  Start with the assumption that they do
+  ** match (rc==0).  Change rc to non-zero if a discrepancy
+  ** is found.
+  */
+  rc = sqlite3BitvecTest(0,0) + sqlite3BitvecTest(pBitvec, sz+1)
+          + sqlite3BitvecTest(pBitvec, 0)
+          + (sqlite3BitvecSize(pBitvec) - sz);
+  for(i=1; i<=sz; i++){
+    if(  (TESTBIT(pV,i))!=sqlite3BitvecTest(pBitvec,i) ){
+      rc = i;
+      break;
+    }
+  }
+
+  /* Free allocated structure */
+bitvec_end:
+  sqlite3_free(pTmpSpace);
+  sqlite3_free(pV);
+  sqlite3BitvecDestroy(pBitvec);
+  return rc;
+}
+#endif /* SQLITE_UNTESTABLE */
diff --git a/src/btmutex.c b/src/btmutex.c
new file mode 100644
index 0000000..232831e
--- /dev/null
+++ b/src/btmutex.c
@@ -0,0 +1,309 @@
+/*
+** 2007 August 27
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to implement mutexes on Btree objects.
+** This code really belongs in btree.c.  But btree.c is getting too
+** big and we want to break it down some.  This packaged seemed like
+** a good breakout.
+*/
+#include "btreeInt.h"
+#ifndef SQLITE_OMIT_SHARED_CACHE
+#if SQLITE_THREADSAFE
+
+/*
+** Obtain the BtShared mutex associated with B-Tree handle p. Also,
+** set BtShared.db to the database handle associated with p and the
+** p->locked boolean to true.
+*/
+static void lockBtreeMutex(Btree *p){
+  assert( p->locked==0 );
+  assert( sqlite3_mutex_notheld(p->pBt->mutex) );
+  assert( sqlite3_mutex_held(p->db->mutex) );
+
+  sqlite3_mutex_enter(p->pBt->mutex);
+  p->pBt->db = p->db;
+  p->locked = 1;
+}
+
+/*
+** Release the BtShared mutex associated with B-Tree handle p and
+** clear the p->locked boolean.
+*/
+static void SQLITE_NOINLINE unlockBtreeMutex(Btree *p){
+  BtShared *pBt = p->pBt;
+  assert( p->locked==1 );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  assert( p->db==pBt->db );
+
+  sqlite3_mutex_leave(pBt->mutex);
+  p->locked = 0;
+}
+
+/* Forward reference */
+static void SQLITE_NOINLINE btreeLockCarefully(Btree *p);
+
+/*
+** Enter a mutex on the given BTree object.
+**
+** If the object is not sharable, then no mutex is ever required
+** and this routine is a no-op.  The underlying mutex is non-recursive.
+** But we keep a reference count in Btree.wantToLock so the behavior
+** of this interface is recursive.
+**
+** To avoid deadlocks, multiple Btrees are locked in the same order
+** by all database connections.  The p->pNext is a list of other
+** Btrees belonging to the same database connection as the p Btree
+** which need to be locked after p.  If we cannot get a lock on
+** p, then first unlock all of the others on p->pNext, then wait
+** for the lock to become available on p, then relock all of the
+** subsequent Btrees that desire a lock.
+*/
+void sqlite3BtreeEnter(Btree *p){
+  /* Some basic sanity checking on the Btree.  The list of Btrees
+  ** connected by pNext and pPrev should be in sorted order by
+  ** Btree.pBt value. All elements of the list should belong to
+  ** the same connection. Only shared Btrees are on the list. */
+  assert( p->pNext==0 || p->pNext->pBt>p->pBt );
+  assert( p->pPrev==0 || p->pPrev->pBt<p->pBt );
+  assert( p->pNext==0 || p->pNext->db==p->db );
+  assert( p->pPrev==0 || p->pPrev->db==p->db );
+  assert( p->sharable || (p->pNext==0 && p->pPrev==0) );
+
+  /* Check for locking consistency */
+  assert( !p->locked || p->wantToLock>0 );
+  assert( p->sharable || p->wantToLock==0 );
+
+  /* We should already hold a lock on the database connection */
+  assert( sqlite3_mutex_held(p->db->mutex) );
+
+  /* Unless the database is sharable and unlocked, then BtShared.db
+  ** should already be set correctly. */
+  assert( (p->locked==0 && p->sharable) || p->pBt->db==p->db );
+
+  if( !p->sharable ) return;
+  p->wantToLock++;
+  if( p->locked ) return;
+  btreeLockCarefully(p);
+}
+
+/* This is a helper function for sqlite3BtreeLock(). By moving
+** complex, but seldom used logic, out of sqlite3BtreeLock() and
+** into this routine, we avoid unnecessary stack pointer changes
+** and thus help the sqlite3BtreeLock() routine to run much faster
+** in the common case.
+*/
+static void SQLITE_NOINLINE btreeLockCarefully(Btree *p){
+  Btree *pLater;
+
+  /* In most cases, we should be able to acquire the lock we
+  ** want without having to go through the ascending lock
+  ** procedure that follows.  Just be sure not to block.
+  */
+  if( sqlite3_mutex_try(p->pBt->mutex)==SQLITE_OK ){
+    p->pBt->db = p->db;
+    p->locked = 1;
+    return;
+  }
+
+  /* To avoid deadlock, first release all locks with a larger
+  ** BtShared address.  Then acquire our lock.  Then reacquire
+  ** the other BtShared locks that we used to hold in ascending
+  ** order.
+  */
+  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
+    assert( pLater->sharable );
+    assert( pLater->pNext==0 || pLater->pNext->pBt>pLater->pBt );
+    assert( !pLater->locked || pLater->wantToLock>0 );
+    if( pLater->locked ){
+      unlockBtreeMutex(pLater);
+    }
+  }
+  lockBtreeMutex(p);
+  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
+    if( pLater->wantToLock ){
+      lockBtreeMutex(pLater);
+    }
+  }
+}
+
+
+/*
+** Exit the recursive mutex on a Btree.
+*/
+void sqlite3BtreeLeave(Btree *p){
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  if( p->sharable ){
+    assert( p->wantToLock>0 );
+    p->wantToLock--;
+    if( p->wantToLock==0 ){
+      unlockBtreeMutex(p);
+    }
+  }
+}
+
+#ifndef NDEBUG
+/*
+** Return true if the BtShared mutex is held on the btree, or if the
+** B-Tree is not marked as sharable.
+**
+** This routine is used only from within assert() statements.
+*/
+int sqlite3BtreeHoldsMutex(Btree *p){
+  assert( p->sharable==0 || p->locked==0 || p->wantToLock>0 );
+  assert( p->sharable==0 || p->locked==0 || p->db==p->pBt->db );
+  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->pBt->mutex) );
+  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->db->mutex) );
+
+  return (p->sharable==0 || p->locked);
+}
+#endif
+
+
+/*
+** Enter the mutex on every Btree associated with a database
+** connection.  This is needed (for example) prior to parsing
+** a statement since we will be comparing table and column names
+** against all schemas and we do not want those schemas being
+** reset out from under us.
+**
+** There is a corresponding leave-all procedures.
+**
+** Enter the mutexes in ascending order by BtShared pointer address
+** to avoid the possibility of deadlock when two threads with
+** two or more btrees in common both try to lock all their btrees
+** at the same instant.
+*/
+static void SQLITE_NOINLINE btreeEnterAll(sqlite3 *db){
+  int i;
+  int skipOk = 1;
+  Btree *p;
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(i=0; i<db->nDb; i++){
+    p = db->aDb[i].pBt;
+    if( p && p->sharable ){
+      sqlite3BtreeEnter(p);
+      skipOk = 0;
+    }
+  }
+  db->noSharedCache = skipOk;
+}
+void sqlite3BtreeEnterAll(sqlite3 *db){
+  if( db->noSharedCache==0 ) btreeEnterAll(db);
+}
+static void SQLITE_NOINLINE btreeLeaveAll(sqlite3 *db){
+  int i;
+  Btree *p;
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(i=0; i<db->nDb; i++){
+    p = db->aDb[i].pBt;
+    if( p ) sqlite3BtreeLeave(p);
+  }
+}
+void sqlite3BtreeLeaveAll(sqlite3 *db){
+  if( db->noSharedCache==0 ) btreeLeaveAll(db);
+}
+
+#ifndef NDEBUG
+/*
+** Return true if the current thread holds the database connection
+** mutex and all required BtShared mutexes.
+**
+** This routine is used inside assert() statements only.
+*/
+int sqlite3BtreeHoldsAllMutexes(sqlite3 *db){
+  int i;
+  if( !sqlite3_mutex_held(db->mutex) ){
+    return 0;
+  }
+  for(i=0; i<db->nDb; i++){
+    Btree *p;
+    p = db->aDb[i].pBt;
+    if( p && p->sharable &&
+         (p->wantToLock==0 || !sqlite3_mutex_held(p->pBt->mutex)) ){
+      return 0;
+    }
+  }
+  return 1;
+}
+#endif /* NDEBUG */
+
+#ifndef NDEBUG
+/*
+** Return true if the correct mutexes are held for accessing the
+** db->aDb[iDb].pSchema structure.  The mutexes required for schema
+** access are:
+**
+**   (1) The mutex on db
+**   (2) if iDb!=1, then the mutex on db->aDb[iDb].pBt.
+**
+** If pSchema is not NULL, then iDb is computed from pSchema and
+** db using sqlite3SchemaToIndex().
+*/
+int sqlite3SchemaMutexHeld(sqlite3 *db, int iDb, Schema *pSchema){
+  Btree *p;
+  assert( db!=0 );
+  if( db->pVfs==0 && db->nDb==0 ) return 1;
+  if( pSchema ) iDb = sqlite3SchemaToIndex(db, pSchema);
+  assert( iDb>=0 && iDb<db->nDb );
+  if( !sqlite3_mutex_held(db->mutex) ) return 0;
+  if( iDb==1 ) return 1;
+  p = db->aDb[iDb].pBt;
+  assert( p!=0 );
+  return p->sharable==0 || p->locked==1;
+}
+#endif /* NDEBUG */
+
+#else /* SQLITE_THREADSAFE>0 above.  SQLITE_THREADSAFE==0 below */
+/*
+** The following are special cases for mutex enter routines for use
+** in single threaded applications that use shared cache.  Except for
+** these two routines, all mutex operations are no-ops in that case and
+** are null #defines in btree.h.
+**
+** If shared cache is disabled, then all btree mutex routines, including
+** the ones below, are no-ops and are null #defines in btree.h.
+*/
+
+void sqlite3BtreeEnter(Btree *p){
+  p->pBt->db = p->db;
+}
+void sqlite3BtreeEnterAll(sqlite3 *db){
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *p = db->aDb[i].pBt;
+    if( p ){
+      p->pBt->db = p->db;
+    }
+  }
+}
+#endif /* if SQLITE_THREADSAFE */
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Enter a mutex on a Btree given a cursor owned by that Btree. 
+**
+** These entry points are used by incremental I/O only. Enter() is required 
+** any time OMIT_SHARED_CACHE is not defined, regardless of whether or not 
+** the build is threadsafe. Leave() is only required by threadsafe builds.
+*/
+void sqlite3BtreeEnterCursor(BtCursor *pCur){
+  sqlite3BtreeEnter(pCur->pBtree);
+}
+# if SQLITE_THREADSAFE
+void sqlite3BtreeLeaveCursor(BtCursor *pCur){
+  sqlite3BtreeLeave(pCur->pBtree);
+}
+# endif
+#endif /* ifndef SQLITE_OMIT_INCRBLOB */
+
+#endif /* ifndef SQLITE_OMIT_SHARED_CACHE */
diff --git a/src/btree.c b/src/btree.c
new file mode 100644
index 0000000..c41fb81
--- /dev/null
+++ b/src/btree.c
@@ -0,0 +1,11386 @@
+/*
+** 2004 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements an external (disk-based) database using BTrees.
+** See the header comment on "btreeInt.h" for additional information.
+** Including a description of file format and an overview of operation.
+*/
+#include "btreeInt.h"
+
+/*
+** The header string that appears at the beginning of every
+** SQLite database.
+*/
+static const char zMagicHeader[] = SQLITE_FILE_HEADER;
+
+/*
+** Set this global variable to 1 to enable tracing using the TRACE
+** macro.
+*/
+#if 0
+int sqlite3BtreeTrace=1;  /* True to enable tracing */
+# define TRACE(X)  if(sqlite3BtreeTrace){printf X;fflush(stdout);}
+#else
+# define TRACE(X)
+#endif
+
+/*
+** Extract a 2-byte big-endian integer from an array of unsigned bytes.
+** But if the value is zero, make it 65536.
+**
+** This routine is used to extract the "offset to cell content area" value
+** from the header of a btree page.  If the page size is 65536 and the page
+** is empty, the offset should be 65536, but the 2-byte value stores zero.
+** This routine makes the necessary adjustment to 65536.
+*/
+#define get2byteNotZero(X)  (((((int)get2byte(X))-1)&0xffff)+1)
+
+/*
+** Values passed as the 5th argument to allocateBtreePage()
+*/
+#define BTALLOC_ANY   0           /* Allocate any page */
+#define BTALLOC_EXACT 1           /* Allocate exact page if possible */
+#define BTALLOC_LE    2           /* Allocate any page <= the parameter */
+
+/*
+** Macro IfNotOmitAV(x) returns (x) if SQLITE_OMIT_AUTOVACUUM is not
+** defined, or 0 if it is. For example:
+**
+**   bIncrVacuum = IfNotOmitAV(pBtShared->incrVacuum);
+*/
+#ifndef SQLITE_OMIT_AUTOVACUUM
+#define IfNotOmitAV(expr) (expr)
+#else
+#define IfNotOmitAV(expr) 0
+#endif
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** A list of BtShared objects that are eligible for participation
+** in shared cache.  This variable has file scope during normal builds,
+** but the test harness needs to access it so we make it global for
+** test builds.
+**
+** Access to this variable is protected by SQLITE_MUTEX_STATIC_MAIN.
+*/
+#ifdef SQLITE_TEST
+BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
+#else
+static BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
+#endif
+#endif /* SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Enable or disable the shared pager and schema features.
+**
+** This routine has no effect on existing database connections.
+** The shared cache setting effects only future calls to
+** sqlite3_open(), sqlite3_open16(), or sqlite3_open_v2().
+*/
+int sqlite3_enable_shared_cache(int enable){
+  sqlite3GlobalConfig.sharedCacheEnabled = enable;
+  return SQLITE_OK;
+}
+#endif
+
+
+
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  /*
+  ** The functions querySharedCacheTableLock(), setSharedCacheTableLock(),
+  ** and clearAllSharedCacheTableLocks()
+  ** manipulate entries in the BtShared.pLock linked list used to store
+  ** shared-cache table level locks. If the library is compiled with the
+  ** shared-cache feature disabled, then there is only ever one user
+  ** of each BtShared structure and so this locking is not necessary.
+  ** So define the lock related functions as no-ops.
+  */
+  #define querySharedCacheTableLock(a,b,c) SQLITE_OK
+  #define setSharedCacheTableLock(a,b,c) SQLITE_OK
+  #define clearAllSharedCacheTableLocks(a)
+  #define downgradeAllSharedCacheTableLocks(a)
+  #define hasSharedCacheTableLock(a,b,c,d) 1
+  #define hasReadConflicts(a, b) 0
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Return and reset the seek counter for a Btree object.
+*/
+sqlite3_uint64 sqlite3BtreeSeekCount(Btree *pBt){
+  u64 n =  pBt->nSeek;
+  pBt->nSeek = 0;
+  return n;
+}
+#endif
+
+/*
+** Implementation of the SQLITE_CORRUPT_PAGE() macro. Takes a single
+** (MemPage*) as an argument. The (MemPage*) must not be NULL.
+**
+** If SQLITE_DEBUG is not defined, then this macro is equivalent to
+** SQLITE_CORRUPT_BKPT. Or, if SQLITE_DEBUG is set, then the log message
+** normally produced as a side-effect of SQLITE_CORRUPT_BKPT is augmented
+** with the page number and filename associated with the (MemPage*).
+*/
+#ifdef SQLITE_DEBUG
+int corruptPageError(int lineno, MemPage *p){
+  char *zMsg;
+  sqlite3BeginBenignMalloc();
+  zMsg = sqlite3_mprintf("database corruption page %u of %s",
+             p->pgno, sqlite3PagerFilename(p->pBt->pPager, 0)
+  );
+  sqlite3EndBenignMalloc();
+  if( zMsg ){
+    sqlite3ReportError(SQLITE_CORRUPT, lineno, zMsg);
+  }
+  sqlite3_free(zMsg);
+  return SQLITE_CORRUPT_BKPT;
+}
+# define SQLITE_CORRUPT_PAGE(pMemPage) corruptPageError(__LINE__, pMemPage)
+#else
+# define SQLITE_CORRUPT_PAGE(pMemPage) SQLITE_CORRUPT_PGNO(pMemPage->pgno)
+#endif
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+
+#ifdef SQLITE_DEBUG
+/*
+**** This function is only used as part of an assert() statement. ***
+**
+** Check to see if pBtree holds the required locks to read or write to the
+** table with root page iRoot.   Return 1 if it does and 0 if not.
+**
+** For example, when writing to a table with root-page iRoot via
+** Btree connection pBtree:
+**
+**    assert( hasSharedCacheTableLock(pBtree, iRoot, 0, WRITE_LOCK) );
+**
+** When writing to an index that resides in a sharable database, the
+** caller should have first obtained a lock specifying the root page of
+** the corresponding table. This makes things a bit more complicated,
+** as this module treats each table as a separate structure. To determine
+** the table corresponding to the index being written, this
+** function has to search through the database schema.
+**
+** Instead of a lock on the table/index rooted at page iRoot, the caller may
+** hold a write-lock on the schema table (root page 1). This is also
+** acceptable.
+*/
+static int hasSharedCacheTableLock(
+  Btree *pBtree,         /* Handle that must hold lock */
+  Pgno iRoot,            /* Root page of b-tree */
+  int isIndex,           /* True if iRoot is the root of an index b-tree */
+  int eLockType          /* Required lock type (READ_LOCK or WRITE_LOCK) */
+){
+  Schema *pSchema = (Schema *)pBtree->pBt->pSchema;
+  Pgno iTab = 0;
+  BtLock *pLock;
+
+  /* If this database is not shareable, or if the client is reading
+  ** and has the read-uncommitted flag set, then no lock is required.
+  ** Return true immediately.
+  */
+  if( (pBtree->sharable==0)
+   || (eLockType==READ_LOCK && (pBtree->db->flags & SQLITE_ReadUncommit))
+  ){
+    return 1;
+  }
+
+  /* If the client is reading  or writing an index and the schema is
+  ** not loaded, then it is too difficult to actually check to see if
+  ** the correct locks are held.  So do not bother - just return true.
+  ** This case does not come up very often anyhow.
+  */
+  if( isIndex && (!pSchema || (pSchema->schemaFlags&DB_SchemaLoaded)==0) ){
+    return 1;
+  }
+
+  /* Figure out the root-page that the lock should be held on. For table
+  ** b-trees, this is just the root page of the b-tree being read or
+  ** written. For index b-trees, it is the root page of the associated
+  ** table.  */
+  if( isIndex ){
+    HashElem *p;
+    int bSeen = 0;
+    for(p=sqliteHashFirst(&pSchema->idxHash); p; p=sqliteHashNext(p)){
+      Index *pIdx = (Index *)sqliteHashData(p);
+      if( pIdx->tnum==iRoot ){
+        if( bSeen ){
+          /* Two or more indexes share the same root page.  There must
+          ** be imposter tables.  So just return true.  The assert is not
+          ** useful in that case. */
+          return 1;
+        }
+        iTab = pIdx->pTable->tnum;
+        bSeen = 1;
+      }
+    }
+  }else{
+    iTab = iRoot;
+  }
+
+  /* Search for the required lock. Either a write-lock on root-page iTab, a
+  ** write-lock on the schema table, or (if the client is reading) a
+  ** read-lock on iTab will suffice. Return 1 if any of these are found.  */
+  for(pLock=pBtree->pBt->pLock; pLock; pLock=pLock->pNext){
+    if( pLock->pBtree==pBtree
+     && (pLock->iTable==iTab || (pLock->eLock==WRITE_LOCK && pLock->iTable==1))
+     && pLock->eLock>=eLockType
+    ){
+      return 1;
+    }
+  }
+
+  /* Failed to find the required lock. */
+  return 0;
+}
+#endif /* SQLITE_DEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+**** This function may be used as part of assert() statements only. ****
+**
+** Return true if it would be illegal for pBtree to write into the
+** table or index rooted at iRoot because other shared connections are
+** simultaneously reading that same table or index.
+**
+** It is illegal for pBtree to write if some other Btree object that
+** shares the same BtShared object is currently reading or writing
+** the iRoot table.  Except, if the other Btree object has the
+** read-uncommitted flag set, then it is OK for the other object to
+** have a read cursor.
+**
+** For example, before writing to any part of the table or index
+** rooted at page iRoot, one should call:
+**
+**    assert( !hasReadConflicts(pBtree, iRoot) );
+*/
+static int hasReadConflicts(Btree *pBtree, Pgno iRoot){
+  BtCursor *p;
+  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
+    if( p->pgnoRoot==iRoot
+     && p->pBtree!=pBtree
+     && 0==(p->pBtree->db->flags & SQLITE_ReadUncommit)
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+#endif    /* #ifdef SQLITE_DEBUG */
+
+/*
+** Query to see if Btree handle p may obtain a lock of type eLock
+** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
+** SQLITE_OK if the lock may be obtained (by calling
+** setSharedCacheTableLock()), or SQLITE_LOCKED if not.
+*/
+static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
+  BtShared *pBt = p->pBt;
+  BtLock *pIter;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
+  assert( p->db!=0 );
+  assert( !(p->db->flags&SQLITE_ReadUncommit)||eLock==WRITE_LOCK||iTab==1 );
+ 
+  /* If requesting a write-lock, then the Btree must have an open write
+  ** transaction on this file. And, obviously, for this to be so there
+  ** must be an open write transaction on the file itself.
+  */
+  assert( eLock==READ_LOCK || (p==pBt->pWriter && p->inTrans==TRANS_WRITE) );
+  assert( eLock==READ_LOCK || pBt->inTransaction==TRANS_WRITE );
+ 
+  /* This routine is a no-op if the shared-cache is not enabled */
+  if( !p->sharable ){
+    return SQLITE_OK;
+  }
+
+  /* If some other connection is holding an exclusive lock, the
+  ** requested lock may not be obtained.
+  */
+  if( pBt->pWriter!=p && (pBt->btsFlags & BTS_EXCLUSIVE)!=0 ){
+    sqlite3ConnectionBlocked(p->db, pBt->pWriter->db);
+    return SQLITE_LOCKED_SHAREDCACHE;
+  }
+
+  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
+    /* The condition (pIter->eLock!=eLock) in the following if(...)
+    ** statement is a simplification of:
+    **
+    **   (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
+    **
+    ** since we know that if eLock==WRITE_LOCK, then no other connection
+    ** may hold a WRITE_LOCK on any table in this file (since there can
+    ** only be a single writer).
+    */
+    assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
+    assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
+    if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
+      sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
+      if( eLock==WRITE_LOCK ){
+        assert( p==pBt->pWriter );
+        pBt->btsFlags |= BTS_PENDING;
+      }
+      return SQLITE_LOCKED_SHAREDCACHE;
+    }
+  }
+  return SQLITE_OK;
+}
+#endif /* !SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Add a lock on the table with root-page iTable to the shared-btree used
+** by Btree handle p. Parameter eLock must be either READ_LOCK or
+** WRITE_LOCK.
+**
+** This function assumes the following:
+**
+**   (a) The specified Btree object p is connected to a sharable
+**       database (one with the BtShared.sharable flag set), and
+**
+**   (b) No other Btree objects hold a lock that conflicts
+**       with the requested lock (i.e. querySharedCacheTableLock() has
+**       already been called and returned SQLITE_OK).
+**
+** SQLITE_OK is returned if the lock is added successfully. SQLITE_NOMEM
+** is returned if a malloc attempt fails.
+*/
+static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
+  BtShared *pBt = p->pBt;
+  BtLock *pLock = 0;
+  BtLock *pIter;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
+  assert( p->db!=0 );
+
+  /* A connection with the read-uncommitted flag set will never try to
+  ** obtain a read-lock using this function. The only read-lock obtained
+  ** by a connection in read-uncommitted mode is on the sqlite_schema
+  ** table, and that lock is obtained in BtreeBeginTrans().  */
+  assert( 0==(p->db->flags&SQLITE_ReadUncommit) || eLock==WRITE_LOCK );
+
+  /* This function should only be called on a sharable b-tree after it
+  ** has been determined that no other b-tree holds a conflicting lock.  */
+  assert( p->sharable );
+  assert( SQLITE_OK==querySharedCacheTableLock(p, iTable, eLock) );
+
+  /* First search the list for an existing lock on this table. */
+  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
+    if( pIter->iTable==iTable && pIter->pBtree==p ){
+      pLock = pIter;
+      break;
+    }
+  }
+
+  /* If the above search did not find a BtLock struct associating Btree p
+  ** with table iTable, allocate one and link it into the list.
+  */
+  if( !pLock ){
+    pLock = (BtLock *)sqlite3MallocZero(sizeof(BtLock));
+    if( !pLock ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    pLock->iTable = iTable;
+    pLock->pBtree = p;
+    pLock->pNext = pBt->pLock;
+    pBt->pLock = pLock;
+  }
+
+  /* Set the BtLock.eLock variable to the maximum of the current lock
+  ** and the requested lock. This means if a write-lock was already held
+  ** and a read-lock requested, we don't incorrectly downgrade the lock.
+  */
+  assert( WRITE_LOCK>READ_LOCK );
+  if( eLock>pLock->eLock ){
+    pLock->eLock = eLock;
+  }
+
+  return SQLITE_OK;
+}
+#endif /* !SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Release all the table locks (locks obtained via calls to
+** the setSharedCacheTableLock() procedure) held by Btree object p.
+**
+** This function assumes that Btree p has an open read or write
+** transaction. If it does not, then the BTS_PENDING flag
+** may be incorrectly cleared.
+*/
+static void clearAllSharedCacheTableLocks(Btree *p){
+  BtShared *pBt = p->pBt;
+  BtLock **ppIter = &pBt->pLock;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( p->sharable || 0==*ppIter );
+  assert( p->inTrans>0 );
+
+  while( *ppIter ){
+    BtLock *pLock = *ppIter;
+    assert( (pBt->btsFlags & BTS_EXCLUSIVE)==0 || pBt->pWriter==pLock->pBtree );
+    assert( pLock->pBtree->inTrans>=pLock->eLock );
+    if( pLock->pBtree==p ){
+      *ppIter = pLock->pNext;
+      assert( pLock->iTable!=1 || pLock==&p->lock );
+      if( pLock->iTable!=1 ){
+        sqlite3_free(pLock);
+      }
+    }else{
+      ppIter = &pLock->pNext;
+    }
+  }
+
+  assert( (pBt->btsFlags & BTS_PENDING)==0 || pBt->pWriter );
+  if( pBt->pWriter==p ){
+    pBt->pWriter = 0;
+    pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
+  }else if( pBt->nTransaction==2 ){
+    /* This function is called when Btree p is concluding its
+    ** transaction. If there currently exists a writer, and p is not
+    ** that writer, then the number of locks held by connections other
+    ** than the writer must be about to drop to zero. In this case
+    ** set the BTS_PENDING flag to 0.
+    **
+    ** If there is not currently a writer, then BTS_PENDING must
+    ** be zero already. So this next line is harmless in that case.
+    */
+    pBt->btsFlags &= ~BTS_PENDING;
+  }
+}
+
+/*
+** This function changes all write-locks held by Btree p into read-locks.
+*/
+static void downgradeAllSharedCacheTableLocks(Btree *p){
+  BtShared *pBt = p->pBt;
+  if( pBt->pWriter==p ){
+    BtLock *pLock;
+    pBt->pWriter = 0;
+    pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
+    for(pLock=pBt->pLock; pLock; pLock=pLock->pNext){
+      assert( pLock->eLock==READ_LOCK || pLock->pBtree==p );
+      pLock->eLock = READ_LOCK;
+    }
+  }
+}
+
+#endif /* SQLITE_OMIT_SHARED_CACHE */
+
+static void releasePage(MemPage *pPage);         /* Forward reference */
+static void releasePageOne(MemPage *pPage);      /* Forward reference */
+static void releasePageNotNull(MemPage *pPage);  /* Forward reference */
+
+/*
+***** This routine is used inside of assert() only ****
+**
+** Verify that the cursor holds the mutex on its BtShared
+*/
+#ifdef SQLITE_DEBUG
+static int cursorHoldsMutex(BtCursor *p){
+  return sqlite3_mutex_held(p->pBt->mutex);
+}
+
+/* Verify that the cursor and the BtShared agree about what is the current
+** database connetion. This is important in shared-cache mode. If the database
+** connection pointers get out-of-sync, it is possible for routines like
+** btreeInitPage() to reference an stale connection pointer that references a
+** a connection that has already closed.  This routine is used inside assert()
+** statements only and for the purpose of double-checking that the btree code
+** does keep the database connection pointers up-to-date.
+*/
+static int cursorOwnsBtShared(BtCursor *p){
+  assert( cursorHoldsMutex(p) );
+  return (p->pBtree->db==p->pBt->db);
+}
+#endif
+
+/*
+** Invalidate the overflow cache of the cursor passed as the first argument.
+** on the shared btree structure pBt.
+*/
+#define invalidateOverflowCache(pCur) (pCur->curFlags &= ~BTCF_ValidOvfl)
+
+/*
+** Invalidate the overflow page-list cache for all cursors opened
+** on the shared btree structure pBt.
+*/
+static void invalidateAllOverflowCache(BtShared *pBt){
+  BtCursor *p;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  for(p=pBt->pCursor; p; p=p->pNext){
+    invalidateOverflowCache(p);
+  }
+}
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** This function is called before modifying the contents of a table
+** to invalidate any incrblob cursors that are open on the
+** row or one of the rows being modified.
+**
+** If argument isClearTable is true, then the entire contents of the
+** table is about to be deleted. In this case invalidate all incrblob
+** cursors open on any row within the table with root-page pgnoRoot.
+**
+** Otherwise, if argument isClearTable is false, then the row with
+** rowid iRow is being replaced or deleted. In this case invalidate
+** only those incrblob cursors open on that specific row.
+*/
+static void invalidateIncrblobCursors(
+  Btree *pBtree,          /* The database file to check */
+  Pgno pgnoRoot,          /* The table that might be changing */
+  i64 iRow,               /* The rowid that might be changing */
+  int isClearTable        /* True if all rows are being deleted */
+){
+  BtCursor *p;
+  assert( pBtree->hasIncrblobCur );
+  assert( sqlite3BtreeHoldsMutex(pBtree) );
+  pBtree->hasIncrblobCur = 0;
+  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
+    if( (p->curFlags & BTCF_Incrblob)!=0 ){
+      pBtree->hasIncrblobCur = 1;
+      if( p->pgnoRoot==pgnoRoot && (isClearTable || p->info.nKey==iRow) ){
+        p->eState = CURSOR_INVALID;
+      }
+    }
+  }
+}
+
+#else
+  /* Stub function when INCRBLOB is omitted */
+  #define invalidateIncrblobCursors(w,x,y,z)
+#endif /* SQLITE_OMIT_INCRBLOB */
+
+/*
+** Set bit pgno of the BtShared.pHasContent bitvec. This is called
+** when a page that previously contained data becomes a free-list leaf
+** page.
+**
+** The BtShared.pHasContent bitvec exists to work around an obscure
+** bug caused by the interaction of two useful IO optimizations surrounding
+** free-list leaf pages:
+**
+**   1) When all data is deleted from a page and the page becomes
+**      a free-list leaf page, the page is not written to the database
+**      (as free-list leaf pages contain no meaningful data). Sometimes
+**      such a page is not even journalled (as it will not be modified,
+**      why bother journalling it?).
+**
+**   2) When a free-list leaf page is reused, its content is not read
+**      from the database or written to the journal file (why should it
+**      be, if it is not at all meaningful?).
+**
+** By themselves, these optimizations work fine and provide a handy
+** performance boost to bulk delete or insert operations. However, if
+** a page is moved to the free-list and then reused within the same
+** transaction, a problem comes up. If the page is not journalled when
+** it is moved to the free-list and it is also not journalled when it
+** is extracted from the free-list and reused, then the original data
+** may be lost. In the event of a rollback, it may not be possible
+** to restore the database to its original configuration.
+**
+** The solution is the BtShared.pHasContent bitvec. Whenever a page is
+** moved to become a free-list leaf page, the corresponding bit is
+** set in the bitvec. Whenever a leaf page is extracted from the free-list,
+** optimization 2 above is omitted if the corresponding bit is already
+** set in BtShared.pHasContent. The contents of the bitvec are cleared
+** at the end of every transaction.
+*/
+static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
+  int rc = SQLITE_OK;
+  if( !pBt->pHasContent ){
+    assert( pgno<=pBt->nPage );
+    pBt->pHasContent = sqlite3BitvecCreate(pBt->nPage);
+    if( !pBt->pHasContent ){
+      rc = SQLITE_NOMEM_BKPT;
+    }
+  }
+  if( rc==SQLITE_OK && pgno<=sqlite3BitvecSize(pBt->pHasContent) ){
+    rc = sqlite3BitvecSet(pBt->pHasContent, pgno);
+  }
+  return rc;
+}
+
+/*
+** Query the BtShared.pHasContent vector.
+**
+** This function is called when a free-list leaf page is removed from the
+** free-list for reuse. It returns false if it is safe to retrieve the
+** page from the pager layer with the 'no-content' flag set. True otherwise.
+*/
+static int btreeGetHasContent(BtShared *pBt, Pgno pgno){
+  Bitvec *p = pBt->pHasContent;
+  return p && (pgno>sqlite3BitvecSize(p) || sqlite3BitvecTestNotNull(p, pgno));
+}
+
+/*
+** Clear (destroy) the BtShared.pHasContent bitvec. This should be
+** invoked at the conclusion of each write-transaction.
+*/
+static void btreeClearHasContent(BtShared *pBt){
+  sqlite3BitvecDestroy(pBt->pHasContent);
+  pBt->pHasContent = 0;
+}
+
+/*
+** Release all of the apPage[] pages for a cursor.
+*/
+static void btreeReleaseAllCursorPages(BtCursor *pCur){
+  int i;
+  if( pCur->iPage>=0 ){
+    for(i=0; i<pCur->iPage; i++){
+      releasePageNotNull(pCur->apPage[i]);
+    }
+    releasePageNotNull(pCur->pPage);
+    pCur->iPage = -1;
+  }
+}
+
+/*
+** The cursor passed as the only argument must point to a valid entry
+** when this function is called (i.e. have eState==CURSOR_VALID). This
+** function saves the current cursor key in variables pCur->nKey and
+** pCur->pKey. SQLITE_OK is returned if successful or an SQLite error
+** code otherwise.
+**
+** If the cursor is open on an intkey table, then the integer key
+** (the rowid) is stored in pCur->nKey and pCur->pKey is left set to
+** NULL. If the cursor is open on a non-intkey table, then pCur->pKey is
+** set to point to a malloced buffer pCur->nKey bytes in size containing
+** the key.
+*/
+static int saveCursorKey(BtCursor *pCur){
+  int rc = SQLITE_OK;
+  assert( CURSOR_VALID==pCur->eState );
+  assert( 0==pCur->pKey );
+  assert( cursorHoldsMutex(pCur) );
+
+  if( pCur->curIntKey ){
+    /* Only the rowid is required for a table btree */
+    pCur->nKey = sqlite3BtreeIntegerKey(pCur);
+  }else{
+    /* For an index btree, save the complete key content. It is possible
+    ** that the current key is corrupt. In that case, it is possible that
+    ** the sqlite3VdbeRecordUnpack() function may overread the buffer by
+    ** up to the size of 1 varint plus 1 8-byte value when the cursor
+    ** position is restored. Hence the 17 bytes of padding allocated
+    ** below. */
+    void *pKey;
+    pCur->nKey = sqlite3BtreePayloadSize(pCur);
+    pKey = sqlite3Malloc( pCur->nKey + 9 + 8 );
+    if( pKey ){
+      rc = sqlite3BtreePayload(pCur, 0, (int)pCur->nKey, pKey);
+      if( rc==SQLITE_OK ){
+        memset(((u8*)pKey)+pCur->nKey, 0, 9+8);
+        pCur->pKey = pKey;
+      }else{
+        sqlite3_free(pKey);
+      }
+    }else{
+      rc = SQLITE_NOMEM_BKPT;
+    }
+  }
+  assert( !pCur->curIntKey || !pCur->pKey );
+  return rc;
+}
+
+/*
+** Save the current cursor position in the variables BtCursor.nKey
+** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
+**
+** The caller must ensure that the cursor is valid (has eState==CURSOR_VALID)
+** prior to calling this routine. 
+*/
+static int saveCursorPosition(BtCursor *pCur){
+  int rc;
+
+  assert( CURSOR_VALID==pCur->eState || CURSOR_SKIPNEXT==pCur->eState );
+  assert( 0==pCur->pKey );
+  assert( cursorHoldsMutex(pCur) );
+
+  if( pCur->curFlags & BTCF_Pinned ){
+    return SQLITE_CONSTRAINT_PINNED;
+  }
+  if( pCur->eState==CURSOR_SKIPNEXT ){
+    pCur->eState = CURSOR_VALID;
+  }else{
+    pCur->skipNext = 0;
+  }
+
+  rc = saveCursorKey(pCur);
+  if( rc==SQLITE_OK ){
+    btreeReleaseAllCursorPages(pCur);
+    pCur->eState = CURSOR_REQUIRESEEK;
+  }
+
+  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl|BTCF_AtLast);
+  return rc;
+}
+
+/* Forward reference */
+static int SQLITE_NOINLINE saveCursorsOnList(BtCursor*,Pgno,BtCursor*);
+
+/*
+** Save the positions of all cursors (except pExcept) that are open on
+** the table with root-page iRoot.  "Saving the cursor position" means that
+** the location in the btree is remembered in such a way that it can be
+** moved back to the same spot after the btree has been modified.  This
+** routine is called just before cursor pExcept is used to modify the
+** table, for example in BtreeDelete() or BtreeInsert().
+**
+** If there are two or more cursors on the same btree, then all such
+** cursors should have their BTCF_Multiple flag set.  The btreeCursor()
+** routine enforces that rule.  This routine only needs to be called in
+** the uncommon case when pExpect has the BTCF_Multiple flag set.
+**
+** If pExpect!=NULL and if no other cursors are found on the same root-page,
+** then the BTCF_Multiple flag on pExpect is cleared, to avoid another
+** pointless call to this routine.
+**
+** Implementation note:  This routine merely checks to see if any cursors
+** need to be saved.  It calls out to saveCursorsOnList() in the (unusual)
+** event that cursors are in need to being saved.
+*/
+static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
+  BtCursor *p;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( pExcept==0 || pExcept->pBt==pBt );
+  for(p=pBt->pCursor; p; p=p->pNext){
+    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break;
+  }
+  if( p ) return saveCursorsOnList(p, iRoot, pExcept);
+  if( pExcept ) pExcept->curFlags &= ~BTCF_Multiple;
+  return SQLITE_OK;
+}
+
+/* This helper routine to saveAllCursors does the actual work of saving
+** the cursors if and when a cursor is found that actually requires saving.
+** The common case is that no cursors need to be saved, so this routine is
+** broken out from its caller to avoid unnecessary stack pointer movement.
+*/
+static int SQLITE_NOINLINE saveCursorsOnList(
+  BtCursor *p,         /* The first cursor that needs saving */
+  Pgno iRoot,          /* Only save cursor with this iRoot. Save all if zero */
+  BtCursor *pExcept    /* Do not save this cursor */
+){
+  do{
+    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ){
+      if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
+        int rc = saveCursorPosition(p);
+        if( SQLITE_OK!=rc ){
+          return rc;
+        }
+      }else{
+        testcase( p->iPage>=0 );
+        btreeReleaseAllCursorPages(p);
+      }
+    }
+    p = p->pNext;
+  }while( p );
+  return SQLITE_OK;
+}
+
+/*
+** Clear the current cursor position.
+*/
+void sqlite3BtreeClearCursor(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  sqlite3_free(pCur->pKey);
+  pCur->pKey = 0;
+  pCur->eState = CURSOR_INVALID;
+}
+
+/*
+** In this version of BtreeMoveto, pKey is a packed index record
+** such as is generated by the OP_MakeRecord opcode.  Unpack the
+** record and then call sqlite3BtreeIndexMoveto() to do the work.
+*/
+static int btreeMoveto(
+  BtCursor *pCur,     /* Cursor open on the btree to be searched */
+  const void *pKey,   /* Packed key if the btree is an index */
+  i64 nKey,           /* Integer key for tables.  Size of pKey for indices */
+  int bias,           /* Bias search to the high end */
+  int *pRes           /* Write search results here */
+){
+  int rc;                    /* Status code */
+  UnpackedRecord *pIdxKey;   /* Unpacked index key */
+
+  if( pKey ){
+    KeyInfo *pKeyInfo = pCur->pKeyInfo;
+    assert( nKey==(i64)(int)nKey );
+    pIdxKey = sqlite3VdbeAllocUnpackedRecord(pKeyInfo);
+    if( pIdxKey==0 ) return SQLITE_NOMEM_BKPT;
+    sqlite3VdbeRecordUnpack(pKeyInfo, (int)nKey, pKey, pIdxKey);
+    if( pIdxKey->nField==0 || pIdxKey->nField>pKeyInfo->nAllField ){
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = sqlite3BtreeIndexMoveto(pCur, pIdxKey, pRes);
+    }
+    sqlite3DbFree(pCur->pKeyInfo->db, pIdxKey);
+  }else{
+    pIdxKey = 0;
+    rc = sqlite3BtreeTableMoveto(pCur, nKey, bias, pRes);
+  }
+  return rc;
+}
+
+/*
+** Restore the cursor to the position it was in (or as close to as possible)
+** when saveCursorPosition() was called. Note that this call deletes the
+** saved position info stored by saveCursorPosition(), so there can be
+** at most one effective restoreCursorPosition() call after each
+** saveCursorPosition().
+*/
+static int btreeRestoreCursorPosition(BtCursor *pCur){
+  int rc;
+  int skipNext = 0;
+  assert( cursorOwnsBtShared(pCur) );
+  assert( pCur->eState>=CURSOR_REQUIRESEEK );
+  if( pCur->eState==CURSOR_FAULT ){
+    return pCur->skipNext;
+  }
+  pCur->eState = CURSOR_INVALID;
+  if( sqlite3FaultSim(410) ){
+    rc = SQLITE_IOERR;
+  }else{
+    rc = btreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &skipNext);
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3_free(pCur->pKey);
+    pCur->pKey = 0;
+    assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
+    if( skipNext ) pCur->skipNext = skipNext;
+    if( pCur->skipNext && pCur->eState==CURSOR_VALID ){
+      pCur->eState = CURSOR_SKIPNEXT;
+    }
+  }
+  return rc;
+}
+
+#define restoreCursorPosition(p) \
+  (p->eState>=CURSOR_REQUIRESEEK ? \
+         btreeRestoreCursorPosition(p) : \
+         SQLITE_OK)
+
+/*
+** Determine whether or not a cursor has moved from the position where
+** it was last placed, or has been invalidated for any other reason.
+** Cursors can move when the row they are pointing at is deleted out
+** from under them, for example.  Cursor might also move if a btree
+** is rebalanced.
+**
+** Calling this routine with a NULL cursor pointer returns false.
+**
+** Use the separate sqlite3BtreeCursorRestore() routine to restore a cursor
+** back to where it ought to be if this routine returns true.
+*/
+int sqlite3BtreeCursorHasMoved(BtCursor *pCur){
+  assert( EIGHT_BYTE_ALIGNMENT(pCur)
+       || pCur==sqlite3BtreeFakeValidCursor() );
+  assert( offsetof(BtCursor, eState)==0 );
+  assert( sizeof(pCur->eState)==1 );
+  return CURSOR_VALID != *(u8*)pCur;
+}
+
+/*
+** Return a pointer to a fake BtCursor object that will always answer
+** false to the sqlite3BtreeCursorHasMoved() routine above.  The fake
+** cursor returned must not be used with any other Btree interface.
+*/
+BtCursor *sqlite3BtreeFakeValidCursor(void){
+  static u8 fakeCursor = CURSOR_VALID;
+  assert( offsetof(BtCursor, eState)==0 );
+  return (BtCursor*)&fakeCursor;
+}
+
+/*
+** This routine restores a cursor back to its original position after it
+** has been moved by some outside activity (such as a btree rebalance or
+** a row having been deleted out from under the cursor). 
+**
+** On success, the *pDifferentRow parameter is false if the cursor is left
+** pointing at exactly the same row.  *pDifferntRow is the row the cursor
+** was pointing to has been deleted, forcing the cursor to point to some
+** nearby row.
+**
+** This routine should only be called for a cursor that just returned
+** TRUE from sqlite3BtreeCursorHasMoved().
+*/
+int sqlite3BtreeCursorRestore(BtCursor *pCur, int *pDifferentRow){
+  int rc;
+
+  assert( pCur!=0 );
+  assert( pCur->eState!=CURSOR_VALID );
+  rc = restoreCursorPosition(pCur);
+  if( rc ){
+    *pDifferentRow = 1;
+    return rc;
+  }
+  if( pCur->eState!=CURSOR_VALID ){
+    *pDifferentRow = 1;
+  }else{
+    *pDifferentRow = 0;
+  }
+  return SQLITE_OK;
+}
+
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+/*
+** Provide hints to the cursor.  The particular hint given (and the type
+** and number of the varargs parameters) is determined by the eHintType
+** parameter.  See the definitions of the BTREE_HINT_* macros for details.
+*/
+void sqlite3BtreeCursorHint(BtCursor *pCur, int eHintType, ...){
+  /* Used only by system that substitute their own storage engine */
+#ifdef SQLITE_DEBUG
+  if( ALWAYS(eHintType==BTREE_HINT_RANGE) ){
+    va_list ap;
+    Expr *pExpr;
+    Walker w;
+    memset(&w, 0, sizeof(w));
+    w.xExprCallback = sqlite3CursorRangeHintExprCheck;
+    va_start(ap, eHintType);
+    pExpr = va_arg(ap, Expr*);
+    w.u.aMem = va_arg(ap, Mem*);
+    va_end(ap);
+    assert( pExpr!=0 );
+    assert( w.u.aMem!=0 );
+    sqlite3WalkExpr(&w, pExpr);
+  }
+#endif /* SQLITE_DEBUG */
+}
+#endif /* SQLITE_ENABLE_CURSOR_HINTS */
+
+
+/*
+** Provide flag hints to the cursor.
+*/
+void sqlite3BtreeCursorHintFlags(BtCursor *pCur, unsigned x){
+  assert( x==BTREE_SEEK_EQ || x==BTREE_BULKLOAD || x==0 );
+  pCur->hints = x;
+}
+
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Given a page number of a regular database page, return the page
+** number for the pointer-map page that contains the entry for the
+** input page number.
+**
+** Return 0 (not a valid page) for pgno==1 since there is
+** no pointer map associated with page 1.  The integrity_check logic
+** requires that ptrmapPageno(*,1)!=1.
+*/
+static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
+  int nPagesPerMapPage;
+  Pgno iPtrMap, ret;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pgno<2 ) return 0;
+  nPagesPerMapPage = (pBt->usableSize/5)+1;
+  iPtrMap = (pgno-2)/nPagesPerMapPage;
+  ret = (iPtrMap*nPagesPerMapPage) + 2;
+  if( ret==PENDING_BYTE_PAGE(pBt) ){
+    ret++;
+  }
+  return ret;
+}
+
+/*
+** Write an entry into the pointer map.
+**
+** This routine updates the pointer map entry for page number 'key'
+** so that it maps to type 'eType' and parent page number 'pgno'.
+**
+** If *pRC is initially non-zero (non-SQLITE_OK) then this routine is
+** a no-op.  If an error occurs, the appropriate error code is written
+** into *pRC.
+*/
+static void ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent, int *pRC){
+  DbPage *pDbPage;  /* The pointer map page */
+  u8 *pPtrmap;      /* The pointer map data */
+  Pgno iPtrmap;     /* The pointer map page number */
+  int offset;       /* Offset in pointer map page */
+  int rc;           /* Return code from subfunctions */
+
+  if( *pRC ) return;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  /* The super-journal page number must never be used as a pointer map page */
+  assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );
+
+  assert( pBt->autoVacuum );
+  if( key==0 ){
+    *pRC = SQLITE_CORRUPT_BKPT;
+    return;
+  }
+  iPtrmap = PTRMAP_PAGENO(pBt, key);
+  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage, 0);
+  if( rc!=SQLITE_OK ){
+    *pRC = rc;
+    return;
+  }
+  if( ((char*)sqlite3PagerGetExtra(pDbPage))[0]!=0 ){
+    /* The first byte of the extra data is the MemPage.isInit byte.
+    ** If that byte is set, it means this page is also being used
+    ** as a btree page. */
+    *pRC = SQLITE_CORRUPT_BKPT;
+    goto ptrmap_exit;
+  }
+  offset = PTRMAP_PTROFFSET(iPtrmap, key);
+  if( offset<0 ){
+    *pRC = SQLITE_CORRUPT_BKPT;
+    goto ptrmap_exit;
+  }
+  assert( offset <= (int)pBt->usableSize-5 );
+  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
+
+  if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
+    TRACE(("PTRMAP_UPDATE: %u->(%u,%u)\n", key, eType, parent));
+    *pRC= rc = sqlite3PagerWrite(pDbPage);
+    if( rc==SQLITE_OK ){
+      pPtrmap[offset] = eType;
+      put4byte(&pPtrmap[offset+1], parent);
+    }
+  }
+
+ptrmap_exit:
+  sqlite3PagerUnref(pDbPage);
+}
+
+/*
+** Read an entry from the pointer map.
+**
+** This routine retrieves the pointer map entry for page 'key', writing
+** the type and parent page number to *pEType and *pPgno respectively.
+** An error code is returned if something goes wrong, otherwise SQLITE_OK.
+*/
+static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
+  DbPage *pDbPage;   /* The pointer map page */
+  int iPtrmap;       /* Pointer map page index */
+  u8 *pPtrmap;       /* Pointer map page data */
+  int offset;        /* Offset of entry in pointer map */
+  int rc;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+
+  iPtrmap = PTRMAP_PAGENO(pBt, key);
+  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage, 0);
+  if( rc!=0 ){
+    return rc;
+  }
+  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
+
+  offset = PTRMAP_PTROFFSET(iPtrmap, key);
+  if( offset<0 ){
+    sqlite3PagerUnref(pDbPage);
+    return SQLITE_CORRUPT_BKPT;
+  }
+  assert( offset <= (int)pBt->usableSize-5 );
+  assert( pEType!=0 );
+  *pEType = pPtrmap[offset];
+  if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
+
+  sqlite3PagerUnref(pDbPage);
+  if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_PGNO(iPtrmap);
+  return SQLITE_OK;
+}
+
+#else /* if defined SQLITE_OMIT_AUTOVACUUM */
+  #define ptrmapPut(w,x,y,z,rc)
+  #define ptrmapGet(w,x,y,z) SQLITE_OK
+  #define ptrmapPutOvflPtr(x, y, z, rc)
+#endif
+
+/*
+** Given a btree page and a cell index (0 means the first cell on
+** the page, 1 means the second cell, and so forth) return a pointer
+** to the cell content.
+**
+** findCellPastPtr() does the same except it skips past the initial
+** 4-byte child pointer found on interior pages, if there is one.
+**
+** This routine works only for pages that do not contain overflow cells.
+*/
+#define findCell(P,I) \
+  ((P)->aData + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
+#define findCellPastPtr(P,I) \
+  ((P)->aDataOfst + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
+
+
+/*
+** This is common tail processing for btreeParseCellPtr() and
+** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
+** on a single B-tree page.  Make necessary adjustments to the CellInfo
+** structure.
+*/
+static SQLITE_NOINLINE void btreeParseCellAdjustSizeForOverflow(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  /* If the payload will not fit completely on the local page, we have
+  ** to decide how much to store locally and how much to spill onto
+  ** overflow pages.  The strategy is to minimize the amount of unused
+  ** space on overflow pages while keeping the amount of local storage
+  ** in between minLocal and maxLocal.
+  **
+  ** Warning:  changing the way overflow payload is distributed in any
+  ** way will result in an incompatible file format.
+  */
+  int minLocal;  /* Minimum amount of payload held locally */
+  int maxLocal;  /* Maximum amount of payload held locally */
+  int surplus;   /* Overflow payload available for local storage */
+
+  minLocal = pPage->minLocal;
+  maxLocal = pPage->maxLocal;
+  surplus = minLocal + (pInfo->nPayload - minLocal)%(pPage->pBt->usableSize-4);
+  testcase( surplus==maxLocal );
+  testcase( surplus==maxLocal+1 );
+  if( surplus <= maxLocal ){
+    pInfo->nLocal = (u16)surplus;
+  }else{
+    pInfo->nLocal = (u16)minLocal;
+  }
+  pInfo->nSize = (u16)(&pInfo->pPayload[pInfo->nLocal] - pCell) + 4;
+}
+
+/*
+** Given a record with nPayload bytes of payload stored within btree
+** page pPage, return the number of bytes of payload stored locally.
+*/
+static int btreePayloadToLocal(MemPage *pPage, i64 nPayload){
+  int maxLocal;  /* Maximum amount of payload held locally */
+  maxLocal = pPage->maxLocal;
+  if( nPayload<=maxLocal ){
+    return nPayload;
+  }else{
+    int minLocal;  /* Minimum amount of payload held locally */
+    int surplus;   /* Overflow payload available for local storage */
+    minLocal = pPage->minLocal;
+    surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize-4);
+    return ( surplus <= maxLocal ) ? surplus : minLocal;
+  }
+}
+
+/*
+** The following routines are implementations of the MemPage.xParseCell()
+** method.
+**
+** Parse a cell content block and fill in the CellInfo structure.
+**
+** btreeParseCellPtr()        =>   table btree leaf nodes
+** btreeParseCellNoPayload()  =>   table btree internal nodes
+** btreeParseCellPtrIndex()   =>   index btree nodes
+**
+** There is also a wrapper function btreeParseCell() that works for
+** all MemPage types and that references the cell by index rather than
+** by pointer.
+*/
+static void btreeParseCellPtrNoPayload(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->leaf==0 );
+  assert( pPage->childPtrSize==4 );
+#ifndef SQLITE_DEBUG
+  UNUSED_PARAMETER(pPage);
+#endif
+  pInfo->nSize = 4 + getVarint(&pCell[4], (u64*)&pInfo->nKey);
+  pInfo->nPayload = 0;
+  pInfo->nLocal = 0;
+  pInfo->pPayload = 0;
+  return;
+}
+static void btreeParseCellPtr(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  u8 *pIter;              /* For scanning through pCell */
+  u32 nPayload;           /* Number of bytes of cell payload */
+  u64 iKey;               /* Extracted Key value */
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->leaf==0 || pPage->leaf==1 );
+  assert( pPage->intKeyLeaf );
+  assert( pPage->childPtrSize==0 );
+  pIter = pCell;
+
+  /* The next block of code is equivalent to:
+  **
+  **     pIter += getVarint32(pIter, nPayload);
+  **
+  ** The code is inlined to avoid a function call.
+  */
+  nPayload = *pIter;
+  if( nPayload>=0x80 ){
+    u8 *pEnd = &pIter[8];
+    nPayload &= 0x7f;
+    do{
+      nPayload = (nPayload<<7) | (*++pIter & 0x7f);
+    }while( (*pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+
+  /* The next block of code is equivalent to:
+  **
+  **     pIter += getVarint(pIter, (u64*)&pInfo->nKey);
+  **
+  ** The code is inlined and the loop is unrolled for performance.
+  ** This routine is a high-runner.
+  */
+  iKey = *pIter;
+  if( iKey>=0x80 ){
+    u8 x;
+    iKey = (iKey<<7) ^ (x = *++pIter);
+    if( x>=0x80 ){
+      iKey = (iKey<<7) ^ (x = *++pIter);
+      if( x>=0x80 ){
+        iKey = (iKey<<7) ^ 0x10204000 ^ (x = *++pIter);
+        if( x>=0x80 ){
+          iKey = (iKey<<7) ^ 0x4000 ^ (x = *++pIter);
+          if( x>=0x80 ){
+            iKey = (iKey<<7) ^ 0x4000 ^ (x = *++pIter);
+            if( x>=0x80 ){
+              iKey = (iKey<<7) ^ 0x4000 ^ (x = *++pIter);
+              if( x>=0x80 ){
+                iKey = (iKey<<7) ^ 0x4000 ^ (x = *++pIter);
+                if( x>=0x80 ){
+                  iKey = (iKey<<8) ^ 0x8000 ^ (*++pIter);
+                }
+              }
+            }
+          }
+        }
+      }else{
+        iKey ^= 0x204000;
+      }
+    }else{
+      iKey ^= 0x4000;
+    }
+  }
+  pIter++;
+
+  pInfo->nKey = *(i64*)&iKey;
+  pInfo->nPayload = nPayload;
+  pInfo->pPayload = pIter;
+  testcase( nPayload==pPage->maxLocal );
+  testcase( nPayload==(u32)pPage->maxLocal+1 );
+  if( nPayload<=pPage->maxLocal ){
+    /* This is the (easy) common case where the entire payload fits
+    ** on the local page.  No overflow is required.
+    */
+    pInfo->nSize = nPayload + (u16)(pIter - pCell);
+    if( pInfo->nSize<4 ) pInfo->nSize = 4;
+    pInfo->nLocal = (u16)nPayload;
+  }else{
+    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
+  }
+}
+static void btreeParseCellPtrIndex(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  u8 *pIter;              /* For scanning through pCell */
+  u32 nPayload;           /* Number of bytes of cell payload */
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->leaf==0 || pPage->leaf==1 );
+  assert( pPage->intKeyLeaf==0 );
+  pIter = pCell + pPage->childPtrSize;
+  nPayload = *pIter;
+  if( nPayload>=0x80 ){
+    u8 *pEnd = &pIter[8];
+    nPayload &= 0x7f;
+    do{
+      nPayload = (nPayload<<7) | (*++pIter & 0x7f);
+    }while( *(pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+  pInfo->nKey = nPayload;
+  pInfo->nPayload = nPayload;
+  pInfo->pPayload = pIter;
+  testcase( nPayload==pPage->maxLocal );
+  testcase( nPayload==(u32)pPage->maxLocal+1 );
+  if( nPayload<=pPage->maxLocal ){
+    /* This is the (easy) common case where the entire payload fits
+    ** on the local page.  No overflow is required.
+    */
+    pInfo->nSize = nPayload + (u16)(pIter - pCell);
+    if( pInfo->nSize<4 ) pInfo->nSize = 4;
+    pInfo->nLocal = (u16)nPayload;
+  }else{
+    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
+  }
+}
+static void btreeParseCell(
+  MemPage *pPage,         /* Page containing the cell */
+  int iCell,              /* The cell index.  First cell is 0 */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  pPage->xParseCell(pPage, findCell(pPage, iCell), pInfo);
+}
+
+/*
+** The following routines are implementations of the MemPage.xCellSize
+** method.
+**
+** Compute the total number of bytes that a Cell needs in the cell
+** data area of the btree-page.  The return number includes the cell
+** data header and the local payload, but not any overflow page or
+** the space used by the cell pointer.
+**
+** cellSizePtrNoPayload()    =>   table internal nodes
+** cellSizePtrTableLeaf()    =>   table leaf nodes
+** cellSizePtr()             =>   index internal nodes
+** cellSizeIdxLeaf()         =>   index leaf nodes
+*/
+static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
+  u8 *pIter = pCell + 4;                   /* For looping over bytes of pCell */
+  u8 *pEnd;                                /* End mark for a varint */
+  u32 nSize;                               /* Size value to return */
+
+#ifdef SQLITE_DEBUG
+  /* The value returned by this function should always be the same as
+  ** the (CellInfo.nSize) value found by doing a full parse of the
+  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
+  ** this function verifies that this invariant is not violated. */
+  CellInfo debuginfo;
+  pPage->xParseCell(pPage, pCell, &debuginfo);
+#endif
+
+  assert( pPage->childPtrSize==4 );
+  nSize = *pIter;
+  if( nSize>=0x80 ){
+    pEnd = &pIter[8];
+    nSize &= 0x7f;
+    do{
+      nSize = (nSize<<7) | (*++pIter & 0x7f);
+    }while( *(pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+  testcase( nSize==pPage->maxLocal );
+  testcase( nSize==(u32)pPage->maxLocal+1 );
+  if( nSize<=pPage->maxLocal ){
+    nSize += (u32)(pIter - pCell);
+    assert( nSize>4 );
+  }else{
+    int minLocal = pPage->minLocal;
+    nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
+    testcase( nSize==pPage->maxLocal );
+    testcase( nSize==(u32)pPage->maxLocal+1 );
+    if( nSize>pPage->maxLocal ){
+      nSize = minLocal;
+    }
+    nSize += 4 + (u16)(pIter - pCell);
+  }
+  assert( nSize==debuginfo.nSize || CORRUPT_DB );
+  return (u16)nSize;
+}
+static u16 cellSizePtrIdxLeaf(MemPage *pPage, u8 *pCell){
+  u8 *pIter = pCell;                       /* For looping over bytes of pCell */
+  u8 *pEnd;                                /* End mark for a varint */
+  u32 nSize;                               /* Size value to return */
+
+#ifdef SQLITE_DEBUG
+  /* The value returned by this function should always be the same as
+  ** the (CellInfo.nSize) value found by doing a full parse of the
+  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
+  ** this function verifies that this invariant is not violated. */
+  CellInfo debuginfo;
+  pPage->xParseCell(pPage, pCell, &debuginfo);
+#endif
+
+  assert( pPage->childPtrSize==0 );
+  nSize = *pIter;
+  if( nSize>=0x80 ){
+    pEnd = &pIter[8];
+    nSize &= 0x7f;
+    do{
+      nSize = (nSize<<7) | (*++pIter & 0x7f);
+    }while( *(pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+  testcase( nSize==pPage->maxLocal );
+  testcase( nSize==(u32)pPage->maxLocal+1 );
+  if( nSize<=pPage->maxLocal ){
+    nSize += (u32)(pIter - pCell);
+    if( nSize<4 ) nSize = 4;
+  }else{
+    int minLocal = pPage->minLocal;
+    nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
+    testcase( nSize==pPage->maxLocal );
+    testcase( nSize==(u32)pPage->maxLocal+1 );
+    if( nSize>pPage->maxLocal ){
+      nSize = minLocal;
+    }
+    nSize += 4 + (u16)(pIter - pCell);
+  }
+  assert( nSize==debuginfo.nSize || CORRUPT_DB );
+  return (u16)nSize;
+}
+static u16 cellSizePtrNoPayload(MemPage *pPage, u8 *pCell){
+  u8 *pIter = pCell + 4; /* For looping over bytes of pCell */
+  u8 *pEnd;              /* End mark for a varint */
+
+#ifdef SQLITE_DEBUG
+  /* The value returned by this function should always be the same as
+  ** the (CellInfo.nSize) value found by doing a full parse of the
+  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
+  ** this function verifies that this invariant is not violated. */
+  CellInfo debuginfo;
+  pPage->xParseCell(pPage, pCell, &debuginfo);
+#else
+  UNUSED_PARAMETER(pPage);
+#endif
+
+  assert( pPage->childPtrSize==4 );
+  pEnd = pIter + 9;
+  while( (*pIter++)&0x80 && pIter<pEnd );
+  assert( debuginfo.nSize==(u16)(pIter - pCell) || CORRUPT_DB );
+  return (u16)(pIter - pCell);
+}
+static u16 cellSizePtrTableLeaf(MemPage *pPage, u8 *pCell){
+  u8 *pIter = pCell;   /* For looping over bytes of pCell */
+  u8 *pEnd;            /* End mark for a varint */
+  u32 nSize;           /* Size value to return */
+
+#ifdef SQLITE_DEBUG
+  /* The value returned by this function should always be the same as
+  ** the (CellInfo.nSize) value found by doing a full parse of the
+  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
+  ** this function verifies that this invariant is not violated. */
+  CellInfo debuginfo;
+  pPage->xParseCell(pPage, pCell, &debuginfo);
+#endif
+
+  nSize = *pIter;
+  if( nSize>=0x80 ){
+    pEnd = &pIter[8];
+    nSize &= 0x7f;
+    do{
+      nSize = (nSize<<7) | (*++pIter & 0x7f);
+    }while( *(pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+  /* pIter now points at the 64-bit integer key value, a variable length
+  ** integer. The following block moves pIter to point at the first byte
+  ** past the end of the key value. */
+  if( (*pIter++)&0x80
+   && (*pIter++)&0x80
+   && (*pIter++)&0x80
+   && (*pIter++)&0x80
+   && (*pIter++)&0x80
+   && (*pIter++)&0x80
+   && (*pIter++)&0x80
+   && (*pIter++)&0x80 ){ pIter++; }
+  testcase( nSize==pPage->maxLocal );
+  testcase( nSize==(u32)pPage->maxLocal+1 );
+  if( nSize<=pPage->maxLocal ){
+    nSize += (u32)(pIter - pCell);
+    if( nSize<4 ) nSize = 4;
+  }else{
+    int minLocal = pPage->minLocal;
+    nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
+    testcase( nSize==pPage->maxLocal );
+    testcase( nSize==(u32)pPage->maxLocal+1 );
+    if( nSize>pPage->maxLocal ){
+      nSize = minLocal;
+    }
+    nSize += 4 + (u16)(pIter - pCell);
+  }
+  assert( nSize==debuginfo.nSize || CORRUPT_DB );
+  return (u16)nSize;
+}
+
+
+#ifdef SQLITE_DEBUG
+/* This variation on cellSizePtr() is used inside of assert() statements
+** only. */
+static u16 cellSize(MemPage *pPage, int iCell){
+  return pPage->xCellSize(pPage, findCell(pPage, iCell));
+}
+#endif
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** The cell pCell is currently part of page pSrc but will ultimately be part
+** of pPage.  (pSrc and pPage are often the same.)  If pCell contains a
+** pointer to an overflow page, insert an entry into the pointer-map for
+** the overflow page that will be valid after pCell has been moved to pPage.
+*/
+static void ptrmapPutOvflPtr(MemPage *pPage, MemPage *pSrc, u8 *pCell,int *pRC){
+  CellInfo info;
+  if( *pRC ) return;
+  assert( pCell!=0 );
+  pPage->xParseCell(pPage, pCell, &info);
+  if( info.nLocal<info.nPayload ){
+    Pgno ovfl;
+    if( SQLITE_OVERFLOW(pSrc->aDataEnd, pCell, pCell+info.nLocal) ){
+      testcase( pSrc!=pPage );
+      *pRC = SQLITE_CORRUPT_BKPT;
+      return;
+    }
+    ovfl = get4byte(&pCell[info.nSize-4]);
+    ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
+  }
+}
+#endif
+
+
+/*
+** Defragment the page given. This routine reorganizes cells within the
+** page so that there are no free-blocks on the free-block list.
+**
+** Parameter nMaxFrag is the maximum amount of fragmented space that may be
+** present in the page after this routine returns.
+**
+** EVIDENCE-OF: R-44582-60138 SQLite may from time to time reorganize a
+** b-tree page so that there are no freeblocks or fragment bytes, all
+** unused bytes are contained in the unallocated space region, and all
+** cells are packed tightly at the end of the page.
+*/
+static int defragmentPage(MemPage *pPage, int nMaxFrag){
+  int i;                     /* Loop counter */
+  int pc;                    /* Address of the i-th cell */
+  int hdr;                   /* Offset to the page header */
+  int size;                  /* Size of a cell */
+  int usableSize;            /* Number of usable bytes on a page */
+  int cellOffset;            /* Offset to the cell pointer array */
+  int cbrk;                  /* Offset to the cell content area */
+  int nCell;                 /* Number of cells on the page */
+  unsigned char *data;       /* The page data */
+  unsigned char *temp;       /* Temp area for cell content */
+  unsigned char *src;        /* Source of content */
+  int iCellFirst;            /* First allowable cell index */
+  int iCellLast;             /* Last possible cell index */
+  int iCellStart;            /* First cell offset in input */
+
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( pPage->pBt!=0 );
+  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
+  assert( pPage->nOverflow==0 );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  data = pPage->aData;
+  hdr = pPage->hdrOffset;
+  cellOffset = pPage->cellOffset;
+  nCell = pPage->nCell;
+  assert( nCell==get2byte(&data[hdr+3]) || CORRUPT_DB );
+  iCellFirst = cellOffset + 2*nCell;
+  usableSize = pPage->pBt->usableSize;
+
+  /* This block handles pages with two or fewer free blocks and nMaxFrag
+  ** or fewer fragmented bytes. In this case it is faster to move the
+  ** two (or one) blocks of cells using memmove() and add the required
+  ** offsets to each pointer in the cell-pointer array than it is to
+  ** reconstruct the entire page.  */
+  if( (int)data[hdr+7]<=nMaxFrag ){
+    int iFree = get2byte(&data[hdr+1]);
+    if( iFree>usableSize-4 ) return SQLITE_CORRUPT_PAGE(pPage);
+    if( iFree ){
+      int iFree2 = get2byte(&data[iFree]);
+      if( iFree2>usableSize-4 ) return SQLITE_CORRUPT_PAGE(pPage);
+      if( 0==iFree2 || (data[iFree2]==0 && data[iFree2+1]==0) ){
+        u8 *pEnd = &data[cellOffset + nCell*2];
+        u8 *pAddr;
+        int sz2 = 0;
+        int sz = get2byte(&data[iFree+2]);
+        int top = get2byte(&data[hdr+5]);
+        if( top>=iFree ){
+          return SQLITE_CORRUPT_PAGE(pPage);
+        }
+        if( iFree2 ){
+          if( iFree+sz>iFree2 ) return SQLITE_CORRUPT_PAGE(pPage);
+          sz2 = get2byte(&data[iFree2+2]);
+          if( iFree2+sz2 > usableSize ) return SQLITE_CORRUPT_PAGE(pPage);
+          memmove(&data[iFree+sz+sz2], &data[iFree+sz], iFree2-(iFree+sz));
+          sz += sz2;
+        }else if( iFree+sz>usableSize ){
+          return SQLITE_CORRUPT_PAGE(pPage);
+        }
+
+        cbrk = top+sz;
+        assert( cbrk+(iFree-top) <= usableSize );
+        memmove(&data[cbrk], &data[top], iFree-top);
+        for(pAddr=&data[cellOffset]; pAddr<pEnd; pAddr+=2){
+          pc = get2byte(pAddr);
+          if( pc<iFree ){ put2byte(pAddr, pc+sz); }
+          else if( pc<iFree2 ){ put2byte(pAddr, pc+sz2); }
+        }
+        goto defragment_out;
+      }
+    }
+  }
+
+  cbrk = usableSize;
+  iCellLast = usableSize - 4;
+  iCellStart = get2byte(&data[hdr+5]);
+  if( nCell>0 ){
+    temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
+    memcpy(temp, data, usableSize);
+    src = temp;
+    for(i=0; i<nCell; i++){
+      u8 *pAddr;     /* The i-th cell pointer */
+      pAddr = &data[cellOffset + i*2];
+      pc = get2byte(pAddr);
+      testcase( pc==iCellFirst );
+      testcase( pc==iCellLast );
+      /* These conditions have already been verified in btreeInitPage()
+      ** if PRAGMA cell_size_check=ON.
+      */
+      if( pc>iCellLast ){
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      assert( pc>=0 && pc<=iCellLast );
+      size = pPage->xCellSize(pPage, &src[pc]);
+      cbrk -= size;
+      if( cbrk<iCellStart || pc+size>usableSize ){
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      assert( cbrk+size<=usableSize && cbrk>=iCellStart );
+      testcase( cbrk+size==usableSize );
+      testcase( pc+size==usableSize );
+      put2byte(pAddr, cbrk);
+      memcpy(&data[cbrk], &src[pc], size);
+    }
+  }
+  data[hdr+7] = 0;
+
+defragment_out:
+  assert( pPage->nFree>=0 );
+  if( data[hdr+7]+cbrk-iCellFirst!=pPage->nFree ){
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+  assert( cbrk>=iCellFirst );
+  put2byte(&data[hdr+5], cbrk);
+  data[hdr+1] = 0;
+  data[hdr+2] = 0;
+  memset(&data[iCellFirst], 0, cbrk-iCellFirst);
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  return SQLITE_OK;
+}
+
+/*
+** Search the free-list on page pPg for space to store a cell nByte bytes in
+** size. If one can be found, return a pointer to the space and remove it
+** from the free-list.
+**
+** If no suitable space can be found on the free-list, return NULL.
+**
+** This function may detect corruption within pPg.  If corruption is
+** detected then *pRc is set to SQLITE_CORRUPT and NULL is returned.
+**
+** Slots on the free list that are between 1 and 3 bytes larger than nByte
+** will be ignored if adding the extra space to the fragmentation count
+** causes the fragmentation count to exceed 60.
+*/
+static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
+  const int hdr = pPg->hdrOffset;            /* Offset to page header */
+  u8 * const aData = pPg->aData;             /* Page data */
+  int iAddr = hdr + 1;                       /* Address of ptr to pc */
+  u8 *pTmp = &aData[iAddr];                  /* Temporary ptr into aData[] */
+  int pc = get2byte(pTmp);                   /* Address of a free slot */
+  int x;                                     /* Excess size of the slot */
+  int maxPC = pPg->pBt->usableSize - nByte;  /* Max address for a usable slot */
+  int size;                                  /* Size of the free slot */
+
+  assert( pc>0 );
+  while( pc<=maxPC ){
+    /* EVIDENCE-OF: R-22710-53328 The third and fourth bytes of each
+    ** freeblock form a big-endian integer which is the size of the freeblock
+    ** in bytes, including the 4-byte header. */
+    pTmp = &aData[pc+2];
+    size = get2byte(pTmp);
+    if( (x = size - nByte)>=0 ){
+      testcase( x==4 );
+      testcase( x==3 );
+      if( x<4 ){
+        /* EVIDENCE-OF: R-11498-58022 In a well-formed b-tree page, the total
+        ** number of bytes in fragments may not exceed 60. */
+        if( aData[hdr+7]>57 ) return 0;
+
+        /* Remove the slot from the free-list. Update the number of
+        ** fragmented bytes within the page. */
+        memcpy(&aData[iAddr], &aData[pc], 2);
+        aData[hdr+7] += (u8)x;
+        return &aData[pc];
+      }else if( x+pc > maxPC ){
+        /* This slot extends off the end of the usable part of the page */
+        *pRc = SQLITE_CORRUPT_PAGE(pPg);
+        return 0;
+      }else{
+        /* The slot remains on the free-list. Reduce its size to account
+        ** for the portion used by the new allocation. */
+        put2byte(&aData[pc+2], x);
+      }
+      return &aData[pc + x];
+    }
+    iAddr = pc;
+    pTmp = &aData[pc];
+    pc = get2byte(pTmp);
+    if( pc<=iAddr ){
+      if( pc ){
+        /* The next slot in the chain comes before the current slot */
+        *pRc = SQLITE_CORRUPT_PAGE(pPg);
+      }
+      return 0;
+    }
+  }
+  if( pc>maxPC+nByte-4 ){
+    /* The free slot chain extends off the end of the page */
+    *pRc = SQLITE_CORRUPT_PAGE(pPg);
+  }
+  return 0;
+}
+
+/*
+** Allocate nByte bytes of space from within the B-Tree page passed
+** as the first argument. Write into *pIdx the index into pPage->aData[]
+** of the first byte of allocated space. Return either SQLITE_OK or
+** an error code (usually SQLITE_CORRUPT).
+**
+** The caller guarantees that there is sufficient space to make the
+** allocation.  This routine might need to defragment in order to bring
+** all the space together, however.  This routine will avoid using
+** the first two bytes past the cell pointer area since presumably this
+** allocation is being made in order to insert a new cell, so we will
+** also end up needing a new cell pointer.
+*/
+static SQLITE_INLINE int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
+  const int hdr = pPage->hdrOffset;    /* Local cache of pPage->hdrOffset */
+  u8 * const data = pPage->aData;      /* Local cache of pPage->aData */
+  int top;                             /* First byte of cell content area */
+  int rc = SQLITE_OK;                  /* Integer return code */
+  u8 *pTmp;                            /* Temp ptr into data[] */
+  int gap;        /* First byte of gap between cell pointers and cell content */
+ 
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( pPage->pBt );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( nByte>=0 );  /* Minimum cell size is 4 */
+  assert( pPage->nFree>=nByte );
+  assert( pPage->nOverflow==0 );
+  assert( nByte < (int)(pPage->pBt->usableSize-8) );
+
+  assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
+  gap = pPage->cellOffset + 2*pPage->nCell;
+  assert( gap<=65536 );
+  /* EVIDENCE-OF: R-29356-02391 If the database uses a 65536-byte page size
+  ** and the reserved space is zero (the usual value for reserved space)
+  ** then the cell content offset of an empty page wants to be 65536.
+  ** However, that integer is too large to be stored in a 2-byte unsigned
+  ** integer, so a value of 0 is used in its place. */
+  pTmp = &data[hdr+5];
+  top = get2byte(pTmp);
+  if( gap>top ){
+    if( top==0 && pPage->pBt->usableSize==65536 ){
+      top = 65536;
+    }else{
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+  }else if( top>(int)pPage->pBt->usableSize ){
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+
+  /* If there is enough space between gap and top for one more cell pointer,
+  ** and if the freelist is not empty, then search the
+  ** freelist looking for a slot big enough to satisfy the request.
+  */
+  testcase( gap+2==top );
+  testcase( gap+1==top );
+  testcase( gap==top );
+  if( (data[hdr+2] || data[hdr+1]) && gap+2<=top ){
+    u8 *pSpace = pageFindSlot(pPage, nByte, &rc);
+    if( pSpace ){
+      int g2;
+      assert( pSpace+nByte<=data+pPage->pBt->usableSize );
+      *pIdx = g2 = (int)(pSpace-data);
+      if( g2<=gap ){
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }else{
+        return SQLITE_OK;
+      }
+    }else if( rc ){
+      return rc;
+    }
+  }
+
+  /* The request could not be fulfilled using a freelist slot.  Check
+  ** to see if defragmentation is necessary.
+  */
+  testcase( gap+2+nByte==top );
+  if( gap+2+nByte>top ){
+    assert( pPage->nCell>0 || CORRUPT_DB );
+    assert( pPage->nFree>=0 );
+    rc = defragmentPage(pPage, MIN(4, pPage->nFree - (2+nByte)));
+    if( rc ) return rc;
+    top = get2byteNotZero(&data[hdr+5]);
+    assert( gap+2+nByte<=top );
+  }
+
+
+  /* Allocate memory from the gap in between the cell pointer array
+  ** and the cell content area.  The btreeComputeFreeSpace() call has already
+  ** validated the freelist.  Given that the freelist is valid, there
+  ** is no way that the allocation can extend off the end of the page.
+  ** The assert() below verifies the previous sentence.
+  */
+  top -= nByte;
+  put2byte(&data[hdr+5], top);
+  assert( top+nByte <= (int)pPage->pBt->usableSize );
+  *pIdx = top;
+  return SQLITE_OK;
+}
+
+/*
+** Return a section of the pPage->aData to the freelist.
+** The first byte of the new free block is pPage->aData[iStart]
+** and the size of the block is iSize bytes.
+**
+** Adjacent freeblocks are coalesced.
+**
+** Even though the freeblock list was checked by btreeComputeFreeSpace(),
+** that routine will not detect overlap between cells or freeblocks.  Nor
+** does it detect cells or freeblocks that encroach into the reserved bytes
+** at the end of the page.  So do additional corruption checks inside this
+** routine and return SQLITE_CORRUPT if any problems are found.
+*/
+static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
+  u16 iPtr;                             /* Address of ptr to next freeblock */
+  u16 iFreeBlk;                         /* Address of the next freeblock */
+  u8 hdr;                               /* Page header size.  0 or 100 */
+  u8 nFrag = 0;                         /* Reduction in fragmentation */
+  u16 iOrigSize = iSize;                /* Original value of iSize */
+  u16 x;                                /* Offset to cell content area */
+  u32 iEnd = iStart + iSize;            /* First byte past the iStart buffer */
+  unsigned char *data = pPage->aData;   /* Page content */
+  u8 *pTmp;                             /* Temporary ptr into data[] */
+
+  assert( pPage->pBt!=0 );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( CORRUPT_DB || iStart>=pPage->hdrOffset+6+pPage->childPtrSize );
+  assert( CORRUPT_DB || iEnd <= pPage->pBt->usableSize );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( iSize>=4 );   /* Minimum cell size is 4 */
+  assert( CORRUPT_DB || iStart<=pPage->pBt->usableSize-4 );
+
+  /* The list of freeblocks must be in ascending order.  Find the
+  ** spot on the list where iStart should be inserted.
+  */
+  hdr = pPage->hdrOffset;
+  iPtr = hdr + 1;
+  if( data[iPtr+1]==0 && data[iPtr]==0 ){
+    iFreeBlk = 0;  /* Shortcut for the case when the freelist is empty */
+  }else{
+    while( (iFreeBlk = get2byte(&data[iPtr]))<iStart ){
+      if( iFreeBlk<=iPtr ){
+        if( iFreeBlk==0 ) break; /* TH3: corrupt082.100 */
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      iPtr = iFreeBlk;
+    }
+    if( iFreeBlk>pPage->pBt->usableSize-4 ){ /* TH3: corrupt081.100 */
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+    assert( iFreeBlk>iPtr || iFreeBlk==0 || CORRUPT_DB );
+ 
+    /* At this point:
+    **    iFreeBlk:   First freeblock after iStart, or zero if none
+    **    iPtr:       The address of a pointer to iFreeBlk
+    **
+    ** Check to see if iFreeBlk should be coalesced onto the end of iStart.
+    */
+    if( iFreeBlk && iEnd+3>=iFreeBlk ){
+      nFrag = iFreeBlk - iEnd;
+      if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_PAGE(pPage);
+      iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
+      if( iEnd > pPage->pBt->usableSize ){
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      iSize = iEnd - iStart;
+      iFreeBlk = get2byte(&data[iFreeBlk]);
+    }
+ 
+    /* If iPtr is another freeblock (that is, if iPtr is not the freelist
+    ** pointer in the page header) then check to see if iStart should be
+    ** coalesced onto the end of iPtr.
+    */
+    if( iPtr>hdr+1 ){
+      int iPtrEnd = iPtr + get2byte(&data[iPtr+2]);
+      if( iPtrEnd+3>=iStart ){
+        if( iPtrEnd>iStart ) return SQLITE_CORRUPT_PAGE(pPage);
+        nFrag += iStart - iPtrEnd;
+        iSize = iEnd - iPtr;
+        iStart = iPtr;
+      }
+    }
+    if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_PAGE(pPage);
+    data[hdr+7] -= nFrag;
+  }
+  pTmp = &data[hdr+5];
+  x = get2byte(pTmp);
+  if( pPage->pBt->btsFlags & BTS_FAST_SECURE ){
+    /* Overwrite deleted information with zeros when the secure_delete
+    ** option is enabled */
+    memset(&data[iStart], 0, iSize);
+  }
+  if( iStart<=x ){
+    /* The new freeblock is at the beginning of the cell content area,
+    ** so just extend the cell content area rather than create another
+    ** freelist entry */
+    if( iStart<x ) return SQLITE_CORRUPT_PAGE(pPage);
+    if( iPtr!=hdr+1 ) return SQLITE_CORRUPT_PAGE(pPage);
+    put2byte(&data[hdr+1], iFreeBlk);
+    put2byte(&data[hdr+5], iEnd);
+  }else{
+    /* Insert the new freeblock into the freelist */
+    put2byte(&data[iPtr], iStart);
+    put2byte(&data[iStart], iFreeBlk);
+    put2byte(&data[iStart+2], iSize);
+  }
+  pPage->nFree += iOrigSize;
+  return SQLITE_OK;
+}
+
+/*
+** Decode the flags byte (the first byte of the header) for a page
+** and initialize fields of the MemPage structure accordingly.
+**
+** Only the following combinations are supported.  Anything different
+** indicates a corrupt database files:
+**
+**         PTF_ZERODATA                             (0x02,  2)
+**         PTF_LEAFDATA | PTF_INTKEY                (0x05,  5)
+**         PTF_ZERODATA | PTF_LEAF                  (0x0a, 10)
+**         PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF     (0x0d, 13)
+*/
+static int decodeFlags(MemPage *pPage, int flagByte){
+  BtShared *pBt;     /* A copy of pPage->pBt */
+
+  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  pBt = pPage->pBt;
+  pPage->max1bytePayload = pBt->max1bytePayload;
+  if( flagByte>=(PTF_ZERODATA | PTF_LEAF) ){
+    pPage->childPtrSize = 0;
+    pPage->leaf = 1;
+    if( flagByte==(PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF) ){
+      pPage->intKeyLeaf = 1;
+      pPage->xCellSize = cellSizePtrTableLeaf;
+      pPage->xParseCell = btreeParseCellPtr;
+      pPage->intKey = 1;
+      pPage->maxLocal = pBt->maxLeaf;
+      pPage->minLocal = pBt->minLeaf;
+    }else if( flagByte==(PTF_ZERODATA | PTF_LEAF) ){
+      pPage->intKey = 0;
+      pPage->intKeyLeaf = 0;
+      pPage->xCellSize = cellSizePtrIdxLeaf;
+      pPage->xParseCell = btreeParseCellPtrIndex;
+      pPage->maxLocal = pBt->maxLocal;
+      pPage->minLocal = pBt->minLocal;
+    }else{
+      pPage->intKey = 0;
+      pPage->intKeyLeaf = 0;
+      pPage->xCellSize = cellSizePtrIdxLeaf;
+      pPage->xParseCell = btreeParseCellPtrIndex;
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+  }else{
+    pPage->childPtrSize = 4;
+    pPage->leaf = 0;
+    if( flagByte==(PTF_ZERODATA) ){
+      pPage->intKey = 0;
+      pPage->intKeyLeaf = 0;
+      pPage->xCellSize = cellSizePtr;
+      pPage->xParseCell = btreeParseCellPtrIndex;
+      pPage->maxLocal = pBt->maxLocal;
+      pPage->minLocal = pBt->minLocal;
+    }else if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
+      pPage->intKeyLeaf = 0;
+      pPage->xCellSize = cellSizePtrNoPayload;
+      pPage->xParseCell = btreeParseCellPtrNoPayload;
+      pPage->intKey = 1;
+      pPage->maxLocal = pBt->maxLeaf;
+      pPage->minLocal = pBt->minLeaf;
+    }else{
+      pPage->intKey = 0;
+      pPage->intKeyLeaf = 0;
+      pPage->xCellSize = cellSizePtr;
+      pPage->xParseCell = btreeParseCellPtrIndex;
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Compute the amount of freespace on the page.  In other words, fill
+** in the pPage->nFree field.
+*/
+static int btreeComputeFreeSpace(MemPage *pPage){
+  int pc;            /* Address of a freeblock within pPage->aData[] */
+  u8 hdr;            /* Offset to beginning of page header */
+  u8 *data;          /* Equal to pPage->aData */
+  int usableSize;    /* Amount of usable space on each page */
+  int nFree;         /* Number of unused bytes on the page */
+  int top;           /* First byte of the cell content area */
+  int iCellFirst;    /* First allowable cell or freeblock offset */
+  int iCellLast;     /* Last possible cell or freeblock offset */
+
+  assert( pPage->pBt!=0 );
+  assert( pPage->pBt->db!=0 );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
+  assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
+  assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
+  assert( pPage->isInit==1 );
+  assert( pPage->nFree<0 );
+
+  usableSize = pPage->pBt->usableSize;
+  hdr = pPage->hdrOffset;
+  data = pPage->aData;
+  /* EVIDENCE-OF: R-58015-48175 The two-byte integer at offset 5 designates
+  ** the start of the cell content area. A zero value for this integer is
+  ** interpreted as 65536. */
+  top = get2byteNotZero(&data[hdr+5]);
+  iCellFirst = hdr + 8 + pPage->childPtrSize + 2*pPage->nCell;
+  iCellLast = usableSize - 4;
+
+  /* Compute the total free space on the page
+  ** EVIDENCE-OF: R-23588-34450 The two-byte integer at offset 1 gives the
+  ** start of the first freeblock on the page, or is zero if there are no
+  ** freeblocks. */
+  pc = get2byte(&data[hdr+1]);
+  nFree = data[hdr+7] + top;  /* Init nFree to non-freeblock free space */
+  if( pc>0 ){
+    u32 next, size;
+    if( pc<top ){
+      /* EVIDENCE-OF: R-55530-52930 In a well-formed b-tree page, there will
+      ** always be at least one cell before the first freeblock.
+      */
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+    while( 1 ){
+      if( pc>iCellLast ){
+        /* Freeblock off the end of the page */
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      next = get2byte(&data[pc]);
+      size = get2byte(&data[pc+2]);
+      nFree = nFree + size;
+      if( next<=pc+size+3 ) break;
+      pc = next;
+    }
+    if( next>0 ){
+      /* Freeblock not in ascending order */
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+    if( pc+size>(unsigned int)usableSize ){
+      /* Last freeblock extends past page end */
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+  }
+
+  /* At this point, nFree contains the sum of the offset to the start
+  ** of the cell-content area plus the number of free bytes within
+  ** the cell-content area. If this is greater than the usable-size
+  ** of the page, then the page must be corrupted. This check also
+  ** serves to verify that the offset to the start of the cell-content
+  ** area, according to the page header, lies within the page.
+  */
+  if( nFree>usableSize || nFree<iCellFirst ){
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+  pPage->nFree = (u16)(nFree - iCellFirst);
+  return SQLITE_OK;
+}
+
+/*
+** Do additional sanity check after btreeInitPage() if
+** PRAGMA cell_size_check=ON
+*/
+static SQLITE_NOINLINE int btreeCellSizeCheck(MemPage *pPage){
+  int iCellFirst;    /* First allowable cell or freeblock offset */
+  int iCellLast;     /* Last possible cell or freeblock offset */
+  int i;             /* Index into the cell pointer array */
+  int sz;            /* Size of a cell */
+  int pc;            /* Address of a freeblock within pPage->aData[] */
+  u8 *data;          /* Equal to pPage->aData */
+  int usableSize;    /* Maximum usable space on the page */
+  int cellOffset;    /* Start of cell content area */
+
+  iCellFirst = pPage->cellOffset + 2*pPage->nCell;
+  usableSize = pPage->pBt->usableSize;
+  iCellLast = usableSize - 4;
+  data = pPage->aData;
+  cellOffset = pPage->cellOffset;
+  if( !pPage->leaf ) iCellLast--;
+  for(i=0; i<pPage->nCell; i++){
+    pc = get2byteAligned(&data[cellOffset+i*2]);
+    testcase( pc==iCellFirst );
+    testcase( pc==iCellLast );
+    if( pc<iCellFirst || pc>iCellLast ){
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+    sz = pPage->xCellSize(pPage, &data[pc]);
+    testcase( pc+sz==usableSize );
+    if( pc+sz>usableSize ){
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Initialize the auxiliary information for a disk block.
+**
+** Return SQLITE_OK on success.  If we see that the page does
+** not contain a well-formed database page, then return
+** SQLITE_CORRUPT.  Note that a return of SQLITE_OK does not
+** guarantee that the page is well-formed.  It only shows that
+** we failed to detect any corruption.
+*/
+static int btreeInitPage(MemPage *pPage){
+  u8 *data;          /* Equal to pPage->aData */
+  BtShared *pBt;        /* The main btree structure */
+
+  assert( pPage->pBt!=0 );
+  assert( pPage->pBt->db!=0 );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
+  assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
+  assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
+  assert( pPage->isInit==0 );
+
+  pBt = pPage->pBt;
+  data = pPage->aData + pPage->hdrOffset;
+  /* EVIDENCE-OF: R-28594-02890 The one-byte flag at offset 0 indicating
+  ** the b-tree page type. */
+  if( decodeFlags(pPage, data[0]) ){
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+  assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
+  pPage->maskPage = (u16)(pBt->pageSize - 1);
+  pPage->nOverflow = 0;
+  pPage->cellOffset = pPage->hdrOffset + 8 + pPage->childPtrSize;
+  pPage->aCellIdx = data + pPage->childPtrSize + 8;
+  pPage->aDataEnd = pPage->aData + pBt->pageSize;
+  pPage->aDataOfst = pPage->aData + pPage->childPtrSize;
+  /* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
+  ** number of cells on the page. */
+  pPage->nCell = get2byte(&data[3]);
+  if( pPage->nCell>MX_CELL(pBt) ){
+    /* To many cells for a single page.  The page must be corrupt */
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+  testcase( pPage->nCell==MX_CELL(pBt) );
+  /* EVIDENCE-OF: R-24089-57979 If a page contains no cells (which is only
+  ** possible for a root page of a table that contains no rows) then the
+  ** offset to the cell content area will equal the page size minus the
+  ** bytes of reserved space. */
+  assert( pPage->nCell>0
+       || get2byteNotZero(&data[5])==(int)pBt->usableSize
+       || CORRUPT_DB );
+  pPage->nFree = -1;  /* Indicate that this value is yet uncomputed */
+  pPage->isInit = 1;
+  if( pBt->db->flags & SQLITE_CellSizeCk ){
+    return btreeCellSizeCheck(pPage);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Set up a raw page so that it looks like a database page holding
+** no entries.
+*/
+static void zeroPage(MemPage *pPage, int flags){
+  unsigned char *data = pPage->aData;
+  BtShared *pBt = pPage->pBt;
+  u8 hdr = pPage->hdrOffset;
+  u16 first;
+
+  assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno || CORRUPT_DB );
+  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
+  assert( sqlite3PagerGetData(pPage->pDbPage) == data );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pBt->btsFlags & BTS_FAST_SECURE ){
+    memset(&data[hdr], 0, pBt->usableSize - hdr);
+  }
+  data[hdr] = (char)flags;
+  first = hdr + ((flags&PTF_LEAF)==0 ? 12 : 8);
+  memset(&data[hdr+1], 0, 4);
+  data[hdr+7] = 0;
+  put2byte(&data[hdr+5], pBt->usableSize);
+  pPage->nFree = (u16)(pBt->usableSize - first);
+  decodeFlags(pPage, flags);
+  pPage->cellOffset = first;
+  pPage->aDataEnd = &data[pBt->pageSize];
+  pPage->aCellIdx = &data[first];
+  pPage->aDataOfst = &data[pPage->childPtrSize];
+  pPage->nOverflow = 0;
+  assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
+  pPage->maskPage = (u16)(pBt->pageSize - 1);
+  pPage->nCell = 0;
+  pPage->isInit = 1;
+}
+
+
+/*
+** Convert a DbPage obtained from the pager into a MemPage used by
+** the btree layer.
+*/
+static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
+  MemPage *pPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
+  if( pgno!=pPage->pgno ){
+    pPage->aData = sqlite3PagerGetData(pDbPage);
+    pPage->pDbPage = pDbPage;
+    pPage->pBt = pBt;
+    pPage->pgno = pgno;
+    pPage->hdrOffset = pgno==1 ? 100 : 0;
+  }
+  assert( pPage->aData==sqlite3PagerGetData(pDbPage) );
+  return pPage;
+}
+
+/*
+** Get a page from the pager.  Initialize the MemPage.pBt and
+** MemPage.aData elements if needed.  See also: btreeGetUnusedPage().
+**
+** If the PAGER_GET_NOCONTENT flag is set, it means that we do not care
+** about the content of the page at this time.  So do not go to the disk
+** to fetch the content.  Just fill in the content with zeros for now.
+** If in the future we call sqlite3PagerWrite() on this page, that
+** means we have started to be concerned about content and the disk
+** read should occur at that point.
+*/
+static int btreeGetPage(
+  BtShared *pBt,       /* The btree */
+  Pgno pgno,           /* Number of the page to fetch */
+  MemPage **ppPage,    /* Return the page in this parameter */
+  int flags            /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
+){
+  int rc;
+  DbPage *pDbPage;
+
+  assert( flags==0 || flags==PAGER_GET_NOCONTENT || flags==PAGER_GET_READONLY );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  rc = sqlite3PagerGet(pBt->pPager, pgno, (DbPage**)&pDbPage, flags);
+  if( rc ) return rc;
+  *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve a page from the pager cache. If the requested page is not
+** already in the pager cache return NULL. Initialize the MemPage.pBt and
+** MemPage.aData elements if needed.
+*/
+static MemPage *btreePageLookup(BtShared *pBt, Pgno pgno){
+  DbPage *pDbPage;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
+  if( pDbPage ){
+    return btreePageFromDbPage(pDbPage, pgno, pBt);
+  }
+  return 0;
+}
+
+/*
+** Return the size of the database file in pages. If there is any kind of
+** error, return ((unsigned int)-1).
+*/
+static Pgno btreePagecount(BtShared *pBt){
+  return pBt->nPage;
+}
+Pgno sqlite3BtreeLastPage(Btree *p){
+  assert( sqlite3BtreeHoldsMutex(p) );
+  return btreePagecount(p->pBt);
+}
+
+/*
+** Get a page from the pager and initialize it.
+*/
+static int getAndInitPage(
+  BtShared *pBt,                  /* The database file */
+  Pgno pgno,                      /* Number of the page to get */
+  MemPage **ppPage,               /* Write the page pointer here */
+  int bReadOnly                   /* True for a read-only page */
+){
+  int rc;
+  DbPage *pDbPage;
+  MemPage *pPage;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+
+  if( pgno>btreePagecount(pBt) ){
+    *ppPage = 0;
+    return SQLITE_CORRUPT_BKPT;
+  }
+  rc = sqlite3PagerGet(pBt->pPager, pgno, (DbPage**)&pDbPage, bReadOnly);
+  if( rc ){
+    *ppPage = 0;
+    return rc;
+  }
+  pPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
+  if( pPage->isInit==0 ){
+    btreePageFromDbPage(pDbPage, pgno, pBt);
+    rc = btreeInitPage(pPage);
+    if( rc!=SQLITE_OK ){
+      releasePage(pPage);
+      *ppPage = 0;
+      return rc;
+    }
+  }
+  assert( pPage->pgno==pgno || CORRUPT_DB );
+  assert( pPage->aData==sqlite3PagerGetData(pDbPage) );
+  *ppPage = pPage;
+  return SQLITE_OK;
+}
+
+/*
+** Release a MemPage.  This should be called once for each prior
+** call to btreeGetPage.
+**
+** Page1 is a special case and must be released using releasePageOne().
+*/
+static void releasePageNotNull(MemPage *pPage){
+  assert( pPage->aData );
+  assert( pPage->pBt );
+  assert( pPage->pDbPage!=0 );
+  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
+  assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  sqlite3PagerUnrefNotNull(pPage->pDbPage);
+}
+static void releasePage(MemPage *pPage){
+  if( pPage ) releasePageNotNull(pPage);
+}
+static void releasePageOne(MemPage *pPage){
+  assert( pPage!=0 );
+  assert( pPage->aData );
+  assert( pPage->pBt );
+  assert( pPage->pDbPage!=0 );
+  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
+  assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  sqlite3PagerUnrefPageOne(pPage->pDbPage);
+}
+
+/*
+** Get an unused page.
+**
+** This works just like btreeGetPage() with the addition:
+**
+**   *  If the page is already in use for some other purpose, immediately
+**      release it and return an SQLITE_CURRUPT error.
+**   *  Make sure the isInit flag is clear
+*/
+static int btreeGetUnusedPage(
+  BtShared *pBt,       /* The btree */
+  Pgno pgno,           /* Number of the page to fetch */
+  MemPage **ppPage,    /* Return the page in this parameter */
+  int flags            /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
+){
+  int rc = btreeGetPage(pBt, pgno, ppPage, flags);
+  if( rc==SQLITE_OK ){
+    if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
+      releasePage(*ppPage);
+      *ppPage = 0;
+      return SQLITE_CORRUPT_BKPT;
+    }
+    (*ppPage)->isInit = 0;
+  }else{
+    *ppPage = 0;
+  }
+  return rc;
+}
+
+
+/*
+** During a rollback, when the pager reloads information into the cache
+** so that the cache is restored to its original state at the start of
+** the transaction, for each page restored this routine is called.
+**
+** This routine needs to reset the extra data section at the end of the
+** page to agree with the restored data.
+*/
+static void pageReinit(DbPage *pData){
+  MemPage *pPage;
+  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
+  assert( sqlite3PagerPageRefcount(pData)>0 );
+  if( pPage->isInit ){
+    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+    pPage->isInit = 0;
+    if( sqlite3PagerPageRefcount(pData)>1 ){
+      /* pPage might not be a btree page;  it might be an overflow page
+      ** or ptrmap page or a free page.  In those cases, the following
+      ** call to btreeInitPage() will likely return SQLITE_CORRUPT.
+      ** But no harm is done by this.  And it is very important that
+      ** btreeInitPage() be called on every btree page so we make
+      ** the call for every page that comes in for re-initializing. */
+      btreeInitPage(pPage);
+    }
+  }
+}
+
+/*
+** Invoke the busy handler for a btree.
+*/
+static int btreeInvokeBusyHandler(void *pArg){
+  BtShared *pBt = (BtShared*)pArg;
+  assert( pBt->db );
+  assert( sqlite3_mutex_held(pBt->db->mutex) );
+  return sqlite3InvokeBusyHandler(&pBt->db->busyHandler);
+}
+
+/*
+** Open a database file.
+**
+** zFilename is the name of the database file.  If zFilename is NULL
+** then an ephemeral database is created.  The ephemeral database might
+** be exclusively in memory, or it might use a disk-based memory cache.
+** Either way, the ephemeral database will be automatically deleted
+** when sqlite3BtreeClose() is called.
+**
+** If zFilename is ":memory:" then an in-memory database is created
+** that is automatically destroyed when it is closed.
+**
+** The "flags" parameter is a bitmask that might contain bits like
+** BTREE_OMIT_JOURNAL and/or BTREE_MEMORY.
+**
+** If the database is already opened in the same database connection
+** and we are in shared cache mode, then the open will fail with an
+** SQLITE_CONSTRAINT error.  We cannot allow two or more BtShared
+** objects in the same database connection since doing so will lead
+** to problems with locking.
+*/
+int sqlite3BtreeOpen(
+  sqlite3_vfs *pVfs,      /* VFS to use for this b-tree */
+  const char *zFilename,  /* Name of the file containing the BTree database */
+  sqlite3 *db,            /* Associated database handle */
+  Btree **ppBtree,        /* Pointer to new Btree object written here */
+  int flags,              /* Options */
+  int vfsFlags            /* Flags passed through to sqlite3_vfs.xOpen() */
+){
+  BtShared *pBt = 0;             /* Shared part of btree structure */
+  Btree *p;                      /* Handle to return */
+  sqlite3_mutex *mutexOpen = 0;  /* Prevents a race condition. Ticket #3537 */
+  int rc = SQLITE_OK;            /* Result code from this function */
+  u8 nReserve;                   /* Byte of unused space on each page */
+  unsigned char zDbHeader[100];  /* Database header content */
+
+  /* True if opening an ephemeral, temporary database */
+  const int isTempDb = zFilename==0 || zFilename[0]==0;
+
+  /* Set the variable isMemdb to true for an in-memory database, or
+  ** false for a file-based database.
+  */
+#ifdef SQLITE_OMIT_MEMORYDB
+  const int isMemdb = 0;
+#else
+  const int isMemdb = (zFilename && strcmp(zFilename, ":memory:")==0)
+                       || (isTempDb && sqlite3TempInMemory(db))
+                       || (vfsFlags & SQLITE_OPEN_MEMORY)!=0;
+#endif
+
+  assert( db!=0 );
+  assert( pVfs!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( (flags&0xff)==flags );   /* flags fit in 8 bits */
+
+  /* Only a BTREE_SINGLE database can be BTREE_UNORDERED */
+  assert( (flags & BTREE_UNORDERED)==0 || (flags & BTREE_SINGLE)!=0 );
+
+  /* A BTREE_SINGLE database is always a temporary and/or ephemeral */
+  assert( (flags & BTREE_SINGLE)==0 || isTempDb );
+
+  if( isMemdb ){
+    flags |= BTREE_MEMORY;
+  }
+  if( (vfsFlags & SQLITE_OPEN_MAIN_DB)!=0 && (isMemdb || isTempDb) ){
+    vfsFlags = (vfsFlags & ~SQLITE_OPEN_MAIN_DB) | SQLITE_OPEN_TEMP_DB;
+  }
+  p = sqlite3MallocZero(sizeof(Btree));
+  if( !p ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  p->inTrans = TRANS_NONE;
+  p->db = db;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  p->lock.pBtree = p;
+  p->lock.iTable = 1;
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
+  /*
+  ** If this Btree is a candidate for shared cache, try to find an
+  ** existing BtShared object that we can share with
+  */
+  if( isTempDb==0 && (isMemdb==0 || (vfsFlags&SQLITE_OPEN_URI)!=0) ){
+    if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
+      int nFilename = sqlite3Strlen30(zFilename)+1;
+      int nFullPathname = pVfs->mxPathname+1;
+      char *zFullPathname = sqlite3Malloc(MAX(nFullPathname,nFilename));
+      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
+
+      p->sharable = 1;
+      if( !zFullPathname ){
+        sqlite3_free(p);
+        return SQLITE_NOMEM_BKPT;
+      }
+      if( isMemdb ){
+        memcpy(zFullPathname, zFilename, nFilename);
+      }else{
+        rc = sqlite3OsFullPathname(pVfs, zFilename,
+                                   nFullPathname, zFullPathname);
+        if( rc ){
+          if( rc==SQLITE_OK_SYMLINK ){
+            rc = SQLITE_OK;
+          }else{
+            sqlite3_free(zFullPathname);
+            sqlite3_free(p);
+            return rc;
+          }
+        }
+      }
+#if SQLITE_THREADSAFE
+      mutexOpen = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
+      sqlite3_mutex_enter(mutexOpen);
+      mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
+      sqlite3_mutex_enter(mutexShared);
+#endif
+      for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
+        assert( pBt->nRef>0 );
+        if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager, 0))
+                 && sqlite3PagerVfs(pBt->pPager)==pVfs ){
+          int iDb;
+          for(iDb=db->nDb-1; iDb>=0; iDb--){
+            Btree *pExisting = db->aDb[iDb].pBt;
+            if( pExisting && pExisting->pBt==pBt ){
+              sqlite3_mutex_leave(mutexShared);
+              sqlite3_mutex_leave(mutexOpen);
+              sqlite3_free(zFullPathname);
+              sqlite3_free(p);
+              return SQLITE_CONSTRAINT;
+            }
+          }
+          p->pBt = pBt;
+          pBt->nRef++;
+          break;
+        }
+      }
+      sqlite3_mutex_leave(mutexShared);
+      sqlite3_free(zFullPathname);
+    }
+#ifdef SQLITE_DEBUG
+    else{
+      /* In debug mode, we mark all persistent databases as sharable
+      ** even when they are not.  This exercises the locking code and
+      ** gives more opportunity for asserts(sqlite3_mutex_held())
+      ** statements to find locking problems.
+      */
+      p->sharable = 1;
+    }
+#endif
+  }
+#endif
+  if( pBt==0 ){
+    /*
+    ** The following asserts make sure that structures used by the btree are
+    ** the right size.  This is to guard against size changes that result
+    ** when compiling on a different architecture.
+    */
+    assert( sizeof(i64)==8 );
+    assert( sizeof(u64)==8 );
+    assert( sizeof(u32)==4 );
+    assert( sizeof(u16)==2 );
+    assert( sizeof(Pgno)==4 );
+
+    /* Suppress false-positive compiler warning from PVS-Studio */
+    memset(&zDbHeader[16], 0, 8);
+ 
+    pBt = sqlite3MallocZero( sizeof(*pBt) );
+    if( pBt==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+      goto btree_open_out;
+    }
+    rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
+                          sizeof(MemPage), flags, vfsFlags, pageReinit);
+    if( rc==SQLITE_OK ){
+      sqlite3PagerSetMmapLimit(pBt->pPager, db->szMmap);
+      rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
+    }
+    if( rc!=SQLITE_OK ){
+      goto btree_open_out;
+    }
+    pBt->openFlags = (u8)flags;
+    pBt->db = db;
+    sqlite3PagerSetBusyHandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
+    p->pBt = pBt;
+ 
+    pBt->pCursor = 0;
+    pBt->pPage1 = 0;
+    if( sqlite3PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
+#if defined(SQLITE_SECURE_DELETE)
+    pBt->btsFlags |= BTS_SECURE_DELETE;
+#elif defined(SQLITE_FAST_SECURE_DELETE)
+    pBt->btsFlags |= BTS_OVERWRITE;
+#endif
+    /* EVIDENCE-OF: R-51873-39618 The page size for a database file is
+    ** determined by the 2-byte integer located at an offset of 16 bytes from
+    ** the beginning of the database file. */
+    pBt->pageSize = (zDbHeader[16]<<8) | (zDbHeader[17]<<16);
+    if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
+         || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
+      pBt->pageSize = 0;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      /* If the magic name ":memory:" will create an in-memory database, then
+      ** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
+      ** SQLITE_DEFAULT_AUTOVACUUM is true. On the other hand, if
+      ** SQLITE_OMIT_MEMORYDB has been defined, then ":memory:" is just a
+      ** regular file-name. In this case the auto-vacuum applies as per normal.
+      */
+      if( zFilename && !isMemdb ){
+        pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
+        pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
+      }
+#endif
+      nReserve = 0;
+    }else{
+      /* EVIDENCE-OF: R-37497-42412 The size of the reserved region is
+      ** determined by the one-byte unsigned integer found at an offset of 20
+      ** into the database file header. */
+      nReserve = zDbHeader[20];
+      pBt->btsFlags |= BTS_PAGESIZE_FIXED;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
+      pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
+#endif
+    }
+    rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
+    if( rc ) goto btree_open_out;
+    pBt->usableSize = pBt->pageSize - nReserve;
+    assert( (pBt->pageSize & 7)==0 );  /* 8-byte alignment of pageSize */
+  
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
+    /* Add the new BtShared object to the linked list sharable BtShareds.
+    */
+    pBt->nRef = 1;
+    if( p->sharable ){
+      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
+      MUTEX_LOGIC( mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);)
+      if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
+        pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
+        if( pBt->mutex==0 ){
+          rc = SQLITE_NOMEM_BKPT;
+          goto btree_open_out;
+        }
+      }
+      sqlite3_mutex_enter(mutexShared);
+      pBt->pNext = GLOBAL(BtShared*,sqlite3SharedCacheList);
+      GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt;
+      sqlite3_mutex_leave(mutexShared);
+    }
+#endif
+  }
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
+  /* If the new Btree uses a sharable pBtShared, then link the new
+  ** Btree into the list of all sharable Btrees for the same connection.
+  ** The list is kept in ascending order by pBt address.
+  */
+  if( p->sharable ){
+    int i;
+    Btree *pSib;
+    for(i=0; i<db->nDb; i++){
+      if( (pSib = db->aDb[i].pBt)!=0 && pSib->sharable ){
+        while( pSib->pPrev ){ pSib = pSib->pPrev; }
+        if( (uptr)p->pBt<(uptr)pSib->pBt ){
+          p->pNext = pSib;
+          p->pPrev = 0;
+          pSib->pPrev = p;
+        }else{
+          while( pSib->pNext && (uptr)pSib->pNext->pBt<(uptr)p->pBt ){
+            pSib = pSib->pNext;
+          }
+          p->pNext = pSib->pNext;
+          p->pPrev = pSib;
+          if( p->pNext ){
+            p->pNext->pPrev = p;
+          }
+          pSib->pNext = p;
+        }
+        break;
+      }
+    }
+  }
+#endif
+  *ppBtree = p;
+
+btree_open_out:
+  if( rc!=SQLITE_OK ){
+    if( pBt && pBt->pPager ){
+      sqlite3PagerClose(pBt->pPager, 0);
+    }
+    sqlite3_free(pBt);
+    sqlite3_free(p);
+    *ppBtree = 0;
+  }else{
+    sqlite3_file *pFile;
+
+    /* If the B-Tree was successfully opened, set the pager-cache size to the
+    ** default value. Except, when opening on an existing shared pager-cache,
+    ** do not change the pager-cache size.
+    */
+    if( sqlite3BtreeSchema(p, 0, 0)==0 ){
+      sqlite3BtreeSetCacheSize(p, SQLITE_DEFAULT_CACHE_SIZE);
+    }
+
+    pFile = sqlite3PagerFile(pBt->pPager);
+    if( pFile->pMethods ){
+      sqlite3OsFileControlHint(pFile, SQLITE_FCNTL_PDB, (void*)&pBt->db);
+    }
+  }
+  if( mutexOpen ){
+    assert( sqlite3_mutex_held(mutexOpen) );
+    sqlite3_mutex_leave(mutexOpen);
+  }
+  assert( rc!=SQLITE_OK || sqlite3BtreeConnectionCount(*ppBtree)>0 );
+  return rc;
+}
+
+/*
+** Decrement the BtShared.nRef counter.  When it reaches zero,
+** remove the BtShared structure from the sharing list.  Return
+** true if the BtShared.nRef counter reaches zero and return
+** false if it is still positive.
+*/
+static int removeFromSharingList(BtShared *pBt){
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  MUTEX_LOGIC( sqlite3_mutex *pMainMtx; )
+  BtShared *pList;
+  int removed = 0;
+
+  assert( sqlite3_mutex_notheld(pBt->mutex) );
+  MUTEX_LOGIC( pMainMtx = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN); )
+  sqlite3_mutex_enter(pMainMtx);
+  pBt->nRef--;
+  if( pBt->nRef<=0 ){
+    if( GLOBAL(BtShared*,sqlite3SharedCacheList)==pBt ){
+      GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt->pNext;
+    }else{
+      pList = GLOBAL(BtShared*,sqlite3SharedCacheList);
+      while( ALWAYS(pList) && pList->pNext!=pBt ){
+        pList=pList->pNext;
+      }
+      if( ALWAYS(pList) ){
+        pList->pNext = pBt->pNext;
+      }
+    }
+    if( SQLITE_THREADSAFE ){
+      sqlite3_mutex_free(pBt->mutex);
+    }
+    removed = 1;
+  }
+  sqlite3_mutex_leave(pMainMtx);
+  return removed;
+#else
+  return 1;
+#endif
+}
+
+/*
+** Make sure pBt->pTmpSpace points to an allocation of
+** MX_CELL_SIZE(pBt) bytes with a 4-byte prefix for a left-child
+** pointer.
+*/
+static SQLITE_NOINLINE int allocateTempSpace(BtShared *pBt){
+  assert( pBt!=0 );
+  assert( pBt->pTmpSpace==0 );
+  /* This routine is called only by btreeCursor() when allocating the
+  ** first write cursor for the BtShared object */
+  assert( pBt->pCursor!=0 && (pBt->pCursor->curFlags & BTCF_WriteFlag)!=0 );
+  pBt->pTmpSpace = sqlite3PageMalloc( pBt->pageSize );
+  if( pBt->pTmpSpace==0 ){
+    BtCursor *pCur = pBt->pCursor;
+    pBt->pCursor = pCur->pNext;  /* Unlink the cursor */
+    memset(pCur, 0, sizeof(*pCur));
+    return SQLITE_NOMEM_BKPT;
+  }
+
+  /* One of the uses of pBt->pTmpSpace is to format cells before
+  ** inserting them into a leaf page (function fillInCell()). If
+  ** a cell is less than 4 bytes in size, it is rounded up to 4 bytes
+  ** by the various routines that manipulate binary cells. Which
+  ** can mean that fillInCell() only initializes the first 2 or 3
+  ** bytes of pTmpSpace, but that the first 4 bytes are copied from
+  ** it into a database page. This is not actually a problem, but it
+  ** does cause a valgrind error when the 1 or 2 bytes of uninitialized
+  ** data is passed to system call write(). So to avoid this error,
+  ** zero the first 4 bytes of temp space here.
+  **
+  ** Also:  Provide four bytes of initialized space before the
+  ** beginning of pTmpSpace as an area available to prepend the
+  ** left-child pointer to the beginning of a cell.
+  */
+  memset(pBt->pTmpSpace, 0, 8);
+  pBt->pTmpSpace += 4;
+  return SQLITE_OK;
+}
+
+/*
+** Free the pBt->pTmpSpace allocation
+*/
+static void freeTempSpace(BtShared *pBt){
+  if( pBt->pTmpSpace ){
+    pBt->pTmpSpace -= 4;
+    sqlite3PageFree(pBt->pTmpSpace);
+    pBt->pTmpSpace = 0;
+  }
+}
+
+/*
+** Close an open database and invalidate all cursors.
+*/
+int sqlite3BtreeClose(Btree *p){
+  BtShared *pBt = p->pBt;
+
+  /* Close all cursors opened via this handle.  */
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+
+  /* Verify that no other cursors have this Btree open */
+#ifdef SQLITE_DEBUG
+  {
+    BtCursor *pCur = pBt->pCursor;
+    while( pCur ){
+      BtCursor *pTmp = pCur;
+      pCur = pCur->pNext;
+      assert( pTmp->pBtree!=p );
+
+    }
+  }
+#endif
+
+  /* Rollback any active transaction and free the handle structure.
+  ** The call to sqlite3BtreeRollback() drops any table-locks held by
+  ** this handle.
+  */
+  sqlite3BtreeRollback(p, SQLITE_OK, 0);
+  sqlite3BtreeLeave(p);
+
+  /* If there are still other outstanding references to the shared-btree
+  ** structure, return now. The remainder of this procedure cleans
+  ** up the shared-btree.
+  */
+  assert( p->wantToLock==0 && p->locked==0 );
+  if( !p->sharable || removeFromSharingList(pBt) ){
+    /* The pBt is no longer on the sharing list, so we can access
+    ** it without having to hold the mutex.
+    **
+    ** Clean out and delete the BtShared object.
+    */
+    assert( !pBt->pCursor );
+    sqlite3PagerClose(pBt->pPager, p->db);
+    if( pBt->xFreeSchema && pBt->pSchema ){
+      pBt->xFreeSchema(pBt->pSchema);
+    }
+    sqlite3DbFree(0, pBt->pSchema);
+    freeTempSpace(pBt);
+    sqlite3_free(pBt);
+  }
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  assert( p->wantToLock==0 );
+  assert( p->locked==0 );
+  if( p->pPrev ) p->pPrev->pNext = p->pNext;
+  if( p->pNext ) p->pNext->pPrev = p->pPrev;
+#endif
+
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Change the "soft" limit on the number of pages in the cache.
+** Unused and unmodified pages will be recycled when the number of
+** pages in the cache exceeds this soft limit.  But the size of the
+** cache is allowed to grow larger than this limit if it contains
+** dirty pages or pages still in active use.
+*/
+int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
+  BtShared *pBt = p->pBt;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  sqlite3PagerSetCachesize(pBt->pPager, mxPage);
+  sqlite3BtreeLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Change the "spill" limit on the number of pages in the cache.
+** If the number of pages exceeds this limit during a write transaction,
+** the pager might attempt to "spill" pages to the journal early in
+** order to free up memory.
+**
+** The value returned is the current spill size.  If zero is passed
+** as an argument, no changes are made to the spill size setting, so
+** using mxPage of 0 is a way to query the current spill size.
+*/
+int sqlite3BtreeSetSpillSize(Btree *p, int mxPage){
+  BtShared *pBt = p->pBt;
+  int res;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  res = sqlite3PagerSetSpillsize(pBt->pPager, mxPage);
+  sqlite3BtreeLeave(p);
+  return res;
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/*
+** Change the limit on the amount of the database file that may be
+** memory mapped.
+*/
+int sqlite3BtreeSetMmapLimit(Btree *p, sqlite3_int64 szMmap){
+  BtShared *pBt = p->pBt;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  sqlite3PagerSetMmapLimit(pBt->pPager, szMmap);
+  sqlite3BtreeLeave(p);
+  return SQLITE_OK;
+}
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
+
+/*
+** Change the way data is synced to disk in order to increase or decrease
+** how well the database resists damage due to OS crashes and power
+** failures.  Level 1 is the same as asynchronous (no syncs() occur and
+** there is a high probability of damage)  Level 2 is the default.  There
+** is a very low but non-zero probability of damage.  Level 3 reduces the
+** probability of damage to near zero but with a write performance reduction.
+*/
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+int sqlite3BtreeSetPagerFlags(
+  Btree *p,              /* The btree to set the safety level on */
+  unsigned pgFlags       /* Various PAGER_* flags */
+){
+  BtShared *pBt = p->pBt;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  sqlite3PagerSetFlags(pBt->pPager, pgFlags);
+  sqlite3BtreeLeave(p);
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Change the default pages size and the number of reserved bytes per page.
+** Or, if the page size has already been fixed, return SQLITE_READONLY
+** without changing anything.
+**
+** The page size must be a power of 2 between 512 and 65536.  If the page
+** size supplied does not meet this constraint then the page size is not
+** changed.
+**
+** Page sizes are constrained to be a power of two so that the region
+** of the database file used for locking (beginning at PENDING_BYTE,
+** the first byte past the 1GB boundary, 0x40000000) needs to occur
+** at the beginning of a page.
+**
+** If parameter nReserve is less than zero, then the number of reserved
+** bytes per page is left unchanged.
+**
+** If the iFix!=0 then the BTS_PAGESIZE_FIXED flag is set so that the page size
+** and autovacuum mode can no longer be changed.
+*/
+int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
+  int rc = SQLITE_OK;
+  int x;
+  BtShared *pBt = p->pBt;
+  assert( nReserve>=0 && nReserve<=255 );
+  sqlite3BtreeEnter(p);
+  pBt->nReserveWanted = nReserve;
+  x = pBt->pageSize - pBt->usableSize;
+  if( nReserve<x ) nReserve = x;
+  if( pBt->btsFlags & BTS_PAGESIZE_FIXED ){
+    sqlite3BtreeLeave(p);
+    return SQLITE_READONLY;
+  }
+  assert( nReserve>=0 && nReserve<=255 );
+  if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
+        ((pageSize-1)&pageSize)==0 ){
+    assert( (pageSize & 7)==0 );
+    assert( !pBt->pCursor );
+    if( nReserve>32 && pageSize==512 ) pageSize = 1024;
+    pBt->pageSize = (u32)pageSize;
+    freeTempSpace(pBt);
+  }
+  rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
+  pBt->usableSize = pBt->pageSize - (u16)nReserve;
+  if( iFix ) pBt->btsFlags |= BTS_PAGESIZE_FIXED;
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Return the currently defined page size
+*/
+int sqlite3BtreeGetPageSize(Btree *p){
+  return p->pBt->pageSize;
+}
+
+/*
+** This function is similar to sqlite3BtreeGetReserve(), except that it
+** may only be called if it is guaranteed that the b-tree mutex is already
+** held.
+**
+** This is useful in one special case in the backup API code where it is
+** known that the shared b-tree mutex is held, but the mutex on the
+** database handle that owns *p is not. In this case if sqlite3BtreeEnter()
+** were to be called, it might collide with some other operation on the
+** database handle that owns *p, causing undefined behavior.
+*/
+int sqlite3BtreeGetReserveNoMutex(Btree *p){
+  int n;
+  assert( sqlite3_mutex_held(p->pBt->mutex) );
+  n = p->pBt->pageSize - p->pBt->usableSize;
+  return n;
+}
+
+/*
+** Return the number of bytes of space at the end of every page that
+** are intentionally left unused.  This is the "reserved" space that is
+** sometimes used by extensions.
+**
+** The value returned is the larger of the current reserve size and
+** the latest reserve size requested by SQLITE_FILECTRL_RESERVE_BYTES.
+** The amount of reserve can only grow - never shrink.
+*/
+int sqlite3BtreeGetRequestedReserve(Btree *p){
+  int n1, n2;
+  sqlite3BtreeEnter(p);
+  n1 = (int)p->pBt->nReserveWanted;
+  n2 = sqlite3BtreeGetReserveNoMutex(p);
+  sqlite3BtreeLeave(p);
+  return n1>n2 ? n1 : n2;
+}
+
+
+/*
+** Set the maximum page count for a database if mxPage is positive.
+** No changes are made if mxPage is 0 or negative.
+** Regardless of the value of mxPage, return the maximum page count.
+*/
+Pgno sqlite3BtreeMaxPageCount(Btree *p, Pgno mxPage){
+  Pgno n;
+  sqlite3BtreeEnter(p);
+  n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
+  sqlite3BtreeLeave(p);
+  return n;
+}
+
+/*
+** Change the values for the BTS_SECURE_DELETE and BTS_OVERWRITE flags:
+**
+**    newFlag==0       Both BTS_SECURE_DELETE and BTS_OVERWRITE are cleared
+**    newFlag==1       BTS_SECURE_DELETE set and BTS_OVERWRITE is cleared
+**    newFlag==2       BTS_SECURE_DELETE cleared and BTS_OVERWRITE is set
+**    newFlag==(-1)    No changes
+**
+** This routine acts as a query if newFlag is less than zero
+**
+** With BTS_OVERWRITE set, deleted content is overwritten by zeros, but
+** freelist leaf pages are not written back to the database.  Thus in-page
+** deleted content is cleared, but freelist deleted content is not.
+**
+** With BTS_SECURE_DELETE, operation is like BTS_OVERWRITE with the addition
+** that freelist leaf pages are written back into the database, increasing
+** the amount of disk I/O.
+*/
+int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
+  int b;
+  if( p==0 ) return 0;
+  sqlite3BtreeEnter(p);
+  assert( BTS_OVERWRITE==BTS_SECURE_DELETE*2 );
+  assert( BTS_FAST_SECURE==(BTS_OVERWRITE|BTS_SECURE_DELETE) );
+  if( newFlag>=0 ){
+    p->pBt->btsFlags &= ~BTS_FAST_SECURE;
+    p->pBt->btsFlags |= BTS_SECURE_DELETE*newFlag;
+  }
+  b = (p->pBt->btsFlags & BTS_FAST_SECURE)/BTS_SECURE_DELETE;
+  sqlite3BtreeLeave(p);
+  return b;
+}
+
+/*
+** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
+** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
+** is disabled. The default value for the auto-vacuum property is
+** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
+*/
+int sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  return SQLITE_READONLY;
+#else
+  BtShared *pBt = p->pBt;
+  int rc = SQLITE_OK;
+  u8 av = (u8)autoVacuum;
+
+  sqlite3BtreeEnter(p);
+  if( (pBt->btsFlags & BTS_PAGESIZE_FIXED)!=0 && (av ?1:0)!=pBt->autoVacuum ){
+    rc = SQLITE_READONLY;
+  }else{
+    pBt->autoVacuum = av ?1:0;
+    pBt->incrVacuum = av==2 ?1:0;
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+#endif
+}
+
+/*
+** Return the value of the 'auto-vacuum' property. If auto-vacuum is
+** enabled 1 is returned. Otherwise 0.
+*/
+int sqlite3BtreeGetAutoVacuum(Btree *p){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  return BTREE_AUTOVACUUM_NONE;
+#else
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = (
+    (!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
+    (!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
+    BTREE_AUTOVACUUM_INCR
+  );
+  sqlite3BtreeLeave(p);
+  return rc;
+#endif
+}
+
+/*
+** If the user has not set the safety-level for this database connection
+** using "PRAGMA synchronous", and if the safety-level is not already
+** set to the value passed to this function as the second parameter,
+** set it so.
+*/
+#if SQLITE_DEFAULT_SYNCHRONOUS!=SQLITE_DEFAULT_WAL_SYNCHRONOUS \
+    && !defined(SQLITE_OMIT_WAL)
+static void setDefaultSyncFlag(BtShared *pBt, u8 safety_level){
+  sqlite3 *db;
+  Db *pDb;
+  if( (db=pBt->db)!=0 && (pDb=db->aDb)!=0 ){
+    while( pDb->pBt==0 || pDb->pBt->pBt!=pBt ){ pDb++; }
+    if( pDb->bSyncSet==0
+     && pDb->safety_level!=safety_level
+     && pDb!=&db->aDb[1]
+    ){
+      pDb->safety_level = safety_level;
+      sqlite3PagerSetFlags(pBt->pPager,
+          pDb->safety_level | (db->flags & PAGER_FLAGS_MASK));
+    }
+  }
+}
+#else
+# define setDefaultSyncFlag(pBt,safety_level)
+#endif
+
+/* Forward declaration */
+static int newDatabase(BtShared*);
+
+
+/*
+** Get a reference to pPage1 of the database file.  This will
+** also acquire a readlock on that file.
+**
+** SQLITE_OK is returned on success.  If the file is not a
+** well-formed database file, then SQLITE_CORRUPT is returned.
+** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
+** is returned if we run out of memory.
+*/
+static int lockBtree(BtShared *pBt){
+  int rc;              /* Result code from subfunctions */
+  MemPage *pPage1;     /* Page 1 of the database file */
+  u32 nPage;           /* Number of pages in the database */
+  u32 nPageFile = 0;   /* Number of pages in the database file */
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( pBt->pPage1==0 );
+  rc = sqlite3PagerSharedLock(pBt->pPager);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = btreeGetPage(pBt, 1, &pPage1, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Do some checking to help insure the file we opened really is
+  ** a valid database file.
+  */
+  nPage = get4byte(28+(u8*)pPage1->aData);
+  sqlite3PagerPagecount(pBt->pPager, (int*)&nPageFile);
+  if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
+    nPage = nPageFile;
+  }
+  if( (pBt->db->flags & SQLITE_ResetDatabase)!=0 ){
+    nPage = 0;
+  }
+  if( nPage>0 ){
+    u32 pageSize;
+    u32 usableSize;
+    u8 *page1 = pPage1->aData;
+    rc = SQLITE_NOTADB;
+    /* EVIDENCE-OF: R-43737-39999 Every valid SQLite database file begins
+    ** with the following 16 bytes (in hex): 53 51 4c 69 74 65 20 66 6f 72 6d
+    ** 61 74 20 33 00. */
+    if( memcmp(page1, zMagicHeader, 16)!=0 ){
+      goto page1_init_failed;
+    }
+
+#ifdef SQLITE_OMIT_WAL
+    if( page1[18]>1 ){
+      pBt->btsFlags |= BTS_READ_ONLY;
+    }
+    if( page1[19]>1 ){
+      goto page1_init_failed;
+    }
+#else
+    if( page1[18]>2 ){
+      pBt->btsFlags |= BTS_READ_ONLY;
+    }
+    if( page1[19]>2 ){
+      goto page1_init_failed;
+    }
+
+    /* If the read version is set to 2, this database should be accessed
+    ** in WAL mode. If the log is not already open, open it now. Then
+    ** return SQLITE_OK and return without populating BtShared.pPage1.
+    ** The caller detects this and calls this function again. This is
+    ** required as the version of page 1 currently in the page1 buffer
+    ** may not be the latest version - there may be a newer one in the log
+    ** file.
+    */
+    if( page1[19]==2 && (pBt->btsFlags & BTS_NO_WAL)==0 ){
+      int isOpen = 0;
+      rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
+      if( rc!=SQLITE_OK ){
+        goto page1_init_failed;
+      }else{
+        setDefaultSyncFlag(pBt, SQLITE_DEFAULT_WAL_SYNCHRONOUS+1);
+        if( isOpen==0 ){
+          releasePageOne(pPage1);
+          return SQLITE_OK;
+        }
+      }
+      rc = SQLITE_NOTADB;
+    }else{
+      setDefaultSyncFlag(pBt, SQLITE_DEFAULT_SYNCHRONOUS+1);
+    }
+#endif
+
+    /* EVIDENCE-OF: R-15465-20813 The maximum and minimum embedded payload
+    ** fractions and the leaf payload fraction values must be 64, 32, and 32.
+    **
+    ** The original design allowed these amounts to vary, but as of
+    ** version 3.6.0, we require them to be fixed.
+    */
+    if( memcmp(&page1[21], "\100\040\040",3)!=0 ){
+      goto page1_init_failed;
+    }
+    /* EVIDENCE-OF: R-51873-39618 The page size for a database file is
+    ** determined by the 2-byte integer located at an offset of 16 bytes from
+    ** the beginning of the database file. */
+    pageSize = (page1[16]<<8) | (page1[17]<<16);
+    /* EVIDENCE-OF: R-25008-21688 The size of a page is a power of two
+    ** between 512 and 65536 inclusive. */
+    if( ((pageSize-1)&pageSize)!=0
+     || pageSize>SQLITE_MAX_PAGE_SIZE
+     || pageSize<=256
+    ){
+      goto page1_init_failed;
+    }
+    assert( (pageSize & 7)==0 );
+    /* EVIDENCE-OF: R-59310-51205 The "reserved space" size in the 1-byte
+    ** integer at offset 20 is the number of bytes of space at the end of
+    ** each page to reserve for extensions.
+    **
+    ** EVIDENCE-OF: R-37497-42412 The size of the reserved region is
+    ** determined by the one-byte unsigned integer found at an offset of 20
+    ** into the database file header. */
+    usableSize = pageSize - page1[20];
+    if( (u32)pageSize!=pBt->pageSize ){
+      /* After reading the first page of the database assuming a page size
+      ** of BtShared.pageSize, we have discovered that the page-size is
+      ** actually pageSize. Unlock the database, leave pBt->pPage1 at
+      ** zero and return SQLITE_OK. The caller will call this function
+      ** again with the correct page-size.
+      */
+      releasePageOne(pPage1);
+      pBt->usableSize = usableSize;
+      pBt->pageSize = pageSize;
+      pBt->btsFlags |= BTS_PAGESIZE_FIXED;
+      freeTempSpace(pBt);
+      rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize,
+                                   pageSize-usableSize);
+      return rc;
+    }
+    if( nPage>nPageFile ){
+      if( sqlite3WritableSchema(pBt->db)==0 ){
+        rc = SQLITE_CORRUPT_BKPT;
+        goto page1_init_failed;
+      }else{
+        nPage = nPageFile;
+      }
+    }
+    /* EVIDENCE-OF: R-28312-64704 However, the usable size is not allowed to
+    ** be less than 480. In other words, if the page size is 512, then the
+    ** reserved space size cannot exceed 32. */
+    if( usableSize<480 ){
+      goto page1_init_failed;
+    }
+    pBt->btsFlags |= BTS_PAGESIZE_FIXED;
+    pBt->pageSize = pageSize;
+    pBt->usableSize = usableSize;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
+    pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
+#endif
+  }
+
+  /* maxLocal is the maximum amount of payload to store locally for
+  ** a cell.  Make sure it is small enough so that at least minFanout
+  ** cells can will fit on one page.  We assume a 10-byte page header.
+  ** Besides the payload, the cell must store:
+  **     2-byte pointer to the cell
+  **     4-byte child pointer
+  **     9-byte nKey value
+  **     4-byte nData value
+  **     4-byte overflow page pointer
+  ** So a cell consists of a 2-byte pointer, a header which is as much as
+  ** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
+  ** page pointer.
+  */
+  pBt->maxLocal = (u16)((pBt->usableSize-12)*64/255 - 23);
+  pBt->minLocal = (u16)((pBt->usableSize-12)*32/255 - 23);
+  pBt->maxLeaf = (u16)(pBt->usableSize - 35);
+  pBt->minLeaf = (u16)((pBt->usableSize-12)*32/255 - 23);
+  if( pBt->maxLocal>127 ){
+    pBt->max1bytePayload = 127;
+  }else{
+    pBt->max1bytePayload = (u8)pBt->maxLocal;
+  }
+  assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
+  pBt->pPage1 = pPage1;
+  pBt->nPage = nPage;
+  return SQLITE_OK;
+
+page1_init_failed:
+  releasePageOne(pPage1);
+  pBt->pPage1 = 0;
+  return rc;
+}
+
+#ifndef NDEBUG
+/*
+** Return the number of cursors open on pBt. This is for use
+** in assert() expressions, so it is only compiled if NDEBUG is not
+** defined.
+**
+** Only write cursors are counted if wrOnly is true.  If wrOnly is
+** false then all cursors are counted.
+**
+** For the purposes of this routine, a cursor is any cursor that
+** is capable of reading or writing to the database.  Cursors that
+** have been tripped into the CURSOR_FAULT state are not counted.
+*/
+static int countValidCursors(BtShared *pBt, int wrOnly){
+  BtCursor *pCur;
+  int r = 0;
+  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
+    if( (wrOnly==0 || (pCur->curFlags & BTCF_WriteFlag)!=0)
+     && pCur->eState!=CURSOR_FAULT ) r++;
+  }
+  return r;
+}
+#endif
+
+/*
+** If there are no outstanding cursors and we are not in the middle
+** of a transaction but there is a read lock on the database, then
+** this routine unrefs the first page of the database file which
+** has the effect of releasing the read lock.
+**
+** If there is a transaction in progress, this routine is a no-op.
+*/
+static void unlockBtreeIfUnused(BtShared *pBt){
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( countValidCursors(pBt,0)==0 || pBt->inTransaction>TRANS_NONE );
+  if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
+    MemPage *pPage1 = pBt->pPage1;
+    assert( pPage1->aData );
+    assert( sqlite3PagerRefcount(pBt->pPager)==1 );
+    pBt->pPage1 = 0;
+    releasePageOne(pPage1);
+  }
+}
+
+/*
+** If pBt points to an empty file then convert that empty file
+** into a new empty database by initializing the first page of
+** the database.
+*/
+static int newDatabase(BtShared *pBt){
+  MemPage *pP1;
+  unsigned char *data;
+  int rc;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pBt->nPage>0 ){
+    return SQLITE_OK;
+  }
+  pP1 = pBt->pPage1;
+  assert( pP1!=0 );
+  data = pP1->aData;
+  rc = sqlite3PagerWrite(pP1->pDbPage);
+  if( rc ) return rc;
+  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
+  assert( sizeof(zMagicHeader)==16 );
+  data[16] = (u8)((pBt->pageSize>>8)&0xff);
+  data[17] = (u8)((pBt->pageSize>>16)&0xff);
+  data[18] = 1;
+  data[19] = 1;
+  assert( pBt->usableSize<=pBt->pageSize && pBt->usableSize+255>=pBt->pageSize);
+  data[20] = (u8)(pBt->pageSize - pBt->usableSize);
+  data[21] = 64;
+  data[22] = 32;
+  data[23] = 32;
+  memset(&data[24], 0, 100-24);
+  zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
+  pBt->btsFlags |= BTS_PAGESIZE_FIXED;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
+  assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
+  put4byte(&data[36 + 4*4], pBt->autoVacuum);
+  put4byte(&data[36 + 7*4], pBt->incrVacuum);
+#endif
+  pBt->nPage = 1;
+  data[31] = 1;
+  return SQLITE_OK;
+}
+
+/*
+** Initialize the first page of the database file (creating a database
+** consisting of a single page and no schema objects). Return SQLITE_OK
+** if successful, or an SQLite error code otherwise.
+*/
+int sqlite3BtreeNewDb(Btree *p){
+  int rc;
+  sqlite3BtreeEnter(p);
+  p->pBt->nPage = 0;
+  rc = newDatabase(p->pBt);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Attempt to start a new transaction. A write-transaction
+** is started if the second argument is nonzero, otherwise a read-
+** transaction.  If the second argument is 2 or more and exclusive
+** transaction is started, meaning that no other process is allowed
+** to access the database.  A preexisting transaction may not be
+** upgraded to exclusive by calling this routine a second time - the
+** exclusivity flag only works for a new transaction.
+**
+** A write-transaction must be started before attempting any
+** changes to the database.  None of the following routines
+** will work unless a transaction is started first:
+**
+**      sqlite3BtreeCreateTable()
+**      sqlite3BtreeCreateIndex()
+**      sqlite3BtreeClearTable()
+**      sqlite3BtreeDropTable()
+**      sqlite3BtreeInsert()
+**      sqlite3BtreeDelete()
+**      sqlite3BtreeUpdateMeta()
+**
+** If an initial attempt to acquire the lock fails because of lock contention
+** and the database was previously unlocked, then invoke the busy handler
+** if there is one.  But if there was previously a read-lock, do not
+** invoke the busy handler - just return SQLITE_BUSY.  SQLITE_BUSY is
+** returned when there is already a read-lock in order to avoid a deadlock.
+**
+** Suppose there are two processes A and B.  A has a read lock and B has
+** a reserved lock.  B tries to promote to exclusive but is blocked because
+** of A's read lock.  A tries to promote to reserved but is blocked by B.
+** One or the other of the two processes must give way or there can be
+** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
+** when A already has a read lock, we encourage A to give up and let B
+** proceed.
+*/
+static SQLITE_NOINLINE int btreeBeginTrans(
+  Btree *p,                 /* The btree in which to start the transaction */
+  int wrflag,               /* True to start a write transaction */
+  int *pSchemaVersion       /* Put schema version number here, if not NULL */
+){
+  BtShared *pBt = p->pBt;
+  Pager *pPager = pBt->pPager;
+  int rc = SQLITE_OK;
+
+  sqlite3BtreeEnter(p);
+  btreeIntegrity(p);
+
+  /* If the btree is already in a write-transaction, or it
+  ** is already in a read-transaction and a read-transaction
+  ** is requested, this is a no-op.
+  */
+  if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
+    goto trans_begun;
+  }
+  assert( pBt->inTransaction==TRANS_WRITE || IfNotOmitAV(pBt->bDoTruncate)==0 );
+
+  if( (p->db->flags & SQLITE_ResetDatabase)
+   && sqlite3PagerIsreadonly(pPager)==0
+  ){
+    pBt->btsFlags &= ~BTS_READ_ONLY;
+  }
+
+  /* Write transactions are not possible on a read-only database */
+  if( (pBt->btsFlags & BTS_READ_ONLY)!=0 && wrflag ){
+    rc = SQLITE_READONLY;
+    goto trans_begun;
+  }
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  {
+    sqlite3 *pBlock = 0;
+    /* If another database handle has already opened a write transaction
+    ** on this shared-btree structure and a second write transaction is
+    ** requested, return SQLITE_LOCKED.
+    */
+    if( (wrflag && pBt->inTransaction==TRANS_WRITE)
+     || (pBt->btsFlags & BTS_PENDING)!=0
+    ){
+      pBlock = pBt->pWriter->db;
+    }else if( wrflag>1 ){
+      BtLock *pIter;
+      for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
+        if( pIter->pBtree!=p ){
+          pBlock = pIter->pBtree->db;
+          break;
+        }
+      }
+    }
+    if( pBlock ){
+      sqlite3ConnectionBlocked(p->db, pBlock);
+      rc = SQLITE_LOCKED_SHAREDCACHE;
+      goto trans_begun;
+    }
+  }
+#endif
+
+  /* Any read-only or read-write transaction implies a read-lock on
+  ** page 1. So if some other shared-cache client already has a write-lock
+  ** on page 1, the transaction cannot be opened. */
+  rc = querySharedCacheTableLock(p, SCHEMA_ROOT, READ_LOCK);
+  if( SQLITE_OK!=rc ) goto trans_begun;
+
+  pBt->btsFlags &= ~BTS_INITIALLY_EMPTY;
+  if( pBt->nPage==0 ) pBt->btsFlags |= BTS_INITIALLY_EMPTY;
+  do {
+    sqlite3PagerWalDb(pPager, p->db);
+
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    /* If transitioning from no transaction directly to a write transaction,
+    ** block for the WRITER lock first if possible. */
+    if( pBt->pPage1==0 && wrflag ){
+      assert( pBt->inTransaction==TRANS_NONE );
+      rc = sqlite3PagerWalWriteLock(pPager, 1);
+      if( rc!=SQLITE_BUSY && rc!=SQLITE_OK ) break;
+    }
+#endif
+
+    /* Call lockBtree() until either pBt->pPage1 is populated or
+    ** lockBtree() returns something other than SQLITE_OK. lockBtree()
+    ** may return SQLITE_OK but leave pBt->pPage1 set to 0 if after
+    ** reading page 1 it discovers that the page-size of the database
+    ** file is not pBt->pageSize. In this case lockBtree() will update
+    ** pBt->pageSize to the page-size of the file on disk.
+    */
+    while( pBt->pPage1==0 && SQLITE_OK==(rc = lockBtree(pBt)) );
+
+    if( rc==SQLITE_OK && wrflag ){
+      if( (pBt->btsFlags & BTS_READ_ONLY)!=0 ){
+        rc = SQLITE_READONLY;
+      }else{
+        rc = sqlite3PagerBegin(pPager, wrflag>1, sqlite3TempInMemory(p->db));
+        if( rc==SQLITE_OK ){
+          rc = newDatabase(pBt);
+        }else if( rc==SQLITE_BUSY_SNAPSHOT && pBt->inTransaction==TRANS_NONE ){
+          /* if there was no transaction opened when this function was
+          ** called and SQLITE_BUSY_SNAPSHOT is returned, change the error
+          ** code to SQLITE_BUSY. */
+          rc = SQLITE_BUSY;
+        }
+      }
+    }
+ 
+    if( rc!=SQLITE_OK ){
+      (void)sqlite3PagerWalWriteLock(pPager, 0);
+      unlockBtreeIfUnused(pBt);
+    }
+  }while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
+          btreeInvokeBusyHandler(pBt) );
+  sqlite3PagerWalDb(pPager, 0);
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  if( rc==SQLITE_BUSY_TIMEOUT ) rc = SQLITE_BUSY;
+#endif
+
+  if( rc==SQLITE_OK ){
+    if( p->inTrans==TRANS_NONE ){
+      pBt->nTransaction++;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+      if( p->sharable ){
+        assert( p->lock.pBtree==p && p->lock.iTable==1 );
+        p->lock.eLock = READ_LOCK;
+        p->lock.pNext = pBt->pLock;
+        pBt->pLock = &p->lock;
+      }
+#endif
+    }
+    p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
+    if( p->inTrans>pBt->inTransaction ){
+      pBt->inTransaction = p->inTrans;
+    }
+    if( wrflag ){
+      MemPage *pPage1 = pBt->pPage1;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+      assert( !pBt->pWriter );
+      pBt->pWriter = p;
+      pBt->btsFlags &= ~BTS_EXCLUSIVE;
+      if( wrflag>1 ) pBt->btsFlags |= BTS_EXCLUSIVE;
+#endif
+
+      /* If the db-size header field is incorrect (as it may be if an old
+      ** client has been writing the database file), update it now. Doing
+      ** this sooner rather than later means the database size can safely
+      ** re-read the database size from page 1 if a savepoint or transaction
+      ** rollback occurs within the transaction.
+      */
+      if( pBt->nPage!=get4byte(&pPage1->aData[28]) ){
+        rc = sqlite3PagerWrite(pPage1->pDbPage);
+        if( rc==SQLITE_OK ){
+          put4byte(&pPage1->aData[28], pBt->nPage);
+        }
+      }
+    }
+  }
+
+trans_begun:
+  if( rc==SQLITE_OK ){
+    if( pSchemaVersion ){
+      *pSchemaVersion = get4byte(&pBt->pPage1->aData[40]);
+    }
+    if( wrflag ){
+      /* This call makes sure that the pager has the correct number of
+      ** open savepoints. If the second parameter is greater than 0 and
+      ** the sub-journal is not already open, then it will be opened here.
+      */
+      rc = sqlite3PagerOpenSavepoint(pPager, p->db->nSavepoint);
+    }
+  }
+
+  btreeIntegrity(p);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+int sqlite3BtreeBeginTrans(Btree *p, int wrflag, int *pSchemaVersion){
+  BtShared *pBt;
+  if( p->sharable
+   || p->inTrans==TRANS_NONE
+   || (p->inTrans==TRANS_READ && wrflag!=0)
+  ){
+    return btreeBeginTrans(p,wrflag,pSchemaVersion);
+  }
+  pBt = p->pBt;
+  if( pSchemaVersion ){
+    *pSchemaVersion = get4byte(&pBt->pPage1->aData[40]);
+  }
+  if( wrflag ){
+    /* This call makes sure that the pager has the correct number of
+    ** open savepoints. If the second parameter is greater than 0 and
+    ** the sub-journal is not already open, then it will be opened here.
+    */
+    return sqlite3PagerOpenSavepoint(pBt->pPager, p->db->nSavepoint);
+  }else{
+    return SQLITE_OK;
+  }
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+
+/*
+** Set the pointer-map entries for all children of page pPage. Also, if
+** pPage contains cells that point to overflow pages, set the pointer
+** map entries for the overflow pages as well.
+*/
+static int setChildPtrmaps(MemPage *pPage){
+  int i;                             /* Counter variable */
+  int nCell;                         /* Number of cells in page pPage */
+  int rc;                            /* Return code */
+  BtShared *pBt = pPage->pBt;
+  Pgno pgno = pPage->pgno;
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  rc = pPage->isInit ? SQLITE_OK : btreeInitPage(pPage);
+  if( rc!=SQLITE_OK ) return rc;
+  nCell = pPage->nCell;
+
+  for(i=0; i<nCell; i++){
+    u8 *pCell = findCell(pPage, i);
+
+    ptrmapPutOvflPtr(pPage, pPage, pCell, &rc);
+
+    if( !pPage->leaf ){
+      Pgno childPgno = get4byte(pCell);
+      ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
+    }
+  }
+
+  if( !pPage->leaf ){
+    Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
+  }
+
+  return rc;
+}
+
+/*
+** Somewhere on pPage is a pointer to page iFrom.  Modify this pointer so
+** that it points to iTo. Parameter eType describes the type of pointer to
+** be modified, as  follows:
+**
+** PTRMAP_BTREE:     pPage is a btree-page. The pointer points at a child
+**                   page of pPage.
+**
+** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
+**                   page pointed to by one of the cells on pPage.
+**
+** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
+**                   overflow page in the list.
+*/
+static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  if( eType==PTRMAP_OVERFLOW2 ){
+    /* The pointer is always the first 4 bytes of the page in this case.  */
+    if( get4byte(pPage->aData)!=iFrom ){
+      return SQLITE_CORRUPT_PAGE(pPage);
+    }
+    put4byte(pPage->aData, iTo);
+  }else{
+    int i;
+    int nCell;
+    int rc;
+
+    rc = pPage->isInit ? SQLITE_OK : btreeInitPage(pPage);
+    if( rc ) return rc;
+    nCell = pPage->nCell;
+
+    for(i=0; i<nCell; i++){
+      u8 *pCell = findCell(pPage, i);
+      if( eType==PTRMAP_OVERFLOW1 ){
+        CellInfo info;
+        pPage->xParseCell(pPage, pCell, &info);
+        if( info.nLocal<info.nPayload ){
+          if( pCell+info.nSize > pPage->aData+pPage->pBt->usableSize ){
+            return SQLITE_CORRUPT_PAGE(pPage);
+          }
+          if( iFrom==get4byte(pCell+info.nSize-4) ){
+            put4byte(pCell+info.nSize-4, iTo);
+            break;
+          }
+        }
+      }else{
+        if( pCell+4 > pPage->aData+pPage->pBt->usableSize ){
+          return SQLITE_CORRUPT_PAGE(pPage);
+        }
+        if( get4byte(pCell)==iFrom ){
+          put4byte(pCell, iTo);
+          break;
+        }
+      }
+    }
+ 
+    if( i==nCell ){
+      if( eType!=PTRMAP_BTREE ||
+          get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
+    }
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** Move the open database page pDbPage to location iFreePage in the
+** database. The pDbPage reference remains valid.
+**
+** The isCommit flag indicates that there is no need to remember that
+** the journal needs to be sync()ed before database page pDbPage->pgno
+** can be written to. The caller has already promised not to write to that
+** page.
+*/
+static int relocatePage(
+  BtShared *pBt,           /* Btree */
+  MemPage *pDbPage,        /* Open page to move */
+  u8 eType,                /* Pointer map 'type' entry for pDbPage */
+  Pgno iPtrPage,           /* Pointer map 'page-no' entry for pDbPage */
+  Pgno iFreePage,          /* The location to move pDbPage to */
+  int isCommit             /* isCommit flag passed to sqlite3PagerMovepage */
+){
+  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
+  Pgno iDbPage = pDbPage->pgno;
+  Pager *pPager = pBt->pPager;
+  int rc;
+
+  assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 ||
+      eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( pDbPage->pBt==pBt );
+  if( iDbPage<3 ) return SQLITE_CORRUPT_BKPT;
+
+  /* Move page iDbPage from its current location to page number iFreePage */
+  TRACE(("AUTOVACUUM: Moving %u to free page %u (ptr page %u type %u)\n",
+      iDbPage, iFreePage, iPtrPage, eType));
+  rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage, isCommit);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  pDbPage->pgno = iFreePage;
+
+  /* If pDbPage was a btree-page, then it may have child pages and/or cells
+  ** that point to overflow pages. The pointer map entries for all these
+  ** pages need to be changed.
+  **
+  ** If pDbPage is an overflow page, then the first 4 bytes may store a
+  ** pointer to a subsequent overflow page. If this is the case, then
+  ** the pointer map needs to be updated for the subsequent overflow page.
+  */
+  if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
+    rc = setChildPtrmaps(pDbPage);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }else{
+    Pgno nextOvfl = get4byte(pDbPage->aData);
+    if( nextOvfl!=0 ){
+      ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage, &rc);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+  }
+
+  /* Fix the database pointer on page iPtrPage that pointed at iDbPage so
+  ** that it points at iFreePage. Also fix the pointer map entry for
+  ** iPtrPage.
+  */
+  if( eType!=PTRMAP_ROOTPAGE ){
+    rc = btreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    rc = sqlite3PagerWrite(pPtrPage->pDbPage);
+    if( rc!=SQLITE_OK ){
+      releasePage(pPtrPage);
+      return rc;
+    }
+    rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
+    releasePage(pPtrPage);
+    if( rc==SQLITE_OK ){
+      ptrmapPut(pBt, iFreePage, eType, iPtrPage, &rc);
+    }
+  }
+  return rc;
+}
+
+/* Forward declaration required by incrVacuumStep(). */
+static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
+
+/*
+** Perform a single step of an incremental-vacuum. If successful, return
+** SQLITE_OK. If there is no work to do (and therefore no point in
+** calling this function again), return SQLITE_DONE. Or, if an error
+** occurs, return some other error code.
+**
+** More specifically, this function attempts to re-organize the database so
+** that the last page of the file currently in use is no longer in use.
+**
+** Parameter nFin is the number of pages that this database would contain
+** were this function called until it returns SQLITE_DONE.
+**
+** If the bCommit parameter is non-zero, this function assumes that the
+** caller will keep calling incrVacuumStep() until it returns SQLITE_DONE
+** or an error. bCommit is passed true for an auto-vacuum-on-commit
+** operation, or false for an incremental vacuum.
+*/
+static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg, int bCommit){
+  Pgno nFreeList;           /* Number of pages still on the free-list */
+  int rc;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( iLastPg>nFin );
+
+  if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
+    u8 eType;
+    Pgno iPtrPage;
+
+    nFreeList = get4byte(&pBt->pPage1->aData[36]);
+    if( nFreeList==0 ){
+      return SQLITE_DONE;
+    }
+
+    rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    if( eType==PTRMAP_ROOTPAGE ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+
+    if( eType==PTRMAP_FREEPAGE ){
+      if( bCommit==0 ){
+        /* Remove the page from the files free-list. This is not required
+        ** if bCommit is non-zero. In that case, the free-list will be
+        ** truncated to zero after this function returns, so it doesn't
+        ** matter if it still contains some garbage entries.
+        */
+        Pgno iFreePg;
+        MemPage *pFreePg;
+        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, BTALLOC_EXACT);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        assert( iFreePg==iLastPg );
+        releasePage(pFreePg);
+      }
+    } else {
+      Pgno iFreePg;             /* Index of free page to move pLastPg to */
+      MemPage *pLastPg;
+      u8 eMode = BTALLOC_ANY;   /* Mode parameter for allocateBtreePage() */
+      Pgno iNear = 0;           /* nearby parameter for allocateBtreePage() */
+
+      rc = btreeGetPage(pBt, iLastPg, &pLastPg, 0);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+
+      /* If bCommit is zero, this loop runs exactly once and page pLastPg
+      ** is swapped with the first free page pulled off the free list.
+      **
+      ** On the other hand, if bCommit is greater than zero, then keep
+      ** looping until a free-page located within the first nFin pages
+      ** of the file is found.
+      */
+      if( bCommit==0 ){
+        eMode = BTALLOC_LE;
+        iNear = nFin;
+      }
+      do {
+        MemPage *pFreePg;
+        Pgno dbSize = btreePagecount(pBt);
+        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iNear, eMode);
+        if( rc!=SQLITE_OK ){
+          releasePage(pLastPg);
+          return rc;
+        }
+        releasePage(pFreePg);
+        if( iFreePg>dbSize ){
+          releasePage(pLastPg);
+          return SQLITE_CORRUPT_BKPT;
+        }
+      }while( bCommit && iFreePg>nFin );
+      assert( iFreePg<iLastPg );
+     
+      rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, bCommit);
+      releasePage(pLastPg);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+  }
+
+  if( bCommit==0 ){
+    do {
+      iLastPg--;
+    }while( iLastPg==PENDING_BYTE_PAGE(pBt) || PTRMAP_ISPAGE(pBt, iLastPg) );
+    pBt->bDoTruncate = 1;
+    pBt->nPage = iLastPg;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The database opened by the first argument is an auto-vacuum database
+** nOrig pages in size containing nFree free pages. Return the expected
+** size of the database in pages following an auto-vacuum operation.
+*/
+static Pgno finalDbSize(BtShared *pBt, Pgno nOrig, Pgno nFree){
+  int nEntry;                     /* Number of entries on one ptrmap page */
+  Pgno nPtrmap;                   /* Number of PtrMap pages to be freed */
+  Pgno nFin;                      /* Return value */
+
+  nEntry = pBt->usableSize/5;
+  nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
+  nFin = nOrig - nFree - nPtrmap;
+  if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
+    nFin--;
+  }
+  while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
+    nFin--;
+  }
+
+  return nFin;
+}
+
+/*
+** A write-transaction must be opened before calling this function.
+** It performs a single unit of work towards an incremental vacuum.
+**
+** If the incremental vacuum is finished after this function has run,
+** SQLITE_DONE is returned. If it is not finished, but no error occurred,
+** SQLITE_OK is returned. Otherwise an SQLite error code.
+*/
+int sqlite3BtreeIncrVacuum(Btree *p){
+  int rc;
+  BtShared *pBt = p->pBt;
+
+  sqlite3BtreeEnter(p);
+  assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
+  if( !pBt->autoVacuum ){
+    rc = SQLITE_DONE;
+  }else{
+    Pgno nOrig = btreePagecount(pBt);
+    Pgno nFree = get4byte(&pBt->pPage1->aData[36]);
+    Pgno nFin = finalDbSize(pBt, nOrig, nFree);
+
+    if( nOrig<nFin || nFree>=nOrig ){
+      rc = SQLITE_CORRUPT_BKPT;
+    }else if( nFree>0 ){
+      rc = saveAllCursors(pBt, 0, 0);
+      if( rc==SQLITE_OK ){
+        invalidateAllOverflowCache(pBt);
+        rc = incrVacuumStep(pBt, nFin, nOrig, 0);
+      }
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+        put4byte(&pBt->pPage1->aData[28], pBt->nPage);
+      }
+    }else{
+      rc = SQLITE_DONE;
+    }
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** This routine is called prior to sqlite3PagerCommit when a transaction
+** is committed for an auto-vacuum database.
+*/
+static int autoVacuumCommit(Btree *p){
+  int rc = SQLITE_OK;
+  Pager *pPager;
+  BtShared *pBt;
+  sqlite3 *db;
+  VVA_ONLY( int nRef );
+
+  assert( p!=0 );
+  pBt = p->pBt; 
+  pPager = pBt->pPager;
+  VVA_ONLY( nRef = sqlite3PagerRefcount(pPager); )
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  invalidateAllOverflowCache(pBt);
+  assert(pBt->autoVacuum);
+  if( !pBt->incrVacuum ){
+    Pgno nFin;         /* Number of pages in database after autovacuuming */
+    Pgno nFree;        /* Number of pages on the freelist initially */
+    Pgno nVac;         /* Number of pages to vacuum */
+    Pgno iFree;        /* The next page to be freed */
+    Pgno nOrig;        /* Database size before freeing */
+
+    nOrig = btreePagecount(pBt);
+    if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
+      /* It is not possible to create a database for which the final page
+      ** is either a pointer-map page or the pending-byte page. If one
+      ** is encountered, this indicates corruption.
+      */
+      return SQLITE_CORRUPT_BKPT;
+    }
+
+    nFree = get4byte(&pBt->pPage1->aData[36]);
+    db = p->db;
+    if( db->xAutovacPages ){
+      int iDb;
+      for(iDb=0; ALWAYS(iDb<db->nDb); iDb++){
+        if( db->aDb[iDb].pBt==p ) break;
+      }
+      nVac = db->xAutovacPages(
+        db->pAutovacPagesArg,
+        db->aDb[iDb].zDbSName,
+        nOrig,
+        nFree,
+        pBt->pageSize
+      );
+      if( nVac>nFree ){
+        nVac = nFree;
+      }
+      if( nVac==0 ){
+        return SQLITE_OK;
+      }
+    }else{
+      nVac = nFree;
+    }
+    nFin = finalDbSize(pBt, nOrig, nVac);
+    if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;
+    if( nFin<nOrig ){
+      rc = saveAllCursors(pBt, 0, 0);
+    }
+    for(iFree=nOrig; iFree>nFin && rc==SQLITE_OK; iFree--){
+      rc = incrVacuumStep(pBt, nFin, iFree, nVac==nFree);
+    }
+    if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
+      rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+      if( nVac==nFree ){
+        put4byte(&pBt->pPage1->aData[32], 0);
+        put4byte(&pBt->pPage1->aData[36], 0);
+      }
+      put4byte(&pBt->pPage1->aData[28], nFin);
+      pBt->bDoTruncate = 1;
+      pBt->nPage = nFin;
+    }
+    if( rc!=SQLITE_OK ){
+      sqlite3PagerRollback(pPager);
+    }
+  }
+
+  assert( nRef>=sqlite3PagerRefcount(pPager) );
+  return rc;
+}
+
+#else /* ifndef SQLITE_OMIT_AUTOVACUUM */
+# define setChildPtrmaps(x) SQLITE_OK
+#endif
+
+/*
+** This routine does the first phase of a two-phase commit.  This routine
+** causes a rollback journal to be created (if it does not already exist)
+** and populated with enough information so that if a power loss occurs
+** the database can be restored to its original state by playing back
+** the journal.  Then the contents of the journal are flushed out to
+** the disk.  After the journal is safely on oxide, the changes to the
+** database are written into the database file and flushed to oxide.
+** At the end of this call, the rollback journal still exists on the
+** disk and we are still holding all locks, so the transaction has not
+** committed.  See sqlite3BtreeCommitPhaseTwo() for the second phase of the
+** commit process.
+**
+** This call is a no-op if no write-transaction is currently active on pBt.
+**
+** Otherwise, sync the database file for the btree pBt. zSuperJrnl points to
+** the name of a super-journal file that should be written into the
+** individual journal file, or is NULL, indicating no super-journal file
+** (single database transaction).
+**
+** When this is called, the super-journal should already have been
+** created, populated with this journal pointer and synced to disk.
+**
+** Once this is routine has returned, the only thing required to commit
+** the write-transaction for this database file is to delete the journal.
+*/
+int sqlite3BtreeCommitPhaseOne(Btree *p, const char *zSuperJrnl){
+  int rc = SQLITE_OK;
+  if( p->inTrans==TRANS_WRITE ){
+    BtShared *pBt = p->pBt;
+    sqlite3BtreeEnter(p);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum ){
+      rc = autoVacuumCommit(p);
+      if( rc!=SQLITE_OK ){
+        sqlite3BtreeLeave(p);
+        return rc;
+      }
+    }
+    if( pBt->bDoTruncate ){
+      sqlite3PagerTruncateImage(pBt->pPager, pBt->nPage);
+    }
+#endif
+    rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zSuperJrnl, 0);
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+
+/*
+** This function is called from both BtreeCommitPhaseTwo() and BtreeRollback()
+** at the conclusion of a transaction.
+*/
+static void btreeEndTransaction(Btree *p){
+  BtShared *pBt = p->pBt;
+  sqlite3 *db = p->db;
+  assert( sqlite3BtreeHoldsMutex(p) );
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  pBt->bDoTruncate = 0;
+#endif
+  if( p->inTrans>TRANS_NONE && db->nVdbeRead>1 ){
+    /* If there are other active statements that belong to this database
+    ** handle, downgrade to a read-only transaction. The other statements
+    ** may still be reading from the database.  */
+    downgradeAllSharedCacheTableLocks(p);
+    p->inTrans = TRANS_READ;
+  }else{
+    /* If the handle had any kind of transaction open, decrement the
+    ** transaction count of the shared btree. If the transaction count
+    ** reaches 0, set the shared state to TRANS_NONE. The unlockBtreeIfUnused()
+    ** call below will unlock the pager.  */
+    if( p->inTrans!=TRANS_NONE ){
+      clearAllSharedCacheTableLocks(p);
+      pBt->nTransaction--;
+      if( 0==pBt->nTransaction ){
+        pBt->inTransaction = TRANS_NONE;
+      }
+    }
+
+    /* Set the current transaction state to TRANS_NONE and unlock the
+    ** pager if this call closed the only read or write transaction.  */
+    p->inTrans = TRANS_NONE;
+    unlockBtreeIfUnused(pBt);
+  }
+
+  btreeIntegrity(p);
+}
+
+/*
+** Commit the transaction currently in progress.
+**
+** This routine implements the second phase of a 2-phase commit.  The
+** sqlite3BtreeCommitPhaseOne() routine does the first phase and should
+** be invoked prior to calling this routine.  The sqlite3BtreeCommitPhaseOne()
+** routine did all the work of writing information out to disk and flushing the
+** contents so that they are written onto the disk platter.  All this
+** routine has to do is delete or truncate or zero the header in the
+** the rollback journal (which causes the transaction to commit) and
+** drop locks.
+**
+** Normally, if an error occurs while the pager layer is attempting to
+** finalize the underlying journal file, this function returns an error and
+** the upper layer will attempt a rollback. However, if the second argument
+** is non-zero then this b-tree transaction is part of a multi-file
+** transaction. In this case, the transaction has already been committed
+** (by deleting a super-journal file) and the caller will ignore this
+** functions return code. So, even if an error occurs in the pager layer,
+** reset the b-tree objects internal state to indicate that the write
+** transaction has been closed. This is quite safe, as the pager will have
+** transitioned to the error state.
+**
+** This will release the write lock on the database file.  If there
+** are no active cursors, it also releases the read lock.
+*/
+int sqlite3BtreeCommitPhaseTwo(Btree *p, int bCleanup){
+
+  if( p->inTrans==TRANS_NONE ) return SQLITE_OK;
+  sqlite3BtreeEnter(p);
+  btreeIntegrity(p);
+
+  /* If the handle has a write-transaction open, commit the shared-btrees
+  ** transaction and set the shared state to TRANS_READ.
+  */
+  if( p->inTrans==TRANS_WRITE ){
+    int rc;
+    BtShared *pBt = p->pBt;
+    assert( pBt->inTransaction==TRANS_WRITE );
+    assert( pBt->nTransaction>0 );
+    rc = sqlite3PagerCommitPhaseTwo(pBt->pPager);
+    if( rc!=SQLITE_OK && bCleanup==0 ){
+      sqlite3BtreeLeave(p);
+      return rc;
+    }
+    p->iBDataVersion--;  /* Compensate for pPager->iDataVersion++; */
+    pBt->inTransaction = TRANS_READ;
+    btreeClearHasContent(pBt);
+  }
+
+  btreeEndTransaction(p);
+  sqlite3BtreeLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Do both phases of a commit.
+*/
+int sqlite3BtreeCommit(Btree *p){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = sqlite3BtreeCommitPhaseOne(p, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3BtreeCommitPhaseTwo(p, 0);
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** This routine sets the state to CURSOR_FAULT and the error
+** code to errCode for every cursor on any BtShared that pBtree
+** references.  Or if the writeOnly flag is set to 1, then only
+** trip write cursors and leave read cursors unchanged.
+**
+** Every cursor is a candidate to be tripped, including cursors
+** that belong to other database connections that happen to be
+** sharing the cache with pBtree.
+**
+** This routine gets called when a rollback occurs. If the writeOnly
+** flag is true, then only write-cursors need be tripped - read-only
+** cursors save their current positions so that they may continue
+** following the rollback. Or, if writeOnly is false, all cursors are
+** tripped. In general, writeOnly is false if the transaction being
+** rolled back modified the database schema. In this case b-tree root
+** pages may be moved or deleted from the database altogether, making
+** it unsafe for read cursors to continue.
+**
+** If the writeOnly flag is true and an error is encountered while
+** saving the current position of a read-only cursor, all cursors,
+** including all read-cursors are tripped.
+**
+** SQLITE_OK is returned if successful, or if an error occurs while
+** saving a cursor position, an SQLite error code.
+*/
+int sqlite3BtreeTripAllCursors(Btree *pBtree, int errCode, int writeOnly){
+  BtCursor *p;
+  int rc = SQLITE_OK;
+
+  assert( (writeOnly==0 || writeOnly==1) && BTCF_WriteFlag==1 );
+  if( pBtree ){
+    sqlite3BtreeEnter(pBtree);
+    for(p=pBtree->pBt->pCursor; p; p=p->pNext){
+      if( writeOnly && (p->curFlags & BTCF_WriteFlag)==0 ){
+        if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
+          rc = saveCursorPosition(p);
+          if( rc!=SQLITE_OK ){
+            (void)sqlite3BtreeTripAllCursors(pBtree, rc, 0);
+            break;
+          }
+        }
+      }else{
+        sqlite3BtreeClearCursor(p);
+        p->eState = CURSOR_FAULT;
+        p->skipNext = errCode;
+      }
+      btreeReleaseAllCursorPages(p);
+    }
+    sqlite3BtreeLeave(pBtree);
+  }
+  return rc;
+}
+
+/*
+** Set the pBt->nPage field correctly, according to the current
+** state of the database.  Assume pBt->pPage1 is valid.
+*/
+static void btreeSetNPage(BtShared *pBt, MemPage *pPage1){
+  int nPage = get4byte(&pPage1->aData[28]);
+  testcase( nPage==0 );
+  if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
+  testcase( pBt->nPage!=(u32)nPage );
+  pBt->nPage = nPage;
+}
+
+/*
+** Rollback the transaction in progress.
+**
+** If tripCode is not SQLITE_OK then cursors will be invalidated (tripped).
+** Only write cursors are tripped if writeOnly is true but all cursors are
+** tripped if writeOnly is false.  Any attempt to use
+** a tripped cursor will result in an error.
+**
+** This will release the write lock on the database file.  If there
+** are no active cursors, it also releases the read lock.
+*/
+int sqlite3BtreeRollback(Btree *p, int tripCode, int writeOnly){
+  int rc;
+  BtShared *pBt = p->pBt;
+  MemPage *pPage1;
+
+  assert( writeOnly==1 || writeOnly==0 );
+  assert( tripCode==SQLITE_ABORT_ROLLBACK || tripCode==SQLITE_OK );
+  sqlite3BtreeEnter(p);
+  if( tripCode==SQLITE_OK ){
+    rc = tripCode = saveAllCursors(pBt, 0, 0);
+    if( rc ) writeOnly = 0;
+  }else{
+    rc = SQLITE_OK;
+  }
+  if( tripCode ){
+    int rc2 = sqlite3BtreeTripAllCursors(p, tripCode, writeOnly);
+    assert( rc==SQLITE_OK || (writeOnly==0 && rc2==SQLITE_OK) );
+    if( rc2!=SQLITE_OK ) rc = rc2;
+  }
+  btreeIntegrity(p);
+
+  if( p->inTrans==TRANS_WRITE ){
+    int rc2;
+
+    assert( TRANS_WRITE==pBt->inTransaction );
+    rc2 = sqlite3PagerRollback(pBt->pPager);
+    if( rc2!=SQLITE_OK ){
+      rc = rc2;
+    }
+
+    /* The rollback may have destroyed the pPage1->aData value.  So
+    ** call btreeGetPage() on page 1 again to make
+    ** sure pPage1->aData is set correctly. */
+    if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
+      btreeSetNPage(pBt, pPage1);
+      releasePageOne(pPage1);
+    }
+    assert( countValidCursors(pBt, 1)==0 );
+    pBt->inTransaction = TRANS_READ;
+    btreeClearHasContent(pBt);
+  }
+
+  btreeEndTransaction(p);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Start a statement subtransaction. The subtransaction can be rolled
+** back independently of the main transaction. You must start a transaction
+** before starting a subtransaction. The subtransaction is ended automatically
+** if the main transaction commits or rolls back.
+**
+** Statement subtransactions are used around individual SQL statements
+** that are contained within a BEGIN...COMMIT block.  If a constraint
+** error occurs within the statement, the effect of that one statement
+** can be rolled back without having to rollback the entire transaction.
+**
+** A statement sub-transaction is implemented as an anonymous savepoint. The
+** value passed as the second parameter is the total number of savepoints,
+** including the new anonymous savepoint, open on the B-Tree. i.e. if there
+** are no active savepoints and no other statement-transactions open,
+** iStatement is 1. This anonymous savepoint can be released or rolled back
+** using the sqlite3BtreeSavepoint() function.
+*/
+int sqlite3BtreeBeginStmt(Btree *p, int iStatement){
+  int rc;
+  BtShared *pBt = p->pBt;
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans==TRANS_WRITE );
+  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
+  assert( iStatement>0 );
+  assert( iStatement>p->db->nSavepoint );
+  assert( pBt->inTransaction==TRANS_WRITE );
+  /* At the pager level, a statement transaction is a savepoint with
+  ** an index greater than all savepoints created explicitly using
+  ** SQL statements. It is illegal to open, release or rollback any
+  ** such savepoints while the statement transaction savepoint is active.
+  */
+  rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** The second argument to this function, op, is always SAVEPOINT_ROLLBACK
+** or SAVEPOINT_RELEASE. This function either releases or rolls back the
+** savepoint identified by parameter iSavepoint, depending on the value
+** of op.
+**
+** Normally, iSavepoint is greater than or equal to zero. However, if op is
+** SAVEPOINT_ROLLBACK, then iSavepoint may also be -1. In this case the
+** contents of the entire transaction are rolled back. This is different
+** from a normal transaction rollback, as no locks are released and the
+** transaction remains open.
+*/
+int sqlite3BtreeSavepoint(Btree *p, int op, int iSavepoint){
+  int rc = SQLITE_OK;
+  if( p && p->inTrans==TRANS_WRITE ){
+    BtShared *pBt = p->pBt;
+    assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
+    assert( iSavepoint>=0 || (iSavepoint==-1 && op==SAVEPOINT_ROLLBACK) );
+    sqlite3BtreeEnter(p);
+    if( op==SAVEPOINT_ROLLBACK ){
+      rc = saveAllCursors(pBt, 0, 0);
+    }
+    if( rc==SQLITE_OK ){
+      rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
+    }
+    if( rc==SQLITE_OK ){
+      if( iSavepoint<0 && (pBt->btsFlags & BTS_INITIALLY_EMPTY)!=0 ){
+        pBt->nPage = 0;
+      }
+      rc = newDatabase(pBt);
+      btreeSetNPage(pBt, pBt->pPage1);
+
+      /* pBt->nPage might be zero if the database was corrupt when
+      ** the transaction was started. Otherwise, it must be at least 1.  */
+      assert( CORRUPT_DB || pBt->nPage>0 );
+    }
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+
+/*
+** Create a new cursor for the BTree whose root is on the page
+** iTable. If a read-only cursor is requested, it is assumed that
+** the caller already has at least a read-only transaction open
+** on the database already. If a write-cursor is requested, then
+** the caller is assumed to have an open write transaction.
+**
+** If the BTREE_WRCSR bit of wrFlag is clear, then the cursor can only
+** be used for reading.  If the BTREE_WRCSR bit is set, then the cursor
+** can be used for reading or for writing if other conditions for writing
+** are also met.  These are the conditions that must be met in order
+** for writing to be allowed:
+**
+** 1:  The cursor must have been opened with wrFlag containing BTREE_WRCSR
+**
+** 2:  Other database connections that share the same pager cache
+**     but which are not in the READ_UNCOMMITTED state may not have
+**     cursors open with wrFlag==0 on the same table.  Otherwise
+**     the changes made by this write cursor would be visible to
+**     the read cursors in the other database connection.
+**
+** 3:  The database must be writable (not on read-only media)
+**
+** 4:  There must be an active transaction.
+**
+** The BTREE_FORDELETE bit of wrFlag may optionally be set if BTREE_WRCSR
+** is set.  If FORDELETE is set, that is a hint to the implementation that
+** this cursor will only be used to seek to and delete entries of an index
+** as part of a larger DELETE statement.  The FORDELETE hint is not used by
+** this implementation.  But in a hypothetical alternative storage engine
+** in which index entries are automatically deleted when corresponding table
+** rows are deleted, the FORDELETE flag is a hint that all SEEK and DELETE
+** operations on this cursor can be no-ops and all READ operations can
+** return a null row (2-bytes: 0x01 0x00).
+**
+** No checking is done to make sure that page iTable really is the
+** root page of a b-tree.  If it is not, then the cursor acquired
+** will not work correctly.
+**
+** It is assumed that the sqlite3BtreeCursorZero() has been called
+** on pCur to initialize the memory space prior to invoking this routine.
+*/
+static int btreeCursor(
+  Btree *p,                              /* The btree */
+  Pgno iTable,                           /* Root page of table to open */
+  int wrFlag,                            /* 1 to write. 0 read-only */
+  struct KeyInfo *pKeyInfo,              /* First arg to comparison function */
+  BtCursor *pCur                         /* Space for new cursor */
+){
+  BtShared *pBt = p->pBt;                /* Shared b-tree handle */
+  BtCursor *pX;                          /* Looping over other all cursors */
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( wrFlag==0
+       || wrFlag==BTREE_WRCSR
+       || wrFlag==(BTREE_WRCSR|BTREE_FORDELETE)
+  );
+
+  /* The following assert statements verify that if this is a sharable
+  ** b-tree database, the connection is holding the required table locks,
+  ** and that no other connection has any open cursor that conflicts with
+  ** this lock.  The iTable<1 term disables the check for corrupt schemas. */
+  assert( hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, (wrFlag?2:1))
+          || iTable<1 );
+  assert( wrFlag==0 || !hasReadConflicts(p, iTable) );
+
+  /* Assert that the caller has opened the required transaction. */
+  assert( p->inTrans>TRANS_NONE );
+  assert( wrFlag==0 || p->inTrans==TRANS_WRITE );
+  assert( pBt->pPage1 && pBt->pPage1->aData );
+  assert( wrFlag==0 || (pBt->btsFlags & BTS_READ_ONLY)==0 );
+
+  if( iTable<=1 ){
+    if( iTable<1 ){
+      return SQLITE_CORRUPT_BKPT;
+    }else if( btreePagecount(pBt)==0 ){
+      assert( wrFlag==0 );
+      iTable = 0;
+    }
+  }
+
+  /* Now that no other errors can occur, finish filling in the BtCursor
+  ** variables and link the cursor into the BtShared list.  */
+  pCur->pgnoRoot = iTable;
+  pCur->iPage = -1;
+  pCur->pKeyInfo = pKeyInfo;
+  pCur->pBtree = p;
+  pCur->pBt = pBt;
+  pCur->curFlags = 0;
+  /* If there are two or more cursors on the same btree, then all such
+  ** cursors *must* have the BTCF_Multiple flag set. */
+  for(pX=pBt->pCursor; pX; pX=pX->pNext){
+    if( pX->pgnoRoot==iTable ){
+      pX->curFlags |= BTCF_Multiple;
+      pCur->curFlags = BTCF_Multiple;
+    }
+  }
+  pCur->eState = CURSOR_INVALID;
+  pCur->pNext = pBt->pCursor;
+  pBt->pCursor = pCur;
+  if( wrFlag ){
+    pCur->curFlags |= BTCF_WriteFlag;
+    pCur->curPagerFlags = 0;
+    if( pBt->pTmpSpace==0 ) return allocateTempSpace(pBt);
+  }else{
+    pCur->curPagerFlags = PAGER_GET_READONLY;
+  }
+  return SQLITE_OK;
+}
+static int btreeCursorWithLock(
+  Btree *p,                              /* The btree */
+  Pgno iTable,                           /* Root page of table to open */
+  int wrFlag,                            /* 1 to write. 0 read-only */
+  struct KeyInfo *pKeyInfo,              /* First arg to comparison function */
+  BtCursor *pCur                         /* Space for new cursor */
+){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+int sqlite3BtreeCursor(
+  Btree *p,                                   /* The btree */
+  Pgno iTable,                                /* Root page of table to open */
+  int wrFlag,                                 /* 1 to write. 0 read-only */
+  struct KeyInfo *pKeyInfo,                   /* First arg to xCompare() */
+  BtCursor *pCur                              /* Write new cursor here */
+){
+  if( p->sharable ){
+    return btreeCursorWithLock(p, iTable, wrFlag, pKeyInfo, pCur);
+  }else{
+    return btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
+  }
+}
+
+/*
+** Return the size of a BtCursor object in bytes.
+**
+** This interfaces is needed so that users of cursors can preallocate
+** sufficient storage to hold a cursor.  The BtCursor object is opaque
+** to users so they cannot do the sizeof() themselves - they must call
+** this routine.
+*/
+int sqlite3BtreeCursorSize(void){
+  return ROUND8(sizeof(BtCursor));
+}
+
+/*
+** Initialize memory that will be converted into a BtCursor object.
+**
+** The simple approach here would be to memset() the entire object
+** to zero.  But it turns out that the apPage[] and aiIdx[] arrays
+** do not need to be zeroed and they are large, so we can save a lot
+** of run-time by skipping the initialization of those elements.
+*/
+void sqlite3BtreeCursorZero(BtCursor *p){
+  memset(p, 0, offsetof(BtCursor, BTCURSOR_FIRST_UNINIT));
+}
+
+/*
+** Close a cursor.  The read lock on the database file is released
+** when the last cursor is closed.
+*/
+int sqlite3BtreeCloseCursor(BtCursor *pCur){
+  Btree *pBtree = pCur->pBtree;
+  if( pBtree ){
+    BtShared *pBt = pCur->pBt;
+    sqlite3BtreeEnter(pBtree);
+    assert( pBt->pCursor!=0 );
+    if( pBt->pCursor==pCur ){
+      pBt->pCursor = pCur->pNext;
+    }else{
+      BtCursor *pPrev = pBt->pCursor;
+      do{
+        if( pPrev->pNext==pCur ){
+          pPrev->pNext = pCur->pNext;
+          break;
+        }
+        pPrev = pPrev->pNext;
+      }while( ALWAYS(pPrev) );
+    }
+    btreeReleaseAllCursorPages(pCur);
+    unlockBtreeIfUnused(pBt);
+    sqlite3_free(pCur->aOverflow);
+    sqlite3_free(pCur->pKey);
+    if( (pBt->openFlags & BTREE_SINGLE) && pBt->pCursor==0 ){
+      /* Since the BtShared is not sharable, there is no need to
+      ** worry about the missing sqlite3BtreeLeave() call here.  */
+      assert( pBtree->sharable==0 );
+      sqlite3BtreeClose(pBtree);
+    }else{
+      sqlite3BtreeLeave(pBtree);
+    }
+    pCur->pBtree = 0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Make sure the BtCursor* given in the argument has a valid
+** BtCursor.info structure.  If it is not already valid, call
+** btreeParseCell() to fill it in.
+**
+** BtCursor.info is a cache of the information in the current cell.
+** Using this cache reduces the number of calls to btreeParseCell().
+*/
+#ifndef NDEBUG
+  static int cellInfoEqual(CellInfo *a, CellInfo *b){
+    if( a->nKey!=b->nKey ) return 0;
+    if( a->pPayload!=b->pPayload ) return 0;
+    if( a->nPayload!=b->nPayload ) return 0;
+    if( a->nLocal!=b->nLocal ) return 0;
+    if( a->nSize!=b->nSize ) return 0;
+    return 1;
+  }
+  static void assertCellInfo(BtCursor *pCur){
+    CellInfo info;
+    memset(&info, 0, sizeof(info));
+    btreeParseCell(pCur->pPage, pCur->ix, &info);
+    assert( CORRUPT_DB || cellInfoEqual(&info, &pCur->info) );
+  }
+#else
+  #define assertCellInfo(x)
+#endif
+static SQLITE_NOINLINE void getCellInfo(BtCursor *pCur){
+  if( pCur->info.nSize==0 ){
+    pCur->curFlags |= BTCF_ValidNKey;
+    btreeParseCell(pCur->pPage,pCur->ix,&pCur->info);
+  }else{
+    assertCellInfo(pCur);
+  }
+}
+
+#ifndef NDEBUG  /* The next routine used only within assert() statements */
+/*
+** Return true if the given BtCursor is valid.  A valid cursor is one
+** that is currently pointing to a row in a (non-empty) table.
+** This is a verification routine is used only within assert() statements.
+*/
+int sqlite3BtreeCursorIsValid(BtCursor *pCur){
+  return pCur && pCur->eState==CURSOR_VALID;
+}
+#endif /* NDEBUG */
+int sqlite3BtreeCursorIsValidNN(BtCursor *pCur){
+  assert( pCur!=0 );
+  return pCur->eState==CURSOR_VALID;
+}
+
+/*
+** Return the value of the integer key or "rowid" for a table btree.
+** This routine is only valid for a cursor that is pointing into a
+** ordinary table btree.  If the cursor points to an index btree or
+** is invalid, the result of this routine is undefined.
+*/
+i64 sqlite3BtreeIntegerKey(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->curIntKey );
+  getCellInfo(pCur);
+  return pCur->info.nKey;
+}
+
+/*
+** Pin or unpin a cursor.
+*/
+void sqlite3BtreeCursorPin(BtCursor *pCur){
+  assert( (pCur->curFlags & BTCF_Pinned)==0 );
+  pCur->curFlags |= BTCF_Pinned;
+}
+void sqlite3BtreeCursorUnpin(BtCursor *pCur){
+  assert( (pCur->curFlags & BTCF_Pinned)!=0 );
+  pCur->curFlags &= ~BTCF_Pinned;
+}
+
+/*
+** Return the offset into the database file for the start of the
+** payload to which the cursor is pointing.
+*/
+i64 sqlite3BtreeOffset(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  getCellInfo(pCur);
+  return (i64)pCur->pBt->pageSize*((i64)pCur->pPage->pgno - 1) +
+         (i64)(pCur->info.pPayload - pCur->pPage->aData);
+}
+
+/*
+** Return the number of bytes of payload for the entry that pCur is
+** currently pointing to.  For table btrees, this will be the amount
+** of data.  For index btrees, this will be the size of the key.
+**
+** The caller must guarantee that the cursor is pointing to a non-NULL
+** valid entry.  In other words, the calling procedure must guarantee
+** that the cursor has Cursor.eState==CURSOR_VALID.
+*/
+u32 sqlite3BtreePayloadSize(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  getCellInfo(pCur);
+  return pCur->info.nPayload;
+}
+
+/*
+** Return an upper bound on the size of any record for the table
+** that the cursor is pointing into.
+**
+** This is an optimization.  Everything will still work if this
+** routine always returns 2147483647 (which is the largest record
+** that SQLite can handle) or more.  But returning a smaller value might
+** prevent large memory allocations when trying to interpret a
+** corrupt database.
+**
+** The current implementation merely returns the size of the underlying
+** database file.
+*/
+sqlite3_int64 sqlite3BtreeMaxRecordSize(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  return pCur->pBt->pageSize * (sqlite3_int64)pCur->pBt->nPage;
+}
+
+/*
+** Given the page number of an overflow page in the database (parameter
+** ovfl), this function finds the page number of the next page in the
+** linked list of overflow pages. If possible, it uses the auto-vacuum
+** pointer-map data instead of reading the content of page ovfl to do so.
+**
+** If an error occurs an SQLite error code is returned. Otherwise:
+**
+** The page number of the next overflow page in the linked list is
+** written to *pPgnoNext. If page ovfl is the last page in its linked
+** list, *pPgnoNext is set to zero.
+**
+** If ppPage is not NULL, and a reference to the MemPage object corresponding
+** to page number pOvfl was obtained, then *ppPage is set to point to that
+** reference. It is the responsibility of the caller to call releasePage()
+** on *ppPage to free the reference. In no reference was obtained (because
+** the pointer-map was used to obtain the value for *pPgnoNext), then
+** *ppPage is set to zero.
+*/
+static int getOverflowPage(
+  BtShared *pBt,               /* The database file */
+  Pgno ovfl,                   /* Current overflow page number */
+  MemPage **ppPage,            /* OUT: MemPage handle (may be NULL) */
+  Pgno *pPgnoNext              /* OUT: Next overflow page number */
+){
+  Pgno next = 0;
+  MemPage *pPage = 0;
+  int rc = SQLITE_OK;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert(pPgnoNext);
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  /* Try to find the next page in the overflow list using the
+  ** autovacuum pointer-map pages. Guess that the next page in
+  ** the overflow list is page number (ovfl+1). If that guess turns
+  ** out to be wrong, fall back to loading the data of page
+  ** number ovfl to determine the next page number.
+  */
+  if( pBt->autoVacuum ){
+    Pgno pgno;
+    Pgno iGuess = ovfl+1;
+    u8 eType;
+
+    while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
+      iGuess++;
+    }
+
+    if( iGuess<=btreePagecount(pBt) ){
+      rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
+      if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
+        next = iGuess;
+        rc = SQLITE_DONE;
+      }
+    }
+  }
+#endif
+
+  assert( next==0 || rc==SQLITE_DONE );
+  if( rc==SQLITE_OK ){
+    rc = btreeGetPage(pBt, ovfl, &pPage, (ppPage==0) ? PAGER_GET_READONLY : 0);
+    assert( rc==SQLITE_OK || pPage==0 );
+    if( rc==SQLITE_OK ){
+      next = get4byte(pPage->aData);
+    }
+  }
+
+  *pPgnoNext = next;
+  if( ppPage ){
+    *ppPage = pPage;
+  }else{
+    releasePage(pPage);
+  }
+  return (rc==SQLITE_DONE ? SQLITE_OK : rc);
+}
+
+/*
+** Copy data from a buffer to a page, or from a page to a buffer.
+**
+** pPayload is a pointer to data stored on database page pDbPage.
+** If argument eOp is false, then nByte bytes of data are copied
+** from pPayload to the buffer pointed at by pBuf. If eOp is true,
+** then sqlite3PagerWrite() is called on pDbPage and nByte bytes
+** of data are copied from the buffer pBuf to pPayload.
+**
+** SQLITE_OK is returned on success, otherwise an error code.
+*/
+static int copyPayload(
+  void *pPayload,           /* Pointer to page data */
+  void *pBuf,               /* Pointer to buffer */
+  int nByte,                /* Number of bytes to copy */
+  int eOp,                  /* 0 -> copy from page, 1 -> copy to page */
+  DbPage *pDbPage           /* Page containing pPayload */
+){
+  if( eOp ){
+    /* Copy data from buffer to page (a write operation) */
+    int rc = sqlite3PagerWrite(pDbPage);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    memcpy(pPayload, pBuf, nByte);
+  }else{
+    /* Copy data from page to buffer (a read operation) */
+    memcpy(pBuf, pPayload, nByte);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This function is used to read or overwrite payload information
+** for the entry that the pCur cursor is pointing to. The eOp
+** argument is interpreted as follows:
+**
+**   0: The operation is a read. Populate the overflow cache.
+**   1: The operation is a write. Populate the overflow cache.
+**
+** A total of "amt" bytes are read or written beginning at "offset".
+** Data is read to or from the buffer pBuf.
+**
+** The content being read or written might appear on the main page
+** or be scattered out on multiple overflow pages.
+**
+** If the current cursor entry uses one or more overflow pages
+** this function may allocate space for and lazily populate
+** the overflow page-list cache array (BtCursor.aOverflow).
+** Subsequent calls use this cache to make seeking to the supplied offset
+** more efficient.
+**
+** Once an overflow page-list cache has been allocated, it must be
+** invalidated if some other cursor writes to the same table, or if
+** the cursor is moved to a different row. Additionally, in auto-vacuum
+** mode, the following events may invalidate an overflow page-list cache.
+**
+**   * An incremental vacuum,
+**   * A commit in auto_vacuum="full" mode,
+**   * Creating a table (may require moving an overflow page).
+*/
+static int accessPayload(
+  BtCursor *pCur,      /* Cursor pointing to entry to read from */
+  u32 offset,          /* Begin reading this far into payload */
+  u32 amt,             /* Read this many bytes */
+  unsigned char *pBuf, /* Write the bytes into this buffer */
+  int eOp              /* zero to read. non-zero to write. */
+){
+  unsigned char *aPayload;
+  int rc = SQLITE_OK;
+  int iIdx = 0;
+  MemPage *pPage = pCur->pPage;               /* Btree page of current entry */
+  BtShared *pBt = pCur->pBt;                  /* Btree this cursor belongs to */
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+  unsigned char * const pBufStart = pBuf;     /* Start of original out buffer */
+#endif
+
+  assert( pPage );
+  assert( eOp==0 || eOp==1 );
+  assert( pCur->eState==CURSOR_VALID );
+  if( pCur->ix>=pPage->nCell ){
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+  assert( cursorHoldsMutex(pCur) );
+
+  getCellInfo(pCur);
+  aPayload = pCur->info.pPayload;
+  assert( offset+amt <= pCur->info.nPayload );
+
+  assert( aPayload > pPage->aData );
+  if( (uptr)(aPayload - pPage->aData) > (pBt->usableSize - pCur->info.nLocal) ){
+    /* Trying to read or write past the end of the data is an error.  The
+    ** conditional above is really:
+    **    &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
+    ** but is recast into its current form to avoid integer overflow problems
+    */
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+
+  /* Check if data must be read/written to/from the btree page itself. */
+  if( offset<pCur->info.nLocal ){
+    int a = amt;
+    if( a+offset>pCur->info.nLocal ){
+      a = pCur->info.nLocal - offset;
+    }
+    rc = copyPayload(&aPayload[offset], pBuf, a, eOp, pPage->pDbPage);
+    offset = 0;
+    pBuf += a;
+    amt -= a;
+  }else{
+    offset -= pCur->info.nLocal;
+  }
+
+
+  if( rc==SQLITE_OK && amt>0 ){
+    const u32 ovflSize = pBt->usableSize - 4;  /* Bytes content per ovfl page */
+    Pgno nextPage;
+
+    nextPage = get4byte(&aPayload[pCur->info.nLocal]);
+
+    /* If the BtCursor.aOverflow[] has not been allocated, allocate it now.
+    **
+    ** The aOverflow[] array is sized at one entry for each overflow page
+    ** in the overflow chain. The page number of the first overflow page is
+    ** stored in aOverflow[0], etc. A value of 0 in the aOverflow[] array
+    ** means "not yet known" (the cache is lazily populated).
+    */
+    if( (pCur->curFlags & BTCF_ValidOvfl)==0 ){
+      int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
+      if( pCur->aOverflow==0
+       || nOvfl*(int)sizeof(Pgno) > sqlite3MallocSize(pCur->aOverflow)
+      ){
+        Pgno *aNew = (Pgno*)sqlite3Realloc(
+            pCur->aOverflow, nOvfl*2*sizeof(Pgno)
+        );
+        if( aNew==0 ){
+          return SQLITE_NOMEM_BKPT;
+        }else{
+          pCur->aOverflow = aNew;
+        }
+      }
+      memset(pCur->aOverflow, 0, nOvfl*sizeof(Pgno));
+      pCur->curFlags |= BTCF_ValidOvfl;
+    }else{
+      /* If the overflow page-list cache has been allocated and the
+      ** entry for the first required overflow page is valid, skip
+      ** directly to it.
+      */
+      if( pCur->aOverflow[offset/ovflSize] ){
+        iIdx = (offset/ovflSize);
+        nextPage = pCur->aOverflow[iIdx];
+        offset = (offset%ovflSize);
+      }
+    }
+
+    assert( rc==SQLITE_OK && amt>0 );
+    while( nextPage ){
+      /* If required, populate the overflow page-list cache. */
+      if( nextPage > pBt->nPage ) return SQLITE_CORRUPT_BKPT;
+      assert( pCur->aOverflow[iIdx]==0
+              || pCur->aOverflow[iIdx]==nextPage
+              || CORRUPT_DB );
+      pCur->aOverflow[iIdx] = nextPage;
+
+      if( offset>=ovflSize ){
+        /* The only reason to read this page is to obtain the page
+        ** number for the next page in the overflow chain. The page
+        ** data is not required. So first try to lookup the overflow
+        ** page-list cache, if any, then fall back to the getOverflowPage()
+        ** function.
+        */
+        assert( pCur->curFlags & BTCF_ValidOvfl );
+        assert( pCur->pBtree->db==pBt->db );
+        if( pCur->aOverflow[iIdx+1] ){
+          nextPage = pCur->aOverflow[iIdx+1];
+        }else{
+          rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
+        }
+        offset -= ovflSize;
+      }else{
+        /* Need to read this page properly. It contains some of the
+        ** range of data that is being read (eOp==0) or written (eOp!=0).
+        */
+        int a = amt;
+        if( a + offset > ovflSize ){
+          a = ovflSize - offset;
+        }
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+        /* If all the following are true:
+        **
+        **   1) this is a read operation, and
+        **   2) data is required from the start of this overflow page, and
+        **   3) there are no dirty pages in the page-cache
+        **   4) the database is file-backed, and
+        **   5) the page is not in the WAL file
+        **   6) at least 4 bytes have already been read into the output buffer
+        **
+        ** then data can be read directly from the database file into the
+        ** output buffer, bypassing the page-cache altogether. This speeds
+        ** up loading large records that span many overflow pages.
+        */
+        if( eOp==0                                             /* (1) */
+         && offset==0                                          /* (2) */
+         && sqlite3PagerDirectReadOk(pBt->pPager, nextPage)    /* (3,4,5) */
+         && &pBuf[-4]>=pBufStart                               /* (6) */
+        ){
+          sqlite3_file *fd = sqlite3PagerFile(pBt->pPager);
+          u8 aSave[4];
+          u8 *aWrite = &pBuf[-4];
+          assert( aWrite>=pBufStart );                         /* due to (6) */
+          memcpy(aSave, aWrite, 4);
+          rc = sqlite3OsRead(fd, aWrite, a+4, (i64)pBt->pageSize*(nextPage-1));
+          nextPage = get4byte(aWrite);
+          memcpy(aWrite, aSave, 4);
+        }else
+#endif
+
+        {
+          DbPage *pDbPage;
+          rc = sqlite3PagerGet(pBt->pPager, nextPage, &pDbPage,
+              (eOp==0 ? PAGER_GET_READONLY : 0)
+          );
+          if( rc==SQLITE_OK ){
+            aPayload = sqlite3PagerGetData(pDbPage);
+            nextPage = get4byte(aPayload);
+            rc = copyPayload(&aPayload[offset+4], pBuf, a, eOp, pDbPage);
+            sqlite3PagerUnref(pDbPage);
+            offset = 0;
+          }
+        }
+        amt -= a;
+        if( amt==0 ) return rc;
+        pBuf += a;
+      }
+      if( rc ) break;
+      iIdx++;
+    }
+  }
+
+  if( rc==SQLITE_OK && amt>0 ){
+    /* Overflow chain ends prematurely */
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+  return rc;
+}
+
+/*
+** Read part of the payload for the row at which that cursor pCur is currently
+** pointing.  "amt" bytes will be transferred into pBuf[].  The transfer
+** begins at "offset".
+**
+** pCur can be pointing to either a table or an index b-tree.
+** If pointing to a table btree, then the content section is read.  If
+** pCur is pointing to an index b-tree then the key section is read.
+**
+** For sqlite3BtreePayload(), the caller must ensure that pCur is pointing
+** to a valid row in the table.  For sqlite3BtreePayloadChecked(), the
+** cursor might be invalid or might need to be restored before being read.
+**
+** Return SQLITE_OK on success or an error code if anything goes
+** wrong.  An error is returned if "offset+amt" is larger than
+** the available payload.
+*/
+int sqlite3BtreePayload(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->iPage>=0 && pCur->pPage );
+  return accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
+}
+
+/*
+** This variant of sqlite3BtreePayload() works even if the cursor has not
+** in the CURSOR_VALID state.  It is only used by the sqlite3_blob_read()
+** interface.
+*/
+#ifndef SQLITE_OMIT_INCRBLOB
+static SQLITE_NOINLINE int accessPayloadChecked(
+  BtCursor *pCur,
+  u32 offset,
+  u32 amt,
+  void *pBuf
+){
+  int rc;
+  if ( pCur->eState==CURSOR_INVALID ){
+    return SQLITE_ABORT;
+  }
+  assert( cursorOwnsBtShared(pCur) );
+  rc = btreeRestoreCursorPosition(pCur);
+  return rc ? rc : accessPayload(pCur, offset, amt, pBuf, 0);
+}
+int sqlite3BtreePayloadChecked(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
+  if( pCur->eState==CURSOR_VALID ){
+    assert( cursorOwnsBtShared(pCur) );
+    return accessPayload(pCur, offset, amt, pBuf, 0);
+  }else{
+    return accessPayloadChecked(pCur, offset, amt, pBuf);
+  }
+}
+#endif /* SQLITE_OMIT_INCRBLOB */
+
+/*
+** Return a pointer to payload information from the entry that the
+** pCur cursor is pointing to.  The pointer is to the beginning of
+** the key if index btrees (pPage->intKey==0) and is the data for
+** table btrees (pPage->intKey==1). The number of bytes of available
+** key/data is written into *pAmt.  If *pAmt==0, then the value
+** returned will not be a valid pointer.
+**
+** This routine is an optimization.  It is common for the entire key
+** and data to fit on the local page and for there to be no overflow
+** pages.  When that is so, this routine can be used to access the
+** key and data without making a copy.  If the key and/or data spills
+** onto overflow pages, then accessPayload() must be used to reassemble
+** the key/data and copy it into a preallocated buffer.
+**
+** The pointer returned by this routine looks directly into the cached
+** page of the database.  The data might change or move the next time
+** any btree routine is called.
+*/
+static const void *fetchPayload(
+  BtCursor *pCur,      /* Cursor pointing to entry to read from */
+  u32 *pAmt            /* Write the number of available bytes here */
+){
+  int amt;
+  assert( pCur!=0 && pCur->iPage>=0 && pCur->pPage);
+  assert( pCur->eState==CURSOR_VALID );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  assert( cursorOwnsBtShared(pCur) );
+  assert( pCur->ix<pCur->pPage->nCell || CORRUPT_DB );
+  assert( pCur->info.nSize>0 );
+  assert( pCur->info.pPayload>pCur->pPage->aData || CORRUPT_DB );
+  assert( pCur->info.pPayload<pCur->pPage->aDataEnd ||CORRUPT_DB);
+  amt = pCur->info.nLocal;
+  if( amt>(int)(pCur->pPage->aDataEnd - pCur->info.pPayload) ){
+    /* There is too little space on the page for the expected amount
+    ** of local content. Database must be corrupt. */
+    assert( CORRUPT_DB );
+    amt = MAX(0, (int)(pCur->pPage->aDataEnd - pCur->info.pPayload));
+  }
+  *pAmt = (u32)amt;
+  return (void*)pCur->info.pPayload;
+}
+
+
+/*
+** For the entry that cursor pCur is point to, return as
+** many bytes of the key or data as are available on the local
+** b-tree page.  Write the number of available bytes into *pAmt.
+**
+** The pointer returned is ephemeral.  The key/data may move
+** or be destroyed on the next call to any Btree routine,
+** including calls from other threads against the same cache.
+** Hence, a mutex on the BtShared should be held prior to calling
+** this routine.
+**
+** These routines is used to get quick access to key and data
+** in the common case where no overflow pages are used.
+*/
+const void *sqlite3BtreePayloadFetch(BtCursor *pCur, u32 *pAmt){
+  return fetchPayload(pCur, pAmt);
+}
+
+
+/*
+** Move the cursor down to a new child page.  The newPgno argument is the
+** page number of the child page to move to.
+**
+** This function returns SQLITE_CORRUPT if the page-header flags field of
+** the new child page does not match the flags field of the parent (i.e.
+** if an intkey page appears to be the parent of a non-intkey page, or
+** vice-versa).
+*/
+static int moveToChild(BtCursor *pCur, u32 newPgno){
+  int rc;
+  assert( cursorOwnsBtShared(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
+  assert( pCur->iPage>=0 );
+  if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  pCur->info.nSize = 0;
+  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+  pCur->aiIdx[pCur->iPage] = pCur->ix;
+  pCur->apPage[pCur->iPage] = pCur->pPage;
+  pCur->ix = 0;
+  pCur->iPage++;
+  rc = getAndInitPage(pCur->pBt, newPgno, &pCur->pPage, pCur->curPagerFlags);
+  assert( pCur->pPage!=0 || rc!=SQLITE_OK );
+  if( rc==SQLITE_OK
+   && (pCur->pPage->nCell<1 || pCur->pPage->intKey!=pCur->curIntKey)
+  ){
+    releasePage(pCur->pPage);
+    rc = SQLITE_CORRUPT_PGNO(newPgno);
+  }
+  if( rc ){
+    pCur->pPage = pCur->apPage[--pCur->iPage];
+  }
+  return rc;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Page pParent is an internal (non-leaf) tree page. This function
+** asserts that page number iChild is the left-child if the iIdx'th
+** cell in page pParent. Or, if iIdx is equal to the total number of
+** cells in pParent, that page number iChild is the right-child of
+** the page.
+*/
+static void assertParentIndex(MemPage *pParent, int iIdx, Pgno iChild){
+  if( CORRUPT_DB ) return;  /* The conditions tested below might not be true
+                            ** in a corrupt database */
+  assert( iIdx<=pParent->nCell );
+  if( iIdx==pParent->nCell ){
+    assert( get4byte(&pParent->aData[pParent->hdrOffset+8])==iChild );
+  }else{
+    assert( get4byte(findCell(pParent, iIdx))==iChild );
+  }
+}
+#else
+#  define assertParentIndex(x,y,z)
+#endif
+
+/*
+** Move the cursor up to the parent page.
+**
+** pCur->idx is set to the cell index that contains the pointer
+** to the page we are coming from.  If we are coming from the
+** right-most child page then pCur->idx is set to one more than
+** the largest cell index.
+*/
+static void moveToParent(BtCursor *pCur){
+  MemPage *pLeaf;
+  assert( cursorOwnsBtShared(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->iPage>0 );
+  assert( pCur->pPage );
+  assertParentIndex(
+    pCur->apPage[pCur->iPage-1],
+    pCur->aiIdx[pCur->iPage-1],
+    pCur->pPage->pgno
+  );
+  testcase( pCur->aiIdx[pCur->iPage-1] > pCur->apPage[pCur->iPage-1]->nCell );
+  pCur->info.nSize = 0;
+  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+  pCur->ix = pCur->aiIdx[pCur->iPage-1];
+  pLeaf = pCur->pPage;
+  pCur->pPage = pCur->apPage[--pCur->iPage];
+  releasePageNotNull(pLeaf);
+}
+
+/*
+** Move the cursor to point to the root page of its b-tree structure.
+**
+** If the table has a virtual root page, then the cursor is moved to point
+** to the virtual root page instead of the actual root page. A table has a
+** virtual root page when the actual root page contains no cells and a
+** single child page. This can only happen with the table rooted at page 1.
+**
+** If the b-tree structure is empty, the cursor state is set to
+** CURSOR_INVALID and this routine returns SQLITE_EMPTY. Otherwise,
+** the cursor is set to point to the first cell located on the root
+** (or virtual root) page and the cursor state is set to CURSOR_VALID.
+**
+** If this function returns successfully, it may be assumed that the
+** page-header flags indicate that the [virtual] root-page is the expected
+** kind of b-tree page (i.e. if when opening the cursor the caller did not
+** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
+** indicating a table b-tree, or if the caller did specify a KeyInfo
+** structure the flags byte is set to 0x02 or 0x0A, indicating an index
+** b-tree).
+*/
+static int moveToRoot(BtCursor *pCur){
+  MemPage *pRoot;
+  int rc = SQLITE_OK;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
+  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
+  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
+  assert( pCur->eState < CURSOR_REQUIRESEEK || pCur->iPage<0 );
+  assert( pCur->pgnoRoot>0 || pCur->iPage<0 );
+
+  if( pCur->iPage>=0 ){
+    if( pCur->iPage ){
+      releasePageNotNull(pCur->pPage);
+      while( --pCur->iPage ){
+        releasePageNotNull(pCur->apPage[pCur->iPage]);
+      }
+      pRoot = pCur->pPage = pCur->apPage[0];
+      goto skip_init;
+    }
+  }else if( pCur->pgnoRoot==0 ){
+    pCur->eState = CURSOR_INVALID;
+    return SQLITE_EMPTY;
+  }else{
+    assert( pCur->iPage==(-1) );
+    if( pCur->eState>=CURSOR_REQUIRESEEK ){
+      if( pCur->eState==CURSOR_FAULT ){
+        assert( pCur->skipNext!=SQLITE_OK );
+        return pCur->skipNext;
+      }
+      sqlite3BtreeClearCursor(pCur);
+    }
+    rc = getAndInitPage(pCur->pBt, pCur->pgnoRoot, &pCur->pPage,
+                        pCur->curPagerFlags);
+    if( rc!=SQLITE_OK ){
+      pCur->eState = CURSOR_INVALID;
+      return rc;
+    }
+    pCur->iPage = 0;
+    pCur->curIntKey = pCur->pPage->intKey;
+  }
+  pRoot = pCur->pPage;
+  assert( pRoot->pgno==pCur->pgnoRoot || CORRUPT_DB );
+
+  /* If pCur->pKeyInfo is not NULL, then the caller that opened this cursor
+  ** expected to open it on an index b-tree. Otherwise, if pKeyInfo is
+  ** NULL, the caller expects a table b-tree. If this is not the case,
+  ** return an SQLITE_CORRUPT error.
+  **
+  ** Earlier versions of SQLite assumed that this test could not fail
+  ** if the root page was already loaded when this function was called (i.e.
+  ** if pCur->iPage>=0). But this is not so if the database is corrupted
+  ** in such a way that page pRoot is linked into a second b-tree table
+  ** (or the freelist).  */
+  assert( pRoot->intKey==1 || pRoot->intKey==0 );
+  if( pRoot->isInit==0 || (pCur->pKeyInfo==0)!=pRoot->intKey ){
+    return SQLITE_CORRUPT_PAGE(pCur->pPage);
+  }
+
+skip_init: 
+  pCur->ix = 0;
+  pCur->info.nSize = 0;
+  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidNKey|BTCF_ValidOvfl);
+
+  if( pRoot->nCell>0 ){
+    pCur->eState = CURSOR_VALID;
+  }else if( !pRoot->leaf ){
+    Pgno subpage;
+    if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
+    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
+    pCur->eState = CURSOR_VALID;
+    rc = moveToChild(pCur, subpage);
+  }else{
+    pCur->eState = CURSOR_INVALID;
+    rc = SQLITE_EMPTY;
+  }
+  return rc;
+}
+
+/*
+** Move the cursor down to the left-most leaf entry beneath the
+** entry to which it is currently pointing.
+**
+** The left-most leaf is the one with the smallest key - the first
+** in ascending order.
+*/
+static int moveToLeftmost(BtCursor *pCur){
+  Pgno pgno;
+  int rc = SQLITE_OK;
+  MemPage *pPage;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  while( rc==SQLITE_OK && !(pPage = pCur->pPage)->leaf ){
+    assert( pCur->ix<pPage->nCell );
+    pgno = get4byte(findCell(pPage, pCur->ix));
+    rc = moveToChild(pCur, pgno);
+  }
+  return rc;
+}
+
+/*
+** Move the cursor down to the right-most leaf entry beneath the
+** page to which it is currently pointing.  Notice the difference
+** between moveToLeftmost() and moveToRightmost().  moveToLeftmost()
+** finds the left-most entry beneath the *entry* whereas moveToRightmost()
+** finds the right-most entry beneath the *page*.
+**
+** The right-most entry is the one with the largest key - the last
+** key in ascending order.
+*/
+static int moveToRightmost(BtCursor *pCur){
+  Pgno pgno;
+  int rc = SQLITE_OK;
+  MemPage *pPage = 0;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  while( !(pPage = pCur->pPage)->leaf ){
+    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    pCur->ix = pPage->nCell;
+    rc = moveToChild(pCur, pgno);
+    if( rc ) return rc;
+  }
+  pCur->ix = pPage->nCell-1;
+  assert( pCur->info.nSize==0 );
+  assert( (pCur->curFlags & BTCF_ValidNKey)==0 );
+  return SQLITE_OK;
+}
+
+/* Move the cursor to the first entry in the table.  Return SQLITE_OK
+** on success.  Set *pRes to 0 if the cursor actually points to something
+** or set *pRes to 1 if the table is empty.
+*/
+int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
+  int rc;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  rc = moveToRoot(pCur);
+  if( rc==SQLITE_OK ){
+    assert( pCur->pPage->nCell>0 );
+    *pRes = 0;
+    rc = moveToLeftmost(pCur);
+  }else if( rc==SQLITE_EMPTY ){
+    assert( pCur->pgnoRoot==0 || (pCur->pPage!=0 && pCur->pPage->nCell==0) );
+    *pRes = 1;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/* Move the cursor to the last entry in the table.  Return SQLITE_OK
+** on success.  Set *pRes to 0 if the cursor actually points to something
+** or set *pRes to 1 if the table is empty.
+*/
+static SQLITE_NOINLINE int btreeLast(BtCursor *pCur, int *pRes){
+  int rc = moveToRoot(pCur);
+  if( rc==SQLITE_OK ){
+    assert( pCur->eState==CURSOR_VALID );
+    *pRes = 0;
+    rc = moveToRightmost(pCur);
+    if( rc==SQLITE_OK ){
+      pCur->curFlags |= BTCF_AtLast;
+    }else{
+      pCur->curFlags &= ~BTCF_AtLast;
+    }
+  }else if( rc==SQLITE_EMPTY ){
+    assert( pCur->pgnoRoot==0 || pCur->pPage->nCell==0 );
+    *pRes = 1;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
+  assert( cursorOwnsBtShared(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+
+  /* If the cursor already points to the last entry, this is a no-op. */
+  if( CURSOR_VALID==pCur->eState && (pCur->curFlags & BTCF_AtLast)!=0 ){
+#ifdef SQLITE_DEBUG
+    /* This block serves to assert() that the cursor really does point
+    ** to the last entry in the b-tree. */
+    int ii;
+    for(ii=0; ii<pCur->iPage; ii++){
+      assert( pCur->aiIdx[ii]==pCur->apPage[ii]->nCell );
+    }
+    assert( pCur->ix==pCur->pPage->nCell-1 || CORRUPT_DB );
+    testcase( pCur->ix!=pCur->pPage->nCell-1 );
+    /* ^-- dbsqlfuzz b92b72e4de80b5140c30ab71372ca719b8feb618 */
+    assert( pCur->pPage->leaf );
+#endif
+    *pRes = 0;
+    return SQLITE_OK;
+  }
+  return btreeLast(pCur, pRes);
+}
+
+/* Move the cursor so that it points to an entry in a table (a.k.a INTKEY)
+** table near the key intKey.   Return a success code.
+**
+** If an exact match is not found, then the cursor is always
+** left pointing at a leaf page which would hold the entry if it
+** were present.  The cursor might point to an entry that comes
+** before or after the key.
+**
+** An integer is written into *pRes which is the result of
+** comparing the key with the entry to which the cursor is
+** pointing.  The meaning of the integer written into
+** *pRes is as follows:
+**
+**     *pRes<0      The cursor is left pointing at an entry that
+**                  is smaller than intKey or if the table is empty
+**                  and the cursor is therefore left point to nothing.
+**
+**     *pRes==0     The cursor is left pointing at an entry that
+**                  exactly matches intKey.
+**
+**     *pRes>0      The cursor is left pointing at an entry that
+**                  is larger than intKey.
+*/
+int sqlite3BtreeTableMoveto(
+  BtCursor *pCur,          /* The cursor to be moved */
+  i64 intKey,              /* The table key */
+  int biasRight,           /* If true, bias the search to the high end */
+  int *pRes                /* Write search results here */
+){
+  int rc;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  assert( pRes );
+  assert( pCur->pKeyInfo==0 );
+  assert( pCur->eState!=CURSOR_VALID || pCur->curIntKey!=0 );
+
+  /* If the cursor is already positioned at the point we are trying
+  ** to move to, then just return without doing any work */
+  if( pCur->eState==CURSOR_VALID && (pCur->curFlags & BTCF_ValidNKey)!=0 ){
+    if( pCur->info.nKey==intKey ){
+      *pRes = 0;
+      return SQLITE_OK;
+    }
+    if( pCur->info.nKey<intKey ){
+      if( (pCur->curFlags & BTCF_AtLast)!=0 ){
+        *pRes = -1;
+        return SQLITE_OK;
+      }
+      /* If the requested key is one more than the previous key, then
+      ** try to get there using sqlite3BtreeNext() rather than a full
+      ** binary search.  This is an optimization only.  The correct answer
+      ** is still obtained without this case, only a little more slowly. */
+      if( pCur->info.nKey+1==intKey ){
+        *pRes = 0;
+        rc = sqlite3BtreeNext(pCur, 0);
+        if( rc==SQLITE_OK ){
+          getCellInfo(pCur);
+          if( pCur->info.nKey==intKey ){
+            return SQLITE_OK;
+          }
+        }else if( rc!=SQLITE_DONE ){
+          return rc;
+        }
+      }
+    }
+  }
+
+#ifdef SQLITE_DEBUG
+  pCur->pBtree->nSeek++;   /* Performance measurement during testing */
+#endif
+
+  rc = moveToRoot(pCur);
+  if( rc ){
+    if( rc==SQLITE_EMPTY ){
+      assert( pCur->pgnoRoot==0 || pCur->pPage->nCell==0 );
+      *pRes = -1;
+      return SQLITE_OK;
+    }
+    return rc;
+  }
+  assert( pCur->pPage );
+  assert( pCur->pPage->isInit );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->pPage->nCell > 0 );
+  assert( pCur->iPage==0 || pCur->apPage[0]->intKey==pCur->curIntKey );
+  assert( pCur->curIntKey );
+
+  for(;;){
+    int lwr, upr, idx, c;
+    Pgno chldPg;
+    MemPage *pPage = pCur->pPage;
+    u8 *pCell;                          /* Pointer to current cell in pPage */
+
+    /* pPage->nCell must be greater than zero. If this is the root-page
+    ** the cursor would have been INVALID above and this for(;;) loop
+    ** not run. If this is not the root-page, then the moveToChild() routine
+    ** would have already detected db corruption. Similarly, pPage must
+    ** be the right kind (index or table) of b-tree page. Otherwise
+    ** a moveToChild() or moveToRoot() call would have detected corruption.  */
+    assert( pPage->nCell>0 );
+    assert( pPage->intKey );
+    lwr = 0;
+    upr = pPage->nCell-1;
+    assert( biasRight==0 || biasRight==1 );
+    idx = upr>>(1-biasRight); /* idx = biasRight ? upr : (lwr+upr)/2; */
+    for(;;){
+      i64 nCellKey;
+      pCell = findCellPastPtr(pPage, idx);
+      if( pPage->intKeyLeaf ){
+        while( 0x80 <= *(pCell++) ){
+          if( pCell>=pPage->aDataEnd ){
+            return SQLITE_CORRUPT_PAGE(pPage);
+          }
+        }
+      }
+      getVarint(pCell, (u64*)&nCellKey);
+      if( nCellKey<intKey ){
+        lwr = idx+1;
+        if( lwr>upr ){ c = -1; break; }
+      }else if( nCellKey>intKey ){
+        upr = idx-1;
+        if( lwr>upr ){ c = +1; break; }
+      }else{
+        assert( nCellKey==intKey );
+        pCur->ix = (u16)idx;
+        if( !pPage->leaf ){
+          lwr = idx;
+          goto moveto_table_next_layer;
+        }else{
+          pCur->curFlags |= BTCF_ValidNKey;
+          pCur->info.nKey = nCellKey;
+          pCur->info.nSize = 0;
+          *pRes = 0;
+          return SQLITE_OK;
+        }
+      }
+      assert( lwr+upr>=0 );
+      idx = (lwr+upr)>>1;  /* idx = (lwr+upr)/2; */
+    }
+    assert( lwr==upr+1 || !pPage->leaf );
+    assert( pPage->isInit );
+    if( pPage->leaf ){
+      assert( pCur->ix<pCur->pPage->nCell );
+      pCur->ix = (u16)idx;
+      *pRes = c;
+      rc = SQLITE_OK;
+      goto moveto_table_finish;
+    }
+moveto_table_next_layer:
+    if( lwr>=pPage->nCell ){
+      chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    }else{
+      chldPg = get4byte(findCell(pPage, lwr));
+    }
+    pCur->ix = (u16)lwr;
+    rc = moveToChild(pCur, chldPg);
+    if( rc ) break;
+  }
+moveto_table_finish:
+  pCur->info.nSize = 0;
+  assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
+  return rc;
+}
+
+/*
+** Compare the "idx"-th cell on the page the cursor pCur is currently
+** pointing to to pIdxKey using xRecordCompare.  Return negative or
+** zero if the cell is less than or equal pIdxKey.  Return positive
+** if unknown.
+**
+**    Return value negative:     Cell at pCur[idx] less than pIdxKey
+**
+**    Return value is zero:      Cell at pCur[idx] equals pIdxKey
+**
+**    Return value positive:     Nothing is known about the relationship
+**                               of the cell at pCur[idx] and pIdxKey.
+**
+** This routine is part of an optimization.  It is always safe to return
+** a positive value as that will cause the optimization to be skipped.
+*/
+static int indexCellCompare(
+  BtCursor *pCur,
+  int idx,
+  UnpackedRecord *pIdxKey,
+  RecordCompare xRecordCompare
+){
+  MemPage *pPage = pCur->pPage;
+  int c;
+  int nCell;  /* Size of the pCell cell in bytes */
+  u8 *pCell = findCellPastPtr(pPage, idx);
+
+  nCell = pCell[0];
+  if( nCell<=pPage->max1bytePayload ){
+    /* This branch runs if the record-size field of the cell is a
+    ** single byte varint and the record fits entirely on the main
+    ** b-tree page.  */
+    testcase( pCell+nCell+1==pPage->aDataEnd );
+    c = xRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
+  }else if( !(pCell[1] & 0x80)
+    && (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
+  ){
+    /* The record-size field is a 2 byte varint and the record
+    ** fits entirely on the main b-tree page.  */
+    testcase( pCell+nCell+2==pPage->aDataEnd );
+    c = xRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
+  }else{
+    /* If the record extends into overflow pages, do not attempt
+    ** the optimization. */
+    c = 99;
+  }
+  return c;
+}
+
+/*
+** Return true (non-zero) if pCur is current pointing to the last
+** page of a table.
+*/
+static int cursorOnLastPage(BtCursor *pCur){
+  int i;
+  assert( pCur->eState==CURSOR_VALID );
+  for(i=0; i<pCur->iPage; i++){
+    MemPage *pPage = pCur->apPage[i];
+    if( pCur->aiIdx[i]<pPage->nCell ) return 0;
+  }
+  return 1;
+}
+
+/* Move the cursor so that it points to an entry in an index table
+** near the key pIdxKey.   Return a success code.
+**
+** If an exact match is not found, then the cursor is always
+** left pointing at a leaf page which would hold the entry if it
+** were present.  The cursor might point to an entry that comes
+** before or after the key.
+**
+** An integer is written into *pRes which is the result of
+** comparing the key with the entry to which the cursor is
+** pointing.  The meaning of the integer written into
+** *pRes is as follows:
+**
+**     *pRes<0      The cursor is left pointing at an entry that
+**                  is smaller than pIdxKey or if the table is empty
+**                  and the cursor is therefore left point to nothing.
+**
+**     *pRes==0     The cursor is left pointing at an entry that
+**                  exactly matches pIdxKey.
+**
+**     *pRes>0      The cursor is left pointing at an entry that
+**                  is larger than pIdxKey.
+**
+** The pIdxKey->eqSeen field is set to 1 if there
+** exists an entry in the table that exactly matches pIdxKey. 
+*/
+int sqlite3BtreeIndexMoveto(
+  BtCursor *pCur,          /* The cursor to be moved */
+  UnpackedRecord *pIdxKey, /* Unpacked index key */
+  int *pRes                /* Write search results here */
+){
+  int rc;
+  RecordCompare xRecordCompare;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  assert( pRes );
+  assert( pCur->pKeyInfo!=0 );
+
+#ifdef SQLITE_DEBUG
+  pCur->pBtree->nSeek++;   /* Performance measurement during testing */
+#endif
+
+  xRecordCompare = sqlite3VdbeFindCompare(pIdxKey);
+  pIdxKey->errCode = 0;
+  assert( pIdxKey->default_rc==1
+       || pIdxKey->default_rc==0
+       || pIdxKey->default_rc==-1
+  );
+
+
+  /* Check to see if we can skip a lot of work.  Two cases:
+  **
+  **    (1) If the cursor is already pointing to the very last cell
+  **        in the table and the pIdxKey search key is greater than or
+  **        equal to that last cell, then no movement is required.
+  **
+  **    (2) If the cursor is on the last page of the table and the first
+  **        cell on that last page is less than or equal to the pIdxKey
+  **        search key, then we can start the search on the current page
+  **        without needing to go back to root.
+  */
+  if( pCur->eState==CURSOR_VALID
+   && pCur->pPage->leaf
+   && cursorOnLastPage(pCur)
+  ){
+    int c;
+    if( pCur->ix==pCur->pPage->nCell-1
+     && (c = indexCellCompare(pCur, pCur->ix, pIdxKey, xRecordCompare))<=0
+     && pIdxKey->errCode==SQLITE_OK
+    ){
+      *pRes = c;
+      return SQLITE_OK;  /* Cursor already pointing at the correct spot */
+    }
+    if( pCur->iPage>0
+     && indexCellCompare(pCur, 0, pIdxKey, xRecordCompare)<=0
+     && pIdxKey->errCode==SQLITE_OK
+    ){
+      pCur->curFlags &= ~BTCF_ValidOvfl;
+      if( !pCur->pPage->isInit ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+      goto bypass_moveto_root;  /* Start search on the current page */
+    }
+    pIdxKey->errCode = SQLITE_OK;
+  }
+
+  rc = moveToRoot(pCur);
+  if( rc ){
+    if( rc==SQLITE_EMPTY ){
+      assert( pCur->pgnoRoot==0 || pCur->pPage->nCell==0 );
+      *pRes = -1;
+      return SQLITE_OK;
+    }
+    return rc;
+  }
+
+bypass_moveto_root:
+  assert( pCur->pPage );
+  assert( pCur->pPage->isInit );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->pPage->nCell > 0 );
+  assert( pCur->curIntKey==0 );
+  assert( pIdxKey!=0 );
+  for(;;){
+    int lwr, upr, idx, c;
+    Pgno chldPg;
+    MemPage *pPage = pCur->pPage;
+    u8 *pCell;                          /* Pointer to current cell in pPage */
+
+    /* pPage->nCell must be greater than zero. If this is the root-page
+    ** the cursor would have been INVALID above and this for(;;) loop
+    ** not run. If this is not the root-page, then the moveToChild() routine
+    ** would have already detected db corruption. Similarly, pPage must
+    ** be the right kind (index or table) of b-tree page. Otherwise
+    ** a moveToChild() or moveToRoot() call would have detected corruption.  */
+    assert( pPage->nCell>0 );
+    assert( pPage->intKey==0 );
+    lwr = 0;
+    upr = pPage->nCell-1;
+    idx = upr>>1; /* idx = (lwr+upr)/2; */
+    for(;;){
+      int nCell;  /* Size of the pCell cell in bytes */
+      pCell = findCellPastPtr(pPage, idx);
+
+      /* The maximum supported page-size is 65536 bytes. This means that
+      ** the maximum number of record bytes stored on an index B-Tree
+      ** page is less than 16384 bytes and may be stored as a 2-byte
+      ** varint. This information is used to attempt to avoid parsing
+      ** the entire cell by checking for the cases where the record is
+      ** stored entirely within the b-tree page by inspecting the first
+      ** 2 bytes of the cell.
+      */
+      nCell = pCell[0];
+      if( nCell<=pPage->max1bytePayload ){
+        /* This branch runs if the record-size field of the cell is a
+        ** single byte varint and the record fits entirely on the main
+        ** b-tree page.  */
+        testcase( pCell+nCell+1==pPage->aDataEnd );
+        c = xRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
+      }else if( !(pCell[1] & 0x80)
+        && (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
+      ){
+        /* The record-size field is a 2 byte varint and the record
+        ** fits entirely on the main b-tree page.  */
+        testcase( pCell+nCell+2==pPage->aDataEnd );
+        c = xRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
+      }else{
+        /* The record flows over onto one or more overflow pages. In
+        ** this case the whole cell needs to be parsed, a buffer allocated
+        ** and accessPayload() used to retrieve the record into the
+        ** buffer before VdbeRecordCompare() can be called.
+        **
+        ** If the record is corrupt, the xRecordCompare routine may read
+        ** up to two varints past the end of the buffer. An extra 18
+        ** bytes of padding is allocated at the end of the buffer in
+        ** case this happens.  */
+        void *pCellKey;
+        u8 * const pCellBody = pCell - pPage->childPtrSize;
+        const int nOverrun = 18;  /* Size of the overrun padding */
+        pPage->xParseCell(pPage, pCellBody, &pCur->info);
+        nCell = (int)pCur->info.nKey;
+        testcase( nCell<0 );   /* True if key size is 2^32 or more */
+        testcase( nCell==0 );  /* Invalid key size:  0x80 0x80 0x00 */
+        testcase( nCell==1 );  /* Invalid key size:  0x80 0x80 0x01 */
+        testcase( nCell==2 );  /* Minimum legal index key size */
+        if( nCell<2 || nCell/pCur->pBt->usableSize>pCur->pBt->nPage ){
+          rc = SQLITE_CORRUPT_PAGE(pPage);
+          goto moveto_index_finish;
+        }
+        pCellKey = sqlite3Malloc( nCell+nOverrun );
+        if( pCellKey==0 ){
+          rc = SQLITE_NOMEM_BKPT;
+          goto moveto_index_finish;
+        }
+        pCur->ix = (u16)idx;
+        rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 0);
+        memset(((u8*)pCellKey)+nCell,0,nOverrun); /* Fix uninit warnings */
+        pCur->curFlags &= ~BTCF_ValidOvfl;
+        if( rc ){
+          sqlite3_free(pCellKey);
+          goto moveto_index_finish;
+        }
+        c = sqlite3VdbeRecordCompare(nCell, pCellKey, pIdxKey);
+        sqlite3_free(pCellKey);
+      }
+      assert(
+          (pIdxKey->errCode!=SQLITE_CORRUPT || c==0)
+       && (pIdxKey->errCode!=SQLITE_NOMEM || pCur->pBtree->db->mallocFailed)
+      );
+      if( c<0 ){
+        lwr = idx+1;
+      }else if( c>0 ){
+        upr = idx-1;
+      }else{
+        assert( c==0 );
+        *pRes = 0;
+        rc = SQLITE_OK;
+        pCur->ix = (u16)idx;
+        if( pIdxKey->errCode ) rc = SQLITE_CORRUPT_BKPT;
+        goto moveto_index_finish;
+      }
+      if( lwr>upr ) break;
+      assert( lwr+upr>=0 );
+      idx = (lwr+upr)>>1;  /* idx = (lwr+upr)/2 */
+    }
+    assert( lwr==upr+1 || (pPage->intKey && !pPage->leaf) );
+    assert( pPage->isInit );
+    if( pPage->leaf ){
+      assert( pCur->ix<pCur->pPage->nCell || CORRUPT_DB );
+      pCur->ix = (u16)idx;
+      *pRes = c;
+      rc = SQLITE_OK;
+      goto moveto_index_finish;
+    }
+    if( lwr>=pPage->nCell ){
+      chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    }else{
+      chldPg = get4byte(findCell(pPage, lwr));
+    }
+
+    /* This block is similar to an in-lined version of:
+    **
+    **    pCur->ix = (u16)lwr;
+    **    rc = moveToChild(pCur, chldPg);
+    **    if( rc ) break;
+    */
+    pCur->info.nSize = 0;
+    pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+    if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+    pCur->aiIdx[pCur->iPage] = (u16)lwr;
+    pCur->apPage[pCur->iPage] = pCur->pPage;
+    pCur->ix = 0;
+    pCur->iPage++;
+    rc = getAndInitPage(pCur->pBt, chldPg, &pCur->pPage, pCur->curPagerFlags);
+    if( rc==SQLITE_OK
+     && (pCur->pPage->nCell<1 || pCur->pPage->intKey!=pCur->curIntKey)
+    ){
+      releasePage(pCur->pPage);
+      rc = SQLITE_CORRUPT_PGNO(chldPg);
+    }
+    if( rc ){
+      pCur->pPage = pCur->apPage[--pCur->iPage];
+      break;
+    }
+    /*
+    ***** End of in-lined moveToChild() call */
+ }
+moveto_index_finish:
+  pCur->info.nSize = 0;
+  assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
+  return rc;
+}
+
+
+/*
+** Return TRUE if the cursor is not pointing at an entry of the table.
+**
+** TRUE will be returned after a call to sqlite3BtreeNext() moves
+** past the last entry in the table or sqlite3BtreePrev() moves past
+** the first entry.  TRUE is also returned if the table is empty.
+*/
+int sqlite3BtreeEof(BtCursor *pCur){
+  /* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
+  ** have been deleted? This API will need to change to return an error code
+  ** as well as the boolean result value.
+  */
+  return (CURSOR_VALID!=pCur->eState);
+}
+
+/*
+** Return an estimate for the number of rows in the table that pCur is
+** pointing to.  Return a negative number if no estimate is currently
+** available.
+*/
+i64 sqlite3BtreeRowCountEst(BtCursor *pCur){
+  i64 n;
+  u8 i;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+
+  /* Currently this interface is only called by the OP_IfSmaller
+  ** opcode, and it that case the cursor will always be valid and
+  ** will always point to a leaf node. */
+  if( NEVER(pCur->eState!=CURSOR_VALID) ) return -1;
+  if( NEVER(pCur->pPage->leaf==0) ) return -1;
+
+  n = pCur->pPage->nCell;
+  for(i=0; i<pCur->iPage; i++){
+    n *= pCur->apPage[i]->nCell;
+  }
+  return n;
+}
+
+/*
+** Advance the cursor to the next entry in the database.
+** Return value:
+**
+**    SQLITE_OK        success
+**    SQLITE_DONE      cursor is already pointing at the last element
+**    otherwise        some kind of error occurred
+**
+** The main entry point is sqlite3BtreeNext().  That routine is optimized
+** for the common case of merely incrementing the cell counter BtCursor.aiIdx
+** to the next cell on the current page.  The (slower) btreeNext() helper
+** routine is called when it is necessary to move to a different page or
+** to restore the cursor.
+**
+** If bit 0x01 of the F argument in sqlite3BtreeNext(C,F) is 1, then the
+** cursor corresponds to an SQL index and this routine could have been
+** skipped if the SQL index had been a unique index.  The F argument
+** is a hint to the implement.  SQLite btree implementation does not use
+** this hint, but COMDB2 does.
+*/
+static SQLITE_NOINLINE int btreeNext(BtCursor *pCur){
+  int rc;
+  int idx;
+  MemPage *pPage;
+
+  assert( cursorOwnsBtShared(pCur) );
+  if( pCur->eState!=CURSOR_VALID ){
+    assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
+    rc = restoreCursorPosition(pCur);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    if( CURSOR_INVALID==pCur->eState ){
+      return SQLITE_DONE;
+    }
+    if( pCur->eState==CURSOR_SKIPNEXT ){
+      pCur->eState = CURSOR_VALID;
+      if( pCur->skipNext>0 ) return SQLITE_OK;
+    }
+  }
+
+  pPage = pCur->pPage;
+  idx = ++pCur->ix;
+  if( sqlite3FaultSim(412) ) pPage->isInit = 0;
+  if( !pPage->isInit ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+
+  if( idx>=pPage->nCell ){
+    if( !pPage->leaf ){
+      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
+      if( rc ) return rc;
+      return moveToLeftmost(pCur);
+    }
+    do{
+      if( pCur->iPage==0 ){
+        pCur->eState = CURSOR_INVALID;
+        return SQLITE_DONE;
+      }
+      moveToParent(pCur);
+      pPage = pCur->pPage;
+    }while( pCur->ix>=pPage->nCell );
+    if( pPage->intKey ){
+      return sqlite3BtreeNext(pCur, 0);
+    }else{
+      return SQLITE_OK;
+    }
+  }
+  if( pPage->leaf ){
+    return SQLITE_OK;
+  }else{
+    return moveToLeftmost(pCur);
+  }
+}
+int sqlite3BtreeNext(BtCursor *pCur, int flags){
+  MemPage *pPage;
+  UNUSED_PARAMETER( flags );  /* Used in COMDB2 but not native SQLite */
+  assert( cursorOwnsBtShared(pCur) );
+  assert( flags==0 || flags==1 );
+  pCur->info.nSize = 0;
+  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+  if( pCur->eState!=CURSOR_VALID ) return btreeNext(pCur);
+  pPage = pCur->pPage;
+  if( (++pCur->ix)>=pPage->nCell ){
+    pCur->ix--;
+    return btreeNext(pCur);
+  }
+  if( pPage->leaf ){
+    return SQLITE_OK;
+  }else{
+    return moveToLeftmost(pCur);
+  }
+}
+
+/*
+** Step the cursor to the back to the previous entry in the database.
+** Return values:
+**
+**     SQLITE_OK     success
+**     SQLITE_DONE   the cursor is already on the first element of the table
+**     otherwise     some kind of error occurred
+**
+** The main entry point is sqlite3BtreePrevious().  That routine is optimized
+** for the common case of merely decrementing the cell counter BtCursor.aiIdx
+** to the previous cell on the current page.  The (slower) btreePrevious()
+** helper routine is called when it is necessary to move to a different page
+** or to restore the cursor.
+**
+** If bit 0x01 of the F argument to sqlite3BtreePrevious(C,F) is 1, then
+** the cursor corresponds to an SQL index and this routine could have been
+** skipped if the SQL index had been a unique index.  The F argument is a
+** hint to the implement.  The native SQLite btree implementation does not
+** use this hint, but COMDB2 does.
+*/
+static SQLITE_NOINLINE int btreePrevious(BtCursor *pCur){
+  int rc;
+  MemPage *pPage;
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
+  assert( pCur->info.nSize==0 );
+  if( pCur->eState!=CURSOR_VALID ){
+    rc = restoreCursorPosition(pCur);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    if( CURSOR_INVALID==pCur->eState ){
+      return SQLITE_DONE;
+    }
+    if( CURSOR_SKIPNEXT==pCur->eState ){
+      pCur->eState = CURSOR_VALID;
+      if( pCur->skipNext<0 ) return SQLITE_OK;
+    }
+  }
+
+  pPage = pCur->pPage;
+  if( sqlite3FaultSim(412) ) pPage->isInit = 0;
+  if( !pPage->isInit ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  if( !pPage->leaf ){
+    int idx = pCur->ix;
+    rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
+    if( rc ) return rc;
+    rc = moveToRightmost(pCur);
+  }else{
+    while( pCur->ix==0 ){
+      if( pCur->iPage==0 ){
+        pCur->eState = CURSOR_INVALID;
+        return SQLITE_DONE;
+      }
+      moveToParent(pCur);
+    }
+    assert( pCur->info.nSize==0 );
+    assert( (pCur->curFlags & (BTCF_ValidOvfl))==0 );
+
+    pCur->ix--;
+    pPage = pCur->pPage;
+    if( pPage->intKey && !pPage->leaf ){
+      rc = sqlite3BtreePrevious(pCur, 0);
+    }else{
+      rc = SQLITE_OK;
+    }
+  }
+  return rc;
+}
+int sqlite3BtreePrevious(BtCursor *pCur, int flags){
+  assert( cursorOwnsBtShared(pCur) );
+  assert( flags==0 || flags==1 );
+  UNUSED_PARAMETER( flags );  /* Used in COMDB2 but not native SQLite */
+  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey);
+  pCur->info.nSize = 0;
+  if( pCur->eState!=CURSOR_VALID
+   || pCur->ix==0
+   || pCur->pPage->leaf==0
+  ){
+    return btreePrevious(pCur);
+  }
+  pCur->ix--;
+  return SQLITE_OK;
+}
+
+/*
+** Allocate a new page from the database file.
+**
+** The new page is marked as dirty.  (In other words, sqlite3PagerWrite()
+** has already been called on the new page.)  The new page has also
+** been referenced and the calling routine is responsible for calling
+** sqlite3PagerUnref() on the new page when it is done.
+**
+** SQLITE_OK is returned on success.  Any other return value indicates
+** an error.  *ppPage is set to NULL in the event of an error.
+**
+** If the "nearby" parameter is not 0, then an effort is made to
+** locate a page close to the page number "nearby".  This can be used in an
+** attempt to keep related pages close to each other in the database file,
+** which in turn can make database access faster.
+**
+** If the eMode parameter is BTALLOC_EXACT and the nearby page exists
+** anywhere on the free-list, then it is guaranteed to be returned.  If
+** eMode is BTALLOC_LT then the page returned will be less than or equal
+** to nearby if any such page exists.  If eMode is BTALLOC_ANY then there
+** are no restrictions on which page is returned.
+*/
+static int allocateBtreePage(
+  BtShared *pBt,         /* The btree */
+  MemPage **ppPage,      /* Store pointer to the allocated page here */
+  Pgno *pPgno,           /* Store the page number here */
+  Pgno nearby,           /* Search for a page near this one */
+  u8 eMode               /* BTALLOC_EXACT, BTALLOC_LT, or BTALLOC_ANY */
+){
+  MemPage *pPage1;
+  int rc;
+  u32 n;     /* Number of pages on the freelist */
+  u32 k;     /* Number of leaves on the trunk of the freelist */
+  MemPage *pTrunk = 0;
+  MemPage *pPrevTrunk = 0;
+  Pgno mxPage;     /* Total size of the database file */
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( eMode==BTALLOC_ANY || (nearby>0 && IfNotOmitAV(pBt->autoVacuum)) );
+  pPage1 = pBt->pPage1;
+  mxPage = btreePagecount(pBt);
+  /* EVIDENCE-OF: R-21003-45125 The 4-byte big-endian integer at offset 36
+  ** stores the total number of pages on the freelist. */
+  n = get4byte(&pPage1->aData[36]);
+  testcase( n==mxPage-1 );
+  if( n>=mxPage ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  if( n>0 ){
+    /* There are pages on the freelist.  Reuse one of those pages. */
+    Pgno iTrunk;
+    u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
+    u32 nSearch = 0;   /* Count of the number of search attempts */
+   
+    /* If eMode==BTALLOC_EXACT and a query of the pointer-map
+    ** shows that the page 'nearby' is somewhere on the free-list, then
+    ** the entire-list will be searched for that page.
+    */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( eMode==BTALLOC_EXACT ){
+      if( nearby<=mxPage ){
+        u8 eType;
+        assert( nearby>0 );
+        assert( pBt->autoVacuum );
+        rc = ptrmapGet(pBt, nearby, &eType, 0);
+        if( rc ) return rc;
+        if( eType==PTRMAP_FREEPAGE ){
+          searchList = 1;
+        }
+      }
+    }else if( eMode==BTALLOC_LE ){
+      searchList = 1;
+    }
+#endif
+
+    /* Decrement the free-list count by 1. Set iTrunk to the index of the
+    ** first free-list trunk page. iPrevTrunk is initially 1.
+    */
+    rc = sqlite3PagerWrite(pPage1->pDbPage);
+    if( rc ) return rc;
+    put4byte(&pPage1->aData[36], n-1);
+
+    /* The code within this loop is run only once if the 'searchList' variable
+    ** is not true. Otherwise, it runs once for each trunk-page on the
+    ** free-list until the page 'nearby' is located (eMode==BTALLOC_EXACT)
+    ** or until a page less than 'nearby' is located (eMode==BTALLOC_LT)
+    */
+    do {
+      pPrevTrunk = pTrunk;
+      if( pPrevTrunk ){
+        /* EVIDENCE-OF: R-01506-11053 The first integer on a freelist trunk page
+        ** is the page number of the next freelist trunk page in the list or
+        ** zero if this is the last freelist trunk page. */
+        iTrunk = get4byte(&pPrevTrunk->aData[0]);
+      }else{
+        /* EVIDENCE-OF: R-59841-13798 The 4-byte big-endian integer at offset 32
+        ** stores the page number of the first page of the freelist, or zero if
+        ** the freelist is empty. */
+        iTrunk = get4byte(&pPage1->aData[32]);
+      }
+      testcase( iTrunk==mxPage );
+      if( iTrunk>mxPage || nSearch++ > n ){
+        rc = SQLITE_CORRUPT_PGNO(pPrevTrunk ? pPrevTrunk->pgno : 1);
+      }else{
+        rc = btreeGetUnusedPage(pBt, iTrunk, &pTrunk, 0);
+      }
+      if( rc ){
+        pTrunk = 0;
+        goto end_allocate_page;
+      }
+      assert( pTrunk!=0 );
+      assert( pTrunk->aData!=0 );
+      /* EVIDENCE-OF: R-13523-04394 The second integer on a freelist trunk page
+      ** is the number of leaf page pointers to follow. */
+      k = get4byte(&pTrunk->aData[4]);
+      if( k==0 && !searchList ){
+        /* The trunk has no leaves and the list is not being searched.
+        ** So extract the trunk page itself and use it as the newly
+        ** allocated page */
+        assert( pPrevTrunk==0 );
+        rc = sqlite3PagerWrite(pTrunk->pDbPage);
+        if( rc ){
+          goto end_allocate_page;
+        }
+        *pPgno = iTrunk;
+        memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
+        *ppPage = pTrunk;
+        pTrunk = 0;
+        TRACE(("ALLOCATE: %u trunk - %u free pages left\n", *pPgno, n-1));
+      }else if( k>(u32)(pBt->usableSize/4 - 2) ){
+        /* Value of k is out of range.  Database corruption */
+        rc = SQLITE_CORRUPT_PGNO(iTrunk);
+        goto end_allocate_page;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      }else if( searchList
+            && (nearby==iTrunk || (iTrunk<nearby && eMode==BTALLOC_LE))
+      ){
+        /* The list is being searched and this trunk page is the page
+        ** to allocate, regardless of whether it has leaves.
+        */
+        *pPgno = iTrunk;
+        *ppPage = pTrunk;
+        searchList = 0;
+        rc = sqlite3PagerWrite(pTrunk->pDbPage);
+        if( rc ){
+          goto end_allocate_page;
+        }
+        if( k==0 ){
+          if( !pPrevTrunk ){
+            memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
+          }else{
+            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
+            if( rc!=SQLITE_OK ){
+              goto end_allocate_page;
+            }
+            memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
+          }
+        }else{
+          /* The trunk page is required by the caller but it contains
+          ** pointers to free-list leaves. The first leaf becomes a trunk
+          ** page in this case.
+          */
+          MemPage *pNewTrunk;
+          Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
+          if( iNewTrunk>mxPage ){
+            rc = SQLITE_CORRUPT_PGNO(iTrunk);
+            goto end_allocate_page;
+          }
+          testcase( iNewTrunk==mxPage );
+          rc = btreeGetUnusedPage(pBt, iNewTrunk, &pNewTrunk, 0);
+          if( rc!=SQLITE_OK ){
+            goto end_allocate_page;
+          }
+          rc = sqlite3PagerWrite(pNewTrunk->pDbPage);
+          if( rc!=SQLITE_OK ){
+            releasePage(pNewTrunk);
+            goto end_allocate_page;
+          }
+          memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
+          put4byte(&pNewTrunk->aData[4], k-1);
+          memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
+          releasePage(pNewTrunk);
+          if( !pPrevTrunk ){
+            assert( sqlite3PagerIswriteable(pPage1->pDbPage) );
+            put4byte(&pPage1->aData[32], iNewTrunk);
+          }else{
+            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
+            if( rc ){
+              goto end_allocate_page;
+            }
+            put4byte(&pPrevTrunk->aData[0], iNewTrunk);
+          }
+        }
+        pTrunk = 0;
+        TRACE(("ALLOCATE: %u trunk - %u free pages left\n", *pPgno, n-1));
+#endif
+      }else if( k>0 ){
+        /* Extract a leaf from the trunk */
+        u32 closest;
+        Pgno iPage;
+        unsigned char *aData = pTrunk->aData;
+        if( nearby>0 ){
+          u32 i;
+          closest = 0;
+          if( eMode==BTALLOC_LE ){
+            for(i=0; i<k; i++){
+              iPage = get4byte(&aData[8+i*4]);
+              if( iPage<=nearby ){
+                closest = i;
+                break;
+              }
+            }
+          }else{
+            int dist;
+            dist = sqlite3AbsInt32(get4byte(&aData[8]) - nearby);
+            for(i=1; i<k; i++){
+              int d2 = sqlite3AbsInt32(get4byte(&aData[8+i*4]) - nearby);
+              if( d2<dist ){
+                closest = i;
+                dist = d2;
+              }
+            }
+          }
+        }else{
+          closest = 0;
+        }
+
+        iPage = get4byte(&aData[8+closest*4]);
+        testcase( iPage==mxPage );
+        if( iPage>mxPage || iPage<2 ){
+          rc = SQLITE_CORRUPT_PGNO(iTrunk);
+          goto end_allocate_page;
+        }
+        testcase( iPage==mxPage );
+        if( !searchList
+         || (iPage==nearby || (iPage<nearby && eMode==BTALLOC_LE))
+        ){
+          int noContent;
+          *pPgno = iPage;
+          TRACE(("ALLOCATE: %u was leaf %u of %u on trunk %u"
+                 ": %u more free pages\n",
+                 *pPgno, closest+1, k, pTrunk->pgno, n-1));
+          rc = sqlite3PagerWrite(pTrunk->pDbPage);
+          if( rc ) goto end_allocate_page;
+          if( closest<k-1 ){
+            memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
+          }
+          put4byte(&aData[4], k-1);
+          noContent = !btreeGetHasContent(pBt, *pPgno)? PAGER_GET_NOCONTENT : 0;
+          rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, noContent);
+          if( rc==SQLITE_OK ){
+            rc = sqlite3PagerWrite((*ppPage)->pDbPage);
+            if( rc!=SQLITE_OK ){
+              releasePage(*ppPage);
+              *ppPage = 0;
+            }
+          }
+          searchList = 0;
+        }
+      }
+      releasePage(pPrevTrunk);
+      pPrevTrunk = 0;
+    }while( searchList );
+  }else{
+    /* There are no pages on the freelist, so append a new page to the
+    ** database image.
+    **
+    ** Normally, new pages allocated by this block can be requested from the
+    ** pager layer with the 'no-content' flag set. This prevents the pager
+    ** from trying to read the pages content from disk. However, if the
+    ** current transaction has already run one or more incremental-vacuum
+    ** steps, then the page we are about to allocate may contain content
+    ** that is required in the event of a rollback. In this case, do
+    ** not set the no-content flag. This causes the pager to load and journal
+    ** the current page content before overwriting it.
+    **
+    ** Note that the pager will not actually attempt to load or journal
+    ** content for any page that really does lie past the end of the database
+    ** file on disk. So the effects of disabling the no-content optimization
+    ** here are confined to those pages that lie between the end of the
+    ** database image and the end of the database file.
+    */
+    int bNoContent = (0==IfNotOmitAV(pBt->bDoTruncate))? PAGER_GET_NOCONTENT:0;
+
+    rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+    if( rc ) return rc;
+    pBt->nPage++;
+    if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
+      /* If *pPgno refers to a pointer-map page, allocate two new pages
+      ** at the end of the file instead of one. The first allocated page
+      ** becomes a new pointer-map page, the second is used by the caller.
+      */
+      MemPage *pPg = 0;
+      TRACE(("ALLOCATE: %u from end of file (pointer-map page)\n", pBt->nPage));
+      assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
+      rc = btreeGetUnusedPage(pBt, pBt->nPage, &pPg, bNoContent);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerWrite(pPg->pDbPage);
+        releasePage(pPg);
+      }
+      if( rc ) return rc;
+      pBt->nPage++;
+      if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
+    }
+#endif
+    put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
+    *pPgno = pBt->nPage;
+
+    assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
+    rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, bNoContent);
+    if( rc ) return rc;
+    rc = sqlite3PagerWrite((*ppPage)->pDbPage);
+    if( rc!=SQLITE_OK ){
+      releasePage(*ppPage);
+      *ppPage = 0;
+    }
+    TRACE(("ALLOCATE: %u from end of file\n", *pPgno));
+  }
+
+  assert( CORRUPT_DB || *pPgno!=PENDING_BYTE_PAGE(pBt) );
+
+end_allocate_page:
+  releasePage(pTrunk);
+  releasePage(pPrevTrunk);
+  assert( rc!=SQLITE_OK || sqlite3PagerPageRefcount((*ppPage)->pDbPage)<=1 );
+  assert( rc!=SQLITE_OK || (*ppPage)->isInit==0 );
+  return rc;
+}
+
+/*
+** This function is used to add page iPage to the database file free-list.
+** It is assumed that the page is not already a part of the free-list.
+**
+** The value passed as the second argument to this function is optional.
+** If the caller happens to have a pointer to the MemPage object
+** corresponding to page iPage handy, it may pass it as the second value.
+** Otherwise, it may pass NULL.
+**
+** If a pointer to a MemPage object is passed as the second argument,
+** its reference count is not altered by this function.
+*/
+static int freePage2(BtShared *pBt, MemPage *pMemPage, Pgno iPage){
+  MemPage *pTrunk = 0;                /* Free-list trunk page */
+  Pgno iTrunk = 0;                    /* Page number of free-list trunk page */
+  MemPage *pPage1 = pBt->pPage1;      /* Local reference to page 1 */
+  MemPage *pPage;                     /* Page being freed. May be NULL. */
+  int rc;                             /* Return Code */
+  u32 nFree;                          /* Initial number of pages on free-list */
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( CORRUPT_DB || iPage>1 );
+  assert( !pMemPage || pMemPage->pgno==iPage );
+
+  if( iPage<2 || iPage>pBt->nPage ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  if( pMemPage ){
+    pPage = pMemPage;
+    sqlite3PagerRef(pPage->pDbPage);
+  }else{
+    pPage = btreePageLookup(pBt, iPage);
+  }
+
+  /* Increment the free page count on pPage1 */
+  rc = sqlite3PagerWrite(pPage1->pDbPage);
+  if( rc ) goto freepage_out;
+  nFree = get4byte(&pPage1->aData[36]);
+  put4byte(&pPage1->aData[36], nFree+1);
+
+  if( pBt->btsFlags & BTS_SECURE_DELETE ){
+    /* If the secure_delete option is enabled, then
+    ** always fully overwrite deleted information with zeros.
+    */
+    if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
+     ||            ((rc = sqlite3PagerWrite(pPage->pDbPage))!=0)
+    ){
+      goto freepage_out;
+    }
+    memset(pPage->aData, 0, pPage->pBt->pageSize);
+  }
+
+  /* If the database supports auto-vacuum, write an entry in the pointer-map
+  ** to indicate that the page is free.
+  */
+  if( ISAUTOVACUUM(pBt) ){
+    ptrmapPut(pBt, iPage, PTRMAP_FREEPAGE, 0, &rc);
+    if( rc ) goto freepage_out;
+  }
+
+  /* Now manipulate the actual database free-list structure. There are two
+  ** possibilities. If the free-list is currently empty, or if the first
+  ** trunk page in the free-list is full, then this page will become a
+  ** new free-list trunk page. Otherwise, it will become a leaf of the
+  ** first trunk page in the current free-list. This block tests if it
+  ** is possible to add the page as a new free-list leaf.
+  */
+  if( nFree!=0 ){
+    u32 nLeaf;                /* Initial number of leaf cells on trunk page */
+
+    iTrunk = get4byte(&pPage1->aData[32]);
+    if( iTrunk>btreePagecount(pBt) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto freepage_out;
+    }
+    rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
+    if( rc!=SQLITE_OK ){
+      goto freepage_out;
+    }
+
+    nLeaf = get4byte(&pTrunk->aData[4]);
+    assert( pBt->usableSize>32 );
+    if( nLeaf > (u32)pBt->usableSize/4 - 2 ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto freepage_out;
+    }
+    if( nLeaf < (u32)pBt->usableSize/4 - 8 ){
+      /* In this case there is room on the trunk page to insert the page
+      ** being freed as a new leaf.
+      **
+      ** Note that the trunk page is not really full until it contains
+      ** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
+      ** coded.  But due to a coding error in versions of SQLite prior to
+      ** 3.6.0, databases with freelist trunk pages holding more than
+      ** usableSize/4 - 8 entries will be reported as corrupt.  In order
+      ** to maintain backwards compatibility with older versions of SQLite,
+      ** we will continue to restrict the number of entries to usableSize/4 - 8
+      ** for now.  At some point in the future (once everyone has upgraded
+      ** to 3.6.0 or later) we should consider fixing the conditional above
+      ** to read "usableSize/4-2" instead of "usableSize/4-8".
+      **
+      ** EVIDENCE-OF: R-19920-11576 However, newer versions of SQLite still
+      ** avoid using the last six entries in the freelist trunk page array in
+      ** order that database files created by newer versions of SQLite can be
+      ** read by older versions of SQLite.
+      */
+      rc = sqlite3PagerWrite(pTrunk->pDbPage);
+      if( rc==SQLITE_OK ){
+        put4byte(&pTrunk->aData[4], nLeaf+1);
+        put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
+        if( pPage && (pBt->btsFlags & BTS_SECURE_DELETE)==0 ){
+          sqlite3PagerDontWrite(pPage->pDbPage);
+        }
+        rc = btreeSetHasContent(pBt, iPage);
+      }
+      TRACE(("FREE-PAGE: %u leaf on trunk page %u\n",pPage->pgno,pTrunk->pgno));
+      goto freepage_out;
+    }
+  }
+
+  /* If control flows to this point, then it was not possible to add the
+  ** the page being freed as a leaf page of the first trunk in the free-list.
+  ** Possibly because the free-list is empty, or possibly because the
+  ** first trunk in the free-list is full. Either way, the page being freed
+  ** will become the new first trunk page in the free-list.
+  */
+  if( pPage==0 && SQLITE_OK!=(rc = btreeGetPage(pBt, iPage, &pPage, 0)) ){
+    goto freepage_out;
+  }
+  rc = sqlite3PagerWrite(pPage->pDbPage);
+  if( rc!=SQLITE_OK ){
+    goto freepage_out;
+  }
+  put4byte(pPage->aData, iTrunk);
+  put4byte(&pPage->aData[4], 0);
+  put4byte(&pPage1->aData[32], iPage);
+  TRACE(("FREE-PAGE: %u new trunk page replacing %u\n", pPage->pgno, iTrunk));
+
+freepage_out:
+  if( pPage ){
+    pPage->isInit = 0;
+  }
+  releasePage(pPage);
+  releasePage(pTrunk);
+  return rc;
+}
+static void freePage(MemPage *pPage, int *pRC){
+  if( (*pRC)==SQLITE_OK ){
+    *pRC = freePage2(pPage->pBt, pPage, pPage->pgno);
+  }
+}
+
+/*
+** Free the overflow pages associated with the given Cell.
+*/
+static SQLITE_NOINLINE int clearCellOverflow(
+  MemPage *pPage,          /* The page that contains the Cell */
+  unsigned char *pCell,    /* First byte of the Cell */
+  CellInfo *pInfo          /* Size information about the cell */
+){
+  BtShared *pBt;
+  Pgno ovflPgno;
+  int rc;
+  int nOvfl;
+  u32 ovflPageSize;
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pInfo->nLocal!=pInfo->nPayload );
+  testcase( pCell + pInfo->nSize == pPage->aDataEnd );
+  testcase( pCell + (pInfo->nSize-1) == pPage->aDataEnd );
+  if( pCell + pInfo->nSize > pPage->aDataEnd ){
+    /* Cell extends past end of page */
+    return SQLITE_CORRUPT_PAGE(pPage);
+  }
+  ovflPgno = get4byte(pCell + pInfo->nSize - 4);
+  pBt = pPage->pBt;
+  assert( pBt->usableSize > 4 );
+  ovflPageSize = pBt->usableSize - 4;
+  nOvfl = (pInfo->nPayload - pInfo->nLocal + ovflPageSize - 1)/ovflPageSize;
+  assert( nOvfl>0 ||
+    (CORRUPT_DB && (pInfo->nPayload + ovflPageSize)<ovflPageSize)
+  );
+  while( nOvfl-- ){
+    Pgno iNext = 0;
+    MemPage *pOvfl = 0;
+    if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
+      /* 0 is not a legal page number and page 1 cannot be an
+      ** overflow page. Therefore if ovflPgno<2 or past the end of the
+      ** file the database must be corrupt. */
+      return SQLITE_CORRUPT_BKPT;
+    }
+    if( nOvfl ){
+      rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
+      if( rc ) return rc;
+    }
+
+    if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
+     && sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
+    ){
+      /* There is no reason any cursor should have an outstanding reference
+      ** to an overflow page belonging to a cell that is being deleted/updated.
+      ** So if there exists more than one reference to this page, then it
+      ** must not really be an overflow page and the database must be corrupt.
+      ** It is helpful to detect this before calling freePage2(), as
+      ** freePage2() may zero the page contents if secure-delete mode is
+      ** enabled. If this 'overflow' page happens to be a page that the
+      ** caller is iterating through or using in some other way, this
+      ** can be problematic.
+      */
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = freePage2(pBt, pOvfl, ovflPgno);
+    }
+
+    if( pOvfl ){
+      sqlite3PagerUnref(pOvfl->pDbPage);
+    }
+    if( rc ) return rc;
+    ovflPgno = iNext;
+  }
+  return SQLITE_OK;
+}
+
+/* Call xParseCell to compute the size of a cell.  If the cell contains
+** overflow, then invoke cellClearOverflow to clear out that overflow.
+** Store the result code (SQLITE_OK or some error code) in rc.
+**
+** Implemented as macro to force inlining for performance.
+*/
+#define BTREE_CLEAR_CELL(rc, pPage, pCell, sInfo)   \
+  pPage->xParseCell(pPage, pCell, &sInfo);          \
+  if( sInfo.nLocal!=sInfo.nPayload ){               \
+    rc = clearCellOverflow(pPage, pCell, &sInfo);   \
+  }else{                                            \
+    rc = SQLITE_OK;                                 \
+  }
+
+
+/*
+** Create the byte sequence used to represent a cell on page pPage
+** and write that byte sequence into pCell[].  Overflow pages are
+** allocated and filled in as necessary.  The calling procedure
+** is responsible for making sure sufficient space has been allocated
+** for pCell[].
+**
+** Note that pCell does not necessary need to point to the pPage->aData
+** area.  pCell might point to some temporary storage.  The cell will
+** be constructed in this temporary area then copied into pPage->aData
+** later.
+*/
+static int fillInCell(
+  MemPage *pPage,                /* The page that contains the cell */
+  unsigned char *pCell,          /* Complete text of the cell */
+  const BtreePayload *pX,        /* Payload with which to construct the cell */
+  int *pnSize                    /* Write cell size here */
+){
+  int nPayload;
+  const u8 *pSrc;
+  int nSrc, n, rc, mn;
+  int spaceLeft;
+  MemPage *pToRelease;
+  unsigned char *pPrior;
+  unsigned char *pPayload;
+  BtShared *pBt;
+  Pgno pgnoOvfl;
+  int nHeader;
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+
+  /* pPage is not necessarily writeable since pCell might be auxiliary
+  ** buffer space that is separate from the pPage buffer area */
+  assert( pCell<pPage->aData || pCell>=&pPage->aData[pPage->pBt->pageSize]
+            || sqlite3PagerIswriteable(pPage->pDbPage) );
+
+  /* Fill in the header. */
+  nHeader = pPage->childPtrSize;
+  if( pPage->intKey ){
+    nPayload = pX->nData + pX->nZero;
+    pSrc = pX->pData;
+    nSrc = pX->nData;
+    assert( pPage->intKeyLeaf ); /* fillInCell() only called for leaves */
+    nHeader += putVarint32(&pCell[nHeader], nPayload);
+    nHeader += putVarint(&pCell[nHeader], *(u64*)&pX->nKey);
+  }else{
+    assert( pX->nKey<=0x7fffffff && pX->pKey!=0 );
+    nSrc = nPayload = (int)pX->nKey;
+    pSrc = pX->pKey;
+    nHeader += putVarint32(&pCell[nHeader], nPayload);
+  }
+ 
+  /* Fill in the payload */
+  pPayload = &pCell[nHeader];
+  if( nPayload<=pPage->maxLocal ){
+    /* This is the common case where everything fits on the btree page
+    ** and no overflow pages are required. */
+    n = nHeader + nPayload;
+    testcase( n==3 );
+    testcase( n==4 );
+    if( n<4 ) n = 4;
+    *pnSize = n;
+    assert( nSrc<=nPayload );
+    testcase( nSrc<nPayload );
+    memcpy(pPayload, pSrc, nSrc);
+    memset(pPayload+nSrc, 0, nPayload-nSrc);
+    return SQLITE_OK;
+  }
+
+  /* If we reach this point, it means that some of the content will need
+  ** to spill onto overflow pages.
+  */
+  mn = pPage->minLocal;
+  n = mn + (nPayload - mn) % (pPage->pBt->usableSize - 4);
+  testcase( n==pPage->maxLocal );
+  testcase( n==pPage->maxLocal+1 );
+  if( n > pPage->maxLocal ) n = mn;
+  spaceLeft = n;
+  *pnSize = n + nHeader + 4;
+  pPrior = &pCell[nHeader+n];
+  pToRelease = 0;
+  pgnoOvfl = 0;
+  pBt = pPage->pBt;
+
+  /* At this point variables should be set as follows:
+  **
+  **   nPayload           Total payload size in bytes
+  **   pPayload           Begin writing payload here
+  **   spaceLeft          Space available at pPayload.  If nPayload>spaceLeft,
+  **                      that means content must spill into overflow pages.
+  **   *pnSize            Size of the local cell (not counting overflow pages)
+  **   pPrior             Where to write the pgno of the first overflow page
+  **
+  ** Use a call to btreeParseCellPtr() to verify that the values above
+  ** were computed correctly.
+  */
+#ifdef SQLITE_DEBUG
+  {
+    CellInfo info;
+    pPage->xParseCell(pPage, pCell, &info);
+    assert( nHeader==(int)(info.pPayload - pCell) );
+    assert( info.nKey==pX->nKey );
+    assert( *pnSize == info.nSize );
+    assert( spaceLeft == info.nLocal );
+  }
+#endif
+
+  /* Write the payload into the local Cell and any extra into overflow pages */
+  while( 1 ){
+    n = nPayload;
+    if( n>spaceLeft ) n = spaceLeft;
+
+    /* If pToRelease is not zero than pPayload points into the data area
+    ** of pToRelease.  Make sure pToRelease is still writeable. */
+    assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
+
+    /* If pPayload is part of the data area of pPage, then make sure pPage
+    ** is still writeable */
+    assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
+            || sqlite3PagerIswriteable(pPage->pDbPage) );
+
+    if( nSrc>=n ){
+      memcpy(pPayload, pSrc, n);
+    }else if( nSrc>0 ){
+      n = nSrc;
+      memcpy(pPayload, pSrc, n);
+    }else{
+      memset(pPayload, 0, n);
+    }
+    nPayload -= n;
+    if( nPayload<=0 ) break;
+    pPayload += n;
+    pSrc += n;
+    nSrc -= n;
+    spaceLeft -= n;
+    if( spaceLeft==0 ){
+      MemPage *pOvfl = 0;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
+      if( pBt->autoVacuum ){
+        do{
+          pgnoOvfl++;
+        } while(
+          PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt)
+        );
+      }
+#endif
+      rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, 0);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      /* If the database supports auto-vacuum, and the second or subsequent
+      ** overflow page is being allocated, add an entry to the pointer-map
+      ** for that page now.
+      **
+      ** If this is the first overflow page, then write a partial entry
+      ** to the pointer-map. If we write nothing to this pointer-map slot,
+      ** then the optimistic overflow chain processing in clearCell()
+      ** may misinterpret the uninitialized values and delete the
+      ** wrong pages from the database.
+      */
+      if( pBt->autoVacuum && rc==SQLITE_OK ){
+        u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
+        ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap, &rc);
+        if( rc ){
+          releasePage(pOvfl);
+        }
+      }
+#endif
+      if( rc ){
+        releasePage(pToRelease);
+        return rc;
+      }
+
+      /* If pToRelease is not zero than pPrior points into the data area
+      ** of pToRelease.  Make sure pToRelease is still writeable. */
+      assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
+
+      /* If pPrior is part of the data area of pPage, then make sure pPage
+      ** is still writeable */
+      assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
+            || sqlite3PagerIswriteable(pPage->pDbPage) );
+
+      put4byte(pPrior, pgnoOvfl);
+      releasePage(pToRelease);
+      pToRelease = pOvfl;
+      pPrior = pOvfl->aData;
+      put4byte(pPrior, 0);
+      pPayload = &pOvfl->aData[4];
+      spaceLeft = pBt->usableSize - 4;
+    }
+  }
+  releasePage(pToRelease);
+  return SQLITE_OK;
+}
+
+/*
+** Remove the i-th cell from pPage.  This routine effects pPage only.
+** The cell content is not freed or deallocated.  It is assumed that
+** the cell content has been copied someplace else.  This routine just
+** removes the reference to the cell from pPage.
+**
+** "sz" must be the number of bytes in the cell.
+*/
+static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){
+  u32 pc;         /* Offset to cell content of cell being deleted */
+  u8 *data;       /* pPage->aData */
+  u8 *ptr;        /* Used to move bytes around within data[] */
+  int rc;         /* The return code */
+  int hdr;        /* Beginning of the header.  0 most pages.  100 page 1 */
+
+  if( *pRC ) return;
+  assert( idx>=0 );
+  assert( idx<pPage->nCell );
+  assert( CORRUPT_DB || sz==cellSize(pPage, idx) );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->nFree>=0 );
+  data = pPage->aData;
+  ptr = &pPage->aCellIdx[2*idx];
+  assert( pPage->pBt->usableSize > (u32)(ptr-data) );
+  pc = get2byte(ptr);
+  hdr = pPage->hdrOffset;
+  testcase( pc==(u32)get2byte(&data[hdr+5]) );
+  testcase( pc+sz==pPage->pBt->usableSize );
+  if( pc+sz > pPage->pBt->usableSize ){
+    *pRC = SQLITE_CORRUPT_BKPT;
+    return;
+  }
+  rc = freeSpace(pPage, pc, sz);
+  if( rc ){
+    *pRC = rc;
+    return;
+  }
+  pPage->nCell--;
+  if( pPage->nCell==0 ){
+    memset(&data[hdr+1], 0, 4);
+    data[hdr+7] = 0;
+    put2byte(&data[hdr+5], pPage->pBt->usableSize);
+    pPage->nFree = pPage->pBt->usableSize - pPage->hdrOffset
+                       - pPage->childPtrSize - 8;
+  }else{
+    memmove(ptr, ptr+2, 2*(pPage->nCell - idx));
+    put2byte(&data[hdr+3], pPage->nCell);
+    pPage->nFree += 2;
+  }
+}
+
+/*
+** Insert a new cell on pPage at cell index "i".  pCell points to the
+** content of the cell.
+**
+** If the cell content will fit on the page, then put it there.  If it
+** will not fit, then make a copy of the cell content into pTemp if
+** pTemp is not null.  Regardless of pTemp, allocate a new entry
+** in pPage->apOvfl[] and make it point to the cell content (either
+** in pTemp or the original pCell) and also record its index.
+** Allocating a new entry in pPage->aCell[] implies that
+** pPage->nOverflow is incremented.
+**
+** The insertCellFast() routine below works exactly the same as
+** insertCell() except that it lacks the pTemp and iChild parameters
+** which are assumed zero.  Other than that, the two routines are the
+** same.
+**
+** Fixes or enhancements to this routine should be reflected in
+** insertCellFast()!
+*/
+static int insertCell(
+  MemPage *pPage,   /* Page into which we are copying */
+  int i,            /* New cell becomes the i-th cell of the page */
+  u8 *pCell,        /* Content of the new cell */
+  int sz,           /* Bytes of content in pCell */
+  u8 *pTemp,        /* Temp storage space for pCell, if needed */
+  Pgno iChild       /* If non-zero, replace first 4 bytes with this value */
+){
+  int idx = 0;      /* Where to write new cell content in data[] */
+  int j;            /* Loop counter */
+  u8 *data;         /* The content of the whole page */
+  u8 *pIns;         /* The point in pPage->aCellIdx[] where no cell inserted */
+
+  assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
+  assert( MX_CELL(pPage->pBt)<=10921 );
+  assert( pPage->nCell<=MX_CELL(pPage->pBt) || CORRUPT_DB );
+  assert( pPage->nOverflow<=ArraySize(pPage->apOvfl) );
+  assert( ArraySize(pPage->apOvfl)==ArraySize(pPage->aiOvfl) );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( sz==pPage->xCellSize(pPage, pCell) || CORRUPT_DB );
+  assert( pPage->nFree>=0 );
+  assert( iChild>0 );
+  if( pPage->nOverflow || sz+2>pPage->nFree ){
+    if( pTemp ){
+      memcpy(pTemp, pCell, sz);
+      pCell = pTemp;
+    }
+    put4byte(pCell, iChild);
+    j = pPage->nOverflow++;
+    /* Comparison against ArraySize-1 since we hold back one extra slot
+    ** as a contingency.  In other words, never need more than 3 overflow
+    ** slots but 4 are allocated, just to be safe. */
+    assert( j < ArraySize(pPage->apOvfl)-1 );
+    pPage->apOvfl[j] = pCell;
+    pPage->aiOvfl[j] = (u16)i;
+
+    /* When multiple overflows occur, they are always sequential and in
+    ** sorted order.  This invariants arise because multiple overflows can
+    ** only occur when inserting divider cells into the parent page during
+    ** balancing, and the dividers are adjacent and sorted.
+    */
+    assert( j==0 || pPage->aiOvfl[j-1]<(u16)i ); /* Overflows in sorted order */
+    assert( j==0 || i==pPage->aiOvfl[j-1]+1 );   /* Overflows are sequential */
+  }else{
+    int rc = sqlite3PagerWrite(pPage->pDbPage);
+    if( NEVER(rc!=SQLITE_OK) ){
+      return rc;
+    }
+    assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+    data = pPage->aData;
+    assert( &data[pPage->cellOffset]==pPage->aCellIdx );
+    rc = allocateSpace(pPage, sz, &idx);
+    if( rc ){ return rc; }
+    /* The allocateSpace() routine guarantees the following properties
+    ** if it returns successfully */
+    assert( idx >= 0 );
+    assert( idx >= pPage->cellOffset+2*pPage->nCell+2 || CORRUPT_DB );
+    assert( idx+sz <= (int)pPage->pBt->usableSize );
+    pPage->nFree -= (u16)(2 + sz);
+    /* In a corrupt database where an entry in the cell index section of
+    ** a btree page has a value of 3 or less, the pCell value might point
+    ** as many as 4 bytes in front of the start of the aData buffer for
+    ** the source page.  Make sure this does not cause problems by not
+    ** reading the first 4 bytes */
+    memcpy(&data[idx+4], pCell+4, sz-4);
+    put4byte(&data[idx], iChild);
+    pIns = pPage->aCellIdx + i*2;
+    memmove(pIns+2, pIns, 2*(pPage->nCell - i));
+    put2byte(pIns, idx);
+    pPage->nCell++;
+    /* increment the cell count */
+    if( (++data[pPage->hdrOffset+4])==0 ) data[pPage->hdrOffset+3]++;
+    assert( get2byte(&data[pPage->hdrOffset+3])==pPage->nCell || CORRUPT_DB );
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pPage->pBt->autoVacuum ){
+      int rc2 = SQLITE_OK;
+      /* The cell may contain a pointer to an overflow page. If so, write
+      ** the entry for the overflow page into the pointer map.
+      */
+      ptrmapPutOvflPtr(pPage, pPage, pCell, &rc2);
+      if( rc2 ) return rc2;
+    }
+#endif
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This variant of insertCell() assumes that the pTemp and iChild
+** parameters are both zero.  Use this variant in sqlite3BtreeInsert()
+** for performance improvement, and also so that this variant is only
+** called from that one place, and is thus inlined, and thus runs must
+** faster.
+**
+** Fixes or enhancements to this routine should be reflected into
+** the insertCell() routine.
+*/
+static int insertCellFast(
+  MemPage *pPage,   /* Page into which we are copying */
+  int i,            /* New cell becomes the i-th cell of the page */
+  u8 *pCell,        /* Content of the new cell */
+  int sz            /* Bytes of content in pCell */
+){
+  int idx = 0;      /* Where to write new cell content in data[] */
+  int j;            /* Loop counter */
+  u8 *data;         /* The content of the whole page */
+  u8 *pIns;         /* The point in pPage->aCellIdx[] where no cell inserted */
+
+  assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
+  assert( MX_CELL(pPage->pBt)<=10921 );
+  assert( pPage->nCell<=MX_CELL(pPage->pBt) || CORRUPT_DB );
+  assert( pPage->nOverflow<=ArraySize(pPage->apOvfl) );
+  assert( ArraySize(pPage->apOvfl)==ArraySize(pPage->aiOvfl) );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( sz==pPage->xCellSize(pPage, pCell) || CORRUPT_DB );
+  assert( pPage->nFree>=0 );
+  assert( pPage->nOverflow==0 );
+  if( sz+2>pPage->nFree ){
+    j = pPage->nOverflow++;
+    /* Comparison against ArraySize-1 since we hold back one extra slot
+    ** as a contingency.  In other words, never need more than 3 overflow
+    ** slots but 4 are allocated, just to be safe. */
+    assert( j < ArraySize(pPage->apOvfl)-1 );
+    pPage->apOvfl[j] = pCell;
+    pPage->aiOvfl[j] = (u16)i;
+
+    /* When multiple overflows occur, they are always sequential and in
+    ** sorted order.  This invariants arise because multiple overflows can
+    ** only occur when inserting divider cells into the parent page during
+    ** balancing, and the dividers are adjacent and sorted.
+    */
+    assert( j==0 || pPage->aiOvfl[j-1]<(u16)i ); /* Overflows in sorted order */
+    assert( j==0 || i==pPage->aiOvfl[j-1]+1 );   /* Overflows are sequential */
+  }else{
+    int rc = sqlite3PagerWrite(pPage->pDbPage);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+    data = pPage->aData;
+    assert( &data[pPage->cellOffset]==pPage->aCellIdx );
+    rc = allocateSpace(pPage, sz, &idx);
+    if( rc ){ return rc; }
+    /* The allocateSpace() routine guarantees the following properties
+    ** if it returns successfully */
+    assert( idx >= 0 );
+    assert( idx >= pPage->cellOffset+2*pPage->nCell+2 || CORRUPT_DB );
+    assert( idx+sz <= (int)pPage->pBt->usableSize );
+    pPage->nFree -= (u16)(2 + sz);
+    memcpy(&data[idx], pCell, sz);
+    pIns = pPage->aCellIdx + i*2;
+    memmove(pIns+2, pIns, 2*(pPage->nCell - i));
+    put2byte(pIns, idx);
+    pPage->nCell++;
+    /* increment the cell count */
+    if( (++data[pPage->hdrOffset+4])==0 ) data[pPage->hdrOffset+3]++;
+    assert( get2byte(&data[pPage->hdrOffset+3])==pPage->nCell || CORRUPT_DB );
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pPage->pBt->autoVacuum ){
+      int rc2 = SQLITE_OK;
+      /* The cell may contain a pointer to an overflow page. If so, write
+      ** the entry for the overflow page into the pointer map.
+      */
+      ptrmapPutOvflPtr(pPage, pPage, pCell, &rc2);
+      if( rc2 ) return rc2;
+    }
+#endif
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The following parameters determine how many adjacent pages get involved
+** in a balancing operation.  NN is the number of neighbors on either side
+** of the page that participate in the balancing operation.  NB is the
+** total number of pages that participate, including the target page and
+** NN neighbors on either side.
+**
+** The minimum value of NN is 1 (of course).  Increasing NN above 1
+** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
+** in exchange for a larger degradation in INSERT and UPDATE performance.
+** The value of NN appears to give the best results overall.
+**
+** (Later:) The description above makes it seem as if these values are
+** tunable - as if you could change them and recompile and it would all work.
+** But that is unlikely.  NB has been 3 since the inception of SQLite and
+** we have never tested any other value.
+*/
+#define NN 1             /* Number of neighbors on either side of pPage */
+#define NB 3             /* (NN*2+1): Total pages involved in the balance */
+
+/*
+** A CellArray object contains a cache of pointers and sizes for a
+** consecutive sequence of cells that might be held on multiple pages.
+**
+** The cells in this array are the divider cell or cells from the pParent
+** page plus up to three child pages.  There are a total of nCell cells.
+**
+** pRef is a pointer to one of the pages that contributes cells.  This is
+** used to access information such as MemPage.intKey and MemPage.pBt->pageSize
+** which should be common to all pages that contribute cells to this array.
+**
+** apCell[] and szCell[] hold, respectively, pointers to the start of each
+** cell and the size of each cell.  Some of the apCell[] pointers might refer
+** to overflow cells.  In other words, some apCel[] pointers might not point
+** to content area of the pages.
+**
+** A szCell[] of zero means the size of that cell has not yet been computed.
+**
+** The cells come from as many as four different pages:
+**
+**             -----------
+**             | Parent  |
+**             -----------
+**            /     |     \
+**           /      |      \
+**  ---------   ---------   ---------
+**  |Child-1|   |Child-2|   |Child-3|
+**  ---------   ---------   ---------
+**
+** The order of cells is in the array is for an index btree is:
+**
+**       1.  All cells from Child-1 in order
+**       2.  The first divider cell from Parent
+**       3.  All cells from Child-2 in order
+**       4.  The second divider cell from Parent
+**       5.  All cells from Child-3 in order
+**
+** For a table-btree (with rowids) the items 2 and 4 are empty because
+** content exists only in leaves and there are no divider cells.
+**
+** For an index btree, the apEnd[] array holds pointer to the end of page
+** for Child-1, the Parent, Child-2, the Parent (again), and Child-3,
+** respectively. The ixNx[] array holds the number of cells contained in
+** each of these 5 stages, and all stages to the left.  Hence:
+**
+**    ixNx[0] = Number of cells in Child-1.
+**    ixNx[1] = Number of cells in Child-1 plus 1 for first divider.
+**    ixNx[2] = Number of cells in Child-1 and Child-2 + 1 for 1st divider.
+**    ixNx[3] = Number of cells in Child-1 and Child-2 + both divider cells
+**    ixNx[4] = Total number of cells.
+**
+** For a table-btree, the concept is similar, except only apEnd[0]..apEnd[2]
+** are used and they point to the leaf pages only, and the ixNx value are:
+**
+**    ixNx[0] = Number of cells in Child-1.
+**    ixNx[1] = Number of cells in Child-1 and Child-2.
+**    ixNx[2] = Total number of cells.
+**
+** Sometimes when deleting, a child page can have zero cells.  In those
+** cases, ixNx[] entries with higher indexes, and the corresponding apEnd[]
+** entries, shift down.  The end result is that each ixNx[] entry should
+** be larger than the previous
+*/
+typedef struct CellArray CellArray;
+struct CellArray {
+  int nCell;              /* Number of cells in apCell[] */
+  MemPage *pRef;          /* Reference page */
+  u8 **apCell;            /* All cells begin balanced */
+  u16 *szCell;            /* Local size of all cells in apCell[] */
+  u8 *apEnd[NB*2];        /* MemPage.aDataEnd values */
+  int ixNx[NB*2];         /* Index of at which we move to the next apEnd[] */
+};
+
+/*
+** Make sure the cell sizes at idx, idx+1, ..., idx+N-1 have been
+** computed.
+*/
+static void populateCellCache(CellArray *p, int idx, int N){
+  MemPage *pRef = p->pRef;
+  u16 *szCell = p->szCell;
+  assert( idx>=0 && idx+N<=p->nCell );
+  while( N>0 ){
+    assert( p->apCell[idx]!=0 );
+    if( szCell[idx]==0 ){
+      szCell[idx] = pRef->xCellSize(pRef, p->apCell[idx]);
+    }else{
+      assert( CORRUPT_DB ||
+              szCell[idx]==pRef->xCellSize(pRef, p->apCell[idx]) );
+    }
+    idx++;
+    N--;
+  }
+}
+
+/*
+** Return the size of the Nth element of the cell array
+*/
+static SQLITE_NOINLINE u16 computeCellSize(CellArray *p, int N){
+  assert( N>=0 && N<p->nCell );
+  assert( p->szCell[N]==0 );
+  p->szCell[N] = p->pRef->xCellSize(p->pRef, p->apCell[N]);
+  return p->szCell[N];
+}
+static u16 cachedCellSize(CellArray *p, int N){
+  assert( N>=0 && N<p->nCell );
+  if( p->szCell[N] ) return p->szCell[N];
+  return computeCellSize(p, N);
+}
+
+/*
+** Array apCell[] contains pointers to nCell b-tree page cells. The
+** szCell[] array contains the size in bytes of each cell. This function
+** replaces the current contents of page pPg with the contents of the cell
+** array.
+**
+** Some of the cells in apCell[] may currently be stored in pPg. This
+** function works around problems caused by this by making a copy of any
+** such cells before overwriting the page data.
+**
+** The MemPage.nFree field is invalidated by this function. It is the
+** responsibility of the caller to set it correctly.
+*/
+static int rebuildPage(
+  CellArray *pCArray,             /* Content to be added to page pPg */
+  int iFirst,                     /* First cell in pCArray to use */
+  int nCell,                      /* Final number of cells on page */
+  MemPage *pPg                    /* The page to be reconstructed */
+){
+  const int hdr = pPg->hdrOffset;          /* Offset of header on pPg */
+  u8 * const aData = pPg->aData;           /* Pointer to data for pPg */
+  const int usableSize = pPg->pBt->usableSize;
+  u8 * const pEnd = &aData[usableSize];
+  int i = iFirst;                 /* Which cell to copy from pCArray*/
+  u32 j;                          /* Start of cell content area */
+  int iEnd = i+nCell;             /* Loop terminator */
+  u8 *pCellptr = pPg->aCellIdx;
+  u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
+  u8 *pData;
+  int k;                          /* Current slot in pCArray->apEnd[] */
+  u8 *pSrcEnd;                    /* Current pCArray->apEnd[k] value */
+
+  assert( nCell>0 );
+  assert( i<iEnd );
+  j = get2byte(&aData[hdr+5]);
+  if( j>(u32)usableSize ){ j = 0; }
+  memcpy(&pTmp[j], &aData[j], usableSize - j);
+
+  for(k=0; ALWAYS(k<NB*2) && pCArray->ixNx[k]<=i; k++){}
+  pSrcEnd = pCArray->apEnd[k];
+
+  pData = pEnd;
+  while( 1/*exit by break*/ ){
+    u8 *pCell = pCArray->apCell[i];
+    u16 sz = pCArray->szCell[i];
+    assert( sz>0 );
+    if( SQLITE_WITHIN(pCell,aData+j,pEnd) ){
+      if( ((uptr)(pCell+sz))>(uptr)pEnd ) return SQLITE_CORRUPT_BKPT;
+      pCell = &pTmp[pCell - aData];
+    }else if( (uptr)(pCell+sz)>(uptr)pSrcEnd
+           && (uptr)(pCell)<(uptr)pSrcEnd
+    ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+
+    pData -= sz;
+    put2byte(pCellptr, (pData - aData));
+    pCellptr += 2;
+    if( pData < pCellptr ) return SQLITE_CORRUPT_BKPT;
+    memmove(pData, pCell, sz);
+    assert( sz==pPg->xCellSize(pPg, pCell) || CORRUPT_DB );
+    i++;
+    if( i>=iEnd ) break;
+    if( pCArray->ixNx[k]<=i ){
+      k++;
+      pSrcEnd = pCArray->apEnd[k];
+    }
+  }
+
+  /* The pPg->nFree field is now set incorrectly. The caller will fix it. */
+  pPg->nCell = nCell;
+  pPg->nOverflow = 0;
+
+  put2byte(&aData[hdr+1], 0);
+  put2byte(&aData[hdr+3], pPg->nCell);
+  put2byte(&aData[hdr+5], pData - aData);
+  aData[hdr+7] = 0x00;
+  return SQLITE_OK;
+}
+
+/*
+** The pCArray objects contains pointers to b-tree cells and the cell sizes.
+** This function attempts to add the cells stored in the array to page pPg.
+** If it cannot (because the page needs to be defragmented before the cells
+** will fit), non-zero is returned. Otherwise, if the cells are added
+** successfully, zero is returned.
+**
+** Argument pCellptr points to the first entry in the cell-pointer array
+** (part of page pPg) to populate. After cell apCell[0] is written to the
+** page body, a 16-bit offset is written to pCellptr. And so on, for each
+** cell in the array. It is the responsibility of the caller to ensure
+** that it is safe to overwrite this part of the cell-pointer array.
+**
+** When this function is called, *ppData points to the start of the
+** content area on page pPg. If the size of the content area is extended,
+** *ppData is updated to point to the new start of the content area
+** before returning.
+**
+** Finally, argument pBegin points to the byte immediately following the
+** end of the space required by this page for the cell-pointer area (for
+** all cells - not just those inserted by the current call). If the content
+** area must be extended to before this point in order to accommodate all
+** cells in apCell[], then the cells do not fit and non-zero is returned.
+*/
+static int pageInsertArray(
+  MemPage *pPg,                   /* Page to add cells to */
+  u8 *pBegin,                     /* End of cell-pointer array */
+  u8 **ppData,                    /* IN/OUT: Page content-area pointer */
+  u8 *pCellptr,                   /* Pointer to cell-pointer area */
+  int iFirst,                     /* Index of first cell to add */
+  int nCell,                      /* Number of cells to add to pPg */
+  CellArray *pCArray              /* Array of cells */
+){
+  int i = iFirst;                 /* Loop counter - cell index to insert */
+  u8 *aData = pPg->aData;         /* Complete page */
+  u8 *pData = *ppData;            /* Content area.  A subset of aData[] */
+  int iEnd = iFirst + nCell;      /* End of loop. One past last cell to ins */
+  int k;                          /* Current slot in pCArray->apEnd[] */
+  u8 *pEnd;                       /* Maximum extent of cell data */
+  assert( CORRUPT_DB || pPg->hdrOffset==0 );    /* Never called on page 1 */
+  if( iEnd<=iFirst ) return 0;
+  for(k=0; ALWAYS(k<NB*2) && pCArray->ixNx[k]<=i ; k++){}
+  pEnd = pCArray->apEnd[k];
+  while( 1 /*Exit by break*/ ){
+    int sz, rc;
+    u8 *pSlot;
+    assert( pCArray->szCell[i]!=0 );
+    sz = pCArray->szCell[i];
+    if( (aData[1]==0 && aData[2]==0) || (pSlot = pageFindSlot(pPg,sz,&rc))==0 ){
+      if( (pData - pBegin)<sz ) return 1;
+      pData -= sz;
+      pSlot = pData;
+    }
+    /* pSlot and pCArray->apCell[i] will never overlap on a well-formed
+    ** database.  But they might for a corrupt database.  Hence use memmove()
+    ** since memcpy() sends SIGABORT with overlapping buffers on OpenBSD */
+    assert( (pSlot+sz)<=pCArray->apCell[i]
+         || pSlot>=(pCArray->apCell[i]+sz)
+         || CORRUPT_DB );
+    if( (uptr)(pCArray->apCell[i]+sz)>(uptr)pEnd
+     && (uptr)(pCArray->apCell[i])<(uptr)pEnd
+    ){
+      assert( CORRUPT_DB );
+      (void)SQLITE_CORRUPT_BKPT;
+      return 1;
+    }
+    memmove(pSlot, pCArray->apCell[i], sz);
+    put2byte(pCellptr, (pSlot - aData));
+    pCellptr += 2;
+    i++;
+    if( i>=iEnd ) break;
+    if( pCArray->ixNx[k]<=i ){
+      k++;
+      pEnd = pCArray->apEnd[k];
+    }
+  }
+  *ppData = pData;
+  return 0;
+}
+
+/*
+** The pCArray object contains pointers to b-tree cells and their sizes.
+**
+** This function adds the space associated with each cell in the array
+** that is currently stored within the body of pPg to the pPg free-list.
+** The cell-pointers and other fields of the page are not updated.
+**
+** This function returns the total number of cells added to the free-list.
+*/
+static int pageFreeArray(
+  MemPage *pPg,                   /* Page to edit */
+  int iFirst,                     /* First cell to delete */
+  int nCell,                      /* Cells to delete */
+  CellArray *pCArray              /* Array of cells */
+){
+  u8 * const aData = pPg->aData;
+  u8 * const pEnd = &aData[pPg->pBt->usableSize];
+  u8 * const pStart = &aData[pPg->hdrOffset + 8 + pPg->childPtrSize];
+  int nRet = 0;
+  int i, j;
+  int iEnd = iFirst + nCell;
+  int nFree = 0;
+  int aOfst[10];
+  int aAfter[10];
+
+  for(i=iFirst; i<iEnd; i++){
+    u8 *pCell = pCArray->apCell[i];
+    if( SQLITE_WITHIN(pCell, pStart, pEnd) ){
+      int sz;
+      int iAfter;
+      int iOfst;
+      /* No need to use cachedCellSize() here.  The sizes of all cells that
+      ** are to be freed have already been computing while deciding which
+      ** cells need freeing */
+      sz = pCArray->szCell[i];  assert( sz>0 );
+      iOfst = (u16)(pCell - aData);
+      iAfter = iOfst+sz;
+      for(j=0; j<nFree; j++){
+        if( aOfst[j]==iAfter ){
+          aOfst[j] = iOfst;
+          break;
+        }else if( aAfter[j]==iOfst ){
+          aAfter[j] = iAfter;
+          break;
+        }
+      }
+      if( j>=nFree ){
+        if( nFree>=(int)(sizeof(aOfst)/sizeof(aOfst[0])) ){
+          for(j=0; j<nFree; j++){
+            freeSpace(pPg, aOfst[j], aAfter[j]-aOfst[j]);
+          }
+          nFree = 0;
+        }
+        aOfst[nFree] = iOfst;
+        aAfter[nFree] = iAfter;
+        if( &aData[iAfter]>pEnd ) return 0;
+        nFree++;
+      }
+      nRet++;
+    }
+  }
+  for(j=0; j<nFree; j++){
+    freeSpace(pPg, aOfst[j], aAfter[j]-aOfst[j]);
+  }
+  return nRet;
+}
+
+/*
+** pCArray contains pointers to and sizes of all cells in the page being
+** balanced.  The current page, pPg, has pPg->nCell cells starting with
+** pCArray->apCell[iOld].  After balancing, this page should hold nNew cells
+** starting at apCell[iNew].
+**
+** This routine makes the necessary adjustments to pPg so that it contains
+** the correct cells after being balanced.
+**
+** The pPg->nFree field is invalid when this function returns. It is the
+** responsibility of the caller to set it correctly.
+*/
+static int editPage(
+  MemPage *pPg,                   /* Edit this page */
+  int iOld,                       /* Index of first cell currently on page */
+  int iNew,                       /* Index of new first cell on page */
+  int nNew,                       /* Final number of cells on page */
+  CellArray *pCArray              /* Array of cells and sizes */
+){
+  u8 * const aData = pPg->aData;
+  const int hdr = pPg->hdrOffset;
+  u8 *pBegin = &pPg->aCellIdx[nNew * 2];
+  int nCell = pPg->nCell;       /* Cells stored on pPg */
+  u8 *pData;
+  u8 *pCellptr;
+  int i;
+  int iOldEnd = iOld + pPg->nCell + pPg->nOverflow;
+  int iNewEnd = iNew + nNew;
+
+#ifdef SQLITE_DEBUG
+  u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
+  memcpy(pTmp, aData, pPg->pBt->usableSize);
+#endif
+
+  /* Remove cells from the start and end of the page */
+  assert( nCell>=0 );
+  if( iOld<iNew ){
+    int nShift = pageFreeArray(pPg, iOld, iNew-iOld, pCArray);
+    if( NEVER(nShift>nCell) ) return SQLITE_CORRUPT_BKPT;
+    memmove(pPg->aCellIdx, &pPg->aCellIdx[nShift*2], nCell*2);
+    nCell -= nShift;
+  }
+  if( iNewEnd < iOldEnd ){
+    int nTail = pageFreeArray(pPg, iNewEnd, iOldEnd - iNewEnd, pCArray);
+    assert( nCell>=nTail );
+    nCell -= nTail;
+  }
+
+  pData = &aData[get2byte(&aData[hdr+5])];
+  if( pData<pBegin ) goto editpage_fail;
+  if( NEVER(pData>pPg->aDataEnd) ) goto editpage_fail;
+
+  /* Add cells to the start of the page */
+  if( iNew<iOld ){
+    int nAdd = MIN(nNew,iOld-iNew);
+    assert( (iOld-iNew)<nNew || nCell==0 || CORRUPT_DB );
+    assert( nAdd>=0 );
+    pCellptr = pPg->aCellIdx;
+    memmove(&pCellptr[nAdd*2], pCellptr, nCell*2);
+    if( pageInsertArray(
+          pPg, pBegin, &pData, pCellptr,
+          iNew, nAdd, pCArray
+    ) ) goto editpage_fail;
+    nCell += nAdd;
+  }
+
+  /* Add any overflow cells */
+  for(i=0; i<pPg->nOverflow; i++){
+    int iCell = (iOld + pPg->aiOvfl[i]) - iNew;
+    if( iCell>=0 && iCell<nNew ){
+      pCellptr = &pPg->aCellIdx[iCell * 2];
+      if( nCell>iCell ){
+        memmove(&pCellptr[2], pCellptr, (nCell - iCell) * 2);
+      }
+      nCell++;
+      cachedCellSize(pCArray, iCell+iNew);
+      if( pageInsertArray(
+            pPg, pBegin, &pData, pCellptr,
+            iCell+iNew, 1, pCArray
+      ) ) goto editpage_fail;
+    }
+  }
+
+  /* Append cells to the end of the page */
+  assert( nCell>=0 );
+  pCellptr = &pPg->aCellIdx[nCell*2];
+  if( pageInsertArray(
+        pPg, pBegin, &pData, pCellptr,
+        iNew+nCell, nNew-nCell, pCArray
+  ) ) goto editpage_fail;
+
+  pPg->nCell = nNew;
+  pPg->nOverflow = 0;
+
+  put2byte(&aData[hdr+3], pPg->nCell);
+  put2byte(&aData[hdr+5], pData - aData);
+
+#ifdef SQLITE_DEBUG
+  for(i=0; i<nNew && !CORRUPT_DB; i++){
+    u8 *pCell = pCArray->apCell[i+iNew];
+    int iOff = get2byteAligned(&pPg->aCellIdx[i*2]);
+    if( SQLITE_WITHIN(pCell, aData, &aData[pPg->pBt->usableSize]) ){
+      pCell = &pTmp[pCell - aData];
+    }
+    assert( 0==memcmp(pCell, &aData[iOff],
+            pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
+  }
+#endif
+
+  return SQLITE_OK;
+ editpage_fail:
+  /* Unable to edit this page. Rebuild it from scratch instead. */
+  if( nNew<1 ) return SQLITE_CORRUPT_BKPT;
+  populateCellCache(pCArray, iNew, nNew);
+  return rebuildPage(pCArray, iNew, nNew, pPg);
+}
+
+
+#ifndef SQLITE_OMIT_QUICKBALANCE
+/*
+** This version of balance() handles the common special case where
+** a new entry is being inserted on the extreme right-end of the
+** tree, in other words, when the new entry will become the largest
+** entry in the tree.
+**
+** Instead of trying to balance the 3 right-most leaf pages, just add
+** a new page to the right-hand side and put the one new entry in
+** that page.  This leaves the right side of the tree somewhat
+** unbalanced.  But odds are that we will be inserting new entries
+** at the end soon afterwards so the nearly empty page will quickly
+** fill up.  On average.
+**
+** pPage is the leaf page which is the right-most page in the tree.
+** pParent is its parent.  pPage must have a single overflow entry
+** which is also the right-most entry on the page.
+**
+** The pSpace buffer is used to store a temporary copy of the divider
+** cell that will be inserted into pParent. Such a cell consists of a 4
+** byte page number followed by a variable length integer. In other
+** words, at most 13 bytes. Hence the pSpace buffer must be at
+** least 13 bytes in size.
+*/
+static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
+  BtShared *const pBt = pPage->pBt;    /* B-Tree Database */
+  MemPage *pNew;                       /* Newly allocated page */
+  int rc;                              /* Return Code */
+  Pgno pgnoNew;                        /* Page number of pNew */
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+  assert( pPage->nOverflow==1 );
+ 
+  if( pPage->nCell==0 ) return SQLITE_CORRUPT_BKPT;  /* dbfuzz001.test */
+  assert( pPage->nFree>=0 );
+  assert( pParent->nFree>=0 );
+
+  /* Allocate a new page. This page will become the right-sibling of
+  ** pPage. Make the parent page writable, so that the new divider cell
+  ** may be inserted. If both these operations are successful, proceed.
+  */
+  rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
+
+  if( rc==SQLITE_OK ){
+
+    u8 *pOut = &pSpace[4];
+    u8 *pCell = pPage->apOvfl[0];
+    u16 szCell = pPage->xCellSize(pPage, pCell);
+    u8 *pStop;
+    CellArray b;
+
+    assert( sqlite3PagerIswriteable(pNew->pDbPage) );
+    assert( CORRUPT_DB || pPage->aData[0]==(PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF) );
+    zeroPage(pNew, PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF);
+    b.nCell = 1;
+    b.pRef = pPage;
+    b.apCell = &pCell;
+    b.szCell = &szCell;
+    b.apEnd[0] = pPage->aDataEnd;
+    b.ixNx[0] = 2;
+    rc = rebuildPage(&b, 0, 1, pNew);
+    if( NEVER(rc) ){
+      releasePage(pNew);
+      return rc;
+    }
+    pNew->nFree = pBt->usableSize - pNew->cellOffset - 2 - szCell;
+
+    /* If this is an auto-vacuum database, update the pointer map
+    ** with entries for the new page, and any pointer from the
+    ** cell on the page to an overflow page. If either of these
+    ** operations fails, the return code is set, but the contents
+    ** of the parent page are still manipulated by the code below.
+    ** That is Ok, at this point the parent page is guaranteed to
+    ** be marked as dirty. Returning an error code will cause a
+    ** rollback, undoing any changes made to the parent page.
+    */
+    if( ISAUTOVACUUM(pBt) ){
+      ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno, &rc);
+      if( szCell>pNew->minLocal ){
+        ptrmapPutOvflPtr(pNew, pNew, pCell, &rc);
+      }
+    }
+ 
+    /* Create a divider cell to insert into pParent. The divider cell
+    ** consists of a 4-byte page number (the page number of pPage) and
+    ** a variable length key value (which must be the same value as the
+    ** largest key on pPage).
+    **
+    ** To find the largest key value on pPage, first find the right-most
+    ** cell on pPage. The first two fields of this cell are the
+    ** record-length (a variable length integer at most 32-bits in size)
+    ** and the key value (a variable length integer, may have any value).
+    ** The first of the while(...) loops below skips over the record-length
+    ** field. The second while(...) loop copies the key value from the
+    ** cell on pPage into the pSpace buffer.
+    */
+    pCell = findCell(pPage, pPage->nCell-1);
+    pStop = &pCell[9];
+    while( (*(pCell++)&0x80) && pCell<pStop );
+    pStop = &pCell[9];
+    while( ((*(pOut++) = *(pCell++))&0x80) && pCell<pStop );
+
+    /* Insert the new divider cell into pParent. */
+    if( rc==SQLITE_OK ){
+      rc = insertCell(pParent, pParent->nCell, pSpace, (int)(pOut-pSpace),
+                      0, pPage->pgno);
+    }
+
+    /* Set the right-child pointer of pParent to point to the new page. */
+    put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
+ 
+    /* Release the reference to the new page. */
+    releasePage(pNew);
+  }
+
+  return rc;
+}
+#endif /* SQLITE_OMIT_QUICKBALANCE */
+
+#if 0
+/*
+** This function does not contribute anything to the operation of SQLite.
+** it is sometimes activated temporarily while debugging code responsible
+** for setting pointer-map entries.
+*/
+static int ptrmapCheckPages(MemPage **apPage, int nPage){
+  int i, j;
+  for(i=0; i<nPage; i++){
+    Pgno n;
+    u8 e;
+    MemPage *pPage = apPage[i];
+    BtShared *pBt = pPage->pBt;
+    assert( pPage->isInit );
+
+    for(j=0; j<pPage->nCell; j++){
+      CellInfo info;
+      u8 *z;
+    
+      z = findCell(pPage, j);
+      pPage->xParseCell(pPage, z, &info);
+      if( info.nLocal<info.nPayload ){
+        Pgno ovfl = get4byte(&z[info.nSize-4]);
+        ptrmapGet(pBt, ovfl, &e, &n);
+        assert( n==pPage->pgno && e==PTRMAP_OVERFLOW1 );
+      }
+      if( !pPage->leaf ){
+        Pgno child = get4byte(z);
+        ptrmapGet(pBt, child, &e, &n);
+        assert( n==pPage->pgno && e==PTRMAP_BTREE );
+      }
+    }
+    if( !pPage->leaf ){
+      Pgno child = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+      ptrmapGet(pBt, child, &e, &n);
+      assert( n==pPage->pgno && e==PTRMAP_BTREE );
+    }
+  }
+  return 1;
+}
+#endif
+
+/*
+** This function is used to copy the contents of the b-tree node stored
+** on page pFrom to page pTo. If page pFrom was not a leaf page, then
+** the pointer-map entries for each child page are updated so that the
+** parent page stored in the pointer map is page pTo. If pFrom contained
+** any cells with overflow page pointers, then the corresponding pointer
+** map entries are also updated so that the parent page is page pTo.
+**
+** If pFrom is currently carrying any overflow cells (entries in the
+** MemPage.apOvfl[] array), they are not copied to pTo.
+**
+** Before returning, page pTo is reinitialized using btreeInitPage().
+**
+** The performance of this function is not critical. It is only used by
+** the balance_shallower() and balance_deeper() procedures, neither of
+** which are called often under normal circumstances.
+*/
+static void copyNodeContent(MemPage *pFrom, MemPage *pTo, int *pRC){
+  if( (*pRC)==SQLITE_OK ){
+    BtShared * const pBt = pFrom->pBt;
+    u8 * const aFrom = pFrom->aData;
+    u8 * const aTo = pTo->aData;
+    int const iFromHdr = pFrom->hdrOffset;
+    int const iToHdr = ((pTo->pgno==1) ? 100 : 0);
+    int rc;
+    int iData;
+ 
+ 
+    assert( pFrom->isInit );
+    assert( pFrom->nFree>=iToHdr );
+    assert( get2byte(&aFrom[iFromHdr+5]) <= (int)pBt->usableSize );
+ 
+    /* Copy the b-tree node content from page pFrom to page pTo. */
+    iData = get2byte(&aFrom[iFromHdr+5]);
+    memcpy(&aTo[iData], &aFrom[iData], pBt->usableSize-iData);
+    memcpy(&aTo[iToHdr], &aFrom[iFromHdr], pFrom->cellOffset + 2*pFrom->nCell);
+ 
+    /* Reinitialize page pTo so that the contents of the MemPage structure
+    ** match the new data. The initialization of pTo can actually fail under
+    ** fairly obscure circumstances, even though it is a copy of initialized
+    ** page pFrom.
+    */
+    pTo->isInit = 0;
+    rc = btreeInitPage(pTo);
+    if( rc==SQLITE_OK ) rc = btreeComputeFreeSpace(pTo);
+    if( rc!=SQLITE_OK ){
+      *pRC = rc;
+      return;
+    }
+ 
+    /* If this is an auto-vacuum database, update the pointer-map entries
+    ** for any b-tree or overflow pages that pTo now contains the pointers to.
+    */
+    if( ISAUTOVACUUM(pBt) ){
+      *pRC = setChildPtrmaps(pTo);
+    }
+  }
+}
+
+/*
+** This routine redistributes cells on the iParentIdx'th child of pParent
+** (hereafter "the page") and up to 2 siblings so that all pages have about the
+** same amount of free space. Usually a single sibling on either side of the
+** page are used in the balancing, though both siblings might come from one
+** side if the page is the first or last child of its parent. If the page
+** has fewer than 2 siblings (something which can only happen if the page
+** is a root page or a child of a root page) then all available siblings
+** participate in the balancing.
+**
+** The number of siblings of the page might be increased or decreased by
+** one or two in an effort to keep pages nearly full but not over full.
+**
+** Note that when this routine is called, some of the cells on the page
+** might not actually be stored in MemPage.aData[]. This can happen
+** if the page is overfull. This routine ensures that all cells allocated
+** to the page and its siblings fit into MemPage.aData[] before returning.
+**
+** In the course of balancing the page and its siblings, cells may be
+** inserted into or removed from the parent page (pParent). Doing so
+** may cause the parent page to become overfull or underfull. If this
+** happens, it is the responsibility of the caller to invoke the correct
+** balancing routine to fix this problem (see the balance() routine).
+**
+** If this routine fails for any reason, it might leave the database
+** in a corrupted state. So if this routine fails, the database should
+** be rolled back.
+**
+** The third argument to this function, aOvflSpace, is a pointer to a
+** buffer big enough to hold one page. If while inserting cells into the parent
+** page (pParent) the parent page becomes overfull, this buffer is
+** used to store the parent's overflow cells. Because this function inserts
+** a maximum of four divider cells into the parent page, and the maximum
+** size of a cell stored within an internal node is always less than 1/4
+** of the page-size, the aOvflSpace[] buffer is guaranteed to be large
+** enough for all overflow cells.
+**
+** If aOvflSpace is set to a null pointer, this function returns
+** SQLITE_NOMEM.
+*/
+static int balance_nonroot(
+  MemPage *pParent,               /* Parent page of siblings being balanced */
+  int iParentIdx,                 /* Index of "the page" in pParent */
+  u8 *aOvflSpace,                 /* page-size bytes of space for parent ovfl */
+  int isRoot,                     /* True if pParent is a root-page */
+  int bBulk                       /* True if this call is part of a bulk load */
+){
+  BtShared *pBt;               /* The whole database */
+  int nMaxCells = 0;           /* Allocated size of apCell, szCell, aFrom. */
+  int nNew = 0;                /* Number of pages in apNew[] */
+  int nOld;                    /* Number of pages in apOld[] */
+  int i, j, k;                 /* Loop counters */
+  int nxDiv;                   /* Next divider slot in pParent->aCell[] */
+  int rc = SQLITE_OK;          /* The return code */
+  u16 leafCorrection;          /* 4 if pPage is a leaf.  0 if not */
+  int leafData;                /* True if pPage is a leaf of a LEAFDATA tree */
+  int usableSpace;             /* Bytes in pPage beyond the header */
+  int pageFlags;               /* Value of pPage->aData[0] */
+  int iSpace1 = 0;             /* First unused byte of aSpace1[] */
+  int iOvflSpace = 0;          /* First unused byte of aOvflSpace[] */
+  int szScratch;               /* Size of scratch memory requested */
+  MemPage *apOld[NB];          /* pPage and up to two siblings */
+  MemPage *apNew[NB+2];        /* pPage and up to NB siblings after balancing */
+  u8 *pRight;                  /* Location in parent of right-sibling pointer */
+  u8 *apDiv[NB-1];             /* Divider cells in pParent */
+  int cntNew[NB+2];            /* Index in b.paCell[] of cell after i-th page */
+  int cntOld[NB+2];            /* Old index in b.apCell[] */
+  int szNew[NB+2];             /* Combined size of cells placed on i-th page */
+  u8 *aSpace1;                 /* Space for copies of dividers cells */
+  Pgno pgno;                   /* Temp var to store a page number in */
+  u8 abDone[NB+2];             /* True after i'th new page is populated */
+  Pgno aPgno[NB+2];            /* Page numbers of new pages before shuffling */
+  CellArray b;                 /* Parsed information on cells being balanced */
+
+  memset(abDone, 0, sizeof(abDone));
+  memset(&b, 0, sizeof(b));
+  pBt = pParent->pBt;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+
+  /* At this point pParent may have at most one overflow cell. And if
+  ** this overflow cell is present, it must be the cell with
+  ** index iParentIdx. This scenario comes about when this function
+  ** is called (indirectly) from sqlite3BtreeDelete().
+  */
+  assert( pParent->nOverflow==0 || pParent->nOverflow==1 );
+  assert( pParent->nOverflow==0 || pParent->aiOvfl[0]==iParentIdx );
+
+  if( !aOvflSpace ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  assert( pParent->nFree>=0 );
+
+  /* Find the sibling pages to balance. Also locate the cells in pParent
+  ** that divide the siblings. An attempt is made to find NN siblings on
+  ** either side of pPage. More siblings are taken from one side, however,
+  ** if there are fewer than NN siblings on the other side. If pParent
+  ** has NB or fewer children then all children of pParent are taken. 
+  **
+  ** This loop also drops the divider cells from the parent page. This
+  ** way, the remainder of the function does not have to deal with any
+  ** overflow cells in the parent page, since if any existed they will
+  ** have already been removed.
+  */
+  i = pParent->nOverflow + pParent->nCell;
+  if( i<2 ){
+    nxDiv = 0;
+  }else{
+    assert( bBulk==0 || bBulk==1 );
+    if( iParentIdx==0 ){                
+      nxDiv = 0;
+    }else if( iParentIdx==i ){
+      nxDiv = i-2+bBulk;
+    }else{
+      nxDiv = iParentIdx-1;
+    }
+    i = 2-bBulk;
+  }
+  nOld = i+1;
+  if( (i+nxDiv-pParent->nOverflow)==pParent->nCell ){
+    pRight = &pParent->aData[pParent->hdrOffset+8];
+  }else{
+    pRight = findCell(pParent, i+nxDiv-pParent->nOverflow);
+  }
+  pgno = get4byte(pRight);
+  while( 1 ){
+    if( rc==SQLITE_OK ){
+      rc = getAndInitPage(pBt, pgno, &apOld[i], 0);
+    }
+    if( rc ){
+      memset(apOld, 0, (i+1)*sizeof(MemPage*));
+      goto balance_cleanup;
+    }
+    if( apOld[i]->nFree<0 ){
+      rc = btreeComputeFreeSpace(apOld[i]);
+      if( rc ){
+        memset(apOld, 0, (i)*sizeof(MemPage*));
+        goto balance_cleanup;
+      }
+    }
+    nMaxCells += apOld[i]->nCell + ArraySize(pParent->apOvfl);
+    if( (i--)==0 ) break;
+
+    if( pParent->nOverflow && i+nxDiv==pParent->aiOvfl[0] ){
+      apDiv[i] = pParent->apOvfl[0];
+      pgno = get4byte(apDiv[i]);
+      szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
+      pParent->nOverflow = 0;
+    }else{
+      apDiv[i] = findCell(pParent, i+nxDiv-pParent->nOverflow);
+      pgno = get4byte(apDiv[i]);
+      szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
+
+      /* Drop the cell from the parent page. apDiv[i] still points to
+      ** the cell within the parent, even though it has been dropped.
+      ** This is safe because dropping a cell only overwrites the first
+      ** four bytes of it, and this function does not need the first
+      ** four bytes of the divider cell. So the pointer is safe to use
+      ** later on. 
+      **
+      ** But not if we are in secure-delete mode. In secure-delete mode,
+      ** the dropCell() routine will overwrite the entire cell with zeroes.
+      ** In this case, temporarily copy the cell into the aOvflSpace[]
+      ** buffer. It will be copied out again as soon as the aSpace[] buffer
+      ** is allocated.  */
+      if( pBt->btsFlags & BTS_FAST_SECURE ){
+        int iOff;
+
+        /* If the following if() condition is not true, the db is corrupted.
+        ** The call to dropCell() below will detect this.  */
+        iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
+        if( (iOff+szNew[i])<=(int)pBt->usableSize ){
+          memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
+          apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
+        }
+      }
+      dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
+    }
+  }
+
+  /* Make nMaxCells a multiple of 4 in order to preserve 8-byte
+  ** alignment */
+  nMaxCells = (nMaxCells + 3)&~3;
+
+  /*
+  ** Allocate space for memory structures
+  */
+  szScratch =
+       nMaxCells*sizeof(u8*)                       /* b.apCell */
+     + nMaxCells*sizeof(u16)                       /* b.szCell */
+     + pBt->pageSize;                              /* aSpace1 */
+
+  assert( szScratch<=7*(int)pBt->pageSize );
+  b.apCell = sqlite3StackAllocRaw(0, szScratch );
+  if( b.apCell==0 ){
+    rc = SQLITE_NOMEM_BKPT;
+    goto balance_cleanup;
+  }
+  b.szCell = (u16*)&b.apCell[nMaxCells];
+  aSpace1 = (u8*)&b.szCell[nMaxCells];
+  assert( EIGHT_BYTE_ALIGNMENT(aSpace1) );
+
+  /*
+  ** Load pointers to all cells on sibling pages and the divider cells
+  ** into the local b.apCell[] array.  Make copies of the divider cells
+  ** into space obtained from aSpace1[]. The divider cells have already
+  ** been removed from pParent.
+  **
+  ** If the siblings are on leaf pages, then the child pointers of the
+  ** divider cells are stripped from the cells before they are copied
+  ** into aSpace1[].  In this way, all cells in b.apCell[] are without
+  ** child pointers.  If siblings are not leaves, then all cell in
+  ** b.apCell[] include child pointers.  Either way, all cells in b.apCell[]
+  ** are alike.
+  **
+  ** leafCorrection:  4 if pPage is a leaf.  0 if pPage is not a leaf.
+  **       leafData:  1 if pPage holds key+data and pParent holds only keys.
+  */
+  b.pRef = apOld[0];
+  leafCorrection = b.pRef->leaf*4;
+  leafData = b.pRef->intKeyLeaf;
+  for(i=0; i<nOld; i++){
+    MemPage *pOld = apOld[i];
+    int limit = pOld->nCell;
+    u8 *aData = pOld->aData;
+    u16 maskPage = pOld->maskPage;
+    u8 *piCell = aData + pOld->cellOffset;
+    u8 *piEnd;
+    VVA_ONLY( int nCellAtStart = b.nCell; )
+
+    /* Verify that all sibling pages are of the same "type" (table-leaf,
+    ** table-interior, index-leaf, or index-interior).
+    */
+    if( pOld->aData[0]!=apOld[0]->aData[0] ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto balance_cleanup;
+    }
+
+    /* Load b.apCell[] with pointers to all cells in pOld.  If pOld
+    ** contains overflow cells, include them in the b.apCell[] array
+    ** in the correct spot.
+    **
+    ** Note that when there are multiple overflow cells, it is always the
+    ** case that they are sequential and adjacent.  This invariant arises
+    ** because multiple overflows can only occurs when inserting divider
+    ** cells into a parent on a prior balance, and divider cells are always
+    ** adjacent and are inserted in order.  There is an assert() tagged
+    ** with "NOTE 1" in the overflow cell insertion loop to prove this
+    ** invariant.
+    **
+    ** This must be done in advance.  Once the balance starts, the cell
+    ** offset section of the btree page will be overwritten and we will no
+    ** long be able to find the cells if a pointer to each cell is not saved
+    ** first.
+    */
+    memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*(limit+pOld->nOverflow));
+    if( pOld->nOverflow>0 ){
+      if( NEVER(limit<pOld->aiOvfl[0]) ){
+        rc = SQLITE_CORRUPT_BKPT;
+        goto balance_cleanup;
+      }
+      limit = pOld->aiOvfl[0];
+      for(j=0; j<limit; j++){
+        b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
+        piCell += 2;
+        b.nCell++;
+      }
+      for(k=0; k<pOld->nOverflow; k++){
+        assert( k==0 || pOld->aiOvfl[k-1]+1==pOld->aiOvfl[k] );/* NOTE 1 */
+        b.apCell[b.nCell] = pOld->apOvfl[k];
+        b.nCell++;
+      }
+    }
+    piEnd = aData + pOld->cellOffset + 2*pOld->nCell;
+    while( piCell<piEnd ){
+      assert( b.nCell<nMaxCells );
+      b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
+      piCell += 2;
+      b.nCell++;
+    }
+    assert( (b.nCell-nCellAtStart)==(pOld->nCell+pOld->nOverflow) );
+
+    cntOld[i] = b.nCell;
+    if( i<nOld-1 && !leafData){
+      u16 sz = (u16)szNew[i];
+      u8 *pTemp;
+      assert( b.nCell<nMaxCells );
+      b.szCell[b.nCell] = sz;
+      pTemp = &aSpace1[iSpace1];
+      iSpace1 += sz;
+      assert( sz<=pBt->maxLocal+23 );
+      assert( iSpace1 <= (int)pBt->pageSize );
+      memcpy(pTemp, apDiv[i], sz);
+      b.apCell[b.nCell] = pTemp+leafCorrection;
+      assert( leafCorrection==0 || leafCorrection==4 );
+      b.szCell[b.nCell] = b.szCell[b.nCell] - leafCorrection;
+      if( !pOld->leaf ){
+        assert( leafCorrection==0 );
+        assert( pOld->hdrOffset==0 || CORRUPT_DB );
+        /* The right pointer of the child page pOld becomes the left
+        ** pointer of the divider cell */
+        memcpy(b.apCell[b.nCell], &pOld->aData[8], 4);
+      }else{
+        assert( leafCorrection==4 );
+        while( b.szCell[b.nCell]<4 ){
+          /* Do not allow any cells smaller than 4 bytes. If a smaller cell
+          ** does exist, pad it with 0x00 bytes. */
+          assert( b.szCell[b.nCell]==3 || CORRUPT_DB );
+          assert( b.apCell[b.nCell]==&aSpace1[iSpace1-3] || CORRUPT_DB );
+          aSpace1[iSpace1++] = 0x00;
+          b.szCell[b.nCell]++;
+        }
+      }
+      b.nCell++;
+    }
+  }
+
+  /*
+  ** Figure out the number of pages needed to hold all b.nCell cells.
+  ** Store this number in "k".  Also compute szNew[] which is the total
+  ** size of all cells on the i-th page and cntNew[] which is the index
+  ** in b.apCell[] of the cell that divides page i from page i+1. 
+  ** cntNew[k] should equal b.nCell.
+  **
+  ** Values computed by this block:
+  **
+  **           k: The total number of sibling pages
+  **    szNew[i]: Spaced used on the i-th sibling page.
+  **   cntNew[i]: Index in b.apCell[] and b.szCell[] for the first cell to
+  **              the right of the i-th sibling page.
+  ** usableSpace: Number of bytes of space available on each sibling.
+  **
+  */
+  usableSpace = pBt->usableSize - 12 + leafCorrection;
+  for(i=k=0; i<nOld; i++, k++){
+    MemPage *p = apOld[i];
+    b.apEnd[k] = p->aDataEnd;
+    b.ixNx[k] = cntOld[i];
+    if( k && b.ixNx[k]==b.ixNx[k-1] ){
+      k--;  /* Omit b.ixNx[] entry for child pages with no cells */
+    }
+    if( !leafData ){
+      k++;
+      b.apEnd[k] = pParent->aDataEnd;
+      b.ixNx[k] = cntOld[i]+1;
+    }
+    assert( p->nFree>=0 );
+    szNew[i] = usableSpace - p->nFree;
+    for(j=0; j<p->nOverflow; j++){
+      szNew[i] += 2 + p->xCellSize(p, p->apOvfl[j]);
+    }
+    cntNew[i] = cntOld[i];
+  }
+  k = nOld;
+  for(i=0; i<k; i++){
+    int sz;
+    while( szNew[i]>usableSpace ){
+      if( i+1>=k ){
+        k = i+2;
+        if( k>NB+2 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
+        szNew[k-1] = 0;
+        cntNew[k-1] = b.nCell;
+      }
+      sz = 2 + cachedCellSize(&b, cntNew[i]-1);
+      szNew[i] -= sz;
+      if( !leafData ){
+        if( cntNew[i]<b.nCell ){
+          sz = 2 + cachedCellSize(&b, cntNew[i]);
+        }else{
+          sz = 0;
+        }
+      }
+      szNew[i+1] += sz;
+      cntNew[i]--;
+    }
+    while( cntNew[i]<b.nCell ){
+      sz = 2 + cachedCellSize(&b, cntNew[i]);
+      if( szNew[i]+sz>usableSpace ) break;
+      szNew[i] += sz;
+      cntNew[i]++;
+      if( !leafData ){
+        if( cntNew[i]<b.nCell ){
+          sz = 2 + cachedCellSize(&b, cntNew[i]);
+        }else{
+          sz = 0;
+        }
+      }
+      szNew[i+1] -= sz;
+    }
+    if( cntNew[i]>=b.nCell ){
+      k = i+1;
+    }else if( cntNew[i] <= (i>0 ? cntNew[i-1] : 0) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto balance_cleanup;
+    }
+  }
+
+  /*
+  ** The packing computed by the previous block is biased toward the siblings
+  ** on the left side (siblings with smaller keys). The left siblings are
+  ** always nearly full, while the right-most sibling might be nearly empty.
+  ** The next block of code attempts to adjust the packing of siblings to
+  ** get a better balance.
+  **
+  ** This adjustment is more than an optimization.  The packing above might
+  ** be so out of balance as to be illegal.  For example, the right-most
+  ** sibling might be completely empty.  This adjustment is not optional.
+  */
+  for(i=k-1; i>0; i--){
+    int szRight = szNew[i];  /* Size of sibling on the right */
+    int szLeft = szNew[i-1]; /* Size of sibling on the left */
+    int r;              /* Index of right-most cell in left sibling */
+    int d;              /* Index of first cell to the left of right sibling */
+
+    r = cntNew[i-1] - 1;
+    d = r + 1 - leafData;
+    (void)cachedCellSize(&b, d);
+    do{
+      int szR, szD;
+      assert( d<nMaxCells );
+      assert( r<nMaxCells );
+      szR = cachedCellSize(&b, r);
+      szD = b.szCell[d];
+      if( szRight!=0
+       && (bBulk || szRight+szD+2 > szLeft-(szR+(i==k-1?0:2)))){
+        break;
+      }
+      szRight += szD + 2;
+      szLeft -= szR + 2;
+      cntNew[i-1] = r;
+      r--;
+      d--;
+    }while( r>=0 );
+    szNew[i] = szRight;
+    szNew[i-1] = szLeft;
+    if( cntNew[i-1] <= (i>1 ? cntNew[i-2] : 0) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto balance_cleanup;
+    }
+  }
+
+  /* Sanity check:  For a non-corrupt database file one of the following
+  ** must be true:
+  **    (1) We found one or more cells (cntNew[0])>0), or
+  **    (2) pPage is a virtual root page.  A virtual root page is when
+  **        the real root page is page 1 and we are the only child of
+  **        that page.
+  */
+  assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) || CORRUPT_DB);
+  TRACE(("BALANCE: old: %u(nc=%u) %u(nc=%u) %u(nc=%u)\n",
+    apOld[0]->pgno, apOld[0]->nCell,
+    nOld>=2 ? apOld[1]->pgno : 0, nOld>=2 ? apOld[1]->nCell : 0,
+    nOld>=3 ? apOld[2]->pgno : 0, nOld>=3 ? apOld[2]->nCell : 0
+  ));
+
+  /*
+  ** Allocate k new pages.  Reuse old pages where possible.
+  */
+  pageFlags = apOld[0]->aData[0];
+  for(i=0; i<k; i++){
+    MemPage *pNew;
+    if( i<nOld ){
+      pNew = apNew[i] = apOld[i];
+      apOld[i] = 0;
+      rc = sqlite3PagerWrite(pNew->pDbPage);
+      nNew++;
+      if( sqlite3PagerPageRefcount(pNew->pDbPage)!=1+(i==(iParentIdx-nxDiv))
+       && rc==SQLITE_OK
+      ){
+        rc = SQLITE_CORRUPT_BKPT;
+      }
+      if( rc ) goto balance_cleanup;
+    }else{
+      assert( i>0 );
+      rc = allocateBtreePage(pBt, &pNew, &pgno, (bBulk ? 1 : pgno), 0);
+      if( rc ) goto balance_cleanup;
+      zeroPage(pNew, pageFlags);
+      apNew[i] = pNew;
+      nNew++;
+      cntOld[i] = b.nCell;
+
+      /* Set the pointer-map entry for the new sibling page. */
+      if( ISAUTOVACUUM(pBt) ){
+        ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno, &rc);
+        if( rc!=SQLITE_OK ){
+          goto balance_cleanup;
+        }
+      }
+    }
+  }
+
+  /*
+  ** Reassign page numbers so that the new pages are in ascending order.
+  ** This helps to keep entries in the disk file in order so that a scan
+  ** of the table is closer to a linear scan through the file. That in turn
+  ** helps the operating system to deliver pages from the disk more rapidly.
+  **
+  ** An O(N*N) sort algorithm is used, but since N is never more than NB+2
+  ** (5), that is not a performance concern.
+  **
+  ** When NB==3, this one optimization makes the database about 25% faster
+  ** for large insertions and deletions.
+  */
+  for(i=0; i<nNew; i++){
+    aPgno[i] = apNew[i]->pgno;
+    assert( apNew[i]->pDbPage->flags & PGHDR_WRITEABLE );
+    assert( apNew[i]->pDbPage->flags & PGHDR_DIRTY );
+  }
+  for(i=0; i<nNew-1; i++){
+    int iB = i;
+    for(j=i+1; j<nNew; j++){
+      if( apNew[j]->pgno < apNew[iB]->pgno ) iB = j;
+    }
+
+    /* If apNew[i] has a page number that is bigger than any of the
+    ** subsequence apNew[i] entries, then swap apNew[i] with the subsequent
+    ** entry that has the smallest page number (which we know to be
+    ** entry apNew[iB]).
+    */
+    if( iB!=i ){
+      Pgno pgnoA = apNew[i]->pgno;
+      Pgno pgnoB = apNew[iB]->pgno;
+      Pgno pgnoTemp = (PENDING_BYTE/pBt->pageSize)+1;
+      u16 fgA = apNew[i]->pDbPage->flags;
+      u16 fgB = apNew[iB]->pDbPage->flags;
+      sqlite3PagerRekey(apNew[i]->pDbPage, pgnoTemp, fgB);
+      sqlite3PagerRekey(apNew[iB]->pDbPage, pgnoA, fgA);
+      sqlite3PagerRekey(apNew[i]->pDbPage, pgnoB, fgB);
+      apNew[i]->pgno = pgnoB;
+      apNew[iB]->pgno = pgnoA;
+    }
+  }
+
+  TRACE(("BALANCE: new: %u(%u nc=%u) %u(%u nc=%u) %u(%u nc=%u) "
+         "%u(%u nc=%u) %u(%u nc=%u)\n",
+    apNew[0]->pgno, szNew[0], cntNew[0],
+    nNew>=2 ? apNew[1]->pgno : 0, nNew>=2 ? szNew[1] : 0,
+    nNew>=2 ? cntNew[1] - cntNew[0] - !leafData : 0,
+    nNew>=3 ? apNew[2]->pgno : 0, nNew>=3 ? szNew[2] : 0,
+    nNew>=3 ? cntNew[2] - cntNew[1] - !leafData : 0,
+    nNew>=4 ? apNew[3]->pgno : 0, nNew>=4 ? szNew[3] : 0,
+    nNew>=4 ? cntNew[3] - cntNew[2] - !leafData : 0,
+    nNew>=5 ? apNew[4]->pgno : 0, nNew>=5 ? szNew[4] : 0,
+    nNew>=5 ? cntNew[4] - cntNew[3] - !leafData : 0
+  ));
+
+  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+  assert( nNew>=1 && nNew<=ArraySize(apNew) );
+  assert( apNew[nNew-1]!=0 );
+  put4byte(pRight, apNew[nNew-1]->pgno);
+
+  /* If the sibling pages are not leaves, ensure that the right-child pointer
+  ** of the right-most new sibling page is set to the value that was
+  ** originally in the same field of the right-most old sibling page. */
+  if( (pageFlags & PTF_LEAF)==0 && nOld!=nNew ){
+    MemPage *pOld = (nNew>nOld ? apNew : apOld)[nOld-1];
+    memcpy(&apNew[nNew-1]->aData[8], &pOld->aData[8], 4);
+  }
+
+  /* Make any required updates to pointer map entries associated with
+  ** cells stored on sibling pages following the balance operation. Pointer
+  ** map entries associated with divider cells are set by the insertCell()
+  ** routine. The associated pointer map entries are:
+  **
+  **   a) if the cell contains a reference to an overflow chain, the
+  **      entry associated with the first page in the overflow chain, and
+  **
+  **   b) if the sibling pages are not leaves, the child page associated
+  **      with the cell.
+  **
+  ** If the sibling pages are not leaves, then the pointer map entry
+  ** associated with the right-child of each sibling may also need to be
+  ** updated. This happens below, after the sibling pages have been
+  ** populated, not here.
+  */
+  if( ISAUTOVACUUM(pBt) ){
+    MemPage *pOld;
+    MemPage *pNew = pOld = apNew[0];
+    int cntOldNext = pNew->nCell + pNew->nOverflow;
+    int iNew = 0;
+    int iOld = 0;
+
+    for(i=0; i<b.nCell; i++){
+      u8 *pCell = b.apCell[i];
+      while( i==cntOldNext ){
+        iOld++;
+        assert( iOld<nNew || iOld<nOld );
+        assert( iOld>=0 && iOld<NB );
+        pOld = iOld<nNew ? apNew[iOld] : apOld[iOld];
+        cntOldNext += pOld->nCell + pOld->nOverflow + !leafData;
+      }
+      if( i==cntNew[iNew] ){
+        pNew = apNew[++iNew];
+        if( !leafData ) continue;
+      }
+
+      /* Cell pCell is destined for new sibling page pNew. Originally, it
+      ** was either part of sibling page iOld (possibly an overflow cell),
+      ** or else the divider cell to the left of sibling page iOld. So,
+      ** if sibling page iOld had the same page number as pNew, and if
+      ** pCell really was a part of sibling page iOld (not a divider or
+      ** overflow cell), we can skip updating the pointer map entries.  */
+      if( iOld>=nNew
+       || pNew->pgno!=aPgno[iOld]
+       || !SQLITE_WITHIN(pCell,pOld->aData,pOld->aDataEnd)
+      ){
+        if( !leafCorrection ){
+          ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno, &rc);
+        }
+        if( cachedCellSize(&b,i)>pNew->minLocal ){
+          ptrmapPutOvflPtr(pNew, pOld, pCell, &rc);
+        }
+        if( rc ) goto balance_cleanup;
+      }
+    }
+  }
+
+  /* Insert new divider cells into pParent. */
+  for(i=0; i<nNew-1; i++){
+    u8 *pCell;
+    u8 *pTemp;
+    int sz;
+    u8 *pSrcEnd;
+    MemPage *pNew = apNew[i];
+    j = cntNew[i];
+
+    assert( j<nMaxCells );
+    assert( b.apCell[j]!=0 );
+    pCell = b.apCell[j];
+    sz = b.szCell[j] + leafCorrection;
+    pTemp = &aOvflSpace[iOvflSpace];
+    if( !pNew->leaf ){
+      memcpy(&pNew->aData[8], pCell, 4);
+    }else if( leafData ){
+      /* If the tree is a leaf-data tree, and the siblings are leaves,
+      ** then there is no divider cell in b.apCell[]. Instead, the divider
+      ** cell consists of the integer key for the right-most cell of
+      ** the sibling-page assembled above only.
+      */
+      CellInfo info;
+      j--;
+      pNew->xParseCell(pNew, b.apCell[j], &info);
+      pCell = pTemp;
+      sz = 4 + putVarint(&pCell[4], info.nKey);
+      pTemp = 0;
+    }else{
+      pCell -= 4;
+      /* Obscure case for non-leaf-data trees: If the cell at pCell was
+      ** previously stored on a leaf node, and its reported size was 4
+      ** bytes, then it may actually be smaller than this
+      ** (see btreeParseCellPtr(), 4 bytes is the minimum size of
+      ** any cell). But it is important to pass the correct size to
+      ** insertCell(), so reparse the cell now.
+      **
+      ** This can only happen for b-trees used to evaluate "IN (SELECT ...)"
+      ** and WITHOUT ROWID tables with exactly one column which is the
+      ** primary key.
+      */
+      if( b.szCell[j]==4 ){
+        assert(leafCorrection==4);
+        sz = pParent->xCellSize(pParent, pCell);
+      }
+    }
+    iOvflSpace += sz;
+    assert( sz<=pBt->maxLocal+23 );
+    assert( iOvflSpace <= (int)pBt->pageSize );
+    for(k=0; ALWAYS(k<NB*2) && b.ixNx[k]<=j; k++){}
+    pSrcEnd = b.apEnd[k];
+    if( SQLITE_OVERFLOW(pSrcEnd, pCell, pCell+sz) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto balance_cleanup;
+    }
+    rc = insertCell(pParent, nxDiv+i, pCell, sz, pTemp, pNew->pgno);
+    if( rc!=SQLITE_OK ) goto balance_cleanup;
+    assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+  }
+
+  /* Now update the actual sibling pages. The order in which they are updated
+  ** is important, as this code needs to avoid disrupting any page from which
+  ** cells may still to be read. In practice, this means:
+  **
+  **  (1) If cells are moving left (from apNew[iPg] to apNew[iPg-1])
+  **      then it is not safe to update page apNew[iPg] until after
+  **      the left-hand sibling apNew[iPg-1] has been updated.
+  **
+  **  (2) If cells are moving right (from apNew[iPg] to apNew[iPg+1])
+  **      then it is not safe to update page apNew[iPg] until after
+  **      the right-hand sibling apNew[iPg+1] has been updated.
+  **
+  ** If neither of the above apply, the page is safe to update.
+  **
+  ** The iPg value in the following loop starts at nNew-1 goes down
+  ** to 0, then back up to nNew-1 again, thus making two passes over
+  ** the pages.  On the initial downward pass, only condition (1) above
+  ** needs to be tested because (2) will always be true from the previous
+  ** step.  On the upward pass, both conditions are always true, so the
+  ** upwards pass simply processes pages that were missed on the downward
+  ** pass.
+  */
+  for(i=1-nNew; i<nNew; i++){
+    int iPg = i<0 ? -i : i;
+    assert( iPg>=0 && iPg<nNew );
+    assert( iPg>=1 || i>=0 );
+    assert( iPg<ArraySize(cntOld) );
+    if( abDone[iPg] ) continue;         /* Skip pages already processed */
+    if( i>=0                            /* On the upwards pass, or... */
+     || cntOld[iPg-1]>=cntNew[iPg-1]    /* Condition (1) is true */
+    ){
+      int iNew;
+      int iOld;
+      int nNewCell;
+
+      /* Verify condition (1):  If cells are moving left, update iPg
+      ** only after iPg-1 has already been updated. */
+      assert( iPg==0 || cntOld[iPg-1]>=cntNew[iPg-1] || abDone[iPg-1] );
+
+      /* Verify condition (2):  If cells are moving right, update iPg
+      ** only after iPg+1 has already been updated. */
+      assert( cntNew[iPg]>=cntOld[iPg] || abDone[iPg+1] );
+
+      if( iPg==0 ){
+        iNew = iOld = 0;
+        nNewCell = cntNew[0];
+      }else{
+        iOld = iPg<nOld ? (cntOld[iPg-1] + !leafData) : b.nCell;
+        iNew = cntNew[iPg-1] + !leafData;
+        nNewCell = cntNew[iPg] - iNew;
+      }
+
+      rc = editPage(apNew[iPg], iOld, iNew, nNewCell, &b);
+      if( rc ) goto balance_cleanup;
+      abDone[iPg]++;
+      apNew[iPg]->nFree = usableSpace-szNew[iPg];
+      assert( apNew[iPg]->nOverflow==0 );
+      assert( apNew[iPg]->nCell==nNewCell );
+    }
+  }
+
+  /* All pages have been processed exactly once */
+  assert( memcmp(abDone, "\01\01\01\01\01", nNew)==0 );
+
+  assert( nOld>0 );
+  assert( nNew>0 );
+
+  if( isRoot && pParent->nCell==0 && pParent->hdrOffset<=apNew[0]->nFree ){
+    /* The root page of the b-tree now contains no cells. The only sibling
+    ** page is the right-child of the parent. Copy the contents of the
+    ** child page into the parent, decreasing the overall height of the
+    ** b-tree structure by one. This is described as the "balance-shallower"
+    ** sub-algorithm in some documentation.
+    **
+    ** If this is an auto-vacuum database, the call to copyNodeContent()
+    ** sets all pointer-map entries corresponding to database image pages
+    ** for which the pointer is stored within the content being copied.
+    **
+    ** It is critical that the child page be defragmented before being
+    ** copied into the parent, because if the parent is page 1 then it will
+    ** by smaller than the child due to the database header, and so all the
+    ** free space needs to be up front.
+    */
+    assert( nNew==1 || CORRUPT_DB );
+    rc = defragmentPage(apNew[0], -1);
+    testcase( rc!=SQLITE_OK );
+    assert( apNew[0]->nFree ==
+        (get2byteNotZero(&apNew[0]->aData[5]) - apNew[0]->cellOffset
+          - apNew[0]->nCell*2)
+      || rc!=SQLITE_OK
+    );
+    copyNodeContent(apNew[0], pParent, &rc);
+    freePage(apNew[0], &rc);
+  }else if( ISAUTOVACUUM(pBt) && !leafCorrection ){
+    /* Fix the pointer map entries associated with the right-child of each
+    ** sibling page. All other pointer map entries have already been taken
+    ** care of.  */
+    for(i=0; i<nNew; i++){
+      u32 key = get4byte(&apNew[i]->aData[8]);
+      ptrmapPut(pBt, key, PTRMAP_BTREE, apNew[i]->pgno, &rc);
+    }
+  }
+
+  assert( pParent->isInit );
+  TRACE(("BALANCE: finished: old=%u new=%u cells=%u\n",
+          nOld, nNew, b.nCell));
+
+  /* Free any old pages that were not reused as new pages.
+  */
+  for(i=nNew; i<nOld; i++){
+    freePage(apOld[i], &rc);
+  }
+
+#if 0
+  if( ISAUTOVACUUM(pBt) && rc==SQLITE_OK && apNew[0]->isInit ){
+    /* The ptrmapCheckPages() contains assert() statements that verify that
+    ** all pointer map pages are set correctly. This is helpful while
+    ** debugging. This is usually disabled because a corrupt database may
+    ** cause an assert() statement to fail.  */
+    ptrmapCheckPages(apNew, nNew);
+    ptrmapCheckPages(&pParent, 1);
+  }
+#endif
+
+  /*
+  ** Cleanup before returning.
+  */
+balance_cleanup:
+  sqlite3StackFree(0, b.apCell);
+  for(i=0; i<nOld; i++){
+    releasePage(apOld[i]);
+  }
+  for(i=0; i<nNew; i++){
+    releasePage(apNew[i]);
+  }
+
+  return rc;
+}
+
+
+/*
+** This function is called when the root page of a b-tree structure is
+** overfull (has one or more overflow pages).
+**
+** A new child page is allocated and the contents of the current root
+** page, including overflow cells, are copied into the child. The root
+** page is then overwritten to make it an empty page with the right-child
+** pointer pointing to the new page.
+**
+** Before returning, all pointer-map entries corresponding to pages
+** that the new child-page now contains pointers to are updated. The
+** entry corresponding to the new right-child pointer of the root
+** page is also updated.
+**
+** If successful, *ppChild is set to contain a reference to the child
+** page and SQLITE_OK is returned. In this case the caller is required
+** to call releasePage() on *ppChild exactly once. If an error occurs,
+** an error code is returned and *ppChild is set to 0.
+*/
+static int balance_deeper(MemPage *pRoot, MemPage **ppChild){
+  int rc;                        /* Return value from subprocedures */
+  MemPage *pChild = 0;           /* Pointer to a new child page */
+  Pgno pgnoChild = 0;            /* Page number of the new child page */
+  BtShared *pBt = pRoot->pBt;    /* The BTree */
+
+  assert( pRoot->nOverflow>0 );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+
+  /* Make pRoot, the root page of the b-tree, writable. Allocate a new
+  ** page that will become the new right-child of pPage. Copy the contents
+  ** of the node stored on pRoot into the new child page.
+  */
+  rc = sqlite3PagerWrite(pRoot->pDbPage);
+  if( rc==SQLITE_OK ){
+    rc = allocateBtreePage(pBt,&pChild,&pgnoChild,pRoot->pgno,0);
+    copyNodeContent(pRoot, pChild, &rc);
+    if( ISAUTOVACUUM(pBt) ){
+      ptrmapPut(pBt, pgnoChild, PTRMAP_BTREE, pRoot->pgno, &rc);
+    }
+  }
+  if( rc ){
+    *ppChild = 0;
+    releasePage(pChild);
+    return rc;
+  }
+  assert( sqlite3PagerIswriteable(pChild->pDbPage) );
+  assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
+  assert( pChild->nCell==pRoot->nCell || CORRUPT_DB );
+
+  TRACE(("BALANCE: copy root %u into %u\n", pRoot->pgno, pChild->pgno));
+
+  /* Copy the overflow cells from pRoot to pChild */
+  memcpy(pChild->aiOvfl, pRoot->aiOvfl,
+         pRoot->nOverflow*sizeof(pRoot->aiOvfl[0]));
+  memcpy(pChild->apOvfl, pRoot->apOvfl,
+         pRoot->nOverflow*sizeof(pRoot->apOvfl[0]));
+  pChild->nOverflow = pRoot->nOverflow;
+
+  /* Zero the contents of pRoot. Then install pChild as the right-child. */
+  zeroPage(pRoot, pChild->aData[0] & ~PTF_LEAF);
+  put4byte(&pRoot->aData[pRoot->hdrOffset+8], pgnoChild);
+
+  *ppChild = pChild;
+  return SQLITE_OK;
+}
+
+/*
+** Return SQLITE_CORRUPT if any cursor other than pCur is currently valid
+** on the same B-tree as pCur.
+**
+** This can occur if a database is corrupt with two or more SQL tables
+** pointing to the same b-tree.  If an insert occurs on one SQL table
+** and causes a BEFORE TRIGGER to do a secondary insert on the other SQL
+** table linked to the same b-tree.  If the secondary insert causes a
+** rebalance, that can change content out from under the cursor on the
+** first SQL table, violating invariants on the first insert.
+*/
+static int anotherValidCursor(BtCursor *pCur){
+  BtCursor *pOther;
+  for(pOther=pCur->pBt->pCursor; pOther; pOther=pOther->pNext){
+    if( pOther!=pCur
+     && pOther->eState==CURSOR_VALID
+     && pOther->pPage==pCur->pPage
+    ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The page that pCur currently points to has just been modified in
+** some way. This function figures out if this modification means the
+** tree needs to be balanced, and if so calls the appropriate balancing
+** routine. Balancing routines are:
+**
+**   balance_quick()
+**   balance_deeper()
+**   balance_nonroot()
+*/
+static int balance(BtCursor *pCur){
+  int rc = SQLITE_OK;
+  u8 aBalanceQuickSpace[13];
+  u8 *pFree = 0;
+
+  VVA_ONLY( int balance_quick_called = 0 );
+  VVA_ONLY( int balance_deeper_called = 0 );
+
+  do {
+    int iPage;
+    MemPage *pPage = pCur->pPage;
+
+    if( NEVER(pPage->nFree<0) && btreeComputeFreeSpace(pPage) ) break;
+    if( pPage->nOverflow==0 && pPage->nFree*3<=(int)pCur->pBt->usableSize*2 ){
+      /* No rebalance required as long as:
+      **   (1) There are no overflow cells
+      **   (2) The amount of free space on the page is less than 2/3rds of
+      **       the total usable space on the page. */
+      break;
+    }else if( (iPage = pCur->iPage)==0 ){
+      if( pPage->nOverflow && (rc = anotherValidCursor(pCur))==SQLITE_OK ){
+        /* The root page of the b-tree is overfull. In this case call the
+        ** balance_deeper() function to create a new child for the root-page
+        ** and copy the current contents of the root-page to it. The
+        ** next iteration of the do-loop will balance the child page.
+        */
+        assert( balance_deeper_called==0 );
+        VVA_ONLY( balance_deeper_called++ );
+        rc = balance_deeper(pPage, &pCur->apPage[1]);
+        if( rc==SQLITE_OK ){
+          pCur->iPage = 1;
+          pCur->ix = 0;
+          pCur->aiIdx[0] = 0;
+          pCur->apPage[0] = pPage;
+          pCur->pPage = pCur->apPage[1];
+          assert( pCur->pPage->nOverflow );
+        }
+      }else{
+        break;
+      }
+    }else if( sqlite3PagerPageRefcount(pPage->pDbPage)>1 ){
+      /* The page being written is not a root page, and there is currently
+      ** more than one reference to it. This only happens if the page is one
+      ** of its own ancestor pages. Corruption. */
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      MemPage * const pParent = pCur->apPage[iPage-1];
+      int const iIdx = pCur->aiIdx[iPage-1];
+
+      rc = sqlite3PagerWrite(pParent->pDbPage);
+      if( rc==SQLITE_OK && pParent->nFree<0 ){
+        rc = btreeComputeFreeSpace(pParent);
+      }
+      if( rc==SQLITE_OK ){
+#ifndef SQLITE_OMIT_QUICKBALANCE
+        if( pPage->intKeyLeaf
+         && pPage->nOverflow==1
+         && pPage->aiOvfl[0]==pPage->nCell
+         && pParent->pgno!=1
+         && pParent->nCell==iIdx
+        ){
+          /* Call balance_quick() to create a new sibling of pPage on which
+          ** to store the overflow cell. balance_quick() inserts a new cell
+          ** into pParent, which may cause pParent overflow. If this
+          ** happens, the next iteration of the do-loop will balance pParent
+          ** use either balance_nonroot() or balance_deeper(). Until this
+          ** happens, the overflow cell is stored in the aBalanceQuickSpace[]
+          ** buffer.
+          **
+          ** The purpose of the following assert() is to check that only a
+          ** single call to balance_quick() is made for each call to this
+          ** function. If this were not verified, a subtle bug involving reuse
+          ** of the aBalanceQuickSpace[] might sneak in.
+          */
+          assert( balance_quick_called==0 );
+          VVA_ONLY( balance_quick_called++ );
+          rc = balance_quick(pParent, pPage, aBalanceQuickSpace);
+        }else
+#endif
+        {
+          /* In this case, call balance_nonroot() to redistribute cells
+          ** between pPage and up to 2 of its sibling pages. This involves
+          ** modifying the contents of pParent, which may cause pParent to
+          ** become overfull or underfull. The next iteration of the do-loop
+          ** will balance the parent page to correct this.
+          **
+          ** If the parent page becomes overfull, the overflow cell or cells
+          ** are stored in the pSpace buffer allocated immediately below.
+          ** A subsequent iteration of the do-loop will deal with this by
+          ** calling balance_nonroot() (balance_deeper() may be called first,
+          ** but it doesn't deal with overflow cells - just moves them to a
+          ** different page). Once this subsequent call to balance_nonroot()
+          ** has completed, it is safe to release the pSpace buffer used by
+          ** the previous call, as the overflow cell data will have been
+          ** copied either into the body of a database page or into the new
+          ** pSpace buffer passed to the latter call to balance_nonroot().
+          */
+          u8 *pSpace = sqlite3PageMalloc(pCur->pBt->pageSize);
+          rc = balance_nonroot(pParent, iIdx, pSpace, iPage==1,
+                               pCur->hints&BTREE_BULKLOAD);
+          if( pFree ){
+            /* If pFree is not NULL, it points to the pSpace buffer used
+            ** by a previous call to balance_nonroot(). Its contents are
+            ** now stored either on real database pages or within the
+            ** new pSpace buffer, so it may be safely freed here. */
+            sqlite3PageFree(pFree);
+          }
+
+          /* The pSpace buffer will be freed after the next call to
+          ** balance_nonroot(), or just before this function returns, whichever
+          ** comes first. */
+          pFree = pSpace;
+        }
+      }
+
+      pPage->nOverflow = 0;
+
+      /* The next iteration of the do-loop balances the parent page. */
+      releasePage(pPage);
+      pCur->iPage--;
+      assert( pCur->iPage>=0 );
+      pCur->pPage = pCur->apPage[pCur->iPage];
+    }
+  }while( rc==SQLITE_OK );
+
+  if( pFree ){
+    sqlite3PageFree(pFree);
+  }
+  return rc;
+}
+
+/* Overwrite content from pX into pDest.  Only do the write if the
+** content is different from what is already there.
+*/
+static int btreeOverwriteContent(
+  MemPage *pPage,           /* MemPage on which writing will occur */
+  u8 *pDest,                /* Pointer to the place to start writing */
+  const BtreePayload *pX,   /* Source of data to write */
+  int iOffset,              /* Offset of first byte to write */
+  int iAmt                  /* Number of bytes to be written */
+){
+  int nData = pX->nData - iOffset;
+  if( nData<=0 ){
+    /* Overwriting with zeros */
+    int i;
+    for(i=0; i<iAmt && pDest[i]==0; i++){}
+    if( i<iAmt ){
+      int rc = sqlite3PagerWrite(pPage->pDbPage);
+      if( rc ) return rc;
+      memset(pDest + i, 0, iAmt - i);
+    }
+  }else{
+    if( nData<iAmt ){
+      /* Mixed read data and zeros at the end.  Make a recursive call
+      ** to write the zeros then fall through to write the real data */
+      int rc = btreeOverwriteContent(pPage, pDest+nData, pX, iOffset+nData,
+                                 iAmt-nData);
+      if( rc ) return rc;
+      iAmt = nData;
+    }
+    if( memcmp(pDest, ((u8*)pX->pData) + iOffset, iAmt)!=0 ){
+      int rc = sqlite3PagerWrite(pPage->pDbPage);
+      if( rc ) return rc;
+      /* In a corrupt database, it is possible for the source and destination
+      ** buffers to overlap.  This is harmless since the database is already
+      ** corrupt but it does cause valgrind and ASAN warnings.  So use
+      ** memmove(). */
+      memmove(pDest, ((u8*)pX->pData) + iOffset, iAmt);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Overwrite the cell that cursor pCur is pointing to with fresh content
+** contained in pX.  In this variant, pCur is pointing to an overflow
+** cell.
+*/
+static SQLITE_NOINLINE int btreeOverwriteOverflowCell(
+  BtCursor *pCur,                     /* Cursor pointing to cell to overwrite */
+  const BtreePayload *pX              /* Content to write into the cell */
+){
+  int iOffset;                        /* Next byte of pX->pData to write */
+  int nTotal = pX->nData + pX->nZero; /* Total bytes of to write */
+  int rc;                             /* Return code */
+  MemPage *pPage = pCur->pPage;       /* Page being written */
+  BtShared *pBt;                      /* Btree */
+  Pgno ovflPgno;                      /* Next overflow page to write */
+  u32 ovflPageSize;                   /* Size to write on overflow page */
+
+  assert( pCur->info.nLocal<nTotal );  /* pCur is an overflow cell */
+
+  /* Overwrite the local portion first */
+  rc = btreeOverwriteContent(pPage, pCur->info.pPayload, pX,
+                             0, pCur->info.nLocal);
+  if( rc ) return rc;
+
+  /* Now overwrite the overflow pages */
+  iOffset = pCur->info.nLocal;
+  assert( nTotal>=0 );
+  assert( iOffset>=0 );
+  ovflPgno = get4byte(pCur->info.pPayload + iOffset);
+  pBt = pPage->pBt;
+  ovflPageSize = pBt->usableSize - 4;
+  do{
+    rc = btreeGetPage(pBt, ovflPgno, &pPage, 0);
+    if( rc ) return rc;
+    if( sqlite3PagerPageRefcount(pPage->pDbPage)!=1 || pPage->isInit ){
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      if( iOffset+ovflPageSize<(u32)nTotal ){
+        ovflPgno = get4byte(pPage->aData);
+      }else{
+        ovflPageSize = nTotal - iOffset;
+      }
+      rc = btreeOverwriteContent(pPage, pPage->aData+4, pX,
+                                 iOffset, ovflPageSize);
+    }
+    sqlite3PagerUnref(pPage->pDbPage);
+    if( rc ) return rc;
+    iOffset += ovflPageSize;
+  }while( iOffset<nTotal );
+  return SQLITE_OK;   
+}
+
+/*
+** Overwrite the cell that cursor pCur is pointing to with fresh content
+** contained in pX.
+*/
+static int btreeOverwriteCell(BtCursor *pCur, const BtreePayload *pX){
+  int nTotal = pX->nData + pX->nZero; /* Total bytes of to write */
+  MemPage *pPage = pCur->pPage;       /* Page being written */
+
+  if( pCur->info.pPayload + pCur->info.nLocal > pPage->aDataEnd
+   || pCur->info.pPayload < pPage->aData + pPage->cellOffset
+  ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  if( pCur->info.nLocal==nTotal ){
+    /* The entire cell is local */
+    return btreeOverwriteContent(pPage, pCur->info.pPayload, pX,
+                                 0, pCur->info.nLocal);
+  }else{
+    /* The cell contains overflow content */
+    return btreeOverwriteOverflowCell(pCur, pX);
+  }
+}
+
+
+/*
+** Insert a new record into the BTree.  The content of the new record
+** is described by the pX object.  The pCur cursor is used only to
+** define what table the record should be inserted into, and is left
+** pointing at a random location.
+**
+** For a table btree (used for rowid tables), only the pX.nKey value of
+** the key is used. The pX.pKey value must be NULL.  The pX.nKey is the
+** rowid or INTEGER PRIMARY KEY of the row.  The pX.nData,pData,nZero fields
+** hold the content of the row.
+**
+** For an index btree (used for indexes and WITHOUT ROWID tables), the
+** key is an arbitrary byte sequence stored in pX.pKey,nKey.  The
+** pX.pData,nData,nZero fields must be zero.
+**
+** If the seekResult parameter is non-zero, then a successful call to
+** sqlite3BtreeIndexMoveto() to seek cursor pCur to (pKey,nKey) has already
+** been performed.  In other words, if seekResult!=0 then the cursor
+** is currently pointing to a cell that will be adjacent to the cell
+** to be inserted.  If seekResult<0 then pCur points to a cell that is
+** smaller then (pKey,nKey).  If seekResult>0 then pCur points to a cell
+** that is larger than (pKey,nKey).
+**
+** If seekResult==0, that means pCur is pointing at some unknown location.
+** In that case, this routine must seek the cursor to the correct insertion
+** point for (pKey,nKey) before doing the insertion.  For index btrees,
+** if pX->nMem is non-zero, then pX->aMem contains pointers to the unpacked
+** key values and pX->aMem can be used instead of pX->pKey to avoid having
+** to decode the key.
+*/
+int sqlite3BtreeInsert(
+  BtCursor *pCur,                /* Insert data into the table of this cursor */
+  const BtreePayload *pX,        /* Content of the row to be inserted */
+  int flags,                     /* True if this is likely an append */
+  int seekResult                 /* Result of prior IndexMoveto() call */
+){
+  int rc;
+  int loc = seekResult;          /* -1: before desired location  +1: after */
+  int szNew = 0;
+  int idx;
+  MemPage *pPage;
+  Btree *p = pCur->pBtree;
+  unsigned char *oldCell;
+  unsigned char *newCell = 0;
+
+  assert( (flags & (BTREE_SAVEPOSITION|BTREE_APPEND|BTREE_PREFORMAT))==flags );
+  assert( (flags & BTREE_PREFORMAT)==0 || seekResult || pCur->pKeyInfo==0 );
+
+  /* Save the positions of any other cursors open on this table.
+  **
+  ** In some cases, the call to btreeMoveto() below is a no-op. For
+  ** example, when inserting data into a table with auto-generated integer
+  ** keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the
+  ** integer key to use. It then calls this function to actually insert the
+  ** data into the intkey B-Tree. In this case btreeMoveto() recognizes
+  ** that the cursor is already where it needs to be and returns without
+  ** doing any work. To avoid thwarting these optimizations, it is important
+  ** not to clear the cursor here.
+  */
+  if( pCur->curFlags & BTCF_Multiple ){
+    rc = saveAllCursors(p->pBt, pCur->pgnoRoot, pCur);
+    if( rc ) return rc;
+    if( loc && pCur->iPage<0 ){
+      /* This can only happen if the schema is corrupt such that there is more
+      ** than one table or index with the same root page as used by the cursor.
+      ** Which can only happen if the SQLITE_NoSchemaError flag was set when
+      ** the schema was loaded. This cannot be asserted though, as a user might
+      ** set the flag, load the schema, and then unset the flag.  */
+      return SQLITE_CORRUPT_BKPT;
+    }
+  }
+
+  /* Ensure that the cursor is not in the CURSOR_FAULT state and that it
+  ** points to a valid cell.
+  */
+  if( pCur->eState>=CURSOR_REQUIRESEEK ){
+    testcase( pCur->eState==CURSOR_REQUIRESEEK );
+    testcase( pCur->eState==CURSOR_FAULT );
+    rc = moveToRoot(pCur);
+    if( rc && rc!=SQLITE_EMPTY ) return rc;
+  }
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( (pCur->curFlags & BTCF_WriteFlag)!=0
+              && p->pBt->inTransaction==TRANS_WRITE
+              && (p->pBt->btsFlags & BTS_READ_ONLY)==0 );
+  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
+
+  /* Assert that the caller has been consistent. If this cursor was opened
+  ** expecting an index b-tree, then the caller should be inserting blob
+  ** keys with no associated data. If the cursor was opened expecting an
+  ** intkey table, the caller should be inserting integer keys with a
+  ** blob of associated data.  */
+  assert( (flags & BTREE_PREFORMAT) || (pX->pKey==0)==(pCur->pKeyInfo==0) );
+
+  if( pCur->pKeyInfo==0 ){
+    assert( pX->pKey==0 );
+    /* If this is an insert into a table b-tree, invalidate any incrblob
+    ** cursors open on the row being replaced */
+    if( p->hasIncrblobCur ){
+      invalidateIncrblobCursors(p, pCur->pgnoRoot, pX->nKey, 0);
+    }
+
+    /* If BTREE_SAVEPOSITION is set, the cursor must already be pointing
+    ** to a row with the same key as the new entry being inserted.
+    */
+#ifdef SQLITE_DEBUG
+    if( flags & BTREE_SAVEPOSITION ){
+      assert( pCur->curFlags & BTCF_ValidNKey );
+      assert( pX->nKey==pCur->info.nKey );
+      assert( loc==0 );
+    }
+#endif
+
+    /* On the other hand, BTREE_SAVEPOSITION==0 does not imply
+    ** that the cursor is not pointing to a row to be overwritten.
+    ** So do a complete check.
+    */
+    if( (pCur->curFlags&BTCF_ValidNKey)!=0 && pX->nKey==pCur->info.nKey ){
+      /* The cursor is pointing to the entry that is to be
+      ** overwritten */
+      assert( pX->nData>=0 && pX->nZero>=0 );
+      if( pCur->info.nSize!=0
+       && pCur->info.nPayload==(u32)pX->nData+pX->nZero
+      ){
+        /* New entry is the same size as the old.  Do an overwrite */
+        return btreeOverwriteCell(pCur, pX);
+      }
+      assert( loc==0 );
+    }else if( loc==0 ){
+      /* The cursor is *not* pointing to the cell to be overwritten, nor
+      ** to an adjacent cell.  Move the cursor so that it is pointing either
+      ** to the cell to be overwritten or an adjacent cell.
+      */
+      rc = sqlite3BtreeTableMoveto(pCur, pX->nKey,
+               (flags & BTREE_APPEND)!=0, &loc);
+      if( rc ) return rc;
+    }
+  }else{
+    /* This is an index or a WITHOUT ROWID table */
+
+    /* If BTREE_SAVEPOSITION is set, the cursor must already be pointing
+    ** to a row with the same key as the new entry being inserted.
+    */
+    assert( (flags & BTREE_SAVEPOSITION)==0 || loc==0 );
+
+    /* If the cursor is not already pointing either to the cell to be
+    ** overwritten, or if a new cell is being inserted, if the cursor is
+    ** not pointing to an immediately adjacent cell, then move the cursor
+    ** so that it does.
+    */
+    if( loc==0 && (flags & BTREE_SAVEPOSITION)==0 ){
+      if( pX->nMem ){
+        UnpackedRecord r;
+        r.pKeyInfo = pCur->pKeyInfo;
+        r.aMem = pX->aMem;
+        r.nField = pX->nMem;
+        r.default_rc = 0;
+        r.eqSeen = 0;
+        rc = sqlite3BtreeIndexMoveto(pCur, &r, &loc);
+      }else{
+        rc = btreeMoveto(pCur, pX->pKey, pX->nKey,
+                    (flags & BTREE_APPEND)!=0, &loc);
+      }
+      if( rc ) return rc;
+    }
+
+    /* If the cursor is currently pointing to an entry to be overwritten
+    ** and the new content is the same as as the old, then use the
+    ** overwrite optimization.
+    */
+    if( loc==0 ){
+      getCellInfo(pCur);
+      if( pCur->info.nKey==pX->nKey ){
+        BtreePayload x2;
+        x2.pData = pX->pKey;
+        x2.nData = pX->nKey;
+        x2.nZero = 0;
+        return btreeOverwriteCell(pCur, &x2);
+      }
+    }
+  }
+  assert( pCur->eState==CURSOR_VALID
+       || (pCur->eState==CURSOR_INVALID && loc) || CORRUPT_DB );
+
+  pPage = pCur->pPage;
+  assert( pPage->intKey || pX->nKey>=0 || (flags & BTREE_PREFORMAT) );
+  assert( pPage->leaf || !pPage->intKey );
+  if( pPage->nFree<0 ){
+    if( NEVER(pCur->eState>CURSOR_INVALID) ){
+     /* ^^^^^--- due to the moveToRoot() call above */
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = btreeComputeFreeSpace(pPage);
+    }
+    if( rc ) return rc;
+  }
+
+  TRACE(("INSERT: table=%u nkey=%lld ndata=%u page=%u %s\n",
+          pCur->pgnoRoot, pX->nKey, pX->nData, pPage->pgno,
+          loc==0 ? "overwrite" : "new entry"));
+  assert( pPage->isInit || CORRUPT_DB );
+  newCell = p->pBt->pTmpSpace;
+  assert( newCell!=0 );
+  assert( BTREE_PREFORMAT==OPFLAG_PREFORMAT );
+  if( flags & BTREE_PREFORMAT ){
+    rc = SQLITE_OK;
+    szNew = p->pBt->nPreformatSize;
+    if( szNew<4 ) szNew = 4;
+    if( ISAUTOVACUUM(p->pBt) && szNew>pPage->maxLocal ){
+      CellInfo info;
+      pPage->xParseCell(pPage, newCell, &info);
+      if( info.nPayload!=info.nLocal ){
+        Pgno ovfl = get4byte(&newCell[szNew-4]);
+        ptrmapPut(p->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, &rc);
+        if( NEVER(rc) ) goto end_insert;
+      }
+    }
+  }else{
+    rc = fillInCell(pPage, newCell, pX, &szNew);
+    if( rc ) goto end_insert;
+  }
+  assert( szNew==pPage->xCellSize(pPage, newCell) );
+  assert( szNew <= MX_CELL_SIZE(p->pBt) );
+  idx = pCur->ix;
+  pCur->info.nSize = 0;
+  if( loc==0 ){
+    CellInfo info;
+    assert( idx>=0 );
+    if( idx>=pPage->nCell ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+    rc = sqlite3PagerWrite(pPage->pDbPage);
+    if( rc ){
+      goto end_insert;
+    }
+    oldCell = findCell(pPage, idx);
+    if( !pPage->leaf ){
+      memcpy(newCell, oldCell, 4);
+    }
+    BTREE_CLEAR_CELL(rc, pPage, oldCell, info);
+    testcase( pCur->curFlags & BTCF_ValidOvfl );
+    invalidateOverflowCache(pCur);
+    if( info.nSize==szNew && info.nLocal==info.nPayload
+     && (!ISAUTOVACUUM(p->pBt) || szNew<pPage->minLocal)
+    ){
+      /* Overwrite the old cell with the new if they are the same size.
+      ** We could also try to do this if the old cell is smaller, then add
+      ** the leftover space to the free list.  But experiments show that
+      ** doing that is no faster then skipping this optimization and just
+      ** calling dropCell() and insertCell().
+      **
+      ** This optimization cannot be used on an autovacuum database if the
+      ** new entry uses overflow pages, as the insertCell() call below is
+      ** necessary to add the PTRMAP_OVERFLOW1 pointer-map entry.  */
+      assert( rc==SQLITE_OK ); /* clearCell never fails when nLocal==nPayload */
+      if( oldCell < pPage->aData+pPage->hdrOffset+10 ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+      if( oldCell+szNew > pPage->aDataEnd ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+      memcpy(oldCell, newCell, szNew);
+      return SQLITE_OK;
+    }
+    dropCell(pPage, idx, info.nSize, &rc);
+    if( rc ) goto end_insert;
+  }else if( loc<0 && pPage->nCell>0 ){
+    assert( pPage->leaf );
+    idx = ++pCur->ix;
+    pCur->curFlags &= ~BTCF_ValidNKey;
+  }else{
+    assert( pPage->leaf );
+  }
+  rc = insertCellFast(pPage, idx, newCell, szNew);
+  assert( pPage->nOverflow==0 || rc==SQLITE_OK );
+  assert( rc!=SQLITE_OK || pPage->nCell>0 || pPage->nOverflow>0 );
+
+  /* If no error has occurred and pPage has an overflow cell, call balance()
+  ** to redistribute the cells within the tree. Since balance() may move
+  ** the cursor, zero the BtCursor.info.nSize and BTCF_ValidNKey
+  ** variables.
+  **
+  ** Previous versions of SQLite called moveToRoot() to move the cursor
+  ** back to the root page as balance() used to invalidate the contents
+  ** of BtCursor.apPage[] and BtCursor.aiIdx[]. Instead of doing that,
+  ** set the cursor state to "invalid". This makes common insert operations
+  ** slightly faster.
+  **
+  ** There is a subtle but important optimization here too. When inserting
+  ** multiple records into an intkey b-tree using a single cursor (as can
+  ** happen while processing an "INSERT INTO ... SELECT" statement), it
+  ** is advantageous to leave the cursor pointing to the last entry in
+  ** the b-tree if possible. If the cursor is left pointing to the last
+  ** entry in the table, and the next row inserted has an integer key
+  ** larger than the largest existing key, it is possible to insert the
+  ** row without seeking the cursor. This can be a big performance boost.
+  */
+  if( pPage->nOverflow ){
+    assert( rc==SQLITE_OK );
+    pCur->curFlags &= ~(BTCF_ValidNKey);
+    rc = balance(pCur);
+
+    /* Must make sure nOverflow is reset to zero even if the balance()
+    ** fails. Internal data structure corruption will result otherwise.
+    ** Also, set the cursor state to invalid. This stops saveCursorPosition()
+    ** from trying to save the current position of the cursor.  */
+    pCur->pPage->nOverflow = 0;
+    pCur->eState = CURSOR_INVALID;
+    if( (flags & BTREE_SAVEPOSITION) && rc==SQLITE_OK ){
+      btreeReleaseAllCursorPages(pCur);
+      if( pCur->pKeyInfo ){
+        assert( pCur->pKey==0 );
+        pCur->pKey = sqlite3Malloc( pX->nKey );
+        if( pCur->pKey==0 ){
+          rc = SQLITE_NOMEM;
+        }else{
+          memcpy(pCur->pKey, pX->pKey, pX->nKey);
+        }
+      }
+      pCur->eState = CURSOR_REQUIRESEEK;
+      pCur->nKey = pX->nKey;
+    }
+  }
+  assert( pCur->iPage<0 || pCur->pPage->nOverflow==0 );
+
+end_insert:
+  return rc;
+}
+
+/*
+** This function is used as part of copying the current row from cursor
+** pSrc into cursor pDest. If the cursors are open on intkey tables, then
+** parameter iKey is used as the rowid value when the record is copied
+** into pDest. Otherwise, the record is copied verbatim.
+**
+** This function does not actually write the new value to cursor pDest.
+** Instead, it creates and populates any required overflow pages and
+** writes the data for the new cell into the BtShared.pTmpSpace buffer
+** for the destination database. The size of the cell, in bytes, is left
+** in BtShared.nPreformatSize. The caller completes the insertion by
+** calling sqlite3BtreeInsert() with the BTREE_PREFORMAT flag specified.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+int sqlite3BtreeTransferRow(BtCursor *pDest, BtCursor *pSrc, i64 iKey){
+  BtShared *pBt = pDest->pBt;
+  u8 *aOut = pBt->pTmpSpace;    /* Pointer to next output buffer */
+  const u8 *aIn;                /* Pointer to next input buffer */
+  u32 nIn;                      /* Size of input buffer aIn[] */
+  u32 nRem;                     /* Bytes of data still to copy */
+
+  getCellInfo(pSrc);
+  if( pSrc->info.nPayload<0x80 ){
+    *(aOut++) = pSrc->info.nPayload;
+  }else{
+    aOut += sqlite3PutVarint(aOut, pSrc->info.nPayload);
+  }
+  if( pDest->pKeyInfo==0 ) aOut += putVarint(aOut, iKey);
+  nIn = pSrc->info.nLocal;
+  aIn = pSrc->info.pPayload;
+  if( aIn+nIn>pSrc->pPage->aDataEnd ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  nRem = pSrc->info.nPayload;
+  if( nIn==nRem && nIn<pDest->pPage->maxLocal ){
+    memcpy(aOut, aIn, nIn);
+    pBt->nPreformatSize = nIn + (aOut - pBt->pTmpSpace);
+    return SQLITE_OK;
+  }else{
+    int rc = SQLITE_OK;
+    Pager *pSrcPager = pSrc->pBt->pPager;
+    u8 *pPgnoOut = 0;
+    Pgno ovflIn = 0;
+    DbPage *pPageIn = 0;
+    MemPage *pPageOut = 0;
+    u32 nOut;                     /* Size of output buffer aOut[] */
+
+    nOut = btreePayloadToLocal(pDest->pPage, pSrc->info.nPayload);
+    pBt->nPreformatSize = nOut + (aOut - pBt->pTmpSpace);
+    if( nOut<pSrc->info.nPayload ){
+      pPgnoOut = &aOut[nOut];
+      pBt->nPreformatSize += 4;
+    }
+ 
+    if( nRem>nIn ){
+      if( aIn+nIn+4>pSrc->pPage->aDataEnd ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+      ovflIn = get4byte(&pSrc->info.pPayload[nIn]);
+    }
+ 
+    do {
+      nRem -= nOut;
+      do{
+        assert( nOut>0 );
+        if( nIn>0 ){
+          int nCopy = MIN(nOut, nIn);
+          memcpy(aOut, aIn, nCopy);
+          nOut -= nCopy;
+          nIn -= nCopy;
+          aOut += nCopy;
+          aIn += nCopy;
+        }
+        if( nOut>0 ){
+          sqlite3PagerUnref(pPageIn);
+          pPageIn = 0;
+          rc = sqlite3PagerGet(pSrcPager, ovflIn, &pPageIn, PAGER_GET_READONLY);
+          if( rc==SQLITE_OK ){
+            aIn = (const u8*)sqlite3PagerGetData(pPageIn);
+            ovflIn = get4byte(aIn);
+            aIn += 4;
+            nIn = pSrc->pBt->usableSize - 4;
+          }
+        }
+      }while( rc==SQLITE_OK && nOut>0 );
+ 
+      if( rc==SQLITE_OK && nRem>0 && ALWAYS(pPgnoOut) ){
+        Pgno pgnoNew;
+        MemPage *pNew = 0;
+        rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
+        put4byte(pPgnoOut, pgnoNew);
+        if( ISAUTOVACUUM(pBt) && pPageOut ){
+          ptrmapPut(pBt, pgnoNew, PTRMAP_OVERFLOW2, pPageOut->pgno, &rc);
+        }
+        releasePage(pPageOut);
+        pPageOut = pNew;
+        if( pPageOut ){
+          pPgnoOut = pPageOut->aData;
+          put4byte(pPgnoOut, 0);
+          aOut = &pPgnoOut[4];
+          nOut = MIN(pBt->usableSize - 4, nRem);
+        }
+      }
+    }while( nRem>0 && rc==SQLITE_OK );
+ 
+    releasePage(pPageOut);
+    sqlite3PagerUnref(pPageIn);
+    return rc;
+  }
+}
+
+/*
+** Delete the entry that the cursor is pointing to.
+**
+** If the BTREE_SAVEPOSITION bit of the flags parameter is zero, then
+** the cursor is left pointing at an arbitrary location after the delete.
+** But if that bit is set, then the cursor is left in a state such that
+** the next call to BtreeNext() or BtreePrev() moves it to the same row
+** as it would have been on if the call to BtreeDelete() had been omitted.
+**
+** The BTREE_AUXDELETE bit of flags indicates that is one of several deletes
+** associated with a single table entry and its indexes.  Only one of those
+** deletes is considered the "primary" delete.  The primary delete occurs
+** on a cursor that is not a BTREE_FORDELETE cursor.  All but one delete
+** operation on non-FORDELETE cursors is tagged with the AUXDELETE flag.
+** The BTREE_AUXDELETE bit is a hint that is not used by this implementation,
+** but which might be used by alternative storage engines.
+*/
+int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
+  Btree *p = pCur->pBtree;
+  BtShared *pBt = p->pBt;             
+  int rc;                    /* Return code */
+  MemPage *pPage;            /* Page to delete cell from */
+  unsigned char *pCell;      /* Pointer to cell to delete */
+  int iCellIdx;              /* Index of cell to delete */
+  int iCellDepth;            /* Depth of node containing pCell */
+  CellInfo info;             /* Size of the cell being deleted */
+  u8 bPreserve;              /* Keep cursor valid.  2 for CURSOR_SKIPNEXT */
+
+  assert( cursorOwnsBtShared(pCur) );
+  assert( pBt->inTransaction==TRANS_WRITE );
+  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
+  assert( pCur->curFlags & BTCF_WriteFlag );
+  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
+  assert( !hasReadConflicts(p, pCur->pgnoRoot) );
+  assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_AUXDELETE))==0 );
+  if( pCur->eState!=CURSOR_VALID ){
+    if( pCur->eState>=CURSOR_REQUIRESEEK ){
+      rc = btreeRestoreCursorPosition(pCur);
+      assert( rc!=SQLITE_OK || CORRUPT_DB || pCur->eState==CURSOR_VALID );
+      if( rc || pCur->eState!=CURSOR_VALID ) return rc;
+    }else{
+      return SQLITE_CORRUPT_BKPT;
+    }
+  }
+  assert( pCur->eState==CURSOR_VALID );
+
+  iCellDepth = pCur->iPage;
+  iCellIdx = pCur->ix;
+  pPage = pCur->pPage;
+  if( pPage->nCell<=iCellIdx ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  pCell = findCell(pPage, iCellIdx);
+  if( pPage->nFree<0 && btreeComputeFreeSpace(pPage) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  if( pCell<&pPage->aCellIdx[pPage->nCell] ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+
+  /* If the BTREE_SAVEPOSITION bit is on, then the cursor position must
+  ** be preserved following this delete operation. If the current delete
+  ** will cause a b-tree rebalance, then this is done by saving the cursor
+  ** key and leaving the cursor in CURSOR_REQUIRESEEK state before
+  ** returning.
+  **
+  ** If the current delete will not cause a rebalance, then the cursor
+  ** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
+  ** before or after the deleted entry.
+  **
+  ** The bPreserve value records which path is required:
+  **
+  **    bPreserve==0         Not necessary to save the cursor position
+  **    bPreserve==1         Use CURSOR_REQUIRESEEK to save the cursor position
+  **    bPreserve==2         Cursor won't move.  Set CURSOR_SKIPNEXT.
+  */
+  bPreserve = (flags & BTREE_SAVEPOSITION)!=0;
+  if( bPreserve ){
+    if( !pPage->leaf
+     || (pPage->nFree+pPage->xCellSize(pPage,pCell)+2) >
+                                                   (int)(pBt->usableSize*2/3)
+     || pPage->nCell==1  /* See dbfuzz001.test for a test case */
+    ){
+      /* A b-tree rebalance will be required after deleting this entry.
+      ** Save the cursor key.  */
+      rc = saveCursorKey(pCur);
+      if( rc ) return rc;
+    }else{
+      bPreserve = 2;
+    }
+  }
+
+  /* If the page containing the entry to delete is not a leaf page, move
+  ** the cursor to the largest entry in the tree that is smaller than
+  ** the entry being deleted. This cell will replace the cell being deleted
+  ** from the internal node. The 'previous' entry is used for this instead
+  ** of the 'next' entry, as the previous entry is always a part of the
+  ** sub-tree headed by the child page of the cell being deleted. This makes
+  ** balancing the tree following the delete operation easier.  */
+  if( !pPage->leaf ){
+    rc = sqlite3BtreePrevious(pCur, 0);
+    assert( rc!=SQLITE_DONE );
+    if( rc ) return rc;
+  }
+
+  /* Save the positions of any other cursors open on this table before
+  ** making any modifications.  */
+  if( pCur->curFlags & BTCF_Multiple ){
+    rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
+    if( rc ) return rc;
+  }
+
+  /* If this is a delete operation to remove a row from a table b-tree,
+  ** invalidate any incrblob cursors open on the row being deleted.  */
+  if( pCur->pKeyInfo==0 && p->hasIncrblobCur ){
+    invalidateIncrblobCursors(p, pCur->pgnoRoot, pCur->info.nKey, 0);
+  }
+
+  /* Make the page containing the entry to be deleted writable. Then free any
+  ** overflow pages associated with the entry and finally remove the cell
+  ** itself from within the page.  */
+  rc = sqlite3PagerWrite(pPage->pDbPage);
+  if( rc ) return rc;
+  BTREE_CLEAR_CELL(rc, pPage, pCell, info);
+  dropCell(pPage, iCellIdx, info.nSize, &rc);
+  if( rc ) return rc;
+
+  /* If the cell deleted was not located on a leaf page, then the cursor
+  ** is currently pointing to the largest entry in the sub-tree headed
+  ** by the child-page of the cell that was just deleted from an internal
+  ** node. The cell from the leaf node needs to be moved to the internal
+  ** node to replace the deleted cell.  */
+  if( !pPage->leaf ){
+    MemPage *pLeaf = pCur->pPage;
+    int nCell;
+    Pgno n;
+    unsigned char *pTmp;
+
+    if( pLeaf->nFree<0 ){
+      rc = btreeComputeFreeSpace(pLeaf);
+      if( rc ) return rc;
+    }
+    if( iCellDepth<pCur->iPage-1 ){
+      n = pCur->apPage[iCellDepth+1]->pgno;
+    }else{
+      n = pCur->pPage->pgno;
+    }
+    pCell = findCell(pLeaf, pLeaf->nCell-1);
+    if( pCell<&pLeaf->aData[4] ) return SQLITE_CORRUPT_BKPT;
+    nCell = pLeaf->xCellSize(pLeaf, pCell);
+    assert( MX_CELL_SIZE(pBt) >= nCell );
+    pTmp = pBt->pTmpSpace;
+    assert( pTmp!=0 );
+    rc = sqlite3PagerWrite(pLeaf->pDbPage);
+    if( rc==SQLITE_OK ){
+      rc = insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n);
+    }
+    dropCell(pLeaf, pLeaf->nCell-1, nCell, &rc);
+    if( rc ) return rc;
+  }
+
+  /* Balance the tree. If the entry deleted was located on a leaf page,
+  ** then the cursor still points to that page. In this case the first
+  ** call to balance() repairs the tree, and the if(...) condition is
+  ** never true.
+  **
+  ** Otherwise, if the entry deleted was on an internal node page, then
+  ** pCur is pointing to the leaf page from which a cell was removed to
+  ** replace the cell deleted from the internal node. This is slightly
+  ** tricky as the leaf node may be underfull, and the internal node may
+  ** be either under or overfull. In this case run the balancing algorithm
+  ** on the leaf node first. If the balance proceeds far enough up the
+  ** tree that we can be sure that any problem in the internal node has
+  ** been corrected, so be it. Otherwise, after balancing the leaf node,
+  ** walk the cursor up the tree to the internal node and balance it as
+  ** well.  */
+  assert( pCur->pPage->nOverflow==0 );
+  assert( pCur->pPage->nFree>=0 );
+  if( pCur->pPage->nFree*3<=(int)pCur->pBt->usableSize*2 ){
+    /* Optimization: If the free space is less than 2/3rds of the page,
+    ** then balance() will always be a no-op.  No need to invoke it. */
+    rc = SQLITE_OK;
+  }else{
+    rc = balance(pCur);
+  }
+  if( rc==SQLITE_OK && pCur->iPage>iCellDepth ){
+    releasePageNotNull(pCur->pPage);
+    pCur->iPage--;
+    while( pCur->iPage>iCellDepth ){
+      releasePage(pCur->apPage[pCur->iPage--]);
+    }
+    pCur->pPage = pCur->apPage[pCur->iPage];
+    rc = balance(pCur);
+  }
+
+  if( rc==SQLITE_OK ){
+    if( bPreserve>1 ){
+      assert( (pCur->iPage==iCellDepth || CORRUPT_DB) );
+      assert( pPage==pCur->pPage || CORRUPT_DB );
+      assert( (pPage->nCell>0 || CORRUPT_DB) && iCellIdx<=pPage->nCell );
+      pCur->eState = CURSOR_SKIPNEXT;
+      if( iCellIdx>=pPage->nCell ){
+        pCur->skipNext = -1;
+        pCur->ix = pPage->nCell-1;
+      }else{
+        pCur->skipNext = 1;
+      }
+    }else{
+      rc = moveToRoot(pCur);
+      if( bPreserve ){
+        btreeReleaseAllCursorPages(pCur);
+        pCur->eState = CURSOR_REQUIRESEEK;
+      }
+      if( rc==SQLITE_EMPTY ) rc = SQLITE_OK;
+    }
+  }
+  return rc;
+}
+
+/*
+** Create a new BTree table.  Write into *piTable the page
+** number for the root page of the new table.
+**
+** The type of type is determined by the flags parameter.  Only the
+** following values of flags are currently in use.  Other values for
+** flags might not work:
+**
+**     BTREE_INTKEY|BTREE_LEAFDATA     Used for SQL tables with rowid keys
+**     BTREE_ZERODATA                  Used for SQL indices
+*/
+static int btreeCreateTable(Btree *p, Pgno *piTable, int createTabFlags){
+  BtShared *pBt = p->pBt;
+  MemPage *pRoot;
+  Pgno pgnoRoot;
+  int rc;
+  int ptfFlags;          /* Page-type flags for the root page of new table */
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( pBt->inTransaction==TRANS_WRITE );
+  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
+
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
+  if( rc ){
+    return rc;
+  }
+#else
+  if( pBt->autoVacuum ){
+    Pgno pgnoMove;      /* Move a page here to make room for the root-page */
+    MemPage *pPageMove; /* The page to move to. */
+
+    /* Creating a new table may probably require moving an existing database
+    ** to make room for the new tables root page. In case this page turns
+    ** out to be an overflow page, delete all overflow page-map caches
+    ** held by open cursors.
+    */
+    invalidateAllOverflowCache(pBt);
+
+    /* Read the value of meta[3] from the database to determine where the
+    ** root page of the new table should go. meta[3] is the largest root-page
+    ** created so far, so the new root-page is (meta[3]+1).
+    */
+    sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
+    if( pgnoRoot>btreePagecount(pBt) ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+    pgnoRoot++;
+
+    /* The new root-page may not be allocated on a pointer-map page, or the
+    ** PENDING_BYTE page.
+    */
+    while( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
+        pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
+      pgnoRoot++;
+    }
+    assert( pgnoRoot>=3 );
+
+    /* Allocate a page. The page that currently resides at pgnoRoot will
+    ** be moved to the allocated page (unless the allocated page happens
+    ** to reside at pgnoRoot).
+    */
+    rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, BTALLOC_EXACT);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+
+    if( pgnoMove!=pgnoRoot ){
+      /* pgnoRoot is the page that will be used for the root-page of
+      ** the new table (assuming an error did not occur). But we were
+      ** allocated pgnoMove. If required (i.e. if it was not allocated
+      ** by extending the file), the current page at position pgnoMove
+      ** is already journaled.
+      */
+      u8 eType = 0;
+      Pgno iPtrPage = 0;
+
+      /* Save the positions of any open cursors. This is required in
+      ** case they are holding a reference to an xFetch reference
+      ** corresponding to page pgnoRoot.  */
+      rc = saveAllCursors(pBt, 0, 0);
+      releasePage(pPageMove);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+
+      /* Move the page currently at pgnoRoot to pgnoMove. */
+      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
+      if( eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
+        rc = SQLITE_CORRUPT_BKPT;
+      }
+      if( rc!=SQLITE_OK ){
+        releasePage(pRoot);
+        return rc;
+      }
+      assert( eType!=PTRMAP_ROOTPAGE );
+      assert( eType!=PTRMAP_FREEPAGE );
+      rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove, 0);
+      releasePage(pRoot);
+
+      /* Obtain the page at pgnoRoot */
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      rc = sqlite3PagerWrite(pRoot->pDbPage);
+      if( rc!=SQLITE_OK ){
+        releasePage(pRoot);
+        return rc;
+      }
+    }else{
+      pRoot = pPageMove;
+    }
+
+    /* Update the pointer-map and meta-data with the new root-page number. */
+    ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0, &rc);
+    if( rc ){
+      releasePage(pRoot);
+      return rc;
+    }
+
+    /* When the new root page was allocated, page 1 was made writable in
+    ** order either to increase the database filesize, or to decrement the
+    ** freelist count.  Hence, the sqlite3BtreeUpdateMeta() call cannot fail.
+    */
+    assert( sqlite3PagerIswriteable(pBt->pPage1->pDbPage) );
+    rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
+    if( NEVER(rc) ){
+      releasePage(pRoot);
+      return rc;
+    }
+
+  }else{
+    rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
+    if( rc ) return rc;
+  }
+#endif
+  assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
+  if( createTabFlags & BTREE_INTKEY ){
+    ptfFlags = PTF_INTKEY | PTF_LEAFDATA | PTF_LEAF;
+  }else{
+    ptfFlags = PTF_ZERODATA | PTF_LEAF;
+  }
+  zeroPage(pRoot, ptfFlags);
+  sqlite3PagerUnref(pRoot->pDbPage);
+  assert( (pBt->openFlags & BTREE_SINGLE)==0 || pgnoRoot==2 );
+  *piTable = pgnoRoot;
+  return SQLITE_OK;
+}
+int sqlite3BtreeCreateTable(Btree *p, Pgno *piTable, int flags){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = btreeCreateTable(p, piTable, flags);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Erase the given database page and all its children.  Return
+** the page to the freelist.
+*/
+static int clearDatabasePage(
+  BtShared *pBt,           /* The BTree that contains the table */
+  Pgno pgno,               /* Page number to clear */
+  int freePageFlag,        /* Deallocate page if true */
+  i64 *pnChange            /* Add number of Cells freed to this counter */
+){
+  MemPage *pPage;
+  int rc;
+  unsigned char *pCell;
+  int i;
+  int hdr;
+  CellInfo info;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pgno>btreePagecount(pBt) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  rc = getAndInitPage(pBt, pgno, &pPage, 0);
+  if( rc ) return rc;
+  if( (pBt->openFlags & BTREE_SINGLE)==0
+   && sqlite3PagerPageRefcount(pPage->pDbPage) != (1 + (pgno==1))
+  ){
+    rc = SQLITE_CORRUPT_BKPT;
+    goto cleardatabasepage_out;
+  }
+  hdr = pPage->hdrOffset;
+  for(i=0; i<pPage->nCell; i++){
+    pCell = findCell(pPage, i);
+    if( !pPage->leaf ){
+      rc = clearDatabasePage(pBt, get4byte(pCell), 1, pnChange);
+      if( rc ) goto cleardatabasepage_out;
+    }
+    BTREE_CLEAR_CELL(rc, pPage, pCell, info);
+    if( rc ) goto cleardatabasepage_out;
+  }
+  if( !pPage->leaf ){
+    rc = clearDatabasePage(pBt, get4byte(&pPage->aData[hdr+8]), 1, pnChange);
+    if( rc ) goto cleardatabasepage_out;
+    if( pPage->intKey ) pnChange = 0;
+  }
+  if( pnChange ){
+    testcase( !pPage->intKey );
+    *pnChange += pPage->nCell;
+  }
+  if( freePageFlag ){
+    freePage(pPage, &rc);
+  }else if( (rc = sqlite3PagerWrite(pPage->pDbPage))==0 ){
+    zeroPage(pPage, pPage->aData[hdr] | PTF_LEAF);
+  }
+
+cleardatabasepage_out:
+  releasePage(pPage);
+  return rc;
+}
+
+/*
+** Delete all information from a single table in the database.  iTable is
+** the page number of the root of the table.  After this routine returns,
+** the root page is empty, but still exists.
+**
+** This routine will fail with SQLITE_LOCKED if there are any open
+** read cursors on the table.  Open write cursors are moved to the
+** root of the table.
+**
+** If pnChange is not NULL, then the integer value pointed to by pnChange
+** is incremented by the number of entries in the table.
+*/
+int sqlite3BtreeClearTable(Btree *p, int iTable, i64 *pnChange){
+  int rc;
+  BtShared *pBt = p->pBt;
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans==TRANS_WRITE );
+
+  rc = saveAllCursors(pBt, (Pgno)iTable, 0);
+
+  if( SQLITE_OK==rc ){
+    /* Invalidate all incrblob cursors open on table iTable (assuming iTable
+    ** is the root of a table b-tree - if it is not, the following call is
+    ** a no-op).  */
+    if( p->hasIncrblobCur ){
+      invalidateIncrblobCursors(p, (Pgno)iTable, 0, 1);
+    }
+    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Delete all information from the single table that pCur is open on.
+**
+** This routine only work for pCur on an ephemeral table.
+*/
+int sqlite3BtreeClearTableOfCursor(BtCursor *pCur){
+  return sqlite3BtreeClearTable(pCur->pBtree, pCur->pgnoRoot, 0);
+}
+
+/*
+** Erase all information in a table and add the root of the table to
+** the freelist.  Except, the root of the principle table (the one on
+** page 1) is never added to the freelist.
+**
+** This routine will fail with SQLITE_LOCKED if there are any open
+** cursors on the table.
+**
+** If AUTOVACUUM is enabled and the page at iTable is not the last
+** root page in the database file, then the last root page
+** in the database file is moved into the slot formerly occupied by
+** iTable and that last slot formerly occupied by the last root page
+** is added to the freelist instead of iTable.  In this say, all
+** root pages are kept at the beginning of the database file, which
+** is necessary for AUTOVACUUM to work right.  *piMoved is set to the
+** page number that used to be the last root page in the file before
+** the move.  If no page gets moved, *piMoved is set to 0.
+** The last root page is recorded in meta[3] and the value of
+** meta[3] is updated by this procedure.
+*/
+static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
+  int rc;
+  MemPage *pPage = 0;
+  BtShared *pBt = p->pBt;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( p->inTrans==TRANS_WRITE );
+  assert( iTable>=2 );
+  if( iTable>btreePagecount(pBt) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+
+  rc = sqlite3BtreeClearTable(p, iTable, 0);
+  if( rc ) return rc;
+  rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
+  if( NEVER(rc) ){
+    releasePage(pPage);
+    return rc;
+  }
+
+  *piMoved = 0;
+
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  freePage(pPage, &rc);
+  releasePage(pPage);
+#else
+  if( pBt->autoVacuum ){
+    Pgno maxRootPgno;
+    sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);
+
+    if( iTable==maxRootPgno ){
+      /* If the table being dropped is the table with the largest root-page
+      ** number in the database, put the root page on the free list.
+      */
+      freePage(pPage, &rc);
+      releasePage(pPage);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }else{
+      /* The table being dropped does not have the largest root-page
+      ** number in the database. So move the page that does into the
+      ** gap left by the deleted root-page.
+      */
+      MemPage *pMove;
+      releasePage(pPage);
+      rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable, 0);
+      releasePage(pMove);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      pMove = 0;
+      rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
+      freePage(pMove, &rc);
+      releasePage(pMove);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      *piMoved = maxRootPgno;
+    }
+
+    /* Set the new 'max-root-page' value in the database header. This
+    ** is the old value less one, less one more if that happens to
+    ** be a root-page number, less one again if that is the
+    ** PENDING_BYTE_PAGE.
+    */
+    maxRootPgno--;
+    while( maxRootPgno==PENDING_BYTE_PAGE(pBt)
+           || PTRMAP_ISPAGE(pBt, maxRootPgno) ){
+      maxRootPgno--;
+    }
+    assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );
+
+    rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
+  }else{
+    freePage(pPage, &rc);
+    releasePage(pPage);
+  }
+#endif
+  return rc; 
+}
+int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = btreeDropTable(p, iTable, piMoved);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+
+/*
+** This function may only be called if the b-tree connection already
+** has a read or write transaction open on the database.
+**
+** Read the meta-information out of a database file.  Meta[0]
+** is the number of free pages currently in the database.  Meta[1]
+** through meta[15] are available for use by higher layers.  Meta[0]
+** is read-only, the others are read/write.
+**
+** The schema layer numbers meta values differently.  At the schema
+** layer (and the SetCookie and ReadCookie opcodes) the number of
+** free pages is not visible.  So Cookie[0] is the same as Meta[1].
+**
+** This routine treats Meta[BTREE_DATA_VERSION] as a special case.  Instead
+** of reading the value out of the header, it instead loads the "DataVersion"
+** from the pager.  The BTREE_DATA_VERSION value is not actually stored in the
+** database file.  It is a number computed by the pager.  But its access
+** pattern is the same as header meta values, and so it is convenient to
+** read it from this routine.
+*/
+void sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
+  BtShared *pBt = p->pBt;
+
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans>TRANS_NONE );
+  assert( SQLITE_OK==querySharedCacheTableLock(p, SCHEMA_ROOT, READ_LOCK) );
+  assert( pBt->pPage1 );
+  assert( idx>=0 && idx<=15 );
+
+  if( idx==BTREE_DATA_VERSION ){
+    *pMeta = sqlite3PagerDataVersion(pBt->pPager) + p->iBDataVersion;
+  }else{
+    *pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);
+  }
+
+  /* If auto-vacuum is disabled in this build and this is an auto-vacuum
+  ** database, mark the database as read-only.  */
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ){
+    pBt->btsFlags |= BTS_READ_ONLY;
+  }
+#endif
+
+  sqlite3BtreeLeave(p);
+}
+
+/*
+** Write meta-information back into the database.  Meta[0] is
+** read-only and may not be written.
+*/
+int sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
+  BtShared *pBt = p->pBt;
+  unsigned char *pP1;
+  int rc;
+  assert( idx>=1 && idx<=15 );
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans==TRANS_WRITE );
+  assert( pBt->pPage1!=0 );
+  pP1 = pBt->pPage1->aData;
+  rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+  if( rc==SQLITE_OK ){
+    put4byte(&pP1[36 + idx*4], iMeta);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( idx==BTREE_INCR_VACUUM ){
+      assert( pBt->autoVacuum || iMeta==0 );
+      assert( iMeta==0 || iMeta==1 );
+      pBt->incrVacuum = (u8)iMeta;
+    }
+#endif
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** The first argument, pCur, is a cursor opened on some b-tree. Count the
+** number of entries in the b-tree and write the result to *pnEntry.
+**
+** SQLITE_OK is returned if the operation is successfully executed.
+** Otherwise, if an error is encountered (i.e. an IO error or database
+** corruption) an SQLite error code is returned.
+*/
+int sqlite3BtreeCount(sqlite3 *db, BtCursor *pCur, i64 *pnEntry){
+  i64 nEntry = 0;                      /* Value to return in *pnEntry */
+  int rc;                              /* Return code */
+
+  rc = moveToRoot(pCur);
+  if( rc==SQLITE_EMPTY ){
+    *pnEntry = 0;
+    return SQLITE_OK;
+  }
+
+  /* Unless an error occurs, the following loop runs one iteration for each
+  ** page in the B-Tree structure (not including overflow pages).
+  */
+  while( rc==SQLITE_OK && !AtomicLoad(&db->u1.isInterrupted) ){
+    int iIdx;                          /* Index of child node in parent */
+    MemPage *pPage;                    /* Current page of the b-tree */
+
+    /* If this is a leaf page or the tree is not an int-key tree, then
+    ** this page contains countable entries. Increment the entry counter
+    ** accordingly.
+    */
+    pPage = pCur->pPage;
+    if( pPage->leaf || !pPage->intKey ){
+      nEntry += pPage->nCell;
+    }
+
+    /* pPage is a leaf node. This loop navigates the cursor so that it
+    ** points to the first interior cell that it points to the parent of
+    ** the next page in the tree that has not yet been visited. The
+    ** pCur->aiIdx[pCur->iPage] value is set to the index of the parent cell
+    ** of the page, or to the number of cells in the page if the next page
+    ** to visit is the right-child of its parent.
+    **
+    ** If all pages in the tree have been visited, return SQLITE_OK to the
+    ** caller.
+    */
+    if( pPage->leaf ){
+      do {
+        if( pCur->iPage==0 ){
+          /* All pages of the b-tree have been visited. Return successfully. */
+          *pnEntry = nEntry;
+          return moveToRoot(pCur);
+        }
+        moveToParent(pCur);
+      }while ( pCur->ix>=pCur->pPage->nCell );
+
+      pCur->ix++;
+      pPage = pCur->pPage;
+    }
+
+    /* Descend to the child node of the cell that the cursor currently
+    ** points at. This is the right-child if (iIdx==pPage->nCell).
+    */
+    iIdx = pCur->ix;
+    if( iIdx==pPage->nCell ){
+      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
+    }else{
+      rc = moveToChild(pCur, get4byte(findCell(pPage, iIdx)));
+    }
+  }
+
+  /* An error has occurred. Return an error code. */
+  return rc;
+}
+
+/*
+** Return the pager associated with a BTree.  This routine is used for
+** testing and debugging only.
+*/
+Pager *sqlite3BtreePager(Btree *p){
+  return p->pBt->pPager;
+}
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/*
+** Record an OOM error during integrity_check
+*/
+static void checkOom(IntegrityCk *pCheck){
+  pCheck->rc = SQLITE_NOMEM;
+  pCheck->mxErr = 0;  /* Causes integrity_check processing to stop */
+  if( pCheck->nErr==0 ) pCheck->nErr++;
+}
+
+/*
+** Invoke the progress handler, if appropriate.  Also check for an
+** interrupt.
+*/
+static void checkProgress(IntegrityCk *pCheck){
+  sqlite3 *db = pCheck->db;
+  if( AtomicLoad(&db->u1.isInterrupted) ){
+    pCheck->rc = SQLITE_INTERRUPT;
+    pCheck->nErr++;
+    pCheck->mxErr = 0;
+  }
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  if( db->xProgress ){
+    assert( db->nProgressOps>0 );
+    pCheck->nStep++;
+    if( (pCheck->nStep % db->nProgressOps)==0
+     && db->xProgress(db->pProgressArg)
+    ){
+      pCheck->rc = SQLITE_INTERRUPT;
+      pCheck->nErr++;
+      pCheck->mxErr = 0;
+    }
+  }
+#endif
+}
+
+/*
+** Append a message to the error message string.
+*/
+static void checkAppendMsg(
+  IntegrityCk *pCheck,
+  const char *zFormat,
+  ...
+){
+  va_list ap;
+  checkProgress(pCheck);
+  if( !pCheck->mxErr ) return;
+  pCheck->mxErr--;
+  pCheck->nErr++;
+  va_start(ap, zFormat);
+  if( pCheck->errMsg.nChar ){
+    sqlite3_str_append(&pCheck->errMsg, "\n", 1);
+  }
+  if( pCheck->zPfx ){
+    sqlite3_str_appendf(&pCheck->errMsg, pCheck->zPfx,
+                        pCheck->v0, pCheck->v1, pCheck->v2);
+  }
+  sqlite3_str_vappendf(&pCheck->errMsg, zFormat, ap);
+  va_end(ap);
+  if( pCheck->errMsg.accError==SQLITE_NOMEM ){
+    checkOom(pCheck);
+  }
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+
+/*
+** Return non-zero if the bit in the IntegrityCk.aPgRef[] array that
+** corresponds to page iPg is already set.
+*/
+static int getPageReferenced(IntegrityCk *pCheck, Pgno iPg){
+  assert( pCheck->aPgRef!=0 );
+  assert( iPg<=pCheck->nCkPage && sizeof(pCheck->aPgRef[0])==1 );
+  return (pCheck->aPgRef[iPg/8] & (1 << (iPg & 0x07)));
+}
+
+/*
+** Set the bit in the IntegrityCk.aPgRef[] array that corresponds to page iPg.
+*/
+static void setPageReferenced(IntegrityCk *pCheck, Pgno iPg){
+  assert( pCheck->aPgRef!=0 );
+  assert( iPg<=pCheck->nCkPage && sizeof(pCheck->aPgRef[0])==1 );
+  pCheck->aPgRef[iPg/8] |= (1 << (iPg & 0x07));
+}
+
+
+/*
+** Add 1 to the reference count for page iPage.  If this is the second
+** reference to the page, add an error message to pCheck->zErrMsg.
+** Return 1 if there are 2 or more references to the page and 0 if
+** if this is the first reference to the page.
+**
+** Also check that the page number is in bounds.
+*/
+static int checkRef(IntegrityCk *pCheck, Pgno iPage){
+  if( iPage>pCheck->nCkPage || iPage==0 ){
+    checkAppendMsg(pCheck, "invalid page number %u", iPage);
+    return 1;
+  }
+  if( getPageReferenced(pCheck, iPage) ){
+    checkAppendMsg(pCheck, "2nd reference to page %u", iPage);
+    return 1;
+  }
+  setPageReferenced(pCheck, iPage);
+  return 0;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Check that the entry in the pointer-map for page iChild maps to
+** page iParent, pointer type ptrType. If not, append an error message
+** to pCheck.
+*/
+static void checkPtrmap(
+  IntegrityCk *pCheck,   /* Integrity check context */
+  Pgno iChild,           /* Child page number */
+  u8 eType,              /* Expected pointer map type */
+  Pgno iParent           /* Expected pointer map parent page number */
+){
+  int rc;
+  u8 ePtrmapType;
+  Pgno iPtrmapParent;
+
+  rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) checkOom(pCheck);
+    checkAppendMsg(pCheck, "Failed to read ptrmap key=%u", iChild);
+    return;
+  }
+
+  if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
+    checkAppendMsg(pCheck,
+      "Bad ptr map entry key=%u expected=(%u,%u) got=(%u,%u)",
+      iChild, eType, iParent, ePtrmapType, iPtrmapParent);
+  }
+}
+#endif
+
+/*
+** Check the integrity of the freelist or of an overflow page list.
+** Verify that the number of pages on the list is N.
+*/
+static void checkList(
+  IntegrityCk *pCheck,  /* Integrity checking context */
+  int isFreeList,       /* True for a freelist.  False for overflow page list */
+  Pgno iPage,           /* Page number for first page in the list */
+  u32 N                 /* Expected number of pages in the list */
+){
+  int i;
+  u32 expected = N;
+  int nErrAtStart = pCheck->nErr;
+  while( iPage!=0 && pCheck->mxErr ){
+    DbPage *pOvflPage;
+    unsigned char *pOvflData;
+    if( checkRef(pCheck, iPage) ) break;
+    N--;
+    if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage, 0) ){
+      checkAppendMsg(pCheck, "failed to get page %u", iPage);
+      break;
+    }
+    pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
+    if( isFreeList ){
+      u32 n = (u32)get4byte(&pOvflData[4]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pCheck->pBt->autoVacuum ){
+        checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0);
+      }
+#endif
+      if( n>pCheck->pBt->usableSize/4-2 ){
+        checkAppendMsg(pCheck,
+           "freelist leaf count too big on page %u", iPage);
+        N--;
+      }else{
+        for(i=0; i<(int)n; i++){
+          Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+          if( pCheck->pBt->autoVacuum ){
+            checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0);
+          }
+#endif
+          checkRef(pCheck, iFreePage);
+        }
+        N -= n;
+      }
+    }
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    else{
+      /* If this database supports auto-vacuum and iPage is not the last
+      ** page in this overflow list, check that the pointer-map entry for
+      ** the following page matches iPage.
+      */
+      if( pCheck->pBt->autoVacuum && N>0 ){
+        i = get4byte(pOvflData);
+        checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage);
+      }
+    }
+#endif
+    iPage = get4byte(pOvflData);
+    sqlite3PagerUnref(pOvflPage);
+  }
+  if( N && nErrAtStart==pCheck->nErr ){
+    checkAppendMsg(pCheck,
+      "%s is %u but should be %u",
+      isFreeList ? "size" : "overflow list length",
+      expected-N, expected);
+  }
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+/*
+** An implementation of a min-heap.
+**
+** aHeap[0] is the number of elements on the heap.  aHeap[1] is the
+** root element.  The daughter nodes of aHeap[N] are aHeap[N*2]
+** and aHeap[N*2+1].
+**
+** The heap property is this:  Every node is less than or equal to both
+** of its daughter nodes.  A consequence of the heap property is that the
+** root node aHeap[1] is always the minimum value currently in the heap.
+**
+** The btreeHeapInsert() routine inserts an unsigned 32-bit number onto
+** the heap, preserving the heap property.  The btreeHeapPull() routine
+** removes the root element from the heap (the minimum value in the heap)
+** and then moves other nodes around as necessary to preserve the heap
+** property.
+**
+** This heap is used for cell overlap and coverage testing.  Each u32
+** entry represents the span of a cell or freeblock on a btree page. 
+** The upper 16 bits are the index of the first byte of a range and the
+** lower 16 bits are the index of the last byte of that range.
+*/
+static void btreeHeapInsert(u32 *aHeap, u32 x){
+  u32 j, i;
+  assert( aHeap!=0 );
+  i = ++aHeap[0];
+  aHeap[i] = x;
+  while( (j = i/2)>0 && aHeap[j]>aHeap[i] ){
+    x = aHeap[j];
+    aHeap[j] = aHeap[i];
+    aHeap[i] = x;
+    i = j;
+  }
+}
+static int btreeHeapPull(u32 *aHeap, u32 *pOut){
+  u32 j, i, x;
+  if( (x = aHeap[0])==0 ) return 0;
+  *pOut = aHeap[1];
+  aHeap[1] = aHeap[x];
+  aHeap[x] = 0xffffffff;
+  aHeap[0]--;
+  i = 1;
+  while( (j = i*2)<=aHeap[0] ){
+    if( aHeap[j]>aHeap[j+1] ) j++;
+    if( aHeap[i]<aHeap[j] ) break;
+    x = aHeap[i];
+    aHeap[i] = aHeap[j];
+    aHeap[j] = x;
+    i = j;
+  }
+  return 1; 
+}
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/*
+** Do various sanity checks on a single page of a tree.  Return
+** the tree depth.  Root pages return 0.  Parents of root pages
+** return 1, and so forth.
+**
+** These checks are done:
+**
+**      1.  Make sure that cells and freeblocks do not overlap
+**          but combine to completely cover the page.
+**      2.  Make sure integer cell keys are in order.
+**      3.  Check the integrity of overflow pages.
+**      4.  Recursively call checkTreePage on all children.
+**      5.  Verify that the depth of all children is the same.
+*/
+static int checkTreePage(
+  IntegrityCk *pCheck,  /* Context for the sanity check */
+  Pgno iPage,           /* Page number of the page to check */
+  i64 *piMinKey,        /* Write minimum integer primary key here */
+  i64 maxKey            /* Error if integer primary key greater than this */
+){
+  MemPage *pPage = 0;      /* The page being analyzed */
+  int i;                   /* Loop counter */
+  int rc;                  /* Result code from subroutine call */
+  int depth = -1, d2;      /* Depth of a subtree */
+  int pgno;                /* Page number */
+  int nFrag;               /* Number of fragmented bytes on the page */
+  int hdr;                 /* Offset to the page header */
+  int cellStart;           /* Offset to the start of the cell pointer array */
+  int nCell;               /* Number of cells */
+  int doCoverageCheck = 1; /* True if cell coverage checking should be done */
+  int keyCanBeEqual = 1;   /* True if IPK can be equal to maxKey
+                           ** False if IPK must be strictly less than maxKey */
+  u8 *data;                /* Page content */
+  u8 *pCell;               /* Cell content */
+  u8 *pCellIdx;            /* Next element of the cell pointer array */
+  BtShared *pBt;           /* The BtShared object that owns pPage */
+  u32 pc;                  /* Address of a cell */
+  u32 usableSize;          /* Usable size of the page */
+  u32 contentOffset;       /* Offset to the start of the cell content area */
+  u32 *heap = 0;           /* Min-heap used for checking cell coverage */
+  u32 x, prev = 0;         /* Next and previous entry on the min-heap */
+  const char *saved_zPfx = pCheck->zPfx;
+  int saved_v1 = pCheck->v1;
+  int saved_v2 = pCheck->v2;
+  u8 savedIsInit = 0;
+
+  /* Check that the page exists
+  */
+  checkProgress(pCheck);
+  if( pCheck->mxErr==0 ) goto end_of_check;
+  pBt = pCheck->pBt;
+  usableSize = pBt->usableSize;
+  if( iPage==0 ) return 0;
+  if( checkRef(pCheck, iPage) ) return 0;
+  pCheck->zPfx = "Tree %u page %u: ";
+  pCheck->v1 = iPage;
+  if( (rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0 ){
+    checkAppendMsg(pCheck,
+       "unable to get the page. error code=%d", rc);
+    if( rc==SQLITE_IOERR_NOMEM ) pCheck->rc = SQLITE_NOMEM;
+    goto end_of_check;
+  }
+
+  /* Clear MemPage.isInit to make sure the corruption detection code in
+  ** btreeInitPage() is executed.  */
+  savedIsInit = pPage->isInit;
+  pPage->isInit = 0;
+  if( (rc = btreeInitPage(pPage))!=0 ){
+    assert( rc==SQLITE_CORRUPT );  /* The only possible error from InitPage */
+    checkAppendMsg(pCheck,
+                   "btreeInitPage() returns error code %d", rc);
+    goto end_of_check;
+  }
+  if( (rc = btreeComputeFreeSpace(pPage))!=0 ){
+    assert( rc==SQLITE_CORRUPT );
+    checkAppendMsg(pCheck, "free space corruption", rc);
+    goto end_of_check;
+  }
+  data = pPage->aData;
+  hdr = pPage->hdrOffset;
+
+  /* Set up for cell analysis */
+  pCheck->zPfx = "Tree %u page %u cell %u: ";
+  contentOffset = get2byteNotZero(&data[hdr+5]);
+  assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
+
+  /* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
+  ** number of cells on the page. */
+  nCell = get2byte(&data[hdr+3]);
+  assert( pPage->nCell==nCell );
+
+  /* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
+  ** immediately follows the b-tree page header. */
+  cellStart = hdr + 12 - 4*pPage->leaf;
+  assert( pPage->aCellIdx==&data[cellStart] );
+  pCellIdx = &data[cellStart + 2*(nCell-1)];
+
+  if( !pPage->leaf ){
+    /* Analyze the right-child page of internal pages */
+    pgno = get4byte(&data[hdr+8]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum ){
+      pCheck->zPfx = "Tree %u page %u right child: ";
+      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
+    }
+#endif
+    depth = checkTreePage(pCheck, pgno, &maxKey, maxKey);
+    keyCanBeEqual = 0;
+  }else{
+    /* For leaf pages, the coverage check will occur in the same loop
+    ** as the other cell checks, so initialize the heap.  */
+    heap = pCheck->heap;
+    heap[0] = 0;
+  }
+
+  /* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
+  ** integer offsets to the cell contents. */
+  for(i=nCell-1; i>=0 && pCheck->mxErr; i--){
+    CellInfo info;
+
+    /* Check cell size */
+    pCheck->v2 = i;
+    assert( pCellIdx==&data[cellStart + i*2] );
+    pc = get2byteAligned(pCellIdx);
+    pCellIdx -= 2;
+    if( pc<contentOffset || pc>usableSize-4 ){
+      checkAppendMsg(pCheck, "Offset %u out of range %u..%u",
+                             pc, contentOffset, usableSize-4);
+      doCoverageCheck = 0;
+      continue;
+    }
+    pCell = &data[pc];
+    pPage->xParseCell(pPage, pCell, &info);
+    if( pc+info.nSize>usableSize ){
+      checkAppendMsg(pCheck, "Extends off end of page");
+      doCoverageCheck = 0;
+      continue;
+    }
+
+    /* Check for integer primary key out of range */
+    if( pPage->intKey ){
+      if( keyCanBeEqual ? (info.nKey > maxKey) : (info.nKey >= maxKey) ){
+        checkAppendMsg(pCheck, "Rowid %lld out of order", info.nKey);
+      }
+      maxKey = info.nKey;
+      keyCanBeEqual = 0;     /* Only the first key on the page may ==maxKey */
+    }
+
+    /* Check the content overflow list */
+    if( info.nPayload>info.nLocal ){
+      u32 nPage;       /* Number of pages on the overflow chain */
+      Pgno pgnoOvfl;   /* First page of the overflow chain */
+      assert( pc + info.nSize - 4 <= usableSize );
+      nPage = (info.nPayload - info.nLocal + usableSize - 5)/(usableSize - 4);
+      pgnoOvfl = get4byte(&pCell[info.nSize - 4]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pBt->autoVacuum ){
+        checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage);
+      }
+#endif
+      checkList(pCheck, 0, pgnoOvfl, nPage);
+    }
+
+    if( !pPage->leaf ){
+      /* Check sanity of left child page for internal pages */
+      pgno = get4byte(pCell);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pBt->autoVacuum ){
+        checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
+      }
+#endif
+      d2 = checkTreePage(pCheck, pgno, &maxKey, maxKey);
+      keyCanBeEqual = 0;
+      if( d2!=depth ){
+        checkAppendMsg(pCheck, "Child page depth differs");
+        depth = d2;
+      }
+    }else{
+      /* Populate the coverage-checking heap for leaf pages */
+      btreeHeapInsert(heap, (pc<<16)|(pc+info.nSize-1));
+    }
+  }
+  *piMinKey = maxKey;
+
+  /* Check for complete coverage of the page
+  */
+  pCheck->zPfx = 0;
+  if( doCoverageCheck && pCheck->mxErr>0 ){
+    /* For leaf pages, the min-heap has already been initialized and the
+    ** cells have already been inserted.  But for internal pages, that has
+    ** not yet been done, so do it now */
+    if( !pPage->leaf ){
+      heap = pCheck->heap;
+      heap[0] = 0;
+      for(i=nCell-1; i>=0; i--){
+        u32 size;
+        pc = get2byteAligned(&data[cellStart+i*2]);
+        size = pPage->xCellSize(pPage, &data[pc]);
+        btreeHeapInsert(heap, (pc<<16)|(pc+size-1));
+      }
+    }
+    /* Add the freeblocks to the min-heap
+    **
+    ** EVIDENCE-OF: R-20690-50594 The second field of the b-tree page header
+    ** is the offset of the first freeblock, or zero if there are no
+    ** freeblocks on the page.
+    */
+    i = get2byte(&data[hdr+1]);
+    while( i>0 ){
+      int size, j;
+      assert( (u32)i<=usableSize-4 ); /* Enforced by btreeComputeFreeSpace() */
+      size = get2byte(&data[i+2]);
+      assert( (u32)(i+size)<=usableSize ); /* due to btreeComputeFreeSpace() */
+      btreeHeapInsert(heap, (((u32)i)<<16)|(i+size-1));
+      /* EVIDENCE-OF: R-58208-19414 The first 2 bytes of a freeblock are a
+      ** big-endian integer which is the offset in the b-tree page of the next
+      ** freeblock in the chain, or zero if the freeblock is the last on the
+      ** chain. */
+      j = get2byte(&data[i]);
+      /* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
+      ** increasing offset. */
+      assert( j==0 || j>i+size );     /* Enforced by btreeComputeFreeSpace() */
+      assert( (u32)j<=usableSize-4 ); /* Enforced by btreeComputeFreeSpace() */
+      i = j;
+    }
+    /* Analyze the min-heap looking for overlap between cells and/or
+    ** freeblocks, and counting the number of untracked bytes in nFrag.
+    **
+    ** Each min-heap entry is of the form:    (start_address<<16)|end_address.
+    ** There is an implied first entry the covers the page header, the cell
+    ** pointer index, and the gap between the cell pointer index and the start
+    ** of cell content. 
+    **
+    ** The loop below pulls entries from the min-heap in order and compares
+    ** the start_address against the previous end_address.  If there is an
+    ** overlap, that means bytes are used multiple times.  If there is a gap,
+    ** that gap is added to the fragmentation count.
+    */
+    nFrag = 0;
+    prev = contentOffset - 1;   /* Implied first min-heap entry */
+    while( btreeHeapPull(heap,&x) ){
+      if( (prev&0xffff)>=(x>>16) ){
+        checkAppendMsg(pCheck,
+          "Multiple uses for byte %u of page %u", x>>16, iPage);
+        break;
+      }else{
+        nFrag += (x>>16) - (prev&0xffff) - 1;
+        prev = x;
+      }
+    }
+    nFrag += usableSize - (prev&0xffff) - 1;
+    /* EVIDENCE-OF: R-43263-13491 The total number of bytes in all fragments
+    ** is stored in the fifth field of the b-tree page header.
+    ** EVIDENCE-OF: R-07161-27322 The one-byte integer at offset 7 gives the
+    ** number of fragmented free bytes within the cell content area.
+    */
+    if( heap[0]==0 && nFrag!=data[hdr+7] ){
+      checkAppendMsg(pCheck,
+          "Fragmentation of %u bytes reported as %u on page %u",
+          nFrag, data[hdr+7], iPage);
+    }
+  }
+
+end_of_check:
+  if( !doCoverageCheck ) pPage->isInit = savedIsInit;
+  releasePage(pPage);
+  pCheck->zPfx = saved_zPfx;
+  pCheck->v1 = saved_v1;
+  pCheck->v2 = saved_v2;
+  return depth+1;
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/*
+** This routine does a complete check of the given BTree file.  aRoot[] is
+** an array of pages numbers were each page number is the root page of
+** a table.  nRoot is the number of entries in aRoot.
+**
+** A read-only or read-write transaction must be opened before calling
+** this function.
+**
+** Write the number of error seen in *pnErr.  Except for some memory
+** allocation errors,  an error message held in memory obtained from
+** malloc is returned if *pnErr is non-zero.  If *pnErr==0 then NULL is
+** returned.  If a memory allocation error occurs, NULL is returned.
+**
+** If the first entry in aRoot[] is 0, that indicates that the list of
+** root pages is incomplete.  This is a "partial integrity-check".  This
+** happens when performing an integrity check on a single table.  The
+** zero is skipped, of course.  But in addition, the freelist checks
+** and the checks to make sure every page is referenced are also skipped,
+** since obviously it is not possible to know which pages are covered by
+** the unverified btrees.  Except, if aRoot[1] is 1, then the freelist
+** checks are still performed.
+*/
+int sqlite3BtreeIntegrityCheck(
+  sqlite3 *db,  /* Database connection that is running the check */
+  Btree *p,     /* The btree to be checked */
+  Pgno *aRoot,  /* An array of root pages numbers for individual trees */
+  int nRoot,    /* Number of entries in aRoot[] */
+  int mxErr,    /* Stop reporting errors after this many */
+  int *pnErr,   /* OUT: Write number of errors seen to this variable */
+  char **pzOut  /* OUT: Write the error message string here */
+){
+  Pgno i;
+  IntegrityCk sCheck;
+  BtShared *pBt = p->pBt;
+  u64 savedDbFlags = pBt->db->flags;
+  char zErr[100];
+  int bPartial = 0;            /* True if not checking all btrees */
+  int bCkFreelist = 1;         /* True to scan the freelist */
+  VVA_ONLY( int nRef );
+  assert( nRoot>0 );
+
+  /* aRoot[0]==0 means this is a partial check */
+  if( aRoot[0]==0 ){
+    assert( nRoot>1 );
+    bPartial = 1;
+    if( aRoot[1]!=1 ) bCkFreelist = 0;
+  }
+
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans>TRANS_NONE && pBt->inTransaction>TRANS_NONE );
+  VVA_ONLY( nRef = sqlite3PagerRefcount(pBt->pPager) );
+  assert( nRef>=0 );
+  memset(&sCheck, 0, sizeof(sCheck));
+  sCheck.db = db;
+  sCheck.pBt = pBt;
+  sCheck.pPager = pBt->pPager;
+  sCheck.nCkPage = btreePagecount(sCheck.pBt);
+  sCheck.mxErr = mxErr;
+  sqlite3StrAccumInit(&sCheck.errMsg, 0, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
+  sCheck.errMsg.printfFlags = SQLITE_PRINTF_INTERNAL;
+  if( sCheck.nCkPage==0 ){
+    goto integrity_ck_cleanup;
+  }
+
+  sCheck.aPgRef = sqlite3MallocZero((sCheck.nCkPage / 8)+ 1);
+  if( !sCheck.aPgRef ){
+    checkOom(&sCheck);
+    goto integrity_ck_cleanup;
+  }
+  sCheck.heap = (u32*)sqlite3PageMalloc( pBt->pageSize );
+  if( sCheck.heap==0 ){
+    checkOom(&sCheck);
+    goto integrity_ck_cleanup;
+  }
+
+  i = PENDING_BYTE_PAGE(pBt);
+  if( i<=sCheck.nCkPage ) setPageReferenced(&sCheck, i);
+
+  /* Check the integrity of the freelist
+  */
+  if( bCkFreelist ){
+    sCheck.zPfx = "Freelist: ";
+    checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
+              get4byte(&pBt->pPage1->aData[36]));
+    sCheck.zPfx = 0;
+  }
+
+  /* Check all the tables.
+  */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  if( !bPartial ){
+    if( pBt->autoVacuum ){
+      Pgno mx = 0;
+      Pgno mxInHdr;
+      for(i=0; (int)i<nRoot; i++) if( mx<aRoot[i] ) mx = aRoot[i];
+      mxInHdr = get4byte(&pBt->pPage1->aData[52]);
+      if( mx!=mxInHdr ){
+        checkAppendMsg(&sCheck,
+          "max rootpage (%u) disagrees with header (%u)",
+          mx, mxInHdr
+        );
+      }
+    }else if( get4byte(&pBt->pPage1->aData[64])!=0 ){
+      checkAppendMsg(&sCheck,
+        "incremental_vacuum enabled with a max rootpage of zero"
+      );
+    }
+  }
+#endif
+  testcase( pBt->db->flags & SQLITE_CellSizeCk );
+  pBt->db->flags &= ~(u64)SQLITE_CellSizeCk;
+  for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
+    i64 notUsed;
+    if( aRoot[i]==0 ) continue;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum && aRoot[i]>1 && !bPartial ){
+      checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0);
+    }
+#endif
+    sCheck.v0 = aRoot[i];
+    checkTreePage(&sCheck, aRoot[i], &notUsed, LARGEST_INT64);
+  }
+  pBt->db->flags = savedDbFlags;
+
+  /* Make sure every page in the file is referenced
+  */
+  if( !bPartial ){
+    for(i=1; i<=sCheck.nCkPage && sCheck.mxErr; i++){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+      if( getPageReferenced(&sCheck, i)==0 ){
+        checkAppendMsg(&sCheck, "Page %u: never used", i);
+      }
+#else
+      /* If the database supports auto-vacuum, make sure no tables contain
+      ** references to pointer-map pages.
+      */
+      if( getPageReferenced(&sCheck, i)==0 &&
+         (PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
+        checkAppendMsg(&sCheck, "Page %u: never used", i);
+      }
+      if( getPageReferenced(&sCheck, i)!=0 &&
+         (PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
+        checkAppendMsg(&sCheck, "Page %u: pointer map referenced", i);
+      }
+#endif
+    }
+  }
+
+  /* Clean  up and report errors.
+  */
+integrity_ck_cleanup:
+  sqlite3PageFree(sCheck.heap);
+  sqlite3_free(sCheck.aPgRef);
+  *pnErr = sCheck.nErr;
+  if( sCheck.nErr==0 ){
+    sqlite3_str_reset(&sCheck.errMsg);
+    *pzOut = 0;
+  }else{
+    *pzOut = sqlite3StrAccumFinish(&sCheck.errMsg);
+  }
+  /* Make sure this analysis did not leave any unref() pages. */
+  assert( nRef==sqlite3PagerRefcount(pBt->pPager) );
+  sqlite3BtreeLeave(p);
+  return sCheck.rc;
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+/*
+** Return the full pathname of the underlying database file.  Return
+** an empty string if the database is in-memory or a TEMP database.
+**
+** The pager filename is invariant as long as the pager is
+** open so it is safe to access without the BtShared mutex.
+*/
+const char *sqlite3BtreeGetFilename(Btree *p){
+  assert( p->pBt->pPager!=0 );
+  return sqlite3PagerFilename(p->pBt->pPager, 1);
+}
+
+/*
+** Return the pathname of the journal file for this database. The return
+** value of this routine is the same regardless of whether the journal file
+** has been created or not.
+**
+** The pager journal filename is invariant as long as the pager is
+** open so it is safe to access without the BtShared mutex.
+*/
+const char *sqlite3BtreeGetJournalname(Btree *p){
+  assert( p->pBt->pPager!=0 );
+  return sqlite3PagerJournalname(p->pBt->pPager);
+}
+
+/*
+** Return one of SQLITE_TXN_NONE, SQLITE_TXN_READ, or SQLITE_TXN_WRITE
+** to describe the current transaction state of Btree p.
+*/
+int sqlite3BtreeTxnState(Btree *p){
+  assert( p==0 || sqlite3_mutex_held(p->db->mutex) );
+  return p ? p->inTrans : 0;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Run a checkpoint on the Btree passed as the first argument.
+**
+** Return SQLITE_LOCKED if this or any other connection has an open
+** transaction on the shared-cache the argument Btree is connected to.
+**
+** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
+*/
+int sqlite3BtreeCheckpoint(Btree *p, int eMode, int *pnLog, int *pnCkpt){
+  int rc = SQLITE_OK;
+  if( p ){
+    BtShared *pBt = p->pBt;
+    sqlite3BtreeEnter(p);
+    if( pBt->inTransaction!=TRANS_NONE ){
+      rc = SQLITE_LOCKED;
+    }else{
+      rc = sqlite3PagerCheckpoint(pBt->pPager, p->db, eMode, pnLog, pnCkpt);
+    }
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+#endif
+
+/*
+** Return true if there is currently a backup running on Btree p.
+*/
+int sqlite3BtreeIsInBackup(Btree *p){
+  assert( p );
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  return p->nBackup!=0;
+}
+
+/*
+** This function returns a pointer to a blob of memory associated with
+** a single shared-btree. The memory is used by client code for its own
+** purposes (for example, to store a high-level schema associated with
+** the shared-btree). The btree layer manages reference counting issues.
+**
+** The first time this is called on a shared-btree, nBytes bytes of memory
+** are allocated, zeroed, and returned to the caller. For each subsequent
+** call the nBytes parameter is ignored and a pointer to the same blob
+** of memory returned.
+**
+** If the nBytes parameter is 0 and the blob of memory has not yet been
+** allocated, a null pointer is returned. If the blob has already been
+** allocated, it is returned as normal.
+**
+** Just before the shared-btree is closed, the function passed as the
+** xFree argument when the memory allocation was made is invoked on the
+** blob of allocated memory. The xFree function should not call sqlite3_free()
+** on the memory, the btree layer does that.
+*/
+void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
+  BtShared *pBt = p->pBt;
+  sqlite3BtreeEnter(p);
+  if( !pBt->pSchema && nBytes ){
+    pBt->pSchema = sqlite3DbMallocZero(0, nBytes);
+    pBt->xFreeSchema = xFree;
+  }
+  sqlite3BtreeLeave(p);
+  return pBt->pSchema;
+}
+
+/*
+** Return SQLITE_LOCKED_SHAREDCACHE if another user of the same shared
+** btree as the argument handle holds an exclusive lock on the
+** sqlite_schema table. Otherwise SQLITE_OK.
+*/
+int sqlite3BtreeSchemaLocked(Btree *p){
+  int rc;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  rc = querySharedCacheTableLock(p, SCHEMA_ROOT, READ_LOCK);
+  assert( rc==SQLITE_OK || rc==SQLITE_LOCKED_SHAREDCACHE );
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Obtain a lock on the table whose root page is iTab.  The
+** lock is a write lock if isWritelock is true or a read lock
+** if it is false.
+*/
+int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
+  int rc = SQLITE_OK;
+  assert( p->inTrans!=TRANS_NONE );
+  if( p->sharable ){
+    u8 lockType = READ_LOCK + isWriteLock;
+    assert( READ_LOCK+1==WRITE_LOCK );
+    assert( isWriteLock==0 || isWriteLock==1 );
+
+    sqlite3BtreeEnter(p);
+    rc = querySharedCacheTableLock(p, iTab, lockType);
+    if( rc==SQLITE_OK ){
+      rc = setSharedCacheTableLock(p, iTab, lockType);
+    }
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+#endif
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Argument pCsr must be a cursor opened for writing on an
+** INTKEY table currently pointing at a valid table entry.
+** This function modifies the data stored as part of that entry.
+**
+** Only the data content may only be modified, it is not possible to
+** change the length of the data stored. If this function is called with
+** parameters that attempt to write past the end of the existing data,
+** no modifications are made and SQLITE_CORRUPT is returned.
+*/
+int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
+  int rc;
+  assert( cursorOwnsBtShared(pCsr) );
+  assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
+  assert( pCsr->curFlags & BTCF_Incrblob );
+
+  rc = restoreCursorPosition(pCsr);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  assert( pCsr->eState!=CURSOR_REQUIRESEEK );
+  if( pCsr->eState!=CURSOR_VALID ){
+    return SQLITE_ABORT;
+  }
+
+  /* Save the positions of all other cursors open on this table. This is
+  ** required in case any of them are holding references to an xFetch
+  ** version of the b-tree page modified by the accessPayload call below.
+  **
+  ** Note that pCsr must be open on a INTKEY table and saveCursorPosition()
+  ** and hence saveAllCursors() cannot fail on a BTREE_INTKEY table, hence
+  ** saveAllCursors can only return SQLITE_OK.
+  */
+  VVA_ONLY(rc =) saveAllCursors(pCsr->pBt, pCsr->pgnoRoot, pCsr);
+  assert( rc==SQLITE_OK );
+
+  /* Check some assumptions:
+  **   (a) the cursor is open for writing,
+  **   (b) there is a read/write transaction open,
+  **   (c) the connection holds a write-lock on the table (if required),
+  **   (d) there are no conflicting read-locks, and
+  **   (e) the cursor points at a valid row of an intKey table.
+  */
+  if( (pCsr->curFlags & BTCF_WriteFlag)==0 ){
+    return SQLITE_READONLY;
+  }
+  assert( (pCsr->pBt->btsFlags & BTS_READ_ONLY)==0
+              && pCsr->pBt->inTransaction==TRANS_WRITE );
+  assert( hasSharedCacheTableLock(pCsr->pBtree, pCsr->pgnoRoot, 0, 2) );
+  assert( !hasReadConflicts(pCsr->pBtree, pCsr->pgnoRoot) );
+  assert( pCsr->pPage->intKey );
+
+  return accessPayload(pCsr, offset, amt, (unsigned char *)z, 1);
+}
+
+/*
+** Mark this cursor as an incremental blob cursor.
+*/
+void sqlite3BtreeIncrblobCursor(BtCursor *pCur){
+  pCur->curFlags |= BTCF_Incrblob;
+  pCur->pBtree->hasIncrblobCur = 1;
+}
+#endif
+
+/*
+** Set both the "read version" (single byte at byte offset 18) and
+** "write version" (single byte at byte offset 19) fields in the database
+** header to iVersion.
+*/
+int sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
+  BtShared *pBt = pBtree->pBt;
+  int rc;                         /* Return code */
+
+  assert( iVersion==1 || iVersion==2 );
+
+  /* If setting the version fields to 1, do not automatically open the
+  ** WAL connection, even if the version fields are currently set to 2.
+  */
+  pBt->btsFlags &= ~BTS_NO_WAL;
+  if( iVersion==1 ) pBt->btsFlags |= BTS_NO_WAL;
+
+  rc = sqlite3BtreeBeginTrans(pBtree, 0, 0);
+  if( rc==SQLITE_OK ){
+    u8 *aData = pBt->pPage1->aData;
+    if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
+      rc = sqlite3BtreeBeginTrans(pBtree, 2, 0);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+        if( rc==SQLITE_OK ){
+          aData[18] = (u8)iVersion;
+          aData[19] = (u8)iVersion;
+        }
+      }
+    }
+  }
+
+  pBt->btsFlags &= ~BTS_NO_WAL;
+  return rc;
+}
+
+/*
+** Return true if the cursor has a hint specified.  This routine is
+** only used from within assert() statements
+*/
+int sqlite3BtreeCursorHasHint(BtCursor *pCsr, unsigned int mask){
+  return (pCsr->hints & mask)!=0;
+}
+
+/*
+** Return true if the given Btree is read-only.
+*/
+int sqlite3BtreeIsReadonly(Btree *p){
+  return (p->pBt->btsFlags & BTS_READ_ONLY)!=0;
+}
+
+/*
+** Return the size of the header added to each page by this module.
+*/
+int sqlite3HeaderSizeBtree(void){ return ROUND8(sizeof(MemPage)); }
+
+/*
+** If no transaction is active and the database is not a temp-db, clear
+** the in-memory pager cache.
+*/
+void sqlite3BtreeClearCache(Btree *p){
+  BtShared *pBt = p->pBt;
+  if( pBt->inTransaction==TRANS_NONE ){
+    sqlite3PagerClearCache(pBt->pPager);
+  }
+}
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE)
+/*
+** Return true if the Btree passed as the only argument is sharable.
+*/
+int sqlite3BtreeSharable(Btree *p){
+  return p->sharable;
+}
+
+/*
+** Return the number of connections to the BtShared object accessed by
+** the Btree handle passed as the only argument. For private caches
+** this is always 1. For shared caches it may be 1 or greater.
+*/
+int sqlite3BtreeConnectionCount(Btree *p){
+  testcase( p->sharable );
+  return p->pBt->nRef;
+}
+#endif
diff --git a/src/btree.h b/src/btree.h
new file mode 100644
index 0000000..b45ace7
--- /dev/null
+++ b/src/btree.h
@@ -0,0 +1,420 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the sqlite B-Tree file
+** subsystem.  See comments in the source code for a detailed description
+** of what each interface routine does.
+*/
+#ifndef SQLITE_BTREE_H
+#define SQLITE_BTREE_H
+
+/* TODO: This definition is just included so other modules compile. It
+** needs to be revisited.
+*/
+#define SQLITE_N_BTREE_META 16
+
+/*
+** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
+** it must be turned on for each database using "PRAGMA auto_vacuum = 1".
+*/
+#ifndef SQLITE_DEFAULT_AUTOVACUUM
+  #define SQLITE_DEFAULT_AUTOVACUUM 0
+#endif
+
+#define BTREE_AUTOVACUUM_NONE 0        /* Do not do auto-vacuum */
+#define BTREE_AUTOVACUUM_FULL 1        /* Do full auto-vacuum */
+#define BTREE_AUTOVACUUM_INCR 2        /* Incremental vacuum */
+
+/*
+** Forward declarations of structure
+*/
+typedef struct Btree Btree;
+typedef struct BtCursor BtCursor;
+typedef struct BtShared BtShared;
+typedef struct BtreePayload BtreePayload;
+
+
+int sqlite3BtreeOpen(
+  sqlite3_vfs *pVfs,       /* VFS to use with this b-tree */
+  const char *zFilename,   /* Name of database file to open */
+  sqlite3 *db,             /* Associated database connection */
+  Btree **ppBtree,         /* Return open Btree* here */
+  int flags,               /* Flags */
+  int vfsFlags             /* Flags passed through to VFS open */
+);
+
+/* The flags parameter to sqlite3BtreeOpen can be the bitwise or of the
+** following values.
+**
+** NOTE:  These values must match the corresponding PAGER_ values in
+** pager.h.
+*/
+#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
+#define BTREE_MEMORY        2  /* This is an in-memory DB */
+#define BTREE_SINGLE        4  /* The file contains at most 1 b-tree */
+#define BTREE_UNORDERED     8  /* Use of a hash implementation is OK */
+
+int sqlite3BtreeClose(Btree*);
+int sqlite3BtreeSetCacheSize(Btree*,int);
+int sqlite3BtreeSetSpillSize(Btree*,int);
+#if SQLITE_MAX_MMAP_SIZE>0
+  int sqlite3BtreeSetMmapLimit(Btree*,sqlite3_int64);
+#endif
+int sqlite3BtreeSetPagerFlags(Btree*,unsigned);
+int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
+int sqlite3BtreeGetPageSize(Btree*);
+Pgno sqlite3BtreeMaxPageCount(Btree*,Pgno);
+Pgno sqlite3BtreeLastPage(Btree*);
+int sqlite3BtreeSecureDelete(Btree*,int);
+int sqlite3BtreeGetRequestedReserve(Btree*);
+int sqlite3BtreeGetReserveNoMutex(Btree *p);
+int sqlite3BtreeSetAutoVacuum(Btree *, int);
+int sqlite3BtreeGetAutoVacuum(Btree *);
+int sqlite3BtreeBeginTrans(Btree*,int,int*);
+int sqlite3BtreeCommitPhaseOne(Btree*, const char*);
+int sqlite3BtreeCommitPhaseTwo(Btree*, int);
+int sqlite3BtreeCommit(Btree*);
+int sqlite3BtreeRollback(Btree*,int,int);
+int sqlite3BtreeBeginStmt(Btree*,int);
+int sqlite3BtreeCreateTable(Btree*, Pgno*, int flags);
+int sqlite3BtreeTxnState(Btree*);
+int sqlite3BtreeIsInBackup(Btree*);
+
+void *sqlite3BtreeSchema(Btree *, int, void(*)(void *));
+int sqlite3BtreeSchemaLocked(Btree *pBtree);
+#ifndef SQLITE_OMIT_SHARED_CACHE
+int sqlite3BtreeLockTable(Btree *pBtree, int iTab, u8 isWriteLock);
+#endif
+
+/* Savepoints are named, nestable SQL transactions mostly implemented */ 
+/* in vdbe.c and pager.c See https://sqlite.org/lang_savepoint.html */
+int sqlite3BtreeSavepoint(Btree *, int, int);
+
+/* "Checkpoint" only refers to WAL. See https://sqlite.org/wal.html#ckpt */
+#ifndef SQLITE_OMIT_WAL
+  int sqlite3BtreeCheckpoint(Btree*, int, int *, int *);  
+#endif
+
+const char *sqlite3BtreeGetFilename(Btree *);
+const char *sqlite3BtreeGetJournalname(Btree *);
+int sqlite3BtreeCopyFile(Btree *, Btree *);
+
+int sqlite3BtreeIncrVacuum(Btree *);
+
+/* The flags parameter to sqlite3BtreeCreateTable can be the bitwise OR
+** of the flags shown below.
+**
+** Every SQLite table must have either BTREE_INTKEY or BTREE_BLOBKEY set.
+** With BTREE_INTKEY, the table key is a 64-bit integer and arbitrary data
+** is stored in the leaves.  (BTREE_INTKEY is used for SQL tables.)  With
+** BTREE_BLOBKEY, the key is an arbitrary BLOB and no content is stored
+** anywhere - the key is the content.  (BTREE_BLOBKEY is used for SQL
+** indices.)
+*/
+#define BTREE_INTKEY     1    /* Table has only 64-bit signed integer keys */
+#define BTREE_BLOBKEY    2    /* Table has keys only - no data */
+
+int sqlite3BtreeDropTable(Btree*, int, int*);
+int sqlite3BtreeClearTable(Btree*, int, i64*);
+int sqlite3BtreeClearTableOfCursor(BtCursor*);
+int sqlite3BtreeTripAllCursors(Btree*, int, int);
+
+void sqlite3BtreeGetMeta(Btree *pBtree, int idx, u32 *pValue);
+int sqlite3BtreeUpdateMeta(Btree*, int idx, u32 value);
+
+int sqlite3BtreeNewDb(Btree *p);
+
+/*
+** The second parameter to sqlite3BtreeGetMeta or sqlite3BtreeUpdateMeta
+** should be one of the following values. The integer values are assigned 
+** to constants so that the offset of the corresponding field in an
+** SQLite database header may be found using the following formula:
+**
+**   offset = 36 + (idx * 4)
+**
+** For example, the free-page-count field is located at byte offset 36 of
+** the database file header. The incr-vacuum-flag field is located at
+** byte offset 64 (== 36+4*7).
+**
+** The BTREE_DATA_VERSION value is not really a value stored in the header.
+** It is a read-only number computed by the pager.  But we merge it with
+** the header value access routines since its access pattern is the same.
+** Call it a "virtual meta value".
+*/
+#define BTREE_FREE_PAGE_COUNT     0
+#define BTREE_SCHEMA_VERSION      1
+#define BTREE_FILE_FORMAT         2
+#define BTREE_DEFAULT_CACHE_SIZE  3
+#define BTREE_LARGEST_ROOT_PAGE   4
+#define BTREE_TEXT_ENCODING       5
+#define BTREE_USER_VERSION        6
+#define BTREE_INCR_VACUUM         7
+#define BTREE_APPLICATION_ID      8
+#define BTREE_DATA_VERSION        15  /* A virtual meta-value */
+
+/*
+** Kinds of hints that can be passed into the sqlite3BtreeCursorHint()
+** interface.
+**
+** BTREE_HINT_RANGE  (arguments: Expr*, Mem*)
+**
+**     The first argument is an Expr* (which is guaranteed to be constant for
+**     the lifetime of the cursor) that defines constraints on which rows
+**     might be fetched with this cursor.  The Expr* tree may contain
+**     TK_REGISTER nodes that refer to values stored in the array of registers
+**     passed as the second parameter.  In other words, if Expr.op==TK_REGISTER
+**     then the value of the node is the value in Mem[pExpr.iTable].  Any
+**     TK_COLUMN node in the expression tree refers to the Expr.iColumn-th
+**     column of the b-tree of the cursor.  The Expr tree will not contain
+**     any function calls nor subqueries nor references to b-trees other than
+**     the cursor being hinted.
+**
+**     The design of the _RANGE hint is aid b-tree implementations that try
+**     to prefetch content from remote machines - to provide those
+**     implementations with limits on what needs to be prefetched and thereby
+**     reduce network bandwidth.
+**
+** Note that BTREE_HINT_FLAGS with BTREE_BULKLOAD is the only hint used by
+** standard SQLite.  The other hints are provided for extensions that use
+** the SQLite parser and code generator but substitute their own storage
+** engine.
+*/
+#define BTREE_HINT_RANGE 0       /* Range constraints on queries */
+
+/*
+** Values that may be OR'd together to form the argument to the
+** BTREE_HINT_FLAGS hint for sqlite3BtreeCursorHint():
+**
+** The BTREE_BULKLOAD flag is set on index cursors when the index is going
+** to be filled with content that is already in sorted order.
+**
+** The BTREE_SEEK_EQ flag is set on cursors that will get OP_SeekGE or
+** OP_SeekLE opcodes for a range search, but where the range of entries
+** selected will all have the same key.  In other words, the cursor will
+** be used only for equality key searches.
+**
+*/
+#define BTREE_BULKLOAD 0x00000001  /* Used to full index in sorted order */
+#define BTREE_SEEK_EQ  0x00000002  /* EQ seeks only - no range seeks */
+
+/* 
+** Flags passed as the third argument to sqlite3BtreeCursor().
+**
+** For read-only cursors the wrFlag argument is always zero. For read-write
+** cursors it may be set to either (BTREE_WRCSR|BTREE_FORDELETE) or just
+** (BTREE_WRCSR). If the BTREE_FORDELETE bit is set, then the cursor will
+** only be used by SQLite for the following:
+**
+**   * to seek to and then delete specific entries, and/or
+**
+**   * to read values that will be used to create keys that other
+**     BTREE_FORDELETE cursors will seek to and delete.
+**
+** The BTREE_FORDELETE flag is an optimization hint.  It is not used by
+** by this, the native b-tree engine of SQLite, but it is available to
+** alternative storage engines that might be substituted in place of this
+** b-tree system.  For alternative storage engines in which a delete of
+** the main table row automatically deletes corresponding index rows,
+** the FORDELETE flag hint allows those alternative storage engines to
+** skip a lot of work.  Namely:  FORDELETE cursors may treat all SEEK
+** and DELETE operations as no-ops, and any READ operation against a
+** FORDELETE cursor may return a null row: 0x01 0x00.
+*/
+#define BTREE_WRCSR     0x00000004     /* read-write cursor */
+#define BTREE_FORDELETE 0x00000008     /* Cursor is for seek/delete only */
+
+int sqlite3BtreeCursor(
+  Btree*,                              /* BTree containing table to open */
+  Pgno iTable,                         /* Index of root page */
+  int wrFlag,                          /* 1 for writing.  0 for read-only */
+  struct KeyInfo*,                     /* First argument to compare function */
+  BtCursor *pCursor                    /* Space to write cursor structure */
+);
+BtCursor *sqlite3BtreeFakeValidCursor(void);
+int sqlite3BtreeCursorSize(void);
+void sqlite3BtreeCursorZero(BtCursor*);
+void sqlite3BtreeCursorHintFlags(BtCursor*, unsigned);
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+void sqlite3BtreeCursorHint(BtCursor*, int, ...);
+#endif
+
+int sqlite3BtreeCloseCursor(BtCursor*);
+int sqlite3BtreeTableMoveto(
+  BtCursor*,
+  i64 intKey,
+  int bias,
+  int *pRes
+);
+int sqlite3BtreeIndexMoveto(
+  BtCursor*,
+  UnpackedRecord *pUnKey,
+  int *pRes
+);
+int sqlite3BtreeCursorHasMoved(BtCursor*);
+int sqlite3BtreeCursorRestore(BtCursor*, int*);
+int sqlite3BtreeDelete(BtCursor*, u8 flags);
+
+/* Allowed flags for sqlite3BtreeDelete() and sqlite3BtreeInsert() */
+#define BTREE_SAVEPOSITION 0x02  /* Leave cursor pointing at NEXT or PREV */
+#define BTREE_AUXDELETE    0x04  /* not the primary delete operation */
+#define BTREE_APPEND       0x08  /* Insert is likely an append */
+#define BTREE_PREFORMAT    0x80  /* Inserted data is a preformated cell */
+
+/* An instance of the BtreePayload object describes the content of a single
+** entry in either an index or table btree.
+**
+** Index btrees (used for indexes and also WITHOUT ROWID tables) contain
+** an arbitrary key and no data.  These btrees have pKey,nKey set to the
+** key and the pData,nData,nZero fields are uninitialized.  The aMem,nMem
+** fields give an array of Mem objects that are a decomposition of the key.
+** The nMem field might be zero, indicating that no decomposition is available.
+**
+** Table btrees (used for rowid tables) contain an integer rowid used as
+** the key and passed in the nKey field.  The pKey field is zero.  
+** pData,nData hold the content of the new entry.  nZero extra zero bytes
+** are appended to the end of the content when constructing the entry.
+** The aMem,nMem fields are uninitialized for table btrees.
+**
+** Field usage summary:
+**
+**               Table BTrees                   Index Btrees
+**
+**   pKey        always NULL                    encoded key
+**   nKey        the ROWID                      length of pKey
+**   pData       data                           not used
+**   aMem        not used                       decomposed key value
+**   nMem        not used                       entries in aMem
+**   nData       length of pData                not used
+**   nZero       extra zeros after pData        not used
+**
+** This object is used to pass information into sqlite3BtreeInsert().  The
+** same information used to be passed as five separate parameters.  But placing
+** the information into this object helps to keep the interface more 
+** organized and understandable, and it also helps the resulting code to
+** run a little faster by using fewer registers for parameter passing.
+*/
+struct BtreePayload {
+  const void *pKey;       /* Key content for indexes.  NULL for tables */
+  sqlite3_int64 nKey;     /* Size of pKey for indexes.  PRIMARY KEY for tabs */
+  const void *pData;      /* Data for tables. */
+  sqlite3_value *aMem;    /* First of nMem value in the unpacked pKey */
+  u16 nMem;               /* Number of aMem[] value.  Might be zero */
+  int nData;              /* Size of pData.  0 if none. */
+  int nZero;              /* Extra zero data appended after pData,nData */
+};
+
+int sqlite3BtreeInsert(BtCursor*, const BtreePayload *pPayload,
+                       int flags, int seekResult);
+int sqlite3BtreeFirst(BtCursor*, int *pRes);
+int sqlite3BtreeLast(BtCursor*, int *pRes);
+int sqlite3BtreeNext(BtCursor*, int flags);
+int sqlite3BtreeEof(BtCursor*);
+int sqlite3BtreePrevious(BtCursor*, int flags);
+i64 sqlite3BtreeIntegerKey(BtCursor*);
+void sqlite3BtreeCursorPin(BtCursor*);
+void sqlite3BtreeCursorUnpin(BtCursor*);
+i64 sqlite3BtreeOffset(BtCursor*);
+int sqlite3BtreePayload(BtCursor*, u32 offset, u32 amt, void*);
+const void *sqlite3BtreePayloadFetch(BtCursor*, u32 *pAmt);
+u32 sqlite3BtreePayloadSize(BtCursor*);
+sqlite3_int64 sqlite3BtreeMaxRecordSize(BtCursor*);
+
+int sqlite3BtreeIntegrityCheck(
+  sqlite3 *db,  /* Database connection that is running the check */
+  Btree *p,     /* The btree to be checked */
+  Pgno *aRoot,  /* An array of root pages numbers for individual trees */
+  int nRoot,    /* Number of entries in aRoot[] */
+  int mxErr,    /* Stop reporting errors after this many */
+  int *pnErr,   /* OUT: Write number of errors seen to this variable */
+  char **pzOut  /* OUT: Write the error message string here */
+);
+struct Pager *sqlite3BtreePager(Btree*);
+i64 sqlite3BtreeRowCountEst(BtCursor*);
+
+#ifndef SQLITE_OMIT_INCRBLOB
+int sqlite3BtreePayloadChecked(BtCursor*, u32 offset, u32 amt, void*);
+int sqlite3BtreePutData(BtCursor*, u32 offset, u32 amt, void*);
+void sqlite3BtreeIncrblobCursor(BtCursor *);
+#endif
+void sqlite3BtreeClearCursor(BtCursor *);
+int sqlite3BtreeSetVersion(Btree *pBt, int iVersion);
+int sqlite3BtreeCursorHasHint(BtCursor*, unsigned int mask);
+int sqlite3BtreeIsReadonly(Btree *pBt);
+int sqlite3HeaderSizeBtree(void);
+
+#ifdef SQLITE_DEBUG
+sqlite3_uint64 sqlite3BtreeSeekCount(Btree*);
+#else
+# define sqlite3BtreeSeekCount(X) 0
+#endif
+
+#ifndef NDEBUG
+int sqlite3BtreeCursorIsValid(BtCursor*);
+#endif
+int sqlite3BtreeCursorIsValidNN(BtCursor*);
+
+int sqlite3BtreeCount(sqlite3*, BtCursor*, i64*);
+
+#ifdef SQLITE_TEST
+int sqlite3BtreeCursorInfo(BtCursor*, int*, int);
+void sqlite3BtreeCursorList(Btree*);
+#endif
+
+#ifndef SQLITE_OMIT_WAL
+  int sqlite3BtreeCheckpoint(Btree*, int, int *, int *);
+#endif
+
+int sqlite3BtreeTransferRow(BtCursor*, BtCursor*, i64);
+
+void sqlite3BtreeClearCache(Btree*);
+
+/*
+** If we are not using shared cache, then there is no need to
+** use mutexes to access the BtShared structures.  So make the
+** Enter and Leave procedures no-ops.
+*/
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  void sqlite3BtreeEnter(Btree*);
+  void sqlite3BtreeEnterAll(sqlite3*);
+  int sqlite3BtreeSharable(Btree*);
+  void sqlite3BtreeEnterCursor(BtCursor*);
+  int sqlite3BtreeConnectionCount(Btree*);
+#else
+# define sqlite3BtreeEnter(X) 
+# define sqlite3BtreeEnterAll(X)
+# define sqlite3BtreeSharable(X) 0
+# define sqlite3BtreeEnterCursor(X)
+# define sqlite3BtreeConnectionCount(X) 1
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE
+  void sqlite3BtreeLeave(Btree*);
+  void sqlite3BtreeLeaveCursor(BtCursor*);
+  void sqlite3BtreeLeaveAll(sqlite3*);
+#ifndef NDEBUG
+  /* These routines are used inside assert() statements only. */
+  int sqlite3BtreeHoldsMutex(Btree*);
+  int sqlite3BtreeHoldsAllMutexes(sqlite3*);
+  int sqlite3SchemaMutexHeld(sqlite3*,int,Schema*);
+#endif
+#else
+
+# define sqlite3BtreeLeave(X)
+# define sqlite3BtreeLeaveCursor(X)
+# define sqlite3BtreeLeaveAll(X)
+
+# define sqlite3BtreeHoldsMutex(X) 1
+# define sqlite3BtreeHoldsAllMutexes(X) 1
+# define sqlite3SchemaMutexHeld(X,Y,Z) 1
+#endif
+
+
+#endif /* SQLITE_BTREE_H */
diff --git a/src/btreeInt.h b/src/btreeInt.h
new file mode 100644
index 0000000..67a7db2
--- /dev/null
+++ b/src/btreeInt.h
@@ -0,0 +1,733 @@
+/*
+** 2004 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements an external (disk-based) database using BTrees.
+** For a detailed discussion of BTrees, refer to
+**
+**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
+**     "Sorting And Searching", pages 473-480. Addison-Wesley
+**     Publishing Company, Reading, Massachusetts.
+**
+** The basic idea is that each page of the file contains N database
+** entries and N+1 pointers to subpages.
+**
+**   ----------------------------------------------------------------
+**   |  Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
+**   ----------------------------------------------------------------
+**
+** All of the keys on the page that Ptr(0) points to have values less
+** than Key(0).  All of the keys on page Ptr(1) and its subpages have
+** values greater than Key(0) and less than Key(1).  All of the keys
+** on Ptr(N) and its subpages have values greater than Key(N-1).  And
+** so forth.
+**
+** Finding a particular key requires reading O(log(M)) pages from the 
+** disk where M is the number of entries in the tree.
+**
+** In this implementation, a single file can hold one or more separate 
+** BTrees.  Each BTree is identified by the index of its root page.  The
+** key and data for any entry are combined to form the "payload".  A
+** fixed amount of payload can be carried directly on the database
+** page.  If the payload is larger than the preset amount then surplus
+** bytes are stored on overflow pages.  The payload for an entry
+** and the preceding pointer are combined to form a "Cell".  Each 
+** page has a small header which contains the Ptr(N) pointer and other
+** information such as the size of key and data.
+**
+** FORMAT DETAILS
+**
+** The file is divided into pages.  The first page is called page 1,
+** the second is page 2, and so forth.  A page number of zero indicates
+** "no such page".  The page size can be any power of 2 between 512 and 65536.
+** Each page can be either a btree page, a freelist page, an overflow
+** page, or a pointer-map page.
+**
+** The first page is always a btree page.  The first 100 bytes of the first
+** page contain a special header (the "file header") that describes the file.
+** The format of the file header is as follows:
+**
+**   OFFSET   SIZE    DESCRIPTION
+**      0      16     Header string: "SQLite format 3\000"
+**     16       2     Page size in bytes.  (1 means 65536)
+**     18       1     File format write version
+**     19       1     File format read version
+**     20       1     Bytes of unused space at the end of each page
+**     21       1     Max embedded payload fraction (must be 64)
+**     22       1     Min embedded payload fraction (must be 32)
+**     23       1     Min leaf payload fraction (must be 32)
+**     24       4     File change counter
+**     28       4     The size of the database in pages
+**     32       4     First freelist page
+**     36       4     Number of freelist pages in the file
+**     40      60     15 4-byte meta values passed to higher layers
+**
+**     40       4     Schema cookie
+**     44       4     File format of schema layer
+**     48       4     Size of page cache
+**     52       4     Largest root-page (auto/incr_vacuum)
+**     56       4     1=UTF-8 2=UTF16le 3=UTF16be
+**     60       4     User version
+**     64       4     Incremental vacuum mode
+**     68       4     Application-ID
+**     72      20     unused
+**     92       4     The version-valid-for number
+**     96       4     SQLITE_VERSION_NUMBER
+**
+** All of the integer values are big-endian (most significant byte first).
+**
+** The file change counter is incremented when the database is changed
+** This counter allows other processes to know when the file has changed
+** and thus when they need to flush their cache.
+**
+** The max embedded payload fraction is the amount of the total usable
+** space in a page that can be consumed by a single cell for standard
+** B-tree (non-LEAFDATA) tables.  A value of 255 means 100%.  The default
+** is to limit the maximum cell size so that at least 4 cells will fit
+** on one page.  Thus the default max embedded payload fraction is 64.
+**
+** If the payload for a cell is larger than the max payload, then extra
+** payload is spilled to overflow pages.  Once an overflow page is allocated,
+** as many bytes as possible are moved into the overflow pages without letting
+** the cell size drop below the min embedded payload fraction.
+**
+** The min leaf payload fraction is like the min embedded payload fraction
+** except that it applies to leaf nodes in a LEAFDATA tree.  The maximum
+** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
+** not specified in the header.
+**
+** Each btree pages is divided into three sections:  The header, the
+** cell pointer array, and the cell content area.  Page 1 also has a 100-byte
+** file header that occurs before the page header.
+**
+**      |----------------|
+**      | file header    |   100 bytes.  Page 1 only.
+**      |----------------|
+**      | page header    |   8 bytes for leaves.  12 bytes for interior nodes
+**      |----------------|
+**      | cell pointer   |   |  2 bytes per cell.  Sorted order.
+**      | array          |   |  Grows downward
+**      |                |   v
+**      |----------------|
+**      | unallocated    |
+**      | space          |
+**      |----------------|   ^  Grows upwards
+**      | cell content   |   |  Arbitrary order interspersed with freeblocks.
+**      | area           |   |  and free space fragments.
+**      |----------------|
+**
+** The page headers looks like this:
+**
+**   OFFSET   SIZE     DESCRIPTION
+**      0       1      Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
+**      1       2      byte offset to the first freeblock
+**      3       2      number of cells on this page
+**      5       2      first byte of the cell content area
+**      7       1      number of fragmented free bytes
+**      8       4      Right child (the Ptr(N) value).  Omitted on leaves.
+**
+** The flags define the format of this btree page.  The leaf flag means that
+** this page has no children.  The zerodata flag means that this page carries
+** only keys and no data.  The intkey flag means that the key is an integer
+** which is stored in the key size entry of the cell header rather than in
+** the payload area.
+**
+** The cell pointer array begins on the first byte after the page header.
+** The cell pointer array contains zero or more 2-byte numbers which are
+** offsets from the beginning of the page to the cell content in the cell
+** content area.  The cell pointers occur in sorted order.  The system strives
+** to keep free space after the last cell pointer so that new cells can
+** be easily added without having to defragment the page.
+**
+** Cell content is stored at the very end of the page and grows toward the
+** beginning of the page.
+**
+** Unused space within the cell content area is collected into a linked list of
+** freeblocks.  Each freeblock is at least 4 bytes in size.  The byte offset
+** to the first freeblock is given in the header.  Freeblocks occur in
+** increasing order.  Because a freeblock must be at least 4 bytes in size,
+** any group of 3 or fewer unused bytes in the cell content area cannot
+** exist on the freeblock chain.  A group of 3 or fewer free bytes is called
+** a fragment.  The total number of bytes in all fragments is recorded.
+** in the page header at offset 7.
+**
+**    SIZE    DESCRIPTION
+**      2     Byte offset of the next freeblock
+**      2     Bytes in this freeblock
+**
+** Cells are of variable length.  Cells are stored in the cell content area at
+** the end of the page.  Pointers to the cells are in the cell pointer array
+** that immediately follows the page header.  Cells is not necessarily
+** contiguous or in order, but cell pointers are contiguous and in order.
+**
+** Cell content makes use of variable length integers.  A variable
+** length integer is 1 to 9 bytes where the lower 7 bits of each 
+** byte are used.  The integer consists of all bytes that have bit 8 set and
+** the first byte with bit 8 clear.  The most significant byte of the integer
+** appears first.  A variable-length integer may not be more than 9 bytes long.
+** As a special case, all 8 bits of the 9th byte are used as data.  This
+** allows a 64-bit integer to be encoded in 9 bytes.
+**
+**    0x00                      becomes  0x00000000
+**    0x7f                      becomes  0x0000007f
+**    0x81 0x00                 becomes  0x00000080
+**    0x82 0x00                 becomes  0x00000100
+**    0x80 0x7f                 becomes  0x0000007f
+**    0x81 0x91 0xd1 0xac 0x78  becomes  0x12345678
+**    0x81 0x81 0x81 0x81 0x01  becomes  0x10204081
+**
+** Variable length integers are used for rowids and to hold the number of
+** bytes of key and data in a btree cell.
+**
+** The content of a cell looks like this:
+**
+**    SIZE    DESCRIPTION
+**      4     Page number of the left child. Omitted if leaf flag is set.
+**     var    Number of bytes of data. Omitted if the zerodata flag is set.
+**     var    Number of bytes of key. Or the key itself if intkey flag is set.
+**      *     Payload
+**      4     First page of the overflow chain.  Omitted if no overflow
+**
+** Overflow pages form a linked list.  Each page except the last is completely
+** filled with data (pagesize - 4 bytes).  The last page can have as little
+** as 1 byte of data.
+**
+**    SIZE    DESCRIPTION
+**      4     Page number of next overflow page
+**      *     Data
+**
+** Freelist pages come in two subtypes: trunk pages and leaf pages.  The
+** file header points to the first in a linked list of trunk page.  Each trunk
+** page points to multiple leaf pages.  The content of a leaf page is
+** unspecified.  A trunk page looks like this:
+**
+**    SIZE    DESCRIPTION
+**      4     Page number of next trunk page
+**      4     Number of leaf pointers on this page
+**      *     zero or more pages numbers of leaves
+*/
+#include "sqliteInt.h"
+
+
+/* The following value is the maximum cell size assuming a maximum page
+** size give above.
+*/
+#define MX_CELL_SIZE(pBt)  ((int)(pBt->pageSize-8))
+
+/* The maximum number of cells on a single page of the database.  This
+** assumes a minimum cell size of 6 bytes  (4 bytes for the cell itself
+** plus 2 bytes for the index to the cell in the page header).  Such
+** small cells will be rare, but they are possible.
+*/
+#define MX_CELL(pBt) ((pBt->pageSize-8)/6)
+
+/* Forward declarations */
+typedef struct MemPage MemPage;
+typedef struct BtLock BtLock;
+typedef struct CellInfo CellInfo;
+
+/*
+** This is a magic string that appears at the beginning of every
+** SQLite database in order to identify the file as a real database.
+**
+** You can change this value at compile-time by specifying a
+** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The
+** header must be exactly 16 bytes including the zero-terminator so
+** the string itself should be 15 characters long.  If you change
+** the header, then your custom library will not be able to read 
+** databases generated by the standard tools and the standard tools
+** will not be able to read databases created by your custom library.
+*/
+#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
+#  define SQLITE_FILE_HEADER "SQLite format 3"
+#endif
+
+/*
+** Page type flags.  An ORed combination of these flags appear as the
+** first byte of on-disk image of every BTree page.
+*/
+#define PTF_INTKEY    0x01
+#define PTF_ZERODATA  0x02
+#define PTF_LEAFDATA  0x04
+#define PTF_LEAF      0x08
+
+/*
+** An instance of this object stores information about each a single database
+** page that has been loaded into memory.  The information in this object
+** is derived from the raw on-disk page content.
+**
+** As each database page is loaded into memory, the pager allocates an
+** instance of this object and zeros the first 8 bytes.  (This is the
+** "extra" information associated with each page of the pager.)
+**
+** Access to all fields of this structure is controlled by the mutex
+** stored in MemPage.pBt->mutex.
+*/
+struct MemPage {
+  u8 isInit;           /* True if previously initialized. MUST BE FIRST! */
+  u8 intKey;           /* True if table b-trees.  False for index b-trees */
+  u8 intKeyLeaf;       /* True if the leaf of an intKey table */
+  Pgno pgno;           /* Page number for this page */
+  /* Only the first 8 bytes (above) are zeroed by pager.c when a new page
+  ** is allocated. All fields that follow must be initialized before use */
+  u8 leaf;             /* True if a leaf page */
+  u8 hdrOffset;        /* 100 for page 1.  0 otherwise */
+  u8 childPtrSize;     /* 0 if leaf==1.  4 if leaf==0 */
+  u8 max1bytePayload;  /* min(maxLocal,127) */
+  u8 nOverflow;        /* Number of overflow cell bodies in aCell[] */
+  u16 maxLocal;        /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
+  u16 minLocal;        /* Copy of BtShared.minLocal or BtShared.minLeaf */
+  u16 cellOffset;      /* Index in aData of first cell pointer */
+  int nFree;           /* Number of free bytes on the page. -1 for unknown */
+  u16 nCell;           /* Number of cells on this page, local and ovfl */
+  u16 maskPage;        /* Mask for page offset */
+  u16 aiOvfl[4];       /* Insert the i-th overflow cell before the aiOvfl-th
+                       ** non-overflow cell */
+  u8 *apOvfl[4];       /* Pointers to the body of overflow cells */
+  BtShared *pBt;       /* Pointer to BtShared that this page is part of */
+  u8 *aData;           /* Pointer to disk image of the page data */
+  u8 *aDataEnd;        /* One byte past the end of the entire page - not just
+                       ** the usable space, the entire page.  Used to prevent
+                       ** corruption-induced buffer overflow. */
+  u8 *aCellIdx;        /* The cell index area */
+  u8 *aDataOfst;       /* Same as aData for leaves.  aData+4 for interior */
+  DbPage *pDbPage;     /* Pager page handle */
+  u16 (*xCellSize)(MemPage*,u8*);             /* cellSizePtr method */
+  void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */
+};
+
+/*
+** A linked list of the following structures is stored at BtShared.pLock.
+** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 
+** is opened on the table with root page BtShared.iTable. Locks are removed
+** from this list when a transaction is committed or rolled back, or when
+** a btree handle is closed.
+*/
+struct BtLock {
+  Btree *pBtree;        /* Btree handle holding this lock */
+  Pgno iTable;          /* Root page of table */
+  u8 eLock;             /* READ_LOCK or WRITE_LOCK */
+  BtLock *pNext;        /* Next in BtShared.pLock list */
+};
+
+/* Candidate values for BtLock.eLock */
+#define READ_LOCK     1
+#define WRITE_LOCK    2
+
+/* A Btree handle
+**
+** A database connection contains a pointer to an instance of
+** this object for every database file that it has open.  This structure
+** is opaque to the database connection.  The database connection cannot
+** see the internals of this structure and only deals with pointers to
+** this structure.
+**
+** For some database files, the same underlying database cache might be 
+** shared between multiple connections.  In that case, each connection
+** has it own instance of this object.  But each instance of this object
+** points to the same BtShared object.  The database cache and the
+** schema associated with the database file are all contained within
+** the BtShared object.
+**
+** All fields in this structure are accessed under sqlite3.mutex.
+** The pBt pointer itself may not be changed while there exists cursors 
+** in the referenced BtShared that point back to this Btree since those
+** cursors have to go through this Btree to find their BtShared and
+** they often do so without holding sqlite3.mutex.
+*/
+struct Btree {
+  sqlite3 *db;       /* The database connection holding this btree */
+  BtShared *pBt;     /* Sharable content of this btree */
+  u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
+  u8 sharable;       /* True if we can share pBt with another db */
+  u8 locked;         /* True if db currently has pBt locked */
+  u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */
+  int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */
+  int nBackup;       /* Number of backup operations reading this btree */
+  u32 iBDataVersion; /* Combines with pBt->pPager->iDataVersion */
+  Btree *pNext;      /* List of other sharable Btrees from the same db */
+  Btree *pPrev;      /* Back pointer of the same list */
+#ifdef SQLITE_DEBUG
+  u64 nSeek;         /* Calls to sqlite3BtreeMovetoUnpacked() */
+#endif
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  BtLock lock;       /* Object used to lock page 1 */
+#endif
+};
+
+/*
+** Btree.inTrans may take one of the following values.
+**
+** If the shared-data extension is enabled, there may be multiple users
+** of the Btree structure. At most one of these may open a write transaction,
+** but any number may have active read transactions.
+**
+** These values must match SQLITE_TXN_NONE, SQLITE_TXN_READ, and
+** SQLITE_TXN_WRITE
+*/
+#define TRANS_NONE  0
+#define TRANS_READ  1
+#define TRANS_WRITE 2
+
+#if TRANS_NONE!=SQLITE_TXN_NONE
+# error wrong numeric code for no-transaction
+#endif
+#if TRANS_READ!=SQLITE_TXN_READ
+# error wrong numeric code for read-transaction
+#endif
+#if TRANS_WRITE!=SQLITE_TXN_WRITE
+# error wrong numeric code for write-transaction
+#endif
+
+
+/*
+** An instance of this object represents a single database file.
+** 
+** A single database file can be in use at the same time by two
+** or more database connections.  When two or more connections are
+** sharing the same database file, each connection has it own
+** private Btree object for the file and each of those Btrees points
+** to this one BtShared object.  BtShared.nRef is the number of
+** connections currently sharing this database file.
+**
+** Fields in this structure are accessed under the BtShared.mutex
+** mutex, except for nRef and pNext which are accessed under the
+** global SQLITE_MUTEX_STATIC_MAIN mutex.  The pPager field
+** may not be modified once it is initially set as long as nRef>0.
+** The pSchema field may be set once under BtShared.mutex and
+** thereafter is unchanged as long as nRef>0.
+**
+** isPending:
+**
+**   If a BtShared client fails to obtain a write-lock on a database
+**   table (because there exists one or more read-locks on the table),
+**   the shared-cache enters 'pending-lock' state and isPending is
+**   set to true.
+**
+**   The shared-cache leaves the 'pending lock' state when either of
+**   the following occur:
+**
+**     1) The current writer (BtShared.pWriter) concludes its transaction, OR
+**     2) The number of locks held by other connections drops to zero.
+**
+**   while in the 'pending-lock' state, no connection may start a new
+**   transaction.
+**
+**   This feature is included to help prevent writer-starvation.
+*/
+struct BtShared {
+  Pager *pPager;        /* The page cache */
+  sqlite3 *db;          /* Database connection currently using this Btree */
+  BtCursor *pCursor;    /* A list of all open cursors */
+  MemPage *pPage1;      /* First page of the database */
+  u8 openFlags;         /* Flags to sqlite3BtreeOpen() */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  u8 autoVacuum;        /* True if auto-vacuum is enabled */
+  u8 incrVacuum;        /* True if incr-vacuum is enabled */
+  u8 bDoTruncate;       /* True to truncate db on commit */
+#endif
+  u8 inTransaction;     /* Transaction state */
+  u8 max1bytePayload;   /* Maximum first byte of cell for a 1-byte payload */
+  u8 nReserveWanted;    /* Desired number of extra bytes per page */
+  u16 btsFlags;         /* Boolean parameters.  See BTS_* macros below */
+  u16 maxLocal;         /* Maximum local payload in non-LEAFDATA tables */
+  u16 minLocal;         /* Minimum local payload in non-LEAFDATA tables */
+  u16 maxLeaf;          /* Maximum local payload in a LEAFDATA table */
+  u16 minLeaf;          /* Minimum local payload in a LEAFDATA table */
+  u32 pageSize;         /* Total number of bytes on a page */
+  u32 usableSize;       /* Number of usable bytes on each page */
+  int nTransaction;     /* Number of open transactions (read + write) */
+  u32 nPage;            /* Number of pages in the database */
+  void *pSchema;        /* Pointer to space allocated by sqlite3BtreeSchema() */
+  void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */
+  sqlite3_mutex *mutex; /* Non-recursive mutex required to access this object */
+  Bitvec *pHasContent;  /* Set of pages moved to free-list this transaction */
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  int nRef;             /* Number of references to this structure */
+  BtShared *pNext;      /* Next on a list of sharable BtShared structs */
+  BtLock *pLock;        /* List of locks held on this shared-btree struct */
+  Btree *pWriter;       /* Btree with currently open write transaction */
+#endif
+  u8 *pTmpSpace;        /* Temp space sufficient to hold a single cell */
+  int nPreformatSize;   /* Size of last cell written by TransferRow() */
+};
+
+/*
+** Allowed values for BtShared.btsFlags
+*/
+#define BTS_READ_ONLY        0x0001   /* Underlying file is readonly */
+#define BTS_PAGESIZE_FIXED   0x0002   /* Page size can no longer be changed */
+#define BTS_SECURE_DELETE    0x0004   /* PRAGMA secure_delete is enabled */
+#define BTS_OVERWRITE        0x0008   /* Overwrite deleted content with zeros */
+#define BTS_FAST_SECURE      0x000c   /* Combination of the previous two */
+#define BTS_INITIALLY_EMPTY  0x0010   /* Database was empty at trans start */
+#define BTS_NO_WAL           0x0020   /* Do not open write-ahead-log files */
+#define BTS_EXCLUSIVE        0x0040   /* pWriter has an exclusive lock */
+#define BTS_PENDING          0x0080   /* Waiting for read-locks to clear */
+
+/*
+** An instance of the following structure is used to hold information
+** about a cell.  The parseCellPtr() function fills in this structure
+** based on information extract from the raw disk page.
+*/
+struct CellInfo {
+  i64 nKey;      /* The key for INTKEY tables, or nPayload otherwise */
+  u8 *pPayload;  /* Pointer to the start of payload */
+  u32 nPayload;  /* Bytes of payload */
+  u16 nLocal;    /* Amount of payload held locally, not on overflow */
+  u16 nSize;     /* Size of the cell content on the main b-tree page */
+};
+
+/*
+** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
+** this will be declared corrupt. This value is calculated based on a
+** maximum database size of 2^31 pages a minimum fanout of 2 for a
+** root-node and 3 for all other internal nodes.
+**
+** If a tree that appears to be taller than this is encountered, it is
+** assumed that the database is corrupt.
+*/
+#define BTCURSOR_MAX_DEPTH 20
+
+/*
+** A cursor is a pointer to a particular entry within a particular
+** b-tree within a database file.
+**
+** The entry is identified by its MemPage and the index in
+** MemPage.aCell[] of the entry.
+**
+** A single database file can be shared by two more database connections,
+** but cursors cannot be shared.  Each cursor is associated with a
+** particular database connection identified BtCursor.pBtree.db.
+**
+** Fields in this structure are accessed under the BtShared.mutex
+** found at self->pBt->mutex. 
+**
+** skipNext meaning:
+** The meaning of skipNext depends on the value of eState:
+**
+**   eState            Meaning of skipNext
+**   VALID             skipNext is meaningless and is ignored
+**   INVALID           skipNext is meaningless and is ignored
+**   SKIPNEXT          sqlite3BtreeNext() is a no-op if skipNext>0 and
+**                     sqlite3BtreePrevious() is no-op if skipNext<0.
+**   REQUIRESEEK       restoreCursorPosition() restores the cursor to
+**                     eState=SKIPNEXT if skipNext!=0
+**   FAULT             skipNext holds the cursor fault error code.
+*/
+struct BtCursor {
+  u8 eState;                /* One of the CURSOR_XXX constants (see below) */
+  u8 curFlags;              /* zero or more BTCF_* flags defined below */
+  u8 curPagerFlags;         /* Flags to send to sqlite3PagerGet() */
+  u8 hints;                 /* As configured by CursorSetHints() */
+  int skipNext;    /* Prev() is noop if negative. Next() is noop if positive.
+                   ** Error code if eState==CURSOR_FAULT */
+  Btree *pBtree;            /* The Btree to which this cursor belongs */
+  Pgno *aOverflow;          /* Cache of overflow page locations */
+  void *pKey;               /* Saved key that was cursor last known position */
+  /* All fields above are zeroed when the cursor is allocated.  See
+  ** sqlite3BtreeCursorZero().  Fields that follow must be manually
+  ** initialized. */
+#define BTCURSOR_FIRST_UNINIT pBt   /* Name of first uninitialized field */
+  BtShared *pBt;            /* The BtShared this cursor points to */
+  BtCursor *pNext;          /* Forms a linked list of all cursors */
+  CellInfo info;            /* A parse of the cell we are pointing at */
+  i64 nKey;                 /* Size of pKey, or last integer key */
+  Pgno pgnoRoot;            /* The root page of this tree */
+  i8 iPage;                 /* Index of current page in apPage */
+  u8 curIntKey;             /* Value of apPage[0]->intKey */
+  u16 ix;                   /* Current index for apPage[iPage] */
+  u16 aiIdx[BTCURSOR_MAX_DEPTH-1];     /* Current index in apPage[i] */
+  struct KeyInfo *pKeyInfo;            /* Arg passed to comparison function */
+  MemPage *pPage;                        /* Current page */
+  MemPage *apPage[BTCURSOR_MAX_DEPTH-1]; /* Stack of parents of current page */
+};
+
+/*
+** Legal values for BtCursor.curFlags
+*/
+#define BTCF_WriteFlag    0x01   /* True if a write cursor */
+#define BTCF_ValidNKey    0x02   /* True if info.nKey is valid */
+#define BTCF_ValidOvfl    0x04   /* True if aOverflow is valid */
+#define BTCF_AtLast       0x08   /* Cursor is pointing to the last entry */
+#define BTCF_Incrblob     0x10   /* True if an incremental I/O handle */
+#define BTCF_Multiple     0x20   /* Maybe another cursor on the same btree */
+#define BTCF_Pinned       0x40   /* Cursor is busy and cannot be moved */
+
+/*
+** Potential values for BtCursor.eState.
+**
+** CURSOR_INVALID:
+**   Cursor does not point to a valid entry. This can happen (for example) 
+**   because the table is empty or because BtreeCursorFirst() has not been
+**   called.
+**
+** CURSOR_VALID:
+**   Cursor points to a valid entry. getPayload() etc. may be called.
+**
+** CURSOR_SKIPNEXT:
+**   Cursor is valid except that the Cursor.skipNext field is non-zero
+**   indicating that the next sqlite3BtreeNext() or sqlite3BtreePrevious()
+**   operation should be a no-op.
+**
+** CURSOR_REQUIRESEEK:
+**   The table that this cursor was opened on still exists, but has been 
+**   modified since the cursor was last used. The cursor position is saved
+**   in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in 
+**   this state, restoreCursorPosition() can be called to attempt to
+**   seek the cursor to the saved position.
+**
+** CURSOR_FAULT:
+**   An unrecoverable error (an I/O error or a malloc failure) has occurred
+**   on a different connection that shares the BtShared cache with this
+**   cursor.  The error has left the cache in an inconsistent state.
+**   Do nothing else with this cursor.  Any attempt to use the cursor
+**   should return the error code stored in BtCursor.skipNext
+*/
+#define CURSOR_VALID             0
+#define CURSOR_INVALID           1
+#define CURSOR_SKIPNEXT          2
+#define CURSOR_REQUIRESEEK       3
+#define CURSOR_FAULT             4
+
+/* 
+** The database page the PENDING_BYTE occupies. This page is never used.
+*/
+#define PENDING_BYTE_PAGE(pBt)  ((Pgno)((PENDING_BYTE/((pBt)->pageSize))+1))
+
+/*
+** These macros define the location of the pointer-map entry for a 
+** database page. The first argument to each is the number of usable
+** bytes on each page of the database (often 1024). The second is the
+** page number to look up in the pointer map.
+**
+** PTRMAP_PAGENO returns the database page number of the pointer-map
+** page that stores the required pointer. PTRMAP_PTROFFSET returns
+** the offset of the requested map entry.
+**
+** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
+** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
+** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
+** this test.
+*/
+#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
+#define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1))
+#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
+
+/*
+** The pointer map is a lookup table that identifies the parent page for
+** each child page in the database file.  The parent page is the page that
+** contains a pointer to the child.  Every page in the database contains
+** 0 or 1 parent pages.  (In this context 'database page' refers
+** to any page that is not part of the pointer map itself.)  Each pointer map
+** entry consists of a single byte 'type' and a 4 byte parent page number.
+** The PTRMAP_XXX identifiers below are the valid types.
+**
+** The purpose of the pointer map is to facility moving pages from one
+** position in the file to another as part of autovacuum.  When a page
+** is moved, the pointer in its parent must be updated to point to the
+** new location.  The pointer map is used to locate the parent page quickly.
+**
+** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
+**                  used in this case.
+**
+** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number 
+**                  is not used in this case.
+**
+** PTRMAP_OVERFLOW1: The database page is the first page in a list of 
+**                   overflow pages. The page number identifies the page that
+**                   contains the cell with a pointer to this overflow page.
+**
+** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
+**                   overflow pages. The page-number identifies the previous
+**                   page in the overflow page list.
+**
+** PTRMAP_BTREE: The database page is a non-root btree page. The page number
+**               identifies the parent page in the btree.
+*/
+#define PTRMAP_ROOTPAGE 1
+#define PTRMAP_FREEPAGE 2
+#define PTRMAP_OVERFLOW1 3
+#define PTRMAP_OVERFLOW2 4
+#define PTRMAP_BTREE 5
+
+/* A bunch of assert() statements to check the transaction state variables
+** of handle p (type Btree*) are internally consistent.
+*/
+#define btreeIntegrity(p) \
+  assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
+  assert( p->pBt->inTransaction>=p->inTrans ); 
+
+
+/*
+** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
+** if the database supports auto-vacuum or not. Because it is used
+** within an expression that is an argument to another macro 
+** (sqliteMallocRaw), it is not possible to use conditional compilation.
+** So, this macro is defined instead.
+*/
+#ifndef SQLITE_OMIT_AUTOVACUUM
+#define ISAUTOVACUUM(pBt) (pBt->autoVacuum)
+#else
+#define ISAUTOVACUUM(pBt) 0
+#endif
+
+
+/*
+** This structure is passed around through all the PRAGMA integrity_check
+** checking routines in order to keep track of some global state information.
+**
+** The aRef[] array is allocated so that there is 1 bit for each page in
+** the database. As the integrity-check proceeds, for each page used in
+** the database the corresponding bit is set. This allows integrity-check to 
+** detect pages that are used twice and orphaned pages (both of which 
+** indicate corruption).
+*/
+typedef struct IntegrityCk IntegrityCk;
+struct IntegrityCk {
+  BtShared *pBt;    /* The tree being checked out */
+  Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */
+  u8 *aPgRef;       /* 1 bit per page in the db (see above) */
+  Pgno nCkPage;     /* Pages in the database.  0 for partial check */
+  int mxErr;        /* Stop accumulating errors when this reaches zero */
+  int nErr;         /* Number of messages written to zErrMsg so far */
+  int rc;           /* SQLITE_OK, SQLITE_NOMEM, or SQLITE_INTERRUPT */
+  u32 nStep;        /* Number of steps into the integrity_check process */
+  const char *zPfx; /* Error message prefix */
+  Pgno v0;          /* Value for first %u substitution in zPfx (root page) */
+  Pgno v1;          /* Value for second %u substitution in zPfx (current pg) */
+  int v2;           /* Value for third %d substitution in zPfx */
+  StrAccum errMsg;  /* Accumulate the error message text here */
+  u32 *heap;        /* Min-heap used for analyzing cell coverage */
+  sqlite3 *db;      /* Database connection running the check */
+};
+
+/*
+** Routines to read or write a two- and four-byte big-endian integer values.
+*/
+#define get2byte(x)   ((x)[0]<<8 | (x)[1])
+#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
+#define get4byte sqlite3Get4byte
+#define put4byte sqlite3Put4byte
+
+/*
+** get2byteAligned(), unlike get2byte(), requires that its argument point to a
+** two-byte aligned address.  get2byteAligned() is only used for accessing the
+** cell addresses in a btree header.
+*/
+#if SQLITE_BYTEORDER==4321
+# define get2byteAligned(x)  (*(u16*)(x))
+#elif SQLITE_BYTEORDER==1234 && GCC_VERSION>=4008000
+# define get2byteAligned(x)  __builtin_bswap16(*(u16*)(x))
+#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+# define get2byteAligned(x)  _byteswap_ushort(*(u16*)(x))
+#else
+# define get2byteAligned(x)  ((x)[0]<<8 | (x)[1])
+#endif
diff --git a/src/build.c b/src/build.c
new file mode 100644
index 0000000..a2553da
--- /dev/null
+++ b/src/build.c
@@ -0,0 +1,5703 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the SQLite parser
+** when syntax rules are reduced.  The routines in this file handle the
+** following kinds of SQL syntax:
+**
+**     CREATE TABLE
+**     DROP TABLE
+**     CREATE INDEX
+**     DROP INDEX
+**     creating ID lists
+**     BEGIN TRANSACTION
+**     COMMIT
+**     ROLLBACK
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** The TableLock structure is only used by the sqlite3TableLock() and
+** codeTableLocks() functions.
+*/
+struct TableLock {
+  int iDb;               /* The database containing the table to be locked */
+  Pgno iTab;             /* The root page of the table to be locked */
+  u8 isWriteLock;        /* True for write lock.  False for a read lock */
+  const char *zLockName; /* Name of the table */
+};
+
+/*
+** Record the fact that we want to lock a table at run-time. 
+**
+** The table to be locked has root page iTab and is found in database iDb.
+** A read or a write lock can be taken depending on isWritelock.
+**
+** This routine just records the fact that the lock is desired.  The
+** code to make the lock occur is generated by a later call to
+** codeTableLocks() which occurs during sqlite3FinishCoding().
+*/
+static SQLITE_NOINLINE void lockTable(
+  Parse *pParse,     /* Parsing context */
+  int iDb,           /* Index of the database containing the table to lock */
+  Pgno iTab,         /* Root page number of the table to be locked */
+  u8 isWriteLock,    /* True for a write lock */
+  const char *zName  /* Name of the table to be locked */
+){
+  Parse *pToplevel;
+  int i;
+  int nBytes;
+  TableLock *p;
+  assert( iDb>=0 );
+
+  pToplevel = sqlite3ParseToplevel(pParse);
+  for(i=0; i<pToplevel->nTableLock; i++){
+    p = &pToplevel->aTableLock[i];
+    if( p->iDb==iDb && p->iTab==iTab ){
+      p->isWriteLock = (p->isWriteLock || isWriteLock);
+      return;
+    }
+  }
+
+  nBytes = sizeof(TableLock) * (pToplevel->nTableLock+1);
+  pToplevel->aTableLock =
+      sqlite3DbReallocOrFree(pToplevel->db, pToplevel->aTableLock, nBytes);
+  if( pToplevel->aTableLock ){
+    p = &pToplevel->aTableLock[pToplevel->nTableLock++];
+    p->iDb = iDb;
+    p->iTab = iTab;
+    p->isWriteLock = isWriteLock;
+    p->zLockName = zName;
+  }else{
+    pToplevel->nTableLock = 0;
+    sqlite3OomFault(pToplevel->db);
+  }
+}
+void sqlite3TableLock(
+  Parse *pParse,     /* Parsing context */
+  int iDb,           /* Index of the database containing the table to lock */
+  Pgno iTab,         /* Root page number of the table to be locked */
+  u8 isWriteLock,    /* True for a write lock */
+  const char *zName  /* Name of the table to be locked */
+){
+  if( iDb==1 ) return;
+  if( !sqlite3BtreeSharable(pParse->db->aDb[iDb].pBt) ) return;
+  lockTable(pParse, iDb, iTab, isWriteLock, zName);
+}
+
+/*
+** Code an OP_TableLock instruction for each table locked by the
+** statement (configured by calls to sqlite3TableLock()).
+*/
+static void codeTableLocks(Parse *pParse){
+  int i;
+  Vdbe *pVdbe = pParse->pVdbe;
+  assert( pVdbe!=0 );
+
+  for(i=0; i<pParse->nTableLock; i++){
+    TableLock *p = &pParse->aTableLock[i];
+    int p1 = p->iDb;
+    sqlite3VdbeAddOp4(pVdbe, OP_TableLock, p1, p->iTab, p->isWriteLock,
+                      p->zLockName, P4_STATIC);
+  }
+}
+#else
+  #define codeTableLocks(x)
+#endif
+
+/*
+** Return TRUE if the given yDbMask object is empty - if it contains no
+** 1 bits.  This routine is used by the DbMaskAllZero() and DbMaskNotZero()
+** macros when SQLITE_MAX_ATTACHED is greater than 30.
+*/
+#if SQLITE_MAX_ATTACHED>30
+int sqlite3DbMaskAllZero(yDbMask m){
+  int i;
+  for(i=0; i<sizeof(yDbMask); i++) if( m[i] ) return 0;
+  return 1;
+}
+#endif
+
+/*
+** This routine is called after a single SQL statement has been
+** parsed and a VDBE program to execute that statement has been
+** prepared.  This routine puts the finishing touches on the
+** VDBE program and resets the pParse structure for the next
+** parse.
+**
+** Note that if an error occurred, it might be the case that
+** no VDBE code was generated.
+*/
+void sqlite3FinishCoding(Parse *pParse){
+  sqlite3 *db;
+  Vdbe *v;
+  int iDb, i;
+
+  assert( pParse->pToplevel==0 );
+  db = pParse->db;
+  assert( db->pParse==pParse );
+  if( pParse->nested ) return;
+  if( pParse->nErr ){
+    if( db->mallocFailed ) pParse->rc = SQLITE_NOMEM;
+    return;
+  }
+  assert( db->mallocFailed==0 );
+
+  /* Begin by generating some termination code at the end of the
+  ** vdbe program
+  */
+  v = pParse->pVdbe;
+  if( v==0 ){
+    if( db->init.busy ){
+      pParse->rc = SQLITE_DONE;
+      return;
+    }
+    v = sqlite3GetVdbe(pParse);
+    if( v==0 ) pParse->rc = SQLITE_ERROR;
+  }
+  assert( !pParse->isMultiWrite
+       || sqlite3VdbeAssertMayAbort(v, pParse->mayAbort));
+  if( v ){
+    if( pParse->bReturning ){
+      Returning *pReturning = pParse->u1.pReturning;
+      int addrRewind;
+      int reg;
+
+      if( pReturning->nRetCol ){
+        sqlite3VdbeAddOp0(v, OP_FkCheck);
+        addrRewind =
+           sqlite3VdbeAddOp1(v, OP_Rewind, pReturning->iRetCur);
+        VdbeCoverage(v);
+        reg = pReturning->iRetReg;
+        for(i=0; i<pReturning->nRetCol; i++){
+          sqlite3VdbeAddOp3(v, OP_Column, pReturning->iRetCur, i, reg+i);
+        }
+        sqlite3VdbeAddOp2(v, OP_ResultRow, reg, i);
+        sqlite3VdbeAddOp2(v, OP_Next, pReturning->iRetCur, addrRewind+1);
+        VdbeCoverage(v);
+        sqlite3VdbeJumpHere(v, addrRewind);
+      }
+    }
+    sqlite3VdbeAddOp0(v, OP_Halt);
+
+#if SQLITE_USER_AUTHENTICATION
+    if( pParse->nTableLock>0 && db->init.busy==0 ){
+      sqlite3UserAuthInit(db);
+      if( db->auth.authLevel<UAUTH_User ){
+        sqlite3ErrorMsg(pParse, "user not authenticated");
+        pParse->rc = SQLITE_AUTH_USER;
+        return;
+      }
+    }
+#endif
+
+    /* The cookie mask contains one bit for each database file open.
+    ** (Bit 0 is for main, bit 1 is for temp, and so forth.)  Bits are
+    ** set for each database that is used.  Generate code to start a
+    ** transaction on each used database and to verify the schema cookie
+    ** on each used database.
+    */
+    assert( pParse->nErr>0 || sqlite3VdbeGetOp(v, 0)->opcode==OP_Init );
+    sqlite3VdbeJumpHere(v, 0);
+    assert( db->nDb>0 );
+    iDb = 0;
+    do{
+      Schema *pSchema;
+      if( DbMaskTest(pParse->cookieMask, iDb)==0 ) continue;
+      sqlite3VdbeUsesBtree(v, iDb);
+      pSchema = db->aDb[iDb].pSchema;
+      sqlite3VdbeAddOp4Int(v,
+        OP_Transaction,                    /* Opcode */
+        iDb,                               /* P1 */
+        DbMaskTest(pParse->writeMask,iDb), /* P2 */
+        pSchema->schema_cookie,            /* P3 */
+        pSchema->iGeneration               /* P4 */
+      );
+      if( db->init.busy==0 ) sqlite3VdbeChangeP5(v, 1);
+      VdbeComment((v,
+            "usesStmtJournal=%d", pParse->mayAbort && pParse->isMultiWrite));
+    }while( ++iDb<db->nDb );
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    for(i=0; i<pParse->nVtabLock; i++){
+      char *vtab = (char *)sqlite3GetVTable(db, pParse->apVtabLock[i]);
+      sqlite3VdbeAddOp4(v, OP_VBegin, 0, 0, 0, vtab, P4_VTAB);
+    }
+    pParse->nVtabLock = 0;
+#endif
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+    /* Once all the cookies have been verified and transactions opened,
+    ** obtain the required table-locks. This is a no-op unless the
+    ** shared-cache feature is enabled.
+    */
+    if( pParse->nTableLock ) codeTableLocks(pParse);
+#endif
+
+    /* Initialize any AUTOINCREMENT data structures required.
+    */
+    if( pParse->pAinc ) sqlite3AutoincrementBegin(pParse);
+
+    /* Code constant expressions that were factored out of inner loops. 
+    */
+    if( pParse->pConstExpr ){
+      ExprList *pEL = pParse->pConstExpr;
+      pParse->okConstFactor = 0;
+      for(i=0; i<pEL->nExpr; i++){
+        assert( pEL->a[i].u.iConstExprReg>0 );
+        sqlite3ExprCode(pParse, pEL->a[i].pExpr, pEL->a[i].u.iConstExprReg);
+      }
+    }
+
+    if( pParse->bReturning ){
+      Returning *pRet = pParse->u1.pReturning;
+      if( pRet->nRetCol ){
+        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pRet->iRetCur, pRet->nRetCol);
+      }
+    }
+
+    /* Finally, jump back to the beginning of the executable code. */
+    sqlite3VdbeGoto(v, 1);
+  }
+
+  /* Get the VDBE program ready for execution
+  */
+  assert( v!=0 || pParse->nErr );
+  assert( db->mallocFailed==0 || pParse->nErr );
+  if( pParse->nErr==0 ){
+    /* A minimum of one cursor is required if autoincrement is used
+    *  See ticket [a696379c1f08866] */
+    assert( pParse->pAinc==0 || pParse->nTab>0 );
+    sqlite3VdbeMakeReady(v, pParse);
+    pParse->rc = SQLITE_DONE;
+  }else{
+    pParse->rc = SQLITE_ERROR;
+  }
+}
+
+/*
+** Run the parser and code generator recursively in order to generate
+** code for the SQL statement given onto the end of the pParse context
+** currently under construction.  Notes:
+**
+**   *  The final OP_Halt is not appended and other initialization
+**      and finalization steps are omitted because those are handling by the
+**      outermost parser.
+**
+**   *  Built-in SQL functions always take precedence over application-defined
+**      SQL functions.  In other words, it is not possible to override a
+**      built-in function.
+*/
+void sqlite3NestedParse(Parse *pParse, const char *zFormat, ...){
+  va_list ap;
+  char *zSql;
+  sqlite3 *db = pParse->db;
+  u32 savedDbFlags = db->mDbFlags;
+  char saveBuf[PARSE_TAIL_SZ];
+
+  if( pParse->nErr ) return;
+  if( pParse->eParseMode ) return;
+  assert( pParse->nested<10 );  /* Nesting should only be of limited depth */
+  va_start(ap, zFormat);
+  zSql = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  if( zSql==0 ){
+    /* This can result either from an OOM or because the formatted string
+    ** exceeds SQLITE_LIMIT_LENGTH.  In the latter case, we need to set
+    ** an error */
+    if( !db->mallocFailed ) pParse->rc = SQLITE_TOOBIG;
+    pParse->nErr++;
+    return;
+  }
+  pParse->nested++;
+  memcpy(saveBuf, PARSE_TAIL(pParse), PARSE_TAIL_SZ);
+  memset(PARSE_TAIL(pParse), 0, PARSE_TAIL_SZ);
+  db->mDbFlags |= DBFLAG_PreferBuiltin;
+  sqlite3RunParser(pParse, zSql);
+  db->mDbFlags = savedDbFlags;
+  sqlite3DbFree(db, zSql);
+  memcpy(PARSE_TAIL(pParse), saveBuf, PARSE_TAIL_SZ);
+  pParse->nested--;
+}
+
+#if SQLITE_USER_AUTHENTICATION
+/*
+** Return TRUE if zTable is the name of the system table that stores the
+** list of users and their access credentials.
+*/
+int sqlite3UserAuthTable(const char *zTable){
+  return sqlite3_stricmp(zTable, "sqlite_user")==0;
+}
+#endif
+
+/*
+** Locate the in-memory structure that describes a particular database
+** table given the name of that table and (optionally) the name of the
+** database containing the table.  Return NULL if not found.
+**
+** If zDatabase is 0, all databases are searched for the table and the
+** first matching table is returned.  (No checking for duplicate table
+** names is done.)  The search order is TEMP first, then MAIN, then any
+** auxiliary databases added using the ATTACH command.
+**
+** See also sqlite3LocateTable().
+*/
+Table *sqlite3FindTable(sqlite3 *db, const char *zName, const char *zDatabase){
+  Table *p = 0;
+  int i;
+
+  /* All mutexes are required for schema access.  Make sure we hold them. */
+  assert( zDatabase!=0 || sqlite3BtreeHoldsAllMutexes(db) );
+#if SQLITE_USER_AUTHENTICATION
+  /* Only the admin user is allowed to know that the sqlite_user table
+  ** exists */
+  if( db->auth.authLevel<UAUTH_Admin && sqlite3UserAuthTable(zName)!=0 ){
+    return 0;
+  }
+#endif
+  if( zDatabase ){
+    for(i=0; i<db->nDb; i++){
+      if( sqlite3StrICmp(zDatabase, db->aDb[i].zDbSName)==0 ) break;
+    }
+    if( i>=db->nDb ){
+      /* No match against the official names.  But always match "main"
+      ** to schema 0 as a legacy fallback. */
+      if( sqlite3StrICmp(zDatabase,"main")==0 ){
+        i = 0;
+      }else{
+        return 0;
+      }
+    }
+    p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
+    if( p==0 && sqlite3StrNICmp(zName, "sqlite_", 7)==0 ){
+      if( i==1 ){
+        if( sqlite3StrICmp(zName+7, &PREFERRED_TEMP_SCHEMA_TABLE[7])==0
+         || sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0
+         || sqlite3StrICmp(zName+7, &LEGACY_SCHEMA_TABLE[7])==0
+        ){
+          p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash,
+                              LEGACY_TEMP_SCHEMA_TABLE);
+        }
+      }else{
+        if( sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0 ){
+          p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash,
+                              LEGACY_SCHEMA_TABLE);
+        }
+      }
+    }
+  }else{
+    /* Match against TEMP first */
+    p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash, zName);
+    if( p ) return p;
+    /* The main database is second */
+    p = sqlite3HashFind(&db->aDb[0].pSchema->tblHash, zName);
+    if( p ) return p;
+    /* Attached databases are in order of attachment */
+    for(i=2; i<db->nDb; i++){
+      assert( sqlite3SchemaMutexHeld(db, i, 0) );
+      p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
+      if( p ) break;
+    }
+    if( p==0 && sqlite3StrNICmp(zName, "sqlite_", 7)==0 ){
+      if( sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0 ){
+        p = sqlite3HashFind(&db->aDb[0].pSchema->tblHash, LEGACY_SCHEMA_TABLE);
+      }else if( sqlite3StrICmp(zName+7, &PREFERRED_TEMP_SCHEMA_TABLE[7])==0 ){
+        p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash,
+                            LEGACY_TEMP_SCHEMA_TABLE);
+      }
+    }
+  }
+  return p;
+}
+
+/*
+** Locate the in-memory structure that describes a particular database
+** table given the name of that table and (optionally) the name of the
+** database containing the table.  Return NULL if not found.  Also leave an
+** error message in pParse->zErrMsg.
+**
+** The difference between this routine and sqlite3FindTable() is that this
+** routine leaves an error message in pParse->zErrMsg where
+** sqlite3FindTable() does not.
+*/
+Table *sqlite3LocateTable(
+  Parse *pParse,         /* context in which to report errors */
+  u32 flags,             /* LOCATE_VIEW or LOCATE_NOERR */
+  const char *zName,     /* Name of the table we are looking for */
+  const char *zDbase     /* Name of the database.  Might be NULL */
+){
+  Table *p;
+  sqlite3 *db = pParse->db;
+
+  /* Read the database schema. If an error occurs, leave an error message
+  ** and code in pParse and return NULL. */
+  if( (db->mDbFlags & DBFLAG_SchemaKnownOk)==0
+   && SQLITE_OK!=sqlite3ReadSchema(pParse)
+  ){
+    return 0;
+  }
+
+  p = sqlite3FindTable(db, zName, zDbase);
+  if( p==0 ){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    /* If zName is the not the name of a table in the schema created using
+    ** CREATE, then check to see if it is the name of an virtual table that
+    ** can be an eponymous virtual table. */
+    if( (pParse->prepFlags & SQLITE_PREPARE_NO_VTAB)==0 && db->init.busy==0 ){
+      Module *pMod = (Module*)sqlite3HashFind(&db->aModule, zName);
+      if( pMod==0 && sqlite3_strnicmp(zName, "pragma_", 7)==0 ){
+        pMod = sqlite3PragmaVtabRegister(db, zName);
+      }
+      if( pMod && sqlite3VtabEponymousTableInit(pParse, pMod) ){
+        testcase( pMod->pEpoTab==0 );
+        return pMod->pEpoTab;
+      }
+    }
+#endif
+    if( flags & LOCATE_NOERR ) return 0;
+    pParse->checkSchema = 1;
+  }else if( IsVirtual(p) && (pParse->prepFlags & SQLITE_PREPARE_NO_VTAB)!=0 ){
+    p = 0;
+  }
+
+  if( p==0 ){
+    const char *zMsg = flags & LOCATE_VIEW ? "no such view" : "no such table";
+    if( zDbase ){
+      sqlite3ErrorMsg(pParse, "%s: %s.%s", zMsg, zDbase, zName);
+    }else{
+      sqlite3ErrorMsg(pParse, "%s: %s", zMsg, zName);
+    }
+  }else{
+    assert( HasRowid(p) || p->iPKey<0 );
+  }
+
+  return p;
+}
+
+/*
+** Locate the table identified by *p.
+**
+** This is a wrapper around sqlite3LocateTable(). The difference between
+** sqlite3LocateTable() and this function is that this function restricts
+** the search to schema (p->pSchema) if it is not NULL. p->pSchema may be
+** non-NULL if it is part of a view or trigger program definition. See
+** sqlite3FixSrcList() for details.
+*/
+Table *sqlite3LocateTableItem(
+  Parse *pParse,
+  u32 flags,
+  SrcItem *p
+){
+  const char *zDb;
+  assert( p->pSchema==0 || p->zDatabase==0 );
+  if( p->pSchema ){
+    int iDb = sqlite3SchemaToIndex(pParse->db, p->pSchema);
+    zDb = pParse->db->aDb[iDb].zDbSName;
+  }else{
+    zDb = p->zDatabase;
+  }
+  return sqlite3LocateTable(pParse, flags, p->zName, zDb);
+}
+
+/*
+** Return the preferred table name for system tables.  Translate legacy
+** names into the new preferred names, as appropriate.
+*/
+const char *sqlite3PreferredTableName(const char *zName){
+  if( sqlite3StrNICmp(zName, "sqlite_", 7)==0 ){
+    if( sqlite3StrICmp(zName+7, &LEGACY_SCHEMA_TABLE[7])==0 ){
+      return PREFERRED_SCHEMA_TABLE;
+    }
+    if( sqlite3StrICmp(zName+7, &LEGACY_TEMP_SCHEMA_TABLE[7])==0 ){
+      return PREFERRED_TEMP_SCHEMA_TABLE;
+    }
+  }
+  return zName;
+}
+
+/*
+** Locate the in-memory structure that describes
+** a particular index given the name of that index
+** and the name of the database that contains the index.
+** Return NULL if not found.
+**
+** If zDatabase is 0, all databases are searched for the
+** table and the first matching index is returned.  (No checking
+** for duplicate index names is done.)  The search order is
+** TEMP first, then MAIN, then any auxiliary databases added
+** using the ATTACH command.
+*/
+Index *sqlite3FindIndex(sqlite3 *db, const char *zName, const char *zDb){
+  Index *p = 0;
+  int i;
+  /* All mutexes are required for schema access.  Make sure we hold them. */
+  assert( zDb!=0 || sqlite3BtreeHoldsAllMutexes(db) );
+  for(i=OMIT_TEMPDB; i<db->nDb; i++){
+    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
+    Schema *pSchema = db->aDb[j].pSchema;
+    assert( pSchema );
+    if( zDb && sqlite3DbIsNamed(db, j, zDb)==0 ) continue;
+    assert( sqlite3SchemaMutexHeld(db, j, 0) );
+    p = sqlite3HashFind(&pSchema->idxHash, zName);
+    if( p ) break;
+  }
+  return p;
+}
+
+/*
+** Reclaim the memory used by an index
+*/
+void sqlite3FreeIndex(sqlite3 *db, Index *p){
+#ifndef SQLITE_OMIT_ANALYZE
+  sqlite3DeleteIndexSamples(db, p);
+#endif
+  sqlite3ExprDelete(db, p->pPartIdxWhere);
+  sqlite3ExprListDelete(db, p->aColExpr);
+  sqlite3DbFree(db, p->zColAff);
+  if( p->isResized ) sqlite3DbFree(db, (void *)p->azColl);
+#ifdef SQLITE_ENABLE_STAT4
+  sqlite3_free(p->aiRowEst);
+#endif
+  sqlite3DbFree(db, p);
+}
+
+/*
+** For the index called zIdxName which is found in the database iDb,
+** unlike that index from its Table then remove the index from
+** the index hash table and free all memory structures associated
+** with the index.
+*/
+void sqlite3UnlinkAndDeleteIndex(sqlite3 *db, int iDb, const char *zIdxName){
+  Index *pIndex;
+  Hash *pHash;
+
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  pHash = &db->aDb[iDb].pSchema->idxHash;
+  pIndex = sqlite3HashInsert(pHash, zIdxName, 0);
+  if( ALWAYS(pIndex) ){
+    if( pIndex->pTable->pIndex==pIndex ){
+      pIndex->pTable->pIndex = pIndex->pNext;
+    }else{
+      Index *p;
+      /* Justification of ALWAYS();  The index must be on the list of
+      ** indices. */
+      p = pIndex->pTable->pIndex;
+      while( ALWAYS(p) && p->pNext!=pIndex ){ p = p->pNext; }
+      if( ALWAYS(p && p->pNext==pIndex) ){
+        p->pNext = pIndex->pNext;
+      }
+    }
+    sqlite3FreeIndex(db, pIndex);
+  }
+  db->mDbFlags |= DBFLAG_SchemaChange;
+}
+
+/*
+** Look through the list of open database files in db->aDb[] and if
+** any have been closed, remove them from the list.  Reallocate the
+** db->aDb[] structure to a smaller size, if possible.
+**
+** Entry 0 (the "main" database) and entry 1 (the "temp" database)
+** are never candidates for being collapsed.
+*/
+void sqlite3CollapseDatabaseArray(sqlite3 *db){
+  int i, j;
+  for(i=j=2; i<db->nDb; i++){
+    struct Db *pDb = &db->aDb[i];
+    if( pDb->pBt==0 ){
+      sqlite3DbFree(db, pDb->zDbSName);
+      pDb->zDbSName = 0;
+      continue;
+    }
+    if( j<i ){
+      db->aDb[j] = db->aDb[i];
+    }
+    j++;
+  }
+  db->nDb = j;
+  if( db->nDb<=2 && db->aDb!=db->aDbStatic ){
+    memcpy(db->aDbStatic, db->aDb, 2*sizeof(db->aDb[0]));
+    sqlite3DbFree(db, db->aDb);
+    db->aDb = db->aDbStatic;
+  }
+}
+
+/*
+** Reset the schema for the database at index iDb.  Also reset the
+** TEMP schema.  The reset is deferred if db->nSchemaLock is not zero.
+** Deferred resets may be run by calling with iDb<0.
+*/
+void sqlite3ResetOneSchema(sqlite3 *db, int iDb){
+  int i;
+  assert( iDb<db->nDb );
+
+  if( iDb>=0 ){
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    DbSetProperty(db, iDb, DB_ResetWanted);
+    DbSetProperty(db, 1, DB_ResetWanted);
+    db->mDbFlags &= ~DBFLAG_SchemaKnownOk;
+  }
+
+  if( db->nSchemaLock==0 ){
+    for(i=0; i<db->nDb; i++){
+      if( DbHasProperty(db, i, DB_ResetWanted) ){
+        sqlite3SchemaClear(db->aDb[i].pSchema);
+      }
+    }
+  }
+}
+
+/*
+** Erase all schema information from all attached databases (including
+** "main" and "temp") for a single database connection.
+*/
+void sqlite3ResetAllSchemasOfConnection(sqlite3 *db){
+  int i;
+  sqlite3BtreeEnterAll(db);
+  for(i=0; i<db->nDb; i++){
+    Db *pDb = &db->aDb[i];
+    if( pDb->pSchema ){
+      if( db->nSchemaLock==0 ){
+        sqlite3SchemaClear(pDb->pSchema);
+      }else{
+        DbSetProperty(db, i, DB_ResetWanted);
+      }
+    }
+  }
+  db->mDbFlags &= ~(DBFLAG_SchemaChange|DBFLAG_SchemaKnownOk);
+  sqlite3VtabUnlockList(db);
+  sqlite3BtreeLeaveAll(db);
+  if( db->nSchemaLock==0 ){
+    sqlite3CollapseDatabaseArray(db);
+  }
+}
+
+/*
+** This routine is called when a commit occurs.
+*/
+void sqlite3CommitInternalChanges(sqlite3 *db){
+  db->mDbFlags &= ~DBFLAG_SchemaChange;
+}
+
+/*
+** Set the expression associated with a column.  This is usually
+** the DEFAULT value, but might also be the expression that computes
+** the value for a generated column.
+*/
+void sqlite3ColumnSetExpr(
+  Parse *pParse,    /* Parsing context */
+  Table *pTab,      /* The table containing the column */
+  Column *pCol,     /* The column to receive the new DEFAULT expression */
+  Expr *pExpr       /* The new default expression */
+){
+  ExprList *pList;
+  assert( IsOrdinaryTable(pTab) );
+  pList = pTab->u.tab.pDfltList;
+  if( pCol->iDflt==0
+   || NEVER(pList==0)
+   || NEVER(pList->nExpr<pCol->iDflt)
+  ){
+    pCol->iDflt = pList==0 ? 1 : pList->nExpr+1;
+    pTab->u.tab.pDfltList = sqlite3ExprListAppend(pParse, pList, pExpr);
+  }else{
+    sqlite3ExprDelete(pParse->db, pList->a[pCol->iDflt-1].pExpr);
+    pList->a[pCol->iDflt-1].pExpr = pExpr;
+  }
+}
+
+/*
+** Return the expression associated with a column.  The expression might be
+** the DEFAULT clause or the AS clause of a generated column.
+** Return NULL if the column has no associated expression.
+*/
+Expr *sqlite3ColumnExpr(Table *pTab, Column *pCol){
+  if( pCol->iDflt==0 ) return 0;
+  if( !IsOrdinaryTable(pTab) ) return 0;
+  if( NEVER(pTab->u.tab.pDfltList==0) ) return 0;
+  if( NEVER(pTab->u.tab.pDfltList->nExpr<pCol->iDflt) ) return 0;
+  return pTab->u.tab.pDfltList->a[pCol->iDflt-1].pExpr;
+}
+
+/*
+** Set the collating sequence name for a column.
+*/
+void sqlite3ColumnSetColl(
+  sqlite3 *db,
+  Column *pCol,
+  const char *zColl
+){
+  i64 nColl;
+  i64 n;
+  char *zNew;
+  assert( zColl!=0 );
+  n = sqlite3Strlen30(pCol->zCnName) + 1;
+  if( pCol->colFlags & COLFLAG_HASTYPE ){
+    n += sqlite3Strlen30(pCol->zCnName+n) + 1;
+  }
+  nColl = sqlite3Strlen30(zColl) + 1;
+  zNew = sqlite3DbRealloc(db, pCol->zCnName, nColl+n);
+  if( zNew ){
+    pCol->zCnName = zNew;
+    memcpy(pCol->zCnName + n, zColl, nColl);
+    pCol->colFlags |= COLFLAG_HASCOLL;
+  }
+}
+
+/*
+** Return the collating sequence name for a column
+*/
+const char *sqlite3ColumnColl(Column *pCol){
+  const char *z;
+  if( (pCol->colFlags & COLFLAG_HASCOLL)==0 ) return 0;
+  z = pCol->zCnName;
+  while( *z ){ z++; }
+  if( pCol->colFlags & COLFLAG_HASTYPE ){
+    do{ z++; }while( *z );
+  }
+  return z+1;
+}
+
+/*
+** Delete memory allocated for the column names of a table or view (the
+** Table.aCol[] array).
+*/
+void sqlite3DeleteColumnNames(sqlite3 *db, Table *pTable){
+  int i;
+  Column *pCol;
+  assert( pTable!=0 );
+  assert( db!=0 );
+  if( (pCol = pTable->aCol)!=0 ){
+    for(i=0; i<pTable->nCol; i++, pCol++){
+      assert( pCol->zCnName==0 || pCol->hName==sqlite3StrIHash(pCol->zCnName) );
+      sqlite3DbFree(db, pCol->zCnName);
+    }
+    sqlite3DbNNFreeNN(db, pTable->aCol);
+    if( IsOrdinaryTable(pTable) ){
+      sqlite3ExprListDelete(db, pTable->u.tab.pDfltList);
+    }
+    if( db->pnBytesFreed==0 ){
+      pTable->aCol = 0;
+      pTable->nCol = 0;
+      if( IsOrdinaryTable(pTable) ){
+        pTable->u.tab.pDfltList = 0;
+      }
+    }
+  }
+}
+
+/*
+** Remove the memory data structures associated with the given
+** Table.  No changes are made to disk by this routine.
+**
+** This routine just deletes the data structure.  It does not unlink
+** the table data structure from the hash table.  But it does destroy
+** memory structures of the indices and foreign keys associated with
+** the table.
+**
+** The db parameter is optional.  It is needed if the Table object
+** contains lookaside memory.  (Table objects in the schema do not use
+** lookaside memory, but some ephemeral Table objects do.)  Or the
+** db parameter can be used with db->pnBytesFreed to measure the memory
+** used by the Table object.
+*/
+static void SQLITE_NOINLINE deleteTable(sqlite3 *db, Table *pTable){
+  Index *pIndex, *pNext;
+
+#ifdef SQLITE_DEBUG
+  /* Record the number of outstanding lookaside allocations in schema Tables
+  ** prior to doing any free() operations. Since schema Tables do not use
+  ** lookaside, this number should not change.
+  **
+  ** If malloc has already failed, it may be that it failed while allocating
+  ** a Table object that was going to be marked ephemeral. So do not check
+  ** that no lookaside memory is used in this case either. */
+  int nLookaside = 0;
+  assert( db!=0 );
+  if( !db->mallocFailed && (pTable->tabFlags & TF_Ephemeral)==0 ){
+    nLookaside = sqlite3LookasideUsed(db, 0);
+  }
+#endif
+
+  /* Delete all indices associated with this table. */
+  for(pIndex = pTable->pIndex; pIndex; pIndex=pNext){
+    pNext = pIndex->pNext;
+    assert( pIndex->pSchema==pTable->pSchema
+         || (IsVirtual(pTable) && pIndex->idxType!=SQLITE_IDXTYPE_APPDEF) );
+    if( db->pnBytesFreed==0 && !IsVirtual(pTable) ){
+      char *zName = pIndex->zName;
+      TESTONLY ( Index *pOld = ) sqlite3HashInsert(
+         &pIndex->pSchema->idxHash, zName, 0
+      );
+      assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pIndex->pSchema) );
+      assert( pOld==pIndex || pOld==0 );
+    }
+    sqlite3FreeIndex(db, pIndex);
+  }
+
+  if( IsOrdinaryTable(pTable) ){
+    sqlite3FkDelete(db, pTable);
+  }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  else if( IsVirtual(pTable) ){
+    sqlite3VtabClear(db, pTable);
+  }
+#endif
+  else{
+    assert( IsView(pTable) );
+    sqlite3SelectDelete(db, pTable->u.view.pSelect);
+  }
+
+  /* Delete the Table structure itself.
+  */
+  sqlite3DeleteColumnNames(db, pTable);
+  sqlite3DbFree(db, pTable->zName);
+  sqlite3DbFree(db, pTable->zColAff);
+  sqlite3ExprListDelete(db, pTable->pCheck);
+  sqlite3DbFree(db, pTable);
+
+  /* Verify that no lookaside memory was used by schema tables */
+  assert( nLookaside==0 || nLookaside==sqlite3LookasideUsed(db,0) );
+}
+void sqlite3DeleteTable(sqlite3 *db, Table *pTable){
+  /* Do not delete the table until the reference count reaches zero. */
+  assert( db!=0 );
+  if( !pTable ) return;
+  if( db->pnBytesFreed==0 && (--pTable->nTabRef)>0 ) return;
+  deleteTable(db, pTable);
+}
+void sqlite3DeleteTableGeneric(sqlite3 *db, void *pTable){
+  sqlite3DeleteTable(db, (Table*)pTable);
+}
+
+
+/*
+** Unlink the given table from the hash tables and the delete the
+** table structure with all its indices and foreign keys.
+*/
+void sqlite3UnlinkAndDeleteTable(sqlite3 *db, int iDb, const char *zTabName){
+  Table *p;
+  Db *pDb;
+
+  assert( db!=0 );
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( zTabName );
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  testcase( zTabName[0]==0 );  /* Zero-length table names are allowed */
+  pDb = &db->aDb[iDb];
+  p = sqlite3HashInsert(&pDb->pSchema->tblHash, zTabName, 0);
+  sqlite3DeleteTable(db, p);
+  db->mDbFlags |= DBFLAG_SchemaChange;
+}
+
+/*
+** Given a token, return a string that consists of the text of that
+** token.  Space to hold the returned string
+** is obtained from sqliteMalloc() and must be freed by the calling
+** function.
+**
+** Any quotation marks (ex:  "name", 'name', [name], or `name`) that
+** surround the body of the token are removed.
+**
+** Tokens are often just pointers into the original SQL text and so
+** are not \000 terminated and are not persistent.  The returned string
+** is \000 terminated and is persistent.
+*/
+char *sqlite3NameFromToken(sqlite3 *db, const Token *pName){
+  char *zName;
+  if( pName ){
+    zName = sqlite3DbStrNDup(db, (const char*)pName->z, pName->n);
+    sqlite3Dequote(zName);
+  }else{
+    zName = 0;
+  }
+  return zName;
+}
+
+/*
+** Open the sqlite_schema table stored in database number iDb for
+** writing. The table is opened using cursor 0.
+*/
+void sqlite3OpenSchemaTable(Parse *p, int iDb){
+  Vdbe *v = sqlite3GetVdbe(p);
+  sqlite3TableLock(p, iDb, SCHEMA_ROOT, 1, LEGACY_SCHEMA_TABLE);
+  sqlite3VdbeAddOp4Int(v, OP_OpenWrite, 0, SCHEMA_ROOT, iDb, 5);
+  if( p->nTab==0 ){
+    p->nTab = 1;
+  }
+}
+
+/*
+** Parameter zName points to a nul-terminated buffer containing the name
+** of a database ("main", "temp" or the name of an attached db). This
+** function returns the index of the named database in db->aDb[], or
+** -1 if the named db cannot be found.
+*/
+int sqlite3FindDbName(sqlite3 *db, const char *zName){
+  int i = -1;         /* Database number */
+  if( zName ){
+    Db *pDb;
+    for(i=(db->nDb-1), pDb=&db->aDb[i]; i>=0; i--, pDb--){
+      if( 0==sqlite3_stricmp(pDb->zDbSName, zName) ) break;
+      /* "main" is always an acceptable alias for the primary database
+      ** even if it has been renamed using SQLITE_DBCONFIG_MAINDBNAME. */
+      if( i==0 && 0==sqlite3_stricmp("main", zName) ) break;
+    }
+  }
+  return i;
+}
+
+/*
+** The token *pName contains the name of a database (either "main" or
+** "temp" or the name of an attached db). This routine returns the
+** index of the named database in db->aDb[], or -1 if the named db
+** does not exist.
+*/
+int sqlite3FindDb(sqlite3 *db, Token *pName){
+  int i;                               /* Database number */
+  char *zName;                         /* Name we are searching for */
+  zName = sqlite3NameFromToken(db, pName);
+  i = sqlite3FindDbName(db, zName);
+  sqlite3DbFree(db, zName);
+  return i;
+}
+
+/* The table or view or trigger name is passed to this routine via tokens
+** pName1 and pName2. If the table name was fully qualified, for example:
+**
+** CREATE TABLE xxx.yyy (...);
+**
+** Then pName1 is set to "xxx" and pName2 "yyy". On the other hand if
+** the table name is not fully qualified, i.e.:
+**
+** CREATE TABLE yyy(...);
+**
+** Then pName1 is set to "yyy" and pName2 is "".
+**
+** This routine sets the *ppUnqual pointer to point at the token (pName1 or
+** pName2) that stores the unqualified table name.  The index of the
+** database "xxx" is returned.
+*/
+int sqlite3TwoPartName(
+  Parse *pParse,      /* Parsing and code generating context */
+  Token *pName1,      /* The "xxx" in the name "xxx.yyy" or "xxx" */
+  Token *pName2,      /* The "yyy" in the name "xxx.yyy" */
+  Token **pUnqual     /* Write the unqualified object name here */
+){
+  int iDb;                    /* Database holding the object */
+  sqlite3 *db = pParse->db;
+
+  assert( pName2!=0 );
+  if( pName2->n>0 ){
+    if( db->init.busy ) {
+      sqlite3ErrorMsg(pParse, "corrupt database");
+      return -1;
+    }
+    *pUnqual = pName2;
+    iDb = sqlite3FindDb(db, pName1);
+    if( iDb<0 ){
+      sqlite3ErrorMsg(pParse, "unknown database %T", pName1);
+      return -1;
+    }
+  }else{
+    assert( db->init.iDb==0 || db->init.busy || IN_SPECIAL_PARSE
+             || (db->mDbFlags & DBFLAG_Vacuum)!=0);
+    iDb = db->init.iDb;
+    *pUnqual = pName1;
+  }
+  return iDb;
+}
+
+/*
+** True if PRAGMA writable_schema is ON
+*/
+int sqlite3WritableSchema(sqlite3 *db){
+  testcase( (db->flags&(SQLITE_WriteSchema|SQLITE_Defensive))==0 );
+  testcase( (db->flags&(SQLITE_WriteSchema|SQLITE_Defensive))==
+               SQLITE_WriteSchema );
+  testcase( (db->flags&(SQLITE_WriteSchema|SQLITE_Defensive))==
+               SQLITE_Defensive );
+  testcase( (db->flags&(SQLITE_WriteSchema|SQLITE_Defensive))==
+               (SQLITE_WriteSchema|SQLITE_Defensive) );
+  return (db->flags&(SQLITE_WriteSchema|SQLITE_Defensive))==SQLITE_WriteSchema;
+}
+
+/*
+** This routine is used to check if the UTF-8 string zName is a legal
+** unqualified name for a new schema object (table, index, view or
+** trigger). All names are legal except those that begin with the string
+** "sqlite_" (in upper, lower or mixed case). This portion of the namespace
+** is reserved for internal use.
+**
+** When parsing the sqlite_schema table, this routine also checks to
+** make sure the "type", "name", and "tbl_name" columns are consistent
+** with the SQL.
+*/
+int sqlite3CheckObjectName(
+  Parse *pParse,            /* Parsing context */
+  const char *zName,        /* Name of the object to check */
+  const char *zType,        /* Type of this object */
+  const char *zTblName      /* Parent table name for triggers and indexes */
+){
+  sqlite3 *db = pParse->db;
+  if( sqlite3WritableSchema(db)
+   || db->init.imposterTable
+   || !sqlite3Config.bExtraSchemaChecks
+  ){
+    /* Skip these error checks for writable_schema=ON */
+    return SQLITE_OK;
+  }
+  if( db->init.busy ){
+    if( sqlite3_stricmp(zType, db->init.azInit[0])
+     || sqlite3_stricmp(zName, db->init.azInit[1])
+     || sqlite3_stricmp(zTblName, db->init.azInit[2])
+    ){
+      sqlite3ErrorMsg(pParse, ""); /* corruptSchema() will supply the error */
+      return SQLITE_ERROR;
+    }
+  }else{
+    if( (pParse->nested==0 && 0==sqlite3StrNICmp(zName, "sqlite_", 7))
+     || (sqlite3ReadOnlyShadowTables(db) && sqlite3ShadowTableName(db, zName))
+    ){
+      sqlite3ErrorMsg(pParse, "object name reserved for internal use: %s",
+                      zName);
+      return SQLITE_ERROR;
+    }
+
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Return the PRIMARY KEY index of a table
+*/
+Index *sqlite3PrimaryKeyIndex(Table *pTab){
+  Index *p;
+  for(p=pTab->pIndex; p && !IsPrimaryKeyIndex(p); p=p->pNext){}
+  return p;
+}
+
+/*
+** Convert an table column number into a index column number.  That is,
+** for the column iCol in the table (as defined by the CREATE TABLE statement)
+** find the (first) offset of that column in index pIdx.  Or return -1
+** if column iCol is not used in index pIdx.
+*/
+i16 sqlite3TableColumnToIndex(Index *pIdx, i16 iCol){
+  int i;
+  for(i=0; i<pIdx->nColumn; i++){
+    if( iCol==pIdx->aiColumn[i] ) return i;
+  }
+  return -1;
+}
+
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+/* Convert a storage column number into a table column number.
+**
+** The storage column number (0,1,2,....) is the index of the value
+** as it appears in the record on disk.  The true column number
+** is the index (0,1,2,...) of the column in the CREATE TABLE statement.
+**
+** The storage column number is less than the table column number if
+** and only there are VIRTUAL columns to the left.
+**
+** If SQLITE_OMIT_GENERATED_COLUMNS, this routine is a no-op macro.
+*/
+i16 sqlite3StorageColumnToTable(Table *pTab, i16 iCol){
+  if( pTab->tabFlags & TF_HasVirtual ){
+    int i;
+    for(i=0; i<=iCol; i++){
+      if( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL ) iCol++;
+    }
+  }
+  return iCol;
+}
+#endif
+
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+/* Convert a table column number into a storage column number.
+**
+** The storage column number (0,1,2,....) is the index of the value
+** as it appears in the record on disk.  Or, if the input column is
+** the N-th virtual column (zero-based) then the storage number is
+** the number of non-virtual columns in the table plus N. 
+**
+** The true column number is the index (0,1,2,...) of the column in
+** the CREATE TABLE statement.
+**
+** If the input column is a VIRTUAL column, then it should not appear
+** in storage.  But the value sometimes is cached in registers that
+** follow the range of registers used to construct storage.  This
+** avoids computing the same VIRTUAL column multiple times, and provides
+** values for use by OP_Param opcodes in triggers.  Hence, if the
+** input column is a VIRTUAL table, put it after all the other columns.
+**
+** In the following, N means "normal column", S means STORED, and
+** V means VIRTUAL.  Suppose the CREATE TABLE has columns like this:
+**
+**        CREATE TABLE ex(N,S,V,N,S,V,N,S,V);
+**                     -- 0 1 2 3 4 5 6 7 8
+**
+** Then the mapping from this function is as follows:
+**
+**    INPUTS:     0 1 2 3 4 5 6 7 8
+**    OUTPUTS:    0 1 6 2 3 7 4 5 8
+**
+** So, in other words, this routine shifts all the virtual columns to
+** the end.
+**
+** If SQLITE_OMIT_GENERATED_COLUMNS then there are no virtual columns and
+** this routine is a no-op macro.  If the pTab does not have any virtual
+** columns, then this routine is no-op that always return iCol.  If iCol
+** is negative (indicating the ROWID column) then this routine return iCol.
+*/
+i16 sqlite3TableColumnToStorage(Table *pTab, i16 iCol){
+  int i;
+  i16 n;
+  assert( iCol<pTab->nCol );
+  if( (pTab->tabFlags & TF_HasVirtual)==0 || iCol<0 ) return iCol;
+  for(i=0, n=0; i<iCol; i++){
+    if( (pTab->aCol[i].colFlags & COLFLAG_VIRTUAL)==0 ) n++;
+  }
+  if( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL ){
+    /* iCol is a virtual column itself */
+    return pTab->nNVCol + i - n;
+  }else{
+    /* iCol is a normal or stored column */
+    return n;
+  }
+}
+#endif
+
+/*
+** Insert a single OP_JournalMode query opcode in order to force the
+** prepared statement to return false for sqlite3_stmt_readonly().  This
+** is used by CREATE TABLE IF NOT EXISTS and similar if the table already
+** exists, so that the prepared statement for CREATE TABLE IF NOT EXISTS
+** will return false for sqlite3_stmt_readonly() even if that statement
+** is a read-only no-op.
+*/
+static void sqlite3ForceNotReadOnly(Parse *pParse){
+  int iReg = ++pParse->nMem;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3VdbeAddOp3(v, OP_JournalMode, 0, iReg, PAGER_JOURNALMODE_QUERY);
+    sqlite3VdbeUsesBtree(v, 0);
+  }
+}
+
+/*
+** Begin constructing a new table representation in memory.  This is
+** the first of several action routines that get called in response
+** to a CREATE TABLE statement.  In particular, this routine is called
+** after seeing tokens "CREATE" and "TABLE" and the table name. The isTemp
+** flag is true if the table should be stored in the auxiliary database
+** file instead of in the main database file.  This is normally the case
+** when the "TEMP" or "TEMPORARY" keyword occurs in between
+** CREATE and TABLE.
+**
+** The new table record is initialized and put in pParse->pNewTable.
+** As more of the CREATE TABLE statement is parsed, additional action
+** routines will be called to add more information to this record.
+** At the end of the CREATE TABLE statement, the sqlite3EndTable() routine
+** is called to complete the construction of the new table record.
+*/
+void sqlite3StartTable(
+  Parse *pParse,   /* Parser context */
+  Token *pName1,   /* First part of the name of the table or view */
+  Token *pName2,   /* Second part of the name of the table or view */
+  int isTemp,      /* True if this is a TEMP table */
+  int isView,      /* True if this is a VIEW */
+  int isVirtual,   /* True if this is a VIRTUAL table */
+  int noErr        /* Do nothing if table already exists */
+){
+  Table *pTable;
+  char *zName = 0; /* The name of the new table */
+  sqlite3 *db = pParse->db;
+  Vdbe *v;
+  int iDb;         /* Database number to create the table in */
+  Token *pName;    /* Unqualified name of the table to create */
+
+  if( db->init.busy && db->init.newTnum==1 ){
+    /* Special case:  Parsing the sqlite_schema or sqlite_temp_schema schema */
+    iDb = db->init.iDb;
+    zName = sqlite3DbStrDup(db, SCHEMA_TABLE(iDb));
+    pName = pName1;
+  }else{
+    /* The common case */
+    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+    if( iDb<0 ) return;
+    if( !OMIT_TEMPDB && isTemp && pName2->n>0 && iDb!=1 ){
+      /* If creating a temp table, the name may not be qualified. Unless
+      ** the database name is "temp" anyway.  */
+      sqlite3ErrorMsg(pParse, "temporary table name must be unqualified");
+      return;
+    }
+    if( !OMIT_TEMPDB && isTemp ) iDb = 1;
+    zName = sqlite3NameFromToken(db, pName);
+    if( IN_RENAME_OBJECT ){
+      sqlite3RenameTokenMap(pParse, (void*)zName, pName);
+    }
+  }
+  pParse->sNameToken = *pName;
+  if( zName==0 ) return;
+  if( sqlite3CheckObjectName(pParse, zName, isView?"view":"table", zName) ){
+    goto begin_table_error;
+  }
+  if( db->init.iDb==1 ) isTemp = 1;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  assert( isTemp==0 || isTemp==1 );
+  assert( isView==0 || isView==1 );
+  {
+    static const u8 aCode[] = {
+       SQLITE_CREATE_TABLE,
+       SQLITE_CREATE_TEMP_TABLE,
+       SQLITE_CREATE_VIEW,
+       SQLITE_CREATE_TEMP_VIEW
+    };
+    char *zDb = db->aDb[iDb].zDbSName;
+    if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(isTemp), 0, zDb) ){
+      goto begin_table_error;
+    }
+    if( !isVirtual && sqlite3AuthCheck(pParse, (int)aCode[isTemp+2*isView],
+                                       zName, 0, zDb) ){
+      goto begin_table_error;
+    }
+  }
+#endif
+
+  /* Make sure the new table name does not collide with an existing
+  ** index or table name in the same database.  Issue an error message if
+  ** it does. The exception is if the statement being parsed was passed
+  ** to an sqlite3_declare_vtab() call. In that case only the column names
+  ** and types will be used, so there is no need to test for namespace
+  ** collisions.
+  */
+  if( !IN_SPECIAL_PARSE ){
+    char *zDb = db->aDb[iDb].zDbSName;
+    if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+      goto begin_table_error;
+    }
+    pTable = sqlite3FindTable(db, zName, zDb);
+    if( pTable ){
+      if( !noErr ){
+        sqlite3ErrorMsg(pParse, "%s %T already exists",
+                        (IsView(pTable)? "view" : "table"), pName);
+      }else{
+        assert( !db->init.busy || CORRUPT_DB );
+        sqlite3CodeVerifySchema(pParse, iDb);
+        sqlite3ForceNotReadOnly(pParse);
+      }
+      goto begin_table_error;
+    }
+    if( sqlite3FindIndex(db, zName, zDb)!=0 ){
+      sqlite3ErrorMsg(pParse, "there is already an index named %s", zName);
+      goto begin_table_error;
+    }
+  }
+
+  pTable = sqlite3DbMallocZero(db, sizeof(Table));
+  if( pTable==0 ){
+    assert( db->mallocFailed );
+    pParse->rc = SQLITE_NOMEM_BKPT;
+    pParse->nErr++;
+    goto begin_table_error;
+  }
+  pTable->zName = zName;
+  pTable->iPKey = -1;
+  pTable->pSchema = db->aDb[iDb].pSchema;
+  pTable->nTabRef = 1;
+#ifdef SQLITE_DEFAULT_ROWEST
+  pTable->nRowLogEst = sqlite3LogEst(SQLITE_DEFAULT_ROWEST);
+#else
+  pTable->nRowLogEst = 200; assert( 200==sqlite3LogEst(1048576) );
+#endif
+  assert( pParse->pNewTable==0 );
+  pParse->pNewTable = pTable;
+
+  /* Begin generating the code that will insert the table record into
+  ** the schema table.  Note in particular that we must go ahead
+  ** and allocate the record number for the table entry now.  Before any
+  ** PRIMARY KEY or UNIQUE keywords are parsed.  Those keywords will cause
+  ** indices to be created and the table record must come before the
+  ** indices.  Hence, the record number for the table must be allocated
+  ** now.
+  */
+  if( !db->init.busy && (v = sqlite3GetVdbe(pParse))!=0 ){
+    int addr1;
+    int fileFormat;
+    int reg1, reg2, reg3;
+    /* nullRow[] is an OP_Record encoding of a row containing 5 NULLs */
+    static const char nullRow[] = { 6, 0, 0, 0, 0, 0 };
+    sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( isVirtual ){
+      sqlite3VdbeAddOp0(v, OP_VBegin);
+    }
+#endif
+
+    /* If the file format and encoding in the database have not been set,
+    ** set them now.
+    */
+    reg1 = pParse->regRowid = ++pParse->nMem;
+    reg2 = pParse->regRoot = ++pParse->nMem;
+    reg3 = ++pParse->nMem;
+    sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, reg3, BTREE_FILE_FORMAT);
+    sqlite3VdbeUsesBtree(v, iDb);
+    addr1 = sqlite3VdbeAddOp1(v, OP_If, reg3); VdbeCoverage(v);
+    fileFormat = (db->flags & SQLITE_LegacyFileFmt)!=0 ?
+                  1 : SQLITE_MAX_FILE_FORMAT;
+    sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, fileFormat);
+    sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_TEXT_ENCODING, ENC(db));
+    sqlite3VdbeJumpHere(v, addr1);
+
+    /* This just creates a place-holder record in the sqlite_schema table.
+    ** The record created does not contain anything yet.  It will be replaced
+    ** by the real entry in code generated at sqlite3EndTable().
+    **
+    ** The rowid for the new entry is left in register pParse->regRowid.
+    ** The root page number of the new table is left in reg pParse->regRoot.
+    ** The rowid and root page number values are needed by the code that
+    ** sqlite3EndTable will generate.
+    */
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+    if( isView || isVirtual ){
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, reg2);
+    }else
+#endif
+    {
+      assert( !pParse->bReturning );
+      pParse->u1.addrCrTab =
+         sqlite3VdbeAddOp3(v, OP_CreateBtree, iDb, reg2, BTREE_INTKEY);
+    }
+    sqlite3OpenSchemaTable(pParse, iDb);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, 0, reg1);
+    sqlite3VdbeAddOp4(v, OP_Blob, 6, reg3, 0, nullRow, P4_STATIC);
+    sqlite3VdbeAddOp3(v, OP_Insert, 0, reg3, reg1);
+    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+    sqlite3VdbeAddOp0(v, OP_Close);
+  }
+
+  /* Normal (non-error) return. */
+  return;
+
+  /* If an error occurs, we jump here */
+begin_table_error:
+  pParse->checkSchema = 1;
+  sqlite3DbFree(db, zName);
+  return;
+}
+
+/* Set properties of a table column based on the (magical)
+** name of the column.
+*/
+#if SQLITE_ENABLE_HIDDEN_COLUMNS
+void sqlite3ColumnPropertiesFromName(Table *pTab, Column *pCol){
+  if( sqlite3_strnicmp(pCol->zCnName, "__hidden__", 10)==0 ){
+    pCol->colFlags |= COLFLAG_HIDDEN;
+    if( pTab ) pTab->tabFlags |= TF_HasHidden;
+  }else if( pTab && pCol!=pTab->aCol && (pCol[-1].colFlags & COLFLAG_HIDDEN) ){
+    pTab->tabFlags |= TF_OOOHidden;
+  }
+}
+#endif
+
+/*
+** Clean up the data structures associated with the RETURNING clause.
+*/
+static void sqlite3DeleteReturning(sqlite3 *db, void *pArg){
+  Returning *pRet = (Returning*)pArg;
+  Hash *pHash;
+  pHash = &(db->aDb[1].pSchema->trigHash);
+  sqlite3HashInsert(pHash, pRet->zName, 0);
+  sqlite3ExprListDelete(db, pRet->pReturnEL);
+  sqlite3DbFree(db, pRet);
+}
+
+/*
+** Add the RETURNING clause to the parse currently underway.
+**
+** This routine creates a special TEMP trigger that will fire for each row
+** of the DML statement.  That TEMP trigger contains a single SELECT
+** statement with a result set that is the argument of the RETURNING clause.
+** The trigger has the Trigger.bReturning flag and an opcode of
+** TK_RETURNING instead of TK_SELECT, so that the trigger code generator
+** knows to handle it specially.  The TEMP trigger is automatically
+** removed at the end of the parse.
+**
+** When this routine is called, we do not yet know if the RETURNING clause
+** is attached to a DELETE, INSERT, or UPDATE, so construct it as a
+** RETURNING trigger instead.  It will then be converted into the appropriate
+** type on the first call to sqlite3TriggersExist().
+*/
+void sqlite3AddReturning(Parse *pParse, ExprList *pList){
+  Returning *pRet;
+  Hash *pHash;
+  sqlite3 *db = pParse->db;
+  if( pParse->pNewTrigger ){
+    sqlite3ErrorMsg(pParse, "cannot use RETURNING in a trigger");
+  }else{
+    assert( pParse->bReturning==0 || pParse->ifNotExists );
+  }
+  pParse->bReturning = 1;
+  pRet = sqlite3DbMallocZero(db, sizeof(*pRet));
+  if( pRet==0 ){
+    sqlite3ExprListDelete(db, pList);
+    return;
+  }
+  pParse->u1.pReturning = pRet;
+  pRet->pParse = pParse;
+  pRet->pReturnEL = pList;
+  sqlite3ParserAddCleanup(pParse, sqlite3DeleteReturning, pRet);
+  testcase( pParse->earlyCleanup );
+  if( db->mallocFailed ) return;
+  sqlite3_snprintf(sizeof(pRet->zName), pRet->zName,
+                   "sqlite_returning_%p", pParse);
+  pRet->retTrig.zName = pRet->zName;
+  pRet->retTrig.op = TK_RETURNING;
+  pRet->retTrig.tr_tm = TRIGGER_AFTER;
+  pRet->retTrig.bReturning = 1;
+  pRet->retTrig.pSchema = db->aDb[1].pSchema;
+  pRet->retTrig.pTabSchema = db->aDb[1].pSchema;
+  pRet->retTrig.step_list = &pRet->retTStep;
+  pRet->retTStep.op = TK_RETURNING;
+  pRet->retTStep.pTrig = &pRet->retTrig;
+  pRet->retTStep.pExprList = pList;
+  pHash = &(db->aDb[1].pSchema->trigHash);
+  assert( sqlite3HashFind(pHash, pRet->zName)==0
+          || pParse->nErr  || pParse->ifNotExists );
+  if( sqlite3HashInsert(pHash, pRet->zName, &pRet->retTrig)
+          ==&pRet->retTrig ){
+    sqlite3OomFault(db);
+  }
+}
+
+/*
+** Add a new column to the table currently being constructed.
+**
+** The parser calls this routine once for each column declaration
+** in a CREATE TABLE statement.  sqlite3StartTable() gets called
+** first to get things going.  Then this routine is called for each
+** column.
+*/
+void sqlite3AddColumn(Parse *pParse, Token sName, Token sType){
+  Table *p;
+  int i;
+  char *z;
+  char *zType;
+  Column *pCol;
+  sqlite3 *db = pParse->db;
+  u8 hName;
+  Column *aNew;
+  u8 eType = COLTYPE_CUSTOM;
+  u8 szEst = 1;
+  char affinity = SQLITE_AFF_BLOB;
+
+  if( (p = pParse->pNewTable)==0 ) return;
+  if( p->nCol+1>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many columns on %s", p->zName);
+    return;
+  }
+  if( !IN_RENAME_OBJECT ) sqlite3DequoteToken(&sName);
+
+  /* Because keywords GENERATE ALWAYS can be converted into identifiers
+  ** by the parser, we can sometimes end up with a typename that ends
+  ** with "generated always".  Check for this case and omit the surplus
+  ** text. */
+  if( sType.n>=16
+   && sqlite3_strnicmp(sType.z+(sType.n-6),"always",6)==0
+  ){
+    sType.n -= 6;
+    while( ALWAYS(sType.n>0) && sqlite3Isspace(sType.z[sType.n-1]) ) sType.n--;
+    if( sType.n>=9
+     && sqlite3_strnicmp(sType.z+(sType.n-9),"generated",9)==0
+    ){
+      sType.n -= 9;
+      while( sType.n>0 && sqlite3Isspace(sType.z[sType.n-1]) ) sType.n--;
+    }
+  }
+
+  /* Check for standard typenames.  For standard typenames we will
+  ** set the Column.eType field rather than storing the typename after
+  ** the column name, in order to save space. */
+  if( sType.n>=3 ){
+    sqlite3DequoteToken(&sType);
+    for(i=0; i<SQLITE_N_STDTYPE; i++){
+       if( sType.n==sqlite3StdTypeLen[i]
+        && sqlite3_strnicmp(sType.z, sqlite3StdType[i], sType.n)==0
+       ){
+         sType.n = 0;
+         eType = i+1;
+         affinity = sqlite3StdTypeAffinity[i];
+         if( affinity<=SQLITE_AFF_TEXT ) szEst = 5;
+         break;
+       }
+    }
+  }
+
+  z = sqlite3DbMallocRaw(db, (i64)sName.n + 1 + (i64)sType.n + (sType.n>0) );
+  if( z==0 ) return;
+  if( IN_RENAME_OBJECT ) sqlite3RenameTokenMap(pParse, (void*)z, &sName);
+  memcpy(z, sName.z, sName.n);
+  z[sName.n] = 0;
+  sqlite3Dequote(z);
+  hName = sqlite3StrIHash(z);
+  for(i=0; i<p->nCol; i++){
+    if( p->aCol[i].hName==hName && sqlite3StrICmp(z, p->aCol[i].zCnName)==0 ){
+      sqlite3ErrorMsg(pParse, "duplicate column name: %s", z);
+      sqlite3DbFree(db, z);
+      return;
+    }
+  }
+  aNew = sqlite3DbRealloc(db,p->aCol,((i64)p->nCol+1)*sizeof(p->aCol[0]));
+  if( aNew==0 ){
+    sqlite3DbFree(db, z);
+    return;
+  }
+  p->aCol = aNew;
+  pCol = &p->aCol[p->nCol];
+  memset(pCol, 0, sizeof(p->aCol[0]));
+  pCol->zCnName = z;
+  pCol->hName = hName;
+  sqlite3ColumnPropertiesFromName(p, pCol);
+
+  if( sType.n==0 ){
+    /* If there is no type specified, columns have the default affinity
+    ** 'BLOB' with a default size of 4 bytes. */
+    pCol->affinity = affinity;
+    pCol->eCType = eType;
+    pCol->szEst = szEst;
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    if( affinity==SQLITE_AFF_BLOB ){
+      if( 4>=sqlite3GlobalConfig.szSorterRef ){
+        pCol->colFlags |= COLFLAG_SORTERREF;
+      }
+    }
+#endif
+  }else{
+    zType = z + sqlite3Strlen30(z) + 1;
+    memcpy(zType, sType.z, sType.n);
+    zType[sType.n] = 0;
+    sqlite3Dequote(zType);
+    pCol->affinity = sqlite3AffinityType(zType, pCol);
+    pCol->colFlags |= COLFLAG_HASTYPE;
+  }
+  p->nCol++;
+  p->nNVCol++;
+  pParse->constraintName.n = 0;
+}
+
+/*
+** This routine is called by the parser while in the middle of
+** parsing a CREATE TABLE statement.  A "NOT NULL" constraint has
+** been seen on a column.  This routine sets the notNull flag on
+** the column currently under construction.
+*/
+void sqlite3AddNotNull(Parse *pParse, int onError){
+  Table *p;
+  Column *pCol;
+  p = pParse->pNewTable;
+  if( p==0 || NEVER(p->nCol<1) ) return;
+  pCol = &p->aCol[p->nCol-1];
+  pCol->notNull = (u8)onError;
+  p->tabFlags |= TF_HasNotNull;
+
+  /* Set the uniqNotNull flag on any UNIQUE or PK indexes already created
+  ** on this column.  */
+  if( pCol->colFlags & COLFLAG_UNIQUE ){
+    Index *pIdx;
+    for(pIdx=p->pIndex; pIdx; pIdx=pIdx->pNext){
+      assert( pIdx->nKeyCol==1 && pIdx->onError!=OE_None );
+      if( pIdx->aiColumn[0]==p->nCol-1 ){
+        pIdx->uniqNotNull = 1;
+      }
+    }
+  }
+}
+
+/*
+** Scan the column type name zType (length nType) and return the
+** associated affinity type.
+**
+** This routine does a case-independent search of zType for the
+** substrings in the following table. If one of the substrings is
+** found, the corresponding affinity is returned. If zType contains
+** more than one of the substrings, entries toward the top of
+** the table take priority. For example, if zType is 'BLOBINT',
+** SQLITE_AFF_INTEGER is returned.
+**
+** Substring     | Affinity
+** --------------------------------
+** 'INT'         | SQLITE_AFF_INTEGER
+** 'CHAR'        | SQLITE_AFF_TEXT
+** 'CLOB'        | SQLITE_AFF_TEXT
+** 'TEXT'        | SQLITE_AFF_TEXT
+** 'BLOB'        | SQLITE_AFF_BLOB
+** 'REAL'        | SQLITE_AFF_REAL
+** 'FLOA'        | SQLITE_AFF_REAL
+** 'DOUB'        | SQLITE_AFF_REAL
+**
+** If none of the substrings in the above table are found,
+** SQLITE_AFF_NUMERIC is returned.
+*/
+char sqlite3AffinityType(const char *zIn, Column *pCol){
+  u32 h = 0;
+  char aff = SQLITE_AFF_NUMERIC;
+  const char *zChar = 0;
+
+  assert( zIn!=0 );
+  while( zIn[0] ){
+    u8 x = *(u8*)zIn;
+    h = (h<<8) + sqlite3UpperToLower[x];
+    zIn++;
+    if( h==(('c'<<24)+('h'<<16)+('a'<<8)+'r') ){             /* CHAR */
+      aff = SQLITE_AFF_TEXT;
+      zChar = zIn;
+    }else if( h==(('c'<<24)+('l'<<16)+('o'<<8)+'b') ){       /* CLOB */
+      aff = SQLITE_AFF_TEXT;
+    }else if( h==(('t'<<24)+('e'<<16)+('x'<<8)+'t') ){       /* TEXT */
+      aff = SQLITE_AFF_TEXT;
+    }else if( h==(('b'<<24)+('l'<<16)+('o'<<8)+'b')          /* BLOB */
+        && (aff==SQLITE_AFF_NUMERIC || aff==SQLITE_AFF_REAL) ){
+      aff = SQLITE_AFF_BLOB;
+      if( zIn[0]=='(' ) zChar = zIn;
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    }else if( h==(('r'<<24)+('e'<<16)+('a'<<8)+'l')          /* REAL */
+        && aff==SQLITE_AFF_NUMERIC ){
+      aff = SQLITE_AFF_REAL;
+    }else if( h==(('f'<<24)+('l'<<16)+('o'<<8)+'a')          /* FLOA */
+        && aff==SQLITE_AFF_NUMERIC ){
+      aff = SQLITE_AFF_REAL;
+    }else if( h==(('d'<<24)+('o'<<16)+('u'<<8)+'b')          /* DOUB */
+        && aff==SQLITE_AFF_NUMERIC ){
+      aff = SQLITE_AFF_REAL;
+#endif
+    }else if( (h&0x00FFFFFF)==(('i'<<16)+('n'<<8)+'t') ){    /* INT */
+      aff = SQLITE_AFF_INTEGER;
+      break;
+    }
+  }
+
+  /* If pCol is not NULL, store an estimate of the field size.  The
+  ** estimate is scaled so that the size of an integer is 1.  */
+  if( pCol ){
+    int v = 0;   /* default size is approx 4 bytes */
+    if( aff<SQLITE_AFF_NUMERIC ){
+      if( zChar ){
+        while( zChar[0] ){
+          if( sqlite3Isdigit(zChar[0]) ){
+            /* BLOB(k), VARCHAR(k), CHAR(k) -> r=(k/4+1) */
+            sqlite3GetInt32(zChar, &v);
+            break;
+          }
+          zChar++;
+        }
+      }else{
+        v = 16;   /* BLOB, TEXT, CLOB -> r=5  (approx 20 bytes)*/
+      }
+    }
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    if( v>=sqlite3GlobalConfig.szSorterRef ){
+      pCol->colFlags |= COLFLAG_SORTERREF;
+    }
+#endif
+    v = v/4 + 1;
+    if( v>255 ) v = 255;
+    pCol->szEst = v;
+  }
+  return aff;
+}
+
+/*
+** The expression is the default value for the most recently added column
+** of the table currently under construction.
+**
+** Default value expressions must be constant.  Raise an exception if this
+** is not the case.
+**
+** This routine is called by the parser while in the middle of
+** parsing a CREATE TABLE statement.
+*/
+void sqlite3AddDefaultValue(
+  Parse *pParse,           /* Parsing context */
+  Expr *pExpr,             /* The parsed expression of the default value */
+  const char *zStart,      /* Start of the default value text */
+  const char *zEnd         /* First character past end of default value text */
+){
+  Table *p;
+  Column *pCol;
+  sqlite3 *db = pParse->db;
+  p = pParse->pNewTable;
+  if( p!=0 ){
+    int isInit = db->init.busy && db->init.iDb!=1;
+    pCol = &(p->aCol[p->nCol-1]);
+    if( !sqlite3ExprIsConstantOrFunction(pExpr, isInit) ){
+      sqlite3ErrorMsg(pParse, "default value of column [%s] is not constant",
+          pCol->zCnName);
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+    }else if( pCol->colFlags & COLFLAG_GENERATED ){
+      testcase( pCol->colFlags & COLFLAG_VIRTUAL );
+      testcase( pCol->colFlags & COLFLAG_STORED );
+      sqlite3ErrorMsg(pParse, "cannot use DEFAULT on a generated column");
+#endif
+    }else{
+      /* A copy of pExpr is used instead of the original, as pExpr contains
+      ** tokens that point to volatile memory.
+      */
+      Expr x, *pDfltExpr;
+      memset(&x, 0, sizeof(x));
+      x.op = TK_SPAN;
+      x.u.zToken = sqlite3DbSpanDup(db, zStart, zEnd);
+      x.pLeft = pExpr;
+      x.flags = EP_Skip;
+      pDfltExpr = sqlite3ExprDup(db, &x, EXPRDUP_REDUCE);
+      sqlite3DbFree(db, x.u.zToken);
+      sqlite3ColumnSetExpr(pParse, p, pCol, pDfltExpr);
+    }
+  }
+  if( IN_RENAME_OBJECT ){
+    sqlite3RenameExprUnmap(pParse, pExpr);
+  }
+  sqlite3ExprDelete(db, pExpr);
+}
+
+/*
+** Backwards Compatibility Hack:
+**
+** Historical versions of SQLite accepted strings as column names in
+** indexes and PRIMARY KEY constraints and in UNIQUE constraints.  Example:
+**
+**     CREATE TABLE xyz(a,b,c,d,e,PRIMARY KEY('a'),UNIQUE('b','c' COLLATE trim)
+**     CREATE INDEX abc ON xyz('c','d' DESC,'e' COLLATE nocase DESC);
+**
+** This is goofy.  But to preserve backwards compatibility we continue to
+** accept it.  This routine does the necessary conversion.  It converts
+** the expression given in its argument from a TK_STRING into a TK_ID
+** if the expression is just a TK_STRING with an optional COLLATE clause.
+** If the expression is anything other than TK_STRING, the expression is
+** unchanged.
+*/
+static void sqlite3StringToId(Expr *p){
+  if( p->op==TK_STRING ){
+    p->op = TK_ID;
+  }else if( p->op==TK_COLLATE && p->pLeft->op==TK_STRING ){
+    p->pLeft->op = TK_ID;
+  }
+}
+
+/*
+** Tag the given column as being part of the PRIMARY KEY
+*/
+static void makeColumnPartOfPrimaryKey(Parse *pParse, Column *pCol){
+  pCol->colFlags |= COLFLAG_PRIMKEY;
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  if( pCol->colFlags & COLFLAG_GENERATED ){
+    testcase( pCol->colFlags & COLFLAG_VIRTUAL );
+    testcase( pCol->colFlags & COLFLAG_STORED );
+    sqlite3ErrorMsg(pParse,
+      "generated columns cannot be part of the PRIMARY KEY");
+  }
+#endif         
+}
+
+/*
+** Designate the PRIMARY KEY for the table.  pList is a list of names
+** of columns that form the primary key.  If pList is NULL, then the
+** most recently added column of the table is the primary key.
+**
+** A table can have at most one primary key.  If the table already has
+** a primary key (and this is the second primary key) then create an
+** error.
+**
+** If the PRIMARY KEY is on a single column whose datatype is INTEGER,
+** then we will try to use that column as the rowid.  Set the Table.iPKey
+** field of the table under construction to be the index of the
+** INTEGER PRIMARY KEY column.  Table.iPKey is set to -1 if there is
+** no INTEGER PRIMARY KEY.
+**
+** If the key is not an INTEGER PRIMARY KEY, then create a unique
+** index for the key.  No index is created for INTEGER PRIMARY KEYs.
+*/
+void sqlite3AddPrimaryKey(
+  Parse *pParse,    /* Parsing context */
+  ExprList *pList,  /* List of field names to be indexed */
+  int onError,      /* What to do with a uniqueness conflict */
+  int autoInc,      /* True if the AUTOINCREMENT keyword is present */
+  int sortOrder     /* SQLITE_SO_ASC or SQLITE_SO_DESC */
+){
+  Table *pTab = pParse->pNewTable;
+  Column *pCol = 0;
+  int iCol = -1, i;
+  int nTerm;
+  if( pTab==0 ) goto primary_key_exit;
+  if( pTab->tabFlags & TF_HasPrimaryKey ){
+    sqlite3ErrorMsg(pParse,
+      "table \"%s\" has more than one primary key", pTab->zName);
+    goto primary_key_exit;
+  }
+  pTab->tabFlags |= TF_HasPrimaryKey;
+  if( pList==0 ){
+    iCol = pTab->nCol - 1;
+    pCol = &pTab->aCol[iCol];
+    makeColumnPartOfPrimaryKey(pParse, pCol);
+    nTerm = 1;
+  }else{
+    nTerm = pList->nExpr;
+    for(i=0; i<nTerm; i++){
+      Expr *pCExpr = sqlite3ExprSkipCollate(pList->a[i].pExpr);
+      assert( pCExpr!=0 );
+      sqlite3StringToId(pCExpr);
+      if( pCExpr->op==TK_ID ){
+        const char *zCName;
+        assert( !ExprHasProperty(pCExpr, EP_IntValue) );
+        zCName = pCExpr->u.zToken;
+        for(iCol=0; iCol<pTab->nCol; iCol++){
+          if( sqlite3StrICmp(zCName, pTab->aCol[iCol].zCnName)==0 ){
+            pCol = &pTab->aCol[iCol];
+            makeColumnPartOfPrimaryKey(pParse, pCol);
+            break;
+          }
+        }
+      }
+    }
+  }
+  if( nTerm==1
+   && pCol
+   && pCol->eCType==COLTYPE_INTEGER
+   && sortOrder!=SQLITE_SO_DESC
+  ){
+    if( IN_RENAME_OBJECT && pList ){
+      Expr *pCExpr = sqlite3ExprSkipCollate(pList->a[0].pExpr);
+      sqlite3RenameTokenRemap(pParse, &pTab->iPKey, pCExpr);
+    }
+    pTab->iPKey = iCol;
+    pTab->keyConf = (u8)onError;
+    assert( autoInc==0 || autoInc==1 );
+    pTab->tabFlags |= autoInc*TF_Autoincrement;
+    if( pList ) pParse->iPkSortOrder = pList->a[0].fg.sortFlags;
+    (void)sqlite3HasExplicitNulls(pParse, pList);
+  }else if( autoInc ){
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+    sqlite3ErrorMsg(pParse, "AUTOINCREMENT is only allowed on an "
+       "INTEGER PRIMARY KEY");
+#endif
+  }else{
+    sqlite3CreateIndex(pParse, 0, 0, 0, pList, onError, 0,
+                           0, sortOrder, 0, SQLITE_IDXTYPE_PRIMARYKEY);
+    pList = 0;
+  }
+
+primary_key_exit:
+  sqlite3ExprListDelete(pParse->db, pList);
+  return;
+}
+
+/*
+** Add a new CHECK constraint to the table currently under construction.
+*/
+void sqlite3AddCheckConstraint(
+  Parse *pParse,      /* Parsing context */
+  Expr *pCheckExpr,   /* The check expression */
+  const char *zStart, /* Opening "(" */
+  const char *zEnd    /* Closing ")" */
+){
+#ifndef SQLITE_OMIT_CHECK
+  Table *pTab = pParse->pNewTable;
+  sqlite3 *db = pParse->db;
+  if( pTab && !IN_DECLARE_VTAB
+   && !sqlite3BtreeIsReadonly(db->aDb[db->init.iDb].pBt)
+  ){
+    pTab->pCheck = sqlite3ExprListAppend(pParse, pTab->pCheck, pCheckExpr);
+    if( pParse->constraintName.n ){
+      sqlite3ExprListSetName(pParse, pTab->pCheck, &pParse->constraintName, 1);
+    }else{
+      Token t;
+      for(zStart++; sqlite3Isspace(zStart[0]); zStart++){}
+      while( sqlite3Isspace(zEnd[-1]) ){ zEnd--; }
+      t.z = zStart;
+      t.n = (int)(zEnd - t.z);
+      sqlite3ExprListSetName(pParse, pTab->pCheck, &t, 1);   
+    }
+  }else
+#endif
+  {
+    sqlite3ExprDelete(pParse->db, pCheckExpr);
+  }
+}
+
+/*
+** Set the collation function of the most recently parsed table column
+** to the CollSeq given.
+*/
+void sqlite3AddCollateType(Parse *pParse, Token *pToken){
+  Table *p;
+  int i;
+  char *zColl;              /* Dequoted name of collation sequence */
+  sqlite3 *db;
+
+  if( (p = pParse->pNewTable)==0 || IN_RENAME_OBJECT ) return;
+  i = p->nCol-1;
+  db = pParse->db;
+  zColl = sqlite3NameFromToken(db, pToken);
+  if( !zColl ) return;
+
+  if( sqlite3LocateCollSeq(pParse, zColl) ){
+    Index *pIdx;
+    sqlite3ColumnSetColl(db, &p->aCol[i], zColl);
+ 
+    /* If the column is declared as "<name> PRIMARY KEY COLLATE <type>",
+    ** then an index may have been created on this column before the
+    ** collation type was added. Correct this if it is the case.
+    */
+    for(pIdx=p->pIndex; pIdx; pIdx=pIdx->pNext){
+      assert( pIdx->nKeyCol==1 );
+      if( pIdx->aiColumn[0]==i ){
+        pIdx->azColl[0] = sqlite3ColumnColl(&p->aCol[i]);
+      }
+    }
+  }
+  sqlite3DbFree(db, zColl);
+}
+
+/* Change the most recently parsed column to be a GENERATED ALWAYS AS
+** column.
+*/
+void sqlite3AddGenerated(Parse *pParse, Expr *pExpr, Token *pType){
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  u8 eType = COLFLAG_VIRTUAL;
+  Table *pTab = pParse->pNewTable;
+  Column *pCol;
+  if( pTab==0 ){
+    /* generated column in an CREATE TABLE IF NOT EXISTS that already exists */
+    goto generated_done;
+  }
+  pCol = &(pTab->aCol[pTab->nCol-1]);
+  if( IN_DECLARE_VTAB ){
+    sqlite3ErrorMsg(pParse, "virtual tables cannot use computed columns");
+    goto generated_done;
+  }
+  if( pCol->iDflt>0 ) goto generated_error;
+  if( pType ){
+    if( pType->n==7 && sqlite3StrNICmp("virtual",pType->z,7)==0 ){
+      /* no-op */
+    }else if( pType->n==6 && sqlite3StrNICmp("stored",pType->z,6)==0 ){
+      eType = COLFLAG_STORED;
+    }else{
+      goto generated_error;
+    }
+  }
+  if( eType==COLFLAG_VIRTUAL ) pTab->nNVCol--;
+  pCol->colFlags |= eType;
+  assert( TF_HasVirtual==COLFLAG_VIRTUAL );
+  assert( TF_HasStored==COLFLAG_STORED );
+  pTab->tabFlags |= eType;
+  if( pCol->colFlags & COLFLAG_PRIMKEY ){
+    makeColumnPartOfPrimaryKey(pParse, pCol); /* For the error message */
+  }
+  if( ALWAYS(pExpr) && pExpr->op==TK_ID ){
+    /* The value of a generated column needs to be a real expression, not
+    ** just a reference to another column, in order for covering index
+    ** optimizations to work correctly.  So if the value is not an expression,
+    ** turn it into one by adding a unary "+" operator. */
+    pExpr = sqlite3PExpr(pParse, TK_UPLUS, pExpr, 0);
+  }
+  if( pExpr && pExpr->op!=TK_RAISE ) pExpr->affExpr = pCol->affinity;
+  sqlite3ColumnSetExpr(pParse, pTab, pCol, pExpr);
+  pExpr = 0;
+  goto generated_done;
+
+generated_error:
+  sqlite3ErrorMsg(pParse, "error in generated column \"%s\"",
+                  pCol->zCnName);
+generated_done:
+  sqlite3ExprDelete(pParse->db, pExpr);
+#else
+  /* Throw and error for the GENERATED ALWAYS AS clause if the
+  ** SQLITE_OMIT_GENERATED_COLUMNS compile-time option is used. */
+  sqlite3ErrorMsg(pParse, "generated columns not supported");
+  sqlite3ExprDelete(pParse->db, pExpr);
+#endif
+}
+
+/*
+** Generate code that will increment the schema cookie.
+**
+** The schema cookie is used to determine when the schema for the
+** database changes.  After each schema change, the cookie value
+** changes.  When a process first reads the schema it records the
+** cookie.  Thereafter, whenever it goes to access the database,
+** it checks the cookie to make sure the schema has not changed
+** since it was last read.
+**
+** This plan is not completely bullet-proof.  It is possible for
+** the schema to change multiple times and for the cookie to be
+** set back to prior value.  But schema changes are infrequent
+** and the probability of hitting the same cookie value is only
+** 1 chance in 2^32.  So we're safe enough.
+**
+** IMPLEMENTATION-OF: R-34230-56049 SQLite automatically increments
+** the schema-version whenever the schema changes.
+*/
+void sqlite3ChangeCookie(Parse *pParse, int iDb){
+  sqlite3 *db = pParse->db;
+  Vdbe *v = pParse->pVdbe;
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_SCHEMA_VERSION,
+                   (int)(1+(unsigned)db->aDb[iDb].pSchema->schema_cookie));
+}
+
+/*
+** Measure the number of characters needed to output the given
+** identifier.  The number returned includes any quotes used
+** but does not include the null terminator.
+**
+** The estimate is conservative.  It might be larger that what is
+** really needed.
+*/
+static int identLength(const char *z){
+  int n;
+  for(n=0; *z; n++, z++){
+    if( *z=='"' ){ n++; }
+  }
+  return n + 2;
+}
+
+/*
+** The first parameter is a pointer to an output buffer. The second
+** parameter is a pointer to an integer that contains the offset at
+** which to write into the output buffer. This function copies the
+** nul-terminated string pointed to by the third parameter, zSignedIdent,
+** to the specified offset in the buffer and updates *pIdx to refer
+** to the first byte after the last byte written before returning.
+**
+** If the string zSignedIdent consists entirely of alphanumeric
+** characters, does not begin with a digit and is not an SQL keyword,
+** then it is copied to the output buffer exactly as it is. Otherwise,
+** it is quoted using double-quotes.
+*/
+static void identPut(char *z, int *pIdx, char *zSignedIdent){
+  unsigned char *zIdent = (unsigned char*)zSignedIdent;
+  int i, j, needQuote;
+  i = *pIdx;
+
+  for(j=0; zIdent[j]; j++){
+    if( !sqlite3Isalnum(zIdent[j]) && zIdent[j]!='_' ) break;
+  }
+  needQuote = sqlite3Isdigit(zIdent[0])
+            || sqlite3KeywordCode(zIdent, j)!=TK_ID
+            || zIdent[j]!=0
+            || j==0;
+
+  if( needQuote ) z[i++] = '"';
+  for(j=0; zIdent[j]; j++){
+    z[i++] = zIdent[j];
+    if( zIdent[j]=='"' ) z[i++] = '"';
+  }
+  if( needQuote ) z[i++] = '"';
+  z[i] = 0;
+  *pIdx = i;
+}
+
+/*
+** Generate a CREATE TABLE statement appropriate for the given
+** table.  Memory to hold the text of the statement is obtained
+** from sqliteMalloc() and must be freed by the calling function.
+*/
+static char *createTableStmt(sqlite3 *db, Table *p){
+  int i, k, n;
+  char *zStmt;
+  char *zSep, *zSep2, *zEnd;
+  Column *pCol;
+  n = 0;
+  for(pCol = p->aCol, i=0; i<p->nCol; i++, pCol++){
+    n += identLength(pCol->zCnName) + 5;
+  }
+  n += identLength(p->zName);
+  if( n<50 ){
+    zSep = "";
+    zSep2 = ",";
+    zEnd = ")";
+  }else{
+    zSep = "\n  ";
+    zSep2 = ",\n  ";
+    zEnd = "\n)";
+  }
+  n += 35 + 6*p->nCol;
+  zStmt = sqlite3DbMallocRaw(0, n);
+  if( zStmt==0 ){
+    sqlite3OomFault(db);
+    return 0;
+  }
+  sqlite3_snprintf(n, zStmt, "CREATE TABLE ");
+  k = sqlite3Strlen30(zStmt);
+  identPut(zStmt, &k, p->zName);
+  zStmt[k++] = '(';
+  for(pCol=p->aCol, i=0; i<p->nCol; i++, pCol++){
+    static const char * const azType[] = {
+        /* SQLITE_AFF_BLOB    */ "",
+        /* SQLITE_AFF_TEXT    */ " TEXT",
+        /* SQLITE_AFF_NUMERIC */ " NUM",
+        /* SQLITE_AFF_INTEGER */ " INT",
+        /* SQLITE_AFF_REAL    */ " REAL",
+        /* SQLITE_AFF_FLEXNUM */ " NUM",
+    };
+    int len;
+    const char *zType;
+
+    sqlite3_snprintf(n-k, &zStmt[k], zSep);
+    k += sqlite3Strlen30(&zStmt[k]);
+    zSep = zSep2;
+    identPut(zStmt, &k, pCol->zCnName);
+    assert( pCol->affinity-SQLITE_AFF_BLOB >= 0 );
+    assert( pCol->affinity-SQLITE_AFF_BLOB < ArraySize(azType) );
+    testcase( pCol->affinity==SQLITE_AFF_BLOB );
+    testcase( pCol->affinity==SQLITE_AFF_TEXT );
+    testcase( pCol->affinity==SQLITE_AFF_NUMERIC );
+    testcase( pCol->affinity==SQLITE_AFF_INTEGER );
+    testcase( pCol->affinity==SQLITE_AFF_REAL );
+    testcase( pCol->affinity==SQLITE_AFF_FLEXNUM );
+   
+    zType = azType[pCol->affinity - SQLITE_AFF_BLOB];
+    len = sqlite3Strlen30(zType);
+    assert( pCol->affinity==SQLITE_AFF_BLOB
+            || pCol->affinity==SQLITE_AFF_FLEXNUM
+            || pCol->affinity==sqlite3AffinityType(zType, 0) );
+    memcpy(&zStmt[k], zType, len);
+    k += len;
+    assert( k<=n );
+  }
+  sqlite3_snprintf(n-k, &zStmt[k], "%s", zEnd);
+  return zStmt;
+}
+
+/*
+** Resize an Index object to hold N columns total.  Return SQLITE_OK
+** on success and SQLITE_NOMEM on an OOM error.
+*/
+static int resizeIndexObject(sqlite3 *db, Index *pIdx, int N){
+  char *zExtra;
+  int nByte;
+  if( pIdx->nColumn>=N ) return SQLITE_OK;
+  assert( pIdx->isResized==0 );
+  nByte = (sizeof(char*) + sizeof(LogEst) + sizeof(i16) + 1)*N;
+  zExtra = sqlite3DbMallocZero(db, nByte);
+  if( zExtra==0 ) return SQLITE_NOMEM_BKPT;
+  memcpy(zExtra, pIdx->azColl, sizeof(char*)*pIdx->nColumn);
+  pIdx->azColl = (const char**)zExtra;
+  zExtra += sizeof(char*)*N;
+  memcpy(zExtra, pIdx->aiRowLogEst, sizeof(LogEst)*(pIdx->nKeyCol+1));
+  pIdx->aiRowLogEst = (LogEst*)zExtra;
+  zExtra += sizeof(LogEst)*N;
+  memcpy(zExtra, pIdx->aiColumn, sizeof(i16)*pIdx->nColumn);
+  pIdx->aiColumn = (i16*)zExtra;
+  zExtra += sizeof(i16)*N;
+  memcpy(zExtra, pIdx->aSortOrder, pIdx->nColumn);
+  pIdx->aSortOrder = (u8*)zExtra;
+  pIdx->nColumn = N;
+  pIdx->isResized = 1;
+  return SQLITE_OK;
+}
+
+/*
+** Estimate the total row width for a table.
+*/
+static void estimateTableWidth(Table *pTab){
+  unsigned wTable = 0;
+  const Column *pTabCol;
+  int i;
+  for(i=pTab->nCol, pTabCol=pTab->aCol; i>0; i--, pTabCol++){
+    wTable += pTabCol->szEst;
+  }
+  if( pTab->iPKey<0 ) wTable++;
+  pTab->szTabRow = sqlite3LogEst(wTable*4);
+}
+
+/*
+** Estimate the average size of a row for an index.
+*/
+static void estimateIndexWidth(Index *pIdx){
+  unsigned wIndex = 0;
+  int i;
+  const Column *aCol = pIdx->pTable->aCol;
+  for(i=0; i<pIdx->nColumn; i++){
+    i16 x = pIdx->aiColumn[i];
+    assert( x<pIdx->pTable->nCol );
+    wIndex += x<0 ? 1 : aCol[x].szEst;
+  }
+  pIdx->szIdxRow = sqlite3LogEst(wIndex*4);
+}
+
+/* Return true if column number x is any of the first nCol entries of aiCol[].
+** This is used to determine if the column number x appears in any of the
+** first nCol entries of an index.
+*/
+static int hasColumn(const i16 *aiCol, int nCol, int x){
+  while( nCol-- > 0 ){
+    if( x==*(aiCol++) ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Return true if any of the first nKey entries of index pIdx exactly
+** match the iCol-th entry of pPk.  pPk is always a WITHOUT ROWID
+** PRIMARY KEY index.  pIdx is an index on the same table.  pIdx may
+** or may not be the same index as pPk.
+**
+** The first nKey entries of pIdx are guaranteed to be ordinary columns,
+** not a rowid or expression.
+**
+** This routine differs from hasColumn() in that both the column and the
+** collating sequence must match for this routine, but for hasColumn() only
+** the column name must match.
+*/
+static int isDupColumn(Index *pIdx, int nKey, Index *pPk, int iCol){
+  int i, j;
+  assert( nKey<=pIdx->nColumn );
+  assert( iCol<MAX(pPk->nColumn,pPk->nKeyCol) );
+  assert( pPk->idxType==SQLITE_IDXTYPE_PRIMARYKEY );
+  assert( pPk->pTable->tabFlags & TF_WithoutRowid );
+  assert( pPk->pTable==pIdx->pTable );
+  testcase( pPk==pIdx );
+  j = pPk->aiColumn[iCol];
+  assert( j!=XN_ROWID && j!=XN_EXPR );
+  for(i=0; i<nKey; i++){
+    assert( pIdx->aiColumn[i]>=0 || j>=0 );
+    if( pIdx->aiColumn[i]==j
+     && sqlite3StrICmp(pIdx->azColl[i], pPk->azColl[iCol])==0
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/* Recompute the colNotIdxed field of the Index.
+**
+** colNotIdxed is a bitmask that has a 0 bit representing each indexed
+** columns that are within the first 63 columns of the table and a 1 for
+** all other bits (all columns that are not in the index).  The
+** high-order bit of colNotIdxed is always 1.  All unindexed columns
+** of the table have a 1.
+**
+** 2019-10-24:  For the purpose of this computation, virtual columns are
+** not considered to be covered by the index, even if they are in the
+** index, because we do not trust the logic in whereIndexExprTrans() to be
+** able to find all instances of a reference to the indexed table column
+** and convert them into references to the index.  Hence we always want
+** the actual table at hand in order to recompute the virtual column, if
+** necessary.
+**
+** The colNotIdxed mask is AND-ed with the SrcList.a[].colUsed mask
+** to determine if the index is covering index.
+*/
+static void recomputeColumnsNotIndexed(Index *pIdx){
+  Bitmask m = 0;
+  int j;
+  Table *pTab = pIdx->pTable;
+  for(j=pIdx->nColumn-1; j>=0; j--){
+    int x = pIdx->aiColumn[j];
+    if( x>=0 && (pTab->aCol[x].colFlags & COLFLAG_VIRTUAL)==0 ){
+      testcase( x==BMS-1 );
+      testcase( x==BMS-2 );
+      if( x<BMS-1 ) m |= MASKBIT(x);
+    }
+  }
+  pIdx->colNotIdxed = ~m;
+  assert( (pIdx->colNotIdxed>>63)==1 );  /* See note-20221022-a */
+}
+
+/*
+** This routine runs at the end of parsing a CREATE TABLE statement that
+** has a WITHOUT ROWID clause.  The job of this routine is to convert both
+** internal schema data structures and the generated VDBE code so that they
+** are appropriate for a WITHOUT ROWID table instead of a rowid table.
+** Changes include:
+**
+**     (1)  Set all columns of the PRIMARY KEY schema object to be NOT NULL.
+**     (2)  Convert P3 parameter of the OP_CreateBtree from BTREE_INTKEY
+**          into BTREE_BLOBKEY.
+**     (3)  Bypass the creation of the sqlite_schema table entry
+**          for the PRIMARY KEY as the primary key index is now
+**          identified by the sqlite_schema table entry of the table itself.
+**     (4)  Set the Index.tnum of the PRIMARY KEY Index object in the
+**          schema to the rootpage from the main table.
+**     (5)  Add all table columns to the PRIMARY KEY Index object
+**          so that the PRIMARY KEY is a covering index.  The surplus
+**          columns are part of KeyInfo.nAllField and are not used for
+**          sorting or lookup or uniqueness checks.
+**     (6)  Replace the rowid tail on all automatically generated UNIQUE
+**          indices with the PRIMARY KEY columns.
+**
+** For virtual tables, only (1) is performed.
+*/
+static void convertToWithoutRowidTable(Parse *pParse, Table *pTab){
+  Index *pIdx;
+  Index *pPk;
+  int nPk;
+  int nExtra;
+  int i, j;
+  sqlite3 *db = pParse->db;
+  Vdbe *v = pParse->pVdbe;
+
+  /* Mark every PRIMARY KEY column as NOT NULL (except for imposter tables)
+  */
+  if( !db->init.imposterTable ){
+    for(i=0; i<pTab->nCol; i++){
+      if( (pTab->aCol[i].colFlags & COLFLAG_PRIMKEY)!=0
+       && (pTab->aCol[i].notNull==OE_None)
+      ){
+        pTab->aCol[i].notNull = OE_Abort;
+      }
+    }
+    pTab->tabFlags |= TF_HasNotNull;
+  }
+
+  /* Convert the P3 operand of the OP_CreateBtree opcode from BTREE_INTKEY
+  ** into BTREE_BLOBKEY.
+  */
+  assert( !pParse->bReturning );
+  if( pParse->u1.addrCrTab ){
+    assert( v );
+    sqlite3VdbeChangeP3(v, pParse->u1.addrCrTab, BTREE_BLOBKEY);
+  }
+
+  /* Locate the PRIMARY KEY index.  Or, if this table was originally
+  ** an INTEGER PRIMARY KEY table, create a new PRIMARY KEY index.
+  */
+  if( pTab->iPKey>=0 ){
+    ExprList *pList;
+    Token ipkToken;
+    sqlite3TokenInit(&ipkToken, pTab->aCol[pTab->iPKey].zCnName);
+    pList = sqlite3ExprListAppend(pParse, 0,
+                  sqlite3ExprAlloc(db, TK_ID, &ipkToken, 0));
+    if( pList==0 ){
+      pTab->tabFlags &= ~TF_WithoutRowid;
+      return;
+    }
+    if( IN_RENAME_OBJECT ){
+      sqlite3RenameTokenRemap(pParse, pList->a[0].pExpr, &pTab->iPKey);
+    }
+    pList->a[0].fg.sortFlags = pParse->iPkSortOrder;
+    assert( pParse->pNewTable==pTab );
+    pTab->iPKey = -1;
+    sqlite3CreateIndex(pParse, 0, 0, 0, pList, pTab->keyConf, 0, 0, 0, 0,
+                       SQLITE_IDXTYPE_PRIMARYKEY);
+    if( pParse->nErr ){
+      pTab->tabFlags &= ~TF_WithoutRowid;
+      return;
+    }
+    assert( db->mallocFailed==0 );
+    pPk = sqlite3PrimaryKeyIndex(pTab);
+    assert( pPk->nKeyCol==1 );
+  }else{
+    pPk = sqlite3PrimaryKeyIndex(pTab);
+    assert( pPk!=0 );
+
+    /*
+    ** Remove all redundant columns from the PRIMARY KEY.  For example, change
+    ** "PRIMARY KEY(a,b,a,b,c,b,c,d)" into just "PRIMARY KEY(a,b,c,d)".  Later
+    ** code assumes the PRIMARY KEY contains no repeated columns.
+    */
+    for(i=j=1; i<pPk->nKeyCol; i++){
+      if( isDupColumn(pPk, j, pPk, i) ){
+        pPk->nColumn--;
+      }else{
+        testcase( hasColumn(pPk->aiColumn, j, pPk->aiColumn[i]) );
+        pPk->azColl[j] = pPk->azColl[i];
+        pPk->aSortOrder[j] = pPk->aSortOrder[i];
+        pPk->aiColumn[j++] = pPk->aiColumn[i];
+      }
+    }
+    pPk->nKeyCol = j;
+  }
+  assert( pPk!=0 );
+  pPk->isCovering = 1;
+  if( !db->init.imposterTable ) pPk->uniqNotNull = 1;
+  nPk = pPk->nColumn = pPk->nKeyCol;
+
+  /* Bypass the creation of the PRIMARY KEY btree and the sqlite_schema
+  ** table entry. This is only required if currently generating VDBE
+  ** code for a CREATE TABLE (not when parsing one as part of reading
+  ** a database schema).  */
+  if( v && pPk->tnum>0 ){
+    assert( db->init.busy==0 );
+    sqlite3VdbeChangeOpcode(v, (int)pPk->tnum, OP_Goto);
+  }
+
+  /* The root page of the PRIMARY KEY is the table root page */
+  pPk->tnum = pTab->tnum;
+
+  /* Update the in-memory representation of all UNIQUE indices by converting
+  ** the final rowid column into one or more columns of the PRIMARY KEY.
+  */
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    int n;
+    if( IsPrimaryKeyIndex(pIdx) ) continue;
+    for(i=n=0; i<nPk; i++){
+      if( !isDupColumn(pIdx, pIdx->nKeyCol, pPk, i) ){
+        testcase( hasColumn(pIdx->aiColumn, pIdx->nKeyCol, pPk->aiColumn[i]) );
+        n++;
+      }
+    }
+    if( n==0 ){
+      /* This index is a superset of the primary key */
+      pIdx->nColumn = pIdx->nKeyCol;
+      continue;
+    }
+    if( resizeIndexObject(db, pIdx, pIdx->nKeyCol+n) ) return;
+    for(i=0, j=pIdx->nKeyCol; i<nPk; i++){
+      if( !isDupColumn(pIdx, pIdx->nKeyCol, pPk, i) ){
+        testcase( hasColumn(pIdx->aiColumn, pIdx->nKeyCol, pPk->aiColumn[i]) );
+        pIdx->aiColumn[j] = pPk->aiColumn[i];
+        pIdx->azColl[j] = pPk->azColl[i];
+        if( pPk->aSortOrder[i] ){
+          /* See ticket https://www.sqlite.org/src/info/bba7b69f9849b5bf */
+          pIdx->bAscKeyBug = 1;
+        }
+        j++;
+      }
+    }
+    assert( pIdx->nColumn>=pIdx->nKeyCol+n );
+    assert( pIdx->nColumn>=j );
+  }
+
+  /* Add all table columns to the PRIMARY KEY index
+  */
+  nExtra = 0;
+  for(i=0; i<pTab->nCol; i++){
+    if( !hasColumn(pPk->aiColumn, nPk, i)
+     && (pTab->aCol[i].colFlags & COLFLAG_VIRTUAL)==0 ) nExtra++;
+  }
+  if( resizeIndexObject(db, pPk, nPk+nExtra) ) return;
+  for(i=0, j=nPk; i<pTab->nCol; i++){
+    if( !hasColumn(pPk->aiColumn, j, i)
+     && (pTab->aCol[i].colFlags & COLFLAG_VIRTUAL)==0
+    ){
+      assert( j<pPk->nColumn );
+      pPk->aiColumn[j] = i;
+      pPk->azColl[j] = sqlite3StrBINARY;
+      j++;
+    }
+  }
+  assert( pPk->nColumn==j );
+  assert( pTab->nNVCol<=j );
+  recomputeColumnsNotIndexed(pPk);
+}
+
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Return true if pTab is a virtual table and zName is a shadow table name
+** for that virtual table.
+*/
+int sqlite3IsShadowTableOf(sqlite3 *db, Table *pTab, const char *zName){
+  int nName;                    /* Length of zName */
+  Module *pMod;                 /* Module for the virtual table */
+
+  if( !IsVirtual(pTab) ) return 0;
+  nName = sqlite3Strlen30(pTab->zName);
+  if( sqlite3_strnicmp(zName, pTab->zName, nName)!=0 ) return 0;
+  if( zName[nName]!='_' ) return 0;
+  pMod = (Module*)sqlite3HashFind(&db->aModule, pTab->u.vtab.azArg[0]);
+  if( pMod==0 ) return 0;
+  if( pMod->pModule->iVersion<3 ) return 0;
+  if( pMod->pModule->xShadowName==0 ) return 0;
+  return pMod->pModule->xShadowName(zName+nName+1);
+}
+#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Table pTab is a virtual table.  If it the virtual table implementation
+** exists and has an xShadowName method, then loop over all other ordinary
+** tables within the same schema looking for shadow tables of pTab, and mark
+** any shadow tables seen using the TF_Shadow flag.
+*/
+void sqlite3MarkAllShadowTablesOf(sqlite3 *db, Table *pTab){
+  int nName;                    /* Length of pTab->zName */
+  Module *pMod;                 /* Module for the virtual table */
+  HashElem *k;                  /* For looping through the symbol table */
+
+  assert( IsVirtual(pTab) );
+  pMod = (Module*)sqlite3HashFind(&db->aModule, pTab->u.vtab.azArg[0]);
+  if( pMod==0 ) return;
+  if( NEVER(pMod->pModule==0) ) return;
+  if( pMod->pModule->iVersion<3 ) return;
+  if( pMod->pModule->xShadowName==0 ) return;
+  assert( pTab->zName!=0 );
+  nName = sqlite3Strlen30(pTab->zName);
+  for(k=sqliteHashFirst(&pTab->pSchema->tblHash); k; k=sqliteHashNext(k)){
+    Table *pOther = sqliteHashData(k);
+    assert( pOther->zName!=0 );
+    if( !IsOrdinaryTable(pOther) ) continue;
+    if( pOther->tabFlags & TF_Shadow ) continue;
+    if( sqlite3StrNICmp(pOther->zName, pTab->zName, nName)==0
+     && pOther->zName[nName]=='_'
+     && pMod->pModule->xShadowName(pOther->zName+nName+1)
+    ){
+      pOther->tabFlags |= TF_Shadow;
+    }
+  }
+}
+#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Return true if zName is a shadow table name in the current database
+** connection.
+**
+** zName is temporarily modified while this routine is running, but is
+** restored to its original value prior to this routine returning.
+*/
+int sqlite3ShadowTableName(sqlite3 *db, const char *zName){
+  char *zTail;                  /* Pointer to the last "_" in zName */
+  Table *pTab;                  /* Table that zName is a shadow of */
+  zTail = strrchr(zName, '_');
+  if( zTail==0 ) return 0;
+  *zTail = 0;
+  pTab = sqlite3FindTable(db, zName, 0);
+  *zTail = '_';
+  if( pTab==0 ) return 0;
+  if( !IsVirtual(pTab) ) return 0;
+  return sqlite3IsShadowTableOf(db, pTab, zName);
+}
+#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
+
+
+#ifdef SQLITE_DEBUG
+/*
+** Mark all nodes of an expression as EP_Immutable, indicating that
+** they should not be changed.  Expressions attached to a table or
+** index definition are tagged this way to help ensure that we do
+** not pass them into code generator routines by mistake.
+*/
+static int markImmutableExprStep(Walker *pWalker, Expr *pExpr){
+  (void)pWalker;
+  ExprSetVVAProperty(pExpr, EP_Immutable);
+  return WRC_Continue;
+}
+static void markExprListImmutable(ExprList *pList){
+  if( pList ){
+    Walker w;
+    memset(&w, 0, sizeof(w));
+    w.xExprCallback = markImmutableExprStep;
+    w.xSelectCallback = sqlite3SelectWalkNoop;
+    w.xSelectCallback2 = 0;
+    sqlite3WalkExprList(&w, pList);
+  }
+}
+#else
+#define markExprListImmutable(X)  /* no-op */
+#endif /* SQLITE_DEBUG */
+
+
+/*
+** This routine is called to report the final ")" that terminates
+** a CREATE TABLE statement.
+**
+** The table structure that other action routines have been building
+** is added to the internal hash tables, assuming no errors have
+** occurred.
+**
+** An entry for the table is made in the schema table on disk, unless
+** this is a temporary table or db->init.busy==1.  When db->init.busy==1
+** it means we are reading the sqlite_schema table because we just
+** connected to the database or because the sqlite_schema table has
+** recently changed, so the entry for this table already exists in
+** the sqlite_schema table.  We do not want to create it again.
+**
+** If the pSelect argument is not NULL, it means that this routine
+** was called to create a table generated from a
+** "CREATE TABLE ... AS SELECT ..." statement.  The column names of
+** the new table will match the result set of the SELECT.
+*/
+void sqlite3EndTable(
+  Parse *pParse,          /* Parse context */
+  Token *pCons,           /* The ',' token after the last column defn. */
+  Token *pEnd,            /* The ')' before options in the CREATE TABLE */
+  u32 tabOpts,            /* Extra table options. Usually 0. */
+  Select *pSelect         /* Select from a "CREATE ... AS SELECT" */
+){
+  Table *p;                 /* The new table */
+  sqlite3 *db = pParse->db; /* The database connection */
+  int iDb;                  /* Database in which the table lives */
+  Index *pIdx;              /* An implied index of the table */
+
+  if( pEnd==0 && pSelect==0 ){
+    return;
+  }
+  p = pParse->pNewTable;
+  if( p==0 ) return;
+
+  if( pSelect==0 && sqlite3ShadowTableName(db, p->zName) ){
+    p->tabFlags |= TF_Shadow;
+  }
+
+  /* If the db->init.busy is 1 it means we are reading the SQL off the
+  ** "sqlite_schema" or "sqlite_temp_schema" table on the disk.
+  ** So do not write to the disk again.  Extract the root page number
+  ** for the table from the db->init.newTnum field.  (The page number
+  ** should have been put there by the sqliteOpenCb routine.)
+  **
+  ** If the root page number is 1, that means this is the sqlite_schema
+  ** table itself.  So mark it read-only.
+  */
+  if( db->init.busy ){
+    if( pSelect || (!IsOrdinaryTable(p) && db->init.newTnum) ){
+      sqlite3ErrorMsg(pParse, "");
+      return;
+    }
+    p->tnum = db->init.newTnum;
+    if( p->tnum==1 ) p->tabFlags |= TF_Readonly;
+  }
+
+  /* Special processing for tables that include the STRICT keyword:
+  **
+  **   *  Do not allow custom column datatypes.  Every column must have
+  **      a datatype that is one of INT, INTEGER, REAL, TEXT, or BLOB.
+  **
+  **   *  If a PRIMARY KEY is defined, other than the INTEGER PRIMARY KEY,
+  **      then all columns of the PRIMARY KEY must have a NOT NULL
+  **      constraint.
+  */
+  if( tabOpts & TF_Strict ){
+    int ii;
+    p->tabFlags |= TF_Strict;
+    for(ii=0; ii<p->nCol; ii++){
+      Column *pCol = &p->aCol[ii];
+      if( pCol->eCType==COLTYPE_CUSTOM ){
+        if( pCol->colFlags & COLFLAG_HASTYPE ){
+          sqlite3ErrorMsg(pParse,
+            "unknown datatype for %s.%s: \"%s\"",
+            p->zName, pCol->zCnName, sqlite3ColumnType(pCol, "")
+          );
+        }else{
+          sqlite3ErrorMsg(pParse, "missing datatype for %s.%s",
+                          p->zName, pCol->zCnName);
+        }
+        return;
+      }else if( pCol->eCType==COLTYPE_ANY ){
+        pCol->affinity = SQLITE_AFF_BLOB;
+      }
+      if( (pCol->colFlags & COLFLAG_PRIMKEY)!=0
+       && p->iPKey!=ii
+       && pCol->notNull == OE_None
+      ){
+        pCol->notNull = OE_Abort;
+        p->tabFlags |= TF_HasNotNull;
+      }
+    }   
+  }
+
+  assert( (p->tabFlags & TF_HasPrimaryKey)==0
+       || p->iPKey>=0 || sqlite3PrimaryKeyIndex(p)!=0 );
+  assert( (p->tabFlags & TF_HasPrimaryKey)!=0
+       || (p->iPKey<0 && sqlite3PrimaryKeyIndex(p)==0) );
+
+  /* Special processing for WITHOUT ROWID Tables */
+  if( tabOpts & TF_WithoutRowid ){
+    if( (p->tabFlags & TF_Autoincrement) ){
+      sqlite3ErrorMsg(pParse,
+          "AUTOINCREMENT not allowed on WITHOUT ROWID tables");
+      return;
+    }
+    if( (p->tabFlags & TF_HasPrimaryKey)==0 ){
+      sqlite3ErrorMsg(pParse, "PRIMARY KEY missing on table %s", p->zName);
+      return;
+    }
+    p->tabFlags |= TF_WithoutRowid | TF_NoVisibleRowid;
+    convertToWithoutRowidTable(pParse, p);
+  }
+  iDb = sqlite3SchemaToIndex(db, p->pSchema);
+
+#ifndef SQLITE_OMIT_CHECK
+  /* Resolve names in all CHECK constraint expressions.
+  */
+  if( p->pCheck ){
+    sqlite3ResolveSelfReference(pParse, p, NC_IsCheck, 0, p->pCheck);
+    if( pParse->nErr ){
+      /* If errors are seen, delete the CHECK constraints now, else they might
+      ** actually be used if PRAGMA writable_schema=ON is set. */
+      sqlite3ExprListDelete(db, p->pCheck);
+      p->pCheck = 0;
+    }else{
+      markExprListImmutable(p->pCheck);
+    }
+  }
+#endif /* !defined(SQLITE_OMIT_CHECK) */
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  if( p->tabFlags & TF_HasGenerated ){
+    int ii, nNG = 0;
+    testcase( p->tabFlags & TF_HasVirtual );
+    testcase( p->tabFlags & TF_HasStored );
+    for(ii=0; ii<p->nCol; ii++){
+      u32 colFlags = p->aCol[ii].colFlags;
+      if( (colFlags & COLFLAG_GENERATED)!=0 ){
+        Expr *pX = sqlite3ColumnExpr(p, &p->aCol[ii]);
+        testcase( colFlags & COLFLAG_VIRTUAL );
+        testcase( colFlags & COLFLAG_STORED );
+        if( sqlite3ResolveSelfReference(pParse, p, NC_GenCol, pX, 0) ){
+          /* If there are errors in resolving the expression, change the
+          ** expression to a NULL.  This prevents code generators that operate
+          ** on the expression from inserting extra parts into the expression
+          ** tree that have been allocated from lookaside memory, which is
+          ** illegal in a schema and will lead to errors or heap corruption
+          ** when the database connection closes. */
+          sqlite3ColumnSetExpr(pParse, p, &p->aCol[ii],
+               sqlite3ExprAlloc(db, TK_NULL, 0, 0));
+        }
+      }else{
+        nNG++;
+      }
+    }
+    if( nNG==0 ){
+      sqlite3ErrorMsg(pParse, "must have at least one non-generated column");
+      return;
+    }
+  }
+#endif
+
+  /* Estimate the average row size for the table and for all implied indices */
+  estimateTableWidth(p);
+  for(pIdx=p->pIndex; pIdx; pIdx=pIdx->pNext){
+    estimateIndexWidth(pIdx);
+  }
+
+  /* If not initializing, then create a record for the new table
+  ** in the schema table of the database.
+  **
+  ** If this is a TEMPORARY table, write the entry into the auxiliary
+  ** file instead of into the main database file.
+  */
+  if( !db->init.busy ){
+    int n;
+    Vdbe *v;
+    char *zType;    /* "view" or "table" */
+    char *zType2;   /* "VIEW" or "TABLE" */
+    char *zStmt;    /* Text of the CREATE TABLE or CREATE VIEW statement */
+
+    v = sqlite3GetVdbe(pParse);
+    if( NEVER(v==0) ) return;
+
+    sqlite3VdbeAddOp1(v, OP_Close, 0);
+
+    /*
+    ** Initialize zType for the new view or table.
+    */
+    if( IsOrdinaryTable(p) ){
+      /* A regular table */
+      zType = "table";
+      zType2 = "TABLE";
+#ifndef SQLITE_OMIT_VIEW
+    }else{
+      /* A view */
+      zType = "view";
+      zType2 = "VIEW";
+#endif
+    }
+
+    /* If this is a CREATE TABLE xx AS SELECT ..., execute the SELECT
+    ** statement to populate the new table. The root-page number for the
+    ** new table is in register pParse->regRoot.
+    **
+    ** Once the SELECT has been coded by sqlite3Select(), it is in a
+    ** suitable state to query for the column names and types to be used
+    ** by the new table.
+    **
+    ** A shared-cache write-lock is not required to write to the new table,
+    ** as a schema-lock must have already been obtained to create it. Since
+    ** a schema-lock excludes all other database users, the write-lock would
+    ** be redundant.
+    */
+    if( pSelect ){
+      SelectDest dest;    /* Where the SELECT should store results */
+      int regYield;       /* Register holding co-routine entry-point */
+      int addrTop;        /* Top of the co-routine */
+      int regRec;         /* A record to be insert into the new table */
+      int regRowid;       /* Rowid of the next row to insert */
+      int addrInsLoop;    /* Top of the loop for inserting rows */
+      Table *pSelTab;     /* A table that describes the SELECT results */
+
+      if( IN_SPECIAL_PARSE ){
+        pParse->rc = SQLITE_ERROR;
+        pParse->nErr++;
+        return;
+      }
+      regYield = ++pParse->nMem;
+      regRec = ++pParse->nMem;
+      regRowid = ++pParse->nMem;
+      assert(pParse->nTab==1);
+      sqlite3MayAbort(pParse);
+      sqlite3VdbeAddOp3(v, OP_OpenWrite, 1, pParse->regRoot, iDb);
+      sqlite3VdbeChangeP5(v, OPFLAG_P2ISREG);
+      pParse->nTab = 2;
+      addrTop = sqlite3VdbeCurrentAddr(v) + 1;
+      sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, addrTop);
+      if( pParse->nErr ) return;
+      pSelTab = sqlite3ResultSetOfSelect(pParse, pSelect, SQLITE_AFF_BLOB);
+      if( pSelTab==0 ) return;
+      assert( p->aCol==0 );
+      p->nCol = p->nNVCol = pSelTab->nCol;
+      p->aCol = pSelTab->aCol;
+      pSelTab->nCol = 0;
+      pSelTab->aCol = 0;
+      sqlite3DeleteTable(db, pSelTab);
+      sqlite3SelectDestInit(&dest, SRT_Coroutine, regYield);
+      sqlite3Select(pParse, pSelect, &dest);
+      if( pParse->nErr ) return;
+      sqlite3VdbeEndCoroutine(v, regYield);
+      sqlite3VdbeJumpHere(v, addrTop - 1);
+      addrInsLoop = sqlite3VdbeAddOp1(v, OP_Yield, dest.iSDParm);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, dest.iSdst, dest.nSdst, regRec);
+      sqlite3TableAffinity(v, p, 0);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, 1, regRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, 1, regRec, regRowid);
+      sqlite3VdbeGoto(v, addrInsLoop);
+      sqlite3VdbeJumpHere(v, addrInsLoop);
+      sqlite3VdbeAddOp1(v, OP_Close, 1);
+    }
+
+    /* Compute the complete text of the CREATE statement */
+    if( pSelect ){
+      zStmt = createTableStmt(db, p);
+    }else{
+      Token *pEnd2 = tabOpts ? &pParse->sLastToken : pEnd;
+      n = (int)(pEnd2->z - pParse->sNameToken.z);
+      if( pEnd2->z[0]!=';' ) n += pEnd2->n;
+      zStmt = sqlite3MPrintf(db,
+          "CREATE %s %.*s", zType2, n, pParse->sNameToken.z
+      );
+    }
+
+    /* A slot for the record has already been allocated in the
+    ** schema table.  We just need to update that slot with all
+    ** the information we've collected.
+    */
+    sqlite3NestedParse(pParse,
+      "UPDATE %Q." LEGACY_SCHEMA_TABLE
+      " SET type='%s', name=%Q, tbl_name=%Q, rootpage=#%d, sql=%Q"
+      " WHERE rowid=#%d",
+      db->aDb[iDb].zDbSName,
+      zType,
+      p->zName,
+      p->zName,
+      pParse->regRoot,
+      zStmt,
+      pParse->regRowid
+    );
+    sqlite3DbFree(db, zStmt);
+    sqlite3ChangeCookie(pParse, iDb);
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+    /* Check to see if we need to create an sqlite_sequence table for
+    ** keeping track of autoincrement keys.
+    */
+    if( (p->tabFlags & TF_Autoincrement)!=0 && !IN_SPECIAL_PARSE ){
+      Db *pDb = &db->aDb[iDb];
+      assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+      if( pDb->pSchema->pSeqTab==0 ){
+        sqlite3NestedParse(pParse,
+          "CREATE TABLE %Q.sqlite_sequence(name,seq)",
+          pDb->zDbSName
+        );
+      }
+    }
+#endif
+
+    /* Reparse everything to update our internal data structures */
+    sqlite3VdbeAddParseSchemaOp(v, iDb,
+           sqlite3MPrintf(db, "tbl_name='%q' AND type!='trigger'", p->zName),0);
+
+    /* Test for cycles in generated columns and illegal expressions
+    ** in CHECK constraints and in DEFAULT clauses. */
+    if( p->tabFlags & TF_HasGenerated ){
+      sqlite3VdbeAddOp4(v, OP_SqlExec, 1, 0, 0,
+             sqlite3MPrintf(db, "SELECT*FROM\"%w\".\"%w\"",
+                   db->aDb[iDb].zDbSName, p->zName), P4_DYNAMIC);
+    }
+    sqlite3VdbeAddOp4(v, OP_SqlExec, 1, 0, 0,
+           sqlite3MPrintf(db, "PRAGMA \"%w\".integrity_check(%Q)",
+                 db->aDb[iDb].zDbSName, p->zName), P4_DYNAMIC);
+  }
+
+  /* Add the table to the in-memory representation of the database.
+  */
+  if( db->init.busy ){
+    Table *pOld;
+    Schema *pSchema = p->pSchema;
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    assert( HasRowid(p) || p->iPKey<0 );
+    pOld = sqlite3HashInsert(&pSchema->tblHash, p->zName, p);
+    if( pOld ){
+      assert( p==pOld );  /* Malloc must have failed inside HashInsert() */
+      sqlite3OomFault(db);
+      return;
+    }
+    pParse->pNewTable = 0;
+    db->mDbFlags |= DBFLAG_SchemaChange;
+
+    /* If this is the magic sqlite_sequence table used by autoincrement,
+    ** then record a pointer to this table in the main database structure
+    ** so that INSERT can find the table easily.  */
+    assert( !pParse->nested );
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+    if( strcmp(p->zName, "sqlite_sequence")==0 ){
+      assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+      p->pSchema->pSeqTab = p;
+    }
+#endif
+  }
+
+#ifndef SQLITE_OMIT_ALTERTABLE
+  if( !pSelect && IsOrdinaryTable(p) ){
+    assert( pCons && pEnd );
+    if( pCons->z==0 ){
+      pCons = pEnd;
+    }
+    p->u.tab.addColOffset = 13 + (int)(pCons->z - pParse->sNameToken.z);
+  }
+#endif
+}
+
+#ifndef SQLITE_OMIT_VIEW
+/*
+** The parser calls this routine in order to create a new VIEW
+*/
+void sqlite3CreateView(
+  Parse *pParse,     /* The parsing context */
+  Token *pBegin,     /* The CREATE token that begins the statement */
+  Token *pName1,     /* The token that holds the name of the view */
+  Token *pName2,     /* The token that holds the name of the view */
+  ExprList *pCNames, /* Optional list of view column names */
+  Select *pSelect,   /* A SELECT statement that will become the new view */
+  int isTemp,        /* TRUE for a TEMPORARY view */
+  int noErr          /* Suppress error messages if VIEW already exists */
+){
+  Table *p;
+  int n;
+  const char *z;
+  Token sEnd;
+  DbFixer sFix;
+  Token *pName = 0;
+  int iDb;
+  sqlite3 *db = pParse->db;
+
+  if( pParse->nVar>0 ){
+    sqlite3ErrorMsg(pParse, "parameters are not allowed in views");
+    goto create_view_fail;
+  }
+  sqlite3StartTable(pParse, pName1, pName2, isTemp, 1, 0, noErr);
+  p = pParse->pNewTable;
+  if( p==0 || pParse->nErr ) goto create_view_fail;
+
+  /* Legacy versions of SQLite allowed the use of the magic "rowid" column
+  ** on a view, even though views do not have rowids.  The following flag
+  ** setting fixes this problem.  But the fix can be disabled by compiling
+  ** with -DSQLITE_ALLOW_ROWID_IN_VIEW in case there are legacy apps that
+  ** depend upon the old buggy behavior. */
+#ifndef SQLITE_ALLOW_ROWID_IN_VIEW
+  p->tabFlags |= TF_NoVisibleRowid;
+#endif
+
+  sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+  iDb = sqlite3SchemaToIndex(db, p->pSchema);
+  sqlite3FixInit(&sFix, pParse, iDb, "view", pName);
+  if( sqlite3FixSelect(&sFix, pSelect) ) goto create_view_fail;
+
+  /* Make a copy of the entire SELECT statement that defines the view.
+  ** This will force all the Expr.token.z values to be dynamically
+  ** allocated rather than point to the input string - which means that
+  ** they will persist after the current sqlite3_exec() call returns.
+  */
+  pSelect->selFlags |= SF_View;
+  if( IN_RENAME_OBJECT ){
+    p->u.view.pSelect = pSelect;
+    pSelect = 0;
+  }else{
+    p->u.view.pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
+  }
+  p->pCheck = sqlite3ExprListDup(db, pCNames, EXPRDUP_REDUCE);
+  p->eTabType = TABTYP_VIEW;
+  if( db->mallocFailed ) goto create_view_fail;
+
+  /* Locate the end of the CREATE VIEW statement.  Make sEnd point to
+  ** the end.
+  */
+  sEnd = pParse->sLastToken;
+  assert( sEnd.z[0]!=0 || sEnd.n==0 );
+  if( sEnd.z[0]!=';' ){
+    sEnd.z += sEnd.n;
+  }
+  sEnd.n = 0;
+  n = (int)(sEnd.z - pBegin->z);
+  assert( n>0 );
+  z = pBegin->z;
+  while( sqlite3Isspace(z[n-1]) ){ n--; }
+  sEnd.z = &z[n-1];
+  sEnd.n = 1;
+
+  /* Use sqlite3EndTable() to add the view to the schema table */
+  sqlite3EndTable(pParse, 0, &sEnd, 0, 0);
+
+create_view_fail:
+  sqlite3SelectDelete(db, pSelect);
+  if( IN_RENAME_OBJECT ){
+    sqlite3RenameExprlistUnmap(pParse, pCNames);
+  }
+  sqlite3ExprListDelete(db, pCNames);
+  return;
+}
+#endif /* SQLITE_OMIT_VIEW */
+
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+/*
+** The Table structure pTable is really a VIEW.  Fill in the names of
+** the columns of the view in the pTable structure.  Return the number
+** of errors.  If an error is seen leave an error message in pParse->zErrMsg.
+*/
+static SQLITE_NOINLINE int viewGetColumnNames(Parse *pParse, Table *pTable){
+  Table *pSelTab;   /* A fake table from which we get the result set */
+  Select *pSel;     /* Copy of the SELECT that implements the view */
+  int nErr = 0;     /* Number of errors encountered */
+  sqlite3 *db = pParse->db;  /* Database connection for malloc errors */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  int rc;
+#endif
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  sqlite3_xauth xAuth;       /* Saved xAuth pointer */
+#endif
+
+  assert( pTable );
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTable) ){
+    db->nSchemaLock++;
+    rc = sqlite3VtabCallConnect(pParse, pTable);
+    db->nSchemaLock--;
+    return rc;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_VIEW
+  /* A positive nCol means the columns names for this view are
+  ** already known.  This routine is not called unless either the
+  ** table is virtual or nCol is zero.
+  */
+  assert( pTable->nCol<=0 );
+
+  /* A negative nCol is a special marker meaning that we are currently
+  ** trying to compute the column names.  If we enter this routine with
+  ** a negative nCol, it means two or more views form a loop, like this:
+  **
+  **     CREATE VIEW one AS SELECT * FROM two;
+  **     CREATE VIEW two AS SELECT * FROM one;
+  **
+  ** Actually, the error above is now caught prior to reaching this point.
+  ** But the following test is still important as it does come up
+  ** in the following:
+  **
+  **     CREATE TABLE main.ex1(a);
+  **     CREATE TEMP VIEW ex1 AS SELECT a FROM ex1;
+  **     SELECT * FROM temp.ex1;
+  */
+  if( pTable->nCol<0 ){
+    sqlite3ErrorMsg(pParse, "view %s is circularly defined", pTable->zName);
+    return 1;
+  }
+  assert( pTable->nCol>=0 );
+
+  /* If we get this far, it means we need to compute the table names.
+  ** Note that the call to sqlite3ResultSetOfSelect() will expand any
+  ** "*" elements in the results set of the view and will assign cursors
+  ** to the elements of the FROM clause.  But we do not want these changes
+  ** to be permanent.  So the computation is done on a copy of the SELECT
+  ** statement that defines the view.
+  */
+  assert( IsView(pTable) );
+  pSel = sqlite3SelectDup(db, pTable->u.view.pSelect, 0);
+  if( pSel ){
+    u8 eParseMode = pParse->eParseMode;
+    int nTab = pParse->nTab;
+    int nSelect = pParse->nSelect;
+    pParse->eParseMode = PARSE_MODE_NORMAL;
+    sqlite3SrcListAssignCursors(pParse, pSel->pSrc);
+    pTable->nCol = -1;
+    DisableLookaside;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    xAuth = db->xAuth;
+    db->xAuth = 0;
+    pSelTab = sqlite3ResultSetOfSelect(pParse, pSel, SQLITE_AFF_NONE);
+    db->xAuth = xAuth;
+#else
+    pSelTab = sqlite3ResultSetOfSelect(pParse, pSel, SQLITE_AFF_NONE);
+#endif
+    pParse->nTab = nTab;
+    pParse->nSelect = nSelect;
+    if( pSelTab==0 ){
+      pTable->nCol = 0;
+      nErr++;
+    }else if( pTable->pCheck ){
+      /* CREATE VIEW name(arglist) AS ...
+      ** The names of the columns in the table are taken from
+      ** arglist which is stored in pTable->pCheck.  The pCheck field
+      ** normally holds CHECK constraints on an ordinary table, but for
+      ** a VIEW it holds the list of column names.
+      */
+      sqlite3ColumnsFromExprList(pParse, pTable->pCheck,
+                                 &pTable->nCol, &pTable->aCol);
+      if( pParse->nErr==0
+       && pTable->nCol==pSel->pEList->nExpr
+      ){
+        assert( db->mallocFailed==0 );
+        sqlite3SubqueryColumnTypes(pParse, pTable, pSel, SQLITE_AFF_NONE);
+      }
+    }else{
+      /* CREATE VIEW name AS...  without an argument list.  Construct
+      ** the column names from the SELECT statement that defines the view.
+      */
+      assert( pTable->aCol==0 );
+      pTable->nCol = pSelTab->nCol;
+      pTable->aCol = pSelTab->aCol;
+      pTable->tabFlags |= (pSelTab->tabFlags & COLFLAG_NOINSERT);
+      pSelTab->nCol = 0;
+      pSelTab->aCol = 0;
+      assert( sqlite3SchemaMutexHeld(db, 0, pTable->pSchema) );
+    }
+    pTable->nNVCol = pTable->nCol;
+    sqlite3DeleteTable(db, pSelTab);
+    sqlite3SelectDelete(db, pSel);
+    EnableLookaside;
+    pParse->eParseMode = eParseMode;
+  } else {
+    nErr++;
+  }
+  pTable->pSchema->schemaFlags |= DB_UnresetViews;
+  if( db->mallocFailed ){
+    sqlite3DeleteColumnNames(db, pTable);
+  }
+#endif /* SQLITE_OMIT_VIEW */
+  return nErr; 
+}
+int sqlite3ViewGetColumnNames(Parse *pParse, Table *pTable){
+  assert( pTable!=0 );
+  if( !IsVirtual(pTable) && pTable->nCol>0 ) return 0;
+  return viewGetColumnNames(pParse, pTable);
+}
+#endif /* !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE) */
+
+#ifndef SQLITE_OMIT_VIEW
+/*
+** Clear the column names from every VIEW in database idx.
+*/
+static void sqliteViewResetAll(sqlite3 *db, int idx){
+  HashElem *i;
+  assert( sqlite3SchemaMutexHeld(db, idx, 0) );
+  if( !DbHasProperty(db, idx, DB_UnresetViews) ) return;
+  for(i=sqliteHashFirst(&db->aDb[idx].pSchema->tblHash); i;i=sqliteHashNext(i)){
+    Table *pTab = sqliteHashData(i);
+    if( IsView(pTab) ){
+      sqlite3DeleteColumnNames(db, pTab);
+    }
+  }
+  DbClearProperty(db, idx, DB_UnresetViews);
+}
+#else
+# define sqliteViewResetAll(A,B)
+#endif /* SQLITE_OMIT_VIEW */
+
+/*
+** This function is called by the VDBE to adjust the internal schema
+** used by SQLite when the btree layer moves a table root page. The
+** root-page of a table or index in database iDb has changed from iFrom
+** to iTo.
+**
+** Ticket #1728:  The symbol table might still contain information
+** on tables and/or indices that are the process of being deleted.
+** If you are unlucky, one of those deleted indices or tables might
+** have the same rootpage number as the real table or index that is
+** being moved.  So we cannot stop searching after the first match
+** because the first match might be for one of the deleted indices
+** or tables and not the table/index that is actually being moved.
+** We must continue looping until all tables and indices with
+** rootpage==iFrom have been converted to have a rootpage of iTo
+** in order to be certain that we got the right one.
+*/
+#ifndef SQLITE_OMIT_AUTOVACUUM
+void sqlite3RootPageMoved(sqlite3 *db, int iDb, Pgno iFrom, Pgno iTo){
+  HashElem *pElem;
+  Hash *pHash;
+  Db *pDb;
+
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  pDb = &db->aDb[iDb];
+  pHash = &pDb->pSchema->tblHash;
+  for(pElem=sqliteHashFirst(pHash); pElem; pElem=sqliteHashNext(pElem)){
+    Table *pTab = sqliteHashData(pElem);
+    if( pTab->tnum==iFrom ){
+      pTab->tnum = iTo;
+    }
+  }
+  pHash = &pDb->pSchema->idxHash;
+  for(pElem=sqliteHashFirst(pHash); pElem; pElem=sqliteHashNext(pElem)){
+    Index *pIdx = sqliteHashData(pElem);
+    if( pIdx->tnum==iFrom ){
+      pIdx->tnum = iTo;
+    }
+  }
+}
+#endif
+
+/*
+** Write code to erase the table with root-page iTable from database iDb.
+** Also write code to modify the sqlite_schema table and internal schema
+** if a root-page of another table is moved by the btree-layer whilst
+** erasing iTable (this can happen with an auto-vacuum database).
+*/
+static void destroyRootPage(Parse *pParse, int iTable, int iDb){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int r1 = sqlite3GetTempReg(pParse);
+  if( iTable<2 ) sqlite3ErrorMsg(pParse, "corrupt schema");
+  sqlite3VdbeAddOp3(v, OP_Destroy, iTable, r1, iDb);
+  sqlite3MayAbort(pParse);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  /* OP_Destroy stores an in integer r1. If this integer
+  ** is non-zero, then it is the root page number of a table moved to
+  ** location iTable. The following code modifies the sqlite_schema table to
+  ** reflect this.
+  **
+  ** The "#NNN" in the SQL is a special constant that means whatever value
+  ** is in register NNN.  See grammar rules associated with the TK_REGISTER
+  ** token for additional information.
+  */
+  sqlite3NestedParse(pParse,
+     "UPDATE %Q." LEGACY_SCHEMA_TABLE
+     " SET rootpage=%d WHERE #%d AND rootpage=#%d",
+     pParse->db->aDb[iDb].zDbSName, iTable, r1, r1);
+#endif
+  sqlite3ReleaseTempReg(pParse, r1);
+}
+
+/*
+** Write VDBE code to erase table pTab and all associated indices on disk.
+** Code to update the sqlite_schema tables and internal schema definitions
+** in case a root-page belonging to another table is moved by the btree layer
+** is also added (this can happen with an auto-vacuum database).
+*/
+static void destroyTable(Parse *pParse, Table *pTab){
+  /* If the database may be auto-vacuum capable (if SQLITE_OMIT_AUTOVACUUM
+  ** is not defined), then it is important to call OP_Destroy on the
+  ** table and index root-pages in order, starting with the numerically
+  ** largest root-page number. This guarantees that none of the root-pages
+  ** to be destroyed is relocated by an earlier OP_Destroy. i.e. if the
+  ** following were coded:
+  **
+  ** OP_Destroy 4 0
+  ** ...
+  ** OP_Destroy 5 0
+  **
+  ** and root page 5 happened to be the largest root-page number in the
+  ** database, then root page 5 would be moved to page 4 by the
+  ** "OP_Destroy 4 0" opcode. The subsequent "OP_Destroy 5 0" would hit
+  ** a free-list page.
+  */
+  Pgno iTab = pTab->tnum;
+  Pgno iDestroyed = 0;
+
+  while( 1 ){
+    Index *pIdx;
+    Pgno iLargest = 0;
+
+    if( iDestroyed==0 || iTab<iDestroyed ){
+      iLargest = iTab;
+    }
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      Pgno iIdx = pIdx->tnum;
+      assert( pIdx->pSchema==pTab->pSchema );
+      if( (iDestroyed==0 || (iIdx<iDestroyed)) && iIdx>iLargest ){
+        iLargest = iIdx;
+      }
+    }
+    if( iLargest==0 ){
+      return;
+    }else{
+      int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+      assert( iDb>=0 && iDb<pParse->db->nDb );
+      destroyRootPage(pParse, iLargest, iDb);
+      iDestroyed = iLargest;
+    }
+  }
+}
+
+/*
+** Remove entries from the sqlite_statN tables (for N in (1,2,3))
+** after a DROP INDEX or DROP TABLE command.
+*/
+static void sqlite3ClearStatTables(
+  Parse *pParse,         /* The parsing context */
+  int iDb,               /* The database number */
+  const char *zType,     /* "idx" or "tbl" */
+  const char *zName      /* Name of index or table */
+){
+  int i;
+  const char *zDbName = pParse->db->aDb[iDb].zDbSName;
+  for(i=1; i<=4; i++){
+    char zTab[24];
+    sqlite3_snprintf(sizeof(zTab),zTab,"sqlite_stat%d",i);
+    if( sqlite3FindTable(pParse->db, zTab, zDbName) ){
+      sqlite3NestedParse(pParse,
+        "DELETE FROM %Q.%s WHERE %s=%Q",
+        zDbName, zTab, zType, zName
+      );
+    }
+  }
+}
+
+/*
+** Generate code to drop a table.
+*/
+void sqlite3CodeDropTable(Parse *pParse, Table *pTab, int iDb, int isView){
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  Trigger *pTrigger;
+  Db *pDb = &db->aDb[iDb];
+
+  v = sqlite3GetVdbe(pParse);
+  assert( v!=0 );
+  sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTab) ){
+    sqlite3VdbeAddOp0(v, OP_VBegin);
+  }
+#endif
+
+  /* Drop all triggers associated with the table being dropped. Code
+  ** is generated to remove entries from sqlite_schema and/or
+  ** sqlite_temp_schema if required.
+  */
+  pTrigger = sqlite3TriggerList(pParse, pTab);
+  while( pTrigger ){
+    assert( pTrigger->pSchema==pTab->pSchema ||
+        pTrigger->pSchema==db->aDb[1].pSchema );
+    sqlite3DropTriggerPtr(pParse, pTrigger);
+    pTrigger = pTrigger->pNext;
+  }
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  /* Remove any entries of the sqlite_sequence table associated with
+  ** the table being dropped. This is done before the table is dropped
+  ** at the btree level, in case the sqlite_sequence table needs to
+  ** move as a result of the drop (can happen in auto-vacuum mode).
+  */
+  if( pTab->tabFlags & TF_Autoincrement ){
+    sqlite3NestedParse(pParse,
+      "DELETE FROM %Q.sqlite_sequence WHERE name=%Q",
+      pDb->zDbSName, pTab->zName
+    );
+  }
+#endif
+
+  /* Drop all entries in the schema table that refer to the
+  ** table. The program name loops through the schema table and deletes
+  ** every row that refers to a table of the same name as the one being
+  ** dropped. Triggers are handled separately because a trigger can be
+  ** created in the temp database that refers to a table in another
+  ** database.
+  */
+  sqlite3NestedParse(pParse,
+      "DELETE FROM %Q." LEGACY_SCHEMA_TABLE
+      " WHERE tbl_name=%Q and type!='trigger'",
+      pDb->zDbSName, pTab->zName);
+  if( !isView && !IsVirtual(pTab) ){
+    destroyTable(pParse, pTab);
+  }
+
+  /* Remove the table entry from SQLite's internal schema and modify
+  ** the schema cookie.
+  */
+  if( IsVirtual(pTab) ){
+    sqlite3VdbeAddOp4(v, OP_VDestroy, iDb, 0, 0, pTab->zName, 0);
+    sqlite3MayAbort(pParse);
+  }
+  sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
+  sqlite3ChangeCookie(pParse, iDb);
+  sqliteViewResetAll(db, iDb);
+}
+
+/*
+** Return TRUE if shadow tables should be read-only in the current
+** context.
+*/
+int sqlite3ReadOnlyShadowTables(sqlite3 *db){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( (db->flags & SQLITE_Defensive)!=0
+   && db->pVtabCtx==0
+   && db->nVdbeExec==0
+   && !sqlite3VtabInSync(db)
+  ){
+    return 1;
+  }
+#endif
+  return 0;
+}
+
+/*
+** Return true if it is not allowed to drop the given table
+*/
+static int tableMayNotBeDropped(sqlite3 *db, Table *pTab){
+  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
+    if( sqlite3StrNICmp(pTab->zName+7, "stat", 4)==0 ) return 0;
+    if( sqlite3StrNICmp(pTab->zName+7, "parameters", 10)==0 ) return 0;
+    return 1;
+  }
+  if( (pTab->tabFlags & TF_Shadow)!=0 && sqlite3ReadOnlyShadowTables(db) ){
+    return 1;
+  }
+  if( pTab->tabFlags & TF_Eponymous ){
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** This routine is called to do the work of a DROP TABLE statement.
+** pName is the name of the table to be dropped.
+*/
+void sqlite3DropTable(Parse *pParse, SrcList *pName, int isView, int noErr){
+  Table *pTab;
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  if( db->mallocFailed ){
+    goto exit_drop_table;
+  }
+  assert( pParse->nErr==0 );
+  assert( pName->nSrc==1 );
+  if( sqlite3ReadSchema(pParse) ) goto exit_drop_table;
+  if( noErr ) db->suppressErr++;
+  assert( isView==0 || isView==LOCATE_VIEW );
+  pTab = sqlite3LocateTableItem(pParse, isView, &pName->a[0]);
+  if( noErr ) db->suppressErr--;
+
+  if( pTab==0 ){
+    if( noErr ){
+      sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }
+    goto exit_drop_table;
+  }
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb>=0 && iDb<db->nDb );
+
+  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
+  ** it is initialized.
+  */
+  if( IsVirtual(pTab) && sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto exit_drop_table;
+  }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code;
+    const char *zTab = SCHEMA_TABLE(iDb);
+    const char *zDb = db->aDb[iDb].zDbSName;
+    const char *zArg2 = 0;
+    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb)){
+      goto exit_drop_table;
+    }
+    if( isView ){
+      if( !OMIT_TEMPDB && iDb==1 ){
+        code = SQLITE_DROP_TEMP_VIEW;
+      }else{
+        code = SQLITE_DROP_VIEW;
+      }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    }else if( IsVirtual(pTab) ){
+      code = SQLITE_DROP_VTABLE;
+      zArg2 = sqlite3GetVTable(db, pTab)->pMod->zName;
+#endif
+    }else{
+      if( !OMIT_TEMPDB && iDb==1 ){
+        code = SQLITE_DROP_TEMP_TABLE;
+      }else{
+        code = SQLITE_DROP_TABLE;
+      }
+    }
+    if( sqlite3AuthCheck(pParse, code, pTab->zName, zArg2, zDb) ){
+      goto exit_drop_table;
+    }
+    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
+      goto exit_drop_table;
+    }
+  }
+#endif
+  if( tableMayNotBeDropped(db, pTab) ){
+    sqlite3ErrorMsg(pParse, "table %s may not be dropped", pTab->zName);
+    goto exit_drop_table;
+  }
+
+#ifndef SQLITE_OMIT_VIEW
+  /* Ensure DROP TABLE is not used on a view, and DROP VIEW is not used
+  ** on a table.
+  */
+  if( isView && !IsView(pTab) ){
+    sqlite3ErrorMsg(pParse, "use DROP TABLE to delete table %s", pTab->zName);
+    goto exit_drop_table;
+  }
+  if( !isView && IsView(pTab) ){
+    sqlite3ErrorMsg(pParse, "use DROP VIEW to delete view %s", pTab->zName);
+    goto exit_drop_table;
+  }
+#endif
+
+  /* Generate code to remove the table from the schema table
+  ** on disk.
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3BeginWriteOperation(pParse, 1, iDb);
+    if( !isView ){
+      sqlite3ClearStatTables(pParse, iDb, "tbl", pTab->zName);
+      sqlite3FkDropTable(pParse, pName, pTab);
+    }
+    sqlite3CodeDropTable(pParse, pTab, iDb, isView);
+  }
+
+exit_drop_table:
+  sqlite3SrcListDelete(db, pName);
+}
+
+/*
+** This routine is called to create a new foreign key on the table
+** currently under construction.  pFromCol determines which columns
+** in the current table point to the foreign key.  If pFromCol==0 then
+** connect the key to the last column inserted.  pTo is the name of
+** the table referred to (a.k.a the "parent" table).  pToCol is a list
+** of tables in the parent pTo table.  flags contains all
+** information about the conflict resolution algorithms specified
+** in the ON DELETE, ON UPDATE and ON INSERT clauses.
+**
+** An FKey structure is created and added to the table currently
+** under construction in the pParse->pNewTable field.
+**
+** The foreign key is set for IMMEDIATE processing.  A subsequent call
+** to sqlite3DeferForeignKey() might change this to DEFERRED.
+*/
+void sqlite3CreateForeignKey(
+  Parse *pParse,       /* Parsing context */
+  ExprList *pFromCol,  /* Columns in this table that point to other table */
+  Token *pTo,          /* Name of the other table */
+  ExprList *pToCol,    /* Columns in the other table */
+  int flags            /* Conflict resolution algorithms. */
+){
+  sqlite3 *db = pParse->db;
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  FKey *pFKey = 0;
+  FKey *pNextTo;
+  Table *p = pParse->pNewTable;
+  i64 nByte;
+  int i;
+  int nCol;
+  char *z;
+
+  assert( pTo!=0 );
+  if( p==0 || IN_DECLARE_VTAB ) goto fk_end;
+  if( pFromCol==0 ){
+    int iCol = p->nCol-1;
+    if( NEVER(iCol<0) ) goto fk_end;
+    if( pToCol && pToCol->nExpr!=1 ){
+      sqlite3ErrorMsg(pParse, "foreign key on %s"
+         " should reference only one column of table %T",
+         p->aCol[iCol].zCnName, pTo);
+      goto fk_end;
+    }
+    nCol = 1;
+  }else if( pToCol && pToCol->nExpr!=pFromCol->nExpr ){
+    sqlite3ErrorMsg(pParse,
+        "number of columns in foreign key does not match the number of "
+        "columns in the referenced table");
+    goto fk_end;
+  }else{
+    nCol = pFromCol->nExpr;
+  }
+  nByte = sizeof(*pFKey) + (nCol-1)*sizeof(pFKey->aCol[0]) + pTo->n + 1;
+  if( pToCol ){
+    for(i=0; i<pToCol->nExpr; i++){
+      nByte += sqlite3Strlen30(pToCol->a[i].zEName) + 1;
+    }
+  }
+  pFKey = sqlite3DbMallocZero(db, nByte );
+  if( pFKey==0 ){
+    goto fk_end;
+  }
+  pFKey->pFrom = p;
+  assert( IsOrdinaryTable(p) );
+  pFKey->pNextFrom = p->u.tab.pFKey;
+  z = (char*)&pFKey->aCol[nCol];
+  pFKey->zTo = z;
+  if( IN_RENAME_OBJECT ){
+    sqlite3RenameTokenMap(pParse, (void*)z, pTo);
+  }
+  memcpy(z, pTo->z, pTo->n);
+  z[pTo->n] = 0;
+  sqlite3Dequote(z);
+  z += pTo->n+1;
+  pFKey->nCol = nCol;
+  if( pFromCol==0 ){
+    pFKey->aCol[0].iFrom = p->nCol-1;
+  }else{
+    for(i=0; i<nCol; i++){
+      int j;
+      for(j=0; j<p->nCol; j++){
+        if( sqlite3StrICmp(p->aCol[j].zCnName, pFromCol->a[i].zEName)==0 ){
+          pFKey->aCol[i].iFrom = j;
+          break;
+        }
+      }
+      if( j>=p->nCol ){
+        sqlite3ErrorMsg(pParse,
+          "unknown column \"%s\" in foreign key definition",
+          pFromCol->a[i].zEName);
+        goto fk_end;
+      }
+      if( IN_RENAME_OBJECT ){
+        sqlite3RenameTokenRemap(pParse, &pFKey->aCol[i], pFromCol->a[i].zEName);
+      }
+    }
+  }
+  if( pToCol ){
+    for(i=0; i<nCol; i++){
+      int n = sqlite3Strlen30(pToCol->a[i].zEName);
+      pFKey->aCol[i].zCol = z;
+      if( IN_RENAME_OBJECT ){
+        sqlite3RenameTokenRemap(pParse, z, pToCol->a[i].zEName);
+      }
+      memcpy(z, pToCol->a[i].zEName, n);
+      z[n] = 0;
+      z += n+1;
+    }
+  }
+  pFKey->isDeferred = 0;
+  pFKey->aAction[0] = (u8)(flags & 0xff);            /* ON DELETE action */
+  pFKey->aAction[1] = (u8)((flags >> 8 ) & 0xff);    /* ON UPDATE action */
+
+  assert( sqlite3SchemaMutexHeld(db, 0, p->pSchema) );
+  pNextTo = (FKey *)sqlite3HashInsert(&p->pSchema->fkeyHash,
+      pFKey->zTo, (void *)pFKey
+  );
+  if( pNextTo==pFKey ){
+    sqlite3OomFault(db);
+    goto fk_end;
+  }
+  if( pNextTo ){
+    assert( pNextTo->pPrevTo==0 );
+    pFKey->pNextTo = pNextTo;
+    pNextTo->pPrevTo = pFKey;
+  }
+
+  /* Link the foreign key to the table as the last step.
+  */
+  assert( IsOrdinaryTable(p) );
+  p->u.tab.pFKey = pFKey;
+  pFKey = 0;
+
+fk_end:
+  sqlite3DbFree(db, pFKey);
+#endif /* !defined(SQLITE_OMIT_FOREIGN_KEY) */
+  sqlite3ExprListDelete(db, pFromCol);
+  sqlite3ExprListDelete(db, pToCol);
+}
+
+/*
+** This routine is called when an INITIALLY IMMEDIATE or INITIALLY DEFERRED
+** clause is seen as part of a foreign key definition.  The isDeferred
+** parameter is 1 for INITIALLY DEFERRED and 0 for INITIALLY IMMEDIATE.
+** The behavior of the most recently created foreign key is adjusted
+** accordingly.
+*/
+void sqlite3DeferForeignKey(Parse *pParse, int isDeferred){
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  Table *pTab;
+  FKey *pFKey;
+  if( (pTab = pParse->pNewTable)==0 ) return;
+  if( NEVER(!IsOrdinaryTable(pTab)) ) return;
+  if( (pFKey = pTab->u.tab.pFKey)==0 ) return;
+  assert( isDeferred==0 || isDeferred==1 ); /* EV: R-30323-21917 */
+  pFKey->isDeferred = (u8)isDeferred;
+#endif
+}
+
+/*
+** Generate code that will erase and refill index *pIdx.  This is
+** used to initialize a newly created index or to recompute the
+** content of an index in response to a REINDEX command.
+**
+** if memRootPage is not negative, it means that the index is newly
+** created.  The register specified by memRootPage contains the
+** root page number of the index.  If memRootPage is negative, then
+** the index already exists and must be cleared before being refilled and
+** the root page number of the index is taken from pIndex->tnum.
+*/
+static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
+  Table *pTab = pIndex->pTable;  /* The table that is indexed */
+  int iTab = pParse->nTab++;     /* Btree cursor used for pTab */
+  int iIdx = pParse->nTab++;     /* Btree cursor used for pIndex */
+  int iSorter;                   /* Cursor opened by OpenSorter (if in use) */
+  int addr1;                     /* Address of top of loop */
+  int addr2;                     /* Address to jump to for next iteration */
+  Pgno tnum;                     /* Root page of index */
+  int iPartIdxLabel;             /* Jump to this label to skip a row */
+  Vdbe *v;                       /* Generate code into this virtual machine */
+  KeyInfo *pKey;                 /* KeyInfo for index */
+  int regRecord;                 /* Register holding assembled index record */
+  sqlite3 *db = pParse->db;      /* The database connection */
+  int iDb = sqlite3SchemaToIndex(db, pIndex->pSchema);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( sqlite3AuthCheck(pParse, SQLITE_REINDEX, pIndex->zName, 0,
+      db->aDb[iDb].zDbSName ) ){
+    return;
+  }
+#endif
+
+  /* Require a write-lock on the table to perform this operation */
+  sqlite3TableLock(pParse, iDb, pTab->tnum, 1, pTab->zName);
+
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) return;
+  if( memRootPage>=0 ){
+    tnum = (Pgno)memRootPage;
+  }else{
+    tnum = pIndex->tnum;
+  }
+  pKey = sqlite3KeyInfoOfIndex(pParse, pIndex);
+  assert( pKey!=0 || pParse->nErr );
+
+  /* Open the sorter cursor if we are to use one. */
+  iSorter = pParse->nTab++;
+  sqlite3VdbeAddOp4(v, OP_SorterOpen, iSorter, 0, pIndex->nKeyCol, (char*)
+                    sqlite3KeyInfoRef(pKey), P4_KEYINFO);
+
+  /* Open the table. Loop through all rows of the table, inserting index
+  ** records into the sorter. */
+  sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
+  addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0); VdbeCoverage(v);
+  regRecord = sqlite3GetTempReg(pParse);
+  sqlite3MultiWrite(pParse);
+
+  sqlite3GenerateIndexKey(pParse,pIndex,iTab,regRecord,0,&iPartIdxLabel,0,0);
+  sqlite3VdbeAddOp2(v, OP_SorterInsert, iSorter, regRecord);
+  sqlite3ResolvePartIdxLabel(pParse, iPartIdxLabel);
+  sqlite3VdbeAddOp2(v, OP_Next, iTab, addr1+1); VdbeCoverage(v);
+  sqlite3VdbeJumpHere(v, addr1);
+  if( memRootPage<0 ) sqlite3VdbeAddOp2(v, OP_Clear, tnum, iDb);
+  sqlite3VdbeAddOp4(v, OP_OpenWrite, iIdx, (int)tnum, iDb,
+                    (char *)pKey, P4_KEYINFO);
+  sqlite3VdbeChangeP5(v, OPFLAG_BULKCSR|((memRootPage>=0)?OPFLAG_P2ISREG:0));
+
+  addr1 = sqlite3VdbeAddOp2(v, OP_SorterSort, iSorter, 0); VdbeCoverage(v);
+  if( IsUniqueIndex(pIndex) ){
+    int j2 = sqlite3VdbeGoto(v, 1);
+    addr2 = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeVerifyAbortable(v, OE_Abort);
+    sqlite3VdbeAddOp4Int(v, OP_SorterCompare, iSorter, j2, regRecord,
+                         pIndex->nKeyCol); VdbeCoverage(v);
+    sqlite3UniqueConstraint(pParse, OE_Abort, pIndex);
+    sqlite3VdbeJumpHere(v, j2);
+  }else{
+    /* Most CREATE INDEX and REINDEX statements that are not UNIQUE can not
+    ** abort. The exception is if one of the indexed expressions contains a
+    ** user function that throws an exception when it is evaluated. But the
+    ** overhead of adding a statement journal to a CREATE INDEX statement is
+    ** very small (since most of the pages written do not contain content that
+    ** needs to be restored if the statement aborts), so we call
+    ** sqlite3MayAbort() for all CREATE INDEX statements.  */
+    sqlite3MayAbort(pParse);
+    addr2 = sqlite3VdbeCurrentAddr(v);
+  }
+  sqlite3VdbeAddOp3(v, OP_SorterData, iSorter, regRecord, iIdx);
+  if( !pIndex->bAscKeyBug ){
+    /* This OP_SeekEnd opcode makes index insert for a REINDEX go much
+    ** faster by avoiding unnecessary seeks.  But the optimization does
+    ** not work for UNIQUE constraint indexes on WITHOUT ROWID tables
+    ** with DESC primary keys, since those indexes have there keys in
+    ** a different order from the main table.
+    ** See ticket: https://www.sqlite.org/src/info/bba7b69f9849b5bf
+    */
+    sqlite3VdbeAddOp1(v, OP_SeekEnd, iIdx);
+  }
+  sqlite3VdbeAddOp2(v, OP_IdxInsert, iIdx, regRecord);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+  sqlite3ReleaseTempReg(pParse, regRecord);
+  sqlite3VdbeAddOp2(v, OP_SorterNext, iSorter, addr2); VdbeCoverage(v);
+  sqlite3VdbeJumpHere(v, addr1);
+
+  sqlite3VdbeAddOp1(v, OP_Close, iTab);
+  sqlite3VdbeAddOp1(v, OP_Close, iIdx);
+  sqlite3VdbeAddOp1(v, OP_Close, iSorter);
+}
+
+/*
+** Allocate heap space to hold an Index object with nCol columns.
+**
+** Increase the allocation size to provide an extra nExtra bytes
+** of 8-byte aligned space after the Index object and return a
+** pointer to this extra space in *ppExtra.
+*/
+Index *sqlite3AllocateIndexObject(
+  sqlite3 *db,         /* Database connection */
+  i16 nCol,            /* Total number of columns in the index */
+  int nExtra,          /* Number of bytes of extra space to alloc */
+  char **ppExtra       /* Pointer to the "extra" space */
+){
+  Index *p;            /* Allocated index object */
+  int nByte;           /* Bytes of space for Index object + arrays */
+
+  nByte = ROUND8(sizeof(Index)) +              /* Index structure  */
+          ROUND8(sizeof(char*)*nCol) +         /* Index.azColl     */
+          ROUND8(sizeof(LogEst)*(nCol+1) +     /* Index.aiRowLogEst   */
+                 sizeof(i16)*nCol +            /* Index.aiColumn   */
+                 sizeof(u8)*nCol);             /* Index.aSortOrder */
+  p = sqlite3DbMallocZero(db, nByte + nExtra);
+  if( p ){
+    char *pExtra = ((char*)p)+ROUND8(sizeof(Index));
+    p->azColl = (const char**)pExtra; pExtra += ROUND8(sizeof(char*)*nCol);
+    p->aiRowLogEst = (LogEst*)pExtra; pExtra += sizeof(LogEst)*(nCol+1);
+    p->aiColumn = (i16*)pExtra;       pExtra += sizeof(i16)*nCol;
+    p->aSortOrder = (u8*)pExtra;
+    p->nColumn = nCol;
+    p->nKeyCol = nCol - 1;
+    *ppExtra = ((char*)p) + nByte;
+  }
+  return p;
+}
+
+/*
+** If expression list pList contains an expression that was parsed with
+** an explicit "NULLS FIRST" or "NULLS LAST" clause, leave an error in
+** pParse and return non-zero. Otherwise, return zero.
+*/
+int sqlite3HasExplicitNulls(Parse *pParse, ExprList *pList){
+  if( pList ){
+    int i;
+    for(i=0; i<pList->nExpr; i++){
+      if( pList->a[i].fg.bNulls ){
+        u8 sf = pList->a[i].fg.sortFlags;
+        sqlite3ErrorMsg(pParse, "unsupported use of NULLS %s",
+            (sf==0 || sf==3) ? "FIRST" : "LAST"
+        );
+        return 1;
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** Create a new index for an SQL table.  pName1.pName2 is the name of the index
+** and pTblList is the name of the table that is to be indexed.  Both will
+** be NULL for a primary key or an index that is created to satisfy a
+** UNIQUE constraint.  If pTable and pIndex are NULL, use pParse->pNewTable
+** as the table to be indexed.  pParse->pNewTable is a table that is
+** currently being constructed by a CREATE TABLE statement.
+**
+** pList is a list of columns to be indexed.  pList will be NULL if this
+** is a primary key or unique-constraint on the most recent column added
+** to the table currently under construction. 
+*/
+void sqlite3CreateIndex(
+  Parse *pParse,     /* All information about this parse */
+  Token *pName1,     /* First part of index name. May be NULL */
+  Token *pName2,     /* Second part of index name. May be NULL */
+  SrcList *pTblName, /* Table to index. Use pParse->pNewTable if 0 */
+  ExprList *pList,   /* A list of columns to be indexed */
+  int onError,       /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
+  Token *pStart,     /* The CREATE token that begins this statement */
+  Expr *pPIWhere,    /* WHERE clause for partial indices */
+  int sortOrder,     /* Sort order of primary key when pList==NULL */
+  int ifNotExist,    /* Omit error if index already exists */
+  u8 idxType         /* The index type */
+){
+  Table *pTab = 0;     /* Table to be indexed */
+  Index *pIndex = 0;   /* The index to be created */
+  char *zName = 0;     /* Name of the index */
+  int nName;           /* Number of characters in zName */
+  int i, j;
+  DbFixer sFix;        /* For assigning database names to pTable */
+  int sortOrderMask;   /* 1 to honor DESC in index.  0 to ignore. */
+  sqlite3 *db = pParse->db;
+  Db *pDb;             /* The specific table containing the indexed database */
+  int iDb;             /* Index of the database that is being written */
+  Token *pName = 0;    /* Unqualified name of the index to create */
+  struct ExprList_item *pListItem; /* For looping over pList */
+  int nExtra = 0;                  /* Space allocated for zExtra[] */
+  int nExtraCol;                   /* Number of extra columns needed */
+  char *zExtra = 0;                /* Extra space after the Index object */
+  Index *pPk = 0;      /* PRIMARY KEY index for WITHOUT ROWID tables */
+
+  assert( db->pParse==pParse );
+  if( pParse->nErr ){
+    goto exit_create_index;
+  }
+  assert( db->mallocFailed==0 );
+  if( IN_DECLARE_VTAB && idxType!=SQLITE_IDXTYPE_PRIMARYKEY ){
+    goto exit_create_index;
+  }
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    goto exit_create_index;
+  }
+  if( sqlite3HasExplicitNulls(pParse, pList) ){
+    goto exit_create_index;
+  }
+
+  /*
+  ** Find the table that is to be indexed.  Return early if not found.
+  */
+  if( pTblName!=0 ){
+
+    /* Use the two-part index name to determine the database
+    ** to search for the table. 'Fix' the table name to this db
+    ** before looking up the table.
+    */
+    assert( pName1 && pName2 );
+    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+    if( iDb<0 ) goto exit_create_index;
+    assert( pName && pName->z );
+
+#ifndef SQLITE_OMIT_TEMPDB
+    /* If the index name was unqualified, check if the table
+    ** is a temp table. If so, set the database to 1. Do not do this
+    ** if initializing a database schema.
+    */
+    if( !db->init.busy ){
+      pTab = sqlite3SrcListLookup(pParse, pTblName);
+      if( pName2->n==0 && pTab && pTab->pSchema==db->aDb[1].pSchema ){
+        iDb = 1;
+      }
+    }
+#endif
+
+    sqlite3FixInit(&sFix, pParse, iDb, "index", pName);
+    if( sqlite3FixSrcList(&sFix, pTblName) ){
+      /* Because the parser constructs pTblName from a single identifier,
+      ** sqlite3FixSrcList can never fail. */
+      assert(0);
+    }
+    pTab = sqlite3LocateTableItem(pParse, 0, &pTblName->a[0]);
+    assert( db->mallocFailed==0 || pTab==0 );
+    if( pTab==0 ) goto exit_create_index;
+    if( iDb==1 && db->aDb[iDb].pSchema!=pTab->pSchema ){
+      sqlite3ErrorMsg(pParse,
+           "cannot create a TEMP index on non-TEMP table \"%s\"",
+           pTab->zName);
+      goto exit_create_index;
+    }
+    if( !HasRowid(pTab) ) pPk = sqlite3PrimaryKeyIndex(pTab);
+  }else{
+    assert( pName==0 );
+    assert( pStart==0 );
+    pTab = pParse->pNewTable;
+    if( !pTab ) goto exit_create_index;
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  }
+  pDb = &db->aDb[iDb];
+
+  assert( pTab!=0 );
+  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0
+       && db->init.busy==0
+       && pTblName!=0
+#if SQLITE_USER_AUTHENTICATION
+       && sqlite3UserAuthTable(pTab->zName)==0
+#endif
+  ){
+    sqlite3ErrorMsg(pParse, "table %s may not be indexed", pTab->zName);
+    goto exit_create_index;
+  }
+#ifndef SQLITE_OMIT_VIEW
+  if( IsView(pTab) ){
+    sqlite3ErrorMsg(pParse, "views may not be indexed");
+    goto exit_create_index;
+  }
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTab) ){
+    sqlite3ErrorMsg(pParse, "virtual tables may not be indexed");
+    goto exit_create_index;
+  }
+#endif
+
+  /*
+  ** Find the name of the index.  Make sure there is not already another
+  ** index or table with the same name. 
+  **
+  ** Exception:  If we are reading the names of permanent indices from the
+  ** sqlite_schema table (because some other process changed the schema) and
+  ** one of the index names collides with the name of a temporary table or
+  ** index, then we will continue to process this index.
+  **
+  ** If pName==0 it means that we are
+  ** dealing with a primary key or UNIQUE constraint.  We have to invent our
+  ** own name.
+  */
+  if( pName ){
+    zName = sqlite3NameFromToken(db, pName);
+    if( zName==0 ) goto exit_create_index;
+    assert( pName->z!=0 );
+    if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName,"index",pTab->zName) ){
+      goto exit_create_index;
+    }
+    if( !IN_RENAME_OBJECT ){
+      if( !db->init.busy ){
+        if( sqlite3FindTable(db, zName, pDb->zDbSName)!=0 ){
+          sqlite3ErrorMsg(pParse, "there is already a table named %s", zName);
+          goto exit_create_index;
+        }
+      }
+      if( sqlite3FindIndex(db, zName, pDb->zDbSName)!=0 ){
+        if( !ifNotExist ){
+          sqlite3ErrorMsg(pParse, "index %s already exists", zName);
+        }else{
+          assert( !db->init.busy );
+          sqlite3CodeVerifySchema(pParse, iDb);
+          sqlite3ForceNotReadOnly(pParse);
+        }
+        goto exit_create_index;
+      }
+    }
+  }else{
+    int n;
+    Index *pLoop;
+    for(pLoop=pTab->pIndex, n=1; pLoop; pLoop=pLoop->pNext, n++){}
+    zName = sqlite3MPrintf(db, "sqlite_autoindex_%s_%d", pTab->zName, n);
+    if( zName==0 ){
+      goto exit_create_index;
+    }
+
+    /* Automatic index names generated from within sqlite3_declare_vtab()
+    ** must have names that are distinct from normal automatic index names.
+    ** The following statement converts "sqlite3_autoindex..." into
+    ** "sqlite3_butoindex..." in order to make the names distinct.
+    ** The "vtab_err.test" test demonstrates the need of this statement. */
+    if( IN_SPECIAL_PARSE ) zName[7]++;
+  }
+
+  /* Check for authorization to create an index.
+  */
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( !IN_RENAME_OBJECT ){
+    const char *zDb = pDb->zDbSName;
+    if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(iDb), 0, zDb) ){
+      goto exit_create_index;
+    }
+    i = SQLITE_CREATE_INDEX;
+    if( !OMIT_TEMPDB && iDb==1 ) i = SQLITE_CREATE_TEMP_INDEX;
+    if( sqlite3AuthCheck(pParse, i, zName, pTab->zName, zDb) ){
+      goto exit_create_index;
+    }
+  }
+#endif
+
+  /* If pList==0, it means this routine was called to make a primary
+  ** key out of the last column added to the table under construction.
+  ** So create a fake list to simulate this.
+  */
+  if( pList==0 ){
+    Token prevCol;
+    Column *pCol = &pTab->aCol[pTab->nCol-1];
+    pCol->colFlags |= COLFLAG_UNIQUE;
+    sqlite3TokenInit(&prevCol, pCol->zCnName);
+    pList = sqlite3ExprListAppend(pParse, 0,
+              sqlite3ExprAlloc(db, TK_ID, &prevCol, 0));
+    if( pList==0 ) goto exit_create_index;
+    assert( pList->nExpr==1 );
+    sqlite3ExprListSetSortOrder(pList, sortOrder, SQLITE_SO_UNDEFINED);
+  }else{
+    sqlite3ExprListCheckLength(pParse, pList, "index");
+    if( pParse->nErr ) goto exit_create_index;
+  }
+
+  /* Figure out how many bytes of space are required to store explicitly
+  ** specified collation sequence names.
+  */
+  for(i=0; i<pList->nExpr; i++){
+    Expr *pExpr = pList->a[i].pExpr;
+    assert( pExpr!=0 );
+    if( pExpr->op==TK_COLLATE ){
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      nExtra += (1 + sqlite3Strlen30(pExpr->u.zToken));
+    }
+  }
+
+  /*
+  ** Allocate the index structure.
+  */
+  nName = sqlite3Strlen30(zName);
+  nExtraCol = pPk ? pPk->nKeyCol : 1;
+  assert( pList->nExpr + nExtraCol <= 32767 /* Fits in i16 */ );
+  pIndex = sqlite3AllocateIndexObject(db, pList->nExpr + nExtraCol,
+                                      nName + nExtra + 1, &zExtra);
+  if( db->mallocFailed ){
+    goto exit_create_index;
+  }
+  assert( EIGHT_BYTE_ALIGNMENT(pIndex->aiRowLogEst) );
+  assert( EIGHT_BYTE_ALIGNMENT(pIndex->azColl) );
+  pIndex->zName = zExtra;
+  zExtra += nName + 1;
+  memcpy(pIndex->zName, zName, nName+1);
+  pIndex->pTable = pTab;
+  pIndex->onError = (u8)onError;
+  pIndex->uniqNotNull = onError!=OE_None;
+  pIndex->idxType = idxType;
+  pIndex->pSchema = db->aDb[iDb].pSchema;
+  pIndex->nKeyCol = pList->nExpr;
+  if( pPIWhere ){
+    sqlite3ResolveSelfReference(pParse, pTab, NC_PartIdx, pPIWhere, 0);
+    pIndex->pPartIdxWhere = pPIWhere;
+    pPIWhere = 0;
+  }
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+
+  /* Check to see if we should honor DESC requests on index columns
+  */
+  if( pDb->pSchema->file_format>=4 ){
+    sortOrderMask = -1;   /* Honor DESC */
+  }else{
+    sortOrderMask = 0;    /* Ignore DESC */
+  }
+
+  /* Analyze the list of expressions that form the terms of the index and
+  ** report any errors.  In the common case where the expression is exactly
+  ** a table column, store that column in aiColumn[].  For general expressions,
+  ** populate pIndex->aColExpr and store XN_EXPR (-2) in aiColumn[].
+  **
+  ** TODO: Issue a warning if two or more columns of the index are identical.
+  ** TODO: Issue a warning if the table primary key is used as part of the
+  ** index key.
+  */
+  pListItem = pList->a;
+  if( IN_RENAME_OBJECT ){
+    pIndex->aColExpr = pList;
+    pList = 0;
+  }
+  for(i=0; i<pIndex->nKeyCol; i++, pListItem++){
+    Expr *pCExpr;                  /* The i-th index expression */
+    int requestedSortOrder;        /* ASC or DESC on the i-th expression */
+    const char *zColl;             /* Collation sequence name */
+
+    sqlite3StringToId(pListItem->pExpr);
+    sqlite3ResolveSelfReference(pParse, pTab, NC_IdxExpr, pListItem->pExpr, 0);
+    if( pParse->nErr ) goto exit_create_index;
+    pCExpr = sqlite3ExprSkipCollate(pListItem->pExpr);
+    if( pCExpr->op!=TK_COLUMN ){
+      if( pTab==pParse->pNewTable ){
+        sqlite3ErrorMsg(pParse, "expressions prohibited in PRIMARY KEY and "
+                                "UNIQUE constraints");
+        goto exit_create_index;
+      }
+      if( pIndex->aColExpr==0 ){
+        pIndex->aColExpr = pList;
+        pList = 0;
+      }
+      j = XN_EXPR;
+      pIndex->aiColumn[i] = XN_EXPR;
+      pIndex->uniqNotNull = 0;
+      pIndex->bHasExpr = 1;
+    }else{
+      j = pCExpr->iColumn;
+      assert( j<=0x7fff );
+      if( j<0 ){
+        j = pTab->iPKey;
+      }else{
+        if( pTab->aCol[j].notNull==0 ){
+          pIndex->uniqNotNull = 0;
+        }
+        if( pTab->aCol[j].colFlags & COLFLAG_VIRTUAL ){
+          pIndex->bHasVCol = 1;
+          pIndex->bHasExpr = 1;
+        }
+      }
+      pIndex->aiColumn[i] = (i16)j;
+    }
+    zColl = 0;
+    if( pListItem->pExpr->op==TK_COLLATE ){
+      int nColl;
+      assert( !ExprHasProperty(pListItem->pExpr, EP_IntValue) );
+      zColl = pListItem->pExpr->u.zToken;
+      nColl = sqlite3Strlen30(zColl) + 1;
+      assert( nExtra>=nColl );
+      memcpy(zExtra, zColl, nColl);
+      zColl = zExtra;
+      zExtra += nColl;
+      nExtra -= nColl;
+    }else if( j>=0 ){
+      zColl = sqlite3ColumnColl(&pTab->aCol[j]);
+    }
+    if( !zColl ) zColl = sqlite3StrBINARY;
+    if( !db->init.busy && !sqlite3LocateCollSeq(pParse, zColl) ){
+      goto exit_create_index;
+    }
+    pIndex->azColl[i] = zColl;
+    requestedSortOrder = pListItem->fg.sortFlags & sortOrderMask;
+    pIndex->aSortOrder[i] = (u8)requestedSortOrder;
+  }
+
+  /* Append the table key to the end of the index.  For WITHOUT ROWID
+  ** tables (when pPk!=0) this will be the declared PRIMARY KEY.  For
+  ** normal tables (when pPk==0) this will be the rowid.
+  */
+  if( pPk ){
+    for(j=0; j<pPk->nKeyCol; j++){
+      int x = pPk->aiColumn[j];
+      assert( x>=0 );
+      if( isDupColumn(pIndex, pIndex->nKeyCol, pPk, j) ){
+        pIndex->nColumn--;
+      }else{
+        testcase( hasColumn(pIndex->aiColumn,pIndex->nKeyCol,x) );
+        pIndex->aiColumn[i] = x;
+        pIndex->azColl[i] = pPk->azColl[j];
+        pIndex->aSortOrder[i] = pPk->aSortOrder[j];
+        i++;
+      }
+    }
+    assert( i==pIndex->nColumn );
+  }else{
+    pIndex->aiColumn[i] = XN_ROWID;
+    pIndex->azColl[i] = sqlite3StrBINARY;
+  }
+  sqlite3DefaultRowEst(pIndex);
+  if( pParse->pNewTable==0 ) estimateIndexWidth(pIndex);
+
+  /* If this index contains every column of its table, then mark
+  ** it as a covering index */
+  assert( HasRowid(pTab)
+      || pTab->iPKey<0 || sqlite3TableColumnToIndex(pIndex, pTab->iPKey)>=0 );
+  recomputeColumnsNotIndexed(pIndex);
+  if( pTblName!=0 && pIndex->nColumn>=pTab->nCol ){
+    pIndex->isCovering = 1;
+    for(j=0; j<pTab->nCol; j++){
+      if( j==pTab->iPKey ) continue;
+      if( sqlite3TableColumnToIndex(pIndex,j)>=0 ) continue;
+      pIndex->isCovering = 0;
+      break;
+    }
+  }
+
+  if( pTab==pParse->pNewTable ){
+    /* This routine has been called to create an automatic index as a
+    ** result of a PRIMARY KEY or UNIQUE clause on a column definition, or
+    ** a PRIMARY KEY or UNIQUE clause following the column definitions.
+    ** i.e. one of:
+    **
+    ** CREATE TABLE t(x PRIMARY KEY, y);
+    ** CREATE TABLE t(x, y, UNIQUE(x, y));
+    **
+    ** Either way, check to see if the table already has such an index. If
+    ** so, don't bother creating this one. This only applies to
+    ** automatically created indices. Users can do as they wish with
+    ** explicit indices.
+    **
+    ** Two UNIQUE or PRIMARY KEY constraints are considered equivalent
+    ** (and thus suppressing the second one) even if they have different
+    ** sort orders.
+    **
+    ** If there are different collating sequences or if the columns of
+    ** the constraint occur in different orders, then the constraints are
+    ** considered distinct and both result in separate indices.
+    */
+    Index *pIdx;
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      int k;
+      assert( IsUniqueIndex(pIdx) );
+      assert( pIdx->idxType!=SQLITE_IDXTYPE_APPDEF );
+      assert( IsUniqueIndex(pIndex) );
+
+      if( pIdx->nKeyCol!=pIndex->nKeyCol ) continue;
+      for(k=0; k<pIdx->nKeyCol; k++){
+        const char *z1;
+        const char *z2;
+        assert( pIdx->aiColumn[k]>=0 );
+        if( pIdx->aiColumn[k]!=pIndex->aiColumn[k] ) break;
+        z1 = pIdx->azColl[k];
+        z2 = pIndex->azColl[k];
+        if( sqlite3StrICmp(z1, z2) ) break;
+      }
+      if( k==pIdx->nKeyCol ){
+        if( pIdx->onError!=pIndex->onError ){
+          /* This constraint creates the same index as a previous
+          ** constraint specified somewhere in the CREATE TABLE statement.
+          ** However the ON CONFLICT clauses are different. If both this
+          ** constraint and the previous equivalent constraint have explicit
+          ** ON CONFLICT clauses this is an error. Otherwise, use the
+          ** explicitly specified behavior for the index.
+          */
+          if( !(pIdx->onError==OE_Default || pIndex->onError==OE_Default) ){
+            sqlite3ErrorMsg(pParse,
+                "conflicting ON CONFLICT clauses specified", 0);
+          }
+          if( pIdx->onError==OE_Default ){
+            pIdx->onError = pIndex->onError;
+          }
+        }
+        if( idxType==SQLITE_IDXTYPE_PRIMARYKEY ) pIdx->idxType = idxType;
+        if( IN_RENAME_OBJECT ){
+          pIndex->pNext = pParse->pNewIndex;
+          pParse->pNewIndex = pIndex;
+          pIndex = 0;
+        }
+        goto exit_create_index;
+      }
+    }
+  }
+
+  if( !IN_RENAME_OBJECT ){
+
+    /* Link the new Index structure to its table and to the other
+    ** in-memory database structures.
+    */
+    assert( pParse->nErr==0 );
+    if( db->init.busy ){
+      Index *p;
+      assert( !IN_SPECIAL_PARSE );
+      assert( sqlite3SchemaMutexHeld(db, 0, pIndex->pSchema) );
+      if( pTblName!=0 ){
+        pIndex->tnum = db->init.newTnum;
+        if( sqlite3IndexHasDuplicateRootPage(pIndex) ){
+          sqlite3ErrorMsg(pParse, "invalid rootpage");
+          pParse->rc = SQLITE_CORRUPT_BKPT;
+          goto exit_create_index;
+        }
+      }
+      p = sqlite3HashInsert(&pIndex->pSchema->idxHash,
+          pIndex->zName, pIndex);
+      if( p ){
+        assert( p==pIndex );  /* Malloc must have failed */
+        sqlite3OomFault(db);
+        goto exit_create_index;
+      }
+      db->mDbFlags |= DBFLAG_SchemaChange;
+    }
+
+    /* If this is the initial CREATE INDEX statement (or CREATE TABLE if the
+    ** index is an implied index for a UNIQUE or PRIMARY KEY constraint) then
+    ** emit code to allocate the index rootpage on disk and make an entry for
+    ** the index in the sqlite_schema table and populate the index with
+    ** content.  But, do not do this if we are simply reading the sqlite_schema
+    ** table to parse the schema, or if this index is the PRIMARY KEY index
+    ** of a WITHOUT ROWID table.
+    **
+    ** If pTblName==0 it means this index is generated as an implied PRIMARY KEY
+    ** or UNIQUE index in a CREATE TABLE statement.  Since the table
+    ** has just been created, it contains no data and the index initialization
+    ** step can be skipped.
+    */
+    else if( HasRowid(pTab) || pTblName!=0 ){
+      Vdbe *v;
+      char *zStmt;
+      int iMem = ++pParse->nMem;
+
+      v = sqlite3GetVdbe(pParse);
+      if( v==0 ) goto exit_create_index;
+
+      sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+      /* Create the rootpage for the index using CreateIndex. But before
+      ** doing so, code a Noop instruction and store its address in
+      ** Index.tnum. This is required in case this index is actually a
+      ** PRIMARY KEY and the table is actually a WITHOUT ROWID table. In
+      ** that case the convertToWithoutRowidTable() routine will replace
+      ** the Noop with a Goto to jump over the VDBE code generated below. */
+      pIndex->tnum = (Pgno)sqlite3VdbeAddOp0(v, OP_Noop);
+      sqlite3VdbeAddOp3(v, OP_CreateBtree, iDb, iMem, BTREE_BLOBKEY);
+
+      /* Gather the complete text of the CREATE INDEX statement into
+      ** the zStmt variable
+      */
+      assert( pName!=0 || pStart==0 );
+      if( pStart ){
+        int n = (int)(pParse->sLastToken.z - pName->z) + pParse->sLastToken.n;
+        if( pName->z[n-1]==';' ) n--;
+        /* A named index with an explicit CREATE INDEX statement */
+        zStmt = sqlite3MPrintf(db, "CREATE%s INDEX %.*s",
+            onError==OE_None ? "" : " UNIQUE", n, pName->z);
+      }else{
+        /* An automatic index created by a PRIMARY KEY or UNIQUE constraint */
+        /* zStmt = sqlite3MPrintf(""); */
+        zStmt = 0;
+      }
+
+      /* Add an entry in sqlite_schema for this index
+      */
+      sqlite3NestedParse(pParse,
+         "INSERT INTO %Q." LEGACY_SCHEMA_TABLE " VALUES('index',%Q,%Q,#%d,%Q);",
+         db->aDb[iDb].zDbSName,
+         pIndex->zName,
+         pTab->zName,
+         iMem,
+         zStmt
+      );
+      sqlite3DbFree(db, zStmt);
+
+      /* Fill the index with data and reparse the schema. Code an OP_Expire
+      ** to invalidate all pre-compiled statements.
+      */
+      if( pTblName ){
+        sqlite3RefillIndex(pParse, pIndex, iMem);
+        sqlite3ChangeCookie(pParse, iDb);
+        sqlite3VdbeAddParseSchemaOp(v, iDb,
+            sqlite3MPrintf(db, "name='%q' AND type='index'", pIndex->zName), 0);
+        sqlite3VdbeAddOp2(v, OP_Expire, 0, 1);
+      }
+
+      sqlite3VdbeJumpHere(v, (int)pIndex->tnum);
+    }
+  }
+  if( db->init.busy || pTblName==0 ){
+    pIndex->pNext = pTab->pIndex;
+    pTab->pIndex = pIndex;
+    pIndex = 0;
+  }
+  else if( IN_RENAME_OBJECT ){
+    assert( pParse->pNewIndex==0 );
+    pParse->pNewIndex = pIndex;
+    pIndex = 0;
+  }
+
+  /* Clean up before exiting */
+exit_create_index:
+  if( pIndex ) sqlite3FreeIndex(db, pIndex);
+  if( pTab ){
+    /* Ensure all REPLACE indexes on pTab are at the end of the pIndex list.
+    ** The list was already ordered when this routine was entered, so at this
+    ** point at most a single index (the newly added index) will be out of
+    ** order.  So we have to reorder at most one index. */
+    Index **ppFrom;
+    Index *pThis;
+    for(ppFrom=&pTab->pIndex; (pThis = *ppFrom)!=0; ppFrom=&pThis->pNext){
+      Index *pNext;
+      if( pThis->onError!=OE_Replace ) continue;
+      while( (pNext = pThis->pNext)!=0 && pNext->onError!=OE_Replace ){
+        *ppFrom = pNext;
+        pThis->pNext = pNext->pNext;
+        pNext->pNext = pThis;
+        ppFrom = &pNext->pNext;
+      }
+      break;
+    }
+#ifdef SQLITE_DEBUG
+    /* Verify that all REPLACE indexes really are now at the end
+    ** of the index list.  In other words, no other index type ever
+    ** comes after a REPLACE index on the list. */
+    for(pThis = pTab->pIndex; pThis; pThis=pThis->pNext){
+      assert( pThis->onError!=OE_Replace
+           || pThis->pNext==0
+           || pThis->pNext->onError==OE_Replace );
+    }
+#endif
+  }
+  sqlite3ExprDelete(db, pPIWhere);
+  sqlite3ExprListDelete(db, pList);
+  sqlite3SrcListDelete(db, pTblName);
+  sqlite3DbFree(db, zName);
+}
+
+/*
+** Fill the Index.aiRowEst[] array with default information - information
+** to be used when we have not run the ANALYZE command.
+**
+** aiRowEst[0] is supposed to contain the number of elements in the index.
+** Since we do not know, guess 1 million.  aiRowEst[1] is an estimate of the
+** number of rows in the table that match any particular value of the
+** first column of the index.  aiRowEst[2] is an estimate of the number
+** of rows that match any particular combination of the first 2 columns
+** of the index.  And so forth.  It must always be the case that
+*
+**           aiRowEst[N]<=aiRowEst[N-1]
+**           aiRowEst[N]>=1
+**
+** Apart from that, we have little to go on besides intuition as to
+** how aiRowEst[] should be initialized.  The numbers generated here
+** are based on typical values found in actual indices.
+*/
+void sqlite3DefaultRowEst(Index *pIdx){
+               /*                10,  9,  8,  7,  6 */
+  static const LogEst aVal[] = { 33, 32, 30, 28, 26 };
+  LogEst *a = pIdx->aiRowLogEst;
+  LogEst x;
+  int nCopy = MIN(ArraySize(aVal), pIdx->nKeyCol);
+  int i;
+
+  /* Indexes with default row estimates should not have stat1 data */
+  assert( !pIdx->hasStat1 );
+
+  /* Set the first entry (number of rows in the index) to the estimated
+  ** number of rows in the table, or half the number of rows in the table
+  ** for a partial index.
+  **
+  ** 2020-05-27:  If some of the stat data is coming from the sqlite_stat1
+  ** table but other parts we are having to guess at, then do not let the
+  ** estimated number of rows in the table be less than 1000 (LogEst 99).
+  ** Failure to do this can cause the indexes for which we do not have
+  ** stat1 data to be ignored by the query planner.
+  */
+  x = pIdx->pTable->nRowLogEst;
+  assert( 99==sqlite3LogEst(1000) );
+  if( x<99 ){
+    pIdx->pTable->nRowLogEst = x = 99;
+  }
+  if( pIdx->pPartIdxWhere!=0 ){ x -= 10;  assert( 10==sqlite3LogEst(2) ); }
+  a[0] = x;
+
+  /* Estimate that a[1] is 10, a[2] is 9, a[3] is 8, a[4] is 7, a[5] is
+  ** 6 and each subsequent value (if any) is 5.  */
+  memcpy(&a[1], aVal, nCopy*sizeof(LogEst));
+  for(i=nCopy+1; i<=pIdx->nKeyCol; i++){
+    a[i] = 23;                    assert( 23==sqlite3LogEst(5) );
+  }
+
+  assert( 0==sqlite3LogEst(1) );
+  if( IsUniqueIndex(pIdx) ) a[pIdx->nKeyCol] = 0;
+}
+
+/*
+** This routine will drop an existing named index.  This routine
+** implements the DROP INDEX statement.
+*/
+void sqlite3DropIndex(Parse *pParse, SrcList *pName, int ifExists){
+  Index *pIndex;
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  if( db->mallocFailed ){
+    goto exit_drop_index;
+  }
+  assert( pParse->nErr==0 );   /* Never called with prior non-OOM errors */
+  assert( pName->nSrc==1 );
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    goto exit_drop_index;
+  }
+  pIndex = sqlite3FindIndex(db, pName->a[0].zName, pName->a[0].zDatabase);
+  if( pIndex==0 ){
+    if( !ifExists ){
+      sqlite3ErrorMsg(pParse, "no such index: %S", pName->a);
+    }else{
+      sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }
+    pParse->checkSchema = 1;
+    goto exit_drop_index;
+  }
+  if( pIndex->idxType!=SQLITE_IDXTYPE_APPDEF ){
+    sqlite3ErrorMsg(pParse, "index associated with UNIQUE "
+      "or PRIMARY KEY constraint cannot be dropped", 0);
+    goto exit_drop_index;
+  }
+  iDb = sqlite3SchemaToIndex(db, pIndex->pSchema);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code = SQLITE_DROP_INDEX;
+    Table *pTab = pIndex->pTable;
+    const char *zDb = db->aDb[iDb].zDbSName;
+    const char *zTab = SCHEMA_TABLE(iDb);
+    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
+      goto exit_drop_index;
+    }
+    if( !OMIT_TEMPDB && iDb==1 ) code = SQLITE_DROP_TEMP_INDEX;
+    if( sqlite3AuthCheck(pParse, code, pIndex->zName, pTab->zName, zDb) ){
+      goto exit_drop_index;
+    }
+  }
+#endif
+
+  /* Generate code to remove the index and from the schema table */
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3BeginWriteOperation(pParse, 1, iDb);
+    sqlite3NestedParse(pParse,
+       "DELETE FROM %Q." LEGACY_SCHEMA_TABLE " WHERE name=%Q AND type='index'",
+       db->aDb[iDb].zDbSName, pIndex->zName
+    );
+    sqlite3ClearStatTables(pParse, iDb, "idx", pIndex->zName);
+    sqlite3ChangeCookie(pParse, iDb);
+    destroyRootPage(pParse, pIndex->tnum, iDb);
+    sqlite3VdbeAddOp4(v, OP_DropIndex, iDb, 0, 0, pIndex->zName, 0);
+  }
+
+exit_drop_index:
+  sqlite3SrcListDelete(db, pName);
+}
+
+/*
+** pArray is a pointer to an array of objects. Each object in the
+** array is szEntry bytes in size. This routine uses sqlite3DbRealloc()
+** to extend the array so that there is space for a new object at the end.
+**
+** When this function is called, *pnEntry contains the current size of
+** the array (in entries - so the allocation is ((*pnEntry) * szEntry) bytes
+** in total).
+**
+** If the realloc() is successful (i.e. if no OOM condition occurs), the
+** space allocated for the new object is zeroed, *pnEntry updated to
+** reflect the new size of the array and a pointer to the new allocation
+** returned. *pIdx is set to the index of the new array entry in this case.
+**
+** Otherwise, if the realloc() fails, *pIdx is set to -1, *pnEntry remains
+** unchanged and a copy of pArray returned.
+*/
+void *sqlite3ArrayAllocate(
+  sqlite3 *db,      /* Connection to notify of malloc failures */
+  void *pArray,     /* Array of objects.  Might be reallocated */
+  int szEntry,      /* Size of each object in the array */
+  int *pnEntry,     /* Number of objects currently in use */
+  int *pIdx         /* Write the index of a new slot here */
+){
+  char *z;
+  sqlite3_int64 n = *pIdx = *pnEntry;
+  if( (n & (n-1))==0 ){
+    sqlite3_int64 sz = (n==0) ? 1 : 2*n;
+    void *pNew = sqlite3DbRealloc(db, pArray, sz*szEntry);
+    if( pNew==0 ){
+      *pIdx = -1;
+      return pArray;
+    }
+    pArray = pNew;
+  }
+  z = (char*)pArray;
+  memset(&z[n * szEntry], 0, szEntry);
+  ++*pnEntry;
+  return pArray;
+}
+
+/*
+** Append a new element to the given IdList.  Create a new IdList if
+** need be.
+**
+** A new IdList is returned, or NULL if malloc() fails.
+*/
+IdList *sqlite3IdListAppend(Parse *pParse, IdList *pList, Token *pToken){
+  sqlite3 *db = pParse->db;
+  int i;
+  if( pList==0 ){
+    pList = sqlite3DbMallocZero(db, sizeof(IdList) );
+    if( pList==0 ) return 0;
+  }else{
+    IdList *pNew;
+    pNew = sqlite3DbRealloc(db, pList,
+                 sizeof(IdList) + pList->nId*sizeof(pList->a));
+    if( pNew==0 ){
+      sqlite3IdListDelete(db, pList);
+      return 0;
+    }
+    pList = pNew;
+  }
+  i = pList->nId++;
+  pList->a[i].zName = sqlite3NameFromToken(db, pToken);
+  if( IN_RENAME_OBJECT && pList->a[i].zName ){
+    sqlite3RenameTokenMap(pParse, (void*)pList->a[i].zName, pToken);
+  }
+  return pList;
+}
+
+/*
+** Delete an IdList.
+*/
+void sqlite3IdListDelete(sqlite3 *db, IdList *pList){
+  int i;
+  assert( db!=0 );
+  if( pList==0 ) return;
+  assert( pList->eU4!=EU4_EXPR ); /* EU4_EXPR mode is not currently used */
+  for(i=0; i<pList->nId; i++){
+    sqlite3DbFree(db, pList->a[i].zName);
+  }
+  sqlite3DbNNFreeNN(db, pList);
+}
+
+/*
+** Return the index in pList of the identifier named zId.  Return -1
+** if not found.
+*/
+int sqlite3IdListIndex(IdList *pList, const char *zName){
+  int i;
+  assert( pList!=0 );
+  for(i=0; i<pList->nId; i++){
+    if( sqlite3StrICmp(pList->a[i].zName, zName)==0 ) return i;
+  }
+  return -1;
+}
+
+/*
+** Maximum size of a SrcList object.
+** The SrcList object is used to represent the FROM clause of a
+** SELECT statement, and the query planner cannot deal with more
+** than 64 tables in a join.  So any value larger than 64 here
+** is sufficient for most uses.  Smaller values, like say 10, are
+** appropriate for small and memory-limited applications.
+*/
+#ifndef SQLITE_MAX_SRCLIST
+# define SQLITE_MAX_SRCLIST 200
+#endif
+
+/*
+** Expand the space allocated for the given SrcList object by
+** creating nExtra new slots beginning at iStart.  iStart is zero based.
+** New slots are zeroed.
+**
+** For example, suppose a SrcList initially contains two entries: A,B.
+** To append 3 new entries onto the end, do this:
+**
+**    sqlite3SrcListEnlarge(db, pSrclist, 3, 2);
+**
+** After the call above it would contain:  A, B, nil, nil, nil.
+** If the iStart argument had been 1 instead of 2, then the result
+** would have been:  A, nil, nil, nil, B.  To prepend the new slots,
+** the iStart value would be 0.  The result then would
+** be: nil, nil, nil, A, B.
+**
+** If a memory allocation fails or the SrcList becomes too large, leave
+** the original SrcList unchanged, return NULL, and leave an error message
+** in pParse.
+*/
+SrcList *sqlite3SrcListEnlarge(
+  Parse *pParse,     /* Parsing context into which errors are reported */
+  SrcList *pSrc,     /* The SrcList to be enlarged */
+  int nExtra,        /* Number of new slots to add to pSrc->a[] */
+  int iStart         /* Index in pSrc->a[] of first new slot */
+){
+  int i;
+
+  /* Sanity checking on calling parameters */
+  assert( iStart>=0 );
+  assert( nExtra>=1 );
+  assert( pSrc!=0 );
+  assert( iStart<=pSrc->nSrc );
+
+  /* Allocate additional space if needed */
+  if( (u32)pSrc->nSrc+nExtra>pSrc->nAlloc ){
+    SrcList *pNew;
+    sqlite3_int64 nAlloc = 2*(sqlite3_int64)pSrc->nSrc+nExtra;
+    sqlite3 *db = pParse->db;
+
+    if( pSrc->nSrc+nExtra>=SQLITE_MAX_SRCLIST ){
+      sqlite3ErrorMsg(pParse, "too many FROM clause terms, max: %d",
+                      SQLITE_MAX_SRCLIST);
+      return 0;
+    }
+    if( nAlloc>SQLITE_MAX_SRCLIST ) nAlloc = SQLITE_MAX_SRCLIST;
+    pNew = sqlite3DbRealloc(db, pSrc,
+               sizeof(*pSrc) + (nAlloc-1)*sizeof(pSrc->a[0]) );
+    if( pNew==0 ){
+      assert( db->mallocFailed );
+      return 0;
+    }
+    pSrc = pNew;
+    pSrc->nAlloc = nAlloc;
+  }
+
+  /* Move existing slots that come after the newly inserted slots
+  ** out of the way */
+  for(i=pSrc->nSrc-1; i>=iStart; i--){
+    pSrc->a[i+nExtra] = pSrc->a[i];
+  }
+  pSrc->nSrc += nExtra;
+
+  /* Zero the newly allocated slots */
+  memset(&pSrc->a[iStart], 0, sizeof(pSrc->a[0])*nExtra);
+  for(i=iStart; i<iStart+nExtra; i++){
+    pSrc->a[i].iCursor = -1;
+  }
+
+  /* Return a pointer to the enlarged SrcList */
+  return pSrc;
+}
+
+
+/*
+** Append a new table name to the given SrcList.  Create a new SrcList if
+** need be.  A new entry is created in the SrcList even if pTable is NULL.
+**
+** A SrcList is returned, or NULL if there is an OOM error or if the
+** SrcList grows to large.  The returned
+** SrcList might be the same as the SrcList that was input or it might be
+** a new one.  If an OOM error does occurs, then the prior value of pList
+** that is input to this routine is automatically freed.
+**
+** If pDatabase is not null, it means that the table has an optional
+** database name prefix.  Like this:  "database.table".  The pDatabase
+** points to the table name and the pTable points to the database name.
+** The SrcList.a[].zName field is filled with the table name which might
+** come from pTable (if pDatabase is NULL) or from pDatabase. 
+** SrcList.a[].zDatabase is filled with the database name from pTable,
+** or with NULL if no database is specified.
+**
+** In other words, if call like this:
+**
+**         sqlite3SrcListAppend(D,A,B,0);
+**
+** Then B is a table name and the database name is unspecified.  If called
+** like this:
+**
+**         sqlite3SrcListAppend(D,A,B,C);
+**
+** Then C is the table name and B is the database name.  If C is defined
+** then so is B.  In other words, we never have a case where:
+**
+**         sqlite3SrcListAppend(D,A,0,C);
+**
+** Both pTable and pDatabase are assumed to be quoted.  They are dequoted
+** before being added to the SrcList.
+*/
+SrcList *sqlite3SrcListAppend(
+  Parse *pParse,      /* Parsing context, in which errors are reported */
+  SrcList *pList,     /* Append to this SrcList. NULL creates a new SrcList */
+  Token *pTable,      /* Table to append */
+  Token *pDatabase    /* Database of the table */
+){
+  SrcItem *pItem;
+  sqlite3 *db;
+  assert( pDatabase==0 || pTable!=0 );  /* Cannot have C without B */
+  assert( pParse!=0 );
+  assert( pParse->db!=0 );
+  db = pParse->db;
+  if( pList==0 ){
+    pList = sqlite3DbMallocRawNN(pParse->db, sizeof(SrcList) );
+    if( pList==0 ) return 0;
+    pList->nAlloc = 1;
+    pList->nSrc = 1;
+    memset(&pList->a[0], 0, sizeof(pList->a[0]));
+    pList->a[0].iCursor = -1;
+  }else{
+    SrcList *pNew = sqlite3SrcListEnlarge(pParse, pList, 1, pList->nSrc);
+    if( pNew==0 ){
+      sqlite3SrcListDelete(db, pList);
+      return 0;
+    }else{
+      pList = pNew;
+    }
+  }
+  pItem = &pList->a[pList->nSrc-1];
+  if( pDatabase && pDatabase->z==0 ){
+    pDatabase = 0;
+  }
+  if( pDatabase ){
+    pItem->zName = sqlite3NameFromToken(db, pDatabase);
+    pItem->zDatabase = sqlite3NameFromToken(db, pTable);
+  }else{
+    pItem->zName = sqlite3NameFromToken(db, pTable);
+    pItem->zDatabase = 0;
+  }
+  return pList;
+}
+
+/*
+** Assign VdbeCursor index numbers to all tables in a SrcList
+*/
+void sqlite3SrcListAssignCursors(Parse *pParse, SrcList *pList){
+  int i;
+  SrcItem *pItem;
+  assert( pList || pParse->db->mallocFailed );
+  if( ALWAYS(pList) ){
+    for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){
+      if( pItem->iCursor>=0 ) continue;
+      pItem->iCursor = pParse->nTab++;
+      if( pItem->pSelect ){
+        sqlite3SrcListAssignCursors(pParse, pItem->pSelect->pSrc);
+      }
+    }
+  }
+}
+
+/*
+** Delete an entire SrcList including all its substructure.
+*/
+void sqlite3SrcListDelete(sqlite3 *db, SrcList *pList){
+  int i;
+  SrcItem *pItem;
+  assert( db!=0 );
+  if( pList==0 ) return;
+  for(pItem=pList->a, i=0; i<pList->nSrc; i++, pItem++){
+    if( pItem->zDatabase ) sqlite3DbNNFreeNN(db, pItem->zDatabase);
+    if( pItem->zName ) sqlite3DbNNFreeNN(db, pItem->zName);
+    if( pItem->zAlias ) sqlite3DbNNFreeNN(db, pItem->zAlias);
+    if( pItem->fg.isIndexedBy ) sqlite3DbFree(db, pItem->u1.zIndexedBy);
+    if( pItem->fg.isTabFunc ) sqlite3ExprListDelete(db, pItem->u1.pFuncArg);
+    sqlite3DeleteTable(db, pItem->pTab);
+    if( pItem->pSelect ) sqlite3SelectDelete(db, pItem->pSelect);
+    if( pItem->fg.isUsing ){
+      sqlite3IdListDelete(db, pItem->u3.pUsing);
+    }else if( pItem->u3.pOn ){
+      sqlite3ExprDelete(db, pItem->u3.pOn);
+    }
+  }
+  sqlite3DbNNFreeNN(db, pList);
+}
+
+/*
+** This routine is called by the parser to add a new term to the
+** end of a growing FROM clause.  The "p" parameter is the part of
+** the FROM clause that has already been constructed.  "p" is NULL
+** if this is the first term of the FROM clause.  pTable and pDatabase
+** are the name of the table and database named in the FROM clause term.
+** pDatabase is NULL if the database name qualifier is missing - the
+** usual case.  If the term has an alias, then pAlias points to the
+** alias token.  If the term is a subquery, then pSubquery is the
+** SELECT statement that the subquery encodes.  The pTable and
+** pDatabase parameters are NULL for subqueries.  The pOn and pUsing
+** parameters are the content of the ON and USING clauses.
+**
+** Return a new SrcList which encodes is the FROM with the new
+** term added.
+*/
+SrcList *sqlite3SrcListAppendFromTerm(
+  Parse *pParse,          /* Parsing context */
+  SrcList *p,             /* The left part of the FROM clause already seen */
+  Token *pTable,          /* Name of the table to add to the FROM clause */
+  Token *pDatabase,       /* Name of the database containing pTable */
+  Token *pAlias,          /* The right-hand side of the AS subexpression */
+  Select *pSubquery,      /* A subquery used in place of a table name */
+  OnOrUsing *pOnUsing     /* Either the ON clause or the USING clause */
+){
+  SrcItem *pItem;
+  sqlite3 *db = pParse->db;
+  if( !p && pOnUsing!=0 && (pOnUsing->pOn || pOnUsing->pUsing) ){
+    sqlite3ErrorMsg(pParse, "a JOIN clause is required before %s",
+      (pOnUsing->pOn ? "ON" : "USING")
+    );
+    goto append_from_error;
+  }
+  p = sqlite3SrcListAppend(pParse, p, pTable, pDatabase);
+  if( p==0 ){
+    goto append_from_error;
+  }
+  assert( p->nSrc>0 );
+  pItem = &p->a[p->nSrc-1];
+  assert( (pTable==0)==(pDatabase==0) );
+  assert( pItem->zName==0 || pDatabase!=0 );
+  if( IN_RENAME_OBJECT && pItem->zName ){
+    Token *pToken = (ALWAYS(pDatabase) && pDatabase->z) ? pDatabase : pTable;
+    sqlite3RenameTokenMap(pParse, pItem->zName, pToken);
+  }
+  assert( pAlias!=0 );
+  if( pAlias->n ){
+    pItem->zAlias = sqlite3NameFromToken(db, pAlias);
+  }
+  if( pSubquery ){
+    pItem->pSelect = pSubquery;
+    if( pSubquery->selFlags & SF_NestedFrom ){
+      pItem->fg.isNestedFrom = 1;
+    }
+  }
+  assert( pOnUsing==0 || pOnUsing->pOn==0 || pOnUsing->pUsing==0 );
+  assert( pItem->fg.isUsing==0 );
+  if( pOnUsing==0 ){
+    pItem->u3.pOn = 0;
+  }else if( pOnUsing->pUsing ){
+    pItem->fg.isUsing = 1;
+    pItem->u3.pUsing = pOnUsing->pUsing;
+  }else{
+    pItem->u3.pOn = pOnUsing->pOn;
+  }
+  return p;
+
+append_from_error:
+  assert( p==0 );
+  sqlite3ClearOnOrUsing(db, pOnUsing);
+  sqlite3SelectDelete(db, pSubquery);
+  return 0;
+}
+
+/*
+** Add an INDEXED BY or NOT INDEXED clause to the most recently added
+** element of the source-list passed as the second argument.
+*/
+void sqlite3SrcListIndexedBy(Parse *pParse, SrcList *p, Token *pIndexedBy){
+  assert( pIndexedBy!=0 );
+  if( p && pIndexedBy->n>0 ){
+    SrcItem *pItem;
+    assert( p->nSrc>0 );
+    pItem = &p->a[p->nSrc-1];
+    assert( pItem->fg.notIndexed==0 );
+    assert( pItem->fg.isIndexedBy==0 );
+    assert( pItem->fg.isTabFunc==0 );
+    if( pIndexedBy->n==1 && !pIndexedBy->z ){
+      /* A "NOT INDEXED" clause was supplied. See parse.y
+      ** construct "indexed_opt" for details. */
+      pItem->fg.notIndexed = 1;
+    }else{
+      pItem->u1.zIndexedBy = sqlite3NameFromToken(pParse->db, pIndexedBy);
+      pItem->fg.isIndexedBy = 1;
+      assert( pItem->fg.isCte==0 );  /* No collision on union u2 */
+    }
+  }
+}
+
+/*
+** Append the contents of SrcList p2 to SrcList p1 and return the resulting
+** SrcList. Or, if an error occurs, return NULL. In all cases, p1 and p2
+** are deleted by this function.
+*/
+SrcList *sqlite3SrcListAppendList(Parse *pParse, SrcList *p1, SrcList *p2){
+  assert( p1 && p1->nSrc==1 );
+  if( p2 ){
+    SrcList *pNew = sqlite3SrcListEnlarge(pParse, p1, p2->nSrc, 1);
+    if( pNew==0 ){
+      sqlite3SrcListDelete(pParse->db, p2);
+    }else{
+      p1 = pNew;
+      memcpy(&p1->a[1], p2->a, p2->nSrc*sizeof(SrcItem));
+      sqlite3DbFree(pParse->db, p2);
+      p1->a[0].fg.jointype |= (JT_LTORJ & p1->a[1].fg.jointype);
+    }
+  }
+  return p1;
+}
+
+/*
+** Add the list of function arguments to the SrcList entry for a
+** table-valued-function.
+*/
+void sqlite3SrcListFuncArgs(Parse *pParse, SrcList *p, ExprList *pList){
+  if( p ){
+    SrcItem *pItem = &p->a[p->nSrc-1];
+    assert( pItem->fg.notIndexed==0 );
+    assert( pItem->fg.isIndexedBy==0 );
+    assert( pItem->fg.isTabFunc==0 );
+    pItem->u1.pFuncArg = pList;
+    pItem->fg.isTabFunc = 1;
+  }else{
+    sqlite3ExprListDelete(pParse->db, pList);
+  }
+}
+
+/*
+** When building up a FROM clause in the parser, the join operator
+** is initially attached to the left operand.  But the code generator
+** expects the join operator to be on the right operand.  This routine
+** Shifts all join operators from left to right for an entire FROM
+** clause.
+**
+** Example: Suppose the join is like this:
+**
+**           A natural cross join B
+**
+** The operator is "natural cross join".  The A and B operands are stored
+** in p->a[0] and p->a[1], respectively.  The parser initially stores the
+** operator with A.  This routine shifts that operator over to B.
+**
+** Additional changes:
+**
+**   *   All tables to the left of the right-most RIGHT JOIN are tagged with
+**       JT_LTORJ (mnemonic: Left Table Of Right Join) so that the
+**       code generator can easily tell that the table is part of
+**       the left operand of at least one RIGHT JOIN.
+*/
+void sqlite3SrcListShiftJoinType(Parse *pParse, SrcList *p){
+  (void)pParse;
+  if( p && p->nSrc>1 ){
+    int i = p->nSrc-1;
+    u8 allFlags = 0;
+    do{
+      allFlags |= p->a[i].fg.jointype = p->a[i-1].fg.jointype;
+    }while( (--i)>0 );
+    p->a[0].fg.jointype = 0;
+
+    /* All terms to the left of a RIGHT JOIN should be tagged with the
+    ** JT_LTORJ flags */
+    if( allFlags & JT_RIGHT ){
+      for(i=p->nSrc-1; ALWAYS(i>0) && (p->a[i].fg.jointype&JT_RIGHT)==0; i--){}
+      i--;
+      assert( i>=0 );
+      do{
+        p->a[i].fg.jointype |= JT_LTORJ;
+      }while( (--i)>=0 );
+    }
+  }
+}
+
+/*
+** Generate VDBE code for a BEGIN statement.
+*/
+void sqlite3BeginTransaction(Parse *pParse, int type){
+  sqlite3 *db;
+  Vdbe *v;
+  int i;
+
+  assert( pParse!=0 );
+  db = pParse->db;
+  assert( db!=0 );
+  if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "BEGIN", 0, 0) ){
+    return;
+  }
+  v = sqlite3GetVdbe(pParse);
+  if( !v ) return;
+  if( type!=TK_DEFERRED ){
+    for(i=0; i<db->nDb; i++){
+      int eTxnType;
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt && sqlite3BtreeIsReadonly(pBt) ){
+        eTxnType = 0;  /* Read txn */
+      }else if( type==TK_EXCLUSIVE ){
+        eTxnType = 2;  /* Exclusive txn */
+      }else{
+        eTxnType = 1;  /* Write txn */
+      }
+      sqlite3VdbeAddOp2(v, OP_Transaction, i, eTxnType);
+      sqlite3VdbeUsesBtree(v, i);
+    }
+  }
+  sqlite3VdbeAddOp0(v, OP_AutoCommit);
+}
+
+/*
+** Generate VDBE code for a COMMIT or ROLLBACK statement.
+** Code for ROLLBACK is generated if eType==TK_ROLLBACK.  Otherwise
+** code is generated for a COMMIT.
+*/
+void sqlite3EndTransaction(Parse *pParse, int eType){
+  Vdbe *v;
+  int isRollback;
+
+  assert( pParse!=0 );
+  assert( pParse->db!=0 );
+  assert( eType==TK_COMMIT || eType==TK_END || eType==TK_ROLLBACK );
+  isRollback = eType==TK_ROLLBACK;
+  if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION,
+       isRollback ? "ROLLBACK" : "COMMIT", 0, 0) ){
+    return;
+  }
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3VdbeAddOp2(v, OP_AutoCommit, 1, isRollback);
+  }
+}
+
+/*
+** This function is called by the parser when it parses a command to create,
+** release or rollback an SQL savepoint.
+*/
+void sqlite3Savepoint(Parse *pParse, int op, Token *pName){
+  char *zName = sqlite3NameFromToken(pParse->db, pName);
+  if( zName ){
+    Vdbe *v = sqlite3GetVdbe(pParse);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    static const char * const az[] = { "BEGIN", "RELEASE", "ROLLBACK" };
+    assert( !SAVEPOINT_BEGIN && SAVEPOINT_RELEASE==1 && SAVEPOINT_ROLLBACK==2 );
+#endif
+    if( !v || sqlite3AuthCheck(pParse, SQLITE_SAVEPOINT, az[op], zName, 0) ){
+      sqlite3DbFree(pParse->db, zName);
+      return;
+    }
+    sqlite3VdbeAddOp4(v, OP_Savepoint, op, 0, 0, zName, P4_DYNAMIC);
+  }
+}
+
+/*
+** Make sure the TEMP database is open and available for use.  Return
+** the number of errors.  Leave any error messages in the pParse structure.
+*/
+int sqlite3OpenTempDatabase(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  if( db->aDb[1].pBt==0 && !pParse->explain ){
+    int rc;
+    Btree *pBt;
+    static const int flags =
+          SQLITE_OPEN_READWRITE |
+          SQLITE_OPEN_CREATE |
+          SQLITE_OPEN_EXCLUSIVE |
+          SQLITE_OPEN_DELETEONCLOSE |
+          SQLITE_OPEN_TEMP_DB;
+
+    rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pBt, 0, flags);
+    if( rc!=SQLITE_OK ){
+      sqlite3ErrorMsg(pParse, "unable to open a temporary database "
+        "file for storing temporary tables");
+      pParse->rc = rc;
+      return 1;
+    }
+    db->aDb[1].pBt = pBt;
+    assert( db->aDb[1].pSchema );
+    if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, 0, 0) ){
+      sqlite3OomFault(db);
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Record the fact that the schema cookie will need to be verified
+** for database iDb.  The code to actually verify the schema cookie
+** will occur at the end of the top-level VDBE and will be generated
+** later, by sqlite3FinishCoding().
+*/
+static void sqlite3CodeVerifySchemaAtToplevel(Parse *pToplevel, int iDb){
+  assert( iDb>=0 && iDb<pToplevel->db->nDb );
+  assert( pToplevel->db->aDb[iDb].pBt!=0 || iDb==1 );
+  assert( iDb<SQLITE_MAX_DB );
+  assert( sqlite3SchemaMutexHeld(pToplevel->db, iDb, 0) );
+  if( DbMaskTest(pToplevel->cookieMask, iDb)==0 ){
+    DbMaskSet(pToplevel->cookieMask, iDb);
+    if( !OMIT_TEMPDB && iDb==1 ){
+      sqlite3OpenTempDatabase(pToplevel);
+    }
+  }
+}
+void sqlite3CodeVerifySchema(Parse *pParse, int iDb){
+  sqlite3CodeVerifySchemaAtToplevel(sqlite3ParseToplevel(pParse), iDb);
+}
+
+
+/*
+** If argument zDb is NULL, then call sqlite3CodeVerifySchema() for each
+** attached database. Otherwise, invoke it for the database named zDb only.
+*/
+void sqlite3CodeVerifyNamedSchema(Parse *pParse, const char *zDb){
+  sqlite3 *db = pParse->db;
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Db *pDb = &db->aDb[i];
+    if( pDb->pBt && (!zDb || 0==sqlite3StrICmp(zDb, pDb->zDbSName)) ){
+      sqlite3CodeVerifySchema(pParse, i);
+    }
+  }
+}
+
+/*
+** Generate VDBE code that prepares for doing an operation that
+** might change the database.
+**
+** This routine starts a new transaction if we are not already within
+** a transaction.  If we are already within a transaction, then a checkpoint
+** is set if the setStatement parameter is true.  A checkpoint should
+** be set for operations that might fail (due to a constraint) part of
+** the way through and which will need to undo some writes without having to
+** rollback the whole transaction.  For operations where all constraints
+** can be checked before any changes are made to the database, it is never
+** necessary to undo a write and the checkpoint should not be set.
+*/
+void sqlite3BeginWriteOperation(Parse *pParse, int setStatement, int iDb){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  sqlite3CodeVerifySchemaAtToplevel(pToplevel, iDb);
+  DbMaskSet(pToplevel->writeMask, iDb);
+  pToplevel->isMultiWrite |= setStatement;
+}
+
+/*
+** Indicate that the statement currently under construction might write
+** more than one entry (example: deleting one row then inserting another,
+** inserting multiple rows in a table, or inserting a row and index entries.)
+** If an abort occurs after some of these writes have completed, then it will
+** be necessary to undo the completed writes.
+*/
+void sqlite3MultiWrite(Parse *pParse){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  pToplevel->isMultiWrite = 1;
+}
+
+/*
+** The code generator calls this routine if is discovers that it is
+** possible to abort a statement prior to completion.  In order to
+** perform this abort without corrupting the database, we need to make
+** sure that the statement is protected by a statement transaction.
+**
+** Technically, we only need to set the mayAbort flag if the
+** isMultiWrite flag was previously set.  There is a time dependency
+** such that the abort must occur after the multiwrite.  This makes
+** some statements involving the REPLACE conflict resolution algorithm
+** go a little faster.  But taking advantage of this time dependency
+** makes it more difficult to prove that the code is correct (in
+** particular, it prevents us from writing an effective
+** implementation of sqlite3AssertMayAbort()) and so we have chosen
+** to take the safe route and skip the optimization.
+*/
+void sqlite3MayAbort(Parse *pParse){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  pToplevel->mayAbort = 1;
+}
+
+/*
+** Code an OP_Halt that causes the vdbe to return an SQLITE_CONSTRAINT
+** error. The onError parameter determines which (if any) of the statement
+** and/or current transaction is rolled back.
+*/
+void sqlite3HaltConstraint(
+  Parse *pParse,    /* Parsing context */
+  int errCode,      /* extended error code */
+  int onError,      /* Constraint type */
+  char *p4,         /* Error message */
+  i8 p4type,        /* P4_STATIC or P4_TRANSIENT */
+  u8 p5Errmsg       /* P5_ErrMsg type */
+){
+  Vdbe *v;
+  assert( pParse->pVdbe!=0 );
+  v = sqlite3GetVdbe(pParse);
+  assert( (errCode&0xff)==SQLITE_CONSTRAINT || pParse->nested );
+  if( onError==OE_Abort ){
+    sqlite3MayAbort(pParse);
+  }
+  sqlite3VdbeAddOp4(v, OP_Halt, errCode, onError, 0, p4, p4type);
+  sqlite3VdbeChangeP5(v, p5Errmsg);
+}
+
+/*
+** Code an OP_Halt due to UNIQUE or PRIMARY KEY constraint violation.
+*/
+void sqlite3UniqueConstraint(
+  Parse *pParse,    /* Parsing context */
+  int onError,      /* Constraint type */
+  Index *pIdx       /* The index that triggers the constraint */
+){
+  char *zErr;
+  int j;
+  StrAccum errMsg;
+  Table *pTab = pIdx->pTable;
+
+  sqlite3StrAccumInit(&errMsg, pParse->db, 0, 0,
+                      pParse->db->aLimit[SQLITE_LIMIT_LENGTH]);
+  if( pIdx->aColExpr ){
+    sqlite3_str_appendf(&errMsg, "index '%q'", pIdx->zName);
+  }else{
+    for(j=0; j<pIdx->nKeyCol; j++){
+      char *zCol;
+      assert( pIdx->aiColumn[j]>=0 );
+      zCol = pTab->aCol[pIdx->aiColumn[j]].zCnName;
+      if( j ) sqlite3_str_append(&errMsg, ", ", 2);
+      sqlite3_str_appendall(&errMsg, pTab->zName);
+      sqlite3_str_append(&errMsg, ".", 1);
+      sqlite3_str_appendall(&errMsg, zCol);
+    }
+  }
+  zErr = sqlite3StrAccumFinish(&errMsg);
+  sqlite3HaltConstraint(pParse,
+    IsPrimaryKeyIndex(pIdx) ? SQLITE_CONSTRAINT_PRIMARYKEY
+                            : SQLITE_CONSTRAINT_UNIQUE,
+    onError, zErr, P4_DYNAMIC, P5_ConstraintUnique);
+}
+
+
+/*
+** Code an OP_Halt due to non-unique rowid.
+*/
+void sqlite3RowidConstraint(
+  Parse *pParse,    /* Parsing context */
+  int onError,      /* Conflict resolution algorithm */
+  Table *pTab       /* The table with the non-unique rowid */
+){
+  char *zMsg;
+  int rc;
+  if( pTab->iPKey>=0 ){
+    zMsg = sqlite3MPrintf(pParse->db, "%s.%s", pTab->zName,
+                          pTab->aCol[pTab->iPKey].zCnName);
+    rc = SQLITE_CONSTRAINT_PRIMARYKEY;
+  }else{
+    zMsg = sqlite3MPrintf(pParse->db, "%s.rowid", pTab->zName);
+    rc = SQLITE_CONSTRAINT_ROWID;
+  }
+  sqlite3HaltConstraint(pParse, rc, onError, zMsg, P4_DYNAMIC,
+                        P5_ConstraintUnique);
+}
+
+/*
+** Check to see if pIndex uses the collating sequence pColl.  Return
+** true if it does and false if it does not.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+static int collationMatch(const char *zColl, Index *pIndex){
+  int i;
+  assert( zColl!=0 );
+  for(i=0; i<pIndex->nColumn; i++){
+    const char *z = pIndex->azColl[i];
+    assert( z!=0 || pIndex->aiColumn[i]<0 );
+    if( pIndex->aiColumn[i]>=0 && 0==sqlite3StrICmp(z, zColl) ){
+      return 1;
+    }
+  }
+  return 0;
+}
+#endif
+
+/*
+** Recompute all indices of pTab that use the collating sequence pColl.
+** If pColl==0 then recompute all indices of pTab.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+static void reindexTable(Parse *pParse, Table *pTab, char const *zColl){
+  if( !IsVirtual(pTab) ){
+    Index *pIndex;              /* An index associated with pTab */
+
+    for(pIndex=pTab->pIndex; pIndex; pIndex=pIndex->pNext){
+      if( zColl==0 || collationMatch(zColl, pIndex) ){
+        int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+        sqlite3BeginWriteOperation(pParse, 0, iDb);
+        sqlite3RefillIndex(pParse, pIndex, -1);
+      }
+    }
+  }
+}
+#endif
+
+/*
+** Recompute all indices of all tables in all databases where the
+** indices use the collating sequence pColl.  If pColl==0 then recompute
+** all indices everywhere.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+static void reindexDatabases(Parse *pParse, char const *zColl){
+  Db *pDb;                    /* A single database */
+  int iDb;                    /* The database index number */
+  sqlite3 *db = pParse->db;   /* The database connection */
+  HashElem *k;                /* For looping over tables in pDb */
+  Table *pTab;                /* A table in the database */
+
+  assert( sqlite3BtreeHoldsAllMutexes(db) );  /* Needed for schema access */
+  for(iDb=0, pDb=db->aDb; iDb<db->nDb; iDb++, pDb++){
+    assert( pDb!=0 );
+    for(k=sqliteHashFirst(&pDb->pSchema->tblHash);  k; k=sqliteHashNext(k)){
+      pTab = (Table*)sqliteHashData(k);
+      reindexTable(pParse, pTab, zColl);
+    }
+  }
+}
+#endif
+
+/*
+** Generate code for the REINDEX command.
+**
+**        REINDEX                            -- 1
+**        REINDEX  <collation>               -- 2
+**        REINDEX  ?<database>.?<tablename>  -- 3
+**        REINDEX  ?<database>.?<indexname>  -- 4
+**
+** Form 1 causes all indices in all attached databases to be rebuilt.
+** Form 2 rebuilds all indices in all databases that use the named
+** collating function.  Forms 3 and 4 rebuild the named index or all
+** indices associated with the named table.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+void sqlite3Reindex(Parse *pParse, Token *pName1, Token *pName2){
+  CollSeq *pColl;             /* Collating sequence to be reindexed, or NULL */
+  char *z;                    /* Name of a table or index */
+  const char *zDb;            /* Name of the database */
+  Table *pTab;                /* A table in the database */
+  Index *pIndex;              /* An index associated with pTab */
+  int iDb;                    /* The database index number */
+  sqlite3 *db = pParse->db;   /* The database connection */
+  Token *pObjName;            /* Name of the table or index to be reindexed */
+
+  /* Read the database schema. If an error occurs, leave an error message
+  ** and code in pParse and return NULL. */
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    return;
+  }
+
+  if( pName1==0 ){
+    reindexDatabases(pParse, 0);
+    return;
+  }else if( NEVER(pName2==0) || pName2->z==0 ){
+    char *zColl;
+    assert( pName1->z );
+    zColl = sqlite3NameFromToken(pParse->db, pName1);
+    if( !zColl ) return;
+    pColl = sqlite3FindCollSeq(db, ENC(db), zColl, 0);
+    if( pColl ){
+      reindexDatabases(pParse, zColl);
+      sqlite3DbFree(db, zColl);
+      return;
+    }
+    sqlite3DbFree(db, zColl);
+  }
+  iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pObjName);
+  if( iDb<0 ) return;
+  z = sqlite3NameFromToken(db, pObjName);
+  if( z==0 ) return;
+  zDb = pName2->n ? db->aDb[iDb].zDbSName : 0;
+  pTab = sqlite3FindTable(db, z, zDb);
+  if( pTab ){
+    reindexTable(pParse, pTab, 0);
+    sqlite3DbFree(db, z);
+    return;
+  }
+  pIndex = sqlite3FindIndex(db, z, zDb);
+  sqlite3DbFree(db, z);
+  if( pIndex ){
+    iDb = sqlite3SchemaToIndex(db, pIndex->pTable->pSchema);
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    sqlite3RefillIndex(pParse, pIndex, -1);
+    return;
+  }
+  sqlite3ErrorMsg(pParse, "unable to identify the object to be reindexed");
+}
+#endif
+
+/*
+** Return a KeyInfo structure that is appropriate for the given Index.
+**
+** The caller should invoke sqlite3KeyInfoUnref() on the returned object
+** when it has finished using it.
+*/
+KeyInfo *sqlite3KeyInfoOfIndex(Parse *pParse, Index *pIdx){
+  int i;
+  int nCol = pIdx->nColumn;
+  int nKey = pIdx->nKeyCol;
+  KeyInfo *pKey;
+  if( pParse->nErr ) return 0;
+  if( pIdx->uniqNotNull ){
+    pKey = sqlite3KeyInfoAlloc(pParse->db, nKey, nCol-nKey);
+  }else{
+    pKey = sqlite3KeyInfoAlloc(pParse->db, nCol, 0);
+  }
+  if( pKey ){
+    assert( sqlite3KeyInfoIsWriteable(pKey) );
+    for(i=0; i<nCol; i++){
+      const char *zColl = pIdx->azColl[i];
+      pKey->aColl[i] = zColl==sqlite3StrBINARY ? 0 :
+                        sqlite3LocateCollSeq(pParse, zColl);
+      pKey->aSortFlags[i] = pIdx->aSortOrder[i];
+      assert( 0==(pKey->aSortFlags[i] & KEYINFO_ORDER_BIGNULL) );
+    }
+    if( pParse->nErr ){
+      assert( pParse->rc==SQLITE_ERROR_MISSING_COLLSEQ );
+      if( pIdx->bNoQuery==0 ){
+        /* Deactivate the index because it contains an unknown collating
+        ** sequence.  The only way to reactive the index is to reload the
+        ** schema.  Adding the missing collating sequence later does not
+        ** reactive the index.  The application had the chance to register
+        ** the missing index using the collation-needed callback.  For
+        ** simplicity, SQLite will not give the application a second chance.
+        */
+        pIdx->bNoQuery = 1;
+        pParse->rc = SQLITE_ERROR_RETRY;
+      }
+      sqlite3KeyInfoUnref(pKey);
+      pKey = 0;
+    }
+  }
+  return pKey;
+}
+
+#ifndef SQLITE_OMIT_CTE
+/*
+** Create a new CTE object
+*/
+Cte *sqlite3CteNew(
+  Parse *pParse,          /* Parsing context */
+  Token *pName,           /* Name of the common-table */
+  ExprList *pArglist,     /* Optional column name list for the table */
+  Select *pQuery,         /* Query used to initialize the table */
+  u8 eM10d                /* The MATERIALIZED flag */
+){
+  Cte *pNew;
+  sqlite3 *db = pParse->db;
+
+  pNew = sqlite3DbMallocZero(db, sizeof(*pNew));
+  assert( pNew!=0 || db->mallocFailed );
+
+  if( db->mallocFailed ){
+    sqlite3ExprListDelete(db, pArglist);
+    sqlite3SelectDelete(db, pQuery);
+  }else{
+    pNew->pSelect = pQuery;
+    pNew->pCols = pArglist;
+    pNew->zName = sqlite3NameFromToken(pParse->db, pName);
+    pNew->eM10d = eM10d;
+  }
+  return pNew;
+}
+
+/*
+** Clear information from a Cte object, but do not deallocate storage
+** for the object itself.
+*/
+static void cteClear(sqlite3 *db, Cte *pCte){
+  assert( pCte!=0 );
+  sqlite3ExprListDelete(db, pCte->pCols);
+  sqlite3SelectDelete(db, pCte->pSelect);
+  sqlite3DbFree(db, pCte->zName);
+}
+
+/*
+** Free the contents of the CTE object passed as the second argument.
+*/
+void sqlite3CteDelete(sqlite3 *db, Cte *pCte){
+  assert( pCte!=0 );
+  cteClear(db, pCte);
+  sqlite3DbFree(db, pCte);
+}
+
+/*
+** This routine is invoked once per CTE by the parser while parsing a
+** WITH clause.  The CTE described by the third argument is added to
+** the WITH clause of the second argument.  If the second argument is
+** NULL, then a new WITH argument is created.
+*/
+With *sqlite3WithAdd(
+  Parse *pParse,          /* Parsing context */
+  With *pWith,            /* Existing WITH clause, or NULL */
+  Cte *pCte               /* CTE to add to the WITH clause */
+){
+  sqlite3 *db = pParse->db;
+  With *pNew;
+  char *zName;
+
+  if( pCte==0 ){
+    return pWith;
+  }
+
+  /* Check that the CTE name is unique within this WITH clause. If
+  ** not, store an error in the Parse structure. */
+  zName = pCte->zName;
+  if( zName && pWith ){
+    int i;
+    for(i=0; i<pWith->nCte; i++){
+      if( sqlite3StrICmp(zName, pWith->a[i].zName)==0 ){
+        sqlite3ErrorMsg(pParse, "duplicate WITH table name: %s", zName);
+      }
+    }
+  }
+
+  if( pWith ){
+    sqlite3_int64 nByte = sizeof(*pWith) + (sizeof(pWith->a[1]) * pWith->nCte);
+    pNew = sqlite3DbRealloc(db, pWith, nByte);
+  }else{
+    pNew = sqlite3DbMallocZero(db, sizeof(*pWith));
+  }
+  assert( (pNew!=0 && zName!=0) || db->mallocFailed );
+
+  if( db->mallocFailed ){
+    sqlite3CteDelete(db, pCte);
+    pNew = pWith;
+  }else{
+    pNew->a[pNew->nCte++] = *pCte;
+    sqlite3DbFree(db, pCte);
+  }
+
+  return pNew;
+}
+
+/*
+** Free the contents of the With object passed as the second argument.
+*/
+void sqlite3WithDelete(sqlite3 *db, With *pWith){
+  if( pWith ){
+    int i;
+    for(i=0; i<pWith->nCte; i++){
+      cteClear(db, &pWith->a[i]);
+    }
+    sqlite3DbFree(db, pWith);
+  }
+}
+void sqlite3WithDeleteGeneric(sqlite3 *db, void *pWith){
+  sqlite3WithDelete(db, (With*)pWith);
+}
+#endif /* !defined(SQLITE_OMIT_CTE) */
diff --git a/src/callback.c b/src/callback.c
new file mode 100644
index 0000000..c36d51a
--- /dev/null
+++ b/src/callback.c
@@ -0,0 +1,540 @@
+/*
+** 2005 May 23 
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains functions used to access the internal hash tables
+** of user defined functions and collation sequences.
+*/
+
+#include "sqliteInt.h"
+
+/*
+** Invoke the 'collation needed' callback to request a collation sequence
+** in the encoding enc of name zName, length nName.
+*/
+static void callCollNeeded(sqlite3 *db, int enc, const char *zName){
+  assert( !db->xCollNeeded || !db->xCollNeeded16 );
+  if( db->xCollNeeded ){
+    char *zExternal = sqlite3DbStrDup(db, zName);
+    if( !zExternal ) return;
+    db->xCollNeeded(db->pCollNeededArg, db, enc, zExternal);
+    sqlite3DbFree(db, zExternal);
+  }
+#ifndef SQLITE_OMIT_UTF16
+  if( db->xCollNeeded16 ){
+    char const *zExternal;
+    sqlite3_value *pTmp = sqlite3ValueNew(db);
+    sqlite3ValueSetStr(pTmp, -1, zName, SQLITE_UTF8, SQLITE_STATIC);
+    zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);
+    if( zExternal ){
+      db->xCollNeeded16(db->pCollNeededArg, db, (int)ENC(db), zExternal);
+    }
+    sqlite3ValueFree(pTmp);
+  }
+#endif
+}
+
+/*
+** This routine is called if the collation factory fails to deliver a
+** collation function in the best encoding but there may be other versions
+** of this collation function (for other text encodings) available. Use one
+** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if
+** possible.
+*/
+static int synthCollSeq(sqlite3 *db, CollSeq *pColl){
+  CollSeq *pColl2;
+  char *z = pColl->zName;
+  int i;
+  static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };
+  for(i=0; i<3; i++){
+    pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, 0);
+    if( pColl2->xCmp!=0 ){
+      memcpy(pColl, pColl2, sizeof(CollSeq));
+      pColl->xDel = 0;         /* Do not copy the destructor */
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_ERROR;
+}
+
+/*
+** This routine is called on a collation sequence before it is used to
+** check that it is defined. An undefined collation sequence exists when
+** a database is loaded that contains references to collation sequences
+** that have not been defined by sqlite3_create_collation() etc.
+**
+** If required, this routine calls the 'collation needed' callback to
+** request a definition of the collating sequence. If this doesn't work, 
+** an equivalent collating sequence that uses a text encoding different
+** from the main database is substituted, if one is available.
+*/
+int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){
+  if( pColl && pColl->xCmp==0 ){
+    const char *zName = pColl->zName;
+    sqlite3 *db = pParse->db;
+    CollSeq *p = sqlite3GetCollSeq(pParse, ENC(db), pColl, zName);
+    if( !p ){
+      return SQLITE_ERROR;
+    }
+    assert( p==pColl );
+  }
+  return SQLITE_OK;
+}
+
+
+
+/*
+** Locate and return an entry from the db.aCollSeq hash table. If the entry
+** specified by zName and nName is not found and parameter 'create' is
+** true, then create a new entry. Otherwise return NULL.
+**
+** Each pointer stored in the sqlite3.aCollSeq hash table contains an
+** array of three CollSeq structures. The first is the collation sequence
+** preferred for UTF-8, the second UTF-16le, and the third UTF-16be.
+**
+** Stored immediately after the three collation sequences is a copy of
+** the collation sequence name. A pointer to this string is stored in
+** each collation sequence structure.
+*/
+static CollSeq *findCollSeqEntry(
+  sqlite3 *db,          /* Database connection */
+  const char *zName,    /* Name of the collating sequence */
+  int create            /* Create a new entry if true */
+){
+  CollSeq *pColl;
+  pColl = sqlite3HashFind(&db->aCollSeq, zName);
+
+  if( 0==pColl && create ){
+    int nName = sqlite3Strlen30(zName) + 1;
+    pColl = sqlite3DbMallocZero(db, 3*sizeof(*pColl) + nName);
+    if( pColl ){
+      CollSeq *pDel = 0;
+      pColl[0].zName = (char*)&pColl[3];
+      pColl[0].enc = SQLITE_UTF8;
+      pColl[1].zName = (char*)&pColl[3];
+      pColl[1].enc = SQLITE_UTF16LE;
+      pColl[2].zName = (char*)&pColl[3];
+      pColl[2].enc = SQLITE_UTF16BE;
+      memcpy(pColl[0].zName, zName, nName);
+      pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, pColl);
+
+      /* If a malloc() failure occurred in sqlite3HashInsert(), it will 
+      ** return the pColl pointer to be deleted (because it wasn't added
+      ** to the hash table).
+      */
+      assert( pDel==0 || pDel==pColl );
+      if( pDel!=0 ){
+        sqlite3OomFault(db);
+        sqlite3DbFree(db, pDel);
+        pColl = 0;
+      }
+    }
+  }
+  return pColl;
+}
+
+/*
+** Parameter zName points to a UTF-8 encoded string nName bytes long.
+** Return the CollSeq* pointer for the collation sequence named zName
+** for the encoding 'enc' from the database 'db'.
+**
+** If the entry specified is not found and 'create' is true, then create a
+** new entry.  Otherwise return NULL.
+**
+** A separate function sqlite3LocateCollSeq() is a wrapper around
+** this routine.  sqlite3LocateCollSeq() invokes the collation factory
+** if necessary and generates an error message if the collating sequence
+** cannot be found.
+**
+** See also: sqlite3LocateCollSeq(), sqlite3GetCollSeq()
+*/
+CollSeq *sqlite3FindCollSeq(
+  sqlite3 *db,          /* Database connection to search */
+  u8 enc,               /* Desired text encoding */
+  const char *zName,    /* Name of the collating sequence.  Might be NULL */
+  int create            /* True to create CollSeq if doesn't already exist */
+){
+  CollSeq *pColl;
+  assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
+  assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );
+  if( zName ){
+    pColl = findCollSeqEntry(db, zName, create);
+    if( pColl ) pColl += enc-1;
+  }else{
+    pColl = db->pDfltColl;
+  }
+  return pColl;
+}
+
+/*
+** Change the text encoding for a database connection. This means that
+** the pDfltColl must change as well.
+*/
+void sqlite3SetTextEncoding(sqlite3 *db, u8 enc){
+  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
+  db->enc = enc;
+  /* EVIDENCE-OF: R-08308-17224 The default collating function for all
+  ** strings is BINARY. 
+  */
+  db->pDfltColl = sqlite3FindCollSeq(db, enc, sqlite3StrBINARY, 0);
+  sqlite3ExpirePreparedStatements(db, 1);
+}
+
+/*
+** This function is responsible for invoking the collation factory callback
+** or substituting a collation sequence of a different encoding when the
+** requested collation sequence is not available in the desired encoding.
+** 
+** If it is not NULL, then pColl must point to the database native encoding 
+** collation sequence with name zName, length nName.
+**
+** The return value is either the collation sequence to be used in database
+** db for collation type name zName, length nName, or NULL, if no collation
+** sequence can be found.  If no collation is found, leave an error message.
+**
+** See also: sqlite3LocateCollSeq(), sqlite3FindCollSeq()
+*/
+CollSeq *sqlite3GetCollSeq(
+  Parse *pParse,        /* Parsing context */
+  u8 enc,               /* The desired encoding for the collating sequence */
+  CollSeq *pColl,       /* Collating sequence with native encoding, or NULL */
+  const char *zName     /* Collating sequence name */
+){
+  CollSeq *p;
+  sqlite3 *db = pParse->db;
+
+  p = pColl;
+  if( !p ){
+    p = sqlite3FindCollSeq(db, enc, zName, 0);
+  }
+  if( !p || !p->xCmp ){
+    /* No collation sequence of this type for this encoding is registered.
+    ** Call the collation factory to see if it can supply us with one.
+    */
+    callCollNeeded(db, enc, zName);
+    p = sqlite3FindCollSeq(db, enc, zName, 0);
+  }
+  if( p && !p->xCmp && synthCollSeq(db, p) ){
+    p = 0;
+  }
+  assert( !p || p->xCmp );
+  if( p==0 ){
+    sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
+    pParse->rc = SQLITE_ERROR_MISSING_COLLSEQ;
+  }
+  return p;
+}
+
+/*
+** This function returns the collation sequence for database native text
+** encoding identified by the string zName.
+**
+** If the requested collation sequence is not available, or not available
+** in the database native encoding, the collation factory is invoked to
+** request it. If the collation factory does not supply such a sequence,
+** and the sequence is available in another text encoding, then that is
+** returned instead.
+**
+** If no versions of the requested collations sequence are available, or
+** another error occurs, NULL is returned and an error message written into
+** pParse.
+**
+** This routine is a wrapper around sqlite3FindCollSeq().  This routine
+** invokes the collation factory if the named collation cannot be found
+** and generates an error message.
+**
+** See also: sqlite3FindCollSeq(), sqlite3GetCollSeq()
+*/
+CollSeq *sqlite3LocateCollSeq(Parse *pParse, const char *zName){
+  sqlite3 *db = pParse->db;
+  u8 enc = ENC(db);
+  u8 initbusy = db->init.busy;
+  CollSeq *pColl;
+
+  pColl = sqlite3FindCollSeq(db, enc, zName, initbusy);
+  if( !initbusy && (!pColl || !pColl->xCmp) ){
+    pColl = sqlite3GetCollSeq(pParse, enc, pColl, zName);
+  }
+
+  return pColl;
+}
+
+/* During the search for the best function definition, this procedure
+** is called to test how well the function passed as the first argument
+** matches the request for a function with nArg arguments in a system
+** that uses encoding enc. The value returned indicates how well the
+** request is matched. A higher value indicates a better match.
+**
+** If nArg is -1 that means to only return a match (non-zero) if p->nArg
+** is also -1.  In other words, we are searching for a function that
+** takes a variable number of arguments.
+**
+** If nArg is -2 that means that we are searching for any function 
+** regardless of the number of arguments it uses, so return a positive
+** match score for any
+**
+** The returned value is always between 0 and 6, as follows:
+**
+** 0: Not a match.
+** 1: UTF8/16 conversion required and function takes any number of arguments.
+** 2: UTF16 byte order change required and function takes any number of args.
+** 3: encoding matches and function takes any number of arguments
+** 4: UTF8/16 conversion required - argument count matches exactly
+** 5: UTF16 byte order conversion required - argument count matches exactly
+** 6: Perfect match:  encoding and argument count match exactly.
+**
+** If nArg==(-2) then any function with a non-null xSFunc is
+** a perfect match and any function with xSFunc NULL is
+** a non-match.
+*/
+#define FUNC_PERFECT_MATCH 6  /* The score for a perfect match */
+static int matchQuality(
+  FuncDef *p,     /* The function we are evaluating for match quality */
+  int nArg,       /* Desired number of arguments.  (-1)==any */
+  u8 enc          /* Desired text encoding */
+){
+  int match;
+  assert( p->nArg>=-1 );
+
+  /* Wrong number of arguments means "no match" */
+  if( p->nArg!=nArg ){
+    if( nArg==(-2) ) return (p->xSFunc==0) ? 0 : FUNC_PERFECT_MATCH;
+    if( p->nArg>=0 ) return 0;
+  }
+
+  /* Give a better score to a function with a specific number of arguments
+  ** than to function that accepts any number of arguments. */
+  if( p->nArg==nArg ){
+    match = 4;
+  }else{
+    match = 1;
+  }
+
+  /* Bonus points if the text encoding matches */
+  if( enc==(p->funcFlags & SQLITE_FUNC_ENCMASK) ){
+    match += 2;  /* Exact encoding match */
+  }else if( (enc & p->funcFlags & 2)!=0 ){
+    match += 1;  /* Both are UTF16, but with different byte orders */
+  }
+
+  return match;
+}
+
+/*
+** Search a FuncDefHash for a function with the given name.  Return
+** a pointer to the matching FuncDef if found, or 0 if there is no match.
+*/
+FuncDef *sqlite3FunctionSearch(
+  int h,               /* Hash of the name */
+  const char *zFunc    /* Name of function */
+){
+  FuncDef *p;
+  for(p=sqlite3BuiltinFunctions.a[h]; p; p=p->u.pHash){
+    assert( p->funcFlags & SQLITE_FUNC_BUILTIN );
+    if( sqlite3StrICmp(p->zName, zFunc)==0 ){
+      return p;
+    }
+  }
+  return 0;
+}
+
+/*
+** Insert a new FuncDef into a FuncDefHash hash table.
+*/
+void sqlite3InsertBuiltinFuncs(
+  FuncDef *aDef,      /* List of global functions to be inserted */
+  int nDef            /* Length of the apDef[] list */
+){
+  int i;
+  for(i=0; i<nDef; i++){
+    FuncDef *pOther;
+    const char *zName = aDef[i].zName;
+    int nName = sqlite3Strlen30(zName);
+    int h = SQLITE_FUNC_HASH(zName[0], nName);
+    assert( aDef[i].funcFlags & SQLITE_FUNC_BUILTIN );
+    pOther = sqlite3FunctionSearch(h, zName);
+    if( pOther ){
+      assert( pOther!=&aDef[i] && pOther->pNext!=&aDef[i] );
+      aDef[i].pNext = pOther->pNext;
+      pOther->pNext = &aDef[i];
+    }else{
+      aDef[i].pNext = 0;
+      aDef[i].u.pHash = sqlite3BuiltinFunctions.a[h];
+      sqlite3BuiltinFunctions.a[h] = &aDef[i];
+    }
+  }
+}
+  
+  
+
+/*
+** Locate a user function given a name, a number of arguments and a flag
+** indicating whether the function prefers UTF-16 over UTF-8.  Return a
+** pointer to the FuncDef structure that defines that function, or return
+** NULL if the function does not exist.
+**
+** If the createFlag argument is true, then a new (blank) FuncDef
+** structure is created and liked into the "db" structure if a
+** no matching function previously existed.
+**
+** If nArg is -2, then the first valid function found is returned.  A
+** function is valid if xSFunc is non-zero.  The nArg==(-2)
+** case is used to see if zName is a valid function name for some number
+** of arguments.  If nArg is -2, then createFlag must be 0.
+**
+** If createFlag is false, then a function with the required name and
+** number of arguments may be returned even if the eTextRep flag does not
+** match that requested.
+*/
+FuncDef *sqlite3FindFunction(
+  sqlite3 *db,       /* An open database */
+  const char *zName, /* Name of the function.  zero-terminated */
+  int nArg,          /* Number of arguments.  -1 means any number */
+  u8 enc,            /* Preferred text encoding */
+  u8 createFlag      /* Create new entry if true and does not otherwise exist */
+){
+  FuncDef *p;         /* Iterator variable */
+  FuncDef *pBest = 0; /* Best match found so far */
+  int bestScore = 0;  /* Score of best match */
+  int h;              /* Hash value */
+  int nName;          /* Length of the name */
+
+  assert( nArg>=(-2) );
+  assert( nArg>=(-1) || createFlag==0 );
+  nName = sqlite3Strlen30(zName);
+
+  /* First search for a match amongst the application-defined functions.
+  */
+  p = (FuncDef*)sqlite3HashFind(&db->aFunc, zName);
+  while( p ){
+    int score = matchQuality(p, nArg, enc);
+    if( score>bestScore ){
+      pBest = p;
+      bestScore = score;
+    }
+    p = p->pNext;
+  }
+
+  /* If no match is found, search the built-in functions.
+  **
+  ** If the DBFLAG_PreferBuiltin flag is set, then search the built-in
+  ** functions even if a prior app-defined function was found.  And give
+  ** priority to built-in functions.
+  **
+  ** Except, if createFlag is true, that means that we are trying to
+  ** install a new function.  Whatever FuncDef structure is returned it will
+  ** have fields overwritten with new information appropriate for the
+  ** new function.  But the FuncDefs for built-in functions are read-only.
+  ** So we must not search for built-ins when creating a new function.
+  */ 
+  if( !createFlag && (pBest==0 || (db->mDbFlags & DBFLAG_PreferBuiltin)!=0) ){
+    bestScore = 0;
+    h = SQLITE_FUNC_HASH(sqlite3UpperToLower[(u8)zName[0]], nName);
+    p = sqlite3FunctionSearch(h, zName);
+    while( p ){
+      int score = matchQuality(p, nArg, enc);
+      if( score>bestScore ){
+        pBest = p;
+        bestScore = score;
+      }
+      p = p->pNext;
+    }
+  }
+
+  /* If the createFlag parameter is true and the search did not reveal an
+  ** exact match for the name, number of arguments and encoding, then add a
+  ** new entry to the hash table and return it.
+  */
+  if( createFlag && bestScore<FUNC_PERFECT_MATCH && 
+      (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
+    FuncDef *pOther;
+    u8 *z;
+    pBest->zName = (const char*)&pBest[1];
+    pBest->nArg = (u16)nArg;
+    pBest->funcFlags = enc;
+    memcpy((char*)&pBest[1], zName, nName+1);
+    for(z=(u8*)pBest->zName; *z; z++) *z = sqlite3UpperToLower[*z];
+    pOther = (FuncDef*)sqlite3HashInsert(&db->aFunc, pBest->zName, pBest);
+    if( pOther==pBest ){
+      sqlite3DbFree(db, pBest);
+      sqlite3OomFault(db);
+      return 0;
+    }else{
+      pBest->pNext = pOther;
+    }
+  }
+
+  if( pBest && (pBest->xSFunc || createFlag) ){
+    return pBest;
+  }
+  return 0;
+}
+
+/*
+** Free all resources held by the schema structure. The void* argument points
+** at a Schema struct. This function does not call sqlite3DbFree(db, ) on the 
+** pointer itself, it just cleans up subsidiary resources (i.e. the contents
+** of the schema hash tables).
+**
+** The Schema.cache_size variable is not cleared.
+*/
+void sqlite3SchemaClear(void *p){
+  Hash temp1;
+  Hash temp2;
+  HashElem *pElem;
+  Schema *pSchema = (Schema *)p;
+  sqlite3 xdb;
+
+  memset(&xdb, 0, sizeof(xdb));
+  temp1 = pSchema->tblHash;
+  temp2 = pSchema->trigHash;
+  sqlite3HashInit(&pSchema->trigHash);
+  sqlite3HashClear(&pSchema->idxHash);
+  for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){
+    sqlite3DeleteTrigger(&xdb, (Trigger*)sqliteHashData(pElem));
+  }
+  sqlite3HashClear(&temp2);
+  sqlite3HashInit(&pSchema->tblHash);
+  for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){
+    Table *pTab = sqliteHashData(pElem);
+    sqlite3DeleteTable(&xdb, pTab);
+  }
+  sqlite3HashClear(&temp1);
+  sqlite3HashClear(&pSchema->fkeyHash);
+  pSchema->pSeqTab = 0;
+  if( pSchema->schemaFlags & DB_SchemaLoaded ){
+    pSchema->iGeneration++;
+  }
+  pSchema->schemaFlags &= ~(DB_SchemaLoaded|DB_ResetWanted);
+}
+
+/*
+** Find and return the schema associated with a BTree.  Create
+** a new one if necessary.
+*/
+Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
+  Schema * p;
+  if( pBt ){
+    p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
+  }else{
+    p = (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
+  }
+  if( !p ){
+    sqlite3OomFault(db);
+  }else if ( 0==p->file_format ){
+    sqlite3HashInit(&p->tblHash);
+    sqlite3HashInit(&p->idxHash);
+    sqlite3HashInit(&p->trigHash);
+    sqlite3HashInit(&p->fkeyHash);
+    p->enc = SQLITE_UTF8;
+  }
+  return p;
+}
diff --git a/src/complete.c b/src/complete.c
new file mode 100644
index 0000000..bb2c030
--- /dev/null
+++ b/src/complete.c
@@ -0,0 +1,290 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** An tokenizer for SQL
+**
+** This file contains C code that implements the sqlite3_complete() API.
+** This code used to be part of the tokenizer.c source file.  But by
+** separating it out, the code will be automatically omitted from
+** static links that do not use it.
+*/
+#include "sqliteInt.h"
+#ifndef SQLITE_OMIT_COMPLETE
+
+/*
+** This is defined in tokenize.c.  We just have to import the definition.
+*/
+#ifndef SQLITE_AMALGAMATION
+#ifdef SQLITE_ASCII
+#define IdChar(C)  ((sqlite3CtypeMap[(unsigned char)C]&0x46)!=0)
+#endif
+#ifdef SQLITE_EBCDIC
+extern const char sqlite3IsEbcdicIdChar[];
+#define IdChar(C)  (((c=C)>=0x42 && sqlite3IsEbcdicIdChar[c-0x40]))
+#endif
+#endif /* SQLITE_AMALGAMATION */
+
+
+/*
+** Token types used by the sqlite3_complete() routine.  See the header
+** comments on that procedure for additional information.
+*/
+#define tkSEMI    0
+#define tkWS      1
+#define tkOTHER   2
+#ifndef SQLITE_OMIT_TRIGGER
+#define tkEXPLAIN 3
+#define tkCREATE  4
+#define tkTEMP    5
+#define tkTRIGGER 6
+#define tkEND     7
+#endif
+
+/*
+** Return TRUE if the given SQL string ends in a semicolon.
+**
+** Special handling is require for CREATE TRIGGER statements.
+** Whenever the CREATE TRIGGER keywords are seen, the statement
+** must end with ";END;".
+**
+** This implementation uses a state machine with 8 states:
+**
+**   (0) INVALID   We have not yet seen a non-whitespace character.
+**
+**   (1) START     At the beginning or end of an SQL statement.  This routine
+**                 returns 1 if it ends in the START state and 0 if it ends
+**                 in any other state.
+**
+**   (2) NORMAL    We are in the middle of statement which ends with a single
+**                 semicolon.
+**
+**   (3) EXPLAIN   The keyword EXPLAIN has been seen at the beginning of 
+**                 a statement.
+**
+**   (4) CREATE    The keyword CREATE has been seen at the beginning of a
+**                 statement, possibly preceded by EXPLAIN and/or followed by
+**                 TEMP or TEMPORARY
+**
+**   (5) TRIGGER   We are in the middle of a trigger definition that must be
+**                 ended by a semicolon, the keyword END, and another semicolon.
+**
+**   (6) SEMI      We've seen the first semicolon in the ";END;" that occurs at
+**                 the end of a trigger definition.
+**
+**   (7) END       We've seen the ";END" of the ";END;" that occurs at the end
+**                 of a trigger definition.
+**
+** Transitions between states above are determined by tokens extracted
+** from the input.  The following tokens are significant:
+**
+**   (0) tkSEMI      A semicolon.
+**   (1) tkWS        Whitespace.
+**   (2) tkOTHER     Any other SQL token.
+**   (3) tkEXPLAIN   The "explain" keyword.
+**   (4) tkCREATE    The "create" keyword.
+**   (5) tkTEMP      The "temp" or "temporary" keyword.
+**   (6) tkTRIGGER   The "trigger" keyword.
+**   (7) tkEND       The "end" keyword.
+**
+** Whitespace never causes a state transition and is always ignored.
+** This means that a SQL string of all whitespace is invalid.
+**
+** If we compile with SQLITE_OMIT_TRIGGER, all of the computation needed
+** to recognize the end of a trigger can be omitted.  All we have to do
+** is look for a semicolon that is not part of an string or comment.
+*/
+int sqlite3_complete(const char *zSql){
+  u8 state = 0;   /* Current state, using numbers defined in header comment */
+  u8 token;       /* Value of the next token */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  /* A complex statement machine used to detect the end of a CREATE TRIGGER
+  ** statement.  This is the normal case.
+  */
+  static const u8 trans[8][8] = {
+                     /* Token:                                                */
+     /* State:       **  SEMI  WS  OTHER  EXPLAIN  CREATE  TEMP  TRIGGER  END */
+     /* 0 INVALID: */ {    1,  0,     2,       3,      4,    2,       2,   2, },
+     /* 1   START: */ {    1,  1,     2,       3,      4,    2,       2,   2, },
+     /* 2  NORMAL: */ {    1,  2,     2,       2,      2,    2,       2,   2, },
+     /* 3 EXPLAIN: */ {    1,  3,     3,       2,      4,    2,       2,   2, },
+     /* 4  CREATE: */ {    1,  4,     2,       2,      2,    4,       5,   2, },
+     /* 5 TRIGGER: */ {    6,  5,     5,       5,      5,    5,       5,   5, },
+     /* 6    SEMI: */ {    6,  6,     5,       5,      5,    5,       5,   7, },
+     /* 7     END: */ {    1,  7,     5,       5,      5,    5,       5,   5, },
+  };
+#else
+  /* If triggers are not supported by this compile then the statement machine
+  ** used to detect the end of a statement is much simpler
+  */
+  static const u8 trans[3][3] = {
+                     /* Token:           */
+     /* State:       **  SEMI  WS  OTHER */
+     /* 0 INVALID: */ {    1,  0,     2, },
+     /* 1   START: */ {    1,  1,     2, },
+     /* 2  NORMAL: */ {    1,  2,     2, },
+  };
+#endif /* SQLITE_OMIT_TRIGGER */
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( zSql==0 ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+
+  while( *zSql ){
+    switch( *zSql ){
+      case ';': {  /* A semicolon */
+        token = tkSEMI;
+        break;
+      }
+      case ' ':
+      case '\r':
+      case '\t':
+      case '\n':
+      case '\f': {  /* White space is ignored */
+        token = tkWS;
+        break;
+      }
+      case '/': {   /* C-style comments */
+        if( zSql[1]!='*' ){
+          token = tkOTHER;
+          break;
+        }
+        zSql += 2;
+        while( zSql[0] && (zSql[0]!='*' || zSql[1]!='/') ){ zSql++; }
+        if( zSql[0]==0 ) return 0;
+        zSql++;
+        token = tkWS;
+        break;
+      }
+      case '-': {   /* SQL-style comments from "--" to end of line */
+        if( zSql[1]!='-' ){
+          token = tkOTHER;
+          break;
+        }
+        while( *zSql && *zSql!='\n' ){ zSql++; }
+        if( *zSql==0 ) return state==1;
+        token = tkWS;
+        break;
+      }
+      case '[': {   /* Microsoft-style identifiers in [...] */
+        zSql++;
+        while( *zSql && *zSql!=']' ){ zSql++; }
+        if( *zSql==0 ) return 0;
+        token = tkOTHER;
+        break;
+      }
+      case '`':     /* Grave-accent quoted symbols used by MySQL */
+      case '"':     /* single- and double-quoted strings */
+      case '\'': {
+        int c = *zSql;
+        zSql++;
+        while( *zSql && *zSql!=c ){ zSql++; }
+        if( *zSql==0 ) return 0;
+        token = tkOTHER;
+        break;
+      }
+      default: {
+#ifdef SQLITE_EBCDIC
+        unsigned char c;
+#endif
+        if( IdChar((u8)*zSql) ){
+          /* Keywords and unquoted identifiers */
+          int nId;
+          for(nId=1; IdChar(zSql[nId]); nId++){}
+#ifdef SQLITE_OMIT_TRIGGER
+          token = tkOTHER;
+#else
+          switch( *zSql ){
+            case 'c': case 'C': {
+              if( nId==6 && sqlite3StrNICmp(zSql, "create", 6)==0 ){
+                token = tkCREATE;
+              }else{
+                token = tkOTHER;
+              }
+              break;
+            }
+            case 't': case 'T': {
+              if( nId==7 && sqlite3StrNICmp(zSql, "trigger", 7)==0 ){
+                token = tkTRIGGER;
+              }else if( nId==4 && sqlite3StrNICmp(zSql, "temp", 4)==0 ){
+                token = tkTEMP;
+              }else if( nId==9 && sqlite3StrNICmp(zSql, "temporary", 9)==0 ){
+                token = tkTEMP;
+              }else{
+                token = tkOTHER;
+              }
+              break;
+            }
+            case 'e':  case 'E': {
+              if( nId==3 && sqlite3StrNICmp(zSql, "end", 3)==0 ){
+                token = tkEND;
+              }else
+#ifndef SQLITE_OMIT_EXPLAIN
+              if( nId==7 && sqlite3StrNICmp(zSql, "explain", 7)==0 ){
+                token = tkEXPLAIN;
+              }else
+#endif
+              {
+                token = tkOTHER;
+              }
+              break;
+            }
+            default: {
+              token = tkOTHER;
+              break;
+            }
+          }
+#endif /* SQLITE_OMIT_TRIGGER */
+          zSql += nId-1;
+        }else{
+          /* Operators and special symbols */
+          token = tkOTHER;
+        }
+        break;
+      }
+    }
+    state = trans[state][token];
+    zSql++;
+  }
+  return state==1;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** This routine is the same as the sqlite3_complete() routine described
+** above, except that the parameter is required to be UTF-16 encoded, not
+** UTF-8.
+*/
+int sqlite3_complete16(const void *zSql){
+  sqlite3_value *pVal;
+  char const *zSql8;
+  int rc;
+
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, zSql, SQLITE_UTF16NATIVE, SQLITE_STATIC);
+  zSql8 = sqlite3ValueText(pVal, SQLITE_UTF8);
+  if( zSql8 ){
+    rc = sqlite3_complete(zSql8);
+  }else{
+    rc = SQLITE_NOMEM_BKPT;
+  }
+  sqlite3ValueFree(pVal);
+  return rc & 0xff;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+#endif /* SQLITE_OMIT_COMPLETE */
diff --git a/src/ctime.c b/src/ctime.c
new file mode 100644
index 0000000..cf76129
--- /dev/null
+++ b/src/ctime.c
@@ -0,0 +1,793 @@
+/* DO NOT EDIT!
+** This file is automatically generated by the script in the canonical
+** SQLite source tree at tool/mkctimec.tcl.
+**
+** To modify this header, edit any of the various lists in that script
+** which specify categories of generated conditionals in this file.
+*/
+
+/*
+** 2010 February 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements routines used to report what compile-time options
+** SQLite was built with.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS /* IMP: R-16824-07538 */
+
+/*
+** Include the configuration header output by 'configure' if we're using the
+** autoconf-based build
+*/
+#if defined(_HAVE_SQLITE_CONFIG_H) && !defined(SQLITECONFIG_H)
+#include "sqlite_cfg.h"
+#define SQLITECONFIG_H 1
+#endif
+
+/* These macros are provided to "stringify" the value of the define
+** for those options in which the value is meaningful. */
+#define CTIMEOPT_VAL_(opt) #opt
+#define CTIMEOPT_VAL(opt) CTIMEOPT_VAL_(opt)
+
+/* Like CTIMEOPT_VAL, but especially for SQLITE_DEFAULT_LOOKASIDE. This
+** option requires a separate macro because legal values contain a single
+** comma. e.g. (-DSQLITE_DEFAULT_LOOKASIDE="100,100") */
+#define CTIMEOPT_VAL2_(opt1,opt2) #opt1 "," #opt2
+#define CTIMEOPT_VAL2(opt) CTIMEOPT_VAL2_(opt)
+#include "sqliteInt.h"
+
+/*
+** An array of names of all compile-time options.  This array should 
+** be sorted A-Z.
+**
+** This array looks large, but in a typical installation actually uses
+** only a handful of compile-time options, so most times this array is usually
+** rather short and uses little memory space.
+*/
+static const char * const sqlite3azCompileOpt[] = {
+
+#ifdef SQLITE_32BIT_ROWID
+  "32BIT_ROWID",
+#endif
+#ifdef SQLITE_4_BYTE_ALIGNED_MALLOC
+  "4_BYTE_ALIGNED_MALLOC",
+#endif
+#ifdef SQLITE_ALLOW_COVERING_INDEX_SCAN
+# if SQLITE_ALLOW_COVERING_INDEX_SCAN != 1
+  "ALLOW_COVERING_INDEX_SCAN=" CTIMEOPT_VAL(SQLITE_ALLOW_COVERING_INDEX_SCAN),
+# endif
+#endif
+#ifdef SQLITE_ALLOW_URI_AUTHORITY
+  "ALLOW_URI_AUTHORITY",
+#endif
+#ifdef SQLITE_ATOMIC_INTRINSICS
+  "ATOMIC_INTRINSICS=" CTIMEOPT_VAL(SQLITE_ATOMIC_INTRINSICS),
+#endif
+#ifdef SQLITE_BITMASK_TYPE
+  "BITMASK_TYPE=" CTIMEOPT_VAL(SQLITE_BITMASK_TYPE),
+#endif
+#ifdef SQLITE_BUG_COMPATIBLE_20160819
+  "BUG_COMPATIBLE_20160819",
+#endif
+#ifdef SQLITE_CASE_SENSITIVE_LIKE
+  "CASE_SENSITIVE_LIKE",
+#endif
+#ifdef SQLITE_CHECK_PAGES
+  "CHECK_PAGES",
+#endif
+#if defined(__clang__) && defined(__clang_major__)
+  "COMPILER=clang-" CTIMEOPT_VAL(__clang_major__) "."
+                    CTIMEOPT_VAL(__clang_minor__) "."
+                    CTIMEOPT_VAL(__clang_patchlevel__),
+#elif defined(_MSC_VER)
+  "COMPILER=msvc-" CTIMEOPT_VAL(_MSC_VER),
+#elif defined(__GNUC__) && defined(__VERSION__)
+  "COMPILER=gcc-" __VERSION__,
+#endif
+#ifdef SQLITE_COVERAGE_TEST
+  "COVERAGE_TEST",
+#endif
+#ifdef SQLITE_DEBUG
+  "DEBUG",
+#endif
+#ifdef SQLITE_DEFAULT_AUTOMATIC_INDEX
+  "DEFAULT_AUTOMATIC_INDEX",
+#endif
+#ifdef SQLITE_DEFAULT_AUTOVACUUM
+  "DEFAULT_AUTOVACUUM",
+#endif
+#ifdef SQLITE_DEFAULT_CACHE_SIZE
+  "DEFAULT_CACHE_SIZE=" CTIMEOPT_VAL(SQLITE_DEFAULT_CACHE_SIZE),
+#endif
+#ifdef SQLITE_DEFAULT_CKPTFULLFSYNC
+  "DEFAULT_CKPTFULLFSYNC",
+#endif
+#ifdef SQLITE_DEFAULT_FILE_FORMAT
+  "DEFAULT_FILE_FORMAT=" CTIMEOPT_VAL(SQLITE_DEFAULT_FILE_FORMAT),
+#endif
+#ifdef SQLITE_DEFAULT_FILE_PERMISSIONS
+  "DEFAULT_FILE_PERMISSIONS=" CTIMEOPT_VAL(SQLITE_DEFAULT_FILE_PERMISSIONS),
+#endif
+#ifdef SQLITE_DEFAULT_FOREIGN_KEYS
+  "DEFAULT_FOREIGN_KEYS",
+#endif
+#ifdef SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT
+  "DEFAULT_JOURNAL_SIZE_LIMIT=" CTIMEOPT_VAL(SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT),
+#endif
+#ifdef SQLITE_DEFAULT_LOCKING_MODE
+  "DEFAULT_LOCKING_MODE=" CTIMEOPT_VAL(SQLITE_DEFAULT_LOCKING_MODE),
+#endif
+#ifdef SQLITE_DEFAULT_LOOKASIDE
+  "DEFAULT_LOOKASIDE=" CTIMEOPT_VAL2(SQLITE_DEFAULT_LOOKASIDE),
+#endif
+#ifdef SQLITE_DEFAULT_MEMSTATUS
+# if SQLITE_DEFAULT_MEMSTATUS != 1
+  "DEFAULT_MEMSTATUS=" CTIMEOPT_VAL(SQLITE_DEFAULT_MEMSTATUS),
+# endif
+#endif
+#ifdef SQLITE_DEFAULT_MMAP_SIZE
+  "DEFAULT_MMAP_SIZE=" CTIMEOPT_VAL(SQLITE_DEFAULT_MMAP_SIZE),
+#endif
+#ifdef SQLITE_DEFAULT_PAGE_SIZE
+  "DEFAULT_PAGE_SIZE=" CTIMEOPT_VAL(SQLITE_DEFAULT_PAGE_SIZE),
+#endif
+#ifdef SQLITE_DEFAULT_PCACHE_INITSZ
+  "DEFAULT_PCACHE_INITSZ=" CTIMEOPT_VAL(SQLITE_DEFAULT_PCACHE_INITSZ),
+#endif
+#ifdef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
+  "DEFAULT_PROXYDIR_PERMISSIONS=" CTIMEOPT_VAL(SQLITE_DEFAULT_PROXYDIR_PERMISSIONS),
+#endif
+#ifdef SQLITE_DEFAULT_RECURSIVE_TRIGGERS
+  "DEFAULT_RECURSIVE_TRIGGERS",
+#endif
+#ifdef SQLITE_DEFAULT_ROWEST
+  "DEFAULT_ROWEST=" CTIMEOPT_VAL(SQLITE_DEFAULT_ROWEST),
+#endif
+#ifdef SQLITE_DEFAULT_SECTOR_SIZE
+  "DEFAULT_SECTOR_SIZE=" CTIMEOPT_VAL(SQLITE_DEFAULT_SECTOR_SIZE),
+#endif
+#ifdef SQLITE_DEFAULT_SYNCHRONOUS
+  "DEFAULT_SYNCHRONOUS=" CTIMEOPT_VAL(SQLITE_DEFAULT_SYNCHRONOUS),
+#endif
+#ifdef SQLITE_DEFAULT_WAL_AUTOCHECKPOINT
+  "DEFAULT_WAL_AUTOCHECKPOINT=" CTIMEOPT_VAL(SQLITE_DEFAULT_WAL_AUTOCHECKPOINT),
+#endif
+#ifdef SQLITE_DEFAULT_WAL_SYNCHRONOUS
+  "DEFAULT_WAL_SYNCHRONOUS=" CTIMEOPT_VAL(SQLITE_DEFAULT_WAL_SYNCHRONOUS),
+#endif
+#ifdef SQLITE_DEFAULT_WORKER_THREADS
+  "DEFAULT_WORKER_THREADS=" CTIMEOPT_VAL(SQLITE_DEFAULT_WORKER_THREADS),
+#endif
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+  "DIRECT_OVERFLOW_READ",
+#endif
+#ifdef SQLITE_DISABLE_DIRSYNC
+  "DISABLE_DIRSYNC",
+#endif
+#ifdef SQLITE_DISABLE_FTS3_UNICODE
+  "DISABLE_FTS3_UNICODE",
+#endif
+#ifdef SQLITE_DISABLE_FTS4_DEFERRED
+  "DISABLE_FTS4_DEFERRED",
+#endif
+#ifdef SQLITE_DISABLE_INTRINSIC
+  "DISABLE_INTRINSIC",
+#endif
+#ifdef SQLITE_DISABLE_LFS
+  "DISABLE_LFS",
+#endif
+#ifdef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
+  "DISABLE_PAGECACHE_OVERFLOW_STATS",
+#endif
+#ifdef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
+  "DISABLE_SKIPAHEAD_DISTINCT",
+#endif
+#ifdef SQLITE_DQS
+  "DQS=" CTIMEOPT_VAL(SQLITE_DQS),
+#endif
+#ifdef SQLITE_ENABLE_8_3_NAMES
+  "ENABLE_8_3_NAMES=" CTIMEOPT_VAL(SQLITE_ENABLE_8_3_NAMES),
+#endif
+#ifdef SQLITE_ENABLE_API_ARMOR
+  "ENABLE_API_ARMOR",
+#endif
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  "ENABLE_ATOMIC_WRITE",
+#endif
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+  "ENABLE_BATCH_ATOMIC_WRITE",
+#endif
+#ifdef SQLITE_ENABLE_BYTECODE_VTAB
+  "ENABLE_BYTECODE_VTAB",
+#endif
+#ifdef SQLITE_ENABLE_CEROD
+  "ENABLE_CEROD=" CTIMEOPT_VAL(SQLITE_ENABLE_CEROD),
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  "ENABLE_COLUMN_METADATA",
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+  "ENABLE_COLUMN_USED_MASK",
+#endif
+#ifdef SQLITE_ENABLE_COSTMULT
+  "ENABLE_COSTMULT",
+#endif
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+  "ENABLE_CURSOR_HINTS",
+#endif
+#ifdef SQLITE_ENABLE_DBPAGE_VTAB
+  "ENABLE_DBPAGE_VTAB",
+#endif
+#ifdef SQLITE_ENABLE_DBSTAT_VTAB
+  "ENABLE_DBSTAT_VTAB",
+#endif
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  "ENABLE_EXPENSIVE_ASSERT",
+#endif
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  "ENABLE_EXPLAIN_COMMENTS",
+#endif
+#ifdef SQLITE_ENABLE_FTS3
+  "ENABLE_FTS3",
+#endif
+#ifdef SQLITE_ENABLE_FTS3_PARENTHESIS
+  "ENABLE_FTS3_PARENTHESIS",
+#endif
+#ifdef SQLITE_ENABLE_FTS3_TOKENIZER
+  "ENABLE_FTS3_TOKENIZER",
+#endif
+#ifdef SQLITE_ENABLE_FTS4
+  "ENABLE_FTS4",
+#endif
+#ifdef SQLITE_ENABLE_FTS5
+  "ENABLE_FTS5",
+#endif
+#ifdef SQLITE_ENABLE_GEOPOLY
+  "ENABLE_GEOPOLY",
+#endif
+#ifdef SQLITE_ENABLE_HIDDEN_COLUMNS
+  "ENABLE_HIDDEN_COLUMNS",
+#endif
+#ifdef SQLITE_ENABLE_ICU
+  "ENABLE_ICU",
+#endif
+#ifdef SQLITE_ENABLE_IOTRACE
+  "ENABLE_IOTRACE",
+#endif
+#ifdef SQLITE_ENABLE_LOAD_EXTENSION
+  "ENABLE_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+  "ENABLE_LOCKING_STYLE=" CTIMEOPT_VAL(SQLITE_ENABLE_LOCKING_STYLE),
+#endif
+#ifdef SQLITE_ENABLE_MATH_FUNCTIONS
+  "ENABLE_MATH_FUNCTIONS",
+#endif
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  "ENABLE_MEMORY_MANAGEMENT",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS3
+  "ENABLE_MEMSYS3",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS5
+  "ENABLE_MEMSYS5",
+#endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+  "ENABLE_MULTIPLEX",
+#endif
+#ifdef SQLITE_ENABLE_NORMALIZE
+  "ENABLE_NORMALIZE",
+#endif
+#ifdef SQLITE_ENABLE_NULL_TRIM
+  "ENABLE_NULL_TRIM",
+#endif
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+  "ENABLE_OFFSET_SQL_FUNC",
+#endif
+#ifdef SQLITE_ENABLE_OVERSIZE_CELL_CHECK
+  "ENABLE_OVERSIZE_CELL_CHECK",
+#endif
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  "ENABLE_PREUPDATE_HOOK",
+#endif
+#ifdef SQLITE_ENABLE_QPSG
+  "ENABLE_QPSG",
+#endif
+#ifdef SQLITE_ENABLE_RBU
+  "ENABLE_RBU",
+#endif
+#ifdef SQLITE_ENABLE_RTREE
+  "ENABLE_RTREE",
+#endif
+#ifdef SQLITE_ENABLE_SESSION
+  "ENABLE_SESSION",
+#endif
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  "ENABLE_SNAPSHOT",
+#endif
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+  "ENABLE_SORTER_REFERENCES",
+#endif
+#ifdef SQLITE_ENABLE_SQLLOG
+  "ENABLE_SQLLOG",
+#endif
+#ifdef SQLITE_ENABLE_STAT4
+  "ENABLE_STAT4",
+#endif
+#ifdef SQLITE_ENABLE_STMTVTAB
+  "ENABLE_STMTVTAB",
+#endif
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  "ENABLE_STMT_SCANSTATUS",
+#endif
+#ifdef SQLITE_ENABLE_TREETRACE
+  "ENABLE_TREETRACE",
+#endif
+#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
+  "ENABLE_UNKNOWN_SQL_FUNCTION",
+#endif
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  "ENABLE_UNLOCK_NOTIFY",
+#endif
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  "ENABLE_UPDATE_DELETE_LIMIT",
+#endif
+#ifdef SQLITE_ENABLE_URI_00_ERROR
+  "ENABLE_URI_00_ERROR",
+#endif
+#ifdef SQLITE_ENABLE_VFSTRACE
+  "ENABLE_VFSTRACE",
+#endif
+#ifdef SQLITE_ENABLE_WHERETRACE
+  "ENABLE_WHERETRACE",
+#endif
+#ifdef SQLITE_ENABLE_ZIPVFS
+  "ENABLE_ZIPVFS",
+#endif
+#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
+  "EXPLAIN_ESTIMATED_ROWS",
+#endif
+#ifdef SQLITE_EXTRA_AUTOEXT
+  "EXTRA_AUTOEXT=" CTIMEOPT_VAL(SQLITE_EXTRA_AUTOEXT),
+#endif
+#ifdef SQLITE_EXTRA_IFNULLROW
+  "EXTRA_IFNULLROW",
+#endif
+#ifdef SQLITE_EXTRA_INIT
+  "EXTRA_INIT=" CTIMEOPT_VAL(SQLITE_EXTRA_INIT),
+#endif
+#ifdef SQLITE_EXTRA_SHUTDOWN
+  "EXTRA_SHUTDOWN=" CTIMEOPT_VAL(SQLITE_EXTRA_SHUTDOWN),
+#endif
+#ifdef SQLITE_FTS3_MAX_EXPR_DEPTH
+  "FTS3_MAX_EXPR_DEPTH=" CTIMEOPT_VAL(SQLITE_FTS3_MAX_EXPR_DEPTH),
+#endif
+#ifdef SQLITE_FTS5_ENABLE_TEST_MI
+  "FTS5_ENABLE_TEST_MI",
+#endif
+#ifdef SQLITE_FTS5_NO_WITHOUT_ROWID
+  "FTS5_NO_WITHOUT_ROWID",
+#endif
+#if HAVE_ISNAN || SQLITE_HAVE_ISNAN
+  "HAVE_ISNAN",
+#endif
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+# if SQLITE_HOMEGROWN_RECURSIVE_MUTEX != 1
+  "HOMEGROWN_RECURSIVE_MUTEX=" CTIMEOPT_VAL(SQLITE_HOMEGROWN_RECURSIVE_MUTEX),
+# endif
+#endif
+#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
+  "IGNORE_AFP_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  "IGNORE_FLOCK_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_INLINE_MEMCPY
+  "INLINE_MEMCPY",
+#endif
+#ifdef SQLITE_INT64_TYPE
+  "INT64_TYPE",
+#endif
+#ifdef SQLITE_INTEGRITY_CHECK_ERROR_MAX
+  "INTEGRITY_CHECK_ERROR_MAX=" CTIMEOPT_VAL(SQLITE_INTEGRITY_CHECK_ERROR_MAX),
+#endif
+#ifdef SQLITE_LEGACY_JSON_VALID
+  "LEGACY_JSON_VALID",
+#endif
+#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+  "LIKE_DOESNT_MATCH_BLOBS",
+#endif
+#ifdef SQLITE_LOCK_TRACE
+  "LOCK_TRACE",
+#endif
+#ifdef SQLITE_LOG_CACHE_SPILL
+  "LOG_CACHE_SPILL",
+#endif
+#ifdef SQLITE_MALLOC_SOFT_LIMIT
+  "MALLOC_SOFT_LIMIT=" CTIMEOPT_VAL(SQLITE_MALLOC_SOFT_LIMIT),
+#endif
+#ifdef SQLITE_MAX_ATTACHED
+  "MAX_ATTACHED=" CTIMEOPT_VAL(SQLITE_MAX_ATTACHED),
+#endif
+#ifdef SQLITE_MAX_COLUMN
+  "MAX_COLUMN=" CTIMEOPT_VAL(SQLITE_MAX_COLUMN),
+#endif
+#ifdef SQLITE_MAX_COMPOUND_SELECT
+  "MAX_COMPOUND_SELECT=" CTIMEOPT_VAL(SQLITE_MAX_COMPOUND_SELECT),
+#endif
+#ifdef SQLITE_MAX_DEFAULT_PAGE_SIZE
+  "MAX_DEFAULT_PAGE_SIZE=" CTIMEOPT_VAL(SQLITE_MAX_DEFAULT_PAGE_SIZE),
+#endif
+#ifdef SQLITE_MAX_EXPR_DEPTH
+  "MAX_EXPR_DEPTH=" CTIMEOPT_VAL(SQLITE_MAX_EXPR_DEPTH),
+#endif
+#ifdef SQLITE_MAX_FUNCTION_ARG
+  "MAX_FUNCTION_ARG=" CTIMEOPT_VAL(SQLITE_MAX_FUNCTION_ARG),
+#endif
+#ifdef SQLITE_MAX_LENGTH
+  "MAX_LENGTH=" CTIMEOPT_VAL(SQLITE_MAX_LENGTH),
+#endif
+#ifdef SQLITE_MAX_LIKE_PATTERN_LENGTH
+  "MAX_LIKE_PATTERN_LENGTH=" CTIMEOPT_VAL(SQLITE_MAX_LIKE_PATTERN_LENGTH),
+#endif
+#ifdef SQLITE_MAX_MEMORY
+  "MAX_MEMORY=" CTIMEOPT_VAL(SQLITE_MAX_MEMORY),
+#endif
+#ifdef SQLITE_MAX_MMAP_SIZE
+  "MAX_MMAP_SIZE=" CTIMEOPT_VAL(SQLITE_MAX_MMAP_SIZE),
+#endif
+#ifdef SQLITE_MAX_MMAP_SIZE_
+  "MAX_MMAP_SIZE_=" CTIMEOPT_VAL(SQLITE_MAX_MMAP_SIZE_),
+#endif
+#ifdef SQLITE_MAX_PAGE_COUNT
+  "MAX_PAGE_COUNT=" CTIMEOPT_VAL(SQLITE_MAX_PAGE_COUNT),
+#endif
+#ifdef SQLITE_MAX_PAGE_SIZE
+  "MAX_PAGE_SIZE=" CTIMEOPT_VAL(SQLITE_MAX_PAGE_SIZE),
+#endif
+#ifdef SQLITE_MAX_SCHEMA_RETRY
+  "MAX_SCHEMA_RETRY=" CTIMEOPT_VAL(SQLITE_MAX_SCHEMA_RETRY),
+#endif
+#ifdef SQLITE_MAX_SQL_LENGTH
+  "MAX_SQL_LENGTH=" CTIMEOPT_VAL(SQLITE_MAX_SQL_LENGTH),
+#endif
+#ifdef SQLITE_MAX_TRIGGER_DEPTH
+  "MAX_TRIGGER_DEPTH=" CTIMEOPT_VAL(SQLITE_MAX_TRIGGER_DEPTH),
+#endif
+#ifdef SQLITE_MAX_VARIABLE_NUMBER
+  "MAX_VARIABLE_NUMBER=" CTIMEOPT_VAL(SQLITE_MAX_VARIABLE_NUMBER),
+#endif
+#ifdef SQLITE_MAX_VDBE_OP
+  "MAX_VDBE_OP=" CTIMEOPT_VAL(SQLITE_MAX_VDBE_OP),
+#endif
+#ifdef SQLITE_MAX_WORKER_THREADS
+  "MAX_WORKER_THREADS=" CTIMEOPT_VAL(SQLITE_MAX_WORKER_THREADS),
+#endif
+#ifdef SQLITE_MEMDEBUG
+  "MEMDEBUG",
+#endif
+#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+  "MIXED_ENDIAN_64BIT_FLOAT",
+#endif
+#ifdef SQLITE_MMAP_READWRITE
+  "MMAP_READWRITE",
+#endif
+#ifdef SQLITE_MUTEX_NOOP
+  "MUTEX_NOOP",
+#endif
+#ifdef SQLITE_MUTEX_OMIT
+  "MUTEX_OMIT",
+#endif
+#ifdef SQLITE_MUTEX_PTHREADS
+  "MUTEX_PTHREADS",
+#endif
+#ifdef SQLITE_MUTEX_W32
+  "MUTEX_W32",
+#endif
+#ifdef SQLITE_NEED_ERR_NAME
+  "NEED_ERR_NAME",
+#endif
+#ifdef SQLITE_NO_SYNC
+  "NO_SYNC",
+#endif
+#ifdef SQLITE_OMIT_ALTERTABLE
+  "OMIT_ALTERTABLE",
+#endif
+#ifdef SQLITE_OMIT_ANALYZE
+  "OMIT_ANALYZE",
+#endif
+#ifdef SQLITE_OMIT_ATTACH
+  "OMIT_ATTACH",
+#endif
+#ifdef SQLITE_OMIT_AUTHORIZATION
+  "OMIT_AUTHORIZATION",
+#endif
+#ifdef SQLITE_OMIT_AUTOINCREMENT
+  "OMIT_AUTOINCREMENT",
+#endif
+#ifdef SQLITE_OMIT_AUTOINIT
+  "OMIT_AUTOINIT",
+#endif
+#ifdef SQLITE_OMIT_AUTOMATIC_INDEX
+  "OMIT_AUTOMATIC_INDEX",
+#endif
+#ifdef SQLITE_OMIT_AUTORESET
+  "OMIT_AUTORESET",
+#endif
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  "OMIT_AUTOVACUUM",
+#endif
+#ifdef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  "OMIT_BETWEEN_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_BLOB_LITERAL
+  "OMIT_BLOB_LITERAL",
+#endif
+#ifdef SQLITE_OMIT_CAST
+  "OMIT_CAST",
+#endif
+#ifdef SQLITE_OMIT_CHECK
+  "OMIT_CHECK",
+#endif
+#ifdef SQLITE_OMIT_COMPLETE
+  "OMIT_COMPLETE",
+#endif
+#ifdef SQLITE_OMIT_COMPOUND_SELECT
+  "OMIT_COMPOUND_SELECT",
+#endif
+#ifdef SQLITE_OMIT_CONFLICT_CLAUSE
+  "OMIT_CONFLICT_CLAUSE",
+#endif
+#ifdef SQLITE_OMIT_CTE
+  "OMIT_CTE",
+#endif
+#if defined(SQLITE_OMIT_DATETIME_FUNCS) || defined(SQLITE_OMIT_FLOATING_POINT)
+  "OMIT_DATETIME_FUNCS",
+#endif
+#ifdef SQLITE_OMIT_DECLTYPE
+  "OMIT_DECLTYPE",
+#endif
+#ifdef SQLITE_OMIT_DEPRECATED
+  "OMIT_DEPRECATED",
+#endif
+#ifdef SQLITE_OMIT_DESERIALIZE
+  "OMIT_DESERIALIZE",
+#endif
+#ifdef SQLITE_OMIT_DISKIO
+  "OMIT_DISKIO",
+#endif
+#ifdef SQLITE_OMIT_EXPLAIN
+  "OMIT_EXPLAIN",
+#endif
+#ifdef SQLITE_OMIT_FLAG_PRAGMAS
+  "OMIT_FLAG_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  "OMIT_FLOATING_POINT",
+#endif
+#ifdef SQLITE_OMIT_FOREIGN_KEY
+  "OMIT_FOREIGN_KEY",
+#endif
+#ifdef SQLITE_OMIT_GET_TABLE
+  "OMIT_GET_TABLE",
+#endif
+#ifdef SQLITE_OMIT_HEX_INTEGER
+  "OMIT_HEX_INTEGER",
+#endif
+#ifdef SQLITE_OMIT_INCRBLOB
+  "OMIT_INCRBLOB",
+#endif
+#ifdef SQLITE_OMIT_INTEGRITY_CHECK
+  "OMIT_INTEGRITY_CHECK",
+#endif
+#ifdef SQLITE_OMIT_INTROSPECTION_PRAGMAS
+  "OMIT_INTROSPECTION_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_JSON
+  "OMIT_JSON",
+#endif
+#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
+  "OMIT_LIKE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  "OMIT_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_OMIT_LOCALTIME
+  "OMIT_LOCALTIME",
+#endif
+#ifdef SQLITE_OMIT_LOOKASIDE
+  "OMIT_LOOKASIDE",
+#endif
+#ifdef SQLITE_OMIT_MEMORYDB
+  "OMIT_MEMORYDB",
+#endif
+#ifdef SQLITE_OMIT_OR_OPTIMIZATION
+  "OMIT_OR_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_PAGER_PRAGMAS
+  "OMIT_PAGER_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_PARSER_TRACE
+  "OMIT_PARSER_TRACE",
+#endif
+#ifdef SQLITE_OMIT_POPEN
+  "OMIT_POPEN",
+#endif
+#ifdef SQLITE_OMIT_PRAGMA
+  "OMIT_PRAGMA",
+#endif
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+  "OMIT_PROGRESS_CALLBACK",
+#endif
+#ifdef SQLITE_OMIT_QUICKBALANCE
+  "OMIT_QUICKBALANCE",
+#endif
+#ifdef SQLITE_OMIT_REINDEX
+  "OMIT_REINDEX",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_PRAGMAS
+  "OMIT_SCHEMA_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  "OMIT_SCHEMA_VERSION_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SEH
+  "OMIT_SEH",
+#endif
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  "OMIT_SHARED_CACHE",
+#endif
+#ifdef SQLITE_OMIT_SHUTDOWN_DIRECTORIES
+  "OMIT_SHUTDOWN_DIRECTORIES",
+#endif
+#ifdef SQLITE_OMIT_SUBQUERY
+  "OMIT_SUBQUERY",
+#endif
+#ifdef SQLITE_OMIT_TCL_VARIABLE
+  "OMIT_TCL_VARIABLE",
+#endif
+#ifdef SQLITE_OMIT_TEMPDB
+  "OMIT_TEMPDB",
+#endif
+#ifdef SQLITE_OMIT_TEST_CONTROL
+  "OMIT_TEST_CONTROL",
+#endif
+#ifdef SQLITE_OMIT_TRACE
+# if SQLITE_OMIT_TRACE != 1
+  "OMIT_TRACE=" CTIMEOPT_VAL(SQLITE_OMIT_TRACE),
+# endif
+#endif
+#ifdef SQLITE_OMIT_TRIGGER
+  "OMIT_TRIGGER",
+#endif
+#ifdef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  "OMIT_TRUNCATE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_UTF16
+  "OMIT_UTF16",
+#endif
+#ifdef SQLITE_OMIT_VACUUM
+  "OMIT_VACUUM",
+#endif
+#ifdef SQLITE_OMIT_VIEW
+  "OMIT_VIEW",
+#endif
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  "OMIT_VIRTUALTABLE",
+#endif
+#ifdef SQLITE_OMIT_WAL
+  "OMIT_WAL",
+#endif
+#ifdef SQLITE_OMIT_WSD
+  "OMIT_WSD",
+#endif
+#ifdef SQLITE_OMIT_XFER_OPT
+  "OMIT_XFER_OPT",
+#endif
+#ifdef SQLITE_PERFORMANCE_TRACE
+  "PERFORMANCE_TRACE",
+#endif
+#ifdef SQLITE_POWERSAFE_OVERWRITE
+# if SQLITE_POWERSAFE_OVERWRITE != 1
+  "POWERSAFE_OVERWRITE=" CTIMEOPT_VAL(SQLITE_POWERSAFE_OVERWRITE),
+# endif
+#endif
+#ifdef SQLITE_PREFER_PROXY_LOCKING
+  "PREFER_PROXY_LOCKING",
+#endif
+#ifdef SQLITE_PROXY_DEBUG
+  "PROXY_DEBUG",
+#endif
+#ifdef SQLITE_REVERSE_UNORDERED_SELECTS
+  "REVERSE_UNORDERED_SELECTS",
+#endif
+#ifdef SQLITE_RTREE_INT_ONLY
+  "RTREE_INT_ONLY",
+#endif
+#ifdef SQLITE_SECURE_DELETE
+  "SECURE_DELETE",
+#endif
+#ifdef SQLITE_SMALL_STACK
+  "SMALL_STACK",
+#endif
+#ifdef SQLITE_SORTER_PMASZ
+  "SORTER_PMASZ=" CTIMEOPT_VAL(SQLITE_SORTER_PMASZ),
+#endif
+#ifdef SQLITE_SOUNDEX
+  "SOUNDEX",
+#endif
+#ifdef SQLITE_STAT4_SAMPLES
+  "STAT4_SAMPLES=" CTIMEOPT_VAL(SQLITE_STAT4_SAMPLES),
+#endif
+#ifdef SQLITE_STMTJRNL_SPILL
+  "STMTJRNL_SPILL=" CTIMEOPT_VAL(SQLITE_STMTJRNL_SPILL),
+#endif
+#ifdef SQLITE_SUBSTR_COMPATIBILITY
+  "SUBSTR_COMPATIBILITY",
+#endif
+#if (!defined(SQLITE_WIN32_MALLOC) \
+     && !defined(SQLITE_ZERO_MALLOC) \
+     && !defined(SQLITE_MEMDEBUG) \
+    ) || defined(SQLITE_SYSTEM_MALLOC)
+  "SYSTEM_MALLOC",
+#endif
+#ifdef SQLITE_TCL
+  "TCL",
+#endif
+#ifdef SQLITE_TEMP_STORE
+  "TEMP_STORE=" CTIMEOPT_VAL(SQLITE_TEMP_STORE),
+#endif
+#ifdef SQLITE_TEST
+  "TEST",
+#endif
+#if defined(SQLITE_THREADSAFE)
+  "THREADSAFE=" CTIMEOPT_VAL(SQLITE_THREADSAFE),
+#elif defined(THREADSAFE)
+  "THREADSAFE=" CTIMEOPT_VAL(THREADSAFE),
+#else
+  "THREADSAFE=1",
+#endif
+#ifdef SQLITE_UNLINK_AFTER_CLOSE
+  "UNLINK_AFTER_CLOSE",
+#endif
+#ifdef SQLITE_UNTESTABLE
+  "UNTESTABLE",
+#endif
+#ifdef SQLITE_USER_AUTHENTICATION
+  "USER_AUTHENTICATION",
+#endif
+#ifdef SQLITE_USE_ALLOCA
+  "USE_ALLOCA",
+#endif
+#ifdef SQLITE_USE_FCNTL_TRACE
+  "USE_FCNTL_TRACE",
+#endif
+#ifdef SQLITE_USE_URI
+  "USE_URI",
+#endif
+#ifdef SQLITE_VDBE_COVERAGE
+  "VDBE_COVERAGE",
+#endif
+#ifdef SQLITE_WIN32_MALLOC
+  "WIN32_MALLOC",
+#endif
+#ifdef SQLITE_ZERO_MALLOC
+  "ZERO_MALLOC",
+#endif
+
+} ;
+
+const char **sqlite3CompileOptions(int *pnOpt){
+  *pnOpt = sizeof(sqlite3azCompileOpt) / sizeof(sqlite3azCompileOpt[0]);
+  return (const char**)sqlite3azCompileOpt;
+}
+
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
diff --git a/src/date.c b/src/date.c
new file mode 100644
index 0000000..e493542
--- /dev/null
+++ b/src/date.c
@@ -0,0 +1,1624 @@
+/*
+** 2003 October 31
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement date and time
+** functions for SQLite.  
+**
+** There is only one exported symbol in this file - the function
+** sqlite3RegisterDateTimeFunctions() found at the bottom of the file.
+** All other code has file scope.
+**
+** SQLite processes all times and dates as julian day numbers.  The
+** dates and times are stored as the number of days since noon
+** in Greenwich on November 24, 4714 B.C. according to the Gregorian
+** calendar system. 
+**
+** 1970-01-01 00:00:00 is JD 2440587.5
+** 2000-01-01 00:00:00 is JD 2451544.5
+**
+** This implementation requires years to be expressed as a 4-digit number
+** which means that only dates between 0000-01-01 and 9999-12-31 can
+** be represented, even though julian day numbers allow a much wider
+** range of dates.
+**
+** The Gregorian calendar system is used for all dates and times,
+** even those that predate the Gregorian calendar.  Historians usually
+** use the julian calendar for dates prior to 1582-10-15 and for some
+** dates afterwards, depending on locale.  Beware of this difference.
+**
+** The conversion algorithms are implemented based on descriptions
+** in the following text:
+**
+**      Jean Meeus
+**      Astronomical Algorithms, 2nd Edition, 1998
+**      ISBN 0-943396-61-1
+**      Willmann-Bell, Inc
+**      Richmond, Virginia (USA)
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <assert.h>
+#include <time.h>
+
+#ifndef SQLITE_OMIT_DATETIME_FUNCS
+
+/*
+** The MSVC CRT on Windows CE may not have a localtime() function.
+** So declare a substitute.  The substitute function itself is
+** defined in "os_win.c".
+*/
+#if !defined(SQLITE_OMIT_LOCALTIME) && defined(_WIN32_WCE) && \
+    (!defined(SQLITE_MSVC_LOCALTIME_API) || !SQLITE_MSVC_LOCALTIME_API)
+struct tm *__cdecl localtime(const time_t *);
+#endif
+
+/*
+** A structure for holding a single date and time.
+*/
+typedef struct DateTime DateTime;
+struct DateTime {
+  sqlite3_int64 iJD;  /* The julian day number times 86400000 */
+  int Y, M, D;        /* Year, month, and day */
+  int h, m;           /* Hour and minutes */
+  int tz;             /* Timezone offset in minutes */
+  double s;           /* Seconds */
+  char validJD;       /* True (1) if iJD is valid */
+  char rawS;          /* Raw numeric value stored in s */
+  char validYMD;      /* True (1) if Y,M,D are valid */
+  char validHMS;      /* True (1) if h,m,s are valid */
+  char validTZ;       /* True (1) if tz is valid */
+  char tzSet;         /* Timezone was set explicitly */
+  char isError;       /* An overflow has occurred */
+  char useSubsec;     /* Display subsecond precision */
+};
+
+
+/*
+** Convert zDate into one or more integers according to the conversion
+** specifier zFormat.
+**
+** zFormat[] contains 4 characters for each integer converted, except for
+** the last integer which is specified by three characters.  The meaning
+** of a four-character format specifiers ABCD is:
+**
+**    A:   number of digits to convert.  Always "2" or "4".
+**    B:   minimum value.  Always "0" or "1".
+**    C:   maximum value, decoded as:
+**           a:  12
+**           b:  14
+**           c:  24
+**           d:  31
+**           e:  59
+**           f:  9999
+**    D:   the separator character, or \000 to indicate this is the
+**         last number to convert.
+**
+** Example:  To translate an ISO-8601 date YYYY-MM-DD, the format would
+** be "40f-21a-20c".  The "40f-" indicates the 4-digit year followed by "-".
+** The "21a-" indicates the 2-digit month followed by "-".  The "20c" indicates
+** the 2-digit day which is the last integer in the set.
+**
+** The function returns the number of successful conversions.
+*/
+static int getDigits(const char *zDate, const char *zFormat, ...){
+  /* The aMx[] array translates the 3rd character of each format
+  ** spec into a max size:    a   b   c   d   e      f */
+  static const u16 aMx[] = { 12, 14, 24, 31, 59, 14712 };
+  va_list ap;
+  int cnt = 0;
+  char nextC;
+  va_start(ap, zFormat);
+  do{
+    char N = zFormat[0] - '0';
+    char min = zFormat[1] - '0';
+    int val = 0;
+    u16 max;
+
+    assert( zFormat[2]>='a' && zFormat[2]<='f' );
+    max = aMx[zFormat[2] - 'a'];
+    nextC = zFormat[3];
+    val = 0;
+    while( N-- ){
+      if( !sqlite3Isdigit(*zDate) ){
+        goto end_getDigits;
+      }
+      val = val*10 + *zDate - '0';
+      zDate++;
+    }
+    if( val<(int)min || val>(int)max || (nextC!=0 && nextC!=*zDate) ){
+      goto end_getDigits;
+    }
+    *va_arg(ap,int*) = val;
+    zDate++;
+    cnt++;
+    zFormat += 4;
+  }while( nextC );
+end_getDigits:
+  va_end(ap);
+  return cnt;
+}
+
+/*
+** Parse a timezone extension on the end of a date-time.
+** The extension is of the form:
+**
+**        (+/-)HH:MM
+**
+** Or the "zulu" notation:
+**
+**        Z
+**
+** If the parse is successful, write the number of minutes
+** of change in p->tz and return 0.  If a parser error occurs,
+** return non-zero.
+**
+** A missing specifier is not considered an error.
+*/
+static int parseTimezone(const char *zDate, DateTime *p){
+  int sgn = 0;
+  int nHr, nMn;
+  int c;
+  while( sqlite3Isspace(*zDate) ){ zDate++; }
+  p->tz = 0;
+  c = *zDate;
+  if( c=='-' ){
+    sgn = -1;
+  }else if( c=='+' ){
+    sgn = +1;
+  }else if( c=='Z' || c=='z' ){
+    zDate++;
+    goto zulu_time;
+  }else{
+    return c!=0;
+  }
+  zDate++;
+  if( getDigits(zDate, "20b:20e", &nHr, &nMn)!=2 ){
+    return 1;
+  }
+  zDate += 5;
+  p->tz = sgn*(nMn + nHr*60);
+zulu_time:
+  while( sqlite3Isspace(*zDate) ){ zDate++; }
+  p->tzSet = 1;
+  return *zDate!=0;
+}
+
+/*
+** Parse times of the form HH:MM or HH:MM:SS or HH:MM:SS.FFFF.
+** The HH, MM, and SS must each be exactly 2 digits.  The
+** fractional seconds FFFF can be one or more digits.
+**
+** Return 1 if there is a parsing error and 0 on success.
+*/
+static int parseHhMmSs(const char *zDate, DateTime *p){
+  int h, m, s;
+  double ms = 0.0;
+  if( getDigits(zDate, "20c:20e", &h, &m)!=2 ){
+    return 1;
+  }
+  zDate += 5;
+  if( *zDate==':' ){
+    zDate++;
+    if( getDigits(zDate, "20e", &s)!=1 ){
+      return 1;
+    }
+    zDate += 2;
+    if( *zDate=='.' && sqlite3Isdigit(zDate[1]) ){
+      double rScale = 1.0;
+      zDate++;
+      while( sqlite3Isdigit(*zDate) ){
+        ms = ms*10.0 + *zDate - '0';
+        rScale *= 10.0;
+        zDate++;
+      }
+      ms /= rScale;
+    }
+  }else{
+    s = 0;
+  }
+  p->validJD = 0;
+  p->rawS = 0;
+  p->validHMS = 1;
+  p->h = h;
+  p->m = m;
+  p->s = s + ms;
+  if( parseTimezone(zDate, p) ) return 1;
+  p->validTZ = (p->tz!=0)?1:0;
+  return 0;
+}
+
+/*
+** Put the DateTime object into its error state.
+*/
+static void datetimeError(DateTime *p){
+  memset(p, 0, sizeof(*p));
+  p->isError = 1;
+}
+
+/*
+** Convert from YYYY-MM-DD HH:MM:SS to julian day.  We always assume
+** that the YYYY-MM-DD is according to the Gregorian calendar.
+**
+** Reference:  Meeus page 61
+*/
+static void computeJD(DateTime *p){
+  int Y, M, D, A, B, X1, X2;
+
+  if( p->validJD ) return;
+  if( p->validYMD ){
+    Y = p->Y;
+    M = p->M;
+    D = p->D;
+  }else{
+    Y = 2000;  /* If no YMD specified, assume 2000-Jan-01 */
+    M = 1;
+    D = 1;
+  }
+  if( Y<-4713 || Y>9999 || p->rawS ){
+    datetimeError(p);
+    return;
+  }
+  if( M<=2 ){
+    Y--;
+    M += 12;
+  }
+  A = Y/100;
+  B = 2 - A + (A/4);
+  X1 = 36525*(Y+4716)/100;
+  X2 = 306001*(M+1)/10000;
+  p->iJD = (sqlite3_int64)((X1 + X2 + D + B - 1524.5 ) * 86400000);
+  p->validJD = 1;
+  if( p->validHMS ){
+    p->iJD += p->h*3600000 + p->m*60000 + (sqlite3_int64)(p->s*1000 + 0.5);
+    if( p->validTZ ){
+      p->iJD -= p->tz*60000;
+      p->validYMD = 0;
+      p->validHMS = 0;
+      p->validTZ = 0;
+    }
+  }
+}
+
+/*
+** Parse dates of the form
+**
+**     YYYY-MM-DD HH:MM:SS.FFF
+**     YYYY-MM-DD HH:MM:SS
+**     YYYY-MM-DD HH:MM
+**     YYYY-MM-DD
+**
+** Write the result into the DateTime structure and return 0
+** on success and 1 if the input string is not a well-formed
+** date.
+*/
+static int parseYyyyMmDd(const char *zDate, DateTime *p){
+  int Y, M, D, neg;
+
+  if( zDate[0]=='-' ){
+    zDate++;
+    neg = 1;
+  }else{
+    neg = 0;
+  }
+  if( getDigits(zDate, "40f-21a-21d", &Y, &M, &D)!=3 ){
+    return 1;
+  }
+  zDate += 10;
+  while( sqlite3Isspace(*zDate) || 'T'==*(u8*)zDate ){ zDate++; }
+  if( parseHhMmSs(zDate, p)==0 ){
+    /* We got the time */
+  }else if( *zDate==0 ){
+    p->validHMS = 0;
+  }else{
+    return 1;
+  }
+  p->validJD = 0;
+  p->validYMD = 1;
+  p->Y = neg ? -Y : Y;
+  p->M = M;
+  p->D = D;
+  if( p->validTZ ){
+    computeJD(p);
+  }
+  return 0;
+}
+
+/*
+** Set the time to the current time reported by the VFS.
+**
+** Return the number of errors.
+*/
+static int setDateTimeToCurrent(sqlite3_context *context, DateTime *p){
+  p->iJD = sqlite3StmtCurrentTime(context);
+  if( p->iJD>0 ){
+    p->validJD = 1;
+    return 0;
+  }else{
+    return 1;
+  }
+}
+
+/*
+** Input "r" is a numeric quantity which might be a julian day number,
+** or the number of seconds since 1970.  If the value if r is within
+** range of a julian day number, install it as such and set validJD.
+** If the value is a valid unix timestamp, put it in p->s and set p->rawS.
+*/
+static void setRawDateNumber(DateTime *p, double r){
+  p->s = r;
+  p->rawS = 1;
+  if( r>=0.0 && r<5373484.5 ){
+    p->iJD = (sqlite3_int64)(r*86400000.0 + 0.5);
+    p->validJD = 1;
+  }
+}
+
+/*
+** Attempt to parse the given string into a julian day number.  Return
+** the number of errors.
+**
+** The following are acceptable forms for the input string:
+**
+**      YYYY-MM-DD HH:MM:SS.FFF  +/-HH:MM
+**      DDDD.DD 
+**      now
+**
+** In the first form, the +/-HH:MM is always optional.  The fractional
+** seconds extension (the ".FFF") is optional.  The seconds portion
+** (":SS.FFF") is option.  The year and date can be omitted as long
+** as there is a time string.  The time string can be omitted as long
+** as there is a year and date.
+*/
+static int parseDateOrTime(
+  sqlite3_context *context, 
+  const char *zDate, 
+  DateTime *p
+){
+  double r;
+  if( parseYyyyMmDd(zDate,p)==0 ){
+    return 0;
+  }else if( parseHhMmSs(zDate, p)==0 ){
+    return 0;
+  }else if( sqlite3StrICmp(zDate,"now")==0 && sqlite3NotPureFunc(context) ){
+    return setDateTimeToCurrent(context, p);
+  }else if( sqlite3AtoF(zDate, &r, sqlite3Strlen30(zDate), SQLITE_UTF8)>0 ){
+    setRawDateNumber(p, r);
+    return 0;
+  }else if( (sqlite3StrICmp(zDate,"subsec")==0
+             || sqlite3StrICmp(zDate,"subsecond")==0)
+           && sqlite3NotPureFunc(context) ){
+    p->useSubsec = 1;
+    return setDateTimeToCurrent(context, p);
+  }
+  return 1;
+}
+
+/* The julian day number for 9999-12-31 23:59:59.999 is 5373484.4999999.
+** Multiplying this by 86400000 gives 464269060799999 as the maximum value
+** for DateTime.iJD.
+**
+** But some older compilers (ex: gcc 4.2.1 on older Macs) cannot deal with 
+** such a large integer literal, so we have to encode it.
+*/
+#define INT_464269060799999  ((((i64)0x1a640)<<32)|0x1072fdff)
+
+/*
+** Return TRUE if the given julian day number is within range.
+**
+** The input is the JulianDay times 86400000.
+*/
+static int validJulianDay(sqlite3_int64 iJD){
+  return iJD>=0 && iJD<=INT_464269060799999;
+}
+
+/*
+** Compute the Year, Month, and Day from the julian day number.
+*/
+static void computeYMD(DateTime *p){
+  int Z, A, B, C, D, E, X1;
+  if( p->validYMD ) return;
+  if( !p->validJD ){
+    p->Y = 2000;
+    p->M = 1;
+    p->D = 1;
+  }else if( !validJulianDay(p->iJD) ){
+    datetimeError(p);
+    return;
+  }else{
+    Z = (int)((p->iJD + 43200000)/86400000);
+    A = (int)((Z - 1867216.25)/36524.25);
+    A = Z + 1 + A - (A/4);
+    B = A + 1524;
+    C = (int)((B - 122.1)/365.25);
+    D = (36525*(C&32767))/100;
+    E = (int)((B-D)/30.6001);
+    X1 = (int)(30.6001*E);
+    p->D = B - D - X1;
+    p->M = E<14 ? E-1 : E-13;
+    p->Y = p->M>2 ? C - 4716 : C - 4715;
+  }
+  p->validYMD = 1;
+}
+
+/*
+** Compute the Hour, Minute, and Seconds from the julian day number.
+*/
+static void computeHMS(DateTime *p){
+  int day_ms, day_min; /* milliseconds, minutes into the day */
+  if( p->validHMS ) return;
+  computeJD(p);
+  day_ms = (int)((p->iJD + 43200000) % 86400000);
+  p->s = (day_ms % 60000)/1000.0;
+  day_min = day_ms/60000;
+  p->m = day_min % 60;
+  p->h = day_min / 60;
+  p->rawS = 0;
+  p->validHMS = 1;
+}
+
+/*
+** Compute both YMD and HMS
+*/
+static void computeYMD_HMS(DateTime *p){
+  computeYMD(p);
+  computeHMS(p);
+}
+
+/*
+** Clear the YMD and HMS and the TZ
+*/
+static void clearYMD_HMS_TZ(DateTime *p){
+  p->validYMD = 0;
+  p->validHMS = 0;
+  p->validTZ = 0;
+}
+
+#ifndef SQLITE_OMIT_LOCALTIME
+/*
+** On recent Windows platforms, the localtime_s() function is available
+** as part of the "Secure CRT". It is essentially equivalent to 
+** localtime_r() available under most POSIX platforms, except that the 
+** order of the parameters is reversed.
+**
+** See http://msdn.microsoft.com/en-us/library/a442x3ye(VS.80).aspx.
+**
+** If the user has not indicated to use localtime_r() or localtime_s()
+** already, check for an MSVC build environment that provides 
+** localtime_s().
+*/
+#if !HAVE_LOCALTIME_R && !HAVE_LOCALTIME_S \
+    && defined(_MSC_VER) && defined(_CRT_INSECURE_DEPRECATE)
+#undef  HAVE_LOCALTIME_S
+#define HAVE_LOCALTIME_S 1
+#endif
+
+/*
+** The following routine implements the rough equivalent of localtime_r()
+** using whatever operating-system specific localtime facility that
+** is available.  This routine returns 0 on success and
+** non-zero on any kind of error.
+**
+** If the sqlite3GlobalConfig.bLocaltimeFault variable is non-zero then this
+** routine will always fail.  If bLocaltimeFault is nonzero and
+** sqlite3GlobalConfig.xAltLocaltime is not NULL, then xAltLocaltime() is
+** invoked in place of the OS-defined localtime() function.
+**
+** EVIDENCE-OF: R-62172-00036 In this implementation, the standard C
+** library function localtime_r() is used to assist in the calculation of
+** local time.
+*/
+static int osLocaltime(time_t *t, struct tm *pTm){
+  int rc;
+#if !HAVE_LOCALTIME_R && !HAVE_LOCALTIME_S
+  struct tm *pX;
+#if SQLITE_THREADSAFE>0
+  sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
+#endif
+  sqlite3_mutex_enter(mutex);
+  pX = localtime(t);
+#ifndef SQLITE_UNTESTABLE
+  if( sqlite3GlobalConfig.bLocaltimeFault ){
+    if( sqlite3GlobalConfig.xAltLocaltime!=0
+     && 0==sqlite3GlobalConfig.xAltLocaltime((const void*)t,(void*)pTm)
+    ){
+      pX = pTm;
+    }else{
+      pX = 0;
+    }
+  }
+#endif
+  if( pX ) *pTm = *pX;
+#if SQLITE_THREADSAFE>0
+  sqlite3_mutex_leave(mutex);
+#endif
+  rc = pX==0;
+#else
+#ifndef SQLITE_UNTESTABLE
+  if( sqlite3GlobalConfig.bLocaltimeFault ){
+    if( sqlite3GlobalConfig.xAltLocaltime!=0 ){
+      return sqlite3GlobalConfig.xAltLocaltime((const void*)t,(void*)pTm);
+    }else{
+      return 1;
+    }
+  }
+#endif
+#if HAVE_LOCALTIME_R
+  rc = localtime_r(t, pTm)==0;
+#else
+  rc = localtime_s(pTm, t);
+#endif /* HAVE_LOCALTIME_R */
+#endif /* HAVE_LOCALTIME_R || HAVE_LOCALTIME_S */
+  return rc;
+}
+#endif /* SQLITE_OMIT_LOCALTIME */
+
+
+#ifndef SQLITE_OMIT_LOCALTIME
+/*
+** Assuming the input DateTime is UTC, move it to its localtime equivalent.
+*/
+static int toLocaltime(
+  DateTime *p,                   /* Date at which to calculate offset */
+  sqlite3_context *pCtx          /* Write error here if one occurs */
+){
+  time_t t;
+  struct tm sLocal;
+  int iYearDiff;
+
+  /* Initialize the contents of sLocal to avoid a compiler warning. */
+  memset(&sLocal, 0, sizeof(sLocal));
+
+  computeJD(p);
+  if( p->iJD<2108667600*(i64)100000 /* 1970-01-01 */
+   || p->iJD>2130141456*(i64)100000 /* 2038-01-18 */
+  ){
+    /* EVIDENCE-OF: R-55269-29598 The localtime_r() C function normally only
+    ** works for years between 1970 and 2037. For dates outside this range,
+    ** SQLite attempts to map the year into an equivalent year within this
+    ** range, do the calculation, then map the year back.
+    */
+    DateTime x = *p;
+    computeYMD_HMS(&x);
+    iYearDiff = (2000 + x.Y%4) - x.Y;
+    x.Y += iYearDiff;
+    x.validJD = 0;
+    computeJD(&x);
+    t = (time_t)(x.iJD/1000 -  21086676*(i64)10000);
+  }else{
+    iYearDiff = 0;
+    t = (time_t)(p->iJD/1000 -  21086676*(i64)10000);
+  }
+  if( osLocaltime(&t, &sLocal) ){
+    sqlite3_result_error(pCtx, "local time unavailable", -1);
+    return SQLITE_ERROR;
+  }
+  p->Y = sLocal.tm_year + 1900 - iYearDiff;
+  p->M = sLocal.tm_mon + 1;
+  p->D = sLocal.tm_mday;
+  p->h = sLocal.tm_hour;
+  p->m = sLocal.tm_min;
+  p->s = sLocal.tm_sec + (p->iJD%1000)*0.001;
+  p->validYMD = 1;
+  p->validHMS = 1;
+  p->validJD = 0;
+  p->rawS = 0;
+  p->validTZ = 0;
+  p->isError = 0;
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_LOCALTIME */
+
+/*
+** The following table defines various date transformations of the form
+**
+**            'NNN days'
+**
+** Where NNN is an arbitrary floating-point number and "days" can be one
+** of several units of time.
+*/
+static const struct {
+  u8 nName;           /* Length of the name */
+  char zName[7];      /* Name of the transformation */
+  float rLimit;       /* Maximum NNN value for this transform */
+  float rXform;       /* Constant used for this transform */
+} aXformType[] = {
+  { 6, "second", 4.6427e+14,       1.0  },
+  { 6, "minute", 7.7379e+12,      60.0  },
+  { 4, "hour",   1.2897e+11,    3600.0  },
+  { 3, "day",    5373485.0,    86400.0  },
+  { 5, "month",  176546.0,   2592000.0  },
+  { 4, "year",   14713.0,   31536000.0  },
+};
+
+/*
+** If the DateTime p is raw number, try to figure out if it is
+** a julian day number of a unix timestamp.  Set the p value
+** appropriately.
+*/
+static void autoAdjustDate(DateTime *p){
+  if( !p->rawS || p->validJD ){
+    p->rawS = 0;
+  }else if( p->s>=-21086676*(i64)10000        /* -4713-11-24 12:00:00 */
+         && p->s<=(25340230*(i64)10000)+799   /*  9999-12-31 23:59:59 */
+  ){
+    double r = p->s*1000.0 + 210866760000000.0;
+    clearYMD_HMS_TZ(p);
+    p->iJD = (sqlite3_int64)(r + 0.5);
+    p->validJD = 1;
+    p->rawS = 0;
+  }
+}
+
+/*
+** Process a modifier to a date-time stamp.  The modifiers are
+** as follows:
+**
+**     NNN days
+**     NNN hours
+**     NNN minutes
+**     NNN.NNNN seconds
+**     NNN months
+**     NNN years
+**     start of month
+**     start of year
+**     start of week
+**     start of day
+**     weekday N
+**     unixepoch
+**     localtime
+**     utc
+**
+** Return 0 on success and 1 if there is any kind of error. If the error
+** is in a system call (i.e. localtime()), then an error message is written
+** to context pCtx. If the error is an unrecognized modifier, no error is
+** written to pCtx.
+*/
+static int parseModifier(
+  sqlite3_context *pCtx,      /* Function context */
+  const char *z,              /* The text of the modifier */
+  int n,                      /* Length of zMod in bytes */
+  DateTime *p,                /* The date/time value to be modified */
+  int idx                     /* Parameter index of the modifier */
+){
+  int rc = 1;
+  double r;
+  switch(sqlite3UpperToLower[(u8)z[0]] ){
+    case 'a': {
+      /*
+      **    auto
+      **
+      ** If rawS is available, then interpret as a julian day number, or
+      ** a unix timestamp, depending on its magnitude.
+      */
+      if( sqlite3_stricmp(z, "auto")==0 ){
+        if( idx>1 ) return 1; /* IMP: R-33611-57934 */
+        autoAdjustDate(p);
+        rc = 0;
+      }
+      break;
+    }
+    case 'j': {
+      /*
+      **    julianday
+      **
+      ** Always interpret the prior number as a julian-day value.  If this
+      ** is not the first modifier, or if the prior argument is not a numeric
+      ** value in the allowed range of julian day numbers understood by
+      ** SQLite (0..5373484.5) then the result will be NULL.
+      */
+      if( sqlite3_stricmp(z, "julianday")==0 ){
+        if( idx>1 ) return 1;  /* IMP: R-31176-64601 */
+        if( p->validJD && p->rawS ){
+          rc = 0;
+          p->rawS = 0;
+        }
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_LOCALTIME
+    case 'l': {
+      /*    localtime
+      **
+      ** Assuming the current time value is UTC (a.k.a. GMT), shift it to
+      ** show local time.
+      */
+      if( sqlite3_stricmp(z, "localtime")==0 && sqlite3NotPureFunc(pCtx) ){
+        rc = toLocaltime(p, pCtx);
+      }
+      break;
+    }
+#endif
+    case 'u': {
+      /*
+      **    unixepoch
+      **
+      ** Treat the current value of p->s as the number of
+      ** seconds since 1970.  Convert to a real julian day number.
+      */
+      if( sqlite3_stricmp(z, "unixepoch")==0 && p->rawS ){
+        if( idx>1 ) return 1;  /* IMP: R-49255-55373 */
+        r = p->s*1000.0 + 210866760000000.0;
+        if( r>=0.0 && r<464269060800000.0 ){
+          clearYMD_HMS_TZ(p);
+          p->iJD = (sqlite3_int64)(r + 0.5);
+          p->validJD = 1;
+          p->rawS = 0;
+          rc = 0;
+        }
+      }
+#ifndef SQLITE_OMIT_LOCALTIME
+      else if( sqlite3_stricmp(z, "utc")==0 && sqlite3NotPureFunc(pCtx) ){
+        if( p->tzSet==0 ){
+          i64 iOrigJD;              /* Original localtime */
+          i64 iGuess;               /* Guess at the corresponding utc time */
+          int cnt = 0;              /* Safety to prevent infinite loop */
+          i64 iErr;                 /* Guess is off by this much */
+
+          computeJD(p);
+          iGuess = iOrigJD = p->iJD;
+          iErr = 0;
+          do{
+            DateTime new;
+            memset(&new, 0, sizeof(new));
+            iGuess -= iErr;
+            new.iJD = iGuess;
+            new.validJD = 1;
+            rc = toLocaltime(&new, pCtx);
+            if( rc ) return rc;
+            computeJD(&new);
+            iErr = new.iJD - iOrigJD;
+          }while( iErr && cnt++<3 );
+          memset(p, 0, sizeof(*p));
+          p->iJD = iGuess;
+          p->validJD = 1;
+          p->tzSet = 1;
+        }
+        rc = SQLITE_OK;
+      }
+#endif
+      break;
+    }
+    case 'w': {
+      /*
+      **    weekday N
+      **
+      ** Move the date to the same time on the next occurrence of
+      ** weekday N where 0==Sunday, 1==Monday, and so forth.  If the
+      ** date is already on the appropriate weekday, this is a no-op.
+      */
+      if( sqlite3_strnicmp(z, "weekday ", 8)==0
+               && sqlite3AtoF(&z[8], &r, sqlite3Strlen30(&z[8]), SQLITE_UTF8)>0
+               && r>=0.0 && r<7.0 && (n=(int)r)==r ){
+        sqlite3_int64 Z;
+        computeYMD_HMS(p);
+        p->validTZ = 0;
+        p->validJD = 0;
+        computeJD(p);
+        Z = ((p->iJD + 129600000)/86400000) % 7;
+        if( Z>n ) Z -= 7;
+        p->iJD += (n - Z)*86400000;
+        clearYMD_HMS_TZ(p);
+        rc = 0;
+      }
+      break;
+    }
+    case 's': {
+      /*
+      **    start of TTTTT
+      **
+      ** Move the date backwards to the beginning of the current day,
+      ** or month or year.
+      **
+      **    subsecond
+      **    subsec
+      **
+      ** Show subsecond precision in the output of datetime() and
+      ** unixepoch() and strftime('%s').
+      */
+      if( sqlite3_strnicmp(z, "start of ", 9)!=0 ){
+        if( sqlite3_stricmp(z, "subsec")==0
+         || sqlite3_stricmp(z, "subsecond")==0
+        ){
+          p->useSubsec = 1;
+          rc = 0;
+        }
+        break;
+      }        
+      if( !p->validJD && !p->validYMD && !p->validHMS ) break;
+      z += 9;
+      computeYMD(p);
+      p->validHMS = 1;
+      p->h = p->m = 0;
+      p->s = 0.0;
+      p->rawS = 0;
+      p->validTZ = 0;
+      p->validJD = 0;
+      if( sqlite3_stricmp(z,"month")==0 ){
+        p->D = 1;
+        rc = 0;
+      }else if( sqlite3_stricmp(z,"year")==0 ){
+        p->M = 1;
+        p->D = 1;
+        rc = 0;
+      }else if( sqlite3_stricmp(z,"day")==0 ){
+        rc = 0;
+      }
+      break;
+    }
+    case '+':
+    case '-':
+    case '0':
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9': {
+      double rRounder;
+      int i;
+      int Y,M,D,h,m,x;
+      const char *z2 = z;
+      char z0 = z[0];
+      for(n=1; z[n]; n++){
+        if( z[n]==':' ) break;
+        if( sqlite3Isspace(z[n]) ) break;
+        if( z[n]=='-' ){
+          if( n==5 && getDigits(&z[1], "40f", &Y)==1 ) break;
+          if( n==6 && getDigits(&z[1], "50f", &Y)==1 ) break;
+        }
+      }
+      if( sqlite3AtoF(z, &r, n, SQLITE_UTF8)<=0 ){
+        assert( rc==1 );
+        break;
+      }
+      if( z[n]=='-' ){
+        /* A modifier of the form (+|-)YYYY-MM-DD adds or subtracts the
+        ** specified number of years, months, and days.  MM is limited to
+        ** the range 0-11 and DD is limited to 0-30.
+        */
+        if( z0!='+' && z0!='-' ) break;  /* Must start with +/- */
+        if( n==5 ){
+          if( getDigits(&z[1], "40f-20a-20d", &Y, &M, &D)!=3 ) break;
+        }else{
+          assert( n==6 );
+          if( getDigits(&z[1], "50f-20a-20d", &Y, &M, &D)!=3 ) break;
+          z++;
+        }
+        if( M>=12 ) break;                   /* M range 0..11 */
+        if( D>=31 ) break;                   /* D range 0..30 */
+        computeYMD_HMS(p);
+        p->validJD = 0;
+        if( z0=='-' ){
+          p->Y -= Y;
+          p->M -= M;
+          D = -D;
+        }else{
+          p->Y += Y;
+          p->M += M;
+        }
+        x = p->M>0 ? (p->M-1)/12 : (p->M-12)/12;
+        p->Y += x;
+        p->M -= x*12;
+        computeJD(p);
+        p->validHMS = 0;
+        p->validYMD = 0;
+        p->iJD += (i64)D*86400000;
+        if( z[11]==0 ){
+          rc = 0;
+          break;
+        }
+        if( sqlite3Isspace(z[11])
+         && getDigits(&z[12], "20c:20e", &h, &m)==2
+        ){
+          z2 = &z[12];
+          n = 2;
+        }else{
+          break;
+        }
+      }
+      if( z2[n]==':' ){
+        /* A modifier of the form (+|-)HH:MM:SS.FFF adds (or subtracts) the
+        ** specified number of hours, minutes, seconds, and fractional seconds
+        ** to the time.  The ".FFF" may be omitted.  The ":SS.FFF" may be
+        ** omitted.
+        */
+
+        DateTime tx;
+        sqlite3_int64 day;
+        if( !sqlite3Isdigit(*z2) ) z2++;
+        memset(&tx, 0, sizeof(tx));
+        if( parseHhMmSs(z2, &tx) ) break;
+        computeJD(&tx);
+        tx.iJD -= 43200000;
+        day = tx.iJD/86400000;
+        tx.iJD -= day*86400000;
+        if( z0=='-' ) tx.iJD = -tx.iJD;
+        computeJD(p);
+        clearYMD_HMS_TZ(p);
+        p->iJD += tx.iJD;
+        rc = 0;
+        break;
+      }
+
+      /* If control reaches this point, it means the transformation is
+      ** one of the forms like "+NNN days".  */
+      z += n;
+      while( sqlite3Isspace(*z) ) z++;
+      n = sqlite3Strlen30(z);
+      if( n>10 || n<3 ) break;
+      if( sqlite3UpperToLower[(u8)z[n-1]]=='s' ) n--;
+      computeJD(p);
+      assert( rc==1 );
+      rRounder = r<0 ? -0.5 : +0.5;
+      for(i=0; i<ArraySize(aXformType); i++){
+        if( aXformType[i].nName==n
+         && sqlite3_strnicmp(aXformType[i].zName, z, n)==0
+         && r>-aXformType[i].rLimit && r<aXformType[i].rLimit
+        ){
+          switch( i ){
+            case 4: { /* Special processing to add months */
+              assert( strcmp(aXformType[i].zName,"month")==0 );
+              computeYMD_HMS(p);
+              p->M += (int)r;
+              x = p->M>0 ? (p->M-1)/12 : (p->M-12)/12;
+              p->Y += x;
+              p->M -= x*12;
+              p->validJD = 0;
+              r -= (int)r;
+              break;
+            }
+            case 5: { /* Special processing to add years */
+              int y = (int)r;
+              assert( strcmp(aXformType[i].zName,"year")==0 );
+              computeYMD_HMS(p);
+              p->Y += y;
+              p->validJD = 0;
+              r -= (int)r;
+              break;
+            }
+          }
+          computeJD(p);
+          p->iJD += (sqlite3_int64)(r*1000.0*aXformType[i].rXform + rRounder);
+          rc = 0;
+          break;
+        }
+      }
+      clearYMD_HMS_TZ(p);
+      break;
+    }
+    default: {
+      break;
+    }
+  }
+  return rc;
+}
+
+/*
+** Process time function arguments.  argv[0] is a date-time stamp.
+** argv[1] and following are modifiers.  Parse them all and write
+** the resulting time into the DateTime structure p.  Return 0
+** on success and 1 if there are any errors.
+**
+** If there are zero parameters (if even argv[0] is undefined)
+** then assume a default value of "now" for argv[0].
+*/
+static int isDate(
+  sqlite3_context *context, 
+  int argc, 
+  sqlite3_value **argv, 
+  DateTime *p
+){
+  int i, n;
+  const unsigned char *z;
+  int eType;
+  memset(p, 0, sizeof(*p));
+  if( argc==0 ){
+    if( !sqlite3NotPureFunc(context) ) return 1;
+    return setDateTimeToCurrent(context, p);
+  }
+  if( (eType = sqlite3_value_type(argv[0]))==SQLITE_FLOAT
+                   || eType==SQLITE_INTEGER ){
+    setRawDateNumber(p, sqlite3_value_double(argv[0]));
+  }else{
+    z = sqlite3_value_text(argv[0]);
+    if( !z || parseDateOrTime(context, (char*)z, p) ){
+      return 1;
+    }
+  }
+  for(i=1; i<argc; i++){
+    z = sqlite3_value_text(argv[i]);
+    n = sqlite3_value_bytes(argv[i]);
+    if( z==0 || parseModifier(context, (char*)z, n, p, i) ) return 1;
+  }
+  computeJD(p);
+  if( p->isError || !validJulianDay(p->iJD) ) return 1;
+  if( argc==1 && p->validYMD && p->D>28 ){
+    /* Make sure a YYYY-MM-DD is normalized.
+    ** Example: 2023-02-31 -> 2023-03-03 */
+    assert( p->validJD );
+    p->validYMD = 0;  
+  }
+  return 0;
+}
+
+
+/*
+** The following routines implement the various date and time functions
+** of SQLite.
+*/
+
+/*
+**    julianday( TIMESTRING, MOD, MOD, ...)
+**
+** Return the julian day number of the date specified in the arguments
+*/
+static void juliandayFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    computeJD(&x);
+    sqlite3_result_double(context, x.iJD/86400000.0);
+  }
+}
+
+/*
+**    unixepoch( TIMESTRING, MOD, MOD, ...)
+**
+** Return the number of seconds (including fractional seconds) since
+** the unix epoch of 1970-01-01 00:00:00 GMT.
+*/
+static void unixepochFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    computeJD(&x);
+    if( x.useSubsec ){
+      sqlite3_result_double(context, (x.iJD - 21086676*(i64)10000000)/1000.0);
+    }else{
+      sqlite3_result_int64(context, x.iJD/1000 - 21086676*(i64)10000);
+    }
+  }
+}
+
+/*
+**    datetime( TIMESTRING, MOD, MOD, ...)
+**
+** Return YYYY-MM-DD HH:MM:SS
+*/
+static void datetimeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    int Y, s, n;
+    char zBuf[32];
+    computeYMD_HMS(&x);
+    Y = x.Y;
+    if( Y<0 ) Y = -Y;
+    zBuf[1] = '0' + (Y/1000)%10;
+    zBuf[2] = '0' + (Y/100)%10;
+    zBuf[3] = '0' + (Y/10)%10;
+    zBuf[4] = '0' + (Y)%10;
+    zBuf[5] = '-';
+    zBuf[6] = '0' + (x.M/10)%10;
+    zBuf[7] = '0' + (x.M)%10;
+    zBuf[8] = '-';
+    zBuf[9] = '0' + (x.D/10)%10;
+    zBuf[10] = '0' + (x.D)%10;
+    zBuf[11] = ' ';
+    zBuf[12] = '0' + (x.h/10)%10;
+    zBuf[13] = '0' + (x.h)%10;
+    zBuf[14] = ':';
+    zBuf[15] = '0' + (x.m/10)%10;
+    zBuf[16] = '0' + (x.m)%10;
+    zBuf[17] = ':';
+    if( x.useSubsec ){
+      s = (int)(1000.0*x.s + 0.5);
+      zBuf[18] = '0' + (s/10000)%10;
+      zBuf[19] = '0' + (s/1000)%10;
+      zBuf[20] = '.';
+      zBuf[21] = '0' + (s/100)%10;
+      zBuf[22] = '0' + (s/10)%10;
+      zBuf[23] = '0' + (s)%10;
+      zBuf[24] = 0;
+      n = 24;
+    }else{
+      s = (int)x.s;
+      zBuf[18] = '0' + (s/10)%10;
+      zBuf[19] = '0' + (s)%10;
+      zBuf[20] = 0;
+      n = 20;
+    }
+    if( x.Y<0 ){
+      zBuf[0] = '-';
+      sqlite3_result_text(context, zBuf, n, SQLITE_TRANSIENT);
+    }else{
+      sqlite3_result_text(context, &zBuf[1], n-1, SQLITE_TRANSIENT);
+    }
+  }
+}
+
+/*
+**    time( TIMESTRING, MOD, MOD, ...)
+**
+** Return HH:MM:SS
+*/
+static void timeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    int s, n;
+    char zBuf[16];
+    computeHMS(&x);
+    zBuf[0] = '0' + (x.h/10)%10;
+    zBuf[1] = '0' + (x.h)%10;
+    zBuf[2] = ':';
+    zBuf[3] = '0' + (x.m/10)%10;
+    zBuf[4] = '0' + (x.m)%10;
+    zBuf[5] = ':';
+    if( x.useSubsec ){
+      s = (int)(1000.0*x.s + 0.5);
+      zBuf[6] = '0' + (s/10000)%10;
+      zBuf[7] = '0' + (s/1000)%10;
+      zBuf[8] = '.';
+      zBuf[9] = '0' + (s/100)%10;
+      zBuf[10] = '0' + (s/10)%10;
+      zBuf[11] = '0' + (s)%10;
+      zBuf[12] = 0;
+      n = 12;
+    }else{
+      s = (int)x.s;
+      zBuf[6] = '0' + (s/10)%10;
+      zBuf[7] = '0' + (s)%10;
+      zBuf[8] = 0;
+      n = 8;
+    }
+    sqlite3_result_text(context, zBuf, n, SQLITE_TRANSIENT);
+  }
+}
+
+/*
+**    date( TIMESTRING, MOD, MOD, ...)
+**
+** Return YYYY-MM-DD
+*/
+static void dateFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    int Y;
+    char zBuf[16];
+    computeYMD(&x);
+    Y = x.Y;
+    if( Y<0 ) Y = -Y;
+    zBuf[1] = '0' + (Y/1000)%10;
+    zBuf[2] = '0' + (Y/100)%10;
+    zBuf[3] = '0' + (Y/10)%10;
+    zBuf[4] = '0' + (Y)%10;
+    zBuf[5] = '-';
+    zBuf[6] = '0' + (x.M/10)%10;
+    zBuf[7] = '0' + (x.M)%10;
+    zBuf[8] = '-';
+    zBuf[9] = '0' + (x.D/10)%10;
+    zBuf[10] = '0' + (x.D)%10;
+    zBuf[11] = 0;
+    if( x.Y<0 ){
+      zBuf[0] = '-';
+      sqlite3_result_text(context, zBuf, 11, SQLITE_TRANSIENT);
+    }else{
+      sqlite3_result_text(context, &zBuf[1], 10, SQLITE_TRANSIENT);
+    }
+  }
+}
+
+/*
+**    strftime( FORMAT, TIMESTRING, MOD, MOD, ...)
+**
+** Return a string described by FORMAT.  Conversions as follows:
+**
+**   %d  day of month
+**   %f  ** fractional seconds  SS.SSS
+**   %H  hour 00-24
+**   %j  day of year 000-366
+**   %J  ** julian day number
+**   %m  month 01-12
+**   %M  minute 00-59
+**   %s  seconds since 1970-01-01
+**   %S  seconds 00-59
+**   %w  day of week 0-6  Sunday==0
+**   %W  week of year 00-53
+**   %Y  year 0000-9999
+**   %%  %
+*/
+static void strftimeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  size_t i,j;
+  sqlite3 *db;
+  const char *zFmt;
+  sqlite3_str sRes;
+
+
+  if( argc==0 ) return;
+  zFmt = (const char*)sqlite3_value_text(argv[0]);
+  if( zFmt==0 || isDate(context, argc-1, argv+1, &x) ) return;
+  db = sqlite3_context_db_handle(context);
+  sqlite3StrAccumInit(&sRes, 0, 0, 0, db->aLimit[SQLITE_LIMIT_LENGTH]);
+
+  computeJD(&x);
+  computeYMD_HMS(&x);
+  for(i=j=0; zFmt[i]; i++){
+    char cf;
+    if( zFmt[i]!='%' ) continue;
+    if( j<i ) sqlite3_str_append(&sRes, zFmt+j, (int)(i-j));
+    i++;
+    j = i + 1;
+    cf = zFmt[i];
+    switch( cf ){
+      case 'd':  /* Fall thru */
+      case 'e': {
+        sqlite3_str_appendf(&sRes, cf=='d' ? "%02d" : "%2d", x.D);
+        break;
+      }
+      case 'f': {
+        double s = x.s;
+        if( s>59.999 ) s = 59.999;
+        sqlite3_str_appendf(&sRes, "%06.3f", s);
+        break;
+      }
+      case 'F': {
+        sqlite3_str_appendf(&sRes, "%04d-%02d-%02d", x.Y, x.M, x.D);
+        break;
+      }
+      case 'H':
+      case 'k': {
+        sqlite3_str_appendf(&sRes, cf=='H' ? "%02d" : "%2d", x.h);
+        break;
+      }
+      case 'I': /* Fall thru */
+      case 'l': {
+        int h = x.h;
+        if( h>12 ) h -= 12;
+        if( h==0 ) h = 12;
+        sqlite3_str_appendf(&sRes, cf=='I' ? "%02d" : "%2d", h);
+        break;
+      }
+      case 'W': /* Fall thru */
+      case 'j': {
+        int nDay;             /* Number of days since 1st day of year */
+        DateTime y = x;
+        y.validJD = 0;
+        y.M = 1;
+        y.D = 1;
+        computeJD(&y);
+        nDay = (int)((x.iJD-y.iJD+43200000)/86400000);
+        if( cf=='W' ){
+          int wd;   /* 0=Monday, 1=Tuesday, ... 6=Sunday */
+          wd = (int)(((x.iJD+43200000)/86400000)%7);
+          sqlite3_str_appendf(&sRes,"%02d",(nDay+7-wd)/7);
+        }else{
+          sqlite3_str_appendf(&sRes,"%03d",nDay+1);
+        }
+        break;
+      }
+      case 'J': {
+        sqlite3_str_appendf(&sRes,"%.16g",x.iJD/86400000.0);
+        break;
+      }
+      case 'm': {
+        sqlite3_str_appendf(&sRes,"%02d",x.M);
+        break;
+      }
+      case 'M': {
+        sqlite3_str_appendf(&sRes,"%02d",x.m);
+        break;
+      }
+      case 'p': /* Fall thru */
+      case 'P': {
+        if( x.h>=12 ){
+          sqlite3_str_append(&sRes, cf=='p' ? "PM" : "pm", 2);
+        }else{
+          sqlite3_str_append(&sRes, cf=='p' ? "AM" : "am", 2);
+        }
+        break;
+      }
+      case 'R': {
+        sqlite3_str_appendf(&sRes, "%02d:%02d", x.h, x.m);
+        break;
+      }
+      case 's': {
+        if( x.useSubsec ){
+          sqlite3_str_appendf(&sRes,"%.3f",
+                (x.iJD - 21086676*(i64)10000000)/1000.0);
+        }else{
+          i64 iS = (i64)(x.iJD/1000 - 21086676*(i64)10000);
+          sqlite3_str_appendf(&sRes,"%lld",iS);
+        }
+        break;
+      }
+      case 'S': {
+        sqlite3_str_appendf(&sRes,"%02d",(int)x.s);
+        break;
+      }
+      case 'T': {
+        sqlite3_str_appendf(&sRes,"%02d:%02d:%02d", x.h, x.m, (int)x.s);
+        break;
+      }
+      case 'u': /* Fall thru */
+      case 'w': {
+        char c = (char)(((x.iJD+129600000)/86400000) % 7) + '0';
+        if( c=='0' && cf=='u' ) c = '7';
+        sqlite3_str_appendchar(&sRes, 1, c);
+        break;
+      }
+      case 'Y': {
+        sqlite3_str_appendf(&sRes,"%04d",x.Y);
+        break;
+      }
+      case '%': {
+        sqlite3_str_appendchar(&sRes, 1, '%');
+        break;
+      }
+      default: {
+        sqlite3_str_reset(&sRes);
+        return;
+      }
+    }
+  }
+  if( j<i ) sqlite3_str_append(&sRes, zFmt+j, (int)(i-j));
+  sqlite3ResultStrAccum(context, &sRes);
+}
+
+/*
+** current_time()
+**
+** This function returns the same value as time('now').
+*/
+static void ctimeFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  timeFunc(context, 0, 0);
+}
+
+/*
+** current_date()
+**
+** This function returns the same value as date('now').
+*/
+static void cdateFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  dateFunc(context, 0, 0);
+}
+
+/*
+** timediff(DATE1, DATE2)
+**
+** Return the amount of time that must be added to DATE2 in order to
+** convert it into DATE2.  The time difference format is:
+**
+**     +YYYY-MM-DD HH:MM:SS.SSS
+**
+** The initial "+" becomes "-" if DATE1 occurs before DATE2.  For
+** date/time values A and B, the following invariant should hold:
+**
+**     datetime(A) == (datetime(B, timediff(A,B))
+**
+** Both DATE arguments must be either a julian day number, or an
+** ISO-8601 string.  The unix timestamps are not supported by this
+** routine.
+*/
+static void timediffFunc(
+  sqlite3_context *context,
+  int NotUsed1,
+  sqlite3_value **argv
+){
+  char sign;
+  int Y, M;
+  DateTime d1, d2;
+  sqlite3_str sRes;
+  UNUSED_PARAMETER(NotUsed1);
+  if( isDate(context, 1, &argv[0], &d1) ) return;
+  if( isDate(context, 1, &argv[1], &d2) ) return;
+  computeYMD_HMS(&d1);
+  computeYMD_HMS(&d2);
+  if( d1.iJD>=d2.iJD ){
+    sign = '+';
+    Y = d1.Y - d2.Y;
+    if( Y ){
+      d2.Y = d1.Y;
+      d2.validJD = 0;
+      computeJD(&d2);
+    }
+    M = d1.M - d2.M;
+    if( M<0 ){
+      Y--;
+      M += 12;
+    }
+    if( M!=0 ){
+      d2.M = d1.M;
+      d2.validJD = 0;
+      computeJD(&d2);
+    }
+    while( d1.iJD<d2.iJD ){
+      M--;
+      if( M<0 ){
+        M = 11;
+        Y--;
+      }
+      d2.M--;
+      if( d2.M<1 ){
+        d2.M = 12;
+        d2.Y--;
+      }
+      d2.validJD = 0;
+      computeJD(&d2);
+    }
+    d1.iJD -= d2.iJD;
+    d1.iJD += (u64)1486995408 * (u64)100000;
+  }else /* d1<d2 */{
+    sign = '-';
+    Y = d2.Y - d1.Y;
+    if( Y ){
+      d2.Y = d1.Y;
+      d2.validJD = 0;
+      computeJD(&d2);
+    }
+    M = d2.M - d1.M;
+    if( M<0 ){
+      Y--;
+      M += 12;
+    }
+    if( M!=0 ){
+      d2.M = d1.M;
+      d2.validJD = 0;
+      computeJD(&d2);
+    }
+    while( d1.iJD>d2.iJD ){
+      M--;
+      if( M<0 ){
+        M = 11;
+        Y--;
+      }
+      d2.M++;
+      if( d2.M>12 ){
+        d2.M = 1;
+        d2.Y++;
+      }
+      d2.validJD = 0;
+      computeJD(&d2);
+    }
+    d1.iJD = d2.iJD - d1.iJD;
+    d1.iJD += (u64)1486995408 * (u64)100000;
+  }
+  d1.validYMD = 0;
+  d1.validHMS = 0;
+  d1.validTZ = 0;
+  computeYMD_HMS(&d1);
+  sqlite3StrAccumInit(&sRes, 0, 0, 0, 100);
+  sqlite3_str_appendf(&sRes, "%c%04d-%02d-%02d %02d:%02d:%06.3f",
+       sign, Y, M, d1.D-1, d1.h, d1.m, d1.s);
+  sqlite3ResultStrAccum(context, &sRes);
+}
+
+
+/*
+** current_timestamp()
+**
+** This function returns the same value as datetime('now').
+*/
+static void ctimestampFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  datetimeFunc(context, 0, 0);
+}
+#endif /* !defined(SQLITE_OMIT_DATETIME_FUNCS) */
+
+#ifdef SQLITE_OMIT_DATETIME_FUNCS
+/*
+** If the library is compiled to omit the full-scale date and time
+** handling (to get a smaller binary), the following minimal version
+** of the functions current_time(), current_date() and current_timestamp()
+** are included instead. This is to support column declarations that
+** include "DEFAULT CURRENT_TIME" etc.
+**
+** This function uses the C-library functions time(), gmtime()
+** and strftime(). The format string to pass to strftime() is supplied
+** as the user-data for the function.
+*/
+static void currentTimeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  time_t t;
+  char *zFormat = (char *)sqlite3_user_data(context);
+  sqlite3_int64 iT;
+  struct tm *pTm;
+  struct tm sNow;
+  char zBuf[20];
+
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+
+  iT = sqlite3StmtCurrentTime(context);
+  if( iT<=0 ) return;
+  t = iT/1000 - 10000*(sqlite3_int64)21086676;
+#if HAVE_GMTIME_R
+  pTm = gmtime_r(&t, &sNow);
+#else
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN));
+  pTm = gmtime(&t);
+  if( pTm ) memcpy(&sNow, pTm, sizeof(sNow));
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN));
+#endif
+  if( pTm ){
+    strftime(zBuf, 20, zFormat, &sNow);
+    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+  }
+}
+#endif
+
+/*
+** This function registered all of the above C functions as SQL
+** functions.  This should be the only routine in this file with
+** external linkage.
+*/
+void sqlite3RegisterDateTimeFunctions(void){
+  static FuncDef aDateTimeFuncs[] = {
+#ifndef SQLITE_OMIT_DATETIME_FUNCS
+    PURE_DATE(julianday,        -1, 0, 0, juliandayFunc ),
+    PURE_DATE(unixepoch,        -1, 0, 0, unixepochFunc ),
+    PURE_DATE(date,             -1, 0, 0, dateFunc      ),
+    PURE_DATE(time,             -1, 0, 0, timeFunc      ),
+    PURE_DATE(datetime,         -1, 0, 0, datetimeFunc  ),
+    PURE_DATE(strftime,         -1, 0, 0, strftimeFunc  ),
+    PURE_DATE(timediff,          2, 0, 0, timediffFunc  ),
+    DFUNCTION(current_time,      0, 0, 0, ctimeFunc     ),
+    DFUNCTION(current_timestamp, 0, 0, 0, ctimestampFunc),
+    DFUNCTION(current_date,      0, 0, 0, cdateFunc     ),
+#else
+    STR_FUNCTION(current_time,      0, "%H:%M:%S",          0, currentTimeFunc),
+    STR_FUNCTION(current_date,      0, "%Y-%m-%d",          0, currentTimeFunc),
+    STR_FUNCTION(current_timestamp, 0, "%Y-%m-%d %H:%M:%S", 0, currentTimeFunc),
+#endif
+  };
+  sqlite3InsertBuiltinFuncs(aDateTimeFuncs, ArraySize(aDateTimeFuncs));
+}
diff --git a/src/dbpage.c b/src/dbpage.c
new file mode 100644
index 0000000..73c31f0
--- /dev/null
+++ b/src/dbpage.c
@@ -0,0 +1,435 @@
+/*
+** 2017-10-11
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains an implementation of the "sqlite_dbpage" virtual table.
+**
+** The sqlite_dbpage virtual table is used to read or write whole raw
+** pages of the database file.  The pager interface is used so that 
+** uncommitted changes and changes recorded in the WAL file are correctly
+** retrieved.
+**
+** Usage example:
+**
+**    SELECT data FROM sqlite_dbpage('aux1') WHERE pgno=123;
+**
+** This is an eponymous virtual table so it does not need to be created before
+** use.  The optional argument to the sqlite_dbpage() table name is the
+** schema for the database file that is to be read.  The default schema is
+** "main".
+**
+** The data field of sqlite_dbpage table can be updated.  The new
+** value must be a BLOB which is the correct page size, otherwise the
+** update fails.  Rows may not be deleted or inserted.
+*/
+
+#include "sqliteInt.h"   /* Requires access to internal data structures */
+#if (defined(SQLITE_ENABLE_DBPAGE_VTAB) || defined(SQLITE_TEST)) \
+    && !defined(SQLITE_OMIT_VIRTUALTABLE)
+
+typedef struct DbpageTable DbpageTable;
+typedef struct DbpageCursor DbpageCursor;
+
+struct DbpageCursor {
+  sqlite3_vtab_cursor base;       /* Base class.  Must be first */
+  int pgno;                       /* Current page number */
+  int mxPgno;                     /* Last page to visit on this scan */
+  Pager *pPager;                  /* Pager being read/written */
+  DbPage *pPage1;                 /* Page 1 of the database */
+  int iDb;                        /* Index of database to analyze */
+  int szPage;                     /* Size of each page in bytes */
+};
+
+struct DbpageTable {
+  sqlite3_vtab base;              /* Base class.  Must be first */
+  sqlite3 *db;                    /* The database */
+};
+
+/* Columns */
+#define DBPAGE_COLUMN_PGNO    0
+#define DBPAGE_COLUMN_DATA    1
+#define DBPAGE_COLUMN_SCHEMA  2
+
+
+
+/*
+** Connect to or create a dbpagevfs virtual table.
+*/
+static int dbpageConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  DbpageTable *pTab = 0;
+  int rc = SQLITE_OK;
+  (void)pAux;
+  (void)argc;
+  (void)argv;
+  (void)pzErr;
+
+  sqlite3_vtab_config(db, SQLITE_VTAB_DIRECTONLY);
+  sqlite3_vtab_config(db, SQLITE_VTAB_USES_ALL_SCHEMAS);
+  rc = sqlite3_declare_vtab(db, 
+          "CREATE TABLE x(pgno INTEGER PRIMARY KEY, data BLOB, schema HIDDEN)");
+  if( rc==SQLITE_OK ){
+    pTab = (DbpageTable *)sqlite3_malloc64(sizeof(DbpageTable));
+    if( pTab==0 ) rc = SQLITE_NOMEM_BKPT;
+  }
+
+  assert( rc==SQLITE_OK || pTab==0 );
+  if( rc==SQLITE_OK ){
+    memset(pTab, 0, sizeof(DbpageTable));
+    pTab->db = db;
+  }
+
+  *ppVtab = (sqlite3_vtab*)pTab;
+  return rc;
+}
+
+/*
+** Disconnect from or destroy a dbpagevfs virtual table.
+*/
+static int dbpageDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+
+/*
+** idxNum:
+**
+**     0     schema=main, full table scan
+**     1     schema=main, pgno=?1
+**     2     schema=?1, full table scan
+**     3     schema=?1, pgno=?2
+*/
+static int dbpageBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int i;
+  int iPlan = 0;
+  (void)tab;
+
+  /* If there is a schema= constraint, it must be honored.  Report a
+  ** ridiculously large estimated cost if the schema= constraint is
+  ** unavailable
+  */
+  for(i=0; i<pIdxInfo->nConstraint; i++){
+    struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i];
+    if( p->iColumn!=DBPAGE_COLUMN_SCHEMA ) continue;
+    if( p->op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
+    if( !p->usable ){
+      /* No solution. */
+      return SQLITE_CONSTRAINT;
+    }
+    iPlan = 2;
+    pIdxInfo->aConstraintUsage[i].argvIndex = 1;
+    pIdxInfo->aConstraintUsage[i].omit = 1;
+    break;
+  }
+
+  /* If we reach this point, it means that either there is no schema=
+  ** constraint (in which case we use the "main" schema) or else the
+  ** schema constraint was accepted.  Lower the estimated cost accordingly
+  */
+  pIdxInfo->estimatedCost = 1.0e6;
+
+  /* Check for constraints against pgno */
+  for(i=0; i<pIdxInfo->nConstraint; i++){
+    struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i];
+    if( p->usable && p->iColumn<=0 && p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      pIdxInfo->estimatedRows = 1;
+      pIdxInfo->idxFlags = SQLITE_INDEX_SCAN_UNIQUE;
+      pIdxInfo->estimatedCost = 1.0;
+      pIdxInfo->aConstraintUsage[i].argvIndex = iPlan ? 2 : 1;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+      iPlan |= 1;
+      break;
+    }
+  }
+  pIdxInfo->idxNum = iPlan;
+
+  if( pIdxInfo->nOrderBy>=1
+   && pIdxInfo->aOrderBy[0].iColumn<=0
+   && pIdxInfo->aOrderBy[0].desc==0
+  ){
+    pIdxInfo->orderByConsumed = 1;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Open a new dbpagevfs cursor.
+*/
+static int dbpageOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  DbpageCursor *pCsr;
+
+  pCsr = (DbpageCursor *)sqlite3_malloc64(sizeof(DbpageCursor));
+  if( pCsr==0 ){
+    return SQLITE_NOMEM_BKPT;
+  }else{
+    memset(pCsr, 0, sizeof(DbpageCursor));
+    pCsr->base.pVtab = pVTab;
+    pCsr->pgno = -1;
+  }
+
+  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+/*
+** Close a dbpagevfs cursor.
+*/
+static int dbpageClose(sqlite3_vtab_cursor *pCursor){
+  DbpageCursor *pCsr = (DbpageCursor *)pCursor;
+  if( pCsr->pPage1 ) sqlite3PagerUnrefPageOne(pCsr->pPage1);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/*
+** Move a dbpagevfs cursor to the next entry in the file.
+*/
+static int dbpageNext(sqlite3_vtab_cursor *pCursor){
+  int rc = SQLITE_OK;
+  DbpageCursor *pCsr = (DbpageCursor *)pCursor;
+  pCsr->pgno++;
+  return rc;
+}
+
+static int dbpageEof(sqlite3_vtab_cursor *pCursor){
+  DbpageCursor *pCsr = (DbpageCursor *)pCursor;
+  return pCsr->pgno > pCsr->mxPgno;
+}
+
+/*
+** idxNum:
+**
+**     0     schema=main, full table scan
+**     1     schema=main, pgno=?1
+**     2     schema=?1, full table scan
+**     3     schema=?1, pgno=?2
+**
+** idxStr is not used
+*/
+static int dbpageFilter(
+  sqlite3_vtab_cursor *pCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  DbpageCursor *pCsr = (DbpageCursor *)pCursor;
+  DbpageTable *pTab = (DbpageTable *)pCursor->pVtab;
+  int rc;
+  sqlite3 *db = pTab->db;
+  Btree *pBt;
+
+  (void)idxStr;
+  
+  /* Default setting is no rows of result */
+  pCsr->pgno = 1; 
+  pCsr->mxPgno = 0;
+
+  if( idxNum & 2 ){
+    const char *zSchema;
+    assert( argc>=1 );
+    zSchema = (const char*)sqlite3_value_text(argv[0]);
+    pCsr->iDb = sqlite3FindDbName(db, zSchema);
+    if( pCsr->iDb<0 ) return SQLITE_OK;
+  }else{
+    pCsr->iDb = 0;
+  }
+  pBt = db->aDb[pCsr->iDb].pBt;
+  if( NEVER(pBt==0) ) return SQLITE_OK;
+  pCsr->pPager = sqlite3BtreePager(pBt);
+  pCsr->szPage = sqlite3BtreeGetPageSize(pBt);
+  pCsr->mxPgno = sqlite3BtreeLastPage(pBt);
+  if( idxNum & 1 ){
+    assert( argc>(idxNum>>1) );
+    pCsr->pgno = sqlite3_value_int(argv[idxNum>>1]);
+    if( pCsr->pgno<1 || pCsr->pgno>pCsr->mxPgno ){
+      pCsr->pgno = 1;
+      pCsr->mxPgno = 0;
+    }else{
+      pCsr->mxPgno = pCsr->pgno;
+    }
+  }else{
+    assert( pCsr->pgno==1 );
+  }
+  if( pCsr->pPage1 ) sqlite3PagerUnrefPageOne(pCsr->pPage1);
+  rc = sqlite3PagerGet(pCsr->pPager, 1, &pCsr->pPage1, 0);
+  return rc;
+}
+
+static int dbpageColumn(
+  sqlite3_vtab_cursor *pCursor, 
+  sqlite3_context *ctx, 
+  int i
+){
+  DbpageCursor *pCsr = (DbpageCursor *)pCursor;
+  int rc = SQLITE_OK;
+  switch( i ){
+    case 0: {           /* pgno */
+      sqlite3_result_int(ctx, pCsr->pgno);
+      break;
+    }
+    case 1: {           /* data */
+      DbPage *pDbPage = 0;
+      if( pCsr->pgno==((PENDING_BYTE/pCsr->szPage)+1) ){
+        /* The pending byte page. Assume it is zeroed out. Attempting to
+        ** request this page from the page is an SQLITE_CORRUPT error. */
+        sqlite3_result_zeroblob(ctx, pCsr->szPage);
+      }else{
+        rc = sqlite3PagerGet(pCsr->pPager, pCsr->pgno, (DbPage**)&pDbPage, 0);
+        if( rc==SQLITE_OK ){
+          sqlite3_result_blob(ctx, sqlite3PagerGetData(pDbPage), pCsr->szPage,
+              SQLITE_TRANSIENT);
+        }
+        sqlite3PagerUnref(pDbPage);
+      }
+      break;
+    }
+    default: {          /* schema */
+      sqlite3 *db = sqlite3_context_db_handle(ctx);
+      sqlite3_result_text(ctx, db->aDb[pCsr->iDb].zDbSName, -1, SQLITE_STATIC);
+      break;
+    }
+  }
+  return rc;
+}
+
+static int dbpageRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
+  DbpageCursor *pCsr = (DbpageCursor *)pCursor;
+  *pRowid = pCsr->pgno;
+  return SQLITE_OK;
+}
+
+static int dbpageUpdate(
+  sqlite3_vtab *pVtab,
+  int argc,
+  sqlite3_value **argv,
+  sqlite_int64 *pRowid
+){
+  DbpageTable *pTab = (DbpageTable *)pVtab;
+  Pgno pgno;
+  DbPage *pDbPage = 0;
+  int rc = SQLITE_OK;
+  char *zErr = 0;
+  const char *zSchema;
+  int iDb;
+  Btree *pBt;
+  Pager *pPager;
+  int szPage;
+
+  (void)pRowid;
+  if( pTab->db->flags & SQLITE_Defensive ){
+    zErr = "read-only";
+    goto update_fail;
+  }
+  if( argc==1 ){
+    zErr = "cannot delete";
+    goto update_fail;
+  }
+  pgno = sqlite3_value_int(argv[0]);
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL
+   || (Pgno)sqlite3_value_int(argv[1])!=pgno
+  ){
+    zErr = "cannot insert";
+    goto update_fail;
+  }
+  zSchema = (const char*)sqlite3_value_text(argv[4]);
+  iDb = ALWAYS(zSchema) ? sqlite3FindDbName(pTab->db, zSchema) : -1;
+  if( NEVER(iDb<0) ){
+    zErr = "no such schema";
+    goto update_fail;
+  }
+  pBt = pTab->db->aDb[iDb].pBt;
+  if( NEVER(pgno<1) || NEVER(pBt==0) || NEVER(pgno>sqlite3BtreeLastPage(pBt)) ){
+    zErr = "bad page number";
+    goto update_fail;
+  }
+  szPage = sqlite3BtreeGetPageSize(pBt);
+  if( sqlite3_value_type(argv[3])!=SQLITE_BLOB 
+   || sqlite3_value_bytes(argv[3])!=szPage
+  ){
+    zErr = "bad page value";
+    goto update_fail;
+  }
+  pPager = sqlite3BtreePager(pBt);
+  rc = sqlite3PagerGet(pPager, pgno, (DbPage**)&pDbPage, 0);
+  if( rc==SQLITE_OK ){
+    const void *pData = sqlite3_value_blob(argv[3]);
+    assert( pData!=0 || pTab->db->mallocFailed );
+    if( pData
+     && (rc = sqlite3PagerWrite(pDbPage))==SQLITE_OK
+    ){
+      memcpy(sqlite3PagerGetData(pDbPage), pData, szPage);
+    }
+  }
+  sqlite3PagerUnref(pDbPage);
+  return rc;
+
+update_fail:
+  sqlite3_free(pVtab->zErrMsg);
+  pVtab->zErrMsg = sqlite3_mprintf("%s", zErr);
+  return SQLITE_ERROR;
+}
+
+/* Since we do not know in advance which database files will be
+** written by the sqlite_dbpage virtual table, start a write transaction
+** on them all.
+*/
+static int dbpageBegin(sqlite3_vtab *pVtab){
+  DbpageTable *pTab = (DbpageTable *)pVtab;
+  sqlite3 *db = pTab->db;
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ) (void)sqlite3BtreeBeginTrans(pBt, 1, 0);
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** Invoke this routine to register the "dbpage" virtual table module
+*/
+int sqlite3DbpageRegister(sqlite3 *db){
+  static sqlite3_module dbpage_module = {
+    0,                            /* iVersion */
+    dbpageConnect,                /* xCreate */
+    dbpageConnect,                /* xConnect */
+    dbpageBestIndex,              /* xBestIndex */
+    dbpageDisconnect,             /* xDisconnect */
+    dbpageDisconnect,             /* xDestroy */
+    dbpageOpen,                   /* xOpen - open a cursor */
+    dbpageClose,                  /* xClose - close a cursor */
+    dbpageFilter,                 /* xFilter - configure scan constraints */
+    dbpageNext,                   /* xNext - advance a cursor */
+    dbpageEof,                    /* xEof - check for end of scan */
+    dbpageColumn,                 /* xColumn - read data */
+    dbpageRowid,                  /* xRowid - read data */
+    dbpageUpdate,                 /* xUpdate */
+    dbpageBegin,                  /* xBegin */
+    0,                            /* xSync */
+    0,                            /* xCommit */
+    0,                            /* xRollback */
+    0,                            /* xFindMethod */
+    0,                            /* xRename */
+    0,                            /* xSavepoint */
+    0,                            /* xRelease */
+    0,                            /* xRollbackTo */
+    0,                            /* xShadowName */
+    0                             /* xIntegrity */
+  };
+  return sqlite3_create_module(db, "sqlite_dbpage", &dbpage_module, 0);
+}
+#elif defined(SQLITE_ENABLE_DBPAGE_VTAB)
+int sqlite3DbpageRegister(sqlite3 *db){ return SQLITE_OK; }
+#endif /* SQLITE_ENABLE_DBSTAT_VTAB */
diff --git a/src/dbstat.c b/src/dbstat.c
new file mode 100644
index 0000000..c70d806
--- /dev/null
+++ b/src/dbstat.c
@@ -0,0 +1,905 @@
+/*
+** 2010 July 12
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains an implementation of the "dbstat" virtual table.
+**
+** The dbstat virtual table is used to extract low-level storage
+** information from an SQLite database in order to implement the
+** "sqlite3_analyzer" utility.  See the ../tool/spaceanal.tcl script
+** for an example implementation.
+**
+** Additional information is available on the "dbstat.html" page of the
+** official SQLite documentation.
+*/
+
+#include "sqliteInt.h"   /* Requires access to internal data structures */
+#if (defined(SQLITE_ENABLE_DBSTAT_VTAB) || defined(SQLITE_TEST)) \
+    && !defined(SQLITE_OMIT_VIRTUALTABLE)
+
+/*
+** The pager and btree modules arrange objects in memory so that there are
+** always approximately 200 bytes of addressable memory following each page
+** buffer. This way small buffer overreads caused by corrupt database pages
+** do not cause undefined behaviour. This module pads each page buffer
+** by the following number of bytes for the same purpose.
+*/
+#define DBSTAT_PAGE_PADDING_BYTES 256
+
+/*
+** Page paths:
+** 
+**   The value of the 'path' column describes the path taken from the 
+**   root-node of the b-tree structure to each page. The value of the 
+**   root-node path is '/'.
+**
+**   The value of the path for the left-most child page of the root of
+**   a b-tree is '/000/'. (Btrees store content ordered from left to right
+**   so the pages to the left have smaller keys than the pages to the right.)
+**   The next to left-most child of the root page is
+**   '/001', and so on, each sibling page identified by a 3-digit hex 
+**   value. The children of the 451st left-most sibling have paths such
+**   as '/1c2/000/, '/1c2/001/' etc.
+**
+**   Overflow pages are specified by appending a '+' character and a 
+**   six-digit hexadecimal value to the path to the cell they are linked
+**   from. For example, the three overflow pages in a chain linked from 
+**   the left-most cell of the 450th child of the root page are identified
+**   by the paths:
+**
+**      '/1c2/000+000000'         // First page in overflow chain
+**      '/1c2/000+000001'         // Second page in overflow chain
+**      '/1c2/000+000002'         // Third page in overflow chain
+**
+**   If the paths are sorted using the BINARY collation sequence, then
+**   the overflow pages associated with a cell will appear earlier in the
+**   sort-order than its child page:
+**
+**      '/1c2/000/'               // Left-most child of 451st child of root
+*/
+static const char zDbstatSchema[] = 
+  "CREATE TABLE x("
+  " name       TEXT,"          /*  0 Name of table or index */
+  " path       TEXT,"          /*  1 Path to page from root (NULL for agg) */
+  " pageno     INTEGER,"       /*  2 Page number (page count for aggregates) */
+  " pagetype   TEXT,"          /*  3 'internal', 'leaf', 'overflow', or NULL */
+  " ncell      INTEGER,"       /*  4 Cells on page (0 for overflow) */
+  " payload    INTEGER,"       /*  5 Bytes of payload on this page */
+  " unused     INTEGER,"       /*  6 Bytes of unused space on this page */
+  " mx_payload INTEGER,"       /*  7 Largest payload size of all cells */
+  " pgoffset   INTEGER,"       /*  8 Offset of page in file (NULL for agg) */
+  " pgsize     INTEGER,"       /*  9 Size of the page (sum for aggregate) */
+  " schema     TEXT HIDDEN,"   /* 10 Database schema being analyzed */
+  " aggregate  BOOLEAN HIDDEN" /* 11 aggregate info for each table */
+  ")"
+;
+
+/* Forward reference to data structured used in this module */
+typedef struct StatTable StatTable;
+typedef struct StatCursor StatCursor;
+typedef struct StatPage StatPage;
+typedef struct StatCell StatCell;
+
+/* Size information for a single cell within a btree page */
+struct StatCell {
+  int nLocal;                     /* Bytes of local payload */
+  u32 iChildPg;                   /* Child node (or 0 if this is a leaf) */
+  int nOvfl;                      /* Entries in aOvfl[] */
+  u32 *aOvfl;                     /* Array of overflow page numbers */
+  int nLastOvfl;                  /* Bytes of payload on final overflow page */
+  int iOvfl;                      /* Iterates through aOvfl[] */
+};
+
+/* Size information for a single btree page */
+struct StatPage {
+  u32 iPgno;                      /* Page number */
+  u8 *aPg;                        /* Page buffer from sqlite3_malloc() */
+  int iCell;                      /* Current cell */
+  char *zPath;                    /* Path to this page */
+
+  /* Variables populated by statDecodePage(): */
+  u8 flags;                       /* Copy of flags byte */
+  int nCell;                      /* Number of cells on page */
+  int nUnused;                    /* Number of unused bytes on page */
+  StatCell *aCell;                /* Array of parsed cells */
+  u32 iRightChildPg;              /* Right-child page number (or 0) */
+  int nMxPayload;                 /* Largest payload of any cell on the page */
+};
+
+/* The cursor for scanning the dbstat virtual table */
+struct StatCursor {
+  sqlite3_vtab_cursor base;       /* base class.  MUST BE FIRST! */
+  sqlite3_stmt *pStmt;            /* Iterates through set of root pages */
+  u8 isEof;                       /* After pStmt has returned SQLITE_DONE */
+  u8 isAgg;                       /* Aggregate results for each table */
+  int iDb;                        /* Schema used for this query */
+
+  StatPage aPage[32];             /* Pages in path to current page */
+  int iPage;                      /* Current entry in aPage[] */
+
+  /* Values to return. */
+  u32 iPageno;                    /* Value of 'pageno' column */
+  char *zName;                    /* Value of 'name' column */
+  char *zPath;                    /* Value of 'path' column */
+  char *zPagetype;                /* Value of 'pagetype' column */
+  int nPage;                      /* Number of pages in current btree */
+  int nCell;                      /* Value of 'ncell' column */
+  int nMxPayload;                 /* Value of 'mx_payload' column */
+  i64 nUnused;                    /* Value of 'unused' column */
+  i64 nPayload;                   /* Value of 'payload' column */
+  i64 iOffset;                    /* Value of 'pgOffset' column */
+  i64 szPage;                     /* Value of 'pgSize' column */
+};
+
+/* An instance of the DBSTAT virtual table */
+struct StatTable {
+  sqlite3_vtab base;              /* base class.  MUST BE FIRST! */
+  sqlite3 *db;                    /* Database connection that owns this vtab */
+  int iDb;                        /* Index of database to analyze */
+};
+
+#ifndef get2byte
+# define get2byte(x)   ((x)[0]<<8 | (x)[1])
+#endif
+
+/*
+** Connect to or create a new DBSTAT virtual table.
+*/
+static int statConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  StatTable *pTab = 0;
+  int rc = SQLITE_OK;
+  int iDb;
+  (void)pAux;
+
+  if( argc>=4 ){
+    Token nm;
+    sqlite3TokenInit(&nm, (char*)argv[3]);
+    iDb = sqlite3FindDb(db, &nm);
+    if( iDb<0 ){
+      *pzErr = sqlite3_mprintf("no such database: %s", argv[3]);
+      return SQLITE_ERROR;
+    }
+  }else{
+    iDb = 0;
+  }
+  sqlite3_vtab_config(db, SQLITE_VTAB_DIRECTONLY);
+  rc = sqlite3_declare_vtab(db, zDbstatSchema);
+  if( rc==SQLITE_OK ){
+    pTab = (StatTable *)sqlite3_malloc64(sizeof(StatTable));
+    if( pTab==0 ) rc = SQLITE_NOMEM_BKPT;
+  }
+
+  assert( rc==SQLITE_OK || pTab==0 );
+  if( rc==SQLITE_OK ){
+    memset(pTab, 0, sizeof(StatTable));
+    pTab->db = db;
+    pTab->iDb = iDb;
+  }
+
+  *ppVtab = (sqlite3_vtab*)pTab;
+  return rc;
+}
+
+/*
+** Disconnect from or destroy the DBSTAT virtual table.
+*/
+static int statDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+
+/*
+** Compute the best query strategy and return the result in idxNum.
+**
+**   idxNum-Bit        Meaning
+**   ----------        ----------------------------------------------
+**      0x01           There is a schema=? term in the WHERE clause
+**      0x02           There is a name=? term in the WHERE clause
+**      0x04           There is an aggregate=? term in the WHERE clause
+**      0x08           Output should be ordered by name and path
+*/
+static int statBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int i;
+  int iSchema = -1;
+  int iName = -1;
+  int iAgg = -1;
+  (void)tab;
+
+  /* Look for a valid schema=? constraint.  If found, change the idxNum to
+  ** 1 and request the value of that constraint be sent to xFilter.  And
+  ** lower the cost estimate to encourage the constrained version to be
+  ** used.
+  */
+  for(i=0; i<pIdxInfo->nConstraint; i++){
+    if( pIdxInfo->aConstraint[i].op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
+    if( pIdxInfo->aConstraint[i].usable==0 ){
+      /* Force DBSTAT table should always be the right-most table in a join */
+      return SQLITE_CONSTRAINT;
+    }
+    switch( pIdxInfo->aConstraint[i].iColumn ){
+      case 0: {    /* name */
+        iName = i;
+        break;
+      }
+      case 10: {   /* schema */
+        iSchema = i;
+        break;
+      }
+      case 11: {   /* aggregate */
+        iAgg = i;
+        break;
+      }
+    }
+  }
+  i = 0;
+  if( iSchema>=0 ){
+    pIdxInfo->aConstraintUsage[iSchema].argvIndex = ++i;
+    pIdxInfo->aConstraintUsage[iSchema].omit = 1;
+    pIdxInfo->idxNum |= 0x01;
+  }
+  if( iName>=0 ){
+    pIdxInfo->aConstraintUsage[iName].argvIndex = ++i;
+    pIdxInfo->idxNum |= 0x02;
+  }
+  if( iAgg>=0 ){
+    pIdxInfo->aConstraintUsage[iAgg].argvIndex = ++i;
+    pIdxInfo->idxNum |= 0x04;
+  }
+  pIdxInfo->estimatedCost = 1.0;
+
+  /* Records are always returned in ascending order of (name, path). 
+  ** If this will satisfy the client, set the orderByConsumed flag so that 
+  ** SQLite does not do an external sort.
+  */
+  if( ( pIdxInfo->nOrderBy==1
+     && pIdxInfo->aOrderBy[0].iColumn==0
+     && pIdxInfo->aOrderBy[0].desc==0
+     ) ||
+      ( pIdxInfo->nOrderBy==2
+     && pIdxInfo->aOrderBy[0].iColumn==0
+     && pIdxInfo->aOrderBy[0].desc==0
+     && pIdxInfo->aOrderBy[1].iColumn==1
+     && pIdxInfo->aOrderBy[1].desc==0
+     )
+  ){
+    pIdxInfo->orderByConsumed = 1;
+    pIdxInfo->idxNum |= 0x08;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Open a new DBSTAT cursor.
+*/
+static int statOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  StatTable *pTab = (StatTable *)pVTab;
+  StatCursor *pCsr;
+
+  pCsr = (StatCursor *)sqlite3_malloc64(sizeof(StatCursor));
+  if( pCsr==0 ){
+    return SQLITE_NOMEM_BKPT;
+  }else{
+    memset(pCsr, 0, sizeof(StatCursor));
+    pCsr->base.pVtab = pVTab;
+    pCsr->iDb = pTab->iDb;
+  }
+
+  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+static void statClearCells(StatPage *p){
+  int i;
+  if( p->aCell ){
+    for(i=0; i<p->nCell; i++){
+      sqlite3_free(p->aCell[i].aOvfl);
+    }
+    sqlite3_free(p->aCell);
+  }
+  p->nCell = 0;
+  p->aCell = 0;
+}
+
+static void statClearPage(StatPage *p){
+  u8 *aPg = p->aPg;
+  statClearCells(p);
+  sqlite3_free(p->zPath);
+  memset(p, 0, sizeof(StatPage));
+  p->aPg = aPg;
+}
+
+static void statResetCsr(StatCursor *pCsr){
+  int i;
+  /* In some circumstances, specifically if an OOM has occurred, the call
+  ** to sqlite3_reset() may cause the pager to be reset (emptied). It is
+  ** important that statClearPage() is called to free any page refs before
+  ** this happens. dbsqlfuzz 9ed3e4e3816219d3509d711636c38542bf3f40b1. */
+  for(i=0; i<ArraySize(pCsr->aPage); i++){
+    statClearPage(&pCsr->aPage[i]);
+    sqlite3_free(pCsr->aPage[i].aPg);
+    pCsr->aPage[i].aPg = 0;
+  }
+  sqlite3_reset(pCsr->pStmt);
+  pCsr->iPage = 0;
+  sqlite3_free(pCsr->zPath);
+  pCsr->zPath = 0;
+  pCsr->isEof = 0;
+}
+
+/* Resize the space-used counters inside of the cursor */
+static void statResetCounts(StatCursor *pCsr){
+  pCsr->nCell = 0;
+  pCsr->nMxPayload = 0;
+  pCsr->nUnused = 0;
+  pCsr->nPayload = 0;
+  pCsr->szPage = 0;
+  pCsr->nPage = 0;
+}
+
+/*
+** Close a DBSTAT cursor.
+*/
+static int statClose(sqlite3_vtab_cursor *pCursor){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  statResetCsr(pCsr);
+  sqlite3_finalize(pCsr->pStmt);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/*
+** For a single cell on a btree page, compute the number of bytes of
+** content (payload) stored on that page.  That is to say, compute the
+** number of bytes of content not found on overflow pages.
+*/
+static int getLocalPayload(
+  int nUsable,                    /* Usable bytes per page */
+  u8 flags,                       /* Page flags */
+  int nTotal                      /* Total record (payload) size */
+){
+  int nLocal;
+  int nMinLocal;
+  int nMaxLocal;
+ 
+  if( flags==0x0D ){              /* Table leaf node */
+    nMinLocal = (nUsable - 12) * 32 / 255 - 23;
+    nMaxLocal = nUsable - 35;
+  }else{                          /* Index interior and leaf nodes */
+    nMinLocal = (nUsable - 12) * 32 / 255 - 23;
+    nMaxLocal = (nUsable - 12) * 64 / 255 - 23;
+  }
+
+  nLocal = nMinLocal + (nTotal - nMinLocal) % (nUsable - 4);
+  if( nLocal>nMaxLocal ) nLocal = nMinLocal;
+  return nLocal;
+}
+
+/* Populate the StatPage object with information about the all
+** cells found on the page currently under analysis.
+*/
+static int statDecodePage(Btree *pBt, StatPage *p){
+  int nUnused;
+  int iOff;
+  int nHdr;
+  int isLeaf;
+  int szPage;
+
+  u8 *aData = p->aPg;
+  u8 *aHdr = &aData[p->iPgno==1 ? 100 : 0];
+
+  p->flags = aHdr[0];
+  if( p->flags==0x0A || p->flags==0x0D ){
+    isLeaf = 1;
+    nHdr = 8;
+  }else if( p->flags==0x05 || p->flags==0x02 ){
+    isLeaf = 0;
+    nHdr = 12;
+  }else{
+    goto statPageIsCorrupt;
+  }
+  if( p->iPgno==1 ) nHdr += 100;
+  p->nCell = get2byte(&aHdr[3]);
+  p->nMxPayload = 0;
+  szPage = sqlite3BtreeGetPageSize(pBt);
+
+  nUnused = get2byte(&aHdr[5]) - nHdr - 2*p->nCell;
+  nUnused += (int)aHdr[7];
+  iOff = get2byte(&aHdr[1]);
+  while( iOff ){
+    int iNext;
+    if( iOff>=szPage ) goto statPageIsCorrupt;
+    nUnused += get2byte(&aData[iOff+2]);
+    iNext = get2byte(&aData[iOff]);
+    if( iNext<iOff+4 && iNext>0 ) goto statPageIsCorrupt;
+    iOff = iNext;
+  }
+  p->nUnused = nUnused;
+  p->iRightChildPg = isLeaf ? 0 : sqlite3Get4byte(&aHdr[8]);
+
+  if( p->nCell ){
+    int i;                        /* Used to iterate through cells */
+    int nUsable;                  /* Usable bytes per page */
+
+    sqlite3BtreeEnter(pBt);
+    nUsable = szPage - sqlite3BtreeGetReserveNoMutex(pBt);
+    sqlite3BtreeLeave(pBt);
+    p->aCell = sqlite3_malloc64((p->nCell+1) * sizeof(StatCell));
+    if( p->aCell==0 ) return SQLITE_NOMEM_BKPT;
+    memset(p->aCell, 0, (p->nCell+1) * sizeof(StatCell));
+
+    for(i=0; i<p->nCell; i++){
+      StatCell *pCell = &p->aCell[i];
+
+      iOff = get2byte(&aData[nHdr+i*2]);
+      if( iOff<nHdr || iOff>=szPage ) goto statPageIsCorrupt;
+      if( !isLeaf ){
+        pCell->iChildPg = sqlite3Get4byte(&aData[iOff]);
+        iOff += 4;
+      }
+      if( p->flags==0x05 ){
+        /* A table interior node. nPayload==0. */
+      }else{
+        u32 nPayload;             /* Bytes of payload total (local+overflow) */
+        int nLocal;               /* Bytes of payload stored locally */
+        iOff += getVarint32(&aData[iOff], nPayload);
+        if( p->flags==0x0D ){
+          u64 dummy;
+          iOff += sqlite3GetVarint(&aData[iOff], &dummy);
+        }
+        if( nPayload>(u32)p->nMxPayload ) p->nMxPayload = nPayload;
+        nLocal = getLocalPayload(nUsable, p->flags, nPayload);
+        if( nLocal<0 ) goto statPageIsCorrupt;
+        pCell->nLocal = nLocal;
+        assert( nPayload>=(u32)nLocal );
+        assert( nLocal<=(nUsable-35) );
+        if( nPayload>(u32)nLocal ){
+          int j;
+          int nOvfl = ((nPayload - nLocal) + nUsable-4 - 1) / (nUsable - 4);
+          if( iOff+nLocal+4>nUsable || nPayload>0x7fffffff ){
+            goto statPageIsCorrupt;
+          }
+          pCell->nLastOvfl = (nPayload-nLocal) - (nOvfl-1) * (nUsable-4);
+          pCell->nOvfl = nOvfl;
+          pCell->aOvfl = sqlite3_malloc64(sizeof(u32)*nOvfl);
+          if( pCell->aOvfl==0 ) return SQLITE_NOMEM_BKPT;
+          pCell->aOvfl[0] = sqlite3Get4byte(&aData[iOff+nLocal]);
+          for(j=1; j<nOvfl; j++){
+            int rc;
+            u32 iPrev = pCell->aOvfl[j-1];
+            DbPage *pPg = 0;
+            rc = sqlite3PagerGet(sqlite3BtreePager(pBt), iPrev, &pPg, 0);
+            if( rc!=SQLITE_OK ){
+              assert( pPg==0 );
+              return rc;
+            } 
+            pCell->aOvfl[j] = sqlite3Get4byte(sqlite3PagerGetData(pPg));
+            sqlite3PagerUnref(pPg);
+          }
+        }
+      }
+    }
+  }
+
+  return SQLITE_OK;
+
+statPageIsCorrupt:
+  p->flags = 0;
+  statClearCells(p);
+  return SQLITE_OK;
+}
+
+/*
+** Populate the pCsr->iOffset and pCsr->szPage member variables. Based on
+** the current value of pCsr->iPageno.
+*/
+static void statSizeAndOffset(StatCursor *pCsr){
+  StatTable *pTab = (StatTable *)((sqlite3_vtab_cursor *)pCsr)->pVtab;
+  Btree *pBt = pTab->db->aDb[pTab->iDb].pBt;
+  Pager *pPager = sqlite3BtreePager(pBt);
+  sqlite3_file *fd;
+  sqlite3_int64 x[2];
+
+  /* If connected to a ZIPVFS backend, find the page size and
+  ** offset from ZIPVFS.
+  */
+  fd = sqlite3PagerFile(pPager);
+  x[0] = pCsr->iPageno;
+  if( sqlite3OsFileControl(fd, 230440, &x)==SQLITE_OK ){
+    pCsr->iOffset = x[0];
+    pCsr->szPage += x[1];
+  }else{
+    /* Not ZIPVFS: The default page size and offset */
+    pCsr->szPage += sqlite3BtreeGetPageSize(pBt);
+    pCsr->iOffset = (i64)pCsr->szPage * (pCsr->iPageno - 1);
+  }
+}
+
+/*
+** Load a copy of the page data for page iPg into the buffer belonging
+** to page object pPg. Allocate the buffer if necessary. Return SQLITE_OK
+** if successful, or an SQLite error code otherwise.
+*/
+static int statGetPage(
+  Btree *pBt,                     /* Load page from this b-tree */
+  u32 iPg,                        /* Page number to load */
+  StatPage *pPg                   /* Load page into this object */
+){
+  int pgsz = sqlite3BtreeGetPageSize(pBt);
+  DbPage *pDbPage = 0;
+  int rc;
+
+  if( pPg->aPg==0 ){
+    pPg->aPg = (u8*)sqlite3_malloc(pgsz + DBSTAT_PAGE_PADDING_BYTES);
+    if( pPg->aPg==0 ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    memset(&pPg->aPg[pgsz], 0, DBSTAT_PAGE_PADDING_BYTES);
+  }
+
+  rc = sqlite3PagerGet(sqlite3BtreePager(pBt), iPg, &pDbPage, 0);
+  if( rc==SQLITE_OK ){
+    const u8 *a = sqlite3PagerGetData(pDbPage);
+    memcpy(pPg->aPg, a, pgsz);
+    sqlite3PagerUnref(pDbPage);
+  }
+
+  return rc;
+}
+
+/*
+** Move a DBSTAT cursor to the next entry.  Normally, the next
+** entry will be the next page, but in aggregated mode (pCsr->isAgg!=0),
+** the next entry is the next btree.
+*/
+static int statNext(sqlite3_vtab_cursor *pCursor){
+  int rc;
+  int nPayload;
+  char *z;
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  StatTable *pTab = (StatTable *)pCursor->pVtab;
+  Btree *pBt = pTab->db->aDb[pCsr->iDb].pBt;
+  Pager *pPager = sqlite3BtreePager(pBt);
+
+  sqlite3_free(pCsr->zPath);
+  pCsr->zPath = 0;
+
+statNextRestart:
+  if( pCsr->iPage<0 ){
+    /* Start measuring space on the next btree */
+    statResetCounts(pCsr);
+    rc = sqlite3_step(pCsr->pStmt);
+    if( rc==SQLITE_ROW ){
+      int nPage;
+      u32 iRoot = (u32)sqlite3_column_int64(pCsr->pStmt, 1);
+      sqlite3PagerPagecount(pPager, &nPage);
+      if( nPage==0 ){
+        pCsr->isEof = 1;
+        return sqlite3_reset(pCsr->pStmt);
+      }
+      rc = statGetPage(pBt, iRoot, &pCsr->aPage[0]);
+      pCsr->aPage[0].iPgno = iRoot;
+      pCsr->aPage[0].iCell = 0;
+      if( !pCsr->isAgg ){
+        pCsr->aPage[0].zPath = z = sqlite3_mprintf("/");
+        if( z==0 ) rc = SQLITE_NOMEM_BKPT;
+      }
+      pCsr->iPage = 0;
+      pCsr->nPage = 1;
+    }else{
+      pCsr->isEof = 1;
+      return sqlite3_reset(pCsr->pStmt);
+    }
+  }else{
+    /* Continue analyzing the btree previously started */
+    StatPage *p = &pCsr->aPage[pCsr->iPage];
+    if( !pCsr->isAgg ) statResetCounts(pCsr);
+    while( p->iCell<p->nCell ){
+      StatCell *pCell = &p->aCell[p->iCell];
+      while( pCell->iOvfl<pCell->nOvfl ){
+        int nUsable, iOvfl;
+        sqlite3BtreeEnter(pBt);
+        nUsable = sqlite3BtreeGetPageSize(pBt) - 
+                        sqlite3BtreeGetReserveNoMutex(pBt);
+        sqlite3BtreeLeave(pBt);
+        pCsr->nPage++;
+        statSizeAndOffset(pCsr);
+        if( pCell->iOvfl<pCell->nOvfl-1 ){
+          pCsr->nPayload += nUsable - 4;
+        }else{
+          pCsr->nPayload += pCell->nLastOvfl;
+          pCsr->nUnused += nUsable - 4 - pCell->nLastOvfl;
+        }
+        iOvfl = pCell->iOvfl;
+        pCell->iOvfl++;
+        if( !pCsr->isAgg ){
+          pCsr->zName = (char *)sqlite3_column_text(pCsr->pStmt, 0);
+          pCsr->iPageno = pCell->aOvfl[iOvfl];
+          pCsr->zPagetype = "overflow";
+          pCsr->zPath = z = sqlite3_mprintf(
+              "%s%.3x+%.6x", p->zPath, p->iCell, iOvfl
+          );
+          return z==0 ? SQLITE_NOMEM_BKPT : SQLITE_OK;
+        }
+      }
+      if( p->iRightChildPg ) break;
+      p->iCell++;
+    }
+
+    if( !p->iRightChildPg || p->iCell>p->nCell ){
+      statClearPage(p);
+      pCsr->iPage--;
+      if( pCsr->isAgg && pCsr->iPage<0 ){
+        /* label-statNext-done:  When computing aggregate space usage over
+        ** an entire btree, this is the exit point from this function */
+        return SQLITE_OK;
+      }
+      goto statNextRestart; /* Tail recursion */
+    }
+    pCsr->iPage++;
+    if( pCsr->iPage>=ArraySize(pCsr->aPage) ){
+      statResetCsr(pCsr);
+      return SQLITE_CORRUPT_BKPT;
+    }
+    assert( p==&pCsr->aPage[pCsr->iPage-1] );
+
+    if( p->iCell==p->nCell ){
+      p[1].iPgno = p->iRightChildPg;
+    }else{
+      p[1].iPgno = p->aCell[p->iCell].iChildPg;
+    }
+    rc = statGetPage(pBt, p[1].iPgno, &p[1]);
+    pCsr->nPage++;
+    p[1].iCell = 0;
+    if( !pCsr->isAgg ){
+      p[1].zPath = z = sqlite3_mprintf("%s%.3x/", p->zPath, p->iCell);
+      if( z==0 ) rc = SQLITE_NOMEM_BKPT;
+    }
+    p->iCell++;
+  }
+
+
+  /* Populate the StatCursor fields with the values to be returned
+  ** by the xColumn() and xRowid() methods.
+  */
+  if( rc==SQLITE_OK ){
+    int i;
+    StatPage *p = &pCsr->aPage[pCsr->iPage];
+    pCsr->zName = (char *)sqlite3_column_text(pCsr->pStmt, 0);
+    pCsr->iPageno = p->iPgno;
+
+    rc = statDecodePage(pBt, p);
+    if( rc==SQLITE_OK ){
+      statSizeAndOffset(pCsr);
+
+      switch( p->flags ){
+        case 0x05:             /* table internal */
+        case 0x02:             /* index internal */
+          pCsr->zPagetype = "internal";
+          break;
+        case 0x0D:             /* table leaf */
+        case 0x0A:             /* index leaf */
+          pCsr->zPagetype = "leaf";
+          break;
+        default:
+          pCsr->zPagetype = "corrupted";
+          break;
+      }
+      pCsr->nCell += p->nCell;
+      pCsr->nUnused += p->nUnused;
+      if( p->nMxPayload>pCsr->nMxPayload ) pCsr->nMxPayload = p->nMxPayload;
+      if( !pCsr->isAgg ){
+        pCsr->zPath = z = sqlite3_mprintf("%s", p->zPath);
+        if( z==0 ) rc = SQLITE_NOMEM_BKPT;
+      }
+      nPayload = 0;
+      for(i=0; i<p->nCell; i++){
+        nPayload += p->aCell[i].nLocal;
+      }
+      pCsr->nPayload += nPayload;
+
+      /* If computing aggregate space usage by btree, continue with the
+      ** next page.  The loop will exit via the return at label-statNext-done
+      */
+      if( pCsr->isAgg ) goto statNextRestart;
+    }
+  }
+
+  return rc;
+}
+
+static int statEof(sqlite3_vtab_cursor *pCursor){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  return pCsr->isEof;
+}
+
+/* Initialize a cursor according to the query plan idxNum using the
+** arguments in argv[0].  See statBestIndex() for a description of the
+** meaning of the bits in idxNum.
+*/
+static int statFilter(
+  sqlite3_vtab_cursor *pCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  StatTable *pTab = (StatTable*)(pCursor->pVtab);
+  sqlite3_str *pSql;      /* Query of btrees to analyze */
+  char *zSql;             /* String value of pSql */
+  int iArg = 0;           /* Count of argv[] parameters used so far */
+  int rc = SQLITE_OK;     /* Result of this operation */
+  const char *zName = 0;  /* Only provide analysis of this table */
+  (void)argc;
+  (void)idxStr;
+
+  statResetCsr(pCsr);
+  sqlite3_finalize(pCsr->pStmt);
+  pCsr->pStmt = 0;
+  if( idxNum & 0x01 ){
+    /* schema=? constraint is present.  Get its value */
+    const char *zDbase = (const char*)sqlite3_value_text(argv[iArg++]);
+    pCsr->iDb = sqlite3FindDbName(pTab->db, zDbase);
+    if( pCsr->iDb<0 ){
+      pCsr->iDb = 0;
+      pCsr->isEof = 1;
+      return SQLITE_OK;
+    }
+  }else{
+    pCsr->iDb = pTab->iDb;
+  }
+  if( idxNum & 0x02 ){
+    /* name=? constraint is present */
+    zName = (const char*)sqlite3_value_text(argv[iArg++]);
+  }
+  if( idxNum & 0x04 ){
+    /* aggregate=? constraint is present */
+    pCsr->isAgg = sqlite3_value_double(argv[iArg++])!=0.0;
+  }else{
+    pCsr->isAgg = 0;
+  }
+  pSql = sqlite3_str_new(pTab->db);
+  sqlite3_str_appendf(pSql,
+      "SELECT * FROM ("
+        "SELECT 'sqlite_schema' AS name,1 AS rootpage,'table' AS type"
+        " UNION ALL "
+        "SELECT name,rootpage,type"
+        " FROM \"%w\".sqlite_schema WHERE rootpage!=0)",
+      pTab->db->aDb[pCsr->iDb].zDbSName);
+  if( zName ){
+    sqlite3_str_appendf(pSql, "WHERE name=%Q", zName);
+  }
+  if( idxNum & 0x08 ){
+    sqlite3_str_appendf(pSql, " ORDER BY name");
+  }
+  zSql = sqlite3_str_finish(pSql);
+  if( zSql==0 ){
+    return SQLITE_NOMEM_BKPT;
+  }else{
+    rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pStmt, 0);
+    sqlite3_free(zSql);
+  }
+
+  if( rc==SQLITE_OK ){
+    pCsr->iPage = -1;
+    rc = statNext(pCursor);
+  }
+  return rc;
+}
+
+static int statColumn(
+  sqlite3_vtab_cursor *pCursor, 
+  sqlite3_context *ctx, 
+  int i
+){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  switch( i ){
+    case 0:            /* name */
+      sqlite3_result_text(ctx, pCsr->zName, -1, SQLITE_TRANSIENT);
+      break;
+    case 1:            /* path */
+      if( !pCsr->isAgg ){
+        sqlite3_result_text(ctx, pCsr->zPath, -1, SQLITE_TRANSIENT);
+      }
+      break;
+    case 2:            /* pageno */
+      if( pCsr->isAgg ){
+        sqlite3_result_int64(ctx, pCsr->nPage);
+      }else{
+        sqlite3_result_int64(ctx, pCsr->iPageno);
+      }
+      break;
+    case 3:            /* pagetype */
+      if( !pCsr->isAgg ){
+        sqlite3_result_text(ctx, pCsr->zPagetype, -1, SQLITE_STATIC);
+      }
+      break;
+    case 4:            /* ncell */
+      sqlite3_result_int64(ctx, pCsr->nCell);
+      break;
+    case 5:            /* payload */
+      sqlite3_result_int64(ctx, pCsr->nPayload);
+      break;
+    case 6:            /* unused */
+      sqlite3_result_int64(ctx, pCsr->nUnused);
+      break;
+    case 7:            /* mx_payload */
+      sqlite3_result_int64(ctx, pCsr->nMxPayload);
+      break;
+    case 8:            /* pgoffset */
+      if( !pCsr->isAgg ){
+        sqlite3_result_int64(ctx, pCsr->iOffset);
+      }
+      break;
+    case 9:            /* pgsize */
+      sqlite3_result_int64(ctx, pCsr->szPage);
+      break;
+    case 10: {         /* schema */
+      sqlite3 *db = sqlite3_context_db_handle(ctx);
+      int iDb = pCsr->iDb;
+      sqlite3_result_text(ctx, db->aDb[iDb].zDbSName, -1, SQLITE_STATIC);
+      break;
+    }
+    default: {         /* aggregate */
+      sqlite3_result_int(ctx, pCsr->isAgg);
+      break;
+    }
+  }
+  return SQLITE_OK;
+}
+
+static int statRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  *pRowid = pCsr->iPageno;
+  return SQLITE_OK;
+}
+
+/*
+** Invoke this routine to register the "dbstat" virtual table module
+*/
+int sqlite3DbstatRegister(sqlite3 *db){
+  static sqlite3_module dbstat_module = {
+    0,                            /* iVersion */
+    statConnect,                  /* xCreate */
+    statConnect,                  /* xConnect */
+    statBestIndex,                /* xBestIndex */
+    statDisconnect,               /* xDisconnect */
+    statDisconnect,               /* xDestroy */
+    statOpen,                     /* xOpen - open a cursor */
+    statClose,                    /* xClose - close a cursor */
+    statFilter,                   /* xFilter - configure scan constraints */
+    statNext,                     /* xNext - advance a cursor */
+    statEof,                      /* xEof - check for end of scan */
+    statColumn,                   /* xColumn - read data */
+    statRowid,                    /* xRowid - read data */
+    0,                            /* xUpdate */
+    0,                            /* xBegin */
+    0,                            /* xSync */
+    0,                            /* xCommit */
+    0,                            /* xRollback */
+    0,                            /* xFindMethod */
+    0,                            /* xRename */
+    0,                            /* xSavepoint */
+    0,                            /* xRelease */
+    0,                            /* xRollbackTo */
+    0,                            /* xShadowName */
+    0                             /* xIntegrity */
+  };
+  return sqlite3_create_module(db, "dbstat", &dbstat_module, 0);
+}
+#elif defined(SQLITE_ENABLE_DBSTAT_VTAB)
+int sqlite3DbstatRegister(sqlite3 *db){ return SQLITE_OK; }
+#endif /* SQLITE_ENABLE_DBSTAT_VTAB */
diff --git a/src/delete.c b/src/delete.c
new file mode 100644
index 0000000..2baff5b
--- /dev/null
+++ b/src/delete.c
@@ -0,0 +1,1028 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** in order to generate code for DELETE FROM statements.
+*/
+#include "sqliteInt.h"
+
+/*
+** While a SrcList can in general represent multiple tables and subqueries
+** (as in the FROM clause of a SELECT statement) in this case it contains
+** the name of a single table, as one might find in an INSERT, DELETE,
+** or UPDATE statement.  Look up that table in the symbol table and
+** return a pointer.  Set an error message and return NULL if the table
+** name is not found or if any other error occurs.
+**
+** The following fields are initialized appropriate in pSrc:
+**
+**    pSrc->a[0].pTab       Pointer to the Table object
+**    pSrc->a[0].pIndex     Pointer to the INDEXED BY index, if there is one
+**
+*/
+Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
+  SrcItem *pItem = pSrc->a;
+  Table *pTab;
+  assert( pItem && pSrc->nSrc>=1 );
+  pTab = sqlite3LocateTableItem(pParse, 0, pItem);
+  if( pItem->pTab ) sqlite3DeleteTable(pParse->db, pItem->pTab);
+  pItem->pTab = pTab;
+  pItem->fg.notCte = 1;
+  if( pTab ){
+    pTab->nTabRef++;
+    if( pItem->fg.isIndexedBy && sqlite3IndexedByLookup(pParse, pItem) ){
+      pTab = 0;
+    }
+  }
+  return pTab;
+}
+
+/* Generate byte-code that will report the number of rows modified
+** by a DELETE, INSERT, or UPDATE statement.
+*/
+void sqlite3CodeChangeCount(Vdbe *v, int regCounter, const char *zColName){
+  sqlite3VdbeAddOp0(v, OP_FkCheck);
+  sqlite3VdbeAddOp2(v, OP_ResultRow, regCounter, 1);
+  sqlite3VdbeSetNumCols(v, 1);
+  sqlite3VdbeSetColName(v, 0, COLNAME_NAME, zColName, SQLITE_STATIC);
+}
+
+/* Return true if table pTab is read-only.
+**
+** A table is read-only if any of the following are true:
+**
+**   1) It is a virtual table and no implementation of the xUpdate method
+**      has been provided
+**
+**   2) A trigger is currently being coded and the table is a virtual table
+**      that is SQLITE_VTAB_DIRECTONLY or if PRAGMA trusted_schema=OFF and
+**      the table is not SQLITE_VTAB_INNOCUOUS.
+**
+**   3) It is a system table (i.e. sqlite_schema), this call is not
+**      part of a nested parse and writable_schema pragma has not
+**      been specified
+**
+**   4) The table is a shadow table, the database connection is in
+**      defensive mode, and the current sqlite3_prepare()
+**      is for a top-level SQL statement.
+*/
+static int vtabIsReadOnly(Parse *pParse, Table *pTab){
+  if( sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0 ){
+    return 1;
+  }
+
+  /* Within triggers:
+  **   *  Do not allow DELETE, INSERT, or UPDATE of SQLITE_VTAB_DIRECTONLY
+  **      virtual tables
+  **   *  Only allow DELETE, INSERT, or UPDATE of non-SQLITE_VTAB_INNOCUOUS
+  **      virtual tables if PRAGMA trusted_schema=ON.
+  */
+  if( pParse->pToplevel!=0
+   && pTab->u.vtab.p->eVtabRisk >
+           ((pParse->db->flags & SQLITE_TrustedSchema)!=0)
+  ){
+    sqlite3ErrorMsg(pParse, "unsafe use of virtual table \"%s\"",
+      pTab->zName);
+  }
+  return 0;
+}
+static int tabIsReadOnly(Parse *pParse, Table *pTab){
+  sqlite3 *db;
+  if( IsVirtual(pTab) ){
+    return vtabIsReadOnly(pParse, pTab);
+  }
+  if( (pTab->tabFlags & (TF_Readonly|TF_Shadow))==0 ) return 0;
+  db = pParse->db;
+  if( (pTab->tabFlags & TF_Readonly)!=0 ){
+    return sqlite3WritableSchema(db)==0 && pParse->nested==0;
+  }
+  assert( pTab->tabFlags & TF_Shadow );
+  return sqlite3ReadOnlyShadowTables(db);
+}
+
+/*
+** Check to make sure the given table is writable.
+**
+** If pTab is not writable  ->  generate an error message and return 1.
+** If pTab is writable but other errors have occurred -> return 1.
+** If pTab is writable and no prior errors -> return 0;
+*/
+int sqlite3IsReadOnly(Parse *pParse, Table *pTab, Trigger *pTrigger){
+  if( tabIsReadOnly(pParse, pTab) ){
+    sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
+    return 1;
+  }
+#ifndef SQLITE_OMIT_VIEW
+  if( IsView(pTab)
+   && (pTrigger==0 || (pTrigger->bReturning && pTrigger->pNext==0))
+  ){
+    sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
+    return 1;
+  }
+#endif
+  return 0;
+}
+
+
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+/*
+** Evaluate a view and store its result in an ephemeral table.  The
+** pWhere argument is an optional WHERE clause that restricts the
+** set of rows in the view that are to be added to the ephemeral table.
+*/
+void sqlite3MaterializeView(
+  Parse *pParse,       /* Parsing context */
+  Table *pView,        /* View definition */
+  Expr *pWhere,        /* Optional WHERE clause to be added */
+  ExprList *pOrderBy,  /* Optional ORDER BY clause */
+  Expr *pLimit,        /* Optional LIMIT clause */
+  int iCur             /* Cursor number for ephemeral table */
+){
+  SelectDest dest;
+  Select *pSel;
+  SrcList *pFrom;
+  sqlite3 *db = pParse->db;
+  int iDb = sqlite3SchemaToIndex(db, pView->pSchema);
+  pWhere = sqlite3ExprDup(db, pWhere, 0);
+  pFrom = sqlite3SrcListAppend(pParse, 0, 0, 0);
+  if( pFrom ){
+    assert( pFrom->nSrc==1 );
+    pFrom->a[0].zName = sqlite3DbStrDup(db, pView->zName);
+    pFrom->a[0].zDatabase = sqlite3DbStrDup(db, db->aDb[iDb].zDbSName);
+    assert( pFrom->a[0].fg.isUsing==0 );
+    assert( pFrom->a[0].u3.pOn==0 );
+  }
+  pSel = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, pOrderBy,
+                          SF_IncludeHidden, pLimit);
+  sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
+  sqlite3Select(pParse, pSel, &dest);
+  sqlite3SelectDelete(db, pSel);
+}
+#endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */
+
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
+/*
+** Generate an expression tree to implement the WHERE, ORDER BY,
+** and LIMIT/OFFSET portion of DELETE and UPDATE statements.
+**
+**     DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;
+**                            \__________________________/
+**                               pLimitWhere (pInClause)
+*/
+Expr *sqlite3LimitWhere(
+  Parse *pParse,               /* The parser context */
+  SrcList *pSrc,               /* the FROM clause -- which tables to scan */
+  Expr *pWhere,                /* The WHERE clause.  May be null */
+  ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
+  Expr *pLimit,                /* The LIMIT clause.  May be null */
+  char *zStmtType              /* Either DELETE or UPDATE.  For err msgs. */
+){
+  sqlite3 *db = pParse->db;
+  Expr *pLhs = NULL;           /* LHS of IN(SELECT...) operator */
+  Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
+  ExprList *pEList = NULL;     /* Expression list containing only pSelectRowid*/
+  SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
+  Select *pSelect = NULL;      /* Complete SELECT tree */
+  Table *pTab;
+
+  /* Check that there isn't an ORDER BY without a LIMIT clause.
+  */
+  if( pOrderBy && pLimit==0 ) {
+    sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
+    sqlite3ExprDelete(pParse->db, pWhere);
+    sqlite3ExprListDelete(pParse->db, pOrderBy);
+    return 0;
+  }
+
+  /* We only need to generate a select expression if there
+  ** is a limit/offset term to enforce.
+  */
+  if( pLimit == 0 ) {
+    return pWhere;
+  }
+
+  /* Generate a select expression tree to enforce the limit/offset
+  ** term for the DELETE or UPDATE statement.  For example:
+  **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
+  ** becomes:
+  **   DELETE FROM table_a WHERE rowid IN (
+  **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
+  **   );
+  */
+
+  pTab = pSrc->a[0].pTab;
+  if( HasRowid(pTab) ){
+    pLhs = sqlite3PExpr(pParse, TK_ROW, 0, 0);
+    pEList = sqlite3ExprListAppend(
+        pParse, 0, sqlite3PExpr(pParse, TK_ROW, 0, 0)
+    );
+  }else{
+    Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+    assert( pPk!=0 );
+    assert( pPk->nKeyCol>=1 );
+    if( pPk->nKeyCol==1 ){
+      const char *zName;
+      assert( pPk->aiColumn[0]>=0 && pPk->aiColumn[0]<pTab->nCol );
+      zName = pTab->aCol[pPk->aiColumn[0]].zCnName;
+      pLhs = sqlite3Expr(db, TK_ID, zName);
+      pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ID, zName));
+    }else{
+      int i;
+      for(i=0; i<pPk->nKeyCol; i++){
+        Expr *p;
+        assert( pPk->aiColumn[i]>=0 && pPk->aiColumn[i]<pTab->nCol );
+        p = sqlite3Expr(db, TK_ID, pTab->aCol[pPk->aiColumn[i]].zCnName);
+        pEList = sqlite3ExprListAppend(pParse, pEList, p);
+      }
+      pLhs = sqlite3PExpr(pParse, TK_VECTOR, 0, 0);
+      if( pLhs ){
+        pLhs->x.pList = sqlite3ExprListDup(db, pEList, 0);
+      }
+    }
+  }
+
+  /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
+  ** and the SELECT subtree. */
+  pSrc->a[0].pTab = 0;
+  pSelectSrc = sqlite3SrcListDup(db, pSrc, 0);
+  pSrc->a[0].pTab = pTab;
+  if( pSrc->a[0].fg.isIndexedBy ){
+    assert( pSrc->a[0].fg.isCte==0 );
+    pSrc->a[0].u2.pIBIndex = 0;
+    pSrc->a[0].fg.isIndexedBy = 0;
+    sqlite3DbFree(db, pSrc->a[0].u1.zIndexedBy);
+  }else if( pSrc->a[0].fg.isCte ){
+    pSrc->a[0].u2.pCteUse->nUse++;
+  }
+
+  /* generate the SELECT expression tree. */
+  pSelect = sqlite3SelectNew(pParse, pEList, pSelectSrc, pWhere, 0 ,0,
+      pOrderBy,0,pLimit
+  );
+
+  /* now generate the new WHERE rowid IN clause for the DELETE/UPDATE */
+  pInClause = sqlite3PExpr(pParse, TK_IN, pLhs, 0);
+  sqlite3PExprAddSelect(pParse, pInClause, pSelect);
+  return pInClause;
+}
+#endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) */
+       /*      && !defined(SQLITE_OMIT_SUBQUERY) */
+
+/*
+** Generate code for a DELETE FROM statement.
+**
+**     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
+**                 \________/       \________________/
+**                  pTabList              pWhere
+*/
+void sqlite3DeleteFrom(
+  Parse *pParse,         /* The parser context */
+  SrcList *pTabList,     /* The table from which we should delete things */
+  Expr *pWhere,          /* The WHERE clause.  May be null */
+  ExprList *pOrderBy,    /* ORDER BY clause. May be null */
+  Expr *pLimit           /* LIMIT clause. May be null */
+){
+  Vdbe *v;               /* The virtual database engine */
+  Table *pTab;           /* The table from which records will be deleted */
+  int i;                 /* Loop counter */
+  WhereInfo *pWInfo;     /* Information about the WHERE clause */
+  Index *pIdx;           /* For looping over indices of the table */
+  int iTabCur;           /* Cursor number for the table */
+  int iDataCur = 0;      /* VDBE cursor for the canonical data source */
+  int iIdxCur = 0;       /* Cursor number of the first index */
+  int nIdx;              /* Number of indices */
+  sqlite3 *db;           /* Main database structure */
+  AuthContext sContext;  /* Authorization context */
+  NameContext sNC;       /* Name context to resolve expressions in */
+  int iDb;               /* Database number */
+  int memCnt = 0;        /* Memory cell used for change counting */
+  int rcauth;            /* Value returned by authorization callback */
+  int eOnePass;          /* ONEPASS_OFF or _SINGLE or _MULTI */
+  int aiCurOnePass[2];   /* The write cursors opened by WHERE_ONEPASS */
+  u8 *aToOpen = 0;       /* Open cursor iTabCur+j if aToOpen[j] is true */
+  Index *pPk;            /* The PRIMARY KEY index on the table */
+  int iPk = 0;           /* First of nPk registers holding PRIMARY KEY value */
+  i16 nPk = 1;           /* Number of columns in the PRIMARY KEY */
+  int iKey;              /* Memory cell holding key of row to be deleted */
+  i16 nKey;              /* Number of memory cells in the row key */
+  int iEphCur = 0;       /* Ephemeral table holding all primary key values */
+  int iRowSet = 0;       /* Register for rowset of rows to delete */
+  int addrBypass = 0;    /* Address of jump over the delete logic */
+  int addrLoop = 0;      /* Top of the delete loop */
+  int addrEphOpen = 0;   /* Instruction to open the Ephemeral table */
+  int bComplex;          /* True if there are triggers or FKs or
+                         ** subqueries in the WHERE clause */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  int isView;                  /* True if attempting to delete from a view */
+  Trigger *pTrigger;           /* List of table triggers, if required */
+#endif
+
+  memset(&sContext, 0, sizeof(sContext));
+  db = pParse->db;
+  assert( db->pParse==pParse );
+  if( pParse->nErr ){
+    goto delete_from_cleanup;
+  }
+  assert( db->mallocFailed==0 );
+  assert( pTabList->nSrc==1 );
+
+  /* Locate the table which we want to delete.  This table has to be
+  ** put in an SrcList structure because some of the subroutines we
+  ** will be calling are designed to work with multiple tables and expect
+  ** an SrcList* parameter instead of just a Table* parameter.
+  */
+  pTab = sqlite3SrcListLookup(pParse, pTabList);
+  if( pTab==0 )  goto delete_from_cleanup;
+
+  /* Figure out if we have any triggers and if the table being
+  ** deleted from is a view
+  */
+#ifndef SQLITE_OMIT_TRIGGER
+  pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
+  isView = IsView(pTab);
+#else
+# define pTrigger 0
+# define isView 0
+#endif
+  bComplex = pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0);
+#ifdef SQLITE_OMIT_VIEW
+# undef isView
+# define isView 0
+#endif
+
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x10000 ){
+    sqlite3TreeViewLine(0, "In sqlite3Delete() at %s:%d", __FILE__, __LINE__);
+    sqlite3TreeViewDelete(pParse->pWith, pTabList, pWhere,
+                          pOrderBy, pLimit, pTrigger);
+  }
+#endif
+
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  if( !isView ){
+    pWhere = sqlite3LimitWhere(
+        pParse, pTabList, pWhere, pOrderBy, pLimit, "DELETE"
+    );
+    pOrderBy = 0;
+    pLimit = 0;
+  }
+#endif
+
+  /* If pTab is really a view, make sure it has been initialized.
+  */
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto delete_from_cleanup;
+  }
+
+  if( sqlite3IsReadOnly(pParse, pTab, pTrigger) ){
+    goto delete_from_cleanup;
+  }
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb<db->nDb );
+  rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0,
+                            db->aDb[iDb].zDbSName);
+  assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
+  if( rcauth==SQLITE_DENY ){
+    goto delete_from_cleanup;
+  }
+  assert(!isView || pTrigger);
+
+  /* Assign cursor numbers to the table and all its indices.
+  */
+  assert( pTabList->nSrc==1 );
+  iTabCur = pTabList->a[0].iCursor = pParse->nTab++;
+  for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){
+    pParse->nTab++;
+  }
+
+  /* Start the view context
+  */
+  if( isView ){
+    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
+  }
+
+  /* Begin generating code.
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ){
+    goto delete_from_cleanup;
+  }
+  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
+  sqlite3BeginWriteOperation(pParse, bComplex, iDb);
+
+  /* If we are trying to delete from a view, realize that view into
+  ** an ephemeral table.
+  */
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+  if( isView ){
+    sqlite3MaterializeView(pParse, pTab,
+        pWhere, pOrderBy, pLimit, iTabCur
+    );
+    iDataCur = iIdxCur = iTabCur;
+    pOrderBy = 0;
+    pLimit = 0;
+  }
+#endif
+
+  /* Resolve the column names in the WHERE clause.
+  */
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = pParse;
+  sNC.pSrcList = pTabList;
+  if( sqlite3ResolveExprNames(&sNC, pWhere) ){
+    goto delete_from_cleanup;
+  }
+
+  /* Initialize the counter of the number of rows deleted, if
+  ** we are counting rows.
+  */
+  if( (db->flags & SQLITE_CountRows)!=0
+   && !pParse->nested
+   && !pParse->pTriggerTab
+   && !pParse->bReturning
+  ){
+    memCnt = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);
+  }
+
+#ifndef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  /* Special case: A DELETE without a WHERE clause deletes everything.
+  ** It is easier just to erase the whole table. Prior to version 3.6.5,
+  ** this optimization caused the row change count (the value returned by
+  ** API function sqlite3_count_changes) to be set incorrectly.
+  **
+  ** The "rcauth==SQLITE_OK" terms is the
+  ** IMPLEMENTATION-OF: R-17228-37124 If the action code is SQLITE_DELETE and
+  ** the callback returns SQLITE_IGNORE then the DELETE operation proceeds but
+  ** the truncate optimization is disabled and all rows are deleted
+  ** individually.
+  */
+  if( rcauth==SQLITE_OK
+   && pWhere==0
+   && !bComplex
+   && !IsVirtual(pTab)
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+   && db->xPreUpdateCallback==0
+#endif
+  ){
+    assert( !isView );
+    sqlite3TableLock(pParse, iDb, pTab->tnum, 1, pTab->zName);
+    if( HasRowid(pTab) ){
+      sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt ? memCnt : -1,
+                        pTab->zName, P4_STATIC);
+    }
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      assert( pIdx->pSchema==pTab->pSchema );
+      if( IsPrimaryKeyIndex(pIdx) && !HasRowid(pTab) ){
+        sqlite3VdbeAddOp3(v, OP_Clear, pIdx->tnum, iDb, memCnt ? memCnt : -1);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);
+      }
+    }
+  }else
+#endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
+  {
+    u16 wcf = WHERE_ONEPASS_DESIRED|WHERE_DUPLICATES_OK;
+    if( sNC.ncFlags & NC_Subquery ) bComplex = 1;
+    wcf |= (bComplex ? 0 : WHERE_ONEPASS_MULTIROW);
+    if( HasRowid(pTab) ){
+      /* For a rowid table, initialize the RowSet to an empty set */
+      pPk = 0;
+      assert( nPk==1 );
+      iRowSet = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
+    }else{
+      /* For a WITHOUT ROWID table, create an ephemeral table used to
+      ** hold all primary keys for rows to be deleted. */
+      pPk = sqlite3PrimaryKeyIndex(pTab);
+      assert( pPk!=0 );
+      nPk = pPk->nKeyCol;
+      iPk = pParse->nMem+1;
+      pParse->nMem += nPk;
+      iEphCur = pParse->nTab++;
+      addrEphOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEphCur, nPk);
+      sqlite3VdbeSetP4KeyInfo(pParse, pPk);
+    }
+ 
+    /* Construct a query to find the rowid or primary key for every row
+    ** to be deleted, based on the WHERE clause. Set variable eOnePass
+    ** to indicate the strategy used to implement this delete:
+    **
+    **  ONEPASS_OFF:    Two-pass approach - use a FIFO for rowids/PK values.
+    **  ONEPASS_SINGLE: One-pass approach - at most one row deleted.
+    **  ONEPASS_MULTI:  One-pass approach - any number of rows may be deleted.
+    */
+    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0,0,wcf,iTabCur+1);
+    if( pWInfo==0 ) goto delete_from_cleanup;
+    eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
+    assert( IsVirtual(pTab)==0 || eOnePass!=ONEPASS_MULTI );
+    assert( IsVirtual(pTab) || bComplex || eOnePass!=ONEPASS_OFF
+            || OptimizationDisabled(db, SQLITE_OnePass) );
+    if( eOnePass!=ONEPASS_SINGLE ) sqlite3MultiWrite(pParse);
+    if( sqlite3WhereUsesDeferredSeek(pWInfo) ){
+      sqlite3VdbeAddOp1(v, OP_FinishSeek, iTabCur);
+    }
+ 
+    /* Keep track of the number of rows to be deleted */
+    if( memCnt ){
+      sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
+    }
+ 
+    /* Extract the rowid or primary key for the current row */
+    if( pPk ){
+      for(i=0; i<nPk; i++){
+        assert( pPk->aiColumn[i]>=0 );
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur,
+                                        pPk->aiColumn[i], iPk+i);
+      }
+      iKey = iPk;
+    }else{
+      iKey = ++pParse->nMem;
+      sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur, -1, iKey);
+    }
+ 
+    if( eOnePass!=ONEPASS_OFF ){
+      /* For ONEPASS, no need to store the rowid/primary-key. There is only
+      ** one, so just keep it in its register(s) and fall through to the
+      ** delete code.  */
+      nKey = nPk; /* OP_Found will use an unpacked key */
+      aToOpen = sqlite3DbMallocRawNN(db, nIdx+2);
+      if( aToOpen==0 ){
+        sqlite3WhereEnd(pWInfo);
+        goto delete_from_cleanup;
+      }
+      memset(aToOpen, 1, nIdx+1);
+      aToOpen[nIdx+1] = 0;
+      if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iTabCur] = 0;
+      if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iTabCur] = 0;
+      if( addrEphOpen ) sqlite3VdbeChangeToNoop(v, addrEphOpen);
+      addrBypass = sqlite3VdbeMakeLabel(pParse);
+    }else{
+      if( pPk ){
+        /* Add the PK key for this row to the temporary table */
+        iKey = ++pParse->nMem;
+        nKey = 0;   /* Zero tells OP_Found to use a composite key */
+        sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, iKey,
+            sqlite3IndexAffinityStr(pParse->db, pPk), nPk);
+        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iEphCur, iKey, iPk, nPk);
+      }else{
+        /* Add the rowid of the row to be deleted to the RowSet */
+        nKey = 1;  /* OP_DeferredSeek always uses a single rowid */
+        sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iKey);
+      }
+      sqlite3WhereEnd(pWInfo);
+    }
+ 
+    /* Unless this is a view, open cursors for the table we are
+    ** deleting from and all its indices. If this is a view, then the
+    ** only effect this statement has is to fire the INSTEAD OF
+    ** triggers.
+    */
+    if( !isView ){
+      int iAddrOnce = 0;
+      if( eOnePass==ONEPASS_MULTI ){
+        iAddrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+      }
+      testcase( IsVirtual(pTab) );
+      sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, OPFLAG_FORDELETE,
+                                 iTabCur, aToOpen, &iDataCur, &iIdxCur);
+      assert( pPk || IsVirtual(pTab) || iDataCur==iTabCur );
+      assert( pPk || IsVirtual(pTab) || iIdxCur==iDataCur+1 );
+      if( eOnePass==ONEPASS_MULTI ){
+        sqlite3VdbeJumpHereOrPopInst(v, iAddrOnce);
+      }
+    }
+ 
+    /* Set up a loop over the rowids/primary-keys that were found in the
+    ** where-clause loop above.
+    */
+    if( eOnePass!=ONEPASS_OFF ){
+      assert( nKey==nPk );  /* OP_Found will use an unpacked key */
+      if( !IsVirtual(pTab) && aToOpen[iDataCur-iTabCur] ){
+        assert( pPk!=0 || IsView(pTab) );
+        sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, addrBypass, iKey, nKey);
+        VdbeCoverage(v);
+      }
+    }else if( pPk ){
+      addrLoop = sqlite3VdbeAddOp1(v, OP_Rewind, iEphCur); VdbeCoverage(v);
+      if( IsVirtual(pTab) ){
+        sqlite3VdbeAddOp3(v, OP_Column, iEphCur, 0, iKey);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_RowData, iEphCur, iKey);
+      }
+      assert( nKey==0 );  /* OP_Found will use a composite key */
+    }else{
+      addrLoop = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, 0, iKey);
+      VdbeCoverage(v);
+      assert( nKey==1 );
+    } 
+ 
+    /* Delete the row */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( IsVirtual(pTab) ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
+      sqlite3VtabMakeWritable(pParse, pTab);
+      assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
+      sqlite3MayAbort(pParse);
+      if( eOnePass==ONEPASS_SINGLE ){
+        sqlite3VdbeAddOp1(v, OP_Close, iTabCur);
+        if( sqlite3IsToplevel(pParse) ){
+          pParse->isMultiWrite = 0;
+        }
+      }
+      sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iKey, pVTab, P4_VTAB);
+      sqlite3VdbeChangeP5(v, OE_Abort);
+    }else
+#endif
+    {
+      int count = (pParse->nested==0);    /* True to count changes */
+      sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
+          iKey, nKey, count, OE_Default, eOnePass, aiCurOnePass[1]);
+    }
+ 
+    /* End of the loop over all rowids/primary-keys. */
+    if( eOnePass!=ONEPASS_OFF ){
+      sqlite3VdbeResolveLabel(v, addrBypass);
+      sqlite3WhereEnd(pWInfo);
+    }else if( pPk ){
+      sqlite3VdbeAddOp2(v, OP_Next, iEphCur, addrLoop+1); VdbeCoverage(v);
+      sqlite3VdbeJumpHere(v, addrLoop);
+    }else{
+      sqlite3VdbeGoto(v, addrLoop);
+      sqlite3VdbeJumpHere(v, addrLoop);
+    }    
+  } /* End non-truncate path */
+
+  /* Update the sqlite_sequence table by storing the content of the
+  ** maximum rowid counter values recorded while inserting into
+  ** autoincrement tables.
+  */
+  if( pParse->nested==0 && pParse->pTriggerTab==0 ){
+    sqlite3AutoincrementEnd(pParse);
+  }
+
+  /* Return the number of rows that were deleted. If this routine is
+  ** generating code because of a call to sqlite3NestedParse(), do not
+  ** invoke the callback function.
+  */
+  if( memCnt ){
+    sqlite3CodeChangeCount(v, memCnt, "rows deleted");
+  }
+
+delete_from_cleanup:
+  sqlite3AuthContextPop(&sContext);
+  sqlite3SrcListDelete(db, pTabList);
+  sqlite3ExprDelete(db, pWhere);
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT)
+  sqlite3ExprListDelete(db, pOrderBy);
+  sqlite3ExprDelete(db, pLimit);
+#endif
+  if( aToOpen ) sqlite3DbNNFreeNN(db, aToOpen);
+  return;
+}
+/* Make sure "isView" and other macros defined above are undefined. Otherwise
+** they may interfere with compilation of other functions in this file
+** (or in another file, if this file becomes part of the amalgamation).  */
+#ifdef isView
+ #undef isView
+#endif
+#ifdef pTrigger
+ #undef pTrigger
+#endif
+
+/*
+** This routine generates VDBE code that causes a single row of a
+** single table to be deleted.  Both the original table entry and
+** all indices are removed.
+**
+** Preconditions:
+**
+**   1.  iDataCur is an open cursor on the btree that is the canonical data
+**       store for the table.  (This will be either the table itself,
+**       in the case of a rowid table, or the PRIMARY KEY index in the case
+**       of a WITHOUT ROWID table.)
+**
+**   2.  Read/write cursors for all indices of pTab must be open as
+**       cursor number iIdxCur+i for the i-th index.
+**
+**   3.  The primary key for the row to be deleted must be stored in a
+**       sequence of nPk memory cells starting at iPk.  If nPk==0 that means
+**       that a search record formed from OP_MakeRecord is contained in the
+**       single memory location iPk.
+**
+** eMode:
+**   Parameter eMode may be passed either ONEPASS_OFF (0), ONEPASS_SINGLE, or
+**   ONEPASS_MULTI.  If eMode is not ONEPASS_OFF, then the cursor
+**   iDataCur already points to the row to delete. If eMode is ONEPASS_OFF
+**   then this function must seek iDataCur to the entry identified by iPk
+**   and nPk before reading from it.
+**
+**   If eMode is ONEPASS_MULTI, then this call is being made as part
+**   of a ONEPASS delete that affects multiple rows. In this case, if
+**   iIdxNoSeek is a valid cursor number (>=0) and is not the same as
+**   iDataCur, then its position should be preserved following the delete
+**   operation. Or, if iIdxNoSeek is not a valid cursor number, the
+**   position of iDataCur should be preserved instead.
+**
+** iIdxNoSeek:
+**   If iIdxNoSeek is a valid cursor number (>=0) not equal to iDataCur,
+**   then it identifies an index cursor (from within array of cursors
+**   starting at iIdxCur) that already points to the index entry to be deleted.
+**   Except, this optimization is disabled if there are BEFORE triggers since
+**   the trigger body might have moved the cursor.
+*/
+void sqlite3GenerateRowDelete(
+  Parse *pParse,     /* Parsing context */
+  Table *pTab,       /* Table containing the row to be deleted */
+  Trigger *pTrigger, /* List of triggers to (potentially) fire */
+  int iDataCur,      /* Cursor from which column data is extracted */
+  int iIdxCur,       /* First index cursor */
+  int iPk,           /* First memory cell containing the PRIMARY KEY */
+  i16 nPk,           /* Number of PRIMARY KEY memory cells */
+  u8 count,          /* If non-zero, increment the row change counter */
+  u8 onconf,         /* Default ON CONFLICT policy for triggers */
+  u8 eMode,          /* ONEPASS_OFF, _SINGLE, or _MULTI.  See above */
+  int iIdxNoSeek     /* Cursor number of cursor that does not need seeking */
+){
+  Vdbe *v = pParse->pVdbe;        /* Vdbe */
+  int iOld = 0;                   /* First register in OLD.* array */
+  int iLabel;                     /* Label resolved to end of generated code */
+  u8 opSeek;                      /* Seek opcode */
+
+  /* Vdbe is guaranteed to have been allocated by this stage. */
+  assert( v );
+  VdbeModuleComment((v, "BEGIN: GenRowDel(%d,%d,%d,%d)",
+                         iDataCur, iIdxCur, iPk, (int)nPk));
+
+  /* Seek cursor iCur to the row to delete. If this row no longer exists
+  ** (this can happen if a trigger program has already deleted it), do
+  ** not attempt to delete it or fire any DELETE triggers.  */
+  iLabel = sqlite3VdbeMakeLabel(pParse);
+  opSeek = HasRowid(pTab) ? OP_NotExists : OP_NotFound;
+  if( eMode==ONEPASS_OFF ){
+    sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
+    VdbeCoverageIf(v, opSeek==OP_NotExists);
+    VdbeCoverageIf(v, opSeek==OP_NotFound);
+  }
+
+  /* If there are any triggers to fire, allocate a range of registers to
+  ** use for the old.* references in the triggers.  */
+  if( sqlite3FkRequired(pParse, pTab, 0, 0) || pTrigger ){
+    u32 mask;                     /* Mask of OLD.* columns in use */
+    int iCol;                     /* Iterator used while populating OLD.* */
+    int addrStart;                /* Start of BEFORE trigger programs */
+
+    /* TODO: Could use temporary registers here. Also could attempt to
+    ** avoid copying the contents of the rowid register.  */
+    mask = sqlite3TriggerColmask(
+        pParse, pTrigger, 0, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onconf
+    );
+    mask |= sqlite3FkOldmask(pParse, pTab);
+    iOld = pParse->nMem+1;
+    pParse->nMem += (1 + pTab->nCol);
+
+    /* Populate the OLD.* pseudo-table register array. These values will be
+    ** used by any BEFORE and AFTER triggers that exist.  */
+    sqlite3VdbeAddOp2(v, OP_Copy, iPk, iOld);
+    for(iCol=0; iCol<pTab->nCol; iCol++){
+      testcase( mask!=0xffffffff && iCol==31 );
+      testcase( mask!=0xffffffff && iCol==32 );
+      if( mask==0xffffffff || (iCol<=31 && (mask & MASKBIT32(iCol))!=0) ){
+        int kk = sqlite3TableColumnToStorage(pTab, iCol);
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, iCol, iOld+kk+1);
+      }
+    }
+
+    /* Invoke BEFORE DELETE trigger programs. */
+    addrStart = sqlite3VdbeCurrentAddr(v);
+    sqlite3CodeRowTrigger(pParse, pTrigger,
+        TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
+    );
+
+    /* If any BEFORE triggers were coded, then seek the cursor to the
+    ** row to be deleted again. It may be that the BEFORE triggers moved
+    ** the cursor or already deleted the row that the cursor was
+    ** pointing to.
+    **
+    ** Also disable the iIdxNoSeek optimization since the BEFORE trigger
+    ** may have moved that cursor.
+    */
+    if( addrStart<sqlite3VdbeCurrentAddr(v) ){
+      sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
+      VdbeCoverageIf(v, opSeek==OP_NotExists);
+      VdbeCoverageIf(v, opSeek==OP_NotFound);
+      testcase( iIdxNoSeek>=0 );
+      iIdxNoSeek = -1;
+    }
+
+    /* Do FK processing. This call checks that any FK constraints that
+    ** refer to this table (i.e. constraints attached to other tables)
+    ** are not violated by deleting this row.  */
+    sqlite3FkCheck(pParse, pTab, iOld, 0, 0, 0);
+  }
+
+  /* Delete the index and table entries. Skip this step if pTab is really
+  ** a view (in which case the only effect of the DELETE statement is to
+  ** fire the INSTEAD OF triggers). 
+  **
+  ** If variable 'count' is non-zero, then this OP_Delete instruction should
+  ** invoke the update-hook. The pre-update-hook, on the other hand should
+  ** be invoked unless table pTab is a system table. The difference is that
+  ** the update-hook is not invoked for rows removed by REPLACE, but the
+  ** pre-update-hook is.
+  */
+  if( !IsView(pTab) ){
+    u8 p5 = 0;
+    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,iIdxNoSeek);
+    sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, (count?OPFLAG_NCHANGE:0));
+    if( pParse->nested==0 || 0==sqlite3_stricmp(pTab->zName, "sqlite_stat1") ){
+      sqlite3VdbeAppendP4(v, (char*)pTab, P4_TABLE);
+    }
+    if( eMode!=ONEPASS_OFF ){
+      sqlite3VdbeChangeP5(v, OPFLAG_AUXDELETE);
+    }
+    if( iIdxNoSeek>=0 && iIdxNoSeek!=iDataCur ){
+      sqlite3VdbeAddOp1(v, OP_Delete, iIdxNoSeek);
+    }
+    if( eMode==ONEPASS_MULTI ) p5 |= OPFLAG_SAVEPOSITION;
+    sqlite3VdbeChangeP5(v, p5);
+  }
+
+  /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
+  ** handle rows (possibly in other tables) that refer via a foreign key
+  ** to the row just deleted. */
+  sqlite3FkActions(pParse, pTab, 0, iOld, 0, 0);
+
+  /* Invoke AFTER DELETE trigger programs. */
+  if( pTrigger ){
+    sqlite3CodeRowTrigger(pParse, pTrigger,
+        TK_DELETE, 0, TRIGGER_AFTER, pTab, iOld, onconf, iLabel
+    );
+  }
+
+  /* Jump here if the row had already been deleted before any BEFORE
+  ** trigger programs were invoked. Or if a trigger program throws a
+  ** RAISE(IGNORE) exception.  */
+  sqlite3VdbeResolveLabel(v, iLabel);
+  VdbeModuleComment((v, "END: GenRowDel()"));
+}
+
+/*
+** This routine generates VDBE code that causes the deletion of all
+** index entries associated with a single row of a single table, pTab
+**
+** Preconditions:
+**
+**   1.  A read/write cursor "iDataCur" must be open on the canonical storage
+**       btree for the table pTab.  (This will be either the table itself
+**       for rowid tables or to the primary key index for WITHOUT ROWID
+**       tables.)
+**
+**   2.  Read/write cursors for all indices of pTab must be open as
+**       cursor number iIdxCur+i for the i-th index.  (The pTab->pIndex
+**       index is the 0-th index.)
+**
+**   3.  The "iDataCur" cursor must be already be positioned on the row
+**       that is to be deleted.
+*/
+void sqlite3GenerateRowIndexDelete(
+  Parse *pParse,     /* Parsing and code generating context */
+  Table *pTab,       /* Table containing the row to be deleted */
+  int iDataCur,      /* Cursor of table holding data. */
+  int iIdxCur,       /* First index cursor */
+  int *aRegIdx,      /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */
+  int iIdxNoSeek     /* Do not delete from this cursor */
+){
+  int i;             /* Index loop counter */
+  int r1 = -1;       /* Register holding an index key */
+  int iPartIdxLabel; /* Jump destination for skipping partial index entries */
+  Index *pIdx;       /* Current index */
+  Index *pPrior = 0; /* Prior index */
+  Vdbe *v;           /* The prepared statement under construction */
+  Index *pPk;        /* PRIMARY KEY index, or NULL for rowid tables */
+
+  v = pParse->pVdbe;
+  pPk = HasRowid(pTab) ? 0 : sqlite3PrimaryKeyIndex(pTab);
+  for(i=0, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
+    assert( iIdxCur+i!=iDataCur || pPk==pIdx );
+    if( aRegIdx!=0 && aRegIdx[i]==0 ) continue;
+    if( pIdx==pPk ) continue;
+    if( iIdxCur+i==iIdxNoSeek ) continue;
+    VdbeModuleComment((v, "GenRowIdxDel for %s", pIdx->zName));
+    r1 = sqlite3GenerateIndexKey(pParse, pIdx, iDataCur, 0, 1,
+        &iPartIdxLabel, pPrior, r1);
+    sqlite3VdbeAddOp3(v, OP_IdxDelete, iIdxCur+i, r1,
+        pIdx->uniqNotNull ? pIdx->nKeyCol : pIdx->nColumn);
+    sqlite3VdbeChangeP5(v, 1);  /* Cause IdxDelete to error if no entry found */
+    sqlite3ResolvePartIdxLabel(pParse, iPartIdxLabel);
+    pPrior = pIdx;
+  }
+}
+
+/*
+** Generate code that will assemble an index key and stores it in register
+** regOut.  The key with be for index pIdx which is an index on pTab.
+** iCur is the index of a cursor open on the pTab table and pointing to
+** the entry that needs indexing.  If pTab is a WITHOUT ROWID table, then
+** iCur must be the cursor of the PRIMARY KEY index.
+**
+** Return a register number which is the first in a block of
+** registers that holds the elements of the index key.  The
+** block of registers has already been deallocated by the time
+** this routine returns.
+**
+** If *piPartIdxLabel is not NULL, fill it in with a label and jump
+** to that label if pIdx is a partial index that should be skipped.
+** The label should be resolved using sqlite3ResolvePartIdxLabel().
+** A partial index should be skipped if its WHERE clause evaluates
+** to false or null.  If pIdx is not a partial index, *piPartIdxLabel
+** will be set to zero which is an empty label that is ignored by
+** sqlite3ResolvePartIdxLabel().
+**
+** The pPrior and regPrior parameters are used to implement a cache to
+** avoid unnecessary register loads.  If pPrior is not NULL, then it is
+** a pointer to a different index for which an index key has just been
+** computed into register regPrior.  If the current pIdx index is generating
+** its key into the same sequence of registers and if pPrior and pIdx share
+** a column in common, then the register corresponding to that column already
+** holds the correct value and the loading of that register is skipped.
+** This optimization is helpful when doing a DELETE or an INTEGRITY_CHECK
+** on a table with multiple indices, and especially with the ROWID or
+** PRIMARY KEY columns of the index.
+*/
+int sqlite3GenerateIndexKey(
+  Parse *pParse,       /* Parsing context */
+  Index *pIdx,         /* The index for which to generate a key */
+  int iDataCur,        /* Cursor number from which to take column data */
+  int regOut,          /* Put the new key into this register if not 0 */
+  int prefixOnly,      /* Compute only a unique prefix of the key */
+  int *piPartIdxLabel, /* OUT: Jump to this label to skip partial index */
+  Index *pPrior,       /* Previously generated index key */
+  int regPrior         /* Register holding previous generated key */
+){
+  Vdbe *v = pParse->pVdbe;
+  int j;
+  int regBase;
+  int nCol;
+
+  if( piPartIdxLabel ){
+    if( pIdx->pPartIdxWhere ){
+      *piPartIdxLabel = sqlite3VdbeMakeLabel(pParse);
+      pParse->iSelfTab = iDataCur + 1;
+      sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, *piPartIdxLabel,
+                            SQLITE_JUMPIFNULL);
+      pParse->iSelfTab = 0;
+      pPrior = 0; /* Ticket a9efb42811fa41ee 2019-11-02;
+                  ** pPartIdxWhere may have corrupted regPrior registers */
+    }else{
+      *piPartIdxLabel = 0;
+    }
+  }
+  nCol = (prefixOnly && pIdx->uniqNotNull) ? pIdx->nKeyCol : pIdx->nColumn;
+  regBase = sqlite3GetTempRange(pParse, nCol);
+  if( pPrior && (regBase!=regPrior || pPrior->pPartIdxWhere) ) pPrior = 0;
+  for(j=0; j<nCol; j++){
+    if( pPrior
+     && pPrior->aiColumn[j]==pIdx->aiColumn[j]
+     && pPrior->aiColumn[j]!=XN_EXPR
+    ){
+      /* This column was already computed by the previous index */
+      continue;
+    }
+    sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iDataCur, j, regBase+j);
+    if( pIdx->aiColumn[j]>=0 ){
+      /* If the column affinity is REAL but the number is an integer, then it
+      ** might be stored in the table as an integer (using a compact
+      ** representation) then converted to REAL by an OP_RealAffinity opcode.
+      ** But we are getting ready to store this value back into an index, where
+      ** it should be converted by to INTEGER again.  So omit the
+      ** OP_RealAffinity opcode if it is present */
+      sqlite3VdbeDeletePriorOpcode(v, OP_RealAffinity);
+    }
+  }
+  if( regOut ){
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regOut);
+  }
+  sqlite3ReleaseTempRange(pParse, regBase, nCol);
+  return regBase;
+}
+
+/*
+** If a prior call to sqlite3GenerateIndexKey() generated a jump-over label
+** because it was a partial index, then this routine should be called to
+** resolve that label.
+*/
+void sqlite3ResolvePartIdxLabel(Parse *pParse, int iLabel){
+  if( iLabel ){
+    sqlite3VdbeResolveLabel(pParse->pVdbe, iLabel);
+  }
+}
diff --git a/src/expr.c b/src/expr.c
new file mode 100644
index 0000000..f9b280b
--- /dev/null
+++ b/src/expr.c
@@ -0,0 +1,7016 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains routines used for analyzing expressions and
+** for generating VDBE code that evaluates expressions in SQLite.
+*/
+#include "sqliteInt.h"
+
+/* Forward declarations */
+static void exprCodeBetween(Parse*,Expr*,int,void(*)(Parse*,Expr*,int,int),int);
+static int exprCodeVector(Parse *pParse, Expr *p, int *piToFree);
+
+/*
+** Return the affinity character for a single column of a table.
+*/
+char sqlite3TableColumnAffinity(const Table *pTab, int iCol){
+  if( iCol<0 || NEVER(iCol>=pTab->nCol) ) return SQLITE_AFF_INTEGER;
+  return pTab->aCol[iCol].affinity;
+}
+
+/*
+** Return the 'affinity' of the expression pExpr if any.
+**
+** If pExpr is a column, a reference to a column via an 'AS' alias,
+** or a sub-select with a column as the return value, then the
+** affinity of that column is returned. Otherwise, 0x00 is returned,
+** indicating no affinity for the expression.
+**
+** i.e. the WHERE clause expressions in the following statements all
+** have an affinity:
+**
+** CREATE TABLE t1(a);
+** SELECT * FROM t1 WHERE a;
+** SELECT a AS b FROM t1 WHERE b;
+** SELECT * FROM t1 WHERE (select a from t1);
+*/
+char sqlite3ExprAffinity(const Expr *pExpr){
+  int op;
+  op = pExpr->op;
+  while( 1 /* exit-by-break */ ){
+    if( op==TK_COLUMN || (op==TK_AGG_COLUMN && pExpr->y.pTab!=0) ){
+      assert( ExprUseYTab(pExpr) );
+      assert( pExpr->y.pTab!=0 );
+      return sqlite3TableColumnAffinity(pExpr->y.pTab, pExpr->iColumn);
+    }
+    if( op==TK_SELECT ){
+      assert( ExprUseXSelect(pExpr) );
+      assert( pExpr->x.pSelect!=0 );
+      assert( pExpr->x.pSelect->pEList!=0 );
+      assert( pExpr->x.pSelect->pEList->a[0].pExpr!=0 );
+      return sqlite3ExprAffinity(pExpr->x.pSelect->pEList->a[0].pExpr);
+    }
+#ifndef SQLITE_OMIT_CAST
+    if( op==TK_CAST ){
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      return sqlite3AffinityType(pExpr->u.zToken, 0);
+    }
+#endif
+    if( op==TK_SELECT_COLUMN ){
+      assert( pExpr->pLeft!=0 && ExprUseXSelect(pExpr->pLeft) );
+      assert( pExpr->iColumn < pExpr->iTable );
+      assert( pExpr->iColumn >= 0 );
+      assert( pExpr->iTable==pExpr->pLeft->x.pSelect->pEList->nExpr );
+      return sqlite3ExprAffinity(
+          pExpr->pLeft->x.pSelect->pEList->a[pExpr->iColumn].pExpr
+      );
+    }
+    if( op==TK_VECTOR ){
+      assert( ExprUseXList(pExpr) );
+      return sqlite3ExprAffinity(pExpr->x.pList->a[0].pExpr);
+    }
+    if( ExprHasProperty(pExpr, EP_Skip|EP_IfNullRow) ){
+      assert( pExpr->op==TK_COLLATE
+           || pExpr->op==TK_IF_NULL_ROW
+           || (pExpr->op==TK_REGISTER && pExpr->op2==TK_IF_NULL_ROW) );
+      pExpr = pExpr->pLeft;
+      op = pExpr->op;
+      continue;
+    }
+    if( op!=TK_REGISTER || (op = pExpr->op2)==TK_REGISTER ) break;
+  }
+  return pExpr->affExpr;
+}
+
+/*
+** Make a guess at all the possible datatypes of the result that could
+** be returned by an expression.  Return a bitmask indicating the answer:
+**
+**     0x01         Numeric
+**     0x02         Text
+**     0x04         Blob
+**
+** If the expression must return NULL, then 0x00 is returned.
+*/
+int sqlite3ExprDataType(const Expr *pExpr){
+  while( pExpr ){
+    switch( pExpr->op ){
+      case TK_COLLATE:
+      case TK_IF_NULL_ROW:
+      case TK_UPLUS:  {
+        pExpr = pExpr->pLeft;
+        break;
+      }
+      case TK_NULL: {
+        pExpr = 0;
+        break;
+      }
+      case TK_STRING: {
+        return 0x02;
+      }
+      case TK_BLOB: {
+        return 0x04;
+      }
+      case TK_CONCAT: {
+        return 0x06;
+      }
+      case TK_VARIABLE:
+      case TK_AGG_FUNCTION:
+      case TK_FUNCTION: {
+        return 0x07;
+      }
+      case TK_COLUMN:
+      case TK_AGG_COLUMN:
+      case TK_SELECT:
+      case TK_CAST:
+      case TK_SELECT_COLUMN:
+      case TK_VECTOR:  {
+        int aff = sqlite3ExprAffinity(pExpr);
+        if( aff>=SQLITE_AFF_NUMERIC ) return 0x05;
+        if( aff==SQLITE_AFF_TEXT )    return 0x06;
+        return 0x07;
+      }
+      case TK_CASE: {
+        int res = 0;
+        int ii;
+        ExprList *pList = pExpr->x.pList;
+        assert( ExprUseXList(pExpr) && pList!=0 );
+        assert( pList->nExpr > 0);
+        for(ii=1; ii<pList->nExpr; ii+=2){
+          res |= sqlite3ExprDataType(pList->a[ii].pExpr);
+        }
+        if( pList->nExpr % 2 ){
+          res |= sqlite3ExprDataType(pList->a[pList->nExpr-1].pExpr);
+        }
+        return res;
+      }
+      default: {
+        return 0x01;
+      }
+    } /* End of switch(op) */
+  } /* End of while(pExpr) */
+  return 0x00;
+}
+
+/*
+** Set the collating sequence for expression pExpr to be the collating
+** sequence named by pToken.   Return a pointer to a new Expr node that
+** implements the COLLATE operator.
+**
+** If a memory allocation error occurs, that fact is recorded in pParse->db
+** and the pExpr parameter is returned unchanged.
+*/
+Expr *sqlite3ExprAddCollateToken(
+  const Parse *pParse,     /* Parsing context */
+  Expr *pExpr,             /* Add the "COLLATE" clause to this expression */
+  const Token *pCollName,  /* Name of collating sequence */
+  int dequote              /* True to dequote pCollName */
+){
+  if( pCollName->n>0 ){
+    Expr *pNew = sqlite3ExprAlloc(pParse->db, TK_COLLATE, pCollName, dequote);
+    if( pNew ){
+      pNew->pLeft = pExpr;
+      pNew->flags |= EP_Collate|EP_Skip;
+      pExpr = pNew;
+    }
+  }
+  return pExpr;
+}
+Expr *sqlite3ExprAddCollateString(
+  const Parse *pParse,  /* Parsing context */
+  Expr *pExpr,          /* Add the "COLLATE" clause to this expression */
+  const char *zC        /* The collating sequence name */
+){
+  Token s;
+  assert( zC!=0 );
+  sqlite3TokenInit(&s, (char*)zC);
+  return sqlite3ExprAddCollateToken(pParse, pExpr, &s, 0);
+}
+
+/*
+** Skip over any TK_COLLATE operators.
+*/
+Expr *sqlite3ExprSkipCollate(Expr *pExpr){
+  while( pExpr && ExprHasProperty(pExpr, EP_Skip) ){
+    assert( pExpr->op==TK_COLLATE );
+    pExpr = pExpr->pLeft;
+  }  
+  return pExpr;
+}
+
+/*
+** Skip over any TK_COLLATE operators and/or any unlikely()
+** or likelihood() or likely() functions at the root of an
+** expression.
+*/
+Expr *sqlite3ExprSkipCollateAndLikely(Expr *pExpr){
+  while( pExpr && ExprHasProperty(pExpr, EP_Skip|EP_Unlikely) ){
+    if( ExprHasProperty(pExpr, EP_Unlikely) ){
+      assert( ExprUseXList(pExpr) );
+      assert( pExpr->x.pList->nExpr>0 );
+      assert( pExpr->op==TK_FUNCTION );
+      pExpr = pExpr->x.pList->a[0].pExpr;
+    }else{
+      assert( pExpr->op==TK_COLLATE );
+      pExpr = pExpr->pLeft;
+    }
+  }  
+  return pExpr;
+}
+
+/*
+** Return the collation sequence for the expression pExpr. If
+** there is no defined collating sequence, return NULL.
+**
+** See also: sqlite3ExprNNCollSeq()
+**
+** The sqlite3ExprNNCollSeq() works the same exact that it returns the
+** default collation if pExpr has no defined collation.
+**
+** The collating sequence might be determined by a COLLATE operator
+** or by the presence of a column with a defined collating sequence.
+** COLLATE operators take first precedence.  Left operands take
+** precedence over right operands.
+*/
+CollSeq *sqlite3ExprCollSeq(Parse *pParse, const Expr *pExpr){
+  sqlite3 *db = pParse->db;
+  CollSeq *pColl = 0;
+  const Expr *p = pExpr;
+  while( p ){
+    int op = p->op;
+    if( op==TK_REGISTER ) op = p->op2;
+    if( (op==TK_AGG_COLUMN && p->y.pTab!=0)
+     || op==TK_COLUMN || op==TK_TRIGGER
+    ){
+      int j;
+      assert( ExprUseYTab(p) );
+      assert( p->y.pTab!=0 );
+      if( (j = p->iColumn)>=0 ){
+        const char *zColl = sqlite3ColumnColl(&p->y.pTab->aCol[j]);
+        pColl = sqlite3FindCollSeq(db, ENC(db), zColl, 0);
+      }
+      break;
+    }
+    if( op==TK_CAST || op==TK_UPLUS ){
+      p = p->pLeft;
+      continue;
+    }
+    if( op==TK_VECTOR ){
+      assert( ExprUseXList(p) );
+      p = p->x.pList->a[0].pExpr;
+      continue;
+    }
+    if( op==TK_COLLATE ){
+      assert( !ExprHasProperty(p, EP_IntValue) );
+      pColl = sqlite3GetCollSeq(pParse, ENC(db), 0, p->u.zToken);
+      break;
+    }
+    if( p->flags & EP_Collate ){
+      if( p->pLeft && (p->pLeft->flags & EP_Collate)!=0 ){
+        p = p->pLeft;
+      }else{
+        Expr *pNext  = p->pRight;
+        /* The Expr.x union is never used at the same time as Expr.pRight */
+        assert( !ExprUseXList(p) || p->x.pList==0 || p->pRight==0 );
+        if( ExprUseXList(p) && p->x.pList!=0 && !db->mallocFailed ){
+          int i;
+          for(i=0; i<p->x.pList->nExpr; i++){
+            if( ExprHasProperty(p->x.pList->a[i].pExpr, EP_Collate) ){
+              pNext = p->x.pList->a[i].pExpr;
+              break;
+            }
+          }
+        }
+        p = pNext;
+      }
+    }else{
+      break;
+    }
+  }
+  if( sqlite3CheckCollSeq(pParse, pColl) ){
+    pColl = 0;
+  }
+  return pColl;
+}
+
+/*
+** Return the collation sequence for the expression pExpr. If
+** there is no defined collating sequence, return a pointer to the
+** default collation sequence.
+**
+** See also: sqlite3ExprCollSeq()
+**
+** The sqlite3ExprCollSeq() routine works the same except that it
+** returns NULL if there is no defined collation.
+*/
+CollSeq *sqlite3ExprNNCollSeq(Parse *pParse, const Expr *pExpr){
+  CollSeq *p = sqlite3ExprCollSeq(pParse, pExpr);
+  if( p==0 ) p = pParse->db->pDfltColl;
+  assert( p!=0 );
+  return p;
+}
+
+/*
+** Return TRUE if the two expressions have equivalent collating sequences.
+*/
+int sqlite3ExprCollSeqMatch(Parse *pParse, const Expr *pE1, const Expr *pE2){
+  CollSeq *pColl1 = sqlite3ExprNNCollSeq(pParse, pE1);
+  CollSeq *pColl2 = sqlite3ExprNNCollSeq(pParse, pE2);
+  return sqlite3StrICmp(pColl1->zName, pColl2->zName)==0;
+}
+
+/*
+** pExpr is an operand of a comparison operator.  aff2 is the
+** type affinity of the other operand.  This routine returns the
+** type affinity that should be used for the comparison operator.
+*/
+char sqlite3CompareAffinity(const Expr *pExpr, char aff2){
+  char aff1 = sqlite3ExprAffinity(pExpr);
+  if( aff1>SQLITE_AFF_NONE && aff2>SQLITE_AFF_NONE ){
+    /* Both sides of the comparison are columns. If one has numeric
+    ** affinity, use that. Otherwise use no affinity.
+    */
+    if( sqlite3IsNumericAffinity(aff1) || sqlite3IsNumericAffinity(aff2) ){
+      return SQLITE_AFF_NUMERIC;
+    }else{
+      return SQLITE_AFF_BLOB;
+    }
+  }else{
+    /* One side is a column, the other is not. Use the columns affinity. */
+    assert( aff1<=SQLITE_AFF_NONE || aff2<=SQLITE_AFF_NONE );
+    return (aff1<=SQLITE_AFF_NONE ? aff2 : aff1) | SQLITE_AFF_NONE;
+  }
+}
+
+/*
+** pExpr is a comparison operator.  Return the type affinity that should
+** be applied to both operands prior to doing the comparison.
+*/
+static char comparisonAffinity(const Expr *pExpr){
+  char aff;
+  assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||
+          pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||
+          pExpr->op==TK_NE || pExpr->op==TK_IS || pExpr->op==TK_ISNOT );
+  assert( pExpr->pLeft );
+  aff = sqlite3ExprAffinity(pExpr->pLeft);
+  if( pExpr->pRight ){
+    aff = sqlite3CompareAffinity(pExpr->pRight, aff);
+  }else if( ExprUseXSelect(pExpr) ){
+    aff = sqlite3CompareAffinity(pExpr->x.pSelect->pEList->a[0].pExpr, aff);
+  }else if( aff==0 ){
+    aff = SQLITE_AFF_BLOB;
+  }
+  return aff;
+}
+
+/*
+** pExpr is a comparison expression, eg. '=', '<', IN(...) etc.
+** idx_affinity is the affinity of an indexed column. Return true
+** if the index with affinity idx_affinity may be used to implement
+** the comparison in pExpr.
+*/
+int sqlite3IndexAffinityOk(const Expr *pExpr, char idx_affinity){
+  char aff = comparisonAffinity(pExpr);
+  if( aff<SQLITE_AFF_TEXT ){
+    return 1;
+  }
+  if( aff==SQLITE_AFF_TEXT ){
+    return idx_affinity==SQLITE_AFF_TEXT;
+  }
+  return sqlite3IsNumericAffinity(idx_affinity);
+}
+
+/*
+** Return the P5 value that should be used for a binary comparison
+** opcode (OP_Eq, OP_Ge etc.) used to compare pExpr1 and pExpr2.
+*/
+static u8 binaryCompareP5(
+  const Expr *pExpr1,   /* Left operand */
+  const Expr *pExpr2,   /* Right operand */
+  int jumpIfNull        /* Extra flags added to P5 */
+){
+  u8 aff = (char)sqlite3ExprAffinity(pExpr2);
+  aff = (u8)sqlite3CompareAffinity(pExpr1, aff) | (u8)jumpIfNull;
+  return aff;
+}
+
+/*
+** Return a pointer to the collation sequence that should be used by
+** a binary comparison operator comparing pLeft and pRight.
+**
+** If the left hand expression has a collating sequence type, then it is
+** used. Otherwise the collation sequence for the right hand expression
+** is used, or the default (BINARY) if neither expression has a collating
+** type.
+**
+** Argument pRight (but not pLeft) may be a null pointer. In this case,
+** it is not considered.
+*/
+CollSeq *sqlite3BinaryCompareCollSeq(
+  Parse *pParse,
+  const Expr *pLeft,
+  const Expr *pRight
+){
+  CollSeq *pColl;
+  assert( pLeft );
+  if( pLeft->flags & EP_Collate ){
+    pColl = sqlite3ExprCollSeq(pParse, pLeft);
+  }else if( pRight && (pRight->flags & EP_Collate)!=0 ){
+    pColl = sqlite3ExprCollSeq(pParse, pRight);
+  }else{
+    pColl = sqlite3ExprCollSeq(pParse, pLeft);
+    if( !pColl ){
+      pColl = sqlite3ExprCollSeq(pParse, pRight);
+    }
+  }
+  return pColl;
+}
+
+/* Expression p is a comparison operator.  Return a collation sequence
+** appropriate for the comparison operator.
+**
+** This is normally just a wrapper around sqlite3BinaryCompareCollSeq().
+** However, if the OP_Commuted flag is set, then the order of the operands
+** is reversed in the sqlite3BinaryCompareCollSeq() call so that the
+** correct collating sequence is found.
+*/
+CollSeq *sqlite3ExprCompareCollSeq(Parse *pParse, const Expr *p){
+  if( ExprHasProperty(p, EP_Commuted) ){
+    return sqlite3BinaryCompareCollSeq(pParse, p->pRight, p->pLeft);
+  }else{
+    return sqlite3BinaryCompareCollSeq(pParse, p->pLeft, p->pRight);
+  }
+}
+
+/*
+** Generate code for a comparison operator.
+*/
+static int codeCompare(
+  Parse *pParse,    /* The parsing (and code generating) context */
+  Expr *pLeft,      /* The left operand */
+  Expr *pRight,     /* The right operand */
+  int opcode,       /* The comparison opcode */
+  int in1, int in2, /* Register holding operands */
+  int dest,         /* Jump here if true.  */
+  int jumpIfNull,   /* If true, jump if either operand is NULL */
+  int isCommuted    /* The comparison has been commuted */
+){
+  int p5;
+  int addr;
+  CollSeq *p4;
+
+  if( pParse->nErr ) return 0;
+  if( isCommuted ){
+    p4 = sqlite3BinaryCompareCollSeq(pParse, pRight, pLeft);
+  }else{
+    p4 = sqlite3BinaryCompareCollSeq(pParse, pLeft, pRight);
+  }
+  p5 = binaryCompareP5(pLeft, pRight, jumpIfNull);
+  addr = sqlite3VdbeAddOp4(pParse->pVdbe, opcode, in2, dest, in1,
+                           (void*)p4, P4_COLLSEQ);
+  sqlite3VdbeChangeP5(pParse->pVdbe, (u8)p5);
+  return addr;
+}
+
+/*
+** Return true if expression pExpr is a vector, or false otherwise.
+**
+** A vector is defined as any expression that results in two or more
+** columns of result.  Every TK_VECTOR node is an vector because the
+** parser will not generate a TK_VECTOR with fewer than two entries.
+** But a TK_SELECT might be either a vector or a scalar. It is only
+** considered a vector if it has two or more result columns.
+*/
+int sqlite3ExprIsVector(const Expr *pExpr){
+  return sqlite3ExprVectorSize(pExpr)>1;
+}
+
+/*
+** If the expression passed as the only argument is of type TK_VECTOR
+** return the number of expressions in the vector. Or, if the expression
+** is a sub-select, return the number of columns in the sub-select. For
+** any other type of expression, return 1.
+*/
+int sqlite3ExprVectorSize(const Expr *pExpr){
+  u8 op = pExpr->op;
+  if( op==TK_REGISTER ) op = pExpr->op2;
+  if( op==TK_VECTOR ){
+    assert( ExprUseXList(pExpr) );
+    return pExpr->x.pList->nExpr;
+  }else if( op==TK_SELECT ){
+    assert( ExprUseXSelect(pExpr) );
+    return pExpr->x.pSelect->pEList->nExpr;
+  }else{
+    return 1;
+  }
+}
+
+/*
+** Return a pointer to a subexpression of pVector that is the i-th
+** column of the vector (numbered starting with 0).  The caller must
+** ensure that i is within range.
+**
+** If pVector is really a scalar (and "scalar" here includes subqueries
+** that return a single column!) then return pVector unmodified.
+**
+** pVector retains ownership of the returned subexpression.
+**
+** If the vector is a (SELECT ...) then the expression returned is
+** just the expression for the i-th term of the result set, and may
+** not be ready for evaluation because the table cursor has not yet
+** been positioned.
+*/
+Expr *sqlite3VectorFieldSubexpr(Expr *pVector, int i){
+  assert( i<sqlite3ExprVectorSize(pVector) || pVector->op==TK_ERROR );
+  if( sqlite3ExprIsVector(pVector) ){
+    assert( pVector->op2==0 || pVector->op==TK_REGISTER );
+    if( pVector->op==TK_SELECT || pVector->op2==TK_SELECT ){
+      assert( ExprUseXSelect(pVector) );
+      return pVector->x.pSelect->pEList->a[i].pExpr;
+    }else{
+      assert( ExprUseXList(pVector) );
+      return pVector->x.pList->a[i].pExpr;
+    }
+  }
+  return pVector;
+}
+
+/*
+** Compute and return a new Expr object which when passed to
+** sqlite3ExprCode() will generate all necessary code to compute
+** the iField-th column of the vector expression pVector.
+**
+** It is ok for pVector to be a scalar (as long as iField==0). 
+** In that case, this routine works like sqlite3ExprDup().
+**
+** The caller owns the returned Expr object and is responsible for
+** ensuring that the returned value eventually gets freed.
+**
+** The caller retains ownership of pVector.  If pVector is a TK_SELECT,
+** then the returned object will reference pVector and so pVector must remain
+** valid for the life of the returned object.  If pVector is a TK_VECTOR
+** or a scalar expression, then it can be deleted as soon as this routine
+** returns.
+**
+** A trick to cause a TK_SELECT pVector to be deleted together with
+** the returned Expr object is to attach the pVector to the pRight field
+** of the returned TK_SELECT_COLUMN Expr object.
+*/
+Expr *sqlite3ExprForVectorField(
+  Parse *pParse,       /* Parsing context */
+  Expr *pVector,       /* The vector.  List of expressions or a sub-SELECT */
+  int iField,          /* Which column of the vector to return */
+  int nField           /* Total number of columns in the vector */
+){
+  Expr *pRet;
+  if( pVector->op==TK_SELECT ){
+    assert( ExprUseXSelect(pVector) );
+    /* The TK_SELECT_COLUMN Expr node:
+    **
+    ** pLeft:           pVector containing TK_SELECT.  Not deleted.
+    ** pRight:          not used.  But recursively deleted.
+    ** iColumn:         Index of a column in pVector
+    ** iTable:          0 or the number of columns on the LHS of an assignment
+    ** pLeft->iTable:   First in an array of register holding result, or 0
+    **                  if the result is not yet computed.
+    **
+    ** sqlite3ExprDelete() specifically skips the recursive delete of
+    ** pLeft on TK_SELECT_COLUMN nodes.  But pRight is followed, so pVector
+    ** can be attached to pRight to cause this node to take ownership of
+    ** pVector.  Typically there will be multiple TK_SELECT_COLUMN nodes
+    ** with the same pLeft pointer to the pVector, but only one of them
+    ** will own the pVector.
+    */
+    pRet = sqlite3PExpr(pParse, TK_SELECT_COLUMN, 0, 0);
+    if( pRet ){
+      ExprSetProperty(pRet, EP_FullSize);
+      pRet->iTable = nField;
+      pRet->iColumn = iField;
+      pRet->pLeft = pVector;
+    }
+  }else{
+    if( pVector->op==TK_VECTOR ){
+      Expr **ppVector;
+      assert( ExprUseXList(pVector) );
+      ppVector = &pVector->x.pList->a[iField].pExpr;
+      pVector = *ppVector;
+      if( IN_RENAME_OBJECT ){
+        /* This must be a vector UPDATE inside a trigger */
+        *ppVector = 0;
+        return pVector;
+      }
+    }
+    pRet = sqlite3ExprDup(pParse->db, pVector, 0);
+  }
+  return pRet;
+}
+
+/*
+** If expression pExpr is of type TK_SELECT, generate code to evaluate
+** it. Return the register in which the result is stored (or, if the
+** sub-select returns more than one column, the first in an array
+** of registers in which the result is stored).
+**
+** If pExpr is not a TK_SELECT expression, return 0.
+*/
+static int exprCodeSubselect(Parse *pParse, Expr *pExpr){
+  int reg = 0;
+#ifndef SQLITE_OMIT_SUBQUERY
+  if( pExpr->op==TK_SELECT ){
+    reg = sqlite3CodeSubselect(pParse, pExpr);
+  }
+#endif
+  return reg;
+}
+
+/*
+** Argument pVector points to a vector expression - either a TK_VECTOR
+** or TK_SELECT that returns more than one column. This function returns
+** the register number of a register that contains the value of
+** element iField of the vector.
+**
+** If pVector is a TK_SELECT expression, then code for it must have
+** already been generated using the exprCodeSubselect() routine. In this
+** case parameter regSelect should be the first in an array of registers
+** containing the results of the sub-select.
+**
+** If pVector is of type TK_VECTOR, then code for the requested field
+** is generated. In this case (*pRegFree) may be set to the number of
+** a temporary register to be freed by the caller before returning.
+**
+** Before returning, output parameter (*ppExpr) is set to point to the
+** Expr object corresponding to element iElem of the vector.
+*/
+static int exprVectorRegister(
+  Parse *pParse,                  /* Parse context */
+  Expr *pVector,                  /* Vector to extract element from */
+  int iField,                     /* Field to extract from pVector */
+  int regSelect,                  /* First in array of registers */
+  Expr **ppExpr,                  /* OUT: Expression element */
+  int *pRegFree                   /* OUT: Temp register to free */
+){
+  u8 op = pVector->op;
+  assert( op==TK_VECTOR || op==TK_REGISTER || op==TK_SELECT || op==TK_ERROR );
+  if( op==TK_REGISTER ){
+    *ppExpr = sqlite3VectorFieldSubexpr(pVector, iField);
+    return pVector->iTable+iField;
+  }
+  if( op==TK_SELECT ){
+    assert( ExprUseXSelect(pVector) );
+    *ppExpr = pVector->x.pSelect->pEList->a[iField].pExpr;
+     return regSelect+iField;
+  }
+  if( op==TK_VECTOR ){
+    assert( ExprUseXList(pVector) );
+    *ppExpr = pVector->x.pList->a[iField].pExpr;
+    return sqlite3ExprCodeTemp(pParse, *ppExpr, pRegFree);
+  }
+  return 0;
+}
+
+/*
+** Expression pExpr is a comparison between two vector values. Compute
+** the result of the comparison (1, 0, or NULL) and write that
+** result into register dest.
+**
+** The caller must satisfy the following preconditions:
+**
+**    if pExpr->op==TK_IS:      op==TK_EQ and p5==SQLITE_NULLEQ
+**    if pExpr->op==TK_ISNOT:   op==TK_NE and p5==SQLITE_NULLEQ
+**    otherwise:                op==pExpr->op and p5==0
+*/
+static void codeVectorCompare(
+  Parse *pParse,        /* Code generator context */
+  Expr *pExpr,          /* The comparison operation */
+  int dest,             /* Write results into this register */
+  u8 op,                /* Comparison operator */
+  u8 p5                 /* SQLITE_NULLEQ or zero */
+){
+  Vdbe *v = pParse->pVdbe;
+  Expr *pLeft = pExpr->pLeft;
+  Expr *pRight = pExpr->pRight;
+  int nLeft = sqlite3ExprVectorSize(pLeft);
+  int i;
+  int regLeft = 0;
+  int regRight = 0;
+  u8 opx = op;
+  int addrCmp = 0;
+  int addrDone = sqlite3VdbeMakeLabel(pParse);
+  int isCommuted = ExprHasProperty(pExpr,EP_Commuted);
+
+  assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );
+  if( pParse->nErr ) return;
+  if( nLeft!=sqlite3ExprVectorSize(pRight) ){
+    sqlite3ErrorMsg(pParse, "row value misused");
+    return;
+  }
+  assert( pExpr->op==TK_EQ || pExpr->op==TK_NE
+       || pExpr->op==TK_IS || pExpr->op==TK_ISNOT
+       || pExpr->op==TK_LT || pExpr->op==TK_GT
+       || pExpr->op==TK_LE || pExpr->op==TK_GE
+  );
+  assert( pExpr->op==op || (pExpr->op==TK_IS && op==TK_EQ)
+            || (pExpr->op==TK_ISNOT && op==TK_NE) );
+  assert( p5==0 || pExpr->op!=op );
+  assert( p5==SQLITE_NULLEQ || pExpr->op==op );
+
+  if( op==TK_LE ) opx = TK_LT;
+  if( op==TK_GE ) opx = TK_GT;
+  if( op==TK_NE ) opx = TK_EQ;
+
+  regLeft = exprCodeSubselect(pParse, pLeft);
+  regRight = exprCodeSubselect(pParse, pRight);
+
+  sqlite3VdbeAddOp2(v, OP_Integer, 1, dest);
+  for(i=0; 1 /*Loop exits by "break"*/; i++){
+    int regFree1 = 0, regFree2 = 0;
+    Expr *pL = 0, *pR = 0;
+    int r1, r2;
+    assert( i>=0 && i<nLeft );
+    if( addrCmp ) sqlite3VdbeJumpHere(v, addrCmp);
+    r1 = exprVectorRegister(pParse, pLeft, i, regLeft, &pL, &regFree1);
+    r2 = exprVectorRegister(pParse, pRight, i, regRight, &pR, &regFree2);
+    addrCmp = sqlite3VdbeCurrentAddr(v);
+    codeCompare(pParse, pL, pR, opx, r1, r2, addrDone, p5, isCommuted);
+    testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
+    testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
+    testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
+    testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
+    testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
+    testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);
+    sqlite3ReleaseTempReg(pParse, regFree1);
+    sqlite3ReleaseTempReg(pParse, regFree2);
+    if( (opx==TK_LT || opx==TK_GT) && i<nLeft-1 ){
+      addrCmp = sqlite3VdbeAddOp0(v, OP_ElseEq);
+      testcase(opx==TK_LT); VdbeCoverageIf(v,opx==TK_LT);
+      testcase(opx==TK_GT); VdbeCoverageIf(v,opx==TK_GT);
+    }
+    if( p5==SQLITE_NULLEQ ){
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, dest);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_ZeroOrNull, r1, dest, r2);
+    }
+    if( i==nLeft-1 ){
+      break;
+    }
+    if( opx==TK_EQ ){
+      sqlite3VdbeAddOp2(v, OP_NotNull, dest, addrDone); VdbeCoverage(v);
+    }else{
+      assert( op==TK_LT || op==TK_GT || op==TK_LE || op==TK_GE );
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrDone);
+      if( i==nLeft-2 ) opx = op;
+    }
+  }
+  sqlite3VdbeJumpHere(v, addrCmp);
+  sqlite3VdbeResolveLabel(v, addrDone);
+  if( op==TK_NE ){
+    sqlite3VdbeAddOp2(v, OP_Not, dest, dest);
+  }
+}
+
+#if SQLITE_MAX_EXPR_DEPTH>0
+/*
+** Check that argument nHeight is less than or equal to the maximum
+** expression depth allowed. If it is not, leave an error message in
+** pParse.
+*/
+int sqlite3ExprCheckHeight(Parse *pParse, int nHeight){
+  int rc = SQLITE_OK;
+  int mxHeight = pParse->db->aLimit[SQLITE_LIMIT_EXPR_DEPTH];
+  if( nHeight>mxHeight ){
+    sqlite3ErrorMsg(pParse,
+       "Expression tree is too large (maximum depth %d)", mxHeight
+    );
+    rc = SQLITE_ERROR;
+  }
+  return rc;
+}
+
+/* The following three functions, heightOfExpr(), heightOfExprList()
+** and heightOfSelect(), are used to determine the maximum height
+** of any expression tree referenced by the structure passed as the
+** first argument.
+**
+** If this maximum height is greater than the current value pointed
+** to by pnHeight, the second parameter, then set *pnHeight to that
+** value.
+*/
+static void heightOfExpr(const Expr *p, int *pnHeight){
+  if( p ){
+    if( p->nHeight>*pnHeight ){
+      *pnHeight = p->nHeight;
+    }
+  }
+}
+static void heightOfExprList(const ExprList *p, int *pnHeight){
+  if( p ){
+    int i;
+    for(i=0; i<p->nExpr; i++){
+      heightOfExpr(p->a[i].pExpr, pnHeight);
+    }
+  }
+}
+static void heightOfSelect(const Select *pSelect, int *pnHeight){
+  const Select *p;
+  for(p=pSelect; p; p=p->pPrior){
+    heightOfExpr(p->pWhere, pnHeight);
+    heightOfExpr(p->pHaving, pnHeight);
+    heightOfExpr(p->pLimit, pnHeight);
+    heightOfExprList(p->pEList, pnHeight);
+    heightOfExprList(p->pGroupBy, pnHeight);
+    heightOfExprList(p->pOrderBy, pnHeight);
+  }
+}
+
+/*
+** Set the Expr.nHeight variable in the structure passed as an
+** argument. An expression with no children, Expr.pList or
+** Expr.pSelect member has a height of 1. Any other expression
+** has a height equal to the maximum height of any other
+** referenced Expr plus one.
+**
+** Also propagate EP_Propagate flags up from Expr.x.pList to Expr.flags,
+** if appropriate.
+*/
+static void exprSetHeight(Expr *p){
+  int nHeight = p->pLeft ? p->pLeft->nHeight : 0;
+  if( NEVER(p->pRight) && p->pRight->nHeight>nHeight ){
+    nHeight = p->pRight->nHeight;
+  }
+  if( ExprUseXSelect(p) ){
+    heightOfSelect(p->x.pSelect, &nHeight);
+  }else if( p->x.pList ){
+    heightOfExprList(p->x.pList, &nHeight);
+    p->flags |= EP_Propagate & sqlite3ExprListFlags(p->x.pList);
+  }
+  p->nHeight = nHeight + 1;
+}
+
+/*
+** Set the Expr.nHeight variable using the exprSetHeight() function. If
+** the height is greater than the maximum allowed expression depth,
+** leave an error in pParse.
+**
+** Also propagate all EP_Propagate flags from the Expr.x.pList into
+** Expr.flags.
+*/
+void sqlite3ExprSetHeightAndFlags(Parse *pParse, Expr *p){
+  if( pParse->nErr ) return;
+  exprSetHeight(p);
+  sqlite3ExprCheckHeight(pParse, p->nHeight);
+}
+
+/*
+** Return the maximum height of any expression tree referenced
+** by the select statement passed as an argument.
+*/
+int sqlite3SelectExprHeight(const Select *p){
+  int nHeight = 0;
+  heightOfSelect(p, &nHeight);
+  return nHeight;
+}
+#else /* ABOVE:  Height enforcement enabled.  BELOW: Height enforcement off */
+/*
+** Propagate all EP_Propagate flags from the Expr.x.pList into
+** Expr.flags.
+*/
+void sqlite3ExprSetHeightAndFlags(Parse *pParse, Expr *p){
+  if( pParse->nErr ) return;
+  if( p && ExprUseXList(p) && p->x.pList ){
+    p->flags |= EP_Propagate & sqlite3ExprListFlags(p->x.pList);
+  }
+}
+#define exprSetHeight(y)
+#endif /* SQLITE_MAX_EXPR_DEPTH>0 */
+
+/*
+** Set the error offset for an Expr node, if possible.
+*/
+void sqlite3ExprSetErrorOffset(Expr *pExpr, int iOfst){
+  if( pExpr==0 ) return;
+  if( NEVER(ExprUseWJoin(pExpr)) ) return;
+  pExpr->w.iOfst = iOfst;
+}
+
+/*
+** This routine is the core allocator for Expr nodes.
+**
+** Construct a new expression node and return a pointer to it.  Memory
+** for this node and for the pToken argument is a single allocation
+** obtained from sqlite3DbMalloc().  The calling function
+** is responsible for making sure the node eventually gets freed.
+**
+** If dequote is true, then the token (if it exists) is dequoted.
+** If dequote is false, no dequoting is performed.  The deQuote
+** parameter is ignored if pToken is NULL or if the token does not
+** appear to be quoted.  If the quotes were of the form "..." (double-quotes)
+** then the EP_DblQuoted flag is set on the expression node.
+**
+** Special case:  If op==TK_INTEGER and pToken points to a string that
+** can be translated into a 32-bit integer, then the token is not
+** stored in u.zToken.  Instead, the integer values is written
+** into u.iValue and the EP_IntValue flag is set.  No extra storage
+** is allocated to hold the integer text and the dequote flag is ignored.
+*/
+Expr *sqlite3ExprAlloc(
+  sqlite3 *db,            /* Handle for sqlite3DbMallocRawNN() */
+  int op,                 /* Expression opcode */
+  const Token *pToken,    /* Token argument.  Might be NULL */
+  int dequote             /* True to dequote */
+){
+  Expr *pNew;
+  int nExtra = 0;
+  int iValue = 0;
+
+  assert( db!=0 );
+  if( pToken ){
+    if( op!=TK_INTEGER || pToken->z==0
+          || sqlite3GetInt32(pToken->z, &iValue)==0 ){
+      nExtra = pToken->n+1;
+      assert( iValue>=0 );
+    }
+  }
+  pNew = sqlite3DbMallocRawNN(db, sizeof(Expr)+nExtra);
+  if( pNew ){
+    memset(pNew, 0, sizeof(Expr));
+    pNew->op = (u8)op;
+    pNew->iAgg = -1;
+    if( pToken ){
+      if( nExtra==0 ){
+        pNew->flags |= EP_IntValue|EP_Leaf|(iValue?EP_IsTrue:EP_IsFalse);
+        pNew->u.iValue = iValue;
+      }else{
+        pNew->u.zToken = (char*)&pNew[1];
+        assert( pToken->z!=0 || pToken->n==0 );
+        if( pToken->n ) memcpy(pNew->u.zToken, pToken->z, pToken->n);
+        pNew->u.zToken[pToken->n] = 0;
+        if( dequote && sqlite3Isquote(pNew->u.zToken[0]) ){
+          sqlite3DequoteExpr(pNew);
+        }
+      }
+    }
+#if SQLITE_MAX_EXPR_DEPTH>0
+    pNew->nHeight = 1;
+#endif 
+  }
+  return pNew;
+}
+
+/*
+** Allocate a new expression node from a zero-terminated token that has
+** already been dequoted.
+*/
+Expr *sqlite3Expr(
+  sqlite3 *db,            /* Handle for sqlite3DbMallocZero() (may be null) */
+  int op,                 /* Expression opcode */
+  const char *zToken      /* Token argument.  Might be NULL */
+){
+  Token x;
+  x.z = zToken;
+  x.n = sqlite3Strlen30(zToken);
+  return sqlite3ExprAlloc(db, op, &x, 0);
+}
+
+/*
+** Attach subtrees pLeft and pRight to the Expr node pRoot.
+**
+** If pRoot==NULL that means that a memory allocation error has occurred.
+** In that case, delete the subtrees pLeft and pRight.
+*/
+void sqlite3ExprAttachSubtrees(
+  sqlite3 *db,
+  Expr *pRoot,
+  Expr *pLeft,
+  Expr *pRight
+){
+  if( pRoot==0 ){
+    assert( db->mallocFailed );
+    sqlite3ExprDelete(db, pLeft);
+    sqlite3ExprDelete(db, pRight);
+  }else{
+    assert( ExprUseXList(pRoot) );
+    assert( pRoot->x.pSelect==0 );
+    if( pRight ){
+      pRoot->pRight = pRight;
+      pRoot->flags |= EP_Propagate & pRight->flags;
+#if SQLITE_MAX_EXPR_DEPTH>0
+      pRoot->nHeight = pRight->nHeight+1;
+    }else{
+      pRoot->nHeight = 1;
+#endif
+    }
+    if( pLeft ){
+      pRoot->pLeft = pLeft;
+      pRoot->flags |= EP_Propagate & pLeft->flags;
+#if SQLITE_MAX_EXPR_DEPTH>0
+      if( pLeft->nHeight>=pRoot->nHeight ){
+        pRoot->nHeight = pLeft->nHeight+1;
+      }
+#endif
+    }
+  }
+}
+
+/*
+** Allocate an Expr node which joins as many as two subtrees.
+**
+** One or both of the subtrees can be NULL.  Return a pointer to the new
+** Expr node.  Or, if an OOM error occurs, set pParse->db->mallocFailed,
+** free the subtrees and return NULL.
+*/
+Expr *sqlite3PExpr(
+  Parse *pParse,          /* Parsing context */
+  int op,                 /* Expression opcode */
+  Expr *pLeft,            /* Left operand */
+  Expr *pRight            /* Right operand */
+){
+  Expr *p;
+  p = sqlite3DbMallocRawNN(pParse->db, sizeof(Expr));
+  if( p ){
+    memset(p, 0, sizeof(Expr));
+    p->op = op & 0xff;
+    p->iAgg = -1;
+    sqlite3ExprAttachSubtrees(pParse->db, p, pLeft, pRight);
+    sqlite3ExprCheckHeight(pParse, p->nHeight);
+  }else{
+    sqlite3ExprDelete(pParse->db, pLeft);
+    sqlite3ExprDelete(pParse->db, pRight);
+  }
+  return p;
+}
+
+/*
+** Add pSelect to the Expr.x.pSelect field.  Or, if pExpr is NULL (due
+** do a memory allocation failure) then delete the pSelect object.
+*/
+void sqlite3PExprAddSelect(Parse *pParse, Expr *pExpr, Select *pSelect){
+  if( pExpr ){
+    pExpr->x.pSelect = pSelect;
+    ExprSetProperty(pExpr, EP_xIsSelect|EP_Subquery);
+    sqlite3ExprSetHeightAndFlags(pParse, pExpr);
+  }else{
+    assert( pParse->db->mallocFailed );
+    sqlite3SelectDelete(pParse->db, pSelect);
+  }
+}
+
+/*
+** Expression list pEList is a list of vector values. This function
+** converts the contents of pEList to a VALUES(...) Select statement
+** returning 1 row for each element of the list. For example, the
+** expression list:
+**
+**   ( (1,2), (3,4) (5,6) )
+**
+** is translated to the equivalent of:
+**
+**   VALUES(1,2), (3,4), (5,6)
+**
+** Each of the vector values in pEList must contain exactly nElem terms.
+** If a list element that is not a vector or does not contain nElem terms,
+** an error message is left in pParse.
+**
+** This is used as part of processing IN(...) expressions with a list
+** of vectors on the RHS. e.g. "... IN ((1,2), (3,4), (5,6))".
+*/
+Select *sqlite3ExprListToValues(Parse *pParse, int nElem, ExprList *pEList){
+  int ii;
+  Select *pRet = 0;
+  assert( nElem>1 );
+  for(ii=0; ii<pEList->nExpr; ii++){
+    Select *pSel;
+    Expr *pExpr = pEList->a[ii].pExpr;
+    int nExprElem;
+    if( pExpr->op==TK_VECTOR ){
+      assert( ExprUseXList(pExpr) );
+      nExprElem = pExpr->x.pList->nExpr;
+    }else{
+      nExprElem = 1;
+    }
+    if( nExprElem!=nElem ){
+      sqlite3ErrorMsg(pParse, "IN(...) element has %d term%s - expected %d",
+          nExprElem, nExprElem>1?"s":"", nElem
+      );
+      break;
+    }
+    assert( ExprUseXList(pExpr) );
+    pSel = sqlite3SelectNew(pParse, pExpr->x.pList, 0, 0, 0, 0, 0, SF_Values,0);
+    pExpr->x.pList = 0;
+    if( pSel ){
+      if( pRet ){
+        pSel->op = TK_ALL;
+        pSel->pPrior = pRet;
+      }
+      pRet = pSel;
+    }
+  }
+
+  if( pRet && pRet->pPrior ){
+    pRet->selFlags |= SF_MultiValue;
+  }
+  sqlite3ExprListDelete(pParse->db, pEList);
+  return pRet;
+}
+
+/*
+** Join two expressions using an AND operator.  If either expression is
+** NULL, then just return the other expression.
+**
+** If one side or the other of the AND is known to be false, and neither side
+** is part of an ON clause, then instead of returning an AND expression,
+** just return a constant expression with a value of false.
+*/
+Expr *sqlite3ExprAnd(Parse *pParse, Expr *pLeft, Expr *pRight){
+  sqlite3 *db = pParse->db;
+  if( pLeft==0  ){
+    return pRight;
+  }else if( pRight==0 ){
+    return pLeft;
+  }else{
+    u32 f = pLeft->flags | pRight->flags;
+    if( (f&(EP_OuterON|EP_InnerON|EP_IsFalse))==EP_IsFalse
+     && !IN_RENAME_OBJECT
+    ){
+      sqlite3ExprDeferredDelete(pParse, pLeft);
+      sqlite3ExprDeferredDelete(pParse, pRight);
+      return sqlite3Expr(db, TK_INTEGER, "0");
+    }else{
+      return sqlite3PExpr(pParse, TK_AND, pLeft, pRight);
+    }
+  }
+}
+
+/*
+** Construct a new expression node for a function with multiple
+** arguments.
+*/
+Expr *sqlite3ExprFunction(
+  Parse *pParse,        /* Parsing context */
+  ExprList *pList,      /* Argument list */
+  const Token *pToken,  /* Name of the function */
+  int eDistinct         /* SF_Distinct or SF_ALL or 0 */
+){
+  Expr *pNew;
+  sqlite3 *db = pParse->db;
+  assert( pToken );
+  pNew = sqlite3ExprAlloc(db, TK_FUNCTION, pToken, 1);
+  if( pNew==0 ){
+    sqlite3ExprListDelete(db, pList); /* Avoid memory leak when malloc fails */
+    return 0;
+  }
+  assert( !ExprHasProperty(pNew, EP_InnerON|EP_OuterON) );
+  pNew->w.iOfst = (int)(pToken->z - pParse->zTail);
+  if( pList
+   && pList->nExpr > pParse->db->aLimit[SQLITE_LIMIT_FUNCTION_ARG]
+   && !pParse->nested
+  ){
+    sqlite3ErrorMsg(pParse, "too many arguments on function %T", pToken);
+  }
+  pNew->x.pList = pList;
+  ExprSetProperty(pNew, EP_HasFunc);
+  assert( ExprUseXList(pNew) );
+  sqlite3ExprSetHeightAndFlags(pParse, pNew);
+  if( eDistinct==SF_Distinct ) ExprSetProperty(pNew, EP_Distinct);
+  return pNew;
+}
+
+/*
+** Report an error when attempting to use an ORDER BY clause within
+** the arguments of a non-aggregate function.
+*/
+void sqlite3ExprOrderByAggregateError(Parse *pParse, Expr *p){
+  sqlite3ErrorMsg(pParse,
+     "ORDER BY may not be used with non-aggregate %#T()", p
+  );
+}
+
+/*
+** Attach an ORDER BY clause to a function call.
+**
+**     functionname( arguments ORDER BY sortlist )
+**     \_____________________/          \______/
+**             pExpr                    pOrderBy
+**
+** The ORDER BY clause is inserted into a new Expr node of type TK_ORDER
+** and added to the Expr.pLeft field of the parent TK_FUNCTION node.
+*/
+void sqlite3ExprAddFunctionOrderBy(
+  Parse *pParse,        /* Parsing context */
+  Expr *pExpr,          /* The function call to which ORDER BY is to be added */
+  ExprList *pOrderBy    /* The ORDER BY clause to add */
+){
+  Expr *pOB;
+  sqlite3 *db = pParse->db;
+  if( NEVER(pOrderBy==0) ){
+    assert( db->mallocFailed );
+    return;
+  }
+  if( pExpr==0 ){
+    assert( db->mallocFailed );
+    sqlite3ExprListDelete(db, pOrderBy);
+    return;
+  }
+  assert( pExpr->op==TK_FUNCTION );
+  assert( pExpr->pLeft==0 );
+  assert( ExprUseXList(pExpr) );
+  if( pExpr->x.pList==0 || NEVER(pExpr->x.pList->nExpr==0) ){
+    /* Ignore ORDER BY on zero-argument aggregates */
+    sqlite3ParserAddCleanup(pParse, sqlite3ExprListDeleteGeneric, pOrderBy);
+    return;
+  }
+  if( IsWindowFunc(pExpr) ){
+    sqlite3ExprOrderByAggregateError(pParse, pExpr);
+    sqlite3ExprListDelete(db, pOrderBy);
+    return;
+  }
+
+  pOB = sqlite3ExprAlloc(db, TK_ORDER, 0, 0);
+  if( pOB==0 ){
+    sqlite3ExprListDelete(db, pOrderBy);
+    return;
+  }
+  pOB->x.pList = pOrderBy;
+  assert( ExprUseXList(pOB) );
+  pExpr->pLeft = pOB;
+  ExprSetProperty(pOB, EP_FullSize);
+}
+
+/*
+** Check to see if a function is usable according to current access
+** rules:
+**
+**    SQLITE_FUNC_DIRECT    -     Only usable from top-level SQL
+**
+**    SQLITE_FUNC_UNSAFE    -     Usable if TRUSTED_SCHEMA or from
+**                                top-level SQL
+**
+** If the function is not usable, create an error.
+*/
+void sqlite3ExprFunctionUsable(
+  Parse *pParse,         /* Parsing and code generating context */
+  const Expr *pExpr,     /* The function invocation */
+  const FuncDef *pDef    /* The function being invoked */
+){
+  assert( !IN_RENAME_OBJECT );
+  assert( (pDef->funcFlags & (SQLITE_FUNC_DIRECT|SQLITE_FUNC_UNSAFE))!=0 );
+  if( ExprHasProperty(pExpr, EP_FromDDL) ){
+    if( (pDef->funcFlags & SQLITE_FUNC_DIRECT)!=0
+     || (pParse->db->flags & SQLITE_TrustedSchema)==0
+    ){
+      /* Functions prohibited in triggers and views if:
+      **     (1) tagged with SQLITE_DIRECTONLY
+      **     (2) not tagged with SQLITE_INNOCUOUS (which means it
+      **         is tagged with SQLITE_FUNC_UNSAFE) and
+      **         SQLITE_DBCONFIG_TRUSTED_SCHEMA is off (meaning
+      **         that the schema is possibly tainted).
+      */
+      sqlite3ErrorMsg(pParse, "unsafe use of %#T()", pExpr);
+    }
+  }
+}
+
+/*
+** Assign a variable number to an expression that encodes a wildcard
+** in the original SQL statement. 
+**
+** Wildcards consisting of a single "?" are assigned the next sequential
+** variable number.
+**
+** Wildcards of the form "?nnn" are assigned the number "nnn".  We make
+** sure "nnn" is not too big to avoid a denial of service attack when
+** the SQL statement comes from an external source.
+**
+** Wildcards of the form ":aaa", "@aaa", or "$aaa" are assigned the same number
+** as the previous instance of the same wildcard.  Or if this is the first
+** instance of the wildcard, the next sequential variable number is
+** assigned.
+*/
+void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr, u32 n){
+  sqlite3 *db = pParse->db;
+  const char *z;
+  ynVar x;
+
+  if( pExpr==0 ) return;
+  assert( !ExprHasProperty(pExpr, EP_IntValue|EP_Reduced|EP_TokenOnly) );
+  z = pExpr->u.zToken;
+  assert( z!=0 );
+  assert( z[0]!=0 );
+  assert( n==(u32)sqlite3Strlen30(z) );
+  if( z[1]==0 ){
+    /* Wildcard of the form "?".  Assign the next variable number */
+    assert( z[0]=='?' );
+    x = (ynVar)(++pParse->nVar);
+  }else{
+    int doAdd = 0;
+    if( z[0]=='?' ){
+      /* Wildcard of the form "?nnn".  Convert "nnn" to an integer and
+      ** use it as the variable number */
+      i64 i;
+      int bOk;
+      if( n==2 ){ /*OPTIMIZATION-IF-TRUE*/
+        i = z[1]-'0';  /* The common case of ?N for a single digit N */
+        bOk = 1;
+      }else{
+        bOk = 0==sqlite3Atoi64(&z[1], &i, n-1, SQLITE_UTF8);
+      }
+      testcase( i==0 );
+      testcase( i==1 );
+      testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]-1 );
+      testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] );
+      if( bOk==0 || i<1 || i>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){
+        sqlite3ErrorMsg(pParse, "variable number must be between ?1 and ?%d",
+            db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]);
+        sqlite3RecordErrorOffsetOfExpr(pParse->db, pExpr);
+        return;
+      }
+      x = (ynVar)i;
+      if( x>pParse->nVar ){
+        pParse->nVar = (int)x;
+        doAdd = 1;
+      }else if( sqlite3VListNumToName(pParse->pVList, x)==0 ){
+        doAdd = 1;
+      }
+    }else{
+      /* Wildcards like ":aaa", "$aaa" or "@aaa".  Reuse the same variable
+      ** number as the prior appearance of the same name, or if the name
+      ** has never appeared before, reuse the same variable number
+      */
+      x = (ynVar)sqlite3VListNameToNum(pParse->pVList, z, n);
+      if( x==0 ){
+        x = (ynVar)(++pParse->nVar);
+        doAdd = 1;
+      }
+    }
+    if( doAdd ){
+      pParse->pVList = sqlite3VListAdd(db, pParse->pVList, z, n, x);
+    }
+  }
+  pExpr->iColumn = x;
+  if( x>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){
+    sqlite3ErrorMsg(pParse, "too many SQL variables");
+    sqlite3RecordErrorOffsetOfExpr(pParse->db, pExpr);
+  }
+}
+
+/*
+** Recursively delete an expression tree.
+*/
+static SQLITE_NOINLINE void sqlite3ExprDeleteNN(sqlite3 *db, Expr *p){
+  assert( p!=0 );
+  assert( db!=0 );
+  assert( !ExprUseUValue(p) || p->u.iValue>=0 );
+  assert( !ExprUseYWin(p) || !ExprUseYSub(p) );
+  assert( !ExprUseYWin(p) || p->y.pWin!=0 || db->mallocFailed );
+  assert( p->op!=TK_FUNCTION || !ExprUseYSub(p) );
+#ifdef SQLITE_DEBUG
+  if( ExprHasProperty(p, EP_Leaf) && !ExprHasProperty(p, EP_TokenOnly) ){
+    assert( p->pLeft==0 );
+    assert( p->pRight==0 );
+    assert( !ExprUseXSelect(p) || p->x.pSelect==0 );
+    assert( !ExprUseXList(p) || p->x.pList==0 );
+  }
+#endif
+  if( !ExprHasProperty(p, (EP_TokenOnly|EP_Leaf)) ){
+    /* The Expr.x union is never used at the same time as Expr.pRight */
+    assert( (ExprUseXList(p) && p->x.pList==0) || p->pRight==0 );
+    if( p->pLeft && p->op!=TK_SELECT_COLUMN ) sqlite3ExprDeleteNN(db, p->pLeft);
+    if( p->pRight ){
+      assert( !ExprHasProperty(p, EP_WinFunc) );
+      sqlite3ExprDeleteNN(db, p->pRight);
+    }else if( ExprUseXSelect(p) ){
+      assert( !ExprHasProperty(p, EP_WinFunc) );
+      sqlite3SelectDelete(db, p->x.pSelect);
+    }else{
+      sqlite3ExprListDelete(db, p->x.pList);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      if( ExprHasProperty(p, EP_WinFunc) ){
+        sqlite3WindowDelete(db, p->y.pWin);
+      }
+#endif
+    }
+  }
+  if( !ExprHasProperty(p, EP_Static) ){
+    sqlite3DbNNFreeNN(db, p);
+  }
+}
+void sqlite3ExprDelete(sqlite3 *db, Expr *p){
+  if( p ) sqlite3ExprDeleteNN(db, p);
+}
+void sqlite3ExprDeleteGeneric(sqlite3 *db, void *p){
+  if( ALWAYS(p) ) sqlite3ExprDeleteNN(db, (Expr*)p);
+}
+
+/*
+** Clear both elements of an OnOrUsing object
+*/
+void sqlite3ClearOnOrUsing(sqlite3 *db, OnOrUsing *p){
+  if( p==0 ){
+    /* Nothing to clear */
+  }else if( p->pOn ){
+    sqlite3ExprDeleteNN(db, p->pOn);
+  }else if( p->pUsing ){
+    sqlite3IdListDelete(db, p->pUsing);
+  }
+}
+
+/*
+** Arrange to cause pExpr to be deleted when the pParse is deleted.
+** This is similar to sqlite3ExprDelete() except that the delete is
+** deferred until the pParse is deleted.
+**
+** The pExpr might be deleted immediately on an OOM error.
+**
+** The deferred delete is (currently) implemented by adding the
+** pExpr to the pParse->pConstExpr list with a register number of 0.
+*/
+void sqlite3ExprDeferredDelete(Parse *pParse, Expr *pExpr){
+  sqlite3ParserAddCleanup(pParse, sqlite3ExprDeleteGeneric, pExpr);
+}
+
+/* Invoke sqlite3RenameExprUnmap() and sqlite3ExprDelete() on the
+** expression.
+*/
+void sqlite3ExprUnmapAndDelete(Parse *pParse, Expr *p){
+  if( p ){
+    if( IN_RENAME_OBJECT ){
+      sqlite3RenameExprUnmap(pParse, p);
+    }
+    sqlite3ExprDeleteNN(pParse->db, p);
+  }
+}
+
+/*
+** Return the number of bytes allocated for the expression structure
+** passed as the first argument. This is always one of EXPR_FULLSIZE,
+** EXPR_REDUCEDSIZE or EXPR_TOKENONLYSIZE.
+*/
+static int exprStructSize(const Expr *p){
+  if( ExprHasProperty(p, EP_TokenOnly) ) return EXPR_TOKENONLYSIZE;
+  if( ExprHasProperty(p, EP_Reduced) ) return EXPR_REDUCEDSIZE;
+  return EXPR_FULLSIZE;
+}
+
+/*
+** The dupedExpr*Size() routines each return the number of bytes required
+** to store a copy of an expression or expression tree.  They differ in
+** how much of the tree is measured.
+**
+**     dupedExprStructSize()     Size of only the Expr structure
+**     dupedExprNodeSize()       Size of Expr + space for token
+**     dupedExprSize()           Expr + token + subtree components
+**
+***************************************************************************
+**
+** The dupedExprStructSize() function returns two values OR-ed together: 
+** (1) the space required for a copy of the Expr structure only and
+** (2) the EP_xxx flags that indicate what the structure size should be.
+** The return values is always one of:
+**
+**      EXPR_FULLSIZE
+**      EXPR_REDUCEDSIZE   | EP_Reduced
+**      EXPR_TOKENONLYSIZE | EP_TokenOnly
+**
+** The size of the structure can be found by masking the return value
+** of this routine with 0xfff.  The flags can be found by masking the
+** return value with EP_Reduced|EP_TokenOnly.
+**
+** Note that with flags==EXPRDUP_REDUCE, this routines works on full-size
+** (unreduced) Expr objects as they or originally constructed by the parser.
+** During expression analysis, extra information is computed and moved into
+** later parts of the Expr object and that extra information might get chopped
+** off if the expression is reduced.  Note also that it does not work to
+** make an EXPRDUP_REDUCE copy of a reduced expression.  It is only legal
+** to reduce a pristine expression tree from the parser.  The implementation
+** of dupedExprStructSize() contain multiple assert() statements that attempt
+** to enforce this constraint.
+*/
+static int dupedExprStructSize(const Expr *p, int flags){
+  int nSize;
+  assert( flags==EXPRDUP_REDUCE || flags==0 ); /* Only one flag value allowed */
+  assert( EXPR_FULLSIZE<=0xfff );
+  assert( (0xfff & (EP_Reduced|EP_TokenOnly))==0 );
+  if( 0==flags || ExprHasProperty(p, EP_FullSize) ){
+    nSize = EXPR_FULLSIZE;
+  }else{
+    assert( !ExprHasProperty(p, EP_TokenOnly|EP_Reduced) );
+    assert( !ExprHasProperty(p, EP_OuterON) );
+    assert( !ExprHasVVAProperty(p, EP_NoReduce) );
+    if( p->pLeft || p->x.pList ){
+      nSize = EXPR_REDUCEDSIZE | EP_Reduced;
+    }else{
+      assert( p->pRight==0 );
+      nSize = EXPR_TOKENONLYSIZE | EP_TokenOnly;
+    }
+  }
+  return nSize;
+}
+
+/*
+** This function returns the space in bytes required to store the copy
+** of the Expr structure and a copy of the Expr.u.zToken string (if that
+** string is defined.)
+*/
+static int dupedExprNodeSize(const Expr *p, int flags){
+  int nByte = dupedExprStructSize(p, flags) & 0xfff;
+  if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
+    nByte += sqlite3Strlen30NN(p->u.zToken)+1;
+  }
+  return ROUND8(nByte);
+}
+
+/*
+** Return the number of bytes required to create a duplicate of the
+** expression passed as the first argument.
+**
+** The value returned includes space to create a copy of the Expr struct
+** itself and the buffer referred to by Expr.u.zToken, if any.
+**
+** The return value includes space to duplicate all Expr nodes in the
+** tree formed by Expr.pLeft and Expr.pRight, but not any other
+** substructure such as Expr.x.pList, Expr.x.pSelect, and Expr.y.pWin.
+*/
+static int dupedExprSize(const Expr *p){
+  int nByte;
+  assert( p!=0 );
+  nByte = dupedExprNodeSize(p, EXPRDUP_REDUCE);
+  if( p->pLeft ) nByte += dupedExprSize(p->pLeft);
+  if( p->pRight ) nByte += dupedExprSize(p->pRight);
+  assert( nByte==ROUND8(nByte) );
+  return nByte;
+}
+
+/*
+** An EdupBuf is a memory allocation used to stored multiple Expr objects
+** together with their Expr.zToken content.  This is used to help implement
+** compression while doing sqlite3ExprDup().  The top-level Expr does the
+** allocation for itself and many of its decendents, then passes an instance
+** of the structure down into exprDup() so that they decendents can have
+** access to that memory.
+*/
+typedef struct EdupBuf EdupBuf;
+struct EdupBuf {
+  u8 *zAlloc;          /* Memory space available for storage */
+#ifdef SQLITE_DEBUG
+  u8 *zEnd;            /* First byte past the end of memory */
+#endif
+};
+
+/*
+** This function is similar to sqlite3ExprDup(), except that if pEdupBuf
+** is not NULL then it points to memory that can be used to store a copy
+** of the input Expr p together with its p->u.zToken (if any).  pEdupBuf
+** is updated with the new buffer tail prior to returning.
+*/
+static Expr *exprDup(
+  sqlite3 *db,          /* Database connection (for memory allocation) */
+  const Expr *p,        /* Expr tree to be duplicated */
+  int dupFlags,         /* EXPRDUP_REDUCE for compression.  0 if not */
+  EdupBuf *pEdupBuf     /* Preallocated storage space, or NULL */
+){
+  Expr *pNew;           /* Value to return */
+  EdupBuf sEdupBuf;     /* Memory space from which to build Expr object */
+  u32 staticFlag;       /* EP_Static if space not obtained from malloc */
+  int nToken = -1;       /* Space needed for p->u.zToken.  -1 means unknown */
+
+  assert( db!=0 );
+  assert( p );
+  assert( dupFlags==0 || dupFlags==EXPRDUP_REDUCE );
+  assert( pEdupBuf==0 || dupFlags==EXPRDUP_REDUCE );
+
+  /* Figure out where to write the new Expr structure. */
+  if( pEdupBuf ){
+    sEdupBuf.zAlloc = pEdupBuf->zAlloc;
+#ifdef SQLITE_DEBUG
+    sEdupBuf.zEnd = pEdupBuf->zEnd;
+#endif
+    staticFlag = EP_Static;
+    assert( sEdupBuf.zAlloc!=0 );
+    assert( dupFlags==EXPRDUP_REDUCE );
+  }else{
+    int nAlloc;
+    if( dupFlags ){
+      nAlloc = dupedExprSize(p);
+    }else if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
+      nToken = sqlite3Strlen30NN(p->u.zToken)+1;
+      nAlloc = ROUND8(EXPR_FULLSIZE + nToken);
+    }else{
+      nToken = 0;
+      nAlloc = ROUND8(EXPR_FULLSIZE);
+    }
+    assert( nAlloc==ROUND8(nAlloc) );
+    sEdupBuf.zAlloc = sqlite3DbMallocRawNN(db, nAlloc);
+#ifdef SQLITE_DEBUG
+    sEdupBuf.zEnd = sEdupBuf.zAlloc ? sEdupBuf.zAlloc+nAlloc : 0;
+#endif
+    
+    staticFlag = 0;
+  }
+  pNew = (Expr *)sEdupBuf.zAlloc;
+  assert( EIGHT_BYTE_ALIGNMENT(pNew) );
+
+  if( pNew ){
+    /* Set nNewSize to the size allocated for the structure pointed to
+    ** by pNew. This is either EXPR_FULLSIZE, EXPR_REDUCEDSIZE or
+    ** EXPR_TOKENONLYSIZE. nToken is set to the number of bytes consumed
+    ** by the copy of the p->u.zToken string (if any).
+    */
+    const unsigned nStructSize = dupedExprStructSize(p, dupFlags);
+    int nNewSize = nStructSize & 0xfff;
+    if( nToken<0 ){
+      if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
+        nToken = sqlite3Strlen30(p->u.zToken) + 1;
+      }else{
+        nToken = 0;
+      }
+    }
+    if( dupFlags ){
+      assert( (int)(sEdupBuf.zEnd - sEdupBuf.zAlloc) >= nNewSize+nToken );
+      assert( ExprHasProperty(p, EP_Reduced)==0 );
+      memcpy(sEdupBuf.zAlloc, p, nNewSize);
+    }else{
+      u32 nSize = (u32)exprStructSize(p);
+      assert( (int)(sEdupBuf.zEnd - sEdupBuf.zAlloc) >=
+                                                   (int)EXPR_FULLSIZE+nToken );
+      memcpy(sEdupBuf.zAlloc, p, nSize);
+      if( nSize<EXPR_FULLSIZE ){
+        memset(&sEdupBuf.zAlloc[nSize], 0, EXPR_FULLSIZE-nSize);
+      }
+      nNewSize = EXPR_FULLSIZE;
+    }
+
+    /* Set the EP_Reduced, EP_TokenOnly, and EP_Static flags appropriately. */
+    pNew->flags &= ~(EP_Reduced|EP_TokenOnly|EP_Static);
+    pNew->flags |= nStructSize & (EP_Reduced|EP_TokenOnly);
+    pNew->flags |= staticFlag;
+    ExprClearVVAProperties(pNew);
+    if( dupFlags ){
+      ExprSetVVAProperty(pNew, EP_Immutable);
+    }
+
+    /* Copy the p->u.zToken string, if any. */
+    assert( nToken>=0 );
+    if( nToken>0 ){
+      char *zToken = pNew->u.zToken = (char*)&sEdupBuf.zAlloc[nNewSize];
+      memcpy(zToken, p->u.zToken, nToken);
+      nNewSize += nToken;
+    }
+    sEdupBuf.zAlloc += ROUND8(nNewSize);
+
+    if( ((p->flags|pNew->flags)&(EP_TokenOnly|EP_Leaf))==0 ){
+
+      /* Fill in the pNew->x.pSelect or pNew->x.pList member. */
+      if( ExprUseXSelect(p) ){
+        pNew->x.pSelect = sqlite3SelectDup(db, p->x.pSelect, dupFlags);
+      }else{
+        pNew->x.pList = sqlite3ExprListDup(db, p->x.pList,
+                           p->op!=TK_ORDER ? dupFlags : 0);
+      }
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      if( ExprHasProperty(p, EP_WinFunc) ){
+        pNew->y.pWin = sqlite3WindowDup(db, pNew, p->y.pWin);
+        assert( ExprHasProperty(pNew, EP_WinFunc) );
+      }
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+      /* Fill in pNew->pLeft and pNew->pRight. */
+      if( dupFlags ){
+        if( p->op==TK_SELECT_COLUMN ){
+          pNew->pLeft = p->pLeft;
+          assert( p->pRight==0 
+               || p->pRight==p->pLeft
+               || ExprHasProperty(p->pLeft, EP_Subquery) );
+        }else{
+          pNew->pLeft = p->pLeft ?
+                      exprDup(db, p->pLeft, EXPRDUP_REDUCE, &sEdupBuf) : 0;
+        }
+        pNew->pRight = p->pRight ?
+                       exprDup(db, p->pRight, EXPRDUP_REDUCE, &sEdupBuf) : 0;
+      }else{
+        if( p->op==TK_SELECT_COLUMN ){
+          pNew->pLeft = p->pLeft;
+          assert( p->pRight==0 
+               || p->pRight==p->pLeft
+               || ExprHasProperty(p->pLeft, EP_Subquery) );
+        }else{
+          pNew->pLeft = sqlite3ExprDup(db, p->pLeft, 0);
+        }
+        pNew->pRight = sqlite3ExprDup(db, p->pRight, 0);
+      }
+    }
+  }
+  if( pEdupBuf ) memcpy(pEdupBuf, &sEdupBuf, sizeof(sEdupBuf));
+  assert( sEdupBuf.zAlloc <= sEdupBuf.zEnd );
+  return pNew;
+}
+
+/*
+** Create and return a deep copy of the object passed as the second
+** argument. If an OOM condition is encountered, NULL is returned
+** and the db->mallocFailed flag set.
+*/
+#ifndef SQLITE_OMIT_CTE
+With *sqlite3WithDup(sqlite3 *db, With *p){
+  With *pRet = 0;
+  if( p ){
+    sqlite3_int64 nByte = sizeof(*p) + sizeof(p->a[0]) * (p->nCte-1);
+    pRet = sqlite3DbMallocZero(db, nByte);
+    if( pRet ){
+      int i;
+      pRet->nCte = p->nCte;
+      for(i=0; i<p->nCte; i++){
+        pRet->a[i].pSelect = sqlite3SelectDup(db, p->a[i].pSelect, 0);
+        pRet->a[i].pCols = sqlite3ExprListDup(db, p->a[i].pCols, 0);
+        pRet->a[i].zName = sqlite3DbStrDup(db, p->a[i].zName);
+        pRet->a[i].eM10d = p->a[i].eM10d;
+      }
+    }
+  }
+  return pRet;
+}
+#else
+# define sqlite3WithDup(x,y) 0
+#endif
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+/*
+** The gatherSelectWindows() procedure and its helper routine
+** gatherSelectWindowsCallback() are used to scan all the expressions
+** an a newly duplicated SELECT statement and gather all of the Window
+** objects found there, assembling them onto the linked list at Select->pWin.
+*/
+static int gatherSelectWindowsCallback(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_FUNCTION && ExprHasProperty(pExpr, EP_WinFunc) ){
+    Select *pSelect = pWalker->u.pSelect;
+    Window *pWin = pExpr->y.pWin;
+    assert( pWin );
+    assert( IsWindowFunc(pExpr) );
+    assert( pWin->ppThis==0 );
+    sqlite3WindowLink(pSelect, pWin);
+  }
+  return WRC_Continue;
+}
+static int gatherSelectWindowsSelectCallback(Walker *pWalker, Select *p){
+  return p==pWalker->u.pSelect ? WRC_Continue : WRC_Prune;
+}
+static void gatherSelectWindows(Select *p){
+  Walker w;
+  w.xExprCallback = gatherSelectWindowsCallback;
+  w.xSelectCallback = gatherSelectWindowsSelectCallback;
+  w.xSelectCallback2 = 0;
+  w.pParse = 0;
+  w.u.pSelect = p;
+  sqlite3WalkSelect(&w, p);
+}
+#endif
+
+
+/*
+** The following group of routines make deep copies of expressions,
+** expression lists, ID lists, and select statements.  The copies can
+** be deleted (by being passed to their respective ...Delete() routines)
+** without effecting the originals.
+**
+** The expression list, ID, and source lists return by sqlite3ExprListDup(),
+** sqlite3IdListDup(), and sqlite3SrcListDup() can not be further expanded
+** by subsequent calls to sqlite*ListAppend() routines.
+**
+** Any tables that the SrcList might point to are not duplicated.
+**
+** The flags parameter contains a combination of the EXPRDUP_XXX flags.
+** If the EXPRDUP_REDUCE flag is set, then the structure returned is a
+** truncated version of the usual Expr structure that will be stored as
+** part of the in-memory representation of the database schema.
+*/
+Expr *sqlite3ExprDup(sqlite3 *db, const Expr *p, int flags){
+  assert( flags==0 || flags==EXPRDUP_REDUCE );
+  return p ? exprDup(db, p, flags, 0) : 0;
+}
+ExprList *sqlite3ExprListDup(sqlite3 *db, const ExprList *p, int flags){
+  ExprList *pNew;
+  struct ExprList_item *pItem;
+  const struct ExprList_item *pOldItem;
+  int i;
+  Expr *pPriorSelectColOld = 0;
+  Expr *pPriorSelectColNew = 0;
+  assert( db!=0 );
+  if( p==0 ) return 0;
+  pNew = sqlite3DbMallocRawNN(db, sqlite3DbMallocSize(db, p));
+  if( pNew==0 ) return 0;
+  pNew->nExpr = p->nExpr;
+  pNew->nAlloc = p->nAlloc;
+  pItem = pNew->a;
+  pOldItem = p->a;
+  for(i=0; i<p->nExpr; i++, pItem++, pOldItem++){
+    Expr *pOldExpr = pOldItem->pExpr;
+    Expr *pNewExpr;
+    pItem->pExpr = sqlite3ExprDup(db, pOldExpr, flags);
+    if( pOldExpr
+     && pOldExpr->op==TK_SELECT_COLUMN
+     && (pNewExpr = pItem->pExpr)!=0
+    ){
+      if( pNewExpr->pRight ){
+        pPriorSelectColOld = pOldExpr->pRight;
+        pPriorSelectColNew = pNewExpr->pRight;
+        pNewExpr->pLeft = pNewExpr->pRight;
+      }else{
+        if( pOldExpr->pLeft!=pPriorSelectColOld ){
+          pPriorSelectColOld = pOldExpr->pLeft;
+          pPriorSelectColNew = sqlite3ExprDup(db, pPriorSelectColOld, flags);
+          pNewExpr->pRight = pPriorSelectColNew;
+        }
+        pNewExpr->pLeft = pPriorSelectColNew;
+      }
+    }
+    pItem->zEName = sqlite3DbStrDup(db, pOldItem->zEName);
+    pItem->fg = pOldItem->fg;
+    pItem->fg.done = 0;
+    pItem->u = pOldItem->u;
+  }
+  return pNew;
+}
+
+/*
+** If cursors, triggers, views and subqueries are all omitted from
+** the build, then none of the following routines, except for
+** sqlite3SelectDup(), can be called. sqlite3SelectDup() is sometimes
+** called with a NULL argument.
+*/
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER) \
+ || !defined(SQLITE_OMIT_SUBQUERY)
+SrcList *sqlite3SrcListDup(sqlite3 *db, const SrcList *p, int flags){
+  SrcList *pNew;
+  int i;
+  int nByte;
+  assert( db!=0 );
+  if( p==0 ) return 0;
+  nByte = sizeof(*p) + (p->nSrc>0 ? sizeof(p->a[0]) * (p->nSrc-1) : 0);
+  pNew = sqlite3DbMallocRawNN(db, nByte );
+  if( pNew==0 ) return 0;
+  pNew->nSrc = pNew->nAlloc = p->nSrc;
+  for(i=0; i<p->nSrc; i++){
+    SrcItem *pNewItem = &pNew->a[i];
+    const SrcItem *pOldItem = &p->a[i];
+    Table *pTab;
+    pNewItem->pSchema = pOldItem->pSchema;
+    pNewItem->zDatabase = sqlite3DbStrDup(db, pOldItem->zDatabase);
+    pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
+    pNewItem->zAlias = sqlite3DbStrDup(db, pOldItem->zAlias);
+    pNewItem->fg = pOldItem->fg;
+    pNewItem->iCursor = pOldItem->iCursor;
+    pNewItem->addrFillSub = pOldItem->addrFillSub;
+    pNewItem->regReturn = pOldItem->regReturn;
+    if( pNewItem->fg.isIndexedBy ){
+      pNewItem->u1.zIndexedBy = sqlite3DbStrDup(db, pOldItem->u1.zIndexedBy);
+    }
+    pNewItem->u2 = pOldItem->u2;
+    if( pNewItem->fg.isCte ){
+      pNewItem->u2.pCteUse->nUse++;
+    }
+    if( pNewItem->fg.isTabFunc ){
+      pNewItem->u1.pFuncArg =
+          sqlite3ExprListDup(db, pOldItem->u1.pFuncArg, flags);
+    }
+    pTab = pNewItem->pTab = pOldItem->pTab;
+    if( pTab ){
+      pTab->nTabRef++;
+    }
+    pNewItem->pSelect = sqlite3SelectDup(db, pOldItem->pSelect, flags);
+    if( pOldItem->fg.isUsing ){
+      assert( pNewItem->fg.isUsing );
+      pNewItem->u3.pUsing = sqlite3IdListDup(db, pOldItem->u3.pUsing);
+    }else{
+      pNewItem->u3.pOn = sqlite3ExprDup(db, pOldItem->u3.pOn, flags);
+    }
+    pNewItem->colUsed = pOldItem->colUsed;
+  }
+  return pNew;
+}
+IdList *sqlite3IdListDup(sqlite3 *db, const IdList *p){
+  IdList *pNew;
+  int i;
+  assert( db!=0 );
+  if( p==0 ) return 0;
+  assert( p->eU4!=EU4_EXPR );
+  pNew = sqlite3DbMallocRawNN(db, sizeof(*pNew)+(p->nId-1)*sizeof(p->a[0]) );
+  if( pNew==0 ) return 0;
+  pNew->nId = p->nId;
+  pNew->eU4 = p->eU4;
+  for(i=0; i<p->nId; i++){
+    struct IdList_item *pNewItem = &pNew->a[i];
+    const struct IdList_item *pOldItem = &p->a[i];
+    pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
+    pNewItem->u4 = pOldItem->u4;
+  }
+  return pNew;
+}
+Select *sqlite3SelectDup(sqlite3 *db, const Select *pDup, int flags){
+  Select *pRet = 0;
+  Select *pNext = 0;
+  Select **pp = &pRet;
+  const Select *p;
+
+  assert( db!=0 );
+  for(p=pDup; p; p=p->pPrior){
+    Select *pNew = sqlite3DbMallocRawNN(db, sizeof(*p) );
+    if( pNew==0 ) break;
+    pNew->pEList = sqlite3ExprListDup(db, p->pEList, flags);
+    pNew->pSrc = sqlite3SrcListDup(db, p->pSrc, flags);
+    pNew->pWhere = sqlite3ExprDup(db, p->pWhere, flags);
+    pNew->pGroupBy = sqlite3ExprListDup(db, p->pGroupBy, flags);
+    pNew->pHaving = sqlite3ExprDup(db, p->pHaving, flags);
+    pNew->pOrderBy = sqlite3ExprListDup(db, p->pOrderBy, flags);
+    pNew->op = p->op;
+    pNew->pNext = pNext;
+    pNew->pPrior = 0;
+    pNew->pLimit = sqlite3ExprDup(db, p->pLimit, flags);
+    pNew->iLimit = 0;
+    pNew->iOffset = 0;
+    pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
+    pNew->addrOpenEphm[0] = -1;
+    pNew->addrOpenEphm[1] = -1;
+    pNew->nSelectRow = p->nSelectRow;
+    pNew->pWith = sqlite3WithDup(db, p->pWith);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    pNew->pWin = 0;
+    pNew->pWinDefn = sqlite3WindowListDup(db, p->pWinDefn);
+    if( p->pWin && db->mallocFailed==0 ) gatherSelectWindows(pNew);
+#endif
+    pNew->selId = p->selId;
+    if( db->mallocFailed ){
+      /* Any prior OOM might have left the Select object incomplete.
+      ** Delete the whole thing rather than allow an incomplete Select
+      ** to be used by the code generator. */
+      pNew->pNext = 0;
+      sqlite3SelectDelete(db, pNew);
+      break;
+    }
+    *pp = pNew;
+    pp = &pNew->pPrior;
+    pNext = pNew;
+  }
+
+  return pRet;
+}
+#else
+Select *sqlite3SelectDup(sqlite3 *db, const Select *p, int flags){
+  assert( p==0 );
+  return 0;
+}
+#endif
+
+
+/*
+** Add a new element to the end of an expression list.  If pList is
+** initially NULL, then create a new expression list.
+**
+** The pList argument must be either NULL or a pointer to an ExprList
+** obtained from a prior call to sqlite3ExprListAppend().
+**
+** If a memory allocation error occurs, the entire list is freed and
+** NULL is returned.  If non-NULL is returned, then it is guaranteed
+** that the new entry was successfully appended.
+*/
+static const struct ExprList_item zeroItem = {0};
+SQLITE_NOINLINE ExprList *sqlite3ExprListAppendNew(
+  sqlite3 *db,            /* Database handle.  Used for memory allocation */
+  Expr *pExpr             /* Expression to be appended. Might be NULL */
+){
+  struct ExprList_item *pItem;
+  ExprList *pList;
+
+  pList = sqlite3DbMallocRawNN(db, sizeof(ExprList)+sizeof(pList->a[0])*4 );
+  if( pList==0 ){
+    sqlite3ExprDelete(db, pExpr);
+    return 0;
+  }
+  pList->nAlloc = 4;
+  pList->nExpr = 1;
+  pItem = &pList->a[0];
+  *pItem = zeroItem;
+  pItem->pExpr = pExpr;
+  return pList;
+}
+SQLITE_NOINLINE ExprList *sqlite3ExprListAppendGrow(
+  sqlite3 *db,            /* Database handle.  Used for memory allocation */
+  ExprList *pList,        /* List to which to append. Might be NULL */
+  Expr *pExpr             /* Expression to be appended. Might be NULL */
+){
+  struct ExprList_item *pItem;
+  ExprList *pNew;
+  pList->nAlloc *= 2;
+  pNew = sqlite3DbRealloc(db, pList,
+       sizeof(*pList)+(pList->nAlloc-1)*sizeof(pList->a[0]));
+  if( pNew==0 ){
+    sqlite3ExprListDelete(db, pList);
+    sqlite3ExprDelete(db, pExpr);
+    return 0;
+  }else{
+    pList = pNew;
+  }
+  pItem = &pList->a[pList->nExpr++];
+  *pItem = zeroItem;
+  pItem->pExpr = pExpr;
+  return pList;
+}
+ExprList *sqlite3ExprListAppend(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pList,        /* List to which to append. Might be NULL */
+  Expr *pExpr             /* Expression to be appended. Might be NULL */
+){
+  struct ExprList_item *pItem;
+  if( pList==0 ){
+    return sqlite3ExprListAppendNew(pParse->db,pExpr);
+  }
+  if( pList->nAlloc<pList->nExpr+1 ){
+    return sqlite3ExprListAppendGrow(pParse->db,pList,pExpr);
+  }
+  pItem = &pList->a[pList->nExpr++];
+  *pItem = zeroItem;
+  pItem->pExpr = pExpr;
+  return pList;
+}
+
+/*
+** pColumns and pExpr form a vector assignment which is part of the SET
+** clause of an UPDATE statement.  Like this:
+**
+**        (a,b,c) = (expr1,expr2,expr3)
+** Or:    (a,b,c) = (SELECT x,y,z FROM ....)
+**
+** For each term of the vector assignment, append new entries to the
+** expression list pList.  In the case of a subquery on the RHS, append
+** TK_SELECT_COLUMN expressions.
+*/
+ExprList *sqlite3ExprListAppendVector(
+  Parse *pParse,         /* Parsing context */
+  ExprList *pList,       /* List to which to append. Might be NULL */
+  IdList *pColumns,      /* List of names of LHS of the assignment */
+  Expr *pExpr            /* Vector expression to be appended. Might be NULL */
+){
+  sqlite3 *db = pParse->db;
+  int n;
+  int i;
+  int iFirst = pList ? pList->nExpr : 0;
+  /* pColumns can only be NULL due to an OOM but an OOM will cause an
+  ** exit prior to this routine being invoked */
+  if( NEVER(pColumns==0) ) goto vector_append_error;
+  if( pExpr==0 ) goto vector_append_error;
+
+  /* If the RHS is a vector, then we can immediately check to see that
+  ** the size of the RHS and LHS match.  But if the RHS is a SELECT,
+  ** wildcards ("*") in the result set of the SELECT must be expanded before
+  ** we can do the size check, so defer the size check until code generation.
+  */
+  if( pExpr->op!=TK_SELECT && pColumns->nId!=(n=sqlite3ExprVectorSize(pExpr)) ){
+    sqlite3ErrorMsg(pParse, "%d columns assigned %d values",
+                    pColumns->nId, n);
+    goto vector_append_error;
+  }
+
+  for(i=0; i<pColumns->nId; i++){
+    Expr *pSubExpr = sqlite3ExprForVectorField(pParse, pExpr, i, pColumns->nId);
+    assert( pSubExpr!=0 || db->mallocFailed );
+    if( pSubExpr==0 ) continue;
+    pList = sqlite3ExprListAppend(pParse, pList, pSubExpr);
+    if( pList ){
+      assert( pList->nExpr==iFirst+i+1 );
+      pList->a[pList->nExpr-1].zEName = pColumns->a[i].zName;
+      pColumns->a[i].zName = 0;
+    }
+  }
+
+  if( !db->mallocFailed && pExpr->op==TK_SELECT && ALWAYS(pList!=0) ){
+    Expr *pFirst = pList->a[iFirst].pExpr;
+    assert( pFirst!=0 );
+    assert( pFirst->op==TK_SELECT_COLUMN );
+    
+    /* Store the SELECT statement in pRight so it will be deleted when
+    ** sqlite3ExprListDelete() is called */
+    pFirst->pRight = pExpr;
+    pExpr = 0;
+
+    /* Remember the size of the LHS in iTable so that we can check that
+    ** the RHS and LHS sizes match during code generation. */
+    pFirst->iTable = pColumns->nId;
+  }
+
+vector_append_error:
+  sqlite3ExprUnmapAndDelete(pParse, pExpr);
+  sqlite3IdListDelete(db, pColumns);
+  return pList;
+}
+
+/*
+** Set the sort order for the last element on the given ExprList.
+*/
+void sqlite3ExprListSetSortOrder(ExprList *p, int iSortOrder, int eNulls){
+  struct ExprList_item *pItem;
+  if( p==0 ) return;
+  assert( p->nExpr>0 );
+
+  assert( SQLITE_SO_UNDEFINED<0 && SQLITE_SO_ASC==0 && SQLITE_SO_DESC>0 );
+  assert( iSortOrder==SQLITE_SO_UNDEFINED
+       || iSortOrder==SQLITE_SO_ASC
+       || iSortOrder==SQLITE_SO_DESC
+  );
+  assert( eNulls==SQLITE_SO_UNDEFINED
+       || eNulls==SQLITE_SO_ASC
+       || eNulls==SQLITE_SO_DESC
+  );
+
+  pItem = &p->a[p->nExpr-1];
+  assert( pItem->fg.bNulls==0 );
+  if( iSortOrder==SQLITE_SO_UNDEFINED ){
+    iSortOrder = SQLITE_SO_ASC;
+  }
+  pItem->fg.sortFlags = (u8)iSortOrder;
+
+  if( eNulls!=SQLITE_SO_UNDEFINED ){
+    pItem->fg.bNulls = 1;
+    if( iSortOrder!=eNulls ){
+      pItem->fg.sortFlags |= KEYINFO_ORDER_BIGNULL;
+    }
+  }
+}
+
+/*
+** Set the ExprList.a[].zEName element of the most recently added item
+** on the expression list.
+**
+** pList might be NULL following an OOM error.  But pName should never be
+** NULL.  If a memory allocation fails, the pParse->db->mallocFailed flag
+** is set.
+*/
+void sqlite3ExprListSetName(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pList,        /* List to which to add the span. */
+  const Token *pName,     /* Name to be added */
+  int dequote             /* True to cause the name to be dequoted */
+){
+  assert( pList!=0 || pParse->db->mallocFailed!=0 );
+  assert( pParse->eParseMode!=PARSE_MODE_UNMAP || dequote==0 );
+  if( pList ){
+    struct ExprList_item *pItem;
+    assert( pList->nExpr>0 );
+    pItem = &pList->a[pList->nExpr-1];
+    assert( pItem->zEName==0 );
+    assert( pItem->fg.eEName==ENAME_NAME );
+    pItem->zEName = sqlite3DbStrNDup(pParse->db, pName->z, pName->n);
+    if( dequote ){
+      /* If dequote==0, then pName->z does not point to part of a DDL
+      ** statement handled by the parser. And so no token need be added
+      ** to the token-map.  */
+      sqlite3Dequote(pItem->zEName);
+      if( IN_RENAME_OBJECT ){
+        sqlite3RenameTokenMap(pParse, (const void*)pItem->zEName, pName);
+      }
+    }
+  }
+}
+
+/*
+** Set the ExprList.a[].zSpan element of the most recently added item
+** on the expression list.
+**
+** pList might be NULL following an OOM error.  But pSpan should never be
+** NULL.  If a memory allocation fails, the pParse->db->mallocFailed flag
+** is set.
+*/
+void sqlite3ExprListSetSpan(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pList,        /* List to which to add the span. */
+  const char *zStart,     /* Start of the span */
+  const char *zEnd        /* End of the span */
+){
+  sqlite3 *db = pParse->db;
+  assert( pList!=0 || db->mallocFailed!=0 );
+  if( pList ){
+    struct ExprList_item *pItem = &pList->a[pList->nExpr-1];
+    assert( pList->nExpr>0 );
+    if( pItem->zEName==0 ){
+      pItem->zEName = sqlite3DbSpanDup(db, zStart, zEnd);
+      pItem->fg.eEName = ENAME_SPAN;
+    }
+  }
+}
+
+/*
+** If the expression list pEList contains more than iLimit elements,
+** leave an error message in pParse.
+*/
+void sqlite3ExprListCheckLength(
+  Parse *pParse,
+  ExprList *pEList,
+  const char *zObject
+){
+  int mx = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];
+  testcase( pEList && pEList->nExpr==mx );
+  testcase( pEList && pEList->nExpr==mx+1 );
+  if( pEList && pEList->nExpr>mx ){
+    sqlite3ErrorMsg(pParse, "too many columns in %s", zObject);
+  }
+}
+
+/*
+** Delete an entire expression list.
+*/
+static SQLITE_NOINLINE void exprListDeleteNN(sqlite3 *db, ExprList *pList){
+  int i = pList->nExpr;
+  struct ExprList_item *pItem =  pList->a;
+  assert( pList->nExpr>0 );
+  assert( db!=0 );
+  do{
+    sqlite3ExprDelete(db, pItem->pExpr);
+    if( pItem->zEName ) sqlite3DbNNFreeNN(db, pItem->zEName);
+    pItem++;
+  }while( --i>0 );
+  sqlite3DbNNFreeNN(db, pList);
+}
+void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){
+  if( pList ) exprListDeleteNN(db, pList);
+}
+void sqlite3ExprListDeleteGeneric(sqlite3 *db, void *pList){
+  if( ALWAYS(pList) ) exprListDeleteNN(db, (ExprList*)pList);
+}
+
+/*
+** Return the bitwise-OR of all Expr.flags fields in the given
+** ExprList.
+*/
+u32 sqlite3ExprListFlags(const ExprList *pList){
+  int i;
+  u32 m = 0;
+  assert( pList!=0 );
+  for(i=0; i<pList->nExpr; i++){
+     Expr *pExpr = pList->a[i].pExpr;
+     assert( pExpr!=0 );
+     m |= pExpr->flags;
+  }
+  return m;
+}
+
+/*
+** This is a SELECT-node callback for the expression walker that
+** always "fails".  By "fail" in this case, we mean set
+** pWalker->eCode to zero and abort.
+**
+** This callback is used by multiple expression walkers.
+*/
+int sqlite3SelectWalkFail(Walker *pWalker, Select *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  pWalker->eCode = 0;
+  return WRC_Abort;
+}
+
+/*
+** Check the input string to see if it is "true" or "false" (in any case).
+**
+**       If the string is....           Return
+**         "true"                         EP_IsTrue
+**         "false"                        EP_IsFalse
+**         anything else                  0
+*/
+u32 sqlite3IsTrueOrFalse(const char *zIn){
+  if( sqlite3StrICmp(zIn, "true")==0  ) return EP_IsTrue;
+  if( sqlite3StrICmp(zIn, "false")==0 ) return EP_IsFalse;
+  return 0;
+}
+
+
+/*
+** If the input expression is an ID with the name "true" or "false"
+** then convert it into an TK_TRUEFALSE term.  Return non-zero if
+** the conversion happened, and zero if the expression is unaltered.
+*/
+int sqlite3ExprIdToTrueFalse(Expr *pExpr){
+  u32 v;
+  assert( pExpr->op==TK_ID || pExpr->op==TK_STRING );
+  if( !ExprHasProperty(pExpr, EP_Quoted|EP_IntValue)
+   && (v = sqlite3IsTrueOrFalse(pExpr->u.zToken))!=0
+  ){
+    pExpr->op = TK_TRUEFALSE;
+    ExprSetProperty(pExpr, v);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** The argument must be a TK_TRUEFALSE Expr node.  Return 1 if it is TRUE
+** and 0 if it is FALSE.
+*/
+int sqlite3ExprTruthValue(const Expr *pExpr){
+  pExpr = sqlite3ExprSkipCollateAndLikely((Expr*)pExpr);
+  assert( pExpr->op==TK_TRUEFALSE );
+  assert( !ExprHasProperty(pExpr, EP_IntValue) );
+  assert( sqlite3StrICmp(pExpr->u.zToken,"true")==0
+       || sqlite3StrICmp(pExpr->u.zToken,"false")==0 );
+  return pExpr->u.zToken[4]==0;
+}
+
+/*
+** If pExpr is an AND or OR expression, try to simplify it by eliminating
+** terms that are always true or false.  Return the simplified expression.
+** Or return the original expression if no simplification is possible.
+**
+** Examples:
+**
+**     (x<10) AND true                =>   (x<10)
+**     (x<10) AND false               =>   false
+**     (x<10) AND (y=22 OR false)     =>   (x<10) AND (y=22)
+**     (x<10) AND (y=22 OR true)      =>   (x<10)
+**     (y=22) OR true                 =>   true
+*/
+Expr *sqlite3ExprSimplifiedAndOr(Expr *pExpr){
+  assert( pExpr!=0 );
+  if( pExpr->op==TK_AND || pExpr->op==TK_OR ){
+    Expr *pRight = sqlite3ExprSimplifiedAndOr(pExpr->pRight);
+    Expr *pLeft = sqlite3ExprSimplifiedAndOr(pExpr->pLeft);
+    if( ExprAlwaysTrue(pLeft) || ExprAlwaysFalse(pRight) ){
+      pExpr = pExpr->op==TK_AND ? pRight : pLeft;
+    }else if( ExprAlwaysTrue(pRight) || ExprAlwaysFalse(pLeft) ){
+      pExpr = pExpr->op==TK_AND ? pLeft : pRight;
+    }
+  }
+  return pExpr;
+}
+
+
+/*
+** These routines are Walker callbacks used to check expressions to
+** see if they are "constant" for some definition of constant.  The
+** Walker.eCode value determines the type of "constant" we are looking
+** for.
+**
+** These callback routines are used to implement the following:
+**
+**     sqlite3ExprIsConstant()                  pWalker->eCode==1
+**     sqlite3ExprIsConstantNotJoin()           pWalker->eCode==2
+**     sqlite3ExprIsTableConstant()             pWalker->eCode==3
+**     sqlite3ExprIsConstantOrFunction()        pWalker->eCode==4 or 5
+**
+** In all cases, the callbacks set Walker.eCode=0 and abort if the expression
+** is found to not be a constant.
+**
+** The sqlite3ExprIsConstantOrFunction() is used for evaluating DEFAULT
+** expressions in a CREATE TABLE statement.  The Walker.eCode value is 5
+** when parsing an existing schema out of the sqlite_schema table and 4
+** when processing a new CREATE TABLE statement.  A bound parameter raises
+** an error for new statements, but is silently converted
+** to NULL for existing schemas.  This allows sqlite_schema tables that
+** contain a bound parameter because they were generated by older versions
+** of SQLite to be parsed by newer versions of SQLite without raising a
+** malformed schema error.
+*/
+static int exprNodeIsConstant(Walker *pWalker, Expr *pExpr){
+
+  /* If pWalker->eCode is 2 then any term of the expression that comes from
+  ** the ON or USING clauses of an outer join disqualifies the expression
+  ** from being considered constant. */
+  if( pWalker->eCode==2 && ExprHasProperty(pExpr, EP_OuterON) ){
+    pWalker->eCode = 0;
+    return WRC_Abort;
+  }
+
+  switch( pExpr->op ){
+    /* Consider functions to be constant if all their arguments are constant
+    ** and either pWalker->eCode==4 or 5 or the function has the
+    ** SQLITE_FUNC_CONST flag. */
+    case TK_FUNCTION:
+      if( (pWalker->eCode>=4 || ExprHasProperty(pExpr,EP_ConstFunc))
+       && !ExprHasProperty(pExpr, EP_WinFunc)
+      ){
+        if( pWalker->eCode==5 ) ExprSetProperty(pExpr, EP_FromDDL);
+        return WRC_Continue;
+      }else{
+        pWalker->eCode = 0;
+        return WRC_Abort;
+      }
+    case TK_ID:
+      /* Convert "true" or "false" in a DEFAULT clause into the
+      ** appropriate TK_TRUEFALSE operator */
+      if( sqlite3ExprIdToTrueFalse(pExpr) ){
+        return WRC_Prune;
+      }
+      /* no break */ deliberate_fall_through
+    case TK_COLUMN:
+    case TK_AGG_FUNCTION:
+    case TK_AGG_COLUMN:
+      testcase( pExpr->op==TK_ID );
+      testcase( pExpr->op==TK_COLUMN );
+      testcase( pExpr->op==TK_AGG_FUNCTION );
+      testcase( pExpr->op==TK_AGG_COLUMN );
+      if( ExprHasProperty(pExpr, EP_FixedCol) && pWalker->eCode!=2 ){
+        return WRC_Continue;
+      }
+      if( pWalker->eCode==3 && pExpr->iTable==pWalker->u.iCur ){
+        return WRC_Continue;
+      }
+      /* no break */ deliberate_fall_through
+    case TK_IF_NULL_ROW:
+    case TK_REGISTER:
+    case TK_DOT:
+      testcase( pExpr->op==TK_REGISTER );
+      testcase( pExpr->op==TK_IF_NULL_ROW );
+      testcase( pExpr->op==TK_DOT );
+      pWalker->eCode = 0;
+      return WRC_Abort;
+    case TK_VARIABLE:
+      if( pWalker->eCode==5 ){
+        /* Silently convert bound parameters that appear inside of CREATE
+        ** statements into a NULL when parsing the CREATE statement text out
+        ** of the sqlite_schema table */
+        pExpr->op = TK_NULL;
+      }else if( pWalker->eCode==4 ){
+        /* A bound parameter in a CREATE statement that originates from
+        ** sqlite3_prepare() causes an error */
+        pWalker->eCode = 0;
+        return WRC_Abort;
+      }
+      /* no break */ deliberate_fall_through
+    default:
+      testcase( pExpr->op==TK_SELECT ); /* sqlite3SelectWalkFail() disallows */
+      testcase( pExpr->op==TK_EXISTS ); /* sqlite3SelectWalkFail() disallows */
+      return WRC_Continue;
+  }
+}
+static int exprIsConst(Expr *p, int initFlag, int iCur){
+  Walker w;
+  w.eCode = initFlag;
+  w.xExprCallback = exprNodeIsConstant;
+  w.xSelectCallback = sqlite3SelectWalkFail;
+#ifdef SQLITE_DEBUG
+  w.xSelectCallback2 = sqlite3SelectWalkAssert2;
+#endif
+  w.u.iCur = iCur;
+  sqlite3WalkExpr(&w, p);
+  return w.eCode;
+}
+
+/*
+** Walk an expression tree.  Return non-zero if the expression is constant
+** and 0 if it involves variables or function calls.
+**
+** For the purposes of this function, a double-quoted string (ex: "abc")
+** is considered a variable but a single-quoted string (ex: 'abc') is
+** a constant.
+*/
+int sqlite3ExprIsConstant(Expr *p){
+  return exprIsConst(p, 1, 0);
+}
+
+/*
+** Walk an expression tree.  Return non-zero if
+**
+**   (1) the expression is constant, and
+**   (2) the expression does originate in the ON or USING clause
+**       of a LEFT JOIN, and
+**   (3) the expression does not contain any EP_FixedCol TK_COLUMN
+**       operands created by the constant propagation optimization.
+**
+** When this routine returns true, it indicates that the expression
+** can be added to the pParse->pConstExpr list and evaluated once when
+** the prepared statement starts up.  See sqlite3ExprCodeRunJustOnce().
+*/
+int sqlite3ExprIsConstantNotJoin(Expr *p){
+  return exprIsConst(p, 2, 0);
+}
+
+/*
+** Walk an expression tree.  Return non-zero if the expression is constant
+** for any single row of the table with cursor iCur.  In other words, the
+** expression must not refer to any non-deterministic function nor any
+** table other than iCur.
+*/
+int sqlite3ExprIsTableConstant(Expr *p, int iCur){
+  return exprIsConst(p, 3, iCur);
+}
+
+/*
+** Check pExpr to see if it is an constraint on the single data source
+** pSrc = &pSrcList->a[iSrc].  In other words, check to see if pExpr
+** constrains pSrc but does not depend on any other tables or data
+** sources anywhere else in the query.  Return true (non-zero) if pExpr
+** is a constraint on pSrc only.
+**
+** This is an optimization.  False negatives will perhaps cause slower
+** queries, but false positives will yield incorrect answers.  So when in
+** doubt, return 0.
+**
+** To be an single-source constraint, the following must be true:
+**
+**   (1)  pExpr cannot refer to any table other than pSrc->iCursor.
+**
+**   (2)  pExpr cannot use subqueries or non-deterministic functions.
+**
+**   (3)  pSrc cannot be part of the left operand for a RIGHT JOIN.
+**        (Is there some way to relax this constraint?)
+**
+**   (4)  If pSrc is the right operand of a LEFT JOIN, then...
+**         (4a)  pExpr must come from an ON clause..
+**         (4b)  and specifically the ON clause associated with the LEFT JOIN.
+**
+**   (5)  If pSrc is not the right operand of a LEFT JOIN or the left
+**        operand of a RIGHT JOIN, then pExpr must be from the WHERE
+**        clause, not an ON clause.
+**
+**   (6) Either:
+**
+**       (6a) pExpr does not originate in an ON or USING clause, or
+**
+**       (6b) The ON or USING clause from which pExpr is derived is
+**            not to the left of a RIGHT JOIN (or FULL JOIN).
+**
+**       Without this restriction, accepting pExpr as a single-table
+**       constraint might move the the ON/USING filter expression
+**       from the left side of a RIGHT JOIN over to the right side,
+**       which leads to incorrect answers.  See also restriction (9)
+**       on push-down.
+*/
+int sqlite3ExprIsSingleTableConstraint(
+  Expr *pExpr,                 /* The constraint */
+  const SrcList *pSrcList,     /* Complete FROM clause */
+  int iSrc                     /* Which element of pSrcList to use */
+){
+  const SrcItem *pSrc = &pSrcList->a[iSrc];
+  if( pSrc->fg.jointype & JT_LTORJ ){
+    return 0;  /* rule (3) */
+  }
+  if( pSrc->fg.jointype & JT_LEFT ){
+    if( !ExprHasProperty(pExpr, EP_OuterON) ) return 0;   /* rule (4a) */
+    if( pExpr->w.iJoin!=pSrc->iCursor ) return 0;         /* rule (4b) */
+  }else{
+    if( ExprHasProperty(pExpr, EP_OuterON) ) return 0;    /* rule (5) */
+  }
+  if( ExprHasProperty(pExpr, EP_OuterON|EP_InnerON)  /* (6a) */
+   && (pSrcList->a[0].fg.jointype & JT_LTORJ)!=0     /* Fast pre-test of (6b) */
+  ){
+    int jj;
+    for(jj=0; jj<iSrc; jj++){
+      if( pExpr->w.iJoin==pSrcList->a[jj].iCursor ){
+        if( (pSrcList->a[jj].fg.jointype & JT_LTORJ)!=0 ){
+          return 0;  /* restriction (6) */
+        }
+        break;
+      }
+    }
+  }
+  return sqlite3ExprIsTableConstant(pExpr, pSrc->iCursor); /* rules (1), (2) */
+}
+
+
+/*
+** sqlite3WalkExpr() callback used by sqlite3ExprIsConstantOrGroupBy().
+*/
+static int exprNodeIsConstantOrGroupBy(Walker *pWalker, Expr *pExpr){
+  ExprList *pGroupBy = pWalker->u.pGroupBy;
+  int i;
+
+  /* Check if pExpr is identical to any GROUP BY term. If so, consider
+  ** it constant.  */
+  for(i=0; i<pGroupBy->nExpr; i++){
+    Expr *p = pGroupBy->a[i].pExpr;
+    if( sqlite3ExprCompare(0, pExpr, p, -1)<2 ){
+      CollSeq *pColl = sqlite3ExprNNCollSeq(pWalker->pParse, p);
+      if( sqlite3IsBinary(pColl) ){
+        return WRC_Prune;
+      }
+    }
+  }
+
+  /* Check if pExpr is a sub-select. If so, consider it variable. */
+  if( ExprUseXSelect(pExpr) ){
+    pWalker->eCode = 0;
+    return WRC_Abort;
+  }
+
+  return exprNodeIsConstant(pWalker, pExpr);
+}
+
+/*
+** Walk the expression tree passed as the first argument. Return non-zero
+** if the expression consists entirely of constants or copies of terms
+** in pGroupBy that sort with the BINARY collation sequence.
+**
+** This routine is used to determine if a term of the HAVING clause can
+** be promoted into the WHERE clause.  In order for such a promotion to work,
+** the value of the HAVING clause term must be the same for all members of
+** a "group".  The requirement that the GROUP BY term must be BINARY
+** assumes that no other collating sequence will have a finer-grained
+** grouping than binary.  In other words (A=B COLLATE binary) implies
+** A=B in every other collating sequence.  The requirement that the
+** GROUP BY be BINARY is stricter than necessary.  It would also work
+** to promote HAVING clauses that use the same alternative collating
+** sequence as the GROUP BY term, but that is much harder to check,
+** alternative collating sequences are uncommon, and this is only an
+** optimization, so we take the easy way out and simply require the
+** GROUP BY to use the BINARY collating sequence.
+*/
+int sqlite3ExprIsConstantOrGroupBy(Parse *pParse, Expr *p, ExprList *pGroupBy){
+  Walker w;
+  w.eCode = 1;
+  w.xExprCallback = exprNodeIsConstantOrGroupBy;
+  w.xSelectCallback = 0;
+  w.u.pGroupBy = pGroupBy;
+  w.pParse = pParse;
+  sqlite3WalkExpr(&w, p);
+  return w.eCode;
+}
+
+/*
+** Walk an expression tree for the DEFAULT field of a column definition
+** in a CREATE TABLE statement.  Return non-zero if the expression is
+** acceptable for use as a DEFAULT.  That is to say, return non-zero if
+** the expression is constant or a function call with constant arguments.
+** Return and 0 if there are any variables.
+**
+** isInit is true when parsing from sqlite_schema.  isInit is false when
+** processing a new CREATE TABLE statement.  When isInit is true, parameters
+** (such as ? or $abc) in the expression are converted into NULL.  When
+** isInit is false, parameters raise an error.  Parameters should not be
+** allowed in a CREATE TABLE statement, but some legacy versions of SQLite
+** allowed it, so we need to support it when reading sqlite_schema for
+** backwards compatibility.
+**
+** If isInit is true, set EP_FromDDL on every TK_FUNCTION node.
+**
+** For the purposes of this function, a double-quoted string (ex: "abc")
+** is considered a variable but a single-quoted string (ex: 'abc') is
+** a constant.
+*/
+int sqlite3ExprIsConstantOrFunction(Expr *p, u8 isInit){
+  assert( isInit==0 || isInit==1 );
+  return exprIsConst(p, 4+isInit, 0);
+}
+
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+/*
+** Walk an expression tree.  Return 1 if the expression contains a
+** subquery of some kind.  Return 0 if there are no subqueries.
+*/
+int sqlite3ExprContainsSubquery(Expr *p){
+  Walker w;
+  w.eCode = 1;
+  w.xExprCallback = sqlite3ExprWalkNoop;
+  w.xSelectCallback = sqlite3SelectWalkFail;
+#ifdef SQLITE_DEBUG
+  w.xSelectCallback2 = sqlite3SelectWalkAssert2;
+#endif
+  sqlite3WalkExpr(&w, p);
+  return w.eCode==0;
+}
+#endif
+
+/*
+** If the expression p codes a constant integer that is small enough
+** to fit in a 32-bit integer, return 1 and put the value of the integer
+** in *pValue.  If the expression is not an integer or if it is too big
+** to fit in a signed 32-bit integer, return 0 and leave *pValue unchanged.
+*/
+int sqlite3ExprIsInteger(const Expr *p, int *pValue){
+  int rc = 0;
+  if( NEVER(p==0) ) return 0;  /* Used to only happen following on OOM */
+
+  /* If an expression is an integer literal that fits in a signed 32-bit
+  ** integer, then the EP_IntValue flag will have already been set */
+  assert( p->op!=TK_INTEGER || (p->flags & EP_IntValue)!=0
+           || sqlite3GetInt32(p->u.zToken, &rc)==0 );
+
+  if( p->flags & EP_IntValue ){
+    *pValue = p->u.iValue;
+    return 1;
+  }
+  switch( p->op ){
+    case TK_UPLUS: {
+      rc = sqlite3ExprIsInteger(p->pLeft, pValue);
+      break;
+    }
+    case TK_UMINUS: {
+      int v = 0;
+      if( sqlite3ExprIsInteger(p->pLeft, &v) ){
+        assert( ((unsigned int)v)!=0x80000000 );
+        *pValue = -v;
+        rc = 1;
+      }
+      break;
+    }
+    default: break;
+  }
+  return rc;
+}
+
+/*
+** Return FALSE if there is no chance that the expression can be NULL.
+**
+** If the expression might be NULL or if the expression is too complex
+** to tell return TRUE. 
+**
+** This routine is used as an optimization, to skip OP_IsNull opcodes
+** when we know that a value cannot be NULL.  Hence, a false positive
+** (returning TRUE when in fact the expression can never be NULL) might
+** be a small performance hit but is otherwise harmless.  On the other
+** hand, a false negative (returning FALSE when the result could be NULL)
+** will likely result in an incorrect answer.  So when in doubt, return
+** TRUE.
+*/
+int sqlite3ExprCanBeNull(const Expr *p){
+  u8 op;
+  assert( p!=0 );
+  while( p->op==TK_UPLUS || p->op==TK_UMINUS ){
+    p = p->pLeft;
+    assert( p!=0 );
+  }
+  op = p->op;
+  if( op==TK_REGISTER ) op = p->op2;
+  switch( op ){
+    case TK_INTEGER:
+    case TK_STRING:
+    case TK_FLOAT:
+    case TK_BLOB:
+      return 0;
+    case TK_COLUMN:
+      assert( ExprUseYTab(p) );
+      return ExprHasProperty(p, EP_CanBeNull) ||
+             NEVER(p->y.pTab==0) ||  /* Reference to column of index on expr */
+             (p->iColumn>=0
+              && p->y.pTab->aCol!=0 /* Possible due to prior error */
+              && ALWAYS(p->iColumn<p->y.pTab->nCol)
+              && p->y.pTab->aCol[p->iColumn].notNull==0);
+    default:
+      return 1;
+  }
+}
+
+/*
+** Return TRUE if the given expression is a constant which would be
+** unchanged by OP_Affinity with the affinity given in the second
+** argument.
+**
+** This routine is used to determine if the OP_Affinity operation
+** can be omitted.  When in doubt return FALSE.  A false negative
+** is harmless.  A false positive, however, can result in the wrong
+** answer.
+*/
+int sqlite3ExprNeedsNoAffinityChange(const Expr *p, char aff){
+  u8 op;
+  int unaryMinus = 0;
+  if( aff==SQLITE_AFF_BLOB ) return 1;
+  while( p->op==TK_UPLUS || p->op==TK_UMINUS ){
+    if( p->op==TK_UMINUS ) unaryMinus = 1;
+    p = p->pLeft;
+  }
+  op = p->op;
+  if( op==TK_REGISTER ) op = p->op2;
+  switch( op ){
+    case TK_INTEGER: {
+      return aff>=SQLITE_AFF_NUMERIC;
+    }
+    case TK_FLOAT: {
+      return aff>=SQLITE_AFF_NUMERIC;
+    }
+    case TK_STRING: {
+      return !unaryMinus && aff==SQLITE_AFF_TEXT;
+    }
+    case TK_BLOB: {
+      return !unaryMinus;
+    }
+    case TK_COLUMN: {
+      assert( p->iTable>=0 );  /* p cannot be part of a CHECK constraint */
+      return aff>=SQLITE_AFF_NUMERIC && p->iColumn<0;
+    }
+    default: {
+      return 0;
+    }
+  }
+}
+
+/*
+** Return TRUE if the given string is a row-id column name.
+*/
+int sqlite3IsRowid(const char *z){
+  if( sqlite3StrICmp(z, "_ROWID_")==0 ) return 1;
+  if( sqlite3StrICmp(z, "ROWID")==0 ) return 1;
+  if( sqlite3StrICmp(z, "OID")==0 ) return 1;
+  return 0;
+}
+
+/*
+** Return a pointer to a buffer containing a usable rowid alias for table
+** pTab. An alias is usable if there is not an explicit user-defined column 
+** of the same name.
+*/
+const char *sqlite3RowidAlias(Table *pTab){
+  const char *azOpt[] = {"_ROWID_", "ROWID", "OID"};
+  int ii;
+  assert( VisibleRowid(pTab) );
+  for(ii=0; ii<ArraySize(azOpt); ii++){
+    int iCol;
+    for(iCol=0; iCol<pTab->nCol; iCol++){
+      if( sqlite3_stricmp(azOpt[ii], pTab->aCol[iCol].zCnName)==0 ) break;
+    }
+    if( iCol==pTab->nCol ){
+      return azOpt[ii];
+    }
+  }
+  return 0;
+}
+
+/*
+** pX is the RHS of an IN operator.  If pX is a SELECT statement
+** that can be simplified to a direct table access, then return
+** a pointer to the SELECT statement.  If pX is not a SELECT statement,
+** or if the SELECT statement needs to be materialized into a transient
+** table, then return NULL.
+*/
+#ifndef SQLITE_OMIT_SUBQUERY
+static Select *isCandidateForInOpt(const Expr *pX){
+  Select *p;
+  SrcList *pSrc;
+  ExprList *pEList;
+  Table *pTab;
+  int i;
+  if( !ExprUseXSelect(pX) ) return 0;                 /* Not a subquery */
+  if( ExprHasProperty(pX, EP_VarSelect)  ) return 0;  /* Correlated subq */
+  p = pX->x.pSelect;
+  if( p->pPrior ) return 0;              /* Not a compound SELECT */
+  if( p->selFlags & (SF_Distinct|SF_Aggregate) ){
+    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
+    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
+    return 0; /* No DISTINCT keyword and no aggregate functions */
+  }
+  assert( p->pGroupBy==0 );              /* Has no GROUP BY clause */
+  if( p->pLimit ) return 0;              /* Has no LIMIT clause */
+  if( p->pWhere ) return 0;              /* Has no WHERE clause */
+  pSrc = p->pSrc;
+  assert( pSrc!=0 );
+  if( pSrc->nSrc!=1 ) return 0;          /* Single term in FROM clause */
+  if( pSrc->a[0].pSelect ) return 0;     /* FROM is not a subquery or view */
+  pTab = pSrc->a[0].pTab;
+  assert( pTab!=0 );
+  assert( !IsView(pTab)  );              /* FROM clause is not a view */
+  if( IsVirtual(pTab) ) return 0;        /* FROM clause not a virtual table */
+  pEList = p->pEList;
+  assert( pEList!=0 );
+  /* All SELECT results must be columns. */
+  for(i=0; i<pEList->nExpr; i++){
+    Expr *pRes = pEList->a[i].pExpr;
+    if( pRes->op!=TK_COLUMN ) return 0;
+    assert( pRes->iTable==pSrc->a[0].iCursor );  /* Not a correlated subquery */
+  }
+  return p;
+}
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Generate code that checks the left-most column of index table iCur to see if
+** it contains any NULL entries.  Cause the register at regHasNull to be set
+** to a non-NULL value if iCur contains no NULLs.  Cause register regHasNull
+** to be set to NULL if iCur contains one or more NULL values.
+*/
+static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
+  int addr1;
+  sqlite3VdbeAddOp2(v, OP_Integer, 0, regHasNull);
+  addr1 = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
+  sqlite3VdbeAddOp3(v, OP_Column, iCur, 0, regHasNull);
+  sqlite3VdbeChangeP5(v, OPFLAG_TYPEOFARG);
+  VdbeComment((v, "first_entry_in(%d)", iCur));
+  sqlite3VdbeJumpHere(v, addr1);
+}
+#endif
+
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** The argument is an IN operator with a list (not a subquery) on the
+** right-hand side.  Return TRUE if that list is constant.
+*/
+static int sqlite3InRhsIsConstant(Expr *pIn){
+  Expr *pLHS;
+  int res;
+  assert( !ExprHasProperty(pIn, EP_xIsSelect) );
+  pLHS = pIn->pLeft;
+  pIn->pLeft = 0;
+  res = sqlite3ExprIsConstant(pIn);
+  pIn->pLeft = pLHS;
+  return res;
+}
+#endif
+
+/*
+** This function is used by the implementation of the IN (...) operator.
+** The pX parameter is the expression on the RHS of the IN operator, which
+** might be either a list of expressions or a subquery.
+**
+** The job of this routine is to find or create a b-tree object that can
+** be used either to test for membership in the RHS set or to iterate through
+** all members of the RHS set, skipping duplicates.
+**
+** A cursor is opened on the b-tree object that is the RHS of the IN operator
+** and the *piTab parameter is set to the index of that cursor.
+**
+** The returned value of this function indicates the b-tree type, as follows:
+**
+**   IN_INDEX_ROWID      - The cursor was opened on a database table.
+**   IN_INDEX_INDEX_ASC  - The cursor was opened on an ascending index.
+**   IN_INDEX_INDEX_DESC - The cursor was opened on a descending index.
+**   IN_INDEX_EPH        - The cursor was opened on a specially created and
+**                         populated ephemeral table.
+**   IN_INDEX_NOOP       - No cursor was allocated.  The IN operator must be
+**                         implemented as a sequence of comparisons.
+**
+** An existing b-tree might be used if the RHS expression pX is a simple
+** subquery such as:
+**
+**     SELECT <column1>, <column2>... FROM <table>
+**
+** If the RHS of the IN operator is a list or a more complex subquery, then
+** an ephemeral table might need to be generated from the RHS and then
+** pX->iTable made to point to the ephemeral table instead of an
+** existing table.  In this case, the creation and initialization of the
+** ephemeral table might be put inside of a subroutine, the EP_Subrtn flag
+** will be set on pX and the pX->y.sub fields will be set to show where
+** the subroutine is coded.
+**
+** The inFlags parameter must contain, at a minimum, one of the bits
+** IN_INDEX_MEMBERSHIP or IN_INDEX_LOOP but not both.  If inFlags contains
+** IN_INDEX_MEMBERSHIP, then the generated table will be used for a fast
+** membership test.  When the IN_INDEX_LOOP bit is set, the IN index will
+** be used to loop over all values of the RHS of the IN operator.
+**
+** When IN_INDEX_LOOP is used (and the b-tree will be used to iterate
+** through the set members) then the b-tree must not contain duplicates.
+** An ephemeral table will be created unless the selected columns are guaranteed
+** to be unique - either because it is an INTEGER PRIMARY KEY or due to
+** a UNIQUE constraint or index.
+**
+** When IN_INDEX_MEMBERSHIP is used (and the b-tree will be used
+** for fast set membership tests) then an ephemeral table must
+** be used unless <columns> is a single INTEGER PRIMARY KEY column or an
+** index can be found with the specified <columns> as its left-most.
+**
+** If the IN_INDEX_NOOP_OK and IN_INDEX_MEMBERSHIP are both set and
+** if the RHS of the IN operator is a list (not a subquery) then this
+** routine might decide that creating an ephemeral b-tree for membership
+** testing is too expensive and return IN_INDEX_NOOP.  In that case, the
+** calling routine should implement the IN operator using a sequence
+** of Eq or Ne comparison operations.
+**
+** When the b-tree is being used for membership tests, the calling function
+** might need to know whether or not the RHS side of the IN operator
+** contains a NULL.  If prRhsHasNull is not a NULL pointer and
+** if there is any chance that the (...) might contain a NULL value at
+** runtime, then a register is allocated and the register number written
+** to *prRhsHasNull. If there is no chance that the (...) contains a
+** NULL value, then *prRhsHasNull is left unchanged.
+**
+** If a register is allocated and its location stored in *prRhsHasNull, then
+** the value in that register will be NULL if the b-tree contains one or more
+** NULL values, and it will be some non-NULL value if the b-tree contains no
+** NULL values.
+**
+** If the aiMap parameter is not NULL, it must point to an array containing
+** one element for each column returned by the SELECT statement on the RHS
+** of the IN(...) operator. The i'th entry of the array is populated with the
+** offset of the index column that matches the i'th column returned by the
+** SELECT. For example, if the expression and selected index are:
+**
+**   (?,?,?) IN (SELECT a, b, c FROM t1)
+**   CREATE INDEX i1 ON t1(b, c, a);
+**
+** then aiMap[] is populated with {2, 0, 1}.
+*/
+#ifndef SQLITE_OMIT_SUBQUERY
+int sqlite3FindInIndex(
+  Parse *pParse,             /* Parsing context */
+  Expr *pX,                  /* The IN expression */
+  u32 inFlags,               /* IN_INDEX_LOOP, _MEMBERSHIP, and/or _NOOP_OK */
+  int *prRhsHasNull,         /* Register holding NULL status.  See notes */
+  int *aiMap,                /* Mapping from Index fields to RHS fields */
+  int *piTab                 /* OUT: index to use */
+){
+  Select *p;                            /* SELECT to the right of IN operator */
+  int eType = 0;                        /* Type of RHS table. IN_INDEX_* */
+  int iTab;                             /* Cursor of the RHS table */
+  int mustBeUnique;                     /* True if RHS must be unique */
+  Vdbe *v = sqlite3GetVdbe(pParse);     /* Virtual machine being coded */
+
+  assert( pX->op==TK_IN );
+  mustBeUnique = (inFlags & IN_INDEX_LOOP)!=0;
+  iTab = pParse->nTab++;
+
+  /* If the RHS of this IN(...) operator is a SELECT, and if it matters
+  ** whether or not the SELECT result contains NULL values, check whether
+  ** or not NULL is actually possible (it may not be, for example, due
+  ** to NOT NULL constraints in the schema). If no NULL values are possible,
+  ** set prRhsHasNull to 0 before continuing.  */
+  if( prRhsHasNull && ExprUseXSelect(pX) ){
+    int i;
+    ExprList *pEList = pX->x.pSelect->pEList;
+    for(i=0; i<pEList->nExpr; i++){
+      if( sqlite3ExprCanBeNull(pEList->a[i].pExpr) ) break;
+    }
+    if( i==pEList->nExpr ){
+      prRhsHasNull = 0;
+    }
+  }
+
+  /* Check to see if an existing table or index can be used to
+  ** satisfy the query.  This is preferable to generating a new
+  ** ephemeral table.  */
+  if( pParse->nErr==0 && (p = isCandidateForInOpt(pX))!=0 ){
+    sqlite3 *db = pParse->db;              /* Database connection */
+    Table *pTab;                           /* Table <table>. */
+    int iDb;                               /* Database idx for pTab */
+    ExprList *pEList = p->pEList;
+    int nExpr = pEList->nExpr;
+
+    assert( p->pEList!=0 );             /* Because of isCandidateForInOpt(p) */
+    assert( p->pEList->a[0].pExpr!=0 ); /* Because of isCandidateForInOpt(p) */
+    assert( p->pSrc!=0 );               /* Because of isCandidateForInOpt(p) */
+    pTab = p->pSrc->a[0].pTab;
+
+    /* Code an OP_Transaction and OP_TableLock for <table>. */
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    assert( iDb>=0 && iDb<SQLITE_MAX_DB );
+    sqlite3CodeVerifySchema(pParse, iDb);
+    sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+
+    assert(v);  /* sqlite3GetVdbe() has always been previously called */
+    if( nExpr==1 && pEList->a[0].pExpr->iColumn<0 ){
+      /* The "x IN (SELECT rowid FROM table)" case */
+      int iAddr = sqlite3VdbeAddOp0(v, OP_Once);
+      VdbeCoverage(v);
+
+      sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
+      eType = IN_INDEX_ROWID;
+      ExplainQueryPlan((pParse, 0,
+            "USING ROWID SEARCH ON TABLE %s FOR IN-OPERATOR",pTab->zName));
+      sqlite3VdbeJumpHere(v, iAddr);
+    }else{
+      Index *pIdx;                         /* Iterator variable */
+      int affinity_ok = 1;
+      int i;
+
+      /* Check that the affinity that will be used to perform each
+      ** comparison is the same as the affinity of each column in table
+      ** on the RHS of the IN operator.  If it not, it is not possible to
+      ** use any index of the RHS table.  */
+      for(i=0; i<nExpr && affinity_ok; i++){
+        Expr *pLhs = sqlite3VectorFieldSubexpr(pX->pLeft, i);
+        int iCol = pEList->a[i].pExpr->iColumn;
+        char idxaff = sqlite3TableColumnAffinity(pTab,iCol); /* RHS table */
+        char cmpaff = sqlite3CompareAffinity(pLhs, idxaff);
+        testcase( cmpaff==SQLITE_AFF_BLOB );
+        testcase( cmpaff==SQLITE_AFF_TEXT );
+        switch( cmpaff ){
+          case SQLITE_AFF_BLOB:
+            break;
+          case SQLITE_AFF_TEXT:
+            /* sqlite3CompareAffinity() only returns TEXT if one side or the
+            ** other has no affinity and the other side is TEXT.  Hence,
+            ** the only way for cmpaff to be TEXT is for idxaff to be TEXT
+            ** and for the term on the LHS of the IN to have no affinity. */
+            assert( idxaff==SQLITE_AFF_TEXT );
+            break;
+          default:
+            affinity_ok = sqlite3IsNumericAffinity(idxaff);
+        }
+      }
+
+      if( affinity_ok ){
+        /* Search for an existing index that will work for this IN operator */
+        for(pIdx=pTab->pIndex; pIdx && eType==0; pIdx=pIdx->pNext){
+          Bitmask colUsed;      /* Columns of the index used */
+          Bitmask mCol;         /* Mask for the current column */
+          if( pIdx->nColumn<nExpr ) continue;
+          if( pIdx->pPartIdxWhere!=0 ) continue;
+          /* Maximum nColumn is BMS-2, not BMS-1, so that we can compute
+          ** BITMASK(nExpr) without overflowing */
+          testcase( pIdx->nColumn==BMS-2 );
+          testcase( pIdx->nColumn==BMS-1 );
+          if( pIdx->nColumn>=BMS-1 ) continue;
+          if( mustBeUnique ){
+            if( pIdx->nKeyCol>nExpr
+             ||(pIdx->nColumn>nExpr && !IsUniqueIndex(pIdx))
+            ){
+              continue;  /* This index is not unique over the IN RHS columns */
+            }
+          }
+ 
+          colUsed = 0;   /* Columns of index used so far */
+          for(i=0; i<nExpr; i++){
+            Expr *pLhs = sqlite3VectorFieldSubexpr(pX->pLeft, i);
+            Expr *pRhs = pEList->a[i].pExpr;
+            CollSeq *pReq = sqlite3BinaryCompareCollSeq(pParse, pLhs, pRhs);
+            int j;
+ 
+            for(j=0; j<nExpr; j++){
+              if( pIdx->aiColumn[j]!=pRhs->iColumn ) continue;
+              assert( pIdx->azColl[j] );
+              if( pReq!=0 && sqlite3StrICmp(pReq->zName, pIdx->azColl[j])!=0 ){
+                continue;
+              }
+              break;
+            }
+            if( j==nExpr ) break;
+            mCol = MASKBIT(j);
+            if( mCol & colUsed ) break; /* Each column used only once */
+            colUsed |= mCol;
+            if( aiMap ) aiMap[i] = j;
+          }
+ 
+          assert( i==nExpr || colUsed!=(MASKBIT(nExpr)-1) );
+          if( colUsed==(MASKBIT(nExpr)-1) ){
+            /* If we reach this point, that means the index pIdx is usable */
+            int iAddr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+            ExplainQueryPlan((pParse, 0,
+                              "USING INDEX %s FOR IN-OPERATOR",pIdx->zName));
+            sqlite3VdbeAddOp3(v, OP_OpenRead, iTab, pIdx->tnum, iDb);
+            sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
+            VdbeComment((v, "%s", pIdx->zName));
+            assert( IN_INDEX_INDEX_DESC == IN_INDEX_INDEX_ASC+1 );
+            eType = IN_INDEX_INDEX_ASC + pIdx->aSortOrder[0];
+ 
+            if( prRhsHasNull ){
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+              i64 mask = (1<<nExpr)-1;
+              sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed,
+                  iTab, 0, 0, (u8*)&mask, P4_INT64);
+#endif
+              *prRhsHasNull = ++pParse->nMem;
+              if( nExpr==1 ){
+                sqlite3SetHasNullFlag(v, iTab, *prRhsHasNull);
+              }
+            }
+            sqlite3VdbeJumpHere(v, iAddr);
+          }
+        } /* End loop over indexes */
+      } /* End if( affinity_ok ) */
+    } /* End if not an rowid index */
+  } /* End attempt to optimize using an index */
+
+  /* If no preexisting index is available for the IN clause
+  ** and IN_INDEX_NOOP is an allowed reply
+  ** and the RHS of the IN operator is a list, not a subquery
+  ** and the RHS is not constant or has two or fewer terms,
+  ** then it is not worth creating an ephemeral table to evaluate
+  ** the IN operator so return IN_INDEX_NOOP.
+  */
+  if( eType==0
+   && (inFlags & IN_INDEX_NOOP_OK)
+   && ExprUseXList(pX)
+   && (!sqlite3InRhsIsConstant(pX) || pX->x.pList->nExpr<=2)
+  ){
+    pParse->nTab--;  /* Back out the allocation of the unused cursor */
+    iTab = -1;       /* Cursor is not allocated */
+    eType = IN_INDEX_NOOP;
+  }
+
+  if( eType==0 ){
+    /* Could not find an existing table or index to use as the RHS b-tree.
+    ** We will have to generate an ephemeral table to do the job.
+    */
+    u32 savedNQueryLoop = pParse->nQueryLoop;
+    int rMayHaveNull = 0;
+    eType = IN_INDEX_EPH;
+    if( inFlags & IN_INDEX_LOOP ){
+      pParse->nQueryLoop = 0;
+    }else if( prRhsHasNull ){
+      *prRhsHasNull = rMayHaveNull = ++pParse->nMem;
+    }
+    assert( pX->op==TK_IN );
+    sqlite3CodeRhsOfIN(pParse, pX, iTab);
+    if( rMayHaveNull ){
+      sqlite3SetHasNullFlag(v, iTab, rMayHaveNull);
+    }
+    pParse->nQueryLoop = savedNQueryLoop;
+  }
+
+  if( aiMap && eType!=IN_INDEX_INDEX_ASC && eType!=IN_INDEX_INDEX_DESC ){
+    int i, n;
+    n = sqlite3ExprVectorSize(pX->pLeft);
+    for(i=0; i<n; i++) aiMap[i] = i;
+  }
+  *piTab = iTab;
+  return eType;
+}
+#endif
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Argument pExpr is an (?, ?...) IN(...) expression. This
+** function allocates and returns a nul-terminated string containing
+** the affinities to be used for each column of the comparison.
+**
+** It is the responsibility of the caller to ensure that the returned
+** string is eventually freed using sqlite3DbFree().
+*/
+static char *exprINAffinity(Parse *pParse, const Expr *pExpr){
+  Expr *pLeft = pExpr->pLeft;
+  int nVal = sqlite3ExprVectorSize(pLeft);
+  Select *pSelect = ExprUseXSelect(pExpr) ? pExpr->x.pSelect : 0;
+  char *zRet;
+
+  assert( pExpr->op==TK_IN );
+  zRet = sqlite3DbMallocRaw(pParse->db, nVal+1);
+  if( zRet ){
+    int i;
+    for(i=0; i<nVal; i++){
+      Expr *pA = sqlite3VectorFieldSubexpr(pLeft, i);
+      char a = sqlite3ExprAffinity(pA);
+      if( pSelect ){
+        zRet[i] = sqlite3CompareAffinity(pSelect->pEList->a[i].pExpr, a);
+      }else{
+        zRet[i] = a;
+      }
+    }
+    zRet[nVal] = '\0';
+  }
+  return zRet;
+}
+#endif
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Load the Parse object passed as the first argument with an error
+** message of the form:
+**
+**   "sub-select returns N columns - expected M"
+*/  
+void sqlite3SubselectError(Parse *pParse, int nActual, int nExpect){
+  if( pParse->nErr==0 ){
+    const char *zFmt = "sub-select returns %d columns - expected %d";
+    sqlite3ErrorMsg(pParse, zFmt, nActual, nExpect);
+  }
+}
+#endif
+
+/*
+** Expression pExpr is a vector that has been used in a context where
+** it is not permitted. If pExpr is a sub-select vector, this routine
+** loads the Parse object with a message of the form:
+**
+**   "sub-select returns N columns - expected 1"
+**
+** Or, if it is a regular scalar vector:
+**
+**   "row value misused"
+*/  
+void sqlite3VectorErrorMsg(Parse *pParse, Expr *pExpr){
+#ifndef SQLITE_OMIT_SUBQUERY
+  if( ExprUseXSelect(pExpr) ){
+    sqlite3SubselectError(pParse, pExpr->x.pSelect->pEList->nExpr, 1);
+  }else
+#endif
+  {
+    sqlite3ErrorMsg(pParse, "row value misused");
+  }
+}
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Generate code that will construct an ephemeral table containing all terms
+** in the RHS of an IN operator.  The IN operator can be in either of two
+** forms:
+**
+**     x IN (4,5,11)              -- IN operator with list on right-hand side
+**     x IN (SELECT a FROM b)     -- IN operator with subquery on the right
+**
+** The pExpr parameter is the IN operator.  The cursor number for the
+** constructed ephemeral table is returned.  The first time the ephemeral
+** table is computed, the cursor number is also stored in pExpr->iTable,
+** however the cursor number returned might not be the same, as it might
+** have been duplicated using OP_OpenDup.
+**
+** If the LHS expression ("x" in the examples) is a column value, or
+** the SELECT statement returns a column value, then the affinity of that
+** column is used to build the index keys. If both 'x' and the
+** SELECT... statement are columns, then numeric affinity is used
+** if either column has NUMERIC or INTEGER affinity. If neither
+** 'x' nor the SELECT... statement are columns, then numeric affinity
+** is used.
+*/
+void sqlite3CodeRhsOfIN(
+  Parse *pParse,          /* Parsing context */
+  Expr *pExpr,            /* The IN operator */
+  int iTab                /* Use this cursor number */
+){
+  int addrOnce = 0;           /* Address of the OP_Once instruction at top */
+  int addr;                   /* Address of OP_OpenEphemeral instruction */
+  Expr *pLeft;                /* the LHS of the IN operator */
+  KeyInfo *pKeyInfo = 0;      /* Key information */
+  int nVal;                   /* Size of vector pLeft */
+  Vdbe *v;                    /* The prepared statement under construction */
+
+  v = pParse->pVdbe;
+  assert( v!=0 );
+
+  /* The evaluation of the IN must be repeated every time it
+  ** is encountered if any of the following is true:
+  **
+  **    *  The right-hand side is a correlated subquery
+  **    *  The right-hand side is an expression list containing variables
+  **    *  We are inside a trigger
+  **
+  ** If all of the above are false, then we can compute the RHS just once
+  ** and reuse it many names.
+  */
+  if( !ExprHasProperty(pExpr, EP_VarSelect) && pParse->iSelfTab==0 ){
+    /* Reuse of the RHS is allowed */
+    /* If this routine has already been coded, but the previous code
+    ** might not have been invoked yet, so invoke it now as a subroutine.
+    */
+    if( ExprHasProperty(pExpr, EP_Subrtn) ){
+      addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+      if( ExprUseXSelect(pExpr) ){
+        ExplainQueryPlan((pParse, 0, "REUSE LIST SUBQUERY %d",
+              pExpr->x.pSelect->selId));
+      }
+      assert( ExprUseYSub(pExpr) );
+      sqlite3VdbeAddOp2(v, OP_Gosub, pExpr->y.sub.regReturn,
+                        pExpr->y.sub.iAddr);
+      assert( iTab!=pExpr->iTable );
+      sqlite3VdbeAddOp2(v, OP_OpenDup, iTab, pExpr->iTable);
+      sqlite3VdbeJumpHere(v, addrOnce);
+      return;
+    }
+
+    /* Begin coding the subroutine */
+    assert( !ExprUseYWin(pExpr) );
+    ExprSetProperty(pExpr, EP_Subrtn);
+    assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
+    pExpr->y.sub.regReturn = ++pParse->nMem;
+    pExpr->y.sub.iAddr =
+      sqlite3VdbeAddOp2(v, OP_BeginSubrtn, 0, pExpr->y.sub.regReturn) + 1;
+
+    addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+  }
+
+  /* Check to see if this is a vector IN operator */
+  pLeft = pExpr->pLeft;
+  nVal = sqlite3ExprVectorSize(pLeft);
+
+  /* Construct the ephemeral table that will contain the content of
+  ** RHS of the IN operator.
+  */
+  pExpr->iTable = iTab;
+  addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pExpr->iTable, nVal);
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  if( ExprUseXSelect(pExpr) ){
+    VdbeComment((v, "Result of SELECT %u", pExpr->x.pSelect->selId));
+  }else{
+    VdbeComment((v, "RHS of IN operator"));
+  }
+#endif
+  pKeyInfo = sqlite3KeyInfoAlloc(pParse->db, nVal, 1);
+
+  if( ExprUseXSelect(pExpr) ){
+    /* Case 1:     expr IN (SELECT ...)
+    **
+    ** Generate code to write the results of the select into the temporary
+    ** table allocated and opened above.
+    */
+    Select *pSelect = pExpr->x.pSelect;
+    ExprList *pEList = pSelect->pEList;
+
+    ExplainQueryPlan((pParse, 1, "%sLIST SUBQUERY %d",
+        addrOnce?"":"CORRELATED ", pSelect->selId
+    ));
+    /* If the LHS and RHS of the IN operator do not match, that
+    ** error will have been caught long before we reach this point. */
+    if( ALWAYS(pEList->nExpr==nVal) ){
+      Select *pCopy;
+      SelectDest dest;
+      int i;
+      int rc;
+      sqlite3SelectDestInit(&dest, SRT_Set, iTab);
+      dest.zAffSdst = exprINAffinity(pParse, pExpr);
+      pSelect->iLimit = 0;
+      testcase( pSelect->selFlags & SF_Distinct );
+      testcase( pKeyInfo==0 ); /* Caused by OOM in sqlite3KeyInfoAlloc() */
+      pCopy = sqlite3SelectDup(pParse->db, pSelect, 0);
+      rc = pParse->db->mallocFailed ? 1 :sqlite3Select(pParse, pCopy, &dest);
+      sqlite3SelectDelete(pParse->db, pCopy);
+      sqlite3DbFree(pParse->db, dest.zAffSdst);
+      if( rc ){
+        sqlite3KeyInfoUnref(pKeyInfo);
+        return;
+      }     
+      assert( pKeyInfo!=0 ); /* OOM will cause exit after sqlite3Select() */
+      assert( pEList!=0 );
+      assert( pEList->nExpr>0 );
+      assert( sqlite3KeyInfoIsWriteable(pKeyInfo) );
+      for(i=0; i<nVal; i++){
+        Expr *p = sqlite3VectorFieldSubexpr(pLeft, i);
+        pKeyInfo->aColl[i] = sqlite3BinaryCompareCollSeq(
+            pParse, p, pEList->a[i].pExpr
+        );
+      }
+    }
+  }else if( ALWAYS(pExpr->x.pList!=0) ){
+    /* Case 2:     expr IN (exprlist)
+    **
+    ** For each expression, build an index key from the evaluation and
+    ** store it in the temporary table. If <expr> is a column, then use
+    ** that columns affinity when building index keys. If <expr> is not
+    ** a column, use numeric affinity.
+    */
+    char affinity;            /* Affinity of the LHS of the IN */
+    int i;
+    ExprList *pList = pExpr->x.pList;
+    struct ExprList_item *pItem;
+    int r1, r2;
+    affinity = sqlite3ExprAffinity(pLeft);
+    if( affinity<=SQLITE_AFF_NONE ){
+      affinity = SQLITE_AFF_BLOB;
+    }else if( affinity==SQLITE_AFF_REAL ){
+      affinity = SQLITE_AFF_NUMERIC;
+    }
+    if( pKeyInfo ){
+      assert( sqlite3KeyInfoIsWriteable(pKeyInfo) );
+      pKeyInfo->aColl[0] = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
+    }
+
+    /* Loop through each expression in <exprlist>. */
+    r1 = sqlite3GetTempReg(pParse);
+    r2 = sqlite3GetTempReg(pParse);
+    for(i=pList->nExpr, pItem=pList->a; i>0; i--, pItem++){
+      Expr *pE2 = pItem->pExpr;
+
+      /* If the expression is not constant then we will need to
+      ** disable the test that was generated above that makes sure
+      ** this code only executes once.  Because for a non-constant
+      ** expression we need to rerun this code each time.
+      */
+      if( addrOnce && !sqlite3ExprIsConstant(pE2) ){
+        sqlite3VdbeChangeToNoop(v, addrOnce-1);
+        sqlite3VdbeChangeToNoop(v, addrOnce);
+        ExprClearProperty(pExpr, EP_Subrtn);
+        addrOnce = 0;
+      }
+
+      /* Evaluate the expression and insert it into the temp table */
+      sqlite3ExprCode(pParse, pE2, r1);
+      sqlite3VdbeAddOp4(v, OP_MakeRecord, r1, 1, r2, &affinity, 1);
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iTab, r2, r1, 1);
+    }
+    sqlite3ReleaseTempReg(pParse, r1);
+    sqlite3ReleaseTempReg(pParse, r2);
+  }
+  if( pKeyInfo ){
+    sqlite3VdbeChangeP4(v, addr, (void *)pKeyInfo, P4_KEYINFO);
+  }
+  if( addrOnce ){
+    sqlite3VdbeAddOp1(v, OP_NullRow, iTab);
+    sqlite3VdbeJumpHere(v, addrOnce);
+    /* Subroutine return */
+    assert( ExprUseYSub(pExpr) );
+    assert( sqlite3VdbeGetOp(v,pExpr->y.sub.iAddr-1)->opcode==OP_BeginSubrtn
+            || pParse->nErr );
+    sqlite3VdbeAddOp3(v, OP_Return, pExpr->y.sub.regReturn,
+                      pExpr->y.sub.iAddr, 1);
+    VdbeCoverage(v);
+    sqlite3ClearTempRegCache(pParse);
+  }
+}
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+/*
+** Generate code for scalar subqueries used as a subquery expression
+** or EXISTS operator:
+**
+**     (SELECT a FROM b)          -- subquery
+**     EXISTS (SELECT a FROM b)   -- EXISTS subquery
+**
+** The pExpr parameter is the SELECT or EXISTS operator to be coded.
+**
+** Return the register that holds the result.  For a multi-column SELECT,
+** the result is stored in a contiguous array of registers and the
+** return value is the register of the left-most result column.
+** Return 0 if an error occurs.
+*/
+#ifndef SQLITE_OMIT_SUBQUERY
+int sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
+  int addrOnce = 0;           /* Address of OP_Once at top of subroutine */
+  int rReg = 0;               /* Register storing resulting */
+  Select *pSel;               /* SELECT statement to encode */
+  SelectDest dest;            /* How to deal with SELECT result */
+  int nReg;                   /* Registers to allocate */
+  Expr *pLimit;               /* New limit expression */
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  int addrExplain;            /* Address of OP_Explain instruction */
+#endif
+
+  Vdbe *v = pParse->pVdbe;
+  assert( v!=0 );
+  if( pParse->nErr ) return 0;
+  testcase( pExpr->op==TK_EXISTS );
+  testcase( pExpr->op==TK_SELECT );
+  assert( pExpr->op==TK_EXISTS || pExpr->op==TK_SELECT );
+  assert( ExprUseXSelect(pExpr) );
+  pSel = pExpr->x.pSelect;
+
+  /* If this routine has already been coded, then invoke it as a
+  ** subroutine. */
+  if( ExprHasProperty(pExpr, EP_Subrtn) ){
+    ExplainQueryPlan((pParse, 0, "REUSE SUBQUERY %d", pSel->selId));
+    assert( ExprUseYSub(pExpr) );
+    sqlite3VdbeAddOp2(v, OP_Gosub, pExpr->y.sub.regReturn,
+                      pExpr->y.sub.iAddr);
+    return pExpr->iTable;
+  }
+
+  /* Begin coding the subroutine */
+  assert( !ExprUseYWin(pExpr) );
+  assert( !ExprHasProperty(pExpr, EP_Reduced|EP_TokenOnly) );
+  ExprSetProperty(pExpr, EP_Subrtn);
+  pExpr->y.sub.regReturn = ++pParse->nMem;
+  pExpr->y.sub.iAddr =
+    sqlite3VdbeAddOp2(v, OP_BeginSubrtn, 0, pExpr->y.sub.regReturn) + 1;
+
+  /* The evaluation of the EXISTS/SELECT must be repeated every time it
+  ** is encountered if any of the following is true:
+  **
+  **    *  The right-hand side is a correlated subquery
+  **    *  The right-hand side is an expression list containing variables
+  **    *  We are inside a trigger
+  **
+  ** If all of the above are false, then we can run this code just once
+  ** save the results, and reuse the same result on subsequent invocations.
+  */
+  if( !ExprHasProperty(pExpr, EP_VarSelect) ){
+    addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+  }
+ 
+  /* For a SELECT, generate code to put the values for all columns of
+  ** the first row into an array of registers and return the index of
+  ** the first register.
+  **
+  ** If this is an EXISTS, write an integer 0 (not exists) or 1 (exists)
+  ** into a register and return that register number.
+  **
+  ** In both cases, the query is augmented with "LIMIT 1".  Any
+  ** preexisting limit is discarded in place of the new LIMIT 1.
+  */
+  ExplainQueryPlan2(addrExplain, (pParse, 1, "%sSCALAR SUBQUERY %d",
+        addrOnce?"":"CORRELATED ", pSel->selId));
+  sqlite3VdbeScanStatusCounters(v, addrExplain, addrExplain, -1);
+  nReg = pExpr->op==TK_SELECT ? pSel->pEList->nExpr : 1;
+  sqlite3SelectDestInit(&dest, 0, pParse->nMem+1);
+  pParse->nMem += nReg;
+  if( pExpr->op==TK_SELECT ){
+    dest.eDest = SRT_Mem;
+    dest.iSdst = dest.iSDParm;
+    dest.nSdst = nReg;
+    sqlite3VdbeAddOp3(v, OP_Null, 0, dest.iSDParm, dest.iSDParm+nReg-1);
+    VdbeComment((v, "Init subquery result"));
+  }else{
+    dest.eDest = SRT_Exists;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
+    VdbeComment((v, "Init EXISTS result"));
+  }
+  if( pSel->pLimit ){
+    /* The subquery already has a limit.  If the pre-existing limit is X
+    ** then make the new limit X<>0 so that the new limit is either 1 or 0 */
+    sqlite3 *db = pParse->db;
+    pLimit = sqlite3Expr(db, TK_INTEGER, "0");
+    if( pLimit ){
+      pLimit->affExpr = SQLITE_AFF_NUMERIC;
+      pLimit = sqlite3PExpr(pParse, TK_NE,
+                            sqlite3ExprDup(db, pSel->pLimit->pLeft, 0), pLimit);
+    }
+    sqlite3ExprDeferredDelete(pParse, pSel->pLimit->pLeft);
+    pSel->pLimit->pLeft = pLimit;
+  }else{
+    /* If there is no pre-existing limit add a limit of 1 */
+    pLimit = sqlite3Expr(pParse->db, TK_INTEGER, "1");
+    pSel->pLimit = sqlite3PExpr(pParse, TK_LIMIT, pLimit, 0);
+  }
+  pSel->iLimit = 0;
+  if( sqlite3Select(pParse, pSel, &dest) ){
+    pExpr->op2 = pExpr->op;
+    pExpr->op = TK_ERROR;
+    return 0;
+  }
+  pExpr->iTable = rReg = dest.iSDParm;
+  ExprSetVVAProperty(pExpr, EP_NoReduce);
+  if( addrOnce ){
+    sqlite3VdbeJumpHere(v, addrOnce);
+  }
+  sqlite3VdbeScanStatusRange(v, addrExplain, addrExplain, -1);
+
+  /* Subroutine return */
+  assert( ExprUseYSub(pExpr) );
+  assert( sqlite3VdbeGetOp(v,pExpr->y.sub.iAddr-1)->opcode==OP_BeginSubrtn
+          || pParse->nErr );
+  sqlite3VdbeAddOp3(v, OP_Return, pExpr->y.sub.regReturn,
+                    pExpr->y.sub.iAddr, 1);
+  VdbeCoverage(v);
+  sqlite3ClearTempRegCache(pParse);
+  return rReg;
+}
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Expr pIn is an IN(...) expression. This function checks that the
+** sub-select on the RHS of the IN() operator has the same number of
+** columns as the vector on the LHS. Or, if the RHS of the IN() is not
+** a sub-query, that the LHS is a vector of size 1.
+*/
+int sqlite3ExprCheckIN(Parse *pParse, Expr *pIn){
+  int nVector = sqlite3ExprVectorSize(pIn->pLeft);
+  if( ExprUseXSelect(pIn) && !pParse->db->mallocFailed ){
+    if( nVector!=pIn->x.pSelect->pEList->nExpr ){
+      sqlite3SubselectError(pParse, pIn->x.pSelect->pEList->nExpr, nVector);
+      return 1;
+    }
+  }else if( nVector!=1 ){
+    sqlite3VectorErrorMsg(pParse, pIn->pLeft);
+    return 1;
+  }
+  return 0;
+}
+#endif
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Generate code for an IN expression.
+**
+**      x IN (SELECT ...)
+**      x IN (value, value, ...)
+**
+** The left-hand side (LHS) is a scalar or vector expression.  The
+** right-hand side (RHS) is an array of zero or more scalar values, or a
+** subquery.  If the RHS is a subquery, the number of result columns must
+** match the number of columns in the vector on the LHS.  If the RHS is
+** a list of values, the LHS must be a scalar.
+**
+** The IN operator is true if the LHS value is contained within the RHS.
+** The result is false if the LHS is definitely not in the RHS.  The
+** result is NULL if the presence of the LHS in the RHS cannot be
+** determined due to NULLs.
+**
+** This routine generates code that jumps to destIfFalse if the LHS is not
+** contained within the RHS.  If due to NULLs we cannot determine if the LHS
+** is contained in the RHS then jump to destIfNull.  If the LHS is contained
+** within the RHS then fall through.
+**
+** See the separate in-operator.md documentation file in the canonical
+** SQLite source tree for additional information.
+*/
+static void sqlite3ExprCodeIN(
+  Parse *pParse,        /* Parsing and code generating context */
+  Expr *pExpr,          /* The IN expression */
+  int destIfFalse,      /* Jump here if LHS is not contained in the RHS */
+  int destIfNull        /* Jump here if the results are unknown due to NULLs */
+){
+  int rRhsHasNull = 0;  /* Register that is true if RHS contains NULL values */
+  int eType;            /* Type of the RHS */
+  int rLhs;             /* Register(s) holding the LHS values */
+  int rLhsOrig;         /* LHS values prior to reordering by aiMap[] */
+  Vdbe *v;              /* Statement under construction */
+  int *aiMap = 0;       /* Map from vector field to index column */
+  char *zAff = 0;       /* Affinity string for comparisons */
+  int nVector;          /* Size of vectors for this IN operator */
+  int iDummy;           /* Dummy parameter to exprCodeVector() */
+  Expr *pLeft;          /* The LHS of the IN operator */
+  int i;                /* loop counter */
+  int destStep2;        /* Where to jump when NULLs seen in step 2 */
+  int destStep6 = 0;    /* Start of code for Step 6 */
+  int addrTruthOp;      /* Address of opcode that determines the IN is true */
+  int destNotNull;      /* Jump here if a comparison is not true in step 6 */
+  int addrTop;          /* Top of the step-6 loop */
+  int iTab = 0;         /* Index to use */
+  u8 okConstFactor = pParse->okConstFactor;
+
+  assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );
+  pLeft = pExpr->pLeft;
+  if( sqlite3ExprCheckIN(pParse, pExpr) ) return;
+  zAff = exprINAffinity(pParse, pExpr);
+  nVector = sqlite3ExprVectorSize(pExpr->pLeft);
+  aiMap = (int*)sqlite3DbMallocZero(
+      pParse->db, nVector*(sizeof(int) + sizeof(char)) + 1
+  );
+  if( pParse->db->mallocFailed ) goto sqlite3ExprCodeIN_oom_error;
+
+  /* Attempt to compute the RHS. After this step, if anything other than
+  ** IN_INDEX_NOOP is returned, the table opened with cursor iTab
+  ** contains the values that make up the RHS. If IN_INDEX_NOOP is returned,
+  ** the RHS has not yet been coded.  */
+  v = pParse->pVdbe;
+  assert( v!=0 );       /* OOM detected prior to this routine */
+  VdbeNoopComment((v, "begin IN expr"));
+  eType = sqlite3FindInIndex(pParse, pExpr,
+                             IN_INDEX_MEMBERSHIP | IN_INDEX_NOOP_OK,
+                             destIfFalse==destIfNull ? 0 : &rRhsHasNull,
+                             aiMap, &iTab);
+
+  assert( pParse->nErr || nVector==1 || eType==IN_INDEX_EPH
+       || eType==IN_INDEX_INDEX_ASC || eType==IN_INDEX_INDEX_DESC
+  );
+#ifdef SQLITE_DEBUG
+  /* Confirm that aiMap[] contains nVector integer values between 0 and
+  ** nVector-1. */
+  for(i=0; i<nVector; i++){
+    int j, cnt;
+    for(cnt=j=0; j<nVector; j++) if( aiMap[j]==i ) cnt++;
+    assert( cnt==1 );
+  }
+#endif
+
+  /* Code the LHS, the <expr> from "<expr> IN (...)". If the LHS is a
+  ** vector, then it is stored in an array of nVector registers starting
+  ** at r1.
+  **
+  ** sqlite3FindInIndex() might have reordered the fields of the LHS vector
+  ** so that the fields are in the same order as an existing index.   The
+  ** aiMap[] array contains a mapping from the original LHS field order to
+  ** the field order that matches the RHS index.
+  **
+  ** Avoid factoring the LHS of the IN(...) expression out of the loop,
+  ** even if it is constant, as OP_Affinity may be used on the register
+  ** by code generated below.  */
+  assert( pParse->okConstFactor==okConstFactor );
+  pParse->okConstFactor = 0;
+  rLhsOrig = exprCodeVector(pParse, pLeft, &iDummy);
+  pParse->okConstFactor = okConstFactor;
+  for(i=0; i<nVector && aiMap[i]==i; i++){} /* Are LHS fields reordered? */
+  if( i==nVector ){
+    /* LHS fields are not reordered */
+    rLhs = rLhsOrig;
+  }else{
+    /* Need to reorder the LHS fields according to aiMap */
+    rLhs = sqlite3GetTempRange(pParse, nVector);
+    for(i=0; i<nVector; i++){
+      sqlite3VdbeAddOp3(v, OP_Copy, rLhsOrig+i, rLhs+aiMap[i], 0);
+    }
+  }
+
+  /* If sqlite3FindInIndex() did not find or create an index that is
+  ** suitable for evaluating the IN operator, then evaluate using a
+  ** sequence of comparisons.
+  **
+  ** This is step (1) in the in-operator.md optimized algorithm.
+  */
+  if( eType==IN_INDEX_NOOP ){
+    ExprList *pList;
+    CollSeq *pColl;
+    int labelOk = sqlite3VdbeMakeLabel(pParse);
+    int r2, regToFree;
+    int regCkNull = 0;
+    int ii;
+    assert( ExprUseXList(pExpr) );
+    pList = pExpr->x.pList;
+    pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
+    if( destIfNull!=destIfFalse ){
+      regCkNull = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp3(v, OP_BitAnd, rLhs, rLhs, regCkNull);
+    }
+    for(ii=0; ii<pList->nExpr; ii++){
+      r2 = sqlite3ExprCodeTemp(pParse, pList->a[ii].pExpr, &regToFree);
+      if( regCkNull && sqlite3ExprCanBeNull(pList->a[ii].pExpr) ){
+        sqlite3VdbeAddOp3(v, OP_BitAnd, regCkNull, r2, regCkNull);
+      }
+      sqlite3ReleaseTempReg(pParse, regToFree);
+      if( ii<pList->nExpr-1 || destIfNull!=destIfFalse ){
+        int op = rLhs!=r2 ? OP_Eq : OP_NotNull;
+        sqlite3VdbeAddOp4(v, op, rLhs, labelOk, r2,
+                          (void*)pColl, P4_COLLSEQ);
+        VdbeCoverageIf(v, ii<pList->nExpr-1 && op==OP_Eq);
+        VdbeCoverageIf(v, ii==pList->nExpr-1 && op==OP_Eq);
+        VdbeCoverageIf(v, ii<pList->nExpr-1 && op==OP_NotNull);
+        VdbeCoverageIf(v, ii==pList->nExpr-1 && op==OP_NotNull);
+        sqlite3VdbeChangeP5(v, zAff[0]);
+      }else{
+        int op = rLhs!=r2 ? OP_Ne : OP_IsNull;
+        assert( destIfNull==destIfFalse );
+        sqlite3VdbeAddOp4(v, op, rLhs, destIfFalse, r2,
+                          (void*)pColl, P4_COLLSEQ);
+        VdbeCoverageIf(v, op==OP_Ne);
+        VdbeCoverageIf(v, op==OP_IsNull);
+        sqlite3VdbeChangeP5(v, zAff[0] | SQLITE_JUMPIFNULL);
+      }
+    }
+    if( regCkNull ){
+      sqlite3VdbeAddOp2(v, OP_IsNull, regCkNull, destIfNull); VdbeCoverage(v);
+      sqlite3VdbeGoto(v, destIfFalse);
+    }
+    sqlite3VdbeResolveLabel(v, labelOk);
+    sqlite3ReleaseTempReg(pParse, regCkNull);
+    goto sqlite3ExprCodeIN_finished;
+  }
+
+  /* Step 2: Check to see if the LHS contains any NULL columns.  If the
+  ** LHS does contain NULLs then the result must be either FALSE or NULL.
+  ** We will then skip the binary search of the RHS.
+  */
+  if( destIfNull==destIfFalse ){
+    destStep2 = destIfFalse;
+  }else{
+    destStep2 = destStep6 = sqlite3VdbeMakeLabel(pParse);
+  }
+  for(i=0; i<nVector; i++){
+    Expr *p = sqlite3VectorFieldSubexpr(pExpr->pLeft, i);
+    if( pParse->nErr ) goto sqlite3ExprCodeIN_oom_error;
+    if( sqlite3ExprCanBeNull(p) ){
+      sqlite3VdbeAddOp2(v, OP_IsNull, rLhs+i, destStep2);
+      VdbeCoverage(v);
+    }
+  }
+
+  /* Step 3.  The LHS is now known to be non-NULL.  Do the binary search
+  ** of the RHS using the LHS as a probe.  If found, the result is
+  ** true.
+  */
+  if( eType==IN_INDEX_ROWID ){
+    /* In this case, the RHS is the ROWID of table b-tree and so we also
+    ** know that the RHS is non-NULL.  Hence, we combine steps 3 and 4
+    ** into a single opcode. */
+    sqlite3VdbeAddOp3(v, OP_SeekRowid, iTab, destIfFalse, rLhs);
+    VdbeCoverage(v);
+    addrTruthOp = sqlite3VdbeAddOp0(v, OP_Goto);  /* Return True */
+  }else{
+    sqlite3VdbeAddOp4(v, OP_Affinity, rLhs, nVector, 0, zAff, nVector);
+    if( destIfFalse==destIfNull ){
+      /* Combine Step 3 and Step 5 into a single opcode */
+      sqlite3VdbeAddOp4Int(v, OP_NotFound, iTab, destIfFalse,
+                           rLhs, nVector); VdbeCoverage(v);
+      goto sqlite3ExprCodeIN_finished;
+    }
+    /* Ordinary Step 3, for the case where FALSE and NULL are distinct */
+    addrTruthOp = sqlite3VdbeAddOp4Int(v, OP_Found, iTab, 0,
+                                      rLhs, nVector); VdbeCoverage(v);
+  }
+
+  /* Step 4.  If the RHS is known to be non-NULL and we did not find
+  ** an match on the search above, then the result must be FALSE.
+  */
+  if( rRhsHasNull && nVector==1 ){
+    sqlite3VdbeAddOp2(v, OP_NotNull, rRhsHasNull, destIfFalse);
+    VdbeCoverage(v);
+  }
+
+  /* Step 5.  If we do not care about the difference between NULL and
+  ** FALSE, then just return false.
+  */
+  if( destIfFalse==destIfNull ) sqlite3VdbeGoto(v, destIfFalse);
+
+  /* Step 6: Loop through rows of the RHS.  Compare each row to the LHS.
+  ** If any comparison is NULL, then the result is NULL.  If all
+  ** comparisons are FALSE then the final result is FALSE.
+  **
+  ** For a scalar LHS, it is sufficient to check just the first row
+  ** of the RHS.
+  */
+  if( destStep6 ) sqlite3VdbeResolveLabel(v, destStep6);
+  addrTop = sqlite3VdbeAddOp2(v, OP_Rewind, iTab, destIfFalse);
+  VdbeCoverage(v);
+  if( nVector>1 ){
+    destNotNull = sqlite3VdbeMakeLabel(pParse);
+  }else{
+    /* For nVector==1, combine steps 6 and 7 by immediately returning
+    ** FALSE if the first comparison is not NULL */
+    destNotNull = destIfFalse;
+  }
+  for(i=0; i<nVector; i++){
+    Expr *p;
+    CollSeq *pColl;
+    int r3 = sqlite3GetTempReg(pParse);
+    p = sqlite3VectorFieldSubexpr(pLeft, i);
+    pColl = sqlite3ExprCollSeq(pParse, p);
+    sqlite3VdbeAddOp3(v, OP_Column, iTab, i, r3);
+    sqlite3VdbeAddOp4(v, OP_Ne, rLhs+i, destNotNull, r3,
+                      (void*)pColl, P4_COLLSEQ);
+    VdbeCoverage(v);
+    sqlite3ReleaseTempReg(pParse, r3);
+  }
+  sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfNull);
+  if( nVector>1 ){
+    sqlite3VdbeResolveLabel(v, destNotNull);
+    sqlite3VdbeAddOp2(v, OP_Next, iTab, addrTop+1);
+    VdbeCoverage(v);
+
+    /* Step 7:  If we reach this point, we know that the result must
+    ** be false. */
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
+  }
+
+  /* Jumps here in order to return true. */
+  sqlite3VdbeJumpHere(v, addrTruthOp);
+
+sqlite3ExprCodeIN_finished:
+  if( rLhs!=rLhsOrig ) sqlite3ReleaseTempReg(pParse, rLhs);
+  VdbeComment((v, "end IN expr"));
+sqlite3ExprCodeIN_oom_error:
+  sqlite3DbFree(pParse->db, aiMap);
+  sqlite3DbFree(pParse->db, zAff);
+}
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/*
+** Generate an instruction that will put the floating point
+** value described by z[0..n-1] into register iMem.
+**
+** The z[] string will probably not be zero-terminated.  But the
+** z[n] character is guaranteed to be something that does not look
+** like the continuation of the number.
+*/
+static void codeReal(Vdbe *v, const char *z, int negateFlag, int iMem){
+  if( ALWAYS(z!=0) ){
+    double value;
+    sqlite3AtoF(z, &value, sqlite3Strlen30(z), SQLITE_UTF8);
+    assert( !sqlite3IsNaN(value) ); /* The new AtoF never returns NaN */
+    if( negateFlag ) value = -value;
+    sqlite3VdbeAddOp4Dup8(v, OP_Real, 0, iMem, 0, (u8*)&value, P4_REAL);
+  }
+}
+#endif
+
+
+/*
+** Generate an instruction that will put the integer describe by
+** text z[0..n-1] into register iMem.
+**
+** Expr.u.zToken is always UTF8 and zero-terminated.
+*/
+static void codeInteger(Parse *pParse, Expr *pExpr, int negFlag, int iMem){
+  Vdbe *v = pParse->pVdbe;
+  if( pExpr->flags & EP_IntValue ){
+    int i = pExpr->u.iValue;
+    assert( i>=0 );
+    if( negFlag ) i = -i;
+    sqlite3VdbeAddOp2(v, OP_Integer, i, iMem);
+  }else{
+    int c;
+    i64 value;
+    const char *z = pExpr->u.zToken;
+    assert( z!=0 );
+    c = sqlite3DecOrHexToI64(z, &value);
+    if( (c==3 && !negFlag) || (c==2) || (negFlag && value==SMALLEST_INT64)){
+#ifdef SQLITE_OMIT_FLOATING_POINT
+      sqlite3ErrorMsg(pParse, "oversized integer: %s%#T", negFlag?"-":"",pExpr);
+#else
+#ifndef SQLITE_OMIT_HEX_INTEGER
+      if( sqlite3_strnicmp(z,"0x",2)==0 ){
+        sqlite3ErrorMsg(pParse, "hex literal too big: %s%#T",
+                        negFlag?"-":"",pExpr);
+      }else
+#endif
+      {
+        codeReal(v, z, negFlag, iMem);
+      }
+#endif
+    }else{
+      if( negFlag ){ value = c==3 ? SMALLEST_INT64 : -value; }
+      sqlite3VdbeAddOp4Dup8(v, OP_Int64, 0, iMem, 0, (u8*)&value, P4_INT64);
+    }
+  }
+}
+
+
+/* Generate code that will load into register regOut a value that is
+** appropriate for the iIdxCol-th column of index pIdx.
+*/
+void sqlite3ExprCodeLoadIndexColumn(
+  Parse *pParse,  /* The parsing context */
+  Index *pIdx,    /* The index whose column is to be loaded */
+  int iTabCur,    /* Cursor pointing to a table row */
+  int iIdxCol,    /* The column of the index to be loaded */
+  int regOut      /* Store the index column value in this register */
+){
+  i16 iTabCol = pIdx->aiColumn[iIdxCol];
+  if( iTabCol==XN_EXPR ){
+    assert( pIdx->aColExpr );
+    assert( pIdx->aColExpr->nExpr>iIdxCol );
+    pParse->iSelfTab = iTabCur + 1;
+    sqlite3ExprCodeCopy(pParse, pIdx->aColExpr->a[iIdxCol].pExpr, regOut);
+    pParse->iSelfTab = 0;
+  }else{
+    sqlite3ExprCodeGetColumnOfTable(pParse->pVdbe, pIdx->pTable, iTabCur,
+                                    iTabCol, regOut);
+  }
+}
+
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+/*
+** Generate code that will compute the value of generated column pCol
+** and store the result in register regOut
+*/
+void sqlite3ExprCodeGeneratedColumn(
+  Parse *pParse,     /* Parsing context */
+  Table *pTab,       /* Table containing the generated column */
+  Column *pCol,      /* The generated column */
+  int regOut         /* Put the result in this register */
+){
+  int iAddr;
+  Vdbe *v = pParse->pVdbe;
+  int nErr = pParse->nErr;
+  assert( v!=0 );
+  assert( pParse->iSelfTab!=0 );
+  if( pParse->iSelfTab>0 ){
+    iAddr = sqlite3VdbeAddOp3(v, OP_IfNullRow, pParse->iSelfTab-1, 0, regOut);
+  }else{
+    iAddr = 0;
+  }
+  sqlite3ExprCodeCopy(pParse, sqlite3ColumnExpr(pTab,pCol), regOut);
+  if( pCol->affinity>=SQLITE_AFF_TEXT ){
+    sqlite3VdbeAddOp4(v, OP_Affinity, regOut, 1, 0, &pCol->affinity, 1);
+  }
+  if( iAddr ) sqlite3VdbeJumpHere(v, iAddr);
+  if( pParse->nErr>nErr ) pParse->db->errByteOffset = -1;
+}
+#endif /* SQLITE_OMIT_GENERATED_COLUMNS */
+
+/*
+** Generate code to extract the value of the iCol-th column of a table.
+*/
+void sqlite3ExprCodeGetColumnOfTable(
+  Vdbe *v,        /* Parsing context */
+  Table *pTab,    /* The table containing the value */
+  int iTabCur,    /* The table cursor.  Or the PK cursor for WITHOUT ROWID */
+  int iCol,       /* Index of the column to extract */
+  int regOut      /* Extract the value into this register */
+){
+  Column *pCol;
+  assert( v!=0 );
+  assert( pTab!=0 );
+  assert( iCol!=XN_EXPR );
+  if( iCol<0 || iCol==pTab->iPKey ){
+    sqlite3VdbeAddOp2(v, OP_Rowid, iTabCur, regOut);
+    VdbeComment((v, "%s.rowid", pTab->zName));
+  }else{
+    int op;
+    int x;
+    if( IsVirtual(pTab) ){
+      op = OP_VColumn;
+      x = iCol;
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+    }else if( (pCol = &pTab->aCol[iCol])->colFlags & COLFLAG_VIRTUAL ){
+      Parse *pParse = sqlite3VdbeParser(v);
+      if( pCol->colFlags & COLFLAG_BUSY ){
+        sqlite3ErrorMsg(pParse, "generated column loop on \"%s\"",
+                        pCol->zCnName);
+      }else{
+        int savedSelfTab = pParse->iSelfTab;
+        pCol->colFlags |= COLFLAG_BUSY;
+        pParse->iSelfTab = iTabCur+1;
+        sqlite3ExprCodeGeneratedColumn(pParse, pTab, pCol, regOut);
+        pParse->iSelfTab = savedSelfTab;
+        pCol->colFlags &= ~COLFLAG_BUSY;
+      }
+      return;
+#endif
+    }else if( !HasRowid(pTab) ){
+      testcase( iCol!=sqlite3TableColumnToStorage(pTab, iCol) );
+      x = sqlite3TableColumnToIndex(sqlite3PrimaryKeyIndex(pTab), iCol);
+      op = OP_Column;
+    }else{
+      x = sqlite3TableColumnToStorage(pTab,iCol);
+      testcase( x!=iCol );
+      op = OP_Column;
+    }
+    sqlite3VdbeAddOp3(v, op, iTabCur, x, regOut);
+    sqlite3ColumnDefault(v, pTab, iCol, regOut);
+  }
+}
+
+/*
+** Generate code that will extract the iColumn-th column from
+** table pTab and store the column value in register iReg.
+**
+** There must be an open cursor to pTab in iTable when this routine
+** is called.  If iColumn<0 then code is generated that extracts the rowid.
+*/
+int sqlite3ExprCodeGetColumn(
+  Parse *pParse,   /* Parsing and code generating context */
+  Table *pTab,     /* Description of the table we are reading from */
+  int iColumn,     /* Index of the table column */
+  int iTable,      /* The cursor pointing to the table */
+  int iReg,        /* Store results here */
+  u8 p5            /* P5 value for OP_Column + FLAGS */
+){
+  assert( pParse->pVdbe!=0 );
+  assert( (p5 & (OPFLAG_NOCHNG|OPFLAG_TYPEOFARG|OPFLAG_LENGTHARG))==p5 );
+  assert( IsVirtual(pTab) || (p5 & OPFLAG_NOCHNG)==0 );
+  sqlite3ExprCodeGetColumnOfTable(pParse->pVdbe, pTab, iTable, iColumn, iReg);
+  if( p5 ){
+    VdbeOp *pOp = sqlite3VdbeGetLastOp(pParse->pVdbe);
+    if( pOp->opcode==OP_Column ) pOp->p5 = p5;
+    if( pOp->opcode==OP_VColumn ) pOp->p5 = (p5 & OPFLAG_NOCHNG);
+  }
+  return iReg;
+}
+
+/*
+** Generate code to move content from registers iFrom...iFrom+nReg-1
+** over to iTo..iTo+nReg-1.
+*/
+void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
+  sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);
+}
+
+/*
+** Convert a scalar expression node to a TK_REGISTER referencing
+** register iReg.  The caller must ensure that iReg already contains
+** the correct value for the expression.
+*/
+static void exprToRegister(Expr *pExpr, int iReg){
+  Expr *p = sqlite3ExprSkipCollateAndLikely(pExpr);
+  if( NEVER(p==0) ) return;
+  p->op2 = p->op;
+  p->op = TK_REGISTER;
+  p->iTable = iReg;
+  ExprClearProperty(p, EP_Skip);
+}
+
+/*
+** Evaluate an expression (either a vector or a scalar expression) and store
+** the result in contiguous temporary registers.  Return the index of
+** the first register used to store the result.
+**
+** If the returned result register is a temporary scalar, then also write
+** that register number into *piFreeable.  If the returned result register
+** is not a temporary or if the expression is a vector set *piFreeable
+** to 0.
+*/
+static int exprCodeVector(Parse *pParse, Expr *p, int *piFreeable){
+  int iResult;
+  int nResult = sqlite3ExprVectorSize(p);
+  if( nResult==1 ){
+    iResult = sqlite3ExprCodeTemp(pParse, p, piFreeable);
+  }else{
+    *piFreeable = 0;
+    if( p->op==TK_SELECT ){
+#if SQLITE_OMIT_SUBQUERY
+      iResult = 0;
+#else
+      iResult = sqlite3CodeSubselect(pParse, p);
+#endif
+    }else{
+      int i;
+      iResult = pParse->nMem+1;
+      pParse->nMem += nResult;
+      assert( ExprUseXList(p) );
+      for(i=0; i<nResult; i++){
+        sqlite3ExprCodeFactorable(pParse, p->x.pList->a[i].pExpr, i+iResult);
+      }
+    }
+  }
+  return iResult;
+}
+
+/*
+** If the last opcode is a OP_Copy, then set the do-not-merge flag (p5)
+** so that a subsequent copy will not be merged into this one.
+*/
+static void setDoNotMergeFlagOnCopy(Vdbe *v){
+  if( sqlite3VdbeGetLastOp(v)->opcode==OP_Copy ){
+    sqlite3VdbeChangeP5(v, 1);  /* Tag trailing OP_Copy as not mergeable */
+  }
+}
+
+/*
+** Generate code to implement special SQL functions that are implemented
+** in-line rather than by using the usual callbacks.
+*/
+static int exprCodeInlineFunction(
+  Parse *pParse,        /* Parsing context */
+  ExprList *pFarg,      /* List of function arguments */
+  int iFuncId,          /* Function ID.  One of the INTFUNC_... values */
+  int target            /* Store function result in this register */
+){
+  int nFarg;
+  Vdbe *v = pParse->pVdbe;
+  assert( v!=0 );
+  assert( pFarg!=0 );
+  nFarg = pFarg->nExpr;
+  assert( nFarg>0 );  /* All in-line functions have at least one argument */
+  switch( iFuncId ){
+    case INLINEFUNC_coalesce: {
+      /* Attempt a direct implementation of the built-in COALESCE() and
+      ** IFNULL() functions.  This avoids unnecessary evaluation of
+      ** arguments past the first non-NULL argument.
+      */
+      int endCoalesce = sqlite3VdbeMakeLabel(pParse);
+      int i;
+      assert( nFarg>=2 );
+      sqlite3ExprCode(pParse, pFarg->a[0].pExpr, target);
+      for(i=1; i<nFarg; i++){
+        sqlite3VdbeAddOp2(v, OP_NotNull, target, endCoalesce);
+        VdbeCoverage(v);
+        sqlite3ExprCode(pParse, pFarg->a[i].pExpr, target);
+      }
+      setDoNotMergeFlagOnCopy(v);
+      sqlite3VdbeResolveLabel(v, endCoalesce);
+      break;
+    }
+    case INLINEFUNC_iif: {
+      Expr caseExpr;
+      memset(&caseExpr, 0, sizeof(caseExpr));
+      caseExpr.op = TK_CASE;
+      caseExpr.x.pList = pFarg;
+      return sqlite3ExprCodeTarget(pParse, &caseExpr, target);
+    }
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+    case INLINEFUNC_sqlite_offset: {
+      Expr *pArg = pFarg->a[0].pExpr;
+      if( pArg->op==TK_COLUMN && pArg->iTable>=0 ){
+        sqlite3VdbeAddOp3(v, OP_Offset, pArg->iTable, pArg->iColumn, target);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      }
+      break;
+    }
+#endif
+    default: {  
+      /* The UNLIKELY() function is a no-op.  The result is the value
+      ** of the first argument.
+      */
+      assert( nFarg==1 || nFarg==2 );
+      target = sqlite3ExprCodeTarget(pParse, pFarg->a[0].pExpr, target);
+      break;
+    }
+
+  /***********************************************************************
+  ** Test-only SQL functions that are only usable if enabled
+  ** via SQLITE_TESTCTRL_INTERNAL_FUNCTIONS
+  */
+#if !defined(SQLITE_UNTESTABLE)
+    case INLINEFUNC_expr_compare: {
+      /* Compare two expressions using sqlite3ExprCompare() */
+      assert( nFarg==2 );
+      sqlite3VdbeAddOp2(v, OP_Integer,
+         sqlite3ExprCompare(0,pFarg->a[0].pExpr, pFarg->a[1].pExpr,-1),
+         target);
+      break;
+    }
+
+    case INLINEFUNC_expr_implies_expr: {
+      /* Compare two expressions using sqlite3ExprImpliesExpr() */
+      assert( nFarg==2 );
+      sqlite3VdbeAddOp2(v, OP_Integer,
+         sqlite3ExprImpliesExpr(pParse,pFarg->a[0].pExpr, pFarg->a[1].pExpr,-1),
+         target);
+      break;
+    }
+
+    case INLINEFUNC_implies_nonnull_row: {
+      /* Result of sqlite3ExprImpliesNonNullRow() */
+      Expr *pA1;
+      assert( nFarg==2 );
+      pA1 = pFarg->a[1].pExpr;
+      if( pA1->op==TK_COLUMN ){
+        sqlite3VdbeAddOp2(v, OP_Integer,
+           sqlite3ExprImpliesNonNullRow(pFarg->a[0].pExpr,pA1->iTable,1),
+           target);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      }
+      break;
+    }
+
+    case INLINEFUNC_affinity: {
+      /* The AFFINITY() function evaluates to a string that describes
+      ** the type affinity of the argument.  This is used for testing of
+      ** the SQLite type logic.
+      */
+      const char *azAff[] = { "blob", "text", "numeric", "integer",
+                              "real", "flexnum" };
+      char aff;
+      assert( nFarg==1 );
+      aff = sqlite3ExprAffinity(pFarg->a[0].pExpr);
+      assert( aff<=SQLITE_AFF_NONE
+           || (aff>=SQLITE_AFF_BLOB && aff<=SQLITE_AFF_FLEXNUM) );
+      sqlite3VdbeLoadString(v, target,
+              (aff<=SQLITE_AFF_NONE) ? "none" : azAff[aff-SQLITE_AFF_BLOB]);
+      break;
+    }
+#endif /* !defined(SQLITE_UNTESTABLE) */
+  }
+  return target;
+}
+
+/*
+** Check to see if pExpr is one of the indexed expressions on pParse->pIdxEpr.
+** If it is, then resolve the expression by reading from the index and
+** return the register into which the value has been read.  If pExpr is
+** not an indexed expression, then return negative.
+*/
+static SQLITE_NOINLINE int sqlite3IndexedExprLookup(
+  Parse *pParse,   /* The parsing context */
+  Expr *pExpr,     /* The expression to potentially bypass */
+  int target       /* Where to store the result of the expression */
+){
+  IndexedExpr *p;
+  Vdbe *v;
+  for(p=pParse->pIdxEpr; p; p=p->pIENext){
+    u8 exprAff;
+    int iDataCur = p->iDataCur;
+    if( iDataCur<0 ) continue;
+    if( pParse->iSelfTab ){
+      if( p->iDataCur!=pParse->iSelfTab-1 ) continue;
+      iDataCur = -1;
+    }
+    if( sqlite3ExprCompare(0, pExpr, p->pExpr, iDataCur)!=0 ) continue;
+    assert( p->aff>=SQLITE_AFF_BLOB && p->aff<=SQLITE_AFF_NUMERIC );
+    exprAff = sqlite3ExprAffinity(pExpr);
+    if( (exprAff<=SQLITE_AFF_BLOB && p->aff!=SQLITE_AFF_BLOB)
+     || (exprAff==SQLITE_AFF_TEXT && p->aff!=SQLITE_AFF_TEXT)
+     || (exprAff>=SQLITE_AFF_NUMERIC && p->aff!=SQLITE_AFF_NUMERIC)
+    ){
+      /* Affinity mismatch on a generated column */
+      continue;
+    }
+
+    v = pParse->pVdbe;
+    assert( v!=0 );
+    if( p->bMaybeNullRow ){
+      /* If the index is on a NULL row due to an outer join, then we
+      ** cannot extract the value from the index.  The value must be
+      ** computed using the original expression. */
+      int addr = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp3(v, OP_IfNullRow, p->iIdxCur, addr+3, target);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_Column, p->iIdxCur, p->iIdxCol, target);
+      VdbeComment((v, "%s expr-column %d", p->zIdxName, p->iIdxCol));
+      sqlite3VdbeGoto(v, 0);
+      p = pParse->pIdxEpr;
+      pParse->pIdxEpr = 0;
+      sqlite3ExprCode(pParse, pExpr, target);
+      pParse->pIdxEpr = p;
+      sqlite3VdbeJumpHere(v, addr+2);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_Column, p->iIdxCur, p->iIdxCol, target);
+      VdbeComment((v, "%s expr-column %d", p->zIdxName, p->iIdxCol));
+    }
+    return target;
+  }
+  return -1;  /* Not found */
+}
+
+
+/*
+** Expresion pExpr is guaranteed to be a TK_COLUMN or equivalent. This
+** function checks the Parse.pIdxPartExpr list to see if this column
+** can be replaced with a constant value. If so, it generates code to
+** put the constant value in a register (ideally, but not necessarily, 
+** register iTarget) and returns the register number.
+**
+** Or, if the TK_COLUMN cannot be replaced by a constant, zero is 
+** returned.
+*/
+static int exprPartidxExprLookup(Parse *pParse, Expr *pExpr, int iTarget){
+  IndexedExpr *p;
+  for(p=pParse->pIdxPartExpr; p; p=p->pIENext){
+    if( pExpr->iColumn==p->iIdxCol && pExpr->iTable==p->iDataCur ){
+      Vdbe *v = pParse->pVdbe;
+      int addr = 0;
+      int ret;
+
+      if( p->bMaybeNullRow ){
+        addr = sqlite3VdbeAddOp1(v, OP_IfNullRow, p->iIdxCur);
+      }
+      ret = sqlite3ExprCodeTarget(pParse, p->pExpr, iTarget);
+      sqlite3VdbeAddOp4(pParse->pVdbe, OP_Affinity, ret, 1, 0,
+                        (const char*)&p->aff, 1);
+      if( addr ){
+        sqlite3VdbeJumpHere(v, addr);
+        sqlite3VdbeChangeP3(v, addr, ret);
+      }
+      return ret;
+    }
+  }
+  return 0;
+}
+
+
+/*
+** Generate code into the current Vdbe to evaluate the given
+** expression.  Attempt to store the results in register "target".
+** Return the register where results are stored.
+**
+** With this routine, there is no guarantee that results will
+** be stored in target.  The result might be stored in some other
+** register if it is convenient to do so.  The calling function
+** must check the return code and move the results to the desired
+** register.
+*/
+int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
+  Vdbe *v = pParse->pVdbe;  /* The VM under construction */
+  int op;                   /* The opcode being coded */
+  int inReg = target;       /* Results stored in register inReg */
+  int regFree1 = 0;         /* If non-zero free this temporary register */
+  int regFree2 = 0;         /* If non-zero free this temporary register */
+  int r1, r2;               /* Various register numbers */
+  Expr tempX;               /* Temporary expression node */
+  int p5 = 0;
+
+  assert( target>0 && target<=pParse->nMem );
+  assert( v!=0 );
+
+expr_code_doover:
+  if( pExpr==0 ){
+    op = TK_NULL;
+  }else if( pParse->pIdxEpr!=0
+   && !ExprHasProperty(pExpr, EP_Leaf)
+   && (r1 = sqlite3IndexedExprLookup(pParse, pExpr, target))>=0
+  ){
+    return r1;
+  }else{
+    assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );
+    op = pExpr->op;
+  }
+  assert( op!=TK_ORDER );
+  switch( op ){
+    case TK_AGG_COLUMN: {
+      AggInfo *pAggInfo = pExpr->pAggInfo;
+      struct AggInfo_col *pCol;
+      assert( pAggInfo!=0 );
+      assert( pExpr->iAgg>=0 );
+      if( pExpr->iAgg>=pAggInfo->nColumn ){
+        /* Happens when the left table of a RIGHT JOIN is null and
+        ** is using an expression index */
+        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+#ifdef SQLITE_VDBE_COVERAGE
+        /* Verify that the OP_Null above is exercised by tests
+        ** tag-20230325-2 */
+        sqlite3VdbeAddOp3(v, OP_NotNull, target, 1, 20230325);
+        VdbeCoverageNeverTaken(v);
+#endif
+        break;
+      }
+      pCol = &pAggInfo->aCol[pExpr->iAgg];
+      if( !pAggInfo->directMode ){
+        return AggInfoColumnReg(pAggInfo, pExpr->iAgg);
+      }else if( pAggInfo->useSortingIdx ){
+        Table *pTab = pCol->pTab;
+        sqlite3VdbeAddOp3(v, OP_Column, pAggInfo->sortingIdxPTab,
+                              pCol->iSorterColumn, target);
+        if( pTab==0 ){
+          /* No comment added */
+        }else if( pCol->iColumn<0 ){
+          VdbeComment((v,"%s.rowid",pTab->zName));
+        }else{
+          VdbeComment((v,"%s.%s",
+              pTab->zName, pTab->aCol[pCol->iColumn].zCnName));
+          if( pTab->aCol[pCol->iColumn].affinity==SQLITE_AFF_REAL ){
+            sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
+          }
+        }
+        return target;
+      }else if( pExpr->y.pTab==0 ){
+        /* This case happens when the argument to an aggregate function
+        ** is rewritten by aggregateConvertIndexedExprRefToColumn() */
+        sqlite3VdbeAddOp3(v, OP_Column, pExpr->iTable, pExpr->iColumn, target);
+        return target;
+      }
+      /* Otherwise, fall thru into the TK_COLUMN case */
+      /* no break */ deliberate_fall_through
+    }
+    case TK_COLUMN: {
+      int iTab = pExpr->iTable;
+      int iReg;
+      if( ExprHasProperty(pExpr, EP_FixedCol) ){
+        /* This COLUMN expression is really a constant due to WHERE clause
+        ** constraints, and that constant is coded by the pExpr->pLeft
+        ** expression.  However, make sure the constant has the correct
+        ** datatype by applying the Affinity of the table column to the
+        ** constant.
+        */
+        int aff;
+        iReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft,target);
+        assert( ExprUseYTab(pExpr) );
+        assert( pExpr->y.pTab!=0 );
+        aff = sqlite3TableColumnAffinity(pExpr->y.pTab, pExpr->iColumn);
+        if( aff>SQLITE_AFF_BLOB ){
+          static const char zAff[] = "B\000C\000D\000E\000F";
+          assert( SQLITE_AFF_BLOB=='A' );
+          assert( SQLITE_AFF_TEXT=='B' );
+          sqlite3VdbeAddOp4(v, OP_Affinity, iReg, 1, 0,
+                            &zAff[(aff-'B')*2], P4_STATIC);
+        }
+        return iReg;
+      }
+      if( iTab<0 ){
+        if( pParse->iSelfTab<0 ){
+          /* Other columns in the same row for CHECK constraints or
+          ** generated columns or for inserting into partial index.
+          ** The row is unpacked into registers beginning at
+          ** 0-(pParse->iSelfTab).  The rowid (if any) is in a register
+          ** immediately prior to the first column.
+          */
+          Column *pCol;
+          Table *pTab;
+          int iSrc;
+          int iCol = pExpr->iColumn;
+          assert( ExprUseYTab(pExpr) );
+          pTab = pExpr->y.pTab;
+          assert( pTab!=0 );
+          assert( iCol>=XN_ROWID );
+          assert( iCol<pTab->nCol );
+          if( iCol<0 ){
+            return -1-pParse->iSelfTab;
+          }
+          pCol = pTab->aCol + iCol;
+          testcase( iCol!=sqlite3TableColumnToStorage(pTab,iCol) );
+          iSrc = sqlite3TableColumnToStorage(pTab, iCol) - pParse->iSelfTab;
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+          if( pCol->colFlags & COLFLAG_GENERATED ){
+            if( pCol->colFlags & COLFLAG_BUSY ){
+              sqlite3ErrorMsg(pParse, "generated column loop on \"%s\"",
+                              pCol->zCnName);
+              return 0;
+            }
+            pCol->colFlags |= COLFLAG_BUSY;
+            if( pCol->colFlags & COLFLAG_NOTAVAIL ){
+              sqlite3ExprCodeGeneratedColumn(pParse, pTab, pCol, iSrc);
+            }
+            pCol->colFlags &= ~(COLFLAG_BUSY|COLFLAG_NOTAVAIL);
+            return iSrc;
+          }else
+#endif /* SQLITE_OMIT_GENERATED_COLUMNS */
+          if( pCol->affinity==SQLITE_AFF_REAL ){
+            sqlite3VdbeAddOp2(v, OP_SCopy, iSrc, target);
+            sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
+            return target;
+          }else{
+            return iSrc;
+          }
+        }else{
+          /* Coding an expression that is part of an index where column names
+          ** in the index refer to the table to which the index belongs */
+          iTab = pParse->iSelfTab - 1;
+        }
+      }
+      else if( pParse->pIdxPartExpr 
+       && 0!=(r1 = exprPartidxExprLookup(pParse, pExpr, target))
+      ){
+        return r1;
+      }
+      assert( ExprUseYTab(pExpr) );
+      assert( pExpr->y.pTab!=0 );
+      iReg = sqlite3ExprCodeGetColumn(pParse, pExpr->y.pTab,
+                               pExpr->iColumn, iTab, target,
+                               pExpr->op2);
+      return iReg;
+    }
+    case TK_INTEGER: {
+      codeInteger(pParse, pExpr, 0, target);
+      return target;
+    }
+    case TK_TRUEFALSE: {
+      sqlite3VdbeAddOp2(v, OP_Integer, sqlite3ExprTruthValue(pExpr), target);
+      return target;
+    }
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    case TK_FLOAT: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      codeReal(v, pExpr->u.zToken, 0, target);
+      return target;
+    }
+#endif
+    case TK_STRING: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3VdbeLoadString(v, target, pExpr->u.zToken);
+      return target;
+    }
+    default: {
+      /* Make NULL the default case so that if a bug causes an illegal
+      ** Expr node to be passed into this function, it will be handled
+      ** sanely and not crash.  But keep the assert() to bring the problem
+      ** to the attention of the developers. */
+      assert( op==TK_NULL || op==TK_ERROR || pParse->db->mallocFailed );
+      sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      return target;
+    }
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+    case TK_BLOB: {
+      int n;
+      const char *z;
+      char *zBlob;
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      assert( pExpr->u.zToken[0]=='x' || pExpr->u.zToken[0]=='X' );
+      assert( pExpr->u.zToken[1]=='\'' );
+      z = &pExpr->u.zToken[2];
+      n = sqlite3Strlen30(z) - 1;
+      assert( z[n]=='\'' );
+      zBlob = sqlite3HexToBlob(sqlite3VdbeDb(v), z, n);
+      sqlite3VdbeAddOp4(v, OP_Blob, n/2, target, 0, zBlob, P4_DYNAMIC);
+      return target;
+    }
+#endif
+    case TK_VARIABLE: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      assert( pExpr->u.zToken!=0 );
+      assert( pExpr->u.zToken[0]!=0 );
+      sqlite3VdbeAddOp2(v, OP_Variable, pExpr->iColumn, target);
+      if( pExpr->u.zToken[1]!=0 ){
+        const char *z = sqlite3VListNumToName(pParse->pVList, pExpr->iColumn);
+        assert( pExpr->u.zToken[0]=='?' || (z && !strcmp(pExpr->u.zToken, z)) );
+        pParse->pVList[0] = 0; /* Indicate VList may no longer be enlarged */
+        sqlite3VdbeAppendP4(v, (char*)z, P4_STATIC);
+      }
+      return target;
+    }
+    case TK_REGISTER: {
+      return pExpr->iTable;
+    }
+#ifndef SQLITE_OMIT_CAST
+    case TK_CAST: {
+      /* Expressions of the form:   CAST(pLeft AS token) */
+      sqlite3ExprCode(pParse, pExpr->pLeft, target);
+      assert( inReg==target );
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3VdbeAddOp2(v, OP_Cast, target,
+                        sqlite3AffinityType(pExpr->u.zToken, 0));
+      return inReg;
+    }
+#endif /* SQLITE_OMIT_CAST */
+    case TK_IS:
+    case TK_ISNOT:
+      op = (op==TK_IS) ? TK_EQ : TK_NE;
+      p5 = SQLITE_NULLEQ;
+      /* fall-through */
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_NE:
+    case TK_EQ: {
+      Expr *pLeft = pExpr->pLeft;
+      if( sqlite3ExprIsVector(pLeft) ){
+        codeVectorCompare(pParse, pExpr, target, op, p5);
+      }else{
+        r1 = sqlite3ExprCodeTemp(pParse, pLeft, &regFree1);
+        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+        sqlite3VdbeAddOp2(v, OP_Integer, 1, inReg);
+        codeCompare(pParse, pLeft, pExpr->pRight, op, r1, r2,
+            sqlite3VdbeCurrentAddr(v)+2, p5,
+            ExprHasProperty(pExpr,EP_Commuted));
+        assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
+        assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
+        assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
+        assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
+        assert(TK_EQ==OP_Eq); testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
+        assert(TK_NE==OP_Ne); testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);
+        if( p5==SQLITE_NULLEQ ){
+          sqlite3VdbeAddOp2(v, OP_Integer, 0, inReg);
+        }else{
+          sqlite3VdbeAddOp3(v, OP_ZeroOrNull, r1, inReg, r2);
+        }
+        testcase( regFree1==0 );
+        testcase( regFree2==0 );
+      }
+      break;
+    }
+    case TK_AND:
+    case TK_OR:
+    case TK_PLUS:
+    case TK_STAR:
+    case TK_MINUS:
+    case TK_REM:
+    case TK_BITAND:
+    case TK_BITOR:
+    case TK_SLASH:
+    case TK_LSHIFT:
+    case TK_RSHIFT:
+    case TK_CONCAT: {
+      assert( TK_AND==OP_And );            testcase( op==TK_AND );
+      assert( TK_OR==OP_Or );              testcase( op==TK_OR );
+      assert( TK_PLUS==OP_Add );           testcase( op==TK_PLUS );
+      assert( TK_MINUS==OP_Subtract );     testcase( op==TK_MINUS );
+      assert( TK_REM==OP_Remainder );      testcase( op==TK_REM );
+      assert( TK_BITAND==OP_BitAnd );      testcase( op==TK_BITAND );
+      assert( TK_BITOR==OP_BitOr );        testcase( op==TK_BITOR );
+      assert( TK_SLASH==OP_Divide );       testcase( op==TK_SLASH );
+      assert( TK_LSHIFT==OP_ShiftLeft );   testcase( op==TK_LSHIFT );
+      assert( TK_RSHIFT==OP_ShiftRight );  testcase( op==TK_RSHIFT );
+      assert( TK_CONCAT==OP_Concat );      testcase( op==TK_CONCAT );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      sqlite3VdbeAddOp3(v, op, r2, r1, target);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_UMINUS: {
+      Expr *pLeft = pExpr->pLeft;
+      assert( pLeft );
+      if( pLeft->op==TK_INTEGER ){
+        codeInteger(pParse, pLeft, 1, target);
+        return target;
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      }else if( pLeft->op==TK_FLOAT ){
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        codeReal(v, pLeft->u.zToken, 1, target);
+        return target;
+#endif
+      }else{
+        tempX.op = TK_INTEGER;
+        tempX.flags = EP_IntValue|EP_TokenOnly;
+        tempX.u.iValue = 0;
+        ExprClearVVAProperties(&tempX);
+        r1 = sqlite3ExprCodeTemp(pParse, &tempX, &regFree1);
+        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree2);
+        sqlite3VdbeAddOp3(v, OP_Subtract, r2, r1, target);
+        testcase( regFree2==0 );
+      }
+      break;
+    }
+    case TK_BITNOT:
+    case TK_NOT: {
+      assert( TK_BITNOT==OP_BitNot );   testcase( op==TK_BITNOT );
+      assert( TK_NOT==OP_Not );         testcase( op==TK_NOT );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      testcase( regFree1==0 );
+      sqlite3VdbeAddOp2(v, op, r1, inReg);
+      break;
+    }
+    case TK_TRUTH: {
+      int isTrue;    /* IS TRUE or IS NOT TRUE */
+      int bNormal;   /* IS TRUE or IS FALSE */
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      testcase( regFree1==0 );
+      isTrue = sqlite3ExprTruthValue(pExpr->pRight);
+      bNormal = pExpr->op2==TK_IS;
+      testcase( isTrue && bNormal);
+      testcase( !isTrue && bNormal);
+      sqlite3VdbeAddOp4Int(v, OP_IsTrue, r1, inReg, !isTrue, isTrue ^ bNormal);
+      break;
+    }
+    case TK_ISNULL:
+    case TK_NOTNULL: {
+      int addr;
+      assert( TK_ISNULL==OP_IsNull );   testcase( op==TK_ISNULL );
+      assert( TK_NOTNULL==OP_NotNull ); testcase( op==TK_NOTNULL );
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, target);
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      testcase( regFree1==0 );
+      addr = sqlite3VdbeAddOp1(v, op, r1);
+      VdbeCoverageIf(v, op==TK_ISNULL);
+      VdbeCoverageIf(v, op==TK_NOTNULL);
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, target);
+      sqlite3VdbeJumpHere(v, addr);
+      break;
+    }
+    case TK_AGG_FUNCTION: {
+      AggInfo *pInfo = pExpr->pAggInfo;
+      if( pInfo==0
+       || NEVER(pExpr->iAgg<0)
+       || NEVER(pExpr->iAgg>=pInfo->nFunc)
+      ){
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        sqlite3ErrorMsg(pParse, "misuse of aggregate: %#T()", pExpr);
+      }else{
+        return AggInfoFuncReg(pInfo, pExpr->iAgg);
+      }
+      break;
+    }
+    case TK_FUNCTION: {
+      ExprList *pFarg;       /* List of function arguments */
+      int nFarg;             /* Number of function arguments */
+      FuncDef *pDef;         /* The function definition object */
+      const char *zId;       /* The function name */
+      u32 constMask = 0;     /* Mask of function arguments that are constant */
+      int i;                 /* Loop counter */
+      sqlite3 *db = pParse->db;  /* The database connection */
+      u8 enc = ENC(db);      /* The text encoding used by this database */
+      CollSeq *pColl = 0;    /* A collating sequence */
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      if( ExprHasProperty(pExpr, EP_WinFunc) ){
+        return pExpr->y.pWin->regResult;
+      }
+#endif
+
+      if( ConstFactorOk(pParse) && sqlite3ExprIsConstantNotJoin(pExpr) ){
+        /* SQL functions can be expensive. So try to avoid running them
+        ** multiple times if we know they always give the same result */
+        return sqlite3ExprCodeRunJustOnce(pParse, pExpr, -1);
+      }
+      assert( !ExprHasProperty(pExpr, EP_TokenOnly) );
+      assert( ExprUseXList(pExpr) );
+      pFarg = pExpr->x.pList;
+      nFarg = pFarg ? pFarg->nExpr : 0;
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      zId = pExpr->u.zToken;
+      pDef = sqlite3FindFunction(db, zId, nFarg, enc, 0);
+#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
+      if( pDef==0 && pParse->explain ){
+        pDef = sqlite3FindFunction(db, "unknown", nFarg, enc, 0);
+      }
+#endif
+      if( pDef==0 || pDef->xFinalize!=0 ){
+        sqlite3ErrorMsg(pParse, "unknown function: %#T()", pExpr);
+        break;
+      }
+      if( (pDef->funcFlags & SQLITE_FUNC_INLINE)!=0 && ALWAYS(pFarg!=0) ){
+        assert( (pDef->funcFlags & SQLITE_FUNC_UNSAFE)==0 );
+        assert( (pDef->funcFlags & SQLITE_FUNC_DIRECT)==0 );
+        return exprCodeInlineFunction(pParse, pFarg,
+             SQLITE_PTR_TO_INT(pDef->pUserData), target);
+      }else if( pDef->funcFlags & (SQLITE_FUNC_DIRECT|SQLITE_FUNC_UNSAFE) ){
+        sqlite3ExprFunctionUsable(pParse, pExpr, pDef);
+      }
+
+      for(i=0; i<nFarg; i++){
+        if( i<32 && sqlite3ExprIsConstant(pFarg->a[i].pExpr) ){
+          testcase( i==31 );
+          constMask |= MASKBIT32(i);
+        }
+        if( (pDef->funcFlags & SQLITE_FUNC_NEEDCOLL)!=0 && !pColl ){
+          pColl = sqlite3ExprCollSeq(pParse, pFarg->a[i].pExpr);
+        }
+      }
+      if( pFarg ){
+        if( constMask ){
+          r1 = pParse->nMem+1;
+          pParse->nMem += nFarg;
+        }else{
+          r1 = sqlite3GetTempRange(pParse, nFarg);
+        }
+
+        /* For length() and typeof() and octet_length() functions,
+        ** set the P5 parameter to the OP_Column opcode to OPFLAG_LENGTHARG
+        ** or OPFLAG_TYPEOFARG or OPFLAG_BYTELENARG respectively, to avoid
+        ** unnecessary data loading.
+        */
+        if( (pDef->funcFlags & (SQLITE_FUNC_LENGTH|SQLITE_FUNC_TYPEOF))!=0 ){
+          u8 exprOp;
+          assert( nFarg==1 );
+          assert( pFarg->a[0].pExpr!=0 );
+          exprOp = pFarg->a[0].pExpr->op;
+          if( exprOp==TK_COLUMN || exprOp==TK_AGG_COLUMN ){
+            assert( SQLITE_FUNC_LENGTH==OPFLAG_LENGTHARG );
+            assert( SQLITE_FUNC_TYPEOF==OPFLAG_TYPEOFARG );
+            assert( SQLITE_FUNC_BYTELEN==OPFLAG_BYTELENARG );
+            assert( (OPFLAG_LENGTHARG|OPFLAG_TYPEOFARG)==OPFLAG_BYTELENARG );
+            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_LENGTHARG );
+            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_TYPEOFARG );
+            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_BYTELENARG);
+            pFarg->a[0].pExpr->op2 = pDef->funcFlags & OPFLAG_BYTELENARG;
+          }
+        }
+
+        sqlite3ExprCodeExprList(pParse, pFarg, r1, 0, SQLITE_ECEL_FACTOR);
+      }else{
+        r1 = 0;
+      }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+      /* Possibly overload the function if the first argument is
+      ** a virtual table column.
+      **
+      ** For infix functions (LIKE, GLOB, REGEXP, and MATCH) use the
+      ** second argument, not the first, as the argument to test to
+      ** see if it is a column in a virtual table.  This is done because
+      ** the left operand of infix functions (the operand we want to
+      ** control overloading) ends up as the second argument to the
+      ** function.  The expression "A glob B" is equivalent to
+      ** "glob(B,A).  We want to use the A in "A glob B" to test
+      ** for function overloading.  But we use the B term in "glob(B,A)".
+      */
+      if( nFarg>=2 && ExprHasProperty(pExpr, EP_InfixFunc) ){
+        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[1].pExpr);
+      }else if( nFarg>0 ){
+        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[0].pExpr);
+      }
+#endif
+      if( pDef->funcFlags & SQLITE_FUNC_NEEDCOLL ){
+        if( !pColl ) pColl = db->pDfltColl;
+        sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
+      }
+      sqlite3VdbeAddFunctionCall(pParse, constMask, r1, target, nFarg,
+                                 pDef, pExpr->op2);
+      if( nFarg ){
+        if( constMask==0 ){
+          sqlite3ReleaseTempRange(pParse, r1, nFarg);
+        }else{
+          sqlite3VdbeReleaseRegisters(pParse, r1, nFarg, constMask, 1);
+        }
+      }
+      return target;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_EXISTS:
+    case TK_SELECT: {
+      int nCol;
+      testcase( op==TK_EXISTS );
+      testcase( op==TK_SELECT );
+      if( pParse->db->mallocFailed ){
+        return 0;
+      }else if( op==TK_SELECT
+             && ALWAYS( ExprUseXSelect(pExpr) )
+             && (nCol = pExpr->x.pSelect->pEList->nExpr)!=1
+      ){
+        sqlite3SubselectError(pParse, nCol, 1);
+      }else{
+        return sqlite3CodeSubselect(pParse, pExpr);
+      }
+      break;
+    }
+    case TK_SELECT_COLUMN: {
+      int n;
+      Expr *pLeft = pExpr->pLeft;
+      if( pLeft->iTable==0 || pParse->withinRJSubrtn > pLeft->op2 ){
+        pLeft->iTable = sqlite3CodeSubselect(pParse, pLeft);
+        pLeft->op2 = pParse->withinRJSubrtn;
+      }
+      assert( pLeft->op==TK_SELECT || pLeft->op==TK_ERROR );
+      n = sqlite3ExprVectorSize(pLeft);
+      if( pExpr->iTable!=n ){
+        sqlite3ErrorMsg(pParse, "%d columns assigned %d values",
+                                pExpr->iTable, n);
+      }
+      return pLeft->iTable + pExpr->iColumn;
+    }
+    case TK_IN: {
+      int destIfFalse = sqlite3VdbeMakeLabel(pParse);
+      int destIfNull = sqlite3VdbeMakeLabel(pParse);
+      sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      sqlite3ExprCodeIN(pParse, pExpr, destIfFalse, destIfNull);
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, target);
+      sqlite3VdbeResolveLabel(v, destIfFalse);
+      sqlite3VdbeAddOp2(v, OP_AddImm, target, 0);
+      sqlite3VdbeResolveLabel(v, destIfNull);
+      return target;
+    }
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+
+    /*
+    **    x BETWEEN y AND z
+    **
+    ** This is equivalent to
+    **
+    **    x>=y AND x<=z
+    **
+    ** X is stored in pExpr->pLeft.
+    ** Y is stored in pExpr->pList->a[0].pExpr.
+    ** Z is stored in pExpr->pList->a[1].pExpr.
+    */
+    case TK_BETWEEN: {
+      exprCodeBetween(pParse, pExpr, target, 0, 0);
+      return target;
+    }
+    case TK_COLLATE: {
+      if( !ExprHasProperty(pExpr, EP_Collate) ){
+        /* A TK_COLLATE Expr node without the EP_Collate tag is a so-called
+        ** "SOFT-COLLATE" that is added to constraints that are pushed down
+        ** from outer queries into sub-queries by the push-down optimization.
+        ** Clear subtypes as subtypes may not cross a subquery boundary.
+        */
+        assert( pExpr->pLeft );
+        sqlite3ExprCode(pParse, pExpr->pLeft, target);
+        sqlite3VdbeAddOp1(v, OP_ClrSubtype, target);
+        return target;
+      }else{
+        pExpr = pExpr->pLeft;
+        goto expr_code_doover; /* 2018-04-28: Prevent deep recursion. */
+      }
+    }
+    case TK_SPAN:
+    case TK_UPLUS: {
+      pExpr = pExpr->pLeft;
+      goto expr_code_doover; /* 2018-04-28: Prevent deep recursion. OSSFuzz. */
+    }
+
+    case TK_TRIGGER: {
+      /* If the opcode is TK_TRIGGER, then the expression is a reference
+      ** to a column in the new.* or old.* pseudo-tables available to
+      ** trigger programs. In this case Expr.iTable is set to 1 for the
+      ** new.* pseudo-table, or 0 for the old.* pseudo-table. Expr.iColumn
+      ** is set to the column of the pseudo-table to read, or to -1 to
+      ** read the rowid field.
+      **
+      ** The expression is implemented using an OP_Param opcode. The p1
+      ** parameter is set to 0 for an old.rowid reference, or to (i+1)
+      ** to reference another column of the old.* pseudo-table, where
+      ** i is the index of the column. For a new.rowid reference, p1 is
+      ** set to (n+1), where n is the number of columns in each pseudo-table.
+      ** For a reference to any other column in the new.* pseudo-table, p1
+      ** is set to (n+2+i), where n and i are as defined previously. For
+      ** example, if the table on which triggers are being fired is
+      ** declared as:
+      **
+      **   CREATE TABLE t1(a, b);
+      **
+      ** Then p1 is interpreted as follows:
+      **
+      **   p1==0   ->    old.rowid     p1==3   ->    new.rowid
+      **   p1==1   ->    old.a         p1==4   ->    new.a
+      **   p1==2   ->    old.b         p1==5   ->    new.b      
+      */
+      Table *pTab;
+      int iCol;
+      int p1;
+
+      assert( ExprUseYTab(pExpr) );
+      pTab = pExpr->y.pTab;
+      iCol = pExpr->iColumn;
+      p1 = pExpr->iTable * (pTab->nCol+1) + 1
+                     + sqlite3TableColumnToStorage(pTab, iCol);
+
+      assert( pExpr->iTable==0 || pExpr->iTable==1 );
+      assert( iCol>=-1 && iCol<pTab->nCol );
+      assert( pTab->iPKey<0 || iCol!=pTab->iPKey );
+      assert( p1>=0 && p1<(pTab->nCol*2+2) );
+
+      sqlite3VdbeAddOp2(v, OP_Param, p1, target);
+      VdbeComment((v, "r[%d]=%s.%s", target,
+        (pExpr->iTable ? "new" : "old"),
+        (pExpr->iColumn<0 ? "rowid" : pExpr->y.pTab->aCol[iCol].zCnName)
+      ));
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      /* If the column has REAL affinity, it may currently be stored as an
+      ** integer. Use OP_RealAffinity to make sure it is really real.
+      **
+      ** EVIDENCE-OF: R-60985-57662 SQLite will convert the value back to
+      ** floating point when extracting it from the record.  */
+      if( iCol>=0 && pTab->aCol[iCol].affinity==SQLITE_AFF_REAL ){
+        sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
+      }
+#endif
+      break;
+    }
+
+    case TK_VECTOR: {
+      sqlite3ErrorMsg(pParse, "row value misused");
+      break;
+    }
+
+    /* TK_IF_NULL_ROW Expr nodes are inserted ahead of expressions
+    ** that derive from the right-hand table of a LEFT JOIN.  The
+    ** Expr.iTable value is the table number for the right-hand table.
+    ** The expression is only evaluated if that table is not currently
+    ** on a LEFT JOIN NULL row.
+    */
+    case TK_IF_NULL_ROW: {
+      int addrINR;
+      u8 okConstFactor = pParse->okConstFactor;
+      AggInfo *pAggInfo = pExpr->pAggInfo;
+      if( pAggInfo ){
+        assert( pExpr->iAgg>=0 && pExpr->iAgg<pAggInfo->nColumn );
+        if( !pAggInfo->directMode ){
+          inReg = AggInfoColumnReg(pAggInfo, pExpr->iAgg);
+          break;
+        }
+        if( pExpr->pAggInfo->useSortingIdx ){
+          sqlite3VdbeAddOp3(v, OP_Column, pAggInfo->sortingIdxPTab,
+                            pAggInfo->aCol[pExpr->iAgg].iSorterColumn,
+                            target);
+          inReg = target;
+          break;
+        }
+      }
+      addrINR = sqlite3VdbeAddOp3(v, OP_IfNullRow, pExpr->iTable, 0, target);
+      /* The OP_IfNullRow opcode above can overwrite the result register with
+      ** NULL.  So we have to ensure that the result register is not a value
+      ** that is suppose to be a constant.  Two defenses are needed:
+      **   (1)  Temporarily disable factoring of constant expressions
+      **   (2)  Make sure the computed value really is stored in register
+      **        "target" and not someplace else.
+      */
+      pParse->okConstFactor = 0;   /* note (1) above */
+      sqlite3ExprCode(pParse, pExpr->pLeft, target);
+      assert( target==inReg );
+      pParse->okConstFactor = okConstFactor;
+      sqlite3VdbeJumpHere(v, addrINR);
+      break;
+    }
+
+    /*
+    ** Form A:
+    **   CASE x WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END
+    **
+    ** Form B:
+    **   CASE WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END
+    **
+    ** Form A is can be transformed into the equivalent form B as follows:
+    **   CASE WHEN x=e1 THEN r1 WHEN x=e2 THEN r2 ...
+    **        WHEN x=eN THEN rN ELSE y END
+    **
+    ** X (if it exists) is in pExpr->pLeft.
+    ** Y is in the last element of pExpr->x.pList if pExpr->x.pList->nExpr is
+    ** odd.  The Y is also optional.  If the number of elements in x.pList
+    ** is even, then Y is omitted and the "otherwise" result is NULL.
+    ** Ei is in pExpr->pList->a[i*2] and Ri is pExpr->pList->a[i*2+1].
+    **
+    ** The result of the expression is the Ri for the first matching Ei,
+    ** or if there is no matching Ei, the ELSE term Y, or if there is
+    ** no ELSE term, NULL.
+    */
+    case TK_CASE: {
+      int endLabel;                     /* GOTO label for end of CASE stmt */
+      int nextCase;                     /* GOTO label for next WHEN clause */
+      int nExpr;                        /* 2x number of WHEN terms */
+      int i;                            /* Loop counter */
+      ExprList *pEList;                 /* List of WHEN terms */
+      struct ExprList_item *aListelem;  /* Array of WHEN terms */
+      Expr opCompare;                   /* The X==Ei expression */
+      Expr *pX;                         /* The X expression */
+      Expr *pTest = 0;                  /* X==Ei (form A) or just Ei (form B) */
+      Expr *pDel = 0;
+      sqlite3 *db = pParse->db;
+
+      assert( ExprUseXList(pExpr) && pExpr->x.pList!=0 );
+      assert(pExpr->x.pList->nExpr > 0);
+      pEList = pExpr->x.pList;
+      aListelem = pEList->a;
+      nExpr = pEList->nExpr;
+      endLabel = sqlite3VdbeMakeLabel(pParse);
+      if( (pX = pExpr->pLeft)!=0 ){
+        pDel = sqlite3ExprDup(db, pX, 0);
+        if( db->mallocFailed ){
+          sqlite3ExprDelete(db, pDel);
+          break;
+        }
+        testcase( pX->op==TK_COLUMN );
+        exprToRegister(pDel, exprCodeVector(pParse, pDel, &regFree1));
+        testcase( regFree1==0 );
+        memset(&opCompare, 0, sizeof(opCompare));
+        opCompare.op = TK_EQ;
+        opCompare.pLeft = pDel;
+        pTest = &opCompare;
+        /* Ticket b351d95f9cd5ef17e9d9dbae18f5ca8611190001:
+        ** The value in regFree1 might get SCopy-ed into the file result.
+        ** So make sure that the regFree1 register is not reused for other
+        ** purposes and possibly overwritten.  */
+        regFree1 = 0;
+      }
+      for(i=0; i<nExpr-1; i=i+2){
+        if( pX ){
+          assert( pTest!=0 );
+          opCompare.pRight = aListelem[i].pExpr;
+        }else{
+          pTest = aListelem[i].pExpr;
+        }
+        nextCase = sqlite3VdbeMakeLabel(pParse);
+        testcase( pTest->op==TK_COLUMN );
+        sqlite3ExprIfFalse(pParse, pTest, nextCase, SQLITE_JUMPIFNULL);
+        testcase( aListelem[i+1].pExpr->op==TK_COLUMN );
+        sqlite3ExprCode(pParse, aListelem[i+1].pExpr, target);
+        sqlite3VdbeGoto(v, endLabel);
+        sqlite3VdbeResolveLabel(v, nextCase);
+      }
+      if( (nExpr&1)!=0 ){
+        sqlite3ExprCode(pParse, pEList->a[nExpr-1].pExpr, target);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      }
+      sqlite3ExprDelete(db, pDel);
+      setDoNotMergeFlagOnCopy(v);
+      sqlite3VdbeResolveLabel(v, endLabel);
+      break;
+    }
+#ifndef SQLITE_OMIT_TRIGGER
+    case TK_RAISE: {
+      assert( pExpr->affExpr==OE_Rollback
+           || pExpr->affExpr==OE_Abort
+           || pExpr->affExpr==OE_Fail
+           || pExpr->affExpr==OE_Ignore
+      );
+      if( !pParse->pTriggerTab && !pParse->nested ){
+        sqlite3ErrorMsg(pParse,
+                       "RAISE() may only be used within a trigger-program");
+        return 0;
+      }
+      if( pExpr->affExpr==OE_Abort ){
+        sqlite3MayAbort(pParse);
+      }
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      if( pExpr->affExpr==OE_Ignore ){
+        sqlite3VdbeAddOp4(
+            v, OP_Halt, SQLITE_OK, OE_Ignore, 0, pExpr->u.zToken,0);
+        VdbeCoverage(v);
+      }else{
+        sqlite3HaltConstraint(pParse,
+             pParse->pTriggerTab ? SQLITE_CONSTRAINT_TRIGGER : SQLITE_ERROR,
+             pExpr->affExpr, pExpr->u.zToken, 0, 0);
+      }
+
+      break;
+    }
+#endif
+  }
+  sqlite3ReleaseTempReg(pParse, regFree1);
+  sqlite3ReleaseTempReg(pParse, regFree2);
+  return inReg;
+}
+
+/*
+** Generate code that will evaluate expression pExpr just one time
+** per prepared statement execution.
+**
+** If the expression uses functions (that might throw an exception) then
+** guard them with an OP_Once opcode to ensure that the code is only executed
+** once. If no functions are involved, then factor the code out and put it at
+** the end of the prepared statement in the initialization section.
+**
+** If regDest>0 then the result is always stored in that register and the
+** result is not reusable.  If regDest<0 then this routine is free to
+** store the value wherever it wants.  The register where the expression
+** is stored is returned.  When regDest<0, two identical expressions might
+** code to the same register, if they do not contain function calls and hence
+** are factored out into the initialization section at the end of the
+** prepared statement.
+*/
+int sqlite3ExprCodeRunJustOnce(
+  Parse *pParse,    /* Parsing context */
+  Expr *pExpr,      /* The expression to code when the VDBE initializes */
+  int regDest       /* Store the value in this register */
+){
+  ExprList *p;
+  assert( ConstFactorOk(pParse) );
+  assert( regDest!=0 );
+  p = pParse->pConstExpr;
+  if( regDest<0 && p ){
+    struct ExprList_item *pItem;
+    int i;
+    for(pItem=p->a, i=p->nExpr; i>0; pItem++, i--){
+      if( pItem->fg.reusable
+       && sqlite3ExprCompare(0,pItem->pExpr,pExpr,-1)==0
+      ){
+        return pItem->u.iConstExprReg;
+      }
+    }
+  }
+  pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
+  if( pExpr!=0 && ExprHasProperty(pExpr, EP_HasFunc) ){
+    Vdbe *v = pParse->pVdbe;
+    int addr;
+    assert( v );
+    addr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+    pParse->okConstFactor = 0;
+    if( !pParse->db->mallocFailed ){
+      if( regDest<0 ) regDest = ++pParse->nMem;
+      sqlite3ExprCode(pParse, pExpr, regDest);
+    }
+    pParse->okConstFactor = 1;
+    sqlite3ExprDelete(pParse->db, pExpr);
+    sqlite3VdbeJumpHere(v, addr);
+  }else{
+    p = sqlite3ExprListAppend(pParse, p, pExpr);
+    if( p ){
+       struct ExprList_item *pItem = &p->a[p->nExpr-1];
+       pItem->fg.reusable = regDest<0;
+       if( regDest<0 ) regDest = ++pParse->nMem;
+       pItem->u.iConstExprReg = regDest;
+    }
+    pParse->pConstExpr = p;
+  }
+  return regDest;
+}
+
+/*
+** Generate code to evaluate an expression and store the results
+** into a register.  Return the register number where the results
+** are stored.
+**
+** If the register is a temporary register that can be deallocated,
+** then write its number into *pReg.  If the result register is not
+** a temporary, then set *pReg to zero.
+**
+** If pExpr is a constant, then this routine might generate this
+** code to fill the register in the initialization section of the
+** VDBE program, in order to factor it out of the evaluation loop.
+*/
+int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){
+  int r2;
+  pExpr = sqlite3ExprSkipCollateAndLikely(pExpr);
+  if( ConstFactorOk(pParse)
+   && ALWAYS(pExpr!=0)
+   && pExpr->op!=TK_REGISTER
+   && sqlite3ExprIsConstantNotJoin(pExpr)
+  ){
+    *pReg  = 0;
+    r2 = sqlite3ExprCodeRunJustOnce(pParse, pExpr, -1);
+  }else{
+    int r1 = sqlite3GetTempReg(pParse);
+    r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
+    if( r2==r1 ){
+      *pReg = r1;
+    }else{
+      sqlite3ReleaseTempReg(pParse, r1);
+      *pReg = 0;
+    }
+  }
+  return r2;
+}
+
+/*
+** Generate code that will evaluate expression pExpr and store the
+** results in register target.  The results are guaranteed to appear
+** in register target.
+*/
+void sqlite3ExprCode(Parse *pParse, Expr *pExpr, int target){
+  int inReg;
+
+  assert( pExpr==0 || !ExprHasVVAProperty(pExpr,EP_Immutable) );
+  assert( target>0 && target<=pParse->nMem );
+  assert( pParse->pVdbe!=0 || pParse->db->mallocFailed );
+  if( pParse->pVdbe==0 ) return;
+  inReg = sqlite3ExprCodeTarget(pParse, pExpr, target);
+  if( inReg!=target ){
+    u8 op;
+    Expr *pX = sqlite3ExprSkipCollateAndLikely(pExpr);
+    testcase( pX!=pExpr );
+    if( ALWAYS(pX)
+     && (ExprHasProperty(pX,EP_Subquery) || pX->op==TK_REGISTER)
+    ){
+      op = OP_Copy;
+    }else{
+      op = OP_SCopy;
+    }
+    sqlite3VdbeAddOp2(pParse->pVdbe, op, inReg, target);
+  }
+}
+
+/*
+** Make a transient copy of expression pExpr and then code it using
+** sqlite3ExprCode().  This routine works just like sqlite3ExprCode()
+** except that the input expression is guaranteed to be unchanged.
+*/
+void sqlite3ExprCodeCopy(Parse *pParse, Expr *pExpr, int target){
+  sqlite3 *db = pParse->db;
+  pExpr = sqlite3ExprDup(db, pExpr, 0);
+  if( !db->mallocFailed ) sqlite3ExprCode(pParse, pExpr, target);
+  sqlite3ExprDelete(db, pExpr);
+}
+
+/*
+** Generate code that will evaluate expression pExpr and store the
+** results in register target.  The results are guaranteed to appear
+** in register target.  If the expression is constant, then this routine
+** might choose to code the expression at initialization time.
+*/
+void sqlite3ExprCodeFactorable(Parse *pParse, Expr *pExpr, int target){
+  if( pParse->okConstFactor && sqlite3ExprIsConstantNotJoin(pExpr) ){
+    sqlite3ExprCodeRunJustOnce(pParse, pExpr, target);
+  }else{
+    sqlite3ExprCodeCopy(pParse, pExpr, target);
+  }
+}
+
+/*
+** Generate code that pushes the value of every element of the given
+** expression list into a sequence of registers beginning at target.
+**
+** Return the number of elements evaluated.  The number returned will
+** usually be pList->nExpr but might be reduced if SQLITE_ECEL_OMITREF
+** is defined.
+**
+** The SQLITE_ECEL_DUP flag prevents the arguments from being
+** filled using OP_SCopy.  OP_Copy must be used instead.
+**
+** The SQLITE_ECEL_FACTOR argument allows constant arguments to be
+** factored out into initialization code.
+**
+** The SQLITE_ECEL_REF flag means that expressions in the list with
+** ExprList.a[].u.x.iOrderByCol>0 have already been evaluated and stored
+** in registers at srcReg, and so the value can be copied from there.
+** If SQLITE_ECEL_OMITREF is also set, then the values with u.x.iOrderByCol>0
+** are simply omitted rather than being copied from srcReg.
+*/
+int sqlite3ExprCodeExprList(
+  Parse *pParse,     /* Parsing context */
+  ExprList *pList,   /* The expression list to be coded */
+  int target,        /* Where to write results */
+  int srcReg,        /* Source registers if SQLITE_ECEL_REF */
+  u8 flags           /* SQLITE_ECEL_* flags */
+){
+  struct ExprList_item *pItem;
+  int i, j, n;
+  u8 copyOp = (flags & SQLITE_ECEL_DUP) ? OP_Copy : OP_SCopy;
+  Vdbe *v = pParse->pVdbe;
+  assert( pList!=0 );
+  assert( target>0 );
+  assert( pParse->pVdbe!=0 );  /* Never gets this far otherwise */
+  n = pList->nExpr;
+  if( !ConstFactorOk(pParse) ) flags &= ~SQLITE_ECEL_FACTOR;
+  for(pItem=pList->a, i=0; i<n; i++, pItem++){
+    Expr *pExpr = pItem->pExpr;
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    if( pItem->fg.bSorterRef ){
+      i--;
+      n--;
+    }else
+#endif
+    if( (flags & SQLITE_ECEL_REF)!=0 && (j = pItem->u.x.iOrderByCol)>0 ){
+      if( flags & SQLITE_ECEL_OMITREF ){
+        i--;
+        n--;
+      }else{
+        sqlite3VdbeAddOp2(v, copyOp, j+srcReg-1, target+i);
+      }
+    }else if( (flags & SQLITE_ECEL_FACTOR)!=0
+           && sqlite3ExprIsConstantNotJoin(pExpr)
+    ){
+      sqlite3ExprCodeRunJustOnce(pParse, pExpr, target+i);
+    }else{
+      int inReg = sqlite3ExprCodeTarget(pParse, pExpr, target+i);
+      if( inReg!=target+i ){
+        VdbeOp *pOp;
+        if( copyOp==OP_Copy
+         && (pOp=sqlite3VdbeGetLastOp(v))->opcode==OP_Copy
+         && pOp->p1+pOp->p3+1==inReg
+         && pOp->p2+pOp->p3+1==target+i
+         && pOp->p5==0  /* The do-not-merge flag must be clear */
+        ){
+          pOp->p3++;
+        }else{
+          sqlite3VdbeAddOp2(v, copyOp, inReg, target+i);
+        }
+      }
+    }
+  }
+  return n;
+}
+
+/*
+** Generate code for a BETWEEN operator.
+**
+**    x BETWEEN y AND z
+**
+** The above is equivalent to
+**
+**    x>=y AND x<=z
+**
+** Code it as such, taking care to do the common subexpression
+** elimination of x.
+**
+** The xJumpIf parameter determines details:
+**
+**    NULL:                   Store the boolean result in reg[dest]
+**    sqlite3ExprIfTrue:      Jump to dest if true
+**    sqlite3ExprIfFalse:     Jump to dest if false
+**
+** The jumpIfNull parameter is ignored if xJumpIf is NULL.
+*/
+static void exprCodeBetween(
+  Parse *pParse,    /* Parsing and code generating context */
+  Expr *pExpr,      /* The BETWEEN expression */
+  int dest,         /* Jump destination or storage location */
+  void (*xJump)(Parse*,Expr*,int,int), /* Action to take */
+  int jumpIfNull    /* Take the jump if the BETWEEN is NULL */
+){
+  Expr exprAnd;     /* The AND operator in  x>=y AND x<=z  */
+  Expr compLeft;    /* The  x>=y  term */
+  Expr compRight;   /* The  x<=z  term */
+  int regFree1 = 0; /* Temporary use register */
+  Expr *pDel = 0;
+  sqlite3 *db = pParse->db;
+
+  memset(&compLeft, 0, sizeof(Expr));
+  memset(&compRight, 0, sizeof(Expr));
+  memset(&exprAnd, 0, sizeof(Expr));
+
+  assert( ExprUseXList(pExpr) );
+  pDel = sqlite3ExprDup(db, pExpr->pLeft, 0);
+  if( db->mallocFailed==0 ){
+    exprAnd.op = TK_AND;
+    exprAnd.pLeft = &compLeft;
+    exprAnd.pRight = &compRight;
+    compLeft.op = TK_GE;
+    compLeft.pLeft = pDel;
+    compLeft.pRight = pExpr->x.pList->a[0].pExpr;
+    compRight.op = TK_LE;
+    compRight.pLeft = pDel;
+    compRight.pRight = pExpr->x.pList->a[1].pExpr;
+    exprToRegister(pDel, exprCodeVector(pParse, pDel, &regFree1));
+    if( xJump ){
+      xJump(pParse, &exprAnd, dest, jumpIfNull);
+    }else{
+      /* Mark the expression is being from the ON or USING clause of a join
+      ** so that the sqlite3ExprCodeTarget() routine will not attempt to move
+      ** it into the Parse.pConstExpr list.  We should use a new bit for this,
+      ** for clarity, but we are out of bits in the Expr.flags field so we
+      ** have to reuse the EP_OuterON bit.  Bummer. */
+      pDel->flags |= EP_OuterON;
+      sqlite3ExprCodeTarget(pParse, &exprAnd, dest);
+    }
+    sqlite3ReleaseTempReg(pParse, regFree1);
+  }
+  sqlite3ExprDelete(db, pDel);
+
+  /* Ensure adequate test coverage */
+  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull==0 && regFree1==0 );
+  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull==0 && regFree1!=0 );
+  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull!=0 && regFree1==0 );
+  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull!=0 && regFree1!=0 );
+  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull==0 && regFree1==0 );
+  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull==0 && regFree1!=0 );
+  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull!=0 && regFree1==0 );
+  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull!=0 && regFree1!=0 );
+  testcase( xJump==0 );
+}
+
+/*
+** Generate code for a boolean expression such that a jump is made
+** to the label "dest" if the expression is true but execution
+** continues straight thru if the expression is false.
+**
+** If the expression evaluates to NULL (neither true nor false), then
+** take the jump if the jumpIfNull flag is SQLITE_JUMPIFNULL.
+**
+** This code depends on the fact that certain token values (ex: TK_EQ)
+** are the same as opcode values (ex: OP_Eq) that implement the corresponding
+** operation.  Special comments in vdbe.c and the mkopcodeh.awk script in
+** the make process cause these values to align.  Assert()s in the code
+** below verify that the numbers are aligned correctly.
+*/
+void sqlite3ExprIfTrue(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
+  Vdbe *v = pParse->pVdbe;
+  int op = 0;
+  int regFree1 = 0;
+  int regFree2 = 0;
+  int r1, r2;
+
+  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
+  if( NEVER(v==0) )     return;  /* Existence of VDBE checked by caller */
+  if( NEVER(pExpr==0) ) return;  /* No way this can happen */
+  assert( !ExprHasVVAProperty(pExpr, EP_Immutable) );
+  op = pExpr->op;
+  switch( op ){
+    case TK_AND:
+    case TK_OR: {
+      Expr *pAlt = sqlite3ExprSimplifiedAndOr(pExpr);
+      if( pAlt!=pExpr ){
+        sqlite3ExprIfTrue(pParse, pAlt, dest, jumpIfNull);
+      }else if( op==TK_AND ){
+        int d2 = sqlite3VdbeMakeLabel(pParse);
+        testcase( jumpIfNull==0 );
+        sqlite3ExprIfFalse(pParse, pExpr->pLeft, d2,
+                           jumpIfNull^SQLITE_JUMPIFNULL);
+        sqlite3ExprIfTrue(pParse, pExpr->pRight, dest, jumpIfNull);
+        sqlite3VdbeResolveLabel(v, d2);
+      }else{
+        testcase( jumpIfNull==0 );
+        sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);
+        sqlite3ExprIfTrue(pParse, pExpr->pRight, dest, jumpIfNull);
+      }
+      break;
+    }
+    case TK_NOT: {
+      testcase( jumpIfNull==0 );
+      sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);
+      break;
+    }
+    case TK_TRUTH: {
+      int isNot;      /* IS NOT TRUE or IS NOT FALSE */
+      int isTrue;     /* IS TRUE or IS NOT TRUE */
+      testcase( jumpIfNull==0 );
+      isNot = pExpr->op2==TK_ISNOT;
+      isTrue = sqlite3ExprTruthValue(pExpr->pRight);
+      testcase( isTrue && isNot );
+      testcase( !isTrue && isNot );
+      if( isTrue ^ isNot ){
+        sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest,
+                          isNot ? SQLITE_JUMPIFNULL : 0);
+      }else{
+        sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest,
+                           isNot ? SQLITE_JUMPIFNULL : 0);
+      }
+      break;
+    }
+    case TK_IS:
+    case TK_ISNOT:
+      testcase( op==TK_IS );
+      testcase( op==TK_ISNOT );
+      op = (op==TK_IS) ? TK_EQ : TK_NE;
+      jumpIfNull = SQLITE_NULLEQ;
+      /* no break */ deliberate_fall_through
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_NE:
+    case TK_EQ: {
+      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
+      testcase( jumpIfNull==0 );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, dest, jumpIfNull, ExprHasProperty(pExpr,EP_Commuted));
+      assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
+      assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
+      assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
+      assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
+      assert(TK_EQ==OP_Eq); testcase(op==OP_Eq);
+      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull==SQLITE_NULLEQ);
+      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull!=SQLITE_NULLEQ);
+      assert(TK_NE==OP_Ne); testcase(op==OP_Ne);
+      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull==SQLITE_NULLEQ);
+      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull!=SQLITE_NULLEQ);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_ISNULL:
+    case TK_NOTNULL: {
+      assert( TK_ISNULL==OP_IsNull );   testcase( op==TK_ISNULL );
+      assert( TK_NOTNULL==OP_NotNull ); testcase( op==TK_NOTNULL );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      sqlite3VdbeTypeofColumn(v, r1);
+      sqlite3VdbeAddOp2(v, op, r1, dest);
+      VdbeCoverageIf(v, op==TK_ISNULL);
+      VdbeCoverageIf(v, op==TK_NOTNULL);
+      testcase( regFree1==0 );
+      break;
+    }
+    case TK_BETWEEN: {
+      testcase( jumpIfNull==0 );
+      exprCodeBetween(pParse, pExpr, dest, sqlite3ExprIfTrue, jumpIfNull);
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_IN: {
+      int destIfFalse = sqlite3VdbeMakeLabel(pParse);
+      int destIfNull = jumpIfNull ? dest : destIfFalse;
+      sqlite3ExprCodeIN(pParse, pExpr, destIfFalse, destIfNull);
+      sqlite3VdbeGoto(v, dest);
+      sqlite3VdbeResolveLabel(v, destIfFalse);
+      break;
+    }
+#endif
+    default: {
+    default_expr:
+      if( ExprAlwaysTrue(pExpr) ){
+        sqlite3VdbeGoto(v, dest);
+      }else if( ExprAlwaysFalse(pExpr) ){
+        /* No-op */
+      }else{
+        r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
+        sqlite3VdbeAddOp3(v, OP_If, r1, dest, jumpIfNull!=0);
+        VdbeCoverage(v);
+        testcase( regFree1==0 );
+        testcase( jumpIfNull==0 );
+      }
+      break;
+    }
+  }
+  sqlite3ReleaseTempReg(pParse, regFree1);
+  sqlite3ReleaseTempReg(pParse, regFree2); 
+}
+
+/*
+** Generate code for a boolean expression such that a jump is made
+** to the label "dest" if the expression is false but execution
+** continues straight thru if the expression is true.
+**
+** If the expression evaluates to NULL (neither true nor false) then
+** jump if jumpIfNull is SQLITE_JUMPIFNULL or fall through if jumpIfNull
+** is 0.
+*/
+void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
+  Vdbe *v = pParse->pVdbe;
+  int op = 0;
+  int regFree1 = 0;
+  int regFree2 = 0;
+  int r1, r2;
+
+  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
+  if( NEVER(v==0) ) return; /* Existence of VDBE checked by caller */
+  if( pExpr==0 )    return;
+  assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );
+
+  /* The value of pExpr->op and op are related as follows:
+  **
+  **       pExpr->op            op
+  **       ---------          ----------
+  **       TK_ISNULL          OP_NotNull
+  **       TK_NOTNULL         OP_IsNull
+  **       TK_NE              OP_Eq
+  **       TK_EQ              OP_Ne
+  **       TK_GT              OP_Le
+  **       TK_LE              OP_Gt
+  **       TK_GE              OP_Lt
+  **       TK_LT              OP_Ge
+  **
+  ** For other values of pExpr->op, op is undefined and unused.
+  ** The value of TK_ and OP_ constants are arranged such that we
+  ** can compute the mapping above using the following expression.
+  ** Assert()s verify that the computation is correct.
+  */
+  op = ((pExpr->op+(TK_ISNULL&1))^1)-(TK_ISNULL&1);
+
+  /* Verify correct alignment of TK_ and OP_ constants
+  */
+  assert( pExpr->op!=TK_ISNULL || op==OP_NotNull );
+  assert( pExpr->op!=TK_NOTNULL || op==OP_IsNull );
+  assert( pExpr->op!=TK_NE || op==OP_Eq );
+  assert( pExpr->op!=TK_EQ || op==OP_Ne );
+  assert( pExpr->op!=TK_LT || op==OP_Ge );
+  assert( pExpr->op!=TK_LE || op==OP_Gt );
+  assert( pExpr->op!=TK_GT || op==OP_Le );
+  assert( pExpr->op!=TK_GE || op==OP_Lt );
+
+  switch( pExpr->op ){
+    case TK_AND:
+    case TK_OR: {
+      Expr *pAlt = sqlite3ExprSimplifiedAndOr(pExpr);
+      if( pAlt!=pExpr ){
+        sqlite3ExprIfFalse(pParse, pAlt, dest, jumpIfNull);
+      }else if( pExpr->op==TK_AND ){
+        testcase( jumpIfNull==0 );
+        sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);
+        sqlite3ExprIfFalse(pParse, pExpr->pRight, dest, jumpIfNull);
+      }else{
+        int d2 = sqlite3VdbeMakeLabel(pParse);
+        testcase( jumpIfNull==0 );
+        sqlite3ExprIfTrue(pParse, pExpr->pLeft, d2,
+                          jumpIfNull^SQLITE_JUMPIFNULL);
+        sqlite3ExprIfFalse(pParse, pExpr->pRight, dest, jumpIfNull);
+        sqlite3VdbeResolveLabel(v, d2);
+      }
+      break;
+    }
+    case TK_NOT: {
+      testcase( jumpIfNull==0 );
+      sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);
+      break;
+    }
+    case TK_TRUTH: {
+      int isNot;   /* IS NOT TRUE or IS NOT FALSE */
+      int isTrue;  /* IS TRUE or IS NOT TRUE */
+      testcase( jumpIfNull==0 );
+      isNot = pExpr->op2==TK_ISNOT;
+      isTrue = sqlite3ExprTruthValue(pExpr->pRight);
+      testcase( isTrue && isNot );
+      testcase( !isTrue && isNot );
+      if( isTrue ^ isNot ){
+        /* IS TRUE and IS NOT FALSE */
+        sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest,
+                           isNot ? 0 : SQLITE_JUMPIFNULL);
+
+      }else{
+        /* IS FALSE and IS NOT TRUE */
+        sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest,
+                          isNot ? 0 : SQLITE_JUMPIFNULL);
+      }
+      break;
+    }
+    case TK_IS:
+    case TK_ISNOT:
+      testcase( pExpr->op==TK_IS );
+      testcase( pExpr->op==TK_ISNOT );
+      op = (pExpr->op==TK_IS) ? TK_NE : TK_EQ;
+      jumpIfNull = SQLITE_NULLEQ;
+      /* no break */ deliberate_fall_through
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_NE:
+    case TK_EQ: {
+      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
+      testcase( jumpIfNull==0 );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, dest, jumpIfNull,ExprHasProperty(pExpr,EP_Commuted));
+      assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
+      assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
+      assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
+      assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
+      assert(TK_EQ==OP_Eq); testcase(op==OP_Eq);
+      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull!=SQLITE_NULLEQ);
+      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull==SQLITE_NULLEQ);
+      assert(TK_NE==OP_Ne); testcase(op==OP_Ne);
+      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull!=SQLITE_NULLEQ);
+      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull==SQLITE_NULLEQ);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_ISNULL:
+    case TK_NOTNULL: {
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      sqlite3VdbeTypeofColumn(v, r1);
+      sqlite3VdbeAddOp2(v, op, r1, dest);
+      testcase( op==TK_ISNULL );   VdbeCoverageIf(v, op==TK_ISNULL);
+      testcase( op==TK_NOTNULL );  VdbeCoverageIf(v, op==TK_NOTNULL);
+      testcase( regFree1==0 );
+      break;
+    }
+    case TK_BETWEEN: {
+      testcase( jumpIfNull==0 );
+      exprCodeBetween(pParse, pExpr, dest, sqlite3ExprIfFalse, jumpIfNull);
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_IN: {
+      if( jumpIfNull ){
+        sqlite3ExprCodeIN(pParse, pExpr, dest, dest);
+      }else{
+        int destIfNull = sqlite3VdbeMakeLabel(pParse);
+        sqlite3ExprCodeIN(pParse, pExpr, dest, destIfNull);
+        sqlite3VdbeResolveLabel(v, destIfNull);
+      }
+      break;
+    }
+#endif
+    default: {
+    default_expr:
+      if( ExprAlwaysFalse(pExpr) ){
+        sqlite3VdbeGoto(v, dest);
+      }else if( ExprAlwaysTrue(pExpr) ){
+        /* no-op */
+      }else{
+        r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
+        sqlite3VdbeAddOp3(v, OP_IfNot, r1, dest, jumpIfNull!=0);
+        VdbeCoverage(v);
+        testcase( regFree1==0 );
+        testcase( jumpIfNull==0 );
+      }
+      break;
+    }
+  }
+  sqlite3ReleaseTempReg(pParse, regFree1);
+  sqlite3ReleaseTempReg(pParse, regFree2);
+}
+
+/*
+** Like sqlite3ExprIfFalse() except that a copy is made of pExpr before
+** code generation, and that copy is deleted after code generation. This
+** ensures that the original pExpr is unchanged.
+*/
+void sqlite3ExprIfFalseDup(Parse *pParse, Expr *pExpr, int dest,int jumpIfNull){
+  sqlite3 *db = pParse->db;
+  Expr *pCopy = sqlite3ExprDup(db, pExpr, 0);
+  if( db->mallocFailed==0 ){
+    sqlite3ExprIfFalse(pParse, pCopy, dest, jumpIfNull);
+  }
+  sqlite3ExprDelete(db, pCopy);
+}
+
+/*
+** Expression pVar is guaranteed to be an SQL variable. pExpr may be any
+** type of expression.
+**
+** If pExpr is a simple SQL value - an integer, real, string, blob
+** or NULL value - then the VDBE currently being prepared is configured
+** to re-prepare each time a new value is bound to variable pVar.
+**
+** Additionally, if pExpr is a simple SQL value and the value is the
+** same as that currently bound to variable pVar, non-zero is returned.
+** Otherwise, if the values are not the same or if pExpr is not a simple
+** SQL value, zero is returned.
+*/
+static int exprCompareVariable(
+  const Parse *pParse,
+  const Expr *pVar,
+  const Expr *pExpr
+){
+  int res = 0;
+  int iVar;
+  sqlite3_value *pL, *pR = 0;
+ 
+  sqlite3ValueFromExpr(pParse->db, pExpr, SQLITE_UTF8, SQLITE_AFF_BLOB, &pR);
+  if( pR ){
+    iVar = pVar->iColumn;
+    sqlite3VdbeSetVarmask(pParse->pVdbe, iVar);
+    pL = sqlite3VdbeGetBoundValue(pParse->pReprepare, iVar, SQLITE_AFF_BLOB);
+    if( pL ){
+      if( sqlite3_value_type(pL)==SQLITE_TEXT ){
+        sqlite3_value_text(pL); /* Make sure the encoding is UTF-8 */
+      }
+      res =  0==sqlite3MemCompare(pL, pR, 0);
+    }
+    sqlite3ValueFree(pR);
+    sqlite3ValueFree(pL);
+  }
+
+  return res;
+}
+
+/*
+** Do a deep comparison of two expression trees.  Return 0 if the two
+** expressions are completely identical.  Return 1 if they differ only
+** by a COLLATE operator at the top level.  Return 2 if there are differences
+** other than the top-level COLLATE operator.
+**
+** If any subelement of pB has Expr.iTable==(-1) then it is allowed
+** to compare equal to an equivalent element in pA with Expr.iTable==iTab.
+**
+** The pA side might be using TK_REGISTER.  If that is the case and pB is
+** not using TK_REGISTER but is otherwise equivalent, then still return 0.
+**
+** Sometimes this routine will return 2 even if the two expressions
+** really are equivalent.  If we cannot prove that the expressions are
+** identical, we return 2 just to be safe.  So if this routine
+** returns 2, then you do not really know for certain if the two
+** expressions are the same.  But if you get a 0 or 1 return, then you
+** can be sure the expressions are the same.  In the places where
+** this routine is used, it does not hurt to get an extra 2 - that
+** just might result in some slightly slower code.  But returning
+** an incorrect 0 or 1 could lead to a malfunction.
+**
+** If pParse is not NULL then TK_VARIABLE terms in pA with bindings in
+** pParse->pReprepare can be matched against literals in pB.  The
+** pParse->pVdbe->expmask bitmask is updated for each variable referenced.
+** If pParse is NULL (the normal case) then any TK_VARIABLE term in
+** Argument pParse should normally be NULL. If it is not NULL and pA or
+** pB causes a return value of 2.
+*/
+int sqlite3ExprCompare(
+  const Parse *pParse,
+  const Expr *pA,
+  const Expr *pB,
+  int iTab
+){
+  u32 combinedFlags;
+  if( pA==0 || pB==0 ){
+    return pB==pA ? 0 : 2;
+  }
+  if( pParse && pA->op==TK_VARIABLE && exprCompareVariable(pParse, pA, pB) ){
+    return 0;
+  }
+  combinedFlags = pA->flags | pB->flags;
+  if( combinedFlags & EP_IntValue ){
+    if( (pA->flags&pB->flags&EP_IntValue)!=0 && pA->u.iValue==pB->u.iValue ){
+      return 0;
+    }
+    return 2;
+  }
+  if( pA->op!=pB->op || pA->op==TK_RAISE ){
+    if( pA->op==TK_COLLATE && sqlite3ExprCompare(pParse, pA->pLeft,pB,iTab)<2 ){
+      return 1;
+    }
+    if( pB->op==TK_COLLATE && sqlite3ExprCompare(pParse, pA,pB->pLeft,iTab)<2 ){
+      return 1;
+    }
+    if( pA->op==TK_AGG_COLUMN && pB->op==TK_COLUMN
+     && pB->iTable<0 && pA->iTable==iTab
+    ){
+      /* fall through */
+    }else{
+      return 2;
+    }
+  }
+  assert( !ExprHasProperty(pA, EP_IntValue) );
+  assert( !ExprHasProperty(pB, EP_IntValue) );
+  if( pA->u.zToken ){
+    if( pA->op==TK_FUNCTION || pA->op==TK_AGG_FUNCTION ){
+      if( sqlite3StrICmp(pA->u.zToken,pB->u.zToken)!=0 ) return 2;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      assert( pA->op==pB->op );
+      if( ExprHasProperty(pA,EP_WinFunc)!=ExprHasProperty(pB,EP_WinFunc) ){
+        return 2;
+      }
+      if( ExprHasProperty(pA,EP_WinFunc) ){
+        if( sqlite3WindowCompare(pParse, pA->y.pWin, pB->y.pWin, 1)!=0 ){
+          return 2;
+        }
+      }
+#endif
+    }else if( pA->op==TK_NULL ){
+      return 0;
+    }else if( pA->op==TK_COLLATE ){
+      if( sqlite3_stricmp(pA->u.zToken,pB->u.zToken)!=0 ) return 2;
+    }else
+    if( pB->u.zToken!=0
+     && pA->op!=TK_COLUMN
+     && pA->op!=TK_AGG_COLUMN
+     && strcmp(pA->u.zToken,pB->u.zToken)!=0
+    ){
+      return 2;
+    }
+  }
+  if( (pA->flags & (EP_Distinct|EP_Commuted))
+     != (pB->flags & (EP_Distinct|EP_Commuted)) ) return 2;
+  if( ALWAYS((combinedFlags & EP_TokenOnly)==0) ){
+    if( combinedFlags & EP_xIsSelect ) return 2;
+    if( (combinedFlags & EP_FixedCol)==0
+     && sqlite3ExprCompare(pParse, pA->pLeft, pB->pLeft, iTab) ) return 2;
+    if( sqlite3ExprCompare(pParse, pA->pRight, pB->pRight, iTab) ) return 2;
+    if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList, iTab) ) return 2;
+    if( pA->op!=TK_STRING
+     && pA->op!=TK_TRUEFALSE
+     && ALWAYS((combinedFlags & EP_Reduced)==0)
+    ){
+      if( pA->iColumn!=pB->iColumn ) return 2;
+      if( pA->op2!=pB->op2 && pA->op==TK_TRUTH ) return 2;
+      if( pA->op!=TK_IN && pA->iTable!=pB->iTable && pA->iTable!=iTab ){
+        return 2;
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** Compare two ExprList objects.  Return 0 if they are identical, 1
+** if they are certainly different, or 2 if it is not possible to
+** determine if they are identical or not.
+**
+** If any subelement of pB has Expr.iTable==(-1) then it is allowed
+** to compare equal to an equivalent element in pA with Expr.iTable==iTab.
+**
+** This routine might return non-zero for equivalent ExprLists.  The
+** only consequence will be disabled optimizations.  But this routine
+** must never return 0 if the two ExprList objects are different, or
+** a malfunction will result.
+**
+** Two NULL pointers are considered to be the same.  But a NULL pointer
+** always differs from a non-NULL pointer.
+*/
+int sqlite3ExprListCompare(const ExprList *pA, const ExprList *pB, int iTab){
+  int i;
+  if( pA==0 && pB==0 ) return 0;
+  if( pA==0 || pB==0 ) return 1;
+  if( pA->nExpr!=pB->nExpr ) return 1;
+  for(i=0; i<pA->nExpr; i++){
+    int res;
+    Expr *pExprA = pA->a[i].pExpr;
+    Expr *pExprB = pB->a[i].pExpr;
+    if( pA->a[i].fg.sortFlags!=pB->a[i].fg.sortFlags ) return 1;
+    if( (res = sqlite3ExprCompare(0, pExprA, pExprB, iTab)) ) return res;
+  }
+  return 0;
+}
+
+/*
+** Like sqlite3ExprCompare() except COLLATE operators at the top-level
+** are ignored.
+*/
+int sqlite3ExprCompareSkip(Expr *pA,Expr *pB, int iTab){
+  return sqlite3ExprCompare(0,
+             sqlite3ExprSkipCollate(pA),
+             sqlite3ExprSkipCollate(pB),
+             iTab);
+}
+
+/*
+** Return non-zero if Expr p can only be true if pNN is not NULL.
+**
+** Or if seenNot is true, return non-zero if Expr p can only be
+** non-NULL if pNN is not NULL
+*/
+static int exprImpliesNotNull(
+  const Parse *pParse,/* Parsing context */
+  const Expr *p,      /* The expression to be checked */
+  const Expr *pNN,    /* The expression that is NOT NULL */
+  int iTab,           /* Table being evaluated */
+  int seenNot         /* Return true only if p can be any non-NULL value */
+){
+  assert( p );
+  assert( pNN );
+  if( sqlite3ExprCompare(pParse, p, pNN, iTab)==0 ){
+    return pNN->op!=TK_NULL;
+  }
+  switch( p->op ){
+    case TK_IN: {
+      if( seenNot && ExprHasProperty(p, EP_xIsSelect) ) return 0;
+      assert( ExprUseXSelect(p) || (p->x.pList!=0 && p->x.pList->nExpr>0) );
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
+    }
+    case TK_BETWEEN: {
+      ExprList *pList;
+      assert( ExprUseXList(p) );
+      pList = p->x.pList;
+      assert( pList!=0 );
+      assert( pList->nExpr==2 );
+      if( seenNot ) return 0;
+      if( exprImpliesNotNull(pParse, pList->a[0].pExpr, pNN, iTab, 1)
+       || exprImpliesNotNull(pParse, pList->a[1].pExpr, pNN, iTab, 1)
+      ){
+        return 1;
+      }
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
+    }
+    case TK_EQ:
+    case TK_NE:
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_PLUS:
+    case TK_MINUS:
+    case TK_BITOR:
+    case TK_LSHIFT:
+    case TK_RSHIFT:
+    case TK_CONCAT:
+      seenNot = 1;
+      /* no break */ deliberate_fall_through
+    case TK_STAR:
+    case TK_REM:
+    case TK_BITAND:
+    case TK_SLASH: {
+      if( exprImpliesNotNull(pParse, p->pRight, pNN, iTab, seenNot) ) return 1;
+      /* no break */ deliberate_fall_through
+    }
+    case TK_SPAN:
+    case TK_COLLATE:
+    case TK_UPLUS:
+    case TK_UMINUS: {
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
+    }
+    case TK_TRUTH: {
+      if( seenNot ) return 0;
+      if( p->op2!=TK_IS ) return 0;
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
+    }
+    case TK_BITNOT:
+    case TK_NOT: {
+      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
+    }
+  }
+  return 0;
+}
+
+/*
+** Return true if we can prove the pE2 will always be true if pE1 is
+** true.  Return false if we cannot complete the proof or if pE2 might
+** be false.  Examples:
+**
+**     pE1: x==5       pE2: x==5             Result: true
+**     pE1: x>0        pE2: x==5             Result: false
+**     pE1: x=21       pE2: x=21 OR y=43     Result: true
+**     pE1: x!=123     pE2: x IS NOT NULL    Result: true
+**     pE1: x!=?1      pE2: x IS NOT NULL    Result: true
+**     pE1: x IS NULL  pE2: x IS NOT NULL    Result: false
+**     pE1: x IS ?2    pE2: x IS NOT NULL    Result: false
+**
+** When comparing TK_COLUMN nodes between pE1 and pE2, if pE2 has
+** Expr.iTable<0 then assume a table number given by iTab.
+**
+** If pParse is not NULL, then the values of bound variables in pE1 are
+** compared against literal values in pE2 and pParse->pVdbe->expmask is
+** modified to record which bound variables are referenced.  If pParse
+** is NULL, then false will be returned if pE1 contains any bound variables.
+**
+** When in doubt, return false.  Returning true might give a performance
+** improvement.  Returning false might cause a performance reduction, but
+** it will always give the correct answer and is hence always safe.
+*/
+int sqlite3ExprImpliesExpr(
+  const Parse *pParse,
+  const Expr *pE1,
+  const Expr *pE2,
+  int iTab
+){
+  if( sqlite3ExprCompare(pParse, pE1, pE2, iTab)==0 ){
+    return 1;
+  }
+  if( pE2->op==TK_OR
+   && (sqlite3ExprImpliesExpr(pParse, pE1, pE2->pLeft, iTab)
+             || sqlite3ExprImpliesExpr(pParse, pE1, pE2->pRight, iTab) )
+  ){
+    return 1;
+  }
+  if( pE2->op==TK_NOTNULL
+   && exprImpliesNotNull(pParse, pE1, pE2->pLeft, iTab, 0)
+  ){
+    return 1;
+  }
+  return 0;
+}
+
+/* This is a helper function to impliesNotNullRow().  In this routine,
+** set pWalker->eCode to one only if *both* of the input expressions
+** separately have the implies-not-null-row property.
+*/
+static void bothImplyNotNullRow(Walker *pWalker, Expr *pE1, Expr *pE2){
+  if( pWalker->eCode==0 ){
+    sqlite3WalkExpr(pWalker, pE1);
+    if( pWalker->eCode ){
+      pWalker->eCode = 0;
+      sqlite3WalkExpr(pWalker, pE2);
+    }
+  }
+}
+
+/*
+** This is the Expr node callback for sqlite3ExprImpliesNonNullRow().
+** If the expression node requires that the table at pWalker->iCur
+** have one or more non-NULL column, then set pWalker->eCode to 1 and abort.
+**
+** pWalker->mWFlags is non-zero if this inquiry is being undertaking on
+** behalf of a RIGHT JOIN (or FULL JOIN).  That makes a difference when
+** evaluating terms in the ON clause of an inner join.
+**
+** This routine controls an optimization.  False positives (setting
+** pWalker->eCode to 1 when it should not be) are deadly, but false-negatives
+** (never setting pWalker->eCode) is a harmless missed optimization.
+*/
+static int impliesNotNullRow(Walker *pWalker, Expr *pExpr){
+  testcase( pExpr->op==TK_AGG_COLUMN );
+  testcase( pExpr->op==TK_AGG_FUNCTION );
+  if( ExprHasProperty(pExpr, EP_OuterON) ) return WRC_Prune;
+  if( ExprHasProperty(pExpr, EP_InnerON) && pWalker->mWFlags ){
+    /* If iCur is used in an inner-join ON clause to the left of a
+    ** RIGHT JOIN, that does *not* mean that the table must be non-null.
+    ** But it is difficult to check for that condition precisely.
+    ** To keep things simple, any use of iCur from any inner-join is
+    ** ignored while attempting to simplify a RIGHT JOIN. */
+    return WRC_Prune;
+  }
+  switch( pExpr->op ){
+    case TK_ISNOT:
+    case TK_ISNULL:
+    case TK_NOTNULL:
+    case TK_IS:
+    case TK_VECTOR:
+    case TK_FUNCTION:
+    case TK_TRUTH:
+    case TK_CASE:
+      testcase( pExpr->op==TK_ISNOT );
+      testcase( pExpr->op==TK_ISNULL );
+      testcase( pExpr->op==TK_NOTNULL );
+      testcase( pExpr->op==TK_IS );
+      testcase( pExpr->op==TK_VECTOR );
+      testcase( pExpr->op==TK_FUNCTION );
+      testcase( pExpr->op==TK_TRUTH );
+      testcase( pExpr->op==TK_CASE );
+      return WRC_Prune;
+
+    case TK_COLUMN:
+      if( pWalker->u.iCur==pExpr->iTable ){
+        pWalker->eCode = 1;
+        return WRC_Abort;
+      }
+      return WRC_Prune;
+
+    case TK_OR:
+    case TK_AND:
+      /* Both sides of an AND or OR must separately imply non-null-row.
+      ** Consider these cases:
+      **    1.  NOT (x AND y)
+      **    2.  x OR y
+      ** If only one of x or y is non-null-row, then the overall expression
+      ** can be true if the other arm is false (case 1) or true (case 2).
+      */
+      testcase( pExpr->op==TK_OR );
+      testcase( pExpr->op==TK_AND );
+      bothImplyNotNullRow(pWalker, pExpr->pLeft, pExpr->pRight);
+      return WRC_Prune;
+       
+    case TK_IN:
+      /* Beware of "x NOT IN ()" and "x NOT IN (SELECT 1 WHERE false)",
+      ** both of which can be true.  But apart from these cases, if
+      ** the left-hand side of the IN is NULL then the IN itself will be
+      ** NULL. */
+      if( ExprUseXList(pExpr) && ALWAYS(pExpr->x.pList->nExpr>0) ){
+        sqlite3WalkExpr(pWalker, pExpr->pLeft);
+      }
+      return WRC_Prune;
+
+    case TK_BETWEEN:
+      /* In "x NOT BETWEEN y AND z" either x must be non-null-row or else
+      ** both y and z must be non-null row */
+      assert( ExprUseXList(pExpr) );
+      assert( pExpr->x.pList->nExpr==2 );
+      sqlite3WalkExpr(pWalker, pExpr->pLeft);
+      bothImplyNotNullRow(pWalker, pExpr->x.pList->a[0].pExpr,
+                                   pExpr->x.pList->a[1].pExpr);
+      return WRC_Prune;
+
+    /* Virtual tables are allowed to use constraints like x=NULL.  So
+    ** a term of the form x=y does not prove that y is not null if x
+    ** is the column of a virtual table */
+    case TK_EQ:
+    case TK_NE:
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE: {
+      Expr *pLeft = pExpr->pLeft;
+      Expr *pRight = pExpr->pRight;
+      testcase( pExpr->op==TK_EQ );
+      testcase( pExpr->op==TK_NE );
+      testcase( pExpr->op==TK_LT );
+      testcase( pExpr->op==TK_LE );
+      testcase( pExpr->op==TK_GT );
+      testcase( pExpr->op==TK_GE );
+      /* The y.pTab=0 assignment in wherecode.c always happens after the
+      ** impliesNotNullRow() test */
+      assert( pLeft->op!=TK_COLUMN || ExprUseYTab(pLeft) );
+      assert( pRight->op!=TK_COLUMN || ExprUseYTab(pRight) );
+      if( (pLeft->op==TK_COLUMN
+           && ALWAYS(pLeft->y.pTab!=0)
+           && IsVirtual(pLeft->y.pTab))
+       || (pRight->op==TK_COLUMN
+           && ALWAYS(pRight->y.pTab!=0)
+           && IsVirtual(pRight->y.pTab))
+      ){
+        return WRC_Prune;
+      }
+      /* no break */ deliberate_fall_through
+    }
+    default:
+      return WRC_Continue;
+  }
+}
+
+/*
+** Return true (non-zero) if expression p can only be true if at least
+** one column of table iTab is non-null.  In other words, return true
+** if expression p will always be NULL or false if every column of iTab
+** is NULL.
+**
+** False negatives are acceptable.  In other words, it is ok to return
+** zero even if expression p will never be true of every column of iTab
+** is NULL.  A false negative is merely a missed optimization opportunity.
+**
+** False positives are not allowed, however.  A false positive may result
+** in an incorrect answer.
+**
+** Terms of p that are marked with EP_OuterON (and hence that come from
+** the ON or USING clauses of OUTER JOINS) are excluded from the analysis.
+**
+** This routine is used to check if a LEFT JOIN can be converted into
+** an ordinary JOIN.  The p argument is the WHERE clause.  If the WHERE
+** clause requires that some column of the right table of the LEFT JOIN
+** be non-NULL, then the LEFT JOIN can be safely converted into an
+** ordinary join.
+*/
+int sqlite3ExprImpliesNonNullRow(Expr *p, int iTab, int isRJ){
+  Walker w;
+  p = sqlite3ExprSkipCollateAndLikely(p);
+  if( p==0 ) return 0;
+  if( p->op==TK_NOTNULL ){
+    p = p->pLeft;
+  }else{
+    while( p->op==TK_AND ){
+      if( sqlite3ExprImpliesNonNullRow(p->pLeft, iTab, isRJ) ) return 1;
+      p = p->pRight;
+    }
+  }
+  w.xExprCallback = impliesNotNullRow;
+  w.xSelectCallback = 0;
+  w.xSelectCallback2 = 0;
+  w.eCode = 0;
+  w.mWFlags = isRJ!=0;
+  w.u.iCur = iTab;
+  sqlite3WalkExpr(&w, p);
+  return w.eCode;
+}
+
+/*
+** An instance of the following structure is used by the tree walker
+** to determine if an expression can be evaluated by reference to the
+** index only, without having to do a search for the corresponding
+** table entry.  The IdxCover.pIdx field is the index.  IdxCover.iCur
+** is the cursor for the table.
+*/
+struct IdxCover {
+  Index *pIdx;     /* The index to be tested for coverage */
+  int iCur;        /* Cursor number for the table corresponding to the index */
+};
+
+/*
+** Check to see if there are references to columns in table
+** pWalker->u.pIdxCover->iCur can be satisfied using the index
+** pWalker->u.pIdxCover->pIdx.
+*/
+static int exprIdxCover(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_COLUMN
+   && pExpr->iTable==pWalker->u.pIdxCover->iCur
+   && sqlite3TableColumnToIndex(pWalker->u.pIdxCover->pIdx, pExpr->iColumn)<0
+  ){
+    pWalker->eCode = 1;
+    return WRC_Abort;
+  }
+  return WRC_Continue;
+}
+
+/*
+** Determine if an index pIdx on table with cursor iCur contains will
+** the expression pExpr.  Return true if the index does cover the
+** expression and false if the pExpr expression references table columns
+** that are not found in the index pIdx.
+**
+** An index covering an expression means that the expression can be
+** evaluated using only the index and without having to lookup the
+** corresponding table entry.
+*/
+int sqlite3ExprCoveredByIndex(
+  Expr *pExpr,        /* The index to be tested */
+  int iCur,           /* The cursor number for the corresponding table */
+  Index *pIdx         /* The index that might be used for coverage */
+){
+  Walker w;
+  struct IdxCover xcov;
+  memset(&w, 0, sizeof(w));
+  xcov.iCur = iCur;
+  xcov.pIdx = pIdx;
+  w.xExprCallback = exprIdxCover;
+  w.u.pIdxCover = &xcov;
+  sqlite3WalkExpr(&w, pExpr);
+  return !w.eCode;
+}
+
+
+/* Structure used to pass information throughout the Walker in order to
+** implement sqlite3ReferencesSrcList().
+*/
+struct RefSrcList {
+  sqlite3 *db;         /* Database connection used for sqlite3DbRealloc() */
+  SrcList *pRef;       /* Looking for references to these tables */
+  i64 nExclude;        /* Number of tables to exclude from the search */
+  int *aiExclude;      /* Cursor IDs for tables to exclude from the search */
+};
+
+/*
+** Walker SELECT callbacks for sqlite3ReferencesSrcList().
+**
+** When entering a new subquery on the pExpr argument, add all FROM clause
+** entries for that subquery to the exclude list.
+**
+** When leaving the subquery, remove those entries from the exclude list.
+*/
+static int selectRefEnter(Walker *pWalker, Select *pSelect){
+  struct RefSrcList *p = pWalker->u.pRefSrcList;
+  SrcList *pSrc = pSelect->pSrc;
+  i64 i, j;
+  int *piNew;
+  if( pSrc->nSrc==0 ) return WRC_Continue;
+  j = p->nExclude;
+  p->nExclude += pSrc->nSrc;
+  piNew = sqlite3DbRealloc(p->db, p->aiExclude, p->nExclude*sizeof(int));
+  if( piNew==0 ){
+    p->nExclude = 0;
+    return WRC_Abort;
+  }else{
+    p->aiExclude = piNew;
+  }
+  for(i=0; i<pSrc->nSrc; i++, j++){
+     p->aiExclude[j] = pSrc->a[i].iCursor;
+  }
+  return WRC_Continue;
+}
+static void selectRefLeave(Walker *pWalker, Select *pSelect){
+  struct RefSrcList *p = pWalker->u.pRefSrcList;
+  SrcList *pSrc = pSelect->pSrc;
+  if( p->nExclude ){
+    assert( p->nExclude>=pSrc->nSrc );
+    p->nExclude -= pSrc->nSrc;
+  }
+}
+
+/* This is the Walker EXPR callback for sqlite3ReferencesSrcList().
+**
+** Set the 0x01 bit of pWalker->eCode if there is a reference to any
+** of the tables shown in RefSrcList.pRef.
+**
+** Set the 0x02 bit of pWalker->eCode if there is a reference to a
+** table is in neither RefSrcList.pRef nor RefSrcList.aiExclude.
+*/
+static int exprRefToSrcList(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_COLUMN
+   || pExpr->op==TK_AGG_COLUMN
+  ){
+    int i;
+    struct RefSrcList *p = pWalker->u.pRefSrcList;
+    SrcList *pSrc = p->pRef;
+    int nSrc = pSrc ? pSrc->nSrc : 0;
+    for(i=0; i<nSrc; i++){
+      if( pExpr->iTable==pSrc->a[i].iCursor ){
+        pWalker->eCode |= 1;
+        return WRC_Continue;
+      }
+    }
+    for(i=0; i<p->nExclude && p->aiExclude[i]!=pExpr->iTable; i++){}
+    if( i>=p->nExclude ){
+      pWalker->eCode |= 2;
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Check to see if pExpr references any tables in pSrcList.
+** Possible return values:
+**
+**    1         pExpr does references a table in pSrcList.
+**
+**    0         pExpr references some table that is not defined in either
+**              pSrcList or in subqueries of pExpr itself.
+**
+**   -1         pExpr only references no tables at all, or it only
+**              references tables defined in subqueries of pExpr itself.
+**
+** As currently used, pExpr is always an aggregate function call.  That
+** fact is exploited for efficiency.
+*/
+int sqlite3ReferencesSrcList(Parse *pParse, Expr *pExpr, SrcList *pSrcList){
+  Walker w;
+  struct RefSrcList x;
+  assert( pParse->db!=0 );
+  memset(&w, 0, sizeof(w));
+  memset(&x, 0, sizeof(x));
+  w.xExprCallback = exprRefToSrcList;
+  w.xSelectCallback = selectRefEnter;
+  w.xSelectCallback2 = selectRefLeave;
+  w.u.pRefSrcList = &x;
+  x.db = pParse->db;
+  x.pRef = pSrcList;
+  assert( pExpr->op==TK_AGG_FUNCTION );
+  assert( ExprUseXList(pExpr) );
+  sqlite3WalkExprList(&w, pExpr->x.pList);
+  if( pExpr->pLeft ){
+    assert( pExpr->pLeft->op==TK_ORDER );
+    assert( ExprUseXList(pExpr->pLeft) );
+    assert( pExpr->pLeft->x.pList!=0 );
+    sqlite3WalkExprList(&w, pExpr->pLeft->x.pList);
+  }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( ExprHasProperty(pExpr, EP_WinFunc) ){
+    sqlite3WalkExpr(&w, pExpr->y.pWin->pFilter);
+  }
+#endif
+  if( x.aiExclude ) sqlite3DbNNFreeNN(pParse->db, x.aiExclude);
+  if( w.eCode & 0x01 ){
+    return 1;
+  }else if( w.eCode ){
+    return 0;
+  }else{
+    return -1;
+  }
+}
+
+/*
+** This is a Walker expression node callback.
+**
+** For Expr nodes that contain pAggInfo pointers, make sure the AggInfo
+** object that is referenced does not refer directly to the Expr.  If
+** it does, make a copy.  This is done because the pExpr argument is
+** subject to change.
+**
+** The copy is scheduled for deletion using the sqlite3ExprDeferredDelete()
+** which builds on the sqlite3ParserAddCleanup() mechanism.
+*/
+static int agginfoPersistExprCb(Walker *pWalker, Expr *pExpr){
+  if( ALWAYS(!ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced))
+   && pExpr->pAggInfo!=0
+  ){
+    AggInfo *pAggInfo = pExpr->pAggInfo;
+    int iAgg = pExpr->iAgg;
+    Parse *pParse = pWalker->pParse;
+    sqlite3 *db = pParse->db;
+    assert( iAgg>=0 );
+    if( pExpr->op!=TK_AGG_FUNCTION ){
+      if( iAgg<pAggInfo->nColumn
+       && pAggInfo->aCol[iAgg].pCExpr==pExpr
+      ){
+        pExpr = sqlite3ExprDup(db, pExpr, 0);
+        if( pExpr ){
+          pAggInfo->aCol[iAgg].pCExpr = pExpr;
+          sqlite3ExprDeferredDelete(pParse, pExpr);
+        }
+      }
+    }else{
+      assert( pExpr->op==TK_AGG_FUNCTION );
+      if( ALWAYS(iAgg<pAggInfo->nFunc)
+       && pAggInfo->aFunc[iAgg].pFExpr==pExpr
+      ){
+        pExpr = sqlite3ExprDup(db, pExpr, 0);
+        if( pExpr ){
+          pAggInfo->aFunc[iAgg].pFExpr = pExpr;
+          sqlite3ExprDeferredDelete(pParse, pExpr);
+        }
+      }
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Initialize a Walker object so that will persist AggInfo entries referenced
+** by the tree that is walked.
+*/
+void sqlite3AggInfoPersistWalkerInit(Walker *pWalker, Parse *pParse){
+  memset(pWalker, 0, sizeof(*pWalker));
+  pWalker->pParse = pParse;
+  pWalker->xExprCallback = agginfoPersistExprCb;
+  pWalker->xSelectCallback = sqlite3SelectWalkNoop;
+}
+
+/*
+** Add a new element to the pAggInfo->aCol[] array.  Return the index of
+** the new element.  Return a negative number if malloc fails.
+*/
+static int addAggInfoColumn(sqlite3 *db, AggInfo *pInfo){
+  int i;
+  pInfo->aCol = sqlite3ArrayAllocate(
+       db,
+       pInfo->aCol,
+       sizeof(pInfo->aCol[0]),
+       &pInfo->nColumn,
+       &i
+  );
+  return i;
+}   
+
+/*
+** Add a new element to the pAggInfo->aFunc[] array.  Return the index of
+** the new element.  Return a negative number if malloc fails.
+*/
+static int addAggInfoFunc(sqlite3 *db, AggInfo *pInfo){
+  int i;
+  pInfo->aFunc = sqlite3ArrayAllocate(
+       db,
+       pInfo->aFunc,
+       sizeof(pInfo->aFunc[0]),
+       &pInfo->nFunc,
+       &i
+  );
+  return i;
+}
+
+/*
+** Search the AggInfo object for an aCol[] entry that has iTable and iColumn.
+** Return the index in aCol[] of the entry that describes that column.
+**
+** If no prior entry is found, create a new one and return -1.  The
+** new column will have an index of pAggInfo->nColumn-1.
+*/
+static void findOrCreateAggInfoColumn(
+  Parse *pParse,       /* Parsing context */
+  AggInfo *pAggInfo,   /* The AggInfo object to search and/or modify */
+  Expr *pExpr          /* Expr describing the column to find or insert */
+){
+  struct AggInfo_col *pCol;
+  int k;
+
+  assert( pAggInfo->iFirstReg==0 );
+  pCol = pAggInfo->aCol;
+  for(k=0; k<pAggInfo->nColumn; k++, pCol++){
+    if( pCol->pCExpr==pExpr ) return;
+    if( pCol->iTable==pExpr->iTable
+     && pCol->iColumn==pExpr->iColumn
+     && pExpr->op!=TK_IF_NULL_ROW
+    ){
+      goto fix_up_expr;
+    }
+  }
+  k = addAggInfoColumn(pParse->db, pAggInfo);
+  if( k<0 ){
+    /* OOM on resize */
+    assert( pParse->db->mallocFailed );
+    return;
+  }
+  pCol = &pAggInfo->aCol[k];
+  assert( ExprUseYTab(pExpr) );
+  pCol->pTab = pExpr->y.pTab;
+  pCol->iTable = pExpr->iTable;
+  pCol->iColumn = pExpr->iColumn;
+  pCol->iSorterColumn = -1;
+  pCol->pCExpr = pExpr;
+  if( pAggInfo->pGroupBy && pExpr->op!=TK_IF_NULL_ROW ){
+    int j, n;
+    ExprList *pGB = pAggInfo->pGroupBy;
+    struct ExprList_item *pTerm = pGB->a;
+    n = pGB->nExpr;
+    for(j=0; j<n; j++, pTerm++){
+      Expr *pE = pTerm->pExpr;
+      if( pE->op==TK_COLUMN
+       && pE->iTable==pExpr->iTable
+       && pE->iColumn==pExpr->iColumn
+      ){
+        pCol->iSorterColumn = j;
+        break;
+      }
+    }
+  }
+  if( pCol->iSorterColumn<0 ){
+    pCol->iSorterColumn = pAggInfo->nSortingColumn++;
+  }
+fix_up_expr:
+  ExprSetVVAProperty(pExpr, EP_NoReduce);
+  assert( pExpr->pAggInfo==0 || pExpr->pAggInfo==pAggInfo );
+  pExpr->pAggInfo = pAggInfo;
+  if( pExpr->op==TK_COLUMN ){
+    pExpr->op = TK_AGG_COLUMN;
+  }
+  pExpr->iAgg = (i16)k;
+}
+
+/*
+** This is the xExprCallback for a tree walker.  It is used to
+** implement sqlite3ExprAnalyzeAggregates().  See sqlite3ExprAnalyzeAggregates
+** for additional information.
+*/
+static int analyzeAggregate(Walker *pWalker, Expr *pExpr){
+  int i;
+  NameContext *pNC = pWalker->u.pNC;
+  Parse *pParse = pNC->pParse;
+  SrcList *pSrcList = pNC->pSrcList;
+  AggInfo *pAggInfo = pNC->uNC.pAggInfo;
+
+  assert( pNC->ncFlags & NC_UAggInfo );
+  assert( pAggInfo->iFirstReg==0 );
+  switch( pExpr->op ){
+    default: {
+      IndexedExpr *pIEpr;
+      Expr tmp;
+      assert( pParse->iSelfTab==0 );
+      if( (pNC->ncFlags & NC_InAggFunc)==0 ) break;
+      if( pParse->pIdxEpr==0 ) break;
+      for(pIEpr=pParse->pIdxEpr; pIEpr; pIEpr=pIEpr->pIENext){
+        int iDataCur = pIEpr->iDataCur;
+        if( iDataCur<0 ) continue;
+        if( sqlite3ExprCompare(0, pExpr, pIEpr->pExpr, iDataCur)==0 ) break;
+      }
+      if( pIEpr==0 ) break;
+      if( NEVER(!ExprUseYTab(pExpr)) ) break;
+      for(i=0; i<pSrcList->nSrc; i++){
+         if( pSrcList->a[0].iCursor==pIEpr->iDataCur ) break;
+      }
+      if( i>=pSrcList->nSrc ) break;
+      if( NEVER(pExpr->pAggInfo!=0) ) break; /* Resolved by outer context */
+      if( pParse->nErr ){ return WRC_Abort; }
+
+      /* If we reach this point, it means that expression pExpr can be
+      ** translated into a reference to an index column as described by
+      ** pIEpr.
+      */
+      memset(&tmp, 0, sizeof(tmp));
+      tmp.op = TK_AGG_COLUMN;
+      tmp.iTable = pIEpr->iIdxCur;
+      tmp.iColumn = pIEpr->iIdxCol;
+      findOrCreateAggInfoColumn(pParse, pAggInfo, &tmp);
+      if( pParse->nErr ){ return WRC_Abort; }
+      assert( pAggInfo->aCol!=0 );
+      assert( tmp.iAgg<pAggInfo->nColumn );
+      pAggInfo->aCol[tmp.iAgg].pCExpr = pExpr;
+      pExpr->pAggInfo = pAggInfo;
+      pExpr->iAgg = tmp.iAgg;
+      return WRC_Prune;
+    }
+    case TK_IF_NULL_ROW:
+    case TK_AGG_COLUMN:
+    case TK_COLUMN: {
+      testcase( pExpr->op==TK_AGG_COLUMN );
+      testcase( pExpr->op==TK_COLUMN );
+      testcase( pExpr->op==TK_IF_NULL_ROW );
+      /* Check to see if the column is in one of the tables in the FROM
+      ** clause of the aggregate query */
+      if( ALWAYS(pSrcList!=0) ){
+        SrcItem *pItem = pSrcList->a;
+        for(i=0; i<pSrcList->nSrc; i++, pItem++){
+          assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
+          if( pExpr->iTable==pItem->iCursor ){
+            findOrCreateAggInfoColumn(pParse, pAggInfo, pExpr);
+            break;
+          } /* endif pExpr->iTable==pItem->iCursor */
+        } /* end loop over pSrcList */
+      }
+      return WRC_Continue;
+    }
+    case TK_AGG_FUNCTION: {
+      if( (pNC->ncFlags & NC_InAggFunc)==0
+       && pWalker->walkerDepth==pExpr->op2
+       && pExpr->pAggInfo==0
+      ){
+        /* Check to see if pExpr is a duplicate of another aggregate
+        ** function that is already in the pAggInfo structure
+        */
+        struct AggInfo_func *pItem = pAggInfo->aFunc;
+        for(i=0; i<pAggInfo->nFunc; i++, pItem++){
+          if( NEVER(pItem->pFExpr==pExpr) ) break;
+          if( sqlite3ExprCompare(0, pItem->pFExpr, pExpr, -1)==0 ){
+            break;
+          }
+        }
+        if( i>=pAggInfo->nFunc ){
+          /* pExpr is original.  Make a new entry in pAggInfo->aFunc[]
+          */
+          u8 enc = ENC(pParse->db);
+          i = addAggInfoFunc(pParse->db, pAggInfo);
+          if( i>=0 ){
+            int nArg;
+            assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
+            pItem = &pAggInfo->aFunc[i];
+            pItem->pFExpr = pExpr;
+            assert( ExprUseUToken(pExpr) );
+            nArg = pExpr->x.pList ? pExpr->x.pList->nExpr : 0;
+            pItem->pFunc = sqlite3FindFunction(pParse->db,
+                                         pExpr->u.zToken, nArg, enc, 0);
+            assert( pItem->bOBUnique==0 );
+            if( pExpr->pLeft
+             && (pItem->pFunc->funcFlags & SQLITE_FUNC_NEEDCOLL)==0
+            ){
+              /* The NEEDCOLL test above causes any ORDER BY clause on
+              ** aggregate min() or max() to be ignored. */
+              ExprList *pOBList;
+              assert( nArg>0 );
+              assert( pExpr->pLeft->op==TK_ORDER );
+              assert( ExprUseXList(pExpr->pLeft) );
+              pItem->iOBTab = pParse->nTab++;
+              pOBList = pExpr->pLeft->x.pList;
+              assert( pOBList->nExpr>0 );
+              assert( pItem->bOBUnique==0 );
+              if( pOBList->nExpr==1
+               && nArg==1
+               && sqlite3ExprCompare(0,pOBList->a[0].pExpr,
+                               pExpr->x.pList->a[0].pExpr,0)==0
+              ){
+                pItem->bOBPayload = 0;
+                pItem->bOBUnique = ExprHasProperty(pExpr, EP_Distinct);
+              }else{
+                pItem->bOBPayload = 1;
+              }
+              pItem->bUseSubtype =
+                    (pItem->pFunc->funcFlags & SQLITE_SUBTYPE)!=0;
+            }else{
+              pItem->iOBTab = -1;
+            }
+            if( ExprHasProperty(pExpr, EP_Distinct) && !pItem->bOBUnique ){
+              pItem->iDistinct = pParse->nTab++;
+            }else{
+              pItem->iDistinct = -1;
+            }
+          }
+        }
+        /* Make pExpr point to the appropriate pAggInfo->aFunc[] entry
+        */
+        assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
+        ExprSetVVAProperty(pExpr, EP_NoReduce);
+        pExpr->iAgg = (i16)i;
+        pExpr->pAggInfo = pAggInfo;
+        return WRC_Prune;
+      }else{
+        return WRC_Continue;
+      }
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Analyze the pExpr expression looking for aggregate functions and
+** for variables that need to be added to AggInfo object that pNC->pAggInfo
+** points to.  Additional entries are made on the AggInfo object as
+** necessary.
+**
+** This routine should only be called after the expression has been
+** analyzed by sqlite3ResolveExprNames().
+*/
+void sqlite3ExprAnalyzeAggregates(NameContext *pNC, Expr *pExpr){
+  Walker w;
+  w.xExprCallback = analyzeAggregate;
+  w.xSelectCallback = sqlite3WalkerDepthIncrease;
+  w.xSelectCallback2 = sqlite3WalkerDepthDecrease;
+  w.walkerDepth = 0;
+  w.u.pNC = pNC;
+  w.pParse = 0;
+  assert( pNC->pSrcList!=0 );
+  sqlite3WalkExpr(&w, pExpr);
+}
+
+/*
+** Call sqlite3ExprAnalyzeAggregates() for every expression in an
+** expression list.  Return the number of errors.
+**
+** If an error is found, the analysis is cut short.
+*/
+void sqlite3ExprAnalyzeAggList(NameContext *pNC, ExprList *pList){
+  struct ExprList_item *pItem;
+  int i;
+  if( pList ){
+    for(pItem=pList->a, i=0; i<pList->nExpr; i++, pItem++){
+      sqlite3ExprAnalyzeAggregates(pNC, pItem->pExpr);
+    }
+  }
+}
+
+/*
+** Allocate a single new register for use to hold some intermediate result.
+*/
+int sqlite3GetTempReg(Parse *pParse){
+  if( pParse->nTempReg==0 ){
+    return ++pParse->nMem;
+  }
+  return pParse->aTempReg[--pParse->nTempReg];
+}
+
+/*
+** Deallocate a register, making available for reuse for some other
+** purpose.
+*/
+void sqlite3ReleaseTempReg(Parse *pParse, int iReg){
+  if( iReg ){
+    sqlite3VdbeReleaseRegisters(pParse, iReg, 1, 0, 0);
+    if( pParse->nTempReg<ArraySize(pParse->aTempReg) ){
+      pParse->aTempReg[pParse->nTempReg++] = iReg;
+    }
+  }
+}
+
+/*
+** Allocate or deallocate a block of nReg consecutive registers.
+*/
+int sqlite3GetTempRange(Parse *pParse, int nReg){
+  int i, n;
+  if( nReg==1 ) return sqlite3GetTempReg(pParse);
+  i = pParse->iRangeReg;
+  n = pParse->nRangeReg;
+  if( nReg<=n ){
+    pParse->iRangeReg += nReg;
+    pParse->nRangeReg -= nReg;
+  }else{
+    i = pParse->nMem+1;
+    pParse->nMem += nReg;
+  }
+  return i;
+}
+void sqlite3ReleaseTempRange(Parse *pParse, int iReg, int nReg){
+  if( nReg==1 ){
+    sqlite3ReleaseTempReg(pParse, iReg);
+    return;
+  }
+  sqlite3VdbeReleaseRegisters(pParse, iReg, nReg, 0, 0);
+  if( nReg>pParse->nRangeReg ){
+    pParse->nRangeReg = nReg;
+    pParse->iRangeReg = iReg;
+  }
+}
+
+/*
+** Mark all temporary registers as being unavailable for reuse.
+**
+** Always invoke this procedure after coding a subroutine or co-routine
+** that might be invoked from other parts of the code, to ensure that
+** the sub/co-routine does not use registers in common with the code that
+** invokes the sub/co-routine.
+*/
+void sqlite3ClearTempRegCache(Parse *pParse){
+  pParse->nTempReg = 0;
+  pParse->nRangeReg = 0;
+}
+
+/*
+** Make sure sufficient registers have been allocated so that
+** iReg is a valid register number.
+*/
+void sqlite3TouchRegister(Parse *pParse, int iReg){
+  if( pParse->nMem<iReg ) pParse->nMem = iReg;
+}
+
+#if defined(SQLITE_ENABLE_STAT4) || defined(SQLITE_DEBUG)
+/*
+** Return the latest reusable register in the set of all registers.
+** The value returned is no less than iMin.  If any register iMin or
+** greater is in permanent use, then return one more than that last
+** permanent register.
+*/
+int sqlite3FirstAvailableRegister(Parse *pParse, int iMin){
+  const ExprList *pList = pParse->pConstExpr;
+  if( pList ){
+    int i;
+    for(i=0; i<pList->nExpr; i++){
+      if( pList->a[i].u.iConstExprReg>=iMin ){
+        iMin = pList->a[i].u.iConstExprReg + 1;
+      }
+    }
+  }
+  pParse->nTempReg = 0;
+  pParse->nRangeReg = 0;
+  return iMin;
+}
+#endif /* SQLITE_ENABLE_STAT4 || SQLITE_DEBUG */
+
+/*
+** Validate that no temporary register falls within the range of
+** iFirst..iLast, inclusive.  This routine is only call from within assert()
+** statements.
+*/
+#ifdef SQLITE_DEBUG
+int sqlite3NoTempsInRange(Parse *pParse, int iFirst, int iLast){
+  int i;
+  if( pParse->nRangeReg>0
+   && pParse->iRangeReg+pParse->nRangeReg > iFirst
+   && pParse->iRangeReg <= iLast
+  ){
+     return 0;
+  }
+  for(i=0; i<pParse->nTempReg; i++){
+    if( pParse->aTempReg[i]>=iFirst && pParse->aTempReg[i]<=iLast ){
+      return 0;
+    }
+  }
+  if( pParse->pConstExpr ){
+    ExprList *pList = pParse->pConstExpr;
+    for(i=0; i<pList->nExpr; i++){
+      int iReg = pList->a[i].u.iConstExprReg;
+      if( iReg==0 ) continue;
+      if( iReg>=iFirst && iReg<=iLast ) return 0;
+    }
+  }
+  return 1;
+}
+#endif /* SQLITE_DEBUG */
diff --git a/src/fault.c b/src/fault.c
new file mode 100644
index 0000000..5b41b60
--- /dev/null
+++ b/src/fault.c
@@ -0,0 +1,87 @@
+/*
+** 2008 Jan 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code to support the concept of "benign" 
+** malloc failures (when the xMalloc() or xRealloc() method of the
+** sqlite3_mem_methods structure fails to allocate a block of memory
+** and returns 0). 
+**
+** Most malloc failures are non-benign. After they occur, SQLite
+** abandons the current operation and returns an error code (usually
+** SQLITE_NOMEM) to the user. However, sometimes a fault is not necessarily
+** fatal. For example, if a malloc fails while resizing a hash table, this 
+** is completely recoverable simply by not carrying out the resize. The 
+** hash table will continue to function normally.  So a malloc failure 
+** during a hash table resize is a benign fault.
+*/
+
+#include "sqliteInt.h"
+
+#ifndef SQLITE_UNTESTABLE
+
+/*
+** Global variables.
+*/
+typedef struct BenignMallocHooks BenignMallocHooks;
+static SQLITE_WSD struct BenignMallocHooks {
+  void (*xBenignBegin)(void);
+  void (*xBenignEnd)(void);
+} sqlite3Hooks = { 0, 0 };
+
+/* The "wsdHooks" macro will resolve to the appropriate BenignMallocHooks
+** structure.  If writable static data is unsupported on the target,
+** we have to locate the state vector at run-time.  In the more common
+** case where writable static data is supported, wsdHooks can refer directly
+** to the "sqlite3Hooks" state vector declared above.
+*/
+#ifdef SQLITE_OMIT_WSD
+# define wsdHooksInit \
+  BenignMallocHooks *x = &GLOBAL(BenignMallocHooks,sqlite3Hooks)
+# define wsdHooks x[0]
+#else
+# define wsdHooksInit
+# define wsdHooks sqlite3Hooks
+#endif
+
+
+/*
+** Register hooks to call when sqlite3BeginBenignMalloc() and
+** sqlite3EndBenignMalloc() are called, respectively.
+*/
+void sqlite3BenignMallocHooks(
+  void (*xBenignBegin)(void),
+  void (*xBenignEnd)(void)
+){
+  wsdHooksInit;
+  wsdHooks.xBenignBegin = xBenignBegin;
+  wsdHooks.xBenignEnd = xBenignEnd;
+}
+
+/*
+** This (sqlite3EndBenignMalloc()) is called by SQLite code to indicate that
+** subsequent malloc failures are benign. A call to sqlite3EndBenignMalloc()
+** indicates that subsequent malloc failures are non-benign.
+*/
+void sqlite3BeginBenignMalloc(void){
+  wsdHooksInit;
+  if( wsdHooks.xBenignBegin ){
+    wsdHooks.xBenignBegin();
+  }
+}
+void sqlite3EndBenignMalloc(void){
+  wsdHooksInit;
+  if( wsdHooks.xBenignEnd ){
+    wsdHooks.xBenignEnd();
+  }
+}
+
+#endif   /* #ifndef SQLITE_UNTESTABLE */
diff --git a/src/fkey.c b/src/fkey.c
new file mode 100644
index 0000000..bace1ae
--- /dev/null
+++ b/src/fkey.c
@@ -0,0 +1,1482 @@
+/*
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used by the compiler to add foreign key
+** support to compiled SQL statements.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+#ifndef SQLITE_OMIT_TRIGGER
+
+/*
+** Deferred and Immediate FKs
+** --------------------------
+**
+** Foreign keys in SQLite come in two flavours: deferred and immediate.
+** If an immediate foreign key constraint is violated,
+** SQLITE_CONSTRAINT_FOREIGNKEY is returned and the current
+** statement transaction rolled back. If a 
+** deferred foreign key constraint is violated, no action is taken 
+** immediately. However if the application attempts to commit the 
+** transaction before fixing the constraint violation, the attempt fails.
+**
+** Deferred constraints are implemented using a simple counter associated
+** with the database handle. The counter is set to zero each time a 
+** database transaction is opened. Each time a statement is executed 
+** that causes a foreign key violation, the counter is incremented. Each
+** time a statement is executed that removes an existing violation from
+** the database, the counter is decremented. When the transaction is
+** committed, the commit fails if the current value of the counter is
+** greater than zero. This scheme has two big drawbacks:
+**
+**   * When a commit fails due to a deferred foreign key constraint, 
+**     there is no way to tell which foreign constraint is not satisfied,
+**     or which row it is not satisfied for.
+**
+**   * If the database contains foreign key violations when the 
+**     transaction is opened, this may cause the mechanism to malfunction.
+**
+** Despite these problems, this approach is adopted as it seems simpler
+** than the alternatives.
+**
+** INSERT operations:
+**
+**   I.1) For each FK for which the table is the child table, search
+**        the parent table for a match. If none is found increment the
+**        constraint counter.
+**
+**   I.2) For each FK for which the table is the parent table, 
+**        search the child table for rows that correspond to the new
+**        row in the parent table. Decrement the counter for each row
+**        found (as the constraint is now satisfied).
+**
+** DELETE operations:
+**
+**   D.1) For each FK for which the table is the child table, 
+**        search the parent table for a row that corresponds to the 
+**        deleted row in the child table. If such a row is not found, 
+**        decrement the counter.
+**
+**   D.2) For each FK for which the table is the parent table, search 
+**        the child table for rows that correspond to the deleted row 
+**        in the parent table. For each found increment the counter.
+**
+** UPDATE operations:
+**
+**   An UPDATE command requires that all 4 steps above are taken, but only
+**   for FK constraints for which the affected columns are actually 
+**   modified (values must be compared at runtime).
+**
+** Note that I.1 and D.1 are very similar operations, as are I.2 and D.2.
+** This simplifies the implementation a bit.
+**
+** For the purposes of immediate FK constraints, the OR REPLACE conflict
+** resolution is considered to delete rows before the new row is inserted.
+** If a delete caused by OR REPLACE violates an FK constraint, an exception
+** is thrown, even if the FK constraint would be satisfied after the new 
+** row is inserted.
+**
+** Immediate constraints are usually handled similarly. The only difference 
+** is that the counter used is stored as part of each individual statement
+** object (struct Vdbe). If, after the statement has run, its immediate
+** constraint counter is greater than zero,
+** it returns SQLITE_CONSTRAINT_FOREIGNKEY
+** and the statement transaction is rolled back. An exception is an INSERT
+** statement that inserts a single row only (no triggers). In this case,
+** instead of using a counter, an exception is thrown immediately if the
+** INSERT violates a foreign key constraint. This is necessary as such
+** an INSERT does not open a statement transaction.
+**
+** TODO: How should dropping a table be handled? How should renaming a 
+** table be handled?
+**
+**
+** Query API Notes
+** ---------------
+**
+** Before coding an UPDATE or DELETE row operation, the code-generator
+** for those two operations needs to know whether or not the operation
+** requires any FK processing and, if so, which columns of the original
+** row are required by the FK processing VDBE code (i.e. if FKs were
+** implemented using triggers, which of the old.* columns would be 
+** accessed). No information is required by the code-generator before
+** coding an INSERT operation. The functions used by the UPDATE/DELETE
+** generation code to query for this information are:
+**
+**   sqlite3FkRequired() - Test to see if FK processing is required.
+**   sqlite3FkOldmask()  - Query for the set of required old.* columns.
+**
+**
+** Externally accessible module functions
+** --------------------------------------
+**
+**   sqlite3FkCheck()    - Check for foreign key violations.
+**   sqlite3FkActions()  - Code triggers for ON UPDATE/ON DELETE actions.
+**   sqlite3FkDelete()   - Delete an FKey structure.
+*/
+
+/*
+** VDBE Calling Convention
+** -----------------------
+**
+** Example:
+**
+**   For the following INSERT statement:
+**
+**     CREATE TABLE t1(a, b INTEGER PRIMARY KEY, c);
+**     INSERT INTO t1 VALUES(1, 2, 3.1);
+**
+**   Register (x):        2    (type integer)
+**   Register (x+1):      1    (type integer)
+**   Register (x+2):      NULL (type NULL)
+**   Register (x+3):      3.1  (type real)
+*/
+
+/*
+** A foreign key constraint requires that the key columns in the parent
+** table are collectively subject to a UNIQUE or PRIMARY KEY constraint.
+** Given that pParent is the parent table for foreign key constraint pFKey, 
+** search the schema for a unique index on the parent key columns. 
+**
+** If successful, zero is returned. If the parent key is an INTEGER PRIMARY 
+** KEY column, then output variable *ppIdx is set to NULL. Otherwise, *ppIdx 
+** is set to point to the unique index. 
+** 
+** If the parent key consists of a single column (the foreign key constraint
+** is not a composite foreign key), output variable *paiCol is set to NULL.
+** Otherwise, it is set to point to an allocated array of size N, where
+** N is the number of columns in the parent key. The first element of the
+** array is the index of the child table column that is mapped by the FK
+** constraint to the parent table column stored in the left-most column
+** of index *ppIdx. The second element of the array is the index of the
+** child table column that corresponds to the second left-most column of
+** *ppIdx, and so on.
+**
+** If the required index cannot be found, either because:
+**
+**   1) The named parent key columns do not exist, or
+**
+**   2) The named parent key columns do exist, but are not subject to a
+**      UNIQUE or PRIMARY KEY constraint, or
+**
+**   3) No parent key columns were provided explicitly as part of the
+**      foreign key definition, and the parent table does not have a
+**      PRIMARY KEY, or
+**
+**   4) No parent key columns were provided explicitly as part of the
+**      foreign key definition, and the PRIMARY KEY of the parent table 
+**      consists of a different number of columns to the child key in 
+**      the child table.
+**
+** then non-zero is returned, and a "foreign key mismatch" error loaded
+** into pParse. If an OOM error occurs, non-zero is returned and the
+** pParse->db->mallocFailed flag is set.
+*/
+int sqlite3FkLocateIndex(
+  Parse *pParse,                  /* Parse context to store any error in */
+  Table *pParent,                 /* Parent table of FK constraint pFKey */
+  FKey *pFKey,                    /* Foreign key to find index for */
+  Index **ppIdx,                  /* OUT: Unique index on parent table */
+  int **paiCol                    /* OUT: Map of index columns in pFKey */
+){
+  Index *pIdx = 0;                    /* Value to return via *ppIdx */
+  int *aiCol = 0;                     /* Value to return via *paiCol */
+  int nCol = pFKey->nCol;             /* Number of columns in parent key */
+  char *zKey = pFKey->aCol[0].zCol;   /* Name of left-most parent key column */
+
+  /* The caller is responsible for zeroing output parameters. */
+  assert( ppIdx && *ppIdx==0 );
+  assert( !paiCol || *paiCol==0 );
+  assert( pParse );
+
+  /* If this is a non-composite (single column) foreign key, check if it 
+  ** maps to the INTEGER PRIMARY KEY of table pParent. If so, leave *ppIdx 
+  ** and *paiCol set to zero and return early. 
+  **
+  ** Otherwise, for a composite foreign key (more than one column), allocate
+  ** space for the aiCol array (returned via output parameter *paiCol).
+  ** Non-composite foreign keys do not require the aiCol array.
+  */
+  if( nCol==1 ){
+    /* The FK maps to the IPK if any of the following are true:
+    **
+    **   1) There is an INTEGER PRIMARY KEY column and the FK is implicitly 
+    **      mapped to the primary key of table pParent, or
+    **   2) The FK is explicitly mapped to a column declared as INTEGER
+    **      PRIMARY KEY.
+    */
+    if( pParent->iPKey>=0 ){
+      if( !zKey ) return 0;
+      if( !sqlite3StrICmp(pParent->aCol[pParent->iPKey].zCnName, zKey) ){
+        return 0;
+      }
+    }
+  }else if( paiCol ){
+    assert( nCol>1 );
+    aiCol = (int *)sqlite3DbMallocRawNN(pParse->db, nCol*sizeof(int));
+    if( !aiCol ) return 1;
+    *paiCol = aiCol;
+  }
+
+  for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){
+    if( pIdx->nKeyCol==nCol && IsUniqueIndex(pIdx) && pIdx->pPartIdxWhere==0 ){ 
+      /* pIdx is a UNIQUE index (or a PRIMARY KEY) and has the right number
+      ** of columns. If each indexed column corresponds to a foreign key
+      ** column of pFKey, then this index is a winner.  */
+
+      if( zKey==0 ){
+        /* If zKey is NULL, then this foreign key is implicitly mapped to 
+        ** the PRIMARY KEY of table pParent. The PRIMARY KEY index may be 
+        ** identified by the test.  */
+        if( IsPrimaryKeyIndex(pIdx) ){
+          if( aiCol ){
+            int i;
+            for(i=0; i<nCol; i++) aiCol[i] = pFKey->aCol[i].iFrom;
+          }
+          break;
+        }
+      }else{
+        /* If zKey is non-NULL, then this foreign key was declared to
+        ** map to an explicit list of columns in table pParent. Check if this
+        ** index matches those columns. Also, check that the index uses
+        ** the default collation sequences for each column. */
+        int i, j;
+        for(i=0; i<nCol; i++){
+          i16 iCol = pIdx->aiColumn[i];     /* Index of column in parent tbl */
+          const char *zDfltColl;            /* Def. collation for column */
+          char *zIdxCol;                    /* Name of indexed column */
+
+          if( iCol<0 ) break; /* No foreign keys against expression indexes */
+
+          /* If the index uses a collation sequence that is different from
+          ** the default collation sequence for the column, this index is
+          ** unusable. Bail out early in this case.  */
+          zDfltColl = sqlite3ColumnColl(&pParent->aCol[iCol]);
+          if( !zDfltColl ) zDfltColl = sqlite3StrBINARY;
+          if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break;
+
+          zIdxCol = pParent->aCol[iCol].zCnName;
+          for(j=0; j<nCol; j++){
+            if( sqlite3StrICmp(pFKey->aCol[j].zCol, zIdxCol)==0 ){
+              if( aiCol ) aiCol[i] = pFKey->aCol[j].iFrom;
+              break;
+            }
+          }
+          if( j==nCol ) break;
+        }
+        if( i==nCol ) break;      /* pIdx is usable */
+      }
+    }
+  }
+
+  if( !pIdx ){
+    if( !pParse->disableTriggers ){
+      sqlite3ErrorMsg(pParse,
+           "foreign key mismatch - \"%w\" referencing \"%w\"",
+           pFKey->pFrom->zName, pFKey->zTo);
+    }
+    sqlite3DbFree(pParse->db, aiCol);
+    return 1;
+  }
+
+  *ppIdx = pIdx;
+  return 0;
+}
+
+/*
+** This function is called when a row is inserted into or deleted from the 
+** child table of foreign key constraint pFKey. If an SQL UPDATE is executed 
+** on the child table of pFKey, this function is invoked twice for each row
+** affected - once to "delete" the old row, and then again to "insert" the
+** new row.
+**
+** Each time it is called, this function generates VDBE code to locate the
+** row in the parent table that corresponds to the row being inserted into 
+** or deleted from the child table. If the parent row can be found, no 
+** special action is taken. Otherwise, if the parent row can *not* be
+** found in the parent table:
+**
+**   Operation | FK type   | Action taken
+**   --------------------------------------------------------------------------
+**   INSERT      immediate   Increment the "immediate constraint counter".
+**
+**   DELETE      immediate   Decrement the "immediate constraint counter".
+**
+**   INSERT      deferred    Increment the "deferred constraint counter".
+**
+**   DELETE      deferred    Decrement the "deferred constraint counter".
+**
+** These operations are identified in the comment at the top of this file 
+** (fkey.c) as "I.1" and "D.1".
+*/
+static void fkLookupParent(
+  Parse *pParse,        /* Parse context */
+  int iDb,              /* Index of database housing pTab */
+  Table *pTab,          /* Parent table of FK pFKey */
+  Index *pIdx,          /* Unique index on parent key columns in pTab */
+  FKey *pFKey,          /* Foreign key constraint */
+  int *aiCol,           /* Map from parent key columns to child table columns */
+  int regData,          /* Address of array containing child table row */
+  int nIncr,            /* Increment constraint counter by this */
+  int isIgnore          /* If true, pretend pTab contains all NULL values */
+){
+  int i;                                    /* Iterator variable */
+  Vdbe *v = sqlite3GetVdbe(pParse);         /* Vdbe to add code to */
+  int iCur = pParse->nTab - 1;              /* Cursor number to use */
+  int iOk = sqlite3VdbeMakeLabel(pParse);   /* jump here if parent key found */
+
+  sqlite3VdbeVerifyAbortable(v,
+    (!pFKey->isDeferred
+      && !(pParse->db->flags & SQLITE_DeferFKs)
+      && !pParse->pToplevel 
+      && !pParse->isMultiWrite) ? OE_Abort : OE_Ignore);
+
+  /* If nIncr is less than zero, then check at runtime if there are any
+  ** outstanding constraints to resolve. If there are not, there is no need
+  ** to check if deleting this row resolves any outstanding violations.
+  **
+  ** Check if any of the key columns in the child table row are NULL. If 
+  ** any are, then the constraint is considered satisfied. No need to 
+  ** search for a matching row in the parent table.  */
+  if( nIncr<0 ){
+    sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, iOk);
+    VdbeCoverage(v);
+  }
+  for(i=0; i<pFKey->nCol; i++){
+    int iReg = sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[i]) + regData + 1;
+    sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk); VdbeCoverage(v);
+  }
+
+  if( isIgnore==0 ){
+    if( pIdx==0 ){
+      /* If pIdx is NULL, then the parent key is the INTEGER PRIMARY KEY
+      ** column of the parent table (table pTab).  */
+      int iMustBeInt;               /* Address of MustBeInt instruction */
+      int regTemp = sqlite3GetTempReg(pParse);
+  
+      /* Invoke MustBeInt to coerce the child key value to an integer (i.e. 
+      ** apply the affinity of the parent key). If this fails, then there
+      ** is no matching parent key. Before using MustBeInt, make a copy of
+      ** the value. Otherwise, the value inserted into the child key column
+      ** will have INTEGER affinity applied to it, which may not be correct.  */
+      sqlite3VdbeAddOp2(v, OP_SCopy, 
+        sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[0])+1+regData, regTemp);
+      iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0);
+      VdbeCoverage(v);
+  
+      /* If the parent table is the same as the child table, and we are about
+      ** to increment the constraint-counter (i.e. this is an INSERT operation),
+      ** then check if the row being inserted matches itself. If so, do not
+      ** increment the constraint-counter.  */
+      if( pTab==pFKey->pFrom && nIncr==1 ){
+        sqlite3VdbeAddOp3(v, OP_Eq, regData, iOk, regTemp); VdbeCoverage(v);
+        sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
+      }
+  
+      sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
+      sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp); VdbeCoverage(v);
+      sqlite3VdbeGoto(v, iOk);
+      sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
+      sqlite3VdbeJumpHere(v, iMustBeInt);
+      sqlite3ReleaseTempReg(pParse, regTemp);
+    }else{
+      int nCol = pFKey->nCol;
+      int regTemp = sqlite3GetTempRange(pParse, nCol);
+  
+      sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb);
+      sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
+      for(i=0; i<nCol; i++){
+        sqlite3VdbeAddOp2(v, OP_Copy, 
+               sqlite3TableColumnToStorage(pFKey->pFrom, aiCol[i])+1+regData,
+               regTemp+i);
+      }
+  
+      /* If the parent table is the same as the child table, and we are about
+      ** to increment the constraint-counter (i.e. this is an INSERT operation),
+      ** then check if the row being inserted matches itself. If so, do not
+      ** increment the constraint-counter. 
+      **
+      ** If any of the parent-key values are NULL, then the row cannot match 
+      ** itself. So set JUMPIFNULL to make sure we do the OP_Found if any
+      ** of the parent-key values are NULL (at this point it is known that
+      ** none of the child key values are).
+      */
+      if( pTab==pFKey->pFrom && nIncr==1 ){
+        int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1;
+        for(i=0; i<nCol; i++){
+          int iChild = sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[i])
+                              +1+regData;
+          int iParent = 1+regData;
+          iParent += sqlite3TableColumnToStorage(pIdx->pTable,
+                                                 pIdx->aiColumn[i]);
+          assert( pIdx->aiColumn[i]>=0 );
+          assert( aiCol[i]!=pTab->iPKey );
+          if( pIdx->aiColumn[i]==pTab->iPKey ){
+            /* The parent key is a composite key that includes the IPK column */
+            iParent = regData;
+          }
+          sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent); VdbeCoverage(v);
+          sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);
+        }
+        sqlite3VdbeGoto(v, iOk);
+      }
+
+      sqlite3VdbeAddOp4(v, OP_Affinity, regTemp, nCol, 0,
+                        sqlite3IndexAffinityStr(pParse->db,pIdx), nCol);
+      sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regTemp, nCol);
+      VdbeCoverage(v);
+      sqlite3ReleaseTempRange(pParse, regTemp, nCol);
+    }
+  }
+
+  if( !pFKey->isDeferred && !(pParse->db->flags & SQLITE_DeferFKs)
+   && !pParse->pToplevel 
+   && !pParse->isMultiWrite 
+  ){
+    /* Special case: If this is an INSERT statement that will insert exactly
+    ** one row into the table, raise a constraint immediately instead of
+    ** incrementing a counter. This is necessary as the VM code is being
+    ** generated for will not open a statement transaction.  */
+    assert( nIncr==1 );
+    sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY,
+        OE_Abort, 0, P4_STATIC, P5_ConstraintFK);
+  }else{
+    if( nIncr>0 && pFKey->isDeferred==0 ){
+      sqlite3MayAbort(pParse);
+    }
+    sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
+  }
+
+  sqlite3VdbeResolveLabel(v, iOk);
+  sqlite3VdbeAddOp1(v, OP_Close, iCur);
+}
+
+
+/*
+** Return an Expr object that refers to a memory register corresponding
+** to column iCol of table pTab.
+**
+** regBase is the first of an array of register that contains the data
+** for pTab.  regBase itself holds the rowid.  regBase+1 holds the first
+** column.  regBase+2 holds the second column, and so forth.
+*/
+static Expr *exprTableRegister(
+  Parse *pParse,     /* Parsing and code generating context */
+  Table *pTab,       /* The table whose content is at r[regBase]... */
+  int regBase,       /* Contents of table pTab */
+  i16 iCol           /* Which column of pTab is desired */
+){
+  Expr *pExpr;
+  Column *pCol;
+  const char *zColl;
+  sqlite3 *db = pParse->db;
+
+  pExpr = sqlite3Expr(db, TK_REGISTER, 0);
+  if( pExpr ){
+    if( iCol>=0 && iCol!=pTab->iPKey ){
+      pCol = &pTab->aCol[iCol];
+      pExpr->iTable = regBase + sqlite3TableColumnToStorage(pTab,iCol) + 1;
+      pExpr->affExpr = pCol->affinity;
+      zColl = sqlite3ColumnColl(pCol);
+      if( zColl==0 ) zColl = db->pDfltColl->zName;
+      pExpr = sqlite3ExprAddCollateString(pParse, pExpr, zColl);
+    }else{
+      pExpr->iTable = regBase;
+      pExpr->affExpr = SQLITE_AFF_INTEGER;
+    }
+  }
+  return pExpr;
+}
+
+/*
+** Return an Expr object that refers to column iCol of table pTab which
+** has cursor iCur.
+*/
+static Expr *exprTableColumn(
+  sqlite3 *db,      /* The database connection */
+  Table *pTab,      /* The table whose column is desired */
+  int iCursor,      /* The open cursor on the table */
+  i16 iCol          /* The column that is wanted */
+){
+  Expr *pExpr = sqlite3Expr(db, TK_COLUMN, 0);
+  if( pExpr ){
+    assert( ExprUseYTab(pExpr) );
+    pExpr->y.pTab = pTab;
+    pExpr->iTable = iCursor;
+    pExpr->iColumn = iCol;
+  }
+  return pExpr;
+}
+
+/*
+** This function is called to generate code executed when a row is deleted
+** from the parent table of foreign key constraint pFKey and, if pFKey is 
+** deferred, when a row is inserted into the same table. When generating
+** code for an SQL UPDATE operation, this function may be called twice -
+** once to "delete" the old row and once to "insert" the new row.
+**
+** Parameter nIncr is passed -1 when inserting a row (as this may decrease
+** the number of FK violations in the db) or +1 when deleting one (as this
+** may increase the number of FK constraint problems).
+**
+** The code generated by this function scans through the rows in the child
+** table that correspond to the parent table row being deleted or inserted.
+** For each child row found, one of the following actions is taken:
+**
+**   Operation | FK type   | Action taken
+**   --------------------------------------------------------------------------
+**   DELETE      immediate   Increment the "immediate constraint counter".
+**
+**   INSERT      immediate   Decrement the "immediate constraint counter".
+**
+**   DELETE      deferred    Increment the "deferred constraint counter".
+**
+**   INSERT      deferred    Decrement the "deferred constraint counter".
+**
+** These operations are identified in the comment at the top of this file 
+** (fkey.c) as "I.2" and "D.2".
+*/
+static void fkScanChildren(
+  Parse *pParse,                  /* Parse context */
+  SrcList *pSrc,                  /* The child table to be scanned */
+  Table *pTab,                    /* The parent table */
+  Index *pIdx,                    /* Index on parent covering the foreign key */
+  FKey *pFKey,                    /* The foreign key linking pSrc to pTab */
+  int *aiCol,                     /* Map from pIdx cols to child table cols */
+  int regData,                    /* Parent row data starts here */
+  int nIncr                       /* Amount to increment deferred counter by */
+){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  int i;                          /* Iterator variable */
+  Expr *pWhere = 0;               /* WHERE clause to scan with */
+  NameContext sNameContext;       /* Context used to resolve WHERE clause */
+  WhereInfo *pWInfo;              /* Context used by sqlite3WhereXXX() */
+  int iFkIfZero = 0;              /* Address of OP_FkIfZero */
+  Vdbe *v = sqlite3GetVdbe(pParse);
+
+  assert( pIdx==0 || pIdx->pTable==pTab );
+  assert( pIdx==0 || pIdx->nKeyCol==pFKey->nCol );
+  assert( pIdx!=0 || pFKey->nCol==1 );
+  assert( pIdx!=0 || HasRowid(pTab) );
+
+  if( nIncr<0 ){
+    iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0);
+    VdbeCoverage(v);
+  }
+
+  /* Create an Expr object representing an SQL expression like:
+  **
+  **   <parent-key1> = <child-key1> AND <parent-key2> = <child-key2> ...
+  **
+  ** The collation sequence used for the comparison should be that of
+  ** the parent key columns. The affinity of the parent key column should
+  ** be applied to each child key value before the comparison takes place.
+  */
+  for(i=0; i<pFKey->nCol; i++){
+    Expr *pLeft;                  /* Value from parent table row */
+    Expr *pRight;                 /* Column ref to child table */
+    Expr *pEq;                    /* Expression (pLeft = pRight) */
+    i16 iCol;                     /* Index of column in child table */ 
+    const char *zCol;             /* Name of column in child table */
+
+    iCol = pIdx ? pIdx->aiColumn[i] : -1;
+    pLeft = exprTableRegister(pParse, pTab, regData, iCol);
+    iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
+    assert( iCol>=0 );
+    zCol = pFKey->pFrom->aCol[iCol].zCnName;
+    pRight = sqlite3Expr(db, TK_ID, zCol);
+    pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight);
+    pWhere = sqlite3ExprAnd(pParse, pWhere, pEq);
+  }
+
+  /* If the child table is the same as the parent table, then add terms
+  ** to the WHERE clause that prevent this entry from being scanned.
+  ** The added WHERE clause terms are like this:
+  **
+  **     $current_rowid!=rowid
+  **     NOT( $current_a==a AND $current_b==b AND ... )
+  **
+  ** The first form is used for rowid tables.  The second form is used
+  ** for WITHOUT ROWID tables. In the second form, the *parent* key is
+  ** (a,b,...). Either the parent or primary key could be used to 
+  ** uniquely identify the current row, but the parent key is more convenient
+  ** as the required values have already been loaded into registers
+  ** by the caller.
+  */
+  if( pTab==pFKey->pFrom && nIncr>0 ){
+    Expr *pNe;                    /* Expression (pLeft != pRight) */
+    Expr *pLeft;                  /* Value from parent table row */
+    Expr *pRight;                 /* Column ref to child table */
+    if( HasRowid(pTab) ){
+      pLeft = exprTableRegister(pParse, pTab, regData, -1);
+      pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, -1);
+      pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight);
+    }else{
+      Expr *pEq, *pAll = 0;
+      assert( pIdx!=0 );
+      for(i=0; i<pIdx->nKeyCol; i++){
+        i16 iCol = pIdx->aiColumn[i];
+        assert( iCol>=0 );
+        pLeft = exprTableRegister(pParse, pTab, regData, iCol);
+        pRight = sqlite3Expr(db, TK_ID, pTab->aCol[iCol].zCnName);
+        pEq = sqlite3PExpr(pParse, TK_IS, pLeft, pRight);
+        pAll = sqlite3ExprAnd(pParse, pAll, pEq);
+      }
+      pNe = sqlite3PExpr(pParse, TK_NOT, pAll, 0);
+    }
+    pWhere = sqlite3ExprAnd(pParse, pWhere, pNe);
+  }
+
+  /* Resolve the references in the WHERE clause. */
+  memset(&sNameContext, 0, sizeof(NameContext));
+  sNameContext.pSrcList = pSrc;
+  sNameContext.pParse = pParse;
+  sqlite3ResolveExprNames(&sNameContext, pWhere);
+
+  /* Create VDBE to loop through the entries in pSrc that match the WHERE
+  ** clause. For each row found, increment either the deferred or immediate
+  ** foreign key constraint counter. */
+  if( pParse->nErr==0 ){
+    pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0, 0, 0, 0);
+    sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
+    if( pWInfo ){
+      sqlite3WhereEnd(pWInfo);
+    }
+  }
+
+  /* Clean up the WHERE clause constructed above. */
+  sqlite3ExprDelete(db, pWhere);
+  if( iFkIfZero ){
+    sqlite3VdbeJumpHereOrPopInst(v, iFkIfZero);
+  }
+}
+
+/*
+** This function returns a linked list of FKey objects (connected by
+** FKey.pNextTo) holding all children of table pTab.  For example,
+** given the following schema:
+**
+**   CREATE TABLE t1(a PRIMARY KEY);
+**   CREATE TABLE t2(b REFERENCES t1(a);
+**
+** Calling this function with table "t1" as an argument returns a pointer
+** to the FKey structure representing the foreign key constraint on table
+** "t2". Calling this function with "t2" as the argument would return a
+** NULL pointer (as there are no FK constraints for which t2 is the parent
+** table).
+*/
+FKey *sqlite3FkReferences(Table *pTab){
+  return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName);
+}
+
+/*
+** The second argument is a Trigger structure allocated by the 
+** fkActionTrigger() routine. This function deletes the Trigger structure
+** and all of its sub-components.
+**
+** The Trigger structure or any of its sub-components may be allocated from
+** the lookaside buffer belonging to database handle dbMem.
+*/
+static void fkTriggerDelete(sqlite3 *dbMem, Trigger *p){
+  if( p ){
+    TriggerStep *pStep = p->step_list;
+    sqlite3ExprDelete(dbMem, pStep->pWhere);
+    sqlite3ExprListDelete(dbMem, pStep->pExprList);
+    sqlite3SelectDelete(dbMem, pStep->pSelect);
+    sqlite3ExprDelete(dbMem, p->pWhen);
+    sqlite3DbFree(dbMem, p);
+  }
+}
+
+/*
+** Clear the apTrigger[] cache of CASCADE triggers for all foreign keys
+** in a particular database.  This needs to happen when the schema
+** changes.
+*/
+void sqlite3FkClearTriggerCache(sqlite3 *db, int iDb){
+  HashElem *k;
+  Hash *pHash = &db->aDb[iDb].pSchema->tblHash;
+  for(k=sqliteHashFirst(pHash); k; k=sqliteHashNext(k)){
+    Table *pTab = sqliteHashData(k);
+    FKey *pFKey;
+    if( !IsOrdinaryTable(pTab) ) continue;
+    for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
+      fkTriggerDelete(db, pFKey->apTrigger[0]); pFKey->apTrigger[0] = 0;
+      fkTriggerDelete(db, pFKey->apTrigger[1]); pFKey->apTrigger[1] = 0;
+    }
+  }
+}
+
+/*
+** This function is called to generate code that runs when table pTab is
+** being dropped from the database. The SrcList passed as the second argument
+** to this function contains a single entry guaranteed to resolve to
+** table pTab.
+**
+** Normally, no code is required. However, if either
+**
+**   (a) The table is the parent table of a FK constraint, or
+**   (b) The table is the child table of a deferred FK constraint and it is
+**       determined at runtime that there are outstanding deferred FK 
+**       constraint violations in the database,
+**
+** then the equivalent of "DELETE FROM <tbl>" is executed before dropping
+** the table from the database. Triggers are disabled while running this
+** DELETE, but foreign key actions are not.
+*/
+void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){
+  sqlite3 *db = pParse->db;
+  if( (db->flags&SQLITE_ForeignKeys) && IsOrdinaryTable(pTab) ){
+    int iSkip = 0;
+    Vdbe *v = sqlite3GetVdbe(pParse);
+
+    assert( v );                  /* VDBE has already been allocated */
+    assert( IsOrdinaryTable(pTab) );
+    if( sqlite3FkReferences(pTab)==0 ){
+      /* Search for a deferred foreign key constraint for which this table
+      ** is the child table. If one cannot be found, return without 
+      ** generating any VDBE code. If one can be found, then jump over
+      ** the entire DELETE if there are no outstanding deferred constraints
+      ** when this statement is run.  */
+      FKey *p;
+      for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){
+        if( p->isDeferred || (db->flags & SQLITE_DeferFKs) ) break;
+      }
+      if( !p ) return;
+      iSkip = sqlite3VdbeMakeLabel(pParse);
+      sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip); VdbeCoverage(v);
+    }
+
+    pParse->disableTriggers = 1;
+    sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0, 0, 0);
+    pParse->disableTriggers = 0;
+
+    /* If the DELETE has generated immediate foreign key constraint 
+    ** violations, halt the VDBE and return an error at this point, before
+    ** any modifications to the schema are made. This is because statement
+    ** transactions are not able to rollback schema changes.  
+    **
+    ** If the SQLITE_DeferFKs flag is set, then this is not required, as
+    ** the statement transaction will not be rolled back even if FK
+    ** constraints are violated.
+    */
+    if( (db->flags & SQLITE_DeferFKs)==0 ){
+      sqlite3VdbeVerifyAbortable(v, OE_Abort);
+      sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2);
+      VdbeCoverage(v);
+      sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY,
+          OE_Abort, 0, P4_STATIC, P5_ConstraintFK);
+    }
+
+    if( iSkip ){
+      sqlite3VdbeResolveLabel(v, iSkip);
+    }
+  }
+}
+
+
+/*
+** The second argument points to an FKey object representing a foreign key
+** for which pTab is the child table. An UPDATE statement against pTab
+** is currently being processed. For each column of the table that is 
+** actually updated, the corresponding element in the aChange[] array
+** is zero or greater (if a column is unmodified the corresponding element
+** is set to -1). If the rowid column is modified by the UPDATE statement
+** the bChngRowid argument is non-zero.
+**
+** This function returns true if any of the columns that are part of the
+** child key for FK constraint *p are modified.
+*/
+static int fkChildIsModified(
+  Table *pTab,                    /* Table being updated */
+  FKey *p,                        /* Foreign key for which pTab is the child */
+  int *aChange,                   /* Array indicating modified columns */
+  int bChngRowid                  /* True if rowid is modified by this update */
+){
+  int i;
+  for(i=0; i<p->nCol; i++){
+    int iChildKey = p->aCol[i].iFrom;
+    if( aChange[iChildKey]>=0 ) return 1;
+    if( iChildKey==pTab->iPKey && bChngRowid ) return 1;
+  }
+  return 0;
+}
+
+/*
+** The second argument points to an FKey object representing a foreign key
+** for which pTab is the parent table. An UPDATE statement against pTab
+** is currently being processed. For each column of the table that is 
+** actually updated, the corresponding element in the aChange[] array
+** is zero or greater (if a column is unmodified the corresponding element
+** is set to -1). If the rowid column is modified by the UPDATE statement
+** the bChngRowid argument is non-zero.
+**
+** This function returns true if any of the columns that are part of the
+** parent key for FK constraint *p are modified.
+*/
+static int fkParentIsModified(
+  Table *pTab, 
+  FKey *p, 
+  int *aChange, 
+  int bChngRowid
+){
+  int i;
+  for(i=0; i<p->nCol; i++){
+    char *zKey = p->aCol[i].zCol;
+    int iKey;
+    for(iKey=0; iKey<pTab->nCol; iKey++){
+      if( aChange[iKey]>=0 || (iKey==pTab->iPKey && bChngRowid) ){
+        Column *pCol = &pTab->aCol[iKey];
+        if( zKey ){
+          if( 0==sqlite3StrICmp(pCol->zCnName, zKey) ) return 1;
+        }else if( pCol->colFlags & COLFLAG_PRIMKEY ){
+          return 1;
+        }
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** Return true if the parser passed as the first argument is being
+** used to code a trigger that is really a "SET NULL" action belonging
+** to trigger pFKey.
+*/
+static int isSetNullAction(Parse *pParse, FKey *pFKey){
+  Parse *pTop = sqlite3ParseToplevel(pParse);
+  if( pTop->pTriggerPrg ){
+    Trigger *p = pTop->pTriggerPrg->pTrigger;
+    if( (p==pFKey->apTrigger[0] && pFKey->aAction[0]==OE_SetNull)
+     || (p==pFKey->apTrigger[1] && pFKey->aAction[1]==OE_SetNull)
+    ){
+      assert( (pTop->db->flags & SQLITE_FkNoAction)==0 );
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** This function is called when inserting, deleting or updating a row of
+** table pTab to generate VDBE code to perform foreign key constraint 
+** processing for the operation.
+**
+** For a DELETE operation, parameter regOld is passed the index of the
+** first register in an array of (pTab->nCol+1) registers containing the
+** rowid of the row being deleted, followed by each of the column values
+** of the row being deleted, from left to right. Parameter regNew is passed
+** zero in this case.
+**
+** For an INSERT operation, regOld is passed zero and regNew is passed the
+** first register of an array of (pTab->nCol+1) registers containing the new
+** row data.
+**
+** For an UPDATE operation, this function is called twice. Once before
+** the original record is deleted from the table using the calling convention
+** described for DELETE. Then again after the original record is deleted
+** but before the new record is inserted using the INSERT convention. 
+*/
+void sqlite3FkCheck(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Row is being deleted from this table */ 
+  int regOld,                     /* Previous row data is stored here */
+  int regNew,                     /* New row data is stored here */
+  int *aChange,                   /* Array indicating UPDATEd columns (or 0) */
+  int bChngRowid                  /* True if rowid is UPDATEd */
+){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  FKey *pFKey;                    /* Used to iterate through FKs */
+  int iDb;                        /* Index of database containing pTab */
+  const char *zDb;                /* Name of database containing pTab */
+  int isIgnoreErrors = pParse->disableTriggers;
+
+  /* Exactly one of regOld and regNew should be non-zero. */
+  assert( (regOld==0)!=(regNew==0) );
+
+  /* If foreign-keys are disabled, this function is a no-op. */
+  if( (db->flags&SQLITE_ForeignKeys)==0 ) return;
+  if( !IsOrdinaryTable(pTab) ) return;
+
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  zDb = db->aDb[iDb].zDbSName;
+
+  /* Loop through all the foreign key constraints for which pTab is the
+  ** child table (the table that the foreign key definition is part of).  */
+  for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
+    Table *pTo;                   /* Parent table of foreign key pFKey */
+    Index *pIdx = 0;              /* Index on key columns in pTo */
+    int *aiFree = 0;
+    int *aiCol;
+    int iCol;
+    int i;
+    int bIgnore = 0;
+
+    if( aChange 
+     && sqlite3_stricmp(pTab->zName, pFKey->zTo)!=0
+     && fkChildIsModified(pTab, pFKey, aChange, bChngRowid)==0 
+    ){
+      continue;
+    }
+
+    /* Find the parent table of this foreign key. Also find a unique index 
+    ** on the parent key columns in the parent table. If either of these 
+    ** schema items cannot be located, set an error in pParse and return 
+    ** early.  */
+    if( pParse->disableTriggers ){
+      pTo = sqlite3FindTable(db, pFKey->zTo, zDb);
+    }else{
+      pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb);
+    }
+    if( !pTo || sqlite3FkLocateIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){
+      assert( isIgnoreErrors==0 || (regOld!=0 && regNew==0) );
+      if( !isIgnoreErrors || db->mallocFailed ) return;
+      if( pTo==0 ){
+        /* If isIgnoreErrors is true, then a table is being dropped. In this
+        ** case SQLite runs a "DELETE FROM xxx" on the table being dropped
+        ** before actually dropping it in order to check FK constraints.
+        ** If the parent table of an FK constraint on the current table is
+        ** missing, behave as if it is empty. i.e. decrement the relevant
+        ** FK counter for each row of the current table with non-NULL keys.
+        */
+        Vdbe *v = sqlite3GetVdbe(pParse);
+        int iJump = sqlite3VdbeCurrentAddr(v) + pFKey->nCol + 1;
+        for(i=0; i<pFKey->nCol; i++){
+          int iFromCol, iReg;
+          iFromCol = pFKey->aCol[i].iFrom;
+          iReg = sqlite3TableColumnToStorage(pFKey->pFrom,iFromCol) + regOld+1;
+          sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iJump); VdbeCoverage(v);
+        }
+        sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, -1);
+      }
+      continue;
+    }
+    assert( pFKey->nCol==1 || (aiFree && pIdx) );
+
+    if( aiFree ){
+      aiCol = aiFree;
+    }else{
+      iCol = pFKey->aCol[0].iFrom;
+      aiCol = &iCol;
+    }
+    for(i=0; i<pFKey->nCol; i++){
+      if( aiCol[i]==pTab->iPKey ){
+        aiCol[i] = -1;
+      }
+      assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
+#ifndef SQLITE_OMIT_AUTHORIZATION
+      /* Request permission to read the parent key columns. If the 
+      ** authorization callback returns SQLITE_IGNORE, behave as if any
+      ** values read from the parent table are NULL. */
+      if( db->xAuth ){
+        int rcauth;
+        char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zCnName;
+        rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb);
+        bIgnore = (rcauth==SQLITE_IGNORE);
+      }
+#endif
+    }
+
+    /* Take a shared-cache advisory read-lock on the parent table. Allocate 
+    ** a cursor to use to search the unique index on the parent key columns 
+    ** in the parent table.  */
+    sqlite3TableLock(pParse, iDb, pTo->tnum, 0, pTo->zName);
+    pParse->nTab++;
+
+    if( regOld!=0 ){
+      /* A row is being removed from the child table. Search for the parent.
+      ** If the parent does not exist, removing the child row resolves an 
+      ** outstanding foreign key constraint violation. */
+      fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regOld, -1, bIgnore);
+    }
+    if( regNew!=0 && !isSetNullAction(pParse, pFKey) ){
+      /* A row is being added to the child table. If a parent row cannot
+      ** be found, adding the child row has violated the FK constraint. 
+      **
+      ** If this operation is being performed as part of a trigger program
+      ** that is actually a "SET NULL" action belonging to this very 
+      ** foreign key, then omit this scan altogether. As all child key
+      ** values are guaranteed to be NULL, it is not possible for adding
+      ** this row to cause an FK violation.  */
+      fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1, bIgnore);
+    }
+
+    sqlite3DbFree(db, aiFree);
+  }
+
+  /* Loop through all the foreign key constraints that refer to this table.
+  ** (the "child" constraints) */
+  for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
+    Index *pIdx = 0;              /* Foreign key index for pFKey */
+    SrcList *pSrc;
+    int *aiCol = 0;
+
+    if( aChange && fkParentIsModified(pTab, pFKey, aChange, bChngRowid)==0 ){
+      continue;
+    }
+
+    if( !pFKey->isDeferred && !(db->flags & SQLITE_DeferFKs) 
+     && !pParse->pToplevel && !pParse->isMultiWrite 
+    ){
+      assert( regOld==0 && regNew!=0 );
+      /* Inserting a single row into a parent table cannot cause (or fix)
+      ** an immediate foreign key violation. So do nothing in this case.  */
+      continue;
+    }
+
+    if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){
+      if( !isIgnoreErrors || db->mallocFailed ) return;
+      continue;
+    }
+    assert( aiCol || pFKey->nCol==1 );
+
+    /* Create a SrcList structure containing the child table.  We need the
+    ** child table as a SrcList for sqlite3WhereBegin() */
+    pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
+    if( pSrc ){
+      SrcItem *pItem = pSrc->a;
+      pItem->pTab = pFKey->pFrom;
+      pItem->zName = pFKey->pFrom->zName;
+      pItem->pTab->nTabRef++;
+      pItem->iCursor = pParse->nTab++;
+  
+      if( regNew!=0 ){
+        fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regNew, -1);
+      }
+      if( regOld!=0 ){
+        int eAction = pFKey->aAction[aChange!=0];
+        if( (db->flags & SQLITE_FkNoAction) ) eAction = OE_None;
+
+        fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regOld, 1);
+        /* If this is a deferred FK constraint, or a CASCADE or SET NULL
+        ** action applies, then any foreign key violations caused by
+        ** removing the parent key will be rectified by the action trigger.
+        ** So do not set the "may-abort" flag in this case.
+        **
+        ** Note 1: If the FK is declared "ON UPDATE CASCADE", then the
+        ** may-abort flag will eventually be set on this statement anyway
+        ** (when this function is called as part of processing the UPDATE
+        ** within the action trigger).
+        **
+        ** Note 2: At first glance it may seem like SQLite could simply omit
+        ** all OP_FkCounter related scans when either CASCADE or SET NULL
+        ** applies. The trouble starts if the CASCADE or SET NULL action 
+        ** trigger causes other triggers or action rules attached to the 
+        ** child table to fire. In these cases the fk constraint counters
+        ** might be set incorrectly if any OP_FkCounter related scans are 
+        ** omitted.  */
+        if( !pFKey->isDeferred && eAction!=OE_Cascade && eAction!=OE_SetNull ){
+          sqlite3MayAbort(pParse);
+        }
+      }
+      pItem->zName = 0;
+      sqlite3SrcListDelete(db, pSrc);
+    }
+    sqlite3DbFree(db, aiCol);
+  }
+}
+
+#define COLUMN_MASK(x) (((x)>31) ? 0xffffffff : ((u32)1<<(x)))
+
+/*
+** This function is called before generating code to update or delete a 
+** row contained in table pTab.
+*/
+u32 sqlite3FkOldmask(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab                     /* Table being modified */
+){
+  u32 mask = 0;
+  if( pParse->db->flags&SQLITE_ForeignKeys && IsOrdinaryTable(pTab) ){
+    FKey *p;
+    int i;
+    for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){
+      for(i=0; i<p->nCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom);
+    }
+    for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
+      Index *pIdx = 0;
+      sqlite3FkLocateIndex(pParse, pTab, p, &pIdx, 0);
+      if( pIdx ){
+        for(i=0; i<pIdx->nKeyCol; i++){
+          assert( pIdx->aiColumn[i]>=0 );
+          mask |= COLUMN_MASK(pIdx->aiColumn[i]);
+        }
+      }
+    }
+  }
+  return mask;
+}
+
+
+/*
+** This function is called before generating code to update or delete a 
+** row contained in table pTab. If the operation is a DELETE, then
+** parameter aChange is passed a NULL value. For an UPDATE, aChange points
+** to an array of size N, where N is the number of columns in table pTab.
+** If the i'th column is not modified by the UPDATE, then the corresponding 
+** entry in the aChange[] array is set to -1. If the column is modified,
+** the value is 0 or greater. Parameter chngRowid is set to true if the
+** UPDATE statement modifies the rowid fields of the table.
+**
+** If any foreign key processing will be required, this function returns
+** non-zero. If there is no foreign key related processing, this function 
+** returns zero.
+**
+** For an UPDATE, this function returns 2 if:
+**
+**   * There are any FKs for which pTab is the child and the parent table
+**     and any FK processing at all is required (even of a different FK), or
+**
+**   * the UPDATE modifies one or more parent keys for which the action is
+**     not "NO ACTION" (i.e. is CASCADE, SET DEFAULT or SET NULL).
+**
+** Or, assuming some other foreign key processing is required, 1.
+*/
+int sqlite3FkRequired(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being modified */
+  int *aChange,                   /* Non-NULL for UPDATE operations */
+  int chngRowid                   /* True for UPDATE that affects rowid */
+){
+  int eRet = 1;                   /* Value to return if bHaveFK is true */
+  int bHaveFK = 0;                /* If FK processing is required */
+  if( pParse->db->flags&SQLITE_ForeignKeys && IsOrdinaryTable(pTab) ){
+    if( !aChange ){
+      /* A DELETE operation. Foreign key processing is required if the 
+      ** table in question is either the child or parent table for any 
+      ** foreign key constraint.  */
+      bHaveFK = (sqlite3FkReferences(pTab) || pTab->u.tab.pFKey);
+    }else{
+      /* This is an UPDATE. Foreign key processing is only required if the
+      ** operation modifies one or more child or parent key columns. */
+      FKey *p;
+
+      /* Check if any child key columns are being modified. */
+      for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){
+        if( fkChildIsModified(pTab, p, aChange, chngRowid) ){
+          if( 0==sqlite3_stricmp(pTab->zName, p->zTo) ) eRet = 2;
+          bHaveFK = 1;
+        }
+      }
+
+      /* Check if any parent key columns are being modified. */
+      for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
+        if( fkParentIsModified(pTab, p, aChange, chngRowid) ){
+          if( (pParse->db->flags & SQLITE_FkNoAction)==0 
+           && p->aAction[1]!=OE_None 
+          ){
+            return 2;
+          }
+          bHaveFK = 1;
+        }
+      }
+    }
+  }
+  return bHaveFK ? eRet : 0;
+}
+
+/*
+** This function is called when an UPDATE or DELETE operation is being 
+** compiled on table pTab, which is the parent table of foreign-key pFKey.
+** If the current operation is an UPDATE, then the pChanges parameter is
+** passed a pointer to the list of columns being modified. If it is a
+** DELETE, pChanges is passed a NULL pointer.
+**
+** It returns a pointer to a Trigger structure containing a trigger
+** equivalent to the ON UPDATE or ON DELETE action specified by pFKey.
+** If the action is "NO ACTION" then a NULL pointer is returned (these actions
+** require no special handling by the triggers sub-system, code for them is
+** created by fkScanChildren()).
+**
+** For example, if pFKey is the foreign key and pTab is table "p" in 
+** the following schema:
+**
+**   CREATE TABLE p(pk PRIMARY KEY);
+**   CREATE TABLE c(ck REFERENCES p ON DELETE CASCADE);
+**
+** then the returned trigger structure is equivalent to:
+**
+**   CREATE TRIGGER ... DELETE ON p BEGIN
+**     DELETE FROM c WHERE ck = old.pk;
+**   END;
+**
+** The returned pointer is cached as part of the foreign key object. It
+** is eventually freed along with the rest of the foreign key object by 
+** sqlite3FkDelete().
+*/
+static Trigger *fkActionTrigger(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being updated or deleted from */
+  FKey *pFKey,                    /* Foreign key to get action for */
+  ExprList *pChanges              /* Change-list for UPDATE, NULL for DELETE */
+){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  int action;                     /* One of OE_None, OE_Cascade etc. */
+  Trigger *pTrigger;              /* Trigger definition to return */
+  int iAction = (pChanges!=0);    /* 1 for UPDATE, 0 for DELETE */
+
+  action = pFKey->aAction[iAction];
+  if( (db->flags & SQLITE_FkNoAction) ) action = OE_None;
+  if( action==OE_Restrict && (db->flags & SQLITE_DeferFKs) ){
+    return 0;
+  }
+  pTrigger = pFKey->apTrigger[iAction];
+
+  if( action!=OE_None && !pTrigger ){
+    char const *zFrom;            /* Name of child table */
+    int nFrom;                    /* Length in bytes of zFrom */
+    Index *pIdx = 0;              /* Parent key index for this FK */
+    int *aiCol = 0;               /* child table cols -> parent key cols */
+    TriggerStep *pStep = 0;        /* First (only) step of trigger program */
+    Expr *pWhere = 0;             /* WHERE clause of trigger step */
+    ExprList *pList = 0;          /* Changes list if ON UPDATE CASCADE */
+    Select *pSelect = 0;          /* If RESTRICT, "SELECT RAISE(...)" */
+    int i;                        /* Iterator variable */
+    Expr *pWhen = 0;              /* WHEN clause for the trigger */
+
+    if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ) return 0;
+    assert( aiCol || pFKey->nCol==1 );
+
+    for(i=0; i<pFKey->nCol; i++){
+      Token tOld = { "old", 3 };  /* Literal "old" token */
+      Token tNew = { "new", 3 };  /* Literal "new" token */
+      Token tFromCol;             /* Name of column in child table */
+      Token tToCol;               /* Name of column in parent table */
+      int iFromCol;               /* Idx of column in child table */
+      Expr *pEq;                  /* tFromCol = OLD.tToCol */
+
+      iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
+      assert( iFromCol>=0 );
+      assert( pIdx!=0 || (pTab->iPKey>=0 && pTab->iPKey<pTab->nCol) );
+      assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
+      sqlite3TokenInit(&tToCol,
+                   pTab->aCol[pIdx ? pIdx->aiColumn[i] : pTab->iPKey].zCnName);
+      sqlite3TokenInit(&tFromCol, pFKey->pFrom->aCol[iFromCol].zCnName);
+
+      /* Create the expression "OLD.zToCol = zFromCol". It is important
+      ** that the "OLD.zToCol" term is on the LHS of the = operator, so
+      ** that the affinity and collation sequence associated with the
+      ** parent table are used for the comparison. */
+      pEq = sqlite3PExpr(pParse, TK_EQ,
+          sqlite3PExpr(pParse, TK_DOT, 
+            sqlite3ExprAlloc(db, TK_ID, &tOld, 0),
+            sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)),
+          sqlite3ExprAlloc(db, TK_ID, &tFromCol, 0)
+      );
+      pWhere = sqlite3ExprAnd(pParse, pWhere, pEq);
+
+      /* For ON UPDATE, construct the next term of the WHEN clause.
+      ** The final WHEN clause will be like this:
+      **
+      **    WHEN NOT(old.col1 IS new.col1 AND ... AND old.colN IS new.colN)
+      */
+      if( pChanges ){
+        pEq = sqlite3PExpr(pParse, TK_IS,
+            sqlite3PExpr(pParse, TK_DOT, 
+              sqlite3ExprAlloc(db, TK_ID, &tOld, 0),
+              sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)),
+            sqlite3PExpr(pParse, TK_DOT, 
+              sqlite3ExprAlloc(db, TK_ID, &tNew, 0),
+              sqlite3ExprAlloc(db, TK_ID, &tToCol, 0))
+            );
+        pWhen = sqlite3ExprAnd(pParse, pWhen, pEq);
+      }
+  
+      if( action!=OE_Restrict && (action!=OE_Cascade || pChanges) ){
+        Expr *pNew;
+        if( action==OE_Cascade ){
+          pNew = sqlite3PExpr(pParse, TK_DOT, 
+            sqlite3ExprAlloc(db, TK_ID, &tNew, 0),
+            sqlite3ExprAlloc(db, TK_ID, &tToCol, 0));
+        }else if( action==OE_SetDflt ){
+          Column *pCol = pFKey->pFrom->aCol + iFromCol;
+          Expr *pDflt;
+          if( pCol->colFlags & COLFLAG_GENERATED ){
+            testcase( pCol->colFlags & COLFLAG_VIRTUAL );
+            testcase( pCol->colFlags & COLFLAG_STORED );
+            pDflt = 0;
+          }else{
+            pDflt = sqlite3ColumnExpr(pFKey->pFrom, pCol);
+          }
+          if( pDflt ){
+            pNew = sqlite3ExprDup(db, pDflt, 0);
+          }else{
+            pNew = sqlite3ExprAlloc(db, TK_NULL, 0, 0);
+          }
+        }else{
+          pNew = sqlite3ExprAlloc(db, TK_NULL, 0, 0);
+        }
+        pList = sqlite3ExprListAppend(pParse, pList, pNew);
+        sqlite3ExprListSetName(pParse, pList, &tFromCol, 0);
+      }
+    }
+    sqlite3DbFree(db, aiCol);
+
+    zFrom = pFKey->pFrom->zName;
+    nFrom = sqlite3Strlen30(zFrom);
+
+    if( action==OE_Restrict ){
+      int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+      SrcList *pSrc;
+      Expr *pRaise; 
+
+      pRaise = sqlite3Expr(db, TK_RAISE, "FOREIGN KEY constraint failed");
+      if( pRaise ){
+        pRaise->affExpr = OE_Abort;
+      }
+      pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
+      if( pSrc ){
+        assert( pSrc->nSrc==1 );
+        pSrc->a[0].zName = sqlite3DbStrDup(db, zFrom);
+        pSrc->a[0].zDatabase = sqlite3DbStrDup(db, db->aDb[iDb].zDbSName);
+      }
+      pSelect = sqlite3SelectNew(pParse, 
+          sqlite3ExprListAppend(pParse, 0, pRaise),
+          pSrc,
+          pWhere,
+          0, 0, 0, 0, 0
+      );
+      pWhere = 0;
+    }
+
+    /* Disable lookaside memory allocation */
+    DisableLookaside;
+
+    pTrigger = (Trigger *)sqlite3DbMallocZero(db, 
+        sizeof(Trigger) +         /* struct Trigger */
+        sizeof(TriggerStep) +     /* Single step in trigger program */
+        nFrom + 1                 /* Space for pStep->zTarget */
+    );
+    if( pTrigger ){
+      pStep = pTrigger->step_list = (TriggerStep *)&pTrigger[1];
+      pStep->zTarget = (char *)&pStep[1];
+      memcpy((char *)pStep->zTarget, zFrom, nFrom);
+  
+      pStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
+      pStep->pExprList = sqlite3ExprListDup(db, pList, EXPRDUP_REDUCE);
+      pStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
+      if( pWhen ){
+        pWhen = sqlite3PExpr(pParse, TK_NOT, pWhen, 0);
+        pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
+      }
+    }
+
+    /* Re-enable the lookaside buffer, if it was disabled earlier. */
+    EnableLookaside;
+
+    sqlite3ExprDelete(db, pWhere);
+    sqlite3ExprDelete(db, pWhen);
+    sqlite3ExprListDelete(db, pList);
+    sqlite3SelectDelete(db, pSelect);
+    if( db->mallocFailed==1 ){
+      fkTriggerDelete(db, pTrigger);
+      return 0;
+    }
+    assert( pStep!=0 );
+    assert( pTrigger!=0 );
+
+    switch( action ){
+      case OE_Restrict:
+        pStep->op = TK_SELECT;
+        break;
+      case OE_Cascade: 
+        if( !pChanges ){ 
+          pStep->op = TK_DELETE; 
+          break; 
+        }
+        /* no break */ deliberate_fall_through
+      default:
+        pStep->op = TK_UPDATE;
+    }
+    pStep->pTrig = pTrigger;
+    pTrigger->pSchema = pTab->pSchema;
+    pTrigger->pTabSchema = pTab->pSchema;
+    pFKey->apTrigger[iAction] = pTrigger;
+    pTrigger->op = (pChanges ? TK_UPDATE : TK_DELETE);
+  }
+
+  return pTrigger;
+}
+
+/*
+** This function is called when deleting or updating a row to implement
+** any required CASCADE, SET NULL or SET DEFAULT actions.
+*/
+void sqlite3FkActions(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being updated or deleted from */
+  ExprList *pChanges,             /* Change-list for UPDATE, NULL for DELETE */
+  int regOld,                     /* Address of array containing old row */
+  int *aChange,                   /* Array indicating UPDATEd columns (or 0) */
+  int bChngRowid                  /* True if rowid is UPDATEd */
+){
+  /* If foreign-key support is enabled, iterate through all FKs that 
+  ** refer to table pTab. If there is an action associated with the FK 
+  ** for this operation (either update or delete), invoke the associated 
+  ** trigger sub-program.  */
+  if( pParse->db->flags&SQLITE_ForeignKeys ){
+    FKey *pFKey;                  /* Iterator variable */
+    for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
+      if( aChange==0 || fkParentIsModified(pTab, pFKey, aChange, bChngRowid) ){
+        Trigger *pAct = fkActionTrigger(pParse, pTab, pFKey, pChanges);
+        if( pAct ){
+          sqlite3CodeRowTriggerDirect(pParse, pAct, pTab, regOld, OE_Abort, 0);
+        }
+      }
+    }
+  }
+}
+
+#endif /* ifndef SQLITE_OMIT_TRIGGER */
+
+/*
+** Free all memory associated with foreign key definitions attached to
+** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash
+** hash table.
+*/
+void sqlite3FkDelete(sqlite3 *db, Table *pTab){
+  FKey *pFKey;                    /* Iterator variable */
+  FKey *pNext;                    /* Copy of pFKey->pNextFrom */
+
+  assert( IsOrdinaryTable(pTab) );
+  assert( db!=0 );
+  for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pNext){
+    assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) );
+
+    /* Remove the FK from the fkeyHash hash table. */
+    if( db->pnBytesFreed==0 ){
+      if( pFKey->pPrevTo ){
+        pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
+      }else{
+        const char *z = (pFKey->pNextTo ? pFKey->pNextTo->zTo : pFKey->zTo);
+        sqlite3HashInsert(&pTab->pSchema->fkeyHash, z, pFKey->pNextTo);
+      }
+      if( pFKey->pNextTo ){
+        pFKey->pNextTo->pPrevTo = pFKey->pPrevTo;
+      }
+    }
+
+    /* EV: R-30323-21917 Each foreign key constraint in SQLite is
+    ** classified as either immediate or deferred.
+    */
+    assert( pFKey->isDeferred==0 || pFKey->isDeferred==1 );
+
+    /* Delete any triggers created to implement actions for this FK. */
+#ifndef SQLITE_OMIT_TRIGGER
+    fkTriggerDelete(db, pFKey->apTrigger[0]);
+    fkTriggerDelete(db, pFKey->apTrigger[1]);
+#endif
+
+    pNext = pFKey->pNextFrom;
+    sqlite3DbFree(db, pFKey);
+  }
+}
+#endif /* ifndef SQLITE_OMIT_FOREIGN_KEY */
diff --git a/src/func.c b/src/func.c
new file mode 100644
index 0000000..58ef4fe
--- /dev/null
+++ b/src/func.c
@@ -0,0 +1,2755 @@
+/*
+** 2002 February 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C-language implementations for many of the SQL
+** functions of SQLite.  (Some function, and in particular the date and
+** time functions, are implemented separately.)
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <assert.h>
+#ifndef SQLITE_OMIT_FLOATING_POINT
+#include <math.h>
+#endif
+#include "vdbeInt.h"
+
+/*
+** Return the collating function associated with a function.
+*/
+static CollSeq *sqlite3GetFuncCollSeq(sqlite3_context *context){
+  VdbeOp *pOp;
+  assert( context->pVdbe!=0 );
+  pOp = &context->pVdbe->aOp[context->iOp-1];
+  assert( pOp->opcode==OP_CollSeq );
+  assert( pOp->p4type==P4_COLLSEQ );
+  return pOp->p4.pColl;
+}
+
+/*
+** Indicate that the accumulator load should be skipped on this
+** iteration of the aggregate loop.
+*/
+static void sqlite3SkipAccumulatorLoad(sqlite3_context *context){
+  assert( context->isError<=0 );
+  context->isError = -1;
+  context->skipFlag = 1;
+}
+
+/*
+** Implementation of the non-aggregate min() and max() functions
+*/
+static void minmaxFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+  int mask;    /* 0 for min() or 0xffffffff for max() */
+  int iBest;
+  CollSeq *pColl;
+
+  assert( argc>1 );
+  mask = sqlite3_user_data(context)==0 ? 0 : -1;
+  pColl = sqlite3GetFuncCollSeq(context);
+  assert( pColl );
+  assert( mask==-1 || mask==0 );
+  iBest = 0;
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  for(i=1; i<argc; i++){
+    if( sqlite3_value_type(argv[i])==SQLITE_NULL ) return;
+    if( (sqlite3MemCompare(argv[iBest], argv[i], pColl)^mask)>=0 ){
+      testcase( mask==0 );
+      iBest = i;
+    }
+  }
+  sqlite3_result_value(context, argv[iBest]);
+}
+
+/*
+** Return the type of the argument.
+*/
+static void typeofFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  static const char *azType[] = { "integer", "real", "text", "blob", "null" };
+  int i = sqlite3_value_type(argv[0]) - 1;
+  UNUSED_PARAMETER(NotUsed);
+  assert( i>=0 && i<ArraySize(azType) );
+  assert( SQLITE_INTEGER==1 );
+  assert( SQLITE_FLOAT==2 );
+  assert( SQLITE_TEXT==3 );
+  assert( SQLITE_BLOB==4 );
+  assert( SQLITE_NULL==5 );
+  /* EVIDENCE-OF: R-01470-60482 The sqlite3_value_type(V) interface returns
+  ** the datatype code for the initial datatype of the sqlite3_value object
+  ** V. The returned value is one of SQLITE_INTEGER, SQLITE_FLOAT,
+  ** SQLITE_TEXT, SQLITE_BLOB, or SQLITE_NULL. */
+  sqlite3_result_text(context, azType[i], -1, SQLITE_STATIC);
+}
+
+/* subtype(X)
+**
+** Return the subtype of X
+*/
+static void subtypeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  UNUSED_PARAMETER(argc);
+  sqlite3_result_int(context, sqlite3_value_subtype(argv[0]));
+}
+
+/*
+** Implementation of the length() function
+*/
+static void lengthFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_BLOB:
+    case SQLITE_INTEGER:
+    case SQLITE_FLOAT: {
+      sqlite3_result_int(context, sqlite3_value_bytes(argv[0]));
+      break;
+    }
+    case SQLITE_TEXT: {
+      const unsigned char *z = sqlite3_value_text(argv[0]);
+      const unsigned char *z0;
+      unsigned char c;
+      if( z==0 ) return;
+      z0 = z;
+      while( (c = *z)!=0 ){
+        z++;
+        if( c>=0xc0 ){
+          while( (*z & 0xc0)==0x80 ){ z++; z0++; }
+        }
+      }
+      sqlite3_result_int(context, (int)(z-z0));
+      break;
+    }
+    default: {
+      sqlite3_result_null(context);
+      break;
+    }
+  }
+}
+
+/*
+** Implementation of the octet_length() function
+*/
+static void bytelengthFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_BLOB: {
+      sqlite3_result_int(context, sqlite3_value_bytes(argv[0]));
+      break;
+    }
+    case SQLITE_INTEGER:
+    case SQLITE_FLOAT: {
+      i64 m = sqlite3_context_db_handle(context)->enc<=SQLITE_UTF8 ? 1 : 2;
+      sqlite3_result_int64(context, sqlite3_value_bytes(argv[0])*m);
+      break;
+    }
+    case SQLITE_TEXT: {
+      if( sqlite3_value_encoding(argv[0])<=SQLITE_UTF8 ){
+        sqlite3_result_int(context, sqlite3_value_bytes(argv[0]));
+      }else{
+        sqlite3_result_int(context, sqlite3_value_bytes16(argv[0]));
+      }
+      break;
+    }
+    default: {
+      sqlite3_result_null(context);
+      break;
+    }
+  }
+}
+
+/*
+** Implementation of the abs() function.
+**
+** IMP: R-23979-26855 The abs(X) function returns the absolute value of
+** the numeric argument X.
+*/
+static void absFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_INTEGER: {
+      i64 iVal = sqlite3_value_int64(argv[0]);
+      if( iVal<0 ){
+        if( iVal==SMALLEST_INT64 ){
+          /* IMP: R-31676-45509 If X is the integer -9223372036854775808
+          ** then abs(X) throws an integer overflow error since there is no
+          ** equivalent positive 64-bit two complement value. */
+          sqlite3_result_error(context, "integer overflow", -1);
+          return;
+        }
+        iVal = -iVal;
+      }
+      sqlite3_result_int64(context, iVal);
+      break;
+    }
+    case SQLITE_NULL: {
+      /* IMP: R-37434-19929 Abs(X) returns NULL if X is NULL. */
+      sqlite3_result_null(context);
+      break;
+    }
+    default: {
+      /* Because sqlite3_value_double() returns 0.0 if the argument is not
+      ** something that can be converted into a number, we have:
+      ** IMP: R-01992-00519 Abs(X) returns 0.0 if X is a string or blob
+      ** that cannot be converted to a numeric value.
+      */
+      double rVal = sqlite3_value_double(argv[0]);
+      if( rVal<0 ) rVal = -rVal;
+      sqlite3_result_double(context, rVal);
+      break;
+    }
+  }
+}
+
+/*
+** Implementation of the instr() function.
+**
+** instr(haystack,needle) finds the first occurrence of needle
+** in haystack and returns the number of previous characters plus 1,
+** or 0 if needle does not occur within haystack.
+**
+** If both haystack and needle are BLOBs, then the result is one more than
+** the number of bytes in haystack prior to the first occurrence of needle,
+** or 0 if needle never occurs in haystack.
+*/
+static void instrFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *zHaystack;
+  const unsigned char *zNeedle;
+  int nHaystack;
+  int nNeedle;
+  int typeHaystack, typeNeedle;
+  int N = 1;
+  int isText;
+  unsigned char firstChar;
+  sqlite3_value *pC1 = 0;
+  sqlite3_value *pC2 = 0;
+
+  UNUSED_PARAMETER(argc);
+  typeHaystack = sqlite3_value_type(argv[0]);
+  typeNeedle = sqlite3_value_type(argv[1]);
+  if( typeHaystack==SQLITE_NULL || typeNeedle==SQLITE_NULL ) return;
+  nHaystack = sqlite3_value_bytes(argv[0]);
+  nNeedle = sqlite3_value_bytes(argv[1]);
+  if( nNeedle>0 ){
+    if( typeHaystack==SQLITE_BLOB && typeNeedle==SQLITE_BLOB ){
+      zHaystack = sqlite3_value_blob(argv[0]);
+      zNeedle = sqlite3_value_blob(argv[1]);
+      isText = 0;
+    }else if( typeHaystack!=SQLITE_BLOB && typeNeedle!=SQLITE_BLOB ){
+      zHaystack = sqlite3_value_text(argv[0]);
+      zNeedle = sqlite3_value_text(argv[1]);
+      isText = 1;
+    }else{
+      pC1 = sqlite3_value_dup(argv[0]);
+      zHaystack = sqlite3_value_text(pC1);
+      if( zHaystack==0 ) goto endInstrOOM;
+      nHaystack = sqlite3_value_bytes(pC1);
+      pC2 = sqlite3_value_dup(argv[1]);
+      zNeedle = sqlite3_value_text(pC2);
+      if( zNeedle==0 ) goto endInstrOOM;
+      nNeedle = sqlite3_value_bytes(pC2);
+      isText = 1;
+    }
+    if( zNeedle==0 || (nHaystack && zHaystack==0) ) goto endInstrOOM;
+    firstChar = zNeedle[0];
+    while( nNeedle<=nHaystack
+       && (zHaystack[0]!=firstChar || memcmp(zHaystack, zNeedle, nNeedle)!=0)
+    ){
+      N++;
+      do{
+        nHaystack--;
+        zHaystack++;
+      }while( isText && (zHaystack[0]&0xc0)==0x80 );
+    }
+    if( nNeedle>nHaystack ) N = 0;
+  }
+  sqlite3_result_int(context, N);
+endInstr:
+  sqlite3_value_free(pC1);
+  sqlite3_value_free(pC2);
+  return;
+endInstrOOM:
+  sqlite3_result_error_nomem(context);
+  goto endInstr;
+}
+
+/*
+** Implementation of the printf() (a.k.a. format()) SQL function.
+*/
+static void printfFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  PrintfArguments x;
+  StrAccum str;
+  const char *zFormat;
+  int n;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+
+  if( argc>=1 && (zFormat = (const char*)sqlite3_value_text(argv[0]))!=0 ){
+    x.nArg = argc-1;
+    x.nUsed = 0;
+    x.apArg = argv+1;
+    sqlite3StrAccumInit(&str, db, 0, 0, db->aLimit[SQLITE_LIMIT_LENGTH]);
+    str.printfFlags = SQLITE_PRINTF_SQLFUNC;
+    sqlite3_str_appendf(&str, zFormat, &x);
+    n = str.nChar;
+    sqlite3_result_text(context, sqlite3StrAccumFinish(&str), n,
+                        SQLITE_DYNAMIC);
+  }
+}
+
+/*
+** Implementation of the substr() function.
+**
+** substr(x,p1,p2)  returns p2 characters of x[] beginning with p1.
+** p1 is 1-indexed.  So substr(x,1,1) returns the first character
+** of x.  If x is text, then we actually count UTF-8 characters.
+** If x is a blob, then we count bytes.
+**
+** If p1 is negative, then we begin abs(p1) from the end of x[].
+**
+** If p2 is negative, return the p2 characters preceding p1.
+*/
+static void substrFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *z;
+  const unsigned char *z2;
+  int len;
+  int p0type;
+  i64 p1, p2;
+  int negP2 = 0;
+
+  assert( argc==3 || argc==2 );
+  if( sqlite3_value_type(argv[1])==SQLITE_NULL
+   || (argc==3 && sqlite3_value_type(argv[2])==SQLITE_NULL)
+  ){
+    return;
+  }
+  p0type = sqlite3_value_type(argv[0]);
+  p1 = sqlite3_value_int(argv[1]);
+  if( p0type==SQLITE_BLOB ){
+    len = sqlite3_value_bytes(argv[0]);
+    z = sqlite3_value_blob(argv[0]);
+    if( z==0 ) return;
+    assert( len==sqlite3_value_bytes(argv[0]) );
+  }else{
+    z = sqlite3_value_text(argv[0]);
+    if( z==0 ) return;
+    len = 0;
+    if( p1<0 ){
+      for(z2=z; *z2; len++){
+        SQLITE_SKIP_UTF8(z2);
+      }
+    }
+  }
+#ifdef SQLITE_SUBSTR_COMPATIBILITY
+  /* If SUBSTR_COMPATIBILITY is defined then substr(X,0,N) work the same as
+  ** as substr(X,1,N) - it returns the first N characters of X.  This
+  ** is essentially a back-out of the bug-fix in check-in [5fc125d362df4b8]
+  ** from 2009-02-02 for compatibility of applications that exploited the
+  ** old buggy behavior. */
+  if( p1==0 ) p1 = 1; /* <rdar://problem/6778339> */
+#endif
+  if( argc==3 ){
+    p2 = sqlite3_value_int(argv[2]);
+    if( p2<0 ){
+      p2 = -p2;
+      negP2 = 1;
+    }
+  }else{
+    p2 = sqlite3_context_db_handle(context)->aLimit[SQLITE_LIMIT_LENGTH];
+  }
+  if( p1<0 ){
+    p1 += len;
+    if( p1<0 ){
+      p2 += p1;
+      if( p2<0 ) p2 = 0;
+      p1 = 0;
+    }
+  }else if( p1>0 ){
+    p1--;
+  }else if( p2>0 ){
+    p2--;
+  }
+  if( negP2 ){
+    p1 -= p2;
+    if( p1<0 ){
+      p2 += p1;
+      p1 = 0;
+    }
+  }
+  assert( p1>=0 && p2>=0 );
+  if( p0type!=SQLITE_BLOB ){
+    while( *z && p1 ){
+      SQLITE_SKIP_UTF8(z);
+      p1--;
+    }
+    for(z2=z; *z2 && p2; p2--){
+      SQLITE_SKIP_UTF8(z2);
+    }
+    sqlite3_result_text64(context, (char*)z, z2-z, SQLITE_TRANSIENT,
+                          SQLITE_UTF8);
+  }else{
+    if( p1+p2>len ){
+      p2 = len-p1;
+      if( p2<0 ) p2 = 0;
+    }
+    sqlite3_result_blob64(context, (char*)&z[p1], (u64)p2, SQLITE_TRANSIENT);
+  }
+}
+
+/*
+** Implementation of the round() function
+*/
+#ifndef SQLITE_OMIT_FLOATING_POINT
+static void roundFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  int n = 0;
+  double r;
+  char *zBuf;
+  assert( argc==1 || argc==2 );
+  if( argc==2 ){
+    if( SQLITE_NULL==sqlite3_value_type(argv[1]) ) return;
+    n = sqlite3_value_int(argv[1]);
+    if( n>30 ) n = 30;
+    if( n<0 ) n = 0;
+  }
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  r = sqlite3_value_double(argv[0]);
+  /* If Y==0 and X will fit in a 64-bit int,
+  ** handle the rounding directly,
+  ** otherwise use printf.
+  */
+  if( r<-4503599627370496.0 || r>+4503599627370496.0 ){
+    /* The value has no fractional part so there is nothing to round */
+  }else if( n==0 ){ 
+    r = (double)((sqlite_int64)(r+(r<0?-0.5:+0.5)));
+  }else{
+    zBuf = sqlite3_mprintf("%!.*f",n,r);
+    if( zBuf==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }
+    sqlite3AtoF(zBuf, &r, sqlite3Strlen30(zBuf), SQLITE_UTF8);
+    sqlite3_free(zBuf);
+  }
+  sqlite3_result_double(context, r);
+}
+#endif
+
+/*
+** Allocate nByte bytes of space using sqlite3Malloc(). If the
+** allocation fails, call sqlite3_result_error_nomem() to notify
+** the database handle that malloc() has failed and return NULL.
+** If nByte is larger than the maximum string or blob length, then
+** raise an SQLITE_TOOBIG exception and return NULL.
+*/
+static void *contextMalloc(sqlite3_context *context, i64 nByte){
+  char *z;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  assert( nByte>0 );
+  testcase( nByte==db->aLimit[SQLITE_LIMIT_LENGTH] );
+  testcase( nByte==db->aLimit[SQLITE_LIMIT_LENGTH]+1 );
+  if( nByte>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    sqlite3_result_error_toobig(context);
+    z = 0;
+  }else{
+    z = sqlite3Malloc(nByte);
+    if( !z ){
+      sqlite3_result_error_nomem(context);
+    }
+  }
+  return z;
+}
+
+/*
+** Implementation of the upper() and lower() SQL functions.
+*/
+static void upperFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  char *z1;
+  const char *z2;
+  int i, n;
+  UNUSED_PARAMETER(argc);
+  z2 = (char*)sqlite3_value_text(argv[0]);
+  n = sqlite3_value_bytes(argv[0]);
+  /* Verify that the call to _bytes() does not invalidate the _text() pointer */
+  assert( z2==(char*)sqlite3_value_text(argv[0]) );
+  if( z2 ){
+    z1 = contextMalloc(context, ((i64)n)+1);
+    if( z1 ){
+      for(i=0; i<n; i++){
+        z1[i] = (char)sqlite3Toupper(z2[i]);
+      }
+      sqlite3_result_text(context, z1, n, sqlite3_free);
+    }
+  }
+}
+static void lowerFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  char *z1;
+  const char *z2;
+  int i, n;
+  UNUSED_PARAMETER(argc);
+  z2 = (char*)sqlite3_value_text(argv[0]);
+  n = sqlite3_value_bytes(argv[0]);
+  /* Verify that the call to _bytes() does not invalidate the _text() pointer */
+  assert( z2==(char*)sqlite3_value_text(argv[0]) );
+  if( z2 ){
+    z1 = contextMalloc(context, ((i64)n)+1);
+    if( z1 ){
+      for(i=0; i<n; i++){
+        z1[i] = sqlite3Tolower(z2[i]);
+      }
+      sqlite3_result_text(context, z1, n, sqlite3_free);
+    }
+  }
+}
+
+/*
+** Some functions like COALESCE() and IFNULL() and UNLIKELY() are implemented
+** as VDBE code so that unused argument values do not have to be computed.
+** However, we still need some kind of function implementation for this
+** routines in the function table.  The noopFunc macro provides this.
+** noopFunc will never be called so it doesn't matter what the implementation
+** is.  We might as well use the "version()" function as a substitute.
+*/
+#define noopFunc versionFunc   /* Substitute function - never called */
+
+/*
+** Implementation of random().  Return a random integer. 
+*/
+static void randomFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  sqlite_int64 r;
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  sqlite3_randomness(sizeof(r), &r);
+  if( r<0 ){
+    /* We need to prevent a random number of 0x8000000000000000
+    ** (or -9223372036854775808) since when you do abs() of that
+    ** number of you get the same value back again.  To do this
+    ** in a way that is testable, mask the sign bit off of negative
+    ** values, resulting in a positive value.  Then take the
+    ** 2s complement of that positive value.  The end result can
+    ** therefore be no less than -9223372036854775807.
+    */
+    r = -(r & LARGEST_INT64);
+  }
+  sqlite3_result_int64(context, r);
+}
+
+/*
+** Implementation of randomblob(N).  Return a random blob
+** that is N bytes long.
+*/
+static void randomBlob(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_int64 n;
+  unsigned char *p;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  n = sqlite3_value_int64(argv[0]);
+  if( n<1 ){
+    n = 1;
+  }
+  p = contextMalloc(context, n);
+  if( p ){
+    sqlite3_randomness(n, p);
+    sqlite3_result_blob(context, (char*)p, n, sqlite3_free);
+  }
+}
+
+/*
+** Implementation of the last_insert_rowid() SQL function.  The return
+** value is the same as the sqlite3_last_insert_rowid() API function.
+*/
+static void last_insert_rowid(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-51513-12026 The last_insert_rowid() SQL function is a
+  ** wrapper around the sqlite3_last_insert_rowid() C/C++ interface
+  ** function. */
+  sqlite3_result_int64(context, sqlite3_last_insert_rowid(db));
+}
+
+/*
+** Implementation of the changes() SQL function.
+**
+** IMP: R-32760-32347 The changes() SQL function is a wrapper
+** around the sqlite3_changes64() C/C++ function and hence follows the
+** same rules for counting changes.
+*/
+static void changes(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  sqlite3_result_int64(context, sqlite3_changes64(db));
+}
+
+/*
+** Implementation of the total_changes() SQL function.  The return value is
+** the same as the sqlite3_total_changes64() API function.
+*/
+static void total_changes(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-11217-42568 This function is a wrapper around the
+  ** sqlite3_total_changes64() C/C++ interface. */
+  sqlite3_result_int64(context, sqlite3_total_changes64(db));
+}
+
+/*
+** A structure defining how to do GLOB-style comparisons.
+*/
+struct compareInfo {
+  u8 matchAll;          /* "*" or "%" */
+  u8 matchOne;          /* "?" or "_" */
+  u8 matchSet;          /* "[" or 0 */
+  u8 noCase;            /* true to ignore case differences */
+};
+
+/*
+** For LIKE and GLOB matching on EBCDIC machines, assume that every
+** character is exactly one byte in size.  Also, provide the Utf8Read()
+** macro for fast reading of the next character in the common case where
+** the next character is ASCII.
+*/
+#if defined(SQLITE_EBCDIC)
+# define sqlite3Utf8Read(A)        (*((*A)++))
+# define Utf8Read(A)               (*(A++))
+#else
+# define Utf8Read(A)               (A[0]<0x80?*(A++):sqlite3Utf8Read(&A))
+#endif
+
+static const struct compareInfo globInfo = { '*', '?', '[', 0 };
+/* The correct SQL-92 behavior is for the LIKE operator to ignore
+** case.  Thus  'a' LIKE 'A' would be true. */
+static const struct compareInfo likeInfoNorm = { '%', '_',   0, 1 };
+/* If SQLITE_CASE_SENSITIVE_LIKE is defined, then the LIKE operator
+** is case sensitive causing 'a' LIKE 'A' to be false */
+static const struct compareInfo likeInfoAlt = { '%', '_',   0, 0 };
+
+/*
+** Possible error returns from patternMatch()
+*/
+#define SQLITE_MATCH             0
+#define SQLITE_NOMATCH           1
+#define SQLITE_NOWILDCARDMATCH   2
+
+/*
+** Compare two UTF-8 strings for equality where the first string is
+** a GLOB or LIKE expression.  Return values:
+**
+**    SQLITE_MATCH:            Match
+**    SQLITE_NOMATCH:          No match
+**    SQLITE_NOWILDCARDMATCH:  No match in spite of having * or % wildcards.
+**
+** Globbing rules:
+**
+**      '*'       Matches any sequence of zero or more characters.
+**
+**      '?'       Matches exactly one character.
+**
+**     [...]      Matches one character from the enclosed list of
+**                characters.
+**
+**     [^...]     Matches one character not in the enclosed list.
+**
+** With the [...] and [^...] matching, a ']' character can be included
+** in the list by making it the first character after '[' or '^'.  A
+** range of characters can be specified using '-'.  Example:
+** "[a-z]" matches any single lower-case letter.  To match a '-', make
+** it the last character in the list.
+**
+** Like matching rules:
+**
+**      '%'       Matches any sequence of zero or more characters
+**
+***     '_'       Matches any one character
+**
+**      Ec        Where E is the "esc" character and c is any other
+**                character, including '%', '_', and esc, match exactly c.
+**
+** The comments within this routine usually assume glob matching.
+**
+** This routine is usually quick, but can be N**2 in the worst case.
+*/
+static int patternCompare(
+  const u8 *zPattern,              /* The glob pattern */
+  const u8 *zString,               /* The string to compare against the glob */
+  const struct compareInfo *pInfo, /* Information about how to do the compare */
+  u32 matchOther                   /* The escape char (LIKE) or '[' (GLOB) */
+){
+  u32 c, c2;                       /* Next pattern and input string chars */
+  u32 matchOne = pInfo->matchOne;  /* "?" or "_" */
+  u32 matchAll = pInfo->matchAll;  /* "*" or "%" */
+  u8 noCase = pInfo->noCase;       /* True if uppercase==lowercase */
+  const u8 *zEscaped = 0;          /* One past the last escaped input char */
+ 
+  while( (c = Utf8Read(zPattern))!=0 ){
+    if( c==matchAll ){  /* Match "*" */
+      /* Skip over multiple "*" characters in the pattern.  If there
+      ** are also "?" characters, skip those as well, but consume a
+      ** single character of the input string for each "?" skipped */
+      while( (c=Utf8Read(zPattern)) == matchAll
+             || (c == matchOne && matchOne!=0) ){
+        if( c==matchOne && sqlite3Utf8Read(&zString)==0 ){
+          return SQLITE_NOWILDCARDMATCH;
+        }
+      }
+      if( c==0 ){
+        return SQLITE_MATCH;   /* "*" at the end of the pattern matches */
+      }else if( c==matchOther ){
+        if( pInfo->matchSet==0 ){
+          c = sqlite3Utf8Read(&zPattern);
+          if( c==0 ) return SQLITE_NOWILDCARDMATCH;
+        }else{
+          /* "[...]" immediately follows the "*".  We have to do a slow
+          ** recursive search in this case, but it is an unusual case. */
+          assert( matchOther<0x80 );  /* '[' is a single-byte character */
+          while( *zString ){
+            int bMatch = patternCompare(&zPattern[-1],zString,pInfo,matchOther);
+            if( bMatch!=SQLITE_NOMATCH ) return bMatch;
+            SQLITE_SKIP_UTF8(zString);
+          }
+          return SQLITE_NOWILDCARDMATCH;
+        }
+      }
+
+      /* At this point variable c contains the first character of the
+      ** pattern string past the "*".  Search in the input string for the
+      ** first matching character and recursively continue the match from
+      ** that point.
+      **
+      ** For a case-insensitive search, set variable cx to be the same as
+      ** c but in the other case and search the input string for either
+      ** c or cx.
+      */
+      if( c<0x80 ){
+        char zStop[3];
+        int bMatch;
+        if( noCase ){
+          zStop[0] = sqlite3Toupper(c);
+          zStop[1] = sqlite3Tolower(c);
+          zStop[2] = 0;
+        }else{
+          zStop[0] = c;
+          zStop[1] = 0;
+        }
+        while(1){
+          zString += strcspn((const char*)zString, zStop);
+          if( zString[0]==0 ) break;
+          zString++;
+          bMatch = patternCompare(zPattern,zString,pInfo,matchOther);
+          if( bMatch!=SQLITE_NOMATCH ) return bMatch;
+        }
+      }else{
+        int bMatch;
+        while( (c2 = Utf8Read(zString))!=0 ){
+          if( c2!=c ) continue;
+          bMatch = patternCompare(zPattern,zString,pInfo,matchOther);
+          if( bMatch!=SQLITE_NOMATCH ) return bMatch;
+        }
+      }
+      return SQLITE_NOWILDCARDMATCH;
+    }
+    if( c==matchOther ){
+      if( pInfo->matchSet==0 ){
+        c = sqlite3Utf8Read(&zPattern);
+        if( c==0 ) return SQLITE_NOMATCH;
+        zEscaped = zPattern;
+      }else{
+        u32 prior_c = 0;
+        int seen = 0;
+        int invert = 0;
+        c = sqlite3Utf8Read(&zString);
+        if( c==0 ) return SQLITE_NOMATCH;
+        c2 = sqlite3Utf8Read(&zPattern);
+        if( c2=='^' ){
+          invert = 1;
+          c2 = sqlite3Utf8Read(&zPattern);
+        }
+        if( c2==']' ){
+          if( c==']' ) seen = 1;
+          c2 = sqlite3Utf8Read(&zPattern);
+        }
+        while( c2 && c2!=']' ){
+          if( c2=='-' && zPattern[0]!=']' && zPattern[0]!=0 && prior_c>0 ){
+            c2 = sqlite3Utf8Read(&zPattern);
+            if( c>=prior_c && c<=c2 ) seen = 1;
+            prior_c = 0;
+          }else{
+            if( c==c2 ){
+              seen = 1;
+            }
+            prior_c = c2;
+          }
+          c2 = sqlite3Utf8Read(&zPattern);
+        }
+        if( c2==0 || (seen ^ invert)==0 ){
+          return SQLITE_NOMATCH;
+        }
+        continue;
+      }
+    }
+    c2 = Utf8Read(zString);
+    if( c==c2 ) continue;
+    if( noCase  && sqlite3Tolower(c)==sqlite3Tolower(c2) && c<0x80 && c2<0x80 ){
+      continue;
+    }
+    if( c==matchOne && zPattern!=zEscaped && c2!=0 ) continue;
+    return SQLITE_NOMATCH;
+  }
+  return *zString==0 ? SQLITE_MATCH : SQLITE_NOMATCH;
+}
+
+/*
+** The sqlite3_strglob() interface.  Return 0 on a match (like strcmp()) and
+** non-zero if there is no match.
+*/
+int sqlite3_strglob(const char *zGlobPattern, const char *zString){
+  if( zString==0 ){
+    return zGlobPattern!=0;
+  }else if( zGlobPattern==0 ){
+    return 1;
+  }else {
+    return patternCompare((u8*)zGlobPattern, (u8*)zString, &globInfo, '[');
+  }
+}
+
+/*
+** The sqlite3_strlike() interface.  Return 0 on a match and non-zero for
+** a miss - like strcmp().
+*/
+int sqlite3_strlike(const char *zPattern, const char *zStr, unsigned int esc){
+  if( zStr==0 ){
+    return zPattern!=0;
+  }else if( zPattern==0 ){
+    return 1;
+  }else{
+    return patternCompare((u8*)zPattern, (u8*)zStr, &likeInfoNorm, esc);
+  }
+}
+
+/*
+** Count the number of times that the LIKE operator (or GLOB which is
+** just a variation of LIKE) gets called.  This is used for testing
+** only.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_like_count = 0;
+#endif
+
+
+/*
+** Implementation of the like() SQL function.  This function implements
+** the built-in LIKE operator.  The first argument to the function is the
+** pattern and the second argument is the string.  So, the SQL statements:
+**
+**       A LIKE B
+**
+** is implemented as like(B,A).
+**
+** This same function (with a different compareInfo structure) computes
+** the GLOB operator.
+*/
+static void likeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *zA, *zB;
+  u32 escape;
+  int nPat;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  struct compareInfo *pInfo = sqlite3_user_data(context);
+  struct compareInfo backupInfo;
+
+#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+  if( sqlite3_value_type(argv[0])==SQLITE_BLOB
+   || sqlite3_value_type(argv[1])==SQLITE_BLOB
+  ){
+#ifdef SQLITE_TEST
+    sqlite3_like_count++;
+#endif
+    sqlite3_result_int(context, 0);
+    return;
+  }
+#endif
+
+  /* Limit the length of the LIKE or GLOB pattern to avoid problems
+  ** of deep recursion and N*N behavior in patternCompare().
+  */
+  nPat = sqlite3_value_bytes(argv[0]);
+  testcase( nPat==db->aLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH] );
+  testcase( nPat==db->aLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]+1 );
+  if( nPat > db->aLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH] ){
+    sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
+    return;
+  }
+  if( argc==3 ){
+    /* The escape character string must consist of a single UTF-8 character.
+    ** Otherwise, return an error.
+    */
+    const unsigned char *zEsc = sqlite3_value_text(argv[2]);
+    if( zEsc==0 ) return;
+    if( sqlite3Utf8CharLen((char*)zEsc, -1)!=1 ){
+      sqlite3_result_error(context,
+          "ESCAPE expression must be a single character", -1);
+      return;
+    }
+    escape = sqlite3Utf8Read(&zEsc);
+    if( escape==pInfo->matchAll || escape==pInfo->matchOne ){
+      memcpy(&backupInfo, pInfo, sizeof(backupInfo));
+      pInfo = &backupInfo;
+      if( escape==pInfo->matchAll ) pInfo->matchAll = 0;
+      if( escape==pInfo->matchOne ) pInfo->matchOne = 0;
+    }
+  }else{
+    escape = pInfo->matchSet;
+  }
+  zB = sqlite3_value_text(argv[0]);
+  zA = sqlite3_value_text(argv[1]);
+  if( zA && zB ){
+#ifdef SQLITE_TEST
+    sqlite3_like_count++;
+#endif
+    sqlite3_result_int(context,
+                      patternCompare(zB, zA, pInfo, escape)==SQLITE_MATCH);
+  }
+}
+
+/*
+** Implementation of the NULLIF(x,y) function.  The result is the first
+** argument if the arguments are different.  The result is NULL if the
+** arguments are equal to each other.
+*/
+static void nullifFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  CollSeq *pColl = sqlite3GetFuncCollSeq(context);
+  UNUSED_PARAMETER(NotUsed);
+  if( sqlite3MemCompare(argv[0], argv[1], pColl)!=0 ){
+    sqlite3_result_value(context, argv[0]);
+  }
+}
+
+/*
+** Implementation of the sqlite_version() function.  The result is the version
+** of the SQLite library that is running.
+*/
+static void versionFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-48699-48617 This function is an SQL wrapper around the
+  ** sqlite3_libversion() C-interface. */
+  sqlite3_result_text(context, sqlite3_libversion(), -1, SQLITE_STATIC);
+}
+
+/*
+** Implementation of the sqlite_source_id() function. The result is a string
+** that identifies the particular version of the source code used to build
+** SQLite.
+*/
+static void sourceidFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-24470-31136 This function is an SQL wrapper around the
+  ** sqlite3_sourceid() C interface. */
+  sqlite3_result_text(context, sqlite3_sourceid(), -1, SQLITE_STATIC);
+}
+
+/*
+** Implementation of the sqlite_log() function.  This is a wrapper around
+** sqlite3_log().  The return value is NULL.  The function exists purely for
+** its side-effects.
+*/
+static void errlogFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(context);
+  sqlite3_log(sqlite3_value_int(argv[0]), "%s", sqlite3_value_text(argv[1]));
+}
+
+/*
+** Implementation of the sqlite_compileoption_used() function.
+** The result is an integer that identifies if the compiler option
+** was used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptionusedFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zOptName;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-39564-36305 The sqlite_compileoption_used() SQL
+  ** function is a wrapper around the sqlite3_compileoption_used() C/C++
+  ** function.
+  */
+  if( (zOptName = (const char*)sqlite3_value_text(argv[0]))!=0 ){
+    sqlite3_result_int(context, sqlite3_compileoption_used(zOptName));
+  }
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/*
+** Implementation of the sqlite_compileoption_get() function.
+** The result is a string that identifies the compiler options
+** used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptiongetFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int n;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-04922-24076 The sqlite_compileoption_get() SQL function
+  ** is a wrapper around the sqlite3_compileoption_get() C/C++ function.
+  */
+  n = sqlite3_value_int(argv[0]);
+  sqlite3_result_text(context, sqlite3_compileoption_get(n), -1, SQLITE_STATIC);
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/* Array for converting from half-bytes (nybbles) into ASCII hex
+** digits. */
+static const char hexdigits[] = {
+  '0', '1', '2', '3', '4', '5', '6', '7',
+  '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
+};
+
+/*
+** Append to pStr text that is the SQL literal representation of the
+** value contained in pValue.
+*/
+void sqlite3QuoteValue(StrAccum *pStr, sqlite3_value *pValue){
+  /* As currently implemented, the string must be initially empty.
+  ** we might relax this requirement in the future, but that will
+  ** require enhancements to the implementation. */
+  assert( pStr!=0 && pStr->nChar==0 );
+
+  switch( sqlite3_value_type(pValue) ){
+    case SQLITE_FLOAT: {
+      double r1, r2;
+      const char *zVal;
+      r1 = sqlite3_value_double(pValue);
+      sqlite3_str_appendf(pStr, "%!.15g", r1);
+      zVal = sqlite3_str_value(pStr);
+      if( zVal ){
+        sqlite3AtoF(zVal, &r2, pStr->nChar, SQLITE_UTF8);
+        if( r1!=r2 ){
+          sqlite3_str_reset(pStr);
+          sqlite3_str_appendf(pStr, "%!.20e", r1);
+        }
+      }
+      break;
+    }
+    case SQLITE_INTEGER: {
+      sqlite3_str_appendf(pStr, "%lld", sqlite3_value_int64(pValue));
+      break;
+    }
+    case SQLITE_BLOB: {
+      char const *zBlob = sqlite3_value_blob(pValue);
+      i64 nBlob = sqlite3_value_bytes(pValue);
+      assert( zBlob==sqlite3_value_blob(pValue) ); /* No encoding change */
+      sqlite3StrAccumEnlarge(pStr, nBlob*2 + 4);
+      if( pStr->accError==0 ){
+        char *zText = pStr->zText;
+        int i;
+        for(i=0; i<nBlob; i++){
+          zText[(i*2)+2] = hexdigits[(zBlob[i]>>4)&0x0F];
+          zText[(i*2)+3] = hexdigits[(zBlob[i])&0x0F];
+        }
+        zText[(nBlob*2)+2] = '\'';
+        zText[(nBlob*2)+3] = '\0';
+        zText[0] = 'X';
+        zText[1] = '\'';
+        pStr->nChar = nBlob*2 + 3;
+      }
+      break;
+    }
+    case SQLITE_TEXT: {
+      const unsigned char *zArg = sqlite3_value_text(pValue);
+      sqlite3_str_appendf(pStr, "%Q", zArg);
+      break;
+    }
+    default: {
+      assert( sqlite3_value_type(pValue)==SQLITE_NULL );
+      sqlite3_str_append(pStr, "NULL", 4);
+      break;
+    }
+  }
+}
+
+/*
+** Implementation of the QUOTE() function. 
+**
+** The quote(X) function returns the text of an SQL literal which is the
+** value of its argument suitable for inclusion into an SQL statement.
+** Strings are surrounded by single-quotes with escapes on interior quotes
+** as needed. BLOBs are encoded as hexadecimal literals. Strings with
+** embedded NUL characters cannot be represented as string literals in SQL
+** and hence the returned string literal is truncated prior to the first NUL.
+*/
+static void quoteFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  sqlite3_str str;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  sqlite3StrAccumInit(&str, db, 0, 0, db->aLimit[SQLITE_LIMIT_LENGTH]);
+  sqlite3QuoteValue(&str,argv[0]);
+  sqlite3_result_text(context, sqlite3StrAccumFinish(&str), str.nChar,
+                      SQLITE_DYNAMIC);
+  if( str.accError!=SQLITE_OK ){
+    sqlite3_result_null(context);
+    sqlite3_result_error_code(context, str.accError);
+  }
+}
+
+/*
+** The unicode() function.  Return the integer unicode code-point value
+** for the first character of the input string.
+*/
+static void unicodeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *z = sqlite3_value_text(argv[0]);
+  (void)argc;
+  if( z && z[0] ) sqlite3_result_int(context, sqlite3Utf8Read(&z));
+}
+
+/*
+** The char() function takes zero or more arguments, each of which is
+** an integer.  It constructs a string where each character of the string
+** is the unicode character for the corresponding integer argument.
+*/
+static void charFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  unsigned char *z, *zOut;
+  int i;
+  zOut = z = sqlite3_malloc64( argc*4+1 );
+  if( z==0 ){
+    sqlite3_result_error_nomem(context);
+    return;
+  }
+  for(i=0; i<argc; i++){
+    sqlite3_int64 x;
+    unsigned c;
+    x = sqlite3_value_int64(argv[i]);
+    if( x<0 || x>0x10ffff ) x = 0xfffd;
+    c = (unsigned)(x & 0x1fffff);
+    if( c<0x00080 ){
+      *zOut++ = (u8)(c&0xFF);
+    }else if( c<0x00800 ){
+      *zOut++ = 0xC0 + (u8)((c>>6)&0x1F);
+      *zOut++ = 0x80 + (u8)(c & 0x3F);
+    }else if( c<0x10000 ){
+      *zOut++ = 0xE0 + (u8)((c>>12)&0x0F);
+      *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);
+      *zOut++ = 0x80 + (u8)(c & 0x3F);
+    }else{
+      *zOut++ = 0xF0 + (u8)((c>>18) & 0x07);
+      *zOut++ = 0x80 + (u8)((c>>12) & 0x3F);
+      *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);
+      *zOut++ = 0x80 + (u8)(c & 0x3F);
+    }                                                    \
+  }
+  *zOut = 0;
+  sqlite3_result_text64(context, (char*)z, zOut-z, sqlite3_free, SQLITE_UTF8);
+}
+
+/*
+** The hex() function.  Interpret the argument as a blob.  Return
+** a hexadecimal rendering as text.
+*/
+static void hexFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i, n;
+  const unsigned char *pBlob;
+  char *zHex, *z;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  pBlob = sqlite3_value_blob(argv[0]);
+  n = sqlite3_value_bytes(argv[0]);
+  assert( pBlob==sqlite3_value_blob(argv[0]) );  /* No encoding change */
+  z = zHex = contextMalloc(context, ((i64)n)*2 + 1);
+  if( zHex ){
+    for(i=0; i<n; i++, pBlob++){
+      unsigned char c = *pBlob;
+      *(z++) = hexdigits[(c>>4)&0xf];
+      *(z++) = hexdigits[c&0xf];
+    }
+    *z = 0;
+    sqlite3_result_text64(context, zHex, (u64)(z-zHex),
+                          sqlite3_free, SQLITE_UTF8);
+  }
+}
+
+/*
+** Buffer zStr contains nStr bytes of utf-8 encoded text. Return 1 if zStr
+** contains character ch, or 0 if it does not.
+*/
+static int strContainsChar(const u8 *zStr, int nStr, u32 ch){
+  const u8 *zEnd = &zStr[nStr];
+  const u8 *z = zStr;
+  while( z<zEnd ){
+    u32 tst = Utf8Read(z);
+    if( tst==ch ) return 1;
+  }
+  return 0;
+}
+
+/*
+** The unhex() function. This function may be invoked with either one or
+** two arguments. In both cases the first argument is interpreted as text
+** a text value containing a set of pairs of hexadecimal digits which are
+** decoded and returned as a blob.
+**
+** If there is only a single argument, then it must consist only of an
+** even number of hexadecimal digits. Otherwise, return NULL.
+**
+** Or, if there is a second argument, then any character that appears in
+** the second argument is also allowed to appear between pairs of hexadecimal
+** digits in the first argument. If any other character appears in the
+** first argument, or if one of the allowed characters appears between
+** two hexadecimal digits that make up a single byte, NULL is returned.
+**
+** The following expressions are all true:
+**
+**     unhex('ABCD')       IS x'ABCD'
+**     unhex('AB CD')      IS NULL
+**     unhex('AB CD', ' ') IS x'ABCD'
+**     unhex('A BCD', ' ') IS NULL
+*/
+static void unhexFunc(
+  sqlite3_context *pCtx,
+  int argc,
+  sqlite3_value **argv
+){
+  const u8 *zPass = (const u8*)"";
+  int nPass = 0;
+  const u8 *zHex = sqlite3_value_text(argv[0]);
+  int nHex = sqlite3_value_bytes(argv[0]);
+#ifdef SQLITE_DEBUG
+  const u8 *zEnd = zHex ? &zHex[nHex] : 0;
+#endif
+  u8 *pBlob = 0;
+  u8 *p = 0;
+
+  assert( argc==1 || argc==2 );
+  if( argc==2 ){
+    zPass = sqlite3_value_text(argv[1]);
+    nPass = sqlite3_value_bytes(argv[1]);
+  }
+  if( !zHex || !zPass ) return;
+
+  p = pBlob = contextMalloc(pCtx, (nHex/2)+1);
+  if( pBlob ){
+    u8 c;                         /* Most significant digit of next byte */
+    u8 d;                         /* Least significant digit of next byte */
+
+    while( (c = *zHex)!=0x00 ){
+      while( !sqlite3Isxdigit(c) ){
+        u32 ch = Utf8Read(zHex);
+        assert( zHex<=zEnd );
+        if( !strContainsChar(zPass, nPass, ch) ) goto unhex_null;
+        c = *zHex;
+        if( c==0x00 ) goto unhex_done;
+      }
+      zHex++;
+      assert( *zEnd==0x00 );
+      assert( zHex<=zEnd );
+      d = *(zHex++);
+      if( !sqlite3Isxdigit(d) ) goto unhex_null;
+      *(p++) = (sqlite3HexToInt(c)<<4) | sqlite3HexToInt(d);
+    }
+  }
+
+ unhex_done:
+  sqlite3_result_blob(pCtx, pBlob, (p - pBlob), sqlite3_free);
+  return;
+
+ unhex_null:
+  sqlite3_free(pBlob);
+  return;
+}
+
+
+/*
+** The zeroblob(N) function returns a zero-filled blob of size N bytes.
+*/
+static void zeroblobFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  i64 n;
+  int rc;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  n = sqlite3_value_int64(argv[0]);
+  if( n<0 ) n = 0;
+  rc = sqlite3_result_zeroblob64(context, n); /* IMP: R-00293-64994 */
+  if( rc ){
+    sqlite3_result_error_code(context, rc);
+  }
+}
+
+/*
+** The replace() function.  Three arguments are all strings: call
+** them A, B, and C. The result is also a string which is derived
+** from A by replacing every occurrence of B with C.  The match
+** must be exact.  Collating sequences are not used.
+*/
+static void replaceFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *zStr;        /* The input string A */
+  const unsigned char *zPattern;    /* The pattern string B */
+  const unsigned char *zRep;        /* The replacement string C */
+  unsigned char *zOut;              /* The output */
+  int nStr;                /* Size of zStr */
+  int nPattern;            /* Size of zPattern */
+  int nRep;                /* Size of zRep */
+  i64 nOut;                /* Maximum size of zOut */
+  int loopLimit;           /* Last zStr[] that might match zPattern[] */
+  int i, j;                /* Loop counters */
+  unsigned cntExpand;      /* Number zOut expansions */
+  sqlite3 *db = sqlite3_context_db_handle(context);
+
+  assert( argc==3 );
+  UNUSED_PARAMETER(argc);
+  zStr = sqlite3_value_text(argv[0]);
+  if( zStr==0 ) return;
+  nStr = sqlite3_value_bytes(argv[0]);
+  assert( zStr==sqlite3_value_text(argv[0]) );  /* No encoding change */
+  zPattern = sqlite3_value_text(argv[1]);
+  if( zPattern==0 ){
+    assert( sqlite3_value_type(argv[1])==SQLITE_NULL
+            || sqlite3_context_db_handle(context)->mallocFailed );
+    return;
+  }
+  if( zPattern[0]==0 ){
+    assert( sqlite3_value_type(argv[1])!=SQLITE_NULL );
+    sqlite3_result_value(context, argv[0]);
+    return;
+  }
+  nPattern = sqlite3_value_bytes(argv[1]);
+  assert( zPattern==sqlite3_value_text(argv[1]) );  /* No encoding change */
+  zRep = sqlite3_value_text(argv[2]);
+  if( zRep==0 ) return;
+  nRep = sqlite3_value_bytes(argv[2]);
+  assert( zRep==sqlite3_value_text(argv[2]) );
+  nOut = nStr + 1;
+  assert( nOut<SQLITE_MAX_LENGTH );
+  zOut = contextMalloc(context, (i64)nOut);
+  if( zOut==0 ){
+    return;
+  }
+  loopLimit = nStr - nPattern; 
+  cntExpand = 0;
+  for(i=j=0; i<=loopLimit; i++){
+    if( zStr[i]!=zPattern[0] || memcmp(&zStr[i], zPattern, nPattern) ){
+      zOut[j++] = zStr[i];
+    }else{
+      if( nRep>nPattern ){
+        nOut += nRep - nPattern;
+        testcase( nOut-1==db->aLimit[SQLITE_LIMIT_LENGTH] );
+        testcase( nOut-2==db->aLimit[SQLITE_LIMIT_LENGTH] );
+        if( nOut-1>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+          sqlite3_result_error_toobig(context);
+          sqlite3_free(zOut);
+          return;
+        }
+        cntExpand++;
+        if( (cntExpand&(cntExpand-1))==0 ){
+          /* Grow the size of the output buffer only on substitutions
+          ** whose index is a power of two: 1, 2, 4, 8, 16, 32, ... */
+          u8 *zOld;
+          zOld = zOut;
+          zOut = sqlite3Realloc(zOut, (int)nOut + (nOut - nStr - 1));
+          if( zOut==0 ){
+            sqlite3_result_error_nomem(context);
+            sqlite3_free(zOld);
+            return;
+          }
+        }
+      }
+      memcpy(&zOut[j], zRep, nRep);
+      j += nRep;
+      i += nPattern-1;
+    }
+  }
+  assert( j+nStr-i+1<=nOut );
+  memcpy(&zOut[j], &zStr[i], nStr-i);
+  j += nStr - i;
+  assert( j<=nOut );
+  zOut[j] = 0;
+  sqlite3_result_text(context, (char*)zOut, j, sqlite3_free);
+}
+
+/*
+** Implementation of the TRIM(), LTRIM(), and RTRIM() functions.
+** The userdata is 0x1 for left trim, 0x2 for right trim, 0x3 for both.
+*/
+static void trimFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *zIn;         /* Input string */
+  const unsigned char *zCharSet;    /* Set of characters to trim */
+  unsigned int nIn;                 /* Number of bytes in input */
+  int flags;                        /* 1: trimleft  2: trimright  3: trim */
+  int i;                            /* Loop counter */
+  unsigned int *aLen = 0;           /* Length of each character in zCharSet */
+  unsigned char **azChar = 0;       /* Individual characters in zCharSet */
+  int nChar;                        /* Number of characters in zCharSet */
+
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ){
+    return;
+  }
+  zIn = sqlite3_value_text(argv[0]);
+  if( zIn==0 ) return;
+  nIn = (unsigned)sqlite3_value_bytes(argv[0]);
+  assert( zIn==sqlite3_value_text(argv[0]) );
+  if( argc==1 ){
+    static const unsigned lenOne[] = { 1 };
+    static unsigned char * const azOne[] = { (u8*)" " };
+    nChar = 1;
+    aLen = (unsigned*)lenOne;
+    azChar = (unsigned char **)azOne;
+    zCharSet = 0;
+  }else if( (zCharSet = sqlite3_value_text(argv[1]))==0 ){
+    return;
+  }else{
+    const unsigned char *z;
+    for(z=zCharSet, nChar=0; *z; nChar++){
+      SQLITE_SKIP_UTF8(z);
+    }
+    if( nChar>0 ){
+      azChar = contextMalloc(context,
+                     ((i64)nChar)*(sizeof(char*)+sizeof(unsigned)));
+      if( azChar==0 ){
+        return;
+      }
+      aLen = (unsigned*)&azChar[nChar];
+      for(z=zCharSet, nChar=0; *z; nChar++){
+        azChar[nChar] = (unsigned char *)z;
+        SQLITE_SKIP_UTF8(z);
+        aLen[nChar] = (unsigned)(z - azChar[nChar]);
+      }
+    }
+  }
+  if( nChar>0 ){
+    flags = SQLITE_PTR_TO_INT(sqlite3_user_data(context));
+    if( flags & 1 ){
+      while( nIn>0 ){
+        unsigned int len = 0;
+        for(i=0; i<nChar; i++){
+          len = aLen[i];
+          if( len<=nIn && memcmp(zIn, azChar[i], len)==0 ) break;
+        }
+        if( i>=nChar ) break;
+        zIn += len;
+        nIn -= len;
+      }
+    }
+    if( flags & 2 ){
+      while( nIn>0 ){
+        unsigned int len = 0;
+        for(i=0; i<nChar; i++){
+          len = aLen[i];
+          if( len<=nIn && memcmp(&zIn[nIn-len],azChar[i],len)==0 ) break;
+        }
+        if( i>=nChar ) break;
+        nIn -= len;
+      }
+    }
+    if( zCharSet ){
+      sqlite3_free(azChar);
+    }
+  }
+  sqlite3_result_text(context, (char*)zIn, nIn, SQLITE_TRANSIENT);
+}
+
+/* The core implementation of the CONCAT(...) and CONCAT_WS(SEP,...)
+** functions.
+**
+** Return a string value that is the concatenation of all non-null
+** entries in argv[].  Use zSep as the separator.
+*/
+static void concatFuncCore(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv,
+  int nSep,
+  const char *zSep
+){
+  i64 j, k, n = 0;
+  int i;
+  char *z;
+  for(i=0; i<argc; i++){
+    n += sqlite3_value_bytes(argv[i]);
+  }
+  n += (argc-1)*nSep;
+  z = sqlite3_malloc64(n+1);
+  if( z==0 ){
+    sqlite3_result_error_nomem(context);
+    return;
+  }
+  j = 0;
+  for(i=0; i<argc; i++){
+    k = sqlite3_value_bytes(argv[i]);
+    if( k>0 ){
+      const char *v = (const char*)sqlite3_value_text(argv[i]);
+      if( v!=0 ){
+        if( j>0 && nSep>0 ){
+          memcpy(&z[j], zSep, nSep);
+          j += nSep;
+        }
+        memcpy(&z[j], v, k);
+        j += k;
+      }
+    }
+  }
+  z[j] = 0;
+  assert( j<=n );
+  sqlite3_result_text64(context, z, j, sqlite3_free, SQLITE_UTF8);
+}
+
+/*
+** The CONCAT(...) function.  Generate a string result that is the
+** concatentation of all non-null arguments.
+*/
+static void concatFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  concatFuncCore(context, argc, argv, 0, "");
+}
+
+/*
+** The CONCAT_WS(separator, ...) function.
+**
+** Generate a string that is the concatenation of 2nd through the Nth
+** argument.  Use the first argument (which must be non-NULL) as the
+** separator.
+*/
+static void concatwsFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int nSep = sqlite3_value_bytes(argv[0]);
+  const char *zSep = (const char*)sqlite3_value_text(argv[0]);
+  if( zSep==0 ) return;
+  concatFuncCore(context, argc-1, argv+1, nSep, zSep);
+}
+
+
+#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
+/*
+** The "unknown" function is automatically substituted in place of
+** any unrecognized function name when doing an EXPLAIN or EXPLAIN QUERY PLAN
+** when the SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION compile-time option is used.
+** When the "sqlite3" command-line shell is built using this functionality,
+** that allows an EXPLAIN or EXPLAIN QUERY PLAN for complex queries
+** involving application-defined functions to be examined in a generic
+** sqlite3 shell.
+*/
+static void unknownFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  /* no-op */
+  (void)context;
+  (void)argc;
+  (void)argv;
+}
+#endif /*SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION*/
+
+
+/* IMP: R-25361-16150 This function is omitted from SQLite by default. It
+** is only available if the SQLITE_SOUNDEX compile-time option is used
+** when SQLite is built.
+*/
+#ifdef SQLITE_SOUNDEX
+/*
+** Compute the soundex encoding of a word.
+**
+** IMP: R-59782-00072 The soundex(X) function returns a string that is the
+** soundex encoding of the string X.
+*/
+static void soundexFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  char zResult[8];
+  const u8 *zIn;
+  int i, j;
+  static const unsigned char iCode[] = {
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 1, 2, 3, 0, 1, 2, 0, 0, 2, 2, 4, 5, 5, 0,
+    1, 2, 6, 2, 3, 0, 1, 0, 2, 0, 2, 0, 0, 0, 0, 0,
+    0, 0, 1, 2, 3, 0, 1, 2, 0, 0, 2, 2, 4, 5, 5, 0,
+    1, 2, 6, 2, 3, 0, 1, 0, 2, 0, 2, 0, 0, 0, 0, 0,
+  };
+  assert( argc==1 );
+  zIn = (u8*)sqlite3_value_text(argv[0]);
+  if( zIn==0 ) zIn = (u8*)"";
+  for(i=0; zIn[i] && !sqlite3Isalpha(zIn[i]); i++){}
+  if( zIn[i] ){
+    u8 prevcode = iCode[zIn[i]&0x7f];
+    zResult[0] = sqlite3Toupper(zIn[i]);
+    for(j=1; j<4 && zIn[i]; i++){
+      int code = iCode[zIn[i]&0x7f];
+      if( code>0 ){
+        if( code!=prevcode ){
+          prevcode = code;
+          zResult[j++] = code + '0';
+        }
+      }else{
+        prevcode = 0;
+      }
+    }
+    while( j<4 ){
+      zResult[j++] = '0';
+    }
+    zResult[j] = 0;
+    sqlite3_result_text(context, zResult, 4, SQLITE_TRANSIENT);
+  }else{
+    /* IMP: R-64894-50321 The string "?000" is returned if the argument
+    ** is NULL or contains no ASCII alphabetic characters. */
+    sqlite3_result_text(context, "?000", 4, SQLITE_STATIC);
+  }
+}
+#endif /* SQLITE_SOUNDEX */
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** A function that loads a shared-library extension then returns NULL.
+*/
+static void loadExt(sqlite3_context *context, int argc, sqlite3_value **argv){
+  const char *zFile = (const char *)sqlite3_value_text(argv[0]);
+  const char *zProc;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  char *zErrMsg = 0;
+
+  /* Disallow the load_extension() SQL function unless the SQLITE_LoadExtFunc
+  ** flag is set.  See the sqlite3_enable_load_extension() API.
+  */
+  if( (db->flags & SQLITE_LoadExtFunc)==0 ){
+    sqlite3_result_error(context, "not authorized", -1);
+    return;
+  }
+
+  if( argc==2 ){
+    zProc = (const char *)sqlite3_value_text(argv[1]);
+  }else{
+    zProc = 0;
+  }
+  if( zFile && sqlite3_load_extension(db, zFile, zProc, &zErrMsg) ){
+    sqlite3_result_error(context, zErrMsg, -1);
+    sqlite3_free(zErrMsg);
+  }
+}
+#endif
+
+
+/*
+** An instance of the following structure holds the context of a
+** sum() or avg() aggregate computation.
+*/
+typedef struct SumCtx SumCtx;
+struct SumCtx {
+  double rSum;      /* Running sum as as a double */
+  double rErr;      /* Error term for Kahan-Babushka-Neumaier summation */
+  i64 iSum;         /* Running sum as a signed integer */
+  i64 cnt;          /* Number of elements summed */
+  u8 approx;        /* True if any non-integer value was input to the sum */
+  u8 ovrfl;         /* Integer overflow seen */
+};
+
+/*
+** Do one step of the Kahan-Babushka-Neumaier summation.
+**
+** https://en.wikipedia.org/wiki/Kahan_summation_algorithm
+**
+** Variables are marked "volatile" to defeat c89 x86 floating point
+** optimizations can mess up this algorithm.
+*/
+static void kahanBabuskaNeumaierStep(
+  volatile SumCtx *pSum,
+  volatile double r
+){
+  volatile double s = pSum->rSum;
+  volatile double t = s + r;
+  if( fabs(s) > fabs(r) ){
+    pSum->rErr += (s - t) + r;
+  }else{
+    pSum->rErr += (r - t) + s;
+  }
+  pSum->rSum = t;
+}
+
+/*
+** Add a (possibly large) integer to the running sum.
+*/
+static void kahanBabuskaNeumaierStepInt64(volatile SumCtx *pSum, i64 iVal){
+  if( iVal<=-4503599627370496LL || iVal>=+4503599627370496LL ){
+    i64 iBig, iSm;
+    iSm = iVal % 16384;
+    iBig = iVal - iSm;
+    kahanBabuskaNeumaierStep(pSum, iBig);
+    kahanBabuskaNeumaierStep(pSum, iSm);
+  }else{
+    kahanBabuskaNeumaierStep(pSum, (double)iVal);
+  }
+}
+
+/*
+** Initialize the Kahan-Babaska-Neumaier sum from a 64-bit integer
+*/
+static void kahanBabuskaNeumaierInit(
+  volatile SumCtx *p,
+  i64 iVal
+){
+  if( iVal<=-4503599627370496LL || iVal>=+4503599627370496LL ){
+    i64 iSm = iVal % 16384;
+    p->rSum = (double)(iVal - iSm);
+    p->rErr = (double)iSm;
+  }else{
+    p->rSum = (double)iVal;
+    p->rErr = 0.0;
+  }
+}
+
+/*
+** Routines used to compute the sum, average, and total.
+**
+** The SUM() function follows the (broken) SQL standard which means
+** that it returns NULL if it sums over no inputs.  TOTAL returns
+** 0.0 in that case.  In addition, TOTAL always returns a float where
+** SUM might return an integer if it never encounters a floating point
+** value.  TOTAL never fails, but SUM might through an exception if
+** it overflows an integer.
+*/
+static void sumStep(sqlite3_context *context, int argc, sqlite3_value **argv){
+  SumCtx *p;
+  int type;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  type = sqlite3_value_numeric_type(argv[0]);
+  if( p && type!=SQLITE_NULL ){
+    p->cnt++;
+    if( p->approx==0 ){
+      if( type!=SQLITE_INTEGER ){
+        kahanBabuskaNeumaierInit(p, p->iSum);
+        p->approx = 1;
+        kahanBabuskaNeumaierStep(p, sqlite3_value_double(argv[0]));
+      }else{
+        i64 x = p->iSum;
+        if( sqlite3AddInt64(&x, sqlite3_value_int64(argv[0]))==0 ){
+          p->iSum = x;
+        }else{
+          p->ovrfl = 1;
+          kahanBabuskaNeumaierInit(p, p->iSum);
+          p->approx = 1;
+          kahanBabuskaNeumaierStepInt64(p, sqlite3_value_int64(argv[0]));
+        }
+      }
+    }else{
+      if( type==SQLITE_INTEGER ){
+        kahanBabuskaNeumaierStepInt64(p, sqlite3_value_int64(argv[0]));
+      }else{
+        p->ovrfl = 0;
+        kahanBabuskaNeumaierStep(p, sqlite3_value_double(argv[0]));
+      }
+    }
+  }
+}
+#ifndef SQLITE_OMIT_WINDOWFUNC
+static void sumInverse(sqlite3_context *context, int argc, sqlite3_value**argv){
+  SumCtx *p;
+  int type;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  type = sqlite3_value_numeric_type(argv[0]);
+  /* p is always non-NULL because sumStep() will have been called first
+  ** to initialize it */
+  if( ALWAYS(p) && type!=SQLITE_NULL ){
+    assert( p->cnt>0 );
+    p->cnt--;
+    if( !p->approx ){
+      p->iSum -= sqlite3_value_int64(argv[0]);
+    }else if( type==SQLITE_INTEGER ){
+      i64 iVal = sqlite3_value_int64(argv[0]);
+      if( iVal!=SMALLEST_INT64 ){
+        kahanBabuskaNeumaierStepInt64(p, -iVal);
+      }else{
+        kahanBabuskaNeumaierStepInt64(p, LARGEST_INT64);
+        kahanBabuskaNeumaierStepInt64(p, 1);
+      }       
+    }else{
+      kahanBabuskaNeumaierStep(p, -sqlite3_value_double(argv[0]));
+    }
+  }
+}
+#else
+# define sumInverse 0
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+static void sumFinalize(sqlite3_context *context){
+  SumCtx *p;
+  p = sqlite3_aggregate_context(context, 0);
+  if( p && p->cnt>0 ){
+    if( p->approx ){
+      if( p->ovrfl ){
+        sqlite3_result_error(context,"integer overflow",-1);
+      }else if( !sqlite3IsNaN(p->rErr) ){
+        sqlite3_result_double(context, p->rSum+p->rErr);
+      }else{
+        sqlite3_result_double(context, p->rSum);
+      }
+    }else{
+      sqlite3_result_int64(context, p->iSum);
+    }
+  }
+}
+static void avgFinalize(sqlite3_context *context){
+  SumCtx *p;
+  p = sqlite3_aggregate_context(context, 0);
+  if( p && p->cnt>0 ){
+    double r;
+    if( p->approx ){
+      r = p->rSum;
+      if( !sqlite3IsNaN(p->rErr) ) r += p->rErr;
+    }else{
+      r = (double)(p->iSum);
+    }
+    sqlite3_result_double(context, r/(double)p->cnt);
+  }
+}
+static void totalFinalize(sqlite3_context *context){
+  SumCtx *p;
+  double r = 0.0;
+  p = sqlite3_aggregate_context(context, 0);
+  if( p ){
+    if( p->approx ){
+      r = p->rSum;
+      if( !sqlite3IsNaN(p->rErr) ) r += p->rErr;
+    }else{
+      r = (double)(p->iSum);
+    }
+  }
+  sqlite3_result_double(context, r);
+}
+
+/*
+** The following structure keeps track of state information for the
+** count() aggregate function.
+*/
+typedef struct CountCtx CountCtx;
+struct CountCtx {
+  i64 n;
+#ifdef SQLITE_DEBUG
+  int bInverse;                   /* True if xInverse() ever called */
+#endif
+};
+
+/*
+** Routines to implement the count() aggregate function.
+*/
+static void countStep(sqlite3_context *context, int argc, sqlite3_value **argv){
+  CountCtx *p;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( (argc==0 || SQLITE_NULL!=sqlite3_value_type(argv[0])) && p ){
+    p->n++;
+  }
+
+#ifndef SQLITE_OMIT_DEPRECATED
+  /* The sqlite3_aggregate_count() function is deprecated.  But just to make
+  ** sure it still operates correctly, verify that its count agrees with our
+  ** internal count when using count(*) and when the total count can be
+  ** expressed as a 32-bit integer. */
+  assert( argc==1 || p==0 || p->n>0x7fffffff || p->bInverse
+          || p->n==sqlite3_aggregate_count(context) );
+#endif
+}  
+static void countFinalize(sqlite3_context *context){
+  CountCtx *p;
+  p = sqlite3_aggregate_context(context, 0);
+  sqlite3_result_int64(context, p ? p->n : 0);
+}
+#ifndef SQLITE_OMIT_WINDOWFUNC
+static void countInverse(sqlite3_context *ctx, int argc, sqlite3_value **argv){
+  CountCtx *p;
+  p = sqlite3_aggregate_context(ctx, sizeof(*p));
+  /* p is always non-NULL since countStep() will have been called first */
+  if( (argc==0 || SQLITE_NULL!=sqlite3_value_type(argv[0])) && ALWAYS(p) ){
+    p->n--;
+#ifdef SQLITE_DEBUG
+    p->bInverse = 1;
+#endif
+  }
+}  
+#else
+# define countInverse 0
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+/*
+** Routines to implement min() and max() aggregate functions.
+*/
+static void minmaxStep(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  Mem *pArg  = (Mem *)argv[0];
+  Mem *pBest;
+  UNUSED_PARAMETER(NotUsed);
+
+  pBest = (Mem *)sqlite3_aggregate_context(context, sizeof(*pBest));
+  if( !pBest ) return;
+
+  if( sqlite3_value_type(pArg)==SQLITE_NULL ){
+    if( pBest->flags ) sqlite3SkipAccumulatorLoad(context);
+  }else if( pBest->flags ){
+    int max;
+    int cmp;
+    CollSeq *pColl = sqlite3GetFuncCollSeq(context);
+    /* This step function is used for both the min() and max() aggregates,
+    ** the only difference between the two being that the sense of the
+    ** comparison is inverted. For the max() aggregate, the
+    ** sqlite3_user_data() function returns (void *)-1. For min() it
+    ** returns (void *)db, where db is the sqlite3* database pointer.
+    ** Therefore the next statement sets variable 'max' to 1 for the max()
+    ** aggregate, or 0 for min().
+    */
+    max = sqlite3_user_data(context)!=0;
+    cmp = sqlite3MemCompare(pBest, pArg, pColl);
+    if( (max && cmp<0) || (!max && cmp>0) ){
+      sqlite3VdbeMemCopy(pBest, pArg);
+    }else{
+      sqlite3SkipAccumulatorLoad(context);
+    }
+  }else{
+    pBest->db = sqlite3_context_db_handle(context);
+    sqlite3VdbeMemCopy(pBest, pArg);
+  }
+}
+static void minMaxValueFinalize(sqlite3_context *context, int bValue){
+  sqlite3_value *pRes;
+  pRes = (sqlite3_value *)sqlite3_aggregate_context(context, 0);
+  if( pRes ){
+    if( pRes->flags ){
+      sqlite3_result_value(context, pRes);
+    }
+    if( bValue==0 ) sqlite3VdbeMemRelease(pRes);
+  }
+}
+#ifndef SQLITE_OMIT_WINDOWFUNC
+static void minMaxValue(sqlite3_context *context){
+  minMaxValueFinalize(context, 1);
+}
+#else
+# define minMaxValue 0
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+static void minMaxFinalize(sqlite3_context *context){
+  minMaxValueFinalize(context, 0);
+}
+
+/*
+** group_concat(EXPR, ?SEPARATOR?)
+** string_agg(EXPR, SEPARATOR)
+**
+** The SEPARATOR goes before the EXPR string.  This is tragic.  The
+** groupConcatInverse() implementation would have been easier if the
+** SEPARATOR were appended after EXPR.  And the order is undocumented,
+** so we could change it, in theory.  But the old behavior has been
+** around for so long that we dare not, for fear of breaking something.
+*/
+typedef struct {
+  StrAccum str;          /* The accumulated concatenation */
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  int nAccum;            /* Number of strings presently concatenated */
+  int nFirstSepLength;   /* Used to detect separator length change */
+  /* If pnSepLengths!=0, refs an array of inter-string separator lengths,
+  ** stored as actually incorporated into presently accumulated result.
+  ** (Hence, its slots in use number nAccum-1 between method calls.)
+  ** If pnSepLengths==0, nFirstSepLength is the length used throughout.
+  */
+  int *pnSepLengths;
+#endif
+} GroupConcatCtx;
+
+static void groupConcatStep(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zVal;
+  GroupConcatCtx *pGCC;
+  const char *zSep;
+  int nVal, nSep;
+  assert( argc==1 || argc==2 );
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  pGCC = (GroupConcatCtx*)sqlite3_aggregate_context(context, sizeof(*pGCC));
+  if( pGCC ){
+    sqlite3 *db = sqlite3_context_db_handle(context);
+    int firstTerm = pGCC->str.mxAlloc==0;
+    pGCC->str.mxAlloc = db->aLimit[SQLITE_LIMIT_LENGTH];
+    if( argc==1 ){
+      if( !firstTerm ){
+        sqlite3_str_appendchar(&pGCC->str, 1, ',');
+      }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      else{
+        pGCC->nFirstSepLength = 1;
+      }
+#endif
+    }else if( !firstTerm ){
+      zSep = (char*)sqlite3_value_text(argv[1]);
+      nSep = sqlite3_value_bytes(argv[1]);
+      if( zSep ){
+        sqlite3_str_append(&pGCC->str, zSep, nSep);
+      }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      else{
+        nSep = 0;
+      }
+      if( nSep != pGCC->nFirstSepLength || pGCC->pnSepLengths != 0 ){
+        int *pnsl = pGCC->pnSepLengths;
+        if( pnsl == 0 ){
+          /* First separator length variation seen, start tracking them. */
+          pnsl = (int*)sqlite3_malloc64((pGCC->nAccum+1) * sizeof(int));
+          if( pnsl!=0 ){
+            int i = 0, nA = pGCC->nAccum-1;
+            while( i<nA ) pnsl[i++] = pGCC->nFirstSepLength;
+          }
+        }else{
+          pnsl = (int*)sqlite3_realloc64(pnsl, pGCC->nAccum * sizeof(int));
+        }
+        if( pnsl!=0 ){
+          if( ALWAYS(pGCC->nAccum>0) ){
+            pnsl[pGCC->nAccum-1] = nSep;
+          }
+          pGCC->pnSepLengths = pnsl;
+        }else{
+          sqlite3StrAccumSetError(&pGCC->str, SQLITE_NOMEM);
+        }
+      }
+#endif
+    }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    else{
+      pGCC->nFirstSepLength = sqlite3_value_bytes(argv[1]);
+    }
+    pGCC->nAccum += 1;
+#endif
+    zVal = (char*)sqlite3_value_text(argv[0]);
+    nVal = sqlite3_value_bytes(argv[0]);
+    if( zVal ) sqlite3_str_append(&pGCC->str, zVal, nVal);
+  }
+}
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+static void groupConcatInverse(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  GroupConcatCtx *pGCC;
+  assert( argc==1 || argc==2 );
+  (void)argc;  /* Suppress unused parameter warning */
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  pGCC = (GroupConcatCtx*)sqlite3_aggregate_context(context, sizeof(*pGCC));
+  /* pGCC is always non-NULL since groupConcatStep() will have always
+  ** run first to initialize it */
+  if( ALWAYS(pGCC) ){
+    int nVS;
+    /* Must call sqlite3_value_text() to convert the argument into text prior
+    ** to invoking sqlite3_value_bytes(), in case the text encoding is UTF16 */
+    (void)sqlite3_value_text(argv[0]);
+    nVS = sqlite3_value_bytes(argv[0]);
+    pGCC->nAccum -= 1;
+    if( pGCC->pnSepLengths!=0 ){
+      assert(pGCC->nAccum >= 0);
+      if( pGCC->nAccum>0 ){
+        nVS += *pGCC->pnSepLengths;
+        memmove(pGCC->pnSepLengths, pGCC->pnSepLengths+1,
+               (pGCC->nAccum-1)*sizeof(int));
+      }
+    }else{
+      /* If removing single accumulated string, harmlessly over-do. */
+      nVS += pGCC->nFirstSepLength;
+    }
+    if( nVS>=(int)pGCC->str.nChar ){
+      pGCC->str.nChar = 0;
+    }else{
+      pGCC->str.nChar -= nVS;
+      memmove(pGCC->str.zText, &pGCC->str.zText[nVS], pGCC->str.nChar);
+    }
+    if( pGCC->str.nChar==0 ){
+      pGCC->str.mxAlloc = 0;
+      sqlite3_free(pGCC->pnSepLengths);
+      pGCC->pnSepLengths = 0;
+    }
+  }
+}
+#else
+# define groupConcatInverse 0
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+static void groupConcatFinalize(sqlite3_context *context){
+  GroupConcatCtx *pGCC
+    = (GroupConcatCtx*)sqlite3_aggregate_context(context, 0);
+  if( pGCC ){
+    sqlite3ResultStrAccum(context, &pGCC->str);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    sqlite3_free(pGCC->pnSepLengths);
+#endif
+  }
+}
+#ifndef SQLITE_OMIT_WINDOWFUNC
+static void groupConcatValue(sqlite3_context *context){
+  GroupConcatCtx *pGCC
+    = (GroupConcatCtx*)sqlite3_aggregate_context(context, 0);
+  if( pGCC ){
+    StrAccum *pAccum = &pGCC->str;
+    if( pAccum->accError==SQLITE_TOOBIG ){
+      sqlite3_result_error_toobig(context);
+    }else if( pAccum->accError==SQLITE_NOMEM ){
+      sqlite3_result_error_nomem(context);
+    }else{   
+      const char *zText = sqlite3_str_value(pAccum);
+      sqlite3_result_text(context, zText, pAccum->nChar, SQLITE_TRANSIENT);
+    }
+  }
+}
+#else
+# define groupConcatValue 0
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+/*
+** This routine does per-connection function registration.  Most
+** of the built-in functions above are part of the global function set.
+** This routine only deals with those that are not global.
+*/
+void sqlite3RegisterPerConnectionBuiltinFunctions(sqlite3 *db){
+  int rc = sqlite3_overload_function(db, "MATCH", 2);
+  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
+  if( rc==SQLITE_NOMEM ){
+    sqlite3OomFault(db);
+  }
+}
+
+/*
+** Re-register the built-in LIKE functions.  The caseSensitive
+** parameter determines whether or not the LIKE operator is case
+** sensitive.
+*/
+void sqlite3RegisterLikeFunctions(sqlite3 *db, int caseSensitive){
+  FuncDef *pDef;
+  struct compareInfo *pInfo;
+  int flags;
+  int nArg;
+  if( caseSensitive ){
+    pInfo = (struct compareInfo*)&likeInfoAlt;
+    flags = SQLITE_FUNC_LIKE | SQLITE_FUNC_CASE;
+  }else{
+    pInfo = (struct compareInfo*)&likeInfoNorm;
+    flags = SQLITE_FUNC_LIKE;
+  }
+  for(nArg=2; nArg<=3; nArg++){
+    sqlite3CreateFunc(db, "like", nArg, SQLITE_UTF8, pInfo, likeFunc, 
+                      0, 0, 0, 0, 0);
+    pDef = sqlite3FindFunction(db, "like", nArg, SQLITE_UTF8, 0);
+    pDef->funcFlags |= flags;
+    pDef->funcFlags &= ~SQLITE_FUNC_UNSAFE;
+  }
+}
+
+/*
+** pExpr points to an expression which implements a function.  If
+** it is appropriate to apply the LIKE optimization to that function
+** then set aWc[0] through aWc[2] to the wildcard characters and the
+** escape character and then return TRUE.  If the function is not a
+** LIKE-style function then return FALSE.
+**
+** The expression "a LIKE b ESCAPE c" is only considered a valid LIKE
+** operator if c is a string literal that is exactly one byte in length.
+** That one byte is stored in aWc[3].  aWc[3] is set to zero if there is
+** no ESCAPE clause.
+**
+** *pIsNocase is set to true if uppercase and lowercase are equivalent for
+** the function (default for LIKE).  If the function makes the distinction
+** between uppercase and lowercase (as does GLOB) then *pIsNocase is set to
+** false.
+*/
+int sqlite3IsLikeFunction(sqlite3 *db, Expr *pExpr, int *pIsNocase, char *aWc){
+  FuncDef *pDef;
+  int nExpr;
+  assert( pExpr!=0 );
+  assert( pExpr->op==TK_FUNCTION );
+  assert( ExprUseXList(pExpr) );
+  if( !pExpr->x.pList ){
+    return 0;
+  }
+  nExpr = pExpr->x.pList->nExpr;
+  assert( !ExprHasProperty(pExpr, EP_IntValue) );
+  pDef = sqlite3FindFunction(db, pExpr->u.zToken, nExpr, SQLITE_UTF8, 0);
+#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
+  if( pDef==0 ) return 0;
+#endif
+  if( NEVER(pDef==0) || (pDef->funcFlags & SQLITE_FUNC_LIKE)==0 ){
+    return 0;
+  }
+
+  /* The memcpy() statement assumes that the wildcard characters are
+  ** the first three statements in the compareInfo structure.  The
+  ** asserts() that follow verify that assumption
+  */
+  memcpy(aWc, pDef->pUserData, 3);
+  assert( (char*)&likeInfoAlt == (char*)&likeInfoAlt.matchAll );
+  assert( &((char*)&likeInfoAlt)[1] == (char*)&likeInfoAlt.matchOne );
+  assert( &((char*)&likeInfoAlt)[2] == (char*)&likeInfoAlt.matchSet );
+
+  if( nExpr<3 ){
+    aWc[3] = 0;
+  }else{
+    Expr *pEscape = pExpr->x.pList->a[2].pExpr;
+    char *zEscape;
+    if( pEscape->op!=TK_STRING ) return 0;
+    assert( !ExprHasProperty(pEscape, EP_IntValue) );
+    zEscape = pEscape->u.zToken;
+    if( zEscape[0]==0 || zEscape[1]!=0 ) return 0;
+    if( zEscape[0]==aWc[0] ) return 0;
+    if( zEscape[0]==aWc[1] ) return 0;
+    aWc[3] = zEscape[0];
+  }
+
+  *pIsNocase = (pDef->funcFlags & SQLITE_FUNC_CASE)==0;
+  return 1;
+}
+
+/* Mathematical Constants */
+#ifndef M_PI
+# define M_PI   3.141592653589793238462643383279502884
+#endif
+#ifndef M_LN10
+# define M_LN10 2.302585092994045684017991454684364208
+#endif
+#ifndef M_LN2
+# define M_LN2  0.693147180559945309417232121458176568
+#endif
+
+
+/* Extra math functions that require linking with -lm
+*/
+#ifdef SQLITE_ENABLE_MATH_FUNCTIONS
+/*
+** Implementation SQL functions:
+**
+**   ceil(X)
+**   ceiling(X)
+**   floor(X)
+**
+** The sqlite3_user_data() pointer is a pointer to the libm implementation
+** of the underlying C function.
+*/
+static void ceilingFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  assert( argc==1 );
+  switch( sqlite3_value_numeric_type(argv[0]) ){
+    case SQLITE_INTEGER: {
+       sqlite3_result_int64(context, sqlite3_value_int64(argv[0]));
+       break;
+    }
+    case SQLITE_FLOAT: {
+       double (*x)(double) = (double(*)(double))sqlite3_user_data(context);
+       sqlite3_result_double(context, x(sqlite3_value_double(argv[0])));
+       break;
+    }
+    default: {
+       break;
+    }
+  }
+}
+
+/*
+** On some systems, ceil() and floor() are intrinsic function.  You are
+** unable to take a pointer to these functions.  Hence, we here wrap them
+** in our own actual functions.
+*/
+static double xCeil(double x){ return ceil(x); }
+static double xFloor(double x){ return floor(x); }
+
+/*
+** Some systems do not have log2() and log10() in their standard math
+** libraries.
+*/
+#if defined(HAVE_LOG10) && HAVE_LOG10==0
+# define log10(X) (0.4342944819032517867*log(X))
+#endif
+#if defined(HAVE_LOG2) && HAVE_LOG2==0
+# define log2(X) (1.442695040888963456*log(X))
+#endif
+
+
+/*
+** Implementation of SQL functions:
+**
+**   ln(X)       - natural logarithm
+**   log(X)      - log X base 10
+**   log10(X)    - log X base 10
+**   log(B,X)    - log X base B
+*/
+static void logFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  double x, b, ans;
+  assert( argc==1 || argc==2 );
+  switch( sqlite3_value_numeric_type(argv[0]) ){
+    case SQLITE_INTEGER:
+    case SQLITE_FLOAT:
+      x = sqlite3_value_double(argv[0]);
+      if( x<=0.0 ) return;
+      break;
+    default:
+      return;
+  }
+  if( argc==2 ){
+    switch( sqlite3_value_numeric_type(argv[0]) ){
+      case SQLITE_INTEGER:
+      case SQLITE_FLOAT:
+        b = log(x);
+        if( b<=0.0 ) return;
+        x = sqlite3_value_double(argv[1]);
+        if( x<=0.0 ) return;
+        break;
+     default:
+        return;
+    }
+    ans = log(x)/b;
+  }else{
+    switch( SQLITE_PTR_TO_INT(sqlite3_user_data(context)) ){
+      case 1:
+        ans = log10(x);
+        break;
+      case 2:
+        ans = log2(x);
+        break;
+      default:
+        ans = log(x);
+        break;
+    }
+  }
+  sqlite3_result_double(context, ans);
+}
+
+/*
+** Functions to converts degrees to radians and radians to degrees.
+*/
+static double degToRad(double x){ return x*(M_PI/180.0); }
+static double radToDeg(double x){ return x*(180.0/M_PI); }
+
+/*
+** Implementation of 1-argument SQL math functions:
+**
+**   exp(X)  - Compute e to the X-th power
+*/
+static void math1Func(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int type0;
+  double v0, ans;
+  double (*x)(double);
+  assert( argc==1 );
+  type0 = sqlite3_value_numeric_type(argv[0]);
+  if( type0!=SQLITE_INTEGER && type0!=SQLITE_FLOAT ) return;
+  v0 = sqlite3_value_double(argv[0]);
+  x = (double(*)(double))sqlite3_user_data(context);
+  ans = x(v0);
+  sqlite3_result_double(context, ans);
+}
+
+/*
+** Implementation of 2-argument SQL math functions:
+**
+**   power(X,Y)  - Compute X to the Y-th power
+*/
+static void math2Func(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int type0, type1;
+  double v0, v1, ans;
+  double (*x)(double,double);
+  assert( argc==2 );
+  type0 = sqlite3_value_numeric_type(argv[0]);
+  if( type0!=SQLITE_INTEGER && type0!=SQLITE_FLOAT ) return;
+  type1 = sqlite3_value_numeric_type(argv[1]);
+  if( type1!=SQLITE_INTEGER && type1!=SQLITE_FLOAT ) return;
+  v0 = sqlite3_value_double(argv[0]);
+  v1 = sqlite3_value_double(argv[1]);
+  x = (double(*)(double,double))sqlite3_user_data(context);
+  ans = x(v0, v1);
+  sqlite3_result_double(context, ans);
+}
+
+/*
+** Implementation of 0-argument pi() function.
+*/
+static void piFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  assert( argc==0 );
+  (void)argv;
+  sqlite3_result_double(context, M_PI);
+}
+
+#endif /* SQLITE_ENABLE_MATH_FUNCTIONS */
+
+/*
+** Implementation of sign(X) function.
+*/
+static void signFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int type0;
+  double x;
+  UNUSED_PARAMETER(argc);
+  assert( argc==1 );
+  type0 = sqlite3_value_numeric_type(argv[0]);
+  if( type0!=SQLITE_INTEGER && type0!=SQLITE_FLOAT ) return;
+  x = sqlite3_value_double(argv[0]);
+  sqlite3_result_int(context, x<0.0 ? -1 : x>0.0 ? +1 : 0);
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Implementation of fpdecode(x,y,z) function.
+**
+** x is a real number that is to be decoded.  y is the precision.
+** z is the maximum real precision.
+*/
+static void fpdecodeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  FpDecode s;
+  double x;
+  int y, z;
+  char zBuf[100];
+  UNUSED_PARAMETER(argc);
+  assert( argc==3 );
+  x = sqlite3_value_double(argv[0]);
+  y = sqlite3_value_int(argv[1]);
+  z = sqlite3_value_int(argv[2]);
+  sqlite3FpDecode(&s, x, y, z);
+  if( s.isSpecial==2 ){
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "NaN");
+  }else{
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "%c%.*s/%d", s.sign, s.n, s.z, s.iDP);
+  }
+  sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** All of the FuncDef structures in the aBuiltinFunc[] array above
+** to the global function hash table.  This occurs at start-time (as
+** a consequence of calling sqlite3_initialize()).
+**
+** After this routine runs
+*/
+void sqlite3RegisterBuiltinFunctions(void){
+  /*
+  ** The following array holds FuncDef structures for all of the functions
+  ** defined in this file.
+  **
+  ** The array cannot be constant since changes are made to the
+  ** FuncDef.pHash elements at start-time.  The elements of this array
+  ** are read-only after initialization is complete.
+  **
+  ** For peak efficiency, put the most frequently used function last.
+  */
+  static FuncDef aBuiltinFunc[] = {
+/***** Functions only available with SQLITE_TESTCTRL_INTERNAL_FUNCTIONS *****/
+#if !defined(SQLITE_UNTESTABLE)
+    TEST_FUNC(implies_nonnull_row, 2, INLINEFUNC_implies_nonnull_row, 0),
+    TEST_FUNC(expr_compare,        2, INLINEFUNC_expr_compare,        0),
+    TEST_FUNC(expr_implies_expr,   2, INLINEFUNC_expr_implies_expr,   0),
+    TEST_FUNC(affinity,            1, INLINEFUNC_affinity,            0),
+#endif /* !defined(SQLITE_UNTESTABLE) */
+/***** Regular functions *****/
+#ifdef SQLITE_SOUNDEX
+    FUNCTION(soundex,            1, 0, 0, soundexFunc      ),
+#endif
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    SFUNCTION(load_extension,    1, 0, 0, loadExt          ),
+    SFUNCTION(load_extension,    2, 0, 0, loadExt          ),
+#endif
+#if SQLITE_USER_AUTHENTICATION
+    FUNCTION(sqlite_crypt,       2, 0, 0, sqlite3CryptFunc ),
+#endif
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+    DFUNCTION(sqlite_compileoption_used,1, 0, 0, compileoptionusedFunc  ),
+    DFUNCTION(sqlite_compileoption_get, 1, 0, 0, compileoptiongetFunc  ),
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+    INLINE_FUNC(unlikely,        1, INLINEFUNC_unlikely, SQLITE_FUNC_UNLIKELY),
+    INLINE_FUNC(likelihood,      2, INLINEFUNC_unlikely, SQLITE_FUNC_UNLIKELY),
+    INLINE_FUNC(likely,          1, INLINEFUNC_unlikely, SQLITE_FUNC_UNLIKELY),
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+    INLINE_FUNC(sqlite_offset,   1, INLINEFUNC_sqlite_offset, 0 ),
+#endif
+    FUNCTION(ltrim,              1, 1, 0, trimFunc         ),
+    FUNCTION(ltrim,              2, 1, 0, trimFunc         ),
+    FUNCTION(rtrim,              1, 2, 0, trimFunc         ),
+    FUNCTION(rtrim,              2, 2, 0, trimFunc         ),
+    FUNCTION(trim,               1, 3, 0, trimFunc         ),
+    FUNCTION(trim,               2, 3, 0, trimFunc         ),
+    FUNCTION(min,               -1, 0, 1, minmaxFunc       ),
+    FUNCTION(min,                0, 0, 1, 0                ),
+    WAGGREGATE(min, 1, 0, 1, minmaxStep, minMaxFinalize, minMaxValue, 0,
+                                 SQLITE_FUNC_MINMAX|SQLITE_FUNC_ANYORDER ),
+    FUNCTION(max,               -1, 1, 1, minmaxFunc       ),
+    FUNCTION(max,                0, 1, 1, 0                ),
+    WAGGREGATE(max, 1, 1, 1, minmaxStep, minMaxFinalize, minMaxValue, 0,
+                                 SQLITE_FUNC_MINMAX|SQLITE_FUNC_ANYORDER ),
+    FUNCTION2(typeof,            1, 0, 0, typeofFunc,  SQLITE_FUNC_TYPEOF),
+    FUNCTION2(subtype,           1, 0, 0, subtypeFunc, SQLITE_FUNC_TYPEOF),
+    FUNCTION2(length,            1, 0, 0, lengthFunc,  SQLITE_FUNC_LENGTH),
+    FUNCTION2(octet_length,      1, 0, 0, bytelengthFunc,SQLITE_FUNC_BYTELEN),
+    FUNCTION(instr,              2, 0, 0, instrFunc        ),
+    FUNCTION(printf,            -1, 0, 0, printfFunc       ),
+    FUNCTION(format,            -1, 0, 0, printfFunc       ),
+    FUNCTION(unicode,            1, 0, 0, unicodeFunc      ),
+    FUNCTION(char,              -1, 0, 0, charFunc         ),
+    FUNCTION(abs,                1, 0, 0, absFunc          ),
+#ifdef SQLITE_DEBUG
+    FUNCTION(fpdecode,           3, 0, 0, fpdecodeFunc     ),
+#endif
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    FUNCTION(round,              1, 0, 0, roundFunc        ),
+    FUNCTION(round,              2, 0, 0, roundFunc        ),
+#endif
+    FUNCTION(upper,              1, 0, 0, upperFunc        ),
+    FUNCTION(lower,              1, 0, 0, lowerFunc        ),
+    FUNCTION(hex,                1, 0, 0, hexFunc          ),
+    FUNCTION(unhex,              1, 0, 0, unhexFunc        ),
+    FUNCTION(unhex,              2, 0, 0, unhexFunc        ),
+    FUNCTION(concat,            -1, 0, 0, concatFunc       ),
+    FUNCTION(concat,             0, 0, 0, 0                ),
+    FUNCTION(concat_ws,         -1, 0, 0, concatwsFunc     ),
+    FUNCTION(concat_ws,          0, 0, 0, 0                ),
+    FUNCTION(concat_ws,          1, 0, 0, 0                ),
+    INLINE_FUNC(ifnull,          2, INLINEFUNC_coalesce, 0 ),
+    VFUNCTION(random,            0, 0, 0, randomFunc       ),
+    VFUNCTION(randomblob,        1, 0, 0, randomBlob       ),
+    FUNCTION(nullif,             2, 0, 1, nullifFunc       ),
+    DFUNCTION(sqlite_version,    0, 0, 0, versionFunc      ),
+    DFUNCTION(sqlite_source_id,  0, 0, 0, sourceidFunc     ),
+    FUNCTION(sqlite_log,         2, 0, 0, errlogFunc       ),
+    FUNCTION(quote,              1, 0, 0, quoteFunc        ),
+    VFUNCTION(last_insert_rowid, 0, 0, 0, last_insert_rowid),
+    VFUNCTION(changes,           0, 0, 0, changes          ),
+    VFUNCTION(total_changes,     0, 0, 0, total_changes    ),
+    FUNCTION(replace,            3, 0, 0, replaceFunc      ),
+    FUNCTION(zeroblob,           1, 0, 0, zeroblobFunc     ),
+    FUNCTION(substr,             2, 0, 0, substrFunc       ),
+    FUNCTION(substr,             3, 0, 0, substrFunc       ),
+    FUNCTION(substring,          2, 0, 0, substrFunc       ),
+    FUNCTION(substring,          3, 0, 0, substrFunc       ),
+    WAGGREGATE(sum,   1,0,0, sumStep, sumFinalize, sumFinalize, sumInverse, 0),
+    WAGGREGATE(total, 1,0,0, sumStep,totalFinalize,totalFinalize,sumInverse, 0),
+    WAGGREGATE(avg,   1,0,0, sumStep, avgFinalize, avgFinalize, sumInverse, 0),
+    WAGGREGATE(count, 0,0,0, countStep,
+        countFinalize, countFinalize, countInverse,
+        SQLITE_FUNC_COUNT|SQLITE_FUNC_ANYORDER  ),
+    WAGGREGATE(count, 1,0,0, countStep,
+        countFinalize, countFinalize, countInverse, SQLITE_FUNC_ANYORDER ),
+    WAGGREGATE(group_concat, 1, 0, 0, groupConcatStep,
+        groupConcatFinalize, groupConcatValue, groupConcatInverse, 0),
+    WAGGREGATE(group_concat, 2, 0, 0, groupConcatStep,
+        groupConcatFinalize, groupConcatValue, groupConcatInverse, 0),
+    WAGGREGATE(string_agg,   2, 0, 0, groupConcatStep,
+        groupConcatFinalize, groupConcatValue, groupConcatInverse, 0),
+ 
+    LIKEFUNC(glob, 2, &globInfo, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
+#ifdef SQLITE_CASE_SENSITIVE_LIKE
+    LIKEFUNC(like, 2, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
+    LIKEFUNC(like, 3, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
+#else
+    LIKEFUNC(like, 2, &likeInfoNorm, SQLITE_FUNC_LIKE),
+    LIKEFUNC(like, 3, &likeInfoNorm, SQLITE_FUNC_LIKE),
+#endif
+#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
+    FUNCTION(unknown,           -1, 0, 0, unknownFunc      ),
+#endif
+    FUNCTION(coalesce,           1, 0, 0, 0                ),
+    FUNCTION(coalesce,           0, 0, 0, 0                ),
+#ifdef SQLITE_ENABLE_MATH_FUNCTIONS
+    MFUNCTION(ceil,              1, xCeil,     ceilingFunc ),
+    MFUNCTION(ceiling,           1, xCeil,     ceilingFunc ),
+    MFUNCTION(floor,             1, xFloor,    ceilingFunc ),
+#if SQLITE_HAVE_C99_MATH_FUNCS
+    MFUNCTION(trunc,             1, trunc,     ceilingFunc ),
+#endif
+    FUNCTION(ln,                 1, 0, 0,      logFunc     ),
+    FUNCTION(log,                1, 1, 0,      logFunc     ),
+    FUNCTION(log10,              1, 1, 0,      logFunc     ),
+    FUNCTION(log2,               1, 2, 0,      logFunc     ),
+    FUNCTION(log,                2, 0, 0,      logFunc     ),
+    MFUNCTION(exp,               1, exp,       math1Func   ),
+    MFUNCTION(pow,               2, pow,       math2Func   ),
+    MFUNCTION(power,             2, pow,       math2Func   ),
+    MFUNCTION(mod,               2, fmod,      math2Func   ),
+    MFUNCTION(acos,              1, acos,      math1Func   ),
+    MFUNCTION(asin,              1, asin,      math1Func   ),
+    MFUNCTION(atan,              1, atan,      math1Func   ),
+    MFUNCTION(atan2,             2, atan2,     math2Func   ),
+    MFUNCTION(cos,               1, cos,       math1Func   ),
+    MFUNCTION(sin,               1, sin,       math1Func   ),
+    MFUNCTION(tan,               1, tan,       math1Func   ),
+    MFUNCTION(cosh,              1, cosh,      math1Func   ),
+    MFUNCTION(sinh,              1, sinh,      math1Func   ),
+    MFUNCTION(tanh,              1, tanh,      math1Func   ),
+#if SQLITE_HAVE_C99_MATH_FUNCS
+    MFUNCTION(acosh,             1, acosh,     math1Func   ),
+    MFUNCTION(asinh,             1, asinh,     math1Func   ),
+    MFUNCTION(atanh,             1, atanh,     math1Func   ),
+#endif
+    MFUNCTION(sqrt,              1, sqrt,      math1Func   ),
+    MFUNCTION(radians,           1, degToRad,  math1Func   ),
+    MFUNCTION(degrees,           1, radToDeg,  math1Func   ),
+    FUNCTION(pi,                 0, 0, 0,      piFunc      ),
+#endif /* SQLITE_ENABLE_MATH_FUNCTIONS */
+    FUNCTION(sign,               1, 0, 0,      signFunc    ),
+    INLINE_FUNC(coalesce,       -1, INLINEFUNC_coalesce, 0 ),
+    INLINE_FUNC(iif,             3, INLINEFUNC_iif,      0 ),
+  };
+#ifndef SQLITE_OMIT_ALTERTABLE
+  sqlite3AlterFunctions();
+#endif
+  sqlite3WindowFunctions();
+  sqlite3RegisterDateTimeFunctions();
+  sqlite3RegisterJsonFunctions();
+  sqlite3InsertBuiltinFuncs(aBuiltinFunc, ArraySize(aBuiltinFunc));
+
+#if 0  /* Enable to print out how the built-in functions are hashed */
+  {
+    int i;
+    FuncDef *p;
+    for(i=0; i<SQLITE_FUNC_HASH_SZ; i++){
+      printf("FUNC-HASH %02d:", i);
+      for(p=sqlite3BuiltinFunctions.a[i]; p; p=p->u.pHash){
+        int n = sqlite3Strlen30(p->zName);
+        int h = p->zName[0] + n;
+        assert( p->funcFlags & SQLITE_FUNC_BUILTIN );
+        printf(" %s(%d)", p->zName, h);
+      }
+      printf("\n");
+    }
+  }
+#endif
+}
diff --git a/src/global.c b/src/global.c
new file mode 100644
index 0000000..7f27d91
--- /dev/null
+++ b/src/global.c
@@ -0,0 +1,399 @@
+/*
+** 2008 June 13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains definitions of global variables and constants.
+*/
+#include "sqliteInt.h"
+
+/* An array to map all upper-case characters into their corresponding
+** lower-case character. 
+**
+** SQLite only considers US-ASCII (or EBCDIC) characters.  We do not
+** handle case conversions for the UTF character set since the tables
+** involved are nearly as big or bigger than SQLite itself.
+*/
+const unsigned char sqlite3UpperToLower[] = {
+#ifdef SQLITE_ASCII
+      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17,
+     18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
+     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
+     54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 97, 98, 99,100,101,102,103,
+    104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,
+    122, 91, 92, 93, 94, 95, 96, 97, 98, 99,100,101,102,103,104,105,106,107,
+    108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,
+    126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
+    144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,
+    162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,
+    180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,
+    198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,
+    216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,
+    234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,
+    252,253,254,255,
+#endif
+#ifdef SQLITE_EBCDIC
+      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, /* 0x */
+     16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, /* 1x */
+     32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, /* 2x */
+     48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, /* 3x */
+     64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, /* 4x */
+     80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, /* 5x */
+     96, 97, 98, 99,100,101,102,103,104,105,106,107,108,109,110,111, /* 6x */
+    112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127, /* 7x */
+    128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143, /* 8x */
+    144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159, /* 9x */
+    160,161,162,163,164,165,166,167,168,169,170,171,140,141,142,175, /* Ax */
+    176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191, /* Bx */
+    192,129,130,131,132,133,134,135,136,137,202,203,204,205,206,207, /* Cx */
+    208,145,146,147,148,149,150,151,152,153,218,219,220,221,222,223, /* Dx */
+    224,225,162,163,164,165,166,167,168,169,234,235,236,237,238,239, /* Ex */
+    240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255, /* Fx */
+#endif
+/* All of the upper-to-lower conversion data is above.  The following
+** 18 integers are completely unrelated.  They are appended to the
+** sqlite3UpperToLower[] array to avoid UBSAN warnings.  Here's what is
+** going on:
+**
+** The SQL comparison operators (<>, =, >, <=, <, and >=) are implemented
+** by invoking sqlite3MemCompare(A,B) which compares values A and B and
+** returns negative, zero, or positive if A is less then, equal to, or
+** greater than B, respectively.  Then the true false results is found by
+** consulting sqlite3aLTb[opcode], sqlite3aEQb[opcode], or 
+** sqlite3aGTb[opcode] depending on whether the result of compare(A,B)
+** is negative, zero, or positive, where opcode is the specific opcode.
+** The only works because the comparison opcodes are consecutive and in
+** this order: NE EQ GT LE LT GE.  Various assert()s throughout the code
+** ensure that is the case.
+**
+** These elements must be appended to another array.  Otherwise the
+** index (here shown as [256-OP_Ne]) would be out-of-bounds and thus
+** be undefined behavior.  That's goofy, but the C-standards people thought
+** it was a good idea, so here we are.
+*/
+/* NE  EQ  GT  LE  LT  GE  */
+   1,  0,  0,  1,  1,  0,  /* aLTb[]: Use when compare(A,B) less than zero */
+   0,  1,  0,  1,  0,  1,  /* aEQb[]: Use when compare(A,B) equals zero */
+   1,  0,  1,  0,  0,  1   /* aGTb[]: Use when compare(A,B) greater than zero*/
+};
+const unsigned char *sqlite3aLTb = &sqlite3UpperToLower[256-OP_Ne];
+const unsigned char *sqlite3aEQb = &sqlite3UpperToLower[256+6-OP_Ne];
+const unsigned char *sqlite3aGTb = &sqlite3UpperToLower[256+12-OP_Ne];
+
+/*
+** The following 256 byte lookup table is used to support SQLites built-in
+** equivalents to the following standard library functions:
+**
+**   isspace()                        0x01
+**   isalpha()                        0x02
+**   isdigit()                        0x04
+**   isalnum()                        0x06
+**   isxdigit()                       0x08
+**   toupper()                        0x20
+**   SQLite identifier character      0x40   $, _, or non-ascii
+**   Quote character                  0x80
+**
+** Bit 0x20 is set if the mapped character requires translation to upper
+** case. i.e. if the character is a lower-case ASCII character.
+** If x is a lower-case ASCII character, then its upper-case equivalent
+** is (x - 0x20). Therefore toupper() can be implemented as:
+**
+**   (x & ~(map[x]&0x20))
+**
+** The equivalent of tolower() is implemented using the sqlite3UpperToLower[]
+** array. tolower() is used more often than toupper() by SQLite.
+**
+** Bit 0x40 is set if the character is non-alphanumeric and can be used in an 
+** SQLite identifier.  Identifiers are alphanumerics, "_", "$", and any
+** non-ASCII UTF character. Hence the test for whether or not a character is
+** part of an identifier is 0x46.
+*/
+const unsigned char sqlite3CtypeMap[256] = {
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 00..07    ........ */
+  0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00,  /* 08..0f    ........ */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 10..17    ........ */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 18..1f    ........ */
+  0x01, 0x00, 0x80, 0x00, 0x40, 0x00, 0x00, 0x80,  /* 20..27     !"#$%&' */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 28..2f    ()*+,-./ */
+  0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c,  /* 30..37    01234567 */
+  0x0c, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 38..3f    89:;<=>? */
+
+  0x00, 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, 0x02,  /* 40..47    @ABCDEFG */
+  0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,  /* 48..4f    HIJKLMNO */
+  0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,  /* 50..57    PQRSTUVW */
+  0x02, 0x02, 0x02, 0x80, 0x00, 0x00, 0x00, 0x40,  /* 58..5f    XYZ[\]^_ */
+  0x80, 0x2a, 0x2a, 0x2a, 0x2a, 0x2a, 0x2a, 0x22,  /* 60..67    `abcdefg */
+  0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22,  /* 68..6f    hijklmno */
+  0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22,  /* 70..77    pqrstuvw */
+  0x22, 0x22, 0x22, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 78..7f    xyz{|}~. */
+
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 80..87    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 88..8f    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 90..97    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 98..9f    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* a0..a7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* a8..af    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* b0..b7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* b8..bf    ........ */
+
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* c0..c7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* c8..cf    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* d0..d7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* d8..df    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* e0..e7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* e8..ef    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* f0..f7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40   /* f8..ff    ........ */
+};
+
+/* EVIDENCE-OF: R-02982-34736 In order to maintain full backwards
+** compatibility for legacy applications, the URI filename capability is
+** disabled by default.
+**
+** EVIDENCE-OF: R-38799-08373 URI filenames can be enabled or disabled
+** using the SQLITE_USE_URI=1 or SQLITE_USE_URI=0 compile-time options.
+**
+** EVIDENCE-OF: R-43642-56306 By default, URI handling is globally
+** disabled. The default value may be changed by compiling with the
+** SQLITE_USE_URI symbol defined.
+*/
+#ifndef SQLITE_USE_URI
+# define SQLITE_USE_URI 0
+#endif
+
+/* EVIDENCE-OF: R-38720-18127 The default setting is determined by the
+** SQLITE_ALLOW_COVERING_INDEX_SCAN compile-time option, or is "on" if
+** that compile-time option is omitted.
+*/
+#if !defined(SQLITE_ALLOW_COVERING_INDEX_SCAN)
+# define SQLITE_ALLOW_COVERING_INDEX_SCAN 1
+#else
+# if !SQLITE_ALLOW_COVERING_INDEX_SCAN 
+#   error "Compile-time disabling of covering index scan using the\
+ -DSQLITE_ALLOW_COVERING_INDEX_SCAN=0 option is deprecated.\
+ Contact SQLite developers if this is a problem for you, and\
+ delete this #error macro to continue with your build."
+# endif
+#endif
+
+/* The minimum PMA size is set to this value multiplied by the database
+** page size in bytes.
+*/
+#ifndef SQLITE_SORTER_PMASZ
+# define SQLITE_SORTER_PMASZ 250
+#endif
+
+/* Statement journals spill to disk when their size exceeds the following
+** threshold (in bytes). 0 means that statement journals are created and
+** written to disk immediately (the default behavior for SQLite versions
+** before 3.12.0).  -1 means always keep the entire statement journal in
+** memory.  (The statement journal is also always held entirely in memory
+** if journal_mode=MEMORY or if temp_store=MEMORY, regardless of this
+** setting.)
+*/
+#ifndef SQLITE_STMTJRNL_SPILL 
+# define SQLITE_STMTJRNL_SPILL (64*1024)
+#endif
+
+/*
+** The default lookaside-configuration, the format "SZ,N".  SZ is the
+** number of bytes in each lookaside slot (should be a multiple of 8)
+** and N is the number of slots.  The lookaside-configuration can be
+** changed as start-time using sqlite3_config(SQLITE_CONFIG_LOOKASIDE)
+** or at run-time for an individual database connection using
+** sqlite3_db_config(db, SQLITE_DBCONFIG_LOOKASIDE);
+**
+** With the two-size-lookaside enhancement, less lookaside is required.
+** The default configuration of 1200,40 actually provides 30 1200-byte slots
+** and 93 128-byte slots, which is more lookaside than is available
+** using the older 1200,100 configuration without two-size-lookaside.
+*/
+#ifndef SQLITE_DEFAULT_LOOKASIDE
+# ifdef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+#   define SQLITE_DEFAULT_LOOKASIDE 1200,100  /* 120KB of memory */
+# else
+#   define SQLITE_DEFAULT_LOOKASIDE 1200,40   /* 48KB of memory */
+# endif
+#endif
+
+
+/* The default maximum size of an in-memory database created using
+** sqlite3_deserialize()
+*/
+#ifndef SQLITE_MEMDB_DEFAULT_MAXSIZE
+# define SQLITE_MEMDB_DEFAULT_MAXSIZE 1073741824
+#endif
+
+/*
+** The following singleton contains the global configuration for
+** the SQLite library.
+*/
+SQLITE_WSD struct Sqlite3Config sqlite3Config = {
+   SQLITE_DEFAULT_MEMSTATUS,  /* bMemstat */
+   1,                         /* bCoreMutex */
+   SQLITE_THREADSAFE==1,      /* bFullMutex */
+   SQLITE_USE_URI,            /* bOpenUri */
+   SQLITE_ALLOW_COVERING_INDEX_SCAN,   /* bUseCis */
+   0,                         /* bSmallMalloc */
+   1,                         /* bExtraSchemaChecks */
+   sizeof(LONGDOUBLE_TYPE)>8, /* bUseLongDouble */
+#ifdef SQLITE_DEBUG
+   0,                         /* bJsonSelfcheck */
+#endif
+   0x7ffffffe,                /* mxStrlen */
+   0,                         /* neverCorrupt */
+   SQLITE_DEFAULT_LOOKASIDE,  /* szLookaside, nLookaside */
+   SQLITE_STMTJRNL_SPILL,     /* nStmtSpill */
+   {0,0,0,0,0,0,0,0},         /* m */
+   {0,0,0,0,0,0,0,0,0},       /* mutex */
+   {0,0,0,0,0,0,0,0,0,0,0,0,0},/* pcache2 */
+   (void*)0,                  /* pHeap */
+   0,                         /* nHeap */
+   0, 0,                      /* mnHeap, mxHeap */
+   SQLITE_DEFAULT_MMAP_SIZE,  /* szMmap */
+   SQLITE_MAX_MMAP_SIZE,      /* mxMmap */
+   (void*)0,                  /* pPage */
+   0,                         /* szPage */
+   SQLITE_DEFAULT_PCACHE_INITSZ, /* nPage */
+   0,                         /* mxParserStack */
+   0,                         /* sharedCacheEnabled */
+   SQLITE_SORTER_PMASZ,       /* szPma */
+   /* All the rest should always be initialized to zero */
+   0,                         /* isInit */
+   0,                         /* inProgress */
+   0,                         /* isMutexInit */
+   0,                         /* isMallocInit */
+   0,                         /* isPCacheInit */
+   0,                         /* nRefInitMutex */
+   0,                         /* pInitMutex */
+   0,                         /* xLog */
+   0,                         /* pLogArg */
+#ifdef SQLITE_ENABLE_SQLLOG
+   0,                         /* xSqllog */
+   0,                         /* pSqllogArg */
+#endif
+#ifdef SQLITE_VDBE_COVERAGE
+   0,                         /* xVdbeBranch */
+   0,                         /* pVbeBranchArg */
+#endif
+#ifndef SQLITE_OMIT_DESERIALIZE
+   SQLITE_MEMDB_DEFAULT_MAXSIZE,   /* mxMemdbSize */
+#endif
+#ifndef SQLITE_UNTESTABLE
+   0,                         /* xTestCallback */
+#endif
+   0,                         /* bLocaltimeFault */
+   0,                         /* xAltLocaltime */
+   0x7ffffffe,                /* iOnceResetThreshold */
+   SQLITE_DEFAULT_SORTERREF_SIZE,   /* szSorterRef */
+   0,                         /* iPrngSeed */
+#ifdef SQLITE_DEBUG
+   {0,0,0,0,0,0},             /* aTune */
+#endif
+};
+
+/*
+** Hash table for global functions - functions common to all
+** database connections.  After initialization, this table is
+** read-only.
+*/
+FuncDefHash sqlite3BuiltinFunctions;
+
+#if defined(SQLITE_COVERAGE_TEST) || defined(SQLITE_DEBUG)
+/*
+** Counter used for coverage testing.  Does not come into play for
+** release builds.
+**
+** Access to this global variable is not mutex protected.  This might
+** result in TSAN warnings.  But as the variable does not exist in
+** release builds, that should not be a concern.
+*/
+unsigned int sqlite3CoverageCounter;
+#endif /* SQLITE_COVERAGE_TEST || SQLITE_DEBUG */
+
+#ifdef VDBE_PROFILE
+/*
+** The following performance counter can be used in place of
+** sqlite3Hwtime() for profiling.  This is a no-op on standard builds.
+*/
+sqlite3_uint64 sqlite3NProfileCnt = 0;
+#endif
+
+/*
+** The value of the "pending" byte must be 0x40000000 (1 byte past the
+** 1-gibabyte boundary) in a compatible database.  SQLite never uses
+** the database page that contains the pending byte.  It never attempts
+** to read or write that page.  The pending byte page is set aside
+** for use by the VFS layers as space for managing file locks.
+**
+** During testing, it is often desirable to move the pending byte to
+** a different position in the file.  This allows code that has to
+** deal with the pending byte to run on files that are much smaller
+** than 1 GiB.  The sqlite3_test_control() interface can be used to
+** move the pending byte.
+**
+** IMPORTANT:  Changing the pending byte to any value other than
+** 0x40000000 results in an incompatible database file format!
+** Changing the pending byte during operation will result in undefined
+** and incorrect behavior.
+*/
+#ifndef SQLITE_OMIT_WSD
+int sqlite3PendingByte = 0x40000000;
+#endif
+
+/*
+** Tracing flags set by SQLITE_TESTCTRL_TRACEFLAGS.
+*/
+u32 sqlite3TreeTrace = 0;
+u32 sqlite3WhereTrace = 0;
+
+#include "opcodes.h"
+/*
+** Properties of opcodes.  The OPFLG_INITIALIZER macro is
+** created by mkopcodeh.awk during compilation.  Data is obtained
+** from the comments following the "case OP_xxxx:" statements in
+** the vdbe.c file.  
+*/
+const unsigned char sqlite3OpcodeProperty[] = OPFLG_INITIALIZER;
+
+/*
+** Name of the default collating sequence
+*/
+const char sqlite3StrBINARY[] = "BINARY";
+
+/*
+** Standard typenames.  These names must match the COLTYPE_* definitions.
+** Adjust the SQLITE_N_STDTYPE value if adding or removing entries.
+**
+**    sqlite3StdType[]            The actual names of the datatypes.
+**
+**    sqlite3StdTypeLen[]         The length (in bytes) of each entry
+**                                in sqlite3StdType[].
+**
+**    sqlite3StdTypeAffinity[]    The affinity associated with each entry
+**                                in sqlite3StdType[].
+*/
+const unsigned char sqlite3StdTypeLen[] = { 3, 4, 3, 7, 4, 4 };
+const char sqlite3StdTypeAffinity[] = {
+  SQLITE_AFF_NUMERIC,
+  SQLITE_AFF_BLOB,
+  SQLITE_AFF_INTEGER,
+  SQLITE_AFF_INTEGER,
+  SQLITE_AFF_REAL,
+  SQLITE_AFF_TEXT
+};
+const char *sqlite3StdType[] = {
+  "ANY",
+  "BLOB",
+  "INT",
+  "INTEGER",
+  "REAL",
+  "TEXT"
+};
diff --git a/src/hash.c b/src/hash.c
new file mode 100644
index 0000000..8ec043f
--- /dev/null
+++ b/src/hash.c
@@ -0,0 +1,270 @@
+/*
+** 2001 September 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the implementation of generic hash-tables
+** used in SQLite.
+*/
+#include "sqliteInt.h"
+#include <assert.h>
+
+/* Turn bulk memory into a hash table object by initializing the
+** fields of the Hash structure.
+**
+** "pNew" is a pointer to the hash table that is to be initialized.
+*/
+void sqlite3HashInit(Hash *pNew){
+  assert( pNew!=0 );
+  pNew->first = 0;
+  pNew->count = 0;
+  pNew->htsize = 0;
+  pNew->ht = 0;
+}
+
+/* Remove all entries from a hash table.  Reclaim all memory.
+** Call this routine to delete a hash table or to reset a hash table
+** to the empty state.
+*/
+void sqlite3HashClear(Hash *pH){
+  HashElem *elem;         /* For looping over all elements of the table */
+
+  assert( pH!=0 );
+  elem = pH->first;
+  pH->first = 0;
+  sqlite3_free(pH->ht);
+  pH->ht = 0;
+  pH->htsize = 0;
+  while( elem ){
+    HashElem *next_elem = elem->next;
+    sqlite3_free(elem);
+    elem = next_elem;
+  }
+  pH->count = 0;
+}
+
+/*
+** The hashing function.
+*/
+static unsigned int strHash(const char *z){
+  unsigned int h = 0;
+  unsigned char c;
+  while( (c = (unsigned char)*z++)!=0 ){     /*OPTIMIZATION-IF-TRUE*/
+    /* Knuth multiplicative hashing.  (Sorting & Searching, p. 510).
+    ** 0x9e3779b1 is 2654435761 which is the closest prime number to
+    ** (2**32)*golden_ratio, where golden_ratio = (sqrt(5) - 1)/2. */
+    h += sqlite3UpperToLower[c];
+    h *= 0x9e3779b1;
+  }
+  return h;
+}
+
+
+/* Link pNew element into the hash table pH.  If pEntry!=0 then also
+** insert pNew into the pEntry hash bucket.
+*/
+static void insertElement(
+  Hash *pH,              /* The complete hash table */
+  struct _ht *pEntry,    /* The entry into which pNew is inserted */
+  HashElem *pNew         /* The element to be inserted */
+){
+  HashElem *pHead;       /* First element already in pEntry */
+  if( pEntry ){
+    pHead = pEntry->count ? pEntry->chain : 0;
+    pEntry->count++;
+    pEntry->chain = pNew;
+  }else{
+    pHead = 0;
+  }
+  if( pHead ){
+    pNew->next = pHead;
+    pNew->prev = pHead->prev;
+    if( pHead->prev ){ pHead->prev->next = pNew; }
+    else             { pH->first = pNew; }
+    pHead->prev = pNew;
+  }else{
+    pNew->next = pH->first;
+    if( pH->first ){ pH->first->prev = pNew; }
+    pNew->prev = 0;
+    pH->first = pNew;
+  }
+}
+
+
+/* Resize the hash table so that it contains "new_size" buckets.
+**
+** The hash table might fail to resize if sqlite3_malloc() fails or
+** if the new size is the same as the prior size.
+** Return TRUE if the resize occurs and false if not.
+*/
+static int rehash(Hash *pH, unsigned int new_size){
+  struct _ht *new_ht;            /* The new hash table */
+  HashElem *elem, *next_elem;    /* For looping over existing elements */
+
+#if SQLITE_MALLOC_SOFT_LIMIT>0
+  if( new_size*sizeof(struct _ht)>SQLITE_MALLOC_SOFT_LIMIT ){
+    new_size = SQLITE_MALLOC_SOFT_LIMIT/sizeof(struct _ht);
+  }
+  if( new_size==pH->htsize ) return 0;
+#endif
+
+  /* The inability to allocates space for a larger hash table is
+  ** a performance hit but it is not a fatal error.  So mark the
+  ** allocation as a benign. Use sqlite3Malloc()/memset(0) instead of 
+  ** sqlite3MallocZero() to make the allocation, as sqlite3MallocZero()
+  ** only zeroes the requested number of bytes whereas this module will
+  ** use the actual amount of space allocated for the hash table (which
+  ** may be larger than the requested amount).
+  */
+  sqlite3BeginBenignMalloc();
+  new_ht = (struct _ht *)sqlite3Malloc( new_size*sizeof(struct _ht) );
+  sqlite3EndBenignMalloc();
+
+  if( new_ht==0 ) return 0;
+  sqlite3_free(pH->ht);
+  pH->ht = new_ht;
+  pH->htsize = new_size = sqlite3MallocSize(new_ht)/sizeof(struct _ht);
+  memset(new_ht, 0, new_size*sizeof(struct _ht));
+  for(elem=pH->first, pH->first=0; elem; elem = next_elem){
+    unsigned int h = strHash(elem->pKey) % new_size;
+    next_elem = elem->next;
+    insertElement(pH, &new_ht[h], elem);
+  }
+  return 1;
+}
+
+/* This function (for internal use only) locates an element in an
+** hash table that matches the given key.  If no element is found,
+** a pointer to a static null element with HashElem.data==0 is returned.
+** If pH is not NULL, then the hash for this key is written to *pH.
+*/
+static HashElem *findElementWithHash(
+  const Hash *pH,     /* The pH to be searched */
+  const char *pKey,   /* The key we are searching for */
+  unsigned int *pHash /* Write the hash value here */
+){
+  HashElem *elem;                /* Used to loop thru the element list */
+  unsigned int count;            /* Number of elements left to test */
+  unsigned int h;                /* The computed hash */
+  static HashElem nullElement = { 0, 0, 0, 0 };
+
+  if( pH->ht ){   /*OPTIMIZATION-IF-TRUE*/
+    struct _ht *pEntry;
+    h = strHash(pKey) % pH->htsize;
+    pEntry = &pH->ht[h];
+    elem = pEntry->chain;
+    count = pEntry->count;
+  }else{
+    h = 0;
+    elem = pH->first;
+    count = pH->count;
+  }
+  if( pHash ) *pHash = h;
+  while( count ){
+    assert( elem!=0 );
+    if( sqlite3StrICmp(elem->pKey,pKey)==0 ){ 
+      return elem;
+    }
+    elem = elem->next;
+    count--;
+  }
+  return &nullElement;
+}
+
+/* Remove a single entry from the hash table given a pointer to that
+** element and a hash on the element's key.
+*/
+static void removeElementGivenHash(
+  Hash *pH,         /* The pH containing "elem" */
+  HashElem* elem,   /* The element to be removed from the pH */
+  unsigned int h    /* Hash value for the element */
+){
+  struct _ht *pEntry;
+  if( elem->prev ){
+    elem->prev->next = elem->next; 
+  }else{
+    pH->first = elem->next;
+  }
+  if( elem->next ){
+    elem->next->prev = elem->prev;
+  }
+  if( pH->ht ){
+    pEntry = &pH->ht[h];
+    if( pEntry->chain==elem ){
+      pEntry->chain = elem->next;
+    }
+    assert( pEntry->count>0 );
+    pEntry->count--;
+  }
+  sqlite3_free( elem );
+  pH->count--;
+  if( pH->count==0 ){
+    assert( pH->first==0 );
+    assert( pH->count==0 );
+    sqlite3HashClear(pH);
+  }
+}
+
+/* Attempt to locate an element of the hash table pH with a key
+** that matches pKey.  Return the data for this element if it is
+** found, or NULL if there is no match.
+*/
+void *sqlite3HashFind(const Hash *pH, const char *pKey){
+  assert( pH!=0 );
+  assert( pKey!=0 );
+  return findElementWithHash(pH, pKey, 0)->data;
+}
+
+/* Insert an element into the hash table pH.  The key is pKey
+** and the data is "data".
+**
+** If no element exists with a matching key, then a new
+** element is created and NULL is returned.
+**
+** If another element already exists with the same key, then the
+** new data replaces the old data and the old data is returned.
+** The key is not copied in this instance.  If a malloc fails, then
+** the new data is returned and the hash table is unchanged.
+**
+** If the "data" parameter to this function is NULL, then the
+** element corresponding to "key" is removed from the hash table.
+*/
+void *sqlite3HashInsert(Hash *pH, const char *pKey, void *data){
+  unsigned int h;       /* the hash of the key modulo hash table size */
+  HashElem *elem;       /* Used to loop thru the element list */
+  HashElem *new_elem;   /* New element added to the pH */
+
+  assert( pH!=0 );
+  assert( pKey!=0 );
+  elem = findElementWithHash(pH,pKey,&h);
+  if( elem->data ){
+    void *old_data = elem->data;
+    if( data==0 ){
+      removeElementGivenHash(pH,elem,h);
+    }else{
+      elem->data = data;
+      elem->pKey = pKey;
+    }
+    return old_data;
+  }
+  if( data==0 ) return 0;
+  new_elem = (HashElem*)sqlite3Malloc( sizeof(HashElem) );
+  if( new_elem==0 ) return data;
+  new_elem->pKey = pKey;
+  new_elem->data = data;
+  pH->count++;
+  if( pH->count>=10 && pH->count > 2*pH->htsize ){
+    if( rehash(pH, pH->count*2) ){
+      assert( pH->htsize>0 );
+      h = strHash(pKey) % pH->htsize;
+    }
+  }
+  insertElement(pH, pH->ht ? &pH->ht[h] : 0, new_elem);
+  return 0;
+}
diff --git a/src/hash.h b/src/hash.h
new file mode 100644
index 0000000..3f491e4
--- /dev/null
+++ b/src/hash.h
@@ -0,0 +1,96 @@
+/*
+** 2001 September 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the header file for the generic hash-table implementation
+** used in SQLite.
+*/
+#ifndef SQLITE_HASH_H
+#define SQLITE_HASH_H
+
+/* Forward declarations of structures. */
+typedef struct Hash Hash;
+typedef struct HashElem HashElem;
+
+/* A complete hash table is an instance of the following structure.
+** The internals of this structure are intended to be opaque -- client
+** code should not attempt to access or modify the fields of this structure
+** directly.  Change this structure only by using the routines below.
+** However, some of the "procedures" and "functions" for modifying and
+** accessing this structure are really macros, so we can't really make
+** this structure opaque.
+**
+** All elements of the hash table are on a single doubly-linked list.
+** Hash.first points to the head of this list.
+**
+** There are Hash.htsize buckets.  Each bucket points to a spot in
+** the global doubly-linked list.  The contents of the bucket are the
+** element pointed to plus the next _ht.count-1 elements in the list.
+**
+** Hash.htsize and Hash.ht may be zero.  In that case lookup is done
+** by a linear search of the global list.  For small tables, the 
+** Hash.ht table is never allocated because if there are few elements
+** in the table, it is faster to do a linear search than to manage
+** the hash table.
+*/
+struct Hash {
+  unsigned int htsize;      /* Number of buckets in the hash table */
+  unsigned int count;       /* Number of entries in this table */
+  HashElem *first;          /* The first element of the array */
+  struct _ht {              /* the hash table */
+    unsigned int count;        /* Number of entries with this hash */
+    HashElem *chain;           /* Pointer to first entry with this hash */
+  } *ht;
+};
+
+/* Each element in the hash table is an instance of the following 
+** structure.  All elements are stored on a single doubly-linked list.
+**
+** Again, this structure is intended to be opaque, but it can't really
+** be opaque because it is used by macros.
+*/
+struct HashElem {
+  HashElem *next, *prev;       /* Next and previous elements in the table */
+  void *data;                  /* Data associated with this element */
+  const char *pKey;            /* Key associated with this element */
+};
+
+/*
+** Access routines.  To delete, insert a NULL pointer.
+*/
+void sqlite3HashInit(Hash*);
+void *sqlite3HashInsert(Hash*, const char *pKey, void *pData);
+void *sqlite3HashFind(const Hash*, const char *pKey);
+void sqlite3HashClear(Hash*);
+
+/*
+** Macros for looping over all elements of a hash table.  The idiom is
+** like this:
+**
+**   Hash h;
+**   HashElem *p;
+**   ...
+**   for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
+**     SomeStructure *pData = sqliteHashData(p);
+**     // do something with pData
+**   }
+*/
+#define sqliteHashFirst(H)  ((H)->first)
+#define sqliteHashNext(E)   ((E)->next)
+#define sqliteHashData(E)   ((E)->data)
+/* #define sqliteHashKey(E)    ((E)->pKey) // NOT USED */
+/* #define sqliteHashKeysize(E) ((E)->nKey)  // NOT USED */
+
+/*
+** Number of entries in a hash table
+*/
+#define sqliteHashCount(H)  ((H)->count)
+
+#endif /* SQLITE_HASH_H */
diff --git a/src/hwtime.h b/src/hwtime.h
new file mode 100644
index 0000000..f808fa4
--- /dev/null
+++ b/src/hwtime.h
@@ -0,0 +1,85 @@
+/*
+** 2008 May 27
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains inline asm code for retrieving "high-performance"
+** counters for x86 and x86_64 class CPUs.
+*/
+#ifndef SQLITE_HWTIME_H
+#define SQLITE_HWTIME_H
+
+/*
+** The following routine only works on Pentium-class (or newer) processors.
+** It uses the RDTSC opcode to read the cycle count value out of the
+** processor and returns that value.  This can be used for high-res
+** profiling.
+*/
+#if !defined(__STRICT_ANSI__) && \
+    (defined(__GNUC__) || defined(_MSC_VER)) && \
+    (defined(i386) || defined(__i386__) || defined(_M_IX86))
+
+  #if defined(__GNUC__)
+
+  __inline__ sqlite_uint64 sqlite3Hwtime(void){
+     unsigned int lo, hi;
+     __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
+     return (sqlite_uint64)hi << 32 | lo;
+  }
+
+  #elif defined(_MSC_VER)
+
+  __declspec(naked) __inline sqlite_uint64 __cdecl sqlite3Hwtime(void){
+     __asm {
+        rdtsc
+        ret       ; return value at EDX:EAX
+     }
+  }
+
+  #endif
+
+#elif !defined(__STRICT_ANSI__) && (defined(__GNUC__) && defined(__x86_64__))
+
+  __inline__ sqlite_uint64 sqlite3Hwtime(void){
+     unsigned int lo, hi;
+     __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
+     return (sqlite_uint64)hi << 32 | lo;
+  }
+ 
+#elif !defined(__STRICT_ANSI__) && (defined(__GNUC__) && defined(__ppc__))
+
+  __inline__ sqlite_uint64 sqlite3Hwtime(void){
+      unsigned long long retval;
+      unsigned long junk;
+      __asm__ __volatile__ ("\n\
+          1:      mftbu   %1\n\
+                  mftb    %L0\n\
+                  mftbu   %0\n\
+                  cmpw    %0,%1\n\
+                  bne     1b"
+                  : "=r" (retval), "=r" (junk));
+      return retval;
+  }
+
+#else
+
+  /*
+  ** asm() is needed for hardware timing support.  Without asm(),
+  ** disable the sqlite3Hwtime() routine.
+  **
+  ** sqlite3Hwtime() is only used for some obscure debugging
+  ** and analysis configurations, not in any deliverable, so this
+  ** should not be a great loss.
+  */
+  sqlite_uint64 sqlite3Hwtime(void){ return ((sqlite_uint64)0); }
+
+#endif
+
+#endif /* !defined(SQLITE_HWTIME_H) */
diff --git a/src/in-operator.md b/src/in-operator.md
new file mode 100644
index 0000000..e9ad210
--- /dev/null
+++ b/src/in-operator.md
@@ -0,0 +1,107 @@
+IN-Operator Implementation Notes
+================================
+
+## Definitions:
+
+An IN operator has one of the following formats:
+
+>
+     x IN (y1,y2,y3,...,yN)
+     x IN (subquery)
+
+The "x" is referred to as the LHS (left-hand side).  The list or subquery
+on the right is called the RHS (right-hand side).  If the RHS is a list
+it must be a non-empty list.  But if the RHS is a subquery, it can be an
+empty set.
+
+The LHS can be a scalar (a single quantity) or a vector (a list of
+two or or more values) or a subquery that returns one or more columns.
+We use the term "vector" to mean an actually list of values or a
+subquery that returns two or more columns.  An isolated value or
+a subquery that returns a single columns is called a scalar.
+
+The RHS can be a subquery that returns a single column, a subquery
+that returns two or more columns, or a list of scalars.  It is not
+currently support for the RHS to be a list of vectors.
+
+The number of columns for LHS must match the number of columns for
+the RHS.  If the RHS is a list of values, then the LHS must be a 
+scalar.  If the RHS is a subquery returning N columns, then the LHS
+must be a vector of size N.
+
+NULL values can occur in either or both of the LHS and RHS.
+If the LHS contains only
+NULL values then we say that it is a "total-NULL".  If the LHS contains
+some NULL values and some non-NULL values, then it is a "partial-NULL".
+For a scalar, there is no difference between a partial-NULL and a total-NULL.
+The RHS is a partial-NULL if any row contains a NULL value.  The RHS is
+a total-NULL if it contains one or more rows that contain only NULL values.
+The LHS is called "non-NULL" if it contains no NULL values.  The RHS is
+called "non-NULL" if it contains no NULL values in any row.
+
+The result of an IN operator is one of TRUE, FALSE, or NULL.  A NULL result
+means that it cannot be determined if the LHS is contained in the RHS due
+to the presence of NULL values.  In some contexts (for example, when the IN
+operator occurs in a WHERE clause)
+the system only needs a binary result: TRUE or NOT-TRUE.  One can also
+to define a binary result of FALSE and NOT-FALSE, but
+it turns out that no extra optimizations are possible in that case, so if
+the FALSE/NOT-FALSE binary is needed, we have to compute the three-state
+TRUE/FALSE/NULL result and then combine the TRUE and NULL values into 
+NOT-FALSE.
+
+A "NOT IN" operator is computed by first computing the equivalent IN
+operator, then interchanging the TRUE and FALSE results.
+
+## Simple Full-Scan Algorithm
+
+The following algorithm always compute the correct answer.  However, this
+algorithm is suboptimal, especially if there are many rows on the RHS.
+
+  1.  Set the null-flag to false
+  2.  For each row in the RHS:
+      <ol type='a'>
+      <li>  Compare the LHS against the RHS
+      <li>  If the LHS exactly matches the RHS, immediately return TRUE
+      <li>  If the comparison result is NULL, set the null-flag to true
+      </ol>
+  3.  If the null-flag is true, return NULL.
+  4.  Return FALSE
+
+## Optimized Algorithm
+
+The following procedure computes the same answer as the simple full-scan
+algorithm, though it does so with less work in the common case.  This
+is the algorithm that is implemented in SQLite.
+
+  1.  If the RHS is a constant list of length 1 or 2, then rewrite the
+      IN operator as a simple expression.  Implement
+
+            x IN (y1,y2)
+
+      as if it were
+
+            x=y1 OR x=y2
+
+      This is the INDEX_NOOP optimization and is only undertaken if the
+      IN operator is used for membership testing.  If the IN operator is
+      driving a loop, then skip this step entirely.
+
+  2.  Check the LHS to see if it is a partial-NULL and if it is, jump
+      ahead to step 5.
+
+  3.  Do a binary search of the RHS using the LHS as a probe.  If
+      an exact match is found, return TRUE.
+
+  4.  If the RHS is non-NULL then return FALSE.
+
+  5.  If we do not need to distinguish between FALSE and NULL,
+      then return FALSE.
+  
+  6.  For each row in the RHS, compare that row against the LHS and
+      if the result is NULL, immediately return NULL.  In the case
+      of a scalar IN operator, we only need to look at the very first
+      row the RHS because for a scalar RHS, all NULLs will always come 
+      first.  If the RHS is empty, this step is a no-op.
+
+  7.  Return FALSE.
diff --git a/src/insert.c b/src/insert.c
new file mode 100644
index 0000000..1c31ca2
--- /dev/null
+++ b/src/insert.c
@@ -0,0 +1,3165 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle INSERT statements in SQLite.
+*/
+#include "sqliteInt.h"
+
+/*
+** Generate code that will
+**
+**   (1) acquire a lock for table pTab then
+**   (2) open pTab as cursor iCur.
+**
+** If pTab is a WITHOUT ROWID table, then it is the PRIMARY KEY index
+** for that table that is actually opened.
+*/
+void sqlite3OpenTable(
+  Parse *pParse,  /* Generate code into this VDBE */
+  int iCur,       /* The cursor number of the table */
+  int iDb,        /* The database index in sqlite3.aDb[] */
+  Table *pTab,    /* The table to be opened */
+  int opcode      /* OP_OpenRead or OP_OpenWrite */
+){
+  Vdbe *v;
+  assert( !IsVirtual(pTab) );
+  assert( pParse->pVdbe!=0 );
+  v = pParse->pVdbe;
+  assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );
+  if( !pParse->db->noSharedCache ){
+    sqlite3TableLock(pParse, iDb, pTab->tnum,
+                     (opcode==OP_OpenWrite)?1:0, pTab->zName);
+  }
+  if( HasRowid(pTab) ){
+    sqlite3VdbeAddOp4Int(v, opcode, iCur, pTab->tnum, iDb, pTab->nNVCol);
+    VdbeComment((v, "%s", pTab->zName));
+  }else{
+    Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+    assert( pPk!=0 );
+    assert( pPk->tnum==pTab->tnum || CORRUPT_DB );
+    sqlite3VdbeAddOp3(v, opcode, iCur, pPk->tnum, iDb);
+    sqlite3VdbeSetP4KeyInfo(pParse, pPk);
+    VdbeComment((v, "%s", pTab->zName));
+  }
+}
+
+/*
+** Return a pointer to the column affinity string associated with index
+** pIdx. A column affinity string has one character for each column in
+** the table, according to the affinity of the column:
+**
+**  Character      Column affinity
+**  ------------------------------
+**  'A'            BLOB
+**  'B'            TEXT
+**  'C'            NUMERIC
+**  'D'            INTEGER
+**  'F'            REAL
+**
+** An extra 'D' is appended to the end of the string to cover the
+** rowid that appears as the last column in every index.
+**
+** Memory for the buffer containing the column index affinity string
+** is managed along with the rest of the Index structure. It will be
+** released when sqlite3DeleteIndex() is called.
+*/
+static SQLITE_NOINLINE const char *computeIndexAffStr(sqlite3 *db, Index *pIdx){
+  /* The first time a column affinity string for a particular index is
+  ** required, it is allocated and populated here. It is then stored as
+  ** a member of the Index structure for subsequent use.
+  **
+  ** The column affinity string will eventually be deleted by
+  ** sqliteDeleteIndex() when the Index structure itself is cleaned
+  ** up.
+  */
+  int n;
+  Table *pTab = pIdx->pTable;
+  pIdx->zColAff = (char *)sqlite3DbMallocRaw(0, pIdx->nColumn+1);
+  if( !pIdx->zColAff ){
+    sqlite3OomFault(db);
+    return 0;
+  }
+  for(n=0; n<pIdx->nColumn; n++){
+    i16 x = pIdx->aiColumn[n];
+    char aff;
+    if( x>=0 ){
+      aff = pTab->aCol[x].affinity;
+    }else if( x==XN_ROWID ){
+      aff = SQLITE_AFF_INTEGER;
+    }else{
+      assert( x==XN_EXPR );
+      assert( pIdx->bHasExpr );
+      assert( pIdx->aColExpr!=0 );
+      aff = sqlite3ExprAffinity(pIdx->aColExpr->a[n].pExpr);
+    }
+    if( aff<SQLITE_AFF_BLOB ) aff = SQLITE_AFF_BLOB;
+    if( aff>SQLITE_AFF_NUMERIC) aff = SQLITE_AFF_NUMERIC;
+    pIdx->zColAff[n] = aff;
+  }
+  pIdx->zColAff[n] = 0;
+  return pIdx->zColAff;
+}
+const char *sqlite3IndexAffinityStr(sqlite3 *db, Index *pIdx){
+  if( !pIdx->zColAff ) return computeIndexAffStr(db, pIdx);
+  return pIdx->zColAff;
+}
+
+
+/*
+** Compute an affinity string for a table.   Space is obtained
+** from sqlite3DbMalloc().  The caller is responsible for freeing
+** the space when done.
+*/
+char *sqlite3TableAffinityStr(sqlite3 *db, const Table *pTab){
+  char *zColAff;
+  zColAff = (char *)sqlite3DbMallocRaw(db, pTab->nCol+1);
+  if( zColAff ){
+    int i, j;
+    for(i=j=0; i<pTab->nCol; i++){
+      if( (pTab->aCol[i].colFlags & COLFLAG_VIRTUAL)==0 ){
+        zColAff[j++] = pTab->aCol[i].affinity;
+      }
+    }
+    do{
+      zColAff[j--] = 0;
+    }while( j>=0 && zColAff[j]<=SQLITE_AFF_BLOB );
+  }
+  return zColAff; 
+}
+
+/*
+** Make changes to the evolving bytecode to do affinity transformations
+** of values that are about to be gathered into a row for table pTab.
+**
+** For ordinary (legacy, non-strict) tables:
+** -----------------------------------------
+**
+** Compute the affinity string for table pTab, if it has not already been
+** computed.  As an optimization, omit trailing SQLITE_AFF_BLOB affinities.
+**
+** If the affinity string is empty (because it was all SQLITE_AFF_BLOB entries
+** which were then optimized out) then this routine becomes a no-op.
+**
+** Otherwise if iReg>0 then code an OP_Affinity opcode that will set the
+** affinities for register iReg and following.  Or if iReg==0,
+** then just set the P4 operand of the previous opcode (which should  be
+** an OP_MakeRecord) to the affinity string.
+**
+** A column affinity string has one character per column:
+**
+**    Character      Column affinity
+**    ---------      ---------------
+**    'A'            BLOB
+**    'B'            TEXT
+**    'C'            NUMERIC
+**    'D'            INTEGER
+**    'E'            REAL
+**
+** For STRICT tables:
+** ------------------
+**
+** Generate an appropriate OP_TypeCheck opcode that will verify the
+** datatypes against the column definitions in pTab.  If iReg==0, that
+** means an OP_MakeRecord opcode has already been generated and should be
+** the last opcode generated.  The new OP_TypeCheck needs to be inserted
+** before the OP_MakeRecord.  The new OP_TypeCheck should use the same
+** register set as the OP_MakeRecord.  If iReg>0 then register iReg is
+** the first of a series of registers that will form the new record.
+** Apply the type checking to that array of registers.
+*/
+void sqlite3TableAffinity(Vdbe *v, Table *pTab, int iReg){
+  int i;
+  char *zColAff;
+  if( pTab->tabFlags & TF_Strict ){
+    if( iReg==0 ){
+      /* Move the previous opcode (which should be OP_MakeRecord) forward
+      ** by one slot and insert a new OP_TypeCheck where the current
+      ** OP_MakeRecord is found */
+      VdbeOp *pPrev;
+      sqlite3VdbeAppendP4(v, pTab, P4_TABLE);
+      pPrev = sqlite3VdbeGetLastOp(v);
+      assert( pPrev!=0 );
+      assert( pPrev->opcode==OP_MakeRecord || sqlite3VdbeDb(v)->mallocFailed );
+      pPrev->opcode = OP_TypeCheck;
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, pPrev->p1, pPrev->p2, pPrev->p3);
+    }else{
+      /* Insert an isolated OP_Typecheck */
+      sqlite3VdbeAddOp2(v, OP_TypeCheck, iReg, pTab->nNVCol);
+      sqlite3VdbeAppendP4(v, pTab, P4_TABLE);
+    }
+    return;
+  }
+  zColAff = pTab->zColAff;
+  if( zColAff==0 ){
+    zColAff = sqlite3TableAffinityStr(0, pTab);
+    if( !zColAff ){
+      sqlite3OomFault(sqlite3VdbeDb(v));
+      return;
+    }
+    pTab->zColAff = zColAff;
+  }
+  assert( zColAff!=0 );
+  i = sqlite3Strlen30NN(zColAff);
+  if( i ){
+    if( iReg ){
+      sqlite3VdbeAddOp4(v, OP_Affinity, iReg, i, 0, zColAff, i);
+    }else{
+      assert( sqlite3VdbeGetLastOp(v)->opcode==OP_MakeRecord
+              || sqlite3VdbeDb(v)->mallocFailed );
+      sqlite3VdbeChangeP4(v, -1, zColAff, i);
+    }
+  }
+}
+
+/*
+** Return non-zero if the table pTab in database iDb or any of its indices
+** have been opened at any point in the VDBE program. This is used to see if
+** a statement of the form  "INSERT INTO <iDb, pTab> SELECT ..." can
+** run without using a temporary table for the results of the SELECT.
+*/
+static int readsTable(Parse *p, int iDb, Table *pTab){
+  Vdbe *v = sqlite3GetVdbe(p);
+  int i;
+  int iEnd = sqlite3VdbeCurrentAddr(v);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  VTable *pVTab = IsVirtual(pTab) ? sqlite3GetVTable(p->db, pTab) : 0;
+#endif
+
+  for(i=1; i<iEnd; i++){
+    VdbeOp *pOp = sqlite3VdbeGetOp(v, i);
+    assert( pOp!=0 );
+    if( pOp->opcode==OP_OpenRead && pOp->p3==iDb ){
+      Index *pIndex;
+      Pgno tnum = pOp->p2;
+      if( tnum==pTab->tnum ){
+        return 1;
+      }
+      for(pIndex=pTab->pIndex; pIndex; pIndex=pIndex->pNext){
+        if( tnum==pIndex->tnum ){
+          return 1;
+        }
+      }
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( pOp->opcode==OP_VOpen && pOp->p4.pVtab==pVTab ){
+      assert( pOp->p4.pVtab!=0 );
+      assert( pOp->p4type==P4_VTAB );
+      return 1;
+    }
+#endif
+  }
+  return 0;
+}
+
+/* This walker callback will compute the union of colFlags flags for all
+** referenced columns in a CHECK constraint or generated column expression.
+*/
+static int exprColumnFlagUnion(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_COLUMN && pExpr->iColumn>=0 ){
+    assert( pExpr->iColumn < pWalker->u.pTab->nCol );
+    pWalker->eCode |= pWalker->u.pTab->aCol[pExpr->iColumn].colFlags;
+  }
+  return WRC_Continue;
+}
+
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+/*
+** All regular columns for table pTab have been puts into registers
+** starting with iRegStore.  The registers that correspond to STORED
+** or VIRTUAL columns have not yet been initialized.  This routine goes
+** back and computes the values for those columns based on the previously
+** computed normal columns.
+*/
+void sqlite3ComputeGeneratedColumns(
+  Parse *pParse,    /* Parsing context */
+  int iRegStore,    /* Register holding the first column */
+  Table *pTab       /* The table */
+){
+  int i;
+  Walker w;
+  Column *pRedo;
+  int eProgress;
+  VdbeOp *pOp;
+
+  assert( pTab->tabFlags & TF_HasGenerated );
+  testcase( pTab->tabFlags & TF_HasVirtual );
+  testcase( pTab->tabFlags & TF_HasStored );
+
+  /* Before computing generated columns, first go through and make sure
+  ** that appropriate affinity has been applied to the regular columns
+  */
+  sqlite3TableAffinity(pParse->pVdbe, pTab, iRegStore);
+  if( (pTab->tabFlags & TF_HasStored)!=0 ){
+    pOp = sqlite3VdbeGetLastOp(pParse->pVdbe);
+    if( pOp->opcode==OP_Affinity ){
+      /* Change the OP_Affinity argument to '@' (NONE) for all stored
+      ** columns.  '@' is the no-op affinity and those columns have not
+      ** yet been computed. */
+      int ii, jj;
+      char *zP4 = pOp->p4.z;
+      assert( zP4!=0 );
+      assert( pOp->p4type==P4_DYNAMIC );
+      for(ii=jj=0; zP4[jj]; ii++){
+        if( pTab->aCol[ii].colFlags & COLFLAG_VIRTUAL ){
+          continue;
+        }
+        if( pTab->aCol[ii].colFlags & COLFLAG_STORED ){
+          zP4[jj] = SQLITE_AFF_NONE;
+        }
+        jj++;
+      }
+    }else if( pOp->opcode==OP_TypeCheck ){
+      /* If an OP_TypeCheck was generated because the table is STRICT,
+      ** then set the P3 operand to indicate that generated columns should
+      ** not be checked */
+      pOp->p3 = 1;
+    }
+  }
+
+  /* Because there can be multiple generated columns that refer to one another,
+  ** this is a two-pass algorithm.  On the first pass, mark all generated
+  ** columns as "not available".
+  */
+  for(i=0; i<pTab->nCol; i++){
+    if( pTab->aCol[i].colFlags & COLFLAG_GENERATED ){
+      testcase( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL );
+      testcase( pTab->aCol[i].colFlags & COLFLAG_STORED );
+      pTab->aCol[i].colFlags |= COLFLAG_NOTAVAIL;
+    }
+  }
+
+  w.u.pTab = pTab;
+  w.xExprCallback = exprColumnFlagUnion;
+  w.xSelectCallback = 0;
+  w.xSelectCallback2 = 0;
+
+  /* On the second pass, compute the value of each NOT-AVAILABLE column.
+  ** Companion code in the TK_COLUMN case of sqlite3ExprCodeTarget() will
+  ** compute dependencies and mark remove the COLSPAN_NOTAVAIL mark, as
+  ** they are needed.
+  */
+  pParse->iSelfTab = -iRegStore;
+  do{
+    eProgress = 0;
+    pRedo = 0;
+    for(i=0; i<pTab->nCol; i++){
+      Column *pCol = pTab->aCol + i;
+      if( (pCol->colFlags & COLFLAG_NOTAVAIL)!=0 ){
+        int x;
+        pCol->colFlags |= COLFLAG_BUSY;
+        w.eCode = 0;
+        sqlite3WalkExpr(&w, sqlite3ColumnExpr(pTab, pCol));
+        pCol->colFlags &= ~COLFLAG_BUSY;
+        if( w.eCode & COLFLAG_NOTAVAIL ){
+          pRedo = pCol;
+          continue;
+        }
+        eProgress = 1;
+        assert( pCol->colFlags & COLFLAG_GENERATED );
+        x = sqlite3TableColumnToStorage(pTab, i) + iRegStore;
+        sqlite3ExprCodeGeneratedColumn(pParse, pTab, pCol, x);
+        pCol->colFlags &= ~COLFLAG_NOTAVAIL;
+      }
+    }
+  }while( pRedo && eProgress );
+  if( pRedo ){
+    sqlite3ErrorMsg(pParse, "generated column loop on \"%s\"", pRedo->zCnName);
+  }
+  pParse->iSelfTab = 0;
+}
+#endif /* SQLITE_OMIT_GENERATED_COLUMNS */
+
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+/*
+** Locate or create an AutoincInfo structure associated with table pTab
+** which is in database iDb.  Return the register number for the register
+** that holds the maximum rowid.  Return zero if pTab is not an AUTOINCREMENT
+** table.  (Also return zero when doing a VACUUM since we do not want to
+** update the AUTOINCREMENT counters during a VACUUM.)
+**
+** There is at most one AutoincInfo structure per table even if the
+** same table is autoincremented multiple times due to inserts within
+** triggers.  A new AutoincInfo structure is created if this is the
+** first use of table pTab.  On 2nd and subsequent uses, the original
+** AutoincInfo structure is used.
+**
+** Four consecutive registers are allocated:
+**
+**   (1)  The name of the pTab table.
+**   (2)  The maximum ROWID of pTab.
+**   (3)  The rowid in sqlite_sequence of pTab
+**   (4)  The original value of the max ROWID in pTab, or NULL if none
+**
+** The 2nd register is the one that is returned.  That is all the
+** insert routine needs to know about.
+*/
+static int autoIncBegin(
+  Parse *pParse,      /* Parsing context */
+  int iDb,            /* Index of the database holding pTab */
+  Table *pTab         /* The table we are writing to */
+){
+  int memId = 0;      /* Register holding maximum rowid */
+  assert( pParse->db->aDb[iDb].pSchema!=0 );
+  if( (pTab->tabFlags & TF_Autoincrement)!=0
+   && (pParse->db->mDbFlags & DBFLAG_Vacuum)==0
+  ){
+    Parse *pToplevel = sqlite3ParseToplevel(pParse);
+    AutoincInfo *pInfo;
+    Table *pSeqTab = pParse->db->aDb[iDb].pSchema->pSeqTab;
+
+    /* Verify that the sqlite_sequence table exists and is an ordinary
+    ** rowid table with exactly two columns.
+    ** Ticket d8dc2b3a58cd5dc2918a1d4acb 2018-05-23 */
+    if( pSeqTab==0
+     || !HasRowid(pSeqTab)
+     || NEVER(IsVirtual(pSeqTab))
+     || pSeqTab->nCol!=2
+    ){
+      pParse->nErr++;
+      pParse->rc = SQLITE_CORRUPT_SEQUENCE;
+      return 0;
+    }
+
+    pInfo = pToplevel->pAinc;
+    while( pInfo && pInfo->pTab!=pTab ){ pInfo = pInfo->pNext; }
+    if( pInfo==0 ){
+      pInfo = sqlite3DbMallocRawNN(pParse->db, sizeof(*pInfo));
+      sqlite3ParserAddCleanup(pToplevel, sqlite3DbFree, pInfo);
+      testcase( pParse->earlyCleanup );
+      if( pParse->db->mallocFailed ) return 0;
+      pInfo->pNext = pToplevel->pAinc;
+      pToplevel->pAinc = pInfo;
+      pInfo->pTab = pTab;
+      pInfo->iDb = iDb;
+      pToplevel->nMem++;                  /* Register to hold name of table */
+      pInfo->regCtr = ++pToplevel->nMem;  /* Max rowid register */
+      pToplevel->nMem +=2;       /* Rowid in sqlite_sequence + orig max val */
+    }
+    memId = pInfo->regCtr;
+  }
+  return memId;
+}
+
+/*
+** This routine generates code that will initialize all of the
+** register used by the autoincrement tracker. 
+*/
+void sqlite3AutoincrementBegin(Parse *pParse){
+  AutoincInfo *p;            /* Information about an AUTOINCREMENT */
+  sqlite3 *db = pParse->db;  /* The database connection */
+  Db *pDb;                   /* Database only autoinc table */
+  int memId;                 /* Register holding max rowid */
+  Vdbe *v = pParse->pVdbe;   /* VDBE under construction */
+
+  /* This routine is never called during trigger-generation.  It is
+  ** only called from the top-level */
+  assert( pParse->pTriggerTab==0 );
+  assert( sqlite3IsToplevel(pParse) );
+
+  assert( v );   /* We failed long ago if this is not so */
+  for(p = pParse->pAinc; p; p = p->pNext){
+    static const int iLn = VDBE_OFFSET_LINENO(2);
+    static const VdbeOpList autoInc[] = {
+      /* 0  */ {OP_Null,    0,  0, 0},
+      /* 1  */ {OP_Rewind,  0, 10, 0},
+      /* 2  */ {OP_Column,  0,  0, 0},
+      /* 3  */ {OP_Ne,      0,  9, 0},
+      /* 4  */ {OP_Rowid,   0,  0, 0},
+      /* 5  */ {OP_Column,  0,  1, 0},
+      /* 6  */ {OP_AddImm,  0,  0, 0},
+      /* 7  */ {OP_Copy,    0,  0, 0},
+      /* 8  */ {OP_Goto,    0, 11, 0},
+      /* 9  */ {OP_Next,    0,  2, 0},
+      /* 10 */ {OP_Integer, 0,  0, 0},
+      /* 11 */ {OP_Close,   0,  0, 0}
+    };
+    VdbeOp *aOp;
+    pDb = &db->aDb[p->iDb];
+    memId = p->regCtr;
+    assert( sqlite3SchemaMutexHeld(db, 0, pDb->pSchema) );
+    sqlite3OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenRead);
+    sqlite3VdbeLoadString(v, memId-1, p->pTab->zName);
+    aOp = sqlite3VdbeAddOpList(v, ArraySize(autoInc), autoInc, iLn);
+    if( aOp==0 ) break;
+    aOp[0].p2 = memId;
+    aOp[0].p3 = memId+2;
+    aOp[2].p3 = memId;
+    aOp[3].p1 = memId-1;
+    aOp[3].p3 = memId;
+    aOp[3].p5 = SQLITE_JUMPIFNULL;
+    aOp[4].p2 = memId+1;
+    aOp[5].p3 = memId;
+    aOp[6].p1 = memId;
+    aOp[7].p2 = memId+2;
+    aOp[7].p1 = memId;
+    aOp[10].p2 = memId;
+    if( pParse->nTab==0 ) pParse->nTab = 1;
+  }
+}
+
+/*
+** Update the maximum rowid for an autoincrement calculation.
+**
+** This routine should be called when the regRowid register holds a
+** new rowid that is about to be inserted.  If that new rowid is
+** larger than the maximum rowid in the memId memory cell, then the
+** memory cell is updated.
+*/
+static void autoIncStep(Parse *pParse, int memId, int regRowid){
+  if( memId>0 ){
+    sqlite3VdbeAddOp2(pParse->pVdbe, OP_MemMax, memId, regRowid);
+  }
+}
+
+/*
+** This routine generates the code needed to write autoincrement
+** maximum rowid values back into the sqlite_sequence register.
+** Every statement that might do an INSERT into an autoincrement
+** table (either directly or through triggers) needs to call this
+** routine just before the "exit" code.
+*/
+static SQLITE_NOINLINE void autoIncrementEnd(Parse *pParse){
+  AutoincInfo *p;
+  Vdbe *v = pParse->pVdbe;
+  sqlite3 *db = pParse->db;
+
+  assert( v );
+  for(p = pParse->pAinc; p; p = p->pNext){
+    static const int iLn = VDBE_OFFSET_LINENO(2);
+    static const VdbeOpList autoIncEnd[] = {
+      /* 0 */ {OP_NotNull,     0, 2, 0},
+      /* 1 */ {OP_NewRowid,    0, 0, 0},
+      /* 2 */ {OP_MakeRecord,  0, 2, 0},
+      /* 3 */ {OP_Insert,      0, 0, 0},
+      /* 4 */ {OP_Close,       0, 0, 0}
+    };
+    VdbeOp *aOp;
+    Db *pDb = &db->aDb[p->iDb];
+    int iRec;
+    int memId = p->regCtr;
+
+    iRec = sqlite3GetTempReg(pParse);
+    assert( sqlite3SchemaMutexHeld(db, 0, pDb->pSchema) );
+    sqlite3VdbeAddOp3(v, OP_Le, memId+2, sqlite3VdbeCurrentAddr(v)+7, memId);
+    VdbeCoverage(v);
+    sqlite3OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenWrite);
+    aOp = sqlite3VdbeAddOpList(v, ArraySize(autoIncEnd), autoIncEnd, iLn);
+    if( aOp==0 ) break;
+    aOp[0].p1 = memId+1;
+    aOp[1].p2 = memId+1;
+    aOp[2].p1 = memId-1;
+    aOp[2].p3 = iRec;
+    aOp[3].p2 = iRec;
+    aOp[3].p3 = memId+1;
+    aOp[3].p5 = OPFLAG_APPEND;
+    sqlite3ReleaseTempReg(pParse, iRec);
+  }
+}
+void sqlite3AutoincrementEnd(Parse *pParse){
+  if( pParse->pAinc ) autoIncrementEnd(pParse);
+}
+#else
+/*
+** If SQLITE_OMIT_AUTOINCREMENT is defined, then the three routines
+** above are all no-ops
+*/
+# define autoIncBegin(A,B,C) (0)
+# define autoIncStep(A,B,C)
+#endif /* SQLITE_OMIT_AUTOINCREMENT */
+
+
+/* Forward declaration */
+static int xferOptimization(
+  Parse *pParse,        /* Parser context */
+  Table *pDest,         /* The table we are inserting into */
+  Select *pSelect,      /* A SELECT statement to use as the data source */
+  int onError,          /* How to handle constraint errors */
+  int iDbDest           /* The database of pDest */
+);
+
+/*
+** This routine is called to handle SQL of the following forms:
+**
+**    insert into TABLE (IDLIST) values(EXPRLIST),(EXPRLIST),...
+**    insert into TABLE (IDLIST) select
+**    insert into TABLE (IDLIST) default values
+**
+** The IDLIST following the table name is always optional.  If omitted,
+** then a list of all (non-hidden) columns for the table is substituted.
+** The IDLIST appears in the pColumn parameter.  pColumn is NULL if IDLIST
+** is omitted.
+**
+** For the pSelect parameter holds the values to be inserted for the
+** first two forms shown above.  A VALUES clause is really just short-hand
+** for a SELECT statement that omits the FROM clause and everything else
+** that follows.  If the pSelect parameter is NULL, that means that the
+** DEFAULT VALUES form of the INSERT statement is intended.
+**
+** The code generated follows one of four templates.  For a simple
+** insert with data coming from a single-row VALUES clause, the code executes
+** once straight down through.  Pseudo-code follows (we call this
+** the "1st template"):
+**
+**         open write cursor to <table> and its indices
+**         put VALUES clause expressions into registers
+**         write the resulting record into <table>
+**         cleanup
+**
+** The three remaining templates assume the statement is of the form
+**
+**   INSERT INTO <table> SELECT ...
+**
+** If the SELECT clause is of the restricted form "SELECT * FROM <table2>" -
+** in other words if the SELECT pulls all columns from a single table
+** and there is no WHERE or LIMIT or GROUP BY or ORDER BY clauses, and
+** if <table2> and <table1> are distinct tables but have identical
+** schemas, including all the same indices, then a special optimization
+** is invoked that copies raw records from <table2> over to <table1>.
+** See the xferOptimization() function for the implementation of this
+** template.  This is the 2nd template.
+**
+**         open a write cursor to <table>
+**         open read cursor on <table2>
+**         transfer all records in <table2> over to <table>
+**         close cursors
+**         foreach index on <table>
+**           open a write cursor on the <table> index
+**           open a read cursor on the corresponding <table2> index
+**           transfer all records from the read to the write cursors
+**           close cursors
+**         end foreach
+**
+** The 3rd template is for when the second template does not apply
+** and the SELECT clause does not read from <table> at any time.
+** The generated code follows this template:
+**
+**         X <- A
+**         goto B
+**      A: setup for the SELECT
+**         loop over the rows in the SELECT
+**           load values into registers R..R+n
+**           yield X
+**         end loop
+**         cleanup after the SELECT
+**         end-coroutine X
+**      B: open write cursor to <table> and its indices
+**      C: yield X, at EOF goto D
+**         insert the select result into <table> from R..R+n
+**         goto C
+**      D: cleanup
+**
+** The 4th template is used if the insert statement takes its
+** values from a SELECT but the data is being inserted into a table
+** that is also read as part of the SELECT.  In the third form,
+** we have to use an intermediate table to store the results of
+** the select.  The template is like this:
+**
+**         X <- A
+**         goto B
+**      A: setup for the SELECT
+**         loop over the tables in the SELECT
+**           load value into register R..R+n
+**           yield X
+**         end loop
+**         cleanup after the SELECT
+**         end co-routine R
+**      B: open temp table
+**      L: yield X, at EOF goto M
+**         insert row from R..R+n into temp table
+**         goto L
+**      M: open write cursor to <table> and its indices
+**         rewind temp table
+**      C: loop over rows of intermediate table
+**           transfer values form intermediate table into <table>
+**         end loop
+**      D: cleanup
+*/
+void sqlite3Insert(
+  Parse *pParse,        /* Parser context */
+  SrcList *pTabList,    /* Name of table into which we are inserting */
+  Select *pSelect,      /* A SELECT statement to use as the data source */
+  IdList *pColumn,      /* Column names corresponding to IDLIST, or NULL. */
+  int onError,          /* How to handle constraint errors */
+  Upsert *pUpsert       /* ON CONFLICT clauses for upsert, or NULL */
+){
+  sqlite3 *db;          /* The main database structure */
+  Table *pTab;          /* The table to insert into.  aka TABLE */
+  int i, j;             /* Loop counters */
+  Vdbe *v;              /* Generate code into this virtual machine */
+  Index *pIdx;          /* For looping over indices of the table */
+  int nColumn;          /* Number of columns in the data */
+  int nHidden = 0;      /* Number of hidden columns if TABLE is virtual */
+  int iDataCur = 0;     /* VDBE cursor that is the main data repository */
+  int iIdxCur = 0;      /* First index cursor */
+  int ipkColumn = -1;   /* Column that is the INTEGER PRIMARY KEY */
+  int endOfLoop;        /* Label for the end of the insertion loop */
+  int srcTab = 0;       /* Data comes from this temporary cursor if >=0 */
+  int addrInsTop = 0;   /* Jump to label "D" */
+  int addrCont = 0;     /* Top of insert loop. Label "C" in templates 3 and 4 */
+  SelectDest dest;      /* Destination for SELECT on rhs of INSERT */
+  int iDb;              /* Index of database holding TABLE */
+  u8 useTempTable = 0;  /* Store SELECT results in intermediate table */
+  u8 appendFlag = 0;    /* True if the insert is likely to be an append */
+  u8 withoutRowid;      /* 0 for normal table.  1 for WITHOUT ROWID table */
+  u8 bIdListInOrder;    /* True if IDLIST is in table order */
+  ExprList *pList = 0;  /* List of VALUES() to be inserted  */
+  int iRegStore;        /* Register in which to store next column */
+
+  /* Register allocations */
+  int regFromSelect = 0;/* Base register for data coming from SELECT */
+  int regAutoinc = 0;   /* Register holding the AUTOINCREMENT counter */
+  int regRowCount = 0;  /* Memory cell used for the row counter */
+  int regIns;           /* Block of regs holding rowid+data being inserted */
+  int regRowid;         /* registers holding insert rowid */
+  int regData;          /* register holding first column to insert */
+  int *aRegIdx = 0;     /* One register allocated to each index */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  int isView;                 /* True if attempting to insert into a view */
+  Trigger *pTrigger;          /* List of triggers on pTab, if required */
+  int tmask;                  /* Mask of trigger times */
+#endif
+
+  db = pParse->db;
+  assert( db->pParse==pParse );
+  if( pParse->nErr ){
+    goto insert_cleanup;
+  }
+  assert( db->mallocFailed==0 );
+  dest.iSDParm = 0;  /* Suppress a harmless compiler warning */
+
+  /* If the Select object is really just a simple VALUES() list with a
+  ** single row (the common case) then keep that one row of values
+  ** and discard the other (unused) parts of the pSelect object
+  */
+  if( pSelect && (pSelect->selFlags & SF_Values)!=0 && pSelect->pPrior==0 ){
+    pList = pSelect->pEList;
+    pSelect->pEList = 0;
+    sqlite3SelectDelete(db, pSelect);
+    pSelect = 0;
+  }
+
+  /* Locate the table into which we will be inserting new information.
+  */
+  assert( pTabList->nSrc==1 );
+  pTab = sqlite3SrcListLookup(pParse, pTabList);
+  if( pTab==0 ){
+    goto insert_cleanup;
+  }
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb<db->nDb );
+  if( sqlite3AuthCheck(pParse, SQLITE_INSERT, pTab->zName, 0,
+                       db->aDb[iDb].zDbSName) ){
+    goto insert_cleanup;
+  }
+  withoutRowid = !HasRowid(pTab);
+
+  /* Figure out if we have any triggers and if the table being
+  ** inserted into is a view
+  */
+#ifndef SQLITE_OMIT_TRIGGER
+  pTrigger = sqlite3TriggersExist(pParse, pTab, TK_INSERT, 0, &tmask);
+  isView = IsView(pTab);
+#else
+# define pTrigger 0
+# define tmask 0
+# define isView 0
+#endif
+#ifdef SQLITE_OMIT_VIEW
+# undef isView
+# define isView 0
+#endif
+  assert( (pTrigger && tmask) || (pTrigger==0 && tmask==0) );
+
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x10000 ){
+    sqlite3TreeViewLine(0, "In sqlite3Insert() at %s:%d", __FILE__, __LINE__);
+    sqlite3TreeViewInsert(pParse->pWith, pTabList, pColumn, pSelect, pList,
+                          onError, pUpsert, pTrigger);
+  }
+#endif
+
+  /* If pTab is really a view, make sure it has been initialized.
+  ** ViewGetColumnNames() is a no-op if pTab is not a view.
+  */
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto insert_cleanup;
+  }
+
+  /* Cannot insert into a read-only table.
+  */
+  if( sqlite3IsReadOnly(pParse, pTab, pTrigger) ){
+    goto insert_cleanup;
+  }
+
+  /* Allocate a VDBE
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) goto insert_cleanup;
+  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
+  sqlite3BeginWriteOperation(pParse, pSelect || pTrigger, iDb);
+
+#ifndef SQLITE_OMIT_XFER_OPT
+  /* If the statement is of the form
+  **
+  **       INSERT INTO <table1> SELECT * FROM <table2>;
+  **
+  ** Then special optimizations can be applied that make the transfer
+  ** very fast and which reduce fragmentation of indices.
+  **
+  ** This is the 2nd template.
+  */
+  if( pColumn==0
+   && pSelect!=0
+   && pTrigger==0
+   && xferOptimization(pParse, pTab, pSelect, onError, iDb)
+  ){
+    assert( !pTrigger );
+    assert( pList==0 );
+    goto insert_end;
+  }
+#endif /* SQLITE_OMIT_XFER_OPT */
+
+  /* If this is an AUTOINCREMENT table, look up the sequence number in the
+  ** sqlite_sequence table and store it in memory cell regAutoinc.
+  */
+  regAutoinc = autoIncBegin(pParse, iDb, pTab);
+
+  /* Allocate a block registers to hold the rowid and the values
+  ** for all columns of the new row.
+  */
+  regRowid = regIns = pParse->nMem+1;
+  pParse->nMem += pTab->nCol + 1;
+  if( IsVirtual(pTab) ){
+    regRowid++;
+    pParse->nMem++;
+  }
+  regData = regRowid+1;
+
+  /* If the INSERT statement included an IDLIST term, then make sure
+  ** all elements of the IDLIST really are columns of the table and
+  ** remember the column indices.
+  **
+  ** If the table has an INTEGER PRIMARY KEY column and that column
+  ** is named in the IDLIST, then record in the ipkColumn variable
+  ** the index into IDLIST of the primary key column.  ipkColumn is
+  ** the index of the primary key as it appears in IDLIST, not as
+  ** is appears in the original table.  (The index of the INTEGER
+  ** PRIMARY KEY in the original table is pTab->iPKey.)  After this
+  ** loop, if ipkColumn==(-1), that means that integer primary key
+  ** is unspecified, and hence the table is either WITHOUT ROWID or
+  ** it will automatically generated an integer primary key.
+  **
+  ** bIdListInOrder is true if the columns in IDLIST are in storage
+  ** order.  This enables an optimization that avoids shuffling the
+  ** columns into storage order.  False negatives are harmless,
+  ** but false positives will cause database corruption.
+  */
+  bIdListInOrder = (pTab->tabFlags & (TF_OOOHidden|TF_HasStored))==0;
+  if( pColumn ){
+    assert( pColumn->eU4!=EU4_EXPR );
+    pColumn->eU4 = EU4_IDX;
+    for(i=0; i<pColumn->nId; i++){
+      pColumn->a[i].u4.idx = -1;
+    }
+    for(i=0; i<pColumn->nId; i++){
+      for(j=0; j<pTab->nCol; j++){
+        if( sqlite3StrICmp(pColumn->a[i].zName, pTab->aCol[j].zCnName)==0 ){
+          pColumn->a[i].u4.idx = j;
+          if( i!=j ) bIdListInOrder = 0;
+          if( j==pTab->iPKey ){
+            ipkColumn = i;  assert( !withoutRowid );
+          }
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+          if( pTab->aCol[j].colFlags & (COLFLAG_STORED|COLFLAG_VIRTUAL) ){
+            sqlite3ErrorMsg(pParse,
+               "cannot INSERT into generated column \"%s\"",
+               pTab->aCol[j].zCnName);
+            goto insert_cleanup;
+          }
+#endif
+          break;
+        }
+      }
+      if( j>=pTab->nCol ){
+        if( sqlite3IsRowid(pColumn->a[i].zName) && !withoutRowid ){
+          ipkColumn = i;
+          bIdListInOrder = 0;
+        }else{
+          sqlite3ErrorMsg(pParse, "table %S has no column named %s",
+              pTabList->a, pColumn->a[i].zName);
+          pParse->checkSchema = 1;
+          goto insert_cleanup;
+        }
+      }
+    }
+  }
+
+  /* Figure out how many columns of data are supplied.  If the data
+  ** is coming from a SELECT statement, then generate a co-routine that
+  ** produces a single row of the SELECT on each invocation.  The
+  ** co-routine is the common header to the 3rd and 4th templates.
+  */
+  if( pSelect ){
+    /* Data is coming from a SELECT or from a multi-row VALUES clause.
+    ** Generate a co-routine to run the SELECT. */
+    int regYield;       /* Register holding co-routine entry-point */
+    int addrTop;        /* Top of the co-routine */
+    int rc;             /* Result code */
+
+    regYield = ++pParse->nMem;
+    addrTop = sqlite3VdbeCurrentAddr(v) + 1;
+    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, addrTop);
+    sqlite3SelectDestInit(&dest, SRT_Coroutine, regYield);
+    dest.iSdst = bIdListInOrder ? regData : 0;
+    dest.nSdst = pTab->nCol;
+    rc = sqlite3Select(pParse, pSelect, &dest);
+    regFromSelect = dest.iSdst;
+    assert( db->pParse==pParse );
+    if( rc || pParse->nErr ) goto insert_cleanup;
+    assert( db->mallocFailed==0 );
+    sqlite3VdbeEndCoroutine(v, regYield);
+    sqlite3VdbeJumpHere(v, addrTop - 1);                       /* label B: */
+    assert( pSelect->pEList );
+    nColumn = pSelect->pEList->nExpr;
+
+    /* Set useTempTable to TRUE if the result of the SELECT statement
+    ** should be written into a temporary table (template 4).  Set to
+    ** FALSE if each output row of the SELECT can be written directly into
+    ** the destination table (template 3).
+    **
+    ** A temp table must be used if the table being updated is also one
+    ** of the tables being read by the SELECT statement.  Also use a
+    ** temp table in the case of row triggers.
+    */
+    if( pTrigger || readsTable(pParse, iDb, pTab) ){
+      useTempTable = 1;
+    }
+
+    if( useTempTable ){
+      /* Invoke the coroutine to extract information from the SELECT
+      ** and add it to a transient table srcTab.  The code generated
+      ** here is from the 4th template:
+      **
+      **      B: open temp table
+      **      L: yield X, goto M at EOF
+      **         insert row from R..R+n into temp table
+      **         goto L
+      **      M: ...
+      */
+      int regRec;          /* Register to hold packed record */
+      int regTempRowid;    /* Register to hold temp table ROWID */
+      int addrL;           /* Label "L" */
+
+      srcTab = pParse->nTab++;
+      regRec = sqlite3GetTempReg(pParse);
+      regTempRowid = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp2(v, OP_OpenEphemeral, srcTab, nColumn);
+      addrL = sqlite3VdbeAddOp1(v, OP_Yield, dest.iSDParm); VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regFromSelect, nColumn, regRec);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, srcTab, regTempRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, srcTab, regRec, regTempRowid);
+      sqlite3VdbeGoto(v, addrL);
+      sqlite3VdbeJumpHere(v, addrL);
+      sqlite3ReleaseTempReg(pParse, regRec);
+      sqlite3ReleaseTempReg(pParse, regTempRowid);
+    }
+  }else{
+    /* This is the case if the data for the INSERT is coming from a
+    ** single-row VALUES clause
+    */
+    NameContext sNC;
+    memset(&sNC, 0, sizeof(sNC));
+    sNC.pParse = pParse;
+    srcTab = -1;
+    assert( useTempTable==0 );
+    if( pList ){
+      nColumn = pList->nExpr;
+      if( sqlite3ResolveExprListNames(&sNC, pList) ){
+        goto insert_cleanup;
+      }
+    }else{
+      nColumn = 0;
+    }
+  }
+
+  /* If there is no IDLIST term but the table has an integer primary
+  ** key, the set the ipkColumn variable to the integer primary key
+  ** column index in the original table definition.
+  */
+  if( pColumn==0 && nColumn>0 ){
+    ipkColumn = pTab->iPKey;
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+    if( ipkColumn>=0 && (pTab->tabFlags & TF_HasGenerated)!=0 ){
+      testcase( pTab->tabFlags & TF_HasVirtual );
+      testcase( pTab->tabFlags & TF_HasStored );
+      for(i=ipkColumn-1; i>=0; i--){
+        if( pTab->aCol[i].colFlags & COLFLAG_GENERATED ){
+          testcase( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL );
+          testcase( pTab->aCol[i].colFlags & COLFLAG_STORED );
+          ipkColumn--;
+        }
+      }
+    }
+#endif
+
+    /* Make sure the number of columns in the source data matches the number
+    ** of columns to be inserted into the table.
+    */
+    assert( TF_HasHidden==COLFLAG_HIDDEN );
+    assert( TF_HasGenerated==COLFLAG_GENERATED );
+    assert( COLFLAG_NOINSERT==(COLFLAG_GENERATED|COLFLAG_HIDDEN) );
+    if( (pTab->tabFlags & (TF_HasGenerated|TF_HasHidden))!=0 ){
+      for(i=0; i<pTab->nCol; i++){
+        if( pTab->aCol[i].colFlags & COLFLAG_NOINSERT ) nHidden++;
+      }
+    }
+    if( nColumn!=(pTab->nCol-nHidden) ){
+      sqlite3ErrorMsg(pParse,
+         "table %S has %d columns but %d values were supplied",
+         pTabList->a, pTab->nCol-nHidden, nColumn);
+     goto insert_cleanup;
+    }
+  }
+  if( pColumn!=0 && nColumn!=pColumn->nId ){
+    sqlite3ErrorMsg(pParse, "%d values for %d columns", nColumn, pColumn->nId);
+    goto insert_cleanup;
+  }
+   
+  /* Initialize the count of rows to be inserted
+  */
+  if( (db->flags & SQLITE_CountRows)!=0
+   && !pParse->nested
+   && !pParse->pTriggerTab
+   && !pParse->bReturning
+  ){
+    regRowCount = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
+  }
+
+  /* If this is not a view, open the table and and all indices */
+  if( !isView ){
+    int nIdx;
+    nIdx = sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, 0, -1, 0,
+                                      &iDataCur, &iIdxCur);
+    aRegIdx = sqlite3DbMallocRawNN(db, sizeof(int)*(nIdx+2));
+    if( aRegIdx==0 ){
+      goto insert_cleanup;
+    }
+    for(i=0, pIdx=pTab->pIndex; i<nIdx; pIdx=pIdx->pNext, i++){
+      assert( pIdx );
+      aRegIdx[i] = ++pParse->nMem;
+      pParse->nMem += pIdx->nColumn;
+    }
+    aRegIdx[i] = ++pParse->nMem;  /* Register to store the table record */
+  }
+#ifndef SQLITE_OMIT_UPSERT
+  if( pUpsert ){
+    Upsert *pNx;
+    if( IsVirtual(pTab) ){
+      sqlite3ErrorMsg(pParse, "UPSERT not implemented for virtual table \"%s\"",
+              pTab->zName);
+      goto insert_cleanup;
+    }
+    if( IsView(pTab) ){
+      sqlite3ErrorMsg(pParse, "cannot UPSERT a view");
+      goto insert_cleanup;
+    }
+    if( sqlite3HasExplicitNulls(pParse, pUpsert->pUpsertTarget) ){
+      goto insert_cleanup;
+    }
+    pTabList->a[0].iCursor = iDataCur;
+    pNx = pUpsert;
+    do{
+      pNx->pUpsertSrc = pTabList;
+      pNx->regData = regData;
+      pNx->iDataCur = iDataCur;
+      pNx->iIdxCur = iIdxCur;
+      if( pNx->pUpsertTarget ){
+        if( sqlite3UpsertAnalyzeTarget(pParse, pTabList, pNx) ){
+          goto insert_cleanup;
+        }
+      }
+      pNx = pNx->pNextUpsert;
+    }while( pNx!=0 );
+  }
+#endif
+
+
+  /* This is the top of the main insertion loop */
+  if( useTempTable ){
+    /* This block codes the top of loop only.  The complete loop is the
+    ** following pseudocode (template 4):
+    **
+    **         rewind temp table, if empty goto D
+    **      C: loop over rows of intermediate table
+    **           transfer values form intermediate table into <table>
+    **         end loop
+    **      D: ...
+    */
+    addrInsTop = sqlite3VdbeAddOp1(v, OP_Rewind, srcTab); VdbeCoverage(v);
+    addrCont = sqlite3VdbeCurrentAddr(v);
+  }else if( pSelect ){
+    /* This block codes the top of loop only.  The complete loop is the
+    ** following pseudocode (template 3):
+    **
+    **      C: yield X, at EOF goto D
+    **         insert the select result into <table> from R..R+n
+    **         goto C
+    **      D: ...
+    */
+    sqlite3VdbeReleaseRegisters(pParse, regData, pTab->nCol, 0, 0);
+    addrInsTop = addrCont = sqlite3VdbeAddOp1(v, OP_Yield, dest.iSDParm);
+    VdbeCoverage(v);
+    if( ipkColumn>=0 ){
+      /* tag-20191021-001: If the INTEGER PRIMARY KEY is being generated by the
+      ** SELECT, go ahead and copy the value into the rowid slot now, so that
+      ** the value does not get overwritten by a NULL at tag-20191021-002. */
+      sqlite3VdbeAddOp2(v, OP_Copy, regFromSelect+ipkColumn, regRowid);
+    }
+  }
+
+  /* Compute data for ordinary columns of the new entry.  Values
+  ** are written in storage order into registers starting with regData.
+  ** Only ordinary columns are computed in this loop. The rowid
+  ** (if there is one) is computed later and generated columns are
+  ** computed after the rowid since they might depend on the value
+  ** of the rowid.
+  */
+  nHidden = 0;
+  iRegStore = regData;  assert( regData==regRowid+1 );
+  for(i=0; i<pTab->nCol; i++, iRegStore++){
+    int k;
+    u32 colFlags;
+    assert( i>=nHidden );
+    if( i==pTab->iPKey ){
+      /* tag-20191021-002: References to the INTEGER PRIMARY KEY are filled
+      ** using the rowid. So put a NULL in the IPK slot of the record to avoid
+      ** using excess space.  The file format definition requires this extra
+      ** NULL - we cannot optimize further by skipping the column completely */
+      sqlite3VdbeAddOp1(v, OP_SoftNull, iRegStore);
+      continue;
+    }
+    if( ((colFlags = pTab->aCol[i].colFlags) & COLFLAG_NOINSERT)!=0 ){
+      nHidden++;
+      if( (colFlags & COLFLAG_VIRTUAL)!=0 ){
+        /* Virtual columns do not participate in OP_MakeRecord.  So back up
+        ** iRegStore by one slot to compensate for the iRegStore++ in the
+        ** outer for() loop */
+        iRegStore--;
+        continue;
+      }else if( (colFlags & COLFLAG_STORED)!=0 ){
+        /* Stored columns are computed later.  But if there are BEFORE
+        ** triggers, the slots used for stored columns will be OP_Copy-ed
+        ** to a second block of registers, so the register needs to be
+        ** initialized to NULL to avoid an uninitialized register read */
+        if( tmask & TRIGGER_BEFORE ){
+          sqlite3VdbeAddOp1(v, OP_SoftNull, iRegStore);
+        }
+        continue;
+      }else if( pColumn==0 ){
+        /* Hidden columns that are not explicitly named in the INSERT
+        ** get there default value */
+        sqlite3ExprCodeFactorable(pParse,
+            sqlite3ColumnExpr(pTab, &pTab->aCol[i]),
+            iRegStore);
+        continue;
+      }
+    }
+    if( pColumn ){
+      assert( pColumn->eU4==EU4_IDX );
+      for(j=0; j<pColumn->nId && pColumn->a[j].u4.idx!=i; j++){}
+      if( j>=pColumn->nId ){
+        /* A column not named in the insert column list gets its
+        ** default value */
+        sqlite3ExprCodeFactorable(pParse,
+            sqlite3ColumnExpr(pTab, &pTab->aCol[i]),
+            iRegStore);
+        continue;
+      }
+      k = j;
+    }else if( nColumn==0 ){
+      /* This is INSERT INTO ... DEFAULT VALUES.  Load the default value. */
+      sqlite3ExprCodeFactorable(pParse,
+          sqlite3ColumnExpr(pTab, &pTab->aCol[i]),
+          iRegStore);
+      continue;
+    }else{
+      k = i - nHidden;
+    }
+
+    if( useTempTable ){
+      sqlite3VdbeAddOp3(v, OP_Column, srcTab, k, iRegStore);
+    }else if( pSelect ){
+      if( regFromSelect!=regData ){
+        sqlite3VdbeAddOp2(v, OP_SCopy, regFromSelect+k, iRegStore);
+      }
+    }else{
+      Expr *pX = pList->a[k].pExpr;
+      int y = sqlite3ExprCodeTarget(pParse, pX, iRegStore);
+      if( y!=iRegStore ){
+        sqlite3VdbeAddOp2(v,
+          ExprHasProperty(pX, EP_Subquery) ? OP_Copy : OP_SCopy, y, iRegStore);
+      }
+    }
+  }
+
+
+  /* Run the BEFORE and INSTEAD OF triggers, if there are any
+  */
+  endOfLoop = sqlite3VdbeMakeLabel(pParse);
+  if( tmask & TRIGGER_BEFORE ){
+    int regCols = sqlite3GetTempRange(pParse, pTab->nCol+1);
+
+    /* build the NEW.* reference row.  Note that if there is an INTEGER
+    ** PRIMARY KEY into which a NULL is being inserted, that NULL will be
+    ** translated into a unique ID for the row.  But on a BEFORE trigger,
+    ** we do not know what the unique ID will be (because the insert has
+    ** not happened yet) so we substitute a rowid of -1
+    */
+    if( ipkColumn<0 ){
+      sqlite3VdbeAddOp2(v, OP_Integer, -1, regCols);
+    }else{
+      int addr1;
+      assert( !withoutRowid );
+      if( useTempTable ){
+        sqlite3VdbeAddOp3(v, OP_Column, srcTab, ipkColumn, regCols);
+      }else{
+        assert( pSelect==0 );  /* Otherwise useTempTable is true */
+        sqlite3ExprCode(pParse, pList->a[ipkColumn].pExpr, regCols);
+      }
+      addr1 = sqlite3VdbeAddOp1(v, OP_NotNull, regCols); VdbeCoverage(v);
+      sqlite3VdbeAddOp2(v, OP_Integer, -1, regCols);
+      sqlite3VdbeJumpHere(v, addr1);
+      sqlite3VdbeAddOp1(v, OP_MustBeInt, regCols); VdbeCoverage(v);
+    }
+
+    /* Copy the new data already generated. */
+    assert( pTab->nNVCol>0 || pParse->nErr>0 );
+    sqlite3VdbeAddOp3(v, OP_Copy, regRowid+1, regCols+1, pTab->nNVCol-1);
+
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+    /* Compute the new value for generated columns after all other
+    ** columns have already been computed.  This must be done after
+    ** computing the ROWID in case one of the generated columns
+    ** refers to the ROWID. */
+    if( pTab->tabFlags & TF_HasGenerated ){
+      testcase( pTab->tabFlags & TF_HasVirtual );
+      testcase( pTab->tabFlags & TF_HasStored );
+      sqlite3ComputeGeneratedColumns(pParse, regCols+1, pTab);
+    }
+#endif
+
+    /* If this is an INSERT on a view with an INSTEAD OF INSERT trigger,
+    ** do not attempt any conversions before assembling the record.
+    ** If this is a real table, attempt conversions as required by the
+    ** table column affinities.
+    */
+    if( !isView ){
+      sqlite3TableAffinity(v, pTab, regCols+1);
+    }
+
+    /* Fire BEFORE or INSTEAD OF triggers */
+    sqlite3CodeRowTrigger(pParse, pTrigger, TK_INSERT, 0, TRIGGER_BEFORE,
+        pTab, regCols-pTab->nCol-1, onError, endOfLoop);
+
+    sqlite3ReleaseTempRange(pParse, regCols, pTab->nCol+1);
+  }
+
+  if( !isView ){
+    if( IsVirtual(pTab) ){
+      /* The row that the VUpdate opcode will delete: none */
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regIns);
+    }
+    if( ipkColumn>=0 ){
+      /* Compute the new rowid */
+      if( useTempTable ){
+        sqlite3VdbeAddOp3(v, OP_Column, srcTab, ipkColumn, regRowid);
+      }else if( pSelect ){
+        /* Rowid already initialized at tag-20191021-001 */
+      }else{
+        Expr *pIpk = pList->a[ipkColumn].pExpr;
+        if( pIpk->op==TK_NULL && !IsVirtual(pTab) ){
+          sqlite3VdbeAddOp3(v, OP_NewRowid, iDataCur, regRowid, regAutoinc);
+          appendFlag = 1;
+        }else{
+          sqlite3ExprCode(pParse, pList->a[ipkColumn].pExpr, regRowid);
+        }
+      }
+      /* If the PRIMARY KEY expression is NULL, then use OP_NewRowid
+      ** to generate a unique primary key value.
+      */
+      if( !appendFlag ){
+        int addr1;
+        if( !IsVirtual(pTab) ){
+          addr1 = sqlite3VdbeAddOp1(v, OP_NotNull, regRowid); VdbeCoverage(v);
+          sqlite3VdbeAddOp3(v, OP_NewRowid, iDataCur, regRowid, regAutoinc);
+          sqlite3VdbeJumpHere(v, addr1);
+        }else{
+          addr1 = sqlite3VdbeCurrentAddr(v);
+          sqlite3VdbeAddOp2(v, OP_IsNull, regRowid, addr1+2); VdbeCoverage(v);
+        }
+        sqlite3VdbeAddOp1(v, OP_MustBeInt, regRowid); VdbeCoverage(v);
+      }
+    }else if( IsVirtual(pTab) || withoutRowid ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regRowid);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_NewRowid, iDataCur, regRowid, regAutoinc);
+      appendFlag = 1;
+    }
+    autoIncStep(pParse, regAutoinc, regRowid);
+
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+    /* Compute the new value for generated columns after all other
+    ** columns have already been computed.  This must be done after
+    ** computing the ROWID in case one of the generated columns
+    ** is derived from the INTEGER PRIMARY KEY. */
+    if( pTab->tabFlags & TF_HasGenerated ){
+      sqlite3ComputeGeneratedColumns(pParse, regRowid+1, pTab);
+    }
+#endif
+
+    /* Generate code to check constraints and generate index keys and
+    ** do the insertion.
+    */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( IsVirtual(pTab) ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
+      sqlite3VtabMakeWritable(pParse, pTab);
+      sqlite3VdbeAddOp4(v, OP_VUpdate, 1, pTab->nCol+2, regIns, pVTab, P4_VTAB);
+      sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
+      sqlite3MayAbort(pParse);
+    }else
+#endif
+    {
+      int isReplace = 0;/* Set to true if constraints may cause a replace */
+      int bUseSeek;     /* True to use OPFLAG_SEEKRESULT */
+      sqlite3GenerateConstraintChecks(pParse, pTab, aRegIdx, iDataCur, iIdxCur,
+          regIns, 0, ipkColumn>=0, onError, endOfLoop, &isReplace, 0, pUpsert
+      );
+      if( db->flags & SQLITE_ForeignKeys ){
+        sqlite3FkCheck(pParse, pTab, 0, regIns, 0, 0);
+      }
+
+      /* Set the OPFLAG_USESEEKRESULT flag if either (a) there are no REPLACE
+      ** constraints or (b) there are no triggers and this table is not a
+      ** parent table in a foreign key constraint. It is safe to set the
+      ** flag in the second case as if any REPLACE constraint is hit, an
+      ** OP_Delete or OP_IdxDelete instruction will be executed on each
+      ** cursor that is disturbed. And these instructions both clear the
+      ** VdbeCursor.seekResult variable, disabling the OPFLAG_USESEEKRESULT
+      ** functionality.  */
+      bUseSeek = (isReplace==0 || !sqlite3VdbeHasSubProgram(v));
+      sqlite3CompleteInsertion(pParse, pTab, iDataCur, iIdxCur,
+          regIns, aRegIdx, 0, appendFlag, bUseSeek
+      );
+    }
+#ifdef SQLITE_ALLOW_ROWID_IN_VIEW
+  }else if( pParse->bReturning ){
+    /* If there is a RETURNING clause, populate the rowid register with
+    ** constant value -1, in case one or more of the returned expressions
+    ** refer to the "rowid" of the view.  */
+    sqlite3VdbeAddOp2(v, OP_Integer, -1, regRowid);
+#endif
+  }
+
+  /* Update the count of rows that are inserted
+  */
+  if( regRowCount ){
+    sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
+  }
+
+  if( pTrigger ){
+    /* Code AFTER triggers */
+    sqlite3CodeRowTrigger(pParse, pTrigger, TK_INSERT, 0, TRIGGER_AFTER,
+        pTab, regData-2-pTab->nCol, onError, endOfLoop);
+  }
+
+  /* The bottom of the main insertion loop, if the data source
+  ** is a SELECT statement.
+  */
+  sqlite3VdbeResolveLabel(v, endOfLoop);
+  if( useTempTable ){
+    sqlite3VdbeAddOp2(v, OP_Next, srcTab, addrCont); VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addrInsTop);
+    sqlite3VdbeAddOp1(v, OP_Close, srcTab);
+  }else if( pSelect ){
+    sqlite3VdbeGoto(v, addrCont);
+#ifdef SQLITE_DEBUG
+    /* If we are jumping back to an OP_Yield that is preceded by an
+    ** OP_ReleaseReg, set the p5 flag on the OP_Goto so that the
+    ** OP_ReleaseReg will be included in the loop. */
+    if( sqlite3VdbeGetOp(v, addrCont-1)->opcode==OP_ReleaseReg ){
+      assert( sqlite3VdbeGetOp(v, addrCont)->opcode==OP_Yield );
+      sqlite3VdbeChangeP5(v, 1);
+    }
+#endif
+    sqlite3VdbeJumpHere(v, addrInsTop);
+  }
+
+#ifndef SQLITE_OMIT_XFER_OPT
+insert_end:
+#endif /* SQLITE_OMIT_XFER_OPT */
+  /* Update the sqlite_sequence table by storing the content of the
+  ** maximum rowid counter values recorded while inserting into
+  ** autoincrement tables.
+  */
+  if( pParse->nested==0 && pParse->pTriggerTab==0 ){
+    sqlite3AutoincrementEnd(pParse);
+  }
+
+  /*
+  ** Return the number of rows inserted. If this routine is
+  ** generating code because of a call to sqlite3NestedParse(), do not
+  ** invoke the callback function.
+  */
+  if( regRowCount ){
+    sqlite3CodeChangeCount(v, regRowCount, "rows inserted");
+  }
+
+insert_cleanup:
+  sqlite3SrcListDelete(db, pTabList);
+  sqlite3ExprListDelete(db, pList);
+  sqlite3UpsertDelete(db, pUpsert);
+  sqlite3SelectDelete(db, pSelect);
+  sqlite3IdListDelete(db, pColumn);
+  if( aRegIdx ) sqlite3DbNNFreeNN(db, aRegIdx);
+}
+
+/* Make sure "isView" and other macros defined above are undefined. Otherwise
+** they may interfere with compilation of other functions in this file
+** (or in another file, if this file becomes part of the amalgamation).  */
+#ifdef isView
+ #undef isView
+#endif
+#ifdef pTrigger
+ #undef pTrigger
+#endif
+#ifdef tmask
+ #undef tmask
+#endif
+
+/*
+** Meanings of bits in of pWalker->eCode for
+** sqlite3ExprReferencesUpdatedColumn()
+*/
+#define CKCNSTRNT_COLUMN   0x01    /* CHECK constraint uses a changing column */
+#define CKCNSTRNT_ROWID    0x02    /* CHECK constraint references the ROWID */
+
+/* This is the Walker callback from sqlite3ExprReferencesUpdatedColumn().
+*  Set bit 0x01 of pWalker->eCode if pWalker->eCode to 0 and if this
+** expression node references any of the
+** columns that are being modified by an UPDATE statement.
+*/
+static int checkConstraintExprNode(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_COLUMN ){
+    assert( pExpr->iColumn>=0 || pExpr->iColumn==-1 );
+    if( pExpr->iColumn>=0 ){
+      if( pWalker->u.aiCol[pExpr->iColumn]>=0 ){
+        pWalker->eCode |= CKCNSTRNT_COLUMN;
+      }
+    }else{
+      pWalker->eCode |= CKCNSTRNT_ROWID;
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** pExpr is a CHECK constraint on a row that is being UPDATE-ed.  The
+** only columns that are modified by the UPDATE are those for which
+** aiChng[i]>=0, and also the ROWID is modified if chngRowid is true.
+**
+** Return true if CHECK constraint pExpr uses any of the
+** changing columns (or the rowid if it is changing).  In other words,
+** return true if this CHECK constraint must be validated for
+** the new row in the UPDATE statement.
+**
+** 2018-09-15: pExpr might also be an expression for an index-on-expressions.
+** The operation of this routine is the same - return true if an only if
+** the expression uses one or more of columns identified by the second and
+** third arguments.
+*/
+int sqlite3ExprReferencesUpdatedColumn(
+  Expr *pExpr,    /* The expression to be checked */
+  int *aiChng,    /* aiChng[x]>=0 if column x changed by the UPDATE */
+  int chngRowid   /* True if UPDATE changes the rowid */
+){
+  Walker w;
+  memset(&w, 0, sizeof(w));
+  w.eCode = 0;
+  w.xExprCallback = checkConstraintExprNode;
+  w.u.aiCol = aiChng;
+  sqlite3WalkExpr(&w, pExpr);
+  if( !chngRowid ){
+    testcase( (w.eCode & CKCNSTRNT_ROWID)!=0 );
+    w.eCode &= ~CKCNSTRNT_ROWID;
+  }
+  testcase( w.eCode==0 );
+  testcase( w.eCode==CKCNSTRNT_COLUMN );
+  testcase( w.eCode==CKCNSTRNT_ROWID );
+  testcase( w.eCode==(CKCNSTRNT_ROWID|CKCNSTRNT_COLUMN) );
+  return w.eCode!=0;
+}
+
+/*
+** The sqlite3GenerateConstraintChecks() routine usually wants to visit
+** the indexes of a table in the order provided in the Table->pIndex list.
+** However, sometimes (rarely - when there is an upsert) it wants to visit
+** the indexes in a different order.  The following data structures accomplish
+** this.
+**
+** The IndexIterator object is used to walk through all of the indexes
+** of a table in either Index.pNext order, or in some other order established
+** by an array of IndexListTerm objects.
+*/
+typedef struct IndexListTerm IndexListTerm;
+typedef struct IndexIterator IndexIterator;
+struct IndexIterator {
+  int eType;    /* 0 for Index.pNext list.  1 for an array of IndexListTerm */
+  int i;        /* Index of the current item from the list */
+  union {
+    struct {    /* Use this object for eType==0: A Index.pNext list */
+      Index *pIdx;   /* The current Index */
+    } lx;     
+    struct {    /* Use this object for eType==1; Array of IndexListTerm */
+      int nIdx;               /* Size of the array */
+      IndexListTerm *aIdx;    /* Array of IndexListTerms */
+    } ax;
+  } u;
+};
+
+/* When IndexIterator.eType==1, then each index is an array of instances
+** of the following object
+*/
+struct IndexListTerm {
+  Index *p;  /* The index */
+  int ix;    /* Which entry in the original Table.pIndex list is this index*/
+};
+
+/* Return the first index on the list */
+static Index *indexIteratorFirst(IndexIterator *pIter, int *pIx){
+  assert( pIter->i==0 );
+  if( pIter->eType ){
+    *pIx = pIter->u.ax.aIdx[0].ix;
+    return pIter->u.ax.aIdx[0].p;
+  }else{
+    *pIx = 0;
+    return pIter->u.lx.pIdx;
+  }
+}
+
+/* Return the next index from the list.  Return NULL when out of indexes */
+static Index *indexIteratorNext(IndexIterator *pIter, int *pIx){
+  if( pIter->eType ){
+    int i = ++pIter->i;
+    if( i>=pIter->u.ax.nIdx ){
+      *pIx = i;
+      return 0;
+    }
+    *pIx = pIter->u.ax.aIdx[i].ix;
+    return pIter->u.ax.aIdx[i].p;
+  }else{
+    ++(*pIx);
+    pIter->u.lx.pIdx = pIter->u.lx.pIdx->pNext;
+    return pIter->u.lx.pIdx;
+  }
+}
+ 
+/*
+** Generate code to do constraint checks prior to an INSERT or an UPDATE
+** on table pTab.
+**
+** The regNewData parameter is the first register in a range that contains
+** the data to be inserted or the data after the update.  There will be
+** pTab->nCol+1 registers in this range.  The first register (the one
+** that regNewData points to) will contain the new rowid, or NULL in the
+** case of a WITHOUT ROWID table.  The second register in the range will
+** contain the content of the first table column.  The third register will
+** contain the content of the second table column.  And so forth.
+**
+** The regOldData parameter is similar to regNewData except that it contains
+** the data prior to an UPDATE rather than afterwards.  regOldData is zero
+** for an INSERT.  This routine can distinguish between UPDATE and INSERT by
+** checking regOldData for zero.
+**
+** For an UPDATE, the pkChng boolean is true if the true primary key (the
+** rowid for a normal table or the PRIMARY KEY for a WITHOUT ROWID table)
+** might be modified by the UPDATE.  If pkChng is false, then the key of
+** the iDataCur content table is guaranteed to be unchanged by the UPDATE.
+**
+** For an INSERT, the pkChng boolean indicates whether or not the rowid
+** was explicitly specified as part of the INSERT statement.  If pkChng
+** is zero, it means that the either rowid is computed automatically or
+** that the table is a WITHOUT ROWID table and has no rowid.  On an INSERT,
+** pkChng will only be true if the INSERT statement provides an integer
+** value for either the rowid column or its INTEGER PRIMARY KEY alias.
+**
+** The code generated by this routine will store new index entries into
+** registers identified by aRegIdx[].  No index entry is created for
+** indices where aRegIdx[i]==0.  The order of indices in aRegIdx[] is
+** the same as the order of indices on the linked list of indices
+** at pTab->pIndex.
+**
+** (2019-05-07) The generated code also creates a new record for the
+** main table, if pTab is a rowid table, and stores that record in the
+** register identified by aRegIdx[nIdx] - in other words in the first
+** entry of aRegIdx[] past the last index.  It is important that the
+** record be generated during constraint checks to avoid affinity changes
+** to the register content that occur after constraint checks but before
+** the new record is inserted.
+**
+** The caller must have already opened writeable cursors on the main
+** table and all applicable indices (that is to say, all indices for which
+** aRegIdx[] is not zero).  iDataCur is the cursor for the main table when
+** inserting or updating a rowid table, or the cursor for the PRIMARY KEY
+** index when operating on a WITHOUT ROWID table.  iIdxCur is the cursor
+** for the first index in the pTab->pIndex list.  Cursors for other indices
+** are at iIdxCur+N for the N-th element of the pTab->pIndex list.
+**
+** This routine also generates code to check constraints.  NOT NULL,
+** CHECK, and UNIQUE constraints are all checked.  If a constraint fails,
+** then the appropriate action is performed.  There are five possible
+** actions: ROLLBACK, ABORT, FAIL, REPLACE, and IGNORE.
+**
+**  Constraint type  Action       What Happens
+**  ---------------  ----------   ----------------------------------------
+**  any              ROLLBACK     The current transaction is rolled back and
+**                                sqlite3_step() returns immediately with a
+**                                return code of SQLITE_CONSTRAINT.
+**
+**  any              ABORT        Back out changes from the current command
+**                                only (do not do a complete rollback) then
+**                                cause sqlite3_step() to return immediately
+**                                with SQLITE_CONSTRAINT.
+**
+**  any              FAIL         Sqlite3_step() returns immediately with a
+**                                return code of SQLITE_CONSTRAINT.  The
+**                                transaction is not rolled back and any
+**                                changes to prior rows are retained.
+**
+**  any              IGNORE       The attempt in insert or update the current
+**                                row is skipped, without throwing an error.
+**                                Processing continues with the next row.
+**                                (There is an immediate jump to ignoreDest.)
+**
+**  NOT NULL         REPLACE      The NULL value is replace by the default
+**                                value for that column.  If the default value
+**                                is NULL, the action is the same as ABORT.
+**
+**  UNIQUE           REPLACE      The other row that conflicts with the row
+**                                being inserted is removed.
+**
+**  CHECK            REPLACE      Illegal.  The results in an exception.
+**
+** Which action to take is determined by the overrideError parameter.
+** Or if overrideError==OE_Default, then the pParse->onError parameter
+** is used.  Or if pParse->onError==OE_Default then the onError value
+** for the constraint is used.
+*/
+void sqlite3GenerateConstraintChecks(
+  Parse *pParse,       /* The parser context */
+  Table *pTab,         /* The table being inserted or updated */
+  int *aRegIdx,        /* Use register aRegIdx[i] for index i.  0 for unused */
+  int iDataCur,        /* Canonical data cursor (main table or PK index) */
+  int iIdxCur,         /* First index cursor */
+  int regNewData,      /* First register in a range holding values to insert */
+  int regOldData,      /* Previous content.  0 for INSERTs */
+  u8 pkChng,           /* Non-zero if the rowid or PRIMARY KEY changed */
+  u8 overrideError,    /* Override onError to this if not OE_Default */
+  int ignoreDest,      /* Jump to this label on an OE_Ignore resolution */
+  int *pbMayReplace,   /* OUT: Set to true if constraint may cause a replace */
+  int *aiChng,         /* column i is unchanged if aiChng[i]<0 */
+  Upsert *pUpsert      /* ON CONFLICT clauses, if any.  NULL otherwise */
+){
+  Vdbe *v;             /* VDBE under construction */
+  Index *pIdx;         /* Pointer to one of the indices */
+  Index *pPk = 0;      /* The PRIMARY KEY index for WITHOUT ROWID tables */
+  sqlite3 *db;         /* Database connection */
+  int i;               /* loop counter */
+  int ix;              /* Index loop counter */
+  int nCol;            /* Number of columns */
+  int onError;         /* Conflict resolution strategy */
+  int seenReplace = 0; /* True if REPLACE is used to resolve INT PK conflict */
+  int nPkField;        /* Number of fields in PRIMARY KEY. 1 for ROWID tables */
+  Upsert *pUpsertClause = 0;  /* The specific ON CONFLICT clause for pIdx */
+  u8 isUpdate;           /* True if this is an UPDATE operation */
+  u8 bAffinityDone = 0;  /* True if the OP_Affinity operation has been run */
+  int upsertIpkReturn = 0; /* Address of Goto at end of IPK uniqueness check */
+  int upsertIpkDelay = 0;  /* Address of Goto to bypass initial IPK check */
+  int ipkTop = 0;        /* Top of the IPK uniqueness check */
+  int ipkBottom = 0;     /* OP_Goto at the end of the IPK uniqueness check */
+  /* Variables associated with retesting uniqueness constraints after
+  ** replace triggers fire have run */
+  int regTrigCnt;       /* Register used to count replace trigger invocations */
+  int addrRecheck = 0;  /* Jump here to recheck all uniqueness constraints */
+  int lblRecheckOk = 0; /* Each recheck jumps to this label if it passes */
+  Trigger *pTrigger;    /* List of DELETE triggers on the table pTab */
+  int nReplaceTrig = 0; /* Number of replace triggers coded */
+  IndexIterator sIdxIter;  /* Index iterator */
+
+  isUpdate = regOldData!=0;
+  db = pParse->db;
+  v = pParse->pVdbe;
+  assert( v!=0 );
+  assert( !IsView(pTab) );  /* This table is not a VIEW */
+  nCol = pTab->nCol;
+ 
+  /* pPk is the PRIMARY KEY index for WITHOUT ROWID tables and NULL for
+  ** normal rowid tables.  nPkField is the number of key fields in the
+  ** pPk index or 1 for a rowid table.  In other words, nPkField is the
+  ** number of fields in the true primary key of the table. */
+  if( HasRowid(pTab) ){
+    pPk = 0;
+    nPkField = 1;
+  }else{
+    pPk = sqlite3PrimaryKeyIndex(pTab);
+    nPkField = pPk->nKeyCol;
+  }
+
+  /* Record that this module has started */
+  VdbeModuleComment((v, "BEGIN: GenCnstCks(%d,%d,%d,%d,%d)",
+                     iDataCur, iIdxCur, regNewData, regOldData, pkChng));
+
+  /* Test all NOT NULL constraints.
+  */
+  if( pTab->tabFlags & TF_HasNotNull ){
+    int b2ndPass = 0;         /* True if currently running 2nd pass */
+    int nSeenReplace = 0;     /* Number of ON CONFLICT REPLACE operations */
+    int nGenerated = 0;       /* Number of generated columns with NOT NULL */
+    while(1){  /* Make 2 passes over columns. Exit loop via "break" */
+      for(i=0; i<nCol; i++){
+        int iReg;                        /* Register holding column value */
+        Column *pCol = &pTab->aCol[i];   /* The column to check for NOT NULL */
+        int isGenerated;                 /* non-zero if column is generated */
+        onError = pCol->notNull;
+        if( onError==OE_None ) continue; /* No NOT NULL on this column */
+        if( i==pTab->iPKey ){
+          continue;        /* ROWID is never NULL */
+        }
+        isGenerated = pCol->colFlags & COLFLAG_GENERATED;
+        if( isGenerated && !b2ndPass ){
+          nGenerated++;
+          continue;        /* Generated columns processed on 2nd pass */
+        }
+        if( aiChng && aiChng[i]<0 && !isGenerated ){
+          /* Do not check NOT NULL on columns that do not change */
+          continue;
+        }
+        if( overrideError!=OE_Default ){
+          onError = overrideError;
+        }else if( onError==OE_Default ){
+          onError = OE_Abort;
+        }
+        if( onError==OE_Replace ){
+          if( b2ndPass        /* REPLACE becomes ABORT on the 2nd pass */
+           || pCol->iDflt==0  /* REPLACE is ABORT if no DEFAULT value */
+          ){
+            testcase( pCol->colFlags & COLFLAG_VIRTUAL );
+            testcase( pCol->colFlags & COLFLAG_STORED );
+            testcase( pCol->colFlags & COLFLAG_GENERATED );
+            onError = OE_Abort;
+          }else{
+            assert( !isGenerated );
+          }
+        }else if( b2ndPass && !isGenerated ){
+          continue;
+        }
+        assert( onError==OE_Rollback || onError==OE_Abort || onError==OE_Fail
+            || onError==OE_Ignore || onError==OE_Replace );
+        testcase( i!=sqlite3TableColumnToStorage(pTab, i) );
+        iReg = sqlite3TableColumnToStorage(pTab, i) + regNewData + 1;
+        switch( onError ){
+          case OE_Replace: {
+            int addr1 = sqlite3VdbeAddOp1(v, OP_NotNull, iReg);
+            VdbeCoverage(v);
+            assert( (pCol->colFlags & COLFLAG_GENERATED)==0 );
+            nSeenReplace++;
+            sqlite3ExprCodeCopy(pParse,
+               sqlite3ColumnExpr(pTab, pCol), iReg);
+            sqlite3VdbeJumpHere(v, addr1);
+            break;
+          }
+          case OE_Abort:
+            sqlite3MayAbort(pParse);
+            /* no break */ deliberate_fall_through
+          case OE_Rollback:
+          case OE_Fail: {
+            char *zMsg = sqlite3MPrintf(db, "%s.%s", pTab->zName,
+                                        pCol->zCnName);
+            testcase( zMsg==0 && db->mallocFailed==0 );
+            sqlite3VdbeAddOp3(v, OP_HaltIfNull, SQLITE_CONSTRAINT_NOTNULL,
+                              onError, iReg);
+            sqlite3VdbeAppendP4(v, zMsg, P4_DYNAMIC);
+            sqlite3VdbeChangeP5(v, P5_ConstraintNotNull);
+            VdbeCoverage(v);
+            break;
+          }
+          default: {
+            assert( onError==OE_Ignore );
+            sqlite3VdbeAddOp2(v, OP_IsNull, iReg, ignoreDest);
+            VdbeCoverage(v);
+            break;
+          }
+        } /* end switch(onError) */
+      } /* end loop i over columns */
+      if( nGenerated==0 && nSeenReplace==0 ){
+        /* If there are no generated columns with NOT NULL constraints
+        ** and no NOT NULL ON CONFLICT REPLACE constraints, then a single
+        ** pass is sufficient */
+        break;
+      }
+      if( b2ndPass ) break;  /* Never need more than 2 passes */
+      b2ndPass = 1;
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+      if( nSeenReplace>0 && (pTab->tabFlags & TF_HasGenerated)!=0 ){
+        /* If any NOT NULL ON CONFLICT REPLACE constraints fired on the
+        ** first pass, recomputed values for all generated columns, as
+        ** those values might depend on columns affected by the REPLACE.
+        */
+        sqlite3ComputeGeneratedColumns(pParse, regNewData+1, pTab);
+      }
+#endif
+    } /* end of 2-pass loop */
+  } /* end if( has-not-null-constraints ) */
+
+  /* Test all CHECK constraints
+  */
+#ifndef SQLITE_OMIT_CHECK
+  if( pTab->pCheck && (db->flags & SQLITE_IgnoreChecks)==0 ){
+    ExprList *pCheck = pTab->pCheck;
+    pParse->iSelfTab = -(regNewData+1);
+    onError = overrideError!=OE_Default ? overrideError : OE_Abort;
+    for(i=0; i<pCheck->nExpr; i++){
+      int allOk;
+      Expr *pCopy;
+      Expr *pExpr = pCheck->a[i].pExpr;
+      if( aiChng
+       && !sqlite3ExprReferencesUpdatedColumn(pExpr, aiChng, pkChng)
+      ){
+        /* The check constraints do not reference any of the columns being
+        ** updated so there is no point it verifying the check constraint */
+        continue;
+      }
+      if( bAffinityDone==0 ){
+        sqlite3TableAffinity(v, pTab, regNewData+1);
+        bAffinityDone = 1;
+      }
+      allOk = sqlite3VdbeMakeLabel(pParse);
+      sqlite3VdbeVerifyAbortable(v, onError);
+      pCopy = sqlite3ExprDup(db, pExpr, 0);
+      if( !db->mallocFailed ){
+        sqlite3ExprIfTrue(pParse, pCopy, allOk, SQLITE_JUMPIFNULL);
+      }
+      sqlite3ExprDelete(db, pCopy);
+      if( onError==OE_Ignore ){
+        sqlite3VdbeGoto(v, ignoreDest);
+      }else{
+        char *zName = pCheck->a[i].zEName;
+        assert( zName!=0 || pParse->db->mallocFailed );
+        if( onError==OE_Replace ) onError = OE_Abort; /* IMP: R-26383-51744 */
+        sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_CHECK,
+                              onError, zName, P4_TRANSIENT,
+                              P5_ConstraintCheck);
+      }
+      sqlite3VdbeResolveLabel(v, allOk);
+    }
+    pParse->iSelfTab = 0;
+  }
+#endif /* !defined(SQLITE_OMIT_CHECK) */
+
+  /* UNIQUE and PRIMARY KEY constraints should be handled in the following
+  ** order:
+  **
+  **   (1)  OE_Update
+  **   (2)  OE_Abort, OE_Fail, OE_Rollback, OE_Ignore
+  **   (3)  OE_Replace
+  **
+  ** OE_Fail and OE_Ignore must happen before any changes are made.
+  ** OE_Update guarantees that only a single row will change, so it
+  ** must happen before OE_Replace.  Technically, OE_Abort and OE_Rollback
+  ** could happen in any order, but they are grouped up front for
+  ** convenience.
+  **
+  ** 2018-08-14: Ticket https://www.sqlite.org/src/info/908f001483982c43
+  ** The order of constraints used to have OE_Update as (2) and OE_Abort
+  ** and so forth as (1). But apparently PostgreSQL checks the OE_Update
+  ** constraint before any others, so it had to be moved.
+  **
+  ** Constraint checking code is generated in this order:
+  **   (A)  The rowid constraint
+  **   (B)  Unique index constraints that do not have OE_Replace as their
+  **        default conflict resolution strategy
+  **   (C)  Unique index that do use OE_Replace by default.
+  **
+  ** The ordering of (2) and (3) is accomplished by making sure the linked
+  ** list of indexes attached to a table puts all OE_Replace indexes last
+  ** in the list.  See sqlite3CreateIndex() for where that happens.
+  */
+  sIdxIter.eType = 0;
+  sIdxIter.i = 0;
+  sIdxIter.u.ax.aIdx = 0;  /* Silence harmless compiler warning */
+  sIdxIter.u.lx.pIdx = pTab->pIndex;
+  if( pUpsert ){
+    if( pUpsert->pUpsertTarget==0 ){
+      /* There is just on ON CONFLICT clause and it has no constraint-target */
+      assert( pUpsert->pNextUpsert==0 );
+      if( pUpsert->isDoUpdate==0 ){
+        /* A single ON CONFLICT DO NOTHING clause, without a constraint-target.
+        ** Make all unique constraint resolution be OE_Ignore */
+        overrideError = OE_Ignore;
+        pUpsert = 0;
+      }else{
+        /* A single ON CONFLICT DO UPDATE.  Make all resolutions OE_Update */
+        overrideError = OE_Update;
+      }
+    }else if( pTab->pIndex!=0 ){
+      /* Otherwise, we'll need to run the IndexListTerm array version of the
+      ** iterator to ensure that all of the ON CONFLICT conditions are
+      ** checked first and in order. */
+      int nIdx, jj;
+      u64 nByte;
+      Upsert *pTerm;
+      u8 *bUsed;
+      for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){
+         assert( aRegIdx[nIdx]>0 );
+      }
+      sIdxIter.eType = 1;
+      sIdxIter.u.ax.nIdx = nIdx;
+      nByte = (sizeof(IndexListTerm)+1)*nIdx + nIdx;
+      sIdxIter.u.ax.aIdx = sqlite3DbMallocZero(db, nByte);
+      if( sIdxIter.u.ax.aIdx==0 ) return; /* OOM */
+      bUsed = (u8*)&sIdxIter.u.ax.aIdx[nIdx];
+      pUpsert->pToFree = sIdxIter.u.ax.aIdx;
+      for(i=0, pTerm=pUpsert; pTerm; pTerm=pTerm->pNextUpsert){
+        if( pTerm->pUpsertTarget==0 ) break;
+        if( pTerm->pUpsertIdx==0 ) continue;  /* Skip ON CONFLICT for the IPK */
+        jj = 0;
+        pIdx = pTab->pIndex;
+        while( ALWAYS(pIdx!=0) && pIdx!=pTerm->pUpsertIdx ){
+           pIdx = pIdx->pNext;
+           jj++;
+        }
+        if( bUsed[jj] ) continue; /* Duplicate ON CONFLICT clause ignored */
+        bUsed[jj] = 1;
+        sIdxIter.u.ax.aIdx[i].p = pIdx;
+        sIdxIter.u.ax.aIdx[i].ix = jj;
+        i++;
+      }
+      for(jj=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, jj++){
+        if( bUsed[jj] ) continue;
+        sIdxIter.u.ax.aIdx[i].p = pIdx;
+        sIdxIter.u.ax.aIdx[i].ix = jj;
+        i++;
+      }
+      assert( i==nIdx );
+    }
+  }
+
+  /* Determine if it is possible that triggers (either explicitly coded
+  ** triggers or FK resolution actions) might run as a result of deletes
+  ** that happen when OE_Replace conflict resolution occurs. (Call these
+  ** "replace triggers".)  If any replace triggers run, we will need to
+  ** recheck all of the uniqueness constraints after they have all run.
+  ** But on the recheck, the resolution is OE_Abort instead of OE_Replace.
+  **
+  ** If replace triggers are a possibility, then
+  **
+  **   (1) Allocate register regTrigCnt and initialize it to zero.
+  **       That register will count the number of replace triggers that
+  **       fire.  Constraint recheck only occurs if the number is positive.
+  **   (2) Initialize pTrigger to the list of all DELETE triggers on pTab.
+  **   (3) Initialize addrRecheck and lblRecheckOk
+  **
+  ** The uniqueness rechecking code will create a series of tests to run
+  ** in a second pass.  The addrRecheck and lblRecheckOk variables are
+  ** used to link together these tests which are separated from each other
+  ** in the generate bytecode.
+  */
+  if( (db->flags & (SQLITE_RecTriggers|SQLITE_ForeignKeys))==0 ){
+    /* There are not DELETE triggers nor FK constraints.  No constraint
+    ** rechecks are needed. */
+    pTrigger = 0;
+    regTrigCnt = 0;
+  }else{
+    if( db->flags&SQLITE_RecTriggers ){
+      pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
+      regTrigCnt = pTrigger!=0 || sqlite3FkRequired(pParse, pTab, 0, 0);
+    }else{
+      pTrigger = 0;
+      regTrigCnt = sqlite3FkRequired(pParse, pTab, 0, 0);
+    }
+    if( regTrigCnt ){
+      /* Replace triggers might exist.  Allocate the counter and
+      ** initialize it to zero. */
+      regTrigCnt = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, regTrigCnt);
+      VdbeComment((v, "trigger count"));
+      lblRecheckOk = sqlite3VdbeMakeLabel(pParse);
+      addrRecheck = lblRecheckOk;
+    }
+  }
+
+  /* If rowid is changing, make sure the new rowid does not previously
+  ** exist in the table.
+  */
+  if( pkChng && pPk==0 ){
+    int addrRowidOk = sqlite3VdbeMakeLabel(pParse);
+
+    /* Figure out what action to take in case of a rowid collision */
+    onError = pTab->keyConf;
+    if( overrideError!=OE_Default ){
+      onError = overrideError;
+    }else if( onError==OE_Default ){
+      onError = OE_Abort;
+    }
+
+    /* figure out whether or not upsert applies in this case */
+    if( pUpsert ){
+      pUpsertClause = sqlite3UpsertOfIndex(pUpsert,0);
+      if( pUpsertClause!=0 ){
+        if( pUpsertClause->isDoUpdate==0 ){
+          onError = OE_Ignore;  /* DO NOTHING is the same as INSERT OR IGNORE */
+        }else{
+          onError = OE_Update;  /* DO UPDATE */
+        }
+      }
+      if( pUpsertClause!=pUpsert ){
+        /* The first ON CONFLICT clause has a conflict target other than
+        ** the IPK.  We have to jump ahead to that first ON CONFLICT clause
+        ** and then come back here and deal with the IPK afterwards */
+        upsertIpkDelay = sqlite3VdbeAddOp0(v, OP_Goto);
+      }
+    }
+
+    /* If the response to a rowid conflict is REPLACE but the response
+    ** to some other UNIQUE constraint is FAIL or IGNORE, then we need
+    ** to defer the running of the rowid conflict checking until after
+    ** the UNIQUE constraints have run.
+    */
+    if( onError==OE_Replace      /* IPK rule is REPLACE */
+     && onError!=overrideError   /* Rules for other constraints are different */
+     && pTab->pIndex             /* There exist other constraints */
+     && !upsertIpkDelay          /* IPK check already deferred by UPSERT */
+    ){
+      ipkTop = sqlite3VdbeAddOp0(v, OP_Goto)+1;
+      VdbeComment((v, "defer IPK REPLACE until last"));
+    }
+
+    if( isUpdate ){
+      /* pkChng!=0 does not mean that the rowid has changed, only that
+      ** it might have changed.  Skip the conflict logic below if the rowid
+      ** is unchanged. */
+      sqlite3VdbeAddOp3(v, OP_Eq, regNewData, addrRowidOk, regOldData);
+      sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
+      VdbeCoverage(v);
+    }
+
+    /* Check to see if the new rowid already exists in the table.  Skip
+    ** the following conflict logic if it does not. */
+    VdbeNoopComment((v, "uniqueness check for ROWID"));
+    sqlite3VdbeVerifyAbortable(v, onError);
+    sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, addrRowidOk, regNewData);
+    VdbeCoverage(v);
+
+    switch( onError ){
+      default: {
+        onError = OE_Abort;
+        /* no break */ deliberate_fall_through
+      }
+      case OE_Rollback:
+      case OE_Abort:
+      case OE_Fail: {
+        testcase( onError==OE_Rollback );
+        testcase( onError==OE_Abort );
+        testcase( onError==OE_Fail );
+        sqlite3RowidConstraint(pParse, onError, pTab);
+        break;
+      }
+      case OE_Replace: {
+        /* If there are DELETE triggers on this table and the
+        ** recursive-triggers flag is set, call GenerateRowDelete() to
+        ** remove the conflicting row from the table. This will fire
+        ** the triggers and remove both the table and index b-tree entries.
+        **
+        ** Otherwise, if there are no triggers or the recursive-triggers
+        ** flag is not set, but the table has one or more indexes, call
+        ** GenerateRowIndexDelete(). This removes the index b-tree entries
+        ** only. The table b-tree entry will be replaced by the new entry
+        ** when it is inserted. 
+        **
+        ** If either GenerateRowDelete() or GenerateRowIndexDelete() is called,
+        ** also invoke MultiWrite() to indicate that this VDBE may require
+        ** statement rollback (if the statement is aborted after the delete
+        ** takes place). Earlier versions called sqlite3MultiWrite() regardless,
+        ** but being more selective here allows statements like:
+        **
+        **   REPLACE INTO t(rowid) VALUES($newrowid)
+        **
+        ** to run without a statement journal if there are no indexes on the
+        ** table.
+        */
+        if( regTrigCnt ){
+          sqlite3MultiWrite(pParse);
+          sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
+                                   regNewData, 1, 0, OE_Replace, 1, -1);
+          sqlite3VdbeAddOp2(v, OP_AddImm, regTrigCnt, 1); /* incr trigger cnt */
+          nReplaceTrig++;
+        }else{
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+          assert( HasRowid(pTab) );
+          /* This OP_Delete opcode fires the pre-update-hook only. It does
+          ** not modify the b-tree. It is more efficient to let the coming
+          ** OP_Insert replace the existing entry than it is to delete the
+          ** existing entry and then insert a new one. */
+          sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, OPFLAG_ISNOOP);
+          sqlite3VdbeAppendP4(v, pTab, P4_TABLE);
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+          if( pTab->pIndex ){
+            sqlite3MultiWrite(pParse);
+            sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,-1);
+          }
+        }
+        seenReplace = 1;
+        break;
+      }
+#ifndef SQLITE_OMIT_UPSERT
+      case OE_Update: {
+        sqlite3UpsertDoUpdate(pParse, pUpsert, pTab, 0, iDataCur);
+        /* no break */ deliberate_fall_through
+      }
+#endif
+      case OE_Ignore: {
+        testcase( onError==OE_Ignore );
+        sqlite3VdbeGoto(v, ignoreDest);
+        break;
+      }
+    }
+    sqlite3VdbeResolveLabel(v, addrRowidOk);
+    if( pUpsert && pUpsertClause!=pUpsert ){
+      upsertIpkReturn = sqlite3VdbeAddOp0(v, OP_Goto);
+    }else if( ipkTop ){
+      ipkBottom = sqlite3VdbeAddOp0(v, OP_Goto);
+      sqlite3VdbeJumpHere(v, ipkTop-1);
+    }
+  }
+
+  /* Test all UNIQUE constraints by creating entries for each UNIQUE
+  ** index and making sure that duplicate entries do not already exist.
+  ** Compute the revised record entries for indices as we go.
+  **
+  ** This loop also handles the case of the PRIMARY KEY index for a
+  ** WITHOUT ROWID table.
+  */
+  for(pIdx = indexIteratorFirst(&sIdxIter, &ix);
+      pIdx;
+      pIdx = indexIteratorNext(&sIdxIter, &ix)
+  ){
+    int regIdx;          /* Range of registers holding content for pIdx */
+    int regR;            /* Range of registers holding conflicting PK */
+    int iThisCur;        /* Cursor for this UNIQUE index */
+    int addrUniqueOk;    /* Jump here if the UNIQUE constraint is satisfied */
+    int addrConflictCk;  /* First opcode in the conflict check logic */
+
+    if( aRegIdx[ix]==0 ) continue;  /* Skip indices that do not change */
+    if( pUpsert ){
+      pUpsertClause = sqlite3UpsertOfIndex(pUpsert, pIdx);
+      if( upsertIpkDelay && pUpsertClause==pUpsert ){
+        sqlite3VdbeJumpHere(v, upsertIpkDelay);
+      }
+    }
+    addrUniqueOk = sqlite3VdbeMakeLabel(pParse);
+    if( bAffinityDone==0 ){
+      sqlite3TableAffinity(v, pTab, regNewData+1);
+      bAffinityDone = 1;
+    }
+    VdbeNoopComment((v, "prep index %s", pIdx->zName));
+    iThisCur = iIdxCur+ix;
+
+
+    /* Skip partial indices for which the WHERE clause is not true */
+    if( pIdx->pPartIdxWhere ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, aRegIdx[ix]);
+      pParse->iSelfTab = -(regNewData+1);
+      sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, addrUniqueOk,
+                            SQLITE_JUMPIFNULL);
+      pParse->iSelfTab = 0;
+    }
+
+    /* Create a record for this index entry as it should appear after
+    ** the insert or update.  Store that record in the aRegIdx[ix] register
+    */
+    regIdx = aRegIdx[ix]+1;
+    for(i=0; i<pIdx->nColumn; i++){
+      int iField = pIdx->aiColumn[i];
+      int x;
+      if( iField==XN_EXPR ){
+        pParse->iSelfTab = -(regNewData+1);
+        sqlite3ExprCodeCopy(pParse, pIdx->aColExpr->a[i].pExpr, regIdx+i);
+        pParse->iSelfTab = 0;
+        VdbeComment((v, "%s column %d", pIdx->zName, i));
+      }else if( iField==XN_ROWID || iField==pTab->iPKey ){
+        x = regNewData;
+        sqlite3VdbeAddOp2(v, OP_IntCopy, x, regIdx+i);
+        VdbeComment((v, "rowid"));
+      }else{
+        testcase( sqlite3TableColumnToStorage(pTab, iField)!=iField );
+        x = sqlite3TableColumnToStorage(pTab, iField) + regNewData + 1;
+        sqlite3VdbeAddOp2(v, OP_SCopy, x, regIdx+i);
+        VdbeComment((v, "%s", pTab->aCol[iField].zCnName));
+      }
+    }
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, regIdx, pIdx->nColumn, aRegIdx[ix]);
+    VdbeComment((v, "for %s", pIdx->zName));
+#ifdef SQLITE_ENABLE_NULL_TRIM
+    if( pIdx->idxType==SQLITE_IDXTYPE_PRIMARYKEY ){
+      sqlite3SetMakeRecordP5(v, pIdx->pTable);
+    }
+#endif
+    sqlite3VdbeReleaseRegisters(pParse, regIdx, pIdx->nColumn, 0, 0);
+
+    /* In an UPDATE operation, if this index is the PRIMARY KEY index
+    ** of a WITHOUT ROWID table and there has been no change the
+    ** primary key, then no collision is possible.  The collision detection
+    ** logic below can all be skipped. */
+    if( isUpdate && pPk==pIdx && pkChng==0 ){
+      sqlite3VdbeResolveLabel(v, addrUniqueOk);
+      continue;
+    }
+
+    /* Find out what action to take in case there is a uniqueness conflict */
+    onError = pIdx->onError;
+    if( onError==OE_None ){
+      sqlite3VdbeResolveLabel(v, addrUniqueOk);
+      continue;  /* pIdx is not a UNIQUE index */
+    }
+    if( overrideError!=OE_Default ){
+      onError = overrideError;
+    }else if( onError==OE_Default ){
+      onError = OE_Abort;
+    }
+
+    /* Figure out if the upsert clause applies to this index */
+    if( pUpsertClause ){
+      if( pUpsertClause->isDoUpdate==0 ){
+        onError = OE_Ignore;  /* DO NOTHING is the same as INSERT OR IGNORE */
+      }else{
+        onError = OE_Update;  /* DO UPDATE */
+      }
+    }
+
+    /* Collision detection may be omitted if all of the following are true:
+    **   (1) The conflict resolution algorithm is REPLACE
+    **   (2) The table is a WITHOUT ROWID table
+    **   (3) There are no secondary indexes on the table
+    **   (4) No delete triggers need to be fired if there is a conflict
+    **   (5) No FK constraint counters need to be updated if a conflict occurs.
+    **
+    ** This is not possible for ENABLE_PREUPDATE_HOOK builds, as the row
+    ** must be explicitly deleted in order to ensure any pre-update hook
+    ** is invoked.  */
+    assert( IsOrdinaryTable(pTab) );
+#ifndef SQLITE_ENABLE_PREUPDATE_HOOK
+    if( (ix==0 && pIdx->pNext==0)                   /* Condition 3 */
+     && pPk==pIdx                                   /* Condition 2 */
+     && onError==OE_Replace                         /* Condition 1 */
+     && ( 0==(db->flags&SQLITE_RecTriggers) ||      /* Condition 4 */
+          0==sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0))
+     && ( 0==(db->flags&SQLITE_ForeignKeys) ||      /* Condition 5 */
+         (0==pTab->u.tab.pFKey && 0==sqlite3FkReferences(pTab)))
+    ){
+      sqlite3VdbeResolveLabel(v, addrUniqueOk);
+      continue;
+    }
+#endif /* ifndef SQLITE_ENABLE_PREUPDATE_HOOK */
+
+    /* Check to see if the new index entry will be unique */
+    sqlite3VdbeVerifyAbortable(v, onError);
+    addrConflictCk =
+      sqlite3VdbeAddOp4Int(v, OP_NoConflict, iThisCur, addrUniqueOk,
+                           regIdx, pIdx->nKeyCol); VdbeCoverage(v);
+
+    /* Generate code to handle collisions */
+    regR = pIdx==pPk ? regIdx : sqlite3GetTempRange(pParse, nPkField);
+    if( isUpdate || onError==OE_Replace ){
+      if( HasRowid(pTab) ){
+        sqlite3VdbeAddOp2(v, OP_IdxRowid, iThisCur, regR);
+        /* Conflict only if the rowid of the existing index entry
+        ** is different from old-rowid */
+        if( isUpdate ){
+          sqlite3VdbeAddOp3(v, OP_Eq, regR, addrUniqueOk, regOldData);
+          sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
+          VdbeCoverage(v);
+        }
+      }else{
+        int x;
+        /* Extract the PRIMARY KEY from the end of the index entry and
+        ** store it in registers regR..regR+nPk-1 */
+        if( pIdx!=pPk ){
+          for(i=0; i<pPk->nKeyCol; i++){
+            assert( pPk->aiColumn[i]>=0 );
+            x = sqlite3TableColumnToIndex(pIdx, pPk->aiColumn[i]);
+            sqlite3VdbeAddOp3(v, OP_Column, iThisCur, x, regR+i);
+            VdbeComment((v, "%s.%s", pTab->zName,
+                         pTab->aCol[pPk->aiColumn[i]].zCnName));
+          }
+        }
+        if( isUpdate ){
+          /* If currently processing the PRIMARY KEY of a WITHOUT ROWID
+          ** table, only conflict if the new PRIMARY KEY values are actually
+          ** different from the old.  See TH3 withoutrowid04.test.
+          **
+          ** For a UNIQUE index, only conflict if the PRIMARY KEY values
+          ** of the matched index row are different from the original PRIMARY
+          ** KEY values of this row before the update.  */
+          int addrJump = sqlite3VdbeCurrentAddr(v)+pPk->nKeyCol;
+          int op = OP_Ne;
+          int regCmp = (IsPrimaryKeyIndex(pIdx) ? regIdx : regR);
+ 
+          for(i=0; i<pPk->nKeyCol; i++){
+            char *p4 = (char*)sqlite3LocateCollSeq(pParse, pPk->azColl[i]);
+            x = pPk->aiColumn[i];
+            assert( x>=0 );
+            if( i==(pPk->nKeyCol-1) ){
+              addrJump = addrUniqueOk;
+              op = OP_Eq;
+            }
+            x = sqlite3TableColumnToStorage(pTab, x);
+            sqlite3VdbeAddOp4(v, op,
+                regOldData+1+x, addrJump, regCmp+i, p4, P4_COLLSEQ
+            );
+            sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
+            VdbeCoverageIf(v, op==OP_Eq);
+            VdbeCoverageIf(v, op==OP_Ne);
+          }
+        }
+      }
+    }
+
+    /* Generate code that executes if the new index entry is not unique */
+    assert( onError==OE_Rollback || onError==OE_Abort || onError==OE_Fail
+        || onError==OE_Ignore || onError==OE_Replace || onError==OE_Update );
+    switch( onError ){
+      case OE_Rollback:
+      case OE_Abort:
+      case OE_Fail: {
+        testcase( onError==OE_Rollback );
+        testcase( onError==OE_Abort );
+        testcase( onError==OE_Fail );
+        sqlite3UniqueConstraint(pParse, onError, pIdx);
+        break;
+      }
+#ifndef SQLITE_OMIT_UPSERT
+      case OE_Update: {
+        sqlite3UpsertDoUpdate(pParse, pUpsert, pTab, pIdx, iIdxCur+ix);
+        /* no break */ deliberate_fall_through
+      }
+#endif
+      case OE_Ignore: {
+        testcase( onError==OE_Ignore );
+        sqlite3VdbeGoto(v, ignoreDest);
+        break;
+      }
+      default: {
+        int nConflictCk;   /* Number of opcodes in conflict check logic */
+
+        assert( onError==OE_Replace );
+        nConflictCk = sqlite3VdbeCurrentAddr(v) - addrConflictCk;
+        assert( nConflictCk>0 || db->mallocFailed );
+        testcase( nConflictCk<=0 );
+        testcase( nConflictCk>1 );
+        if( regTrigCnt ){
+          sqlite3MultiWrite(pParse);
+          nReplaceTrig++;
+        }
+        if( pTrigger && isUpdate ){
+          sqlite3VdbeAddOp1(v, OP_CursorLock, iDataCur);
+        }
+        sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
+            regR, nPkField, 0, OE_Replace,
+            (pIdx==pPk ? ONEPASS_SINGLE : ONEPASS_OFF), iThisCur);
+        if( pTrigger && isUpdate ){
+          sqlite3VdbeAddOp1(v, OP_CursorUnlock, iDataCur);
+        }
+        if( regTrigCnt ){
+          int addrBypass;  /* Jump destination to bypass recheck logic */
+
+          sqlite3VdbeAddOp2(v, OP_AddImm, regTrigCnt, 1); /* incr trigger cnt */
+          addrBypass = sqlite3VdbeAddOp0(v, OP_Goto);  /* Bypass recheck */
+          VdbeComment((v, "bypass recheck"));
+
+          /* Here we insert code that will be invoked after all constraint
+          ** checks have run, if and only if one or more replace triggers
+          ** fired. */
+          sqlite3VdbeResolveLabel(v, lblRecheckOk);
+          lblRecheckOk = sqlite3VdbeMakeLabel(pParse);
+          if( pIdx->pPartIdxWhere ){
+            /* Bypass the recheck if this partial index is not defined
+            ** for the current row */
+            sqlite3VdbeAddOp2(v, OP_IsNull, regIdx-1, lblRecheckOk);
+            VdbeCoverage(v);
+          }
+          /* Copy the constraint check code from above, except change
+          ** the constraint-ok jump destination to be the address of
+          ** the next retest block */
+          while( nConflictCk>0 ){
+            VdbeOp x;    /* Conflict check opcode to copy */
+            /* The sqlite3VdbeAddOp4() call might reallocate the opcode array.
+            ** Hence, make a complete copy of the opcode, rather than using
+            ** a pointer to the opcode. */
+            x = *sqlite3VdbeGetOp(v, addrConflictCk);
+            if( x.opcode!=OP_IdxRowid ){
+              int p2;      /* New P2 value for copied conflict check opcode */
+              const char *zP4;
+              if( sqlite3OpcodeProperty[x.opcode]&OPFLG_JUMP ){
+                p2 = lblRecheckOk;
+              }else{
+                p2 = x.p2;
+              }
+              zP4 = x.p4type==P4_INT32 ? SQLITE_INT_TO_PTR(x.p4.i) : x.p4.z;
+              sqlite3VdbeAddOp4(v, x.opcode, x.p1, p2, x.p3, zP4, x.p4type);
+              sqlite3VdbeChangeP5(v, x.p5);
+              VdbeCoverageIf(v, p2!=x.p2);
+            }
+            nConflictCk--;
+            addrConflictCk++;
+          }
+          /* If the retest fails, issue an abort */
+          sqlite3UniqueConstraint(pParse, OE_Abort, pIdx);
+
+          sqlite3VdbeJumpHere(v, addrBypass); /* Terminate the recheck bypass */
+        }
+        seenReplace = 1;
+        break;
+      }
+    }
+    sqlite3VdbeResolveLabel(v, addrUniqueOk);
+    if( regR!=regIdx ) sqlite3ReleaseTempRange(pParse, regR, nPkField);
+    if( pUpsertClause
+     && upsertIpkReturn
+     && sqlite3UpsertNextIsIPK(pUpsertClause)
+    ){
+      sqlite3VdbeGoto(v, upsertIpkDelay+1);
+      sqlite3VdbeJumpHere(v, upsertIpkReturn);
+      upsertIpkReturn = 0;
+    }
+  }
+
+  /* If the IPK constraint is a REPLACE, run it last */
+  if( ipkTop ){
+    sqlite3VdbeGoto(v, ipkTop);
+    VdbeComment((v, "Do IPK REPLACE"));
+    assert( ipkBottom>0 );
+    sqlite3VdbeJumpHere(v, ipkBottom);
+  }
+
+  /* Recheck all uniqueness constraints after replace triggers have run */
+  testcase( regTrigCnt!=0 && nReplaceTrig==0 );
+  assert( regTrigCnt!=0 || nReplaceTrig==0 );
+  if( nReplaceTrig ){
+    sqlite3VdbeAddOp2(v, OP_IfNot, regTrigCnt, lblRecheckOk);VdbeCoverage(v);
+    if( !pPk ){
+      if( isUpdate ){
+        sqlite3VdbeAddOp3(v, OP_Eq, regNewData, addrRecheck, regOldData);
+        sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
+        VdbeCoverage(v);
+      }
+      sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, addrRecheck, regNewData);
+      VdbeCoverage(v);
+      sqlite3RowidConstraint(pParse, OE_Abort, pTab);
+    }else{
+      sqlite3VdbeGoto(v, addrRecheck);
+    }
+    sqlite3VdbeResolveLabel(v, lblRecheckOk);
+  }
+
+  /* Generate the table record */
+  if( HasRowid(pTab) ){
+    int regRec = aRegIdx[ix];
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, regNewData+1, pTab->nNVCol, regRec);
+    sqlite3SetMakeRecordP5(v, pTab);
+    if( !bAffinityDone ){
+      sqlite3TableAffinity(v, pTab, 0);
+    }
+  }
+
+  *pbMayReplace = seenReplace;
+  VdbeModuleComment((v, "END: GenCnstCks(%d)", seenReplace));
+}
+
+#ifdef SQLITE_ENABLE_NULL_TRIM
+/*
+** Change the P5 operand on the last opcode (which should be an OP_MakeRecord)
+** to be the number of columns in table pTab that must not be NULL-trimmed.
+**
+** Or if no columns of pTab may be NULL-trimmed, leave P5 at zero.
+*/
+void sqlite3SetMakeRecordP5(Vdbe *v, Table *pTab){
+  u16 i;
+
+  /* Records with omitted columns are only allowed for schema format
+  ** version 2 and later (SQLite version 3.1.4, 2005-02-20). */
+  if( pTab->pSchema->file_format<2 ) return;
+
+  for(i=pTab->nCol-1; i>0; i--){
+    if( pTab->aCol[i].iDflt!=0 ) break;
+    if( pTab->aCol[i].colFlags & COLFLAG_PRIMKEY ) break;
+  }
+  sqlite3VdbeChangeP5(v, i+1);
+}
+#endif
+
+/*
+** Table pTab is a WITHOUT ROWID table that is being written to. The cursor
+** number is iCur, and register regData contains the new record for the
+** PK index. This function adds code to invoke the pre-update hook,
+** if one is registered.
+*/
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+static void codeWithoutRowidPreupdate(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being updated */
+  int iCur,                       /* Cursor number for table */
+  int regData                     /* Data containing new record */
+){
+  Vdbe *v = pParse->pVdbe;
+  int r = sqlite3GetTempReg(pParse);
+  assert( !HasRowid(pTab) );
+  assert( 0==(pParse->db->mDbFlags & DBFLAG_Vacuum) || CORRUPT_DB );
+  sqlite3VdbeAddOp2(v, OP_Integer, 0, r);
+  sqlite3VdbeAddOp4(v, OP_Insert, iCur, regData, r, (char*)pTab, P4_TABLE);
+  sqlite3VdbeChangeP5(v, OPFLAG_ISNOOP);
+  sqlite3ReleaseTempReg(pParse, r);
+}
+#else
+# define codeWithoutRowidPreupdate(a,b,c,d)
+#endif
+
+/*
+** This routine generates code to finish the INSERT or UPDATE operation
+** that was started by a prior call to sqlite3GenerateConstraintChecks.
+** A consecutive range of registers starting at regNewData contains the
+** rowid and the content to be inserted.
+**
+** The arguments to this routine should be the same as the first six
+** arguments to sqlite3GenerateConstraintChecks.
+*/
+void sqlite3CompleteInsertion(
+  Parse *pParse,      /* The parser context */
+  Table *pTab,        /* the table into which we are inserting */
+  int iDataCur,       /* Cursor of the canonical data source */
+  int iIdxCur,        /* First index cursor */
+  int regNewData,     /* Range of content */
+  int *aRegIdx,       /* Register used by each index.  0 for unused indices */
+  int update_flags,   /* True for UPDATE, False for INSERT */
+  int appendBias,     /* True if this is likely to be an append */
+  int useSeekResult   /* True to set the USESEEKRESULT flag on OP_[Idx]Insert */
+){
+  Vdbe *v;            /* Prepared statements under construction */
+  Index *pIdx;        /* An index being inserted or updated */
+  u8 pik_flags;       /* flag values passed to the btree insert */
+  int i;              /* Loop counter */
+
+  assert( update_flags==0
+       || update_flags==OPFLAG_ISUPDATE
+       || update_flags==(OPFLAG_ISUPDATE|OPFLAG_SAVEPOSITION)
+  );
+
+  v = pParse->pVdbe;
+  assert( v!=0 );
+  assert( !IsView(pTab) );  /* This table is not a VIEW */
+  for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
+    /* All REPLACE indexes are at the end of the list */
+    assert( pIdx->onError!=OE_Replace
+         || pIdx->pNext==0
+         || pIdx->pNext->onError==OE_Replace );
+    if( aRegIdx[i]==0 ) continue;
+    if( pIdx->pPartIdxWhere ){
+      sqlite3VdbeAddOp2(v, OP_IsNull, aRegIdx[i], sqlite3VdbeCurrentAddr(v)+2);
+      VdbeCoverage(v);
+    }
+    pik_flags = (useSeekResult ? OPFLAG_USESEEKRESULT : 0);
+    if( IsPrimaryKeyIndex(pIdx) && !HasRowid(pTab) ){
+      pik_flags |= OPFLAG_NCHANGE;
+      pik_flags |= (update_flags & OPFLAG_SAVEPOSITION);
+      if( update_flags==0 ){
+        codeWithoutRowidPreupdate(pParse, pTab, iIdxCur+i, aRegIdx[i]);
+      }
+    }
+    sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iIdxCur+i, aRegIdx[i],
+                         aRegIdx[i]+1,
+                         pIdx->uniqNotNull ? pIdx->nKeyCol: pIdx->nColumn);
+    sqlite3VdbeChangeP5(v, pik_flags);
+  }
+  if( !HasRowid(pTab) ) return;
+  if( pParse->nested ){
+    pik_flags = 0;
+  }else{
+    pik_flags = OPFLAG_NCHANGE;
+    pik_flags |= (update_flags?update_flags:OPFLAG_LASTROWID);
+  }
+  if( appendBias ){
+    pik_flags |= OPFLAG_APPEND;
+  }
+  if( useSeekResult ){
+    pik_flags |= OPFLAG_USESEEKRESULT;
+  }
+  sqlite3VdbeAddOp3(v, OP_Insert, iDataCur, aRegIdx[i], regNewData);
+  if( !pParse->nested ){
+    sqlite3VdbeAppendP4(v, pTab, P4_TABLE);
+  }
+  sqlite3VdbeChangeP5(v, pik_flags);
+}
+
+/*
+** Allocate cursors for the pTab table and all its indices and generate
+** code to open and initialized those cursors.
+**
+** The cursor for the object that contains the complete data (normally
+** the table itself, but the PRIMARY KEY index in the case of a WITHOUT
+** ROWID table) is returned in *piDataCur.  The first index cursor is
+** returned in *piIdxCur.  The number of indices is returned.
+**
+** Use iBase as the first cursor (either the *piDataCur for rowid tables
+** or the first index for WITHOUT ROWID tables) if it is non-negative.
+** If iBase is negative, then allocate the next available cursor.
+**
+** For a rowid table, *piDataCur will be exactly one less than *piIdxCur.
+** For a WITHOUT ROWID table, *piDataCur will be somewhere in the range
+** of *piIdxCurs, depending on where the PRIMARY KEY index appears on the
+** pTab->pIndex list.
+**
+** If pTab is a virtual table, then this routine is a no-op and the
+** *piDataCur and *piIdxCur values are left uninitialized.
+*/
+int sqlite3OpenTableAndIndices(
+  Parse *pParse,   /* Parsing context */
+  Table *pTab,     /* Table to be opened */
+  int op,          /* OP_OpenRead or OP_OpenWrite */
+  u8 p5,           /* P5 value for OP_Open* opcodes (except on WITHOUT ROWID) */
+  int iBase,       /* Use this for the table cursor, if there is one */
+  u8 *aToOpen,     /* If not NULL: boolean for each table and index */
+  int *piDataCur,  /* Write the database source cursor number here */
+  int *piIdxCur    /* Write the first index cursor number here */
+){
+  int i;
+  int iDb;
+  int iDataCur;
+  Index *pIdx;
+  Vdbe *v;
+
+  assert( op==OP_OpenRead || op==OP_OpenWrite );
+  assert( op==OP_OpenWrite || p5==0 );
+  assert( piDataCur!=0 );
+  assert( piIdxCur!=0 );
+  if( IsVirtual(pTab) ){
+    /* This routine is a no-op for virtual tables. Leave the output
+    ** variables *piDataCur and *piIdxCur set to illegal cursor numbers
+    ** for improved error detection. */
+    *piDataCur = *piIdxCur = -999;
+    return 0;
+  }
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  v = pParse->pVdbe;
+  assert( v!=0 );
+  if( iBase<0 ) iBase = pParse->nTab;
+  iDataCur = iBase++;
+  *piDataCur = iDataCur;
+  if( HasRowid(pTab) && (aToOpen==0 || aToOpen[0]) ){
+    sqlite3OpenTable(pParse, iDataCur, iDb, pTab, op);
+  }else if( pParse->db->noSharedCache==0 ){
+    sqlite3TableLock(pParse, iDb, pTab->tnum, op==OP_OpenWrite, pTab->zName);
+  }
+  *piIdxCur = iBase;
+  for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
+    int iIdxCur = iBase++;
+    assert( pIdx->pSchema==pTab->pSchema );
+    if( IsPrimaryKeyIndex(pIdx) && !HasRowid(pTab) ){
+      *piDataCur = iIdxCur;
+      p5 = 0;
+    }
+    if( aToOpen==0 || aToOpen[i+1] ){
+      sqlite3VdbeAddOp3(v, op, iIdxCur, pIdx->tnum, iDb);
+      sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
+      sqlite3VdbeChangeP5(v, p5);
+      VdbeComment((v, "%s", pIdx->zName));
+    }
+  }
+  if( iBase>pParse->nTab ) pParse->nTab = iBase;
+  return i;
+}
+
+
+#ifdef SQLITE_TEST
+/*
+** The following global variable is incremented whenever the
+** transfer optimization is used.  This is used for testing
+** purposes only - to make sure the transfer optimization really
+** is happening when it is supposed to.
+*/
+int sqlite3_xferopt_count;
+#endif /* SQLITE_TEST */
+
+
+#ifndef SQLITE_OMIT_XFER_OPT
+/*
+** Check to see if index pSrc is compatible as a source of data
+** for index pDest in an insert transfer optimization.  The rules
+** for a compatible index:
+**
+**    *   The index is over the same set of columns
+**    *   The same DESC and ASC markings occurs on all columns
+**    *   The same onError processing (OE_Abort, OE_Ignore, etc)
+**    *   The same collating sequence on each column
+**    *   The index has the exact same WHERE clause
+*/
+static int xferCompatibleIndex(Index *pDest, Index *pSrc){
+  int i;
+  assert( pDest && pSrc );
+  assert( pDest->pTable!=pSrc->pTable );
+  if( pDest->nKeyCol!=pSrc->nKeyCol || pDest->nColumn!=pSrc->nColumn ){
+    return 0;   /* Different number of columns */
+  }
+  if( pDest->onError!=pSrc->onError ){
+    return 0;   /* Different conflict resolution strategies */
+  }
+  for(i=0; i<pSrc->nKeyCol; i++){
+    if( pSrc->aiColumn[i]!=pDest->aiColumn[i] ){
+      return 0;   /* Different columns indexed */
+    }
+    if( pSrc->aiColumn[i]==XN_EXPR ){
+      assert( pSrc->aColExpr!=0 && pDest->aColExpr!=0 );
+      if( sqlite3ExprCompare(0, pSrc->aColExpr->a[i].pExpr,
+                             pDest->aColExpr->a[i].pExpr, -1)!=0 ){
+        return 0;   /* Different expressions in the index */
+      }
+    }
+    if( pSrc->aSortOrder[i]!=pDest->aSortOrder[i] ){
+      return 0;   /* Different sort orders */
+    }
+    if( sqlite3_stricmp(pSrc->azColl[i],pDest->azColl[i])!=0 ){
+      return 0;   /* Different collating sequences */
+    }
+  }
+  if( sqlite3ExprCompare(0, pSrc->pPartIdxWhere, pDest->pPartIdxWhere, -1) ){
+    return 0;     /* Different WHERE clauses */
+  }
+
+  /* If no test above fails then the indices must be compatible */
+  return 1;
+}
+
+/*
+** Attempt the transfer optimization on INSERTs of the form
+**
+**     INSERT INTO tab1 SELECT * FROM tab2;
+**
+** The xfer optimization transfers raw records from tab2 over to tab1. 
+** Columns are not decoded and reassembled, which greatly improves
+** performance.  Raw index records are transferred in the same way.
+**
+** The xfer optimization is only attempted if tab1 and tab2 are compatible.
+** There are lots of rules for determining compatibility - see comments
+** embedded in the code for details.
+**
+** This routine returns TRUE if the optimization is guaranteed to be used.
+** Sometimes the xfer optimization will only work if the destination table
+** is empty - a factor that can only be determined at run-time.  In that
+** case, this routine generates code for the xfer optimization but also
+** does a test to see if the destination table is empty and jumps over the
+** xfer optimization code if the test fails.  In that case, this routine
+** returns FALSE so that the caller will know to go ahead and generate
+** an unoptimized transfer.  This routine also returns FALSE if there
+** is no chance that the xfer optimization can be applied.
+**
+** This optimization is particularly useful at making VACUUM run faster.
+*/
+static int xferOptimization(
+  Parse *pParse,        /* Parser context */
+  Table *pDest,         /* The table we are inserting into */
+  Select *pSelect,      /* A SELECT statement to use as the data source */
+  int onError,          /* How to handle constraint errors */
+  int iDbDest           /* The database of pDest */
+){
+  sqlite3 *db = pParse->db;
+  ExprList *pEList;                /* The result set of the SELECT */
+  Table *pSrc;                     /* The table in the FROM clause of SELECT */
+  Index *pSrcIdx, *pDestIdx;       /* Source and destination indices */
+  SrcItem *pItem;                  /* An element of pSelect->pSrc */
+  int i;                           /* Loop counter */
+  int iDbSrc;                      /* The database of pSrc */
+  int iSrc, iDest;                 /* Cursors from source and destination */
+  int addr1, addr2;                /* Loop addresses */
+  int emptyDestTest = 0;           /* Address of test for empty pDest */
+  int emptySrcTest = 0;            /* Address of test for empty pSrc */
+  Vdbe *v;                         /* The VDBE we are building */
+  int regAutoinc;                  /* Memory register used by AUTOINC */
+  int destHasUniqueIdx = 0;        /* True if pDest has a UNIQUE index */
+  int regData, regRowid;           /* Registers holding data and rowid */
+
+  assert( pSelect!=0 );
+  if( pParse->pWith || pSelect->pWith ){
+    /* Do not attempt to process this query if there are an WITH clauses
+    ** attached to it. Proceeding may generate a false "no such table: xxx"
+    ** error if pSelect reads from a CTE named "xxx".  */
+    return 0;
+  }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pDest) ){
+    return 0;   /* tab1 must not be a virtual table */
+  }
+#endif
+  if( onError==OE_Default ){
+    if( pDest->iPKey>=0 ) onError = pDest->keyConf;
+    if( onError==OE_Default ) onError = OE_Abort;
+  }
+  assert(pSelect->pSrc);   /* allocated even if there is no FROM clause */
+  if( pSelect->pSrc->nSrc!=1 ){
+    return 0;   /* FROM clause must have exactly one term */
+  }
+  if( pSelect->pSrc->a[0].pSelect ){
+    return 0;   /* FROM clause cannot contain a subquery */
+  }
+  if( pSelect->pWhere ){
+    return 0;   /* SELECT may not have a WHERE clause */
+  }
+  if( pSelect->pOrderBy ){
+    return 0;   /* SELECT may not have an ORDER BY clause */
+  }
+  /* Do not need to test for a HAVING clause.  If HAVING is present but
+  ** there is no ORDER BY, we will get an error. */
+  if( pSelect->pGroupBy ){
+    return 0;   /* SELECT may not have a GROUP BY clause */
+  }
+  if( pSelect->pLimit ){
+    return 0;   /* SELECT may not have a LIMIT clause */
+  }
+  if( pSelect->pPrior ){
+    return 0;   /* SELECT may not be a compound query */
+  }
+  if( pSelect->selFlags & SF_Distinct ){
+    return 0;   /* SELECT may not be DISTINCT */
+  }
+  pEList = pSelect->pEList;
+  assert( pEList!=0 );
+  if( pEList->nExpr!=1 ){
+    return 0;   /* The result set must have exactly one column */
+  }
+  assert( pEList->a[0].pExpr );
+  if( pEList->a[0].pExpr->op!=TK_ASTERISK ){
+    return 0;   /* The result set must be the special operator "*" */
+  }
+
+  /* At this point we have established that the statement is of the
+  ** correct syntactic form to participate in this optimization.  Now
+  ** we have to check the semantics.
+  */
+  pItem = pSelect->pSrc->a;
+  pSrc = sqlite3LocateTableItem(pParse, 0, pItem);
+  if( pSrc==0 ){
+    return 0;   /* FROM clause does not contain a real table */
+  }
+  if( pSrc->tnum==pDest->tnum && pSrc->pSchema==pDest->pSchema ){
+    testcase( pSrc!=pDest ); /* Possible due to bad sqlite_schema.rootpage */
+    return 0;   /* tab1 and tab2 may not be the same table */
+  }
+  if( HasRowid(pDest)!=HasRowid(pSrc) ){
+    return 0;   /* source and destination must both be WITHOUT ROWID or not */
+  }
+  if( !IsOrdinaryTable(pSrc) ){
+    return 0;   /* tab2 may not be a view or virtual table */
+  }
+  if( pDest->nCol!=pSrc->nCol ){
+    return 0;   /* Number of columns must be the same in tab1 and tab2 */
+  }
+  if( pDest->iPKey!=pSrc->iPKey ){
+    return 0;   /* Both tables must have the same INTEGER PRIMARY KEY */
+  }
+  if( (pDest->tabFlags & TF_Strict)!=0 && (pSrc->tabFlags & TF_Strict)==0 ){
+    return 0;   /* Cannot feed from a non-strict into a strict table */
+  }
+  for(i=0; i<pDest->nCol; i++){
+    Column *pDestCol = &pDest->aCol[i];
+    Column *pSrcCol = &pSrc->aCol[i];
+#ifdef SQLITE_ENABLE_HIDDEN_COLUMNS
+    if( (db->mDbFlags & DBFLAG_Vacuum)==0
+     && (pDestCol->colFlags | pSrcCol->colFlags) & COLFLAG_HIDDEN
+    ){
+      return 0;    /* Neither table may have __hidden__ columns */
+    }
+#endif
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+    /* Even if tables t1 and t2 have identical schemas, if they contain
+    ** generated columns, then this statement is semantically incorrect:
+    **
+    **     INSERT INTO t2 SELECT * FROM t1;
+    **
+    ** The reason is that generated column values are returned by the
+    ** the SELECT statement on the right but the INSERT statement on the
+    ** left wants them to be omitted.
+    **
+    ** Nevertheless, this is a useful notational shorthand to tell SQLite
+    ** to do a bulk transfer all of the content from t1 over to t2.
+    **
+    ** We could, in theory, disable this (except for internal use by the
+    ** VACUUM command where it is actually needed).  But why do that?  It
+    ** seems harmless enough, and provides a useful service.
+    */
+    if( (pDestCol->colFlags & COLFLAG_GENERATED) !=
+        (pSrcCol->colFlags & COLFLAG_GENERATED) ){
+      return 0;    /* Both columns have the same generated-column type */
+    }
+    /* But the transfer is only allowed if both the source and destination
+    ** tables have the exact same expressions for generated columns.
+    ** This requirement could be relaxed for VIRTUAL columns, I suppose.
+    */
+    if( (pDestCol->colFlags & COLFLAG_GENERATED)!=0 ){
+      if( sqlite3ExprCompare(0,
+             sqlite3ColumnExpr(pSrc, pSrcCol),
+             sqlite3ColumnExpr(pDest, pDestCol), -1)!=0 ){
+        testcase( pDestCol->colFlags & COLFLAG_VIRTUAL );
+        testcase( pDestCol->colFlags & COLFLAG_STORED );
+        return 0;  /* Different generator expressions */
+      }
+    }
+#endif
+    if( pDestCol->affinity!=pSrcCol->affinity ){
+      return 0;    /* Affinity must be the same on all columns */
+    }
+    if( sqlite3_stricmp(sqlite3ColumnColl(pDestCol),
+                        sqlite3ColumnColl(pSrcCol))!=0 ){
+      return 0;    /* Collating sequence must be the same on all columns */
+    }
+    if( pDestCol->notNull && !pSrcCol->notNull ){
+      return 0;    /* tab2 must be NOT NULL if tab1 is */
+    }
+    /* Default values for second and subsequent columns need to match. */
+    if( (pDestCol->colFlags & COLFLAG_GENERATED)==0 && i>0 ){
+      Expr *pDestExpr = sqlite3ColumnExpr(pDest, pDestCol);
+      Expr *pSrcExpr = sqlite3ColumnExpr(pSrc, pSrcCol);
+      assert( pDestExpr==0 || pDestExpr->op==TK_SPAN );
+      assert( pDestExpr==0 || !ExprHasProperty(pDestExpr, EP_IntValue) );
+      assert( pSrcExpr==0 || pSrcExpr->op==TK_SPAN );
+      assert( pSrcExpr==0 || !ExprHasProperty(pSrcExpr, EP_IntValue) );
+      if( (pDestExpr==0)!=(pSrcExpr==0)
+       || (pDestExpr!=0 && strcmp(pDestExpr->u.zToken,
+                                       pSrcExpr->u.zToken)!=0)
+      ){
+        return 0;    /* Default values must be the same for all columns */
+      }
+    }
+  }
+  for(pDestIdx=pDest->pIndex; pDestIdx; pDestIdx=pDestIdx->pNext){
+    if( IsUniqueIndex(pDestIdx) ){
+      destHasUniqueIdx = 1;
+    }
+    for(pSrcIdx=pSrc->pIndex; pSrcIdx; pSrcIdx=pSrcIdx->pNext){
+      if( xferCompatibleIndex(pDestIdx, pSrcIdx) ) break;
+    }
+    if( pSrcIdx==0 ){
+      return 0;    /* pDestIdx has no corresponding index in pSrc */
+    }
+    if( pSrcIdx->tnum==pDestIdx->tnum && pSrc->pSchema==pDest->pSchema
+         && sqlite3FaultSim(411)==SQLITE_OK ){
+      /* The sqlite3FaultSim() call allows this corruption test to be
+      ** bypassed during testing, in order to exercise other corruption tests
+      ** further downstream. */
+      return 0;   /* Corrupt schema - two indexes on the same btree */
+    }
+  }
+#ifndef SQLITE_OMIT_CHECK
+  if( pDest->pCheck && sqlite3ExprListCompare(pSrc->pCheck,pDest->pCheck,-1) ){
+    return 0;   /* Tables have different CHECK constraints.  Ticket #2252 */
+  }
+#endif
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  /* Disallow the transfer optimization if the destination table contains
+  ** any foreign key constraints.  This is more restrictive than necessary.
+  ** But the main beneficiary of the transfer optimization is the VACUUM
+  ** command, and the VACUUM command disables foreign key constraints.  So
+  ** the extra complication to make this rule less restrictive is probably
+  ** not worth the effort.  Ticket [6284df89debdfa61db8073e062908af0c9b6118e]
+  */
+  assert( IsOrdinaryTable(pDest) );
+  if( (db->flags & SQLITE_ForeignKeys)!=0 && pDest->u.tab.pFKey!=0 ){
+    return 0;
+  }
+#endif
+  if( (db->flags & SQLITE_CountRows)!=0 ){
+    return 0;  /* xfer opt does not play well with PRAGMA count_changes */
+  }
+
+  /* If we get this far, it means that the xfer optimization is at
+  ** least a possibility, though it might only work if the destination
+  ** table (tab1) is initially empty.
+  */
+#ifdef SQLITE_TEST
+  sqlite3_xferopt_count++;
+#endif
+  iDbSrc = sqlite3SchemaToIndex(db, pSrc->pSchema);
+  v = sqlite3GetVdbe(pParse);
+  sqlite3CodeVerifySchema(pParse, iDbSrc);
+  iSrc = pParse->nTab++;
+  iDest = pParse->nTab++;
+  regAutoinc = autoIncBegin(pParse, iDbDest, pDest);
+  regData = sqlite3GetTempReg(pParse);
+  sqlite3VdbeAddOp2(v, OP_Null, 0, regData);
+  regRowid = sqlite3GetTempReg(pParse);
+  sqlite3OpenTable(pParse, iDest, iDbDest, pDest, OP_OpenWrite);
+  assert( HasRowid(pDest) || destHasUniqueIdx );
+  if( (db->mDbFlags & DBFLAG_Vacuum)==0 && (
+      (pDest->iPKey<0 && pDest->pIndex!=0)          /* (1) */
+   || destHasUniqueIdx                              /* (2) */
+   || (onError!=OE_Abort && onError!=OE_Rollback)   /* (3) */
+  )){
+    /* In some circumstances, we are able to run the xfer optimization
+    ** only if the destination table is initially empty. Unless the
+    ** DBFLAG_Vacuum flag is set, this block generates code to make
+    ** that determination. If DBFLAG_Vacuum is set, then the destination
+    ** table is always empty.
+    **
+    ** Conditions under which the destination must be empty:
+    **
+    ** (1) There is no INTEGER PRIMARY KEY but there are indices.
+    **     (If the destination is not initially empty, the rowid fields
+    **     of index entries might need to change.)
+    **
+    ** (2) The destination has a unique index.  (The xfer optimization
+    **     is unable to test uniqueness.)
+    **
+    ** (3) onError is something other than OE_Abort and OE_Rollback.
+    */
+    addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iDest, 0); VdbeCoverage(v);
+    emptyDestTest = sqlite3VdbeAddOp0(v, OP_Goto);
+    sqlite3VdbeJumpHere(v, addr1);
+  }
+  if( HasRowid(pSrc) ){
+    u8 insFlags;
+    sqlite3OpenTable(pParse, iSrc, iDbSrc, pSrc, OP_OpenRead);
+    emptySrcTest = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0); VdbeCoverage(v);
+    if( pDest->iPKey>=0 ){
+      addr1 = sqlite3VdbeAddOp2(v, OP_Rowid, iSrc, regRowid);
+      if( (db->mDbFlags & DBFLAG_Vacuum)==0 ){
+        sqlite3VdbeVerifyAbortable(v, onError);
+        addr2 = sqlite3VdbeAddOp3(v, OP_NotExists, iDest, 0, regRowid);
+        VdbeCoverage(v);
+        sqlite3RowidConstraint(pParse, onError, pDest);
+        sqlite3VdbeJumpHere(v, addr2);
+      }
+      autoIncStep(pParse, regAutoinc, regRowid);
+    }else if( pDest->pIndex==0 && !(db->mDbFlags & DBFLAG_VacuumInto) ){
+      addr1 = sqlite3VdbeAddOp2(v, OP_NewRowid, iDest, regRowid);
+    }else{
+      addr1 = sqlite3VdbeAddOp2(v, OP_Rowid, iSrc, regRowid);
+      assert( (pDest->tabFlags & TF_Autoincrement)==0 );
+    }
+
+    if( db->mDbFlags & DBFLAG_Vacuum ){
+      sqlite3VdbeAddOp1(v, OP_SeekEnd, iDest);
+      insFlags = OPFLAG_APPEND|OPFLAG_USESEEKRESULT|OPFLAG_PREFORMAT;
+    }else{
+      insFlags = OPFLAG_NCHANGE|OPFLAG_LASTROWID|OPFLAG_APPEND|OPFLAG_PREFORMAT;
+    }
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+    if( (db->mDbFlags & DBFLAG_Vacuum)==0 ){
+      sqlite3VdbeAddOp3(v, OP_RowData, iSrc, regData, 1);
+      insFlags &= ~OPFLAG_PREFORMAT;
+    }else
+#endif
+    {
+      sqlite3VdbeAddOp3(v, OP_RowCell, iDest, iSrc, regRowid);
+    }
+    sqlite3VdbeAddOp3(v, OP_Insert, iDest, regData, regRowid);
+    if( (db->mDbFlags & DBFLAG_Vacuum)==0 ){
+      sqlite3VdbeChangeP4(v, -1, (char*)pDest, P4_TABLE);
+    }
+    sqlite3VdbeChangeP5(v, insFlags);
+
+    sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1); VdbeCoverage(v);
+    sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
+    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
+  }else{
+    sqlite3TableLock(pParse, iDbDest, pDest->tnum, 1, pDest->zName);
+    sqlite3TableLock(pParse, iDbSrc, pSrc->tnum, 0, pSrc->zName);
+  }
+  for(pDestIdx=pDest->pIndex; pDestIdx; pDestIdx=pDestIdx->pNext){
+    u8 idxInsFlags = 0;
+    for(pSrcIdx=pSrc->pIndex; ALWAYS(pSrcIdx); pSrcIdx=pSrcIdx->pNext){
+      if( xferCompatibleIndex(pDestIdx, pSrcIdx) ) break;
+    }
+    assert( pSrcIdx );
+    sqlite3VdbeAddOp3(v, OP_OpenRead, iSrc, pSrcIdx->tnum, iDbSrc);
+    sqlite3VdbeSetP4KeyInfo(pParse, pSrcIdx);
+    VdbeComment((v, "%s", pSrcIdx->zName));
+    sqlite3VdbeAddOp3(v, OP_OpenWrite, iDest, pDestIdx->tnum, iDbDest);
+    sqlite3VdbeSetP4KeyInfo(pParse, pDestIdx);
+    sqlite3VdbeChangeP5(v, OPFLAG_BULKCSR);
+    VdbeComment((v, "%s", pDestIdx->zName));
+    addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0); VdbeCoverage(v);
+    if( db->mDbFlags & DBFLAG_Vacuum ){
+      /* This INSERT command is part of a VACUUM operation, which guarantees
+      ** that the destination table is empty. If all indexed columns use
+      ** collation sequence BINARY, then it can also be assumed that the
+      ** index will be populated by inserting keys in strictly sorted
+      ** order. In this case, instead of seeking within the b-tree as part
+      ** of every OP_IdxInsert opcode, an OP_SeekEnd is added before the
+      ** OP_IdxInsert to seek to the point within the b-tree where each key
+      ** should be inserted. This is faster.
+      **
+      ** If any of the indexed columns use a collation sequence other than
+      ** BINARY, this optimization is disabled. This is because the user
+      ** might change the definition of a collation sequence and then run
+      ** a VACUUM command. In that case keys may not be written in strictly
+      ** sorted order.  */
+      for(i=0; i<pSrcIdx->nColumn; i++){
+        const char *zColl = pSrcIdx->azColl[i];
+        if( sqlite3_stricmp(sqlite3StrBINARY, zColl) ) break;
+      }
+      if( i==pSrcIdx->nColumn ){
+        idxInsFlags = OPFLAG_USESEEKRESULT|OPFLAG_PREFORMAT;
+        sqlite3VdbeAddOp1(v, OP_SeekEnd, iDest);
+        sqlite3VdbeAddOp2(v, OP_RowCell, iDest, iSrc);
+      }
+    }else if( !HasRowid(pSrc) && pDestIdx->idxType==SQLITE_IDXTYPE_PRIMARYKEY ){
+      idxInsFlags |= OPFLAG_NCHANGE;
+    }
+    if( idxInsFlags!=(OPFLAG_USESEEKRESULT|OPFLAG_PREFORMAT) ){
+      sqlite3VdbeAddOp3(v, OP_RowData, iSrc, regData, 1);
+      if( (db->mDbFlags & DBFLAG_Vacuum)==0
+       && !HasRowid(pDest)
+       && IsPrimaryKeyIndex(pDestIdx)
+      ){
+        codeWithoutRowidPreupdate(pParse, pDest, iDest, regData);
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_IdxInsert, iDest, regData);
+    sqlite3VdbeChangeP5(v, idxInsFlags|OPFLAG_APPEND);
+    sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1+1); VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addr1);
+    sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
+    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
+  }
+  if( emptySrcTest ) sqlite3VdbeJumpHere(v, emptySrcTest);
+  sqlite3ReleaseTempReg(pParse, regRowid);
+  sqlite3ReleaseTempReg(pParse, regData);
+  if( emptyDestTest ){
+    sqlite3AutoincrementEnd(pParse);
+    sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_OK, 0);
+    sqlite3VdbeJumpHere(v, emptyDestTest);
+    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
+    return 0;
+  }else{
+    return 1;
+  }
+}
+#endif /* SQLITE_OMIT_XFER_OPT */
diff --git a/src/json.c b/src/json.c
new file mode 100644
index 0000000..70cc4b7
--- /dev/null
+++ b/src/json.c
@@ -0,0 +1,5285 @@
+/*
+** 2015-08-12
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** SQLite JSON functions.
+**
+** This file began as an extension in ext/misc/json1.c in 2015.  That
+** extension proved so useful that it has now been moved into the core.
+**
+** The original design stored all JSON as pure text, canonical RFC-8259.
+** Support for JSON-5 extensions was added with version 3.42.0 (2023-05-16).
+** All generated JSON text still conforms strictly to RFC-8259, but text
+** with JSON-5 extensions is accepted as input.
+**
+** Beginning with version 3.45.0 (circa 2024-01-01), these routines also
+** accept BLOB values that have JSON encoded using a binary representation
+** called "JSONB".  The name JSONB comes from PostgreSQL, however the on-disk
+** format SQLite JSONB is completely different and incompatible with
+** PostgreSQL JSONB.
+**
+** Decoding and interpreting JSONB is still O(N) where N is the size of
+** the input, the same as text JSON.  However, the constant of proportionality
+** for JSONB is much smaller due to faster parsing.  The size of each
+** element in JSONB is encoded in its header, so there is no need to search
+** for delimiters using persnickety syntax rules.  JSONB seems to be about
+** 3x faster than text JSON as a result.  JSONB is also tends to be slightly
+** smaller than text JSON, by 5% or 10%, but there are corner cases where
+** JSONB can be slightly larger.  So you are not far mistaken to say that
+** a JSONB blob is the same size as the equivalent RFC-8259 text.
+**
+**
+** THE JSONB ENCODING:
+**
+** Every JSON element is encoded in JSONB as a header and a payload.
+** The header is between 1 and 9 bytes in size.  The payload is zero
+** or more bytes.
+**
+** The lower 4 bits of the first byte of the header determines the
+** element type:
+**
+**    0:   NULL
+**    1:   TRUE
+**    2:   FALSE
+**    3:   INT        -- RFC-8259 integer literal
+**    4:   INT5       -- JSON5 integer literal
+**    5:   FLOAT      -- RFC-8259 floating point literal
+**    6:   FLOAT5     -- JSON5 floating point literal
+**    7:   TEXT       -- Text literal acceptable to both SQL and JSON
+**    8:   TEXTJ      -- Text containing RFC-8259 escapes
+**    9:   TEXT5      -- Text containing JSON5 and/or RFC-8259 escapes
+**   10:   TEXTRAW    -- Text containing unescaped syntax characters
+**   11:   ARRAY
+**   12:   OBJECT
+**
+** The other three possible values (13-15) are reserved for future
+** enhancements.
+**
+** The upper 4 bits of the first byte determine the size of the header
+** and sometimes also the size of the payload.  If X is the first byte
+** of the element and if X>>4 is between 0 and 11, then the payload
+** will be that many bytes in size and the header is exactly one byte
+** in size.  Other four values for X>>4 (12-15) indicate that the header
+** is more than one byte in size and that the payload size is determined
+** by the remainder of the header, interpreted as a unsigned big-endian
+** integer.
+**
+**   Value of X>>4         Size integer        Total header size
+**   -------------     --------------------    -----------------
+**        12           1 byte (0-255)                2
+**        13           2 byte (0-65535)              3
+**        14           4 byte (0-4294967295)         5
+**        15           8 byte (0-1.8e19)             9
+**
+** The payload size need not be expressed in its minimal form.  For example,
+** if the payload size is 10, the size can be expressed in any of 5 different
+** ways: (1) (X>>4)==10, (2) (X>>4)==12 following by on 0x0a byte,
+** (3) (X>>4)==13 followed by 0x00 and 0x0a, (4) (X>>4)==14 followed by
+** 0x00 0x00 0x00 0x0a, or (5) (X>>4)==15 followed by 7 bytes of 0x00 and
+** a single byte of 0x0a.  The shorter forms are preferred, of course, but
+** sometimes when generating JSONB, the payload size is not known in advance
+** and it is convenient to reserve sufficient header space to cover the
+** largest possible payload size and then come back later and patch up
+** the size when it becomes known, resulting in a non-minimal encoding.
+**
+** The value (X>>4)==15 is not actually used in the current implementation
+** (as SQLite is currently unable handle BLOBs larger than about 2GB)
+** but is included in the design to allow for future enhancements.
+**
+** The payload follows the header.  NULL, TRUE, and FALSE have no payload and
+** their payload size must always be zero.  The payload for INT, INT5,
+** FLOAT, FLOAT5, TEXT, TEXTJ, TEXT5, and TEXTROW is text.  Note that the
+** "..." or '...' delimiters are omitted from the various text encodings.
+** The payload for ARRAY and OBJECT is a list of additional elements that
+** are the content for the array or object.  The payload for an OBJECT
+** must be an even number of elements.  The first element of each pair is
+** the label and must be of type TEXT, TEXTJ, TEXT5, or TEXTRAW.
+**
+** A valid JSONB blob consists of a single element, as described above.
+** Usually this will be an ARRAY or OBJECT element which has many more
+** elements as its content.  But the overall blob is just a single element.
+**
+** Input validation for JSONB blobs simply checks that the element type
+** code is between 0 and 12 and that the total size of the element
+** (header plus payload) is the same as the size of the BLOB.  If those
+** checks are true, the BLOB is assumed to be JSONB and processing continues.
+** Errors are only raised if some other miscoding is discovered during
+** processing.
+**
+** Additional information can be found in the doc/jsonb.md file of the
+** canonical SQLite source tree.
+*/
+#ifndef SQLITE_OMIT_JSON
+#include "sqliteInt.h"
+
+/* JSONB element types
+*/
+#define JSONB_NULL     0   /* "null" */
+#define JSONB_TRUE     1   /* "true" */
+#define JSONB_FALSE    2   /* "false" */
+#define JSONB_INT      3   /* integer acceptable to JSON and SQL */
+#define JSONB_INT5     4   /* integer in 0x000 notation */
+#define JSONB_FLOAT    5   /* float acceptable to JSON and SQL */
+#define JSONB_FLOAT5   6   /* float with JSON5 extensions */
+#define JSONB_TEXT     7   /* Text compatible with both JSON and SQL */
+#define JSONB_TEXTJ    8   /* Text with JSON escapes */
+#define JSONB_TEXT5    9   /* Text with JSON-5 escape */
+#define JSONB_TEXTRAW 10   /* SQL text that needs escaping for JSON */
+#define JSONB_ARRAY   11   /* An array */
+#define JSONB_OBJECT  12   /* An object */
+
+/* Human-readable names for the JSONB values.  The index for each
+** string must correspond to the JSONB_* integer above.
+*/
+static const char * const jsonbType[] = {
+  "null", "true", "false", "integer", "integer", 
+  "real", "real", "text",  "text",    "text",
+  "text", "array", "object", "", "", "", ""
+};
+
+/*
+** Growing our own isspace() routine this way is twice as fast as
+** the library isspace() function, resulting in a 7% overall performance
+** increase for the text-JSON parser.  (Ubuntu14.10 gcc 4.8.4 x64 with -Os).
+*/
+static const char jsonIsSpace[] = {
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 1, 1, 0, 0, 1, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  1, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+};
+#define jsonIsspace(x) (jsonIsSpace[(unsigned char)x])
+
+/*
+** The set of all space characters recognized by jsonIsspace().
+** Useful as the second argument to strspn().
+*/
+static const char jsonSpaces[] = "\011\012\015\040";
+
+/*
+** Characters that are special to JSON.  Control characters,
+** '"' and '\\' and '\''.  Actually, '\'' is not special to
+** canonical JSON, but it is special in JSON-5, so we include
+** it in the set of special characters.
+*/
+static const char jsonIsOk[256] = {
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  1, 1, 0, 1, 1, 1, 1, 0,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 0, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1
+};
+
+/* Objects */
+typedef struct JsonCache JsonCache;
+typedef struct JsonString JsonString;
+typedef struct JsonParse JsonParse;
+
+/*
+** Magic number used for the JSON parse cache in sqlite3_get_auxdata()
+*/
+#define JSON_CACHE_ID    (-429938)  /* Cache entry */
+#define JSON_CACHE_SIZE  4          /* Max number of cache entries */
+
+/*
+** jsonUnescapeOneChar() returns this invalid code point if it encounters
+** a syntax error.
+*/
+#define JSON_INVALID_CHAR 0x99999
+
+/* A cache mapping JSON text into JSONB blobs.
+**
+** Each cache entry is a JsonParse object with the following restrictions:
+**
+**    *   The bReadOnly flag must be set
+**
+**    *   The aBlob[] array must be owned by the JsonParse object.  In other
+**        words, nBlobAlloc must be non-zero.
+**
+**    *   eEdit and delta must be zero.
+**
+**    *   zJson must be an RCStr.  In other words bJsonIsRCStr must be true.
+*/
+struct JsonCache {
+  sqlite3 *db;                    /* Database connection */
+  int nUsed;                      /* Number of active entries in the cache */
+  JsonParse *a[JSON_CACHE_SIZE];  /* One line for each cache entry */
+};
+
+/* An instance of this object represents a JSON string
+** under construction.  Really, this is a generic string accumulator
+** that can be and is used to create strings other than JSON.
+**
+** If the generated string is longer than will fit into the zSpace[] buffer,
+** then it will be an RCStr string.  This aids with caching of large
+** JSON strings.
+*/
+struct JsonString {
+  sqlite3_context *pCtx;   /* Function context - put error messages here */
+  char *zBuf;              /* Append JSON content here */
+  u64 nAlloc;              /* Bytes of storage available in zBuf[] */
+  u64 nUsed;               /* Bytes of zBuf[] currently used */
+  u8 bStatic;              /* True if zBuf is static space */
+  u8 eErr;                 /* True if an error has been encountered */
+  char zSpace[100];        /* Initial static space */
+};
+
+/* Allowed values for JsonString.eErr */
+#define JSTRING_OOM         0x01   /* Out of memory */
+#define JSTRING_MALFORMED   0x02   /* Malformed JSONB */
+#define JSTRING_ERR         0x04   /* Error already sent to sqlite3_result */
+
+/* The "subtype" set for text JSON values passed through using
+** sqlite3_result_subtype() and sqlite3_value_subtype().
+*/
+#define JSON_SUBTYPE  74    /* Ascii for "J" */
+
+/*
+** Bit values for the flags passed into various SQL function implementations
+** via the sqlite3_user_data() value.
+*/
+#define JSON_JSON      0x01        /* Result is always JSON */
+#define JSON_SQL       0x02        /* Result is always SQL */
+#define JSON_ABPATH    0x03        /* Allow abbreviated JSON path specs */
+#define JSON_ISSET     0x04        /* json_set(), not json_insert() */
+#define JSON_BLOB      0x08        /* Use the BLOB output format */
+
+
+/* A parsed JSON value.  Lifecycle:
+**
+**   1.  JSON comes in and is parsed into a JSONB value in aBlob.  The
+**       original text is stored in zJson.  This step is skipped if the
+**       input is JSONB instead of text JSON.
+**
+**   2.  The aBlob[] array is searched using the JSON path notation, if needed.
+**       
+**   3.  Zero or more changes are made to aBlob[] (via json_remove() or
+**       json_replace() or json_patch() or similar).
+**
+**   4.  New JSON text is generated from the aBlob[] for output.  This step
+**       is skipped if the function is one of the jsonb_* functions that
+**       returns JSONB instead of text JSON.
+*/
+struct JsonParse {
+  u8 *aBlob;         /* JSONB representation of JSON value */
+  u32 nBlob;         /* Bytes of aBlob[] actually used */
+  u32 nBlobAlloc;    /* Bytes allocated to aBlob[].  0 if aBlob is external */
+  char *zJson;       /* Json text used for parsing */
+  sqlite3 *db;       /* The database connection to which this object belongs */
+  int nJson;         /* Length of the zJson string in bytes */
+  u32 nJPRef;        /* Number of references to this object */
+  u32 iErr;          /* Error location in zJson[] */
+  u16 iDepth;        /* Nesting depth */
+  u8 nErr;           /* Number of errors seen */
+  u8 oom;            /* Set to true if out of memory */
+  u8 bJsonIsRCStr;   /* True if zJson is an RCStr */
+  u8 hasNonstd;      /* True if input uses non-standard features like JSON5 */
+  u8 bReadOnly;      /* Do not modify. */
+  /* Search and edit information.  See jsonLookupStep() */
+  u8 eEdit;          /* Edit operation to apply */
+  int delta;         /* Size change due to the edit */
+  u32 nIns;          /* Number of bytes to insert */
+  u32 iLabel;        /* Location of label if search landed on an object value */
+  u8 *aIns;          /* Content to be inserted */
+};
+
+/* Allowed values for JsonParse.eEdit */
+#define JEDIT_DEL   1   /* Delete if exists */
+#define JEDIT_REPL  2   /* Overwrite if exists */
+#define JEDIT_INS   3   /* Insert if not exists */
+#define JEDIT_SET   4   /* Insert or overwrite */
+
+/*
+** Maximum nesting depth of JSON for this implementation.
+**
+** This limit is needed to avoid a stack overflow in the recursive
+** descent parser.  A depth of 1000 is far deeper than any sane JSON
+** should go.  Historical note: This limit was 2000 prior to version 3.42.0
+*/
+#ifndef SQLITE_JSON_MAX_DEPTH
+# define JSON_MAX_DEPTH  1000
+#else
+# define JSON_MAX_DEPTH SQLITE_JSON_MAX_DEPTH
+#endif
+
+/*
+** Allowed values for the flgs argument to jsonParseFuncArg();
+*/
+#define JSON_EDITABLE  0x01   /* Generate a writable JsonParse object */
+#define JSON_KEEPERROR 0x02   /* Return non-NULL even if there is an error */
+
+/**************************************************************************
+** Forward references
+**************************************************************************/
+static void jsonReturnStringAsBlob(JsonString*);
+static int jsonFuncArgMightBeBinary(sqlite3_value *pJson);
+static u32 jsonTranslateBlobToText(const JsonParse*,u32,JsonString*);
+static void jsonReturnParse(sqlite3_context*,JsonParse*);
+static JsonParse *jsonParseFuncArg(sqlite3_context*,sqlite3_value*,u32);
+static void jsonParseFree(JsonParse*);
+static u32 jsonbPayloadSize(const JsonParse*, u32, u32*);
+static u32 jsonUnescapeOneChar(const char*, u32, u32*);
+
+/**************************************************************************
+** Utility routines for dealing with JsonCache objects
+**************************************************************************/
+
+/*
+** Free a JsonCache object.
+*/
+static void jsonCacheDelete(JsonCache *p){
+  int i;
+  for(i=0; i<p->nUsed; i++){
+    jsonParseFree(p->a[i]);
+  }
+  sqlite3DbFree(p->db, p);
+}
+static void jsonCacheDeleteGeneric(void *p){
+  jsonCacheDelete((JsonCache*)p);
+}
+
+/*
+** Insert a new entry into the cache.  If the cache is full, expel
+** the least recently used entry.  Return SQLITE_OK on success or a
+** result code otherwise.
+**
+** Cache entries are stored in age order, oldest first.
+*/
+static int jsonCacheInsert(
+  sqlite3_context *ctx,   /* The SQL statement context holding the cache */
+  JsonParse *pParse       /* The parse object to be added to the cache */
+){
+  JsonCache *p;
+
+  assert( pParse->zJson!=0 );
+  assert( pParse->bJsonIsRCStr );
+  assert( pParse->delta==0 );
+  p = sqlite3_get_auxdata(ctx, JSON_CACHE_ID);
+  if( p==0 ){
+    sqlite3 *db = sqlite3_context_db_handle(ctx);
+    p = sqlite3DbMallocZero(db, sizeof(*p));
+    if( p==0 ) return SQLITE_NOMEM;
+    p->db = db;
+    sqlite3_set_auxdata(ctx, JSON_CACHE_ID, p, jsonCacheDeleteGeneric);
+    p = sqlite3_get_auxdata(ctx, JSON_CACHE_ID);
+    if( p==0 ) return SQLITE_NOMEM;
+  }
+  if( p->nUsed >= JSON_CACHE_SIZE ){
+    jsonParseFree(p->a[0]);
+    memmove(p->a, &p->a[1], (JSON_CACHE_SIZE-1)*sizeof(p->a[0]));
+    p->nUsed = JSON_CACHE_SIZE-1;
+  }
+  assert( pParse->nBlobAlloc>0 );
+  pParse->eEdit = 0;
+  pParse->nJPRef++;
+  pParse->bReadOnly = 1;
+  p->a[p->nUsed] = pParse;
+  p->nUsed++;
+  return SQLITE_OK;
+}
+
+/*
+** Search for a cached translation the json text supplied by pArg.  Return
+** the JsonParse object if found.  Return NULL if not found.
+**
+** When a match if found, the matching entry is moved to become the
+** most-recently used entry if it isn't so already.
+**
+** The JsonParse object returned still belongs to the Cache and might
+** be deleted at any moment.  If the caller whants the JsonParse to
+** linger, it needs to increment the nPJRef reference counter.
+*/
+static JsonParse *jsonCacheSearch(
+  sqlite3_context *ctx,    /* The SQL statement context holding the cache */
+  sqlite3_value *pArg      /* Function argument containing SQL text */
+){
+  JsonCache *p;
+  int i;
+  const char *zJson;
+  int nJson;
+
+  if( sqlite3_value_type(pArg)!=SQLITE_TEXT ){
+    return 0;
+  }
+  zJson = (const char*)sqlite3_value_text(pArg);
+  if( zJson==0 ) return 0;
+  nJson = sqlite3_value_bytes(pArg);
+
+  p = sqlite3_get_auxdata(ctx, JSON_CACHE_ID);
+  if( p==0 ){
+    return 0;
+  }
+  for(i=0; i<p->nUsed; i++){
+    if( p->a[i]->zJson==zJson ) break;
+  }
+  if( i>=p->nUsed ){
+    for(i=0; i<p->nUsed; i++){
+      if( p->a[i]->nJson!=nJson ) continue;
+      if( memcmp(p->a[i]->zJson, zJson, nJson)==0 ) break;
+    }
+  }
+  if( i<p->nUsed ){
+    if( i<p->nUsed-1 ){
+      /* Make the matching entry the most recently used entry */
+      JsonParse *tmp = p->a[i];
+      memmove(&p->a[i], &p->a[i+1], (p->nUsed-i-1)*sizeof(tmp));
+      p->a[p->nUsed-1] = tmp;
+      i = p->nUsed - 1;
+    }
+    assert( p->a[i]->delta==0 );
+    return p->a[i];
+  }else{
+    return 0;
+  }
+}
+
+/**************************************************************************
+** Utility routines for dealing with JsonString objects
+**************************************************************************/
+
+/* Turn uninitialized bulk memory into a valid JsonString object
+** holding a zero-length string.
+*/
+static void jsonStringZero(JsonString *p){
+  p->zBuf = p->zSpace;
+  p->nAlloc = sizeof(p->zSpace);
+  p->nUsed = 0;
+  p->bStatic = 1;
+}
+
+/* Initialize the JsonString object
+*/
+static void jsonStringInit(JsonString *p, sqlite3_context *pCtx){
+  p->pCtx = pCtx;
+  p->eErr = 0;
+  jsonStringZero(p);
+}
+
+/* Free all allocated memory and reset the JsonString object back to its
+** initial state.
+*/
+static void jsonStringReset(JsonString *p){
+  if( !p->bStatic ) sqlite3RCStrUnref(p->zBuf);
+  jsonStringZero(p);
+}
+
+/* Report an out-of-memory (OOM) condition
+*/
+static void jsonStringOom(JsonString *p){
+  p->eErr |= JSTRING_OOM;
+  if( p->pCtx ) sqlite3_result_error_nomem(p->pCtx);
+  jsonStringReset(p);
+}
+
+/* Enlarge pJson->zBuf so that it can hold at least N more bytes.
+** Return zero on success.  Return non-zero on an OOM error
+*/
+static int jsonStringGrow(JsonString *p, u32 N){
+  u64 nTotal = N<p->nAlloc ? p->nAlloc*2 : p->nAlloc+N+10;
+  char *zNew;
+  if( p->bStatic ){
+    if( p->eErr ) return 1;
+    zNew = sqlite3RCStrNew(nTotal);
+    if( zNew==0 ){
+      jsonStringOom(p);
+      return SQLITE_NOMEM;
+    }
+    memcpy(zNew, p->zBuf, (size_t)p->nUsed);
+    p->zBuf = zNew;
+    p->bStatic = 0;
+  }else{
+    p->zBuf = sqlite3RCStrResize(p->zBuf, nTotal);
+    if( p->zBuf==0 ){
+      p->eErr |= JSTRING_OOM;
+      jsonStringZero(p);
+      return SQLITE_NOMEM;
+    }
+  }
+  p->nAlloc = nTotal;
+  return SQLITE_OK;
+}
+
+/* Append N bytes from zIn onto the end of the JsonString string.
+*/
+static SQLITE_NOINLINE void jsonStringExpandAndAppend(
+  JsonString *p,
+  const char *zIn,
+  u32 N
+){
+  assert( N>0 );
+  if( jsonStringGrow(p,N) ) return;
+  memcpy(p->zBuf+p->nUsed, zIn, N);
+  p->nUsed += N;
+}
+static void jsonAppendRaw(JsonString *p, const char *zIn, u32 N){
+  if( N==0 ) return;
+  if( N+p->nUsed >= p->nAlloc ){
+    jsonStringExpandAndAppend(p,zIn,N);
+  }else{
+    memcpy(p->zBuf+p->nUsed, zIn, N);
+    p->nUsed += N;
+  }
+}
+static void jsonAppendRawNZ(JsonString *p, const char *zIn, u32 N){
+  assert( N>0 );
+  if( N+p->nUsed >= p->nAlloc ){
+    jsonStringExpandAndAppend(p,zIn,N);
+  }else{
+    memcpy(p->zBuf+p->nUsed, zIn, N);
+    p->nUsed += N;
+  }
+}
+
+
+/* Append formatted text (not to exceed N bytes) to the JsonString.
+*/
+static void jsonPrintf(int N, JsonString *p, const char *zFormat, ...){
+  va_list ap;
+  if( (p->nUsed + N >= p->nAlloc) && jsonStringGrow(p, N) ) return;
+  va_start(ap, zFormat);
+  sqlite3_vsnprintf(N, p->zBuf+p->nUsed, zFormat, ap);
+  va_end(ap);
+  p->nUsed += (int)strlen(p->zBuf+p->nUsed);
+}
+
+/* Append a single character
+*/
+static SQLITE_NOINLINE void jsonAppendCharExpand(JsonString *p, char c){
+  if( jsonStringGrow(p,1) ) return;
+  p->zBuf[p->nUsed++] = c;
+}
+static void jsonAppendChar(JsonString *p, char c){
+  if( p->nUsed>=p->nAlloc ){
+    jsonAppendCharExpand(p,c);
+  }else{
+    p->zBuf[p->nUsed++] = c;
+  }
+}
+
+/* Remove a single character from the end of the string
+*/
+static void jsonStringTrimOneChar(JsonString *p){
+  if( p->eErr==0 ){
+    assert( p->nUsed>0 );
+    p->nUsed--;
+  }
+}
+
+
+/* Make sure there is a zero terminator on p->zBuf[]
+**
+** Return true on success.  Return false if an OOM prevents this
+** from happening.
+*/
+static int jsonStringTerminate(JsonString *p){
+  jsonAppendChar(p, 0);
+  jsonStringTrimOneChar(p);
+  return p->eErr==0;
+}
+
+/* Append a comma separator to the output buffer, if the previous
+** character is not '[' or '{'.
+*/
+static void jsonAppendSeparator(JsonString *p){
+  char c;
+  if( p->nUsed==0 ) return;
+  c = p->zBuf[p->nUsed-1];
+  if( c=='[' || c=='{' ) return;
+  jsonAppendChar(p, ',');
+}
+
+/* Append the N-byte string in zIn to the end of the JsonString string
+** under construction.  Enclose the string in double-quotes ("...") and
+** escape any double-quotes or backslash characters contained within the
+** string.
+**
+** This routine is a high-runner.  There is a measurable performance
+** increase associated with unwinding the jsonIsOk[] loop.
+*/
+static void jsonAppendString(JsonString *p, const char *zIn, u32 N){
+  u32 k;
+  u8 c;
+  const u8 *z = (const u8*)zIn;
+  if( z==0 ) return;
+  if( (N+p->nUsed+2 >= p->nAlloc) && jsonStringGrow(p,N+2)!=0 ) return;
+  p->zBuf[p->nUsed++] = '"';
+  while( 1 /*exit-by-break*/ ){
+    k = 0;
+    /* The following while() is the 4-way unwound equivalent of
+    **
+    **     while( k<N && jsonIsOk[z[k]] ){ k++; }
+    */
+    while( 1 /* Exit by break */ ){
+      if( k+3>=N ){
+        while( k<N && jsonIsOk[z[k]] ){ k++; }
+        break;
+      }
+      if( !jsonIsOk[z[k]] ){
+        break;
+      }
+      if( !jsonIsOk[z[k+1]] ){
+        k += 1;
+        break;
+      }
+      if( !jsonIsOk[z[k+2]] ){
+        k += 2;
+        break;
+      }
+      if( !jsonIsOk[z[k+3]] ){
+        k += 3;
+        break;
+      }else{
+        k += 4;
+      }
+    }
+    if( k>=N ){
+      if( k>0 ){
+        memcpy(&p->zBuf[p->nUsed], z, k);
+        p->nUsed += k;
+      }
+      break;
+    }
+    if( k>0 ){
+      memcpy(&p->zBuf[p->nUsed], z, k);
+      p->nUsed += k;
+      z += k;
+      N -= k;
+    }
+    c = z[0];
+    if( c=='"' || c=='\\' ){
+      json_simple_escape:
+      if( (p->nUsed+N+3 > p->nAlloc) && jsonStringGrow(p,N+3)!=0 ) return;
+      p->zBuf[p->nUsed++] = '\\';
+      p->zBuf[p->nUsed++] = c;
+    }else if( c=='\'' ){
+      p->zBuf[p->nUsed++] = c;
+    }else{
+      static const char aSpecial[] = {
+         0, 0, 0, 0, 0, 0, 0, 0, 'b', 't', 'n', 0, 'f', 'r', 0, 0,
+         0, 0, 0, 0, 0, 0, 0, 0,   0,   0,   0, 0,   0,   0, 0, 0
+      };
+      assert( sizeof(aSpecial)==32 );
+      assert( aSpecial['\b']=='b' );
+      assert( aSpecial['\f']=='f' );
+      assert( aSpecial['\n']=='n' );
+      assert( aSpecial['\r']=='r' );
+      assert( aSpecial['\t']=='t' );
+      assert( c>=0 && c<sizeof(aSpecial) );
+      if( aSpecial[c] ){
+        c = aSpecial[c];
+        goto json_simple_escape;
+      }
+      if( (p->nUsed+N+7 > p->nAlloc) && jsonStringGrow(p,N+7)!=0 ) return;
+      p->zBuf[p->nUsed++] = '\\';
+      p->zBuf[p->nUsed++] = 'u';
+      p->zBuf[p->nUsed++] = '0';
+      p->zBuf[p->nUsed++] = '0';
+      p->zBuf[p->nUsed++] = "0123456789abcdef"[c>>4];
+      p->zBuf[p->nUsed++] = "0123456789abcdef"[c&0xf];
+    }
+    z++;
+    N--;
+  }
+  p->zBuf[p->nUsed++] = '"';
+  assert( p->nUsed<p->nAlloc );
+}
+
+/*
+** Append an sqlite3_value (such as a function parameter) to the JSON
+** string under construction in p.
+*/
+static void jsonAppendSqlValue(
+  JsonString *p,                 /* Append to this JSON string */
+  sqlite3_value *pValue          /* Value to append */
+){
+  switch( sqlite3_value_type(pValue) ){
+    case SQLITE_NULL: {
+      jsonAppendRawNZ(p, "null", 4);
+      break;
+    }
+    case SQLITE_FLOAT: {
+      jsonPrintf(100, p, "%!0.15g", sqlite3_value_double(pValue));
+      break;
+    }
+    case SQLITE_INTEGER: {
+      const char *z = (const char*)sqlite3_value_text(pValue);
+      u32 n = (u32)sqlite3_value_bytes(pValue);
+      jsonAppendRaw(p, z, n);
+      break;
+    }
+    case SQLITE_TEXT: {
+      const char *z = (const char*)sqlite3_value_text(pValue);
+      u32 n = (u32)sqlite3_value_bytes(pValue);
+      if( sqlite3_value_subtype(pValue)==JSON_SUBTYPE ){
+        jsonAppendRaw(p, z, n);
+      }else{
+        jsonAppendString(p, z, n);
+      }
+      break;
+    }
+    default: {
+      if( jsonFuncArgMightBeBinary(pValue) ){
+        JsonParse px;
+        memset(&px, 0, sizeof(px));
+        px.aBlob = (u8*)sqlite3_value_blob(pValue);
+        px.nBlob = sqlite3_value_bytes(pValue);
+        jsonTranslateBlobToText(&px, 0, p);
+      }else if( p->eErr==0 ){
+        sqlite3_result_error(p->pCtx, "JSON cannot hold BLOB values", -1);
+        p->eErr = JSTRING_ERR;
+        jsonStringReset(p);
+      }
+      break;
+    }
+  }
+}
+
+/* Make the text in p (which is probably a generated JSON text string)
+** the result of the SQL function.
+**
+** The JsonString is reset.
+**
+** If pParse and ctx are both non-NULL, then the SQL string in p is
+** loaded into the zJson field of the pParse object as a RCStr and the
+** pParse is added to the cache.
+*/
+static void jsonReturnString(
+  JsonString *p,            /* String to return */
+  JsonParse *pParse,        /* JSONB source or NULL */
+  sqlite3_context *ctx      /* Where to cache */
+){
+  assert( (pParse!=0)==(ctx!=0) );
+  assert( ctx==0 || ctx==p->pCtx );
+  if( p->eErr==0 ){
+    int flags = SQLITE_PTR_TO_INT(sqlite3_user_data(p->pCtx));
+    if( flags & JSON_BLOB ){
+      jsonReturnStringAsBlob(p);
+    }else if( p->bStatic ){
+      sqlite3_result_text64(p->pCtx, p->zBuf, p->nUsed,
+                            SQLITE_TRANSIENT, SQLITE_UTF8);
+    }else if( jsonStringTerminate(p) ){
+      if( pParse && pParse->bJsonIsRCStr==0 && pParse->nBlobAlloc>0 ){
+        int rc;
+        pParse->zJson = sqlite3RCStrRef(p->zBuf);
+        pParse->nJson = p->nUsed;
+        pParse->bJsonIsRCStr = 1;
+        rc = jsonCacheInsert(ctx, pParse);
+        if( rc==SQLITE_NOMEM ){
+          sqlite3_result_error_nomem(ctx);
+          jsonStringReset(p);
+          return;
+        }
+      }
+      sqlite3_result_text64(p->pCtx, sqlite3RCStrRef(p->zBuf), p->nUsed,
+                            sqlite3RCStrUnref,
+                            SQLITE_UTF8);
+    }else{
+      sqlite3_result_error_nomem(p->pCtx);
+    }
+  }else if( p->eErr & JSTRING_OOM ){
+    sqlite3_result_error_nomem(p->pCtx);
+  }else if( p->eErr & JSTRING_MALFORMED ){
+    sqlite3_result_error(p->pCtx, "malformed JSON", -1);
+  }
+  jsonStringReset(p);
+}
+
+/**************************************************************************
+** Utility routines for dealing with JsonParse objects
+**************************************************************************/
+
+/*
+** Reclaim all memory allocated by a JsonParse object.  But do not
+** delete the JsonParse object itself.
+*/
+static void jsonParseReset(JsonParse *pParse){
+  assert( pParse->nJPRef<=1 );
+  if( pParse->bJsonIsRCStr ){
+    sqlite3RCStrUnref(pParse->zJson);
+    pParse->zJson = 0;
+    pParse->nJson = 0;
+    pParse->bJsonIsRCStr = 0;
+  }
+  if( pParse->nBlobAlloc ){
+    sqlite3DbFree(pParse->db, pParse->aBlob);
+    pParse->aBlob = 0;
+    pParse->nBlob = 0;
+    pParse->nBlobAlloc = 0;
+  }
+}
+
+/*
+** Decrement the reference count on the JsonParse object.  When the
+** count reaches zero, free the object.
+*/
+static void jsonParseFree(JsonParse *pParse){
+  if( pParse ){
+    if( pParse->nJPRef>1 ){
+      pParse->nJPRef--;
+    }else{
+      jsonParseReset(pParse);
+      sqlite3DbFree(pParse->db, pParse);
+    }
+  }
+}
+
+/**************************************************************************
+** Utility routines for the JSON text parser
+**************************************************************************/
+
+/*
+** Translate a single byte of Hex into an integer.
+** This routine only gives a correct answer if h really is a valid hexadecimal
+** character:  0..9a..fA..F.  But unlike sqlite3HexToInt(), it does not
+** assert() if the digit is not hex.
+*/
+static u8 jsonHexToInt(int h){
+#ifdef SQLITE_ASCII
+  h += 9*(1&(h>>6));
+#endif
+#ifdef SQLITE_EBCDIC
+  h += 9*(1&~(h>>4));
+#endif
+  return (u8)(h & 0xf);
+}
+
+/*
+** Convert a 4-byte hex string into an integer
+*/
+static u32 jsonHexToInt4(const char *z){
+  u32 v;
+  v = (jsonHexToInt(z[0])<<12)
+    + (jsonHexToInt(z[1])<<8)
+    + (jsonHexToInt(z[2])<<4)
+    + jsonHexToInt(z[3]);
+  return v;
+}
+
+/*
+** Return true if z[] begins with 2 (or more) hexadecimal digits
+*/
+static int jsonIs2Hex(const char *z){
+  return sqlite3Isxdigit(z[0]) && sqlite3Isxdigit(z[1]);
+}
+
+/*
+** Return true if z[] begins with 4 (or more) hexadecimal digits
+*/
+static int jsonIs4Hex(const char *z){
+  return jsonIs2Hex(z) && jsonIs2Hex(&z[2]);
+}
+
+/*
+** Return the number of bytes of JSON5 whitespace at the beginning of
+** the input string z[].
+**
+** JSON5 whitespace consists of any of the following characters:
+**
+**    Unicode  UTF-8         Name
+**    U+0009   09            horizontal tab
+**    U+000a   0a            line feed
+**    U+000b   0b            vertical tab
+**    U+000c   0c            form feed
+**    U+000d   0d            carriage return
+**    U+0020   20            space
+**    U+00a0   c2 a0         non-breaking space
+**    U+1680   e1 9a 80      ogham space mark
+**    U+2000   e2 80 80      en quad
+**    U+2001   e2 80 81      em quad
+**    U+2002   e2 80 82      en space
+**    U+2003   e2 80 83      em space
+**    U+2004   e2 80 84      three-per-em space
+**    U+2005   e2 80 85      four-per-em space
+**    U+2006   e2 80 86      six-per-em space
+**    U+2007   e2 80 87      figure space
+**    U+2008   e2 80 88      punctuation space
+**    U+2009   e2 80 89      thin space
+**    U+200a   e2 80 8a      hair space
+**    U+2028   e2 80 a8      line separator
+**    U+2029   e2 80 a9      paragraph separator
+**    U+202f   e2 80 af      narrow no-break space (NNBSP)
+**    U+205f   e2 81 9f      medium mathematical space (MMSP)
+**    U+3000   e3 80 80      ideographical space
+**    U+FEFF   ef bb bf      byte order mark
+**
+** In addition, comments between '/', '*' and '*', '/' and
+** from '/', '/' to end-of-line are also considered to be whitespace.
+*/
+static int json5Whitespace(const char *zIn){
+  int n = 0;
+  const u8 *z = (u8*)zIn;
+  while( 1 /*exit by "goto whitespace_done"*/ ){
+    switch( z[n] ){
+      case 0x09:
+      case 0x0a:
+      case 0x0b:
+      case 0x0c:
+      case 0x0d:
+      case 0x20: {
+        n++;
+        break;
+      }
+      case '/': {
+        if( z[n+1]=='*' && z[n+2]!=0 ){
+          int j;
+          for(j=n+3; z[j]!='/' || z[j-1]!='*'; j++){
+            if( z[j]==0 ) goto whitespace_done;
+          }
+          n = j+1;
+          break;
+        }else if( z[n+1]=='/' ){
+          int j;
+          char c;
+          for(j=n+2; (c = z[j])!=0; j++){
+            if( c=='\n' || c=='\r' ) break;
+            if( 0xe2==(u8)c && 0x80==(u8)z[j+1]
+             && (0xa8==(u8)z[j+2] || 0xa9==(u8)z[j+2])
+            ){
+              j += 2;
+              break;
+            }
+          }
+          n = j;
+          if( z[n] ) n++;
+          break;
+        }
+        goto whitespace_done;
+      }
+      case 0xc2: {
+        if( z[n+1]==0xa0 ){
+          n += 2;
+          break;
+        }
+        goto whitespace_done;
+      }
+      case 0xe1: {
+        if( z[n+1]==0x9a && z[n+2]==0x80 ){
+          n += 3;
+          break;
+        }
+        goto whitespace_done;
+      }
+      case 0xe2: {
+        if( z[n+1]==0x80 ){
+          u8 c = z[n+2];
+          if( c<0x80 ) goto whitespace_done;
+          if( c<=0x8a || c==0xa8 || c==0xa9 || c==0xaf ){
+            n += 3;
+            break;
+          }
+        }else if( z[n+1]==0x81 && z[n+2]==0x9f ){
+          n += 3;
+          break;
+        }
+        goto whitespace_done;
+      }
+      case 0xe3: {
+        if( z[n+1]==0x80 && z[n+2]==0x80 ){
+          n += 3;
+          break;
+        }
+        goto whitespace_done;
+      }
+      case 0xef: {
+        if( z[n+1]==0xbb && z[n+2]==0xbf ){
+          n += 3;
+          break;
+        }
+        goto whitespace_done;
+      }
+      default: {
+        goto whitespace_done;
+      }
+    }
+  }
+  whitespace_done:
+  return n;
+}
+
+/*
+** Extra floating-point literals to allow in JSON.
+*/
+static const struct NanInfName {
+  char c1;
+  char c2;
+  char n;
+  char eType;
+  char nRepl;
+  char *zMatch;
+  char *zRepl;
+} aNanInfName[] = {
+  { 'i', 'I', 3, JSONB_FLOAT, 7, "inf", "9.0e999" },
+  { 'i', 'I', 8, JSONB_FLOAT, 7, "infinity", "9.0e999" },
+  { 'n', 'N', 3, JSONB_NULL, 4, "NaN", "null" },
+  { 'q', 'Q', 4, JSONB_NULL, 4, "QNaN", "null" },
+  { 's', 'S', 4, JSONB_NULL, 4, "SNaN", "null" },
+};
+
+
+/*
+** Report the wrong number of arguments for json_insert(), json_replace()
+** or json_set().
+*/
+static void jsonWrongNumArgs(
+  sqlite3_context *pCtx,
+  const char *zFuncName
+){
+  char *zMsg = sqlite3_mprintf("json_%s() needs an odd number of arguments",
+                               zFuncName);
+  sqlite3_result_error(pCtx, zMsg, -1);
+  sqlite3_free(zMsg);
+}
+
+/****************************************************************************
+** Utility routines for dealing with the binary BLOB representation of JSON
+****************************************************************************/
+
+/*
+** Expand pParse->aBlob so that it holds at least N bytes.
+**
+** Return the number of errors.
+*/
+static int jsonBlobExpand(JsonParse *pParse, u32 N){
+  u8 *aNew;
+  u32 t;
+  assert( N>pParse->nBlobAlloc );
+  if( pParse->nBlobAlloc==0 ){
+    t = 100;
+  }else{
+    t = pParse->nBlobAlloc*2;
+  }
+  if( t<N ) t = N+100;
+  aNew = sqlite3DbRealloc(pParse->db, pParse->aBlob, t);
+  if( aNew==0 ){ pParse->oom = 1; return 1; }
+  pParse->aBlob = aNew;
+  pParse->nBlobAlloc = t;
+  return 0;
+}
+
+/*
+** If pParse->aBlob is not previously editable (because it is taken
+** from sqlite3_value_blob(), as indicated by the fact that
+** pParse->nBlobAlloc==0 and pParse->nBlob>0) then make it editable
+** by making a copy into space obtained from malloc.
+**
+** Return true on success.  Return false on OOM.
+*/
+static int jsonBlobMakeEditable(JsonParse *pParse, u32 nExtra){
+  u8 *aOld;
+  u32 nSize;
+  assert( !pParse->bReadOnly );
+  if( pParse->oom ) return 0;
+  if( pParse->nBlobAlloc>0 ) return 1;
+  aOld = pParse->aBlob;
+  nSize = pParse->nBlob + nExtra;
+  pParse->aBlob = 0;
+  if( jsonBlobExpand(pParse, nSize) ){
+    return 0;
+  }
+  assert( pParse->nBlobAlloc >= pParse->nBlob + nExtra );
+  memcpy(pParse->aBlob, aOld, pParse->nBlob);
+  return 1;
+}
+
+/* Expand pParse->aBlob and append one bytes.
+*/
+static SQLITE_NOINLINE void jsonBlobExpandAndAppendOneByte(
+  JsonParse *pParse,
+  u8 c
+){
+  jsonBlobExpand(pParse, pParse->nBlob+1);
+  if( pParse->oom==0 ){
+    assert( pParse->nBlob+1<=pParse->nBlobAlloc );
+    pParse->aBlob[pParse->nBlob++] = c;
+  }
+}
+
+/* Append a single character.
+*/
+static void jsonBlobAppendOneByte(JsonParse *pParse, u8 c){
+  if( pParse->nBlob >= pParse->nBlobAlloc ){
+    jsonBlobExpandAndAppendOneByte(pParse, c);
+  }else{
+    pParse->aBlob[pParse->nBlob++] = c;
+  }
+}
+
+/* Slow version of jsonBlobAppendNode() that first resizes the
+** pParse->aBlob structure.
+*/
+static void jsonBlobAppendNode(JsonParse*,u8,u32,const void*);
+static SQLITE_NOINLINE void jsonBlobExpandAndAppendNode(
+  JsonParse *pParse,
+  u8 eType,
+  u32 szPayload,
+  const void *aPayload
+){
+  if( jsonBlobExpand(pParse, pParse->nBlob+szPayload+9) ) return;
+  jsonBlobAppendNode(pParse, eType, szPayload, aPayload);
+}
+
+
+/* Append an node type byte together with the payload size and
+** possibly also the payload.
+**
+** If aPayload is not NULL, then it is a pointer to the payload which
+** is also appended.  If aPayload is NULL, the pParse->aBlob[] array
+** is resized (if necessary) so that it is big enough to hold the
+** payload, but the payload is not appended and pParse->nBlob is left
+** pointing to where the first byte of payload will eventually be.
+*/
+static void jsonBlobAppendNode(
+  JsonParse *pParse,          /* The JsonParse object under construction */
+  u8 eType,                   /* Node type.  One of JSONB_* */
+  u32 szPayload,              /* Number of bytes of payload */
+  const void *aPayload        /* The payload.  Might be NULL */
+){
+  u8 *a;
+  if( pParse->nBlob+szPayload+9 > pParse->nBlobAlloc ){
+    jsonBlobExpandAndAppendNode(pParse,eType,szPayload,aPayload);
+    return;
+  }
+  assert( pParse->aBlob!=0 );
+  a = &pParse->aBlob[pParse->nBlob];
+  if( szPayload<=11 ){
+    a[0] = eType | (szPayload<<4);
+    pParse->nBlob += 1;
+  }else if( szPayload<=0xff ){
+    a[0] = eType | 0xc0;
+    a[1] = szPayload & 0xff;
+    pParse->nBlob += 2;
+  }else if( szPayload<=0xffff ){
+    a[0] = eType | 0xd0;
+    a[1] = (szPayload >> 8) & 0xff;
+    a[2] = szPayload & 0xff;
+    pParse->nBlob += 3;
+  }else{
+    a[0] = eType | 0xe0;
+    a[1] = (szPayload >> 24) & 0xff;
+    a[2] = (szPayload >> 16) & 0xff;
+    a[3] = (szPayload >> 8) & 0xff;
+    a[4] = szPayload & 0xff;
+    pParse->nBlob += 5;
+  }
+  if( aPayload ){
+    pParse->nBlob += szPayload;
+    memcpy(&pParse->aBlob[pParse->nBlob-szPayload], aPayload, szPayload);
+  }
+}
+
+/* Change the payload size for the node at index i to be szPayload.
+*/
+static int jsonBlobChangePayloadSize(
+  JsonParse *pParse,
+  u32 i,
+  u32 szPayload
+){
+  u8 *a;
+  u8 szType;
+  u8 nExtra;
+  u8 nNeeded;
+  int delta;
+  if( pParse->oom ) return 0;
+  a = &pParse->aBlob[i];
+  szType = a[0]>>4;
+  if( szType<=11 ){
+    nExtra = 0;
+  }else if( szType==12 ){
+    nExtra = 1;
+  }else if( szType==13 ){
+    nExtra = 2;
+  }else{
+    nExtra = 4;
+  }
+  if( szPayload<=11 ){
+    nNeeded = 0;
+  }else if( szPayload<=0xff ){
+    nNeeded = 1;
+  }else if( szPayload<=0xffff ){
+    nNeeded = 2;
+  }else{
+    nNeeded = 4;
+  }
+  delta = nNeeded - nExtra;
+  if( delta ){
+    u32 newSize = pParse->nBlob + delta;
+    if( delta>0 ){
+      if( newSize>pParse->nBlobAlloc && jsonBlobExpand(pParse, newSize) ){
+        return 0;  /* OOM error.  Error state recorded in pParse->oom. */
+      }
+      a = &pParse->aBlob[i];
+      memmove(&a[1+delta], &a[1], pParse->nBlob - (i+1));
+    }else{
+      memmove(&a[1], &a[1-delta], pParse->nBlob - (i+1-delta));
+    }
+    pParse->nBlob = newSize;
+  }
+  if( nNeeded==0 ){
+    a[0] = (a[0] & 0x0f) | (szPayload<<4);
+  }else if( nNeeded==1 ){
+    a[0] = (a[0] & 0x0f) | 0xc0;
+    a[1] = szPayload & 0xff;
+  }else if( nNeeded==2 ){
+    a[0] = (a[0] & 0x0f) | 0xd0;
+    a[1] = (szPayload >> 8) & 0xff;
+    a[2] = szPayload & 0xff;
+  }else{
+    a[0] = (a[0] & 0x0f) | 0xe0;
+    a[1] = (szPayload >> 24) & 0xff;
+    a[2] = (szPayload >> 16) & 0xff;
+    a[3] = (szPayload >> 8) & 0xff;
+    a[4] = szPayload & 0xff;
+  }
+  return delta;
+}
+
+/*
+** If z[0] is 'u' and is followed by exactly 4 hexadecimal character,
+** then set *pOp to JSONB_TEXTJ and return true.  If not, do not make
+** any changes to *pOp and return false.
+*/
+static int jsonIs4HexB(const char *z, int *pOp){
+  if( z[0]!='u' ) return 0;
+  if( !jsonIs4Hex(&z[1]) ) return 0;
+  *pOp = JSONB_TEXTJ;
+  return 1;
+}
+
+/*
+** Check a single element of the JSONB in pParse for validity.
+**
+** The element to be checked starts at offset i and must end at on the
+** last byte before iEnd.
+**
+** Return 0 if everything is correct.  Return the 1-based byte offset of the
+** error if a problem is detected.  (In other words, if the error is at offset
+** 0, return 1).
+*/
+static u32 jsonbValidityCheck(
+  const JsonParse *pParse,    /* Input JSONB.  Only aBlob and nBlob are used */
+  u32 i,                      /* Start of element as pParse->aBlob[i] */
+  u32 iEnd,                   /* One more than the last byte of the element */
+  u32 iDepth                  /* Current nesting depth */
+){
+  u32 n, sz, j, k;
+  const u8 *z;
+  u8 x;
+  if( iDepth>JSON_MAX_DEPTH ) return i+1;
+  sz = 0;
+  n = jsonbPayloadSize(pParse, i, &sz);
+  if( NEVER(n==0) ) return i+1;          /* Checked by caller */
+  if( NEVER(i+n+sz!=iEnd) ) return i+1;  /* Checked by caller */
+  z = pParse->aBlob;
+  x = z[i] & 0x0f;
+  switch( x ){
+    case JSONB_NULL:
+    case JSONB_TRUE:
+    case JSONB_FALSE: {
+      return n+sz==1 ? 0 : i+1;
+    }
+    case JSONB_INT: {
+      if( sz<1 ) return i+1;
+      j = i+n;
+      if( z[j]=='-' ){
+        j++;
+        if( sz<2 ) return i+1;
+      }
+      k = i+n+sz;
+      while( j<k ){
+        if( sqlite3Isdigit(z[j]) ){
+          j++;
+        }else{
+          return j+1;
+        }
+      }
+      return 0;
+    }
+    case JSONB_INT5: {
+      if( sz<3 ) return i+1;
+      j = i+n;
+      if( z[j]=='-' ){
+        if( sz<4 ) return i+1;
+        j++;
+      }
+      if( z[j]!='0' ) return i+1;
+      if( z[j+1]!='x' && z[j+1]!='X' ) return j+2;
+      j += 2;
+      k = i+n+sz;
+      while( j<k ){
+        if( sqlite3Isxdigit(z[j]) ){
+          j++;
+        }else{
+          return j+1;
+        }
+      }
+      return 0;
+    }
+    case JSONB_FLOAT:
+    case JSONB_FLOAT5: {
+      u8 seen = 0;   /* 0: initial.  1: '.' seen  2: 'e' seen */
+      if( sz<2 ) return i+1;
+      j = i+n;
+      k = j+sz;
+      if( z[j]=='-' ){
+        j++;
+        if( sz<3 ) return i+1;
+      }
+      if( z[j]=='.' ){
+        if( x==JSONB_FLOAT ) return j+1;
+        if( !sqlite3Isdigit(z[j+1]) ) return j+1;
+        j += 2;
+        seen = 1;
+      }else if( z[j]=='0' && x==JSONB_FLOAT ){
+        if( j+3>k ) return j+1;
+        if( z[j+1]!='.' && z[j+1]!='e' && z[j+1]!='E' ) return j+1;
+        j++;
+      }
+      for(; j<k; j++){
+        if( sqlite3Isdigit(z[j]) ) continue;
+        if( z[j]=='.' ){
+          if( seen>0 ) return j+1;
+          if( x==JSONB_FLOAT && (j==k-1 || !sqlite3Isdigit(z[j+1])) ){
+            return j+1;
+          }
+          seen = 1;
+          continue;
+        }
+        if( z[j]=='e' || z[j]=='E' ){
+          if( seen==2 ) return j+1;
+          if( j==k-1 ) return j+1;
+          if( z[j+1]=='+' || z[j+1]=='-' ){
+            j++;
+            if( j==k-1 ) return j+1;
+          }
+          seen = 2;
+          continue;
+        }
+        return j+1;
+      }
+      if( seen==0 ) return i+1;
+      return 0;
+    }
+    case JSONB_TEXT: {
+      j = i+n;
+      k = j+sz;
+      while( j<k ){
+        if( !jsonIsOk[z[j]] && z[j]!='\'' ) return j+1;
+        j++;
+      }
+      return 0;
+    }
+    case JSONB_TEXTJ:
+    case JSONB_TEXT5: {
+      j = i+n;
+      k = j+sz;
+      while( j<k ){
+        if( !jsonIsOk[z[j]] && z[j]!='\'' ){
+          if( z[j]=='"' ){
+            if( x==JSONB_TEXTJ ) return j+1;
+          }else if( z[j]!='\\' || j+1>=k ){
+            return j+1;
+          }else if( strchr("\"\\/bfnrt",z[j+1])!=0 ){
+            j++;
+          }else if( z[j+1]=='u' ){
+            if( j+5>=k ) return j+1;
+            if( !jsonIs4Hex((const char*)&z[j+2]) ) return j+1;
+            j++;
+          }else if( x!=JSONB_TEXT5 ){
+            return j+1;
+          }else{
+            u32 c = 0;
+            u32 szC = jsonUnescapeOneChar((const char*)&z[j], k-j, &c);
+            if( c==JSON_INVALID_CHAR ) return j+1;
+            j += szC - 1;
+          }
+        }
+        j++;
+      }
+      return 0;
+    }
+    case JSONB_TEXTRAW: {
+      return 0;
+    }
+    case JSONB_ARRAY: {
+      u32 sub;
+      j = i+n;
+      k = j+sz;
+      while( j<k ){
+        sz = 0;
+        n = jsonbPayloadSize(pParse, j, &sz);
+        if( n==0 ) return j+1;
+        if( j+n+sz>k ) return j+1;
+        sub = jsonbValidityCheck(pParse, j, j+n+sz, iDepth+1);
+        if( sub ) return sub;
+        j += n + sz;
+      }
+      assert( j==k );
+      return 0;
+    }
+    case JSONB_OBJECT: {
+      u32 cnt = 0;
+      u32 sub;
+      j = i+n;
+      k = j+sz;
+      while( j<k ){
+        sz = 0;
+        n = jsonbPayloadSize(pParse, j, &sz);
+        if( n==0 ) return j+1;
+        if( j+n+sz>k ) return j+1;
+        if( (cnt & 1)==0 ){
+          x = z[j] & 0x0f;
+          if( x<JSONB_TEXT || x>JSONB_TEXTRAW ) return j+1;
+        }
+        sub = jsonbValidityCheck(pParse, j, j+n+sz, iDepth+1);
+        if( sub ) return sub;
+        cnt++;
+        j += n + sz;
+      }
+      assert( j==k );
+      if( (cnt & 1)!=0 ) return j+1;
+      return 0;
+    }
+    default: {
+      return i+1;
+    }
+  }
+}
+
+/*
+** Translate a single element of JSON text at pParse->zJson[i] into
+** its equivalent binary JSONB representation.  Append the translation into
+** pParse->aBlob[] beginning at pParse->nBlob.  The size of
+** pParse->aBlob[] is increased as necessary.
+**
+** Return the index of the first character past the end of the element parsed,
+** or one of the following special result codes:
+**
+**      0    End of input
+**     -1    Syntax error or OOM
+**     -2    '}' seen   \
+**     -3    ']' seen    \___  For these returns, pParse->iErr is set to
+**     -4    ',' seen    /     the index in zJson[] of the seen character
+**     -5    ':' seen   /
+*/
+static int jsonTranslateTextToBlob(JsonParse *pParse, u32 i){
+  char c;
+  u32 j;
+  u32 iThis, iStart;
+  int x;
+  u8 t;
+  const char *z = pParse->zJson;
+json_parse_restart:
+  switch( (u8)z[i] ){
+  case '{': {
+    /* Parse object */
+    iThis = pParse->nBlob;
+    jsonBlobAppendNode(pParse, JSONB_OBJECT, pParse->nJson-i, 0);
+    if( ++pParse->iDepth > JSON_MAX_DEPTH ){
+      pParse->iErr = i;
+      return -1;
+    }
+    iStart = pParse->nBlob;
+    for(j=i+1;;j++){
+      u32 iBlob = pParse->nBlob;
+      x = jsonTranslateTextToBlob(pParse, j);
+      if( x<=0 ){
+        int op;
+        if( x==(-2) ){
+          j = pParse->iErr;
+          if( pParse->nBlob!=(u32)iStart ) pParse->hasNonstd = 1;
+          break;
+        }
+        j += json5Whitespace(&z[j]);
+        op = JSONB_TEXT;
+        if( sqlite3JsonId1(z[j]) 
+         || (z[j]=='\\' && jsonIs4HexB(&z[j+1], &op))
+        ){
+          int k = j+1;
+          while( (sqlite3JsonId2(z[k]) && json5Whitespace(&z[k])==0)
+            || (z[k]=='\\' && jsonIs4HexB(&z[k+1], &op))
+          ){
+            k++;
+          }
+          assert( iBlob==pParse->nBlob );
+          jsonBlobAppendNode(pParse, op, k-j, &z[j]);
+          pParse->hasNonstd = 1;
+          x = k;
+        }else{
+          if( x!=-1 ) pParse->iErr = j;
+          return -1;
+        }
+      }
+      if( pParse->oom ) return -1;
+      t = pParse->aBlob[iBlob] & 0x0f;
+      if( t<JSONB_TEXT || t>JSONB_TEXTRAW ){
+        pParse->iErr = j;
+        return -1;
+      }
+      j = x;
+      if( z[j]==':' ){
+        j++;
+      }else{
+        if( jsonIsspace(z[j]) ){
+          /* strspn() is not helpful here */
+          do{ j++; }while( jsonIsspace(z[j]) );
+          if( z[j]==':' ){
+            j++;
+            goto parse_object_value;
+          }
+        }
+        x = jsonTranslateTextToBlob(pParse, j);
+        if( x!=(-5) ){
+          if( x!=(-1) ) pParse->iErr = j;
+          return -1;
+        }
+        j = pParse->iErr+1;
+      }
+    parse_object_value:
+      x = jsonTranslateTextToBlob(pParse, j);
+      if( x<=0 ){
+        if( x!=(-1) ) pParse->iErr = j;
+        return -1;
+      }
+      j = x;
+      if( z[j]==',' ){
+        continue;
+      }else if( z[j]=='}' ){
+        break;
+      }else{
+        if( jsonIsspace(z[j]) ){
+          j += 1 + (u32)strspn(&z[j+1], jsonSpaces);
+          if( z[j]==',' ){
+            continue;
+          }else if( z[j]=='}' ){
+            break;
+          }
+        }
+        x = jsonTranslateTextToBlob(pParse, j);
+        if( x==(-4) ){
+          j = pParse->iErr;
+          continue;
+        }
+        if( x==(-2) ){
+          j = pParse->iErr;
+          break;
+        }
+      }
+      pParse->iErr = j;
+      return -1;
+    }
+    jsonBlobChangePayloadSize(pParse, iThis, pParse->nBlob - iStart);
+    pParse->iDepth--;
+    return j+1;
+  }
+  case '[': {
+    /* Parse array */
+    iThis = pParse->nBlob;
+    jsonBlobAppendNode(pParse, JSONB_ARRAY, pParse->nJson - i, 0);
+    iStart = pParse->nBlob;
+    if( pParse->oom ) return -1;
+    if( ++pParse->iDepth > JSON_MAX_DEPTH ){
+      pParse->iErr = i;
+      return -1;
+    }
+    for(j=i+1;;j++){
+      x = jsonTranslateTextToBlob(pParse, j);
+      if( x<=0 ){
+        if( x==(-3) ){
+          j = pParse->iErr;
+          if( pParse->nBlob!=iStart ) pParse->hasNonstd = 1;
+          break;
+        }
+        if( x!=(-1) ) pParse->iErr = j;
+        return -1;
+      }
+      j = x;
+      if( z[j]==',' ){
+        continue;
+      }else if( z[j]==']' ){
+        break;
+      }else{
+        if( jsonIsspace(z[j]) ){
+          j += 1 + (u32)strspn(&z[j+1], jsonSpaces);
+          if( z[j]==',' ){
+            continue;
+          }else if( z[j]==']' ){
+            break;
+          }
+        }
+        x = jsonTranslateTextToBlob(pParse, j);
+        if( x==(-4) ){
+          j = pParse->iErr;
+          continue;
+        }
+        if( x==(-3) ){
+          j = pParse->iErr;
+          break;
+        }
+      }
+      pParse->iErr = j;
+      return -1;
+    }
+    jsonBlobChangePayloadSize(pParse, iThis, pParse->nBlob - iStart);
+    pParse->iDepth--;
+    return j+1;
+  }
+  case '\'': {
+    u8 opcode;
+    char cDelim;
+    pParse->hasNonstd = 1;
+    opcode = JSONB_TEXT;
+    goto parse_string;
+  case '"':
+    /* Parse string */
+    opcode = JSONB_TEXT;
+  parse_string:
+    cDelim = z[i];
+    j = i+1;
+    while( 1 /*exit-by-break*/ ){
+      if( jsonIsOk[(u8)z[j]] ){
+        if( !jsonIsOk[(u8)z[j+1]] ){
+          j += 1;
+        }else if( !jsonIsOk[(u8)z[j+2]] ){
+          j += 2;
+        }else{
+          j += 3;
+          continue;
+        }
+      }
+      c = z[j];
+      if( c==cDelim ){
+        break;
+      }else if( c=='\\' ){
+        c = z[++j];
+        if( c=='"' || c=='\\' || c=='/' || c=='b' || c=='f'
+           || c=='n' || c=='r' || c=='t'
+           || (c=='u' && jsonIs4Hex(&z[j+1])) ){
+          if( opcode==JSONB_TEXT ) opcode = JSONB_TEXTJ;
+        }else if( c=='\'' || c=='0' || c=='v' || c=='\n'
+           || (0xe2==(u8)c && 0x80==(u8)z[j+1]
+                && (0xa8==(u8)z[j+2] || 0xa9==(u8)z[j+2]))
+           || (c=='x' && jsonIs2Hex(&z[j+1])) ){
+          opcode = JSONB_TEXT5;
+          pParse->hasNonstd = 1;
+        }else if( c=='\r' ){
+          if( z[j+1]=='\n' ) j++;
+          opcode = JSONB_TEXT5;
+          pParse->hasNonstd = 1;
+        }else{
+          pParse->iErr = j;
+          return -1;
+        }
+      }else if( c<=0x1f ){
+        /* Control characters are not allowed in strings */
+        pParse->iErr = j;
+        return -1;
+      }else if( c=='"' ){
+        opcode = JSONB_TEXT5;
+      }
+      j++;
+    }
+    jsonBlobAppendNode(pParse, opcode, j-1-i, &z[i+1]);
+    return j+1;
+  }
+  case 't': {
+    if( strncmp(z+i,"true",4)==0 && !sqlite3Isalnum(z[i+4]) ){
+      jsonBlobAppendOneByte(pParse, JSONB_TRUE);
+      return i+4;
+    }
+    pParse->iErr = i;
+    return -1;
+  }
+  case 'f': {
+    if( strncmp(z+i,"false",5)==0 && !sqlite3Isalnum(z[i+5]) ){
+      jsonBlobAppendOneByte(pParse, JSONB_FALSE);
+      return i+5;
+    }
+    pParse->iErr = i;
+    return -1;
+  }
+  case '+': {
+    u8 seenE;
+    pParse->hasNonstd = 1;
+    t = 0x00;            /* Bit 0x01:  JSON5.   Bit 0x02:  FLOAT */
+    goto parse_number;
+  case '.':
+    if( sqlite3Isdigit(z[i+1]) ){
+      pParse->hasNonstd = 1;
+      t = 0x03;          /* Bit 0x01:  JSON5.   Bit 0x02:  FLOAT */
+      seenE = 0;
+      goto parse_number_2;
+    }
+    pParse->iErr = i;
+    return -1;
+  case '-':
+  case '0':
+  case '1':
+  case '2':
+  case '3':
+  case '4':
+  case '5':
+  case '6':
+  case '7':
+  case '8':
+  case '9':
+    /* Parse number */
+    t = 0x00;            /* Bit 0x01:  JSON5.   Bit 0x02:  FLOAT */
+  parse_number:
+    seenE = 0;
+    assert( '-' < '0' );
+    assert( '+' < '0' );
+    assert( '.' < '0' );
+    c = z[i];
+
+    if( c<='0' ){
+      if( c=='0' ){
+        if( (z[i+1]=='x' || z[i+1]=='X') && sqlite3Isxdigit(z[i+2]) ){
+          assert( t==0x00 );
+          pParse->hasNonstd = 1;
+          t = 0x01;
+          for(j=i+3; sqlite3Isxdigit(z[j]); j++){}
+          goto parse_number_finish;
+        }else if( sqlite3Isdigit(z[i+1]) ){
+          pParse->iErr = i+1;
+          return -1;
+        }
+      }else{
+        if( !sqlite3Isdigit(z[i+1]) ){
+          /* JSON5 allows for "+Infinity" and "-Infinity" using exactly
+          ** that case.  SQLite also allows these in any case and it allows
+          ** "+inf" and "-inf". */
+          if( (z[i+1]=='I' || z[i+1]=='i')
+           && sqlite3StrNICmp(&z[i+1], "inf",3)==0
+          ){
+            pParse->hasNonstd = 1;
+            if( z[i]=='-' ){
+              jsonBlobAppendNode(pParse, JSONB_FLOAT, 6, "-9e999");
+            }else{
+              jsonBlobAppendNode(pParse, JSONB_FLOAT, 5, "9e999");
+            }
+            return i + (sqlite3StrNICmp(&z[i+4],"inity",5)==0 ? 9 : 4);
+          }
+          if( z[i+1]=='.' ){
+            pParse->hasNonstd = 1;
+            t |= 0x01;
+            goto parse_number_2;
+          }
+          pParse->iErr = i;
+          return -1;
+        }
+        if( z[i+1]=='0' ){
+          if( sqlite3Isdigit(z[i+2]) ){
+            pParse->iErr = i+1;
+            return -1;
+          }else if( (z[i+2]=='x' || z[i+2]=='X') && sqlite3Isxdigit(z[i+3]) ){
+            pParse->hasNonstd = 1;
+            t |= 0x01;
+            for(j=i+4; sqlite3Isxdigit(z[j]); j++){}
+            goto parse_number_finish;
+          }
+        }
+      }
+    }
+
+  parse_number_2:
+    for(j=i+1;; j++){
+      c = z[j];
+      if( sqlite3Isdigit(c) ) continue;
+      if( c=='.' ){
+        if( (t & 0x02)!=0 ){
+          pParse->iErr = j;
+          return -1;
+        }
+        t |= 0x02;
+        continue;
+      }
+      if( c=='e' || c=='E' ){
+        if( z[j-1]<'0' ){
+          if( ALWAYS(z[j-1]=='.') && ALWAYS(j-2>=i) && sqlite3Isdigit(z[j-2]) ){
+            pParse->hasNonstd = 1;
+            t |= 0x01;
+          }else{
+            pParse->iErr = j;
+            return -1;
+          }
+        }
+        if( seenE ){
+          pParse->iErr = j;
+          return -1;
+        }
+        t |= 0x02;
+        seenE = 1;
+        c = z[j+1];
+        if( c=='+' || c=='-' ){
+          j++;
+          c = z[j+1];
+        }
+        if( c<'0' || c>'9' ){
+          pParse->iErr = j;
+          return -1;
+        }
+        continue;
+      }
+      break;
+    }
+    if( z[j-1]<'0' ){
+      if( ALWAYS(z[j-1]=='.') && ALWAYS(j-2>=i) && sqlite3Isdigit(z[j-2]) ){
+        pParse->hasNonstd = 1;
+        t |= 0x01;
+      }else{
+        pParse->iErr = j;
+        return -1;
+      }
+    }
+  parse_number_finish:
+    assert( JSONB_INT+0x01==JSONB_INT5 );
+    assert( JSONB_FLOAT+0x01==JSONB_FLOAT5 );
+    assert( JSONB_INT+0x02==JSONB_FLOAT );
+    if( z[i]=='+' ) i++;
+    jsonBlobAppendNode(pParse, JSONB_INT+t, j-i, &z[i]);
+    return j;
+  }
+  case '}': {
+    pParse->iErr = i;
+    return -2;  /* End of {...} */
+  }
+  case ']': {
+    pParse->iErr = i;
+    return -3;  /* End of [...] */
+  }
+  case ',': {
+    pParse->iErr = i;
+    return -4;  /* List separator */
+  }
+  case ':': {
+    pParse->iErr = i;
+    return -5;  /* Object label/value separator */
+  }
+  case 0: {
+    return 0;   /* End of file */
+  }
+  case 0x09:
+  case 0x0a:
+  case 0x0d:
+  case 0x20: {
+    i += 1 + (u32)strspn(&z[i+1], jsonSpaces);
+    goto json_parse_restart;
+  }
+  case 0x0b:
+  case 0x0c:
+  case '/':
+  case 0xc2:
+  case 0xe1:
+  case 0xe2:
+  case 0xe3:
+  case 0xef: {
+    j = json5Whitespace(&z[i]);
+    if( j>0 ){
+      i += j;
+      pParse->hasNonstd = 1;
+      goto json_parse_restart;
+    }
+    pParse->iErr = i;
+    return -1;
+  }
+  case 'n': {
+    if( strncmp(z+i,"null",4)==0 && !sqlite3Isalnum(z[i+4]) ){
+      jsonBlobAppendOneByte(pParse, JSONB_NULL);
+      return i+4;
+    }
+    /* fall-through into the default case that checks for NaN */
+  }
+  default: {
+    u32 k;
+    int nn;
+    c = z[i];
+    for(k=0; k<sizeof(aNanInfName)/sizeof(aNanInfName[0]); k++){
+      if( c!=aNanInfName[k].c1 && c!=aNanInfName[k].c2 ) continue;
+      nn = aNanInfName[k].n;
+      if( sqlite3StrNICmp(&z[i], aNanInfName[k].zMatch, nn)!=0 ){
+        continue;
+      }
+      if( sqlite3Isalnum(z[i+nn]) ) continue;
+      if( aNanInfName[k].eType==JSONB_FLOAT ){
+        jsonBlobAppendNode(pParse, JSONB_FLOAT, 5, "9e999");
+      }else{
+        jsonBlobAppendOneByte(pParse, JSONB_NULL);
+      }
+      pParse->hasNonstd = 1;
+      return i + nn;
+    }
+    pParse->iErr = i;
+    return -1;  /* Syntax error */
+  }
+  } /* End switch(z[i]) */
+}
+
+
+/*
+** Parse a complete JSON string.  Return 0 on success or non-zero if there
+** are any errors.  If an error occurs, free all memory held by pParse,
+** but not pParse itself.
+**
+** pParse must be initialized to an empty parse object prior to calling
+** this routine.
+*/
+static int jsonConvertTextToBlob(
+  JsonParse *pParse,           /* Initialize and fill this JsonParse object */
+  sqlite3_context *pCtx        /* Report errors here */
+){
+  int i;
+  const char *zJson = pParse->zJson;
+  i = jsonTranslateTextToBlob(pParse, 0);
+  if( pParse->oom ) i = -1;
+  if( i>0 ){
+#ifdef SQLITE_DEBUG
+    assert( pParse->iDepth==0 );
+    if( sqlite3Config.bJsonSelfcheck ){
+      assert( jsonbValidityCheck(pParse, 0, pParse->nBlob, 0)==0 );
+    }   
+#endif
+    while( jsonIsspace(zJson[i]) ) i++;
+    if( zJson[i] ){
+      i += json5Whitespace(&zJson[i]);
+      if( zJson[i] ){
+        if( pCtx ) sqlite3_result_error(pCtx, "malformed JSON", -1);
+        jsonParseReset(pParse);
+        return 1;
+      }
+      pParse->hasNonstd = 1;
+    }
+  }
+  if( i<=0 ){
+    if( pCtx!=0 ){
+      if( pParse->oom ){
+        sqlite3_result_error_nomem(pCtx);
+      }else{
+        sqlite3_result_error(pCtx, "malformed JSON", -1);
+      }
+    }
+    jsonParseReset(pParse);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** The input string pStr is a well-formed JSON text string.  Convert
+** this into the JSONB format and make it the return value of the
+** SQL function.
+*/
+static void jsonReturnStringAsBlob(JsonString *pStr){
+  JsonParse px;
+  memset(&px, 0, sizeof(px));
+  jsonStringTerminate(pStr);
+  px.zJson = pStr->zBuf;
+  px.nJson = pStr->nUsed;
+  px.db = sqlite3_context_db_handle(pStr->pCtx);
+  (void)jsonTranslateTextToBlob(&px, 0);
+  if( px.oom ){
+    sqlite3DbFree(px.db, px.aBlob);
+    sqlite3_result_error_nomem(pStr->pCtx);
+  }else{
+    assert( px.nBlobAlloc>0 );
+    assert( !px.bReadOnly );
+    sqlite3_result_blob(pStr->pCtx, px.aBlob, px.nBlob, SQLITE_DYNAMIC);
+  }
+}
+
+/* The byte at index i is a node type-code.  This routine
+** determines the payload size for that node and writes that
+** payload size in to *pSz.  It returns the offset from i to the
+** beginning of the payload.  Return 0 on error.
+*/
+static u32 jsonbPayloadSize(const JsonParse *pParse, u32 i, u32 *pSz){
+  u8 x;
+  u32 sz;
+  u32 n;
+  if( NEVER(i>pParse->nBlob) ){
+    *pSz = 0;
+    return 0;
+  }
+  x = pParse->aBlob[i]>>4;
+  if( x<=11 ){
+    sz = x;
+    n = 1;
+  }else if( x==12 ){
+    if( i+1>=pParse->nBlob ){
+      *pSz = 0;
+      return 0;
+    }
+    sz = pParse->aBlob[i+1];
+    n = 2;
+  }else if( x==13 ){
+    if( i+2>=pParse->nBlob ){
+      *pSz = 0;
+      return 0;
+    }
+    sz = (pParse->aBlob[i+1]<<8) + pParse->aBlob[i+2];
+    n = 3;
+  }else if( x==14 ){
+    if( i+4>=pParse->nBlob ){
+      *pSz = 0;
+      return 0;
+    }
+    sz = ((u32)pParse->aBlob[i+1]<<24) + (pParse->aBlob[i+2]<<16) +
+         (pParse->aBlob[i+3]<<8) + pParse->aBlob[i+4];
+    n = 5;
+  }else{
+    if( i+8>=pParse->nBlob
+     || pParse->aBlob[i+1]!=0
+     || pParse->aBlob[i+2]!=0
+     || pParse->aBlob[i+3]!=0
+     || pParse->aBlob[i+4]!=0
+    ){
+      *pSz = 0;
+      return 0;
+    }
+    sz = (pParse->aBlob[i+5]<<24) + (pParse->aBlob[i+6]<<16) +
+         (pParse->aBlob[i+7]<<8) + pParse->aBlob[i+8];
+    n = 9;
+  }
+  if( (i64)i+sz+n > pParse->nBlob
+   && (i64)i+sz+n > pParse->nBlob-pParse->delta
+  ){
+    sz = 0;
+    n = 0;
+  }
+  *pSz = sz;
+  return n;
+}
+
+
+/*
+** Translate the binary JSONB representation of JSON beginning at
+** pParse->aBlob[i] into a JSON text string.  Append the JSON
+** text onto the end of pOut.  Return the index in pParse->aBlob[]
+** of the first byte past the end of the element that is translated.
+**
+** If an error is detected in the BLOB input, the pOut->eErr flag
+** might get set to JSTRING_MALFORMED.  But not all BLOB input errors
+** are detected.  So a malformed JSONB input might either result
+** in an error, or in incorrect JSON.
+**
+** The pOut->eErr JSTRING_OOM flag is set on a OOM.
+*/
+static u32 jsonTranslateBlobToText(
+  const JsonParse *pParse,       /* the complete parse of the JSON */
+  u32 i,                         /* Start rendering at this index */
+  JsonString *pOut               /* Write JSON here */
+){
+  u32 sz, n, j, iEnd;
+
+  n = jsonbPayloadSize(pParse, i, &sz);
+  if( n==0 ){
+    pOut->eErr |= JSTRING_MALFORMED;
+    return pParse->nBlob+1;
+  }
+  switch( pParse->aBlob[i] & 0x0f ){
+    case JSONB_NULL: {
+      jsonAppendRawNZ(pOut, "null", 4);
+      return i+1;
+    }
+    case JSONB_TRUE: {
+      jsonAppendRawNZ(pOut, "true", 4);
+      return i+1;
+    }
+    case JSONB_FALSE: {
+      jsonAppendRawNZ(pOut, "false", 5);
+      return i+1;
+    }
+    case JSONB_INT:
+    case JSONB_FLOAT: {
+      if( sz==0 ) goto malformed_jsonb;
+      jsonAppendRaw(pOut, (const char*)&pParse->aBlob[i+n], sz);
+      break;
+    }
+    case JSONB_INT5: {  /* Integer literal in hexadecimal notation */
+      u32 k = 2;
+      sqlite3_uint64 u = 0;
+      const char *zIn = (const char*)&pParse->aBlob[i+n];
+      int bOverflow = 0;
+      if( sz==0 ) goto malformed_jsonb;
+      if( zIn[0]=='-' ){
+        jsonAppendChar(pOut, '-');
+        k++;
+      }else if( zIn[0]=='+' ){
+        k++;
+      }
+      for(; k<sz; k++){
+        if( !sqlite3Isxdigit(zIn[k]) ){
+          pOut->eErr |= JSTRING_MALFORMED;
+          break;
+        }else if( (u>>60)!=0 ){
+          bOverflow = 1;
+        }else{
+          u = u*16 + sqlite3HexToInt(zIn[k]);
+        }
+      }
+      jsonPrintf(100,pOut,bOverflow?"9.0e999":"%llu", u);
+      break;
+    }
+    case JSONB_FLOAT5: { /* Float literal missing digits beside "." */
+      u32 k = 0;
+      const char *zIn = (const char*)&pParse->aBlob[i+n];
+      if( sz==0 ) goto malformed_jsonb;
+      if( zIn[0]=='-' ){
+        jsonAppendChar(pOut, '-');
+        k++;
+      }
+      if( zIn[k]=='.' ){
+        jsonAppendChar(pOut, '0');
+      }
+      for(; k<sz; k++){
+        jsonAppendChar(pOut, zIn[k]);
+        if( zIn[k]=='.' && (k+1==sz || !sqlite3Isdigit(zIn[k+1])) ){
+          jsonAppendChar(pOut, '0');
+        }
+      }
+      break;
+    }
+    case JSONB_TEXT:
+    case JSONB_TEXTJ: {
+      jsonAppendChar(pOut, '"');
+      jsonAppendRaw(pOut, (const char*)&pParse->aBlob[i+n], sz);
+      jsonAppendChar(pOut, '"');
+      break;
+    }
+    case JSONB_TEXT5: {
+      const char *zIn;
+      u32 k;
+      u32 sz2 = sz;
+      zIn = (const char*)&pParse->aBlob[i+n];
+      jsonAppendChar(pOut, '"');
+      while( sz2>0 ){
+        for(k=0; k<sz2 && zIn[k]!='\\' && zIn[k]!='"'; k++){}
+        if( k>0 ){
+          jsonAppendRawNZ(pOut, zIn, k);
+          if( k>=sz2 ){
+            break;
+          }
+          zIn += k;
+          sz2 -= k;
+        }
+        if( zIn[0]=='"' ){
+          jsonAppendRawNZ(pOut, "\\\"", 2);
+          zIn++;
+          sz2--;
+          continue;
+        }
+        assert( zIn[0]=='\\' );
+        assert( sz2>=1 );
+        if( sz2<2 ){
+          pOut->eErr |= JSTRING_MALFORMED;
+          break;
+        }
+        switch( (u8)zIn[1] ){
+          case '\'':
+            jsonAppendChar(pOut, '\'');
+            break;
+          case 'v':
+            jsonAppendRawNZ(pOut, "\\u0009", 6);
+            break;
+          case 'x':
+            if( sz2<4 ){
+              pOut->eErr |= JSTRING_MALFORMED;
+              sz2 = 2;
+              break;
+            }
+            jsonAppendRawNZ(pOut, "\\u00", 4);
+            jsonAppendRawNZ(pOut, &zIn[2], 2);
+            zIn += 2;
+            sz2 -= 2;
+            break;
+          case '0':
+            jsonAppendRawNZ(pOut, "\\u0000", 6);
+            break;
+          case '\r':
+            if( sz2>2 && zIn[2]=='\n' ){
+              zIn++;
+              sz2--;
+            }
+            break;
+          case '\n':
+            break;
+          case 0xe2:
+            /* '\' followed by either U+2028 or U+2029 is ignored as
+            ** whitespace.  Not that in UTF8, U+2028 is 0xe2 0x80 0x29.
+            ** U+2029 is the same except for the last byte */
+            if( sz2<4
+             || 0x80!=(u8)zIn[2]
+             || (0xa8!=(u8)zIn[3] && 0xa9!=(u8)zIn[3])
+            ){
+              pOut->eErr |= JSTRING_MALFORMED;
+              sz2 = 2;
+              break;
+            }
+            zIn += 2;
+            sz2 -= 2;
+            break;
+          default:
+            jsonAppendRawNZ(pOut, zIn, 2);
+            break;
+        }
+        assert( sz2>=2 );
+        zIn += 2;
+        sz2 -= 2;
+      }
+      jsonAppendChar(pOut, '"');
+      break;
+    }
+    case JSONB_TEXTRAW: {
+      jsonAppendString(pOut, (const char*)&pParse->aBlob[i+n], sz);
+      break;
+    }
+    case JSONB_ARRAY: {
+      jsonAppendChar(pOut, '[');
+      j = i+n;
+      iEnd = j+sz;
+      while( j<iEnd && pOut->eErr==0 ){
+        j = jsonTranslateBlobToText(pParse, j, pOut);
+        jsonAppendChar(pOut, ',');
+      }
+      if( j>iEnd ) pOut->eErr |= JSTRING_MALFORMED;
+      if( sz>0 ) jsonStringTrimOneChar(pOut);
+      jsonAppendChar(pOut, ']');
+      break;
+    }
+    case JSONB_OBJECT: {
+      int x = 0;
+      jsonAppendChar(pOut, '{');
+      j = i+n;
+      iEnd = j+sz;
+      while( j<iEnd && pOut->eErr==0 ){
+        j = jsonTranslateBlobToText(pParse, j, pOut);
+        jsonAppendChar(pOut, (x++ & 1) ? ',' : ':');
+      }
+      if( (x & 1)!=0 || j>iEnd ) pOut->eErr |= JSTRING_MALFORMED;
+      if( sz>0 ) jsonStringTrimOneChar(pOut);
+      jsonAppendChar(pOut, '}');
+      break;
+    }
+
+    default: {
+      malformed_jsonb:
+      pOut->eErr |= JSTRING_MALFORMED;
+      break;
+    }
+  }
+  return i+n+sz;
+}
+
+/* Return true if the input pJson
+**
+** For performance reasons, this routine does not do a detailed check of the
+** input BLOB to ensure that it is well-formed.  Hence, false positives are
+** possible.  False negatives should never occur, however.
+*/
+static int jsonFuncArgMightBeBinary(sqlite3_value *pJson){
+  u32 sz, n;
+  const u8 *aBlob;
+  int nBlob;
+  JsonParse s;
+  if( sqlite3_value_type(pJson)!=SQLITE_BLOB ) return 0;
+  aBlob = sqlite3_value_blob(pJson);
+  nBlob = sqlite3_value_bytes(pJson);
+  if( nBlob<1 ) return 0;
+  if( NEVER(aBlob==0) || (aBlob[0] & 0x0f)>JSONB_OBJECT ) return 0;
+  memset(&s, 0, sizeof(s));
+  s.aBlob = (u8*)aBlob;
+  s.nBlob = nBlob;
+  n = jsonbPayloadSize(&s, 0, &sz);
+  if( n==0 ) return 0;
+  if( sz+n!=(u32)nBlob ) return 0;
+  if( (aBlob[0] & 0x0f)<=JSONB_FALSE && sz>0 ) return 0;
+  return sz+n==(u32)nBlob;
+}
+
+/*
+** Given that a JSONB_ARRAY object starts at offset i, return
+** the number of entries in that array.
+*/
+static u32 jsonbArrayCount(JsonParse *pParse, u32 iRoot){
+  u32 n, sz, i, iEnd;
+  u32 k = 0;
+  n = jsonbPayloadSize(pParse, iRoot, &sz);
+  iEnd = iRoot+n+sz;
+  for(i=iRoot+n; n>0 && i<iEnd; i+=sz+n, k++){
+    n = jsonbPayloadSize(pParse, i, &sz);
+  }
+  return k;
+}
+
+/*
+** Edit the payload size of the element at iRoot by the amount in
+** pParse->delta.
+*/
+static void jsonAfterEditSizeAdjust(JsonParse *pParse, u32 iRoot){
+  u32 sz = 0;
+  u32 nBlob;
+  assert( pParse->delta!=0 );
+  assert( pParse->nBlobAlloc >= pParse->nBlob );
+  nBlob = pParse->nBlob;
+  pParse->nBlob = pParse->nBlobAlloc;
+  (void)jsonbPayloadSize(pParse, iRoot, &sz);
+  pParse->nBlob = nBlob;
+  sz += pParse->delta;
+  pParse->delta += jsonBlobChangePayloadSize(pParse, iRoot, sz);
+}
+
+/*
+** Modify the JSONB blob at pParse->aBlob by removing nDel bytes of
+** content beginning at iDel, and replacing them with nIns bytes of
+** content given by aIns.
+**
+** nDel may be zero, in which case no bytes are removed.  But iDel is
+** still important as new bytes will be insert beginning at iDel.
+**
+** aIns may be zero, in which case space is created to hold nIns bytes
+** beginning at iDel, but that space is uninitialized.
+**
+** Set pParse->oom if an OOM occurs.
+*/
+static void jsonBlobEdit(
+  JsonParse *pParse,     /* The JSONB to be modified is in pParse->aBlob */
+  u32 iDel,              /* First byte to be removed */
+  u32 nDel,              /* Number of bytes to remove */
+  const u8 *aIns,        /* Content to insert */
+  u32 nIns               /* Bytes of content to insert */
+){
+  i64 d = (i64)nIns - (i64)nDel;
+  if( d!=0 ){
+    if( pParse->nBlob + d > pParse->nBlobAlloc ){
+      jsonBlobExpand(pParse, pParse->nBlob+d);
+      if( pParse->oom ) return;
+    }
+    memmove(&pParse->aBlob[iDel+nIns],
+            &pParse->aBlob[iDel+nDel],
+            pParse->nBlob - (iDel+nDel));
+    pParse->nBlob += d;
+    pParse->delta += d;
+  }
+  if( nIns && aIns ) memcpy(&pParse->aBlob[iDel], aIns, nIns);
+}
+
+/*
+** Return the number of escaped newlines to be ignored.
+** An escaped newline is a one of the following byte sequences:
+**
+**    0x5c 0x0a
+**    0x5c 0x0d
+**    0x5c 0x0d 0x0a
+**    0x5c 0xe2 0x80 0xa8
+**    0x5c 0xe2 0x80 0xa9
+*/
+static u32 jsonBytesToBypass(const char *z, u32 n){
+  u32 i = 0;
+  while( i+1<n ){
+    if( z[i]!='\\' ) return i;
+    if( z[i+1]=='\n' ){
+      i += 2;
+      continue;
+    }
+    if( z[i+1]=='\r' ){
+      if( i+2<n && z[i+2]=='\n' ){
+        i += 3;
+      }else{
+        i += 2;
+      }
+      continue;
+    }
+    if( 0xe2==(u8)z[i+1]
+     && i+3<n
+     && 0x80==(u8)z[i+2]
+     && (0xa8==(u8)z[i+3] || 0xa9==(u8)z[i+3])
+    ){
+      i += 4;
+      continue;
+    }
+    break;
+  }
+  return i;
+}
+
+/*
+** Input z[0..n] defines JSON escape sequence including the leading '\\'.
+** Decode that escape sequence into a single character.  Write that
+** character into *piOut.  Return the number of bytes in the escape sequence.
+**
+** If there is a syntax error of some kind (for example too few characters
+** after the '\\' to complete the encoding) then *piOut is set to
+** JSON_INVALID_CHAR.
+*/
+static u32 jsonUnescapeOneChar(const char *z, u32 n, u32 *piOut){
+  assert( n>0 );
+  assert( z[0]=='\\' );
+  if( n<2 ){
+    *piOut = JSON_INVALID_CHAR;
+    return n;
+  }
+  switch( (u8)z[1] ){
+    case 'u': {
+      u32 v, vlo;
+      if( n<6 ){
+        *piOut = JSON_INVALID_CHAR;
+        return n;
+      }
+      v = jsonHexToInt4(&z[2]);
+      if( (v & 0xfc00)==0xd800
+       && n>=12
+       && z[6]=='\\'
+       && z[7]=='u'
+       && ((vlo = jsonHexToInt4(&z[8]))&0xfc00)==0xdc00
+      ){
+        *piOut = ((v&0x3ff)<<10) + (vlo&0x3ff) + 0x10000;
+        return 12;
+      }else{
+        *piOut = v;
+        return 6;
+      }
+    }
+    case 'b': {   *piOut = '\b';  return 2; }
+    case 'f': {   *piOut = '\f';  return 2; }
+    case 'n': {   *piOut = '\n';  return 2; }
+    case 'r': {   *piOut = '\r';  return 2; }
+    case 't': {   *piOut = '\t';  return 2; }
+    case 'v': {   *piOut = '\v';  return 2; }
+    case '0': {   *piOut = 0;     return 2; }
+    case '\'':
+    case '"':
+    case '/':
+    case '\\':{   *piOut = z[1];  return 2; }
+    case 'x': {
+      if( n<4 ){
+        *piOut = JSON_INVALID_CHAR;
+        return n;
+      }
+      *piOut = (jsonHexToInt(z[2])<<4) | jsonHexToInt(z[3]);
+      return 4;
+    }
+    case 0xe2:
+    case '\r':
+    case '\n': {
+      u32 nSkip = jsonBytesToBypass(z, n);
+      if( nSkip==0 ){
+        *piOut = JSON_INVALID_CHAR;
+        return n;
+      }else if( nSkip==n ){
+        *piOut = 0;
+        return n;
+      }else if( z[nSkip]=='\\' ){
+        return nSkip + jsonUnescapeOneChar(&z[nSkip], n-nSkip, piOut);
+      }else{
+        int sz = sqlite3Utf8ReadLimited((u8*)&z[nSkip], n-nSkip, piOut);
+        return nSkip + sz;
+      }
+    }
+    default: {
+      *piOut = JSON_INVALID_CHAR;
+      return 2;
+    }
+  }
+}
+
+
+/*
+** Compare two object labels.  Return 1 if they are equal and
+** 0 if they differ.
+**
+** In this version, we know that one or the other or both of the
+** two comparands contains an escape sequence.
+*/
+static SQLITE_NOINLINE int jsonLabelCompareEscaped(
+  const char *zLeft,          /* The left label */
+  u32 nLeft,                  /* Size of the left label in bytes */
+  int rawLeft,                /* True if zLeft contains no escapes */
+  const char *zRight,         /* The right label */
+  u32 nRight,                 /* Size of the right label in bytes */
+  int rawRight                /* True if zRight is escape-free */
+){
+  u32 cLeft, cRight;
+  assert( rawLeft==0 || rawRight==0 );
+  while( 1 /*exit-by-return*/ ){
+    if( nLeft==0 ){
+      cLeft = 0;
+    }else if( rawLeft || zLeft[0]!='\\' ){
+      cLeft = ((u8*)zLeft)[0];
+      if( cLeft>=0xc0 ){
+        int sz = sqlite3Utf8ReadLimited((u8*)zLeft, nLeft, &cLeft);
+        zLeft += sz;
+        nLeft -= sz;
+      }else{
+        zLeft++;
+        nLeft--;
+      }
+    }else{
+      u32 n = jsonUnescapeOneChar(zLeft, nLeft, &cLeft);
+      zLeft += n;
+      assert( n<=nLeft );
+      nLeft -= n;
+    }
+    if( nRight==0 ){
+      cRight = 0;
+    }else if( rawRight || zRight[0]!='\\' ){
+      cRight = ((u8*)zRight)[0];
+      if( cRight>=0xc0 ){
+        int sz = sqlite3Utf8ReadLimited((u8*)zRight, nRight, &cRight);
+        zRight += sz;
+        nRight -= sz;
+      }else{
+        zRight++;
+        nRight--;
+      }
+    }else{
+      u32 n = jsonUnescapeOneChar(zRight, nRight, &cRight);
+      zRight += n;
+      assert( n<=nRight );
+      nRight -= n;
+    }
+    if( cLeft!=cRight ) return 0;
+    if( cLeft==0 ) return 1;
+  }
+}
+
+/*
+** Compare two object labels.  Return 1 if they are equal and
+** 0 if they differ.  Return -1 if an OOM occurs.
+*/
+static int jsonLabelCompare(
+  const char *zLeft,          /* The left label */
+  u32 nLeft,                  /* Size of the left label in bytes */
+  int rawLeft,                /* True if zLeft contains no escapes */
+  const char *zRight,         /* The right label */
+  u32 nRight,                 /* Size of the right label in bytes */
+  int rawRight                /* True if zRight is escape-free */
+){
+  if( rawLeft && rawRight ){
+    /* Simpliest case:  Neither label contains escapes.  A simple
+    ** memcmp() is sufficient. */
+    if( nLeft!=nRight ) return 0;
+    return memcmp(zLeft, zRight, nLeft)==0;
+  }else{
+    return jsonLabelCompareEscaped(zLeft, nLeft, rawLeft,
+                                   zRight, nRight, rawRight);
+  }
+}
+
+/*
+** Error returns from jsonLookupStep()
+*/
+#define JSON_LOOKUP_ERROR      0xffffffff
+#define JSON_LOOKUP_NOTFOUND   0xfffffffe
+#define JSON_LOOKUP_PATHERROR  0xfffffffd
+#define JSON_LOOKUP_ISERROR(x) ((x)>=JSON_LOOKUP_PATHERROR)
+
+/* Forward declaration */
+static u32 jsonLookupStep(JsonParse*,u32,const char*,u32);
+
+
+/* This helper routine for jsonLookupStep() populates pIns with
+** binary data that is to be inserted into pParse.
+**
+** In the common case, pIns just points to pParse->aIns and pParse->nIns.
+** But if the zPath of the original edit operation includes path elements
+** that go deeper, additional substructure must be created.
+**
+** For example:
+**
+**     json_insert('{}', '$.a.b.c', 123);
+**
+** The search stops at '$.a'  But additional substructure must be
+** created for the ".b.c" part of the patch so that the final result
+** is:  {"a":{"b":{"c"::123}}}.  This routine populates pIns with
+** the binary equivalent of {"b":{"c":123}} so that it can be inserted.
+**
+** The caller is responsible for resetting pIns when it has finished
+** using the substructure.
+*/
+static u32 jsonCreateEditSubstructure(
+  JsonParse *pParse,  /* The original JSONB that is being edited */
+  JsonParse *pIns,    /* Populate this with the blob data to insert */
+  const char *zTail   /* Tail of the path that determins substructure */
+){
+  static const u8 emptyObject[] = { JSONB_ARRAY, JSONB_OBJECT };
+  int rc;
+  memset(pIns, 0, sizeof(*pIns));
+  pIns->db = pParse->db;
+  if( zTail[0]==0 ){
+    /* No substructure.  Just insert what is given in pParse. */
+    pIns->aBlob = pParse->aIns;
+    pIns->nBlob = pParse->nIns;
+    rc = 0;
+  }else{
+    /* Construct the binary substructure */
+    pIns->nBlob = 1;
+    pIns->aBlob = (u8*)&emptyObject[zTail[0]=='.'];
+    pIns->eEdit = pParse->eEdit;
+    pIns->nIns = pParse->nIns;
+    pIns->aIns = pParse->aIns;
+    rc = jsonLookupStep(pIns, 0, zTail, 0);
+    pParse->oom |= pIns->oom;
+  }
+  return rc;  /* Error code only */
+}
+
+/*
+** Search along zPath to find the Json element specified.  Return an
+** index into pParse->aBlob[] for the start of that element's value.
+**
+** If the value found by this routine is the value half of label/value pair
+** within an object, then set pPath->iLabel to the start of the corresponding
+** label, before returning.
+**
+** Return one of the JSON_LOOKUP error codes if problems are seen.
+**
+** This routine will also modify the blob.  If pParse->eEdit is one of
+** JEDIT_DEL, JEDIT_REPL, JEDIT_INS, or JEDIT_SET, then changes might be
+** made to the selected value.  If an edit is performed, then the return
+** value does not necessarily point to the select element.  If an edit
+** is performed, the return value is only useful for detecting error
+** conditions.
+*/
+static u32 jsonLookupStep(
+  JsonParse *pParse,      /* The JSON to search */
+  u32 iRoot,              /* Begin the search at this element of aBlob[] */
+  const char *zPath,      /* The path to search */
+  u32 iLabel              /* Label if iRoot is a value of in an object */
+){
+  u32 i, j, k, nKey, sz, n, iEnd, rc;
+  const char *zKey;
+  u8 x;
+
+  if( zPath[0]==0 ){
+    if( pParse->eEdit && jsonBlobMakeEditable(pParse, pParse->nIns) ){
+      n = jsonbPayloadSize(pParse, iRoot, &sz);
+      sz += n;
+      if( pParse->eEdit==JEDIT_DEL ){
+        if( iLabel>0 ){
+          sz += iRoot - iLabel;
+          iRoot = iLabel;
+        }
+        jsonBlobEdit(pParse, iRoot, sz, 0, 0);
+      }else if( pParse->eEdit==JEDIT_INS ){
+        /* Already exists, so json_insert() is a no-op */
+      }else{
+        /* json_set() or json_replace() */
+        jsonBlobEdit(pParse, iRoot, sz, pParse->aIns, pParse->nIns);
+      }
+    }
+    pParse->iLabel = iLabel;
+    return iRoot;
+  }
+  if( zPath[0]=='.' ){
+    int rawKey = 1;
+    x = pParse->aBlob[iRoot];
+    zPath++;
+    if( zPath[0]=='"' ){
+      zKey = zPath + 1;
+      for(i=1; zPath[i] && zPath[i]!='"'; i++){}
+      nKey = i-1;
+      if( zPath[i] ){
+        i++;
+      }else{
+        return JSON_LOOKUP_PATHERROR;
+      }
+      testcase( nKey==0 );
+      rawKey = memchr(zKey, '\\', nKey)==0;
+    }else{
+      zKey = zPath;
+      for(i=0; zPath[i] && zPath[i]!='.' && zPath[i]!='['; i++){}
+      nKey = i;
+      if( nKey==0 ){
+        return JSON_LOOKUP_PATHERROR;
+      }
+    }
+    if( (x & 0x0f)!=JSONB_OBJECT ) return JSON_LOOKUP_NOTFOUND;
+    n = jsonbPayloadSize(pParse, iRoot, &sz);
+    j = iRoot + n;  /* j is the index of a label */
+    iEnd = j+sz;
+    while( j<iEnd ){
+      int rawLabel;
+      const char *zLabel;
+      x = pParse->aBlob[j] & 0x0f;
+      if( x<JSONB_TEXT || x>JSONB_TEXTRAW ) return JSON_LOOKUP_ERROR;
+      n = jsonbPayloadSize(pParse, j, &sz);
+      if( n==0 ) return JSON_LOOKUP_ERROR;
+      k = j+n;  /* k is the index of the label text */
+      if( k+sz>=iEnd ) return JSON_LOOKUP_ERROR;
+      zLabel = (const char*)&pParse->aBlob[k];
+      rawLabel = x==JSONB_TEXT || x==JSONB_TEXTRAW;
+      if( jsonLabelCompare(zKey, nKey, rawKey, zLabel, sz, rawLabel) ){
+        u32 v = k+sz;  /* v is the index of the value */
+        if( ((pParse->aBlob[v])&0x0f)>JSONB_OBJECT ) return JSON_LOOKUP_ERROR;
+        n = jsonbPayloadSize(pParse, v, &sz);
+        if( n==0 || v+n+sz>iEnd ) return JSON_LOOKUP_ERROR;
+        assert( j>0 );
+        rc = jsonLookupStep(pParse, v, &zPath[i], j);
+        if( pParse->delta ) jsonAfterEditSizeAdjust(pParse, iRoot);
+        return rc;
+      }
+      j = k+sz;
+      if( ((pParse->aBlob[j])&0x0f)>JSONB_OBJECT ) return JSON_LOOKUP_ERROR;
+      n = jsonbPayloadSize(pParse, j, &sz);
+      if( n==0 ) return JSON_LOOKUP_ERROR;
+      j += n+sz;
+    }
+    if( j>iEnd ) return JSON_LOOKUP_ERROR;
+    if( pParse->eEdit>=JEDIT_INS ){
+      u32 nIns;          /* Total bytes to insert (label+value) */
+      JsonParse v;       /* BLOB encoding of the value to be inserted */
+      JsonParse ix;      /* Header of the label to be inserted */
+      testcase( pParse->eEdit==JEDIT_INS );
+      testcase( pParse->eEdit==JEDIT_SET );
+      memset(&ix, 0, sizeof(ix));
+      ix.db = pParse->db;
+      jsonBlobAppendNode(&ix, rawKey?JSONB_TEXTRAW:JSONB_TEXT5, nKey, 0);
+      pParse->oom |= ix.oom;
+      rc = jsonCreateEditSubstructure(pParse, &v, &zPath[i]);
+      if( !JSON_LOOKUP_ISERROR(rc)
+       && jsonBlobMakeEditable(pParse, ix.nBlob+nKey+v.nBlob)
+      ){
+        assert( !pParse->oom );
+        nIns = ix.nBlob + nKey + v.nBlob;
+        jsonBlobEdit(pParse, j, 0, 0, nIns);
+        if( !pParse->oom ){
+          assert( pParse->aBlob!=0 ); /* Because pParse->oom!=0 */
+          assert( ix.aBlob!=0 );      /* Because pPasre->oom!=0 */
+          memcpy(&pParse->aBlob[j], ix.aBlob, ix.nBlob);
+          k = j + ix.nBlob;
+          memcpy(&pParse->aBlob[k], zKey, nKey);
+          k += nKey;
+          memcpy(&pParse->aBlob[k], v.aBlob, v.nBlob);
+          if( ALWAYS(pParse->delta) ) jsonAfterEditSizeAdjust(pParse, iRoot);
+        }
+      }
+      jsonParseReset(&v);
+      jsonParseReset(&ix);
+      return rc;
+    }
+  }else if( zPath[0]=='[' ){
+    x = pParse->aBlob[iRoot] & 0x0f;
+    if( x!=JSONB_ARRAY )  return JSON_LOOKUP_NOTFOUND;
+    n = jsonbPayloadSize(pParse, iRoot, &sz);
+    k = 0;
+    i = 1;
+    while( sqlite3Isdigit(zPath[i]) ){
+      k = k*10 + zPath[i] - '0';
+      i++;
+    }
+    if( i<2 || zPath[i]!=']' ){
+      if( zPath[1]=='#' ){
+        k = jsonbArrayCount(pParse, iRoot);
+        i = 2;
+        if( zPath[2]=='-' && sqlite3Isdigit(zPath[3]) ){
+          unsigned int nn = 0;
+          i = 3;
+          do{
+            nn = nn*10 + zPath[i] - '0';
+            i++;
+          }while( sqlite3Isdigit(zPath[i]) );
+          if( nn>k ) return JSON_LOOKUP_NOTFOUND;
+          k -= nn;
+        }
+        if( zPath[i]!=']' ){
+          return JSON_LOOKUP_PATHERROR;
+        }
+      }else{
+        return JSON_LOOKUP_PATHERROR;
+      }
+    }
+    j = iRoot+n;
+    iEnd = j+sz;
+    while( j<iEnd ){
+      if( k==0 ){
+        rc = jsonLookupStep(pParse, j, &zPath[i+1], 0);
+        if( pParse->delta ) jsonAfterEditSizeAdjust(pParse, iRoot);
+        return rc;
+      }
+      k--;
+      n = jsonbPayloadSize(pParse, j, &sz);
+      if( n==0 ) return JSON_LOOKUP_ERROR;
+      j += n+sz;
+    }
+    if( j>iEnd ) return JSON_LOOKUP_ERROR;
+    if( k>0 ) return JSON_LOOKUP_NOTFOUND;
+    if( pParse->eEdit>=JEDIT_INS ){
+      JsonParse v;
+      testcase( pParse->eEdit==JEDIT_INS );
+      testcase( pParse->eEdit==JEDIT_SET );
+      rc = jsonCreateEditSubstructure(pParse, &v, &zPath[i+1]);
+      if( !JSON_LOOKUP_ISERROR(rc)
+       && jsonBlobMakeEditable(pParse, v.nBlob)
+      ){
+        assert( !pParse->oom );
+        jsonBlobEdit(pParse, j, 0, v.aBlob, v.nBlob);
+      }
+      jsonParseReset(&v);
+      if( pParse->delta ) jsonAfterEditSizeAdjust(pParse, iRoot);
+      return rc;
+    }
+  }else{
+    return JSON_LOOKUP_PATHERROR; 
+  }
+  return JSON_LOOKUP_NOTFOUND;
+}
+
+/*
+** Convert a JSON BLOB into text and make that text the return value
+** of an SQL function.
+*/
+static void jsonReturnTextJsonFromBlob(
+  sqlite3_context *ctx,
+  const u8 *aBlob,
+  u32 nBlob
+){
+  JsonParse x;
+  JsonString s;
+
+  if( NEVER(aBlob==0) ) return;
+  memset(&x, 0, sizeof(x));
+  x.aBlob = (u8*)aBlob;
+  x.nBlob = nBlob;
+  jsonStringInit(&s, ctx);
+  jsonTranslateBlobToText(&x, 0, &s);
+  jsonReturnString(&s, 0, 0);
+}
+
+
+/*
+** Return the value of the BLOB node at index i.
+**
+** If the value is a primitive, return it as an SQL value.
+** If the value is an array or object, return it as either
+** JSON text or the BLOB encoding, depending on the JSON_B flag
+** on the userdata.
+*/
+static void jsonReturnFromBlob(
+  JsonParse *pParse,          /* Complete JSON parse tree */
+  u32 i,                      /* Index of the node */
+  sqlite3_context *pCtx,      /* Return value for this function */
+  int textOnly                /* return text JSON.  Disregard user-data */
+){
+  u32 n, sz;
+  int rc;
+  sqlite3 *db = sqlite3_context_db_handle(pCtx);
+
+  n = jsonbPayloadSize(pParse, i, &sz);
+  if( n==0 ){
+    sqlite3_result_error(pCtx, "malformed JSON", -1);
+    return;
+  }
+  switch( pParse->aBlob[i] & 0x0f ){
+    case JSONB_NULL: {
+      if( sz ) goto returnfromblob_malformed;
+      sqlite3_result_null(pCtx);
+      break;
+    }
+    case JSONB_TRUE: {
+      if( sz ) goto returnfromblob_malformed;
+      sqlite3_result_int(pCtx, 1);
+      break;
+    }
+    case JSONB_FALSE: {
+      if( sz ) goto returnfromblob_malformed;
+      sqlite3_result_int(pCtx, 0);
+      break;
+    }
+    case JSONB_INT5:
+    case JSONB_INT: {
+      sqlite3_int64 iRes = 0;
+      char *z;
+      int bNeg = 0;
+      char x;
+      if( sz==0 ) goto returnfromblob_malformed;
+      x = (char)pParse->aBlob[i+n];
+      if( x=='-' ){
+        if( sz<2 ) goto returnfromblob_malformed;
+        n++;
+        sz--;
+        bNeg = 1;
+      }
+      z = sqlite3DbStrNDup(db, (const char*)&pParse->aBlob[i+n], (int)sz);
+      if( z==0 ) goto returnfromblob_oom;
+      rc = sqlite3DecOrHexToI64(z, &iRes);
+      sqlite3DbFree(db, z);
+      if( rc==0 ){
+        sqlite3_result_int64(pCtx, bNeg ? -iRes : iRes);
+      }else if( rc==3 && bNeg ){
+        sqlite3_result_int64(pCtx, SMALLEST_INT64);
+      }else if( rc==1 ){
+        goto returnfromblob_malformed;
+      }else{
+        if( bNeg ){ n--; sz++; }
+        goto to_double;
+      }
+      break;
+    }
+    case JSONB_FLOAT5:
+    case JSONB_FLOAT: {
+      double r;
+      char *z;
+      if( sz==0 ) goto returnfromblob_malformed;
+    to_double:
+      z = sqlite3DbStrNDup(db, (const char*)&pParse->aBlob[i+n], (int)sz);
+      if( z==0 ) goto returnfromblob_oom;
+      rc = sqlite3AtoF(z, &r, sqlite3Strlen30(z), SQLITE_UTF8);
+      sqlite3DbFree(db, z);
+      if( rc<=0 ) goto returnfromblob_malformed;
+      sqlite3_result_double(pCtx, r);
+      break;
+    }
+    case JSONB_TEXTRAW:
+    case JSONB_TEXT: {
+      sqlite3_result_text(pCtx, (char*)&pParse->aBlob[i+n], sz,
+                          SQLITE_TRANSIENT);
+      break;
+    }
+    case JSONB_TEXT5:
+    case JSONB_TEXTJ: {
+      /* Translate JSON formatted string into raw text */
+      u32 iIn, iOut;
+      const char *z;
+      char *zOut;
+      u32 nOut = sz;
+      z = (const char*)&pParse->aBlob[i+n];
+      zOut = sqlite3DbMallocRaw(db, nOut+1);
+      if( zOut==0 ) goto returnfromblob_oom;
+      for(iIn=iOut=0; iIn<sz; iIn++){
+        char c = z[iIn];
+        if( c=='\\' ){
+          u32 v;
+          u32 szEscape = jsonUnescapeOneChar(&z[iIn], sz-iIn, &v);
+          if( v<=0x7f ){
+            zOut[iOut++] = (char)v;
+          }else if( v<=0x7ff ){
+            assert( szEscape>=2 );
+            zOut[iOut++] = (char)(0xc0 | (v>>6));
+            zOut[iOut++] = 0x80 | (v&0x3f);
+          }else if( v<0x10000 ){
+            assert( szEscape>=3 );
+            zOut[iOut++] = 0xe0 | (v>>12);
+            zOut[iOut++] = 0x80 | ((v>>6)&0x3f);
+            zOut[iOut++] = 0x80 | (v&0x3f);
+          }else if( v==JSON_INVALID_CHAR ){
+            /* Silently ignore illegal unicode */
+          }else{
+            assert( szEscape>=4 );
+            zOut[iOut++] = 0xf0 | (v>>18);
+            zOut[iOut++] = 0x80 | ((v>>12)&0x3f);
+            zOut[iOut++] = 0x80 | ((v>>6)&0x3f);
+            zOut[iOut++] = 0x80 | (v&0x3f);
+          }
+          iIn += szEscape - 1;
+        }else{
+          zOut[iOut++] = c;
+        }
+      } /* end for() */
+      assert( iOut<=nOut );
+      zOut[iOut] = 0;
+      sqlite3_result_text(pCtx, zOut, iOut, SQLITE_DYNAMIC);
+      break;
+    }
+    case JSONB_ARRAY:
+    case JSONB_OBJECT: {
+      int flags = textOnly ? 0 : SQLITE_PTR_TO_INT(sqlite3_user_data(pCtx));
+      if( flags & JSON_BLOB ){
+        sqlite3_result_blob(pCtx, &pParse->aBlob[i], sz+n, SQLITE_TRANSIENT);
+      }else{
+        jsonReturnTextJsonFromBlob(pCtx, &pParse->aBlob[i], sz+n);
+      }
+      break;
+    }
+    default: {
+      goto returnfromblob_malformed;
+    }
+  }
+  return;
+
+returnfromblob_oom:
+  sqlite3_result_error_nomem(pCtx);
+  return;
+
+returnfromblob_malformed:
+  sqlite3_result_error(pCtx, "malformed JSON", -1);
+  return;
+}
+
+/*
+** pArg is a function argument that might be an SQL value or a JSON
+** value.  Figure out what it is and encode it as a JSONB blob.
+** Return the results in pParse.
+**
+** pParse is uninitialized upon entry.  This routine will handle the
+** initialization of pParse.  The result will be contained in
+** pParse->aBlob and pParse->nBlob.  pParse->aBlob might be dynamically
+** allocated (if pParse->nBlobAlloc is greater than zero) in which case
+** the caller is responsible for freeing the space allocated to pParse->aBlob
+** when it has finished with it.  Or pParse->aBlob might be a static string
+** or a value obtained from sqlite3_value_blob(pArg).
+**
+** If the argument is a BLOB that is clearly not a JSONB, then this
+** function might set an error message in ctx and return non-zero.
+** It might also set an error message and return non-zero on an OOM error.
+*/
+static int jsonFunctionArgToBlob(
+  sqlite3_context *ctx,
+  sqlite3_value *pArg,
+  JsonParse *pParse
+){
+  int eType = sqlite3_value_type(pArg);
+  static u8 aNull[] = { 0x00 };
+  memset(pParse, 0, sizeof(pParse[0]));
+  pParse->db = sqlite3_context_db_handle(ctx);
+  switch( eType ){
+    default: {
+      pParse->aBlob = aNull;
+      pParse->nBlob = 1;
+      return 0;
+    }
+    case SQLITE_BLOB: {
+      if( jsonFuncArgMightBeBinary(pArg) ){
+        pParse->aBlob = (u8*)sqlite3_value_blob(pArg);
+        pParse->nBlob = sqlite3_value_bytes(pArg);
+      }else{
+        sqlite3_result_error(ctx, "JSON cannot hold BLOB values", -1);
+        return 1;
+      }
+      break;
+    }
+    case SQLITE_TEXT: {
+      const char *zJson = (const char*)sqlite3_value_text(pArg);
+      int nJson = sqlite3_value_bytes(pArg);
+      if( zJson==0 ) return 1;
+      if( sqlite3_value_subtype(pArg)==JSON_SUBTYPE ){
+        pParse->zJson = (char*)zJson;
+        pParse->nJson = nJson;
+        if( jsonConvertTextToBlob(pParse, ctx) ){
+          sqlite3_result_error(ctx, "malformed JSON", -1);
+          sqlite3DbFree(pParse->db, pParse->aBlob);
+          memset(pParse, 0, sizeof(pParse[0]));
+          return 1;
+        }
+      }else{
+        jsonBlobAppendNode(pParse, JSONB_TEXTRAW, nJson, zJson);
+      }
+      break;
+    }
+    case SQLITE_FLOAT: {
+      double r = sqlite3_value_double(pArg);
+      if( NEVER(sqlite3IsNaN(r)) ){
+        jsonBlobAppendNode(pParse, JSONB_NULL, 0, 0);
+      }else{
+        int n = sqlite3_value_bytes(pArg);
+        const char *z = (const char*)sqlite3_value_text(pArg);
+        if( z==0 ) return 1;
+        if( z[0]=='I' ){
+          jsonBlobAppendNode(pParse, JSONB_FLOAT, 5, "9e999");
+        }else if( z[0]=='-' && z[1]=='I' ){
+          jsonBlobAppendNode(pParse, JSONB_FLOAT, 6, "-9e999");
+        }else{
+          jsonBlobAppendNode(pParse, JSONB_FLOAT, n, z);
+        }
+      }
+      break;
+    }
+    case SQLITE_INTEGER: {
+      int n = sqlite3_value_bytes(pArg);
+      const char *z = (const char*)sqlite3_value_text(pArg);
+      if( z==0 ) return 1;
+      jsonBlobAppendNode(pParse, JSONB_INT, n, z);
+      break;
+    }
+  }
+  if( pParse->oom ){
+    sqlite3_result_error_nomem(ctx);
+    return 1;
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Generate a bad path error.
+**
+** If ctx is not NULL then push the error message into ctx and return NULL.
+** If ctx is NULL, then return the text of the error message.
+*/
+static char *jsonBadPathError(
+  sqlite3_context *ctx,     /* The function call containing the error */
+  const char *zPath         /* The path with the problem */
+){
+  char *zMsg = sqlite3_mprintf("bad JSON path: %Q", zPath);
+  if( ctx==0 ) return zMsg;
+  if( zMsg ){
+    sqlite3_result_error(ctx, zMsg, -1);
+    sqlite3_free(zMsg);
+  }else{
+    sqlite3_result_error_nomem(ctx);
+  }
+  return 0;
+}
+
+/* argv[0] is a BLOB that seems likely to be a JSONB.  Subsequent
+** arguments come in parse where each pair contains a JSON path and
+** content to insert or set at that patch.  Do the updates
+** and return the result.
+**
+** The specific operation is determined by eEdit, which can be one
+** of JEDIT_INS, JEDIT_REPL, or JEDIT_SET.
+*/
+static void jsonInsertIntoBlob(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv,
+  int eEdit                /* JEDIT_INS, JEDIT_REPL, or JEDIT_SET */
+){
+  int i;
+  u32 rc = 0;
+  const char *zPath = 0;
+  int flgs;
+  JsonParse *p;
+  JsonParse ax;
+
+  assert( (argc&1)==1 );
+  flgs = argc==1 ? 0 : JSON_EDITABLE;
+  p = jsonParseFuncArg(ctx, argv[0], flgs);
+  if( p==0 ) return;
+  for(i=1; i<argc-1; i+=2){
+    if( sqlite3_value_type(argv[i])==SQLITE_NULL ) continue;
+    zPath = (const char*)sqlite3_value_text(argv[i]);
+    if( zPath==0 ){
+      sqlite3_result_error_nomem(ctx);
+      jsonParseFree(p);
+      return;
+    }
+    if( zPath[0]!='$' ) goto jsonInsertIntoBlob_patherror;
+    if( jsonFunctionArgToBlob(ctx, argv[i+1], &ax) ){
+      jsonParseReset(&ax);
+      jsonParseFree(p);
+      return;
+    }
+    if( zPath[1]==0 ){
+      if( eEdit==JEDIT_REPL || eEdit==JEDIT_SET ){
+        jsonBlobEdit(p, 0, p->nBlob, ax.aBlob, ax.nBlob);
+      }
+      rc = 0;
+   }else{
+      p->eEdit = eEdit;
+      p->nIns = ax.nBlob;
+      p->aIns = ax.aBlob;
+      p->delta = 0;
+      rc = jsonLookupStep(p, 0, zPath+1, 0);
+    }
+    jsonParseReset(&ax);
+    if( rc==JSON_LOOKUP_NOTFOUND ) continue;
+    if( JSON_LOOKUP_ISERROR(rc) ) goto jsonInsertIntoBlob_patherror;
+  }
+  jsonReturnParse(ctx, p);
+  jsonParseFree(p);
+  return;
+
+jsonInsertIntoBlob_patherror:
+  jsonParseFree(p);
+  if( rc==JSON_LOOKUP_ERROR ){
+    sqlite3_result_error(ctx, "malformed JSON", -1);
+  }else{
+    jsonBadPathError(ctx, zPath);
+  }
+  return;
+}
+
+/*
+** If pArg is a blob that seems like a JSONB blob, then initialize
+** p to point to that JSONB and return TRUE.  If pArg does not seem like
+** a JSONB blob, then return FALSE;
+**
+** This routine is only called if it is already known that pArg is a
+** blob.  The only open question is whether or not the blob appears
+** to be a JSONB blob.
+*/
+static int jsonArgIsJsonb(sqlite3_value *pArg, JsonParse *p){
+  u32 n, sz = 0;
+  p->aBlob = (u8*)sqlite3_value_blob(pArg);
+  p->nBlob = (u32)sqlite3_value_bytes(pArg);
+  if( p->nBlob==0 ){
+    p->aBlob = 0;
+    return 0;
+  }
+  if( NEVER(p->aBlob==0) ){
+    return 0;
+  }
+  if( (p->aBlob[0] & 0x0f)<=JSONB_OBJECT
+   && (n = jsonbPayloadSize(p, 0, &sz))>0
+   && sz+n==p->nBlob
+   && ((p->aBlob[0] & 0x0f)>JSONB_FALSE || sz==0)
+  ){
+    return 1;
+  }
+  p->aBlob = 0;
+  p->nBlob = 0;
+  return 0;
+}
+
+/*
+** Generate a JsonParse object, containing valid JSONB in aBlob and nBlob,
+** from the SQL function argument pArg.  Return a pointer to the new
+** JsonParse object.
+**
+** Ownership of the new JsonParse object is passed to the caller.  The
+** caller should invoke jsonParseFree() on the return value when it
+** has finished using it.
+**
+** If any errors are detected, an appropriate error messages is set
+** using sqlite3_result_error() or the equivalent and this routine
+** returns NULL.  This routine also returns NULL if the pArg argument
+** is an SQL NULL value, but no error message is set in that case.  This
+** is so that SQL functions that are given NULL arguments will return
+** a NULL value.
+*/
+static JsonParse *jsonParseFuncArg(
+  sqlite3_context *ctx,
+  sqlite3_value *pArg,
+  u32 flgs
+){
+  int eType;                   /* Datatype of pArg */
+  JsonParse *p = 0;            /* Value to be returned */
+  JsonParse *pFromCache = 0;   /* Value taken from cache */
+  sqlite3 *db;                 /* The database connection */
+  
+  assert( ctx!=0 );
+  eType = sqlite3_value_type(pArg);
+  if( eType==SQLITE_NULL ){
+    return 0;
+  }
+  pFromCache = jsonCacheSearch(ctx, pArg);
+  if( pFromCache ){
+    pFromCache->nJPRef++;
+    if( (flgs & JSON_EDITABLE)==0 ){
+      return pFromCache;
+    }
+  }
+  db = sqlite3_context_db_handle(ctx);
+rebuild_from_cache:
+  p = sqlite3DbMallocZero(db, sizeof(*p));
+  if( p==0 ) goto json_pfa_oom;
+  memset(p, 0, sizeof(*p));
+  p->db = db;
+  p->nJPRef = 1;
+  if( pFromCache!=0 ){
+    u32 nBlob = pFromCache->nBlob;
+    p->aBlob = sqlite3DbMallocRaw(db, nBlob);
+    if( p->aBlob==0 ) goto json_pfa_oom;
+    memcpy(p->aBlob, pFromCache->aBlob, nBlob);
+    p->nBlobAlloc = p->nBlob = nBlob;
+    p->hasNonstd = pFromCache->hasNonstd;
+    jsonParseFree(pFromCache);
+    return p;
+  }
+  if( eType==SQLITE_BLOB ){
+    if( jsonArgIsJsonb(pArg,p) ){
+      if( (flgs & JSON_EDITABLE)!=0 && jsonBlobMakeEditable(p, 0)==0 ){
+        goto json_pfa_oom;
+      }
+      return p;
+    }
+    /* If the blob is not valid JSONB, fall through into trying to cast
+    ** the blob into text which is then interpreted as JSON.  (tag-20240123-a)
+    **
+    ** This goes against all historical documentation about how the SQLite
+    ** JSON functions were suppose to work.  From the beginning, blob was
+    ** reserved for expansion and a blob value should have raised an error.
+    ** But it did not, due to a bug.  And many applications came to depend
+    ** upon this buggy behavior, espeically when using the CLI and reading
+    ** JSON text using readfile(), which returns a blob.  For this reason
+    ** we will continue to support the bug moving forward.
+    ** See for example https://sqlite.org/forum/forumpost/012136abd5292b8d
+    */
+  }
+  p->zJson = (char*)sqlite3_value_text(pArg);
+  p->nJson = sqlite3_value_bytes(pArg);
+  if( p->nJson==0 ) goto json_pfa_malformed;
+  if( NEVER(p->zJson==0) ) goto json_pfa_oom;
+  if( jsonConvertTextToBlob(p, (flgs & JSON_KEEPERROR) ? 0 : ctx) ){
+    if( flgs & JSON_KEEPERROR ){
+      p->nErr = 1;
+      return p;
+    }else{
+      jsonParseFree(p);
+      return 0;
+    }
+  }else{
+    int isRCStr = sqlite3ValueIsOfClass(pArg, sqlite3RCStrUnref);
+    int rc;
+    if( !isRCStr ){
+      char *zNew = sqlite3RCStrNew( p->nJson );
+      if( zNew==0 ) goto json_pfa_oom;
+      memcpy(zNew, p->zJson, p->nJson);
+      p->zJson = zNew;
+      p->zJson[p->nJson] = 0;
+    }else{
+      sqlite3RCStrRef(p->zJson);
+    }
+    p->bJsonIsRCStr = 1;
+    rc = jsonCacheInsert(ctx, p);
+    if( rc==SQLITE_NOMEM ) goto json_pfa_oom;
+    if( flgs & JSON_EDITABLE ){
+      pFromCache = p;
+      p = 0;
+      goto rebuild_from_cache;
+    }
+  }
+  return p;
+
+json_pfa_malformed:
+  if( flgs & JSON_KEEPERROR ){
+    p->nErr = 1;
+    return p;
+  }else{
+    jsonParseFree(p);
+    sqlite3_result_error(ctx, "malformed JSON", -1);
+    return 0;
+  }
+
+json_pfa_oom:
+  jsonParseFree(pFromCache);
+  jsonParseFree(p);
+  sqlite3_result_error_nomem(ctx);
+  return 0;
+}
+
+/*
+** Make the return value of a JSON function either the raw JSONB blob
+** or make it JSON text, depending on whether the JSON_BLOB flag is
+** set on the function.
+*/
+static void jsonReturnParse(
+  sqlite3_context *ctx,
+  JsonParse *p
+){
+  int flgs;
+  if( p->oom ){
+    sqlite3_result_error_nomem(ctx);
+    return;
+  }
+  flgs = SQLITE_PTR_TO_INT(sqlite3_user_data(ctx));
+  if( flgs & JSON_BLOB ){
+    if( p->nBlobAlloc>0 && !p->bReadOnly ){
+      sqlite3_result_blob(ctx, p->aBlob, p->nBlob, SQLITE_DYNAMIC);
+      p->nBlobAlloc = 0;
+    }else{
+      sqlite3_result_blob(ctx, p->aBlob, p->nBlob, SQLITE_TRANSIENT);
+    }
+  }else{
+    JsonString s;
+    jsonStringInit(&s, ctx);
+    p->delta = 0;
+    jsonTranslateBlobToText(p, 0, &s);
+    jsonReturnString(&s, p, ctx);
+    sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+  }
+}
+
+/****************************************************************************
+** SQL functions used for testing and debugging
+****************************************************************************/
+
+#if SQLITE_DEBUG
+/*
+** Decode JSONB bytes in aBlob[] starting at iStart through but not 
+** including iEnd.  Indent the
+** content by nIndent spaces.
+*/
+static void jsonDebugPrintBlob(
+  JsonParse *pParse, /* JSON content */
+  u32 iStart,        /* Start rendering here */
+  u32 iEnd,          /* Do not render this byte or any byte after this one */
+  int nIndent,       /* Indent by this many spaces */
+  sqlite3_str *pOut  /* Generate output into this sqlite3_str object */
+){
+  while( iStart<iEnd ){
+    u32 i, n, nn, sz = 0;
+    int showContent = 1;
+    u8 x = pParse->aBlob[iStart] & 0x0f;
+    u32 savedNBlob = pParse->nBlob;
+    sqlite3_str_appendf(pOut, "%5d:%*s", iStart, nIndent, "");
+    if( pParse->nBlobAlloc>pParse->nBlob ){
+      pParse->nBlob = pParse->nBlobAlloc;
+    }
+    nn = n = jsonbPayloadSize(pParse, iStart, &sz);
+    if( nn==0 ) nn = 1;
+    if( sz>0 && x<JSONB_ARRAY ){
+      nn += sz;
+    }
+    for(i=0; i<nn; i++){
+      sqlite3_str_appendf(pOut, " %02x", pParse->aBlob[iStart+i]);
+    }
+    if( n==0 ){
+      sqlite3_str_appendf(pOut, "   ERROR invalid node size\n");
+      iStart = n==0 ? iStart+1 : iEnd;
+      continue;
+    }
+    pParse->nBlob = savedNBlob;
+    if( iStart+n+sz>iEnd ){
+      iEnd = iStart+n+sz;
+      if( iEnd>pParse->nBlob ){
+        if( pParse->nBlobAlloc>0 && iEnd>pParse->nBlobAlloc ){
+          iEnd = pParse->nBlobAlloc;
+        }else{
+          iEnd = pParse->nBlob;
+        }
+      }
+    }
+    sqlite3_str_appendall(pOut,"  <-- ");
+    switch( x ){
+      case JSONB_NULL:     sqlite3_str_appendall(pOut,"null"); break;
+      case JSONB_TRUE:     sqlite3_str_appendall(pOut,"true"); break;
+      case JSONB_FALSE:    sqlite3_str_appendall(pOut,"false"); break;
+      case JSONB_INT:      sqlite3_str_appendall(pOut,"int"); break;
+      case JSONB_INT5:     sqlite3_str_appendall(pOut,"int5"); break;
+      case JSONB_FLOAT:    sqlite3_str_appendall(pOut,"float"); break;
+      case JSONB_FLOAT5:   sqlite3_str_appendall(pOut,"float5"); break;
+      case JSONB_TEXT:     sqlite3_str_appendall(pOut,"text"); break;
+      case JSONB_TEXTJ:    sqlite3_str_appendall(pOut,"textj"); break;
+      case JSONB_TEXT5:    sqlite3_str_appendall(pOut,"text5"); break;
+      case JSONB_TEXTRAW:  sqlite3_str_appendall(pOut,"textraw"); break;
+      case JSONB_ARRAY: {
+        sqlite3_str_appendf(pOut,"array, %u bytes\n", sz);
+        jsonDebugPrintBlob(pParse, iStart+n, iStart+n+sz, nIndent+2, pOut);
+        showContent = 0;
+        break;
+      }
+      case JSONB_OBJECT: {
+        sqlite3_str_appendf(pOut, "object, %u bytes\n", sz);
+        jsonDebugPrintBlob(pParse, iStart+n, iStart+n+sz, nIndent+2, pOut);
+        showContent = 0;
+        break;
+      }
+      default: {
+        sqlite3_str_appendall(pOut, "ERROR: unknown node type\n");
+        showContent = 0;
+        break;
+      }
+    }
+    if( showContent ){
+      if( sz==0 && x<=JSONB_FALSE ){
+        sqlite3_str_append(pOut, "\n", 1);
+      }else{
+        u32 i;
+        sqlite3_str_appendall(pOut, ": \"");
+        for(i=iStart+n; i<iStart+n+sz; i++){
+          u8 c = pParse->aBlob[i];
+          if( c<0x20 || c>=0x7f ) c = '.';
+          sqlite3_str_append(pOut, (char*)&c, 1);
+        }
+        sqlite3_str_append(pOut, "\"\n", 2);
+      }
+    }
+    iStart += n + sz;
+  }
+}
+static void jsonShowParse(JsonParse *pParse){
+  sqlite3_str out;
+  char zBuf[1000];
+  if( pParse==0 ){
+    printf("NULL pointer\n");
+    return;
+  }else{
+    printf("nBlobAlloc = %u\n", pParse->nBlobAlloc);
+    printf("nBlob = %u\n", pParse->nBlob);
+    printf("delta = %d\n", pParse->delta);
+    if( pParse->nBlob==0 ) return;
+    printf("content (bytes 0..%u):\n", pParse->nBlob-1);
+  }
+  sqlite3StrAccumInit(&out, 0, zBuf, sizeof(zBuf), 1000000);
+  jsonDebugPrintBlob(pParse, 0, pParse->nBlob, 0, &out);
+  printf("%s", sqlite3_str_value(&out));
+  sqlite3_str_reset(&out);
+}
+#endif /* SQLITE_DEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+** SQL function:   json_parse(JSON)
+**
+** Parse JSON using jsonParseFuncArg().  Return text that is a
+** human-readable dump of the binary JSONB for the input parameter.
+*/
+static void jsonParseFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonParse *p;        /* The parse */
+  sqlite3_str out;
+
+  assert( argc>=1 );
+  sqlite3StrAccumInit(&out, 0, 0, 0, 1000000);
+  p = jsonParseFuncArg(ctx, argv[0], 0);
+  if( p==0 ) return;
+  if( argc==1 ){
+    jsonDebugPrintBlob(p, 0, p->nBlob, 0, &out);
+    sqlite3_result_text64(ctx, out.zText, out.nChar, SQLITE_DYNAMIC, SQLITE_UTF8);
+  }else{
+    jsonShowParse(p);
+  }
+  jsonParseFree(p);
+}
+#endif /* SQLITE_DEBUG */
+
+/****************************************************************************
+** Scalar SQL function implementations
+****************************************************************************/
+
+/*
+** Implementation of the json_quote(VALUE) function.  Return a JSON value
+** corresponding to the SQL value input.  Mostly this means putting
+** double-quotes around strings and returning the unquoted string "null"
+** when given a NULL input.
+*/
+static void jsonQuoteFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonString jx;
+  UNUSED_PARAMETER(argc);
+
+  jsonStringInit(&jx, ctx);
+  jsonAppendSqlValue(&jx, argv[0]);
+  jsonReturnString(&jx, 0, 0);
+  sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+}
+
+/*
+** Implementation of the json_array(VALUE,...) function.  Return a JSON
+** array that contains all values given in arguments.  Or if any argument
+** is a BLOB, throw an error.
+*/
+static void jsonArrayFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+  JsonString jx;
+
+  jsonStringInit(&jx, ctx);
+  jsonAppendChar(&jx, '[');
+  for(i=0; i<argc; i++){
+    jsonAppendSeparator(&jx);
+    jsonAppendSqlValue(&jx, argv[i]);
+  }
+  jsonAppendChar(&jx, ']');
+  jsonReturnString(&jx, 0, 0);
+  sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+}
+
+/*
+** json_array_length(JSON)
+** json_array_length(JSON, PATH)
+**
+** Return the number of elements in the top-level JSON array.
+** Return 0 if the input is not a well-formed JSON array.
+*/
+static void jsonArrayLengthFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonParse *p;          /* The parse */
+  sqlite3_int64 cnt = 0;
+  u32 i;
+  u8 eErr = 0;
+
+  p = jsonParseFuncArg(ctx, argv[0], 0);
+  if( p==0 ) return;
+  if( argc==2 ){
+    const char *zPath = (const char*)sqlite3_value_text(argv[1]);
+    if( zPath==0 ){
+      jsonParseFree(p);
+      return;
+    }
+    i = jsonLookupStep(p, 0, zPath[0]=='$' ? zPath+1 : "@", 0);
+    if( JSON_LOOKUP_ISERROR(i) ){
+      if( i==JSON_LOOKUP_NOTFOUND ){
+        /* no-op */
+      }else if( i==JSON_LOOKUP_PATHERROR ){
+        jsonBadPathError(ctx, zPath);
+      }else{
+        sqlite3_result_error(ctx, "malformed JSON", -1);
+      }
+      eErr = 1;
+      i = 0;
+    }
+  }else{
+    i = 0;
+  }
+  if( (p->aBlob[i] & 0x0f)==JSONB_ARRAY ){
+    cnt = jsonbArrayCount(p, i);
+  }
+  if( !eErr ) sqlite3_result_int64(ctx, cnt);
+  jsonParseFree(p);
+}
+
+/* True if the string is all digits */
+static int jsonAllDigits(const char *z, int n){
+  int i;
+  for(i=0; i<n && sqlite3Isdigit(z[i]); i++){}
+  return i==n;
+}
+
+/* True if the string is all alphanumerics and underscores */
+static int jsonAllAlphanum(const char *z, int n){
+  int i;
+  for(i=0; i<n && (sqlite3Isalnum(z[i]) || z[i]=='_'); i++){}
+  return i==n;
+}
+
+/*
+** json_extract(JSON, PATH, ...)
+** "->"(JSON,PATH)
+** "->>"(JSON,PATH)
+**
+** Return the element described by PATH.  Return NULL if that PATH element
+** is not found.
+**
+** If JSON_JSON is set or if more that one PATH argument is supplied then
+** always return a JSON representation of the result.  If JSON_SQL is set,
+** then always return an SQL representation of the result.  If neither flag
+** is present and argc==2, then return JSON for objects and arrays and SQL
+** for all other values.
+**
+** When multiple PATH arguments are supplied, the result is a JSON array
+** containing the result of each PATH.
+**
+** Abbreviated JSON path expressions are allows if JSON_ABPATH, for
+** compatibility with PG.
+*/
+static void jsonExtractFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonParse *p = 0;      /* The parse */
+  int flags;             /* Flags associated with the function */
+  int i;                 /* Loop counter */
+  JsonString jx;         /* String for array result */
+
+  if( argc<2 ) return;
+  p = jsonParseFuncArg(ctx, argv[0], 0);
+  if( p==0 ) return;
+  flags = SQLITE_PTR_TO_INT(sqlite3_user_data(ctx));
+  jsonStringInit(&jx, ctx);
+  if( argc>2 ){
+    jsonAppendChar(&jx, '[');
+  }
+  for(i=1; i<argc; i++){
+    /* With a single PATH argument */
+    const char *zPath = (const char*)sqlite3_value_text(argv[i]);
+    int nPath;
+    u32 j;
+    if( zPath==0 ) goto json_extract_error;
+    nPath = sqlite3Strlen30(zPath);
+    if( zPath[0]=='$' ){
+      j = jsonLookupStep(p, 0, zPath+1, 0);
+    }else if( (flags & JSON_ABPATH) ){
+      /* The -> and ->> operators accept abbreviated PATH arguments.  This
+      ** is mostly for compatibility with PostgreSQL, but also for
+      ** convenience.
+      **
+      **     NUMBER   ==>  $[NUMBER]     // PG compatible
+      **     LABEL    ==>  $.LABEL       // PG compatible
+      **     [NUMBER] ==>  $[NUMBER]     // Not PG.  Purely for convenience
+      */
+      jsonStringInit(&jx, ctx);
+      if( jsonAllDigits(zPath, nPath) ){
+        jsonAppendRawNZ(&jx, "[", 1);
+        jsonAppendRaw(&jx, zPath, nPath);
+        jsonAppendRawNZ(&jx, "]", 2);
+      }else if( jsonAllAlphanum(zPath, nPath) ){
+        jsonAppendRawNZ(&jx, ".", 1);
+        jsonAppendRaw(&jx, zPath, nPath);
+      }else if( zPath[0]=='[' && nPath>=3 && zPath[nPath-1]==']' ){
+        jsonAppendRaw(&jx, zPath, nPath);
+      }else{
+        jsonAppendRawNZ(&jx, ".\"", 2);
+        jsonAppendRaw(&jx, zPath, nPath);
+        jsonAppendRawNZ(&jx, "\"", 1);
+      }
+      jsonStringTerminate(&jx);
+      j = jsonLookupStep(p, 0, jx.zBuf, 0);
+      jsonStringReset(&jx);
+    }else{
+      jsonBadPathError(ctx, zPath);
+      goto json_extract_error;
+    }
+    if( j<p->nBlob ){
+      if( argc==2 ){
+        if( flags & JSON_JSON ){
+          jsonStringInit(&jx, ctx);
+          jsonTranslateBlobToText(p, j, &jx);
+          jsonReturnString(&jx, 0, 0);
+          jsonStringReset(&jx);
+          assert( (flags & JSON_BLOB)==0 );
+          sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+        }else{
+          jsonReturnFromBlob(p, j, ctx, 0);
+          if( (flags & (JSON_SQL|JSON_BLOB))==0
+           && (p->aBlob[j]&0x0f)>=JSONB_ARRAY
+          ){
+            sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+          }
+        }
+      }else{
+        jsonAppendSeparator(&jx);
+        jsonTranslateBlobToText(p, j, &jx);
+      }
+    }else if( j==JSON_LOOKUP_NOTFOUND ){
+      if( argc==2 ){
+        goto json_extract_error;  /* Return NULL if not found */
+      }else{
+        jsonAppendSeparator(&jx);
+        jsonAppendRawNZ(&jx, "null", 4);
+      }
+    }else if( j==JSON_LOOKUP_ERROR ){
+      sqlite3_result_error(ctx, "malformed JSON", -1);
+      goto json_extract_error;
+    }else{
+      jsonBadPathError(ctx, zPath);
+      goto json_extract_error;
+    }
+  }
+  if( argc>2 ){
+    jsonAppendChar(&jx, ']');
+    jsonReturnString(&jx, 0, 0);
+    if( (flags & JSON_BLOB)==0 ){
+      sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+    }
+  }
+json_extract_error:
+  jsonStringReset(&jx);
+  jsonParseFree(p);
+  return;
+}
+
+/*
+** Return codes for jsonMergePatch()
+*/
+#define JSON_MERGE_OK          0     /* Success */
+#define JSON_MERGE_BADTARGET   1     /* Malformed TARGET blob */
+#define JSON_MERGE_BADPATCH    2     /* Malformed PATCH blob */
+#define JSON_MERGE_OOM         3     /* Out-of-memory condition */
+
+/*
+** RFC-7396 MergePatch for two JSONB blobs.
+**
+** pTarget is the target. pPatch is the patch.  The target is updated
+** in place.  The patch is read-only.
+**
+** The original RFC-7396 algorithm is this:
+**
+**   define MergePatch(Target, Patch):
+**     if Patch is an Object:
+**       if Target is not an Object:
+**         Target = {} # Ignore the contents and set it to an empty Object
+**     for each Name/Value pair in Patch:
+**         if Value is null:
+**           if Name exists in Target:
+**             remove the Name/Value pair from Target
+**         else:
+**           Target[Name] = MergePatch(Target[Name], Value)
+**       return Target
+**     else:
+**       return Patch
+**
+** Here is an equivalent algorithm restructured to show the actual
+** implementation:
+**
+** 01   define MergePatch(Target, Patch):
+** 02      if Patch is not an Object:
+** 03         return Patch
+** 04      else: // if Patch is an Object
+** 05         if Target is not an Object:
+** 06            Target = {}
+** 07      for each Name/Value pair in Patch:
+** 08         if Name exists in Target:
+** 09            if Value is null:
+** 10               remove the Name/Value pair from Target
+** 11            else
+** 12               Target[name] = MergePatch(Target[Name], Value)
+** 13         else if Value is not NULL:
+** 14            if Value is not an Object:
+** 15               Target[name] = Value
+** 16            else:
+** 17               Target[name] = MergePatch('{}',value)
+** 18      return Target
+**  |
+**  ^---- Line numbers referenced in comments in the implementation
+*/
+static int jsonMergePatch(
+  JsonParse *pTarget,      /* The JSON parser that contains the TARGET */
+  u32 iTarget,             /* Index of TARGET in pTarget->aBlob[] */
+  const JsonParse *pPatch, /* The PATCH */
+  u32 iPatch               /* Index of PATCH in pPatch->aBlob[] */
+){
+  u8 x;             /* Type of a single node */
+  u32 n, sz=0;      /* Return values from jsonbPayloadSize() */
+  u32 iTCursor;     /* Cursor position while scanning the target object */
+  u32 iTStart;      /* First label in the target object */
+  u32 iTEndBE;      /* Original first byte past end of target, before edit */
+  u32 iTEnd;        /* Current first byte past end of target */
+  u8 eTLabel;       /* Node type of the target label */
+  u32 iTLabel = 0;  /* Index of the label */
+  u32 nTLabel = 0;  /* Header size in bytes for the target label */
+  u32 szTLabel = 0; /* Size of the target label payload */
+  u32 iTValue = 0;  /* Index of the target value */
+  u32 nTValue = 0;  /* Header size of the target value */
+  u32 szTValue = 0; /* Payload size for the target value */
+
+  u32 iPCursor;     /* Cursor position while scanning the patch */
+  u32 iPEnd;        /* First byte past the end of the patch */
+  u8 ePLabel;       /* Node type of the patch label */
+  u32 iPLabel;      /* Start of patch label */
+  u32 nPLabel;      /* Size of header on the patch label */
+  u32 szPLabel;     /* Payload size of the patch label */
+  u32 iPValue;      /* Start of patch value */
+  u32 nPValue;      /* Header size for the patch value */
+  u32 szPValue;     /* Payload size of the patch value */
+
+  assert( iTarget>=0 && iTarget<pTarget->nBlob );
+  assert( iPatch>=0 && iPatch<pPatch->nBlob );
+  x = pPatch->aBlob[iPatch] & 0x0f;
+  if( x!=JSONB_OBJECT ){  /* Algorithm line 02 */
+    u32 szPatch;        /* Total size of the patch, header+payload */
+    u32 szTarget;       /* Total size of the target, header+payload */
+    n = jsonbPayloadSize(pPatch, iPatch, &sz);
+    szPatch = n+sz;
+    sz = 0;
+    n = jsonbPayloadSize(pTarget, iTarget, &sz);
+    szTarget = n+sz;
+    jsonBlobEdit(pTarget, iTarget, szTarget, pPatch->aBlob+iPatch, szPatch);
+    return pTarget->oom ? JSON_MERGE_OOM : JSON_MERGE_OK;  /* Line 03 */
+  }
+  x = pTarget->aBlob[iTarget] & 0x0f;
+  if( x!=JSONB_OBJECT ){  /* Algorithm line 05 */
+    n = jsonbPayloadSize(pTarget, iTarget, &sz);
+    jsonBlobEdit(pTarget, iTarget+n, sz, 0, 0);
+    x = pTarget->aBlob[iTarget];
+    pTarget->aBlob[iTarget] = (x & 0xf0) | JSONB_OBJECT;
+  }
+  n = jsonbPayloadSize(pPatch, iPatch, &sz);
+  if( NEVER(n==0) ) return JSON_MERGE_BADPATCH;
+  iPCursor = iPatch+n;
+  iPEnd = iPCursor+sz;
+  n = jsonbPayloadSize(pTarget, iTarget, &sz);
+  if( NEVER(n==0) ) return JSON_MERGE_BADTARGET;
+  iTStart = iTarget+n;
+  iTEndBE = iTStart+sz;
+
+  while( iPCursor<iPEnd ){  /* Algorithm line 07 */
+    iPLabel = iPCursor;
+    ePLabel = pPatch->aBlob[iPCursor] & 0x0f;
+    if( ePLabel<JSONB_TEXT || ePLabel>JSONB_TEXTRAW ){
+      return JSON_MERGE_BADPATCH;
+    }
+    nPLabel = jsonbPayloadSize(pPatch, iPCursor, &szPLabel);
+    if( nPLabel==0 ) return JSON_MERGE_BADPATCH;
+    iPValue = iPCursor + nPLabel + szPLabel;
+    if( iPValue>=iPEnd ) return JSON_MERGE_BADPATCH;
+    nPValue = jsonbPayloadSize(pPatch, iPValue, &szPValue);
+    if( nPValue==0 ) return JSON_MERGE_BADPATCH;
+    iPCursor = iPValue + nPValue + szPValue;
+    if( iPCursor>iPEnd ) return JSON_MERGE_BADPATCH;
+
+    iTCursor = iTStart;
+    iTEnd = iTEndBE + pTarget->delta;
+    while( iTCursor<iTEnd ){
+      int isEqual;   /* true if the patch and target labels match */
+      iTLabel = iTCursor;
+      eTLabel = pTarget->aBlob[iTCursor] & 0x0f;
+      if( eTLabel<JSONB_TEXT || eTLabel>JSONB_TEXTRAW ){
+        return JSON_MERGE_BADTARGET;
+      }
+      nTLabel = jsonbPayloadSize(pTarget, iTCursor, &szTLabel);
+      if( nTLabel==0 ) return JSON_MERGE_BADTARGET;
+      iTValue = iTLabel + nTLabel + szTLabel;
+      if( iTValue>=iTEnd ) return JSON_MERGE_BADTARGET;
+      nTValue = jsonbPayloadSize(pTarget, iTValue, &szTValue);
+      if( nTValue==0 ) return JSON_MERGE_BADTARGET;
+      if( iTValue + nTValue + szTValue > iTEnd ) return JSON_MERGE_BADTARGET;
+      isEqual = jsonLabelCompare(
+                   (const char*)&pPatch->aBlob[iPLabel+nPLabel],
+                   szPLabel,
+                   (ePLabel==JSONB_TEXT || ePLabel==JSONB_TEXTRAW),
+                   (const char*)&pTarget->aBlob[iTLabel+nTLabel],
+                   szTLabel,
+                   (eTLabel==JSONB_TEXT || eTLabel==JSONB_TEXTRAW));
+      if( isEqual ) break;
+      iTCursor = iTValue + nTValue + szTValue;
+    }
+    x = pPatch->aBlob[iPValue] & 0x0f;
+    if( iTCursor<iTEnd ){
+      /* A match was found.  Algorithm line 08 */
+      if( x==0 ){
+        /* Patch value is NULL.  Algorithm line 09 */
+        jsonBlobEdit(pTarget, iTLabel, nTLabel+szTLabel+nTValue+szTValue, 0,0);
+        /*  vvvvvv----- No OOM on a delete-only edit */
+        if( NEVER(pTarget->oom) ) return JSON_MERGE_OOM;
+      }else{
+        /* Algorithm line 12 */
+        int rc, savedDelta = pTarget->delta;
+        pTarget->delta = 0;
+        rc = jsonMergePatch(pTarget, iTValue, pPatch, iPValue);
+        if( rc ) return rc;
+        pTarget->delta += savedDelta;
+      }        
+    }else if( x>0 ){  /* Algorithm line 13 */
+      /* No match and patch value is not NULL */
+      u32 szNew = szPLabel+nPLabel;
+      if( (pPatch->aBlob[iPValue] & 0x0f)!=JSONB_OBJECT ){  /* Line 14 */
+        jsonBlobEdit(pTarget, iTEnd, 0, 0, szPValue+nPValue+szNew);
+        if( pTarget->oom ) return JSON_MERGE_OOM;
+        memcpy(&pTarget->aBlob[iTEnd], &pPatch->aBlob[iPLabel], szNew);
+        memcpy(&pTarget->aBlob[iTEnd+szNew], 
+               &pPatch->aBlob[iPValue], szPValue+nPValue);
+      }else{
+        int rc, savedDelta;
+        jsonBlobEdit(pTarget, iTEnd, 0, 0, szNew+1);
+        if( pTarget->oom ) return JSON_MERGE_OOM;
+        memcpy(&pTarget->aBlob[iTEnd], &pPatch->aBlob[iPLabel], szNew);
+        pTarget->aBlob[iTEnd+szNew] = 0x00;
+        savedDelta = pTarget->delta;
+        pTarget->delta = 0;
+        rc = jsonMergePatch(pTarget, iTEnd+szNew,pPatch,iPValue);
+        if( rc ) return rc;
+        pTarget->delta += savedDelta;
+      }
+    }
+  }
+  if( pTarget->delta ) jsonAfterEditSizeAdjust(pTarget, iTarget);
+  return pTarget->oom ? JSON_MERGE_OOM : JSON_MERGE_OK;
+}
+
+
+/*
+** Implementation of the json_mergepatch(JSON1,JSON2) function.  Return a JSON
+** object that is the result of running the RFC 7396 MergePatch() algorithm
+** on the two arguments.
+*/
+static void jsonPatchFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonParse *pTarget;    /* The TARGET */
+  JsonParse *pPatch;     /* The PATCH */
+  int rc;                /* Result code */
+
+  UNUSED_PARAMETER(argc);
+  assert( argc==2 );
+  pTarget = jsonParseFuncArg(ctx, argv[0], JSON_EDITABLE);
+  if( pTarget==0 ) return;
+  pPatch = jsonParseFuncArg(ctx, argv[1], 0);
+  if( pPatch ){
+    rc = jsonMergePatch(pTarget, 0, pPatch, 0);
+    if( rc==JSON_MERGE_OK ){
+      jsonReturnParse(ctx, pTarget);
+    }else if( rc==JSON_MERGE_OOM ){
+      sqlite3_result_error_nomem(ctx);
+    }else{
+      sqlite3_result_error(ctx, "malformed JSON", -1);
+    }
+    jsonParseFree(pPatch);
+  }
+  jsonParseFree(pTarget);
+}
+
+
+/*
+** Implementation of the json_object(NAME,VALUE,...) function.  Return a JSON
+** object that contains all name/value given in arguments.  Or if any name
+** is not a string or if any value is a BLOB, throw an error.
+*/
+static void jsonObjectFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+  JsonString jx;
+  const char *z;
+  u32 n;
+
+  if( argc&1 ){
+    sqlite3_result_error(ctx, "json_object() requires an even number "
+                                  "of arguments", -1);
+    return;
+  }
+  jsonStringInit(&jx, ctx);
+  jsonAppendChar(&jx, '{');
+  for(i=0; i<argc; i+=2){
+    if( sqlite3_value_type(argv[i])!=SQLITE_TEXT ){
+      sqlite3_result_error(ctx, "json_object() labels must be TEXT", -1);
+      jsonStringReset(&jx);
+      return;
+    }
+    jsonAppendSeparator(&jx);
+    z = (const char*)sqlite3_value_text(argv[i]);
+    n = sqlite3_value_bytes(argv[i]);
+    jsonAppendString(&jx, z, n);
+    jsonAppendChar(&jx, ':');
+    jsonAppendSqlValue(&jx, argv[i+1]);
+  }
+  jsonAppendChar(&jx, '}');
+  jsonReturnString(&jx, 0, 0);
+  sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+}
+
+
+/*
+** json_remove(JSON, PATH, ...)
+**
+** Remove the named elements from JSON and return the result.  malformed
+** JSON or PATH arguments result in an error.
+*/
+static void jsonRemoveFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonParse *p;          /* The parse */
+  const char *zPath = 0; /* Path of element to be removed */
+  int i;                 /* Loop counter */
+  u32 rc;                /* Subroutine return code */
+
+  if( argc<1 ) return;
+  p = jsonParseFuncArg(ctx, argv[0], argc>1 ? JSON_EDITABLE : 0);
+  if( p==0 ) return;
+  for(i=1; i<argc; i++){
+    zPath = (const char*)sqlite3_value_text(argv[i]);
+    if( zPath==0 ){
+      goto json_remove_done;
+    }
+    if( zPath[0]!='$' ){
+      goto json_remove_patherror;
+    }
+    if( zPath[1]==0 ){
+      /* json_remove(j,'$') returns NULL */
+      goto json_remove_done;
+    }
+    p->eEdit = JEDIT_DEL;
+    p->delta = 0;
+    rc = jsonLookupStep(p, 0, zPath+1, 0);
+    if( JSON_LOOKUP_ISERROR(rc) ){
+      if( rc==JSON_LOOKUP_NOTFOUND ){
+        continue;  /* No-op */
+      }else if( rc==JSON_LOOKUP_PATHERROR ){
+        jsonBadPathError(ctx, zPath);
+      }else{
+        sqlite3_result_error(ctx, "malformed JSON", -1);
+      }
+      goto json_remove_done;
+    }
+  }
+  jsonReturnParse(ctx, p);
+  jsonParseFree(p);
+  return;
+
+json_remove_patherror:
+  jsonBadPathError(ctx, zPath);
+
+json_remove_done:
+  jsonParseFree(p);
+  return;
+}
+
+/*
+** json_replace(JSON, PATH, VALUE, ...)
+**
+** Replace the value at PATH with VALUE.  If PATH does not already exist,
+** this routine is a no-op.  If JSON or PATH is malformed, throw an error.
+*/
+static void jsonReplaceFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  if( argc<1 ) return;
+  if( (argc&1)==0 ) {
+    jsonWrongNumArgs(ctx, "replace");
+    return;
+  }
+  jsonInsertIntoBlob(ctx, argc, argv, JEDIT_REPL);
+}
+
+
+/*
+** json_set(JSON, PATH, VALUE, ...)
+**
+** Set the value at PATH to VALUE.  Create the PATH if it does not already
+** exist.  Overwrite existing values that do exist.
+** If JSON or PATH is malformed, throw an error.
+**
+** json_insert(JSON, PATH, VALUE, ...)
+**
+** Create PATH and initialize it to VALUE.  If PATH already exists, this
+** routine is a no-op.  If JSON or PATH is malformed, throw an error.
+*/
+static void jsonSetFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+
+  int flags = SQLITE_PTR_TO_INT(sqlite3_user_data(ctx));
+  int bIsSet = (flags&JSON_ISSET)!=0;
+
+  if( argc<1 ) return;
+  if( (argc&1)==0 ) {
+    jsonWrongNumArgs(ctx, bIsSet ? "set" : "insert");
+    return;
+  }
+  jsonInsertIntoBlob(ctx, argc, argv, bIsSet ? JEDIT_SET : JEDIT_INS);
+}
+
+/*
+** json_type(JSON)
+** json_type(JSON, PATH)
+**
+** Return the top-level "type" of a JSON string.  json_type() raises an
+** error if either the JSON or PATH inputs are not well-formed.
+*/
+static void jsonTypeFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonParse *p;          /* The parse */
+  const char *zPath = 0;
+  u32 i;
+
+  p = jsonParseFuncArg(ctx, argv[0], 0);
+  if( p==0 ) return;
+  if( argc==2 ){
+    zPath = (const char*)sqlite3_value_text(argv[1]);
+    if( zPath==0 ) goto json_type_done;
+    if( zPath[0]!='$' ){
+      jsonBadPathError(ctx, zPath);
+      goto json_type_done;
+    }
+    i = jsonLookupStep(p, 0, zPath+1, 0);
+    if( JSON_LOOKUP_ISERROR(i) ){
+      if( i==JSON_LOOKUP_NOTFOUND ){
+        /* no-op */
+      }else if( i==JSON_LOOKUP_PATHERROR ){
+        jsonBadPathError(ctx, zPath);
+      }else{
+        sqlite3_result_error(ctx, "malformed JSON", -1);
+      }
+      goto json_type_done;
+    }
+  }else{
+    i = 0;
+  }
+  sqlite3_result_text(ctx, jsonbType[p->aBlob[i]&0x0f], -1, SQLITE_STATIC);
+json_type_done:
+  jsonParseFree(p);
+}
+
+/*
+** json_valid(JSON)
+** json_valid(JSON, FLAGS)
+**
+** Check the JSON argument to see if it is well-formed.  The FLAGS argument
+** encodes the various constraints on what is meant by "well-formed":
+**
+**     0x01      Canonical RFC-8259 JSON text
+**     0x02      JSON text with optional JSON-5 extensions
+**     0x04      Superficially appears to be JSONB
+**     0x08      Strictly well-formed JSONB
+**
+** If the FLAGS argument is omitted, it defaults to 1.  Useful values for
+** FLAGS include:
+**
+**    1          Strict canonical JSON text
+**    2          JSON text perhaps with JSON-5 extensions
+**    4          Superficially appears to be JSONB
+**    5          Canonical JSON text or superficial JSONB
+**    6          JSON-5 text or superficial JSONB
+**    8          Strict JSONB
+**    9          Canonical JSON text or strict JSONB
+**    10         JSON-5 text or strict JSONB
+**
+** Other flag combinations are redundant.  For example, every canonical
+** JSON text is also well-formed JSON-5 text, so FLAG values 2 and 3
+** are the same.  Similarly, any input that passes a strict JSONB validation
+** will also pass the superficial validation so 12 through 15 are the same
+** as 8 through 11 respectively.
+**
+** This routine runs in linear time to validate text and when doing strict
+** JSONB validation.  Superficial JSONB validation is constant time,
+** assuming the BLOB is already in memory.  The performance advantage
+** of superficial JSONB validation is why that option is provided.
+** Application developers can choose to do fast superficial validation or
+** slower strict validation, according to their specific needs.
+**
+** Only the lower four bits of the FLAGS argument are currently used.
+** Higher bits are reserved for future expansion.   To facilitate
+** compatibility, the current implementation raises an error if any bit
+** in FLAGS is set other than the lower four bits.
+**
+** The original circa 2015 implementation of the JSON routines in
+** SQLite only supported canonical RFC-8259 JSON text and the json_valid()
+** function only accepted one argument.  That is why the default value
+** for the FLAGS argument is 1, since FLAGS=1 causes this routine to only
+** recognize canonical RFC-8259 JSON text as valid.  The extra FLAGS
+** argument was added when the JSON routines were extended to support
+** JSON5-like extensions and binary JSONB stored in BLOBs.
+**
+** Return Values:
+**
+**   *   Raise an error if FLAGS is outside the range of 1 to 15.
+**   *   Return NULL if the input is NULL
+**   *   Return 1 if the input is well-formed.
+**   *   Return 0 if the input is not well-formed.
+*/
+static void jsonValidFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonParse *p;          /* The parse */
+  u8 flags = 1;
+  u8 res = 0;
+  if( argc==2 ){
+    i64 f = sqlite3_value_int64(argv[1]);
+    if( f<1 || f>15 ){
+      sqlite3_result_error(ctx, "FLAGS parameter to json_valid() must be"
+                                " between 1 and 15", -1);
+      return;
+    }
+    flags = f & 0x0f;
+  }
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_NULL: {
+#ifdef SQLITE_LEGACY_JSON_VALID
+      /* Incorrect legacy behavior was to return FALSE for a NULL input */
+      sqlite3_result_int(ctx, 0);
+#endif
+      return;
+    }
+    case SQLITE_BLOB: {
+      if( jsonFuncArgMightBeBinary(argv[0]) ){
+        if( flags & 0x04 ){
+          /* Superficial checking only - accomplished by the
+          ** jsonFuncArgMightBeBinary() call above. */
+          res = 1;
+        }else if( flags & 0x08 ){
+          /* Strict checking.  Check by translating BLOB->TEXT->BLOB.  If
+          ** no errors occur, call that a "strict check". */
+          JsonParse px;
+          u32 iErr;
+          memset(&px, 0, sizeof(px));
+          px.aBlob = (u8*)sqlite3_value_blob(argv[0]);
+          px.nBlob = sqlite3_value_bytes(argv[0]);
+          iErr = jsonbValidityCheck(&px, 0, px.nBlob, 1);
+          res = iErr==0;
+        }
+        break;
+      }
+      /* Fall through into interpreting the input as text.  See note
+      ** above at tag-20240123-a. */
+      /* no break */ deliberate_fall_through
+    }
+    default: {
+      JsonParse px;
+      if( (flags & 0x3)==0 ) break;
+      memset(&px, 0, sizeof(px));
+     
+      p = jsonParseFuncArg(ctx, argv[0], JSON_KEEPERROR);
+      if( p ){
+        if( p->oom ){
+          sqlite3_result_error_nomem(ctx);
+        }else if( p->nErr ){
+          /* no-op */
+        }else if( (flags & 0x02)!=0 || p->hasNonstd==0 ){
+          res = 1;
+        }
+        jsonParseFree(p);
+      }else{
+        sqlite3_result_error_nomem(ctx);
+      }
+      break;
+    }
+  }
+  sqlite3_result_int(ctx, res);
+}
+
+/*
+** json_error_position(JSON)
+**
+** If the argument is NULL, return NULL
+**
+** If the argument is BLOB, do a full validity check and return non-zero
+** if the check fails.  The return value is the approximate 1-based offset
+** to the byte of the element that contains the first error.
+**
+** Otherwise interpret the argument is TEXT (even if it is numeric) and
+** return the 1-based character position for where the parser first recognized
+** that the input was not valid JSON, or return 0 if the input text looks
+** ok.  JSON-5 extensions are accepted.
+*/
+static void jsonErrorFunc(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  i64 iErrPos = 0;       /* Error position to be returned */
+  JsonParse s;
+
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  memset(&s, 0, sizeof(s));
+  s.db = sqlite3_context_db_handle(ctx);
+  if( jsonFuncArgMightBeBinary(argv[0]) ){
+    s.aBlob = (u8*)sqlite3_value_blob(argv[0]);
+    s.nBlob = sqlite3_value_bytes(argv[0]);
+    iErrPos = (i64)jsonbValidityCheck(&s, 0, s.nBlob, 1);
+  }else{
+    s.zJson = (char*)sqlite3_value_text(argv[0]);
+    if( s.zJson==0 ) return;  /* NULL input or OOM */
+    s.nJson = sqlite3_value_bytes(argv[0]);
+    if( jsonConvertTextToBlob(&s,0) ){
+      if( s.oom ){
+        iErrPos = -1;
+      }else{
+        /* Convert byte-offset s.iErr into a character offset */
+        u32 k;
+        assert( s.zJson!=0 );  /* Because s.oom is false */
+        for(k=0; k<s.iErr && ALWAYS(s.zJson[k]); k++){
+          if( (s.zJson[k] & 0xc0)!=0x80 ) iErrPos++;
+        }
+        iErrPos++;
+      }
+    }
+  }
+  jsonParseReset(&s);
+  if( iErrPos<0 ){
+    sqlite3_result_error_nomem(ctx);
+  }else{
+    sqlite3_result_int64(ctx, iErrPos);
+  }
+}
+
+/****************************************************************************
+** Aggregate SQL function implementations
+****************************************************************************/
+/*
+** json_group_array(VALUE)
+**
+** Return a JSON array composed of all values in the aggregate.
+*/
+static void jsonArrayStep(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonString *pStr;
+  UNUSED_PARAMETER(argc);
+  pStr = (JsonString*)sqlite3_aggregate_context(ctx, sizeof(*pStr));
+  if( pStr ){
+    if( pStr->zBuf==0 ){
+      jsonStringInit(pStr, ctx);
+      jsonAppendChar(pStr, '[');
+    }else if( pStr->nUsed>1 ){
+      jsonAppendChar(pStr, ',');
+    }
+    pStr->pCtx = ctx;
+    jsonAppendSqlValue(pStr, argv[0]);
+  }
+}
+static void jsonArrayCompute(sqlite3_context *ctx, int isFinal){
+  JsonString *pStr;
+  pStr = (JsonString*)sqlite3_aggregate_context(ctx, 0);
+  if( pStr ){
+    int flags;
+    pStr->pCtx = ctx;
+    jsonAppendChar(pStr, ']');
+    flags = SQLITE_PTR_TO_INT(sqlite3_user_data(ctx));
+    if( pStr->eErr ){
+      jsonReturnString(pStr, 0, 0);
+      return;
+    }else if( flags & JSON_BLOB ){
+      jsonReturnStringAsBlob(pStr);
+      if( isFinal ){
+        if( !pStr->bStatic ) sqlite3RCStrUnref(pStr->zBuf);
+      }else{
+        jsonStringTrimOneChar(pStr);
+      }
+      return;
+    }else if( isFinal ){
+      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed,
+                          pStr->bStatic ? SQLITE_TRANSIENT :
+                              sqlite3RCStrUnref);
+      pStr->bStatic = 1;
+    }else{
+      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed, SQLITE_TRANSIENT);
+      jsonStringTrimOneChar(pStr);
+    }
+  }else{
+    sqlite3_result_text(ctx, "[]", 2, SQLITE_STATIC);
+  }
+  sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+}
+static void jsonArrayValue(sqlite3_context *ctx){
+  jsonArrayCompute(ctx, 0);
+}
+static void jsonArrayFinal(sqlite3_context *ctx){
+  jsonArrayCompute(ctx, 1);
+}
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+/*
+** This method works for both json_group_array() and json_group_object().
+** It works by removing the first element of the group by searching forward
+** to the first comma (",") that is not within a string and deleting all
+** text through that comma.
+*/
+static void jsonGroupInverse(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  unsigned int i;
+  int inStr = 0;
+  int nNest = 0;
+  char *z;
+  char c;
+  JsonString *pStr;
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+  pStr = (JsonString*)sqlite3_aggregate_context(ctx, 0);
+#ifdef NEVER
+  /* pStr is always non-NULL since jsonArrayStep() or jsonObjectStep() will
+  ** always have been called to initialize it */
+  if( NEVER(!pStr) ) return;
+#endif
+  z = pStr->zBuf;
+  for(i=1; i<pStr->nUsed && ((c = z[i])!=',' || inStr || nNest); i++){
+    if( c=='"' ){
+      inStr = !inStr;
+    }else if( c=='\\' ){
+      i++;
+    }else if( !inStr ){
+      if( c=='{' || c=='[' ) nNest++;
+      if( c=='}' || c==']' ) nNest--;
+    }
+  }
+  if( i<pStr->nUsed ){
+    pStr->nUsed -= i;
+    memmove(&z[1], &z[i+1], (size_t)pStr->nUsed-1);
+    z[pStr->nUsed] = 0;
+  }else{
+    pStr->nUsed = 1;
+  }
+}
+#else
+# define jsonGroupInverse 0
+#endif
+
+
+/*
+** json_group_obj(NAME,VALUE)
+**
+** Return a JSON object composed of all names and values in the aggregate.
+*/
+static void jsonObjectStep(
+  sqlite3_context *ctx,
+  int argc,
+  sqlite3_value **argv
+){
+  JsonString *pStr;
+  const char *z;
+  u32 n;
+  UNUSED_PARAMETER(argc);
+  pStr = (JsonString*)sqlite3_aggregate_context(ctx, sizeof(*pStr));
+  if( pStr ){
+    if( pStr->zBuf==0 ){
+      jsonStringInit(pStr, ctx);
+      jsonAppendChar(pStr, '{');
+    }else if( pStr->nUsed>1 ){
+      jsonAppendChar(pStr, ',');
+    }
+    pStr->pCtx = ctx;
+    z = (const char*)sqlite3_value_text(argv[0]);
+    n = sqlite3Strlen30(z);
+    jsonAppendString(pStr, z, n);
+    jsonAppendChar(pStr, ':');
+    jsonAppendSqlValue(pStr, argv[1]);
+  }
+}
+static void jsonObjectCompute(sqlite3_context *ctx, int isFinal){
+  JsonString *pStr;
+  pStr = (JsonString*)sqlite3_aggregate_context(ctx, 0);
+  if( pStr ){
+    int flags;
+    jsonAppendChar(pStr, '}');
+    pStr->pCtx = ctx;
+    flags = SQLITE_PTR_TO_INT(sqlite3_user_data(ctx));
+    if( pStr->eErr ){
+      jsonReturnString(pStr, 0, 0);
+      return;
+    }else if( flags & JSON_BLOB ){
+      jsonReturnStringAsBlob(pStr);
+      if( isFinal ){
+        if( !pStr->bStatic ) sqlite3RCStrUnref(pStr->zBuf);
+      }else{
+        jsonStringTrimOneChar(pStr);
+      }
+      return;
+    }else if( isFinal ){
+      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed,
+                          pStr->bStatic ? SQLITE_TRANSIENT :
+                          sqlite3RCStrUnref);
+      pStr->bStatic = 1;
+    }else{
+      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed, SQLITE_TRANSIENT);
+      jsonStringTrimOneChar(pStr);
+    }
+  }else{
+    sqlite3_result_text(ctx, "{}", 2, SQLITE_STATIC);
+  }
+  sqlite3_result_subtype(ctx, JSON_SUBTYPE);
+}
+static void jsonObjectValue(sqlite3_context *ctx){
+  jsonObjectCompute(ctx, 0);
+}
+static void jsonObjectFinal(sqlite3_context *ctx){
+  jsonObjectCompute(ctx, 1);
+}
+
+
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/****************************************************************************
+** The json_each virtual table
+****************************************************************************/
+typedef struct JsonParent JsonParent;
+struct JsonParent {
+  u32 iHead;                 /* Start of object or array */
+  u32 iValue;                /* Start of the value */
+  u32 iEnd;                  /* First byte past the end */
+  u32 nPath;                 /* Length of path */
+  i64 iKey;                  /* Key for JSONB_ARRAY */
+};
+
+typedef struct JsonEachCursor JsonEachCursor;
+struct JsonEachCursor {
+  sqlite3_vtab_cursor base;  /* Base class - must be first */
+  u32 iRowid;                /* The rowid */
+  u32 i;                     /* Index in sParse.aBlob[] of current row */
+  u32 iEnd;                  /* EOF when i equals or exceeds this value */
+  u32 nRoot;                 /* Size of the root path in bytes */
+  u8 eType;                  /* Type of the container for element i */
+  u8 bRecursive;             /* True for json_tree().  False for json_each() */
+  u32 nParent;               /* Current nesting depth */
+  u32 nParentAlloc;          /* Space allocated for aParent[] */
+  JsonParent *aParent;       /* Parent elements of i */
+  sqlite3 *db;               /* Database connection */
+  JsonString path;           /* Current path */
+  JsonParse sParse;          /* Parse of the input JSON */
+};
+typedef struct JsonEachConnection JsonEachConnection;
+struct JsonEachConnection {
+  sqlite3_vtab base;         /* Base class - must be first */
+  sqlite3 *db;               /* Database connection */
+};
+
+
+/* Constructor for the json_each virtual table */
+static int jsonEachConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  JsonEachConnection *pNew;
+  int rc;
+
+/* Column numbers */
+#define JEACH_KEY     0
+#define JEACH_VALUE   1
+#define JEACH_TYPE    2
+#define JEACH_ATOM    3
+#define JEACH_ID      4
+#define JEACH_PARENT  5
+#define JEACH_FULLKEY 6
+#define JEACH_PATH    7
+/* The xBestIndex method assumes that the JSON and ROOT columns are
+** the last two columns in the table.  Should this ever changes, be
+** sure to update the xBestIndex method. */
+#define JEACH_JSON    8
+#define JEACH_ROOT    9
+
+  UNUSED_PARAMETER(pzErr);
+  UNUSED_PARAMETER(argv);
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(pAux);
+  rc = sqlite3_declare_vtab(db,
+     "CREATE TABLE x(key,value,type,atom,id,parent,fullkey,path,"
+                    "json HIDDEN,root HIDDEN)");
+  if( rc==SQLITE_OK ){
+    pNew = (JsonEachConnection*)sqlite3DbMallocZero(db, sizeof(*pNew));
+    *ppVtab = (sqlite3_vtab*)pNew;
+    if( pNew==0 ) return SQLITE_NOMEM;
+    sqlite3_vtab_config(db, SQLITE_VTAB_INNOCUOUS);
+    pNew->db = db;
+  }
+  return rc;
+}
+
+/* destructor for json_each virtual table */
+static int jsonEachDisconnect(sqlite3_vtab *pVtab){
+  JsonEachConnection *p = (JsonEachConnection*)pVtab;
+  sqlite3DbFree(p->db, pVtab);
+  return SQLITE_OK;
+}
+
+/* constructor for a JsonEachCursor object for json_each(). */
+static int jsonEachOpenEach(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
+  JsonEachConnection *pVtab = (JsonEachConnection*)p;
+  JsonEachCursor *pCur;
+
+  UNUSED_PARAMETER(p);
+  pCur = sqlite3DbMallocZero(pVtab->db, sizeof(*pCur));
+  if( pCur==0 ) return SQLITE_NOMEM;
+  pCur->db = pVtab->db;
+  jsonStringZero(&pCur->path);
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/* constructor for a JsonEachCursor object for json_tree(). */
+static int jsonEachOpenTree(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
+  int rc = jsonEachOpenEach(p, ppCursor);
+  if( rc==SQLITE_OK ){
+    JsonEachCursor *pCur = (JsonEachCursor*)*ppCursor;
+    pCur->bRecursive = 1;
+  }
+  return rc;
+}
+
+/* Reset a JsonEachCursor back to its original state.  Free any memory
+** held. */
+static void jsonEachCursorReset(JsonEachCursor *p){
+  jsonParseReset(&p->sParse);
+  jsonStringReset(&p->path);
+  sqlite3DbFree(p->db, p->aParent);
+  p->iRowid = 0;
+  p->i = 0;
+  p->aParent = 0;
+  p->nParent = 0;
+  p->nParentAlloc = 0;
+  p->iEnd = 0;
+  p->eType = 0;
+}
+
+/* Destructor for a jsonEachCursor object */
+static int jsonEachClose(sqlite3_vtab_cursor *cur){
+  JsonEachCursor *p = (JsonEachCursor*)cur;
+  jsonEachCursorReset(p);
+  
+  sqlite3DbFree(p->db, cur);
+  return SQLITE_OK;
+}
+
+/* Return TRUE if the jsonEachCursor object has been advanced off the end
+** of the JSON object */
+static int jsonEachEof(sqlite3_vtab_cursor *cur){
+  JsonEachCursor *p = (JsonEachCursor*)cur;
+  return p->i >= p->iEnd;
+}
+
+/*
+** If the cursor is currently pointing at the label of a object entry,
+** then return the index of the value.  For all other cases, return the
+** current pointer position, which is the value.
+*/
+static int jsonSkipLabel(JsonEachCursor *p){
+  if( p->eType==JSONB_OBJECT ){
+    u32 sz = 0;
+    u32 n = jsonbPayloadSize(&p->sParse, p->i, &sz);
+    return p->i + n + sz;
+  }else{
+    return p->i;
+  }
+}
+
+/*
+** Append the path name for the current element.
+*/
+static void jsonAppendPathName(JsonEachCursor *p){
+  assert( p->nParent>0 );
+  assert( p->eType==JSONB_ARRAY || p->eType==JSONB_OBJECT );
+  if( p->eType==JSONB_ARRAY ){
+    jsonPrintf(30, &p->path, "[%lld]", p->aParent[p->nParent-1].iKey);
+  }else{
+    u32 n, sz = 0, k, i;
+    const char *z;
+    int needQuote = 0;
+    n = jsonbPayloadSize(&p->sParse, p->i, &sz);
+    k = p->i + n;
+    z = (const char*)&p->sParse.aBlob[k];
+    if( sz==0 || !sqlite3Isalpha(z[0]) ){
+      needQuote = 1;
+    }else{
+      for(i=0; i<sz; i++){
+        if( !sqlite3Isalnum(z[i]) ){
+          needQuote = 1;
+          break;
+        }
+      }
+    }
+    if( needQuote ){
+      jsonPrintf(sz+4,&p->path,".\"%.*s\"", sz, z);
+    }else{
+      jsonPrintf(sz+2,&p->path,".%.*s", sz, z);
+    }
+  }
+}
+
+/* Advance the cursor to the next element for json_tree() */
+static int jsonEachNext(sqlite3_vtab_cursor *cur){
+  JsonEachCursor *p = (JsonEachCursor*)cur;
+  int rc = SQLITE_OK;
+  if( p->bRecursive ){
+    u8 x;
+    u8 levelChange = 0;
+    u32 n, sz = 0;
+    u32 i = jsonSkipLabel(p);
+    x = p->sParse.aBlob[i] & 0x0f;
+    n = jsonbPayloadSize(&p->sParse, i, &sz);
+    if( x==JSONB_OBJECT || x==JSONB_ARRAY ){
+      JsonParent *pParent;
+      if( p->nParent>=p->nParentAlloc ){
+        JsonParent *pNew;
+        u64 nNew;
+        nNew = p->nParentAlloc*2 + 3;
+        pNew = sqlite3DbRealloc(p->db, p->aParent, sizeof(JsonParent)*nNew);
+        if( pNew==0 ) return SQLITE_NOMEM;
+        p->nParentAlloc = (u32)nNew;
+        p->aParent = pNew;
+      }
+      levelChange = 1;
+      pParent = &p->aParent[p->nParent];
+      pParent->iHead = p->i;
+      pParent->iValue = i;
+      pParent->iEnd = i + n + sz;
+      pParent->iKey = -1;
+      pParent->nPath = (u32)p->path.nUsed;
+      if( p->eType && p->nParent ){
+        jsonAppendPathName(p);
+        if( p->path.eErr ) rc = SQLITE_NOMEM;
+      }
+      p->nParent++;
+      p->i = i + n;
+    }else{
+      p->i = i + n + sz;
+    }
+    while( p->nParent>0 && p->i >= p->aParent[p->nParent-1].iEnd ){
+      p->nParent--;
+      p->path.nUsed = p->aParent[p->nParent].nPath;
+      levelChange = 1;
+    }
+    if( levelChange ){
+      if( p->nParent>0 ){
+        JsonParent *pParent = &p->aParent[p->nParent-1];
+        u32 iVal = pParent->iValue;
+        p->eType = p->sParse.aBlob[iVal] & 0x0f;
+      }else{
+        p->eType = 0;
+      }
+    }
+  }else{
+    u32 n, sz = 0;
+    u32 i = jsonSkipLabel(p);
+    n = jsonbPayloadSize(&p->sParse, i, &sz);
+    p->i = i + n + sz;
+  }
+  if( p->eType==JSONB_ARRAY && p->nParent ){
+    p->aParent[p->nParent-1].iKey++;
+  }
+  p->iRowid++;
+  return rc;
+}
+
+/* Length of the path for rowid==0 in bRecursive mode.
+*/
+static int jsonEachPathLength(JsonEachCursor *p){
+  u32 n = p->path.nUsed;
+  char *z = p->path.zBuf;
+  if( p->iRowid==0 && p->bRecursive && n>=2 ){
+    while( n>1 ){
+      n--;
+      if( z[n]=='[' || z[n]=='.' ){
+        u32 x, sz = 0;
+        char cSaved = z[n];
+        z[n] = 0;
+        assert( p->sParse.eEdit==0 );
+        x = jsonLookupStep(&p->sParse, 0, z+1, 0);
+        z[n] = cSaved;
+        if( JSON_LOOKUP_ISERROR(x) ) continue;
+        if( x + jsonbPayloadSize(&p->sParse, x, &sz) == p->i ) break;
+      }
+    }
+  }
+  return n;
+}
+
+/* Return the value of a column */
+static int jsonEachColumn(
+  sqlite3_vtab_cursor *cur,   /* The cursor */
+  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
+  int iColumn                 /* Which column to return */
+){
+  JsonEachCursor *p = (JsonEachCursor*)cur;
+  switch( iColumn ){
+    case JEACH_KEY: {
+      if( p->nParent==0 ){
+        u32 n, j;
+        if( p->nRoot==1 ) break;
+        j = jsonEachPathLength(p);
+        n = p->nRoot - j;
+        if( n==0 ){
+          break;
+        }else if( p->path.zBuf[j]=='[' ){
+          i64 x;
+          sqlite3Atoi64(&p->path.zBuf[j+1], &x, n-1, SQLITE_UTF8);
+          sqlite3_result_int64(ctx, x);
+        }else if( p->path.zBuf[j+1]=='"' ){
+          sqlite3_result_text(ctx, &p->path.zBuf[j+2], n-3, SQLITE_TRANSIENT);
+        }else{
+          sqlite3_result_text(ctx, &p->path.zBuf[j+1], n-1, SQLITE_TRANSIENT);
+        }
+        break;
+      }
+      if( p->eType==JSONB_OBJECT ){
+        jsonReturnFromBlob(&p->sParse, p->i, ctx, 1);
+      }else{
+        assert( p->eType==JSONB_ARRAY );
+        sqlite3_result_int64(ctx, p->aParent[p->nParent-1].iKey);
+      }
+      break;
+    }
+    case JEACH_VALUE: {
+      u32 i = jsonSkipLabel(p);
+      jsonReturnFromBlob(&p->sParse, i, ctx, 1);
+      break;
+    }
+    case JEACH_TYPE: {
+      u32 i = jsonSkipLabel(p);
+      u8 eType = p->sParse.aBlob[i] & 0x0f;
+      sqlite3_result_text(ctx, jsonbType[eType], -1, SQLITE_STATIC);
+      break;
+    }
+    case JEACH_ATOM: {
+      u32 i = jsonSkipLabel(p);
+      if( (p->sParse.aBlob[i] & 0x0f)<JSONB_ARRAY ){
+        jsonReturnFromBlob(&p->sParse, i, ctx, 1);
+      }
+      break;
+    }
+    case JEACH_ID: {
+      sqlite3_result_int64(ctx, (sqlite3_int64)p->i);
+      break;
+    }
+    case JEACH_PARENT: {
+      if( p->nParent>0 && p->bRecursive ){
+        sqlite3_result_int64(ctx, p->aParent[p->nParent-1].iHead);
+      }
+      break;
+    }
+    case JEACH_FULLKEY: {
+      u64 nBase = p->path.nUsed;
+      if( p->nParent ) jsonAppendPathName(p);
+      sqlite3_result_text64(ctx, p->path.zBuf, p->path.nUsed,
+                            SQLITE_TRANSIENT, SQLITE_UTF8);
+      p->path.nUsed = nBase;
+      break;
+    }
+    case JEACH_PATH: {
+      u32 n = jsonEachPathLength(p);
+      sqlite3_result_text64(ctx, p->path.zBuf, n,
+                            SQLITE_TRANSIENT, SQLITE_UTF8);
+      break;
+    }
+    default: {
+      sqlite3_result_text(ctx, p->path.zBuf, p->nRoot, SQLITE_STATIC);
+      break;
+    }
+    case JEACH_JSON: {
+      if( p->sParse.zJson==0 ){
+        sqlite3_result_blob(ctx, p->sParse.aBlob, p->sParse.nBlob,
+                            SQLITE_STATIC);
+      }else{
+        sqlite3_result_text(ctx, p->sParse.zJson, -1, SQLITE_STATIC);
+      }
+      break;
+    }
+  }
+  return SQLITE_OK;
+}
+
+/* Return the current rowid value */
+static int jsonEachRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  JsonEachCursor *p = (JsonEachCursor*)cur;
+  *pRowid = p->iRowid;
+  return SQLITE_OK;
+}
+
+/* The query strategy is to look for an equality constraint on the json
+** column.  Without such a constraint, the table cannot operate.  idxNum is
+** 1 if the constraint is found, 3 if the constraint and zRoot are found,
+** and 0 otherwise.
+*/
+static int jsonEachBestIndex(
+  sqlite3_vtab *tab,
+  sqlite3_index_info *pIdxInfo
+){
+  int i;                     /* Loop counter or computed array index */
+  int aIdx[2];               /* Index of constraints for JSON and ROOT */
+  int unusableMask = 0;      /* Mask of unusable JSON and ROOT constraints */
+  int idxMask = 0;           /* Mask of usable == constraints JSON and ROOT */
+  const struct sqlite3_index_constraint *pConstraint;
+
+  /* This implementation assumes that JSON and ROOT are the last two
+  ** columns in the table */
+  assert( JEACH_ROOT == JEACH_JSON+1 );
+  UNUSED_PARAMETER(tab);
+  aIdx[0] = aIdx[1] = -1;
+  pConstraint = pIdxInfo->aConstraint;
+  for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
+    int iCol;
+    int iMask;
+    if( pConstraint->iColumn < JEACH_JSON ) continue;
+    iCol = pConstraint->iColumn - JEACH_JSON;
+    assert( iCol==0 || iCol==1 );
+    testcase( iCol==0 );
+    iMask = 1 << iCol;
+    if( pConstraint->usable==0 ){
+      unusableMask |= iMask;
+    }else if( pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      aIdx[iCol] = i;
+      idxMask |= iMask;
+    }
+  }
+  if( pIdxInfo->nOrderBy>0
+   && pIdxInfo->aOrderBy[0].iColumn<0
+   && pIdxInfo->aOrderBy[0].desc==0
+  ){
+    pIdxInfo->orderByConsumed = 1;
+  }
+
+  if( (unusableMask & ~idxMask)!=0 ){
+    /* If there are any unusable constraints on JSON or ROOT, then reject
+    ** this entire plan */
+    return SQLITE_CONSTRAINT;
+  }
+  if( aIdx[0]<0 ){
+    /* No JSON input.  Leave estimatedCost at the huge value that it was
+    ** initialized to to discourage the query planner from selecting this
+    ** plan. */
+    pIdxInfo->idxNum = 0;
+  }else{
+    pIdxInfo->estimatedCost = 1.0;
+    i = aIdx[0];
+    pIdxInfo->aConstraintUsage[i].argvIndex = 1;
+    pIdxInfo->aConstraintUsage[i].omit = 1;
+    if( aIdx[1]<0 ){
+      pIdxInfo->idxNum = 1;  /* Only JSON supplied.  Plan 1 */
+    }else{
+      i = aIdx[1];
+      pIdxInfo->aConstraintUsage[i].argvIndex = 2;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+      pIdxInfo->idxNum = 3;  /* Both JSON and ROOT are supplied.  Plan 3 */
+    }
+  }
+  return SQLITE_OK;
+}
+
+/* Start a search on a new JSON string */
+static int jsonEachFilter(
+  sqlite3_vtab_cursor *cur,
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  JsonEachCursor *p = (JsonEachCursor*)cur;
+  const char *zRoot = 0;
+  u32 i, n, sz;
+
+  UNUSED_PARAMETER(idxStr);
+  UNUSED_PARAMETER(argc);
+  jsonEachCursorReset(p);
+  if( idxNum==0 ) return SQLITE_OK;
+  memset(&p->sParse, 0, sizeof(p->sParse));
+  p->sParse.nJPRef = 1;
+  p->sParse.db = p->db;
+  if( jsonFuncArgMightBeBinary(argv[0]) ){
+    p->sParse.nBlob = sqlite3_value_bytes(argv[0]);
+    p->sParse.aBlob = (u8*)sqlite3_value_blob(argv[0]);
+  }else{
+    p->sParse.zJson = (char*)sqlite3_value_text(argv[0]);
+    p->sParse.nJson = sqlite3_value_bytes(argv[0]);
+    if( p->sParse.zJson==0 ){
+      p->i = p->iEnd = 0;
+      return SQLITE_OK;
+    }      
+    if( jsonConvertTextToBlob(&p->sParse, 0) ){
+      if( p->sParse.oom ){
+        return SQLITE_NOMEM;
+      }
+      goto json_each_malformed_input;
+    }
+  }
+  if( idxNum==3 ){
+    zRoot = (const char*)sqlite3_value_text(argv[1]);
+    if( zRoot==0 ) return SQLITE_OK;
+    if( zRoot[0]!='$' ){
+      sqlite3_free(cur->pVtab->zErrMsg);
+      cur->pVtab->zErrMsg = jsonBadPathError(0, zRoot);
+      jsonEachCursorReset(p);
+      return cur->pVtab->zErrMsg ? SQLITE_ERROR : SQLITE_NOMEM;
+    }
+    p->nRoot = sqlite3Strlen30(zRoot);
+    if( zRoot[1]==0 ){
+      i = p->i = 0;
+      p->eType = 0;
+    }else{
+      i = jsonLookupStep(&p->sParse, 0, zRoot+1, 0);
+      if( JSON_LOOKUP_ISERROR(i) ){
+        if( i==JSON_LOOKUP_NOTFOUND ){
+          p->i = 0;
+          p->eType = 0;
+          p->iEnd = 0;
+          return SQLITE_OK;
+        }
+        sqlite3_free(cur->pVtab->zErrMsg);
+        cur->pVtab->zErrMsg = jsonBadPathError(0, zRoot);
+        jsonEachCursorReset(p);
+        return cur->pVtab->zErrMsg ? SQLITE_ERROR : SQLITE_NOMEM;
+      }
+      if( p->sParse.iLabel ){
+        p->i = p->sParse.iLabel;
+        p->eType = JSONB_OBJECT;
+      }else{
+        p->i = i;
+        p->eType = JSONB_ARRAY;
+      }
+    }
+    jsonAppendRaw(&p->path, zRoot, p->nRoot);
+  }else{
+    i = p->i = 0;
+    p->eType = 0;
+    p->nRoot = 1;
+    jsonAppendRaw(&p->path, "$", 1);
+  }
+  p->nParent = 0;
+  n = jsonbPayloadSize(&p->sParse, i, &sz);
+  p->iEnd = i+n+sz;
+  if( (p->sParse.aBlob[i] & 0x0f)>=JSONB_ARRAY && !p->bRecursive ){
+    p->i = i + n;
+    p->eType = p->sParse.aBlob[i] & 0x0f;
+    p->aParent = sqlite3DbMallocZero(p->db, sizeof(JsonParent));
+    if( p->aParent==0 ) return SQLITE_NOMEM;
+    p->nParent = 1;
+    p->nParentAlloc = 1;
+    p->aParent[0].iKey = 0;
+    p->aParent[0].iEnd = p->iEnd;
+    p->aParent[0].iHead = p->i;
+    p->aParent[0].iValue = i;
+  }
+  return SQLITE_OK;
+
+json_each_malformed_input:
+  sqlite3_free(cur->pVtab->zErrMsg);
+  cur->pVtab->zErrMsg = sqlite3_mprintf("malformed JSON");
+  jsonEachCursorReset(p);
+  return cur->pVtab->zErrMsg ? SQLITE_ERROR : SQLITE_NOMEM;
+}
+
+/* The methods of the json_each virtual table */
+static sqlite3_module jsonEachModule = {
+  0,                         /* iVersion */
+  0,                         /* xCreate */
+  jsonEachConnect,           /* xConnect */
+  jsonEachBestIndex,         /* xBestIndex */
+  jsonEachDisconnect,        /* xDisconnect */
+  0,                         /* xDestroy */
+  jsonEachOpenEach,          /* xOpen - open a cursor */
+  jsonEachClose,             /* xClose - close a cursor */
+  jsonEachFilter,            /* xFilter - configure scan constraints */
+  jsonEachNext,              /* xNext - advance a cursor */
+  jsonEachEof,               /* xEof - check for end of scan */
+  jsonEachColumn,            /* xColumn - read data */
+  jsonEachRowid,             /* xRowid - read data */
+  0,                         /* xUpdate */
+  0,                         /* xBegin */
+  0,                         /* xSync */
+  0,                         /* xCommit */
+  0,                         /* xRollback */
+  0,                         /* xFindMethod */
+  0,                         /* xRename */
+  0,                         /* xSavepoint */
+  0,                         /* xRelease */
+  0,                         /* xRollbackTo */
+  0,                         /* xShadowName */
+  0                          /* xIntegrity */
+};
+
+/* The methods of the json_tree virtual table. */
+static sqlite3_module jsonTreeModule = {
+  0,                         /* iVersion */
+  0,                         /* xCreate */
+  jsonEachConnect,           /* xConnect */
+  jsonEachBestIndex,         /* xBestIndex */
+  jsonEachDisconnect,        /* xDisconnect */
+  0,                         /* xDestroy */
+  jsonEachOpenTree,          /* xOpen - open a cursor */
+  jsonEachClose,             /* xClose - close a cursor */
+  jsonEachFilter,            /* xFilter - configure scan constraints */
+  jsonEachNext,              /* xNext - advance a cursor */
+  jsonEachEof,               /* xEof - check for end of scan */
+  jsonEachColumn,            /* xColumn - read data */
+  jsonEachRowid,             /* xRowid - read data */
+  0,                         /* xUpdate */
+  0,                         /* xBegin */
+  0,                         /* xSync */
+  0,                         /* xCommit */
+  0,                         /* xRollback */
+  0,                         /* xFindMethod */
+  0,                         /* xRename */
+  0,                         /* xSavepoint */
+  0,                         /* xRelease */
+  0,                         /* xRollbackTo */
+  0,                         /* xShadowName */
+  0                          /* xIntegrity */
+};
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+#endif /* !defined(SQLITE_OMIT_JSON) */
+
+/*
+** Register JSON functions.
+*/
+void sqlite3RegisterJsonFunctions(void){
+#ifndef SQLITE_OMIT_JSON
+  static FuncDef aJsonFunc[] = {
+    /*   sqlite3_result_subtype() ----,  ,--- sqlite3_value_subtype()       */
+    /*                                |  |                                  */
+    /*             Uses cache ------, |  | ,---- Returns JSONB              */
+    /*                              | |  | |                                */
+    /*     Number of arguments ---, | |  | | ,--- Flags                     */
+    /*                            | | |  | | |                              */
+    JFUNCTION(json,               1,1,1, 0,0,0,          jsonRemoveFunc),
+    JFUNCTION(jsonb,              1,1,0, 0,1,0,          jsonRemoveFunc),
+    JFUNCTION(json_array,        -1,0,1, 1,0,0,          jsonArrayFunc),
+    JFUNCTION(jsonb_array,       -1,0,1, 1,1,0,          jsonArrayFunc),
+    JFUNCTION(json_array_length,  1,1,0, 0,0,0,          jsonArrayLengthFunc),
+    JFUNCTION(json_array_length,  2,1,0, 0,0,0,          jsonArrayLengthFunc),
+    JFUNCTION(json_error_position,1,1,0, 0,0,0,          jsonErrorFunc),
+    JFUNCTION(json_extract,      -1,1,1, 0,0,0,          jsonExtractFunc),
+    JFUNCTION(jsonb_extract,     -1,1,0, 0,1,0,          jsonExtractFunc),
+    JFUNCTION(->,                 2,1,1, 0,0,JSON_JSON,  jsonExtractFunc),
+    JFUNCTION(->>,                2,1,0, 0,0,JSON_SQL,   jsonExtractFunc),
+    JFUNCTION(json_insert,       -1,1,1, 1,0,0,          jsonSetFunc),
+    JFUNCTION(jsonb_insert,      -1,1,0, 1,1,0,          jsonSetFunc),
+    JFUNCTION(json_object,       -1,0,1, 1,0,0,          jsonObjectFunc),
+    JFUNCTION(jsonb_object,      -1,0,1, 1,1,0,          jsonObjectFunc),
+    JFUNCTION(json_patch,         2,1,1, 0,0,0,          jsonPatchFunc),
+    JFUNCTION(jsonb_patch,        2,1,0, 0,1,0,          jsonPatchFunc),
+    JFUNCTION(json_quote,         1,0,1, 1,0,0,          jsonQuoteFunc),
+    JFUNCTION(json_remove,       -1,1,1, 0,0,0,          jsonRemoveFunc),
+    JFUNCTION(jsonb_remove,      -1,1,0, 0,1,0,          jsonRemoveFunc),
+    JFUNCTION(json_replace,      -1,1,1, 1,0,0,          jsonReplaceFunc),
+    JFUNCTION(jsonb_replace,     -1,1,0, 1,1,0,          jsonReplaceFunc),
+    JFUNCTION(json_set,          -1,1,1, 1,0,JSON_ISSET, jsonSetFunc),
+    JFUNCTION(jsonb_set,         -1,1,0, 1,1,JSON_ISSET, jsonSetFunc),
+    JFUNCTION(json_type,          1,1,0, 0,0,0,          jsonTypeFunc),
+    JFUNCTION(json_type,          2,1,0, 0,0,0,          jsonTypeFunc),
+    JFUNCTION(json_valid,         1,1,0, 0,0,0,          jsonValidFunc),
+    JFUNCTION(json_valid,         2,1,0, 0,0,0,          jsonValidFunc),
+#if SQLITE_DEBUG
+    JFUNCTION(json_parse,         1,1,0, 0,0,0,          jsonParseFunc),
+#endif
+    WAGGREGATE(json_group_array,  1, 0, 0,
+       jsonArrayStep, jsonArrayFinal, jsonArrayValue, jsonGroupInverse,
+       SQLITE_SUBTYPE|SQLITE_RESULT_SUBTYPE|SQLITE_UTF8|
+       SQLITE_DETERMINISTIC),
+    WAGGREGATE(jsonb_group_array, 1, JSON_BLOB, 0,
+       jsonArrayStep, jsonArrayFinal, jsonArrayValue, jsonGroupInverse,
+       SQLITE_SUBTYPE|SQLITE_RESULT_SUBTYPE|SQLITE_UTF8|SQLITE_DETERMINISTIC),
+    WAGGREGATE(json_group_object, 2, 0, 0,
+       jsonObjectStep, jsonObjectFinal, jsonObjectValue, jsonGroupInverse,
+       SQLITE_SUBTYPE|SQLITE_RESULT_SUBTYPE|SQLITE_UTF8|SQLITE_DETERMINISTIC),
+    WAGGREGATE(jsonb_group_object,2, JSON_BLOB, 0,
+       jsonObjectStep, jsonObjectFinal, jsonObjectValue, jsonGroupInverse,
+       SQLITE_SUBTYPE|SQLITE_RESULT_SUBTYPE|SQLITE_UTF8|
+       SQLITE_DETERMINISTIC)
+  };
+  sqlite3InsertBuiltinFuncs(aJsonFunc, ArraySize(aJsonFunc));
+#endif
+}
+
+#if  !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_JSON)
+/*
+** Register the JSON table-valued functions
+*/
+int sqlite3JsonTableFunctions(sqlite3 *db){
+  int rc = SQLITE_OK;
+  static const struct {
+    const char *zName;
+    sqlite3_module *pModule;
+  } aMod[] = {
+    { "json_each",            &jsonEachModule               },
+    { "json_tree",            &jsonTreeModule               },
+  };
+  unsigned int i;
+  for(i=0; i<sizeof(aMod)/sizeof(aMod[0]) && rc==SQLITE_OK; i++){
+    rc = sqlite3_create_module(db, aMod[i].zName, aMod[i].pModule, 0);
+  }
+  return rc;
+}
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_JSON) */
diff --git a/src/legacy.c b/src/legacy.c
new file mode 100644
index 0000000..867587e
--- /dev/null
+++ b/src/legacy.c
@@ -0,0 +1,141 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Main file for the SQLite library.  The routines in this file
+** implement the programmer interface to the library.  Routines in
+** other files are for internal use by SQLite and should not be
+** accessed by users of the library.
+*/
+
+#include "sqliteInt.h"
+
+/*
+** Execute SQL code.  Return one of the SQLITE_ success/failure
+** codes.  Also write an error message into memory obtained from
+** malloc() and make *pzErrMsg point to that message.
+**
+** If the SQL is a query, then for each row in the query result
+** the xCallback() function is called.  pArg becomes the first
+** argument to xCallback().  If xCallback=NULL then no callback
+** is invoked, even for queries.
+*/
+int sqlite3_exec(
+  sqlite3 *db,                /* The database on which the SQL executes */
+  const char *zSql,           /* The SQL to be executed */
+  sqlite3_callback xCallback, /* Invoke this callback routine */
+  void *pArg,                 /* First argument to xCallback() */
+  char **pzErrMsg             /* Write error messages here */
+){
+  int rc = SQLITE_OK;         /* Return code */
+  const char *zLeftover;      /* Tail of unprocessed SQL */
+  sqlite3_stmt *pStmt = 0;    /* The current SQL statement */
+  char **azCols = 0;          /* Names of result columns */
+  int callbackIsInit;         /* True if callback data is initialized */
+
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+  if( zSql==0 ) zSql = "";
+
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3Error(db, SQLITE_OK);
+  while( rc==SQLITE_OK && zSql[0] ){
+    int nCol = 0;
+    char **azVals = 0;
+
+    pStmt = 0;
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, &zLeftover);
+    assert( rc==SQLITE_OK || pStmt==0 );
+    if( rc!=SQLITE_OK ){
+      continue;
+    }
+    if( !pStmt ){
+      /* this happens for a comment or white-space */
+      zSql = zLeftover;
+      continue;
+    }
+    callbackIsInit = 0;
+
+    while( 1 ){
+      int i;
+      rc = sqlite3_step(pStmt);
+
+      /* Invoke the callback function if required */
+      if( xCallback && (SQLITE_ROW==rc || 
+          (SQLITE_DONE==rc && !callbackIsInit
+                           && db->flags&SQLITE_NullCallback)) ){
+        if( !callbackIsInit ){
+          nCol = sqlite3_column_count(pStmt);
+          azCols = sqlite3DbMallocRaw(db, (2*nCol+1)*sizeof(const char*));
+          if( azCols==0 ){
+            goto exec_out;
+          }
+          for(i=0; i<nCol; i++){
+            azCols[i] = (char *)sqlite3_column_name(pStmt, i);
+            /* sqlite3VdbeSetColName() installs column names as UTF8
+            ** strings so there is no way for sqlite3_column_name() to fail. */
+            assert( azCols[i]!=0 );
+          }
+          callbackIsInit = 1;
+        }
+        if( rc==SQLITE_ROW ){
+          azVals = &azCols[nCol];
+          for(i=0; i<nCol; i++){
+            azVals[i] = (char *)sqlite3_column_text(pStmt, i);
+            if( !azVals[i] && sqlite3_column_type(pStmt, i)!=SQLITE_NULL ){
+              sqlite3OomFault(db);
+              goto exec_out;
+            }
+          }
+          azVals[i] = 0;
+        }
+        if( xCallback(pArg, nCol, azVals, azCols) ){
+          /* EVIDENCE-OF: R-38229-40159 If the callback function to
+          ** sqlite3_exec() returns non-zero, then sqlite3_exec() will
+          ** return SQLITE_ABORT. */
+          rc = SQLITE_ABORT;
+          sqlite3VdbeFinalize((Vdbe *)pStmt);
+          pStmt = 0;
+          sqlite3Error(db, SQLITE_ABORT);
+          goto exec_out;
+        }
+      }
+
+      if( rc!=SQLITE_ROW ){
+        rc = sqlite3VdbeFinalize((Vdbe *)pStmt);
+        pStmt = 0;
+        zSql = zLeftover;
+        while( sqlite3Isspace(zSql[0]) ) zSql++;
+        break;
+      }
+    }
+
+    sqlite3DbFree(db, azCols);
+    azCols = 0;
+  }
+
+exec_out:
+  if( pStmt ) sqlite3VdbeFinalize((Vdbe *)pStmt);
+  sqlite3DbFree(db, azCols);
+
+  rc = sqlite3ApiExit(db, rc);
+  if( rc!=SQLITE_OK && pzErrMsg ){
+    *pzErrMsg = sqlite3DbStrDup(0, sqlite3_errmsg(db));
+    if( *pzErrMsg==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+      sqlite3Error(db, SQLITE_NOMEM);
+    }
+  }else if( pzErrMsg ){
+    *pzErrMsg = 0;
+  }
+
+  assert( (rc&db->errMask)==rc );
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
diff --git a/src/loadext.c b/src/loadext.c
new file mode 100644
index 0000000..7e0ae25
--- /dev/null
+++ b/src/loadext.c
@@ -0,0 +1,921 @@
+/*
+** 2006 June 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to dynamically load extensions into
+** the SQLite library.
+*/
+
+#ifndef SQLITE_CORE
+  #define SQLITE_CORE 1  /* Disable the API redefinition in sqlite3ext.h */
+#endif
+#include "sqlite3ext.h"
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Some API routines are omitted when various features are
+** excluded from a build of SQLite.  Substitute a NULL pointer
+** for any missing APIs.
+*/
+#ifndef SQLITE_ENABLE_COLUMN_METADATA
+# define sqlite3_column_database_name   0
+# define sqlite3_column_database_name16 0
+# define sqlite3_column_table_name      0
+# define sqlite3_column_table_name16    0
+# define sqlite3_column_origin_name     0
+# define sqlite3_column_origin_name16   0
+#endif
+
+#ifdef SQLITE_OMIT_AUTHORIZATION
+# define sqlite3_set_authorizer         0
+#endif
+
+#ifdef SQLITE_OMIT_UTF16
+# define sqlite3_bind_text16            0
+# define sqlite3_collation_needed16     0
+# define sqlite3_column_decltype16      0
+# define sqlite3_column_name16          0
+# define sqlite3_column_text16          0
+# define sqlite3_complete16             0
+# define sqlite3_create_collation16     0
+# define sqlite3_create_function16      0
+# define sqlite3_errmsg16               0
+# define sqlite3_open16                 0
+# define sqlite3_prepare16              0
+# define sqlite3_prepare16_v2           0
+# define sqlite3_prepare16_v3           0
+# define sqlite3_result_error16         0
+# define sqlite3_result_text16          0
+# define sqlite3_result_text16be        0
+# define sqlite3_result_text16le        0
+# define sqlite3_value_text16           0
+# define sqlite3_value_text16be         0
+# define sqlite3_value_text16le         0
+# define sqlite3_column_database_name16 0
+# define sqlite3_column_table_name16    0
+# define sqlite3_column_origin_name16   0
+#endif
+
+#ifdef SQLITE_OMIT_COMPLETE
+# define sqlite3_complete 0
+# define sqlite3_complete16 0
+#endif
+
+#ifdef SQLITE_OMIT_DECLTYPE
+# define sqlite3_column_decltype16      0
+# define sqlite3_column_decltype        0
+#endif
+
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+# define sqlite3_progress_handler 0
+#endif
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+# define sqlite3_create_module 0
+# define sqlite3_create_module_v2 0
+# define sqlite3_declare_vtab 0
+# define sqlite3_vtab_config 0
+# define sqlite3_vtab_on_conflict 0
+# define sqlite3_vtab_collation 0
+#endif
+
+#ifdef SQLITE_OMIT_SHARED_CACHE
+# define sqlite3_enable_shared_cache 0
+#endif
+
+#if defined(SQLITE_OMIT_TRACE) || defined(SQLITE_OMIT_DEPRECATED)
+# define sqlite3_profile       0
+# define sqlite3_trace         0
+#endif
+
+#ifdef SQLITE_OMIT_GET_TABLE
+# define sqlite3_free_table    0
+# define sqlite3_get_table     0
+#endif
+
+#ifdef SQLITE_OMIT_INCRBLOB
+#define sqlite3_bind_zeroblob  0
+#define sqlite3_blob_bytes     0
+#define sqlite3_blob_close     0
+#define sqlite3_blob_open      0
+#define sqlite3_blob_read      0
+#define sqlite3_blob_write     0
+#define sqlite3_blob_reopen    0
+#endif
+
+#if defined(SQLITE_OMIT_TRACE)
+# define sqlite3_trace_v2      0
+#endif
+
+/*
+** The following structure contains pointers to all SQLite API routines.
+** A pointer to this structure is passed into extensions when they are
+** loaded so that the extension can make calls back into the SQLite
+** library.
+**
+** When adding new APIs, add them to the bottom of this structure
+** in order to preserve backwards compatibility.
+**
+** Extensions that use newer APIs should first call the
+** sqlite3_libversion_number() to make sure that the API they
+** intend to use is supported by the library.  Extensions should
+** also check to make sure that the pointer to the function is
+** not NULL before calling it.
+*/
+static const sqlite3_api_routines sqlite3Apis = {
+  sqlite3_aggregate_context,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_aggregate_count,
+#else
+  0,
+#endif
+  sqlite3_bind_blob,
+  sqlite3_bind_double,
+  sqlite3_bind_int,
+  sqlite3_bind_int64,
+  sqlite3_bind_null,
+  sqlite3_bind_parameter_count,
+  sqlite3_bind_parameter_index,
+  sqlite3_bind_parameter_name,
+  sqlite3_bind_text,
+  sqlite3_bind_text16,
+  sqlite3_bind_value,
+  sqlite3_busy_handler,
+  sqlite3_busy_timeout,
+  sqlite3_changes,
+  sqlite3_close,
+  sqlite3_collation_needed,
+  sqlite3_collation_needed16,
+  sqlite3_column_blob,
+  sqlite3_column_bytes,
+  sqlite3_column_bytes16,
+  sqlite3_column_count,
+  sqlite3_column_database_name,
+  sqlite3_column_database_name16,
+  sqlite3_column_decltype,
+  sqlite3_column_decltype16,
+  sqlite3_column_double,
+  sqlite3_column_int,
+  sqlite3_column_int64,
+  sqlite3_column_name,
+  sqlite3_column_name16,
+  sqlite3_column_origin_name,
+  sqlite3_column_origin_name16,
+  sqlite3_column_table_name,
+  sqlite3_column_table_name16,
+  sqlite3_column_text,
+  sqlite3_column_text16,
+  sqlite3_column_type,
+  sqlite3_column_value,
+  sqlite3_commit_hook,
+  sqlite3_complete,
+  sqlite3_complete16,
+  sqlite3_create_collation,
+  sqlite3_create_collation16,
+  sqlite3_create_function,
+  sqlite3_create_function16,
+  sqlite3_create_module,
+  sqlite3_data_count,
+  sqlite3_db_handle,
+  sqlite3_declare_vtab,
+  sqlite3_enable_shared_cache,
+  sqlite3_errcode,
+  sqlite3_errmsg,
+  sqlite3_errmsg16,
+  sqlite3_exec,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_expired,
+#else
+  0,
+#endif
+  sqlite3_finalize,
+  sqlite3_free,
+  sqlite3_free_table,
+  sqlite3_get_autocommit,
+  sqlite3_get_auxdata,
+  sqlite3_get_table,
+  0,     /* Was sqlite3_global_recover(), but that function is deprecated */
+  sqlite3_interrupt,
+  sqlite3_last_insert_rowid,
+  sqlite3_libversion,
+  sqlite3_libversion_number,
+  sqlite3_malloc,
+  sqlite3_mprintf,
+  sqlite3_open,
+  sqlite3_open16,
+  sqlite3_prepare,
+  sqlite3_prepare16,
+  sqlite3_profile,
+  sqlite3_progress_handler,
+  sqlite3_realloc,
+  sqlite3_reset,
+  sqlite3_result_blob,
+  sqlite3_result_double,
+  sqlite3_result_error,
+  sqlite3_result_error16,
+  sqlite3_result_int,
+  sqlite3_result_int64,
+  sqlite3_result_null,
+  sqlite3_result_text,
+  sqlite3_result_text16,
+  sqlite3_result_text16be,
+  sqlite3_result_text16le,
+  sqlite3_result_value,
+  sqlite3_rollback_hook,
+  sqlite3_set_authorizer,
+  sqlite3_set_auxdata,
+  sqlite3_snprintf,
+  sqlite3_step,
+  sqlite3_table_column_metadata,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_thread_cleanup,
+#else
+  0,
+#endif
+  sqlite3_total_changes,
+  sqlite3_trace,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_transfer_bindings,
+#else
+  0,
+#endif
+  sqlite3_update_hook,
+  sqlite3_user_data,
+  sqlite3_value_blob,
+  sqlite3_value_bytes,
+  sqlite3_value_bytes16,
+  sqlite3_value_double,
+  sqlite3_value_int,
+  sqlite3_value_int64,
+  sqlite3_value_numeric_type,
+  sqlite3_value_text,
+  sqlite3_value_text16,
+  sqlite3_value_text16be,
+  sqlite3_value_text16le,
+  sqlite3_value_type,
+  sqlite3_vmprintf,
+  /*
+  ** The original API set ends here.  All extensions can call any
+  ** of the APIs above provided that the pointer is not NULL.  But
+  ** before calling APIs that follow, extension should check the
+  ** sqlite3_libversion_number() to make sure they are dealing with
+  ** a library that is new enough to support that API.
+  *************************************************************************
+  */
+  sqlite3_overload_function,
+
+  /*
+  ** Added after 3.3.13
+  */
+  sqlite3_prepare_v2,
+  sqlite3_prepare16_v2,
+  sqlite3_clear_bindings,
+
+  /*
+  ** Added for 3.4.1
+  */
+  sqlite3_create_module_v2,
+
+  /*
+  ** Added for 3.5.0
+  */
+  sqlite3_bind_zeroblob,
+  sqlite3_blob_bytes,
+  sqlite3_blob_close,
+  sqlite3_blob_open,
+  sqlite3_blob_read,
+  sqlite3_blob_write,
+  sqlite3_create_collation_v2,
+  sqlite3_file_control,
+  sqlite3_memory_highwater,
+  sqlite3_memory_used,
+#ifdef SQLITE_MUTEX_OMIT
+  0, 
+  0, 
+  0,
+  0,
+  0,
+#else
+  sqlite3_mutex_alloc,
+  sqlite3_mutex_enter,
+  sqlite3_mutex_free,
+  sqlite3_mutex_leave,
+  sqlite3_mutex_try,
+#endif
+  sqlite3_open_v2,
+  sqlite3_release_memory,
+  sqlite3_result_error_nomem,
+  sqlite3_result_error_toobig,
+  sqlite3_sleep,
+  sqlite3_soft_heap_limit,
+  sqlite3_vfs_find,
+  sqlite3_vfs_register,
+  sqlite3_vfs_unregister,
+
+  /*
+  ** Added for 3.5.8
+  */
+  sqlite3_threadsafe,
+  sqlite3_result_zeroblob,
+  sqlite3_result_error_code,
+  sqlite3_test_control,
+  sqlite3_randomness,
+  sqlite3_context_db_handle,
+
+  /*
+  ** Added for 3.6.0
+  */
+  sqlite3_extended_result_codes,
+  sqlite3_limit,
+  sqlite3_next_stmt,
+  sqlite3_sql,
+  sqlite3_status,
+
+  /*
+  ** Added for 3.7.4
+  */
+  sqlite3_backup_finish,
+  sqlite3_backup_init,
+  sqlite3_backup_pagecount,
+  sqlite3_backup_remaining,
+  sqlite3_backup_step,
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  sqlite3_compileoption_get,
+  sqlite3_compileoption_used,
+#else
+  0,
+  0,
+#endif
+  sqlite3_create_function_v2,
+  sqlite3_db_config,
+  sqlite3_db_mutex,
+  sqlite3_db_status,
+  sqlite3_extended_errcode,
+  sqlite3_log,
+  sqlite3_soft_heap_limit64,
+  sqlite3_sourceid,
+  sqlite3_stmt_status,
+  sqlite3_strnicmp,
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  sqlite3_unlock_notify,
+#else
+  0,
+#endif
+#ifndef SQLITE_OMIT_WAL
+  sqlite3_wal_autocheckpoint,
+  sqlite3_wal_checkpoint,
+  sqlite3_wal_hook,
+#else
+  0,
+  0,
+  0,
+#endif
+  sqlite3_blob_reopen,
+  sqlite3_vtab_config,
+  sqlite3_vtab_on_conflict,
+  sqlite3_close_v2,
+  sqlite3_db_filename,
+  sqlite3_db_readonly,
+  sqlite3_db_release_memory,
+  sqlite3_errstr,
+  sqlite3_stmt_busy,
+  sqlite3_stmt_readonly,
+  sqlite3_stricmp,
+  sqlite3_uri_boolean,
+  sqlite3_uri_int64,
+  sqlite3_uri_parameter,
+  sqlite3_vsnprintf,
+  sqlite3_wal_checkpoint_v2,
+  /* Version 3.8.7 and later */
+  sqlite3_auto_extension,
+  sqlite3_bind_blob64,
+  sqlite3_bind_text64,
+  sqlite3_cancel_auto_extension,
+  sqlite3_load_extension,
+  sqlite3_malloc64,
+  sqlite3_msize,
+  sqlite3_realloc64,
+  sqlite3_reset_auto_extension,
+  sqlite3_result_blob64,
+  sqlite3_result_text64,
+  sqlite3_strglob,
+  /* Version 3.8.11 and later */
+  (sqlite3_value*(*)(const sqlite3_value*))sqlite3_value_dup,
+  sqlite3_value_free,
+  sqlite3_result_zeroblob64,
+  sqlite3_bind_zeroblob64,
+  /* Version 3.9.0 and later */
+  sqlite3_value_subtype,
+  sqlite3_result_subtype,
+  /* Version 3.10.0 and later */
+  sqlite3_status64,
+  sqlite3_strlike,
+  sqlite3_db_cacheflush,
+  /* Version 3.12.0 and later */
+  sqlite3_system_errno,
+  /* Version 3.14.0 and later */
+  sqlite3_trace_v2,
+  sqlite3_expanded_sql,
+  /* Version 3.18.0 and later */
+  sqlite3_set_last_insert_rowid,
+  /* Version 3.20.0 and later */
+  sqlite3_prepare_v3,
+  sqlite3_prepare16_v3,
+  sqlite3_bind_pointer,
+  sqlite3_result_pointer,
+  sqlite3_value_pointer,
+  /* Version 3.22.0 and later */
+  sqlite3_vtab_nochange,
+  sqlite3_value_nochange,
+  sqlite3_vtab_collation,
+  /* Version 3.24.0 and later */
+  sqlite3_keyword_count,
+  sqlite3_keyword_name,
+  sqlite3_keyword_check,
+  sqlite3_str_new,
+  sqlite3_str_finish,
+  sqlite3_str_appendf,
+  sqlite3_str_vappendf,
+  sqlite3_str_append,
+  sqlite3_str_appendall,
+  sqlite3_str_appendchar,
+  sqlite3_str_reset,
+  sqlite3_str_errcode,
+  sqlite3_str_length,
+  sqlite3_str_value,
+  /* Version 3.25.0 and later */
+  sqlite3_create_window_function,
+  /* Version 3.26.0 and later */
+#ifdef SQLITE_ENABLE_NORMALIZE
+  sqlite3_normalized_sql,
+#else
+  0,
+#endif
+  /* Version 3.28.0 and later */
+  sqlite3_stmt_isexplain,
+  sqlite3_value_frombind,
+  /* Version 3.30.0 and later */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_drop_modules,
+#else
+  0,
+#endif
+  /* Version 3.31.0 and later */
+  sqlite3_hard_heap_limit64,
+  sqlite3_uri_key,
+  sqlite3_filename_database,
+  sqlite3_filename_journal,
+  sqlite3_filename_wal,
+  /* Version 3.32.0 and later */
+  sqlite3_create_filename,
+  sqlite3_free_filename,
+  sqlite3_database_file_object,
+  /* Version 3.34.0 and later */
+  sqlite3_txn_state,
+  /* Version 3.36.1 and later */
+  sqlite3_changes64,
+  sqlite3_total_changes64,
+  /* Version 3.37.0 and later */
+  sqlite3_autovacuum_pages,
+  /* Version 3.38.0 and later */
+  sqlite3_error_offset,
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_vtab_rhs_value,
+  sqlite3_vtab_distinct,
+  sqlite3_vtab_in,
+  sqlite3_vtab_in_first,
+  sqlite3_vtab_in_next,
+#else
+  0,
+  0,
+  0,
+  0,
+  0,
+#endif
+  /* Version 3.39.0 and later */
+#ifndef SQLITE_OMIT_DESERIALIZE
+  sqlite3_deserialize,
+  sqlite3_serialize,
+#else
+  0,
+  0,
+#endif
+  sqlite3_db_name,
+  /* Version 3.40.0 and later */
+  sqlite3_value_encoding,
+  /* Version 3.41.0 and later */
+  sqlite3_is_interrupted,
+  /* Version 3.43.0 and later */
+  sqlite3_stmt_explain,
+  /* Version 3.44.0 and later */
+  sqlite3_get_clientdata,
+  sqlite3_set_clientdata
+};
+
+/* True if x is the directory separator character
+*/
+#if SQLITE_OS_WIN
+# define DirSep(X)  ((X)=='/'||(X)=='\\')
+#else
+# define DirSep(X)  ((X)=='/')
+#endif
+
+/*
+** Attempt to load an SQLite extension library contained in the file
+** zFile.  The entry point is zProc.  zProc may be 0 in which case a
+** default entry point name (sqlite3_extension_init) is used.  Use
+** of the default name is recommended.
+**
+** Return SQLITE_OK on success and SQLITE_ERROR if something goes wrong.
+**
+** If an error occurs and pzErrMsg is not 0, then fill *pzErrMsg with 
+** error message text.  The calling function should free this memory
+** by calling sqlite3DbFree(db, ).
+*/
+static int sqlite3LoadExtension(
+  sqlite3 *db,          /* Load the extension into this database connection */
+  const char *zFile,    /* Name of the shared library containing extension */
+  const char *zProc,    /* Entry point.  Use "sqlite3_extension_init" if 0 */
+  char **pzErrMsg       /* Put error message here if not 0 */
+){
+  sqlite3_vfs *pVfs = db->pVfs;
+  void *handle;
+  sqlite3_loadext_entry xInit;
+  char *zErrmsg = 0;
+  const char *zEntry;
+  char *zAltEntry = 0;
+  void **aHandle;
+  u64 nMsg = strlen(zFile);
+  int ii;
+  int rc;
+
+  /* Shared library endings to try if zFile cannot be loaded as written */
+  static const char *azEndings[] = {
+#if SQLITE_OS_WIN
+     "dll"   
+#elif defined(__APPLE__)
+     "dylib"
+#else
+     "so"
+#endif
+  };
+
+
+  if( pzErrMsg ) *pzErrMsg = 0;
+
+  /* Ticket #1863.  To avoid a creating security problems for older
+  ** applications that relink against newer versions of SQLite, the
+  ** ability to run load_extension is turned off by default.  One
+  ** must call either sqlite3_enable_load_extension(db) or
+  ** sqlite3_db_config(db, SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION, 1, 0)
+  ** to turn on extension loading.
+  */
+  if( (db->flags & SQLITE_LoadExtension)==0 ){
+    if( pzErrMsg ){
+      *pzErrMsg = sqlite3_mprintf("not authorized");
+    }
+    return SQLITE_ERROR;
+  }
+
+  zEntry = zProc ? zProc : "sqlite3_extension_init";
+
+  /* tag-20210611-1.  Some dlopen() implementations will segfault if given
+  ** an oversize filename.  Most filesystems have a pathname limit of 4K,
+  ** so limit the extension filename length to about twice that.
+  ** https://sqlite.org/forum/forumpost/08a0d6d9bf
+  **
+  ** Later (2023-03-25): Save an extra 6 bytes for the filename suffix.
+  ** See https://sqlite.org/forum/forumpost/24083b579d.
+  */
+  if( nMsg>SQLITE_MAX_PATHLEN ) goto extension_not_found;
+
+  /* Do not allow sqlite3_load_extension() to link to a copy of the
+  ** running application, by passing in an empty filename. */
+  if( nMsg==0 ) goto extension_not_found;
+    
+  handle = sqlite3OsDlOpen(pVfs, zFile);
+#if SQLITE_OS_UNIX || SQLITE_OS_WIN
+  for(ii=0; ii<ArraySize(azEndings) && handle==0; ii++){
+    char *zAltFile = sqlite3_mprintf("%s.%s", zFile, azEndings[ii]);
+    if( zAltFile==0 ) return SQLITE_NOMEM_BKPT;
+    if( nMsg+strlen(azEndings[ii])+1<=SQLITE_MAX_PATHLEN ){
+      handle = sqlite3OsDlOpen(pVfs, zAltFile);
+    }
+    sqlite3_free(zAltFile);
+  }
+#endif
+  if( handle==0 ) goto extension_not_found;
+  xInit = (sqlite3_loadext_entry)sqlite3OsDlSym(pVfs, handle, zEntry);
+
+  /* If no entry point was specified and the default legacy
+  ** entry point name "sqlite3_extension_init" was not found, then
+  ** construct an entry point name "sqlite3_X_init" where the X is
+  ** replaced by the lowercase value of every ASCII alphabetic 
+  ** character in the filename after the last "/" upto the first ".",
+  ** and eliding the first three characters if they are "lib".  
+  ** Examples:
+  **
+  **    /usr/local/lib/libExample5.4.3.so ==>  sqlite3_example_init
+  **    C:/lib/mathfuncs.dll              ==>  sqlite3_mathfuncs_init
+  */
+  if( xInit==0 && zProc==0 ){
+    int iFile, iEntry, c;
+    int ncFile = sqlite3Strlen30(zFile);
+    zAltEntry = sqlite3_malloc64(ncFile+30);
+    if( zAltEntry==0 ){
+      sqlite3OsDlClose(pVfs, handle);
+      return SQLITE_NOMEM_BKPT;
+    }
+    memcpy(zAltEntry, "sqlite3_", 8);
+    for(iFile=ncFile-1; iFile>=0 && !DirSep(zFile[iFile]); iFile--){}
+    iFile++;
+    if( sqlite3_strnicmp(zFile+iFile, "lib", 3)==0 ) iFile += 3;
+    for(iEntry=8; (c = zFile[iFile])!=0 && c!='.'; iFile++){
+      if( sqlite3Isalpha(c) ){
+        zAltEntry[iEntry++] = (char)sqlite3UpperToLower[(unsigned)c];
+      }
+    }
+    memcpy(zAltEntry+iEntry, "_init", 6);
+    zEntry = zAltEntry;
+    xInit = (sqlite3_loadext_entry)sqlite3OsDlSym(pVfs, handle, zEntry);
+  }
+  if( xInit==0 ){
+    if( pzErrMsg ){
+      nMsg += strlen(zEntry) + 300;
+      *pzErrMsg = zErrmsg = sqlite3_malloc64(nMsg);
+      if( zErrmsg ){
+        assert( nMsg<0x7fffffff );  /* zErrmsg would be NULL if not so */
+        sqlite3_snprintf((int)nMsg, zErrmsg,
+            "no entry point [%s] in shared library [%s]", zEntry, zFile);
+        sqlite3OsDlError(pVfs, nMsg-1, zErrmsg);
+      }
+    }
+    sqlite3OsDlClose(pVfs, handle);
+    sqlite3_free(zAltEntry);
+    return SQLITE_ERROR;
+  }
+  sqlite3_free(zAltEntry);
+  rc = xInit(db, &zErrmsg, &sqlite3Apis);
+  if( rc ){
+    if( rc==SQLITE_OK_LOAD_PERMANENTLY ) return SQLITE_OK;
+    if( pzErrMsg ){
+      *pzErrMsg = sqlite3_mprintf("error during initialization: %s", zErrmsg);
+    }
+    sqlite3_free(zErrmsg);
+    sqlite3OsDlClose(pVfs, handle);
+    return SQLITE_ERROR;
+  }
+
+  /* Append the new shared library handle to the db->aExtension array. */
+  aHandle = sqlite3DbMallocZero(db, sizeof(handle)*(db->nExtension+1));
+  if( aHandle==0 ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  if( db->nExtension>0 ){
+    memcpy(aHandle, db->aExtension, sizeof(handle)*db->nExtension);
+  }
+  sqlite3DbFree(db, db->aExtension);
+  db->aExtension = aHandle;
+
+  db->aExtension[db->nExtension++] = handle;
+  return SQLITE_OK;
+
+extension_not_found:
+  if( pzErrMsg ){
+    nMsg += 300;
+    *pzErrMsg = zErrmsg = sqlite3_malloc64(nMsg);
+    if( zErrmsg ){
+      assert( nMsg<0x7fffffff );  /* zErrmsg would be NULL if not so */
+      sqlite3_snprintf((int)nMsg, zErrmsg,
+          "unable to open shared library [%.*s]", SQLITE_MAX_PATHLEN, zFile);
+      sqlite3OsDlError(pVfs, nMsg-1, zErrmsg);
+    }
+  }
+  return SQLITE_ERROR;
+}
+int sqlite3_load_extension(
+  sqlite3 *db,          /* Load the extension into this database connection */
+  const char *zFile,    /* Name of the shared library containing extension */
+  const char *zProc,    /* Entry point.  Use "sqlite3_extension_init" if 0 */
+  char **pzErrMsg       /* Put error message here if not 0 */
+){
+  int rc;
+  sqlite3_mutex_enter(db->mutex);
+  rc = sqlite3LoadExtension(db, zFile, zProc, pzErrMsg);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Call this routine when the database connection is closing in order
+** to clean up loaded extensions
+*/
+void sqlite3CloseExtensions(sqlite3 *db){
+  int i;
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(i=0; i<db->nExtension; i++){
+    sqlite3OsDlClose(db->pVfs, db->aExtension[i]);
+  }
+  sqlite3DbFree(db, db->aExtension);
+}
+
+/*
+** Enable or disable extension loading.  Extension loading is disabled by
+** default so as not to open security holes in older applications.
+*/
+int sqlite3_enable_load_extension(sqlite3 *db, int onoff){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  if( onoff ){
+    db->flags |= SQLITE_LoadExtension|SQLITE_LoadExtFunc;
+  }else{
+    db->flags &= ~(u64)(SQLITE_LoadExtension|SQLITE_LoadExtFunc);
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+#endif /* !defined(SQLITE_OMIT_LOAD_EXTENSION) */
+
+/*
+** The following object holds the list of automatically loaded
+** extensions.
+**
+** This list is shared across threads.  The SQLITE_MUTEX_STATIC_MAIN
+** mutex must be held while accessing this list.
+*/
+typedef struct sqlite3AutoExtList sqlite3AutoExtList;
+static SQLITE_WSD struct sqlite3AutoExtList {
+  u32 nExt;              /* Number of entries in aExt[] */
+  void (**aExt)(void);   /* Pointers to the extension init functions */
+} sqlite3Autoext = { 0, 0 };
+
+/* The "wsdAutoext" macro will resolve to the autoextension
+** state vector.  If writable static data is unsupported on the target,
+** we have to locate the state vector at run-time.  In the more common
+** case where writable static data is supported, wsdStat can refer directly
+** to the "sqlite3Autoext" state vector declared above.
+*/
+#ifdef SQLITE_OMIT_WSD
+# define wsdAutoextInit \
+  sqlite3AutoExtList *x = &GLOBAL(sqlite3AutoExtList,sqlite3Autoext)
+# define wsdAutoext x[0]
+#else
+# define wsdAutoextInit
+# define wsdAutoext sqlite3Autoext
+#endif
+
+
+/*
+** Register a statically linked extension that is automatically
+** loaded by every new database connection.
+*/
+int sqlite3_auto_extension(
+  void (*xInit)(void)
+){
+  int rc = SQLITE_OK;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( xInit==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ){
+    return rc;
+  }else
+#endif
+  {
+    u32 i;
+#if SQLITE_THREADSAFE
+    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
+#endif
+    wsdAutoextInit;
+    sqlite3_mutex_enter(mutex);
+    for(i=0; i<wsdAutoext.nExt; i++){
+      if( wsdAutoext.aExt[i]==xInit ) break;
+    }
+    if( i==wsdAutoext.nExt ){
+      u64 nByte = (wsdAutoext.nExt+1)*sizeof(wsdAutoext.aExt[0]);
+      void (**aNew)(void);
+      aNew = sqlite3_realloc64(wsdAutoext.aExt, nByte);
+      if( aNew==0 ){
+        rc = SQLITE_NOMEM_BKPT;
+      }else{
+        wsdAutoext.aExt = aNew;
+        wsdAutoext.aExt[wsdAutoext.nExt] = xInit;
+        wsdAutoext.nExt++;
+      }
+    }
+    sqlite3_mutex_leave(mutex);
+    assert( (rc&0xff)==rc );
+    return rc;
+  }
+}
+
+/*
+** Cancel a prior call to sqlite3_auto_extension.  Remove xInit from the
+** set of routines that is invoked for each new database connection, if it
+** is currently on the list.  If xInit is not on the list, then this
+** routine is a no-op.
+**
+** Return 1 if xInit was found on the list and removed.  Return 0 if xInit
+** was not on the list.
+*/
+int sqlite3_cancel_auto_extension(
+  void (*xInit)(void)
+){
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
+#endif
+  int i;
+  int n = 0;
+  wsdAutoextInit;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( xInit==0 ) return 0;
+#endif
+  sqlite3_mutex_enter(mutex);
+  for(i=(int)wsdAutoext.nExt-1; i>=0; i--){
+    if( wsdAutoext.aExt[i]==xInit ){
+      wsdAutoext.nExt--;
+      wsdAutoext.aExt[i] = wsdAutoext.aExt[wsdAutoext.nExt];
+      n++;
+      break;
+    }
+  }
+  sqlite3_mutex_leave(mutex);
+  return n;
+}
+
+/*
+** Reset the automatic extension loading mechanism.
+*/
+void sqlite3_reset_auto_extension(void){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize()==SQLITE_OK )
+#endif
+  {
+#if SQLITE_THREADSAFE
+    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
+#endif
+    wsdAutoextInit;
+    sqlite3_mutex_enter(mutex);
+    sqlite3_free(wsdAutoext.aExt);
+    wsdAutoext.aExt = 0;
+    wsdAutoext.nExt = 0;
+    sqlite3_mutex_leave(mutex);
+  }
+}
+
+/*
+** Load all automatic extensions.
+**
+** If anything goes wrong, set an error in the database connection.
+*/
+void sqlite3AutoLoadExtensions(sqlite3 *db){
+  u32 i;
+  int go = 1;
+  int rc;
+  sqlite3_loadext_entry xInit;
+
+  wsdAutoextInit;
+  if( wsdAutoext.nExt==0 ){
+    /* Common case: early out without every having to acquire a mutex */
+    return;
+  }
+  for(i=0; go; i++){
+    char *zErrmsg;
+#if SQLITE_THREADSAFE
+    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
+#endif
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+    const sqlite3_api_routines *pThunk = 0;
+#else
+    const sqlite3_api_routines *pThunk = &sqlite3Apis;
+#endif
+    sqlite3_mutex_enter(mutex);
+    if( i>=wsdAutoext.nExt ){
+      xInit = 0;
+      go = 0;
+    }else{
+      xInit = (sqlite3_loadext_entry)wsdAutoext.aExt[i];
+    }
+    sqlite3_mutex_leave(mutex);
+    zErrmsg = 0;
+    if( xInit && (rc = xInit(db, &zErrmsg, pThunk))!=0 ){
+      sqlite3ErrorWithMsg(db, rc,
+            "automatic extension loading failed: %s", zErrmsg);
+      go = 0;
+    }
+    sqlite3_free(zErrmsg);
+  }
+}
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..0342998
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,5098 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Main file for the SQLite library.  The routines in this file
+** implement the programmer interface to the library.  Routines in
+** other files are for internal use by SQLite and should not be
+** accessed by users of the library.
+*/
+#include "sqliteInt.h"
+
+#ifdef SQLITE_ENABLE_FTS3
+# include "fts3.h"
+#endif
+#ifdef SQLITE_ENABLE_RTREE
+# include "rtree.h"
+#endif
+#if defined(SQLITE_ENABLE_ICU) || defined(SQLITE_ENABLE_ICU_COLLATIONS)
+# include "sqliteicu.h"
+#endif
+
+/*
+** This is an extension initializer that is a no-op and always
+** succeeds, except that it fails if the fault-simulation is set
+** to 500.
+*/
+static int sqlite3TestExtInit(sqlite3 *db){
+  (void)db;
+  return sqlite3FaultSim(500);
+}
+
+
+/*
+** Forward declarations of external module initializer functions
+** for modules that need them.
+*/
+#ifdef SQLITE_ENABLE_FTS5
+int sqlite3Fts5Init(sqlite3*);
+#endif
+#ifdef SQLITE_ENABLE_STMTVTAB
+int sqlite3StmtVtabInit(sqlite3*);
+#endif
+#ifdef SQLITE_EXTRA_AUTOEXT
+int SQLITE_EXTRA_AUTOEXT(sqlite3*);
+#endif
+/*
+** An array of pointers to extension initializer functions for
+** built-in extensions.
+*/
+static int (*const sqlite3BuiltinExtensions[])(sqlite3*) = {
+#ifdef SQLITE_ENABLE_FTS3
+  sqlite3Fts3Init,
+#endif
+#ifdef SQLITE_ENABLE_FTS5
+  sqlite3Fts5Init,
+#endif
+#if defined(SQLITE_ENABLE_ICU) || defined(SQLITE_ENABLE_ICU_COLLATIONS)
+  sqlite3IcuInit,
+#endif
+#ifdef SQLITE_ENABLE_RTREE
+  sqlite3RtreeInit,
+#endif
+#ifdef SQLITE_ENABLE_DBPAGE_VTAB
+  sqlite3DbpageRegister,
+#endif
+#ifdef SQLITE_ENABLE_DBSTAT_VTAB
+  sqlite3DbstatRegister,
+#endif
+  sqlite3TestExtInit,
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_JSON)
+  sqlite3JsonTableFunctions,
+#endif
+#ifdef SQLITE_ENABLE_STMTVTAB
+  sqlite3StmtVtabInit,
+#endif
+#ifdef SQLITE_ENABLE_BYTECODE_VTAB
+  sqlite3VdbeBytecodeVtabInit,
+#endif
+#ifdef SQLITE_EXTRA_AUTOEXT
+  SQLITE_EXTRA_AUTOEXT,
+#endif
+};
+
+#ifndef SQLITE_AMALGAMATION
+/* IMPLEMENTATION-OF: R-46656-45156 The sqlite3_version[] string constant
+** contains the text of SQLITE_VERSION macro.
+*/
+const char sqlite3_version[] = SQLITE_VERSION;
+#endif
+
+/* IMPLEMENTATION-OF: R-53536-42575 The sqlite3_libversion() function returns
+** a pointer to the to the sqlite3_version[] string constant.
+*/
+const char *sqlite3_libversion(void){ return sqlite3_version; }
+
+/* IMPLEMENTATION-OF: R-25063-23286 The sqlite3_sourceid() function returns a
+** pointer to a string constant whose value is the same as the
+** SQLITE_SOURCE_ID C preprocessor macro. Except if SQLite is built using
+** an edited copy of the amalgamation, then the last four characters of
+** the hash might be different from SQLITE_SOURCE_ID.
+*/
+const char *sqlite3_sourceid(void){ return SQLITE_SOURCE_ID; }
+
+/* IMPLEMENTATION-OF: R-35210-63508 The sqlite3_libversion_number() function
+** returns an integer equal to SQLITE_VERSION_NUMBER.
+*/
+int sqlite3_libversion_number(void){ return SQLITE_VERSION_NUMBER; }
+
+/* IMPLEMENTATION-OF: R-20790-14025 The sqlite3_threadsafe() function returns
+** zero if and only if SQLite was compiled with mutexing code omitted due to
+** the SQLITE_THREADSAFE compile-time option being set to 0.
+*/
+int sqlite3_threadsafe(void){ return SQLITE_THREADSAFE; }
+
+/*
+** When compiling the test fixture or with debugging enabled (on Win32),
+** this variable being set to non-zero will cause OSTRACE macros to emit
+** extra diagnostic information.
+*/
+#ifdef SQLITE_HAVE_OS_TRACE
+# ifndef SQLITE_DEBUG_OS_TRACE
+#   define SQLITE_DEBUG_OS_TRACE 0
+# endif
+  int sqlite3OSTrace = SQLITE_DEBUG_OS_TRACE;
+#endif
+
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+/*
+** If the following function pointer is not NULL and if
+** SQLITE_ENABLE_IOTRACE is enabled, then messages describing
+** I/O active are written using this function.  These messages
+** are intended for debugging activity only.
+*/
+SQLITE_API void (SQLITE_CDECL *sqlite3IoTrace)(const char*, ...) = 0;
+#endif
+
+/*
+** If the following global variable points to a string which is the
+** name of a directory, then that directory will be used to store
+** temporary files.
+**
+** See also the "PRAGMA temp_store_directory" SQL command.
+*/
+char *sqlite3_temp_directory = 0;
+
+/*
+** If the following global variable points to a string which is the
+** name of a directory, then that directory will be used to store
+** all database files specified with a relative pathname.
+**
+** See also the "PRAGMA data_store_directory" SQL command.
+*/
+char *sqlite3_data_directory = 0;
+
+/*
+** Determine whether or not high-precision (long double) floating point
+** math works correctly on CPU currently running.
+*/
+static SQLITE_NOINLINE int hasHighPrecisionDouble(int rc){
+  if( sizeof(LONGDOUBLE_TYPE)<=8 ){
+    /* If the size of "long double" is not more than 8, then
+    ** high-precision math is not possible. */
+    return 0;
+  }else{
+    /* Just because sizeof(long double)>8 does not mean that the underlying
+    ** hardware actually supports high-precision floating point.  For example,
+    ** clearing the 0x100 bit in the floating-point control word on Intel
+    ** processors will make long double work like double, even though long
+    ** double takes up more space.  The only way to determine if long double
+    ** actually works is to run an experiment. */
+    LONGDOUBLE_TYPE a, b, c;
+    rc++;
+    a = 1.0+rc*0.1;
+    b = 1.0e+18+rc*25.0;
+    c = a+b;
+    return b!=c;
+  }
+}
+
+
+/*
+** Initialize SQLite. 
+**
+** This routine must be called to initialize the memory allocation,
+** VFS, and mutex subsystems prior to doing any serious work with
+** SQLite.  But as long as you do not compile with SQLITE_OMIT_AUTOINIT
+** this routine will be called automatically by key routines such as
+** sqlite3_open(). 
+**
+** This routine is a no-op except on its very first call for the process,
+** or for the first call after a call to sqlite3_shutdown.
+**
+** The first thread to call this routine runs the initialization to
+** completion.  If subsequent threads call this routine before the first
+** thread has finished the initialization process, then the subsequent
+** threads must block until the first thread finishes with the initialization.
+**
+** The first thread might call this routine recursively.  Recursive
+** calls to this routine should not block, of course.  Otherwise the
+** initialization process would never complete.
+**
+** Let X be the first thread to enter this routine.  Let Y be some other
+** thread.  Then while the initial invocation of this routine by X is
+** incomplete, it is required that:
+**
+**    *  Calls to this routine from Y must block until the outer-most
+**       call by X completes.
+**
+**    *  Recursive calls to this routine from thread X return immediately
+**       without blocking.
+*/
+int sqlite3_initialize(void){
+  MUTEX_LOGIC( sqlite3_mutex *pMainMtx; )      /* The main static mutex */
+  int rc;                                      /* Result code */
+#ifdef SQLITE_EXTRA_INIT
+  int bRunExtraInit = 0;                       /* Extra initialization needed */
+#endif
+
+#ifdef SQLITE_OMIT_WSD
+  rc = sqlite3_wsd_init(4096, 24);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+#endif
+
+  /* If the following assert() fails on some obscure processor/compiler
+  ** combination, the work-around is to set the correct pointer
+  ** size at compile-time using -DSQLITE_PTRSIZE=n compile-time option */
+  assert( SQLITE_PTRSIZE==sizeof(char*) );
+
+  /* If SQLite is already completely initialized, then this call
+  ** to sqlite3_initialize() should be a no-op.  But the initialization
+  ** must be complete.  So isInit must not be set until the very end
+  ** of this routine.
+  */
+  if( sqlite3GlobalConfig.isInit ){
+    sqlite3MemoryBarrier();
+    return SQLITE_OK;
+  }
+
+  /* Make sure the mutex subsystem is initialized.  If unable to
+  ** initialize the mutex subsystem, return early with the error.
+  ** If the system is so sick that we are unable to allocate a mutex,
+  ** there is not much SQLite is going to be able to do.
+  **
+  ** The mutex subsystem must take care of serializing its own
+  ** initialization.
+  */
+  rc = sqlite3MutexInit();
+  if( rc ) return rc;
+
+  /* Initialize the malloc() system and the recursive pInitMutex mutex.
+  ** This operation is protected by the STATIC_MAIN mutex.  Note that
+  ** MutexAlloc() is called for a static mutex prior to initializing the
+  ** malloc subsystem - this implies that the allocation of a static
+  ** mutex must not require support from the malloc subsystem.
+  */
+  MUTEX_LOGIC( pMainMtx = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN); )
+  sqlite3_mutex_enter(pMainMtx);
+  sqlite3GlobalConfig.isMutexInit = 1;
+  if( !sqlite3GlobalConfig.isMallocInit ){
+    rc = sqlite3MallocInit();
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3GlobalConfig.isMallocInit = 1;
+    if( !sqlite3GlobalConfig.pInitMutex ){
+      sqlite3GlobalConfig.pInitMutex =
+           sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
+      if( sqlite3GlobalConfig.bCoreMutex && !sqlite3GlobalConfig.pInitMutex ){
+        rc = SQLITE_NOMEM_BKPT;
+      }
+    }
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3GlobalConfig.nRefInitMutex++;
+  }
+  sqlite3_mutex_leave(pMainMtx);
+
+  /* If rc is not SQLITE_OK at this point, then either the malloc
+  ** subsystem could not be initialized or the system failed to allocate
+  ** the pInitMutex mutex. Return an error in either case.  */
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* Do the rest of the initialization under the recursive mutex so
+  ** that we will be able to handle recursive calls into
+  ** sqlite3_initialize().  The recursive calls normally come through
+  ** sqlite3_os_init() when it invokes sqlite3_vfs_register(), but other
+  ** recursive calls might also be possible.
+  **
+  ** IMPLEMENTATION-OF: R-00140-37445 SQLite automatically serializes calls
+  ** to the xInit method, so the xInit method need not be threadsafe.
+  **
+  ** The following mutex is what serializes access to the appdef pcache xInit
+  ** methods.  The sqlite3_pcache_methods.xInit() all is embedded in the
+  ** call to sqlite3PcacheInitialize().
+  */
+  sqlite3_mutex_enter(sqlite3GlobalConfig.pInitMutex);
+  if( sqlite3GlobalConfig.isInit==0 && sqlite3GlobalConfig.inProgress==0 ){
+    sqlite3GlobalConfig.inProgress = 1;
+#ifdef SQLITE_ENABLE_SQLLOG
+    {
+      extern void sqlite3_init_sqllog(void);
+      sqlite3_init_sqllog();
+    }
+#endif
+    memset(&sqlite3BuiltinFunctions, 0, sizeof(sqlite3BuiltinFunctions));
+    sqlite3RegisterBuiltinFunctions();
+    if( sqlite3GlobalConfig.isPCacheInit==0 ){
+      rc = sqlite3PcacheInitialize();
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3GlobalConfig.isPCacheInit = 1;
+      rc = sqlite3OsInit();
+    }
+#ifndef SQLITE_OMIT_DESERIALIZE
+    if( rc==SQLITE_OK ){
+      rc = sqlite3MemdbInit();
+    }
+#endif
+    if( rc==SQLITE_OK ){
+      sqlite3PCacheBufferSetup( sqlite3GlobalConfig.pPage,
+          sqlite3GlobalConfig.szPage, sqlite3GlobalConfig.nPage);
+      sqlite3MemoryBarrier();
+      sqlite3GlobalConfig.isInit = 1;
+#ifdef SQLITE_EXTRA_INIT
+      bRunExtraInit = 1;
+#endif
+    }
+    sqlite3GlobalConfig.inProgress = 0;
+  }
+  sqlite3_mutex_leave(sqlite3GlobalConfig.pInitMutex);
+
+  /* Go back under the static mutex and clean up the recursive
+  ** mutex to prevent a resource leak.
+  */
+  sqlite3_mutex_enter(pMainMtx);
+  sqlite3GlobalConfig.nRefInitMutex--;
+  if( sqlite3GlobalConfig.nRefInitMutex<=0 ){
+    assert( sqlite3GlobalConfig.nRefInitMutex==0 );
+    sqlite3_mutex_free(sqlite3GlobalConfig.pInitMutex);
+    sqlite3GlobalConfig.pInitMutex = 0;
+  }
+  sqlite3_mutex_leave(pMainMtx);
+
+  /* The following is just a sanity check to make sure SQLite has
+  ** been compiled correctly.  It is important to run this code, but
+  ** we don't want to run it too often and soak up CPU cycles for no
+  ** reason.  So we run it once during initialization.
+  */
+#ifndef NDEBUG
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  /* This section of code's only "output" is via assert() statements. */
+  if( rc==SQLITE_OK ){
+    u64 x = (((u64)1)<<63)-1;
+    double y;
+    assert(sizeof(x)==8);
+    assert(sizeof(x)==sizeof(y));
+    memcpy(&y, &x, 8);
+    assert( sqlite3IsNaN(y) );
+  }
+#endif
+#endif
+
+  /* Do extra initialization steps requested by the SQLITE_EXTRA_INIT
+  ** compile-time option.
+  */
+#ifdef SQLITE_EXTRA_INIT
+  if( bRunExtraInit ){
+    int SQLITE_EXTRA_INIT(const char*);
+    rc = SQLITE_EXTRA_INIT(0);
+  }
+#endif
+
+  /* Experimentally determine if high-precision floating point is
+  ** available. */
+#ifndef SQLITE_OMIT_WSD
+  sqlite3Config.bUseLongDouble = hasHighPrecisionDouble(rc);
+#endif
+
+  return rc;
+}
+
+/*
+** Undo the effects of sqlite3_initialize().  Must not be called while
+** there are outstanding database connections or memory allocations or
+** while any part of SQLite is otherwise in use in any thread.  This
+** routine is not threadsafe.  But it is safe to invoke this routine
+** on when SQLite is already shut down.  If SQLite is already shut down
+** when this routine is invoked, then this routine is a harmless no-op.
+*/
+int sqlite3_shutdown(void){
+#ifdef SQLITE_OMIT_WSD
+  int rc = sqlite3_wsd_init(4096, 24);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+#endif
+
+  if( sqlite3GlobalConfig.isInit ){
+#ifdef SQLITE_EXTRA_SHUTDOWN
+    void SQLITE_EXTRA_SHUTDOWN(void);
+    SQLITE_EXTRA_SHUTDOWN();
+#endif
+    sqlite3_os_end();
+    sqlite3_reset_auto_extension();
+    sqlite3GlobalConfig.isInit = 0;
+  }
+  if( sqlite3GlobalConfig.isPCacheInit ){
+    sqlite3PcacheShutdown();
+    sqlite3GlobalConfig.isPCacheInit = 0;
+  }
+  if( sqlite3GlobalConfig.isMallocInit ){
+    sqlite3MallocEnd();
+    sqlite3GlobalConfig.isMallocInit = 0;
+
+#ifndef SQLITE_OMIT_SHUTDOWN_DIRECTORIES
+    /* The heap subsystem has now been shutdown and these values are supposed
+    ** to be NULL or point to memory that was obtained from sqlite3_malloc(),
+    ** which would rely on that heap subsystem; therefore, make sure these
+    ** values cannot refer to heap memory that was just invalidated when the
+    ** heap subsystem was shutdown.  This is only done if the current call to
+    ** this function resulted in the heap subsystem actually being shutdown.
+    */
+    sqlite3_data_directory = 0;
+    sqlite3_temp_directory = 0;
+#endif
+  }
+  if( sqlite3GlobalConfig.isMutexInit ){
+    sqlite3MutexEnd();
+    sqlite3GlobalConfig.isMutexInit = 0;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** This API allows applications to modify the global configuration of
+** the SQLite library at run-time.
+**
+** This routine should only be called when there are no outstanding
+** database connections or memory allocations.  This routine is not
+** threadsafe.  Failure to heed these warnings can lead to unpredictable
+** behavior.
+*/
+int sqlite3_config(int op, ...){
+  va_list ap;
+  int rc = SQLITE_OK;
+
+  /* sqlite3_config() normally returns SQLITE_MISUSE if it is invoked while
+  ** the SQLite library is in use.  Except, a few selected opcodes
+  ** are allowed.
+  */
+  if( sqlite3GlobalConfig.isInit ){
+    static const u64 mAnytimeConfigOption = 0
+       | MASKBIT64( SQLITE_CONFIG_LOG )
+       | MASKBIT64( SQLITE_CONFIG_PCACHE_HDRSZ )
+    ;
+    if( op<0 || op>63 || (MASKBIT64(op) & mAnytimeConfigOption)==0 ){
+      return SQLITE_MISUSE_BKPT;
+    }
+    testcase( op==SQLITE_CONFIG_LOG );
+    testcase( op==SQLITE_CONFIG_PCACHE_HDRSZ );
+  }
+
+  va_start(ap, op);
+  switch( op ){
+
+    /* Mutex configuration options are only available in a threadsafe
+    ** compile.
+    */
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0  /* IMP: R-54466-46756 */
+    case SQLITE_CONFIG_SINGLETHREAD: {
+      /* EVIDENCE-OF: R-02748-19096 This option sets the threading mode to
+      ** Single-thread. */
+      sqlite3GlobalConfig.bCoreMutex = 0;  /* Disable mutex on core */
+      sqlite3GlobalConfig.bFullMutex = 0;  /* Disable mutex on connections */
+      break;
+    }
+#endif
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-20520-54086 */
+    case SQLITE_CONFIG_MULTITHREAD: {
+      /* EVIDENCE-OF: R-14374-42468 This option sets the threading mode to
+      ** Multi-thread. */
+      sqlite3GlobalConfig.bCoreMutex = 1;  /* Enable mutex on core */
+      sqlite3GlobalConfig.bFullMutex = 0;  /* Disable mutex on connections */
+      break;
+    }
+#endif
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-59593-21810 */
+    case SQLITE_CONFIG_SERIALIZED: {
+      /* EVIDENCE-OF: R-41220-51800 This option sets the threading mode to
+      ** Serialized. */
+      sqlite3GlobalConfig.bCoreMutex = 1;  /* Enable mutex on core */
+      sqlite3GlobalConfig.bFullMutex = 1;  /* Enable mutex on connections */
+      break;
+    }
+#endif
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-63666-48755 */
+    case SQLITE_CONFIG_MUTEX: {
+      /* Specify an alternative mutex implementation */
+      sqlite3GlobalConfig.mutex = *va_arg(ap, sqlite3_mutex_methods*);
+      break;
+    }
+#endif
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-14450-37597 */
+    case SQLITE_CONFIG_GETMUTEX: {
+      /* Retrieve the current mutex implementation */
+      *va_arg(ap, sqlite3_mutex_methods*) = sqlite3GlobalConfig.mutex;
+      break;
+    }
+#endif
+
+    case SQLITE_CONFIG_MALLOC: {
+      /* EVIDENCE-OF: R-55594-21030 The SQLITE_CONFIG_MALLOC option takes a
+      ** single argument which is a pointer to an instance of the
+      ** sqlite3_mem_methods structure. The argument specifies alternative
+      ** low-level memory allocation routines to be used in place of the memory
+      ** allocation routines built into SQLite. */
+      sqlite3GlobalConfig.m = *va_arg(ap, sqlite3_mem_methods*);
+      break;
+    }
+    case SQLITE_CONFIG_GETMALLOC: {
+      /* EVIDENCE-OF: R-51213-46414 The SQLITE_CONFIG_GETMALLOC option takes a
+      ** single argument which is a pointer to an instance of the
+      ** sqlite3_mem_methods structure. The sqlite3_mem_methods structure is
+      ** filled with the currently defined memory allocation routines. */
+      if( sqlite3GlobalConfig.m.xMalloc==0 ) sqlite3MemSetDefault();
+      *va_arg(ap, sqlite3_mem_methods*) = sqlite3GlobalConfig.m;
+      break;
+    }
+    case SQLITE_CONFIG_MEMSTATUS: {
+      assert( !sqlite3GlobalConfig.isInit );  /* Cannot change at runtime */
+      /* EVIDENCE-OF: R-61275-35157 The SQLITE_CONFIG_MEMSTATUS option takes
+      ** single argument of type int, interpreted as a boolean, which enables
+      ** or disables the collection of memory allocation statistics. */
+      sqlite3GlobalConfig.bMemstat = va_arg(ap, int);
+      break;
+    }
+    case SQLITE_CONFIG_SMALL_MALLOC: {
+      sqlite3GlobalConfig.bSmallMalloc = va_arg(ap, int);
+      break;
+    }
+    case SQLITE_CONFIG_PAGECACHE: {
+      /* EVIDENCE-OF: R-18761-36601 There are three arguments to
+      ** SQLITE_CONFIG_PAGECACHE: A pointer to 8-byte aligned memory (pMem),
+      ** the size of each page cache line (sz), and the number of cache lines
+      ** (N). */
+      sqlite3GlobalConfig.pPage = va_arg(ap, void*);
+      sqlite3GlobalConfig.szPage = va_arg(ap, int);
+      sqlite3GlobalConfig.nPage = va_arg(ap, int);
+      break;
+    }
+    case SQLITE_CONFIG_PCACHE_HDRSZ: {
+      /* EVIDENCE-OF: R-39100-27317 The SQLITE_CONFIG_PCACHE_HDRSZ option takes
+      ** a single parameter which is a pointer to an integer and writes into
+      ** that integer the number of extra bytes per page required for each page
+      ** in SQLITE_CONFIG_PAGECACHE. */
+      *va_arg(ap, int*) =
+          sqlite3HeaderSizeBtree() +
+          sqlite3HeaderSizePcache() +
+          sqlite3HeaderSizePcache1();
+      break;
+    }
+
+    case SQLITE_CONFIG_PCACHE: {
+      /* no-op */
+      break;
+    }
+    case SQLITE_CONFIG_GETPCACHE: {
+      /* now an error */
+      rc = SQLITE_ERROR;
+      break;
+    }
+
+    case SQLITE_CONFIG_PCACHE2: {
+      /* EVIDENCE-OF: R-63325-48378 The SQLITE_CONFIG_PCACHE2 option takes a
+      ** single argument which is a pointer to an sqlite3_pcache_methods2
+      ** object. This object specifies the interface to a custom page cache
+      ** implementation. */
+      sqlite3GlobalConfig.pcache2 = *va_arg(ap, sqlite3_pcache_methods2*);
+      break;
+    }
+    case SQLITE_CONFIG_GETPCACHE2: {
+      /* EVIDENCE-OF: R-22035-46182 The SQLITE_CONFIG_GETPCACHE2 option takes a
+      ** single argument which is a pointer to an sqlite3_pcache_methods2
+      ** object. SQLite copies of the current page cache implementation into
+      ** that object. */
+      if( sqlite3GlobalConfig.pcache2.xInit==0 ){
+        sqlite3PCacheSetDefault();
+      }
+      *va_arg(ap, sqlite3_pcache_methods2*) = sqlite3GlobalConfig.pcache2;
+      break;
+    }
+
+/* EVIDENCE-OF: R-06626-12911 The SQLITE_CONFIG_HEAP option is only
+** available if SQLite is compiled with either SQLITE_ENABLE_MEMSYS3 or
+** SQLITE_ENABLE_MEMSYS5 and returns SQLITE_ERROR if invoked otherwise. */
+#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
+    case SQLITE_CONFIG_HEAP: {
+      /* EVIDENCE-OF: R-19854-42126 There are three arguments to
+      ** SQLITE_CONFIG_HEAP: An 8-byte aligned pointer to the memory, the
+      ** number of bytes in the memory buffer, and the minimum allocation size.
+      */
+      sqlite3GlobalConfig.pHeap = va_arg(ap, void*);
+      sqlite3GlobalConfig.nHeap = va_arg(ap, int);
+      sqlite3GlobalConfig.mnReq = va_arg(ap, int);
+
+      if( sqlite3GlobalConfig.mnReq<1 ){
+        sqlite3GlobalConfig.mnReq = 1;
+      }else if( sqlite3GlobalConfig.mnReq>(1<<12) ){
+        /* cap min request size at 2^12 */
+        sqlite3GlobalConfig.mnReq = (1<<12);
+      }
+
+      if( sqlite3GlobalConfig.pHeap==0 ){
+        /* EVIDENCE-OF: R-49920-60189 If the first pointer (the memory pointer)
+        ** is NULL, then SQLite reverts to using its default memory allocator
+        ** (the system malloc() implementation), undoing any prior invocation of
+        ** SQLITE_CONFIG_MALLOC.
+        **
+        ** Setting sqlite3GlobalConfig.m to all zeros will cause malloc to
+        ** revert to its default implementation when sqlite3_initialize() is run
+        */
+        memset(&sqlite3GlobalConfig.m, 0, sizeof(sqlite3GlobalConfig.m));
+      }else{
+        /* EVIDENCE-OF: R-61006-08918 If the memory pointer is not NULL then the
+        ** alternative memory allocator is engaged to handle all of SQLites
+        ** memory allocation needs. */
+#ifdef SQLITE_ENABLE_MEMSYS3
+        sqlite3GlobalConfig.m = *sqlite3MemGetMemsys3();
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS5
+        sqlite3GlobalConfig.m = *sqlite3MemGetMemsys5();
+#endif
+      }
+      break;
+    }
+#endif
+
+    case SQLITE_CONFIG_LOOKASIDE: {
+      sqlite3GlobalConfig.szLookaside = va_arg(ap, int);
+      sqlite3GlobalConfig.nLookaside = va_arg(ap, int);
+      break;
+    }
+   
+    /* Record a pointer to the logger function and its first argument.
+    ** The default is NULL.  Logging is disabled if the function pointer is
+    ** NULL.
+    */
+    case SQLITE_CONFIG_LOG: {
+      /* MSVC is picky about pulling func ptrs from va lists.
+      ** http://support.microsoft.com/kb/47961
+      ** sqlite3GlobalConfig.xLog = va_arg(ap, void(*)(void*,int,const char*));
+      */
+      typedef void(*LOGFUNC_t)(void*,int,const char*);
+      LOGFUNC_t xLog = va_arg(ap, LOGFUNC_t);
+      void *pLogArg = va_arg(ap, void*);
+      AtomicStore(&sqlite3GlobalConfig.xLog, xLog);
+      AtomicStore(&sqlite3GlobalConfig.pLogArg, pLogArg);
+      break;
+    }
+
+    /* EVIDENCE-OF: R-55548-33817 The compile-time setting for URI filenames
+    ** can be changed at start-time using the
+    ** sqlite3_config(SQLITE_CONFIG_URI,1) or
+    ** sqlite3_config(SQLITE_CONFIG_URI,0) configuration calls.
+    */
+    case SQLITE_CONFIG_URI: {
+      /* EVIDENCE-OF: R-25451-61125 The SQLITE_CONFIG_URI option takes a single
+      ** argument of type int. If non-zero, then URI handling is globally
+      ** enabled. If the parameter is zero, then URI handling is globally
+      ** disabled. */
+      int bOpenUri = va_arg(ap, int);
+      AtomicStore(&sqlite3GlobalConfig.bOpenUri, bOpenUri);
+      break;
+    }
+
+    case SQLITE_CONFIG_COVERING_INDEX_SCAN: {
+      /* EVIDENCE-OF: R-36592-02772 The SQLITE_CONFIG_COVERING_INDEX_SCAN
+      ** option takes a single integer argument which is interpreted as a
+      ** boolean in order to enable or disable the use of covering indices for
+      ** full table scans in the query optimizer. */
+      sqlite3GlobalConfig.bUseCis = va_arg(ap, int);
+      break;
+    }
+
+#ifdef SQLITE_ENABLE_SQLLOG
+    case SQLITE_CONFIG_SQLLOG: {
+      typedef void(*SQLLOGFUNC_t)(void*, sqlite3*, const char*, int);
+      sqlite3GlobalConfig.xSqllog = va_arg(ap, SQLLOGFUNC_t);
+      sqlite3GlobalConfig.pSqllogArg = va_arg(ap, void *);
+      break;
+    }
+#endif
+
+    case SQLITE_CONFIG_MMAP_SIZE: {
+      /* EVIDENCE-OF: R-58063-38258 SQLITE_CONFIG_MMAP_SIZE takes two 64-bit
+      ** integer (sqlite3_int64) values that are the default mmap size limit
+      ** (the default setting for PRAGMA mmap_size) and the maximum allowed
+      ** mmap size limit. */
+      sqlite3_int64 szMmap = va_arg(ap, sqlite3_int64);
+      sqlite3_int64 mxMmap = va_arg(ap, sqlite3_int64);
+      /* EVIDENCE-OF: R-53367-43190 If either argument to this option is
+      ** negative, then that argument is changed to its compile-time default.
+      **
+      ** EVIDENCE-OF: R-34993-45031 The maximum allowed mmap size will be
+      ** silently truncated if necessary so that it does not exceed the
+      ** compile-time maximum mmap size set by the SQLITE_MAX_MMAP_SIZE
+      ** compile-time option.
+      */
+      if( mxMmap<0 || mxMmap>SQLITE_MAX_MMAP_SIZE ){
+        mxMmap = SQLITE_MAX_MMAP_SIZE;
+      }
+      if( szMmap<0 ) szMmap = SQLITE_DEFAULT_MMAP_SIZE;
+      if( szMmap>mxMmap) szMmap = mxMmap;
+      sqlite3GlobalConfig.mxMmap = mxMmap;
+      sqlite3GlobalConfig.szMmap = szMmap;
+      break;
+    }
+
+#if SQLITE_OS_WIN && defined(SQLITE_WIN32_MALLOC) /* IMP: R-04780-55815 */
+    case SQLITE_CONFIG_WIN32_HEAPSIZE: {
+      /* EVIDENCE-OF: R-34926-03360 SQLITE_CONFIG_WIN32_HEAPSIZE takes a 32-bit
+      ** unsigned integer value that specifies the maximum size of the created
+      ** heap. */
+      sqlite3GlobalConfig.nHeap = va_arg(ap, int);
+      break;
+    }
+#endif
+
+    case SQLITE_CONFIG_PMASZ: {
+      sqlite3GlobalConfig.szPma = va_arg(ap, unsigned int);
+      break;
+    }
+
+    case SQLITE_CONFIG_STMTJRNL_SPILL: {
+      sqlite3GlobalConfig.nStmtSpill = va_arg(ap, int);
+      break;
+    }
+
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    case SQLITE_CONFIG_SORTERREF_SIZE: {
+      int iVal = va_arg(ap, int);
+      if( iVal<0 ){
+        iVal = SQLITE_DEFAULT_SORTERREF_SIZE;
+      }
+      sqlite3GlobalConfig.szSorterRef = (u32)iVal;
+      break;
+    }
+#endif /* SQLITE_ENABLE_SORTER_REFERENCES */
+
+#ifndef SQLITE_OMIT_DESERIALIZE
+    case SQLITE_CONFIG_MEMDB_MAXSIZE: {
+      sqlite3GlobalConfig.mxMemdbSize = va_arg(ap, sqlite3_int64);
+      break;
+    }
+#endif /* SQLITE_OMIT_DESERIALIZE */
+
+    default: {
+      rc = SQLITE_ERROR;
+      break;
+    }
+  }
+  va_end(ap);
+  return rc;
+}
+
+/*
+** Set up the lookaside buffers for a database connection.
+** Return SQLITE_OK on success. 
+** If lookaside is already active, return SQLITE_BUSY.
+**
+** The sz parameter is the number of bytes in each lookaside slot.
+** The cnt parameter is the number of slots.  If pStart is NULL the
+** space for the lookaside memory is obtained from sqlite3_malloc().
+** If pStart is not NULL then it is sz*cnt bytes of memory to use for
+** the lookaside memory.
+*/
+static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
+#ifndef SQLITE_OMIT_LOOKASIDE
+  void *pStart;
+  sqlite3_int64 szAlloc = sz*(sqlite3_int64)cnt;
+  int nBig;   /* Number of full-size slots */
+  int nSm;    /* Number smaller LOOKASIDE_SMALL-byte slots */
+ 
+  if( sqlite3LookasideUsed(db,0)>0 ){
+    return SQLITE_BUSY;
+  }
+  /* Free any existing lookaside buffer for this handle before
+  ** allocating a new one so we don't have to have space for
+  ** both at the same time.
+  */
+  if( db->lookaside.bMalloced ){
+    sqlite3_free(db->lookaside.pStart);
+  }
+  /* The size of a lookaside slot after ROUNDDOWN8 needs to be larger
+  ** than a pointer to be useful.
+  */
+  sz = ROUNDDOWN8(sz);  /* IMP: R-33038-09382 */
+  if( sz<=(int)sizeof(LookasideSlot*) ) sz = 0;
+  if( cnt<0 ) cnt = 0;
+  if( sz==0 || cnt==0 ){
+    sz = 0;
+    pStart = 0;
+  }else if( pBuf==0 ){
+    sqlite3BeginBenignMalloc();
+    pStart = sqlite3Malloc( szAlloc );  /* IMP: R-61949-35727 */
+    sqlite3EndBenignMalloc();
+    if( pStart ) szAlloc = sqlite3MallocSize(pStart);
+  }else{
+    pStart = pBuf;
+  }
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+  if( sz>=LOOKASIDE_SMALL*3 ){
+    nBig = szAlloc/(3*LOOKASIDE_SMALL+sz);
+    nSm = (szAlloc - sz*nBig)/LOOKASIDE_SMALL;
+  }else if( sz>=LOOKASIDE_SMALL*2 ){
+    nBig = szAlloc/(LOOKASIDE_SMALL+sz);
+    nSm = (szAlloc - sz*nBig)/LOOKASIDE_SMALL;
+  }else
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+  if( sz>0 ){
+    nBig = szAlloc/sz;
+    nSm = 0;
+  }else{
+    nBig = nSm = 0;
+  }
+  db->lookaside.pStart = pStart;
+  db->lookaside.pInit = 0;
+  db->lookaside.pFree = 0;
+  db->lookaside.sz = (u16)sz;
+  db->lookaside.szTrue = (u16)sz;
+  if( pStart ){
+    int i;
+    LookasideSlot *p;
+    assert( sz > (int)sizeof(LookasideSlot*) );
+    p = (LookasideSlot*)pStart;
+    for(i=0; i<nBig; i++){
+      p->pNext = db->lookaside.pInit;
+      db->lookaside.pInit = p;
+      p = (LookasideSlot*)&((u8*)p)[sz];
+    }
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+    db->lookaside.pSmallInit = 0;
+    db->lookaside.pSmallFree = 0;
+    db->lookaside.pMiddle = p;
+    for(i=0; i<nSm; i++){
+      p->pNext = db->lookaside.pSmallInit;
+      db->lookaside.pSmallInit = p;
+      p = (LookasideSlot*)&((u8*)p)[LOOKASIDE_SMALL];
+    }
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+    assert( ((uptr)p)<=szAlloc + (uptr)pStart );
+    db->lookaside.pEnd = p;
+    db->lookaside.bDisable = 0;
+    db->lookaside.bMalloced = pBuf==0 ?1:0;
+    db->lookaside.nSlot = nBig+nSm;
+  }else{
+    db->lookaside.pStart = 0;
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+    db->lookaside.pSmallInit = 0;
+    db->lookaside.pSmallFree = 0;
+    db->lookaside.pMiddle = 0;
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+    db->lookaside.pEnd = 0;
+    db->lookaside.bDisable = 1;
+    db->lookaside.sz = 0;
+    db->lookaside.bMalloced = 0;
+    db->lookaside.nSlot = 0;
+  }
+  db->lookaside.pTrueEnd = db->lookaside.pEnd;
+  assert( sqlite3LookasideUsed(db,0)==0 );
+#endif /* SQLITE_OMIT_LOOKASIDE */
+  return SQLITE_OK;
+}
+
+/*
+** Return the mutex associated with a database connection.
+*/
+sqlite3_mutex *sqlite3_db_mutex(sqlite3 *db){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return db->mutex;
+}
+
+/*
+** Free up as much memory as we can from the given database
+** connection.
+*/
+int sqlite3_db_release_memory(sqlite3 *db){
+  int i;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3BtreeEnterAll(db);
+  for(i=0; i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ){
+      Pager *pPager = sqlite3BtreePager(pBt);
+      sqlite3PagerShrink(pPager);
+    }
+  }
+  sqlite3BtreeLeaveAll(db);
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+/*
+** Flush any dirty pages in the pager-cache for any attached database
+** to disk.
+*/
+int sqlite3_db_cacheflush(sqlite3 *db){
+  int i;
+  int rc = SQLITE_OK;
+  int bSeenBusy = 0;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3BtreeEnterAll(db);
+  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt && sqlite3BtreeTxnState(pBt)==SQLITE_TXN_WRITE ){
+      Pager *pPager = sqlite3BtreePager(pBt);
+      rc = sqlite3PagerFlush(pPager);
+      if( rc==SQLITE_BUSY ){
+        bSeenBusy = 1;
+        rc = SQLITE_OK;
+      }
+    }
+  }
+  sqlite3BtreeLeaveAll(db);
+  sqlite3_mutex_leave(db->mutex);
+  return ((rc==SQLITE_OK && bSeenBusy) ? SQLITE_BUSY : rc);
+}
+
+/*
+** Configuration settings for an individual database connection
+*/
+int sqlite3_db_config(sqlite3 *db, int op, ...){
+  va_list ap;
+  int rc;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  va_start(ap, op);
+  switch( op ){
+    case SQLITE_DBCONFIG_MAINDBNAME: {
+      /* IMP: R-06824-28531 */
+      /* IMP: R-36257-52125 */
+      db->aDb[0].zDbSName = va_arg(ap,char*);
+      rc = SQLITE_OK;
+      break;
+    }
+    case SQLITE_DBCONFIG_LOOKASIDE: {
+      void *pBuf = va_arg(ap, void*); /* IMP: R-26835-10964 */
+      int sz = va_arg(ap, int);       /* IMP: R-47871-25994 */
+      int cnt = va_arg(ap, int);      /* IMP: R-04460-53386 */
+      rc = setupLookaside(db, pBuf, sz, cnt);
+      break;
+    }
+    default: {
+      static const struct {
+        int op;      /* The opcode */
+        u32 mask;    /* Mask of the bit in sqlite3.flags to set/clear */
+      } aFlagOp[] = {
+        { SQLITE_DBCONFIG_ENABLE_FKEY,           SQLITE_ForeignKeys    },
+        { SQLITE_DBCONFIG_ENABLE_TRIGGER,        SQLITE_EnableTrigger  },
+        { SQLITE_DBCONFIG_ENABLE_VIEW,           SQLITE_EnableView     },
+        { SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER, SQLITE_Fts3Tokenizer  },
+        { SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION, SQLITE_LoadExtension  },
+        { SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE,      SQLITE_NoCkptOnClose  },
+        { SQLITE_DBCONFIG_ENABLE_QPSG,           SQLITE_EnableQPSG     },
+        { SQLITE_DBCONFIG_TRIGGER_EQP,           SQLITE_TriggerEQP     },
+        { SQLITE_DBCONFIG_RESET_DATABASE,        SQLITE_ResetDatabase  },
+        { SQLITE_DBCONFIG_DEFENSIVE,             SQLITE_Defensive      },
+        { SQLITE_DBCONFIG_WRITABLE_SCHEMA,       SQLITE_WriteSchema|
+                                                 SQLITE_NoSchemaError  },
+        { SQLITE_DBCONFIG_LEGACY_ALTER_TABLE,    SQLITE_LegacyAlter    },
+        { SQLITE_DBCONFIG_DQS_DDL,               SQLITE_DqsDDL         },
+        { SQLITE_DBCONFIG_DQS_DML,               SQLITE_DqsDML         },
+        { SQLITE_DBCONFIG_LEGACY_FILE_FORMAT,    SQLITE_LegacyFileFmt  },
+        { SQLITE_DBCONFIG_TRUSTED_SCHEMA,        SQLITE_TrustedSchema  },
+        { SQLITE_DBCONFIG_STMT_SCANSTATUS,       SQLITE_StmtScanStatus },
+        { SQLITE_DBCONFIG_REVERSE_SCANORDER,     SQLITE_ReverseOrder   },
+      };
+      unsigned int i;
+      rc = SQLITE_ERROR; /* IMP: R-42790-23372 */
+      for(i=0; i<ArraySize(aFlagOp); i++){
+        if( aFlagOp[i].op==op ){
+          int onoff = va_arg(ap, int);
+          int *pRes = va_arg(ap, int*);
+          u64 oldFlags = db->flags;
+          if( onoff>0 ){
+            db->flags |= aFlagOp[i].mask;
+          }else if( onoff==0 ){
+            db->flags &= ~(u64)aFlagOp[i].mask;
+          }
+          if( oldFlags!=db->flags ){
+            sqlite3ExpirePreparedStatements(db, 0);
+          }
+          if( pRes ){
+            *pRes = (db->flags & aFlagOp[i].mask)!=0;
+          }
+          rc = SQLITE_OK;
+          break;
+        }
+      }
+      break;
+    }
+  }
+  va_end(ap);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** This is the default collating function named "BINARY" which is always
+** available.
+*/
+static int binCollFunc(
+  void *NotUsed,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  int rc, n;
+  UNUSED_PARAMETER(NotUsed);
+  n = nKey1<nKey2 ? nKey1 : nKey2;
+  /* EVIDENCE-OF: R-65033-28449 The built-in BINARY collation compares
+  ** strings byte by byte using the memcmp() function from the standard C
+  ** library. */
+  assert( pKey1 && pKey2 );
+  rc = memcmp(pKey1, pKey2, n);
+  if( rc==0 ){
+    rc = nKey1 - nKey2;
+  }
+  return rc;
+}
+
+/*
+** This is the collating function named "RTRIM" which is always
+** available.  Ignore trailing spaces.
+*/
+static int rtrimCollFunc(
+  void *pUser,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  const u8 *pK1 = (const u8*)pKey1;
+  const u8 *pK2 = (const u8*)pKey2;
+  while( nKey1 && pK1[nKey1-1]==' ' ) nKey1--;
+  while( nKey2 && pK2[nKey2-1]==' ' ) nKey2--;
+  return binCollFunc(pUser, nKey1, pKey1, nKey2, pKey2);
+}
+
+/*
+** Return true if CollSeq is the default built-in BINARY.
+*/
+int sqlite3IsBinary(const CollSeq *p){
+  assert( p==0 || p->xCmp!=binCollFunc || strcmp(p->zName,"BINARY")==0 );
+  return p==0 || p->xCmp==binCollFunc;
+}
+
+/*
+** Another built-in collating sequence: NOCASE.
+**
+** This collating sequence is intended to be used for "case independent
+** comparison". SQLite's knowledge of upper and lower case equivalents
+** extends only to the 26 characters used in the English language.
+**
+** At the moment there is only a UTF-8 implementation.
+*/
+static int nocaseCollatingFunc(
+  void *NotUsed,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  int r = sqlite3StrNICmp(
+      (const char *)pKey1, (const char *)pKey2, (nKey1<nKey2)?nKey1:nKey2);
+  UNUSED_PARAMETER(NotUsed);
+  if( 0==r ){
+    r = nKey1-nKey2;
+  }
+  return r;
+}
+
+/*
+** Return the ROWID of the most recent insert
+*/
+sqlite_int64 sqlite3_last_insert_rowid(sqlite3 *db){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return db->lastRowid;
+}
+
+/*
+** Set the value returned by the sqlite3_last_insert_rowid() API function.
+*/
+void sqlite3_set_last_insert_rowid(sqlite3 *db, sqlite3_int64 iRowid){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  db->lastRowid = iRowid;
+  sqlite3_mutex_leave(db->mutex);
+}
+
+/*
+** Return the number of changes in the most recent call to sqlite3_exec().
+*/
+sqlite3_int64 sqlite3_changes64(sqlite3 *db){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return db->nChange;
+}
+int sqlite3_changes(sqlite3 *db){
+  return (int)sqlite3_changes64(db);
+}
+
+/*
+** Return the number of changes since the database handle was opened.
+*/
+sqlite3_int64 sqlite3_total_changes64(sqlite3 *db){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return db->nTotalChange;
+}
+int sqlite3_total_changes(sqlite3 *db){
+  return (int)sqlite3_total_changes64(db);
+}
+
+/*
+** Close all open savepoints. This function only manipulates fields of the
+** database handle object, it does not close any savepoints that may be open
+** at the b-tree/pager level.
+*/
+void sqlite3CloseSavepoints(sqlite3 *db){
+  while( db->pSavepoint ){
+    Savepoint *pTmp = db->pSavepoint;
+    db->pSavepoint = pTmp->pNext;
+    sqlite3DbFree(db, pTmp);
+  }
+  db->nSavepoint = 0;
+  db->nStatement = 0;
+  db->isTransactionSavepoint = 0;
+}
+
+/*
+** Invoke the destructor function associated with FuncDef p, if any. Except,
+** if this is not the last copy of the function, do not invoke it. Multiple
+** copies of a single function are created when create_function() is called
+** with SQLITE_ANY as the encoding.
+*/
+static void functionDestroy(sqlite3 *db, FuncDef *p){
+  FuncDestructor *pDestructor;
+  assert( (p->funcFlags & SQLITE_FUNC_BUILTIN)==0 );
+  pDestructor = p->u.pDestructor;
+  if( pDestructor ){
+    pDestructor->nRef--;
+    if( pDestructor->nRef==0 ){
+      pDestructor->xDestroy(pDestructor->pUserData);
+      sqlite3DbFree(db, pDestructor);
+    }
+  }
+}
+
+/*
+** Disconnect all sqlite3_vtab objects that belong to database connection
+** db. This is called when db is being closed.
+*/
+static void disconnectAllVtab(sqlite3 *db){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  int i;
+  HashElem *p;
+  sqlite3BtreeEnterAll(db);
+  for(i=0; i<db->nDb; i++){
+    Schema *pSchema = db->aDb[i].pSchema;
+    if( pSchema ){
+      for(p=sqliteHashFirst(&pSchema->tblHash); p; p=sqliteHashNext(p)){
+        Table *pTab = (Table *)sqliteHashData(p);
+        if( IsVirtual(pTab) ) sqlite3VtabDisconnect(db, pTab);
+      }
+    }
+  }
+  for(p=sqliteHashFirst(&db->aModule); p; p=sqliteHashNext(p)){
+    Module *pMod = (Module *)sqliteHashData(p);
+    if( pMod->pEpoTab ){
+      sqlite3VtabDisconnect(db, pMod->pEpoTab);
+    }
+  }
+  sqlite3VtabUnlockList(db);
+  sqlite3BtreeLeaveAll(db);
+#else
+  UNUSED_PARAMETER(db);
+#endif
+}
+
+/*
+** Return TRUE if database connection db has unfinalized prepared
+** statements or unfinished sqlite3_backup objects. 
+*/
+static int connectionIsBusy(sqlite3 *db){
+  int j;
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( db->pVdbe ) return 1;
+  for(j=0; j<db->nDb; j++){
+    Btree *pBt = db->aDb[j].pBt;
+    if( pBt && sqlite3BtreeIsInBackup(pBt) ) return 1;
+  }
+  return 0;
+}
+
+/*
+** Close an existing SQLite database
+*/
+static int sqlite3Close(sqlite3 *db, int forceZombie){
+  if( !db ){
+    /* EVIDENCE-OF: R-63257-11740 Calling sqlite3_close() or
+    ** sqlite3_close_v2() with a NULL pointer argument is a harmless no-op. */
+    return SQLITE_OK;
+  }
+  if( !sqlite3SafetyCheckSickOrOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  sqlite3_mutex_enter(db->mutex);
+  if( db->mTrace & SQLITE_TRACE_CLOSE ){
+    db->trace.xV2(SQLITE_TRACE_CLOSE, db->pTraceArg, db, 0);
+  }
+
+  /* Force xDisconnect calls on all virtual tables */
+  disconnectAllVtab(db);
+
+  /* If a transaction is open, the disconnectAllVtab() call above
+  ** will not have called the xDisconnect() method on any virtual
+  ** tables in the db->aVTrans[] array. The following sqlite3VtabRollback()
+  ** call will do so. We need to do this before the check for active
+  ** SQL statements below, as the v-table implementation may be storing
+  ** some prepared statements internally.
+  */
+  sqlite3VtabRollback(db);
+
+  /* Legacy behavior (sqlite3_close() behavior) is to return
+  ** SQLITE_BUSY if the connection can not be closed immediately.
+  */
+  if( !forceZombie && connectionIsBusy(db) ){
+    sqlite3ErrorWithMsg(db, SQLITE_BUSY, "unable to close due to unfinalized "
+       "statements or unfinished backups");
+    sqlite3_mutex_leave(db->mutex);
+    return SQLITE_BUSY;
+  }
+
+#ifdef SQLITE_ENABLE_SQLLOG
+  if( sqlite3GlobalConfig.xSqllog ){
+    /* Closing the handle. Fourth parameter is passed the value 2. */
+    sqlite3GlobalConfig.xSqllog(sqlite3GlobalConfig.pSqllogArg, db, 0, 2);
+  }
+#endif
+
+  while( db->pDbData ){
+    DbClientData *p = db->pDbData;
+    db->pDbData = p->pNext;
+    assert( p->pData!=0 );
+    if( p->xDestructor ) p->xDestructor(p->pData);
+    sqlite3_free(p);
+  }
+
+  /* Convert the connection into a zombie and then close it.
+  */
+  db->eOpenState = SQLITE_STATE_ZOMBIE;
+  sqlite3LeaveMutexAndCloseZombie(db);
+  return SQLITE_OK;
+}
+
+/*
+** Return the transaction state for a single databse, or the maximum
+** transaction state over all attached databases if zSchema is null.
+*/
+int sqlite3_txn_state(sqlite3 *db, const char *zSchema){
+  int iDb, nDb;
+  int iTxn = -1;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return -1;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  if( zSchema ){
+    nDb = iDb = sqlite3FindDbName(db, zSchema);
+    if( iDb<0 ) nDb--;
+  }else{
+    iDb = 0;
+    nDb = db->nDb-1;
+  }
+  for(; iDb<=nDb; iDb++){
+    Btree *pBt = db->aDb[iDb].pBt;
+    int x = pBt!=0 ? sqlite3BtreeTxnState(pBt) : SQLITE_TXN_NONE;
+    if( x>iTxn ) iTxn = x;
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return iTxn;
+}
+
+/*
+** Two variations on the public interface for closing a database
+** connection. The sqlite3_close() version returns SQLITE_BUSY and
+** leaves the connection open if there are unfinalized prepared
+** statements or unfinished sqlite3_backups.  The sqlite3_close_v2()
+** version forces the connection to become a zombie if there are
+** unclosed resources, and arranges for deallocation when the last
+** prepare statement or sqlite3_backup closes.
+*/
+int sqlite3_close(sqlite3 *db){ return sqlite3Close(db,0); }
+int sqlite3_close_v2(sqlite3 *db){ return sqlite3Close(db,1); }
+
+
+/*
+** Close the mutex on database connection db.
+**
+** Furthermore, if database connection db is a zombie (meaning that there
+** has been a prior call to sqlite3_close(db) or sqlite3_close_v2(db)) and
+** every sqlite3_stmt has now been finalized and every sqlite3_backup has
+** finished, then free all resources.
+*/
+void sqlite3LeaveMutexAndCloseZombie(sqlite3 *db){
+  HashElem *i;                    /* Hash table iterator */
+  int j;
+
+  /* If there are outstanding sqlite3_stmt or sqlite3_backup objects
+  ** or if the connection has not yet been closed by sqlite3_close_v2(),
+  ** then just leave the mutex and return.
+  */
+  if( db->eOpenState!=SQLITE_STATE_ZOMBIE || connectionIsBusy(db) ){
+    sqlite3_mutex_leave(db->mutex);
+    return;
+  }
+
+  /* If we reach this point, it means that the database connection has
+  ** closed all sqlite3_stmt and sqlite3_backup objects and has been
+  ** passed to sqlite3_close (meaning that it is a zombie).  Therefore,
+  ** go ahead and free all resources.
+  */
+
+  /* If a transaction is open, roll it back. This also ensures that if
+  ** any database schemas have been modified by an uncommitted transaction
+  ** they are reset. And that the required b-tree mutex is held to make
+  ** the pager rollback and schema reset an atomic operation. */
+  sqlite3RollbackAll(db, SQLITE_OK);
+
+  /* Free any outstanding Savepoint structures. */
+  sqlite3CloseSavepoints(db);
+
+  /* Close all database connections */
+  for(j=0; j<db->nDb; j++){
+    struct Db *pDb = &db->aDb[j];
+    if( pDb->pBt ){
+      sqlite3BtreeClose(pDb->pBt);
+      pDb->pBt = 0;
+      if( j!=1 ){
+        pDb->pSchema = 0;
+      }
+    }
+  }
+  /* Clear the TEMP schema separately and last */
+  if( db->aDb[1].pSchema ){
+    sqlite3SchemaClear(db->aDb[1].pSchema);
+  }
+  sqlite3VtabUnlockList(db);
+
+  /* Free up the array of auxiliary databases */
+  sqlite3CollapseDatabaseArray(db);
+  assert( db->nDb<=2 );
+  assert( db->aDb==db->aDbStatic );
+
+  /* Tell the code in notify.c that the connection no longer holds any
+  ** locks and does not require any further unlock-notify callbacks.
+  */
+  sqlite3ConnectionClosed(db);
+
+  for(i=sqliteHashFirst(&db->aFunc); i; i=sqliteHashNext(i)){
+    FuncDef *pNext, *p;
+    p = sqliteHashData(i);
+    do{
+      functionDestroy(db, p);
+      pNext = p->pNext;
+      sqlite3DbFree(db, p);
+      p = pNext;
+    }while( p );
+  }
+  sqlite3HashClear(&db->aFunc);
+  for(i=sqliteHashFirst(&db->aCollSeq); i; i=sqliteHashNext(i)){
+    CollSeq *pColl = (CollSeq *)sqliteHashData(i);
+    /* Invoke any destructors registered for collation sequence user data. */
+    for(j=0; j<3; j++){
+      if( pColl[j].xDel ){
+        pColl[j].xDel(pColl[j].pUser);
+      }
+    }
+    sqlite3DbFree(db, pColl);
+  }
+  sqlite3HashClear(&db->aCollSeq);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  for(i=sqliteHashFirst(&db->aModule); i; i=sqliteHashNext(i)){
+    Module *pMod = (Module *)sqliteHashData(i);
+    sqlite3VtabEponymousTableClear(db, pMod);
+    sqlite3VtabModuleUnref(db, pMod);
+  }
+  sqlite3HashClear(&db->aModule);
+#endif
+
+  sqlite3Error(db, SQLITE_OK); /* Deallocates any cached error strings. */
+  sqlite3ValueFree(db->pErr);
+  sqlite3CloseExtensions(db);
+#if SQLITE_USER_AUTHENTICATION
+  sqlite3_free(db->auth.zAuthUser);
+  sqlite3_free(db->auth.zAuthPW);
+#endif
+
+  db->eOpenState = SQLITE_STATE_ERROR;
+
+  /* The temp-database schema is allocated differently from the other schema
+  ** objects (using sqliteMalloc() directly, instead of sqlite3BtreeSchema()).
+  ** So it needs to be freed here. Todo: Why not roll the temp schema into
+  ** the same sqliteMalloc() as the one that allocates the database
+  ** structure?
+  */
+  sqlite3DbFree(db, db->aDb[1].pSchema);
+  if( db->xAutovacDestr ){
+    db->xAutovacDestr(db->pAutovacPagesArg);
+  }
+  sqlite3_mutex_leave(db->mutex);
+  db->eOpenState = SQLITE_STATE_CLOSED;
+  sqlite3_mutex_free(db->mutex);
+  assert( sqlite3LookasideUsed(db,0)==0 );
+  if( db->lookaside.bMalloced ){
+    sqlite3_free(db->lookaside.pStart);
+  }
+  sqlite3_free(db);
+}
+
+/*
+** Rollback all database files.  If tripCode is not SQLITE_OK, then
+** any write cursors are invalidated ("tripped" - as in "tripping a circuit
+** breaker") and made to return tripCode if there are any further
+** attempts to use that cursor.  Read cursors remain open and valid
+** but are "saved" in case the table pages are moved around.
+*/
+void sqlite3RollbackAll(sqlite3 *db, int tripCode){
+  int i;
+  int inTrans = 0;
+  int schemaChange;
+  assert( sqlite3_mutex_held(db->mutex) );
+  sqlite3BeginBenignMalloc();
+
+  /* Obtain all b-tree mutexes before making any calls to BtreeRollback().
+  ** This is important in case the transaction being rolled back has
+  ** modified the database schema. If the b-tree mutexes are not taken
+  ** here, then another shared-cache connection might sneak in between
+  ** the database rollback and schema reset, which can cause false
+  ** corruption reports in some cases.  */
+  sqlite3BtreeEnterAll(db);
+  schemaChange = (db->mDbFlags & DBFLAG_SchemaChange)!=0 && db->init.busy==0;
+
+  for(i=0; i<db->nDb; i++){
+    Btree *p = db->aDb[i].pBt;
+    if( p ){
+      if( sqlite3BtreeTxnState(p)==SQLITE_TXN_WRITE ){
+        inTrans = 1;
+      }
+      sqlite3BtreeRollback(p, tripCode, !schemaChange);
+    }
+  }
+  sqlite3VtabRollback(db);
+  sqlite3EndBenignMalloc();
+
+  if( schemaChange ){
+    sqlite3ExpirePreparedStatements(db, 0);
+    sqlite3ResetAllSchemasOfConnection(db);
+  }
+  sqlite3BtreeLeaveAll(db);
+
+  /* Any deferred constraint violations have now been resolved. */
+  db->nDeferredCons = 0;
+  db->nDeferredImmCons = 0;
+  db->flags &= ~(u64)(SQLITE_DeferFKs|SQLITE_CorruptRdOnly);
+
+  /* If one has been configured, invoke the rollback-hook callback */
+  if( db->xRollbackCallback && (inTrans || !db->autoCommit) ){
+    db->xRollbackCallback(db->pRollbackArg);
+  }
+}
+
+/*
+** Return a static string containing the name corresponding to the error code
+** specified in the argument.
+*/
+#if defined(SQLITE_NEED_ERR_NAME)
+const char *sqlite3ErrName(int rc){
+  const char *zName = 0;
+  int i, origRc = rc;
+  for(i=0; i<2 && zName==0; i++, rc &= 0xff){
+    switch( rc ){
+      case SQLITE_OK:                 zName = "SQLITE_OK";                break;
+      case SQLITE_ERROR:              zName = "SQLITE_ERROR";             break;
+      case SQLITE_ERROR_SNAPSHOT:     zName = "SQLITE_ERROR_SNAPSHOT";    break;
+      case SQLITE_INTERNAL:           zName = "SQLITE_INTERNAL";          break;
+      case SQLITE_PERM:               zName = "SQLITE_PERM";              break;
+      case SQLITE_ABORT:              zName = "SQLITE_ABORT";             break;
+      case SQLITE_ABORT_ROLLBACK:     zName = "SQLITE_ABORT_ROLLBACK";    break;
+      case SQLITE_BUSY:               zName = "SQLITE_BUSY";              break;
+      case SQLITE_BUSY_RECOVERY:      zName = "SQLITE_BUSY_RECOVERY";     break;
+      case SQLITE_BUSY_SNAPSHOT:      zName = "SQLITE_BUSY_SNAPSHOT";     break;
+      case SQLITE_LOCKED:             zName = "SQLITE_LOCKED";            break;
+      case SQLITE_LOCKED_SHAREDCACHE: zName = "SQLITE_LOCKED_SHAREDCACHE";break;
+      case SQLITE_NOMEM:              zName = "SQLITE_NOMEM";             break;
+      case SQLITE_READONLY:           zName = "SQLITE_READONLY";          break;
+      case SQLITE_READONLY_RECOVERY:  zName = "SQLITE_READONLY_RECOVERY"; break;
+      case SQLITE_READONLY_CANTINIT:  zName = "SQLITE_READONLY_CANTINIT"; break;
+      case SQLITE_READONLY_ROLLBACK:  zName = "SQLITE_READONLY_ROLLBACK"; break;
+      case SQLITE_READONLY_DBMOVED:   zName = "SQLITE_READONLY_DBMOVED";  break;
+      case SQLITE_READONLY_DIRECTORY: zName = "SQLITE_READONLY_DIRECTORY";break;
+      case SQLITE_INTERRUPT:          zName = "SQLITE_INTERRUPT";         break;
+      case SQLITE_IOERR:              zName = "SQLITE_IOERR";             break;
+      case SQLITE_IOERR_READ:         zName = "SQLITE_IOERR_READ";        break;
+      case SQLITE_IOERR_SHORT_READ:   zName = "SQLITE_IOERR_SHORT_READ";  break;
+      case SQLITE_IOERR_WRITE:        zName = "SQLITE_IOERR_WRITE";       break;
+      case SQLITE_IOERR_FSYNC:        zName = "SQLITE_IOERR_FSYNC";       break;
+      case SQLITE_IOERR_DIR_FSYNC:    zName = "SQLITE_IOERR_DIR_FSYNC";   break;
+      case SQLITE_IOERR_TRUNCATE:     zName = "SQLITE_IOERR_TRUNCATE";    break;
+      case SQLITE_IOERR_FSTAT:        zName = "SQLITE_IOERR_FSTAT";       break;
+      case SQLITE_IOERR_UNLOCK:       zName = "SQLITE_IOERR_UNLOCK";      break;
+      case SQLITE_IOERR_RDLOCK:       zName = "SQLITE_IOERR_RDLOCK";      break;
+      case SQLITE_IOERR_DELETE:       zName = "SQLITE_IOERR_DELETE";      break;
+      case SQLITE_IOERR_NOMEM:        zName = "SQLITE_IOERR_NOMEM";       break;
+      case SQLITE_IOERR_ACCESS:       zName = "SQLITE_IOERR_ACCESS";      break;
+      case SQLITE_IOERR_CHECKRESERVEDLOCK:
+                                zName = "SQLITE_IOERR_CHECKRESERVEDLOCK"; break;
+      case SQLITE_IOERR_LOCK:         zName = "SQLITE_IOERR_LOCK";        break;
+      case SQLITE_IOERR_CLOSE:        zName = "SQLITE_IOERR_CLOSE";       break;
+      case SQLITE_IOERR_DIR_CLOSE:    zName = "SQLITE_IOERR_DIR_CLOSE";   break;
+      case SQLITE_IOERR_SHMOPEN:      zName = "SQLITE_IOERR_SHMOPEN";     break;
+      case SQLITE_IOERR_SHMSIZE:      zName = "SQLITE_IOERR_SHMSIZE";     break;
+      case SQLITE_IOERR_SHMLOCK:      zName = "SQLITE_IOERR_SHMLOCK";     break;
+      case SQLITE_IOERR_SHMMAP:       zName = "SQLITE_IOERR_SHMMAP";      break;
+      case SQLITE_IOERR_SEEK:         zName = "SQLITE_IOERR_SEEK";        break;
+      case SQLITE_IOERR_DELETE_NOENT: zName = "SQLITE_IOERR_DELETE_NOENT";break;
+      case SQLITE_IOERR_MMAP:         zName = "SQLITE_IOERR_MMAP";        break;
+      case SQLITE_IOERR_GETTEMPPATH:  zName = "SQLITE_IOERR_GETTEMPPATH"; break;
+      case SQLITE_IOERR_CONVPATH:     zName = "SQLITE_IOERR_CONVPATH";    break;
+      case SQLITE_CORRUPT:            zName = "SQLITE_CORRUPT";           break;
+      case SQLITE_CORRUPT_VTAB:       zName = "SQLITE_CORRUPT_VTAB";      break;
+      case SQLITE_NOTFOUND:           zName = "SQLITE_NOTFOUND";          break;
+      case SQLITE_FULL:               zName = "SQLITE_FULL";              break;
+      case SQLITE_CANTOPEN:           zName = "SQLITE_CANTOPEN";          break;
+      case SQLITE_CANTOPEN_NOTEMPDIR: zName = "SQLITE_CANTOPEN_NOTEMPDIR";break;
+      case SQLITE_CANTOPEN_ISDIR:     zName = "SQLITE_CANTOPEN_ISDIR";    break;
+      case SQLITE_CANTOPEN_FULLPATH:  zName = "SQLITE_CANTOPEN_FULLPATH"; break;
+      case SQLITE_CANTOPEN_CONVPATH:  zName = "SQLITE_CANTOPEN_CONVPATH"; break;
+      case SQLITE_CANTOPEN_SYMLINK:   zName = "SQLITE_CANTOPEN_SYMLINK";  break;
+      case SQLITE_PROTOCOL:           zName = "SQLITE_PROTOCOL";          break;
+      case SQLITE_EMPTY:              zName = "SQLITE_EMPTY";             break;
+      case SQLITE_SCHEMA:             zName = "SQLITE_SCHEMA";            break;
+      case SQLITE_TOOBIG:             zName = "SQLITE_TOOBIG";            break;
+      case SQLITE_CONSTRAINT:         zName = "SQLITE_CONSTRAINT";        break;
+      case SQLITE_CONSTRAINT_UNIQUE:  zName = "SQLITE_CONSTRAINT_UNIQUE"; break;
+      case SQLITE_CONSTRAINT_TRIGGER: zName = "SQLITE_CONSTRAINT_TRIGGER";break;
+      case SQLITE_CONSTRAINT_FOREIGNKEY:
+                                zName = "SQLITE_CONSTRAINT_FOREIGNKEY";   break;
+      case SQLITE_CONSTRAINT_CHECK:   zName = "SQLITE_CONSTRAINT_CHECK";  break;
+      case SQLITE_CONSTRAINT_PRIMARYKEY:
+                                zName = "SQLITE_CONSTRAINT_PRIMARYKEY";   break;
+      case SQLITE_CONSTRAINT_NOTNULL: zName = "SQLITE_CONSTRAINT_NOTNULL";break;
+      case SQLITE_CONSTRAINT_COMMITHOOK:
+                                zName = "SQLITE_CONSTRAINT_COMMITHOOK";   break;
+      case SQLITE_CONSTRAINT_VTAB:    zName = "SQLITE_CONSTRAINT_VTAB";   break;
+      case SQLITE_CONSTRAINT_FUNCTION:
+                                zName = "SQLITE_CONSTRAINT_FUNCTION";     break;
+      case SQLITE_CONSTRAINT_ROWID:   zName = "SQLITE_CONSTRAINT_ROWID";  break;
+      case SQLITE_MISMATCH:           zName = "SQLITE_MISMATCH";          break;
+      case SQLITE_MISUSE:             zName = "SQLITE_MISUSE";            break;
+      case SQLITE_NOLFS:              zName = "SQLITE_NOLFS";             break;
+      case SQLITE_AUTH:               zName = "SQLITE_AUTH";              break;
+      case SQLITE_FORMAT:             zName = "SQLITE_FORMAT";            break;
+      case SQLITE_RANGE:              zName = "SQLITE_RANGE";             break;
+      case SQLITE_NOTADB:             zName = "SQLITE_NOTADB";            break;
+      case SQLITE_ROW:                zName = "SQLITE_ROW";               break;
+      case SQLITE_NOTICE:             zName = "SQLITE_NOTICE";            break;
+      case SQLITE_NOTICE_RECOVER_WAL: zName = "SQLITE_NOTICE_RECOVER_WAL";break;
+      case SQLITE_NOTICE_RECOVER_ROLLBACK:
+                                zName = "SQLITE_NOTICE_RECOVER_ROLLBACK"; break;
+      case SQLITE_NOTICE_RBU:         zName = "SQLITE_NOTICE_RBU"; break;
+      case SQLITE_WARNING:            zName = "SQLITE_WARNING";           break;
+      case SQLITE_WARNING_AUTOINDEX:  zName = "SQLITE_WARNING_AUTOINDEX"; break;
+      case SQLITE_DONE:               zName = "SQLITE_DONE";              break;
+    }
+  }
+  if( zName==0 ){
+    static char zBuf[50];
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "SQLITE_UNKNOWN(%d)", origRc);
+    zName = zBuf;
+  }
+  return zName;
+}
+#endif
+
+/*
+** Return a static string that describes the kind of error specified in the
+** argument.
+*/
+const char *sqlite3ErrStr(int rc){
+  static const char* const aMsg[] = {
+    /* SQLITE_OK          */ "not an error",
+    /* SQLITE_ERROR       */ "SQL logic error",
+    /* SQLITE_INTERNAL    */ 0,
+    /* SQLITE_PERM        */ "access permission denied",
+    /* SQLITE_ABORT       */ "query aborted",
+    /* SQLITE_BUSY        */ "database is locked",
+    /* SQLITE_LOCKED      */ "database table is locked",
+    /* SQLITE_NOMEM       */ "out of memory",
+    /* SQLITE_READONLY    */ "attempt to write a readonly database",
+    /* SQLITE_INTERRUPT   */ "interrupted",
+    /* SQLITE_IOERR       */ "disk I/O error",
+    /* SQLITE_CORRUPT     */ "database disk image is malformed",
+    /* SQLITE_NOTFOUND    */ "unknown operation",
+    /* SQLITE_FULL        */ "database or disk is full",
+    /* SQLITE_CANTOPEN    */ "unable to open database file",
+    /* SQLITE_PROTOCOL    */ "locking protocol",
+    /* SQLITE_EMPTY       */ 0,
+    /* SQLITE_SCHEMA      */ "database schema has changed",
+    /* SQLITE_TOOBIG      */ "string or blob too big",
+    /* SQLITE_CONSTRAINT  */ "constraint failed",
+    /* SQLITE_MISMATCH    */ "datatype mismatch",
+    /* SQLITE_MISUSE      */ "bad parameter or other API misuse",
+#ifdef SQLITE_DISABLE_LFS
+    /* SQLITE_NOLFS       */ "large file support is disabled",
+#else
+    /* SQLITE_NOLFS       */ 0,
+#endif
+    /* SQLITE_AUTH        */ "authorization denied",
+    /* SQLITE_FORMAT      */ 0,
+    /* SQLITE_RANGE       */ "column index out of range",
+    /* SQLITE_NOTADB      */ "file is not a database",
+    /* SQLITE_NOTICE      */ "notification message",
+    /* SQLITE_WARNING     */ "warning message",
+  };
+  const char *zErr = "unknown error";
+  switch( rc ){
+    case SQLITE_ABORT_ROLLBACK: {
+      zErr = "abort due to ROLLBACK";
+      break;
+    }
+    case SQLITE_ROW: {
+      zErr = "another row available";
+      break;
+    }
+    case SQLITE_DONE: {
+      zErr = "no more rows available";
+      break;
+    }
+    default: {
+      rc &= 0xff;
+      if( ALWAYS(rc>=0) && rc<ArraySize(aMsg) && aMsg[rc]!=0 ){
+        zErr = aMsg[rc];
+      }
+      break;
+    }
+  }
+  return zErr;
+}
+
+/*
+** This routine implements a busy callback that sleeps and tries
+** again until a timeout value is reached.  The timeout value is
+** an integer number of milliseconds passed in as the first
+** argument.
+**
+** Return non-zero to retry the lock.  Return zero to stop trying
+** and cause SQLite to return SQLITE_BUSY.
+*/
+static int sqliteDefaultBusyCallback(
+  void *ptr,               /* Database connection */
+  int count                /* Number of times table has been busy */
+){
+#if SQLITE_OS_WIN || !defined(HAVE_NANOSLEEP) || HAVE_NANOSLEEP
+  /* This case is for systems that have support for sleeping for fractions of
+  ** a second.  Examples:  All windows systems, unix systems with nanosleep() */
+  static const u8 delays[] =
+     { 1, 2, 5, 10, 15, 20, 25, 25,  25,  50,  50, 100 };
+  static const u8 totals[] =
+     { 0, 1, 3,  8, 18, 33, 53, 78, 103, 128, 178, 228 };
+# define NDELAY ArraySize(delays)
+  sqlite3 *db = (sqlite3 *)ptr;
+  int tmout = db->busyTimeout;
+  int delay, prior;
+
+  assert( count>=0 );
+  if( count < NDELAY ){
+    delay = delays[count];
+    prior = totals[count];
+  }else{
+    delay = delays[NDELAY-1];
+    prior = totals[NDELAY-1] + delay*(count-(NDELAY-1));
+  }
+  if( prior + delay > tmout ){
+    delay = tmout - prior;
+    if( delay<=0 ) return 0;
+  }
+  sqlite3OsSleep(db->pVfs, delay*1000);
+  return 1;
+#else
+  /* This case for unix systems that lack usleep() support.  Sleeping
+  ** must be done in increments of whole seconds */
+  sqlite3 *db = (sqlite3 *)ptr;
+  int tmout = ((sqlite3 *)ptr)->busyTimeout;
+  if( (count+1)*1000 > tmout ){
+    return 0;
+  }
+  sqlite3OsSleep(db->pVfs, 1000000);
+  return 1;
+#endif
+}
+
+/*
+** Invoke the given busy handler.
+**
+** This routine is called when an operation failed to acquire a
+** lock on VFS file pFile.
+**
+** If this routine returns non-zero, the lock is retried.  If it
+** returns 0, the operation aborts with an SQLITE_BUSY error.
+*/
+int sqlite3InvokeBusyHandler(BusyHandler *p){
+  int rc;
+  if( p->xBusyHandler==0 || p->nBusy<0 ) return 0;
+  rc = p->xBusyHandler(p->pBusyArg, p->nBusy);
+  if( rc==0 ){
+    p->nBusy = -1;
+  }else{
+    p->nBusy++;
+  }
+  return rc;
+}
+
+/*
+** This routine sets the busy callback for an Sqlite database to the
+** given callback function with the given argument.
+*/
+int sqlite3_busy_handler(
+  sqlite3 *db,
+  int (*xBusy)(void*,int),
+  void *pArg
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  db->busyHandler.xBusyHandler = xBusy;
+  db->busyHandler.pBusyArg = pArg;
+  db->busyHandler.nBusy = 0;
+  db->busyTimeout = 0;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+/*
+** This routine sets the progress callback for an Sqlite database to the
+** given callback function with the given argument. The progress callback will
+** be invoked every nOps opcodes.
+*/
+void sqlite3_progress_handler(
+  sqlite3 *db,
+  int nOps,
+  int (*xProgress)(void*),
+  void *pArg
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  if( nOps>0 ){
+    db->xProgress = xProgress;
+    db->nProgressOps = (unsigned)nOps;
+    db->pProgressArg = pArg;
+  }else{
+    db->xProgress = 0;
+    db->nProgressOps = 0;
+    db->pProgressArg = 0;
+  }
+  sqlite3_mutex_leave(db->mutex);
+}
+#endif
+
+
+/*
+** This routine installs a default busy handler that waits for the
+** specified number of milliseconds before returning 0.
+*/
+int sqlite3_busy_timeout(sqlite3 *db, int ms){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  if( ms>0 ){
+    sqlite3_busy_handler(db, (int(*)(void*,int))sqliteDefaultBusyCallback,
+                             (void*)db);
+    db->busyTimeout = ms;
+  }else{
+    sqlite3_busy_handler(db, 0, 0);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Cause any pending operation to stop at its earliest opportunity.
+*/
+void sqlite3_interrupt(sqlite3 *db){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db)
+   && (db==0 || db->eOpenState!=SQLITE_STATE_ZOMBIE)
+  ){
+    (void)SQLITE_MISUSE_BKPT;
+    return;
+  }
+#endif
+  AtomicStore(&db->u1.isInterrupted, 1);
+}
+
+/*
+** Return true or false depending on whether or not an interrupt is
+** pending on connection db.
+*/
+int sqlite3_is_interrupted(sqlite3 *db){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db)
+   && (db==0 || db->eOpenState!=SQLITE_STATE_ZOMBIE)
+  ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return AtomicLoad(&db->u1.isInterrupted)!=0;
+}
+
+/*
+** This function is exactly the same as sqlite3_create_function(), except
+** that it is designed to be called by internal code. The difference is
+** that if a malloc() fails in sqlite3_create_function(), an error code
+** is returned and the mallocFailed flag cleared.
+*/
+int sqlite3CreateFunc(
+  sqlite3 *db,
+  const char *zFunctionName,
+  int nArg,
+  int enc,
+  void *pUserData,
+  void (*xSFunc)(sqlite3_context*,int,sqlite3_value **),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value **),
+  void (*xFinal)(sqlite3_context*),
+  void (*xValue)(sqlite3_context*),
+  void (*xInverse)(sqlite3_context*,int,sqlite3_value **),
+  FuncDestructor *pDestructor
+){
+  FuncDef *p;
+  int extraFlags;
+
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( xValue==0 || xSFunc==0 );
+  if( zFunctionName==0                /* Must have a valid name */
+   || (xSFunc!=0 && xFinal!=0)        /* Not both xSFunc and xFinal */
+   || ((xFinal==0)!=(xStep==0))       /* Both or neither of xFinal and xStep */
+   || ((xValue==0)!=(xInverse==0))    /* Both or neither of xValue, xInverse */
+   || (nArg<-1 || nArg>SQLITE_MAX_FUNCTION_ARG)
+   || (255<sqlite3Strlen30(zFunctionName))
+  ){
+    return SQLITE_MISUSE_BKPT;
+  }
+
+  assert( SQLITE_FUNC_CONSTANT==SQLITE_DETERMINISTIC );
+  assert( SQLITE_FUNC_DIRECT==SQLITE_DIRECTONLY );
+  extraFlags = enc &  (SQLITE_DETERMINISTIC|SQLITE_DIRECTONLY|
+                       SQLITE_SUBTYPE|SQLITE_INNOCUOUS|SQLITE_RESULT_SUBTYPE);
+  enc &= (SQLITE_FUNC_ENCMASK|SQLITE_ANY);
+
+  /* The SQLITE_INNOCUOUS flag is the same bit as SQLITE_FUNC_UNSAFE.  But
+  ** the meaning is inverted.  So flip the bit. */
+  assert( SQLITE_FUNC_UNSAFE==SQLITE_INNOCUOUS );
+  extraFlags ^= SQLITE_FUNC_UNSAFE;  /* tag-20230109-1 */
+
+ 
+#ifndef SQLITE_OMIT_UTF16
+  /* If SQLITE_UTF16 is specified as the encoding type, transform this
+  ** to one of SQLITE_UTF16LE or SQLITE_UTF16BE using the
+  ** SQLITE_UTF16NATIVE macro. SQLITE_UTF16 is not used internally.
+  **
+  ** If SQLITE_ANY is specified, add three versions of the function
+  ** to the hash table.
+  */
+  switch( enc ){
+    case SQLITE_UTF16:
+      enc = SQLITE_UTF16NATIVE;
+      break;
+    case SQLITE_ANY: {
+      int rc;
+      rc = sqlite3CreateFunc(db, zFunctionName, nArg,
+           (SQLITE_UTF8|extraFlags)^SQLITE_FUNC_UNSAFE, /* tag-20230109-1 */
+           pUserData, xSFunc, xStep, xFinal, xValue, xInverse, pDestructor);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3CreateFunc(db, zFunctionName, nArg,
+             (SQLITE_UTF16LE|extraFlags)^SQLITE_FUNC_UNSAFE, /* tag-20230109-1*/
+             pUserData, xSFunc, xStep, xFinal, xValue, xInverse, pDestructor);
+      }
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      enc = SQLITE_UTF16BE;
+      break;
+    }
+    case SQLITE_UTF8:
+    case SQLITE_UTF16LE:
+    case SQLITE_UTF16BE:
+      break;
+    default:
+      enc = SQLITE_UTF8;
+      break;
+  }
+#else
+  enc = SQLITE_UTF8;
+#endif
+ 
+  /* Check if an existing function is being overridden or deleted. If so,
+  ** and there are active VMs, then return SQLITE_BUSY. If a function
+  ** is being overridden/deleted but there are no active VMs, allow the
+  ** operation to continue but invalidate all precompiled statements.
+  */
+  p = sqlite3FindFunction(db, zFunctionName, nArg, (u8)enc, 0);
+  if( p && (p->funcFlags & SQLITE_FUNC_ENCMASK)==(u32)enc && p->nArg==nArg ){
+    if( db->nVdbeActive ){
+      sqlite3ErrorWithMsg(db, SQLITE_BUSY,
+        "unable to delete/modify user-function due to active statements");
+      assert( !db->mallocFailed );
+      return SQLITE_BUSY;
+    }else{
+      sqlite3ExpirePreparedStatements(db, 0);
+    }
+  }else if( xSFunc==0 && xFinal==0 ){
+    /* Trying to delete a function that does not exist.  This is a no-op.
+    ** https://sqlite.org/forum/forumpost/726219164b */
+    return SQLITE_OK;
+  }
+
+  p = sqlite3FindFunction(db, zFunctionName, nArg, (u8)enc, 1);
+  assert(p || db->mallocFailed);
+  if( !p ){
+    return SQLITE_NOMEM_BKPT;
+  }
+
+  /* If an older version of the function with a configured destructor is
+  ** being replaced invoke the destructor function here. */
+  functionDestroy(db, p);
+
+  if( pDestructor ){
+    pDestructor->nRef++;
+  }
+  p->u.pDestructor = pDestructor;
+  p->funcFlags = (p->funcFlags & SQLITE_FUNC_ENCMASK) | extraFlags;
+  testcase( p->funcFlags & SQLITE_DETERMINISTIC );
+  testcase( p->funcFlags & SQLITE_DIRECTONLY );
+  p->xSFunc = xSFunc ? xSFunc : xStep;
+  p->xFinalize = xFinal;
+  p->xValue = xValue;
+  p->xInverse = xInverse;
+  p->pUserData = pUserData;
+  p->nArg = (u16)nArg;
+  return SQLITE_OK;
+}
+
+/*
+** Worker function used by utf-8 APIs that create new functions:
+**
+**    sqlite3_create_function()
+**    sqlite3_create_function_v2()
+**    sqlite3_create_window_function()
+*/
+static int createFunctionApi(
+  sqlite3 *db,
+  const char *zFunc,
+  int nArg,
+  int enc,
+  void *p,
+  void (*xSFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*),
+  void (*xValue)(sqlite3_context*),
+  void (*xInverse)(sqlite3_context*,int,sqlite3_value**),
+  void(*xDestroy)(void*)
+){
+  int rc = SQLITE_ERROR;
+  FuncDestructor *pArg = 0;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  if( xDestroy ){
+    pArg = (FuncDestructor *)sqlite3Malloc(sizeof(FuncDestructor));
+    if( !pArg ){
+      sqlite3OomFault(db);
+      xDestroy(p);
+      goto out;
+    }
+    pArg->nRef = 0;
+    pArg->xDestroy = xDestroy;
+    pArg->pUserData = p;
+  }
+  rc = sqlite3CreateFunc(db, zFunc, nArg, enc, p,
+      xSFunc, xStep, xFinal, xValue, xInverse, pArg
+  );
+  if( pArg && pArg->nRef==0 ){
+    assert( rc!=SQLITE_OK || (xStep==0 && xFinal==0) );
+    xDestroy(p);
+    sqlite3_free(pArg);
+  }
+
+ out:
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Create new user functions.
+*/
+int sqlite3_create_function(
+  sqlite3 *db,
+  const char *zFunc,
+  int nArg,
+  int enc,
+  void *p,
+  void (*xSFunc)(sqlite3_context*,int,sqlite3_value **),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value **),
+  void (*xFinal)(sqlite3_context*)
+){
+  return createFunctionApi(db, zFunc, nArg, enc, p, xSFunc, xStep,
+                                    xFinal, 0, 0, 0);
+}
+int sqlite3_create_function_v2(
+  sqlite3 *db,
+  const char *zFunc,
+  int nArg,
+  int enc,
+  void *p,
+  void (*xSFunc)(sqlite3_context*,int,sqlite3_value **),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value **),
+  void (*xFinal)(sqlite3_context*),
+  void (*xDestroy)(void *)
+){
+  return createFunctionApi(db, zFunc, nArg, enc, p, xSFunc, xStep,
+                                    xFinal, 0, 0, xDestroy);
+}
+int sqlite3_create_window_function(
+  sqlite3 *db,
+  const char *zFunc,
+  int nArg,
+  int enc,
+  void *p,
+  void (*xStep)(sqlite3_context*,int,sqlite3_value **),
+  void (*xFinal)(sqlite3_context*),
+  void (*xValue)(sqlite3_context*),
+  void (*xInverse)(sqlite3_context*,int,sqlite3_value **),
+  void (*xDestroy)(void *)
+){
+  return createFunctionApi(db, zFunc, nArg, enc, p, 0, xStep,
+                                    xFinal, xValue, xInverse, xDestroy);
+}
+
+#ifndef SQLITE_OMIT_UTF16
+int sqlite3_create_function16(
+  sqlite3 *db,
+  const void *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *p,
+  void (*xSFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*)
+){
+  int rc;
+  char *zFunc8;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zFunctionName==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  assert( !db->mallocFailed );
+  zFunc8 = sqlite3Utf16to8(db, zFunctionName, -1, SQLITE_UTF16NATIVE);
+  rc = sqlite3CreateFunc(db, zFunc8, nArg, eTextRep, p, xSFunc,xStep,xFinal,0,0,0);
+  sqlite3DbFree(db, zFunc8);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+#endif
+
+
+/*
+** The following is the implementation of an SQL function that always
+** fails with an error message stating that the function is used in the
+** wrong context.  The sqlite3_overload_function() API might construct
+** SQL function that use this routine so that the functions will exist
+** for name resolution but are actually overloaded by the xFindFunction
+** method of virtual tables.
+*/
+static void sqlite3InvalidFunction(
+  sqlite3_context *context,  /* The function calling context */
+  int NotUsed,               /* Number of arguments to the function */
+  sqlite3_value **NotUsed2   /* Value of each argument */
+){
+  const char *zName = (const char*)sqlite3_user_data(context);
+  char *zErr;
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  zErr = sqlite3_mprintf(
+      "unable to use function %s in the requested context", zName);
+  sqlite3_result_error(context, zErr, -1);
+  sqlite3_free(zErr);
+}
+
+/*
+** Declare that a function has been overloaded by a virtual table.
+**
+** If the function already exists as a regular global function, then
+** this routine is a no-op.  If the function does not exist, then create
+** a new one that always throws a run-time error. 
+**
+** When virtual tables intend to provide an overloaded function, they
+** should call this routine to make sure the global function exists.
+** A global function must exist in order for name resolution to work
+** properly.
+*/
+int sqlite3_overload_function(
+  sqlite3 *db,
+  const char *zName,
+  int nArg
+){
+  int rc;
+  char *zCopy;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zName==0 || nArg<-2 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  rc = sqlite3FindFunction(db, zName, nArg, SQLITE_UTF8, 0)!=0;
+  sqlite3_mutex_leave(db->mutex);
+  if( rc ) return SQLITE_OK;
+  zCopy = sqlite3_mprintf("%s", zName);
+  if( zCopy==0 ) return SQLITE_NOMEM;
+  return sqlite3_create_function_v2(db, zName, nArg, SQLITE_UTF8,
+                           zCopy, sqlite3InvalidFunction, 0, 0, sqlite3_free);
+}
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** Register a trace function.  The pArg from the previously registered trace
+** is returned. 
+**
+** A NULL trace function means that no tracing is executes.  A non-NULL
+** trace is a pointer to a function that is invoked at the start of each
+** SQL statement.
+*/
+#ifndef SQLITE_OMIT_DEPRECATED
+void *sqlite3_trace(sqlite3 *db, void(*xTrace)(void*,const char*), void *pArg){
+  void *pOld;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pOld = db->pTraceArg;
+  db->mTrace = xTrace ? SQLITE_TRACE_LEGACY : 0;
+  db->trace.xLegacy = xTrace;
+  db->pTraceArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pOld;
+}
+#endif /* SQLITE_OMIT_DEPRECATED */
+
+/* Register a trace callback using the version-2 interface.
+*/
+int sqlite3_trace_v2(
+  sqlite3 *db,                               /* Trace this connection */
+  unsigned mTrace,                           /* Mask of events to be traced */
+  int(*xTrace)(unsigned,void*,void*,void*),  /* Callback to invoke */
+  void *pArg                                 /* Context */
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  if( mTrace==0 ) xTrace = 0;
+  if( xTrace==0 ) mTrace = 0;
+  db->mTrace = mTrace;
+  db->trace.xV2 = xTrace;
+  db->pTraceArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Register a profile function.  The pArg from the previously registered
+** profile function is returned. 
+**
+** A NULL profile function means that no profiling is executes.  A non-NULL
+** profile is a pointer to a function that is invoked at the conclusion of
+** each SQL statement that is run.
+*/
+void *sqlite3_profile(
+  sqlite3 *db,
+  void (*xProfile)(void*,const char*,sqlite_uint64),
+  void *pArg
+){
+  void *pOld;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pOld = db->pProfileArg;
+  db->xProfile = xProfile;
+  db->pProfileArg = pArg;
+  db->mTrace &= SQLITE_TRACE_NONLEGACY_MASK;
+  if( db->xProfile ) db->mTrace |= SQLITE_TRACE_XPROFILE;
+  sqlite3_mutex_leave(db->mutex);
+  return pOld;
+}
+#endif /* SQLITE_OMIT_DEPRECATED */
+#endif /* SQLITE_OMIT_TRACE */
+
+/*
+** Register a function to be invoked when a transaction commits.
+** If the invoked function returns non-zero, then the commit becomes a
+** rollback.
+*/
+void *sqlite3_commit_hook(
+  sqlite3 *db,              /* Attach the hook to this database */
+  int (*xCallback)(void*),  /* Function to invoke on each commit */
+  void *pArg                /* Argument to the function */
+){
+  void *pOld;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pOld = db->pCommitArg;
+  db->xCommitCallback = xCallback;
+  db->pCommitArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pOld;
+}
+
+/*
+** Register a callback to be invoked each time a row is updated,
+** inserted or deleted using this database connection.
+*/
+void *sqlite3_update_hook(
+  sqlite3 *db,              /* Attach the hook to this database */
+  void (*xCallback)(void*,int,char const *,char const *,sqlite_int64),
+  void *pArg                /* Argument to the function */
+){
+  void *pRet;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pUpdateArg;
+  db->xUpdateCallback = xCallback;
+  db->pUpdateArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+}
+
+/*
+** Register a callback to be invoked each time a transaction is rolled
+** back by this database connection.
+*/
+void *sqlite3_rollback_hook(
+  sqlite3 *db,              /* Attach the hook to this database */
+  void (*xCallback)(void*), /* Callback function */
+  void *pArg                /* Argument to the function */
+){
+  void *pRet;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pRollbackArg;
+  db->xRollbackCallback = xCallback;
+  db->pRollbackArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+}
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** Register a callback to be invoked each time a row is updated,
+** inserted or deleted using this database connection.
+*/
+void *sqlite3_preupdate_hook(
+  sqlite3 *db,              /* Attach the hook to this database */
+  void(*xCallback)(         /* Callback function */
+    void*,sqlite3*,int,char const*,char const*,sqlite3_int64,sqlite3_int64),
+  void *pArg                /* First callback argument */
+){
+  void *pRet;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( db==0 ){
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pPreUpdateArg;
+  db->xPreUpdateCallback = xCallback;
+  db->pPreUpdateArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+
+/*
+** Register a function to be invoked prior to each autovacuum that
+** determines the number of pages to vacuum.
+*/
+int sqlite3_autovacuum_pages(
+  sqlite3 *db,                 /* Attach the hook to this database */
+  unsigned int (*xCallback)(void*,const char*,u32,u32,u32),
+  void *pArg,                  /* Argument to the function */
+  void (*xDestructor)(void*)   /* Destructor for pArg */
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    if( xDestructor ) xDestructor(pArg);
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  if( db->xAutovacDestr ){
+    db->xAutovacDestr(db->pAutovacPagesArg);
+  }
+  db->xAutovacPages = xCallback;
+  db->pAutovacPagesArg = pArg;
+  db->xAutovacDestr = xDestructor;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** The sqlite3_wal_hook() callback registered by sqlite3_wal_autocheckpoint().
+** Invoke sqlite3_wal_checkpoint if the number of frames in the log file
+** is greater than sqlite3.pWalArg cast to an integer (the value configured by
+** wal_autocheckpoint()).
+*/
+int sqlite3WalDefaultHook(
+  void *pClientData,     /* Argument */
+  sqlite3 *db,           /* Connection */
+  const char *zDb,       /* Database */
+  int nFrame             /* Size of WAL */
+){
+  if( nFrame>=SQLITE_PTR_TO_INT(pClientData) ){
+    sqlite3BeginBenignMalloc();
+    sqlite3_wal_checkpoint(db, zDb);
+    sqlite3EndBenignMalloc();
+  }
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_WAL */
+
+/*
+** Configure an sqlite3_wal_hook() callback to automatically checkpoint
+** a database after committing a transaction if there are nFrame or
+** more frames in the log file. Passing zero or a negative value as the
+** nFrame parameter disables automatic checkpoints entirely.
+**
+** The callback registered by this function replaces any existing callback
+** registered using sqlite3_wal_hook(). Likewise, registering a callback
+** using sqlite3_wal_hook() disables the automatic checkpoint mechanism
+** configured by this function.
+*/
+int sqlite3_wal_autocheckpoint(sqlite3 *db, int nFrame){
+#ifdef SQLITE_OMIT_WAL
+  UNUSED_PARAMETER(db);
+  UNUSED_PARAMETER(nFrame);
+#else
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  if( nFrame>0 ){
+    sqlite3_wal_hook(db, sqlite3WalDefaultHook, SQLITE_INT_TO_PTR(nFrame));
+  }else{
+    sqlite3_wal_hook(db, 0, 0);
+  }
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Register a callback to be invoked each time a transaction is written
+** into the write-ahead-log by this database connection.
+*/
+void *sqlite3_wal_hook(
+  sqlite3 *db,                    /* Attach the hook to this db handle */
+  int(*xCallback)(void *, sqlite3*, const char*, int),
+  void *pArg                      /* First argument passed to xCallback() */
+){
+#ifndef SQLITE_OMIT_WAL
+  void *pRet;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pWalArg;
+  db->xWalCallback = xCallback;
+  db->pWalArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+#else
+  return 0;
+#endif
+}
+
+/*
+** Checkpoint database zDb.
+*/
+int sqlite3_wal_checkpoint_v2(
+  sqlite3 *db,                    /* Database handle */
+  const char *zDb,                /* Name of attached database (or NULL) */
+  int eMode,                      /* SQLITE_CHECKPOINT_* value */
+  int *pnLog,                     /* OUT: Size of WAL log in frames */
+  int *pnCkpt                     /* OUT: Total number of frames checkpointed */
+){
+#ifdef SQLITE_OMIT_WAL
+  return SQLITE_OK;
+#else
+  int rc;                         /* Return code */
+  int iDb;                        /* Schema to checkpoint */
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+
+  /* Initialize the output variables to -1 in case an error occurs. */
+  if( pnLog ) *pnLog = -1;
+  if( pnCkpt ) *pnCkpt = -1;
+
+  assert( SQLITE_CHECKPOINT_PASSIVE==0 );
+  assert( SQLITE_CHECKPOINT_FULL==1 );
+  assert( SQLITE_CHECKPOINT_RESTART==2 );
+  assert( SQLITE_CHECKPOINT_TRUNCATE==3 );
+  if( eMode<SQLITE_CHECKPOINT_PASSIVE || eMode>SQLITE_CHECKPOINT_TRUNCATE ){
+    /* EVIDENCE-OF: R-03996-12088 The M parameter must be a valid checkpoint
+    ** mode: */
+    return SQLITE_MISUSE_BKPT;
+  }
+
+  sqlite3_mutex_enter(db->mutex);
+  if( zDb && zDb[0] ){
+    iDb = sqlite3FindDbName(db, zDb);
+  }else{
+    iDb = SQLITE_MAX_DB;   /* This means process all schemas */
+  }
+  if( iDb<0 ){
+    rc = SQLITE_ERROR;
+    sqlite3ErrorWithMsg(db, SQLITE_ERROR, "unknown database: %s", zDb);
+  }else{
+    db->busyHandler.nBusy = 0;
+    rc = sqlite3Checkpoint(db, iDb, eMode, pnLog, pnCkpt);
+    sqlite3Error(db, rc);
+  }
+  rc = sqlite3ApiExit(db, rc);
+
+  /* If there are no active statements, clear the interrupt flag at this
+  ** point.  */
+  if( db->nVdbeActive==0 ){
+    AtomicStore(&db->u1.isInterrupted, 0);
+  }
+
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+#endif
+}
+
+
+/*
+** Checkpoint database zDb. If zDb is NULL, or if the buffer zDb points
+** to contains a zero-length string, all attached databases are
+** checkpointed.
+*/
+int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb){
+  /* EVIDENCE-OF: R-41613-20553 The sqlite3_wal_checkpoint(D,X) is equivalent to
+  ** sqlite3_wal_checkpoint_v2(D,X,SQLITE_CHECKPOINT_PASSIVE,0,0). */
+  return sqlite3_wal_checkpoint_v2(db,zDb,SQLITE_CHECKPOINT_PASSIVE,0,0);
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Run a checkpoint on database iDb. This is a no-op if database iDb is
+** not currently open in WAL mode.
+**
+** If a transaction is open on the database being checkpointed, this
+** function returns SQLITE_LOCKED and a checkpoint is not attempted. If
+** an error occurs while running the checkpoint, an SQLite error code is
+** returned (i.e. SQLITE_IOERR). Otherwise, SQLITE_OK.
+**
+** The mutex on database handle db should be held by the caller. The mutex
+** associated with the specific b-tree being checkpointed is taken by
+** this function while the checkpoint is running.
+**
+** If iDb is passed SQLITE_MAX_DB then all attached databases are
+** checkpointed. If an error is encountered it is returned immediately -
+** no attempt is made to checkpoint any remaining databases.
+**
+** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL, RESTART
+** or TRUNCATE.
+*/
+int sqlite3Checkpoint(sqlite3 *db, int iDb, int eMode, int *pnLog, int *pnCkpt){
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* Used to iterate through attached dbs */
+  int bBusy = 0;                  /* True if SQLITE_BUSY has been encountered */
+
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( !pnLog || *pnLog==-1 );
+  assert( !pnCkpt || *pnCkpt==-1 );
+  testcase( iDb==SQLITE_MAX_ATTACHED ); /* See forum post a006d86f72 */
+  testcase( iDb==SQLITE_MAX_DB );
+
+  for(i=0; i<db->nDb && rc==SQLITE_OK; i++){
+    if( i==iDb || iDb==SQLITE_MAX_DB ){
+      rc = sqlite3BtreeCheckpoint(db->aDb[i].pBt, eMode, pnLog, pnCkpt);
+      pnLog = 0;
+      pnCkpt = 0;
+      if( rc==SQLITE_BUSY ){
+        bBusy = 1;
+        rc = SQLITE_OK;
+      }
+    }
+  }
+
+  return (rc==SQLITE_OK && bBusy) ? SQLITE_BUSY : rc;
+}
+#endif /* SQLITE_OMIT_WAL */
+
+/*
+** This function returns true if main-memory should be used instead of
+** a temporary file for transient pager files and statement journals.
+** The value returned depends on the value of db->temp_store (runtime
+** parameter) and the compile time value of SQLITE_TEMP_STORE. The
+** following table describes the relationship between these two values
+** and this functions return value.
+**
+**   SQLITE_TEMP_STORE     db->temp_store     Location of temporary database
+**   -----------------     --------------     ------------------------------
+**   0                     any                file      (return 0)
+**   1                     1                  file      (return 0)
+**   1                     2                  memory    (return 1)
+**   1                     0                  file      (return 0)
+**   2                     1                  file      (return 0)
+**   2                     2                  memory    (return 1)
+**   2                     0                  memory    (return 1)
+**   3                     any                memory    (return 1)
+*/
+int sqlite3TempInMemory(const sqlite3 *db){
+#if SQLITE_TEMP_STORE==1
+  return ( db->temp_store==2 );
+#endif
+#if SQLITE_TEMP_STORE==2
+  return ( db->temp_store!=1 );
+#endif
+#if SQLITE_TEMP_STORE==3
+  UNUSED_PARAMETER(db);
+  return 1;
+#endif
+#if SQLITE_TEMP_STORE<1 || SQLITE_TEMP_STORE>3
+  UNUSED_PARAMETER(db);
+  return 0;
+#endif
+}
+
+/*
+** Return UTF-8 encoded English language explanation of the most recent
+** error.
+*/
+const char *sqlite3_errmsg(sqlite3 *db){
+  const char *z;
+  if( !db ){
+    return sqlite3ErrStr(SQLITE_NOMEM_BKPT);
+  }
+  if( !sqlite3SafetyCheckSickOrOk(db) ){
+    return sqlite3ErrStr(SQLITE_MISUSE_BKPT);
+  }
+  sqlite3_mutex_enter(db->mutex);
+  if( db->mallocFailed ){
+    z = sqlite3ErrStr(SQLITE_NOMEM_BKPT);
+  }else{
+    testcase( db->pErr==0 );
+    z = db->errCode ? (char*)sqlite3_value_text(db->pErr) : 0;
+    assert( !db->mallocFailed );
+    if( z==0 ){
+      z = sqlite3ErrStr(db->errCode);
+    }
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return z;
+}
+
+/*
+** Return the byte offset of the most recent error
+*/
+int sqlite3_error_offset(sqlite3 *db){
+  int iOffset = -1;
+  if( db && sqlite3SafetyCheckSickOrOk(db) && db->errCode ){
+    sqlite3_mutex_enter(db->mutex);
+    iOffset = db->errByteOffset;
+    sqlite3_mutex_leave(db->mutex);
+  }
+  return iOffset;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Return UTF-16 encoded English language explanation of the most recent
+** error.
+*/
+const void *sqlite3_errmsg16(sqlite3 *db){
+  static const u16 outOfMem[] = {
+    'o', 'u', 't', ' ', 'o', 'f', ' ', 'm', 'e', 'm', 'o', 'r', 'y', 0
+  };
+  static const u16 misuse[] = {
+    'b', 'a', 'd', ' ', 'p', 'a', 'r', 'a', 'm', 'e', 't', 'e', 'r', ' ',
+    'o', 'r', ' ', 'o', 't', 'h', 'e', 'r', ' ', 'A', 'P', 'I', ' ',
+    'm', 'i', 's', 'u', 's', 'e', 0
+  };
+
+  const void *z;
+  if( !db ){
+    return (void *)outOfMem;
+  }
+  if( !sqlite3SafetyCheckSickOrOk(db) ){
+    return (void *)misuse;
+  }
+  sqlite3_mutex_enter(db->mutex);
+  if( db->mallocFailed ){
+    z = (void *)outOfMem;
+  }else{
+    z = sqlite3_value_text16(db->pErr);
+    if( z==0 ){
+      sqlite3ErrorWithMsg(db, db->errCode, sqlite3ErrStr(db->errCode));
+      z = sqlite3_value_text16(db->pErr);
+    }
+    /* A malloc() may have failed within the call to sqlite3_value_text16()
+    ** above. If this is the case, then the db->mallocFailed flag needs to
+    ** be cleared before returning. Do this directly, instead of via
+    ** sqlite3ApiExit(), to avoid setting the database handle error message.
+    */
+    sqlite3OomClear(db);
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return z;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Return the most recent error code generated by an SQLite routine. If NULL is
+** passed to this function, we assume a malloc() failed during sqlite3_open().
+*/
+int sqlite3_errcode(sqlite3 *db){
+  if( db && !sqlite3SafetyCheckSickOrOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( !db || db->mallocFailed ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  return db->errCode & db->errMask;
+}
+int sqlite3_extended_errcode(sqlite3 *db){
+  if( db && !sqlite3SafetyCheckSickOrOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( !db || db->mallocFailed ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  return db->errCode;
+}
+int sqlite3_system_errno(sqlite3 *db){
+  return db ? db->iSysErrno : 0;
+} 
+
+/*
+** Return a string that describes the kind of error specified in the
+** argument.  For now, this simply calls the internal sqlite3ErrStr()
+** function.
+*/
+const char *sqlite3_errstr(int rc){
+  return sqlite3ErrStr(rc);
+}
+
+/*
+** Create a new collating function for database "db".  The name is zName
+** and the encoding is enc.
+*/
+static int createCollation(
+  sqlite3* db,
+  const char *zName,
+  u8 enc,
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*),
+  void(*xDel)(void*)
+){
+  CollSeq *pColl;
+  int enc2;
+ 
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  /* If SQLITE_UTF16 is specified as the encoding type, transform this
+  ** to one of SQLITE_UTF16LE or SQLITE_UTF16BE using the
+  ** SQLITE_UTF16NATIVE macro. SQLITE_UTF16 is not used internally.
+  */
+  enc2 = enc;
+  testcase( enc2==SQLITE_UTF16 );
+  testcase( enc2==SQLITE_UTF16_ALIGNED );
+  if( enc2==SQLITE_UTF16 || enc2==SQLITE_UTF16_ALIGNED ){
+    enc2 = SQLITE_UTF16NATIVE;
+  }
+  if( enc2<SQLITE_UTF8 || enc2>SQLITE_UTF16BE ){
+    return SQLITE_MISUSE_BKPT;
+  }
+
+  /* Check if this call is removing or replacing an existing collation
+  ** sequence. If so, and there are active VMs, return busy. If there
+  ** are no active VMs, invalidate any pre-compiled statements.
+  */
+  pColl = sqlite3FindCollSeq(db, (u8)enc2, zName, 0);
+  if( pColl && pColl->xCmp ){
+    if( db->nVdbeActive ){
+      sqlite3ErrorWithMsg(db, SQLITE_BUSY,
+        "unable to delete/modify collation sequence due to active statements");
+      return SQLITE_BUSY;
+    }
+    sqlite3ExpirePreparedStatements(db, 0);
+
+    /* If collation sequence pColl was created directly by a call to
+    ** sqlite3_create_collation, and not generated by synthCollSeq(),
+    ** then any copies made by synthCollSeq() need to be invalidated.
+    ** Also, collation destructor - CollSeq.xDel() - function may need
+    ** to be called.
+    */
+    if( (pColl->enc & ~SQLITE_UTF16_ALIGNED)==enc2 ){
+      CollSeq *aColl = sqlite3HashFind(&db->aCollSeq, zName);
+      int j;
+      for(j=0; j<3; j++){
+        CollSeq *p = &aColl[j];
+        if( p->enc==pColl->enc ){
+          if( p->xDel ){
+            p->xDel(p->pUser);
+          }
+          p->xCmp = 0;
+        }
+      }
+    }
+  }
+
+  pColl = sqlite3FindCollSeq(db, (u8)enc2, zName, 1);
+  if( pColl==0 ) return SQLITE_NOMEM_BKPT;
+  pColl->xCmp = xCompare;
+  pColl->pUser = pCtx;
+  pColl->xDel = xDel;
+  pColl->enc = (u8)(enc2 | (enc & SQLITE_UTF16_ALIGNED));
+  sqlite3Error(db, SQLITE_OK);
+  return SQLITE_OK;
+}
+
+
+/*
+** This array defines hard upper bounds on limit values.  The
+** initializer must be kept in sync with the SQLITE_LIMIT_*
+** #defines in sqlite3.h.
+*/
+static const int aHardLimit[] = {
+  SQLITE_MAX_LENGTH,
+  SQLITE_MAX_SQL_LENGTH,
+  SQLITE_MAX_COLUMN,
+  SQLITE_MAX_EXPR_DEPTH,
+  SQLITE_MAX_COMPOUND_SELECT,
+  SQLITE_MAX_VDBE_OP,
+  SQLITE_MAX_FUNCTION_ARG,
+  SQLITE_MAX_ATTACHED,
+  SQLITE_MAX_LIKE_PATTERN_LENGTH,
+  SQLITE_MAX_VARIABLE_NUMBER,      /* IMP: R-38091-32352 */
+  SQLITE_MAX_TRIGGER_DEPTH,
+  SQLITE_MAX_WORKER_THREADS,
+};
+
+/*
+** Make sure the hard limits are set to reasonable values
+*/
+#if SQLITE_MAX_LENGTH<100
+# error SQLITE_MAX_LENGTH must be at least 100
+#endif
+#if SQLITE_MAX_SQL_LENGTH<100
+# error SQLITE_MAX_SQL_LENGTH must be at least 100
+#endif
+#if SQLITE_MAX_SQL_LENGTH>SQLITE_MAX_LENGTH
+# error SQLITE_MAX_SQL_LENGTH must not be greater than SQLITE_MAX_LENGTH
+#endif
+#if SQLITE_MAX_COMPOUND_SELECT<2
+# error SQLITE_MAX_COMPOUND_SELECT must be at least 2
+#endif
+#if SQLITE_MAX_VDBE_OP<40
+# error SQLITE_MAX_VDBE_OP must be at least 40
+#endif
+#if SQLITE_MAX_FUNCTION_ARG<0 || SQLITE_MAX_FUNCTION_ARG>127
+# error SQLITE_MAX_FUNCTION_ARG must be between 0 and 127
+#endif
+#if SQLITE_MAX_ATTACHED<0 || SQLITE_MAX_ATTACHED>125
+# error SQLITE_MAX_ATTACHED must be between 0 and 125
+#endif
+#if SQLITE_MAX_LIKE_PATTERN_LENGTH<1
+# error SQLITE_MAX_LIKE_PATTERN_LENGTH must be at least 1
+#endif
+#if SQLITE_MAX_COLUMN>32767
+# error SQLITE_MAX_COLUMN must not exceed 32767
+#endif
+#if SQLITE_MAX_TRIGGER_DEPTH<1
+# error SQLITE_MAX_TRIGGER_DEPTH must be at least 1
+#endif
+#if SQLITE_MAX_WORKER_THREADS<0 || SQLITE_MAX_WORKER_THREADS>50
+# error SQLITE_MAX_WORKER_THREADS must be between 0 and 50
+#endif
+
+
+/*
+** Change the value of a limit.  Report the old value.
+** If an invalid limit index is supplied, report -1.
+** Make no changes but still report the old value if the
+** new limit is negative.
+**
+** A new lower limit does not shrink existing constructs.
+** It merely prevents new constructs that exceed the limit
+** from forming.
+*/
+int sqlite3_limit(sqlite3 *db, int limitId, int newLimit){
+  int oldLimit;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return -1;
+  }
+#endif
+
+  /* EVIDENCE-OF: R-30189-54097 For each limit category SQLITE_LIMIT_NAME
+  ** there is a hard upper bound set at compile-time by a C preprocessor
+  ** macro called SQLITE_MAX_NAME. (The "_LIMIT_" in the name is changed to
+  ** "_MAX_".)
+  */
+  assert( aHardLimit[SQLITE_LIMIT_LENGTH]==SQLITE_MAX_LENGTH );
+  assert( aHardLimit[SQLITE_LIMIT_SQL_LENGTH]==SQLITE_MAX_SQL_LENGTH );
+  assert( aHardLimit[SQLITE_LIMIT_COLUMN]==SQLITE_MAX_COLUMN );
+  assert( aHardLimit[SQLITE_LIMIT_EXPR_DEPTH]==SQLITE_MAX_EXPR_DEPTH );
+  assert( aHardLimit[SQLITE_LIMIT_COMPOUND_SELECT]==SQLITE_MAX_COMPOUND_SELECT);
+  assert( aHardLimit[SQLITE_LIMIT_VDBE_OP]==SQLITE_MAX_VDBE_OP );
+  assert( aHardLimit[SQLITE_LIMIT_FUNCTION_ARG]==SQLITE_MAX_FUNCTION_ARG );
+  assert( aHardLimit[SQLITE_LIMIT_ATTACHED]==SQLITE_MAX_ATTACHED );
+  assert( aHardLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]==
+                                               SQLITE_MAX_LIKE_PATTERN_LENGTH );
+  assert( aHardLimit[SQLITE_LIMIT_VARIABLE_NUMBER]==SQLITE_MAX_VARIABLE_NUMBER);
+  assert( aHardLimit[SQLITE_LIMIT_TRIGGER_DEPTH]==SQLITE_MAX_TRIGGER_DEPTH );
+  assert( aHardLimit[SQLITE_LIMIT_WORKER_THREADS]==SQLITE_MAX_WORKER_THREADS );
+  assert( SQLITE_LIMIT_WORKER_THREADS==(SQLITE_N_LIMIT-1) );
+
+
+  if( limitId<0 || limitId>=SQLITE_N_LIMIT ){
+    return -1;
+  }
+  oldLimit = db->aLimit[limitId];
+  if( newLimit>=0 ){                   /* IMP: R-52476-28732 */
+    if( newLimit>aHardLimit[limitId] ){
+      newLimit = aHardLimit[limitId];  /* IMP: R-51463-25634 */
+    }else if( newLimit<1 && limitId==SQLITE_LIMIT_LENGTH ){
+      newLimit = 1;
+    }
+    db->aLimit[limitId] = newLimit;
+  }
+  return oldLimit;                     /* IMP: R-53341-35419 */
+}
+
+/*
+** This function is used to parse both URIs and non-URI filenames passed by the
+** user to API functions sqlite3_open() or sqlite3_open_v2(), and for database
+** URIs specified as part of ATTACH statements.
+**
+** The first argument to this function is the name of the VFS to use (or
+** a NULL to signify the default VFS) if the URI does not contain a "vfs=xxx"
+** query parameter. The second argument contains the URI (or non-URI filename)
+** itself. When this function is called the *pFlags variable should contain
+** the default flags to open the database handle with. The value stored in
+** *pFlags may be updated before returning if the URI filename contains
+** "cache=xxx" or "mode=xxx" query parameters.
+**
+** If successful, SQLITE_OK is returned. In this case *ppVfs is set to point to
+** the VFS that should be used to open the database file. *pzFile is set to
+** point to a buffer containing the name of the file to open.  The value
+** stored in *pzFile is a database name acceptable to sqlite3_uri_parameter()
+** and is in the same format as names created using sqlite3_create_filename().
+** The caller must invoke sqlite3_free_filename() (not sqlite3_free()!) on
+** the value returned in *pzFile to avoid a memory leak.
+**
+** If an error occurs, then an SQLite error code is returned and *pzErrMsg
+** may be set to point to a buffer containing an English language error
+** message. It is the responsibility of the caller to eventually release
+** this buffer by calling sqlite3_free().
+*/
+int sqlite3ParseUri(
+  const char *zDefaultVfs,        /* VFS to use if no "vfs=xxx" query option */
+  const char *zUri,               /* Nul-terminated URI to parse */
+  unsigned int *pFlags,           /* IN/OUT: SQLITE_OPEN_XXX flags */
+  sqlite3_vfs **ppVfs,            /* OUT: VFS to use */
+  char **pzFile,                  /* OUT: Filename component of URI */
+  char **pzErrMsg                 /* OUT: Error message (if rc!=SQLITE_OK) */
+){
+  int rc = SQLITE_OK;
+  unsigned int flags = *pFlags;
+  const char *zVfs = zDefaultVfs;
+  char *zFile;
+  char c;
+  int nUri = sqlite3Strlen30(zUri);
+
+  assert( *pzErrMsg==0 );
+
+  if( ((flags & SQLITE_OPEN_URI)                     /* IMP: R-48725-32206 */
+       || AtomicLoad(&sqlite3GlobalConfig.bOpenUri)) /* IMP: R-51689-46548 */
+   && nUri>=5 && memcmp(zUri, "file:", 5)==0         /* IMP: R-57884-37496 */
+  ){
+    char *zOpt;
+    int eState;                   /* Parser state when parsing URI */
+    int iIn;                      /* Input character index */
+    int iOut = 0;                 /* Output character index */
+    u64 nByte = nUri+8;           /* Bytes of space to allocate */
+
+    /* Make sure the SQLITE_OPEN_URI flag is set to indicate to the VFS xOpen
+    ** method that there may be extra parameters following the file-name.  */
+    flags |= SQLITE_OPEN_URI;
+
+    for(iIn=0; iIn<nUri; iIn++) nByte += (zUri[iIn]=='&');
+    zFile = sqlite3_malloc64(nByte);
+    if( !zFile ) return SQLITE_NOMEM_BKPT;
+
+    memset(zFile, 0, 4);  /* 4-byte of 0x00 is the start of DB name marker */
+    zFile += 4;
+
+    iIn = 5;
+#ifdef SQLITE_ALLOW_URI_AUTHORITY
+    if( strncmp(zUri+5, "///", 3)==0 ){
+      iIn = 7;
+      /* The following condition causes URIs with five leading / characters
+      ** like file://///host/path to be converted into UNCs like //host/path.
+      ** The correct URI for that UNC has only two or four leading / characters
+      ** file://host/path or file:////host/path.  But 5 leading slashes is a
+      ** common error, we are told, so we handle it as a special case. */
+      if( strncmp(zUri+7, "///", 3)==0 ){ iIn++; }
+    }else if( strncmp(zUri+5, "//localhost/", 12)==0 ){
+      iIn = 16;
+    }
+#else
+    /* Discard the scheme and authority segments of the URI. */
+    if( zUri[5]=='/' && zUri[6]=='/' ){
+      iIn = 7;
+      while( zUri[iIn] && zUri[iIn]!='/' ) iIn++;
+      if( iIn!=7 && (iIn!=16 || memcmp("localhost", &zUri[7], 9)) ){
+        *pzErrMsg = sqlite3_mprintf("invalid uri authority: %.*s",
+            iIn-7, &zUri[7]);
+        rc = SQLITE_ERROR;
+        goto parse_uri_out;
+      }
+    }
+#endif
+
+    /* Copy the filename and any query parameters into the zFile buffer.
+    ** Decode %HH escape codes along the way.
+    **
+    ** Within this loop, variable eState may be set to 0, 1 or 2, depending
+    ** on the parsing context. As follows:
+    **
+    **   0: Parsing file-name.
+    **   1: Parsing name section of a name=value query parameter.
+    **   2: Parsing value section of a name=value query parameter.
+    */
+    eState = 0;
+    while( (c = zUri[iIn])!=0 && c!='#' ){
+      iIn++;
+      if( c=='%'
+       && sqlite3Isxdigit(zUri[iIn])
+       && sqlite3Isxdigit(zUri[iIn+1])
+      ){
+        int octet = (sqlite3HexToInt(zUri[iIn++]) << 4);
+        octet += sqlite3HexToInt(zUri[iIn++]);
+
+        assert( octet>=0 && octet<256 );
+        if( octet==0 ){
+#ifndef SQLITE_ENABLE_URI_00_ERROR
+          /* This branch is taken when "%00" appears within the URI. In this
+          ** case we ignore all text in the remainder of the path, name or
+          ** value currently being parsed. So ignore the current character
+          ** and skip to the next "?", "=" or "&", as appropriate. */
+          while( (c = zUri[iIn])!=0 && c!='#'
+              && (eState!=0 || c!='?')
+              && (eState!=1 || (c!='=' && c!='&'))
+              && (eState!=2 || c!='&')
+          ){
+            iIn++;
+          }
+          continue;
+#else
+          /* If ENABLE_URI_00_ERROR is defined, "%00" in a URI is an error. */
+          *pzErrMsg = sqlite3_mprintf("unexpected %%00 in uri");
+          rc = SQLITE_ERROR;
+          goto parse_uri_out;
+#endif
+        }
+        c = octet;
+      }else if( eState==1 && (c=='&' || c=='=') ){
+        if( zFile[iOut-1]==0 ){
+          /* An empty option name. Ignore this option altogether. */
+          while( zUri[iIn] && zUri[iIn]!='#' && zUri[iIn-1]!='&' ) iIn++;
+          continue;
+        }
+        if( c=='&' ){
+          zFile[iOut++] = '\0';
+        }else{
+          eState = 2;
+        }
+        c = 0;
+      }else if( (eState==0 && c=='?') || (eState==2 && c=='&') ){
+        c = 0;
+        eState = 1;
+      }
+      zFile[iOut++] = c;
+    }
+    if( eState==1 ) zFile[iOut++] = '\0';
+    memset(zFile+iOut, 0, 4); /* end-of-options + empty journal filenames */
+
+    /* Check if there were any options specified that should be interpreted
+    ** here. Options that are interpreted here include "vfs" and those that
+    ** correspond to flags that may be passed to the sqlite3_open_v2()
+    ** method. */
+    zOpt = &zFile[sqlite3Strlen30(zFile)+1];
+    while( zOpt[0] ){
+      int nOpt = sqlite3Strlen30(zOpt);
+      char *zVal = &zOpt[nOpt+1];
+      int nVal = sqlite3Strlen30(zVal);
+
+      if( nOpt==3 && memcmp("vfs", zOpt, 3)==0 ){
+        zVfs = zVal;
+      }else{
+        struct OpenMode {
+          const char *z;
+          int mode;
+        } *aMode = 0;
+        char *zModeType = 0;
+        int mask = 0;
+        int limit = 0;
+
+        if( nOpt==5 && memcmp("cache", zOpt, 5)==0 ){
+          static struct OpenMode aCacheMode[] = {
+            { "shared",  SQLITE_OPEN_SHAREDCACHE },
+            { "private", SQLITE_OPEN_PRIVATECACHE },
+            { 0, 0 }
+          };
+
+          mask = SQLITE_OPEN_SHAREDCACHE|SQLITE_OPEN_PRIVATECACHE;
+          aMode = aCacheMode;
+          limit = mask;
+          zModeType = "cache";
+        }
+        if( nOpt==4 && memcmp("mode", zOpt, 4)==0 ){
+          static struct OpenMode aOpenMode[] = {
+            { "ro",  SQLITE_OPEN_READONLY },
+            { "rw",  SQLITE_OPEN_READWRITE },
+            { "rwc", SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE },
+            { "memory", SQLITE_OPEN_MEMORY },
+            { 0, 0 }
+          };
+
+          mask = SQLITE_OPEN_READONLY | SQLITE_OPEN_READWRITE
+                   | SQLITE_OPEN_CREATE | SQLITE_OPEN_MEMORY;
+          aMode = aOpenMode;
+          limit = mask & flags;
+          zModeType = "access";
+        }
+
+        if( aMode ){
+          int i;
+          int mode = 0;
+          for(i=0; aMode[i].z; i++){
+            const char *z = aMode[i].z;
+            if( nVal==sqlite3Strlen30(z) && 0==memcmp(zVal, z, nVal) ){
+              mode = aMode[i].mode;
+              break;
+            }
+          }
+          if( mode==0 ){
+            *pzErrMsg = sqlite3_mprintf("no such %s mode: %s", zModeType, zVal);
+            rc = SQLITE_ERROR;
+            goto parse_uri_out;
+          }
+          if( (mode & ~SQLITE_OPEN_MEMORY)>limit ){
+            *pzErrMsg = sqlite3_mprintf("%s mode not allowed: %s",
+                                        zModeType, zVal);
+            rc = SQLITE_PERM;
+            goto parse_uri_out;
+          }
+          flags = (flags & ~mask) | mode;
+        }
+      }
+
+      zOpt = &zVal[nVal+1];
+    }
+
+  }else{
+    zFile = sqlite3_malloc64(nUri+8);
+    if( !zFile ) return SQLITE_NOMEM_BKPT;
+    memset(zFile, 0, 4);
+    zFile += 4;
+    if( nUri ){
+      memcpy(zFile, zUri, nUri);
+    }
+    memset(zFile+nUri, 0, 4);
+    flags &= ~SQLITE_OPEN_URI;
+  }
+
+  *ppVfs = sqlite3_vfs_find(zVfs);
+  if( *ppVfs==0 ){
+    *pzErrMsg = sqlite3_mprintf("no such vfs: %s", zVfs);
+    rc = SQLITE_ERROR;
+  }
+ parse_uri_out:
+  if( rc!=SQLITE_OK ){
+    sqlite3_free_filename(zFile);
+    zFile = 0;
+  }
+  *pFlags = flags;
+  *pzFile = zFile;
+  return rc;
+}
+
+/*
+** This routine does the core work of extracting URI parameters from a
+** database filename for the sqlite3_uri_parameter() interface.
+*/
+static const char *uriParameter(const char *zFilename, const char *zParam){
+  zFilename += sqlite3Strlen30(zFilename) + 1;
+  while( ALWAYS(zFilename!=0) && zFilename[0] ){
+    int x = strcmp(zFilename, zParam);
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+    if( x==0 ) return zFilename;
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+  }
+  return 0;
+}
+
+
+
+/*
+** This routine does the work of opening a database on behalf of
+** sqlite3_open() and sqlite3_open16(). The database filename "zFilename" 
+** is UTF-8 encoded.
+*/
+static int openDatabase(
+  const char *zFilename, /* Database filename UTF-8 encoded */
+  sqlite3 **ppDb,        /* OUT: Returned database handle */
+  unsigned int flags,    /* Operational flags */
+  const char *zVfs       /* Name of the VFS to use */
+){
+  sqlite3 *db;                    /* Store allocated handle here */
+  int rc;                         /* Return code */
+  int isThreadsafe;               /* True for threadsafe connections */
+  char *zOpen = 0;                /* Filename argument to pass to BtreeOpen() */
+  char *zErrMsg = 0;              /* Error message from sqlite3ParseUri() */
+  int i;                          /* Loop counter */
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( ppDb==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  *ppDb = 0;
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+
+  if( sqlite3GlobalConfig.bCoreMutex==0 ){
+    isThreadsafe = 0;
+  }else if( flags & SQLITE_OPEN_NOMUTEX ){
+    isThreadsafe = 0;
+  }else if( flags & SQLITE_OPEN_FULLMUTEX ){
+    isThreadsafe = 1;
+  }else{
+    isThreadsafe = sqlite3GlobalConfig.bFullMutex;
+  }
+
+  if( flags & SQLITE_OPEN_PRIVATECACHE ){
+    flags &= ~SQLITE_OPEN_SHAREDCACHE;
+  }else if( sqlite3GlobalConfig.sharedCacheEnabled ){
+    flags |= SQLITE_OPEN_SHAREDCACHE;
+  }
+
+  /* Remove harmful bits from the flags parameter
+  **
+  ** The SQLITE_OPEN_NOMUTEX and SQLITE_OPEN_FULLMUTEX flags were
+  ** dealt with in the previous code block.  Besides these, the only
+  ** valid input flags for sqlite3_open_v2() are SQLITE_OPEN_READONLY,
+  ** SQLITE_OPEN_READWRITE, SQLITE_OPEN_CREATE, SQLITE_OPEN_SHAREDCACHE,
+  ** SQLITE_OPEN_PRIVATECACHE, SQLITE_OPEN_EXRESCODE, and some reserved
+  ** bits.  Silently mask off all other flags.
+  */
+  flags &=  ~( SQLITE_OPEN_DELETEONCLOSE |
+               SQLITE_OPEN_EXCLUSIVE |
+               SQLITE_OPEN_MAIN_DB |
+               SQLITE_OPEN_TEMP_DB |
+               SQLITE_OPEN_TRANSIENT_DB |
+               SQLITE_OPEN_MAIN_JOURNAL |
+               SQLITE_OPEN_TEMP_JOURNAL |
+               SQLITE_OPEN_SUBJOURNAL |
+               SQLITE_OPEN_SUPER_JOURNAL |
+               SQLITE_OPEN_NOMUTEX |
+               SQLITE_OPEN_FULLMUTEX |
+               SQLITE_OPEN_WAL
+             );
+
+  /* Allocate the sqlite data structure */
+  db = sqlite3MallocZero( sizeof(sqlite3) );
+  if( db==0 ) goto opendb_out;
+  if( isThreadsafe
+#ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS
+   || sqlite3GlobalConfig.bCoreMutex
+#endif
+  ){
+    db->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
+    if( db->mutex==0 ){
+      sqlite3_free(db);
+      db = 0;
+      goto opendb_out;
+    }
+    if( isThreadsafe==0 ){
+      sqlite3MutexWarnOnContention(db->mutex);
+    }
+  }
+  sqlite3_mutex_enter(db->mutex);
+  db->errMask = (flags & SQLITE_OPEN_EXRESCODE)!=0 ? 0xffffffff : 0xff;
+  db->nDb = 2;
+  db->eOpenState = SQLITE_STATE_BUSY;
+  db->aDb = db->aDbStatic;
+  db->lookaside.bDisable = 1;
+  db->lookaside.sz = 0;
+
+  assert( sizeof(db->aLimit)==sizeof(aHardLimit) );
+  memcpy(db->aLimit, aHardLimit, sizeof(db->aLimit));
+  db->aLimit[SQLITE_LIMIT_WORKER_THREADS] = SQLITE_DEFAULT_WORKER_THREADS;
+  db->autoCommit = 1;
+  db->nextAutovac = -1;
+  db->szMmap = sqlite3GlobalConfig.szMmap;
+  db->nextPagesize = 0;
+  db->init.azInit = sqlite3StdType; /* Any array of string ptrs will do */
+#ifdef SQLITE_ENABLE_SORTER_MMAP
+  /* Beginning with version 3.37.0, using the VFS xFetch() API to memory-map
+  ** the temporary files used to do external sorts (see code in vdbesort.c)
+  ** is disabled. It can still be used either by defining
+  ** SQLITE_ENABLE_SORTER_MMAP at compile time or by using the
+  ** SQLITE_TESTCTRL_SORTER_MMAP test-control at runtime. */
+  db->nMaxSorterMmap = 0x7FFFFFFF;
+#endif
+  db->flags |= SQLITE_ShortColNames
+                 | SQLITE_EnableTrigger
+                 | SQLITE_EnableView
+                 | SQLITE_CacheSpill
+#if !defined(SQLITE_TRUSTED_SCHEMA) || SQLITE_TRUSTED_SCHEMA+0!=0
+                 | SQLITE_TrustedSchema
+#endif
+/* The SQLITE_DQS compile-time option determines the default settings
+** for SQLITE_DBCONFIG_DQS_DDL and SQLITE_DBCONFIG_DQS_DML.
+**
+**    SQLITE_DQS     SQLITE_DBCONFIG_DQS_DDL    SQLITE_DBCONFIG_DQS_DML
+**    ----------     -----------------------    -----------------------
+**     undefined               on                          on
+**         3                   on                          on
+**         2                   on                         off
+**         1                  off                          on
+**         0                  off                         off
+**
+** Legacy behavior is 3 (double-quoted string literals are allowed anywhere)
+** and so that is the default.  But developers are encouraged to use
+** -DSQLITE_DQS=0 (best) or -DSQLITE_DQS=1 (second choice) if possible.
+*/
+#if !defined(SQLITE_DQS)
+# define SQLITE_DQS 3
+#endif
+#if (SQLITE_DQS&1)==1
+                 | SQLITE_DqsDML
+#endif
+#if (SQLITE_DQS&2)==2
+                 | SQLITE_DqsDDL
+#endif
+
+#if !defined(SQLITE_DEFAULT_AUTOMATIC_INDEX) || SQLITE_DEFAULT_AUTOMATIC_INDEX
+                 | SQLITE_AutoIndex
+#endif
+#if SQLITE_DEFAULT_CKPTFULLFSYNC
+                 | SQLITE_CkptFullFSync
+#endif
+#if SQLITE_DEFAULT_FILE_FORMAT<4
+                 | SQLITE_LegacyFileFmt
+#endif
+#ifdef SQLITE_ENABLE_LOAD_EXTENSION
+                 | SQLITE_LoadExtension
+#endif
+#if SQLITE_DEFAULT_RECURSIVE_TRIGGERS
+                 | SQLITE_RecTriggers
+#endif
+#if defined(SQLITE_DEFAULT_FOREIGN_KEYS) && SQLITE_DEFAULT_FOREIGN_KEYS
+                 | SQLITE_ForeignKeys
+#endif
+#if defined(SQLITE_REVERSE_UNORDERED_SELECTS)
+                 | SQLITE_ReverseOrder
+#endif
+#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
+                 | SQLITE_CellSizeCk
+#endif
+#if defined(SQLITE_ENABLE_FTS3_TOKENIZER)
+                 | SQLITE_Fts3Tokenizer
+#endif
+#if defined(SQLITE_ENABLE_QPSG)
+                 | SQLITE_EnableQPSG
+#endif
+#if defined(SQLITE_DEFAULT_DEFENSIVE)
+                 | SQLITE_Defensive
+#endif
+#if defined(SQLITE_DEFAULT_LEGACY_ALTER_TABLE)
+                 | SQLITE_LegacyAlter
+#endif
+#if defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+                 | SQLITE_StmtScanStatus
+#endif
+      ;
+  sqlite3HashInit(&db->aCollSeq);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3HashInit(&db->aModule);
+#endif
+
+  /* Add the default collation sequence BINARY. BINARY works for both UTF-8
+  ** and UTF-16, so add a version for each to avoid any unnecessary
+  ** conversions. The only error that can occur here is a malloc() failure.
+  **
+  ** EVIDENCE-OF: R-52786-44878 SQLite defines three built-in collating
+  ** functions:
+  */
+  createCollation(db, sqlite3StrBINARY, SQLITE_UTF8, 0, binCollFunc, 0);
+  createCollation(db, sqlite3StrBINARY, SQLITE_UTF16BE, 0, binCollFunc, 0);
+  createCollation(db, sqlite3StrBINARY, SQLITE_UTF16LE, 0, binCollFunc, 0);
+  createCollation(db, "NOCASE", SQLITE_UTF8, 0, nocaseCollatingFunc, 0);
+  createCollation(db, "RTRIM", SQLITE_UTF8, 0, rtrimCollFunc, 0);
+  if( db->mallocFailed ){
+    goto opendb_out;
+  }
+
+#if SQLITE_OS_UNIX && defined(SQLITE_OS_KV_OPTIONAL)
+  /* Process magic filenames ":localStorage:" and ":sessionStorage:" */
+  if( zFilename && zFilename[0]==':' ){
+    if( strcmp(zFilename, ":localStorage:")==0 ){
+      zFilename = "file:local?vfs=kvvfs";
+      flags |= SQLITE_OPEN_URI;
+    }else if( strcmp(zFilename, ":sessionStorage:")==0 ){
+      zFilename = "file:session?vfs=kvvfs";
+      flags |= SQLITE_OPEN_URI;
+    }
+  }
+#endif /* SQLITE_OS_UNIX && defined(SQLITE_OS_KV_OPTIONAL) */
+
+  /* Parse the filename/URI argument
+  **
+  ** Only allow sensible combinations of bits in the flags argument. 
+  ** Throw an error if any non-sense combination is used.  If we
+  ** do not block illegal combinations here, it could trigger
+  ** assert() statements in deeper layers.  Sensible combinations
+  ** are:
+  **
+  **  1:  SQLITE_OPEN_READONLY
+  **  2:  SQLITE_OPEN_READWRITE
+  **  6:  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE
+  */
+  db->openFlags = flags;
+  assert( SQLITE_OPEN_READONLY  == 0x01 );
+  assert( SQLITE_OPEN_READWRITE == 0x02 );
+  assert( SQLITE_OPEN_CREATE    == 0x04 );
+  testcase( (1<<(flags&7))==0x02 ); /* READONLY */
+  testcase( (1<<(flags&7))==0x04 ); /* READWRITE */
+  testcase( (1<<(flags&7))==0x40 ); /* READWRITE | CREATE */
+  if( ((1<<(flags&7)) & 0x46)==0 ){
+    rc = SQLITE_MISUSE_BKPT;  /* IMP: R-18321-05872 */
+  }else{
+    rc = sqlite3ParseUri(zVfs, zFilename, &flags, &db->pVfs, &zOpen, &zErrMsg);
+  }
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_NOMEM ) sqlite3OomFault(db);
+    sqlite3ErrorWithMsg(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
+    sqlite3_free(zErrMsg);
+    goto opendb_out;
+  }
+  assert( db->pVfs!=0 );
+#if SQLITE_OS_KV || defined(SQLITE_OS_KV_OPTIONAL)
+  if( sqlite3_stricmp(db->pVfs->zName, "kvvfs")==0 ){
+    db->temp_store = 2;
+  }
+#endif
+
+  /* Open the backend database driver */
+  rc = sqlite3BtreeOpen(db->pVfs, zOpen, db, &db->aDb[0].pBt, 0,
+                        flags | SQLITE_OPEN_MAIN_DB);
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_IOERR_NOMEM ){
+      rc = SQLITE_NOMEM_BKPT;
+    }
+    sqlite3Error(db, rc);
+    goto opendb_out;
+  }
+  sqlite3BtreeEnter(db->aDb[0].pBt);
+  db->aDb[0].pSchema = sqlite3SchemaGet(db, db->aDb[0].pBt);
+  if( !db->mallocFailed ){
+    sqlite3SetTextEncoding(db, SCHEMA_ENC(db));
+  }
+  sqlite3BtreeLeave(db->aDb[0].pBt);
+  db->aDb[1].pSchema = sqlite3SchemaGet(db, 0);
+
+  /* The default safety_level for the main database is FULL; for the temp
+  ** database it is OFF. This matches the pager layer defaults. 
+  */
+  db->aDb[0].zDbSName = "main";
+  db->aDb[0].safety_level = SQLITE_DEFAULT_SYNCHRONOUS+1;
+  db->aDb[1].zDbSName = "temp";
+  db->aDb[1].safety_level = PAGER_SYNCHRONOUS_OFF;
+
+  db->eOpenState = SQLITE_STATE_OPEN;
+  if( db->mallocFailed ){
+    goto opendb_out;
+  }
+
+  /* Register all built-in functions, but do not attempt to read the
+  ** database schema yet. This is delayed until the first time the database
+  ** is accessed.
+  */
+  sqlite3Error(db, SQLITE_OK);
+  sqlite3RegisterPerConnectionBuiltinFunctions(db);
+  rc = sqlite3_errcode(db);
+
+
+  /* Load compiled-in extensions */
+  for(i=0; rc==SQLITE_OK && i<ArraySize(sqlite3BuiltinExtensions); i++){
+    rc = sqlite3BuiltinExtensions[i](db);
+  }
+
+  /* Load automatic extensions - extensions that have been registered
+  ** using the sqlite3_automatic_extension() API.
+  */
+  if( rc==SQLITE_OK ){
+    sqlite3AutoLoadExtensions(db);
+    rc = sqlite3_errcode(db);
+    if( rc!=SQLITE_OK ){
+      goto opendb_out;
+    }
+  }
+
+#ifdef SQLITE_ENABLE_INTERNAL_FUNCTIONS
+  /* Testing use only!!! The -DSQLITE_ENABLE_INTERNAL_FUNCTIONS=1 compile-time
+  ** option gives access to internal functions by default. 
+  ** Testing use only!!! */
+  db->mDbFlags |= DBFLAG_InternalFunc;
+#endif
+
+  /* -DSQLITE_DEFAULT_LOCKING_MODE=1 makes EXCLUSIVE the default locking
+  ** mode.  -DSQLITE_DEFAULT_LOCKING_MODE=0 make NORMAL the default locking
+  ** mode.  Doing nothing at all also makes NORMAL the default.
+  */
+#ifdef SQLITE_DEFAULT_LOCKING_MODE
+  db->dfltLockMode = SQLITE_DEFAULT_LOCKING_MODE;
+  sqlite3PagerLockingMode(sqlite3BtreePager(db->aDb[0].pBt),
+                          SQLITE_DEFAULT_LOCKING_MODE);
+#endif
+
+  if( rc ) sqlite3Error(db, rc);
+
+  /* Enable the lookaside-malloc subsystem */
+  setupLookaside(db, 0, sqlite3GlobalConfig.szLookaside,
+                        sqlite3GlobalConfig.nLookaside);
+
+  sqlite3_wal_autocheckpoint(db, SQLITE_DEFAULT_WAL_AUTOCHECKPOINT);
+
+opendb_out:
+  if( db ){
+    assert( db->mutex!=0 || isThreadsafe==0
+           || sqlite3GlobalConfig.bFullMutex==0 );
+    sqlite3_mutex_leave(db->mutex);
+  }
+  rc = sqlite3_errcode(db);
+  assert( db!=0 || (rc&0xff)==SQLITE_NOMEM );
+  if( (rc&0xff)==SQLITE_NOMEM ){
+    sqlite3_close(db);
+    db = 0;
+  }else if( rc!=SQLITE_OK ){
+    db->eOpenState = SQLITE_STATE_SICK;
+  }
+  *ppDb = db;
+#ifdef SQLITE_ENABLE_SQLLOG
+  if( sqlite3GlobalConfig.xSqllog ){
+    /* Opening a db handle. Fourth parameter is passed 0. */
+    void *pArg = sqlite3GlobalConfig.pSqllogArg;
+    sqlite3GlobalConfig.xSqllog(pArg, db, zFilename, 0);
+  }
+#endif
+  sqlite3_free_filename(zOpen);
+  return rc;
+}
+
+
+/*
+** Open a new database handle.
+*/
+int sqlite3_open(
+  const char *zFilename,
+  sqlite3 **ppDb
+){
+  return openDatabase(zFilename, ppDb,
+                      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0);
+}
+int sqlite3_open_v2(
+  const char *filename,   /* Database filename (UTF-8) */
+  sqlite3 **ppDb,         /* OUT: SQLite db handle */
+  int flags,              /* Flags */
+  const char *zVfs        /* Name of VFS module to use */
+){
+  return openDatabase(filename, ppDb, (unsigned int)flags, zVfs);
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Open a new database handle.
+*/
+int sqlite3_open16(
+  const void *zFilename,
+  sqlite3 **ppDb
+){
+  char const *zFilename8;   /* zFilename encoded in UTF-8 instead of UTF-16 */
+  sqlite3_value *pVal;
+  int rc;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( ppDb==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  *ppDb = 0;
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+  if( zFilename==0 ) zFilename = "\000\000";
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, zFilename, SQLITE_UTF16NATIVE, SQLITE_STATIC);
+  zFilename8 = sqlite3ValueText(pVal, SQLITE_UTF8);
+  if( zFilename8 ){
+    rc = openDatabase(zFilename8, ppDb,
+                      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0);
+    assert( *ppDb || rc==SQLITE_NOMEM );
+    if( rc==SQLITE_OK && !DbHasProperty(*ppDb, 0, DB_SchemaLoaded) ){
+      SCHEMA_ENC(*ppDb) = ENC(*ppDb) = SQLITE_UTF16NATIVE;
+    }
+  }else{
+    rc = SQLITE_NOMEM_BKPT;
+  }
+  sqlite3ValueFree(pVal);
+
+  return rc & 0xff;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Register a new collation sequence with the database handle db.
+*/
+int sqlite3_create_collation(
+  sqlite3* db,
+  const char *zName,
+  int enc,
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+){
+  return sqlite3_create_collation_v2(db, zName, enc, pCtx, xCompare, 0);
+}
+
+/*
+** Register a new collation sequence with the database handle db.
+*/
+int sqlite3_create_collation_v2(
+  sqlite3* db,
+  const char *zName,
+  int enc,
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*),
+  void(*xDel)(void*)
+){
+  int rc;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zName==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  assert( !db->mallocFailed );
+  rc = createCollation(db, zName, (u8)enc, pCtx, xCompare, xDel);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Register a new collation sequence with the database handle db.
+*/
+int sqlite3_create_collation16(
+  sqlite3* db,
+  const void *zName,
+  int enc,
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+){
+  int rc = SQLITE_OK;
+  char *zName8;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zName==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  assert( !db->mallocFailed );
+  zName8 = sqlite3Utf16to8(db, zName, -1, SQLITE_UTF16NATIVE);
+  if( zName8 ){
+    rc = createCollation(db, zName8, (u8)enc, pCtx, xCompare, 0);
+    sqlite3DbFree(db, zName8);
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Register a collation sequence factory callback with the database handle
+** db. Replace any previously installed collation sequence factory.
+*/
+int sqlite3_collation_needed(
+  sqlite3 *db,
+  void *pCollNeededArg,
+  void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*)
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  db->xCollNeeded = xCollNeeded;
+  db->xCollNeeded16 = 0;
+  db->pCollNeededArg = pCollNeededArg;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Register a collation sequence factory callback with the database handle
+** db. Replace any previously installed collation sequence factory.
+*/
+int sqlite3_collation_needed16(
+  sqlite3 *db,
+  void *pCollNeededArg,
+  void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*)
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  db->xCollNeeded = 0;
+  db->xCollNeeded16 = xCollNeeded16;
+  db->pCollNeededArg = pCollNeededArg;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Find existing client data.
+*/
+void *sqlite3_get_clientdata(sqlite3 *db, const char *zName){
+  DbClientData *p;
+  sqlite3_mutex_enter(db->mutex);
+  for(p=db->pDbData; p; p=p->pNext){
+    if( strcmp(p->zName, zName)==0 ){
+      void *pResult = p->pData;
+      sqlite3_mutex_leave(db->mutex);
+      return pResult;
+    }
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return 0;
+}
+
+/*
+** Add new client data to a database connection.
+*/
+int sqlite3_set_clientdata(
+  sqlite3 *db,                   /* Attach client data to this connection */
+  const char *zName,             /* Name of the client data */
+  void *pData,                   /* The client data itself */
+  void (*xDestructor)(void*)     /* Destructor */
+){
+  DbClientData *p, **pp;
+  sqlite3_mutex_enter(db->mutex);
+  pp = &db->pDbData;
+  for(p=db->pDbData; p && strcmp(p->zName,zName); p=p->pNext){
+    pp = &p->pNext;
+  }
+  if( p ){
+    assert( p->pData!=0 );
+    if( p->xDestructor ) p->xDestructor(p->pData);
+    if( pData==0 ){
+      *pp = p->pNext;
+      sqlite3_free(p);
+      sqlite3_mutex_leave(db->mutex);
+      return SQLITE_OK;
+    }
+  }else if( pData==0 ){
+    sqlite3_mutex_leave(db->mutex);
+    return SQLITE_OK;
+  }else{
+    size_t n = strlen(zName);
+    p = sqlite3_malloc64( sizeof(DbClientData)+n+1 );
+    if( p==0 ){
+      if( xDestructor ) xDestructor(pData);
+      sqlite3_mutex_leave(db->mutex);
+      return SQLITE_NOMEM;
+    }
+    memcpy(p->zName, zName, n+1);
+    p->pNext = db->pDbData;
+    db->pDbData = p;
+  }
+  p->pData = pData;
+  p->xDestructor = xDestructor;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** This function is now an anachronism. It used to be used to recover from a
+** malloc() failure, but SQLite now does this automatically.
+*/
+int sqlite3_global_recover(void){
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Test to see whether or not the database connection is in autocommit
+** mode.  Return TRUE if it is and FALSE if not.  Autocommit mode is on
+** by default.  Autocommit is disabled by a BEGIN statement and reenabled
+** by the next COMMIT or ROLLBACK.
+*/
+int sqlite3_get_autocommit(sqlite3 *db){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  return db->autoCommit;
+}
+
+/*
+** The following routines are substitutes for constants SQLITE_CORRUPT,
+** SQLITE_MISUSE, SQLITE_CANTOPEN, SQLITE_NOMEM and possibly other error
+** constants.  They serve two purposes:
+**
+**   1.  Serve as a convenient place to set a breakpoint in a debugger
+**       to detect when version error conditions occurs.
+**
+**   2.  Invoke sqlite3_log() to provide the source code location where
+**       a low-level error is first detected.
+*/
+int sqlite3ReportError(int iErr, int lineno, const char *zType){
+  sqlite3_log(iErr, "%s at line %d of [%.10s]",
+              zType, lineno, 20+sqlite3_sourceid());
+  return iErr;
+}
+int sqlite3CorruptError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  return sqlite3ReportError(SQLITE_CORRUPT, lineno, "database corruption");
+}
+int sqlite3MisuseError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  return sqlite3ReportError(SQLITE_MISUSE, lineno, "misuse");
+}
+int sqlite3CantopenError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  return sqlite3ReportError(SQLITE_CANTOPEN, lineno, "cannot open file");
+}
+#if defined(SQLITE_DEBUG) || defined(SQLITE_ENABLE_CORRUPT_PGNO)
+int sqlite3CorruptPgnoError(int lineno, Pgno pgno){
+  char zMsg[100];
+  sqlite3_snprintf(sizeof(zMsg), zMsg, "database corruption page %d", pgno);
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  return sqlite3ReportError(SQLITE_CORRUPT, lineno, zMsg);
+}
+#endif
+#ifdef SQLITE_DEBUG
+int sqlite3NomemError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  return sqlite3ReportError(SQLITE_NOMEM, lineno, "OOM");
+}
+int sqlite3IoerrnomemError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  return sqlite3ReportError(SQLITE_IOERR_NOMEM, lineno, "I/O OOM error");
+}
+#endif
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** This is a convenience routine that makes sure that all thread-specific
+** data for this thread has been deallocated.
+**
+** SQLite no longer uses thread-specific data so this routine is now a
+** no-op.  It is retained for historical compatibility.
+*/
+void sqlite3_thread_cleanup(void){
+}
+#endif
+
+/*
+** Return meta information about a specific column of a database table.
+** See comment in sqlite3.h (sqlite.h.in) for details.
+*/
+int sqlite3_table_column_metadata(
+  sqlite3 *db,                /* Connection handle */
+  const char *zDbName,        /* Database name or NULL */
+  const char *zTableName,     /* Table name */
+  const char *zColumnName,    /* Column name */
+  char const **pzDataType,    /* OUTPUT: Declared data type */
+  char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
+  int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
+  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
+  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
+){
+  int rc;
+  char *zErrMsg = 0;
+  Table *pTab = 0;
+  Column *pCol = 0;
+  int iCol = 0;
+  char const *zDataType = 0;
+  char const *zCollSeq = 0;
+  int notnull = 0;
+  int primarykey = 0;
+  int autoinc = 0;
+
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zTableName==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+
+  /* Ensure the database schema has been loaded */
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3BtreeEnterAll(db);
+  rc = sqlite3Init(db, &zErrMsg);
+  if( SQLITE_OK!=rc ){
+    goto error_out;
+  }
+
+  /* Locate the table in question */
+  pTab = sqlite3FindTable(db, zTableName, zDbName);
+  if( !pTab || IsView(pTab) ){
+    pTab = 0;
+    goto error_out;
+  }
+
+  /* Find the column for which info is requested */
+  if( zColumnName==0 ){
+    /* Query for existence of table only */
+  }else{
+    for(iCol=0; iCol<pTab->nCol; iCol++){
+      pCol = &pTab->aCol[iCol];
+      if( 0==sqlite3StrICmp(pCol->zCnName, zColumnName) ){
+        break;
+      }
+    }
+    if( iCol==pTab->nCol ){
+      if( HasRowid(pTab) && sqlite3IsRowid(zColumnName) ){
+        iCol = pTab->iPKey;
+        pCol = iCol>=0 ? &pTab->aCol[iCol] : 0;
+      }else{
+        pTab = 0;
+        goto error_out;
+      }
+    }
+  }
+
+  /* The following block stores the meta information that will be returned
+  ** to the caller in local variables zDataType, zCollSeq, notnull, primarykey
+  ** and autoinc. At this point there are two possibilities:
+  **
+  **     1. The specified column name was rowid", "oid" or "_rowid_"
+  **        and there is no explicitly declared IPK column.
+  **
+  **     2. The table is not a view and the column name identified an
+  **        explicitly declared column. Copy meta information from *pCol.
+  */
+  if( pCol ){
+    zDataType = sqlite3ColumnType(pCol,0);
+    zCollSeq = sqlite3ColumnColl(pCol);
+    notnull = pCol->notNull!=0;
+    primarykey  = (pCol->colFlags & COLFLAG_PRIMKEY)!=0;
+    autoinc = pTab->iPKey==iCol && (pTab->tabFlags & TF_Autoincrement)!=0;
+  }else{
+    zDataType = "INTEGER";
+    primarykey = 1;
+  }
+  if( !zCollSeq ){
+    zCollSeq = sqlite3StrBINARY;
+  }
+
+error_out:
+  sqlite3BtreeLeaveAll(db);
+
+  /* Whether the function call succeeded or failed, set the output parameters
+  ** to whatever their local counterparts contain. If an error did occur,
+  ** this has the effect of zeroing all output parameters.
+  */
+  if( pzDataType ) *pzDataType = zDataType;
+  if( pzCollSeq ) *pzCollSeq = zCollSeq;
+  if( pNotNull ) *pNotNull = notnull;
+  if( pPrimaryKey ) *pPrimaryKey = primarykey;
+  if( pAutoinc ) *pAutoinc = autoinc;
+
+  if( SQLITE_OK==rc && !pTab ){
+    sqlite3DbFree(db, zErrMsg);
+    zErrMsg = sqlite3MPrintf(db, "no such table column: %s.%s", zTableName,
+        zColumnName);
+    rc = SQLITE_ERROR;
+  }
+  sqlite3ErrorWithMsg(db, rc, (zErrMsg?"%s":0), zErrMsg);
+  sqlite3DbFree(db, zErrMsg);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+*/
+int sqlite3_sleep(int ms){
+  sqlite3_vfs *pVfs;
+  int rc;
+  pVfs = sqlite3_vfs_find(0);
+  if( pVfs==0 ) return 0;
+
+  /* This function works in milliseconds, but the underlying OsSleep()
+  ** API uses microseconds. Hence the 1000's.
+  */
+  rc = (sqlite3OsSleep(pVfs, ms<0 ? 0 : 1000*ms)/1000);
+  return rc;
+}
+
+/*
+** Enable or disable the extended result codes.
+*/
+int sqlite3_extended_result_codes(sqlite3 *db, int onoff){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  db->errMask = onoff ? 0xffffffff : 0xff;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+/*
+** Invoke the xFileControl method on a particular database.
+*/
+int sqlite3_file_control(sqlite3 *db, const char *zDbName, int op, void *pArg){
+  int rc = SQLITE_ERROR;
+  Btree *pBtree;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pBtree = sqlite3DbNameToBtree(db, zDbName);
+  if( pBtree ){
+    Pager *pPager;
+    sqlite3_file *fd;
+    sqlite3BtreeEnter(pBtree);
+    pPager = sqlite3BtreePager(pBtree);
+    assert( pPager!=0 );
+    fd = sqlite3PagerFile(pPager);
+    assert( fd!=0 );
+    if( op==SQLITE_FCNTL_FILE_POINTER ){
+      *(sqlite3_file**)pArg = fd;
+      rc = SQLITE_OK;
+    }else if( op==SQLITE_FCNTL_VFS_POINTER ){
+      *(sqlite3_vfs**)pArg = sqlite3PagerVfs(pPager);
+      rc = SQLITE_OK;
+    }else if( op==SQLITE_FCNTL_JOURNAL_POINTER ){
+      *(sqlite3_file**)pArg = sqlite3PagerJrnlFile(pPager);
+      rc = SQLITE_OK;
+    }else if( op==SQLITE_FCNTL_DATA_VERSION ){
+      *(unsigned int*)pArg = sqlite3PagerDataVersion(pPager);
+      rc = SQLITE_OK;
+    }else if( op==SQLITE_FCNTL_RESERVE_BYTES ){
+      int iNew = *(int*)pArg;
+      *(int*)pArg = sqlite3BtreeGetRequestedReserve(pBtree);
+      if( iNew>=0 && iNew<=255 ){
+        sqlite3BtreeSetPageSize(pBtree, 0, iNew, 0);
+      }
+      rc = SQLITE_OK;
+    }else if( op==SQLITE_FCNTL_RESET_CACHE ){
+      sqlite3BtreeClearCache(pBtree);
+      rc = SQLITE_OK;
+    }else{
+      int nSave = db->busyHandler.nBusy;
+      rc = sqlite3OsFileControl(fd, op, pArg);
+      db->busyHandler.nBusy = nSave;
+    }
+    sqlite3BtreeLeave(pBtree);
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Interface to the testing logic.
+*/
+int sqlite3_test_control(int op, ...){
+  int rc = 0;
+#ifdef SQLITE_UNTESTABLE
+  UNUSED_PARAMETER(op);
+#else
+  va_list ap;
+  va_start(ap, op);
+  switch( op ){
+
+    /*
+    ** Save the current state of the PRNG.
+    */
+    case SQLITE_TESTCTRL_PRNG_SAVE: {
+      sqlite3PrngSaveState();
+      break;
+    }
+
+    /*
+    ** Restore the state of the PRNG to the last state saved using
+    ** PRNG_SAVE.  If PRNG_SAVE has never before been called, then
+    ** this verb acts like PRNG_RESET.
+    */
+    case SQLITE_TESTCTRL_PRNG_RESTORE: {
+      sqlite3PrngRestoreState();
+      break;
+    }
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_SEED, int x, sqlite3 *db);
+    **
+    ** Control the seed for the pseudo-random number generator (PRNG) that
+    ** is built into SQLite.  Cases:
+    **
+    **    x!=0 && db!=0       Seed the PRNG to the current value of the
+    **                        schema cookie in the main database for db, or
+    **                        x if the schema cookie is zero.  This case
+    **                        is convenient to use with database fuzzers
+    **                        as it allows the fuzzer some control over the
+    **                        the PRNG seed.
+    **
+    **    x!=0 && db==0       Seed the PRNG to the value of x.
+    **
+    **    x==0 && db==0       Revert to default behavior of using the
+    **                        xRandomness method on the primary VFS.
+    **
+    ** This test-control also resets the PRNG so that the new seed will
+    ** be used for the next call to sqlite3_randomness().
+    */
+#ifndef SQLITE_OMIT_WSD
+    case SQLITE_TESTCTRL_PRNG_SEED: {
+      int x = va_arg(ap, int);
+      int y;
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      assert( db==0 || db->aDb[0].pSchema!=0 );
+      if( db && (y = db->aDb[0].pSchema->schema_cookie)!=0 ){ x = y; }
+      sqlite3Config.iPrngSeed = x;
+      sqlite3_randomness(0,0);
+      break;
+    }
+#endif
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_FK_NO_ACTION, sqlite3 *db, int b);
+    **
+    ** If b is true, then activate the SQLITE_FkNoAction setting.  If b is
+    ** false then clearn that setting.  If the SQLITE_FkNoAction setting is
+    ** abled, all foreign key ON DELETE and ON UPDATE actions behave as if
+    ** they were NO ACTION, regardless of how they are defined.
+    **
+    ** NB:  One must usually run "PRAGMA writable_schema=RESET" after
+    ** using this test-control, before it will take full effect.  failing
+    ** to reset the schema can result in some unexpected behavior.
+    */
+    case SQLITE_TESTCTRL_FK_NO_ACTION: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      int b = va_arg(ap, int);
+      if( b ){
+        db->flags |= SQLITE_FkNoAction;
+      }else{
+        db->flags &= ~SQLITE_FkNoAction;
+      }
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(BITVEC_TEST, size, program)
+    **
+    ** Run a test against a Bitvec object of size.  The program argument
+    ** is an array of integers that defines the test.  Return -1 on a
+    ** memory allocation error, 0 on success, or non-zero for an error.
+    ** See the sqlite3BitvecBuiltinTest() for additional information.
+    */
+    case SQLITE_TESTCTRL_BITVEC_TEST: {
+      int sz = va_arg(ap, int);
+      int *aProg = va_arg(ap, int*);
+      rc = sqlite3BitvecBuiltinTest(sz, aProg);
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(FAULT_INSTALL, xCallback)
+    **
+    ** Arrange to invoke xCallback() whenever sqlite3FaultSim() is called,
+    ** if xCallback is not NULL.
+    **
+    ** As a test of the fault simulator mechanism itself, sqlite3FaultSim(0)
+    ** is called immediately after installing the new callback and the return
+    ** value from sqlite3FaultSim(0) becomes the return from
+    ** sqlite3_test_control().
+    */
+    case SQLITE_TESTCTRL_FAULT_INSTALL: {
+      /* A bug in MSVC prevents it from understanding pointers to functions
+      ** types in the second argument to va_arg().  Work around the problem
+      ** using a typedef.
+      ** http://support.microsoft.com/kb/47961  <-- dead hyperlink
+      ** Search at http://web.archive.org/ to find the 2015-03-16 archive
+      ** of the link above to see the original text.
+      ** sqlite3GlobalConfig.xTestCallback = va_arg(ap, int(*)(int));
+      */
+      typedef int(*sqlite3FaultFuncType)(int);
+      sqlite3GlobalConfig.xTestCallback = va_arg(ap, sqlite3FaultFuncType);
+      rc = sqlite3FaultSim(0);
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(BENIGN_MALLOC_HOOKS, xBegin, xEnd)
+    **
+    ** Register hooks to call to indicate which malloc() failures
+    ** are benign.
+    */
+    case SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS: {
+      typedef void (*void_function)(void);
+      void_function xBenignBegin;
+      void_function xBenignEnd;
+      xBenignBegin = va_arg(ap, void_function);
+      xBenignEnd = va_arg(ap, void_function);
+      sqlite3BenignMallocHooks(xBenignBegin, xBenignEnd);
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(SQLITE_TESTCTRL_PENDING_BYTE, unsigned int X)
+    **
+    ** Set the PENDING byte to the value in the argument, if X>0.
+    ** Make no changes if X==0.  Return the value of the pending byte
+    ** as it existing before this routine was called.
+    **
+    ** IMPORTANT:  Changing the PENDING byte from 0x40000000 results in
+    ** an incompatible database file format.  Changing the PENDING byte
+    ** while any database connection is open results in undefined and
+    ** deleterious behavior.
+    */
+    case SQLITE_TESTCTRL_PENDING_BYTE: {
+      rc = PENDING_BYTE;
+#ifndef SQLITE_OMIT_WSD
+      {
+        unsigned int newVal = va_arg(ap, unsigned int);
+        if( newVal ) sqlite3PendingByte = newVal;
+      }
+#endif
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(SQLITE_TESTCTRL_ASSERT, int X)
+    **
+    ** This action provides a run-time test to see whether or not
+    ** assert() was enabled at compile-time.  If X is true and assert()
+    ** is enabled, then the return value is true.  If X is true and
+    ** assert() is disabled, then the return value is zero.  If X is
+    ** false and assert() is enabled, then the assertion fires and the
+    ** process aborts.  If X is false and assert() is disabled, then the
+    ** return value is zero.
+    */
+    case SQLITE_TESTCTRL_ASSERT: {
+      volatile int x = 0;
+      assert( /*side-effects-ok*/ (x = va_arg(ap,int))!=0 );
+      rc = x;
+#if defined(SQLITE_DEBUG)
+      /* Invoke these debugging routines so that the compiler does not
+      ** issue "defined but not used" warnings. */
+      if( x==9999 ){
+        sqlite3ShowExpr(0);
+        sqlite3ShowExpr(0);
+        sqlite3ShowExprList(0);
+        sqlite3ShowIdList(0);
+        sqlite3ShowSrcList(0);
+        sqlite3ShowWith(0);
+        sqlite3ShowUpsert(0);
+#ifndef SQLITE_OMIT_TRIGGER
+        sqlite3ShowTriggerStep(0);
+        sqlite3ShowTriggerStepList(0);
+        sqlite3ShowTrigger(0);
+        sqlite3ShowTriggerList(0);
+#endif
+#ifndef SQLITE_OMIT_WINDOWFUNC
+        sqlite3ShowWindow(0);
+        sqlite3ShowWinFunc(0);
+#endif
+        sqlite3ShowSelect(0);
+      }
+#endif
+      break;
+    }
+
+
+    /*
+    **  sqlite3_test_control(SQLITE_TESTCTRL_ALWAYS, int X)
+    **
+    ** This action provides a run-time test to see how the ALWAYS and
+    ** NEVER macros were defined at compile-time.
+    **
+    ** The return value is ALWAYS(X) if X is true, or 0 if X is false.
+    **
+    ** The recommended test is X==2.  If the return value is 2, that means
+    ** ALWAYS() and NEVER() are both no-op pass-through macros, which is the
+    ** default setting.  If the return value is 1, then ALWAYS() is either
+    ** hard-coded to true or else it asserts if its argument is false.
+    ** The first behavior (hard-coded to true) is the case if
+    ** SQLITE_TESTCTRL_ASSERT shows that assert() is disabled and the second
+    ** behavior (assert if the argument to ALWAYS() is false) is the case if
+    ** SQLITE_TESTCTRL_ASSERT shows that assert() is enabled.
+    **
+    ** The run-time test procedure might look something like this:
+    **
+    **    if( sqlite3_test_control(SQLITE_TESTCTRL_ALWAYS, 2)==2 ){
+    **      // ALWAYS() and NEVER() are no-op pass-through macros
+    **    }else if( sqlite3_test_control(SQLITE_TESTCTRL_ASSERT, 1) ){
+    **      // ALWAYS(x) asserts that x is true. NEVER(x) asserts x is false.
+    **    }else{
+    **      // ALWAYS(x) is a constant 1.  NEVER(x) is a constant 0.
+    **    }
+    */
+    case SQLITE_TESTCTRL_ALWAYS: {
+      int x = va_arg(ap,int);
+      rc = x ? ALWAYS(x) : 0;
+      break;
+    }
+
+    /*
+    **   sqlite3_test_control(SQLITE_TESTCTRL_BYTEORDER);
+    **
+    ** The integer returned reveals the byte-order of the computer on which
+    ** SQLite is running:
+    **
+    **       1     big-endian,    determined at run-time
+    **      10     little-endian, determined at run-time
+    **  432101     big-endian,    determined at compile-time
+    **  123410     little-endian, determined at compile-time
+    */
+    case SQLITE_TESTCTRL_BYTEORDER: {
+      rc = SQLITE_BYTEORDER*100 + SQLITE_LITTLEENDIAN*10 + SQLITE_BIGENDIAN;
+      break;
+    }
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS, sqlite3 *db, int N)
+    **
+    ** Enable or disable various optimizations for testing purposes.  The
+    ** argument N is a bitmask of optimizations to be disabled.  For normal
+    ** operation N should be 0.  The idea is that a test program (like the
+    ** SQL Logic Test or SLT test module) can run the same SQL multiple times
+    ** with various optimizations disabled to verify that the same answer
+    ** is obtained in every case.
+    */
+    case SQLITE_TESTCTRL_OPTIMIZATIONS: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      db->dbOptFlags = va_arg(ap, u32);
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_LOCALTIME_FAULT, onoff, xAlt);
+    **
+    ** If parameter onoff is 1, subsequent calls to localtime() fail.
+    ** If 2, then invoke xAlt() instead of localtime().  If 0, normal
+    ** processing.
+    **
+    ** xAlt arguments are void pointers, but they really want to be:
+    **
+    **    int xAlt(const time_t*, struct tm*);
+    **
+    ** xAlt should write results in to struct tm object of its 2nd argument
+    ** and return zero on success, or return non-zero on failure.
+    */
+    case SQLITE_TESTCTRL_LOCALTIME_FAULT: {
+      sqlite3GlobalConfig.bLocaltimeFault = va_arg(ap, int);
+      if( sqlite3GlobalConfig.bLocaltimeFault==2 ){
+        typedef int(*sqlite3LocaltimeType)(const void*,void*);
+        sqlite3GlobalConfig.xAltLocaltime = va_arg(ap, sqlite3LocaltimeType);
+      }else{
+        sqlite3GlobalConfig.xAltLocaltime = 0;
+      }
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_INTERNAL_FUNCTIONS, sqlite3*);
+    **
+    ** Toggle the ability to use internal functions on or off for
+    ** the database connection given in the argument.
+    */
+    case SQLITE_TESTCTRL_INTERNAL_FUNCTIONS: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      db->mDbFlags ^= DBFLAG_InternalFunc;
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_NEVER_CORRUPT, int);
+    **
+    ** Set or clear a flag that indicates that the database file is always well-
+    ** formed and never corrupt.  This flag is clear by default, indicating that
+    ** database files might have arbitrary corruption.  Setting the flag during
+    ** testing causes certain assert() statements in the code to be activated
+    ** that demonstrate invariants on well-formed database files.
+    */
+    case SQLITE_TESTCTRL_NEVER_CORRUPT: {
+      sqlite3GlobalConfig.neverCorrupt = va_arg(ap, int);
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_EXTRA_SCHEMA_CHECKS, int);
+    **
+    ** Set or clear a flag that causes SQLite to verify that type, name,
+    ** and tbl_name fields of the sqlite_schema table.  This is normally
+    ** on, but it is sometimes useful to turn it off for testing.
+    **
+    ** 2020-07-22:  Disabling EXTRA_SCHEMA_CHECKS also disables the
+    ** verification of rootpage numbers when parsing the schema.  This
+    ** is useful to make it easier to reach strange internal error states
+    ** during testing.  The EXTRA_SCHEMA_CHECKS setting is always enabled
+    ** in production.
+    */
+    case SQLITE_TESTCTRL_EXTRA_SCHEMA_CHECKS: {
+      sqlite3GlobalConfig.bExtraSchemaChecks = va_arg(ap, int);
+      break;
+    }
+
+    /* Set the threshold at which OP_Once counters reset back to zero.
+    ** By default this is 0x7ffffffe (over 2 billion), but that value is
+    ** too big to test in a reasonable amount of time, so this control is
+    ** provided to set a small and easily reachable reset value.
+    */
+    case SQLITE_TESTCTRL_ONCE_RESET_THRESHOLD: {
+      sqlite3GlobalConfig.iOnceResetThreshold = va_arg(ap, int);
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_VDBE_COVERAGE, xCallback, ptr);
+    **
+    ** Set the VDBE coverage callback function to xCallback with context
+    ** pointer ptr.
+    */
+    case SQLITE_TESTCTRL_VDBE_COVERAGE: {
+#ifdef SQLITE_VDBE_COVERAGE
+      typedef void (*branch_callback)(void*,unsigned int,
+                                      unsigned char,unsigned char);
+      sqlite3GlobalConfig.xVdbeBranch = va_arg(ap,branch_callback);
+      sqlite3GlobalConfig.pVdbeBranchArg = va_arg(ap,void*);
+#endif
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_SORTER_MMAP, db, nMax); */
+    case SQLITE_TESTCTRL_SORTER_MMAP: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      db->nMaxSorterMmap = va_arg(ap, int);
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_ISINIT);
+    **
+    ** Return SQLITE_OK if SQLite has been initialized and SQLITE_ERROR if
+    ** not.
+    */
+    case SQLITE_TESTCTRL_ISINIT: {
+      if( sqlite3GlobalConfig.isInit==0 ) rc = SQLITE_ERROR;
+      break;
+    }
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, db, dbName, onOff, tnum);
+    **
+    ** This test control is used to create imposter tables.  "db" is a pointer
+    ** to the database connection.  dbName is the database name (ex: "main" or
+    ** "temp") which will receive the imposter.  "onOff" turns imposter mode on
+    ** or off.  "tnum" is the root page of the b-tree to which the imposter
+    ** table should connect.
+    **
+    ** Enable imposter mode only when the schema has already been parsed.  Then
+    ** run a single CREATE TABLE statement to construct the imposter table in
+    ** the parsed schema.  Then turn imposter mode back off again.
+    **
+    ** If onOff==0 and tnum>0 then reset the schema for all databases, causing
+    ** the schema to be reparsed the next time it is needed.  This has the
+    ** effect of erasing all imposter tables.
+    */
+    case SQLITE_TESTCTRL_IMPOSTER: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      int iDb;
+      sqlite3_mutex_enter(db->mutex);
+      iDb = sqlite3FindDbName(db, va_arg(ap,const char*));
+      if( iDb>=0 ){
+        db->init.iDb = iDb;
+        db->init.busy = db->init.imposterTable = va_arg(ap,int);
+        db->init.newTnum = va_arg(ap,int);
+        if( db->init.busy==0 && db->init.newTnum>0 ){
+          sqlite3ResetAllSchemasOfConnection(db);
+        }
+      }
+      sqlite3_mutex_leave(db->mutex);
+      break;
+    }
+
+#if defined(YYCOVERAGE)
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_PARSER_COVERAGE, FILE *out)
+    **
+    ** This test control (only available when SQLite is compiled with
+    ** -DYYCOVERAGE) writes a report onto "out" that shows all
+    ** state/lookahead combinations in the parser state machine
+    ** which are never exercised.  If any state is missed, make the
+    ** return code SQLITE_ERROR.
+    */
+    case SQLITE_TESTCTRL_PARSER_COVERAGE: {
+      FILE *out = va_arg(ap, FILE*);
+      if( sqlite3ParserCoverage(out) ) rc = SQLITE_ERROR;
+      break;
+    }
+#endif /* defined(YYCOVERAGE) */
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_RESULT_INTREAL, sqlite3_context*);
+    **
+    ** This test-control causes the most recent sqlite3_result_int64() value
+    ** to be interpreted as a MEM_IntReal instead of as an MEM_Int.  Normally,
+    ** MEM_IntReal values only arise during an INSERT operation of integer
+    ** values into a REAL column, so they can be challenging to test.  This
+    ** test-control enables us to write an intreal() SQL function that can
+    ** inject an intreal() value at arbitrary places in an SQL statement,
+    ** for testing purposes.
+    */
+    case SQLITE_TESTCTRL_RESULT_INTREAL: {
+      sqlite3_context *pCtx = va_arg(ap, sqlite3_context*);
+      sqlite3ResultIntReal(pCtx);
+      break;
+    }
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_SEEK_COUNT,
+    **    sqlite3 *db,    // Database connection
+    **    u64 *pnSeek     // Write seek count here
+    **  );
+    **
+    ** This test-control queries the seek-counter on the "main" database
+    ** file.  The seek-counter is written into *pnSeek and is then reset.
+    ** The seek-count is only available if compiled with SQLITE_DEBUG.
+    */
+    case SQLITE_TESTCTRL_SEEK_COUNT: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      u64 *pn = va_arg(ap, sqlite3_uint64*);
+      *pn = sqlite3BtreeSeekCount(db->aDb->pBt);
+      (void)db;  /* Silence harmless unused variable warning */
+      break;
+    }
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, op, ptr)
+    **
+    **  "ptr" is a pointer to a u32. 
+    **
+    **   op==0       Store the current sqlite3TreeTrace in *ptr
+    **   op==1       Set sqlite3TreeTrace to the value *ptr
+    **   op==2       Store the current sqlite3WhereTrace in *ptr
+    **   op==3       Set sqlite3WhereTrace to the value *ptr
+    */
+    case SQLITE_TESTCTRL_TRACEFLAGS: {
+       int opTrace = va_arg(ap, int);
+       u32 *ptr = va_arg(ap, u32*);
+       switch( opTrace ){
+         case 0:   *ptr = sqlite3TreeTrace;      break;
+         case 1:   sqlite3TreeTrace = *ptr;      break;
+         case 2:   *ptr = sqlite3WhereTrace;     break;
+         case 3:   sqlite3WhereTrace = *ptr;     break;
+       }
+       break;
+    }
+
+    /* sqlite3_test_control(SQLITE_TESTCTRL_LOGEST,
+    **      double fIn,     // Input value
+    **      int *pLogEst,   // sqlite3LogEstFromDouble(fIn)
+    **      u64 *pInt,      // sqlite3LogEstToInt(*pLogEst)
+    **      int *pLogEst2   // sqlite3LogEst(*pInt)
+    ** );
+    **
+    ** Test access for the LogEst conversion routines.
+    */
+    case SQLITE_TESTCTRL_LOGEST: {
+      double rIn = va_arg(ap, double);
+      LogEst rLogEst = sqlite3LogEstFromDouble(rIn);
+      int *pI1 = va_arg(ap,int*);
+      u64 *pU64 = va_arg(ap,u64*);
+      int *pI2 = va_arg(ap,int*);
+      *pI1 = rLogEst;
+      *pU64 = sqlite3LogEstToInt(rLogEst);
+      *pI2 = sqlite3LogEst(*pU64);
+      break;
+    }
+
+#if !defined(SQLITE_OMIT_WSD)
+    /* sqlite3_test_control(SQLITE_TESTCTRL_USELONGDOUBLE, int X);
+    **
+    **   X<0     Make no changes to the bUseLongDouble.  Just report value.
+    **   X==0    Disable bUseLongDouble
+    **   X==1    Enable bUseLongDouble
+    **   X>=2    Set bUseLongDouble to its default value for this platform
+    */
+    case SQLITE_TESTCTRL_USELONGDOUBLE: {
+      int b = va_arg(ap, int);
+      if( b>=2 ) b = hasHighPrecisionDouble(b);
+      if( b>=0 ) sqlite3Config.bUseLongDouble = b>0;
+      rc = sqlite3Config.bUseLongDouble!=0;
+      break;
+    }
+#endif
+
+
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_OMIT_WSD)
+    /* sqlite3_test_control(SQLITE_TESTCTRL_TUNE, id, *piValue)
+    **
+    ** If "id" is an integer between 1 and SQLITE_NTUNE then set the value
+    ** of the id-th tuning parameter to *piValue.  If "id" is between -1
+    ** and -SQLITE_NTUNE, then write the current value of the (-id)-th
+    ** tuning parameter into *piValue.
+    **
+    ** Tuning parameters are for use during transient development builds,
+    ** to help find the best values for constants in the query planner.
+    ** Access tuning parameters using the Tuning(ID) macro.  Set the
+    ** parameters in the CLI using ".testctrl tune ID VALUE".
+    **
+    ** Transient use only.  Tuning parameters should not be used in
+    ** checked-in code.
+    */
+    case SQLITE_TESTCTRL_TUNE: {
+      int id = va_arg(ap, int);
+      int *piValue = va_arg(ap, int*);
+      if( id>0 && id<=SQLITE_NTUNE ){
+        Tuning(id) = *piValue;
+      }else if( id<0 && id>=-SQLITE_NTUNE ){
+        *piValue = Tuning(-id);
+      }else{
+        rc = SQLITE_NOTFOUND;
+      }
+      break;
+    }
+#endif
+
+    /* sqlite3_test_control(SQLITE_TESTCTRL_JSON_SELFCHECK, &onOff);
+    **
+    ** Activate or deactivate validation of JSONB that is generated from
+    ** text.  Off by default, as the validation is slow.  Validation is
+    ** only available if compiled using SQLITE_DEBUG.
+    **
+    ** If onOff is initially 1, then turn it on.  If onOff is initially
+    ** off, turn it off.  If onOff is initially -1, then change onOff
+    ** to be the current setting.
+    */
+    case SQLITE_TESTCTRL_JSON_SELFCHECK: {
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_OMIT_WSD)
+      int *pOnOff = va_arg(ap, int*);
+      if( *pOnOff<0 ){
+        *pOnOff = sqlite3Config.bJsonSelfcheck;
+      }else{
+        sqlite3Config.bJsonSelfcheck = (u8)((*pOnOff)&0xff);
+      }
+#endif
+      break;
+    }
+  }
+  va_end(ap);
+#endif /* SQLITE_UNTESTABLE */
+  return rc;
+}
+
+/*
+** The Pager stores the Database filename, Journal filename, and WAL filename
+** consecutively in memory, in that order.  The database filename is prefixed
+** by four zero bytes.  Locate the start of the database filename by searching
+** backwards for the first byte following four consecutive zero bytes.
+**
+** This only works if the filename passed in was obtained from the Pager.
+*/
+static const char *databaseName(const char *zName){
+  while( zName[-1]!=0 || zName[-2]!=0 || zName[-3]!=0 || zName[-4]!=0 ){
+    zName--;
+  }
+  return zName;
+}
+
+/*
+** Append text z[] to the end of p[].  Return a pointer to the first
+** character after then zero terminator on the new text in p[].
+*/
+static char *appendText(char *p, const char *z){
+  size_t n = strlen(z);
+  memcpy(p, z, n+1);
+  return p+n+1;
+}
+
+/*
+** Allocate memory to hold names for a database, journal file, WAL file,
+** and query parameters.  The pointer returned is valid for use by
+** sqlite3_filename_database() and sqlite3_uri_parameter() and related
+** functions.
+**
+** Memory layout must be compatible with that generated by the pager
+** and expected by sqlite3_uri_parameter() and databaseName().
+*/
+const char *sqlite3_create_filename(
+  const char *zDatabase,
+  const char *zJournal,
+  const char *zWal,
+  int nParam,
+  const char **azParam
+){
+  sqlite3_int64 nByte;
+  int i;
+  char *pResult, *p;
+  nByte = strlen(zDatabase) + strlen(zJournal) + strlen(zWal) + 10;
+  for(i=0; i<nParam*2; i++){
+    nByte += strlen(azParam[i])+1;
+  }
+  pResult = p = sqlite3_malloc64( nByte );
+  if( p==0 ) return 0;
+  memset(p, 0, 4);
+  p += 4;
+  p = appendText(p, zDatabase);
+  for(i=0; i<nParam*2; i++){
+    p = appendText(p, azParam[i]);
+  }
+  *(p++) = 0;
+  p = appendText(p, zJournal);
+  p = appendText(p, zWal);
+  *(p++) = 0;
+  *(p++) = 0;
+  assert( (sqlite3_int64)(p - pResult)==nByte );
+  return pResult + 4;
+}
+
+/*
+** Free memory obtained from sqlite3_create_filename().  It is a severe
+** error to call this routine with any parameter other than a pointer
+** previously obtained from sqlite3_create_filename() or a NULL pointer.
+*/
+void sqlite3_free_filename(const char *p){
+  if( p==0 ) return;
+  p = databaseName(p);
+  sqlite3_free((char*)p - 4);
+}
+
+
+/*
+** This is a utility routine, useful to VFS implementations, that checks
+** to see if a database file was a URI that contained a specific query
+** parameter, and if so obtains the value of the query parameter.
+**
+** The zFilename argument is the filename pointer passed into the xOpen()
+** method of a VFS implementation.  The zParam argument is the name of the
+** query parameter we seek.  This routine returns the value of the zParam
+** parameter if it exists.  If the parameter does not exist, this routine
+** returns a NULL pointer.
+*/
+const char *sqlite3_uri_parameter(const char *zFilename, const char *zParam){
+  if( zFilename==0 || zParam==0 ) return 0;
+  zFilename = databaseName(zFilename);
+  return uriParameter(zFilename, zParam);
+}
+
+/*
+** Return a pointer to the name of Nth query parameter of the filename.
+*/
+const char *sqlite3_uri_key(const char *zFilename, int N){
+  if( zFilename==0 || N<0 ) return 0;
+  zFilename = databaseName(zFilename);
+  zFilename += sqlite3Strlen30(zFilename) + 1;
+  while( ALWAYS(zFilename) && zFilename[0] && (N--)>0 ){
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+  }
+  return zFilename[0] ? zFilename : 0;
+}
+
+/*
+** Return a boolean value for a query parameter.
+*/
+int sqlite3_uri_boolean(const char *zFilename, const char *zParam, int bDflt){
+  const char *z = sqlite3_uri_parameter(zFilename, zParam);
+  bDflt = bDflt!=0;
+  return z ? sqlite3GetBoolean(z, bDflt) : bDflt;
+}
+
+/*
+** Return a 64-bit integer value for a query parameter.
+*/
+sqlite3_int64 sqlite3_uri_int64(
+  const char *zFilename,    /* Filename as passed to xOpen */
+  const char *zParam,       /* URI parameter sought */
+  sqlite3_int64 bDflt       /* return if parameter is missing */
+){
+  const char *z = sqlite3_uri_parameter(zFilename, zParam);
+  sqlite3_int64 v;
+  if( z && sqlite3DecOrHexToI64(z, &v)==0 ){
+    bDflt = v;
+  }
+  return bDflt;
+}
+
+/*
+** Translate a filename that was handed to a VFS routine into the corresponding
+** database, journal, or WAL file.
+**
+** It is an error to pass this routine a filename string that was not
+** passed into the VFS from the SQLite core.  Doing so is similar to
+** passing free() a pointer that was not obtained from malloc() - it is
+** an error that we cannot easily detect but that will likely cause memory
+** corruption.
+*/
+const char *sqlite3_filename_database(const char *zFilename){
+  if( zFilename==0 ) return 0;
+  return databaseName(zFilename);
+}
+const char *sqlite3_filename_journal(const char *zFilename){
+  if( zFilename==0 ) return 0;
+  zFilename = databaseName(zFilename);
+  zFilename += sqlite3Strlen30(zFilename) + 1;
+  while( ALWAYS(zFilename) && zFilename[0] ){
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+  }
+  return zFilename + 1;
+}
+const char *sqlite3_filename_wal(const char *zFilename){
+#ifdef SQLITE_OMIT_WAL
+  return 0;
+#else
+  zFilename = sqlite3_filename_journal(zFilename);
+  if( zFilename ) zFilename += sqlite3Strlen30(zFilename) + 1;
+  return zFilename;
+#endif
+}
+
+/*
+** Return the Btree pointer identified by zDbName.  Return NULL if not found.
+*/
+Btree *sqlite3DbNameToBtree(sqlite3 *db, const char *zDbName){
+  int iDb = zDbName ? sqlite3FindDbName(db, zDbName) : 0;
+  return iDb<0 ? 0 : db->aDb[iDb].pBt;
+}
+
+/*
+** Return the name of the N-th database schema.  Return NULL if N is out
+** of range.
+*/
+const char *sqlite3_db_name(sqlite3 *db, int N){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  if( N<0 || N>=db->nDb ){
+    return 0;
+  }else{
+    return db->aDb[N].zDbSName;
+  }
+}
+
+/*
+** Return the filename of the database associated with a database
+** connection.
+*/
+const char *sqlite3_db_filename(sqlite3 *db, const char *zDbName){
+  Btree *pBt;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  pBt = sqlite3DbNameToBtree(db, zDbName);
+  return pBt ? sqlite3BtreeGetFilename(pBt) : 0;
+}
+
+/*
+** Return 1 if database is read-only or 0 if read/write.  Return -1 if
+** no such database exists.
+*/
+int sqlite3_db_readonly(sqlite3 *db, const char *zDbName){
+  Btree *pBt;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return -1;
+  }
+#endif
+  pBt = sqlite3DbNameToBtree(db, zDbName);
+  return pBt ? sqlite3BtreeIsReadonly(pBt) : -1;
+}
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Obtain a snapshot handle for the snapshot of database zDb currently
+** being read by handle db.
+*/
+int sqlite3_snapshot_get(
+  sqlite3 *db,
+  const char *zDb,
+  sqlite3_snapshot **ppSnapshot
+){
+  int rc = SQLITE_ERROR;
+#ifndef SQLITE_OMIT_WAL
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+
+  if( db->autoCommit==0 ){
+    int iDb = sqlite3FindDbName(db, zDb);
+    if( iDb==0 || iDb>1 ){
+      Btree *pBt = db->aDb[iDb].pBt;
+      if( SQLITE_TXN_WRITE!=sqlite3BtreeTxnState(pBt) ){
+        rc = sqlite3BtreeBeginTrans(pBt, 0, 0);
+        if( rc==SQLITE_OK ){
+          rc = sqlite3PagerSnapshotGet(sqlite3BtreePager(pBt), ppSnapshot);
+        }
+      }
+    }
+  }
+
+  sqlite3_mutex_leave(db->mutex);
+#endif   /* SQLITE_OMIT_WAL */
+  return rc;
+}
+
+/*
+** Open a read-transaction on the snapshot identified by pSnapshot.
+*/
+int sqlite3_snapshot_open(
+  sqlite3 *db,
+  const char *zDb,
+  sqlite3_snapshot *pSnapshot
+){
+  int rc = SQLITE_ERROR;
+#ifndef SQLITE_OMIT_WAL
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  if( db->autoCommit==0 ){
+    int iDb;
+    iDb = sqlite3FindDbName(db, zDb);
+    if( iDb==0 || iDb>1 ){
+      Btree *pBt = db->aDb[iDb].pBt;
+      if( sqlite3BtreeTxnState(pBt)!=SQLITE_TXN_WRITE ){
+        Pager *pPager = sqlite3BtreePager(pBt);
+        int bUnlock = 0;
+        if( sqlite3BtreeTxnState(pBt)!=SQLITE_TXN_NONE ){
+          if( db->nVdbeActive==0 ){
+            rc = sqlite3PagerSnapshotCheck(pPager, pSnapshot);
+            if( rc==SQLITE_OK ){
+              bUnlock = 1;
+              rc = sqlite3BtreeCommit(pBt);
+            }
+          }
+        }else{
+          rc = SQLITE_OK;
+        }
+        if( rc==SQLITE_OK ){
+          rc = sqlite3PagerSnapshotOpen(pPager, pSnapshot);
+        }
+        if( rc==SQLITE_OK ){
+          rc = sqlite3BtreeBeginTrans(pBt, 0, 0);
+          sqlite3PagerSnapshotOpen(pPager, 0);
+        }
+        if( bUnlock ){
+          sqlite3PagerSnapshotUnlock(pPager);
+        }
+      }
+    }
+  }
+
+  sqlite3_mutex_leave(db->mutex);
+#endif   /* SQLITE_OMIT_WAL */
+  return rc;
+}
+
+/*
+** Recover as many snapshots as possible from the wal file associated with
+** schema zDb of database db.
+*/
+int sqlite3_snapshot_recover(sqlite3 *db, const char *zDb){
+  int rc = SQLITE_ERROR;
+#ifndef SQLITE_OMIT_WAL
+  int iDb;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+
+  sqlite3_mutex_enter(db->mutex);
+  iDb = sqlite3FindDbName(db, zDb);
+  if( iDb==0 || iDb>1 ){
+    Btree *pBt = db->aDb[iDb].pBt;
+    if( SQLITE_TXN_NONE==sqlite3BtreeTxnState(pBt) ){
+      rc = sqlite3BtreeBeginTrans(pBt, 0, 0);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerSnapshotRecover(sqlite3BtreePager(pBt));
+        sqlite3BtreeCommit(pBt);
+      }
+    }
+  }
+  sqlite3_mutex_leave(db->mutex);
+#endif   /* SQLITE_OMIT_WAL */
+  return rc;
+}
+
+/*
+** Free a snapshot handle obtained from sqlite3_snapshot_get().
+*/
+void sqlite3_snapshot_free(sqlite3_snapshot *pSnapshot){
+  sqlite3_free(pSnapshot);
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+/*
+** Given the name of a compile-time option, return true if that option
+** was used and false if not.
+**
+** The name can optionally begin with "SQLITE_" but the "SQLITE_" prefix
+** is not required for a match.
+*/
+int sqlite3_compileoption_used(const char *zOptName){
+  int i, n;
+  int nOpt;
+  const char **azCompileOpt;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( zOptName==0 ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+
+  azCompileOpt = sqlite3CompileOptions(&nOpt);
+
+  if( sqlite3StrNICmp(zOptName, "SQLITE_", 7)==0 ) zOptName += 7;
+  n = sqlite3Strlen30(zOptName);
+
+  /* Since nOpt is normally in single digits, a linear search is
+  ** adequate. No need for a binary search. */
+  for(i=0; i<nOpt; i++){
+    if( sqlite3StrNICmp(zOptName, azCompileOpt[i], n)==0
+     && sqlite3IsIdChar((unsigned char)azCompileOpt[i][n])==0
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Return the N-th compile-time option string.  If N is out of range,
+** return a NULL pointer.
+*/
+const char *sqlite3_compileoption_get(int N){
+  int nOpt;
+  const char **azCompileOpt;
+  azCompileOpt = sqlite3CompileOptions(&nOpt);
+  if( N>=0 && N<nOpt ){
+    return azCompileOpt[N];
+  }
+  return 0;
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
diff --git a/src/malloc.c b/src/malloc.c
new file mode 100644
index 0000000..3567506
--- /dev/null
+++ b/src/malloc.c
@@ -0,0 +1,900 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** Memory allocation functions used throughout sqlite.
+*/
+#include "sqliteInt.h"
+#include <stdarg.h>
+
+/*
+** Attempt to release up to n bytes of non-essential memory currently
+** held by SQLite. An example of non-essential memory is memory used to
+** cache database pages that are not currently in use.
+*/
+int sqlite3_release_memory(int n){
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  return sqlite3PcacheReleaseMemory(n);
+#else
+  /* IMPLEMENTATION-OF: R-34391-24921 The sqlite3_release_memory() routine
+  ** is a no-op returning zero if SQLite is not compiled with
+  ** SQLITE_ENABLE_MEMORY_MANAGEMENT. */
+  UNUSED_PARAMETER(n);
+  return 0;
+#endif
+}
+
+/*
+** Default value of the hard heap limit.  0 means "no limit".
+*/
+#ifndef SQLITE_MAX_MEMORY
+# define SQLITE_MAX_MEMORY 0
+#endif
+
+/*
+** State information local to the memory allocation subsystem.
+*/
+static SQLITE_WSD struct Mem0Global {
+  sqlite3_mutex *mutex;         /* Mutex to serialize access */
+  sqlite3_int64 alarmThreshold; /* The soft heap limit */
+  sqlite3_int64 hardLimit;      /* The hard upper bound on memory */
+
+  /*
+  ** True if heap is nearly "full" where "full" is defined by the
+  ** sqlite3_soft_heap_limit() setting.
+  */
+  int nearlyFull;
+} mem0 = { 0, SQLITE_MAX_MEMORY, SQLITE_MAX_MEMORY, 0 };
+
+#define mem0 GLOBAL(struct Mem0Global, mem0)
+
+/*
+** Return the memory allocator mutex. sqlite3_status() needs it.
+*/
+sqlite3_mutex *sqlite3MallocMutex(void){
+  return mem0.mutex;
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Deprecated external interface.  It used to set an alarm callback
+** that was invoked when memory usage grew too large.  Now it is a
+** no-op.
+*/
+int sqlite3_memory_alarm(
+  void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
+  void *pArg,
+  sqlite3_int64 iThreshold
+){
+  (void)xCallback;
+  (void)pArg;
+  (void)iThreshold;
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Set the soft heap-size limit for the library.  An argument of
+** zero disables the limit.  A negative argument is a no-op used to
+** obtain the return value.
+**
+** The return value is the value of the heap limit just before this
+** interface was called.
+**
+** If the hard heap limit is enabled, then the soft heap limit cannot
+** be disabled nor raised above the hard heap limit.
+*/
+sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 n){
+  sqlite3_int64 priorLimit;
+  sqlite3_int64 excess;
+  sqlite3_int64 nUsed;
+#ifndef SQLITE_OMIT_AUTOINIT
+  int rc = sqlite3_initialize();
+  if( rc ) return -1;
+#endif
+  sqlite3_mutex_enter(mem0.mutex);
+  priorLimit = mem0.alarmThreshold;
+  if( n<0 ){
+    sqlite3_mutex_leave(mem0.mutex);
+    return priorLimit;
+  }
+  if( mem0.hardLimit>0 && (n>mem0.hardLimit || n==0) ){
+    n = mem0.hardLimit;
+  }
+  mem0.alarmThreshold = n;
+  nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
+  AtomicStore(&mem0.nearlyFull, n>0 && n<=nUsed);
+  sqlite3_mutex_leave(mem0.mutex);
+  excess = sqlite3_memory_used() - n;
+  if( excess>0 ) sqlite3_release_memory((int)(excess & 0x7fffffff));
+  return priorLimit;
+}
+void sqlite3_soft_heap_limit(int n){
+  if( n<0 ) n = 0;
+  sqlite3_soft_heap_limit64(n);
+}
+
+/*
+** Set the hard heap-size limit for the library. An argument of zero
+** disables the hard heap limit.  A negative argument is a no-op used
+** to obtain the return value without affecting the hard heap limit.
+**
+** The return value is the value of the hard heap limit just prior to
+** calling this interface.
+**
+** Setting the hard heap limit will also activate the soft heap limit
+** and constrain the soft heap limit to be no more than the hard heap
+** limit.
+*/
+sqlite3_int64 sqlite3_hard_heap_limit64(sqlite3_int64 n){
+  sqlite3_int64 priorLimit;
+#ifndef SQLITE_OMIT_AUTOINIT
+  int rc = sqlite3_initialize();
+  if( rc ) return -1;
+#endif
+  sqlite3_mutex_enter(mem0.mutex);
+  priorLimit = mem0.hardLimit;
+  if( n>=0 ){
+    mem0.hardLimit = n;
+    if( n<mem0.alarmThreshold || mem0.alarmThreshold==0 ){
+      mem0.alarmThreshold = n;
+    }
+  }
+  sqlite3_mutex_leave(mem0.mutex);
+  return priorLimit;
+}
+
+
+/*
+** Initialize the memory allocation subsystem.
+*/
+int sqlite3MallocInit(void){
+  int rc;
+  if( sqlite3GlobalConfig.m.xMalloc==0 ){
+    sqlite3MemSetDefault();
+  }
+  mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
+      || sqlite3GlobalConfig.nPage<=0 ){
+    sqlite3GlobalConfig.pPage = 0;
+    sqlite3GlobalConfig.szPage = 0;
+  }
+  rc = sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
+  if( rc!=SQLITE_OK ) memset(&mem0, 0, sizeof(mem0));
+  return rc;
+}
+
+/*
+** Return true if the heap is currently under memory pressure - in other
+** words if the amount of heap used is close to the limit set by
+** sqlite3_soft_heap_limit().
+*/
+int sqlite3HeapNearlyFull(void){
+  return AtomicLoad(&mem0.nearlyFull);
+}
+
+/*
+** Deinitialize the memory allocation subsystem.
+*/
+void sqlite3MallocEnd(void){
+  if( sqlite3GlobalConfig.m.xShutdown ){
+    sqlite3GlobalConfig.m.xShutdown(sqlite3GlobalConfig.m.pAppData);
+  }
+  memset(&mem0, 0, sizeof(mem0));
+}
+
+/*
+** Return the amount of memory currently checked out.
+*/
+sqlite3_int64 sqlite3_memory_used(void){
+  sqlite3_int64 res, mx;
+  sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, 0);
+  return res;
+}
+
+/*
+** Return the maximum amount of memory that has ever been
+** checked out since either the beginning of this process
+** or since the most recent reset.
+*/
+sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
+  sqlite3_int64 res, mx;
+  sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, resetFlag);
+  return mx;
+}
+
+/*
+** Trigger the alarm 
+*/
+static void sqlite3MallocAlarm(int nByte){
+  if( mem0.alarmThreshold<=0 ) return;
+  sqlite3_mutex_leave(mem0.mutex);
+  sqlite3_release_memory(nByte);
+  sqlite3_mutex_enter(mem0.mutex);
+}
+
+/*
+** Do a memory allocation with statistics and alarms.  Assume the
+** lock is already held.
+*/
+static void mallocWithAlarm(int n, void **pp){
+  void *p;
+  int nFull;
+  assert( sqlite3_mutex_held(mem0.mutex) );
+  assert( n>0 );
+
+  /* In Firefox (circa 2017-02-08), xRoundup() is remapped to an internal
+  ** implementation of malloc_good_size(), which must be called in debug
+  ** mode and specifically when the DMD "Dark Matter Detector" is enabled
+  ** or else a crash results.  Hence, do not attempt to optimize out the
+  ** following xRoundup() call. */
+  nFull = sqlite3GlobalConfig.m.xRoundup(n);
+
+  sqlite3StatusHighwater(SQLITE_STATUS_MALLOC_SIZE, n);
+  if( mem0.alarmThreshold>0 ){
+    sqlite3_int64 nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
+    if( nUsed >= mem0.alarmThreshold - nFull ){
+      AtomicStore(&mem0.nearlyFull, 1);
+      sqlite3MallocAlarm(nFull);
+      if( mem0.hardLimit ){
+        nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
+        if( nUsed >= mem0.hardLimit - nFull ){
+          *pp = 0;
+          return;
+        }
+      }
+    }else{
+      AtomicStore(&mem0.nearlyFull, 0);
+    }
+  }
+  p = sqlite3GlobalConfig.m.xMalloc(nFull);
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  if( p==0 && mem0.alarmThreshold>0 ){
+    sqlite3MallocAlarm(nFull);
+    p = sqlite3GlobalConfig.m.xMalloc(nFull);
+  }
+#endif
+  if( p ){
+    nFull = sqlite3MallocSize(p);
+    sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nFull);
+    sqlite3StatusUp(SQLITE_STATUS_MALLOC_COUNT, 1);
+  }
+  *pp = p;
+}
+
+/*
+** Maximum size of any single memory allocation.
+**
+** This is not a limit on the total amount of memory used.  This is
+** a limit on the size parameter to sqlite3_malloc() and sqlite3_realloc().
+**
+** The upper bound is slightly less than 2GiB:  0x7ffffeff == 2,147,483,391
+** This provides a 256-byte safety margin for defense against 32-bit 
+** signed integer overflow bugs when computing memory allocation sizes.
+** Paranoid applications might want to reduce the maximum allocation size
+** further for an even larger safety margin.  0x3fffffff or 0x0fffffff
+** or even smaller would be reasonable upper bounds on the size of a memory
+** allocations for most applications.
+*/
+#ifndef SQLITE_MAX_ALLOCATION_SIZE
+# define SQLITE_MAX_ALLOCATION_SIZE  2147483391
+#endif
+#if SQLITE_MAX_ALLOCATION_SIZE>2147483391
+# error Maximum size for SQLITE_MAX_ALLOCATION_SIZE is 2147483391
+#endif
+
+/*
+** Allocate memory.  This routine is like sqlite3_malloc() except that it
+** assumes the memory subsystem has already been initialized.
+*/
+void *sqlite3Malloc(u64 n){
+  void *p;
+  if( n==0 || n>SQLITE_MAX_ALLOCATION_SIZE ){
+    p = 0;
+  }else if( sqlite3GlobalConfig.bMemstat ){
+    sqlite3_mutex_enter(mem0.mutex);
+    mallocWithAlarm((int)n, &p);
+    sqlite3_mutex_leave(mem0.mutex);
+  }else{
+    p = sqlite3GlobalConfig.m.xMalloc((int)n);
+  }
+  assert( EIGHT_BYTE_ALIGNMENT(p) );  /* IMP: R-11148-40995 */
+  return p;
+}
+
+/*
+** This version of the memory allocation is for use by the application.
+** First make sure the memory subsystem is initialized, then do the
+** allocation.
+*/
+void *sqlite3_malloc(int n){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return n<=0 ? 0 : sqlite3Malloc(n);
+}
+void *sqlite3_malloc64(sqlite3_uint64 n){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return sqlite3Malloc(n);
+}
+
+/*
+** TRUE if p is a lookaside memory allocation from db
+*/
+#ifndef SQLITE_OMIT_LOOKASIDE
+static int isLookaside(sqlite3 *db, const void *p){
+  return SQLITE_WITHIN(p, db->lookaside.pStart, db->lookaside.pTrueEnd);
+}
+#else
+#define isLookaside(A,B) 0
+#endif
+
+/*
+** Return the size of a memory allocation previously obtained from
+** sqlite3Malloc() or sqlite3_malloc().
+*/
+int sqlite3MallocSize(const void *p){
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+  return sqlite3GlobalConfig.m.xSize((void*)p);
+}
+static int lookasideMallocSize(sqlite3 *db, const void *p){
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE    
+  return p<db->lookaside.pMiddle ? db->lookaside.szTrue : LOOKASIDE_SMALL;
+#else
+  return db->lookaside.szTrue;
+#endif  
+}
+int sqlite3DbMallocSize(sqlite3 *db, const void *p){
+  assert( p!=0 );
+#ifdef SQLITE_DEBUG
+  if( db==0 ){
+    assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+  }else if( !isLookaside(db,p) ){
+    assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+    assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+  }
+#endif
+  if( db ){
+    if( ((uptr)p)<(uptr)(db->lookaside.pTrueEnd) ){
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+      if( ((uptr)p)>=(uptr)(db->lookaside.pMiddle) ){
+        assert( sqlite3_mutex_held(db->mutex) );
+        return LOOKASIDE_SMALL;
+      }
+#endif
+      if( ((uptr)p)>=(uptr)(db->lookaside.pStart) ){
+        assert( sqlite3_mutex_held(db->mutex) );
+        return db->lookaside.szTrue;
+      }
+    }
+  }
+  return sqlite3GlobalConfig.m.xSize((void*)p);
+}
+sqlite3_uint64 sqlite3_msize(void *p){
+  assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+  return p ? sqlite3GlobalConfig.m.xSize(p) : 0;
+}
+
+/*
+** Free memory previously obtained from sqlite3Malloc().
+*/
+void sqlite3_free(void *p){
+  if( p==0 ) return;  /* IMP: R-49053-54554 */
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+  assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
+  if( sqlite3GlobalConfig.bMemstat ){
+    sqlite3_mutex_enter(mem0.mutex);
+    sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, sqlite3MallocSize(p));
+    sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
+    sqlite3GlobalConfig.m.xFree(p);
+    sqlite3_mutex_leave(mem0.mutex);
+  }else{
+    sqlite3GlobalConfig.m.xFree(p);
+  }
+}
+
+/*
+** Add the size of memory allocation "p" to the count in
+** *db->pnBytesFreed.
+*/
+static SQLITE_NOINLINE void measureAllocationSize(sqlite3 *db, void *p){
+  *db->pnBytesFreed += sqlite3DbMallocSize(db,p);
+}
+
+/*
+** Free memory that might be associated with a particular database
+** connection.  Calling sqlite3DbFree(D,X) for X==0 is a harmless no-op.
+** The sqlite3DbFreeNN(D,X) version requires that X be non-NULL.
+*/
+void sqlite3DbFreeNN(sqlite3 *db, void *p){
+  assert( db==0 || sqlite3_mutex_held(db->mutex) );
+  assert( p!=0 );
+  if( db ){
+    if( ((uptr)p)<(uptr)(db->lookaside.pEnd) ){
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+      if( ((uptr)p)>=(uptr)(db->lookaside.pMiddle) ){
+        LookasideSlot *pBuf = (LookasideSlot*)p;
+        assert( db->pnBytesFreed==0 );
+#ifdef SQLITE_DEBUG
+        memset(p, 0xaa, LOOKASIDE_SMALL);  /* Trash freed content */
+#endif
+        pBuf->pNext = db->lookaside.pSmallFree;
+        db->lookaside.pSmallFree = pBuf;
+        return;
+      }
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+      if( ((uptr)p)>=(uptr)(db->lookaside.pStart) ){
+        LookasideSlot *pBuf = (LookasideSlot*)p;
+        assert( db->pnBytesFreed==0 );
+#ifdef SQLITE_DEBUG
+        memset(p, 0xaa, db->lookaside.szTrue);  /* Trash freed content */
+#endif
+        pBuf->pNext = db->lookaside.pFree;
+        db->lookaside.pFree = pBuf;
+        return;
+      }
+    }
+    if( db->pnBytesFreed ){
+      measureAllocationSize(db, p);
+      return;
+    }
+  }
+  assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+  assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+  assert( db!=0 || sqlite3MemdebugNoType(p, MEMTYPE_LOOKASIDE) );
+  sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+  sqlite3_free(p);
+}
+void sqlite3DbNNFreeNN(sqlite3 *db, void *p){
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( p!=0 );
+  if( ((uptr)p)<(uptr)(db->lookaside.pEnd) ){
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+    if( ((uptr)p)>=(uptr)(db->lookaside.pMiddle) ){
+      LookasideSlot *pBuf = (LookasideSlot*)p;
+      assert( db->pnBytesFreed==0 );
+#ifdef SQLITE_DEBUG
+      memset(p, 0xaa, LOOKASIDE_SMALL);  /* Trash freed content */
+#endif
+      pBuf->pNext = db->lookaside.pSmallFree;
+      db->lookaside.pSmallFree = pBuf;
+      return;
+    }
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+    if( ((uptr)p)>=(uptr)(db->lookaside.pStart) ){
+      LookasideSlot *pBuf = (LookasideSlot*)p;
+      assert( db->pnBytesFreed==0 );
+#ifdef SQLITE_DEBUG
+      memset(p, 0xaa, db->lookaside.szTrue);  /* Trash freed content */
+#endif
+      pBuf->pNext = db->lookaside.pFree;
+      db->lookaside.pFree = pBuf;
+      return;
+    }
+  }
+  if( db->pnBytesFreed ){
+    measureAllocationSize(db, p);
+    return;
+  }
+  assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+  assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+  sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+  sqlite3_free(p);
+}
+void sqlite3DbFree(sqlite3 *db, void *p){
+  assert( db==0 || sqlite3_mutex_held(db->mutex) );
+  if( p ) sqlite3DbFreeNN(db, p);
+}
+
+/*
+** Change the size of an existing memory allocation
+*/
+void *sqlite3Realloc(void *pOld, u64 nBytes){
+  int nOld, nNew, nDiff;
+  void *pNew;
+  assert( sqlite3MemdebugHasType(pOld, MEMTYPE_HEAP) );
+  assert( sqlite3MemdebugNoType(pOld, (u8)~MEMTYPE_HEAP) );
+  if( pOld==0 ){
+    return sqlite3Malloc(nBytes); /* IMP: R-04300-56712 */
+  }
+  if( nBytes==0 ){
+    sqlite3_free(pOld); /* IMP: R-26507-47431 */
+    return 0;
+  }
+  if( nBytes>=0x7fffff00 ){
+    /* The 0x7ffff00 limit term is explained in comments on sqlite3Malloc() */
+    return 0;
+  }
+  nOld = sqlite3MallocSize(pOld);
+  /* IMPLEMENTATION-OF: R-46199-30249 SQLite guarantees that the second
+  ** argument to xRealloc is always a value returned by a prior call to
+  ** xRoundup. */
+  nNew = sqlite3GlobalConfig.m.xRoundup((int)nBytes);
+  if( nOld==nNew ){
+    pNew = pOld;
+  }else if( sqlite3GlobalConfig.bMemstat ){
+    sqlite3_int64 nUsed;
+    sqlite3_mutex_enter(mem0.mutex);
+    sqlite3StatusHighwater(SQLITE_STATUS_MALLOC_SIZE, (int)nBytes);
+    nDiff = nNew - nOld;
+    if( nDiff>0 && (nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED)) >= 
+          mem0.alarmThreshold-nDiff ){
+      sqlite3MallocAlarm(nDiff);
+      if( mem0.hardLimit>0 && nUsed >= mem0.hardLimit - nDiff ){
+        sqlite3_mutex_leave(mem0.mutex);
+        return 0;
+      }
+    }
+    pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+    if( pNew==0 && mem0.alarmThreshold>0 ){
+      sqlite3MallocAlarm((int)nBytes);
+      pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
+    }
+#endif
+    if( pNew ){
+      nNew = sqlite3MallocSize(pNew);
+      sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nNew-nOld);
+    }
+    sqlite3_mutex_leave(mem0.mutex);
+  }else{
+    pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
+  }
+  assert( EIGHT_BYTE_ALIGNMENT(pNew) ); /* IMP: R-11148-40995 */
+  return pNew;
+}
+
+/*
+** The public interface to sqlite3Realloc.  Make sure that the memory
+** subsystem is initialized prior to invoking sqliteRealloc.
+*/
+void *sqlite3_realloc(void *pOld, int n){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  if( n<0 ) n = 0;  /* IMP: R-26507-47431 */
+  return sqlite3Realloc(pOld, n);
+}
+void *sqlite3_realloc64(void *pOld, sqlite3_uint64 n){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return sqlite3Realloc(pOld, n);
+}
+
+
+/*
+** Allocate and zero memory.
+*/ 
+void *sqlite3MallocZero(u64 n){
+  void *p = sqlite3Malloc(n);
+  if( p ){
+    memset(p, 0, (size_t)n);
+  }
+  return p;
+}
+
+/*
+** Allocate and zero memory.  If the allocation fails, make
+** the mallocFailed flag in the connection pointer.
+*/
+void *sqlite3DbMallocZero(sqlite3 *db, u64 n){
+  void *p;
+  testcase( db==0 );
+  p = sqlite3DbMallocRaw(db, n);
+  if( p ) memset(p, 0, (size_t)n);
+  return p;
+}
+
+
+/* Finish the work of sqlite3DbMallocRawNN for the unusual and
+** slower case when the allocation cannot be fulfilled using lookaside.
+*/
+static SQLITE_NOINLINE void *dbMallocRawFinish(sqlite3 *db, u64 n){
+  void *p;
+  assert( db!=0 );
+  p = sqlite3Malloc(n);
+  if( !p ) sqlite3OomFault(db);
+  sqlite3MemdebugSetType(p, 
+         (db->lookaside.bDisable==0) ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP);
+  return p;
+}
+
+/*
+** Allocate memory, either lookaside (if possible) or heap.  
+** If the allocation fails, set the mallocFailed flag in
+** the connection pointer.
+**
+** If db!=0 and db->mallocFailed is true (indicating a prior malloc
+** failure on the same database connection) then always return 0.
+** Hence for a particular database connection, once malloc starts
+** failing, it fails consistently until mallocFailed is reset.
+** This is an important assumption.  There are many places in the
+** code that do things like this:
+**
+**         int *a = (int*)sqlite3DbMallocRaw(db, 100);
+**         int *b = (int*)sqlite3DbMallocRaw(db, 200);
+**         if( b ) a[10] = 9;
+**
+** In other words, if a subsequent malloc (ex: "b") worked, it is assumed
+** that all prior mallocs (ex: "a") worked too.
+**
+** The sqlite3MallocRawNN() variant guarantees that the "db" parameter is
+** not a NULL pointer.
+*/
+void *sqlite3DbMallocRaw(sqlite3 *db, u64 n){
+  void *p;
+  if( db ) return sqlite3DbMallocRawNN(db, n);
+  p = sqlite3Malloc(n);
+  sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+  return p;
+}
+void *sqlite3DbMallocRawNN(sqlite3 *db, u64 n){
+#ifndef SQLITE_OMIT_LOOKASIDE
+  LookasideSlot *pBuf;
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( db->pnBytesFreed==0 );
+  if( n>db->lookaside.sz ){
+    if( !db->lookaside.bDisable ){
+      db->lookaside.anStat[1]++;      
+    }else if( db->mallocFailed ){
+      return 0;
+    }
+    return dbMallocRawFinish(db, n);
+  }
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+  if( n<=LOOKASIDE_SMALL ){
+    if( (pBuf = db->lookaside.pSmallFree)!=0 ){
+      db->lookaside.pSmallFree = pBuf->pNext;
+      db->lookaside.anStat[0]++;
+      return (void*)pBuf;
+    }else if( (pBuf = db->lookaside.pSmallInit)!=0 ){
+      db->lookaside.pSmallInit = pBuf->pNext;
+      db->lookaside.anStat[0]++;
+      return (void*)pBuf;
+    }
+  }
+#endif
+  if( (pBuf = db->lookaside.pFree)!=0 ){
+    db->lookaside.pFree = pBuf->pNext;
+    db->lookaside.anStat[0]++;
+    return (void*)pBuf;
+  }else if( (pBuf = db->lookaside.pInit)!=0 ){
+    db->lookaside.pInit = pBuf->pNext;
+    db->lookaside.anStat[0]++;
+    return (void*)pBuf;
+  }else{
+    db->lookaside.anStat[2]++;
+  }
+#else
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( db->pnBytesFreed==0 );
+  if( db->mallocFailed ){
+    return 0;
+  }
+#endif
+  return dbMallocRawFinish(db, n);
+}
+
+/* Forward declaration */
+static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n);
+
+/*
+** Resize the block of memory pointed to by p to n bytes. If the
+** resize fails, set the mallocFailed flag in the connection object.
+*/
+void *sqlite3DbRealloc(sqlite3 *db, void *p, u64 n){
+  assert( db!=0 );
+  if( p==0 ) return sqlite3DbMallocRawNN(db, n);
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( ((uptr)p)<(uptr)db->lookaside.pEnd ){
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+    if( ((uptr)p)>=(uptr)db->lookaside.pMiddle ){
+      if( n<=LOOKASIDE_SMALL ) return p;
+    }else
+#endif
+    if( ((uptr)p)>=(uptr)db->lookaside.pStart ){
+      if( n<=db->lookaside.szTrue ) return p;
+    }
+  }
+  return dbReallocFinish(db, p, n);
+}
+static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n){
+  void *pNew = 0;
+  assert( db!=0 );
+  assert( p!=0 );
+  if( db->mallocFailed==0 ){
+    if( isLookaside(db, p) ){
+      pNew = sqlite3DbMallocRawNN(db, n);
+      if( pNew ){
+        memcpy(pNew, p, lookasideMallocSize(db, p));
+        sqlite3DbFree(db, p);
+      }
+    }else{
+      assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+      assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+      pNew = sqlite3Realloc(p, n);
+      if( !pNew ){
+        sqlite3OomFault(db);
+      }
+      sqlite3MemdebugSetType(pNew,
+            (db->lookaside.bDisable==0 ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP));
+    }
+  }
+  return pNew;
+}
+
+/*
+** Attempt to reallocate p.  If the reallocation fails, then free p
+** and set the mallocFailed flag in the database connection.
+*/
+void *sqlite3DbReallocOrFree(sqlite3 *db, void *p, u64 n){
+  void *pNew;
+  pNew = sqlite3DbRealloc(db, p, n);
+  if( !pNew ){
+    sqlite3DbFree(db, p);
+  }
+  return pNew;
+}
+
+/*
+** Make a copy of a string in memory obtained from sqliteMalloc(). These 
+** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This
+** is because when memory debugging is turned on, these two functions are 
+** called via macros that record the current file and line number in the
+** ThreadData structure.
+*/
+char *sqlite3DbStrDup(sqlite3 *db, const char *z){
+  char *zNew;
+  size_t n;
+  if( z==0 ){
+    return 0;
+  }
+  n = strlen(z) + 1;
+  zNew = sqlite3DbMallocRaw(db, n);
+  if( zNew ){
+    memcpy(zNew, z, n);
+  }
+  return zNew;
+}
+char *sqlite3DbStrNDup(sqlite3 *db, const char *z, u64 n){
+  char *zNew;
+  assert( db!=0 );
+  assert( z!=0 || n==0 );
+  assert( (n&0x7fffffff)==n );
+  zNew = z ? sqlite3DbMallocRawNN(db, n+1) : 0;
+  if( zNew ){
+    memcpy(zNew, z, (size_t)n);
+    zNew[n] = 0;
+  }
+  return zNew;
+}
+
+/*
+** The text between zStart and zEnd represents a phrase within a larger
+** SQL statement.  Make a copy of this phrase in space obtained form
+** sqlite3DbMalloc().  Omit leading and trailing whitespace.
+*/
+char *sqlite3DbSpanDup(sqlite3 *db, const char *zStart, const char *zEnd){
+  int n;
+#ifdef SQLITE_DEBUG
+  /* Because of the way the parser works, the span is guaranteed to contain
+  ** at least one non-space character */
+  for(n=0; sqlite3Isspace(zStart[n]); n++){ assert( &zStart[n]<zEnd ); }
+#endif
+  while( sqlite3Isspace(zStart[0]) ) zStart++;
+  n = (int)(zEnd - zStart);
+  while( sqlite3Isspace(zStart[n-1]) ) n--;
+  return sqlite3DbStrNDup(db, zStart, n);
+}
+
+/*
+** Free any prior content in *pz and replace it with a copy of zNew.
+*/
+void sqlite3SetString(char **pz, sqlite3 *db, const char *zNew){
+  char *z = sqlite3DbStrDup(db, zNew);
+  sqlite3DbFree(db, *pz);
+  *pz = z;
+}
+
+/*
+** Call this routine to record the fact that an OOM (out-of-memory) error
+** has happened.  This routine will set db->mallocFailed, and also
+** temporarily disable the lookaside memory allocator and interrupt
+** any running VDBEs.
+**
+** Always return a NULL pointer so that this routine can be invoked using
+**
+**      return sqlite3OomFault(db);
+**
+** and thereby avoid unnecessary stack frame allocations for the overwhelmingly
+** common case where no OOM occurs.
+*/
+void *sqlite3OomFault(sqlite3 *db){
+  if( db->mallocFailed==0 && db->bBenignMalloc==0 ){
+    db->mallocFailed = 1;
+    if( db->nVdbeExec>0 ){
+      AtomicStore(&db->u1.isInterrupted, 1);
+    }
+    DisableLookaside;
+    if( db->pParse ){
+      Parse *pParse;
+      sqlite3ErrorMsg(db->pParse, "out of memory");
+      db->pParse->rc = SQLITE_NOMEM_BKPT;
+      for(pParse=db->pParse->pOuterParse; pParse; pParse = pParse->pOuterParse){
+        pParse->nErr++;
+        pParse->rc = SQLITE_NOMEM;
+      } 
+    }
+  }
+  return 0;
+}
+
+/*
+** This routine reactivates the memory allocator and clears the
+** db->mallocFailed flag as necessary.
+**
+** The memory allocator is not restarted if there are running
+** VDBEs.
+*/
+void sqlite3OomClear(sqlite3 *db){
+  if( db->mallocFailed && db->nVdbeExec==0 ){
+    db->mallocFailed = 0;
+    AtomicStore(&db->u1.isInterrupted, 0);
+    assert( db->lookaside.bDisable>0 );
+    EnableLookaside;
+  }
+}
+
+/*
+** Take actions at the end of an API call to deal with error codes.
+*/
+static SQLITE_NOINLINE int apiHandleError(sqlite3 *db, int rc){
+  if( db->mallocFailed || rc==SQLITE_IOERR_NOMEM ){
+    sqlite3OomClear(db);
+    sqlite3Error(db, SQLITE_NOMEM);
+    return SQLITE_NOMEM_BKPT;
+  }
+  return rc & db->errMask;
+}
+
+/*
+** This function must be called before exiting any API function (i.e. 
+** returning control to the user) that has called sqlite3_malloc or
+** sqlite3_realloc.
+**
+** The returned value is normally a copy of the second argument to this
+** function. However, if a malloc() failure has occurred since the previous
+** invocation SQLITE_NOMEM is returned instead. 
+**
+** If an OOM as occurred, then the connection error-code (the value
+** returned by sqlite3_errcode()) is set to SQLITE_NOMEM.
+*/
+int sqlite3ApiExit(sqlite3* db, int rc){
+  /* If the db handle must hold the connection handle mutex here.
+  ** Otherwise the read (and possible write) of db->mallocFailed 
+  ** is unsafe, as is the call to sqlite3Error().
+  */
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( db->mallocFailed || rc ){
+    return apiHandleError(db, rc);
+  }
+  return 0;
+}
diff --git a/src/mem0.c b/src/mem0.c
new file mode 100644
index 0000000..0d0b666
--- /dev/null
+++ b/src/mem0.c
@@ -0,0 +1,59 @@
+/*
+** 2008 October 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a no-op memory allocation drivers for use when
+** SQLITE_ZERO_MALLOC is defined.  The allocation drivers implemented
+** here always fail.  SQLite will not operate with these drivers.  These
+** are merely placeholders.  Real drivers must be substituted using
+** sqlite3_config() before SQLite will operate.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is the default.  It is
+** used when no other memory allocator is specified using compile-time
+** macros.
+*/
+#ifdef SQLITE_ZERO_MALLOC
+
+/*
+** No-op versions of all memory allocation routines
+*/
+static void *sqlite3MemMalloc(int nByte){ return 0; }
+static void sqlite3MemFree(void *pPrior){ return; }
+static void *sqlite3MemRealloc(void *pPrior, int nByte){ return 0; }
+static int sqlite3MemSize(void *pPrior){ return 0; }
+static int sqlite3MemRoundup(int n){ return n; }
+static int sqlite3MemInit(void *NotUsed){ return SQLITE_OK; }
+static void sqlite3MemShutdown(void *NotUsed){ return; }
+
+/*
+** This routine is the only routine in this file with external linkage.
+**
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file.
+*/
+void sqlite3MemSetDefault(void){
+  static const sqlite3_mem_methods defaultMethods = {
+     sqlite3MemMalloc,
+     sqlite3MemFree,
+     sqlite3MemRealloc,
+     sqlite3MemSize,
+     sqlite3MemRoundup,
+     sqlite3MemInit,
+     sqlite3MemShutdown,
+     0
+  };
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods);
+}
+
+#endif /* SQLITE_ZERO_MALLOC */
diff --git a/src/mem1.c b/src/mem1.c
new file mode 100644
index 0000000..12f96be
--- /dev/null
+++ b/src/mem1.c
@@ -0,0 +1,291 @@
+/*
+** 2007 August 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains low-level memory allocation drivers for when
+** SQLite will use the standard C-library malloc/realloc/free interface
+** to obtain the memory it needs.
+**
+** This file contains implementations of the low-level memory allocation
+** routines specified in the sqlite3_mem_methods object.  The content of
+** this file is only used if SQLITE_SYSTEM_MALLOC is defined.  The
+** SQLITE_SYSTEM_MALLOC macro is defined automatically if neither the
+** SQLITE_MEMDEBUG nor the SQLITE_WIN32_MALLOC macros are defined.  The
+** default configuration is to use memory allocation routines in this
+** file.
+**
+** C-preprocessor macro summary:
+**
+**    HAVE_MALLOC_USABLE_SIZE     The configure script sets this symbol if
+**                                the malloc_usable_size() interface exists
+**                                on the target platform.  Or, this symbol
+**                                can be set manually, if desired.
+**                                If an equivalent interface exists by
+**                                a different name, using a separate -D
+**                                option to rename it.
+**
+**    SQLITE_WITHOUT_ZONEMALLOC   Some older macs lack support for the zone
+**                                memory allocator.  Set this symbol to enable
+**                                building on older macs.
+**
+**    SQLITE_WITHOUT_MSIZE        Set this symbol to disable the use of
+**                                _msize() on windows systems.  This might
+**                                be necessary when compiling for Delphi,
+**                                for example.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is the default.  It is
+** used when no other memory allocator is specified using compile-time
+** macros.
+*/
+#ifdef SQLITE_SYSTEM_MALLOC
+#if defined(__APPLE__) && !defined(SQLITE_WITHOUT_ZONEMALLOC)
+
+/*
+** Use the zone allocator available on apple products unless the
+** SQLITE_WITHOUT_ZONEMALLOC symbol is defined.
+*/
+#include <sys/sysctl.h>
+#include <malloc/malloc.h>
+#ifdef SQLITE_MIGHT_BE_SINGLE_CORE
+#include <libkern/OSAtomic.h>
+#endif /* SQLITE_MIGHT_BE_SINGLE_CORE */
+static malloc_zone_t* _sqliteZone_;
+#define SQLITE_MALLOC(x) malloc_zone_malloc(_sqliteZone_, (x))
+#define SQLITE_FREE(x) malloc_zone_free(_sqliteZone_, (x));
+#define SQLITE_REALLOC(x,y) malloc_zone_realloc(_sqliteZone_, (x), (y))
+#define SQLITE_MALLOCSIZE(x) \
+        (_sqliteZone_ ? _sqliteZone_->size(_sqliteZone_,x) : malloc_size(x))
+
+#else /* if not __APPLE__ */
+
+/*
+** Use standard C library malloc and free on non-Apple systems.  
+** Also used by Apple systems if SQLITE_WITHOUT_ZONEMALLOC is defined.
+*/
+#define SQLITE_MALLOC(x)             malloc(x)
+#define SQLITE_FREE(x)               free(x)
+#define SQLITE_REALLOC(x,y)          realloc((x),(y))
+
+/*
+** The malloc.h header file is needed for malloc_usable_size() function
+** on some systems (e.g. Linux).
+*/
+#if HAVE_MALLOC_H && HAVE_MALLOC_USABLE_SIZE
+#  define SQLITE_USE_MALLOC_H 1
+#  define SQLITE_USE_MALLOC_USABLE_SIZE 1
+/*
+** The MSVCRT has malloc_usable_size(), but it is called _msize().  The
+** use of _msize() is automatic, but can be disabled by compiling with
+** -DSQLITE_WITHOUT_MSIZE.  Using the _msize() function also requires
+** the malloc.h header file.
+*/
+#elif defined(_MSC_VER) && !defined(SQLITE_WITHOUT_MSIZE)
+#  define SQLITE_USE_MALLOC_H
+#  define SQLITE_USE_MSIZE
+#endif
+
+/*
+** Include the malloc.h header file, if necessary.  Also set define macro
+** SQLITE_MALLOCSIZE to the appropriate function name, which is _msize()
+** for MSVC and malloc_usable_size() for most other systems (e.g. Linux).
+** The memory size function can always be overridden manually by defining
+** the macro SQLITE_MALLOCSIZE to the desired function name.
+*/
+#if defined(SQLITE_USE_MALLOC_H)
+#  include <malloc.h>
+#  if defined(SQLITE_USE_MALLOC_USABLE_SIZE)
+#    if !defined(SQLITE_MALLOCSIZE)
+#      define SQLITE_MALLOCSIZE(x)   malloc_usable_size(x)
+#    endif
+#  elif defined(SQLITE_USE_MSIZE)
+#    if !defined(SQLITE_MALLOCSIZE)
+#      define SQLITE_MALLOCSIZE      _msize
+#    endif
+#  endif
+#endif /* defined(SQLITE_USE_MALLOC_H) */
+
+#endif /* __APPLE__ or not __APPLE__ */
+
+/*
+** Like malloc(), but remember the size of the allocation
+** so that we can find it later using sqlite3MemSize().
+**
+** For this low-level routine, we are guaranteed that nByte>0 because
+** cases of nByte<=0 will be intercepted and dealt with by higher level
+** routines.
+*/
+static void *sqlite3MemMalloc(int nByte){
+#ifdef SQLITE_MALLOCSIZE
+  void *p;
+  testcase( ROUND8(nByte)==nByte );
+  p = SQLITE_MALLOC( nByte );
+  if( p==0 ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes of memory", nByte);
+  }
+  return p;
+#else
+  sqlite3_int64 *p;
+  assert( nByte>0 );
+  testcase( ROUND8(nByte)!=nByte );
+  p = SQLITE_MALLOC( nByte+8 );
+  if( p ){
+    p[0] = nByte;
+    p++;
+  }else{
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes of memory", nByte);
+  }
+  return (void *)p;
+#endif
+}
+
+/*
+** Like free() but works for allocations obtained from sqlite3MemMalloc()
+** or sqlite3MemRealloc().
+**
+** For this low-level routine, we already know that pPrior!=0 since
+** cases where pPrior==0 will have been intercepted and dealt with
+** by higher-level routines.
+*/
+static void sqlite3MemFree(void *pPrior){
+#ifdef SQLITE_MALLOCSIZE
+  SQLITE_FREE(pPrior);
+#else
+  sqlite3_int64 *p = (sqlite3_int64*)pPrior;
+  assert( pPrior!=0 );
+  p--;
+  SQLITE_FREE(p);
+#endif
+}
+
+/*
+** Report the allocated size of a prior return from xMalloc()
+** or xRealloc().
+*/
+static int sqlite3MemSize(void *pPrior){
+#ifdef SQLITE_MALLOCSIZE
+  assert( pPrior!=0 );
+  return (int)SQLITE_MALLOCSIZE(pPrior);
+#else
+  sqlite3_int64 *p;
+  assert( pPrior!=0 );
+  p = (sqlite3_int64*)pPrior;
+  p--;
+  return (int)p[0];
+#endif
+}
+
+/*
+** Like realloc().  Resize an allocation previously obtained from
+** sqlite3MemMalloc().
+**
+** For this low-level interface, we know that pPrior!=0.  Cases where
+** pPrior==0 while have been intercepted by higher-level routine and
+** redirected to xMalloc.  Similarly, we know that nByte>0 because
+** cases where nByte<=0 will have been intercepted by higher-level
+** routines and redirected to xFree.
+*/
+static void *sqlite3MemRealloc(void *pPrior, int nByte){
+#ifdef SQLITE_MALLOCSIZE
+  void *p = SQLITE_REALLOC(pPrior, nByte);
+  if( p==0 ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM,
+      "failed memory resize %u to %u bytes",
+      SQLITE_MALLOCSIZE(pPrior), nByte);
+  }
+  return p;
+#else
+  sqlite3_int64 *p = (sqlite3_int64*)pPrior;
+  assert( pPrior!=0 && nByte>0 );
+  assert( nByte==ROUND8(nByte) ); /* EV: R-46199-30249 */
+  p--;
+  p = SQLITE_REALLOC(p, nByte+8 );
+  if( p ){
+    p[0] = nByte;
+    p++;
+  }else{
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM,
+      "failed memory resize %u to %u bytes",
+      sqlite3MemSize(pPrior), nByte);
+  }
+  return (void*)p;
+#endif
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int sqlite3MemRoundup(int n){
+  return ROUND8(n);
+}
+
+/*
+** Initialize this module.
+*/
+static int sqlite3MemInit(void *NotUsed){
+#if defined(__APPLE__) && !defined(SQLITE_WITHOUT_ZONEMALLOC)
+  int cpuCount;
+  size_t len;
+  if( _sqliteZone_ ){
+    return SQLITE_OK;
+  }
+  len = sizeof(cpuCount);
+  /* One usually wants to use hw.activecpu for MT decisions, but not here */
+  sysctlbyname("hw.ncpu", &cpuCount, &len, NULL, 0);
+  if( cpuCount>1 ){
+    /* defer MT decisions to system malloc */
+    _sqliteZone_ = malloc_default_zone();
+  }else{
+    /* only 1 core, use our own zone to contention over global locks,
+    ** e.g. we have our own dedicated locks */
+    _sqliteZone_ = malloc_create_zone(4096, 0);
+    malloc_set_zone_name(_sqliteZone_, "Sqlite_Heap");
+  }
+#endif /*  defined(__APPLE__) && !defined(SQLITE_WITHOUT_ZONEMALLOC) */
+  UNUSED_PARAMETER(NotUsed);
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void sqlite3MemShutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  return;
+}
+
+/*
+** This routine is the only routine in this file with external linkage.
+**
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file.
+*/
+void sqlite3MemSetDefault(void){
+  static const sqlite3_mem_methods defaultMethods = {
+     sqlite3MemMalloc,
+     sqlite3MemFree,
+     sqlite3MemRealloc,
+     sqlite3MemSize,
+     sqlite3MemRoundup,
+     sqlite3MemInit,
+     sqlite3MemShutdown,
+     0
+  };
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods);
+}
+
+#endif /* SQLITE_SYSTEM_MALLOC */
diff --git a/src/mem2.c b/src/mem2.c
new file mode 100644
index 0000000..04d6298
--- /dev/null
+++ b/src/mem2.c
@@ -0,0 +1,528 @@
+/*
+** 2007 August 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains low-level memory allocation drivers for when
+** SQLite will use the standard C-library malloc/realloc/free interface
+** to obtain the memory it needs while adding lots of additional debugging
+** information to each allocation in order to help detect and fix memory
+** leaks and memory usage errors.
+**
+** This file contains implementations of the low-level memory allocation
+** routines specified in the sqlite3_mem_methods object.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is used only if the
+** SQLITE_MEMDEBUG macro is defined
+*/
+#ifdef SQLITE_MEMDEBUG
+
+/*
+** The backtrace functionality is only available with GLIBC
+*/
+#ifdef __GLIBC__
+  extern int backtrace(void**,int);
+  extern void backtrace_symbols_fd(void*const*,int,int);
+#else
+# define backtrace(A,B) 1
+# define backtrace_symbols_fd(A,B,C)
+#endif
+#include <stdio.h>
+
+/*
+** Each memory allocation looks like this:
+**
+**  ------------------------------------------------------------------------
+**  | Title |  backtrace pointers |  MemBlockHdr |  allocation |  EndGuard |
+**  ------------------------------------------------------------------------
+**
+** The application code sees only a pointer to the allocation.  We have
+** to back up from the allocation pointer to find the MemBlockHdr.  The
+** MemBlockHdr tells us the size of the allocation and the number of
+** backtrace pointers.  There is also a guard word at the end of the
+** MemBlockHdr.
+*/
+struct MemBlockHdr {
+  i64 iSize;                          /* Size of this allocation */
+  struct MemBlockHdr *pNext, *pPrev;  /* Linked list of all unfreed memory */
+  char nBacktrace;                    /* Number of backtraces on this alloc */
+  char nBacktraceSlots;               /* Available backtrace slots */
+  u8 nTitle;                          /* Bytes of title; includes '\0' */
+  u8 eType;                           /* Allocation type code */
+  int iForeGuard;                     /* Guard word for sanity */
+};
+
+/*
+** Guard words
+*/
+#define FOREGUARD 0x80F5E153
+#define REARGUARD 0xE4676B53
+
+/*
+** Number of malloc size increments to track.
+*/
+#define NCSIZE  1000
+
+/*
+** All of the static variables used by this module are collected
+** into a single structure named "mem".  This is to keep the
+** static variables organized and to reduce namespace pollution
+** when this module is combined with other in the amalgamation.
+*/
+static struct {
+  
+  /*
+  ** Mutex to control access to the memory allocation subsystem.
+  */
+  sqlite3_mutex *mutex;
+
+  /*
+  ** Head and tail of a linked list of all outstanding allocations
+  */
+  struct MemBlockHdr *pFirst;
+  struct MemBlockHdr *pLast;
+  
+  /*
+  ** The number of levels of backtrace to save in new allocations.
+  */
+  int nBacktrace;
+  void (*xBacktrace)(int, int, void **);
+
+  /*
+  ** Title text to insert in front of each block
+  */
+  int nTitle;        /* Bytes of zTitle to save.  Includes '\0' and padding */
+  char zTitle[100];  /* The title text */
+
+  /* 
+  ** sqlite3MallocDisallow() increments the following counter.
+  ** sqlite3MallocAllow() decrements it.
+  */
+  int disallow; /* Do not allow memory allocation */
+
+  /*
+  ** Gather statistics on the sizes of memory allocations.
+  ** nAlloc[i] is the number of allocation attempts of i*8
+  ** bytes.  i==NCSIZE is the number of allocation attempts for
+  ** sizes more than NCSIZE*8 bytes.
+  */
+  int nAlloc[NCSIZE];      /* Total number of allocations */
+  int nCurrent[NCSIZE];    /* Current number of allocations */
+  int mxCurrent[NCSIZE];   /* Highwater mark for nCurrent */
+
+} mem;
+
+
+/*
+** Adjust memory usage statistics
+*/
+static void adjustStats(int iSize, int increment){
+  int i = ROUND8(iSize)/8;
+  if( i>NCSIZE-1 ){
+    i = NCSIZE - 1;
+  }
+  if( increment>0 ){
+    mem.nAlloc[i]++;
+    mem.nCurrent[i]++;
+    if( mem.nCurrent[i]>mem.mxCurrent[i] ){
+      mem.mxCurrent[i] = mem.nCurrent[i];
+    }
+  }else{
+    mem.nCurrent[i]--;
+    assert( mem.nCurrent[i]>=0 );
+  }
+}
+
+/*
+** Given an allocation, find the MemBlockHdr for that allocation.
+**
+** This routine checks the guards at either end of the allocation and
+** if they are incorrect it asserts.
+*/
+static struct MemBlockHdr *sqlite3MemsysGetHeader(const void *pAllocation){
+  struct MemBlockHdr *p;
+  int *pInt;
+  u8 *pU8;
+  int nReserve;
+
+  p = (struct MemBlockHdr*)pAllocation;
+  p--;
+  assert( p->iForeGuard==(int)FOREGUARD );
+  nReserve = ROUND8(p->iSize);
+  pInt = (int*)pAllocation;
+  pU8 = (u8*)pAllocation;
+  assert( pInt[nReserve/sizeof(int)]==(int)REARGUARD );
+  /* This checks any of the "extra" bytes allocated due
+  ** to rounding up to an 8 byte boundary to ensure 
+  ** they haven't been overwritten.
+  */
+  while( nReserve-- > p->iSize ) assert( pU8[nReserve]==0x65 );
+  return p;
+}
+
+/*
+** Return the number of bytes currently allocated at address p.
+*/
+static int sqlite3MemSize(void *p){
+  struct MemBlockHdr *pHdr;
+  if( !p ){
+    return 0;
+  }
+  pHdr = sqlite3MemsysGetHeader(p);
+  return (int)pHdr->iSize;
+}
+
+/*
+** Initialize the memory allocation subsystem.
+*/
+static int sqlite3MemInit(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  assert( (sizeof(struct MemBlockHdr)&7) == 0 );
+  if( !sqlite3GlobalConfig.bMemstat ){
+    /* If memory status is enabled, then the malloc.c wrapper will already
+    ** hold the STATIC_MEM mutex when the routines here are invoked. */
+    mem.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize the memory allocation subsystem.
+*/
+static void sqlite3MemShutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  mem.mutex = 0;
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int sqlite3MemRoundup(int n){
+  return ROUND8(n);
+}
+
+/*
+** Fill a buffer with pseudo-random bytes.  This is used to preset
+** the content of a new memory allocation to unpredictable values and
+** to clear the content of a freed allocation to unpredictable values.
+*/
+static void randomFill(char *pBuf, int nByte){
+  unsigned int x, y, r;
+  x = SQLITE_PTR_TO_INT(pBuf);
+  y = nByte | 1;
+  while( nByte >= 4 ){
+    x = (x>>1) ^ (-(int)(x&1) & 0xd0000001);
+    y = y*1103515245 + 12345;
+    r = x ^ y;
+    *(int*)pBuf = r;
+    pBuf += 4;
+    nByte -= 4;
+  }
+  while( nByte-- > 0 ){
+    x = (x>>1) ^ (-(int)(x&1) & 0xd0000001);
+    y = y*1103515245 + 12345;
+    r = x ^ y;
+    *(pBuf++) = r & 0xff;
+  }
+}
+
+/*
+** Allocate nByte bytes of memory.
+*/
+static void *sqlite3MemMalloc(int nByte){
+  struct MemBlockHdr *pHdr;
+  void **pBt;
+  char *z;
+  int *pInt;
+  void *p = 0;
+  int totalSize;
+  int nReserve;
+  sqlite3_mutex_enter(mem.mutex);
+  assert( mem.disallow==0 );
+  nReserve = ROUND8(nByte);
+  totalSize = nReserve + sizeof(*pHdr) + sizeof(int) +
+               mem.nBacktrace*sizeof(void*) + mem.nTitle;
+  p = malloc(totalSize);
+  if( p ){
+    z = p;
+    pBt = (void**)&z[mem.nTitle];
+    pHdr = (struct MemBlockHdr*)&pBt[mem.nBacktrace];
+    pHdr->pNext = 0;
+    pHdr->pPrev = mem.pLast;
+    if( mem.pLast ){
+      mem.pLast->pNext = pHdr;
+    }else{
+      mem.pFirst = pHdr;
+    }
+    mem.pLast = pHdr;
+    pHdr->iForeGuard = FOREGUARD;
+    pHdr->eType = MEMTYPE_HEAP;
+    pHdr->nBacktraceSlots = mem.nBacktrace;
+    pHdr->nTitle = mem.nTitle;
+    if( mem.nBacktrace ){
+      void *aAddr[40];
+      pHdr->nBacktrace = backtrace(aAddr, mem.nBacktrace+1)-1;
+      memcpy(pBt, &aAddr[1], pHdr->nBacktrace*sizeof(void*));
+      assert(pBt[0]);
+      if( mem.xBacktrace ){
+        mem.xBacktrace(nByte, pHdr->nBacktrace-1, &aAddr[1]);
+      }
+    }else{
+      pHdr->nBacktrace = 0;
+    }
+    if( mem.nTitle ){
+      memcpy(z, mem.zTitle, mem.nTitle);
+    }
+    pHdr->iSize = nByte;
+    adjustStats(nByte, +1);
+    pInt = (int*)&pHdr[1];
+    pInt[nReserve/sizeof(int)] = REARGUARD;
+    randomFill((char*)pInt, nByte);
+    memset(((char*)pInt)+nByte, 0x65, nReserve-nByte);
+    p = (void*)pInt;
+  }
+  sqlite3_mutex_leave(mem.mutex);
+  return p; 
+}
+
+/*
+** Free memory.
+*/
+static void sqlite3MemFree(void *pPrior){
+  struct MemBlockHdr *pHdr;
+  void **pBt;
+  char *z;
+  assert( sqlite3GlobalConfig.bMemstat || sqlite3GlobalConfig.bCoreMutex==0 
+       || mem.mutex!=0 );
+  pHdr = sqlite3MemsysGetHeader(pPrior);
+  pBt = (void**)pHdr;
+  pBt -= pHdr->nBacktraceSlots;
+  sqlite3_mutex_enter(mem.mutex);
+  if( pHdr->pPrev ){
+    assert( pHdr->pPrev->pNext==pHdr );
+    pHdr->pPrev->pNext = pHdr->pNext;
+  }else{
+    assert( mem.pFirst==pHdr );
+    mem.pFirst = pHdr->pNext;
+  }
+  if( pHdr->pNext ){
+    assert( pHdr->pNext->pPrev==pHdr );
+    pHdr->pNext->pPrev = pHdr->pPrev;
+  }else{
+    assert( mem.pLast==pHdr );
+    mem.pLast = pHdr->pPrev;
+  }
+  z = (char*)pBt;
+  z -= pHdr->nTitle;
+  adjustStats((int)pHdr->iSize, -1);
+  randomFill(z, sizeof(void*)*pHdr->nBacktraceSlots + sizeof(*pHdr) +
+                (int)pHdr->iSize + sizeof(int) + pHdr->nTitle);
+  free(z);
+  sqlite3_mutex_leave(mem.mutex);  
+}
+
+/*
+** Change the size of an existing memory allocation.
+**
+** For this debugging implementation, we *always* make a copy of the
+** allocation into a new place in memory.  In this way, if the 
+** higher level code is using pointer to the old allocation, it is 
+** much more likely to break and we are much more liking to find
+** the error.
+*/
+static void *sqlite3MemRealloc(void *pPrior, int nByte){
+  struct MemBlockHdr *pOldHdr;
+  void *pNew;
+  assert( mem.disallow==0 );
+  assert( (nByte & 7)==0 );     /* EV: R-46199-30249 */
+  pOldHdr = sqlite3MemsysGetHeader(pPrior);
+  pNew = sqlite3MemMalloc(nByte);
+  if( pNew ){
+    memcpy(pNew, pPrior, (int)(nByte<pOldHdr->iSize ? nByte : pOldHdr->iSize));
+    if( nByte>pOldHdr->iSize ){
+      randomFill(&((char*)pNew)[pOldHdr->iSize], nByte - (int)pOldHdr->iSize);
+    }
+    sqlite3MemFree(pPrior);
+  }
+  return pNew;
+}
+
+/*
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file.
+*/
+void sqlite3MemSetDefault(void){
+  static const sqlite3_mem_methods defaultMethods = {
+     sqlite3MemMalloc,
+     sqlite3MemFree,
+     sqlite3MemRealloc,
+     sqlite3MemSize,
+     sqlite3MemRoundup,
+     sqlite3MemInit,
+     sqlite3MemShutdown,
+     0
+  };
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods);
+}
+
+/*
+** Set the "type" of an allocation.
+*/
+void sqlite3MemdebugSetType(void *p, u8 eType){
+  if( p && sqlite3GlobalConfig.m.xFree==sqlite3MemFree ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );
+    pHdr->eType = eType;
+  }
+}
+
+/*
+** Return TRUE if the mask of type in eType matches the type of the
+** allocation p.  Also return true if p==NULL.
+**
+** This routine is designed for use within an assert() statement, to
+** verify the type of an allocation.  For example:
+**
+**     assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+*/
+int sqlite3MemdebugHasType(const void *p, u8 eType){
+  int rc = 1;
+  if( p && sqlite3GlobalConfig.m.xFree==sqlite3MemFree ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );         /* Allocation is valid */
+    if( (pHdr->eType&eType)==0 ){
+      rc = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Return TRUE if the mask of type in eType matches no bits of the type of the
+** allocation p.  Also return true if p==NULL.
+**
+** This routine is designed for use within an assert() statement, to
+** verify the type of an allocation.  For example:
+**
+**     assert( sqlite3MemdebugNoType(p, MEMTYPE_LOOKASIDE) );
+*/
+int sqlite3MemdebugNoType(const void *p, u8 eType){
+  int rc = 1;
+  if( p && sqlite3GlobalConfig.m.xFree==sqlite3MemFree ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );         /* Allocation is valid */
+    if( (pHdr->eType&eType)!=0 ){
+      rc = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Set the number of backtrace levels kept for each allocation.
+** A value of zero turns off backtracing.  The number is always rounded
+** up to a multiple of 2.
+*/
+void sqlite3MemdebugBacktrace(int depth){
+  if( depth<0 ){ depth = 0; }
+  if( depth>20 ){ depth = 20; }
+  depth = (depth+1)&0xfe;
+  mem.nBacktrace = depth;
+}
+
+void sqlite3MemdebugBacktraceCallback(void (*xBacktrace)(int, int, void **)){
+  mem.xBacktrace = xBacktrace;
+}
+
+/*
+** Set the title string for subsequent allocations.
+*/
+void sqlite3MemdebugSettitle(const char *zTitle){
+  unsigned int n = sqlite3Strlen30(zTitle) + 1;
+  sqlite3_mutex_enter(mem.mutex);
+  if( n>=sizeof(mem.zTitle) ) n = sizeof(mem.zTitle)-1;
+  memcpy(mem.zTitle, zTitle, n);
+  mem.zTitle[n] = 0;
+  mem.nTitle = ROUND8(n);
+  sqlite3_mutex_leave(mem.mutex);
+}
+
+void sqlite3MemdebugSync(){
+  struct MemBlockHdr *pHdr;
+  for(pHdr=mem.pFirst; pHdr; pHdr=pHdr->pNext){
+    void **pBt = (void**)pHdr;
+    pBt -= pHdr->nBacktraceSlots;
+    mem.xBacktrace((int)pHdr->iSize, pHdr->nBacktrace-1, &pBt[1]);
+  }
+}
+
+/*
+** Open the file indicated and write a log of all unfreed memory 
+** allocations into that log.
+*/
+void sqlite3MemdebugDump(const char *zFilename){
+  FILE *out;
+  struct MemBlockHdr *pHdr;
+  void **pBt;
+  int i;
+  out = fopen(zFilename, "w");
+  if( out==0 ){
+    fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
+                    zFilename);
+    return;
+  }
+  for(pHdr=mem.pFirst; pHdr; pHdr=pHdr->pNext){
+    char *z = (char*)pHdr;
+    z -= pHdr->nBacktraceSlots*sizeof(void*) + pHdr->nTitle;
+    fprintf(out, "**** %lld bytes at %p from %s ****\n", 
+            pHdr->iSize, &pHdr[1], pHdr->nTitle ? z : "???");
+    if( pHdr->nBacktrace ){
+      fflush(out);
+      pBt = (void**)pHdr;
+      pBt -= pHdr->nBacktraceSlots;
+      backtrace_symbols_fd(pBt, pHdr->nBacktrace, fileno(out));
+      fprintf(out, "\n");
+    }
+  }
+  fprintf(out, "COUNTS:\n");
+  for(i=0; i<NCSIZE-1; i++){
+    if( mem.nAlloc[i] ){
+      fprintf(out, "   %5d: %10d %10d %10d\n", 
+            i*8, mem.nAlloc[i], mem.nCurrent[i], mem.mxCurrent[i]);
+    }
+  }
+  if( mem.nAlloc[NCSIZE-1] ){
+    fprintf(out, "   %5d: %10d %10d %10d\n",
+             NCSIZE*8-8, mem.nAlloc[NCSIZE-1],
+             mem.nCurrent[NCSIZE-1], mem.mxCurrent[NCSIZE-1]);
+  }
+  fclose(out);
+}
+
+/*
+** Return the number of times sqlite3MemMalloc() has been called.
+*/
+int sqlite3MemdebugMallocCount(){
+  int i;
+  int nTotal = 0;
+  for(i=0; i<NCSIZE; i++){
+    nTotal += mem.nAlloc[i];
+  }
+  return nTotal;
+}
+
+
+#endif /* SQLITE_MEMDEBUG */
diff --git a/src/mem3.c b/src/mem3.c
new file mode 100644
index 0000000..16463d6
--- /dev/null
+++ b/src/mem3.c
@@ -0,0 +1,687 @@
+/*
+** 2007 October 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement a memory
+** allocation subsystem for use by SQLite. 
+**
+** This version of the memory allocation subsystem omits all
+** use of malloc(). The SQLite user supplies a block of memory
+** before calling sqlite3_initialize() from which allocations
+** are made and returned by the xMalloc() and xRealloc() 
+** implementations. Once sqlite3_initialize() has been called,
+** the amount of memory available to SQLite is fixed and cannot
+** be changed.
+**
+** This version of the memory allocation subsystem is included
+** in the build only if SQLITE_ENABLE_MEMSYS3 is defined.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is only built into the library
+** SQLITE_ENABLE_MEMSYS3 is defined. Defining this symbol does not
+** mean that the library will use a memory-pool by default, just that
+** it is available. The mempool allocator is activated by calling
+** sqlite3_config().
+*/
+#ifdef SQLITE_ENABLE_MEMSYS3
+
+/*
+** Maximum size (in Mem3Blocks) of a "small" chunk.
+*/
+#define MX_SMALL 10
+
+
+/*
+** Number of freelist hash slots
+*/
+#define N_HASH  61
+
+/*
+** A memory allocation (also called a "chunk") consists of two or 
+** more blocks where each block is 8 bytes.  The first 8 bytes are 
+** a header that is not returned to the user.
+**
+** A chunk is two or more blocks that is either checked out or
+** free.  The first block has format u.hdr.  u.hdr.size4x is 4 times the
+** size of the allocation in blocks if the allocation is free.
+** The u.hdr.size4x&1 bit is true if the chunk is checked out and
+** false if the chunk is on the freelist.  The u.hdr.size4x&2 bit
+** is true if the previous chunk is checked out and false if the
+** previous chunk is free.  The u.hdr.prevSize field is the size of
+** the previous chunk in blocks if the previous chunk is on the
+** freelist. If the previous chunk is checked out, then
+** u.hdr.prevSize can be part of the data for that chunk and should
+** not be read or written.
+**
+** We often identify a chunk by its index in mem3.aPool[].  When
+** this is done, the chunk index refers to the second block of
+** the chunk.  In this way, the first chunk has an index of 1.
+** A chunk index of 0 means "no such chunk" and is the equivalent
+** of a NULL pointer.
+**
+** The second block of free chunks is of the form u.list.  The
+** two fields form a double-linked list of chunks of related sizes.
+** Pointers to the head of the list are stored in mem3.aiSmall[] 
+** for smaller chunks and mem3.aiHash[] for larger chunks.
+**
+** The second block of a chunk is user data if the chunk is checked 
+** out.  If a chunk is checked out, the user data may extend into
+** the u.hdr.prevSize value of the following chunk.
+*/
+typedef struct Mem3Block Mem3Block;
+struct Mem3Block {
+  union {
+    struct {
+      u32 prevSize;   /* Size of previous chunk in Mem3Block elements */
+      u32 size4x;     /* 4x the size of current chunk in Mem3Block elements */
+    } hdr;
+    struct {
+      u32 next;       /* Index in mem3.aPool[] of next free chunk */
+      u32 prev;       /* Index in mem3.aPool[] of previous free chunk */
+    } list;
+  } u;
+};
+
+/*
+** All of the static variables used by this module are collected
+** into a single structure named "mem3".  This is to keep the
+** static variables organized and to reduce namespace pollution
+** when this module is combined with other in the amalgamation.
+*/
+static SQLITE_WSD struct Mem3Global {
+  /*
+  ** Memory available for allocation. nPool is the size of the array
+  ** (in Mem3Blocks) pointed to by aPool less 2.
+  */
+  u32 nPool;
+  Mem3Block *aPool;
+
+  /*
+  ** True if we are evaluating an out-of-memory callback.
+  */
+  int alarmBusy;
+  
+  /*
+  ** Mutex to control access to the memory allocation subsystem.
+  */
+  sqlite3_mutex *mutex;
+  
+  /*
+  ** The minimum amount of free space that we have seen.
+  */
+  u32 mnKeyBlk;
+
+  /*
+  ** iKeyBlk is the index of the key chunk.  Most new allocations
+  ** occur off of this chunk.  szKeyBlk is the size (in Mem3Blocks)
+  ** of the current key chunk.  iKeyBlk is 0 if there is no key chunk.
+  ** The key chunk is not in either the aiHash[] or aiSmall[].
+  */
+  u32 iKeyBlk;
+  u32 szKeyBlk;
+
+  /*
+  ** Array of lists of free blocks according to the block size 
+  ** for smaller chunks, or a hash on the block size for larger
+  ** chunks.
+  */
+  u32 aiSmall[MX_SMALL-1];   /* For sizes 2 through MX_SMALL, inclusive */
+  u32 aiHash[N_HASH];        /* For sizes MX_SMALL+1 and larger */
+} mem3 = { 97535575 };
+
+#define mem3 GLOBAL(struct Mem3Global, mem3)
+
+/*
+** Unlink the chunk at mem3.aPool[i] from list it is currently
+** on.  *pRoot is the list that i is a member of.
+*/
+static void memsys3UnlinkFromList(u32 i, u32 *pRoot){
+  u32 next = mem3.aPool[i].u.list.next;
+  u32 prev = mem3.aPool[i].u.list.prev;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  if( prev==0 ){
+    *pRoot = next;
+  }else{
+    mem3.aPool[prev].u.list.next = next;
+  }
+  if( next ){
+    mem3.aPool[next].u.list.prev = prev;
+  }
+  mem3.aPool[i].u.list.next = 0;
+  mem3.aPool[i].u.list.prev = 0;
+}
+
+/*
+** Unlink the chunk at index i from 
+** whatever list is currently a member of.
+*/
+static void memsys3Unlink(u32 i){
+  u32 size, hash;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
+  assert( i>=1 );
+  size = mem3.aPool[i-1].u.hdr.size4x/4;
+  assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
+  assert( size>=2 );
+  if( size <= MX_SMALL ){
+    memsys3UnlinkFromList(i, &mem3.aiSmall[size-2]);
+  }else{
+    hash = size % N_HASH;
+    memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
+  }
+}
+
+/*
+** Link the chunk at mem3.aPool[i] so that is on the list rooted
+** at *pRoot.
+*/
+static void memsys3LinkIntoList(u32 i, u32 *pRoot){
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  mem3.aPool[i].u.list.next = *pRoot;
+  mem3.aPool[i].u.list.prev = 0;
+  if( *pRoot ){
+    mem3.aPool[*pRoot].u.list.prev = i;
+  }
+  *pRoot = i;
+}
+
+/*
+** Link the chunk at index i into either the appropriate
+** small chunk list, or into the large chunk hash table.
+*/
+static void memsys3Link(u32 i){
+  u32 size, hash;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( i>=1 );
+  assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
+  size = mem3.aPool[i-1].u.hdr.size4x/4;
+  assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
+  assert( size>=2 );
+  if( size <= MX_SMALL ){
+    memsys3LinkIntoList(i, &mem3.aiSmall[size-2]);
+  }else{
+    hash = size % N_HASH;
+    memsys3LinkIntoList(i, &mem3.aiHash[hash]);
+  }
+}
+
+/*
+** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
+** will already be held (obtained by code in malloc.c) if
+** sqlite3GlobalConfig.bMemStat is true.
+*/
+static void memsys3Enter(void){
+  if( sqlite3GlobalConfig.bMemstat==0 && mem3.mutex==0 ){
+    mem3.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  }
+  sqlite3_mutex_enter(mem3.mutex);
+}
+static void memsys3Leave(void){
+  sqlite3_mutex_leave(mem3.mutex);
+}
+
+/*
+** Called when we are unable to satisfy an allocation of nBytes.
+*/
+static void memsys3OutOfMemory(int nByte){
+  if( !mem3.alarmBusy ){
+    mem3.alarmBusy = 1;
+    assert( sqlite3_mutex_held(mem3.mutex) );
+    sqlite3_mutex_leave(mem3.mutex);
+    sqlite3_release_memory(nByte);
+    sqlite3_mutex_enter(mem3.mutex);
+    mem3.alarmBusy = 0;
+  }
+}
+
+
+/*
+** Chunk i is a free chunk that has been unlinked.  Adjust its 
+** size parameters for check-out and return a pointer to the 
+** user portion of the chunk.
+*/
+static void *memsys3Checkout(u32 i, u32 nBlock){
+  u32 x;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( i>=1 );
+  assert( mem3.aPool[i-1].u.hdr.size4x/4==nBlock );
+  assert( mem3.aPool[i+nBlock-1].u.hdr.prevSize==nBlock );
+  x = mem3.aPool[i-1].u.hdr.size4x;
+  mem3.aPool[i-1].u.hdr.size4x = nBlock*4 | 1 | (x&2);
+  mem3.aPool[i+nBlock-1].u.hdr.prevSize = nBlock;
+  mem3.aPool[i+nBlock-1].u.hdr.size4x |= 2;
+  return &mem3.aPool[i];
+}
+
+/*
+** Carve a piece off of the end of the mem3.iKeyBlk free chunk.
+** Return a pointer to the new allocation.  Or, if the key chunk
+** is not large enough, return 0.
+*/
+static void *memsys3FromKeyBlk(u32 nBlock){
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( mem3.szKeyBlk>=nBlock );
+  if( nBlock>=mem3.szKeyBlk-1 ){
+    /* Use the entire key chunk */
+    void *p = memsys3Checkout(mem3.iKeyBlk, mem3.szKeyBlk);
+    mem3.iKeyBlk = 0;
+    mem3.szKeyBlk = 0;
+    mem3.mnKeyBlk = 0;
+    return p;
+  }else{
+    /* Split the key block.  Return the tail. */
+    u32 newi, x;
+    newi = mem3.iKeyBlk + mem3.szKeyBlk - nBlock;
+    assert( newi > mem3.iKeyBlk+1 );
+    mem3.aPool[mem3.iKeyBlk+mem3.szKeyBlk-1].u.hdr.prevSize = nBlock;
+    mem3.aPool[mem3.iKeyBlk+mem3.szKeyBlk-1].u.hdr.size4x |= 2;
+    mem3.aPool[newi-1].u.hdr.size4x = nBlock*4 + 1;
+    mem3.szKeyBlk -= nBlock;
+    mem3.aPool[newi-1].u.hdr.prevSize = mem3.szKeyBlk;
+    x = mem3.aPool[mem3.iKeyBlk-1].u.hdr.size4x & 2;
+    mem3.aPool[mem3.iKeyBlk-1].u.hdr.size4x = mem3.szKeyBlk*4 | x;
+    if( mem3.szKeyBlk < mem3.mnKeyBlk ){
+      mem3.mnKeyBlk = mem3.szKeyBlk;
+    }
+    return (void*)&mem3.aPool[newi];
+  }
+}
+
+/*
+** *pRoot is the head of a list of free chunks of the same size
+** or same size hash.  In other words, *pRoot is an entry in either
+** mem3.aiSmall[] or mem3.aiHash[].  
+**
+** This routine examines all entries on the given list and tries
+** to coalesce each entries with adjacent free chunks.  
+**
+** If it sees a chunk that is larger than mem3.iKeyBlk, it replaces 
+** the current mem3.iKeyBlk with the new larger chunk.  In order for
+** this mem3.iKeyBlk replacement to work, the key chunk must be
+** linked into the hash tables.  That is not the normal state of
+** affairs, of course.  The calling routine must link the key
+** chunk before invoking this routine, then must unlink the (possibly
+** changed) key chunk once this routine has finished.
+*/
+static void memsys3Merge(u32 *pRoot){
+  u32 iNext, prev, size, i, x;
+
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  for(i=*pRoot; i>0; i=iNext){
+    iNext = mem3.aPool[i].u.list.next;
+    size = mem3.aPool[i-1].u.hdr.size4x;
+    assert( (size&1)==0 );
+    if( (size&2)==0 ){
+      memsys3UnlinkFromList(i, pRoot);
+      assert( i > mem3.aPool[i-1].u.hdr.prevSize );
+      prev = i - mem3.aPool[i-1].u.hdr.prevSize;
+      if( prev==iNext ){
+        iNext = mem3.aPool[prev].u.list.next;
+      }
+      memsys3Unlink(prev);
+      size = i + size/4 - prev;
+      x = mem3.aPool[prev-1].u.hdr.size4x & 2;
+      mem3.aPool[prev-1].u.hdr.size4x = size*4 | x;
+      mem3.aPool[prev+size-1].u.hdr.prevSize = size;
+      memsys3Link(prev);
+      i = prev;
+    }else{
+      size /= 4;
+    }
+    if( size>mem3.szKeyBlk ){
+      mem3.iKeyBlk = i;
+      mem3.szKeyBlk = size;
+    }
+  }
+}
+
+/*
+** Return a block of memory of at least nBytes in size.
+** Return NULL if unable.
+**
+** This function assumes that the necessary mutexes, if any, are
+** already held by the caller. Hence "Unsafe".
+*/
+static void *memsys3MallocUnsafe(int nByte){
+  u32 i;
+  u32 nBlock;
+  u32 toFree;
+
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( sizeof(Mem3Block)==8 );
+  if( nByte<=12 ){
+    nBlock = 2;
+  }else{
+    nBlock = (nByte + 11)/8;
+  }
+  assert( nBlock>=2 );
+
+  /* STEP 1:
+  ** Look for an entry of the correct size in either the small
+  ** chunk table or in the large chunk hash table.  This is
+  ** successful most of the time (about 9 times out of 10).
+  */
+  if( nBlock <= MX_SMALL ){
+    i = mem3.aiSmall[nBlock-2];
+    if( i>0 ){
+      memsys3UnlinkFromList(i, &mem3.aiSmall[nBlock-2]);
+      return memsys3Checkout(i, nBlock);
+    }
+  }else{
+    int hash = nBlock % N_HASH;
+    for(i=mem3.aiHash[hash]; i>0; i=mem3.aPool[i].u.list.next){
+      if( mem3.aPool[i-1].u.hdr.size4x/4==nBlock ){
+        memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
+        return memsys3Checkout(i, nBlock);
+      }
+    }
+  }
+
+  /* STEP 2:
+  ** Try to satisfy the allocation by carving a piece off of the end
+  ** of the key chunk.  This step usually works if step 1 fails.
+  */
+  if( mem3.szKeyBlk>=nBlock ){
+    return memsys3FromKeyBlk(nBlock);
+  }
+
+
+  /* STEP 3:  
+  ** Loop through the entire memory pool.  Coalesce adjacent free
+  ** chunks.  Recompute the key chunk as the largest free chunk.
+  ** Then try again to satisfy the allocation by carving a piece off
+  ** of the end of the key chunk.  This step happens very
+  ** rarely (we hope!)
+  */
+  for(toFree=nBlock*16; toFree<(mem3.nPool*16); toFree *= 2){
+    memsys3OutOfMemory(toFree);
+    if( mem3.iKeyBlk ){
+      memsys3Link(mem3.iKeyBlk);
+      mem3.iKeyBlk = 0;
+      mem3.szKeyBlk = 0;
+    }
+    for(i=0; i<N_HASH; i++){
+      memsys3Merge(&mem3.aiHash[i]);
+    }
+    for(i=0; i<MX_SMALL-1; i++){
+      memsys3Merge(&mem3.aiSmall[i]);
+    }
+    if( mem3.szKeyBlk ){
+      memsys3Unlink(mem3.iKeyBlk);
+      if( mem3.szKeyBlk>=nBlock ){
+        return memsys3FromKeyBlk(nBlock);
+      }
+    }
+  }
+
+  /* If none of the above worked, then we fail. */
+  return 0;
+}
+
+/*
+** Free an outstanding memory allocation.
+**
+** This function assumes that the necessary mutexes, if any, are
+** already held by the caller. Hence "Unsafe".
+*/
+static void memsys3FreeUnsafe(void *pOld){
+  Mem3Block *p = (Mem3Block*)pOld;
+  int i;
+  u32 size, x;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( p>mem3.aPool && p<&mem3.aPool[mem3.nPool] );
+  i = p - mem3.aPool;
+  assert( (mem3.aPool[i-1].u.hdr.size4x&1)==1 );
+  size = mem3.aPool[i-1].u.hdr.size4x/4;
+  assert( i+size<=mem3.nPool+1 );
+  mem3.aPool[i-1].u.hdr.size4x &= ~1;
+  mem3.aPool[i+size-1].u.hdr.prevSize = size;
+  mem3.aPool[i+size-1].u.hdr.size4x &= ~2;
+  memsys3Link(i);
+
+  /* Try to expand the key using the newly freed chunk */
+  if( mem3.iKeyBlk ){
+    while( (mem3.aPool[mem3.iKeyBlk-1].u.hdr.size4x&2)==0 ){
+      size = mem3.aPool[mem3.iKeyBlk-1].u.hdr.prevSize;
+      mem3.iKeyBlk -= size;
+      mem3.szKeyBlk += size;
+      memsys3Unlink(mem3.iKeyBlk);
+      x = mem3.aPool[mem3.iKeyBlk-1].u.hdr.size4x & 2;
+      mem3.aPool[mem3.iKeyBlk-1].u.hdr.size4x = mem3.szKeyBlk*4 | x;
+      mem3.aPool[mem3.iKeyBlk+mem3.szKeyBlk-1].u.hdr.prevSize = mem3.szKeyBlk;
+    }
+    x = mem3.aPool[mem3.iKeyBlk-1].u.hdr.size4x & 2;
+    while( (mem3.aPool[mem3.iKeyBlk+mem3.szKeyBlk-1].u.hdr.size4x&1)==0 ){
+      memsys3Unlink(mem3.iKeyBlk+mem3.szKeyBlk);
+      mem3.szKeyBlk += mem3.aPool[mem3.iKeyBlk+mem3.szKeyBlk-1].u.hdr.size4x/4;
+      mem3.aPool[mem3.iKeyBlk-1].u.hdr.size4x = mem3.szKeyBlk*4 | x;
+      mem3.aPool[mem3.iKeyBlk+mem3.szKeyBlk-1].u.hdr.prevSize = mem3.szKeyBlk;
+    }
+  }
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes.  The
+** size returned omits the 8-byte header overhead.  This only
+** works for chunks that are currently checked out.
+*/
+static int memsys3Size(void *p){
+  Mem3Block *pBlock;
+  assert( p!=0 );
+  pBlock = (Mem3Block*)p;
+  assert( (pBlock[-1].u.hdr.size4x&1)!=0 );
+  return (pBlock[-1].u.hdr.size4x&~3)*2 - 4;
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int memsys3Roundup(int n){
+  if( n<=12 ){
+    return 12;
+  }else{
+    return ((n+11)&~7) - 4;
+  }
+}
+
+/*
+** Allocate nBytes of memory.
+*/
+static void *memsys3Malloc(int nBytes){
+  sqlite3_int64 *p;
+  assert( nBytes>0 );          /* malloc.c filters out 0 byte requests */
+  memsys3Enter();
+  p = memsys3MallocUnsafe(nBytes);
+  memsys3Leave();
+  return (void*)p; 
+}
+
+/*
+** Free memory.
+*/
+static void memsys3Free(void *pPrior){
+  assert( pPrior );
+  memsys3Enter();
+  memsys3FreeUnsafe(pPrior);
+  memsys3Leave();
+}
+
+/*
+** Change the size of an existing memory allocation
+*/
+static void *memsys3Realloc(void *pPrior, int nBytes){
+  int nOld;
+  void *p;
+  if( pPrior==0 ){
+    return sqlite3_malloc(nBytes);
+  }
+  if( nBytes<=0 ){
+    sqlite3_free(pPrior);
+    return 0;
+  }
+  nOld = memsys3Size(pPrior);
+  if( nBytes<=nOld && nBytes>=nOld-128 ){
+    return pPrior;
+  }
+  memsys3Enter();
+  p = memsys3MallocUnsafe(nBytes);
+  if( p ){
+    if( nOld<nBytes ){
+      memcpy(p, pPrior, nOld);
+    }else{
+      memcpy(p, pPrior, nBytes);
+    }
+    memsys3FreeUnsafe(pPrior);
+  }
+  memsys3Leave();
+  return p;
+}
+
+/*
+** Initialize this module.
+*/
+static int memsys3Init(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  if( !sqlite3GlobalConfig.pHeap ){
+    return SQLITE_ERROR;
+  }
+
+  /* Store a pointer to the memory block in global structure mem3. */
+  assert( sizeof(Mem3Block)==8 );
+  mem3.aPool = (Mem3Block *)sqlite3GlobalConfig.pHeap;
+  mem3.nPool = (sqlite3GlobalConfig.nHeap / sizeof(Mem3Block)) - 2;
+
+  /* Initialize the key block. */
+  mem3.szKeyBlk = mem3.nPool;
+  mem3.mnKeyBlk = mem3.szKeyBlk;
+  mem3.iKeyBlk = 1;
+  mem3.aPool[0].u.hdr.size4x = (mem3.szKeyBlk<<2) + 2;
+  mem3.aPool[mem3.nPool].u.hdr.prevSize = mem3.nPool;
+  mem3.aPool[mem3.nPool].u.hdr.size4x = 1;
+
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void memsys3Shutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  mem3.mutex = 0;
+  return;
+}
+
+
+
+/*
+** Open the file indicated and write a log of all unfreed memory 
+** allocations into that log.
+*/
+void sqlite3Memsys3Dump(const char *zFilename){
+#ifdef SQLITE_DEBUG
+  FILE *out;
+  u32 i, j;
+  u32 size;
+  if( zFilename==0 || zFilename[0]==0 ){
+    out = stdout;
+  }else{
+    out = fopen(zFilename, "w");
+    if( out==0 ){
+      fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
+                      zFilename);
+      return;
+    }
+  }
+  memsys3Enter();
+  fprintf(out, "CHUNKS:\n");
+  for(i=1; i<=mem3.nPool; i+=size/4){
+    size = mem3.aPool[i-1].u.hdr.size4x;
+    if( size/4<=1 ){
+      fprintf(out, "%p size error\n", &mem3.aPool[i]);
+      assert( 0 );
+      break;
+    }
+    if( (size&1)==0 && mem3.aPool[i+size/4-1].u.hdr.prevSize!=size/4 ){
+      fprintf(out, "%p tail size does not match\n", &mem3.aPool[i]);
+      assert( 0 );
+      break;
+    }
+    if( ((mem3.aPool[i+size/4-1].u.hdr.size4x&2)>>1)!=(size&1) ){
+      fprintf(out, "%p tail checkout bit is incorrect\n", &mem3.aPool[i]);
+      assert( 0 );
+      break;
+    }
+    if( size&1 ){
+      fprintf(out, "%p %6d bytes checked out\n", &mem3.aPool[i], (size/4)*8-8);
+    }else{
+      fprintf(out, "%p %6d bytes free%s\n", &mem3.aPool[i], (size/4)*8-8,
+                  i==mem3.iKeyBlk ? " **key**" : "");
+    }
+  }
+  for(i=0; i<MX_SMALL-1; i++){
+    if( mem3.aiSmall[i]==0 ) continue;
+    fprintf(out, "small(%2d):", i);
+    for(j = mem3.aiSmall[i]; j>0; j=mem3.aPool[j].u.list.next){
+      fprintf(out, " %p(%d)", &mem3.aPool[j],
+              (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
+    }
+    fprintf(out, "\n"); 
+  }
+  for(i=0; i<N_HASH; i++){
+    if( mem3.aiHash[i]==0 ) continue;
+    fprintf(out, "hash(%2d):", i);
+    for(j = mem3.aiHash[i]; j>0; j=mem3.aPool[j].u.list.next){
+      fprintf(out, " %p(%d)", &mem3.aPool[j],
+              (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
+    }
+    fprintf(out, "\n"); 
+  }
+  fprintf(out, "key=%d\n", mem3.iKeyBlk);
+  fprintf(out, "nowUsed=%d\n", mem3.nPool*8 - mem3.szKeyBlk*8);
+  fprintf(out, "mxUsed=%d\n", mem3.nPool*8 - mem3.mnKeyBlk*8);
+  sqlite3_mutex_leave(mem3.mutex);
+  if( out==stdout ){
+    fflush(stdout);
+  }else{
+    fclose(out);
+  }
+#else
+  UNUSED_PARAMETER(zFilename);
+#endif
+}
+
+/*
+** This routine is the only routine in this file with external 
+** linkage.
+**
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file. The
+** arguments specify the block of memory to manage.
+**
+** This routine is only called by sqlite3_config(), and therefore
+** is not required to be threadsafe (it is not).
+*/
+const sqlite3_mem_methods *sqlite3MemGetMemsys3(void){
+  static const sqlite3_mem_methods mempoolMethods = {
+     memsys3Malloc,
+     memsys3Free,
+     memsys3Realloc,
+     memsys3Size,
+     memsys3Roundup,
+     memsys3Init,
+     memsys3Shutdown,
+     0
+  };
+  return &mempoolMethods;
+}
+
+#endif /* SQLITE_ENABLE_MEMSYS3 */
diff --git a/src/mem5.c b/src/mem5.c
new file mode 100644
index 0000000..02f4c27
--- /dev/null
+++ b/src/mem5.c
@@ -0,0 +1,585 @@
+/*
+** 2007 October 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement a memory
+** allocation subsystem for use by SQLite. 
+**
+** This version of the memory allocation subsystem omits all
+** use of malloc(). The application gives SQLite a block of memory
+** before calling sqlite3_initialize() from which allocations
+** are made and returned by the xMalloc() and xRealloc() 
+** implementations. Once sqlite3_initialize() has been called,
+** the amount of memory available to SQLite is fixed and cannot
+** be changed.
+**
+** This version of the memory allocation subsystem is included
+** in the build only if SQLITE_ENABLE_MEMSYS5 is defined.
+**
+** This memory allocator uses the following algorithm:
+**
+**   1.  All memory allocation sizes are rounded up to a power of 2.
+**
+**   2.  If two adjacent free blocks are the halves of a larger block,
+**       then the two blocks are coalesced into the single larger block.
+**
+**   3.  New memory is allocated from the first available free block.
+**
+** This algorithm is described in: J. M. Robson. "Bounds for Some Functions
+** Concerning Dynamic Storage Allocation". Journal of the Association for
+** Computing Machinery, Volume 21, Number 8, July 1974, pages 491-499.
+** 
+** Let n be the size of the largest allocation divided by the minimum
+** allocation size (after rounding all sizes up to a power of 2.)  Let M
+** be the maximum amount of memory ever outstanding at one time.  Let
+** N be the total amount of memory available for allocation.  Robson
+** proved that this memory allocator will never breakdown due to 
+** fragmentation as long as the following constraint holds:
+**
+**      N >=  M*(1 + log2(n)/2) - n + 1
+**
+** The sqlite3_status() logic tracks the maximum values of n and M so
+** that an application can, at any time, verify this constraint.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is used only when 
+** SQLITE_ENABLE_MEMSYS5 is defined.
+*/
+#ifdef SQLITE_ENABLE_MEMSYS5
+
+/*
+** A minimum allocation is an instance of the following structure.
+** Larger allocations are an array of these structures where the
+** size of the array is a power of 2.
+**
+** The size of this object must be a power of two.  That fact is
+** verified in memsys5Init().
+*/
+typedef struct Mem5Link Mem5Link;
+struct Mem5Link {
+  int next;       /* Index of next free chunk */
+  int prev;       /* Index of previous free chunk */
+};
+
+/*
+** Maximum size of any allocation is ((1<<LOGMAX)*mem5.szAtom). Since
+** mem5.szAtom is always at least 8 and 32-bit integers are used,
+** it is not actually possible to reach this limit.
+*/
+#define LOGMAX 30
+
+/*
+** Masks used for mem5.aCtrl[] elements.
+*/
+#define CTRL_LOGSIZE  0x1f    /* Log2 Size of this block */
+#define CTRL_FREE     0x20    /* True if not checked out */
+
+/*
+** All of the static variables used by this module are collected
+** into a single structure named "mem5".  This is to keep the
+** static variables organized and to reduce namespace pollution
+** when this module is combined with other in the amalgamation.
+*/
+static SQLITE_WSD struct Mem5Global {
+  /*
+  ** Memory available for allocation
+  */
+  int szAtom;      /* Smallest possible allocation in bytes */
+  int nBlock;      /* Number of szAtom sized blocks in zPool */
+  u8 *zPool;       /* Memory available to be allocated */
+  
+  /*
+  ** Mutex to control access to the memory allocation subsystem.
+  */
+  sqlite3_mutex *mutex;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  /*
+  ** Performance statistics
+  */
+  u64 nAlloc;         /* Total number of calls to malloc */
+  u64 totalAlloc;     /* Total of all malloc calls - includes internal frag */
+  u64 totalExcess;    /* Total internal fragmentation */
+  u32 currentOut;     /* Current checkout, including internal fragmentation */
+  u32 currentCount;   /* Current number of distinct checkouts */
+  u32 maxOut;         /* Maximum instantaneous currentOut */
+  u32 maxCount;       /* Maximum instantaneous currentCount */
+  u32 maxRequest;     /* Largest allocation (exclusive of internal frag) */
+#endif
+  
+  /*
+  ** Lists of free blocks.  aiFreelist[0] is a list of free blocks of
+  ** size mem5.szAtom.  aiFreelist[1] holds blocks of size szAtom*2.
+  ** aiFreelist[2] holds free blocks of size szAtom*4.  And so forth.
+  */
+  int aiFreelist[LOGMAX+1];
+
+  /*
+  ** Space for tracking which blocks are checked out and the size
+  ** of each block.  One byte per block.
+  */
+  u8 *aCtrl;
+
+} mem5;
+
+/*
+** Access the static variable through a macro for SQLITE_OMIT_WSD.
+*/
+#define mem5 GLOBAL(struct Mem5Global, mem5)
+
+/*
+** Assuming mem5.zPool is divided up into an array of Mem5Link
+** structures, return a pointer to the idx-th such link.
+*/
+#define MEM5LINK(idx) ((Mem5Link *)(&mem5.zPool[(idx)*mem5.szAtom]))
+
+/*
+** Unlink the chunk at mem5.aPool[i] from list it is currently
+** on.  It should be found on mem5.aiFreelist[iLogsize].
+*/
+static void memsys5Unlink(int i, int iLogsize){
+  int next, prev;
+  assert( i>=0 && i<mem5.nBlock );
+  assert( iLogsize>=0 && iLogsize<=LOGMAX );
+  assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
+
+  next = MEM5LINK(i)->next;
+  prev = MEM5LINK(i)->prev;
+  if( prev<0 ){
+    mem5.aiFreelist[iLogsize] = next;
+  }else{
+    MEM5LINK(prev)->next = next;
+  }
+  if( next>=0 ){
+    MEM5LINK(next)->prev = prev;
+  }
+}
+
+/*
+** Link the chunk at mem5.aPool[i] so that is on the iLogsize
+** free list.
+*/
+static void memsys5Link(int i, int iLogsize){
+  int x;
+  assert( sqlite3_mutex_held(mem5.mutex) );
+  assert( i>=0 && i<mem5.nBlock );
+  assert( iLogsize>=0 && iLogsize<=LOGMAX );
+  assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
+
+  x = MEM5LINK(i)->next = mem5.aiFreelist[iLogsize];
+  MEM5LINK(i)->prev = -1;
+  if( x>=0 ){
+    assert( x<mem5.nBlock );
+    MEM5LINK(x)->prev = i;
+  }
+  mem5.aiFreelist[iLogsize] = i;
+}
+
+/*
+** Obtain or release the mutex needed to access global data structures.
+*/
+static void memsys5Enter(void){
+  sqlite3_mutex_enter(mem5.mutex);
+}
+static void memsys5Leave(void){
+  sqlite3_mutex_leave(mem5.mutex);
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes.
+** This only works for chunks that are currently checked out.
+*/
+static int memsys5Size(void *p){
+  int iSize, i;
+  assert( p!=0 );
+  i = (int)(((u8 *)p-mem5.zPool)/mem5.szAtom);
+  assert( i>=0 && i<mem5.nBlock );
+  iSize = mem5.szAtom * (1 << (mem5.aCtrl[i]&CTRL_LOGSIZE));
+  return iSize;
+}
+
+/*
+** Return a block of memory of at least nBytes in size.
+** Return NULL if unable.  Return NULL if nBytes==0.
+**
+** The caller guarantees that nByte is positive.
+**
+** The caller has obtained a mutex prior to invoking this
+** routine so there is never any chance that two or more
+** threads can be in this routine at the same time.
+*/
+static void *memsys5MallocUnsafe(int nByte){
+  int i;           /* Index of a mem5.aPool[] slot */
+  int iBin;        /* Index into mem5.aiFreelist[] */
+  int iFullSz;     /* Size of allocation rounded up to power of 2 */
+  int iLogsize;    /* Log2 of iFullSz/POW2_MIN */
+
+  /* nByte must be a positive */
+  assert( nByte>0 );
+
+  /* No more than 1GiB per allocation */
+  if( nByte > 0x40000000 ) return 0;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  /* Keep track of the maximum allocation request.  Even unfulfilled
+  ** requests are counted */
+  if( (u32)nByte>mem5.maxRequest ){
+    mem5.maxRequest = nByte;
+  }
+#endif
+
+
+  /* Round nByte up to the next valid power of two */
+  for(iFullSz=mem5.szAtom,iLogsize=0; iFullSz<nByte; iFullSz*=2,iLogsize++){}
+
+  /* Make sure mem5.aiFreelist[iLogsize] contains at least one free
+  ** block.  If not, then split a block of the next larger power of
+  ** two in order to create a new free block of size iLogsize.
+  */
+  for(iBin=iLogsize; iBin<=LOGMAX && mem5.aiFreelist[iBin]<0; iBin++){}
+  if( iBin>LOGMAX ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes", nByte);
+    return 0;
+  }
+  i = mem5.aiFreelist[iBin];
+  memsys5Unlink(i, iBin);
+  while( iBin>iLogsize ){
+    int newSize;
+
+    iBin--;
+    newSize = 1 << iBin;
+    mem5.aCtrl[i+newSize] = CTRL_FREE | iBin;
+    memsys5Link(i+newSize, iBin);
+  }
+  mem5.aCtrl[i] = iLogsize;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  /* Update allocator performance statistics. */
+  mem5.nAlloc++;
+  mem5.totalAlloc += iFullSz;
+  mem5.totalExcess += iFullSz - nByte;
+  mem5.currentCount++;
+  mem5.currentOut += iFullSz;
+  if( mem5.maxCount<mem5.currentCount ) mem5.maxCount = mem5.currentCount;
+  if( mem5.maxOut<mem5.currentOut ) mem5.maxOut = mem5.currentOut;
+#endif
+
+#ifdef SQLITE_DEBUG
+  /* Make sure the allocated memory does not assume that it is set to zero
+  ** or retains a value from a previous allocation */
+  memset(&mem5.zPool[i*mem5.szAtom], 0xAA, iFullSz);
+#endif
+
+  /* Return a pointer to the allocated memory. */
+  return (void*)&mem5.zPool[i*mem5.szAtom];
+}
+
+/*
+** Free an outstanding memory allocation.
+*/
+static void memsys5FreeUnsafe(void *pOld){
+  u32 size, iLogsize;
+  int iBlock;
+
+  /* Set iBlock to the index of the block pointed to by pOld in 
+  ** the array of mem5.szAtom byte blocks pointed to by mem5.zPool.
+  */
+  iBlock = (int)(((u8 *)pOld-mem5.zPool)/mem5.szAtom);
+
+  /* Check that the pointer pOld points to a valid, non-free block. */
+  assert( iBlock>=0 && iBlock<mem5.nBlock );
+  assert( ((u8 *)pOld-mem5.zPool)%mem5.szAtom==0 );
+  assert( (mem5.aCtrl[iBlock] & CTRL_FREE)==0 );
+
+  iLogsize = mem5.aCtrl[iBlock] & CTRL_LOGSIZE;
+  size = 1<<iLogsize;
+  assert( iBlock+size-1<(u32)mem5.nBlock );
+
+  mem5.aCtrl[iBlock] |= CTRL_FREE;
+  mem5.aCtrl[iBlock+size-1] |= CTRL_FREE;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  assert( mem5.currentCount>0 );
+  assert( mem5.currentOut>=(size*mem5.szAtom) );
+  mem5.currentCount--;
+  mem5.currentOut -= size*mem5.szAtom;
+  assert( mem5.currentOut>0 || mem5.currentCount==0 );
+  assert( mem5.currentCount>0 || mem5.currentOut==0 );
+#endif
+
+  mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
+  while( ALWAYS(iLogsize<LOGMAX) ){
+    int iBuddy;
+    if( (iBlock>>iLogsize) & 1 ){
+      iBuddy = iBlock - size;
+      assert( iBuddy>=0 );
+    }else{
+      iBuddy = iBlock + size;
+      if( iBuddy>=mem5.nBlock ) break;
+    }
+    if( mem5.aCtrl[iBuddy]!=(CTRL_FREE | iLogsize) ) break;
+    memsys5Unlink(iBuddy, iLogsize);
+    iLogsize++;
+    if( iBuddy<iBlock ){
+      mem5.aCtrl[iBuddy] = CTRL_FREE | iLogsize;
+      mem5.aCtrl[iBlock] = 0;
+      iBlock = iBuddy;
+    }else{
+      mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
+      mem5.aCtrl[iBuddy] = 0;
+    }
+    size *= 2;
+  }
+
+#ifdef SQLITE_DEBUG
+  /* Overwrite freed memory with the 0x55 bit pattern to verify that it is
+  ** not used after being freed */
+  memset(&mem5.zPool[iBlock*mem5.szAtom], 0x55, size);
+#endif
+
+  memsys5Link(iBlock, iLogsize);
+}
+
+/*
+** Allocate nBytes of memory.
+*/
+static void *memsys5Malloc(int nBytes){
+  sqlite3_int64 *p = 0;
+  if( nBytes>0 ){
+    memsys5Enter();
+    p = memsys5MallocUnsafe(nBytes);
+    memsys5Leave();
+  }
+  return (void*)p; 
+}
+
+/*
+** Free memory.
+**
+** The outer layer memory allocator prevents this routine from
+** being called with pPrior==0.
+*/
+static void memsys5Free(void *pPrior){
+  assert( pPrior!=0 );
+  memsys5Enter();
+  memsys5FreeUnsafe(pPrior);
+  memsys5Leave();  
+}
+
+/*
+** Change the size of an existing memory allocation.
+**
+** The outer layer memory allocator prevents this routine from
+** being called with pPrior==0.  
+**
+** nBytes is always a value obtained from a prior call to
+** memsys5Round().  Hence nBytes is always a non-negative power
+** of two.  If nBytes==0 that means that an oversize allocation
+** (an allocation larger than 0x40000000) was requested and this
+** routine should return 0 without freeing pPrior.
+*/
+static void *memsys5Realloc(void *pPrior, int nBytes){
+  int nOld;
+  void *p;
+  assert( pPrior!=0 );
+  assert( (nBytes&(nBytes-1))==0 );  /* EV: R-46199-30249 */
+  assert( nBytes>=0 );
+  if( nBytes==0 ){
+    return 0;
+  }
+  nOld = memsys5Size(pPrior);
+  if( nBytes<=nOld ){
+    return pPrior;
+  }
+  p = memsys5Malloc(nBytes);
+  if( p ){
+    memcpy(p, pPrior, nOld);
+    memsys5Free(pPrior);
+  }
+  return p;
+}
+
+/*
+** Round up a request size to the next valid allocation size.  If
+** the allocation is too large to be handled by this allocation system,
+** return 0.
+**
+** All allocations must be a power of two and must be expressed by a
+** 32-bit signed integer.  Hence the largest allocation is 0x40000000
+** or 1073741824 bytes.
+*/
+static int memsys5Roundup(int n){
+  int iFullSz;
+  if( n<=mem5.szAtom*2 ){
+    if( n<=mem5.szAtom ) return mem5.szAtom;
+    return mem5.szAtom*2;
+  }
+  if( n>0x10000000 ){
+    if( n>0x40000000 ) return 0;
+    if( n>0x20000000 ) return 0x40000000;
+    return 0x20000000;
+  }
+  for(iFullSz=mem5.szAtom*8; iFullSz<n; iFullSz *= 4);
+  if( (iFullSz/2)>=(i64)n ) return iFullSz/2;
+  return iFullSz;
+}
+
+/*
+** Return the ceiling of the logarithm base 2 of iValue.
+**
+** Examples:   memsys5Log(1) -> 0
+**             memsys5Log(2) -> 1
+**             memsys5Log(4) -> 2
+**             memsys5Log(5) -> 3
+**             memsys5Log(8) -> 3
+**             memsys5Log(9) -> 4
+*/
+static int memsys5Log(int iValue){
+  int iLog;
+  for(iLog=0; (iLog<(int)((sizeof(int)*8)-1)) && (1<<iLog)<iValue; iLog++);
+  return iLog;
+}
+
+/*
+** Initialize the memory allocator.
+**
+** This routine is not threadsafe.  The caller must be holding a mutex
+** to prevent multiple threads from entering at the same time.
+*/
+static int memsys5Init(void *NotUsed){
+  int ii;            /* Loop counter */
+  int nByte;         /* Number of bytes of memory available to this allocator */
+  u8 *zByte;         /* Memory usable by this allocator */
+  int nMinLog;       /* Log base 2 of minimum allocation size in bytes */
+  int iOffset;       /* An offset into mem5.aCtrl[] */
+
+  UNUSED_PARAMETER(NotUsed);
+
+  /* For the purposes of this routine, disable the mutex */
+  mem5.mutex = 0;
+
+  /* The size of a Mem5Link object must be a power of two.  Verify that
+  ** this is case.
+  */
+  assert( (sizeof(Mem5Link)&(sizeof(Mem5Link)-1))==0 );
+
+  nByte = sqlite3GlobalConfig.nHeap;
+  zByte = (u8*)sqlite3GlobalConfig.pHeap;
+  assert( zByte!=0 );  /* sqlite3_config() does not allow otherwise */
+
+  /* boundaries on sqlite3GlobalConfig.mnReq are enforced in sqlite3_config() */
+  nMinLog = memsys5Log(sqlite3GlobalConfig.mnReq);
+  mem5.szAtom = (1<<nMinLog);
+  while( (int)sizeof(Mem5Link)>mem5.szAtom ){
+    mem5.szAtom = mem5.szAtom << 1;
+  }
+
+  mem5.nBlock = (nByte / (mem5.szAtom+sizeof(u8)));
+  mem5.zPool = zByte;
+  mem5.aCtrl = (u8 *)&mem5.zPool[mem5.nBlock*mem5.szAtom];
+
+  for(ii=0; ii<=LOGMAX; ii++){
+    mem5.aiFreelist[ii] = -1;
+  }
+
+  iOffset = 0;
+  for(ii=LOGMAX; ii>=0; ii--){
+    int nAlloc = (1<<ii);
+    if( (iOffset+nAlloc)<=mem5.nBlock ){
+      mem5.aCtrl[iOffset] = ii | CTRL_FREE;
+      memsys5Link(iOffset, ii);
+      iOffset += nAlloc;
+    }
+    assert((iOffset+nAlloc)>mem5.nBlock);
+  }
+
+  /* If a mutex is required for normal operation, allocate one */
+  if( sqlite3GlobalConfig.bMemstat==0 ){
+    mem5.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void memsys5Shutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  mem5.mutex = 0;
+  return;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Open the file indicated and write a log of all unfreed memory 
+** allocations into that log.
+*/
+void sqlite3Memsys5Dump(const char *zFilename){
+  FILE *out;
+  int i, j, n;
+  int nMinLog;
+
+  if( zFilename==0 || zFilename[0]==0 ){
+    out = stdout;
+  }else{
+    out = fopen(zFilename, "w");
+    if( out==0 ){
+      fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
+                      zFilename);
+      return;
+    }
+  }
+  memsys5Enter();
+  nMinLog = memsys5Log(mem5.szAtom);
+  for(i=0; i<=LOGMAX && i+nMinLog<32; i++){
+    for(n=0, j=mem5.aiFreelist[i]; j>=0; j = MEM5LINK(j)->next, n++){}
+    fprintf(out, "freelist items of size %d: %d\n", mem5.szAtom << i, n);
+  }
+  fprintf(out, "mem5.nAlloc       = %llu\n", mem5.nAlloc);
+  fprintf(out, "mem5.totalAlloc   = %llu\n", mem5.totalAlloc);
+  fprintf(out, "mem5.totalExcess  = %llu\n", mem5.totalExcess);
+  fprintf(out, "mem5.currentOut   = %u\n", mem5.currentOut);
+  fprintf(out, "mem5.currentCount = %u\n", mem5.currentCount);
+  fprintf(out, "mem5.maxOut       = %u\n", mem5.maxOut);
+  fprintf(out, "mem5.maxCount     = %u\n", mem5.maxCount);
+  fprintf(out, "mem5.maxRequest   = %u\n", mem5.maxRequest);
+  memsys5Leave();
+  if( out==stdout ){
+    fflush(stdout);
+  }else{
+    fclose(out);
+  }
+}
+#endif
+
+/*
+** This routine is the only routine in this file with external 
+** linkage. It returns a pointer to a static sqlite3_mem_methods
+** struct populated with the memsys5 methods.
+*/
+const sqlite3_mem_methods *sqlite3MemGetMemsys5(void){
+  static const sqlite3_mem_methods memsys5Methods = {
+     memsys5Malloc,
+     memsys5Free,
+     memsys5Realloc,
+     memsys5Size,
+     memsys5Roundup,
+     memsys5Init,
+     memsys5Shutdown,
+     0
+  };
+  return &memsys5Methods;
+}
+
+#endif /* SQLITE_ENABLE_MEMSYS5 */
diff --git a/src/memdb.c b/src/memdb.c
new file mode 100644
index 0000000..657cb9c
--- /dev/null
+++ b/src/memdb.c
@@ -0,0 +1,928 @@
+/*
+** 2016-09-07
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file implements an in-memory VFS. A database is held as a contiguous
+** block of memory.
+**
+** This file also implements interface sqlite3_serialize() and
+** sqlite3_deserialize().
+*/
+#include "sqliteInt.h"
+#ifndef SQLITE_OMIT_DESERIALIZE
+
+/*
+** Forward declaration of objects used by this utility
+*/
+typedef struct sqlite3_vfs MemVfs;
+typedef struct MemFile MemFile;
+typedef struct MemStore MemStore;
+
+/* Access to a lower-level VFS that (might) implement dynamic loading,
+** access to randomness, etc.
+*/
+#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))
+
+/* Storage for a memdb file.
+**
+** An memdb object can be shared or separate.  Shared memdb objects can be
+** used by more than one database connection.  Mutexes are used by shared
+** memdb objects to coordinate access.  Separate memdb objects are only
+** connected to a single database connection and do not require additional
+** mutexes.
+**
+** Shared memdb objects have .zFName!=0 and .pMutex!=0.  They are created
+** using "file:/name?vfs=memdb".  The first character of the name must be
+** "/" or else the object will be a separate memdb object.  All shared
+** memdb objects are stored in memdb_g.apMemStore[] in an arbitrary order.
+**
+** Separate memdb objects are created using a name that does not begin
+** with "/" or using sqlite3_deserialize().
+**
+** Access rules for shared MemStore objects:
+**
+**   *  .zFName is initialized when the object is created and afterwards
+**      is unchanged until the object is destroyed.  So it can be accessed
+**      at any time as long as we know the object is not being destroyed,
+**      which means while either the SQLITE_MUTEX_STATIC_VFS1 or
+**      .pMutex is held or the object is not part of memdb_g.apMemStore[].
+**
+**   *  Can .pMutex can only be changed while holding the 
+**      SQLITE_MUTEX_STATIC_VFS1 mutex or while the object is not part
+**      of memdb_g.apMemStore[].
+**
+**   *  Other fields can only be changed while holding the .pMutex mutex
+**      or when the .nRef is less than zero and the object is not part of
+**      memdb_g.apMemStore[].
+**
+**   *  The .aData pointer has the added requirement that it can can only
+**      be changed (for resizing) when nMmap is zero.
+**      
+*/
+struct MemStore {
+  sqlite3_int64 sz;               /* Size of the file */
+  sqlite3_int64 szAlloc;          /* Space allocated to aData */
+  sqlite3_int64 szMax;            /* Maximum allowed size of the file */
+  unsigned char *aData;           /* content of the file */
+  sqlite3_mutex *pMutex;          /* Used by shared stores only */
+  int nMmap;                      /* Number of memory mapped pages */
+  unsigned mFlags;                /* Flags */
+  int nRdLock;                    /* Number of readers */
+  int nWrLock;                    /* Number of writers.  (Always 0 or 1) */
+  int nRef;                       /* Number of users of this MemStore */
+  char *zFName;                   /* The filename for shared stores */
+};
+
+/* An open file */
+struct MemFile {
+  sqlite3_file base;              /* IO methods */
+  MemStore *pStore;               /* The storage */
+  int eLock;                      /* Most recent lock against this file */
+};
+
+/*
+** File-scope variables for holding the memdb files that are accessible
+** to multiple database connections in separate threads.
+**
+** Must hold SQLITE_MUTEX_STATIC_VFS1 to access any part of this object.
+*/
+static struct MemFS {
+  int nMemStore;                  /* Number of shared MemStore objects */
+  MemStore **apMemStore;          /* Array of all shared MemStore objects */
+} memdb_g;
+
+/*
+** Methods for MemFile
+*/
+static int memdbClose(sqlite3_file*);
+static int memdbRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int memdbWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int memdbTruncate(sqlite3_file*, sqlite3_int64 size);
+static int memdbSync(sqlite3_file*, int flags);
+static int memdbFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int memdbLock(sqlite3_file*, int);
+static int memdbUnlock(sqlite3_file*, int);
+/* static int memdbCheckReservedLock(sqlite3_file*, int *pResOut);// not used */
+static int memdbFileControl(sqlite3_file*, int op, void *pArg);
+/* static int memdbSectorSize(sqlite3_file*); // not used */
+static int memdbDeviceCharacteristics(sqlite3_file*);
+static int memdbFetch(sqlite3_file*, sqlite3_int64 iOfst, int iAmt, void **pp);
+static int memdbUnfetch(sqlite3_file*, sqlite3_int64 iOfst, void *p);
+
+/*
+** Methods for MemVfs
+*/
+static int memdbOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+/* static int memdbDelete(sqlite3_vfs*, const char *zName, int syncDir); */
+static int memdbAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int memdbFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *memdbDlOpen(sqlite3_vfs*, const char *zFilename);
+static void memdbDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*memdbDlSym(sqlite3_vfs *pVfs, void *p, const char*zSym))(void);
+static void memdbDlClose(sqlite3_vfs*, void*);
+static int memdbRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int memdbSleep(sqlite3_vfs*, int microseconds);
+/* static int memdbCurrentTime(sqlite3_vfs*, double*); */
+static int memdbGetLastError(sqlite3_vfs*, int, char *);
+static int memdbCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+
+static sqlite3_vfs memdb_vfs = {
+  2,                           /* iVersion */
+  0,                           /* szOsFile (set when registered) */
+  1024,                        /* mxPathname */
+  0,                           /* pNext */
+  "memdb",                     /* zName */
+  0,                           /* pAppData (set when registered) */ 
+  memdbOpen,                   /* xOpen */
+  0, /* memdbDelete, */        /* xDelete */
+  memdbAccess,                 /* xAccess */
+  memdbFullPathname,           /* xFullPathname */
+  memdbDlOpen,                 /* xDlOpen */
+  memdbDlError,                /* xDlError */
+  memdbDlSym,                  /* xDlSym */
+  memdbDlClose,                /* xDlClose */
+  memdbRandomness,             /* xRandomness */
+  memdbSleep,                  /* xSleep */
+  0, /* memdbCurrentTime, */   /* xCurrentTime */
+  memdbGetLastError,           /* xGetLastError */
+  memdbCurrentTimeInt64,       /* xCurrentTimeInt64 */
+  0,                           /* xSetSystemCall */
+  0,                           /* xGetSystemCall */
+  0,                           /* xNextSystemCall */
+};
+
+static const sqlite3_io_methods memdb_io_methods = {
+  3,                              /* iVersion */
+  memdbClose,                      /* xClose */
+  memdbRead,                       /* xRead */
+  memdbWrite,                      /* xWrite */
+  memdbTruncate,                   /* xTruncate */
+  memdbSync,                       /* xSync */
+  memdbFileSize,                   /* xFileSize */
+  memdbLock,                       /* xLock */
+  memdbUnlock,                     /* xUnlock */
+  0, /* memdbCheckReservedLock, */ /* xCheckReservedLock */
+  memdbFileControl,                /* xFileControl */
+  0, /* memdbSectorSize,*/         /* xSectorSize */
+  memdbDeviceCharacteristics,      /* xDeviceCharacteristics */
+  0,                               /* xShmMap */
+  0,                               /* xShmLock */
+  0,                               /* xShmBarrier */
+  0,                               /* xShmUnmap */
+  memdbFetch,                      /* xFetch */
+  memdbUnfetch                     /* xUnfetch */
+};
+
+/*
+** Enter/leave the mutex on a MemStore
+*/
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE==0
+static void memdbEnter(MemStore *p){
+  UNUSED_PARAMETER(p);
+}
+static void memdbLeave(MemStore *p){
+  UNUSED_PARAMETER(p);
+}
+#else
+static void memdbEnter(MemStore *p){
+  sqlite3_mutex_enter(p->pMutex);
+}
+static void memdbLeave(MemStore *p){
+  sqlite3_mutex_leave(p->pMutex);
+}
+#endif
+
+
+
+/*
+** Close an memdb-file.
+** Free the underlying MemStore object when its refcount drops to zero
+** or less.
+*/
+static int memdbClose(sqlite3_file *pFile){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  if( p->zFName ){
+    int i;
+#ifndef SQLITE_MUTEX_OMIT
+    sqlite3_mutex *pVfsMutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1);
+#endif
+    sqlite3_mutex_enter(pVfsMutex);
+    for(i=0; ALWAYS(i<memdb_g.nMemStore); i++){
+      if( memdb_g.apMemStore[i]==p ){
+        memdbEnter(p);
+        if( p->nRef==1 ){
+          memdb_g.apMemStore[i] = memdb_g.apMemStore[--memdb_g.nMemStore];
+          if( memdb_g.nMemStore==0 ){
+            sqlite3_free(memdb_g.apMemStore);
+            memdb_g.apMemStore = 0;
+          }
+        }
+        break;
+      }
+    }
+    sqlite3_mutex_leave(pVfsMutex);
+  }else{
+    memdbEnter(p);
+  }
+  p->nRef--;
+  if( p->nRef<=0 ){
+    if( p->mFlags & SQLITE_DESERIALIZE_FREEONCLOSE ){
+      sqlite3_free(p->aData);
+    }
+    memdbLeave(p);
+    sqlite3_mutex_free(p->pMutex);
+    sqlite3_free(p);
+  }else{
+    memdbLeave(p);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Read data from an memdb-file.
+*/
+static int memdbRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  memdbEnter(p);
+  if( iOfst+iAmt>p->sz ){
+    memset(zBuf, 0, iAmt);
+    if( iOfst<p->sz ) memcpy(zBuf, p->aData+iOfst, p->sz - iOfst);
+    memdbLeave(p);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  memcpy(zBuf, p->aData+iOfst, iAmt);
+  memdbLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Try to enlarge the memory allocation to hold at least sz bytes
+*/
+static int memdbEnlarge(MemStore *p, sqlite3_int64 newSz){
+  unsigned char *pNew;
+  if( (p->mFlags & SQLITE_DESERIALIZE_RESIZEABLE)==0 || NEVER(p->nMmap>0) ){
+    return SQLITE_FULL;
+  }
+  if( newSz>p->szMax ){
+    return SQLITE_FULL;
+  }
+  newSz *= 2;
+  if( newSz>p->szMax ) newSz = p->szMax;
+  pNew = sqlite3Realloc(p->aData, newSz);
+  if( pNew==0 ) return SQLITE_IOERR_NOMEM;
+  p->aData = pNew;
+  p->szAlloc = newSz;
+  return SQLITE_OK;
+}
+
+/*
+** Write data to an memdb-file.
+*/
+static int memdbWrite(
+  sqlite3_file *pFile,
+  const void *z,
+  int iAmt,
+  sqlite_int64 iOfst
+){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  memdbEnter(p);
+  if( NEVER(p->mFlags & SQLITE_DESERIALIZE_READONLY) ){
+    /* Can't happen: memdbLock() will return SQLITE_READONLY before
+    ** reaching this point */
+    memdbLeave(p);
+    return SQLITE_IOERR_WRITE;
+  }
+  if( iOfst+iAmt>p->sz ){
+    int rc;
+    if( iOfst+iAmt>p->szAlloc
+     && (rc = memdbEnlarge(p, iOfst+iAmt))!=SQLITE_OK
+    ){
+      memdbLeave(p);
+      return rc;
+    }
+    if( iOfst>p->sz ) memset(p->aData+p->sz, 0, iOfst-p->sz);
+    p->sz = iOfst+iAmt;
+  }
+  memcpy(p->aData+iOfst, z, iAmt);
+  memdbLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Truncate an memdb-file.
+**
+** In rollback mode (which is always the case for memdb, as it does not
+** support WAL mode) the truncate() method is only used to reduce
+** the size of a file, never to increase the size.
+*/
+static int memdbTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  int rc = SQLITE_OK;
+  memdbEnter(p);
+  if( size>p->sz ){
+    /* This can only happen with a corrupt wal mode db */
+    rc = SQLITE_CORRUPT;
+  }else{
+    p->sz = size; 
+  }
+  memdbLeave(p);
+  return rc;
+}
+
+/*
+** Sync an memdb-file.
+*/
+static int memdbSync(sqlite3_file *pFile, int flags){
+  UNUSED_PARAMETER(pFile);
+  UNUSED_PARAMETER(flags);
+  return SQLITE_OK;
+}
+
+/*
+** Return the current file-size of an memdb-file.
+*/
+static int memdbFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  memdbEnter(p);
+  *pSize = p->sz;
+  memdbLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Lock an memdb-file.
+*/
+static int memdbLock(sqlite3_file *pFile, int eLock){
+  MemFile *pThis = (MemFile*)pFile;
+  MemStore *p = pThis->pStore;
+  int rc = SQLITE_OK;
+  if( eLock<=pThis->eLock ) return SQLITE_OK;
+  memdbEnter(p);
+
+  assert( p->nWrLock==0 || p->nWrLock==1 );
+  assert( pThis->eLock<=SQLITE_LOCK_SHARED || p->nWrLock==1 );
+  assert( pThis->eLock==SQLITE_LOCK_NONE || p->nRdLock>=1 );
+
+  if( eLock>SQLITE_LOCK_SHARED && (p->mFlags & SQLITE_DESERIALIZE_READONLY) ){
+    rc = SQLITE_READONLY;
+  }else{
+    switch( eLock ){
+      case SQLITE_LOCK_SHARED: {
+        assert( pThis->eLock==SQLITE_LOCK_NONE );
+        if( p->nWrLock>0 ){
+          rc = SQLITE_BUSY;
+        }else{
+          p->nRdLock++;
+        }
+        break;
+      };
+  
+      case SQLITE_LOCK_RESERVED:
+      case SQLITE_LOCK_PENDING: {
+        assert( pThis->eLock>=SQLITE_LOCK_SHARED );
+        if( ALWAYS(pThis->eLock==SQLITE_LOCK_SHARED) ){
+          if( p->nWrLock>0 ){
+            rc = SQLITE_BUSY;
+          }else{
+            p->nWrLock = 1;
+          }
+        }
+        break;
+      }
+  
+      default: {
+        assert(  eLock==SQLITE_LOCK_EXCLUSIVE );
+        assert( pThis->eLock>=SQLITE_LOCK_SHARED );
+        if( p->nRdLock>1 ){
+          rc = SQLITE_BUSY;
+        }else if( pThis->eLock==SQLITE_LOCK_SHARED ){
+          p->nWrLock = 1;
+        }
+        break;
+      }
+    }
+  }
+  if( rc==SQLITE_OK ) pThis->eLock = eLock;
+  memdbLeave(p);
+  return rc;
+}
+
+/*
+** Unlock an memdb-file.
+*/
+static int memdbUnlock(sqlite3_file *pFile, int eLock){
+  MemFile *pThis = (MemFile*)pFile;
+  MemStore *p = pThis->pStore;
+  if( eLock>=pThis->eLock ) return SQLITE_OK;
+  memdbEnter(p);
+
+  assert( eLock==SQLITE_LOCK_SHARED || eLock==SQLITE_LOCK_NONE );
+  if( eLock==SQLITE_LOCK_SHARED ){
+    if( ALWAYS(pThis->eLock>SQLITE_LOCK_SHARED) ){
+      p->nWrLock--;
+    }
+  }else{
+    if( pThis->eLock>SQLITE_LOCK_SHARED ){
+      p->nWrLock--;
+    }
+    p->nRdLock--;
+  }
+
+  pThis->eLock = eLock;
+  memdbLeave(p);
+  return SQLITE_OK;
+}
+
+#if 0
+/*
+** This interface is only used for crash recovery, which does not
+** occur on an in-memory database.
+*/
+static int memdbCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+#endif
+
+
+/*
+** File control method. For custom operations on an memdb-file.
+*/
+static int memdbFileControl(sqlite3_file *pFile, int op, void *pArg){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  int rc = SQLITE_NOTFOUND;
+  memdbEnter(p);
+  if( op==SQLITE_FCNTL_VFSNAME ){
+    *(char**)pArg = sqlite3_mprintf("memdb(%p,%lld)", p->aData, p->sz);
+    rc = SQLITE_OK;
+  }
+  if( op==SQLITE_FCNTL_SIZE_LIMIT ){
+    sqlite3_int64 iLimit = *(sqlite3_int64*)pArg;
+    if( iLimit<p->sz ){
+      if( iLimit<0 ){
+        iLimit = p->szMax;
+      }else{
+        iLimit = p->sz;
+      }
+    }
+    p->szMax = iLimit;
+    *(sqlite3_int64*)pArg = iLimit;
+    rc = SQLITE_OK;
+  }
+  memdbLeave(p);
+  return rc;
+}
+
+#if 0  /* Not used because of SQLITE_IOCAP_POWERSAFE_OVERWRITE */
+/*
+** Return the sector-size in bytes for an memdb-file.
+*/
+static int memdbSectorSize(sqlite3_file *pFile){
+  return 1024;
+}
+#endif
+
+/*
+** Return the device characteristic flags supported by an memdb-file.
+*/
+static int memdbDeviceCharacteristics(sqlite3_file *pFile){
+  UNUSED_PARAMETER(pFile);
+  return SQLITE_IOCAP_ATOMIC | 
+         SQLITE_IOCAP_POWERSAFE_OVERWRITE |
+         SQLITE_IOCAP_SAFE_APPEND |
+         SQLITE_IOCAP_SEQUENTIAL;
+}
+
+/* Fetch a page of a memory-mapped file */
+static int memdbFetch(
+  sqlite3_file *pFile,
+  sqlite3_int64 iOfst,
+  int iAmt,
+  void **pp
+){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  memdbEnter(p);
+  if( iOfst+iAmt>p->sz || (p->mFlags & SQLITE_DESERIALIZE_RESIZEABLE)!=0 ){
+    *pp = 0;
+  }else{
+    p->nMmap++;
+    *pp = (void*)(p->aData + iOfst);
+  }
+  memdbLeave(p);
+  return SQLITE_OK;
+}
+
+/* Release a memory-mapped page */
+static int memdbUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *pPage){
+  MemStore *p = ((MemFile*)pFile)->pStore;
+  UNUSED_PARAMETER(iOfst);
+  UNUSED_PARAMETER(pPage);
+  memdbEnter(p);
+  p->nMmap--;
+  memdbLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Open an mem file handle.
+*/
+static int memdbOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFd,
+  int flags,
+  int *pOutFlags
+){
+  MemFile *pFile = (MemFile*)pFd;
+  MemStore *p = 0;
+  int szName;
+  UNUSED_PARAMETER(pVfs);
+
+  memset(pFile, 0, sizeof(*pFile));
+  szName = sqlite3Strlen30(zName);
+  if( szName>1 && (zName[0]=='/' || zName[0]=='\\') ){
+    int i;
+#ifndef SQLITE_MUTEX_OMIT
+    sqlite3_mutex *pVfsMutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1);
+#endif
+    sqlite3_mutex_enter(pVfsMutex);
+    for(i=0; i<memdb_g.nMemStore; i++){
+      if( strcmp(memdb_g.apMemStore[i]->zFName,zName)==0 ){
+        p = memdb_g.apMemStore[i];
+        break;
+      }
+    }
+    if( p==0 ){
+      MemStore **apNew;
+      p = sqlite3Malloc( sizeof(*p) + szName + 3 );
+      if( p==0 ){
+        sqlite3_mutex_leave(pVfsMutex);
+        return SQLITE_NOMEM;
+      }
+      apNew = sqlite3Realloc(memdb_g.apMemStore,
+                             sizeof(apNew[0])*(memdb_g.nMemStore+1) );
+      if( apNew==0 ){
+        sqlite3_free(p);
+        sqlite3_mutex_leave(pVfsMutex);
+        return SQLITE_NOMEM;
+      }
+      apNew[memdb_g.nMemStore++] = p;
+      memdb_g.apMemStore = apNew;
+      memset(p, 0, sizeof(*p));
+      p->mFlags = SQLITE_DESERIALIZE_RESIZEABLE|SQLITE_DESERIALIZE_FREEONCLOSE;
+      p->szMax = sqlite3GlobalConfig.mxMemdbSize;
+      p->zFName = (char*)&p[1];
+      memcpy(p->zFName, zName, szName+1);
+      p->pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+      if( p->pMutex==0 ){
+        memdb_g.nMemStore--;
+        sqlite3_free(p);
+        sqlite3_mutex_leave(pVfsMutex);
+        return SQLITE_NOMEM;
+      }
+      p->nRef = 1;
+      memdbEnter(p);
+    }else{
+      memdbEnter(p);
+      p->nRef++;
+    }
+    sqlite3_mutex_leave(pVfsMutex);
+  }else{
+    p = sqlite3Malloc( sizeof(*p) );
+    if( p==0 ){
+      return SQLITE_NOMEM;
+    }
+    memset(p, 0, sizeof(*p));
+    p->mFlags = SQLITE_DESERIALIZE_RESIZEABLE | SQLITE_DESERIALIZE_FREEONCLOSE;
+    p->szMax = sqlite3GlobalConfig.mxMemdbSize;
+  }
+  pFile->pStore = p;
+  if( pOutFlags!=0 ){
+    *pOutFlags = flags | SQLITE_OPEN_MEMORY;
+  }
+  pFd->pMethods = &memdb_io_methods;
+  memdbLeave(p);
+  return SQLITE_OK;
+}
+
+#if 0 /* Only used to delete rollback journals, super-journals, and WAL
+      ** files, none of which exist in memdb.  So this routine is never used */
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int memdbDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  return SQLITE_IOERR_DELETE;
+}
+#endif
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+**
+** With memdb, no files ever exist on disk.  So always return false.
+*/
+static int memdbAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  UNUSED_PARAMETER(pVfs);
+  UNUSED_PARAMETER(zPath);
+  UNUSED_PARAMETER(flags);
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (INST_MAX_PATHNAME+1) bytes.
+*/
+static int memdbFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  UNUSED_PARAMETER(pVfs);
+  sqlite3_snprintf(nOut, zOut, "%s", zPath);
+  return SQLITE_OK;
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *memdbDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return ORIGVFS(pVfs)->xDlOpen(ORIGVFS(pVfs), zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void memdbDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  ORIGVFS(pVfs)->xDlError(ORIGVFS(pVfs), nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*memdbDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return ORIGVFS(pVfs)->xDlSym(ORIGVFS(pVfs), p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void memdbDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  ORIGVFS(pVfs)->xDlClose(ORIGVFS(pVfs), pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int memdbRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return ORIGVFS(pVfs)->xRandomness(ORIGVFS(pVfs), nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int memdbSleep(sqlite3_vfs *pVfs, int nMicro){
+  return ORIGVFS(pVfs)->xSleep(ORIGVFS(pVfs), nMicro);
+}
+
+#if 0  /* Never used.  Modern cores only call xCurrentTimeInt64() */
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int memdbCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return ORIGVFS(pVfs)->xCurrentTime(ORIGVFS(pVfs), pTimeOut);
+}
+#endif
+
+static int memdbGetLastError(sqlite3_vfs *pVfs, int a, char *b){
+  return ORIGVFS(pVfs)->xGetLastError(ORIGVFS(pVfs), a, b);
+}
+static int memdbCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){
+  return ORIGVFS(pVfs)->xCurrentTimeInt64(ORIGVFS(pVfs), p);
+}
+
+/*
+** Translate a database connection pointer and schema name into a
+** MemFile pointer.
+*/
+static MemFile *memdbFromDbSchema(sqlite3 *db, const char *zSchema){
+  MemFile *p = 0;
+  MemStore *pStore;
+  int rc = sqlite3_file_control(db, zSchema, SQLITE_FCNTL_FILE_POINTER, &p);
+  if( rc ) return 0;
+  if( p->base.pMethods!=&memdb_io_methods ) return 0;
+  pStore = p->pStore;
+  memdbEnter(pStore);
+  if( pStore->zFName!=0 ) p = 0;
+  memdbLeave(pStore);
+  return p;
+}
+
+/*
+** Return the serialization of a database
+*/
+unsigned char *sqlite3_serialize(
+  sqlite3 *db,              /* The database connection */
+  const char *zSchema,      /* Which database within the connection */
+  sqlite3_int64 *piSize,    /* Write size here, if not NULL */
+  unsigned int mFlags       /* Maybe SQLITE_SERIALIZE_NOCOPY */
+){
+  MemFile *p;
+  int iDb;
+  Btree *pBt;
+  sqlite3_int64 sz;
+  int szPage = 0;
+  sqlite3_stmt *pStmt = 0;
+  unsigned char *pOut;
+  char *zSql;
+  int rc;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+
+  if( zSchema==0 ) zSchema = db->aDb[0].zDbSName;
+  p = memdbFromDbSchema(db, zSchema);
+  iDb = sqlite3FindDbName(db, zSchema);
+  if( piSize ) *piSize = -1;
+  if( iDb<0 ) return 0;
+  if( p ){
+    MemStore *pStore = p->pStore;
+    assert( pStore->pMutex==0 );
+    if( piSize ) *piSize = pStore->sz;
+    if( mFlags & SQLITE_SERIALIZE_NOCOPY ){
+      pOut = pStore->aData;
+    }else{
+      pOut = sqlite3_malloc64( pStore->sz );
+      if( pOut ) memcpy(pOut, pStore->aData, pStore->sz);
+    }
+    return pOut;
+  }
+  pBt = db->aDb[iDb].pBt;
+  if( pBt==0 ) return 0;
+  szPage = sqlite3BtreeGetPageSize(pBt);
+  zSql = sqlite3_mprintf("PRAGMA \"%w\".page_count", zSchema);
+  rc = zSql ? sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0) : SQLITE_NOMEM;
+  sqlite3_free(zSql);
+  if( rc ) return 0;
+  rc = sqlite3_step(pStmt);
+  if( rc!=SQLITE_ROW ){
+    pOut = 0;
+  }else{
+    sz = sqlite3_column_int64(pStmt, 0)*szPage;
+    if( piSize ) *piSize = sz;
+    if( mFlags & SQLITE_SERIALIZE_NOCOPY ){
+      pOut = 0;
+    }else{
+      pOut = sqlite3_malloc64( sz );
+      if( pOut ){
+        int nPage = sqlite3_column_int(pStmt, 0);
+        Pager *pPager = sqlite3BtreePager(pBt);
+        int pgno;
+        for(pgno=1; pgno<=nPage; pgno++){
+          DbPage *pPage = 0;
+          unsigned char *pTo = pOut + szPage*(sqlite3_int64)(pgno-1);
+          rc = sqlite3PagerGet(pPager, pgno, (DbPage**)&pPage, 0);
+          if( rc==SQLITE_OK ){
+            memcpy(pTo, sqlite3PagerGetData(pPage), szPage);
+          }else{
+            memset(pTo, 0, szPage);
+          }
+          sqlite3PagerUnref(pPage);       
+        }
+      }
+    }
+  }
+  sqlite3_finalize(pStmt);
+  return pOut;
+}
+
+/* Convert zSchema to a MemDB and initialize its content.
+*/
+int sqlite3_deserialize(
+  sqlite3 *db,            /* The database connection */
+  const char *zSchema,    /* Which DB to reopen with the deserialization */
+  unsigned char *pData,   /* The serialized database content */
+  sqlite3_int64 szDb,     /* Number bytes in the deserialization */
+  sqlite3_int64 szBuf,    /* Total size of buffer pData[] */
+  unsigned mFlags         /* Zero or more SQLITE_DESERIALIZE_* flags */
+){
+  MemFile *p;
+  char *zSql;
+  sqlite3_stmt *pStmt = 0;
+  int rc;
+  int iDb;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( szDb<0 ) return SQLITE_MISUSE_BKPT;
+  if( szBuf<0 ) return SQLITE_MISUSE_BKPT;
+#endif
+
+  sqlite3_mutex_enter(db->mutex);
+  if( zSchema==0 ) zSchema = db->aDb[0].zDbSName;
+  iDb = sqlite3FindDbName(db, zSchema);
+  testcase( iDb==1 );
+  if( iDb<2 && iDb!=0 ){
+    rc = SQLITE_ERROR;
+    goto end_deserialize;
+  }
+  zSql = sqlite3_mprintf("ATTACH x AS %Q", zSchema);
+  if( zSql==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+  }
+  if( rc ) goto end_deserialize;
+  db->init.iDb = (u8)iDb;
+  db->init.reopenMemdb = 1;
+  rc = sqlite3_step(pStmt);
+  db->init.reopenMemdb = 0;
+  if( rc!=SQLITE_DONE ){
+    rc = SQLITE_ERROR;
+    goto end_deserialize;
+  }
+  p = memdbFromDbSchema(db, zSchema);
+  if( p==0 ){
+    rc = SQLITE_ERROR;
+  }else{
+    MemStore *pStore = p->pStore;
+    pStore->aData = pData;
+    pData = 0;
+    pStore->sz = szDb;
+    pStore->szAlloc = szBuf;
+    pStore->szMax = szBuf;
+    if( pStore->szMax<sqlite3GlobalConfig.mxMemdbSize ){
+      pStore->szMax = sqlite3GlobalConfig.mxMemdbSize;
+    }
+    pStore->mFlags = mFlags;
+    rc = SQLITE_OK;
+  }
+
+end_deserialize:
+  sqlite3_finalize(pStmt);
+  if( pData && (mFlags & SQLITE_DESERIALIZE_FREEONCLOSE)!=0 ){
+    sqlite3_free(pData);
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Return true if the VFS is the memvfs.
+*/
+int sqlite3IsMemdb(const sqlite3_vfs *pVfs){
+  return pVfs==&memdb_vfs;
+}
+
+/* 
+** This routine is called when the extension is loaded.
+** Register the new VFS.
+*/
+int sqlite3MemdbInit(void){
+  sqlite3_vfs *pLower = sqlite3_vfs_find(0);
+  unsigned int sz;
+  if( NEVER(pLower==0) ) return SQLITE_ERROR;
+  sz = pLower->szOsFile;
+  memdb_vfs.pAppData = pLower;
+  /* The following conditional can only be true when compiled for
+  ** Windows x86 and SQLITE_MAX_MMAP_SIZE=0.  We always leave
+  ** it in, to be safe, but it is marked as NO_TEST since there
+  ** is no way to reach it under most builds. */
+  if( sz<sizeof(MemFile) ) sz = sizeof(MemFile); /*NO_TEST*/
+  memdb_vfs.szOsFile = sz;
+  return sqlite3_vfs_register(&memdb_vfs, 0);
+}
+#endif /* SQLITE_OMIT_DESERIALIZE */
diff --git a/src/memjournal.c b/src/memjournal.c
new file mode 100644
index 0000000..9343801
--- /dev/null
+++ b/src/memjournal.c
@@ -0,0 +1,440 @@
+/*
+** 2008 October 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code use to implement an in-memory rollback journal.
+** The in-memory rollback journal is used to journal transactions for
+** ":memory:" databases and when the journal_mode=MEMORY pragma is used.
+**
+** Update:  The in-memory journal is also used to temporarily cache
+** smaller journals that are not critical for power-loss recovery.
+** For example, statement journals that are not too big will be held
+** entirely in memory, thus reducing the number of file I/O calls, and
+** more importantly, reducing temporary file creation events.  If these
+** journals become too large for memory, they are spilled to disk.  But
+** in the common case, they are usually small and no file I/O needs to
+** occur.
+*/
+#include "sqliteInt.h"
+
+/* Forward references to internal structures */
+typedef struct MemJournal MemJournal;
+typedef struct FilePoint FilePoint;
+typedef struct FileChunk FileChunk;
+
+/*
+** The rollback journal is composed of a linked list of these structures.
+**
+** The zChunk array is always at least 8 bytes in size - usually much more.
+** Its actual size is stored in the MemJournal.nChunkSize variable.
+*/
+struct FileChunk {
+  FileChunk *pNext;               /* Next chunk in the journal */
+  u8 zChunk[8];                   /* Content of this chunk */
+};
+
+/*
+** By default, allocate this many bytes of memory for each FileChunk object.
+*/
+#define MEMJOURNAL_DFLT_FILECHUNKSIZE 1024
+
+/*
+** For chunk size nChunkSize, return the number of bytes that should
+** be allocated for each FileChunk structure.
+*/
+#define fileChunkSize(nChunkSize) (sizeof(FileChunk) + ((nChunkSize)-8))
+
+/*
+** An instance of this object serves as a cursor into the rollback journal.
+** The cursor can be either for reading or writing.
+*/
+struct FilePoint {
+  sqlite3_int64 iOffset;          /* Offset from the beginning of the file */
+  FileChunk *pChunk;              /* Specific chunk into which cursor points */
+};
+
+/*
+** This structure is a subclass of sqlite3_file. Each open memory-journal
+** is an instance of this class.
+*/
+struct MemJournal {
+  const sqlite3_io_methods *pMethod; /* Parent class. MUST BE FIRST */
+  int nChunkSize;                 /* In-memory chunk-size */
+
+  int nSpill;                     /* Bytes of data before flushing */
+  FileChunk *pFirst;              /* Head of in-memory chunk-list */
+  FilePoint endpoint;             /* Pointer to the end of the file */
+  FilePoint readpoint;            /* Pointer to the end of the last xRead() */
+
+  int flags;                      /* xOpen flags */
+  sqlite3_vfs *pVfs;              /* The "real" underlying VFS */
+  const char *zJournal;           /* Name of the journal file */
+};
+
+/*
+** Read data from the in-memory journal file.  This is the implementation
+** of the sqlite3_vfs.xRead method.
+*/
+static int memjrnlRead(
+  sqlite3_file *pJfd,    /* The journal file from which to read */
+  void *zBuf,            /* Put the results here */
+  int iAmt,              /* Number of bytes to read */
+  sqlite_int64 iOfst     /* Begin reading at this offset */
+){
+  MemJournal *p = (MemJournal *)pJfd;
+  u8 *zOut = zBuf;
+  int nRead = iAmt;
+  int iChunkOffset;
+  FileChunk *pChunk;
+
+  if( (iAmt+iOfst)>p->endpoint.iOffset ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  assert( p->readpoint.iOffset==0 || p->readpoint.pChunk!=0 );
+  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
+    sqlite3_int64 iOff = 0;
+    for(pChunk=p->pFirst; 
+        ALWAYS(pChunk) && (iOff+p->nChunkSize)<=iOfst;
+        pChunk=pChunk->pNext
+    ){
+      iOff += p->nChunkSize;
+    }
+  }else{
+    pChunk = p->readpoint.pChunk;
+    assert( pChunk!=0 );
+  }
+
+  iChunkOffset = (int)(iOfst%p->nChunkSize);
+  do {
+    int iSpace = p->nChunkSize - iChunkOffset;
+    int nCopy = MIN(nRead, (p->nChunkSize - iChunkOffset));
+    memcpy(zOut, (u8*)pChunk->zChunk + iChunkOffset, nCopy);
+    zOut += nCopy;
+    nRead -= iSpace;
+    iChunkOffset = 0;
+  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
+  p->readpoint.iOffset = pChunk ? iOfst+iAmt : 0;
+  p->readpoint.pChunk = pChunk;
+
+  return SQLITE_OK;
+}
+
+/*
+** Free the list of FileChunk structures headed at MemJournal.pFirst.
+*/
+static void memjrnlFreeChunks(FileChunk *pFirst){
+  FileChunk *pIter;
+  FileChunk *pNext;
+  for(pIter=pFirst; pIter; pIter=pNext){
+    pNext = pIter->pNext;
+    sqlite3_free(pIter);
+  } 
+}
+
+/*
+** Flush the contents of memory to a real file on disk.
+*/
+static int memjrnlCreateFile(MemJournal *p){
+  int rc;
+  sqlite3_file *pReal = (sqlite3_file*)p;
+  MemJournal copy = *p;
+
+  memset(p, 0, sizeof(MemJournal));
+  rc = sqlite3OsOpen(copy.pVfs, copy.zJournal, pReal, copy.flags, 0);
+  if( rc==SQLITE_OK ){
+    int nChunk = copy.nChunkSize;
+    i64 iOff = 0;
+    FileChunk *pIter;
+    for(pIter=copy.pFirst; pIter; pIter=pIter->pNext){
+      if( iOff + nChunk > copy.endpoint.iOffset ){
+        nChunk = copy.endpoint.iOffset - iOff;
+      }
+      rc = sqlite3OsWrite(pReal, (u8*)pIter->zChunk, nChunk, iOff);
+      if( rc ) break;
+      iOff += nChunk;
+    }
+    if( rc==SQLITE_OK ){
+      /* No error has occurred. Free the in-memory buffers. */
+      memjrnlFreeChunks(copy.pFirst);
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    /* If an error occurred while creating or writing to the file, restore
+    ** the original before returning. This way, SQLite uses the in-memory
+    ** journal data to roll back changes made to the internal page-cache
+    ** before this function was called.  */
+    sqlite3OsClose(pReal);
+    *p = copy;
+  }
+  return rc;
+}
+
+
+/* Forward reference */
+static int memjrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size);
+
+/*
+** Write data to the file.
+*/
+static int memjrnlWrite(
+  sqlite3_file *pJfd,    /* The journal file into which to write */
+  const void *zBuf,      /* Take data to be written from here */
+  int iAmt,              /* Number of bytes to write */
+  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
+){
+  MemJournal *p = (MemJournal *)pJfd;
+  int nWrite = iAmt;
+  u8 *zWrite = (u8 *)zBuf;
+
+  /* If the file should be created now, create it and write the new data
+  ** into the file on disk. */
+  if( p->nSpill>0 && (iAmt+iOfst)>p->nSpill ){
+    int rc = memjrnlCreateFile(p);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3OsWrite(pJfd, zBuf, iAmt, iOfst);
+    }
+    return rc;
+  }
+
+  /* If the contents of this write should be stored in memory */
+  else{
+    /* An in-memory journal file should only ever be appended to. Random
+    ** access writes are not required. The only exception to this is when
+    ** the in-memory journal is being used by a connection using the
+    ** atomic-write optimization. In this case the first 28 bytes of the
+    ** journal file may be written as part of committing the transaction. */
+    assert( iOfst<=p->endpoint.iOffset );
+    if( iOfst>0 && iOfst!=p->endpoint.iOffset ){
+      memjrnlTruncate(pJfd, iOfst);
+    }
+    if( iOfst==0 && p->pFirst ){
+      assert( p->nChunkSize>iAmt );
+      memcpy((u8*)p->pFirst->zChunk, zBuf, iAmt);
+    }else{
+      while( nWrite>0 ){
+        FileChunk *pChunk = p->endpoint.pChunk;
+        int iChunkOffset = (int)(p->endpoint.iOffset%p->nChunkSize);
+        int iSpace = MIN(nWrite, p->nChunkSize - iChunkOffset);
+
+        assert( pChunk!=0 || iChunkOffset==0 );
+        if( iChunkOffset==0 ){
+          /* New chunk is required to extend the file. */
+          FileChunk *pNew = sqlite3_malloc(fileChunkSize(p->nChunkSize));
+          if( !pNew ){
+            return SQLITE_IOERR_NOMEM_BKPT;
+          }
+          pNew->pNext = 0;
+          if( pChunk ){
+            assert( p->pFirst );
+            pChunk->pNext = pNew;
+          }else{
+            assert( !p->pFirst );
+            p->pFirst = pNew;
+          }
+          pChunk = p->endpoint.pChunk = pNew;
+        }
+
+        assert( pChunk!=0 );
+        memcpy((u8*)pChunk->zChunk + iChunkOffset, zWrite, iSpace);
+        zWrite += iSpace;
+        nWrite -= iSpace;
+        p->endpoint.iOffset += iSpace;
+      }
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Truncate the in-memory file.
+*/
+static int memjrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size){
+  MemJournal *p = (MemJournal *)pJfd;
+  assert( p->endpoint.pChunk==0 || p->endpoint.pChunk->pNext==0 );
+  if( size<p->endpoint.iOffset ){
+    FileChunk *pIter = 0;
+    if( size==0 ){
+      memjrnlFreeChunks(p->pFirst);
+      p->pFirst = 0;
+    }else{
+      i64 iOff = p->nChunkSize;
+      for(pIter=p->pFirst; ALWAYS(pIter) && iOff<size; pIter=pIter->pNext){
+        iOff += p->nChunkSize;
+      }
+      if( ALWAYS(pIter) ){
+        memjrnlFreeChunks(pIter->pNext);
+        pIter->pNext = 0;
+      }
+    }
+
+    p->endpoint.pChunk = pIter;
+    p->endpoint.iOffset = size;
+    p->readpoint.pChunk = 0;
+    p->readpoint.iOffset = 0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Close the file.
+*/
+static int memjrnlClose(sqlite3_file *pJfd){
+  MemJournal *p = (MemJournal *)pJfd;
+  memjrnlFreeChunks(p->pFirst);
+  return SQLITE_OK;
+}
+
+/*
+** Sync the file.
+**
+** If the real file has been created, call its xSync method. Otherwise, 
+** syncing an in-memory journal is a no-op. 
+*/
+static int memjrnlSync(sqlite3_file *pJfd, int flags){
+  UNUSED_PARAMETER2(pJfd, flags);
+  return SQLITE_OK;
+}
+
+/*
+** Query the size of the file in bytes.
+*/
+static int memjrnlFileSize(sqlite3_file *pJfd, sqlite_int64 *pSize){
+  MemJournal *p = (MemJournal *)pJfd;
+  *pSize = (sqlite_int64) p->endpoint.iOffset;
+  return SQLITE_OK;
+}
+
+/*
+** Table of methods for MemJournal sqlite3_file object.
+*/
+static const struct sqlite3_io_methods MemJournalMethods = {
+  1,                /* iVersion */
+  memjrnlClose,     /* xClose */
+  memjrnlRead,      /* xRead */
+  memjrnlWrite,     /* xWrite */
+  memjrnlTruncate,  /* xTruncate */
+  memjrnlSync,      /* xSync */
+  memjrnlFileSize,  /* xFileSize */
+  0,                /* xLock */
+  0,                /* xUnlock */
+  0,                /* xCheckReservedLock */
+  0,                /* xFileControl */
+  0,                /* xSectorSize */
+  0,                /* xDeviceCharacteristics */
+  0,                /* xShmMap */
+  0,                /* xShmLock */
+  0,                /* xShmBarrier */
+  0,                /* xShmUnmap */
+  0,                /* xFetch */
+  0                 /* xUnfetch */
+};
+
+/* 
+** Open a journal file. 
+**
+** The behaviour of the journal file depends on the value of parameter 
+** nSpill. If nSpill is 0, then the journal file is always create and 
+** accessed using the underlying VFS. If nSpill is less than zero, then
+** all content is always stored in main-memory. Finally, if nSpill is a
+** positive value, then the journal file is initially created in-memory
+** but may be flushed to disk later on. In this case the journal file is
+** flushed to disk either when it grows larger than nSpill bytes in size,
+** or when sqlite3JournalCreate() is called.
+*/
+int sqlite3JournalOpen(
+  sqlite3_vfs *pVfs,         /* The VFS to use for actual file I/O */
+  const char *zName,         /* Name of the journal file */
+  sqlite3_file *pJfd,        /* Preallocated, blank file handle */
+  int flags,                 /* Opening flags */
+  int nSpill                 /* Bytes buffered before opening the file */
+){
+  MemJournal *p = (MemJournal*)pJfd;
+
+  assert( zName || nSpill<0 || (flags & SQLITE_OPEN_EXCLUSIVE) );
+
+  /* Zero the file-handle object. If nSpill was passed zero, initialize
+  ** it using the sqlite3OsOpen() function of the underlying VFS. In this
+  ** case none of the code in this module is executed as a result of calls
+  ** made on the journal file-handle.  */
+  memset(p, 0, sizeof(MemJournal));
+  if( nSpill==0 ){
+    return sqlite3OsOpen(pVfs, zName, pJfd, flags, 0);
+  }
+
+  if( nSpill>0 ){
+    p->nChunkSize = nSpill;
+  }else{
+    p->nChunkSize = 8 + MEMJOURNAL_DFLT_FILECHUNKSIZE - sizeof(FileChunk);
+    assert( MEMJOURNAL_DFLT_FILECHUNKSIZE==fileChunkSize(p->nChunkSize) );
+  }
+
+  pJfd->pMethods = (const sqlite3_io_methods*)&MemJournalMethods;
+  p->nSpill = nSpill;
+  p->flags = flags;
+  p->zJournal = zName;
+  p->pVfs = pVfs;
+  return SQLITE_OK;
+}
+
+/*
+** Open an in-memory journal file.
+*/
+void sqlite3MemJournalOpen(sqlite3_file *pJfd){
+  sqlite3JournalOpen(0, 0, pJfd, 0, -1);
+}
+
+#if defined(SQLITE_ENABLE_ATOMIC_WRITE) \
+ || defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+/*
+** If the argument p points to a MemJournal structure that is not an 
+** in-memory-only journal file (i.e. is one that was opened with a +ve
+** nSpill parameter or as SQLITE_OPEN_MAIN_JOURNAL), and the underlying 
+** file has not yet been created, create it now.
+*/
+int sqlite3JournalCreate(sqlite3_file *pJfd){
+  int rc = SQLITE_OK;
+  MemJournal *p = (MemJournal*)pJfd;
+  if( pJfd->pMethods==&MemJournalMethods && (
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+     p->nSpill>0
+#else
+     /* While this appears to not be possible without ATOMIC_WRITE, the
+     ** paths are complex, so it seems prudent to leave the test in as
+     ** a NEVER(), in case our analysis is subtly flawed. */
+     NEVER(p->nSpill>0)
+#endif
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+     || (p->flags & SQLITE_OPEN_MAIN_JOURNAL)
+#endif
+  )){
+    rc = memjrnlCreateFile(p);
+  }
+  return rc;
+}
+#endif
+
+/*
+** The file-handle passed as the only argument is open on a journal file.
+** Return true if this "journal file" is currently stored in heap memory,
+** or false otherwise.
+*/
+int sqlite3JournalIsInMemory(sqlite3_file *p){
+  return p->pMethods==&MemJournalMethods;
+}
+
+/* 
+** Return the number of bytes required to store a JournalFile that uses vfs
+** pVfs to create the underlying on-disk files.
+*/
+int sqlite3JournalSize(sqlite3_vfs *pVfs){
+  return MAX(pVfs->szOsFile, (int)sizeof(MemJournal));
+}
diff --git a/src/msvc.h b/src/msvc.h
new file mode 100644
index 0000000..10675e9
--- /dev/null
+++ b/src/msvc.h
@@ -0,0 +1,45 @@
+/*
+** 2015 January 12
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that is specific to MSVC.
+*/
+#ifndef SQLITE_MSVC_H
+#define SQLITE_MSVC_H
+
+#if defined(_MSC_VER)
+#pragma warning(disable : 4054)
+#pragma warning(disable : 4055)
+#pragma warning(disable : 4100)
+#pragma warning(disable : 4127)
+#pragma warning(disable : 4130)
+#pragma warning(disable : 4152)
+#pragma warning(disable : 4189)
+#pragma warning(disable : 4206)
+#pragma warning(disable : 4210)
+#pragma warning(disable : 4232)
+#pragma warning(disable : 4244)
+#pragma warning(disable : 4305)
+#pragma warning(disable : 4306)
+#pragma warning(disable : 4702)
+#pragma warning(disable : 4706)
+#endif /* defined(_MSC_VER) */
+
+#if defined(_MSC_VER) && !defined(_WIN64)
+#undef SQLITE_4_BYTE_ALIGNED_MALLOC
+#define SQLITE_4_BYTE_ALIGNED_MALLOC
+#endif /* defined(_MSC_VER) && !defined(_WIN64) */
+
+#if !defined(HAVE_LOG2) && defined(_MSC_VER) && _MSC_VER<1800
+#define HAVE_LOG2 0
+#endif /* !defined(HAVE_LOG2) && defined(_MSC_VER) && _MSC_VER<1800 */
+
+#endif /* SQLITE_MSVC_H */
diff --git a/src/mutex.c b/src/mutex.c
new file mode 100644
index 0000000..381ffbd
--- /dev/null
+++ b/src/mutex.c
@@ -0,0 +1,361 @@
+/*
+** 2007 August 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes.
+**
+** This file contains code that is common across all mutex implementations.
+*/
+#include "sqliteInt.h"
+
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_MUTEX_OMIT)
+/*
+** For debugging purposes, record when the mutex subsystem is initialized
+** and uninitialized so that we can assert() if there is an attempt to
+** allocate a mutex while the system is uninitialized.
+*/
+static SQLITE_WSD int mutexIsInit = 0;
+#endif /* SQLITE_DEBUG && !defined(SQLITE_MUTEX_OMIT) */
+
+
+#ifndef SQLITE_MUTEX_OMIT
+
+#ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS
+/*
+** This block (enclosed by SQLITE_ENABLE_MULTITHREADED_CHECKS) contains
+** the implementation of a wrapper around the system default mutex
+** implementation (sqlite3DefaultMutex()). 
+**
+** Most calls are passed directly through to the underlying default
+** mutex implementation. Except, if a mutex is configured by calling
+** sqlite3MutexWarnOnContention() on it, then if contention is ever
+** encountered within xMutexEnter() a warning is emitted via sqlite3_log().
+**
+** This type of mutex is used as the database handle mutex when testing
+** apps that usually use SQLITE_CONFIG_MULTITHREAD mode.
+*/
+
+/* 
+** Type for all mutexes used when SQLITE_ENABLE_MULTITHREADED_CHECKS
+** is defined. Variable CheckMutex.mutex is a pointer to the real mutex
+** allocated by the system mutex implementation. Variable iType is usually set
+** to the type of mutex requested - SQLITE_MUTEX_RECURSIVE, SQLITE_MUTEX_FAST
+** or one of the static mutex identifiers. Or, if this is a recursive mutex
+** that has been configured using sqlite3MutexWarnOnContention(), it is
+** set to SQLITE_MUTEX_WARNONCONTENTION.
+*/
+typedef struct CheckMutex CheckMutex;
+struct CheckMutex {
+  int iType;
+  sqlite3_mutex *mutex;
+};
+
+#define SQLITE_MUTEX_WARNONCONTENTION  (-1)
+
+/* 
+** Pointer to real mutex methods object used by the CheckMutex
+** implementation. Set by checkMutexInit(). 
+*/
+static SQLITE_WSD const sqlite3_mutex_methods *pGlobalMutexMethods;
+
+#ifdef SQLITE_DEBUG
+static int checkMutexHeld(sqlite3_mutex *p){
+  return pGlobalMutexMethods->xMutexHeld(((CheckMutex*)p)->mutex);
+}
+static int checkMutexNotheld(sqlite3_mutex *p){
+  return pGlobalMutexMethods->xMutexNotheld(((CheckMutex*)p)->mutex);
+}
+#endif
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static int checkMutexInit(void){ 
+  pGlobalMutexMethods = sqlite3DefaultMutex();
+  return SQLITE_OK; 
+}
+static int checkMutexEnd(void){ 
+  pGlobalMutexMethods = 0;
+  return SQLITE_OK; 
+}
+
+/*
+** Allocate a mutex.
+*/
+static sqlite3_mutex *checkMutexAlloc(int iType){
+  static CheckMutex staticMutexes[] = {
+    {2, 0}, {3, 0}, {4, 0}, {5, 0},
+    {6, 0}, {7, 0}, {8, 0}, {9, 0},
+    {10, 0}, {11, 0}, {12, 0}, {13, 0}
+  };
+  CheckMutex *p = 0;
+
+  assert( SQLITE_MUTEX_RECURSIVE==1 && SQLITE_MUTEX_FAST==0 );
+  if( iType<2 ){
+    p = sqlite3MallocZero(sizeof(CheckMutex));
+    if( p==0 ) return 0;
+    p->iType = iType;
+  }else{
+#ifdef SQLITE_ENABLE_API_ARMOR
+    if( iType-2>=ArraySize(staticMutexes) ){
+      (void)SQLITE_MISUSE_BKPT;
+      return 0;
+    }
+#endif
+    p = &staticMutexes[iType-2];
+  }
+
+  if( p->mutex==0 ){
+    p->mutex = pGlobalMutexMethods->xMutexAlloc(iType);
+    if( p->mutex==0 ){
+      if( iType<2 ){
+        sqlite3_free(p);
+      }
+      p = 0;
+    }
+  }
+
+  return (sqlite3_mutex*)p;
+}
+
+/*
+** Free a mutex.
+*/
+static void checkMutexFree(sqlite3_mutex *p){
+  assert( SQLITE_MUTEX_RECURSIVE<2 );
+  assert( SQLITE_MUTEX_FAST<2 );
+  assert( SQLITE_MUTEX_WARNONCONTENTION<2 );
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( ((CheckMutex*)p)->iType<2 )
+#endif
+  {
+    CheckMutex *pCheck = (CheckMutex*)p;
+    pGlobalMutexMethods->xMutexFree(pCheck->mutex);
+    sqlite3_free(pCheck);
+  }
+#ifdef SQLITE_ENABLE_API_ARMOR
+  else{
+    (void)SQLITE_MISUSE_BKPT;
+  }
+#endif
+}
+
+/*
+** Enter the mutex.
+*/
+static void checkMutexEnter(sqlite3_mutex *p){
+  CheckMutex *pCheck = (CheckMutex*)p;
+  if( pCheck->iType==SQLITE_MUTEX_WARNONCONTENTION ){
+    if( SQLITE_OK==pGlobalMutexMethods->xMutexTry(pCheck->mutex) ){
+      return;
+    }
+    sqlite3_log(SQLITE_MISUSE, 
+        "illegal multi-threaded access to database connection"
+    );
+  }
+  pGlobalMutexMethods->xMutexEnter(pCheck->mutex);
+}
+
+/*
+** Enter the mutex (do not block).
+*/
+static int checkMutexTry(sqlite3_mutex *p){
+  CheckMutex *pCheck = (CheckMutex*)p;
+  return pGlobalMutexMethods->xMutexTry(pCheck->mutex);
+}
+
+/*
+** Leave the mutex.
+*/
+static void checkMutexLeave(sqlite3_mutex *p){
+  CheckMutex *pCheck = (CheckMutex*)p;
+  pGlobalMutexMethods->xMutexLeave(pCheck->mutex);
+}
+
+sqlite3_mutex_methods const *multiThreadedCheckMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    checkMutexInit,
+    checkMutexEnd,
+    checkMutexAlloc,
+    checkMutexFree,
+    checkMutexEnter,
+    checkMutexTry,
+    checkMutexLeave,
+#ifdef SQLITE_DEBUG
+    checkMutexHeld,
+    checkMutexNotheld
+#else
+    0,
+    0
+#endif
+  };
+  return &sMutex;
+}
+
+/*
+** Mark the SQLITE_MUTEX_RECURSIVE mutex passed as the only argument as
+** one on which there should be no contention.
+*/
+void sqlite3MutexWarnOnContention(sqlite3_mutex *p){
+  if( sqlite3GlobalConfig.mutex.xMutexAlloc==checkMutexAlloc ){
+    CheckMutex *pCheck = (CheckMutex*)p;
+    assert( pCheck->iType==SQLITE_MUTEX_RECURSIVE );
+    pCheck->iType = SQLITE_MUTEX_WARNONCONTENTION;
+  }
+}
+#endif   /* ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS */
+
+/*
+** Initialize the mutex system.
+*/
+int sqlite3MutexInit(void){ 
+  int rc = SQLITE_OK;
+  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
+    /* If the xMutexAlloc method has not been set, then the user did not
+    ** install a mutex implementation via sqlite3_config() prior to 
+    ** sqlite3_initialize() being called. This block copies pointers to
+    ** the default implementation into the sqlite3GlobalConfig structure.
+    */
+    sqlite3_mutex_methods const *pFrom;
+    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
+
+    if( sqlite3GlobalConfig.bCoreMutex ){
+#ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS
+      pFrom = multiThreadedCheckMutex();
+#else
+      pFrom = sqlite3DefaultMutex();
+#endif
+    }else{
+      pFrom = sqlite3NoopMutex();
+    }
+    pTo->xMutexInit = pFrom->xMutexInit;
+    pTo->xMutexEnd = pFrom->xMutexEnd;
+    pTo->xMutexFree = pFrom->xMutexFree;
+    pTo->xMutexEnter = pFrom->xMutexEnter;
+    pTo->xMutexTry = pFrom->xMutexTry;
+    pTo->xMutexLeave = pFrom->xMutexLeave;
+    pTo->xMutexHeld = pFrom->xMutexHeld;
+    pTo->xMutexNotheld = pFrom->xMutexNotheld;
+    sqlite3MemoryBarrier();
+    pTo->xMutexAlloc = pFrom->xMutexAlloc;
+  }
+  assert( sqlite3GlobalConfig.mutex.xMutexInit );
+  rc = sqlite3GlobalConfig.mutex.xMutexInit();
+
+#ifdef SQLITE_DEBUG
+  GLOBAL(int, mutexIsInit) = 1;
+#endif
+
+  sqlite3MemoryBarrier();
+  return rc;
+}
+
+/*
+** Shutdown the mutex system. This call frees resources allocated by
+** sqlite3MutexInit().
+*/
+int sqlite3MutexEnd(void){
+  int rc = SQLITE_OK;
+  if( sqlite3GlobalConfig.mutex.xMutexEnd ){
+    rc = sqlite3GlobalConfig.mutex.xMutexEnd();
+  }
+
+#ifdef SQLITE_DEBUG
+  GLOBAL(int, mutexIsInit) = 0;
+#endif
+
+  return rc;
+}
+
+/*
+** Retrieve a pointer to a static mutex or allocate a new dynamic one.
+*/
+sqlite3_mutex *sqlite3_mutex_alloc(int id){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( id<=SQLITE_MUTEX_RECURSIVE && sqlite3_initialize() ) return 0;
+  if( id>SQLITE_MUTEX_RECURSIVE && sqlite3MutexInit() ) return 0;
+#endif
+  assert( sqlite3GlobalConfig.mutex.xMutexAlloc );
+  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
+}
+
+sqlite3_mutex *sqlite3MutexAlloc(int id){
+  if( !sqlite3GlobalConfig.bCoreMutex ){
+    return 0;
+  }
+  assert( GLOBAL(int, mutexIsInit) );
+  assert( sqlite3GlobalConfig.mutex.xMutexAlloc );
+  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
+}
+
+/*
+** Free a dynamic mutex.
+*/
+void sqlite3_mutex_free(sqlite3_mutex *p){
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexFree );
+    sqlite3GlobalConfig.mutex.xMutexFree(p);
+  }
+}
+
+/*
+** Obtain the mutex p. If some other thread already has the mutex, block
+** until it can be obtained.
+*/
+void sqlite3_mutex_enter(sqlite3_mutex *p){
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexEnter );
+    sqlite3GlobalConfig.mutex.xMutexEnter(p);
+  }
+}
+
+/*
+** Obtain the mutex p. If successful, return SQLITE_OK. Otherwise, if another
+** thread holds the mutex and it cannot be obtained, return SQLITE_BUSY.
+*/
+int sqlite3_mutex_try(sqlite3_mutex *p){
+  int rc = SQLITE_OK;
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexTry );
+    return sqlite3GlobalConfig.mutex.xMutexTry(p);
+  }
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was previously
+** entered by the same thread.  The behavior is undefined if the mutex 
+** is not currently entered. If a NULL pointer is passed as an argument
+** this function is a no-op.
+*/
+void sqlite3_mutex_leave(sqlite3_mutex *p){
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexLeave );
+    sqlite3GlobalConfig.mutex.xMutexLeave(p);
+  }
+}
+
+#ifndef NDEBUG
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use inside assert() statements.
+*/
+int sqlite3_mutex_held(sqlite3_mutex *p){
+  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexHeld );
+  return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p);
+}
+int sqlite3_mutex_notheld(sqlite3_mutex *p){
+  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld );
+  return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p);
+}
+#endif
+
+#endif /* !defined(SQLITE_MUTEX_OMIT) */
diff --git a/src/mutex.h b/src/mutex.h
new file mode 100644
index 0000000..a6806a2
--- /dev/null
+++ b/src/mutex.h
@@ -0,0 +1,71 @@
+/*
+** 2007 August 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the common header for all mutex implementations.
+** The sqliteInt.h header #includes this file so that it is available
+** to all source files.  We break it out in an effort to keep the code
+** better organized.
+**
+** NOTE:  source files should *not* #include this header file directly.
+** Source files should #include the sqliteInt.h file and let that file
+** include this one indirectly.
+*/
+
+
+/*
+** Figure out what version of the code to use.  The choices are
+**
+**   SQLITE_MUTEX_OMIT         No mutex logic.  Not even stubs.  The
+**                             mutexes implementation cannot be overridden
+**                             at start-time.
+**
+**   SQLITE_MUTEX_NOOP         For single-threaded applications.  No
+**                             mutual exclusion is provided.  But this
+**                             implementation can be overridden at
+**                             start-time.
+**
+**   SQLITE_MUTEX_PTHREADS     For multi-threaded applications on Unix.
+**
+**   SQLITE_MUTEX_W32          For multi-threaded applications on Win32.
+*/
+#if !SQLITE_THREADSAFE
+# define SQLITE_MUTEX_OMIT
+#endif
+#if SQLITE_THREADSAFE && !defined(SQLITE_MUTEX_NOOP)
+#  if SQLITE_OS_UNIX
+#    define SQLITE_MUTEX_PTHREADS
+#  elif SQLITE_OS_WIN
+#    define SQLITE_MUTEX_W32
+#  else
+#    define SQLITE_MUTEX_NOOP
+#  endif
+#endif
+
+#ifdef SQLITE_MUTEX_OMIT
+/*
+** If this is a no-op implementation, implement everything as macros.
+*/
+#define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
+#define sqlite3_mutex_free(X)
+#define sqlite3_mutex_enter(X)    
+#define sqlite3_mutex_try(X)      SQLITE_OK
+#define sqlite3_mutex_leave(X)    
+#define sqlite3_mutex_held(X)     ((void)(X),1)
+#define sqlite3_mutex_notheld(X)  ((void)(X),1)
+#define sqlite3MutexAlloc(X)      ((sqlite3_mutex*)8)
+#define sqlite3MutexInit()        SQLITE_OK
+#define sqlite3MutexEnd()
+#define MUTEX_LOGIC(X)
+#else
+#define MUTEX_LOGIC(X)            X
+int sqlite3_mutex_held(sqlite3_mutex*);
+#endif /* defined(SQLITE_MUTEX_OMIT) */
diff --git a/src/mutex_noop.c b/src/mutex_noop.c
new file mode 100644
index 0000000..ecc84b4
--- /dev/null
+++ b/src/mutex_noop.c
@@ -0,0 +1,215 @@
+/*
+** 2008 October 07
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes.
+**
+** This implementation in this file does not provide any mutual
+** exclusion and is thus suitable for use only in applications
+** that use SQLite in a single thread.  The routines defined
+** here are place-holders.  Applications can substitute working
+** mutex routines at start-time using the
+**
+**     sqlite3_config(SQLITE_CONFIG_MUTEX,...)
+**
+** interface.
+**
+** If compiled with SQLITE_DEBUG, then additional logic is inserted
+** that does error checking on mutexes to make sure they are being
+** called correctly.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_MUTEX_OMIT
+
+#ifndef SQLITE_DEBUG
+/*
+** Stub routines for all mutex methods.
+**
+** This routines provide no mutual exclusion or error checking.
+*/
+static int noopMutexInit(void){ return SQLITE_OK; }
+static int noopMutexEnd(void){ return SQLITE_OK; }
+static sqlite3_mutex *noopMutexAlloc(int id){ 
+  UNUSED_PARAMETER(id);
+  return (sqlite3_mutex*)8; 
+}
+static void noopMutexFree(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+static void noopMutexEnter(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+static int noopMutexTry(sqlite3_mutex *p){
+  UNUSED_PARAMETER(p);
+  return SQLITE_OK;
+}
+static void noopMutexLeave(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+
+sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    noopMutexInit,
+    noopMutexEnd,
+    noopMutexAlloc,
+    noopMutexFree,
+    noopMutexEnter,
+    noopMutexTry,
+    noopMutexLeave,
+
+    0,
+    0,
+  };
+
+  return &sMutex;
+}
+#endif /* !SQLITE_DEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+** In this implementation, error checking is provided for testing
+** and debugging purposes.  The mutexes still do not provide any
+** mutual exclusion.
+*/
+
+/*
+** The mutex object
+*/
+typedef struct sqlite3_debug_mutex {
+  int id;     /* The mutex type */
+  int cnt;    /* Number of entries without a matching leave */
+} sqlite3_debug_mutex;
+
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use inside assert() statements.
+*/
+static int debugMutexHeld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  return p==0 || p->cnt>0;
+}
+static int debugMutexNotheld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  return p==0 || p->cnt==0;
+}
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static int debugMutexInit(void){ return SQLITE_OK; }
+static int debugMutexEnd(void){ return SQLITE_OK; }
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated. 
+*/
+static sqlite3_mutex *debugMutexAlloc(int id){
+  static sqlite3_debug_mutex aStatic[SQLITE_MUTEX_STATIC_VFS3 - 1];
+  sqlite3_debug_mutex *pNew = 0;
+  switch( id ){
+    case SQLITE_MUTEX_FAST:
+    case SQLITE_MUTEX_RECURSIVE: {
+      pNew = sqlite3Malloc(sizeof(*pNew));
+      if( pNew ){
+        pNew->id = id;
+        pNew->cnt = 0;
+      }
+      break;
+    }
+    default: {
+#ifdef SQLITE_ENABLE_API_ARMOR
+      if( id-2<0 || id-2>=ArraySize(aStatic) ){
+        (void)SQLITE_MISUSE_BKPT;
+        return 0;
+      }
+#endif
+      pNew = &aStatic[id-2];
+      pNew->id = id;
+      break;
+    }
+  }
+  return (sqlite3_mutex*)pNew;
+}
+
+/*
+** This routine deallocates a previously allocated mutex.
+*/
+static void debugMutexFree(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->cnt==0 );
+  if( p->id==SQLITE_MUTEX_RECURSIVE || p->id==SQLITE_MUTEX_FAST ){
+    sqlite3_free(p);
+  }else{
+#ifdef SQLITE_ENABLE_API_ARMOR
+    (void)SQLITE_MISUSE_BKPT;
+#endif
+  }
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void debugMutexEnter(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+  p->cnt++;
+}
+static int debugMutexTry(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+  p->cnt++;
+  return SQLITE_OK;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void debugMutexLeave(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( debugMutexHeld(pX) );
+  p->cnt--;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+}
+
+sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    debugMutexInit,
+    debugMutexEnd,
+    debugMutexAlloc,
+    debugMutexFree,
+    debugMutexEnter,
+    debugMutexTry,
+    debugMutexLeave,
+
+    debugMutexHeld,
+    debugMutexNotheld
+  };
+
+  return &sMutex;
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** If compiled with SQLITE_MUTEX_NOOP, then the no-op mutex implementation
+** is used regardless of the run-time threadsafety setting.
+*/
+#ifdef SQLITE_MUTEX_NOOP
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  return sqlite3NoopMutex();
+}
+#endif /* defined(SQLITE_MUTEX_NOOP) */
+#endif /* !defined(SQLITE_MUTEX_OMIT) */
diff --git a/src/mutex_unix.c b/src/mutex_unix.c
new file mode 100644
index 0000000..beae877
--- /dev/null
+++ b/src/mutex_unix.c
@@ -0,0 +1,394 @@
+/*
+** 2007 August 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes for pthreads
+*/
+#include "sqliteInt.h"
+
+/*
+** The code in this file is only used if we are compiling threadsafe
+** under unix with pthreads.
+**
+** Note that this implementation requires a version of pthreads that
+** supports recursive mutexes.
+*/
+#ifdef SQLITE_MUTEX_PTHREADS
+
+#include <pthread.h>
+
+/*
+** The sqlite3_mutex.id, sqlite3_mutex.nRef, and sqlite3_mutex.owner fields
+** are necessary under two conditions:  (1) Debug builds and (2) using
+** home-grown mutexes.  Encapsulate these conditions into a single #define.
+*/
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HOMEGROWN_RECURSIVE_MUTEX)
+# define SQLITE_MUTEX_NREF 1
+#else
+# define SQLITE_MUTEX_NREF 0
+#endif
+
+/*
+** Each recursive mutex is an instance of the following structure.
+*/
+struct sqlite3_mutex {
+  pthread_mutex_t mutex;     /* Mutex controlling the lock */
+#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
+  int id;                    /* Mutex type */
+#endif
+#if SQLITE_MUTEX_NREF
+  volatile int nRef;         /* Number of entrances */
+  volatile pthread_t owner;  /* Thread that is within this mutex */
+  int trace;                 /* True to trace changes */
+#endif
+};
+#if SQLITE_MUTEX_NREF
+# define SQLITE3_MUTEX_INITIALIZER(id) \
+     {PTHREAD_MUTEX_INITIALIZER,id,0,(pthread_t)0,0}
+#elif defined(SQLITE_ENABLE_API_ARMOR)
+# define SQLITE3_MUTEX_INITIALIZER(id) { PTHREAD_MUTEX_INITIALIZER, id }
+#else
+#define SQLITE3_MUTEX_INITIALIZER(id) { PTHREAD_MUTEX_INITIALIZER }
+#endif
+
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use only inside assert() statements.  On some platforms,
+** there might be race conditions that can cause these routines to
+** deliver incorrect results.  In particular, if pthread_equal() is
+** not an atomic operation, then these routines might delivery
+** incorrect results.  On most platforms, pthread_equal() is a
+** comparison of two integers and is therefore atomic.  But we are
+** told that HPUX is not such a platform.  If so, then these routines
+** will not always work correctly on HPUX.
+**
+** On those platforms where pthread_equal() is not atomic, SQLite
+** should be compiled without -DSQLITE_DEBUG and with -DNDEBUG to
+** make sure no assert() statements are evaluated and hence these
+** routines are never called.
+*/
+#if !defined(NDEBUG) || defined(SQLITE_DEBUG)
+static int pthreadMutexHeld(sqlite3_mutex *p){
+  return (p->nRef!=0 && pthread_equal(p->owner, pthread_self()));
+}
+static int pthreadMutexNotheld(sqlite3_mutex *p){
+  return p->nRef==0 || pthread_equal(p->owner, pthread_self())==0;
+}
+#endif
+
+/*
+** Try to provide a memory barrier operation, needed for initialization
+** and also for the implementation of xShmBarrier in the VFS in cases
+** where SQLite is compiled without mutexes.
+*/
+void sqlite3MemoryBarrier(void){
+#if defined(SQLITE_MEMORY_BARRIER)
+  SQLITE_MEMORY_BARRIER;
+#elif defined(__GNUC__) && GCC_VERSION>=4001000
+  __sync_synchronize();
+#endif
+}
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static int pthreadMutexInit(void){ return SQLITE_OK; }
+static int pthreadMutexEnd(void){ return SQLITE_OK; }
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated.  SQLite
+** will unwind its stack and return an error.  The argument
+** to sqlite3_mutex_alloc() is one of these integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST
+** <li>  SQLITE_MUTEX_RECURSIVE
+** <li>  SQLITE_MUTEX_STATIC_MAIN
+** <li>  SQLITE_MUTEX_STATIC_MEM
+** <li>  SQLITE_MUTEX_STATIC_OPEN
+** <li>  SQLITE_MUTEX_STATIC_PRNG
+** <li>  SQLITE_MUTEX_STATIC_LRU
+** <li>  SQLITE_MUTEX_STATIC_PMEM
+** <li>  SQLITE_MUTEX_STATIC_APP1
+** <li>  SQLITE_MUTEX_STATIC_APP2
+** <li>  SQLITE_MUTEX_STATIC_APP3
+** <li>  SQLITE_MUTEX_STATIC_VFS1
+** <li>  SQLITE_MUTEX_STATIC_VFS2
+** <li>  SQLITE_MUTEX_STATIC_VFS3
+** </ul>
+**
+** The first two constants cause sqlite3_mutex_alloc() to create
+** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  But SQLite will only request a recursive mutex in
+** cases where it really needs one.  If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** The other allowed parameters to sqlite3_mutex_alloc() each return
+** a pointer to a static preexisting mutex.  Six static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  But for the static
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+*/
+static sqlite3_mutex *pthreadMutexAlloc(int iType){
+  static sqlite3_mutex staticMutexes[] = {
+    SQLITE3_MUTEX_INITIALIZER(2),
+    SQLITE3_MUTEX_INITIALIZER(3),
+    SQLITE3_MUTEX_INITIALIZER(4),
+    SQLITE3_MUTEX_INITIALIZER(5),
+    SQLITE3_MUTEX_INITIALIZER(6),
+    SQLITE3_MUTEX_INITIALIZER(7),
+    SQLITE3_MUTEX_INITIALIZER(8),
+    SQLITE3_MUTEX_INITIALIZER(9),
+    SQLITE3_MUTEX_INITIALIZER(10),
+    SQLITE3_MUTEX_INITIALIZER(11),
+    SQLITE3_MUTEX_INITIALIZER(12),
+    SQLITE3_MUTEX_INITIALIZER(13)
+  };
+  sqlite3_mutex *p;
+  switch( iType ){
+    case SQLITE_MUTEX_RECURSIVE: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+        /* If recursive mutexes are not available, we will have to
+        ** build our own.  See below. */
+        pthread_mutex_init(&p->mutex, 0);
+#else
+        /* Use a recursive mutex if it is available */
+        pthread_mutexattr_t recursiveAttr;
+        pthread_mutexattr_init(&recursiveAttr);
+        pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE);
+        pthread_mutex_init(&p->mutex, &recursiveAttr);
+        pthread_mutexattr_destroy(&recursiveAttr);
+#endif
+#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
+        p->id = SQLITE_MUTEX_RECURSIVE;
+#endif
+      }
+      break;
+    }
+    case SQLITE_MUTEX_FAST: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+        pthread_mutex_init(&p->mutex, 0);
+#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
+        p->id = SQLITE_MUTEX_FAST;
+#endif
+      }
+      break;
+    }
+    default: {
+#ifdef SQLITE_ENABLE_API_ARMOR
+      if( iType-2<0 || iType-2>=ArraySize(staticMutexes) ){
+        (void)SQLITE_MISUSE_BKPT;
+        return 0;
+      }
+#endif
+      p = &staticMutexes[iType-2];
+      break;
+    }
+  }
+#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
+  assert( p==0 || p->id==iType );
+#endif
+  return p;
+}
+
+
+/*
+** This routine deallocates a previously
+** allocated mutex.  SQLite is careful to deallocate every
+** mutex that it allocates.
+*/
+static void pthreadMutexFree(sqlite3_mutex *p){
+  assert( p->nRef==0 );
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE )
+#endif
+  {
+    pthread_mutex_destroy(&p->mutex);
+    sqlite3_free(p);
+  }
+#ifdef SQLITE_ENABLE_API_ARMOR
+  else{
+    (void)SQLITE_MISUSE_BKPT;
+  }
+#endif
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void pthreadMutexEnter(sqlite3_mutex *p){
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
+
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  /* If recursive mutexes are not available, then we have to grow
+  ** our own.  This implementation assumes that pthread_equal()
+  ** is atomic - that it cannot be deceived into thinking self
+  ** and p->owner are equal if p->owner changes between two values
+  ** that are not equal to self while the comparison is taking place.
+  ** This implementation also assumes a coherent cache - that
+  ** separate processes cannot read different values from the same
+  ** address at the same time.  If either of these two conditions
+  ** are not met, then the mutexes will fail and problems will result.
+  */
+  {
+    pthread_t self = pthread_self();
+    if( p->nRef>0 && pthread_equal(p->owner, self) ){
+      p->nRef++;
+    }else{
+      pthread_mutex_lock(&p->mutex);
+      assert( p->nRef==0 );
+      p->owner = self;
+      p->nRef = 1;
+    }
+  }
+#else
+  /* Use the built-in recursive mutexes if they are available.
+  */
+  pthread_mutex_lock(&p->mutex);
+#if SQLITE_MUTEX_NREF
+  assert( p->nRef>0 || p->owner==0 );
+  p->owner = pthread_self();
+  p->nRef++;
+#endif
+#endif
+
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+}
+static int pthreadMutexTry(sqlite3_mutex *p){
+  int rc;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
+
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  /* If recursive mutexes are not available, then we have to grow
+  ** our own.  This implementation assumes that pthread_equal()
+  ** is atomic - that it cannot be deceived into thinking self
+  ** and p->owner are equal if p->owner changes between two values
+  ** that are not equal to self while the comparison is taking place.
+  ** This implementation also assumes a coherent cache - that
+  ** separate processes cannot read different values from the same
+  ** address at the same time.  If either of these two conditions
+  ** are not met, then the mutexes will fail and problems will result.
+  */
+  {
+    pthread_t self = pthread_self();
+    if( p->nRef>0 && pthread_equal(p->owner, self) ){
+      p->nRef++;
+      rc = SQLITE_OK;
+    }else if( pthread_mutex_trylock(&p->mutex)==0 ){
+      assert( p->nRef==0 );
+      p->owner = self;
+      p->nRef = 1;
+      rc = SQLITE_OK;
+    }else{
+      rc = SQLITE_BUSY;
+    }
+  }
+#else
+  /* Use the built-in recursive mutexes if they are available.
+  */
+  if( pthread_mutex_trylock(&p->mutex)==0 ){
+#if SQLITE_MUTEX_NREF
+    p->owner = pthread_self();
+    p->nRef++;
+#endif
+    rc = SQLITE_OK;
+  }else{
+    rc = SQLITE_BUSY;
+  }
+#endif
+
+#ifdef SQLITE_DEBUG
+  if( rc==SQLITE_OK && p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void pthreadMutexLeave(sqlite3_mutex *p){
+  assert( pthreadMutexHeld(p) );
+#if SQLITE_MUTEX_NREF
+  p->nRef--;
+  if( p->nRef==0 ) p->owner = 0;
+#endif
+  assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  if( p->nRef==0 ){
+    pthread_mutex_unlock(&p->mutex);
+  }
+#else
+  pthread_mutex_unlock(&p->mutex);
+#endif
+
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+}
+
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    pthreadMutexInit,
+    pthreadMutexEnd,
+    pthreadMutexAlloc,
+    pthreadMutexFree,
+    pthreadMutexEnter,
+    pthreadMutexTry,
+    pthreadMutexLeave,
+#ifdef SQLITE_DEBUG
+    pthreadMutexHeld,
+    pthreadMutexNotheld
+#else
+    0,
+    0
+#endif
+  };
+
+  return &sMutex;
+}
+
+#endif /* SQLITE_MUTEX_PTHREADS */
diff --git a/src/mutex_w32.c b/src/mutex_w32.c
new file mode 100644
index 0000000..7eb5b50
--- /dev/null
+++ b/src/mutex_w32.c
@@ -0,0 +1,399 @@
+/*
+** 2007 August 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes for Win32.
+*/
+#include "sqliteInt.h"
+
+#if SQLITE_OS_WIN
+/*
+** Include code that is common to all os_*.c files
+*/
+#include "os_common.h"
+
+/*
+** Include the header file for the Windows VFS.
+*/
+#include "os_win.h"
+#endif
+
+/*
+** The code in this file is only used if we are compiling multithreaded
+** on a Win32 system.
+*/
+#ifdef SQLITE_MUTEX_W32
+
+/*
+** Each recursive mutex is an instance of the following structure.
+*/
+struct sqlite3_mutex {
+  CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
+  int id;                    /* Mutex type */
+#ifdef SQLITE_DEBUG
+  volatile int nRef;         /* Number of entrances */
+  volatile DWORD owner;      /* Thread holding this mutex */
+  volatile LONG trace;       /* True to trace changes */
+#endif
+};
+
+/*
+** These are the initializer values used when declaring a "static" mutex
+** on Win32.  It should be noted that all mutexes require initialization
+** on the Win32 platform.
+*/
+#define SQLITE_W32_MUTEX_INITIALIZER { 0 }
+
+#ifdef SQLITE_DEBUG
+#define SQLITE3_MUTEX_INITIALIZER(id) { SQLITE_W32_MUTEX_INITIALIZER, id, \
+                                    0L, (DWORD)0, 0 }
+#else
+#define SQLITE3_MUTEX_INITIALIZER(id) { SQLITE_W32_MUTEX_INITIALIZER, id }
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use only inside assert() statements.
+*/
+static int winMutexHeld(sqlite3_mutex *p){
+  return p->nRef!=0 && p->owner==GetCurrentThreadId();
+}
+
+static int winMutexNotheld2(sqlite3_mutex *p, DWORD tid){
+  return p->nRef==0 || p->owner!=tid;
+}
+
+static int winMutexNotheld(sqlite3_mutex *p){
+  DWORD tid = GetCurrentThreadId();
+  return winMutexNotheld2(p, tid);
+}
+#endif
+
+/*
+** Try to provide a memory barrier operation, needed for initialization
+** and also for the xShmBarrier method of the VFS in cases when SQLite is
+** compiled without mutexes (SQLITE_THREADSAFE=0).
+*/
+void sqlite3MemoryBarrier(void){
+#if defined(SQLITE_MEMORY_BARRIER)
+  SQLITE_MEMORY_BARRIER;
+#elif defined(__GNUC__)
+  __sync_synchronize();
+#elif MSVC_VERSION>=1400
+  _ReadWriteBarrier();
+#elif defined(MemoryBarrier)
+  MemoryBarrier();
+#endif
+}
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static sqlite3_mutex winMutex_staticMutexes[] = {
+  SQLITE3_MUTEX_INITIALIZER(2),
+  SQLITE3_MUTEX_INITIALIZER(3),
+  SQLITE3_MUTEX_INITIALIZER(4),
+  SQLITE3_MUTEX_INITIALIZER(5),
+  SQLITE3_MUTEX_INITIALIZER(6),
+  SQLITE3_MUTEX_INITIALIZER(7),
+  SQLITE3_MUTEX_INITIALIZER(8),
+  SQLITE3_MUTEX_INITIALIZER(9),
+  SQLITE3_MUTEX_INITIALIZER(10),
+  SQLITE3_MUTEX_INITIALIZER(11),
+  SQLITE3_MUTEX_INITIALIZER(12),
+  SQLITE3_MUTEX_INITIALIZER(13)
+};
+
+static int winMutex_isInit = 0;
+static int winMutex_isNt = -1; /* <0 means "need to query" */
+
+/* As the winMutexInit() and winMutexEnd() functions are called as part
+** of the sqlite3_initialize() and sqlite3_shutdown() processing, the
+** "interlocked" magic used here is probably not strictly necessary.
+*/
+static LONG SQLITE_WIN32_VOLATILE winMutex_lock = 0;
+
+int sqlite3_win32_is_nt(void); /* os_win.c */
+void sqlite3_win32_sleep(DWORD milliseconds); /* os_win.c */
+
+static int winMutexInit(void){
+  /* The first to increment to 1 does actual initialization */
+  if( InterlockedCompareExchange(&winMutex_lock, 1, 0)==0 ){
+    int i;
+    for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
+#if SQLITE_OS_WINRT
+      InitializeCriticalSectionEx(&winMutex_staticMutexes[i].mutex, 0, 0);
+#else
+      InitializeCriticalSection(&winMutex_staticMutexes[i].mutex);
+#endif
+    }
+    winMutex_isInit = 1;
+  }else{
+    /* Another thread is (in the process of) initializing the static
+    ** mutexes */
+    while( !winMutex_isInit ){
+      sqlite3_win32_sleep(1);
+    }
+  }
+  return SQLITE_OK;
+}
+
+static int winMutexEnd(void){
+  /* The first to decrement to 0 does actual shutdown
+  ** (which should be the last to shutdown.) */
+  if( InterlockedCompareExchange(&winMutex_lock, 0, 1)==1 ){
+    if( winMutex_isInit==1 ){
+      int i;
+      for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
+        DeleteCriticalSection(&winMutex_staticMutexes[i].mutex);
+      }
+      winMutex_isInit = 0;
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated.  SQLite
+** will unwind its stack and return an error.  The argument
+** to sqlite3_mutex_alloc() is one of these integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST
+** <li>  SQLITE_MUTEX_RECURSIVE
+** <li>  SQLITE_MUTEX_STATIC_MAIN
+** <li>  SQLITE_MUTEX_STATIC_MEM
+** <li>  SQLITE_MUTEX_STATIC_OPEN
+** <li>  SQLITE_MUTEX_STATIC_PRNG
+** <li>  SQLITE_MUTEX_STATIC_LRU
+** <li>  SQLITE_MUTEX_STATIC_PMEM
+** <li>  SQLITE_MUTEX_STATIC_APP1
+** <li>  SQLITE_MUTEX_STATIC_APP2
+** <li>  SQLITE_MUTEX_STATIC_APP3
+** <li>  SQLITE_MUTEX_STATIC_VFS1
+** <li>  SQLITE_MUTEX_STATIC_VFS2
+** <li>  SQLITE_MUTEX_STATIC_VFS3
+** </ul>
+**
+** The first two constants cause sqlite3_mutex_alloc() to create
+** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  But SQLite will only request a recursive mutex in
+** cases where it really needs one.  If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** The other allowed parameters to sqlite3_mutex_alloc() each return
+** a pointer to a static preexisting mutex.  Six static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  But for the static
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+*/
+static sqlite3_mutex *winMutexAlloc(int iType){
+  sqlite3_mutex *p;
+
+  switch( iType ){
+    case SQLITE_MUTEX_FAST:
+    case SQLITE_MUTEX_RECURSIVE: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+        p->id = iType;
+#ifdef SQLITE_DEBUG
+#ifdef SQLITE_WIN32_MUTEX_TRACE_DYNAMIC
+        p->trace = 1;
+#endif
+#endif
+#if SQLITE_OS_WINRT
+        InitializeCriticalSectionEx(&p->mutex, 0, 0);
+#else
+        InitializeCriticalSection(&p->mutex);
+#endif
+      }
+      break;
+    }
+    default: {
+#ifdef SQLITE_ENABLE_API_ARMOR
+      if( iType-2<0 || iType-2>=ArraySize(winMutex_staticMutexes) ){
+        (void)SQLITE_MISUSE_BKPT;
+        return 0;
+      }
+#endif
+      p = &winMutex_staticMutexes[iType-2];
+#ifdef SQLITE_DEBUG
+#ifdef SQLITE_WIN32_MUTEX_TRACE_STATIC
+      InterlockedCompareExchange(&p->trace, 1, 0);
+#endif
+#endif
+      break;
+    }
+  }
+  assert( p==0 || p->id==iType );
+  return p;
+}
+
+
+/*
+** This routine deallocates a previously
+** allocated mutex.  SQLite is careful to deallocate every
+** mutex that it allocates.
+*/
+static void winMutexFree(sqlite3_mutex *p){
+  assert( p );
+  assert( p->nRef==0 && p->owner==0 );
+  if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ){
+    DeleteCriticalSection(&p->mutex);
+    sqlite3_free(p);
+  }else{
+#ifdef SQLITE_ENABLE_API_ARMOR
+    (void)SQLITE_MISUSE_BKPT;
+#endif
+  }
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void winMutexEnter(sqlite3_mutex *p){
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  DWORD tid = GetCurrentThreadId();
+#endif
+#ifdef SQLITE_DEBUG
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
+#else
+  assert( p );
+#endif
+  assert( winMutex_isInit==1 );
+  EnterCriticalSection(&p->mutex);
+#ifdef SQLITE_DEBUG
+  assert( p->nRef>0 || p->owner==0 );
+  p->owner = tid;
+  p->nRef++;
+  if( p->trace ){
+    OSTRACE(("ENTER-MUTEX tid=%lu, mutex(%d)=%p (%d), nRef=%d\n",
+             tid, p->id, p, p->trace, p->nRef));
+  }
+#endif
+}
+
+static int winMutexTry(sqlite3_mutex *p){
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  DWORD tid = GetCurrentThreadId();
+#endif
+  int rc = SQLITE_BUSY;
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
+  /*
+  ** The sqlite3_mutex_try() routine is very rarely used, and when it
+  ** is used it is merely an optimization.  So it is OK for it to always
+  ** fail.
+  **
+  ** The TryEnterCriticalSection() interface is only available on WinNT.
+  ** And some windows compilers complain if you try to use it without
+  ** first doing some #defines that prevent SQLite from building on Win98.
+  ** For that reason, we will omit this optimization for now.  See
+  ** ticket #2685.
+  */
+#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0400
+  assert( winMutex_isInit==1 );
+  assert( winMutex_isNt>=-1 && winMutex_isNt<=1 );
+  if( winMutex_isNt<0 ){
+    winMutex_isNt = sqlite3_win32_is_nt();
+  }
+  assert( winMutex_isNt==0 || winMutex_isNt==1 );
+  if( winMutex_isNt && TryEnterCriticalSection(&p->mutex) ){
+#ifdef SQLITE_DEBUG
+    p->owner = tid;
+    p->nRef++;
+#endif
+    rc = SQLITE_OK;
+  }
+#else
+  UNUSED_PARAMETER(p);
+#endif
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    OSTRACE(("TRY-MUTEX tid=%lu, mutex(%d)=%p (%d), owner=%lu, nRef=%d, rc=%s\n",
+             tid, p->id, p, p->trace, p->owner, p->nRef, sqlite3ErrName(rc)));
+  }
+#endif
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void winMutexLeave(sqlite3_mutex *p){
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  DWORD tid = GetCurrentThreadId();
+#endif
+  assert( p );
+#ifdef SQLITE_DEBUG
+  assert( p->nRef>0 );
+  assert( p->owner==tid );
+  p->nRef--;
+  if( p->nRef==0 ) p->owner = 0;
+  assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+#endif
+  assert( winMutex_isInit==1 );
+  LeaveCriticalSection(&p->mutex);
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    OSTRACE(("LEAVE-MUTEX tid=%lu, mutex(%d)=%p (%d), nRef=%d\n",
+             tid, p->id, p, p->trace, p->nRef));
+  }
+#endif
+}
+
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    winMutexInit,
+    winMutexEnd,
+    winMutexAlloc,
+    winMutexFree,
+    winMutexEnter,
+    winMutexTry,
+    winMutexLeave,
+#ifdef SQLITE_DEBUG
+    winMutexHeld,
+    winMutexNotheld
+#else
+    0,
+    0
+#endif
+  };
+  return &sMutex;
+}
+
+#endif /* SQLITE_MUTEX_W32 */
diff --git a/src/notify.c b/src/notify.c
new file mode 100644
index 0000000..6a4cab8
--- /dev/null
+++ b/src/notify.c
@@ -0,0 +1,335 @@
+/*
+** 2009 March 3
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of the sqlite3_unlock_notify()
+** API method and its associated functionality.
+*/
+#include "sqliteInt.h"
+#include "btreeInt.h"
+
+/* Omit this entire file if SQLITE_ENABLE_UNLOCK_NOTIFY is not defined. */
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+
+/*
+** Public interfaces:
+**
+**   sqlite3ConnectionBlocked()
+**   sqlite3ConnectionUnlocked()
+**   sqlite3ConnectionClosed()
+**   sqlite3_unlock_notify()
+*/
+
+#define assertMutexHeld() \
+  assert( sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN)) )
+
+/*
+** Head of a linked list of all sqlite3 objects created by this process
+** for which either sqlite3.pBlockingConnection or sqlite3.pUnlockConnection
+** is not NULL. This variable may only accessed while the STATIC_MAIN
+** mutex is held.
+*/
+static sqlite3 *SQLITE_WSD sqlite3BlockedList = 0;
+
+#ifndef NDEBUG
+/*
+** This function is a complex assert() that verifies the following 
+** properties of the blocked connections list:
+**
+**   1) Each entry in the list has a non-NULL value for either 
+**      pUnlockConnection or pBlockingConnection, or both.
+**
+**   2) All entries in the list that share a common value for 
+**      xUnlockNotify are grouped together.
+**
+**   3) If the argument db is not NULL, then none of the entries in the
+**      blocked connections list have pUnlockConnection or pBlockingConnection
+**      set to db. This is used when closing connection db.
+*/
+static void checkListProperties(sqlite3 *db){
+  sqlite3 *p;
+  for(p=sqlite3BlockedList; p; p=p->pNextBlocked){
+    int seen = 0;
+    sqlite3 *p2;
+
+    /* Verify property (1) */
+    assert( p->pUnlockConnection || p->pBlockingConnection );
+
+    /* Verify property (2) */
+    for(p2=sqlite3BlockedList; p2!=p; p2=p2->pNextBlocked){
+      if( p2->xUnlockNotify==p->xUnlockNotify ) seen = 1;
+      assert( p2->xUnlockNotify==p->xUnlockNotify || !seen );
+      assert( db==0 || p->pUnlockConnection!=db );
+      assert( db==0 || p->pBlockingConnection!=db );
+    }
+  }
+}
+#else
+# define checkListProperties(x)
+#endif
+
+/*
+** Remove connection db from the blocked connections list. If connection
+** db is not currently a part of the list, this function is a no-op.
+*/
+static void removeFromBlockedList(sqlite3 *db){
+  sqlite3 **pp;
+  assertMutexHeld();
+  for(pp=&sqlite3BlockedList; *pp; pp = &(*pp)->pNextBlocked){
+    if( *pp==db ){
+      *pp = (*pp)->pNextBlocked;
+      break;
+    }
+  }
+}
+
+/*
+** Add connection db to the blocked connections list. It is assumed
+** that it is not already a part of the list.
+*/
+static void addToBlockedList(sqlite3 *db){
+  sqlite3 **pp;
+  assertMutexHeld();
+  for(
+    pp=&sqlite3BlockedList; 
+    *pp && (*pp)->xUnlockNotify!=db->xUnlockNotify; 
+    pp=&(*pp)->pNextBlocked
+  );
+  db->pNextBlocked = *pp;
+  *pp = db;
+}
+
+/*
+** Obtain the STATIC_MAIN mutex.
+*/
+static void enterMutex(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN));
+  checkListProperties(0);
+}
+
+/*
+** Release the STATIC_MAIN mutex.
+*/
+static void leaveMutex(void){
+  assertMutexHeld();
+  checkListProperties(0);
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN));
+}
+
+/*
+** Register an unlock-notify callback.
+**
+** This is called after connection "db" has attempted some operation
+** but has received an SQLITE_LOCKED error because another connection
+** (call it pOther) in the same process was busy using the same shared
+** cache.  pOther is found by looking at db->pBlockingConnection.
+**
+** If there is no blocking connection, the callback is invoked immediately,
+** before this routine returns.
+**
+** If pOther is already blocked on db, then report SQLITE_LOCKED, to indicate
+** a deadlock.
+**
+** Otherwise, make arrangements to invoke xNotify when pOther drops
+** its locks.
+**
+** Each call to this routine overrides any prior callbacks registered
+** on the same "db".  If xNotify==0 then any prior callbacks are immediately
+** cancelled.
+*/
+int sqlite3_unlock_notify(
+  sqlite3 *db,
+  void (*xNotify)(void **, int),
+  void *pArg
+){
+  int rc = SQLITE_OK;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  enterMutex();
+
+  if( xNotify==0 ){
+    removeFromBlockedList(db);
+    db->pBlockingConnection = 0;
+    db->pUnlockConnection = 0;
+    db->xUnlockNotify = 0;
+    db->pUnlockArg = 0;
+  }else if( 0==db->pBlockingConnection ){
+    /* The blocking transaction has been concluded. Or there never was a 
+    ** blocking transaction. In either case, invoke the notify callback
+    ** immediately. 
+    */
+    xNotify(&pArg, 1);
+  }else{
+    sqlite3 *p;
+
+    for(p=db->pBlockingConnection; p && p!=db; p=p->pUnlockConnection){}
+    if( p ){
+      rc = SQLITE_LOCKED;              /* Deadlock detected. */
+    }else{
+      db->pUnlockConnection = db->pBlockingConnection;
+      db->xUnlockNotify = xNotify;
+      db->pUnlockArg = pArg;
+      removeFromBlockedList(db);
+      addToBlockedList(db);
+    }
+  }
+
+  leaveMutex();
+  assert( !db->mallocFailed );
+  sqlite3ErrorWithMsg(db, rc, (rc?"database is deadlocked":0));
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** This function is called while stepping or preparing a statement 
+** associated with connection db. The operation will return SQLITE_LOCKED
+** to the user because it requires a lock that will not be available
+** until connection pBlocker concludes its current transaction.
+*/
+void sqlite3ConnectionBlocked(sqlite3 *db, sqlite3 *pBlocker){
+  enterMutex();
+  if( db->pBlockingConnection==0 && db->pUnlockConnection==0 ){
+    addToBlockedList(db);
+  }
+  db->pBlockingConnection = pBlocker;
+  leaveMutex();
+}
+
+/*
+** This function is called when
+** the transaction opened by database db has just finished. Locks held 
+** by database connection db have been released.
+**
+** This function loops through each entry in the blocked connections
+** list and does the following:
+**
+**   1) If the sqlite3.pBlockingConnection member of a list entry is
+**      set to db, then set pBlockingConnection=0.
+**
+**   2) If the sqlite3.pUnlockConnection member of a list entry is
+**      set to db, then invoke the configured unlock-notify callback and
+**      set pUnlockConnection=0.
+**
+**   3) If the two steps above mean that pBlockingConnection==0 and
+**      pUnlockConnection==0, remove the entry from the blocked connections
+**      list.
+*/
+void sqlite3ConnectionUnlocked(sqlite3 *db){
+  void (*xUnlockNotify)(void **, int) = 0; /* Unlock-notify cb to invoke */
+  int nArg = 0;                            /* Number of entries in aArg[] */
+  sqlite3 **pp;                            /* Iterator variable */
+  void **aArg;               /* Arguments to the unlock callback */
+  void **aDyn = 0;           /* Dynamically allocated space for aArg[] */
+  void *aStatic[16];         /* Starter space for aArg[].  No malloc required */
+
+  aArg = aStatic;
+  enterMutex();         /* Enter STATIC_MAIN mutex */
+
+  /* This loop runs once for each entry in the blocked-connections list. */
+  for(pp=&sqlite3BlockedList; *pp; /* no-op */ ){
+    sqlite3 *p = *pp;
+
+    /* Step 1. */
+    if( p->pBlockingConnection==db ){
+      p->pBlockingConnection = 0;
+    }
+
+    /* Step 2. */
+    if( p->pUnlockConnection==db ){
+      assert( p->xUnlockNotify );
+      if( p->xUnlockNotify!=xUnlockNotify && nArg!=0 ){
+        xUnlockNotify(aArg, nArg);
+        nArg = 0;
+      }
+
+      sqlite3BeginBenignMalloc();
+      assert( aArg==aDyn || (aDyn==0 && aArg==aStatic) );
+      assert( nArg<=(int)ArraySize(aStatic) || aArg==aDyn );
+      if( (!aDyn && nArg==(int)ArraySize(aStatic))
+       || (aDyn && nArg==(int)(sqlite3MallocSize(aDyn)/sizeof(void*)))
+      ){
+        /* The aArg[] array needs to grow. */
+        void **pNew = (void **)sqlite3Malloc(nArg*sizeof(void *)*2);
+        if( pNew ){
+          memcpy(pNew, aArg, nArg*sizeof(void *));
+          sqlite3_free(aDyn);
+          aDyn = aArg = pNew;
+        }else{
+          /* This occurs when the array of context pointers that need to
+          ** be passed to the unlock-notify callback is larger than the
+          ** aStatic[] array allocated on the stack and the attempt to 
+          ** allocate a larger array from the heap has failed.
+          **
+          ** This is a difficult situation to handle. Returning an error
+          ** code to the caller is insufficient, as even if an error code
+          ** is returned the transaction on connection db will still be
+          ** closed and the unlock-notify callbacks on blocked connections
+          ** will go unissued. This might cause the application to wait
+          ** indefinitely for an unlock-notify callback that will never 
+          ** arrive.
+          **
+          ** Instead, invoke the unlock-notify callback with the context
+          ** array already accumulated. We can then clear the array and
+          ** begin accumulating any further context pointers without 
+          ** requiring any dynamic allocation. This is sub-optimal because
+          ** it means that instead of one callback with a large array of
+          ** context pointers the application will receive two or more
+          ** callbacks with smaller arrays of context pointers, which will
+          ** reduce the applications ability to prioritize multiple 
+          ** connections. But it is the best that can be done under the
+          ** circumstances.
+          */
+          xUnlockNotify(aArg, nArg);
+          nArg = 0;
+        }
+      }
+      sqlite3EndBenignMalloc();
+
+      aArg[nArg++] = p->pUnlockArg;
+      xUnlockNotify = p->xUnlockNotify;
+      p->pUnlockConnection = 0;
+      p->xUnlockNotify = 0;
+      p->pUnlockArg = 0;
+    }
+
+    /* Step 3. */
+    if( p->pBlockingConnection==0 && p->pUnlockConnection==0 ){
+      /* Remove connection p from the blocked connections list. */
+      *pp = p->pNextBlocked;
+      p->pNextBlocked = 0;
+    }else{
+      pp = &p->pNextBlocked;
+    }
+  }
+
+  if( nArg!=0 ){
+    xUnlockNotify(aArg, nArg);
+  }
+  sqlite3_free(aDyn);
+  leaveMutex();         /* Leave STATIC_MAIN mutex */
+}
+
+/*
+** This is called when the database connection passed as an argument is 
+** being closed. The connection is removed from the blocked list.
+*/
+void sqlite3ConnectionClosed(sqlite3 *db){
+  sqlite3ConnectionUnlocked(db);
+  enterMutex();
+  removeFromBlockedList(db);
+  checkListProperties(db);
+  leaveMutex();
+}
+#endif
diff --git a/src/os.c b/src/os.c
new file mode 100644
index 0000000..a9fc732
--- /dev/null
+++ b/src/os.c
@@ -0,0 +1,447 @@
+/*
+** 2005 November 29
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains OS interface code that is common to all
+** architectures.
+*/
+#include "sqliteInt.h"
+
+/*
+** If we compile with the SQLITE_TEST macro set, then the following block
+** of code will give us the ability to simulate a disk I/O error.  This
+** is used for testing the I/O recovery logic.
+*/
+#if defined(SQLITE_TEST)
+int sqlite3_io_error_hit = 0;            /* Total number of I/O Errors */
+int sqlite3_io_error_hardhit = 0;        /* Number of non-benign errors */
+int sqlite3_io_error_pending = 0;        /* Count down to first I/O error */
+int sqlite3_io_error_persist = 0;        /* True if I/O errors persist */
+int sqlite3_io_error_benign = 0;         /* True if errors are benign */
+int sqlite3_diskfull_pending = 0;
+int sqlite3_diskfull = 0;
+#endif /* defined(SQLITE_TEST) */
+
+/*
+** When testing, also keep a count of the number of open files.
+*/
+#if defined(SQLITE_TEST)
+int sqlite3_open_file_count = 0;
+#endif /* defined(SQLITE_TEST) */
+
+/*
+** The default SQLite sqlite3_vfs implementations do not allocate
+** memory (actually, os_unix.c allocates a small amount of memory
+** from within OsOpen()), but some third-party implementations may.
+** So we test the effects of a malloc() failing and the sqlite3OsXXX()
+** function returning SQLITE_IOERR_NOMEM using the DO_OS_MALLOC_TEST macro.
+**
+** The following functions are instrumented for malloc() failure
+** testing:
+**
+**     sqlite3OsRead()
+**     sqlite3OsWrite()
+**     sqlite3OsSync()
+**     sqlite3OsFileSize()
+**     sqlite3OsLock()
+**     sqlite3OsCheckReservedLock()
+**     sqlite3OsFileControl()
+**     sqlite3OsShmMap()
+**     sqlite3OsOpen()
+**     sqlite3OsDelete()
+**     sqlite3OsAccess()
+**     sqlite3OsFullPathname()
+**
+*/
+#if defined(SQLITE_TEST)
+int sqlite3_memdebug_vfs_oom_test = 1;
+  #define DO_OS_MALLOC_TEST(x)                                       \
+  if (sqlite3_memdebug_vfs_oom_test && (!x || !sqlite3JournalIsInMemory(x))) { \
+    void *pTstAlloc = sqlite3Malloc(10);                             \
+    if (!pTstAlloc) return SQLITE_IOERR_NOMEM_BKPT;                  \
+    sqlite3_free(pTstAlloc);                                         \
+  }
+#else
+  #define DO_OS_MALLOC_TEST(x)
+#endif
+
+/*
+** The following routines are convenience wrappers around methods
+** of the sqlite3_file object.  This is mostly just syntactic sugar. All
+** of this would be completely automatic if SQLite were coded using
+** C++ instead of plain old C.
+*/
+void sqlite3OsClose(sqlite3_file *pId){
+  if( pId->pMethods ){
+    pId->pMethods->xClose(pId);
+    pId->pMethods = 0;
+  }
+}
+int sqlite3OsRead(sqlite3_file *id, void *pBuf, int amt, i64 offset){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xRead(id, pBuf, amt, offset);
+}
+int sqlite3OsWrite(sqlite3_file *id, const void *pBuf, int amt, i64 offset){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xWrite(id, pBuf, amt, offset);
+}
+int sqlite3OsTruncate(sqlite3_file *id, i64 size){
+  return id->pMethods->xTruncate(id, size);
+}
+int sqlite3OsSync(sqlite3_file *id, int flags){
+  DO_OS_MALLOC_TEST(id);
+  return flags ? id->pMethods->xSync(id, flags) : SQLITE_OK;
+}
+int sqlite3OsFileSize(sqlite3_file *id, i64 *pSize){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xFileSize(id, pSize);
+}
+int sqlite3OsLock(sqlite3_file *id, int lockType){
+  DO_OS_MALLOC_TEST(id);
+  assert( lockType>=SQLITE_LOCK_SHARED && lockType<=SQLITE_LOCK_EXCLUSIVE );
+  return id->pMethods->xLock(id, lockType);
+}
+int sqlite3OsUnlock(sqlite3_file *id, int lockType){
+  assert( lockType==SQLITE_LOCK_NONE || lockType==SQLITE_LOCK_SHARED );
+  return id->pMethods->xUnlock(id, lockType);
+}
+int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xCheckReservedLock(id, pResOut);
+}
+
+/*
+** Use sqlite3OsFileControl() when we are doing something that might fail
+** and we need to know about the failures.  Use sqlite3OsFileControlHint()
+** when simply tossing information over the wall to the VFS and we do not
+** really care if the VFS receives and understands the information since it
+** is only a hint and can be safely ignored.  The sqlite3OsFileControlHint()
+** routine has no return value since the return value would be meaningless.
+*/
+int sqlite3OsFileControl(sqlite3_file *id, int op, void *pArg){
+  if( id->pMethods==0 ) return SQLITE_NOTFOUND;
+#ifdef SQLITE_TEST
+  if( op!=SQLITE_FCNTL_COMMIT_PHASETWO
+   && op!=SQLITE_FCNTL_LOCK_TIMEOUT
+   && op!=SQLITE_FCNTL_CKPT_DONE
+   && op!=SQLITE_FCNTL_CKPT_START
+  ){
+    /* Faults are not injected into COMMIT_PHASETWO because, assuming SQLite
+    ** is using a regular VFS, it is called after the corresponding
+    ** transaction has been committed. Injecting a fault at this point
+    ** confuses the test scripts - the COMMIT command returns SQLITE_NOMEM
+    ** but the transaction is committed anyway.
+    **
+    ** The core must call OsFileControl() though, not OsFileControlHint(),
+    ** as if a custom VFS (e.g. zipvfs) returns an error here, it probably
+    ** means the commit really has failed and an error should be returned
+    ** to the user.
+    **
+    ** The CKPT_DONE and CKPT_START file-controls are write-only signals
+    ** to the cksumvfs.  Their return code is meaningless and is ignored
+    ** by the SQLite core, so there is no point in simulating OOMs for them.
+    */
+    DO_OS_MALLOC_TEST(id);
+  }
+#endif
+  return id->pMethods->xFileControl(id, op, pArg);
+}
+void sqlite3OsFileControlHint(sqlite3_file *id, int op, void *pArg){
+  if( id->pMethods ) (void)id->pMethods->xFileControl(id, op, pArg);
+}
+
+int sqlite3OsSectorSize(sqlite3_file *id){
+  int (*xSectorSize)(sqlite3_file*) = id->pMethods->xSectorSize;
+  return (xSectorSize ? xSectorSize(id) : SQLITE_DEFAULT_SECTOR_SIZE);
+}
+int sqlite3OsDeviceCharacteristics(sqlite3_file *id){
+  if( NEVER(id->pMethods==0) ) return 0;
+  return id->pMethods->xDeviceCharacteristics(id);
+}
+#ifndef SQLITE_OMIT_WAL
+int sqlite3OsShmLock(sqlite3_file *id, int offset, int n, int flags){
+  return id->pMethods->xShmLock(id, offset, n, flags);
+}
+void sqlite3OsShmBarrier(sqlite3_file *id){
+  id->pMethods->xShmBarrier(id);
+}
+int sqlite3OsShmUnmap(sqlite3_file *id, int deleteFlag){
+  return id->pMethods->xShmUnmap(id, deleteFlag);
+}
+int sqlite3OsShmMap(
+  sqlite3_file *id,               /* Database file handle */
+  int iPage,
+  int pgsz,
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Pointer to mapping */
+){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xShmMap(id, iPage, pgsz, bExtend, pp);
+}
+#endif /* SQLITE_OMIT_WAL */
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/* The real implementation of xFetch and xUnfetch */
+int sqlite3OsFetch(sqlite3_file *id, i64 iOff, int iAmt, void **pp){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xFetch(id, iOff, iAmt, pp);
+}
+int sqlite3OsUnfetch(sqlite3_file *id, i64 iOff, void *p){
+  return id->pMethods->xUnfetch(id, iOff, p);
+}
+#else
+/* No-op stubs to use when memory-mapped I/O is disabled */
+int sqlite3OsFetch(sqlite3_file *id, i64 iOff, int iAmt, void **pp){
+  *pp = 0;
+  return SQLITE_OK;
+}
+int sqlite3OsUnfetch(sqlite3_file *id, i64 iOff, void *p){
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** The next group of routines are convenience wrappers around the
+** VFS methods.
+*/
+int sqlite3OsOpen(
+  sqlite3_vfs *pVfs,
+  const char *zPath,
+  sqlite3_file *pFile,
+  int flags,
+  int *pFlagsOut
+){
+  int rc;
+  DO_OS_MALLOC_TEST(0);
+  /* 0x87f7f is a mask of SQLITE_OPEN_ flags that are valid to be passed
+  ** down into the VFS layer.  Some SQLITE_OPEN_ flags (for example,
+  ** SQLITE_OPEN_FULLMUTEX or SQLITE_OPEN_SHAREDCACHE) are blocked before
+  ** reaching the VFS. */
+  assert( zPath || (flags & SQLITE_OPEN_EXCLUSIVE) );
+  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x1087f7f, pFlagsOut);
+  assert( rc==SQLITE_OK || pFile->pMethods==0 );
+  return rc;
+}
+int sqlite3OsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  DO_OS_MALLOC_TEST(0);
+  assert( dirSync==0 || dirSync==1 );
+  return pVfs->xDelete!=0 ? pVfs->xDelete(pVfs, zPath, dirSync) : SQLITE_OK;
+}
+int sqlite3OsAccess(
+  sqlite3_vfs *pVfs,
+  const char *zPath,
+  int flags,
+  int *pResOut
+){
+  DO_OS_MALLOC_TEST(0);
+  return pVfs->xAccess(pVfs, zPath, flags, pResOut);
+}
+int sqlite3OsFullPathname(
+  sqlite3_vfs *pVfs,
+  const char *zPath,
+  int nPathOut,
+  char *zPathOut
+){
+  DO_OS_MALLOC_TEST(0);
+  zPathOut[0] = 0;
+  return pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut);
+}
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+void *sqlite3OsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  assert( zPath!=0 );
+  assert( strlen(zPath)<=SQLITE_MAX_PATHLEN );  /* tag-20210611-1 */
+  return pVfs->xDlOpen(pVfs, zPath);
+}
+void sqlite3OsDlError(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  pVfs->xDlError(pVfs, nByte, zBufOut);
+}
+void (*sqlite3OsDlSym(sqlite3_vfs *pVfs, void *pHdle, const char *zSym))(void){
+  return pVfs->xDlSym(pVfs, pHdle, zSym);
+}
+void sqlite3OsDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  pVfs->xDlClose(pVfs, pHandle);
+}
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+int sqlite3OsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  if( sqlite3Config.iPrngSeed ){
+    memset(zBufOut, 0, nByte);
+    if( ALWAYS(nByte>(signed)sizeof(unsigned)) ) nByte = sizeof(unsigned int);
+    memcpy(zBufOut, &sqlite3Config.iPrngSeed, nByte);
+    return SQLITE_OK;
+  }else{
+    return pVfs->xRandomness(pVfs, nByte, zBufOut);
+  }
+
+}
+int sqlite3OsSleep(sqlite3_vfs *pVfs, int nMicro){
+  return pVfs->xSleep(pVfs, nMicro);
+}
+int sqlite3OsGetLastError(sqlite3_vfs *pVfs){
+  return pVfs->xGetLastError ? pVfs->xGetLastError(pVfs, 0, 0) : 0;
+}
+int sqlite3OsCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  int rc;
+  /* IMPLEMENTATION-OF: R-49045-42493 SQLite will use the xCurrentTimeInt64()
+  ** method to get the current date and time if that method is available
+  ** (if iVersion is 2 or greater and the function pointer is not NULL) and
+  ** will fall back to xCurrentTime() if xCurrentTimeInt64() is
+  ** unavailable.
+  */
+  if( pVfs->iVersion>=2 && pVfs->xCurrentTimeInt64 ){
+    rc = pVfs->xCurrentTimeInt64(pVfs, pTimeOut);
+  }else{
+    double r;
+    rc = pVfs->xCurrentTime(pVfs, &r);
+    *pTimeOut = (sqlite3_int64)(r*86400000.0);
+  }
+  return rc;
+}
+
+int sqlite3OsOpenMalloc(
+  sqlite3_vfs *pVfs,
+  const char *zFile,
+  sqlite3_file **ppFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  sqlite3_file *pFile;
+  pFile = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile);
+  if( pFile ){
+    rc = sqlite3OsOpen(pVfs, zFile, pFile, flags, pOutFlags);
+    if( rc!=SQLITE_OK ){
+      sqlite3_free(pFile);
+      *ppFile = 0;
+    }else{
+      *ppFile = pFile;
+    }
+  }else{
+    *ppFile = 0;
+    rc = SQLITE_NOMEM_BKPT;
+  }
+  assert( *ppFile!=0 || rc!=SQLITE_OK );
+  return rc;
+}
+void sqlite3OsCloseFree(sqlite3_file *pFile){
+  assert( pFile );
+  sqlite3OsClose(pFile);
+  sqlite3_free(pFile);
+}
+
+/*
+** This function is a wrapper around the OS specific implementation of
+** sqlite3_os_init(). The purpose of the wrapper is to provide the
+** ability to simulate a malloc failure, so that the handling of an
+** error in sqlite3_os_init() by the upper layers can be tested.
+*/
+int sqlite3OsInit(void){
+  void *p = sqlite3_malloc(10);
+  if( p==0 ) return SQLITE_NOMEM_BKPT;
+  sqlite3_free(p);
+  return sqlite3_os_init();
+}
+
+/*
+** The list of all registered VFS implementations.
+*/
+static sqlite3_vfs * SQLITE_WSD vfsList = 0;
+#define vfsList GLOBAL(sqlite3_vfs *, vfsList)
+
+/*
+** Locate a VFS by name.  If no name is given, simply return the
+** first VFS on the list.
+*/
+sqlite3_vfs *sqlite3_vfs_find(const char *zVfs){
+  sqlite3_vfs *pVfs = 0;
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex;
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  int rc = sqlite3_initialize();
+  if( rc ) return 0;
+#endif
+#if SQLITE_THREADSAFE
+  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN);
+#endif
+  sqlite3_mutex_enter(mutex);
+  for(pVfs = vfsList; pVfs; pVfs=pVfs->pNext){
+    if( zVfs==0 ) break;
+    if( strcmp(zVfs, pVfs->zName)==0 ) break;
+  }
+  sqlite3_mutex_leave(mutex);
+  return pVfs;
+}
+
+/*
+** Unlink a VFS from the linked list
+*/
+static void vfsUnlink(sqlite3_vfs *pVfs){
+  assert( sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN)) );
+  if( pVfs==0 ){
+    /* No-op */
+  }else if( vfsList==pVfs ){
+    vfsList = pVfs->pNext;
+  }else if( vfsList ){
+    sqlite3_vfs *p = vfsList;
+    while( p->pNext && p->pNext!=pVfs ){
+      p = p->pNext;
+    }
+    if( p->pNext==pVfs ){
+      p->pNext = pVfs->pNext;
+    }
+  }
+}
+
+/*
+** Register a VFS with the system.  It is harmless to register the same
+** VFS multiple times.  The new VFS becomes the default if makeDflt is
+** true.
+*/
+int sqlite3_vfs_register(sqlite3_vfs *pVfs, int makeDflt){
+  MUTEX_LOGIC(sqlite3_mutex *mutex;)
+#ifndef SQLITE_OMIT_AUTOINIT
+  int rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pVfs==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+
+  MUTEX_LOGIC( mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN); )
+  sqlite3_mutex_enter(mutex);
+  vfsUnlink(pVfs);
+  if( makeDflt || vfsList==0 ){
+    pVfs->pNext = vfsList;
+    vfsList = pVfs;
+  }else{
+    pVfs->pNext = vfsList->pNext;
+    vfsList->pNext = pVfs;
+  }
+  assert(vfsList);
+  sqlite3_mutex_leave(mutex);
+  return SQLITE_OK;
+}
+
+/*
+** Unregister a VFS so that it is no longer accessible.
+*/
+int sqlite3_vfs_unregister(sqlite3_vfs *pVfs){
+  MUTEX_LOGIC(sqlite3_mutex *mutex;)
+#ifndef SQLITE_OMIT_AUTOINIT
+  int rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+  MUTEX_LOGIC( mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN); )
+  sqlite3_mutex_enter(mutex);
+  vfsUnlink(pVfs);
+  sqlite3_mutex_leave(mutex);
+  return SQLITE_OK;
+}
diff --git a/src/os.h b/src/os.h
new file mode 100644
index 0000000..aeb0172
--- /dev/null
+++ b/src/os.h
@@ -0,0 +1,225 @@
+/*
+** 2001 September 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This header file (together with is companion C source-code file
+** "os.c") attempt to abstract the underlying operating system so that
+** the SQLite library will work on both POSIX and windows systems.
+**
+** This header file is #include-ed by sqliteInt.h and thus ends up
+** being included by every source file.
+*/
+#ifndef _SQLITE_OS_H_
+#define _SQLITE_OS_H_
+
+/*
+** Attempt to automatically detect the operating system and setup the
+** necessary pre-processor macros for it.
+*/
+#include "os_setup.h"
+
+/* If the SET_FULLSYNC macro is not defined above, then make it
+** a no-op
+*/
+#ifndef SET_FULLSYNC
+# define SET_FULLSYNC(x,y)
+#endif
+
+/* Maximum pathname length.  Note: FILENAME_MAX defined by stdio.h
+*/
+#ifndef SQLITE_MAX_PATHLEN
+# define SQLITE_MAX_PATHLEN FILENAME_MAX
+#endif
+
+/* Maximum number of symlinks that will be resolved while trying to
+** expand a filename in xFullPathname() in the VFS.
+*/
+#ifndef SQLITE_MAX_SYMLINK
+# define SQLITE_MAX_SYMLINK 200
+#endif
+
+/*
+** The default size of a disk sector
+*/
+#ifndef SQLITE_DEFAULT_SECTOR_SIZE
+# define SQLITE_DEFAULT_SECTOR_SIZE 4096
+#endif
+
+/*
+** Temporary files are named starting with this prefix followed by 16 random
+** alphanumeric characters, and no file extension. They are stored in the
+** OS's standard temporary file directory, and are deleted prior to exit.
+** If sqlite is being embedded in another program, you may wish to change the
+** prefix to reflect your program's name, so that if your program exits
+** prematurely, old temporary files can be easily identified. This can be done
+** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.
+**
+** 2006-10-31:  The default prefix used to be "sqlite_".  But then
+** Mcafee started using SQLite in their anti-virus product and it
+** started putting files with the "sqlite" name in the c:/temp folder.
+** This annoyed many windows users.  Those users would then do a 
+** Google search for "sqlite", find the telephone numbers of the
+** developers and call to wake them up at night and complain.
+** For this reason, the default name prefix is changed to be "sqlite" 
+** spelled backwards.  So the temp files are still identified, but
+** anybody smart enough to figure out the code is also likely smart
+** enough to know that calling the developer will not help get rid
+** of the file.
+*/
+#ifndef SQLITE_TEMP_FILE_PREFIX
+# define SQLITE_TEMP_FILE_PREFIX "etilqs_"
+#endif
+
+/*
+** The following values may be passed as the second argument to
+** sqlite3OsLock(). The various locks exhibit the following semantics:
+**
+** SHARED:    Any number of processes may hold a SHARED lock simultaneously.
+** RESERVED:  A single process may hold a RESERVED lock on a file at
+**            any time. Other processes may hold and obtain new SHARED locks.
+** PENDING:   A single process may hold a PENDING lock on a file at
+**            any one time. Existing SHARED locks may persist, but no new
+**            SHARED locks may be obtained by other processes.
+** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks.
+**
+** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a
+** process that requests an EXCLUSIVE lock may actually obtain a PENDING
+** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to
+** sqlite3OsLock().
+*/
+#define NO_LOCK         0
+#define SHARED_LOCK     1
+#define RESERVED_LOCK   2
+#define PENDING_LOCK    3
+#define EXCLUSIVE_LOCK  4
+
+/*
+** File Locking Notes:  (Mostly about windows but also some info for Unix)
+**
+** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
+** those functions are not available.  So we use only LockFile() and
+** UnlockFile().
+**
+** LockFile() prevents not just writing but also reading by other processes.
+** A SHARED_LOCK is obtained by locking a single randomly-chosen 
+** byte out of a specific range of bytes. The lock byte is obtained at 
+** random so two separate readers can probably access the file at the 
+** same time, unless they are unlucky and choose the same lock byte.
+** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
+** There can only be one writer.  A RESERVED_LOCK is obtained by locking
+** a single byte of the file that is designated as the reserved lock byte.
+** A PENDING_LOCK is obtained by locking a designated byte different from
+** the RESERVED_LOCK byte.
+**
+** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,
+** which means we can use reader/writer locks.  When reader/writer locks
+** are used, the lock is placed on the same range of bytes that is used
+** for probabilistic locking in Win95/98/ME.  Hence, the locking scheme
+** will support two or more Win95 readers or two or more WinNT readers.
+** But a single Win95 reader will lock out all WinNT readers and a single
+** WinNT reader will lock out all other Win95 readers.
+**
+** The following #defines specify the range of bytes used for locking.
+** SHARED_SIZE is the number of bytes available in the pool from which
+** a random byte is selected for a shared lock.  The pool of bytes for
+** shared locks begins at SHARED_FIRST. 
+**
+** The same locking strategy and
+** byte ranges are used for Unix.  This leaves open the possibility of having
+** clients on win95, winNT, and unix all talking to the same shared file
+** and all locking correctly.  To do so would require that samba (or whatever
+** tool is being used for file sharing) implements locks correctly between
+** windows and unix.  I'm guessing that isn't likely to happen, but by
+** using the same locking range we are at least open to the possibility.
+**
+** Locking in windows is manditory.  For this reason, we cannot store
+** actual data in the bytes used for locking.  The pager never allocates
+** the pages involved in locking therefore.  SHARED_SIZE is selected so
+** that all locks will fit on a single page even at the minimum page size.
+** PENDING_BYTE defines the beginning of the locks.  By default PENDING_BYTE
+** is set high so that we don't have to allocate an unused page except
+** for very large databases.  But one should test the page skipping logic 
+** by setting PENDING_BYTE low and running the entire regression suite.
+**
+** Changing the value of PENDING_BYTE results in a subtly incompatible
+** file format.  Depending on how it is changed, you might not notice
+** the incompatibility right away, even running a full regression test.
+** The default location of PENDING_BYTE is the first byte past the
+** 1GB boundary.
+**
+*/
+#ifdef SQLITE_OMIT_WSD
+# define PENDING_BYTE     (0x40000000)
+#else
+# define PENDING_BYTE      sqlite3PendingByte
+#endif
+#define RESERVED_BYTE     (PENDING_BYTE+1)
+#define SHARED_FIRST      (PENDING_BYTE+2)
+#define SHARED_SIZE       510
+
+/*
+** Wrapper around OS specific sqlite3_os_init() function.
+*/
+int sqlite3OsInit(void);
+
+/* 
+** Functions for accessing sqlite3_file methods 
+*/
+void sqlite3OsClose(sqlite3_file*);
+int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset);
+int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
+int sqlite3OsTruncate(sqlite3_file*, i64 size);
+int sqlite3OsSync(sqlite3_file*, int);
+int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
+int sqlite3OsLock(sqlite3_file*, int);
+int sqlite3OsUnlock(sqlite3_file*, int);
+int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut);
+int sqlite3OsFileControl(sqlite3_file*,int,void*);
+void sqlite3OsFileControlHint(sqlite3_file*,int,void*);
+#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
+int sqlite3OsSectorSize(sqlite3_file *id);
+int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
+#ifndef SQLITE_OMIT_WAL
+int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
+int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
+void sqlite3OsShmBarrier(sqlite3_file *id);
+int sqlite3OsShmUnmap(sqlite3_file *id, int);
+#endif /* SQLITE_OMIT_WAL */
+int sqlite3OsFetch(sqlite3_file *id, i64, int, void **);
+int sqlite3OsUnfetch(sqlite3_file *, i64, void *);
+
+
+/* 
+** Functions for accessing sqlite3_vfs methods 
+*/
+int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
+int sqlite3OsDelete(sqlite3_vfs *, const char *, int);
+int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut);
+int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+void *sqlite3OsDlOpen(sqlite3_vfs *, const char *);
+void sqlite3OsDlError(sqlite3_vfs *, int, char *);
+void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void);
+void sqlite3OsDlClose(sqlite3_vfs *, void *);
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
+int sqlite3OsSleep(sqlite3_vfs *, int);
+int sqlite3OsGetLastError(sqlite3_vfs*);
+int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*);
+
+/*
+** Convenience functions for opening and closing files using 
+** sqlite3_malloc() to obtain space for the file-handle structure.
+*/
+int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);
+void sqlite3OsCloseFree(sqlite3_file *);
+
+#endif /* _SQLITE_OS_H_ */
diff --git a/src/os_common.h b/src/os_common.h
new file mode 100644
index 0000000..5b532af
--- /dev/null
+++ b/src/os_common.h
@@ -0,0 +1,99 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains macros and a little bit of code that is common to
+** all of the platform-specific files (os_*.c) and is #included into those
+** files.
+**
+** This file should be #included by the os_*.c files only.  It is not a
+** general purpose header file.
+*/
+#ifndef _OS_COMMON_H_
+#define _OS_COMMON_H_
+
+/*
+** At least two bugs have slipped in because we changed the MEMORY_DEBUG
+** macro to SQLITE_DEBUG and some older makefiles have not yet made the
+** switch.  The following code should catch this problem at compile-time.
+*/
+#ifdef MEMORY_DEBUG
+# error "The MEMORY_DEBUG macro is obsolete.  Use SQLITE_DEBUG instead."
+#endif
+
+/*
+** Macros for performance tracing.  Normally turned off.  Only works
+** on i486 hardware.
+*/
+#ifdef SQLITE_PERFORMANCE_TRACE
+
+static sqlite_uint64 g_start;
+static sqlite_uint64 g_elapsed;
+#define TIMER_START       g_start=sqlite3Hwtime()
+#define TIMER_END         g_elapsed=sqlite3Hwtime()-g_start
+#define TIMER_ELAPSED     g_elapsed
+#else
+#define TIMER_START
+#define TIMER_END
+#define TIMER_ELAPSED     ((sqlite_uint64)0)
+#endif
+
+/*
+** If we compile with the SQLITE_TEST macro set, then the following block
+** of code will give us the ability to simulate a disk I/O error.  This
+** is used for testing the I/O recovery logic.
+*/
+#if defined(SQLITE_TEST)
+extern int sqlite3_io_error_hit;
+extern int sqlite3_io_error_hardhit;
+extern int sqlite3_io_error_pending;
+extern int sqlite3_io_error_persist;
+extern int sqlite3_io_error_benign;
+extern int sqlite3_diskfull_pending;
+extern int sqlite3_diskfull;
+#define SimulateIOErrorBenign(X) sqlite3_io_error_benign=(X)
+#define SimulateIOError(CODE)  \
+  if( (sqlite3_io_error_persist && sqlite3_io_error_hit) \
+       || sqlite3_io_error_pending-- == 1 )  \
+              { local_ioerr(); CODE; }
+static void local_ioerr(){
+  IOTRACE(("IOERR\n"));
+  sqlite3_io_error_hit++;
+  if( !sqlite3_io_error_benign ) sqlite3_io_error_hardhit++;
+}
+#define SimulateDiskfullError(CODE) \
+   if( sqlite3_diskfull_pending ){ \
+     if( sqlite3_diskfull_pending == 1 ){ \
+       local_ioerr(); \
+       sqlite3_diskfull = 1; \
+       sqlite3_io_error_hit = 1; \
+       CODE; \
+     }else{ \
+       sqlite3_diskfull_pending--; \
+     } \
+   }
+#else
+#define SimulateIOErrorBenign(X)
+#define SimulateIOError(A)
+#define SimulateDiskfullError(A)
+#endif /* defined(SQLITE_TEST) */
+
+/*
+** When testing, keep a count of the number of open files.
+*/
+#if defined(SQLITE_TEST)
+extern int sqlite3_open_file_count;
+#define OpenCounter(X)  sqlite3_open_file_count+=(X)
+#else
+#define OpenCounter(X)
+#endif /* defined(SQLITE_TEST) */
+
+#endif /* !defined(_OS_COMMON_H_) */
diff --git a/src/os_kv.c b/src/os_kv.c
new file mode 100644
index 0000000..5e0ea49
--- /dev/null
+++ b/src/os_kv.c
@@ -0,0 +1,979 @@
+/*
+** 2022-09-06
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains an experimental VFS layer that operates on a
+** Key/Value storage engine where both keys and values must be pure
+** text.
+*/
+#include <sqliteInt.h>
+#if SQLITE_OS_KV || (SQLITE_OS_UNIX && defined(SQLITE_OS_KV_OPTIONAL))
+
+/*****************************************************************************
+** Debugging logic
+*/
+
+/* SQLITE_KV_TRACE() is used for tracing calls to kvstorage routines. */
+#if 0
+#define SQLITE_KV_TRACE(X)  printf X
+#else
+#define SQLITE_KV_TRACE(X)
+#endif
+
+/* SQLITE_KV_LOG() is used for tracing calls to the VFS interface */
+#if 0
+#define SQLITE_KV_LOG(X)  printf X
+#else
+#define SQLITE_KV_LOG(X)
+#endif
+
+
+/*
+** Forward declaration of objects used by this VFS implementation
+*/
+typedef struct KVVfsFile KVVfsFile;
+
+/* A single open file.  There are only two files represented by this
+** VFS - the database and the rollback journal.
+*/
+struct KVVfsFile {
+  sqlite3_file base;              /* IO methods */
+  const char *zClass;             /* Storage class */
+  int isJournal;                  /* True if this is a journal file */
+  unsigned int nJrnl;             /* Space allocated for aJrnl[] */
+  char *aJrnl;                    /* Journal content */
+  int szPage;                     /* Last known page size */
+  sqlite3_int64 szDb;             /* Database file size.  -1 means unknown */
+  char *aData;                    /* Buffer to hold page data */
+};
+#define SQLITE_KVOS_SZ 133073
+
+/*
+** Methods for KVVfsFile
+*/
+static int kvvfsClose(sqlite3_file*);
+static int kvvfsReadDb(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int kvvfsReadJrnl(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int kvvfsWriteDb(sqlite3_file*,const void*,int iAmt, sqlite3_int64);
+static int kvvfsWriteJrnl(sqlite3_file*,const void*,int iAmt, sqlite3_int64);
+static int kvvfsTruncateDb(sqlite3_file*, sqlite3_int64 size);
+static int kvvfsTruncateJrnl(sqlite3_file*, sqlite3_int64 size);
+static int kvvfsSyncDb(sqlite3_file*, int flags);
+static int kvvfsSyncJrnl(sqlite3_file*, int flags);
+static int kvvfsFileSizeDb(sqlite3_file*, sqlite3_int64 *pSize);
+static int kvvfsFileSizeJrnl(sqlite3_file*, sqlite3_int64 *pSize);
+static int kvvfsLock(sqlite3_file*, int);
+static int kvvfsUnlock(sqlite3_file*, int);
+static int kvvfsCheckReservedLock(sqlite3_file*, int *pResOut);
+static int kvvfsFileControlDb(sqlite3_file*, int op, void *pArg);
+static int kvvfsFileControlJrnl(sqlite3_file*, int op, void *pArg);
+static int kvvfsSectorSize(sqlite3_file*);
+static int kvvfsDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Methods for sqlite3_vfs
+*/
+static int kvvfsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int kvvfsDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int kvvfsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int kvvfsFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *kvvfsDlOpen(sqlite3_vfs*, const char *zFilename);
+static int kvvfsRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int kvvfsSleep(sqlite3_vfs*, int microseconds);
+static int kvvfsCurrentTime(sqlite3_vfs*, double*);
+static int kvvfsCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+
+static sqlite3_vfs sqlite3OsKvvfsObject = {
+  1,                              /* iVersion */
+  sizeof(KVVfsFile),              /* szOsFile */
+  1024,                           /* mxPathname */
+  0,                              /* pNext */
+  "kvvfs",                        /* zName */
+  0,                              /* pAppData */
+  kvvfsOpen,                      /* xOpen */
+  kvvfsDelete,                    /* xDelete */
+  kvvfsAccess,                    /* xAccess */
+  kvvfsFullPathname,              /* xFullPathname */
+  kvvfsDlOpen,                    /* xDlOpen */
+  0,                              /* xDlError */
+  0,                              /* xDlSym */
+  0,                              /* xDlClose */
+  kvvfsRandomness,                /* xRandomness */
+  kvvfsSleep,                     /* xSleep */
+  kvvfsCurrentTime,               /* xCurrentTime */
+  0,                              /* xGetLastError */
+  kvvfsCurrentTimeInt64           /* xCurrentTimeInt64 */
+};
+
+/* Methods for sqlite3_file objects referencing a database file
+*/
+static sqlite3_io_methods kvvfs_db_io_methods = {
+  1,                              /* iVersion */
+  kvvfsClose,                     /* xClose */
+  kvvfsReadDb,                    /* xRead */
+  kvvfsWriteDb,                   /* xWrite */
+  kvvfsTruncateDb,                /* xTruncate */
+  kvvfsSyncDb,                    /* xSync */
+  kvvfsFileSizeDb,                /* xFileSize */
+  kvvfsLock,                      /* xLock */
+  kvvfsUnlock,                    /* xUnlock */
+  kvvfsCheckReservedLock,         /* xCheckReservedLock */
+  kvvfsFileControlDb,             /* xFileControl */
+  kvvfsSectorSize,                /* xSectorSize */
+  kvvfsDeviceCharacteristics,     /* xDeviceCharacteristics */
+  0,                              /* xShmMap */
+  0,                              /* xShmLock */
+  0,                              /* xShmBarrier */
+  0,                              /* xShmUnmap */
+  0,                              /* xFetch */
+  0                               /* xUnfetch */
+};
+
+/* Methods for sqlite3_file objects referencing a rollback journal
+*/
+static sqlite3_io_methods kvvfs_jrnl_io_methods = {
+  1,                              /* iVersion */
+  kvvfsClose,                     /* xClose */
+  kvvfsReadJrnl,                  /* xRead */
+  kvvfsWriteJrnl,                 /* xWrite */
+  kvvfsTruncateJrnl,              /* xTruncate */
+  kvvfsSyncJrnl,                  /* xSync */
+  kvvfsFileSizeJrnl,              /* xFileSize */
+  kvvfsLock,                      /* xLock */
+  kvvfsUnlock,                    /* xUnlock */
+  kvvfsCheckReservedLock,         /* xCheckReservedLock */
+  kvvfsFileControlJrnl,           /* xFileControl */
+  kvvfsSectorSize,                /* xSectorSize */
+  kvvfsDeviceCharacteristics,     /* xDeviceCharacteristics */
+  0,                              /* xShmMap */
+  0,                              /* xShmLock */
+  0,                              /* xShmBarrier */
+  0,                              /* xShmUnmap */
+  0,                              /* xFetch */
+  0                               /* xUnfetch */
+};
+
+/****** Storage subsystem **************************************************/
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+/* Forward declarations for the low-level storage engine
+*/
+static int kvstorageWrite(const char*, const char *zKey, const char *zData);
+static int kvstorageDelete(const char*, const char *zKey);
+static int kvstorageRead(const char*, const char *zKey, char *zBuf, int nBuf);
+#define KVSTORAGE_KEY_SZ  32
+
+/* Expand the key name with an appropriate prefix and put the result
+** zKeyOut[].  The zKeyOut[] buffer is assumed to hold at least
+** KVSTORAGE_KEY_SZ bytes.
+*/
+static void kvstorageMakeKey(
+  const char *zClass,
+  const char *zKeyIn,
+  char *zKeyOut
+){
+  sqlite3_snprintf(KVSTORAGE_KEY_SZ, zKeyOut, "kvvfs-%s-%s", zClass, zKeyIn);
+}
+
+/* Write content into a key.  zClass is the particular namespace of the
+** underlying key/value store to use - either "local" or "session".
+**
+** Both zKey and zData are zero-terminated pure text strings.
+**
+** Return the number of errors.
+*/
+static int kvstorageWrite(
+  const char *zClass,
+  const char *zKey,
+  const char *zData
+){
+  FILE *fd;
+  char zXKey[KVSTORAGE_KEY_SZ];
+  kvstorageMakeKey(zClass, zKey, zXKey);
+  fd = fopen(zXKey, "wb");
+  if( fd ){
+    SQLITE_KV_TRACE(("KVVFS-WRITE  %-15s (%d) %.50s%s\n", zXKey,
+                 (int)strlen(zData), zData,
+                 strlen(zData)>50 ? "..." : ""));
+    fputs(zData, fd);
+    fclose(fd);
+    return 0;
+  }else{
+    return 1;
+  }
+}
+
+/* Delete a key (with its corresponding data) from the key/value
+** namespace given by zClass.  If the key does not previously exist,
+** this routine is a no-op.
+*/
+static int kvstorageDelete(const char *zClass, const char *zKey){
+  char zXKey[KVSTORAGE_KEY_SZ];
+  kvstorageMakeKey(zClass, zKey, zXKey);
+  unlink(zXKey);
+  SQLITE_KV_TRACE(("KVVFS-DELETE %-15s\n", zXKey));
+  return 0;
+}
+
+/* Read the value associated with a zKey from the key/value namespace given
+** by zClass and put the text data associated with that key in the first
+** nBuf bytes of zBuf[].  The value might be truncated if zBuf is not large
+** enough to hold it all.  The value put into zBuf must always be zero
+** terminated, even if it gets truncated because nBuf is not large enough.
+**
+** Return the total number of bytes in the data, without truncation, and
+** not counting the final zero terminator.   Return -1 if the key does
+** not exist.
+**
+** If nBuf<=0 then this routine simply returns the size of the data without
+** actually reading it.
+*/
+static int kvstorageRead(
+  const char *zClass,
+  const char *zKey,
+  char *zBuf,
+  int nBuf
+){
+  FILE *fd;
+  struct stat buf;
+  char zXKey[KVSTORAGE_KEY_SZ];
+  kvstorageMakeKey(zClass, zKey, zXKey);
+  if( access(zXKey, R_OK)!=0
+   || stat(zXKey, &buf)!=0
+   || !S_ISREG(buf.st_mode)
+  ){
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (-1)\n", zXKey));
+    return -1;
+  }
+  if( nBuf<=0 ){
+    return (int)buf.st_size;
+  }else if( nBuf==1 ){
+    zBuf[0] = 0;
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (%d)\n", zXKey,
+                 (int)buf.st_size));
+    return (int)buf.st_size;
+  }
+  if( nBuf > buf.st_size + 1 ){
+    nBuf = buf.st_size + 1;
+  }
+  fd = fopen(zXKey, "rb");
+  if( fd==0 ){
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (-1)\n", zXKey));
+    return -1;
+  }else{
+    sqlite3_int64 n = fread(zBuf, 1, nBuf-1, fd);
+    fclose(fd);
+    zBuf[n] = 0;
+    SQLITE_KV_TRACE(("KVVFS-READ   %-15s (%lld) %.50s%s\n", zXKey,
+                 n, zBuf, n>50 ? "..." : ""));
+    return (int)n;
+  }
+}
+
+/*
+** An internal level of indirection which enables us to replace the
+** kvvfs i/o methods with JavaScript implementations in WASM builds.
+** Maintenance reminder: if this struct changes in any way, the JSON
+** rendering of its structure must be updated in
+** sqlite3_wasm_enum_json(). There are no binary compatibility
+** concerns, so it does not need an iVersion member. This file is
+** necessarily always compiled together with sqlite3_wasm_enum_json(),
+** and JS code dynamically creates the mapping of members based on
+** that JSON description.
+*/
+typedef struct sqlite3_kvvfs_methods sqlite3_kvvfs_methods;
+struct sqlite3_kvvfs_methods {
+  int (*xRead)(const char *zClass, const char *zKey, char *zBuf, int nBuf);
+  int (*xWrite)(const char *zClass, const char *zKey, const char *zData);
+  int (*xDelete)(const char *zClass, const char *zKey);
+  const int nKeySize;
+};
+
+/*
+** This object holds the kvvfs I/O methods which may be swapped out
+** for JavaScript-side implementations in WASM builds. In such builds
+** it cannot be const, but in native builds it should be so that
+** the compiler can hopefully optimize this level of indirection out.
+** That said, kvvfs is intended primarily for use in WASM builds.
+**
+** Note that this is not explicitly flagged as static because the
+** amalgamation build will tag it with SQLITE_PRIVATE.
+*/
+#ifndef SQLITE_WASM
+const
+#endif
+sqlite3_kvvfs_methods sqlite3KvvfsMethods = {
+kvstorageRead,
+kvstorageWrite,
+kvstorageDelete,
+KVSTORAGE_KEY_SZ
+};
+
+/****** Utility subroutines ************************************************/
+
+/*
+** Encode binary into the text encoded used to persist on disk.
+** The output text is stored in aOut[], which must be at least
+** nData+1 bytes in length.
+**
+** Return the actual length of the encoded text, not counting the
+** zero terminator at the end.
+**
+** Encoding format
+** ---------------
+**
+**   *  Non-zero bytes are encoded as upper-case hexadecimal
+**
+**   *  A sequence of one or more zero-bytes that are not at the
+**      beginning of the buffer are encoded as a little-endian
+**      base-26 number using a..z.  "a" means 0.  "b" means 1,
+**      "z" means 25.  "ab" means 26.  "ac" means 52.  And so forth.
+**
+**   *  Because there is no overlap between the encoding characters
+**      of hexadecimal and base-26 numbers, it is always clear where
+**      one stops and the next begins.
+*/
+static int kvvfsEncode(const char *aData, int nData, char *aOut){
+  int i, j;
+  const unsigned char *a = (const unsigned char*)aData;
+  for(i=j=0; i<nData; i++){
+    unsigned char c = a[i];
+    if( c!=0 ){
+      aOut[j++] = "0123456789ABCDEF"[c>>4];
+      aOut[j++] = "0123456789ABCDEF"[c&0xf];
+    }else{
+      /* A sequence of 1 or more zeros is stored as a little-endian
+      ** base-26 number using a..z as the digits. So one zero is "b".
+      ** Two zeros is "c". 25 zeros is "z", 26 zeros is "ab", 27 is "bb",
+      ** and so forth.
+      */
+      int k;
+      for(k=1; i+k<nData && a[i+k]==0; k++){}
+      i += k-1;
+      while( k>0 ){
+        aOut[j++] = 'a'+(k%26);
+        k /= 26;
+      }
+    }
+  }
+  aOut[j] = 0;
+  return j;
+}
+
+static const signed char kvvfsHexValue[256] = {
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+   0,  1,  2,  3,  4,  5,  6,  7,    8,  9, -1, -1, -1, -1, -1, -1,
+  -1, 10, 11, 12, 13, 14, 15, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1,   -1, -1, -1, -1, -1, -1, -1, -1
+};
+
+/*
+** Decode the text encoding back to binary.  The binary content is
+** written into pOut, which must be at least nOut bytes in length.
+**
+** The return value is the number of bytes actually written into aOut[].
+*/
+static int kvvfsDecode(const char *a, char *aOut, int nOut){
+  int i, j;
+  int c;
+  const unsigned char *aIn = (const unsigned char*)a;
+  i = 0;
+  j = 0;
+  while( 1 ){
+    c = kvvfsHexValue[aIn[i]];
+    if( c<0 ){
+      int n = 0;
+      int mult = 1;
+      c = aIn[i];
+      if( c==0 ) break;
+      while( c>='a' && c<='z' ){
+        n += (c - 'a')*mult;
+        mult *= 26;
+        c = aIn[++i];
+      }
+      if( j+n>nOut ) return -1;
+      memset(&aOut[j], 0, n);
+      j += n;
+      if( c==0 || mult==1 ) break; /* progress stalled if mult==1 */
+    }else{
+      aOut[j] = c<<4;
+      c = kvvfsHexValue[aIn[++i]];
+      if( c<0 ) break;
+      aOut[j++] += c;
+      i++;
+    }
+  }
+  return j;
+}
+
+/*
+** Decode a complete journal file.  Allocate space in pFile->aJrnl
+** and store the decoding there.  Or leave pFile->aJrnl set to NULL
+** if an error is encountered.
+**
+** The first few characters of the text encoding will be a little-endian
+** base-26 number (digits a..z) that is the total number of bytes
+** in the decoded journal file image.  This base-26 number is followed
+** by a single space, then the encoding of the journal.  The space
+** separator is required to act as a terminator for the base-26 number.
+*/
+static void kvvfsDecodeJournal(
+  KVVfsFile *pFile,      /* Store decoding in pFile->aJrnl */
+  const char *zTxt,      /* Text encoding.  Zero-terminated */
+  int nTxt               /* Bytes in zTxt, excluding zero terminator */
+){
+  unsigned int n = 0;
+  int c, i, mult;
+  i = 0;
+  mult = 1;
+  while( (c = zTxt[i++])>='a' && c<='z' ){
+    n += (zTxt[i] - 'a')*mult;
+    mult *= 26;
+  }
+  sqlite3_free(pFile->aJrnl);
+  pFile->aJrnl = sqlite3_malloc64( n );
+  if( pFile->aJrnl==0 ){
+    pFile->nJrnl = 0;
+    return;
+  }
+  pFile->nJrnl = n;
+  n = kvvfsDecode(zTxt+i, pFile->aJrnl, pFile->nJrnl);
+  if( n<pFile->nJrnl ){
+    sqlite3_free(pFile->aJrnl);
+    pFile->aJrnl = 0;
+    pFile->nJrnl = 0;
+  }
+}
+
+/*
+** Read or write the "sz" element, containing the database file size.
+*/
+static sqlite3_int64 kvvfsReadFileSize(KVVfsFile *pFile){
+  char zData[50];
+  zData[0] = 0;
+  sqlite3KvvfsMethods.xRead(pFile->zClass, "sz", zData, sizeof(zData)-1);
+  return strtoll(zData, 0, 0);
+}
+static int kvvfsWriteFileSize(KVVfsFile *pFile, sqlite3_int64 sz){
+  char zData[50];
+  sqlite3_snprintf(sizeof(zData), zData, "%lld", sz);
+  return sqlite3KvvfsMethods.xWrite(pFile->zClass, "sz", zData);
+}
+
+/****** sqlite3_io_methods methods ******************************************/
+
+/*
+** Close an kvvfs-file.
+*/
+static int kvvfsClose(sqlite3_file *pProtoFile){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+
+  SQLITE_KV_LOG(("xClose %s %s\n", pFile->zClass, 
+             pFile->isJournal ? "journal" : "db"));
+  sqlite3_free(pFile->aJrnl);
+  sqlite3_free(pFile->aData);
+  return SQLITE_OK;
+}
+
+/*
+** Read from the -journal file.
+*/
+static int kvvfsReadJrnl(
+  sqlite3_file *pProtoFile,
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  assert( pFile->isJournal );
+  SQLITE_KV_LOG(("xRead('%s-journal',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  if( pFile->aJrnl==0 ){
+    int szTxt = kvstorageRead(pFile->zClass, "jrnl", 0, 0);
+    char *aTxt;
+    if( szTxt<=4 ){
+      return SQLITE_IOERR;
+    }
+    aTxt = sqlite3_malloc64( szTxt+1 );
+    if( aTxt==0 ) return SQLITE_NOMEM;
+    kvstorageRead(pFile->zClass, "jrnl", aTxt, szTxt+1);
+    kvvfsDecodeJournal(pFile, aTxt, szTxt);
+    sqlite3_free(aTxt);
+    if( pFile->aJrnl==0 ) return SQLITE_IOERR;
+  }
+  if( iOfst+iAmt>pFile->nJrnl ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  memcpy(zBuf, pFile->aJrnl+iOfst, iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Read from the database file.
+*/
+static int kvvfsReadDb(
+  sqlite3_file *pProtoFile,
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  unsigned int pgno;
+  int got, n;
+  char zKey[30];
+  char *aData = pFile->aData;
+  assert( iOfst>=0 );
+  assert( iAmt>=0 );
+  SQLITE_KV_LOG(("xRead('%s-db',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  if( iOfst+iAmt>=512 ){
+    if( (iOfst % iAmt)!=0 ){
+      return SQLITE_IOERR_READ;
+    }
+    if( (iAmt & (iAmt-1))!=0 || iAmt<512 || iAmt>65536 ){
+      return SQLITE_IOERR_READ;
+    }
+    pFile->szPage = iAmt;
+    pgno = 1 + iOfst/iAmt;
+  }else{
+    pgno = 1;
+  }
+  sqlite3_snprintf(sizeof(zKey), zKey, "%u", pgno);
+  got = sqlite3KvvfsMethods.xRead(pFile->zClass, zKey,
+                                  aData, SQLITE_KVOS_SZ-1);
+  if( got<0 ){
+    n = 0;
+  }else{
+    aData[got] = 0;
+    if( iOfst+iAmt<512 ){
+      int k = iOfst+iAmt;
+      aData[k*2] = 0;
+      n = kvvfsDecode(aData, &aData[2000], SQLITE_KVOS_SZ-2000);
+      if( n>=iOfst+iAmt ){
+        memcpy(zBuf, &aData[2000+iOfst], iAmt);
+        n = iAmt;
+      }else{
+        n = 0;
+      }
+    }else{
+      n = kvvfsDecode(aData, zBuf, iAmt);
+    }
+  }
+  if( n<iAmt ){
+    memset(zBuf+n, 0, iAmt-n);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** Write into the -journal file.
+*/
+static int kvvfsWriteJrnl(
+  sqlite3_file *pProtoFile,
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  sqlite3_int64 iEnd = iOfst+iAmt;
+  SQLITE_KV_LOG(("xWrite('%s-journal',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  if( iEnd>=0x10000000 ) return SQLITE_FULL;
+  if( pFile->aJrnl==0 || pFile->nJrnl<iEnd ){
+    char *aNew = sqlite3_realloc(pFile->aJrnl, iEnd);
+    if( aNew==0 ){
+      return SQLITE_IOERR_NOMEM;
+    }
+    pFile->aJrnl = aNew;
+    if( pFile->nJrnl<iOfst ){
+      memset(pFile->aJrnl+pFile->nJrnl, 0, iOfst-pFile->nJrnl);
+    }
+    pFile->nJrnl = iEnd;
+  }
+  memcpy(pFile->aJrnl+iOfst, zBuf, iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Write into the database file.
+*/
+static int kvvfsWriteDb(
+  sqlite3_file *pProtoFile,
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  unsigned int pgno;
+  char zKey[30];
+  char *aData = pFile->aData;
+  SQLITE_KV_LOG(("xWrite('%s-db',%d,%lld)\n", pFile->zClass, iAmt, iOfst));
+  assert( iAmt>=512 && iAmt<=65536 );
+  assert( (iAmt & (iAmt-1))==0 );
+  assert( pFile->szPage<0 || pFile->szPage==iAmt );
+  pFile->szPage = iAmt;
+  pgno = 1 + iOfst/iAmt;
+  sqlite3_snprintf(sizeof(zKey), zKey, "%u", pgno);
+  kvvfsEncode(zBuf, iAmt, aData);
+  if( sqlite3KvvfsMethods.xWrite(pFile->zClass, zKey, aData) ){
+    return SQLITE_IOERR;
+  }
+  if( iOfst+iAmt > pFile->szDb ){
+    pFile->szDb = iOfst + iAmt;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Truncate an kvvfs-file.
+*/
+static int kvvfsTruncateJrnl(sqlite3_file *pProtoFile, sqlite_int64 size){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  SQLITE_KV_LOG(("xTruncate('%s-journal',%lld)\n", pFile->zClass, size));
+  assert( size==0 );
+  sqlite3KvvfsMethods.xDelete(pFile->zClass, "jrnl");
+  sqlite3_free(pFile->aJrnl);
+  pFile->aJrnl = 0;
+  pFile->nJrnl = 0;
+  return SQLITE_OK;
+}
+static int kvvfsTruncateDb(sqlite3_file *pProtoFile, sqlite_int64 size){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  if( pFile->szDb>size
+   && pFile->szPage>0 
+   && (size % pFile->szPage)==0
+  ){
+    char zKey[50];
+    unsigned int pgno, pgnoMax;
+    SQLITE_KV_LOG(("xTruncate('%s-db',%lld)\n", pFile->zClass, size));
+    pgno = 1 + size/pFile->szPage;
+    pgnoMax = 2 + pFile->szDb/pFile->szPage;
+    while( pgno<=pgnoMax ){
+      sqlite3_snprintf(sizeof(zKey), zKey, "%u", pgno);
+      sqlite3KvvfsMethods.xDelete(pFile->zClass, zKey);
+      pgno++;
+    }
+    pFile->szDb = size;
+    return kvvfsWriteFileSize(pFile, size) ? SQLITE_IOERR : SQLITE_OK;
+  }
+  return SQLITE_IOERR;
+}
+
+/*
+** Sync an kvvfs-file.
+*/
+static int kvvfsSyncJrnl(sqlite3_file *pProtoFile, int flags){
+  int i, n;
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  char *zOut;
+  SQLITE_KV_LOG(("xSync('%s-journal')\n", pFile->zClass));
+  if( pFile->nJrnl<=0 ){
+    return kvvfsTruncateJrnl(pProtoFile, 0);
+  }
+  zOut = sqlite3_malloc64( pFile->nJrnl*2 + 50 );
+  if( zOut==0 ){
+    return SQLITE_IOERR_NOMEM;
+  }
+  n = pFile->nJrnl;
+  i = 0;
+  do{
+    zOut[i++] = 'a' + (n%26);
+    n /= 26;
+  }while( n>0 );
+  zOut[i++] = ' ';
+  kvvfsEncode(pFile->aJrnl, pFile->nJrnl, &zOut[i]);
+  i = sqlite3KvvfsMethods.xWrite(pFile->zClass, "jrnl", zOut);
+  sqlite3_free(zOut);
+  return i ? SQLITE_IOERR : SQLITE_OK;
+}
+static int kvvfsSyncDb(sqlite3_file *pProtoFile, int flags){
+  return SQLITE_OK;
+}
+
+/*
+** Return the current file-size of an kvvfs-file.
+*/
+static int kvvfsFileSizeJrnl(sqlite3_file *pProtoFile, sqlite_int64 *pSize){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  SQLITE_KV_LOG(("xFileSize('%s-journal')\n", pFile->zClass));
+  *pSize = pFile->nJrnl;
+  return SQLITE_OK;
+}
+static int kvvfsFileSizeDb(sqlite3_file *pProtoFile, sqlite_int64 *pSize){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  SQLITE_KV_LOG(("xFileSize('%s-db')\n", pFile->zClass));
+  if( pFile->szDb>=0 ){
+    *pSize = pFile->szDb;
+  }else{
+    *pSize = kvvfsReadFileSize(pFile);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Lock an kvvfs-file.
+*/
+static int kvvfsLock(sqlite3_file *pProtoFile, int eLock){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  assert( !pFile->isJournal );
+  SQLITE_KV_LOG(("xLock(%s,%d)\n", pFile->zClass, eLock));
+
+  if( eLock!=SQLITE_LOCK_NONE ){
+    pFile->szDb = kvvfsReadFileSize(pFile);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Unlock an kvvfs-file.
+*/
+static int kvvfsUnlock(sqlite3_file *pProtoFile, int eLock){
+  KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+  assert( !pFile->isJournal );
+  SQLITE_KV_LOG(("xUnlock(%s,%d)\n", pFile->zClass, eLock));
+  if( eLock==SQLITE_LOCK_NONE ){
+    pFile->szDb = -1;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an kvvfs-file.
+*/
+static int kvvfsCheckReservedLock(sqlite3_file *pProtoFile, int *pResOut){
+  SQLITE_KV_LOG(("xCheckReservedLock\n"));
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** File control method. For custom operations on an kvvfs-file.
+*/
+static int kvvfsFileControlJrnl(sqlite3_file *pProtoFile, int op, void *pArg){
+  SQLITE_KV_LOG(("xFileControl(%d) on journal\n", op));
+  return SQLITE_NOTFOUND;
+}
+static int kvvfsFileControlDb(sqlite3_file *pProtoFile, int op, void *pArg){
+  SQLITE_KV_LOG(("xFileControl(%d) on database\n", op));
+  if( op==SQLITE_FCNTL_SYNC ){
+    KVVfsFile *pFile = (KVVfsFile *)pProtoFile;
+    int rc = SQLITE_OK;
+    SQLITE_KV_LOG(("xSync('%s-db')\n", pFile->zClass));
+    if( pFile->szDb>0 && 0!=kvvfsWriteFileSize(pFile, pFile->szDb) ){
+      rc = SQLITE_IOERR;
+    }
+    return rc;
+  }
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** Return the sector-size in bytes for an kvvfs-file.
+*/
+static int kvvfsSectorSize(sqlite3_file *pFile){
+  return 512;
+}
+
+/*
+** Return the device characteristic flags supported by an kvvfs-file.
+*/
+static int kvvfsDeviceCharacteristics(sqlite3_file *pProtoFile){
+  return 0;
+}
+
+/****** sqlite3_vfs methods *************************************************/
+
+/*
+** Open an kvvfs file handle.
+*/
+static int kvvfsOpen(
+  sqlite3_vfs *pProtoVfs,
+  const char *zName,
+  sqlite3_file *pProtoFile,
+  int flags,
+  int *pOutFlags
+){
+  KVVfsFile *pFile = (KVVfsFile*)pProtoFile;
+  if( zName==0 ) zName = "";
+  SQLITE_KV_LOG(("xOpen(\"%s\")\n", zName));
+  if( strcmp(zName, "local")==0
+   || strcmp(zName, "session")==0
+  ){
+    pFile->isJournal = 0;
+    pFile->base.pMethods = &kvvfs_db_io_methods;
+  }else
+  if( strcmp(zName, "local-journal")==0 
+   || strcmp(zName, "session-journal")==0
+  ){
+    pFile->isJournal = 1;
+    pFile->base.pMethods = &kvvfs_jrnl_io_methods;
+  }else{
+    return SQLITE_CANTOPEN;
+  }
+  if( zName[0]=='s' ){
+    pFile->zClass = "session";
+  }else{
+    pFile->zClass = "local";
+  }
+  pFile->aData = sqlite3_malloc64(SQLITE_KVOS_SZ);
+  if( pFile->aData==0 ){
+    return SQLITE_NOMEM;
+  }
+  pFile->aJrnl = 0;
+  pFile->nJrnl = 0;
+  pFile->szPage = -1;
+  pFile->szDb = -1;
+  return SQLITE_OK;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int kvvfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  if( strcmp(zPath, "local-journal")==0 ){
+    sqlite3KvvfsMethods.xDelete("local", "jrnl");
+  }else
+  if( strcmp(zPath, "session-journal")==0 ){
+    sqlite3KvvfsMethods.xDelete("session", "jrnl");
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int kvvfsAccess(
+  sqlite3_vfs *pProtoVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  SQLITE_KV_LOG(("xAccess(\"%s\")\n", zPath));
+  if( strcmp(zPath, "local-journal")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("local", "jrnl", 0, 0)>0;
+  }else
+  if( strcmp(zPath, "session-journal")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("session", "jrnl", 0, 0)>0;
+  }else
+  if( strcmp(zPath, "local")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("local", "sz", 0, 0)>0;
+  }else
+  if( strcmp(zPath, "session")==0 ){
+    *pResOut = sqlite3KvvfsMethods.xRead("session", "sz", 0, 0)>0;
+  }else
+  {
+    *pResOut = 0;
+  }
+  SQLITE_KV_LOG(("xAccess returns %d\n",*pResOut));
+  return SQLITE_OK;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (INST_MAX_PATHNAME+1) bytes.
+*/
+static int kvvfsFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  size_t nPath;
+#ifdef SQLITE_OS_KV_ALWAYS_LOCAL
+  zPath = "local";
+#endif
+  nPath = strlen(zPath);
+  SQLITE_KV_LOG(("xFullPathname(\"%s\")\n", zPath));
+  if( nOut<nPath+1 ) nPath = nOut - 1;
+  memcpy(zOut, zPath, nPath);
+  zOut[nPath] = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *kvvfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return 0;
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int kvvfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  memset(zBufOut, 0, nByte);
+  return nByte;
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int kvvfsSleep(sqlite3_vfs *pVfs, int nMicro){
+  return SQLITE_OK;
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int kvvfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  sqlite3_int64 i = 0;
+  int rc;
+  rc = kvvfsCurrentTimeInt64(0, &i);
+  *pTimeOut = i/86400000.0;
+  return rc;
+}
+#include <sys/time.h>
+static int kvvfsCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+  struct timeval sNow;
+  (void)gettimeofday(&sNow, 0);  /* Cannot fail given valid arguments */
+  *pTimeOut = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OS_KV || SQLITE_OS_UNIX */
+
+#if SQLITE_OS_KV
+/* 
+** This routine is called initialize the KV-vfs as the default VFS.
+*/
+int sqlite3_os_init(void){
+  return sqlite3_vfs_register(&sqlite3OsKvvfsObject, 1);
+}
+int sqlite3_os_end(void){
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OS_KV */
+
+#if SQLITE_OS_UNIX && defined(SQLITE_OS_KV_OPTIONAL)
+int sqlite3KvvfsInit(void){
+  return sqlite3_vfs_register(&sqlite3OsKvvfsObject, 0);
+}
+#endif
diff --git a/src/os_setup.h b/src/os_setup.h
new file mode 100644
index 0000000..a82f86f
--- /dev/null
+++ b/src/os_setup.h
@@ -0,0 +1,91 @@
+/*
+** 2013 November 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains pre-processor directives related to operating system
+** detection and/or setup.
+*/
+#ifndef SQLITE_OS_SETUP_H
+#define SQLITE_OS_SETUP_H
+
+/*
+** Figure out if we are dealing with Unix, Windows, or some other operating
+** system.
+**
+** After the following block of preprocess macros, all of 
+**
+**    SQLITE_OS_KV
+**    SQLITE_OS_OTHER
+**    SQLITE_OS_UNIX
+**    SQLITE_OS_WIN
+**
+** will defined to either 1 or 0. One of them will be 1. The others will be 0.
+** If none of the macros are initially defined, then select either
+** SQLITE_OS_UNIX or SQLITE_OS_WIN depending on the target platform.
+**
+** If SQLITE_OS_OTHER=1 is specified at compile-time, then the application
+** must provide its own VFS implementation together with sqlite3_os_init()
+** and sqlite3_os_end() routines.
+*/
+#if !defined(SQLITE_OS_KV) && !defined(SQLITE_OS_OTHER) && \
+       !defined(SQLITE_OS_UNIX) && !defined(SQLITE_OS_WIN)
+#  if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || \
+          defined(__MINGW32__) || defined(__BORLANDC__)
+#    define SQLITE_OS_WIN 1
+#    define SQLITE_OS_UNIX 0
+#  else
+#    define SQLITE_OS_WIN 0
+#    define SQLITE_OS_UNIX 1
+#  endif
+#endif
+#if SQLITE_OS_OTHER+1>1
+#  undef SQLITE_OS_KV
+#  define SQLITE_OS_KV 0
+#  undef SQLITE_OS_UNIX
+#  define SQLITE_OS_UNIX 0
+#  undef SQLITE_OS_WIN
+#  define SQLITE_OS_WIN 0
+#endif
+#if SQLITE_OS_KV+1>1
+#  undef SQLITE_OS_OTHER
+#  define SQLITE_OS_OTHER 0
+#  undef SQLITE_OS_UNIX
+#  define SQLITE_OS_UNIX 0
+#  undef SQLITE_OS_WIN
+#  define SQLITE_OS_WIN 0
+#  define SQLITE_OMIT_LOAD_EXTENSION 1
+#  define SQLITE_OMIT_WAL 1
+#  define SQLITE_OMIT_DEPRECATED 1
+#  undef SQLITE_TEMP_STORE
+#  define SQLITE_TEMP_STORE 3  /* Always use memory for temporary storage */
+#  define SQLITE_DQS 0
+#  define SQLITE_OMIT_SHARED_CACHE 1
+#  define SQLITE_OMIT_AUTOINIT 1
+#endif
+#if SQLITE_OS_UNIX+1>1
+#  undef SQLITE_OS_KV
+#  define SQLITE_OS_KV 0
+#  undef SQLITE_OS_OTHER
+#  define SQLITE_OS_OTHER 0
+#  undef SQLITE_OS_WIN
+#  define SQLITE_OS_WIN 0
+#endif
+#if SQLITE_OS_WIN+1>1
+#  undef SQLITE_OS_KV
+#  define SQLITE_OS_KV 0
+#  undef SQLITE_OS_OTHER
+#  define SQLITE_OS_OTHER 0
+#  undef SQLITE_OS_UNIX
+#  define SQLITE_OS_UNIX 0
+#endif
+
+
+#endif /* SQLITE_OS_SETUP_H */
diff --git a/src/os_unix.c b/src/os_unix.c
new file mode 100644
index 0000000..4b3d63c
--- /dev/null
+++ b/src/os_unix.c
@@ -0,0 +1,8279 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains the VFS implementation for unix-like operating systems
+** include Linux, MacOSX, *BSD, QNX, VxWorks, AIX, HPUX, and others.
+**
+** There are actually several different VFS implementations in this file.
+** The differences are in the way that file locking is done.  The default
+** implementation uses Posix Advisory Locks.  Alternative implementations
+** use flock(), dot-files, various proprietary locking schemas, or simply
+** skip locking all together.
+**
+** This source file is organized into divisions where the logic for various
+** subfunctions is contained within the appropriate division.  PLEASE
+** KEEP THE STRUCTURE OF THIS FILE INTACT.  New code should be placed
+** in the correct division and should be clearly labelled.
+**
+** The layout of divisions is as follows:
+**
+**   *  General-purpose declarations and utility functions.
+**   *  Unique file ID logic used by VxWorks.
+**   *  Various locking primitive implementations (all except proxy locking):
+**      + for Posix Advisory Locks
+**      + for no-op locks
+**      + for dot-file locks
+**      + for flock() locking
+**      + for named semaphore locks (VxWorks only)
+**      + for AFP filesystem locks (MacOSX only)
+**   *  sqlite3_file methods not associated with locking.
+**   *  Definitions of sqlite3_io_methods objects for all locking
+**      methods plus "finder" functions for each locking method.
+**   *  sqlite3_vfs method implementations.
+**   *  Locking primitives for the proxy uber-locking-method. (MacOSX only)
+**   *  Definitions of sqlite3_vfs objects for all locking methods
+**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
+*/
+#include "sqliteInt.h"
+#if SQLITE_OS_UNIX              /* This file is used on unix only */
+
+/*
+** There are various methods for file locking used for concurrency
+** control:
+**
+**   1. POSIX locking (the default),
+**   2. No locking,
+**   3. Dot-file locking,
+**   4. flock() locking,
+**   5. AFP locking (OSX only),
+**   6. Named POSIX semaphores (VXWorks only),
+**   7. proxy locking. (OSX only)
+**
+** Styles 4, 5, and 7 are only available of SQLITE_ENABLE_LOCKING_STYLE
+** is defined to 1.  The SQLITE_ENABLE_LOCKING_STYLE also enables automatic
+** selection of the appropriate locking style based on the filesystem
+** where the database is located.
+*/
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+
+/* Use pread() and pwrite() if they are available */
+#if defined(__APPLE__) || defined(__linux__)
+# define HAVE_PREAD 1
+# define HAVE_PWRITE 1
+#endif
+#if defined(HAVE_PREAD64) && defined(HAVE_PWRITE64)
+# undef USE_PREAD
+# define USE_PREAD64 1
+#elif defined(HAVE_PREAD) && defined(HAVE_PWRITE)
+# undef USE_PREAD64
+# define USE_PREAD 1
+#endif
+
+/*
+** standard include files.
+*/
+#include <sys/types.h>   /* amalgamator: keep */
+#include <sys/stat.h>    /* amalgamator: keep */
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <unistd.h>      /* amalgamator: keep */
+#include <time.h>
+#include <sys/time.h>    /* amalgamator: keep */
+#include <errno.h>
+#if (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0) \
+  && !defined(SQLITE_WASI)
+# include <sys/mman.h>
+#endif
+
+#if SQLITE_ENABLE_LOCKING_STYLE
+# include <sys/ioctl.h>
+# include <sys/file.h>
+# include <sys/param.h>
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+/*
+** Try to determine if gethostuuid() is available based on standard
+** macros.  This might sometimes compute the wrong value for some
+** obscure platforms.  For those cases, simply compile with one of
+** the following:
+**
+**    -DHAVE_GETHOSTUUID=0
+**    -DHAVE_GETHOSTUUID=1
+**
+** None if this matters except when building on Apple products with
+** -DSQLITE_ENABLE_LOCKING_STYLE.
+*/
+#ifndef HAVE_GETHOSTUUID
+# define HAVE_GETHOSTUUID 0
+# if defined(__APPLE__) && ((__MAC_OS_X_VERSION_MIN_REQUIRED > 1050) || \
+                            (__IPHONE_OS_VERSION_MIN_REQUIRED > 2000))
+#    if (!defined(TARGET_OS_EMBEDDED) || (TARGET_OS_EMBEDDED==0)) \
+        && (!defined(TARGET_IPHONE_SIMULATOR) || (TARGET_IPHONE_SIMULATOR==0))\
+        && (!defined(TARGET_OS_MACCATALYST) || (TARGET_OS_MACCATALYST==0))
+#      undef HAVE_GETHOSTUUID
+#      define HAVE_GETHOSTUUID 1
+#    else
+#      warning "gethostuuid() is disabled."
+#    endif
+#  endif
+#endif
+
+
+#if OS_VXWORKS
+# include <sys/ioctl.h>
+# include <semaphore.h>
+# include <limits.h>
+#endif /* OS_VXWORKS */
+
+#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
+# include <sys/mount.h>
+#endif
+
+#ifdef HAVE_UTIME
+# include <utime.h>
+#endif
+
+/*
+** Allowed values of unixFile.fsFlags
+*/
+#define SQLITE_FSFLAGS_IS_MSDOS     0x1
+
+/*
+** If we are to be thread-safe, include the pthreads header.
+*/
+#if SQLITE_THREADSAFE
+# include <pthread.h>
+#endif
+
+/*
+** Default permissions when creating a new file
+*/
+#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
+# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
+#endif
+
+/*
+** Default permissions when creating auto proxy dir
+*/
+#ifndef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
+# define SQLITE_DEFAULT_PROXYDIR_PERMISSIONS 0755
+#endif
+
+/*
+** Maximum supported path-length.
+*/
+#define MAX_PATHNAME 512
+
+/*
+** Maximum supported symbolic links
+*/
+#define SQLITE_MAX_SYMLINKS 100
+
+/*
+** Remove and stub certain info for WASI (WebAssembly System
+** Interface) builds.
+*/
+#ifdef SQLITE_WASI
+# undef HAVE_FCHMOD
+# undef HAVE_FCHOWN
+# undef HAVE_MREMAP
+# define HAVE_MREMAP 0
+# ifndef SQLITE_DEFAULT_UNIX_VFS
+#  define SQLITE_DEFAULT_UNIX_VFS "unix-dotfile"
+   /* ^^^ should SQLITE_DEFAULT_UNIX_VFS be "unix-none"? */
+# endif
+# ifndef F_RDLCK
+#  define F_RDLCK 0
+#  define F_WRLCK 1
+#  define F_UNLCK 2
+#  if __LONG_MAX == 0x7fffffffL
+#   define F_GETLK 12
+#   define F_SETLK 13
+#   define F_SETLKW 14
+#  else
+#   define F_GETLK 5
+#   define F_SETLK 6
+#   define F_SETLKW 7
+#  endif
+# endif
+#else /* !SQLITE_WASI */
+# ifndef HAVE_FCHMOD
+#  define HAVE_FCHMOD
+# endif
+#endif /* SQLITE_WASI */
+
+#ifdef SQLITE_WASI
+# define osGetpid(X) (pid_t)1
+#else
+/* Always cast the getpid() return type for compatibility with
+** kernel modules in VxWorks. */
+# define osGetpid(X) (pid_t)getpid()
+#endif
+
+/*
+** Only set the lastErrno if the error code is a real error and not
+** a normal expected return code of SQLITE_BUSY or SQLITE_OK
+*/
+#define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))
+
+/* Forward references */
+typedef struct unixShm unixShm;               /* Connection shared memory */
+typedef struct unixShmNode unixShmNode;       /* Shared memory instance */
+typedef struct unixInodeInfo unixInodeInfo;   /* An i-node */
+typedef struct UnixUnusedFd UnixUnusedFd;     /* An unused file descriptor */
+
+/*
+** Sometimes, after a file handle is closed by SQLite, the file descriptor
+** cannot be closed immediately. In these cases, instances of the following
+** structure are used to store the file descriptor while waiting for an
+** opportunity to either close or reuse it.
+*/
+struct UnixUnusedFd {
+  int fd;                   /* File descriptor to close */
+  int flags;                /* Flags this file descriptor was opened with */
+  UnixUnusedFd *pNext;      /* Next unused file descriptor on same file */
+};
+
+/*
+** The unixFile structure is subclass of sqlite3_file specific to the unix
+** VFS implementations.
+*/
+typedef struct unixFile unixFile;
+struct unixFile {
+  sqlite3_io_methods const *pMethod;  /* Always the first entry */
+  sqlite3_vfs *pVfs;                  /* The VFS that created this unixFile */
+  unixInodeInfo *pInode;              /* Info about locks on this inode */
+  int h;                              /* The file descriptor */
+  unsigned char eFileLock;            /* The type of lock held on this fd */
+  unsigned short int ctrlFlags;       /* Behavioral bits.  UNIXFILE_* flags */
+  int lastErrno;                      /* The unix errno from last I/O error */
+  void *lockingContext;               /* Locking style specific state */
+  UnixUnusedFd *pPreallocatedUnused;  /* Pre-allocated UnixUnusedFd */
+  const char *zPath;                  /* Name of the file */
+  unixShm *pShm;                      /* Shared memory segment information */
+  int szChunk;                        /* Configured by FCNTL_CHUNK_SIZE */
+#if SQLITE_MAX_MMAP_SIZE>0
+  int nFetchOut;                      /* Number of outstanding xFetch refs */
+  sqlite3_int64 mmapSize;             /* Usable size of mapping at pMapRegion */
+  sqlite3_int64 mmapSizeActual;       /* Actual size of mapping at pMapRegion */
+  sqlite3_int64 mmapSizeMax;          /* Configured FCNTL_MMAP_SIZE value */
+  void *pMapRegion;                   /* Memory mapped region */
+#endif
+  int sectorSize;                     /* Device sector size */
+  int deviceCharacteristics;          /* Precomputed device characteristics */
+#if SQLITE_ENABLE_LOCKING_STYLE
+  int openFlags;                      /* The flags specified at open() */
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
+  unsigned fsFlags;                   /* cached details from statfs() */
+#endif
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  unsigned iBusyTimeout;              /* Wait this many millisec on locks */
+#endif
+#if OS_VXWORKS
+  struct vxworksFileId *pId;          /* Unique file ID */
+#endif
+#ifdef SQLITE_DEBUG
+  /* The next group of variables are used to track whether or not the
+  ** transaction counter in bytes 24-27 of database files are updated
+  ** whenever any part of the database changes.  An assertion fault will
+  ** occur if a file is updated without also updating the transaction
+  ** counter.  This test is made to avoid new problems similar to the
+  ** one described by ticket #3584.
+  */
+  unsigned char transCntrChng;   /* True if the transaction counter changed */
+  unsigned char dbUpdate;        /* True if any part of database file changed */
+  unsigned char inNormalWrite;   /* True if in a normal write operation */
+
+#endif
+
+#ifdef SQLITE_TEST
+  /* In test mode, increase the size of this structure a bit so that
+  ** it is larger than the struct CrashFile defined in test6.c.
+  */
+  char aPadding[32];
+#endif
+};
+
+/* This variable holds the process id (pid) from when the xRandomness()
+** method was called.  If xOpen() is called from a different process id,
+** indicating that a fork() has occurred, the PRNG will be reset.
+*/
+static pid_t randomnessPid = 0;
+
+/*
+** Allowed values for the unixFile.ctrlFlags bitmask:
+*/
+#define UNIXFILE_EXCL        0x01     /* Connections from one process only */
+#define UNIXFILE_RDONLY      0x02     /* Connection is read only */
+#define UNIXFILE_PERSIST_WAL 0x04     /* Persistent WAL mode */
+#ifndef SQLITE_DISABLE_DIRSYNC
+# define UNIXFILE_DIRSYNC    0x08     /* Directory sync needed */
+#else
+# define UNIXFILE_DIRSYNC    0x00
+#endif
+#define UNIXFILE_PSOW        0x10     /* SQLITE_IOCAP_POWERSAFE_OVERWRITE */
+#define UNIXFILE_DELETE      0x20     /* Delete on close */
+#define UNIXFILE_URI         0x40     /* Filename might have query parameters */
+#define UNIXFILE_NOLOCK      0x80     /* Do no file locking */
+
+/*
+** Include code that is common to all os_*.c files
+*/
+#include "os_common.h"
+
+/*
+** Define various macros that are missing from some systems.
+*/
+#ifndef O_LARGEFILE
+# define O_LARGEFILE 0
+#endif
+#ifdef SQLITE_DISABLE_LFS
+# undef O_LARGEFILE
+# define O_LARGEFILE 0
+#endif
+#ifndef O_NOFOLLOW
+# define O_NOFOLLOW 0
+#endif
+#ifndef O_BINARY
+# define O_BINARY 0
+#endif
+
+/*
+** The threadid macro resolves to the thread-id or to 0.  Used for
+** testing and debugging only.
+*/
+#if SQLITE_THREADSAFE
+#define threadid pthread_self()
+#else
+#define threadid 0
+#endif
+
+/*
+** HAVE_MREMAP defaults to true on Linux and false everywhere else.
+*/
+#if !defined(HAVE_MREMAP)
+# if defined(__linux__) && defined(_GNU_SOURCE)
+#  define HAVE_MREMAP 1
+# else
+#  define HAVE_MREMAP 0
+# endif
+#endif
+
+/*
+** Explicitly call the 64-bit version of lseek() on Android. Otherwise, lseek()
+** is the 32-bit version, even if _FILE_OFFSET_BITS=64 is defined.
+*/
+#ifdef __ANDROID__
+# define lseek lseek64
+#endif
+
+#ifdef __linux__
+/*
+** Linux-specific IOCTL magic numbers used for controlling F2FS
+*/
+#define F2FS_IOCTL_MAGIC        0xf5
+#define F2FS_IOC_START_ATOMIC_WRITE     _IO(F2FS_IOCTL_MAGIC, 1)
+#define F2FS_IOC_COMMIT_ATOMIC_WRITE    _IO(F2FS_IOCTL_MAGIC, 2)
+#define F2FS_IOC_START_VOLATILE_WRITE   _IO(F2FS_IOCTL_MAGIC, 3)
+#define F2FS_IOC_ABORT_VOLATILE_WRITE   _IO(F2FS_IOCTL_MAGIC, 5)
+#define F2FS_IOC_GET_FEATURES           _IOR(F2FS_IOCTL_MAGIC, 12, u32)
+#define F2FS_FEATURE_ATOMIC_WRITE 0x0004
+#endif /* __linux__ */
+
+
+/*
+** Different Unix systems declare open() in different ways.  Same use
+** open(const char*,int,mode_t).  Others use open(const char*,int,...).
+** The difference is important when using a pointer to the function.
+**
+** The safest way to deal with the problem is to always use this wrapper
+** which always has the same well-defined interface.
+*/
+static int posixOpen(const char *zFile, int flags, int mode){
+  return open(zFile, flags, mode);
+}
+
+/* Forward reference */
+static int openDirectory(const char*, int*);
+static int unixGetpagesize(void);
+
+/*
+** Many system calls are accessed through pointer-to-functions so that
+** they may be overridden at runtime to facilitate fault injection during
+** testing and sandboxing.  The following array holds the names and pointers
+** to all overrideable system calls.
+*/
+static struct unix_syscall {
+  const char *zName;            /* Name of the system call */
+  sqlite3_syscall_ptr pCurrent; /* Current value of the system call */
+  sqlite3_syscall_ptr pDefault; /* Default value */
+} aSyscall[] = {
+  { "open",         (sqlite3_syscall_ptr)posixOpen,  0  },
+#define osOpen      ((int(*)(const char*,int,int))aSyscall[0].pCurrent)
+
+  { "close",        (sqlite3_syscall_ptr)close,      0  },
+#define osClose     ((int(*)(int))aSyscall[1].pCurrent)
+
+  { "access",       (sqlite3_syscall_ptr)access,     0  },
+#define osAccess    ((int(*)(const char*,int))aSyscall[2].pCurrent)
+
+  { "getcwd",       (sqlite3_syscall_ptr)getcwd,     0  },
+#define osGetcwd    ((char*(*)(char*,size_t))aSyscall[3].pCurrent)
+
+  { "stat",         (sqlite3_syscall_ptr)stat,       0  },
+#define osStat      ((int(*)(const char*,struct stat*))aSyscall[4].pCurrent)
+
+/*
+** The DJGPP compiler environment looks mostly like Unix, but it
+** lacks the fcntl() system call.  So redefine fcntl() to be something
+** that always succeeds.  This means that locking does not occur under
+** DJGPP.  But it is DOS - what did you expect?
+*/
+#ifdef __DJGPP__
+  { "fstat",        0,                 0  },
+#define osFstat(a,b,c)    0
+#else   
+  { "fstat",        (sqlite3_syscall_ptr)fstat,      0  },
+#define osFstat     ((int(*)(int,struct stat*))aSyscall[5].pCurrent)
+#endif
+
+  { "ftruncate",    (sqlite3_syscall_ptr)ftruncate,  0  },
+#define osFtruncate ((int(*)(int,off_t))aSyscall[6].pCurrent)
+
+  { "fcntl",        (sqlite3_syscall_ptr)fcntl,      0  },
+#define osFcntl     ((int(*)(int,int,...))aSyscall[7].pCurrent)
+
+  { "read",         (sqlite3_syscall_ptr)read,       0  },
+#define osRead      ((ssize_t(*)(int,void*,size_t))aSyscall[8].pCurrent)
+
+#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
+  { "pread",        (sqlite3_syscall_ptr)pread,      0  },
+#else
+  { "pread",        (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPread     ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].pCurrent)
+
+#if defined(USE_PREAD64)
+  { "pread64",      (sqlite3_syscall_ptr)pread64,    0  },
+#else
+  { "pread64",      (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPread64 ((ssize_t(*)(int,void*,size_t,off64_t))aSyscall[10].pCurrent)
+
+  { "write",        (sqlite3_syscall_ptr)write,      0  },
+#define osWrite     ((ssize_t(*)(int,const void*,size_t))aSyscall[11].pCurrent)
+
+#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
+  { "pwrite",       (sqlite3_syscall_ptr)pwrite,     0  },
+#else
+  { "pwrite",       (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPwrite    ((ssize_t(*)(int,const void*,size_t,off_t))\
+                    aSyscall[12].pCurrent)
+
+#if defined(USE_PREAD64)
+  { "pwrite64",     (sqlite3_syscall_ptr)pwrite64,   0  },
+#else
+  { "pwrite64",     (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPwrite64  ((ssize_t(*)(int,const void*,size_t,off64_t))\
+                    aSyscall[13].pCurrent)
+
+#if defined(HAVE_FCHMOD)
+  { "fchmod",       (sqlite3_syscall_ptr)fchmod,          0  },
+#else
+  { "fchmod",       (sqlite3_syscall_ptr)0,               0  },
+#endif
+#define osFchmod    ((int(*)(int,mode_t))aSyscall[14].pCurrent)
+
+#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
+  { "fallocate",    (sqlite3_syscall_ptr)posix_fallocate,  0 },
+#else
+  { "fallocate",    (sqlite3_syscall_ptr)0,                0 },
+#endif
+#define osFallocate ((int(*)(int,off_t,off_t))aSyscall[15].pCurrent)
+
+  { "unlink",       (sqlite3_syscall_ptr)unlink,           0 },
+#define osUnlink    ((int(*)(const char*))aSyscall[16].pCurrent)
+
+  { "openDirectory",    (sqlite3_syscall_ptr)openDirectory,      0 },
+#define osOpenDirectory ((int(*)(const char*,int*))aSyscall[17].pCurrent)
+
+  { "mkdir",        (sqlite3_syscall_ptr)mkdir,           0 },
+#define osMkdir     ((int(*)(const char*,mode_t))aSyscall[18].pCurrent)
+
+  { "rmdir",        (sqlite3_syscall_ptr)rmdir,           0 },
+#define osRmdir     ((int(*)(const char*))aSyscall[19].pCurrent)
+
+#if defined(HAVE_FCHOWN)
+  { "fchown",       (sqlite3_syscall_ptr)fchown,          0 },
+#else
+  { "fchown",       (sqlite3_syscall_ptr)0,               0 },
+#endif
+#define osFchown    ((int(*)(int,uid_t,gid_t))aSyscall[20].pCurrent)
+
+#if defined(HAVE_FCHOWN)
+  { "geteuid",      (sqlite3_syscall_ptr)geteuid,         0 },
+#else
+  { "geteuid",      (sqlite3_syscall_ptr)0,               0 },
+#endif
+#define osGeteuid   ((uid_t(*)(void))aSyscall[21].pCurrent)
+
+#if (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0) \
+  && !defined(SQLITE_WASI)
+  { "mmap",         (sqlite3_syscall_ptr)mmap,            0 },
+#else
+  { "mmap",         (sqlite3_syscall_ptr)0,               0 },
+#endif
+#define osMmap ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[22].pCurrent)
+
+#if (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0) \
+  && !defined(SQLITE_WASI)
+  { "munmap",       (sqlite3_syscall_ptr)munmap,          0 },
+#else
+  { "munmap",       (sqlite3_syscall_ptr)0,               0 },
+#endif
+#define osMunmap ((int(*)(void*,size_t))aSyscall[23].pCurrent)
+
+#if HAVE_MREMAP && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
+  { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },
+#else
+  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
+#endif
+#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[24].pCurrent)
+
+#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
+  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },
+#else
+  { "getpagesize",  (sqlite3_syscall_ptr)0,               0 },
+#endif
+#define osGetpagesize ((int(*)(void))aSyscall[25].pCurrent)
+
+#if defined(HAVE_READLINK)
+  { "readlink",     (sqlite3_syscall_ptr)readlink,        0 },
+#else
+  { "readlink",     (sqlite3_syscall_ptr)0,               0 },
+#endif
+#define osReadlink ((ssize_t(*)(const char*,char*,size_t))aSyscall[26].pCurrent)
+
+#if defined(HAVE_LSTAT)
+  { "lstat",         (sqlite3_syscall_ptr)lstat,          0 },
+#else
+  { "lstat",         (sqlite3_syscall_ptr)0,              0 },
+#endif
+#define osLstat      ((int(*)(const char*,struct stat*))aSyscall[27].pCurrent)
+
+#if defined(__linux__) && defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+# ifdef __ANDROID__
+  { "ioctl", (sqlite3_syscall_ptr)(int(*)(int, int, ...))ioctl, 0 },
+#define osIoctl ((int(*)(int,int,...))aSyscall[28].pCurrent)
+# else
+  { "ioctl",         (sqlite3_syscall_ptr)ioctl,          0 },
+#define osIoctl ((int(*)(int,unsigned long,...))aSyscall[28].pCurrent)
+# endif
+#else
+  { "ioctl",         (sqlite3_syscall_ptr)0,              0 },
+#endif
+
+}; /* End of the overrideable system calls */
+
+
+/*
+** On some systems, calls to fchown() will trigger a message in a security
+** log if they come from non-root processes.  So avoid calling fchown() if
+** we are not running as root.
+*/
+static int robustFchown(int fd, uid_t uid, gid_t gid){
+#if defined(HAVE_FCHOWN)
+  return osGeteuid() ? 0 : osFchown(fd,uid,gid);
+#else
+  return 0;
+#endif
+}
+
+/*
+** This is the xSetSystemCall() method of sqlite3_vfs for all of the
+** "unix" VFSes.  Return SQLITE_OK upon successfully updating the
+** system call pointer, or SQLITE_NOTFOUND if there is no configurable
+** system call named zName.
+*/
+static int unixSetSystemCall(
+  sqlite3_vfs *pNotUsed,        /* The VFS pointer.  Not used */
+  const char *zName,            /* Name of system call to override */
+  sqlite3_syscall_ptr pNewFunc  /* Pointer to new system call value */
+){
+  unsigned int i;
+  int rc = SQLITE_NOTFOUND;
+
+  UNUSED_PARAMETER(pNotUsed);
+  if( zName==0 ){
+    /* If no zName is given, restore all system calls to their default
+    ** settings and return NULL
+    */
+    rc = SQLITE_OK;
+    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+      if( aSyscall[i].pDefault ){
+        aSyscall[i].pCurrent = aSyscall[i].pDefault;
+      }
+    }
+  }else{
+    /* If zName is specified, operate on only the one system call
+    ** specified.
+    */
+    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+      if( strcmp(zName, aSyscall[i].zName)==0 ){
+        if( aSyscall[i].pDefault==0 ){
+          aSyscall[i].pDefault = aSyscall[i].pCurrent;
+        }
+        rc = SQLITE_OK;
+        if( pNewFunc==0 ) pNewFunc = aSyscall[i].pDefault;
+        aSyscall[i].pCurrent = pNewFunc;
+        break;
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Return the value of a system call.  Return NULL if zName is not a
+** recognized system call name.  NULL is also returned if the system call
+** is currently undefined.
+*/
+static sqlite3_syscall_ptr unixGetSystemCall(
+  sqlite3_vfs *pNotUsed,
+  const char *zName
+){
+  unsigned int i;
+
+  UNUSED_PARAMETER(pNotUsed);
+  for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+    if( strcmp(zName, aSyscall[i].zName)==0 ) return aSyscall[i].pCurrent;
+  }
+  return 0;
+}
+
+/*
+** Return the name of the first system call after zName.  If zName==NULL
+** then return the name of the first system call.  Return NULL if zName
+** is the last system call or if zName is not the name of a valid
+** system call.
+*/
+static const char *unixNextSystemCall(sqlite3_vfs *p, const char *zName){
+  int i = -1;
+
+  UNUSED_PARAMETER(p);
+  if( zName ){
+    for(i=0; i<ArraySize(aSyscall)-1; i++){
+      if( strcmp(zName, aSyscall[i].zName)==0 ) break;
+    }
+  }
+  for(i++; i<ArraySize(aSyscall); i++){
+    if( aSyscall[i].pCurrent!=0 ) return aSyscall[i].zName;
+  }
+  return 0;
+}
+
+/*
+** Do not accept any file descriptor less than this value, in order to avoid
+** opening database file using file descriptors that are commonly used for
+** standard input, output, and error.
+*/
+#ifndef SQLITE_MINIMUM_FILE_DESCRIPTOR
+# define SQLITE_MINIMUM_FILE_DESCRIPTOR 3
+#endif
+
+/*
+** Invoke open().  Do so multiple times, until it either succeeds or
+** fails for some reason other than EINTR.
+**
+** If the file creation mode "m" is 0 then set it to the default for
+** SQLite.  The default is SQLITE_DEFAULT_FILE_PERMISSIONS (normally
+** 0644) as modified by the system umask.  If m is not 0, then
+** make the file creation mode be exactly m ignoring the umask.
+**
+** The m parameter will be non-zero only when creating -wal, -journal,
+** and -shm files.  We want those files to have *exactly* the same
+** permissions as their original database, unadulterated by the umask.
+** In that way, if a database file is -rw-rw-rw or -rw-rw-r-, and a
+** transaction crashes and leaves behind hot journals, then any
+** process that is able to write to the database will also be able to
+** recover the hot journals.
+*/
+static int robust_open(const char *z, int f, mode_t m){
+  int fd;
+  mode_t m2 = m ? m : SQLITE_DEFAULT_FILE_PERMISSIONS;
+  while(1){
+#if defined(O_CLOEXEC)
+    fd = osOpen(z,f|O_CLOEXEC,m2);
+#else
+    fd = osOpen(z,f,m2);
+#endif
+    if( fd<0 ){
+      if( errno==EINTR ) continue;
+      break;
+    }
+    if( fd>=SQLITE_MINIMUM_FILE_DESCRIPTOR ) break;
+    if( (f & (O_EXCL|O_CREAT))==(O_EXCL|O_CREAT) ){
+      (void)osUnlink(z);
+    }
+    osClose(fd);
+    sqlite3_log(SQLITE_WARNING,
+                "attempt to open \"%s\" as file descriptor %d", z, fd);
+    fd = -1;
+    if( osOpen("/dev/null", O_RDONLY, m)<0 ) break;
+  }
+  if( fd>=0 ){
+    if( m!=0 ){
+      struct stat statbuf;
+      if( osFstat(fd, &statbuf)==0
+       && statbuf.st_size==0
+       && (statbuf.st_mode&0777)!=m
+      ){
+        osFchmod(fd, m);
+      }
+    }
+#if defined(FD_CLOEXEC) && (!defined(O_CLOEXEC) || O_CLOEXEC==0)
+    osFcntl(fd, F_SETFD, osFcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
+#endif
+  }
+  return fd;
+}
+
+/*
+** Helper functions to obtain and relinquish the global mutex. The
+** global mutex is used to protect the unixInodeInfo and
+** vxworksFileId objects used by this file, all of which may be
+** shared by multiple threads.
+**
+** Function unixMutexHeld() is used to assert() that the global mutex
+** is held when required. This function is only used as part of assert()
+** statements. e.g.
+**
+**   unixEnterMutex()
+**     assert( unixMutexHeld() );
+**   unixEnterLeave()
+**
+** To prevent deadlock, the global unixBigLock must must be acquired
+** before the unixInodeInfo.pLockMutex mutex, if both are held.  It is
+** OK to get the pLockMutex without holding unixBigLock first, but if
+** that happens, the unixBigLock mutex must not be acquired until after
+** pLockMutex is released.
+**
+**      OK:     enter(unixBigLock),  enter(pLockInfo)
+**      OK:     enter(unixBigLock)
+**      OK:     enter(pLockInfo)
+**   ERROR:     enter(pLockInfo), enter(unixBigLock)
+*/
+static sqlite3_mutex *unixBigLock = 0;
+static void unixEnterMutex(void){
+  assert( sqlite3_mutex_notheld(unixBigLock) );  /* Not a recursive mutex */
+  sqlite3_mutex_enter(unixBigLock);
+}
+static void unixLeaveMutex(void){
+  assert( sqlite3_mutex_held(unixBigLock) );
+  sqlite3_mutex_leave(unixBigLock);
+}
+#ifdef SQLITE_DEBUG
+static int unixMutexHeld(void) {
+  return sqlite3_mutex_held(unixBigLock);
+}
+#endif
+
+
+#ifdef SQLITE_HAVE_OS_TRACE
+/*
+** Helper function for printing out trace information from debugging
+** binaries. This returns the string representation of the supplied
+** integer lock-type.
+*/
+static const char *azFileLock(int eFileLock){
+  switch( eFileLock ){
+    case NO_LOCK: return "NONE";
+    case SHARED_LOCK: return "SHARED";
+    case RESERVED_LOCK: return "RESERVED";
+    case PENDING_LOCK: return "PENDING";
+    case EXCLUSIVE_LOCK: return "EXCLUSIVE";
+  }
+  return "ERROR";
+}
+#endif
+
+#ifdef SQLITE_LOCK_TRACE
+/*
+** Print out information about all locking operations.
+**
+** This routine is used for troubleshooting locks on multithreaded
+** platforms.  Enable by compiling with the -DSQLITE_LOCK_TRACE
+** command-line option on the compiler.  This code is normally
+** turned off.
+*/
+static int lockTrace(int fd, int op, struct flock *p){
+  char *zOpName, *zType;
+  int s;
+  int savedErrno;
+  if( op==F_GETLK ){
+    zOpName = "GETLK";
+  }else if( op==F_SETLK ){
+    zOpName = "SETLK";
+  }else{
+    s = osFcntl(fd, op, p);
+    sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
+    return s;
+  }
+  if( p->l_type==F_RDLCK ){
+    zType = "RDLCK";
+  }else if( p->l_type==F_WRLCK ){
+    zType = "WRLCK";
+  }else if( p->l_type==F_UNLCK ){
+    zType = "UNLCK";
+  }else{
+    assert( 0 );
+  }
+  assert( p->l_whence==SEEK_SET );
+  s = osFcntl(fd, op, p);
+  savedErrno = errno;
+  sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
+     threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
+     (int)p->l_pid, s);
+  if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
+    struct flock l2;
+    l2 = *p;
+    osFcntl(fd, F_GETLK, &l2);
+    if( l2.l_type==F_RDLCK ){
+      zType = "RDLCK";
+    }else if( l2.l_type==F_WRLCK ){
+      zType = "WRLCK";
+    }else if( l2.l_type==F_UNLCK ){
+      zType = "UNLCK";
+    }else{
+      assert( 0 );
+    }
+    sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
+       zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
+  }
+  errno = savedErrno;
+  return s;
+}
+#undef osFcntl
+#define osFcntl lockTrace
+#endif /* SQLITE_LOCK_TRACE */
+
+/*
+** Retry ftruncate() calls that fail due to EINTR
+**
+** All calls to ftruncate() within this file should be made through
+** this wrapper.  On the Android platform, bypassing the logic below
+** could lead to a corrupt database.
+*/
+static int robust_ftruncate(int h, sqlite3_int64 sz){
+  int rc;
+#ifdef __ANDROID__
+  /* On Android, ftruncate() always uses 32-bit offsets, even if
+  ** _FILE_OFFSET_BITS=64 is defined. This means it is unsafe to attempt to
+  ** truncate a file to any size larger than 2GiB. Silently ignore any
+  ** such attempts.  */
+  if( sz>(sqlite3_int64)0x7FFFFFFF ){
+    rc = SQLITE_OK;
+  }else
+#endif
+  do{ rc = osFtruncate(h,sz); }while( rc<0 && errno==EINTR );
+  return rc;
+}
+
+/*
+** This routine translates a standard POSIX errno code into something
+** useful to the clients of the sqlite3 functions.  Specifically, it is
+** intended to translate a variety of "try again" errors into SQLITE_BUSY
+** and a variety of "please close the file descriptor NOW" errors into
+** SQLITE_IOERR
+**
+** Errors during initialization of locks, or file system support for locks,
+** should handle ENOLCK, ENOTSUP, EOPNOTSUPP separately.
+*/
+static int sqliteErrorFromPosixError(int posixError, int sqliteIOErr) {
+  assert( (sqliteIOErr == SQLITE_IOERR_LOCK) ||
+          (sqliteIOErr == SQLITE_IOERR_UNLOCK) ||
+          (sqliteIOErr == SQLITE_IOERR_RDLOCK) ||
+          (sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) );
+  switch (posixError) {
+  case EACCES:
+  case EAGAIN:
+  case ETIMEDOUT:
+  case EBUSY:
+  case EINTR:
+  case ENOLCK:
+    /* random NFS retry error, unless during file system support
+     * introspection, in which it actually means what it says */
+    return SQLITE_BUSY;
+  
+  case EPERM:
+    return SQLITE_PERM;
+  
+  default:
+    return sqliteIOErr;
+  }
+}
+
+
+/******************************************************************************
+****************** Begin Unique File ID Utility Used By VxWorks ***************
+**
+** On most versions of unix, we can get a unique ID for a file by concatenating
+** the device number and the inode number.  But this does not work on VxWorks.
+** On VxWorks, a unique file id must be based on the canonical filename.
+**
+** A pointer to an instance of the following structure can be used as a
+** unique file ID in VxWorks.  Each instance of this structure contains
+** a copy of the canonical filename.  There is also a reference count.
+** The structure is reclaimed when the number of pointers to it drops to
+** zero.
+**
+** There are never very many files open at one time and lookups are not
+** a performance-critical path, so it is sufficient to put these
+** structures on a linked list.
+*/
+struct vxworksFileId {
+  struct vxworksFileId *pNext;  /* Next in a list of them all */
+  int nRef;                     /* Number of references to this one */
+  int nName;                    /* Length of the zCanonicalName[] string */
+  char *zCanonicalName;         /* Canonical filename */
+};
+
+#if OS_VXWORKS
+/*
+** All unique filenames are held on a linked list headed by this
+** variable:
+*/
+static struct vxworksFileId *vxworksFileList = 0;
+
+/*
+** Simplify a filename into its canonical form
+** by making the following changes:
+**
+**  * removing any trailing and duplicate /
+**  * convert /./ into just /
+**  * convert /A/../ where A is any simple name into just /
+**
+** Changes are made in-place.  Return the new name length.
+**
+** The original filename is in z[0..n-1].  Return the number of
+** characters in the simplified name.
+*/
+static int vxworksSimplifyName(char *z, int n){
+  int i, j;
+  while( n>1 && z[n-1]=='/' ){ n--; }
+  for(i=j=0; i<n; i++){
+    if( z[i]=='/' ){
+      if( z[i+1]=='/' ) continue;
+      if( z[i+1]=='.' && i+2<n && z[i+2]=='/' ){
+        i += 1;
+        continue;
+      }
+      if( z[i+1]=='.' && i+3<n && z[i+2]=='.' && z[i+3]=='/' ){
+        while( j>0 && z[j-1]!='/' ){ j--; }
+        if( j>0 ){ j--; }
+        i += 2;
+        continue;
+      }
+    }
+    z[j++] = z[i];
+  }
+  z[j] = 0;
+  return j;
+}
+
+/*
+** Find a unique file ID for the given absolute pathname.  Return
+** a pointer to the vxworksFileId object.  This pointer is the unique
+** file ID.
+**
+** The nRef field of the vxworksFileId object is incremented before
+** the object is returned.  A new vxworksFileId object is created
+** and added to the global list if necessary.
+**
+** If a memory allocation error occurs, return NULL.
+*/
+static struct vxworksFileId *vxworksFindFileId(const char *zAbsoluteName){
+  struct vxworksFileId *pNew;         /* search key and new file ID */
+  struct vxworksFileId *pCandidate;   /* For looping over existing file IDs */
+  int n;                              /* Length of zAbsoluteName string */
+
+  assert( zAbsoluteName[0]=='/' );
+  n = (int)strlen(zAbsoluteName);
+  pNew = sqlite3_malloc64( sizeof(*pNew) + (n+1) );
+  if( pNew==0 ) return 0;
+  pNew->zCanonicalName = (char*)&pNew[1];
+  memcpy(pNew->zCanonicalName, zAbsoluteName, n+1);
+  n = vxworksSimplifyName(pNew->zCanonicalName, n);
+
+  /* Search for an existing entry that matching the canonical name.
+  ** If found, increment the reference count and return a pointer to
+  ** the existing file ID.
+  */
+  unixEnterMutex();
+  for(pCandidate=vxworksFileList; pCandidate; pCandidate=pCandidate->pNext){
+    if( pCandidate->nName==n
+     && memcmp(pCandidate->zCanonicalName, pNew->zCanonicalName, n)==0
+    ){
+       sqlite3_free(pNew);
+       pCandidate->nRef++;
+       unixLeaveMutex();
+       return pCandidate;
+    }
+  }
+
+  /* No match was found.  We will make a new file ID */
+  pNew->nRef = 1;
+  pNew->nName = n;
+  pNew->pNext = vxworksFileList;
+  vxworksFileList = pNew;
+  unixLeaveMutex();
+  return pNew;
+}
+
+/*
+** Decrement the reference count on a vxworksFileId object.  Free
+** the object when the reference count reaches zero.
+*/
+static void vxworksReleaseFileId(struct vxworksFileId *pId){
+  unixEnterMutex();
+  assert( pId->nRef>0 );
+  pId->nRef--;
+  if( pId->nRef==0 ){
+    struct vxworksFileId **pp;
+    for(pp=&vxworksFileList; *pp && *pp!=pId; pp = &((*pp)->pNext)){}
+    assert( *pp==pId );
+    *pp = pId->pNext;
+    sqlite3_free(pId);
+  }
+  unixLeaveMutex();
+}
+#endif /* OS_VXWORKS */
+/*************** End of Unique File ID Utility Used By VxWorks ****************
+******************************************************************************/
+
+
+/******************************************************************************
+*************************** Posix Advisory Locking ****************************
+**
+** POSIX advisory locks are broken by design.  ANSI STD 1003.1 (1996)
+** section 6.5.2.2 lines 483 through 490 specify that when a process
+** sets or clears a lock, that operation overrides any prior locks set
+** by the same process.  It does not explicitly say so, but this implies
+** that it overrides locks set by the same process using a different
+** file descriptor.  Consider this test case:
+**
+**       int fd1 = open("./file1", O_RDWR|O_CREAT, 0644);
+**       int fd2 = open("./file2", O_RDWR|O_CREAT, 0644);
+**
+** Suppose ./file1 and ./file2 are really the same file (because
+** one is a hard or symbolic link to the other) then if you set
+** an exclusive lock on fd1, then try to get an exclusive lock
+** on fd2, it works.  I would have expected the second lock to
+** fail since there was already a lock on the file due to fd1.
+** But not so.  Since both locks came from the same process, the
+** second overrides the first, even though they were on different
+** file descriptors opened on different file names.
+**
+** This means that we cannot use POSIX locks to synchronize file access
+** among competing threads of the same process.  POSIX locks will work fine
+** to synchronize access for threads in separate processes, but not
+** threads within the same process.
+**
+** To work around the problem, SQLite has to manage file locks internally
+** on its own.  Whenever a new database is opened, we have to find the
+** specific inode of the database file (the inode is determined by the
+** st_dev and st_ino fields of the stat structure that fstat() fills in)
+** and check for locks already existing on that inode.  When locks are
+** created or removed, we have to look at our own internal record of the
+** locks to see if another thread has previously set a lock on that same
+** inode.
+**
+** (Aside: The use of inode numbers as unique IDs does not work on VxWorks.
+** For VxWorks, we have to use the alternative unique ID system based on
+** canonical filename and implemented in the previous division.)
+**
+** The sqlite3_file structure for POSIX is no longer just an integer file
+** descriptor.  It is now a structure that holds the integer file
+** descriptor and a pointer to a structure that describes the internal
+** locks on the corresponding inode.  There is one locking structure
+** per inode, so if the same inode is opened twice, both unixFile structures
+** point to the same locking structure.  The locking structure keeps
+** a reference count (so we will know when to delete it) and a "cnt"
+** field that tells us its internal lock status.  cnt==0 means the
+** file is unlocked.  cnt==-1 means the file has an exclusive lock.
+** cnt>0 means there are cnt shared locks on the file.
+**
+** Any attempt to lock or unlock a file first checks the locking
+** structure.  The fcntl() system call is only invoked to set a
+** POSIX lock if the internal lock structure transitions between
+** a locked and an unlocked state.
+**
+** But wait:  there are yet more problems with POSIX advisory locks.
+**
+** If you close a file descriptor that points to a file that has locks,
+** all locks on that file that are owned by the current process are
+** released.  To work around this problem, each unixInodeInfo object
+** maintains a count of the number of pending locks on the inode.
+** When an attempt is made to close an unixFile, if there are
+** other unixFile open on the same inode that are holding locks, the call
+** to close() the file descriptor is deferred until all of the locks clear.
+** The unixInodeInfo structure keeps a list of file descriptors that need to
+** be closed and that list is walked (and cleared) when the last lock
+** clears.
+**
+** Yet another problem:  LinuxThreads do not play well with posix locks.
+**
+** Many older versions of linux use the LinuxThreads library which is
+** not posix compliant.  Under LinuxThreads, a lock created by thread
+** A cannot be modified or overridden by a different thread B.
+** Only thread A can modify the lock.  Locking behavior is correct
+** if the application uses the newer Native Posix Thread Library (NPTL)
+** on linux - with NPTL a lock created by thread A can override locks
+** in thread B.  But there is no way to know at compile-time which
+** threading library is being used.  So there is no way to know at
+** compile-time whether or not thread A can override locks on thread B.
+** One has to do a run-time check to discover the behavior of the
+** current process.
+**
+** SQLite used to support LinuxThreads.  But support for LinuxThreads
+** was dropped beginning with version 3.7.0.  SQLite will still work with
+** LinuxThreads provided that (1) there is no more than one connection
+** per database file in the same process and (2) database connections
+** do not move across threads.
+*/
+
+/*
+** An instance of the following structure serves as the key used
+** to locate a particular unixInodeInfo object.
+*/
+struct unixFileId {
+  dev_t dev;                  /* Device number */
+#if OS_VXWORKS
+  struct vxworksFileId *pId;  /* Unique file ID for vxworks. */
+#else
+  /* We are told that some versions of Android contain a bug that
+  ** sizes ino_t at only 32-bits instead of 64-bits. (See
+  ** https://android-review.googlesource.com/#/c/115351/3/dist/sqlite3.c)
+  ** To work around this, always allocate 64-bits for the inode number.
+  ** On small machines that only have 32-bit inodes, this wastes 4 bytes,
+  ** but that should not be a big deal. */
+  /* WAS:  ino_t ino;   */
+  u64 ino;                   /* Inode number */
+#endif
+};
+
+/*
+** An instance of the following structure is allocated for each open
+** inode.
+**
+** A single inode can have multiple file descriptors, so each unixFile
+** structure contains a pointer to an instance of this object and this
+** object keeps a count of the number of unixFile pointing to it.
+**
+** Mutex rules:
+**
+**  (1) Only the pLockMutex mutex must be held in order to read or write
+**      any of the locking fields:
+**          nShared, nLock, eFileLock, bProcessLock, pUnused
+**
+**  (2) When nRef>0, then the following fields are unchanging and can
+**      be read (but not written) without holding any mutex:
+**          fileId, pLockMutex
+**
+**  (3) With the exceptions above, all the fields may only be read
+**      or written while holding the global unixBigLock mutex.
+**
+** Deadlock prevention:  The global unixBigLock mutex may not
+** be acquired while holding the pLockMutex mutex.  If both unixBigLock
+** and pLockMutex are needed, then unixBigLock must be acquired first.
+*/
+struct unixInodeInfo {
+  struct unixFileId fileId;       /* The lookup key */
+  sqlite3_mutex *pLockMutex;      /* Hold this mutex for... */
+  int nShared;                      /* Number of SHARED locks held */
+  int nLock;                        /* Number of outstanding file locks */
+  unsigned char eFileLock;          /* One of SHARED_LOCK, RESERVED_LOCK etc. */
+  unsigned char bProcessLock;       /* An exclusive process lock is held */
+  UnixUnusedFd *pUnused;            /* Unused file descriptors to close */
+  int nRef;                       /* Number of pointers to this structure */
+  unixShmNode *pShmNode;          /* Shared memory associated with this inode */
+  unixInodeInfo *pNext;           /* List of all unixInodeInfo objects */
+  unixInodeInfo *pPrev;           /*    .... doubly linked */
+#if SQLITE_ENABLE_LOCKING_STYLE
+  unsigned long long sharedByte;  /* for AFP simulated shared lock */
+#endif
+#if OS_VXWORKS
+  sem_t *pSem;                    /* Named POSIX semaphore */
+  char aSemName[MAX_PATHNAME+2];  /* Name of that semaphore */
+#endif
+};
+
+/*
+** A lists of all unixInodeInfo objects.
+**
+** Must hold unixBigLock in order to read or write this variable.
+*/
+static unixInodeInfo *inodeList = 0;  /* All unixInodeInfo objects */
+
+#ifdef SQLITE_DEBUG
+/*
+** True if the inode mutex (on the unixFile.pFileMutex field) is held, or not.
+** This routine is used only within assert() to help verify correct mutex
+** usage.
+*/
+int unixFileMutexHeld(unixFile *pFile){
+  assert( pFile->pInode );
+  return sqlite3_mutex_held(pFile->pInode->pLockMutex);
+}
+int unixFileMutexNotheld(unixFile *pFile){
+  assert( pFile->pInode );
+  return sqlite3_mutex_notheld(pFile->pInode->pLockMutex);
+}
+#endif
+
+/*
+**
+** This function - unixLogErrorAtLine(), is only ever called via the macro
+** unixLogError().
+**
+** It is invoked after an error occurs in an OS function and errno has been
+** set. It logs a message using sqlite3_log() containing the current value of
+** errno and, if possible, the human-readable equivalent from strerror() or
+** strerror_r().
+**
+** The first argument passed to the macro should be the error code that
+** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN).
+** The two subsequent arguments should be the name of the OS function that
+** failed (e.g. "unlink", "open") and the associated file-system path,
+** if any.
+*/
+#define unixLogError(a,b,c)     unixLogErrorAtLine(a,b,c,__LINE__)
+static int unixLogErrorAtLine(
+  int errcode,                    /* SQLite error code */
+  const char *zFunc,              /* Name of OS function that failed */
+  const char *zPath,              /* File path associated with error */
+  int iLine                       /* Source line number where error occurred */
+){
+  char *zErr;                     /* Message from strerror() or equivalent */
+  int iErrno = errno;             /* Saved syscall error number */
+
+  /* If this is not a threadsafe build (SQLITE_THREADSAFE==0), then use
+  ** the strerror() function to obtain the human-readable error message
+  ** equivalent to errno. Otherwise, use strerror_r().
+  */
+#if SQLITE_THREADSAFE && defined(HAVE_STRERROR_R)
+  char aErr[80];
+  memset(aErr, 0, sizeof(aErr));
+  zErr = aErr;
+
+  /* If STRERROR_R_CHAR_P (set by autoconf scripts) or __USE_GNU is defined,
+  ** assume that the system provides the GNU version of strerror_r() that
+  ** returns a pointer to a buffer containing the error message. That pointer
+  ** may point to aErr[], or it may point to some static storage somewhere.
+  ** Otherwise, assume that the system provides the POSIX version of
+  ** strerror_r(), which always writes an error message into aErr[].
+  **
+  ** If the code incorrectly assumes that it is the POSIX version that is
+  ** available, the error message will often be an empty string. Not a
+  ** huge problem. Incorrectly concluding that the GNU version is available
+  ** could lead to a segfault though.
+  */
+#if defined(STRERROR_R_CHAR_P) || defined(__USE_GNU)
+  zErr =
+# endif
+  strerror_r(iErrno, aErr, sizeof(aErr)-1);
+
+#elif SQLITE_THREADSAFE
+  /* This is a threadsafe build, but strerror_r() is not available. */
+  zErr = "";
+#else
+  /* Non-threadsafe build, use strerror(). */
+  zErr = strerror(iErrno);
+#endif
+
+  if( zPath==0 ) zPath = "";
+  sqlite3_log(errcode,
+      "os_unix.c:%d: (%d) %s(%s) - %s",
+      iLine, iErrno, zFunc, zPath, zErr
+  );
+
+  return errcode;
+}
+
+/*
+** Close a file descriptor.
+**
+** We assume that close() almost always works, since it is only in a
+** very sick application or on a very sick platform that it might fail.
+** If it does fail, simply leak the file descriptor, but do log the
+** error.
+**
+** Note that it is not safe to retry close() after EINTR since the
+** file descriptor might have already been reused by another thread.
+** So we don't even try to recover from an EINTR.  Just log the error
+** and move on.
+*/
+static void robust_close(unixFile *pFile, int h, int lineno){
+  if( osClose(h) ){
+    unixLogErrorAtLine(SQLITE_IOERR_CLOSE, "close",
+                       pFile ? pFile->zPath : 0, lineno);
+  }
+}
+
+/*
+** Set the pFile->lastErrno.  Do this in a subroutine as that provides
+** a convenient place to set a breakpoint.
+*/
+static void storeLastErrno(unixFile *pFile, int error){
+  pFile->lastErrno = error;
+}
+
+/*
+** Close all file descriptors accumulated in the unixInodeInfo->pUnused list.
+*/
+static void closePendingFds(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
+  UnixUnusedFd *p;
+  UnixUnusedFd *pNext;
+  assert( unixFileMutexHeld(pFile) );
+  for(p=pInode->pUnused; p; p=pNext){
+    pNext = p->pNext;
+    robust_close(pFile, p->fd, __LINE__);
+    sqlite3_free(p);
+  }
+  pInode->pUnused = 0;
+}
+
+/*
+** Release a unixInodeInfo structure previously allocated by findInodeInfo().
+**
+** The global mutex must be held when this routine is called, but the mutex
+** on the inode being deleted must NOT be held.
+*/
+static void releaseInodeInfo(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
+  assert( unixMutexHeld() );
+  assert( unixFileMutexNotheld(pFile) );
+  if( ALWAYS(pInode) ){
+    pInode->nRef--;
+    if( pInode->nRef==0 ){
+      assert( pInode->pShmNode==0 );
+      sqlite3_mutex_enter(pInode->pLockMutex);
+      closePendingFds(pFile);
+      sqlite3_mutex_leave(pInode->pLockMutex);
+      if( pInode->pPrev ){
+        assert( pInode->pPrev->pNext==pInode );
+        pInode->pPrev->pNext = pInode->pNext;
+      }else{
+        assert( inodeList==pInode );
+        inodeList = pInode->pNext;
+      }
+      if( pInode->pNext ){
+        assert( pInode->pNext->pPrev==pInode );
+        pInode->pNext->pPrev = pInode->pPrev;
+      }
+      sqlite3_mutex_free(pInode->pLockMutex);
+      sqlite3_free(pInode);
+    }
+  }
+}
+
+/*
+** Given a file descriptor, locate the unixInodeInfo object that
+** describes that file descriptor.  Create a new one if necessary.  The
+** return value might be uninitialized if an error occurs.
+**
+** The global mutex must held when calling this routine.
+**
+** Return an appropriate error code.
+*/
+static int findInodeInfo(
+  unixFile *pFile,               /* Unix file with file desc used in the key */
+  unixInodeInfo **ppInode        /* Return the unixInodeInfo object here */
+){
+  int rc;                        /* System call return code */
+  int fd;                        /* The file descriptor for pFile */
+  struct unixFileId fileId;      /* Lookup key for the unixInodeInfo */
+  struct stat statbuf;           /* Low-level file information */
+  unixInodeInfo *pInode = 0;     /* Candidate unixInodeInfo object */
+
+  assert( unixMutexHeld() );
+
+  /* Get low-level information about the file that we can used to
+  ** create a unique name for the file.
+  */
+  fd = pFile->h;
+  rc = osFstat(fd, &statbuf);
+  if( rc!=0 ){
+    storeLastErrno(pFile, errno);
+#if defined(EOVERFLOW) && defined(SQLITE_DISABLE_LFS)
+    if( pFile->lastErrno==EOVERFLOW ) return SQLITE_NOLFS;
+#endif
+    return SQLITE_IOERR;
+  }
+
+#ifdef __APPLE__
+  /* On OS X on an msdos filesystem, the inode number is reported
+  ** incorrectly for zero-size files.  See ticket #3260.  To work
+  ** around this problem (we consider it a bug in OS X, not SQLite)
+  ** we always increase the file size to 1 by writing a single byte
+  ** prior to accessing the inode number.  The one byte written is
+  ** an ASCII 'S' character which also happens to be the first byte
+  ** in the header of every SQLite database.  In this way, if there
+  ** is a race condition such that another thread has already populated
+  ** the first page of the database, no damage is done.
+  */
+  if( statbuf.st_size==0 && (pFile->fsFlags & SQLITE_FSFLAGS_IS_MSDOS)!=0 ){
+    do{ rc = osWrite(fd, "S", 1); }while( rc<0 && errno==EINTR );
+    if( rc!=1 ){
+      storeLastErrno(pFile, errno);
+      return SQLITE_IOERR;
+    }
+    rc = osFstat(fd, &statbuf);
+    if( rc!=0 ){
+      storeLastErrno(pFile, errno);
+      return SQLITE_IOERR;
+    }
+  }
+#endif
+
+  memset(&fileId, 0, sizeof(fileId));
+  fileId.dev = statbuf.st_dev;
+#if OS_VXWORKS
+  fileId.pId = pFile->pId;
+#else
+  fileId.ino = (u64)statbuf.st_ino;
+#endif
+  assert( unixMutexHeld() );
+  pInode = inodeList;
+  while( pInode && memcmp(&fileId, &pInode->fileId, sizeof(fileId)) ){
+    pInode = pInode->pNext;
+  }
+  if( pInode==0 ){
+    pInode = sqlite3_malloc64( sizeof(*pInode) );
+    if( pInode==0 ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    memset(pInode, 0, sizeof(*pInode));
+    memcpy(&pInode->fileId, &fileId, sizeof(fileId));
+    if( sqlite3GlobalConfig.bCoreMutex ){
+      pInode->pLockMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+      if( pInode->pLockMutex==0 ){
+        sqlite3_free(pInode);
+        return SQLITE_NOMEM_BKPT;
+      }
+    }
+    pInode->nRef = 1;
+    assert( unixMutexHeld() );
+    pInode->pNext = inodeList;
+    pInode->pPrev = 0;
+    if( inodeList ) inodeList->pPrev = pInode;
+    inodeList = pInode;
+  }else{
+    pInode->nRef++;
+  }
+  *ppInode = pInode;
+  return SQLITE_OK;
+}
+
+/*
+** Return TRUE if pFile has been renamed or unlinked since it was first opened.
+*/
+static int fileHasMoved(unixFile *pFile){
+#if OS_VXWORKS
+  return pFile->pInode!=0 && pFile->pId!=pFile->pInode->fileId.pId;
+#else
+  struct stat buf;
+  return pFile->pInode!=0 &&
+      (osStat(pFile->zPath, &buf)!=0
+         || (u64)buf.st_ino!=pFile->pInode->fileId.ino);
+#endif
+}
+
+
+/*
+** Check a unixFile that is a database.  Verify the following:
+**
+** (1) There is exactly one hard link on the file
+** (2) The file is not a symbolic link
+** (3) The file has not been renamed or unlinked
+**
+** Issue sqlite3_log(SQLITE_WARNING,...) messages if anything is not right.
+*/
+static void verifyDbFile(unixFile *pFile){
+  struct stat buf;
+  int rc;
+
+  /* These verifications occurs for the main database only */
+  if( pFile->ctrlFlags & UNIXFILE_NOLOCK ) return;
+
+  rc = osFstat(pFile->h, &buf);
+  if( rc!=0 ){
+    sqlite3_log(SQLITE_WARNING, "cannot fstat db file %s", pFile->zPath);
+    return;
+  }
+  if( buf.st_nlink==0 ){
+    sqlite3_log(SQLITE_WARNING, "file unlinked while open: %s", pFile->zPath);
+    return;
+  }
+  if( buf.st_nlink>1 ){
+    sqlite3_log(SQLITE_WARNING, "multiple links to file: %s", pFile->zPath);
+    return;
+  }
+  if( fileHasMoved(pFile) ){
+    sqlite3_log(SQLITE_WARNING, "file renamed while open: %s", pFile->zPath);
+    return;
+  }
+}
+
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+
+  assert( pFile );
+  assert( pFile->eFileLock<=SHARED_LOCK );
+  sqlite3_mutex_enter(pFile->pInode->pLockMutex);
+
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+
+  /* Otherwise see if some other process holds it.
+  */
+#ifndef __DJGPP__
+  if( !reserved && !pFile->pInode->bProcessLock ){
+    struct flock lock;
+    lock.l_whence = SEEK_SET;
+    lock.l_start = RESERVED_BYTE;
+    lock.l_len = 1;
+    lock.l_type = F_WRLCK;
+    if( osFcntl(pFile->h, F_GETLK, &lock) ){
+      rc = SQLITE_IOERR_CHECKRESERVEDLOCK;
+      storeLastErrno(pFile, errno);
+    } else if( lock.l_type!=F_UNLCK ){
+      reserved = 1;
+    }
+  }
+#endif
+
+  sqlite3_mutex_leave(pFile->pInode->pLockMutex);
+  OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
+
+  *pResOut = reserved;
+  return rc;
+}
+
+/* Forward declaration*/
+static int unixSleep(sqlite3_vfs*,int);
+
+/*
+** Set a posix-advisory-lock.
+**
+** There are two versions of this routine.  If compiled with
+** SQLITE_ENABLE_SETLK_TIMEOUT then the routine has an extra parameter
+** which is a pointer to a unixFile.  If the unixFile->iBusyTimeout
+** value is set, then it is the number of milliseconds to wait before
+** failing the lock.  The iBusyTimeout value is always reset back to
+** zero on each call.
+**
+** If SQLITE_ENABLE_SETLK_TIMEOUT is not defined, then do a non-blocking
+** attempt to set the lock.
+*/
+#ifndef SQLITE_ENABLE_SETLK_TIMEOUT
+# define osSetPosixAdvisoryLock(h,x,t) osFcntl(h,F_SETLK,x)
+#else
+static int osSetPosixAdvisoryLock(
+  int h,                /* The file descriptor on which to take the lock */
+  struct flock *pLock,  /* The description of the lock */
+  unixFile *pFile       /* Structure holding timeout value */
+){
+  int tm = pFile->iBusyTimeout;
+  int rc = osFcntl(h,F_SETLK,pLock);
+  while( rc<0 && tm>0 ){
+    /* On systems that support some kind of blocking file lock with a timeout,
+    ** make appropriate changes here to invoke that blocking file lock.  On
+    ** generic posix, however, there is no such API.  So we simply try the
+    ** lock once every millisecond until either the timeout expires, or until
+    ** the lock is obtained. */
+    unixSleep(0,1000);
+    rc = osFcntl(h,F_SETLK,pLock);
+    tm--;
+  }
+  return rc;
+}
+#endif /* SQLITE_ENABLE_SETLK_TIMEOUT */
+
+
+/*
+** Attempt to set a system-lock on the file pFile.  The lock is
+** described by pLock.
+**
+** If the pFile was opened read/write from unix-excl, then the only lock
+** ever obtained is an exclusive lock, and it is obtained exactly once
+** the first time any lock is attempted.  All subsequent system locking
+** operations become no-ops.  Locking operations still happen internally,
+** in order to coordinate access between separate database connections
+** within this process, but all of that is handled in memory and the
+** operating system does not participate.
+**
+** This function is a pass-through to fcntl(F_SETLK) if pFile is using
+** any VFS other than "unix-excl" or if pFile is opened on "unix-excl"
+** and is read-only.
+**
+** Zero is returned if the call completes successfully, or -1 if a call
+** to fcntl() fails. In this case, errno is set appropriately (by fcntl()).
+*/
+static int unixFileLock(unixFile *pFile, struct flock *pLock){
+  int rc;
+  unixInodeInfo *pInode = pFile->pInode;
+  assert( pInode!=0 );
+  assert( sqlite3_mutex_held(pInode->pLockMutex) );
+  if( (pFile->ctrlFlags & (UNIXFILE_EXCL|UNIXFILE_RDONLY))==UNIXFILE_EXCL ){
+    if( pInode->bProcessLock==0 ){
+      struct flock lock;
+      assert( pInode->nLock==0 );
+      lock.l_whence = SEEK_SET;
+      lock.l_start = SHARED_FIRST;
+      lock.l_len = SHARED_SIZE;
+      lock.l_type = F_WRLCK;
+      rc = osSetPosixAdvisoryLock(pFile->h, &lock, pFile);
+      if( rc<0 ) return rc;
+      pInode->bProcessLock = 1;
+      pInode->nLock++;
+    }else{
+      rc = 0;
+    }
+  }else{
+    rc = osSetPosixAdvisoryLock(pFile->h, pLock, pFile);
+  }
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int unixLock(sqlite3_file *id, int eFileLock){
+  /* The following describes the implementation of the various locks and
+  ** lock transitions in terms of the POSIX advisory shared and exclusive
+  ** lock primitives (called read-locks and write-locks below, to avoid
+  ** confusion with SQLite lock names). The algorithms are complicated
+  ** slightly in order to be compatible with Windows95 systems simultaneously
+  ** accessing the same database file, in case that is ever required.
+  **
+  ** Symbols defined in os.h identify the 'pending byte' and the 'reserved
+  ** byte', each single bytes at well known offsets, and the 'shared byte
+  ** range', a range of 510 bytes at a well known offset.
+  **
+  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
+  ** byte'.  If this is successful, 'shared byte range' is read-locked
+  ** and the lock on the 'pending byte' released.  (Legacy note:  When
+  ** SQLite was first developed, Windows95 systems were still very common,
+  ** and Windows95 lacks a shared-lock capability.  So on Windows95, a
+  ** single randomly selected by from the 'shared byte range' is locked.
+  ** Windows95 is now pretty much extinct, but this work-around for the
+  ** lack of shared-locks on Windows95 lives on, for backwards
+  ** compatibility.)
+  **
+  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
+  ** A RESERVED lock is implemented by grabbing a write-lock on the
+  ** 'reserved byte'.
+  **
+  ** An EXCLUSIVE lock may only be requested after either a SHARED or
+  ** RESERVED lock is held. An EXCLUSIVE lock is implemented by obtaining
+  ** a write-lock on the entire 'shared byte range'. Since all other locks
+  ** require a read-lock on one of the bytes within this range, this ensures
+  ** that no other locks are held on the database.
+  **
+  ** If a process that holds a RESERVED lock requests an EXCLUSIVE, then
+  ** a PENDING lock is obtained first. A PENDING lock is implemented by
+  ** obtaining a write-lock on the 'pending byte'. This ensures that no new
+  ** SHARED locks can be obtained, but existing SHARED locks are allowed to
+  ** persist. If the call to this function fails to obtain the EXCLUSIVE
+  ** lock in this case, it holds the PENDING lock instead. The client may
+  ** then re-attempt the EXCLUSIVE lock later on, after existing SHARED
+  ** locks have cleared.
+  */
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  struct flock lock;
+  int tErrno = 0;
+
+  assert( pFile );
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
+      azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+      azFileLock(pFile->pInode->eFileLock), pFile->pInode->nShared,
+      osGetpid(0)));
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** unixFile, do nothing. Don't use the end_lock: exit path, as
+  ** unixEnterMutex() hasn't been called yet.
+  */
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
+            azFileLock(eFileLock)));
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct.
+  **  (1) We never move from unlocked to anything higher than shared lock.
+  **  (2) SQLite never explicitly requests a pending lock.
+  **  (3) A shared lock is always held when a reserve lock is requested.
+  */
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
+
+  /* This mutex is needed because pFile->pInode is shared across threads
+  */
+  pInode = pFile->pInode;
+  sqlite3_mutex_enter(pInode->pLockMutex);
+
+  /* If some thread using this PID has a lock via a different unixFile*
+  ** handle that precludes the requested lock, return BUSY.
+  */
+  if( (pFile->eFileLock!=pInode->eFileLock &&
+          (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
+  ){
+    rc = SQLITE_BUSY;
+    goto end_lock;
+  }
+
+  /* If a SHARED lock is requested, and some thread using this PID already
+  ** has a SHARED or RESERVED lock, then increment reference counts and
+  ** return SQLITE_OK.
+  */
+  if( eFileLock==SHARED_LOCK &&
+      (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
+    goto end_lock;
+  }
+
+
+  /* A PENDING lock is needed before acquiring a SHARED lock and before
+  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
+  ** be released.
+  */
+  lock.l_len = 1L;
+  lock.l_whence = SEEK_SET;
+  if( eFileLock==SHARED_LOCK
+   || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock==RESERVED_LOCK)
+  ){
+    lock.l_type = (eFileLock==SHARED_LOCK?F_RDLCK:F_WRLCK);
+    lock.l_start = PENDING_BYTE;
+    if( unixFileLock(pFile, &lock) ){
+      tErrno = errno;
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+      if( rc!=SQLITE_BUSY ){
+        storeLastErrno(pFile, tErrno);
+      }
+      goto end_lock;
+    }else if( eFileLock==EXCLUSIVE_LOCK ){
+      pFile->eFileLock = PENDING_LOCK;
+      pInode->eFileLock = PENDING_LOCK;
+    }
+  }
+
+
+  /* If control gets to this point, then actually go ahead and make
+  ** operating system calls for the specified lock.
+  */
+  if( eFileLock==SHARED_LOCK ){
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
+    assert( rc==SQLITE_OK );
+
+    /* Now get the read-lock */
+    lock.l_start = SHARED_FIRST;
+    lock.l_len = SHARED_SIZE;
+    if( unixFileLock(pFile, &lock) ){
+      tErrno = errno;
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+    }
+
+    /* Drop the temporary PENDING lock */
+    lock.l_start = PENDING_BYTE;
+    lock.l_len = 1L;
+    lock.l_type = F_UNLCK;
+    if( unixFileLock(pFile, &lock) && rc==SQLITE_OK ){
+      /* This could happen with a network mount */
+      tErrno = errno;
+      rc = SQLITE_IOERR_UNLOCK;
+    }
+
+    if( rc ){
+      if( rc!=SQLITE_BUSY ){
+        storeLastErrno(pFile, tErrno);
+      }
+      goto end_lock;
+    }else{
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
+    }
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
+    /* We are trying for an exclusive lock but another thread in this
+    ** same process is still holding a shared lock. */
+    rc = SQLITE_BUSY;
+  }else{
+    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
+    ** assumed that there is a SHARED or greater lock on the file
+    ** already.
+    */
+    assert( 0!=pFile->eFileLock );
+    lock.l_type = F_WRLCK;
+
+    assert( eFileLock==RESERVED_LOCK || eFileLock==EXCLUSIVE_LOCK );
+    if( eFileLock==RESERVED_LOCK ){
+      lock.l_start = RESERVED_BYTE;
+      lock.l_len = 1L;
+    }else{
+      lock.l_start = SHARED_FIRST;
+      lock.l_len = SHARED_SIZE;
+    }
+
+    if( unixFileLock(pFile, &lock) ){
+      tErrno = errno;
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+      if( rc!=SQLITE_BUSY ){
+        storeLastErrno(pFile, tErrno);
+      }
+    }
+  }
+
+
+#ifdef SQLITE_DEBUG
+  /* Set up the transaction-counter change checking flags when
+  ** transitioning from a SHARED to a RESERVED lock.  The change
+  ** from SHARED to RESERVED marks the beginning of a normal
+  ** write operation (not a hot journal rollback).
+  */
+  if( rc==SQLITE_OK
+   && pFile->eFileLock<=SHARED_LOCK
+   && eFileLock==RESERVED_LOCK
+  ){
+    pFile->transCntrChng = 0;
+    pFile->dbUpdate = 0;
+    pFile->inNormalWrite = 1;
+  }
+#endif
+
+  if( rc==SQLITE_OK ){
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }
+
+end_lock:
+  sqlite3_mutex_leave(pInode->pLockMutex);
+  OSTRACE(("LOCK    %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock),
+      rc==SQLITE_OK ? "ok" : "failed"));
+  return rc;
+}
+
+/*
+** Add the file descriptor used by file handle pFile to the corresponding
+** pUnused list.
+*/
+static void setPendingFd(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
+  UnixUnusedFd *p = pFile->pPreallocatedUnused;
+  assert( unixFileMutexHeld(pFile) );
+  p->pNext = pInode->pUnused;
+  pInode->pUnused = p;
+  pFile->h = -1;
+  pFile->pPreallocatedUnused = 0;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+**
+** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED
+** the byte range is divided into 2 parts and the first part is unlocked then
+** set to a read lock, then the other part is simply unlocked.  This works
+** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to
+** remove the write lock on a region when a read lock is set.
+*/
+static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  struct flock lock;
+  int rc = SQLITE_OK;
+
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock,
+      pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+      osGetpid(0)));
+
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
+    return SQLITE_OK;
+  }
+  pInode = pFile->pInode;
+  sqlite3_mutex_enter(pInode->pLockMutex);
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
+
+#ifdef SQLITE_DEBUG
+    /* When reducing a lock such that other processes can start
+    ** reading the database file again, make sure that the
+    ** transaction counter was updated if any part of the database
+    ** file changed.  If the transaction counter is not updated,
+    ** other connections to the same file might not realize that
+    ** the file has changed and hence might not know to flush their
+    ** cache.  The use of a stale cache can lead to database corruption.
+    */
+    pFile->inNormalWrite = 0;
+#endif
+
+    /* downgrading to a shared lock on NFS involves clearing the write lock
+    ** before establishing the readlock - to avoid a race condition we downgrade
+    ** the lock in 2 blocks, so that part of the range will be covered by a
+    ** write lock until the rest is covered by a read lock:
+    **  1:   [WWWWW]
+    **  2:   [....W]
+    **  3:   [RRRRW]
+    **  4:   [RRRR.]
+    */
+    if( eFileLock==SHARED_LOCK ){
+#if !defined(__APPLE__) || !SQLITE_ENABLE_LOCKING_STYLE
+      (void)handleNFSUnlock;
+      assert( handleNFSUnlock==0 );
+#endif
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+      if( handleNFSUnlock ){
+        int tErrno;               /* Error code from system call errors */
+        off_t divSize = SHARED_SIZE - 1;
+      
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( unixFileLock(pFile, &lock)==(-1) ){
+          tErrno = errno;
+          rc = SQLITE_IOERR_UNLOCK;
+          storeLastErrno(pFile, tErrno);
+          goto end_unlock;
+        }
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( unixFileLock(pFile, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            storeLastErrno(pFile, tErrno);
+          }
+          goto end_unlock;
+        }
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST+divSize;
+        lock.l_len = SHARED_SIZE-divSize;
+        if( unixFileLock(pFile, &lock)==(-1) ){
+          tErrno = errno;
+          rc = SQLITE_IOERR_UNLOCK;
+          storeLastErrno(pFile, tErrno);
+          goto end_unlock;
+        }
+      }else
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+      {
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = SHARED_SIZE;
+        if( unixFileLock(pFile, &lock) ){
+          /* In theory, the call to unixFileLock() cannot fail because another
+          ** process is holding an incompatible lock. If it does, this
+          ** indicates that the other process is not following the locking
+          ** protocol. If this happens, return SQLITE_IOERR_RDLOCK. Returning
+          ** SQLITE_BUSY would confuse the upper layer (in practice it causes
+          ** an assert to fail). */
+          rc = SQLITE_IOERR_RDLOCK;
+          storeLastErrno(pFile, errno);
+          goto end_unlock;
+        }
+      }
+    }
+    lock.l_type = F_UNLCK;
+    lock.l_whence = SEEK_SET;
+    lock.l_start = PENDING_BYTE;
+    lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
+    if( unixFileLock(pFile, &lock)==0 ){
+      pInode->eFileLock = SHARED_LOCK;
+    }else{
+      rc = SQLITE_IOERR_UNLOCK;
+      storeLastErrno(pFile, errno);
+      goto end_unlock;
+    }
+  }
+  if( eFileLock==NO_LOCK ){
+    /* Decrement the shared lock counter.  Release the lock using an
+    ** OS call only when all threads in this same process have released
+    ** the lock.
+    */
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
+      lock.l_type = F_UNLCK;
+      lock.l_whence = SEEK_SET;
+      lock.l_start = lock.l_len = 0L;
+      if( unixFileLock(pFile, &lock)==0 ){
+        pInode->eFileLock = NO_LOCK;
+      }else{
+        rc = SQLITE_IOERR_UNLOCK;
+        storeLastErrno(pFile, errno);
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
+      }
+    }
+
+    /* Decrement the count of locks against this same file.  When the
+    ** count reaches zero, close any other file descriptors whose close
+    ** was deferred because of outstanding locks.
+    */
+    pInode->nLock--;
+    assert( pInode->nLock>=0 );
+    if( pInode->nLock==0 ) closePendingFds(pFile);
+  }
+
+end_unlock:
+  sqlite3_mutex_leave(pInode->pLockMutex);
+  if( rc==SQLITE_OK ){
+    pFile->eFileLock = eFileLock;
+  }
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int unixUnlock(sqlite3_file *id, int eFileLock){
+#if SQLITE_MAX_MMAP_SIZE>0
+  assert( eFileLock==SHARED_LOCK || ((unixFile *)id)->nFetchOut==0 );
+#endif
+  return posixUnlock(id, eFileLock, 0);
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+static int unixMapfile(unixFile *pFd, i64 nByte);
+static void unixUnmapfile(unixFile *pFd);
+#endif
+
+/*
+** This function performs the parts of the "close file" operation
+** common to all locking schemes. It closes the directory and file
+** handles, if they are valid, and sets all fields of the unixFile
+** structure to 0.
+**
+** It is *not* necessary to hold the mutex when this routine is called,
+** even on VxWorks.  A mutex will be acquired on VxWorks by the
+** vxworksReleaseFileId() routine.
+*/
+static int closeUnixFile(sqlite3_file *id){
+  unixFile *pFile = (unixFile*)id;
+#if SQLITE_MAX_MMAP_SIZE>0
+  unixUnmapfile(pFile);
+#endif
+  if( pFile->h>=0 ){
+    robust_close(pFile, pFile->h, __LINE__);
+    pFile->h = -1;
+  }
+#if OS_VXWORKS
+  if( pFile->pId ){
+    if( pFile->ctrlFlags & UNIXFILE_DELETE ){
+      osUnlink(pFile->pId->zCanonicalName);
+    }
+    vxworksReleaseFileId(pFile->pId);
+    pFile->pId = 0;
+  }
+#endif
+#ifdef SQLITE_UNLINK_AFTER_CLOSE
+  if( pFile->ctrlFlags & UNIXFILE_DELETE ){
+    osUnlink(pFile->zPath);
+    sqlite3_free(*(char**)&pFile->zPath);
+    pFile->zPath = 0;
+  }
+#endif
+  OSTRACE(("CLOSE   %-3d\n", pFile->h));
+  OpenCounter(-1);
+  sqlite3_free(pFile->pPreallocatedUnused);
+  memset(pFile, 0, sizeof(unixFile));
+  return SQLITE_OK;
+}
+
+/*
+** Close a file.
+*/
+static int unixClose(sqlite3_file *id){
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile *)id;
+  unixInodeInfo *pInode = pFile->pInode;
+
+  assert( pInode!=0 );
+  verifyDbFile(pFile);
+  unixUnlock(id, NO_LOCK);
+  assert( unixFileMutexNotheld(pFile) );
+  unixEnterMutex();
+
+  /* unixFile.pInode is always valid here. Otherwise, a different close
+  ** routine (e.g. nolockClose()) would be called instead.
+  */
+  assert( pFile->pInode->nLock>0 || pFile->pInode->bProcessLock==0 );
+  sqlite3_mutex_enter(pInode->pLockMutex);
+  if( pInode->nLock ){
+    /* If there are outstanding locks, do not actually close the file just
+    ** yet because that would clear those locks.  Instead, add the file
+    ** descriptor to pInode->pUnused list.  It will be automatically closed
+    ** when the last lock is cleared.
+    */
+    setPendingFd(pFile);
+  }
+  sqlite3_mutex_leave(pInode->pLockMutex);
+  releaseInodeInfo(pFile);
+  assert( pFile->pShm==0 );
+  rc = closeUnixFile(id);
+  unixLeaveMutex();
+  return rc;
+}
+
+/************** End of the posix advisory lock implementation *****************
+******************************************************************************/
+
+/******************************************************************************
+****************************** No-op Locking **********************************
+**
+** Of the various locking implementations available, this is by far the
+** simplest:  locking is ignored.  No attempt is made to lock the database
+** file for reading or writing.
+**
+** This locking mode is appropriate for use on read-only databases
+** (ex: databases that are burned into CD-ROM, for example.)  It can
+** also be used if the application employs some external mechanism to
+** prevent simultaneous access of the same database by two or more
+** database connections.  But there is a serious risk of database
+** corruption if this locking mode is used in situations where multiple
+** database connections are accessing the same database file at the same
+** time and one or more of those connections are writing.
+*/
+
+static int nolockCheckReservedLock(sqlite3_file *NotUsed, int *pResOut){
+  UNUSED_PARAMETER(NotUsed);
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+static int nolockLock(sqlite3_file *NotUsed, int NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return SQLITE_OK;
+}
+static int nolockUnlock(sqlite3_file *NotUsed, int NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return SQLITE_OK;
+}
+
+/*
+** Close the file.
+*/
+static int nolockClose(sqlite3_file *id) {
+  return closeUnixFile(id);
+}
+
+/******************* End of the no-op lock implementation *********************
+******************************************************************************/
+
+/******************************************************************************
+************************* Begin dot-file Locking ******************************
+**
+** The dotfile locking implementation uses the existence of separate lock
+** files (really a directory) to control access to the database.  This works
+** on just about every filesystem imaginable.  But there are serious downsides:
+**
+**    (1)  There is zero concurrency.  A single reader blocks all other
+**         connections from reading or writing the database.
+**
+**    (2)  An application crash or power loss can leave stale lock files
+**         sitting around that need to be cleared manually.
+**
+** Nevertheless, a dotlock is an appropriate locking mode for use if no
+** other locking strategy is available.
+**
+** Dotfile locking works by creating a subdirectory in the same directory as
+** the database and with the same name but with a ".lock" extension added.
+** The existence of a lock directory implies an EXCLUSIVE lock.  All other
+** lock types (SHARED, RESERVED, PENDING) are mapped into EXCLUSIVE.
+*/
+
+/*
+** The file suffix added to the data base filename in order to create the
+** lock directory.
+*/
+#define DOTLOCK_SUFFIX ".lock"
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+**
+** In dotfile locking, either a lock exists or it does not.  So in this
+** variation of CheckReservedLock(), *pResOut is set to true if any lock
+** is held on the file and false if the file is unlocked.
+*/
+static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) {
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+
+  assert( pFile );
+  reserved = osAccess((const char*)pFile->lockingContext, 0)==0;
+  OSTRACE(("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved));
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+**
+** With dotfile locking, we really only support state (4): EXCLUSIVE.
+** But we track the other locking levels internally.
+*/
+static int dotlockLock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  char *zLockFile = (char *)pFile->lockingContext;
+  int rc = SQLITE_OK;
+
+
+  /* If we have any lock, then the lock file already exists.  All we have
+  ** to do is adjust our internal record of the lock level.
+  */
+  if( pFile->eFileLock > NO_LOCK ){
+    pFile->eFileLock = eFileLock;
+    /* Always update the timestamp on the old file */
+#ifdef HAVE_UTIME
+    utime(zLockFile, NULL);
+#else
+    utimes(zLockFile, NULL);
+#endif
+    return SQLITE_OK;
+  }
+
+  /* grab an exclusive lock */
+  rc = osMkdir(zLockFile, 0777);
+  if( rc<0 ){
+    /* failed to open/create the lock directory */
+    int tErrno = errno;
+    if( EEXIST == tErrno ){
+      rc = SQLITE_BUSY;
+    } else {
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+      if( rc!=SQLITE_BUSY ){
+        storeLastErrno(pFile, tErrno);
+      }
+    }
+    return rc;
+  }
+
+  /* got it, set the type and return ok */
+  pFile->eFileLock = eFileLock;
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+**
+** When the locking level reaches NO_LOCK, delete the lock file.
+*/
+static int dotlockUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  char *zLockFile = (char *)pFile->lockingContext;
+  int rc;
+
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, eFileLock,
+           pFile->eFileLock, osGetpid(0)));
+  assert( eFileLock<=SHARED_LOCK );
+
+  /* no-op if possible */
+  if( pFile->eFileLock==eFileLock ){
+    return SQLITE_OK;
+  }
+
+  /* To downgrade to shared, simply update our internal notion of the
+  ** lock state.  No need to mess with the file on disk.
+  */
+  if( eFileLock==SHARED_LOCK ){
+    pFile->eFileLock = SHARED_LOCK;
+    return SQLITE_OK;
+  }
+
+  /* To fully unlock the database, delete the lock file */
+  assert( eFileLock==NO_LOCK );
+  rc = osRmdir(zLockFile);
+  if( rc<0 ){
+    int tErrno = errno;
+    if( tErrno==ENOENT ){
+      rc = SQLITE_OK;
+    }else{
+      rc = SQLITE_IOERR_UNLOCK;
+      storeLastErrno(pFile, tErrno);
+    }
+    return rc;
+  }
+  pFile->eFileLock = NO_LOCK;
+  return SQLITE_OK;
+}
+
+/*
+** Close a file.  Make sure the lock has been released before closing.
+*/
+static int dotlockClose(sqlite3_file *id) {
+  unixFile *pFile = (unixFile*)id;
+  assert( id!=0 );
+  dotlockUnlock(id, NO_LOCK);
+  sqlite3_free(pFile->lockingContext);
+  return closeUnixFile(id);
+}
+/****************** End of the dot-file lock implementation *******************
+******************************************************************************/
+
+/******************************************************************************
+************************** Begin flock Locking ********************************
+**
+** Use the flock() system call to do file locking.
+**
+** flock() locking is like dot-file locking in that the various
+** fine-grain locking levels supported by SQLite are collapsed into
+** a single exclusive lock.  In other words, SHARED, RESERVED, and
+** PENDING locks are the same thing as an EXCLUSIVE lock.  SQLite
+** still works when you do this, but concurrency is reduced since
+** only a single process can be reading the database at a time.
+**
+** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off
+*/
+#if SQLITE_ENABLE_LOCKING_STYLE
+
+/*
+** Retry flock() calls that fail with EINTR
+*/
+#ifdef EINTR
+static int robust_flock(int fd, int op){
+  int rc;
+  do{ rc = flock(fd,op); }while( rc<0 && errno==EINTR );
+  return rc;
+}
+#else
+# define robust_flock(a,b) flock(a,b)
+#endif
+   
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int flockCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+
+  assert( pFile );
+
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+
+  /* Otherwise see if some other process holds it. */
+  if( !reserved ){
+    /* attempt to get the lock */
+    int lrc = robust_flock(pFile->h, LOCK_EX | LOCK_NB);
+    if( !lrc ){
+      /* got the lock, unlock it */
+      lrc = robust_flock(pFile->h, LOCK_UN);
+      if ( lrc ) {
+        int tErrno = errno;
+        /* unlock failed with an error */
+        lrc = SQLITE_IOERR_UNLOCK;
+        storeLastErrno(pFile, tErrno);
+        rc = lrc;
+      }
+    } else {
+      int tErrno = errno;
+      reserved = 1;
+      /* someone else might have it reserved */
+      lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+      if( IS_LOCK_ERROR(lrc) ){
+        storeLastErrno(pFile, tErrno);
+        rc = lrc;
+      }
+    }
+  }
+  OSTRACE(("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved));
+
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  if( (rc & 0xff) == SQLITE_IOERR ){
+    rc = SQLITE_OK;
+    reserved=1;
+  }
+#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** flock() only really support EXCLUSIVE locks.  We track intermediate
+** lock states in the sqlite3_file structure, but all locks SHARED or
+** above are really EXCLUSIVE locks and exclude all other processes from
+** access the file.
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int flockLock(sqlite3_file *id, int eFileLock) {
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+
+  assert( pFile );
+
+  /* if we already have a lock, it is exclusive.
+  ** Just adjust level and punt on outta here. */
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
+    return SQLITE_OK;
+  }
+
+  /* grab an exclusive lock */
+
+  if (robust_flock(pFile->h, LOCK_EX | LOCK_NB)) {
+    int tErrno = errno;
+    /* didn't get, must be busy */
+    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+    if( IS_LOCK_ERROR(rc) ){
+      storeLastErrno(pFile, tErrno);
+    }
+  } else {
+    /* got it, set the type and return ok */
+    pFile->eFileLock = eFileLock;
+  }
+  OSTRACE(("LOCK    %d %s %s (flock)\n", pFile->h, azFileLock(eFileLock),
+           rc==SQLITE_OK ? "ok" : "failed"));
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  if( (rc & 0xff) == SQLITE_IOERR ){
+    rc = SQLITE_BUSY;
+  }
+#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
+  return rc;
+}
+
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int flockUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, eFileLock,
+           pFile->eFileLock, osGetpid(0)));
+  assert( eFileLock<=SHARED_LOCK );
+
+  /* no-op if possible */
+  if( pFile->eFileLock==eFileLock ){
+    return SQLITE_OK;
+  }
+
+  /* shared can just be set because we always have an exclusive */
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
+    return SQLITE_OK;
+  }
+
+  /* no, really, unlock. */
+  if( robust_flock(pFile->h, LOCK_UN) ){
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+    return SQLITE_OK;
+#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
+    return SQLITE_IOERR_UNLOCK;
+  }else{
+    pFile->eFileLock = NO_LOCK;
+    return SQLITE_OK;
+  }
+}
+
+/*
+** Close a file.
+*/
+static int flockClose(sqlite3_file *id) {
+  assert( id!=0 );
+  flockUnlock(id, NO_LOCK);
+  return closeUnixFile(id);
+}
+
+#endif /* SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORK */
+
+/******************* End of the flock lock implementation *********************
+******************************************************************************/
+
+/******************************************************************************
+************************ Begin Named Semaphore Locking ************************
+**
+** Named semaphore locking is only supported on VxWorks.
+**
+** Semaphore locking is like dot-lock and flock in that it really only
+** supports EXCLUSIVE locking.  Only a single process can read or write
+** the database file at a time.  This reduces potential concurrency, but
+** makes the lock implementation much easier.
+*/
+#if OS_VXWORKS
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int semXCheckReservedLock(sqlite3_file *id, int *pResOut) {
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+
+  assert( pFile );
+
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+
+  /* Otherwise see if some other process holds it. */
+  if( !reserved ){
+    sem_t *pSem = pFile->pInode->pSem;
+
+    if( sem_trywait(pSem)==-1 ){
+      int tErrno = errno;
+      if( EAGAIN != tErrno ){
+        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK);
+        storeLastErrno(pFile, tErrno);
+      } else {
+        /* someone else has the lock when we are in NO_LOCK */
+        reserved = (pFile->eFileLock < SHARED_LOCK);
+      }
+    }else{
+      /* we could have it if we want it */
+      sem_post(pSem);
+    }
+  }
+  OSTRACE(("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved));
+
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** Semaphore locks only really support EXCLUSIVE locks.  We track intermediate
+** lock states in the sqlite3_file structure, but all locks SHARED or
+** above are really EXCLUSIVE locks and exclude all other processes from
+** access the file.
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int semXLock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  sem_t *pSem = pFile->pInode->pSem;
+  int rc = SQLITE_OK;
+
+  /* if we already have a lock, it is exclusive.
+  ** Just adjust level and punt on outta here. */
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
+    rc = SQLITE_OK;
+    goto sem_end_lock;
+  }
+
+  /* lock semaphore now but bail out when already locked. */
+  if( sem_trywait(pSem)==-1 ){
+    rc = SQLITE_BUSY;
+    goto sem_end_lock;
+  }
+
+  /* got it, set the type and return ok */
+  pFile->eFileLock = eFileLock;
+
+ sem_end_lock:
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int semXUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  sem_t *pSem = pFile->pInode->pSem;
+
+  assert( pFile );
+  assert( pSem );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, eFileLock,
+           pFile->eFileLock, osGetpid(0)));
+  assert( eFileLock<=SHARED_LOCK );
+
+  /* no-op if possible */
+  if( pFile->eFileLock==eFileLock ){
+    return SQLITE_OK;
+  }
+
+  /* shared can just be set because we always have an exclusive */
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
+    return SQLITE_OK;
+  }
+
+  /* no, really unlock. */
+  if ( sem_post(pSem)==-1 ) {
+    int rc, tErrno = errno;
+    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
+    if( IS_LOCK_ERROR(rc) ){
+      storeLastErrno(pFile, tErrno);
+    }
+    return rc;
+  }
+  pFile->eFileLock = NO_LOCK;
+  return SQLITE_OK;
+}
+
+/*
+ ** Close a file.
+ */
+static int semXClose(sqlite3_file *id) {
+  if( id ){
+    unixFile *pFile = (unixFile*)id;
+    semXUnlock(id, NO_LOCK);
+    assert( pFile );
+    assert( unixFileMutexNotheld(pFile) );
+    unixEnterMutex();
+    releaseInodeInfo(pFile);
+    unixLeaveMutex();
+    closeUnixFile(id);
+  }
+  return SQLITE_OK;
+}
+
+#endif /* OS_VXWORKS */
+/*
+** Named semaphore locking is only available on VxWorks.
+**
+*************** End of the named semaphore lock implementation ****************
+******************************************************************************/
+
+
+/******************************************************************************
+*************************** Begin AFP Locking *********************************
+**
+** AFP is the Apple Filing Protocol.  AFP is a network filesystem found
+** on Apple Macintosh computers - both OS9 and OSX.
+**
+** Third-party implementations of AFP are available.  But this code here
+** only works on OSX.
+*/
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/*
+** The afpLockingContext structure contains all afp lock specific state
+*/
+typedef struct afpLockingContext afpLockingContext;
+struct afpLockingContext {
+  int reserved;
+  const char *dbPath;             /* Name of the open file */
+};
+
+struct ByteRangeLockPB2
+{
+  unsigned long long offset;        /* offset to first byte to lock */
+  unsigned long long length;        /* nbr of bytes to lock */
+  unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
+  unsigned char unLockFlag;         /* 1 = unlock, 0 = lock */
+  unsigned char startEndFlag;       /* 1=rel to end of fork, 0=rel to start */
+  int fd;                           /* file desc to assoc this lock with */
+};
+
+#define afpfsByteRangeLock2FSCTL        _IOWR('z', 23, struct ByteRangeLockPB2)
+
+/*
+** This is a utility for setting or clearing a bit-range lock on an
+** AFP filesystem.
+**
+** Return SQLITE_OK on success, SQLITE_BUSY on failure.
+*/
+static int afpSetLock(
+  const char *path,              /* Name of the file to be locked or unlocked */
+  unixFile *pFile,               /* Open file descriptor on path */
+  unsigned long long offset,     /* First byte to be locked */
+  unsigned long long length,     /* Number of bytes to lock */
+  int setLockFlag                /* True to set lock.  False to clear lock */
+){
+  struct ByteRangeLockPB2 pb;
+  int err;
+
+  pb.unLockFlag = setLockFlag ? 0 : 1;
+  pb.startEndFlag = 0;
+  pb.offset = offset;
+  pb.length = length;
+  pb.fd = pFile->h;
+
+  OSTRACE(("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n",
+    (setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""),
+    offset, length));
+  err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
+  if ( err==-1 ) {
+    int rc;
+    int tErrno = errno;
+    OSTRACE(("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
+             path, tErrno, strerror(tErrno)));
+#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
+    rc = SQLITE_BUSY;
+#else
+    rc = sqliteErrorFromPosixError(tErrno,
+                    setLockFlag ? SQLITE_IOERR_LOCK : SQLITE_IOERR_UNLOCK);
+#endif /* SQLITE_IGNORE_AFP_LOCK_ERRORS */
+    if( IS_LOCK_ERROR(rc) ){
+      storeLastErrno(pFile, tErrno);
+    }
+    return rc;
+  } else {
+    return SQLITE_OK;
+  }
+}
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+  afpLockingContext *context;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+
+  assert( pFile );
+  context = (afpLockingContext *) pFile->lockingContext;
+  if( context->reserved ){
+    *pResOut = 1;
+    return SQLITE_OK;
+  }
+  sqlite3_mutex_enter(pFile->pInode->pLockMutex);
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+
+  /* Otherwise see if some other process holds it.
+   */
+  if( !reserved ){
+    /* lock the RESERVED byte */
+    int lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
+    if( SQLITE_OK==lrc ){
+      /* if we succeeded in taking the reserved lock, unlock it to restore
+      ** the original state */
+      lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
+    } else {
+      /* if we failed to get the lock then someone else must have it */
+      reserved = 1;
+    }
+    if( IS_LOCK_ERROR(lrc) ){
+      rc=lrc;
+    }
+  }
+
+  sqlite3_mutex_leave(pFile->pInode->pLockMutex);
+  OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
+
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int afpLock(sqlite3_file *id, int eFileLock){
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode = pFile->pInode;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+
+  assert( pFile );
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (afp)\n", pFile->h,
+           azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+           azFileLock(pInode->eFileLock), pInode->nShared , osGetpid(0)));
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
+  ** unixEnterMutex() hasn't been called yet.
+  */
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
+           azFileLock(eFileLock)));
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct
+  **  (1) We never move from unlocked to anything higher than shared lock.
+  **  (2) SQLite never explicitly requests a pending lock.
+  **  (3) A shared lock is always held when a reserve lock is requested.
+  */
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
+
+  /* This mutex is needed because pFile->pInode is shared across threads
+  */
+  pInode = pFile->pInode;
+  sqlite3_mutex_enter(pInode->pLockMutex);
+
+  /* If some thread using this PID has a lock via a different unixFile*
+  ** handle that precludes the requested lock, return BUSY.
+  */
+  if( (pFile->eFileLock!=pInode->eFileLock &&
+       (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
+     ){
+    rc = SQLITE_BUSY;
+    goto afp_end_lock;
+  }
+
+  /* If a SHARED lock is requested, and some thread using this PID already
+  ** has a SHARED or RESERVED lock, then increment reference counts and
+  ** return SQLITE_OK.
+  */
+  if( eFileLock==SHARED_LOCK &&
+     (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
+    goto afp_end_lock;
+  }
+  
+  /* A PENDING lock is needed before acquiring a SHARED lock and before
+  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
+  ** be released.
+  */
+  if( eFileLock==SHARED_LOCK
+      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
+  ){
+    int failed;
+    failed = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 1);
+    if (failed) {
+      rc = failed;
+      goto afp_end_lock;
+    }
+  }
+
+  /* If control gets to this point, then actually go ahead and make
+  ** operating system calls for the specified lock.
+  */
+  if( eFileLock==SHARED_LOCK ){
+    int lrc1, lrc2, lrc1Errno = 0;
+    long lk, mask;
+  
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
+      
+    mask = (sizeof(long)==8) ? LARGEST_INT64 : 0x7fffffff;
+    /* Now get the read-lock SHARED_LOCK */
+    /* note that the quality of the randomness doesn't matter that much */
+    lk = random();
+    pInode->sharedByte = (lk & mask)%(SHARED_SIZE - 1);
+    lrc1 = afpSetLock(context->dbPath, pFile,
+          SHARED_FIRST+pInode->sharedByte, 1, 1);
+    if( IS_LOCK_ERROR(lrc1) ){
+      lrc1Errno = pFile->lastErrno;
+    }
+    /* Drop the temporary PENDING lock */
+    lrc2 = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
+  
+    if( IS_LOCK_ERROR(lrc1) ) {
+      storeLastErrno(pFile, lrc1Errno);
+      rc = lrc1;
+      goto afp_end_lock;
+    } else if( IS_LOCK_ERROR(lrc2) ){
+      rc = lrc2;
+      goto afp_end_lock;
+    } else if( lrc1 != SQLITE_OK ) {
+      rc = lrc1;
+    } else {
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
+    }
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
+    /* We are trying for an exclusive lock but another thread in this
+     ** same process is still holding a shared lock. */
+    rc = SQLITE_BUSY;
+  }else{
+    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
+    ** assumed that there is a SHARED or greater lock on the file
+    ** already.
+    */
+    int failed = 0;
+    assert( 0!=pFile->eFileLock );
+    if (eFileLock >= RESERVED_LOCK && pFile->eFileLock < RESERVED_LOCK) {
+        /* Acquire a RESERVED lock */
+        failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
+      if( !failed ){
+        context->reserved = 1;
+      }
+    }
+    if (!failed && eFileLock == EXCLUSIVE_LOCK) {
+      /* Acquire an EXCLUSIVE lock */
+
+      /* Remove the shared lock before trying the range.  we'll need to
+      ** reestablish the shared lock if we can't get the  afpUnlock
+      */
+      if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST +
+                         pInode->sharedByte, 1, 0)) ){
+        int failed2 = SQLITE_OK;
+        /* now attempt to get the exclusive lock range */
+        failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST,
+                               SHARED_SIZE, 1);
+        if( failed && (failed2 = afpSetLock(context->dbPath, pFile,
+                       SHARED_FIRST + pInode->sharedByte, 1, 1)) ){
+          /* Can't reestablish the shared lock.  Sqlite can't deal, this is
+          ** a critical I/O error
+          */
+          rc = ((failed & 0xff) == SQLITE_IOERR) ? failed2 :
+               SQLITE_IOERR_LOCK;
+          goto afp_end_lock;
+        }
+      }else{
+        rc = failed;
+      }
+    }
+    if( failed ){
+      rc = failed;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }else if( eFileLock==EXCLUSIVE_LOCK ){
+    pFile->eFileLock = PENDING_LOCK;
+    pInode->eFileLock = PENDING_LOCK;
+  }
+
+afp_end_lock:
+  sqlite3_mutex_leave(pInode->pLockMutex);
+  OSTRACE(("LOCK    %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock),
+         rc==SQLITE_OK ? "ok" : "failed"));
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int afpUnlock(sqlite3_file *id, int eFileLock) {
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  int skipShared = 0;
+
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock,
+           pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+           osGetpid(0)));
+
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
+    return SQLITE_OK;
+  }
+  pInode = pFile->pInode;
+  sqlite3_mutex_enter(pInode->pLockMutex);
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
+  
+#ifdef SQLITE_DEBUG
+    /* When reducing a lock such that other processes can start
+    ** reading the database file again, make sure that the
+    ** transaction counter was updated if any part of the database
+    ** file changed.  If the transaction counter is not updated,
+    ** other connections to the same file might not realize that
+    ** the file has changed and hence might not know to flush their
+    ** cache.  The use of a stale cache can lead to database corruption.
+    */
+    assert( pFile->inNormalWrite==0
+           || pFile->dbUpdate==0
+           || pFile->transCntrChng==1 );
+    pFile->inNormalWrite = 0;
+#endif
+  
+    if( pFile->eFileLock==EXCLUSIVE_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
+      if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1) ){
+        /* only re-establish the shared lock if necessary */
+        int sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 1);
+      } else {
+        skipShared = 1;
+      }
+    }
+    if( rc==SQLITE_OK && pFile->eFileLock>=PENDING_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
+    }
+    if( rc==SQLITE_OK && pFile->eFileLock>=RESERVED_LOCK && context->reserved ){
+      rc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
+      if( !rc ){
+        context->reserved = 0;
+      }
+    }
+    if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1)){
+      pInode->eFileLock = SHARED_LOCK;
+    }
+  }
+  if( rc==SQLITE_OK && eFileLock==NO_LOCK ){
+
+    /* Decrement the shared lock counter.  Release the lock using an
+    ** OS call only when all threads in this same process have released
+    ** the lock.
+    */
+    unsigned long long sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
+      if( !skipShared ){
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 0);
+      }
+      if( !rc ){
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      pInode->nLock--;
+      assert( pInode->nLock>=0 );
+      if( pInode->nLock==0 ) closePendingFds(pFile);
+    }
+  }
+
+  sqlite3_mutex_leave(pInode->pLockMutex);
+  if( rc==SQLITE_OK ){
+    pFile->eFileLock = eFileLock;
+  }
+  return rc;
+}
+
+/*
+** Close a file & cleanup AFP specific locking context
+*/
+static int afpClose(sqlite3_file *id) {
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  assert( id!=0 );
+  afpUnlock(id, NO_LOCK);
+  assert( unixFileMutexNotheld(pFile) );
+  unixEnterMutex();
+  if( pFile->pInode ){
+    unixInodeInfo *pInode = pFile->pInode;
+    sqlite3_mutex_enter(pInode->pLockMutex);
+    if( pInode->nLock ){
+      /* If there are outstanding locks, do not actually close the file just
+      ** yet because that would clear those locks.  Instead, add the file
+      ** descriptor to pInode->aPending.  It will be automatically closed when
+      ** the last lock is cleared.
+      */
+      setPendingFd(pFile);
+    }
+    sqlite3_mutex_leave(pInode->pLockMutex);
+  }
+  releaseInodeInfo(pFile);
+  sqlite3_free(pFile->lockingContext);
+  rc = closeUnixFile(id);
+  unixLeaveMutex();
+  return rc;
+}
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The code above is the AFP lock implementation.  The code is specific
+** to MacOSX and does not work on other unix platforms.  No alternative
+** is available.  If you don't compile for a mac, then the "unix-afp"
+** VFS is not available.
+**
+********************* End of the AFP lock implementation **********************
+******************************************************************************/
+
+/******************************************************************************
+*************************** Begin NFS Locking ********************************/
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/*
+ ** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+ ** must be either NO_LOCK or SHARED_LOCK.
+ **
+ ** If the locking level of the file descriptor is already at or below
+ ** the requested locking level, this routine is a no-op.
+ */
+static int nfsUnlock(sqlite3_file *id, int eFileLock){
+  return posixUnlock(id, eFileLock, 1);
+}
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The code above is the NFS lock implementation.  The code is specific
+** to MacOSX and does not work on other unix platforms.  No alternative
+** is available.
+**
+********************* End of the NFS lock implementation **********************
+******************************************************************************/
+
+/******************************************************************************
+**************** Non-locking sqlite3_file methods *****************************
+**
+** The next division contains implementations for all methods of the
+** sqlite3_file object other than the locking methods.  The locking
+** methods were defined in divisions above (one locking method per
+** division).  Those methods that are common to all locking modes
+** are gather together into this division.
+*/
+
+/*
+** Seek to the offset passed as the second argument, then read cnt
+** bytes into pBuf. Return the number of bytes actually read.
+**
+** To avoid stomping the errno value on a failed read the lastErrno value
+** is set before returning.
+*/
+static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
+  int got;
+  int prior = 0;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
+  i64 newOffset;
+#endif
+  TIMER_START;
+  assert( cnt==(cnt&0x1ffff) );
+  assert( id->h>2 );
+  do{
+#if defined(USE_PREAD)
+    got = osPread(id->h, pBuf, cnt, offset);
+    SimulateIOError( got = -1 );
+#elif defined(USE_PREAD64)
+    got = osPread64(id->h, pBuf, cnt, offset);
+    SimulateIOError( got = -1 );
+#else
+    newOffset = lseek(id->h, offset, SEEK_SET);
+    SimulateIOError( newOffset = -1 );
+    if( newOffset<0 ){
+      storeLastErrno((unixFile*)id, errno);
+      return -1;
+    }
+    got = osRead(id->h, pBuf, cnt);
+#endif
+    if( got==cnt ) break;
+    if( got<0 ){
+      if( errno==EINTR ){ got = 1; continue; }
+      prior = 0;
+      storeLastErrno((unixFile*)id,  errno);
+      break;
+    }else if( got>0 ){
+      cnt -= got;
+      offset += got;
+      prior += got;
+      pBuf = (void*)(got + (char*)pBuf);
+    }
+  }while( got>0 );
+  TIMER_END;
+  OSTRACE(("READ    %-3d %5d %7lld %llu\n",
+            id->h, got+prior, offset-prior, TIMER_ELAPSED));
+  return got+prior;
+}
+
+/*
+** Read data from a file into a buffer.  Return SQLITE_OK if all
+** bytes were read successfully and SQLITE_IOERR if anything goes
+** wrong.
+*/
+static int unixRead(
+  sqlite3_file *id,
+  void *pBuf,
+  int amt,
+  sqlite3_int64 offset
+){
+  unixFile *pFile = (unixFile *)id;
+  int got;
+  assert( id );
+  assert( offset>=0 );
+  assert( amt>0 );
+
+  /* If this is a database file (not a journal, super-journal or temp
+  ** file), the bytes in the locking range should never be read or written. */
+#if 0
+  assert( pFile->pPreallocatedUnused==0
+       || offset>=PENDING_BYTE+512
+       || offset+amt<=PENDING_BYTE
+  );
+#endif
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  /* Deal with as much of this read request as possible by transferring
+  ** data from the memory mapping using memcpy().  */
+  if( offset<pFile->mmapSize ){
+    if( offset+amt <= pFile->mmapSize ){
+      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], amt);
+      return SQLITE_OK;
+    }else{
+      int nCopy = pFile->mmapSize - offset;
+      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], nCopy);
+      pBuf = &((u8 *)pBuf)[nCopy];
+      amt -= nCopy;
+      offset += nCopy;
+    }
+  }
+#endif
+
+  got = seekAndRead(pFile, offset, pBuf, amt);
+  if( got==amt ){
+    return SQLITE_OK;
+  }else if( got<0 ){
+    /* pFile->lastErrno has been set by seekAndRead().
+    ** Usually we return SQLITE_IOERR_READ here, though for some
+    ** kinds of errors we return SQLITE_IOERR_CORRUPTFS.  The
+    ** SQLITE_IOERR_CORRUPTFS will be converted into SQLITE_CORRUPT
+    ** prior to returning to the application by the sqlite3ApiExit()
+    ** routine.
+    */
+    switch( pFile->lastErrno ){
+      case ERANGE:
+      case EIO:
+#ifdef ENXIO
+      case ENXIO:
+#endif
+#ifdef EDEVERR
+      case EDEVERR:
+#endif
+        return SQLITE_IOERR_CORRUPTFS;
+    }
+    return SQLITE_IOERR_READ;
+  }else{
+    storeLastErrno(pFile, 0);   /* not a system error */
+    /* Unread parts of the buffer must be zero-filled */
+    memset(&((char*)pBuf)[got], 0, amt-got);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+}
+
+/*
+** Attempt to seek the file-descriptor passed as the first argument to
+** absolute offset iOff, then attempt to write nBuf bytes of data from
+** pBuf to it. If an error occurs, return -1 and set *piErrno. Otherwise,
+** return the actual number of bytes written (which may be less than
+** nBuf).
+*/
+static int seekAndWriteFd(
+  int fd,                         /* File descriptor to write to */
+  i64 iOff,                       /* File offset to begin writing at */
+  const void *pBuf,               /* Copy data from this buffer to the file */
+  int nBuf,                       /* Size of buffer pBuf in bytes */
+  int *piErrno                    /* OUT: Error number if error occurs */
+){
+  int rc = 0;                     /* Value returned by system call */
+
+  assert( nBuf==(nBuf&0x1ffff) );
+  assert( fd>2 );
+  assert( piErrno!=0 );
+  nBuf &= 0x1ffff;
+  TIMER_START;
+
+#if defined(USE_PREAD)
+  do{ rc = (int)osPwrite(fd, pBuf, nBuf, iOff); }while( rc<0 && errno==EINTR );
+#elif defined(USE_PREAD64)
+  do{ rc = (int)osPwrite64(fd, pBuf, nBuf, iOff);}while( rc<0 && errno==EINTR);
+#else
+  do{
+    i64 iSeek = lseek(fd, iOff, SEEK_SET);
+    SimulateIOError( iSeek = -1 );
+    if( iSeek<0 ){
+      rc = -1;
+      break;
+    }
+    rc = osWrite(fd, pBuf, nBuf);
+  }while( rc<0 && errno==EINTR );
+#endif
+
+  TIMER_END;
+  OSTRACE(("WRITE   %-3d %5d %7lld %llu\n", fd, rc, iOff, TIMER_ELAPSED));
+
+  if( rc<0 ) *piErrno = errno;
+  return rc;
+}
+
+
+/*
+** Seek to the offset in id->offset then read cnt bytes into pBuf.
+** Return the number of bytes actually read.  Update the offset.
+**
+** To avoid stomping the errno value on a failed write the lastErrno value
+** is set before returning.
+*/
+static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
+  return seekAndWriteFd(id->h, offset, pBuf, cnt, &id->lastErrno);
+}
+
+
+/*
+** Write data from a buffer into a file.  Return SQLITE_OK on success
+** or some other error code on failure.
+*/
+static int unixWrite(
+  sqlite3_file *id,
+  const void *pBuf,
+  int amt,
+  sqlite3_int64 offset
+){
+  unixFile *pFile = (unixFile*)id;
+  int wrote = 0;
+  assert( id );
+  assert( amt>0 );
+
+  /* If this is a database file (not a journal, super-journal or temp
+  ** file), the bytes in the locking range should never be read or written. */
+#if 0
+  assert( pFile->pPreallocatedUnused==0
+       || offset>=PENDING_BYTE+512
+       || offset+amt<=PENDING_BYTE
+  );
+#endif
+
+#ifdef SQLITE_DEBUG
+  /* If we are doing a normal write to a database file (as opposed to
+  ** doing a hot-journal rollback or a write to some file other than a
+  ** normal database file) then record the fact that the database
+  ** has changed.  If the transaction counter is modified, record that
+  ** fact too.
+  */
+  if( pFile->inNormalWrite ){
+    pFile->dbUpdate = 1;  /* The database has been modified */
+    if( offset<=24 && offset+amt>=27 ){
+      int rc;
+      char oldCntr[4];
+      SimulateIOErrorBenign(1);
+      rc = seekAndRead(pFile, 24, oldCntr, 4);
+      SimulateIOErrorBenign(0);
+      if( rc!=4 || memcmp(oldCntr, &((char*)pBuf)[24-offset], 4)!=0 ){
+        pFile->transCntrChng = 1;  /* The transaction counter has changed */
+      }
+    }
+  }
+#endif
+
+#if defined(SQLITE_MMAP_READWRITE) && SQLITE_MAX_MMAP_SIZE>0
+  /* Deal with as much of this write request as possible by transferring
+  ** data from the memory mapping using memcpy().  */
+  if( offset<pFile->mmapSize ){
+    if( offset+amt <= pFile->mmapSize ){
+      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, amt);
+      return SQLITE_OK;
+    }else{
+      int nCopy = pFile->mmapSize - offset;
+      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, nCopy);
+      pBuf = &((u8 *)pBuf)[nCopy];
+      amt -= nCopy;
+      offset += nCopy;
+    }
+  }
+#endif
+
+  while( (wrote = seekAndWrite(pFile, offset, pBuf, amt))<amt && wrote>0 ){
+    amt -= wrote;
+    offset += wrote;
+    pBuf = &((char*)pBuf)[wrote];
+  }
+  SimulateIOError(( wrote=(-1), amt=1 ));
+  SimulateDiskfullError(( wrote=0, amt=1 ));
+
+  if( amt>wrote ){
+    if( wrote<0 && pFile->lastErrno!=ENOSPC ){
+      /* lastErrno set by seekAndWrite */
+      return SQLITE_IOERR_WRITE;
+    }else{
+      storeLastErrno(pFile, 0); /* not a system error */
+      return SQLITE_FULL;
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Count the number of fullsyncs and normal syncs.  This is used to test
+** that syncs and fullsyncs are occurring at the right times.
+*/
+int sqlite3_sync_count = 0;
+int sqlite3_fullsync_count = 0;
+#endif
+
+/*
+** We do not trust systems to provide a working fdatasync().  Some do.
+** Others do no.  To be safe, we will stick with the (slightly slower)
+** fsync(). If you know that your system does support fdatasync() correctly,
+** then simply compile with -Dfdatasync=fdatasync or -DHAVE_FDATASYNC
+*/
+#if !defined(fdatasync) && !HAVE_FDATASYNC
+# define fdatasync fsync
+#endif
+
+/*
+** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not
+** the F_FULLFSYNC macro is defined.  F_FULLFSYNC is currently
+** only available on Mac OS X.  But that could change.
+*/
+#ifdef F_FULLFSYNC
+# define HAVE_FULLFSYNC 1
+#else
+# define HAVE_FULLFSYNC 0
+#endif
+
+
+/*
+** The fsync() system call does not work as advertised on many
+** unix systems.  The following procedure is an attempt to make
+** it work better.
+**
+** The SQLITE_NO_SYNC macro disables all fsync()s.  This is useful
+** for testing when we want to run through the test suite quickly.
+** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
+** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
+** or power failure will likely corrupt the database file.
+**
+** SQLite sets the dataOnly flag if the size of the file is unchanged.
+** The idea behind dataOnly is that it should only write the file content
+** to disk, not the inode.  We only set dataOnly if the file size is
+** unchanged since the file size is part of the inode.  However,
+** Ted Ts'o tells us that fdatasync() will also write the inode if the
+** file size has changed.  The only real difference between fdatasync()
+** and fsync(), Ted tells us, is that fdatasync() will not flush the
+** inode if the mtime or owner or other inode attributes have changed.
+** We only care about the file size, not the other file attributes, so
+** as far as SQLite is concerned, an fdatasync() is always adequate.
+** So, we always use fdatasync() if it is available, regardless of
+** the value of the dataOnly flag.
+*/
+static int full_fsync(int fd, int fullSync, int dataOnly){
+  int rc;
+
+  /* The following "ifdef/elif/else/" block has the same structure as
+  ** the one below. It is replicated here solely to avoid cluttering
+  ** up the real code with the UNUSED_PARAMETER() macros.
+  */
+#ifdef SQLITE_NO_SYNC
+  UNUSED_PARAMETER(fd);
+  UNUSED_PARAMETER(fullSync);
+  UNUSED_PARAMETER(dataOnly);
+#elif HAVE_FULLFSYNC
+  UNUSED_PARAMETER(dataOnly);
+#else
+  UNUSED_PARAMETER(fullSync);
+  UNUSED_PARAMETER(dataOnly);
+#endif
+
+  /* Record the number of times that we do a normal fsync() and
+  ** FULLSYNC.  This is used during testing to verify that this procedure
+  ** gets called with the correct arguments.
+  */
+#ifdef SQLITE_TEST
+  if( fullSync ) sqlite3_fullsync_count++;
+  sqlite3_sync_count++;
+#endif
+
+  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
+  ** no-op.  But go ahead and call fstat() to validate the file
+  ** descriptor as we need a method to provoke a failure during
+  ** coverage testing.
+  */
+#ifdef SQLITE_NO_SYNC
+  {
+    struct stat buf;
+    rc = osFstat(fd, &buf);
+  }
+#elif HAVE_FULLFSYNC
+  if( fullSync ){
+    rc = osFcntl(fd, F_FULLFSYNC, 0);
+  }else{
+    rc = 1;
+  }
+  /* If the FULLFSYNC failed, fall back to attempting an fsync().
+  ** It shouldn't be possible for fullfsync to fail on the local
+  ** file system (on OSX), so failure indicates that FULLFSYNC
+  ** isn't supported for this file system. So, attempt an fsync
+  ** and (for now) ignore the overhead of a superfluous fcntl call.
+  ** It'd be better to detect fullfsync support once and avoid
+  ** the fcntl call every time sync is called.
+  */
+  if( rc ) rc = fsync(fd);
+
+#elif defined(__APPLE__)
+  /* fdatasync() on HFS+ doesn't yet flush the file size if it changed correctly
+  ** so currently we default to the macro that redefines fdatasync to fsync
+  */
+  rc = fsync(fd);
+#else
+  rc = fdatasync(fd);
+#if OS_VXWORKS
+  if( rc==-1 && errno==ENOTSUP ){
+    rc = fsync(fd);
+  }
+#endif /* OS_VXWORKS */
+#endif /* ifdef SQLITE_NO_SYNC elif HAVE_FULLFSYNC */
+
+  if( OS_VXWORKS && rc!= -1 ){
+    rc = 0;
+  }
+  return rc;
+}
+
+/*
+** Open a file descriptor to the directory containing file zFilename.
+** If successful, *pFd is set to the opened file descriptor and
+** SQLITE_OK is returned. If an error occurs, either SQLITE_NOMEM
+** or SQLITE_CANTOPEN is returned and *pFd is set to an undefined
+** value.
+**
+** The directory file descriptor is used for only one thing - to
+** fsync() a directory to make sure file creation and deletion events
+** are flushed to disk.  Such fsyncs are not needed on newer
+** journaling filesystems, but are required on older filesystems.
+**
+** This routine can be overridden using the xSetSysCall interface.
+** The ability to override this routine was added in support of the
+** chromium sandbox.  Opening a directory is a security risk (we are
+** told) so making it overrideable allows the chromium sandbox to
+** replace this routine with a harmless no-op.  To make this routine
+** a no-op, replace it with a stub that returns SQLITE_OK but leaves
+** *pFd set to a negative number.
+**
+** If SQLITE_OK is returned, the caller is responsible for closing
+** the file descriptor *pFd using close().
+*/
+static int openDirectory(const char *zFilename, int *pFd){
+  int ii;
+  int fd = -1;
+  char zDirname[MAX_PATHNAME+1];
+
+  sqlite3_snprintf(MAX_PATHNAME, zDirname, "%s", zFilename);
+  for(ii=(int)strlen(zDirname); ii>0 && zDirname[ii]!='/'; ii--);
+  if( ii>0 ){
+    zDirname[ii] = '\0';
+  }else{
+    if( zDirname[0]!='/' ) zDirname[0] = '.';
+    zDirname[1] = 0;
+  }
+  fd = robust_open(zDirname, O_RDONLY|O_BINARY, 0);
+  if( fd>=0 ){
+    OSTRACE(("OPENDIR %-3d %s\n", fd, zDirname));
+  }
+  *pFd = fd;
+  if( fd>=0 ) return SQLITE_OK;
+  return unixLogError(SQLITE_CANTOPEN_BKPT, "openDirectory", zDirname);
+}
+
+/*
+** Make sure all writes to a particular file are committed to disk.
+**
+** If dataOnly==0 then both the file itself and its metadata (file
+** size, access time, etc) are synced.  If dataOnly!=0 then only the
+** file data is synced.
+**
+** Under Unix, also make sure that the directory entry for the file
+** has been created by fsync-ing the directory that contains the file.
+** If we do not do this and we encounter a power failure, the directory
+** entry for the journal might not exist after we reboot.  The next
+** SQLite to access the file will not know that the journal exists (because
+** the directory entry for the journal was never created) and the transaction
+** will not roll back - possibly leading to database corruption.
+*/
+static int unixSync(sqlite3_file *id, int flags){
+  int rc;
+  unixFile *pFile = (unixFile*)id;
+
+  int isDataOnly = (flags&SQLITE_SYNC_DATAONLY);
+  int isFullsync = (flags&0x0F)==SQLITE_SYNC_FULL;
+
+  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
+  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
+      || (flags&0x0F)==SQLITE_SYNC_FULL
+  );
+
+  /* Unix cannot, but some systems may return SQLITE_FULL from here. This
+  ** line is to test that doing so does not cause any problems.
+  */
+  SimulateDiskfullError( return SQLITE_FULL );
+
+  assert( pFile );
+  OSTRACE(("SYNC    %-3d\n", pFile->h));
+  rc = full_fsync(pFile->h, isFullsync, isDataOnly);
+  SimulateIOError( rc=1 );
+  if( rc ){
+    storeLastErrno(pFile, errno);
+    return unixLogError(SQLITE_IOERR_FSYNC, "full_fsync", pFile->zPath);
+  }
+
+  /* Also fsync the directory containing the file if the DIRSYNC flag
+  ** is set.  This is a one-time occurrence.  Many systems (examples: AIX)
+  ** are unable to fsync a directory, so ignore errors on the fsync.
+  */
+  if( pFile->ctrlFlags & UNIXFILE_DIRSYNC ){
+    int dirfd;
+    OSTRACE(("DIRSYNC %s (have_fullfsync=%d fullsync=%d)\n", pFile->zPath,
+            HAVE_FULLFSYNC, isFullsync));
+    rc = osOpenDirectory(pFile->zPath, &dirfd);
+    if( rc==SQLITE_OK ){
+      full_fsync(dirfd, 0, 0);
+      robust_close(pFile, dirfd, __LINE__);
+    }else{
+      assert( rc==SQLITE_CANTOPEN );
+      rc = SQLITE_OK;
+    }
+    pFile->ctrlFlags &= ~UNIXFILE_DIRSYNC;
+  }
+  return rc;
+}
+
+/*
+** Truncate an open file to a specified size
+*/
+static int unixTruncate(sqlite3_file *id, i64 nByte){
+  unixFile *pFile = (unixFile *)id;
+  int rc;
+  assert( pFile );
+  SimulateIOError( return SQLITE_IOERR_TRUNCATE );
+
+  /* If the user has configured a chunk-size for this file, truncate the
+  ** file so that it consists of an integer number of chunks (i.e. the
+  ** actual file size after the operation may be larger than the requested
+  ** size).
+  */
+  if( pFile->szChunk>0 ){
+    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
+  }
+
+  rc = robust_ftruncate(pFile->h, nByte);
+  if( rc ){
+    storeLastErrno(pFile, errno);
+    return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
+  }else{
+#ifdef SQLITE_DEBUG
+    /* If we are doing a normal write to a database file (as opposed to
+    ** doing a hot-journal rollback or a write to some file other than a
+    ** normal database file) and we truncate the file to zero length,
+    ** that effectively updates the change counter.  This might happen
+    ** when restoring a database using the backup API from a zero-length
+    ** source.
+    */
+    if( pFile->inNormalWrite && nByte==0 ){
+      pFile->transCntrChng = 1;
+    }
+#endif
+
+#if SQLITE_MAX_MMAP_SIZE>0
+    /* If the file was just truncated to a size smaller than the currently
+    ** mapped region, reduce the effective mapping size as well. SQLite will
+    ** use read() and write() to access data beyond this point from now on.
+    */
+    if( nByte<pFile->mmapSize ){
+      pFile->mmapSize = nByte;
+    }
+#endif
+
+    return SQLITE_OK;
+  }
+}
+
+/*
+** Determine the current size of a file in bytes
+*/
+static int unixFileSize(sqlite3_file *id, i64 *pSize){
+  int rc;
+  struct stat buf;
+  assert( id );
+  rc = osFstat(((unixFile*)id)->h, &buf);
+  SimulateIOError( rc=1 );
+  if( rc!=0 ){
+    storeLastErrno((unixFile*)id, errno);
+    return SQLITE_IOERR_FSTAT;
+  }
+  *pSize = buf.st_size;
+
+  /* When opening a zero-size database, the findInodeInfo() procedure
+  ** writes a single byte into that file in order to work around a bug
+  ** in the OS-X msdos filesystem.  In order to avoid problems with upper
+  ** layers, we need to report this file size as zero even though it is
+  ** really 1.   Ticket #3260.
+  */
+  if( *pSize==1 ) *pSize = 0;
+
+
+  return SQLITE_OK;
+}
+
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+/*
+** Handler for proxy-locking file-control verbs.  Defined below in the
+** proxying locking division.
+*/
+static int proxyFileControl(sqlite3_file*,int,void*);
+#endif
+
+/*
+** This function is called to handle the SQLITE_FCNTL_SIZE_HINT
+** file-control operation.  Enlarge the database to nBytes in size
+** (rounded up to the next chunk-size).  If the database is already
+** nBytes or larger, this routine is a no-op.
+*/
+static int fcntlSizeHint(unixFile *pFile, i64 nByte){
+  if( pFile->szChunk>0 ){
+    i64 nSize;                    /* Required file size */
+    struct stat buf;              /* Used to hold return values of fstat() */
+ 
+    if( osFstat(pFile->h, &buf) ){
+      return SQLITE_IOERR_FSTAT;
+    }
+
+    nSize = ((nByte+pFile->szChunk-1) / pFile->szChunk) * pFile->szChunk;
+    if( nSize>(i64)buf.st_size ){
+
+#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
+      /* The code below is handling the return value of osFallocate()
+      ** correctly. posix_fallocate() is defined to "returns zero on success,
+      ** or an error number on  failure". See the manpage for details. */
+      int err;
+      do{
+        err = osFallocate(pFile->h, buf.st_size, nSize-buf.st_size);
+      }while( err==EINTR );
+      if( err && err!=EINVAL ) return SQLITE_IOERR_WRITE;
+#else
+      /* If the OS does not have posix_fallocate(), fake it. Write a
+      ** single byte to the last byte in each block that falls entirely
+      ** within the extended region. Then, if required, a single byte
+      ** at offset (nSize-1), to set the size of the file correctly.
+      ** This is a similar technique to that used by glibc on systems
+      ** that do not have a real fallocate() call.
+      */
+      int nBlk = buf.st_blksize;  /* File-system block size */
+      int nWrite = 0;             /* Number of bytes written by seekAndWrite */
+      i64 iWrite;                 /* Next offset to write to */
+
+      iWrite = (buf.st_size/nBlk)*nBlk + nBlk - 1;
+      assert( iWrite>=buf.st_size );
+      assert( ((iWrite+1)%nBlk)==0 );
+      for(/*no-op*/; iWrite<nSize+nBlk-1; iWrite+=nBlk ){
+        if( iWrite>=nSize ) iWrite = nSize - 1;
+        nWrite = seekAndWrite(pFile, iWrite, "", 1);
+        if( nWrite!=1 ) return SQLITE_IOERR_WRITE;
+      }
+#endif
+    }
+  }
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  if( pFile->mmapSizeMax>0 && nByte>pFile->mmapSize ){
+    int rc;
+    if( pFile->szChunk<=0 ){
+      if( robust_ftruncate(pFile->h, nByte) ){
+        storeLastErrno(pFile, errno);
+        return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
+      }
+    }
+
+    rc = unixMapfile(pFile, nByte);
+    return rc;
+  }
+#endif
+
+  return SQLITE_OK;
+}
+
+/*
+** If *pArg is initially negative then this is a query.  Set *pArg to
+** 1 or 0 depending on whether or not bit mask of pFile->ctrlFlags is set.
+**
+** If *pArg is 0 or 1, then clear or set the mask bit of pFile->ctrlFlags.
+*/
+static void unixModeBit(unixFile *pFile, unsigned char mask, int *pArg){
+  if( *pArg<0 ){
+    *pArg = (pFile->ctrlFlags & mask)!=0;
+  }else if( (*pArg)==0 ){
+    pFile->ctrlFlags &= ~mask;
+  }else{
+    pFile->ctrlFlags |= mask;
+  }
+}
+
+/* Forward declaration */
+static int unixGetTempname(int nBuf, char *zBuf);
+#ifndef SQLITE_OMIT_WAL
+ static int unixFcntlExternalReader(unixFile*, int*);
+#endif
+
+/*
+** Information and control of an open file handle.
+*/
+static int unixFileControl(sqlite3_file *id, int op, void *pArg){
+  unixFile *pFile = (unixFile*)id;
+  switch( op ){
+#if defined(__linux__) && defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+    case SQLITE_FCNTL_BEGIN_ATOMIC_WRITE: {
+      int rc = osIoctl(pFile->h, F2FS_IOC_START_ATOMIC_WRITE);
+      return rc ? SQLITE_IOERR_BEGIN_ATOMIC : SQLITE_OK;
+    }
+    case SQLITE_FCNTL_COMMIT_ATOMIC_WRITE: {
+      int rc = osIoctl(pFile->h, F2FS_IOC_COMMIT_ATOMIC_WRITE);
+      return rc ? SQLITE_IOERR_COMMIT_ATOMIC : SQLITE_OK;
+    }
+    case SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE: {
+      int rc = osIoctl(pFile->h, F2FS_IOC_ABORT_VOLATILE_WRITE);
+      return rc ? SQLITE_IOERR_ROLLBACK_ATOMIC : SQLITE_OK;
+    }
+#endif /* __linux__ && SQLITE_ENABLE_BATCH_ATOMIC_WRITE */
+
+    case SQLITE_FCNTL_LOCKSTATE: {
+      *(int*)pArg = pFile->eFileLock;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_LAST_ERRNO: {
+      *(int*)pArg = pFile->lastErrno;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      pFile->szChunk = *(int *)pArg;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SIZE_HINT: {
+      int rc;
+      SimulateIOErrorBenign(1);
+      rc = fcntlSizeHint(pFile, *(i64 *)pArg);
+      SimulateIOErrorBenign(0);
+      return rc;
+    }
+    case SQLITE_FCNTL_PERSIST_WAL: {
+      unixModeBit(pFile, UNIXFILE_PERSIST_WAL, (int*)pArg);
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_POWERSAFE_OVERWRITE: {
+      unixModeBit(pFile, UNIXFILE_PSOW, (int*)pArg);
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_VFSNAME: {
+      *(char**)pArg = sqlite3_mprintf("%s", pFile->pVfs->zName);
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_TEMPFILENAME: {
+      char *zTFile = sqlite3_malloc64( pFile->pVfs->mxPathname );
+      if( zTFile ){
+        unixGetTempname(pFile->pVfs->mxPathname, zTFile);
+        *(char**)pArg = zTFile;
+      }
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_HAS_MOVED: {
+      *(int*)pArg = fileHasMoved(pFile);
+      return SQLITE_OK;
+    }
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    case SQLITE_FCNTL_LOCK_TIMEOUT: {
+      int iOld = pFile->iBusyTimeout;
+#if SQLITE_ENABLE_SETLK_TIMEOUT==1
+      pFile->iBusyTimeout = *(int*)pArg;
+#elif SQLITE_ENABLE_SETLK_TIMEOUT==2
+      pFile->iBusyTimeout = !!(*(int*)pArg);
+#else
+# error "SQLITE_ENABLE_SETLK_TIMEOUT must be set to 1 or 2"
+#endif
+      *(int*)pArg = iOld;
+      return SQLITE_OK;
+    }
+#endif
+#if SQLITE_MAX_MMAP_SIZE>0
+    case SQLITE_FCNTL_MMAP_SIZE: {
+      i64 newLimit = *(i64*)pArg;
+      int rc = SQLITE_OK;
+      if( newLimit>sqlite3GlobalConfig.mxMmap ){
+        newLimit = sqlite3GlobalConfig.mxMmap;
+      }
+
+      /* The value of newLimit may be eventually cast to (size_t) and passed
+      ** to mmap(). Restrict its value to 2GB if (size_t) is not at least a
+      ** 64-bit type. */
+      if( newLimit>0 && sizeof(size_t)<8 ){
+        newLimit = (newLimit & 0x7FFFFFFF);
+      }
+
+      *(i64*)pArg = pFile->mmapSizeMax;
+      if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){
+        pFile->mmapSizeMax = newLimit;
+        if( pFile->mmapSize>0 ){
+          unixUnmapfile(pFile);
+          rc = unixMapfile(pFile, -1);
+        }
+      }
+      return rc;
+    }
+#endif
+#ifdef SQLITE_DEBUG
+    /* The pager calls this method to signal that it has done
+    ** a rollback and that the database is therefore unchanged and
+    ** it hence it is OK for the transaction change counter to be
+    ** unchanged.
+    */
+    case SQLITE_FCNTL_DB_UNCHANGED: {
+      ((unixFile*)id)->dbUpdate = 0;
+      return SQLITE_OK;
+    }
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+    case SQLITE_FCNTL_SET_LOCKPROXYFILE:
+    case SQLITE_FCNTL_GET_LOCKPROXYFILE: {
+      return proxyFileControl(id,op,pArg);
+    }
+#endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) */
+
+    case SQLITE_FCNTL_EXTERNAL_READER: {
+#ifndef SQLITE_OMIT_WAL
+      return unixFcntlExternalReader((unixFile*)id, (int*)pArg);
+#else
+      *(int*)pArg = 0;
+      return SQLITE_OK;
+#endif
+    }
+  }
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** If pFd->sectorSize is non-zero when this function is called, it is a
+** no-op. Otherwise, the values of pFd->sectorSize and
+** pFd->deviceCharacteristics are set according to the file-system
+** characteristics.
+**
+** There are two versions of this function. One for QNX and one for all
+** other systems.
+*/
+#ifndef __QNXNTO__
+static void setDeviceCharacteristics(unixFile *pFd){
+  assert( pFd->deviceCharacteristics==0 || pFd->sectorSize!=0 );
+  if( pFd->sectorSize==0 ){
+#if defined(__linux__) && defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+    int res;
+    u32 f = 0;
+
+    /* Check for support for F2FS atomic batch writes. */
+    res = osIoctl(pFd->h, F2FS_IOC_GET_FEATURES, &f);
+    if( res==0 && (f & F2FS_FEATURE_ATOMIC_WRITE) ){
+      pFd->deviceCharacteristics = SQLITE_IOCAP_BATCH_ATOMIC;
+    }
+#endif /* __linux__ && SQLITE_ENABLE_BATCH_ATOMIC_WRITE */
+
+    /* Set the POWERSAFE_OVERWRITE flag if requested. */
+    if( pFd->ctrlFlags & UNIXFILE_PSOW ){
+      pFd->deviceCharacteristics |= SQLITE_IOCAP_POWERSAFE_OVERWRITE;
+    }
+
+    pFd->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
+  }
+}
+#else
+#include <sys/dcmd_blk.h>
+#include <sys/statvfs.h>
+static void setDeviceCharacteristics(unixFile *pFile){
+  if( pFile->sectorSize == 0 ){
+    struct statvfs fsInfo;
+     
+    /* Set defaults for non-supported filesystems */
+    pFile->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
+    pFile->deviceCharacteristics = 0;
+    if( fstatvfs(pFile->h, &fsInfo) == -1 ) {
+      return;
+    }
+
+    if( !strcmp(fsInfo.f_basetype, "tmp") ) {
+      pFile->sectorSize = fsInfo.f_bsize;
+      pFile->deviceCharacteristics =
+        SQLITE_IOCAP_ATOMIC4K |       /* All ram filesystem writes are atomic */
+        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
+                                      ** the write succeeds */
+        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
+                                      ** so it is ordered */
+        0;
+    }else if( strstr(fsInfo.f_basetype, "etfs") ){
+      pFile->sectorSize = fsInfo.f_bsize;
+      pFile->deviceCharacteristics =
+        /* etfs cluster size writes are atomic */
+        (pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) |
+        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
+                                      ** the write succeeds */
+        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
+                                      ** so it is ordered */
+        0;
+    }else if( !strcmp(fsInfo.f_basetype, "qnx6") ){
+      pFile->sectorSize = fsInfo.f_bsize;
+      pFile->deviceCharacteristics =
+        SQLITE_IOCAP_ATOMIC |         /* All filesystem writes are atomic */
+        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
+                                      ** the write succeeds */
+        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
+                                      ** so it is ordered */
+        0;
+    }else if( !strcmp(fsInfo.f_basetype, "qnx4") ){
+      pFile->sectorSize = fsInfo.f_bsize;
+      pFile->deviceCharacteristics =
+        /* full bitset of atomics from max sector size and smaller */
+        ((pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) << 1) - 2 |
+        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
+                                      ** so it is ordered */
+        0;
+    }else if( strstr(fsInfo.f_basetype, "dos") ){
+      pFile->sectorSize = fsInfo.f_bsize;
+      pFile->deviceCharacteristics =
+        /* full bitset of atomics from max sector size and smaller */
+        ((pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) << 1) - 2 |
+        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
+                                      ** so it is ordered */
+        0;
+    }else{
+      pFile->deviceCharacteristics =
+        SQLITE_IOCAP_ATOMIC512 |      /* blocks are atomic */
+        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
+                                      ** the write succeeds */
+        0;
+    }
+  }
+  /* Last chance verification.  If the sector size isn't a multiple of 512
+  ** then it isn't valid.*/
+  if( pFile->sectorSize % 512 != 0 ){
+    pFile->deviceCharacteristics = 0;
+    pFile->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
+  }
+}
+#endif
+
+/*
+** Return the sector size in bytes of the underlying block device for
+** the specified file. This is almost always 512 bytes, but may be
+** larger for some devices.
+**
+** SQLite code assumes this function cannot fail. It also assumes that
+** if two files are created in the same file-system directory (i.e.
+** a database and its journal file) that the sector size will be the
+** same for both.
+*/
+static int unixSectorSize(sqlite3_file *id){
+  unixFile *pFd = (unixFile*)id;
+  setDeviceCharacteristics(pFd);
+  return pFd->sectorSize;
+}
+
+/*
+** Return the device characteristics for the file.
+**
+** This VFS is set up to return SQLITE_IOCAP_POWERSAFE_OVERWRITE by default.
+** However, that choice is controversial since technically the underlying
+** file system does not always provide powersafe overwrites.  (In other
+** words, after a power-loss event, parts of the file that were never
+** written might end up being altered.)  However, non-PSOW behavior is very,
+** very rare.  And asserting PSOW makes a large reduction in the amount
+** of required I/O for journaling, since a lot of padding is eliminated.
+**  Hence, while POWERSAFE_OVERWRITE is on by default, there is a file-control
+** available to turn it off and URI query parameter available to turn it off.
+*/
+static int unixDeviceCharacteristics(sqlite3_file *id){
+  unixFile *pFd = (unixFile*)id;
+  setDeviceCharacteristics(pFd);
+  return pFd->deviceCharacteristics;
+}
+
+#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
+
+/*
+** Return the system page size.
+**
+** This function should not be called directly by other code in this file.
+** Instead, it should be called via macro osGetpagesize().
+*/
+static int unixGetpagesize(void){
+#if OS_VXWORKS
+  return 1024;
+#elif defined(_BSD_SOURCE)
+  return getpagesize();
+#else
+  return (int)sysconf(_SC_PAGESIZE);
+#endif
+}
+
+#endif /* !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0 */
+
+#ifndef SQLITE_OMIT_WAL
+
+/*
+** Object used to represent an shared memory buffer.
+**
+** When multiple threads all reference the same wal-index, each thread
+** has its own unixShm object, but they all point to a single instance
+** of this unixShmNode object.  In other words, each wal-index is opened
+** only once per process.
+**
+** Each unixShmNode object is connected to a single unixInodeInfo object.
+** We could coalesce this object into unixInodeInfo, but that would mean
+** every open file that does not use shared memory (in other words, most
+** open files) would have to carry around this extra information.  So
+** the unixInodeInfo object contains a pointer to this unixShmNode object
+** and the unixShmNode object is created only when needed.
+**
+** unixMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**
+** The following fields are read-only after the object is created:
+**
+**      hShm
+**      zFilename
+**
+** Either unixShmNode.pShmMutex must be held or unixShmNode.nRef==0 and
+** unixMutexHeld() is true when reading or writing any other field
+** in this structure.
+**
+** aLock[SQLITE_SHM_NLOCK]:
+**   This array records the various locks held by clients on each of the
+**   SQLITE_SHM_NLOCK slots. If the aLock[] entry is set to 0, then no
+**   locks are held by the process on this slot. If it is set to -1, then
+**   some client holds an EXCLUSIVE lock on the locking slot. If the aLock[]
+**   value is set to a positive value, then it is the number of shared 
+**   locks currently held on the slot.
+**
+** aMutex[SQLITE_SHM_NLOCK]:
+**   Normally, when SQLITE_ENABLE_SETLK_TIMEOUT is not defined, mutex 
+**   pShmMutex is used to protect the aLock[] array and the right to
+**   call fcntl() on unixShmNode.hShm to obtain or release locks.
+**
+**   If SQLITE_ENABLE_SETLK_TIMEOUT is defined though, we use an array
+**   of mutexes - one for each locking slot. To read or write locking
+**   slot aLock[iSlot], the caller must hold the corresponding mutex
+**   aMutex[iSlot]. Similarly, to call fcntl() to obtain or release a
+**   lock corresponding to slot iSlot, mutex aMutex[iSlot] must be held.
+*/
+struct unixShmNode {
+  unixInodeInfo *pInode;     /* unixInodeInfo that owns this SHM node */
+  sqlite3_mutex *pShmMutex;  /* Mutex to access this object */
+  char *zFilename;           /* Name of the mmapped file */
+  int hShm;                  /* Open file descriptor */
+  int szRegion;              /* Size of shared-memory regions */
+  u16 nRegion;               /* Size of array apRegion */
+  u8 isReadonly;             /* True if read-only */
+  u8 isUnlocked;             /* True if no DMS lock held */
+  char **apRegion;           /* Array of mapped shared-memory regions */
+  int nRef;                  /* Number of unixShm objects pointing to this */
+  unixShm *pFirst;           /* All unixShm objects pointing to this */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  sqlite3_mutex *aMutex[SQLITE_SHM_NLOCK];
+#endif
+  int aLock[SQLITE_SHM_NLOCK];  /* # shared locks on slot, -1==excl lock */
+#ifdef SQLITE_DEBUG
+  u8 nextShmId;              /* Next available unixShm.id value */
+#endif
+};
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** The following fields are initialized when this object is created and
+** are read-only thereafter:
+**
+**    unixShm.pShmNode
+**    unixShm.id
+**
+** All other fields are read/write.  The unixShm.pShmNode->pShmMutex must
+** be held while accessing any read/write fields.
+*/
+struct unixShm {
+  unixShmNode *pShmNode;     /* The underlying unixShmNode object */
+  unixShm *pNext;            /* Next unixShm with the same unixShmNode */
+  u8 hasMutex;               /* True if holding the unixShmNode->pShmMutex */
+  u8 id;                     /* Id of this connection within its unixShmNode */
+  u16 sharedMask;            /* Mask of shared locks held */
+  u16 exclMask;              /* Mask of exclusive locks held */
+};
+
+/*
+** Constants used for locking
+*/
+#define UNIX_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)         /* first lock byte */
+#define UNIX_SHM_DMS    (UNIX_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Use F_GETLK to check whether or not there are any readers with open
+** wal-mode transactions in other processes on database file pFile. If
+** no error occurs, return SQLITE_OK and set (*piOut) to 1 if there are
+** such transactions, or 0 otherwise. If an error occurs, return an
+** SQLite error code. The final value of *piOut is undefined in this
+** case.
+*/
+static int unixFcntlExternalReader(unixFile *pFile, int *piOut){
+  int rc = SQLITE_OK;
+  *piOut = 0;
+  if( pFile->pShm){
+    unixShmNode *pShmNode = pFile->pShm->pShmNode;
+    struct flock f;
+
+    memset(&f, 0, sizeof(f));
+    f.l_type = F_WRLCK;
+    f.l_whence = SEEK_SET;
+    f.l_start = UNIX_SHM_BASE + 3;
+    f.l_len = SQLITE_SHM_NLOCK - 3;
+
+    sqlite3_mutex_enter(pShmNode->pShmMutex);
+    if( osFcntl(pShmNode->hShm, F_GETLK, &f)<0 ){
+      rc = SQLITE_IOERR_LOCK;
+    }else{
+      *piOut = (f.l_type!=F_UNLCK);
+    }
+    sqlite3_mutex_leave(pShmNode->pShmMutex);
+  }
+
+  return rc;
+}
+
+
+/*
+** Apply posix advisory locks for all bytes from ofst through ofst+n-1.
+**
+** Locks block if the mask is exactly UNIX_SHM_C and are non-blocking
+** otherwise.
+*/
+static int unixShmSystemLock(
+  unixFile *pFile,       /* Open connection to the WAL file */
+  int lockType,          /* F_UNLCK, F_RDLCK, or F_WRLCK */
+  int ofst,              /* First byte of the locking range */
+  int n                  /* Number of bytes to lock */
+){
+  unixShmNode *pShmNode; /* Apply locks to this open shared-memory segment */
+  struct flock f;        /* The posix advisory locking structure */
+  int rc = SQLITE_OK;    /* Result code form fcntl() */
+
+  pShmNode = pFile->pInode->pShmNode;
+
+  /* Assert that the parameters are within expected range and that the
+  ** correct mutex or mutexes are held. */
+  assert( pShmNode->nRef>=0 );
+  assert( (ofst==UNIX_SHM_DMS && n==1)
+       || (ofst>=UNIX_SHM_BASE && ofst+n<=(UNIX_SHM_BASE+SQLITE_SHM_NLOCK))
+  );
+  if( ofst==UNIX_SHM_DMS ){
+    assert( pShmNode->nRef>0 || unixMutexHeld() );
+    assert( pShmNode->nRef==0 || sqlite3_mutex_held(pShmNode->pShmMutex) );
+  }else{
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    int ii;
+    for(ii=ofst-UNIX_SHM_BASE; ii<ofst-UNIX_SHM_BASE+n; ii++){
+      assert( sqlite3_mutex_held(pShmNode->aMutex[ii]) );
+    }
+#else
+    assert( sqlite3_mutex_held(pShmNode->pShmMutex) );
+    assert( pShmNode->nRef>0 );
+#endif
+  }
+
+  /* Shared locks never span more than one byte */
+  assert( n==1 || lockType!=F_RDLCK );
+
+  /* Locks are within range */
+  assert( n>=1 && n<=SQLITE_SHM_NLOCK );
+  assert( ofst>=UNIX_SHM_BASE && ofst<=(UNIX_SHM_DMS+SQLITE_SHM_NLOCK) );
+
+  if( pShmNode->hShm>=0 ){
+    int res;
+    /* Initialize the locking parameters */
+    f.l_type = lockType;
+    f.l_whence = SEEK_SET;
+    f.l_start = ofst;
+    f.l_len = n;
+    res = osSetPosixAdvisoryLock(pShmNode->hShm, &f, pFile);
+    if( res==-1 ){
+#if defined(SQLITE_ENABLE_SETLK_TIMEOUT) && SQLITE_ENABLE_SETLK_TIMEOUT==1
+      rc = (pFile->iBusyTimeout ? SQLITE_BUSY_TIMEOUT : SQLITE_BUSY);
+#else
+      rc = SQLITE_BUSY;
+#endif
+    }
+  }
+
+  /* Do debug tracing */
+#ifdef SQLITE_DEBUG
+  OSTRACE(("SHM-LOCK "));
+  if( rc==SQLITE_OK ){
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d..%d ok\n", ofst, ofst+n-1));
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock %d..%d ok\n", ofst, ofst+n-1));
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d..%d ok\n", ofst, ofst+n-1));
+    }
+  }else{
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d..%d failed\n", ofst, ofst+n-1));
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock %d..%d failed\n", ofst, ofst+n-1));
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d..%d failed\n", ofst, ofst+n-1));
+    }
+  }
+#endif
+
+  return rc;      
+}
+
+/*
+** Return the minimum number of 32KB shm regions that should be mapped at
+** a time, assuming that each mapping must be an integer multiple of the
+** current system page-size.
+**
+** Usually, this is 1. The exception seems to be systems that are configured
+** to use 64KB pages - in this case each mapping must cover at least two
+** shm regions.
+*/
+static int unixShmRegionPerMap(void){
+  int shmsz = 32*1024;            /* SHM region size */
+  int pgsz = osGetpagesize();   /* System page size */
+  assert( ((pgsz-1)&pgsz)==0 );   /* Page size must be a power of 2 */
+  if( pgsz<shmsz ) return 1;
+  return pgsz/shmsz;
+}
+
+/*
+** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void unixShmPurge(unixFile *pFd){
+  unixShmNode *p = pFd->pInode->pShmNode;
+  assert( unixMutexHeld() );
+  if( p && ALWAYS(p->nRef==0) ){
+    int nShmPerMap = unixShmRegionPerMap();
+    int i;
+    assert( p->pInode==pFd->pInode );
+    sqlite3_mutex_free(p->pShmMutex);
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    for(i=0; i<SQLITE_SHM_NLOCK; i++){
+      sqlite3_mutex_free(p->aMutex[i]);
+    }
+#endif
+    for(i=0; i<p->nRegion; i+=nShmPerMap){
+      if( p->hShm>=0 ){
+        osMunmap(p->apRegion[i], p->szRegion);
+      }else{
+        sqlite3_free(p->apRegion[i]);
+      }
+    }
+    sqlite3_free(p->apRegion);
+    if( p->hShm>=0 ){
+      robust_close(pFd, p->hShm, __LINE__);
+      p->hShm = -1;
+    }
+    p->pInode->pShmNode = 0;
+    sqlite3_free(p);
+  }
+}
+
+/*
+** The DMS lock has not yet been taken on shm file pShmNode. Attempt to
+** take it now. Return SQLITE_OK if successful, or an SQLite error
+** code otherwise.
+**
+** If the DMS cannot be locked because this is a readonly_shm=1
+** connection and no other process already holds a lock, return
+** SQLITE_READONLY_CANTINIT and set pShmNode->isUnlocked=1.
+*/
+static int unixLockSharedMemory(unixFile *pDbFd, unixShmNode *pShmNode){
+  struct flock lock;
+  int rc = SQLITE_OK;
+
+  /* Use F_GETLK to determine the locks other processes are holding
+  ** on the DMS byte. If it indicates that another process is holding
+  ** a SHARED lock, then this process may also take a SHARED lock
+  ** and proceed with opening the *-shm file.
+  **
+  ** Or, if no other process is holding any lock, then this process
+  ** is the first to open it. In this case take an EXCLUSIVE lock on the
+  ** DMS byte and truncate the *-shm file to zero bytes in size. Then
+  ** downgrade to a SHARED lock on the DMS byte.
+  **
+  ** If another process is holding an EXCLUSIVE lock on the DMS byte,
+  ** return SQLITE_BUSY to the caller (it will try again). An earlier
+  ** version of this code attempted the SHARED lock at this point. But
+  ** this introduced a subtle race condition: if the process holding
+  ** EXCLUSIVE failed just before truncating the *-shm file, then this
+  ** process might open and use the *-shm file without truncating it.
+  ** And if the *-shm file has been corrupted by a power failure or
+  ** system crash, the database itself may also become corrupt.  */
+  lock.l_whence = SEEK_SET;
+  lock.l_start = UNIX_SHM_DMS;
+  lock.l_len = 1;
+  lock.l_type = F_WRLCK;
+  if( osFcntl(pShmNode->hShm, F_GETLK, &lock)!=0 ) {
+    rc = SQLITE_IOERR_LOCK;
+  }else if( lock.l_type==F_UNLCK ){
+    if( pShmNode->isReadonly ){
+      pShmNode->isUnlocked = 1;
+      rc = SQLITE_READONLY_CANTINIT;
+    }else{
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+      /* Do not use a blocking lock here. If the lock cannot be obtained
+      ** immediately, it means some other connection is truncating the
+      ** *-shm file. And after it has done so, it will not release its
+      ** lock, but only downgrade it to a shared lock. So no point in
+      ** blocking here. The call below to obtain the shared DMS lock may 
+      ** use a blocking lock. */
+      int iSaveTimeout = pDbFd->iBusyTimeout;
+      pDbFd->iBusyTimeout = 0;
+#endif
+      rc = unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1);
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+      pDbFd->iBusyTimeout = iSaveTimeout;
+#endif
+      /* The first connection to attach must truncate the -shm file.  We
+      ** truncate to 3 bytes (an arbitrary small number, less than the
+      ** -shm header size) rather than 0 as a system debugging aid, to
+      ** help detect if a -shm file truncation is legitimate or is the work
+      ** or a rogue process. */
+      if( rc==SQLITE_OK && robust_ftruncate(pShmNode->hShm, 3) ){
+        rc = unixLogError(SQLITE_IOERR_SHMOPEN,"ftruncate",pShmNode->zFilename);
+      }
+    }
+  }else if( lock.l_type==F_WRLCK ){
+    rc = SQLITE_BUSY;
+  }
+
+  if( rc==SQLITE_OK ){
+    assert( lock.l_type==F_UNLCK || lock.l_type==F_RDLCK );
+    rc = unixShmSystemLock(pDbFd, F_RDLCK, UNIX_SHM_DMS, 1);
+  }
+  return rc;
+}
+
+/*
+** Open a shared-memory area associated with open database file pDbFd.
+** This particular implementation uses mmapped files.
+**
+** The file used to implement shared-memory is in the same directory
+** as the open database file and has the same name as the open database
+** file with the "-shm" suffix added.  For example, if the database file
+** is "/home/user1/config.db" then the file that is created and mmapped
+** for shared memory will be called "/home/user1/config.db-shm".
+**
+** Another approach to is to use files in /dev/shm or /dev/tmp or an
+** some other tmpfs mount. But if a file in a different directory
+** from the database file is used, then differing access permissions
+** or a chroot() might cause two different processes on the same
+** database to end up using different files for shared memory -
+** meaning that their memory would not really be shared - resulting
+** in database corruption.  Nevertheless, this tmpfs file usage
+** can be enabled at compile-time using -DSQLITE_SHM_DIRECTORY="/dev/shm"
+** or the equivalent.  The use of the SQLITE_SHM_DIRECTORY compile-time
+** option results in an incompatible build of SQLite;  builds of SQLite
+** that with differing SQLITE_SHM_DIRECTORY settings attempt to use the
+** same database file at the same time, database corruption will likely
+** result. The SQLITE_SHM_DIRECTORY compile-time option is considered
+** "unsupported" and may go away in a future SQLite release.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+**
+** If the original database file (pDbFd) is using the "unix-excl" VFS
+** that means that an exclusive lock is held on the database file and
+** that no other processes are able to read or write the database.  In
+** that case, we do not really need shared memory.  No shared memory
+** file is created.  The shared memory will be simulated with heap memory.
+*/
+static int unixOpenSharedMemory(unixFile *pDbFd){
+  struct unixShm *p = 0;          /* The connection to be opened */
+  struct unixShmNode *pShmNode;   /* The underlying mmapped file */
+  int rc = SQLITE_OK;             /* Result code */
+  unixInodeInfo *pInode;          /* The inode of fd */
+  char *zShm;             /* Name of the file used for SHM */
+  int nShmFilename;               /* Size of the SHM filename in bytes */
+
+  /* Allocate space for the new unixShm object. */
+  p = sqlite3_malloc64( sizeof(*p) );
+  if( p==0 ) return SQLITE_NOMEM_BKPT;
+  memset(p, 0, sizeof(*p));
+  assert( pDbFd->pShm==0 );
+
+  /* Check to see if a unixShmNode object already exists. Reuse an existing
+  ** one if present. Create a new one if necessary.
+  */
+  assert( unixFileMutexNotheld(pDbFd) );
+  unixEnterMutex();
+  pInode = pDbFd->pInode;
+  pShmNode = pInode->pShmNode;
+  if( pShmNode==0 ){
+    struct stat sStat;                 /* fstat() info for database file */
+#ifndef SQLITE_SHM_DIRECTORY
+    const char *zBasePath = pDbFd->zPath;
+#endif
+
+    /* Call fstat() to figure out the permissions on the database file. If
+    ** a new *-shm file is created, an attempt will be made to create it
+    ** with the same permissions.
+    */
+    if( osFstat(pDbFd->h, &sStat) ){
+      rc = SQLITE_IOERR_FSTAT;
+      goto shm_open_err;
+    }
+
+#ifdef SQLITE_SHM_DIRECTORY
+    nShmFilename = sizeof(SQLITE_SHM_DIRECTORY) + 31;
+#else
+    nShmFilename = 6 + (int)strlen(zBasePath);
+#endif
+    pShmNode = sqlite3_malloc64( sizeof(*pShmNode) + nShmFilename );
+    if( pShmNode==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+      goto shm_open_err;
+    }
+    memset(pShmNode, 0, sizeof(*pShmNode)+nShmFilename);
+    zShm = pShmNode->zFilename = (char*)&pShmNode[1];
+#ifdef SQLITE_SHM_DIRECTORY
+    sqlite3_snprintf(nShmFilename, zShm,
+                     SQLITE_SHM_DIRECTORY "/sqlite-shm-%x-%x",
+                     (u32)sStat.st_ino, (u32)sStat.st_dev);
+#else
+    sqlite3_snprintf(nShmFilename, zShm, "%s-shm", zBasePath);
+    sqlite3FileSuffix3(pDbFd->zPath, zShm);
+#endif
+    pShmNode->hShm = -1;
+    pDbFd->pInode->pShmNode = pShmNode;
+    pShmNode->pInode = pDbFd->pInode;
+    if( sqlite3GlobalConfig.bCoreMutex ){
+      pShmNode->pShmMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+      if( pShmNode->pShmMutex==0 ){
+        rc = SQLITE_NOMEM_BKPT;
+        goto shm_open_err;
+      }
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+      {
+        int ii;
+        for(ii=0; ii<SQLITE_SHM_NLOCK; ii++){
+          pShmNode->aMutex[ii] = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+          if( pShmNode->aMutex[ii]==0 ){
+            rc = SQLITE_NOMEM_BKPT;
+            goto shm_open_err;
+          }
+        }
+      }
+#endif
+    }
+
+    if( pInode->bProcessLock==0 ){
+      if( 0==sqlite3_uri_boolean(pDbFd->zPath, "readonly_shm", 0) ){
+        pShmNode->hShm = robust_open(zShm, O_RDWR|O_CREAT|O_NOFOLLOW,
+                                     (sStat.st_mode&0777));
+      }
+      if( pShmNode->hShm<0 ){
+        pShmNode->hShm = robust_open(zShm, O_RDONLY|O_NOFOLLOW,
+                                     (sStat.st_mode&0777));
+        if( pShmNode->hShm<0 ){
+          rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShm);
+          goto shm_open_err;
+        }
+        pShmNode->isReadonly = 1;
+      }
+
+      /* If this process is running as root, make sure that the SHM file
+      ** is owned by the same user that owns the original database.  Otherwise,
+      ** the original owner will not be able to connect.
+      */
+      robustFchown(pShmNode->hShm, sStat.st_uid, sStat.st_gid);
+
+      rc = unixLockSharedMemory(pDbFd, pShmNode);
+      if( rc!=SQLITE_OK && rc!=SQLITE_READONLY_CANTINIT ) goto shm_open_err;
+    }
+  }
+
+  /* Make the new connection a child of the unixShmNode */
+  p->pShmNode = pShmNode;
+#ifdef SQLITE_DEBUG
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  unixLeaveMutex();
+
+  /* The reference count on pShmNode has already been incremented under
+  ** the cover of the unixEnterMutex() mutex and the pointer from the
+  ** new (struct unixShm) object to the pShmNode has been set. All that is
+  ** left to do is to link the new object into the linked list starting
+  ** at pShmNode->pFirst. This must be done while holding the
+  ** pShmNode->pShmMutex.
+  */
+  sqlite3_mutex_enter(pShmNode->pShmMutex);
+  p->pNext = pShmNode->pFirst;
+  pShmNode->pFirst = p;
+  sqlite3_mutex_leave(pShmNode->pShmMutex);
+  return rc;
+
+  /* Jump here on any error */
+shm_open_err:
+  unixShmPurge(pDbFd);       /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  unixLeaveMutex();
+  return rc;
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the
+** shared-memory associated with the database file fd. Shared-memory regions
+** are numbered starting from zero. Each shared-memory region is szRegion
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the bExtend parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If
+** bExtend is non-zero and the requested shared-memory region has not yet
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes
+** address space (if it is not already), *pp is set to point to the mapped
+** memory and SQLITE_OK returned.
+*/
+static int unixShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  unixFile *pDbFd = (unixFile*)fd;
+  unixShm *p;
+  unixShmNode *pShmNode;
+  int rc = SQLITE_OK;
+  int nShmPerMap = unixShmRegionPerMap();
+  int nReqRegion;
+
+  /* If the shared-memory file has not yet been opened, open it now. */
+  if( pDbFd->pShm==0 ){
+    rc = unixOpenSharedMemory(pDbFd);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+
+  p = pDbFd->pShm;
+  pShmNode = p->pShmNode;
+  sqlite3_mutex_enter(pShmNode->pShmMutex);
+  if( pShmNode->isUnlocked ){
+    rc = unixLockSharedMemory(pDbFd, pShmNode);
+    if( rc!=SQLITE_OK ) goto shmpage_out;
+    pShmNode->isUnlocked = 0;
+  }
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+  assert( pShmNode->pInode==pDbFd->pInode );
+  assert( pShmNode->hShm>=0 || pDbFd->pInode->bProcessLock==1 );
+  assert( pShmNode->hShm<0 || pDbFd->pInode->bProcessLock==0 );
+
+  /* Minimum number of regions required to be mapped. */
+  nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;
+
+  if( pShmNode->nRegion<nReqRegion ){
+    char **apNew;                      /* New apRegion[] array */
+    int nByte = nReqRegion*szRegion;   /* Minimum required file size */
+    struct stat sStat;                 /* Used by fstat() */
+
+    pShmNode->szRegion = szRegion;
+
+    if( pShmNode->hShm>=0 ){
+      /* The requested region is not mapped into this processes address space.
+      ** Check to see if it has been allocated (i.e. if the wal-index file is
+      ** large enough to contain the requested region).
+      */
+      if( osFstat(pShmNode->hShm, &sStat) ){
+        rc = SQLITE_IOERR_SHMSIZE;
+        goto shmpage_out;
+      }
+
+      if( sStat.st_size<nByte ){
+        /* The requested memory region does not exist. If bExtend is set to
+        ** false, exit early. *pp will be set to NULL and SQLITE_OK returned.
+        */
+        if( !bExtend ){
+          goto shmpage_out;
+        }
+
+        /* Alternatively, if bExtend is true, extend the file. Do this by
+        ** writing a single byte to the end of each (OS) page being
+        ** allocated or extended. Technically, we need only write to the
+        ** last page in order to extend the file. But writing to all new
+        ** pages forces the OS to allocate them immediately, which reduces
+        ** the chances of SIGBUS while accessing the mapped region later on.
+        */
+        else{
+          static const int pgsz = 4096;
+          int iPg;
+
+          /* Write to the last byte of each newly allocated or extended page */
+          assert( (nByte % pgsz)==0 );
+          for(iPg=(sStat.st_size/pgsz); iPg<(nByte/pgsz); iPg++){
+            int x = 0;
+            if( seekAndWriteFd(pShmNode->hShm, iPg*pgsz + pgsz-1,"",1,&x)!=1 ){
+              const char *zFile = pShmNode->zFilename;
+              rc = unixLogError(SQLITE_IOERR_SHMSIZE, "write", zFile);
+              goto shmpage_out;
+            }
+          }
+        }
+      }
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (char **)sqlite3_realloc(
+        pShmNode->apRegion, nReqRegion*sizeof(char *)
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM_BKPT;
+      goto shmpage_out;
+    }
+    pShmNode->apRegion = apNew;
+    while( pShmNode->nRegion<nReqRegion ){
+      int nMap = szRegion*nShmPerMap;
+      int i;
+      void *pMem;
+      if( pShmNode->hShm>=0 ){
+        pMem = osMmap(0, nMap,
+            pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE,
+            MAP_SHARED, pShmNode->hShm, szRegion*(i64)pShmNode->nRegion
+        );
+        if( pMem==MAP_FAILED ){
+          rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);
+          goto shmpage_out;
+        }
+      }else{
+        pMem = sqlite3_malloc64(nMap);
+        if( pMem==0 ){
+          rc = SQLITE_NOMEM_BKPT;
+          goto shmpage_out;
+        }
+        memset(pMem, 0, nMap);
+      }
+
+      for(i=0; i<nShmPerMap; i++){
+        pShmNode->apRegion[pShmNode->nRegion+i] = &((char*)pMem)[szRegion*i];
+      }
+      pShmNode->nRegion += nShmPerMap;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    *pp = pShmNode->apRegion[iRegion];
+  }else{
+    *pp = 0;
+  }
+  if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
+  sqlite3_mutex_leave(pShmNode->pShmMutex);
+  return rc;
+}
+
+/*
+** Check that the pShmNode->aLock[] array comports with the locking bitmasks
+** held by each client. Return true if it does, or false otherwise. This
+** is to be used in an assert(). e.g.
+**
+**     assert( assertLockingArrayOk(pShmNode) );
+*/
+#ifdef SQLITE_DEBUG
+static int assertLockingArrayOk(unixShmNode *pShmNode){
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  return 1;
+#else
+  unixShm *pX;
+  int aLock[SQLITE_SHM_NLOCK];
+
+  memset(aLock, 0, sizeof(aLock));
+  for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+    int i;
+    for(i=0; i<SQLITE_SHM_NLOCK; i++){
+      if( pX->exclMask & (1<<i) ){
+        assert( aLock[i]==0 );
+        aLock[i] = -1;
+      }else if( pX->sharedMask & (1<<i) ){
+        assert( aLock[i]>=0 );
+        aLock[i]++;
+      }
+    }
+  }
+
+  assert( 0==memcmp(pShmNode->aLock, aLock, sizeof(aLock)) );
+  return (memcmp(pShmNode->aLock, aLock, sizeof(aLock))==0);
+#endif
+}
+#endif
+
+/*
+** Change the lock state for a shared-memory segment.
+**
+** Note that the relationship between SHARED and EXCLUSIVE locks is a little
+** different here than in posix.  In xShmLock(), one can go from unlocked
+** to shared and back or from unlocked to exclusive and back.  But one may
+** not go from shared to exclusive or from exclusive to shared.
+*/
+static int unixShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  unixFile *pDbFd = (unixFile*)fd;      /* Connection holding shared memory */
+  unixShm *p;                           /* The shared memory being locked */
+  unixShmNode *pShmNode;                /* The underlying file iNode */
+  int rc = SQLITE_OK;                   /* Result code */
+  u16 mask = (1<<(ofst+n)) - (1<<ofst); /* Mask of locks to take or release */
+  int *aLock;
+
+  p = pDbFd->pShm;
+  if( p==0 ) return SQLITE_IOERR_SHMLOCK;
+  pShmNode = p->pShmNode;
+  if( NEVER(pShmNode==0) ) return SQLITE_IOERR_SHMLOCK;
+  aLock = pShmNode->aLock;
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+  assert( pShmNode->hShm>=0 || pDbFd->pInode->bProcessLock==1 );
+  assert( pShmNode->hShm<0 || pDbFd->pInode->bProcessLock==0 );
+
+  /* Check that, if this to be a blocking lock, no locks that occur later
+  ** in the following list than the lock being obtained are already held:
+  **
+  **   1. Checkpointer lock (ofst==1).
+  **   2. Write lock (ofst==0).
+  **   3. Read locks (ofst>=3 && ofst<SQLITE_SHM_NLOCK).
+  **
+  ** In other words, if this is a blocking lock, none of the locks that
+  ** occur later in the above list than the lock being obtained may be
+  ** held.
+  **
+  ** It is not permitted to block on the RECOVER lock.
+  */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  {
+    u16 lockMask = (p->exclMask|p->sharedMask);
+    assert( (flags & SQLITE_SHM_UNLOCK) || pDbFd->iBusyTimeout==0 || (
+          (ofst!=2)                                   /* not RECOVER */
+       && (ofst!=1 || lockMask==0 || lockMask==2)
+       && (ofst!=0 || lockMask<3)
+       && (ofst<3  || lockMask<(1<<ofst))
+    ));
+  }
+#endif
+
+  /* Check if there is any work to do. There are three cases:
+  **
+  **    a) An unlock operation where there are locks to unlock,
+  **    b) An shared lock where the requested lock is not already held
+  **    c) An exclusive lock where the requested lock is not already held
+  **
+  ** The SQLite core never requests an exclusive lock that it already holds.
+  ** This is assert()ed below.
+  */
+  assert( flags!=(SQLITE_SHM_EXCLUSIVE|SQLITE_SHM_LOCK) 
+       || 0==(p->exclMask & mask) 
+  );
+  if( ((flags & SQLITE_SHM_UNLOCK) && ((p->exclMask|p->sharedMask) & mask))
+   || (flags==(SQLITE_SHM_SHARED|SQLITE_SHM_LOCK) && 0==(p->sharedMask & mask))
+   || (flags==(SQLITE_SHM_EXCLUSIVE|SQLITE_SHM_LOCK))
+  ){
+
+    /* Take the required mutexes. In SETLK_TIMEOUT mode (blocking locks), if
+    ** this is an attempt on an exclusive lock use sqlite3_mutex_try(). If any
+    ** other thread is holding this mutex, then it is either holding or about
+    ** to hold a lock exclusive to the one being requested, and we may
+    ** therefore return SQLITE_BUSY to the caller.
+    **
+    ** Doing this prevents some deadlock scenarios. For example, thread 1 may
+    ** be a checkpointer blocked waiting on the WRITER lock. And thread 2
+    ** may be a normal SQL client upgrading to a write transaction. In this
+    ** case thread 2 does a non-blocking request for the WRITER lock. But -
+    ** if it were to use sqlite3_mutex_enter() then it would effectively
+    ** become a (doomed) blocking request, as thread 2 would block until thread
+    ** 1 obtained WRITER and released the mutex. Since thread 2 already holds
+    ** a lock on a read-locking slot at this point, this breaks the
+    ** anti-deadlock rules (see above).  */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    int iMutex;
+    for(iMutex=ofst; iMutex<ofst+n; iMutex++){
+      if( flags==(SQLITE_SHM_LOCK|SQLITE_SHM_EXCLUSIVE) ){
+        rc = sqlite3_mutex_try(pShmNode->aMutex[iMutex]);
+        if( rc!=SQLITE_OK ) goto leave_shmnode_mutexes;
+      }else{
+        sqlite3_mutex_enter(pShmNode->aMutex[iMutex]);
+      }
+    }
+#else
+    sqlite3_mutex_enter(pShmNode->pShmMutex);
+#endif
+
+    if( ALWAYS(rc==SQLITE_OK) ){
+      if( flags & SQLITE_SHM_UNLOCK ){
+        /* Case (a) - unlock.  */
+        int bUnlock = 1;
+        assert( (p->exclMask & p->sharedMask)==0 );
+        assert( !(flags & SQLITE_SHM_EXCLUSIVE) || (p->exclMask & mask)==mask );
+        assert( !(flags & SQLITE_SHM_SHARED) || (p->sharedMask & mask)==mask );
+  
+        /* If this is a SHARED lock being unlocked, it is possible that other
+        ** clients within this process are holding the same SHARED lock. In
+        ** this case, set bUnlock to 0 so that the posix lock is not removed
+        ** from the file-descriptor below.  */
+        if( flags & SQLITE_SHM_SHARED ){
+          assert( n==1 );
+          assert( aLock[ofst]>=1 );
+          if( aLock[ofst]>1 ){
+            bUnlock = 0;
+            aLock[ofst]--;
+            p->sharedMask &= ~mask;
+          }
+        }
+  
+        if( bUnlock ){
+          rc = unixShmSystemLock(pDbFd, F_UNLCK, ofst+UNIX_SHM_BASE, n);
+          if( rc==SQLITE_OK ){
+            memset(&aLock[ofst], 0, sizeof(int)*n);
+            p->sharedMask &= ~mask;
+            p->exclMask &= ~mask;
+          }
+        }
+      }else if( flags & SQLITE_SHM_SHARED ){
+        /* Case (b) - a shared lock.  */
+  
+        if( aLock[ofst]<0 ){
+          /* An exclusive lock is held by some other connection. BUSY. */ 
+          rc = SQLITE_BUSY;
+        }else if( aLock[ofst]==0 ){
+          rc = unixShmSystemLock(pDbFd, F_RDLCK, ofst+UNIX_SHM_BASE, n);
+        }
+  
+        /* Get the local shared locks */
+        if( rc==SQLITE_OK ){
+          p->sharedMask |= mask;
+          aLock[ofst]++;
+        }
+      }else{
+        /* Case (c) - an exclusive lock.  */
+        int ii;
+  
+        assert( flags==(SQLITE_SHM_LOCK|SQLITE_SHM_EXCLUSIVE) );
+        assert( (p->sharedMask & mask)==0 );
+        assert( (p->exclMask & mask)==0 );
+  
+        /* Make sure no sibling connections hold locks that will block this
+        ** lock.  If any do, return SQLITE_BUSY right away.  */
+        for(ii=ofst; ii<ofst+n; ii++){
+          if( aLock[ii] ){
+            rc = SQLITE_BUSY;
+            break;
+          }
+        }
+  
+        /* Get the exclusive locks at the system level. Then if successful
+        ** also update the in-memory values. */
+        if( rc==SQLITE_OK ){
+          rc = unixShmSystemLock(pDbFd, F_WRLCK, ofst+UNIX_SHM_BASE, n);
+          if( rc==SQLITE_OK ){
+            p->exclMask |= mask;
+            for(ii=ofst; ii<ofst+n; ii++){
+              aLock[ii] = -1;
+            }
+          }
+        }
+      }
+      assert( assertLockingArrayOk(pShmNode) );
+    }
+
+    /* Drop the mutexes acquired above. */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  leave_shmnode_mutexes:
+    for(iMutex--; iMutex>=ofst; iMutex--){
+      sqlite3_mutex_leave(pShmNode->aMutex[iMutex]);
+    }
+#else
+    sqlite3_mutex_leave(pShmNode->pShmMutex);
+#endif
+  }
+
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
+           p->id, osGetpid(0), p->sharedMask, p->exclMask));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void unixShmBarrier(
+  sqlite3_file *fd                /* Database file holding the shared memory */
+){
+  UNUSED_PARAMETER(fd);
+  sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
+  assert( fd->pMethods->xLock==nolockLock
+       || unixFileMutexNotheld((unixFile*)fd)
+  );
+  unixEnterMutex();               /* Also mutex, for redundancy */
+  unixLeaveMutex();
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying
+** storage if deleteFlag is true.
+**
+** If there is no shared memory associated with the connection then this
+** routine is a harmless no-op.
+*/
+static int unixShmUnmap(
+  sqlite3_file *fd,               /* The underlying database file */
+  int deleteFlag                  /* Delete shared-memory if true */
+){
+  unixShm *p;                     /* The connection to be closed */
+  unixShmNode *pShmNode;          /* The underlying shared-memory file */
+  unixShm **pp;                   /* For looping over sibling connections */
+  unixFile *pDbFd;                /* The underlying database file */
+
+  pDbFd = (unixFile*)fd;
+  p = pDbFd->pShm;
+  if( p==0 ) return SQLITE_OK;
+  pShmNode = p->pShmNode;
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->pShmMutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->pShmMutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  assert( unixFileMutexNotheld(pDbFd) );
+  unixEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    if( deleteFlag && pShmNode->hShm>=0 ){
+      osUnlink(pShmNode->zFilename);
+    }
+    unixShmPurge(pDbFd);
+  }
+  unixLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+
+#else
+# define unixShmMap     0
+# define unixShmLock    0
+# define unixShmBarrier 0
+# define unixShmUnmap   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/*
+** If it is currently memory mapped, unmap file pFd.
+*/
+static void unixUnmapfile(unixFile *pFd){
+  assert( pFd->nFetchOut==0 );
+  if( pFd->pMapRegion ){
+    osMunmap(pFd->pMapRegion, pFd->mmapSizeActual);
+    pFd->pMapRegion = 0;
+    pFd->mmapSize = 0;
+    pFd->mmapSizeActual = 0;
+  }
+}
+
+/*
+** Attempt to set the size of the memory mapping maintained by file
+** descriptor pFd to nNew bytes. Any existing mapping is discarded.
+**
+** If successful, this function sets the following variables:
+**
+**       unixFile.pMapRegion
+**       unixFile.mmapSize
+**       unixFile.mmapSizeActual
+**
+** If unsuccessful, an error message is logged via sqlite3_log() and
+** the three variables above are zeroed. In this case SQLite should
+** continue accessing the database using the xRead() and xWrite()
+** methods.
+*/
+static void unixRemapfile(
+  unixFile *pFd,                  /* File descriptor object */
+  i64 nNew                        /* Required mapping size */
+){
+  const char *zErr = "mmap";
+  int h = pFd->h;                      /* File descriptor open on db file */
+  u8 *pOrig = (u8 *)pFd->pMapRegion;   /* Pointer to current file mapping */
+  i64 nOrig = pFd->mmapSizeActual;     /* Size of pOrig region in bytes */
+  u8 *pNew = 0;                        /* Location of new mapping */
+  int flags = PROT_READ;               /* Flags to pass to mmap() */
+
+  assert( pFd->nFetchOut==0 );
+  assert( nNew>pFd->mmapSize );
+  assert( nNew<=pFd->mmapSizeMax );
+  assert( nNew>0 );
+  assert( pFd->mmapSizeActual>=pFd->mmapSize );
+  assert( MAP_FAILED!=0 );
+
+#ifdef SQLITE_MMAP_READWRITE
+  if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
+#endif
+
+  if( pOrig ){
+#if HAVE_MREMAP
+    i64 nReuse = pFd->mmapSize;
+#else
+    const int szSyspage = osGetpagesize();
+    i64 nReuse = (pFd->mmapSize & ~(szSyspage-1));
+#endif
+    u8 *pReq = &pOrig[nReuse];
+
+    /* Unmap any pages of the existing mapping that cannot be reused. */
+    if( nReuse!=nOrig ){
+      osMunmap(pReq, nOrig-nReuse);
+    }
+
+#if HAVE_MREMAP
+    pNew = osMremap(pOrig, nReuse, nNew, MREMAP_MAYMOVE);
+    zErr = "mremap";
+#else
+    pNew = osMmap(pReq, nNew-nReuse, flags, MAP_SHARED, h, nReuse);
+    if( pNew!=MAP_FAILED ){
+      if( pNew!=pReq ){
+        osMunmap(pNew, nNew - nReuse);
+        pNew = 0;
+      }else{
+        pNew = pOrig;
+      }
+    }
+#endif
+
+    /* The attempt to extend the existing mapping failed. Free it. */
+    if( pNew==MAP_FAILED || pNew==0 ){
+      osMunmap(pOrig, nReuse);
+    }
+  }
+
+  /* If pNew is still NULL, try to create an entirely new mapping. */
+  if( pNew==0 ){
+    pNew = osMmap(0, nNew, flags, MAP_SHARED, h, 0);
+  }
+
+  if( pNew==MAP_FAILED ){
+    pNew = 0;
+    nNew = 0;
+    unixLogError(SQLITE_OK, zErr, pFd->zPath);
+
+    /* If the mmap() above failed, assume that all subsequent mmap() calls
+    ** will probably fail too. Fall back to using xRead/xWrite exclusively
+    ** in this case.  */
+    pFd->mmapSizeMax = 0;
+  }
+  pFd->pMapRegion = (void *)pNew;
+  pFd->mmapSize = pFd->mmapSizeActual = nNew;
+}
+
+/*
+** Memory map or remap the file opened by file-descriptor pFd (if the file
+** is already mapped, the existing mapping is replaced by the new). Or, if
+** there already exists a mapping for this file, and there are still
+** outstanding xFetch() references to it, this function is a no-op.
+**
+** If parameter nByte is non-negative, then it is the requested size of
+** the mapping to create. Otherwise, if nByte is less than zero, then the
+** requested size is the size of the file on disk. The actual size of the
+** created mapping is either the requested size or the value configured
+** using SQLITE_FCNTL_MMAP_LIMIT, whichever is smaller.
+**
+** SQLITE_OK is returned if no error occurs (even if the mapping is not
+** recreated as a result of outstanding references) or an SQLite error
+** code otherwise.
+*/
+static int unixMapfile(unixFile *pFd, i64 nMap){
+  assert( nMap>=0 || pFd->nFetchOut==0 );
+  assert( nMap>0 || (pFd->mmapSize==0 && pFd->pMapRegion==0) );
+  if( pFd->nFetchOut>0 ) return SQLITE_OK;
+
+  if( nMap<0 ){
+    struct stat statbuf;          /* Low-level file information */
+    if( osFstat(pFd->h, &statbuf) ){
+      return SQLITE_IOERR_FSTAT;
+    }
+    nMap = statbuf.st_size;
+  }
+  if( nMap>pFd->mmapSizeMax ){
+    nMap = pFd->mmapSizeMax;
+  }
+
+  assert( nMap>0 || (pFd->mmapSize==0 && pFd->pMapRegion==0) );
+  if( nMap!=pFd->mmapSize ){
+    unixRemapfile(pFd, nMap);
+  }
+
+  return SQLITE_OK;
+}
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
+
+/*
+** If possible, return a pointer to a mapping of file fd starting at offset
+** iOff. The mapping must be valid for at least nAmt bytes.
+**
+** If such a pointer can be obtained, store it in *pp and return SQLITE_OK.
+** Or, if one cannot but no error occurs, set *pp to 0 and return SQLITE_OK.
+** Finally, if an error does occur, return an SQLite error code. The final
+** value of *pp is undefined in this case.
+**
+** If this function does return a pointer, the caller must eventually
+** release the reference by calling unixUnfetch().
+*/
+static int unixFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
+#if SQLITE_MAX_MMAP_SIZE>0
+  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
+#endif
+  *pp = 0;
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  if( pFd->mmapSizeMax>0 ){
+    /* Ensure that there is always at least a 256 byte buffer of addressable
+    ** memory following the returned page. If the database is corrupt,
+    ** SQLite may overread the page slightly (in practice only a few bytes,
+    ** but 256 is safe, round, number).  */
+    const int nEofBuffer = 256;
+    if( pFd->pMapRegion==0 ){
+      int rc = unixMapfile(pFd, -1);
+      if( rc!=SQLITE_OK ) return rc;
+    }
+    if( pFd->mmapSize >= (iOff+nAmt+nEofBuffer) ){
+      *pp = &((u8 *)pFd->pMapRegion)[iOff];
+      pFd->nFetchOut++;
+    }
+  }
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** If the third argument is non-NULL, then this function releases a
+** reference obtained by an earlier call to unixFetch(). The second
+** argument passed to this function must be the same as the corresponding
+** argument that was passed to the unixFetch() invocation.
+**
+** Or, if the third argument is NULL, then this function is being called
+** to inform the VFS layer that, according to POSIX, any existing mapping
+** may now be invalid and should be unmapped.
+*/
+static int unixUnfetch(sqlite3_file *fd, i64 iOff, void *p){
+#if SQLITE_MAX_MMAP_SIZE>0
+  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
+  UNUSED_PARAMETER(iOff);
+
+  /* If p==0 (unmap the entire file) then there must be no outstanding
+  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
+  ** then there must be at least one outstanding.  */
+  assert( (p==0)==(pFd->nFetchOut==0) );
+
+  /* If p!=0, it must match the iOff value. */
+  assert( p==0 || p==&((u8 *)pFd->pMapRegion)[iOff] );
+
+  if( p ){
+    pFd->nFetchOut--;
+  }else{
+    unixUnmapfile(pFd);
+  }
+
+  assert( pFd->nFetchOut>=0 );
+#else
+  UNUSED_PARAMETER(fd);
+  UNUSED_PARAMETER(p);
+  UNUSED_PARAMETER(iOff);
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Here ends the implementation of all sqlite3_file methods.
+**
+********************** End sqlite3_file Methods *******************************
+******************************************************************************/
+
+/*
+** This division contains definitions of sqlite3_io_methods objects that
+** implement various file locking strategies.  It also contains definitions
+** of "finder" functions.  A finder-function is used to locate the appropriate
+** sqlite3_io_methods object for a particular database file.  The pAppData
+** field of the sqlite3_vfs VFS objects are initialized to be pointers to
+** the correct finder-function for that VFS.
+**
+** Most finder functions return a pointer to a fixed sqlite3_io_methods
+** object.  The only interesting finder-function is autolockIoFinder, which
+** looks at the filesystem type and tries to guess the best locking
+** strategy from that.
+**
+** For finder-function F, two objects are created:
+**
+**    (1) The real finder-function named "FImpt()".
+**
+**    (2) A constant pointer to this function named just "F".
+**
+**
+** A pointer to the F pointer is used as the pAppData value for VFS
+** objects.  We have to do this instead of letting pAppData point
+** directly at the finder-function since C90 rules prevent a void*
+** from be cast into a function pointer.
+**
+**
+** Each instance of this macro generates two objects:
+**
+**   *  A constant sqlite3_io_methods object call METHOD that has locking
+**      methods CLOSE, LOCK, UNLOCK, CKRESLOCK.
+**
+**   *  An I/O method finder function called FINDER that returns a pointer
+**      to the METHOD object in the previous bullet.
+*/
+#define IOMETHODS(FINDER,METHOD,VERSION,CLOSE,LOCK,UNLOCK,CKLOCK,SHMMAP)     \
+static const sqlite3_io_methods METHOD = {                                   \
+   VERSION,                    /* iVersion */                                \
+   CLOSE,                      /* xClose */                                  \
+   unixRead,                   /* xRead */                                   \
+   unixWrite,                  /* xWrite */                                  \
+   unixTruncate,               /* xTruncate */                               \
+   unixSync,                   /* xSync */                                   \
+   unixFileSize,               /* xFileSize */                               \
+   LOCK,                       /* xLock */                                   \
+   UNLOCK,                     /* xUnlock */                                 \
+   CKLOCK,                     /* xCheckReservedLock */                      \
+   unixFileControl,            /* xFileControl */                            \
+   unixSectorSize,             /* xSectorSize */                             \
+   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
+   SHMMAP,                     /* xShmMap */                                 \
+   unixShmLock,                /* xShmLock */                                \
+   unixShmBarrier,             /* xShmBarrier */                             \
+   unixShmUnmap,               /* xShmUnmap */                               \
+   unixFetch,                  /* xFetch */                                  \
+   unixUnfetch,                /* xUnfetch */                                \
+};                                                                           \
+static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
+  UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
+  return &METHOD;                                                            \
+}                                                                            \
+static const sqlite3_io_methods *(*const FINDER)(const char*,unixFile *p)    \
+    = FINDER##Impl;
+
+/*
+** Here are all of the sqlite3_io_methods objects for each of the
+** locking strategies.  Functions that return pointers to these methods
+** are also created.
+*/
+IOMETHODS(
+  posixIoFinder,            /* Finder function name */
+  posixIoMethods,           /* sqlite3_io_methods object name */
+  3,                        /* shared memory and mmap are enabled */
+  unixClose,                /* xClose method */
+  unixLock,                 /* xLock method */
+  unixUnlock,               /* xUnlock method */
+  unixCheckReservedLock,    /* xCheckReservedLock method */
+  unixShmMap                /* xShmMap method */
+)
+IOMETHODS(
+  nolockIoFinder,           /* Finder function name */
+  nolockIoMethods,          /* sqlite3_io_methods object name */
+  3,                        /* shared memory and mmap are enabled */
+  nolockClose,              /* xClose method */
+  nolockLock,               /* xLock method */
+  nolockUnlock,             /* xUnlock method */
+  nolockCheckReservedLock,  /* xCheckReservedLock method */
+  0                         /* xShmMap method */
+)
+IOMETHODS(
+  dotlockIoFinder,          /* Finder function name */
+  dotlockIoMethods,         /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  dotlockClose,             /* xClose method */
+  dotlockLock,              /* xLock method */
+  dotlockUnlock,            /* xUnlock method */
+  dotlockCheckReservedLock, /* xCheckReservedLock method */
+  0                         /* xShmMap method */
+)
+
+#if SQLITE_ENABLE_LOCKING_STYLE
+IOMETHODS(
+  flockIoFinder,            /* Finder function name */
+  flockIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  flockClose,               /* xClose method */
+  flockLock,                /* xLock method */
+  flockUnlock,              /* xUnlock method */
+  flockCheckReservedLock,   /* xCheckReservedLock method */
+  0                         /* xShmMap method */
+)
+#endif
+
+#if OS_VXWORKS
+IOMETHODS(
+  semIoFinder,              /* Finder function name */
+  semIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  semXClose,                /* xClose method */
+  semXLock,                 /* xLock method */
+  semXUnlock,               /* xUnlock method */
+  semXCheckReservedLock,    /* xCheckReservedLock method */
+  0                         /* xShmMap method */
+)
+#endif
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+IOMETHODS(
+  afpIoFinder,              /* Finder function name */
+  afpIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  afpClose,                 /* xClose method */
+  afpLock,                  /* xLock method */
+  afpUnlock,                /* xUnlock method */
+  afpCheckReservedLock,     /* xCheckReservedLock method */
+  0                         /* xShmMap method */
+)
+#endif
+
+/*
+** The proxy locking method is a "super-method" in the sense that it
+** opens secondary file descriptors for the conch and lock files and
+** it uses proxy, dot-file, AFP, and flock() locking methods on those
+** secondary files.  For this reason, the division that implements
+** proxy locking is located much further down in the file.  But we need
+** to go ahead and define the sqlite3_io_methods and finder function
+** for proxy locking here.  So we forward declare the I/O methods.
+*/
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+static int proxyClose(sqlite3_file*);
+static int proxyLock(sqlite3_file*, int);
+static int proxyUnlock(sqlite3_file*, int);
+static int proxyCheckReservedLock(sqlite3_file*, int*);
+IOMETHODS(
+  proxyIoFinder,            /* Finder function name */
+  proxyIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  proxyClose,               /* xClose method */
+  proxyLock,                /* xLock method */
+  proxyUnlock,              /* xUnlock method */
+  proxyCheckReservedLock,   /* xCheckReservedLock method */
+  0                         /* xShmMap method */
+)
+#endif
+
+/* nfs lockd on OSX 10.3+ doesn't clear write locks when a read lock is set */
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+IOMETHODS(
+  nfsIoFinder,               /* Finder function name */
+  nfsIoMethods,              /* sqlite3_io_methods object name */
+  1,                         /* shared memory is disabled */
+  unixClose,                 /* xClose method */
+  unixLock,                  /* xLock method */
+  nfsUnlock,                 /* xUnlock method */
+  unixCheckReservedLock,     /* xCheckReservedLock method */
+  0                          /* xShmMap method */
+)
+#endif
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/*
+** This "finder" function attempts to determine the best locking strategy
+** for the database file "filePath".  It then returns the sqlite3_io_methods
+** object that implements that strategy.
+**
+** This is for MacOSX only.
+*/
+static const sqlite3_io_methods *autolockIoFinderImpl(
+  const char *filePath,    /* name of the database file */
+  unixFile *pNew           /* open file object for the database file */
+){
+  static const struct Mapping {
+    const char *zFilesystem;              /* Filesystem type name */
+    const sqlite3_io_methods *pMethods;   /* Appropriate locking method */
+  } aMap[] = {
+    { "hfs",    &posixIoMethods },
+    { "ufs",    &posixIoMethods },
+    { "afpfs",  &afpIoMethods },
+    { "smbfs",  &afpIoMethods },
+    { "webdav", &nolockIoMethods },
+    { 0, 0 }
+  };
+  int i;
+  struct statfs fsInfo;
+  struct flock lockInfo;
+
+  if( !filePath ){
+    /* If filePath==NULL that means we are dealing with a transient file
+    ** that does not need to be locked. */
+    return &nolockIoMethods;
+  }
+  if( statfs(filePath, &fsInfo) != -1 ){
+    if( fsInfo.f_flags & MNT_RDONLY ){
+      return &nolockIoMethods;
+    }
+    for(i=0; aMap[i].zFilesystem; i++){
+      if( strcmp(fsInfo.f_fstypename, aMap[i].zFilesystem)==0 ){
+        return aMap[i].pMethods;
+      }
+    }
+  }
+
+  /* Default case. Handles, amongst others, "nfs".
+  ** Test byte-range lock using fcntl(). If the call succeeds,
+  ** assume that the file-system supports POSIX style locks.
+  */
+  lockInfo.l_len = 1;
+  lockInfo.l_start = 0;
+  lockInfo.l_whence = SEEK_SET;
+  lockInfo.l_type = F_RDLCK;
+  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
+    if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){
+      return &nfsIoMethods;
+    } else {
+      return &posixIoMethods;
+    }
+  }else{
+    return &dotlockIoMethods;
+  }
+}
+static const sqlite3_io_methods
+  *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl;
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+
+#if OS_VXWORKS
+/*
+** This "finder" function for VxWorks checks to see if posix advisory
+** locking works.  If it does, then that is what is used.  If it does not
+** work, then fallback to named semaphore locking.
+*/
+static const sqlite3_io_methods *vxworksIoFinderImpl(
+  const char *filePath,    /* name of the database file */
+  unixFile *pNew           /* the open file object */
+){
+  struct flock lockInfo;
+
+  if( !filePath ){
+    /* If filePath==NULL that means we are dealing with a transient file
+    ** that does not need to be locked. */
+    return &nolockIoMethods;
+  }
+
+  /* Test if fcntl() is supported and use POSIX style locks.
+  ** Otherwise fall back to the named semaphore method.
+  */
+  lockInfo.l_len = 1;
+  lockInfo.l_start = 0;
+  lockInfo.l_whence = SEEK_SET;
+  lockInfo.l_type = F_RDLCK;
+  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
+    return &posixIoMethods;
+  }else{
+    return &semIoMethods;
+  }
+}
+static const sqlite3_io_methods
+  *(*const vxworksIoFinder)(const char*,unixFile*) = vxworksIoFinderImpl;
+
+#endif /* OS_VXWORKS */
+
+/*
+** An abstract type for a pointer to an IO method finder function:
+*/
+typedef const sqlite3_io_methods *(*finder_type)(const char*,unixFile*);
+
+
+/****************************************************************************
+**************************** sqlite3_vfs methods ****************************
+**
+** This division contains the implementation of methods on the
+** sqlite3_vfs object.
+*/
+
+/*
+** Initialize the contents of the unixFile structure pointed to by pId.
+*/
+static int fillInUnixFile(
+  sqlite3_vfs *pVfs,      /* Pointer to vfs object */
+  int h,                  /* Open file descriptor of file being opened */
+  sqlite3_file *pId,      /* Write to the unixFile structure here */
+  const char *zFilename,  /* Name of the file being opened */
+  int ctrlFlags           /* Zero or more UNIXFILE_* values */
+){
+  const sqlite3_io_methods *pLockingStyle;
+  unixFile *pNew = (unixFile *)pId;
+  int rc = SQLITE_OK;
+
+  assert( pNew->pInode==NULL );
+
+  /* No locking occurs in temporary files */
+  assert( zFilename!=0 || (ctrlFlags & UNIXFILE_NOLOCK)!=0 );
+
+  OSTRACE(("OPEN    %-3d %s\n", h, zFilename));
+  pNew->h = h;
+  pNew->pVfs = pVfs;
+  pNew->zPath = zFilename;
+  pNew->ctrlFlags = (u8)ctrlFlags;
+#if SQLITE_MAX_MMAP_SIZE>0
+  pNew->mmapSizeMax = sqlite3GlobalConfig.szMmap;
+#endif
+  if( sqlite3_uri_boolean(((ctrlFlags & UNIXFILE_URI) ? zFilename : 0),
+                           "psow", SQLITE_POWERSAFE_OVERWRITE) ){
+    pNew->ctrlFlags |= UNIXFILE_PSOW;
+  }
+  if( strcmp(pVfs->zName,"unix-excl")==0 ){
+    pNew->ctrlFlags |= UNIXFILE_EXCL;
+  }
+
+#if OS_VXWORKS
+  pNew->pId = vxworksFindFileId(zFilename);
+  if( pNew->pId==0 ){
+    ctrlFlags |= UNIXFILE_NOLOCK;
+    rc = SQLITE_NOMEM_BKPT;
+  }
+#endif
+
+  if( ctrlFlags & UNIXFILE_NOLOCK ){
+    pLockingStyle = &nolockIoMethods;
+  }else{
+    pLockingStyle = (**(finder_type*)pVfs->pAppData)(zFilename, pNew);
+#if SQLITE_ENABLE_LOCKING_STYLE
+    /* Cache zFilename in the locking context (AFP and dotlock override) for
+    ** proxyLock activation is possible (remote proxy is based on db name)
+    ** zFilename remains valid until file is closed, to support */
+    pNew->lockingContext = (void*)zFilename;
+#endif
+  }
+
+  if( pLockingStyle == &posixIoMethods
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+    || pLockingStyle == &nfsIoMethods
+#endif
+  ){
+    unixEnterMutex();
+    rc = findInodeInfo(pNew, &pNew->pInode);
+    if( rc!=SQLITE_OK ){
+      /* If an error occurred in findInodeInfo(), close the file descriptor
+      ** immediately, before releasing the mutex. findInodeInfo() may fail
+      ** in two scenarios:
+      **
+      **   (a) A call to fstat() failed.
+      **   (b) A malloc failed.
+      **
+      ** Scenario (b) may only occur if the process is holding no other
+      ** file descriptors open on the same file. If there were other file
+      ** descriptors on this file, then no malloc would be required by
+      ** findInodeInfo(). If this is the case, it is quite safe to close
+      ** handle h - as it is guaranteed that no posix locks will be released
+      ** by doing so.
+      **
+      ** If scenario (a) caused the error then things are not so safe. The
+      ** implicit assumption here is that if fstat() fails, things are in
+      ** such bad shape that dropping a lock or two doesn't matter much.
+      */
+      robust_close(pNew, h, __LINE__);
+      h = -1;
+    }
+    unixLeaveMutex();
+  }
+
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+  else if( pLockingStyle == &afpIoMethods ){
+    /* AFP locking uses the file path so it needs to be included in
+    ** the afpLockingContext.
+    */
+    afpLockingContext *pCtx;
+    pNew->lockingContext = pCtx = sqlite3_malloc64( sizeof(*pCtx) );
+    if( pCtx==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+    }else{
+      /* NB: zFilename exists and remains valid until the file is closed
+      ** according to requirement F11141.  So we do not need to make a
+      ** copy of the filename. */
+      pCtx->dbPath = zFilename;
+      pCtx->reserved = 0;
+      srandomdev();
+      unixEnterMutex();
+      rc = findInodeInfo(pNew, &pNew->pInode);
+      if( rc!=SQLITE_OK ){
+        sqlite3_free(pNew->lockingContext);
+        robust_close(pNew, h, __LINE__);
+        h = -1;
+      }
+      unixLeaveMutex();      
+    }
+  }
+#endif
+
+  else if( pLockingStyle == &dotlockIoMethods ){
+    /* Dotfile locking uses the file path so it needs to be included in
+    ** the dotlockLockingContext
+    */
+    char *zLockFile;
+    int nFilename;
+    assert( zFilename!=0 );
+    nFilename = (int)strlen(zFilename) + 6;
+    zLockFile = (char *)sqlite3_malloc64(nFilename);
+    if( zLockFile==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+    }else{
+      sqlite3_snprintf(nFilename, zLockFile, "%s" DOTLOCK_SUFFIX, zFilename);
+    }
+    pNew->lockingContext = zLockFile;
+  }
+
+#if OS_VXWORKS
+  else if( pLockingStyle == &semIoMethods ){
+    /* Named semaphore locking uses the file path so it needs to be
+    ** included in the semLockingContext
+    */
+    unixEnterMutex();
+    rc = findInodeInfo(pNew, &pNew->pInode);
+    if( (rc==SQLITE_OK) && (pNew->pInode->pSem==NULL) ){
+      char *zSemName = pNew->pInode->aSemName;
+      int n;
+      sqlite3_snprintf(MAX_PATHNAME, zSemName, "/%s.sem",
+                       pNew->pId->zCanonicalName);
+      for( n=1; zSemName[n]; n++ )
+        if( zSemName[n]=='/' ) zSemName[n] = '_';
+      pNew->pInode->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
+      if( pNew->pInode->pSem == SEM_FAILED ){
+        rc = SQLITE_NOMEM_BKPT;
+        pNew->pInode->aSemName[0] = '\0';
+      }
+    }
+    unixLeaveMutex();
+  }
+#endif
+
+  storeLastErrno(pNew, 0);
+#if OS_VXWORKS
+  if( rc!=SQLITE_OK ){
+    if( h>=0 ) robust_close(pNew, h, __LINE__);
+    h = -1;
+    osUnlink(zFilename);
+    pNew->ctrlFlags |= UNIXFILE_DELETE;
+  }
+#endif
+  if( rc!=SQLITE_OK ){
+    if( h>=0 ) robust_close(pNew, h, __LINE__);
+  }else{
+    pId->pMethods = pLockingStyle;
+    OpenCounter(+1);
+    verifyDbFile(pNew);
+  }
+  return rc;
+}
+
+/*
+** Directories to consider for temp files.
+*/
+static const char *azTempDirs[] = {
+  0,
+  0,
+  "/var/tmp",
+  "/usr/tmp",
+  "/tmp",
+  "."
+};
+
+/*
+** Initialize first two members of azTempDirs[] array.
+*/
+static void unixTempFileInit(void){
+  azTempDirs[0] = getenv("SQLITE_TMPDIR");
+  azTempDirs[1] = getenv("TMPDIR");
+}
+
+/*
+** Return the name of a directory in which to put temporary files.
+** If no suitable temporary file directory can be found, return NULL.
+*/
+static const char *unixTempFileDir(void){
+  unsigned int i = 0;
+  struct stat buf;
+  const char *zDir = sqlite3_temp_directory;
+
+  while(1){
+    if( zDir!=0
+     && osStat(zDir, &buf)==0
+     && S_ISDIR(buf.st_mode)
+     && osAccess(zDir, 03)==0
+    ){
+      return zDir;
+    }
+    if( i>=sizeof(azTempDirs)/sizeof(azTempDirs[0]) ) break;
+    zDir = azTempDirs[i++];
+  }
+  return 0;
+}
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be allocated
+** by the calling process and must be big enough to hold at least
+** pVfs->mxPathname bytes.
+*/
+static int unixGetTempname(int nBuf, char *zBuf){
+  const char *zDir;
+  int iLimit = 0;
+  int rc = SQLITE_OK;
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing.
+  */
+  zBuf[0] = 0;
+  SimulateIOError( return SQLITE_IOERR );
+
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+  zDir = unixTempFileDir();
+  if( zDir==0 ){
+    rc = SQLITE_IOERR_GETTEMPPATH;
+  }else{
+    do{
+      u64 r;
+      sqlite3_randomness(sizeof(r), &r);
+      assert( nBuf>2 );
+      zBuf[nBuf-2] = 0;
+      sqlite3_snprintf(nBuf, zBuf, "%s/"SQLITE_TEMP_FILE_PREFIX"%llx%c",
+                       zDir, r, 0);
+      if( zBuf[nBuf-2]!=0 || (iLimit++)>10 ){
+        rc = SQLITE_ERROR;
+        break;
+      }
+    }while( osAccess(zBuf,0)==0 );
+  }
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+  return rc;
+}
+
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+/*
+** Routine to transform a unixFile into a proxy-locking unixFile.
+** Implementation in the proxy-lock division, but used by unixOpen()
+** if SQLITE_PREFER_PROXY_LOCKING is defined.
+*/
+static int proxyTransformUnixFile(unixFile*, const char*);
+#endif
+
+/*
+** Search for an unused file descriptor that was opened on the database
+** file (not a journal or super-journal file) identified by pathname
+** zPath with SQLITE_OPEN_XXX flags matching those passed as the second
+** argument to this function.
+**
+** Such a file descriptor may exist if a database connection was closed
+** but the associated file descriptor could not be closed because some
+** other file descriptor open on the same file is holding a file-lock.
+** Refer to comments in the unixClose() function and the lengthy comment
+** describing "Posix Advisory Locking" at the start of this file for
+** further details. Also, ticket #4018.
+**
+** If a suitable file descriptor is found, then it is returned. If no
+** such file descriptor is located, -1 is returned.
+*/
+static UnixUnusedFd *findReusableFd(const char *zPath, int flags){
+  UnixUnusedFd *pUnused = 0;
+
+  /* Do not search for an unused file descriptor on vxworks. Not because
+  ** vxworks would not benefit from the change (it might, we're not sure),
+  ** but because no way to test it is currently available. It is better
+  ** not to risk breaking vxworks support for the sake of such an obscure
+  ** feature.  */
+#if !OS_VXWORKS
+  struct stat sStat;                   /* Results of stat() call */
+
+  unixEnterMutex();
+
+  /* A stat() call may fail for various reasons. If this happens, it is
+  ** almost certain that an open() call on the same path will also fail.
+  ** For this reason, if an error occurs in the stat() call here, it is
+  ** ignored and -1 is returned. The caller will try to open a new file
+  ** descriptor on the same path, fail, and return an error to SQLite.
+  **
+  ** Even if a subsequent open() call does succeed, the consequences of
+  ** not searching for a reusable file descriptor are not dire.  */
+  if( inodeList!=0 && 0==osStat(zPath, &sStat) ){
+    unixInodeInfo *pInode;
+
+    pInode = inodeList;
+    while( pInode && (pInode->fileId.dev!=sStat.st_dev
+                     || pInode->fileId.ino!=(u64)sStat.st_ino) ){
+       pInode = pInode->pNext;
+    }
+    if( pInode ){
+      UnixUnusedFd **pp;
+      assert( sqlite3_mutex_notheld(pInode->pLockMutex) );
+      sqlite3_mutex_enter(pInode->pLockMutex);
+      flags &= (SQLITE_OPEN_READONLY|SQLITE_OPEN_READWRITE);
+      for(pp=&pInode->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
+      pUnused = *pp;
+      if( pUnused ){
+        *pp = pUnused->pNext;
+      }
+      sqlite3_mutex_leave(pInode->pLockMutex);
+    }
+  }
+  unixLeaveMutex();
+#endif    /* if !OS_VXWORKS */
+  return pUnused;
+}
+
+/*
+** Find the mode, uid and gid of file zFile.
+*/
+static int getFileMode(
+  const char *zFile,              /* File name */
+  mode_t *pMode,                  /* OUT: Permissions of zFile */
+  uid_t *pUid,                    /* OUT: uid of zFile. */
+  gid_t *pGid                     /* OUT: gid of zFile. */
+){
+  struct stat sStat;              /* Output of stat() on database file */
+  int rc = SQLITE_OK;
+  if( 0==osStat(zFile, &sStat) ){
+    *pMode = sStat.st_mode & 0777;
+    *pUid = sStat.st_uid;
+    *pGid = sStat.st_gid;
+  }else{
+    rc = SQLITE_IOERR_FSTAT;
+  }
+  return rc;
+}
+
+/*
+** This function is called by unixOpen() to determine the unix permissions
+** to create new files with. If no error occurs, then SQLITE_OK is returned
+** and a value suitable for passing as the third argument to open(2) is
+** written to *pMode. If an IO error occurs, an SQLite error code is
+** returned and the value of *pMode is not modified.
+**
+** In most cases, this routine sets *pMode to 0, which will become
+** an indication to robust_open() to create the file using
+** SQLITE_DEFAULT_FILE_PERMISSIONS adjusted by the umask.
+** But if the file being opened is a WAL or regular journal file, then
+** this function queries the file-system for the permissions on the
+** corresponding database file and sets *pMode to this value. Whenever
+** possible, WAL and journal files are created using the same permissions
+** as the associated database file.
+**
+** If the SQLITE_ENABLE_8_3_NAMES option is enabled, then the
+** original filename is unavailable.  But 8_3_NAMES is only used for
+** FAT filesystems and permissions do not matter there, so just use
+** the default permissions.  In 8_3_NAMES mode, leave *pMode set to zero.
+*/
+static int findCreateFileMode(
+  const char *zPath,              /* Path of file (possibly) being created */
+  int flags,                      /* Flags passed as 4th argument to xOpen() */
+  mode_t *pMode,                  /* OUT: Permissions to open file with */
+  uid_t *pUid,                    /* OUT: uid to set on the file */
+  gid_t *pGid                     /* OUT: gid to set on the file */
+){
+  int rc = SQLITE_OK;             /* Return Code */
+  *pMode = 0;
+  *pUid = 0;
+  *pGid = 0;
+  if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){
+    char zDb[MAX_PATHNAME+1];     /* Database file path */
+    int nDb;                      /* Number of valid bytes in zDb */
+
+    /* zPath is a path to a WAL or journal file. The following block derives
+    ** the path to the associated database file from zPath. This block handles
+    ** the following naming conventions:
+    **
+    **   "<path to db>-journal"
+    **   "<path to db>-wal"
+    **   "<path to db>-journalNN"
+    **   "<path to db>-walNN"
+    **
+    ** where NN is a decimal number. The NN naming schemes are
+    ** used by the test_multiplex.c module.
+    **
+    ** In normal operation, the journal file name will always contain
+    ** a '-' character.  However in 8+3 filename mode, or if a corrupt
+    ** rollback journal specifies a super-journal with a goofy name, then
+    ** the '-' might be missing or the '-' might be the first character in
+    ** the filename.  In that case, just return SQLITE_OK with *pMode==0.
+    */
+    nDb = sqlite3Strlen30(zPath) - 1;
+    while( nDb>0 && zPath[nDb]!='.' ){
+      if( zPath[nDb]=='-' ){
+        memcpy(zDb, zPath, nDb);
+        zDb[nDb] = '\0';
+        rc = getFileMode(zDb, pMode, pUid, pGid);
+        break;
+      }
+      nDb--;
+    }
+  }else if( flags & SQLITE_OPEN_DELETEONCLOSE ){
+    *pMode = 0600;
+  }else if( flags & SQLITE_OPEN_URI ){
+    /* If this is a main database file and the file was opened using a URI
+    ** filename, check for the "modeof" parameter. If present, interpret
+    ** its value as a filename and try to copy the mode, uid and gid from
+    ** that file.  */
+    const char *z = sqlite3_uri_parameter(zPath, "modeof");
+    if( z ){
+      rc = getFileMode(z, pMode, pUid, pGid);
+    }
+  }
+  return rc;
+}
+
+/*
+** Open the file zPath.
+**
+** Previously, the SQLite OS layer used three functions in place of this
+** one:
+**
+**     sqlite3OsOpenReadWrite();
+**     sqlite3OsOpenReadOnly();
+**     sqlite3OsOpenExclusive();
+**
+** These calls correspond to the following combinations of flags:
+**
+**     ReadWrite() ->     (READWRITE | CREATE)
+**     ReadOnly()  ->     (READONLY)
+**     OpenExclusive() -> (READWRITE | CREATE | EXCLUSIVE)
+**
+** The old OpenExclusive() accepted a boolean argument - "delFlag". If
+** true, the file was configured to be automatically deleted when the
+** file handle closed. To achieve the same effect using this new
+** interface, add the DELETEONCLOSE flag to those specified above for
+** OpenExclusive().
+*/
+static int unixOpen(
+  sqlite3_vfs *pVfs,           /* The VFS for which this is the xOpen method */
+  const char *zPath,           /* Pathname of file to be opened */
+  sqlite3_file *pFile,         /* The file descriptor to be filled in */
+  int flags,                   /* Input flags to control the opening */
+  int *pOutFlags               /* Output flags returned to SQLite core */
+){
+  unixFile *p = (unixFile *)pFile;
+  int fd = -1;                   /* File descriptor returned by open() */
+  int openFlags = 0;             /* Flags to pass to open() */
+  int eType = flags&0x0FFF00;  /* Type of file to open */
+  int noLock;                    /* True to omit locking primitives */
+  int rc = SQLITE_OK;            /* Function Return Code */
+  int ctrlFlags = 0;             /* UNIXFILE_* flags */
+
+  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
+  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
+  int isCreate     = (flags & SQLITE_OPEN_CREATE);
+  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
+  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+#if SQLITE_ENABLE_LOCKING_STYLE
+  int isAutoProxy  = (flags & SQLITE_OPEN_AUTOPROXY);
+#endif
+#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
+  struct statfs fsInfo;
+#endif
+
+  /* If creating a super- or main-file journal, this function will open
+  ** a file-descriptor on the directory too. The first time unixSync()
+  ** is called the directory file descriptor will be fsync()ed and close()d.
+  */
+  int isNewJrnl = (isCreate && (
+        eType==SQLITE_OPEN_SUPER_JOURNAL
+     || eType==SQLITE_OPEN_MAIN_JOURNAL
+     || eType==SQLITE_OPEN_WAL
+  ));
+
+  /* If argument zPath is a NULL pointer, this function is required to open
+  ** a temporary file. Use this buffer to store the file name in.
+  */
+  char zTmpname[MAX_PATHNAME+2];
+  const char *zName = zPath;
+
+  /* Check the following statements are true:
+  **
+  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and
+  **   (b) if CREATE is set, then READWRITE must also be set, and
+  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
+  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
+  */
+  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
+  assert(isCreate==0 || isReadWrite);
+  assert(isExclusive==0 || isCreate);
+  assert(isDelete==0 || isCreate);
+
+  /* The main DB, main journal, WAL file and super-journal are never
+  ** automatically deleted. Nor are they ever temporary files.  */
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_SUPER_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
+
+  /* Assert that the upper layer has set one of the "file-type" flags. */
+  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB
+       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL
+       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_SUPER_JOURNAL
+       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
+  );
+
+  /* Detect a pid change and reset the PRNG.  There is a race condition
+  ** here such that two or more threads all trying to open databases at
+  ** the same instant might all reset the PRNG.  But multiple resets
+  ** are harmless.
+  */
+  if( randomnessPid!=osGetpid(0) ){
+    randomnessPid = osGetpid(0);
+    sqlite3_randomness(0,0);
+  }
+  memset(p, 0, sizeof(unixFile));
+
+#ifdef SQLITE_ASSERT_NO_FILES
+  /* Applications that never read or write a persistent disk files */
+  assert( zName==0 );
+#endif
+
+  if( eType==SQLITE_OPEN_MAIN_DB ){
+    UnixUnusedFd *pUnused;
+    pUnused = findReusableFd(zName, flags);
+    if( pUnused ){
+      fd = pUnused->fd;
+    }else{
+      pUnused = sqlite3_malloc64(sizeof(*pUnused));
+      if( !pUnused ){
+        return SQLITE_NOMEM_BKPT;
+      }
+    }
+    p->pPreallocatedUnused = pUnused;
+
+    /* Database filenames are double-zero terminated if they are not
+    ** URIs with parameters.  Hence, they can always be passed into
+    ** sqlite3_uri_parameter(). */
+    assert( (flags & SQLITE_OPEN_URI) || zName[strlen(zName)+1]==0 );
+
+  }else if( !zName ){
+    /* If zName is NULL, the upper layer is requesting a temp file. */
+    assert(isDelete && !isNewJrnl);
+    rc = unixGetTempname(pVfs->mxPathname, zTmpname);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    zName = zTmpname;
+
+    /* Generated temporary filenames are always double-zero terminated
+    ** for use by sqlite3_uri_parameter(). */
+    assert( zName[strlen(zName)+1]==0 );
+  }
+
+  /* Determine the value of the flags parameter passed to POSIX function
+  ** open(). These must be calculated even if open() is not called, as
+  ** they may be stored as part of the file handle and used by the
+  ** 'conch file' locking functions later on.  */
+  if( isReadonly )  openFlags |= O_RDONLY;
+  if( isReadWrite ) openFlags |= O_RDWR;
+  if( isCreate )    openFlags |= O_CREAT;
+  if( isExclusive ) openFlags |= (O_EXCL|O_NOFOLLOW);
+  openFlags |= (O_LARGEFILE|O_BINARY|O_NOFOLLOW);
+
+  if( fd<0 ){
+    mode_t openMode;              /* Permissions to create file with */
+    uid_t uid;                    /* Userid for the file */
+    gid_t gid;                    /* Groupid for the file */
+    rc = findCreateFileMode(zName, flags, &openMode, &uid, &gid);
+    if( rc!=SQLITE_OK ){
+      assert( !p->pPreallocatedUnused );
+      assert( eType==SQLITE_OPEN_WAL || eType==SQLITE_OPEN_MAIN_JOURNAL );
+      return rc;
+    }
+    fd = robust_open(zName, openFlags, openMode);
+    OSTRACE(("OPENX   %-3d %s 0%o\n", fd, zName, openFlags));
+    assert( !isExclusive || (openFlags & O_CREAT)!=0 );
+    if( fd<0 ){
+      if( isNewJrnl && errno==EACCES && osAccess(zName, F_OK) ){
+        /* If unable to create a journal because the directory is not
+        ** writable, change the error code to indicate that. */
+        rc = SQLITE_READONLY_DIRECTORY;
+      }else if( errno!=EISDIR && isReadWrite ){
+        /* Failed to open the file for read/write access. Try read-only. */
+        flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
+        openFlags &= ~(O_RDWR|O_CREAT);
+        flags |= SQLITE_OPEN_READONLY;
+        openFlags |= O_RDONLY;
+        isReadonly = 1;
+        fd = robust_open(zName, openFlags, openMode);
+      }
+    }
+    if( fd<0 ){
+      int rc2 = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zName);
+      if( rc==SQLITE_OK ) rc = rc2;
+      goto open_finished;
+    }
+
+    /* The owner of the rollback journal or WAL file should always be the
+    ** same as the owner of the database file.  Try to ensure that this is
+    ** the case.  The chown() system call will be a no-op if the current
+    ** process lacks root privileges, be we should at least try.  Without
+    ** this step, if a root process opens a database file, it can leave
+    ** behinds a journal/WAL that is owned by root and hence make the
+    ** database inaccessible to unprivileged processes.
+    **
+    ** If openMode==0, then that means uid and gid are not set correctly
+    ** (probably because SQLite is configured to use 8+3 filename mode) and
+    ** in that case we do not want to attempt the chown().
+    */
+    if( openMode && (flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL))!=0 ){
+      robustFchown(fd, uid, gid);
+    }
+  }
+  assert( fd>=0 );
+  if( pOutFlags ){
+    *pOutFlags = flags;
+  }
+
+  if( p->pPreallocatedUnused ){
+    p->pPreallocatedUnused->fd = fd;
+    p->pPreallocatedUnused->flags =
+                          flags & (SQLITE_OPEN_READONLY|SQLITE_OPEN_READWRITE);
+  }
+
+  if( isDelete ){
+#if OS_VXWORKS
+    zPath = zName;
+#elif defined(SQLITE_UNLINK_AFTER_CLOSE)
+    zPath = sqlite3_mprintf("%s", zName);
+    if( zPath==0 ){
+      robust_close(p, fd, __LINE__);
+      return SQLITE_NOMEM_BKPT;
+    }
+#else
+    osUnlink(zName);
+#endif
+  }
+#if SQLITE_ENABLE_LOCKING_STYLE
+  else{
+    p->openFlags = openFlags;
+  }
+#endif
+
+#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
+  if( fstatfs(fd, &fsInfo) == -1 ){
+    storeLastErrno(p, errno);
+    robust_close(p, fd, __LINE__);
+    return SQLITE_IOERR_ACCESS;
+  }
+  if (0 == strncmp("msdos", fsInfo.f_fstypename, 5)) {
+    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
+  }
+  if (0 == strncmp("exfat", fsInfo.f_fstypename, 5)) {
+    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
+  }
+#endif
+
+  /* Set up appropriate ctrlFlags */
+  if( isDelete )                ctrlFlags |= UNIXFILE_DELETE;
+  if( isReadonly )              ctrlFlags |= UNIXFILE_RDONLY;
+  noLock = eType!=SQLITE_OPEN_MAIN_DB;
+  if( noLock )                  ctrlFlags |= UNIXFILE_NOLOCK;
+  if( isNewJrnl )               ctrlFlags |= UNIXFILE_DIRSYNC;
+  if( flags & SQLITE_OPEN_URI ) ctrlFlags |= UNIXFILE_URI;
+
+#if SQLITE_ENABLE_LOCKING_STYLE
+#if SQLITE_PREFER_PROXY_LOCKING
+  isAutoProxy = 1;
+#endif
+  if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){
+    char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
+    int useProxy = 0;
+
+    /* SQLITE_FORCE_PROXY_LOCKING==1 means force always use proxy, 0 means
+    ** never use proxy, NULL means use proxy for non-local files only.  */
+    if( envforce!=NULL ){
+      useProxy = atoi(envforce)>0;
+    }else{
+      useProxy = !(fsInfo.f_flags&MNT_LOCAL);
+    }
+    if( useProxy ){
+      rc = fillInUnixFile(pVfs, fd, pFile, zPath, ctrlFlags);
+      if( rc==SQLITE_OK ){
+        rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:");
+        if( rc!=SQLITE_OK ){
+          /* Use unixClose to clean up the resources added in fillInUnixFile
+          ** and clear all the structure's references.  Specifically,
+          ** pFile->pMethods will be NULL so sqlite3OsClose will be a no-op
+          */
+          unixClose(pFile);
+          return rc;
+        }
+      }
+      goto open_finished;
+    }
+  }
+#endif
+
+  assert( zPath==0 || zPath[0]=='/'
+      || eType==SQLITE_OPEN_SUPER_JOURNAL || eType==SQLITE_OPEN_MAIN_JOURNAL
+  );
+  rc = fillInUnixFile(pVfs, fd, pFile, zPath, ctrlFlags);
+
+open_finished:
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(p->pPreallocatedUnused);
+  }
+  return rc;
+}
+
+
+/*
+** Delete the file at zPath. If the dirSync argument is true, fsync()
+** the directory after deleting the file.
+*/
+static int unixDelete(
+  sqlite3_vfs *NotUsed,     /* VFS containing this as the xDelete method */
+  const char *zPath,        /* Name of file to be deleted */
+  int dirSync               /* If true, fsync() directory after deleting file */
+){
+  int rc = SQLITE_OK;
+  UNUSED_PARAMETER(NotUsed);
+  SimulateIOError(return SQLITE_IOERR_DELETE);
+  if( osUnlink(zPath)==(-1) ){
+    if( errno==ENOENT
+#if OS_VXWORKS
+        || osAccess(zPath,0)!=0
+#endif
+    ){
+      rc = SQLITE_IOERR_DELETE_NOENT;
+    }else{
+      rc = unixLogError(SQLITE_IOERR_DELETE, "unlink", zPath);
+    }
+    return rc;
+  }
+#ifndef SQLITE_DISABLE_DIRSYNC
+  if( (dirSync & 1)!=0 ){
+    int fd;
+    rc = osOpenDirectory(zPath, &fd);
+    if( rc==SQLITE_OK ){
+      if( full_fsync(fd,0,0) ){
+        rc = unixLogError(SQLITE_IOERR_DIR_FSYNC, "fsync", zPath);
+      }
+      robust_close(0, fd, __LINE__);
+    }else{
+      assert( rc==SQLITE_CANTOPEN );
+      rc = SQLITE_OK;
+    }
+  }
+#endif
+  return rc;
+}
+
+/*
+** Test the existence of or access permissions of file zPath. The
+** test performed depends on the value of flags:
+**
+**     SQLITE_ACCESS_EXISTS: Return 1 if the file exists
+**     SQLITE_ACCESS_READWRITE: Return 1 if the file is read and writable.
+**     SQLITE_ACCESS_READONLY: Return 1 if the file is readable.
+**
+** Otherwise return 0.
+*/
+static int unixAccess(
+  sqlite3_vfs *NotUsed,   /* The VFS containing this xAccess method */
+  const char *zPath,      /* Path of the file to examine */
+  int flags,              /* What do we want to learn about the zPath file? */
+  int *pResOut            /* Write result boolean here */
+){
+  UNUSED_PARAMETER(NotUsed);
+  SimulateIOError( return SQLITE_IOERR_ACCESS; );
+  assert( pResOut!=0 );
+
+  /* The spec says there are three possible values for flags.  But only
+  ** two of them are actually used */
+  assert( flags==SQLITE_ACCESS_EXISTS || flags==SQLITE_ACCESS_READWRITE );
+
+  if( flags==SQLITE_ACCESS_EXISTS ){
+    struct stat buf;
+    *pResOut = 0==osStat(zPath, &buf) &&
+                (!S_ISREG(buf.st_mode) || buf.st_size>0);
+  }else{
+    *pResOut = osAccess(zPath, W_OK|R_OK)==0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** A pathname under construction
+*/
+typedef struct DbPath DbPath;
+struct DbPath {
+  int rc;           /* Non-zero following any error */
+  int nSymlink;     /* Number of symlinks resolved */
+  char *zOut;       /* Write the pathname here */
+  int nOut;         /* Bytes of space available to zOut[] */
+  int nUsed;        /* Bytes of zOut[] currently being used */
+};
+
+/* Forward reference */
+static void appendAllPathElements(DbPath*,const char*);
+
+/*
+** Append a single path element to the DbPath under construction
+*/
+static void appendOnePathElement(
+  DbPath *pPath,       /* Path under construction, to which to append zName */
+  const char *zName,   /* Name to append to pPath.  Not zero-terminated */
+  int nName            /* Number of significant bytes in zName */
+){
+  assert( nName>0 );
+  assert( zName!=0 );
+  if( zName[0]=='.' ){
+    if( nName==1 ) return;
+    if( zName[1]=='.' && nName==2 ){
+      if( pPath->nUsed>1 ){
+        assert( pPath->zOut[0]=='/' );
+        while( pPath->zOut[--pPath->nUsed]!='/' ){}
+      }
+      return;
+    }
+  }
+  if( pPath->nUsed + nName + 2 >= pPath->nOut ){
+    pPath->rc = SQLITE_ERROR;
+    return;
+  }
+  pPath->zOut[pPath->nUsed++] = '/';
+  memcpy(&pPath->zOut[pPath->nUsed], zName, nName);
+  pPath->nUsed += nName;
+#if defined(HAVE_READLINK) && defined(HAVE_LSTAT)
+  if( pPath->rc==SQLITE_OK ){
+    const char *zIn;
+    struct stat buf;
+    pPath->zOut[pPath->nUsed] = 0;
+    zIn = pPath->zOut;
+    if( osLstat(zIn, &buf)!=0 ){
+      if( errno!=ENOENT ){
+        pPath->rc = unixLogError(SQLITE_CANTOPEN_BKPT, "lstat", zIn);
+      }
+    }else if( S_ISLNK(buf.st_mode) ){
+      ssize_t got;
+      char zLnk[SQLITE_MAX_PATHLEN+2];
+      if( pPath->nSymlink++ > SQLITE_MAX_SYMLINK ){
+        pPath->rc = SQLITE_CANTOPEN_BKPT;
+        return;
+      }
+      got = osReadlink(zIn, zLnk, sizeof(zLnk)-2);
+      if( got<=0 || got>=(ssize_t)sizeof(zLnk)-2 ){
+        pPath->rc = unixLogError(SQLITE_CANTOPEN_BKPT, "readlink", zIn);
+        return;
+      }
+      zLnk[got] = 0;
+      if( zLnk[0]=='/' ){
+        pPath->nUsed = 0;
+      }else{
+        pPath->nUsed -= nName + 1;
+      }
+      appendAllPathElements(pPath, zLnk);
+    }
+  }
+#endif
+}
+
+/*
+** Append all path elements in zPath to the DbPath under construction.
+*/
+static void appendAllPathElements(
+  DbPath *pPath,       /* Path under construction, to which to append zName */
+  const char *zPath    /* Path to append to pPath.  Is zero-terminated */
+){
+  int i = 0;
+  int j = 0;
+  do{
+    while( zPath[i] && zPath[i]!='/' ){ i++; }
+    if( i>j ){
+      appendOnePathElement(pPath, &zPath[j], i-j);
+    }
+    j = i+1;
+  }while( zPath[i++] );
+}
+
+/*
+** Turn a relative pathname into a full pathname. The relative path
+** is stored as a nul-terminated string in the buffer pointed to by
+** zPath.
+**
+** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes
+** (in this case, MAX_PATHNAME bytes). The full-path is written to
+** this buffer before returning.
+*/
+static int unixFullPathname(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zPath,            /* Possibly relative input path */
+  int nOut,                     /* Size of output buffer in bytes */
+  char *zOut                    /* Output buffer */
+){
+  DbPath path;
+  UNUSED_PARAMETER(pVfs);
+  path.rc = 0;
+  path.nUsed = 0;
+  path.nSymlink = 0;
+  path.nOut = nOut;
+  path.zOut = zOut;
+  if( zPath[0]!='/' ){
+    char zPwd[SQLITE_MAX_PATHLEN+2];
+    if( osGetcwd(zPwd, sizeof(zPwd)-2)==0 ){
+      return unixLogError(SQLITE_CANTOPEN_BKPT, "getcwd", zPath);
+    }
+    appendAllPathElements(&path, zPwd);
+  }
+  appendAllPathElements(&path, zPath);
+  zOut[path.nUsed] = 0;
+  if( path.rc || path.nUsed<2 ) return SQLITE_CANTOPEN_BKPT;
+  if( path.nSymlink ) return SQLITE_OK_SYMLINK;
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+#include <dlfcn.h>
+static void *unixDlOpen(sqlite3_vfs *NotUsed, const char *zFilename){
+  UNUSED_PARAMETER(NotUsed);
+  return dlopen(zFilename, RTLD_NOW | RTLD_GLOBAL);
+}
+
+/*
+** SQLite calls this function immediately after a call to unixDlSym() or
+** unixDlOpen() fails (returns a null pointer). If a more detailed error
+** message is available, it is written to zBufOut. If no error message
+** is available, zBufOut is left unmodified and SQLite uses a default
+** error message.
+*/
+static void unixDlError(sqlite3_vfs *NotUsed, int nBuf, char *zBufOut){
+  const char *zErr;
+  UNUSED_PARAMETER(NotUsed);
+  unixEnterMutex();
+  zErr = dlerror();
+  if( zErr ){
+    sqlite3_snprintf(nBuf, zBufOut, "%s", zErr);
+  }
+  unixLeaveMutex();
+}
+static void (*unixDlSym(sqlite3_vfs *NotUsed, void *p, const char*zSym))(void){
+  /*
+  ** GCC with -pedantic-errors says that C90 does not allow a void* to be
+  ** cast into a pointer to a function.  And yet the library dlsym() routine
+  ** returns a void* which is really a pointer to a function.  So how do we
+  ** use dlsym() with -pedantic-errors?
+  **
+  ** Variable x below is defined to be a pointer to a function taking
+  ** parameters void* and const char* and returning a pointer to a function.
+  ** We initialize x by assigning it a pointer to the dlsym() function.
+  ** (That assignment requires a cast.)  Then we call the function that
+  ** x points to.
+  **
+  ** This work-around is unlikely to work correctly on any system where
+  ** you really cannot cast a function pointer into void*.  But then, on the
+  ** other hand, dlsym() will not work on such a system either, so we have
+  ** not really lost anything.
+  */
+  void (*(*x)(void*,const char*))(void);
+  UNUSED_PARAMETER(NotUsed);
+  x = (void(*(*)(void*,const char*))(void))dlsym;
+  return (*x)(p, zSym);
+}
+static void unixDlClose(sqlite3_vfs *NotUsed, void *pHandle){
+  UNUSED_PARAMETER(NotUsed);
+  dlclose(pHandle);
+}
+#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
+  #define unixDlOpen  0
+  #define unixDlError 0
+  #define unixDlSym   0
+  #define unixDlClose 0
+#endif
+
+/*
+** Write nBuf bytes of random data to the supplied buffer zBuf.
+*/
+static int unixRandomness(sqlite3_vfs *NotUsed, int nBuf, char *zBuf){
+  UNUSED_PARAMETER(NotUsed);
+  assert((size_t)nBuf>=(sizeof(time_t)+sizeof(int)));
+
+  /* We have to initialize zBuf to prevent valgrind from reporting
+  ** errors.  The reports issued by valgrind are incorrect - we would
+  ** prefer that the randomness be increased by making use of the
+  ** uninitialized space in zBuf - but valgrind errors tend to worry
+  ** some users.  Rather than argue, it seems easier just to initialize
+  ** the whole array and silence valgrind, even if that means less randomness
+  ** in the random seed.
+  **
+  ** When testing, initializing zBuf[] to zero is all we do.  That means
+  ** that we always use the same random number sequence.  This makes the
+  ** tests repeatable.
+  */
+  memset(zBuf, 0, nBuf);
+  randomnessPid = osGetpid(0);
+#if !defined(SQLITE_TEST) && !defined(SQLITE_OMIT_RANDOMNESS)
+  {
+    int fd, got;
+    fd = robust_open("/dev/urandom", O_RDONLY, 0);
+    if( fd<0 ){
+      time_t t;
+      time(&t);
+      memcpy(zBuf, &t, sizeof(t));
+      memcpy(&zBuf[sizeof(t)], &randomnessPid, sizeof(randomnessPid));
+      assert( sizeof(t)+sizeof(randomnessPid)<=(size_t)nBuf );
+      nBuf = sizeof(t) + sizeof(randomnessPid);
+    }else{
+      do{ got = osRead(fd, zBuf, nBuf); }while( got<0 && errno==EINTR );
+      robust_close(0, fd, __LINE__);
+    }
+  }
+#endif
+  return nBuf;
+}
+
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+** The argument is the number of microseconds we want to sleep.
+** The return value is the number of microseconds of sleep actually
+** requested from the underlying operating system, a number which
+** might be greater than or equal to the argument, but not less
+** than the argument.
+*/
+static int unixSleep(sqlite3_vfs *NotUsed, int microseconds){
+#if !defined(HAVE_NANOSLEEP) || HAVE_NANOSLEEP+0
+  struct timespec sp;
+  sp.tv_sec = microseconds / 1000000;
+  sp.tv_nsec = (microseconds % 1000000) * 1000;
+
+  /* Almost all modern unix systems support nanosleep().  But if you are
+  ** compiling for one of the rare exceptions, you can use
+  ** -DHAVE_NANOSLEEP=0 (perhaps in conjuction with -DHAVE_USLEEP if
+  ** usleep() is available) in order to bypass the use of nanosleep() */
+  nanosleep(&sp, NULL);
+
+  UNUSED_PARAMETER(NotUsed);
+  return microseconds;
+#elif defined(HAVE_USLEEP) && HAVE_USLEEP
+  if( microseconds>=1000000 ) sleep(microseconds/1000000);
+  if( microseconds%1000000 ) usleep(microseconds%1000000);
+  UNUSED_PARAMETER(NotUsed);
+  return microseconds;
+#else
+  int seconds = (microseconds+999999)/1000000;
+  sleep(seconds);
+  UNUSED_PARAMETER(NotUsed);
+  return seconds*1000000;
+#endif
+}
+
+/*
+** The following variable, if set to a non-zero value, is interpreted as
+** the number of seconds since 1970 and is used to set the result of
+** sqlite3OsCurrentTime() during testing.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
+#endif
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return SQLITE_OK.  Return SQLITE_ERROR if the time and date
+** cannot be found.
+*/
+static int unixCurrentTimeInt64(sqlite3_vfs *NotUsed, sqlite3_int64 *piNow){
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+  int rc = SQLITE_OK;
+#if defined(NO_GETTOD)
+  time_t t;
+  time(&t);
+  *piNow = ((sqlite3_int64)t)*1000 + unixEpoch;
+#elif OS_VXWORKS
+  struct timespec sNow;
+  clock_gettime(CLOCK_REALTIME, &sNow);
+  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_nsec/1000000;
+#else
+  struct timeval sNow;
+  (void)gettimeofday(&sNow, 0);  /* Cannot fail given valid arguments */
+  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
+#endif
+
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
+  }
+#endif
+  UNUSED_PARAMETER(NotUsed);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Find the current time (in Universal Coordinated Time).  Write the
+** current time and date as a Julian Day number into *prNow and
+** return 0.  Return 1 if the time and date cannot be found.
+*/
+static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){
+  sqlite3_int64 i = 0;
+  int rc;
+  UNUSED_PARAMETER(NotUsed);
+  rc = unixCurrentTimeInt64(0, &i);
+  *prNow = i/86400000.0;
+  return rc;
+}
+#else
+# define unixCurrentTime 0
+#endif
+
+/*
+** The xGetLastError() method is designed to return a better
+** low-level error message when operating-system problems come up
+** during SQLite operation.  Only the integer return code is currently
+** used.
+*/
+static int unixGetLastError(sqlite3_vfs *NotUsed, int NotUsed2, char *NotUsed3){
+  UNUSED_PARAMETER(NotUsed);
+  UNUSED_PARAMETER(NotUsed2);
+  UNUSED_PARAMETER(NotUsed3);
+  return errno;
+}
+
+
+/*
+************************ End of sqlite3_vfs methods ***************************
+******************************************************************************/
+
+/******************************************************************************
+************************** Begin Proxy Locking ********************************
+**
+** Proxy locking is a "uber-locking-method" in this sense:  It uses the
+** other locking methods on secondary lock files.  Proxy locking is a
+** meta-layer over top of the primitive locking implemented above.  For
+** this reason, the division that implements of proxy locking is deferred
+** until late in the file (here) after all of the other I/O methods have
+** been defined - so that the primitive locking methods are available
+** as services to help with the implementation of proxy locking.
+**
+****
+**
+** The default locking schemes in SQLite use byte-range locks on the
+** database file to coordinate safe, concurrent access by multiple readers
+** and writers [http://sqlite.org/lockingv3.html].  The five file locking
+** states (UNLOCKED, PENDING, SHARED, RESERVED, EXCLUSIVE) are implemented
+** as POSIX read & write locks over fixed set of locations (via fsctl),
+** on AFP and SMB only exclusive byte-range locks are available via fsctl
+** with _IOWR('z', 23, struct ByteRangeLockPB2) to track the same 5 states.
+** To simulate a F_RDLCK on the shared range, on AFP a randomly selected
+** address in the shared range is taken for a SHARED lock, the entire
+** shared range is taken for an EXCLUSIVE lock):
+**
+**      PENDING_BYTE        0x40000000
+**      RESERVED_BYTE       0x40000001
+**      SHARED_RANGE        0x40000002 -> 0x40000200
+**
+** This works well on the local file system, but shows a nearly 100x
+** slowdown in read performance on AFP because the AFP client disables
+** the read cache when byte-range locks are present.  Enabling the read
+** cache exposes a cache coherency problem that is present on all OS X
+** supported network file systems.  NFS and AFP both observe the
+** close-to-open semantics for ensuring cache coherency
+** [http://nfs.sourceforge.net/#faq_a8], which does not effectively
+** address the requirements for concurrent database access by multiple
+** readers and writers
+** [http://www.nabble.com/SQLite-on-NFS-cache-coherency-td15655701.html].
+**
+** To address the performance and cache coherency issues, proxy file locking
+** changes the way database access is controlled by limiting access to a
+** single host at a time and moving file locks off of the database file
+** and onto a proxy file on the local file system.
+**
+**
+** Using proxy locks
+** -----------------
+**
+** C APIs
+**
+**  sqlite3_file_control(db, dbname, SQLITE_FCNTL_SET_LOCKPROXYFILE,
+**                       <proxy_path> | ":auto:");
+**  sqlite3_file_control(db, dbname, SQLITE_FCNTL_GET_LOCKPROXYFILE,
+**                       &<proxy_path>);
+**
+**
+** SQL pragmas
+**
+**  PRAGMA [database.]lock_proxy_file=<proxy_path> | :auto:
+**  PRAGMA [database.]lock_proxy_file
+**
+** Specifying ":auto:" means that if there is a conch file with a matching
+** host ID in it, the proxy path in the conch file will be used, otherwise
+** a proxy path based on the user's temp dir
+** (via confstr(_CS_DARWIN_USER_TEMP_DIR,...)) will be used and the
+** actual proxy file name is generated from the name and path of the
+** database file.  For example:
+**
+**       For database path "/Users/me/foo.db"
+**       The lock path will be "<tmpdir>/sqliteplocks/_Users_me_foo.db:auto:")
+**
+** Once a lock proxy is configured for a database connection, it can not
+** be removed, however it may be switched to a different proxy path via
+** the above APIs (assuming the conch file is not being held by another
+** connection or process).
+**
+**
+** How proxy locking works
+** -----------------------
+**
+** Proxy file locking relies primarily on two new supporting files:
+**
+**   *  conch file to limit access to the database file to a single host
+**      at a time
+**
+**   *  proxy file to act as a proxy for the advisory locks normally
+**      taken on the database
+**
+** The conch file - to use a proxy file, sqlite must first "hold the conch"
+** by taking an sqlite-style shared lock on the conch file, reading the
+** contents and comparing the host's unique host ID (see below) and lock
+** proxy path against the values stored in the conch.  The conch file is
+** stored in the same directory as the database file and the file name
+** is patterned after the database file name as ".<databasename>-conch".
+** If the conch file does not exist, or its contents do not match the
+** host ID and/or proxy path, then the lock is escalated to an exclusive
+** lock and the conch file contents is updated with the host ID and proxy
+** path and the lock is downgraded to a shared lock again.  If the conch
+** is held by another process (with a shared lock), the exclusive lock
+** will fail and SQLITE_BUSY is returned.
+**
+** The proxy file - a single-byte file used for all advisory file locks
+** normally taken on the database file.   This allows for safe sharing
+** of the database file for multiple readers and writers on the same
+** host (the conch ensures that they all use the same local lock file).
+**
+** Requesting the lock proxy does not immediately take the conch, it is
+** only taken when the first request to lock database file is made.
+** This matches the semantics of the traditional locking behavior, where
+** opening a connection to a database file does not take a lock on it.
+** The shared lock and an open file descriptor are maintained until
+** the connection to the database is closed.
+**
+** The proxy file and the lock file are never deleted so they only need
+** to be created the first time they are used.
+**
+** Configuration options
+** ---------------------
+**
+**  SQLITE_PREFER_PROXY_LOCKING
+**
+**       Database files accessed on non-local file systems are
+**       automatically configured for proxy locking, lock files are
+**       named automatically using the same logic as
+**       PRAGMA lock_proxy_file=":auto:"
+**  
+**  SQLITE_PROXY_DEBUG
+**
+**       Enables the logging of error messages during host id file
+**       retrieval and creation
+**
+**  LOCKPROXYDIR
+**
+**       Overrides the default directory used for lock proxy files that
+**       are named automatically via the ":auto:" setting
+**
+**  SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
+**
+**       Permissions to use when creating a directory for storing the
+**       lock proxy files, only used when LOCKPROXYDIR is not set.
+**  
+**  
+** As mentioned above, when compiled with SQLITE_PREFER_PROXY_LOCKING,
+** setting the environment variable SQLITE_FORCE_PROXY_LOCKING to 1 will
+** force proxy locking to be used for every database file opened, and 0
+** will force automatic proxy locking to be disabled for all database
+** files (explicitly calling the SQLITE_FCNTL_SET_LOCKPROXYFILE pragma or
+** sqlite_file_control API is not affected by SQLITE_FORCE_PROXY_LOCKING).
+*/
+
+/*
+** Proxy locking is only available on MacOSX
+*/
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+
+/*
+** The proxyLockingContext has the path and file structures for the remote
+** and local proxy files in it
+*/
+typedef struct proxyLockingContext proxyLockingContext;
+struct proxyLockingContext {
+  unixFile *conchFile;         /* Open conch file */
+  char *conchFilePath;         /* Name of the conch file */
+  unixFile *lockProxy;         /* Open proxy lock file */
+  char *lockProxyPath;         /* Name of the proxy lock file */
+  char *dbPath;                /* Name of the open file */
+  int conchHeld;               /* 1 if the conch is held, -1 if lockless */
+  int nFails;                  /* Number of conch taking failures */
+  void *oldLockingContext;     /* Original lockingcontext to restore on close */
+  sqlite3_io_methods const *pOldMethod;     /* Original I/O methods for close */
+};
+
+/*
+** The proxy lock file path for the database at dbPath is written into lPath,
+** which must point to valid, writable memory large enough for a maxLen length
+** file path.
+*/
+static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
+  int len;
+  int dbLen;
+  int i;
+
+#ifdef LOCKPROXYDIR
+  len = strlcpy(lPath, LOCKPROXYDIR, maxLen);
+#else
+# ifdef _CS_DARWIN_USER_TEMP_DIR
+  {
+    if( !confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen) ){
+      OSTRACE(("GETLOCKPATH  failed %s errno=%d pid=%d\n",
+               lPath, errno, osGetpid(0)));
+      return SQLITE_IOERR_LOCK;
+    }
+    len = strlcat(lPath, "sqliteplocks", maxLen);  
+  }
+# else
+  len = strlcpy(lPath, "/tmp/", maxLen);
+# endif
+#endif
+
+  if( lPath[len-1]!='/' ){
+    len = strlcat(lPath, "/", maxLen);
+  }
+
+  /* transform the db path to a unique cache name */
+  dbLen = (int)strlen(dbPath);
+  for( i=0; i<dbLen && (i+len+7)<(int)maxLen; i++){
+    char c = dbPath[i];
+    lPath[i+len] = (c=='/')?'_':c;
+  }
+  lPath[i+len]='\0';
+  strlcat(lPath, ":auto:", maxLen);
+  OSTRACE(("GETLOCKPATH  proxy lock path=%s pid=%d\n", lPath, osGetpid(0)));
+  return SQLITE_OK;
+}
+
+/*
+ ** Creates the lock file and any missing directories in lockPath
+ */
+static int proxyCreateLockPath(const char *lockPath){
+  int i, len;
+  char buf[MAXPATHLEN];
+  int start = 0;
+
+  assert(lockPath!=NULL);
+  /* try to create all the intermediate directories */
+  len = (int)strlen(lockPath);
+  buf[0] = lockPath[0];
+  for( i=1; i<len; i++ ){
+    if( lockPath[i] == '/' && (i - start > 0) ){
+      /* only mkdir if leaf dir != "." or "/" or ".." */
+      if( i-start>2 || (i-start==1 && buf[start] != '.' && buf[start] != '/')
+         || (i-start==2 && buf[start] != '.' && buf[start+1] != '.') ){
+        buf[i]='\0';
+        if( osMkdir(buf, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
+          int err=errno;
+          if( err!=EEXIST ) {
+            OSTRACE(("CREATELOCKPATH  FAILED creating %s, "
+                     "'%s' proxy lock path=%s pid=%d\n",
+                     buf, strerror(err), lockPath, osGetpid(0)));
+            return err;
+          }
+        }
+      }
+      start=i+1;
+    }
+    buf[i] = lockPath[i];
+  }
+  OSTRACE(("CREATELOCKPATH  proxy lock path=%s pid=%d\n",lockPath,osGetpid(0)));
+  return 0;
+}
+
+/*
+** Create a new VFS file descriptor (stored in memory obtained from
+** sqlite3_malloc) and open the file named "path" in the file descriptor.
+**
+** The caller is responsible not only for closing the file descriptor
+** but also for freeing the memory associated with the file descriptor.
+*/
+static int proxyCreateUnixFile(
+    const char *path,        /* path for the new unixFile */
+    unixFile **ppFile,       /* unixFile created and returned by ref */
+    int islockfile           /* if non zero missing dirs will be created */
+) {
+  int fd = -1;
+  unixFile *pNew;
+  int rc = SQLITE_OK;
+  int openFlags = O_RDWR | O_CREAT | O_NOFOLLOW;
+  sqlite3_vfs dummyVfs;
+  int terrno = 0;
+  UnixUnusedFd *pUnused = NULL;
+
+  /* 1. first try to open/create the file
+  ** 2. if that fails, and this is a lock file (not-conch), try creating
+  ** the parent directories and then try again.
+  ** 3. if that fails, try to open the file read-only
+  ** otherwise return BUSY (if lock file) or CANTOPEN for the conch file
+  */
+  pUnused = findReusableFd(path, openFlags);
+  if( pUnused ){
+    fd = pUnused->fd;
+  }else{
+    pUnused = sqlite3_malloc64(sizeof(*pUnused));
+    if( !pUnused ){
+      return SQLITE_NOMEM_BKPT;
+    }
+  }
+  if( fd<0 ){
+    fd = robust_open(path, openFlags, 0);
+    terrno = errno;
+    if( fd<0 && errno==ENOENT && islockfile ){
+      if( proxyCreateLockPath(path) == SQLITE_OK ){
+        fd = robust_open(path, openFlags, 0);
+      }
+    }
+  }
+  if( fd<0 ){
+    openFlags = O_RDONLY | O_NOFOLLOW;
+    fd = robust_open(path, openFlags, 0);
+    terrno = errno;
+  }
+  if( fd<0 ){
+    if( islockfile ){
+      return SQLITE_BUSY;
+    }
+    switch (terrno) {
+      case EACCES:
+        return SQLITE_PERM;
+      case EIO:
+        return SQLITE_IOERR_LOCK; /* even though it is the conch */
+      default:
+        return SQLITE_CANTOPEN_BKPT;
+    }
+  }
+
+  pNew = (unixFile *)sqlite3_malloc64(sizeof(*pNew));
+  if( pNew==NULL ){
+    rc = SQLITE_NOMEM_BKPT;
+    goto end_create_proxy;
+  }
+  memset(pNew, 0, sizeof(unixFile));
+  pNew->openFlags = openFlags;
+  memset(&dummyVfs, 0, sizeof(dummyVfs));
+  dummyVfs.pAppData = (void*)&autolockIoFinder;
+  dummyVfs.zName = "dummy";
+  pUnused->fd = fd;
+  pUnused->flags = openFlags;
+  pNew->pPreallocatedUnused = pUnused;
+
+  rc = fillInUnixFile(&dummyVfs, fd, (sqlite3_file*)pNew, path, 0);
+  if( rc==SQLITE_OK ){
+    *ppFile = pNew;
+    return SQLITE_OK;
+  }
+end_create_proxy:  
+  robust_close(pNew, fd, __LINE__);
+  sqlite3_free(pNew);
+  sqlite3_free(pUnused);
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+/* simulate multiple hosts by creating unique hostid file paths */
+int sqlite3_hostid_num = 0;
+#endif
+
+#define PROXY_HOSTIDLEN    16  /* conch file host id length */
+
+#if HAVE_GETHOSTUUID
+/* Not always defined in the headers as it ought to be */
+extern int gethostuuid(uuid_t id, const struct timespec *wait);
+#endif
+
+/* get the host ID via gethostuuid(), pHostID must point to PROXY_HOSTIDLEN
+** bytes of writable memory.
+*/
+static int proxyGetHostID(unsigned char *pHostID, int *pError){
+  assert(PROXY_HOSTIDLEN == sizeof(uuid_t));
+  memset(pHostID, 0, PROXY_HOSTIDLEN);
+#if HAVE_GETHOSTUUID
+  {
+    struct timespec timeout = {1, 0}; /* 1 sec timeout */
+    if( gethostuuid(pHostID, &timeout) ){
+      int err = errno;
+      if( pError ){
+        *pError = err;
+      }
+      return SQLITE_IOERR;
+    }
+  }
+#else
+  UNUSED_PARAMETER(pError);
+#endif
+#ifdef SQLITE_TEST
+  /* simulate multiple hosts by creating unique hostid file paths */
+  if( sqlite3_hostid_num != 0){
+    pHostID[0] = (char)(pHostID[0] + (char)(sqlite3_hostid_num & 0xFF));
+  }
+#endif
+
+  return SQLITE_OK;
+}
+
+/* The conch file contains the header, host id and lock file path
+ */
+#define PROXY_CONCHVERSION 2   /* 1-byte header, 16-byte host id, path */
+#define PROXY_HEADERLEN    1   /* conch file header length */
+#define PROXY_PATHINDEX    (PROXY_HEADERLEN+PROXY_HOSTIDLEN)
+#define PROXY_MAXCONCHLEN  (PROXY_HEADERLEN+PROXY_HOSTIDLEN+MAXPATHLEN)
+
+/*
+** Takes an open conch file, copies the contents to a new path and then moves
+** it back.  The newly created file's file descriptor is assigned to the
+** conch file structure and finally the original conch file descriptor is
+** closed.  Returns zero if successful.
+*/
+static int proxyBreakConchLock(unixFile *pFile, uuid_t myHostID){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+  unixFile *conchFile = pCtx->conchFile;
+  char tPath[MAXPATHLEN];
+  char buf[PROXY_MAXCONCHLEN];
+  char *cPath = pCtx->conchFilePath;
+  size_t readLen = 0;
+  size_t pathLen = 0;
+  char errmsg[64] = "";
+  int fd = -1;
+  int rc = -1;
+  UNUSED_PARAMETER(myHostID);
+
+  /* create a new path by replace the trailing '-conch' with '-break' */
+  pathLen = strlcpy(tPath, cPath, MAXPATHLEN);
+  if( pathLen>MAXPATHLEN || pathLen<6 ||
+     (strlcpy(&tPath[pathLen-5], "break", 6) != 5) ){
+    sqlite3_snprintf(sizeof(errmsg),errmsg,"path error (len %d)",(int)pathLen);
+    goto end_breaklock;
+  }
+  /* read the conch content */
+  readLen = osPread(conchFile->h, buf, PROXY_MAXCONCHLEN, 0);
+  if( readLen<PROXY_PATHINDEX ){
+    sqlite3_snprintf(sizeof(errmsg),errmsg,"read error (len %d)",(int)readLen);
+    goto end_breaklock;
+  }
+  /* write it out to the temporary break file */
+  fd = robust_open(tPath, (O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW), 0);
+  if( fd<0 ){
+    sqlite3_snprintf(sizeof(errmsg), errmsg, "create failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( osPwrite(fd, buf, readLen, 0) != (ssize_t)readLen ){
+    sqlite3_snprintf(sizeof(errmsg), errmsg, "write failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( rename(tPath, cPath) ){
+    sqlite3_snprintf(sizeof(errmsg), errmsg, "rename failed (%d)", errno);
+    goto end_breaklock;
+  }
+  rc = 0;
+  fprintf(stderr, "broke stale lock on %s\n", cPath);
+  robust_close(pFile, conchFile->h, __LINE__);
+  conchFile->h = fd;
+  conchFile->openFlags = O_RDWR | O_CREAT;
+
+end_breaklock:
+  if( rc ){
+    if( fd>=0 ){
+      osUnlink(tPath);
+      robust_close(pFile, fd, __LINE__);
+    }
+    fprintf(stderr, "failed to break stale lock on %s, %s\n", cPath, errmsg);
+  }
+  return rc;
+}
+
+/* Take the requested lock on the conch file and break a stale lock if the
+** host id matches.
+*/
+static int proxyConchLock(unixFile *pFile, uuid_t myHostID, int lockType){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+  unixFile *conchFile = pCtx->conchFile;
+  int rc = SQLITE_OK;
+  int nTries = 0;
+  struct timespec conchModTime;
+
+  memset(&conchModTime, 0, sizeof(conchModTime));
+  do {
+    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+    nTries ++;
+    if( rc==SQLITE_BUSY ){
+      /* If the lock failed (busy):
+       * 1st try: get the mod time of the conch, wait 0.5s and try again.
+       * 2nd try: fail if the mod time changed or host id is different, wait
+       *           10 sec and try again
+       * 3rd try: break the lock unless the mod time has changed.
+       */
+      struct stat buf;
+      if( osFstat(conchFile->h, &buf) ){
+        storeLastErrno(pFile, errno);
+        return SQLITE_IOERR_LOCK;
+      }
+    
+      if( nTries==1 ){
+        conchModTime = buf.st_mtimespec;
+        unixSleep(0,500000); /* wait 0.5 sec and try the lock again*/
+        continue;
+      }
+
+      assert( nTries>1 );
+      if( conchModTime.tv_sec != buf.st_mtimespec.tv_sec ||
+         conchModTime.tv_nsec != buf.st_mtimespec.tv_nsec ){
+        return SQLITE_BUSY;
+      }
+    
+      if( nTries==2 ){
+        char tBuf[PROXY_MAXCONCHLEN];
+        int len = osPread(conchFile->h, tBuf, PROXY_MAXCONCHLEN, 0);
+        if( len<0 ){
+          storeLastErrno(pFile, errno);
+          return SQLITE_IOERR_LOCK;
+        }
+        if( len>PROXY_PATHINDEX && tBuf[0]==(char)PROXY_CONCHVERSION){
+          /* don't break the lock if the host id doesn't match */
+          if( 0!=memcmp(&tBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN) ){
+            return SQLITE_BUSY;
+          }
+        }else{
+          /* don't break the lock on short read or a version mismatch */
+          return SQLITE_BUSY;
+        }
+        unixSleep(0,10000000); /* wait 10 sec and try the lock again */
+        continue;
+      }
+    
+      assert( nTries==3 );
+      if( 0==proxyBreakConchLock(pFile, myHostID) ){
+        rc = SQLITE_OK;
+        if( lockType==EXCLUSIVE_LOCK ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);
+        }
+        if( !rc ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+        }
+      }
+    }
+  } while( rc==SQLITE_BUSY && nTries<3 );
+
+  return rc;
+}
+
+/* Takes the conch by taking a shared lock and read the contents conch, if
+** lockPath is non-NULL, the host ID and lock file path must match.  A NULL
+** lockPath means that the lockPath in the conch file will be used if the
+** host IDs match, or a new lock path will be generated automatically
+** and written to the conch file.
+*/
+static int proxyTakeConch(unixFile *pFile){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+
+  if( pCtx->conchHeld!=0 ){
+    return SQLITE_OK;
+  }else{
+    unixFile *conchFile = pCtx->conchFile;
+    uuid_t myHostID;
+    int pError = 0;
+    char readBuf[PROXY_MAXCONCHLEN];
+    char lockPath[MAXPATHLEN];
+    char *tempLockPath = NULL;
+    int rc = SQLITE_OK;
+    int createConch = 0;
+    int hostIdMatch = 0;
+    int readLen = 0;
+    int tryOldLockPath = 0;
+    int forceNewLockPath = 0;
+  
+    OSTRACE(("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
+             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"),
+             osGetpid(0)));
+
+    rc = proxyGetHostID(myHostID, &pError);
+    if( (rc&0xff)==SQLITE_IOERR ){
+      storeLastErrno(pFile, pError);
+      goto end_takeconch;
+    }
+    rc = proxyConchLock(pFile, myHostID, SHARED_LOCK);
+    if( rc!=SQLITE_OK ){
+      goto end_takeconch;
+    }
+    /* read the existing conch file */
+    readLen = seekAndRead((unixFile*)conchFile, 0, readBuf, PROXY_MAXCONCHLEN);
+    if( readLen<0 ){
+      /* I/O error: lastErrno set by seekAndRead */
+      storeLastErrno(pFile, conchFile->lastErrno);
+      rc = SQLITE_IOERR_READ;
+      goto end_takeconch;
+    }else if( readLen<=(PROXY_HEADERLEN+PROXY_HOSTIDLEN) ||
+             readBuf[0]!=(char)PROXY_CONCHVERSION ){
+      /* a short read or version format mismatch means we need to create a new
+      ** conch file.
+      */
+      createConch = 1;
+    }
+    /* if the host id matches and the lock path already exists in the conch
+    ** we'll try to use the path there, if we can't open that path, we'll
+    ** retry with a new auto-generated path
+    */
+    do { /* in case we need to try again for an :auto: named lock file */
+
+      if( !createConch && !forceNewLockPath ){
+        hostIdMatch = !memcmp(&readBuf[PROXY_HEADERLEN], myHostID,
+                                  PROXY_HOSTIDLEN);
+        /* if the conch has data compare the contents */
+        if( !pCtx->lockProxyPath ){
+          /* for auto-named local lock file, just check the host ID and we'll
+           ** use the local lock file path that's already in there
+           */
+          if( hostIdMatch ){
+            size_t pathLen = (readLen - PROXY_PATHINDEX);
+          
+            if( pathLen>=MAXPATHLEN ){
+              pathLen=MAXPATHLEN-1;
+            }
+            memcpy(lockPath, &readBuf[PROXY_PATHINDEX], pathLen);
+            lockPath[pathLen] = 0;
+            tempLockPath = lockPath;
+            tryOldLockPath = 1;
+            /* create a copy of the lock path if the conch is taken */
+            goto end_takeconch;
+          }
+        }else if( hostIdMatch
+               && !strncmp(pCtx->lockProxyPath, &readBuf[PROXY_PATHINDEX],
+                           readLen-PROXY_PATHINDEX)
+        ){
+          /* conch host and lock path match */
+          goto end_takeconch;
+        }
+      }
+    
+      /* if the conch isn't writable and doesn't match, we can't take it */
+      if( (conchFile->openFlags&O_RDWR) == 0 ){
+        rc = SQLITE_BUSY;
+        goto end_takeconch;
+      }
+    
+      /* either the conch didn't match or we need to create a new one */
+      if( !pCtx->lockProxyPath ){
+        proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN);
+        tempLockPath = lockPath;
+        /* create a copy of the lock path _only_ if the conch is taken */
+      }
+    
+      /* update conch with host and path (this will fail if other process
+      ** has a shared lock already), if the host id matches, use the big
+      ** stick.
+      */
+      futimes(conchFile->h, NULL);
+      if( hostIdMatch && !createConch ){
+        if( conchFile->pInode && conchFile->pInode->nShared>1 ){
+          /* We are trying for an exclusive lock but another thread in this
+           ** same process is still holding a shared lock. */
+          rc = SQLITE_BUSY;
+        } else {        
+          rc = proxyConchLock(pFile, myHostID, EXCLUSIVE_LOCK);
+        }
+      }else{
+        rc = proxyConchLock(pFile, myHostID, EXCLUSIVE_LOCK);
+      }
+      if( rc==SQLITE_OK ){
+        char writeBuffer[PROXY_MAXCONCHLEN];
+        int writeSize = 0;
+      
+        writeBuffer[0] = (char)PROXY_CONCHVERSION;
+        memcpy(&writeBuffer[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN);
+        if( pCtx->lockProxyPath!=NULL ){
+          strlcpy(&writeBuffer[PROXY_PATHINDEX], pCtx->lockProxyPath,
+                  MAXPATHLEN);
+        }else{
+          strlcpy(&writeBuffer[PROXY_PATHINDEX], tempLockPath, MAXPATHLEN);
+        }
+        writeSize = PROXY_PATHINDEX + strlen(&writeBuffer[PROXY_PATHINDEX]);
+        robust_ftruncate(conchFile->h, writeSize);
+        rc = unixWrite((sqlite3_file *)conchFile, writeBuffer, writeSize, 0);
+        full_fsync(conchFile->h,0,0);
+        /* If we created a new conch file (not just updated the contents of a
+         ** valid conch file), try to match the permissions of the database
+         */
+        if( rc==SQLITE_OK && createConch ){
+          struct stat buf;
+          int err = osFstat(pFile->h, &buf);
+          if( err==0 ){
+            mode_t cmode = buf.st_mode&(S_IRUSR|S_IWUSR | S_IRGRP|S_IWGRP |
+                                        S_IROTH|S_IWOTH);
+            /* try to match the database file R/W permissions, ignore failure */
+#ifndef SQLITE_PROXY_DEBUG
+            osFchmod(conchFile->h, cmode);
+#else
+            do{
+              rc = osFchmod(conchFile->h, cmode);
+            }while( rc==(-1) && errno==EINTR );
+            if( rc!=0 ){
+              int code = errno;
+              fprintf(stderr, "fchmod %o FAILED with %d %s\n",
+                      cmode, code, strerror(code));
+            } else {
+              fprintf(stderr, "fchmod %o SUCCEDED\n",cmode);
+            }
+          }else{
+            int code = errno;
+            fprintf(stderr, "STAT FAILED[%d] with %d %s\n",
+                    err, code, strerror(code));
+#endif
+          }
+        }
+      }
+      conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
+    
+    end_takeconch:
+      OSTRACE(("TRANSPROXY: CLOSE  %d\n", pFile->h));
+      if( rc==SQLITE_OK && pFile->openFlags ){
+        int fd;
+        if( pFile->h>=0 ){
+          robust_close(pFile, pFile->h, __LINE__);
+        }
+        pFile->h = -1;
+        fd = robust_open(pCtx->dbPath, pFile->openFlags, 0);
+        OSTRACE(("TRANSPROXY: OPEN  %d\n", fd));
+        if( fd>=0 ){
+          pFile->h = fd;
+        }else{
+          rc=SQLITE_CANTOPEN_BKPT; /* SQLITE_BUSY? proxyTakeConch called
+           during locking */
+        }
+      }
+      if( rc==SQLITE_OK && !pCtx->lockProxy ){
+        char *path = tempLockPath ? tempLockPath : pCtx->lockProxyPath;
+        rc = proxyCreateUnixFile(path, &pCtx->lockProxy, 1);
+        if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM && tryOldLockPath ){
+          /* we couldn't create the proxy lock file with the old lock file path
+           ** so try again via auto-naming
+           */
+          forceNewLockPath = 1;
+          tryOldLockPath = 0;
+          continue; /* go back to the do {} while start point, try again */
+        }
+      }
+      if( rc==SQLITE_OK ){
+        /* Need to make a copy of path if we extracted the value
+         ** from the conch file or the path was allocated on the stack
+         */
+        if( tempLockPath ){
+          pCtx->lockProxyPath = sqlite3DbStrDup(0, tempLockPath);
+          if( !pCtx->lockProxyPath ){
+            rc = SQLITE_NOMEM_BKPT;
+          }
+        }
+      }
+      if( rc==SQLITE_OK ){
+        pCtx->conchHeld = 1;
+      
+        if( pCtx->lockProxy->pMethod == &afpIoMethods ){
+          afpLockingContext *afpCtx;
+          afpCtx = (afpLockingContext *)pCtx->lockProxy->lockingContext;
+          afpCtx->dbPath = pCtx->lockProxyPath;
+        }
+      } else {
+        conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
+      }
+      OSTRACE(("TAKECONCH  %d %s\n", conchFile->h,
+               rc==SQLITE_OK?"ok":"failed"));
+      return rc;
+    } while (1); /* in case we need to retry the :auto: lock file -
+                 ** we should never get here except via the 'continue' call. */
+  }
+}
+
+/*
+** If pFile holds a lock on a conch file, then release that lock.
+*/
+static int proxyReleaseConch(unixFile *pFile){
+  int rc = SQLITE_OK;         /* Subroutine return code */
+  proxyLockingContext *pCtx;  /* The locking context for the proxy lock */
+  unixFile *conchFile;        /* Name of the conch file */
+
+  pCtx = (proxyLockingContext *)pFile->lockingContext;
+  conchFile = pCtx->conchFile;
+  OSTRACE(("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
+           (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"),
+           osGetpid(0)));
+  if( pCtx->conchHeld>0 ){
+    rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
+  }
+  pCtx->conchHeld = 0;
+  OSTRACE(("RELEASECONCH  %d %s\n", conchFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
+  return rc;
+}
+
+/*
+** Given the name of a database file, compute the name of its conch file.
+** Store the conch filename in memory obtained from sqlite3_malloc64().
+** Make *pConchPath point to the new name.  Return SQLITE_OK on success
+** or SQLITE_NOMEM if unable to obtain memory.
+**
+** The caller is responsible for ensuring that the allocated memory
+** space is eventually freed.
+**
+** *pConchPath is set to NULL if a memory allocation error occurs.
+*/
+static int proxyCreateConchPathname(char *dbPath, char **pConchPath){
+  int i;                        /* Loop counter */
+  int len = (int)strlen(dbPath); /* Length of database filename - dbPath */
+  char *conchPath;              /* buffer in which to construct conch name */
+
+  /* Allocate space for the conch filename and initialize the name to
+  ** the name of the original database file. */
+  *pConchPath = conchPath = (char *)sqlite3_malloc64(len + 8);
+  if( conchPath==0 ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  memcpy(conchPath, dbPath, len+1);
+
+  /* now insert a "." before the last / character */
+  for( i=(len-1); i>=0; i-- ){
+    if( conchPath[i]=='/' ){
+      i++;
+      break;
+    }
+  }
+  conchPath[i]='.';
+  while ( i<len ){
+    conchPath[i+1]=dbPath[i];
+    i++;
+  }
+
+  /* append the "-conch" suffix to the file */
+  memcpy(&conchPath[i+1], "-conch", 7);
+  assert( (int)strlen(conchPath) == len+7 );
+
+  return SQLITE_OK;
+}
+
+
+/* Takes a fully configured proxy locking-style unix file and switches
+** the local lock file path
+*/
+static int switchLockProxyPath(unixFile *pFile, const char *path) {
+  proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
+  char *oldPath = pCtx->lockProxyPath;
+  int rc = SQLITE_OK;
+
+  if( pFile->eFileLock!=NO_LOCK ){
+    return SQLITE_BUSY;
+  }
+
+  /* nothing to do if the path is NULL, :auto: or matches the existing path */
+  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ||
+    (oldPath && !strncmp(oldPath, path, MAXPATHLEN)) ){
+    return SQLITE_OK;
+  }else{
+    unixFile *lockProxy = pCtx->lockProxy;
+    pCtx->lockProxy=NULL;
+    pCtx->conchHeld = 0;
+    if( lockProxy!=NULL ){
+      rc=lockProxy->pMethod->xClose((sqlite3_file *)lockProxy);
+      if( rc ) return rc;
+      sqlite3_free(lockProxy);
+    }
+    sqlite3_free(oldPath);
+    pCtx->lockProxyPath = sqlite3DbStrDup(0, path);
+  }
+
+  return rc;
+}
+
+/*
+** pFile is a file that has been opened by a prior xOpen call.  dbPath
+** is a string buffer at least MAXPATHLEN+1 characters in size.
+**
+** This routine find the filename associated with pFile and writes it
+** int dbPath.
+*/
+static int proxyGetDbPathForUnixFile(unixFile *pFile, char *dbPath){
+#if defined(__APPLE__)
+  if( pFile->pMethod == &afpIoMethods ){
+    /* afp style keeps a reference to the db path in the filePath field
+    ** of the struct */
+    assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
+    strlcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath,
+            MAXPATHLEN);
+  } else
+#endif
+  if( pFile->pMethod == &dotlockIoMethods ){
+    /* dot lock style uses the locking context to store the dot lock
+    ** file path */
+    int len = strlen((char *)pFile->lockingContext) - strlen(DOTLOCK_SUFFIX);
+    memcpy(dbPath, (char *)pFile->lockingContext, len + 1);
+  }else{
+    /* all other styles use the locking context to store the db file path */
+    assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
+    strlcpy(dbPath, (char *)pFile->lockingContext, MAXPATHLEN);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Takes an already filled in unix file and alters it so all file locking
+** will be performed on the local proxy lock file.  The following fields
+** are preserved in the locking context so that they can be restored and
+** the unix structure properly cleaned up at close time:
+**  ->lockingContext
+**  ->pMethod
+*/
+static int proxyTransformUnixFile(unixFile *pFile, const char *path) {
+  proxyLockingContext *pCtx;
+  char dbPath[MAXPATHLEN+1];       /* Name of the database file */
+  char *lockPath=NULL;
+  int rc = SQLITE_OK;
+
+  if( pFile->eFileLock!=NO_LOCK ){
+    return SQLITE_BUSY;
+  }
+  proxyGetDbPathForUnixFile(pFile, dbPath);
+  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ){
+    lockPath=NULL;
+  }else{
+    lockPath=(char *)path;
+  }
+
+  OSTRACE(("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
+           (lockPath ? lockPath : ":auto:"), osGetpid(0)));
+
+  pCtx = sqlite3_malloc64( sizeof(*pCtx) );
+  if( pCtx==0 ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  memset(pCtx, 0, sizeof(*pCtx));
+
+  rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath);
+  if( rc==SQLITE_OK ){
+    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile, 0);
+    if( rc==SQLITE_CANTOPEN && ((pFile->openFlags&O_RDWR) == 0) ){
+      /* if (a) the open flags are not O_RDWR, (b) the conch isn't there, and
+      ** (c) the file system is read-only, then enable no-locking access.
+      ** Ugh, since O_RDONLY==0x0000 we test for !O_RDWR since unixOpen asserts
+      ** that openFlags will have only one of O_RDONLY or O_RDWR.
+      */
+      struct statfs fsInfo;
+      struct stat conchInfo;
+      int goLockless = 0;
+
+      if( osStat(pCtx->conchFilePath, &conchInfo) == -1 ) {
+        int err = errno;
+        if( (err==ENOENT) && (statfs(dbPath, &fsInfo) != -1) ){
+          goLockless = (fsInfo.f_flags&MNT_RDONLY) == MNT_RDONLY;
+        }
+      }
+      if( goLockless ){
+        pCtx->conchHeld = -1; /* read only FS/ lockless */
+        rc = SQLITE_OK;
+      }
+    }
+  }
+  if( rc==SQLITE_OK && lockPath ){
+    pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
+  }
+
+  if( rc==SQLITE_OK ){
+    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
+    if( pCtx->dbPath==NULL ){
+      rc = SQLITE_NOMEM_BKPT;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    /* all memory is allocated, proxys are created and assigned,
+    ** switch the locking context and pMethod then return.
+    */
+    pCtx->oldLockingContext = pFile->lockingContext;
+    pFile->lockingContext = pCtx;
+    pCtx->pOldMethod = pFile->pMethod;
+    pFile->pMethod = &proxyIoMethods;
+  }else{
+    if( pCtx->conchFile ){
+      pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
+      sqlite3_free(pCtx->conchFile);
+    }
+    sqlite3DbFree(0, pCtx->lockProxyPath);
+    sqlite3_free(pCtx->conchFilePath);
+    sqlite3_free(pCtx);
+  }
+  OSTRACE(("TRANSPROXY  %d %s\n", pFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
+  return rc;
+}
+
+
+/*
+** This routine handles sqlite3_file_control() calls that are specific
+** to proxy locking.
+*/
+static int proxyFileControl(sqlite3_file *id, int op, void *pArg){
+  switch( op ){
+    case SQLITE_FCNTL_GET_LOCKPROXYFILE: {
+      unixFile *pFile = (unixFile*)id;
+      if( pFile->pMethod == &proxyIoMethods ){
+        proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
+        proxyTakeConch(pFile);
+        if( pCtx->lockProxyPath ){
+          *(const char **)pArg = pCtx->lockProxyPath;
+        }else{
+          *(const char **)pArg = ":auto: (not held)";
+        }
+      } else {
+        *(const char **)pArg = NULL;
+      }
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SET_LOCKPROXYFILE: {
+      unixFile *pFile = (unixFile*)id;
+      int rc = SQLITE_OK;
+      int isProxyStyle = (pFile->pMethod == &proxyIoMethods);
+      if( pArg==NULL || (const char *)pArg==0 ){
+        if( isProxyStyle ){
+          /* turn off proxy locking - not supported.  If support is added for
+          ** switching proxy locking mode off then it will need to fail if
+          ** the journal mode is WAL mode.
+          */
+          rc = SQLITE_ERROR /*SQLITE_PROTOCOL? SQLITE_MISUSE?*/;
+        }else{
+          /* turn off proxy locking - already off - NOOP */
+          rc = SQLITE_OK;
+        }
+      }else{
+        const char *proxyPath = (const char *)pArg;
+        if( isProxyStyle ){
+          proxyLockingContext *pCtx =
+            (proxyLockingContext*)pFile->lockingContext;
+          if( !strcmp(pArg, ":auto:")
+           || (pCtx->lockProxyPath &&
+               !strncmp(pCtx->lockProxyPath, proxyPath, MAXPATHLEN))
+          ){
+            rc = SQLITE_OK;
+          }else{
+            rc = switchLockProxyPath(pFile, proxyPath);
+          }
+        }else{
+          /* turn on proxy file locking */
+          rc = proxyTransformUnixFile(pFile, proxyPath);
+        }
+      }
+      return rc;
+    }
+    default: {
+      assert( 0 );  /* The call assures that only valid opcodes are sent */
+    }
+  }
+  /*NOTREACHED*/ assert(0);
+  return SQLITE_ERROR;
+}
+
+/*
+** Within this division (the proxying locking implementation) the procedures
+** above this point are all utilities.  The lock-related methods of the
+** proxy-locking sqlite3_io_method object follow.
+*/
+
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int proxyCheckReservedLock(sqlite3_file *id, int *pResOut) {
+  unixFile *pFile = (unixFile*)id;
+  int rc = proxyTakeConch(pFile);
+  if( rc==SQLITE_OK ){
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
+    }else{ /* conchHeld < 0 is lockless */
+      pResOut=0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int proxyLock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  int rc = proxyTakeConch(pFile);
+  if( rc==SQLITE_OK ){
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xLock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
+  }
+  return rc;
+}
+
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int proxyUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  int rc = proxyTakeConch(pFile);
+  if( rc==SQLITE_OK ){
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
+  }
+  return rc;
+}
+
+/*
+** Close a file that uses proxy locks.
+*/
+static int proxyClose(sqlite3_file *id) {
+  if( ALWAYS(id) ){
+    unixFile *pFile = (unixFile*)id;
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    unixFile *lockProxy = pCtx->lockProxy;
+    unixFile *conchFile = pCtx->conchFile;
+    int rc = SQLITE_OK;
+
+    if( lockProxy ){
+      rc = lockProxy->pMethod->xUnlock((sqlite3_file*)lockProxy, NO_LOCK);
+      if( rc ) return rc;
+      rc = lockProxy->pMethod->xClose((sqlite3_file*)lockProxy);
+      if( rc ) return rc;
+      sqlite3_free(lockProxy);
+      pCtx->lockProxy = 0;
+    }
+    if( conchFile ){
+      if( pCtx->conchHeld ){
+        rc = proxyReleaseConch(pFile);
+        if( rc ) return rc;
+      }
+      rc = conchFile->pMethod->xClose((sqlite3_file*)conchFile);
+      if( rc ) return rc;
+      sqlite3_free(conchFile);
+    }
+    sqlite3DbFree(0, pCtx->lockProxyPath);
+    sqlite3_free(pCtx->conchFilePath);
+    sqlite3DbFree(0, pCtx->dbPath);
+    /* restore the original locking context and pMethod then close it */
+    pFile->lockingContext = pCtx->oldLockingContext;
+    pFile->pMethod = pCtx->pOldMethod;
+    sqlite3_free(pCtx);
+    return pFile->pMethod->xClose(id);
+  }
+  return SQLITE_OK;
+}
+
+
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The proxy locking style is intended for use with AFP filesystems.
+** And since AFP is only supported on MacOSX, the proxy locking is also
+** restricted to MacOSX.
+**
+**
+******************* End of the proxy lock implementation **********************
+******************************************************************************/
+
+/*
+** Initialize the operating system interface.
+**
+** This routine registers all VFS implementations for unix-like operating
+** systems.  This routine, and the sqlite3_os_end() routine that follows,
+** should be the only routines in this file that are visible from other
+** files.
+**
+** This routine is called once during SQLite initialization and by a
+** single thread.  The memory allocation and mutex subsystems have not
+** necessarily been initialized when this routine is called, and so they
+** should not be used.
+*/
+int sqlite3_os_init(void){
+  /*
+  ** The following macro defines an initializer for an sqlite3_vfs object.
+  ** The name of the VFS is NAME.  The pAppData is a pointer to a pointer
+  ** to the "finder" function.  (pAppData is a pointer to a pointer because
+  ** silly C90 rules prohibit a void* from being cast to a function pointer
+  ** and so we have to go through the intermediate pointer to avoid problems
+  ** when compiling with -pedantic-errors on GCC.)
+  **
+  ** The FINDER parameter to this macro is the name of the pointer to the
+  ** finder-function.  The finder-function returns a pointer to the
+  ** sqlite_io_methods object that implements the desired locking
+  ** behaviors.  See the division above that contains the IOMETHODS
+  ** macro for addition information on finder-functions.
+  **
+  ** Most finders simply return a pointer to a fixed sqlite3_io_methods
+  ** object.  But the "autolockIoFinder" available on MacOSX does a little
+  ** more than that; it looks at the filesystem type that hosts the
+  ** database file and tries to choose an locking method appropriate for
+  ** that filesystem time.
+  */
+  #define UNIXVFS(VFSNAME, FINDER) {                        \
+    3,                    /* iVersion */                    \
+    sizeof(unixFile),     /* szOsFile */                    \
+    MAX_PATHNAME,         /* mxPathname */                  \
+    0,                    /* pNext */                       \
+    VFSNAME,              /* zName */                       \
+    (void*)&FINDER,       /* pAppData */                    \
+    unixOpen,             /* xOpen */                       \
+    unixDelete,           /* xDelete */                     \
+    unixAccess,           /* xAccess */                     \
+    unixFullPathname,     /* xFullPathname */               \
+    unixDlOpen,           /* xDlOpen */                     \
+    unixDlError,          /* xDlError */                    \
+    unixDlSym,            /* xDlSym */                      \
+    unixDlClose,          /* xDlClose */                    \
+    unixRandomness,       /* xRandomness */                 \
+    unixSleep,            /* xSleep */                      \
+    unixCurrentTime,      /* xCurrentTime */                \
+    unixGetLastError,     /* xGetLastError */               \
+    unixCurrentTimeInt64, /* xCurrentTimeInt64 */           \
+    unixSetSystemCall,    /* xSetSystemCall */              \
+    unixGetSystemCall,    /* xGetSystemCall */              \
+    unixNextSystemCall,   /* xNextSystemCall */             \
+  }
+
+  /*
+  ** All default VFSes for unix are contained in the following array.
+  **
+  ** Note that the sqlite3_vfs.pNext field of the VFS object is modified
+  ** by the SQLite core when the VFS is registered.  So the following
+  ** array cannot be const.
+  */
+  static sqlite3_vfs aVfs[] = {
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+    UNIXVFS("unix",          autolockIoFinder ),
+#elif OS_VXWORKS
+    UNIXVFS("unix",          vxworksIoFinder ),
+#else
+    UNIXVFS("unix",          posixIoFinder ),
+#endif
+    UNIXVFS("unix-none",     nolockIoFinder ),
+    UNIXVFS("unix-dotfile",  dotlockIoFinder ),
+    UNIXVFS("unix-excl",     posixIoFinder ),
+#if OS_VXWORKS
+    UNIXVFS("unix-namedsem", semIoFinder ),
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE || OS_VXWORKS
+    UNIXVFS("unix-posix",    posixIoFinder ),
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE
+    UNIXVFS("unix-flock",    flockIoFinder ),
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+    UNIXVFS("unix-afp",      afpIoFinder ),
+    UNIXVFS("unix-nfs",      nfsIoFinder ),
+    UNIXVFS("unix-proxy",    proxyIoFinder ),
+#endif
+  };
+  unsigned int i;          /* Loop counter */
+
+  /* Double-check that the aSyscall[] array has been constructed
+  ** correctly.  See ticket [bb3a86e890c8e96ab] */
+  assert( ArraySize(aSyscall)==29 );
+
+  /* Register all VFSes defined in the aVfs[] array */
+  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
+#ifdef SQLITE_DEFAULT_UNIX_VFS
+    sqlite3_vfs_register(&aVfs[i],
+           0==strcmp(aVfs[i].zName,SQLITE_DEFAULT_UNIX_VFS));
+#else
+    sqlite3_vfs_register(&aVfs[i], i==0);
+#endif
+  }
+#ifdef SQLITE_OS_KV_OPTIONAL
+  sqlite3KvvfsInit();
+#endif
+  unixBigLock = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1);
+
+#ifndef SQLITE_OMIT_WAL
+  /* Validate lock assumptions */
+  assert( SQLITE_SHM_NLOCK==8 );  /* Number of available locks */
+  assert( UNIX_SHM_BASE==120  );  /* Start of locking area */
+  /* Locks:
+  **    WRITE       UNIX_SHM_BASE      120
+  **    CKPT        UNIX_SHM_BASE+1    121
+  **    RECOVER     UNIX_SHM_BASE+2    122
+  **    READ-0      UNIX_SHM_BASE+3    123
+  **    READ-1      UNIX_SHM_BASE+4    124
+  **    READ-2      UNIX_SHM_BASE+5    125
+  **    READ-3      UNIX_SHM_BASE+6    126
+  **    READ-4      UNIX_SHM_BASE+7    127
+  **    DMS         UNIX_SHM_BASE+8    128
+  */
+  assert( UNIX_SHM_DMS==128   );  /* Byte offset of the deadman-switch */
+#endif
+
+  /* Initialize temp file dir array. */
+  unixTempFileInit();
+
+  return SQLITE_OK;
+}
+
+/*
+** Shutdown the operating system interface.
+**
+** Some operating systems might need to do some cleanup in this routine,
+** to release dynamically allocated objects.  But not on unix.
+** This routine is a no-op for unix.
+*/
+int sqlite3_os_end(void){
+  unixBigLock = 0;
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_OS_UNIX */
diff --git a/src/os_win.c b/src/os_win.c
new file mode 100644
index 0000000..442c108
--- /dev/null
+++ b/src/os_win.c
@@ -0,0 +1,6211 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that is specific to Windows.
+*/
+#include "sqliteInt.h"
+#if SQLITE_OS_WIN               /* This file is used for Windows only */
+
+/*
+** Include code that is common to all os_*.c files
+*/
+#include "os_common.h"
+
+/*
+** Include the header file for the Windows VFS.
+*/
+#include "os_win.h"
+
+/*
+** Compiling and using WAL mode requires several APIs that are only
+** available in Windows platforms based on the NT kernel.
+*/
+#if !SQLITE_OS_WINNT && !defined(SQLITE_OMIT_WAL)
+#  error "WAL mode requires support from the Windows NT kernel, compile\
+ with SQLITE_OMIT_WAL."
+#endif
+
+#if !SQLITE_OS_WINNT && SQLITE_MAX_MMAP_SIZE>0
+#  error "Memory mapped files require support from the Windows NT kernel,\
+ compile with SQLITE_MAX_MMAP_SIZE=0."
+#endif
+
+/*
+** Are most of the Win32 ANSI APIs available (i.e. with certain exceptions
+** based on the sub-platform)?
+*/
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && !defined(SQLITE_WIN32_NO_ANSI)
+#  define SQLITE_WIN32_HAS_ANSI
+#endif
+
+/*
+** Are most of the Win32 Unicode APIs available (i.e. with certain exceptions
+** based on the sub-platform)?
+*/
+#if (SQLITE_OS_WINCE || SQLITE_OS_WINNT || SQLITE_OS_WINRT) && \
+    !defined(SQLITE_WIN32_NO_WIDE)
+#  define SQLITE_WIN32_HAS_WIDE
+#endif
+
+/*
+** Make sure at least one set of Win32 APIs is available.
+*/
+#if !defined(SQLITE_WIN32_HAS_ANSI) && !defined(SQLITE_WIN32_HAS_WIDE)
+#  error "At least one of SQLITE_WIN32_HAS_ANSI and SQLITE_WIN32_HAS_WIDE\
+ must be defined."
+#endif
+
+/*
+** Define the required Windows SDK version constants if they are not
+** already available.
+*/
+#ifndef NTDDI_WIN8
+#  define NTDDI_WIN8                        0x06020000
+#endif
+
+#ifndef NTDDI_WINBLUE
+#  define NTDDI_WINBLUE                     0x06030000
+#endif
+
+#ifndef NTDDI_WINTHRESHOLD
+#  define NTDDI_WINTHRESHOLD                0x06040000
+#endif
+
+/*
+** Check to see if the GetVersionEx[AW] functions are deprecated on the
+** target system.  GetVersionEx was first deprecated in Win8.1.
+*/
+#ifndef SQLITE_WIN32_GETVERSIONEX
+#  if defined(NTDDI_VERSION) && NTDDI_VERSION >= NTDDI_WINBLUE
+#    define SQLITE_WIN32_GETVERSIONEX   0   /* GetVersionEx() is deprecated */
+#  else
+#    define SQLITE_WIN32_GETVERSIONEX   1   /* GetVersionEx() is current */
+#  endif
+#endif
+
+/*
+** Check to see if the CreateFileMappingA function is supported on the
+** target system.  It is unavailable when using "mincore.lib" on Win10.
+** When compiling for Windows 10, always assume "mincore.lib" is in use.
+*/
+#ifndef SQLITE_WIN32_CREATEFILEMAPPINGA
+#  if defined(NTDDI_VERSION) && NTDDI_VERSION >= NTDDI_WINTHRESHOLD
+#    define SQLITE_WIN32_CREATEFILEMAPPINGA   0
+#  else
+#    define SQLITE_WIN32_CREATEFILEMAPPINGA   1
+#  endif
+#endif
+
+/*
+** This constant should already be defined (in the "WinDef.h" SDK file).
+*/
+#ifndef MAX_PATH
+#  define MAX_PATH                      (260)
+#endif
+
+/*
+** Maximum pathname length (in chars) for Win32.  This should normally be
+** MAX_PATH.
+*/
+#ifndef SQLITE_WIN32_MAX_PATH_CHARS
+#  define SQLITE_WIN32_MAX_PATH_CHARS   (MAX_PATH)
+#endif
+
+/*
+** This constant should already be defined (in the "WinNT.h" SDK file).
+*/
+#ifndef UNICODE_STRING_MAX_CHARS
+#  define UNICODE_STRING_MAX_CHARS      (32767)
+#endif
+
+/*
+** Maximum pathname length (in chars) for WinNT.  This should normally be
+** UNICODE_STRING_MAX_CHARS.
+*/
+#ifndef SQLITE_WINNT_MAX_PATH_CHARS
+#  define SQLITE_WINNT_MAX_PATH_CHARS   (UNICODE_STRING_MAX_CHARS)
+#endif
+
+/*
+** Maximum pathname length (in bytes) for Win32.  The MAX_PATH macro is in
+** characters, so we allocate 4 bytes per character assuming worst-case of
+** 4-bytes-per-character for UTF8.
+*/
+#ifndef SQLITE_WIN32_MAX_PATH_BYTES
+#  define SQLITE_WIN32_MAX_PATH_BYTES   (SQLITE_WIN32_MAX_PATH_CHARS*4)
+#endif
+
+/*
+** Maximum pathname length (in bytes) for WinNT.  This should normally be
+** UNICODE_STRING_MAX_CHARS * sizeof(WCHAR).
+*/
+#ifndef SQLITE_WINNT_MAX_PATH_BYTES
+#  define SQLITE_WINNT_MAX_PATH_BYTES   \
+                            (sizeof(WCHAR) * SQLITE_WINNT_MAX_PATH_CHARS)
+#endif
+
+/*
+** Maximum error message length (in chars) for WinRT.
+*/
+#ifndef SQLITE_WIN32_MAX_ERRMSG_CHARS
+#  define SQLITE_WIN32_MAX_ERRMSG_CHARS (1024)
+#endif
+
+/*
+** Returns non-zero if the character should be treated as a directory
+** separator.
+*/
+#ifndef winIsDirSep
+#  define winIsDirSep(a)                (((a) == '/') || ((a) == '\\'))
+#endif
+
+/*
+** This macro is used when a local variable is set to a value that is
+** [sometimes] not used by the code (e.g. via conditional compilation).
+*/
+#ifndef UNUSED_VARIABLE_VALUE
+#  define UNUSED_VARIABLE_VALUE(x)      (void)(x)
+#endif
+
+/*
+** Returns the character that should be used as the directory separator.
+*/
+#ifndef winGetDirSep
+#  define winGetDirSep()                '\\'
+#endif
+
+/*
+** Do we need to manually define the Win32 file mapping APIs for use with WAL
+** mode or memory mapped files (e.g. these APIs are available in the Windows
+** CE SDK; however, they are not present in the header file)?
+*/
+#if SQLITE_WIN32_FILEMAPPING_API && \
+        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
+/*
+** Two of the file mapping APIs are different under WinRT.  Figure out which
+** set we need.
+*/
+#if SQLITE_OS_WINRT
+WINBASEAPI HANDLE WINAPI CreateFileMappingFromApp(HANDLE, \
+        LPSECURITY_ATTRIBUTES, ULONG, ULONG64, LPCWSTR);
+
+WINBASEAPI LPVOID WINAPI MapViewOfFileFromApp(HANDLE, ULONG, ULONG64, SIZE_T);
+#else
+#if defined(SQLITE_WIN32_HAS_ANSI)
+WINBASEAPI HANDLE WINAPI CreateFileMappingA(HANDLE, LPSECURITY_ATTRIBUTES, \
+        DWORD, DWORD, DWORD, LPCSTR);
+#endif /* defined(SQLITE_WIN32_HAS_ANSI) */
+
+#if defined(SQLITE_WIN32_HAS_WIDE)
+WINBASEAPI HANDLE WINAPI CreateFileMappingW(HANDLE, LPSECURITY_ATTRIBUTES, \
+        DWORD, DWORD, DWORD, LPCWSTR);
+#endif /* defined(SQLITE_WIN32_HAS_WIDE) */
+
+WINBASEAPI LPVOID WINAPI MapViewOfFile(HANDLE, DWORD, DWORD, DWORD, SIZE_T);
+#endif /* SQLITE_OS_WINRT */
+
+/*
+** These file mapping APIs are common to both Win32 and WinRT.
+*/
+
+WINBASEAPI BOOL WINAPI FlushViewOfFile(LPCVOID, SIZE_T);
+WINBASEAPI BOOL WINAPI UnmapViewOfFile(LPCVOID);
+#endif /* SQLITE_WIN32_FILEMAPPING_API */
+
+/*
+** Some Microsoft compilers lack this definition.
+*/
+#ifndef INVALID_FILE_ATTRIBUTES
+# define INVALID_FILE_ATTRIBUTES ((DWORD)-1)
+#endif
+
+#ifndef FILE_FLAG_MASK
+# define FILE_FLAG_MASK          (0xFF3C0000)
+#endif
+
+#ifndef FILE_ATTRIBUTE_MASK
+# define FILE_ATTRIBUTE_MASK     (0x0003FFF7)
+#endif
+
+#ifndef SQLITE_OMIT_WAL
+/* Forward references to structures used for WAL */
+typedef struct winShm winShm;           /* A connection to shared-memory */
+typedef struct winShmNode winShmNode;   /* A region of shared-memory */
+#endif
+
+/*
+** WinCE lacks native support for file locking so we have to fake it
+** with some code of our own.
+*/
+#if SQLITE_OS_WINCE
+typedef struct winceLock {
+  int nReaders;       /* Number of reader locks obtained */
+  BOOL bPending;      /* Indicates a pending lock has been obtained */
+  BOOL bReserved;     /* Indicates a reserved lock has been obtained */
+  BOOL bExclusive;    /* Indicates an exclusive lock has been obtained */
+} winceLock;
+#endif
+
+/*
+** The winFile structure is a subclass of sqlite3_file* specific to the win32
+** portability layer.
+*/
+typedef struct winFile winFile;
+struct winFile {
+  const sqlite3_io_methods *pMethod; /*** Must be first ***/
+  sqlite3_vfs *pVfs;      /* The VFS used to open this file */
+  HANDLE h;               /* Handle for accessing the file */
+  u8 locktype;            /* Type of lock currently held on this file */
+  short sharedLockByte;   /* Randomly chosen byte used as a shared lock */
+  u8 ctrlFlags;           /* Flags.  See WINFILE_* below */
+  DWORD lastErrno;        /* The Windows errno from the last I/O error */
+#ifndef SQLITE_OMIT_WAL
+  winShm *pShm;           /* Instance of shared memory on this file */
+#endif
+  const char *zPath;      /* Full pathname of this file */
+  int szChunk;            /* Chunk size configured by FCNTL_CHUNK_SIZE */
+#if SQLITE_OS_WINCE
+  LPWSTR zDeleteOnClose;  /* Name of file to delete when closing */
+  HANDLE hMutex;          /* Mutex used to control access to shared lock */
+  HANDLE hShared;         /* Shared memory segment used for locking */
+  winceLock local;        /* Locks obtained by this instance of winFile */
+  winceLock *shared;      /* Global shared lock memory for the file  */
+#endif
+#if SQLITE_MAX_MMAP_SIZE>0
+  int nFetchOut;                /* Number of outstanding xFetch references */
+  HANDLE hMap;                  /* Handle for accessing memory mapping */
+  void *pMapRegion;             /* Area memory mapped */
+  sqlite3_int64 mmapSize;       /* Size of mapped region */
+  sqlite3_int64 mmapSizeMax;    /* Configured FCNTL_MMAP_SIZE value */
+#endif
+};
+
+/*
+** The winVfsAppData structure is used for the pAppData member for all of the
+** Win32 VFS variants.
+*/
+typedef struct winVfsAppData winVfsAppData;
+struct winVfsAppData {
+  const sqlite3_io_methods *pMethod; /* The file I/O methods to use. */
+  void *pAppData;                    /* The extra pAppData, if any. */
+  BOOL bNoLock;                      /* Non-zero if locking is disabled. */
+};
+
+/*
+** Allowed values for winFile.ctrlFlags
+*/
+#define WINFILE_RDONLY          0x02   /* Connection is read only */
+#define WINFILE_PERSIST_WAL     0x04   /* Persistent WAL mode */
+#define WINFILE_PSOW            0x10   /* SQLITE_IOCAP_POWERSAFE_OVERWRITE */
+
+/*
+ * The size of the buffer used by sqlite3_win32_write_debug().
+ */
+#ifndef SQLITE_WIN32_DBG_BUF_SIZE
+#  define SQLITE_WIN32_DBG_BUF_SIZE   ((int)(4096-sizeof(DWORD)))
+#endif
+
+/*
+ * If compiled with SQLITE_WIN32_MALLOC on Windows, we will use the
+ * various Win32 API heap functions instead of our own.
+ */
+#ifdef SQLITE_WIN32_MALLOC
+
+/*
+ * If this is non-zero, an isolated heap will be created by the native Win32
+ * allocator subsystem; otherwise, the default process heap will be used.  This
+ * setting has no effect when compiling for WinRT.  By default, this is enabled
+ * and an isolated heap will be created to store all allocated data.
+ *
+ ******************************************************************************
+ * WARNING: It is important to note that when this setting is non-zero and the
+ *          winMemShutdown function is called (e.g. by the sqlite3_shutdown
+ *          function), all data that was allocated using the isolated heap will
+ *          be freed immediately and any attempt to access any of that freed
+ *          data will almost certainly result in an immediate access violation.
+ ******************************************************************************
+ */
+#ifndef SQLITE_WIN32_HEAP_CREATE
+#  define SQLITE_WIN32_HEAP_CREATE        (TRUE)
+#endif
+
+/*
+ * This is the maximum possible initial size of the Win32-specific heap, in
+ * bytes.
+ */
+#ifndef SQLITE_WIN32_HEAP_MAX_INIT_SIZE
+#  define SQLITE_WIN32_HEAP_MAX_INIT_SIZE (4294967295U)
+#endif
+
+/*
+ * This is the extra space for the initial size of the Win32-specific heap,
+ * in bytes.  This value may be zero.
+ */
+#ifndef SQLITE_WIN32_HEAP_INIT_EXTRA
+#  define SQLITE_WIN32_HEAP_INIT_EXTRA  (4194304)
+#endif
+
+/*
+ * Calculate the maximum legal cache size, in pages, based on the maximum
+ * possible initial heap size and the default page size, setting aside the
+ * needed extra space.
+ */
+#ifndef SQLITE_WIN32_MAX_CACHE_SIZE
+#  define SQLITE_WIN32_MAX_CACHE_SIZE   (((SQLITE_WIN32_HEAP_MAX_INIT_SIZE) - \
+                                          (SQLITE_WIN32_HEAP_INIT_EXTRA)) / \
+                                         (SQLITE_DEFAULT_PAGE_SIZE))
+#endif
+
+/*
+ * This is cache size used in the calculation of the initial size of the
+ * Win32-specific heap.  It cannot be negative.
+ */
+#ifndef SQLITE_WIN32_CACHE_SIZE
+#  if SQLITE_DEFAULT_CACHE_SIZE>=0
+#    define SQLITE_WIN32_CACHE_SIZE     (SQLITE_DEFAULT_CACHE_SIZE)
+#  else
+#    define SQLITE_WIN32_CACHE_SIZE     (-(SQLITE_DEFAULT_CACHE_SIZE))
+#  endif
+#endif
+
+/*
+ * Make sure that the calculated cache size, in pages, cannot cause the
+ * initial size of the Win32-specific heap to exceed the maximum amount
+ * of memory that can be specified in the call to HeapCreate.
+ */
+#if SQLITE_WIN32_CACHE_SIZE>SQLITE_WIN32_MAX_CACHE_SIZE
+#  undef SQLITE_WIN32_CACHE_SIZE
+#  define SQLITE_WIN32_CACHE_SIZE       (2000)
+#endif
+
+/*
+ * The initial size of the Win32-specific heap.  This value may be zero.
+ */
+#ifndef SQLITE_WIN32_HEAP_INIT_SIZE
+#  define SQLITE_WIN32_HEAP_INIT_SIZE   ((SQLITE_WIN32_CACHE_SIZE) * \
+                                         (SQLITE_DEFAULT_PAGE_SIZE) + \
+                                         (SQLITE_WIN32_HEAP_INIT_EXTRA))
+#endif
+
+/*
+ * The maximum size of the Win32-specific heap.  This value may be zero.
+ */
+#ifndef SQLITE_WIN32_HEAP_MAX_SIZE
+#  define SQLITE_WIN32_HEAP_MAX_SIZE    (0)
+#endif
+
+/*
+ * The extra flags to use in calls to the Win32 heap APIs.  This value may be
+ * zero for the default behavior.
+ */
+#ifndef SQLITE_WIN32_HEAP_FLAGS
+#  define SQLITE_WIN32_HEAP_FLAGS       (0)
+#endif
+
+
+/*
+** The winMemData structure stores information required by the Win32-specific
+** sqlite3_mem_methods implementation.
+*/
+typedef struct winMemData winMemData;
+struct winMemData {
+#ifndef NDEBUG
+  u32 magic1;   /* Magic number to detect structure corruption. */
+#endif
+  HANDLE hHeap; /* The handle to our heap. */
+  BOOL bOwned;  /* Do we own the heap (i.e. destroy it on shutdown)? */
+#ifndef NDEBUG
+  u32 magic2;   /* Magic number to detect structure corruption. */
+#endif
+};
+
+#ifndef NDEBUG
+#define WINMEM_MAGIC1     0x42b2830b
+#define WINMEM_MAGIC2     0xbd4d7cf4
+#endif
+
+static struct winMemData win_mem_data = {
+#ifndef NDEBUG
+  WINMEM_MAGIC1,
+#endif
+  NULL, FALSE
+#ifndef NDEBUG
+  ,WINMEM_MAGIC2
+#endif
+};
+
+#ifndef NDEBUG
+#define winMemAssertMagic1() assert( win_mem_data.magic1==WINMEM_MAGIC1 )
+#define winMemAssertMagic2() assert( win_mem_data.magic2==WINMEM_MAGIC2 )
+#define winMemAssertMagic()  winMemAssertMagic1(); winMemAssertMagic2();
+#else
+#define winMemAssertMagic()
+#endif
+
+#define winMemGetDataPtr()  &win_mem_data
+#define winMemGetHeap()     win_mem_data.hHeap
+#define winMemGetOwned()    win_mem_data.bOwned
+
+static void *winMemMalloc(int nBytes);
+static void winMemFree(void *pPrior);
+static void *winMemRealloc(void *pPrior, int nBytes);
+static int winMemSize(void *p);
+static int winMemRoundup(int n);
+static int winMemInit(void *pAppData);
+static void winMemShutdown(void *pAppData);
+
+const sqlite3_mem_methods *sqlite3MemGetWin32(void);
+#endif /* SQLITE_WIN32_MALLOC */
+
+/*
+** The following variable is (normally) set once and never changes
+** thereafter.  It records whether the operating system is Win9x
+** or WinNT.
+**
+** 0:   Operating system unknown.
+** 1:   Operating system is Win9x.
+** 2:   Operating system is WinNT.
+**
+** In order to facilitate testing on a WinNT system, the test fixture
+** can manually set this value to 1 to emulate Win98 behavior.
+*/
+#ifdef SQLITE_TEST
+LONG SQLITE_WIN32_VOLATILE sqlite3_os_type = 0;
+#else
+static LONG SQLITE_WIN32_VOLATILE sqlite3_os_type = 0;
+#endif
+
+#ifndef SYSCALL
+#  define SYSCALL sqlite3_syscall_ptr
+#endif
+
+/*
+** This function is not available on Windows CE or WinRT.
+ */
+
+#if SQLITE_OS_WINCE || SQLITE_OS_WINRT
+#  define osAreFileApisANSI()       1
+#endif
+
+/*
+** Many system calls are accessed through pointer-to-functions so that
+** they may be overridden at runtime to facilitate fault injection during
+** testing and sandboxing.  The following array holds the names and pointers
+** to all overrideable system calls.
+*/
+static struct win_syscall {
+  const char *zName;            /* Name of the system call */
+  sqlite3_syscall_ptr pCurrent; /* Current value of the system call */
+  sqlite3_syscall_ptr pDefault; /* Default value */
+} aSyscall[] = {
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
+  { "AreFileApisANSI",         (SYSCALL)AreFileApisANSI,         0 },
+#else
+  { "AreFileApisANSI",         (SYSCALL)0,                       0 },
+#endif
+
+#ifndef osAreFileApisANSI
+#define osAreFileApisANSI ((BOOL(WINAPI*)(VOID))aSyscall[0].pCurrent)
+#endif
+
+#if SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_WIDE)
+  { "CharLowerW",              (SYSCALL)CharLowerW,              0 },
+#else
+  { "CharLowerW",              (SYSCALL)0,                       0 },
+#endif
+
+#define osCharLowerW ((LPWSTR(WINAPI*)(LPWSTR))aSyscall[1].pCurrent)
+
+#if SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_WIDE)
+  { "CharUpperW",              (SYSCALL)CharUpperW,              0 },
+#else
+  { "CharUpperW",              (SYSCALL)0,                       0 },
+#endif
+
+#define osCharUpperW ((LPWSTR(WINAPI*)(LPWSTR))aSyscall[2].pCurrent)
+
+  { "CloseHandle",             (SYSCALL)CloseHandle,             0 },
+
+#define osCloseHandle ((BOOL(WINAPI*)(HANDLE))aSyscall[3].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI)
+  { "CreateFileA",             (SYSCALL)CreateFileA,             0 },
+#else
+  { "CreateFileA",             (SYSCALL)0,                       0 },
+#endif
+
+#define osCreateFileA ((HANDLE(WINAPI*)(LPCSTR,DWORD,DWORD, \
+        LPSECURITY_ATTRIBUTES,DWORD,DWORD,HANDLE))aSyscall[4].pCurrent)
+
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
+  { "CreateFileW",             (SYSCALL)CreateFileW,             0 },
+#else
+  { "CreateFileW",             (SYSCALL)0,                       0 },
+#endif
+
+#define osCreateFileW ((HANDLE(WINAPI*)(LPCWSTR,DWORD,DWORD, \
+        LPSECURITY_ATTRIBUTES,DWORD,DWORD,HANDLE))aSyscall[5].pCurrent)
+
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_ANSI) && \
+        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0) && \
+        SQLITE_WIN32_CREATEFILEMAPPINGA
+  { "CreateFileMappingA",      (SYSCALL)CreateFileMappingA,      0 },
+#else
+  { "CreateFileMappingA",      (SYSCALL)0,                       0 },
+#endif
+
+#define osCreateFileMappingA ((HANDLE(WINAPI*)(HANDLE,LPSECURITY_ATTRIBUTES, \
+        DWORD,DWORD,DWORD,LPCSTR))aSyscall[6].pCurrent)
+
+#if SQLITE_OS_WINCE || (!SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE) && \
+        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0))
+  { "CreateFileMappingW",      (SYSCALL)CreateFileMappingW,      0 },
+#else
+  { "CreateFileMappingW",      (SYSCALL)0,                       0 },
+#endif
+
+#define osCreateFileMappingW ((HANDLE(WINAPI*)(HANDLE,LPSECURITY_ATTRIBUTES, \
+        DWORD,DWORD,DWORD,LPCWSTR))aSyscall[7].pCurrent)
+
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
+  { "CreateMutexW",            (SYSCALL)CreateMutexW,            0 },
+#else
+  { "CreateMutexW",            (SYSCALL)0,                       0 },
+#endif
+
+#define osCreateMutexW ((HANDLE(WINAPI*)(LPSECURITY_ATTRIBUTES,BOOL, \
+        LPCWSTR))aSyscall[8].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI)
+  { "DeleteFileA",             (SYSCALL)DeleteFileA,             0 },
+#else
+  { "DeleteFileA",             (SYSCALL)0,                       0 },
+#endif
+
+#define osDeleteFileA ((BOOL(WINAPI*)(LPCSTR))aSyscall[9].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  { "DeleteFileW",             (SYSCALL)DeleteFileW,             0 },
+#else
+  { "DeleteFileW",             (SYSCALL)0,                       0 },
+#endif
+
+#define osDeleteFileW ((BOOL(WINAPI*)(LPCWSTR))aSyscall[10].pCurrent)
+
+#if SQLITE_OS_WINCE
+  { "FileTimeToLocalFileTime", (SYSCALL)FileTimeToLocalFileTime, 0 },
+#else
+  { "FileTimeToLocalFileTime", (SYSCALL)0,                       0 },
+#endif
+
+#define osFileTimeToLocalFileTime ((BOOL(WINAPI*)(CONST FILETIME*, \
+        LPFILETIME))aSyscall[11].pCurrent)
+
+#if SQLITE_OS_WINCE
+  { "FileTimeToSystemTime",    (SYSCALL)FileTimeToSystemTime,    0 },
+#else
+  { "FileTimeToSystemTime",    (SYSCALL)0,                       0 },
+#endif
+
+#define osFileTimeToSystemTime ((BOOL(WINAPI*)(CONST FILETIME*, \
+        LPSYSTEMTIME))aSyscall[12].pCurrent)
+
+  { "FlushFileBuffers",        (SYSCALL)FlushFileBuffers,        0 },
+
+#define osFlushFileBuffers ((BOOL(WINAPI*)(HANDLE))aSyscall[13].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI)
+  { "FormatMessageA",          (SYSCALL)FormatMessageA,          0 },
+#else
+  { "FormatMessageA",          (SYSCALL)0,                       0 },
+#endif
+
+#define osFormatMessageA ((DWORD(WINAPI*)(DWORD,LPCVOID,DWORD,DWORD,LPSTR, \
+        DWORD,va_list*))aSyscall[14].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  { "FormatMessageW",          (SYSCALL)FormatMessageW,          0 },
+#else
+  { "FormatMessageW",          (SYSCALL)0,                       0 },
+#endif
+
+#define osFormatMessageW ((DWORD(WINAPI*)(DWORD,LPCVOID,DWORD,DWORD,LPWSTR, \
+        DWORD,va_list*))aSyscall[15].pCurrent)
+
+#if !defined(SQLITE_OMIT_LOAD_EXTENSION)
+  { "FreeLibrary",             (SYSCALL)FreeLibrary,             0 },
+#else
+  { "FreeLibrary",             (SYSCALL)0,                       0 },
+#endif
+
+#define osFreeLibrary ((BOOL(WINAPI*)(HMODULE))aSyscall[16].pCurrent)
+
+  { "GetCurrentProcessId",     (SYSCALL)GetCurrentProcessId,     0 },
+
+#define osGetCurrentProcessId ((DWORD(WINAPI*)(VOID))aSyscall[17].pCurrent)
+
+#if !SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_ANSI)
+  { "GetDiskFreeSpaceA",       (SYSCALL)GetDiskFreeSpaceA,       0 },
+#else
+  { "GetDiskFreeSpaceA",       (SYSCALL)0,                       0 },
+#endif
+
+#define osGetDiskFreeSpaceA ((BOOL(WINAPI*)(LPCSTR,LPDWORD,LPDWORD,LPDWORD, \
+        LPDWORD))aSyscall[18].pCurrent)
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
+  { "GetDiskFreeSpaceW",       (SYSCALL)GetDiskFreeSpaceW,       0 },
+#else
+  { "GetDiskFreeSpaceW",       (SYSCALL)0,                       0 },
+#endif
+
+#define osGetDiskFreeSpaceW ((BOOL(WINAPI*)(LPCWSTR,LPDWORD,LPDWORD,LPDWORD, \
+        LPDWORD))aSyscall[19].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI)
+  { "GetFileAttributesA",      (SYSCALL)GetFileAttributesA,      0 },
+#else
+  { "GetFileAttributesA",      (SYSCALL)0,                       0 },
+#endif
+
+#define osGetFileAttributesA ((DWORD(WINAPI*)(LPCSTR))aSyscall[20].pCurrent)
+
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
+  { "GetFileAttributesW",      (SYSCALL)GetFileAttributesW,      0 },
+#else
+  { "GetFileAttributesW",      (SYSCALL)0,                       0 },
+#endif
+
+#define osGetFileAttributesW ((DWORD(WINAPI*)(LPCWSTR))aSyscall[21].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  { "GetFileAttributesExW",    (SYSCALL)GetFileAttributesExW,    0 },
+#else
+  { "GetFileAttributesExW",    (SYSCALL)0,                       0 },
+#endif
+
+#define osGetFileAttributesExW ((BOOL(WINAPI*)(LPCWSTR,GET_FILEEX_INFO_LEVELS, \
+        LPVOID))aSyscall[22].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "GetFileSize",             (SYSCALL)GetFileSize,             0 },
+#else
+  { "GetFileSize",             (SYSCALL)0,                       0 },
+#endif
+
+#define osGetFileSize ((DWORD(WINAPI*)(HANDLE,LPDWORD))aSyscall[23].pCurrent)
+
+#if !SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_ANSI)
+  { "GetFullPathNameA",        (SYSCALL)GetFullPathNameA,        0 },
+#else
+  { "GetFullPathNameA",        (SYSCALL)0,                       0 },
+#endif
+
+#define osGetFullPathNameA ((DWORD(WINAPI*)(LPCSTR,DWORD,LPSTR, \
+        LPSTR*))aSyscall[24].pCurrent)
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
+  { "GetFullPathNameW",        (SYSCALL)GetFullPathNameW,        0 },
+#else
+  { "GetFullPathNameW",        (SYSCALL)0,                       0 },
+#endif
+
+#define osGetFullPathNameW ((DWORD(WINAPI*)(LPCWSTR,DWORD,LPWSTR, \
+        LPWSTR*))aSyscall[25].pCurrent)
+
+  { "GetLastError",            (SYSCALL)GetLastError,            0 },
+
+#define osGetLastError ((DWORD(WINAPI*)(VOID))aSyscall[26].pCurrent)
+
+#if !defined(SQLITE_OMIT_LOAD_EXTENSION)
+#if SQLITE_OS_WINCE
+  /* The GetProcAddressA() routine is only available on Windows CE. */
+  { "GetProcAddressA",         (SYSCALL)GetProcAddressA,         0 },
+#else
+  /* All other Windows platforms expect GetProcAddress() to take
+  ** an ANSI string regardless of the _UNICODE setting */
+  { "GetProcAddressA",         (SYSCALL)GetProcAddress,          0 },
+#endif
+#else
+  { "GetProcAddressA",         (SYSCALL)0,                       0 },
+#endif
+
+#define osGetProcAddressA ((FARPROC(WINAPI*)(HMODULE, \
+        LPCSTR))aSyscall[27].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "GetSystemInfo",           (SYSCALL)GetSystemInfo,           0 },
+#else
+  { "GetSystemInfo",           (SYSCALL)0,                       0 },
+#endif
+
+#define osGetSystemInfo ((VOID(WINAPI*)(LPSYSTEM_INFO))aSyscall[28].pCurrent)
+
+  { "GetSystemTime",           (SYSCALL)GetSystemTime,           0 },
+
+#define osGetSystemTime ((VOID(WINAPI*)(LPSYSTEMTIME))aSyscall[29].pCurrent)
+
+#if !SQLITE_OS_WINCE
+  { "GetSystemTimeAsFileTime", (SYSCALL)GetSystemTimeAsFileTime, 0 },
+#else
+  { "GetSystemTimeAsFileTime", (SYSCALL)0,                       0 },
+#endif
+
+#define osGetSystemTimeAsFileTime ((VOID(WINAPI*)( \
+        LPFILETIME))aSyscall[30].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI)
+  { "GetTempPathA",            (SYSCALL)GetTempPathA,            0 },
+#else
+  { "GetTempPathA",            (SYSCALL)0,                       0 },
+#endif
+
+#define osGetTempPathA ((DWORD(WINAPI*)(DWORD,LPSTR))aSyscall[31].pCurrent)
+
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
+  { "GetTempPathW",            (SYSCALL)GetTempPathW,            0 },
+#else
+  { "GetTempPathW",            (SYSCALL)0,                       0 },
+#endif
+
+#define osGetTempPathW ((DWORD(WINAPI*)(DWORD,LPWSTR))aSyscall[32].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "GetTickCount",            (SYSCALL)GetTickCount,            0 },
+#else
+  { "GetTickCount",            (SYSCALL)0,                       0 },
+#endif
+
+#define osGetTickCount ((DWORD(WINAPI*)(VOID))aSyscall[33].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI) && SQLITE_WIN32_GETVERSIONEX
+  { "GetVersionExA",           (SYSCALL)GetVersionExA,           0 },
+#else
+  { "GetVersionExA",           (SYSCALL)0,                       0 },
+#endif
+
+#define osGetVersionExA ((BOOL(WINAPI*)( \
+        LPOSVERSIONINFOA))aSyscall[34].pCurrent)
+
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE) && \
+        SQLITE_WIN32_GETVERSIONEX
+  { "GetVersionExW",           (SYSCALL)GetVersionExW,           0 },
+#else
+  { "GetVersionExW",           (SYSCALL)0,                       0 },
+#endif
+
+#define osGetVersionExW ((BOOL(WINAPI*)( \
+        LPOSVERSIONINFOW))aSyscall[35].pCurrent)
+
+  { "HeapAlloc",               (SYSCALL)HeapAlloc,               0 },
+
+#define osHeapAlloc ((LPVOID(WINAPI*)(HANDLE,DWORD, \
+        SIZE_T))aSyscall[36].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "HeapCreate",              (SYSCALL)HeapCreate,              0 },
+#else
+  { "HeapCreate",              (SYSCALL)0,                       0 },
+#endif
+
+#define osHeapCreate ((HANDLE(WINAPI*)(DWORD,SIZE_T, \
+        SIZE_T))aSyscall[37].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "HeapDestroy",             (SYSCALL)HeapDestroy,             0 },
+#else
+  { "HeapDestroy",             (SYSCALL)0,                       0 },
+#endif
+
+#define osHeapDestroy ((BOOL(WINAPI*)(HANDLE))aSyscall[38].pCurrent)
+
+  { "HeapFree",                (SYSCALL)HeapFree,                0 },
+
+#define osHeapFree ((BOOL(WINAPI*)(HANDLE,DWORD,LPVOID))aSyscall[39].pCurrent)
+
+  { "HeapReAlloc",             (SYSCALL)HeapReAlloc,             0 },
+
+#define osHeapReAlloc ((LPVOID(WINAPI*)(HANDLE,DWORD,LPVOID, \
+        SIZE_T))aSyscall[40].pCurrent)
+
+  { "HeapSize",                (SYSCALL)HeapSize,                0 },
+
+#define osHeapSize ((SIZE_T(WINAPI*)(HANDLE,DWORD, \
+        LPCVOID))aSyscall[41].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "HeapValidate",            (SYSCALL)HeapValidate,            0 },
+#else
+  { "HeapValidate",            (SYSCALL)0,                       0 },
+#endif
+
+#define osHeapValidate ((BOOL(WINAPI*)(HANDLE,DWORD, \
+        LPCVOID))aSyscall[42].pCurrent)
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
+  { "HeapCompact",             (SYSCALL)HeapCompact,             0 },
+#else
+  { "HeapCompact",             (SYSCALL)0,                       0 },
+#endif
+
+#define osHeapCompact ((UINT(WINAPI*)(HANDLE,DWORD))aSyscall[43].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI) && !defined(SQLITE_OMIT_LOAD_EXTENSION)
+  { "LoadLibraryA",            (SYSCALL)LoadLibraryA,            0 },
+#else
+  { "LoadLibraryA",            (SYSCALL)0,                       0 },
+#endif
+
+#define osLoadLibraryA ((HMODULE(WINAPI*)(LPCSTR))aSyscall[44].pCurrent)
+
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE) && \
+        !defined(SQLITE_OMIT_LOAD_EXTENSION)
+  { "LoadLibraryW",            (SYSCALL)LoadLibraryW,            0 },
+#else
+  { "LoadLibraryW",            (SYSCALL)0,                       0 },
+#endif
+
+#define osLoadLibraryW ((HMODULE(WINAPI*)(LPCWSTR))aSyscall[45].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "LocalFree",               (SYSCALL)LocalFree,               0 },
+#else
+  { "LocalFree",               (SYSCALL)0,                       0 },
+#endif
+
+#define osLocalFree ((HLOCAL(WINAPI*)(HLOCAL))aSyscall[46].pCurrent)
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
+  { "LockFile",                (SYSCALL)LockFile,                0 },
+#else
+  { "LockFile",                (SYSCALL)0,                       0 },
+#endif
+
+#ifndef osLockFile
+#define osLockFile ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
+        DWORD))aSyscall[47].pCurrent)
+#endif
+
+#if !SQLITE_OS_WINCE
+  { "LockFileEx",              (SYSCALL)LockFileEx,              0 },
+#else
+  { "LockFileEx",              (SYSCALL)0,                       0 },
+#endif
+
+#ifndef osLockFileEx
+#define osLockFileEx ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD,DWORD, \
+        LPOVERLAPPED))aSyscall[48].pCurrent)
+#endif
+
+#if SQLITE_OS_WINCE || (!SQLITE_OS_WINRT && \
+        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0))
+  { "MapViewOfFile",           (SYSCALL)MapViewOfFile,           0 },
+#else
+  { "MapViewOfFile",           (SYSCALL)0,                       0 },
+#endif
+
+#define osMapViewOfFile ((LPVOID(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
+        SIZE_T))aSyscall[49].pCurrent)
+
+  { "MultiByteToWideChar",     (SYSCALL)MultiByteToWideChar,     0 },
+
+#define osMultiByteToWideChar ((int(WINAPI*)(UINT,DWORD,LPCSTR,int,LPWSTR, \
+        int))aSyscall[50].pCurrent)
+
+  { "QueryPerformanceCounter", (SYSCALL)QueryPerformanceCounter, 0 },
+
+#define osQueryPerformanceCounter ((BOOL(WINAPI*)( \
+        LARGE_INTEGER*))aSyscall[51].pCurrent)
+
+  { "ReadFile",                (SYSCALL)ReadFile,                0 },
+
+#define osReadFile ((BOOL(WINAPI*)(HANDLE,LPVOID,DWORD,LPDWORD, \
+        LPOVERLAPPED))aSyscall[52].pCurrent)
+
+  { "SetEndOfFile",            (SYSCALL)SetEndOfFile,            0 },
+
+#define osSetEndOfFile ((BOOL(WINAPI*)(HANDLE))aSyscall[53].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "SetFilePointer",          (SYSCALL)SetFilePointer,          0 },
+#else
+  { "SetFilePointer",          (SYSCALL)0,                       0 },
+#endif
+
+#define osSetFilePointer ((DWORD(WINAPI*)(HANDLE,LONG,PLONG, \
+        DWORD))aSyscall[54].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "Sleep",                   (SYSCALL)Sleep,                   0 },
+#else
+  { "Sleep",                   (SYSCALL)0,                       0 },
+#endif
+
+#define osSleep ((VOID(WINAPI*)(DWORD))aSyscall[55].pCurrent)
+
+  { "SystemTimeToFileTime",    (SYSCALL)SystemTimeToFileTime,    0 },
+
+#define osSystemTimeToFileTime ((BOOL(WINAPI*)(CONST SYSTEMTIME*, \
+        LPFILETIME))aSyscall[56].pCurrent)
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
+  { "UnlockFile",              (SYSCALL)UnlockFile,              0 },
+#else
+  { "UnlockFile",              (SYSCALL)0,                       0 },
+#endif
+
+#ifndef osUnlockFile
+#define osUnlockFile ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
+        DWORD))aSyscall[57].pCurrent)
+#endif
+
+#if !SQLITE_OS_WINCE
+  { "UnlockFileEx",            (SYSCALL)UnlockFileEx,            0 },
+#else
+  { "UnlockFileEx",            (SYSCALL)0,                       0 },
+#endif
+
+#define osUnlockFileEx ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
+        LPOVERLAPPED))aSyscall[58].pCurrent)
+
+#if SQLITE_OS_WINCE || !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
+  { "UnmapViewOfFile",         (SYSCALL)UnmapViewOfFile,         0 },
+#else
+  { "UnmapViewOfFile",         (SYSCALL)0,                       0 },
+#endif
+
+#define osUnmapViewOfFile ((BOOL(WINAPI*)(LPCVOID))aSyscall[59].pCurrent)
+
+  { "WideCharToMultiByte",     (SYSCALL)WideCharToMultiByte,     0 },
+
+#define osWideCharToMultiByte ((int(WINAPI*)(UINT,DWORD,LPCWSTR,int,LPSTR,int, \
+        LPCSTR,LPBOOL))aSyscall[60].pCurrent)
+
+  { "WriteFile",               (SYSCALL)WriteFile,               0 },
+
+#define osWriteFile ((BOOL(WINAPI*)(HANDLE,LPCVOID,DWORD,LPDWORD, \
+        LPOVERLAPPED))aSyscall[61].pCurrent)
+
+#if SQLITE_OS_WINRT
+  { "CreateEventExW",          (SYSCALL)CreateEventExW,          0 },
+#else
+  { "CreateEventExW",          (SYSCALL)0,                       0 },
+#endif
+
+#define osCreateEventExW ((HANDLE(WINAPI*)(LPSECURITY_ATTRIBUTES,LPCWSTR, \
+        DWORD,DWORD))aSyscall[62].pCurrent)
+
+#if !SQLITE_OS_WINRT
+  { "WaitForSingleObject",     (SYSCALL)WaitForSingleObject,     0 },
+#else
+  { "WaitForSingleObject",     (SYSCALL)0,                       0 },
+#endif
+
+#define osWaitForSingleObject ((DWORD(WINAPI*)(HANDLE, \
+        DWORD))aSyscall[63].pCurrent)
+
+#if !SQLITE_OS_WINCE
+  { "WaitForSingleObjectEx",   (SYSCALL)WaitForSingleObjectEx,   0 },
+#else
+  { "WaitForSingleObjectEx",   (SYSCALL)0,                       0 },
+#endif
+
+#define osWaitForSingleObjectEx ((DWORD(WINAPI*)(HANDLE,DWORD, \
+        BOOL))aSyscall[64].pCurrent)
+
+#if SQLITE_OS_WINRT
+  { "SetFilePointerEx",        (SYSCALL)SetFilePointerEx,        0 },
+#else
+  { "SetFilePointerEx",        (SYSCALL)0,                       0 },
+#endif
+
+#define osSetFilePointerEx ((BOOL(WINAPI*)(HANDLE,LARGE_INTEGER, \
+        PLARGE_INTEGER,DWORD))aSyscall[65].pCurrent)
+
+#if SQLITE_OS_WINRT
+  { "GetFileInformationByHandleEx", (SYSCALL)GetFileInformationByHandleEx, 0 },
+#else
+  { "GetFileInformationByHandleEx", (SYSCALL)0,                  0 },
+#endif
+
+#define osGetFileInformationByHandleEx ((BOOL(WINAPI*)(HANDLE, \
+        FILE_INFO_BY_HANDLE_CLASS,LPVOID,DWORD))aSyscall[66].pCurrent)
+
+#if SQLITE_OS_WINRT && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
+  { "MapViewOfFileFromApp",    (SYSCALL)MapViewOfFileFromApp,    0 },
+#else
+  { "MapViewOfFileFromApp",    (SYSCALL)0,                       0 },
+#endif
+
+#define osMapViewOfFileFromApp ((LPVOID(WINAPI*)(HANDLE,ULONG,ULONG64, \
+        SIZE_T))aSyscall[67].pCurrent)
+
+#if SQLITE_OS_WINRT
+  { "CreateFile2",             (SYSCALL)CreateFile2,             0 },
+#else
+  { "CreateFile2",             (SYSCALL)0,                       0 },
+#endif
+
+#define osCreateFile2 ((HANDLE(WINAPI*)(LPCWSTR,DWORD,DWORD,DWORD, \
+        LPCREATEFILE2_EXTENDED_PARAMETERS))aSyscall[68].pCurrent)
+
+#if SQLITE_OS_WINRT && !defined(SQLITE_OMIT_LOAD_EXTENSION)
+  { "LoadPackagedLibrary",     (SYSCALL)LoadPackagedLibrary,     0 },
+#else
+  { "LoadPackagedLibrary",     (SYSCALL)0,                       0 },
+#endif
+
+#define osLoadPackagedLibrary ((HMODULE(WINAPI*)(LPCWSTR, \
+        DWORD))aSyscall[69].pCurrent)
+
+#if SQLITE_OS_WINRT
+  { "GetTickCount64",          (SYSCALL)GetTickCount64,          0 },
+#else
+  { "GetTickCount64",          (SYSCALL)0,                       0 },
+#endif
+
+#define osGetTickCount64 ((ULONGLONG(WINAPI*)(VOID))aSyscall[70].pCurrent)
+
+#if SQLITE_OS_WINRT
+  { "GetNativeSystemInfo",     (SYSCALL)GetNativeSystemInfo,     0 },
+#else
+  { "GetNativeSystemInfo",     (SYSCALL)0,                       0 },
+#endif
+
+#define osGetNativeSystemInfo ((VOID(WINAPI*)( \
+        LPSYSTEM_INFO))aSyscall[71].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_ANSI)
+  { "OutputDebugStringA",      (SYSCALL)OutputDebugStringA,      0 },
+#else
+  { "OutputDebugStringA",      (SYSCALL)0,                       0 },
+#endif
+
+#define osOutputDebugStringA ((VOID(WINAPI*)(LPCSTR))aSyscall[72].pCurrent)
+
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  { "OutputDebugStringW",      (SYSCALL)OutputDebugStringW,      0 },
+#else
+  { "OutputDebugStringW",      (SYSCALL)0,                       0 },
+#endif
+
+#define osOutputDebugStringW ((VOID(WINAPI*)(LPCWSTR))aSyscall[73].pCurrent)
+
+  { "GetProcessHeap",          (SYSCALL)GetProcessHeap,          0 },
+
+#define osGetProcessHeap ((HANDLE(WINAPI*)(VOID))aSyscall[74].pCurrent)
+
+#if SQLITE_OS_WINRT && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
+  { "CreateFileMappingFromApp", (SYSCALL)CreateFileMappingFromApp, 0 },
+#else
+  { "CreateFileMappingFromApp", (SYSCALL)0,                      0 },
+#endif
+
+#define osCreateFileMappingFromApp ((HANDLE(WINAPI*)(HANDLE, \
+        LPSECURITY_ATTRIBUTES,ULONG,ULONG64,LPCWSTR))aSyscall[75].pCurrent)
+
+/*
+** NOTE: On some sub-platforms, the InterlockedCompareExchange "function"
+**       is really just a macro that uses a compiler intrinsic (e.g. x64).
+**       So do not try to make this is into a redefinable interface.
+*/
+#if defined(InterlockedCompareExchange)
+  { "InterlockedCompareExchange", (SYSCALL)0,                    0 },
+
+#define osInterlockedCompareExchange InterlockedCompareExchange
+#else
+  { "InterlockedCompareExchange", (SYSCALL)InterlockedCompareExchange, 0 },
+
+#define osInterlockedCompareExchange ((LONG(WINAPI*)(LONG \
+        SQLITE_WIN32_VOLATILE*, LONG,LONG))aSyscall[76].pCurrent)
+#endif /* defined(InterlockedCompareExchange) */
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
+  { "UuidCreate",               (SYSCALL)UuidCreate,             0 },
+#else
+  { "UuidCreate",               (SYSCALL)0,                      0 },
+#endif
+
+#define osUuidCreate ((RPC_STATUS(RPC_ENTRY*)(UUID*))aSyscall[77].pCurrent)
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
+  { "UuidCreateSequential",     (SYSCALL)UuidCreateSequential,   0 },
+#else
+  { "UuidCreateSequential",     (SYSCALL)0,                      0 },
+#endif
+
+#define osUuidCreateSequential \
+        ((RPC_STATUS(RPC_ENTRY*)(UUID*))aSyscall[78].pCurrent)
+
+#if !defined(SQLITE_NO_SYNC) && SQLITE_MAX_MMAP_SIZE>0
+  { "FlushViewOfFile",          (SYSCALL)FlushViewOfFile,        0 },
+#else
+  { "FlushViewOfFile",          (SYSCALL)0,                      0 },
+#endif
+
+#define osFlushViewOfFile \
+        ((BOOL(WINAPI*)(LPCVOID,SIZE_T))aSyscall[79].pCurrent)
+
+}; /* End of the overrideable system calls */
+
+/*
+** This is the xSetSystemCall() method of sqlite3_vfs for all of the
+** "win32" VFSes.  Return SQLITE_OK upon successfully updating the
+** system call pointer, or SQLITE_NOTFOUND if there is no configurable
+** system call named zName.
+*/
+static int winSetSystemCall(
+  sqlite3_vfs *pNotUsed,        /* The VFS pointer.  Not used */
+  const char *zName,            /* Name of system call to override */
+  sqlite3_syscall_ptr pNewFunc  /* Pointer to new system call value */
+){
+  unsigned int i;
+  int rc = SQLITE_NOTFOUND;
+
+  UNUSED_PARAMETER(pNotUsed);
+  if( zName==0 ){
+    /* If no zName is given, restore all system calls to their default
+    ** settings and return NULL
+    */
+    rc = SQLITE_OK;
+    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+      if( aSyscall[i].pDefault ){
+        aSyscall[i].pCurrent = aSyscall[i].pDefault;
+      }
+    }
+  }else{
+    /* If zName is specified, operate on only the one system call
+    ** specified.
+    */
+    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+      if( strcmp(zName, aSyscall[i].zName)==0 ){
+        if( aSyscall[i].pDefault==0 ){
+          aSyscall[i].pDefault = aSyscall[i].pCurrent;
+        }
+        rc = SQLITE_OK;
+        if( pNewFunc==0 ) pNewFunc = aSyscall[i].pDefault;
+        aSyscall[i].pCurrent = pNewFunc;
+        break;
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Return the value of a system call.  Return NULL if zName is not a
+** recognized system call name.  NULL is also returned if the system call
+** is currently undefined.
+*/
+static sqlite3_syscall_ptr winGetSystemCall(
+  sqlite3_vfs *pNotUsed,
+  const char *zName
+){
+  unsigned int i;
+
+  UNUSED_PARAMETER(pNotUsed);
+  for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+    if( strcmp(zName, aSyscall[i].zName)==0 ) return aSyscall[i].pCurrent;
+  }
+  return 0;
+}
+
+/*
+** Return the name of the first system call after zName.  If zName==NULL
+** then return the name of the first system call.  Return NULL if zName
+** is the last system call or if zName is not the name of a valid
+** system call.
+*/
+static const char *winNextSystemCall(sqlite3_vfs *p, const char *zName){
+  int i = -1;
+
+  UNUSED_PARAMETER(p);
+  if( zName ){
+    for(i=0; i<ArraySize(aSyscall)-1; i++){
+      if( strcmp(zName, aSyscall[i].zName)==0 ) break;
+    }
+  }
+  for(i++; i<ArraySize(aSyscall); i++){
+    if( aSyscall[i].pCurrent!=0 ) return aSyscall[i].zName;
+  }
+  return 0;
+}
+
+#ifdef SQLITE_WIN32_MALLOC
+/*
+** If a Win32 native heap has been configured, this function will attempt to
+** compact it.  Upon success, SQLITE_OK will be returned.  Upon failure, one
+** of SQLITE_NOMEM, SQLITE_ERROR, or SQLITE_NOTFOUND will be returned.  The
+** "pnLargest" argument, if non-zero, will be used to return the size of the
+** largest committed free block in the heap, in bytes.
+*/
+int sqlite3_win32_compact_heap(LPUINT pnLargest){
+  int rc = SQLITE_OK;
+  UINT nLargest = 0;
+  HANDLE hHeap;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
+  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
+  if( (nLargest=osHeapCompact(hHeap, SQLITE_WIN32_HEAP_FLAGS))==0 ){
+    DWORD lastErrno = osGetLastError();
+    if( lastErrno==NO_ERROR ){
+      sqlite3_log(SQLITE_NOMEM, "failed to HeapCompact (no space), heap=%p",
+                  (void*)hHeap);
+      rc = SQLITE_NOMEM_BKPT;
+    }else{
+      sqlite3_log(SQLITE_ERROR, "failed to HeapCompact (%lu), heap=%p",
+                  osGetLastError(), (void*)hHeap);
+      rc = SQLITE_ERROR;
+    }
+  }
+#else
+  sqlite3_log(SQLITE_NOTFOUND, "failed to HeapCompact, heap=%p",
+              (void*)hHeap);
+  rc = SQLITE_NOTFOUND;
+#endif
+  if( pnLargest ) *pnLargest = nLargest;
+  return rc;
+}
+
+/*
+** If a Win32 native heap has been configured, this function will attempt to
+** destroy and recreate it.  If the Win32 native heap is not isolated and/or
+** the sqlite3_memory_used() function does not return zero, SQLITE_BUSY will
+** be returned and no changes will be made to the Win32 native heap.
+*/
+int sqlite3_win32_reset_heap(){
+  int rc;
+  MUTEX_LOGIC( sqlite3_mutex *pMainMtx; ) /* The main static mutex */
+  MUTEX_LOGIC( sqlite3_mutex *pMem; )    /* The memsys static mutex */
+  MUTEX_LOGIC( pMainMtx = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN); )
+  MUTEX_LOGIC( pMem = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM); )
+  sqlite3_mutex_enter(pMainMtx);
+  sqlite3_mutex_enter(pMem);
+  winMemAssertMagic();
+  if( winMemGetHeap()!=NULL && winMemGetOwned() && sqlite3_memory_used()==0 ){
+    /*
+    ** At this point, there should be no outstanding memory allocations on
+    ** the heap.  Also, since both the main and memsys locks are currently
+    ** being held by us, no other function (i.e. from another thread) should
+    ** be able to even access the heap.  Attempt to destroy and recreate our
+    ** isolated Win32 native heap now.
+    */
+    assert( winMemGetHeap()!=NULL );
+    assert( winMemGetOwned() );
+    assert( sqlite3_memory_used()==0 );
+    winMemShutdown(winMemGetDataPtr());
+    assert( winMemGetHeap()==NULL );
+    assert( !winMemGetOwned() );
+    assert( sqlite3_memory_used()==0 );
+    rc = winMemInit(winMemGetDataPtr());
+    assert( rc!=SQLITE_OK || winMemGetHeap()!=NULL );
+    assert( rc!=SQLITE_OK || winMemGetOwned() );
+    assert( rc!=SQLITE_OK || sqlite3_memory_used()==0 );
+  }else{
+    /*
+    ** The Win32 native heap cannot be modified because it may be in use.
+    */
+    rc = SQLITE_BUSY;
+  }
+  sqlite3_mutex_leave(pMem);
+  sqlite3_mutex_leave(pMainMtx);
+  return rc;
+}
+#endif /* SQLITE_WIN32_MALLOC */
+
+/*
+** This function outputs the specified (ANSI) string to the Win32 debugger
+** (if available).
+*/
+
+void sqlite3_win32_write_debug(const char *zBuf, int nBuf){
+  char zDbgBuf[SQLITE_WIN32_DBG_BUF_SIZE];
+  int nMin = MIN(nBuf, (SQLITE_WIN32_DBG_BUF_SIZE - 1)); /* may be negative. */
+  if( nMin<-1 ) nMin = -1; /* all negative values become -1. */
+  assert( nMin==-1 || nMin==0 || nMin<SQLITE_WIN32_DBG_BUF_SIZE );
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !zBuf ){
+    (void)SQLITE_MISUSE_BKPT;
+    return;
+  }
+#endif
+#if defined(SQLITE_WIN32_HAS_ANSI)
+  if( nMin>0 ){
+    memset(zDbgBuf, 0, SQLITE_WIN32_DBG_BUF_SIZE);
+    memcpy(zDbgBuf, zBuf, nMin);
+    osOutputDebugStringA(zDbgBuf);
+  }else{
+    osOutputDebugStringA(zBuf);
+  }
+#elif defined(SQLITE_WIN32_HAS_WIDE)
+  memset(zDbgBuf, 0, SQLITE_WIN32_DBG_BUF_SIZE);
+  if ( osMultiByteToWideChar(
+          osAreFileApisANSI() ? CP_ACP : CP_OEMCP, 0, zBuf,
+          nMin, (LPWSTR)zDbgBuf, SQLITE_WIN32_DBG_BUF_SIZE/sizeof(WCHAR))<=0 ){
+    return;
+  }
+  osOutputDebugStringW((LPCWSTR)zDbgBuf);
+#else
+  if( nMin>0 ){
+    memset(zDbgBuf, 0, SQLITE_WIN32_DBG_BUF_SIZE);
+    memcpy(zDbgBuf, zBuf, nMin);
+    fprintf(stderr, "%s", zDbgBuf);
+  }else{
+    fprintf(stderr, "%s", zBuf);
+  }
+#endif
+}
+
+/*
+** The following routine suspends the current thread for at least ms
+** milliseconds.  This is equivalent to the Win32 Sleep() interface.
+*/
+#if SQLITE_OS_WINRT
+static HANDLE sleepObj = NULL;
+#endif
+
+void sqlite3_win32_sleep(DWORD milliseconds){
+#if SQLITE_OS_WINRT
+  if ( sleepObj==NULL ){
+    sleepObj = osCreateEventExW(NULL, NULL, CREATE_EVENT_MANUAL_RESET,
+                                SYNCHRONIZE);
+  }
+  assert( sleepObj!=NULL );
+  osWaitForSingleObjectEx(sleepObj, milliseconds, FALSE);
+#else
+  osSleep(milliseconds);
+#endif
+}
+
+#if SQLITE_MAX_WORKER_THREADS>0 && !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && \
+        SQLITE_THREADSAFE>0
+DWORD sqlite3Win32Wait(HANDLE hObject){
+  DWORD rc;
+  while( (rc = osWaitForSingleObjectEx(hObject, INFINITE,
+                                       TRUE))==WAIT_IO_COMPLETION ){}
+  return rc;
+}
+#endif
+
+/*
+** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
+** or WinCE.  Return false (zero) for Win95, Win98, or WinME.
+**
+** Here is an interesting observation:  Win95, Win98, and WinME lack
+** the LockFileEx() API.  But we can still statically link against that
+** API as long as we don't call it when running Win95/98/ME.  A call to
+** this routine is used to determine if the host is Win95/98/ME or
+** WinNT/2K/XP so that we will know whether or not we can safely call
+** the LockFileEx() API.
+*/
+
+#if !SQLITE_WIN32_GETVERSIONEX
+# define osIsNT()  (1)
+#elif SQLITE_OS_WINCE || SQLITE_OS_WINRT || !defined(SQLITE_WIN32_HAS_ANSI)
+# define osIsNT()  (1)
+#elif !defined(SQLITE_WIN32_HAS_WIDE)
+# define osIsNT()  (0)
+#else
+# define osIsNT()  ((sqlite3_os_type==2) || sqlite3_win32_is_nt())
+#endif
+
+/*
+** This function determines if the machine is running a version of Windows
+** based on the NT kernel.
+*/
+int sqlite3_win32_is_nt(void){
+#if SQLITE_OS_WINRT
+  /*
+  ** NOTE: The WinRT sub-platform is always assumed to be based on the NT
+  **       kernel.
+  */
+  return 1;
+#elif SQLITE_WIN32_GETVERSIONEX
+  if( osInterlockedCompareExchange(&sqlite3_os_type, 0, 0)==0 ){
+#if defined(SQLITE_WIN32_HAS_ANSI)
+    OSVERSIONINFOA sInfo;
+    sInfo.dwOSVersionInfoSize = sizeof(sInfo);
+    osGetVersionExA(&sInfo);
+    osInterlockedCompareExchange(&sqlite3_os_type,
+        (sInfo.dwPlatformId == VER_PLATFORM_WIN32_NT) ? 2 : 1, 0);
+#elif defined(SQLITE_WIN32_HAS_WIDE)
+    OSVERSIONINFOW sInfo;
+    sInfo.dwOSVersionInfoSize = sizeof(sInfo);
+    osGetVersionExW(&sInfo);
+    osInterlockedCompareExchange(&sqlite3_os_type,
+        (sInfo.dwPlatformId == VER_PLATFORM_WIN32_NT) ? 2 : 1, 0);
+#endif
+  }
+  return osInterlockedCompareExchange(&sqlite3_os_type, 2, 2)==2;
+#elif SQLITE_TEST
+  return osInterlockedCompareExchange(&sqlite3_os_type, 2, 2)==2;
+#else
+  /*
+  ** NOTE: All sub-platforms where the GetVersionEx[AW] functions are
+  **       deprecated are always assumed to be based on the NT kernel.
+  */
+  return 1;
+#endif
+}
+
+#ifdef SQLITE_WIN32_MALLOC
+/*
+** Allocate nBytes of memory.
+*/
+static void *winMemMalloc(int nBytes){
+  HANDLE hHeap;
+  void *p;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
+  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+  assert( nBytes>=0 );
+  p = osHeapAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, (SIZE_T)nBytes);
+  if( !p ){
+    sqlite3_log(SQLITE_NOMEM, "failed to HeapAlloc %u bytes (%lu), heap=%p",
+                nBytes, osGetLastError(), (void*)hHeap);
+  }
+  return p;
+}
+
+/*
+** Free memory.
+*/
+static void winMemFree(void *pPrior){
+  HANDLE hHeap;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
+  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) );
+#endif
+  if( !pPrior ) return; /* Passing NULL to HeapFree is undefined. */
+  if( !osHeapFree(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) ){
+    sqlite3_log(SQLITE_NOMEM, "failed to HeapFree block %p (%lu), heap=%p",
+                pPrior, osGetLastError(), (void*)hHeap);
+  }
+}
+
+/*
+** Change the size of an existing memory allocation
+*/
+static void *winMemRealloc(void *pPrior, int nBytes){
+  HANDLE hHeap;
+  void *p;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
+  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) );
+#endif
+  assert( nBytes>=0 );
+  if( !pPrior ){
+    p = osHeapAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, (SIZE_T)nBytes);
+  }else{
+    p = osHeapReAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior, (SIZE_T)nBytes);
+  }
+  if( !p ){
+    sqlite3_log(SQLITE_NOMEM, "failed to %s %u bytes (%lu), heap=%p",
+                pPrior ? "HeapReAlloc" : "HeapAlloc", nBytes, osGetLastError(),
+                (void*)hHeap);
+  }
+  return p;
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes.
+*/
+static int winMemSize(void *p){
+  HANDLE hHeap;
+  SIZE_T n;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
+  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, p) );
+#endif
+  if( !p ) return 0;
+  n = osHeapSize(hHeap, SQLITE_WIN32_HEAP_FLAGS, p);
+  if( n==(SIZE_T)-1 ){
+    sqlite3_log(SQLITE_NOMEM, "failed to HeapSize block %p (%lu), heap=%p",
+                p, osGetLastError(), (void*)hHeap);
+    return 0;
+  }
+  return (int)n;
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int winMemRoundup(int n){
+  return n;
+}
+
+/*
+** Initialize this module.
+*/
+static int winMemInit(void *pAppData){
+  winMemData *pWinMemData = (winMemData *)pAppData;
+
+  if( !pWinMemData ) return SQLITE_ERROR;
+  assert( pWinMemData->magic1==WINMEM_MAGIC1 );
+  assert( pWinMemData->magic2==WINMEM_MAGIC2 );
+
+#if !SQLITE_OS_WINRT && SQLITE_WIN32_HEAP_CREATE
+  if( !pWinMemData->hHeap ){
+    DWORD dwInitialSize = SQLITE_WIN32_HEAP_INIT_SIZE;
+    DWORD dwMaximumSize = (DWORD)sqlite3GlobalConfig.nHeap;
+    if( dwMaximumSize==0 ){
+      dwMaximumSize = SQLITE_WIN32_HEAP_MAX_SIZE;
+    }else if( dwInitialSize>dwMaximumSize ){
+      dwInitialSize = dwMaximumSize;
+    }
+    pWinMemData->hHeap = osHeapCreate(SQLITE_WIN32_HEAP_FLAGS,
+                                      dwInitialSize, dwMaximumSize);
+    if( !pWinMemData->hHeap ){
+      sqlite3_log(SQLITE_NOMEM,
+          "failed to HeapCreate (%lu), flags=%u, initSize=%lu, maxSize=%lu",
+          osGetLastError(), SQLITE_WIN32_HEAP_FLAGS, dwInitialSize,
+          dwMaximumSize);
+      return SQLITE_NOMEM_BKPT;
+    }
+    pWinMemData->bOwned = TRUE;
+    assert( pWinMemData->bOwned );
+  }
+#else
+  pWinMemData->hHeap = osGetProcessHeap();
+  if( !pWinMemData->hHeap ){
+    sqlite3_log(SQLITE_NOMEM,
+        "failed to GetProcessHeap (%lu)", osGetLastError());
+    return SQLITE_NOMEM_BKPT;
+  }
+  pWinMemData->bOwned = FALSE;
+  assert( !pWinMemData->bOwned );
+#endif
+  assert( pWinMemData->hHeap!=0 );
+  assert( pWinMemData->hHeap!=INVALID_HANDLE_VALUE );
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
+  assert( osHeapValidate(pWinMemData->hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void winMemShutdown(void *pAppData){
+  winMemData *pWinMemData = (winMemData *)pAppData;
+
+  if( !pWinMemData ) return;
+  assert( pWinMemData->magic1==WINMEM_MAGIC1 );
+  assert( pWinMemData->magic2==WINMEM_MAGIC2 );
+
+  if( pWinMemData->hHeap ){
+    assert( pWinMemData->hHeap!=INVALID_HANDLE_VALUE );
+#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
+    assert( osHeapValidate(pWinMemData->hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+    if( pWinMemData->bOwned ){
+      if( !osHeapDestroy(pWinMemData->hHeap) ){
+        sqlite3_log(SQLITE_NOMEM, "failed to HeapDestroy (%lu), heap=%p",
+                    osGetLastError(), (void*)pWinMemData->hHeap);
+      }
+      pWinMemData->bOwned = FALSE;
+    }
+    pWinMemData->hHeap = NULL;
+  }
+}
+
+/*
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file. The
+** arguments specify the block of memory to manage.
+**
+** This routine is only called by sqlite3_config(), and therefore
+** is not required to be threadsafe (it is not).
+*/
+const sqlite3_mem_methods *sqlite3MemGetWin32(void){
+  static const sqlite3_mem_methods winMemMethods = {
+    winMemMalloc,
+    winMemFree,
+    winMemRealloc,
+    winMemSize,
+    winMemRoundup,
+    winMemInit,
+    winMemShutdown,
+    &win_mem_data
+  };
+  return &winMemMethods;
+}
+
+void sqlite3MemSetDefault(void){
+  sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetWin32());
+}
+#endif /* SQLITE_WIN32_MALLOC */
+
+/*
+** Convert a UTF-8 string to Microsoft Unicode.
+**
+** Space to hold the returned string is obtained from sqlite3_malloc().
+*/
+static LPWSTR winUtf8ToUnicode(const char *zText){
+  int nChar;
+  LPWSTR zWideText;
+
+  nChar = osMultiByteToWideChar(CP_UTF8, 0, zText, -1, NULL, 0);
+  if( nChar==0 ){
+    return 0;
+  }
+  zWideText = sqlite3MallocZero( nChar*sizeof(WCHAR) );
+  if( zWideText==0 ){
+    return 0;
+  }
+  nChar = osMultiByteToWideChar(CP_UTF8, 0, zText, -1, zWideText,
+                                nChar);
+  if( nChar==0 ){
+    sqlite3_free(zWideText);
+    zWideText = 0;
+  }
+  return zWideText;
+}
+
+/*
+** Convert a Microsoft Unicode string to UTF-8.
+**
+** Space to hold the returned string is obtained from sqlite3_malloc().
+*/
+static char *winUnicodeToUtf8(LPCWSTR zWideText){
+  int nByte;
+  char *zText;
+
+  nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideText, -1, 0, 0, 0, 0);
+  if( nByte == 0 ){
+    return 0;
+  }
+  zText = sqlite3MallocZero( nByte );
+  if( zText==0 ){
+    return 0;
+  }
+  nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideText, -1, zText, nByte,
+                                0, 0);
+  if( nByte == 0 ){
+    sqlite3_free(zText);
+    zText = 0;
+  }
+  return zText;
+}
+
+/*
+** Convert an ANSI string to Microsoft Unicode, using the ANSI or OEM
+** code page.
+**
+** Space to hold the returned string is obtained from sqlite3_malloc().
+*/
+static LPWSTR winMbcsToUnicode(const char *zText, int useAnsi){
+  int nByte;
+  LPWSTR zMbcsText;
+  int codepage = useAnsi ? CP_ACP : CP_OEMCP;
+
+  nByte = osMultiByteToWideChar(codepage, 0, zText, -1, NULL,
+                                0)*sizeof(WCHAR);
+  if( nByte==0 ){
+    return 0;
+  }
+  zMbcsText = sqlite3MallocZero( nByte*sizeof(WCHAR) );
+  if( zMbcsText==0 ){
+    return 0;
+  }
+  nByte = osMultiByteToWideChar(codepage, 0, zText, -1, zMbcsText,
+                                nByte);
+  if( nByte==0 ){
+    sqlite3_free(zMbcsText);
+    zMbcsText = 0;
+  }
+  return zMbcsText;
+}
+
+/*
+** Convert a Microsoft Unicode string to a multi-byte character string,
+** using the ANSI or OEM code page.
+**
+** Space to hold the returned string is obtained from sqlite3_malloc().
+*/
+static char *winUnicodeToMbcs(LPCWSTR zWideText, int useAnsi){
+  int nByte;
+  char *zText;
+  int codepage = useAnsi ? CP_ACP : CP_OEMCP;
+
+  nByte = osWideCharToMultiByte(codepage, 0, zWideText, -1, 0, 0, 0, 0);
+  if( nByte == 0 ){
+    return 0;
+  }
+  zText = sqlite3MallocZero( nByte );
+  if( zText==0 ){
+    return 0;
+  }
+  nByte = osWideCharToMultiByte(codepage, 0, zWideText, -1, zText,
+                                nByte, 0, 0);
+  if( nByte == 0 ){
+    sqlite3_free(zText);
+    zText = 0;
+  }
+  return zText;
+}
+
+/*
+** Convert a multi-byte character string to UTF-8.
+**
+** Space to hold the returned string is obtained from sqlite3_malloc().
+*/
+static char *winMbcsToUtf8(const char *zText, int useAnsi){
+  char *zTextUtf8;
+  LPWSTR zTmpWide;
+
+  zTmpWide = winMbcsToUnicode(zText, useAnsi);
+  if( zTmpWide==0 ){
+    return 0;
+  }
+  zTextUtf8 = winUnicodeToUtf8(zTmpWide);
+  sqlite3_free(zTmpWide);
+  return zTextUtf8;
+}
+
+/*
+** Convert a UTF-8 string to a multi-byte character string.
+**
+** Space to hold the returned string is obtained from sqlite3_malloc().
+*/
+static char *winUtf8ToMbcs(const char *zText, int useAnsi){
+  char *zTextMbcs;
+  LPWSTR zTmpWide;
+
+  zTmpWide = winUtf8ToUnicode(zText);
+  if( zTmpWide==0 ){
+    return 0;
+  }
+  zTextMbcs = winUnicodeToMbcs(zTmpWide, useAnsi);
+  sqlite3_free(zTmpWide);
+  return zTextMbcs;
+}
+
+/*
+** This is a public wrapper for the winUtf8ToUnicode() function.
+*/
+LPWSTR sqlite3_win32_utf8_to_unicode(const char *zText){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !zText ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return winUtf8ToUnicode(zText);
+}
+
+/*
+** This is a public wrapper for the winUnicodeToUtf8() function.
+*/
+char *sqlite3_win32_unicode_to_utf8(LPCWSTR zWideText){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !zWideText ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return winUnicodeToUtf8(zWideText);
+}
+
+/*
+** This is a public wrapper for the winMbcsToUtf8() function.
+*/
+char *sqlite3_win32_mbcs_to_utf8(const char *zText){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !zText ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return winMbcsToUtf8(zText, osAreFileApisANSI());
+}
+
+/*
+** This is a public wrapper for the winMbcsToUtf8() function.
+*/
+char *sqlite3_win32_mbcs_to_utf8_v2(const char *zText, int useAnsi){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !zText ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return winMbcsToUtf8(zText, useAnsi);
+}
+
+/*
+** This is a public wrapper for the winUtf8ToMbcs() function.
+*/
+char *sqlite3_win32_utf8_to_mbcs(const char *zText){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !zText ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return winUtf8ToMbcs(zText, osAreFileApisANSI());
+}
+
+/*
+** This is a public wrapper for the winUtf8ToMbcs() function.
+*/
+char *sqlite3_win32_utf8_to_mbcs_v2(const char *zText, int useAnsi){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !zText ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return winUtf8ToMbcs(zText, useAnsi);
+}
+
+/*
+** This function is the same as sqlite3_win32_set_directory (below); however,
+** it accepts a UTF-8 string.
+*/
+int sqlite3_win32_set_directory8(
+  unsigned long type, /* Identifier for directory being set or reset */
+  const char *zValue  /* New value for directory being set or reset */
+){
+  char **ppDirectory = 0;
+  int rc;
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+  if( type==SQLITE_WIN32_DATA_DIRECTORY_TYPE ){
+    ppDirectory = &sqlite3_data_directory;
+  }else if( type==SQLITE_WIN32_TEMP_DIRECTORY_TYPE ){
+    ppDirectory = &sqlite3_temp_directory;
+  }
+  assert( !ppDirectory || type==SQLITE_WIN32_DATA_DIRECTORY_TYPE
+          || type==SQLITE_WIN32_TEMP_DIRECTORY_TYPE
+  );
+  assert( !ppDirectory || sqlite3MemdebugHasType(*ppDirectory, MEMTYPE_HEAP) );
+  if( ppDirectory ){
+    char *zCopy = 0;
+    if( zValue && zValue[0] ){
+      zCopy = sqlite3_mprintf("%s", zValue);
+      if ( zCopy==0 ){
+        rc = SQLITE_NOMEM_BKPT;
+        goto set_directory8_done;
+      }
+    }
+    sqlite3_free(*ppDirectory);
+    *ppDirectory = zCopy;
+    rc = SQLITE_OK;
+  }else{
+    rc = SQLITE_ERROR;
+  }
+set_directory8_done:
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+  return rc;
+}
+
+/*
+** This function is the same as sqlite3_win32_set_directory (below); however,
+** it accepts a UTF-16 string.
+*/
+int sqlite3_win32_set_directory16(
+  unsigned long type, /* Identifier for directory being set or reset */
+  const void *zValue  /* New value for directory being set or reset */
+){
+  int rc;
+  char *zUtf8 = 0;
+  if( zValue ){
+    zUtf8 = sqlite3_win32_unicode_to_utf8(zValue);
+    if( zUtf8==0 ) return SQLITE_NOMEM_BKPT;
+  }
+  rc = sqlite3_win32_set_directory8(type, zUtf8);
+  if( zUtf8 ) sqlite3_free(zUtf8);
+  return rc;
+}
+
+/*
+** This function sets the data directory or the temporary directory based on
+** the provided arguments.  The type argument must be 1 in order to set the
+** data directory or 2 in order to set the temporary directory.  The zValue
+** argument is the name of the directory to use.  The return value will be
+** SQLITE_OK if successful.
+*/
+int sqlite3_win32_set_directory(
+  unsigned long type, /* Identifier for directory being set or reset */
+  void *zValue        /* New value for directory being set or reset */
+){
+  return sqlite3_win32_set_directory16(type, zValue);
+}
+
+/*
+** The return value of winGetLastErrorMsg
+** is zero if the error message fits in the buffer, or non-zero
+** otherwise (if the message was truncated).
+*/
+static int winGetLastErrorMsg(DWORD lastErrno, int nBuf, char *zBuf){
+  /* FormatMessage returns 0 on failure.  Otherwise it
+  ** returns the number of TCHARs written to the output
+  ** buffer, excluding the terminating null char.
+  */
+  DWORD dwLen = 0;
+  char *zOut = 0;
+
+  if( osIsNT() ){
+#if SQLITE_OS_WINRT
+    WCHAR zTempWide[SQLITE_WIN32_MAX_ERRMSG_CHARS+1];
+    dwLen = osFormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM |
+                             FORMAT_MESSAGE_IGNORE_INSERTS,
+                             NULL,
+                             lastErrno,
+                             0,
+                             zTempWide,
+                             SQLITE_WIN32_MAX_ERRMSG_CHARS,
+                             0);
+#else
+    LPWSTR zTempWide = NULL;
+    dwLen = osFormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                             FORMAT_MESSAGE_FROM_SYSTEM |
+                             FORMAT_MESSAGE_IGNORE_INSERTS,
+                             NULL,
+                             lastErrno,
+                             0,
+                             (LPWSTR) &zTempWide,
+                             0,
+                             0);
+#endif
+    if( dwLen > 0 ){
+      /* allocate a buffer and convert to UTF8 */
+      sqlite3BeginBenignMalloc();
+      zOut = winUnicodeToUtf8(zTempWide);
+      sqlite3EndBenignMalloc();
+#if !SQLITE_OS_WINRT
+      /* free the system buffer allocated by FormatMessage */
+      osLocalFree(zTempWide);
+#endif
+    }
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    char *zTemp = NULL;
+    dwLen = osFormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                             FORMAT_MESSAGE_FROM_SYSTEM |
+                             FORMAT_MESSAGE_IGNORE_INSERTS,
+                             NULL,
+                             lastErrno,
+                             0,
+                             (LPSTR) &zTemp,
+                             0,
+                             0);
+    if( dwLen > 0 ){
+      /* allocate a buffer and convert to UTF8 */
+      sqlite3BeginBenignMalloc();
+      zOut = winMbcsToUtf8(zTemp, osAreFileApisANSI());
+      sqlite3EndBenignMalloc();
+      /* free the system buffer allocated by FormatMessage */
+      osLocalFree(zTemp);
+    }
+  }
+#endif
+  if( 0 == dwLen ){
+    sqlite3_snprintf(nBuf, zBuf, "OsError 0x%lx (%lu)", lastErrno, lastErrno);
+  }else{
+    /* copy a maximum of nBuf chars to output buffer */
+    sqlite3_snprintf(nBuf, zBuf, "%s", zOut);
+    /* free the UTF8 buffer */
+    sqlite3_free(zOut);
+  }
+  return 0;
+}
+
+/*
+**
+** This function - winLogErrorAtLine() - is only ever called via the macro
+** winLogError().
+**
+** This routine is invoked after an error occurs in an OS function.
+** It logs a message using sqlite3_log() containing the current value of
+** error code and, if possible, the human-readable equivalent from
+** FormatMessage.
+**
+** The first argument passed to the macro should be the error code that
+** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN).
+** The two subsequent arguments should be the name of the OS function that
+** failed and the associated file-system path, if any.
+*/
+#define winLogError(a,b,c,d)   winLogErrorAtLine(a,b,c,d,__LINE__)
+static int winLogErrorAtLine(
+  int errcode,                    /* SQLite error code */
+  DWORD lastErrno,                /* Win32 last error */
+  const char *zFunc,              /* Name of OS function that failed */
+  const char *zPath,              /* File path associated with error */
+  int iLine                       /* Source line number where error occurred */
+){
+  char zMsg[500];                 /* Human readable error text */
+  int i;                          /* Loop counter */
+
+  zMsg[0] = 0;
+  winGetLastErrorMsg(lastErrno, sizeof(zMsg), zMsg);
+  assert( errcode!=SQLITE_OK );
+  if( zPath==0 ) zPath = "";
+  for(i=0; zMsg[i] && zMsg[i]!='\r' && zMsg[i]!='\n'; i++){}
+  zMsg[i] = 0;
+  sqlite3_log(errcode,
+      "os_win.c:%d: (%lu) %s(%s) - %s",
+      iLine, lastErrno, zFunc, zPath, zMsg
+  );
+
+  return errcode;
+}
+
+/*
+** The number of times that a ReadFile(), WriteFile(), and DeleteFile()
+** will be retried following a locking error - probably caused by
+** antivirus software.  Also the initial delay before the first retry.
+** The delay increases linearly with each retry.
+*/
+#ifndef SQLITE_WIN32_IOERR_RETRY
+# define SQLITE_WIN32_IOERR_RETRY 10
+#endif
+#ifndef SQLITE_WIN32_IOERR_RETRY_DELAY
+# define SQLITE_WIN32_IOERR_RETRY_DELAY 25
+#endif
+static int winIoerrRetry = SQLITE_WIN32_IOERR_RETRY;
+static int winIoerrRetryDelay = SQLITE_WIN32_IOERR_RETRY_DELAY;
+
+/*
+** The "winIoerrCanRetry1" macro is used to determine if a particular I/O
+** error code obtained via GetLastError() is eligible to be retried.  It
+** must accept the error code DWORD as its only argument and should return
+** non-zero if the error code is transient in nature and the operation
+** responsible for generating the original error might succeed upon being
+** retried.  The argument to this macro should be a variable.
+**
+** Additionally, a macro named "winIoerrCanRetry2" may be defined.  If it
+** is defined, it will be consulted only when the macro "winIoerrCanRetry1"
+** returns zero.  The "winIoerrCanRetry2" macro is completely optional and
+** may be used to include additional error codes in the set that should
+** result in the failing I/O operation being retried by the caller.  If
+** defined, the "winIoerrCanRetry2" macro must exhibit external semantics
+** identical to those of the "winIoerrCanRetry1" macro.
+*/
+#if !defined(winIoerrCanRetry1)
+#define winIoerrCanRetry1(a) (((a)==ERROR_ACCESS_DENIED)        || \
+                              ((a)==ERROR_SHARING_VIOLATION)    || \
+                              ((a)==ERROR_LOCK_VIOLATION)       || \
+                              ((a)==ERROR_DEV_NOT_EXIST)        || \
+                              ((a)==ERROR_NETNAME_DELETED)      || \
+                              ((a)==ERROR_SEM_TIMEOUT)          || \
+                              ((a)==ERROR_NETWORK_UNREACHABLE))
+#endif
+
+/*
+** If a ReadFile() or WriteFile() error occurs, invoke this routine
+** to see if it should be retried.  Return TRUE to retry.  Return FALSE
+** to give up with an error.
+*/
+static int winRetryIoerr(int *pnRetry, DWORD *pError){
+  DWORD e = osGetLastError();
+  if( *pnRetry>=winIoerrRetry ){
+    if( pError ){
+      *pError = e;
+    }
+    return 0;
+  }
+  if( winIoerrCanRetry1(e) ){
+    sqlite3_win32_sleep(winIoerrRetryDelay*(1+*pnRetry));
+    ++*pnRetry;
+    return 1;
+  }
+#if defined(winIoerrCanRetry2)
+  else if( winIoerrCanRetry2(e) ){
+    sqlite3_win32_sleep(winIoerrRetryDelay*(1+*pnRetry));
+    ++*pnRetry;
+    return 1;
+  }
+#endif
+  if( pError ){
+    *pError = e;
+  }
+  return 0;
+}
+
+/*
+** Log a I/O error retry episode.
+*/
+static void winLogIoerr(int nRetry, int lineno){
+  if( nRetry ){
+    sqlite3_log(SQLITE_NOTICE,
+      "delayed %dms for lock/sharing conflict at line %d",
+      winIoerrRetryDelay*nRetry*(nRetry+1)/2, lineno
+    );
+  }
+}
+
+/*
+** This #if does not rely on the SQLITE_OS_WINCE define because the
+** corresponding section in "date.c" cannot use it.
+*/
+#if !defined(SQLITE_OMIT_LOCALTIME) && defined(_WIN32_WCE) && \
+    (!defined(SQLITE_MSVC_LOCALTIME_API) || !SQLITE_MSVC_LOCALTIME_API)
+/*
+** The MSVC CRT on Windows CE may not have a localtime() function.
+** So define a substitute.
+*/
+#  include <time.h>
+struct tm *__cdecl localtime(const time_t *t)
+{
+  static struct tm y;
+  FILETIME uTm, lTm;
+  SYSTEMTIME pTm;
+  sqlite3_int64 t64;
+  t64 = *t;
+  t64 = (t64 + 11644473600)*10000000;
+  uTm.dwLowDateTime = (DWORD)(t64 & 0xFFFFFFFF);
+  uTm.dwHighDateTime= (DWORD)(t64 >> 32);
+  osFileTimeToLocalFileTime(&uTm,&lTm);
+  osFileTimeToSystemTime(&lTm,&pTm);
+  y.tm_year = pTm.wYear - 1900;
+  y.tm_mon = pTm.wMonth - 1;
+  y.tm_wday = pTm.wDayOfWeek;
+  y.tm_mday = pTm.wDay;
+  y.tm_hour = pTm.wHour;
+  y.tm_min = pTm.wMinute;
+  y.tm_sec = pTm.wSecond;
+  return &y;
+}
+#endif
+
+#if SQLITE_OS_WINCE
+/*************************************************************************
+** This section contains code for WinCE only.
+*/
+#define HANDLE_TO_WINFILE(a) (winFile*)&((char*)a)[-(int)offsetof(winFile,h)]
+
+/*
+** Acquire a lock on the handle h
+*/
+static void winceMutexAcquire(HANDLE h){
+   DWORD dwErr;
+   do {
+     dwErr = osWaitForSingleObject(h, INFINITE);
+   } while (dwErr != WAIT_OBJECT_0 && dwErr != WAIT_ABANDONED);
+}
+/*
+** Release a lock acquired by winceMutexAcquire()
+*/
+#define winceMutexRelease(h) ReleaseMutex(h)
+
+/*
+** Create the mutex and shared memory used for locking in the file
+** descriptor pFile
+*/
+static int winceCreateLock(const char *zFilename, winFile *pFile){
+  LPWSTR zTok;
+  LPWSTR zName;
+  DWORD lastErrno;
+  BOOL bLogged = FALSE;
+  BOOL bInit = TRUE;
+
+  zName = winUtf8ToUnicode(zFilename);
+  if( zName==0 ){
+    /* out of memory */
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+
+  /* Initialize the local lockdata */
+  memset(&pFile->local, 0, sizeof(pFile->local));
+
+  /* Replace the backslashes from the filename and lowercase it
+  ** to derive a mutex name. */
+  zTok = osCharLowerW(zName);
+  for (;*zTok;zTok++){
+    if (*zTok == '\\') *zTok = '_';
+  }
+
+  /* Create/open the named mutex */
+  pFile->hMutex = osCreateMutexW(NULL, FALSE, zName);
+  if (!pFile->hMutex){
+    pFile->lastErrno = osGetLastError();
+    sqlite3_free(zName);
+    return winLogError(SQLITE_IOERR, pFile->lastErrno,
+                       "winceCreateLock1", zFilename);
+  }
+
+  /* Acquire the mutex before continuing */
+  winceMutexAcquire(pFile->hMutex);
+
+  /* Since the names of named mutexes, semaphores, file mappings etc are
+  ** case-sensitive, take advantage of that by uppercasing the mutex name
+  ** and using that as the shared filemapping name.
+  */
+  osCharUpperW(zName);
+  pFile->hShared = osCreateFileMappingW(INVALID_HANDLE_VALUE, NULL,
+                                        PAGE_READWRITE, 0, sizeof(winceLock),
+                                        zName);
+
+  /* Set a flag that indicates we're the first to create the memory so it
+  ** must be zero-initialized */
+  lastErrno = osGetLastError();
+  if (lastErrno == ERROR_ALREADY_EXISTS){
+    bInit = FALSE;
+  }
+
+  sqlite3_free(zName);
+
+  /* If we succeeded in making the shared memory handle, map it. */
+  if( pFile->hShared ){
+    pFile->shared = (winceLock*)osMapViewOfFile(pFile->hShared,
+             FILE_MAP_READ|FILE_MAP_WRITE, 0, 0, sizeof(winceLock));
+    /* If mapping failed, close the shared memory handle and erase it */
+    if( !pFile->shared ){
+      pFile->lastErrno = osGetLastError();
+      winLogError(SQLITE_IOERR, pFile->lastErrno,
+                  "winceCreateLock2", zFilename);
+      bLogged = TRUE;
+      osCloseHandle(pFile->hShared);
+      pFile->hShared = NULL;
+    }
+  }
+
+  /* If shared memory could not be created, then close the mutex and fail */
+  if( pFile->hShared==NULL ){
+    if( !bLogged ){
+      pFile->lastErrno = lastErrno;
+      winLogError(SQLITE_IOERR, pFile->lastErrno,
+                  "winceCreateLock3", zFilename);
+      bLogged = TRUE;
+    }
+    winceMutexRelease(pFile->hMutex);
+    osCloseHandle(pFile->hMutex);
+    pFile->hMutex = NULL;
+    return SQLITE_IOERR;
+  }
+
+  /* Initialize the shared memory if we're supposed to */
+  if( bInit ){
+    memset(pFile->shared, 0, sizeof(winceLock));
+  }
+
+  winceMutexRelease(pFile->hMutex);
+  return SQLITE_OK;
+}
+
+/*
+** Destroy the part of winFile that deals with wince locks
+*/
+static void winceDestroyLock(winFile *pFile){
+  if (pFile->hMutex){
+    /* Acquire the mutex */
+    winceMutexAcquire(pFile->hMutex);
+
+    /* The following blocks should probably assert in debug mode, but they
+       are to cleanup in case any locks remained open */
+    if (pFile->local.nReaders){
+      pFile->shared->nReaders --;
+    }
+    if (pFile->local.bReserved){
+      pFile->shared->bReserved = FALSE;
+    }
+    if (pFile->local.bPending){
+      pFile->shared->bPending = FALSE;
+    }
+    if (pFile->local.bExclusive){
+      pFile->shared->bExclusive = FALSE;
+    }
+
+    /* De-reference and close our copy of the shared memory handle */
+    osUnmapViewOfFile(pFile->shared);
+    osCloseHandle(pFile->hShared);
+
+    /* Done with the mutex */
+    winceMutexRelease(pFile->hMutex);
+    osCloseHandle(pFile->hMutex);
+    pFile->hMutex = NULL;
+  }
+}
+
+/*
+** An implementation of the LockFile() API of Windows for CE
+*/
+static BOOL winceLockFile(
+  LPHANDLE phFile,
+  DWORD dwFileOffsetLow,
+  DWORD dwFileOffsetHigh,
+  DWORD nNumberOfBytesToLockLow,
+  DWORD nNumberOfBytesToLockHigh
+){
+  winFile *pFile = HANDLE_TO_WINFILE(phFile);
+  BOOL bReturn = FALSE;
+
+  UNUSED_PARAMETER(dwFileOffsetHigh);
+  UNUSED_PARAMETER(nNumberOfBytesToLockHigh);
+
+  if (!pFile->hMutex) return TRUE;
+  winceMutexAcquire(pFile->hMutex);
+
+  /* Wanting an exclusive lock? */
+  if (dwFileOffsetLow == (DWORD)SHARED_FIRST
+       && nNumberOfBytesToLockLow == (DWORD)SHARED_SIZE){
+    if (pFile->shared->nReaders == 0 && pFile->shared->bExclusive == 0){
+       pFile->shared->bExclusive = TRUE;
+       pFile->local.bExclusive = TRUE;
+       bReturn = TRUE;
+    }
+  }
+
+  /* Want a read-only lock? */
+  else if (dwFileOffsetLow == (DWORD)SHARED_FIRST &&
+           nNumberOfBytesToLockLow == 1){
+    if (pFile->shared->bExclusive == 0){
+      pFile->local.nReaders ++;
+      if (pFile->local.nReaders == 1){
+        pFile->shared->nReaders ++;
+      }
+      bReturn = TRUE;
+    }
+  }
+
+  /* Want a pending lock? */
+  else if (dwFileOffsetLow == (DWORD)PENDING_BYTE
+           && nNumberOfBytesToLockLow == 1){
+    /* If no pending lock has been acquired, then acquire it */
+    if (pFile->shared->bPending == 0) {
+      pFile->shared->bPending = TRUE;
+      pFile->local.bPending = TRUE;
+      bReturn = TRUE;
+    }
+  }
+
+  /* Want a reserved lock? */
+  else if (dwFileOffsetLow == (DWORD)RESERVED_BYTE
+           && nNumberOfBytesToLockLow == 1){
+    if (pFile->shared->bReserved == 0) {
+      pFile->shared->bReserved = TRUE;
+      pFile->local.bReserved = TRUE;
+      bReturn = TRUE;
+    }
+  }
+
+  winceMutexRelease(pFile->hMutex);
+  return bReturn;
+}
+
+/*
+** An implementation of the UnlockFile API of Windows for CE
+*/
+static BOOL winceUnlockFile(
+  LPHANDLE phFile,
+  DWORD dwFileOffsetLow,
+  DWORD dwFileOffsetHigh,
+  DWORD nNumberOfBytesToUnlockLow,
+  DWORD nNumberOfBytesToUnlockHigh
+){
+  winFile *pFile = HANDLE_TO_WINFILE(phFile);
+  BOOL bReturn = FALSE;
+
+  UNUSED_PARAMETER(dwFileOffsetHigh);
+  UNUSED_PARAMETER(nNumberOfBytesToUnlockHigh);
+
+  if (!pFile->hMutex) return TRUE;
+  winceMutexAcquire(pFile->hMutex);
+
+  /* Releasing a reader lock or an exclusive lock */
+  if (dwFileOffsetLow == (DWORD)SHARED_FIRST){
+    /* Did we have an exclusive lock? */
+    if (pFile->local.bExclusive){
+      assert(nNumberOfBytesToUnlockLow == (DWORD)SHARED_SIZE);
+      pFile->local.bExclusive = FALSE;
+      pFile->shared->bExclusive = FALSE;
+      bReturn = TRUE;
+    }
+
+    /* Did we just have a reader lock? */
+    else if (pFile->local.nReaders){
+      assert(nNumberOfBytesToUnlockLow == (DWORD)SHARED_SIZE
+             || nNumberOfBytesToUnlockLow == 1);
+      pFile->local.nReaders --;
+      if (pFile->local.nReaders == 0)
+      {
+        pFile->shared->nReaders --;
+      }
+      bReturn = TRUE;
+    }
+  }
+
+  /* Releasing a pending lock */
+  else if (dwFileOffsetLow == (DWORD)PENDING_BYTE
+           && nNumberOfBytesToUnlockLow == 1){
+    if (pFile->local.bPending){
+      pFile->local.bPending = FALSE;
+      pFile->shared->bPending = FALSE;
+      bReturn = TRUE;
+    }
+  }
+  /* Releasing a reserved lock */
+  else if (dwFileOffsetLow == (DWORD)RESERVED_BYTE
+           && nNumberOfBytesToUnlockLow == 1){
+    if (pFile->local.bReserved) {
+      pFile->local.bReserved = FALSE;
+      pFile->shared->bReserved = FALSE;
+      bReturn = TRUE;
+    }
+  }
+
+  winceMutexRelease(pFile->hMutex);
+  return bReturn;
+}
+/*
+** End of the special code for wince
+*****************************************************************************/
+#endif /* SQLITE_OS_WINCE */
+
+/*
+** Lock a file region.
+*/
+static BOOL winLockFile(
+  LPHANDLE phFile,
+  DWORD flags,
+  DWORD offsetLow,
+  DWORD offsetHigh,
+  DWORD numBytesLow,
+  DWORD numBytesHigh
+){
+#if SQLITE_OS_WINCE
+  /*
+  ** NOTE: Windows CE is handled differently here due its lack of the Win32
+  **       API LockFile.
+  */
+  return winceLockFile(phFile, offsetLow, offsetHigh,
+                       numBytesLow, numBytesHigh);
+#else
+  if( osIsNT() ){
+    OVERLAPPED ovlp;
+    memset(&ovlp, 0, sizeof(OVERLAPPED));
+    ovlp.Offset = offsetLow;
+    ovlp.OffsetHigh = offsetHigh;
+    return osLockFileEx(*phFile, flags, 0, numBytesLow, numBytesHigh, &ovlp);
+  }else{
+    return osLockFile(*phFile, offsetLow, offsetHigh, numBytesLow,
+                      numBytesHigh);
+  }
+#endif
+}
+
+/*
+** Unlock a file region.
+ */
+static BOOL winUnlockFile(
+  LPHANDLE phFile,
+  DWORD offsetLow,
+  DWORD offsetHigh,
+  DWORD numBytesLow,
+  DWORD numBytesHigh
+){
+#if SQLITE_OS_WINCE
+  /*
+  ** NOTE: Windows CE is handled differently here due its lack of the Win32
+  **       API UnlockFile.
+  */
+  return winceUnlockFile(phFile, offsetLow, offsetHigh,
+                         numBytesLow, numBytesHigh);
+#else
+  if( osIsNT() ){
+    OVERLAPPED ovlp;
+    memset(&ovlp, 0, sizeof(OVERLAPPED));
+    ovlp.Offset = offsetLow;
+    ovlp.OffsetHigh = offsetHigh;
+    return osUnlockFileEx(*phFile, 0, numBytesLow, numBytesHigh, &ovlp);
+  }else{
+    return osUnlockFile(*phFile, offsetLow, offsetHigh, numBytesLow,
+                        numBytesHigh);
+  }
+#endif
+}
+
+/*****************************************************************************
+** The next group of routines implement the I/O methods specified
+** by the sqlite3_io_methods object.
+******************************************************************************/
+
+/*
+** Some Microsoft compilers lack this definition.
+*/
+#ifndef INVALID_SET_FILE_POINTER
+# define INVALID_SET_FILE_POINTER ((DWORD)-1)
+#endif
+
+/*
+** Move the current position of the file handle passed as the first
+** argument to offset iOffset within the file. If successful, return 0.
+** Otherwise, set pFile->lastErrno and return non-zero.
+*/
+static int winSeekFile(winFile *pFile, sqlite3_int64 iOffset){
+#if !SQLITE_OS_WINRT
+  LONG upperBits;                 /* Most sig. 32 bits of new offset */
+  LONG lowerBits;                 /* Least sig. 32 bits of new offset */
+  DWORD dwRet;                    /* Value returned by SetFilePointer() */
+  DWORD lastErrno;                /* Value returned by GetLastError() */
+
+  OSTRACE(("SEEK file=%p, offset=%lld\n", pFile->h, iOffset));
+
+  upperBits = (LONG)((iOffset>>32) & 0x7fffffff);
+  lowerBits = (LONG)(iOffset & 0xffffffff);
+
+  /* API oddity: If successful, SetFilePointer() returns a dword
+  ** containing the lower 32-bits of the new file-offset. Or, if it fails,
+  ** it returns INVALID_SET_FILE_POINTER. However according to MSDN,
+  ** INVALID_SET_FILE_POINTER may also be a valid new offset. So to determine
+  ** whether an error has actually occurred, it is also necessary to call
+  ** GetLastError().
+  */
+  dwRet = osSetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
+
+  if( (dwRet==INVALID_SET_FILE_POINTER
+      && ((lastErrno = osGetLastError())!=NO_ERROR)) ){
+    pFile->lastErrno = lastErrno;
+    winLogError(SQLITE_IOERR_SEEK, pFile->lastErrno,
+                "winSeekFile", pFile->zPath);
+    OSTRACE(("SEEK file=%p, rc=SQLITE_IOERR_SEEK\n", pFile->h));
+    return 1;
+  }
+
+  OSTRACE(("SEEK file=%p, rc=SQLITE_OK\n", pFile->h));
+  return 0;
+#else
+  /*
+  ** Same as above, except that this implementation works for WinRT.
+  */
+
+  LARGE_INTEGER x;                /* The new offset */
+  BOOL bRet;                      /* Value returned by SetFilePointerEx() */
+
+  x.QuadPart = iOffset;
+  bRet = osSetFilePointerEx(pFile->h, x, 0, FILE_BEGIN);
+
+  if(!bRet){
+    pFile->lastErrno = osGetLastError();
+    winLogError(SQLITE_IOERR_SEEK, pFile->lastErrno,
+                "winSeekFile", pFile->zPath);
+    OSTRACE(("SEEK file=%p, rc=SQLITE_IOERR_SEEK\n", pFile->h));
+    return 1;
+  }
+
+  OSTRACE(("SEEK file=%p, rc=SQLITE_OK\n", pFile->h));
+  return 0;
+#endif
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/* Forward references to VFS helper methods used for memory mapped files */
+static int winMapfile(winFile*, sqlite3_int64);
+static int winUnmapfile(winFile*);
+#endif
+
+/*
+** Close a file.
+**
+** It is reported that an attempt to close a handle might sometimes
+** fail.  This is a very unreasonable result, but Windows is notorious
+** for being unreasonable so I do not doubt that it might happen.  If
+** the close fails, we pause for 100 milliseconds and try again.  As
+** many as MX_CLOSE_ATTEMPT attempts to close the handle are made before
+** giving up and returning an error.
+*/
+#define MX_CLOSE_ATTEMPT 3
+static int winClose(sqlite3_file *id){
+  int rc, cnt = 0;
+  winFile *pFile = (winFile*)id;
+
+  assert( id!=0 );
+#ifndef SQLITE_OMIT_WAL
+  assert( pFile->pShm==0 );
+#endif
+  assert( pFile->h!=NULL && pFile->h!=INVALID_HANDLE_VALUE );
+  OSTRACE(("CLOSE pid=%lu, pFile=%p, file=%p\n",
+           osGetCurrentProcessId(), pFile, pFile->h));
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  winUnmapfile(pFile);
+#endif
+
+  do{
+    rc = osCloseHandle(pFile->h);
+    /* SimulateIOError( rc=0; cnt=MX_CLOSE_ATTEMPT; ); */
+  }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (sqlite3_win32_sleep(100), 1) );
+#if SQLITE_OS_WINCE
+#define WINCE_DELETION_ATTEMPTS 3
+  {
+    winVfsAppData *pAppData = (winVfsAppData*)pFile->pVfs->pAppData;
+    if( pAppData==NULL || !pAppData->bNoLock ){
+      winceDestroyLock(pFile);
+    }
+  }
+  if( pFile->zDeleteOnClose ){
+    int cnt = 0;
+    while(
+           osDeleteFileW(pFile->zDeleteOnClose)==0
+        && osGetFileAttributesW(pFile->zDeleteOnClose)!=0xffffffff
+        && cnt++ < WINCE_DELETION_ATTEMPTS
+    ){
+       sqlite3_win32_sleep(100);  /* Wait a little before trying again */
+    }
+    sqlite3_free(pFile->zDeleteOnClose);
+  }
+#endif
+  if( rc ){
+    pFile->h = NULL;
+  }
+  OpenCounter(-1);
+  OSTRACE(("CLOSE pid=%lu, pFile=%p, file=%p, rc=%s\n",
+           osGetCurrentProcessId(), pFile, pFile->h, rc ? "ok" : "failed"));
+  return rc ? SQLITE_OK
+            : winLogError(SQLITE_IOERR_CLOSE, osGetLastError(),
+                          "winClose", pFile->zPath);
+}
+
+/*
+** Read data from a file into a buffer.  Return SQLITE_OK if all
+** bytes were read successfully and SQLITE_IOERR if anything goes
+** wrong.
+*/
+static int winRead(
+  sqlite3_file *id,          /* File to read from */
+  void *pBuf,                /* Write content into this buffer */
+  int amt,                   /* Number of bytes to read */
+  sqlite3_int64 offset       /* Begin reading at this offset */
+){
+#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
+  OVERLAPPED overlapped;          /* The offset for ReadFile. */
+#endif
+  winFile *pFile = (winFile*)id;  /* file handle */
+  DWORD nRead;                    /* Number of bytes actually read from file */
+  int nRetry = 0;                 /* Number of retrys */
+
+  assert( id!=0 );
+  assert( amt>0 );
+  assert( offset>=0 );
+  SimulateIOError(return SQLITE_IOERR_READ);
+  OSTRACE(("READ pid=%lu, pFile=%p, file=%p, buffer=%p, amount=%d, "
+           "offset=%lld, lock=%d\n", osGetCurrentProcessId(), pFile,
+           pFile->h, pBuf, amt, offset, pFile->locktype));
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  /* Deal with as much of this read request as possible by transferring
+  ** data from the memory mapping using memcpy().  */
+  if( offset<pFile->mmapSize ){
+    if( offset+amt <= pFile->mmapSize ){
+      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], amt);
+      OSTRACE(("READ-MMAP pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
+               osGetCurrentProcessId(), pFile, pFile->h));
+      return SQLITE_OK;
+    }else{
+      int nCopy = (int)(pFile->mmapSize - offset);
+      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], nCopy);
+      pBuf = &((u8 *)pBuf)[nCopy];
+      amt -= nCopy;
+      offset += nCopy;
+    }
+  }
+#endif
+
+#if SQLITE_OS_WINCE || defined(SQLITE_WIN32_NO_OVERLAPPED)
+  if( winSeekFile(pFile, offset) ){
+    OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_FULL\n",
+             osGetCurrentProcessId(), pFile, pFile->h));
+    return SQLITE_FULL;
+  }
+  while( !osReadFile(pFile->h, pBuf, amt, &nRead, 0) ){
+#else
+  memset(&overlapped, 0, sizeof(OVERLAPPED));
+  overlapped.Offset = (LONG)(offset & 0xffffffff);
+  overlapped.OffsetHigh = (LONG)((offset>>32) & 0x7fffffff);
+  while( !osReadFile(pFile->h, pBuf, amt, &nRead, &overlapped) &&
+         osGetLastError()!=ERROR_HANDLE_EOF ){
+#endif
+    DWORD lastErrno;
+    if( winRetryIoerr(&nRetry, &lastErrno) ) continue;
+    pFile->lastErrno = lastErrno;
+    OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_READ\n",
+             osGetCurrentProcessId(), pFile, pFile->h));
+    return winLogError(SQLITE_IOERR_READ, pFile->lastErrno,
+                       "winRead", pFile->zPath);
+  }
+  winLogIoerr(nRetry, __LINE__);
+  if( nRead<(DWORD)amt ){
+    /* Unread parts of the buffer must be zero-filled */
+    memset(&((char*)pBuf)[nRead], 0, amt-nRead);
+    OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_SHORT_READ\n",
+             osGetCurrentProcessId(), pFile, pFile->h));
+    return SQLITE_IOERR_SHORT_READ;
+  }
+
+  OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
+           osGetCurrentProcessId(), pFile, pFile->h));
+  return SQLITE_OK;
+}
+
+/*
+** Write data from a buffer into a file.  Return SQLITE_OK on success
+** or some other error code on failure.
+*/
+static int winWrite(
+  sqlite3_file *id,               /* File to write into */
+  const void *pBuf,               /* The bytes to be written */
+  int amt,                        /* Number of bytes to write */
+  sqlite3_int64 offset            /* Offset into the file to begin writing at */
+){
+  int rc = 0;                     /* True if error has occurred, else false */
+  winFile *pFile = (winFile*)id;  /* File handle */
+  int nRetry = 0;                 /* Number of retries */
+
+  assert( amt>0 );
+  assert( pFile );
+  SimulateIOError(return SQLITE_IOERR_WRITE);
+  SimulateDiskfullError(return SQLITE_FULL);
+
+  OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, buffer=%p, amount=%d, "
+           "offset=%lld, lock=%d\n", osGetCurrentProcessId(), pFile,
+           pFile->h, pBuf, amt, offset, pFile->locktype));
+
+#if defined(SQLITE_MMAP_READWRITE) && SQLITE_MAX_MMAP_SIZE>0
+  /* Deal with as much of this write request as possible by transferring
+  ** data from the memory mapping using memcpy().  */
+  if( offset<pFile->mmapSize ){
+    if( offset+amt <= pFile->mmapSize ){
+      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, amt);
+      OSTRACE(("WRITE-MMAP pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
+               osGetCurrentProcessId(), pFile, pFile->h));
+      return SQLITE_OK;
+    }else{
+      int nCopy = (int)(pFile->mmapSize - offset);
+      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, nCopy);
+      pBuf = &((u8 *)pBuf)[nCopy];
+      amt -= nCopy;
+      offset += nCopy;
+    }
+  }
+#endif
+
+#if SQLITE_OS_WINCE || defined(SQLITE_WIN32_NO_OVERLAPPED)
+  rc = winSeekFile(pFile, offset);
+  if( rc==0 ){
+#else
+  {
+#endif
+#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
+    OVERLAPPED overlapped;        /* The offset for WriteFile. */
+#endif
+    u8 *aRem = (u8 *)pBuf;        /* Data yet to be written */
+    int nRem = amt;               /* Number of bytes yet to be written */
+    DWORD nWrite;                 /* Bytes written by each WriteFile() call */
+    DWORD lastErrno = NO_ERROR;   /* Value returned by GetLastError() */
+
+#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
+    memset(&overlapped, 0, sizeof(OVERLAPPED));
+    overlapped.Offset = (LONG)(offset & 0xffffffff);
+    overlapped.OffsetHigh = (LONG)((offset>>32) & 0x7fffffff);
+#endif
+
+    while( nRem>0 ){
+#if SQLITE_OS_WINCE || defined(SQLITE_WIN32_NO_OVERLAPPED)
+      if( !osWriteFile(pFile->h, aRem, nRem, &nWrite, 0) ){
+#else
+      if( !osWriteFile(pFile->h, aRem, nRem, &nWrite, &overlapped) ){
+#endif
+        if( winRetryIoerr(&nRetry, &lastErrno) ) continue;
+        break;
+      }
+      assert( nWrite==0 || nWrite<=(DWORD)nRem );
+      if( nWrite==0 || nWrite>(DWORD)nRem ){
+        lastErrno = osGetLastError();
+        break;
+      }
+#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
+      offset += nWrite;
+      overlapped.Offset = (LONG)(offset & 0xffffffff);
+      overlapped.OffsetHigh = (LONG)((offset>>32) & 0x7fffffff);
+#endif
+      aRem += nWrite;
+      nRem -= nWrite;
+    }
+    if( nRem>0 ){
+      pFile->lastErrno = lastErrno;
+      rc = 1;
+    }
+  }
+
+  if( rc ){
+    if(   ( pFile->lastErrno==ERROR_HANDLE_DISK_FULL )
+       || ( pFile->lastErrno==ERROR_DISK_FULL )){
+      OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, rc=SQLITE_FULL\n",
+               osGetCurrentProcessId(), pFile, pFile->h));
+      return winLogError(SQLITE_FULL, pFile->lastErrno,
+                         "winWrite1", pFile->zPath);
+    }
+    OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_WRITE\n",
+             osGetCurrentProcessId(), pFile, pFile->h));
+    return winLogError(SQLITE_IOERR_WRITE, pFile->lastErrno,
+                       "winWrite2", pFile->zPath);
+  }else{
+    winLogIoerr(nRetry, __LINE__);
+  }
+  OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
+           osGetCurrentProcessId(), pFile, pFile->h));
+  return SQLITE_OK;
+}
+
+/*
+** Truncate an open file to a specified size
+*/
+static int winTruncate(sqlite3_file *id, sqlite3_int64 nByte){
+  winFile *pFile = (winFile*)id;  /* File handle object */
+  int rc = SQLITE_OK;             /* Return code for this function */
+  DWORD lastErrno;
+#if SQLITE_MAX_MMAP_SIZE>0
+  sqlite3_int64 oldMmapSize;
+  if( pFile->nFetchOut>0 ){
+    /* File truncation is a no-op if there are outstanding memory mapped
+    ** pages.  This is because truncating the file means temporarily unmapping
+    ** the file, and that might delete memory out from under existing cursors.
+    **
+    ** This can result in incremental vacuum not truncating the file,
+    ** if there is an active read cursor when the incremental vacuum occurs.
+    ** No real harm comes of this - the database file is not corrupted,
+    ** though some folks might complain that the file is bigger than it
+    ** needs to be.
+    **
+    ** The only feasible work-around is to defer the truncation until after
+    ** all references to memory-mapped content are closed.  That is doable,
+    ** but involves adding a few branches in the common write code path which
+    ** could slow down normal operations slightly.  Hence, we have decided for
+    ** now to simply make transactions a no-op if there are pending reads.  We
+    ** can maybe revisit this decision in the future.
+    */
+    return SQLITE_OK;
+  }
+#endif
+
+  assert( pFile );
+  SimulateIOError(return SQLITE_IOERR_TRUNCATE);
+  OSTRACE(("TRUNCATE pid=%lu, pFile=%p, file=%p, size=%lld, lock=%d\n",
+           osGetCurrentProcessId(), pFile, pFile->h, nByte, pFile->locktype));
+
+  /* If the user has configured a chunk-size for this file, truncate the
+  ** file so that it consists of an integer number of chunks (i.e. the
+  ** actual file size after the operation may be larger than the requested
+  ** size).
+  */
+  if( pFile->szChunk>0 ){
+    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
+  }
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  if( pFile->pMapRegion ){
+    oldMmapSize = pFile->mmapSize;
+  }else{
+    oldMmapSize = 0;
+  }
+  winUnmapfile(pFile);
+#endif
+
+  /* SetEndOfFile() returns non-zero when successful, or zero when it fails. */
+  if( winSeekFile(pFile, nByte) ){
+    rc = winLogError(SQLITE_IOERR_TRUNCATE, pFile->lastErrno,
+                     "winTruncate1", pFile->zPath);
+  }else if( 0==osSetEndOfFile(pFile->h) &&
+            ((lastErrno = osGetLastError())!=ERROR_USER_MAPPED_FILE) ){
+    pFile->lastErrno = lastErrno;
+    rc = winLogError(SQLITE_IOERR_TRUNCATE, pFile->lastErrno,
+                     "winTruncate2", pFile->zPath);
+  }
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  if( rc==SQLITE_OK && oldMmapSize>0 ){
+    if( oldMmapSize>nByte ){
+      winMapfile(pFile, -1);
+    }else{
+      winMapfile(pFile, oldMmapSize);
+    }
+  }
+#endif
+
+  OSTRACE(("TRUNCATE pid=%lu, pFile=%p, file=%p, rc=%s\n",
+           osGetCurrentProcessId(), pFile, pFile->h, sqlite3ErrName(rc)));
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Count the number of fullsyncs and normal syncs.  This is used to test
+** that syncs and fullsyncs are occurring at the right times.
+*/
+int sqlite3_sync_count = 0;
+int sqlite3_fullsync_count = 0;
+#endif
+
+/*
+** Make sure all writes to a particular file are committed to disk.
+*/
+static int winSync(sqlite3_file *id, int flags){
+#ifndef SQLITE_NO_SYNC
+  /*
+  ** Used only when SQLITE_NO_SYNC is not defined.
+   */
+  BOOL rc;
+#endif
+#if !defined(NDEBUG) || !defined(SQLITE_NO_SYNC) || \
+    defined(SQLITE_HAVE_OS_TRACE)
+  /*
+  ** Used when SQLITE_NO_SYNC is not defined and by the assert() and/or
+  ** OSTRACE() macros.
+   */
+  winFile *pFile = (winFile*)id;
+#else
+  UNUSED_PARAMETER(id);
+#endif
+
+  assert( pFile );
+  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
+  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
+      || (flags&0x0F)==SQLITE_SYNC_FULL
+  );
+
+  /* Unix cannot, but some systems may return SQLITE_FULL from here. This
+  ** line is to test that doing so does not cause any problems.
+  */
+  SimulateDiskfullError( return SQLITE_FULL );
+
+  OSTRACE(("SYNC pid=%lu, pFile=%p, file=%p, flags=%x, lock=%d\n",
+           osGetCurrentProcessId(), pFile, pFile->h, flags,
+           pFile->locktype));
+
+#ifndef SQLITE_TEST
+  UNUSED_PARAMETER(flags);
+#else
+  if( (flags&0x0F)==SQLITE_SYNC_FULL ){
+    sqlite3_fullsync_count++;
+  }
+  sqlite3_sync_count++;
+#endif
+
+  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
+  ** no-op
+  */
+#ifdef SQLITE_NO_SYNC
+  OSTRACE(("SYNC-NOP pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
+           osGetCurrentProcessId(), pFile, pFile->h));
+  return SQLITE_OK;
+#else
+#if SQLITE_MAX_MMAP_SIZE>0
+  if( pFile->pMapRegion ){
+    if( osFlushViewOfFile(pFile->pMapRegion, 0) ){
+      OSTRACE(("SYNC-MMAP pid=%lu, pFile=%p, pMapRegion=%p, "
+               "rc=SQLITE_OK\n", osGetCurrentProcessId(),
+               pFile, pFile->pMapRegion));
+    }else{
+      pFile->lastErrno = osGetLastError();
+      OSTRACE(("SYNC-MMAP pid=%lu, pFile=%p, pMapRegion=%p, "
+               "rc=SQLITE_IOERR_MMAP\n", osGetCurrentProcessId(),
+               pFile, pFile->pMapRegion));
+      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
+                         "winSync1", pFile->zPath);
+    }
+  }
+#endif
+  rc = osFlushFileBuffers(pFile->h);
+  SimulateIOError( rc=FALSE );
+  if( rc ){
+    OSTRACE(("SYNC pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
+             osGetCurrentProcessId(), pFile, pFile->h));
+    return SQLITE_OK;
+  }else{
+    pFile->lastErrno = osGetLastError();
+    OSTRACE(("SYNC pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_FSYNC\n",
+             osGetCurrentProcessId(), pFile, pFile->h));
+    return winLogError(SQLITE_IOERR_FSYNC, pFile->lastErrno,
+                       "winSync2", pFile->zPath);
+  }
+#endif
+}
+
+/*
+** Determine the current size of a file in bytes
+*/
+static int winFileSize(sqlite3_file *id, sqlite3_int64 *pSize){
+  winFile *pFile = (winFile*)id;
+  int rc = SQLITE_OK;
+
+  assert( id!=0 );
+  assert( pSize!=0 );
+  SimulateIOError(return SQLITE_IOERR_FSTAT);
+  OSTRACE(("SIZE file=%p, pSize=%p\n", pFile->h, pSize));
+
+#if SQLITE_OS_WINRT
+  {
+    FILE_STANDARD_INFO info;
+    if( osGetFileInformationByHandleEx(pFile->h, FileStandardInfo,
+                                     &info, sizeof(info)) ){
+      *pSize = info.EndOfFile.QuadPart;
+    }else{
+      pFile->lastErrno = osGetLastError();
+      rc = winLogError(SQLITE_IOERR_FSTAT, pFile->lastErrno,
+                       "winFileSize", pFile->zPath);
+    }
+  }
+#else
+  {
+    DWORD upperBits;
+    DWORD lowerBits;
+    DWORD lastErrno;
+
+    lowerBits = osGetFileSize(pFile->h, &upperBits);
+    *pSize = (((sqlite3_int64)upperBits)<<32) + lowerBits;
+    if(   (lowerBits == INVALID_FILE_SIZE)
+       && ((lastErrno = osGetLastError())!=NO_ERROR) ){
+      pFile->lastErrno = lastErrno;
+      rc = winLogError(SQLITE_IOERR_FSTAT, pFile->lastErrno,
+                       "winFileSize", pFile->zPath);
+    }
+  }
+#endif
+  OSTRACE(("SIZE file=%p, pSize=%p, *pSize=%lld, rc=%s\n",
+           pFile->h, pSize, *pSize, sqlite3ErrName(rc)));
+  return rc;
+}
+
+/*
+** LOCKFILE_FAIL_IMMEDIATELY is undefined on some Windows systems.
+*/
+#ifndef LOCKFILE_FAIL_IMMEDIATELY
+# define LOCKFILE_FAIL_IMMEDIATELY 1
+#endif
+
+#ifndef LOCKFILE_EXCLUSIVE_LOCK
+# define LOCKFILE_EXCLUSIVE_LOCK 2
+#endif
+
+/*
+** Historically, SQLite has used both the LockFile and LockFileEx functions.
+** When the LockFile function was used, it was always expected to fail
+** immediately if the lock could not be obtained.  Also, it always expected to
+** obtain an exclusive lock.  These flags are used with the LockFileEx function
+** and reflect those expectations; therefore, they should not be changed.
+*/
+#ifndef SQLITE_LOCKFILE_FLAGS
+# define SQLITE_LOCKFILE_FLAGS   (LOCKFILE_FAIL_IMMEDIATELY | \
+                                  LOCKFILE_EXCLUSIVE_LOCK)
+#endif
+
+/*
+** Currently, SQLite never calls the LockFileEx function without wanting the
+** call to fail immediately if the lock cannot be obtained.
+*/
+#ifndef SQLITE_LOCKFILEEX_FLAGS
+# define SQLITE_LOCKFILEEX_FLAGS (LOCKFILE_FAIL_IMMEDIATELY)
+#endif
+
+/*
+** Acquire a reader lock.
+** Different API routines are called depending on whether or not this
+** is Win9x or WinNT.
+*/
+static int winGetReadLock(winFile *pFile){
+  int res;
+  OSTRACE(("READ-LOCK file=%p, lock=%d\n", pFile->h, pFile->locktype));
+  if( osIsNT() ){
+#if SQLITE_OS_WINCE
+    /*
+    ** NOTE: Windows CE is handled differently here due its lack of the Win32
+    **       API LockFileEx.
+    */
+    res = winceLockFile(&pFile->h, SHARED_FIRST, 0, 1, 0);
+#else
+    res = winLockFile(&pFile->h, SQLITE_LOCKFILEEX_FLAGS, SHARED_FIRST, 0,
+                      SHARED_SIZE, 0);
+#endif
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    int lk;
+    sqlite3_randomness(sizeof(lk), &lk);
+    pFile->sharedLockByte = (short)((lk & 0x7fffffff)%(SHARED_SIZE - 1));
+    res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS,
+                      SHARED_FIRST+pFile->sharedLockByte, 0, 1, 0);
+  }
+#endif
+  if( res == 0 ){
+    pFile->lastErrno = osGetLastError();
+    /* No need to log a failure to lock */
+  }
+  OSTRACE(("READ-LOCK file=%p, result=%d\n", pFile->h, res));
+  return res;
+}
+
+/*
+** Undo a readlock
+*/
+static int winUnlockReadLock(winFile *pFile){
+  int res;
+  DWORD lastErrno;
+  OSTRACE(("READ-UNLOCK file=%p, lock=%d\n", pFile->h, pFile->locktype));
+  if( osIsNT() ){
+    res = winUnlockFile(&pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    res = winUnlockFile(&pFile->h, SHARED_FIRST+pFile->sharedLockByte, 0, 1, 0);
+  }
+#endif
+  if( res==0 && ((lastErrno = osGetLastError())!=ERROR_NOT_LOCKED) ){
+    pFile->lastErrno = lastErrno;
+    winLogError(SQLITE_IOERR_UNLOCK, pFile->lastErrno,
+                "winUnlockReadLock", pFile->zPath);
+  }
+  OSTRACE(("READ-UNLOCK file=%p, result=%d\n", pFile->h, res));
+  return res;
+}
+
+/*
+** Lock the file with the lock specified by parameter locktype - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  The winUnlock() routine
+** erases all locks at once and returns us immediately to locking level 0.
+** It is not possible to lower the locking level one step at a time.  You
+** must go straight to locking level 0.
+*/
+static int winLock(sqlite3_file *id, int locktype){
+  int rc = SQLITE_OK;    /* Return code from subroutines */
+  int res = 1;           /* Result of a Windows lock call */
+  int newLocktype;       /* Set pFile->locktype to this value before exiting */
+  int gotPendingLock = 0;/* True if we acquired a PENDING lock this time */
+  winFile *pFile = (winFile*)id;
+  DWORD lastErrno = NO_ERROR;
+
+  assert( id!=0 );
+  OSTRACE(("LOCK file=%p, oldLock=%d(%d), newLock=%d\n",
+           pFile->h, pFile->locktype, pFile->sharedLockByte, locktype));
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** OsFile, do nothing. Don't use the end_lock: exit path, as
+  ** sqlite3OsEnterMutex() hasn't been called yet.
+  */
+  if( pFile->locktype>=locktype ){
+    OSTRACE(("LOCK-HELD file=%p, rc=SQLITE_OK\n", pFile->h));
+    return SQLITE_OK;
+  }
+
+  /* Do not allow any kind of write-lock on a read-only database
+  */
+  if( (pFile->ctrlFlags & WINFILE_RDONLY)!=0 && locktype>=RESERVED_LOCK ){
+    return SQLITE_IOERR_LOCK;
+  }
+
+  /* Make sure the locking sequence is correct
+  */
+  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
+  assert( locktype!=PENDING_LOCK );
+  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+
+  /* Lock the PENDING_LOCK byte if we need to acquire a PENDING lock or
+  ** a SHARED lock.  If we are acquiring a SHARED lock, the acquisition of
+  ** the PENDING_LOCK byte is temporary.
+  */
+  newLocktype = pFile->locktype;
+  if( pFile->locktype==NO_LOCK
+   || (locktype==EXCLUSIVE_LOCK && pFile->locktype<=RESERVED_LOCK)
+  ){
+    int cnt = 3;
+    while( cnt-->0 && (res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS,
+                                         PENDING_BYTE, 0, 1, 0))==0 ){
+      /* Try 3 times to get the pending lock.  This is needed to work
+      ** around problems caused by indexing and/or anti-virus software on
+      ** Windows systems.
+      ** If you are using this code as a model for alternative VFSes, do not
+      ** copy this retry logic.  It is a hack intended for Windows only.
+      */
+      lastErrno = osGetLastError();
+      OSTRACE(("LOCK-PENDING-FAIL file=%p, count=%d, result=%d\n",
+               pFile->h, cnt, res));
+      if( lastErrno==ERROR_INVALID_HANDLE ){
+        pFile->lastErrno = lastErrno;
+        rc = SQLITE_IOERR_LOCK;
+        OSTRACE(("LOCK-FAIL file=%p, count=%d, rc=%s\n",
+                 pFile->h, cnt, sqlite3ErrName(rc)));
+        return rc;
+      }
+      if( cnt ) sqlite3_win32_sleep(1);
+    }
+    gotPendingLock = res;
+    if( !res ){
+      lastErrno = osGetLastError();
+    }
+  }
+
+  /* Acquire a shared lock
+  */
+  if( locktype==SHARED_LOCK && res ){
+    assert( pFile->locktype==NO_LOCK );
+    res = winGetReadLock(pFile);
+    if( res ){
+      newLocktype = SHARED_LOCK;
+    }else{
+      lastErrno = osGetLastError();
+    }
+  }
+
+  /* Acquire a RESERVED lock
+  */
+  if( locktype==RESERVED_LOCK && res ){
+    assert( pFile->locktype==SHARED_LOCK );
+    res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS, RESERVED_BYTE, 0, 1, 0);
+    if( res ){
+      newLocktype = RESERVED_LOCK;
+    }else{
+      lastErrno = osGetLastError();
+    }
+  }
+
+  /* Acquire a PENDING lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res ){
+    newLocktype = PENDING_LOCK;
+    gotPendingLock = 0;
+  }
+
+  /* Acquire an EXCLUSIVE lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res ){
+    assert( pFile->locktype>=SHARED_LOCK );
+    (void)winUnlockReadLock(pFile);
+    res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS, SHARED_FIRST, 0,
+                      SHARED_SIZE, 0);
+    if( res ){
+      newLocktype = EXCLUSIVE_LOCK;
+    }else{
+      lastErrno = osGetLastError();
+      winGetReadLock(pFile);
+    }
+  }
+
+  /* If we are holding a PENDING lock that ought to be released, then
+  ** release it now.
+  */
+  if( gotPendingLock && locktype==SHARED_LOCK ){
+    winUnlockFile(&pFile->h, PENDING_BYTE, 0, 1, 0);
+  }
+
+  /* Update the state of the lock has held in the file descriptor then
+  ** return the appropriate result code.
+  */
+  if( res ){
+    rc = SQLITE_OK;
+  }else{
+    pFile->lastErrno = lastErrno;
+    rc = SQLITE_BUSY;
+    OSTRACE(("LOCK-FAIL file=%p, wanted=%d, got=%d\n",
+             pFile->h, locktype, newLocktype));
+  }
+  pFile->locktype = (u8)newLocktype;
+  OSTRACE(("LOCK file=%p, lock=%d, rc=%s\n",
+           pFile->h, pFile->locktype, sqlite3ErrName(rc)));
+  return rc;
+}
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, return
+** non-zero, otherwise zero.
+*/
+static int winCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int res;
+  winFile *pFile = (winFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+  OSTRACE(("TEST-WR-LOCK file=%p, pResOut=%p\n", pFile->h, pResOut));
+
+  assert( id!=0 );
+  if( pFile->locktype>=RESERVED_LOCK ){
+    res = 1;
+    OSTRACE(("TEST-WR-LOCK file=%p, result=%d (local)\n", pFile->h, res));
+  }else{
+    res = winLockFile(&pFile->h, SQLITE_LOCKFILEEX_FLAGS,RESERVED_BYTE,0,1,0);
+    if( res ){
+      winUnlockFile(&pFile->h, RESERVED_BYTE, 0, 1, 0);
+    }
+    res = !res;
+    OSTRACE(("TEST-WR-LOCK file=%p, result=%d (remote)\n", pFile->h, res));
+  }
+  *pResOut = res;
+  OSTRACE(("TEST-WR-LOCK file=%p, pResOut=%p, *pResOut=%d, rc=SQLITE_OK\n",
+           pFile->h, pResOut, *pResOut));
+  return SQLITE_OK;
+}
+
+/*
+** Lower the locking level on file descriptor id to locktype.  locktype
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+**
+** It is not possible for this routine to fail if the second argument
+** is NO_LOCK.  If the second argument is SHARED_LOCK then this routine
+** might return SQLITE_IOERR;
+*/
+static int winUnlock(sqlite3_file *id, int locktype){
+  int type;
+  winFile *pFile = (winFile*)id;
+  int rc = SQLITE_OK;
+  assert( pFile!=0 );
+  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK file=%p, oldLock=%d(%d), newLock=%d\n",
+           pFile->h, pFile->locktype, pFile->sharedLockByte, locktype));
+  type = pFile->locktype;
+  if( type>=EXCLUSIVE_LOCK ){
+    winUnlockFile(&pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+    if( locktype==SHARED_LOCK && !winGetReadLock(pFile) ){
+      /* This should never happen.  We should always be able to
+      ** reacquire the read lock */
+      rc = winLogError(SQLITE_IOERR_UNLOCK, osGetLastError(),
+                       "winUnlock", pFile->zPath);
+    }
+  }
+  if( type>=RESERVED_LOCK ){
+    winUnlockFile(&pFile->h, RESERVED_BYTE, 0, 1, 0);
+  }
+  if( locktype==NO_LOCK && type>=SHARED_LOCK ){
+    winUnlockReadLock(pFile);
+  }
+  if( type>=PENDING_LOCK ){
+    winUnlockFile(&pFile->h, PENDING_BYTE, 0, 1, 0);
+  }
+  pFile->locktype = (u8)locktype;
+  OSTRACE(("UNLOCK file=%p, lock=%d, rc=%s\n",
+           pFile->h, pFile->locktype, sqlite3ErrName(rc)));
+  return rc;
+}
+
+/******************************************************************************
+****************************** No-op Locking **********************************
+**
+** Of the various locking implementations available, this is by far the
+** simplest:  locking is ignored.  No attempt is made to lock the database
+** file for reading or writing.
+**
+** This locking mode is appropriate for use on read-only databases
+** (ex: databases that are burned into CD-ROM, for example.)  It can
+** also be used if the application employs some external mechanism to
+** prevent simultaneous access of the same database by two or more
+** database connections.  But there is a serious risk of database
+** corruption if this locking mode is used in situations where multiple
+** database connections are accessing the same database file at the same
+** time and one or more of those connections are writing.
+*/
+
+static int winNolockLock(sqlite3_file *id, int locktype){
+  UNUSED_PARAMETER(id);
+  UNUSED_PARAMETER(locktype);
+  return SQLITE_OK;
+}
+
+static int winNolockCheckReservedLock(sqlite3_file *id, int *pResOut){
+  UNUSED_PARAMETER(id);
+  UNUSED_PARAMETER(pResOut);
+  return SQLITE_OK;
+}
+
+static int winNolockUnlock(sqlite3_file *id, int locktype){
+  UNUSED_PARAMETER(id);
+  UNUSED_PARAMETER(locktype);
+  return SQLITE_OK;
+}
+
+/******************* End of the no-op lock implementation *********************
+******************************************************************************/
+
+/*
+** If *pArg is initially negative then this is a query.  Set *pArg to
+** 1 or 0 depending on whether or not bit mask of pFile->ctrlFlags is set.
+**
+** If *pArg is 0 or 1, then clear or set the mask bit of pFile->ctrlFlags.
+*/
+static void winModeBit(winFile *pFile, unsigned char mask, int *pArg){
+  if( *pArg<0 ){
+    *pArg = (pFile->ctrlFlags & mask)!=0;
+  }else if( (*pArg)==0 ){
+    pFile->ctrlFlags &= ~mask;
+  }else{
+    pFile->ctrlFlags |= mask;
+  }
+}
+
+/* Forward references to VFS helper methods used for temporary files */
+static int winGetTempname(sqlite3_vfs *, char **);
+static int winIsDir(const void *);
+static BOOL winIsLongPathPrefix(const char *);
+static BOOL winIsDriveLetterAndColon(const char *);
+
+/*
+** Control and query of the open file handle.
+*/
+static int winFileControl(sqlite3_file *id, int op, void *pArg){
+  winFile *pFile = (winFile*)id;
+  OSTRACE(("FCNTL file=%p, op=%d, pArg=%p\n", pFile->h, op, pArg));
+  switch( op ){
+    case SQLITE_FCNTL_LOCKSTATE: {
+      *(int*)pArg = pFile->locktype;
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_LAST_ERRNO: {
+      *(int*)pArg = (int)pFile->lastErrno;
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      pFile->szChunk = *(int *)pArg;
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SIZE_HINT: {
+      if( pFile->szChunk>0 ){
+        sqlite3_int64 oldSz;
+        int rc = winFileSize(id, &oldSz);
+        if( rc==SQLITE_OK ){
+          sqlite3_int64 newSz = *(sqlite3_int64*)pArg;
+          if( newSz>oldSz ){
+            SimulateIOErrorBenign(1);
+            rc = winTruncate(id, newSz);
+            SimulateIOErrorBenign(0);
+          }
+        }
+        OSTRACE(("FCNTL file=%p, rc=%s\n", pFile->h, sqlite3ErrName(rc)));
+        return rc;
+      }
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_PERSIST_WAL: {
+      winModeBit(pFile, WINFILE_PERSIST_WAL, (int*)pArg);
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_POWERSAFE_OVERWRITE: {
+      winModeBit(pFile, WINFILE_PSOW, (int*)pArg);
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_VFSNAME: {
+      *(char**)pArg = sqlite3_mprintf("%s", pFile->pVfs->zName);
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_WIN32_AV_RETRY: {
+      int *a = (int*)pArg;
+      if( a[0]>0 ){
+        winIoerrRetry = a[0];
+      }else{
+        a[0] = winIoerrRetry;
+      }
+      if( a[1]>0 ){
+        winIoerrRetryDelay = a[1];
+      }else{
+        a[1] = winIoerrRetryDelay;
+      }
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_WIN32_GET_HANDLE: {
+      LPHANDLE phFile = (LPHANDLE)pArg;
+      *phFile = pFile->h;
+      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
+      return SQLITE_OK;
+    }
+#ifdef SQLITE_TEST
+    case SQLITE_FCNTL_WIN32_SET_HANDLE: {
+      LPHANDLE phFile = (LPHANDLE)pArg;
+      HANDLE hOldFile = pFile->h;
+      pFile->h = *phFile;
+      *phFile = hOldFile;
+      OSTRACE(("FCNTL oldFile=%p, newFile=%p, rc=SQLITE_OK\n",
+               hOldFile, pFile->h));
+      return SQLITE_OK;
+    }
+#endif
+    case SQLITE_FCNTL_TEMPFILENAME: {
+      char *zTFile = 0;
+      int rc = winGetTempname(pFile->pVfs, &zTFile);
+      if( rc==SQLITE_OK ){
+        *(char**)pArg = zTFile;
+      }
+      OSTRACE(("FCNTL file=%p, rc=%s\n", pFile->h, sqlite3ErrName(rc)));
+      return rc;
+    }
+#if SQLITE_MAX_MMAP_SIZE>0
+    case SQLITE_FCNTL_MMAP_SIZE: {
+      i64 newLimit = *(i64*)pArg;
+      int rc = SQLITE_OK;
+      if( newLimit>sqlite3GlobalConfig.mxMmap ){
+        newLimit = sqlite3GlobalConfig.mxMmap;
+      }
+
+      /* The value of newLimit may be eventually cast to (SIZE_T) and passed
+      ** to MapViewOfFile(). Restrict its value to 2GB if (SIZE_T) is not at
+      ** least a 64-bit type. */
+      if( newLimit>0 && sizeof(SIZE_T)<8 ){
+        newLimit = (newLimit & 0x7FFFFFFF);
+      }
+
+      *(i64*)pArg = pFile->mmapSizeMax;
+      if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){
+        pFile->mmapSizeMax = newLimit;
+        if( pFile->mmapSize>0 ){
+          winUnmapfile(pFile);
+          rc = winMapfile(pFile, -1);
+        }
+      }
+      OSTRACE(("FCNTL file=%p, rc=%s\n", pFile->h, sqlite3ErrName(rc)));
+      return rc;
+    }
+#endif
+  }
+  OSTRACE(("FCNTL file=%p, rc=SQLITE_NOTFOUND\n", pFile->h));
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** Return the sector size in bytes of the underlying block device for
+** the specified file. This is almost always 512 bytes, but may be
+** larger for some devices.
+**
+** SQLite code assumes this function cannot fail. It also assumes that
+** if two files are created in the same file-system directory (i.e.
+** a database and its journal file) that the sector size will be the
+** same for both.
+*/
+static int winSectorSize(sqlite3_file *id){
+  (void)id;
+  return SQLITE_DEFAULT_SECTOR_SIZE;
+}
+
+/*
+** Return a vector of device characteristics.
+*/
+static int winDeviceCharacteristics(sqlite3_file *id){
+  winFile *p = (winFile*)id;
+  return SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN |
+         ((p->ctrlFlags & WINFILE_PSOW)?SQLITE_IOCAP_POWERSAFE_OVERWRITE:0);
+}
+
+/*
+** Windows will only let you create file view mappings
+** on allocation size granularity boundaries.
+** During sqlite3_os_init() we do a GetSystemInfo()
+** to get the granularity size.
+*/
+static SYSTEM_INFO winSysInfo;
+
+#ifndef SQLITE_OMIT_WAL
+
+/*
+** Helper functions to obtain and relinquish the global mutex. The
+** global mutex is used to protect the winLockInfo objects used by
+** this file, all of which may be shared by multiple threads.
+**
+** Function winShmMutexHeld() is used to assert() that the global mutex
+** is held when required. This function is only used as part of assert()
+** statements. e.g.
+**
+**   winShmEnterMutex()
+**     assert( winShmMutexHeld() );
+**   winShmLeaveMutex()
+*/
+static sqlite3_mutex *winBigLock = 0;
+static void winShmEnterMutex(void){
+  sqlite3_mutex_enter(winBigLock);
+}
+static void winShmLeaveMutex(void){
+  sqlite3_mutex_leave(winBigLock);
+}
+#ifndef NDEBUG
+static int winShmMutexHeld(void) {
+  return sqlite3_mutex_held(winBigLock);
+}
+#endif
+
+/*
+** Object used to represent a single file opened and mmapped to provide
+** shared memory.  When multiple threads all reference the same
+** log-summary, each thread has its own winFile object, but they all
+** point to a single instance of this object.  In other words, each
+** log-summary is opened only once per process.
+**
+** winShmMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**      pNext
+**
+** The following fields are read-only after the object is created:
+**
+**      fid
+**      zFilename
+**
+** Either winShmNode.mutex must be held or winShmNode.nRef==0 and
+** winShmMutexHeld() is true when reading or writing any other field
+** in this structure.
+**
+*/
+struct winShmNode {
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  char *zFilename;           /* Name of the file */
+  winFile hFile;             /* File handle from winOpen */
+
+  int szRegion;              /* Size of shared-memory regions */
+  int nRegion;               /* Size of array apRegion */
+  u8 isReadonly;             /* True if read-only */
+  u8 isUnlocked;             /* True if no DMS lock held */
+
+  struct ShmRegion {
+    HANDLE hMap;             /* File handle from CreateFileMapping */
+    void *pMap;
+  } *aRegion;
+  DWORD lastErrno;           /* The Windows errno from the last I/O error */
+
+  int nRef;                  /* Number of winShm objects pointing to this */
+  winShm *pFirst;            /* All winShm objects pointing to this */
+  winShmNode *pNext;         /* Next in list of all winShmNode objects */
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
+  u8 nextShmId;              /* Next available winShm.id value */
+#endif
+};
+
+/*
+** A global array of all winShmNode objects.
+**
+** The winShmMutexHeld() must be true while reading or writing this list.
+*/
+static winShmNode *winShmNodeList = 0;
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** The following fields are initialized when this object is created and
+** are read-only thereafter:
+**
+**    winShm.pShmNode
+**    winShm.id
+**
+** All other fields are read/write.  The winShm.pShmNode->mutex must be held
+** while accessing any read/write fields.
+*/
+struct winShm {
+  winShmNode *pShmNode;      /* The underlying winShmNode object */
+  winShm *pNext;             /* Next winShm with the same winShmNode */
+  u8 hasMutex;               /* True if holding the winShmNode mutex */
+  u16 sharedMask;            /* Mask of shared locks held */
+  u16 exclMask;              /* Mask of exclusive locks held */
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
+  u8 id;                     /* Id of this connection with its winShmNode */
+#endif
+};
+
+/*
+** Constants used for locking
+*/
+#define WIN_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)        /* first lock byte */
+#define WIN_SHM_DMS    (WIN_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply advisory locks for all n bytes beginning at ofst.
+*/
+#define WINSHM_UNLCK  1
+#define WINSHM_RDLCK  2
+#define WINSHM_WRLCK  3
+static int winShmSystemLock(
+  winShmNode *pFile,    /* Apply locks to this open shared-memory segment */
+  int lockType,         /* WINSHM_UNLCK, WINSHM_RDLCK, or WINSHM_WRLCK */
+  int ofst,             /* Offset to first byte to be locked/unlocked */
+  int nByte             /* Number of bytes to lock or unlock */
+){
+  int rc = 0;           /* Result code form Lock/UnlockFileEx() */
+
+  /* Access to the winShmNode object is serialized by the caller */
+  assert( pFile->nRef==0 || sqlite3_mutex_held(pFile->mutex) );
+
+  OSTRACE(("SHM-LOCK file=%p, lock=%d, offset=%d, size=%d\n",
+           pFile->hFile.h, lockType, ofst, nByte));
+
+  /* Release/Acquire the system-level lock */
+  if( lockType==WINSHM_UNLCK ){
+    rc = winUnlockFile(&pFile->hFile.h, ofst, 0, nByte, 0);
+  }else{
+    /* Initialize the locking parameters */
+    DWORD dwFlags = LOCKFILE_FAIL_IMMEDIATELY;
+    if( lockType == WINSHM_WRLCK ) dwFlags |= LOCKFILE_EXCLUSIVE_LOCK;
+    rc = winLockFile(&pFile->hFile.h, dwFlags, ofst, 0, nByte, 0);
+  }
+
+  if( rc!= 0 ){
+    rc = SQLITE_OK;
+  }else{
+    pFile->lastErrno =  osGetLastError();
+    rc = SQLITE_BUSY;
+  }
+
+  OSTRACE(("SHM-LOCK file=%p, func=%s, errno=%lu, rc=%s\n",
+           pFile->hFile.h, (lockType == WINSHM_UNLCK) ? "winUnlockFile" :
+           "winLockFile", pFile->lastErrno, sqlite3ErrName(rc)));
+
+  return rc;
+}
+
+/* Forward references to VFS methods */
+static int winOpen(sqlite3_vfs*,const char*,sqlite3_file*,int,int*);
+static int winDelete(sqlite3_vfs *,const char*,int);
+
+/*
+** Purge the winShmNodeList list of all entries with winShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void winShmPurge(sqlite3_vfs *pVfs, int deleteFlag){
+  winShmNode **pp;
+  winShmNode *p;
+  assert( winShmMutexHeld() );
+  OSTRACE(("SHM-PURGE pid=%lu, deleteFlag=%d\n",
+           osGetCurrentProcessId(), deleteFlag));
+  pp = &winShmNodeList;
+  while( (p = *pp)!=0 ){
+    if( p->nRef==0 ){
+      int i;
+      if( p->mutex ){ sqlite3_mutex_free(p->mutex); }
+      for(i=0; i<p->nRegion; i++){
+        BOOL bRc = osUnmapViewOfFile(p->aRegion[i].pMap);
+        OSTRACE(("SHM-PURGE-UNMAP pid=%lu, region=%d, rc=%s\n",
+                 osGetCurrentProcessId(), i, bRc ? "ok" : "failed"));
+        UNUSED_VARIABLE_VALUE(bRc);
+        bRc = osCloseHandle(p->aRegion[i].hMap);
+        OSTRACE(("SHM-PURGE-CLOSE pid=%lu, region=%d, rc=%s\n",
+                 osGetCurrentProcessId(), i, bRc ? "ok" : "failed"));
+        UNUSED_VARIABLE_VALUE(bRc);
+      }
+      if( p->hFile.h!=NULL && p->hFile.h!=INVALID_HANDLE_VALUE ){
+        SimulateIOErrorBenign(1);
+        winClose((sqlite3_file *)&p->hFile);
+        SimulateIOErrorBenign(0);
+      }
+      if( deleteFlag ){
+        SimulateIOErrorBenign(1);
+        sqlite3BeginBenignMalloc();
+        winDelete(pVfs, p->zFilename, 0);
+        sqlite3EndBenignMalloc();
+        SimulateIOErrorBenign(0);
+      }
+      *pp = p->pNext;
+      sqlite3_free(p->aRegion);
+      sqlite3_free(p);
+    }else{
+      pp = &p->pNext;
+    }
+  }
+}
+
+/*
+** The DMS lock has not yet been taken on shm file pShmNode. Attempt to
+** take it now. Return SQLITE_OK if successful, or an SQLite error
+** code otherwise.
+**
+** If the DMS cannot be locked because this is a readonly_shm=1
+** connection and no other process already holds a lock, return
+** SQLITE_READONLY_CANTINIT and set pShmNode->isUnlocked=1.
+*/
+static int winLockSharedMemory(winShmNode *pShmNode){
+  int rc = winShmSystemLock(pShmNode, WINSHM_WRLCK, WIN_SHM_DMS, 1);
+
+  if( rc==SQLITE_OK ){
+    if( pShmNode->isReadonly ){
+      pShmNode->isUnlocked = 1;
+      winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
+      return SQLITE_READONLY_CANTINIT;
+    }else if( winTruncate((sqlite3_file*)&pShmNode->hFile, 0) ){
+      winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
+      return winLogError(SQLITE_IOERR_SHMOPEN, osGetLastError(),
+                         "winLockSharedMemory", pShmNode->zFilename);
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
+  }
+
+  return winShmSystemLock(pShmNode, WINSHM_RDLCK, WIN_SHM_DMS, 1);
+}
+
+/*
+** Open the shared-memory area associated with database file pDbFd.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+*/
+static int winOpenSharedMemory(winFile *pDbFd){
+  struct winShm *p;                  /* The connection to be opened */
+  winShmNode *pShmNode = 0;          /* The underlying mmapped file */
+  int rc = SQLITE_OK;                /* Result code */
+  winShmNode *pNew;                  /* Newly allocated winShmNode */
+  int nName;                         /* Size of zName in bytes */
+
+  assert( pDbFd->pShm==0 );    /* Not previously opened */
+
+  /* Allocate space for the new sqlite3_shm object.  Also speculatively
+  ** allocate space for a new winShmNode and filename.
+  */
+  p = sqlite3MallocZero( sizeof(*p) );
+  if( p==0 ) return SQLITE_IOERR_NOMEM_BKPT;
+  nName = sqlite3Strlen30(pDbFd->zPath);
+  pNew = sqlite3MallocZero( sizeof(*pShmNode) + nName + 17 );
+  if( pNew==0 ){
+    sqlite3_free(p);
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+  pNew->zFilename = (char*)&pNew[1];
+  sqlite3_snprintf(nName+15, pNew->zFilename, "%s-shm", pDbFd->zPath);
+  sqlite3FileSuffix3(pDbFd->zPath, pNew->zFilename);
+
+  /* Look to see if there is an existing winShmNode that can be used.
+  ** If no matching winShmNode currently exists, create a new one.
+  */
+  winShmEnterMutex();
+  for(pShmNode = winShmNodeList; pShmNode; pShmNode=pShmNode->pNext){
+    /* TBD need to come up with better match here.  Perhaps
+    ** use FILE_ID_BOTH_DIR_INFO Structure.
+    */
+    if( sqlite3StrICmp(pShmNode->zFilename, pNew->zFilename)==0 ) break;
+  }
+  if( pShmNode ){
+    sqlite3_free(pNew);
+  }else{
+    int inFlags = SQLITE_OPEN_WAL;
+    int outFlags = 0;
+
+    pShmNode = pNew;
+    pNew = 0;
+    ((winFile*)(&pShmNode->hFile))->h = INVALID_HANDLE_VALUE;
+    pShmNode->pNext = winShmNodeList;
+    winShmNodeList = pShmNode;
+
+    if( sqlite3GlobalConfig.bCoreMutex ){
+      pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+      if( pShmNode->mutex==0 ){
+        rc = SQLITE_IOERR_NOMEM_BKPT;
+        goto shm_open_err;
+      }
+    }
+
+    if( 0==sqlite3_uri_boolean(pDbFd->zPath, "readonly_shm", 0) ){
+      inFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE;
+    }else{
+      inFlags |= SQLITE_OPEN_READONLY;
+    }
+    rc = winOpen(pDbFd->pVfs, pShmNode->zFilename,
+                 (sqlite3_file*)&pShmNode->hFile,
+                 inFlags, &outFlags);
+    if( rc!=SQLITE_OK ){
+      rc = winLogError(rc, osGetLastError(), "winOpenShm",
+                       pShmNode->zFilename);
+      goto shm_open_err;
+    }
+    if( outFlags==SQLITE_OPEN_READONLY ) pShmNode->isReadonly = 1;
+
+    rc = winLockSharedMemory(pShmNode);
+    if( rc!=SQLITE_OK && rc!=SQLITE_READONLY_CANTINIT ) goto shm_open_err;
+  }
+
+  /* Make the new connection a child of the winShmNode */
+  p->pShmNode = pShmNode;
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  winShmLeaveMutex();
+
+  /* The reference count on pShmNode has already been incremented under
+  ** the cover of the winShmEnterMutex() mutex and the pointer from the
+  ** new (struct winShm) object to the pShmNode has been set. All that is
+  ** left to do is to link the new object into the linked list starting
+  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex
+  ** mutex.
+  */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  p->pNext = pShmNode->pFirst;
+  pShmNode->pFirst = p;
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+
+  /* Jump here on any error */
+shm_open_err:
+  winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
+  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  sqlite3_free(pNew);
+  winShmLeaveMutex();
+  return rc;
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying
+** storage if deleteFlag is true.
+*/
+static int winShmUnmap(
+  sqlite3_file *fd,          /* Database holding shared memory */
+  int deleteFlag             /* Delete after closing if true */
+){
+  winFile *pDbFd;       /* Database holding shared-memory */
+  winShm *p;            /* The connection to be closed */
+  winShmNode *pShmNode; /* The underlying shared-memory file */
+  winShm **pp;          /* For looping over sibling connections */
+
+  pDbFd = (winFile*)fd;
+  p = pDbFd->pShm;
+  if( p==0 ) return SQLITE_OK;
+  pShmNode = p->pShmNode;
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->mutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  winShmEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    winShmPurge(pDbFd->pVfs, deleteFlag);
+  }
+  winShmLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+*/
+static int winShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  winFile *pDbFd = (winFile*)fd;        /* Connection holding shared memory */
+  winShm *p = pDbFd->pShm;              /* The shared memory being locked */
+  winShm *pX;                           /* For looping over all siblings */
+  winShmNode *pShmNode;
+  int rc = SQLITE_OK;                   /* Result code */
+  u16 mask;                             /* Mask of locks to take or release */
+
+  if( p==0 ) return SQLITE_IOERR_SHMLOCK;
+  pShmNode = p->pShmNode;
+  if( NEVER(pShmNode==0) ) return SQLITE_IOERR_SHMLOCK;
+
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+
+  mask = (u16)((1U<<(ofst+n)) - (1U<<ofst));
+  assert( n>1 || mask==(1<<ofst) );
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( flags & SQLITE_SHM_UNLOCK ){
+    u16 allMask = 0; /* Mask of locks held by siblings */
+
+    /* See if any siblings hold this same lock */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( pX==p ) continue;
+      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
+      allMask |= pX->sharedMask;
+    }
+
+    /* Unlock the system-level locks */
+    if( (mask & allMask)==0 ){
+      rc = winShmSystemLock(pShmNode, WINSHM_UNLCK, ofst+WIN_SHM_BASE, n);
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* Undo the local locks */
+    if( rc==SQLITE_OK ){
+      p->exclMask &= ~mask;
+      p->sharedMask &= ~mask;
+    }
+  }else if( flags & SQLITE_SHM_SHARED ){
+    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
+
+    /* Find out which shared locks are already held by sibling connections.
+    ** If any sibling already holds an exclusive lock, go ahead and return
+    ** SQLITE_BUSY.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+      allShared |= pX->sharedMask;
+    }
+
+    /* Get shared locks at the system level, if necessary */
+    if( rc==SQLITE_OK ){
+      if( (allShared & mask)==0 ){
+        rc = winShmSystemLock(pShmNode, WINSHM_RDLCK, ofst+WIN_SHM_BASE, n);
+      }else{
+        rc = SQLITE_OK;
+      }
+    }
+
+    /* Get the local shared locks */
+    if( rc==SQLITE_OK ){
+      p->sharedMask |= mask;
+    }
+  }else{
+    /* Make sure no sibling connections hold locks that will block this
+    ** lock.  If any do, return SQLITE_BUSY right away.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+    }
+
+    /* Get the exclusive locks at the system level.  Then if successful
+    ** also mark the local connection as being locked.
+    */
+    if( rc==SQLITE_OK ){
+      rc = winShmSystemLock(pShmNode, WINSHM_WRLCK, ofst+WIN_SHM_BASE, n);
+      if( rc==SQLITE_OK ){
+        assert( (p->sharedMask & mask)==0 );
+        p->exclMask |= mask;
+      }
+    }
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  OSTRACE(("SHM-LOCK pid=%lu, id=%d, sharedMask=%03x, exclMask=%03x, rc=%s\n",
+           osGetCurrentProcessId(), p->id, p->sharedMask, p->exclMask,
+           sqlite3ErrName(rc)));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void winShmBarrier(
+  sqlite3_file *fd          /* Database holding the shared memory */
+){
+  UNUSED_PARAMETER(fd);
+  sqlite3MemoryBarrier();   /* compiler-defined memory barrier */
+  winShmEnterMutex();       /* Also mutex, for redundancy */
+  winShmLeaveMutex();
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the
+** shared-memory associated with the database file fd. Shared-memory regions
+** are numbered starting from zero. Each shared-memory region is szRegion
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the isWrite parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If
+** isWrite is non-zero and the requested shared-memory region has not yet
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes
+** address space (if it is not already), *pp is set to point to the mapped
+** memory and SQLITE_OK returned.
+*/
+static int winShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  winFile *pDbFd = (winFile*)fd;
+  winShm *pShm = pDbFd->pShm;
+  winShmNode *pShmNode;
+  DWORD protect = PAGE_READWRITE;
+  DWORD flags = FILE_MAP_WRITE | FILE_MAP_READ;
+  int rc = SQLITE_OK;
+
+  if( !pShm ){
+    rc = winOpenSharedMemory(pDbFd);
+    if( rc!=SQLITE_OK ) return rc;
+    pShm = pDbFd->pShm;
+    assert( pShm!=0 );
+  }
+  pShmNode = pShm->pShmNode;
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( pShmNode->isUnlocked ){
+    rc = winLockSharedMemory(pShmNode);
+    if( rc!=SQLITE_OK ) goto shmpage_out;
+    pShmNode->isUnlocked = 0;
+  }
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+
+  if( pShmNode->nRegion<=iRegion ){
+    struct ShmRegion *apNew;           /* New aRegion[] array */
+    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
+    sqlite3_int64 sz;                  /* Current size of wal-index file */
+
+    pShmNode->szRegion = szRegion;
+
+    /* The requested region is not mapped into this processes address space.
+    ** Check to see if it has been allocated (i.e. if the wal-index file is
+    ** large enough to contain the requested region).
+    */
+    rc = winFileSize((sqlite3_file *)&pShmNode->hFile, &sz);
+    if( rc!=SQLITE_OK ){
+      rc = winLogError(SQLITE_IOERR_SHMSIZE, osGetLastError(),
+                       "winShmMap1", pDbFd->zPath);
+      goto shmpage_out;
+    }
+
+    if( sz<nByte ){
+      /* The requested memory region does not exist. If isWrite is set to
+      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
+      **
+      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
+      ** the requested memory region.
+      */
+      if( !isWrite ) goto shmpage_out;
+      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, nByte);
+      if( rc!=SQLITE_OK ){
+        rc = winLogError(SQLITE_IOERR_SHMSIZE, osGetLastError(),
+                         "winShmMap2", pDbFd->zPath);
+        goto shmpage_out;
+      }
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (struct ShmRegion *)sqlite3_realloc64(
+        pShmNode->aRegion, (iRegion+1)*sizeof(apNew[0])
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM_BKPT;
+      goto shmpage_out;
+    }
+    pShmNode->aRegion = apNew;
+
+    if( pShmNode->isReadonly ){
+      protect = PAGE_READONLY;
+      flags = FILE_MAP_READ;
+    }
+
+    while( pShmNode->nRegion<=iRegion ){
+      HANDLE hMap = NULL;         /* file-mapping handle */
+      void *pMap = 0;             /* Mapped memory region */
+
+#if SQLITE_OS_WINRT
+      hMap = osCreateFileMappingFromApp(pShmNode->hFile.h,
+          NULL, protect, nByte, NULL
+      );
+#elif defined(SQLITE_WIN32_HAS_WIDE)
+      hMap = osCreateFileMappingW(pShmNode->hFile.h,
+          NULL, protect, 0, nByte, NULL
+      );
+#elif defined(SQLITE_WIN32_HAS_ANSI) && SQLITE_WIN32_CREATEFILEMAPPINGA
+      hMap = osCreateFileMappingA(pShmNode->hFile.h,
+          NULL, protect, 0, nByte, NULL
+      );
+#endif
+      OSTRACE(("SHM-MAP-CREATE pid=%lu, region=%d, size=%d, rc=%s\n",
+               osGetCurrentProcessId(), pShmNode->nRegion, nByte,
+               hMap ? "ok" : "failed"));
+      if( hMap ){
+        int iOffset = pShmNode->nRegion*szRegion;
+        int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
+#if SQLITE_OS_WINRT
+        pMap = osMapViewOfFileFromApp(hMap, flags,
+            iOffset - iOffsetShift, szRegion + iOffsetShift
+        );
+#else
+        pMap = osMapViewOfFile(hMap, flags,
+            0, iOffset - iOffsetShift, szRegion + iOffsetShift
+        );
+#endif
+        OSTRACE(("SHM-MAP-MAP pid=%lu, region=%d, offset=%d, size=%d, rc=%s\n",
+                 osGetCurrentProcessId(), pShmNode->nRegion, iOffset,
+                 szRegion, pMap ? "ok" : "failed"));
+      }
+      if( !pMap ){
+        pShmNode->lastErrno = osGetLastError();
+        rc = winLogError(SQLITE_IOERR_SHMMAP, pShmNode->lastErrno,
+                         "winShmMap3", pDbFd->zPath);
+        if( hMap ) osCloseHandle(hMap);
+        goto shmpage_out;
+      }
+
+      pShmNode->aRegion[pShmNode->nRegion].pMap = pMap;
+      pShmNode->aRegion[pShmNode->nRegion].hMap = hMap;
+      pShmNode->nRegion++;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    int iOffset = iRegion*szRegion;
+    int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
+    char *p = (char *)pShmNode->aRegion[iRegion].pMap;
+    *pp = (void *)&p[iOffsetShift];
+  }else{
+    *pp = 0;
+  }
+  if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+}
+
+#else
+# define winShmMap     0
+# define winShmLock    0
+# define winShmBarrier 0
+# define winShmUnmap   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
+/*
+** Cleans up the mapped region of the specified file, if any.
+*/
+#if SQLITE_MAX_MMAP_SIZE>0
+static int winUnmapfile(winFile *pFile){
+  assert( pFile!=0 );
+  OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, hMap=%p, pMapRegion=%p, "
+           "mmapSize=%lld, mmapSizeMax=%lld\n",
+           osGetCurrentProcessId(), pFile, pFile->hMap, pFile->pMapRegion,
+           pFile->mmapSize, pFile->mmapSizeMax));
+  if( pFile->pMapRegion ){
+    if( !osUnmapViewOfFile(pFile->pMapRegion) ){
+      pFile->lastErrno = osGetLastError();
+      OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, pMapRegion=%p, "
+               "rc=SQLITE_IOERR_MMAP\n", osGetCurrentProcessId(), pFile,
+               pFile->pMapRegion));
+      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
+                         "winUnmapfile1", pFile->zPath);
+    }
+    pFile->pMapRegion = 0;
+    pFile->mmapSize = 0;
+  }
+  if( pFile->hMap!=NULL ){
+    if( !osCloseHandle(pFile->hMap) ){
+      pFile->lastErrno = osGetLastError();
+      OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, hMap=%p, rc=SQLITE_IOERR_MMAP\n",
+               osGetCurrentProcessId(), pFile, pFile->hMap));
+      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
+                         "winUnmapfile2", pFile->zPath);
+    }
+    pFile->hMap = NULL;
+  }
+  OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, rc=SQLITE_OK\n",
+           osGetCurrentProcessId(), pFile));
+  return SQLITE_OK;
+}
+
+/*
+** Memory map or remap the file opened by file-descriptor pFd (if the file
+** is already mapped, the existing mapping is replaced by the new). Or, if
+** there already exists a mapping for this file, and there are still
+** outstanding xFetch() references to it, this function is a no-op.
+**
+** If parameter nByte is non-negative, then it is the requested size of
+** the mapping to create. Otherwise, if nByte is less than zero, then the
+** requested size is the size of the file on disk. The actual size of the
+** created mapping is either the requested size or the value configured
+** using SQLITE_FCNTL_MMAP_SIZE, whichever is smaller.
+**
+** SQLITE_OK is returned if no error occurs (even if the mapping is not
+** recreated as a result of outstanding references) or an SQLite error
+** code otherwise.
+*/
+static int winMapfile(winFile *pFd, sqlite3_int64 nByte){
+  sqlite3_int64 nMap = nByte;
+  int rc;
+
+  assert( nMap>=0 || pFd->nFetchOut==0 );
+  OSTRACE(("MAP-FILE pid=%lu, pFile=%p, size=%lld\n",
+           osGetCurrentProcessId(), pFd, nByte));
+
+  if( pFd->nFetchOut>0 ) return SQLITE_OK;
+
+  if( nMap<0 ){
+    rc = winFileSize((sqlite3_file*)pFd, &nMap);
+    if( rc ){
+      OSTRACE(("MAP-FILE pid=%lu, pFile=%p, rc=SQLITE_IOERR_FSTAT\n",
+               osGetCurrentProcessId(), pFd));
+      return SQLITE_IOERR_FSTAT;
+    }
+  }
+  if( nMap>pFd->mmapSizeMax ){
+    nMap = pFd->mmapSizeMax;
+  }
+  nMap &= ~(sqlite3_int64)(winSysInfo.dwPageSize - 1);
+
+  if( nMap==0 && pFd->mmapSize>0 ){
+    winUnmapfile(pFd);
+  }
+  if( nMap!=pFd->mmapSize ){
+    void *pNew = 0;
+    DWORD protect = PAGE_READONLY;
+    DWORD flags = FILE_MAP_READ;
+
+    winUnmapfile(pFd);
+#ifdef SQLITE_MMAP_READWRITE
+    if( (pFd->ctrlFlags & WINFILE_RDONLY)==0 ){
+      protect = PAGE_READWRITE;
+      flags |= FILE_MAP_WRITE;
+    }
+#endif
+#if SQLITE_OS_WINRT
+    pFd->hMap = osCreateFileMappingFromApp(pFd->h, NULL, protect, nMap, NULL);
+#elif defined(SQLITE_WIN32_HAS_WIDE)
+    pFd->hMap = osCreateFileMappingW(pFd->h, NULL, protect,
+                                (DWORD)((nMap>>32) & 0xffffffff),
+                                (DWORD)(nMap & 0xffffffff), NULL);
+#elif defined(SQLITE_WIN32_HAS_ANSI) && SQLITE_WIN32_CREATEFILEMAPPINGA
+    pFd->hMap = osCreateFileMappingA(pFd->h, NULL, protect,
+                                (DWORD)((nMap>>32) & 0xffffffff),
+                                (DWORD)(nMap & 0xffffffff), NULL);
+#endif
+    if( pFd->hMap==NULL ){
+      pFd->lastErrno = osGetLastError();
+      rc = winLogError(SQLITE_IOERR_MMAP, pFd->lastErrno,
+                       "winMapfile1", pFd->zPath);
+      /* Log the error, but continue normal operation using xRead/xWrite */
+      OSTRACE(("MAP-FILE-CREATE pid=%lu, pFile=%p, rc=%s\n",
+               osGetCurrentProcessId(), pFd, sqlite3ErrName(rc)));
+      return SQLITE_OK;
+    }
+    assert( (nMap % winSysInfo.dwPageSize)==0 );
+    assert( sizeof(SIZE_T)==sizeof(sqlite3_int64) || nMap<=0xffffffff );
+#if SQLITE_OS_WINRT
+    pNew = osMapViewOfFileFromApp(pFd->hMap, flags, 0, (SIZE_T)nMap);
+#else
+    pNew = osMapViewOfFile(pFd->hMap, flags, 0, 0, (SIZE_T)nMap);
+#endif
+    if( pNew==NULL ){
+      osCloseHandle(pFd->hMap);
+      pFd->hMap = NULL;
+      pFd->lastErrno = osGetLastError();
+      rc = winLogError(SQLITE_IOERR_MMAP, pFd->lastErrno,
+                       "winMapfile2", pFd->zPath);
+      /* Log the error, but continue normal operation using xRead/xWrite */
+      OSTRACE(("MAP-FILE-MAP pid=%lu, pFile=%p, rc=%s\n",
+               osGetCurrentProcessId(), pFd, sqlite3ErrName(rc)));
+      return SQLITE_OK;
+    }
+    pFd->pMapRegion = pNew;
+    pFd->mmapSize = nMap;
+  }
+
+  OSTRACE(("MAP-FILE pid=%lu, pFile=%p, rc=SQLITE_OK\n",
+           osGetCurrentProcessId(), pFd));
+  return SQLITE_OK;
+}
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
+
+/*
+** If possible, return a pointer to a mapping of file fd starting at offset
+** iOff. The mapping must be valid for at least nAmt bytes.
+**
+** If such a pointer can be obtained, store it in *pp and return SQLITE_OK.
+** Or, if one cannot but no error occurs, set *pp to 0 and return SQLITE_OK.
+** Finally, if an error does occur, return an SQLite error code. The final
+** value of *pp is undefined in this case.
+**
+** If this function does return a pointer, the caller must eventually
+** release the reference by calling winUnfetch().
+*/
+static int winFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
+#if SQLITE_MAX_MMAP_SIZE>0
+  winFile *pFd = (winFile*)fd;   /* The underlying database file */
+#endif
+  *pp = 0;
+
+  OSTRACE(("FETCH pid=%lu, pFile=%p, offset=%lld, amount=%d, pp=%p\n",
+           osGetCurrentProcessId(), fd, iOff, nAmt, pp));
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  if( pFd->mmapSizeMax>0 ){
+    /* Ensure that there is always at least a 256 byte buffer of addressable
+    ** memory following the returned page. If the database is corrupt,
+    ** SQLite may overread the page slightly (in practice only a few bytes,
+    ** but 256 is safe, round, number).  */
+    const int nEofBuffer = 256;
+    if( pFd->pMapRegion==0 ){
+      int rc = winMapfile(pFd, -1);
+      if( rc!=SQLITE_OK ){
+        OSTRACE(("FETCH pid=%lu, pFile=%p, rc=%s\n",
+                 osGetCurrentProcessId(), pFd, sqlite3ErrName(rc)));
+        return rc;
+      }
+    }
+    if( pFd->mmapSize >= (iOff+nAmt+nEofBuffer) ){
+      assert( pFd->pMapRegion!=0 );
+      *pp = &((u8 *)pFd->pMapRegion)[iOff];
+      pFd->nFetchOut++;
+    }
+  }
+#endif
+
+  OSTRACE(("FETCH pid=%lu, pFile=%p, pp=%p, *pp=%p, rc=SQLITE_OK\n",
+           osGetCurrentProcessId(), fd, pp, *pp));
+  return SQLITE_OK;
+}
+
+/*
+** If the third argument is non-NULL, then this function releases a
+** reference obtained by an earlier call to winFetch(). The second
+** argument passed to this function must be the same as the corresponding
+** argument that was passed to the winFetch() invocation.
+**
+** Or, if the third argument is NULL, then this function is being called
+** to inform the VFS layer that, according to POSIX, any existing mapping
+** may now be invalid and should be unmapped.
+*/
+static int winUnfetch(sqlite3_file *fd, i64 iOff, void *p){
+#if SQLITE_MAX_MMAP_SIZE>0
+  winFile *pFd = (winFile*)fd;   /* The underlying database file */
+
+  /* If p==0 (unmap the entire file) then there must be no outstanding
+  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
+  ** then there must be at least one outstanding.  */
+  assert( (p==0)==(pFd->nFetchOut==0) );
+
+  /* If p!=0, it must match the iOff value. */
+  assert( p==0 || p==&((u8 *)pFd->pMapRegion)[iOff] );
+
+  OSTRACE(("UNFETCH pid=%lu, pFile=%p, offset=%lld, p=%p\n",
+           osGetCurrentProcessId(), pFd, iOff, p));
+
+  if( p ){
+    pFd->nFetchOut--;
+  }else{
+    /* FIXME:  If Windows truly always prevents truncating or deleting a
+    ** file while a mapping is held, then the following winUnmapfile() call
+    ** is unnecessary can be omitted - potentially improving
+    ** performance.  */
+    winUnmapfile(pFd);
+  }
+
+  assert( pFd->nFetchOut>=0 );
+#endif
+
+  OSTRACE(("UNFETCH pid=%lu, pFile=%p, rc=SQLITE_OK\n",
+           osGetCurrentProcessId(), fd));
+  return SQLITE_OK;
+}
+
+/*
+** Here ends the implementation of all sqlite3_file methods.
+**
+********************** End sqlite3_file Methods *******************************
+******************************************************************************/
+
+/*
+** This vector defines all the methods that can operate on an
+** sqlite3_file for win32.
+*/
+static const sqlite3_io_methods winIoMethod = {
+  3,                              /* iVersion */
+  winClose,                       /* xClose */
+  winRead,                        /* xRead */
+  winWrite,                       /* xWrite */
+  winTruncate,                    /* xTruncate */
+  winSync,                        /* xSync */
+  winFileSize,                    /* xFileSize */
+  winLock,                        /* xLock */
+  winUnlock,                      /* xUnlock */
+  winCheckReservedLock,           /* xCheckReservedLock */
+  winFileControl,                 /* xFileControl */
+  winSectorSize,                  /* xSectorSize */
+  winDeviceCharacteristics,       /* xDeviceCharacteristics */
+  winShmMap,                      /* xShmMap */
+  winShmLock,                     /* xShmLock */
+  winShmBarrier,                  /* xShmBarrier */
+  winShmUnmap,                    /* xShmUnmap */
+  winFetch,                       /* xFetch */
+  winUnfetch                      /* xUnfetch */
+};
+
+/*
+** This vector defines all the methods that can operate on an
+** sqlite3_file for win32 without performing any locking.
+*/
+static const sqlite3_io_methods winIoNolockMethod = {
+  3,                              /* iVersion */
+  winClose,                       /* xClose */
+  winRead,                        /* xRead */
+  winWrite,                       /* xWrite */
+  winTruncate,                    /* xTruncate */
+  winSync,                        /* xSync */
+  winFileSize,                    /* xFileSize */
+  winNolockLock,                  /* xLock */
+  winNolockUnlock,                /* xUnlock */
+  winNolockCheckReservedLock,     /* xCheckReservedLock */
+  winFileControl,                 /* xFileControl */
+  winSectorSize,                  /* xSectorSize */
+  winDeviceCharacteristics,       /* xDeviceCharacteristics */
+  winShmMap,                      /* xShmMap */
+  winShmLock,                     /* xShmLock */
+  winShmBarrier,                  /* xShmBarrier */
+  winShmUnmap,                    /* xShmUnmap */
+  winFetch,                       /* xFetch */
+  winUnfetch                      /* xUnfetch */
+};
+
+static winVfsAppData winAppData = {
+  &winIoMethod,       /* pMethod */
+  0,                  /* pAppData */
+  0                   /* bNoLock */
+};
+
+static winVfsAppData winNolockAppData = {
+  &winIoNolockMethod, /* pMethod */
+  0,                  /* pAppData */
+  1                   /* bNoLock */
+};
+
+/****************************************************************************
+**************************** sqlite3_vfs methods ****************************
+**
+** This division contains the implementation of methods on the
+** sqlite3_vfs object.
+*/
+
+#if defined(__CYGWIN__)
+/*
+** Convert a filename from whatever the underlying operating system
+** supports for filenames into UTF-8.  Space to hold the result is
+** obtained from malloc and must be freed by the calling function.
+*/
+static char *winConvertToUtf8Filename(const void *zFilename){
+  char *zConverted = 0;
+  if( osIsNT() ){
+    zConverted = winUnicodeToUtf8(zFilename);
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    zConverted = winMbcsToUtf8(zFilename, osAreFileApisANSI());
+  }
+#endif
+  /* caller will handle out of memory */
+  return zConverted;
+}
+#endif
+
+/*
+** Convert a UTF-8 filename into whatever form the underlying
+** operating system wants filenames in.  Space to hold the result
+** is obtained from malloc and must be freed by the calling
+** function.
+*/
+static void *winConvertFromUtf8Filename(const char *zFilename){
+  void *zConverted = 0;
+  if( osIsNT() ){
+    zConverted = winUtf8ToUnicode(zFilename);
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    zConverted = winUtf8ToMbcs(zFilename, osAreFileApisANSI());
+  }
+#endif
+  /* caller will handle out of memory */
+  return zConverted;
+}
+
+/*
+** This function returns non-zero if the specified UTF-8 string buffer
+** ends with a directory separator character or one was successfully
+** added to it.
+*/
+static int winMakeEndInDirSep(int nBuf, char *zBuf){
+  if( zBuf ){
+    int nLen = sqlite3Strlen30(zBuf);
+    if( nLen>0 ){
+      if( winIsDirSep(zBuf[nLen-1]) ){
+        return 1;
+      }else if( nLen+1<nBuf ){
+        zBuf[nLen] = winGetDirSep();
+        zBuf[nLen+1] = '\0';
+        return 1;
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** If sqlite3_temp_directory is defined, take the mutex and return true.
+**
+** If sqlite3_temp_directory is NULL (undefined), omit the mutex and
+** return false.
+*/
+static int winTempDirDefined(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+  if( sqlite3_temp_directory!=0 ) return 1;
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+  return 0;
+}
+
+/*
+** Create a temporary file name and store the resulting pointer into pzBuf.
+** The pointer returned in pzBuf must be freed via sqlite3_free().
+*/
+static int winGetTempname(sqlite3_vfs *pVfs, char **pzBuf){
+  static char zChars[] =
+    "abcdefghijklmnopqrstuvwxyz"
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    "0123456789";
+  size_t i, j;
+  DWORD pid;
+  int nPre = sqlite3Strlen30(SQLITE_TEMP_FILE_PREFIX);
+  int nMax, nBuf, nDir, nLen;
+  char *zBuf;
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing.
+  */
+  SimulateIOError( return SQLITE_IOERR );
+
+  /* Allocate a temporary buffer to store the fully qualified file
+  ** name for the temporary file.  If this fails, we cannot continue.
+  */
+  nMax = pVfs->mxPathname; nBuf = nMax + 2;
+  zBuf = sqlite3MallocZero( nBuf );
+  if( !zBuf ){
+    OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+
+  /* Figure out the effective temporary directory.  First, check if one
+  ** has been explicitly set by the application; otherwise, use the one
+  ** configured by the operating system.
+  */
+  nDir = nMax - (nPre + 15);
+  assert( nDir>0 );
+  if( winTempDirDefined() ){
+    int nDirLen = sqlite3Strlen30(sqlite3_temp_directory);
+    if( nDirLen>0 ){
+      if( !winIsDirSep(sqlite3_temp_directory[nDirLen-1]) ){
+        nDirLen++;
+      }
+      if( nDirLen>nDir ){
+        sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+        sqlite3_free(zBuf);
+        OSTRACE(("TEMP-FILENAME rc=SQLITE_ERROR\n"));
+        return winLogError(SQLITE_ERROR, 0, "winGetTempname1", 0);
+      }
+      sqlite3_snprintf(nMax, zBuf, "%s", sqlite3_temp_directory);
+    }
+    sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+  }
+
+#if defined(__CYGWIN__)
+  else{
+    static const char *azDirs[] = {
+       0, /* getenv("SQLITE_TMPDIR") */
+       0, /* getenv("TMPDIR") */
+       0, /* getenv("TMP") */
+       0, /* getenv("TEMP") */
+       0, /* getenv("USERPROFILE") */
+       "/var/tmp",
+       "/usr/tmp",
+       "/tmp",
+       ".",
+       0        /* List terminator */
+    };
+    unsigned int i;
+    const char *zDir = 0;
+
+    if( !azDirs[0] ) azDirs[0] = getenv("SQLITE_TMPDIR");
+    if( !azDirs[1] ) azDirs[1] = getenv("TMPDIR");
+    if( !azDirs[2] ) azDirs[2] = getenv("TMP");
+    if( !azDirs[3] ) azDirs[3] = getenv("TEMP");
+    if( !azDirs[4] ) azDirs[4] = getenv("USERPROFILE");
+    for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
+      void *zConverted;
+      if( zDir==0 ) continue;
+      /* If the path starts with a drive letter followed by the colon
+      ** character, assume it is already a native Win32 path; otherwise,
+      ** it must be converted to a native Win32 path via the Cygwin API
+      ** prior to using it.
+      */
+      if( winIsDriveLetterAndColon(zDir) ){
+        zConverted = winConvertFromUtf8Filename(zDir);
+        if( !zConverted ){
+          sqlite3_free(zBuf);
+          OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+          return SQLITE_IOERR_NOMEM_BKPT;
+        }
+        if( winIsDir(zConverted) ){
+          sqlite3_snprintf(nMax, zBuf, "%s", zDir);
+          sqlite3_free(zConverted);
+          break;
+        }
+        sqlite3_free(zConverted);
+      }else{
+        zConverted = sqlite3MallocZero( nMax+1 );
+        if( !zConverted ){
+          sqlite3_free(zBuf);
+          OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+          return SQLITE_IOERR_NOMEM_BKPT;
+        }
+        if( cygwin_conv_path(
+                osIsNT() ? CCP_POSIX_TO_WIN_W : CCP_POSIX_TO_WIN_A, zDir,
+                zConverted, nMax+1)<0 ){
+          sqlite3_free(zConverted);
+          sqlite3_free(zBuf);
+          OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_CONVPATH\n"));
+          return winLogError(SQLITE_IOERR_CONVPATH, (DWORD)errno,
+                             "winGetTempname2", zDir);
+        }
+        if( winIsDir(zConverted) ){
+          /* At this point, we know the candidate directory exists and should
+          ** be used.  However, we may need to convert the string containing
+          ** its name into UTF-8 (i.e. if it is UTF-16 right now).
+          */
+          char *zUtf8 = winConvertToUtf8Filename(zConverted);
+          if( !zUtf8 ){
+            sqlite3_free(zConverted);
+            sqlite3_free(zBuf);
+            OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+            return SQLITE_IOERR_NOMEM_BKPT;
+          }
+          sqlite3_snprintf(nMax, zBuf, "%s", zUtf8);
+          sqlite3_free(zUtf8);
+          sqlite3_free(zConverted);
+          break;
+        }
+        sqlite3_free(zConverted);
+      }
+    }
+  }
+#elif !SQLITE_OS_WINRT && !defined(__CYGWIN__)
+  else if( osIsNT() ){
+    char *zMulti;
+    LPWSTR zWidePath = sqlite3MallocZero( nMax*sizeof(WCHAR) );
+    if( !zWidePath ){
+      sqlite3_free(zBuf);
+      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+    if( osGetTempPathW(nMax, zWidePath)==0 ){
+      sqlite3_free(zWidePath);
+      sqlite3_free(zBuf);
+      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_GETTEMPPATH\n"));
+      return winLogError(SQLITE_IOERR_GETTEMPPATH, osGetLastError(),
+                         "winGetTempname2", 0);
+    }
+    zMulti = winUnicodeToUtf8(zWidePath);
+    if( zMulti ){
+      sqlite3_snprintf(nMax, zBuf, "%s", zMulti);
+      sqlite3_free(zMulti);
+      sqlite3_free(zWidePath);
+    }else{
+      sqlite3_free(zWidePath);
+      sqlite3_free(zBuf);
+      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    char *zUtf8;
+    char *zMbcsPath = sqlite3MallocZero( nMax );
+    if( !zMbcsPath ){
+      sqlite3_free(zBuf);
+      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+    if( osGetTempPathA(nMax, zMbcsPath)==0 ){
+      sqlite3_free(zBuf);
+      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_GETTEMPPATH\n"));
+      return winLogError(SQLITE_IOERR_GETTEMPPATH, osGetLastError(),
+                         "winGetTempname3", 0);
+    }
+    zUtf8 = winMbcsToUtf8(zMbcsPath, osAreFileApisANSI());
+    if( zUtf8 ){
+      sqlite3_snprintf(nMax, zBuf, "%s", zUtf8);
+      sqlite3_free(zUtf8);
+    }else{
+      sqlite3_free(zBuf);
+      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+  }
+#endif /* SQLITE_WIN32_HAS_ANSI */
+#endif /* !SQLITE_OS_WINRT */
+
+  /*
+  ** Check to make sure the temporary directory ends with an appropriate
+  ** separator.  If it does not and there is not enough space left to add
+  ** one, fail.
+  */
+  if( !winMakeEndInDirSep(nDir+1, zBuf) ){
+    sqlite3_free(zBuf);
+    OSTRACE(("TEMP-FILENAME rc=SQLITE_ERROR\n"));
+    return winLogError(SQLITE_ERROR, 0, "winGetTempname4", 0);
+  }
+
+  /*
+  ** Check that the output buffer is large enough for the temporary file
+  ** name in the following format:
+  **
+  **   "<temporary_directory>/etilqs_XXXXXXXXXXXXXXX\0\0"
+  **
+  ** If not, return SQLITE_ERROR.  The number 17 is used here in order to
+  ** account for the space used by the 15 character random suffix and the
+  ** two trailing NUL characters.  The final directory separator character
+  ** has already added if it was not already present.
+  */
+  nLen = sqlite3Strlen30(zBuf);
+  if( (nLen + nPre + 17) > nBuf ){
+    sqlite3_free(zBuf);
+    OSTRACE(("TEMP-FILENAME rc=SQLITE_ERROR\n"));
+    return winLogError(SQLITE_ERROR, 0, "winGetTempname5", 0);
+  }
+
+  sqlite3_snprintf(nBuf-16-nLen, zBuf+nLen, SQLITE_TEMP_FILE_PREFIX);
+
+  j = sqlite3Strlen30(zBuf);
+  sqlite3_randomness(15, &zBuf[j]);
+  pid = osGetCurrentProcessId();
+  for(i=0; i<15; i++, j++){
+    zBuf[j] += pid & 0xff;
+    pid >>= 8;
+    zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
+  }
+  zBuf[j] = 0;
+  zBuf[j+1] = 0;
+  *pzBuf = zBuf;
+
+  OSTRACE(("TEMP-FILENAME name=%s, rc=SQLITE_OK\n", zBuf));
+  return SQLITE_OK;
+}
+
+/*
+** Return TRUE if the named file is really a directory.  Return false if
+** it is something other than a directory, or if there is any kind of memory
+** allocation failure.
+*/
+static int winIsDir(const void *zConverted){
+  DWORD attr;
+  int rc = 0;
+  DWORD lastErrno;
+
+  if( osIsNT() ){
+    int cnt = 0;
+    WIN32_FILE_ATTRIBUTE_DATA sAttrData;
+    memset(&sAttrData, 0, sizeof(sAttrData));
+    while( !(rc = osGetFileAttributesExW((LPCWSTR)zConverted,
+                             GetFileExInfoStandard,
+                             &sAttrData)) && winRetryIoerr(&cnt, &lastErrno) ){}
+    if( !rc ){
+      return 0; /* Invalid name? */
+    }
+    attr = sAttrData.dwFileAttributes;
+#if SQLITE_OS_WINCE==0
+  }else{
+    attr = osGetFileAttributesA((char*)zConverted);
+#endif
+  }
+  return (attr!=INVALID_FILE_ATTRIBUTES) && (attr&FILE_ATTRIBUTE_DIRECTORY);
+}
+
+/* forward reference */
+static int winAccess(
+  sqlite3_vfs *pVfs,         /* Not used on win32 */
+  const char *zFilename,     /* Name of file to check */
+  int flags,                 /* Type of test to make on this file */
+  int *pResOut               /* OUT: Result */
+);
+
+/*
+** Open a file.
+*/
+static int winOpen(
+  sqlite3_vfs *pVfs,        /* Used to get maximum path length and AppData */
+  const char *zName,        /* Name of the file (UTF-8) */
+  sqlite3_file *id,         /* Write the SQLite file handle here */
+  int flags,                /* Open mode flags */
+  int *pOutFlags            /* Status return flags */
+){
+  HANDLE h;
+  DWORD lastErrno = 0;
+  DWORD dwDesiredAccess;
+  DWORD dwShareMode;
+  DWORD dwCreationDisposition;
+  DWORD dwFlagsAndAttributes = 0;
+#if SQLITE_OS_WINCE
+  int isTemp = 0;
+#endif
+  winVfsAppData *pAppData;
+  winFile *pFile = (winFile*)id;
+  void *zConverted;              /* Filename in OS encoding */
+  const char *zUtf8Name = zName; /* Filename in UTF-8 encoding */
+  int cnt = 0;
+
+  /* If argument zPath is a NULL pointer, this function is required to open
+  ** a temporary file. Use this buffer to store the file name in.
+  */
+  char *zTmpname = 0; /* For temporary filename, if necessary. */
+
+  int rc = SQLITE_OK;            /* Function Return Code */
+#if !defined(NDEBUG) || SQLITE_OS_WINCE
+  int eType = flags&0xFFFFFF00;  /* Type of file to open */
+#endif
+
+  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
+  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
+  int isCreate     = (flags & SQLITE_OPEN_CREATE);
+  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
+  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+
+#ifndef NDEBUG
+  int isOpenJournal = (isCreate && (
+        eType==SQLITE_OPEN_SUPER_JOURNAL
+     || eType==SQLITE_OPEN_MAIN_JOURNAL
+     || eType==SQLITE_OPEN_WAL
+  ));
+#endif
+
+  OSTRACE(("OPEN name=%s, pFile=%p, flags=%x, pOutFlags=%p\n",
+           zUtf8Name, id, flags, pOutFlags));
+
+  /* Check the following statements are true:
+  **
+  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and
+  **   (b) if CREATE is set, then READWRITE must also be set, and
+  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
+  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
+  */
+  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
+  assert(isCreate==0 || isReadWrite);
+  assert(isExclusive==0 || isCreate);
+  assert(isDelete==0 || isCreate);
+
+  /* The main DB, main journal, WAL file and super-journal are never
+  ** automatically deleted. Nor are they ever temporary files.  */
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_SUPER_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
+
+  /* Assert that the upper layer has set one of the "file-type" flags. */
+  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB
+       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL
+       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_SUPER_JOURNAL
+       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
+  );
+
+  assert( pFile!=0 );
+  memset(pFile, 0, sizeof(winFile));
+  pFile->h = INVALID_HANDLE_VALUE;
+
+#if SQLITE_OS_WINRT
+  if( !zUtf8Name && !sqlite3_temp_directory ){
+    sqlite3_log(SQLITE_ERROR,
+        "sqlite3_temp_directory variable should be set for WinRT");
+  }
+#endif
+
+  /* If the second argument to this function is NULL, generate a
+  ** temporary file name to use
+  */
+  if( !zUtf8Name ){
+    assert( isDelete && !isOpenJournal );
+    rc = winGetTempname(pVfs, &zTmpname);
+    if( rc!=SQLITE_OK ){
+      OSTRACE(("OPEN name=%s, rc=%s", zUtf8Name, sqlite3ErrName(rc)));
+      return rc;
+    }
+    zUtf8Name = zTmpname;
+  }
+
+  /* Database filenames are double-zero terminated if they are not
+  ** URIs with parameters.  Hence, they can always be passed into
+  ** sqlite3_uri_parameter().
+  */
+  assert( (eType!=SQLITE_OPEN_MAIN_DB) || (flags & SQLITE_OPEN_URI) ||
+       zUtf8Name[sqlite3Strlen30(zUtf8Name)+1]==0 );
+
+  /* Convert the filename to the system encoding. */
+  zConverted = winConvertFromUtf8Filename(zUtf8Name);
+  if( zConverted==0 ){
+    sqlite3_free(zTmpname);
+    OSTRACE(("OPEN name=%s, rc=SQLITE_IOERR_NOMEM", zUtf8Name));
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+
+  if( winIsDir(zConverted) ){
+    sqlite3_free(zConverted);
+    sqlite3_free(zTmpname);
+    OSTRACE(("OPEN name=%s, rc=SQLITE_CANTOPEN_ISDIR", zUtf8Name));
+    return SQLITE_CANTOPEN_ISDIR;
+  }
+
+  if( isReadWrite ){
+    dwDesiredAccess = GENERIC_READ | GENERIC_WRITE;
+  }else{
+    dwDesiredAccess = GENERIC_READ;
+  }
+
+  /* SQLITE_OPEN_EXCLUSIVE is used to make sure that a new file is
+  ** created. SQLite doesn't use it to indicate "exclusive access"
+  ** as it is usually understood.
+  */
+  if( isExclusive ){
+    /* Creates a new file, only if it does not already exist. */
+    /* If the file exists, it fails. */
+    dwCreationDisposition = CREATE_NEW;
+  }else if( isCreate ){
+    /* Open existing file, or create if it doesn't exist */
+    dwCreationDisposition = OPEN_ALWAYS;
+  }else{
+    /* Opens a file, only if it exists. */
+    dwCreationDisposition = OPEN_EXISTING;
+  }
+
+  if( 0==sqlite3_uri_boolean(zName, "exclusive", 0) ){
+    dwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
+  }else{
+    dwShareMode = 0;
+  }
+
+  if( isDelete ){
+#if SQLITE_OS_WINCE
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_HIDDEN;
+    isTemp = 1;
+#else
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_TEMPORARY
+                               | FILE_ATTRIBUTE_HIDDEN
+                               | FILE_FLAG_DELETE_ON_CLOSE;
+#endif
+  }else{
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_NORMAL;
+  }
+  /* Reports from the internet are that performance is always
+  ** better if FILE_FLAG_RANDOM_ACCESS is used.  Ticket #2699. */
+#if SQLITE_OS_WINCE
+  dwFlagsAndAttributes |= FILE_FLAG_RANDOM_ACCESS;
+#endif
+
+  if( osIsNT() ){
+#if SQLITE_OS_WINRT
+    CREATEFILE2_EXTENDED_PARAMETERS extendedParameters;
+    extendedParameters.dwSize = sizeof(CREATEFILE2_EXTENDED_PARAMETERS);
+    extendedParameters.dwFileAttributes =
+            dwFlagsAndAttributes & FILE_ATTRIBUTE_MASK;
+    extendedParameters.dwFileFlags = dwFlagsAndAttributes & FILE_FLAG_MASK;
+    extendedParameters.dwSecurityQosFlags = SECURITY_ANONYMOUS;
+    extendedParameters.lpSecurityAttributes = NULL;
+    extendedParameters.hTemplateFile = NULL;
+    do{
+      h = osCreateFile2((LPCWSTR)zConverted,
+                        dwDesiredAccess,
+                        dwShareMode,
+                        dwCreationDisposition,
+                        &extendedParameters);
+      if( h!=INVALID_HANDLE_VALUE ) break;
+      if( isReadWrite ){
+        int rc2, isRO = 0;
+        sqlite3BeginBenignMalloc();
+        rc2 = winAccess(pVfs, zUtf8Name, SQLITE_ACCESS_READ, &isRO);
+        sqlite3EndBenignMalloc();
+        if( rc2==SQLITE_OK && isRO ) break;
+      }
+    }while( winRetryIoerr(&cnt, &lastErrno) );
+#else
+    do{
+      h = osCreateFileW((LPCWSTR)zConverted,
+                        dwDesiredAccess,
+                        dwShareMode, NULL,
+                        dwCreationDisposition,
+                        dwFlagsAndAttributes,
+                        NULL);
+      if( h!=INVALID_HANDLE_VALUE ) break;
+      if( isReadWrite ){
+        int rc2, isRO = 0;
+        sqlite3BeginBenignMalloc();
+        rc2 = winAccess(pVfs, zUtf8Name, SQLITE_ACCESS_READ, &isRO);
+        sqlite3EndBenignMalloc();
+        if( rc2==SQLITE_OK && isRO ) break;
+      }
+    }while( winRetryIoerr(&cnt, &lastErrno) );
+#endif
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    do{
+      h = osCreateFileA((LPCSTR)zConverted,
+                        dwDesiredAccess,
+                        dwShareMode, NULL,
+                        dwCreationDisposition,
+                        dwFlagsAndAttributes,
+                        NULL);
+      if( h!=INVALID_HANDLE_VALUE ) break;
+      if( isReadWrite ){
+        int rc2, isRO = 0;
+        sqlite3BeginBenignMalloc();
+        rc2 = winAccess(pVfs, zUtf8Name, SQLITE_ACCESS_READ, &isRO);
+        sqlite3EndBenignMalloc();
+        if( rc2==SQLITE_OK && isRO ) break;
+      }
+    }while( winRetryIoerr(&cnt, &lastErrno) );
+  }
+#endif
+  winLogIoerr(cnt, __LINE__);
+
+  OSTRACE(("OPEN file=%p, name=%s, access=%lx, rc=%s\n", h, zUtf8Name,
+           dwDesiredAccess, (h==INVALID_HANDLE_VALUE) ? "failed" : "ok"));
+
+  if( h==INVALID_HANDLE_VALUE ){
+    sqlite3_free(zConverted);
+    sqlite3_free(zTmpname);
+    if( isReadWrite && !isExclusive ){
+      return winOpen(pVfs, zName, id,
+         ((flags|SQLITE_OPEN_READONLY) &
+                     ~(SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE)),
+         pOutFlags);
+    }else{
+      pFile->lastErrno = lastErrno;
+      winLogError(SQLITE_CANTOPEN, pFile->lastErrno, "winOpen", zUtf8Name);
+      return SQLITE_CANTOPEN_BKPT;
+    }
+  }
+
+  if( pOutFlags ){
+    if( isReadWrite ){
+      *pOutFlags = SQLITE_OPEN_READWRITE;
+    }else{
+      *pOutFlags = SQLITE_OPEN_READONLY;
+    }
+  }
+
+  OSTRACE(("OPEN file=%p, name=%s, access=%lx, pOutFlags=%p, *pOutFlags=%d, "
+           "rc=%s\n", h, zUtf8Name, dwDesiredAccess, pOutFlags, pOutFlags ?
+           *pOutFlags : 0, (h==INVALID_HANDLE_VALUE) ? "failed" : "ok"));
+
+  pAppData = (winVfsAppData*)pVfs->pAppData;
+
+#if SQLITE_OS_WINCE
+  {
+    if( isReadWrite && eType==SQLITE_OPEN_MAIN_DB
+         && ((pAppData==NULL) || !pAppData->bNoLock)
+         && (rc = winceCreateLock(zName, pFile))!=SQLITE_OK
+    ){
+      osCloseHandle(h);
+      sqlite3_free(zConverted);
+      sqlite3_free(zTmpname);
+      OSTRACE(("OPEN-CE-LOCK name=%s, rc=%s\n", zName, sqlite3ErrName(rc)));
+      return rc;
+    }
+  }
+  if( isTemp ){
+    pFile->zDeleteOnClose = zConverted;
+  }else
+#endif
+  {
+    sqlite3_free(zConverted);
+  }
+
+  sqlite3_free(zTmpname);
+  id->pMethods = pAppData ? pAppData->pMethod : &winIoMethod;
+  pFile->pVfs = pVfs;
+  pFile->h = h;
+  if( isReadonly ){
+    pFile->ctrlFlags |= WINFILE_RDONLY;
+  }
+  if( (flags & SQLITE_OPEN_MAIN_DB)
+   && sqlite3_uri_boolean(zName, "psow", SQLITE_POWERSAFE_OVERWRITE) 
+  ){
+    pFile->ctrlFlags |= WINFILE_PSOW;
+  }
+  pFile->lastErrno = NO_ERROR;
+  pFile->zPath = zName;
+#if SQLITE_MAX_MMAP_SIZE>0
+  pFile->hMap = NULL;
+  pFile->pMapRegion = 0;
+  pFile->mmapSize = 0;
+  pFile->mmapSizeMax = sqlite3GlobalConfig.szMmap;
+#endif
+
+  OpenCounter(+1);
+  return rc;
+}
+
+/*
+** Delete the named file.
+**
+** Note that Windows does not allow a file to be deleted if some other
+** process has it open.  Sometimes a virus scanner or indexing program
+** will open a journal file shortly after it is created in order to do
+** whatever it does.  While this other process is holding the
+** file open, we will be unable to delete it.  To work around this
+** problem, we delay 100 milliseconds and try to delete again.  Up
+** to MX_DELETION_ATTEMPTs deletion attempts are run before giving
+** up and returning an error.
+*/
+static int winDelete(
+  sqlite3_vfs *pVfs,          /* Not used on win32 */
+  const char *zFilename,      /* Name of file to delete */
+  int syncDir                 /* Not used on win32 */
+){
+  int cnt = 0;
+  int rc;
+  DWORD attr;
+  DWORD lastErrno = 0;
+  void *zConverted;
+  UNUSED_PARAMETER(pVfs);
+  UNUSED_PARAMETER(syncDir);
+
+  SimulateIOError(return SQLITE_IOERR_DELETE);
+  OSTRACE(("DELETE name=%s, syncDir=%d\n", zFilename, syncDir));
+
+  zConverted = winConvertFromUtf8Filename(zFilename);
+  if( zConverted==0 ){
+    OSTRACE(("DELETE name=%s, rc=SQLITE_IOERR_NOMEM\n", zFilename));
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+  if( osIsNT() ){
+    do {
+#if SQLITE_OS_WINRT
+      WIN32_FILE_ATTRIBUTE_DATA sAttrData;
+      memset(&sAttrData, 0, sizeof(sAttrData));
+      if ( osGetFileAttributesExW(zConverted, GetFileExInfoStandard,
+                                  &sAttrData) ){
+        attr = sAttrData.dwFileAttributes;
+      }else{
+        lastErrno = osGetLastError();
+        if( lastErrno==ERROR_FILE_NOT_FOUND
+         || lastErrno==ERROR_PATH_NOT_FOUND ){
+          rc = SQLITE_IOERR_DELETE_NOENT; /* Already gone? */
+        }else{
+          rc = SQLITE_ERROR;
+        }
+        break;
+      }
+#else
+      attr = osGetFileAttributesW(zConverted);
+#endif
+      if ( attr==INVALID_FILE_ATTRIBUTES ){
+        lastErrno = osGetLastError();
+        if( lastErrno==ERROR_FILE_NOT_FOUND
+         || lastErrno==ERROR_PATH_NOT_FOUND ){
+          rc = SQLITE_IOERR_DELETE_NOENT; /* Already gone? */
+        }else{
+          rc = SQLITE_ERROR;
+        }
+        break;
+      }
+      if ( attr&FILE_ATTRIBUTE_DIRECTORY ){
+        rc = SQLITE_ERROR; /* Files only. */
+        break;
+      }
+      if ( osDeleteFileW(zConverted) ){
+        rc = SQLITE_OK; /* Deleted OK. */
+        break;
+      }
+      if ( !winRetryIoerr(&cnt, &lastErrno) ){
+        rc = SQLITE_ERROR; /* No more retries. */
+        break;
+      }
+    } while(1);
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    do {
+      attr = osGetFileAttributesA(zConverted);
+      if ( attr==INVALID_FILE_ATTRIBUTES ){
+        lastErrno = osGetLastError();
+        if( lastErrno==ERROR_FILE_NOT_FOUND
+         || lastErrno==ERROR_PATH_NOT_FOUND ){
+          rc = SQLITE_IOERR_DELETE_NOENT; /* Already gone? */
+        }else{
+          rc = SQLITE_ERROR;
+        }
+        break;
+      }
+      if ( attr&FILE_ATTRIBUTE_DIRECTORY ){
+        rc = SQLITE_ERROR; /* Files only. */
+        break;
+      }
+      if ( osDeleteFileA(zConverted) ){
+        rc = SQLITE_OK; /* Deleted OK. */
+        break;
+      }
+      if ( !winRetryIoerr(&cnt, &lastErrno) ){
+        rc = SQLITE_ERROR; /* No more retries. */
+        break;
+      }
+    } while(1);
+  }
+#endif
+  if( rc && rc!=SQLITE_IOERR_DELETE_NOENT ){
+    rc = winLogError(SQLITE_IOERR_DELETE, lastErrno, "winDelete", zFilename);
+  }else{
+    winLogIoerr(cnt, __LINE__);
+  }
+  sqlite3_free(zConverted);
+  OSTRACE(("DELETE name=%s, rc=%s\n", zFilename, sqlite3ErrName(rc)));
+  return rc;
+}
+
+/*
+** Check the existence and status of a file.
+*/
+static int winAccess(
+  sqlite3_vfs *pVfs,         /* Not used on win32 */
+  const char *zFilename,     /* Name of file to check */
+  int flags,                 /* Type of test to make on this file */
+  int *pResOut               /* OUT: Result */
+){
+  DWORD attr;
+  int rc = 0;
+  DWORD lastErrno = 0;
+  void *zConverted;
+  UNUSED_PARAMETER(pVfs);
+
+  SimulateIOError( return SQLITE_IOERR_ACCESS; );
+  OSTRACE(("ACCESS name=%s, flags=%x, pResOut=%p\n",
+           zFilename, flags, pResOut));
+
+  if( zFilename==0 ){
+    *pResOut = 0;
+    OSTRACE(("ACCESS name=%s, pResOut=%p, *pResOut=%d, rc=SQLITE_OK\n",
+             zFilename, pResOut, *pResOut));
+    return SQLITE_OK;
+  }
+
+  zConverted = winConvertFromUtf8Filename(zFilename);
+  if( zConverted==0 ){
+    OSTRACE(("ACCESS name=%s, rc=SQLITE_IOERR_NOMEM\n", zFilename));
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+  if( osIsNT() ){
+    int cnt = 0;
+    WIN32_FILE_ATTRIBUTE_DATA sAttrData;
+    memset(&sAttrData, 0, sizeof(sAttrData));
+    while( !(rc = osGetFileAttributesExW((LPCWSTR)zConverted,
+                             GetFileExInfoStandard,
+                             &sAttrData)) && winRetryIoerr(&cnt, &lastErrno) ){}
+    if( rc ){
+      /* For an SQLITE_ACCESS_EXISTS query, treat a zero-length file
+      ** as if it does not exist.
+      */
+      if(    flags==SQLITE_ACCESS_EXISTS
+          && sAttrData.nFileSizeHigh==0
+          && sAttrData.nFileSizeLow==0 ){
+        attr = INVALID_FILE_ATTRIBUTES;
+      }else{
+        attr = sAttrData.dwFileAttributes;
+      }
+    }else{
+      winLogIoerr(cnt, __LINE__);
+      if( lastErrno!=ERROR_FILE_NOT_FOUND && lastErrno!=ERROR_PATH_NOT_FOUND ){
+        sqlite3_free(zConverted);
+        return winLogError(SQLITE_IOERR_ACCESS, lastErrno, "winAccess",
+                           zFilename);
+      }else{
+        attr = INVALID_FILE_ATTRIBUTES;
+      }
+    }
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    attr = osGetFileAttributesA((char*)zConverted);
+  }
+#endif
+  sqlite3_free(zConverted);
+  switch( flags ){
+    case SQLITE_ACCESS_READ:
+    case SQLITE_ACCESS_EXISTS:
+      rc = attr!=INVALID_FILE_ATTRIBUTES;
+      break;
+    case SQLITE_ACCESS_READWRITE:
+      rc = attr!=INVALID_FILE_ATTRIBUTES &&
+             (attr & FILE_ATTRIBUTE_READONLY)==0;
+      break;
+    default:
+      assert(!"Invalid flags argument");
+  }
+  *pResOut = rc;
+  OSTRACE(("ACCESS name=%s, pResOut=%p, *pResOut=%d, rc=SQLITE_OK\n",
+           zFilename, pResOut, *pResOut));
+  return SQLITE_OK;
+}
+
+/*
+** Returns non-zero if the specified path name starts with the "long path"
+** prefix.
+*/
+static BOOL winIsLongPathPrefix(
+  const char *zPathname
+){
+  return ( zPathname[0]=='\\' && zPathname[1]=='\\'
+        && zPathname[2]=='?'  && zPathname[3]=='\\' );
+}
+
+/*
+** Returns non-zero if the specified path name starts with a drive letter
+** followed by a colon character.
+*/
+static BOOL winIsDriveLetterAndColon(
+  const char *zPathname
+){
+  return ( sqlite3Isalpha(zPathname[0]) && zPathname[1]==':' );
+}
+
+/*
+** Returns non-zero if the specified path name should be used verbatim.  If
+** non-zero is returned from this function, the calling function must simply
+** use the provided path name verbatim -OR- resolve it into a full path name
+** using the GetFullPathName Win32 API function (if available).
+*/
+static BOOL winIsVerbatimPathname(
+  const char *zPathname
+){
+  /*
+  ** If the path name starts with a forward slash or a backslash, it is either
+  ** a legal UNC name, a volume relative path, or an absolute path name in the
+  ** "Unix" format on Windows.  There is no easy way to differentiate between
+  ** the final two cases; therefore, we return the safer return value of TRUE
+  ** so that callers of this function will simply use it verbatim.
+  */
+  if ( winIsDirSep(zPathname[0]) ){
+    return TRUE;
+  }
+
+  /*
+  ** If the path name starts with a letter and a colon it is either a volume
+  ** relative path or an absolute path.  Callers of this function must not
+  ** attempt to treat it as a relative path name (i.e. they should simply use
+  ** it verbatim).
+  */
+  if ( winIsDriveLetterAndColon(zPathname) ){
+    return TRUE;
+  }
+
+  /*
+  ** If we get to this point, the path name should almost certainly be a purely
+  ** relative one (i.e. not a UNC name, not absolute, and not volume relative).
+  */
+  return FALSE;
+}
+
+/*
+** Turn a relative pathname into a full pathname.  Write the full
+** pathname into zOut[].  zOut[] will be at least pVfs->mxPathname
+** bytes in size.
+*/
+static int winFullPathnameNoMutex(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zRelative,        /* Possibly relative input path */
+  int nFull,                    /* Size of output buffer in bytes */
+  char *zFull                   /* Output buffer */
+){
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && !defined(__CYGWIN__)
+  DWORD nByte;
+  void *zConverted;
+  char *zOut;
+#endif
+
+  /* If this path name begins with "/X:" or "\\?\", where "X" is any
+  ** alphabetic character, discard the initial "/" from the pathname.
+  */
+  if( zRelative[0]=='/' && (winIsDriveLetterAndColon(zRelative+1)
+       || winIsLongPathPrefix(zRelative+1)) ){
+    zRelative++;
+  }
+
+#if defined(__CYGWIN__)
+  SimulateIOError( return SQLITE_ERROR );
+  UNUSED_PARAMETER(nFull);
+  assert( nFull>=pVfs->mxPathname );
+  if ( sqlite3_data_directory && !winIsVerbatimPathname(zRelative) ){
+    /*
+    ** NOTE: We are dealing with a relative path name and the data
+    **       directory has been set.  Therefore, use it as the basis
+    **       for converting the relative path name to an absolute
+    **       one by prepending the data directory and a slash.
+    */
+    char *zOut = sqlite3MallocZero( pVfs->mxPathname+1 );
+    if( !zOut ){
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+    if( cygwin_conv_path(
+            (osIsNT() ? CCP_POSIX_TO_WIN_W : CCP_POSIX_TO_WIN_A) |
+            CCP_RELATIVE, zRelative, zOut, pVfs->mxPathname+1)<0 ){
+      sqlite3_free(zOut);
+      return winLogError(SQLITE_CANTOPEN_CONVPATH, (DWORD)errno,
+                         "winFullPathname1", zRelative);
+    }else{
+      char *zUtf8 = winConvertToUtf8Filename(zOut);
+      if( !zUtf8 ){
+        sqlite3_free(zOut);
+        return SQLITE_IOERR_NOMEM_BKPT;
+      }
+      sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s%c%s",
+                       sqlite3_data_directory, winGetDirSep(), zUtf8);
+      sqlite3_free(zUtf8);
+      sqlite3_free(zOut);
+    }
+  }else{
+    char *zOut = sqlite3MallocZero( pVfs->mxPathname+1 );
+    if( !zOut ){
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+    if( cygwin_conv_path(
+            (osIsNT() ? CCP_POSIX_TO_WIN_W : CCP_POSIX_TO_WIN_A),
+            zRelative, zOut, pVfs->mxPathname+1)<0 ){
+      sqlite3_free(zOut);
+      return winLogError(SQLITE_CANTOPEN_CONVPATH, (DWORD)errno,
+                         "winFullPathname2", zRelative);
+    }else{
+      char *zUtf8 = winConvertToUtf8Filename(zOut);
+      if( !zUtf8 ){
+        sqlite3_free(zOut);
+        return SQLITE_IOERR_NOMEM_BKPT;
+      }
+      sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s", zUtf8);
+      sqlite3_free(zUtf8);
+      sqlite3_free(zOut);
+    }
+  }
+  return SQLITE_OK;
+#endif
+
+#if (SQLITE_OS_WINCE || SQLITE_OS_WINRT) && !defined(__CYGWIN__)
+  SimulateIOError( return SQLITE_ERROR );
+  /* WinCE has no concept of a relative pathname, or so I am told. */
+  /* WinRT has no way to convert a relative path to an absolute one. */
+  if ( sqlite3_data_directory && !winIsVerbatimPathname(zRelative) ){
+    /*
+    ** NOTE: We are dealing with a relative path name and the data
+    **       directory has been set.  Therefore, use it as the basis
+    **       for converting the relative path name to an absolute
+    **       one by prepending the data directory and a backslash.
+    */
+    sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s%c%s",
+                     sqlite3_data_directory, winGetDirSep(), zRelative);
+  }else{
+    sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s", zRelative);
+  }
+  return SQLITE_OK;
+#endif
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && !defined(__CYGWIN__)
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. This function could fail if, for example, the
+  ** current working directory has been unlinked.
+  */
+  SimulateIOError( return SQLITE_ERROR );
+  if ( sqlite3_data_directory && !winIsVerbatimPathname(zRelative) ){
+    /*
+    ** NOTE: We are dealing with a relative path name and the data
+    **       directory has been set.  Therefore, use it as the basis
+    **       for converting the relative path name to an absolute
+    **       one by prepending the data directory and a backslash.
+    */
+    sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s%c%s",
+                     sqlite3_data_directory, winGetDirSep(), zRelative);
+    return SQLITE_OK;
+  }
+  zConverted = winConvertFromUtf8Filename(zRelative);
+  if( zConverted==0 ){
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+  if( osIsNT() ){
+    LPWSTR zTemp;
+    nByte = osGetFullPathNameW((LPCWSTR)zConverted, 0, 0, 0);
+    if( nByte==0 ){
+      sqlite3_free(zConverted);
+      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
+                         "winFullPathname1", zRelative);
+    }
+    nByte += 3;
+    zTemp = sqlite3MallocZero( nByte*sizeof(zTemp[0]) );
+    if( zTemp==0 ){
+      sqlite3_free(zConverted);
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+    nByte = osGetFullPathNameW((LPCWSTR)zConverted, nByte, zTemp, 0);
+    if( nByte==0 ){
+      sqlite3_free(zConverted);
+      sqlite3_free(zTemp);
+      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
+                         "winFullPathname2", zRelative);
+    }
+    sqlite3_free(zConverted);
+    zOut = winUnicodeToUtf8(zTemp);
+    sqlite3_free(zTemp);
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    char *zTemp;
+    nByte = osGetFullPathNameA((char*)zConverted, 0, 0, 0);
+    if( nByte==0 ){
+      sqlite3_free(zConverted);
+      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
+                         "winFullPathname3", zRelative);
+    }
+    nByte += 3;
+    zTemp = sqlite3MallocZero( nByte*sizeof(zTemp[0]) );
+    if( zTemp==0 ){
+      sqlite3_free(zConverted);
+      return SQLITE_IOERR_NOMEM_BKPT;
+    }
+    nByte = osGetFullPathNameA((char*)zConverted, nByte, zTemp, 0);
+    if( nByte==0 ){
+      sqlite3_free(zConverted);
+      sqlite3_free(zTemp);
+      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
+                         "winFullPathname4", zRelative);
+    }
+    sqlite3_free(zConverted);
+    zOut = winMbcsToUtf8(zTemp, osAreFileApisANSI());
+    sqlite3_free(zTemp);
+  }
+#endif
+  if( zOut ){
+    sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s", zOut);
+    sqlite3_free(zOut);
+    return SQLITE_OK;
+  }else{
+    return SQLITE_IOERR_NOMEM_BKPT;
+  }
+#endif
+}
+static int winFullPathname(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zRelative,        /* Possibly relative input path */
+  int nFull,                    /* Size of output buffer in bytes */
+  char *zFull                   /* Output buffer */
+){
+  int rc;
+  MUTEX_LOGIC( sqlite3_mutex *pMutex; )
+  MUTEX_LOGIC( pMutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR); )
+  sqlite3_mutex_enter(pMutex);
+  rc = winFullPathnameNoMutex(pVfs, zRelative, nFull, zFull);
+  sqlite3_mutex_leave(pMutex);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+static void *winDlOpen(sqlite3_vfs *pVfs, const char *zFilename){
+  HANDLE h;
+#if defined(__CYGWIN__)
+  int nFull = pVfs->mxPathname+1;
+  char *zFull = sqlite3MallocZero( nFull );
+  void *zConverted = 0;
+  if( zFull==0 ){
+    OSTRACE(("DLOPEN name=%s, handle=%p\n", zFilename, (void*)0));
+    return 0;
+  }
+  if( winFullPathname(pVfs, zFilename, nFull, zFull)!=SQLITE_OK ){
+    sqlite3_free(zFull);
+    OSTRACE(("DLOPEN name=%s, handle=%p\n", zFilename, (void*)0));
+    return 0;
+  }
+  zConverted = winConvertFromUtf8Filename(zFull);
+  sqlite3_free(zFull);
+#else
+  void *zConverted = winConvertFromUtf8Filename(zFilename);
+  UNUSED_PARAMETER(pVfs);
+#endif
+  if( zConverted==0 ){
+    OSTRACE(("DLOPEN name=%s, handle=%p\n", zFilename, (void*)0));
+    return 0;
+  }
+  if( osIsNT() ){
+#if SQLITE_OS_WINRT
+    h = osLoadPackagedLibrary((LPCWSTR)zConverted, 0);
+#else
+    h = osLoadLibraryW((LPCWSTR)zConverted);
+#endif
+  }
+#ifdef SQLITE_WIN32_HAS_ANSI
+  else{
+    h = osLoadLibraryA((char*)zConverted);
+  }
+#endif
+  OSTRACE(("DLOPEN name=%s, handle=%p\n", zFilename, (void*)h));
+  sqlite3_free(zConverted);
+  return (void*)h;
+}
+static void winDlError(sqlite3_vfs *pVfs, int nBuf, char *zBufOut){
+  UNUSED_PARAMETER(pVfs);
+  winGetLastErrorMsg(osGetLastError(), nBuf, zBufOut);
+}
+static void (*winDlSym(sqlite3_vfs *pVfs,void *pH,const char *zSym))(void){
+  FARPROC proc;
+  UNUSED_PARAMETER(pVfs);
+  proc = osGetProcAddressA((HANDLE)pH, zSym);
+  OSTRACE(("DLSYM handle=%p, symbol=%s, address=%p\n",
+           (void*)pH, zSym, (void*)proc));
+  return (void(*)(void))proc;
+}
+static void winDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  UNUSED_PARAMETER(pVfs);
+  osFreeLibrary((HANDLE)pHandle);
+  OSTRACE(("DLCLOSE handle=%p\n", (void*)pHandle));
+}
+#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
+  #define winDlOpen  0
+  #define winDlError 0
+  #define winDlSym   0
+  #define winDlClose 0
+#endif
+
+/* State information for the randomness gatherer. */
+typedef struct EntropyGatherer EntropyGatherer;
+struct EntropyGatherer {
+  unsigned char *a;   /* Gather entropy into this buffer */
+  int na;             /* Size of a[] in bytes */
+  int i;              /* XOR next input into a[i] */
+  int nXor;           /* Number of XOR operations done */
+};
+
+#if !defined(SQLITE_TEST) && !defined(SQLITE_OMIT_RANDOMNESS)
+/* Mix sz bytes of entropy into p. */
+static void xorMemory(EntropyGatherer *p, unsigned char *x, int sz){
+  int j, k;
+  for(j=0, k=p->i; j<sz; j++){
+    p->a[k++] ^= x[j];
+    if( k>=p->na ) k = 0;
+  }
+  p->i = k;
+  p->nXor += sz;
+}
+#endif /* !defined(SQLITE_TEST) && !defined(SQLITE_OMIT_RANDOMNESS) */
+
+/*
+** Write up to nBuf bytes of randomness into zBuf.
+*/
+static int winRandomness(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+#if defined(SQLITE_TEST) || defined(SQLITE_OMIT_RANDOMNESS)
+  UNUSED_PARAMETER(pVfs);
+  memset(zBuf, 0, nBuf);
+  return nBuf;
+#else
+  EntropyGatherer e;
+  UNUSED_PARAMETER(pVfs);
+  memset(zBuf, 0, nBuf);
+  e.a = (unsigned char*)zBuf;
+  e.na = nBuf;
+  e.nXor = 0;
+  e.i = 0;
+  {
+    SYSTEMTIME x;
+    osGetSystemTime(&x);
+    xorMemory(&e, (unsigned char*)&x, sizeof(SYSTEMTIME));
+  }
+  {
+    DWORD pid = osGetCurrentProcessId();
+    xorMemory(&e, (unsigned char*)&pid, sizeof(DWORD));
+  }
+#if SQLITE_OS_WINRT
+  {
+    ULONGLONG cnt = osGetTickCount64();
+    xorMemory(&e, (unsigned char*)&cnt, sizeof(ULONGLONG));
+  }
+#else
+  {
+    DWORD cnt = osGetTickCount();
+    xorMemory(&e, (unsigned char*)&cnt, sizeof(DWORD));
+  }
+#endif /* SQLITE_OS_WINRT */
+  {
+    LARGE_INTEGER i;
+    osQueryPerformanceCounter(&i);
+    xorMemory(&e, (unsigned char*)&i, sizeof(LARGE_INTEGER));
+  }
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
+  {
+    UUID id;
+    memset(&id, 0, sizeof(UUID));
+    osUuidCreate(&id);
+    xorMemory(&e, (unsigned char*)&id, sizeof(UUID));
+    memset(&id, 0, sizeof(UUID));
+    osUuidCreateSequential(&id);
+    xorMemory(&e, (unsigned char*)&id, sizeof(UUID));
+  }
+#endif /* !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID */
+  return e.nXor>nBuf ? nBuf : e.nXor;
+#endif /* defined(SQLITE_TEST) || defined(SQLITE_OMIT_RANDOMNESS) */
+}
+
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+*/
+static int winSleep(sqlite3_vfs *pVfs, int microsec){
+  sqlite3_win32_sleep((microsec+999)/1000);
+  UNUSED_PARAMETER(pVfs);
+  return ((microsec+999)/1000)*1000;
+}
+
+/*
+** The following variable, if set to a non-zero value, is interpreted as
+** the number of seconds since 1970 and is used to set the result of
+** sqlite3OsCurrentTime() during testing.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
+#endif
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return SQLITE_OK.  Return SQLITE_ERROR if the time and date
+** cannot be found.
+*/
+static int winCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *piNow){
+  /* FILETIME structure is a 64-bit value representing the number of
+     100-nanosecond intervals since January 1, 1601 (= JD 2305813.5).
+  */
+  FILETIME ft;
+  static const sqlite3_int64 winFiletimeEpoch = 23058135*(sqlite3_int64)8640000;
+#ifdef SQLITE_TEST
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+#endif
+  /* 2^32 - to avoid use of LL and warnings in gcc */
+  static const sqlite3_int64 max32BitValue =
+      (sqlite3_int64)2000000000 + (sqlite3_int64)2000000000 +
+      (sqlite3_int64)294967296;
+
+#if SQLITE_OS_WINCE
+  SYSTEMTIME time;
+  osGetSystemTime(&time);
+  /* if SystemTimeToFileTime() fails, it returns zero. */
+  if (!osSystemTimeToFileTime(&time,&ft)){
+    return SQLITE_ERROR;
+  }
+#else
+  osGetSystemTimeAsFileTime( &ft );
+#endif
+
+  *piNow = winFiletimeEpoch +
+            ((((sqlite3_int64)ft.dwHighDateTime)*max32BitValue) +
+               (sqlite3_int64)ft.dwLowDateTime)/(sqlite3_int64)10000;
+
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
+  }
+#endif
+  UNUSED_PARAMETER(pVfs);
+  return SQLITE_OK;
+}
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write the
+** current time and date as a Julian Day number into *prNow and
+** return 0.  Return 1 if the time and date cannot be found.
+*/
+static int winCurrentTime(sqlite3_vfs *pVfs, double *prNow){
+  int rc;
+  sqlite3_int64 i;
+  rc = winCurrentTimeInt64(pVfs, &i);
+  if( !rc ){
+    *prNow = i/86400000.0;
+  }
+  return rc;
+}
+
+/*
+** The idea is that this function works like a combination of
+** GetLastError() and FormatMessage() on Windows (or errno and
+** strerror_r() on Unix). After an error is returned by an OS
+** function, SQLite calls this function with zBuf pointing to
+** a buffer of nBuf bytes. The OS layer should populate the
+** buffer with a nul-terminated UTF-8 encoded error message
+** describing the last IO error to have occurred within the calling
+** thread.
+**
+** If the error message is too large for the supplied buffer,
+** it should be truncated. The return value of xGetLastError
+** is zero if the error message fits in the buffer, or non-zero
+** otherwise (if the message was truncated). If non-zero is returned,
+** then it is not necessary to include the nul-terminator character
+** in the output buffer.
+**
+** Not supplying an error message will have no adverse effect
+** on SQLite. It is fine to have an implementation that never
+** returns an error message:
+**
+**   int xGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+**     assert(zBuf[0]=='\0');
+**     return 0;
+**   }
+**
+** However if an error message is supplied, it will be incorporated
+** by sqlite into the error message available to the user using
+** sqlite3_errmsg(), possibly making IO errors easier to debug.
+*/
+static int winGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+  DWORD e = osGetLastError();
+  UNUSED_PARAMETER(pVfs);
+  if( nBuf>0 ) winGetLastErrorMsg(e, nBuf, zBuf);
+  return e;
+}
+
+/*
+** Initialize and deinitialize the operating system interface.
+*/
+int sqlite3_os_init(void){
+  static sqlite3_vfs winVfs = {
+    3,                     /* iVersion */
+    sizeof(winFile),       /* szOsFile */
+    SQLITE_WIN32_MAX_PATH_BYTES, /* mxPathname */
+    0,                     /* pNext */
+    "win32",               /* zName */
+    &winAppData,           /* pAppData */
+    winOpen,               /* xOpen */
+    winDelete,             /* xDelete */
+    winAccess,             /* xAccess */
+    winFullPathname,       /* xFullPathname */
+    winDlOpen,             /* xDlOpen */
+    winDlError,            /* xDlError */
+    winDlSym,              /* xDlSym */
+    winDlClose,            /* xDlClose */
+    winRandomness,         /* xRandomness */
+    winSleep,              /* xSleep */
+    winCurrentTime,        /* xCurrentTime */
+    winGetLastError,       /* xGetLastError */
+    winCurrentTimeInt64,   /* xCurrentTimeInt64 */
+    winSetSystemCall,      /* xSetSystemCall */
+    winGetSystemCall,      /* xGetSystemCall */
+    winNextSystemCall,     /* xNextSystemCall */
+  };
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  static sqlite3_vfs winLongPathVfs = {
+    3,                     /* iVersion */
+    sizeof(winFile),       /* szOsFile */
+    SQLITE_WINNT_MAX_PATH_BYTES, /* mxPathname */
+    0,                     /* pNext */
+    "win32-longpath",      /* zName */
+    &winAppData,           /* pAppData */
+    winOpen,               /* xOpen */
+    winDelete,             /* xDelete */
+    winAccess,             /* xAccess */
+    winFullPathname,       /* xFullPathname */
+    winDlOpen,             /* xDlOpen */
+    winDlError,            /* xDlError */
+    winDlSym,              /* xDlSym */
+    winDlClose,            /* xDlClose */
+    winRandomness,         /* xRandomness */
+    winSleep,              /* xSleep */
+    winCurrentTime,        /* xCurrentTime */
+    winGetLastError,       /* xGetLastError */
+    winCurrentTimeInt64,   /* xCurrentTimeInt64 */
+    winSetSystemCall,      /* xSetSystemCall */
+    winGetSystemCall,      /* xGetSystemCall */
+    winNextSystemCall,     /* xNextSystemCall */
+  };
+#endif
+  static sqlite3_vfs winNolockVfs = {
+    3,                     /* iVersion */
+    sizeof(winFile),       /* szOsFile */
+    SQLITE_WIN32_MAX_PATH_BYTES, /* mxPathname */
+    0,                     /* pNext */
+    "win32-none",          /* zName */
+    &winNolockAppData,     /* pAppData */
+    winOpen,               /* xOpen */
+    winDelete,             /* xDelete */
+    winAccess,             /* xAccess */
+    winFullPathname,       /* xFullPathname */
+    winDlOpen,             /* xDlOpen */
+    winDlError,            /* xDlError */
+    winDlSym,              /* xDlSym */
+    winDlClose,            /* xDlClose */
+    winRandomness,         /* xRandomness */
+    winSleep,              /* xSleep */
+    winCurrentTime,        /* xCurrentTime */
+    winGetLastError,       /* xGetLastError */
+    winCurrentTimeInt64,   /* xCurrentTimeInt64 */
+    winSetSystemCall,      /* xSetSystemCall */
+    winGetSystemCall,      /* xGetSystemCall */
+    winNextSystemCall,     /* xNextSystemCall */
+  };
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  static sqlite3_vfs winLongPathNolockVfs = {
+    3,                     /* iVersion */
+    sizeof(winFile),       /* szOsFile */
+    SQLITE_WINNT_MAX_PATH_BYTES, /* mxPathname */
+    0,                     /* pNext */
+    "win32-longpath-none", /* zName */
+    &winNolockAppData,     /* pAppData */
+    winOpen,               /* xOpen */
+    winDelete,             /* xDelete */
+    winAccess,             /* xAccess */
+    winFullPathname,       /* xFullPathname */
+    winDlOpen,             /* xDlOpen */
+    winDlError,            /* xDlError */
+    winDlSym,              /* xDlSym */
+    winDlClose,            /* xDlClose */
+    winRandomness,         /* xRandomness */
+    winSleep,              /* xSleep */
+    winCurrentTime,        /* xCurrentTime */
+    winGetLastError,       /* xGetLastError */
+    winCurrentTimeInt64,   /* xCurrentTimeInt64 */
+    winSetSystemCall,      /* xSetSystemCall */
+    winGetSystemCall,      /* xGetSystemCall */
+    winNextSystemCall,     /* xNextSystemCall */
+  };
+#endif
+
+  /* Double-check that the aSyscall[] array has been constructed
+  ** correctly.  See ticket [bb3a86e890c8e96ab] */
+  assert( ArraySize(aSyscall)==80 );
+
+  /* get memory map allocation granularity */
+  memset(&winSysInfo, 0, sizeof(SYSTEM_INFO));
+#if SQLITE_OS_WINRT
+  osGetNativeSystemInfo(&winSysInfo);
+#else
+  osGetSystemInfo(&winSysInfo);
+#endif
+  assert( winSysInfo.dwAllocationGranularity>0 );
+  assert( winSysInfo.dwPageSize>0 );
+
+  sqlite3_vfs_register(&winVfs, 1);
+
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  sqlite3_vfs_register(&winLongPathVfs, 0);
+#endif
+
+  sqlite3_vfs_register(&winNolockVfs, 0);
+
+#if defined(SQLITE_WIN32_HAS_WIDE)
+  sqlite3_vfs_register(&winLongPathNolockVfs, 0);
+#endif
+
+#ifndef SQLITE_OMIT_WAL
+  winBigLock = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1);
+#endif
+
+  return SQLITE_OK;
+}
+
+int sqlite3_os_end(void){
+#if SQLITE_OS_WINRT
+  if( sleepObj!=NULL ){
+    osCloseHandle(sleepObj);
+    sleepObj = NULL;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_WAL
+  winBigLock = 0;
+#endif
+
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_OS_WIN */
diff --git a/src/os_win.h b/src/os_win.h
new file mode 100644
index 0000000..27714ed
--- /dev/null
+++ b/src/os_win.h
@@ -0,0 +1,88 @@
+/*
+** 2013 November 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that is specific to Windows.
+*/
+#ifndef SQLITE_OS_WIN_H
+#define SQLITE_OS_WIN_H
+
+/*
+** Include the primary Windows SDK header file.
+*/
+#include "windows.h"
+
+#ifdef __CYGWIN__
+# include <sys/cygwin.h>
+# include <errno.h> /* amalgamator: dontcache */
+#endif
+
+/*
+** Determine if we are dealing with Windows NT.
+**
+** We ought to be able to determine if we are compiling for Windows 9x or
+** Windows NT using the _WIN32_WINNT macro as follows:
+**
+** #if defined(_WIN32_WINNT)
+** # define SQLITE_OS_WINNT 1
+** #else
+** # define SQLITE_OS_WINNT 0
+** #endif
+**
+** However, Visual Studio 2005 does not set _WIN32_WINNT by default, as
+** it ought to, so the above test does not work.  We'll just assume that
+** everything is Windows NT unless the programmer explicitly says otherwise
+** by setting SQLITE_OS_WINNT to 0.
+*/
+#if SQLITE_OS_WIN && !defined(SQLITE_OS_WINNT)
+# define SQLITE_OS_WINNT 1
+#endif
+
+/*
+** Determine if we are dealing with Windows CE - which has a much reduced
+** API.
+*/
+#if defined(_WIN32_WCE)
+# define SQLITE_OS_WINCE 1
+#else
+# define SQLITE_OS_WINCE 0
+#endif
+
+/*
+** Determine if we are dealing with WinRT, which provides only a subset of
+** the full Win32 API.
+*/
+#if !defined(SQLITE_OS_WINRT)
+# define SQLITE_OS_WINRT 0
+#endif
+
+/*
+** For WinCE, some API function parameters do not appear to be declared as
+** volatile.
+*/
+#if SQLITE_OS_WINCE
+# define SQLITE_WIN32_VOLATILE
+#else
+# define SQLITE_WIN32_VOLATILE volatile
+#endif
+
+/*
+** For some Windows sub-platforms, the _beginthreadex() / _endthreadex()
+** functions are not available (e.g. those not using MSVC, Cygwin, etc).
+*/
+#if SQLITE_OS_WIN && !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && \
+    SQLITE_THREADSAFE>0 && !defined(__CYGWIN__)
+# define SQLITE_OS_WIN_THREADS 1
+#else
+# define SQLITE_OS_WIN_THREADS 0
+#endif
+
+#endif /* SQLITE_OS_WIN_H */
diff --git a/src/pager.c b/src/pager.c
new file mode 100644
index 0000000..37588f0
--- /dev/null
+++ b/src/pager.c
@@ -0,0 +1,7800 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the implementation of the page cache subsystem or "pager".
+**
+** The pager is used to access a database disk file.  It implements
+** atomic commit and rollback through the use of a journal file that
+** is separate from the database file.  The pager also implements file
+** locking to prevent two processes from writing the same database
+** file simultaneously, or one process from reading the database while
+** another is writing.
+*/
+#ifndef SQLITE_OMIT_DISKIO
+#include "sqliteInt.h"
+#include "wal.h"
+
+
+/******************* NOTES ON THE DESIGN OF THE PAGER ************************
+**
+** This comment block describes invariants that hold when using a rollback
+** journal.  These invariants do not apply for journal_mode=WAL,
+** journal_mode=MEMORY, or journal_mode=OFF.
+**
+** Within this comment block, a page is deemed to have been synced
+** automatically as soon as it is written when PRAGMA synchronous=OFF.
+** Otherwise, the page is not synced until the xSync method of the VFS
+** is called successfully on the file containing the page.
+**
+** Definition:  A page of the database file is said to be "overwriteable" if
+** one or more of the following are true about the page:
+**
+**     (a)  The original content of the page as it was at the beginning of
+**          the transaction has been written into the rollback journal and
+**          synced.
+**
+**     (b)  The page was a freelist leaf page at the start of the transaction.
+**
+**     (c)  The page number is greater than the largest page that existed in
+**          the database file at the start of the transaction.
+**
+** (1) A page of the database file is never overwritten unless one of the
+**     following are true:
+**
+**     (a) The page and all other pages on the same sector are overwriteable.
+**
+**     (b) The atomic page write optimization is enabled, and the entire
+**         transaction other than the update of the transaction sequence
+**         number consists of a single page change.
+**
+** (2) The content of a page written into the rollback journal exactly matches
+**     both the content in the database when the rollback journal was written
+**     and the content in the database at the beginning of the current
+**     transaction.
+**
+** (3) Writes to the database file are an integer multiple of the page size
+**     in length and are aligned on a page boundary.
+**
+** (4) Reads from the database file are either aligned on a page boundary and
+**     an integer multiple of the page size in length or are taken from the
+**     first 100 bytes of the database file.
+**
+** (5) All writes to the database file are synced prior to the rollback journal
+**     being deleted, truncated, or zeroed.
+**
+** (6) If a super-journal file is used, then all writes to the database file
+**     are synced prior to the super-journal being deleted.
+**
+** Definition: Two databases (or the same database at two points it time)
+** are said to be "logically equivalent" if they give the same answer to
+** all queries.  Note in particular the content of freelist leaf
+** pages can be changed arbitrarily without affecting the logical equivalence
+** of the database.
+**
+** (7) At any time, if any subset, including the empty set and the total set,
+**     of the unsynced changes to a rollback journal are removed and the
+**     journal is rolled back, the resulting database file will be logically
+**     equivalent to the database file at the beginning of the transaction.
+**
+** (8) When a transaction is rolled back, the xTruncate method of the VFS
+**     is called to restore the database file to the same size it was at
+**     the beginning of the transaction.  (In some VFSes, the xTruncate
+**     method is a no-op, but that does not change the fact the SQLite will
+**     invoke it.)
+**
+** (9) Whenever the database file is modified, at least one bit in the range
+**     of bytes from 24 through 39 inclusive will be changed prior to releasing
+**     the EXCLUSIVE lock, thus signaling other connections on the same
+**     database to flush their caches.
+**
+** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
+**      than one billion transactions.
+**
+** (11) A database file is well-formed at the beginning and at the conclusion
+**      of every transaction.
+**
+** (12) An EXCLUSIVE lock is held on the database file when writing to
+**      the database file.
+**
+** (13) A SHARED lock is held on the database file while reading any
+**      content out of the database file.
+**
+******************************************************************************/
+
+/*
+** Macros for troubleshooting.  Normally turned off
+*/
+#if 0
+int sqlite3PagerTrace=1;  /* True to enable tracing */
+#define sqlite3DebugPrintf printf
+#define PAGERTRACE(X)     if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; }
+#else
+#define PAGERTRACE(X)
+#endif
+
+/*
+** The following two macros are used within the PAGERTRACE() macros above
+** to print out file-descriptors.
+**
+** PAGERID() takes a pointer to a Pager struct as its argument. The
+** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
+** struct as its argument.
+*/
+#define PAGERID(p) (SQLITE_PTR_TO_INT(p->fd))
+#define FILEHANDLEID(fd) (SQLITE_PTR_TO_INT(fd))
+
+/*
+** The Pager.eState variable stores the current 'state' of a pager. A
+** pager may be in any one of the seven states shown in the following
+** state diagram.
+**
+**                            OPEN <------+------+
+**                              |         |      |
+**                              V         |      |
+**               +---------> READER-------+      |
+**               |              |                |
+**               |              V                |
+**               |<-------WRITER_LOCKED------> ERROR
+**               |              |                ^ 
+**               |              V                |
+**               |<------WRITER_CACHEMOD-------->|
+**               |              |                |
+**               |              V                |
+**               |<-------WRITER_DBMOD---------->|
+**               |              |                |
+**               |              V                |
+**               +<------WRITER_FINISHED-------->+
+**
+**
+** List of state transitions and the C [function] that performs each:
+**
+**   OPEN              -> READER              [sqlite3PagerSharedLock]
+**   READER            -> OPEN                [pager_unlock]
+**
+**   READER            -> WRITER_LOCKED       [sqlite3PagerBegin]
+**   WRITER_LOCKED     -> WRITER_CACHEMOD     [pager_open_journal]
+**   WRITER_CACHEMOD   -> WRITER_DBMOD        [syncJournal]
+**   WRITER_DBMOD      -> WRITER_FINISHED     [sqlite3PagerCommitPhaseOne]
+**   WRITER_***        -> READER              [pager_end_transaction]
+**
+**   WRITER_***        -> ERROR               [pager_error]
+**   ERROR             -> OPEN                [pager_unlock]
+**
+**
+**  OPEN:
+**
+**    The pager starts up in this state. Nothing is guaranteed in this
+**    state - the file may or may not be locked and the database size is
+**    unknown. The database may not be read or written.
+**
+**    * No read or write transaction is active.
+**    * Any lock, or no lock at all, may be held on the database file.
+**    * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
+**
+**  READER:
+**
+**    In this state all the requirements for reading the database in
+**    rollback (non-WAL) mode are met. Unless the pager is (or recently
+**    was) in exclusive-locking mode, a user-level read transaction is
+**    open. The database size is known in this state.
+**
+**    A connection running with locking_mode=normal enters this state when
+**    it opens a read-transaction on the database and returns to state
+**    OPEN after the read-transaction is completed. However a connection
+**    running in locking_mode=exclusive (including temp databases) remains in
+**    this state even after the read-transaction is closed. The only way
+**    a locking_mode=exclusive connection can transition from READER to OPEN
+**    is via the ERROR state (see below).
+**
+**    * A read transaction may be active (but a write-transaction cannot).
+**    * A SHARED or greater lock is held on the database file.
+**    * The dbSize variable may be trusted (even if a user-level read
+**      transaction is not active). The dbOrigSize and dbFileSize variables
+**      may not be trusted at this point.
+**    * If the database is a WAL database, then the WAL connection is open.
+**    * Even if a read-transaction is not open, it is guaranteed that
+**      there is no hot-journal in the file-system.
+**
+**  WRITER_LOCKED:
+**
+**    The pager moves to this state from READER when a write-transaction
+**    is first opened on the database. In WRITER_LOCKED state, all locks
+**    required to start a write-transaction are held, but no actual
+**    modifications to the cache or database have taken place.
+**
+**    In rollback mode, a RESERVED or (if the transaction was opened with
+**    BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when
+**    moving to this state, but the journal file is not written to or opened
+**    to in this state. If the transaction is committed or rolled back while
+**    in WRITER_LOCKED state, all that is required is to unlock the database
+**    file.
+**
+**    IN WAL mode, WalBeginWriteTransaction() is called to lock the log file.
+**    If the connection is running with locking_mode=exclusive, an attempt
+**    is made to obtain an EXCLUSIVE lock on the database file.
+**
+**    * A write transaction is active.
+**    * If the connection is open in rollback-mode, a RESERVED or greater
+**      lock is held on the database file.
+**    * If the connection is open in WAL-mode, a WAL write transaction
+**      is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
+**      called).
+**    * The dbSize, dbOrigSize and dbFileSize variables are all valid.
+**    * The contents of the pager cache have not been modified.
+**    * The journal file may or may not be open.
+**    * Nothing (not even the first header) has been written to the journal.
+**
+**  WRITER_CACHEMOD:
+**
+**    A pager moves from WRITER_LOCKED state to this state when a page is
+**    first modified by the upper layer. In rollback mode the journal file
+**    is opened (if it is not already open) and a header written to the
+**    start of it. The database file on disk has not been modified.
+**
+**    * A write transaction is active.
+**    * A RESERVED or greater lock is held on the database file.
+**    * The journal file is open and the first header has been written
+**      to it, but the header has not been synced to disk.
+**    * The contents of the page cache have been modified.
+**
+**  WRITER_DBMOD:
+**
+**    The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state
+**    when it modifies the contents of the database file. WAL connections
+**    never enter this state (since they do not modify the database file,
+**    just the log file).
+**
+**    * A write transaction is active.
+**    * An EXCLUSIVE or greater lock is held on the database file.
+**    * The journal file is open and the first header has been written
+**      and synced to disk.
+**    * The contents of the page cache have been modified (and possibly
+**      written to disk).
+**
+**  WRITER_FINISHED:
+**
+**    It is not possible for a WAL connection to enter this state.
+**
+**    A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD
+**    state after the entire transaction has been successfully written into the
+**    database file. In this state the transaction may be committed simply
+**    by finalizing the journal file. Once in WRITER_FINISHED state, it is
+**    not possible to modify the database further. At this point, the upper
+**    layer must either commit or rollback the transaction.
+**
+**    * A write transaction is active.
+**    * An EXCLUSIVE or greater lock is held on the database file.
+**    * All writing and syncing of journal and database data has finished.
+**      If no error occurred, all that remains is to finalize the journal to
+**      commit the transaction. If an error did occur, the caller will need
+**      to rollback the transaction.
+**
+**  ERROR:
+**
+**    The ERROR state is entered when an IO or disk-full error (including
+**    SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it
+**    difficult to be sure that the in-memory pager state (cache contents,
+**    db size etc.) are consistent with the contents of the file-system.
+**
+**    Temporary pager files may enter the ERROR state, but in-memory pagers
+**    cannot.
+**
+**    For example, if an IO error occurs while performing a rollback,
+**    the contents of the page-cache may be left in an inconsistent state.
+**    At this point it would be dangerous to change back to READER state
+**    (as usually happens after a rollback). Any subsequent readers might
+**    report database corruption (due to the inconsistent cache), and if
+**    they upgrade to writers, they may inadvertently corrupt the database
+**    file. To avoid this hazard, the pager switches into the ERROR state
+**    instead of READER following such an error.
+**
+**    Once it has entered the ERROR state, any attempt to use the pager
+**    to read or write data returns an error. Eventually, once all
+**    outstanding transactions have been abandoned, the pager is able to
+**    transition back to OPEN state, discarding the contents of the
+**    page-cache and any other in-memory state at the same time. Everything
+**    is reloaded from disk (and, if necessary, hot-journal rollback performed)
+**    when a read-transaction is next opened on the pager (transitioning
+**    the pager into READER state). At that point the system has recovered
+**    from the error.
+**
+**    Specifically, the pager jumps into the ERROR state if:
+**
+**      1. An error occurs while attempting a rollback. This happens in
+**         function sqlite3PagerRollback().
+**
+**      2. An error occurs while attempting to finalize a journal file
+**         following a commit in function sqlite3PagerCommitPhaseTwo().
+**
+**      3. An error occurs while attempting to write to the journal or
+**         database file in function pagerStress() in order to free up
+**         memory.
+**
+**    In other cases, the error is returned to the b-tree layer. The b-tree
+**    layer then attempts a rollback operation. If the error condition
+**    persists, the pager enters the ERROR state via condition (1) above.
+**
+**    Condition (3) is necessary because it can be triggered by a read-only
+**    statement executed within a transaction. In this case, if the error
+**    code were simply returned to the user, the b-tree layer would not
+**    automatically attempt a rollback, as it assumes that an error in a
+**    read-only statement cannot leave the pager in an internally inconsistent
+**    state.
+**
+**    * The Pager.errCode variable is set to something other than SQLITE_OK.
+**    * There are one or more outstanding references to pages (after the
+**      last reference is dropped the pager should move back to OPEN state).
+**    * The pager is not an in-memory pager.
+**   
+**
+** Notes:
+**
+**   * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
+**     connection is open in WAL mode. A WAL connection is always in one
+**     of the first four states.
+**
+**   * Normally, a connection open in exclusive mode is never in PAGER_OPEN
+**     state. There are two exceptions: immediately after exclusive-mode has
+**     been turned on (and before any read or write transactions are
+**     executed), and when the pager is leaving the "error state".
+**
+**   * See also: assert_pager_state().
+*/
+#define PAGER_OPEN                  0
+#define PAGER_READER                1
+#define PAGER_WRITER_LOCKED         2
+#define PAGER_WRITER_CACHEMOD       3
+#define PAGER_WRITER_DBMOD          4
+#define PAGER_WRITER_FINISHED       5
+#define PAGER_ERROR                 6
+
+/*
+** The Pager.eLock variable is almost always set to one of the
+** following locking-states, according to the lock currently held on
+** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
+** This variable is kept up to date as locks are taken and released by
+** the pagerLockDb() and pagerUnlockDb() wrappers.
+**
+** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY
+** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not
+** the operation was successful. In these circumstances pagerLockDb() and
+** pagerUnlockDb() take a conservative approach - eLock is always updated
+** when unlocking the file, and only updated when locking the file if the
+** VFS call is successful. This way, the Pager.eLock variable may be set
+** to a less exclusive (lower) value than the lock that is actually held
+** at the system level, but it is never set to a more exclusive value.
+**
+** This is usually safe. If an xUnlock fails or appears to fail, there may
+** be a few redundant xLock() calls or a lock may be held for longer than
+** required, but nothing really goes wrong.
+**
+** The exception is when the database file is unlocked as the pager moves
+** from ERROR to OPEN state. At this point there may be a hot-journal file
+** in the file-system that needs to be rolled back (as part of an OPEN->SHARED
+** transition, by the same pager or any other). If the call to xUnlock()
+** fails at this point and the pager is left holding an EXCLUSIVE lock, this
+** can confuse the call to xCheckReservedLock() call made later as part
+** of hot-journal detection.
+**
+** xCheckReservedLock() is defined as returning true "if there is a RESERVED
+** lock held by this process or any others". So xCheckReservedLock may
+** return true because the caller itself is holding an EXCLUSIVE lock (but
+** doesn't know it because of a previous error in xUnlock). If this happens
+** a hot-journal may be mistaken for a journal being created by an active
+** transaction in another process, causing SQLite to read from the database
+** without rolling it back.
+**
+** To work around this, if a call to xUnlock() fails when unlocking the
+** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
+** is only changed back to a real locking state after a successful call
+** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition
+** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK
+** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
+** lock on the database file before attempting to roll it back. See function
+** PagerSharedLock() for more detail.
+**
+** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in
+** PAGER_OPEN state.
+*/
+#define UNKNOWN_LOCK                (EXCLUSIVE_LOCK+1)
+
+/*
+** The maximum allowed sector size. 64KiB. If the xSectorsize() method
+** returns a value larger than this, then MAX_SECTOR_SIZE is used instead.
+** This could conceivably cause corruption following a power failure on
+** such a system. This is currently an undocumented limit.
+*/
+#define MAX_SECTOR_SIZE 0x10000
+
+
+/*
+** An instance of the following structure is allocated for each active
+** savepoint and statement transaction in the system. All such structures
+** are stored in the Pager.aSavepoint[] array, which is allocated and
+** resized using sqlite3Realloc().
+**
+** When a savepoint is created, the PagerSavepoint.iHdrOffset field is
+** set to 0. If a journal-header is written into the main journal while
+** the savepoint is active, then iHdrOffset is set to the byte offset
+** immediately following the last journal record written into the main
+** journal before the journal-header. This is required during savepoint
+** rollback (see pagerPlaybackSavepoint()).
+*/
+typedef struct PagerSavepoint PagerSavepoint;
+struct PagerSavepoint {
+  i64 iOffset;                 /* Starting offset in main journal */
+  i64 iHdrOffset;              /* See above */
+  Bitvec *pInSavepoint;        /* Set of pages in this savepoint */
+  Pgno nOrig;                  /* Original number of pages in file */
+  Pgno iSubRec;                /* Index of first record in sub-journal */
+  int bTruncateOnRelease;      /* If stmt journal may be truncated on RELEASE */
+#ifndef SQLITE_OMIT_WAL
+  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
+#endif
+};
+
+/*
+** Bits of the Pager.doNotSpill flag.  See further description below.
+*/
+#define SPILLFLAG_OFF         0x01 /* Never spill cache.  Set via pragma */
+#define SPILLFLAG_ROLLBACK    0x02 /* Current rolling back, so do not spill */
+#define SPILLFLAG_NOSYNC      0x04 /* Spill is ok, but do not sync */
+
+/*
+** An open page cache is an instance of struct Pager. A description of
+** some of the more important member variables follows:
+**
+** eState
+**
+**   The current 'state' of the pager object. See the comment and state
+**   diagram above for a description of the pager state.
+**
+** eLock
+**
+**   For a real on-disk database, the current lock held on the database file -
+**   NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
+**
+**   For a temporary or in-memory database (neither of which require any
+**   locks), this variable is always set to EXCLUSIVE_LOCK. Since such
+**   databases always have Pager.exclusiveMode==1, this tricks the pager
+**   logic into thinking that it already has all the locks it will ever
+**   need (and no reason to release them).
+**
+**   In some (obscure) circumstances, this variable may also be set to
+**   UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for
+**   details.
+**
+** changeCountDone
+**
+**   This boolean variable is used to make sure that the change-counter
+**   (the 4-byte header field at byte offset 24 of the database file) is
+**   not updated more often than necessary.
+**
+**   It is set to true when the change-counter field is updated, which
+**   can only happen if an exclusive lock is held on the database file.
+**   It is cleared (set to false) whenever an exclusive lock is
+**   relinquished on the database file. Each time a transaction is committed,
+**   The changeCountDone flag is inspected. If it is true, the work of
+**   updating the change-counter is omitted for the current transaction.
+**
+**   This mechanism means that when running in exclusive mode, a connection
+**   need only update the change-counter once, for the first transaction
+**   committed.
+**
+** setSuper
+**
+**   When PagerCommitPhaseOne() is called to commit a transaction, it may
+**   (or may not) specify a super-journal name to be written into the
+**   journal file before it is synced to disk.
+**
+**   Whether or not a journal file contains a super-journal pointer affects
+**   the way in which the journal file is finalized after the transaction is
+**   committed or rolled back when running in "journal_mode=PERSIST" mode.
+**   If a journal file does not contain a super-journal pointer, it is
+**   finalized by overwriting the first journal header with zeroes. If
+**   it does contain a super-journal pointer the journal file is finalized
+**   by truncating it to zero bytes, just as if the connection were
+**   running in "journal_mode=truncate" mode.
+**
+**   Journal files that contain super-journal pointers cannot be finalized
+**   simply by overwriting the first journal-header with zeroes, as the
+**   super-journal pointer could interfere with hot-journal rollback of any
+**   subsequently interrupted transaction that reuses the journal file.
+**
+**   The flag is cleared as soon as the journal file is finalized (either
+**   by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
+**   journal file from being successfully finalized, the setSuper flag
+**   is cleared anyway (and the pager will move to ERROR state).
+**
+** doNotSpill
+**
+**   This variables control the behavior of cache-spills  (calls made by
+**   the pcache module to the pagerStress() routine to write cached data
+**   to the file-system in order to free up memory).
+**
+**   When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set,
+**   writing to the database from pagerStress() is disabled altogether.
+**   The SPILLFLAG_ROLLBACK case is done in a very obscure case that
+**   comes up during savepoint rollback that requires the pcache module
+**   to allocate a new page to prevent the journal file from being written
+**   while it is being traversed by code in pager_playback().  The SPILLFLAG_OFF
+**   case is a user preference.
+**
+**   If the SPILLFLAG_NOSYNC bit is set, writing to the database from
+**   pagerStress() is permitted, but syncing the journal file is not.
+**   This flag is set by sqlite3PagerWrite() when the file-system sector-size
+**   is larger than the database page-size in order to prevent a journal sync
+**   from happening in between the journalling of two pages on the same sector.
+**
+** subjInMemory
+**
+**   This is a boolean variable. If true, then any required sub-journal
+**   is opened as an in-memory journal file. If false, then in-memory
+**   sub-journals are only used for in-memory pager files.
+**
+**   This variable is updated by the upper layer each time a new
+**   write-transaction is opened.
+**
+** dbSize, dbOrigSize, dbFileSize
+**
+**   Variable dbSize is set to the number of pages in the database file.
+**   It is valid in PAGER_READER and higher states (all states except for
+**   OPEN and ERROR).
+**
+**   dbSize is set based on the size of the database file, which may be
+**   larger than the size of the database (the value stored at offset
+**   28 of the database header by the btree). If the size of the file
+**   is not an integer multiple of the page-size, the value stored in
+**   dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2).
+**   Except, any file that is greater than 0 bytes in size is considered
+**   to have at least one page. (i.e. a 1KB file with 2K page-size leads
+**   to dbSize==1).
+**
+**   During a write-transaction, if pages with page-numbers greater than
+**   dbSize are modified in the cache, dbSize is updated accordingly.
+**   Similarly, if the database is truncated using PagerTruncateImage(),
+**   dbSize is updated.
+**
+**   Variables dbOrigSize and dbFileSize are valid in states
+**   PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize
+**   variable at the start of the transaction. It is used during rollback,
+**   and to determine whether or not pages need to be journalled before
+**   being modified.
+**
+**   Throughout a write-transaction, dbFileSize contains the size of
+**   the file on disk in pages. It is set to a copy of dbSize when the
+**   write-transaction is first opened, and updated when VFS calls are made
+**   to write or truncate the database file on disk.
+**
+**   The only reason the dbFileSize variable is required is to suppress
+**   unnecessary calls to xTruncate() after committing a transaction. If,
+**   when a transaction is committed, the dbFileSize variable indicates
+**   that the database file is larger than the database image (Pager.dbSize),
+**   pager_truncate() is called. The pager_truncate() call uses xFilesize()
+**   to measure the database file on disk, and then truncates it if required.
+**   dbFileSize is not used when rolling back a transaction. In this case
+**   pager_truncate() is called unconditionally (which means there may be
+**   a call to xFilesize() that is not strictly required). In either case,
+**   pager_truncate() may cause the file to become smaller or larger.
+**
+** dbHintSize
+**
+**   The dbHintSize variable is used to limit the number of calls made to
+**   the VFS xFileControl(FCNTL_SIZE_HINT) method.
+**
+**   dbHintSize is set to a copy of the dbSize variable when a
+**   write-transaction is opened (at the same time as dbFileSize and
+**   dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called,
+**   dbHintSize is increased to the number of pages that correspond to the
+**   size-hint passed to the method call. See pager_write_pagelist() for
+**   details.
+**
+** errCode
+**
+**   The Pager.errCode variable is only ever used in PAGER_ERROR state. It
+**   is set to zero in all other states. In PAGER_ERROR state, Pager.errCode
+**   is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX
+**   sub-codes.
+**
+** syncFlags, walSyncFlags
+**
+**   syncFlags is either SQLITE_SYNC_NORMAL (0x02) or SQLITE_SYNC_FULL (0x03).
+**   syncFlags is used for rollback mode.  walSyncFlags is used for WAL mode
+**   and contains the flags used to sync the checkpoint operations in the
+**   lower two bits, and sync flags used for transaction commits in the WAL
+**   file in bits 0x04 and 0x08.  In other words, to get the correct sync flags
+**   for checkpoint operations, use (walSyncFlags&0x03) and to get the correct
+**   sync flags for transaction commit, use ((walSyncFlags>>2)&0x03).  Note
+**   that with synchronous=NORMAL in WAL mode, transaction commit is not synced
+**   meaning that the 0x04 and 0x08 bits are both zero.
+*/
+struct Pager {
+  sqlite3_vfs *pVfs;          /* OS functions to use for IO */
+  u8 exclusiveMode;           /* Boolean. True if locking_mode==EXCLUSIVE */
+  u8 journalMode;             /* One of the PAGER_JOURNALMODE_* values */
+  u8 useJournal;              /* Use a rollback journal on this file */
+  u8 noSync;                  /* Do not sync the journal if true */
+  u8 fullSync;                /* Do extra syncs of the journal for robustness */
+  u8 extraSync;               /* sync directory after journal delete */
+  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
+  u8 walSyncFlags;            /* See description above */
+  u8 tempFile;                /* zFilename is a temporary or immutable file */
+  u8 noLock;                  /* Do not lock (except in WAL mode) */
+  u8 readOnly;                /* True for a read-only database */
+  u8 memDb;                   /* True to inhibit all file I/O */
+  u8 memVfs;                  /* VFS-implemented memory database */
+
+  /**************************************************************************
+  ** The following block contains those class members that change during
+  ** routine operation.  Class members not in this block are either fixed
+  ** when the pager is first created or else only change when there is a
+  ** significant mode change (such as changing the page_size, locking_mode,
+  ** or the journal_mode).  From another view, these class members describe
+  ** the "state" of the pager, while other class members describe the
+  ** "configuration" of the pager.
+  */
+  u8 eState;                  /* Pager state (OPEN, READER, WRITER_LOCKED..) */
+  u8 eLock;                   /* Current lock held on database file */
+  u8 changeCountDone;         /* Set after incrementing the change-counter */
+  u8 setSuper;                /* Super-jrnl name is written into jrnl */
+  u8 doNotSpill;              /* Do not spill the cache when non-zero */
+  u8 subjInMemory;            /* True to use in-memory sub-journals */
+  u8 bUseFetch;               /* True to use xFetch() */
+  u8 hasHeldSharedLock;       /* True if a shared lock has ever been held */
+  Pgno dbSize;                /* Number of pages in the database */
+  Pgno dbOrigSize;            /* dbSize before the current transaction */
+  Pgno dbFileSize;            /* Number of pages in the database file */
+  Pgno dbHintSize;            /* Value passed to FCNTL_SIZE_HINT call */
+  int errCode;                /* One of several kinds of errors */
+  int nRec;                   /* Pages journalled since last j-header written */
+  u32 cksumInit;              /* Quasi-random value added to every checksum */
+  u32 nSubRec;                /* Number of records written to sub-journal */
+  Bitvec *pInJournal;         /* One bit for each page in the database file */
+  sqlite3_file *fd;           /* File descriptor for database */
+  sqlite3_file *jfd;          /* File descriptor for main journal */
+  sqlite3_file *sjfd;         /* File descriptor for sub-journal */
+  i64 journalOff;             /* Current write offset in the journal file */
+  i64 journalHdr;             /* Byte offset to previous journal header */
+  sqlite3_backup *pBackup;    /* Pointer to list of ongoing backup processes */
+  PagerSavepoint *aSavepoint; /* Array of active savepoints */
+  int nSavepoint;             /* Number of elements in aSavepoint[] */
+  u32 iDataVersion;           /* Changes whenever database content changes */
+  char dbFileVers[16];        /* Changes whenever database file changes */
+
+  int nMmapOut;               /* Number of mmap pages currently outstanding */
+  sqlite3_int64 szMmap;       /* Desired maximum mmap size */
+  PgHdr *pMmapFreelist;       /* List of free mmap page headers (pDirty) */
+  /*
+  ** End of the routinely-changing class members
+  ***************************************************************************/
+
+  u16 nExtra;                 /* Add this many bytes to each in-memory page */
+  i16 nReserve;               /* Number of unused bytes at end of each page */
+  u32 vfsFlags;               /* Flags for sqlite3_vfs.xOpen() */
+  u32 sectorSize;             /* Assumed sector size during rollback */
+  Pgno mxPgno;                /* Maximum allowed size of the database */
+  Pgno lckPgno;               /* Page number for the locking page */
+  i64 pageSize;               /* Number of bytes in a page */
+  i64 journalSizeLimit;       /* Size limit for persistent journal files */
+  char *zFilename;            /* Name of the database file */
+  char *zJournal;             /* Name of the journal file */
+  int (*xBusyHandler)(void*); /* Function to call when busy */
+  void *pBusyHandlerArg;      /* Context argument for xBusyHandler */
+  u32 aStat[4];               /* Total cache hits, misses, writes, spills */
+#ifdef SQLITE_TEST
+  int nRead;                  /* Database pages read */
+#endif
+  void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
+  int (*xGet)(Pager*,Pgno,DbPage**,int); /* Routine to fetch a patch */
+  char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
+  PCache *pPCache;            /* Pointer to page cache object */
+#ifndef SQLITE_OMIT_WAL
+  Wal *pWal;                  /* Write-ahead log used by "journal_mode=wal" */
+  char *zWal;                 /* File name for write-ahead log */
+#endif
+};
+
+/*
+** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains
+** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS
+** or CACHE_WRITE to sqlite3_db_status().
+*/
+#define PAGER_STAT_HIT   0
+#define PAGER_STAT_MISS  1
+#define PAGER_STAT_WRITE 2
+#define PAGER_STAT_SPILL 3
+
+/*
+** The following global variables hold counters used for
+** testing purposes only.  These variables do not exist in
+** a non-testing build.  These variables are not thread-safe.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_pager_readdb_count = 0;    /* Number of full pages read from DB */
+int sqlite3_pager_writedb_count = 0;   /* Number of full pages written to DB */
+int sqlite3_pager_writej_count = 0;    /* Number of pages written to journal */
+# define PAGER_INCR(v)  v++
+#else
+# define PAGER_INCR(v)
+#endif
+
+
+
+/*
+** Journal files begin with the following magic string.  The data
+** was obtained from /dev/random.  It is used only as a sanity check.
+**
+** Since version 2.8.0, the journal format contains additional sanity
+** checking information.  If the power fails while the journal is being
+** written, semi-random garbage data might appear in the journal
+** file after power is restored.  If an attempt is then made
+** to roll the journal back, the database could be corrupted.  The additional
+** sanity checking data is an attempt to discover the garbage in the
+** journal and ignore it.
+**
+** The sanity checking information for the new journal format consists
+** of a 32-bit checksum on each page of data.  The checksum covers both
+** the page number and the pPager->pageSize bytes of data for the page.
+** This cksum is initialized to a 32-bit random value that appears in the
+** journal file right after the header.  The random initializer is important,
+** because garbage data that appears at the end of a journal is likely
+** data that was once in other files that have now been deleted.  If the
+** garbage data came from an obsolete journal file, the checksums might
+** be correct.  But by initializing the checksum to random value which
+** is different for every journal, we minimize that risk.
+*/
+static const unsigned char aJournalMagic[] = {
+  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
+};
+
+/*
+** The size of the of each page record in the journal is given by
+** the following macro.
+*/
+#define JOURNAL_PG_SZ(pPager)  ((pPager->pageSize) + 8)
+
+/*
+** The journal header size for this pager. This is usually the same
+** size as a single disk sector. See also setSectorSize().
+*/
+#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
+
+/*
+** The macro MEMDB is true if we are dealing with an in-memory database.
+** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
+** the value of MEMDB will be a constant and the compiler will optimize
+** out code that would never execute.
+*/
+#ifdef SQLITE_OMIT_MEMORYDB
+# define MEMDB 0
+#else
+# define MEMDB pPager->memDb
+#endif
+
+/*
+** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch
+** interfaces to access the database using memory-mapped I/O.
+*/
+#if SQLITE_MAX_MMAP_SIZE>0
+# define USEFETCH(x) ((x)->bUseFetch)
+#else
+# define USEFETCH(x) 0
+#endif
+
+/*
+** The argument to this macro is a file descriptor (type sqlite3_file*).
+** Return 0 if it is not open, or non-zero (but not 1) if it is.
+**
+** This is so that expressions can be written as:
+**
+**   if( isOpen(pPager->jfd) ){ ...
+**
+** instead of
+**
+**   if( pPager->jfd->pMethods ){ ...
+*/
+#define isOpen(pFd) ((pFd)->pMethods!=0)
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+/*
+** Return true if page pgno can be read directly from the database file
+** by the b-tree layer. This is the case if:
+**
+**   * the database file is open,
+**   * there are no dirty pages in the cache, and
+**   * the desired page is not currently in the wal file.
+*/
+int sqlite3PagerDirectReadOk(Pager *pPager, Pgno pgno){
+  if( pPager->fd->pMethods==0 ) return 0;
+  if( sqlite3PCacheIsDirty(pPager->pPCache) ) return 0;
+#ifndef SQLITE_OMIT_WAL
+  if( pPager->pWal ){
+    u32 iRead = 0;
+    (void)sqlite3WalFindFrame(pPager->pWal, pgno, &iRead);
+    return iRead==0;
+  }
+#endif
+  return 1;
+}
+#endif
+
+#ifndef SQLITE_OMIT_WAL
+# define pagerUseWal(x) ((x)->pWal!=0)
+#else
+# define pagerUseWal(x) 0
+# define pagerRollbackWal(x) 0
+# define pagerWalFrames(v,w,x,y) 0
+# define pagerOpenWalIfPresent(z) SQLITE_OK
+# define pagerBeginReadTransaction(z) SQLITE_OK
+#endif
+
+#ifndef NDEBUG
+/*
+** Usage:
+**
+**   assert( assert_pager_state(pPager) );
+**
+** This function runs many asserts to try to find inconsistencies in
+** the internal state of the Pager object.
+*/
+static int assert_pager_state(Pager *p){
+  Pager *pPager = p;
+
+  /* State must be valid. */
+  assert( p->eState==PAGER_OPEN
+       || p->eState==PAGER_READER
+       || p->eState==PAGER_WRITER_LOCKED
+       || p->eState==PAGER_WRITER_CACHEMOD
+       || p->eState==PAGER_WRITER_DBMOD
+       || p->eState==PAGER_WRITER_FINISHED
+       || p->eState==PAGER_ERROR
+  );
+
+  /* Regardless of the current state, a temp-file connection always behaves
+  ** as if it has an exclusive lock on the database file. It never updates
+  ** the change-counter field, so the changeCountDone flag is always set.
+  */
+  assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK );
+  assert( p->tempFile==0 || pPager->changeCountDone );
+
+  /* If the useJournal flag is clear, the journal-mode must be "OFF".
+  ** And if the journal-mode is "OFF", the journal file must not be open.
+  */
+  assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal );
+  assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) );
+
+  /* Check that MEMDB implies noSync. And an in-memory journal. Since
+  ** this means an in-memory pager performs no IO at all, it cannot encounter
+  ** either SQLITE_IOERR or SQLITE_FULL during rollback or while finalizing
+  ** a journal file. (although the in-memory journal implementation may
+  ** return SQLITE_IOERR_NOMEM while the journal file is being written). It
+  ** is therefore not possible for an in-memory pager to enter the ERROR
+  ** state.
+  */
+  if( MEMDB ){
+    assert( !isOpen(p->fd) );
+    assert( p->noSync );
+    assert( p->journalMode==PAGER_JOURNALMODE_OFF
+         || p->journalMode==PAGER_JOURNALMODE_MEMORY
+    );
+    assert( p->eState!=PAGER_ERROR && p->eState!=PAGER_OPEN );
+    assert( pagerUseWal(p)==0 );
+  }
+
+  /* If changeCountDone is set, a RESERVED lock or greater must be held
+  ** on the file.
+  */
+  assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
+  assert( p->eLock!=PENDING_LOCK );
+
+  switch( p->eState ){
+    case PAGER_OPEN:
+      assert( !MEMDB );
+      assert( pPager->errCode==SQLITE_OK );
+      assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
+      break;
+
+    case PAGER_READER:
+      assert( pPager->errCode==SQLITE_OK );
+      assert( p->eLock!=UNKNOWN_LOCK );
+      assert( p->eLock>=SHARED_LOCK );
+      break;
+
+    case PAGER_WRITER_LOCKED:
+      assert( p->eLock!=UNKNOWN_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      if( !pagerUseWal(pPager) ){
+        assert( p->eLock>=RESERVED_LOCK );
+      }
+      assert( pPager->dbSize==pPager->dbOrigSize );
+      assert( pPager->dbOrigSize==pPager->dbFileSize );
+      assert( pPager->dbOrigSize==pPager->dbHintSize );
+      assert( pPager->setSuper==0 );
+      break;
+
+    case PAGER_WRITER_CACHEMOD:
+      assert( p->eLock!=UNKNOWN_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      if( !pagerUseWal(pPager) ){
+        /* It is possible that if journal_mode=wal here that neither the
+        ** journal file nor the WAL file are open. This happens during
+        ** a rollback transaction that switches from journal_mode=off
+        ** to journal_mode=wal.
+        */
+        assert( p->eLock>=RESERVED_LOCK );
+        assert( isOpen(p->jfd)
+             || p->journalMode==PAGER_JOURNALMODE_OFF
+             || p->journalMode==PAGER_JOURNALMODE_WAL
+        );
+      }
+      assert( pPager->dbOrigSize==pPager->dbFileSize );
+      assert( pPager->dbOrigSize==pPager->dbHintSize );
+      break;
+
+    case PAGER_WRITER_DBMOD:
+      assert( p->eLock==EXCLUSIVE_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      assert( !pagerUseWal(pPager) );
+      assert( p->eLock>=EXCLUSIVE_LOCK );
+      assert( isOpen(p->jfd)
+           || p->journalMode==PAGER_JOURNALMODE_OFF
+           || p->journalMode==PAGER_JOURNALMODE_WAL
+           || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
+      );
+      assert( pPager->dbOrigSize<=pPager->dbHintSize );
+      break;
+
+    case PAGER_WRITER_FINISHED:
+      assert( p->eLock==EXCLUSIVE_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      assert( !pagerUseWal(pPager) );
+      assert( isOpen(p->jfd)
+           || p->journalMode==PAGER_JOURNALMODE_OFF
+           || p->journalMode==PAGER_JOURNALMODE_WAL
+           || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
+      );
+      break;
+
+    case PAGER_ERROR:
+      /* There must be at least one outstanding reference to the pager if
+      ** in ERROR state. Otherwise the pager should have already dropped
+      ** back to OPEN state.
+      */
+      assert( pPager->errCode!=SQLITE_OK );
+      assert( sqlite3PcacheRefCount(pPager->pPCache)>0 || pPager->tempFile );
+      break;
+  }
+
+  return 1;
+}
+#endif /* ifndef NDEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+** Return a pointer to a human readable string in a static buffer
+** containing the state of the Pager object passed as an argument. This
+** is intended to be used within debuggers. For example, as an alternative
+** to "print *pPager" in gdb:
+**
+** (gdb) printf "%s", print_pager_state(pPager)
+**
+** This routine has external linkage in order to suppress compiler warnings
+** about an unused function.  It is enclosed within SQLITE_DEBUG and so does
+** not appear in normal builds.
+*/
+char *print_pager_state(Pager *p){
+  static char zRet[1024];
+
+  sqlite3_snprintf(1024, zRet,
+      "Filename:      %s\n"
+      "State:         %s errCode=%d\n"
+      "Lock:          %s\n"
+      "Locking mode:  locking_mode=%s\n"
+      "Journal mode:  journal_mode=%s\n"
+      "Backing store: tempFile=%d memDb=%d useJournal=%d\n"
+      "Journal:       journalOff=%lld journalHdr=%lld\n"
+      "Size:          dbsize=%d dbOrigSize=%d dbFileSize=%d\n"
+      , p->zFilename
+      , p->eState==PAGER_OPEN            ? "OPEN" :
+        p->eState==PAGER_READER          ? "READER" :
+        p->eState==PAGER_WRITER_LOCKED   ? "WRITER_LOCKED" :
+        p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
+        p->eState==PAGER_WRITER_DBMOD    ? "WRITER_DBMOD" :
+        p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
+        p->eState==PAGER_ERROR           ? "ERROR" : "?error?"
+      , (int)p->errCode
+      , p->eLock==NO_LOCK         ? "NO_LOCK" :
+        p->eLock==RESERVED_LOCK   ? "RESERVED" :
+        p->eLock==EXCLUSIVE_LOCK  ? "EXCLUSIVE" :
+        p->eLock==SHARED_LOCK     ? "SHARED" :
+        p->eLock==UNKNOWN_LOCK    ? "UNKNOWN" : "?error?"
+      , p->exclusiveMode ? "exclusive" : "normal"
+      , p->journalMode==PAGER_JOURNALMODE_MEMORY   ? "memory" :
+        p->journalMode==PAGER_JOURNALMODE_OFF      ? "off" :
+        p->journalMode==PAGER_JOURNALMODE_DELETE   ? "delete" :
+        p->journalMode==PAGER_JOURNALMODE_PERSIST  ? "persist" :
+        p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" :
+        p->journalMode==PAGER_JOURNALMODE_WAL      ? "wal" : "?error?"
+      , (int)p->tempFile, (int)p->memDb, (int)p->useJournal
+      , p->journalOff, p->journalHdr
+      , (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize
+  );
+
+  return zRet;
+}
+#endif
+
+/* Forward references to the various page getters */
+static int getPageNormal(Pager*,Pgno,DbPage**,int);
+static int getPageError(Pager*,Pgno,DbPage**,int);
+#if SQLITE_MAX_MMAP_SIZE>0
+static int getPageMMap(Pager*,Pgno,DbPage**,int);
+#endif
+
+/*
+** Set the Pager.xGet method for the appropriate routine used to fetch
+** content from the pager.
+*/
+static void setGetterMethod(Pager *pPager){
+  if( pPager->errCode ){
+    pPager->xGet = getPageError;
+#if SQLITE_MAX_MMAP_SIZE>0
+  }else if( USEFETCH(pPager) ){
+    pPager->xGet = getPageMMap;
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
+  }else{
+    pPager->xGet = getPageNormal;
+  }
+}
+
+/*
+** Return true if it is necessary to write page *pPg into the sub-journal.
+** A page needs to be written into the sub-journal if there exists one
+** or more open savepoints for which:
+**
+**   * The page-number is less than or equal to PagerSavepoint.nOrig, and
+**   * The bit corresponding to the page-number is not set in
+**     PagerSavepoint.pInSavepoint.
+*/
+static int subjRequiresPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  PagerSavepoint *p;
+  Pgno pgno = pPg->pgno;
+  int i;
+  for(i=0; i<pPager->nSavepoint; i++){
+    p = &pPager->aSavepoint[i];
+    if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){
+      for(i=i+1; i<pPager->nSavepoint; i++){
+        pPager->aSavepoint[i].bTruncateOnRelease = 0;
+      }
+      return 1;
+    }
+  }
+  return 0;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Return true if the page is already in the journal file.
+*/
+static int pageInJournal(Pager *pPager, PgHdr *pPg){
+  return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
+}
+#endif
+
+/*
+** Read a 32-bit integer from the given file descriptor.  Store the integer
+** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
+** error code is something goes wrong.
+**
+** All values are stored on disk as big-endian.
+*/
+static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
+  unsigned char ac[4];
+  int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
+  if( rc==SQLITE_OK ){
+    *pRes = sqlite3Get4byte(ac);
+  }
+  return rc;
+}
+
+/*
+** Write a 32-bit integer into a string buffer in big-endian byte order.
+*/
+#define put32bits(A,B)  sqlite3Put4byte((u8*)A,B)
+
+
+/*
+** Write a 32-bit integer into the given file descriptor.  Return SQLITE_OK
+** on success or an error code is something goes wrong.
+*/
+static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
+  char ac[4];
+  put32bits(ac, val);
+  return sqlite3OsWrite(fd, ac, 4, offset);
+}
+
+/*
+** Unlock the database file to level eLock, which must be either NO_LOCK
+** or SHARED_LOCK. Regardless of whether or not the call to xUnlock()
+** succeeds, set the Pager.eLock variable to match the (attempted) new lock.
+**
+** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
+** called, do not modify it. See the comment above the #define of
+** UNKNOWN_LOCK for an explanation of this.
+*/
+static int pagerUnlockDb(Pager *pPager, int eLock){
+  int rc = SQLITE_OK;
+
+  assert( !pPager->exclusiveMode || pPager->eLock==eLock );
+  assert( eLock==NO_LOCK || eLock==SHARED_LOCK );
+  assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 );
+  if( isOpen(pPager->fd) ){
+    assert( pPager->eLock>=eLock );
+    rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock);
+    if( pPager->eLock!=UNKNOWN_LOCK ){
+      pPager->eLock = (u8)eLock;
+    }
+    IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
+  }
+  pPager->changeCountDone = pPager->tempFile; /* ticket fb3b3024ea238d5c */
+  return rc;
+}
+
+/*
+** Lock the database file to level eLock, which must be either SHARED_LOCK,
+** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
+** Pager.eLock variable to the new locking state.
+**
+** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
+** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK.
+** See the comment above the #define of UNKNOWN_LOCK for an explanation
+** of this.
+*/
+static int pagerLockDb(Pager *pPager, int eLock){
+  int rc = SQLITE_OK;
+
+  assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK );
+  if( pPager->eLock<eLock || pPager->eLock==UNKNOWN_LOCK ){
+    rc = pPager->noLock ? SQLITE_OK : sqlite3OsLock(pPager->fd, eLock);
+    if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){
+      pPager->eLock = (u8)eLock;
+      IOTRACE(("LOCK %p %d\n", pPager, eLock))
+    }
+  }
+  return rc;
+}
+
+/*
+** This function determines whether or not the atomic-write or
+** atomic-batch-write optimizations can be used with this pager. The
+** atomic-write optimization can be used if:
+**
+**  (a) the value returned by OsDeviceCharacteristics() indicates that
+**      a database page may be written atomically, and
+**  (b) the value returned by OsSectorSize() is less than or equal
+**      to the page size.
+**
+** If it can be used, then the value returned is the size of the journal
+** file when it contains rollback data for exactly one page.
+**
+** The atomic-batch-write optimization can be used if OsDeviceCharacteristics()
+** returns a value with the SQLITE_IOCAP_BATCH_ATOMIC bit set. -1 is
+** returned in this case.
+**
+** If neither optimization can be used, 0 is returned.
+*/
+static int jrnlBufferSize(Pager *pPager){
+  assert( !MEMDB );
+
+#if defined(SQLITE_ENABLE_ATOMIC_WRITE) \
+ || defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+  int dc;                           /* Device characteristics */
+
+  assert( isOpen(pPager->fd) );
+  dc = sqlite3OsDeviceCharacteristics(pPager->fd);
+#else
+  UNUSED_PARAMETER(pPager);
+#endif
+
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+  if( pPager->dbSize>0 && (dc&SQLITE_IOCAP_BATCH_ATOMIC) ){
+    return -1;
+  }
+#endif
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  {
+    int nSector = pPager->sectorSize;
+    int szPage = pPager->pageSize;
+
+    assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+    assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+    if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
+      return 0;
+    }
+  }
+
+  return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
+#endif
+
+  return 0;
+}
+
+/*
+** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
+** on the cache using a hash function.  This is used for testing
+** and debugging only.
+*/
+#ifdef SQLITE_CHECK_PAGES
+/*
+** Return a 32-bit hash of the page data for pPage.
+*/
+static u32 pager_datahash(int nByte, unsigned char *pData){
+  u32 hash = 0;
+  int i;
+  for(i=0; i<nByte; i++){
+    hash = (hash*1039) + pData[i];
+  }
+  return hash;
+}
+static u32 pager_pagehash(PgHdr *pPage){
+  return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
+}
+static void pager_set_pagehash(PgHdr *pPage){
+  pPage->pageHash = pager_pagehash(pPage);
+}
+
+/*
+** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
+** is defined, and NDEBUG is not defined, an assert() statement checks
+** that the page is either dirty or still matches the calculated page-hash.
+*/
+#define CHECK_PAGE(x) checkPage(x)
+static void checkPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
+}
+
+#else
+#define pager_datahash(X,Y)  0
+#define pager_pagehash(X)  0
+#define pager_set_pagehash(X)
+#define CHECK_PAGE(x)
+#endif  /* SQLITE_CHECK_PAGES */
+
+/*
+** When this is called the journal file for pager pPager must be open.
+** This function attempts to read a super-journal file name from the
+** end of the file and, if successful, copies it into memory supplied
+** by the caller. See comments above writeSuperJournal() for the format
+** used to store a super-journal file name at the end of a journal file.
+**
+** zSuper must point to a buffer of at least nSuper bytes allocated by
+** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
+** enough space to write the super-journal name). If the super-journal
+** name in the journal is longer than nSuper bytes (including a
+** nul-terminator), then this is handled as if no super-journal name
+** were present in the journal.
+**
+** If a super-journal file name is present at the end of the journal
+** file, then it is copied into the buffer pointed to by zSuper. A
+** nul-terminator byte is appended to the buffer following the
+** super-journal file name.
+**
+** If it is determined that no super-journal file name is present
+** zSuper[0] is set to 0 and SQLITE_OK returned.
+**
+** If an error occurs while reading from the journal file, an SQLite
+** error code is returned.
+*/
+static int readSuperJournal(sqlite3_file *pJrnl, char *zSuper, u32 nSuper){
+  int rc;                    /* Return code */
+  u32 len;                   /* Length in bytes of super-journal name */
+  i64 szJ;                   /* Total size in bytes of journal file pJrnl */
+  u32 cksum;                 /* MJ checksum value read from journal */
+  u32 u;                     /* Unsigned loop counter */
+  unsigned char aMagic[8];   /* A buffer to hold the magic header */
+  zSuper[0] = '\0';
+
+  if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
+   || szJ<16
+   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
+   || len>=nSuper
+   || len>szJ-16
+   || len==0
+   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
+   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
+   || memcmp(aMagic, aJournalMagic, 8)
+   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zSuper, len, szJ-16-len))
+  ){
+    return rc;
+  }
+
+  /* See if the checksum matches the super-journal name */
+  for(u=0; u<len; u++){
+    cksum -= zSuper[u];
+  }
+  if( cksum ){
+    /* If the checksum doesn't add up, then one or more of the disk sectors
+    ** containing the super-journal filename is corrupted. This means
+    ** definitely roll back, so just return SQLITE_OK and report a (nul)
+    ** super-journal filename.
+    */
+    len = 0;
+  }
+  zSuper[len] = '\0';
+  zSuper[len+1] = '\0';
+  
+  return SQLITE_OK;
+}
+
+/*
+** Return the offset of the sector boundary at or immediately
+** following the value in pPager->journalOff, assuming a sector
+** size of pPager->sectorSize bytes.
+**
+** i.e for a sector size of 512:
+**
+**   Pager.journalOff          Return value
+**   ---------------------------------------
+**   0                         0
+**   512                       512
+**   100                       512
+**   2000                      2048
+**
+*/
+static i64 journalHdrOffset(Pager *pPager){
+  i64 offset = 0;
+  i64 c = pPager->journalOff;
+  if( c ){
+    offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
+  }
+  assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
+  assert( offset>=c );
+  assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
+  return offset;
+}
+
+/*
+** The journal file must be open when this function is called.
+**
+** This function is a no-op if the journal file has not been written to
+** within the current transaction (i.e. if Pager.journalOff==0).
+**
+** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
+** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
+** zero the 28-byte header at the start of the journal file. In either case,
+** if the pager is not in no-sync mode, sync the journal file immediately
+** after writing or truncating it.
+**
+** If Pager.journalSizeLimit is set to a positive, non-zero value, and
+** following the truncation or zeroing described above the size of the
+** journal file in bytes is larger than this value, then truncate the
+** journal file to Pager.journalSizeLimit bytes. The journal file does
+** not need to be synced following this operation.
+**
+** If an IO error occurs, abandon processing and return the IO error code.
+** Otherwise, return SQLITE_OK.
+*/
+static int zeroJournalHdr(Pager *pPager, int doTruncate){
+  int rc = SQLITE_OK;                               /* Return code */
+  assert( isOpen(pPager->jfd) );
+  assert( !sqlite3JournalIsInMemory(pPager->jfd) );
+  if( pPager->journalOff ){
+    const i64 iLimit = pPager->journalSizeLimit;    /* Local cache of jsl */
+
+    IOTRACE(("JZEROHDR %p\n", pPager))
+    if( doTruncate || iLimit==0 ){
+      rc = sqlite3OsTruncate(pPager->jfd, 0);
+    }else{
+      static const char zeroHdr[28] = {0};
+      rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
+    }
+    if( rc==SQLITE_OK && !pPager->noSync ){
+      rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags);
+    }
+
+    /* At this point the transaction is committed but the write lock
+    ** is still held on the file. If there is a size limit configured for
+    ** the persistent journal and the journal file currently consumes more
+    ** space than that limit allows for, truncate it now. There is no need
+    ** to sync the file following this operation.
+    */
+    if( rc==SQLITE_OK && iLimit>0 ){
+      i64 sz;
+      rc = sqlite3OsFileSize(pPager->jfd, &sz);
+      if( rc==SQLITE_OK && sz>iLimit ){
+        rc = sqlite3OsTruncate(pPager->jfd, iLimit);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** The journal file must be open when this routine is called. A journal
+** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
+** current location.
+**
+** The format for the journal header is as follows:
+** - 8 bytes: Magic identifying journal format.
+** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
+** - 4 bytes: Random number used for page hash.
+** - 4 bytes: Initial database page count.
+** - 4 bytes: Sector size used by the process that wrote this journal.
+** - 4 bytes: Database page size.
+**
+** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
+*/
+static int writeJournalHdr(Pager *pPager){
+  int rc = SQLITE_OK;                 /* Return code */
+  char *zHeader = pPager->pTmpSpace;  /* Temporary space used to build header */
+  u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */
+  u32 nWrite;                         /* Bytes of header sector written */
+  int ii;                             /* Loop counter */
+
+  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
+
+  if( nHeader>JOURNAL_HDR_SZ(pPager) ){
+    nHeader = JOURNAL_HDR_SZ(pPager);
+  }
+
+  /* If there are active savepoints and any of them were created
+  ** since the most recent journal header was written, update the
+  ** PagerSavepoint.iHdrOffset fields now.
+  */
+  for(ii=0; ii<pPager->nSavepoint; ii++){
+    if( pPager->aSavepoint[ii].iHdrOffset==0 ){
+      pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff;
+    }
+  }
+
+  pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
+
+  /*
+  ** Write the nRec Field - the number of page records that follow this
+  ** journal header. Normally, zero is written to this value at this time.
+  ** After the records are added to the journal (and the journal synced,
+  ** if in full-sync mode), the zero is overwritten with the true number
+  ** of records (see syncJournal()).
+  **
+  ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
+  ** reading the journal this value tells SQLite to assume that the
+  ** rest of the journal file contains valid page records. This assumption
+  ** is dangerous, as if a failure occurred whilst writing to the journal
+  ** file it may contain some garbage data. There are two scenarios
+  ** where this risk can be ignored:
+  **
+  **   * When the pager is in no-sync mode. Corruption can follow a
+  **     power failure in this case anyway.
+  **
+  **   * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
+  **     that garbage data is never appended to the journal file.
+  */
+  assert( isOpen(pPager->fd) || pPager->noSync );
+  if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
+   || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
+  ){
+    memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+    put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
+  }else{
+    memset(zHeader, 0, sizeof(aJournalMagic)+4);
+  }
+
+
+
+  /* The random check-hash initializer */
+  if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
+    sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
+  }
+#ifdef SQLITE_DEBUG
+  else{
+    /* The Pager.cksumInit variable is usually randomized above to protect
+    ** against there being existing records in the journal file. This is
+    ** dangerous, as following a crash they may be mistaken for records
+    ** written by the current transaction and rolled back into the database
+    ** file, causing corruption. The following assert statements verify
+    ** that this is not required in "journal_mode=memory" mode, as in that
+    ** case the journal file is always 0 bytes in size at this point. 
+    ** It is advantageous to avoid the sqlite3_randomness() call if possible 
+    ** as it takes the global PRNG mutex.  */
+    i64 sz = 0;
+    sqlite3OsFileSize(pPager->jfd, &sz);
+    assert( sz==0 );
+    assert( pPager->journalOff==journalHdrOffset(pPager) );
+    assert( sqlite3JournalIsInMemory(pPager->jfd) );
+  }
+#endif
+  put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
+
+  /* The initial database size */
+  put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize);
+  /* The assumed sector size for this process */
+  put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
+
+  /* The page size */
+  put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
+
+  /* Initializing the tail of the buffer is not necessary.  Everything
+  ** works find if the following memset() is omitted.  But initializing
+  ** the memory prevents valgrind from complaining, so we are willing to
+  ** take the performance hit.
+  */
+  memset(&zHeader[sizeof(aJournalMagic)+20], 0,
+         nHeader-(sizeof(aJournalMagic)+20));
+
+  /* In theory, it is only necessary to write the 28 bytes that the
+  ** journal header consumes to the journal file here. Then increment the
+  ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next
+  ** record is written to the following sector (leaving a gap in the file
+  ** that will be implicitly filled in by the OS).
+  **
+  ** However it has been discovered that on some systems this pattern can
+  ** be significantly slower than contiguously writing data to the file,
+  ** even if that means explicitly writing data to the block of
+  ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
+  ** is done.
+  **
+  ** The loop is required here in case the sector-size is larger than the
+  ** database page size. Since the zHeader buffer is only Pager.pageSize
+  ** bytes in size, more than one call to sqlite3OsWrite() may be required
+  ** to populate the entire journal header sector.
+  */
+  for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
+    IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
+    rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
+    assert( pPager->journalHdr <= pPager->journalOff );
+    pPager->journalOff += nHeader;
+  }
+
+  return rc;
+}
+
+/*
+** The journal file must be open when this is called. A journal header file
+** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
+** file. The current location in the journal file is given by
+** pPager->journalOff. See comments above function writeJournalHdr() for
+** a description of the journal header format.
+**
+** If the header is read successfully, *pNRec is set to the number of
+** page records following this header and *pDbSize is set to the size of the
+** database before the transaction began, in pages. Also, pPager->cksumInit
+** is set to the value read from the journal header. SQLITE_OK is returned
+** in this case.
+**
+** If the journal header file appears to be corrupted, SQLITE_DONE is
+** returned and *pNRec and *PDbSize are undefined.  If JOURNAL_HDR_SZ bytes
+** cannot be read from the journal file an error code is returned.
+*/
+static int readJournalHdr(
+  Pager *pPager,               /* Pager object */
+  int isHot,
+  i64 journalSize,             /* Size of the open journal file in bytes */
+  u32 *pNRec,                  /* OUT: Value read from the nRec field */
+  u32 *pDbSize                 /* OUT: Value of original database size field */
+){
+  int rc;                      /* Return code */
+  unsigned char aMagic[8];     /* A buffer to hold the magic header */
+  i64 iHdrOff;                 /* Offset of journal header being read */
+
+  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
+
+  /* Advance Pager.journalOff to the start of the next sector. If the
+  ** journal file is too small for there to be a header stored at this
+  ** point, return SQLITE_DONE.
+  */
+  pPager->journalOff = journalHdrOffset(pPager);
+  if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
+    return SQLITE_DONE;
+  }
+  iHdrOff = pPager->journalOff;
+
+  /* Read in the first 8 bytes of the journal header. If they do not match
+  ** the  magic string found at the start of each journal header, return
+  ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
+  ** proceed.
+  */
+  if( isHot || iHdrOff!=pPager->journalHdr ){
+    rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
+    if( rc ){
+      return rc;
+    }
+    if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
+      return SQLITE_DONE;
+    }
+  }
+
+  /* Read the first three 32-bit fields of the journal header: The nRec
+  ** field, the checksum-initializer and the database size at the start
+  ** of the transaction. Return an error code if anything goes wrong.
+  */
+  if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
+   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
+   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
+  ){
+    return rc;
+  }
+
+  if( pPager->journalOff==0 ){
+    u32 iPageSize;               /* Page-size field of journal header */
+    u32 iSectorSize;             /* Sector-size field of journal header */
+
+    /* Read the page-size and sector-size journal header fields. */
+    if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
+     || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
+    ){
+      return rc;
+    }
+
+    /* Versions of SQLite prior to 3.5.8 set the page-size field of the
+    ** journal header to zero. In this case, assume that the Pager.pageSize
+    ** variable is already set to the correct page size.
+    */
+    if( iPageSize==0 ){
+      iPageSize = pPager->pageSize;
+    }
+
+    /* Check that the values read from the page-size and sector-size fields
+    ** are within range. To be 'in range', both values need to be a power
+    ** of two greater than or equal to 512 or 32, and not greater than their
+    ** respective compile time maximum limits.
+    */
+    if( iPageSize<512                  || iSectorSize<32
+     || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
+     || ((iPageSize-1)&iPageSize)!=0   || ((iSectorSize-1)&iSectorSize)!=0
+    ){
+      /* If the either the page-size or sector-size in the journal-header is
+      ** invalid, then the process that wrote the journal-header must have
+      ** crashed before the header was synced. In this case stop reading
+      ** the journal file here.
+      */
+      return SQLITE_DONE;
+    }
+
+    /* Update the page-size to match the value read from the journal.
+    ** Use a testcase() macro to make sure that malloc failure within
+    ** PagerSetPagesize() is tested.
+    */
+    rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1);
+    testcase( rc!=SQLITE_OK );
+
+    /* Update the assumed sector-size to match the value used by
+    ** the process that created this journal. If this journal was
+    ** created by a process other than this one, then this routine
+    ** is being called from within pager_playback(). The local value
+    ** of Pager.sectorSize is restored at the end of that routine.
+    */
+    pPager->sectorSize = iSectorSize;
+  }
+
+  pPager->journalOff += JOURNAL_HDR_SZ(pPager);
+  return rc;
+}
+
+
+/*
+** Write the supplied super-journal name into the journal file for pager
+** pPager at the current location. The super-journal name must be the last
+** thing written to a journal file. If the pager is in full-sync mode, the
+** journal file descriptor is advanced to the next sector boundary before
+** anything is written. The format is:
+**
+**   + 4 bytes: PAGER_SJ_PGNO.
+**   + N bytes: super-journal filename in utf-8.
+**   + 4 bytes: N (length of super-journal name in bytes, no nul-terminator).
+**   + 4 bytes: super-journal name checksum.
+**   + 8 bytes: aJournalMagic[].
+**
+** The super-journal page checksum is the sum of the bytes in the super-journal
+** name, where each byte is interpreted as a signed 8-bit integer.
+**
+** If zSuper is a NULL pointer (occurs for a single database transaction),
+** this call is a no-op.
+*/
+static int writeSuperJournal(Pager *pPager, const char *zSuper){
+  int rc;                          /* Return code */
+  int nSuper;                      /* Length of string zSuper */
+  i64 iHdrOff;                     /* Offset of header in journal file */
+  i64 jrnlSize;                    /* Size of journal file on disk */
+  u32 cksum = 0;                   /* Checksum of string zSuper */
+
+  assert( pPager->setSuper==0 );
+  assert( !pagerUseWal(pPager) );
+
+  if( !zSuper
+   || pPager->journalMode==PAGER_JOURNALMODE_MEMORY
+   || !isOpen(pPager->jfd)
+  ){
+    return SQLITE_OK;
+  }
+  pPager->setSuper = 1;
+  assert( pPager->journalHdr <= pPager->journalOff );
+
+  /* Calculate the length in bytes and the checksum of zSuper */
+  for(nSuper=0; zSuper[nSuper]; nSuper++){
+    cksum += zSuper[nSuper];
+  }
+
+  /* If in full-sync mode, advance to the next disk sector before writing
+  ** the super-journal name. This is in case the previous page written to
+  ** the journal has already been synced.
+  */
+  if( pPager->fullSync ){
+    pPager->journalOff = journalHdrOffset(pPager);
+  }
+  iHdrOff = pPager->journalOff;
+
+  /* Write the super-journal data to the end of the journal file. If
+  ** an error occurs, return the error code to the caller.
+  */
+  if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_SJ_PGNO(pPager))))
+   || (0 != (rc = sqlite3OsWrite(pPager->jfd, zSuper, nSuper, iHdrOff+4)))
+   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper, nSuper)))
+   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper+4, cksum)))
+   || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8,
+                                 iHdrOff+4+nSuper+8)))
+  ){
+    return rc;
+  }
+  pPager->journalOff += (nSuper+20);
+
+  /* If the pager is in persistent-journal mode, then the physical
+  ** journal-file may extend past the end of the super-journal name
+  ** and 8 bytes of magic data just written to the file. This is
+  ** dangerous because the code to rollback a hot-journal file
+  ** will not be able to find the super-journal name to determine
+  ** whether or not the journal is hot.
+  **
+  ** Easiest thing to do in this scenario is to truncate the journal
+  ** file to the required size.
+  */
+  if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
+   && jrnlSize>pPager->journalOff
+  ){
+    rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
+  }
+  return rc;
+}
+
+/*
+** Discard the entire contents of the in-memory page-cache.
+*/
+static void pager_reset(Pager *pPager){
+  pPager->iDataVersion++;
+  sqlite3BackupRestart(pPager->pBackup);
+  sqlite3PcacheClear(pPager->pPCache);
+}
+
+/*
+** Return the pPager->iDataVersion value
+*/
+u32 sqlite3PagerDataVersion(Pager *pPager){
+  return pPager->iDataVersion;
+}
+
+/*
+** Free all structures in the Pager.aSavepoint[] array and set both
+** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
+** if it is open and the pager is not in exclusive mode.
+*/
+static void releaseAllSavepoints(Pager *pPager){
+  int ii;               /* Iterator for looping through Pager.aSavepoint */
+  for(ii=0; ii<pPager->nSavepoint; ii++){
+    sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
+  }
+  if( !pPager->exclusiveMode || sqlite3JournalIsInMemory(pPager->sjfd) ){
+    sqlite3OsClose(pPager->sjfd);
+  }
+  sqlite3_free(pPager->aSavepoint);
+  pPager->aSavepoint = 0;
+  pPager->nSavepoint = 0;
+  pPager->nSubRec = 0;
+}
+
+/*
+** Set the bit number pgno in the PagerSavepoint.pInSavepoint
+** bitvecs of all open savepoints. Return SQLITE_OK if successful
+** or SQLITE_NOMEM if a malloc failure occurs.
+*/
+static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
+  int ii;                   /* Loop counter */
+  int rc = SQLITE_OK;       /* Result code */
+
+  for(ii=0; ii<pPager->nSavepoint; ii++){
+    PagerSavepoint *p = &pPager->aSavepoint[ii];
+    if( pgno<=p->nOrig ){
+      rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
+      testcase( rc==SQLITE_NOMEM );
+      assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is a no-op if the pager is in exclusive mode and not
+** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN
+** state.
+**
+** If the pager is not in exclusive-access mode, the database file is
+** completely unlocked. If the file is unlocked and the file-system does
+** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is
+** closed (if it is open).
+**
+** If the pager is in ERROR state when this function is called, the
+** contents of the pager cache are discarded before switching back to
+** the OPEN state. Regardless of whether the pager is in exclusive-mode
+** or not, any journal file left in the file-system will be treated
+** as a hot-journal and rolled back the next time a read-transaction
+** is opened (by this or by any other connection).
+*/
+static void pager_unlock(Pager *pPager){
+
+  assert( pPager->eState==PAGER_READER
+       || pPager->eState==PAGER_OPEN
+       || pPager->eState==PAGER_ERROR
+  );
+
+  sqlite3BitvecDestroy(pPager->pInJournal);
+  pPager->pInJournal = 0;
+  releaseAllSavepoints(pPager);
+
+  if( pagerUseWal(pPager) ){
+    assert( !isOpen(pPager->jfd) );
+    sqlite3WalEndReadTransaction(pPager->pWal);
+    pPager->eState = PAGER_OPEN;
+  }else if( !pPager->exclusiveMode ){
+    int rc;                       /* Error code returned by pagerUnlockDb() */
+    int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;
+
+    /* If the operating system support deletion of open files, then
+    ** close the journal file when dropping the database lock.  Otherwise
+    ** another connection with journal_mode=delete might delete the file
+    ** out from under us.
+    */
+    assert( (PAGER_JOURNALMODE_MEMORY   & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_OFF      & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_WAL      & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_DELETE   & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+    assert( (PAGER_JOURNALMODE_PERSIST  & 5)==1 );
+    if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN)
+     || 1!=(pPager->journalMode & 5)
+    ){
+      sqlite3OsClose(pPager->jfd);
+    }
+
+    /* If the pager is in the ERROR state and the call to unlock the database
+    ** file fails, set the current lock to UNKNOWN_LOCK. See the comment
+    ** above the #define for UNKNOWN_LOCK for an explanation of why this
+    ** is necessary.
+    */
+    rc = pagerUnlockDb(pPager, NO_LOCK);
+    if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
+      pPager->eLock = UNKNOWN_LOCK;
+    }
+
+    /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
+    ** without clearing the error code. This is intentional - the error
+    ** code is cleared and the cache reset in the block below.
+    */
+    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
+    pPager->eState = PAGER_OPEN;
+  }
+
+  /* If Pager.errCode is set, the contents of the pager cache cannot be
+  ** trusted. Now that there are no outstanding references to the pager,
+  ** it can safely move back to PAGER_OPEN state. This happens in both
+  ** normal and exclusive-locking mode.
+  */
+  assert( pPager->errCode==SQLITE_OK || !MEMDB );
+  if( pPager->errCode ){
+    if( pPager->tempFile==0 ){
+      pager_reset(pPager);
+      pPager->changeCountDone = 0;
+      pPager->eState = PAGER_OPEN;
+    }else{
+      pPager->eState = (isOpen(pPager->jfd) ? PAGER_OPEN : PAGER_READER);
+    }
+    if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
+    pPager->errCode = SQLITE_OK;
+    setGetterMethod(pPager);
+  }
+
+  pPager->journalOff = 0;
+  pPager->journalHdr = 0;
+  pPager->setSuper = 0;
+}
+
+/*
+** This function is called whenever an IOERR or FULL error that requires
+** the pager to transition into the ERROR state may have occurred.
+** The first argument is a pointer to the pager structure, the second
+** the error-code about to be returned by a pager API function. The
+** value returned is a copy of the second argument to this function.
+**
+** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the
+** IOERR sub-codes, the pager enters the ERROR state and the error code
+** is stored in Pager.errCode. While the pager remains in the ERROR state,
+** all major API calls on the Pager will immediately return Pager.errCode.
+**
+** The ERROR state indicates that the contents of the pager-cache
+** cannot be trusted. This state can be cleared by completely discarding
+** the contents of the pager-cache. If a transaction was active when
+** the persistent error occurred, then the rollback journal may need
+** to be replayed to restore the contents of the database file (as if
+** it were a hot-journal).
+*/
+static int pager_error(Pager *pPager, int rc){
+  int rc2 = rc & 0xff;
+  assert( rc==SQLITE_OK || !MEMDB );
+  assert(
+       pPager->errCode==SQLITE_FULL ||
+       pPager->errCode==SQLITE_OK ||
+       (pPager->errCode & 0xff)==SQLITE_IOERR
+  );
+  if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){
+    pPager->errCode = rc;
+    pPager->eState = PAGER_ERROR;
+    setGetterMethod(pPager);
+  }
+  return rc;
+}
+
+static int pager_truncate(Pager *pPager, Pgno nPage);
+
+/*
+** The write transaction open on pPager is being committed (bCommit==1)
+** or rolled back (bCommit==0).
+**
+** Return TRUE if and only if all dirty pages should be flushed to disk.
+**
+** Rules:
+**
+**   *  For non-TEMP databases, always sync to disk.  This is necessary
+**      for transactions to be durable.
+**
+**   *  Sync TEMP database only on a COMMIT (not a ROLLBACK) when the backing
+**      file has been created already (via a spill on pagerStress()) and
+**      when the number of dirty pages in memory exceeds 25% of the total
+**      cache size.
+*/
+static int pagerFlushOnCommit(Pager *pPager, int bCommit){
+  if( pPager->tempFile==0 ) return 1;
+  if( !bCommit ) return 0;
+  if( !isOpen(pPager->fd) ) return 0;
+  return (sqlite3PCachePercentDirty(pPager->pPCache)>=25);
+}
+
+/*
+** This routine ends a transaction. A transaction is usually ended by
+** either a COMMIT or a ROLLBACK operation. This routine may be called
+** after rollback of a hot-journal, or if an error occurs while opening
+** the journal file or writing the very first journal-header of a
+** database transaction.
+**
+** This routine is never called in PAGER_ERROR state. If it is called
+** in PAGER_NONE or PAGER_SHARED state and the lock held is less
+** exclusive than a RESERVED lock, it is a no-op.
+**
+** Otherwise, any active savepoints are released.
+**
+** If the journal file is open, then it is "finalized". Once a journal
+** file has been finalized it is not possible to use it to roll back a
+** transaction. Nor will it be considered to be a hot-journal by this
+** or any other database connection. Exactly how a journal is finalized
+** depends on whether or not the pager is running in exclusive mode and
+** the current journal-mode (Pager.journalMode value), as follows:
+**
+**   journalMode==MEMORY
+**     Journal file descriptor is simply closed. This destroys an
+**     in-memory journal.
+**
+**   journalMode==TRUNCATE
+**     Journal file is truncated to zero bytes in size.
+**
+**   journalMode==PERSIST
+**     The first 28 bytes of the journal file are zeroed. This invalidates
+**     the first journal header in the file, and hence the entire journal
+**     file. An invalid journal file cannot be rolled back.
+**
+**   journalMode==DELETE
+**     The journal file is closed and deleted using sqlite3OsDelete().
+**
+**     If the pager is running in exclusive mode, this method of finalizing
+**     the journal file is never used. Instead, if the journalMode is
+**     DELETE and the pager is in exclusive mode, the method described under
+**     journalMode==PERSIST is used instead.
+**
+** After the journal is finalized, the pager moves to PAGER_READER state.
+** If running in non-exclusive rollback mode, the lock on the file is
+** downgraded to a SHARED_LOCK.
+**
+** SQLITE_OK is returned if no error occurs. If an error occurs during
+** any of the IO operations to finalize the journal file or unlock the
+** database then the IO error code is returned to the user. If the
+** operation to finalize the journal file fails, then the code still
+** tries to unlock the database file if not in exclusive mode. If the
+** unlock operation fails as well, then the first error code related
+** to the first error encountered (the journal finalization one) is
+** returned.
+*/
+static int pager_end_transaction(Pager *pPager, int hasSuper, int bCommit){
+  int rc = SQLITE_OK;      /* Error code from journal finalization operation */
+  int rc2 = SQLITE_OK;     /* Error code from db file unlock operation */
+
+  /* Do nothing if the pager does not have an open write transaction
+  ** or at least a RESERVED lock. This function may be called when there
+  ** is no write-transaction active but a RESERVED or greater lock is
+  ** held under two circumstances:
+  **
+  **   1. After a successful hot-journal rollback, it is called with
+  **      eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK.
+  **
+  **   2. If a connection with locking_mode=exclusive holding an EXCLUSIVE
+  **      lock switches back to locking_mode=normal and then executes a
+  **      read-transaction, this function is called with eState==PAGER_READER
+  **      and eLock==EXCLUSIVE_LOCK when the read-transaction is closed.
+  */
+  assert( assert_pager_state(pPager) );
+  assert( pPager->eState!=PAGER_ERROR );
+  if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){
+    return SQLITE_OK;
+  }
+
+  releaseAllSavepoints(pPager);
+  assert( isOpen(pPager->jfd) || pPager->pInJournal==0
+      || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
+  );
+  if( isOpen(pPager->jfd) ){
+    assert( !pagerUseWal(pPager) );
+
+    /* Finalize the journal file. */
+    if( sqlite3JournalIsInMemory(pPager->jfd) ){
+      /* assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ); */
+      sqlite3OsClose(pPager->jfd);
+    }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){
+      if( pPager->journalOff==0 ){
+        rc = SQLITE_OK;
+      }else{
+        rc = sqlite3OsTruncate(pPager->jfd, 0);
+        if( rc==SQLITE_OK && pPager->fullSync ){
+          /* Make sure the new file size is written into the inode right away.
+          ** Otherwise the journal might resurrect following a power loss and
+          ** cause the last transaction to roll back.  See
+          ** https://bugzilla.mozilla.org/show_bug.cgi?id=1072773
+          */
+          rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
+        }
+      }
+      pPager->journalOff = 0;
+    }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+      || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
+    ){
+      rc = zeroJournalHdr(pPager, hasSuper||pPager->tempFile);
+      pPager->journalOff = 0;
+    }else{
+      /* This branch may be executed with Pager.journalMode==MEMORY if
+      ** a hot-journal was just rolled back. In this case the journal
+      ** file should be closed and deleted. If this connection writes to
+      ** the database file, it will do so using an in-memory journal.
+      */
+      int bDelete = !pPager->tempFile;
+      assert( sqlite3JournalIsInMemory(pPager->jfd)==0 );
+      assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE
+           || pPager->journalMode==PAGER_JOURNALMODE_MEMORY
+           || pPager->journalMode==PAGER_JOURNALMODE_WAL
+      );
+      sqlite3OsClose(pPager->jfd);
+      if( bDelete ){
+        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, pPager->extraSync);
+      }
+    }
+  }
+
+#ifdef SQLITE_CHECK_PAGES
+  sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
+  if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){
+    PgHdr *p = sqlite3PagerLookup(pPager, 1);
+    if( p ){
+      p->pageHash = 0;
+      sqlite3PagerUnrefNotNull(p);
+    }
+  }
+#endif
+
+  sqlite3BitvecDestroy(pPager->pInJournal);
+  pPager->pInJournal = 0;
+  pPager->nRec = 0;
+  if( rc==SQLITE_OK ){
+    if( MEMDB || pagerFlushOnCommit(pPager, bCommit) ){
+      sqlite3PcacheCleanAll(pPager->pPCache);
+    }else{
+      sqlite3PcacheClearWritable(pPager->pPCache);
+    }
+    sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
+  }
+
+  if( pagerUseWal(pPager) ){
+    /* Drop the WAL write-lock, if any. Also, if the connection was in
+    ** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE
+    ** lock held on the database file.
+    */
+    rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
+    assert( rc2==SQLITE_OK );
+  }else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){
+    /* This branch is taken when committing a transaction in rollback-journal
+    ** mode if the database file on disk is larger than the database image.
+    ** At this point the journal has been finalized and the transaction
+    ** successfully committed, but the EXCLUSIVE lock is still held on the
+    ** file. So it is safe to truncate the database file to its minimum
+    ** required size.  */
+    assert( pPager->eLock==EXCLUSIVE_LOCK );
+    rc = pager_truncate(pPager, pPager->dbSize);
+  }
+
+  if( rc==SQLITE_OK && bCommit ){
+    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
+    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+  }
+
+  if( !pPager->exclusiveMode
+   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
+  ){
+    rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
+  }
+  pPager->eState = PAGER_READER;
+  pPager->setSuper = 0;
+
+  return (rc==SQLITE_OK?rc2:rc);
+}
+
+/* Forward reference */
+static int pager_playback(Pager *pPager, int isHot);
+
+/*
+** Execute a rollback if a transaction is active and unlock the
+** database file.
+**
+** If the pager has already entered the ERROR state, do not attempt
+** the rollback at this time. Instead, pager_unlock() is called. The
+** call to pager_unlock() will discard all in-memory pages, unlock
+** the database file and move the pager back to OPEN state. If this
+** means that there is a hot-journal left in the file-system, the next
+** connection to obtain a shared lock on the pager (which may be this one)
+** will roll it back.
+**
+** If the pager has not already entered the ERROR state, but an IO or
+** malloc error occurs during a rollback, then this will itself cause
+** the pager to enter the ERROR state. Which will be cleared by the
+** call to pager_unlock(), as described above.
+*/
+static void pagerUnlockAndRollback(Pager *pPager){
+  if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){
+    assert( assert_pager_state(pPager) );
+    if( pPager->eState>=PAGER_WRITER_LOCKED ){
+      sqlite3BeginBenignMalloc();
+      sqlite3PagerRollback(pPager);
+      sqlite3EndBenignMalloc();
+    }else if( !pPager->exclusiveMode ){
+      assert( pPager->eState==PAGER_READER );
+      pager_end_transaction(pPager, 0, 0);
+    }
+  }else if( pPager->eState==PAGER_ERROR
+         && pPager->journalMode==PAGER_JOURNALMODE_MEMORY
+         && isOpen(pPager->jfd)
+  ){
+    /* Special case for a ROLLBACK due to I/O error with an in-memory
+    ** journal:  We have to rollback immediately, before the journal is
+    ** closed, because once it is closed, all content is forgotten. */
+    int errCode = pPager->errCode;
+    u8 eLock = pPager->eLock;
+    pPager->eState = PAGER_OPEN;
+    pPager->errCode = SQLITE_OK;
+    pPager->eLock = EXCLUSIVE_LOCK;
+    pager_playback(pPager, 1);
+    pPager->errCode = errCode;
+    pPager->eLock = eLock;
+  }
+  pager_unlock(pPager);
+}
+
+/*
+** Parameter aData must point to a buffer of pPager->pageSize bytes
+** of data. Compute and return a checksum based on the contents of the
+** page of data and the current value of pPager->cksumInit.
+**
+** This is not a real checksum. It is really just the sum of the
+** random initial value (pPager->cksumInit) and every 200th byte
+** of the page data, starting with byte offset (pPager->pageSize%200).
+** Each byte is interpreted as an 8-bit unsigned integer.
+**
+** Changing the formula used to compute this checksum results in an
+** incompatible journal file format.
+**
+** If journal corruption occurs due to a power failure, the most likely
+** scenario is that one end or the other of the record will be changed.
+** It is much less likely that the two ends of the journal record will be
+** correct and the middle be corrupt.  Thus, this "checksum" scheme,
+** though fast and simple, catches the mostly likely kind of corruption.
+*/
+static u32 pager_cksum(Pager *pPager, const u8 *aData){
+  u32 cksum = pPager->cksumInit;         /* Checksum value to return */
+  int i = pPager->pageSize-200;          /* Loop counter */
+  while( i>0 ){
+    cksum += aData[i];
+    i -= 200;
+  }
+  return cksum;
+}
+
+/*
+** Read a single page from either the journal file (if isMainJrnl==1) or
+** from the sub-journal (if isMainJrnl==0) and playback that page.
+** The page begins at offset *pOffset into the file. The *pOffset
+** value is increased to the start of the next page in the journal.
+**
+** The main rollback journal uses checksums - the statement journal does
+** not.
+**
+** If the page number of the page record read from the (sub-)journal file
+** is greater than the current value of Pager.dbSize, then playback is
+** skipped and SQLITE_OK is returned.
+**
+** If pDone is not NULL, then it is a record of pages that have already
+** been played back.  If the page at *pOffset has already been played back
+** (if the corresponding pDone bit is set) then skip the playback.
+** Make sure the pDone bit corresponding to the *pOffset page is set
+** prior to returning.
+**
+** If the page record is successfully read from the (sub-)journal file
+** and played back, then SQLITE_OK is returned. If an IO error occurs
+** while reading the record from the (sub-)journal file or while writing
+** to the database file, then the IO error code is returned. If data
+** is successfully read from the (sub-)journal file but appears to be
+** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
+** two circumstances:
+**
+**   * If the record page-number is illegal (0 or PAGER_SJ_PGNO), or
+**   * If the record is being rolled back from the main journal file
+**     and the checksum field does not match the record content.
+**
+** Neither of these two scenarios are possible during a savepoint rollback.
+**
+** If this is a savepoint rollback, then memory may have to be dynamically
+** allocated by this function. If this is the case and an allocation fails,
+** SQLITE_NOMEM is returned.
+*/
+static int pager_playback_one_page(
+  Pager *pPager,                /* The pager being played back */
+  i64 *pOffset,                 /* Offset of record to playback */
+  Bitvec *pDone,                /* Bitvec of pages already played back */
+  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
+  int isSavepnt                 /* True for a savepoint rollback */
+){
+  int rc;
+  PgHdr *pPg;                   /* An existing page in the cache */
+  Pgno pgno;                    /* The page number of a page in journal */
+  u32 cksum;                    /* Checksum used for sanity checking */
+  char *aData;                  /* Temporary storage for the page */
+  sqlite3_file *jfd;            /* The file descriptor for the journal file */
+  int isSynced;                 /* True if journal page is synced */
+
+  assert( (isMainJrnl&~1)==0 );      /* isMainJrnl is 0 or 1 */
+  assert( (isSavepnt&~1)==0 );       /* isSavepnt is 0 or 1 */
+  assert( isMainJrnl || pDone );     /* pDone always used on sub-journals */
+  assert( isSavepnt || pDone==0 );   /* pDone never used on non-savepoint */
+
+  aData = pPager->pTmpSpace;
+  assert( aData );         /* Temp storage must have already been allocated */
+  assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
+
+  /* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction
+  ** or savepoint rollback done at the request of the caller) or this is
+  ** a hot-journal rollback. If it is a hot-journal rollback, the pager
+  ** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback
+  ** only reads from the main journal, not the sub-journal.
+  */
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD
+       || (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK)
+  );
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl );
+
+  /* Read the page number and page data from the journal or sub-journal
+  ** file. Return an error code to the caller if an IO error occurs.
+  */
+  jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
+  rc = read32bits(jfd, *pOffset, &pgno);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4);
+  if( rc!=SQLITE_OK ) return rc;
+  *pOffset += pPager->pageSize + 4 + isMainJrnl*4;
+
+  /* Sanity checking on the page.  This is more important that I originally
+  ** thought.  If a power failure occurs while the journal is being written,
+  ** it could cause invalid data to be written into the journal.  We need to
+  ** detect this invalid data (with high probability) and ignore it.
+  */
+  if( pgno==0 || pgno==PAGER_SJ_PGNO(pPager) ){
+    assert( !isSavepnt );
+    return SQLITE_DONE;
+  }
+  if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
+    return SQLITE_OK;
+  }
+  if( isMainJrnl ){
+    rc = read32bits(jfd, (*pOffset)-4, &cksum);
+    if( rc ) return rc;
+    if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){
+      return SQLITE_DONE;
+    }
+  }
+
+  /* If this page has already been played back before during the current
+  ** rollback, then don't bother to play it back again.
+  */
+  if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* When playing back page 1, restore the nReserve setting
+  */
+  if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
+    pPager->nReserve = ((u8*)aData)[20];
+  }
+
+  /* If the pager is in CACHEMOD state, then there must be a copy of this
+  ** page in the pager cache. In this case just update the pager cache,
+  ** not the database file. The page is left marked dirty in this case.
+  **
+  ** An exception to the above rule: If the database is in no-sync mode
+  ** and a page is moved during an incremental vacuum then the page may
+  ** not be in the pager cache. Later: if a malloc() or IO error occurs
+  ** during a Movepage() call, then the page may not be in the cache
+  ** either. So the condition described in the above paragraph is not
+  ** assert()able.
+  **
+  ** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the
+  ** pager cache if it exists and the main file. The page is then marked
+  ** not dirty. Since this code is only executed in PAGER_OPEN state for
+  ** a hot-journal rollback, it is guaranteed that the page-cache is empty
+  ** if the pager is in OPEN state.
+  **
+  ** Ticket #1171:  The statement journal might contain page content that is
+  ** different from the page content at the start of the transaction.
+  ** This occurs when a page is changed prior to the start of a statement
+  ** then changed again within the statement.  When rolling back such a
+  ** statement we must not write to the original database unless we know
+  ** for certain that original page contents are synced into the main rollback
+  ** journal.  Otherwise, a power loss might leave modified data in the
+  ** database file without an entry in the rollback journal that can
+  ** restore the database to its original form.  Two conditions must be
+  ** met before writing to the database files. (1) the database must be
+  ** locked.  (2) we know that the original page content is fully synced
+  ** in the main journal either because the page is not in cache or else
+  ** the page is marked as needSync==0.
+  **
+  ** 2008-04-14:  When attempting to vacuum a corrupt database file, it
+  ** is possible to fail a statement on a database that does not yet exist.
+  ** Do not attempt to write if database file has never been opened.
+  */
+  if( pagerUseWal(pPager) ){
+    pPg = 0;
+  }else{
+    pPg = sqlite3PagerLookup(pPager, pgno);
+  }
+  assert( pPg || !MEMDB );
+  assert( pPager->eState!=PAGER_OPEN || pPg==0 || pPager->tempFile );
+  PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
+           PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
+           (isMainJrnl?"main-journal":"sub-journal")
+  ));
+  if( isMainJrnl ){
+    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
+  }else{
+    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
+  }
+  if( isOpen(pPager->fd)
+   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+   && isSynced
+  ){
+    i64 ofst = (pgno-1)*(i64)pPager->pageSize;
+    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
+    assert( !pagerUseWal(pPager) );
+
+    /* Write the data read from the journal back into the database file.
+    ** This is usually safe even for an encrypted database - as the data
+    ** was encrypted before it was written to the journal file. The exception
+    ** is if the data was just read from an in-memory sub-journal. In that
+    ** case it must be encrypted here before it is copied into the database
+    ** file.  */
+    rc = sqlite3OsWrite(pPager->fd, (u8 *)aData, pPager->pageSize, ofst);
+
+    if( pgno>pPager->dbFileSize ){
+      pPager->dbFileSize = pgno;
+    }
+    if( pPager->pBackup ){
+      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData);
+    }
+  }else if( !isMainJrnl && pPg==0 ){
+    /* If this is a rollback of a savepoint and data was not written to
+    ** the database and the page is not in-memory, there is a potential
+    ** problem. When the page is next fetched by the b-tree layer, it
+    ** will be read from the database file, which may or may not be
+    ** current.
+    **
+    ** There are a couple of different ways this can happen. All are quite
+    ** obscure. When running in synchronous mode, this can only happen
+    ** if the page is on the free-list at the start of the transaction, then
+    ** populated, then moved using sqlite3PagerMovepage().
+    **
+    ** The solution is to add an in-memory page to the cache containing
+    ** the data just read from the sub-journal. Mark the page as dirty
+    ** and if the pager requires a journal-sync, then mark the page as
+    ** requiring a journal-sync before it is written.
+    */
+    assert( isSavepnt );
+    assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)==0 );
+    pPager->doNotSpill |= SPILLFLAG_ROLLBACK;
+    rc = sqlite3PagerGet(pPager, pgno, &pPg, 1);
+    assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 );
+    pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK;
+    if( rc!=SQLITE_OK ) return rc;
+    sqlite3PcacheMakeDirty(pPg);
+  }
+  if( pPg ){
+    /* No page should ever be explicitly rolled back that is in use, except
+    ** for page 1 which is held in use in order to keep the lock on the
+    ** database active. However such a page may be rolled back as a result
+    ** of an internal error resulting in an automatic call to
+    ** sqlite3PagerRollback().
+    */
+    void *pData;
+    pData = pPg->pData;
+    memcpy(pData, (u8*)aData, pPager->pageSize);
+    pPager->xReiniter(pPg);
+    /* It used to be that sqlite3PcacheMakeClean(pPg) was called here.  But
+    ** that call was dangerous and had no detectable benefit since the cache
+    ** is normally cleaned by sqlite3PcacheCleanAll() after rollback and so
+    ** has been removed. */
+    pager_set_pagehash(pPg);
+
+    /* If this was page 1, then restore the value of Pager.dbFileVers.
+    ** Do this before any decoding. */
+    if( pgno==1 ){
+      memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
+    }
+    sqlite3PcacheRelease(pPg);
+  }
+  return rc;
+}
+
+/*
+** Parameter zSuper is the name of a super-journal file. A single journal
+** file that referred to the super-journal file has just been rolled back.
+** This routine checks if it is possible to delete the super-journal file,
+** and does so if it is.
+**
+** Argument zSuper may point to Pager.pTmpSpace. So that buffer is not
+** available for use within this function.
+**
+** When a super-journal file is created, it is populated with the names
+** of all of its child journals, one after another, formatted as utf-8
+** encoded text. The end of each child journal file is marked with a
+** nul-terminator byte (0x00). i.e. the entire contents of a super-journal
+** file for a transaction involving two databases might be:
+**
+**   "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
+**
+** A super-journal file may only be deleted once all of its child
+** journals have been rolled back.
+**
+** This function reads the contents of the super-journal file into
+** memory and loops through each of the child journal names. For
+** each child journal, it checks if:
+**
+**   * if the child journal exists, and if so
+**   * if the child journal contains a reference to super-journal
+**     file zSuper
+**
+** If a child journal can be found that matches both of the criteria
+** above, this function returns without doing anything. Otherwise, if
+** no such child journal can be found, file zSuper is deleted from
+** the file-system using sqlite3OsDelete().
+**
+** If an IO error within this function, an error code is returned. This
+** function allocates memory by calling sqlite3Malloc(). If an allocation
+** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors
+** occur, SQLITE_OK is returned.
+**
+** TODO: This function allocates a single block of memory to load
+** the entire contents of the super-journal file. This could be
+** a couple of kilobytes or so - potentially larger than the page
+** size.
+*/
+static int pager_delsuper(Pager *pPager, const char *zSuper){
+  sqlite3_vfs *pVfs = pPager->pVfs;
+  int rc;                   /* Return code */
+  sqlite3_file *pSuper;     /* Malloc'd super-journal file descriptor */
+  sqlite3_file *pJournal;   /* Malloc'd child-journal file descriptor */
+  char *zSuperJournal = 0;  /* Contents of super-journal file */
+  i64 nSuperJournal;        /* Size of super-journal file */
+  char *zJournal;           /* Pointer to one journal within MJ file */
+  char *zSuperPtr;          /* Space to hold super-journal filename */
+  char *zFree = 0;          /* Free this buffer */
+  int nSuperPtr;            /* Amount of space allocated to zSuperPtr[] */
+
+  /* Allocate space for both the pJournal and pSuper file descriptors.
+  ** If successful, open the super-journal file for reading.
+  */
+  pSuper = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2);
+  if( !pSuper ){
+    rc = SQLITE_NOMEM_BKPT;
+    pJournal = 0;
+  }else{
+    const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL);
+    rc = sqlite3OsOpen(pVfs, zSuper, pSuper, flags, 0);
+    pJournal = (sqlite3_file *)(((u8 *)pSuper) + pVfs->szOsFile);
+  }
+  if( rc!=SQLITE_OK ) goto delsuper_out;
+
+  /* Load the entire super-journal file into space obtained from
+  ** sqlite3_malloc() and pointed to by zSuperJournal.   Also obtain
+  ** sufficient space (in zSuperPtr) to hold the names of super-journal
+  ** files extracted from regular rollback-journals.
+  */
+  rc = sqlite3OsFileSize(pSuper, &nSuperJournal);
+  if( rc!=SQLITE_OK ) goto delsuper_out;
+  nSuperPtr = pVfs->mxPathname+1;
+  zFree = sqlite3Malloc(4 + nSuperJournal + nSuperPtr + 2);
+  if( !zFree ){
+    rc = SQLITE_NOMEM_BKPT;
+    goto delsuper_out;
+  }
+  zFree[0] = zFree[1] = zFree[2] = zFree[3] = 0;
+  zSuperJournal = &zFree[4];
+  zSuperPtr = &zSuperJournal[nSuperJournal+2];
+  rc = sqlite3OsRead(pSuper, zSuperJournal, (int)nSuperJournal, 0);
+  if( rc!=SQLITE_OK ) goto delsuper_out;
+  zSuperJournal[nSuperJournal] = 0;
+  zSuperJournal[nSuperJournal+1] = 0;
+
+  zJournal = zSuperJournal;
+  while( (zJournal-zSuperJournal)<nSuperJournal ){
+    int exists;
+    rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
+    if( rc!=SQLITE_OK ){
+      goto delsuper_out;
+    }
+    if( exists ){
+      /* One of the journals pointed to by the super-journal exists.
+      ** Open it and check if it points at the super-journal. If
+      ** so, return without deleting the super-journal file.
+      ** NB:  zJournal is really a MAIN_JOURNAL.  But call it a
+      ** SUPER_JOURNAL here so that the VFS will not send the zJournal
+      ** name into sqlite3_database_file_object().
+      */
+      int c;
+      int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL);
+      rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
+      if( rc!=SQLITE_OK ){
+        goto delsuper_out;
+      }
+
+      rc = readSuperJournal(pJournal, zSuperPtr, nSuperPtr);
+      sqlite3OsClose(pJournal);
+      if( rc!=SQLITE_OK ){
+        goto delsuper_out;
+      }
+
+      c = zSuperPtr[0]!=0 && strcmp(zSuperPtr, zSuper)==0;
+      if( c ){
+        /* We have a match. Do not delete the super-journal file. */
+        goto delsuper_out;
+      }
+    }
+    zJournal += (sqlite3Strlen30(zJournal)+1);
+  }
+
+  sqlite3OsClose(pSuper);
+  rc = sqlite3OsDelete(pVfs, zSuper, 0);
+
+delsuper_out:
+  sqlite3_free(zFree);
+  if( pSuper ){
+    sqlite3OsClose(pSuper);
+    assert( !isOpen(pJournal) );
+    sqlite3_free(pSuper);
+  }
+  return rc;
+}
+
+
+/*
+** This function is used to change the actual size of the database
+** file in the file-system. This only happens when committing a transaction,
+** or rolling back a transaction (including rolling back a hot-journal).
+**
+** If the main database file is not open, or the pager is not in either
+** DBMOD or OPEN state, this function is a no-op. Otherwise, the size
+** of the file is changed to nPage pages (nPage*pPager->pageSize bytes).
+** If the file on disk is currently larger than nPage pages, then use the VFS
+** xTruncate() method to truncate it.
+**
+** Or, it might be the case that the file on disk is smaller than
+** nPage pages. Some operating system implementations can get confused if
+** you try to truncate a file to some size that is larger than it
+** currently is, so detect this case and write a single zero byte to
+** the end of the new file instead.
+**
+** If successful, return SQLITE_OK. If an IO error occurs while modifying
+** the database file, return the error code to the caller.
+*/
+static int pager_truncate(Pager *pPager, Pgno nPage){
+  int rc = SQLITE_OK;
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( pPager->eState!=PAGER_READER );
+  PAGERTRACE(("Truncate %d npage %u\n", PAGERID(pPager), nPage));
+
+ 
+  if( isOpen(pPager->fd)
+   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+  ){
+    i64 currentSize, newSize;
+    int szPage = pPager->pageSize;
+    assert( pPager->eLock==EXCLUSIVE_LOCK );
+    /* TODO: Is it safe to use Pager.dbFileSize here? */
+    rc = sqlite3OsFileSize(pPager->fd, &currentSize);
+    newSize = szPage*(i64)nPage;
+    if( rc==SQLITE_OK && currentSize!=newSize ){
+      if( currentSize>newSize ){
+        rc = sqlite3OsTruncate(pPager->fd, newSize);
+      }else if( (currentSize+szPage)<=newSize ){
+        char *pTmp = pPager->pTmpSpace;
+        memset(pTmp, 0, szPage);
+        testcase( (newSize-szPage) == currentSize );
+        testcase( (newSize-szPage) >  currentSize );
+        sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &newSize);
+        rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage);
+      }
+      if( rc==SQLITE_OK ){
+        pPager->dbFileSize = nPage;
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Return a sanitized version of the sector-size of OS file pFile. The
+** return value is guaranteed to lie between 32 and MAX_SECTOR_SIZE.
+*/
+int sqlite3SectorSize(sqlite3_file *pFile){
+  int iRet = sqlite3OsSectorSize(pFile);
+  if( iRet<32 ){
+    iRet = 512;
+  }else if( iRet>MAX_SECTOR_SIZE ){
+    assert( MAX_SECTOR_SIZE>=512 );
+    iRet = MAX_SECTOR_SIZE;
+  }
+  return iRet;
+}
+
+/*
+** Set the value of the Pager.sectorSize variable for the given
+** pager based on the value returned by the xSectorSize method
+** of the open database file. The sector size will be used
+** to determine the size and alignment of journal header and
+** super-journal pointers within created journal files.
+**
+** For temporary files the effective sector size is always 512 bytes.
+**
+** Otherwise, for non-temporary files, the effective sector size is
+** the value returned by the xSectorSize() method rounded up to 32 if
+** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it
+** is greater than MAX_SECTOR_SIZE.
+**
+** If the file has the SQLITE_IOCAP_POWERSAFE_OVERWRITE property, then set
+** the effective sector size to its minimum value (512).  The purpose of
+** pPager->sectorSize is to define the "blast radius" of bytes that
+** might change if a crash occurs while writing to a single byte in
+** that range.  But with POWERSAFE_OVERWRITE, the blast radius is zero
+** (that is what POWERSAFE_OVERWRITE means), so we minimize the sector
+** size.  For backwards compatibility of the rollback journal file format,
+** we cannot reduce the effective sector size below 512.
+*/
+static void setSectorSize(Pager *pPager){
+  assert( isOpen(pPager->fd) || pPager->tempFile );
+
+  if( pPager->tempFile
+   || (sqlite3OsDeviceCharacteristics(pPager->fd) &
+              SQLITE_IOCAP_POWERSAFE_OVERWRITE)!=0
+  ){
+    /* Sector size doesn't matter for temporary files. Also, the file
+    ** may not have been opened yet, in which case the OsSectorSize()
+    ** call will segfault. */
+    pPager->sectorSize = 512;
+  }else{
+    pPager->sectorSize = sqlite3SectorSize(pPager->fd);
+  }
+}
+
+/*
+** Playback the journal and thus restore the database file to
+** the state it was in before we started making changes. 
+**
+** The journal file format is as follows:
+**
+**  (1)  8 byte prefix.  A copy of aJournalMagic[].
+**  (2)  4 byte big-endian integer which is the number of valid page records
+**       in the journal.  If this value is 0xffffffff, then compute the
+**       number of page records from the journal size.
+**  (3)  4 byte big-endian integer which is the initial value for the
+**       sanity checksum.
+**  (4)  4 byte integer which is the number of pages to truncate the
+**       database to during a rollback.
+**  (5)  4 byte big-endian integer which is the sector size.  The header
+**       is this many bytes in size.
+**  (6)  4 byte big-endian integer which is the page size.
+**  (7)  zero padding out to the next sector size.
+**  (8)  Zero or more pages instances, each as follows:
+**        +  4 byte page number.
+**        +  pPager->pageSize bytes of data.
+**        +  4 byte checksum
+**
+** When we speak of the journal header, we mean the first 7 items above.
+** Each entry in the journal is an instance of the 8th item.
+**
+** Call the value from the second bullet "nRec".  nRec is the number of
+** valid page entries in the journal.  In most cases, you can compute the
+** value of nRec from the size of the journal file.  But if a power
+** failure occurred while the journal was being written, it could be the
+** case that the size of the journal file had already been increased but
+** the extra entries had not yet made it safely to disk.  In such a case,
+** the value of nRec computed from the file size would be too large.  For
+** that reason, we always use the nRec value in the header.
+**
+** If the nRec value is 0xffffffff it means that nRec should be computed
+** from the file size.  This value is used when the user selects the
+** no-sync option for the journal.  A power failure could lead to corruption
+** in this case.  But for things like temporary table (which will be
+** deleted when the power is restored) we don't care. 
+**
+** If the file opened as the journal file is not a well-formed
+** journal file then all pages up to the first corrupted page are rolled
+** back (or no pages if the journal header is corrupted). The journal file
+** is then deleted and SQLITE_OK returned, just as if no corruption had
+** been encountered.
+**
+** If an I/O or malloc() error occurs, the journal-file is not deleted
+** and an error code is returned.
+**
+** The isHot parameter indicates that we are trying to rollback a journal
+** that might be a hot journal.  Or, it could be that the journal is
+** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
+** If the journal really is hot, reset the pager cache prior rolling
+** back any content.  If the journal is merely persistent, no reset is
+** needed.
+*/
+static int pager_playback(Pager *pPager, int isHot){
+  sqlite3_vfs *pVfs = pPager->pVfs;
+  i64 szJ;                 /* Size of the journal file in bytes */
+  u32 nRec;                /* Number of Records in the journal */
+  u32 u;                   /* Unsigned loop counter */
+  Pgno mxPg = 0;           /* Size of the original file in pages */
+  int rc;                  /* Result code of a subroutine */
+  int res = 1;             /* Value returned by sqlite3OsAccess() */
+  char *zSuper = 0;        /* Name of super-journal file if any */
+  int needPagerReset;      /* True to reset page prior to first page rollback */
+  int nPlayback = 0;       /* Total number of pages restored from journal */
+  u32 savedPageSize = pPager->pageSize;
+
+  /* Figure out how many records are in the journal.  Abort early if
+  ** the journal is empty.
+  */
+  assert( isOpen(pPager->jfd) );
+  rc = sqlite3OsFileSize(pPager->jfd, &szJ);
+  if( rc!=SQLITE_OK ){
+    goto end_playback;
+  }
+
+  /* Read the super-journal name from the journal, if it is present.
+  ** If a super-journal file name is specified, but the file is not
+  ** present on disk, then the journal is not hot and does not need to be
+  ** played back.
+  **
+  ** TODO: Technically the following is an error because it assumes that
+  ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
+  ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
+  ** mxPathname is 512, which is the same as the minimum allowable value
+  ** for pageSize.
+  */
+  zSuper = pPager->pTmpSpace;
+  rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1);
+  if( rc==SQLITE_OK && zSuper[0] ){
+    rc = sqlite3OsAccess(pVfs, zSuper, SQLITE_ACCESS_EXISTS, &res);
+  }
+  zSuper = 0;
+  if( rc!=SQLITE_OK || !res ){
+    goto end_playback;
+  }
+  pPager->journalOff = 0;
+  needPagerReset = isHot;
+
+  /* This loop terminates either when a readJournalHdr() or
+  ** pager_playback_one_page() call returns SQLITE_DONE or an IO error
+  ** occurs.
+  */
+  while( 1 ){
+    /* Read the next journal header from the journal file.  If there are
+    ** not enough bytes left in the journal file for a complete header, or
+    ** it is corrupted, then a process must have failed while writing it.
+    ** This indicates nothing more needs to be rolled back.
+    */
+    rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_DONE ){
+        rc = SQLITE_OK;
+      }
+      goto end_playback;
+    }
+
+    /* If nRec is 0xffffffff, then this journal was created by a process
+    ** working in no-sync mode. This means that the rest of the journal
+    ** file consists of pages, there are no more journal headers. Compute
+    ** the value of nRec based on this assumption.
+    */
+    if( nRec==0xffffffff ){
+      assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
+      nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager));
+    }
+
+    /* If nRec is 0 and this rollback is of a transaction created by this
+    ** process and if this is the final header in the journal, then it means
+    ** that this part of the journal was being filled but has not yet been
+    ** synced to disk.  Compute the number of pages based on the remaining
+    ** size of the file.
+    **
+    ** The third term of the test was added to fix ticket #2565.
+    ** When rolling back a hot journal, nRec==0 always means that the next
+    ** chunk of the journal contains zero pages to be rolled back.  But
+    ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
+    ** the journal, it means that the journal might contain additional
+    ** pages that need to be rolled back and that the number of pages
+    ** should be computed based on the journal file size.
+    */
+    if( nRec==0 && !isHot &&
+        pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
+      nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
+    }
+
+    /* If this is the first header read from the journal, truncate the
+    ** database file back to its original size.
+    */
+    if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
+      rc = pager_truncate(pPager, mxPg);
+      if( rc!=SQLITE_OK ){
+        goto end_playback;
+      }
+      pPager->dbSize = mxPg;
+      if( pPager->mxPgno<mxPg ){
+        pPager->mxPgno = mxPg;
+      }
+    }
+
+    /* Copy original pages out of the journal and back into the
+    ** database file and/or page cache.
+    */
+    for(u=0; u<nRec; u++){
+      if( needPagerReset ){
+        pager_reset(pPager);
+        needPagerReset = 0;
+      }
+      rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
+      if( rc==SQLITE_OK ){
+        nPlayback++;
+      }else{
+        if( rc==SQLITE_DONE ){
+          pPager->journalOff = szJ;
+          break;
+        }else if( rc==SQLITE_IOERR_SHORT_READ ){
+          /* If the journal has been truncated, simply stop reading and
+          ** processing the journal. This might happen if the journal was
+          ** not completely written and synced prior to a crash.  In that
+          ** case, the database should have never been written in the
+          ** first place so it is OK to simply abandon the rollback. */
+          rc = SQLITE_OK;
+          goto end_playback;
+        }else{
+          /* If we are unable to rollback, quit and return the error
+          ** code.  This will cause the pager to enter the error state
+          ** so that no further harm will be done.  Perhaps the next
+          ** process to come along will be able to rollback the database.
+          */
+          goto end_playback;
+        }
+      }
+    }
+  }
+  /*NOTREACHED*/
+  assert( 0 );
+
+end_playback:
+  if( rc==SQLITE_OK ){
+    rc = sqlite3PagerSetPagesize(pPager, &savedPageSize, -1);
+  }
+  /* Following a rollback, the database file should be back in its original
+  ** state prior to the start of the transaction, so invoke the
+  ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
+  ** assertion that the transaction counter was modified.
+  */
+#ifdef SQLITE_DEBUG
+  sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0);
+#endif
+
+  /* If this playback is happening automatically as a result of an IO or
+  ** malloc error that occurred after the change-counter was updated but
+  ** before the transaction was committed, then the change-counter
+  ** modification may just have been reverted. If this happens in exclusive
+  ** mode, then subsequent transactions performed by the connection will not
+  ** update the change-counter at all. This may lead to cache inconsistency
+  ** problems for other processes at some point in the future. So, just
+  ** in case this has happened, clear the changeCountDone flag now.
+  */
+  pPager->changeCountDone = pPager->tempFile;
+
+  if( rc==SQLITE_OK ){
+    /* Leave 4 bytes of space before the super-journal filename in memory.
+    ** This is because it may end up being passed to sqlite3OsOpen(), in
+    ** which case it requires 4 0x00 bytes in memory immediately before
+    ** the filename. */
+    zSuper = &pPager->pTmpSpace[4];
+    rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1);
+    testcase( rc!=SQLITE_OK );
+  }
+  if( rc==SQLITE_OK
+   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+  ){
+    rc = sqlite3PagerSync(pPager, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = pager_end_transaction(pPager, zSuper[0]!='\0', 0);
+    testcase( rc!=SQLITE_OK );
+  }
+  if( rc==SQLITE_OK && zSuper[0] && res ){
+    /* If there was a super-journal and this routine will return success,
+    ** see if it is possible to delete the super-journal.
+    */
+    assert( zSuper==&pPager->pTmpSpace[4] );
+    memset(pPager->pTmpSpace, 0, 4);
+    rc = pager_delsuper(pPager, zSuper);
+    testcase( rc!=SQLITE_OK );
+  }
+  if( isHot && nPlayback ){
+    sqlite3_log(SQLITE_NOTICE_RECOVER_ROLLBACK, "recovered %d pages from %s",
+                nPlayback, pPager->zJournal);
+  }
+
+  /* The Pager.sectorSize variable may have been updated while rolling
+  ** back a journal created by a process with a different sector size
+  ** value. Reset it to the correct value for this process.
+  */
+  setSectorSize(pPager);
+  return rc;
+}
+
+
+/*
+** Read the content for page pPg out of the database file (or out of
+** the WAL if that is where the most recent copy if found) into
+** pPg->pData. A shared lock or greater must be held on the database
+** file before this function is called.
+**
+** If page 1 is read, then the value of Pager.dbFileVers[] is set to
+** the value read from the database file.
+**
+** If an IO error occurs, then the IO error is returned to the caller.
+** Otherwise, SQLITE_OK is returned.
+*/
+static int readDbPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
+  int rc = SQLITE_OK;          /* Return code */
+
+#ifndef SQLITE_OMIT_WAL
+  u32 iFrame = 0;              /* Frame of WAL containing pgno */
+
+  assert( pPager->eState>=PAGER_READER && !MEMDB );
+  assert( isOpen(pPager->fd) );
+
+  if( pagerUseWal(pPager) ){
+    rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame);
+    if( rc ) return rc;
+  }
+  if( iFrame ){
+    rc = sqlite3WalReadFrame(pPager->pWal, iFrame,pPager->pageSize,pPg->pData);
+  }else
+#endif
+  {
+    i64 iOffset = (pPg->pgno-1)*(i64)pPager->pageSize;
+    rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
+    if( rc==SQLITE_IOERR_SHORT_READ ){
+      rc = SQLITE_OK;
+    }
+  }
+
+  if( pPg->pgno==1 ){
+    if( rc ){
+      /* If the read is unsuccessful, set the dbFileVers[] to something
+      ** that will never be a valid file version.  dbFileVers[] is a copy
+      ** of bytes 24..39 of the database.  Bytes 28..31 should always be
+      ** zero or the size of the database in page. Bytes 32..35 and 35..39
+      ** should be page numbers which are never 0xffffffff.  So filling
+      ** pPager->dbFileVers[] with all 0xff bytes should suffice.
+      **
+      ** For an encrypted database, the situation is more complex:  bytes
+      ** 24..39 of the database are white noise.  But the probability of
+      ** white noise equaling 16 bytes of 0xff is vanishingly small so
+      ** we should still be ok.
+      */
+      memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
+    }else{
+      u8 *dbFileVers = &((u8*)pPg->pData)[24];
+      memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
+    }
+  }
+  PAGER_INCR(sqlite3_pager_readdb_count);
+  PAGER_INCR(pPager->nRead);
+  IOTRACE(("PGIN %p %d\n", pPager, pPg->pgno));
+  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
+               PAGERID(pPager), pPg->pgno, pager_pagehash(pPg)));
+
+  return rc;
+}
+
+/*
+** Update the value of the change-counter at offsets 24 and 92 in
+** the header and the sqlite version number at offset 96.
+**
+** This is an unconditional update.  See also the pager_incr_changecounter()
+** routine which only updates the change-counter if the update is actually
+** needed, as determined by the pPager->changeCountDone state variable.
+*/
+static void pager_write_changecounter(PgHdr *pPg){
+  u32 change_counter;
+  if( NEVER(pPg==0) ) return;
+
+  /* Increment the value just read and write it back to byte 24. */
+  change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
+  put32bits(((char*)pPg->pData)+24, change_counter);
+
+  /* Also store the SQLite version number in bytes 96..99 and in
+  ** bytes 92..95 store the change counter for which the version number
+  ** is valid. */
+  put32bits(((char*)pPg->pData)+92, change_counter);
+  put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is invoked once for each page that has already been
+** written into the log file when a WAL transaction is rolled back.
+** Parameter iPg is the page number of said page. The pCtx argument
+** is actually a pointer to the Pager structure.
+**
+** If page iPg is present in the cache, and has no outstanding references,
+** it is discarded. Otherwise, if there are one or more outstanding
+** references, the page content is reloaded from the database. If the
+** attempt to reload content from the database is required and fails,
+** return an SQLite error code. Otherwise, SQLITE_OK.
+*/
+static int pagerUndoCallback(void *pCtx, Pgno iPg){
+  int rc = SQLITE_OK;
+  Pager *pPager = (Pager *)pCtx;
+  PgHdr *pPg;
+
+  assert( pagerUseWal(pPager) );
+  pPg = sqlite3PagerLookup(pPager, iPg);
+  if( pPg ){
+    if( sqlite3PcachePageRefcount(pPg)==1 ){
+      sqlite3PcacheDrop(pPg);
+    }else{
+      rc = readDbPage(pPg);
+      if( rc==SQLITE_OK ){
+        pPager->xReiniter(pPg);
+      }
+      sqlite3PagerUnrefNotNull(pPg);
+    }
+  }
+
+  /* Normally, if a transaction is rolled back, any backup processes are
+  ** updated as data is copied out of the rollback journal and into the
+  ** database. This is not generally possible with a WAL database, as
+  ** rollback involves simply truncating the log file. Therefore, if one
+  ** or more frames have already been written to the log (and therefore
+  ** also copied into the backup databases) as part of this transaction,
+  ** the backups must be restarted.
+  */
+  sqlite3BackupRestart(pPager->pBackup);
+
+  return rc;
+}
+
+/*
+** This function is called to rollback a transaction on a WAL database.
+*/
+static int pagerRollbackWal(Pager *pPager){
+  int rc;                         /* Return Code */
+  PgHdr *pList;                   /* List of dirty pages to revert */
+
+  /* For all pages in the cache that are currently dirty or have already
+  ** been written (but not committed) to the log file, do one of the
+  ** following:
+  **
+  **   + Discard the cached page (if refcount==0), or
+  **   + Reload page content from the database (if refcount>0).
+  */
+  pPager->dbSize = pPager->dbOrigSize;
+  rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
+  pList = sqlite3PcacheDirtyList(pPager->pPCache);
+  while( pList && rc==SQLITE_OK ){
+    PgHdr *pNext = pList->pDirty;
+    rc = pagerUndoCallback((void *)pPager, pList->pgno);
+    pList = pNext;
+  }
+
+  return rc;
+}
+
+/*
+** This function is a wrapper around sqlite3WalFrames(). As well as logging
+** the contents of the list of pages headed by pList (connected by pDirty),
+** this function notifies any active backup processes that the pages have
+** changed.
+**
+** The list of pages passed into this routine is always sorted by page number.
+** Hence, if page 1 appears anywhere on the list, it will be the first page.
+*/
+static int pagerWalFrames(
+  Pager *pPager,                  /* Pager object */
+  PgHdr *pList,                   /* List of frames to log */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit                    /* True if this is a commit */
+){
+  int rc;                         /* Return code */
+  int nList;                      /* Number of pages in pList */
+  PgHdr *p;                       /* For looping over pages */
+
+  assert( pPager->pWal );
+  assert( pList );
+#ifdef SQLITE_DEBUG
+  /* Verify that the page list is in ascending order */
+  for(p=pList; p && p->pDirty; p=p->pDirty){
+    assert( p->pgno < p->pDirty->pgno );
+  }
+#endif
+
+  assert( pList->pDirty==0 || isCommit );
+  if( isCommit ){
+    /* If a WAL transaction is being committed, there is no point in writing
+    ** any pages with page numbers greater than nTruncate into the WAL file.
+    ** They will never be read by any client. So remove them from the pDirty
+    ** list here. */
+    PgHdr **ppNext = &pList;
+    nList = 0;
+    for(p=pList; (*ppNext = p)!=0; p=p->pDirty){
+      if( p->pgno<=nTruncate ){
+        ppNext = &p->pDirty;
+        nList++;
+      }
+    }
+    assert( pList );
+  }else{
+    nList = 1;
+  }
+  pPager->aStat[PAGER_STAT_WRITE] += nList;
+
+  if( pList->pgno==1 ) pager_write_changecounter(pList);
+  rc = sqlite3WalFrames(pPager->pWal,
+      pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags
+  );
+  if( rc==SQLITE_OK && pPager->pBackup ){
+    for(p=pList; p; p=p->pDirty){
+      sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
+    }
+  }
+
+#ifdef SQLITE_CHECK_PAGES
+  pList = sqlite3PcacheDirtyList(pPager->pPCache);
+  for(p=pList; p; p=p->pDirty){
+    pager_set_pagehash(p);
+  }
+#endif
+
+  return rc;
+}
+
+/*
+** Begin a read transaction on the WAL.
+**
+** This routine used to be called "pagerOpenSnapshot()" because it essentially
+** makes a snapshot of the database at the current point in time and preserves
+** that snapshot for use by the reader in spite of concurrently changes by
+** other writers or checkpointers.
+*/
+static int pagerBeginReadTransaction(Pager *pPager){
+  int rc;                         /* Return code */
+  int changed = 0;                /* True if cache must be reset */
+
+  assert( pagerUseWal(pPager) );
+  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
+
+  /* sqlite3WalEndReadTransaction() was not called for the previous
+  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
+  ** are in locking_mode=NORMAL and EndRead() was previously called,
+  ** the duplicate call is harmless.
+  */
+  sqlite3WalEndReadTransaction(pPager->pWal);
+
+  rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
+  if( rc!=SQLITE_OK || changed ){
+    pager_reset(pPager);
+    if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
+  }
+
+  return rc;
+}
+#endif
+
+/*
+** This function is called as part of the transition from PAGER_OPEN
+** to PAGER_READER state to determine the size of the database file
+** in pages (assuming the page size currently stored in Pager.pageSize).
+**
+** If no error occurs, SQLITE_OK is returned and the size of the database
+** in pages is stored in *pnPage. Otherwise, an error code (perhaps
+** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified.
+*/
+static int pagerPagecount(Pager *pPager, Pgno *pnPage){
+  Pgno nPage;                     /* Value to return via *pnPage */
+
+  /* Query the WAL sub-system for the database size. The WalDbsize()
+  ** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or
+  ** if the database size is not available. The database size is not
+  ** available from the WAL sub-system if the log file is empty or
+  ** contains no valid committed transactions.
+  */
+  assert( pPager->eState==PAGER_OPEN );
+  assert( pPager->eLock>=SHARED_LOCK );
+  assert( isOpen(pPager->fd) );
+  assert( pPager->tempFile==0 );
+  nPage = sqlite3WalDbsize(pPager->pWal);
+
+  /* If the number of pages in the database is not available from the
+  ** WAL sub-system, determine the page count based on the size of
+  ** the database file.  If the size of the database file is not an
+  ** integer multiple of the page-size, round up the result.
+  */
+  if( nPage==0 && ALWAYS(isOpen(pPager->fd)) ){
+    i64 n = 0;                    /* Size of db file in bytes */
+    int rc = sqlite3OsFileSize(pPager->fd, &n);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    nPage = (Pgno)((n+pPager->pageSize-1) / pPager->pageSize);
+  }
+
+  /* If the current number of pages in the file is greater than the
+  ** configured maximum pager number, increase the allowed limit so
+  ** that the file can be read.
+  */
+  if( nPage>pPager->mxPgno ){
+    pPager->mxPgno = (Pgno)nPage;
+  }
+
+  *pnPage = nPage;
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists if the database is not empty, or verify that the *-wal file does
+** not exist (by deleting it) if the database file is empty.
+**
+** If the database is not empty and the *-wal file exists, open the pager
+** in WAL mode.  If the database is empty or if no *-wal file exists and
+** if no error occurs, make sure Pager.journalMode is not set to
+** PAGER_JOURNALMODE_WAL.
+**
+** Return SQLITE_OK or an error code.
+**
+** The caller must hold a SHARED lock on the database file to call this
+** function. Because an EXCLUSIVE lock on the db file is required to delete
+** a WAL on a none-empty database, this ensures there is no race condition
+** between the xAccess() below and an xDelete() being executed by some
+** other connection.
+*/
+static int pagerOpenWalIfPresent(Pager *pPager){
+  int rc = SQLITE_OK;
+  assert( pPager->eState==PAGER_OPEN );
+  assert( pPager->eLock>=SHARED_LOCK );
+
+  if( !pPager->tempFile ){
+    int isWal;                    /* True if WAL file exists */
+    rc = sqlite3OsAccess(
+        pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal
+    );
+    if( rc==SQLITE_OK ){
+      if( isWal ){
+        Pgno nPage;                   /* Size of the database file */
+
+        rc = pagerPagecount(pPager, &nPage);
+        if( rc ) return rc;
+        if( nPage==0 ){
+          rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
+        }else{
+          testcase( sqlite3PcachePagecount(pPager->pPCache)==0 );
+          rc = sqlite3PagerOpenWal(pPager, 0);
+        }
+      }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+        pPager->journalMode = PAGER_JOURNALMODE_DELETE;
+      }
+    }
+  }
+  return rc;
+}
+#endif
+
+/*
+** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
+** the entire super-journal file. The case pSavepoint==NULL occurs when
+** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction
+** savepoint.
+**
+** When pSavepoint is not NULL (meaning a non-transaction savepoint is
+** being rolled back), then the rollback consists of up to three stages,
+** performed in the order specified:
+**
+**   * Pages are played back from the main journal starting at byte
+**     offset PagerSavepoint.iOffset and continuing to
+**     PagerSavepoint.iHdrOffset, or to the end of the main journal
+**     file if PagerSavepoint.iHdrOffset is zero.
+**
+**   * If PagerSavepoint.iHdrOffset is not zero, then pages are played
+**     back starting from the journal header immediately following
+**     PagerSavepoint.iHdrOffset to the end of the main journal file.
+**
+**   * Pages are then played back from the sub-journal file, starting
+**     with the PagerSavepoint.iSubRec and continuing to the end of
+**     the journal file.
+**
+** Throughout the rollback process, each time a page is rolled back, the
+** corresponding bit is set in a bitvec structure (variable pDone in the
+** implementation below). This is used to ensure that a page is only
+** rolled back the first time it is encountered in either journal.
+**
+** If pSavepoint is NULL, then pages are only played back from the main
+** journal file. There is no need for a bitvec in this case.
+**
+** In either case, before playback commences the Pager.dbSize variable
+** is reset to the value that it held at the start of the savepoint
+** (or transaction). No page with a page-number greater than this value
+** is played back. If one is encountered it is simply skipped.
+*/
+static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
+  i64 szJ;                 /* Effective size of the main journal */
+  i64 iHdrOff;             /* End of first segment of main-journal records */
+  int rc = SQLITE_OK;      /* Return code */
+  Bitvec *pDone = 0;       /* Bitvec to ensure pages played back only once */
+
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+
+  /* Allocate a bitvec to use to store the set of pages rolled back */
+  if( pSavepoint ){
+    pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
+    if( !pDone ){
+      return SQLITE_NOMEM_BKPT;
+    }
+  }
+
+  /* Set the database size back to the value it was before the savepoint
+  ** being reverted was opened.
+  */
+  pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
+  pPager->changeCountDone = pPager->tempFile;
+
+  if( !pSavepoint && pagerUseWal(pPager) ){
+    return pagerRollbackWal(pPager);
+  }
+
+  /* Use pPager->journalOff as the effective size of the main rollback
+  ** journal.  The actual file might be larger than this in
+  ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST.  But anything
+  ** past pPager->journalOff is off-limits to us.
+  */
+  szJ = pPager->journalOff;
+  assert( pagerUseWal(pPager)==0 || szJ==0 );
+
+  /* Begin by rolling back records from the main journal starting at
+  ** PagerSavepoint.iOffset and continuing to the next journal header.
+  ** There might be records in the main journal that have a page number
+  ** greater than the current database size (pPager->dbSize) but those
+  ** will be skipped automatically.  Pages are added to pDone as they
+  ** are played back.
+  */
+  if( pSavepoint && !pagerUseWal(pPager) ){
+    iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
+    pPager->journalOff = pSavepoint->iOffset;
+    while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
+    }
+    assert( rc!=SQLITE_DONE );
+  }else{
+    pPager->journalOff = 0;
+  }
+
+  /* Continue rolling back records out of the main journal starting at
+  ** the first journal header seen and continuing until the effective end
+  ** of the main journal file.  Continue to skip out-of-range pages and
+  ** continue adding pages rolled back to pDone.
+  */
+  while( rc==SQLITE_OK && pPager->journalOff<szJ ){
+    u32 ii;            /* Loop counter */
+    u32 nJRec = 0;     /* Number of Journal Records */
+    u32 dummy;
+    rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy);
+    assert( rc!=SQLITE_DONE );
+
+    /*
+    ** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff"
+    ** test is related to ticket #2565.  See the discussion in the
+    ** pager_playback() function for additional information.
+    */
+    if( nJRec==0
+     && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
+    ){
+      nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
+    }
+    for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
+    }
+    assert( rc!=SQLITE_DONE );
+  }
+  assert( rc!=SQLITE_OK || pPager->journalOff>=szJ );
+
+  /* Finally,  rollback pages from the sub-journal.  Page that were
+  ** previously rolled back out of the main journal (and are hence in pDone)
+  ** will be skipped.  Out-of-range pages are also skipped.
+  */
+  if( pSavepoint ){
+    u32 ii;            /* Loop counter */
+    i64 offset = (i64)pSavepoint->iSubRec*(4+pPager->pageSize);
+
+    if( pagerUseWal(pPager) ){
+      rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
+    }
+    for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
+      assert( offset==(i64)ii*(4+pPager->pageSize) );
+      rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
+    }
+    assert( rc!=SQLITE_DONE );
+  }
+
+  sqlite3BitvecDestroy(pDone);
+  if( rc==SQLITE_OK ){
+    pPager->journalOff = szJ;
+  }
+
+  return rc;
+}
+
+/*
+** Change the maximum number of in-memory pages that are allowed
+** before attempting to recycle clean and unused pages.
+*/
+void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
+  sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
+}
+
+/*
+** Change the maximum number of in-memory pages that are allowed
+** before attempting to spill pages to journal.
+*/
+int sqlite3PagerSetSpillsize(Pager *pPager, int mxPage){
+  return sqlite3PcacheSetSpillsize(pPager->pPCache, mxPage);
+}
+
+/*
+** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap.
+*/
+static void pagerFixMaplimit(Pager *pPager){
+#if SQLITE_MAX_MMAP_SIZE>0
+  sqlite3_file *fd = pPager->fd;
+  if( isOpen(fd) && fd->pMethods->iVersion>=3 ){
+    sqlite3_int64 sz;
+    sz = pPager->szMmap;
+    pPager->bUseFetch = (sz>0);
+    setGetterMethod(pPager);
+    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz);
+  }
+#endif
+}
+
+/*
+** Change the maximum size of any memory mapping made of the database file.
+*/
+void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){
+  pPager->szMmap = szMmap;
+  pagerFixMaplimit(pPager);
+}
+
+/*
+** Free as much memory as possible from the pager.
+*/
+void sqlite3PagerShrink(Pager *pPager){
+  sqlite3PcacheShrink(pPager->pPCache);
+}
+
+/*
+** Adjust settings of the pager to those specified in the pgFlags parameter.
+**
+** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness
+** of the database to damage due to OS crashes or power failures by
+** changing the number of syncs()s when writing the journals.
+** There are four levels:
+**
+**    OFF       sqlite3OsSync() is never called.  This is the default
+**              for temporary and transient files.
+**
+**    NORMAL    The journal is synced once before writes begin on the
+**              database.  This is normally adequate protection, but
+**              it is theoretically possible, though very unlikely,
+**              that an inopertune power failure could leave the journal
+**              in a state which would cause damage to the database
+**              when it is rolled back.
+**
+**    FULL      The journal is synced twice before writes begin on the
+**              database (with some additional information - the nRec field
+**              of the journal header - being written in between the two
+**              syncs).  If we assume that writing a
+**              single disk sector is atomic, then this mode provides
+**              assurance that the journal will not be corrupted to the
+**              point of causing damage to the database during rollback.
+**
+**    EXTRA     This is like FULL except that is also syncs the directory
+**              that contains the rollback journal after the rollback
+**              journal is unlinked.
+**
+** The above is for a rollback-journal mode.  For WAL mode, OFF continues
+** to mean that no syncs ever occur.  NORMAL means that the WAL is synced
+** prior to the start of checkpoint and that the database file is synced
+** at the conclusion of the checkpoint if the entire content of the WAL
+** was written back into the database.  But no sync operations occur for
+** an ordinary commit in NORMAL mode with WAL.  FULL means that the WAL
+** file is synced following each commit operation, in addition to the
+** syncs associated with NORMAL.  There is no difference between FULL
+** and EXTRA for WAL mode.
+**
+** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL.  The
+** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync
+** using fcntl(F_FULLFSYNC).  SQLITE_SYNC_NORMAL means to do an
+** ordinary fsync() call.  There is no difference between SQLITE_SYNC_FULL
+** and SQLITE_SYNC_NORMAL on platforms other than MacOSX.  But the
+** synchronous=FULL versus synchronous=NORMAL setting determines when
+** the xSync primitive is called and is relevant to all platforms.
+**
+** Numeric values associated with these states are OFF==1, NORMAL=2,
+** and FULL=3.
+*/
+void sqlite3PagerSetFlags(
+  Pager *pPager,        /* The pager to set safety level for */
+  unsigned pgFlags      /* Various flags */
+){
+  unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK;
+  if( pPager->tempFile ){
+    pPager->noSync = 1;
+    pPager->fullSync = 0;
+    pPager->extraSync = 0;
+  }else{
+    pPager->noSync =  level==PAGER_SYNCHRONOUS_OFF ?1:0;
+    pPager->fullSync = level>=PAGER_SYNCHRONOUS_FULL ?1:0;
+    pPager->extraSync = level==PAGER_SYNCHRONOUS_EXTRA ?1:0;
+  }
+  if( pPager->noSync ){
+    pPager->syncFlags = 0;
+  }else if( pgFlags & PAGER_FULLFSYNC ){
+    pPager->syncFlags = SQLITE_SYNC_FULL;
+  }else{
+    pPager->syncFlags = SQLITE_SYNC_NORMAL;
+  }
+  pPager->walSyncFlags = (pPager->syncFlags<<2);
+  if( pPager->fullSync ){
+    pPager->walSyncFlags |= pPager->syncFlags;
+  }
+  if( (pgFlags & PAGER_CKPT_FULLFSYNC) && !pPager->noSync ){
+    pPager->walSyncFlags |= (SQLITE_SYNC_FULL<<2);
+  }
+  if( pgFlags & PAGER_CACHESPILL ){
+    pPager->doNotSpill &= ~SPILLFLAG_OFF;
+  }else{
+    pPager->doNotSpill |= SPILLFLAG_OFF;
+  }
+}
+
+/*
+** The following global variable is incremented whenever the library
+** attempts to open a temporary file.  This information is used for
+** testing and analysis only. 
+*/
+#ifdef SQLITE_TEST
+int sqlite3_opentemp_count = 0;
+#endif
+
+/*
+** Open a temporary file.
+**
+** Write the file descriptor into *pFile. Return SQLITE_OK on success
+** or some other error code if we fail. The OS will automatically
+** delete the temporary file when it is closed.
+**
+** The flags passed to the VFS layer xOpen() call are those specified
+** by parameter vfsFlags ORed with the following:
+**
+**     SQLITE_OPEN_READWRITE
+**     SQLITE_OPEN_CREATE
+**     SQLITE_OPEN_EXCLUSIVE
+**     SQLITE_OPEN_DELETEONCLOSE
+*/
+static int pagerOpentemp(
+  Pager *pPager,        /* The pager object */
+  sqlite3_file *pFile,  /* Write the file descriptor here */
+  int vfsFlags          /* Flags passed through to the VFS */
+){
+  int rc;               /* Return code */
+
+#ifdef SQLITE_TEST
+  sqlite3_opentemp_count++;  /* Used for testing and analysis only */
+#endif
+
+  vfsFlags |=  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
+            SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
+  rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
+  assert( rc!=SQLITE_OK || isOpen(pFile) );
+  return rc;
+}
+
+/*
+** Set the busy handler function.
+**
+** The pager invokes the busy-handler if sqlite3OsLock() returns
+** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
+** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE
+** lock. It does *not* invoke the busy handler when upgrading from
+** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
+** (which occurs during hot-journal rollback). Summary:
+**
+**   Transition                        | Invokes xBusyHandler
+**   --------------------------------------------------------
+**   NO_LOCK       -> SHARED_LOCK      | Yes
+**   SHARED_LOCK   -> RESERVED_LOCK    | No
+**   SHARED_LOCK   -> EXCLUSIVE_LOCK   | No
+**   RESERVED_LOCK -> EXCLUSIVE_LOCK   | Yes
+**
+** If the busy-handler callback returns non-zero, the lock is
+** retried. If it returns zero, then the SQLITE_BUSY error is
+** returned to the caller of the pager API function.
+*/
+void sqlite3PagerSetBusyHandler(
+  Pager *pPager,                       /* Pager object */
+  int (*xBusyHandler)(void *),         /* Pointer to busy-handler function */
+  void *pBusyHandlerArg                /* Argument to pass to xBusyHandler */
+){
+  void **ap;
+  pPager->xBusyHandler = xBusyHandler;
+  pPager->pBusyHandlerArg = pBusyHandlerArg;
+  ap = (void **)&pPager->xBusyHandler;
+  assert( ((int(*)(void *))(ap[0]))==xBusyHandler );
+  assert( ap[1]==pBusyHandlerArg );
+  sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap);
+}
+
+/*
+** Change the page size used by the Pager object. The new page size
+** is passed in *pPageSize.
+**
+** If the pager is in the error state when this function is called, it
+** is a no-op. The value returned is the error state error code (i.e.
+** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL).
+**
+** Otherwise, if all of the following are true:
+**
+**   * the new page size (value of *pPageSize) is valid (a power
+**     of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
+**
+**   * there are no outstanding page references, and
+**
+**   * the database is either not an in-memory database or it is
+**     an in-memory database that currently consists of zero pages.
+**
+** then the pager object page size is set to *pPageSize.
+**
+** If the page size is changed, then this function uses sqlite3PagerMalloc()
+** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt
+** fails, SQLITE_NOMEM is returned and the page size remains unchanged.
+** In all other cases, SQLITE_OK is returned.
+**
+** If the page size is not changed, either because one of the enumerated
+** conditions above is not true, the pager was in error state when this
+** function was called, or because the memory allocation attempt failed,
+** then *pPageSize is set to the old, retained page size before returning.
+*/
+int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){
+  int rc = SQLITE_OK;
+
+  /* It is not possible to do a full assert_pager_state() here, as this
+  ** function may be called from within PagerOpen(), before the state
+  ** of the Pager object is internally consistent.
+  **
+  ** At one point this function returned an error if the pager was in
+  ** PAGER_ERROR state. But since PAGER_ERROR state guarantees that
+  ** there is at least one outstanding page reference, this function
+  ** is a no-op for that case anyhow.
+  */
+
+  u32 pageSize = *pPageSize;
+  assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
+  if( (pPager->memDb==0 || pPager->dbSize==0)
+   && sqlite3PcacheRefCount(pPager->pPCache)==0
+   && pageSize && pageSize!=(u32)pPager->pageSize
+  ){
+    char *pNew = NULL;             /* New temp space */
+    i64 nByte = 0;
+
+    if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){
+      rc = sqlite3OsFileSize(pPager->fd, &nByte);
+    }
+    if( rc==SQLITE_OK ){
+      /* 8 bytes of zeroed overrun space is sufficient so that the b-tree
+      * cell header parser will never run off the end of the allocation */
+      pNew = (char *)sqlite3PageMalloc(pageSize+8);
+      if( !pNew ){
+        rc = SQLITE_NOMEM_BKPT;
+      }else{
+        memset(pNew+pageSize, 0, 8);
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      pager_reset(pPager);
+      rc = sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3PageFree(pPager->pTmpSpace);
+      pPager->pTmpSpace = pNew;
+      pPager->dbSize = (Pgno)((nByte+pageSize-1)/pageSize);
+      pPager->pageSize = pageSize;
+      pPager->lckPgno = (Pgno)(PENDING_BYTE/pageSize) + 1;
+    }else{
+      sqlite3PageFree(pNew);
+    }
+  }
+
+  *pPageSize = pPager->pageSize;
+  if( rc==SQLITE_OK ){
+    if( nReserve<0 ) nReserve = pPager->nReserve;
+    assert( nReserve>=0 && nReserve<1000 );
+    pPager->nReserve = (i16)nReserve;
+    pagerFixMaplimit(pPager);
+  }
+  return rc;
+}
+
+/*
+** Return a pointer to the "temporary page" buffer held internally
+** by the pager.  This is a buffer that is big enough to hold the
+** entire content of a database page.  This buffer is used internally
+** during rollback and will be overwritten whenever a rollback
+** occurs.  But other modules are free to use it too, as long as
+** no rollbacks are happening.
+*/
+void *sqlite3PagerTempSpace(Pager *pPager){
+  return pPager->pTmpSpace;
+}
+
+/*
+** Attempt to set the maximum database page count if mxPage is positive.
+** Make no changes if mxPage is zero or negative.  And never reduce the
+** maximum page count below the current size of the database.
+**
+** Regardless of mxPage, return the current maximum page count.
+*/
+Pgno sqlite3PagerMaxPageCount(Pager *pPager, Pgno mxPage){
+  if( mxPage>0 ){
+    pPager->mxPgno = mxPage;
+  }
+  assert( pPager->eState!=PAGER_OPEN );      /* Called only by OP_MaxPgcnt */
+  /* assert( pPager->mxPgno>=pPager->dbSize ); */
+  /* OP_MaxPgcnt ensures that the parameter passed to this function is not
+  ** less than the total number of valid pages in the database. But this
+  ** may be less than Pager.dbSize, and so the assert() above is not valid */
+  return pPager->mxPgno;
+}
+
+/*
+** The following set of routines are used to disable the simulated
+** I/O error mechanism.  These routines are used to avoid simulated
+** errors in places where we do not care about errors.
+**
+** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
+** and generate no code.
+*/
+#ifdef SQLITE_TEST
+extern int sqlite3_io_error_pending;
+extern int sqlite3_io_error_hit;
+static int saved_cnt;
+void disable_simulated_io_errors(void){
+  saved_cnt = sqlite3_io_error_pending;
+  sqlite3_io_error_pending = -1;
+}
+void enable_simulated_io_errors(void){
+  sqlite3_io_error_pending = saved_cnt;
+}
+#else
+# define disable_simulated_io_errors()
+# define enable_simulated_io_errors()
+#endif
+
+/*
+** Read the first N bytes from the beginning of the file into memory
+** that pDest points to.
+**
+** If the pager was opened on a transient file (zFilename==""), or
+** opened on a file less than N bytes in size, the output buffer is
+** zeroed and SQLITE_OK returned. The rationale for this is that this
+** function is used to read database headers, and a new transient or
+** zero sized database has a header than consists entirely of zeroes.
+**
+** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
+** the error code is returned to the caller and the contents of the
+** output buffer undefined.
+*/
+int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
+  int rc = SQLITE_OK;
+  memset(pDest, 0, N);
+  assert( isOpen(pPager->fd) || pPager->tempFile );
+
+  /* This routine is only called by btree immediately after creating
+  ** the Pager object.  There has not been an opportunity to transition
+  ** to WAL mode yet.
+  */
+  assert( !pagerUseWal(pPager) );
+
+  if( isOpen(pPager->fd) ){
+    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
+    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
+    if( rc==SQLITE_IOERR_SHORT_READ ){
+      rc = SQLITE_OK;
+    }
+  }
+  return rc;
+}
+
+/*
+** This function may only be called when a read-transaction is open on
+** the pager. It returns the total number of pages in the database.
+**
+** However, if the file is between 1 and <page-size> bytes in size, then
+** this is considered a 1 page file.
+*/
+void sqlite3PagerPagecount(Pager *pPager, int *pnPage){
+  assert( pPager->eState>=PAGER_READER );
+  assert( pPager->eState!=PAGER_WRITER_FINISHED );
+  *pnPage = (int)pPager->dbSize;
+}
+
+
+/*
+** Try to obtain a lock of type locktype on the database file. If
+** a similar or greater lock is already held, this function is a no-op
+** (returning SQLITE_OK immediately).
+**
+** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke
+** the busy callback if the lock is currently not available. Repeat
+** until the busy callback returns false or until the attempt to
+** obtain the lock succeeds.
+**
+** Return SQLITE_OK on success and an error code if we cannot obtain
+** the lock. If the lock is obtained successfully, set the Pager.state
+** variable to locktype before returning.
+*/
+static int pager_wait_on_lock(Pager *pPager, int locktype){
+  int rc;                              /* Return code */
+
+  /* Check that this is either a no-op (because the requested lock is
+  ** already held), or one of the transitions that the busy-handler
+  ** may be invoked during, according to the comment above
+  ** sqlite3PagerSetBusyhandler().
+  */
+  assert( (pPager->eLock>=locktype)
+       || (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK)
+       || (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK)
+  );
+
+  do {
+    rc = pagerLockDb(pPager, locktype);
+  }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
+  return rc;
+}
+
+/*
+** Function assertTruncateConstraint(pPager) checks that one of the
+** following is true for all dirty pages currently in the page-cache:
+**
+**   a) The page number is less than or equal to the size of the
+**      current database image, in pages, OR
+**
+**   b) if the page content were written at this time, it would not
+**      be necessary to write the current content out to the sub-journal.
+**
+** If the condition asserted by this function were not true, and the
+** dirty page were to be discarded from the cache via the pagerStress()
+** routine, pagerStress() would not write the current page content to
+** the database file. If a savepoint transaction were rolled back after
+** this happened, the correct behavior would be to restore the current
+** content of the page. However, since this content is not present in either
+** the database file or the portion of the rollback journal and
+** sub-journal rolled back the content could not be restored and the
+** database image would become corrupt. It is therefore fortunate that
+** this circumstance cannot arise.
+*/
+#if defined(SQLITE_DEBUG)
+static void assertTruncateConstraintCb(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  assert( pPg->flags&PGHDR_DIRTY );
+  if( pPg->pgno>pPager->dbSize ){      /* if (a) is false */
+    Pgno pgno = pPg->pgno;
+    int i;
+    for(i=0; i<pPg->pPager->nSavepoint; i++){
+      PagerSavepoint *p = &pPager->aSavepoint[i];
+      assert( p->nOrig<pgno || sqlite3BitvecTestNotNull(p->pInSavepoint,pgno) );
+    }
+  }
+}
+static void assertTruncateConstraint(Pager *pPager){
+  sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb);
+}
+#else
+# define assertTruncateConstraint(pPager)
+#endif
+
+/*
+** Truncate the in-memory database file image to nPage pages. This
+** function does not actually modify the database file on disk. It
+** just sets the internal state of the pager object so that the
+** truncation will be done when the current transaction is committed.
+**
+** This function is only called right before committing a transaction.
+** Once this function has been called, the transaction must either be
+** rolled back or committed. It is not safe to call this function and
+** then continue writing to the database.
+*/
+void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
+  assert( pPager->dbSize>=nPage || CORRUPT_DB );
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
+  pPager->dbSize = nPage;
+
+  /* At one point the code here called assertTruncateConstraint() to
+  ** ensure that all pages being truncated away by this operation are,
+  ** if one or more savepoints are open, present in the savepoint
+  ** journal so that they can be restored if the savepoint is rolled
+  ** back. This is no longer necessary as this function is now only
+  ** called right before committing a transaction. So although the
+  ** Pager object may still have open savepoints (Pager.nSavepoint!=0),
+  ** they cannot be rolled back. So the assertTruncateConstraint() call
+  ** is no longer correct. */
+}
+
+
+/*
+** This function is called before attempting a hot-journal rollback. It
+** syncs the journal file to disk, then sets pPager->journalHdr to the
+** size of the journal file so that the pager_playback() routine knows
+** that the entire journal file has been synced.
+**
+** Syncing a hot-journal to disk before attempting to roll it back ensures
+** that if a power-failure occurs during the rollback, the process that
+** attempts rollback following system recovery sees the same journal
+** content as this process.
+**
+** If everything goes as planned, SQLITE_OK is returned. Otherwise,
+** an SQLite error code.
+*/
+static int pagerSyncHotJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !pPager->noSync ){
+    rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
+  }
+  return rc;
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/*
+** Obtain a reference to a memory mapped page object for page number pgno.
+** The new object will use the pointer pData, obtained from xFetch().
+** If successful, set *ppPage to point to the new page reference
+** and return SQLITE_OK. Otherwise, return an SQLite error code and set
+** *ppPage to zero.
+**
+** Page references obtained by calling this function should be released
+** by calling pagerReleaseMapPage().
+*/
+static int pagerAcquireMapPage(
+  Pager *pPager,                  /* Pager object */
+  Pgno pgno,                      /* Page number */
+  void *pData,                    /* xFetch()'d data for this page */
+  PgHdr **ppPage                  /* OUT: Acquired page object */
+){
+  PgHdr *p;                       /* Memory mapped page to return */
+ 
+  if( pPager->pMmapFreelist ){
+    *ppPage = p = pPager->pMmapFreelist;
+    pPager->pMmapFreelist = p->pDirty;
+    p->pDirty = 0;
+    assert( pPager->nExtra>=8 );
+    memset(p->pExtra, 0, 8);
+  }else{
+    *ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra);
+    if( p==0 ){
+      sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pData);
+      return SQLITE_NOMEM_BKPT;
+    }
+    p->pExtra = (void *)&p[1];
+    p->flags = PGHDR_MMAP;
+    p->nRef = 1;
+    p->pPager = pPager;
+  }
+
+  assert( p->pExtra==(void *)&p[1] );
+  assert( p->pPage==0 );
+  assert( p->flags==PGHDR_MMAP );
+  assert( p->pPager==pPager );
+  assert( p->nRef==1 );
+
+  p->pgno = pgno;
+  p->pData = pData;
+  pPager->nMmapOut++;
+
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Release a reference to page pPg. pPg must have been returned by an
+** earlier call to pagerAcquireMapPage().
+*/
+static void pagerReleaseMapPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  pPager->nMmapOut--;
+  pPg->pDirty = pPager->pMmapFreelist;
+  pPager->pMmapFreelist = pPg;
+
+  assert( pPager->fd->pMethods->iVersion>=3 );
+  sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData);
+}
+
+/*
+** Free all PgHdr objects stored in the Pager.pMmapFreelist list.
+*/
+static void pagerFreeMapHdrs(Pager *pPager){
+  PgHdr *p;
+  PgHdr *pNext;
+  for(p=pPager->pMmapFreelist; p; p=pNext){
+    pNext = p->pDirty;
+    sqlite3_free(p);
+  }
+}
+
+/* Verify that the database file has not be deleted or renamed out from
+** under the pager.  Return SQLITE_OK if the database is still where it ought
+** to be on disk.  Return non-zero (SQLITE_READONLY_DBMOVED or some other error
+** code from sqlite3OsAccess()) if the database has gone missing.
+*/
+static int databaseIsUnmoved(Pager *pPager){
+  int bHasMoved = 0;
+  int rc;
+
+  if( pPager->tempFile ) return SQLITE_OK;
+  if( pPager->dbSize==0 ) return SQLITE_OK;
+  assert( pPager->zFilename && pPager->zFilename[0] );
+  rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_HAS_MOVED, &bHasMoved);
+  if( rc==SQLITE_NOTFOUND ){
+    /* If the HAS_MOVED file-control is unimplemented, assume that the file
+    ** has not been moved.  That is the historical behavior of SQLite: prior to
+    ** version 3.8.3, it never checked */
+    rc = SQLITE_OK;
+  }else if( rc==SQLITE_OK && bHasMoved ){
+    rc = SQLITE_READONLY_DBMOVED;
+  }
+  return rc;
+}
+
+
+/*
+** Shutdown the page cache.  Free all memory and close all files.
+**
+** If a transaction was in progress when this routine is called, that
+** transaction is rolled back.  All outstanding pages are invalidated
+** and their memory is freed.  Any attempt to use a page associated
+** with this page cache after this function returns will likely
+** result in a coredump.
+**
+** This function always succeeds. If a transaction is active an attempt
+** is made to roll it back. If an error occurs during the rollback
+** a hot journal may be left in the filesystem but no error is returned
+** to the caller.
+*/
+int sqlite3PagerClose(Pager *pPager, sqlite3 *db){
+  u8 *pTmp = (u8*)pPager->pTmpSpace;
+  assert( db || pagerUseWal(pPager)==0 );
+  assert( assert_pager_state(pPager) );
+  disable_simulated_io_errors();
+  sqlite3BeginBenignMalloc();
+  pagerFreeMapHdrs(pPager);
+  /* pPager->errCode = 0; */
+  pPager->exclusiveMode = 0;
+#ifndef SQLITE_OMIT_WAL
+  {
+    u8 *a = 0;
+    assert( db || pPager->pWal==0 );
+    if( db && 0==(db->flags & SQLITE_NoCkptOnClose)
+     && SQLITE_OK==databaseIsUnmoved(pPager)
+    ){
+      a = pTmp;
+    }
+    sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags, pPager->pageSize,a);
+    pPager->pWal = 0;
+  }
+#endif
+  pager_reset(pPager);
+  if( MEMDB ){
+    pager_unlock(pPager);
+  }else{
+    /* If it is open, sync the journal file before calling UnlockAndRollback.
+    ** If this is not done, then an unsynced portion of the open journal
+    ** file may be played back into the database. If a power failure occurs
+    ** while this is happening, the database could become corrupt.
+    **
+    ** If an error occurs while trying to sync the journal, shift the pager
+    ** into the ERROR state. This causes UnlockAndRollback to unlock the
+    ** database and close the journal file without attempting to roll it
+    ** back or finalize it. The next database user will have to do hot-journal
+    ** rollback before accessing the database file.
+    */
+    if( isOpen(pPager->jfd) ){
+      pager_error(pPager, pagerSyncHotJournal(pPager));
+    }
+    pagerUnlockAndRollback(pPager);
+  }
+  sqlite3EndBenignMalloc();
+  enable_simulated_io_errors();
+  PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
+  IOTRACE(("CLOSE %p\n", pPager))
+  sqlite3OsClose(pPager->jfd);
+  sqlite3OsClose(pPager->fd);
+  sqlite3PageFree(pTmp);
+  sqlite3PcacheClose(pPager->pPCache);
+  assert( !pPager->aSavepoint && !pPager->pInJournal );
+  assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
+
+  sqlite3_free(pPager);
+  return SQLITE_OK;
+}
+
+#if !defined(NDEBUG) || defined(SQLITE_TEST)
+/*
+** Return the page number for page pPg.
+*/
+Pgno sqlite3PagerPagenumber(DbPage *pPg){
+  return pPg->pgno;
+}
+#endif
+
+/*
+** Increment the reference count for page pPg.
+*/
+void sqlite3PagerRef(DbPage *pPg){
+  sqlite3PcacheRef(pPg);
+}
+
+/*
+** Sync the journal. In other words, make sure all the pages that have
+** been written to the journal have actually reached the surface of the
+** disk and can be restored in the event of a hot-journal rollback.
+**
+** If the Pager.noSync flag is set, then this function is a no-op.
+** Otherwise, the actions required depend on the journal-mode and the
+** device characteristics of the file-system, as follows:
+**
+**   * If the journal file is an in-memory journal file, no action need
+**     be taken.
+**
+**   * Otherwise, if the device does not support the SAFE_APPEND property,
+**     then the nRec field of the most recently written journal header
+**     is updated to contain the number of journal records that have
+**     been written following it. If the pager is operating in full-sync
+**     mode, then the journal file is synced before this field is updated.
+**
+**   * If the device does not support the SEQUENTIAL property, then
+**     journal file is synced.
+**
+** Or, in pseudo-code:
+**
+**   if( NOT <in-memory journal> ){
+**     if( NOT SAFE_APPEND ){
+**       if( <full-sync mode> ) xSync(<journal file>);
+**       <update nRec field>
+**     }
+**     if( NOT SEQUENTIAL ) xSync(<journal file>);
+**   }
+**
+** If successful, this routine clears the PGHDR_NEED_SYNC flag of every
+** page currently held in memory before returning SQLITE_OK. If an IO
+** error is encountered, then the IO error code is returned to the caller.
+*/
+static int syncJournal(Pager *pPager, int newHdr){
+  int rc;                         /* Return code */
+
+  assert( pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+  assert( !pagerUseWal(pPager) );
+
+  rc = sqlite3PagerExclusiveLock(pPager);
+  if( rc!=SQLITE_OK ) return rc;
+
+  if( !pPager->noSync ){
+    assert( !pPager->tempFile );
+    if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
+      const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+      assert( isOpen(pPager->jfd) );
+
+      if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
+        /* This block deals with an obscure problem. If the last connection
+        ** that wrote to this database was operating in persistent-journal
+        ** mode, then the journal file may at this point actually be larger
+        ** than Pager.journalOff bytes. If the next thing in the journal
+        ** file happens to be a journal-header (written as part of the
+        ** previous connection's transaction), and a crash or power-failure
+        ** occurs after nRec is updated but before this connection writes
+        ** anything else to the journal file (or commits/rolls back its
+        ** transaction), then SQLite may become confused when doing the
+        ** hot-journal rollback following recovery. It may roll back all
+        ** of this connections data, then proceed to rolling back the old,
+        ** out-of-date data that follows it. Database corruption.
+        **
+        ** To work around this, if the journal file does appear to contain
+        ** a valid header following Pager.journalOff, then write a 0x00
+        ** byte to the start of it to prevent it from being recognized.
+        **
+        ** Variable iNextHdrOffset is set to the offset at which this
+        ** problematic header will occur, if it exists. aMagic is used
+        ** as a temporary buffer to inspect the first couple of bytes of
+        ** the potential journal header.
+        */
+        i64 iNextHdrOffset;
+        u8 aMagic[8];
+        u8 zHeader[sizeof(aJournalMagic)+4];
+
+        memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+        put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
+
+        iNextHdrOffset = journalHdrOffset(pPager);
+        rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
+        if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
+          static const u8 zerobyte = 0;
+          rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
+        }
+        if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
+          return rc;
+        }
+
+        /* Write the nRec value into the journal file header. If in
+        ** full-synchronous mode, sync the journal first. This ensures that
+        ** all data has really hit the disk before nRec is updated to mark
+        ** it as a candidate for rollback.
+        **
+        ** This is not required if the persistent media supports the
+        ** SAFE_APPEND property. Because in this case it is not possible
+        ** for garbage data to be appended to the file, the nRec field
+        ** is populated with 0xFFFFFFFF when the journal header is written
+        ** and never needs to be updated.
+        */
+        if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+          PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
+          IOTRACE(("JSYNC %p\n", pPager))
+          rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
+          if( rc!=SQLITE_OK ) return rc;
+        }
+        IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
+        rc = sqlite3OsWrite(
+            pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
+        );
+        if( rc!=SQLITE_OK ) return rc;
+      }
+      if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+        PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
+        IOTRACE(("JSYNC %p\n", pPager))
+        rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags|
+          (pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
+        );
+        if( rc!=SQLITE_OK ) return rc;
+      }
+
+      pPager->journalHdr = pPager->journalOff;
+      if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
+        pPager->nRec = 0;
+        rc = writeJournalHdr(pPager);
+        if( rc!=SQLITE_OK ) return rc;
+      }
+    }else{
+      pPager->journalHdr = pPager->journalOff;
+    }
+  }
+
+  /* Unless the pager is in noSync mode, the journal file was just
+  ** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on
+  ** all pages.
+  */
+  sqlite3PcacheClearSyncFlags(pPager->pPCache);
+  pPager->eState = PAGER_WRITER_DBMOD;
+  assert( assert_pager_state(pPager) );
+  return SQLITE_OK;
+}
+
+/*
+** The argument is the first in a linked list of dirty pages connected
+** by the PgHdr.pDirty pointer. This function writes each one of the
+** in-memory pages in the list to the database file. The argument may
+** be NULL, representing an empty list. In this case this function is
+** a no-op.
+**
+** The pager must hold at least a RESERVED lock when this function
+** is called. Before writing anything to the database file, this lock
+** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
+** SQLITE_BUSY is returned and no data is written to the database file.
+**
+** If the pager is a temp-file pager and the actual file-system file
+** is not yet open, it is created and opened before any data is
+** written out.
+**
+** Once the lock has been upgraded and, if necessary, the file opened,
+** the pages are written out to the database file in list order. Writing
+** a page is skipped if it meets either of the following criteria:
+**
+**   * The page number is greater than Pager.dbSize, or
+**   * The PGHDR_DONT_WRITE flag is set on the page.
+**
+** If writing out a page causes the database file to grow, Pager.dbFileSize
+** is updated accordingly. If page 1 is written out, then the value cached
+** in Pager.dbFileVers[] is updated to match the new value stored in
+** the database file.
+**
+** If everything is successful, SQLITE_OK is returned. If an IO error
+** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
+** be obtained, SQLITE_BUSY is returned.
+*/
+static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
+  int rc = SQLITE_OK;                  /* Return code */
+
+  /* This function is only called for rollback pagers in WRITER_DBMOD state. */
+  assert( !pagerUseWal(pPager) );
+  assert( pPager->tempFile || pPager->eState==PAGER_WRITER_DBMOD );
+  assert( pPager->eLock==EXCLUSIVE_LOCK );
+  assert( isOpen(pPager->fd) || pList->pDirty==0 );
+
+  /* If the file is a temp-file has not yet been opened, open it now. It
+  ** is not possible for rc to be other than SQLITE_OK if this branch
+  ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
+  */
+  if( !isOpen(pPager->fd) ){
+    assert( pPager->tempFile && rc==SQLITE_OK );
+    rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
+  }
+
+  /* Before the first write, give the VFS a hint of what the final
+  ** file size will be.
+  */
+  assert( rc!=SQLITE_OK || isOpen(pPager->fd) );
+  if( rc==SQLITE_OK
+   && pPager->dbHintSize<pPager->dbSize
+   && (pList->pDirty || pList->pgno>pPager->dbHintSize)
+  ){
+    sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
+    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
+    pPager->dbHintSize = pPager->dbSize;
+  }
+
+  while( rc==SQLITE_OK && pList ){
+    Pgno pgno = pList->pgno;
+
+    /* If there are dirty pages in the page cache with page numbers greater
+    ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
+    ** make the file smaller (presumably by auto-vacuum code). Do not write
+    ** any such pages to the file.
+    **
+    ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
+    ** set (set by sqlite3PagerDontWrite()).
+    */
+    if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
+      i64 offset = (pgno-1)*(i64)pPager->pageSize;   /* Offset to write */
+      char *pData;                                   /* Data to write */   
+
+      assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
+      if( pList->pgno==1 ) pager_write_changecounter(pList);
+
+      pData = pList->pData;
+
+      /* Write out the page data. */
+      rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
+
+      /* If page 1 was just written, update Pager.dbFileVers to match
+      ** the value now stored in the database file. If writing this
+      ** page caused the database file to grow, update dbFileSize.
+      */
+      if( pgno==1 ){
+        memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
+      }
+      if( pgno>pPager->dbFileSize ){
+        pPager->dbFileSize = pgno;
+      }
+      pPager->aStat[PAGER_STAT_WRITE]++;
+
+      /* Update any backup objects copying the contents of this pager. */
+      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData);
+
+      PAGERTRACE(("STORE %d page %d hash(%08x)\n",
+                   PAGERID(pPager), pgno, pager_pagehash(pList)));
+      IOTRACE(("PGOUT %p %d\n", pPager, pgno));
+      PAGER_INCR(sqlite3_pager_writedb_count);
+    }else{
+      PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
+    }
+    pager_set_pagehash(pList);
+    pList = pList->pDirty;
+  }
+
+  return rc;
+}
+
+/*
+** Ensure that the sub-journal file is open. If it is already open, this
+** function is a no-op.
+**
+** SQLITE_OK is returned if everything goes according to plan. An
+** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen()
+** fails.
+*/
+static int openSubJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !isOpen(pPager->sjfd) ){
+    const int flags =  SQLITE_OPEN_SUBJOURNAL | SQLITE_OPEN_READWRITE
+      | SQLITE_OPEN_CREATE | SQLITE_OPEN_EXCLUSIVE
+      | SQLITE_OPEN_DELETEONCLOSE;
+    int nStmtSpill = sqlite3Config.nStmtSpill;
+    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
+      nStmtSpill = -1;
+    }
+    rc = sqlite3JournalOpen(pPager->pVfs, 0, pPager->sjfd, flags, nStmtSpill);
+  }
+  return rc;
+}
+
+/*
+** Append a record of the current state of page pPg to the sub-journal.
+**
+** If successful, set the bit corresponding to pPg->pgno in the bitvecs
+** for all open savepoints before returning.
+**
+** This function returns SQLITE_OK if everything is successful, an IO
+** error code if the attempt to write to the sub-journal fails, or
+** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
+** bitvec.
+*/
+static int subjournalPage(PgHdr *pPg){
+  int rc = SQLITE_OK;
+  Pager *pPager = pPg->pPager;
+  if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+
+    /* Open the sub-journal, if it has not already been opened */
+    assert( pPager->useJournal );
+    assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
+    assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
+    assert( pagerUseWal(pPager)
+         || pageInJournal(pPager, pPg)
+         || pPg->pgno>pPager->dbOrigSize
+    );
+    rc = openSubJournal(pPager);
+
+    /* If the sub-journal was opened successfully (or was already open),
+    ** write the journal record into the file.  */
+    if( rc==SQLITE_OK ){
+      void *pData = pPg->pData;
+      i64 offset = (i64)pPager->nSubRec*(4+pPager->pageSize);
+      char *pData2;
+      pData2 = pData;
+      PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
+      rc = write32bits(pPager->sjfd, offset, pPg->pgno);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
+      }
+    }
+  }
+  if( rc==SQLITE_OK ){
+    pPager->nSubRec++;
+    assert( pPager->nSavepoint>0 );
+    rc = addToSavepointBitvecs(pPager, pPg->pgno);
+  }
+  return rc;
+}
+static int subjournalPageIfRequired(PgHdr *pPg){
+  if( subjRequiresPage(pPg) ){
+    return subjournalPage(pPg);
+  }else{
+    return SQLITE_OK;
+  }
+}
+
+/*
+** This function is called by the pcache layer when it has reached some
+** soft memory limit. The first argument is a pointer to a Pager object
+** (cast as a void*). The pager is always 'purgeable' (not an in-memory
+** database). The second argument is a reference to a page that is
+** currently dirty but has no outstanding references. The page
+** is always associated with the Pager object passed as the first
+** argument.
+**
+** The job of this function is to make pPg clean by writing its contents
+** out to the database file, if possible. This may involve syncing the
+** journal file.
+**
+** If successful, sqlite3PcacheMakeClean() is called on the page and
+** SQLITE_OK returned. If an IO error occurs while trying to make the
+** page clean, the IO error code is returned. If the page cannot be
+** made clean for some other reason, but no error occurs, then SQLITE_OK
+** is returned by sqlite3PcacheMakeClean() is not called.
+*/
+static int pagerStress(void *p, PgHdr *pPg){
+  Pager *pPager = (Pager *)p;
+  int rc = SQLITE_OK;
+
+  assert( pPg->pPager==pPager );
+  assert( pPg->flags&PGHDR_DIRTY );
+
+  /* The doNotSpill NOSYNC bit is set during times when doing a sync of
+  ** journal (and adding a new header) is not allowed.  This occurs
+  ** during calls to sqlite3PagerWrite() while trying to journal multiple
+  ** pages belonging to the same sector.
+  **
+  ** The doNotSpill ROLLBACK and OFF bits inhibits all cache spilling
+  ** regardless of whether or not a sync is required.  This is set during
+  ** a rollback or by user request, respectively.
+  **
+  ** Spilling is also prohibited when in an error state since that could
+  ** lead to database corruption.   In the current implementation it
+  ** is impossible for sqlite3PcacheFetch() to be called with createFlag==3
+  ** while in the error state, hence it is impossible for this routine to
+  ** be called in the error state.  Nevertheless, we include a NEVER()
+  ** test for the error state as a safeguard against future changes.
+  */
+  if( NEVER(pPager->errCode) ) return SQLITE_OK;
+  testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK );
+  testcase( pPager->doNotSpill & SPILLFLAG_OFF );
+  testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC );
+  if( pPager->doNotSpill
+   && ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0
+      || (pPg->flags & PGHDR_NEED_SYNC)!=0)
+  ){
+    return SQLITE_OK;
+  }
+
+  pPager->aStat[PAGER_STAT_SPILL]++;
+  pPg->pDirty = 0;
+  if( pagerUseWal(pPager) ){
+    /* Write a single frame for this page to the log. */
+    rc = subjournalPageIfRequired(pPg);
+    if( rc==SQLITE_OK ){
+      rc = pagerWalFrames(pPager, pPg, 0, 0);
+    }
+  }else{
+   
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+    if( pPager->tempFile==0 ){
+      rc = sqlite3JournalCreate(pPager->jfd);
+      if( rc!=SQLITE_OK ) return pager_error(pPager, rc);
+    }
+#endif
+ 
+    /* Sync the journal file if required. */
+    if( pPg->flags&PGHDR_NEED_SYNC
+     || pPager->eState==PAGER_WRITER_CACHEMOD
+    ){
+      rc = syncJournal(pPager, 1);
+    }
+ 
+    /* Write the contents of the page out to the database file. */
+    if( rc==SQLITE_OK ){
+      assert( (pPg->flags&PGHDR_NEED_SYNC)==0 );
+      rc = pager_write_pagelist(pPager, pPg);
+    }
+  }
+
+  /* Mark the page as clean. */
+  if( rc==SQLITE_OK ){
+    PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
+    sqlite3PcacheMakeClean(pPg);
+  }
+
+  return pager_error(pPager, rc);
+}
+
+/*
+** Flush all unreferenced dirty pages to disk.
+*/
+int sqlite3PagerFlush(Pager *pPager){
+  int rc = pPager->errCode;
+  if( !MEMDB ){
+    PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache);
+    assert( assert_pager_state(pPager) );
+    while( rc==SQLITE_OK && pList ){
+      PgHdr *pNext = pList->pDirty;
+      if( pList->nRef==0 ){
+        rc = pagerStress((void*)pPager, pList);
+      }
+      pList = pNext;
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Allocate and initialize a new Pager object and put a pointer to it
+** in *ppPager. The pager should eventually be freed by passing it
+** to sqlite3PagerClose().
+**
+** The zFilename argument is the path to the database file to open.
+** If zFilename is NULL then a randomly-named temporary file is created
+** and used as the file to be cached. Temporary files are be deleted
+** automatically when they are closed. If zFilename is ":memory:" then
+** all information is held in cache. It is never written to disk.
+** This can be used to implement an in-memory database.
+**
+** The nExtra parameter specifies the number of bytes of space allocated
+** along with each page reference. This space is available to the user
+** via the sqlite3PagerGetExtra() API.  When a new page is allocated, the
+** first 8 bytes of this space are zeroed but the remainder is uninitialized.
+** (The extra space is used by btree as the MemPage object.)
+**
+** The flags argument is used to specify properties that affect the
+** operation of the pager. It should be passed some bitwise combination
+** of the PAGER_* flags.
+**
+** The vfsFlags parameter is a bitmask to pass to the flags parameter
+** of the xOpen() method of the supplied VFS when opening files.
+**
+** If the pager object is allocated and the specified file opened
+** successfully, SQLITE_OK is returned and *ppPager set to point to
+** the new pager object. If an error occurs, *ppPager is set to NULL
+** and error code returned. This function may return SQLITE_NOMEM
+** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or
+** various SQLITE_IO_XXX errors.
+*/
+int sqlite3PagerOpen(
+  sqlite3_vfs *pVfs,       /* The virtual file system to use */
+  Pager **ppPager,         /* OUT: Return the Pager structure here */
+  const char *zFilename,   /* Name of the database file to open */
+  int nExtra,              /* Extra bytes append to each in-memory page */
+  int flags,               /* flags controlling this file */
+  int vfsFlags,            /* flags passed through to sqlite3_vfs.xOpen() */
+  void (*xReinit)(DbPage*) /* Function to reinitialize pages */
+){
+  u8 *pPtr;
+  Pager *pPager = 0;       /* Pager object to allocate and return */
+  int rc = SQLITE_OK;      /* Return code */
+  int tempFile = 0;        /* True for temp files (incl. in-memory files) */
+  int memDb = 0;           /* True if this is an in-memory file */
+  int memJM = 0;           /* Memory journal mode */
+  int readOnly = 0;        /* True if this is a read-only file */
+  int journalFileSize;     /* Bytes to allocate for each journal fd */
+  char *zPathname = 0;     /* Full path to database file */
+  int nPathname = 0;       /* Number of bytes in zPathname */
+  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
+  int pcacheSize = sqlite3PcacheSize();       /* Bytes to allocate for PCache */
+  u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;  /* Default page size */
+  const char *zUri = 0;    /* URI args to copy */
+  int nUriByte = 1;        /* Number of bytes of URI args at *zUri */
+
+  /* Figure out how much space is required for each journal file-handle
+  ** (there are two of them, the main journal and the sub-journal).  */
+  journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
+
+  /* Set the output variable to NULL in case an error occurs. */
+  *ppPager = 0;
+
+#ifndef SQLITE_OMIT_MEMORYDB
+  if( flags & PAGER_MEMORY ){
+    memDb = 1;
+    if( zFilename && zFilename[0] ){
+      zPathname = sqlite3DbStrDup(0, zFilename);
+      if( zPathname==0  ) return SQLITE_NOMEM_BKPT;
+      nPathname = sqlite3Strlen30(zPathname);
+      zFilename = 0;
+    }
+  }
+#endif
+
+  /* Compute and store the full pathname in an allocated buffer pointed
+  ** to by zPathname, length nPathname. Or, if this is a temporary file,
+  ** leave both nPathname and zPathname set to 0.
+  */
+  if( zFilename && zFilename[0] ){
+    const char *z;
+    nPathname = pVfs->mxPathname+1;
+    zPathname = sqlite3DbMallocRaw(0, nPathname*2);
+    if( zPathname==0 ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
+    rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_OK_SYMLINK ){
+        if( vfsFlags & SQLITE_OPEN_NOFOLLOW ){
+          rc = SQLITE_CANTOPEN_SYMLINK;
+        }else{
+          rc = SQLITE_OK;
+        }
+      }
+    }
+    nPathname = sqlite3Strlen30(zPathname);
+    z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1];
+    while( *z ){
+      z += strlen(z)+1;
+      z += strlen(z)+1;
+    }
+    nUriByte = (int)(&z[1] - zUri);
+    assert( nUriByte>=1 );
+    if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
+      /* This branch is taken when the journal path required by
+      ** the database being opened will be more than pVfs->mxPathname
+      ** bytes in length. This means the database cannot be opened,
+      ** as it will not be possible to open the journal file or even
+      ** check for a hot-journal before reading.
+      */
+      rc = SQLITE_CANTOPEN_BKPT;
+    }
+    if( rc!=SQLITE_OK ){
+      sqlite3DbFree(0, zPathname);
+      return rc;
+    }
+  }
+
+  /* Allocate memory for the Pager structure, PCache object, the
+  ** three file descriptors, the database file name and the journal
+  ** file name. The layout in memory is as follows:
+  **
+  **     Pager object                    (sizeof(Pager) bytes)
+  **     PCache object                   (sqlite3PcacheSize() bytes)
+  **     Database file handle            (pVfs->szOsFile bytes)
+  **     Sub-journal file handle         (journalFileSize bytes)
+  **     Main journal file handle        (journalFileSize bytes)
+  **     Ptr back to the Pager           (sizeof(Pager*) bytes)
+  **     \0\0\0\0 database prefix        (4 bytes)
+  **     Database file name              (nPathname+1 bytes)
+  **     URI query parameters            (nUriByte bytes)
+  **     Journal filename                (nPathname+8+1 bytes)
+  **     WAL filename                    (nPathname+4+1 bytes)
+  **     \0\0\0 terminator               (3 bytes)
+  **
+  ** Some 3rd-party software, over which we have no control, depends on
+  ** the specific order of the filenames and the \0 separators between them
+  ** so that it can (for example) find the database filename given the WAL
+  ** filename without using the sqlite3_filename_database() API.  This is a
+  ** misuse of SQLite and a bug in the 3rd-party software, but the 3rd-party
+  ** software is in widespread use, so we try to avoid changing the filename
+  ** order and formatting if possible.  In particular, the details of the
+  ** filename format expected by 3rd-party software should be as follows:
+  **
+  **   - Main Database Path
+  **   - \0
+  **   - Multiple URI components consisting of:
+  **     - Key
+  **     - \0
+  **     - Value
+  **     - \0
+  **   - \0
+  **   - Journal Path
+  **   - \0
+  **   - WAL Path (zWALName)
+  **   - \0
+  **
+  ** The sqlite3_create_filename() interface and the databaseFilename() utility
+  ** that is used by sqlite3_filename_database() and kin also depend on the
+  ** specific formatting and order of the various filenames, so if the format
+  ** changes here, be sure to change it there as well.
+  */
+  assert( SQLITE_PTRSIZE==sizeof(Pager*) );
+  pPtr = (u8 *)sqlite3MallocZero(
+    ROUND8(sizeof(*pPager)) +            /* Pager structure */
+    ROUND8(pcacheSize) +                 /* PCache object */
+    ROUND8(pVfs->szOsFile) +             /* The main db file */
+    journalFileSize * 2 +                /* The two journal files */
+    SQLITE_PTRSIZE +                     /* Space to hold a pointer */
+    4 +                                  /* Database prefix */
+    nPathname + 1 +                      /* database filename */
+    nUriByte +                           /* query parameters */
+    nPathname + 8 + 1 +                  /* Journal filename */
+#ifndef SQLITE_OMIT_WAL
+    nPathname + 4 + 1 +                  /* WAL filename */
+#endif
+    3                                    /* Terminator */
+  );
+  assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
+  if( !pPtr ){
+    sqlite3DbFree(0, zPathname);
+    return SQLITE_NOMEM_BKPT;
+  }
+  pPager = (Pager*)pPtr;                  pPtr += ROUND8(sizeof(*pPager));
+  pPager->pPCache = (PCache*)pPtr;        pPtr += ROUND8(pcacheSize);
+  pPager->fd = (sqlite3_file*)pPtr;       pPtr += ROUND8(pVfs->szOsFile);
+  pPager->sjfd = (sqlite3_file*)pPtr;     pPtr += journalFileSize;
+  pPager->jfd =  (sqlite3_file*)pPtr;     pPtr += journalFileSize;
+  assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
+  memcpy(pPtr, &pPager, SQLITE_PTRSIZE);  pPtr += SQLITE_PTRSIZE;
+
+  /* Fill in the Pager.zFilename and pPager.zQueryParam fields */
+                                          pPtr += 4;  /* Skip zero prefix */
+  pPager->zFilename = (char*)pPtr;
+  if( nPathname>0 ){
+    memcpy(pPtr, zPathname, nPathname);   pPtr += nPathname + 1;
+    if( zUri ){
+      memcpy(pPtr, zUri, nUriByte);       pPtr += nUriByte;
+    }else{
+                                          pPtr++;
+    }
+  }
+
+
+  /* Fill in Pager.zJournal */
+  if( nPathname>0 ){
+    pPager->zJournal = (char*)pPtr;
+    memcpy(pPtr, zPathname, nPathname);   pPtr += nPathname;
+    memcpy(pPtr, "-journal",8);           pPtr += 8 + 1;
+#ifdef SQLITE_ENABLE_8_3_NAMES
+    sqlite3FileSuffix3(zFilename,pPager->zJournal);
+    pPtr = (u8*)(pPager->zJournal + sqlite3Strlen30(pPager->zJournal)+1);
+#endif
+  }else{
+    pPager->zJournal = 0;
+  }
+
+#ifndef SQLITE_OMIT_WAL
+  /* Fill in Pager.zWal */
+  if( nPathname>0 ){
+    pPager->zWal = (char*)pPtr;
+    memcpy(pPtr, zPathname, nPathname);   pPtr += nPathname;
+    memcpy(pPtr, "-wal", 4);              pPtr += 4 + 1;
+#ifdef SQLITE_ENABLE_8_3_NAMES
+    sqlite3FileSuffix3(zFilename, pPager->zWal);
+    pPtr = (u8*)(pPager->zWal + sqlite3Strlen30(pPager->zWal)+1);
+#endif
+  }else{
+    pPager->zWal = 0;
+  }
+#endif
+  (void)pPtr;  /* Suppress warning about unused pPtr value */
+
+  if( nPathname ) sqlite3DbFree(0, zPathname);
+  pPager->pVfs = pVfs;
+  pPager->vfsFlags = vfsFlags;
+
+  /* Open the pager file.
+  */
+  if( zFilename && zFilename[0] ){
+    int fout = 0;                    /* VFS flags returned by xOpen() */
+    rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
+    assert( !memDb );
+    pPager->memVfs = memJM = (fout&SQLITE_OPEN_MEMORY)!=0;
+    readOnly = (fout&SQLITE_OPEN_READONLY)!=0;
+
+    /* If the file was successfully opened for read/write access,
+    ** choose a default page size in case we have to create the
+    ** database file. The default page size is the maximum of:
+    **
+    **    + SQLITE_DEFAULT_PAGE_SIZE,
+    **    + The value returned by sqlite3OsSectorSize()
+    **    + The largest page size that can be written atomically.
+    */
+    if( rc==SQLITE_OK ){
+      int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+      if( !readOnly ){
+        setSectorSize(pPager);
+        assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE);
+        if( szPageDflt<pPager->sectorSize ){
+          if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
+            szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
+          }else{
+            szPageDflt = (u32)pPager->sectorSize;
+          }
+        }
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+        {
+          int ii;
+          assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+          assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+          assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
+          for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
+            if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
+              szPageDflt = ii;
+            }
+          }
+        }
+#endif
+      }
+      pPager->noLock = sqlite3_uri_boolean(pPager->zFilename, "nolock", 0);
+      if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0
+       || sqlite3_uri_boolean(pPager->zFilename, "immutable", 0) ){
+          vfsFlags |= SQLITE_OPEN_READONLY;
+          goto act_like_temp_file;
+      }
+    }
+  }else{
+    /* If a temporary file is requested, it is not opened immediately.
+    ** In this case we accept the default page size and delay actually
+    ** opening the file until the first call to OsWrite().
+    **
+    ** This branch is also run for an in-memory database. An in-memory
+    ** database is the same as a temp-file that is never written out to
+    ** disk and uses an in-memory rollback journal.
+    **
+    ** This branch also runs for files marked as immutable.
+    */
+act_like_temp_file:
+    tempFile = 1;
+    pPager->eState = PAGER_READER;     /* Pretend we already have a lock */
+    pPager->eLock = EXCLUSIVE_LOCK;    /* Pretend we are in EXCLUSIVE mode */
+    pPager->noLock = 1;                /* Do no locking */
+    readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
+  }
+
+  /* The following call to PagerSetPagesize() serves to set the value of
+  ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
+  */
+  if( rc==SQLITE_OK ){
+    assert( pPager->memDb==0 );
+    rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1);
+    testcase( rc!=SQLITE_OK );
+  }
+
+  /* Initialize the PCache object. */
+  if( rc==SQLITE_OK ){
+    nExtra = ROUND8(nExtra);
+    assert( nExtra>=8 && nExtra<1000 );
+    rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
+                       !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
+  }
+
+  /* If an error occurred above, free the  Pager structure and close the file.
+  */
+  if( rc!=SQLITE_OK ){
+    sqlite3OsClose(pPager->fd);
+    sqlite3PageFree(pPager->pTmpSpace);
+    sqlite3_free(pPager);
+    return rc;
+  }
+
+  PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
+  IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
+
+  pPager->useJournal = (u8)useJournal;
+  /* pPager->stmtOpen = 0; */
+  /* pPager->stmtInUse = 0; */
+  /* pPager->nRef = 0; */
+  /* pPager->stmtSize = 0; */
+  /* pPager->stmtJSize = 0; */
+  /* pPager->nPage = 0; */
+  pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
+  /* pPager->state = PAGER_UNLOCK; */
+  /* pPager->errMask = 0; */
+  pPager->tempFile = (u8)tempFile;
+  assert( tempFile==PAGER_LOCKINGMODE_NORMAL
+          || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
+  assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
+  pPager->exclusiveMode = (u8)tempFile;
+  pPager->changeCountDone = pPager->tempFile;
+  pPager->memDb = (u8)memDb;
+  pPager->readOnly = (u8)readOnly;
+  assert( useJournal || pPager->tempFile );
+  sqlite3PagerSetFlags(pPager, (SQLITE_DEFAULT_SYNCHRONOUS+1)|PAGER_CACHESPILL);
+  /* pPager->pFirst = 0; */
+  /* pPager->pFirstSynced = 0; */
+  /* pPager->pLast = 0; */
+  pPager->nExtra = (u16)nExtra;
+  pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
+  assert( isOpen(pPager->fd) || tempFile );
+  setSectorSize(pPager);
+  if( !useJournal ){
+    pPager->journalMode = PAGER_JOURNALMODE_OFF;
+  }else if( memDb || memJM ){
+    pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
+  }
+  /* pPager->xBusyHandler = 0; */
+  /* pPager->pBusyHandlerArg = 0; */
+  pPager->xReiniter = xReinit;
+  setGetterMethod(pPager);
+  /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
+  /* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */
+
+  *ppPager = pPager;
+  return SQLITE_OK;
+}
+
+/*
+** Return the sqlite3_file for the main database given the name
+** of the corresponding WAL or Journal name as passed into
+** xOpen.
+*/
+sqlite3_file *sqlite3_database_file_object(const char *zName){
+  Pager *pPager;
+  const char *p;
+  while( zName[-1]!=0 || zName[-2]!=0 || zName[-3]!=0 || zName[-4]!=0 ){
+    zName--;
+  }
+  p = zName - 4 - sizeof(Pager*);
+  assert( EIGHT_BYTE_ALIGNMENT(p) );
+  pPager = *(Pager**)p;
+  return pPager->fd;
+}
+
+
+/*
+** This function is called after transitioning from PAGER_UNLOCK to
+** PAGER_SHARED state. It tests if there is a hot journal present in
+** the file-system for the given pager. A hot journal is one that
+** needs to be played back. According to this function, a hot-journal
+** file exists if the following criteria are met:
+**
+**   * The journal file exists in the file system, and
+**   * No process holds a RESERVED or greater lock on the database file, and
+**   * The database file itself is greater than 0 bytes in size, and
+**   * The first byte of the journal file exists and is not 0x00.
+**
+** If the current size of the database file is 0 but a journal file
+** exists, that is probably an old journal left over from a prior
+** database with the same name. In this case the journal file is
+** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
+** is returned.
+**
+** This routine does not check if there is a super-journal filename
+** at the end of the file. If there is, and that super-journal file
+** does not exist, then the journal file is not really hot. In this
+** case this routine will return a false-positive. The pager_playback()
+** routine will discover that the journal file is not really hot and
+** will not roll it back.
+**
+** If a hot-journal file is found to exist, *pExists is set to 1 and
+** SQLITE_OK returned. If no hot-journal file is present, *pExists is
+** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
+** to determine whether or not a hot-journal file exists, the IO error
+** code is returned and the value of *pExists is undefined.
+*/
+static int hasHotJournal(Pager *pPager, int *pExists){
+  sqlite3_vfs * const pVfs = pPager->pVfs;
+  int rc = SQLITE_OK;           /* Return code */
+  int exists = 1;               /* True if a journal file is present */
+  int jrnlOpen = !!isOpen(pPager->jfd);
+
+  assert( pPager->useJournal );
+  assert( isOpen(pPager->fd) );
+  assert( pPager->eState==PAGER_OPEN );
+
+  assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
+    SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
+  ));
+
+  *pExists = 0;
+  if( !jrnlOpen ){
+    rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
+  }
+  if( rc==SQLITE_OK && exists ){
+    int locked = 0;             /* True if some process holds a RESERVED lock */
+
+    /* Race condition here:  Another process might have been holding the
+    ** the RESERVED lock and have a journal open at the sqlite3OsAccess()
+    ** call above, but then delete the journal and drop the lock before
+    ** we get to the following sqlite3OsCheckReservedLock() call.  If that
+    ** is the case, this routine might think there is a hot journal when
+    ** in fact there is none.  This results in a false-positive which will
+    ** be dealt with by the playback routine.  Ticket #3883.
+    */
+    rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
+    if( rc==SQLITE_OK && !locked ){
+      Pgno nPage;                 /* Number of pages in database file */
+
+      assert( pPager->tempFile==0 );
+      rc = pagerPagecount(pPager, &nPage);
+      if( rc==SQLITE_OK ){
+        /* If the database is zero pages in size, that means that either (1) the
+        ** journal is a remnant from a prior database with the same name where
+        ** the database file but not the journal was deleted, or (2) the initial
+        ** transaction that populates a new database is being rolled back.
+        ** In either case, the journal file can be deleted.  However, take care
+        ** not to delete the journal file if it is already open due to
+        ** journal_mode=PERSIST.
+        */
+        if( nPage==0 && !jrnlOpen ){
+          sqlite3BeginBenignMalloc();
+          if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){
+            sqlite3OsDelete(pVfs, pPager->zJournal, 0);
+            if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
+          }
+          sqlite3EndBenignMalloc();
+        }else{
+          /* The journal file exists and no other connection has a reserved
+          ** or greater lock on the database file. Now check that there is
+          ** at least one non-zero bytes at the start of the journal file.
+          ** If there is, then we consider this journal to be hot. If not,
+          ** it can be ignored.
+          */
+          if( !jrnlOpen ){
+            int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
+            rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
+          }
+          if( rc==SQLITE_OK ){
+            u8 first = 0;
+            rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
+            if( rc==SQLITE_IOERR_SHORT_READ ){
+              rc = SQLITE_OK;
+            }
+            if( !jrnlOpen ){
+              sqlite3OsClose(pPager->jfd);
+            }
+            *pExists = (first!=0);
+          }else if( rc==SQLITE_CANTOPEN ){
+            /* If we cannot open the rollback journal file in order to see if
+            ** it has a zero header, that might be due to an I/O error, or
+            ** it might be due to the race condition described above and in
+            ** ticket #3883.  Either way, assume that the journal is hot.
+            ** This might be a false positive.  But if it is, then the
+            ** automatic journal playback and recovery mechanism will deal
+            ** with it under an EXCLUSIVE lock where we do not need to
+            ** worry so much with race conditions.
+            */
+            *pExists = 1;
+            rc = SQLITE_OK;
+          }
+        }
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to obtain a shared lock on the database file.
+** It is illegal to call sqlite3PagerGet() until after this function
+** has been successfully called. If a shared-lock is already held when
+** this function is called, it is a no-op.
+**
+** The following operations are also performed by this function.
+**
+**   1) If the pager is currently in PAGER_OPEN state (no lock held
+**      on the database file), then an attempt is made to obtain a
+**      SHARED lock on the database file. Immediately after obtaining
+**      the SHARED lock, the file-system is checked for a hot-journal,
+**      which is played back if present. Following any hot-journal
+**      rollback, the contents of the cache are validated by checking
+**      the 'change-counter' field of the database file header and
+**      discarded if they are found to be invalid.
+**
+**   2) If the pager is running in exclusive-mode, and there are currently
+**      no outstanding references to any pages, and is in the error state,
+**      then an attempt is made to clear the error state by discarding
+**      the contents of the page cache and rolling back any open journal
+**      file.
+**
+** If everything is successful, SQLITE_OK is returned. If an IO error
+** occurs while locking the database, checking for a hot-journal file or
+** rolling back a journal file, the IO error code is returned.
+*/
+int sqlite3PagerSharedLock(Pager *pPager){
+  int rc = SQLITE_OK;                /* Return code */
+
+  /* This routine is only called from b-tree and only when there are no
+  ** outstanding pages. This implies that the pager state should either
+  ** be OPEN or READER. READER is only possible if the pager is or was in
+  ** exclusive access mode.  */
+  assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
+  assert( pPager->errCode==SQLITE_OK );
+
+  if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){
+    int bHotJournal = 1;          /* True if there exists a hot journal-file */
+
+    assert( !MEMDB );
+    assert( pPager->tempFile==0 || pPager->eLock==EXCLUSIVE_LOCK );
+
+    rc = pager_wait_on_lock(pPager, SHARED_LOCK);
+    if( rc!=SQLITE_OK ){
+      assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
+      goto failed;
+    }
+
+    /* If a journal file exists, and there is no RESERVED lock on the
+    ** database file, then it either needs to be played back or deleted.
+    */
+    if( pPager->eLock<=SHARED_LOCK ){
+      rc = hasHotJournal(pPager, &bHotJournal);
+    }
+    if( rc!=SQLITE_OK ){
+      goto failed;
+    }
+    if( bHotJournal ){
+      if( pPager->readOnly ){
+        rc = SQLITE_READONLY_ROLLBACK;
+        goto failed;
+      }
+
+      /* Get an EXCLUSIVE lock on the database file. At this point it is
+      ** important that a RESERVED lock is not obtained on the way to the
+      ** EXCLUSIVE lock. If it were, another process might open the
+      ** database file, detect the RESERVED lock, and conclude that the
+      ** database is safe to read while this process is still rolling the
+      ** hot-journal back.
+      **
+      ** Because the intermediate RESERVED lock is not requested, any
+      ** other process attempting to access the database file will get to
+      ** this point in the code and fail to obtain its own EXCLUSIVE lock
+      ** on the database file.
+      **
+      ** Unless the pager is in locking_mode=exclusive mode, the lock is
+      ** downgraded to SHARED_LOCK before this function returns.
+      */
+      rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+      if( rc!=SQLITE_OK ){
+        goto failed;
+      }
+
+      /* If it is not already open and the file exists on disk, open the
+      ** journal for read/write access. Write access is required because
+      ** in exclusive-access mode the file descriptor will be kept open
+      ** and possibly used for a transaction later on. Also, write-access
+      ** is usually required to finalize the journal in journal_mode=persist
+      ** mode (and also for journal_mode=truncate on some systems).
+      **
+      ** If the journal does not exist, it usually means that some
+      ** other connection managed to get in and roll it back before
+      ** this connection obtained the exclusive lock above. Or, it
+      ** may mean that the pager was in the error-state when this
+      ** function was called and the journal file does not exist.
+      */
+      if( !isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+        sqlite3_vfs * const pVfs = pPager->pVfs;
+        int bExists;              /* True if journal file exists */
+        rc = sqlite3OsAccess(
+            pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists);
+        if( rc==SQLITE_OK && bExists ){
+          int fout = 0;
+          int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
+          assert( !pPager->tempFile );
+          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
+          assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
+          if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
+            rc = SQLITE_CANTOPEN_BKPT;
+            sqlite3OsClose(pPager->jfd);
+          }
+        }
+      }
+
+      /* Playback and delete the journal.  Drop the database write
+      ** lock and reacquire the read lock. Purge the cache before
+      ** playing back the hot-journal so that we don't end up with
+      ** an inconsistent cache.  Sync the hot journal before playing
+      ** it back since the process that crashed and left the hot journal
+      ** probably did not sync it and we are required to always sync
+      ** the journal before playing it back.
+      */
+      if( isOpen(pPager->jfd) ){
+        assert( rc==SQLITE_OK );
+        rc = pagerSyncHotJournal(pPager);
+        if( rc==SQLITE_OK ){
+          rc = pager_playback(pPager, !pPager->tempFile);
+          pPager->eState = PAGER_OPEN;
+        }
+      }else if( !pPager->exclusiveMode ){
+        pagerUnlockDb(pPager, SHARED_LOCK);
+      }
+
+      if( rc!=SQLITE_OK ){
+        /* This branch is taken if an error occurs while trying to open
+        ** or roll back a hot-journal while holding an EXCLUSIVE lock. The
+        ** pager_unlock() routine will be called before returning to unlock
+        ** the file. If the unlock attempt fails, then Pager.eLock must be
+        ** set to UNKNOWN_LOCK (see the comment above the #define for
+        ** UNKNOWN_LOCK above for an explanation).
+        **
+        ** In order to get pager_unlock() to do this, set Pager.eState to
+        ** PAGER_ERROR now. This is not actually counted as a transition
+        ** to ERROR state in the state diagram at the top of this file,
+        ** since we know that the same call to pager_unlock() will very
+        ** shortly transition the pager object to the OPEN state. Calling
+        ** assert_pager_state() would fail now, as it should not be possible
+        ** to be in ERROR state when there are zero outstanding page
+        ** references.
+        */
+        pager_error(pPager, rc);
+        goto failed;
+      }
+
+      assert( pPager->eState==PAGER_OPEN );
+      assert( (pPager->eLock==SHARED_LOCK)
+           || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
+      );
+    }
+
+    if( !pPager->tempFile && pPager->hasHeldSharedLock ){
+      /* The shared-lock has just been acquired then check to
+      ** see if the database has been modified.  If the database has changed,
+      ** flush the cache.  The hasHeldSharedLock flag prevents this from
+      ** occurring on the very first access to a file, in order to save a
+      ** single unnecessary sqlite3OsRead() call at the start-up.
+      **
+      ** Database changes are detected by looking at 15 bytes beginning
+      ** at offset 24 into the file.  The first 4 of these 16 bytes are
+      ** a 32-bit counter that is incremented with each change.  The
+      ** other bytes change randomly with each file change when
+      ** a codec is in use.
+      **
+      ** There is a vanishingly small chance that a change will not be
+      ** detected.  The chance of an undetected change is so small that
+      ** it can be neglected.
+      */
+      char dbFileVers[sizeof(pPager->dbFileVers)];
+
+      IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
+      rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
+      if( rc!=SQLITE_OK ){
+        if( rc!=SQLITE_IOERR_SHORT_READ ){
+          goto failed;
+        }
+        memset(dbFileVers, 0, sizeof(dbFileVers));
+      }
+
+      if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
+        pager_reset(pPager);
+
+        /* Unmap the database file. It is possible that external processes
+        ** may have truncated the database file and then extended it back
+        ** to its original size while this process was not holding a lock.
+        ** In this case there may exist a Pager.pMap mapping that appears
+        ** to be the right size but is not actually valid. Avoid this
+        ** possibility by unmapping the db here. */
+        if( USEFETCH(pPager) ){
+          sqlite3OsUnfetch(pPager->fd, 0, 0);
+        }
+      }
+    }
+
+    /* If there is a WAL file in the file-system, open this database in WAL
+    ** mode. Otherwise, the following function call is a no-op.
+    */
+    rc = pagerOpenWalIfPresent(pPager);
+#ifndef SQLITE_OMIT_WAL
+    assert( pPager->pWal==0 || rc==SQLITE_OK );
+#endif
+  }
+
+  if( pagerUseWal(pPager) ){
+    assert( rc==SQLITE_OK );
+    rc = pagerBeginReadTransaction(pPager);
+  }
+
+  if( pPager->tempFile==0 && pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
+    rc = pagerPagecount(pPager, &pPager->dbSize);
+  }
+
+ failed:
+  if( rc!=SQLITE_OK ){
+    assert( !MEMDB );
+    pager_unlock(pPager);
+    assert( pPager->eState==PAGER_OPEN );
+  }else{
+    pPager->eState = PAGER_READER;
+    pPager->hasHeldSharedLock = 1;
+  }
+  return rc;
+}
+
+/*
+** If the reference count has reached zero, rollback any active
+** transaction and unlock the pager.
+**
+** Except, in locking_mode=EXCLUSIVE when there is nothing to in
+** the rollback journal, the unlock is not performed and there is
+** nothing to rollback, so this routine is a no-op.
+*/
+static void pagerUnlockIfUnused(Pager *pPager){
+  if( sqlite3PcacheRefCount(pPager->pPCache)==0 ){
+    assert( pPager->nMmapOut==0 ); /* because page1 is never memory mapped */
+    pagerUnlockAndRollback(pPager);
+  }
+}
+
+/*
+** The page getter methods each try to acquire a reference to a
+** page with page number pgno. If the requested reference is
+** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
+**
+** There are different implementations of the getter method depending
+** on the current state of the pager.
+**
+**     getPageNormal()         --  The normal getter
+**     getPageError()          --  Used if the pager is in an error state
+**     getPageMmap()           --  Used if memory-mapped I/O is enabled
+**
+** If the requested page is already in the cache, it is returned.
+** Otherwise, a new page object is allocated and populated with data
+** read from the database file. In some cases, the pcache module may
+** choose not to allocate a new page object and may reuse an existing
+** object with no outstanding references.
+**
+** The extra data appended to a page is always initialized to zeros the
+** first time a page is loaded into memory. If the page requested is
+** already in the cache when this function is called, then the extra
+** data is left as it was when the page object was last used.
+**
+** If the database image is smaller than the requested page or if
+** the flags parameter contains the PAGER_GET_NOCONTENT bit and the
+** requested page is not already stored in the cache, then no
+** actual disk read occurs. In this case the memory image of the
+** page is initialized to all zeros.
+**
+** If PAGER_GET_NOCONTENT is true, it means that we do not care about
+** the contents of the page. This occurs in two scenarios:
+**
+**   a) When reading a free-list leaf page from the database, and
+**
+**   b) When a savepoint is being rolled back and we need to load
+**      a new page into the cache to be filled with the data read
+**      from the savepoint journal.
+**
+** If PAGER_GET_NOCONTENT is true, then the data returned is zeroed instead
+** of being read from the database. Additionally, the bits corresponding
+** to pgno in Pager.pInJournal (bitvec of pages already written to the
+** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
+** savepoints are set. This means if the page is made writable at any
+** point in the future, using a call to sqlite3PagerWrite(), its contents
+** will not be journaled. This saves IO.
+**
+** The acquisition might fail for several reasons.  In all cases,
+** an appropriate error code is returned and *ppPage is set to NULL.
+**
+** See also sqlite3PagerLookup().  Both this routine and Lookup() attempt
+** to find a page in the in-memory cache first.  If the page is not already
+** in memory, this routine goes to disk to read it in whereas Lookup()
+** just returns 0.  This routine acquires a read-lock the first time it
+** has to go to disk, and could also playback an old journal if necessary.
+** Since Lookup() never goes to disk, it never has to deal with locks
+** or journal files.
+*/
+static int getPageNormal(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+  int rc = SQLITE_OK;
+  PgHdr *pPg;
+  u8 noContent;                   /* True if PAGER_GET_NOCONTENT is set */
+  sqlite3_pcache_page *pBase;
+
+  assert( pPager->errCode==SQLITE_OK );
+  assert( pPager->eState>=PAGER_READER );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->hasHeldSharedLock==1 );
+
+  if( pgno==0 ) return SQLITE_CORRUPT_BKPT;
+  pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
+  if( pBase==0 ){
+    pPg = 0;
+    rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
+    if( rc!=SQLITE_OK ) goto pager_acquire_err;
+    if( pBase==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+      goto pager_acquire_err;
+    }
+  }
+  pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
+  assert( pPg==(*ppPage) );
+  assert( pPg->pgno==pgno );
+  assert( pPg->pPager==pPager || pPg->pPager==0 );
+
+  noContent = (flags & PAGER_GET_NOCONTENT)!=0;
+  if( pPg->pPager && !noContent ){
+    /* In this case the pcache already contains an initialized copy of
+    ** the page. Return without further ado.  */
+    assert( pgno!=PAGER_SJ_PGNO(pPager) );
+    pPager->aStat[PAGER_STAT_HIT]++;
+    return SQLITE_OK;
+
+  }else{
+    /* The pager cache has created a new page. Its content needs to
+    ** be initialized. But first some error checks:
+    **
+    ** (*) obsolete.  Was: maximum page number is 2^31
+    ** (2) Never try to fetch the locking page
+    */
+    if( pgno==PAGER_SJ_PGNO(pPager) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto pager_acquire_err;
+    }
+
+    pPg->pPager = pPager;
+
+    assert( !isOpen(pPager->fd) || !MEMDB );
+    if( !isOpen(pPager->fd) || pPager->dbSize<pgno || noContent ){
+      if( pgno>pPager->mxPgno ){
+        rc = SQLITE_FULL;
+        if( pgno<=pPager->dbSize ){
+          sqlite3PcacheRelease(pPg);
+          pPg = 0;
+        }
+        goto pager_acquire_err;
+      }
+      if( noContent ){
+        /* Failure to set the bits in the InJournal bit-vectors is benign.
+        ** It merely means that we might do some extra work to journal a
+        ** page that does not need to be journaled.  Nevertheless, be sure
+        ** to test the case where a malloc error occurs while trying to set
+        ** a bit in a bit vector.
+        */
+        sqlite3BeginBenignMalloc();
+        if( pgno<=pPager->dbOrigSize ){
+          TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno);
+          testcase( rc==SQLITE_NOMEM );
+        }
+        TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno);
+        testcase( rc==SQLITE_NOMEM );
+        sqlite3EndBenignMalloc();
+      }
+      memset(pPg->pData, 0, pPager->pageSize);
+      IOTRACE(("ZERO %p %d\n", pPager, pgno));
+    }else{
+      assert( pPg->pPager==pPager );
+      pPager->aStat[PAGER_STAT_MISS]++;
+      rc = readDbPage(pPg);
+      if( rc!=SQLITE_OK ){
+        goto pager_acquire_err;
+      }
+    }
+    pager_set_pagehash(pPg);
+  }
+  return SQLITE_OK;
+
+pager_acquire_err:
+  assert( rc!=SQLITE_OK );
+  if( pPg ){
+    sqlite3PcacheDrop(pPg);
+  }
+  pagerUnlockIfUnused(pPager);
+  *ppPage = 0;
+  return rc;
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/* The page getter for when memory-mapped I/O is enabled */
+static int getPageMMap(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+  int rc = SQLITE_OK;
+  PgHdr *pPg = 0;
+  u32 iFrame = 0;                 /* Frame to read from WAL file */
+
+  /* It is acceptable to use a read-only (mmap) page for any page except
+  ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
+  ** flag was specified by the caller. And so long as the db is not a
+  ** temporary or in-memory database.  */
+  const int bMmapOk = (pgno>1
+   && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY))
+  );
+
+  assert( USEFETCH(pPager) );
+
+  /* Optimization note:  Adding the "pgno<=1" term before "pgno==0" here
+  ** allows the compiler optimizer to reuse the results of the "pgno>1"
+  ** test in the previous statement, and avoid testing pgno==0 in the
+  ** common case where pgno is large. */
+  if( pgno<=1 && pgno==0 ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  assert( pPager->eState>=PAGER_READER );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->hasHeldSharedLock==1 );
+  assert( pPager->errCode==SQLITE_OK );
+
+  if( bMmapOk && pagerUseWal(pPager) ){
+    rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
+    if( rc!=SQLITE_OK ){
+      *ppPage = 0;
+      return rc;
+    }
+  }
+  if( bMmapOk && iFrame==0 ){
+    void *pData = 0;
+    rc = sqlite3OsFetch(pPager->fd,
+        (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData
+    );
+    if( rc==SQLITE_OK && pData ){
+      if( pPager->eState>PAGER_READER || pPager->tempFile ){
+        pPg = sqlite3PagerLookup(pPager, pgno);
+      }
+      if( pPg==0 ){
+        rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
+      }else{
+        sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
+      }
+      if( pPg ){
+        assert( rc==SQLITE_OK );
+        *ppPage = pPg;
+        return SQLITE_OK;
+      }
+    }
+    if( rc!=SQLITE_OK ){
+      *ppPage = 0;
+      return rc;
+    }
+  }
+  return getPageNormal(pPager, pgno, ppPage, flags);
+}
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
+
+/* The page getter method for when the pager is an error state */
+static int getPageError(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+  UNUSED_PARAMETER(pgno);
+  UNUSED_PARAMETER(flags);
+  assert( pPager->errCode!=SQLITE_OK );
+  *ppPage = 0;
+  return pPager->errCode;
+}
+
+
+/* Dispatch all page fetch requests to the appropriate getter method.
+*/
+int sqlite3PagerGet(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+#if 0   /* Trace page fetch by setting to 1 */
+  int rc;
+  printf("PAGE %u\n", pgno);
+  fflush(stdout);
+  rc = pPager->xGet(pPager, pgno, ppPage, flags);
+  if( rc ){ 
+    printf("PAGE %u failed with 0x%02x\n", pgno, rc);
+    fflush(stdout);
+  }
+  return rc;
+#else
+  /* Normal, high-speed version of sqlite3PagerGet() */
+  return pPager->xGet(pPager, pgno, ppPage, flags);
+#endif
+}
+
+/*
+** Acquire a page if it is already in the in-memory cache.  Do
+** not read the page from disk.  Return a pointer to the page,
+** or 0 if the page is not in cache.
+**
+** See also sqlite3PagerGet().  The difference between this routine
+** and sqlite3PagerGet() is that _get() will go to the disk and read
+** in the page if the page is not already in cache.  This routine
+** returns NULL if the page is not in cache or if a disk I/O error
+** has ever happened.
+*/
+DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
+  sqlite3_pcache_page *pPage;
+  assert( pPager!=0 );
+  assert( pgno!=0 );
+  assert( pPager->pPCache!=0 );
+  pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
+  assert( pPage==0 || pPager->hasHeldSharedLock );
+  if( pPage==0 ) return 0;
+  return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
+}
+
+/*
+** Release a page reference.
+**
+** The sqlite3PagerUnref() and sqlite3PagerUnrefNotNull() may only be used
+** if we know that the page being released is not the last reference to page1.
+** The btree layer always holds page1 open until the end, so these first
+** two routines can be used to release any page other than BtShared.pPage1.
+** The assert() at tag-20230419-2 proves that this constraint is always
+** honored.
+**
+** Use sqlite3PagerUnrefPageOne() to release page1.  This latter routine
+** checks the total number of outstanding pages and if the number of
+** pages reaches zero it drops the database lock.
+*/
+void sqlite3PagerUnrefNotNull(DbPage *pPg){
+  TESTONLY( Pager *pPager = pPg->pPager; )
+  assert( pPg!=0 );
+  if( pPg->flags & PGHDR_MMAP ){
+    assert( pPg->pgno!=1 );  /* Page1 is never memory mapped */
+    pagerReleaseMapPage(pPg);
+  }else{
+    sqlite3PcacheRelease(pPg);
+  }
+  /* Do not use this routine to release the last reference to page1 */
+  assert( sqlite3PcacheRefCount(pPager->pPCache)>0 ); /* tag-20230419-2 */
+}
+void sqlite3PagerUnref(DbPage *pPg){
+  if( pPg ) sqlite3PagerUnrefNotNull(pPg);
+}
+void sqlite3PagerUnrefPageOne(DbPage *pPg){
+  Pager *pPager;
+  assert( pPg!=0 );
+  assert( pPg->pgno==1 );
+  assert( (pPg->flags & PGHDR_MMAP)==0 ); /* Page1 is never memory mapped */
+  pPager = pPg->pPager;
+  sqlite3PcacheRelease(pPg);
+  pagerUnlockIfUnused(pPager);
+}
+
+/*
+** This function is called at the start of every write transaction.
+** There must already be a RESERVED or EXCLUSIVE lock on the database
+** file when this routine is called.
+**
+** Open the journal file for pager pPager and write a journal header
+** to the start of it. If there are active savepoints, open the sub-journal
+** as well. This function is only used when the journal file is being
+** opened to write a rollback log for a transaction. It is not used
+** when opening a hot journal file to roll it back.
+**
+** If the journal file is already open (as it may be in exclusive mode),
+** then this function just writes a journal header to the start of the
+** already open file.
+**
+** Whether or not the journal file is opened by this function, the
+** Pager.pInJournal bitvec structure is allocated.
+**
+** Return SQLITE_OK if everything is successful. Otherwise, return
+** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or
+** an IO error code if opening or writing the journal file fails.
+*/
+static int pager_open_journal(Pager *pPager){
+  int rc = SQLITE_OK;                        /* Return code */
+  sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */
+
+  assert( pPager->eState==PAGER_WRITER_LOCKED );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->pInJournal==0 );
+ 
+  /* If already in the error state, this function is a no-op.  But on
+  ** the other hand, this routine is never called if we are already in
+  ** an error state. */
+  if( NEVER(pPager->errCode) ) return pPager->errCode;
+
+  if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+    pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
+    if( pPager->pInJournal==0 ){
+      return SQLITE_NOMEM_BKPT;
+    }
+ 
+    /* Open the journal file if it is not already open. */
+    if( !isOpen(pPager->jfd) ){
+      if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
+        sqlite3MemJournalOpen(pPager->jfd);
+      }else{
+        int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE;
+        int nSpill;
+
+        if( pPager->tempFile ){
+          flags |= (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL);
+          flags |= SQLITE_OPEN_EXCLUSIVE;
+          nSpill = sqlite3Config.nStmtSpill;
+        }else{
+          flags |= SQLITE_OPEN_MAIN_JOURNAL;
+          nSpill = jrnlBufferSize(pPager);
+        }
+         
+        /* Verify that the database still has the same name as it did when
+        ** it was originally opened. */
+        rc = databaseIsUnmoved(pPager);
+        if( rc==SQLITE_OK ){
+          rc = sqlite3JournalOpen (
+              pVfs, pPager->zJournal, pPager->jfd, flags, nSpill
+          );
+        }
+      }
+      assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
+    }
+ 
+ 
+    /* Write the first journal header to the journal file and open
+    ** the sub-journal if necessary.
+    */
+    if( rc==SQLITE_OK ){
+      /* TODO: Check if all of these are really required. */
+      pPager->nRec = 0;
+      pPager->journalOff = 0;
+      pPager->setSuper = 0;
+      pPager->journalHdr = 0;
+      rc = writeJournalHdr(pPager);
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3BitvecDestroy(pPager->pInJournal);
+    pPager->pInJournal = 0;
+    pPager->journalOff = 0;
+  }else{
+    assert( pPager->eState==PAGER_WRITER_LOCKED );
+    pPager->eState = PAGER_WRITER_CACHEMOD;
+  }
+
+  return rc;
+}
+
+/*
+** Begin a write-transaction on the specified pager object. If a
+** write-transaction has already been opened, this function is a no-op.
+**
+** If the exFlag argument is false, then acquire at least a RESERVED
+** lock on the database file. If exFlag is true, then acquire at least
+** an EXCLUSIVE lock. If such a lock is already held, no locking
+** functions need be called.
+**
+** If the subjInMemory argument is non-zero, then any sub-journal opened
+** within this transaction will be opened as an in-memory file. This
+** has no effect if the sub-journal is already opened (as it may be when
+** running in exclusive mode) or if the transaction does not require a
+** sub-journal. If the subjInMemory argument is zero, then any required
+** sub-journal is implemented in-memory if pPager is an in-memory database,
+** or using a temporary file otherwise.
+*/
+int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
+  int rc = SQLITE_OK;
+
+  if( pPager->errCode ) return pPager->errCode;
+  assert( pPager->eState>=PAGER_READER && pPager->eState<PAGER_ERROR );
+  pPager->subjInMemory = (u8)subjInMemory;
+
+  if( pPager->eState==PAGER_READER ){
+    assert( pPager->pInJournal==0 );
+
+    if( pagerUseWal(pPager) ){
+      /* If the pager is configured to use locking_mode=exclusive, and an
+      ** exclusive lock on the database is not already held, obtain it now.
+      */
+      if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
+        rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        (void)sqlite3WalExclusiveMode(pPager->pWal, 1);
+      }
+
+      /* Grab the write lock on the log file. If successful, upgrade to
+      ** PAGER_RESERVED state. Otherwise, return an error code to the caller.
+      ** The busy-handler is not invoked if another connection already
+      ** holds the write-lock. If possible, the upper layer will call it.
+      */
+      rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
+    }else{
+      /* Obtain a RESERVED lock on the database file. If the exFlag parameter
+      ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
+      ** busy-handler callback can be used when upgrading to the EXCLUSIVE
+      ** lock, but not when obtaining the RESERVED lock.
+      */
+      rc = pagerLockDb(pPager, RESERVED_LOCK);
+      if( rc==SQLITE_OK && exFlag ){
+        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      /* Change to WRITER_LOCKED state.
+      **
+      ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD
+      ** when it has an open transaction, but never to DBMOD or FINISHED.
+      ** This is because in those states the code to roll back savepoint
+      ** transactions may copy data from the sub-journal into the database
+      ** file as well as into the page cache. Which would be incorrect in
+      ** WAL mode.
+      */
+      pPager->eState = PAGER_WRITER_LOCKED;
+      pPager->dbHintSize = pPager->dbSize;
+      pPager->dbFileSize = pPager->dbSize;
+      pPager->dbOrigSize = pPager->dbSize;
+      pPager->journalOff = 0;
+    }
+
+    assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
+    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
+    assert( assert_pager_state(pPager) );
+  }
+
+  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
+  return rc;
+}
+
+/*
+** Write page pPg onto the end of the rollback journal.
+*/
+static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  int rc;
+  u32 cksum;
+  char *pData2;
+  i64 iOff = pPager->journalOff;
+
+  /* We should never write to the journal file the page that
+  ** contains the database locks.  The following assert verifies
+  ** that we do not. */
+  assert( pPg->pgno!=PAGER_SJ_PGNO(pPager) );
+
+  assert( pPager->journalHdr<=pPager->journalOff );
+  pData2 = pPg->pData;
+  cksum = pager_cksum(pPager, (u8*)pData2);
+
+  /* Even if an IO or diskfull error occurs while journalling the
+  ** page in the block above, set the need-sync flag for the page.
+  ** Otherwise, when the transaction is rolled back, the logic in
+  ** playback_one_page() will think that the page needs to be restored
+  ** in the database file. And if an IO error occurs while doing so,
+  ** then corruption may follow.
+  */
+  pPg->flags |= PGHDR_NEED_SYNC;
+
+  rc = write32bits(pPager->jfd, iOff, pPg->pgno);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
+  if( rc!=SQLITE_OK ) return rc;
+
+  IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno,
+           pPager->journalOff, pPager->pageSize));
+  PAGER_INCR(sqlite3_pager_writej_count);
+  PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
+       PAGERID(pPager), pPg->pgno,
+       ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
+
+  pPager->journalOff += 8 + pPager->pageSize;
+  pPager->nRec++;
+  assert( pPager->pInJournal!=0 );
+  rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
+  testcase( rc==SQLITE_NOMEM );
+  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+  rc |= addToSavepointBitvecs(pPager, pPg->pgno);
+  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+  return rc;
+}
+
+/*
+** Mark a single data page as writeable. The page is written into the
+** main journal or sub-journal as required. If the page is written into
+** one of the journals, the corresponding bit is set in the
+** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
+** of any open savepoints as appropriate.
+*/
+static int pager_write(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  int rc = SQLITE_OK;
+
+  /* This routine is not called unless a write-transaction has already
+  ** been started. The journal file may or may not be open at this point.
+  ** It is never called in the ERROR state.
+  */
+  assert( pPager->eState==PAGER_WRITER_LOCKED
+       || pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->errCode==0 );
+  assert( pPager->readOnly==0 );
+  CHECK_PAGE(pPg);
+
+  /* The journal file needs to be opened. Higher level routines have already
+  ** obtained the necessary locks to begin the write-transaction, but the
+  ** rollback journal might not yet be open. Open it now if this is the case.
+  **
+  ** This is done before calling sqlite3PcacheMakeDirty() on the page.
+  ** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then
+  ** an error might occur and the pager would end up in WRITER_LOCKED state
+  ** with pages marked as dirty in the cache.
+  */
+  if( pPager->eState==PAGER_WRITER_LOCKED ){
+    rc = pager_open_journal(pPager);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
+  assert( assert_pager_state(pPager) );
+
+  /* Mark the page that is about to be modified as dirty. */
+  sqlite3PcacheMakeDirty(pPg);
+
+  /* If a rollback journal is in use, them make sure the page that is about
+  ** to change is in the rollback journal, or if the page is a new page off
+  ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC.
+  */
+  assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) );
+  if( pPager->pInJournal!=0
+   && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0
+  ){
+    assert( pagerUseWal(pPager)==0 );
+    if( pPg->pgno<=pPager->dbOrigSize ){
+      rc = pagerAddPageToRollbackJournal(pPg);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }else{
+      if( pPager->eState!=PAGER_WRITER_DBMOD ){
+        pPg->flags |= PGHDR_NEED_SYNC;
+      }
+      PAGERTRACE(("APPEND %d page %d needSync=%d\n",
+              PAGERID(pPager), pPg->pgno,
+             ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
+    }
+  }
+
+  /* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list
+  ** and before writing the page into the rollback journal.  Wait until now,
+  ** after the page has been successfully journalled, before setting the
+  ** PGHDR_WRITEABLE bit that indicates that the page can be safely modified.
+  */
+  pPg->flags |= PGHDR_WRITEABLE;
+ 
+  /* If the statement journal is open and the page is not in it,
+  ** then write the page into the statement journal.
+  */
+  if( pPager->nSavepoint>0 ){
+    rc = subjournalPageIfRequired(pPg);
+  }
+
+  /* Update the database size and return. */
+  if( pPager->dbSize<pPg->pgno ){
+    pPager->dbSize = pPg->pgno;
+  }
+  return rc;
+}
+
+/*
+** This is a variant of sqlite3PagerWrite() that runs when the sector size
+** is larger than the page size.  SQLite makes the (reasonable) assumption that
+** all bytes of a sector are written together by hardware.  Hence, all bytes of
+** a sector need to be journalled in case of a power loss in the middle of
+** a write.
+**
+** Usually, the sector size is less than or equal to the page size, in which
+** case pages can be individually written.  This routine only runs in the
+** exceptional case where the page size is smaller than the sector size.
+*/
+static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){
+  int rc = SQLITE_OK;          /* Return code */
+  Pgno nPageCount;             /* Total number of pages in database file */
+  Pgno pg1;                    /* First page of the sector pPg is located on. */
+  int nPage = 0;               /* Number of pages starting at pg1 to journal */
+  int ii;                      /* Loop counter */
+  int needSync = 0;            /* True if any page has PGHDR_NEED_SYNC */
+  Pager *pPager = pPg->pPager; /* The pager that owns pPg */
+  Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
+
+  /* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow
+  ** a journal header to be written between the pages journaled by
+  ** this function.
+  */
+  assert( !MEMDB );
+  assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)==0 );
+  pPager->doNotSpill |= SPILLFLAG_NOSYNC;
+
+  /* This trick assumes that both the page-size and sector-size are
+  ** an integer power of 2. It sets variable pg1 to the identifier
+  ** of the first page of the sector pPg is located on.
+  */
+  pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
+
+  nPageCount = pPager->dbSize;
+  if( pPg->pgno>nPageCount ){
+    nPage = (pPg->pgno - pg1)+1;
+  }else if( (pg1+nPagePerSector-1)>nPageCount ){
+    nPage = nPageCount+1-pg1;
+  }else{
+    nPage = nPagePerSector;
+  }
+  assert(nPage>0);
+  assert(pg1<=pPg->pgno);
+  assert((pg1+nPage)>pPg->pgno);
+
+  for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
+    Pgno pg = pg1+ii;
+    PgHdr *pPage;
+    if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
+      if( pg!=PAGER_SJ_PGNO(pPager) ){
+        rc = sqlite3PagerGet(pPager, pg, &pPage, 0);
+        if( rc==SQLITE_OK ){
+          rc = pager_write(pPage);
+          if( pPage->flags&PGHDR_NEED_SYNC ){
+            needSync = 1;
+          }
+          sqlite3PagerUnrefNotNull(pPage);
+        }
+      }
+    }else if( (pPage = sqlite3PagerLookup(pPager, pg))!=0 ){
+      if( pPage->flags&PGHDR_NEED_SYNC ){
+        needSync = 1;
+      }
+      sqlite3PagerUnrefNotNull(pPage);
+    }
+  }
+
+  /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages
+  ** starting at pg1, then it needs to be set for all of them. Because
+  ** writing to any of these nPage pages may damage the others, the
+  ** journal file must contain sync()ed copies of all of them
+  ** before any of them can be written out to the database file.
+  */
+  if( rc==SQLITE_OK && needSync ){
+    assert( !MEMDB );
+    for(ii=0; ii<nPage; ii++){
+      PgHdr *pPage = sqlite3PagerLookup(pPager, pg1+ii);
+      if( pPage ){
+        pPage->flags |= PGHDR_NEED_SYNC;
+        sqlite3PagerUnrefNotNull(pPage);
+      }
+    }
+  }
+
+  assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 );
+  pPager->doNotSpill &= ~SPILLFLAG_NOSYNC;
+  return rc;
+}
+
+/*
+** Mark a data page as writeable. This routine must be called before
+** making changes to a page. The caller must check the return value
+** of this function and be careful not to change any page data unless
+** this routine returns SQLITE_OK.
+**
+** The difference between this function and pager_write() is that this
+** function also deals with the special case where 2 or more pages
+** fit on a single disk sector. In this case all co-resident pages
+** must have been written to the journal file before returning.
+**
+** If an error occurs, SQLITE_NOMEM or an IO error code is returned
+** as appropriate. Otherwise, SQLITE_OK.
+*/
+int sqlite3PagerWrite(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  assert( (pPg->flags & PGHDR_MMAP)==0 );
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+  assert( assert_pager_state(pPager) );
+  if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){
+    if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg);
+    return SQLITE_OK;
+  }else if( pPager->errCode ){
+    return pPager->errCode;
+  }else if( pPager->sectorSize > (u32)pPager->pageSize ){
+    assert( pPager->tempFile==0 );
+    return pagerWriteLargeSector(pPg);
+  }else{
+    return pager_write(pPg);
+  }
+}
+
+/*
+** Return TRUE if the page given in the argument was previously passed
+** to sqlite3PagerWrite().  In other words, return TRUE if it is ok
+** to change the content of the page.
+*/
+#ifndef NDEBUG
+int sqlite3PagerIswriteable(DbPage *pPg){
+  return pPg->flags & PGHDR_WRITEABLE;
+}
+#endif
+
+/*
+** A call to this routine tells the pager that it is not necessary to
+** write the information on page pPg back to the disk, even though
+** that page might be marked as dirty.  This happens, for example, when
+** the page has been added as a leaf of the freelist and so its
+** content no longer matters.
+**
+** The overlying software layer calls this routine when all of the data
+** on the given page is unused. The pager marks the page as clean so
+** that it does not get written to disk.
+**
+** Tests show that this optimization can quadruple the speed of large
+** DELETE operations.
+**
+** This optimization cannot be used with a temp-file, as the page may
+** have been dirty at the start of the transaction. In that case, if
+** memory pressure forces page pPg out of the cache, the data does need
+** to be written out to disk so that it may be read back in if the
+** current transaction is rolled back.
+*/
+void sqlite3PagerDontWrite(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  if( !pPager->tempFile && (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
+    PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
+    IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
+    pPg->flags |= PGHDR_DONT_WRITE;
+    pPg->flags &= ~PGHDR_WRITEABLE;
+    testcase( pPg->flags & PGHDR_NEED_SYNC );
+    pager_set_pagehash(pPg);
+  }
+}
+
+/*
+** This routine is called to increment the value of the database file
+** change-counter, stored as a 4-byte big-endian integer starting at
+** byte offset 24 of the pager file.  The secondary change counter at
+** 92 is also updated, as is the SQLite version number at offset 96.
+**
+** But this only happens if the pPager->changeCountDone flag is false.
+** To avoid excess churning of page 1, the update only happens once.
+** See also the pager_write_changecounter() routine that does an
+** unconditional update of the change counters.
+**
+** If the isDirectMode flag is zero, then this is done by calling
+** sqlite3PagerWrite() on page 1, then modifying the contents of the
+** page data. In this case the file will be updated when the current
+** transaction is committed.
+**
+** The isDirectMode flag may only be non-zero if the library was compiled
+** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case,
+** if isDirect is non-zero, then the database file is updated directly
+** by writing an updated version of page 1 using a call to the
+** sqlite3OsWrite() function.
+*/
+static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
+  int rc = SQLITE_OK;
+
+  assert( pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* Declare and initialize constant integer 'isDirect'. If the
+  ** atomic-write optimization is enabled in this build, then isDirect
+  ** is initialized to the value passed as the isDirectMode parameter
+  ** to this function. Otherwise, it is always set to zero.
+  **
+  ** The idea is that if the atomic-write optimization is not
+  ** enabled at compile time, the compiler can omit the tests of
+  ** 'isDirect' below, as well as the block enclosed in the
+  ** "if( isDirect )" condition.
+  */
+#ifndef SQLITE_ENABLE_ATOMIC_WRITE
+# define DIRECT_MODE 0
+  assert( isDirectMode==0 );
+  UNUSED_PARAMETER(isDirectMode);
+#else
+# define DIRECT_MODE isDirectMode
+#endif
+
+  if( !pPager->changeCountDone && pPager->dbSize>0 ){
+    PgHdr *pPgHdr;                /* Reference to page 1 */
+
+    assert( !pPager->tempFile && isOpen(pPager->fd) );
+
+    /* Open page 1 of the file for writing. */
+    rc = sqlite3PagerGet(pPager, 1, &pPgHdr, 0);
+    assert( pPgHdr==0 || rc==SQLITE_OK );
+
+    /* If page one was fetched successfully, and this function is not
+    ** operating in direct-mode, make page 1 writable.  When not in
+    ** direct mode, page 1 is always held in cache and hence the PagerGet()
+    ** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
+    */
+    if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
+      rc = sqlite3PagerWrite(pPgHdr);
+    }
+
+    if( rc==SQLITE_OK ){
+      /* Actually do the update of the change counter */
+      pager_write_changecounter(pPgHdr);
+
+      /* If running in direct mode, write the contents of page 1 to the file. */
+      if( DIRECT_MODE ){
+        const void *zBuf;
+        assert( pPager->dbFileSize>0 );
+        zBuf = pPgHdr->pData;
+        if( rc==SQLITE_OK ){
+          rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
+          pPager->aStat[PAGER_STAT_WRITE]++;
+        }
+        if( rc==SQLITE_OK ){
+          /* Update the pager's copy of the change-counter. Otherwise, the
+          ** next time a read transaction is opened the cache will be
+          ** flushed (as the change-counter values will not match).  */
+          const void *pCopy = (const void *)&((const char *)zBuf)[24];
+          memcpy(&pPager->dbFileVers, pCopy, sizeof(pPager->dbFileVers));
+          pPager->changeCountDone = 1;
+        }
+      }else{
+        pPager->changeCountDone = 1;
+      }
+    }
+
+    /* Release the page reference. */
+    sqlite3PagerUnref(pPgHdr);
+  }
+  return rc;
+}
+
+/*
+** Sync the database file to disk. This is a no-op for in-memory databases
+** or pages with the Pager.noSync flag set.
+**
+** If successful, or if called on a pager for which it is a no-op, this
+** function returns SQLITE_OK. Otherwise, an IO error code is returned.
+*/
+int sqlite3PagerSync(Pager *pPager, const char *zSuper){
+  int rc = SQLITE_OK;
+  void *pArg = (void*)zSuper;
+  rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg);
+  if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+  if( rc==SQLITE_OK && !pPager->noSync ){
+    assert( !MEMDB );
+    rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
+  }
+  return rc;
+}
+
+/*
+** This function may only be called while a write-transaction is active in
+** rollback. If the connection is in WAL mode, this call is a no-op.
+** Otherwise, if the connection does not already have an EXCLUSIVE lock on
+** the database file, an attempt is made to obtain one.
+**
+** If the EXCLUSIVE lock is already held or the attempt to obtain it is
+** successful, or the connection is in WAL mode, SQLITE_OK is returned.
+** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is
+** returned.
+*/
+int sqlite3PagerExclusiveLock(Pager *pPager){
+  int rc = pPager->errCode;
+  assert( assert_pager_state(pPager) );
+  if( rc==SQLITE_OK ){
+    assert( pPager->eState==PAGER_WRITER_CACHEMOD
+         || pPager->eState==PAGER_WRITER_DBMOD
+         || pPager->eState==PAGER_WRITER_LOCKED
+    );
+    assert( assert_pager_state(pPager) );
+    if( 0==pagerUseWal(pPager) ){
+      rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+    }
+  }
+  return rc;
+}
+
+/*
+** Sync the database file for the pager pPager. zSuper points to the name
+** of a super-journal file that should be written into the individual
+** journal file. zSuper may be NULL, which is interpreted as no
+** super-journal (a single database transaction).
+**
+** This routine ensures that:
+**
+**   * The database file change-counter is updated,
+**   * the journal is synced (unless the atomic-write optimization is used),
+**   * all dirty pages are written to the database file,
+**   * the database file is truncated (if required), and
+**   * the database file synced.
+**
+** The only thing that remains to commit the transaction is to finalize
+** (delete, truncate or zero the first part of) the journal file (or
+** delete the super-journal file if specified).
+**
+** Note that if zSuper==NULL, this does not overwrite a previous value
+** passed to an sqlite3PagerCommitPhaseOne() call.
+**
+** If the final parameter - noSync - is true, then the database file itself
+** is not synced. The caller must call sqlite3PagerSync() directly to
+** sync the database file before calling CommitPhaseTwo() to delete the
+** journal file in this case.
+*/
+int sqlite3PagerCommitPhaseOne(
+  Pager *pPager,                  /* Pager object */
+  const char *zSuper,            /* If not NULL, the super-journal name */
+  int noSync                      /* True to omit the xSync on the db file */
+){
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( pPager->eState==PAGER_WRITER_LOCKED
+       || pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+       || pPager->eState==PAGER_ERROR
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* If a prior error occurred, report that error again. */
+  if( NEVER(pPager->errCode) ) return pPager->errCode;
+
+  /* Provide the ability to easily simulate an I/O error during testing */
+  if( sqlite3FaultSim(400) ) return SQLITE_IOERR;
+
+  PAGERTRACE(("DATABASE SYNC: File=%s zSuper=%s nSize=%d\n",
+      pPager->zFilename, zSuper, pPager->dbSize));
+
+  /* If no database changes have been made, return early. */
+  if( pPager->eState<PAGER_WRITER_CACHEMOD ) return SQLITE_OK;
+
+  assert( MEMDB==0 || pPager->tempFile );
+  assert( isOpen(pPager->fd) || pPager->tempFile );
+  if( 0==pagerFlushOnCommit(pPager, 1) ){
+    /* If this is an in-memory db, or no pages have been written to, or this
+    ** function has already been called, it is mostly a no-op.  However, any
+    ** backup in progress needs to be restarted.  */
+    sqlite3BackupRestart(pPager->pBackup);
+  }else{
+    PgHdr *pList;
+    if( pagerUseWal(pPager) ){
+      PgHdr *pPageOne = 0;
+      pList = sqlite3PcacheDirtyList(pPager->pPCache);
+      if( pList==0 ){
+        /* Must have at least one page for the WAL commit flag.
+        ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */
+        rc = sqlite3PagerGet(pPager, 1, &pPageOne, 0);
+        pList = pPageOne;
+        pList->pDirty = 0;
+      }
+      assert( rc==SQLITE_OK );
+      if( ALWAYS(pList) ){
+        rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1);
+      }
+      sqlite3PagerUnref(pPageOne);
+      if( rc==SQLITE_OK ){
+        sqlite3PcacheCleanAll(pPager->pPCache);
+      }
+    }else{
+      /* The bBatch boolean is true if the batch-atomic-write commit method
+      ** should be used.  No rollback journal is created if batch-atomic-write
+      ** is enabled.
+      */
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+      sqlite3_file *fd = pPager->fd;
+      int bBatch = zSuper==0    /* An SQLITE_IOCAP_BATCH_ATOMIC commit */
+        && (sqlite3OsDeviceCharacteristics(fd) & SQLITE_IOCAP_BATCH_ATOMIC)
+        && !pPager->noSync
+        && sqlite3JournalIsInMemory(pPager->jfd);
+#else
+#     define bBatch 0
+#endif
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+      /* The following block updates the change-counter. Exactly how it
+      ** does this depends on whether or not the atomic-update optimization
+      ** was enabled at compile time, and if this transaction meets the
+      ** runtime criteria to use the operation:
+      **
+      **    * The file-system supports the atomic-write property for
+      **      blocks of size page-size, and
+      **    * This commit is not part of a multi-file transaction, and
+      **    * Exactly one page has been modified and store in the journal file.
+      **
+      ** If the optimization was not enabled at compile time, then the
+      ** pager_incr_changecounter() function is called to update the change
+      ** counter in 'indirect-mode'. If the optimization is compiled in but
+      ** is not applicable to this transaction, call sqlite3JournalCreate()
+      ** to make sure the journal file has actually been created, then call
+      ** pager_incr_changecounter() to update the change-counter in indirect
+      ** mode.
+      **
+      ** Otherwise, if the optimization is both enabled and applicable,
+      ** then call pager_incr_changecounter() to update the change-counter
+      ** in 'direct' mode. In this case the journal file will never be
+      ** created for this transaction.
+      */
+      if( bBatch==0 ){
+        PgHdr *pPg;
+        assert( isOpen(pPager->jfd)
+            || pPager->journalMode==PAGER_JOURNALMODE_OFF
+            || pPager->journalMode==PAGER_JOURNALMODE_WAL
+            );
+        if( !zSuper && isOpen(pPager->jfd)
+         && pPager->journalOff==jrnlBufferSize(pPager)
+         && pPager->dbSize>=pPager->dbOrigSize
+         && (!(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
+        ){
+          /* Update the db file change counter via the direct-write method. The
+          ** following call will modify the in-memory representation of page 1
+          ** to include the updated change counter and then write page 1
+          ** directly to the database file. Because of the atomic-write
+          ** property of the host file-system, this is safe.
+          */
+          rc = pager_incr_changecounter(pPager, 1);
+        }else{
+          rc = sqlite3JournalCreate(pPager->jfd);
+          if( rc==SQLITE_OK ){
+            rc = pager_incr_changecounter(pPager, 0);
+          }
+        }
+      }
+#else  /* SQLITE_ENABLE_ATOMIC_WRITE */
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+      if( zSuper ){
+        rc = sqlite3JournalCreate(pPager->jfd);
+        if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+        assert( bBatch==0 );
+      }
+#endif
+      rc = pager_incr_changecounter(pPager, 0);
+#endif /* !SQLITE_ENABLE_ATOMIC_WRITE */
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+ 
+      /* Write the super-journal name into the journal file. If a
+      ** super-journal file name has already been written to the journal file,
+      ** or if zSuper is NULL (no super-journal), then this call is a no-op.
+      */
+      rc = writeSuperJournal(pPager, zSuper);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+ 
+      /* Sync the journal file and write all dirty pages to the database.
+      ** If the atomic-update optimization is being used, this sync will not
+      ** create the journal file or perform any real IO.
+      **
+      ** Because the change-counter page was just modified, unless the
+      ** atomic-update optimization is used it is almost certain that the
+      ** journal requires a sync here. However, in locking_mode=exclusive
+      ** on a system under memory pressure it is just possible that this is
+      ** not the case. In this case it is likely enough that the redundant
+      ** xSync() call will be changed to a no-op by the OS anyhow.
+      */
+      rc = syncJournal(pPager, 0);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+
+      pList = sqlite3PcacheDirtyList(pPager->pPCache);
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+      if( bBatch ){
+        rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_BEGIN_ATOMIC_WRITE, 0);
+        if( rc==SQLITE_OK ){
+          rc = pager_write_pagelist(pPager, pList);
+          if( rc==SQLITE_OK && pPager->dbSize>pPager->dbFileSize ){
+            char *pTmp = pPager->pTmpSpace;
+            int szPage = (int)pPager->pageSize;
+            memset(pTmp, 0, szPage);
+            rc = sqlite3OsWrite(pPager->fd, pTmp, szPage,
+                      ((i64)pPager->dbSize*pPager->pageSize)-szPage);
+          }
+          if( rc==SQLITE_OK ){
+            rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_COMMIT_ATOMIC_WRITE, 0);
+          }
+          if( rc!=SQLITE_OK ){
+            sqlite3OsFileControlHint(fd, SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE, 0);
+          }
+        }
+
+        if( (rc&0xFF)==SQLITE_IOERR && rc!=SQLITE_IOERR_NOMEM ){
+          rc = sqlite3JournalCreate(pPager->jfd);
+          if( rc!=SQLITE_OK ){
+            sqlite3OsClose(pPager->jfd);
+            goto commit_phase_one_exit;
+          }
+          bBatch = 0;
+        }else{
+          sqlite3OsClose(pPager->jfd);
+        }
+      }
+#endif /* SQLITE_ENABLE_BATCH_ATOMIC_WRITE */
+
+      if( bBatch==0 ){
+        rc = pager_write_pagelist(pPager, pList);
+      }
+      if( rc!=SQLITE_OK ){
+        assert( rc!=SQLITE_IOERR_BLOCKED );
+        goto commit_phase_one_exit;
+      }
+      sqlite3PcacheCleanAll(pPager->pPCache);
+
+      /* If the file on disk is smaller than the database image, use
+      ** pager_truncate to grow the file here. This can happen if the database
+      ** image was extended as part of the current transaction and then the
+      ** last page in the db image moved to the free-list. In this case the
+      ** last page is never written out to disk, leaving the database file
+      ** undersized. Fix this now if it is the case.  */
+      if( pPager->dbSize>pPager->dbFileSize ){
+        Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_SJ_PGNO(pPager));
+        assert( pPager->eState==PAGER_WRITER_DBMOD );
+        rc = pager_truncate(pPager, nNew);
+        if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+      }
+ 
+      /* Finally, sync the database file. */
+      if( !noSync ){
+        rc = sqlite3PagerSync(pPager, zSuper);
+      }
+      IOTRACE(("DBSYNC %p\n", pPager))
+    }
+  }
+
+commit_phase_one_exit:
+  if( rc==SQLITE_OK && !pagerUseWal(pPager) ){
+    pPager->eState = PAGER_WRITER_FINISHED;
+  }
+  return rc;
+}
+
+
+/*
+** When this function is called, the database file has been completely
+** updated to reflect the changes made by the current transaction and
+** synced to disk. The journal file still exists in the file-system
+** though, and if a failure occurs at this point it will eventually
+** be used as a hot-journal and the current transaction rolled back.
+**
+** This function finalizes the journal file, either by deleting,
+** truncating or partially zeroing it, so that it cannot be used
+** for hot-journal rollback. Once this is done the transaction is
+** irrevocably committed.
+**
+** If an error occurs, an IO error code is returned and the pager
+** moves into the error state. Otherwise, SQLITE_OK is returned.
+*/
+int sqlite3PagerCommitPhaseTwo(Pager *pPager){
+  int rc = SQLITE_OK;                  /* Return code */
+
+  /* This routine should not be called if a prior error has occurred.
+  ** But if (due to a coding error elsewhere in the system) it does get
+  ** called, just return the same error code without doing anything. */
+  if( NEVER(pPager->errCode) ) return pPager->errCode;
+  pPager->iDataVersion++;
+
+  assert( pPager->eState==PAGER_WRITER_LOCKED
+       || pPager->eState==PAGER_WRITER_FINISHED
+       || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* An optimization. If the database was not actually modified during
+  ** this transaction, the pager is running in exclusive-mode and is
+  ** using persistent journals, then this function is a no-op.
+  **
+  ** The start of the journal file currently contains a single journal
+  ** header with the nRec field set to 0. If such a journal is used as
+  ** a hot-journal during hot-journal rollback, 0 changes will be made
+  ** to the database file. So there is no need to zero the journal
+  ** header. Since the pager is in exclusive mode, there is no need
+  ** to drop any locks either.
+  */
+  if( pPager->eState==PAGER_WRITER_LOCKED
+   && pPager->exclusiveMode
+   && pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+  ){
+    assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
+    pPager->eState = PAGER_READER;
+    return SQLITE_OK;
+  }
+
+  PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
+  rc = pager_end_transaction(pPager, pPager->setSuper, 1);
+  return pager_error(pPager, rc);
+}
+
+/*
+** If a write transaction is open, then all changes made within the
+** transaction are reverted and the current write-transaction is closed.
+** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR
+** state if an error occurs.
+**
+** If the pager is already in PAGER_ERROR state when this function is called,
+** it returns Pager.errCode immediately. No work is performed in this case.
+**
+** Otherwise, in rollback mode, this function performs two functions:
+**
+**   1) It rolls back the journal file, restoring all database file and
+**      in-memory cache pages to the state they were in when the transaction
+**      was opened, and
+**
+**   2) It finalizes the journal file, so that it is not used for hot
+**      rollback at any point in the future.
+**
+** Finalization of the journal file (task 2) is only performed if the
+** rollback is successful.
+**
+** In WAL mode, all cache-entries containing data modified within the
+** current transaction are either expelled from the cache or reverted to
+** their pre-transaction state by re-reading data from the database or
+** WAL files. The WAL transaction is then closed.
+*/
+int sqlite3PagerRollback(Pager *pPager){
+  int rc = SQLITE_OK;                  /* Return code */
+  PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
+
+  /* PagerRollback() is a no-op if called in READER or OPEN state. If
+  ** the pager is already in the ERROR state, the rollback is not
+  ** attempted here. Instead, the error code is returned to the caller.
+  */
+  assert( assert_pager_state(pPager) );
+  if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
+  if( pPager->eState<=PAGER_READER ) return SQLITE_OK;
+
+  if( pagerUseWal(pPager) ){
+    int rc2;
+    rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
+    rc2 = pager_end_transaction(pPager, pPager->setSuper, 0);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){
+    int eState = pPager->eState;
+    rc = pager_end_transaction(pPager, 0, 0);
+    if( !MEMDB && eState>PAGER_WRITER_LOCKED ){
+      /* This can happen using journal_mode=off. Move the pager to the error
+      ** state to indicate that the contents of the cache may not be trusted.
+      ** Any active readers will get SQLITE_ABORT.
+      */
+      pPager->errCode = SQLITE_ABORT;
+      pPager->eState = PAGER_ERROR;
+      setGetterMethod(pPager);
+      return rc;
+    }
+  }else{
+    rc = pager_playback(pPager, 0);
+  }
+
+  assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK );
+  assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT
+          || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR
+          || rc==SQLITE_CANTOPEN
+  );
+
+  /* If an error occurs during a ROLLBACK, we can no longer trust the pager
+  ** cache. So call pager_error() on the way out to make any error persistent.
+  */
+  return pager_error(pPager, rc);
+}
+
+/*
+** Return TRUE if the database file is opened read-only.  Return FALSE
+** if the database is (in theory) writable.
+*/
+u8 sqlite3PagerIsreadonly(Pager *pPager){
+  return pPager->readOnly;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Return the sum of the reference counts for all pages held by pPager.
+*/
+int sqlite3PagerRefcount(Pager *pPager){
+  return sqlite3PcacheRefCount(pPager->pPCache);
+}
+#endif
+
+/*
+** Return the approximate number of bytes of memory currently
+** used by the pager and its associated cache.
+*/
+int sqlite3PagerMemUsed(Pager *pPager){
+  int perPageSize = pPager->pageSize + pPager->nExtra
+    + (int)(sizeof(PgHdr) + 5*sizeof(void*));
+  return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
+           + sqlite3MallocSize(pPager)
+           + pPager->pageSize;
+}
+
+/*
+** Return the number of references to the specified page.
+*/
+int sqlite3PagerPageRefcount(DbPage *pPage){
+  return sqlite3PcachePageRefcount(pPage);
+}
+
+#ifdef SQLITE_TEST
+/*
+** This routine is used for testing and analysis only.
+*/
+int *sqlite3PagerStats(Pager *pPager){
+  static int a[11];
+  a[0] = sqlite3PcacheRefCount(pPager->pPCache);
+  a[1] = sqlite3PcachePagecount(pPager->pPCache);
+  a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
+  a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize;
+  a[4] = pPager->eState;
+  a[5] = pPager->errCode;
+  a[6] = (int)pPager->aStat[PAGER_STAT_HIT] & 0x7fffffff;
+  a[7] = (int)pPager->aStat[PAGER_STAT_MISS] & 0x7fffffff;
+  a[8] = 0;  /* Used to be pPager->nOvfl */
+  a[9] = pPager->nRead;
+  a[10] = (int)pPager->aStat[PAGER_STAT_WRITE] & 0x7fffffff;
+  return a;
+}
+#endif
+
+/*
+** Parameter eStat must be one of SQLITE_DBSTATUS_CACHE_HIT, _MISS, _WRITE,
+** or _WRITE+1.  The SQLITE_DBSTATUS_CACHE_WRITE+1 case is a translation
+** of SQLITE_DBSTATUS_CACHE_SPILL.  The _SPILL case is not contiguous because
+** it was added later.
+**
+** Before returning, *pnVal is incremented by the
+** current cache hit or miss count, according to the value of eStat. If the
+** reset parameter is non-zero, the cache hit or miss count is zeroed before
+** returning.
+*/
+void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, u64 *pnVal){
+
+  assert( eStat==SQLITE_DBSTATUS_CACHE_HIT
+       || eStat==SQLITE_DBSTATUS_CACHE_MISS
+       || eStat==SQLITE_DBSTATUS_CACHE_WRITE
+       || eStat==SQLITE_DBSTATUS_CACHE_WRITE+1
+  );
+
+  assert( SQLITE_DBSTATUS_CACHE_HIT+1==SQLITE_DBSTATUS_CACHE_MISS );
+  assert( SQLITE_DBSTATUS_CACHE_HIT+2==SQLITE_DBSTATUS_CACHE_WRITE );
+  assert( PAGER_STAT_HIT==0 && PAGER_STAT_MISS==1
+           && PAGER_STAT_WRITE==2 && PAGER_STAT_SPILL==3 );
+
+  eStat -= SQLITE_DBSTATUS_CACHE_HIT;
+  *pnVal += pPager->aStat[eStat];
+  if( reset ){
+    pPager->aStat[eStat] = 0;
+  }
+}
+
+/*
+** Return true if this is an in-memory or temp-file backed pager.
+*/
+int sqlite3PagerIsMemdb(Pager *pPager){
+  return pPager->tempFile || pPager->memVfs;
+}
+
+/*
+** Check that there are at least nSavepoint savepoints open. If there are
+** currently less than nSavepoints open, then open one or more savepoints
+** to make up the difference. If the number of savepoints is already
+** equal to nSavepoint, then this function is a no-op.
+**
+** If a memory allocation fails, SQLITE_NOMEM is returned. If an error
+** occurs while opening the sub-journal file, then an IO error code is
+** returned. Otherwise, SQLITE_OK.
+*/
+static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){
+  int rc = SQLITE_OK;                       /* Return code */
+  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */
+  int ii;                                   /* Iterator variable */
+  PagerSavepoint *aNew;                     /* New Pager.aSavepoint array */
+
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+  assert( assert_pager_state(pPager) );
+  assert( nSavepoint>nCurrent && pPager->useJournal );
+
+  /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
+  ** if the allocation fails. Otherwise, zero the new portion in case a
+  ** malloc failure occurs while populating it in the for(...) loop below.
+  */
+  aNew = (PagerSavepoint *)sqlite3Realloc(
+      pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
+  );
+  if( !aNew ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
+  pPager->aSavepoint = aNew;
+
+  /* Populate the PagerSavepoint structures just allocated. */
+  for(ii=nCurrent; ii<nSavepoint; ii++){
+    aNew[ii].nOrig = pPager->dbSize;
+    if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
+      aNew[ii].iOffset = pPager->journalOff;
+    }else{
+      aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
+    }
+    aNew[ii].iSubRec = pPager->nSubRec;
+    aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
+    aNew[ii].bTruncateOnRelease = 1;
+    if( !aNew[ii].pInSavepoint ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    if( pagerUseWal(pPager) ){
+      sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
+    }
+    pPager->nSavepoint = ii+1;
+  }
+  assert( pPager->nSavepoint==nSavepoint );
+  assertTruncateConstraint(pPager);
+  return rc;
+}
+int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+  assert( assert_pager_state(pPager) );
+
+  if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){
+    return pagerOpenSavepoint(pPager, nSavepoint);
+  }else{
+    return SQLITE_OK;
+  }
+}
+
+
+/*
+** This function is called to rollback or release (commit) a savepoint.
+** The savepoint to release or rollback need not be the most recently
+** created savepoint.
+**
+** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
+** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with
+** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes
+** that have occurred since the specified savepoint was created.
+**
+** The savepoint to rollback or release is identified by parameter
+** iSavepoint. A value of 0 means to operate on the outermost savepoint
+** (the first created). A value of (Pager.nSavepoint-1) means operate
+** on the most recently created savepoint. If iSavepoint is greater than
+** (Pager.nSavepoint-1), then this function is a no-op.
+**
+** If a negative value is passed to this function, then the current
+** transaction is rolled back. This is different to calling
+** sqlite3PagerRollback() because this function does not terminate
+** the transaction or unlock the database, it just restores the
+** contents of the database to its original state.
+**
+** In any case, all savepoints with an index greater than iSavepoint
+** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE),
+** then savepoint iSavepoint is also destroyed.
+**
+** This function may return SQLITE_NOMEM if a memory allocation fails,
+** or an IO error code if an IO error occurs while rolling back a
+** savepoint. If no errors occur, SQLITE_OK is returned.
+*/
+int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
+  int rc = pPager->errCode;
+ 
+#ifdef SQLITE_ENABLE_ZIPVFS
+  if( op==SAVEPOINT_RELEASE ) rc = SQLITE_OK;
+#endif
+
+  assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
+  assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK );
+
+  if( rc==SQLITE_OK && iSavepoint<pPager->nSavepoint ){
+    int ii;            /* Iterator variable */
+    int nNew;          /* Number of remaining savepoints after this op. */
+
+    /* Figure out how many savepoints will still be active after this
+    ** operation. Store this value in nNew. Then free resources associated
+    ** with any savepoints that are destroyed by this operation.
+    */
+    nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1);
+    for(ii=nNew; ii<pPager->nSavepoint; ii++){
+      sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
+    }
+    pPager->nSavepoint = nNew;
+
+    /* Truncate the sub-journal so that it only includes the parts
+    ** that are still in use. */
+    if( op==SAVEPOINT_RELEASE ){
+      PagerSavepoint *pRel = &pPager->aSavepoint[nNew];
+      if( pRel->bTruncateOnRelease && isOpen(pPager->sjfd) ){
+        /* Only truncate if it is an in-memory sub-journal. */
+        if( sqlite3JournalIsInMemory(pPager->sjfd) ){
+          i64 sz = (pPager->pageSize+4)*(i64)pRel->iSubRec;
+          rc = sqlite3OsTruncate(pPager->sjfd, sz);
+          assert( rc==SQLITE_OK );
+        }
+        pPager->nSubRec = pRel->iSubRec;
+      }
+    }
+    /* Else this is a rollback operation, playback the specified savepoint.
+    ** If this is a temp-file, it is possible that the journal file has
+    ** not yet been opened. In this case there have been no changes to
+    ** the database file, so the playback operation can be skipped.
+    */
+    else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
+      PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
+      rc = pagerPlaybackSavepoint(pPager, pSavepoint);
+      assert(rc!=SQLITE_DONE);
+    }
+   
+#ifdef SQLITE_ENABLE_ZIPVFS
+    /* If the cache has been modified but the savepoint cannot be rolled
+    ** back journal_mode=off, put the pager in the error state. This way,
+    ** if the VFS used by this pager includes ZipVFS, the entire transaction
+    ** can be rolled back at the ZipVFS level.  */
+    else if(
+        pPager->journalMode==PAGER_JOURNALMODE_OFF
+     && pPager->eState>=PAGER_WRITER_CACHEMOD
+    ){
+      pPager->errCode = SQLITE_ABORT;
+      pPager->eState = PAGER_ERROR;
+      setGetterMethod(pPager);
+    }
+#endif
+  }
+
+  return rc;
+}
+
+/*
+** Return the full pathname of the database file.
+**
+** Except, if the pager is in-memory only, then return an empty string if
+** nullIfMemDb is true.  This routine is called with nullIfMemDb==1 when
+** used to report the filename to the user, for compatibility with legacy
+** behavior.  But when the Btree needs to know the filename for matching to
+** shared cache, it uses nullIfMemDb==0 so that in-memory databases can
+** participate in shared-cache.
+**
+** The return value to this routine is always safe to use with
+** sqlite3_uri_parameter() and sqlite3_filename_database() and friends.
+*/
+const char *sqlite3PagerFilename(const Pager *pPager, int nullIfMemDb){
+  static const char zFake[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
+  if( nullIfMemDb && (pPager->memDb || sqlite3IsMemdb(pPager->pVfs)) ){
+    return &zFake[4];
+  }else{
+    return pPager->zFilename;
+  }
+}
+
+/*
+** Return the VFS structure for the pager.
+*/
+sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
+  return pPager->pVfs;
+}
+
+/*
+** Return the file handle for the database file associated
+** with the pager.  This might return NULL if the file has
+** not yet been opened.
+*/
+sqlite3_file *sqlite3PagerFile(Pager *pPager){
+  return pPager->fd;
+}
+
+/*
+** Return the file handle for the journal file (if it exists).
+** This will be either the rollback journal or the WAL file.
+*/
+sqlite3_file *sqlite3PagerJrnlFile(Pager *pPager){
+#if SQLITE_OMIT_WAL
+  return pPager->jfd;
+#else
+  return pPager->pWal ? sqlite3WalFile(pPager->pWal) : pPager->jfd;
+#endif
+}
+
+/*
+** Return the full pathname of the journal file.
+*/
+const char *sqlite3PagerJournalname(Pager *pPager){
+  return pPager->zJournal;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Move the page pPg to location pgno in the file.
+**
+** There must be no references to the page previously located at
+** pgno (which we call pPgOld) though that page is allowed to be
+** in cache.  If the page previously located at pgno is not already
+** in the rollback journal, it is not put there by by this routine.
+**
+** References to the page pPg remain valid. Updating any
+** meta-data associated with pPg (i.e. data stored in the nExtra bytes
+** allocated along with the page) is the responsibility of the caller.
+**
+** A transaction must be active when this routine is called. It used to be
+** required that a statement transaction was not active, but this restriction
+** has been removed (CREATE INDEX needs to move a page when a statement
+** transaction is active).
+**
+** If the fourth argument, isCommit, is non-zero, then this page is being
+** moved as part of a database reorganization just before the transaction
+** is being committed. In this case, it is guaranteed that the database page
+** pPg refers to will not be written to again within this transaction.
+**
+** This function may return SQLITE_NOMEM or an IO error code if an error
+** occurs. Otherwise, it returns SQLITE_OK.
+*/
+int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
+  PgHdr *pPgOld;               /* The page being overwritten. */
+  Pgno needSyncPgno = 0;       /* Old value of pPg->pgno, if sync is required */
+  int rc;                      /* Return code */
+  Pgno origPgno;               /* The original page number */
+
+  assert( pPg->nRef>0 );
+  assert( pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* In order to be able to rollback, an in-memory database must journal
+  ** the page we are moving from.
+  */
+  assert( pPager->tempFile || !MEMDB );
+  if( pPager->tempFile ){
+    rc = sqlite3PagerWrite(pPg);
+    if( rc ) return rc;
+  }
+
+  /* If the page being moved is dirty and has not been saved by the latest
+  ** savepoint, then save the current contents of the page into the
+  ** sub-journal now. This is required to handle the following scenario:
+  **
+  **   BEGIN;
+  **     <journal page X, then modify it in memory>
+  **     SAVEPOINT one;
+  **       <Move page X to location Y>
+  **     ROLLBACK TO one;
+  **
+  ** If page X were not written to the sub-journal here, it would not
+  ** be possible to restore its contents when the "ROLLBACK TO one"
+  ** statement were is processed.
+  **
+  ** subjournalPage() may need to allocate space to store pPg->pgno into
+  ** one or more savepoint bitvecs. This is the reason this function
+  ** may return SQLITE_NOMEM.
+  */
+  if( (pPg->flags & PGHDR_DIRTY)!=0
+   && SQLITE_OK!=(rc = subjournalPageIfRequired(pPg))
+  ){
+    return rc;
+  }
+
+  PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n",
+      PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
+  IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
+
+  /* If the journal needs to be sync()ed before page pPg->pgno can
+  ** be written to, store pPg->pgno in local variable needSyncPgno.
+  **
+  ** If the isCommit flag is set, there is no need to remember that
+  ** the journal needs to be sync()ed before database page pPg->pgno
+  ** can be written to. The caller has already promised not to write to it.
+  */
+  if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
+    needSyncPgno = pPg->pgno;
+    assert( pPager->journalMode==PAGER_JOURNALMODE_OFF ||
+            pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize );
+    assert( pPg->flags&PGHDR_DIRTY );
+  }
+
+  /* If the cache contains a page with page-number pgno, remove it
+  ** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for
+  ** page pgno before the 'move' operation, it needs to be retained
+  ** for the page moved there.
+  */
+  pPg->flags &= ~PGHDR_NEED_SYNC;
+  pPgOld = sqlite3PagerLookup(pPager, pgno);
+  assert( !pPgOld || pPgOld->nRef==1 || CORRUPT_DB );
+  if( pPgOld ){
+    if( NEVER(pPgOld->nRef>1) ){
+      sqlite3PagerUnrefNotNull(pPgOld);
+      return SQLITE_CORRUPT_BKPT;
+    }
+    pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
+    if( pPager->tempFile ){
+      /* Do not discard pages from an in-memory database since we might
+      ** need to rollback later.  Just move the page out of the way. */
+      sqlite3PcacheMove(pPgOld, pPager->dbSize+1);
+    }else{
+      sqlite3PcacheDrop(pPgOld);
+    }
+  }
+
+  origPgno = pPg->pgno;
+  sqlite3PcacheMove(pPg, pgno);
+  sqlite3PcacheMakeDirty(pPg);
+
+  /* For an in-memory database, make sure the original page continues
+  ** to exist, in case the transaction needs to roll back.  Use pPgOld
+  ** as the original page since it has already been allocated.
+  */
+  if( pPager->tempFile && pPgOld ){
+    sqlite3PcacheMove(pPgOld, origPgno);
+    sqlite3PagerUnrefNotNull(pPgOld);
+  }
+
+  if( needSyncPgno ){
+    /* If needSyncPgno is non-zero, then the journal file needs to be
+    ** sync()ed before any data is written to database file page needSyncPgno.
+    ** Currently, no such page exists in the page-cache and the
+    ** "is journaled" bitvec flag has been set. This needs to be remedied by
+    ** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC
+    ** flag.
+    **
+    ** If the attempt to load the page into the page-cache fails, (due
+    ** to a malloc() or IO failure), clear the bit in the pInJournal[]
+    ** array. Otherwise, if the page is loaded and written again in
+    ** this transaction, it may be written to the database file before
+    ** it is synced into the journal file. This way, it may end up in
+    ** the journal file twice, but that is not a problem.
+    */
+    PgHdr *pPgHdr;
+    rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr, 0);
+    if( rc!=SQLITE_OK ){
+      if( needSyncPgno<=pPager->dbOrigSize ){
+        assert( pPager->pTmpSpace!=0 );
+        sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace);
+      }
+      return rc;
+    }
+    pPgHdr->flags |= PGHDR_NEED_SYNC;
+    sqlite3PcacheMakeDirty(pPgHdr);
+    sqlite3PagerUnrefNotNull(pPgHdr);
+  }
+
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** The page handle passed as the first argument refers to a dirty page
+** with a page number other than iNew. This function changes the page's
+** page number to iNew and sets the value of the PgHdr.flags field to
+** the value passed as the third parameter.
+*/
+void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){
+  assert( pPg->pgno!=iNew );
+  pPg->flags = flags;
+  sqlite3PcacheMove(pPg, iNew);
+}
+
+/*
+** Return a pointer to the data for the specified page.
+*/
+void *sqlite3PagerGetData(DbPage *pPg){
+  assert( pPg->nRef>0 || pPg->pPager->memDb );
+  return pPg->pData;
+}
+
+/*
+** Return a pointer to the Pager.nExtra bytes of "extra" space
+** allocated along with the specified page.
+*/
+void *sqlite3PagerGetExtra(DbPage *pPg){
+  return pPg->pExtra;
+}
+
+/*
+** Get/set the locking-mode for this pager. Parameter eMode must be one
+** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or
+** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
+** the locking-mode is set to the value specified.
+**
+** The returned value is either PAGER_LOCKINGMODE_NORMAL or
+** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
+** locking-mode.
+*/
+int sqlite3PagerLockingMode(Pager *pPager, int eMode){
+  assert( eMode==PAGER_LOCKINGMODE_QUERY
+            || eMode==PAGER_LOCKINGMODE_NORMAL
+            || eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
+  assert( PAGER_LOCKINGMODE_QUERY<0 );
+  assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
+  assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) );
+  if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){
+    pPager->exclusiveMode = (u8)eMode;
+  }
+  return (int)pPager->exclusiveMode;
+}
+
+/*
+** Set the journal-mode for this pager. Parameter eMode must be one of:
+**
+**    PAGER_JOURNALMODE_DELETE
+**    PAGER_JOURNALMODE_TRUNCATE
+**    PAGER_JOURNALMODE_PERSIST
+**    PAGER_JOURNALMODE_OFF
+**    PAGER_JOURNALMODE_MEMORY
+**    PAGER_JOURNALMODE_WAL
+**
+** The journalmode is set to the value specified if the change is allowed.
+** The change may be disallowed for the following reasons:
+**
+**   *  An in-memory database can only have its journal_mode set to _OFF
+**      or _MEMORY.
+**
+**   *  Temporary databases cannot have _WAL journalmode.
+**
+** The returned indicate the current (possibly updated) journal-mode.
+*/
+int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
+  u8 eOld = pPager->journalMode;    /* Prior journalmode */
+
+  /* The eMode parameter is always valid */
+  assert(      eMode==PAGER_JOURNALMODE_DELETE    /* 0 */
+            || eMode==PAGER_JOURNALMODE_PERSIST   /* 1 */
+            || eMode==PAGER_JOURNALMODE_OFF       /* 2 */
+            || eMode==PAGER_JOURNALMODE_TRUNCATE  /* 3 */
+            || eMode==PAGER_JOURNALMODE_MEMORY    /* 4 */
+            || eMode==PAGER_JOURNALMODE_WAL       /* 5 */ );
+
+  /* This routine is only called from the OP_JournalMode opcode, and
+  ** the logic there will never allow a temporary file to be changed
+  ** to WAL mode.
+  */
+  assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL );
+
+  /* Do allow the journalmode of an in-memory database to be set to
+  ** anything other than MEMORY or OFF
+  */
+  if( MEMDB ){
+    assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF );
+    if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){
+      eMode = eOld;
+    }
+  }
+
+  if( eMode!=eOld ){
+
+    /* Change the journal mode. */
+    assert( pPager->eState!=PAGER_ERROR );
+    pPager->journalMode = (u8)eMode;
+
+    /* When transitioning from TRUNCATE or PERSIST to any other journal
+    ** mode except WAL, unless the pager is in locking_mode=exclusive mode,
+    ** delete the journal file.
+    */
+    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+    assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
+    assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
+    assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
+    assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
+    assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
+
+    assert( isOpen(pPager->fd) || pPager->exclusiveMode );
+    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
+      /* In this case we would like to delete the journal file. If it is
+      ** not possible, then that is not a problem. Deleting the journal file
+      ** here is an optimization only.
+      **
+      ** Before deleting the journal file, obtain a RESERVED lock on the
+      ** database file. This ensures that the journal file is not deleted
+      ** while it is in use by some other client.
+      */
+      sqlite3OsClose(pPager->jfd);
+      if( pPager->eLock>=RESERVED_LOCK ){
+        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+      }else{
+        int rc = SQLITE_OK;
+        int state = pPager->eState;
+        assert( state==PAGER_OPEN || state==PAGER_READER );
+        if( state==PAGER_OPEN ){
+          rc = sqlite3PagerSharedLock(pPager);
+        }
+        if( pPager->eState==PAGER_READER ){
+          assert( rc==SQLITE_OK );
+          rc = pagerLockDb(pPager, RESERVED_LOCK);
+        }
+        if( rc==SQLITE_OK ){
+          sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+        }
+        if( rc==SQLITE_OK && state==PAGER_READER ){
+          pagerUnlockDb(pPager, SHARED_LOCK);
+        }else if( state==PAGER_OPEN ){
+          pager_unlock(pPager);
+        }
+        assert( state==pPager->eState );
+      }
+    }else if( eMode==PAGER_JOURNALMODE_OFF || eMode==PAGER_JOURNALMODE_MEMORY ){
+      sqlite3OsClose(pPager->jfd);
+    }
+  }
+
+  /* Return the new journal mode */
+  return (int)pPager->journalMode;
+}
+
+/*
+** Return the current journal mode.
+*/
+int sqlite3PagerGetJournalMode(Pager *pPager){
+  return (int)pPager->journalMode;
+}
+
+/*
+** Return TRUE if the pager is in a state where it is OK to change the
+** journalmode.  Journalmode changes can only happen when the database
+** is unmodified.
+*/
+int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
+  assert( assert_pager_state(pPager) );
+  if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0;
+  if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0;
+  return 1;
+}
+
+/*
+** Get/set the size-limit used for persistent journal files.
+**
+** Setting the size limit to -1 means no limit is enforced.
+** An attempt to set a limit smaller than -1 is a no-op.
+*/
+i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
+  if( iLimit>=-1 ){
+    pPager->journalSizeLimit = iLimit;
+    sqlite3WalLimit(pPager->pWal, iLimit);
+  }
+  return pPager->journalSizeLimit;
+}
+
+/*
+** Return a pointer to the pPager->pBackup variable. The backup module
+** in backup.c maintains the content of this variable. This module
+** uses it opaquely as an argument to sqlite3BackupRestart() and
+** sqlite3BackupUpdate() only.
+*/
+sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
+  return &pPager->pBackup;
+}
+
+#ifndef SQLITE_OMIT_VACUUM
+/*
+** Unless this is an in-memory or temporary database, clear the pager cache.
+*/
+void sqlite3PagerClearCache(Pager *pPager){
+  assert( MEMDB==0 || pPager->tempFile );
+  if( pPager->tempFile==0 ) pager_reset(pPager);
+}
+#endif
+
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is called when the user invokes "PRAGMA wal_checkpoint",
+** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
+** or wal_blocking_checkpoint() API functions.
+**
+** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
+*/
+int sqlite3PagerCheckpoint(
+  Pager *pPager,                  /* Checkpoint on this pager */
+  sqlite3 *db,                    /* Db handle used to check for interrupts */
+  int eMode,                      /* Type of checkpoint */
+  int *pnLog,                     /* OUT: Final number of frames in log */
+  int *pnCkpt                     /* OUT: Final number of checkpointed frames */
+){
+  int rc = SQLITE_OK;
+  if( pPager->pWal==0 && pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+    /* This only happens when a database file is zero bytes in size opened and
+    ** then "PRAGMA journal_mode=WAL" is run and then sqlite3_wal_checkpoint()
+    ** is invoked without any intervening transactions.  We need to start
+    ** a transaction to initialize pWal.  The PRAGMA table_list statement is
+    ** used for this since it starts transactions on every database file,
+    ** including all ATTACHed databases.  This seems expensive for a single
+    ** sqlite3_wal_checkpoint() call, but it happens very rarely.
+    ** https://sqlite.org/forum/forumpost/fd0f19d229156939
+    */
+    sqlite3_exec(db, "PRAGMA table_list",0,0,0);
+  }
+  if( pPager->pWal ){
+    rc = sqlite3WalCheckpoint(pPager->pWal, db, eMode,
+        (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
+        pPager->pBusyHandlerArg,
+        pPager->walSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
+        pnLog, pnCkpt
+    );
+  }
+  return rc;
+}
+
+int sqlite3PagerWalCallback(Pager *pPager){
+  return sqlite3WalCallback(pPager->pWal);
+}
+
+/*
+** Return true if the underlying VFS for the given pager supports the
+** primitives necessary for write-ahead logging.
+*/
+int sqlite3PagerWalSupported(Pager *pPager){
+  const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
+  if( pPager->noLock ) return 0;
+  return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap);
+}
+
+/*
+** Attempt to take an exclusive lock on the database file. If a PENDING lock
+** is obtained instead, immediately release it.
+*/
+static int pagerExclusiveLock(Pager *pPager){
+  int rc;                         /* Return code */
+  u8 eOrigLock;                   /* Original lock */
+
+  assert( pPager->eLock>=SHARED_LOCK );
+  eOrigLock = pPager->eLock;
+  rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+  if( rc!=SQLITE_OK ){
+    /* If the attempt to grab the exclusive lock failed, release the
+    ** pending lock that may have been obtained instead.  */
+    pagerUnlockDb(pPager, eOrigLock);
+  }
+
+  return rc;
+}
+
+/*
+** Call sqlite3WalOpen() to open the WAL handle. If the pager is in
+** exclusive-locking mode when this function is called, take an EXCLUSIVE
+** lock on the database file and use heap-memory to store the wal-index
+** in. Otherwise, use the normal shared-memory.
+*/
+static int pagerOpenWal(Pager *pPager){
+  int rc = SQLITE_OK;
+
+  assert( pPager->pWal==0 && pPager->tempFile==0 );
+  assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
+
+  /* If the pager is already in exclusive-mode, the WAL module will use
+  ** heap-memory for the wal-index instead of the VFS shared-memory
+  ** implementation. Take the exclusive lock now, before opening the WAL
+  ** file, to make sure this is safe.
+  */
+  if( pPager->exclusiveMode ){
+    rc = pagerExclusiveLock(pPager);
+  }
+
+  /* Open the connection to the log file. If this operation fails,
+  ** (e.g. due to malloc() failure), return an error code.
+  */
+  if( rc==SQLITE_OK ){
+    rc = sqlite3WalOpen(pPager->pVfs,
+        pPager->fd, pPager->zWal, pPager->exclusiveMode,
+        pPager->journalSizeLimit, &pPager->pWal
+    );
+  }
+  pagerFixMaplimit(pPager);
+
+  return rc;
+}
+
+
+/*
+** The caller must be holding a SHARED lock on the database file to call
+** this function.
+**
+** If the pager passed as the first argument is open on a real database
+** file (not a temp file or an in-memory database), and the WAL file
+** is not already open, make an attempt to open it now. If successful,
+** return SQLITE_OK. If an error occurs or the VFS used by the pager does
+** not support the xShmXXX() methods, return an error code. *pbOpen is
+** not modified in either case.
+**
+** If the pager is open on a temp-file (or in-memory database), or if
+** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK
+** without doing anything.
+*/
+int sqlite3PagerOpenWal(
+  Pager *pPager,                  /* Pager object */
+  int *pbOpen                     /* OUT: Set to true if call is a no-op */
+){
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( assert_pager_state(pPager) );
+  assert( pPager->eState==PAGER_OPEN   || pbOpen );
+  assert( pPager->eState==PAGER_READER || !pbOpen );
+  assert( pbOpen==0 || *pbOpen==0 );
+  assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );
+
+  if( !pPager->tempFile && !pPager->pWal ){
+    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
+
+    /* Close any rollback journal previously open */
+    sqlite3OsClose(pPager->jfd);
+
+    rc = pagerOpenWal(pPager);
+    if( rc==SQLITE_OK ){
+      pPager->journalMode = PAGER_JOURNALMODE_WAL;
+      pPager->eState = PAGER_OPEN;
+    }
+  }else{
+    *pbOpen = 1;
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to close the connection to the log file prior
+** to switching from WAL to rollback mode.
+**
+** Before closing the log file, this function attempts to take an
+** EXCLUSIVE lock on the database file. If this cannot be obtained, an
+** error (SQLITE_BUSY) is returned and the log connection is not closed.
+** If successful, the EXCLUSIVE lock is not released before returning.
+*/
+int sqlite3PagerCloseWal(Pager *pPager, sqlite3 *db){
+  int rc = SQLITE_OK;
+
+  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
+
+  /* If the log file is not already open, but does exist in the file-system,
+  ** it may need to be checkpointed before the connection can switch to
+  ** rollback mode. Open it now so this can happen.
+  */
+  if( !pPager->pWal ){
+    int logexists = 0;
+    rc = pagerLockDb(pPager, SHARED_LOCK);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3OsAccess(
+          pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists
+      );
+    }
+    if( rc==SQLITE_OK && logexists ){
+      rc = pagerOpenWal(pPager);
+    }
+  }
+   
+  /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
+  ** the database file, the log and log-summary files will be deleted.
+  */
+  if( rc==SQLITE_OK && pPager->pWal ){
+    rc = pagerExclusiveLock(pPager);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags,
+                           pPager->pageSize, (u8*)pPager->pTmpSpace);
+      pPager->pWal = 0;
+      pagerFixMaplimit(pPager);
+      if( rc && !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
+    }
+  }
+  return rc;
+}
+
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+/*
+** If pager pPager is a wal-mode database not in exclusive locking mode,
+** invoke the sqlite3WalWriteLock() function on the associated Wal object
+** with the same db and bLock parameters as were passed to this function.
+** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise.
+*/
+int sqlite3PagerWalWriteLock(Pager *pPager, int bLock){
+  int rc = SQLITE_OK;
+  if( pagerUseWal(pPager) && pPager->exclusiveMode==0 ){
+    rc = sqlite3WalWriteLock(pPager->pWal, bLock);
+  }
+  return rc;
+}
+
+/*
+** Set the database handle used by the wal layer to determine if
+** blocking locks are required.
+*/
+void sqlite3PagerWalDb(Pager *pPager, sqlite3 *db){
+  if( pagerUseWal(pPager) ){
+    sqlite3WalDb(pPager->pWal, db);
+  }
+}
+#endif
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** If this is a WAL database, obtain a snapshot handle for the snapshot
+** currently open. Otherwise, return an error.
+*/
+int sqlite3PagerSnapshotGet(Pager *pPager, sqlite3_snapshot **ppSnapshot){
+  int rc = SQLITE_ERROR;
+  if( pPager->pWal ){
+    rc = sqlite3WalSnapshotGet(pPager->pWal, ppSnapshot);
+  }
+  return rc;
+}
+
+/*
+** If this is a WAL database, store a pointer to pSnapshot. Next time a
+** read transaction is opened, attempt to read from the snapshot it
+** identifies. If this is not a WAL database, return an error.
+*/
+int sqlite3PagerSnapshotOpen(
+  Pager *pPager,
+  sqlite3_snapshot *pSnapshot
+){
+  int rc = SQLITE_OK;
+  if( pPager->pWal ){
+    sqlite3WalSnapshotOpen(pPager->pWal, pSnapshot);
+  }else{
+    rc = SQLITE_ERROR;
+  }
+  return rc;
+}
+
+/*
+** If this is a WAL database, call sqlite3WalSnapshotRecover(). If this
+** is not a WAL database, return an error.
+*/
+int sqlite3PagerSnapshotRecover(Pager *pPager){
+  int rc;
+  if( pPager->pWal ){
+    rc = sqlite3WalSnapshotRecover(pPager->pWal);
+  }else{
+    rc = SQLITE_ERROR;
+  }
+  return rc;
+}
+
+/*
+** The caller currently has a read transaction open on the database.
+** If this is not a WAL database, SQLITE_ERROR is returned. Otherwise,
+** this function takes a SHARED lock on the CHECKPOINTER slot and then
+** checks if the snapshot passed as the second argument is still
+** available. If so, SQLITE_OK is returned.
+**
+** If the snapshot is not available, SQLITE_ERROR is returned. Or, if
+** the CHECKPOINTER lock cannot be obtained, SQLITE_BUSY. If any error
+** occurs (any value other than SQLITE_OK is returned), the CHECKPOINTER
+** lock is released before returning.
+*/
+int sqlite3PagerSnapshotCheck(Pager *pPager, sqlite3_snapshot *pSnapshot){
+  int rc;
+  if( pPager->pWal ){
+    rc = sqlite3WalSnapshotCheck(pPager->pWal, pSnapshot);
+  }else{
+    rc = SQLITE_ERROR;
+  }
+  return rc;
+}
+
+/*
+** Release a lock obtained by an earlier successful call to
+** sqlite3PagerSnapshotCheck().
+*/
+void sqlite3PagerSnapshotUnlock(Pager *pPager){
+  assert( pPager->pWal );
+  sqlite3WalSnapshotUnlock(pPager->pWal);
+}
+
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+#endif /* !SQLITE_OMIT_WAL */
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+/*
+** A read-lock must be held on the pager when this function is called. If
+** the pager is in WAL mode and the WAL file currently contains one or more
+** frames, return the size in bytes of the page images stored within the
+** WAL frames. Otherwise, if this is not a WAL database or the WAL file
+** is empty, return 0.
+*/
+int sqlite3PagerWalFramesize(Pager *pPager){
+  assert( pPager->eState>=PAGER_READER );
+  return sqlite3WalFramesize(pPager->pWal);
+}
+#endif
+
+#if defined(SQLITE_USE_SEH) && !defined(SQLITE_OMIT_WAL)
+int sqlite3PagerWalSystemErrno(Pager *pPager){
+  return sqlite3WalSystemErrno(pPager->pWal);
+}
+#endif
+
+#endif /* SQLITE_OMIT_DISKIO */
diff --git a/src/pager.h b/src/pager.h
new file mode 100644
index 0000000..7ef9a23
--- /dev/null
+++ b/src/pager.h
@@ -0,0 +1,247 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the sqlite page cache
+** subsystem.  The page cache subsystem reads and writes a file a page
+** at a time and provides a journal for rollback.
+*/
+
+#ifndef SQLITE_PAGER_H
+#define SQLITE_PAGER_H
+
+/*
+** Default maximum size for persistent journal files. A negative 
+** value means no limit. This value may be overridden using the 
+** sqlite3PagerJournalSizeLimit() API. See also "PRAGMA journal_size_limit".
+*/
+#ifndef SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT
+  #define SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT -1
+#endif
+
+/*
+** The type used to represent a page number.  The first page in a file
+** is called page 1.  0 is used to represent "not a page".
+*/
+typedef u32 Pgno;
+
+/*
+** Each open file is managed by a separate instance of the "Pager" structure.
+*/
+typedef struct Pager Pager;
+
+/*
+** Handle type for pages.
+*/
+typedef struct PgHdr DbPage;
+
+/*
+** Page number PAGER_SJ_PGNO is never used in an SQLite database (it is
+** reserved for working around a windows/posix incompatibility). It is
+** used in the journal to signify that the remainder of the journal file 
+** is devoted to storing a super-journal name - there are no more pages to
+** roll back. See comments for function writeSuperJournal() in pager.c 
+** for details.
+*/
+#define PAGER_SJ_PGNO_COMPUTED(x) ((Pgno)((PENDING_BYTE/((x)->pageSize))+1))
+#define PAGER_SJ_PGNO(x)          ((x)->lckPgno)
+
+/*
+** Allowed values for the flags parameter to sqlite3PagerOpen().
+**
+** NOTE: These values must match the corresponding BTREE_ values in btree.h.
+*/
+#define PAGER_OMIT_JOURNAL  0x0001    /* Do not use a rollback journal */
+#define PAGER_MEMORY        0x0002    /* In-memory database */
+
+/*
+** Valid values for the second argument to sqlite3PagerLockingMode().
+*/
+#define PAGER_LOCKINGMODE_QUERY      -1
+#define PAGER_LOCKINGMODE_NORMAL      0
+#define PAGER_LOCKINGMODE_EXCLUSIVE   1
+
+/*
+** Numeric constants that encode the journalmode.
+**
+** The numeric values encoded here (other than PAGER_JOURNALMODE_QUERY)
+** are exposed in the API via the "PRAGMA journal_mode" command and
+** therefore cannot be changed without a compatibility break.
+*/
+#define PAGER_JOURNALMODE_QUERY     (-1)  /* Query the value of journalmode */
+#define PAGER_JOURNALMODE_DELETE      0   /* Commit by deleting journal file */
+#define PAGER_JOURNALMODE_PERSIST     1   /* Commit by zeroing journal header */
+#define PAGER_JOURNALMODE_OFF         2   /* Journal omitted.  */
+#define PAGER_JOURNALMODE_TRUNCATE    3   /* Commit by truncating journal */
+#define PAGER_JOURNALMODE_MEMORY      4   /* In-memory journal file */
+#define PAGER_JOURNALMODE_WAL         5   /* Use write-ahead logging */
+
+/*
+** Flags that make up the mask passed to sqlite3PagerGet().
+*/
+#define PAGER_GET_NOCONTENT     0x01  /* Do not load data from disk */
+#define PAGER_GET_READONLY      0x02  /* Read-only page is acceptable */
+
+/*
+** Flags for sqlite3PagerSetFlags()
+**
+** Value constraints (enforced via assert()):
+**    PAGER_FULLFSYNC      == SQLITE_FullFSync
+**    PAGER_CKPT_FULLFSYNC == SQLITE_CkptFullFSync
+**    PAGER_CACHE_SPILL    == SQLITE_CacheSpill
+*/
+#define PAGER_SYNCHRONOUS_OFF       0x01  /* PRAGMA synchronous=OFF */
+#define PAGER_SYNCHRONOUS_NORMAL    0x02  /* PRAGMA synchronous=NORMAL */
+#define PAGER_SYNCHRONOUS_FULL      0x03  /* PRAGMA synchronous=FULL */
+#define PAGER_SYNCHRONOUS_EXTRA     0x04  /* PRAGMA synchronous=EXTRA */
+#define PAGER_SYNCHRONOUS_MASK      0x07  /* Mask for four values above */
+#define PAGER_FULLFSYNC             0x08  /* PRAGMA fullfsync=ON */
+#define PAGER_CKPT_FULLFSYNC        0x10  /* PRAGMA checkpoint_fullfsync=ON */
+#define PAGER_CACHESPILL            0x20  /* PRAGMA cache_spill=ON */
+#define PAGER_FLAGS_MASK            0x38  /* All above except SYNCHRONOUS */
+
+/*
+** The remainder of this file contains the declarations of the functions
+** that make up the Pager sub-system API. See source code comments for 
+** a detailed description of each routine.
+*/
+
+/* Open and close a Pager connection. */ 
+int sqlite3PagerOpen(
+  sqlite3_vfs*,
+  Pager **ppPager,
+  const char*,
+  int,
+  int,
+  int,
+  void(*)(DbPage*)
+);
+int sqlite3PagerClose(Pager *pPager, sqlite3*);
+int sqlite3PagerReadFileheader(Pager*, int, unsigned char*);
+
+/* Functions used to configure a Pager object. */
+void sqlite3PagerSetBusyHandler(Pager*, int(*)(void *), void *);
+int sqlite3PagerSetPagesize(Pager*, u32*, int);
+Pgno sqlite3PagerMaxPageCount(Pager*, Pgno);
+void sqlite3PagerSetCachesize(Pager*, int);
+int sqlite3PagerSetSpillsize(Pager*, int);
+void sqlite3PagerSetMmapLimit(Pager *, sqlite3_int64);
+void sqlite3PagerShrink(Pager*);
+void sqlite3PagerSetFlags(Pager*,unsigned);
+int sqlite3PagerLockingMode(Pager *, int);
+int sqlite3PagerSetJournalMode(Pager *, int);
+int sqlite3PagerGetJournalMode(Pager*);
+int sqlite3PagerOkToChangeJournalMode(Pager*);
+i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
+sqlite3_backup **sqlite3PagerBackupPtr(Pager*);
+int sqlite3PagerFlush(Pager*);
+
+/* Functions used to obtain and release page references. */ 
+int sqlite3PagerGet(Pager *pPager, Pgno pgno, DbPage **ppPage, int clrFlag);
+DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno);
+void sqlite3PagerRef(DbPage*);
+void sqlite3PagerUnref(DbPage*);
+void sqlite3PagerUnrefNotNull(DbPage*);
+void sqlite3PagerUnrefPageOne(DbPage*);
+
+/* Operations on page references. */
+int sqlite3PagerWrite(DbPage*);
+void sqlite3PagerDontWrite(DbPage*);
+int sqlite3PagerMovepage(Pager*,DbPage*,Pgno,int);
+int sqlite3PagerPageRefcount(DbPage*);
+void *sqlite3PagerGetData(DbPage *); 
+void *sqlite3PagerGetExtra(DbPage *); 
+
+/* Functions used to manage pager transactions and savepoints. */
+void sqlite3PagerPagecount(Pager*, int*);
+int sqlite3PagerBegin(Pager*, int exFlag, int);
+int sqlite3PagerCommitPhaseOne(Pager*,const char *zSuper, int);
+int sqlite3PagerExclusiveLock(Pager*);
+int sqlite3PagerSync(Pager *pPager, const char *zSuper);
+int sqlite3PagerCommitPhaseTwo(Pager*);
+int sqlite3PagerRollback(Pager*);
+int sqlite3PagerOpenSavepoint(Pager *pPager, int n);
+int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint);
+int sqlite3PagerSharedLock(Pager *pPager);
+
+#ifndef SQLITE_OMIT_WAL
+  int sqlite3PagerCheckpoint(Pager *pPager, sqlite3*, int, int*, int*);
+  int sqlite3PagerWalSupported(Pager *pPager);
+  int sqlite3PagerWalCallback(Pager *pPager);
+  int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen);
+  int sqlite3PagerCloseWal(Pager *pPager, sqlite3*);
+# ifdef SQLITE_ENABLE_SNAPSHOT
+  int sqlite3PagerSnapshotGet(Pager*, sqlite3_snapshot **ppSnapshot);
+  int sqlite3PagerSnapshotOpen(Pager*, sqlite3_snapshot *pSnapshot);
+  int sqlite3PagerSnapshotRecover(Pager *pPager);
+  int sqlite3PagerSnapshotCheck(Pager *pPager, sqlite3_snapshot *pSnapshot);
+  void sqlite3PagerSnapshotUnlock(Pager *pPager);
+# endif
+#endif
+
+#if !defined(SQLITE_OMIT_WAL) && defined(SQLITE_ENABLE_SETLK_TIMEOUT)
+  int sqlite3PagerWalWriteLock(Pager*, int);
+  void sqlite3PagerWalDb(Pager*, sqlite3*);
+#else
+# define sqlite3PagerWalWriteLock(y,z) SQLITE_OK
+# define sqlite3PagerWalDb(x,y)
+#endif
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+  int sqlite3PagerDirectReadOk(Pager *pPager, Pgno pgno);
+#endif
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+  int sqlite3PagerWalFramesize(Pager *pPager);
+#endif
+
+/* Functions used to query pager state and configuration. */
+u8 sqlite3PagerIsreadonly(Pager*);
+u32 sqlite3PagerDataVersion(Pager*);
+#ifdef SQLITE_DEBUG
+  int sqlite3PagerRefcount(Pager*);
+#endif
+int sqlite3PagerMemUsed(Pager*);
+const char *sqlite3PagerFilename(const Pager*, int);
+sqlite3_vfs *sqlite3PagerVfs(Pager*);
+sqlite3_file *sqlite3PagerFile(Pager*);
+sqlite3_file *sqlite3PagerJrnlFile(Pager*);
+const char *sqlite3PagerJournalname(Pager*);
+void *sqlite3PagerTempSpace(Pager*);
+int sqlite3PagerIsMemdb(Pager*);
+void sqlite3PagerCacheStat(Pager *, int, int, u64*);
+void sqlite3PagerClearCache(Pager*);
+int sqlite3SectorSize(sqlite3_file *);
+
+/* Functions used to truncate the database file. */
+void sqlite3PagerTruncateImage(Pager*,Pgno);
+
+void sqlite3PagerRekey(DbPage*, Pgno, u16);
+
+/* Functions to support testing and debugging. */
+#if !defined(NDEBUG) || defined(SQLITE_TEST)
+  Pgno sqlite3PagerPagenumber(DbPage*);
+  int sqlite3PagerIswriteable(DbPage*);
+#endif
+#ifdef SQLITE_TEST
+  int *sqlite3PagerStats(Pager*);
+  void sqlite3PagerRefdump(Pager*);
+  void disable_simulated_io_errors(void);
+  void enable_simulated_io_errors(void);
+#else
+# define disable_simulated_io_errors()
+# define enable_simulated_io_errors()
+#endif
+
+#if defined(SQLITE_USE_SEH) && !defined(SQLITE_OMIT_WAL)
+int sqlite3PagerWalSystemErrno(Pager*);
+#endif
+
+#endif /* SQLITE_PAGER_H */
diff --git a/src/parse.y b/src/parse.y
new file mode 100644
index 0000000..1949119
--- /dev/null
+++ b/src/parse.y
@@ -0,0 +1,1943 @@
+%include {
+/*
+** 2001-09-15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains SQLite's SQL parser.
+**
+** The canonical source code to this file ("parse.y") is a Lemon grammar 
+** file that specifies the input grammar and actions to take while parsing.
+** That input file is processed by Lemon to generate a C-language 
+** implementation of a parser for the given grammar.  You might be reading
+** this comment as part of the translated C-code.  Edits should be made
+** to the original parse.y sources.
+*/
+}
+
+// All token codes are small integers with #defines that begin with "TK_"
+%token_prefix TK_
+
+// The type of the data attached to each token is Token.  This is also the
+// default type for non-terminals.
+//
+%token_type {Token}
+%default_type {Token}
+
+// An extra argument to the constructor for the parser, which is available
+// to all actions.
+%extra_context {Parse *pParse}
+
+// This code runs whenever there is a syntax error
+//
+%syntax_error {
+  UNUSED_PARAMETER(yymajor);  /* Silence some compiler warnings */
+  if( TOKEN.z[0] ){
+    sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", &TOKEN);
+  }else{
+    sqlite3ErrorMsg(pParse, "incomplete input");
+  }
+}
+%stack_overflow {
+  sqlite3ErrorMsg(pParse, "parser stack overflow");
+}
+
+// The name of the generated procedure that implements the parser
+// is as follows:
+%name sqlite3Parser
+
+// The following text is included near the beginning of the C source
+// code file that implements the parser.
+//
+%include {
+#include "sqliteInt.h"
+
+/*
+** Disable all error recovery processing in the parser push-down
+** automaton.
+*/
+#define YYNOERRORRECOVERY 1
+
+/*
+** Make yytestcase() the same as testcase()
+*/
+#define yytestcase(X) testcase(X)
+
+/*
+** Indicate that sqlite3ParserFree() will never be called with a null
+** pointer.
+*/
+#define YYPARSEFREENEVERNULL 1
+
+/*
+** In the amalgamation, the parse.c file generated by lemon and the
+** tokenize.c file are concatenated.  In that case, sqlite3RunParser()
+** has access to the the size of the yyParser object and so the parser
+** engine can be allocated from stack.  In that case, only the
+** sqlite3ParserInit() and sqlite3ParserFinalize() routines are invoked
+** and the sqlite3ParserAlloc() and sqlite3ParserFree() routines can be
+** omitted.
+*/
+#ifdef SQLITE_AMALGAMATION
+# define sqlite3Parser_ENGINEALWAYSONSTACK 1
+#endif
+
+/*
+** Alternative datatype for the argument to the malloc() routine passed
+** into sqlite3ParserAlloc().  The default is size_t.
+*/
+#define YYMALLOCARGTYPE  u64
+
+/*
+** An instance of the following structure describes the event of a
+** TRIGGER.  "a" is the event type, one of TK_UPDATE, TK_INSERT,
+** TK_DELETE, or TK_INSTEAD.  If the event is of the form
+**
+**      UPDATE ON (a,b,c)
+**
+** Then the "b" IdList records the list "a,b,c".
+*/
+struct TrigEvent { int a; IdList * b; };
+
+struct FrameBound     { int eType; Expr *pExpr; };
+
+/*
+** Disable lookaside memory allocation for objects that might be
+** shared across database connections.
+*/
+static void disableLookaside(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  pParse->disableLookaside++;
+  DisableLookaside;
+}
+
+#if !defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) \
+ && defined(SQLITE_UDL_CAPABLE_PARSER)
+/*
+** Issue an error message if an ORDER BY or LIMIT clause occurs on an
+** UPDATE or DELETE statement.
+*/
+static void updateDeleteLimitError(
+  Parse *pParse,
+  ExprList *pOrderBy,
+  Expr *pLimit
+){
+  if( pOrderBy ){
+    sqlite3ErrorMsg(pParse, "syntax error near \"ORDER BY\"");
+  }else{
+    sqlite3ErrorMsg(pParse, "syntax error near \"LIMIT\"");
+  }
+  sqlite3ExprListDelete(pParse->db, pOrderBy);
+  sqlite3ExprDelete(pParse->db, pLimit);
+}
+#endif /* SQLITE_ENABLE_UPDATE_DELETE_LIMIT */
+
+} // end %include
+
+// Input is a single SQL command
+input ::= cmdlist.
+cmdlist ::= cmdlist ecmd.
+cmdlist ::= ecmd.
+ecmd ::= SEMI.
+ecmd ::= cmdx SEMI.
+%ifndef SQLITE_OMIT_EXPLAIN
+ecmd ::= explain cmdx SEMI.       {NEVER-REDUCE}
+explain ::= EXPLAIN.              { if( pParse->pReprepare==0 ) pParse->explain = 1; }
+explain ::= EXPLAIN QUERY PLAN.   { if( pParse->pReprepare==0 ) pParse->explain = 2; }
+%endif  SQLITE_OMIT_EXPLAIN
+cmdx ::= cmd.           { sqlite3FinishCoding(pParse); }
+
+///////////////////// Begin and end transactions. ////////////////////////////
+//
+
+cmd ::= BEGIN transtype(Y) trans_opt.  {sqlite3BeginTransaction(pParse, Y);}
+trans_opt ::= .
+trans_opt ::= TRANSACTION.
+trans_opt ::= TRANSACTION nm.
+%type transtype {int}
+transtype(A) ::= .             {A = TK_DEFERRED;}
+transtype(A) ::= DEFERRED(X).  {A = @X; /*A-overwrites-X*/}
+transtype(A) ::= IMMEDIATE(X). {A = @X; /*A-overwrites-X*/}
+transtype(A) ::= EXCLUSIVE(X). {A = @X; /*A-overwrites-X*/}
+cmd ::= COMMIT|END(X) trans_opt.   {sqlite3EndTransaction(pParse,@X);}
+cmd ::= ROLLBACK(X) trans_opt.     {sqlite3EndTransaction(pParse,@X);}
+
+savepoint_opt ::= SAVEPOINT.
+savepoint_opt ::= .
+cmd ::= SAVEPOINT nm(X). {
+  sqlite3Savepoint(pParse, SAVEPOINT_BEGIN, &X);
+}
+cmd ::= RELEASE savepoint_opt nm(X). {
+  sqlite3Savepoint(pParse, SAVEPOINT_RELEASE, &X);
+}
+cmd ::= ROLLBACK trans_opt TO savepoint_opt nm(X). {
+  sqlite3Savepoint(pParse, SAVEPOINT_ROLLBACK, &X);
+}
+
+///////////////////// The CREATE TABLE statement ////////////////////////////
+//
+cmd ::= create_table create_table_args.
+create_table ::= createkw temp(T) TABLE ifnotexists(E) nm(Y) dbnm(Z). {
+   sqlite3StartTable(pParse,&Y,&Z,T,0,0,E);
+}
+createkw(A) ::= CREATE(A).  {disableLookaside(pParse);}
+
+%type ifnotexists {int}
+ifnotexists(A) ::= .              {A = 0;}
+ifnotexists(A) ::= IF NOT EXISTS. {A = 1;}
+%type temp {int}
+%ifndef SQLITE_OMIT_TEMPDB
+temp(A) ::= TEMP.  {A = pParse->db->init.busy==0;}
+%endif  SQLITE_OMIT_TEMPDB
+temp(A) ::= .      {A = 0;}
+create_table_args ::= LP columnlist conslist_opt(X) RP(E) table_option_set(F). {
+  sqlite3EndTable(pParse,&X,&E,F,0);
+}
+create_table_args ::= AS select(S). {
+  sqlite3EndTable(pParse,0,0,0,S);
+  sqlite3SelectDelete(pParse->db, S);
+}
+%type table_option_set {u32}
+%type table_option {u32}
+table_option_set(A) ::= .    {A = 0;}
+table_option_set(A) ::= table_option(A).
+table_option_set(A) ::= table_option_set(X) COMMA table_option(Y). {A = X|Y;}
+table_option(A) ::= WITHOUT nm(X). {
+  if( X.n==5 && sqlite3_strnicmp(X.z,"rowid",5)==0 ){
+    A = TF_WithoutRowid | TF_NoVisibleRowid;
+  }else{
+    A = 0;
+    sqlite3ErrorMsg(pParse, "unknown table option: %.*s", X.n, X.z);
+  }
+}
+table_option(A) ::= nm(X). {
+  if( X.n==6 && sqlite3_strnicmp(X.z,"strict",6)==0 ){
+    A = TF_Strict;
+  }else{
+    A = 0;
+    sqlite3ErrorMsg(pParse, "unknown table option: %.*s", X.n, X.z);
+  }
+}
+columnlist ::= columnlist COMMA columnname carglist.
+columnlist ::= columnname carglist.
+columnname(A) ::= nm(A) typetoken(Y). {sqlite3AddColumn(pParse,A,Y);}
+
+// Declare some tokens early in order to influence their values, to 
+// improve performance and reduce the executable size.  The goal here is
+// to get the "jump" operations in ISNULL through ESCAPE to have numeric
+// values that are early enough so that all jump operations are clustered
+// at the beginning.
+//
+%token ABORT ACTION AFTER ANALYZE ASC ATTACH BEFORE BEGIN BY CASCADE CAST.
+%token CONFLICT DATABASE DEFERRED DESC DETACH EACH END EXCLUSIVE EXPLAIN FAIL.
+%token OR AND NOT IS MATCH LIKE_KW BETWEEN IN ISNULL NOTNULL NE EQ.
+%token GT LE LT GE ESCAPE.
+
+// The following directive causes tokens ABORT, AFTER, ASC, etc. to
+// fallback to ID if they will not parse as their original value.
+// This obviates the need for the "id" nonterminal.
+//
+%fallback ID
+  ABORT ACTION AFTER ANALYZE ASC ATTACH BEFORE BEGIN BY CASCADE CAST COLUMNKW
+  CONFLICT DATABASE DEFERRED DESC DETACH DO
+  EACH END EXCLUSIVE EXPLAIN FAIL FOR
+  IGNORE IMMEDIATE INITIALLY INSTEAD LIKE_KW MATCH NO PLAN
+  QUERY KEY OF OFFSET PRAGMA RAISE RECURSIVE RELEASE REPLACE RESTRICT ROW ROWS
+  ROLLBACK SAVEPOINT TEMP TRIGGER VACUUM VIEW VIRTUAL WITH WITHOUT
+  NULLS FIRST LAST
+%ifdef SQLITE_OMIT_COMPOUND_SELECT
+  EXCEPT INTERSECT UNION
+%endif SQLITE_OMIT_COMPOUND_SELECT
+%ifndef SQLITE_OMIT_WINDOWFUNC
+  CURRENT FOLLOWING PARTITION PRECEDING RANGE UNBOUNDED
+  EXCLUDE GROUPS OTHERS TIES
+%endif SQLITE_OMIT_WINDOWFUNC
+%ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  GENERATED ALWAYS
+%endif
+  MATERIALIZED
+  REINDEX RENAME CTIME_KW IF
+  .
+%wildcard ANY.
+
+// Define operator precedence early so that this is the first occurrence
+// of the operator tokens in the grammar.  Keeping the operators together
+// causes them to be assigned integer values that are close together,
+// which keeps parser tables smaller.
+//
+// The token values assigned to these symbols is determined by the order
+// in which lemon first sees them.  It must be the case that ISNULL/NOTNULL,
+// NE/EQ, GT/LE, and GE/LT are separated by only a single value.  See
+// the sqlite3ExprIfFalse() routine for additional information on this
+// constraint.
+//
+%left OR.
+%left AND.
+%right NOT.
+%left IS MATCH LIKE_KW BETWEEN IN ISNULL NOTNULL NE EQ.
+%left GT LE LT GE.
+%right ESCAPE.
+%left BITAND BITOR LSHIFT RSHIFT.
+%left PLUS MINUS.
+%left STAR SLASH REM.
+%left CONCAT PTR.
+%left COLLATE.
+%right BITNOT.
+%nonassoc ON.
+
+// An IDENTIFIER can be a generic identifier, or one of several
+// keywords.  Any non-standard keyword can also be an identifier.
+//
+%token_class id  ID|INDEXED.
+
+// And "ids" is an identifer-or-string.
+//
+%token_class ids  ID|STRING.
+
+// An identifier or a join-keyword
+//
+%token_class idj  ID|INDEXED|JOIN_KW.
+
+// The name of a column or table can be any of the following:
+//
+%type nm {Token}
+nm(A) ::= idj(A).
+nm(A) ::= STRING(A).
+
+// A typetoken is really zero or more tokens that form a type name such
+// as can be found after the column name in a CREATE TABLE statement.
+// Multiple tokens are concatenated to form the value of the typetoken.
+//
+%type typetoken {Token}
+typetoken(A) ::= .   {A.n = 0; A.z = 0;}
+typetoken(A) ::= typename(A).
+typetoken(A) ::= typename(A) LP signed RP(Y). {
+  A.n = (int)(&Y.z[Y.n] - A.z);
+}
+typetoken(A) ::= typename(A) LP signed COMMA signed RP(Y). {
+  A.n = (int)(&Y.z[Y.n] - A.z);
+}
+%type typename {Token}
+typename(A) ::= ids(A).
+typename(A) ::= typename(A) ids(Y). {A.n=Y.n+(int)(Y.z-A.z);}
+signed ::= plus_num.
+signed ::= minus_num.
+
+// The scanpt non-terminal takes a value which is a pointer to the
+// input text just past the last token that has been shifted into
+// the parser.  By surrounding some phrase in the grammar with two
+// scanpt non-terminals, we can capture the input text for that phrase.
+// For example:
+//
+//      something ::= .... scanpt(A) phrase scanpt(Z).
+//
+// The text that is parsed as "phrase" is a string starting at A
+// and containing (int)(Z-A) characters.  There might be some extra
+// whitespace on either end of the text, but that can be removed in
+// post-processing, if needed.
+//
+%type scanpt {const char*}
+scanpt(A) ::= . {
+  assert( yyLookahead!=YYNOCODE );
+  A = yyLookaheadToken.z;
+}
+scantok(A) ::= . {
+  assert( yyLookahead!=YYNOCODE );
+  A = yyLookaheadToken;
+}
+
+// "carglist" is a list of additional constraints that come after the
+// column name and column type in a CREATE TABLE statement.
+//
+carglist ::= carglist ccons.
+carglist ::= .
+ccons ::= CONSTRAINT nm(X).           {pParse->constraintName = X;}
+ccons ::= DEFAULT scantok(A) term(X).
+                            {sqlite3AddDefaultValue(pParse,X,A.z,&A.z[A.n]);}
+ccons ::= DEFAULT LP(A) expr(X) RP(Z).
+                            {sqlite3AddDefaultValue(pParse,X,A.z+1,Z.z);}
+ccons ::= DEFAULT PLUS(A) scantok(Z) term(X).
+                            {sqlite3AddDefaultValue(pParse,X,A.z,&Z.z[Z.n]);}
+ccons ::= DEFAULT MINUS(A) scantok(Z) term(X). {
+  Expr *p = sqlite3PExpr(pParse, TK_UMINUS, X, 0);
+  sqlite3AddDefaultValue(pParse,p,A.z,&Z.z[Z.n]);
+}
+ccons ::= DEFAULT scantok id(X).       {
+  Expr *p = tokenExpr(pParse, TK_STRING, X);
+  if( p ){
+    sqlite3ExprIdToTrueFalse(p);
+    testcase( p->op==TK_TRUEFALSE && sqlite3ExprTruthValue(p) );
+  }
+    sqlite3AddDefaultValue(pParse,p,X.z,X.z+X.n);
+}
+
+// In addition to the type name, we also care about the primary key and
+// UNIQUE constraints.
+//
+ccons ::= NULL onconf.
+ccons ::= NOT NULL onconf(R).    {sqlite3AddNotNull(pParse, R);}
+ccons ::= PRIMARY KEY sortorder(Z) onconf(R) autoinc(I).
+                                 {sqlite3AddPrimaryKey(pParse,0,R,I,Z);}
+ccons ::= UNIQUE onconf(R).      {sqlite3CreateIndex(pParse,0,0,0,0,R,0,0,0,0,
+                                   SQLITE_IDXTYPE_UNIQUE);}
+ccons ::= CHECK LP(A) expr(X) RP(B).  {sqlite3AddCheckConstraint(pParse,X,A.z,B.z);}
+ccons ::= REFERENCES nm(T) eidlist_opt(TA) refargs(R).
+                                 {sqlite3CreateForeignKey(pParse,0,&T,TA,R);}
+ccons ::= defer_subclause(D).    {sqlite3DeferForeignKey(pParse,D);}
+ccons ::= COLLATE ids(C).        {sqlite3AddCollateType(pParse, &C);}
+ccons ::= GENERATED ALWAYS AS generated.
+ccons ::= AS generated.
+generated ::= LP expr(E) RP.          {sqlite3AddGenerated(pParse,E,0);}
+generated ::= LP expr(E) RP ID(TYPE). {sqlite3AddGenerated(pParse,E,&TYPE);}
+
+// The optional AUTOINCREMENT keyword
+%type autoinc {int}
+autoinc(X) ::= .          {X = 0;}
+autoinc(X) ::= AUTOINCR.  {X = 1;}
+
+// The next group of rules parses the arguments to a REFERENCES clause
+// that determine if the referential integrity checking is deferred or
+// or immediate and which determine what action to take if a ref-integ
+// check fails.
+//
+%type refargs {int}
+refargs(A) ::= .                  { A = OE_None*0x0101; /* EV: R-19803-45884 */}
+refargs(A) ::= refargs(A) refarg(Y). { A = (A & ~Y.mask) | Y.value; }
+%type refarg {struct {int value; int mask;}}
+refarg(A) ::= MATCH nm.              { A.value = 0;     A.mask = 0x000000; }
+refarg(A) ::= ON INSERT refact.      { A.value = 0;     A.mask = 0x000000; }
+refarg(A) ::= ON DELETE refact(X).   { A.value = X;     A.mask = 0x0000ff; }
+refarg(A) ::= ON UPDATE refact(X).   { A.value = X<<8;  A.mask = 0x00ff00; }
+%type refact {int}
+refact(A) ::= SET NULL.              { A = OE_SetNull;  /* EV: R-33326-45252 */}
+refact(A) ::= SET DEFAULT.           { A = OE_SetDflt;  /* EV: R-33326-45252 */}
+refact(A) ::= CASCADE.               { A = OE_Cascade;  /* EV: R-33326-45252 */}
+refact(A) ::= RESTRICT.              { A = OE_Restrict; /* EV: R-33326-45252 */}
+refact(A) ::= NO ACTION.             { A = OE_None;     /* EV: R-33326-45252 */}
+%type defer_subclause {int}
+defer_subclause(A) ::= NOT DEFERRABLE init_deferred_pred_opt.     {A = 0;}
+defer_subclause(A) ::= DEFERRABLE init_deferred_pred_opt(X).      {A = X;}
+%type init_deferred_pred_opt {int}
+init_deferred_pred_opt(A) ::= .                       {A = 0;}
+init_deferred_pred_opt(A) ::= INITIALLY DEFERRED.     {A = 1;}
+init_deferred_pred_opt(A) ::= INITIALLY IMMEDIATE.    {A = 0;}
+
+conslist_opt(A) ::= .                         {A.n = 0; A.z = 0;}
+conslist_opt(A) ::= COMMA(A) conslist.
+conslist ::= conslist tconscomma tcons.
+conslist ::= tcons.
+tconscomma ::= COMMA.            {pParse->constraintName.n = 0;}
+tconscomma ::= .
+tcons ::= CONSTRAINT nm(X).      {pParse->constraintName = X;}
+tcons ::= PRIMARY KEY LP sortlist(X) autoinc(I) RP onconf(R).
+                                 {sqlite3AddPrimaryKey(pParse,X,R,I,0);}
+tcons ::= UNIQUE LP sortlist(X) RP onconf(R).
+                                 {sqlite3CreateIndex(pParse,0,0,0,X,R,0,0,0,0,
+                                       SQLITE_IDXTYPE_UNIQUE);}
+tcons ::= CHECK LP(A) expr(E) RP(B) onconf.
+                                 {sqlite3AddCheckConstraint(pParse,E,A.z,B.z);}
+tcons ::= FOREIGN KEY LP eidlist(FA) RP
+          REFERENCES nm(T) eidlist_opt(TA) refargs(R) defer_subclause_opt(D). {
+    sqlite3CreateForeignKey(pParse, FA, &T, TA, R);
+    sqlite3DeferForeignKey(pParse, D);
+}
+%type defer_subclause_opt {int}
+defer_subclause_opt(A) ::= .                    {A = 0;}
+defer_subclause_opt(A) ::= defer_subclause(A).
+
+// The following is a non-standard extension that allows us to declare the
+// default behavior when there is a constraint conflict.
+//
+%type onconf {int}
+%type orconf {int}
+%type resolvetype {int}
+onconf(A) ::= .                              {A = OE_Default;}
+onconf(A) ::= ON CONFLICT resolvetype(X).    {A = X;}
+orconf(A) ::= .                              {A = OE_Default;}
+orconf(A) ::= OR resolvetype(X).             {A = X;}
+resolvetype(A) ::= raisetype(A).
+resolvetype(A) ::= IGNORE.                   {A = OE_Ignore;}
+resolvetype(A) ::= REPLACE.                  {A = OE_Replace;}
+
+////////////////////////// The DROP TABLE /////////////////////////////////////
+//
+cmd ::= DROP TABLE ifexists(E) fullname(X). {
+  sqlite3DropTable(pParse, X, 0, E);
+}
+%type ifexists {int}
+ifexists(A) ::= IF EXISTS.   {A = 1;}
+ifexists(A) ::= .            {A = 0;}
+
+///////////////////// The CREATE VIEW statement /////////////////////////////
+//
+%ifndef SQLITE_OMIT_VIEW
+cmd ::= createkw(X) temp(T) VIEW ifnotexists(E) nm(Y) dbnm(Z) eidlist_opt(C)
+          AS select(S). {
+  sqlite3CreateView(pParse, &X, &Y, &Z, C, S, T, E);
+}
+cmd ::= DROP VIEW ifexists(E) fullname(X). {
+  sqlite3DropTable(pParse, X, 1, E);
+}
+%endif  SQLITE_OMIT_VIEW
+
+//////////////////////// The SELECT statement /////////////////////////////////
+//
+cmd ::= select(X).  {
+  SelectDest dest = {SRT_Output, 0, 0, 0, 0, 0, 0};
+  sqlite3Select(pParse, X, &dest);
+  sqlite3SelectDelete(pParse->db, X);
+}
+
+%type select {Select*}
+%destructor select {sqlite3SelectDelete(pParse->db, $$);}
+%type selectnowith {Select*}
+%destructor selectnowith {sqlite3SelectDelete(pParse->db, $$);}
+%type oneselect {Select*}
+%destructor oneselect {sqlite3SelectDelete(pParse->db, $$);}
+
+%include {
+  /*
+  ** For a compound SELECT statement, make sure p->pPrior->pNext==p for
+  ** all elements in the list.  And make sure list length does not exceed
+  ** SQLITE_LIMIT_COMPOUND_SELECT.
+  */
+  static void parserDoubleLinkSelect(Parse *pParse, Select *p){
+    assert( p!=0 );
+    if( p->pPrior ){
+      Select *pNext = 0, *pLoop = p;
+      int mxSelect, cnt = 1;
+      while(1){
+        pLoop->pNext = pNext;
+        pLoop->selFlags |= SF_Compound;
+        pNext = pLoop;
+        pLoop = pLoop->pPrior;
+        if( pLoop==0 ) break;
+        cnt++;        
+        if( pLoop->pOrderBy || pLoop->pLimit ){
+          sqlite3ErrorMsg(pParse,"%s clause should come after %s not before",
+             pLoop->pOrderBy!=0 ? "ORDER BY" : "LIMIT",
+             sqlite3SelectOpName(pNext->op));
+          break;
+        }
+      }
+      if( (p->selFlags & SF_MultiValue)==0 && 
+        (mxSelect = pParse->db->aLimit[SQLITE_LIMIT_COMPOUND_SELECT])>0 &&
+        cnt>mxSelect
+      ){
+        sqlite3ErrorMsg(pParse, "too many terms in compound SELECT");
+      }
+    }
+  }
+
+  /* Attach a With object describing the WITH clause to a Select
+  ** object describing the query for which the WITH clause is a prefix.
+  */
+  static Select *attachWithToSelect(Parse *pParse, Select *pSelect, With *pWith){
+    if( pSelect ){
+      pSelect->pWith = pWith;
+      parserDoubleLinkSelect(pParse, pSelect);
+    }else{
+      sqlite3WithDelete(pParse->db, pWith);
+    }
+    return pSelect;
+  }
+}
+
+%ifndef SQLITE_OMIT_CTE
+select(A) ::= WITH wqlist(W) selectnowith(X). {A = attachWithToSelect(pParse,X,W);}
+select(A) ::= WITH RECURSIVE wqlist(W) selectnowith(X).
+                                              {A = attachWithToSelect(pParse,X,W);}
+%endif /* SQLITE_OMIT_CTE */
+select(A) ::= selectnowith(A). {
+  Select *p = A;
+  if( p ){
+    parserDoubleLinkSelect(pParse, p);
+  }
+}
+
+selectnowith(A) ::= oneselect(A).
+%ifndef SQLITE_OMIT_COMPOUND_SELECT
+selectnowith(A) ::= selectnowith(A) multiselect_op(Y) oneselect(Z).  {
+  Select *pRhs = Z;
+  Select *pLhs = A;
+  if( pRhs && pRhs->pPrior ){
+    SrcList *pFrom;
+    Token x;
+    x.n = 0;
+    parserDoubleLinkSelect(pParse, pRhs);
+    pFrom = sqlite3SrcListAppendFromTerm(pParse,0,0,0,&x,pRhs,0);
+    pRhs = sqlite3SelectNew(pParse,0,pFrom,0,0,0,0,0,0);
+  }
+  if( pRhs ){
+    pRhs->op = (u8)Y;
+    pRhs->pPrior = pLhs;
+    if( ALWAYS(pLhs) ) pLhs->selFlags &= ~SF_MultiValue;
+    pRhs->selFlags &= ~SF_MultiValue;
+    if( Y!=TK_ALL ) pParse->hasCompound = 1;
+  }else{
+    sqlite3SelectDelete(pParse->db, pLhs);
+  }
+  A = pRhs;
+}
+%type multiselect_op {int}
+multiselect_op(A) ::= UNION(OP).             {A = @OP; /*A-overwrites-OP*/}
+multiselect_op(A) ::= UNION ALL.             {A = TK_ALL;}
+multiselect_op(A) ::= EXCEPT|INTERSECT(OP).  {A = @OP; /*A-overwrites-OP*/}
+%endif SQLITE_OMIT_COMPOUND_SELECT
+
+oneselect(A) ::= SELECT distinct(D) selcollist(W) from(X) where_opt(Y)
+                 groupby_opt(P) having_opt(Q) 
+                 orderby_opt(Z) limit_opt(L). {
+  A = sqlite3SelectNew(pParse,W,X,Y,P,Q,Z,D,L);
+}
+%ifndef SQLITE_OMIT_WINDOWFUNC
+oneselect(A) ::= SELECT distinct(D) selcollist(W) from(X) where_opt(Y)
+                 groupby_opt(P) having_opt(Q) window_clause(R)
+                 orderby_opt(Z) limit_opt(L). {
+  A = sqlite3SelectNew(pParse,W,X,Y,P,Q,Z,D,L);
+  if( A ){
+    A->pWinDefn = R;
+  }else{
+    sqlite3WindowListDelete(pParse->db, R);
+  }
+}
+%endif
+
+
+oneselect(A) ::= values(A).
+
+%type values {Select*}
+%destructor values {sqlite3SelectDelete(pParse->db, $$);}
+values(A) ::= VALUES LP nexprlist(X) RP. {
+  A = sqlite3SelectNew(pParse,X,0,0,0,0,0,SF_Values,0);
+}
+values(A) ::= values(A) COMMA LP nexprlist(Y) RP. {
+  Select *pRight, *pLeft = A;
+  pRight = sqlite3SelectNew(pParse,Y,0,0,0,0,0,SF_Values|SF_MultiValue,0);
+  if( ALWAYS(pLeft) ) pLeft->selFlags &= ~SF_MultiValue;
+  if( pRight ){
+    pRight->op = TK_ALL;
+    pRight->pPrior = pLeft;
+    A = pRight;
+  }else{
+    A = pLeft;
+  }
+}
+
+// The "distinct" nonterminal is true (1) if the DISTINCT keyword is
+// present and false (0) if it is not.
+//
+%type distinct {int}
+distinct(A) ::= DISTINCT.   {A = SF_Distinct;}
+distinct(A) ::= ALL.        {A = SF_All;}
+distinct(A) ::= .           {A = 0;}
+
+// selcollist is a list of expressions that are to become the return
+// values of the SELECT statement.  The "*" in statements like
+// "SELECT * FROM ..." is encoded as a special expression with an
+// opcode of TK_ASTERISK.
+//
+%type selcollist {ExprList*}
+%destructor selcollist {sqlite3ExprListDelete(pParse->db, $$);}
+%type sclp {ExprList*}
+%destructor sclp {sqlite3ExprListDelete(pParse->db, $$);}
+sclp(A) ::= selcollist(A) COMMA.
+sclp(A) ::= .                                {A = 0;}
+selcollist(A) ::= sclp(A) scanpt(B) expr(X) scanpt(Z) as(Y).     {
+   A = sqlite3ExprListAppend(pParse, A, X);
+   if( Y.n>0 ) sqlite3ExprListSetName(pParse, A, &Y, 1);
+   sqlite3ExprListSetSpan(pParse,A,B,Z);
+}
+selcollist(A) ::= sclp(A) scanpt STAR(X). {
+  Expr *p = sqlite3Expr(pParse->db, TK_ASTERISK, 0);
+  sqlite3ExprSetErrorOffset(p, (int)(X.z - pParse->zTail));
+  A = sqlite3ExprListAppend(pParse, A, p);
+}
+selcollist(A) ::= sclp(A) scanpt nm(X) DOT STAR(Y). {
+  Expr *pRight, *pLeft, *pDot;
+  pRight = sqlite3PExpr(pParse, TK_ASTERISK, 0, 0);
+  sqlite3ExprSetErrorOffset(pRight, (int)(Y.z - pParse->zTail));
+  pLeft = tokenExpr(pParse, TK_ID, X);
+  pDot = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight);
+  A = sqlite3ExprListAppend(pParse,A, pDot);
+}
+
+// An option "AS <id>" phrase that can follow one of the expressions that
+// define the result set, or one of the tables in the FROM clause.
+//
+%type as {Token}
+as(X) ::= AS nm(Y).    {X = Y;}
+as(X) ::= ids(X).
+as(X) ::= .            {X.n = 0; X.z = 0;}
+
+
+%type seltablist {SrcList*}
+%destructor seltablist {sqlite3SrcListDelete(pParse->db, $$);}
+%type stl_prefix {SrcList*}
+%destructor stl_prefix {sqlite3SrcListDelete(pParse->db, $$);}
+%type from {SrcList*}
+%destructor from {sqlite3SrcListDelete(pParse->db, $$);}
+
+// A complete FROM clause.
+//
+from(A) ::= .                {A = 0;}
+from(A) ::= FROM seltablist(X). {
+  A = X;
+  sqlite3SrcListShiftJoinType(pParse,A);
+}
+
+// "seltablist" is a "Select Table List" - the content of the FROM clause
+// in a SELECT statement.  "stl_prefix" is a prefix of this list.
+//
+stl_prefix(A) ::= seltablist(A) joinop(Y).    {
+   if( ALWAYS(A && A->nSrc>0) ) A->a[A->nSrc-1].fg.jointype = (u8)Y;
+}
+stl_prefix(A) ::= .                           {A = 0;}
+seltablist(A) ::= stl_prefix(A) nm(Y) dbnm(D) as(Z) on_using(N). {
+  A = sqlite3SrcListAppendFromTerm(pParse,A,&Y,&D,&Z,0,&N);
+}
+seltablist(A) ::= stl_prefix(A) nm(Y) dbnm(D) as(Z) indexed_by(I) on_using(N). {
+  A = sqlite3SrcListAppendFromTerm(pParse,A,&Y,&D,&Z,0,&N);
+  sqlite3SrcListIndexedBy(pParse, A, &I);
+}
+seltablist(A) ::= stl_prefix(A) nm(Y) dbnm(D) LP exprlist(E) RP as(Z) on_using(N). {
+  A = sqlite3SrcListAppendFromTerm(pParse,A,&Y,&D,&Z,0,&N);
+  sqlite3SrcListFuncArgs(pParse, A, E);
+}
+%ifndef SQLITE_OMIT_SUBQUERY
+  seltablist(A) ::= stl_prefix(A) LP select(S) RP as(Z) on_using(N). {
+    A = sqlite3SrcListAppendFromTerm(pParse,A,0,0,&Z,S,&N);
+  }
+  seltablist(A) ::= stl_prefix(A) LP seltablist(F) RP as(Z) on_using(N). {
+    if( A==0 && Z.n==0 && N.pOn==0 && N.pUsing==0 ){
+      A = F;
+    }else if( ALWAYS(F!=0) && F->nSrc==1 ){
+      A = sqlite3SrcListAppendFromTerm(pParse,A,0,0,&Z,0,&N);
+      if( A ){
+        SrcItem *pNew = &A->a[A->nSrc-1];
+        SrcItem *pOld = F->a;
+        pNew->zName = pOld->zName;
+        pNew->zDatabase = pOld->zDatabase;
+        pNew->pSelect = pOld->pSelect;
+        if( pNew->pSelect && (pNew->pSelect->selFlags & SF_NestedFrom)!=0 ){
+          pNew->fg.isNestedFrom = 1;
+        }
+        if( pOld->fg.isTabFunc ){
+          pNew->u1.pFuncArg = pOld->u1.pFuncArg;
+          pOld->u1.pFuncArg = 0;
+          pOld->fg.isTabFunc = 0;
+          pNew->fg.isTabFunc = 1;
+        }
+        pOld->zName = pOld->zDatabase = 0;
+        pOld->pSelect = 0;
+      }
+      sqlite3SrcListDelete(pParse->db, F);
+    }else{
+      Select *pSubquery;
+      sqlite3SrcListShiftJoinType(pParse,F);
+      pSubquery = sqlite3SelectNew(pParse,0,F,0,0,0,0,SF_NestedFrom,0);
+      A = sqlite3SrcListAppendFromTerm(pParse,A,0,0,&Z,pSubquery,&N);
+    }
+  }
+%endif  SQLITE_OMIT_SUBQUERY
+
+%type dbnm {Token}
+dbnm(A) ::= .          {A.z=0; A.n=0;}
+dbnm(A) ::= DOT nm(X). {A = X;}
+
+%type fullname {SrcList*}
+%destructor fullname {sqlite3SrcListDelete(pParse->db, $$);}
+fullname(A) ::= nm(X).  {
+  A = sqlite3SrcListAppend(pParse,0,&X,0);
+  if( IN_RENAME_OBJECT && A ) sqlite3RenameTokenMap(pParse, A->a[0].zName, &X);
+}
+fullname(A) ::= nm(X) DOT nm(Y). {
+  A = sqlite3SrcListAppend(pParse,0,&X,&Y);
+  if( IN_RENAME_OBJECT && A ) sqlite3RenameTokenMap(pParse, A->a[0].zName, &Y);
+}
+
+%type xfullname {SrcList*}
+%destructor xfullname {sqlite3SrcListDelete(pParse->db, $$);}
+xfullname(A) ::= nm(X).  
+   {A = sqlite3SrcListAppend(pParse,0,&X,0); /*A-overwrites-X*/}
+xfullname(A) ::= nm(X) DOT nm(Y).  
+   {A = sqlite3SrcListAppend(pParse,0,&X,&Y); /*A-overwrites-X*/}
+xfullname(A) ::= nm(X) DOT nm(Y) AS nm(Z).  {
+   A = sqlite3SrcListAppend(pParse,0,&X,&Y); /*A-overwrites-X*/
+   if( A ) A->a[0].zAlias = sqlite3NameFromToken(pParse->db, &Z);
+}
+xfullname(A) ::= nm(X) AS nm(Z). {  
+   A = sqlite3SrcListAppend(pParse,0,&X,0); /*A-overwrites-X*/
+   if( A ) A->a[0].zAlias = sqlite3NameFromToken(pParse->db, &Z);
+}
+
+%type joinop {int}
+joinop(X) ::= COMMA|JOIN.              { X = JT_INNER; }
+joinop(X) ::= JOIN_KW(A) JOIN.
+                  {X = sqlite3JoinType(pParse,&A,0,0);  /*X-overwrites-A*/}
+joinop(X) ::= JOIN_KW(A) nm(B) JOIN.
+                  {X = sqlite3JoinType(pParse,&A,&B,0); /*X-overwrites-A*/}
+joinop(X) ::= JOIN_KW(A) nm(B) nm(C) JOIN.
+                  {X = sqlite3JoinType(pParse,&A,&B,&C);/*X-overwrites-A*/}
+
+// There is a parsing abiguity in an upsert statement that uses a
+// SELECT on the RHS of a the INSERT:
+//
+//      INSERT INTO tab SELECT * FROM aaa JOIN bbb ON CONFLICT ...
+//                                        here ----^^
+//
+// When the ON token is encountered, the parser does not know if it is
+// the beginning of an ON CONFLICT clause, or the beginning of an ON
+// clause associated with the JOIN.  The conflict is resolved in favor
+// of the JOIN.  If an ON CONFLICT clause is intended, insert a dummy
+// WHERE clause in between, like this:
+//
+//      INSERT INTO tab SELECT * FROM aaa JOIN bbb WHERE true ON CONFLICT ...
+//
+// The [AND] and [OR] precedence marks in the rules for on_using cause the
+// ON in this context to always be interpreted as belonging to the JOIN.
+//
+%type on_using {OnOrUsing}
+//%destructor on_using {sqlite3ClearOnOrUsing(pParse->db, &$$);}
+on_using(N) ::= ON expr(E).            {N.pOn = E; N.pUsing = 0;}
+on_using(N) ::= USING LP idlist(L) RP. {N.pOn = 0; N.pUsing = L;}
+on_using(N) ::= .                 [OR] {N.pOn = 0; N.pUsing = 0;}
+
+// Note that this block abuses the Token type just a little. If there is
+// no "INDEXED BY" clause, the returned token is empty (z==0 && n==0). If
+// there is an INDEXED BY clause, then the token is populated as per normal,
+// with z pointing to the token data and n containing the number of bytes
+// in the token.
+//
+// If there is a "NOT INDEXED" clause, then (z==0 && n==1), which is 
+// normally illegal. The sqlite3SrcListIndexedBy() function 
+// recognizes and interprets this as a special case.
+//
+%type indexed_opt {Token}
+%type indexed_by  {Token}
+indexed_opt(A) ::= .                 {A.z=0; A.n=0;}
+indexed_opt(A) ::= indexed_by(A).
+indexed_by(A)  ::= INDEXED BY nm(X). {A = X;}
+indexed_by(A)  ::= NOT INDEXED.      {A.z=0; A.n=1;}
+
+%type orderby_opt {ExprList*}
+%destructor orderby_opt {sqlite3ExprListDelete(pParse->db, $$);}
+
+// the sortlist non-terminal stores a list of expression where each
+// expression is optionally followed by ASC or DESC to indicate the
+// sort order.
+//
+%type sortlist {ExprList*}
+%destructor sortlist {sqlite3ExprListDelete(pParse->db, $$);}
+
+orderby_opt(A) ::= .                          {A = 0;}
+orderby_opt(A) ::= ORDER BY sortlist(X).      {A = X;}
+sortlist(A) ::= sortlist(A) COMMA expr(Y) sortorder(Z) nulls(X). {
+  A = sqlite3ExprListAppend(pParse,A,Y);
+  sqlite3ExprListSetSortOrder(A,Z,X);
+}
+sortlist(A) ::= expr(Y) sortorder(Z) nulls(X). {
+  A = sqlite3ExprListAppend(pParse,0,Y); /*A-overwrites-Y*/
+  sqlite3ExprListSetSortOrder(A,Z,X);
+}
+
+%type sortorder {int}
+
+sortorder(A) ::= ASC.           {A = SQLITE_SO_ASC;}
+sortorder(A) ::= DESC.          {A = SQLITE_SO_DESC;}
+sortorder(A) ::= .              {A = SQLITE_SO_UNDEFINED;}
+
+%type nulls {int}
+nulls(A) ::= NULLS FIRST.       {A = SQLITE_SO_ASC;}
+nulls(A) ::= NULLS LAST.        {A = SQLITE_SO_DESC;}
+nulls(A) ::= .                  {A = SQLITE_SO_UNDEFINED;}
+
+%type groupby_opt {ExprList*}
+%destructor groupby_opt {sqlite3ExprListDelete(pParse->db, $$);}
+groupby_opt(A) ::= .                      {A = 0;}
+groupby_opt(A) ::= GROUP BY nexprlist(X). {A = X;}
+
+%type having_opt {Expr*}
+%destructor having_opt {sqlite3ExprDelete(pParse->db, $$);}
+having_opt(A) ::= .                {A = 0;}
+having_opt(A) ::= HAVING expr(X).  {A = X;}
+
+%type limit_opt {Expr*}
+
+// The destructor for limit_opt will never fire in the current grammar.
+// The limit_opt non-terminal only occurs at the end of a single production
+// rule for SELECT statements.  As soon as the rule that create the 
+// limit_opt non-terminal reduces, the SELECT statement rule will also
+// reduce.  So there is never a limit_opt non-terminal on the stack 
+// except as a transient.  So there is never anything to destroy.
+//
+//%destructor limit_opt {sqlite3ExprDelete(pParse->db, $$);}
+limit_opt(A) ::= .       {A = 0;}
+limit_opt(A) ::= LIMIT expr(X).
+                         {A = sqlite3PExpr(pParse,TK_LIMIT,X,0);}
+limit_opt(A) ::= LIMIT expr(X) OFFSET expr(Y). 
+                         {A = sqlite3PExpr(pParse,TK_LIMIT,X,Y);}
+limit_opt(A) ::= LIMIT expr(X) COMMA expr(Y). 
+                         {A = sqlite3PExpr(pParse,TK_LIMIT,Y,X);}
+
+/////////////////////////// The DELETE statement /////////////////////////////
+//
+%if SQLITE_ENABLE_UPDATE_DELETE_LIMIT || SQLITE_UDL_CAPABLE_PARSER
+cmd ::= with DELETE FROM xfullname(X) indexed_opt(I) where_opt_ret(W)
+        orderby_opt(O) limit_opt(L). {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+#ifndef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  if( O || L ){
+    updateDeleteLimitError(pParse,O,L);
+    O = 0;
+    L = 0;
+  }
+#endif
+  sqlite3DeleteFrom(pParse,X,W,O,L);
+}
+%else
+cmd ::= with DELETE FROM xfullname(X) indexed_opt(I) where_opt_ret(W). {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+  sqlite3DeleteFrom(pParse,X,W,0,0);
+}
+%endif
+
+%type where_opt {Expr*}
+%destructor where_opt {sqlite3ExprDelete(pParse->db, $$);}
+%type where_opt_ret {Expr*}
+%destructor where_opt_ret {sqlite3ExprDelete(pParse->db, $$);}
+
+where_opt(A) ::= .                    {A = 0;}
+where_opt(A) ::= WHERE expr(X).       {A = X;}
+where_opt_ret(A) ::= .                                      {A = 0;}
+where_opt_ret(A) ::= WHERE expr(X).                         {A = X;}
+where_opt_ret(A) ::= RETURNING selcollist(X).               
+       {sqlite3AddReturning(pParse,X); A = 0;}
+where_opt_ret(A) ::= WHERE expr(X) RETURNING selcollist(Y).
+       {sqlite3AddReturning(pParse,Y); A = X;}
+
+////////////////////////// The UPDATE command ////////////////////////////////
+//
+%if SQLITE_ENABLE_UPDATE_DELETE_LIMIT || SQLITE_UDL_CAPABLE_PARSER
+cmd ::= with UPDATE orconf(R) xfullname(X) indexed_opt(I) SET setlist(Y) from(F)
+        where_opt_ret(W) orderby_opt(O) limit_opt(L).  {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+  if( F ){
+    SrcList *pFromClause = F;
+    if( pFromClause->nSrc>1 ){
+      Select *pSubquery;
+      Token as;
+      pSubquery = sqlite3SelectNew(pParse,0,pFromClause,0,0,0,0,SF_NestedFrom,0);
+      as.n = 0;
+      as.z = 0;
+      pFromClause = sqlite3SrcListAppendFromTerm(pParse,0,0,0,&as,pSubquery,0);
+    }
+    X = sqlite3SrcListAppendList(pParse, X, pFromClause);
+  }
+  sqlite3ExprListCheckLength(pParse,Y,"set list"); 
+#ifndef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  if( O || L ){
+    updateDeleteLimitError(pParse,O,L);
+    O = 0;
+    L = 0;
+  }
+#endif
+  sqlite3Update(pParse,X,Y,W,R,O,L,0);
+}
+%else
+cmd ::= with UPDATE orconf(R) xfullname(X) indexed_opt(I) SET setlist(Y) from(F)
+        where_opt_ret(W). {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+  sqlite3ExprListCheckLength(pParse,Y,"set list"); 
+  if( F ){
+    SrcList *pFromClause = F;
+    if( pFromClause->nSrc>1 ){
+      Select *pSubquery;
+      Token as;
+      pSubquery = sqlite3SelectNew(pParse,0,pFromClause,0,0,0,0,SF_NestedFrom,0);
+      as.n = 0;
+      as.z = 0;
+      pFromClause = sqlite3SrcListAppendFromTerm(pParse,0,0,0,&as,pSubquery,0);
+    }
+    X = sqlite3SrcListAppendList(pParse, X, pFromClause);
+  }
+  sqlite3Update(pParse,X,Y,W,R,0,0,0);
+}
+%endif
+
+
+
+%type setlist {ExprList*}
+%destructor setlist {sqlite3ExprListDelete(pParse->db, $$);}
+
+setlist(A) ::= setlist(A) COMMA nm(X) EQ expr(Y). {
+  A = sqlite3ExprListAppend(pParse, A, Y);
+  sqlite3ExprListSetName(pParse, A, &X, 1);
+}
+setlist(A) ::= setlist(A) COMMA LP idlist(X) RP EQ expr(Y). {
+  A = sqlite3ExprListAppendVector(pParse, A, X, Y);
+}
+setlist(A) ::= nm(X) EQ expr(Y). {
+  A = sqlite3ExprListAppend(pParse, 0, Y);
+  sqlite3ExprListSetName(pParse, A, &X, 1);
+}
+setlist(A) ::= LP idlist(X) RP EQ expr(Y). {
+  A = sqlite3ExprListAppendVector(pParse, 0, X, Y);
+}
+
+////////////////////////// The INSERT command /////////////////////////////////
+//
+cmd ::= with insert_cmd(R) INTO xfullname(X) idlist_opt(F) select(S)
+        upsert(U). {
+  sqlite3Insert(pParse, X, S, F, R, U);
+}
+cmd ::= with insert_cmd(R) INTO xfullname(X) idlist_opt(F) DEFAULT VALUES returning.
+{
+  sqlite3Insert(pParse, X, 0, F, R, 0);
+}
+
+%type upsert {Upsert*}
+
+// Because upsert only occurs at the tip end of the INSERT rule for cmd,
+// there is never a case where the value of the upsert pointer will not
+// be destroyed by the cmd action.  So comment-out the destructor to
+// avoid unreachable code.
+//%destructor upsert {sqlite3UpsertDelete(pParse->db,$$);}
+upsert(A) ::= . { A = 0; }
+upsert(A) ::= RETURNING selcollist(X).  { A = 0; sqlite3AddReturning(pParse,X); }
+upsert(A) ::= ON CONFLICT LP sortlist(T) RP where_opt(TW)
+              DO UPDATE SET setlist(Z) where_opt(W) upsert(N).
+              { A = sqlite3UpsertNew(pParse->db,T,TW,Z,W,N);}
+upsert(A) ::= ON CONFLICT LP sortlist(T) RP where_opt(TW) DO NOTHING upsert(N).
+              { A = sqlite3UpsertNew(pParse->db,T,TW,0,0,N); }
+upsert(A) ::= ON CONFLICT DO NOTHING returning.
+              { A = sqlite3UpsertNew(pParse->db,0,0,0,0,0); }
+upsert(A) ::= ON CONFLICT DO UPDATE SET setlist(Z) where_opt(W) returning.
+              { A = sqlite3UpsertNew(pParse->db,0,0,Z,W,0);}
+
+returning ::= RETURNING selcollist(X).  {sqlite3AddReturning(pParse,X);}
+returning ::= .
+
+%type insert_cmd {int}
+insert_cmd(A) ::= INSERT orconf(R).   {A = R;}
+insert_cmd(A) ::= REPLACE.            {A = OE_Replace;}
+
+%type idlist_opt {IdList*}
+%destructor idlist_opt {sqlite3IdListDelete(pParse->db, $$);}
+%type idlist {IdList*}
+%destructor idlist {sqlite3IdListDelete(pParse->db, $$);}
+
+idlist_opt(A) ::= .                       {A = 0;}
+idlist_opt(A) ::= LP idlist(X) RP.    {A = X;}
+idlist(A) ::= idlist(A) COMMA nm(Y).
+    {A = sqlite3IdListAppend(pParse,A,&Y);}
+idlist(A) ::= nm(Y).
+    {A = sqlite3IdListAppend(pParse,0,&Y); /*A-overwrites-Y*/}
+
+/////////////////////////// Expression Processing /////////////////////////////
+//
+
+%type expr {Expr*}
+%destructor expr {sqlite3ExprDelete(pParse->db, $$);}
+%type term {Expr*}
+%destructor term {sqlite3ExprDelete(pParse->db, $$);}
+
+%include {
+
+  /* Construct a new Expr object from a single token */
+  static Expr *tokenExpr(Parse *pParse, int op, Token t){
+    Expr *p = sqlite3DbMallocRawNN(pParse->db, sizeof(Expr)+t.n+1);
+    if( p ){
+      /* memset(p, 0, sizeof(Expr)); */
+      p->op = (u8)op;
+      p->affExpr = 0;
+      p->flags = EP_Leaf;
+      ExprClearVVAProperties(p);
+      /* p->iAgg = -1; // Not required */
+      p->pLeft = p->pRight = 0;
+      p->pAggInfo = 0;
+      memset(&p->x, 0, sizeof(p->x));
+      memset(&p->y, 0, sizeof(p->y));
+      p->op2 = 0;
+      p->iTable = 0;
+      p->iColumn = 0;
+      p->u.zToken = (char*)&p[1];
+      memcpy(p->u.zToken, t.z, t.n);
+      p->u.zToken[t.n] = 0;
+      p->w.iOfst = (int)(t.z - pParse->zTail);
+      if( sqlite3Isquote(p->u.zToken[0]) ){
+        sqlite3DequoteExpr(p);
+      }
+#if SQLITE_MAX_EXPR_DEPTH>0
+      p->nHeight = 1;
+#endif  
+      if( IN_RENAME_OBJECT ){
+        return (Expr*)sqlite3RenameTokenMap(pParse, (void*)p, &t);
+      }
+    }
+    return p;
+  }
+
+}
+
+expr(A) ::= term(A).
+expr(A) ::= LP expr(X) RP. {A = X;}
+expr(A) ::= idj(X).          {A=tokenExpr(pParse,TK_ID,X); /*A-overwrites-X*/}
+expr(A) ::= nm(X) DOT nm(Y). {
+  Expr *temp1 = tokenExpr(pParse,TK_ID,X);
+  Expr *temp2 = tokenExpr(pParse,TK_ID,Y);
+  A = sqlite3PExpr(pParse, TK_DOT, temp1, temp2);
+}
+expr(A) ::= nm(X) DOT nm(Y) DOT nm(Z). {
+  Expr *temp1 = tokenExpr(pParse,TK_ID,X);
+  Expr *temp2 = tokenExpr(pParse,TK_ID,Y);
+  Expr *temp3 = tokenExpr(pParse,TK_ID,Z);
+  Expr *temp4 = sqlite3PExpr(pParse, TK_DOT, temp2, temp3);
+  if( IN_RENAME_OBJECT ){
+    sqlite3RenameTokenRemap(pParse, 0, temp1);
+  }
+  A = sqlite3PExpr(pParse, TK_DOT, temp1, temp4);
+}
+term(A) ::= NULL|FLOAT|BLOB(X). {A=tokenExpr(pParse,@X,X); /*A-overwrites-X*/}
+term(A) ::= STRING(X).          {A=tokenExpr(pParse,@X,X); /*A-overwrites-X*/}
+term(A) ::= INTEGER(X). {
+  A = sqlite3ExprAlloc(pParse->db, TK_INTEGER, &X, 1);
+  if( A ) A->w.iOfst = (int)(X.z - pParse->zTail);
+}
+expr(A) ::= VARIABLE(X).     {
+  if( !(X.z[0]=='#' && sqlite3Isdigit(X.z[1])) ){
+    u32 n = X.n;
+    A = tokenExpr(pParse, TK_VARIABLE, X);
+    sqlite3ExprAssignVarNumber(pParse, A, n);
+  }else{
+    /* When doing a nested parse, one can include terms in an expression
+    ** that look like this:   #1 #2 ...  These terms refer to registers
+    ** in the virtual machine.  #N is the N-th register. */
+    Token t = X; /*A-overwrites-X*/
+    assert( t.n>=2 );
+    if( pParse->nested==0 ){
+      sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", &t);
+      A = 0;
+    }else{
+      A = sqlite3PExpr(pParse, TK_REGISTER, 0, 0);
+      if( A ) sqlite3GetInt32(&t.z[1], &A->iTable);
+    }
+  }
+}
+expr(A) ::= expr(A) COLLATE ids(C). {
+  A = sqlite3ExprAddCollateToken(pParse, A, &C, 1);
+}
+%ifndef SQLITE_OMIT_CAST
+expr(A) ::= CAST LP expr(E) AS typetoken(T) RP. {
+  A = sqlite3ExprAlloc(pParse->db, TK_CAST, &T, 1);
+  sqlite3ExprAttachSubtrees(pParse->db, A, E, 0);
+}
+%endif  SQLITE_OMIT_CAST
+
+
+expr(A) ::= idj(X) LP distinct(D) exprlist(Y) RP. {
+  A = sqlite3ExprFunction(pParse, Y, &X, D);
+}
+expr(A) ::= idj(X) LP distinct(D) exprlist(Y) ORDER BY sortlist(O) RP. {
+  A = sqlite3ExprFunction(pParse, Y, &X, D);
+  sqlite3ExprAddFunctionOrderBy(pParse, A, O);
+}
+expr(A) ::= idj(X) LP STAR RP. {
+  A = sqlite3ExprFunction(pParse, 0, &X, 0);
+}
+
+%ifndef SQLITE_OMIT_WINDOWFUNC
+expr(A) ::= idj(X) LP distinct(D) exprlist(Y) RP filter_over(Z). {
+  A = sqlite3ExprFunction(pParse, Y, &X, D);
+  sqlite3WindowAttach(pParse, A, Z);
+}
+expr(A) ::= idj(X) LP distinct(D) exprlist(Y) ORDER BY sortlist(O) RP filter_over(Z). {
+  A = sqlite3ExprFunction(pParse, Y, &X, D);
+  sqlite3WindowAttach(pParse, A, Z);
+  sqlite3ExprAddFunctionOrderBy(pParse, A, O);
+}
+expr(A) ::= idj(X) LP STAR RP filter_over(Z). {
+  A = sqlite3ExprFunction(pParse, 0, &X, 0);
+  sqlite3WindowAttach(pParse, A, Z);
+}
+%endif
+
+term(A) ::= CTIME_KW(OP). {
+  A = sqlite3ExprFunction(pParse, 0, &OP, 0);
+}
+
+expr(A) ::= LP nexprlist(X) COMMA expr(Y) RP. {
+  ExprList *pList = sqlite3ExprListAppend(pParse, X, Y);
+  A = sqlite3PExpr(pParse, TK_VECTOR, 0, 0);
+  if( A ){
+    A->x.pList = pList;
+    if( ALWAYS(pList->nExpr) ){
+      A->flags |= pList->a[0].pExpr->flags & EP_Propagate;
+    }
+  }else{
+    sqlite3ExprListDelete(pParse->db, pList);
+  }
+}
+
+expr(A) ::= expr(A) AND expr(Y).        {A=sqlite3ExprAnd(pParse,A,Y);}
+expr(A) ::= expr(A) OR(OP) expr(Y).     {A=sqlite3PExpr(pParse,@OP,A,Y);}
+expr(A) ::= expr(A) LT|GT|GE|LE(OP) expr(Y).
+                                        {A=sqlite3PExpr(pParse,@OP,A,Y);}
+expr(A) ::= expr(A) EQ|NE(OP) expr(Y).  {A=sqlite3PExpr(pParse,@OP,A,Y);}
+expr(A) ::= expr(A) BITAND|BITOR|LSHIFT|RSHIFT(OP) expr(Y).
+                                        {A=sqlite3PExpr(pParse,@OP,A,Y);}
+expr(A) ::= expr(A) PLUS|MINUS(OP) expr(Y).
+                                        {A=sqlite3PExpr(pParse,@OP,A,Y);}
+expr(A) ::= expr(A) STAR|SLASH|REM(OP) expr(Y).
+                                        {A=sqlite3PExpr(pParse,@OP,A,Y);}
+expr(A) ::= expr(A) CONCAT(OP) expr(Y). {A=sqlite3PExpr(pParse,@OP,A,Y);}
+%type likeop {Token}
+likeop(A) ::= LIKE_KW|MATCH(A).
+likeop(A) ::= NOT LIKE_KW|MATCH(X). {A=X; A.n|=0x80000000; /*A-overwrite-X*/}
+expr(A) ::= expr(A) likeop(OP) expr(Y).  [LIKE_KW]  {
+  ExprList *pList;
+  int bNot = OP.n & 0x80000000;
+  OP.n &= 0x7fffffff;
+  pList = sqlite3ExprListAppend(pParse,0, Y);
+  pList = sqlite3ExprListAppend(pParse,pList, A);
+  A = sqlite3ExprFunction(pParse, pList, &OP, 0);
+  if( bNot ) A = sqlite3PExpr(pParse, TK_NOT, A, 0);
+  if( A ) A->flags |= EP_InfixFunc;
+}
+expr(A) ::= expr(A) likeop(OP) expr(Y) ESCAPE expr(E).  [LIKE_KW]  {
+  ExprList *pList;
+  int bNot = OP.n & 0x80000000;
+  OP.n &= 0x7fffffff;
+  pList = sqlite3ExprListAppend(pParse,0, Y);
+  pList = sqlite3ExprListAppend(pParse,pList, A);
+  pList = sqlite3ExprListAppend(pParse,pList, E);
+  A = sqlite3ExprFunction(pParse, pList, &OP, 0);
+  if( bNot ) A = sqlite3PExpr(pParse, TK_NOT, A, 0);
+  if( A ) A->flags |= EP_InfixFunc;
+}
+
+expr(A) ::= expr(A) ISNULL|NOTNULL(E).   {A = sqlite3PExpr(pParse,@E,A,0);}
+expr(A) ::= expr(A) NOT NULL.    {A = sqlite3PExpr(pParse,TK_NOTNULL,A,0);}
+
+%include {
+  /* A routine to convert a binary TK_IS or TK_ISNOT expression into a
+  ** unary TK_ISNULL or TK_NOTNULL expression. */
+  static void binaryToUnaryIfNull(Parse *pParse, Expr *pY, Expr *pA, int op){
+    sqlite3 *db = pParse->db;
+    if( pA && pY && pY->op==TK_NULL && !IN_RENAME_OBJECT ){
+      pA->op = (u8)op;
+      sqlite3ExprDelete(db, pA->pRight);
+      pA->pRight = 0;
+    }
+  }
+}
+
+//    expr1 IS expr2
+//    expr1 IS NOT expr2
+//
+// If expr2 is NULL then code as TK_ISNULL or TK_NOTNULL.  If expr2
+// is any other expression, code as TK_IS or TK_ISNOT.
+// 
+expr(A) ::= expr(A) IS expr(Y).     {
+  A = sqlite3PExpr(pParse,TK_IS,A,Y);
+  binaryToUnaryIfNull(pParse, Y, A, TK_ISNULL);
+}
+expr(A) ::= expr(A) IS NOT expr(Y). {
+  A = sqlite3PExpr(pParse,TK_ISNOT,A,Y);
+  binaryToUnaryIfNull(pParse, Y, A, TK_NOTNULL);
+}
+expr(A) ::= expr(A) IS NOT DISTINCT FROM expr(Y).     {
+  A = sqlite3PExpr(pParse,TK_IS,A,Y);
+  binaryToUnaryIfNull(pParse, Y, A, TK_ISNULL);
+}
+expr(A) ::= expr(A) IS DISTINCT FROM expr(Y). {
+  A = sqlite3PExpr(pParse,TK_ISNOT,A,Y);
+  binaryToUnaryIfNull(pParse, Y, A, TK_NOTNULL);
+}
+
+expr(A) ::= NOT(B) expr(X).  
+              {A = sqlite3PExpr(pParse, @B, X, 0);/*A-overwrites-B*/}
+expr(A) ::= BITNOT(B) expr(X).
+              {A = sqlite3PExpr(pParse, @B, X, 0);/*A-overwrites-B*/}
+expr(A) ::= PLUS|MINUS(B) expr(X). [BITNOT] {
+  A = sqlite3PExpr(pParse, @B==TK_PLUS ? TK_UPLUS : TK_UMINUS, X, 0);
+  /*A-overwrites-B*/
+}
+
+expr(A) ::= expr(B) PTR(C) expr(D). {
+  ExprList *pList = sqlite3ExprListAppend(pParse, 0, B);
+  pList = sqlite3ExprListAppend(pParse, pList, D);
+  A = sqlite3ExprFunction(pParse, pList, &C, 0);
+}
+
+%type between_op {int}
+between_op(A) ::= BETWEEN.     {A = 0;}
+between_op(A) ::= NOT BETWEEN. {A = 1;}
+expr(A) ::= expr(A) between_op(N) expr(X) AND expr(Y). [BETWEEN] {
+  ExprList *pList = sqlite3ExprListAppend(pParse,0, X);
+  pList = sqlite3ExprListAppend(pParse,pList, Y);
+  A = sqlite3PExpr(pParse, TK_BETWEEN, A, 0);
+  if( A ){
+    A->x.pList = pList;
+  }else{
+    sqlite3ExprListDelete(pParse->db, pList);
+  } 
+  if( N ) A = sqlite3PExpr(pParse, TK_NOT, A, 0);
+}
+%ifndef SQLITE_OMIT_SUBQUERY
+  %type in_op {int}
+  in_op(A) ::= IN.      {A = 0;}
+  in_op(A) ::= NOT IN.  {A = 1;}
+  expr(A) ::= expr(A) in_op(N) LP exprlist(Y) RP. [IN] {
+    if( Y==0 ){
+      /* Expressions of the form
+      **
+      **      expr1 IN ()
+      **      expr1 NOT IN ()
+      **
+      ** simplify to constants 0 (false) and 1 (true), respectively,
+      ** regardless of the value of expr1.
+      */
+      sqlite3ExprUnmapAndDelete(pParse, A);
+      A = sqlite3Expr(pParse->db, TK_STRING, N ? "true" : "false");
+      if( A ) sqlite3ExprIdToTrueFalse(A);
+    }else{
+      Expr *pRHS = Y->a[0].pExpr;
+      if( Y->nExpr==1 && sqlite3ExprIsConstant(pRHS) && A->op!=TK_VECTOR ){
+        Y->a[0].pExpr = 0;
+        sqlite3ExprListDelete(pParse->db, Y);
+        pRHS = sqlite3PExpr(pParse, TK_UPLUS, pRHS, 0);
+        A = sqlite3PExpr(pParse, TK_EQ, A, pRHS);
+      }else if( Y->nExpr==1 && pRHS->op==TK_SELECT ){
+        A = sqlite3PExpr(pParse, TK_IN, A, 0);
+        sqlite3PExprAddSelect(pParse, A, pRHS->x.pSelect);
+        pRHS->x.pSelect = 0;
+        sqlite3ExprListDelete(pParse->db, Y);
+      }else{
+        A = sqlite3PExpr(pParse, TK_IN, A, 0);
+        if( A==0 ){
+          sqlite3ExprListDelete(pParse->db, Y);
+        }else if( A->pLeft->op==TK_VECTOR ){
+          int nExpr = A->pLeft->x.pList->nExpr;
+          Select *pSelectRHS = sqlite3ExprListToValues(pParse, nExpr, Y);
+          if( pSelectRHS ){
+            parserDoubleLinkSelect(pParse, pSelectRHS);
+            sqlite3PExprAddSelect(pParse, A, pSelectRHS);
+          }
+        }else{
+          A->x.pList = Y;
+          sqlite3ExprSetHeightAndFlags(pParse, A);
+        }
+      }
+      if( N ) A = sqlite3PExpr(pParse, TK_NOT, A, 0);
+    }
+  }
+  expr(A) ::= LP select(X) RP. {
+    A = sqlite3PExpr(pParse, TK_SELECT, 0, 0);
+    sqlite3PExprAddSelect(pParse, A, X);
+  }
+  expr(A) ::= expr(A) in_op(N) LP select(Y) RP.  [IN] {
+    A = sqlite3PExpr(pParse, TK_IN, A, 0);
+    sqlite3PExprAddSelect(pParse, A, Y);
+    if( N ) A = sqlite3PExpr(pParse, TK_NOT, A, 0);
+  }
+  expr(A) ::= expr(A) in_op(N) nm(Y) dbnm(Z) paren_exprlist(E). [IN] {
+    SrcList *pSrc = sqlite3SrcListAppend(pParse, 0,&Y,&Z);
+    Select *pSelect = sqlite3SelectNew(pParse, 0,pSrc,0,0,0,0,0,0);
+    if( E )  sqlite3SrcListFuncArgs(pParse, pSelect ? pSrc : 0, E);
+    A = sqlite3PExpr(pParse, TK_IN, A, 0);
+    sqlite3PExprAddSelect(pParse, A, pSelect);
+    if( N ) A = sqlite3PExpr(pParse, TK_NOT, A, 0);
+  }
+  expr(A) ::= EXISTS LP select(Y) RP. {
+    Expr *p;
+    p = A = sqlite3PExpr(pParse, TK_EXISTS, 0, 0);
+    sqlite3PExprAddSelect(pParse, p, Y);
+  }
+%endif SQLITE_OMIT_SUBQUERY
+
+/* CASE expressions */
+expr(A) ::= CASE case_operand(X) case_exprlist(Y) case_else(Z) END. {
+  A = sqlite3PExpr(pParse, TK_CASE, X, 0);
+  if( A ){
+    A->x.pList = Z ? sqlite3ExprListAppend(pParse,Y,Z) : Y;
+    sqlite3ExprSetHeightAndFlags(pParse, A);
+  }else{
+    sqlite3ExprListDelete(pParse->db, Y);
+    sqlite3ExprDelete(pParse->db, Z);
+  }
+}
+%type case_exprlist {ExprList*}
+%destructor case_exprlist {sqlite3ExprListDelete(pParse->db, $$);}
+case_exprlist(A) ::= case_exprlist(A) WHEN expr(Y) THEN expr(Z). {
+  A = sqlite3ExprListAppend(pParse,A, Y);
+  A = sqlite3ExprListAppend(pParse,A, Z);
+}
+case_exprlist(A) ::= WHEN expr(Y) THEN expr(Z). {
+  A = sqlite3ExprListAppend(pParse,0, Y);
+  A = sqlite3ExprListAppend(pParse,A, Z);
+}
+%type case_else {Expr*}
+%destructor case_else {sqlite3ExprDelete(pParse->db, $$);}
+case_else(A) ::=  ELSE expr(X).         {A = X;}
+case_else(A) ::=  .                     {A = 0;} 
+%type case_operand {Expr*}
+%destructor case_operand {sqlite3ExprDelete(pParse->db, $$);}
+case_operand(A) ::= expr(A).
+case_operand(A) ::= .                   {A = 0;} 
+
+%type exprlist {ExprList*}
+%destructor exprlist {sqlite3ExprListDelete(pParse->db, $$);}
+%type nexprlist {ExprList*}
+%destructor nexprlist {sqlite3ExprListDelete(pParse->db, $$);}
+
+exprlist(A) ::= nexprlist(A).
+exprlist(A) ::= .                            {A = 0;}
+nexprlist(A) ::= nexprlist(A) COMMA expr(Y).
+    {A = sqlite3ExprListAppend(pParse,A,Y);}
+nexprlist(A) ::= expr(Y).
+    {A = sqlite3ExprListAppend(pParse,0,Y); /*A-overwrites-Y*/}
+
+%ifndef SQLITE_OMIT_SUBQUERY
+/* A paren_exprlist is an optional expression list contained inside
+** of parenthesis */
+%type paren_exprlist {ExprList*}
+%destructor paren_exprlist {sqlite3ExprListDelete(pParse->db, $$);}
+paren_exprlist(A) ::= .   {A = 0;}
+paren_exprlist(A) ::= LP exprlist(X) RP.  {A = X;}
+%endif SQLITE_OMIT_SUBQUERY
+
+
+///////////////////////////// The CREATE INDEX command ///////////////////////
+//
+cmd ::= createkw(S) uniqueflag(U) INDEX ifnotexists(NE) nm(X) dbnm(D)
+        ON nm(Y) LP sortlist(Z) RP where_opt(W). {
+  sqlite3CreateIndex(pParse, &X, &D, 
+                     sqlite3SrcListAppend(pParse,0,&Y,0), Z, U,
+                      &S, W, SQLITE_SO_ASC, NE, SQLITE_IDXTYPE_APPDEF);
+  if( IN_RENAME_OBJECT && pParse->pNewIndex ){
+    sqlite3RenameTokenMap(pParse, pParse->pNewIndex->zName, &Y);
+  }
+}
+
+%type uniqueflag {int}
+uniqueflag(A) ::= UNIQUE.  {A = OE_Abort;}
+uniqueflag(A) ::= .        {A = OE_None;}
+
+
+// The eidlist non-terminal (Expression Id List) generates an ExprList
+// from a list of identifiers.  The identifier names are in ExprList.a[].zName.
+// This list is stored in an ExprList rather than an IdList so that it
+// can be easily sent to sqlite3ColumnsExprList().
+//
+// eidlist is grouped with CREATE INDEX because it used to be the non-terminal
+// used for the arguments to an index.  That is just an historical accident.
+//
+// IMPORTANT COMPATIBILITY NOTE:  Some prior versions of SQLite accepted
+// COLLATE clauses and ASC or DESC keywords on ID lists in inappropriate
+// places - places that might have been stored in the sqlite_schema table.
+// Those extra features were ignored.  But because they might be in some
+// (busted) old databases, we need to continue parsing them when loading
+// historical schemas.
+//
+%type eidlist {ExprList*}
+%destructor eidlist {sqlite3ExprListDelete(pParse->db, $$);}
+%type eidlist_opt {ExprList*}
+%destructor eidlist_opt {sqlite3ExprListDelete(pParse->db, $$);}
+
+%include {
+  /* Add a single new term to an ExprList that is used to store a
+  ** list of identifiers.  Report an error if the ID list contains
+  ** a COLLATE clause or an ASC or DESC keyword, except ignore the
+  ** error while parsing a legacy schema.
+  */
+  static ExprList *parserAddExprIdListTerm(
+    Parse *pParse,
+    ExprList *pPrior,
+    Token *pIdToken,
+    int hasCollate,
+    int sortOrder
+  ){
+    ExprList *p = sqlite3ExprListAppend(pParse, pPrior, 0);
+    if( (hasCollate || sortOrder!=SQLITE_SO_UNDEFINED)
+        && pParse->db->init.busy==0
+    ){
+      sqlite3ErrorMsg(pParse, "syntax error after column name \"%.*s\"",
+                         pIdToken->n, pIdToken->z);
+    }
+    sqlite3ExprListSetName(pParse, p, pIdToken, 1);
+    return p;
+  }
+} // end %include
+
+eidlist_opt(A) ::= .                         {A = 0;}
+eidlist_opt(A) ::= LP eidlist(X) RP.         {A = X;}
+eidlist(A) ::= eidlist(A) COMMA nm(Y) collate(C) sortorder(Z).  {
+  A = parserAddExprIdListTerm(pParse, A, &Y, C, Z);
+}
+eidlist(A) ::= nm(Y) collate(C) sortorder(Z). {
+  A = parserAddExprIdListTerm(pParse, 0, &Y, C, Z); /*A-overwrites-Y*/
+}
+
+%type collate {int}
+collate(C) ::= .              {C = 0;}
+collate(C) ::= COLLATE ids.   {C = 1;}
+
+
+///////////////////////////// The DROP INDEX command /////////////////////////
+//
+cmd ::= DROP INDEX ifexists(E) fullname(X).   {sqlite3DropIndex(pParse, X, E);}
+
+///////////////////////////// The VACUUM command /////////////////////////////
+//
+%if !SQLITE_OMIT_VACUUM && !SQLITE_OMIT_ATTACH
+%type vinto {Expr*}
+%destructor vinto {sqlite3ExprDelete(pParse->db, $$);}
+cmd ::= VACUUM vinto(Y).                {sqlite3Vacuum(pParse,0,Y);}
+cmd ::= VACUUM nm(X) vinto(Y).          {sqlite3Vacuum(pParse,&X,Y);}
+vinto(A) ::= INTO expr(X).              {A = X;}
+vinto(A) ::= .                          {A = 0;}
+%endif
+
+///////////////////////////// The PRAGMA command /////////////////////////////
+//
+%ifndef SQLITE_OMIT_PRAGMA
+cmd ::= PRAGMA nm(X) dbnm(Z).                {sqlite3Pragma(pParse,&X,&Z,0,0);}
+cmd ::= PRAGMA nm(X) dbnm(Z) EQ nmnum(Y).    {sqlite3Pragma(pParse,&X,&Z,&Y,0);}
+cmd ::= PRAGMA nm(X) dbnm(Z) LP nmnum(Y) RP. {sqlite3Pragma(pParse,&X,&Z,&Y,0);}
+cmd ::= PRAGMA nm(X) dbnm(Z) EQ minus_num(Y). 
+                                             {sqlite3Pragma(pParse,&X,&Z,&Y,1);}
+cmd ::= PRAGMA nm(X) dbnm(Z) LP minus_num(Y) RP.
+                                             {sqlite3Pragma(pParse,&X,&Z,&Y,1);}
+
+nmnum(A) ::= plus_num(A).
+nmnum(A) ::= nm(A).
+nmnum(A) ::= ON(A).
+nmnum(A) ::= DELETE(A).
+nmnum(A) ::= DEFAULT(A).
+%endif SQLITE_OMIT_PRAGMA
+%token_class number INTEGER|FLOAT.
+plus_num(A) ::= PLUS number(X).       {A = X;}
+plus_num(A) ::= number(A).
+minus_num(A) ::= MINUS number(X).     {A = X;}
+//////////////////////////// The CREATE TRIGGER command /////////////////////
+
+%ifndef SQLITE_OMIT_TRIGGER
+
+cmd ::= createkw trigger_decl(A) BEGIN trigger_cmd_list(S) END(Z). {
+  Token all;
+  all.z = A.z;
+  all.n = (int)(Z.z - A.z) + Z.n;
+  sqlite3FinishTrigger(pParse, S, &all);
+}
+
+trigger_decl(A) ::= temp(T) TRIGGER ifnotexists(NOERR) nm(B) dbnm(Z) 
+                    trigger_time(C) trigger_event(D)
+                    ON fullname(E) foreach_clause when_clause(G). {
+  sqlite3BeginTrigger(pParse, &B, &Z, C, D.a, D.b, E, G, T, NOERR);
+  A = (Z.n==0?B:Z); /*A-overwrites-T*/
+}
+
+%type trigger_time {int}
+trigger_time(A) ::= BEFORE|AFTER(X).  { A = @X; /*A-overwrites-X*/ }
+trigger_time(A) ::= INSTEAD OF.  { A = TK_INSTEAD;}
+trigger_time(A) ::= .            { A = TK_BEFORE; }
+
+%type trigger_event {struct TrigEvent}
+%destructor trigger_event {sqlite3IdListDelete(pParse->db, $$.b);}
+trigger_event(A) ::= DELETE|INSERT(X).   {A.a = @X; /*A-overwrites-X*/ A.b = 0;}
+trigger_event(A) ::= UPDATE(X).          {A.a = @X; /*A-overwrites-X*/ A.b = 0;}
+trigger_event(A) ::= UPDATE OF idlist(X).{A.a = TK_UPDATE; A.b = X;}
+
+foreach_clause ::= .
+foreach_clause ::= FOR EACH ROW.
+
+%type when_clause {Expr*}
+%destructor when_clause {sqlite3ExprDelete(pParse->db, $$);}
+when_clause(A) ::= .             { A = 0; }
+when_clause(A) ::= WHEN expr(X). { A = X; }
+
+%type trigger_cmd_list {TriggerStep*}
+%destructor trigger_cmd_list {sqlite3DeleteTriggerStep(pParse->db, $$);}
+trigger_cmd_list(A) ::= trigger_cmd_list(A) trigger_cmd(X) SEMI. {
+  assert( A!=0 );
+  A->pLast->pNext = X;
+  A->pLast = X;
+}
+trigger_cmd_list(A) ::= trigger_cmd(A) SEMI. { 
+  assert( A!=0 );
+  A->pLast = A;
+}
+
+// Disallow qualified table names on INSERT, UPDATE, and DELETE statements
+// within a trigger.  The table to INSERT, UPDATE, or DELETE is always in 
+// the same database as the table that the trigger fires on.
+//
+%type trnm {Token}
+trnm(A) ::= nm(A).
+trnm(A) ::= nm DOT nm(X). {
+  A = X;
+  sqlite3ErrorMsg(pParse, 
+        "qualified table names are not allowed on INSERT, UPDATE, and DELETE "
+        "statements within triggers");
+}
+
+// Disallow the INDEX BY and NOT INDEXED clauses on UPDATE and DELETE
+// statements within triggers.  We make a specific error message for this
+// since it is an exception to the default grammar rules.
+//
+tridxby ::= .
+tridxby ::= INDEXED BY nm. {
+  sqlite3ErrorMsg(pParse,
+        "the INDEXED BY clause is not allowed on UPDATE or DELETE statements "
+        "within triggers");
+}
+tridxby ::= NOT INDEXED. {
+  sqlite3ErrorMsg(pParse,
+        "the NOT INDEXED clause is not allowed on UPDATE or DELETE statements "
+        "within triggers");
+}
+
+
+
+%type trigger_cmd {TriggerStep*}
+%destructor trigger_cmd {sqlite3DeleteTriggerStep(pParse->db, $$);}
+// UPDATE 
+trigger_cmd(A) ::=
+   UPDATE(B) orconf(R) trnm(X) tridxby SET setlist(Y) from(F) where_opt(Z) scanpt(E).  
+   {A = sqlite3TriggerUpdateStep(pParse, &X, F, Y, Z, R, B.z, E);}
+
+// INSERT
+trigger_cmd(A) ::= scanpt(B) insert_cmd(R) INTO
+                      trnm(X) idlist_opt(F) select(S) upsert(U) scanpt(Z). {
+   A = sqlite3TriggerInsertStep(pParse,&X,F,S,R,U,B,Z);/*A-overwrites-R*/
+}
+// DELETE
+trigger_cmd(A) ::= DELETE(B) FROM trnm(X) tridxby where_opt(Y) scanpt(E).
+   {A = sqlite3TriggerDeleteStep(pParse, &X, Y, B.z, E);}
+
+// SELECT
+trigger_cmd(A) ::= scanpt(B) select(X) scanpt(E).
+   {A = sqlite3TriggerSelectStep(pParse->db, X, B, E); /*A-overwrites-X*/}
+
+// The special RAISE expression that may occur in trigger programs
+expr(A) ::= RAISE LP IGNORE RP.  {
+  A = sqlite3PExpr(pParse, TK_RAISE, 0, 0); 
+  if( A ){
+    A->affExpr = OE_Ignore;
+  }
+}
+expr(A) ::= RAISE LP raisetype(T) COMMA nm(Z) RP.  {
+  A = sqlite3ExprAlloc(pParse->db, TK_RAISE, &Z, 1);
+  if( A ) {
+    A->affExpr = (char)T;
+  }
+}
+%endif  !SQLITE_OMIT_TRIGGER
+
+%type raisetype {int}
+raisetype(A) ::= ROLLBACK.  {A = OE_Rollback;}
+raisetype(A) ::= ABORT.     {A = OE_Abort;}
+raisetype(A) ::= FAIL.      {A = OE_Fail;}
+
+
+////////////////////////  DROP TRIGGER statement //////////////////////////////
+%ifndef SQLITE_OMIT_TRIGGER
+cmd ::= DROP TRIGGER ifexists(NOERR) fullname(X). {
+  sqlite3DropTrigger(pParse,X,NOERR);
+}
+%endif  !SQLITE_OMIT_TRIGGER
+
+//////////////////////// ATTACH DATABASE file AS name /////////////////////////
+%ifndef SQLITE_OMIT_ATTACH
+cmd ::= ATTACH database_kw_opt expr(F) AS expr(D) key_opt(K). {
+  sqlite3Attach(pParse, F, D, K);
+}
+cmd ::= DETACH database_kw_opt expr(D). {
+  sqlite3Detach(pParse, D);
+}
+
+%type key_opt {Expr*}
+%destructor key_opt {sqlite3ExprDelete(pParse->db, $$);}
+key_opt(A) ::= .                     { A = 0; }
+key_opt(A) ::= KEY expr(X).          { A = X; }
+
+database_kw_opt ::= DATABASE.
+database_kw_opt ::= .
+%endif SQLITE_OMIT_ATTACH
+
+////////////////////////// REINDEX collation //////////////////////////////////
+%ifndef SQLITE_OMIT_REINDEX
+cmd ::= REINDEX.                {sqlite3Reindex(pParse, 0, 0);}
+cmd ::= REINDEX nm(X) dbnm(Y).  {sqlite3Reindex(pParse, &X, &Y);}
+%endif  SQLITE_OMIT_REINDEX
+
+/////////////////////////////////// ANALYZE ///////////////////////////////////
+%ifndef SQLITE_OMIT_ANALYZE
+cmd ::= ANALYZE.                {sqlite3Analyze(pParse, 0, 0);}
+cmd ::= ANALYZE nm(X) dbnm(Y).  {sqlite3Analyze(pParse, &X, &Y);}
+%endif
+
+//////////////////////// ALTER TABLE table ... ////////////////////////////////
+%ifndef SQLITE_OMIT_ALTERTABLE 
+%ifndef SQLITE_OMIT_VIRTUALTABLE
+cmd ::= ALTER TABLE fullname(X) RENAME TO nm(Z). {
+  sqlite3AlterRenameTable(pParse,X,&Z);
+}
+cmd ::= ALTER TABLE add_column_fullname
+        ADD kwcolumn_opt columnname(Y) carglist. {
+  Y.n = (int)(pParse->sLastToken.z-Y.z) + pParse->sLastToken.n;
+  sqlite3AlterFinishAddColumn(pParse, &Y);
+}
+cmd ::= ALTER TABLE fullname(X) DROP kwcolumn_opt nm(Y). {
+  sqlite3AlterDropColumn(pParse, X, &Y);
+}
+
+add_column_fullname ::= fullname(X). {
+  disableLookaside(pParse);
+  sqlite3AlterBeginAddColumn(pParse, X);
+}
+cmd ::= ALTER TABLE fullname(X) RENAME kwcolumn_opt nm(Y) TO nm(Z). {
+  sqlite3AlterRenameColumn(pParse, X, &Y, &Z);
+}
+
+kwcolumn_opt ::= .
+kwcolumn_opt ::= COLUMNKW.
+
+%endif SQLITE_OMIT_VIRTUALTABLE
+%endif SQLITE_OMIT_ALTERTABLE
+
+//////////////////////// CREATE VIRTUAL TABLE ... /////////////////////////////
+%ifndef SQLITE_OMIT_VIRTUALTABLE
+cmd ::= create_vtab.                       {sqlite3VtabFinishParse(pParse,0);}
+cmd ::= create_vtab LP vtabarglist RP(X).  {sqlite3VtabFinishParse(pParse,&X);}
+create_vtab ::= createkw VIRTUAL TABLE ifnotexists(E)
+                nm(X) dbnm(Y) USING nm(Z). {
+    sqlite3VtabBeginParse(pParse, &X, &Y, &Z, E);
+}
+vtabarglist ::= vtabarg.
+vtabarglist ::= vtabarglist COMMA vtabarg.
+vtabarg ::= .                       {sqlite3VtabArgInit(pParse);}
+vtabarg ::= vtabarg vtabargtoken.
+vtabargtoken ::= ANY(X).            {sqlite3VtabArgExtend(pParse,&X);}
+vtabargtoken ::= lp anylist RP(X).  {sqlite3VtabArgExtend(pParse,&X);}
+lp ::= LP(X).                       {sqlite3VtabArgExtend(pParse,&X);}
+anylist ::= .
+anylist ::= anylist LP anylist RP.
+anylist ::= anylist ANY.
+%endif  SQLITE_OMIT_VIRTUALTABLE
+
+
+//////////////////////// COMMON TABLE EXPRESSIONS ////////////////////////////
+%type wqlist {With*}
+%destructor wqlist {sqlite3WithDelete(pParse->db, $$);}
+%type wqitem {Cte*}
+// %destructor wqitem {sqlite3CteDelete(pParse->db, $$);} // not reachable
+
+with ::= .
+%ifndef SQLITE_OMIT_CTE
+with ::= WITH wqlist(W).              { sqlite3WithPush(pParse, W, 1); }
+with ::= WITH RECURSIVE wqlist(W).    { sqlite3WithPush(pParse, W, 1); }
+
+%type wqas {u8}
+wqas(A)   ::= AS.                  {A = M10d_Any;}
+wqas(A)   ::= AS MATERIALIZED.     {A = M10d_Yes;}
+wqas(A)   ::= AS NOT MATERIALIZED. {A = M10d_No;}
+wqitem(A) ::= nm(X) eidlist_opt(Y) wqas(M) LP select(Z) RP. {
+  A = sqlite3CteNew(pParse, &X, Y, Z, M); /*A-overwrites-X*/
+}
+wqlist(A) ::= wqitem(X). {
+  A = sqlite3WithAdd(pParse, 0, X); /*A-overwrites-X*/
+}
+wqlist(A) ::= wqlist(A) COMMA wqitem(X). {
+  A = sqlite3WithAdd(pParse, A, X);
+}
+%endif  SQLITE_OMIT_CTE
+
+//////////////////////// WINDOW FUNCTION EXPRESSIONS /////////////////////////
+// These must be at the end of this file. Specifically, the rules that
+// introduce tokens WINDOW, OVER and FILTER must appear last. This causes 
+// the integer values assigned to these tokens to be larger than all other 
+// tokens that may be output by the tokenizer except TK_SPACE and TK_ILLEGAL.
+//
+%ifndef SQLITE_OMIT_WINDOWFUNC
+%type windowdefn_list {Window*}
+%destructor windowdefn_list {sqlite3WindowListDelete(pParse->db, $$);}
+windowdefn_list(A) ::= windowdefn(A).
+windowdefn_list(A) ::= windowdefn_list(Y) COMMA windowdefn(Z). {
+  assert( Z!=0 );
+  sqlite3WindowChain(pParse, Z, Y);
+  Z->pNextWin = Y;
+  A = Z;
+}
+
+%type windowdefn {Window*}
+%destructor windowdefn {sqlite3WindowDelete(pParse->db, $$);}
+windowdefn(A) ::= nm(X) AS LP window(Y) RP. {
+  if( ALWAYS(Y) ){
+    Y->zName = sqlite3DbStrNDup(pParse->db, X.z, X.n);
+  }
+  A = Y;
+}
+
+%type window {Window*}
+%destructor window {sqlite3WindowDelete(pParse->db, $$);}
+
+%type frame_opt {Window*}
+%destructor frame_opt {sqlite3WindowDelete(pParse->db, $$);}
+
+%type part_opt {ExprList*}
+%destructor part_opt {sqlite3ExprListDelete(pParse->db, $$);}
+
+%type filter_clause {Expr*}
+%destructor filter_clause {sqlite3ExprDelete(pParse->db, $$);}
+
+%type over_clause {Window*}
+%destructor over_clause {sqlite3WindowDelete(pParse->db, $$);}
+
+%type filter_over {Window*}
+%destructor filter_over {sqlite3WindowDelete(pParse->db, $$);}
+
+%type range_or_rows {int}
+
+%type frame_bound {struct FrameBound}
+%destructor frame_bound {sqlite3ExprDelete(pParse->db, $$.pExpr);}
+%type frame_bound_s {struct FrameBound}
+%destructor frame_bound_s {sqlite3ExprDelete(pParse->db, $$.pExpr);}
+%type frame_bound_e {struct FrameBound}
+%destructor frame_bound_e {sqlite3ExprDelete(pParse->db, $$.pExpr);}
+
+window(A) ::= PARTITION BY nexprlist(X) orderby_opt(Y) frame_opt(Z). {
+  A = sqlite3WindowAssemble(pParse, Z, X, Y, 0);
+}
+window(A) ::= nm(W) PARTITION BY nexprlist(X) orderby_opt(Y) frame_opt(Z). {
+  A = sqlite3WindowAssemble(pParse, Z, X, Y, &W);
+}
+window(A) ::= ORDER BY sortlist(Y) frame_opt(Z). {
+  A = sqlite3WindowAssemble(pParse, Z, 0, Y, 0);
+}
+window(A) ::= nm(W) ORDER BY sortlist(Y) frame_opt(Z). {
+  A = sqlite3WindowAssemble(pParse, Z, 0, Y, &W);
+}
+window(A) ::= frame_opt(A).
+window(A) ::= nm(W) frame_opt(Z). {
+  A = sqlite3WindowAssemble(pParse, Z, 0, 0, &W);
+}
+
+frame_opt(A) ::= .                             { 
+  A = sqlite3WindowAlloc(pParse, 0, TK_UNBOUNDED, 0, TK_CURRENT, 0, 0);
+}
+frame_opt(A) ::= range_or_rows(X) frame_bound_s(Y) frame_exclude_opt(Z). { 
+  A = sqlite3WindowAlloc(pParse, X, Y.eType, Y.pExpr, TK_CURRENT, 0, Z);
+}
+frame_opt(A) ::= range_or_rows(X) BETWEEN frame_bound_s(Y) AND
+                          frame_bound_e(Z) frame_exclude_opt(W). { 
+  A = sqlite3WindowAlloc(pParse, X, Y.eType, Y.pExpr, Z.eType, Z.pExpr, W);
+}
+
+range_or_rows(A) ::= RANGE|ROWS|GROUPS(X).   {A = @X; /*A-overwrites-X*/}
+
+frame_bound_s(A) ::= frame_bound(X).         {A = X;}
+frame_bound_s(A) ::= UNBOUNDED(X) PRECEDING. {A.eType = @X; A.pExpr = 0;}
+frame_bound_e(A) ::= frame_bound(X).         {A = X;}
+frame_bound_e(A) ::= UNBOUNDED(X) FOLLOWING. {A.eType = @X; A.pExpr = 0;}
+
+frame_bound(A) ::= expr(X) PRECEDING|FOLLOWING(Y).
+                                             {A.eType = @Y; A.pExpr = X;}
+frame_bound(A) ::= CURRENT(X) ROW.           {A.eType = @X; A.pExpr = 0;}
+
+%type frame_exclude_opt {u8}
+frame_exclude_opt(A) ::= . {A = 0;}
+frame_exclude_opt(A) ::= EXCLUDE frame_exclude(X). {A = X;}
+
+%type frame_exclude {u8}
+frame_exclude(A) ::= NO(X) OTHERS.   {A = @X; /*A-overwrites-X*/}
+frame_exclude(A) ::= CURRENT(X) ROW. {A = @X; /*A-overwrites-X*/}
+frame_exclude(A) ::= GROUP|TIES(X).  {A = @X; /*A-overwrites-X*/}
+
+
+%type window_clause {Window*}
+%destructor window_clause {sqlite3WindowListDelete(pParse->db, $$);}
+window_clause(A) ::= WINDOW windowdefn_list(B). { A = B; }
+
+filter_over(A) ::= filter_clause(F) over_clause(O). {
+  if( O ){
+    O->pFilter = F;
+  }else{
+    sqlite3ExprDelete(pParse->db, F);
+  }
+  A = O;
+}
+filter_over(A) ::= over_clause(O). {
+  A = O;
+}
+filter_over(A) ::= filter_clause(F). {
+  A = (Window*)sqlite3DbMallocZero(pParse->db, sizeof(Window));
+  if( A ){
+    A->eFrmType = TK_FILTER;
+    A->pFilter = F;
+  }else{
+    sqlite3ExprDelete(pParse->db, F);
+  }
+}
+
+over_clause(A) ::= OVER LP window(Z) RP. {
+  A = Z;
+  assert( A!=0 );
+}
+over_clause(A) ::= OVER nm(Z). {
+  A = (Window*)sqlite3DbMallocZero(pParse->db, sizeof(Window));
+  if( A ){
+    A->zName = sqlite3DbStrNDup(pParse->db, Z.z, Z.n);
+  }
+}
+
+filter_clause(A) ::= FILTER LP WHERE expr(X) RP.  { A = X; }
+%endif /* SQLITE_OMIT_WINDOWFUNC */
+
+/*
+** The code generator needs some extra TK_ token values for tokens that
+** are synthesized and do not actually appear in the grammar:
+*/
+%token
+  COLUMN          /* Reference to a table column */
+  AGG_FUNCTION    /* An aggregate function */
+  AGG_COLUMN      /* An aggregated column */
+  TRUEFALSE       /* True or false keyword */
+  ISNOT           /* Combination of IS and NOT */
+  FUNCTION        /* A function invocation */
+  UMINUS          /* Unary minus */
+  UPLUS           /* Unary plus */
+  TRUTH           /* IS TRUE or IS FALSE or IS NOT TRUE or IS NOT FALSE */
+  REGISTER        /* Reference to a VDBE register */
+  VECTOR          /* Vector */
+  SELECT_COLUMN   /* Choose a single column from a multi-column SELECT */
+  IF_NULL_ROW     /* the if-null-row operator */
+  ASTERISK        /* The "*" in count(*) and similar */
+  SPAN            /* The span operator */
+  ERROR           /* An expression containing an error */
+.
+/* There must be no more than 255 tokens defined above.  If this grammar
+** is extended with new rules and tokens, they must either be so few in
+** number that TK_SPAN is no more than 255, or else the new tokens must
+** appear after this line.
+*/
+%include {
+#if TK_SPAN>255
+# error too many tokens in the grammar
+#endif
+}
+
+/*
+** The TK_SPACE and TK_ILLEGAL tokens must be the last two tokens.  The
+** parser depends on this.  Those tokens are not used in any grammar rule.
+** They are only used by the tokenizer.  Declare them last so that they
+** are guaranteed to be the last two tokens
+*/
+%token SPACE ILLEGAL.
diff --git a/src/pcache.c b/src/pcache.c
new file mode 100644
index 0000000..2974b08
--- /dev/null
+++ b/src/pcache.c
@@ -0,0 +1,935 @@
+/*
+** 2008 August 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements that page cache.
+*/
+#include "sqliteInt.h"
+
+/*
+** A complete page cache is an instance of this structure.  Every
+** entry in the cache holds a single page of the database file.  The
+** btree layer only operates on the cached copy of the database pages.
+**
+** A page cache entry is "clean" if it exactly matches what is currently
+** on disk.  A page is "dirty" if it has been modified and needs to be
+** persisted to disk.
+**
+** pDirty, pDirtyTail, pSynced:
+**   All dirty pages are linked into the doubly linked list using
+**   PgHdr.pDirtyNext and pDirtyPrev. The list is maintained in LRU order
+**   such that p was added to the list more recently than p->pDirtyNext.
+**   PCache.pDirty points to the first (newest) element in the list and
+**   pDirtyTail to the last (oldest).
+**
+**   The PCache.pSynced variable is used to optimize searching for a dirty
+**   page to eject from the cache mid-transaction. It is better to eject
+**   a page that does not require a journal sync than one that does. 
+**   Therefore, pSynced is maintained so that it *almost* always points
+**   to either the oldest page in the pDirty/pDirtyTail list that has a
+**   clear PGHDR_NEED_SYNC flag or to a page that is older than this one
+**   (so that the right page to eject can be found by following pDirtyPrev
+**   pointers).
+*/
+struct PCache {
+  PgHdr *pDirty, *pDirtyTail;         /* List of dirty pages in LRU order */
+  PgHdr *pSynced;                     /* Last synced page in dirty page list */
+  i64 nRefSum;                        /* Sum of ref counts over all pages */
+  int szCache;                        /* Configured cache size */
+  int szSpill;                        /* Size before spilling occurs */
+  int szPage;                         /* Size of every page in this cache */
+  int szExtra;                        /* Size of extra space for each page */
+  u8 bPurgeable;                      /* True if pages are on backing store */
+  u8 eCreate;                         /* eCreate value for for xFetch() */
+  int (*xStress)(void*,PgHdr*);       /* Call to try make a page clean */
+  void *pStress;                      /* Argument to xStress */
+  sqlite3_pcache *pCache;             /* Pluggable cache module */
+};
+
+/********************************** Test and Debug Logic **********************/
+/*
+** Debug tracing macros.  Enable by by changing the "0" to "1" and
+** recompiling.
+**
+** When sqlite3PcacheTrace is 1, single line trace messages are issued.
+** When sqlite3PcacheTrace is 2, a dump of the pcache showing all cache entries
+** is displayed for many operations, resulting in a lot of output.
+*/
+#if defined(SQLITE_DEBUG) && 0
+  int sqlite3PcacheTrace = 2;       /* 0: off  1: simple  2: cache dumps */
+  int sqlite3PcacheMxDump = 9999;   /* Max cache entries for pcacheDump() */
+# define pcacheTrace(X) if(sqlite3PcacheTrace){sqlite3DebugPrintf X;}
+  static void pcachePageTrace(int i, sqlite3_pcache_page *pLower){
+    PgHdr *pPg;
+    unsigned char *a;
+    int j;
+    if( pLower==0 ){
+      printf("%3d: NULL\n", i);
+    }else{
+      pPg = (PgHdr*)pLower->pExtra;
+      printf("%3d: nRef %2lld flgs %02x data ", i, pPg->nRef, pPg->flags);
+      a = (unsigned char *)pLower->pBuf;
+      for(j=0; j<12; j++) printf("%02x", a[j]);
+      printf(" ptr %p\n", pPg);
+    }
+  }
+  static void pcacheDump(PCache *pCache){
+    int N;
+    int i;
+    sqlite3_pcache_page *pLower;
+  
+    if( sqlite3PcacheTrace<2 ) return;
+    if( pCache->pCache==0 ) return;
+    N = sqlite3PcachePagecount(pCache);
+    if( N>sqlite3PcacheMxDump ) N = sqlite3PcacheMxDump;
+    for(i=1; i<=N; i++){
+       pLower = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, i, 0);
+       pcachePageTrace(i, pLower);
+       if( pLower && ((PgHdr*)pLower)->pPage==0 ){
+         sqlite3GlobalConfig.pcache2.xUnpin(pCache->pCache, pLower, 0);
+       }
+    }
+  }
+#else
+# define pcacheTrace(X)
+# define pcachePageTrace(PGNO, X)
+# define pcacheDump(X)
+#endif
+
+/*
+** Return 1 if pPg is on the dirty list for pCache.  Return 0 if not.
+** This routine runs inside of assert() statements only.
+*/
+#if defined(SQLITE_ENABLE_EXPENSIVE_ASSERT)
+static int pageOnDirtyList(PCache *pCache, PgHdr *pPg){
+  PgHdr *p;
+  for(p=pCache->pDirty; p; p=p->pDirtyNext){
+    if( p==pPg ) return 1;
+  }
+  return 0;
+}
+static int pageNotOnDirtyList(PCache *pCache, PgHdr *pPg){
+  PgHdr *p;
+  for(p=pCache->pDirty; p; p=p->pDirtyNext){
+    if( p==pPg ) return 0;
+  }
+  return 1;
+}
+#else
+# define pageOnDirtyList(A,B)    1
+# define pageNotOnDirtyList(A,B) 1
+#endif
+
+/*
+** Check invariants on a PgHdr entry.  Return true if everything is OK.
+** Return false if any invariant is violated.
+**
+** This routine is for use inside of assert() statements only.  For
+** example:
+**
+**          assert( sqlite3PcachePageSanity(pPg) );
+*/
+#ifdef SQLITE_DEBUG
+int sqlite3PcachePageSanity(PgHdr *pPg){
+  PCache *pCache;
+  assert( pPg!=0 );
+  assert( pPg->pgno>0 || pPg->pPager==0 );    /* Page number is 1 or more */
+  pCache = pPg->pCache;
+  assert( pCache!=0 );      /* Every page has an associated PCache */
+  if( pPg->flags & PGHDR_CLEAN ){
+    assert( (pPg->flags & PGHDR_DIRTY)==0 );/* Cannot be both CLEAN and DIRTY */
+    assert( pageNotOnDirtyList(pCache, pPg) );/* CLEAN pages not on dirtylist */
+  }else{
+    assert( (pPg->flags & PGHDR_DIRTY)!=0 );/* If not CLEAN must be DIRTY */
+    assert( pPg->pDirtyNext==0 || pPg->pDirtyNext->pDirtyPrev==pPg );
+    assert( pPg->pDirtyPrev==0 || pPg->pDirtyPrev->pDirtyNext==pPg );
+    assert( pPg->pDirtyPrev!=0 || pCache->pDirty==pPg );
+    assert( pageOnDirtyList(pCache, pPg) );
+  }
+  /* WRITEABLE pages must also be DIRTY */
+  if( pPg->flags & PGHDR_WRITEABLE ){
+    assert( pPg->flags & PGHDR_DIRTY );     /* WRITEABLE implies DIRTY */
+  }
+  /* NEED_SYNC can be set independently of WRITEABLE.  This can happen,
+  ** for example, when using the sqlite3PagerDontWrite() optimization:
+  **    (1)  Page X is journalled, and gets WRITEABLE and NEED_SEEK.
+  **    (2)  Page X moved to freelist, WRITEABLE is cleared
+  **    (3)  Page X reused, WRITEABLE is set again
+  ** If NEED_SYNC had been cleared in step 2, then it would not be reset
+  ** in step 3, and page might be written into the database without first
+  ** syncing the rollback journal, which might cause corruption on a power
+  ** loss.
+  **
+  ** Another example is when the database page size is smaller than the
+  ** disk sector size.  When any page of a sector is journalled, all pages
+  ** in that sector are marked NEED_SYNC even if they are still CLEAN, just
+  ** in case they are later modified, since all pages in the same sector
+  ** must be journalled and synced before any of those pages can be safely
+  ** written.
+  */
+  return 1;
+}
+#endif /* SQLITE_DEBUG */
+
+
+/********************************** Linked List Management ********************/
+
+/* Allowed values for second argument to pcacheManageDirtyList() */
+#define PCACHE_DIRTYLIST_REMOVE   1    /* Remove pPage from dirty list */
+#define PCACHE_DIRTYLIST_ADD      2    /* Add pPage to the dirty list */
+#define PCACHE_DIRTYLIST_FRONT    3    /* Move pPage to the front of the list */
+
+/*
+** Manage pPage's participation on the dirty list.  Bits of the addRemove
+** argument determines what operation to do.  The 0x01 bit means first
+** remove pPage from the dirty list.  The 0x02 means add pPage back to
+** the dirty list.  Doing both moves pPage to the front of the dirty list.
+*/
+static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){
+  PCache *p = pPage->pCache;
+
+  pcacheTrace(("%p.DIRTYLIST.%s %d\n", p,
+                addRemove==1 ? "REMOVE" : addRemove==2 ? "ADD" : "FRONT",
+                pPage->pgno));
+  if( addRemove & PCACHE_DIRTYLIST_REMOVE ){
+    assert( pPage->pDirtyNext || pPage==p->pDirtyTail );
+    assert( pPage->pDirtyPrev || pPage==p->pDirty );
+  
+    /* Update the PCache1.pSynced variable if necessary. */
+    if( p->pSynced==pPage ){
+      p->pSynced = pPage->pDirtyPrev;
+    }
+  
+    if( pPage->pDirtyNext ){
+      pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev;
+    }else{
+      assert( pPage==p->pDirtyTail );
+      p->pDirtyTail = pPage->pDirtyPrev;
+    }
+    if( pPage->pDirtyPrev ){
+      pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
+    }else{
+      /* If there are now no dirty pages in the cache, set eCreate to 2. 
+      ** This is an optimization that allows sqlite3PcacheFetch() to skip
+      ** searching for a dirty page to eject from the cache when it might
+      ** otherwise have to.  */
+      assert( pPage==p->pDirty );
+      p->pDirty = pPage->pDirtyNext;
+      assert( p->bPurgeable || p->eCreate==2 );
+      if( p->pDirty==0 ){         /*OPTIMIZATION-IF-TRUE*/
+        assert( p->bPurgeable==0 || p->eCreate==1 );
+        p->eCreate = 2;
+      }
+    }
+  }
+  if( addRemove & PCACHE_DIRTYLIST_ADD ){
+    pPage->pDirtyPrev = 0;
+    pPage->pDirtyNext = p->pDirty;
+    if( pPage->pDirtyNext ){
+      assert( pPage->pDirtyNext->pDirtyPrev==0 );
+      pPage->pDirtyNext->pDirtyPrev = pPage;
+    }else{
+      p->pDirtyTail = pPage;
+      if( p->bPurgeable ){
+        assert( p->eCreate==2 );
+        p->eCreate = 1;
+      }
+    }
+    p->pDirty = pPage;
+
+    /* If pSynced is NULL and this page has a clear NEED_SYNC flag, set
+    ** pSynced to point to it. Checking the NEED_SYNC flag is an 
+    ** optimization, as if pSynced points to a page with the NEED_SYNC
+    ** flag set sqlite3PcacheFetchStress() searches through all newer 
+    ** entries of the dirty-list for a page with NEED_SYNC clear anyway.  */
+    if( !p->pSynced 
+     && 0==(pPage->flags&PGHDR_NEED_SYNC)   /*OPTIMIZATION-IF-FALSE*/
+    ){
+      p->pSynced = pPage;
+    }
+  }
+  pcacheDump(p);
+}
+
+/*
+** Wrapper around the pluggable caches xUnpin method. If the cache is
+** being used for an in-memory database, this function is a no-op.
+*/
+static void pcacheUnpin(PgHdr *p){
+  if( p->pCache->bPurgeable ){
+    pcacheTrace(("%p.UNPIN %d\n", p->pCache, p->pgno));
+    sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0);
+    pcacheDump(p->pCache);
+  }
+}
+
+/*
+** Compute the number of pages of cache requested.   p->szCache is the
+** cache size requested by the "PRAGMA cache_size" statement.
+*/
+static int numberOfCachePages(PCache *p){
+  if( p->szCache>=0 ){
+    /* IMPLEMENTATION-OF: R-42059-47211 If the argument N is positive then the
+    ** suggested cache size is set to N. */
+    return p->szCache;
+  }else{
+    i64 n;
+    /* IMPLEMENTATION-OF: R-59858-46238 If the argument N is negative, then the
+    ** number of cache pages is adjusted to be a number of pages that would
+    ** use approximately abs(N*1024) bytes of memory based on the current
+    ** page size. */
+    n = ((-1024*(i64)p->szCache)/(p->szPage+p->szExtra));
+    if( n>1000000000 ) n = 1000000000;
+    return (int)n;
+  }
+}
+
+/*************************************************** General Interfaces ******
+**
+** Initialize and shutdown the page cache subsystem. Neither of these 
+** functions are threadsafe.
+*/
+int sqlite3PcacheInitialize(void){
+  if( sqlite3GlobalConfig.pcache2.xInit==0 ){
+    /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the
+    ** built-in default page cache is used instead of the application defined
+    ** page cache. */
+    sqlite3PCacheSetDefault();
+    assert( sqlite3GlobalConfig.pcache2.xInit!=0 );
+  }
+  return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg);
+}
+void sqlite3PcacheShutdown(void){
+  if( sqlite3GlobalConfig.pcache2.xShutdown ){
+    /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */
+    sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg);
+  }
+}
+
+/*
+** Return the size in bytes of a PCache object.
+*/
+int sqlite3PcacheSize(void){ return sizeof(PCache); }
+
+/*
+** Create a new PCache object. Storage space to hold the object
+** has already been allocated and is passed in as the p pointer. 
+** The caller discovers how much space needs to be allocated by 
+** calling sqlite3PcacheSize().
+**
+** szExtra is some extra space allocated for each page.  The first
+** 8 bytes of the extra space will be zeroed as the page is allocated,
+** but remaining content will be uninitialized.  Though it is opaque
+** to this module, the extra space really ends up being the MemPage
+** structure in the pager.
+*/
+int sqlite3PcacheOpen(
+  int szPage,                  /* Size of every page */
+  int szExtra,                 /* Extra space associated with each page */
+  int bPurgeable,              /* True if pages are on backing store */
+  int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */
+  void *pStress,               /* Argument to xStress */
+  PCache *p                    /* Preallocated space for the PCache */
+){
+  memset(p, 0, sizeof(PCache));
+  p->szPage = 1;
+  p->szExtra = szExtra;
+  assert( szExtra>=8 );  /* First 8 bytes will be zeroed */
+  p->bPurgeable = bPurgeable;
+  p->eCreate = 2;
+  p->xStress = xStress;
+  p->pStress = pStress;
+  p->szCache = 100;
+  p->szSpill = 1;
+  pcacheTrace(("%p.OPEN szPage %d bPurgeable %d\n",p,szPage,bPurgeable));
+  return sqlite3PcacheSetPageSize(p, szPage);
+}
+
+/*
+** Change the page size for PCache object. The caller must ensure that there
+** are no outstanding page references when this function is called.
+*/
+int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
+  assert( pCache->nRefSum==0 && pCache->pDirty==0 );
+  if( pCache->szPage ){
+    sqlite3_pcache *pNew;
+    pNew = sqlite3GlobalConfig.pcache2.xCreate(
+                szPage, pCache->szExtra + ROUND8(sizeof(PgHdr)),
+                pCache->bPurgeable
+    );
+    if( pNew==0 ) return SQLITE_NOMEM_BKPT;
+    sqlite3GlobalConfig.pcache2.xCachesize(pNew, numberOfCachePages(pCache));
+    if( pCache->pCache ){
+      sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
+    }
+    pCache->pCache = pNew;
+    pCache->szPage = szPage;
+    pcacheTrace(("%p.PAGESIZE %d\n",pCache,szPage));
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Try to obtain a page from the cache.
+**
+** This routine returns a pointer to an sqlite3_pcache_page object if
+** such an object is already in cache, or if a new one is created.
+** This routine returns a NULL pointer if the object was not in cache
+** and could not be created.
+**
+** The createFlags should be 0 to check for existing pages and should
+** be 3 (not 1, but 3) to try to create a new page.
+**
+** If the createFlag is 0, then NULL is always returned if the page
+** is not already in the cache.  If createFlag is 1, then a new page
+** is created only if that can be done without spilling dirty pages
+** and without exceeding the cache size limit.
+**
+** The caller needs to invoke sqlite3PcacheFetchFinish() to properly
+** initialize the sqlite3_pcache_page object and convert it into a
+** PgHdr object.  The sqlite3PcacheFetch() and sqlite3PcacheFetchFinish()
+** routines are split this way for performance reasons. When separated
+** they can both (usually) operate without having to push values to
+** the stack on entry and pop them back off on exit, which saves a
+** lot of pushing and popping.
+*/
+sqlite3_pcache_page *sqlite3PcacheFetch(
+  PCache *pCache,       /* Obtain the page from this cache */
+  Pgno pgno,            /* Page number to obtain */
+  int createFlag        /* If true, create page if it does not exist already */
+){
+  int eCreate;
+  sqlite3_pcache_page *pRes;
+
+  assert( pCache!=0 );
+  assert( pCache->pCache!=0 );
+  assert( createFlag==3 || createFlag==0 );
+  assert( pCache->eCreate==((pCache->bPurgeable && pCache->pDirty) ? 1 : 2) );
+
+  /* eCreate defines what to do if the page does not exist.
+  **    0     Do not allocate a new page.  (createFlag==0)
+  **    1     Allocate a new page if doing so is inexpensive.
+  **          (createFlag==1 AND bPurgeable AND pDirty)
+  **    2     Allocate a new page even it doing so is difficult.
+  **          (createFlag==1 AND !(bPurgeable AND pDirty)
+  */
+  eCreate = createFlag & pCache->eCreate;
+  assert( eCreate==0 || eCreate==1 || eCreate==2 );
+  assert( createFlag==0 || pCache->eCreate==eCreate );
+  assert( createFlag==0 || eCreate==1+(!pCache->bPurgeable||!pCache->pDirty) );
+  pRes = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);
+  pcacheTrace(("%p.FETCH %d%s (result: %p) ",pCache,pgno,
+               createFlag?" create":"",pRes));
+  pcachePageTrace(pgno, pRes);
+  return pRes;
+}
+
+/*
+** If the sqlite3PcacheFetch() routine is unable to allocate a new
+** page because no clean pages are available for reuse and the cache
+** size limit has been reached, then this routine can be invoked to 
+** try harder to allocate a page.  This routine might invoke the stress
+** callback to spill dirty pages to the journal.  It will then try to
+** allocate the new page and will only fail to allocate a new page on
+** an OOM error.
+**
+** This routine should be invoked only after sqlite3PcacheFetch() fails.
+*/
+int sqlite3PcacheFetchStress(
+  PCache *pCache,                 /* Obtain the page from this cache */
+  Pgno pgno,                      /* Page number to obtain */
+  sqlite3_pcache_page **ppPage    /* Write result here */
+){
+  PgHdr *pPg;
+  if( pCache->eCreate==2 ) return 0;
+
+  if( sqlite3PcachePagecount(pCache)>pCache->szSpill ){
+    /* Find a dirty page to write-out and recycle. First try to find a 
+    ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
+    ** cleared), but if that is not possible settle for any other 
+    ** unreferenced dirty page.
+    **
+    ** If the LRU page in the dirty list that has a clear PGHDR_NEED_SYNC
+    ** flag is currently referenced, then the following may leave pSynced
+    ** set incorrectly (pointing to other than the LRU page with NEED_SYNC
+    ** cleared). This is Ok, as pSynced is just an optimization.  */
+    for(pPg=pCache->pSynced; 
+        pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); 
+        pPg=pPg->pDirtyPrev
+    );
+    pCache->pSynced = pPg;
+    if( !pPg ){
+      for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev);
+    }
+    if( pPg ){
+      int rc;
+#ifdef SQLITE_LOG_CACHE_SPILL
+      sqlite3_log(SQLITE_FULL, 
+                  "spill page %d making room for %d - cache used: %d/%d",
+                  pPg->pgno, pgno,
+                  sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache),
+                numberOfCachePages(pCache));
+#endif
+      pcacheTrace(("%p.SPILL %d\n",pCache,pPg->pgno));
+      rc = pCache->xStress(pCache->pStress, pPg);
+      pcacheDump(pCache);
+      if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
+        return rc;
+      }
+    }
+  }
+  *ppPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2);
+  return *ppPage==0 ? SQLITE_NOMEM_BKPT : SQLITE_OK;
+}
+
+/*
+** This is a helper routine for sqlite3PcacheFetchFinish()
+**
+** In the uncommon case where the page being fetched has not been
+** initialized, this routine is invoked to do the initialization.
+** This routine is broken out into a separate function since it
+** requires extra stack manipulation that can be avoided in the common
+** case.
+*/
+static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit(
+  PCache *pCache,             /* Obtain the page from this cache */
+  Pgno pgno,                  /* Page number obtained */
+  sqlite3_pcache_page *pPage  /* Page obtained by prior PcacheFetch() call */
+){
+  PgHdr *pPgHdr;
+  assert( pPage!=0 );
+  pPgHdr = (PgHdr*)pPage->pExtra;
+  assert( pPgHdr->pPage==0 );
+  memset(&pPgHdr->pDirty, 0, sizeof(PgHdr) - offsetof(PgHdr,pDirty));
+  pPgHdr->pPage = pPage;
+  pPgHdr->pData = pPage->pBuf;
+  pPgHdr->pExtra = (void *)&pPgHdr[1];
+  memset(pPgHdr->pExtra, 0, 8);
+  pPgHdr->pCache = pCache;
+  pPgHdr->pgno = pgno;
+  pPgHdr->flags = PGHDR_CLEAN;
+  return sqlite3PcacheFetchFinish(pCache,pgno,pPage);
+}
+
+/*
+** This routine converts the sqlite3_pcache_page object returned by
+** sqlite3PcacheFetch() into an initialized PgHdr object.  This routine
+** must be called after sqlite3PcacheFetch() in order to get a usable
+** result.
+*/
+PgHdr *sqlite3PcacheFetchFinish(
+  PCache *pCache,             /* Obtain the page from this cache */
+  Pgno pgno,                  /* Page number obtained */
+  sqlite3_pcache_page *pPage  /* Page obtained by prior PcacheFetch() call */
+){
+  PgHdr *pPgHdr;
+
+  assert( pPage!=0 );
+  pPgHdr = (PgHdr *)pPage->pExtra;
+
+  if( !pPgHdr->pPage ){
+    return pcacheFetchFinishWithInit(pCache, pgno, pPage);
+  }
+  pCache->nRefSum++;
+  pPgHdr->nRef++;
+  assert( sqlite3PcachePageSanity(pPgHdr) );
+  return pPgHdr;
+}
+
+/*
+** Decrement the reference count on a page. If the page is clean and the
+** reference count drops to 0, then it is made eligible for recycling.
+*/
+void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
+  assert( p->nRef>0 );
+  p->pCache->nRefSum--;
+  if( (--p->nRef)==0 ){
+    if( p->flags&PGHDR_CLEAN ){
+      pcacheUnpin(p);
+    }else{
+      pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
+      assert( sqlite3PcachePageSanity(p) );
+    }
+  }
+}
+
+/*
+** Increase the reference count of a supplied page by 1.
+*/
+void sqlite3PcacheRef(PgHdr *p){
+  assert(p->nRef>0);
+  assert( sqlite3PcachePageSanity(p) );
+  p->nRef++;
+  p->pCache->nRefSum++;
+}
+
+/*
+** Drop a page from the cache. There must be exactly one reference to the
+** page. This function deletes that reference, so after it returns the
+** page pointed to by p is invalid.
+*/
+void sqlite3PcacheDrop(PgHdr *p){
+  assert( p->nRef==1 );
+  assert( sqlite3PcachePageSanity(p) );
+  if( p->flags&PGHDR_DIRTY ){
+    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
+  }
+  p->pCache->nRefSum--;
+  sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1);
+}
+
+/*
+** Make sure the page is marked as dirty. If it isn't dirty already,
+** make it so.
+*/
+void sqlite3PcacheMakeDirty(PgHdr *p){
+  assert( p->nRef>0 );
+  assert( sqlite3PcachePageSanity(p) );
+  if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){    /*OPTIMIZATION-IF-FALSE*/
+    p->flags &= ~PGHDR_DONT_WRITE;
+    if( p->flags & PGHDR_CLEAN ){
+      p->flags ^= (PGHDR_DIRTY|PGHDR_CLEAN);
+      pcacheTrace(("%p.DIRTY %d\n",p->pCache,p->pgno));
+      assert( (p->flags & (PGHDR_DIRTY|PGHDR_CLEAN))==PGHDR_DIRTY );
+      pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
+      assert( sqlite3PcachePageSanity(p) );
+    }
+    assert( sqlite3PcachePageSanity(p) );
+  }
+}
+
+/*
+** Make sure the page is marked as clean. If it isn't clean already,
+** make it so.
+*/
+void sqlite3PcacheMakeClean(PgHdr *p){
+  assert( sqlite3PcachePageSanity(p) );
+  assert( (p->flags & PGHDR_DIRTY)!=0 );
+  assert( (p->flags & PGHDR_CLEAN)==0 );
+  pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
+  p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
+  p->flags |= PGHDR_CLEAN;
+  pcacheTrace(("%p.CLEAN %d\n",p->pCache,p->pgno));
+  assert( sqlite3PcachePageSanity(p) );
+  if( p->nRef==0 ){
+    pcacheUnpin(p);
+  }
+}
+
+/*
+** Make every page in the cache clean.
+*/
+void sqlite3PcacheCleanAll(PCache *pCache){
+  PgHdr *p;
+  pcacheTrace(("%p.CLEAN-ALL\n",pCache));
+  while( (p = pCache->pDirty)!=0 ){
+    sqlite3PcacheMakeClean(p);
+  }
+}
+
+/*
+** Clear the PGHDR_NEED_SYNC and PGHDR_WRITEABLE flag from all dirty pages.
+*/
+void sqlite3PcacheClearWritable(PCache *pCache){
+  PgHdr *p;
+  pcacheTrace(("%p.CLEAR-WRITEABLE\n",pCache));
+  for(p=pCache->pDirty; p; p=p->pDirtyNext){
+    p->flags &= ~(PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
+  }
+  pCache->pSynced = pCache->pDirtyTail;
+}
+
+/*
+** Clear the PGHDR_NEED_SYNC flag from all dirty pages.
+*/
+void sqlite3PcacheClearSyncFlags(PCache *pCache){
+  PgHdr *p;
+  for(p=pCache->pDirty; p; p=p->pDirtyNext){
+    p->flags &= ~PGHDR_NEED_SYNC;
+  }
+  pCache->pSynced = pCache->pDirtyTail;
+}
+
+/*
+** Change the page number of page p to newPgno. 
+*/
+void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
+  PCache *pCache = p->pCache;
+  sqlite3_pcache_page *pOther;
+  assert( p->nRef>0 );
+  assert( newPgno>0 );
+  assert( sqlite3PcachePageSanity(p) );
+  pcacheTrace(("%p.MOVE %d -> %d\n",pCache,p->pgno,newPgno));
+  pOther = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, newPgno, 0);
+  if( pOther ){
+    PgHdr *pXPage = (PgHdr*)pOther->pExtra;
+    assert( pXPage->nRef==0 );
+    pXPage->nRef++;
+    pCache->nRefSum++;
+    sqlite3PcacheDrop(pXPage);
+  }
+  sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno);
+  p->pgno = newPgno;
+  if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){
+    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
+    assert( sqlite3PcachePageSanity(p) );
+  }
+}
+
+/*
+** Drop every cache entry whose page number is greater than "pgno". The
+** caller must ensure that there are no outstanding references to any pages
+** other than page 1 with a page number greater than pgno.
+**
+** If there is a reference to page 1 and the pgno parameter passed to this
+** function is 0, then the data area associated with page 1 is zeroed, but
+** the page object is not dropped.
+*/
+void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
+  if( pCache->pCache ){
+    PgHdr *p;
+    PgHdr *pNext;
+    pcacheTrace(("%p.TRUNCATE %d\n",pCache,pgno));
+    for(p=pCache->pDirty; p; p=pNext){
+      pNext = p->pDirtyNext;
+      /* This routine never gets call with a positive pgno except right
+      ** after sqlite3PcacheCleanAll().  So if there are dirty pages,
+      ** it must be that pgno==0.
+      */
+      assert( p->pgno>0 );
+      if( p->pgno>pgno ){
+        assert( p->flags&PGHDR_DIRTY );
+        sqlite3PcacheMakeClean(p);
+      }
+    }
+    if( pgno==0 && pCache->nRefSum ){
+      sqlite3_pcache_page *pPage1;
+      pPage1 = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache,1,0);
+      if( ALWAYS(pPage1) ){  /* Page 1 is always available in cache, because
+                             ** pCache->nRefSum>0 */
+        memset(pPage1->pBuf, 0, pCache->szPage);
+        pgno = 1;
+      }
+    }
+    sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);
+  }
+}
+
+/*
+** Close a cache.
+*/
+void sqlite3PcacheClose(PCache *pCache){
+  assert( pCache->pCache!=0 );
+  pcacheTrace(("%p.CLOSE\n",pCache));
+  sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
+}
+
+/* 
+** Discard the contents of the cache.
+*/
+void sqlite3PcacheClear(PCache *pCache){
+  sqlite3PcacheTruncate(pCache, 0);
+}
+
+/*
+** Merge two lists of pages connected by pDirty and in pgno order.
+** Do not bother fixing the pDirtyPrev pointers.
+*/
+static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){
+  PgHdr result, *pTail;
+  pTail = &result;
+  assert( pA!=0 && pB!=0 );
+  for(;;){
+    if( pA->pgno<pB->pgno ){
+      pTail->pDirty = pA;
+      pTail = pA;
+      pA = pA->pDirty;
+      if( pA==0 ){
+        pTail->pDirty = pB;
+        break;
+      }
+    }else{
+      pTail->pDirty = pB;
+      pTail = pB;
+      pB = pB->pDirty;
+      if( pB==0 ){
+        pTail->pDirty = pA;
+        break;
+      }
+    }
+  }
+  return result.pDirty;
+}
+
+/*
+** Sort the list of pages in ascending order by pgno.  Pages are
+** connected by pDirty pointers.  The pDirtyPrev pointers are
+** corrupted by this sort.
+**
+** Since there cannot be more than 2^31 distinct pages in a database,
+** there cannot be more than 31 buckets required by the merge sorter.
+** One extra bucket is added to catch overflow in case something
+** ever changes to make the previous sentence incorrect.
+*/
+#define N_SORT_BUCKET  32
+static PgHdr *pcacheSortDirtyList(PgHdr *pIn){
+  PgHdr *a[N_SORT_BUCKET], *p;
+  int i;
+  memset(a, 0, sizeof(a));
+  while( pIn ){
+    p = pIn;
+    pIn = p->pDirty;
+    p->pDirty = 0;
+    for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){
+      if( a[i]==0 ){
+        a[i] = p;
+        break;
+      }else{
+        p = pcacheMergeDirtyList(a[i], p);
+        a[i] = 0;
+      }
+    }
+    if( NEVER(i==N_SORT_BUCKET-1) ){
+      /* To get here, there need to be 2^(N_SORT_BUCKET) elements in
+      ** the input list.  But that is impossible.
+      */
+      a[i] = pcacheMergeDirtyList(a[i], p);
+    }
+  }
+  p = a[0];
+  for(i=1; i<N_SORT_BUCKET; i++){
+    if( a[i]==0 ) continue;
+    p = p ? pcacheMergeDirtyList(p, a[i]) : a[i];
+  }
+  return p;
+}
+
+/*
+** Return a list of all dirty pages in the cache, sorted by page number.
+*/
+PgHdr *sqlite3PcacheDirtyList(PCache *pCache){
+  PgHdr *p;
+  for(p=pCache->pDirty; p; p=p->pDirtyNext){
+    p->pDirty = p->pDirtyNext;
+  }
+  return pcacheSortDirtyList(pCache->pDirty);
+}
+
+/* 
+** Return the total number of references to all pages held by the cache.
+**
+** This is not the total number of pages referenced, but the sum of the
+** reference count for all pages.
+*/
+i64 sqlite3PcacheRefCount(PCache *pCache){
+  return pCache->nRefSum;
+}
+
+/*
+** Return the number of references to the page supplied as an argument.
+*/
+i64 sqlite3PcachePageRefcount(PgHdr *p){
+  return p->nRef;
+}
+
+/* 
+** Return the total number of pages in the cache.
+*/
+int sqlite3PcachePagecount(PCache *pCache){
+  assert( pCache->pCache!=0 );
+  return sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache);
+}
+
+#ifdef SQLITE_TEST
+/*
+** Get the suggested cache-size value.
+*/
+int sqlite3PcacheGetCachesize(PCache *pCache){
+  return numberOfCachePages(pCache);
+}
+#endif
+
+/*
+** Set the suggested cache-size value.
+*/
+void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
+  assert( pCache->pCache!=0 );
+  pCache->szCache = mxPage;
+  sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache,
+                                         numberOfCachePages(pCache));
+}
+
+/*
+** Set the suggested cache-spill value.  Make no changes if if the
+** argument is zero.  Return the effective cache-spill size, which will
+** be the larger of the szSpill and szCache.
+*/
+int sqlite3PcacheSetSpillsize(PCache *p, int mxPage){
+  int res;
+  assert( p->pCache!=0 );
+  if( mxPage ){
+    if( mxPage<0 ){
+      mxPage = (int)((-1024*(i64)mxPage)/(p->szPage+p->szExtra));
+    }
+    p->szSpill = mxPage;
+  }
+  res = numberOfCachePages(p);
+  if( res<p->szSpill ) res = p->szSpill; 
+  return res;
+}
+
+/*
+** Free up as much memory as possible from the page cache.
+*/
+void sqlite3PcacheShrink(PCache *pCache){
+  assert( pCache->pCache!=0 );
+  sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache);
+}
+
+/*
+** Return the size of the header added by this middleware layer
+** in the page-cache hierarchy.
+*/
+int sqlite3HeaderSizePcache(void){ return ROUND8(sizeof(PgHdr)); }
+
+/*
+** Return the number of dirty pages currently in the cache, as a percentage
+** of the configured cache size.
+*/
+int sqlite3PCachePercentDirty(PCache *pCache){
+  PgHdr *pDirty;
+  int nDirty = 0;
+  int nCache = numberOfCachePages(pCache);
+  for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext) nDirty++;
+  return nCache ? (int)(((i64)nDirty * 100) / nCache) : 0;
+}
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+/* 
+** Return true if there are one or more dirty pages in the cache. Else false.
+*/
+int sqlite3PCacheIsDirty(PCache *pCache){
+  return (pCache->pDirty!=0);
+}
+#endif
+
+#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
+/*
+** For all dirty pages currently in the cache, invoke the specified
+** callback. This is only used if the SQLITE_CHECK_PAGES macro is
+** defined.
+*/
+void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){
+  PgHdr *pDirty;
+  for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){
+    xIter(pDirty);
+  }
+}
+#endif
diff --git a/src/pcache.h b/src/pcache.h
new file mode 100644
index 0000000..f945dab
--- /dev/null
+++ b/src/pcache.h
@@ -0,0 +1,190 @@
+/*
+** 2008 August 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the sqlite page cache
+** subsystem. 
+*/
+
+#ifndef _PCACHE_H_
+
+typedef struct PgHdr PgHdr;
+typedef struct PCache PCache;
+
+/*
+** Every page in the cache is controlled by an instance of the following
+** structure.
+*/
+struct PgHdr {
+  sqlite3_pcache_page *pPage;    /* Pcache object page handle */
+  void *pData;                   /* Page data */
+  void *pExtra;                  /* Extra content */
+  PCache *pCache;                /* PRIVATE: Cache that owns this page */
+  PgHdr *pDirty;                 /* Transient list of dirty sorted by pgno */
+  Pager *pPager;                 /* The pager this page is part of */
+  Pgno pgno;                     /* Page number for this page */
+#ifdef SQLITE_CHECK_PAGES
+  u32 pageHash;                  /* Hash of page content */
+#endif
+  u16 flags;                     /* PGHDR flags defined below */
+
+  /**********************************************************************
+  ** Elements above, except pCache, are public.  All that follow are 
+  ** private to pcache.c and should not be accessed by other modules.
+  ** pCache is grouped with the public elements for efficiency.
+  */
+  i64 nRef;                      /* Number of users of this page */
+  PgHdr *pDirtyNext;             /* Next element in list of dirty pages */
+  PgHdr *pDirtyPrev;             /* Previous element in list of dirty pages */
+                          /* NB: pDirtyNext and pDirtyPrev are undefined if the
+                          ** PgHdr object is not dirty */
+};
+
+/* Bit values for PgHdr.flags */
+#define PGHDR_CLEAN           0x001  /* Page not on the PCache.pDirty list */
+#define PGHDR_DIRTY           0x002  /* Page is on the PCache.pDirty list */
+#define PGHDR_WRITEABLE       0x004  /* Journaled and ready to modify */
+#define PGHDR_NEED_SYNC       0x008  /* Fsync the rollback journal before
+                                     ** writing this page to the database */
+#define PGHDR_DONT_WRITE      0x010  /* Do not write content to disk */
+#define PGHDR_MMAP            0x020  /* This is an mmap page object */
+
+#define PGHDR_WAL_APPEND      0x040  /* Appended to wal file */
+
+/* Initialize and shutdown the page cache subsystem */
+int sqlite3PcacheInitialize(void);
+void sqlite3PcacheShutdown(void);
+
+/* Page cache buffer management:
+** These routines implement SQLITE_CONFIG_PAGECACHE.
+*/
+void sqlite3PCacheBufferSetup(void *, int sz, int n);
+
+/* Create a new pager cache.
+** Under memory stress, invoke xStress to try to make pages clean.
+** Only clean and unpinned pages can be reclaimed.
+*/
+int sqlite3PcacheOpen(
+  int szPage,                    /* Size of every page */
+  int szExtra,                   /* Extra space associated with each page */
+  int bPurgeable,                /* True if pages are on backing store */
+  int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */
+  void *pStress,                 /* Argument to xStress */
+  PCache *pToInit                /* Preallocated space for the PCache */
+);
+
+/* Modify the page-size after the cache has been created. */
+int sqlite3PcacheSetPageSize(PCache *, int);
+
+/* Return the size in bytes of a PCache object.  Used to preallocate
+** storage space.
+*/
+int sqlite3PcacheSize(void);
+
+/* One release per successful fetch.  Page is pinned until released.
+** Reference counted. 
+*/
+sqlite3_pcache_page *sqlite3PcacheFetch(PCache*, Pgno, int createFlag);
+int sqlite3PcacheFetchStress(PCache*, Pgno, sqlite3_pcache_page**);
+PgHdr *sqlite3PcacheFetchFinish(PCache*, Pgno, sqlite3_pcache_page *pPage);
+void sqlite3PcacheRelease(PgHdr*);
+
+void sqlite3PcacheDrop(PgHdr*);         /* Remove page from cache */
+void sqlite3PcacheMakeDirty(PgHdr*);    /* Make sure page is marked dirty */
+void sqlite3PcacheMakeClean(PgHdr*);    /* Mark a single page as clean */
+void sqlite3PcacheCleanAll(PCache*);    /* Mark all dirty list pages as clean */
+void sqlite3PcacheClearWritable(PCache*);
+
+/* Change a page number.  Used by incr-vacuum. */
+void sqlite3PcacheMove(PgHdr*, Pgno);
+
+/* Remove all pages with pgno>x.  Reset the cache if x==0 */
+void sqlite3PcacheTruncate(PCache*, Pgno x);
+
+/* Get a list of all dirty pages in the cache, sorted by page number */
+PgHdr *sqlite3PcacheDirtyList(PCache*);
+
+/* Reset and close the cache object */
+void sqlite3PcacheClose(PCache*);
+
+/* Clear flags from pages of the page cache */
+void sqlite3PcacheClearSyncFlags(PCache *);
+
+/* Discard the contents of the cache */
+void sqlite3PcacheClear(PCache*);
+
+/* Return the total number of outstanding page references */
+i64 sqlite3PcacheRefCount(PCache*);
+
+/* Increment the reference count of an existing page */
+void sqlite3PcacheRef(PgHdr*);
+
+i64 sqlite3PcachePageRefcount(PgHdr*);
+
+/* Return the total number of pages stored in the cache */
+int sqlite3PcachePagecount(PCache*);
+
+#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
+/* Iterate through all dirty pages currently stored in the cache. This
+** interface is only available if SQLITE_CHECK_PAGES is defined when the 
+** library is built.
+*/
+void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *));
+#endif
+
+#if defined(SQLITE_DEBUG)
+/* Check invariants on a PgHdr object */
+int sqlite3PcachePageSanity(PgHdr*);
+#endif
+
+/* Set and get the suggested cache-size for the specified pager-cache.
+**
+** If no global maximum is configured, then the system attempts to limit
+** the total number of pages cached by purgeable pager-caches to the sum
+** of the suggested cache-sizes.
+*/
+void sqlite3PcacheSetCachesize(PCache *, int);
+#ifdef SQLITE_TEST
+int sqlite3PcacheGetCachesize(PCache *);
+#endif
+
+/* Set or get the suggested spill-size for the specified pager-cache.
+**
+** The spill-size is the minimum number of pages in cache before the cache
+** will attempt to spill dirty pages by calling xStress.
+*/
+int sqlite3PcacheSetSpillsize(PCache *, int);
+
+/* Free up as much memory as possible from the page cache */
+void sqlite3PcacheShrink(PCache*);
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+/* Try to return memory used by the pcache module to the main memory heap */
+int sqlite3PcacheReleaseMemory(int);
+#endif
+
+#ifdef SQLITE_TEST
+void sqlite3PcacheStats(int*,int*,int*,int*);
+#endif
+
+void sqlite3PCacheSetDefault(void);
+
+/* Return the header size */
+int sqlite3HeaderSizePcache(void);
+int sqlite3HeaderSizePcache1(void);
+
+/* Number of dirty pages as a percentage of the configured cache size */
+int sqlite3PCachePercentDirty(PCache*);
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+int sqlite3PCacheIsDirty(PCache *pCache);
+#endif
+
+#endif /* _PCACHE_H_ */
diff --git a/src/pcache1.c b/src/pcache1.c
new file mode 100644
index 0000000..1591f01
--- /dev/null
+++ b/src/pcache1.c
@@ -0,0 +1,1280 @@
+/*
+** 2008 November 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements the default page cache implementation (the
+** sqlite3_pcache interface). It also contains part of the implementation
+** of the SQLITE_CONFIG_PAGECACHE and sqlite3_release_memory() features.
+** If the default page cache implementation is overridden, then neither of
+** these two features are available.
+**
+** A Page cache line looks like this:
+**
+**  -------------------------------------------------------------
+**  |  database page content   |  PgHdr1  |  MemPage  |  PgHdr  |
+**  -------------------------------------------------------------
+**
+** The database page content is up front (so that buffer overreads tend to
+** flow harmlessly into the PgHdr1, MemPage, and PgHdr extensions).   MemPage
+** is the extension added by the btree.c module containing information such
+** as the database page number and how that database page is used.  PgHdr
+** is added by the pcache.c layer and contains information used to keep track
+** of which pages are "dirty".  PgHdr1 is an extension added by this
+** module (pcache1.c).  The PgHdr1 header is a subclass of sqlite3_pcache_page.
+** PgHdr1 contains information needed to look up a page by its page number.
+** The superclass sqlite3_pcache_page.pBuf points to the start of the
+** database page content and sqlite3_pcache_page.pExtra points to PgHdr.
+**
+** The size of the extension (MemPage+PgHdr+PgHdr1) can be determined at
+** runtime using sqlite3_config(SQLITE_CONFIG_PCACHE_HDRSZ, &size).  The
+** sizes of the extensions sum to 272 bytes on x64 for 3.8.10, but this
+** size can vary according to architecture, compile-time options, and
+** SQLite library version number.
+**
+** Historical note:  It used to be that if the SQLITE_PCACHE_SEPARATE_HEADER
+** was defined, then the page content would be held in a separate memory
+** allocation from the PgHdr1.  This was intended to avoid clownshoe memory
+** allocations.  However, the btree layer needs a small (16-byte) overrun
+** area after the page content buffer.  The header serves as that overrun
+** area.  Therefore SQLITE_PCACHE_SEPARATE_HEADER was discontinued to avoid
+** any possibility of a memory error.
+**
+** This module tracks pointers to PgHdr1 objects.  Only pcache.c communicates
+** with this module.  Information is passed back and forth as PgHdr1 pointers.
+**
+** The pcache.c and pager.c modules deal pointers to PgHdr objects.
+** The btree.c module deals with pointers to MemPage objects.
+**
+** SOURCE OF PAGE CACHE MEMORY:
+**
+** Memory for a page might come from any of three sources:
+**
+**    (1)  The general-purpose memory allocator - sqlite3Malloc()
+**    (2)  Global page-cache memory provided using sqlite3_config() with
+**         SQLITE_CONFIG_PAGECACHE.
+**    (3)  PCache-local bulk allocation.
+**
+** The third case is a chunk of heap memory (defaulting to 100 pages worth)
+** that is allocated when the page cache is created.  The size of the local
+** bulk allocation can be adjusted using
+**
+**     sqlite3_config(SQLITE_CONFIG_PAGECACHE, (void*)0, 0, N).
+**
+** If N is positive, then N pages worth of memory are allocated using a single
+** sqlite3Malloc() call and that memory is used for the first N pages allocated.
+** Or if N is negative, then -1024*N bytes of memory are allocated and used
+** for as many pages as can be accommodated.
+**
+** Only one of (2) or (3) can be used.  Once the memory available to (2) or
+** (3) is exhausted, subsequent allocations fail over to the general-purpose
+** memory allocator (1).
+**
+** Earlier versions of SQLite used only methods (1) and (2).  But experiments
+** show that method (3) with N==100 provides about a 5% performance boost for
+** common workloads.
+*/
+#include "sqliteInt.h"
+
+typedef struct PCache1 PCache1;
+typedef struct PgHdr1 PgHdr1;
+typedef struct PgFreeslot PgFreeslot;
+typedef struct PGroup PGroup;
+
+/*
+** Each cache entry is represented by an instance of the following
+** structure. A buffer of PgHdr1.pCache->szPage bytes is allocated
+** directly before this structure and is used to cache the page content.
+**
+** When reading a corrupt database file, it is possible that SQLite might
+** read a few bytes (no more than 16 bytes) past the end of the page buffer.
+** It will only read past the end of the page buffer, never write.  This
+** object is positioned immediately after the page buffer to serve as an
+** overrun area, so that overreads are harmless.
+**
+** Variables isBulkLocal and isAnchor were once type "u8". That works,
+** but causes a 2-byte gap in the structure for most architectures (since
+** pointers must be either 4 or 8-byte aligned). As this structure is located
+** in memory directly after the associated page data, if the database is
+** corrupt, code at the b-tree layer may overread the page buffer and
+** read part of this structure before the corruption is detected. This
+** can cause a valgrind error if the uninitialized gap is accessed. Using u16
+** ensures there is no such gap, and therefore no bytes of uninitialized
+** memory in the structure.
+**
+** The pLruNext and pLruPrev pointers form a double-linked circular list
+** of all pages that are unpinned.  The PGroup.lru element (which should be
+** the only element on the list with PgHdr1.isAnchor set to 1) forms the
+** beginning and the end of the list.
+*/
+struct PgHdr1 {
+  sqlite3_pcache_page page; /* Base class. Must be first. pBuf & pExtra */
+  unsigned int iKey;        /* Key value (page number) */
+  u16 isBulkLocal;          /* This page from bulk local storage */
+  u16 isAnchor;             /* This is the PGroup.lru element */
+  PgHdr1 *pNext;            /* Next in hash table chain */
+  PCache1 *pCache;          /* Cache that currently owns this page */
+  PgHdr1 *pLruNext;         /* Next in circular LRU list of unpinned pages */
+  PgHdr1 *pLruPrev;         /* Previous in LRU list of unpinned pages */
+                            /* NB: pLruPrev is only valid if pLruNext!=0 */
+};
+
+/*
+** A page is pinned if it is not on the LRU list.  To be "pinned" means
+** that the page is in active use and must not be deallocated.
+*/
+#define PAGE_IS_PINNED(p)    ((p)->pLruNext==0)
+#define PAGE_IS_UNPINNED(p)  ((p)->pLruNext!=0)
+
+/* Each page cache (or PCache) belongs to a PGroup.  A PGroup is a set
+** of one or more PCaches that are able to recycle each other's unpinned
+** pages when they are under memory pressure.  A PGroup is an instance of
+** the following object.
+**
+** This page cache implementation works in one of two modes:
+**
+**   (1)  Every PCache is the sole member of its own PGroup.  There is
+**        one PGroup per PCache.
+**
+**   (2)  There is a single global PGroup that all PCaches are a member
+**        of.
+**
+** Mode 1 uses more memory (since PCache instances are not able to rob
+** unused pages from other PCaches) but it also operates without a mutex,
+** and is therefore often faster.  Mode 2 requires a mutex in order to be
+** threadsafe, but recycles pages more efficiently.
+**
+** For mode (1), PGroup.mutex is NULL.  For mode (2) there is only a single
+** PGroup which is the pcache1.grp global variable and its mutex is
+** SQLITE_MUTEX_STATIC_LRU.
+*/
+struct PGroup {
+  sqlite3_mutex *mutex;          /* MUTEX_STATIC_LRU or NULL */
+  unsigned int nMaxPage;         /* Sum of nMax for purgeable caches */
+  unsigned int nMinPage;         /* Sum of nMin for purgeable caches */
+  unsigned int mxPinned;         /* nMaxpage + 10 - nMinPage */
+  unsigned int nPurgeable;       /* Number of purgeable pages allocated */
+  PgHdr1 lru;                    /* The beginning and end of the LRU list */
+};
+
+/* Each page cache is an instance of the following object.  Every
+** open database file (including each in-memory database and each
+** temporary or transient database) has a single page cache which
+** is an instance of this object.
+**
+** Pointers to structures of this type are cast and returned as
+** opaque sqlite3_pcache* handles.
+*/
+struct PCache1 {
+  /* Cache configuration parameters. Page size (szPage) and the purgeable
+  ** flag (bPurgeable) and the pnPurgeable pointer are all set when the
+  ** cache is created and are never changed thereafter. nMax may be
+  ** modified at any time by a call to the pcache1Cachesize() method.
+  ** The PGroup mutex must be held when accessing nMax.
+  */
+  PGroup *pGroup;                     /* PGroup this cache belongs to */
+  unsigned int *pnPurgeable;          /* Pointer to pGroup->nPurgeable */
+  int szPage;                         /* Size of database content section */
+  int szExtra;                        /* sizeof(MemPage)+sizeof(PgHdr) */
+  int szAlloc;                        /* Total size of one pcache line */
+  int bPurgeable;                     /* True if cache is purgeable */
+  unsigned int nMin;                  /* Minimum number of pages reserved */
+  unsigned int nMax;                  /* Configured "cache_size" value */
+  unsigned int n90pct;                /* nMax*9/10 */
+  unsigned int iMaxKey;               /* Largest key seen since xTruncate() */
+  unsigned int nPurgeableDummy;       /* pnPurgeable points here when not used*/
+
+  /* Hash table of all pages. The following variables may only be accessed
+  ** when the accessor is holding the PGroup mutex.
+  */
+  unsigned int nRecyclable;           /* Number of pages in the LRU list */
+  unsigned int nPage;                 /* Total number of pages in apHash */
+  unsigned int nHash;                 /* Number of slots in apHash[] */
+  PgHdr1 **apHash;                    /* Hash table for fast lookup by key */
+  PgHdr1 *pFree;                      /* List of unused pcache-local pages */
+  void *pBulk;                        /* Bulk memory used by pcache-local */
+};
+
+/*
+** Free slots in the allocator used to divide up the global page cache
+** buffer provided using the SQLITE_CONFIG_PAGECACHE mechanism.
+*/
+struct PgFreeslot {
+  PgFreeslot *pNext;  /* Next free slot */
+};
+
+/*
+** Global data used by this cache.
+*/
+static SQLITE_WSD struct PCacheGlobal {
+  PGroup grp;                    /* The global PGroup for mode (2) */
+
+  /* Variables related to SQLITE_CONFIG_PAGECACHE settings.  The
+  ** szSlot, nSlot, pStart, pEnd, nReserve, and isInit values are all
+  ** fixed at sqlite3_initialize() time and do not require mutex protection.
+  ** The nFreeSlot and pFree values do require mutex protection.
+  */
+  int isInit;                    /* True if initialized */
+  int separateCache;             /* Use a new PGroup for each PCache */
+  int nInitPage;                 /* Initial bulk allocation size */
+  int szSlot;                    /* Size of each free slot */
+  int nSlot;                     /* The number of pcache slots */
+  int nReserve;                  /* Try to keep nFreeSlot above this */
+  void *pStart, *pEnd;           /* Bounds of global page cache memory */
+  /* Above requires no mutex.  Use mutex below for variable that follow. */
+  sqlite3_mutex *mutex;          /* Mutex for accessing the following: */
+  PgFreeslot *pFree;             /* Free page blocks */
+  int nFreeSlot;                 /* Number of unused pcache slots */
+  /* The following value requires a mutex to change.  We skip the mutex on
+  ** reading because (1) most platforms read a 32-bit integer atomically and
+  ** (2) even if an incorrect value is read, no great harm is done since this
+  ** is really just an optimization. */
+  int bUnderPressure;            /* True if low on PAGECACHE memory */
+} pcache1_g;
+
+/*
+** All code in this file should access the global structure above via the
+** alias "pcache1". This ensures that the WSD emulation is used when
+** compiling for systems that do not support real WSD.
+*/
+#define pcache1 (GLOBAL(struct PCacheGlobal, pcache1_g))
+
+/*
+** Macros to enter and leave the PCache LRU mutex.
+*/
+#if !defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || SQLITE_THREADSAFE==0
+# define pcache1EnterMutex(X)  assert((X)->mutex==0)
+# define pcache1LeaveMutex(X)  assert((X)->mutex==0)
+# define PCACHE1_MIGHT_USE_GROUP_MUTEX 0
+#else
+# define pcache1EnterMutex(X) sqlite3_mutex_enter((X)->mutex)
+# define pcache1LeaveMutex(X) sqlite3_mutex_leave((X)->mutex)
+# define PCACHE1_MIGHT_USE_GROUP_MUTEX 1
+#endif
+
+/******************************************************************************/
+/******** Page Allocation/SQLITE_CONFIG_PCACHE Related Functions **************/
+
+
+/*
+** This function is called during initialization if a static buffer is
+** supplied to use for the page-cache by passing the SQLITE_CONFIG_PAGECACHE
+** verb to sqlite3_config(). Parameter pBuf points to an allocation large
+** enough to contain 'n' buffers of 'sz' bytes each.
+**
+** This routine is called from sqlite3_initialize() and so it is guaranteed
+** to be serialized already.  There is no need for further mutexing.
+*/
+void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
+  if( pcache1.isInit ){
+    PgFreeslot *p;
+    if( pBuf==0 ) sz = n = 0;
+    if( n==0 ) sz = 0;
+    sz = ROUNDDOWN8(sz);
+    pcache1.szSlot = sz;
+    pcache1.nSlot = pcache1.nFreeSlot = n;
+    pcache1.nReserve = n>90 ? 10 : (n/10 + 1);
+    pcache1.pStart = pBuf;
+    pcache1.pFree = 0;
+    pcache1.bUnderPressure = 0;
+    while( n-- ){
+      p = (PgFreeslot*)pBuf;
+      p->pNext = pcache1.pFree;
+      pcache1.pFree = p;
+      pBuf = (void*)&((char*)pBuf)[sz];
+    }
+    pcache1.pEnd = pBuf;
+  }
+}
+
+/*
+** Try to initialize the pCache->pFree and pCache->pBulk fields.  Return
+** true if pCache->pFree ends up containing one or more free pages.
+*/
+static int pcache1InitBulk(PCache1 *pCache){
+  i64 szBulk;
+  char *zBulk;
+  if( pcache1.nInitPage==0 ) return 0;
+  /* Do not bother with a bulk allocation if the cache size very small */
+  if( pCache->nMax<3 ) return 0;
+  sqlite3BeginBenignMalloc();
+  if( pcache1.nInitPage>0 ){
+    szBulk = pCache->szAlloc * (i64)pcache1.nInitPage;
+  }else{
+    szBulk = -1024 * (i64)pcache1.nInitPage;
+  }
+  if( szBulk > pCache->szAlloc*(i64)pCache->nMax ){
+    szBulk = pCache->szAlloc*(i64)pCache->nMax;
+  }
+  zBulk = pCache->pBulk = sqlite3Malloc( szBulk );
+  sqlite3EndBenignMalloc();
+  if( zBulk ){
+    int nBulk = sqlite3MallocSize(zBulk)/pCache->szAlloc;
+    do{
+      PgHdr1 *pX = (PgHdr1*)&zBulk[pCache->szPage];
+      pX->page.pBuf = zBulk;
+      pX->page.pExtra = &pX[1];
+      pX->isBulkLocal = 1;
+      pX->isAnchor = 0;
+      pX->pNext = pCache->pFree;
+      pX->pLruPrev = 0;           /* Initializing this saves a valgrind error */
+      pCache->pFree = pX;
+      zBulk += pCache->szAlloc;
+    }while( --nBulk );
+  }
+  return pCache->pFree!=0;
+}
+
+/*
+** Malloc function used within this file to allocate space from the buffer
+** configured using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no
+** such buffer exists or there is no space left in it, this function falls
+** back to sqlite3Malloc().
+**
+** Multiple threads can run this routine at the same time.  Global variables
+** in pcache1 need to be protected via mutex.
+*/
+static void *pcache1Alloc(int nByte){
+  void *p = 0;
+  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
+  if( nByte<=pcache1.szSlot ){
+    sqlite3_mutex_enter(pcache1.mutex);
+    p = (PgHdr1 *)pcache1.pFree;
+    if( p ){
+      pcache1.pFree = pcache1.pFree->pNext;
+      pcache1.nFreeSlot--;
+      pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
+      assert( pcache1.nFreeSlot>=0 );
+      sqlite3StatusHighwater(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
+      sqlite3StatusUp(SQLITE_STATUS_PAGECACHE_USED, 1);
+    }
+    sqlite3_mutex_leave(pcache1.mutex);
+  }
+  if( p==0 ){
+    /* Memory is not available in the SQLITE_CONFIG_PAGECACHE pool.  Get
+    ** it from sqlite3Malloc instead.
+    */
+    p = sqlite3Malloc(nByte);
+#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
+    if( p ){
+      int sz = sqlite3MallocSize(p);
+      sqlite3_mutex_enter(pcache1.mutex);
+      sqlite3StatusHighwater(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
+      sqlite3StatusUp(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
+      sqlite3_mutex_leave(pcache1.mutex);
+    }
+#endif
+    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
+  }
+  return p;
+}
+
+/*
+** Free an allocated buffer obtained from pcache1Alloc().
+*/
+static void pcache1Free(void *p){
+  if( p==0 ) return;
+  if( SQLITE_WITHIN(p, pcache1.pStart, pcache1.pEnd) ){
+    PgFreeslot *pSlot;
+    sqlite3_mutex_enter(pcache1.mutex);
+    sqlite3StatusDown(SQLITE_STATUS_PAGECACHE_USED, 1);
+    pSlot = (PgFreeslot*)p;
+    pSlot->pNext = pcache1.pFree;
+    pcache1.pFree = pSlot;
+    pcache1.nFreeSlot++;
+    pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
+    assert( pcache1.nFreeSlot<=pcache1.nSlot );
+    sqlite3_mutex_leave(pcache1.mutex);
+  }else{
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
+    {
+      int nFreed = 0;
+      nFreed = sqlite3MallocSize(p);
+      sqlite3_mutex_enter(pcache1.mutex);
+      sqlite3StatusDown(SQLITE_STATUS_PAGECACHE_OVERFLOW, nFreed);
+      sqlite3_mutex_leave(pcache1.mutex);
+    }
+#endif
+    sqlite3_free(p);
+  }
+}
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+/*
+** Return the size of a pcache allocation
+*/
+static int pcache1MemSize(void *p){
+  if( p>=pcache1.pStart && p<pcache1.pEnd ){
+    return pcache1.szSlot;
+  }else{
+    int iSize;
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+    iSize = sqlite3MallocSize(p);
+    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
+    return iSize;
+  }
+}
+#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
+
+/*
+** Allocate a new page object initially associated with cache pCache.
+*/
+static PgHdr1 *pcache1AllocPage(PCache1 *pCache, int benignMalloc){
+  PgHdr1 *p = 0;
+  void *pPg;
+
+  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
+  if( pCache->pFree || (pCache->nPage==0 && pcache1InitBulk(pCache)) ){
+    assert( pCache->pFree!=0 );
+    p = pCache->pFree;
+    pCache->pFree = p->pNext;
+    p->pNext = 0;
+  }else{
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+    /* The group mutex must be released before pcache1Alloc() is called. This
+    ** is because it might call sqlite3_release_memory(), which assumes that
+    ** this mutex is not held. */
+    assert( pcache1.separateCache==0 );
+    assert( pCache->pGroup==&pcache1.grp );
+    pcache1LeaveMutex(pCache->pGroup);
+#endif
+    if( benignMalloc ){ sqlite3BeginBenignMalloc(); }
+    pPg = pcache1Alloc(pCache->szAlloc);
+    if( benignMalloc ){ sqlite3EndBenignMalloc(); }
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+    pcache1EnterMutex(pCache->pGroup);
+#endif
+    if( pPg==0 ) return 0;
+    p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage];
+    p->page.pBuf = pPg;
+    p->page.pExtra = &p[1];
+    p->isBulkLocal = 0;
+    p->isAnchor = 0;
+    p->pLruPrev = 0;           /* Initializing this saves a valgrind error */
+  }
+  (*pCache->pnPurgeable)++;
+  return p;
+}
+
+/*
+** Free a page object allocated by pcache1AllocPage().
+*/
+static void pcache1FreePage(PgHdr1 *p){
+  PCache1 *pCache;
+  assert( p!=0 );
+  pCache = p->pCache;
+  assert( sqlite3_mutex_held(p->pCache->pGroup->mutex) );
+  if( p->isBulkLocal ){
+    p->pNext = pCache->pFree;
+    pCache->pFree = p;
+  }else{
+    pcache1Free(p->page.pBuf);
+  }
+  (*pCache->pnPurgeable)--;
+}
+
+/*
+** Malloc function used by SQLite to obtain space from the buffer configured
+** using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no such buffer
+** exists, this function falls back to sqlite3Malloc().
+*/
+void *sqlite3PageMalloc(int sz){
+  assert( sz<=65536+8 ); /* These allocations are never very large */
+  return pcache1Alloc(sz);
+}
+
+/*
+** Free an allocated buffer obtained from sqlite3PageMalloc().
+*/
+void sqlite3PageFree(void *p){
+  pcache1Free(p);
+}
+
+
+/*
+** Return true if it desirable to avoid allocating a new page cache
+** entry.
+**
+** If memory was allocated specifically to the page cache using
+** SQLITE_CONFIG_PAGECACHE but that memory has all been used, then
+** it is desirable to avoid allocating a new page cache entry because
+** presumably SQLITE_CONFIG_PAGECACHE was suppose to be sufficient
+** for all page cache needs and we should not need to spill the
+** allocation onto the heap.
+**
+** Or, the heap is used for all page cache memory but the heap is
+** under memory pressure, then again it is desirable to avoid
+** allocating a new page cache entry in order to avoid stressing
+** the heap even further.
+*/
+static int pcache1UnderMemoryPressure(PCache1 *pCache){
+  if( pcache1.nSlot && (pCache->szPage+pCache->szExtra)<=pcache1.szSlot ){
+    return pcache1.bUnderPressure;
+  }else{
+    return sqlite3HeapNearlyFull();
+  }
+}
+
+/******************************************************************************/
+/******** General Implementation Functions ************************************/
+
+/*
+** This function is used to resize the hash table used by the cache passed
+** as the first argument.
+**
+** The PCache mutex must be held when this function is called.
+*/
+static void pcache1ResizeHash(PCache1 *p){
+  PgHdr1 **apNew;
+  unsigned int nNew;
+  unsigned int i;
+
+  assert( sqlite3_mutex_held(p->pGroup->mutex) );
+
+  nNew = p->nHash*2;
+  if( nNew<256 ){
+    nNew = 256;
+  }
+
+  pcache1LeaveMutex(p->pGroup);
+  if( p->nHash ){ sqlite3BeginBenignMalloc(); }
+  apNew = (PgHdr1 **)sqlite3MallocZero(sizeof(PgHdr1 *)*nNew);
+  if( p->nHash ){ sqlite3EndBenignMalloc(); }
+  pcache1EnterMutex(p->pGroup);
+  if( apNew ){
+    for(i=0; i<p->nHash; i++){
+      PgHdr1 *pPage;
+      PgHdr1 *pNext = p->apHash[i];
+      while( (pPage = pNext)!=0 ){
+        unsigned int h = pPage->iKey % nNew;
+        pNext = pPage->pNext;
+        pPage->pNext = apNew[h];
+        apNew[h] = pPage;
+      }
+    }
+    sqlite3_free(p->apHash);
+    p->apHash = apNew;
+    p->nHash = nNew;
+  }
+}
+
+/*
+** This function is used internally to remove the page pPage from the
+** PGroup LRU list, if is part of it. If pPage is not part of the PGroup
+** LRU list, then this function is a no-op.
+**
+** The PGroup mutex must be held when this function is called.
+*/
+static PgHdr1 *pcache1PinPage(PgHdr1 *pPage){
+  assert( pPage!=0 );
+  assert( PAGE_IS_UNPINNED(pPage) );
+  assert( pPage->pLruNext );
+  assert( pPage->pLruPrev );
+  assert( sqlite3_mutex_held(pPage->pCache->pGroup->mutex) );
+  pPage->pLruPrev->pLruNext = pPage->pLruNext;
+  pPage->pLruNext->pLruPrev = pPage->pLruPrev;
+  pPage->pLruNext = 0;
+  /* pPage->pLruPrev = 0;
+  ** No need to clear pLruPrev as it is never accessed if pLruNext is 0 */
+  assert( pPage->isAnchor==0 );
+  assert( pPage->pCache->pGroup->lru.isAnchor==1 );
+  pPage->pCache->nRecyclable--;
+  return pPage;
+}
+
+
+/*
+** Remove the page supplied as an argument from the hash table
+** (PCache1.apHash structure) that it is currently stored in.
+** Also free the page if freePage is true.
+**
+** The PGroup mutex must be held when this function is called.
+*/
+static void pcache1RemoveFromHash(PgHdr1 *pPage, int freeFlag){
+  unsigned int h;
+  PCache1 *pCache = pPage->pCache;
+  PgHdr1 **pp;
+
+  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
+  h = pPage->iKey % pCache->nHash;
+  for(pp=&pCache->apHash[h]; (*pp)!=pPage; pp=&(*pp)->pNext);
+  *pp = (*pp)->pNext;
+
+  pCache->nPage--;
+  if( freeFlag ) pcache1FreePage(pPage);
+}
+
+/*
+** If there are currently more than nMaxPage pages allocated, try
+** to recycle pages to reduce the number allocated to nMaxPage.
+*/
+static void pcache1EnforceMaxPage(PCache1 *pCache){
+  PGroup *pGroup = pCache->pGroup;
+  PgHdr1 *p;
+  assert( sqlite3_mutex_held(pGroup->mutex) );
+  while( pGroup->nPurgeable>pGroup->nMaxPage
+      && (p=pGroup->lru.pLruPrev)->isAnchor==0
+  ){
+    assert( p->pCache->pGroup==pGroup );
+    assert( PAGE_IS_UNPINNED(p) );
+    pcache1PinPage(p);
+    pcache1RemoveFromHash(p, 1);
+  }
+  if( pCache->nPage==0 && pCache->pBulk ){
+    sqlite3_free(pCache->pBulk);
+    pCache->pBulk = pCache->pFree = 0;
+  }
+}
+
+/*
+** Discard all pages from cache pCache with a page number (key value)
+** greater than or equal to iLimit. Any pinned pages that meet this
+** criteria are unpinned before they are discarded.
+**
+** The PCache mutex must be held when this function is called.
+*/
+static void pcache1TruncateUnsafe(
+  PCache1 *pCache,             /* The cache to truncate */
+  unsigned int iLimit          /* Drop pages with this pgno or larger */
+){
+  TESTONLY( int nPage = 0; )  /* To assert pCache->nPage is correct */
+  unsigned int h, iStop;
+  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
+  assert( pCache->iMaxKey >= iLimit );
+  assert( pCache->nHash > 0 );
+  if( pCache->iMaxKey - iLimit < pCache->nHash ){
+    /* If we are just shaving the last few pages off the end of the
+    ** cache, then there is no point in scanning the entire hash table.
+    ** Only scan those hash slots that might contain pages that need to
+    ** be removed. */
+    h = iLimit % pCache->nHash;
+    iStop = pCache->iMaxKey % pCache->nHash;
+    TESTONLY( nPage = -10; )  /* Disable the pCache->nPage validity check */
+  }else{
+    /* This is the general case where many pages are being removed.
+    ** It is necessary to scan the entire hash table */
+    h = pCache->nHash/2;
+    iStop = h - 1;
+  }
+  for(;;){
+    PgHdr1 **pp;
+    PgHdr1 *pPage;
+    assert( h<pCache->nHash );
+    pp = &pCache->apHash[h];
+    while( (pPage = *pp)!=0 ){
+      if( pPage->iKey>=iLimit ){
+        pCache->nPage--;
+        *pp = pPage->pNext;
+        if( PAGE_IS_UNPINNED(pPage) ) pcache1PinPage(pPage);
+        pcache1FreePage(pPage);
+      }else{
+        pp = &pPage->pNext;
+        TESTONLY( if( nPage>=0 ) nPage++; )
+      }
+    }
+    if( h==iStop ) break;
+    h = (h+1) % pCache->nHash;
+  }
+  assert( nPage<0 || pCache->nPage==(unsigned)nPage );
+}
+
+/******************************************************************************/
+/******** sqlite3_pcache Methods **********************************************/
+
+/*
+** Implementation of the sqlite3_pcache.xInit method.
+*/
+static int pcache1Init(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  assert( pcache1.isInit==0 );
+  memset(&pcache1, 0, sizeof(pcache1));
+
+
+  /*
+  ** The pcache1.separateCache variable is true if each PCache has its own
+  ** private PGroup (mode-1).  pcache1.separateCache is false if the single
+  ** PGroup in pcache1.grp is used for all page caches (mode-2).
+  **
+  **   *  Always use a unified cache (mode-2) if ENABLE_MEMORY_MANAGEMENT
+  **
+  **   *  Use a unified cache in single-threaded applications that have
+  **      configured a start-time buffer for use as page-cache memory using
+  **      sqlite3_config(SQLITE_CONFIG_PAGECACHE, pBuf, sz, N) with non-NULL
+  **      pBuf argument.
+  **
+  **   *  Otherwise use separate caches (mode-1)
+  */
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT)
+  pcache1.separateCache = 0;
+#elif SQLITE_THREADSAFE
+  pcache1.separateCache = sqlite3GlobalConfig.pPage==0
+                          || sqlite3GlobalConfig.bCoreMutex>0;
+#else
+  pcache1.separateCache = sqlite3GlobalConfig.pPage==0;
+#endif
+
+#if SQLITE_THREADSAFE
+  if( sqlite3GlobalConfig.bCoreMutex ){
+    pcache1.grp.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU);
+    pcache1.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PMEM);
+  }
+#endif
+  if( pcache1.separateCache
+   && sqlite3GlobalConfig.nPage!=0
+   && sqlite3GlobalConfig.pPage==0
+  ){
+    pcache1.nInitPage = sqlite3GlobalConfig.nPage;
+  }else{
+    pcache1.nInitPage = 0;
+  }
+  pcache1.grp.mxPinned = 10;
+  pcache1.isInit = 1;
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of the sqlite3_pcache.xShutdown method.
+** Note that the static mutex allocated in xInit does
+** not need to be freed.
+*/
+static void pcache1Shutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  assert( pcache1.isInit!=0 );
+  memset(&pcache1, 0, sizeof(pcache1));
+}
+
+/* forward declaration */
+static void pcache1Destroy(sqlite3_pcache *p);
+
+/*
+** Implementation of the sqlite3_pcache.xCreate method.
+**
+** Allocate a new cache.
+*/
+static sqlite3_pcache *pcache1Create(int szPage, int szExtra, int bPurgeable){
+  PCache1 *pCache;      /* The newly created page cache */
+  PGroup *pGroup;       /* The group the new page cache will belong to */
+  int sz;               /* Bytes of memory required to allocate the new cache */
+
+  assert( (szPage & (szPage-1))==0 && szPage>=512 && szPage<=65536 );
+  assert( szExtra < 300 );
+
+  sz = sizeof(PCache1) + sizeof(PGroup)*pcache1.separateCache;
+  pCache = (PCache1 *)sqlite3MallocZero(sz);
+  if( pCache ){
+    if( pcache1.separateCache ){
+      pGroup = (PGroup*)&pCache[1];
+      pGroup->mxPinned = 10;
+    }else{
+      pGroup = &pcache1.grp;
+    }
+    pcache1EnterMutex(pGroup);
+    if( pGroup->lru.isAnchor==0 ){
+      pGroup->lru.isAnchor = 1;
+      pGroup->lru.pLruPrev = pGroup->lru.pLruNext = &pGroup->lru;
+    }
+    pCache->pGroup = pGroup;
+    pCache->szPage = szPage;
+    pCache->szExtra = szExtra;
+    pCache->szAlloc = szPage + szExtra + ROUND8(sizeof(PgHdr1));
+    pCache->bPurgeable = (bPurgeable ? 1 : 0);
+    pcache1ResizeHash(pCache);
+    if( bPurgeable ){
+      pCache->nMin = 10;
+      pGroup->nMinPage += pCache->nMin;
+      pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
+      pCache->pnPurgeable = &pGroup->nPurgeable;
+    }else{
+      pCache->pnPurgeable = &pCache->nPurgeableDummy;
+    }
+    pcache1LeaveMutex(pGroup);
+    if( pCache->nHash==0 ){
+      pcache1Destroy((sqlite3_pcache*)pCache);
+      pCache = 0;
+    }
+  }
+  return (sqlite3_pcache *)pCache;
+}
+
+/*
+** Implementation of the sqlite3_pcache.xCachesize method.
+**
+** Configure the cache_size limit for a cache.
+*/
+static void pcache1Cachesize(sqlite3_pcache *p, int nMax){
+  PCache1 *pCache = (PCache1 *)p;
+  u32 n;
+  assert( nMax>=0 );
+  if( pCache->bPurgeable ){
+    PGroup *pGroup = pCache->pGroup;
+    pcache1EnterMutex(pGroup);
+    n = (u32)nMax;
+    if( n > 0x7fff0000 - pGroup->nMaxPage + pCache->nMax ){
+      n = 0x7fff0000 - pGroup->nMaxPage + pCache->nMax;
+    }
+    pGroup->nMaxPage += (n - pCache->nMax);
+    pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
+    pCache->nMax = n;
+    pCache->n90pct = pCache->nMax*9/10;
+    pcache1EnforceMaxPage(pCache);
+    pcache1LeaveMutex(pGroup);
+  }
+}
+
+/*
+** Implementation of the sqlite3_pcache.xShrink method.
+**
+** Free up as much memory as possible.
+*/
+static void pcache1Shrink(sqlite3_pcache *p){
+  PCache1 *pCache = (PCache1*)p;
+  if( pCache->bPurgeable ){
+    PGroup *pGroup = pCache->pGroup;
+    unsigned int savedMaxPage;
+    pcache1EnterMutex(pGroup);
+    savedMaxPage = pGroup->nMaxPage;
+    pGroup->nMaxPage = 0;
+    pcache1EnforceMaxPage(pCache);
+    pGroup->nMaxPage = savedMaxPage;
+    pcache1LeaveMutex(pGroup);
+  }
+}
+
+/*
+** Implementation of the sqlite3_pcache.xPagecount method.
+*/
+static int pcache1Pagecount(sqlite3_pcache *p){
+  int n;
+  PCache1 *pCache = (PCache1*)p;
+  pcache1EnterMutex(pCache->pGroup);
+  n = pCache->nPage;
+  pcache1LeaveMutex(pCache->pGroup);
+  return n;
+}
+
+
+/*
+** Implement steps 3, 4, and 5 of the pcache1Fetch() algorithm described
+** in the header of the pcache1Fetch() procedure.
+**
+** This steps are broken out into a separate procedure because they are
+** usually not needed, and by avoiding the stack initialization required
+** for these steps, the main pcache1Fetch() procedure can run faster.
+*/
+static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2(
+  PCache1 *pCache,
+  unsigned int iKey,
+  int createFlag
+){
+  unsigned int nPinned;
+  PGroup *pGroup = pCache->pGroup;
+  PgHdr1 *pPage = 0;
+
+  /* Step 3: Abort if createFlag is 1 but the cache is nearly full */
+  assert( pCache->nPage >= pCache->nRecyclable );
+  nPinned = pCache->nPage - pCache->nRecyclable;
+  assert( pGroup->mxPinned == pGroup->nMaxPage + 10 - pGroup->nMinPage );
+  assert( pCache->n90pct == pCache->nMax*9/10 );
+  if( createFlag==1 && (
+        nPinned>=pGroup->mxPinned
+     || nPinned>=pCache->n90pct
+     || (pcache1UnderMemoryPressure(pCache) && pCache->nRecyclable<nPinned)
+  )){
+    return 0;
+  }
+
+  if( pCache->nPage>=pCache->nHash ) pcache1ResizeHash(pCache);
+  assert( pCache->nHash>0 && pCache->apHash );
+
+  /* Step 4. Try to recycle a page. */
+  if( pCache->bPurgeable
+   && !pGroup->lru.pLruPrev->isAnchor
+   && ((pCache->nPage+1>=pCache->nMax) || pcache1UnderMemoryPressure(pCache))
+  ){
+    PCache1 *pOther;
+    pPage = pGroup->lru.pLruPrev;
+    assert( PAGE_IS_UNPINNED(pPage) );
+    pcache1RemoveFromHash(pPage, 0);
+    pcache1PinPage(pPage);
+    pOther = pPage->pCache;
+    if( pOther->szAlloc != pCache->szAlloc ){
+      pcache1FreePage(pPage);
+      pPage = 0;
+    }else{
+      pGroup->nPurgeable -= (pOther->bPurgeable - pCache->bPurgeable);
+    }
+  }
+
+  /* Step 5. If a usable page buffer has still not been found,
+  ** attempt to allocate a new one.
+  */
+  if( !pPage ){
+    pPage = pcache1AllocPage(pCache, createFlag==1);
+  }
+
+  if( pPage ){
+    unsigned int h = iKey % pCache->nHash;
+    pCache->nPage++;
+    pPage->iKey = iKey;
+    pPage->pNext = pCache->apHash[h];
+    pPage->pCache = pCache;
+    pPage->pLruNext = 0;
+    /* pPage->pLruPrev = 0;
+    ** No need to clear pLruPrev since it is not accessed when pLruNext==0 */
+    *(void **)pPage->page.pExtra = 0;
+    pCache->apHash[h] = pPage;
+    if( iKey>pCache->iMaxKey ){
+      pCache->iMaxKey = iKey;
+    }
+  }
+  return pPage;
+}
+
+/*
+** Implementation of the sqlite3_pcache.xFetch method.
+**
+** Fetch a page by key value.
+**
+** Whether or not a new page may be allocated by this function depends on
+** the value of the createFlag argument.  0 means do not allocate a new
+** page.  1 means allocate a new page if space is easily available.  2
+** means to try really hard to allocate a new page.
+**
+** For a non-purgeable cache (a cache used as the storage for an in-memory
+** database) there is really no difference between createFlag 1 and 2.  So
+** the calling function (pcache.c) will never have a createFlag of 1 on
+** a non-purgeable cache.
+**
+** There are three different approaches to obtaining space for a page,
+** depending on the value of parameter createFlag (which may be 0, 1 or 2).
+**
+**   1. Regardless of the value of createFlag, the cache is searched for a
+**      copy of the requested page. If one is found, it is returned.
+**
+**   2. If createFlag==0 and the page is not already in the cache, NULL is
+**      returned.
+**
+**   3. If createFlag is 1, and the page is not already in the cache, then
+**      return NULL (do not allocate a new page) if any of the following
+**      conditions are true:
+**
+**       (a) the number of pages pinned by the cache is greater than
+**           PCache1.nMax, or
+**
+**       (b) the number of pages pinned by the cache is greater than
+**           the sum of nMax for all purgeable caches, less the sum of
+**           nMin for all other purgeable caches, or
+**
+**   4. If none of the first three conditions apply and the cache is marked
+**      as purgeable, and if one of the following is true:
+**
+**       (a) The number of pages allocated for the cache is already
+**           PCache1.nMax, or
+**
+**       (b) The number of pages allocated for all purgeable caches is
+**           already equal to or greater than the sum of nMax for all
+**           purgeable caches,
+**
+**       (c) The system is under memory pressure and wants to avoid
+**           unnecessary pages cache entry allocations
+**
+**      then attempt to recycle a page from the LRU list. If it is the right
+**      size, return the recycled buffer. Otherwise, free the buffer and
+**      proceed to step 5.
+**
+**   5. Otherwise, allocate and return a new page buffer.
+**
+** There are two versions of this routine.  pcache1FetchWithMutex() is
+** the general case.  pcache1FetchNoMutex() is a faster implementation for
+** the common case where pGroup->mutex is NULL.  The pcache1Fetch() wrapper
+** invokes the appropriate routine.
+*/
+static PgHdr1 *pcache1FetchNoMutex(
+  sqlite3_pcache *p,
+  unsigned int iKey,
+  int createFlag
+){
+  PCache1 *pCache = (PCache1 *)p;
+  PgHdr1 *pPage = 0;
+
+  /* Step 1: Search the hash table for an existing entry. */
+  pPage = pCache->apHash[iKey % pCache->nHash];
+  while( pPage && pPage->iKey!=iKey ){ pPage = pPage->pNext; }
+
+  /* Step 2: If the page was found in the hash table, then return it.
+  ** If the page was not in the hash table and createFlag is 0, abort.
+  ** Otherwise (page not in hash and createFlag!=0) continue with
+  ** subsequent steps to try to create the page. */
+  if( pPage ){
+    if( PAGE_IS_UNPINNED(pPage) ){
+      return pcache1PinPage(pPage);
+    }else{
+      return pPage;
+    }
+  }else if( createFlag ){
+    /* Steps 3, 4, and 5 implemented by this subroutine */
+    return pcache1FetchStage2(pCache, iKey, createFlag);
+  }else{
+    return 0;
+  }
+}
+#if PCACHE1_MIGHT_USE_GROUP_MUTEX
+static PgHdr1 *pcache1FetchWithMutex(
+  sqlite3_pcache *p,
+  unsigned int iKey,
+  int createFlag
+){
+  PCache1 *pCache = (PCache1 *)p;
+  PgHdr1 *pPage;
+
+  pcache1EnterMutex(pCache->pGroup);
+  pPage = pcache1FetchNoMutex(p, iKey, createFlag);
+  assert( pPage==0 || pCache->iMaxKey>=iKey );
+  pcache1LeaveMutex(pCache->pGroup);
+  return pPage;
+}
+#endif
+static sqlite3_pcache_page *pcache1Fetch(
+  sqlite3_pcache *p,
+  unsigned int iKey,
+  int createFlag
+){
+#if PCACHE1_MIGHT_USE_GROUP_MUTEX || defined(SQLITE_DEBUG)
+  PCache1 *pCache = (PCache1 *)p;
+#endif
+
+  assert( offsetof(PgHdr1,page)==0 );
+  assert( pCache->bPurgeable || createFlag!=1 );
+  assert( pCache->bPurgeable || pCache->nMin==0 );
+  assert( pCache->bPurgeable==0 || pCache->nMin==10 );
+  assert( pCache->nMin==0 || pCache->bPurgeable );
+  assert( pCache->nHash>0 );
+#if PCACHE1_MIGHT_USE_GROUP_MUTEX
+  if( pCache->pGroup->mutex ){
+    return (sqlite3_pcache_page*)pcache1FetchWithMutex(p, iKey, createFlag);
+  }else
+#endif
+  {
+    return (sqlite3_pcache_page*)pcache1FetchNoMutex(p, iKey, createFlag);
+  }
+}
+
+
+/*
+** Implementation of the sqlite3_pcache.xUnpin method.
+**
+** Mark a page as unpinned (eligible for asynchronous recycling).
+*/
+static void pcache1Unpin(
+  sqlite3_pcache *p,
+  sqlite3_pcache_page *pPg,
+  int reuseUnlikely
+){
+  PCache1 *pCache = (PCache1 *)p;
+  PgHdr1 *pPage = (PgHdr1 *)pPg;
+  PGroup *pGroup = pCache->pGroup;
+
+  assert( pPage->pCache==pCache );
+  pcache1EnterMutex(pGroup);
+
+  /* It is an error to call this function if the page is already
+  ** part of the PGroup LRU list.
+  */
+  assert( pPage->pLruNext==0 );
+  assert( PAGE_IS_PINNED(pPage) );
+
+  if( reuseUnlikely || pGroup->nPurgeable>pGroup->nMaxPage ){
+    pcache1RemoveFromHash(pPage, 1);
+  }else{
+    /* Add the page to the PGroup LRU list. */
+    PgHdr1 **ppFirst = &pGroup->lru.pLruNext;
+    pPage->pLruPrev = &pGroup->lru;
+    (pPage->pLruNext = *ppFirst)->pLruPrev = pPage;
+    *ppFirst = pPage;
+    pCache->nRecyclable++;
+  }
+
+  pcache1LeaveMutex(pCache->pGroup);
+}
+
+/*
+** Implementation of the sqlite3_pcache.xRekey method.
+*/
+static void pcache1Rekey(
+  sqlite3_pcache *p,
+  sqlite3_pcache_page *pPg,
+  unsigned int iOld,
+  unsigned int iNew
+){
+  PCache1 *pCache = (PCache1 *)p;
+  PgHdr1 *pPage = (PgHdr1 *)pPg;
+  PgHdr1 **pp;
+  unsigned int hOld, hNew;
+  assert( pPage->iKey==iOld );
+  assert( pPage->pCache==pCache );
+  assert( iOld!=iNew );               /* The page number really is changing */
+
+  pcache1EnterMutex(pCache->pGroup);
+
+  assert( pcache1FetchNoMutex(p, iOld, 0)==pPage ); /* pPg really is iOld */
+  hOld = iOld%pCache->nHash;
+  pp = &pCache->apHash[hOld];
+  while( (*pp)!=pPage ){
+    pp = &(*pp)->pNext;
+  }
+  *pp = pPage->pNext;
+
+  assert( pcache1FetchNoMutex(p, iNew, 0)==0 ); /* iNew not in cache */
+  hNew = iNew%pCache->nHash;
+  pPage->iKey = iNew;
+  pPage->pNext = pCache->apHash[hNew];
+  pCache->apHash[hNew] = pPage;
+  if( iNew>pCache->iMaxKey ){
+    pCache->iMaxKey = iNew;
+  }
+
+  pcache1LeaveMutex(pCache->pGroup);
+}
+
+/*
+** Implementation of the sqlite3_pcache.xTruncate method.
+**
+** Discard all unpinned pages in the cache with a page number equal to
+** or greater than parameter iLimit. Any pinned pages with a page number
+** equal to or greater than iLimit are implicitly unpinned.
+*/
+static void pcache1Truncate(sqlite3_pcache *p, unsigned int iLimit){
+  PCache1 *pCache = (PCache1 *)p;
+  pcache1EnterMutex(pCache->pGroup);
+  if( iLimit<=pCache->iMaxKey ){
+    pcache1TruncateUnsafe(pCache, iLimit);
+    pCache->iMaxKey = iLimit-1;
+  }
+  pcache1LeaveMutex(pCache->pGroup);
+}
+
+/*
+** Implementation of the sqlite3_pcache.xDestroy method.
+**
+** Destroy a cache allocated using pcache1Create().
+*/
+static void pcache1Destroy(sqlite3_pcache *p){
+  PCache1 *pCache = (PCache1 *)p;
+  PGroup *pGroup = pCache->pGroup;
+  assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
+  pcache1EnterMutex(pGroup);
+  if( pCache->nPage ) pcache1TruncateUnsafe(pCache, 0);
+  assert( pGroup->nMaxPage >= pCache->nMax );
+  pGroup->nMaxPage -= pCache->nMax;
+  assert( pGroup->nMinPage >= pCache->nMin );
+  pGroup->nMinPage -= pCache->nMin;
+  pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
+  pcache1EnforceMaxPage(pCache);
+  pcache1LeaveMutex(pGroup);
+  sqlite3_free(pCache->pBulk);
+  sqlite3_free(pCache->apHash);
+  sqlite3_free(pCache);
+}
+
+/*
+** This function is called during initialization (sqlite3_initialize()) to
+** install the default pluggable cache module, assuming the user has not
+** already provided an alternative.
+*/
+void sqlite3PCacheSetDefault(void){
+  static const sqlite3_pcache_methods2 defaultMethods = {
+    1,                       /* iVersion */
+    0,                       /* pArg */
+    pcache1Init,             /* xInit */
+    pcache1Shutdown,         /* xShutdown */
+    pcache1Create,           /* xCreate */
+    pcache1Cachesize,        /* xCachesize */
+    pcache1Pagecount,        /* xPagecount */
+    pcache1Fetch,            /* xFetch */
+    pcache1Unpin,            /* xUnpin */
+    pcache1Rekey,            /* xRekey */
+    pcache1Truncate,         /* xTruncate */
+    pcache1Destroy,          /* xDestroy */
+    pcache1Shrink            /* xShrink */
+  };
+  sqlite3_config(SQLITE_CONFIG_PCACHE2, &defaultMethods);
+}
+
+/*
+** Return the size of the header on each page of this PCACHE implementation.
+*/
+int sqlite3HeaderSizePcache1(void){ return ROUND8(sizeof(PgHdr1)); }
+
+/*
+** Return the global mutex used by this PCACHE implementation.  The
+** sqlite3_status() routine needs access to this mutex.
+*/
+sqlite3_mutex *sqlite3Pcache1Mutex(void){
+  return pcache1.mutex;
+}
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+/*
+** This function is called to free superfluous dynamically allocated memory
+** held by the pager system. Memory in use by any SQLite pager allocated
+** by the current thread may be sqlite3_free()ed.
+**
+** nReq is the number of bytes of memory required. Once this much has
+** been released, the function returns. The return value is the total number
+** of bytes of memory released.
+*/
+int sqlite3PcacheReleaseMemory(int nReq){
+  int nFree = 0;
+  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
+  assert( sqlite3_mutex_notheld(pcache1.mutex) );
+  if( sqlite3GlobalConfig.pPage==0 ){
+    PgHdr1 *p;
+    pcache1EnterMutex(&pcache1.grp);
+    while( (nReq<0 || nFree<nReq)
+       &&  (p=pcache1.grp.lru.pLruPrev)!=0
+       &&  p->isAnchor==0
+    ){
+      nFree += pcache1MemSize(p->page.pBuf);
+      assert( PAGE_IS_UNPINNED(p) );
+      pcache1PinPage(p);
+      pcache1RemoveFromHash(p, 1);
+    }
+    pcache1LeaveMutex(&pcache1.grp);
+  }
+  return nFree;
+}
+#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
+
+#ifdef SQLITE_TEST
+/*
+** This function is used by test procedures to inspect the internal state
+** of the global cache.
+*/
+void sqlite3PcacheStats(
+  int *pnCurrent,      /* OUT: Total number of pages cached */
+  int *pnMax,          /* OUT: Global maximum cache size */
+  int *pnMin,          /* OUT: Sum of PCache1.nMin for purgeable caches */
+  int *pnRecyclable    /* OUT: Total number of pages available for recycling */
+){
+  PgHdr1 *p;
+  int nRecyclable = 0;
+  for(p=pcache1.grp.lru.pLruNext; p && !p->isAnchor; p=p->pLruNext){
+    assert( PAGE_IS_UNPINNED(p) );
+    nRecyclable++;
+  }
+  *pnCurrent = pcache1.grp.nPurgeable;
+  *pnMax = (int)pcache1.grp.nMaxPage;
+  *pnMin = (int)pcache1.grp.nMinPage;
+  *pnRecyclable = nRecyclable;
+}
+#endif
diff --git a/src/pragma.c b/src/pragma.c
new file mode 100644
index 0000000..4c90574
--- /dev/null
+++ b/src/pragma.c
@@ -0,0 +1,2936 @@
+/*
+** 2003 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the PRAGMA command.
+*/
+#include "sqliteInt.h"
+
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+
+/***************************************************************************
+** The "pragma.h" include file is an automatically generated file that
+** that includes the PragType_XXXX macro definitions and the aPragmaName[]
+** object.  This ensures that the aPragmaName[] table is arranged in
+** lexicographical order to facility a binary search of the pragma name.
+** Do not edit pragma.h directly.  Edit and rerun the script in at
+** ../tool/mkpragmatab.tcl. */
+#include "pragma.h"
+
+/*
+** Interpret the given string as a safety level.  Return 0 for OFF,
+** 1 for ON or NORMAL, 2 for FULL, and 3 for EXTRA.  Return 1 for an empty or
+** unrecognized string argument.  The FULL and EXTRA option is disallowed
+** if the omitFull parameter it 1.
+**
+** Note that the values returned are one less that the values that
+** should be passed into sqlite3BtreeSetSafetyLevel().  The is done
+** to support legacy SQL code.  The safety level used to be boolean
+** and older scripts may have used numbers 0 for OFF and 1 for ON.
+*/
+static u8 getSafetyLevel(const char *z, int omitFull, u8 dflt){
+                             /* 123456789 123456789 123 */
+  static const char zText[] = "onoffalseyestruextrafull";
+  static const u8 iOffset[] = {0, 1, 2,  4,    9,  12,  15,   20};
+  static const u8 iLength[] = {2, 2, 3,  5,    3,   4,   5,    4};
+  static const u8 iValue[] =  {1, 0, 0,  0,    1,   1,   3,    2};
+                            /* on no off false yes true extra full */
+  int i, n;
+  if( sqlite3Isdigit(*z) ){
+    return (u8)sqlite3Atoi(z);
+  }
+  n = sqlite3Strlen30(z);
+  for(i=0; i<ArraySize(iLength); i++){
+    if( iLength[i]==n && sqlite3StrNICmp(&zText[iOffset[i]],z,n)==0
+     && (!omitFull || iValue[i]<=1)
+    ){
+      return iValue[i];
+    }
+  }
+  return dflt;
+}
+
+/*
+** Interpret the given string as a boolean value.
+*/
+u8 sqlite3GetBoolean(const char *z, u8 dflt){
+  return getSafetyLevel(z,1,dflt)!=0;
+}
+
+/* The sqlite3GetBoolean() function is used by other modules but the
+** remainder of this file is specific to PRAGMA processing.  So omit
+** the rest of the file if PRAGMAs are omitted from the build.
+*/
+#if !defined(SQLITE_OMIT_PRAGMA)
+
+/*
+** Interpret the given string as a locking mode value.
+*/
+static int getLockingMode(const char *z){
+  if( z ){
+    if( 0==sqlite3StrICmp(z, "exclusive") ) return PAGER_LOCKINGMODE_EXCLUSIVE;
+    if( 0==sqlite3StrICmp(z, "normal") ) return PAGER_LOCKINGMODE_NORMAL;
+  }
+  return PAGER_LOCKINGMODE_QUERY;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Interpret the given string as an auto-vacuum mode value.
+**
+** The following strings, "none", "full" and "incremental" are
+** acceptable, as are their numeric equivalents: 0, 1 and 2 respectively.
+*/
+static int getAutoVacuum(const char *z){
+  int i;
+  if( 0==sqlite3StrICmp(z, "none") ) return BTREE_AUTOVACUUM_NONE;
+  if( 0==sqlite3StrICmp(z, "full") ) return BTREE_AUTOVACUUM_FULL;
+  if( 0==sqlite3StrICmp(z, "incremental") ) return BTREE_AUTOVACUUM_INCR;
+  i = sqlite3Atoi(z);
+  return (u8)((i>=0&&i<=2)?i:0);
+}
+#endif /* ifndef SQLITE_OMIT_AUTOVACUUM */
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+/*
+** Interpret the given string as a temp db location. Return 1 for file
+** backed temporary databases, 2 for the Red-Black tree in memory database
+** and 0 to use the compile-time default.
+*/
+static int getTempStore(const char *z){
+  if( z[0]>='0' && z[0]<='2' ){
+    return z[0] - '0';
+  }else if( sqlite3StrICmp(z, "file")==0 ){
+    return 1;
+  }else if( sqlite3StrICmp(z, "memory")==0 ){
+    return 2;
+  }else{
+    return 0;
+  }
+}
+#endif /* SQLITE_PAGER_PRAGMAS */
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+/*
+** Invalidate temp storage, either when the temp storage is changed
+** from default, or when 'file' and the temp_store_directory has changed
+*/
+static int invalidateTempStorage(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  if( db->aDb[1].pBt!=0 ){
+    if( !db->autoCommit
+     || sqlite3BtreeTxnState(db->aDb[1].pBt)!=SQLITE_TXN_NONE
+    ){
+      sqlite3ErrorMsg(pParse, "temporary storage cannot be changed "
+        "from within a transaction");
+      return SQLITE_ERROR;
+    }
+    sqlite3BtreeClose(db->aDb[1].pBt);
+    db->aDb[1].pBt = 0;
+    sqlite3ResetAllSchemasOfConnection(db);
+  }
+  return SQLITE_OK;
+}
+#endif /* SQLITE_PAGER_PRAGMAS */
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+/*
+** If the TEMP database is open, close it and mark the database schema
+** as needing reloading.  This must be done when using the SQLITE_TEMP_STORE
+** or DEFAULT_TEMP_STORE pragmas.
+*/
+static int changeTempStorage(Parse *pParse, const char *zStorageType){
+  int ts = getTempStore(zStorageType);
+  sqlite3 *db = pParse->db;
+  if( db->temp_store==ts ) return SQLITE_OK;
+  if( invalidateTempStorage( pParse ) != SQLITE_OK ){
+    return SQLITE_ERROR;
+  }
+  db->temp_store = (u8)ts;
+  return SQLITE_OK;
+}
+#endif /* SQLITE_PAGER_PRAGMAS */
+
+/*
+** Set result column names for a pragma.
+*/
+static void setPragmaResultColumnNames(
+  Vdbe *v,                     /* The query under construction */
+  const PragmaName *pPragma    /* The pragma */
+){
+  u8 n = pPragma->nPragCName;
+  sqlite3VdbeSetNumCols(v, n==0 ? 1 : n);
+  if( n==0 ){
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, pPragma->zName, SQLITE_STATIC);
+  }else{
+    int i, j;
+    for(i=0, j=pPragma->iPragCName; i<n; i++, j++){
+      sqlite3VdbeSetColName(v, i, COLNAME_NAME, pragCName[j], SQLITE_STATIC);
+    }
+  }
+}
+
+/*
+** Generate code to return a single integer value.
+*/
+static void returnSingleInt(Vdbe *v, i64 value){
+  sqlite3VdbeAddOp4Dup8(v, OP_Int64, 0, 1, 0, (const u8*)&value, P4_INT64);
+  sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+}
+
+/*
+** Generate code to return a single text value.
+*/
+static void returnSingleText(
+  Vdbe *v,                /* Prepared statement under construction */
+  const char *zValue      /* Value to be returned */
+){
+  if( zValue ){
+    sqlite3VdbeLoadString(v, 1, (const char*)zValue);
+    sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+  }
+}
+
+
+/*
+** Set the safety_level and pager flags for pager iDb.  Or if iDb<0
+** set these values for all pagers.
+*/
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+static void setAllPagerFlags(sqlite3 *db){
+  if( db->autoCommit ){
+    Db *pDb = db->aDb;
+    int n = db->nDb;
+    assert( SQLITE_FullFSync==PAGER_FULLFSYNC );
+    assert( SQLITE_CkptFullFSync==PAGER_CKPT_FULLFSYNC );
+    assert( SQLITE_CacheSpill==PAGER_CACHESPILL );
+    assert( (PAGER_FULLFSYNC | PAGER_CKPT_FULLFSYNC | PAGER_CACHESPILL)
+             ==  PAGER_FLAGS_MASK );
+    assert( (pDb->safety_level & PAGER_SYNCHRONOUS_MASK)==pDb->safety_level );
+    while( (n--) > 0 ){
+      if( pDb->pBt ){
+        sqlite3BtreeSetPagerFlags(pDb->pBt,
+                 pDb->safety_level | (db->flags & PAGER_FLAGS_MASK) );
+      }
+      pDb++;
+    }
+  }
+}
+#else
+# define setAllPagerFlags(X)  /* no-op */
+#endif
+
+
+/*
+** Return a human-readable name for a constraint resolution action.
+*/
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+static const char *actionName(u8 action){
+  const char *zName;
+  switch( action ){
+    case OE_SetNull:  zName = "SET NULL";        break;
+    case OE_SetDflt:  zName = "SET DEFAULT";     break;
+    case OE_Cascade:  zName = "CASCADE";         break;
+    case OE_Restrict: zName = "RESTRICT";        break;
+    default:          zName = "NO ACTION"; 
+                      assert( action==OE_None ); break;
+  }
+  return zName;
+}
+#endif
+
+
+/*
+** Parameter eMode must be one of the PAGER_JOURNALMODE_XXX constants
+** defined in pager.h. This function returns the associated lowercase
+** journal-mode name.
+*/
+const char *sqlite3JournalModename(int eMode){
+  static char * const azModeName[] = {
+    "delete", "persist", "off", "truncate", "memory"
+#ifndef SQLITE_OMIT_WAL
+     , "wal"
+#endif
+  };
+  assert( PAGER_JOURNALMODE_DELETE==0 );
+  assert( PAGER_JOURNALMODE_PERSIST==1 );
+  assert( PAGER_JOURNALMODE_OFF==2 );
+  assert( PAGER_JOURNALMODE_TRUNCATE==3 );
+  assert( PAGER_JOURNALMODE_MEMORY==4 );
+  assert( PAGER_JOURNALMODE_WAL==5 );
+  assert( eMode>=0 && eMode<=ArraySize(azModeName) );
+
+  if( eMode==ArraySize(azModeName) ) return 0;
+  return azModeName[eMode];
+}
+
+/*
+** Locate a pragma in the aPragmaName[] array.
+*/
+static const PragmaName *pragmaLocate(const char *zName){
+  int upr, lwr, mid = 0, rc;
+  lwr = 0;
+  upr = ArraySize(aPragmaName)-1;
+  while( lwr<=upr ){
+    mid = (lwr+upr)/2;
+    rc = sqlite3_stricmp(zName, aPragmaName[mid].zName);
+    if( rc==0 ) break;
+    if( rc<0 ){
+      upr = mid - 1;
+    }else{
+      lwr = mid + 1;
+    }
+  }
+  return lwr>upr ? 0 : &aPragmaName[mid];
+}
+
+/*
+** Create zero or more entries in the output for the SQL functions
+** defined by FuncDef p.
+*/
+static void pragmaFunclistLine(
+  Vdbe *v,               /* The prepared statement being created */
+  FuncDef *p,            /* A particular function definition */
+  int isBuiltin,         /* True if this is a built-in function */
+  int showInternFuncs    /* True if showing internal functions */
+){
+  u32 mask =
+      SQLITE_DETERMINISTIC |
+      SQLITE_DIRECTONLY |
+      SQLITE_SUBTYPE |
+      SQLITE_INNOCUOUS |
+      SQLITE_FUNC_INTERNAL
+  ;
+  if( showInternFuncs ) mask = 0xffffffff;
+  for(; p; p=p->pNext){
+    const char *zType;
+    static const char *azEnc[] = { 0, "utf8", "utf16le", "utf16be" };
+
+    assert( SQLITE_FUNC_ENCMASK==0x3 );
+    assert( strcmp(azEnc[SQLITE_UTF8],"utf8")==0 );
+    assert( strcmp(azEnc[SQLITE_UTF16LE],"utf16le")==0 );
+    assert( strcmp(azEnc[SQLITE_UTF16BE],"utf16be")==0 );
+
+    if( p->xSFunc==0 ) continue;
+    if( (p->funcFlags & SQLITE_FUNC_INTERNAL)!=0
+     && showInternFuncs==0
+    ){
+      continue;
+    }   
+    if( p->xValue!=0 ){
+      zType = "w";
+    }else if( p->xFinalize!=0 ){
+      zType = "a";
+    }else{
+      zType = "s";
+    }
+    sqlite3VdbeMultiLoad(v, 1, "sissii",
+       p->zName, isBuiltin,
+       zType, azEnc[p->funcFlags&SQLITE_FUNC_ENCMASK],
+       p->nArg,
+       (p->funcFlags & mask) ^ SQLITE_INNOCUOUS
+    );
+  }
+}
+
+
+/*
+** Helper subroutine for PRAGMA integrity_check:
+**
+** Generate code to output a single-column result row with a value of the
+** string held in register 3.  Decrement the result count in register 1
+** and halt if the maximum number of result rows have been issued.
+*/
+static int integrityCheckResultRow(Vdbe *v){
+  int addr;
+  sqlite3VdbeAddOp2(v, OP_ResultRow, 3, 1);
+  addr = sqlite3VdbeAddOp3(v, OP_IfPos, 1, sqlite3VdbeCurrentAddr(v)+2, 1);
+  VdbeCoverage(v);
+  sqlite3VdbeAddOp0(v, OP_Halt);
+  return addr;
+}
+
+/*
+** Process a pragma statement. 
+**
+** Pragmas are of this form:
+**
+**      PRAGMA [schema.]id [= value]
+**
+** The identifier might also be a string.  The value is a string, and
+** identifier, or a number.  If minusFlag is true, then the value is
+** a number that was preceded by a minus sign.
+**
+** If the left side is "database.id" then pId1 is the database name
+** and pId2 is the id.  If the left side is just "id" then pId1 is the
+** id and pId2 is any empty string.
+*/
+void sqlite3Pragma(
+  Parse *pParse,
+  Token *pId1,        /* First part of [schema.]id field */
+  Token *pId2,        /* Second part of [schema.]id field, or NULL */
+  Token *pValue,      /* Token for <value>, or NULL */
+  int minusFlag       /* True if a '-' sign preceded <value> */
+){
+  char *zLeft = 0;       /* Nul-terminated UTF-8 string <id> */
+  char *zRight = 0;      /* Nul-terminated UTF-8 string <value>, or NULL */
+  const char *zDb = 0;   /* The database name */
+  Token *pId;            /* Pointer to <id> token */
+  char *aFcntl[4];       /* Argument to SQLITE_FCNTL_PRAGMA */
+  int iDb;               /* Database index for <database> */
+  int rc;                      /* return value form SQLITE_FCNTL_PRAGMA */
+  sqlite3 *db = pParse->db;    /* The database connection */
+  Db *pDb;                     /* The specific database being pragmaed */
+  Vdbe *v = sqlite3GetVdbe(pParse);  /* Prepared statement */
+  const PragmaName *pPragma;   /* The pragma */
+
+  if( v==0 ) return;
+  sqlite3VdbeRunOnlyOnce(v);
+  pParse->nMem = 2;
+
+  /* Interpret the [schema.] part of the pragma statement. iDb is the
+  ** index of the database this pragma is being applied to in db.aDb[]. */
+  iDb = sqlite3TwoPartName(pParse, pId1, pId2, &pId);
+  if( iDb<0 ) return;
+  pDb = &db->aDb[iDb];
+
+  /* If the temp database has been explicitly named as part of the
+  ** pragma, make sure it is open.
+  */
+  if( iDb==1 && sqlite3OpenTempDatabase(pParse) ){
+    return;
+  }
+
+  zLeft = sqlite3NameFromToken(db, pId);
+  if( !zLeft ) return;
+  if( minusFlag ){
+    zRight = sqlite3MPrintf(db, "-%T", pValue);
+  }else{
+    zRight = sqlite3NameFromToken(db, pValue);
+  }
+
+  assert( pId2 );
+  zDb = pId2->n>0 ? pDb->zDbSName : 0;
+  if( sqlite3AuthCheck(pParse, SQLITE_PRAGMA, zLeft, zRight, zDb) ){
+    goto pragma_out;
+  }
+
+  /* Send an SQLITE_FCNTL_PRAGMA file-control to the underlying VFS
+  ** connection.  If it returns SQLITE_OK, then assume that the VFS
+  ** handled the pragma and generate a no-op prepared statement.
+  **
+  ** IMPLEMENTATION-OF: R-12238-55120 Whenever a PRAGMA statement is parsed,
+  ** an SQLITE_FCNTL_PRAGMA file control is sent to the open sqlite3_file
+  ** object corresponding to the database file to which the pragma
+  ** statement refers.
+  **
+  ** IMPLEMENTATION-OF: R-29875-31678 The argument to the SQLITE_FCNTL_PRAGMA
+  ** file control is an array of pointers to strings (char**) in which the
+  ** second element of the array is the name of the pragma and the third
+  ** element is the argument to the pragma or NULL if the pragma has no
+  ** argument.
+  */
+  aFcntl[0] = 0;
+  aFcntl[1] = zLeft;
+  aFcntl[2] = zRight;
+  aFcntl[3] = 0;
+  db->busyHandler.nBusy = 0;
+  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_PRAGMA, (void*)aFcntl);
+  if( rc==SQLITE_OK ){
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, aFcntl[0], SQLITE_TRANSIENT);
+    returnSingleText(v, aFcntl[0]);
+    sqlite3_free(aFcntl[0]);
+    goto pragma_out;
+  }
+  if( rc!=SQLITE_NOTFOUND ){
+    if( aFcntl[0] ){
+      sqlite3ErrorMsg(pParse, "%s", aFcntl[0]);
+      sqlite3_free(aFcntl[0]);
+    }
+    pParse->nErr++;
+    pParse->rc = rc;
+    goto pragma_out;
+  }
+
+  /* Locate the pragma in the lookup table */
+  pPragma = pragmaLocate(zLeft);
+  if( pPragma==0 ){
+    /* IMP: R-43042-22504 No error messages are generated if an
+    ** unknown pragma is issued. */
+    goto pragma_out;
+  }
+
+  /* Make sure the database schema is loaded if the pragma requires that */
+  if( (pPragma->mPragFlg & PragFlg_NeedSchema)!=0 ){
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+  }
+
+  /* Register the result column names for pragmas that return results */
+  if( (pPragma->mPragFlg & PragFlg_NoColumns)==0
+   && ((pPragma->mPragFlg & PragFlg_NoColumns1)==0 || zRight==0)
+  ){
+    setPragmaResultColumnNames(v, pPragma);
+  }
+
+  /* Jump to the appropriate pragma handler */
+  switch( pPragma->ePragTyp ){
+ 
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) && !defined(SQLITE_OMIT_DEPRECATED)
+  /*
+  **  PRAGMA [schema.]default_cache_size
+  **  PRAGMA [schema.]default_cache_size=N
+  **
+  ** The first form reports the current persistent setting for the
+  ** page cache size.  The value returned is the maximum number of
+  ** pages in the page cache.  The second form sets both the current
+  ** page cache size value and the persistent page cache size value
+  ** stored in the database file.
+  **
+  ** Older versions of SQLite would set the default cache size to a
+  ** negative number to indicate synchronous=OFF.  These days, synchronous
+  ** is always on by default regardless of the sign of the default cache
+  ** size.  But continue to take the absolute value of the default cache
+  ** size of historical compatibility.
+  */
+  case PragTyp_DEFAULT_CACHE_SIZE: {
+    static const int iLn = VDBE_OFFSET_LINENO(2);
+    static const VdbeOpList getCacheSize[] = {
+      { OP_Transaction, 0, 0,        0},                         /* 0 */
+      { OP_ReadCookie,  0, 1,        BTREE_DEFAULT_CACHE_SIZE},  /* 1 */
+      { OP_IfPos,       1, 8,        0},
+      { OP_Integer,     0, 2,        0},
+      { OP_Subtract,    1, 2,        1},
+      { OP_IfPos,       1, 8,        0},
+      { OP_Integer,     0, 1,        0},                         /* 6 */
+      { OP_Noop,        0, 0,        0},
+      { OP_ResultRow,   1, 1,        0},
+    };
+    VdbeOp *aOp;
+    sqlite3VdbeUsesBtree(v, iDb);
+    if( !zRight ){
+      pParse->nMem += 2;
+      sqlite3VdbeVerifyNoMallocRequired(v, ArraySize(getCacheSize));
+      aOp = sqlite3VdbeAddOpList(v, ArraySize(getCacheSize), getCacheSize, iLn);
+      if( ONLY_IF_REALLOC_STRESS(aOp==0) ) break;
+      aOp[0].p1 = iDb;
+      aOp[1].p1 = iDb;
+      aOp[6].p1 = SQLITE_DEFAULT_CACHE_SIZE;
+    }else{
+      int size = sqlite3AbsInt32(sqlite3Atoi(zRight));
+      sqlite3BeginWriteOperation(pParse, 0, iDb);
+      sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_DEFAULT_CACHE_SIZE, size);
+      assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+      pDb->pSchema->cache_size = size;
+      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
+    }
+    break;
+  }
+#endif /* !SQLITE_OMIT_PAGER_PRAGMAS && !SQLITE_OMIT_DEPRECATED */
+
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+  /*
+  **  PRAGMA [schema.]page_size
+  **  PRAGMA [schema.]page_size=N
+  **
+  ** The first form reports the current setting for the
+  ** database page size in bytes.  The second form sets the
+  ** database page size value.  The value can only be set if
+  ** the database has not yet been created.
+  */
+  case PragTyp_PAGE_SIZE: {
+    Btree *pBt = pDb->pBt;
+    assert( pBt!=0 );
+    if( !zRight ){
+      int size = ALWAYS(pBt) ? sqlite3BtreeGetPageSize(pBt) : 0;
+      returnSingleInt(v, size);
+    }else{
+      /* Malloc may fail when setting the page-size, as there is an internal
+      ** buffer that the pager module resizes using sqlite3_realloc().
+      */
+      db->nextPagesize = sqlite3Atoi(zRight);
+      if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize,0,0) ){
+        sqlite3OomFault(db);
+      }
+    }
+    break;
+  }
+
+  /*
+  **  PRAGMA [schema.]secure_delete
+  **  PRAGMA [schema.]secure_delete=ON/OFF/FAST
+  **
+  ** The first form reports the current setting for the
+  ** secure_delete flag.  The second form changes the secure_delete
+  ** flag setting and reports the new value.
+  */
+  case PragTyp_SECURE_DELETE: {
+    Btree *pBt = pDb->pBt;
+    int b = -1;
+    assert( pBt!=0 );
+    if( zRight ){
+      if( sqlite3_stricmp(zRight, "fast")==0 ){
+        b = 2;
+      }else{
+        b = sqlite3GetBoolean(zRight, 0);
+      }
+    }
+    if( pId2->n==0 && b>=0 ){
+      int ii;
+      for(ii=0; ii<db->nDb; ii++){
+        sqlite3BtreeSecureDelete(db->aDb[ii].pBt, b);
+      }
+    }
+    b = sqlite3BtreeSecureDelete(pBt, b);
+    returnSingleInt(v, b);
+    break;
+  }
+
+  /*
+  **  PRAGMA [schema.]max_page_count
+  **  PRAGMA [schema.]max_page_count=N
+  **
+  ** The first form reports the current setting for the
+  ** maximum number of pages in the database file.  The
+  ** second form attempts to change this setting.  Both
+  ** forms return the current setting.
+  **
+  ** The absolute value of N is used.  This is undocumented and might
+  ** change.  The only purpose is to provide an easy way to test
+  ** the sqlite3AbsInt32() function.
+  **
+  **  PRAGMA [schema.]page_count
+  **
+  ** Return the number of pages in the specified database.
+  */
+  case PragTyp_PAGE_COUNT: {
+    int iReg;
+    i64 x = 0;
+    sqlite3CodeVerifySchema(pParse, iDb);
+    iReg = ++pParse->nMem;
+    if( sqlite3Tolower(zLeft[0])=='p' ){
+      sqlite3VdbeAddOp2(v, OP_Pagecount, iDb, iReg);
+    }else{
+      if( zRight && sqlite3DecOrHexToI64(zRight,&x)==0 ){
+        if( x<0 ) x = 0;
+        else if( x>0xfffffffe ) x = 0xfffffffe;
+      }else{
+        x = 0;
+      }
+      sqlite3VdbeAddOp3(v, OP_MaxPgcnt, iDb, iReg, (int)x);
+    }
+    sqlite3VdbeAddOp2(v, OP_ResultRow, iReg, 1);
+    break;
+  }
+
+  /*
+  **  PRAGMA [schema.]locking_mode
+  **  PRAGMA [schema.]locking_mode = (normal|exclusive)
+  */
+  case PragTyp_LOCKING_MODE: {
+    const char *zRet = "normal";
+    int eMode = getLockingMode(zRight);
+
+    if( pId2->n==0 && eMode==PAGER_LOCKINGMODE_QUERY ){
+      /* Simple "PRAGMA locking_mode;" statement. This is a query for
+      ** the current default locking mode (which may be different to
+      ** the locking-mode of the main database).
+      */
+      eMode = db->dfltLockMode;
+    }else{
+      Pager *pPager;
+      if( pId2->n==0 ){
+        /* This indicates that no database name was specified as part
+        ** of the PRAGMA command. In this case the locking-mode must be
+        ** set on all attached databases, as well as the main db file.
+        **
+        ** Also, the sqlite3.dfltLockMode variable is set so that
+        ** any subsequently attached databases also use the specified
+        ** locking mode.
+        */
+        int ii;
+        assert(pDb==&db->aDb[0]);
+        for(ii=2; ii<db->nDb; ii++){
+          pPager = sqlite3BtreePager(db->aDb[ii].pBt);
+          sqlite3PagerLockingMode(pPager, eMode);
+        }
+        db->dfltLockMode = (u8)eMode;
+      }
+      pPager = sqlite3BtreePager(pDb->pBt);
+      eMode = sqlite3PagerLockingMode(pPager, eMode);
+    }
+
+    assert( eMode==PAGER_LOCKINGMODE_NORMAL
+            || eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
+    if( eMode==PAGER_LOCKINGMODE_EXCLUSIVE ){
+      zRet = "exclusive";
+    }
+    returnSingleText(v, zRet);
+    break;
+  }
+
+  /*
+  **  PRAGMA [schema.]journal_mode
+  **  PRAGMA [schema.]journal_mode =
+  **                      (delete|persist|off|truncate|memory|wal|off)
+  */
+  case PragTyp_JOURNAL_MODE: {
+    int eMode;        /* One of the PAGER_JOURNALMODE_XXX symbols */
+    int ii;           /* Loop counter */
+
+    if( zRight==0 ){
+      /* If there is no "=MODE" part of the pragma, do a query for the
+      ** current mode */
+      eMode = PAGER_JOURNALMODE_QUERY;
+    }else{
+      const char *zMode;
+      int n = sqlite3Strlen30(zRight);
+      for(eMode=0; (zMode = sqlite3JournalModename(eMode))!=0; eMode++){
+        if( sqlite3StrNICmp(zRight, zMode, n)==0 ) break;
+      }
+      if( !zMode ){
+        /* If the "=MODE" part does not match any known journal mode,
+        ** then do a query */
+        eMode = PAGER_JOURNALMODE_QUERY;
+      }
+      if( eMode==PAGER_JOURNALMODE_OFF && (db->flags & SQLITE_Defensive)!=0 ){
+        /* Do not allow journal-mode "OFF" in defensive since the database
+        ** can become corrupted using ordinary SQL when the journal is off */
+        eMode = PAGER_JOURNALMODE_QUERY;
+      }
+    }
+    if( eMode==PAGER_JOURNALMODE_QUERY && pId2->n==0 ){
+      /* Convert "PRAGMA journal_mode" into "PRAGMA main.journal_mode" */
+      iDb = 0;
+      pId2->n = 1;
+    }
+    for(ii=db->nDb-1; ii>=0; ii--){
+      if( db->aDb[ii].pBt && (ii==iDb || pId2->n==0) ){
+        sqlite3VdbeUsesBtree(v, ii);
+        sqlite3VdbeAddOp3(v, OP_JournalMode, ii, 1, eMode);
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+    break;
+  }
+
+  /*
+  **  PRAGMA [schema.]journal_size_limit
+  **  PRAGMA [schema.]journal_size_limit=N
+  **
+  ** Get or set the size limit on rollback journal files.
+  */
+  case PragTyp_JOURNAL_SIZE_LIMIT: {
+    Pager *pPager = sqlite3BtreePager(pDb->pBt);
+    i64 iLimit = -2;
+    if( zRight ){
+      sqlite3DecOrHexToI64(zRight, &iLimit);
+      if( iLimit<-1 ) iLimit = -1;
+    }
+    iLimit = sqlite3PagerJournalSizeLimit(pPager, iLimit);
+    returnSingleInt(v, iLimit);
+    break;
+  }
+
+#endif /* SQLITE_OMIT_PAGER_PRAGMAS */
+
+  /*
+  **  PRAGMA [schema.]auto_vacuum
+  **  PRAGMA [schema.]auto_vacuum=N
+  **
+  ** Get or set the value of the database 'auto-vacuum' parameter.
+  ** The value is one of:  0 NONE 1 FULL 2 INCREMENTAL
+  */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  case PragTyp_AUTO_VACUUM: {
+    Btree *pBt = pDb->pBt;
+    assert( pBt!=0 );
+    if( !zRight ){
+      returnSingleInt(v, sqlite3BtreeGetAutoVacuum(pBt));
+    }else{
+      int eAuto = getAutoVacuum(zRight);
+      assert( eAuto>=0 && eAuto<=2 );
+      db->nextAutovac = (u8)eAuto;
+      /* Call SetAutoVacuum() to set initialize the internal auto and
+      ** incr-vacuum flags. This is required in case this connection
+      ** creates the database file. It is important that it is created
+      ** as an auto-vacuum capable db.
+      */
+      rc = sqlite3BtreeSetAutoVacuum(pBt, eAuto);
+      if( rc==SQLITE_OK && (eAuto==1 || eAuto==2) ){
+        /* When setting the auto_vacuum mode to either "full" or
+        ** "incremental", write the value of meta[6] in the database
+        ** file. Before writing to meta[6], check that meta[3] indicates
+        ** that this really is an auto-vacuum capable database.
+        */
+        static const int iLn = VDBE_OFFSET_LINENO(2);
+        static const VdbeOpList setMeta6[] = {
+          { OP_Transaction,    0,         1,                 0},    /* 0 */
+          { OP_ReadCookie,     0,         1,         BTREE_LARGEST_ROOT_PAGE},
+          { OP_If,             1,         0,                 0},    /* 2 */
+          { OP_Halt,           SQLITE_OK, OE_Abort,          0},    /* 3 */
+          { OP_SetCookie,      0,         BTREE_INCR_VACUUM, 0},    /* 4 */
+        };
+        VdbeOp *aOp;
+        int iAddr = sqlite3VdbeCurrentAddr(v);
+        sqlite3VdbeVerifyNoMallocRequired(v, ArraySize(setMeta6));
+        aOp = sqlite3VdbeAddOpList(v, ArraySize(setMeta6), setMeta6, iLn);
+        if( ONLY_IF_REALLOC_STRESS(aOp==0) ) break;
+        aOp[0].p1 = iDb;
+        aOp[1].p1 = iDb;
+        aOp[2].p2 = iAddr+4;
+        aOp[4].p1 = iDb;
+        aOp[4].p3 = eAuto - 1;
+        sqlite3VdbeUsesBtree(v, iDb);
+      }
+    }
+    break;
+  }
+#endif
+
+  /*
+  **  PRAGMA [schema.]incremental_vacuum(N)
+  **
+  ** Do N steps of incremental vacuuming on a database.
+  */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  case PragTyp_INCREMENTAL_VACUUM: {
+    int iLimit = 0, addr;
+    if( zRight==0 || !sqlite3GetInt32(zRight, &iLimit) || iLimit<=0 ){
+      iLimit = 0x7fffffff;
+    }
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    sqlite3VdbeAddOp2(v, OP_Integer, iLimit, 1);
+    addr = sqlite3VdbeAddOp1(v, OP_IncrVacuum, iDb); VdbeCoverage(v);
+    sqlite3VdbeAddOp1(v, OP_ResultRow, 1);
+    sqlite3VdbeAddOp2(v, OP_AddImm, 1, -1);
+    sqlite3VdbeAddOp2(v, OP_IfPos, 1, addr); VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addr);
+    break;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+  /*
+  **  PRAGMA [schema.]cache_size
+  **  PRAGMA [schema.]cache_size=N
+  **
+  ** The first form reports the current local setting for the
+  ** page cache size. The second form sets the local
+  ** page cache size value.  If N is positive then that is the
+  ** number of pages in the cache.  If N is negative, then the
+  ** number of pages is adjusted so that the cache uses -N kibibytes
+  ** of memory.
+  */
+  case PragTyp_CACHE_SIZE: {
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( !zRight ){
+      returnSingleInt(v, pDb->pSchema->cache_size);
+    }else{
+      int size = sqlite3Atoi(zRight);
+      pDb->pSchema->cache_size = size;
+      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
+    }
+    break;
+  }
+
+  /*
+  **  PRAGMA [schema.]cache_spill
+  **  PRAGMA cache_spill=BOOLEAN
+  **  PRAGMA [schema.]cache_spill=N
+  **
+  ** The first form reports the current local setting for the
+  ** page cache spill size. The second form turns cache spill on
+  ** or off.  When turning cache spill on, the size is set to the
+  ** current cache_size.  The third form sets a spill size that
+  ** may be different form the cache size.
+  ** If N is positive then that is the
+  ** number of pages in the cache.  If N is negative, then the
+  ** number of pages is adjusted so that the cache uses -N kibibytes
+  ** of memory.
+  **
+  ** If the number of cache_spill pages is less then the number of
+  ** cache_size pages, no spilling occurs until the page count exceeds
+  ** the number of cache_size pages.
+  **
+  ** The cache_spill=BOOLEAN setting applies to all attached schemas,
+  ** not just the schema specified.
+  */
+  case PragTyp_CACHE_SPILL: {
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( !zRight ){
+      returnSingleInt(v,
+         (db->flags & SQLITE_CacheSpill)==0 ? 0 :
+            sqlite3BtreeSetSpillSize(pDb->pBt,0));
+    }else{
+      int size = 1;
+      if( sqlite3GetInt32(zRight, &size) ){
+        sqlite3BtreeSetSpillSize(pDb->pBt, size);
+      }
+      if( sqlite3GetBoolean(zRight, size!=0) ){
+        db->flags |= SQLITE_CacheSpill;
+      }else{
+        db->flags &= ~(u64)SQLITE_CacheSpill;
+      }
+      setAllPagerFlags(db);
+    }
+    break;
+  }
+
+  /*
+  **  PRAGMA [schema.]mmap_size(N)
+  **
+  ** Used to set mapping size limit. The mapping size limit is
+  ** used to limit the aggregate size of all memory mapped regions of the
+  ** database file. If this parameter is set to zero, then memory mapping
+  ** is not used at all.  If N is negative, then the default memory map
+  ** limit determined by sqlite3_config(SQLITE_CONFIG_MMAP_SIZE) is set.
+  ** The parameter N is measured in bytes.
+  **
+  ** This value is advisory.  The underlying VFS is free to memory map
+  ** as little or as much as it wants.  Except, if N is set to 0 then the
+  ** upper layers will never invoke the xFetch interfaces to the VFS.
+  */
+  case PragTyp_MMAP_SIZE: {
+    sqlite3_int64 sz;
+#if SQLITE_MAX_MMAP_SIZE>0
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( zRight ){
+      int ii;
+      sqlite3DecOrHexToI64(zRight, &sz);
+      if( sz<0 ) sz = sqlite3GlobalConfig.szMmap;
+      if( pId2->n==0 ) db->szMmap = sz;
+      for(ii=db->nDb-1; ii>=0; ii--){
+        if( db->aDb[ii].pBt && (ii==iDb || pId2->n==0) ){
+          sqlite3BtreeSetMmapLimit(db->aDb[ii].pBt, sz);
+        }
+      }
+    }
+    sz = -1;
+    rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_MMAP_SIZE, &sz);
+#else
+    sz = 0;
+    rc = SQLITE_OK;
+#endif
+    if( rc==SQLITE_OK ){
+      returnSingleInt(v, sz);
+    }else if( rc!=SQLITE_NOTFOUND ){
+      pParse->nErr++;
+      pParse->rc = rc;
+    }
+    break;
+  }
+
+  /*
+  **   PRAGMA temp_store
+  **   PRAGMA temp_store = "default"|"memory"|"file"
+  **
+  ** Return or set the local value of the temp_store flag.  Changing
+  ** the local value does not make changes to the disk file and the default
+  ** value will be restored the next time the database is opened.
+  **
+  ** Note that it is possible for the library compile-time options to
+  ** override this setting
+  */
+  case PragTyp_TEMP_STORE: {
+    if( !zRight ){
+      returnSingleInt(v, db->temp_store);
+    }else{
+      changeTempStorage(pParse, zRight);
+    }
+    break;
+  }
+
+  /*
+  **   PRAGMA temp_store_directory
+  **   PRAGMA temp_store_directory = ""|"directory_name"
+  **
+  ** Return or set the local value of the temp_store_directory flag.  Changing
+  ** the value sets a specific directory to be used for temporary files.
+  ** Setting to a null string reverts to the default temporary directory search.
+  ** If temporary directory is changed, then invalidateTempStorage.
+  **
+  */
+  case PragTyp_TEMP_STORE_DIRECTORY: {
+    sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+    if( !zRight ){
+      returnSingleText(v, sqlite3_temp_directory);
+    }else{
+#ifndef SQLITE_OMIT_WSD
+      if( zRight[0] ){
+        int res;
+        rc = sqlite3OsAccess(db->pVfs, zRight, SQLITE_ACCESS_READWRITE, &res);
+        if( rc!=SQLITE_OK || res==0 ){
+          sqlite3ErrorMsg(pParse, "not a writable directory");
+          sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+          goto pragma_out;
+        }
+      }
+      if( SQLITE_TEMP_STORE==0
+       || (SQLITE_TEMP_STORE==1 && db->temp_store<=1)
+       || (SQLITE_TEMP_STORE==2 && db->temp_store==1)
+      ){
+        invalidateTempStorage(pParse);
+      }
+      sqlite3_free(sqlite3_temp_directory);
+      if( zRight[0] ){
+        sqlite3_temp_directory = sqlite3_mprintf("%s", zRight);
+      }else{
+        sqlite3_temp_directory = 0;
+      }
+#endif /* SQLITE_OMIT_WSD */
+    }
+    sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+    break;
+  }
+
+#if SQLITE_OS_WIN
+  /*
+  **   PRAGMA data_store_directory
+  **   PRAGMA data_store_directory = ""|"directory_name"
+  **
+  ** Return or set the local value of the data_store_directory flag.  Changing
+  ** the value sets a specific directory to be used for database files that
+  ** were specified with a relative pathname.  Setting to a null string reverts
+  ** to the default database directory, which for database files specified with
+  ** a relative path will probably be based on the current directory for the
+  ** process.  Database file specified with an absolute path are not impacted
+  ** by this setting, regardless of its value.
+  **
+  */
+  case PragTyp_DATA_STORE_DIRECTORY: {
+    sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+    if( !zRight ){
+      returnSingleText(v, sqlite3_data_directory);
+    }else{
+#ifndef SQLITE_OMIT_WSD
+      if( zRight[0] ){
+        int res;
+        rc = sqlite3OsAccess(db->pVfs, zRight, SQLITE_ACCESS_READWRITE, &res);
+        if( rc!=SQLITE_OK || res==0 ){
+          sqlite3ErrorMsg(pParse, "not a writable directory");
+          sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+          goto pragma_out;
+        }
+      }
+      sqlite3_free(sqlite3_data_directory);
+      if( zRight[0] ){
+        sqlite3_data_directory = sqlite3_mprintf("%s", zRight);
+      }else{
+        sqlite3_data_directory = 0;
+      }
+#endif /* SQLITE_OMIT_WSD */
+    }
+    sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_TEMPDIR));
+    break;
+  }
+#endif
+
+#if SQLITE_ENABLE_LOCKING_STYLE
+  /*
+  **   PRAGMA [schema.]lock_proxy_file
+  **   PRAGMA [schema.]lock_proxy_file = ":auto:"|"lock_file_path"
+  **
+  ** Return or set the value of the lock_proxy_file flag.  Changing
+  ** the value sets a specific file to be used for database access locks.
+  **
+  */
+  case PragTyp_LOCK_PROXY_FILE: {
+    if( !zRight ){
+      Pager *pPager = sqlite3BtreePager(pDb->pBt);
+      char *proxy_file_path = NULL;
+      sqlite3_file *pFile = sqlite3PagerFile(pPager);
+      sqlite3OsFileControlHint(pFile, SQLITE_GET_LOCKPROXYFILE,
+                           &proxy_file_path);
+      returnSingleText(v, proxy_file_path);
+    }else{
+      Pager *pPager = sqlite3BtreePager(pDb->pBt);
+      sqlite3_file *pFile = sqlite3PagerFile(pPager);
+      int res;
+      if( zRight[0] ){
+        res=sqlite3OsFileControl(pFile, SQLITE_SET_LOCKPROXYFILE,
+                                     zRight);
+      } else {
+        res=sqlite3OsFileControl(pFile, SQLITE_SET_LOCKPROXYFILE,
+                                     NULL);
+      }
+      if( res!=SQLITE_OK ){
+        sqlite3ErrorMsg(pParse, "failed to set lock proxy file");
+        goto pragma_out;
+      }
+    }
+    break;
+  }
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */     
+   
+  /*
+  **   PRAGMA [schema.]synchronous
+  **   PRAGMA [schema.]synchronous=OFF|ON|NORMAL|FULL|EXTRA
+  **
+  ** Return or set the local value of the synchronous flag.  Changing
+  ** the local value does not make changes to the disk file and the
+  ** default value will be restored the next time the database is
+  ** opened.
+  */
+  case PragTyp_SYNCHRONOUS: {
+    if( !zRight ){
+      returnSingleInt(v, pDb->safety_level-1);
+    }else{
+      if( !db->autoCommit ){
+        sqlite3ErrorMsg(pParse,
+            "Safety level may not be changed inside a transaction");
+      }else if( iDb!=1 ){
+        int iLevel = (getSafetyLevel(zRight,0,1)+1) & PAGER_SYNCHRONOUS_MASK;
+        if( iLevel==0 ) iLevel = 1;
+        pDb->safety_level = iLevel;
+        pDb->bSyncSet = 1;
+        setAllPagerFlags(db);
+      }
+    }
+    break;
+  }
+#endif /* SQLITE_OMIT_PAGER_PRAGMAS */
+
+#ifndef SQLITE_OMIT_FLAG_PRAGMAS
+  case PragTyp_FLAG: {
+    if( zRight==0 ){
+      setPragmaResultColumnNames(v, pPragma);
+      returnSingleInt(v, (db->flags & pPragma->iArg)!=0 );
+    }else{
+      u64 mask = pPragma->iArg;    /* Mask of bits to set or clear. */
+      if( db->autoCommit==0 ){
+        /* Foreign key support may not be enabled or disabled while not
+        ** in auto-commit mode.  */
+        mask &= ~(SQLITE_ForeignKeys);
+      }
+#if SQLITE_USER_AUTHENTICATION
+      if( db->auth.authLevel==UAUTH_User ){
+        /* Do not allow non-admin users to modify the schema arbitrarily */
+        mask &= ~(SQLITE_WriteSchema);
+      }
+#endif
+
+      if( sqlite3GetBoolean(zRight, 0) ){
+        if( (mask & SQLITE_WriteSchema)==0
+         || (db->flags & SQLITE_Defensive)==0
+        ){
+          db->flags |= mask;
+        }
+      }else{
+        db->flags &= ~mask;
+        if( mask==SQLITE_DeferFKs ) db->nDeferredImmCons = 0;
+        if( (mask & SQLITE_WriteSchema)!=0
+         && sqlite3_stricmp(zRight, "reset")==0
+        ){
+          /* IMP: R-60817-01178 If the argument is "RESET" then schema
+          ** writing is disabled (as with "PRAGMA writable_schema=OFF") and,
+          ** in addition, the schema is reloaded. */
+          sqlite3ResetAllSchemasOfConnection(db);
+        }
+      }
+
+      /* Many of the flag-pragmas modify the code generated by the SQL
+      ** compiler (eg. count_changes). So add an opcode to expire all
+      ** compiled SQL statements after modifying a pragma value.
+      */
+      sqlite3VdbeAddOp0(v, OP_Expire);
+      setAllPagerFlags(db);
+    }
+    break;
+  }
+#endif /* SQLITE_OMIT_FLAG_PRAGMAS */
+
+#ifndef SQLITE_OMIT_SCHEMA_PRAGMAS
+  /*
+  **   PRAGMA table_info(<table>)
+  **
+  ** Return a single row for each column of the named table. The columns of
+  ** the returned data set are:
+  **
+  ** cid:        Column id (numbered from left to right, starting at 0)
+  ** name:       Column name
+  ** type:       Column declaration type.
+  ** notnull:    True if 'NOT NULL' is part of column declaration
+  ** dflt_value: The default value for the column, if any.
+  ** pk:         Non-zero for PK fields.
+  */
+  case PragTyp_TABLE_INFO: if( zRight ){
+    Table *pTab;
+    sqlite3CodeVerifyNamedSchema(pParse, zDb);
+    pTab = sqlite3LocateTable(pParse, LOCATE_NOERR, zRight, zDb);
+    if( pTab ){
+      int i, k;
+      int nHidden = 0;
+      Column *pCol;
+      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+      pParse->nMem = 7;
+      sqlite3ViewGetColumnNames(pParse, pTab);
+      for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
+        int isHidden = 0;
+        const Expr *pColExpr;
+        if( pCol->colFlags & COLFLAG_NOINSERT ){
+          if( pPragma->iArg==0 ){
+            nHidden++;
+            continue;
+          }
+          if( pCol->colFlags & COLFLAG_VIRTUAL ){
+            isHidden = 2;  /* GENERATED ALWAYS AS ... VIRTUAL */
+          }else if( pCol->colFlags & COLFLAG_STORED ){
+            isHidden = 3;  /* GENERATED ALWAYS AS ... STORED */
+          }else{ assert( pCol->colFlags & COLFLAG_HIDDEN );
+            isHidden = 1;  /* HIDDEN */
+          }
+        }
+        if( (pCol->colFlags & COLFLAG_PRIMKEY)==0 ){
+          k = 0;
+        }else if( pPk==0 ){
+          k = 1;
+        }else{
+          for(k=1; k<=pTab->nCol && pPk->aiColumn[k-1]!=i; k++){}
+        }
+        pColExpr = sqlite3ColumnExpr(pTab,pCol);
+        assert( pColExpr==0 || pColExpr->op==TK_SPAN || isHidden>=2 );
+        assert( pColExpr==0 || !ExprHasProperty(pColExpr, EP_IntValue)
+                  || isHidden>=2 );
+        sqlite3VdbeMultiLoad(v, 1, pPragma->iArg ? "issisii" : "issisi",
+               i-nHidden,
+               pCol->zCnName,
+               sqlite3ColumnType(pCol,""),
+               pCol->notNull ? 1 : 0,
+               (isHidden>=2 || pColExpr==0) ? 0 : pColExpr->u.zToken,
+               k,
+               isHidden);
+      }
+    }
+  }
+  break;
+
+  /*
+  **   PRAGMA table_list
+  **
+  ** Return a single row for each table, virtual table, or view in the
+  ** entire schema.
+  **
+  ** schema:     Name of attached database hold this table
+  ** name:       Name of the table itself
+  ** type:       "table", "view", "virtual", "shadow"
+  ** ncol:       Number of columns
+  ** wr:         True for a WITHOUT ROWID table
+  ** strict:     True for a STRICT table
+  */
+  case PragTyp_TABLE_LIST: {
+    int ii;
+    pParse->nMem = 6;
+    sqlite3CodeVerifyNamedSchema(pParse, zDb);
+    for(ii=0; ii<db->nDb; ii++){
+      HashElem *k;
+      Hash *pHash;
+      int initNCol;
+      if( zDb && sqlite3_stricmp(zDb, db->aDb[ii].zDbSName)!=0 ) continue;
+
+      /* Ensure that the Table.nCol field is initialized for all views
+      ** and virtual tables.  Each time we initialize a Table.nCol value
+      ** for a table, that can potentially disrupt the hash table, so restart
+      ** the initialization scan.
+      */
+      pHash = &db->aDb[ii].pSchema->tblHash;
+      initNCol = sqliteHashCount(pHash);
+      while( initNCol-- ){
+        for(k=sqliteHashFirst(pHash); 1; k=sqliteHashNext(k) ){
+          Table *pTab;
+          if( k==0 ){ initNCol = 0; break; }
+          pTab = sqliteHashData(k);
+          if( pTab->nCol==0 ){
+            char *zSql = sqlite3MPrintf(db, "SELECT*FROM\"%w\"", pTab->zName);
+            if( zSql ){
+              sqlite3_stmt *pDummy = 0;
+              (void)sqlite3_prepare(db, zSql, -1, &pDummy, 0);
+              (void)sqlite3_finalize(pDummy);
+              sqlite3DbFree(db, zSql);
+            }
+            if( db->mallocFailed ){
+              sqlite3ErrorMsg(db->pParse, "out of memory");
+              db->pParse->rc = SQLITE_NOMEM_BKPT;
+            }
+            pHash = &db->aDb[ii].pSchema->tblHash;
+            break;
+          }
+        }
+      }
+
+      for(k=sqliteHashFirst(pHash); k; k=sqliteHashNext(k) ){
+        Table *pTab = sqliteHashData(k);
+        const char *zType;
+        if( zRight && sqlite3_stricmp(zRight, pTab->zName)!=0 ) continue;
+        if( IsView(pTab) ){
+          zType = "view";
+        }else if( IsVirtual(pTab) ){
+          zType = "virtual";
+        }else if( pTab->tabFlags & TF_Shadow ){
+          zType = "shadow";
+        }else{
+          zType = "table";
+        }
+        sqlite3VdbeMultiLoad(v, 1, "sssiii",
+           db->aDb[ii].zDbSName,
+           sqlite3PreferredTableName(pTab->zName),
+           zType,
+           pTab->nCol,
+           (pTab->tabFlags & TF_WithoutRowid)!=0,
+           (pTab->tabFlags & TF_Strict)!=0
+        );
+      }
+    }
+  }
+  break;
+
+#ifdef SQLITE_DEBUG
+  case PragTyp_STATS: {
+    Index *pIdx;
+    HashElem *i;
+    pParse->nMem = 5;
+    sqlite3CodeVerifySchema(pParse, iDb);
+    for(i=sqliteHashFirst(&pDb->pSchema->tblHash); i; i=sqliteHashNext(i)){
+      Table *pTab = sqliteHashData(i);
+      sqlite3VdbeMultiLoad(v, 1, "ssiii",
+           sqlite3PreferredTableName(pTab->zName),
+           0,
+           pTab->szTabRow,
+           pTab->nRowLogEst,
+           pTab->tabFlags);
+      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+        sqlite3VdbeMultiLoad(v, 2, "siiiX",
+           pIdx->zName,
+           pIdx->szIdxRow,
+           pIdx->aiRowLogEst[0],
+           pIdx->hasStat1);
+        sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 5);
+      }
+    }
+  }
+  break;
+#endif
+
+  case PragTyp_INDEX_INFO: if( zRight ){
+    Index *pIdx;
+    Table *pTab;
+    pIdx = sqlite3FindIndex(db, zRight, zDb);
+    if( pIdx==0 ){
+      /* If there is no index named zRight, check to see if there is a
+      ** WITHOUT ROWID table named zRight, and if there is, show the
+      ** structure of the PRIMARY KEY index for that table. */
+      pTab = sqlite3LocateTable(pParse, LOCATE_NOERR, zRight, zDb);
+      if( pTab && !HasRowid(pTab) ){
+        pIdx = sqlite3PrimaryKeyIndex(pTab);
+      }
+    }
+    if( pIdx ){
+      int iIdxDb = sqlite3SchemaToIndex(db, pIdx->pSchema);
+      int i;
+      int mx;
+      if( pPragma->iArg ){
+        /* PRAGMA index_xinfo (newer version with more rows and columns) */
+        mx = pIdx->nColumn;
+        pParse->nMem = 6;
+      }else{
+        /* PRAGMA index_info (legacy version) */
+        mx = pIdx->nKeyCol;
+        pParse->nMem = 3;
+      }
+      pTab = pIdx->pTable;
+      sqlite3CodeVerifySchema(pParse, iIdxDb);
+      assert( pParse->nMem<=pPragma->nPragCName );
+      for(i=0; i<mx; i++){
+        i16 cnum = pIdx->aiColumn[i];
+        sqlite3VdbeMultiLoad(v, 1, "iisX", i, cnum,
+                             cnum<0 ? 0 : pTab->aCol[cnum].zCnName);
+        if( pPragma->iArg ){
+          sqlite3VdbeMultiLoad(v, 4, "isiX",
+            pIdx->aSortOrder[i],
+            pIdx->azColl[i],
+            i<pIdx->nKeyCol);
+        }
+        sqlite3VdbeAddOp2(v, OP_ResultRow, 1, pParse->nMem);
+      }
+    }
+  }
+  break;
+
+  case PragTyp_INDEX_LIST: if( zRight ){
+    Index *pIdx;
+    Table *pTab;
+    int i;
+    pTab = sqlite3FindTable(db, zRight, zDb);
+    if( pTab ){
+      int iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+      pParse->nMem = 5;
+      sqlite3CodeVerifySchema(pParse, iTabDb);
+      for(pIdx=pTab->pIndex, i=0; pIdx; pIdx=pIdx->pNext, i++){
+        const char *azOrigin[] = { "c", "u", "pk" };
+        sqlite3VdbeMultiLoad(v, 1, "isisi",
+           i,
+           pIdx->zName,
+           IsUniqueIndex(pIdx),
+           azOrigin[pIdx->idxType],
+           pIdx->pPartIdxWhere!=0);
+      }
+    }
+  }
+  break;
+
+  case PragTyp_DATABASE_LIST: {
+    int i;
+    pParse->nMem = 3;
+    for(i=0; i<db->nDb; i++){
+      if( db->aDb[i].pBt==0 ) continue;
+      assert( db->aDb[i].zDbSName!=0 );
+      sqlite3VdbeMultiLoad(v, 1, "iss",
+         i,
+         db->aDb[i].zDbSName,
+         sqlite3BtreeGetFilename(db->aDb[i].pBt));
+    }
+  }
+  break;
+
+  case PragTyp_COLLATION_LIST: {
+    int i = 0;
+    HashElem *p;
+    pParse->nMem = 2;
+    for(p=sqliteHashFirst(&db->aCollSeq); p; p=sqliteHashNext(p)){
+      CollSeq *pColl = (CollSeq *)sqliteHashData(p);
+      sqlite3VdbeMultiLoad(v, 1, "is", i++, pColl->zName);
+    }
+  }
+  break;
+
+#ifndef SQLITE_OMIT_INTROSPECTION_PRAGMAS
+  case PragTyp_FUNCTION_LIST: {
+    int i;
+    HashElem *j;
+    FuncDef *p;
+    int showInternFunc = (db->mDbFlags & DBFLAG_InternalFunc)!=0;
+    pParse->nMem = 6;
+    for(i=0; i<SQLITE_FUNC_HASH_SZ; i++){
+      for(p=sqlite3BuiltinFunctions.a[i]; p; p=p->u.pHash ){
+        assert( p->funcFlags & SQLITE_FUNC_BUILTIN );
+        pragmaFunclistLine(v, p, 1, showInternFunc);
+      }
+    }
+    for(j=sqliteHashFirst(&db->aFunc); j; j=sqliteHashNext(j)){
+      p = (FuncDef*)sqliteHashData(j);
+      assert( (p->funcFlags & SQLITE_FUNC_BUILTIN)==0 );
+      pragmaFunclistLine(v, p, 0, showInternFunc);
+    }
+  }
+  break;
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  case PragTyp_MODULE_LIST: {
+    HashElem *j;
+    pParse->nMem = 1;
+    for(j=sqliteHashFirst(&db->aModule); j; j=sqliteHashNext(j)){
+      Module *pMod = (Module*)sqliteHashData(j);
+      sqlite3VdbeMultiLoad(v, 1, "s", pMod->zName);
+    }
+  }
+  break;
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+  case PragTyp_PRAGMA_LIST: {
+    int i;
+    for(i=0; i<ArraySize(aPragmaName); i++){
+      sqlite3VdbeMultiLoad(v, 1, "s", aPragmaName[i].zName);
+    }
+  }
+  break;
+#endif /* SQLITE_INTROSPECTION_PRAGMAS */
+
+#endif /* SQLITE_OMIT_SCHEMA_PRAGMAS */
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  case PragTyp_FOREIGN_KEY_LIST: if( zRight ){
+    FKey *pFK;
+    Table *pTab;
+    pTab = sqlite3FindTable(db, zRight, zDb);
+    if( pTab && IsOrdinaryTable(pTab) ){
+      pFK = pTab->u.tab.pFKey;
+      if( pFK ){
+        int iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+        int i = 0;
+        pParse->nMem = 8;
+        sqlite3CodeVerifySchema(pParse, iTabDb);
+        while(pFK){
+          int j;
+          for(j=0; j<pFK->nCol; j++){
+            sqlite3VdbeMultiLoad(v, 1, "iissssss",
+                   i,
+                   j,
+                   pFK->zTo,
+                   pTab->aCol[pFK->aCol[j].iFrom].zCnName,
+                   pFK->aCol[j].zCol,
+                   actionName(pFK->aAction[1]),  /* ON UPDATE */
+                   actionName(pFK->aAction[0]),  /* ON DELETE */
+                   "NONE");
+          }
+          ++i;
+          pFK = pFK->pNextFrom;
+        }
+      }
+    }
+  }
+  break;
+#endif /* !defined(SQLITE_OMIT_FOREIGN_KEY) */
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+#ifndef SQLITE_OMIT_TRIGGER
+  case PragTyp_FOREIGN_KEY_CHECK: {
+    FKey *pFK;             /* A foreign key constraint */
+    Table *pTab;           /* Child table contain "REFERENCES" keyword */
+    Table *pParent;        /* Parent table that child points to */
+    Index *pIdx;           /* Index in the parent table */
+    int i;                 /* Loop counter:  Foreign key number for pTab */
+    int j;                 /* Loop counter:  Field of the foreign key */
+    HashElem *k;           /* Loop counter:  Next table in schema */
+    int x;                 /* result variable */
+    int regResult;         /* 3 registers to hold a result row */
+    int regRow;            /* Registers to hold a row from pTab */
+    int addrTop;           /* Top of a loop checking foreign keys */
+    int addrOk;            /* Jump here if the key is OK */
+    int *aiCols;           /* child to parent column mapping */
+
+    regResult = pParse->nMem+1;
+    pParse->nMem += 4;
+    regRow = ++pParse->nMem;
+    k = sqliteHashFirst(&db->aDb[iDb].pSchema->tblHash);
+    while( k ){
+      if( zRight ){
+        pTab = sqlite3LocateTable(pParse, 0, zRight, zDb);
+        k = 0;
+      }else{
+        pTab = (Table*)sqliteHashData(k);
+        k = sqliteHashNext(k);
+      }
+      if( pTab==0 || !IsOrdinaryTable(pTab) || pTab->u.tab.pFKey==0 ) continue;
+      iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+      zDb = db->aDb[iDb].zDbSName;
+      sqlite3CodeVerifySchema(pParse, iDb);
+      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+      sqlite3TouchRegister(pParse, pTab->nCol+regRow);
+      sqlite3OpenTable(pParse, 0, iDb, pTab, OP_OpenRead);
+      sqlite3VdbeLoadString(v, regResult, pTab->zName);
+      assert( IsOrdinaryTable(pTab) );
+      for(i=1, pFK=pTab->u.tab.pFKey; pFK; i++, pFK=pFK->pNextFrom){
+        pParent = sqlite3FindTable(db, pFK->zTo, zDb);
+        if( pParent==0 ) continue;
+        pIdx = 0;
+        sqlite3TableLock(pParse, iDb, pParent->tnum, 0, pParent->zName);
+        x = sqlite3FkLocateIndex(pParse, pParent, pFK, &pIdx, 0);
+        if( x==0 ){
+          if( pIdx==0 ){
+            sqlite3OpenTable(pParse, i, iDb, pParent, OP_OpenRead);
+          }else{
+            sqlite3VdbeAddOp3(v, OP_OpenRead, i, pIdx->tnum, iDb);
+            sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
+          }
+        }else{
+          k = 0;
+          break;
+        }
+      }
+      assert( pParse->nErr>0 || pFK==0 );
+      if( pFK ) break;
+      if( pParse->nTab<i ) pParse->nTab = i;
+      addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, 0); VdbeCoverage(v);
+      assert( IsOrdinaryTable(pTab) );
+      for(i=1, pFK=pTab->u.tab.pFKey; pFK; i++, pFK=pFK->pNextFrom){
+        pParent = sqlite3FindTable(db, pFK->zTo, zDb);
+        pIdx = 0;
+        aiCols = 0;
+        if( pParent ){
+          x = sqlite3FkLocateIndex(pParse, pParent, pFK, &pIdx, &aiCols);
+          assert( x==0 || db->mallocFailed );
+        }
+        addrOk = sqlite3VdbeMakeLabel(pParse);
+
+        /* Generate code to read the child key values into registers
+        ** regRow..regRow+n. If any of the child key values are NULL, this
+        ** row cannot cause an FK violation. Jump directly to addrOk in
+        ** this case. */
+        sqlite3TouchRegister(pParse, regRow + pFK->nCol);
+        for(j=0; j<pFK->nCol; j++){
+          int iCol = aiCols ? aiCols[j] : pFK->aCol[j].iFrom;
+          sqlite3ExprCodeGetColumnOfTable(v, pTab, 0, iCol, regRow+j);
+          sqlite3VdbeAddOp2(v, OP_IsNull, regRow+j, addrOk); VdbeCoverage(v);
+        }
+
+        /* Generate code to query the parent index for a matching parent
+        ** key. If a match is found, jump to addrOk. */
+        if( pIdx ){
+          sqlite3VdbeAddOp4(v, OP_Affinity, regRow, pFK->nCol, 0,
+              sqlite3IndexAffinityStr(db,pIdx), pFK->nCol);
+          sqlite3VdbeAddOp4Int(v, OP_Found, i, addrOk, regRow, pFK->nCol);
+          VdbeCoverage(v);
+        }else if( pParent ){
+          int jmp = sqlite3VdbeCurrentAddr(v)+2;
+          sqlite3VdbeAddOp3(v, OP_SeekRowid, i, jmp, regRow); VdbeCoverage(v);
+          sqlite3VdbeGoto(v, addrOk);
+          assert( pFK->nCol==1 || db->mallocFailed );
+        }
+
+        /* Generate code to report an FK violation to the caller. */
+        if( HasRowid(pTab) ){
+          sqlite3VdbeAddOp2(v, OP_Rowid, 0, regResult+1);
+        }else{
+          sqlite3VdbeAddOp2(v, OP_Null, 0, regResult+1);
+        }
+        sqlite3VdbeMultiLoad(v, regResult+2, "siX", pFK->zTo, i-1);
+        sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, 4);
+        sqlite3VdbeResolveLabel(v, addrOk);
+        sqlite3DbFree(db, aiCols);
+      }
+      sqlite3VdbeAddOp2(v, OP_Next, 0, addrTop+1); VdbeCoverage(v);
+      sqlite3VdbeJumpHere(v, addrTop);
+    }
+  }
+  break;
+#endif /* !defined(SQLITE_OMIT_TRIGGER) */
+#endif /* !defined(SQLITE_OMIT_FOREIGN_KEY) */
+
+#ifndef SQLITE_OMIT_CASE_SENSITIVE_LIKE_PRAGMA
+  /* Reinstall the LIKE and GLOB functions.  The variant of LIKE
+  ** used will be case sensitive or not depending on the RHS.
+  */
+  case PragTyp_CASE_SENSITIVE_LIKE: {
+    if( zRight ){
+      sqlite3RegisterLikeFunctions(db, sqlite3GetBoolean(zRight, 0));
+    }
+  }
+  break;
+#endif /* SQLITE_OMIT_CASE_SENSITIVE_LIKE_PRAGMA */
+
+#ifndef SQLITE_INTEGRITY_CHECK_ERROR_MAX
+# define SQLITE_INTEGRITY_CHECK_ERROR_MAX 100
+#endif
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+  /*    PRAGMA integrity_check
+  **    PRAGMA integrity_check(N)
+  **    PRAGMA quick_check
+  **    PRAGMA quick_check(N)
+  **
+  ** Verify the integrity of the database.
+  **
+  ** The "quick_check" is reduced version of
+  ** integrity_check designed to detect most database corruption
+  ** without the overhead of cross-checking indexes.  Quick_check
+  ** is linear time whereas integrity_check is O(NlogN).
+  **
+  ** The maximum number of errors is 100 by default.  A different default
+  ** can be specified using a numeric parameter N.
+  **
+  ** Or, the parameter N can be the name of a table.  In that case, only
+  ** the one table named is verified.  The freelist is only verified if
+  ** the named table is "sqlite_schema" (or one of its aliases).
+  **
+  ** All schemas are checked by default.  To check just a single
+  ** schema, use the form:
+  **
+  **      PRAGMA schema.integrity_check;
+  */
+  case PragTyp_INTEGRITY_CHECK: {
+    int i, j, addr, mxErr;
+    Table *pObjTab = 0;     /* Check only this one table, if not NULL */
+
+    int isQuick = (sqlite3Tolower(zLeft[0])=='q');
+
+    /* If the PRAGMA command was of the form "PRAGMA <db>.integrity_check",
+    ** then iDb is set to the index of the database identified by <db>.
+    ** In this case, the integrity of database iDb only is verified by
+    ** the VDBE created below.
+    **
+    ** Otherwise, if the command was simply "PRAGMA integrity_check" (or
+    ** "PRAGMA quick_check"), then iDb is set to 0. In this case, set iDb
+    ** to -1 here, to indicate that the VDBE should verify the integrity
+    ** of all attached databases.  */
+    assert( iDb>=0 );
+    assert( iDb==0 || pId2->z );
+    if( pId2->z==0 ) iDb = -1;
+
+    /* Initialize the VDBE program */
+    pParse->nMem = 6;
+
+    /* Set the maximum error count */
+    mxErr = SQLITE_INTEGRITY_CHECK_ERROR_MAX;
+    if( zRight ){
+      if( sqlite3GetInt32(zRight, &mxErr) ){
+        if( mxErr<=0 ){
+          mxErr = SQLITE_INTEGRITY_CHECK_ERROR_MAX;
+        }
+      }else{
+        pObjTab = sqlite3LocateTable(pParse, 0, zRight,
+                      iDb>=0 ? db->aDb[iDb].zDbSName : 0);
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_Integer, mxErr-1, 1); /* reg[1] holds errors left */
+
+    /* Do an integrity check on each database file */
+    for(i=0; i<db->nDb; i++){
+      HashElem *x;     /* For looping over tables in the schema */
+      Hash *pTbls;     /* Set of all tables in the schema */
+      int *aRoot;      /* Array of root page numbers of all btrees */
+      int cnt = 0;     /* Number of entries in aRoot[] */
+      int mxIdx = 0;   /* Maximum number of indexes for any table */
+
+      if( OMIT_TEMPDB && i==1 ) continue;
+      if( iDb>=0 && i!=iDb ) continue;
+
+      sqlite3CodeVerifySchema(pParse, i);
+      pParse->okConstFactor = 0;  /* tag-20230327-1 */
+
+      /* Do an integrity check of the B-Tree
+      **
+      ** Begin by finding the root pages numbers
+      ** for all tables and indices in the database.
+      */
+      assert( sqlite3SchemaMutexHeld(db, i, 0) );
+      pTbls = &db->aDb[i].pSchema->tblHash;
+      for(cnt=0, x=sqliteHashFirst(pTbls); x; x=sqliteHashNext(x)){
+        Table *pTab = sqliteHashData(x);  /* Current table */
+        Index *pIdx;                      /* An index on pTab */
+        int nIdx;                         /* Number of indexes on pTab */
+        if( pObjTab && pObjTab!=pTab ) continue;
+        if( HasRowid(pTab) ) cnt++;
+        for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){ cnt++; }
+        if( nIdx>mxIdx ) mxIdx = nIdx;
+      }
+      if( cnt==0 ) continue;
+      if( pObjTab ) cnt++;
+      aRoot = sqlite3DbMallocRawNN(db, sizeof(int)*(cnt+1));
+      if( aRoot==0 ) break;
+      cnt = 0;
+      if( pObjTab ) aRoot[++cnt] = 0;
+      for(x=sqliteHashFirst(pTbls); x; x=sqliteHashNext(x)){
+        Table *pTab = sqliteHashData(x);
+        Index *pIdx;
+        if( pObjTab && pObjTab!=pTab ) continue;
+        if( HasRowid(pTab) ) aRoot[++cnt] = pTab->tnum;
+        for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+          aRoot[++cnt] = pIdx->tnum;
+        }
+      }
+      aRoot[0] = cnt;
+
+      /* Make sure sufficient number of registers have been allocated */
+      sqlite3TouchRegister(pParse, 8+mxIdx);
+      sqlite3ClearTempRegCache(pParse);
+
+      /* Do the b-tree integrity checks */
+      sqlite3VdbeAddOp4(v, OP_IntegrityCk, 2, cnt, 1, (char*)aRoot,P4_INTARRAY);
+      sqlite3VdbeChangeP5(v, (u8)i);
+      addr = sqlite3VdbeAddOp1(v, OP_IsNull, 2); VdbeCoverage(v);
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0,
+         sqlite3MPrintf(db, "*** in database %s ***\n", db->aDb[i].zDbSName),
+         P4_DYNAMIC);
+      sqlite3VdbeAddOp3(v, OP_Concat, 2, 3, 3);
+      integrityCheckResultRow(v);
+      sqlite3VdbeJumpHere(v, addr);
+
+      /* Make sure all the indices are constructed correctly.
+      */
+      for(x=sqliteHashFirst(pTbls); x; x=sqliteHashNext(x)){
+        Table *pTab = sqliteHashData(x);
+        Index *pIdx, *pPk;
+        Index *pPrior = 0;      /* Previous index */
+        int loopTop;
+        int iDataCur, iIdxCur;
+        int r1 = -1;
+        int bStrict;            /* True for a STRICT table */
+        int r2;                 /* Previous key for WITHOUT ROWID tables */
+        int mxCol;              /* Maximum non-virtual column number */
+
+        if( pObjTab && pObjTab!=pTab ) continue;
+        if( !IsOrdinaryTable(pTab) ){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+          sqlite3_vtab *pVTab;
+          int a1;
+          if( !IsVirtual(pTab) ) continue;
+          if( pTab->nCol<=0 ){
+            const char *zMod = pTab->u.vtab.azArg[0];
+            if( sqlite3HashFind(&db->aModule, zMod)==0 ) continue;
+          }
+          sqlite3ViewGetColumnNames(pParse, pTab);
+          if( pTab->u.vtab.p==0 ) continue;
+          pVTab = pTab->u.vtab.p->pVtab;
+          if( NEVER(pVTab==0) ) continue;
+          if( NEVER(pVTab->pModule==0) ) continue;
+          if( pVTab->pModule->iVersion<4 ) continue;
+          if( pVTab->pModule->xIntegrity==0 ) continue;
+          sqlite3VdbeAddOp3(v, OP_VCheck, i, 3, isQuick);
+          pTab->nTabRef++;
+          sqlite3VdbeAppendP4(v, pTab, P4_TABLEREF);
+          a1 = sqlite3VdbeAddOp1(v, OP_IsNull, 3); VdbeCoverage(v);
+          integrityCheckResultRow(v);
+          sqlite3VdbeJumpHere(v, a1);
+#endif
+          continue;
+        }
+        if( isQuick || HasRowid(pTab) ){
+          pPk = 0;
+          r2 = 0;
+        }else{
+          pPk = sqlite3PrimaryKeyIndex(pTab);
+          r2 = sqlite3GetTempRange(pParse, pPk->nKeyCol);
+          sqlite3VdbeAddOp3(v, OP_Null, 1, r2, r2+pPk->nKeyCol-1);
+        }
+        sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenRead, 0,
+                                   1, 0, &iDataCur, &iIdxCur);
+        /* reg[7] counts the number of entries in the table.
+        ** reg[8+i] counts the number of entries in the i-th index
+        */
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, 7);
+        for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+          sqlite3VdbeAddOp2(v, OP_Integer, 0, 8+j); /* index entries counter */
+        }
+        assert( pParse->nMem>=8+j );
+        assert( sqlite3NoTempsInRange(pParse,1,7+j) );
+        sqlite3VdbeAddOp2(v, OP_Rewind, iDataCur, 0); VdbeCoverage(v);
+        loopTop = sqlite3VdbeAddOp2(v, OP_AddImm, 7, 1);
+
+        /* Fetch the right-most column from the table.  This will cause
+        ** the entire record header to be parsed and sanity checked.  It
+        ** will also prepopulate the cursor column cache that is used
+        ** by the OP_IsType code, so it is a required step.
+        */
+        assert( !IsVirtual(pTab) );
+        if( HasRowid(pTab) ){
+          mxCol = -1;
+          for(j=0; j<pTab->nCol; j++){
+            if( (pTab->aCol[j].colFlags & COLFLAG_VIRTUAL)==0 ) mxCol++;
+          }
+          if( mxCol==pTab->iPKey ) mxCol--;
+        }else{
+          /* COLFLAG_VIRTUAL columns are not included in the WITHOUT ROWID
+          ** PK index column-count, so there is no need to account for them
+          ** in this case. */
+          mxCol = sqlite3PrimaryKeyIndex(pTab)->nColumn-1;
+        }
+        if( mxCol>=0 ){
+          sqlite3VdbeAddOp3(v, OP_Column, iDataCur, mxCol, 3);
+          sqlite3VdbeTypeofColumn(v, 3);
+        }
+
+        if( !isQuick ){
+          if( pPk ){
+            /* Verify WITHOUT ROWID keys are in ascending order */
+            int a1;
+            char *zErr;
+            a1 = sqlite3VdbeAddOp4Int(v, OP_IdxGT, iDataCur, 0,r2,pPk->nKeyCol);
+            VdbeCoverage(v);
+            sqlite3VdbeAddOp1(v, OP_IsNull, r2); VdbeCoverage(v);
+            zErr = sqlite3MPrintf(db,
+                   "row not in PRIMARY KEY order for %s",
+                    pTab->zName);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, zErr, P4_DYNAMIC);
+            integrityCheckResultRow(v);
+            sqlite3VdbeJumpHere(v, a1);
+            sqlite3VdbeJumpHere(v, a1+1);
+            for(j=0; j<pPk->nKeyCol; j++){
+              sqlite3ExprCodeLoadIndexColumn(pParse, pPk, iDataCur, j, r2+j);
+            }
+          }
+        }
+        /* Verify datatypes for all columns:
+        **
+        **   (1) NOT NULL columns may not contain a NULL
+        **   (2) Datatype must be exact for non-ANY columns in STRICT tables
+        **   (3) Datatype for TEXT columns in non-STRICT tables must be
+        **       NULL, TEXT, or BLOB.
+        **   (4) Datatype for numeric columns in non-STRICT tables must not
+        **       be a TEXT value that can be losslessly converted to numeric.
+        */
+        bStrict = (pTab->tabFlags & TF_Strict)!=0;
+        for(j=0; j<pTab->nCol; j++){
+          char *zErr;
+          Column *pCol = pTab->aCol + j;  /* The column to be checked */
+          int labelError;               /* Jump here to report an error */
+          int labelOk;                  /* Jump here if all looks ok */
+          int p1, p3, p4;               /* Operands to the OP_IsType opcode */
+          int doTypeCheck;              /* Check datatypes (besides NOT NULL) */
+
+          if( j==pTab->iPKey ) continue;
+          if( bStrict ){
+            doTypeCheck = pCol->eCType>COLTYPE_ANY;
+          }else{
+            doTypeCheck = pCol->affinity>SQLITE_AFF_BLOB;
+          }
+          if( pCol->notNull==0 && !doTypeCheck ) continue;
+
+          /* Compute the operands that will be needed for OP_IsType */
+          p4 = SQLITE_NULL;
+          if( pCol->colFlags & COLFLAG_VIRTUAL ){
+            sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, j, 3);
+            p1 = -1;
+            p3 = 3;
+          }else{
+            if( pCol->iDflt ){
+              sqlite3_value *pDfltValue = 0;
+              sqlite3ValueFromExpr(db, sqlite3ColumnExpr(pTab,pCol), ENC(db),
+                                   pCol->affinity, &pDfltValue);
+              if( pDfltValue ){
+                p4 = sqlite3_value_type(pDfltValue);
+                sqlite3ValueFree(pDfltValue);
+              }
+            }
+            p1 = iDataCur;
+            if( !HasRowid(pTab) ){
+              testcase( j!=sqlite3TableColumnToStorage(pTab, j) );
+              p3 = sqlite3TableColumnToIndex(sqlite3PrimaryKeyIndex(pTab), j);
+            }else{
+              p3 = sqlite3TableColumnToStorage(pTab,j);
+              testcase( p3!=j);
+            }
+          }
+
+          labelError = sqlite3VdbeMakeLabel(pParse);
+          labelOk = sqlite3VdbeMakeLabel(pParse);
+          if( pCol->notNull ){
+            /* (1) NOT NULL columns may not contain a NULL */
+            int jmp3;
+            int jmp2 = sqlite3VdbeAddOp4Int(v, OP_IsType, p1, labelOk, p3, p4);
+            VdbeCoverage(v);
+            if( p1<0 ){
+              sqlite3VdbeChangeP5(v, 0x0f); /* INT, REAL, TEXT, or BLOB */
+              jmp3 = jmp2;
+            }else{
+              sqlite3VdbeChangeP5(v, 0x0d); /* INT, TEXT, or BLOB */
+              /* OP_IsType does not detect NaN values in the database file
+              ** which should be treated as a NULL.  So if the header type
+              ** is REAL, we have to load the actual data using OP_Column
+              ** to reliably determine if the value is a NULL. */
+              sqlite3VdbeAddOp3(v, OP_Column, p1, p3, 3);
+              jmp3 = sqlite3VdbeAddOp2(v, OP_NotNull, 3, labelOk);
+              VdbeCoverage(v);
+            }           
+            zErr = sqlite3MPrintf(db, "NULL value in %s.%s", pTab->zName,
+                                pCol->zCnName);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, zErr, P4_DYNAMIC);
+            if( doTypeCheck ){
+              sqlite3VdbeGoto(v, labelError);
+              sqlite3VdbeJumpHere(v, jmp2);
+              sqlite3VdbeJumpHere(v, jmp3);
+            }else{
+              /* VDBE byte code will fall thru */
+            }
+          }
+          if( bStrict && doTypeCheck ){
+            /* (2) Datatype must be exact for non-ANY columns in STRICT tables*/
+            static unsigned char aStdTypeMask[] = {
+               0x1f,    /* ANY */
+               0x18,    /* BLOB */
+               0x11,    /* INT */
+               0x11,    /* INTEGER */
+               0x13,    /* REAL */
+               0x14     /* TEXT */
+            };
+            sqlite3VdbeAddOp4Int(v, OP_IsType, p1, labelOk, p3, p4);
+            assert( pCol->eCType>=1 && pCol->eCType<=sizeof(aStdTypeMask) );
+            sqlite3VdbeChangeP5(v, aStdTypeMask[pCol->eCType-1]);
+            VdbeCoverage(v);
+            zErr = sqlite3MPrintf(db, "non-%s value in %s.%s",
+                                  sqlite3StdType[pCol->eCType-1],
+                                  pTab->zName, pTab->aCol[j].zCnName);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, zErr, P4_DYNAMIC);
+          }else if( !bStrict && pCol->affinity==SQLITE_AFF_TEXT ){
+            /* (3) Datatype for TEXT columns in non-STRICT tables must be
+            **     NULL, TEXT, or BLOB. */
+            sqlite3VdbeAddOp4Int(v, OP_IsType, p1, labelOk, p3, p4);
+            sqlite3VdbeChangeP5(v, 0x1c); /* NULL, TEXT, or BLOB */
+            VdbeCoverage(v);
+            zErr = sqlite3MPrintf(db, "NUMERIC value in %s.%s",
+                                  pTab->zName, pTab->aCol[j].zCnName);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, zErr, P4_DYNAMIC);
+          }else if( !bStrict && pCol->affinity>=SQLITE_AFF_NUMERIC ){
+            /* (4) Datatype for numeric columns in non-STRICT tables must not
+            **     be a TEXT value that can be converted to numeric. */
+            sqlite3VdbeAddOp4Int(v, OP_IsType, p1, labelOk, p3, p4);
+            sqlite3VdbeChangeP5(v, 0x1b); /* NULL, INT, FLOAT, or BLOB */
+            VdbeCoverage(v);
+            if( p1>=0 ){
+              sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, j, 3);
+            }
+            sqlite3VdbeAddOp4(v, OP_Affinity, 3, 1, 0, "C", P4_STATIC);
+            sqlite3VdbeAddOp4Int(v, OP_IsType, -1, labelOk, 3, p4);
+            sqlite3VdbeChangeP5(v, 0x1c); /* NULL, TEXT, or BLOB */
+            VdbeCoverage(v);
+            zErr = sqlite3MPrintf(db, "TEXT value in %s.%s",
+                                  pTab->zName, pTab->aCol[j].zCnName);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, zErr, P4_DYNAMIC);
+          }
+          sqlite3VdbeResolveLabel(v, labelError);
+          integrityCheckResultRow(v);
+          sqlite3VdbeResolveLabel(v, labelOk);
+        }
+        /* Verify CHECK constraints */
+        if( pTab->pCheck && (db->flags & SQLITE_IgnoreChecks)==0 ){
+          ExprList *pCheck = sqlite3ExprListDup(db, pTab->pCheck, 0);
+          if( db->mallocFailed==0 ){
+            int addrCkFault = sqlite3VdbeMakeLabel(pParse);
+            int addrCkOk = sqlite3VdbeMakeLabel(pParse);
+            char *zErr;
+            int k;
+            pParse->iSelfTab = iDataCur + 1;
+            for(k=pCheck->nExpr-1; k>0; k--){
+              sqlite3ExprIfFalse(pParse, pCheck->a[k].pExpr, addrCkFault, 0);
+            }
+            sqlite3ExprIfTrue(pParse, pCheck->a[0].pExpr, addrCkOk,
+                SQLITE_JUMPIFNULL);
+            sqlite3VdbeResolveLabel(v, addrCkFault);
+            pParse->iSelfTab = 0;
+            zErr = sqlite3MPrintf(db, "CHECK constraint failed in %s",
+                pTab->zName);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, zErr, P4_DYNAMIC);
+            integrityCheckResultRow(v);
+            sqlite3VdbeResolveLabel(v, addrCkOk);
+          }
+          sqlite3ExprListDelete(db, pCheck);
+        }
+        if( !isQuick ){ /* Omit the remaining tests for quick_check */
+          /* Validate index entries for the current row */
+          for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+            int jmp2, jmp3, jmp4, jmp5, label6;
+            int kk;
+            int ckUniq = sqlite3VdbeMakeLabel(pParse);
+            if( pPk==pIdx ) continue;
+            r1 = sqlite3GenerateIndexKey(pParse, pIdx, iDataCur, 0, 0, &jmp3,
+                                         pPrior, r1);
+            pPrior = pIdx;
+            sqlite3VdbeAddOp2(v, OP_AddImm, 8+j, 1);/* increment entry count */
+            /* Verify that an index entry exists for the current table row */
+            jmp2 = sqlite3VdbeAddOp4Int(v, OP_Found, iIdxCur+j, ckUniq, r1,
+                                        pIdx->nColumn); VdbeCoverage(v);
+            sqlite3VdbeLoadString(v, 3, "row ");
+            sqlite3VdbeAddOp3(v, OP_Concat, 7, 3, 3);
+            sqlite3VdbeLoadString(v, 4, " missing from index ");
+            sqlite3VdbeAddOp3(v, OP_Concat, 4, 3, 3);
+            jmp5 = sqlite3VdbeLoadString(v, 4, pIdx->zName);
+            sqlite3VdbeAddOp3(v, OP_Concat, 4, 3, 3);
+            jmp4 = integrityCheckResultRow(v);
+            sqlite3VdbeJumpHere(v, jmp2);
+
+            /* The OP_IdxRowid opcode is an optimized version of OP_Column
+            ** that extracts the rowid off the end of the index record.
+            ** But it only works correctly if index record does not have
+            ** any extra bytes at the end.  Verify that this is the case. */
+            if( HasRowid(pTab) ){
+              int jmp7;
+              sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur+j, 3);
+              jmp7 = sqlite3VdbeAddOp3(v, OP_Eq, 3, 0, r1+pIdx->nColumn-1);
+              VdbeCoverageNeverNull(v);
+              sqlite3VdbeLoadString(v, 3,
+                 "rowid not at end-of-record for row ");
+              sqlite3VdbeAddOp3(v, OP_Concat, 7, 3, 3);
+              sqlite3VdbeLoadString(v, 4, " of index ");
+              sqlite3VdbeGoto(v, jmp5-1);
+              sqlite3VdbeJumpHere(v, jmp7);
+            }
+
+            /* Any indexed columns with non-BINARY collations must still hold
+            ** the exact same text value as the table. */
+            label6 = 0;
+            for(kk=0; kk<pIdx->nKeyCol; kk++){
+              if( pIdx->azColl[kk]==sqlite3StrBINARY ) continue;
+              if( label6==0 ) label6 = sqlite3VdbeMakeLabel(pParse);
+              sqlite3VdbeAddOp3(v, OP_Column, iIdxCur+j, kk, 3);
+              sqlite3VdbeAddOp3(v, OP_Ne, 3, label6, r1+kk); VdbeCoverage(v);
+            }
+            if( label6 ){
+              int jmp6 = sqlite3VdbeAddOp0(v, OP_Goto);
+              sqlite3VdbeResolveLabel(v, label6);
+              sqlite3VdbeLoadString(v, 3, "row ");
+              sqlite3VdbeAddOp3(v, OP_Concat, 7, 3, 3);
+              sqlite3VdbeLoadString(v, 4, " values differ from index ");
+              sqlite3VdbeGoto(v, jmp5-1);
+              sqlite3VdbeJumpHere(v, jmp6);
+            }
+             
+            /* For UNIQUE indexes, verify that only one entry exists with the
+            ** current key.  The entry is unique if (1) any column is NULL
+            ** or (2) the next entry has a different key */
+            if( IsUniqueIndex(pIdx) ){
+              int uniqOk = sqlite3VdbeMakeLabel(pParse);
+              int jmp6;
+              for(kk=0; kk<pIdx->nKeyCol; kk++){
+                int iCol = pIdx->aiColumn[kk];
+                assert( iCol!=XN_ROWID && iCol<pTab->nCol );
+                if( iCol>=0 && pTab->aCol[iCol].notNull ) continue;
+                sqlite3VdbeAddOp2(v, OP_IsNull, r1+kk, uniqOk);
+                VdbeCoverage(v);
+              }
+              jmp6 = sqlite3VdbeAddOp1(v, OP_Next, iIdxCur+j); VdbeCoverage(v);
+              sqlite3VdbeGoto(v, uniqOk);
+              sqlite3VdbeJumpHere(v, jmp6);
+              sqlite3VdbeAddOp4Int(v, OP_IdxGT, iIdxCur+j, uniqOk, r1,
+                                   pIdx->nKeyCol); VdbeCoverage(v);
+              sqlite3VdbeLoadString(v, 3, "non-unique entry in index ");
+              sqlite3VdbeGoto(v, jmp5);
+              sqlite3VdbeResolveLabel(v, uniqOk);
+            }
+            sqlite3VdbeJumpHere(v, jmp4);
+            sqlite3ResolvePartIdxLabel(pParse, jmp3);
+          }
+        }
+        sqlite3VdbeAddOp2(v, OP_Next, iDataCur, loopTop); VdbeCoverage(v);
+        sqlite3VdbeJumpHere(v, loopTop-1);
+        if( !isQuick ){
+          sqlite3VdbeLoadString(v, 2, "wrong # of entries in index ");
+          for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+            if( pPk==pIdx ) continue;
+            sqlite3VdbeAddOp2(v, OP_Count, iIdxCur+j, 3);
+            addr = sqlite3VdbeAddOp3(v, OP_Eq, 8+j, 0, 3); VdbeCoverage(v);
+            sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
+            sqlite3VdbeLoadString(v, 4, pIdx->zName);
+            sqlite3VdbeAddOp3(v, OP_Concat, 4, 2, 3);
+            integrityCheckResultRow(v);
+            sqlite3VdbeJumpHere(v, addr);
+          }
+          if( pPk ){
+            sqlite3ReleaseTempRange(pParse, r2, pPk->nKeyCol);
+          }
+        }
+      }
+    }
+    {
+      static const int iLn = VDBE_OFFSET_LINENO(2);
+      static const VdbeOpList endCode[] = {
+        { OP_AddImm,      1, 0,        0},    /* 0 */
+        { OP_IfNotZero,   1, 4,        0},    /* 1 */
+        { OP_String8,     0, 3,        0},    /* 2 */
+        { OP_ResultRow,   3, 1,        0},    /* 3 */
+        { OP_Halt,        0, 0,        0},    /* 4 */
+        { OP_String8,     0, 3,        0},    /* 5 */
+        { OP_Goto,        0, 3,        0},    /* 6 */
+      };
+      VdbeOp *aOp;
+
+      aOp = sqlite3VdbeAddOpList(v, ArraySize(endCode), endCode, iLn);
+      if( aOp ){
+        aOp[0].p2 = 1-mxErr;
+        aOp[2].p4type = P4_STATIC;
+        aOp[2].p4.z = "ok";
+        aOp[5].p4type = P4_STATIC;
+        aOp[5].p4.z = (char*)sqlite3ErrStr(SQLITE_CORRUPT);
+      }
+      sqlite3VdbeChangeP3(v, 0, sqlite3VdbeCurrentAddr(v)-2);
+    }
+  }
+  break;
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+#ifndef SQLITE_OMIT_UTF16
+  /*
+  **   PRAGMA encoding
+  **   PRAGMA encoding = "utf-8"|"utf-16"|"utf-16le"|"utf-16be"
+  **
+  ** In its first form, this pragma returns the encoding of the main
+  ** database. If the database is not initialized, it is initialized now.
+  **
+  ** The second form of this pragma is a no-op if the main database file
+  ** has not already been initialized. In this case it sets the default
+  ** encoding that will be used for the main database file if a new file
+  ** is created. If an existing main database file is opened, then the
+  ** default text encoding for the existing database is used.
+  **
+  ** In all cases new databases created using the ATTACH command are
+  ** created to use the same default text encoding as the main database. If
+  ** the main database has not been initialized and/or created when ATTACH
+  ** is executed, this is done before the ATTACH operation.
+  **
+  ** In the second form this pragma sets the text encoding to be used in
+  ** new database files created using this database handle. It is only
+  ** useful if invoked immediately after the main database i
+  */
+  case PragTyp_ENCODING: {
+    static const struct EncName {
+      char *zName;
+      u8 enc;
+    } encnames[] = {
+      { "UTF8",     SQLITE_UTF8        },
+      { "UTF-8",    SQLITE_UTF8        },  /* Must be element [1] */
+      { "UTF-16le", SQLITE_UTF16LE     },  /* Must be element [2] */
+      { "UTF-16be", SQLITE_UTF16BE     },  /* Must be element [3] */
+      { "UTF16le",  SQLITE_UTF16LE     },
+      { "UTF16be",  SQLITE_UTF16BE     },
+      { "UTF-16",   0                  }, /* SQLITE_UTF16NATIVE */
+      { "UTF16",    0                  }, /* SQLITE_UTF16NATIVE */
+      { 0, 0 }
+    };
+    const struct EncName *pEnc;
+    if( !zRight ){    /* "PRAGMA encoding" */
+      if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+      assert( encnames[SQLITE_UTF8].enc==SQLITE_UTF8 );
+      assert( encnames[SQLITE_UTF16LE].enc==SQLITE_UTF16LE );
+      assert( encnames[SQLITE_UTF16BE].enc==SQLITE_UTF16BE );
+      returnSingleText(v, encnames[ENC(pParse->db)].zName);
+    }else{                        /* "PRAGMA encoding = XXX" */
+      /* Only change the value of sqlite.enc if the database handle is not
+      ** initialized. If the main database exists, the new sqlite.enc value
+      ** will be overwritten when the schema is next loaded. If it does not
+      ** already exists, it will be created to use the new encoding value.
+      */
+      if( (db->mDbFlags & DBFLAG_EncodingFixed)==0 ){
+        for(pEnc=&encnames[0]; pEnc->zName; pEnc++){
+          if( 0==sqlite3StrICmp(zRight, pEnc->zName) ){
+            u8 enc = pEnc->enc ? pEnc->enc : SQLITE_UTF16NATIVE;
+            SCHEMA_ENC(db) = enc;
+            sqlite3SetTextEncoding(db, enc);
+            break;
+          }
+        }
+        if( !pEnc->zName ){
+          sqlite3ErrorMsg(pParse, "unsupported encoding: %s", zRight);
+        }
+      }
+    }
+  }
+  break;
+#endif /* SQLITE_OMIT_UTF16 */
+
+#ifndef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  /*
+  **   PRAGMA [schema.]schema_version
+  **   PRAGMA [schema.]schema_version = <integer>
+  **
+  **   PRAGMA [schema.]user_version
+  **   PRAGMA [schema.]user_version = <integer>
+  **
+  **   PRAGMA [schema.]freelist_count
+  **
+  **   PRAGMA [schema.]data_version
+  **
+  **   PRAGMA [schema.]application_id
+  **   PRAGMA [schema.]application_id = <integer>
+  **
+  ** The pragma's schema_version and user_version are used to set or get
+  ** the value of the schema-version and user-version, respectively. Both
+  ** the schema-version and the user-version are 32-bit signed integers
+  ** stored in the database header.
+  **
+  ** The schema-cookie is usually only manipulated internally by SQLite. It
+  ** is incremented by SQLite whenever the database schema is modified (by
+  ** creating or dropping a table or index). The schema version is used by
+  ** SQLite each time a query is executed to ensure that the internal cache
+  ** of the schema used when compiling the SQL query matches the schema of
+  ** the database against which the compiled query is actually executed.
+  ** Subverting this mechanism by using "PRAGMA schema_version" to modify
+  ** the schema-version is potentially dangerous and may lead to program
+  ** crashes or database corruption. Use with caution!
+  **
+  ** The user-version is not used internally by SQLite. It may be used by
+  ** applications for any purpose.
+  */
+  case PragTyp_HEADER_VALUE: {
+    int iCookie = pPragma->iArg;  /* Which cookie to read or write */
+    sqlite3VdbeUsesBtree(v, iDb);
+    if( zRight && (pPragma->mPragFlg & PragFlg_ReadOnly)==0 ){
+      /* Write the specified cookie value */
+      static const VdbeOpList setCookie[] = {
+        { OP_Transaction,    0,  1,  0},    /* 0 */
+        { OP_SetCookie,      0,  0,  0},    /* 1 */
+      };
+      VdbeOp *aOp;
+      sqlite3VdbeVerifyNoMallocRequired(v, ArraySize(setCookie));
+      aOp = sqlite3VdbeAddOpList(v, ArraySize(setCookie), setCookie, 0);
+      if( ONLY_IF_REALLOC_STRESS(aOp==0) ) break;
+      aOp[0].p1 = iDb;
+      aOp[1].p1 = iDb;
+      aOp[1].p2 = iCookie;
+      aOp[1].p3 = sqlite3Atoi(zRight);
+      aOp[1].p5 = 1;
+      if( iCookie==BTREE_SCHEMA_VERSION && (db->flags & SQLITE_Defensive)!=0 ){
+        /* Do not allow the use of PRAGMA schema_version=VALUE in defensive
+        ** mode.  Change the OP_SetCookie opcode into a no-op.  */
+        aOp[1].opcode = OP_Noop;
+      }
+    }else{
+      /* Read the specified cookie value */
+      static const VdbeOpList readCookie[] = {
+        { OP_Transaction,     0,  0,  0},    /* 0 */
+        { OP_ReadCookie,      0,  1,  0},    /* 1 */
+        { OP_ResultRow,       1,  1,  0}
+      };
+      VdbeOp *aOp;
+      sqlite3VdbeVerifyNoMallocRequired(v, ArraySize(readCookie));
+      aOp = sqlite3VdbeAddOpList(v, ArraySize(readCookie),readCookie,0);
+      if( ONLY_IF_REALLOC_STRESS(aOp==0) ) break;
+      aOp[0].p1 = iDb;
+      aOp[1].p1 = iDb;
+      aOp[1].p3 = iCookie;
+      sqlite3VdbeReusable(v);
+    }
+  }
+  break;
+#endif /* SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS */
+
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  /*
+  **   PRAGMA compile_options
+  **
+  ** Return the names of all compile-time options used in this build,
+  ** one option per row.
+  */
+  case PragTyp_COMPILE_OPTIONS: {
+    int i = 0;
+    const char *zOpt;
+    pParse->nMem = 1;
+    while( (zOpt = sqlite3_compileoption_get(i++))!=0 ){
+      sqlite3VdbeLoadString(v, 1, zOpt);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+    }
+    sqlite3VdbeReusable(v);
+  }
+  break;
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+#ifndef SQLITE_OMIT_WAL
+  /*
+  **   PRAGMA [schema.]wal_checkpoint = passive|full|restart|truncate
+  **
+  ** Checkpoint the database.
+  */
+  case PragTyp_WAL_CHECKPOINT: {
+    int iBt = (pId2->z?iDb:SQLITE_MAX_DB);
+    int eMode = SQLITE_CHECKPOINT_PASSIVE;
+    if( zRight ){
+      if( sqlite3StrICmp(zRight, "full")==0 ){
+        eMode = SQLITE_CHECKPOINT_FULL;
+      }else if( sqlite3StrICmp(zRight, "restart")==0 ){
+        eMode = SQLITE_CHECKPOINT_RESTART;
+      }else if( sqlite3StrICmp(zRight, "truncate")==0 ){
+        eMode = SQLITE_CHECKPOINT_TRUNCATE;
+      }
+    }
+    pParse->nMem = 3;
+    sqlite3VdbeAddOp3(v, OP_Checkpoint, iBt, eMode, 1);
+    sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 3);
+  }
+  break;
+
+  /*
+  **   PRAGMA wal_autocheckpoint
+  **   PRAGMA wal_autocheckpoint = N
+  **
+  ** Configure a database connection to automatically checkpoint a database
+  ** after accumulating N frames in the log. Or query for the current value
+  ** of N.
+  */
+  case PragTyp_WAL_AUTOCHECKPOINT: {
+    if( zRight ){
+      sqlite3_wal_autocheckpoint(db, sqlite3Atoi(zRight));
+    }
+    returnSingleInt(v,
+       db->xWalCallback==sqlite3WalDefaultHook ?
+           SQLITE_PTR_TO_INT(db->pWalArg) : 0);
+  }
+  break;
+#endif
+
+  /*
+  **  PRAGMA shrink_memory
+  **
+  ** IMPLEMENTATION-OF: R-23445-46109 This pragma causes the database
+  ** connection on which it is invoked to free up as much memory as it
+  ** can, by calling sqlite3_db_release_memory().
+  */
+  case PragTyp_SHRINK_MEMORY: {
+    sqlite3_db_release_memory(db);
+    break;
+  }
+
+  /*
+  **  PRAGMA optimize
+  **  PRAGMA optimize(MASK)
+  **  PRAGMA schema.optimize
+  **  PRAGMA schema.optimize(MASK)
+  **
+  ** Attempt to optimize the database.  All schemas are optimized in the first
+  ** two forms, and only the specified schema is optimized in the latter two.
+  **
+  ** The details of optimizations performed by this pragma are expected
+  ** to change and improve over time.  Applications should anticipate that
+  ** this pragma will perform new optimizations in future releases.
+  **
+  ** The optional argument is a bitmask of optimizations to perform:
+  **
+  **    0x0001    Debugging mode.  Do not actually perform any optimizations
+  **              but instead return one line of text for each optimization
+  **              that would have been done.  Off by default.
+  **
+  **    0x0002    Run ANALYZE on tables that might benefit.  On by default.
+  **              See below for additional information.
+  **
+  **    0x0004    (Not yet implemented) Record usage and performance
+  **              information from the current session in the
+  **              database file so that it will be available to "optimize"
+  **              pragmas run by future database connections.
+  **
+  **    0x0008    (Not yet implemented) Create indexes that might have
+  **              been helpful to recent queries
+  **
+  ** The default MASK is and always shall be 0xfffe.  0xfffe means perform all
+  ** of the optimizations listed above except Debug Mode, including new
+  ** optimizations that have not yet been invented.  If new optimizations are
+  ** ever added that should be off by default, those off-by-default
+  ** optimizations will have bitmasks of 0x10000 or larger.
+  **
+  ** DETERMINATION OF WHEN TO RUN ANALYZE
+  **
+  ** In the current implementation, a table is analyzed if only if all of
+  ** the following are true:
+  **
+  ** (1) MASK bit 0x02 is set.
+  **
+  ** (2) The query planner used sqlite_stat1-style statistics for one or
+  **     more indexes of the table at some point during the lifetime of
+  **     the current connection.
+  **
+  ** (3) One or more indexes of the table are currently unanalyzed OR
+  **     the number of rows in the table has increased by 25 times or more
+  **     since the last time ANALYZE was run.
+  **
+  ** The rules for when tables are analyzed are likely to change in
+  ** future releases.
+  */
+  case PragTyp_OPTIMIZE: {
+    int iDbLast;           /* Loop termination point for the schema loop */
+    int iTabCur;           /* Cursor for a table whose size needs checking */
+    HashElem *k;           /* Loop over tables of a schema */
+    Schema *pSchema;       /* The current schema */
+    Table *pTab;           /* A table in the schema */
+    Index *pIdx;           /* An index of the table */
+    LogEst szThreshold;    /* Size threshold above which reanalysis needed */
+    char *zSubSql;         /* SQL statement for the OP_SqlExec opcode */
+    u32 opMask;            /* Mask of operations to perform */
+
+    if( zRight ){
+      opMask = (u32)sqlite3Atoi(zRight);
+      if( (opMask & 0x02)==0 ) break;
+    }else{
+      opMask = 0xfffe;
+    }
+    iTabCur = pParse->nTab++;
+    for(iDbLast = zDb?iDb:db->nDb-1; iDb<=iDbLast; iDb++){
+      if( iDb==1 ) continue;
+      sqlite3CodeVerifySchema(pParse, iDb);
+      pSchema = db->aDb[iDb].pSchema;
+      for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
+        pTab = (Table*)sqliteHashData(k);
+
+        /* If table pTab has not been used in a way that would benefit from
+        ** having analysis statistics during the current session, then skip it.
+        ** This also has the effect of skipping virtual tables and views */
+        if( (pTab->tabFlags & TF_StatsUsed)==0 ) continue;
+
+        /* Reanalyze if the table is 25 times larger than the last analysis */
+        szThreshold = pTab->nRowLogEst + 46; assert( sqlite3LogEst(25)==46 );
+        for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+          if( !pIdx->hasStat1 ){
+            szThreshold = 0; /* Always analyze if any index lacks statistics */
+            break;
+          }
+        }
+        if( szThreshold ){
+          sqlite3OpenTable(pParse, iTabCur, iDb, pTab, OP_OpenRead);
+          sqlite3VdbeAddOp3(v, OP_IfSmaller, iTabCur,
+                         sqlite3VdbeCurrentAddr(v)+2+(opMask&1), szThreshold);
+          VdbeCoverage(v);
+        }
+        zSubSql = sqlite3MPrintf(db, "ANALYZE \"%w\".\"%w\"",
+                                 db->aDb[iDb].zDbSName, pTab->zName);
+        if( opMask & 0x01 ){
+          int r1 = sqlite3GetTempReg(pParse);
+          sqlite3VdbeAddOp4(v, OP_String8, 0, r1, 0, zSubSql, P4_DYNAMIC);
+          sqlite3VdbeAddOp2(v, OP_ResultRow, r1, 1);
+        }else{
+          sqlite3VdbeAddOp4(v, OP_SqlExec, 0, 0, 0, zSubSql, P4_DYNAMIC);
+        }
+      }
+    }
+    sqlite3VdbeAddOp0(v, OP_Expire);
+    break;
+  }
+
+  /*
+  **   PRAGMA busy_timeout
+  **   PRAGMA busy_timeout = N
+  **
+  ** Call sqlite3_busy_timeout(db, N).  Return the current timeout value
+  ** if one is set.  If no busy handler or a different busy handler is set
+  ** then 0 is returned.  Setting the busy_timeout to 0 or negative
+  ** disables the timeout.
+  */
+  /*case PragTyp_BUSY_TIMEOUT*/ default: {
+    assert( pPragma->ePragTyp==PragTyp_BUSY_TIMEOUT );
+    if( zRight ){
+      sqlite3_busy_timeout(db, sqlite3Atoi(zRight));
+    }
+    returnSingleInt(v, db->busyTimeout);
+    break;
+  }
+
+  /*
+  **   PRAGMA soft_heap_limit
+  **   PRAGMA soft_heap_limit = N
+  **
+  ** IMPLEMENTATION-OF: R-26343-45930 This pragma invokes the
+  ** sqlite3_soft_heap_limit64() interface with the argument N, if N is
+  ** specified and is a non-negative integer.
+  ** IMPLEMENTATION-OF: R-64451-07163 The soft_heap_limit pragma always
+  ** returns the same integer that would be returned by the
+  ** sqlite3_soft_heap_limit64(-1) C-language function.
+  */
+  case PragTyp_SOFT_HEAP_LIMIT: {
+    sqlite3_int64 N;
+    if( zRight && sqlite3DecOrHexToI64(zRight, &N)==SQLITE_OK ){
+      sqlite3_soft_heap_limit64(N);
+    }
+    returnSingleInt(v, sqlite3_soft_heap_limit64(-1));
+    break;
+  }
+
+  /*
+  **   PRAGMA hard_heap_limit
+  **   PRAGMA hard_heap_limit = N
+  **
+  ** Invoke sqlite3_hard_heap_limit64() to query or set the hard heap
+  ** limit.  The hard heap limit can be activated or lowered by this
+  ** pragma, but not raised or deactivated.  Only the
+  ** sqlite3_hard_heap_limit64() C-language API can raise or deactivate
+  ** the hard heap limit.  This allows an application to set a heap limit
+  ** constraint that cannot be relaxed by an untrusted SQL script.
+  */
+  case PragTyp_HARD_HEAP_LIMIT: {
+    sqlite3_int64 N;
+    if( zRight && sqlite3DecOrHexToI64(zRight, &N)==SQLITE_OK ){
+      sqlite3_int64 iPrior = sqlite3_hard_heap_limit64(-1);
+      if( N>0 && (iPrior==0 || iPrior>N) ) sqlite3_hard_heap_limit64(N);
+    }
+    returnSingleInt(v, sqlite3_hard_heap_limit64(-1));
+    break;
+  }
+
+  /*
+  **   PRAGMA threads
+  **   PRAGMA threads = N
+  **
+  ** Configure the maximum number of worker threads.  Return the new
+  ** maximum, which might be less than requested.
+  */
+  case PragTyp_THREADS: {
+    sqlite3_int64 N;
+    if( zRight
+     && sqlite3DecOrHexToI64(zRight, &N)==SQLITE_OK
+     && N>=0
+    ){
+      sqlite3_limit(db, SQLITE_LIMIT_WORKER_THREADS, (int)(N&0x7fffffff));
+    }
+    returnSingleInt(v, sqlite3_limit(db, SQLITE_LIMIT_WORKER_THREADS, -1));
+    break;
+  }
+
+  /*
+  **   PRAGMA analysis_limit
+  **   PRAGMA analysis_limit = N
+  **
+  ** Configure the maximum number of rows that ANALYZE will examine
+  ** in each index that it looks at.  Return the new limit.
+  */
+  case PragTyp_ANALYSIS_LIMIT: {
+    sqlite3_int64 N;
+    if( zRight
+     && sqlite3DecOrHexToI64(zRight, &N)==SQLITE_OK /* IMP: R-40975-20399 */
+     && N>=0
+    ){
+      db->nAnalysisLimit = (int)(N&0x7fffffff);
+    }
+    returnSingleInt(v, db->nAnalysisLimit); /* IMP: R-57594-65522 */
+    break;
+  }
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  /*
+  ** Report the current state of file logs for all databases
+  */
+  case PragTyp_LOCK_STATUS: {
+    static const char *const azLockName[] = {
+      "unlocked", "shared", "reserved", "pending", "exclusive"
+    };
+    int i;
+    pParse->nMem = 2;
+    for(i=0; i<db->nDb; i++){
+      Btree *pBt;
+      const char *zState = "unknown";
+      int j;
+      if( db->aDb[i].zDbSName==0 ) continue;
+      pBt = db->aDb[i].pBt;
+      if( pBt==0 || sqlite3BtreePager(pBt)==0 ){
+        zState = "closed";
+      }else if( sqlite3_file_control(db, i ? db->aDb[i].zDbSName : 0,
+                                     SQLITE_FCNTL_LOCKSTATE, &j)==SQLITE_OK ){
+         zState = azLockName[j];
+      }
+      sqlite3VdbeMultiLoad(v, 1, "ss", db->aDb[i].zDbSName, zState);
+    }
+    break;
+  }
+#endif
+
+#if defined(SQLITE_ENABLE_CEROD)
+  case PragTyp_ACTIVATE_EXTENSIONS: if( zRight ){
+    if( sqlite3StrNICmp(zRight, "cerod-", 6)==0 ){
+      sqlite3_activate_cerod(&zRight[6]);
+    }
+  }
+  break;
+#endif
+
+  } /* End of the PRAGMA switch */
+
+  /* The following block is a no-op unless SQLITE_DEBUG is defined. Its only
+  ** purpose is to execute assert() statements to verify that if the
+  ** PragFlg_NoColumns1 flag is set and the caller specified an argument
+  ** to the PRAGMA, the implementation has not added any OP_ResultRow
+  ** instructions to the VM.  */
+  if( (pPragma->mPragFlg & PragFlg_NoColumns1) && zRight ){
+    sqlite3VdbeVerifyNoResultRow(v);
+  }
+
+pragma_out:
+  sqlite3DbFree(db, zLeft);
+  sqlite3DbFree(db, zRight);
+}
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*****************************************************************************
+** Implementation of an eponymous virtual table that runs a pragma.
+**
+*/
+typedef struct PragmaVtab PragmaVtab;
+typedef struct PragmaVtabCursor PragmaVtabCursor;
+struct PragmaVtab {
+  sqlite3_vtab base;        /* Base class.  Must be first */
+  sqlite3 *db;              /* The database connection to which it belongs */
+  const PragmaName *pName;  /* Name of the pragma */
+  u8 nHidden;               /* Number of hidden columns */
+  u8 iHidden;               /* Index of the first hidden column */
+};
+struct PragmaVtabCursor {
+  sqlite3_vtab_cursor base; /* Base class.  Must be first */
+  sqlite3_stmt *pPragma;    /* The pragma statement to run */
+  sqlite_int64 iRowid;      /* Current rowid */
+  char *azArg[2];           /* Value of the argument and schema */
+};
+
+/*
+** Pragma virtual table module xConnect method.
+*/
+static int pragmaVtabConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  const PragmaName *pPragma = (const PragmaName*)pAux;
+  PragmaVtab *pTab = 0;
+  int rc;
+  int i, j;
+  char cSep = '(';
+  StrAccum acc;
+  char zBuf[200];
+
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
+  sqlite3_str_appendall(&acc, "CREATE TABLE x");
+  for(i=0, j=pPragma->iPragCName; i<pPragma->nPragCName; i++, j++){
+    sqlite3_str_appendf(&acc, "%c\"%s\"", cSep, pragCName[j]);
+    cSep = ',';
+  }
+  if( i==0 ){
+    sqlite3_str_appendf(&acc, "(\"%s\"", pPragma->zName);
+    i++;
+  }
+  j = 0;
+  if( pPragma->mPragFlg & PragFlg_Result1 ){
+    sqlite3_str_appendall(&acc, ",arg HIDDEN");
+    j++;
+  }
+  if( pPragma->mPragFlg & (PragFlg_SchemaOpt|PragFlg_SchemaReq) ){
+    sqlite3_str_appendall(&acc, ",schema HIDDEN");
+    j++;
+  }
+  sqlite3_str_append(&acc, ")", 1);
+  sqlite3StrAccumFinish(&acc);
+  assert( strlen(zBuf) < sizeof(zBuf)-1 );
+  rc = sqlite3_declare_vtab(db, zBuf);
+  if( rc==SQLITE_OK ){
+    pTab = (PragmaVtab*)sqlite3_malloc(sizeof(PragmaVtab));
+    if( pTab==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memset(pTab, 0, sizeof(PragmaVtab));
+      pTab->pName = pPragma;
+      pTab->db = db;
+      pTab->iHidden = i;
+      pTab->nHidden = j;
+    }
+  }else{
+    *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+  }
+
+  *ppVtab = (sqlite3_vtab*)pTab;
+  return rc;
+}
+
+/*
+** Pragma virtual table module xDisconnect method.
+*/
+static int pragmaVtabDisconnect(sqlite3_vtab *pVtab){
+  PragmaVtab *pTab = (PragmaVtab*)pVtab;
+  sqlite3_free(pTab);
+  return SQLITE_OK;
+}
+
+/* Figure out the best index to use to search a pragma virtual table.
+**
+** There are not really any index choices.  But we want to encourage the
+** query planner to give == constraints on as many hidden parameters as
+** possible, and especially on the first hidden parameter.  So return a
+** high cost if hidden parameters are unconstrained.
+*/
+static int pragmaVtabBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  PragmaVtab *pTab = (PragmaVtab*)tab;
+  const struct sqlite3_index_constraint *pConstraint;
+  int i, j;
+  int seen[2];
+
+  pIdxInfo->estimatedCost = (double)1;
+  if( pTab->nHidden==0 ){ return SQLITE_OK; }
+  pConstraint = pIdxInfo->aConstraint;
+  seen[0] = 0;
+  seen[1] = 0;
+  for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
+    if( pConstraint->usable==0 ) continue;
+    if( pConstraint->op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
+    if( pConstraint->iColumn < pTab->iHidden ) continue;
+    j = pConstraint->iColumn - pTab->iHidden;
+    assert( j < 2 );
+    seen[j] = i+1;
+  }
+  if( seen[0]==0 ){
+    pIdxInfo->estimatedCost = (double)2147483647;
+    pIdxInfo->estimatedRows = 2147483647;
+    return SQLITE_OK;
+  }
+  j = seen[0]-1;
+  pIdxInfo->aConstraintUsage[j].argvIndex = 1;
+  pIdxInfo->aConstraintUsage[j].omit = 1;
+  if( seen[1]==0 ) return SQLITE_OK;
+  pIdxInfo->estimatedCost = (double)20;
+  pIdxInfo->estimatedRows = 20;
+  j = seen[1]-1;
+  pIdxInfo->aConstraintUsage[j].argvIndex = 2;
+  pIdxInfo->aConstraintUsage[j].omit = 1;
+  return SQLITE_OK;
+}
+
+/* Create a new cursor for the pragma virtual table */
+static int pragmaVtabOpen(sqlite3_vtab *pVtab, sqlite3_vtab_cursor **ppCursor){
+  PragmaVtabCursor *pCsr;
+  pCsr = (PragmaVtabCursor*)sqlite3_malloc(sizeof(*pCsr));
+  if( pCsr==0 ) return SQLITE_NOMEM;
+  memset(pCsr, 0, sizeof(PragmaVtabCursor));
+  pCsr->base.pVtab = pVtab;
+  *ppCursor = &pCsr->base;
+  return SQLITE_OK;
+}
+
+/* Clear all content from pragma virtual table cursor. */
+static void pragmaVtabCursorClear(PragmaVtabCursor *pCsr){
+  int i;
+  sqlite3_finalize(pCsr->pPragma);
+  pCsr->pPragma = 0;
+  for(i=0; i<ArraySize(pCsr->azArg); i++){
+    sqlite3_free(pCsr->azArg[i]);
+    pCsr->azArg[i] = 0;
+  }
+}
+
+/* Close a pragma virtual table cursor */
+static int pragmaVtabClose(sqlite3_vtab_cursor *cur){
+  PragmaVtabCursor *pCsr = (PragmaVtabCursor*)cur;
+  pragmaVtabCursorClear(pCsr);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/* Advance the pragma virtual table cursor to the next row */
+static int pragmaVtabNext(sqlite3_vtab_cursor *pVtabCursor){
+  PragmaVtabCursor *pCsr = (PragmaVtabCursor*)pVtabCursor;
+  int rc = SQLITE_OK;
+
+  /* Increment the xRowid value */
+  pCsr->iRowid++;
+  assert( pCsr->pPragma );
+  if( SQLITE_ROW!=sqlite3_step(pCsr->pPragma) ){
+    rc = sqlite3_finalize(pCsr->pPragma);
+    pCsr->pPragma = 0;
+    pragmaVtabCursorClear(pCsr);
+  }
+  return rc;
+}
+
+/*
+** Pragma virtual table module xFilter method.
+*/
+static int pragmaVtabFilter(
+  sqlite3_vtab_cursor *pVtabCursor,
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  PragmaVtabCursor *pCsr = (PragmaVtabCursor*)pVtabCursor;
+  PragmaVtab *pTab = (PragmaVtab*)(pVtabCursor->pVtab);
+  int rc;
+  int i, j;
+  StrAccum acc;
+  char *zSql;
+
+  UNUSED_PARAMETER(idxNum);
+  UNUSED_PARAMETER(idxStr);
+  pragmaVtabCursorClear(pCsr);
+  j = (pTab->pName->mPragFlg & PragFlg_Result1)!=0 ? 0 : 1;
+  for(i=0; i<argc; i++, j++){
+    const char *zText = (const char*)sqlite3_value_text(argv[i]);
+    assert( j<ArraySize(pCsr->azArg) );
+    assert( pCsr->azArg[j]==0 );
+    if( zText ){
+      pCsr->azArg[j] = sqlite3_mprintf("%s", zText);
+      if( pCsr->azArg[j]==0 ){
+        return SQLITE_NOMEM;
+      }
+    }
+  }
+  sqlite3StrAccumInit(&acc, 0, 0, 0, pTab->db->aLimit[SQLITE_LIMIT_SQL_LENGTH]);
+  sqlite3_str_appendall(&acc, "PRAGMA ");
+  if( pCsr->azArg[1] ){
+    sqlite3_str_appendf(&acc, "%Q.", pCsr->azArg[1]);
+  }
+  sqlite3_str_appendall(&acc, pTab->pName->zName);
+  if( pCsr->azArg[0] ){
+    sqlite3_str_appendf(&acc, "=%Q", pCsr->azArg[0]);
+  }
+  zSql = sqlite3StrAccumFinish(&acc);
+  if( zSql==0 ) return SQLITE_NOMEM;
+  rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pPragma, 0);
+  sqlite3_free(zSql);
+  if( rc!=SQLITE_OK ){
+    pTab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pTab->db));
+    return rc;
+  }
+  return pragmaVtabNext(pVtabCursor);
+}
+
+/*
+** Pragma virtual table module xEof method.
+*/
+static int pragmaVtabEof(sqlite3_vtab_cursor *pVtabCursor){
+  PragmaVtabCursor *pCsr = (PragmaVtabCursor*)pVtabCursor;
+  return (pCsr->pPragma==0);
+}
+
+/* The xColumn method simply returns the corresponding column from
+** the PRAGMA. 
+*/
+static int pragmaVtabColumn(
+  sqlite3_vtab_cursor *pVtabCursor,
+  sqlite3_context *ctx,
+  int i
+){
+  PragmaVtabCursor *pCsr = (PragmaVtabCursor*)pVtabCursor;
+  PragmaVtab *pTab = (PragmaVtab*)(pVtabCursor->pVtab);
+  if( i<pTab->iHidden ){
+    sqlite3_result_value(ctx, sqlite3_column_value(pCsr->pPragma, i));
+  }else{
+    sqlite3_result_text(ctx, pCsr->azArg[i-pTab->iHidden],-1,SQLITE_TRANSIENT);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Pragma virtual table module xRowid method.
+*/
+static int pragmaVtabRowid(sqlite3_vtab_cursor *pVtabCursor, sqlite_int64 *p){
+  PragmaVtabCursor *pCsr = (PragmaVtabCursor*)pVtabCursor;
+  *p = pCsr->iRowid;
+  return SQLITE_OK;
+}
+
+/* The pragma virtual table object */
+static const sqlite3_module pragmaVtabModule = {
+  0,                           /* iVersion */
+  0,                           /* xCreate - create a table */
+  pragmaVtabConnect,           /* xConnect - connect to an existing table */
+  pragmaVtabBestIndex,         /* xBestIndex - Determine search strategy */
+  pragmaVtabDisconnect,        /* xDisconnect - Disconnect from a table */
+  0,                           /* xDestroy - Drop a table */
+  pragmaVtabOpen,              /* xOpen - open a cursor */
+  pragmaVtabClose,             /* xClose - close a cursor */
+  pragmaVtabFilter,            /* xFilter - configure scan constraints */
+  pragmaVtabNext,              /* xNext - advance a cursor */
+  pragmaVtabEof,               /* xEof */
+  pragmaVtabColumn,            /* xColumn - read data */
+  pragmaVtabRowid,             /* xRowid - read data */
+  0,                           /* xUpdate - write data */
+  0,                           /* xBegin - begin transaction */
+  0,                           /* xSync - sync transaction */
+  0,                           /* xCommit - commit transaction */
+  0,                           /* xRollback - rollback transaction */
+  0,                           /* xFindFunction - function overloading */
+  0,                           /* xRename - rename the table */
+  0,                           /* xSavepoint */
+  0,                           /* xRelease */
+  0,                           /* xRollbackTo */
+  0,                           /* xShadowName */
+  0                            /* xIntegrity */
+};
+
+/*
+** Check to see if zTabName is really the name of a pragma.  If it is,
+** then register an eponymous virtual table for that pragma and return
+** a pointer to the Module object for the new virtual table.
+*/
+Module *sqlite3PragmaVtabRegister(sqlite3 *db, const char *zName){
+  const PragmaName *pName;
+  assert( sqlite3_strnicmp(zName, "pragma_", 7)==0 );
+  pName = pragmaLocate(zName+7);
+  if( pName==0 ) return 0;
+  if( (pName->mPragFlg & (PragFlg_Result0|PragFlg_Result1))==0 ) return 0;
+  assert( sqlite3HashFind(&db->aModule, zName)==0 );
+  return sqlite3VtabCreateModule(db, zName, &pragmaVtabModule, (void*)pName, 0);
+}
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#endif /* SQLITE_OMIT_PRAGMA */
diff --git a/src/pragma.h b/src/pragma.h
new file mode 100644
index 0000000..7270db1
--- /dev/null
+++ b/src/pragma.h
@@ -0,0 +1,660 @@
+/* DO NOT EDIT!
+** This file is automatically generated by the script at
+** ../tool/mkpragmatab.tcl.  To update the set of pragmas, edit
+** that script and rerun it.
+*/
+
+/* The various pragma types */
+#define PragTyp_ACTIVATE_EXTENSIONS            0
+#define PragTyp_ANALYSIS_LIMIT                 1
+#define PragTyp_HEADER_VALUE                   2
+#define PragTyp_AUTO_VACUUM                    3
+#define PragTyp_FLAG                           4
+#define PragTyp_BUSY_TIMEOUT                   5
+#define PragTyp_CACHE_SIZE                     6
+#define PragTyp_CACHE_SPILL                    7
+#define PragTyp_CASE_SENSITIVE_LIKE            8
+#define PragTyp_COLLATION_LIST                 9
+#define PragTyp_COMPILE_OPTIONS               10
+#define PragTyp_DATA_STORE_DIRECTORY          11
+#define PragTyp_DATABASE_LIST                 12
+#define PragTyp_DEFAULT_CACHE_SIZE            13
+#define PragTyp_ENCODING                      14
+#define PragTyp_FOREIGN_KEY_CHECK             15
+#define PragTyp_FOREIGN_KEY_LIST              16
+#define PragTyp_FUNCTION_LIST                 17
+#define PragTyp_HARD_HEAP_LIMIT               18
+#define PragTyp_INCREMENTAL_VACUUM            19
+#define PragTyp_INDEX_INFO                    20
+#define PragTyp_INDEX_LIST                    21
+#define PragTyp_INTEGRITY_CHECK               22
+#define PragTyp_JOURNAL_MODE                  23
+#define PragTyp_JOURNAL_SIZE_LIMIT            24
+#define PragTyp_LOCK_PROXY_FILE               25
+#define PragTyp_LOCKING_MODE                  26
+#define PragTyp_PAGE_COUNT                    27
+#define PragTyp_MMAP_SIZE                     28
+#define PragTyp_MODULE_LIST                   29
+#define PragTyp_OPTIMIZE                      30
+#define PragTyp_PAGE_SIZE                     31
+#define PragTyp_PRAGMA_LIST                   32
+#define PragTyp_SECURE_DELETE                 33
+#define PragTyp_SHRINK_MEMORY                 34
+#define PragTyp_SOFT_HEAP_LIMIT               35
+#define PragTyp_SYNCHRONOUS                   36
+#define PragTyp_TABLE_INFO                    37
+#define PragTyp_TABLE_LIST                    38
+#define PragTyp_TEMP_STORE                    39
+#define PragTyp_TEMP_STORE_DIRECTORY          40
+#define PragTyp_THREADS                       41
+#define PragTyp_WAL_AUTOCHECKPOINT            42
+#define PragTyp_WAL_CHECKPOINT                43
+#define PragTyp_LOCK_STATUS                   44
+#define PragTyp_STATS                         45
+
+/* Property flags associated with various pragma. */
+#define PragFlg_NeedSchema 0x01 /* Force schema load before running */
+#define PragFlg_NoColumns  0x02 /* OP_ResultRow called with zero columns */
+#define PragFlg_NoColumns1 0x04 /* zero columns if RHS argument is present */
+#define PragFlg_ReadOnly   0x08 /* Read-only HEADER_VALUE */
+#define PragFlg_Result0    0x10 /* Acts as query when no argument */
+#define PragFlg_Result1    0x20 /* Acts as query when has one argument */
+#define PragFlg_SchemaOpt  0x40 /* Schema restricts name search if present */
+#define PragFlg_SchemaReq  0x80 /* Schema required - "main" is default */
+
+/* Names of columns for pragmas that return multi-column result
+** or that return single-column results where the name of the
+** result column is different from the name of the pragma
+*/
+static const char *const pragCName[] = {
+  /*   0 */ "id",          /* Used by: foreign_key_list */
+  /*   1 */ "seq",        
+  /*   2 */ "table",      
+  /*   3 */ "from",       
+  /*   4 */ "to",         
+  /*   5 */ "on_update",  
+  /*   6 */ "on_delete",  
+  /*   7 */ "match",      
+  /*   8 */ "cid",         /* Used by: table_xinfo */
+  /*   9 */ "name",       
+  /*  10 */ "type",       
+  /*  11 */ "notnull",    
+  /*  12 */ "dflt_value", 
+  /*  13 */ "pk",         
+  /*  14 */ "hidden",     
+                           /* table_info reuses 8 */
+  /*  15 */ "schema",      /* Used by: table_list */
+  /*  16 */ "name",       
+  /*  17 */ "type",       
+  /*  18 */ "ncol",       
+  /*  19 */ "wr",         
+  /*  20 */ "strict",     
+  /*  21 */ "seqno",       /* Used by: index_xinfo */
+  /*  22 */ "cid",        
+  /*  23 */ "name",       
+  /*  24 */ "desc",       
+  /*  25 */ "coll",       
+  /*  26 */ "key",        
+  /*  27 */ "name",        /* Used by: function_list */
+  /*  28 */ "builtin",    
+  /*  29 */ "type",       
+  /*  30 */ "enc",        
+  /*  31 */ "narg",       
+  /*  32 */ "flags",      
+  /*  33 */ "tbl",         /* Used by: stats */
+  /*  34 */ "idx",        
+  /*  35 */ "wdth",       
+  /*  36 */ "hght",       
+  /*  37 */ "flgs",       
+  /*  38 */ "seq",         /* Used by: index_list */
+  /*  39 */ "name",       
+  /*  40 */ "unique",     
+  /*  41 */ "origin",     
+  /*  42 */ "partial",    
+  /*  43 */ "table",       /* Used by: foreign_key_check */
+  /*  44 */ "rowid",      
+  /*  45 */ "parent",     
+  /*  46 */ "fkid",       
+                           /* index_info reuses 21 */
+  /*  47 */ "seq",         /* Used by: database_list */
+  /*  48 */ "name",       
+  /*  49 */ "file",       
+  /*  50 */ "busy",        /* Used by: wal_checkpoint */
+  /*  51 */ "log",        
+  /*  52 */ "checkpointed",
+                           /* collation_list reuses 38 */
+  /*  53 */ "database",    /* Used by: lock_status */
+  /*  54 */ "status",     
+  /*  55 */ "cache_size",  /* Used by: default_cache_size */
+                           /* module_list pragma_list reuses 9 */
+  /*  56 */ "timeout",     /* Used by: busy_timeout */
+};
+
+/* Definitions of all built-in pragmas */
+typedef struct PragmaName {
+  const char *const zName; /* Name of pragma */
+  u8 ePragTyp;             /* PragTyp_XXX value */
+  u8 mPragFlg;             /* Zero or more PragFlg_XXX values */
+  u8 iPragCName;           /* Start of column names in pragCName[] */
+  u8 nPragCName;           /* Num of col names. 0 means use pragma name */
+  u64 iArg;                /* Extra argument */
+} PragmaName;
+static const PragmaName aPragmaName[] = {
+#if defined(SQLITE_ENABLE_CEROD)
+ {/* zName:     */ "activate_extensions",
+  /* ePragTyp:  */ PragTyp_ACTIVATE_EXTENSIONS,
+  /* ePragFlg:  */ 0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+ {/* zName:     */ "analysis_limit",
+  /* ePragTyp:  */ PragTyp_ANALYSIS_LIMIT,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#if !defined(SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS)
+ {/* zName:     */ "application_id",
+  /* ePragTyp:  */ PragTyp_HEADER_VALUE,
+  /* ePragFlg:  */ PragFlg_NoColumns1|PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ BTREE_APPLICATION_ID },
+#endif
+#if !defined(SQLITE_OMIT_AUTOVACUUM)
+ {/* zName:     */ "auto_vacuum",
+  /* ePragTyp:  */ PragTyp_AUTO_VACUUM,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+#if !defined(SQLITE_OMIT_AUTOMATIC_INDEX)
+ {/* zName:     */ "automatic_index",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_AutoIndex },
+#endif
+#endif
+ {/* zName:     */ "busy_timeout",
+  /* ePragTyp:  */ PragTyp_BUSY_TIMEOUT,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 56, 1,
+  /* iArg:      */ 0 },
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+ {/* zName:     */ "cache_size",
+  /* ePragTyp:  */ PragTyp_CACHE_SIZE,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "cache_spill",
+  /* ePragTyp:  */ PragTyp_CACHE_SPILL,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_SchemaReq|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_CASE_SENSITIVE_LIKE_PRAGMA)
+ {/* zName:     */ "case_sensitive_like",
+  /* ePragTyp:  */ PragTyp_CASE_SENSITIVE_LIKE,
+  /* ePragFlg:  */ PragFlg_NoColumns,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+ {/* zName:     */ "cell_size_check",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_CellSizeCk },
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "checkpoint_fullfsync",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_CkptFullFSync },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)
+ {/* zName:     */ "collation_list",
+  /* ePragTyp:  */ PragTyp_COLLATION_LIST,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 38, 2,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_COMPILEOPTION_DIAGS)
+ {/* zName:     */ "compile_options",
+  /* ePragTyp:  */ PragTyp_COMPILE_OPTIONS,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "count_changes",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_CountRows },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) && SQLITE_OS_WIN
+ {/* zName:     */ "data_store_directory",
+  /* ePragTyp:  */ PragTyp_DATA_STORE_DIRECTORY,
+  /* ePragFlg:  */ PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS)
+ {/* zName:     */ "data_version",
+  /* ePragTyp:  */ PragTyp_HEADER_VALUE,
+  /* ePragFlg:  */ PragFlg_ReadOnly|PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ BTREE_DATA_VERSION },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)
+ {/* zName:     */ "database_list",
+  /* ePragTyp:  */ PragTyp_DATABASE_LIST,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 47, 3,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) && !defined(SQLITE_OMIT_DEPRECATED)
+ {/* zName:     */ "default_cache_size",
+  /* ePragTyp:  */ PragTyp_DEFAULT_CACHE_SIZE,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq|PragFlg_NoColumns1,
+  /* ColNames:  */ 55, 1,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+ {/* zName:     */ "defer_foreign_keys",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_DeferFKs },
+#endif
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "empty_result_callbacks",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_NullCallback },
+#endif
+#if !defined(SQLITE_OMIT_UTF16)
+ {/* zName:     */ "encoding",
+  /* ePragTyp:  */ PragTyp_ENCODING,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+ {/* zName:     */ "foreign_key_check",
+  /* ePragTyp:  */ PragTyp_FOREIGN_KEY_CHECK,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 43, 4,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FOREIGN_KEY)
+ {/* zName:     */ "foreign_key_list",
+  /* ePragTyp:  */ PragTyp_FOREIGN_KEY_LIST,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 0, 8,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+ {/* zName:     */ "foreign_keys",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_ForeignKeys },
+#endif
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS)
+ {/* zName:     */ "freelist_count",
+  /* ePragTyp:  */ PragTyp_HEADER_VALUE,
+  /* ePragFlg:  */ PragFlg_ReadOnly|PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ BTREE_FREE_PAGE_COUNT },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "full_column_names",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_FullColNames },
+ {/* zName:     */ "fullfsync",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_FullFSync },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)
+#if !defined(SQLITE_OMIT_INTROSPECTION_PRAGMAS)
+ {/* zName:     */ "function_list",
+  /* ePragTyp:  */ PragTyp_FUNCTION_LIST,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 27, 6,
+  /* iArg:      */ 0 },
+#endif
+#endif
+ {/* zName:     */ "hard_heap_limit",
+  /* ePragTyp:  */ PragTyp_HARD_HEAP_LIMIT,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+#if !defined(SQLITE_OMIT_CHECK)
+ {/* zName:     */ "ignore_check_constraints",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_IgnoreChecks },
+#endif
+#endif
+#if !defined(SQLITE_OMIT_AUTOVACUUM)
+ {/* zName:     */ "incremental_vacuum",
+  /* ePragTyp:  */ PragTyp_INCREMENTAL_VACUUM,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_NoColumns,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)
+ {/* zName:     */ "index_info",
+  /* ePragTyp:  */ PragTyp_INDEX_INFO,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 21, 3,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "index_list",
+  /* ePragTyp:  */ PragTyp_INDEX_LIST,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 38, 5,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "index_xinfo",
+  /* ePragTyp:  */ PragTyp_INDEX_INFO,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 21, 6,
+  /* iArg:      */ 1 },
+#endif
+#if !defined(SQLITE_OMIT_INTEGRITY_CHECK)
+ {/* zName:     */ "integrity_check",
+  /* ePragTyp:  */ PragTyp_INTEGRITY_CHECK,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+ {/* zName:     */ "journal_mode",
+  /* ePragTyp:  */ PragTyp_JOURNAL_MODE,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "journal_size_limit",
+  /* ePragTyp:  */ PragTyp_JOURNAL_SIZE_LIMIT,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_SchemaReq,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "legacy_alter_table",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_LegacyAlter },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) && SQLITE_ENABLE_LOCKING_STYLE
+ {/* zName:     */ "lock_proxy_file",
+  /* ePragTyp:  */ PragTyp_LOCK_PROXY_FILE,
+  /* ePragFlg:  */ PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+ {/* zName:     */ "lock_status",
+  /* ePragTyp:  */ PragTyp_LOCK_STATUS,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 53, 2,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+ {/* zName:     */ "locking_mode",
+  /* ePragTyp:  */ PragTyp_LOCKING_MODE,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_SchemaReq,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "max_page_count",
+  /* ePragTyp:  */ PragTyp_PAGE_COUNT,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "mmap_size",
+  /* ePragTyp:  */ PragTyp_MMAP_SIZE,
+  /* ePragFlg:  */ 0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)
+#if !defined(SQLITE_OMIT_VIRTUALTABLE)
+#if !defined(SQLITE_OMIT_INTROSPECTION_PRAGMAS)
+ {/* zName:     */ "module_list",
+  /* ePragTyp:  */ PragTyp_MODULE_LIST,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 9, 1,
+  /* iArg:      */ 0 },
+#endif
+#endif
+#endif
+ {/* zName:     */ "optimize",
+  /* ePragTyp:  */ PragTyp_OPTIMIZE,
+  /* ePragFlg:  */ PragFlg_Result1|PragFlg_NeedSchema,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+ {/* zName:     */ "page_count",
+  /* ePragTyp:  */ PragTyp_PAGE_COUNT,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "page_size",
+  /* ePragTyp:  */ PragTyp_PAGE_SIZE,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_SchemaReq|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+#if defined(SQLITE_DEBUG)
+ {/* zName:     */ "parser_trace",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_ParserTrace },
+#endif
+#endif
+#if !defined(SQLITE_OMIT_INTROSPECTION_PRAGMAS)
+ {/* zName:     */ "pragma_list",
+  /* ePragTyp:  */ PragTyp_PRAGMA_LIST,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 9, 1,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "query_only",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_QueryOnly },
+#endif
+#if !defined(SQLITE_OMIT_INTEGRITY_CHECK)
+ {/* zName:     */ "quick_check",
+  /* ePragTyp:  */ PragTyp_INTEGRITY_CHECK,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "read_uncommitted",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_ReadUncommit },
+ {/* zName:     */ "recursive_triggers",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_RecTriggers },
+ {/* zName:     */ "reverse_unordered_selects",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_ReverseOrder },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS)
+ {/* zName:     */ "schema_version",
+  /* ePragTyp:  */ PragTyp_HEADER_VALUE,
+  /* ePragFlg:  */ PragFlg_NoColumns1|PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ BTREE_SCHEMA_VERSION },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+ {/* zName:     */ "secure_delete",
+  /* ePragTyp:  */ PragTyp_SECURE_DELETE,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "short_column_names",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_ShortColNames },
+#endif
+ {/* zName:     */ "shrink_memory",
+  /* ePragTyp:  */ PragTyp_SHRINK_MEMORY,
+  /* ePragFlg:  */ PragFlg_NoColumns,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "soft_heap_limit",
+  /* ePragTyp:  */ PragTyp_SOFT_HEAP_LIMIT,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+#if defined(SQLITE_DEBUG)
+ {/* zName:     */ "sql_trace",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_SqlTrace },
+#endif
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS) && defined(SQLITE_DEBUG)
+ {/* zName:     */ "stats",
+  /* ePragTyp:  */ PragTyp_STATS,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq,
+  /* ColNames:  */ 33, 5,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+ {/* zName:     */ "synchronous",
+  /* ePragTyp:  */ PragTyp_SYNCHRONOUS,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)
+ {/* zName:     */ "table_info",
+  /* ePragTyp:  */ PragTyp_TABLE_INFO,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 8, 6,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "table_list",
+  /* ePragTyp:  */ PragTyp_TABLE_LIST,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result1,
+  /* ColNames:  */ 15, 6,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "table_xinfo",
+  /* ePragTyp:  */ PragTyp_TABLE_INFO,
+  /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result1|PragFlg_SchemaOpt,
+  /* ColNames:  */ 8, 7,
+  /* iArg:      */ 1 },
+#endif
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
+ {/* zName:     */ "temp_store",
+  /* ePragTyp:  */ PragTyp_TEMP_STORE,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "temp_store_directory",
+  /* ePragTyp:  */ PragTyp_TEMP_STORE_DIRECTORY,
+  /* ePragFlg:  */ PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#endif
+ {/* zName:     */ "threads",
+  /* ePragTyp:  */ PragTyp_THREADS,
+  /* ePragFlg:  */ PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "trusted_schema",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_TrustedSchema },
+#endif
+#if !defined(SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS)
+ {/* zName:     */ "user_version",
+  /* ePragTyp:  */ PragTyp_HEADER_VALUE,
+  /* ePragFlg:  */ PragFlg_NoColumns1|PragFlg_Result0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ BTREE_USER_VERSION },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+#if defined(SQLITE_DEBUG)
+ {/* zName:     */ "vdbe_addoptrace",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_VdbeAddopTrace },
+ {/* zName:     */ "vdbe_debug",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_SqlTrace|SQLITE_VdbeListing|SQLITE_VdbeTrace },
+ {/* zName:     */ "vdbe_eqp",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_VdbeEQP },
+ {/* zName:     */ "vdbe_listing",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_VdbeListing },
+ {/* zName:     */ "vdbe_trace",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_VdbeTrace },
+#endif
+#endif
+#if !defined(SQLITE_OMIT_WAL)
+ {/* zName:     */ "wal_autocheckpoint",
+  /* ePragTyp:  */ PragTyp_WAL_AUTOCHECKPOINT,
+  /* ePragFlg:  */ 0,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ 0 },
+ {/* zName:     */ "wal_checkpoint",
+  /* ePragTyp:  */ PragTyp_WAL_CHECKPOINT,
+  /* ePragFlg:  */ PragFlg_NeedSchema,
+  /* ColNames:  */ 50, 3,
+  /* iArg:      */ 0 },
+#endif
+#if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ {/* zName:     */ "writable_schema",
+  /* ePragTyp:  */ PragTyp_FLAG,
+  /* ePragFlg:  */ PragFlg_Result0|PragFlg_NoColumns1,
+  /* ColNames:  */ 0, 0,
+  /* iArg:      */ SQLITE_WriteSchema|SQLITE_NoSchemaError },
+#endif
+};
+/* Number of pragmas: 68 on by default, 78 total. */
diff --git a/src/prepare.c b/src/prepare.c
new file mode 100644
index 0000000..87569ee
--- /dev/null
+++ b/src/prepare.c
@@ -0,0 +1,1079 @@
+/*
+** 2005 May 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the implementation of the sqlite3_prepare()
+** interface, and routines that contribute to loading the database schema
+** from disk.
+*/
+#include "sqliteInt.h"
+
+/*
+** Fill the InitData structure with an error message that indicates
+** that the database is corrupt.
+*/
+static void corruptSchema(
+  InitData *pData,     /* Initialization context */
+  char **azObj,        /* Type and name of object being parsed */
+  const char *zExtra   /* Error information */
+){
+  sqlite3 *db = pData->db;
+  if( db->mallocFailed ){
+    pData->rc = SQLITE_NOMEM_BKPT;
+  }else if( pData->pzErrMsg[0]!=0 ){
+    /* A error message has already been generated.  Do not overwrite it */
+  }else if( pData->mInitFlags & (INITFLAG_AlterMask) ){
+    static const char *azAlterType[] = {
+       "rename",
+       "drop column",
+       "add column"
+    };
+    *pData->pzErrMsg = sqlite3MPrintf(db, 
+        "error in %s %s after %s: %s", azObj[0], azObj[1], 
+        azAlterType[(pData->mInitFlags&INITFLAG_AlterMask)-1], 
+        zExtra
+    );
+    pData->rc = SQLITE_ERROR;
+  }else if( db->flags & SQLITE_WriteSchema ){
+    pData->rc = SQLITE_CORRUPT_BKPT;
+  }else{
+    char *z;
+    const char *zObj = azObj[1] ? azObj[1] : "?";
+    z = sqlite3MPrintf(db, "malformed database schema (%s)", zObj);
+    if( zExtra && zExtra[0] ) z = sqlite3MPrintf(db, "%z - %s", z, zExtra);
+    *pData->pzErrMsg = z;
+    pData->rc = SQLITE_CORRUPT_BKPT;
+  }
+}
+
+/*
+** Check to see if any sibling index (another index on the same table)
+** of pIndex has the same root page number, and if it does, return true.
+** This would indicate a corrupt schema.
+*/
+int sqlite3IndexHasDuplicateRootPage(Index *pIndex){
+  Index *p;
+  for(p=pIndex->pTable->pIndex; p; p=p->pNext){
+    if( p->tnum==pIndex->tnum && p!=pIndex ) return 1;
+  }
+  return 0;
+}
+
+/* forward declaration */
+static int sqlite3Prepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
+  Vdbe *pReprepare,         /* VM being reprepared */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+);
+
+
+/*
+** This is the callback routine for the code that initializes the
+** database.  See sqlite3Init() below for additional information.
+** This routine is also called from the OP_ParseSchema opcode of the VDBE.
+**
+** Each callback contains the following information:
+**
+**     argv[0] = type of object: "table", "index", "trigger", or "view".
+**     argv[1] = name of thing being created
+**     argv[2] = associated table if an index or trigger
+**     argv[3] = root page number for table or index. 0 for trigger or view.
+**     argv[4] = SQL text for the CREATE statement.
+**
+*/
+int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
+  InitData *pData = (InitData*)pInit;
+  sqlite3 *db = pData->db;
+  int iDb = pData->iDb;
+
+  assert( argc==5 );
+  UNUSED_PARAMETER2(NotUsed, argc);
+  assert( sqlite3_mutex_held(db->mutex) );
+  db->mDbFlags |= DBFLAG_EncodingFixed;
+  if( argv==0 ) return 0;   /* Might happen if EMPTY_RESULT_CALLBACKS are on */
+  pData->nInitRow++;
+  if( db->mallocFailed ){
+    corruptSchema(pData, argv, 0);
+    return 1;
+  }
+
+  assert( iDb>=0 && iDb<db->nDb );
+  if( argv[3]==0 ){
+    corruptSchema(pData, argv, 0);
+  }else if( argv[4]
+         && 'c'==sqlite3UpperToLower[(unsigned char)argv[4][0]]
+         && 'r'==sqlite3UpperToLower[(unsigned char)argv[4][1]] ){
+    /* Call the parser to process a CREATE TABLE, INDEX or VIEW.
+    ** But because db->init.busy is set to 1, no VDBE code is generated
+    ** or executed.  All the parser does is build the internal data
+    ** structures that describe the table, index, or view.
+    **
+    ** No other valid SQL statement, other than the variable CREATE statements,
+    ** can begin with the letters "C" and "R".  Thus, it is not possible run
+    ** any other kind of statement while parsing the schema, even a corrupt
+    ** schema.
+    */
+    int rc;
+    u8 saved_iDb = db->init.iDb;
+    sqlite3_stmt *pStmt;
+    TESTONLY(int rcp);            /* Return code from sqlite3_prepare() */
+
+    assert( db->init.busy );
+    db->init.iDb = iDb;
+    if( sqlite3GetUInt32(argv[3], &db->init.newTnum)==0
+     || (db->init.newTnum>pData->mxPage && pData->mxPage>0)
+    ){
+      if( sqlite3Config.bExtraSchemaChecks ){
+        corruptSchema(pData, argv, "invalid rootpage");
+      }
+    }
+    db->init.orphanTrigger = 0;
+    db->init.azInit = (const char**)argv;
+    pStmt = 0;
+    TESTONLY(rcp = ) sqlite3Prepare(db, argv[4], -1, 0, 0, &pStmt, 0);
+    rc = db->errCode;
+    assert( (rc&0xFF)==(rcp&0xFF) );
+    db->init.iDb = saved_iDb;
+    /* assert( saved_iDb==0 || (db->mDbFlags & DBFLAG_Vacuum)!=0 ); */
+    if( SQLITE_OK!=rc ){
+      if( db->init.orphanTrigger ){
+        assert( iDb==1 );
+      }else{
+        if( rc > pData->rc ) pData->rc = rc;
+        if( rc==SQLITE_NOMEM ){
+          sqlite3OomFault(db);
+        }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED ){
+          corruptSchema(pData, argv, sqlite3_errmsg(db));
+        }
+      }
+    }
+    db->init.azInit = sqlite3StdType; /* Any array of string ptrs will do */
+    sqlite3_finalize(pStmt);
+  }else if( argv[1]==0 || (argv[4]!=0 && argv[4][0]!=0) ){
+    corruptSchema(pData, argv, 0);
+  }else{
+    /* If the SQL column is blank it means this is an index that
+    ** was created to be the PRIMARY KEY or to fulfill a UNIQUE
+    ** constraint for a CREATE TABLE.  The index should have already
+    ** been created when we processed the CREATE TABLE.  All we have
+    ** to do here is record the root page number for that index.
+    */
+    Index *pIndex;
+    pIndex = sqlite3FindIndex(db, argv[1], db->aDb[iDb].zDbSName);
+    if( pIndex==0 ){
+      corruptSchema(pData, argv, "orphan index");
+    }else
+    if( sqlite3GetUInt32(argv[3],&pIndex->tnum)==0
+     || pIndex->tnum<2
+     || pIndex->tnum>pData->mxPage
+     || sqlite3IndexHasDuplicateRootPage(pIndex)
+    ){
+      if( sqlite3Config.bExtraSchemaChecks ){
+        corruptSchema(pData, argv, "invalid rootpage");
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** Attempt to read the database schema and initialize internal
+** data structures for a single database file.  The index of the
+** database file is given by iDb.  iDb==0 is used for the main
+** database.  iDb==1 should never be used.  iDb>=2 is used for
+** auxiliary databases.  Return one of the SQLITE_ error codes to
+** indicate success or failure.
+*/
+int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg, u32 mFlags){
+  int rc;
+  int i;
+#ifndef SQLITE_OMIT_DEPRECATED
+  int size;
+#endif
+  Db *pDb;
+  char const *azArg[6];
+  int meta[5];
+  InitData initData;
+  const char *zSchemaTabName;
+  int openedTransaction = 0;
+  int mask = ((db->mDbFlags & DBFLAG_EncodingFixed) | ~DBFLAG_EncodingFixed);
+
+  assert( (db->mDbFlags & DBFLAG_SchemaKnownOk)==0 );
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( db->aDb[iDb].pSchema );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
+
+  db->init.busy = 1;
+
+  /* Construct the in-memory representation schema tables (sqlite_schema or
+  ** sqlite_temp_schema) by invoking the parser directly.  The appropriate
+  ** table name will be inserted automatically by the parser so we can just
+  ** use the abbreviation "x" here.  The parser will also automatically tag
+  ** the schema table as read-only. */
+  azArg[0] = "table";
+  azArg[1] = zSchemaTabName = SCHEMA_TABLE(iDb);
+  azArg[2] = azArg[1];
+  azArg[3] = "1";
+  azArg[4] = "CREATE TABLE x(type text,name text,tbl_name text,"
+                            "rootpage int,sql text)";
+  azArg[5] = 0;
+  initData.db = db;
+  initData.iDb = iDb;
+  initData.rc = SQLITE_OK;
+  initData.pzErrMsg = pzErrMsg;
+  initData.mInitFlags = mFlags;
+  initData.nInitRow = 0;
+  initData.mxPage = 0;
+  sqlite3InitCallback(&initData, 5, (char **)azArg, 0);
+  db->mDbFlags &= mask;
+  if( initData.rc ){
+    rc = initData.rc;
+    goto error_out;
+  }
+
+  /* Create a cursor to hold the database open
+  */
+  pDb = &db->aDb[iDb];
+  if( pDb->pBt==0 ){
+    assert( iDb==1 );
+    DbSetProperty(db, 1, DB_SchemaLoaded);
+    rc = SQLITE_OK;
+    goto error_out;
+  }
+
+  /* If there is not already a read-only (or read-write) transaction opened
+  ** on the b-tree database, open one now. If a transaction is opened, it 
+  ** will be closed before this function returns.  */
+  sqlite3BtreeEnter(pDb->pBt);
+  if( sqlite3BtreeTxnState(pDb->pBt)==SQLITE_TXN_NONE ){
+    rc = sqlite3BtreeBeginTrans(pDb->pBt, 0, 0);
+    if( rc!=SQLITE_OK ){
+      sqlite3SetString(pzErrMsg, db, sqlite3ErrStr(rc));
+      goto initone_error_out;
+    }
+    openedTransaction = 1;
+  }
+
+  /* Get the database meta information.
+  **
+  ** Meta values are as follows:
+  **    meta[0]   Schema cookie.  Changes with each schema change.
+  **    meta[1]   File format of schema layer.
+  **    meta[2]   Size of the page cache.
+  **    meta[3]   Largest rootpage (auto/incr_vacuum mode)
+  **    meta[4]   Db text encoding. 1:UTF-8 2:UTF-16LE 3:UTF-16BE
+  **    meta[5]   User version
+  **    meta[6]   Incremental vacuum mode
+  **    meta[7]   unused
+  **    meta[8]   unused
+  **    meta[9]   unused
+  **
+  ** Note: The #defined SQLITE_UTF* symbols in sqliteInt.h correspond to
+  ** the possible values of meta[4].
+  */
+  for(i=0; i<ArraySize(meta); i++){
+    sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
+  }
+  if( (db->flags & SQLITE_ResetDatabase)!=0 ){
+    memset(meta, 0, sizeof(meta));
+  }
+  pDb->pSchema->schema_cookie = meta[BTREE_SCHEMA_VERSION-1];
+
+  /* If opening a non-empty database, check the text encoding. For the
+  ** main database, set sqlite3.enc to the encoding of the main database.
+  ** For an attached db, it is an error if the encoding is not the same
+  ** as sqlite3.enc.
+  */
+  if( meta[BTREE_TEXT_ENCODING-1] ){  /* text encoding */
+    if( iDb==0 && (db->mDbFlags & DBFLAG_EncodingFixed)==0 ){
+      u8 encoding;
+#ifndef SQLITE_OMIT_UTF16
+      /* If opening the main database, set ENC(db). */
+      encoding = (u8)meta[BTREE_TEXT_ENCODING-1] & 3;
+      if( encoding==0 ) encoding = SQLITE_UTF8;
+#else
+      encoding = SQLITE_UTF8;
+#endif
+      if( db->nVdbeActive>0 && encoding!=ENC(db)
+       && (db->mDbFlags & DBFLAG_Vacuum)==0
+      ){
+        rc = SQLITE_LOCKED;
+        goto initone_error_out;
+      }else{
+        sqlite3SetTextEncoding(db, encoding);
+      }
+    }else{
+      /* If opening an attached database, the encoding much match ENC(db) */
+      if( (meta[BTREE_TEXT_ENCODING-1] & 3)!=ENC(db) ){
+        sqlite3SetString(pzErrMsg, db, "attached databases must use the same"
+            " text encoding as main database");
+        rc = SQLITE_ERROR;
+        goto initone_error_out;
+      }
+    }
+  }
+  pDb->pSchema->enc = ENC(db);
+
+  if( pDb->pSchema->cache_size==0 ){
+#ifndef SQLITE_OMIT_DEPRECATED
+    size = sqlite3AbsInt32(meta[BTREE_DEFAULT_CACHE_SIZE-1]);
+    if( size==0 ){ size = SQLITE_DEFAULT_CACHE_SIZE; }
+    pDb->pSchema->cache_size = size;
+#else
+    pDb->pSchema->cache_size = SQLITE_DEFAULT_CACHE_SIZE;
+#endif
+    sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
+  }
+
+  /*
+  ** file_format==1    Version 3.0.0.
+  ** file_format==2    Version 3.1.3.  // ALTER TABLE ADD COLUMN
+  ** file_format==3    Version 3.1.4.  // ditto but with non-NULL defaults
+  ** file_format==4    Version 3.3.0.  // DESC indices.  Boolean constants
+  */
+  pDb->pSchema->file_format = (u8)meta[BTREE_FILE_FORMAT-1];
+  if( pDb->pSchema->file_format==0 ){
+    pDb->pSchema->file_format = 1;
+  }
+  if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){
+    sqlite3SetString(pzErrMsg, db, "unsupported file format");
+    rc = SQLITE_ERROR;
+    goto initone_error_out;
+  }
+
+  /* Ticket #2804:  When we open a database in the newer file format,
+  ** clear the legacy_file_format pragma flag so that a VACUUM will
+  ** not downgrade the database and thus invalidate any descending
+  ** indices that the user might have created.
+  */
+  if( iDb==0 && meta[BTREE_FILE_FORMAT-1]>=4 ){
+    db->flags &= ~(u64)SQLITE_LegacyFileFmt;
+  }
+
+  /* Read the schema information out of the schema tables
+  */
+  assert( db->init.busy );
+  initData.mxPage = sqlite3BtreeLastPage(pDb->pBt);
+  {
+    char *zSql;
+    zSql = sqlite3MPrintf(db, 
+        "SELECT*FROM\"%w\".%s ORDER BY rowid",
+        db->aDb[iDb].zDbSName, zSchemaTabName);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    {
+      sqlite3_xauth xAuth;
+      xAuth = db->xAuth;
+      db->xAuth = 0;
+#endif
+      rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+      db->xAuth = xAuth;
+    }
+#endif
+    if( rc==SQLITE_OK ) rc = initData.rc;
+    sqlite3DbFree(db, zSql);
+#ifndef SQLITE_OMIT_ANALYZE
+    if( rc==SQLITE_OK ){
+      sqlite3AnalysisLoad(db, iDb);
+    }
+#endif
+  }
+  assert( pDb == &(db->aDb[iDb]) );
+  if( db->mallocFailed ){
+    rc = SQLITE_NOMEM_BKPT;
+    sqlite3ResetAllSchemasOfConnection(db);
+    pDb = &db->aDb[iDb];
+  }else
+  if( rc==SQLITE_OK || ((db->flags&SQLITE_NoSchemaError) && rc!=SQLITE_NOMEM)){
+    /* Hack: If the SQLITE_NoSchemaError flag is set, then consider
+    ** the schema loaded, even if errors (other than OOM) occurred. In
+    ** this situation the current sqlite3_prepare() operation will fail,
+    ** but the following one will attempt to compile the supplied statement
+    ** against whatever subset of the schema was loaded before the error
+    ** occurred.
+    **
+    ** The primary purpose of this is to allow access to the sqlite_schema
+    ** table even when its contents have been corrupted.
+    */
+    DbSetProperty(db, iDb, DB_SchemaLoaded);
+    rc = SQLITE_OK;
+  }
+
+  /* Jump here for an error that occurs after successfully allocating
+  ** curMain and calling sqlite3BtreeEnter(). For an error that occurs
+  ** before that point, jump to error_out.
+  */
+initone_error_out:
+  if( openedTransaction ){
+    sqlite3BtreeCommit(pDb->pBt);
+  }
+  sqlite3BtreeLeave(pDb->pBt);
+
+error_out:
+  if( rc ){
+    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
+      sqlite3OomFault(db);
+    }
+    sqlite3ResetOneSchema(db, iDb);
+  }
+  db->init.busy = 0;
+  return rc;
+}
+
+/*
+** Initialize all database files - the main database file, the file
+** used to store temporary tables, and any additional database files
+** created using ATTACH statements.  Return a success code.  If an
+** error occurs, write an error message into *pzErrMsg.
+**
+** After a database is initialized, the DB_SchemaLoaded bit is set
+** bit is set in the flags field of the Db structure. 
+*/
+int sqlite3Init(sqlite3 *db, char **pzErrMsg){
+  int i, rc;
+  int commit_internal = !(db->mDbFlags&DBFLAG_SchemaChange);
+  
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( sqlite3BtreeHoldsMutex(db->aDb[0].pBt) );
+  assert( db->init.busy==0 );
+  ENC(db) = SCHEMA_ENC(db);
+  assert( db->nDb>0 );
+  /* Do the main schema first */
+  if( !DbHasProperty(db, 0, DB_SchemaLoaded) ){
+    rc = sqlite3InitOne(db, 0, pzErrMsg, 0);
+    if( rc ) return rc;
+  }
+  /* All other schemas after the main schema. The "temp" schema must be last */
+  for(i=db->nDb-1; i>0; i--){
+    assert( i==1 || sqlite3BtreeHoldsMutex(db->aDb[i].pBt) );
+    if( !DbHasProperty(db, i, DB_SchemaLoaded) ){
+      rc = sqlite3InitOne(db, i, pzErrMsg, 0);
+      if( rc ) return rc;
+    }
+  }
+  if( commit_internal ){
+    sqlite3CommitInternalChanges(db);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This routine is a no-op if the database schema is already initialized.
+** Otherwise, the schema is loaded. An error code is returned.
+*/
+int sqlite3ReadSchema(Parse *pParse){
+  int rc = SQLITE_OK;
+  sqlite3 *db = pParse->db;
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( !db->init.busy ){
+    rc = sqlite3Init(db, &pParse->zErrMsg);
+    if( rc!=SQLITE_OK ){
+      pParse->rc = rc;
+      pParse->nErr++;
+    }else if( db->noSharedCache ){
+      db->mDbFlags |= DBFLAG_SchemaKnownOk;
+    }
+  }
+  return rc;
+}
+
+
+/*
+** Check schema cookies in all databases.  If any cookie is out
+** of date set pParse->rc to SQLITE_SCHEMA.  If all schema cookies
+** make no changes to pParse->rc.
+*/
+static void schemaIsValid(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  int iDb;
+  int rc;
+  int cookie;
+
+  assert( pParse->checkSchema );
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(iDb=0; iDb<db->nDb; iDb++){
+    int openedTransaction = 0;         /* True if a transaction is opened */
+    Btree *pBt = db->aDb[iDb].pBt;     /* Btree database to read cookie from */
+    if( pBt==0 ) continue;
+
+    /* If there is not already a read-only (or read-write) transaction opened
+    ** on the b-tree database, open one now. If a transaction is opened, it 
+    ** will be closed immediately after reading the meta-value. */
+    if( sqlite3BtreeTxnState(pBt)==SQLITE_TXN_NONE ){
+      rc = sqlite3BtreeBeginTrans(pBt, 0, 0);
+      if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
+        sqlite3OomFault(db);
+        pParse->rc = SQLITE_NOMEM;
+      }
+      if( rc!=SQLITE_OK ) return;
+      openedTransaction = 1;
+    }
+
+    /* Read the schema cookie from the database. If it does not match the 
+    ** value stored as part of the in-memory schema representation,
+    ** set Parse.rc to SQLITE_SCHEMA. */
+    sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&cookie);
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( cookie!=db->aDb[iDb].pSchema->schema_cookie ){
+      if( DbHasProperty(db, iDb, DB_SchemaLoaded) ) pParse->rc = SQLITE_SCHEMA;
+      sqlite3ResetOneSchema(db, iDb);
+    }
+
+    /* Close the transaction, if one was opened. */
+    if( openedTransaction ){
+      sqlite3BtreeCommit(pBt);
+    }
+  }
+}
+
+/*
+** Convert a schema pointer into the iDb index that indicates
+** which database file in db->aDb[] the schema refers to.
+**
+** If the same database is attached more than once, the first
+** attached database is returned.
+*/
+int sqlite3SchemaToIndex(sqlite3 *db, Schema *pSchema){
+  int i = -32768;
+
+  /* If pSchema is NULL, then return -32768. This happens when code in 
+  ** expr.c is trying to resolve a reference to a transient table (i.e. one
+  ** created by a sub-select). In this case the return value of this 
+  ** function should never be used.
+  **
+  ** We return -32768 instead of the more usual -1 simply because using
+  ** -32768 as the incorrect index into db->aDb[] is much 
+  ** more likely to cause a segfault than -1 (of course there are assert()
+  ** statements too, but it never hurts to play the odds) and
+  ** -32768 will still fit into a 16-bit signed integer.
+  */
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( pSchema ){
+    for(i=0; 1; i++){
+      assert( i<db->nDb );
+      if( db->aDb[i].pSchema==pSchema ){
+        break;
+      }
+    }
+    assert( i>=0 && i<db->nDb );
+  }
+  return i;
+}
+
+/*
+** Free all memory allocations in the pParse object
+*/
+void sqlite3ParseObjectReset(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  assert( db!=0 );
+  assert( db->pParse==pParse );
+  assert( pParse->nested==0 );
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  if( pParse->aTableLock ) sqlite3DbNNFreeNN(db, pParse->aTableLock);
+#endif
+  while( pParse->pCleanup ){
+    ParseCleanup *pCleanup = pParse->pCleanup;
+    pParse->pCleanup = pCleanup->pNext;
+    pCleanup->xCleanup(db, pCleanup->pPtr);
+    sqlite3DbNNFreeNN(db, pCleanup);
+  }
+  if( pParse->aLabel ) sqlite3DbNNFreeNN(db, pParse->aLabel);
+  if( pParse->pConstExpr ){
+    sqlite3ExprListDelete(db, pParse->pConstExpr);
+  }
+  assert( db->lookaside.bDisable >= pParse->disableLookaside );
+  db->lookaside.bDisable -= pParse->disableLookaside;
+  db->lookaside.sz = db->lookaside.bDisable ? 0 : db->lookaside.szTrue;
+  assert( pParse->db->pParse==pParse );
+  db->pParse = pParse->pOuterParse;
+}
+
+/*
+** Add a new cleanup operation to a Parser.  The cleanup should happen when
+** the parser object is destroyed.  But, beware: the cleanup might happen
+** immediately.
+**
+** Use this mechanism for uncommon cleanups.  There is a higher setup
+** cost for this mechanism (an extra malloc), so it should not be used
+** for common cleanups that happen on most calls.  But for less
+** common cleanups, we save a single NULL-pointer comparison in
+** sqlite3ParseObjectReset(), which reduces the total CPU cycle count.
+**
+** If a memory allocation error occurs, then the cleanup happens immediately.
+** When either SQLITE_DEBUG or SQLITE_COVERAGE_TEST are defined, the
+** pParse->earlyCleanup flag is set in that case.  Calling code show verify
+** that test cases exist for which this happens, to guard against possible
+** use-after-free errors following an OOM.  The preferred way to do this is
+** to immediately follow the call to this routine with:
+**
+**       testcase( pParse->earlyCleanup );
+**
+** This routine returns a copy of its pPtr input (the third parameter)
+** except if an early cleanup occurs, in which case it returns NULL.  So
+** another way to check for early cleanup is to check the return value.
+** Or, stop using the pPtr parameter with this call and use only its
+** return value thereafter.  Something like this:
+**
+**       pObj = sqlite3ParserAddCleanup(pParse, destructor, pObj);
+*/
+void *sqlite3ParserAddCleanup(
+  Parse *pParse,                      /* Destroy when this Parser finishes */
+  void (*xCleanup)(sqlite3*,void*),   /* The cleanup routine */
+  void *pPtr                          /* Pointer to object to be cleaned up */
+){
+  ParseCleanup *pCleanup = sqlite3DbMallocRaw(pParse->db, sizeof(*pCleanup));
+  if( pCleanup ){
+    pCleanup->pNext = pParse->pCleanup;
+    pParse->pCleanup = pCleanup;
+    pCleanup->pPtr = pPtr;
+    pCleanup->xCleanup = xCleanup;
+  }else{
+    xCleanup(pParse->db, pPtr);
+    pPtr = 0;
+#if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
+    pParse->earlyCleanup = 1;
+#endif
+  }
+  return pPtr;
+}
+
+/*
+** Turn bulk memory into a valid Parse object and link that Parse object
+** into database connection db.
+**
+** Call sqlite3ParseObjectReset() to undo this operation.
+**
+** Caution:  Do not confuse this routine with sqlite3ParseObjectInit() which
+** is generated by Lemon.
+*/
+void sqlite3ParseObjectInit(Parse *pParse, sqlite3 *db){
+  memset(PARSE_HDR(pParse), 0, PARSE_HDR_SZ);
+  memset(PARSE_TAIL(pParse), 0, PARSE_TAIL_SZ);
+  assert( db->pParse!=pParse );
+  pParse->pOuterParse = db->pParse;
+  db->pParse = pParse;
+  pParse->db = db;
+  if( db->mallocFailed ) sqlite3ErrorMsg(pParse, "out of memory");
+}
+
+/*
+** Maximum number of times that we will try again to prepare a statement
+** that returns SQLITE_ERROR_RETRY.
+*/
+#ifndef SQLITE_MAX_PREPARE_RETRY
+# define SQLITE_MAX_PREPARE_RETRY 25
+#endif
+
+/*
+** Compile the UTF-8 encoded SQL statement zSql into a statement handle.
+*/
+static int sqlite3Prepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
+  Vdbe *pReprepare,         /* VM being reprepared */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc = SQLITE_OK;       /* Result code */
+  int i;                    /* Loop counter */
+  Parse sParse;             /* Parsing context */
+
+  /* sqlite3ParseObjectInit(&sParse, db); // inlined for performance */
+  memset(PARSE_HDR(&sParse), 0, PARSE_HDR_SZ);
+  memset(PARSE_TAIL(&sParse), 0, PARSE_TAIL_SZ);
+  sParse.pOuterParse = db->pParse;
+  db->pParse = &sParse;
+  sParse.db = db;
+  if( pReprepare ){
+    sParse.pReprepare = pReprepare;
+    sParse.explain = sqlite3_stmt_isexplain((sqlite3_stmt*)pReprepare);
+  }else{
+    assert( sParse.pReprepare==0 );
+  }
+  assert( ppStmt && *ppStmt==0 );
+  if( db->mallocFailed ){
+    sqlite3ErrorMsg(&sParse, "out of memory");
+    db->errCode = rc = SQLITE_NOMEM;
+    goto end_prepare;
+  }
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  /* For a long-term use prepared statement avoid the use of
+  ** lookaside memory.
+  */
+  if( prepFlags & SQLITE_PREPARE_PERSISTENT ){
+    sParse.disableLookaside++;
+    DisableLookaside;
+  }
+  sParse.prepFlags = prepFlags & 0xff;
+
+  /* Check to verify that it is possible to get a read lock on all
+  ** database schemas.  The inability to get a read lock indicates that
+  ** some other database connection is holding a write-lock, which in
+  ** turn means that the other connection has made uncommitted changes
+  ** to the schema.
+  **
+  ** Were we to proceed and prepare the statement against the uncommitted
+  ** schema changes and if those schema changes are subsequently rolled
+  ** back and different changes are made in their place, then when this
+  ** prepared statement goes to run the schema cookie would fail to detect
+  ** the schema change.  Disaster would follow.
+  **
+  ** This thread is currently holding mutexes on all Btrees (because
+  ** of the sqlite3BtreeEnterAll() in sqlite3LockAndPrepare()) so it
+  ** is not possible for another thread to start a new schema change
+  ** while this routine is running.  Hence, we do not need to hold 
+  ** locks on the schema, we just need to make sure nobody else is 
+  ** holding them.
+  **
+  ** Note that setting READ_UNCOMMITTED overrides most lock detection,
+  ** but it does *not* override schema lock detection, so this all still
+  ** works even if READ_UNCOMMITTED is set.
+  */
+  if( !db->noSharedCache ){
+    for(i=0; i<db->nDb; i++) {
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        assert( sqlite3BtreeHoldsMutex(pBt) );
+        rc = sqlite3BtreeSchemaLocked(pBt);
+        if( rc ){
+          const char *zDb = db->aDb[i].zDbSName;
+          sqlite3ErrorWithMsg(db, rc, "database schema is locked: %s", zDb);
+          testcase( db->flags & SQLITE_ReadUncommit );
+          goto end_prepare;
+        }
+      }
+    }
+  }
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( db->pDisconnect ) sqlite3VtabUnlockList(db);
+#endif
+
+  if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){
+    char *zSqlCopy;
+    int mxLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
+    testcase( nBytes==mxLen );
+    testcase( nBytes==mxLen+1 );
+    if( nBytes>mxLen ){
+      sqlite3ErrorWithMsg(db, SQLITE_TOOBIG, "statement too long");
+      rc = sqlite3ApiExit(db, SQLITE_TOOBIG);
+      goto end_prepare;
+    }
+    zSqlCopy = sqlite3DbStrNDup(db, zSql, nBytes);
+    if( zSqlCopy ){
+      sqlite3RunParser(&sParse, zSqlCopy);
+      sParse.zTail = &zSql[sParse.zTail-zSqlCopy];
+      sqlite3DbFree(db, zSqlCopy);
+    }else{
+      sParse.zTail = &zSql[nBytes];
+    }
+  }else{
+    sqlite3RunParser(&sParse, zSql);
+  }
+  assert( 0==sParse.nQueryLoop );
+
+  if( pzTail ){
+    *pzTail = sParse.zTail;
+  }
+
+  if( db->init.busy==0 ){
+    sqlite3VdbeSetSql(sParse.pVdbe, zSql, (int)(sParse.zTail-zSql), prepFlags);
+  }
+  if( db->mallocFailed ){
+    sParse.rc = SQLITE_NOMEM_BKPT;
+    sParse.checkSchema = 0;
+  }
+  if( sParse.rc!=SQLITE_OK && sParse.rc!=SQLITE_DONE ){
+    if( sParse.checkSchema && db->init.busy==0 ){
+      schemaIsValid(&sParse);
+    }
+    if( sParse.pVdbe ){
+      sqlite3VdbeFinalize(sParse.pVdbe);
+    }
+    assert( 0==(*ppStmt) );
+    rc = sParse.rc;
+    if( sParse.zErrMsg ){
+      sqlite3ErrorWithMsg(db, rc, "%s", sParse.zErrMsg);
+      sqlite3DbFree(db, sParse.zErrMsg);
+    }else{
+      sqlite3Error(db, rc);
+    }
+  }else{
+    assert( sParse.zErrMsg==0 );
+    *ppStmt = (sqlite3_stmt*)sParse.pVdbe;
+    rc = SQLITE_OK;
+    sqlite3ErrorClear(db);
+  }
+
+
+  /* Delete any TriggerPrg structures allocated while parsing this statement. */
+  while( sParse.pTriggerPrg ){
+    TriggerPrg *pT = sParse.pTriggerPrg;
+    sParse.pTriggerPrg = pT->pNext;
+    sqlite3DbFree(db, pT);
+  }
+
+end_prepare:
+
+  sqlite3ParseObjectReset(&sParse);
+  return rc;
+}
+static int sqlite3LockAndPrepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
+  Vdbe *pOld,               /* VM being reprepared */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  int cnt = 0;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( ppStmt==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  *ppStmt = 0;
+  if( !sqlite3SafetyCheckOk(db)||zSql==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3BtreeEnterAll(db);
+  do{
+    /* Make multiple attempts to compile the SQL, until it either succeeds
+    ** or encounters a permanent error.  A schema problem after one schema
+    ** reset is considered a permanent error. */
+    rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
+    assert( rc==SQLITE_OK || *ppStmt==0 );
+    if( rc==SQLITE_OK || db->mallocFailed ) break;
+  }while( (rc==SQLITE_ERROR_RETRY && (cnt++)<SQLITE_MAX_PREPARE_RETRY)
+       || (rc==SQLITE_SCHEMA && (sqlite3ResetOneSchema(db,-1), cnt++)==0) );
+  sqlite3BtreeLeaveAll(db);
+  rc = sqlite3ApiExit(db, rc);
+  assert( (rc&db->errMask)==rc );
+  db->busyHandler.nBusy = 0;
+  sqlite3_mutex_leave(db->mutex);
+  assert( rc==SQLITE_OK || (*ppStmt)==0 );
+  return rc;
+}
+
+
+/*
+** Rerun the compilation of a statement after a schema change.
+**
+** If the statement is successfully recompiled, return SQLITE_OK. Otherwise,
+** if the statement cannot be recompiled because another connection has
+** locked the sqlite3_schema table, return SQLITE_LOCKED. If any other error
+** occurs, return SQLITE_SCHEMA.
+*/
+int sqlite3Reprepare(Vdbe *p){
+  int rc;
+  sqlite3_stmt *pNew;
+  const char *zSql;
+  sqlite3 *db;
+  u8 prepFlags;
+
+  assert( sqlite3_mutex_held(sqlite3VdbeDb(p)->mutex) );
+  zSql = sqlite3_sql((sqlite3_stmt *)p);
+  assert( zSql!=0 );  /* Reprepare only called for prepare_v2() statements */
+  db = sqlite3VdbeDb(p);
+  assert( sqlite3_mutex_held(db->mutex) );
+  prepFlags = sqlite3VdbePrepareFlags(p);
+  rc = sqlite3LockAndPrepare(db, zSql, -1, prepFlags, p, &pNew, 0);
+  if( rc ){
+    if( rc==SQLITE_NOMEM ){
+      sqlite3OomFault(db);
+    }
+    assert( pNew==0 );
+    return rc;
+  }else{
+    assert( pNew!=0 );
+  }
+  sqlite3VdbeSwap((Vdbe*)pNew, p);
+  sqlite3TransferBindings(pNew, (sqlite3_stmt*)p);
+  sqlite3VdbeResetStepResult((Vdbe*)pNew);
+  sqlite3VdbeFinalize((Vdbe*)pNew);
+  return SQLITE_OK;
+}
+
+
+/*
+** Two versions of the official API.  Legacy and new use.  In the legacy
+** version, the original SQL text is not saved in the prepared statement
+** and so if a schema change occurs, SQLITE_SCHEMA is returned by
+** sqlite3_step().  In the new version, the original SQL text is retained
+** and the statement is automatically recompiled if an schema change
+** occurs.
+*/
+int sqlite3_prepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3LockAndPrepare(db,zSql,nBytes,0,0,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+int sqlite3_prepare_v2(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  /* EVIDENCE-OF: R-37923-12173 The sqlite3_prepare_v2() interface works
+  ** exactly the same as sqlite3_prepare_v3() with a zero prepFlags
+  ** parameter.
+  **
+  ** Proof in that the 5th parameter to sqlite3LockAndPrepare is 0 */
+  rc = sqlite3LockAndPrepare(db,zSql,nBytes,SQLITE_PREPARE_SAVESQL,0,
+                             ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );
+  return rc;
+}
+int sqlite3_prepare_v3(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  unsigned int prepFlags,   /* Zero or more SQLITE_PREPARE_* flags */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  /* EVIDENCE-OF: R-56861-42673 sqlite3_prepare_v3() differs from
+  ** sqlite3_prepare_v2() only in having the extra prepFlags parameter,
+  ** which is a bit array consisting of zero or more of the
+  ** SQLITE_PREPARE_* flags.
+  **
+  ** Proof by comparison to the implementation of sqlite3_prepare_v2()
+  ** directly above. */
+  rc = sqlite3LockAndPrepare(db,zSql,nBytes,
+                 SQLITE_PREPARE_SAVESQL|(prepFlags&SQLITE_PREPARE_MASK),
+                 0,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );
+  return rc;
+}
+
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Compile the UTF-16 encoded SQL statement zSql into a statement handle.
+*/
+static int sqlite3Prepare16(
+  sqlite3 *db,              /* Database handle. */ 
+  const void *zSql,         /* UTF-16 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const void **pzTail       /* OUT: End of parsed string */
+){
+  /* This function currently works by first transforming the UTF-16
+  ** encoded string to UTF-8, then invoking sqlite3_prepare(). The
+  ** tricky bit is figuring out the pointer to return in *pzTail.
+  */
+  char *zSql8;
+  const char *zTail8 = 0;
+  int rc = SQLITE_OK;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( ppStmt==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  *ppStmt = 0;
+  if( !sqlite3SafetyCheckOk(db)||zSql==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( nBytes>=0 ){
+    int sz;
+    const char *z = (const char*)zSql;
+    for(sz=0; sz<nBytes && (z[sz]!=0 || z[sz+1]!=0); sz += 2){}
+    nBytes = sz;
+  }
+  sqlite3_mutex_enter(db->mutex);
+  zSql8 = sqlite3Utf16to8(db, zSql, nBytes, SQLITE_UTF16NATIVE);
+  if( zSql8 ){
+    rc = sqlite3LockAndPrepare(db, zSql8, -1, prepFlags, 0, ppStmt, &zTail8);
+  }
+
+  if( zTail8 && pzTail ){
+    /* If sqlite3_prepare returns a tail pointer, we calculate the
+    ** equivalent pointer into the UTF-16 string by counting the unicode
+    ** characters between zSql8 and zTail8, and then returning a pointer
+    ** the same number of characters into the UTF-16 string.
+    */
+    int chars_parsed = sqlite3Utf8CharLen(zSql8, (int)(zTail8-zSql8));
+    *pzTail = (u8 *)zSql + sqlite3Utf16ByteLen(zSql, chars_parsed);
+  }
+  sqlite3DbFree(db, zSql8); 
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Two versions of the official API.  Legacy and new use.  In the legacy
+** version, the original SQL text is not saved in the prepared statement
+** and so if a schema change occurs, SQLITE_SCHEMA is returned by
+** sqlite3_step().  In the new version, the original SQL text is retained
+** and the statement is automatically recompiled if an schema change
+** occurs.
+*/
+int sqlite3_prepare16(
+  sqlite3 *db,              /* Database handle. */ 
+  const void *zSql,         /* UTF-16 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const void **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3Prepare16(db,zSql,nBytes,0,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+int sqlite3_prepare16_v2(
+  sqlite3 *db,              /* Database handle. */ 
+  const void *zSql,         /* UTF-16 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const void **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3Prepare16(db,zSql,nBytes,SQLITE_PREPARE_SAVESQL,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+int sqlite3_prepare16_v3(
+  sqlite3 *db,              /* Database handle. */ 
+  const void *zSql,         /* UTF-16 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  unsigned int prepFlags,   /* Zero or more SQLITE_PREPARE_* flags */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const void **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3Prepare16(db,zSql,nBytes,
+         SQLITE_PREPARE_SAVESQL|(prepFlags&SQLITE_PREPARE_MASK),
+         ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+
+#endif /* SQLITE_OMIT_UTF16 */
diff --git a/src/printf.c b/src/printf.c
new file mode 100644
index 0000000..c6b3803
--- /dev/null
+++ b/src/printf.c
@@ -0,0 +1,1437 @@
+/*
+** The "printf" code that follows dates from the 1980's.  It is in
+** the public domain. 
+**
+**************************************************************************
+**
+** This file contains code for a set of "printf"-like routines.  These
+** routines format strings much like the printf() from the standard C
+** library, though the implementation here has enhancements to support
+** SQLite.
+*/
+#include "sqliteInt.h"
+
+/*
+** Conversion types fall into various categories as defined by the
+** following enumeration.
+*/
+#define etRADIX       0 /* non-decimal integer types.  %x %o */
+#define etFLOAT       1 /* Floating point.  %f */
+#define etEXP         2 /* Exponentional notation. %e and %E */
+#define etGENERIC     3 /* Floating or exponential, depending on exponent. %g */
+#define etSIZE        4 /* Return number of characters processed so far. %n */
+#define etSTRING      5 /* Strings. %s */
+#define etDYNSTRING   6 /* Dynamically allocated strings. %z */
+#define etPERCENT     7 /* Percent symbol. %% */
+#define etCHARX       8 /* Characters. %c */
+/* The rest are extensions, not normally found in printf() */
+#define etSQLESCAPE   9 /* Strings with '\'' doubled.  %q */
+#define etSQLESCAPE2 10 /* Strings with '\'' doubled and enclosed in '',
+                          NULL pointers replaced by SQL NULL.  %Q */
+#define etTOKEN      11 /* a pointer to a Token structure */
+#define etSRCITEM    12 /* a pointer to a SrcItem */
+#define etPOINTER    13 /* The %p conversion */
+#define etSQLESCAPE3 14 /* %w -> Strings with '\"' doubled */
+#define etORDINAL    15 /* %r -> 1st, 2nd, 3rd, 4th, etc.  English only */
+#define etDECIMAL    16 /* %d or %u, but not %x, %o */
+
+#define etINVALID    17 /* Any unrecognized conversion type */
+
+
+/*
+** An "etByte" is an 8-bit unsigned value.
+*/
+typedef unsigned char etByte;
+
+/*
+** Each builtin conversion character (ex: the 'd' in "%d") is described
+** by an instance of the following structure
+*/
+typedef struct et_info {   /* Information about each format field */
+  char fmttype;            /* The format field code letter */
+  etByte base;             /* The base for radix conversion */
+  etByte flags;            /* One or more of FLAG_ constants below */
+  etByte type;             /* Conversion paradigm */
+  etByte charset;          /* Offset into aDigits[] of the digits string */
+  etByte prefix;           /* Offset into aPrefix[] of the prefix string */
+} et_info;
+
+/*
+** Allowed values for et_info.flags
+*/
+#define FLAG_SIGNED    1     /* True if the value to convert is signed */
+#define FLAG_STRING    4     /* Allow infinite precision */
+
+
+/*
+** The following table is searched linearly, so it is good to put the
+** most frequently used conversion types first.
+*/
+static const char aDigits[] = "0123456789ABCDEF0123456789abcdef";
+static const char aPrefix[] = "-x0\000X0";
+static const et_info fmtinfo[] = {
+  {  'd', 10, 1, etDECIMAL,    0,  0 },
+  {  's',  0, 4, etSTRING,     0,  0 },
+  {  'g',  0, 1, etGENERIC,    30, 0 },
+  {  'z',  0, 4, etDYNSTRING,  0,  0 },
+  {  'q',  0, 4, etSQLESCAPE,  0,  0 },
+  {  'Q',  0, 4, etSQLESCAPE2, 0,  0 },
+  {  'w',  0, 4, etSQLESCAPE3, 0,  0 },
+  {  'c',  0, 0, etCHARX,      0,  0 },
+  {  'o',  8, 0, etRADIX,      0,  2 },
+  {  'u', 10, 0, etDECIMAL,    0,  0 },
+  {  'x', 16, 0, etRADIX,      16, 1 },
+  {  'X', 16, 0, etRADIX,      0,  4 },
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  {  'f',  0, 1, etFLOAT,      0,  0 },
+  {  'e',  0, 1, etEXP,        30, 0 },
+  {  'E',  0, 1, etEXP,        14, 0 },
+  {  'G',  0, 1, etGENERIC,    14, 0 },
+#endif
+  {  'i', 10, 1, etDECIMAL,    0,  0 },
+  {  'n',  0, 0, etSIZE,       0,  0 },
+  {  '%',  0, 0, etPERCENT,    0,  0 },
+  {  'p', 16, 0, etPOINTER,    0,  1 },
+
+  /* All the rest are undocumented and are for internal use only */
+  {  'T',  0, 0, etTOKEN,      0,  0 },
+  {  'S',  0, 0, etSRCITEM,    0,  0 },
+  {  'r', 10, 1, etORDINAL,    0,  0 },
+};
+
+/* Notes:
+**
+**    %S    Takes a pointer to SrcItem.  Shows name or database.name
+**    %!S   Like %S but prefer the zName over the zAlias
+*/
+
+/*
+** Set the StrAccum object to an error mode.
+*/
+void sqlite3StrAccumSetError(StrAccum *p, u8 eError){
+  assert( eError==SQLITE_NOMEM || eError==SQLITE_TOOBIG );
+  p->accError = eError;
+  if( p->mxAlloc ) sqlite3_str_reset(p);
+  if( eError==SQLITE_TOOBIG ) sqlite3ErrorToParser(p->db, eError);
+}
+
+/*
+** Extra argument values from a PrintfArguments object
+*/
+static sqlite3_int64 getIntArg(PrintfArguments *p){
+  if( p->nArg<=p->nUsed ) return 0;
+  return sqlite3_value_int64(p->apArg[p->nUsed++]);
+}
+static double getDoubleArg(PrintfArguments *p){
+  if( p->nArg<=p->nUsed ) return 0.0;
+  return sqlite3_value_double(p->apArg[p->nUsed++]);
+}
+static char *getTextArg(PrintfArguments *p){
+  if( p->nArg<=p->nUsed ) return 0;
+  return (char*)sqlite3_value_text(p->apArg[p->nUsed++]);
+}
+
+/*
+** Allocate memory for a temporary buffer needed for printf rendering.
+**
+** If the requested size of the temp buffer is larger than the size
+** of the output buffer in pAccum, then cause an SQLITE_TOOBIG error.
+** Do the size check before the memory allocation to prevent rogue
+** SQL from requesting large allocations using the precision or width
+** field of the printf() function.
+*/
+static char *printfTempBuf(sqlite3_str *pAccum, sqlite3_int64 n){
+  char *z;
+  if( pAccum->accError ) return 0;
+  if( n>pAccum->nAlloc && n>pAccum->mxAlloc ){
+    sqlite3StrAccumSetError(pAccum, SQLITE_TOOBIG);
+    return 0;
+  }
+  z = sqlite3DbMallocRaw(pAccum->db, n);
+  if( z==0 ){
+    sqlite3StrAccumSetError(pAccum, SQLITE_NOMEM);
+  }
+  return z;
+}
+
+/*
+** On machines with a small stack size, you can redefine the
+** SQLITE_PRINT_BUF_SIZE to be something smaller, if desired.
+*/
+#ifndef SQLITE_PRINT_BUF_SIZE
+# define SQLITE_PRINT_BUF_SIZE 70
+#endif
+#define etBUFSIZE SQLITE_PRINT_BUF_SIZE  /* Size of the output buffer */
+
+/*
+** Hard limit on the precision of floating-point conversions.
+*/
+#ifndef SQLITE_PRINTF_PRECISION_LIMIT
+# define SQLITE_FP_PRECISION_LIMIT 100000000
+#endif
+
+/*
+** Render a string given by "fmt" into the StrAccum object.
+*/
+void sqlite3_str_vappendf(
+  sqlite3_str *pAccum,       /* Accumulate results here */
+  const char *fmt,           /* Format string */
+  va_list ap                 /* arguments */
+){
+  int c;                     /* Next character in the format string */
+  char *bufpt;               /* Pointer to the conversion buffer */
+  int precision;             /* Precision of the current field */
+  int length;                /* Length of the field */
+  int idx;                   /* A general purpose loop counter */
+  int width;                 /* Width of the current field */
+  etByte flag_leftjustify;   /* True if "-" flag is present */
+  etByte flag_prefix;        /* '+' or ' ' or 0 for prefix */
+  etByte flag_alternateform; /* True if "#" flag is present */
+  etByte flag_altform2;      /* True if "!" flag is present */
+  etByte flag_zeropad;       /* True if field width constant starts with zero */
+  etByte flag_long;          /* 1 for the "l" flag, 2 for "ll", 0 by default */
+  etByte done;               /* Loop termination flag */
+  etByte cThousand;          /* Thousands separator for %d and %u */
+  etByte xtype = etINVALID;  /* Conversion paradigm */
+  u8 bArgList;               /* True for SQLITE_PRINTF_SQLFUNC */
+  char prefix;               /* Prefix character.  "+" or "-" or " " or '\0'. */
+  sqlite_uint64 longvalue;   /* Value for integer types */
+  double realvalue;          /* Value for real types */
+  const et_info *infop;      /* Pointer to the appropriate info structure */
+  char *zOut;                /* Rendering buffer */
+  int nOut;                  /* Size of the rendering buffer */
+  char *zExtra = 0;          /* Malloced memory used by some conversion */
+  int exp, e2;               /* exponent of real numbers */
+  etByte flag_dp;            /* True if decimal point should be shown */
+  etByte flag_rtz;           /* True if trailing zeros should be removed */
+
+  PrintfArguments *pArgList = 0; /* Arguments for SQLITE_PRINTF_SQLFUNC */
+  char buf[etBUFSIZE];       /* Conversion buffer */
+
+  /* pAccum never starts out with an empty buffer that was obtained from 
+  ** malloc().  This precondition is required by the mprintf("%z...")
+  ** optimization. */
+  assert( pAccum->nChar>0 || (pAccum->printfFlags&SQLITE_PRINTF_MALLOCED)==0 );
+
+  bufpt = 0;
+  if( (pAccum->printfFlags & SQLITE_PRINTF_SQLFUNC)!=0 ){
+    pArgList = va_arg(ap, PrintfArguments*);
+    bArgList = 1;
+  }else{
+    bArgList = 0;
+  }
+  for(; (c=(*fmt))!=0; ++fmt){
+    if( c!='%' ){
+      bufpt = (char *)fmt;
+#if HAVE_STRCHRNUL
+      fmt = strchrnul(fmt, '%');
+#else
+      do{ fmt++; }while( *fmt && *fmt != '%' );
+#endif
+      sqlite3_str_append(pAccum, bufpt, (int)(fmt - bufpt));
+      if( *fmt==0 ) break;
+    }
+    if( (c=(*++fmt))==0 ){
+      sqlite3_str_append(pAccum, "%", 1);
+      break;
+    }
+    /* Find out what flags are present */
+    flag_leftjustify = flag_prefix = cThousand =
+     flag_alternateform = flag_altform2 = flag_zeropad = 0;
+    done = 0;
+    width = 0;
+    flag_long = 0;
+    precision = -1;
+    do{
+      switch( c ){
+        case '-':   flag_leftjustify = 1;     break;
+        case '+':   flag_prefix = '+';        break;
+        case ' ':   flag_prefix = ' ';        break;
+        case '#':   flag_alternateform = 1;   break;
+        case '!':   flag_altform2 = 1;        break;
+        case '0':   flag_zeropad = 1;         break;
+        case ',':   cThousand = ',';          break;
+        default:    done = 1;                 break;
+        case 'l': {
+          flag_long = 1;
+          c = *++fmt;
+          if( c=='l' ){
+            c = *++fmt;
+            flag_long = 2;
+          }
+          done = 1;
+          break;
+        }
+        case '1': case '2': case '3': case '4': case '5':
+        case '6': case '7': case '8': case '9': {
+          unsigned wx = c - '0';
+          while( (c = *++fmt)>='0' && c<='9' ){
+            wx = wx*10 + c - '0';
+          }
+          testcase( wx>0x7fffffff );
+          width = wx & 0x7fffffff;
+#ifdef SQLITE_PRINTF_PRECISION_LIMIT
+          if( width>SQLITE_PRINTF_PRECISION_LIMIT ){
+            width = SQLITE_PRINTF_PRECISION_LIMIT;
+          }
+#endif
+          if( c!='.' && c!='l' ){
+            done = 1;
+          }else{
+            fmt--;
+          }
+          break;
+        }
+        case '*': {
+          if( bArgList ){
+            width = (int)getIntArg(pArgList);
+          }else{
+            width = va_arg(ap,int);
+          }
+          if( width<0 ){
+            flag_leftjustify = 1;
+            width = width >= -2147483647 ? -width : 0;
+          }
+#ifdef SQLITE_PRINTF_PRECISION_LIMIT
+          if( width>SQLITE_PRINTF_PRECISION_LIMIT ){
+            width = SQLITE_PRINTF_PRECISION_LIMIT;
+          }
+#endif
+          if( (c = fmt[1])!='.' && c!='l' ){
+            c = *++fmt;
+            done = 1;
+          }
+          break;
+        }
+        case '.': {
+          c = *++fmt;
+          if( c=='*' ){
+            if( bArgList ){
+              precision = (int)getIntArg(pArgList);
+            }else{
+              precision = va_arg(ap,int);
+            }
+            if( precision<0 ){
+              precision = precision >= -2147483647 ? -precision : -1;
+            }
+            c = *++fmt;
+          }else{
+            unsigned px = 0;
+            while( c>='0' && c<='9' ){
+              px = px*10 + c - '0';
+              c = *++fmt;
+            }
+            testcase( px>0x7fffffff );
+            precision = px & 0x7fffffff;
+          }
+#ifdef SQLITE_PRINTF_PRECISION_LIMIT
+          if( precision>SQLITE_PRINTF_PRECISION_LIMIT ){
+            precision = SQLITE_PRINTF_PRECISION_LIMIT;
+          }
+#endif
+          if( c=='l' ){
+            --fmt;
+          }else{
+            done = 1;
+          }
+          break;
+        }
+      }
+    }while( !done && (c=(*++fmt))!=0 );
+
+    /* Fetch the info entry for the field */
+    infop = &fmtinfo[0];
+    xtype = etINVALID;
+    for(idx=0; idx<ArraySize(fmtinfo); idx++){
+      if( c==fmtinfo[idx].fmttype ){
+        infop = &fmtinfo[idx];
+        xtype = infop->type;
+        break;
+      }
+    }
+
+    /*
+    ** At this point, variables are initialized as follows:
+    **
+    **   flag_alternateform          TRUE if a '#' is present.
+    **   flag_altform2               TRUE if a '!' is present.
+    **   flag_prefix                 '+' or ' ' or zero
+    **   flag_leftjustify            TRUE if a '-' is present or if the
+    **                               field width was negative.
+    **   flag_zeropad                TRUE if the width began with 0.
+    **   flag_long                   1 for "l", 2 for "ll"
+    **   width                       The specified field width.  This is
+    **                               always non-negative.  Zero is the default.
+    **   precision                   The specified precision.  The default
+    **                               is -1.
+    **   xtype                       The class of the conversion.
+    **   infop                       Pointer to the appropriate info struct.
+    */
+    assert( width>=0 );
+    assert( precision>=(-1) );
+    switch( xtype ){
+      case etPOINTER:
+        flag_long = sizeof(char*)==sizeof(i64) ? 2 :
+                     sizeof(char*)==sizeof(long int) ? 1 : 0;
+        /* no break */ deliberate_fall_through
+      case etORDINAL:
+      case etRADIX:      
+        cThousand = 0;
+        /* no break */ deliberate_fall_through
+      case etDECIMAL:
+        if( infop->flags & FLAG_SIGNED ){
+          i64 v;
+          if( bArgList ){
+            v = getIntArg(pArgList);
+          }else if( flag_long ){
+            if( flag_long==2 ){
+              v = va_arg(ap,i64) ;
+            }else{
+              v = va_arg(ap,long int);
+            }
+          }else{
+            v = va_arg(ap,int);
+          }
+          if( v<0 ){
+            testcase( v==SMALLEST_INT64 );
+            testcase( v==(-1) );
+            longvalue = ~v;
+            longvalue++;
+            prefix = '-';
+          }else{
+            longvalue = v;
+            prefix = flag_prefix;
+          }
+        }else{
+          if( bArgList ){
+            longvalue = (u64)getIntArg(pArgList);
+          }else if( flag_long ){
+            if( flag_long==2 ){
+              longvalue = va_arg(ap,u64);
+            }else{
+              longvalue = va_arg(ap,unsigned long int);
+            }
+          }else{
+            longvalue = va_arg(ap,unsigned int);
+          }
+          prefix = 0;
+        }
+        if( longvalue==0 ) flag_alternateform = 0;
+        if( flag_zeropad && precision<width-(prefix!=0) ){
+          precision = width-(prefix!=0);
+        }
+        if( precision<etBUFSIZE-10-etBUFSIZE/3 ){
+          nOut = etBUFSIZE;
+          zOut = buf;
+        }else{
+          u64 n;
+          n = (u64)precision + 10;
+          if( cThousand ) n += precision/3;
+          zOut = zExtra = printfTempBuf(pAccum, n);
+          if( zOut==0 ) return;
+          nOut = (int)n;
+        }
+        bufpt = &zOut[nOut-1];
+        if( xtype==etORDINAL ){
+          static const char zOrd[] = "thstndrd";
+          int x = (int)(longvalue % 10);
+          if( x>=4 || (longvalue/10)%10==1 ){
+            x = 0;
+          }
+          *(--bufpt) = zOrd[x*2+1];
+          *(--bufpt) = zOrd[x*2];
+        }
+        {
+          const char *cset = &aDigits[infop->charset];
+          u8 base = infop->base;
+          do{                                           /* Convert to ascii */
+            *(--bufpt) = cset[longvalue%base];
+            longvalue = longvalue/base;
+          }while( longvalue>0 );
+        }
+        length = (int)(&zOut[nOut-1]-bufpt);
+        while( precision>length ){
+          *(--bufpt) = '0';                             /* Zero pad */
+          length++;
+        }
+        if( cThousand ){
+          int nn = (length - 1)/3;  /* Number of "," to insert */
+          int ix = (length - 1)%3 + 1;
+          bufpt -= nn;
+          for(idx=0; nn>0; idx++){
+            bufpt[idx] = bufpt[idx+nn];
+            ix--;
+            if( ix==0 ){
+              bufpt[++idx] = cThousand;
+              nn--;
+              ix = 3;
+            }
+          }
+        }
+        if( prefix ) *(--bufpt) = prefix;               /* Add sign */
+        if( flag_alternateform && infop->prefix ){      /* Add "0" or "0x" */
+          const char *pre;
+          char x;
+          pre = &aPrefix[infop->prefix];
+          for(; (x=(*pre))!=0; pre++) *(--bufpt) = x;
+        }
+        length = (int)(&zOut[nOut-1]-bufpt);
+        break;
+      case etFLOAT:
+      case etEXP:
+      case etGENERIC: {
+        FpDecode s;
+        int iRound;
+        int j;
+
+        if( bArgList ){
+          realvalue = getDoubleArg(pArgList);
+        }else{
+          realvalue = va_arg(ap,double);
+        }
+        if( precision<0 ) precision = 6;         /* Set default precision */
+#ifdef SQLITE_FP_PRECISION_LIMIT
+        if( precision>SQLITE_FP_PRECISION_LIMIT ){
+          precision = SQLITE_FP_PRECISION_LIMIT;
+        }
+#endif
+        if( xtype==etFLOAT ){
+          iRound = -precision;
+        }else if( xtype==etGENERIC ){
+          iRound = precision;
+        }else{
+          iRound = precision+1;
+        }
+        sqlite3FpDecode(&s, realvalue, iRound, flag_altform2 ? 26 : 16);
+        if( s.isSpecial ){
+          if( s.isSpecial==2 ){
+            bufpt = flag_zeropad ? "null" : "NaN";
+            length = sqlite3Strlen30(bufpt);
+            break;
+          }else if( flag_zeropad ){
+            s.z[0] = '9';
+            s.iDP = 1000;
+            s.n = 1;
+          }else{
+            memcpy(buf, "-Inf", 5);
+            bufpt = buf;
+            if( s.sign=='-' ){
+              /* no-op */
+            }else if( flag_prefix ){
+              buf[0] = flag_prefix;
+            }else{
+              bufpt++;
+            }
+            length = sqlite3Strlen30(bufpt);
+            break;
+          }
+        }
+        if( s.sign=='-' ){
+          prefix = '-';
+        }else{
+          prefix = flag_prefix;
+        }
+
+        exp = s.iDP-1;
+        if( xtype==etGENERIC && precision>0 ) precision--;
+
+        /*
+        ** If the field type is etGENERIC, then convert to either etEXP
+        ** or etFLOAT, as appropriate.
+        */
+        if( xtype==etGENERIC ){
+          flag_rtz = !flag_alternateform;
+          if( exp<-4 || exp>precision ){
+            xtype = etEXP;
+          }else{
+            precision = precision - exp;
+            xtype = etFLOAT;
+          }
+        }else{
+          flag_rtz = flag_altform2;
+        }
+        if( xtype==etEXP ){
+          e2 = 0;
+        }else{
+          e2 = s.iDP - 1;
+        }
+        bufpt = buf;
+        {
+          i64 szBufNeeded;           /* Size of a temporary buffer needed */
+          szBufNeeded = MAX(e2,0)+(i64)precision+(i64)width+15;
+          if( cThousand && e2>0 ) szBufNeeded += (e2+2)/3;
+          if( szBufNeeded > etBUFSIZE ){
+            bufpt = zExtra = printfTempBuf(pAccum, szBufNeeded);
+            if( bufpt==0 ) return;
+          }
+        }
+        zOut = bufpt;
+        flag_dp = (precision>0 ?1:0) | flag_alternateform | flag_altform2;
+        /* The sign in front of the number */
+        if( prefix ){
+          *(bufpt++) = prefix;
+        }
+        /* Digits prior to the decimal point */
+        j = 0;
+        if( e2<0 ){
+          *(bufpt++) = '0';
+        }else{
+          for(; e2>=0; e2--){
+            *(bufpt++) = j<s.n ? s.z[j++] : '0';
+            if( cThousand && (e2%3)==0 && e2>1 ) *(bufpt++) = ',';
+          }
+        }
+        /* The decimal point */
+        if( flag_dp ){
+          *(bufpt++) = '.';
+        }
+        /* "0" digits after the decimal point but before the first
+        ** significant digit of the number */
+        for(e2++; e2<0 && precision>0; precision--, e2++){
+          *(bufpt++) = '0';
+        }
+        /* Significant digits after the decimal point */
+        while( (precision--)>0 ){
+          *(bufpt++) = j<s.n ? s.z[j++] : '0';
+        }
+        /* Remove trailing zeros and the "." if no digits follow the "." */
+        if( flag_rtz && flag_dp ){
+          while( bufpt[-1]=='0' ) *(--bufpt) = 0;
+          assert( bufpt>zOut );
+          if( bufpt[-1]=='.' ){
+            if( flag_altform2 ){
+              *(bufpt++) = '0';
+            }else{
+              *(--bufpt) = 0;
+            }
+          }
+        }
+        /* Add the "eNNN" suffix */
+        if( xtype==etEXP ){
+          exp = s.iDP - 1;
+          *(bufpt++) = aDigits[infop->charset];
+          if( exp<0 ){
+            *(bufpt++) = '-'; exp = -exp;
+          }else{
+            *(bufpt++) = '+';
+          }
+          if( exp>=100 ){
+            *(bufpt++) = (char)((exp/100)+'0');        /* 100's digit */
+            exp %= 100;
+          }
+          *(bufpt++) = (char)(exp/10+'0');             /* 10's digit */
+          *(bufpt++) = (char)(exp%10+'0');             /* 1's digit */
+        }
+        *bufpt = 0;
+
+        /* The converted number is in buf[] and zero terminated. Output it.
+        ** Note that the number is in the usual order, not reversed as with
+        ** integer conversions. */
+        length = (int)(bufpt-zOut);
+        bufpt = zOut;
+
+        /* Special case:  Add leading zeros if the flag_zeropad flag is
+        ** set and we are not left justified */
+        if( flag_zeropad && !flag_leftjustify && length < width){
+          int i;
+          int nPad = width - length;
+          for(i=width; i>=nPad; i--){
+            bufpt[i] = bufpt[i-nPad];
+          }
+          i = prefix!=0;
+          while( nPad-- ) bufpt[i++] = '0';
+          length = width;
+        }
+        break;
+      }
+      case etSIZE:
+        if( !bArgList ){
+          *(va_arg(ap,int*)) = pAccum->nChar;
+        }
+        length = width = 0;
+        break;
+      case etPERCENT:
+        buf[0] = '%';
+        bufpt = buf;
+        length = 1;
+        break;
+      case etCHARX:
+        if( bArgList ){
+          bufpt = getTextArg(pArgList);
+          length = 1;
+          if( bufpt ){
+            buf[0] = c = *(bufpt++);
+            if( (c&0xc0)==0xc0 ){
+              while( length<4 && (bufpt[0]&0xc0)==0x80 ){
+                buf[length++] = *(bufpt++);
+              }
+            }
+          }else{
+            buf[0] = 0;
+          }
+        }else{
+          unsigned int ch = va_arg(ap,unsigned int);
+          if( ch<0x00080 ){
+            buf[0] = ch & 0xff;
+            length = 1;
+          }else if( ch<0x00800 ){
+            buf[0] = 0xc0 + (u8)((ch>>6)&0x1f);
+            buf[1] = 0x80 + (u8)(ch & 0x3f);
+            length = 2;
+          }else if( ch<0x10000 ){
+            buf[0] = 0xe0 + (u8)((ch>>12)&0x0f);
+            buf[1] = 0x80 + (u8)((ch>>6) & 0x3f);
+            buf[2] = 0x80 + (u8)(ch & 0x3f);
+            length = 3;
+          }else{
+            buf[0] = 0xf0 + (u8)((ch>>18) & 0x07);
+            buf[1] = 0x80 + (u8)((ch>>12) & 0x3f);
+            buf[2] = 0x80 + (u8)((ch>>6) & 0x3f);
+            buf[3] = 0x80 + (u8)(ch & 0x3f);
+            length = 4;
+          }
+        }
+        if( precision>1 ){
+          i64 nPrior = 1;
+          width -= precision-1;
+          if( width>1 && !flag_leftjustify ){
+            sqlite3_str_appendchar(pAccum, width-1, ' ');
+            width = 0;
+          }
+          sqlite3_str_append(pAccum, buf, length);
+          precision--;
+          while( precision > 1 ){
+            i64 nCopyBytes;
+            if( nPrior > precision-1 ) nPrior = precision - 1;
+            nCopyBytes = length*nPrior;
+            if( nCopyBytes + pAccum->nChar >= pAccum->nAlloc ){
+              sqlite3StrAccumEnlarge(pAccum, nCopyBytes);
+            }
+            if( pAccum->accError ) break;
+            sqlite3_str_append(pAccum,
+                 &pAccum->zText[pAccum->nChar-nCopyBytes], nCopyBytes);
+            precision -= nPrior;
+            nPrior *= 2;
+          }
+        }
+        bufpt = buf;
+        flag_altform2 = 1;
+        goto adjust_width_for_utf8;
+      case etSTRING:
+      case etDYNSTRING:
+        if( bArgList ){
+          bufpt = getTextArg(pArgList);
+          xtype = etSTRING;
+        }else{
+          bufpt = va_arg(ap,char*);
+        }
+        if( bufpt==0 ){
+          bufpt = "";
+        }else if( xtype==etDYNSTRING ){
+          if( pAccum->nChar==0
+           && pAccum->mxAlloc
+           && width==0
+           && precision<0
+           && pAccum->accError==0
+          ){
+            /* Special optimization for sqlite3_mprintf("%z..."):
+            ** Extend an existing memory allocation rather than creating
+            ** a new one. */
+            assert( (pAccum->printfFlags&SQLITE_PRINTF_MALLOCED)==0 );
+            pAccum->zText = bufpt;
+            pAccum->nAlloc = sqlite3DbMallocSize(pAccum->db, bufpt);
+            pAccum->nChar = 0x7fffffff & (int)strlen(bufpt);
+            pAccum->printfFlags |= SQLITE_PRINTF_MALLOCED;
+            length = 0;
+            break;
+          }
+          zExtra = bufpt;
+        }
+        if( precision>=0 ){
+          if( flag_altform2 ){
+            /* Set length to the number of bytes needed in order to display
+            ** precision characters */
+            unsigned char *z = (unsigned char*)bufpt;
+            while( precision-- > 0 && z[0] ){
+              SQLITE_SKIP_UTF8(z);
+            }
+            length = (int)(z - (unsigned char*)bufpt);
+          }else{
+            for(length=0; length<precision && bufpt[length]; length++){}
+          }
+        }else{
+          length = 0x7fffffff & (int)strlen(bufpt);
+        }
+      adjust_width_for_utf8:
+        if( flag_altform2 && width>0 ){
+          /* Adjust width to account for extra bytes in UTF-8 characters */
+          int ii = length - 1;
+          while( ii>=0 ) if( (bufpt[ii--] & 0xc0)==0x80 ) width++;
+        }
+        break;
+      case etSQLESCAPE:           /* %q: Escape ' characters */
+      case etSQLESCAPE2:          /* %Q: Escape ' and enclose in '...' */
+      case etSQLESCAPE3: {        /* %w: Escape " characters */
+        i64 i, j, k, n;
+        int needQuote, isnull;
+        char ch;
+        char q = ((xtype==etSQLESCAPE3)?'"':'\'');   /* Quote character */
+        char *escarg;
+
+        if( bArgList ){
+          escarg = getTextArg(pArgList);
+        }else{
+          escarg = va_arg(ap,char*);
+        }
+        isnull = escarg==0;
+        if( isnull ) escarg = (xtype==etSQLESCAPE2 ? "NULL" : "(NULL)");
+        /* For %q, %Q, and %w, the precision is the number of bytes (or
+        ** characters if the ! flags is present) to use from the input.
+        ** Because of the extra quoting characters inserted, the number
+        ** of output characters may be larger than the precision.
+        */
+        k = precision;
+        for(i=n=0; k!=0 && (ch=escarg[i])!=0; i++, k--){
+          if( ch==q )  n++;
+          if( flag_altform2 && (ch&0xc0)==0xc0 ){
+            while( (escarg[i+1]&0xc0)==0x80 ){ i++; }
+          }
+        }
+        needQuote = !isnull && xtype==etSQLESCAPE2;
+        n += i + 3;
+        if( n>etBUFSIZE ){
+          bufpt = zExtra = printfTempBuf(pAccum, n);
+          if( bufpt==0 ) return;
+        }else{
+          bufpt = buf;
+        }
+        j = 0;
+        if( needQuote ) bufpt[j++] = q;
+        k = i;
+        for(i=0; i<k; i++){
+          bufpt[j++] = ch = escarg[i];
+          if( ch==q ) bufpt[j++] = ch;
+        }
+        if( needQuote ) bufpt[j++] = q;
+        bufpt[j] = 0;
+        length = j;
+        goto adjust_width_for_utf8;
+      }
+      case etTOKEN: {
+        if( (pAccum->printfFlags & SQLITE_PRINTF_INTERNAL)==0 ) return;
+        if( flag_alternateform ){
+          /* %#T means an Expr pointer that uses Expr.u.zToken */
+          Expr *pExpr = va_arg(ap,Expr*);
+          if( ALWAYS(pExpr) && ALWAYS(!ExprHasProperty(pExpr,EP_IntValue)) ){
+            sqlite3_str_appendall(pAccum, (const char*)pExpr->u.zToken);
+            sqlite3RecordErrorOffsetOfExpr(pAccum->db, pExpr);
+          }
+        }else{
+          /* %T means a Token pointer */
+          Token *pToken = va_arg(ap, Token*);
+          assert( bArgList==0 );
+          if( pToken && pToken->n ){
+            sqlite3_str_append(pAccum, (const char*)pToken->z, pToken->n);
+            sqlite3RecordErrorByteOffset(pAccum->db, pToken->z);
+          }
+        }
+        length = width = 0;
+        break;
+      }
+      case etSRCITEM: {
+        SrcItem *pItem;
+        if( (pAccum->printfFlags & SQLITE_PRINTF_INTERNAL)==0 ) return;
+        pItem = va_arg(ap, SrcItem*);
+        assert( bArgList==0 );
+        if( pItem->zAlias && !flag_altform2 ){
+          sqlite3_str_appendall(pAccum, pItem->zAlias);
+        }else if( pItem->zName ){
+          if( pItem->zDatabase ){
+            sqlite3_str_appendall(pAccum, pItem->zDatabase);
+            sqlite3_str_append(pAccum, ".", 1);
+          }
+          sqlite3_str_appendall(pAccum, pItem->zName);
+        }else if( pItem->zAlias ){
+          sqlite3_str_appendall(pAccum, pItem->zAlias);
+        }else{
+          Select *pSel = pItem->pSelect;
+          assert( pSel!=0 );
+          if( pSel->selFlags & SF_NestedFrom ){
+            sqlite3_str_appendf(pAccum, "(join-%u)", pSel->selId);
+          }else{
+            sqlite3_str_appendf(pAccum, "(subquery-%u)", pSel->selId);
+          }
+        }
+        length = width = 0;
+        break;
+      }
+      default: {
+        assert( xtype==etINVALID );
+        return;
+      }
+    }/* End switch over the format type */
+    /*
+    ** The text of the conversion is pointed to by "bufpt" and is
+    ** "length" characters long.  The field width is "width".  Do
+    ** the output.  Both length and width are in bytes, not characters,
+    ** at this point.  If the "!" flag was present on string conversions
+    ** indicating that width and precision should be expressed in characters,
+    ** then the values have been translated prior to reaching this point.
+    */
+    width -= length;
+    if( width>0 ){
+      if( !flag_leftjustify ) sqlite3_str_appendchar(pAccum, width, ' ');
+      sqlite3_str_append(pAccum, bufpt, length);
+      if( flag_leftjustify ) sqlite3_str_appendchar(pAccum, width, ' ');
+    }else{
+      sqlite3_str_append(pAccum, bufpt, length);
+    }
+
+    if( zExtra ){
+      sqlite3DbFree(pAccum->db, zExtra);
+      zExtra = 0;
+    }
+  }/* End for loop over the format string */
+} /* End of function */
+
+
+/*
+** The z string points to the first character of a token that is
+** associated with an error.  If db does not already have an error
+** byte offset recorded, try to compute the error byte offset for
+** z and set the error byte offset in db.
+*/
+void sqlite3RecordErrorByteOffset(sqlite3 *db, const char *z){
+  const Parse *pParse;
+  const char *zText;
+  const char *zEnd;
+  assert( z!=0 );
+  if( NEVER(db==0) ) return;
+  if( db->errByteOffset!=(-2) ) return;
+  pParse = db->pParse;
+  if( NEVER(pParse==0) ) return;
+  zText =pParse->zTail;
+  if( NEVER(zText==0) ) return;
+  zEnd = &zText[strlen(zText)];
+  if( SQLITE_WITHIN(z,zText,zEnd) ){
+    db->errByteOffset = (int)(z-zText);
+  }
+}
+
+/*
+** If pExpr has a byte offset for the start of a token, record that as
+** as the error offset.
+*/
+void sqlite3RecordErrorOffsetOfExpr(sqlite3 *db, const Expr *pExpr){
+  while( pExpr
+     && (ExprHasProperty(pExpr,EP_OuterON|EP_InnerON) || pExpr->w.iOfst<=0)
+  ){
+    pExpr = pExpr->pLeft;
+  }
+  if( pExpr==0 ) return;
+  db->errByteOffset = pExpr->w.iOfst;
+}
+
+/*
+** Enlarge the memory allocation on a StrAccum object so that it is
+** able to accept at least N more bytes of text.
+**
+** Return the number of bytes of text that StrAccum is able to accept
+** after the attempted enlargement.  The value returned might be zero.
+*/
+int sqlite3StrAccumEnlarge(StrAccum *p, i64 N){
+  char *zNew;
+  assert( p->nChar+N >= p->nAlloc ); /* Only called if really needed */
+  if( p->accError ){
+    testcase(p->accError==SQLITE_TOOBIG);
+    testcase(p->accError==SQLITE_NOMEM);
+    return 0;
+  }
+  if( p->mxAlloc==0 ){
+    sqlite3StrAccumSetError(p, SQLITE_TOOBIG);
+    return p->nAlloc - p->nChar - 1;
+  }else{
+    char *zOld = isMalloced(p) ? p->zText : 0;
+    i64 szNew = p->nChar + N + 1;
+    if( szNew+p->nChar<=p->mxAlloc ){
+      /* Force exponential buffer size growth as long as it does not overflow,
+      ** to avoid having to call this routine too often */
+      szNew += p->nChar;
+    }
+    if( szNew > p->mxAlloc ){
+      sqlite3_str_reset(p);
+      sqlite3StrAccumSetError(p, SQLITE_TOOBIG);
+      return 0;
+    }else{
+      p->nAlloc = (int)szNew;
+    }
+    if( p->db ){
+      zNew = sqlite3DbRealloc(p->db, zOld, p->nAlloc);
+    }else{
+      zNew = sqlite3Realloc(zOld, p->nAlloc);
+    }
+    if( zNew ){
+      assert( p->zText!=0 || p->nChar==0 );
+      if( !isMalloced(p) && p->nChar>0 ) memcpy(zNew, p->zText, p->nChar);
+      p->zText = zNew;
+      p->nAlloc = sqlite3DbMallocSize(p->db, zNew);
+      p->printfFlags |= SQLITE_PRINTF_MALLOCED;
+    }else{
+      sqlite3_str_reset(p);
+      sqlite3StrAccumSetError(p, SQLITE_NOMEM);
+      return 0;
+    }
+  }
+  assert( N>=0 && N<=0x7fffffff );
+  return (int)N;
+}
+
+/*
+** Append N copies of character c to the given string buffer.
+*/
+void sqlite3_str_appendchar(sqlite3_str *p, int N, char c){
+  testcase( p->nChar + (i64)N > 0x7fffffff );
+  if( p->nChar+(i64)N >= p->nAlloc && (N = sqlite3StrAccumEnlarge(p, N))<=0 ){
+    return;
+  }
+  while( (N--)>0 ) p->zText[p->nChar++] = c;
+}
+
+/*
+** The StrAccum "p" is not large enough to accept N new bytes of z[].
+** So enlarge if first, then do the append.
+**
+** This is a helper routine to sqlite3_str_append() that does special-case
+** work (enlarging the buffer) using tail recursion, so that the
+** sqlite3_str_append() routine can use fast calling semantics.
+*/
+static void SQLITE_NOINLINE enlargeAndAppend(StrAccum *p, const char *z, int N){
+  N = sqlite3StrAccumEnlarge(p, N);
+  if( N>0 ){
+    memcpy(&p->zText[p->nChar], z, N);
+    p->nChar += N;
+  }
+}
+
+/*
+** Append N bytes of text from z to the StrAccum object.  Increase the
+** size of the memory allocation for StrAccum if necessary.
+*/
+void sqlite3_str_append(sqlite3_str *p, const char *z, int N){
+  assert( z!=0 || N==0 );
+  assert( p->zText!=0 || p->nChar==0 || p->accError );
+  assert( N>=0 );
+  assert( p->accError==0 || p->nAlloc==0 || p->mxAlloc==0 );
+  if( p->nChar+N >= p->nAlloc ){
+    enlargeAndAppend(p,z,N);
+  }else if( N ){
+    assert( p->zText );
+    p->nChar += N;
+    memcpy(&p->zText[p->nChar-N], z, N);
+  }
+}
+
+/*
+** Append the complete text of zero-terminated string z[] to the p string.
+*/
+void sqlite3_str_appendall(sqlite3_str *p, const char *z){
+  sqlite3_str_append(p, z, sqlite3Strlen30(z));
+}
+
+
+/*
+** Finish off a string by making sure it is zero-terminated.
+** Return a pointer to the resulting string.  Return a NULL
+** pointer if any kind of error was encountered.
+*/
+static SQLITE_NOINLINE char *strAccumFinishRealloc(StrAccum *p){
+  char *zText;
+  assert( p->mxAlloc>0 && !isMalloced(p) );
+  zText = sqlite3DbMallocRaw(p->db, p->nChar+1 );
+  if( zText ){
+    memcpy(zText, p->zText, p->nChar+1);
+    p->printfFlags |= SQLITE_PRINTF_MALLOCED;
+  }else{
+    sqlite3StrAccumSetError(p, SQLITE_NOMEM);
+  }
+  p->zText = zText;
+  return zText;
+}
+char *sqlite3StrAccumFinish(StrAccum *p){
+  if( p->zText ){
+    p->zText[p->nChar] = 0;
+    if( p->mxAlloc>0 && !isMalloced(p) ){
+      return strAccumFinishRealloc(p);
+    }
+  }
+  return p->zText;
+}
+
+/*
+** Use the content of the StrAccum passed as the second argument
+** as the result of an SQL function.
+*/
+void sqlite3ResultStrAccum(sqlite3_context *pCtx, StrAccum *p){
+  if( p->accError ){
+    sqlite3_result_error_code(pCtx, p->accError);
+    sqlite3_str_reset(p);
+  }else if( isMalloced(p) ){
+    sqlite3_result_text(pCtx, p->zText, p->nChar, SQLITE_DYNAMIC);
+  }else{
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    sqlite3_str_reset(p);
+  }
+}
+
+/*
+** This singleton is an sqlite3_str object that is returned if
+** sqlite3_malloc() fails to provide space for a real one.  This
+** sqlite3_str object accepts no new text and always returns
+** an SQLITE_NOMEM error.
+*/
+static sqlite3_str sqlite3OomStr = {
+   0, 0, 0, 0, 0, SQLITE_NOMEM, 0
+};
+
+/* Finalize a string created using sqlite3_str_new().
+*/
+char *sqlite3_str_finish(sqlite3_str *p){
+  char *z;
+  if( p!=0 && p!=&sqlite3OomStr ){
+    z = sqlite3StrAccumFinish(p);
+    sqlite3_free(p);
+  }else{
+    z = 0;
+  }
+  return z;
+}
+
+/* Return any error code associated with p */
+int sqlite3_str_errcode(sqlite3_str *p){
+  return p ? p->accError : SQLITE_NOMEM;
+}
+
+/* Return the current length of p in bytes */
+int sqlite3_str_length(sqlite3_str *p){
+  return p ? p->nChar : 0;
+}
+
+/* Return the current value for p */
+char *sqlite3_str_value(sqlite3_str *p){
+  if( p==0 || p->nChar==0 ) return 0;
+  p->zText[p->nChar] = 0;
+  return p->zText;
+}
+
+/*
+** Reset an StrAccum string.  Reclaim all malloced memory.
+*/
+void sqlite3_str_reset(StrAccum *p){
+  if( isMalloced(p) ){
+    sqlite3DbFree(p->db, p->zText);
+    p->printfFlags &= ~SQLITE_PRINTF_MALLOCED;
+  }
+  p->nAlloc = 0;
+  p->nChar = 0;
+  p->zText = 0;
+}
+
+/*
+** Initialize a string accumulator.
+**
+** p:     The accumulator to be initialized.
+** db:    Pointer to a database connection.  May be NULL.  Lookaside
+**        memory is used if not NULL. db->mallocFailed is set appropriately
+**        when not NULL.
+** zBase: An initial buffer.  May be NULL in which case the initial buffer
+**        is malloced.
+** n:     Size of zBase in bytes.  If total space requirements never exceed
+**        n then no memory allocations ever occur.
+** mx:    Maximum number of bytes to accumulate.  If mx==0 then no memory
+**        allocations will ever occur.
+*/
+void sqlite3StrAccumInit(StrAccum *p, sqlite3 *db, char *zBase, int n, int mx){
+  p->zText = zBase;
+  p->db = db;
+  p->nAlloc = n;
+  p->mxAlloc = mx;
+  p->nChar = 0;
+  p->accError = 0;
+  p->printfFlags = 0;
+}
+
+/* Allocate and initialize a new dynamic string object */
+sqlite3_str *sqlite3_str_new(sqlite3 *db){
+  sqlite3_str *p = sqlite3_malloc64(sizeof(*p));
+  if( p ){
+    sqlite3StrAccumInit(p, 0, 0, 0,
+            db ? db->aLimit[SQLITE_LIMIT_LENGTH] : SQLITE_MAX_LENGTH);
+  }else{
+    p = &sqlite3OomStr;
+  }
+  return p;
+}
+
+/*
+** Print into memory obtained from sqliteMalloc().  Use the internal
+** %-conversion extensions.
+*/
+char *sqlite3VMPrintf(sqlite3 *db, const char *zFormat, va_list ap){
+  char *z;
+  char zBase[SQLITE_PRINT_BUF_SIZE];
+  StrAccum acc;
+  assert( db!=0 );
+  sqlite3StrAccumInit(&acc, db, zBase, sizeof(zBase),
+                      db->aLimit[SQLITE_LIMIT_LENGTH]);
+  acc.printfFlags = SQLITE_PRINTF_INTERNAL;
+  sqlite3_str_vappendf(&acc, zFormat, ap);
+  z = sqlite3StrAccumFinish(&acc);
+  if( acc.accError==SQLITE_NOMEM ){
+    sqlite3OomFault(db);
+  }
+  return z;
+}
+
+/*
+** Print into memory obtained from sqliteMalloc().  Use the internal
+** %-conversion extensions.
+*/
+char *sqlite3MPrintf(sqlite3 *db, const char *zFormat, ...){
+  va_list ap;
+  char *z;
+  va_start(ap, zFormat);
+  z = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  return z;
+}
+
+/*
+** Print into memory obtained from sqlite3_malloc().  Omit the internal
+** %-conversion extensions.
+*/
+char *sqlite3_vmprintf(const char *zFormat, va_list ap){
+  char *z;
+  char zBase[SQLITE_PRINT_BUF_SIZE];
+  StrAccum acc;
+
+#ifdef SQLITE_ENABLE_API_ARMOR  
+  if( zFormat==0 ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  sqlite3StrAccumInit(&acc, 0, zBase, sizeof(zBase), SQLITE_MAX_LENGTH);
+  sqlite3_str_vappendf(&acc, zFormat, ap);
+  z = sqlite3StrAccumFinish(&acc);
+  return z;
+}
+
+/*
+** Print into memory obtained from sqlite3_malloc()().  Omit the internal
+** %-conversion extensions.
+*/
+char *sqlite3_mprintf(const char *zFormat, ...){
+  va_list ap;
+  char *z;
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  va_start(ap, zFormat);
+  z = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  return z;
+}
+
+/*
+** sqlite3_snprintf() works like snprintf() except that it ignores the
+** current locale settings.  This is important for SQLite because we
+** are not able to use a "," as the decimal point in place of "." as
+** specified by some locales.
+**
+** Oops:  The first two arguments of sqlite3_snprintf() are backwards
+** from the snprintf() standard.  Unfortunately, it is too late to change
+** this without breaking compatibility, so we just have to live with the
+** mistake.
+**
+** sqlite3_vsnprintf() is the varargs version.
+*/
+char *sqlite3_vsnprintf(int n, char *zBuf, const char *zFormat, va_list ap){
+  StrAccum acc;
+  if( n<=0 ) return zBuf;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( zBuf==0 || zFormat==0 ) {
+    (void)SQLITE_MISUSE_BKPT;
+    if( zBuf ) zBuf[0] = 0;
+    return zBuf;
+  }
+#endif
+  sqlite3StrAccumInit(&acc, 0, zBuf, n, 0);
+  sqlite3_str_vappendf(&acc, zFormat, ap);
+  zBuf[acc.nChar] = 0;
+  return zBuf;
+}
+char *sqlite3_snprintf(int n, char *zBuf, const char *zFormat, ...){
+  StrAccum acc;
+  va_list ap;
+  if( n<=0 ) return zBuf;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( zBuf==0 || zFormat==0 ) {
+    (void)SQLITE_MISUSE_BKPT;
+    if( zBuf ) zBuf[0] = 0;
+    return zBuf;
+  }
+#endif
+  sqlite3StrAccumInit(&acc, 0, zBuf, n, 0);
+  va_start(ap,zFormat);
+  sqlite3_str_vappendf(&acc, zFormat, ap);
+  va_end(ap);
+  zBuf[acc.nChar] = 0;
+  return zBuf;
+}
+
+/*
+** This is the routine that actually formats the sqlite3_log() message.
+** We house it in a separate routine from sqlite3_log() to avoid using
+** stack space on small-stack systems when logging is disabled.
+**
+** sqlite3_log() must render into a static buffer.  It cannot dynamically
+** allocate memory because it might be called while the memory allocator
+** mutex is held.
+**
+** sqlite3_str_vappendf() might ask for *temporary* memory allocations for
+** certain format characters (%q) or for very large precisions or widths.
+** Care must be taken that any sqlite3_log() calls that occur while the
+** memory mutex is held do not use these mechanisms.
+*/
+static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
+  StrAccum acc;                          /* String accumulator */
+  char zMsg[SQLITE_PRINT_BUF_SIZE*3];    /* Complete log message */
+
+  sqlite3StrAccumInit(&acc, 0, zMsg, sizeof(zMsg), 0);
+  sqlite3_str_vappendf(&acc, zFormat, ap);
+  sqlite3GlobalConfig.xLog(sqlite3GlobalConfig.pLogArg, iErrCode,
+                           sqlite3StrAccumFinish(&acc));
+}
+
+/*
+** Format and write a message to the log if logging is enabled.
+*/
+void sqlite3_log(int iErrCode, const char *zFormat, ...){
+  va_list ap;                             /* Vararg list */
+  if( sqlite3GlobalConfig.xLog ){
+    va_start(ap, zFormat);
+    renderLogMsg(iErrCode, zFormat, ap);
+    va_end(ap);
+  }
+}
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
+/*
+** A version of printf() that understands %lld.  Used for debugging.
+** The printf() built into some versions of windows does not understand %lld
+** and segfaults if you give it a long long int.
+*/
+void sqlite3DebugPrintf(const char *zFormat, ...){
+  va_list ap;
+  StrAccum acc;
+  char zBuf[SQLITE_PRINT_BUF_SIZE*10];
+  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
+  va_start(ap,zFormat);
+  sqlite3_str_vappendf(&acc, zFormat, ap);
+  va_end(ap);
+  sqlite3StrAccumFinish(&acc);
+#ifdef SQLITE_OS_TRACE_PROC
+  {
+    extern void SQLITE_OS_TRACE_PROC(const char *zBuf, int nBuf);
+    SQLITE_OS_TRACE_PROC(zBuf, sizeof(zBuf));
+  }
+#else
+  fprintf(stdout,"%s", zBuf);
+  fflush(stdout);
+#endif
+}
+#endif
+
+
+/*
+** variable-argument wrapper around sqlite3_str_vappendf(). The bFlags argument
+** can contain the bit SQLITE_PRINTF_INTERNAL enable internal formats.
+*/
+void sqlite3_str_appendf(StrAccum *p, const char *zFormat, ...){
+  va_list ap;
+  va_start(ap,zFormat);
+  sqlite3_str_vappendf(p, zFormat, ap);
+  va_end(ap);
+}
+
+
+/*****************************************************************************
+** Reference counted string/blob storage
+*****************************************************************************/
+
+/*
+** Increase the reference count of the string by one.
+**
+** The input parameter is returned.
+*/
+char *sqlite3RCStrRef(char *z){
+  RCStr *p = (RCStr*)z;
+  assert( p!=0 );
+  p--;
+  p->nRCRef++;
+  return z;
+}
+
+/*
+** Decrease the reference count by one.  Free the string when the
+** reference count reaches zero.
+*/
+void sqlite3RCStrUnref(void *z){
+  RCStr *p = (RCStr*)z;
+  assert( p!=0 );
+  p--;
+  assert( p->nRCRef>0 );
+  if( p->nRCRef>=2 ){
+    p->nRCRef--;
+  }else{
+    sqlite3_free(p);
+  }
+}
+
+/*
+** Create a new string that is capable of holding N bytes of text, not counting
+** the zero byte at the end.  The string is uninitialized.
+**
+** The reference count is initially 1.  Call sqlite3RCStrUnref() to free the
+** newly allocated string.
+**
+** This routine returns 0 on an OOM.
+*/
+char *sqlite3RCStrNew(u64 N){
+  RCStr *p = sqlite3_malloc64( N + sizeof(*p) + 1 );
+  if( p==0 ) return 0;
+  p->nRCRef = 1;
+  return (char*)&p[1];
+}
+
+/*
+** Change the size of the string so that it is able to hold N bytes.
+** The string might be reallocated, so return the new allocation.
+*/
+char *sqlite3RCStrResize(char *z, u64 N){
+  RCStr *p = (RCStr*)z;
+  RCStr *pNew;
+  assert( p!=0 );
+  p--;
+  assert( p->nRCRef==1 );
+  pNew = sqlite3_realloc64(p, N+sizeof(RCStr)+1);
+  if( pNew==0 ){
+    sqlite3_free(p);
+    return 0;
+  }else{
+    return (char*)&pNew[1];
+  }
+}
diff --git a/src/random.c b/src/random.c
new file mode 100644
index 0000000..ea8431b
--- /dev/null
+++ b/src/random.c
@@ -0,0 +1,157 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code to implement a pseudo-random number
+** generator (PRNG) for SQLite.
+**
+** Random numbers are used by some of the database backends in order
+** to generate random integer keys for tables or random filenames.
+*/
+#include "sqliteInt.h"
+
+
+/* All threads share a single random number generator.
+** This structure is the current state of the generator.
+*/
+static SQLITE_WSD struct sqlite3PrngType {
+  u32 s[16];                 /* 64 bytes of chacha20 state */
+  u8 out[64];                /* Output bytes */
+  u8 n;                      /* Output bytes remaining */
+} sqlite3Prng;
+
+
+/* The RFC-7539 ChaCha20 block function
+*/
+#define ROTL(a,b) (((a) << (b)) | ((a) >> (32 - (b))))
+#define QR(a, b, c, d) ( \
+    a += b, d ^= a, d = ROTL(d,16), \
+    c += d, b ^= c, b = ROTL(b,12), \
+    a += b, d ^= a, d = ROTL(d, 8), \
+    c += d, b ^= c, b = ROTL(b, 7))
+static void chacha_block(u32 *out, const u32 *in){
+  int i;
+  u32 x[16];
+  memcpy(x, in, 64);
+  for(i=0; i<10; i++){
+    QR(x[0], x[4], x[ 8], x[12]);
+    QR(x[1], x[5], x[ 9], x[13]);
+    QR(x[2], x[6], x[10], x[14]);
+    QR(x[3], x[7], x[11], x[15]);
+    QR(x[0], x[5], x[10], x[15]);
+    QR(x[1], x[6], x[11], x[12]);
+    QR(x[2], x[7], x[ 8], x[13]);
+    QR(x[3], x[4], x[ 9], x[14]);
+  }
+  for(i=0; i<16; i++) out[i] = x[i]+in[i];
+}
+
+/*
+** Return N random bytes.
+*/
+void sqlite3_randomness(int N, void *pBuf){
+  unsigned char *zBuf = pBuf;
+
+  /* The "wsdPrng" macro will resolve to the pseudo-random number generator
+  ** state vector.  If writable static data is unsupported on the target,
+  ** we have to locate the state vector at run-time.  In the more common
+  ** case where writable static data is supported, wsdPrng can refer directly
+  ** to the "sqlite3Prng" state vector declared above.
+  */
+#ifdef SQLITE_OMIT_WSD
+  struct sqlite3PrngType *p = &GLOBAL(struct sqlite3PrngType, sqlite3Prng);
+# define wsdPrng p[0]
+#else
+# define wsdPrng sqlite3Prng
+#endif
+
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex;
+#endif
+
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return;
+#endif
+
+#if SQLITE_THREADSAFE
+  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG);
+#endif
+
+  sqlite3_mutex_enter(mutex);
+  if( N<=0 || pBuf==0 ){
+    wsdPrng.s[0] = 0;
+    sqlite3_mutex_leave(mutex);
+    return;
+  }
+
+  /* Initialize the state of the random number generator once,
+  ** the first time this routine is called.
+  */
+  if( wsdPrng.s[0]==0 ){
+    sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+    static const u32 chacha20_init[] = {
+      0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
+    };
+    memcpy(&wsdPrng.s[0], chacha20_init, 16);
+    if( NEVER(pVfs==0) ){
+      memset(&wsdPrng.s[4], 0, 44);
+    }else{
+      sqlite3OsRandomness(pVfs, 44, (char*)&wsdPrng.s[4]);
+    }
+    wsdPrng.s[15] = wsdPrng.s[12];
+    wsdPrng.s[12] = 0;
+    wsdPrng.n = 0;
+  }
+
+  assert( N>0 );
+  while( 1 /* exit by break */ ){
+    if( N<=wsdPrng.n ){
+      memcpy(zBuf, &wsdPrng.out[wsdPrng.n-N], N);
+      wsdPrng.n -= N;
+      break;
+    }
+    if( wsdPrng.n>0 ){
+      memcpy(zBuf, wsdPrng.out, wsdPrng.n);
+      N -= wsdPrng.n;
+      zBuf += wsdPrng.n;
+    }
+    wsdPrng.s[12]++;
+    chacha_block((u32*)wsdPrng.out, wsdPrng.s);
+    wsdPrng.n = 64;
+  }
+  sqlite3_mutex_leave(mutex);
+}
+
+#ifndef SQLITE_UNTESTABLE
+/*
+** For testing purposes, we sometimes want to preserve the state of
+** PRNG and restore the PRNG to its saved state at a later time, or
+** to reset the PRNG to its initial state.  These routines accomplish
+** those tasks.
+**
+** The sqlite3_test_control() interface calls these routines to
+** control the PRNG.
+*/
+static SQLITE_WSD struct sqlite3PrngType sqlite3SavedPrng;
+void sqlite3PrngSaveState(void){
+  memcpy(
+    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
+    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
+    sizeof(sqlite3Prng)
+  );
+}
+void sqlite3PrngRestoreState(void){
+  memcpy(
+    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
+    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
+    sizeof(sqlite3Prng)
+  );
+}
+#endif /* SQLITE_UNTESTABLE */
diff --git a/src/resolve.c b/src/resolve.c
new file mode 100644
index 0000000..b4f03fe
--- /dev/null
+++ b/src/resolve.c
@@ -0,0 +1,2204 @@
+/*
+** 2008 August 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains routines used for walking the parser tree and
+** resolve all identifiers by associating them with a particular
+** table and column.
+*/
+#include "sqliteInt.h"
+
+/*
+** Magic table number to mean the EXCLUDED table in an UPSERT statement.
+*/
+#define EXCLUDED_TABLE_NUMBER  2
+
+/*
+** Walk the expression tree pExpr and increase the aggregate function
+** depth (the Expr.op2 field) by N on every TK_AGG_FUNCTION node.
+** This needs to occur when copying a TK_AGG_FUNCTION node from an
+** outer query into an inner subquery.
+**
+** incrAggFunctionDepth(pExpr,n) is the main routine.  incrAggDepth(..)
+** is a helper function - a callback for the tree walker.
+**
+** See also the sqlite3WindowExtraAggFuncDepth() routine in window.c
+*/
+static int incrAggDepth(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_AGG_FUNCTION ) pExpr->op2 += pWalker->u.n;
+  return WRC_Continue;
+}
+static void incrAggFunctionDepth(Expr *pExpr, int N){
+  if( N>0 ){
+    Walker w;
+    memset(&w, 0, sizeof(w));
+    w.xExprCallback = incrAggDepth;
+    w.u.n = N;
+    sqlite3WalkExpr(&w, pExpr);
+  }
+}
+
+/*
+** Turn the pExpr expression into an alias for the iCol-th column of the
+** result set in pEList.
+**
+** If the reference is followed by a COLLATE operator, then make sure
+** the COLLATE operator is preserved.  For example:
+**
+**     SELECT a+b, c+d FROM t1 ORDER BY 1 COLLATE nocase;
+**
+** Should be transformed into:
+**
+**     SELECT a+b, c+d FROM t1 ORDER BY (a+b) COLLATE nocase;
+**
+** The nSubquery parameter specifies how many levels of subquery the
+** alias is removed from the original expression.  The usual value is
+** zero but it might be more if the alias is contained within a subquery
+** of the original expression.  The Expr.op2 field of TK_AGG_FUNCTION
+** structures must be increased by the nSubquery amount.
+*/
+static void resolveAlias(
+  Parse *pParse,         /* Parsing context */
+  ExprList *pEList,      /* A result set */
+  int iCol,              /* A column in the result set.  0..pEList->nExpr-1 */
+  Expr *pExpr,           /* Transform this into an alias to the result set */
+  int nSubquery          /* Number of subqueries that the label is moving */
+){
+  Expr *pOrig;           /* The iCol-th column of the result set */
+  Expr *pDup;            /* Copy of pOrig */
+  sqlite3 *db;           /* The database connection */
+
+  assert( iCol>=0 && iCol<pEList->nExpr );
+  pOrig = pEList->a[iCol].pExpr;
+  assert( pOrig!=0 );
+  db = pParse->db;
+  pDup = sqlite3ExprDup(db, pOrig, 0);
+  if( db->mallocFailed ){
+    sqlite3ExprDelete(db, pDup);
+    pDup = 0;
+  }else{
+    Expr temp;
+    incrAggFunctionDepth(pDup, nSubquery);
+    if( pExpr->op==TK_COLLATE ){
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      pDup = sqlite3ExprAddCollateString(pParse, pDup, pExpr->u.zToken);
+    }
+    memcpy(&temp, pDup, sizeof(Expr));
+    memcpy(pDup, pExpr, sizeof(Expr));
+    memcpy(pExpr, &temp, sizeof(Expr));
+    if( ExprHasProperty(pExpr, EP_WinFunc) ){
+      if( ALWAYS(pExpr->y.pWin!=0) ){
+        pExpr->y.pWin->pOwner = pExpr;
+      }
+    }
+    sqlite3ExprDeferredDelete(pParse, pDup);
+  }
+}
+
+/*
+** Subqueries store the original database, table and column names for their
+** result sets in ExprList.a[].zSpan, in the form "DATABASE.TABLE.COLUMN",
+** and mark the expression-list item by setting ExprList.a[].fg.eEName
+** to ENAME_TAB.
+**
+** Check to see if the zSpan/eEName of the expression-list item passed to this
+** routine matches the zDb, zTab, and zCol.  If any of zDb, zTab, and zCol are
+** NULL then those fields will match anything. Return true if there is a match,
+** or false otherwise.
+**
+** SF_NestedFrom subqueries also store an entry for the implicit rowid (or
+** _rowid_, or oid) column by setting ExprList.a[].fg.eEName to ENAME_ROWID,
+** and setting zSpan to "DATABASE.TABLE.<rowid-alias>". This type of pItem
+** argument matches if zCol is a rowid alias. If it is not NULL, (*pbRowid)
+** is set to 1 if there is this kind of match.
+*/
+int sqlite3MatchEName(
+  const struct ExprList_item *pItem,
+  const char *zCol,
+  const char *zTab,
+  const char *zDb,
+  int *pbRowid
+){
+  int n;
+  const char *zSpan;
+  int eEName = pItem->fg.eEName;
+  if( eEName!=ENAME_TAB && (eEName!=ENAME_ROWID || NEVER(pbRowid==0)) ){
+    return 0;
+  }
+  assert( pbRowid==0 || *pbRowid==0 );
+  zSpan = pItem->zEName;
+  for(n=0; ALWAYS(zSpan[n]) && zSpan[n]!='.'; n++){}
+  if( zDb && (sqlite3StrNICmp(zSpan, zDb, n)!=0 || zDb[n]!=0) ){
+    return 0;
+  }
+  zSpan += n+1;
+  for(n=0; ALWAYS(zSpan[n]) && zSpan[n]!='.'; n++){}
+  if( zTab && (sqlite3StrNICmp(zSpan, zTab, n)!=0 || zTab[n]!=0) ){
+    return 0;
+  }
+  zSpan += n+1;
+  if( zCol ){
+    if( eEName==ENAME_TAB && sqlite3StrICmp(zSpan, zCol)!=0 ) return 0;
+    if( eEName==ENAME_ROWID && sqlite3IsRowid(zCol)==0 ) return 0;
+  }
+  if( eEName==ENAME_ROWID ) *pbRowid = 1;
+  return 1;
+}
+
+/*
+** Return TRUE if the double-quoted string  mis-feature should be supported.
+*/
+static int areDoubleQuotedStringsEnabled(sqlite3 *db, NameContext *pTopNC){
+  if( db->init.busy ) return 1;  /* Always support for legacy schemas */
+  if( pTopNC->ncFlags & NC_IsDDL ){
+    /* Currently parsing a DDL statement */
+    if( sqlite3WritableSchema(db) && (db->flags & SQLITE_DqsDML)!=0 ){
+      return 1;
+    }
+    return (db->flags & SQLITE_DqsDDL)!=0;
+  }else{
+    /* Currently parsing a DML statement */
+    return (db->flags & SQLITE_DqsDML)!=0;
+  }
+}
+
+/*
+** The argument is guaranteed to be a non-NULL Expr node of type TK_COLUMN.
+** return the appropriate colUsed mask.
+*/
+Bitmask sqlite3ExprColUsed(Expr *pExpr){
+  int n;
+  Table *pExTab;
+
+  n = pExpr->iColumn;
+  assert( ExprUseYTab(pExpr) );
+  pExTab = pExpr->y.pTab;
+  assert( pExTab!=0 );
+  assert( n < pExTab->nCol );
+  if( (pExTab->tabFlags & TF_HasGenerated)!=0
+   && (pExTab->aCol[n].colFlags & COLFLAG_GENERATED)!=0
+  ){
+    testcase( pExTab->nCol==BMS-1 );
+    testcase( pExTab->nCol==BMS );
+    return pExTab->nCol>=BMS ? ALLBITS : MASKBIT(pExTab->nCol)-1;
+  }else{
+    testcase( n==BMS-1 );
+    testcase( n==BMS );
+    if( n>=BMS ) n = BMS-1;
+    return ((Bitmask)1)<<n;
+  }
+}
+
+/*
+** Create a new expression term for the column specified by pMatch and
+** iColumn.  Append this new expression term to the FULL JOIN Match set
+** in *ppList.  Create a new *ppList if this is the first term in the
+** set.
+*/
+static void extendFJMatch(
+  Parse *pParse,          /* Parsing context */
+  ExprList **ppList,      /* ExprList to extend */
+  SrcItem *pMatch,        /* Source table containing the column */
+  i16 iColumn             /* The column number */
+){
+  Expr *pNew = sqlite3ExprAlloc(pParse->db, TK_COLUMN, 0, 0);
+  if( pNew ){
+    pNew->iTable = pMatch->iCursor;
+    pNew->iColumn = iColumn;
+    pNew->y.pTab = pMatch->pTab;
+    assert( (pMatch->fg.jointype & (JT_LEFT|JT_LTORJ))!=0 );
+    ExprSetProperty(pNew, EP_CanBeNull);
+    *ppList = sqlite3ExprListAppend(pParse, *ppList, pNew);
+  }
+}
+
+/*
+** Return TRUE (non-zero) if zTab is a valid name for the schema table pTab.
+*/
+static SQLITE_NOINLINE int isValidSchemaTableName(
+  const char *zTab,         /* Name as it appears in the SQL */
+  Table *pTab,              /* The schema table we are trying to match */
+  Schema *pSchema           /* non-NULL if a database qualifier is present */
+){
+  const char *zLegacy;
+  assert( pTab!=0 );
+  assert( pTab->tnum==1 );
+  if( sqlite3StrNICmp(zTab, "sqlite_", 7)!=0 ) return 0;
+  zLegacy = pTab->zName;
+  if( strcmp(zLegacy+7, &LEGACY_TEMP_SCHEMA_TABLE[7])==0 ){
+    if( sqlite3StrICmp(zTab+7, &PREFERRED_TEMP_SCHEMA_TABLE[7])==0 ){
+      return 1;
+    }
+    if( pSchema==0 ) return 0;
+    if( sqlite3StrICmp(zTab+7, &LEGACY_SCHEMA_TABLE[7])==0 ) return 1;
+    if( sqlite3StrICmp(zTab+7, &PREFERRED_SCHEMA_TABLE[7])==0 ) return 1;
+  }else{
+    if( sqlite3StrICmp(zTab+7, &PREFERRED_SCHEMA_TABLE[7])==0 ) return 1;
+  }
+  return 0;
+}
+
+/*
+** Given the name of a column of the form X.Y.Z or Y.Z or just Z, look up
+** that name in the set of source tables in pSrcList and make the pExpr
+** expression node refer back to that source column.  The following changes
+** are made to pExpr:
+**
+**    pExpr->iDb           Set the index in db->aDb[] of the database X
+**                         (even if X is implied).
+**    pExpr->iTable        Set to the cursor number for the table obtained
+**                         from pSrcList.
+**    pExpr->y.pTab        Points to the Table structure of X.Y (even if
+**                         X and/or Y are implied.)
+**    pExpr->iColumn       Set to the column number within the table.
+**    pExpr->op            Set to TK_COLUMN.
+**    pExpr->pLeft         Any expression this points to is deleted
+**    pExpr->pRight        Any expression this points to is deleted.
+**
+** The zDb variable is the name of the database (the "X").  This value may be
+** NULL meaning that name is of the form Y.Z or Z.  Any available database
+** can be used.  The zTable variable is the name of the table (the "Y").  This
+** value can be NULL if zDb is also NULL.  If zTable is NULL it
+** means that the form of the name is Z and that columns from any table
+** can be used.
+**
+** If the name cannot be resolved unambiguously, leave an error message
+** in pParse and return WRC_Abort.  Return WRC_Prune on success.
+*/
+static int lookupName(
+  Parse *pParse,       /* The parsing context */
+  const char *zDb,     /* Name of the database containing table, or NULL */
+  const char *zTab,    /* Name of table containing column, or NULL */
+  const char *zCol,    /* Name of the column. */
+  NameContext *pNC,    /* The name context used to resolve the name */
+  Expr *pExpr          /* Make this EXPR node point to the selected column */
+){
+  int i, j;                         /* Loop counters */
+  int cnt = 0;                      /* Number of matching column names */
+  int cntTab = 0;                   /* Number of potential "rowid" matches */
+  int nSubquery = 0;                /* How many levels of subquery */
+  sqlite3 *db = pParse->db;         /* The database connection */
+  SrcItem *pItem;                   /* Use for looping over pSrcList items */
+  SrcItem *pMatch = 0;              /* The matching pSrcList item */
+  NameContext *pTopNC = pNC;        /* First namecontext in the list */
+  Schema *pSchema = 0;              /* Schema of the expression */
+  int eNewExprOp = TK_COLUMN;       /* New value for pExpr->op on success */
+  Table *pTab = 0;                  /* Table holding the row */
+  Column *pCol;                     /* A column of pTab */
+  ExprList *pFJMatch = 0;           /* Matches for FULL JOIN .. USING */
+
+  assert( pNC );     /* the name context cannot be NULL. */
+  assert( zCol );    /* The Z in X.Y.Z cannot be NULL */
+  assert( zDb==0 || zTab!=0 );
+  assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
+
+  /* Initialize the node to no-match */
+  pExpr->iTable = -1;
+  ExprSetVVAProperty(pExpr, EP_NoReduce);
+
+  /* Translate the schema name in zDb into a pointer to the corresponding
+  ** schema.  If not found, pSchema will remain NULL and nothing will match
+  ** resulting in an appropriate error message toward the end of this routine
+  */
+  if( zDb ){
+    testcase( pNC->ncFlags & NC_PartIdx );
+    testcase( pNC->ncFlags & NC_IsCheck );
+    if( (pNC->ncFlags & (NC_PartIdx|NC_IsCheck))!=0 ){
+      /* Silently ignore database qualifiers inside CHECK constraints and
+      ** partial indices.  Do not raise errors because that might break
+      ** legacy and because it does not hurt anything to just ignore the
+      ** database name. */
+      zDb = 0;
+    }else{
+      for(i=0; i<db->nDb; i++){
+        assert( db->aDb[i].zDbSName );
+        if( sqlite3StrICmp(db->aDb[i].zDbSName,zDb)==0 ){
+          pSchema = db->aDb[i].pSchema;
+          break;
+        }
+      }
+      if( i==db->nDb && sqlite3StrICmp("main", zDb)==0 ){
+        /* This branch is taken when the main database has been renamed
+        ** using SQLITE_DBCONFIG_MAINDBNAME. */
+        pSchema = db->aDb[0].pSchema;
+        zDb = db->aDb[0].zDbSName;
+      }
+    }
+  }
+
+  /* Start at the inner-most context and move outward until a match is found */
+  assert( pNC && cnt==0 );
+  do{
+    ExprList *pEList;
+    SrcList *pSrcList = pNC->pSrcList;
+
+    if( pSrcList ){
+      for(i=0, pItem=pSrcList->a; i<pSrcList->nSrc; i++, pItem++){
+        u8 hCol;
+        pTab = pItem->pTab;
+        assert( pTab!=0 && pTab->zName!=0 );
+        assert( pTab->nCol>0 || pParse->nErr );
+        assert( (int)pItem->fg.isNestedFrom == IsNestedFrom(pItem->pSelect) );
+        if( pItem->fg.isNestedFrom ){
+          /* In this case, pItem is a subquery that has been formed from a
+          ** parenthesized subset of the FROM clause terms.  Example:
+          **   .... FROM t1 LEFT JOIN (t2 RIGHT JOIN t3 USING(x)) USING(y) ...
+          **                          \_________________________/
+          **             This pItem -------------^
+          */
+          int hit = 0;
+          assert( pItem->pSelect!=0 );
+          pEList = pItem->pSelect->pEList;
+          assert( pEList!=0 );
+          assert( pEList->nExpr==pTab->nCol );
+          for(j=0; j<pEList->nExpr; j++){
+            int bRowid = 0;       /* True if possible rowid match */
+            if( !sqlite3MatchEName(&pEList->a[j], zCol, zTab, zDb, &bRowid) ){
+              continue;
+            }
+            if( bRowid==0 ){
+              if( cnt>0 ){
+                if( pItem->fg.isUsing==0
+                 || sqlite3IdListIndex(pItem->u3.pUsing, zCol)<0
+                ){
+                  /* Two or more tables have the same column name which is
+                  ** not joined by USING.  This is an error.  Signal as much
+                  ** by clearing pFJMatch and letting cnt go above 1. */
+                  sqlite3ExprListDelete(db, pFJMatch);
+                  pFJMatch = 0;
+                }else
+                if( (pItem->fg.jointype & JT_RIGHT)==0 ){
+                  /* An INNER or LEFT JOIN.  Use the left-most table */
+                  continue;
+                }else
+                if( (pItem->fg.jointype & JT_LEFT)==0 ){
+                  /* A RIGHT JOIN.  Use the right-most table */
+                  cnt = 0;
+                  sqlite3ExprListDelete(db, pFJMatch);
+                  pFJMatch = 0;
+                }else{
+                  /* For a FULL JOIN, we must construct a coalesce() func */
+                  extendFJMatch(pParse, &pFJMatch, pMatch, pExpr->iColumn);
+                }
+              }
+              cnt++;
+              hit = 1;
+            }else if( cnt>0 ){
+              /* This is a potential rowid match, but there has already been
+              ** a real match found. So this can be ignored.  */
+              continue;
+            }
+            cntTab++;
+            pMatch = pItem;
+            pExpr->iColumn = j;
+            pEList->a[j].fg.bUsed = 1;
+
+            /* rowid cannot be part of a USING clause - assert() this. */
+            assert( bRowid==0 || pEList->a[j].fg.bUsingTerm==0 );
+            if( pEList->a[j].fg.bUsingTerm ) break;
+          }
+          if( hit || zTab==0 ) continue;
+        }
+        assert( zDb==0 || zTab!=0 );
+        if( zTab ){
+          if( zDb ){
+            if( pTab->pSchema!=pSchema ) continue;
+            if( pSchema==0 && strcmp(zDb,"*")!=0 ) continue;
+          }
+          if( pItem->zAlias!=0 ){
+            if( sqlite3StrICmp(zTab, pItem->zAlias)!=0 ){
+              continue;
+            }
+          }else if( sqlite3StrICmp(zTab, pTab->zName)!=0 ){
+            if( pTab->tnum!=1 ) continue;
+            if( !isValidSchemaTableName(zTab, pTab, pSchema) ) continue;
+          }
+          assert( ExprUseYTab(pExpr) );
+          if( IN_RENAME_OBJECT && pItem->zAlias ){
+            sqlite3RenameTokenRemap(pParse, 0, (void*)&pExpr->y.pTab);
+          }
+        }
+        hCol = sqlite3StrIHash(zCol);
+        for(j=0, pCol=pTab->aCol; j<pTab->nCol; j++, pCol++){
+          if( pCol->hName==hCol
+           && sqlite3StrICmp(pCol->zCnName, zCol)==0
+          ){
+            if( cnt>0 ){
+              if( pItem->fg.isUsing==0
+               || sqlite3IdListIndex(pItem->u3.pUsing, zCol)<0
+              ){
+                /* Two or more tables have the same column name which is
+                ** not joined by USING.  This is an error.  Signal as much
+                ** by clearing pFJMatch and letting cnt go above 1. */
+                sqlite3ExprListDelete(db, pFJMatch);
+                pFJMatch = 0;
+              }else
+              if( (pItem->fg.jointype & JT_RIGHT)==0 ){
+                /* An INNER or LEFT JOIN.  Use the left-most table */
+                continue;
+              }else
+              if( (pItem->fg.jointype & JT_LEFT)==0 ){
+                /* A RIGHT JOIN.  Use the right-most table */
+                cnt = 0;
+                sqlite3ExprListDelete(db, pFJMatch);
+                pFJMatch = 0;
+              }else{
+                /* For a FULL JOIN, we must construct a coalesce() func */
+                extendFJMatch(pParse, &pFJMatch, pMatch, pExpr->iColumn);
+              }
+            }
+            cnt++;
+            pMatch = pItem;
+            /* Substitute the rowid (column -1) for the INTEGER PRIMARY KEY */
+            pExpr->iColumn = j==pTab->iPKey ? -1 : (i16)j;
+            if( pItem->fg.isNestedFrom ){
+              sqlite3SrcItemColumnUsed(pItem, j);
+            }
+            break;
+          }
+        }
+        if( 0==cnt && VisibleRowid(pTab) ){
+          cntTab++;
+          pMatch = pItem;
+        }
+      }
+      if( pMatch ){
+        pExpr->iTable = pMatch->iCursor;
+        assert( ExprUseYTab(pExpr) );
+        pExpr->y.pTab = pMatch->pTab;
+        if( (pMatch->fg.jointype & (JT_LEFT|JT_LTORJ))!=0 ){
+          ExprSetProperty(pExpr, EP_CanBeNull);
+        }
+        pSchema = pExpr->y.pTab->pSchema;
+      }
+    } /* if( pSrcList ) */
+
+#if !defined(SQLITE_OMIT_TRIGGER) || !defined(SQLITE_OMIT_UPSERT)
+    /* If we have not already resolved the name, then maybe
+    ** it is a new.* or old.* trigger argument reference.  Or
+    ** maybe it is an excluded.* from an upsert.  Or maybe it is
+    ** a reference in the RETURNING clause to a table being modified.
+    */
+    if( cnt==0 && zDb==0 ){
+      pTab = 0;
+#ifndef SQLITE_OMIT_TRIGGER
+      if( pParse->pTriggerTab!=0 ){
+        int op = pParse->eTriggerOp;
+        assert( op==TK_DELETE || op==TK_UPDATE || op==TK_INSERT );
+        if( pParse->bReturning ){
+          if( (pNC->ncFlags & NC_UBaseReg)!=0
+           && ALWAYS(zTab==0
+                     || sqlite3StrICmp(zTab,pParse->pTriggerTab->zName)==0)
+          ){
+            pExpr->iTable = op!=TK_DELETE;
+            pTab = pParse->pTriggerTab;
+          }
+        }else if( op!=TK_DELETE && zTab && sqlite3StrICmp("new",zTab) == 0 ){
+          pExpr->iTable = 1;
+          pTab = pParse->pTriggerTab;
+        }else if( op!=TK_INSERT && zTab && sqlite3StrICmp("old",zTab)==0 ){
+          pExpr->iTable = 0;
+          pTab = pParse->pTriggerTab;
+        }
+      }
+#endif /* SQLITE_OMIT_TRIGGER */
+#ifndef SQLITE_OMIT_UPSERT
+      if( (pNC->ncFlags & NC_UUpsert)!=0 && zTab!=0 ){
+        Upsert *pUpsert = pNC->uNC.pUpsert;
+        if( pUpsert && sqlite3StrICmp("excluded",zTab)==0 ){
+          pTab = pUpsert->pUpsertSrc->a[0].pTab;
+          pExpr->iTable = EXCLUDED_TABLE_NUMBER;
+        }
+      }
+#endif /* SQLITE_OMIT_UPSERT */
+
+      if( pTab ){
+        int iCol;
+        u8 hCol = sqlite3StrIHash(zCol);
+        pSchema = pTab->pSchema;
+        cntTab++;
+        for(iCol=0, pCol=pTab->aCol; iCol<pTab->nCol; iCol++, pCol++){
+          if( pCol->hName==hCol
+           && sqlite3StrICmp(pCol->zCnName, zCol)==0
+          ){
+            if( iCol==pTab->iPKey ){
+              iCol = -1;
+            }
+            break;
+          }
+        }
+        if( iCol>=pTab->nCol && sqlite3IsRowid(zCol) && VisibleRowid(pTab) ){
+          /* IMP: R-51414-32910 */
+          iCol = -1;
+        }
+        if( iCol<pTab->nCol ){
+          cnt++;
+          pMatch = 0;
+#ifndef SQLITE_OMIT_UPSERT
+          if( pExpr->iTable==EXCLUDED_TABLE_NUMBER ){
+            testcase( iCol==(-1) );
+            assert( ExprUseYTab(pExpr) );
+            if( IN_RENAME_OBJECT ){
+              pExpr->iColumn = iCol;
+              pExpr->y.pTab = pTab;
+              eNewExprOp = TK_COLUMN;
+            }else{
+              pExpr->iTable = pNC->uNC.pUpsert->regData +
+                 sqlite3TableColumnToStorage(pTab, iCol);
+              eNewExprOp = TK_REGISTER;
+            }
+          }else
+#endif /* SQLITE_OMIT_UPSERT */
+          {
+            assert( ExprUseYTab(pExpr) );
+            pExpr->y.pTab = pTab;
+            if( pParse->bReturning ){
+              eNewExprOp = TK_REGISTER;
+              pExpr->op2 = TK_COLUMN;
+              pExpr->iColumn = iCol;
+              pExpr->iTable = pNC->uNC.iBaseReg + (pTab->nCol+1)*pExpr->iTable +
+                 sqlite3TableColumnToStorage(pTab, iCol) + 1;
+            }else{
+              pExpr->iColumn = (i16)iCol;
+              eNewExprOp = TK_TRIGGER;
+#ifndef SQLITE_OMIT_TRIGGER
+              if( iCol<0 ){
+                pExpr->affExpr = SQLITE_AFF_INTEGER;
+              }else if( pExpr->iTable==0 ){
+                testcase( iCol==31 );
+                testcase( iCol==32 );
+                pParse->oldmask |= (iCol>=32 ? 0xffffffff : (((u32)1)<<iCol));
+              }else{
+                testcase( iCol==31 );
+                testcase( iCol==32 );
+                pParse->newmask |= (iCol>=32 ? 0xffffffff : (((u32)1)<<iCol));
+              }
+#endif /* SQLITE_OMIT_TRIGGER */
+            }
+          }
+        }
+      }
+    }
+#endif /* !defined(SQLITE_OMIT_TRIGGER) || !defined(SQLITE_OMIT_UPSERT) */
+
+    /*
+    ** Perhaps the name is a reference to the ROWID
+    */
+    if( cnt==0
+     && cntTab==1
+     && pMatch
+     && (pNC->ncFlags & (NC_IdxExpr|NC_GenCol))==0
+     && sqlite3IsRowid(zCol)
+     && ALWAYS(VisibleRowid(pMatch->pTab) || pMatch->fg.isNestedFrom)
+    ){
+      cnt = 1;
+      if( pMatch->fg.isNestedFrom==0 ) pExpr->iColumn = -1;
+      pExpr->affExpr = SQLITE_AFF_INTEGER;
+    }
+
+    /*
+    ** If the input is of the form Z (not Y.Z or X.Y.Z) then the name Z
+    ** might refer to an result-set alias.  This happens, for example, when
+    ** we are resolving names in the WHERE clause of the following command:
+    **
+    **     SELECT a+b AS x FROM table WHERE x<10;
+    **
+    ** In cases like this, replace pExpr with a copy of the expression that
+    ** forms the result set entry ("a+b" in the example) and return immediately.
+    ** Note that the expression in the result set should have already been
+    ** resolved by the time the WHERE clause is resolved.
+    **
+    ** The ability to use an output result-set column in the WHERE, GROUP BY,
+    ** or HAVING clauses, or as part of a larger expression in the ORDER BY
+    ** clause is not standard SQL.  This is a (goofy) SQLite extension, that
+    ** is supported for backwards compatibility only. Hence, we issue a warning
+    ** on sqlite3_log() whenever the capability is used.
+    */
+    if( cnt==0
+     && (pNC->ncFlags & NC_UEList)!=0
+     && zTab==0
+    ){
+      pEList = pNC->uNC.pEList;
+      assert( pEList!=0 );
+      for(j=0; j<pEList->nExpr; j++){
+        char *zAs = pEList->a[j].zEName;
+        if( pEList->a[j].fg.eEName==ENAME_NAME
+         && sqlite3_stricmp(zAs, zCol)==0
+        ){
+          Expr *pOrig;
+          assert( pExpr->pLeft==0 && pExpr->pRight==0 );
+          assert( ExprUseXList(pExpr)==0 || pExpr->x.pList==0 );
+          assert( ExprUseXSelect(pExpr)==0 || pExpr->x.pSelect==0 );
+          pOrig = pEList->a[j].pExpr;
+          if( (pNC->ncFlags&NC_AllowAgg)==0 && ExprHasProperty(pOrig, EP_Agg) ){
+            sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
+            return WRC_Abort;
+          }
+          if( ExprHasProperty(pOrig, EP_Win)
+           && ((pNC->ncFlags&NC_AllowWin)==0 || pNC!=pTopNC )
+          ){
+            sqlite3ErrorMsg(pParse, "misuse of aliased window function %s",zAs);
+            return WRC_Abort;
+          }
+          if( sqlite3ExprVectorSize(pOrig)!=1 ){
+            sqlite3ErrorMsg(pParse, "row value misused");
+            return WRC_Abort;
+          }
+          resolveAlias(pParse, pEList, j, pExpr, nSubquery);
+          cnt = 1;
+          pMatch = 0;
+          assert( zTab==0 && zDb==0 );
+          if( IN_RENAME_OBJECT ){
+            sqlite3RenameTokenRemap(pParse, 0, (void*)pExpr);
+          }
+          goto lookupname_end;
+        }
+      }
+    }
+
+    /* Advance to the next name context.  The loop will exit when either
+    ** we have a match (cnt>0) or when we run out of name contexts.
+    */
+    if( cnt ) break;
+    pNC = pNC->pNext;
+    nSubquery++;
+  }while( pNC );
+
+
+  /*
+  ** If X and Y are NULL (in other words if only the column name Z is
+  ** supplied) and the value of Z is enclosed in double-quotes, then
+  ** Z is a string literal if it doesn't match any column names.  In that
+  ** case, we need to return right away and not make any changes to
+  ** pExpr.
+  **
+  ** Because no reference was made to outer contexts, the pNC->nRef
+  ** fields are not changed in any context.
+  */
+  if( cnt==0 && zTab==0 ){
+    assert( pExpr->op==TK_ID );
+    if( ExprHasProperty(pExpr,EP_DblQuoted)
+     && areDoubleQuotedStringsEnabled(db, pTopNC)
+    ){
+      /* If a double-quoted identifier does not match any known column name,
+      ** then treat it as a string.
+      **
+      ** This hack was added in the early days of SQLite in a misguided attempt
+      ** to be compatible with MySQL 3.x, which used double-quotes for strings.
+      ** I now sorely regret putting in this hack. The effect of this hack is
+      ** that misspelled identifier names are silently converted into strings
+      ** rather than causing an error, to the frustration of countless
+      ** programmers. To all those frustrated programmers, my apologies.
+      **
+      ** Someday, I hope to get rid of this hack. Unfortunately there is
+      ** a huge amount of legacy SQL that uses it. So for now, we just
+      ** issue a warning.
+      */
+      sqlite3_log(SQLITE_WARNING,
+        "double-quoted string literal: \"%w\"", zCol);
+#ifdef SQLITE_ENABLE_NORMALIZE
+      sqlite3VdbeAddDblquoteStr(db, pParse->pVdbe, zCol);
+#endif
+      pExpr->op = TK_STRING;
+      memset(&pExpr->y, 0, sizeof(pExpr->y));
+      return WRC_Prune;
+    }
+    if( sqlite3ExprIdToTrueFalse(pExpr) ){
+      return WRC_Prune;
+    }
+  }
+
+  /*
+  ** cnt==0 means there was not match.
+  ** cnt>1 means there were two or more matches.
+  **
+  ** cnt==0 is always an error.  cnt>1 is often an error, but might
+  ** be multiple matches for a NATURAL LEFT JOIN or a LEFT JOIN USING.
+  */
+  assert( pFJMatch==0 || cnt>0 );
+  assert( !ExprHasProperty(pExpr, EP_xIsSelect|EP_IntValue) );
+  if( cnt!=1 ){
+    const char *zErr;
+    if( pFJMatch ){
+      if( pFJMatch->nExpr==cnt-1 ){
+        if( ExprHasProperty(pExpr,EP_Leaf) ){
+          ExprClearProperty(pExpr,EP_Leaf);
+        }else{
+          sqlite3ExprDelete(db, pExpr->pLeft);
+          pExpr->pLeft = 0;
+          sqlite3ExprDelete(db, pExpr->pRight);
+          pExpr->pRight = 0;
+        }
+        extendFJMatch(pParse, &pFJMatch, pMatch, pExpr->iColumn);
+        pExpr->op = TK_FUNCTION;
+        pExpr->u.zToken = "coalesce";
+        pExpr->x.pList = pFJMatch;
+        cnt = 1;
+        goto lookupname_end;
+      }else{
+        sqlite3ExprListDelete(db, pFJMatch);
+        pFJMatch = 0;
+      }
+    }
+    zErr = cnt==0 ? "no such column" : "ambiguous column name";
+    if( zDb ){
+      sqlite3ErrorMsg(pParse, "%s: %s.%s.%s", zErr, zDb, zTab, zCol);
+    }else if( zTab ){
+      sqlite3ErrorMsg(pParse, "%s: %s.%s", zErr, zTab, zCol);
+    }else{
+      sqlite3ErrorMsg(pParse, "%s: %s", zErr, zCol);
+    }
+    sqlite3RecordErrorOffsetOfExpr(pParse->db, pExpr);
+    pParse->checkSchema = 1;
+    pTopNC->nNcErr++;
+    eNewExprOp = TK_NULL;
+  }
+  assert( pFJMatch==0 );
+
+  /* Remove all substructure from pExpr */
+  if( !ExprHasProperty(pExpr,(EP_TokenOnly|EP_Leaf)) ){
+    sqlite3ExprDelete(db, pExpr->pLeft);
+    pExpr->pLeft = 0;
+    sqlite3ExprDelete(db, pExpr->pRight);
+    pExpr->pRight = 0;
+    ExprSetProperty(pExpr, EP_Leaf);
+  }
+
+  /* If a column from a table in pSrcList is referenced, then record
+  ** this fact in the pSrcList.a[].colUsed bitmask.  Column 0 causes
+  ** bit 0 to be set.  Column 1 sets bit 1.  And so forth.  Bit 63 is
+  ** set if the 63rd or any subsequent column is used.
+  **
+  ** The colUsed mask is an optimization used to help determine if an
+  ** index is a covering index.  The correct answer is still obtained
+  ** if the mask contains extra set bits.  However, it is important to
+  ** avoid setting bits beyond the maximum column number of the table.
+  ** (See ticket [b92e5e8ec2cdbaa1]).
+  **
+  ** If a generated column is referenced, set bits for every column
+  ** of the table.
+  */
+  if( pExpr->iColumn>=0 && cnt==1 && pMatch!=0 ){
+    pMatch->colUsed |= sqlite3ExprColUsed(pExpr);
+  }
+
+  pExpr->op = eNewExprOp;
+lookupname_end:
+  if( cnt==1 ){
+    assert( pNC!=0 );
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    if( pParse->db->xAuth
+     && (pExpr->op==TK_COLUMN || pExpr->op==TK_TRIGGER)
+    ){
+      sqlite3AuthRead(pParse, pExpr, pSchema, pNC->pSrcList);
+    }
+#endif
+    /* Increment the nRef value on all name contexts from TopNC up to
+    ** the point where the name matched. */
+    for(;;){
+      assert( pTopNC!=0 );
+      pTopNC->nRef++;
+      if( pTopNC==pNC ) break;
+      pTopNC = pTopNC->pNext;
+    }
+    return WRC_Prune;
+  } else {
+    return WRC_Abort;
+  }
+}
+
+/*
+** Allocate and return a pointer to an expression to load the column iCol
+** from datasource iSrc in SrcList pSrc.
+*/
+Expr *sqlite3CreateColumnExpr(sqlite3 *db, SrcList *pSrc, int iSrc, int iCol){
+  Expr *p = sqlite3ExprAlloc(db, TK_COLUMN, 0, 0);
+  if( p ){
+    SrcItem *pItem = &pSrc->a[iSrc];
+    Table *pTab;
+    assert( ExprUseYTab(p) );
+    pTab = p->y.pTab = pItem->pTab;
+    p->iTable = pItem->iCursor;
+    if( p->y.pTab->iPKey==iCol ){
+      p->iColumn = -1;
+    }else{
+      p->iColumn = (ynVar)iCol;
+      if( (pTab->tabFlags & TF_HasGenerated)!=0
+       && (pTab->aCol[iCol].colFlags & COLFLAG_GENERATED)!=0
+      ){
+        testcase( pTab->nCol==63 );
+        testcase( pTab->nCol==64 );
+        pItem->colUsed = pTab->nCol>=64 ? ALLBITS : MASKBIT(pTab->nCol)-1;
+      }else{
+        testcase( iCol==BMS );
+        testcase( iCol==BMS-1 );
+        pItem->colUsed |= ((Bitmask)1)<<(iCol>=BMS ? BMS-1 : iCol);
+      }
+    }
+  }
+  return p;
+}
+
+/*
+** Report an error that an expression is not valid for some set of
+** pNC->ncFlags values determined by validMask.
+**
+** static void notValid(
+**   Parse *pParse,       // Leave error message here
+**   NameContext *pNC,    // The name context
+**   const char *zMsg,    // Type of error
+**   int validMask,       // Set of contexts for which prohibited
+**   Expr *pExpr          // Invalidate this expression on error
+** ){...}
+**
+** As an optimization, since the conditional is almost always false
+** (because errors are rare), the conditional is moved outside of the
+** function call using a macro.
+*/
+static void notValidImpl(
+   Parse *pParse,       /* Leave error message here */
+   NameContext *pNC,    /* The name context */
+   const char *zMsg,    /* Type of error */
+   Expr *pExpr,         /* Invalidate this expression on error */
+   Expr *pError         /* Associate error with this expression */
+){
+  const char *zIn = "partial index WHERE clauses";
+  if( pNC->ncFlags & NC_IdxExpr )      zIn = "index expressions";
+#ifndef SQLITE_OMIT_CHECK
+  else if( pNC->ncFlags & NC_IsCheck ) zIn = "CHECK constraints";
+#endif
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  else if( pNC->ncFlags & NC_GenCol ) zIn = "generated columns";
+#endif
+  sqlite3ErrorMsg(pParse, "%s prohibited in %s", zMsg, zIn);
+  if( pExpr ) pExpr->op = TK_NULL;
+  sqlite3RecordErrorOffsetOfExpr(pParse->db, pError);
+}
+#define sqlite3ResolveNotValid(P,N,M,X,E,R) \
+  assert( ((X)&~(NC_IsCheck|NC_PartIdx|NC_IdxExpr|NC_GenCol))==0 ); \
+  if( ((N)->ncFlags & (X))!=0 ) notValidImpl(P,N,M,E,R);
+
+/*
+** Expression p should encode a floating point value between 1.0 and 0.0.
+** Return 1024 times this value.  Or return -1 if p is not a floating point
+** value between 1.0 and 0.0.
+*/
+static int exprProbability(Expr *p){
+  double r = -1.0;
+  if( p->op!=TK_FLOAT ) return -1;
+  assert( !ExprHasProperty(p, EP_IntValue) );
+  sqlite3AtoF(p->u.zToken, &r, sqlite3Strlen30(p->u.zToken), SQLITE_UTF8);
+  assert( r>=0.0 );
+  if( r>1.0 ) return -1;
+  return (int)(r*134217728.0);
+}
+
+/*
+** This routine is callback for sqlite3WalkExpr().
+**
+** Resolve symbolic names into TK_COLUMN operators for the current
+** node in the expression tree.  Return 0 to continue the search down
+** the tree or 2 to abort the tree walk.
+**
+** This routine also does error checking and name resolution for
+** function names.  The operator for aggregate functions is changed
+** to TK_AGG_FUNCTION.
+*/
+static int resolveExprStep(Walker *pWalker, Expr *pExpr){
+  NameContext *pNC;
+  Parse *pParse;
+
+  pNC = pWalker->u.pNC;
+  assert( pNC!=0 );
+  pParse = pNC->pParse;
+  assert( pParse==pWalker->pParse );
+
+#ifndef NDEBUG
+  if( pNC->pSrcList && pNC->pSrcList->nAlloc>0 ){
+    SrcList *pSrcList = pNC->pSrcList;
+    int i;
+    for(i=0; i<pNC->pSrcList->nSrc; i++){
+      assert( pSrcList->a[i].iCursor>=0 && pSrcList->a[i].iCursor<pParse->nTab);
+    }
+  }
+#endif
+  switch( pExpr->op ){
+
+    /* The special operator TK_ROW means use the rowid for the first
+    ** column in the FROM clause.  This is used by the LIMIT and ORDER BY
+    ** clause processing on UPDATE and DELETE statements, and by
+    ** UPDATE ... FROM statement processing.
+    */
+    case TK_ROW: {
+      SrcList *pSrcList = pNC->pSrcList;
+      SrcItem *pItem;
+      assert( pSrcList && pSrcList->nSrc>=1 );
+      pItem = pSrcList->a;
+      pExpr->op = TK_COLUMN;
+      assert( ExprUseYTab(pExpr) );
+      pExpr->y.pTab = pItem->pTab;
+      pExpr->iTable = pItem->iCursor;
+      pExpr->iColumn--;
+      pExpr->affExpr = SQLITE_AFF_INTEGER;
+      break;
+    }
+
+    /* An optimization:  Attempt to convert
+    **
+    **      "expr IS NOT NULL"  -->  "TRUE"
+    **      "expr IS NULL"      -->  "FALSE"
+    **
+    ** if we can prove that "expr" is never NULL.  Call this the
+    ** "NOT NULL strength reduction optimization".
+    **
+    ** If this optimization occurs, also restore the NameContext ref-counts
+    ** to the state they where in before the "column" LHS expression was
+    ** resolved.  This prevents "column" from being counted as having been
+    ** referenced, which might prevent a SELECT from being erroneously
+    ** marked as correlated.
+    */
+    case TK_NOTNULL:
+    case TK_ISNULL: {
+      int anRef[8];
+      NameContext *p;
+      int i;
+      for(i=0, p=pNC; p && i<ArraySize(anRef); p=p->pNext, i++){
+        anRef[i] = p->nRef;
+      }
+      sqlite3WalkExpr(pWalker, pExpr->pLeft);
+      if( 0==sqlite3ExprCanBeNull(pExpr->pLeft) && !IN_RENAME_OBJECT ){
+        testcase( ExprHasProperty(pExpr, EP_OuterON) );
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        pExpr->u.iValue = (pExpr->op==TK_NOTNULL);
+        pExpr->flags |= EP_IntValue;
+        pExpr->op = TK_INTEGER;
+
+        for(i=0, p=pNC; p && i<ArraySize(anRef); p=p->pNext, i++){
+          p->nRef = anRef[i];
+        }
+        sqlite3ExprDelete(pParse->db, pExpr->pLeft);
+        pExpr->pLeft = 0;
+      }
+      return WRC_Prune;
+    }
+
+    /* A column name:                    ID
+    ** Or table name and column name:    ID.ID
+    ** Or a database, table and column:  ID.ID.ID
+    **
+    ** The TK_ID and TK_OUT cases are combined so that there will only
+    ** be one call to lookupName().  Then the compiler will in-line
+    ** lookupName() for a size reduction and performance increase.
+    */
+    case TK_ID:
+    case TK_DOT: {
+      const char *zColumn;
+      const char *zTable;
+      const char *zDb;
+      Expr *pRight;
+
+      if( pExpr->op==TK_ID ){
+        zDb = 0;
+        zTable = 0;
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        zColumn = pExpr->u.zToken;
+      }else{
+        Expr *pLeft = pExpr->pLeft;
+        testcase( pNC->ncFlags & NC_IdxExpr );
+        testcase( pNC->ncFlags & NC_GenCol );
+        sqlite3ResolveNotValid(pParse, pNC, "the \".\" operator",
+                               NC_IdxExpr|NC_GenCol, 0, pExpr);
+        pRight = pExpr->pRight;
+        if( pRight->op==TK_ID ){
+          zDb = 0;
+        }else{
+          assert( pRight->op==TK_DOT );
+          assert( !ExprHasProperty(pRight, EP_IntValue) );
+          zDb = pLeft->u.zToken;
+          pLeft = pRight->pLeft;
+          pRight = pRight->pRight;
+        }
+        assert( ExprUseUToken(pLeft) && ExprUseUToken(pRight) );
+        zTable = pLeft->u.zToken;
+        zColumn = pRight->u.zToken;
+        assert( ExprUseYTab(pExpr) );
+        if( IN_RENAME_OBJECT ){
+          sqlite3RenameTokenRemap(pParse, (void*)pExpr, (void*)pRight);
+          sqlite3RenameTokenRemap(pParse, (void*)&pExpr->y.pTab, (void*)pLeft);
+        }
+      }
+      return lookupName(pParse, zDb, zTable, zColumn, pNC, pExpr);
+    }
+
+    /* Resolve function names
+    */
+    case TK_FUNCTION: {
+      ExprList *pList = pExpr->x.pList;    /* The argument list */
+      int n = pList ? pList->nExpr : 0;    /* Number of arguments */
+      int no_such_func = 0;       /* True if no such function exists */
+      int wrong_num_args = 0;     /* True if wrong number of arguments */
+      int is_agg = 0;             /* True if is an aggregate function */
+      const char *zId;            /* The function name. */
+      FuncDef *pDef;              /* Information about the function */
+      u8 enc = ENC(pParse->db);   /* The database encoding */
+      int savedAllowFlags = (pNC->ncFlags & (NC_AllowAgg | NC_AllowWin));
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      Window *pWin = (IsWindowFunc(pExpr) ? pExpr->y.pWin : 0);
+#endif
+      assert( !ExprHasProperty(pExpr, EP_xIsSelect|EP_IntValue) );
+      assert( pExpr->pLeft==0 || pExpr->pLeft->op==TK_ORDER );
+      zId = pExpr->u.zToken;
+      pDef = sqlite3FindFunction(pParse->db, zId, n, enc, 0);
+      if( pDef==0 ){
+        pDef = sqlite3FindFunction(pParse->db, zId, -2, enc, 0);
+        if( pDef==0 ){
+          no_such_func = 1;
+        }else{
+          wrong_num_args = 1;
+        }
+      }else{
+        is_agg = pDef->xFinalize!=0;
+        if( pDef->funcFlags & SQLITE_FUNC_UNLIKELY ){
+          ExprSetProperty(pExpr, EP_Unlikely);
+          if( n==2 ){
+            pExpr->iTable = exprProbability(pList->a[1].pExpr);
+            if( pExpr->iTable<0 ){
+              sqlite3ErrorMsg(pParse,
+                "second argument to %#T() must be a "
+                "constant between 0.0 and 1.0", pExpr);
+              pNC->nNcErr++;
+            }
+          }else{
+            /* EVIDENCE-OF: R-61304-29449 The unlikely(X) function is
+            ** equivalent to likelihood(X, 0.0625).
+            ** EVIDENCE-OF: R-01283-11636 The unlikely(X) function is
+            ** short-hand for likelihood(X,0.0625).
+            ** EVIDENCE-OF: R-36850-34127 The likely(X) function is short-hand
+            ** for likelihood(X,0.9375).
+            ** EVIDENCE-OF: R-53436-40973 The likely(X) function is equivalent
+            ** to likelihood(X,0.9375). */
+            /* TUNING: unlikely() probability is 0.0625.  likely() is 0.9375 */
+            pExpr->iTable = pDef->zName[0]=='u' ? 8388608 : 125829120;
+          }            
+        }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+        {
+          int auth = sqlite3AuthCheck(pParse, SQLITE_FUNCTION, 0,pDef->zName,0);
+          if( auth!=SQLITE_OK ){
+            if( auth==SQLITE_DENY ){
+              sqlite3ErrorMsg(pParse, "not authorized to use function: %#T",
+                                      pExpr);
+              pNC->nNcErr++;
+            }
+            pExpr->op = TK_NULL;
+            return WRC_Prune;
+          }
+        }
+#endif
+        if( pDef->funcFlags & (SQLITE_FUNC_CONSTANT|SQLITE_FUNC_SLOCHNG) ){
+          /* For the purposes of the EP_ConstFunc flag, date and time
+          ** functions and other functions that change slowly are considered
+          ** constant because they are constant for the duration of one query.
+          ** This allows them to be factored out of inner loops. */
+          ExprSetProperty(pExpr,EP_ConstFunc);
+        }
+        if( (pDef->funcFlags & SQLITE_FUNC_CONSTANT)==0 ){
+          /* Clearly non-deterministic functions like random(), but also
+          ** date/time functions that use 'now', and other functions like
+          ** sqlite_version() that might change over time cannot be used
+          ** in an index or generated column.  Curiously, they can be used
+          ** in a CHECK constraint.  SQLServer, MySQL, and PostgreSQL all
+          ** all this. */
+          sqlite3ResolveNotValid(pParse, pNC, "non-deterministic functions",
+                                 NC_IdxExpr|NC_PartIdx|NC_GenCol, 0, pExpr);
+        }else{
+          assert( (NC_SelfRef & 0xff)==NC_SelfRef ); /* Must fit in 8 bits */
+          pExpr->op2 = pNC->ncFlags & NC_SelfRef;
+          if( pNC->ncFlags & NC_FromDDL ) ExprSetProperty(pExpr, EP_FromDDL);
+        }
+        if( (pDef->funcFlags & SQLITE_FUNC_INTERNAL)!=0
+         && pParse->nested==0
+         && (pParse->db->mDbFlags & DBFLAG_InternalFunc)==0
+        ){
+          /* Internal-use-only functions are disallowed unless the
+          ** SQL is being compiled using sqlite3NestedParse() or
+          ** the SQLITE_TESTCTRL_INTERNAL_FUNCTIONS test-control has be
+          ** used to activate internal functions for testing purposes */
+          no_such_func = 1;
+          pDef = 0;
+        }else
+        if( (pDef->funcFlags & (SQLITE_FUNC_DIRECT|SQLITE_FUNC_UNSAFE))!=0
+         && !IN_RENAME_OBJECT
+        ){
+          sqlite3ExprFunctionUsable(pParse, pExpr, pDef);
+        }
+      }
+
+      if( 0==IN_RENAME_OBJECT ){
+#ifndef SQLITE_OMIT_WINDOWFUNC
+        assert( is_agg==0 || (pDef->funcFlags & SQLITE_FUNC_MINMAX)
+          || (pDef->xValue==0 && pDef->xInverse==0)
+          || (pDef->xValue && pDef->xInverse && pDef->xSFunc && pDef->xFinalize)
+        );
+        if( pDef && pDef->xValue==0 && pWin ){
+          sqlite3ErrorMsg(pParse,
+              "%#T() may not be used as a window function", pExpr
+          );
+          pNC->nNcErr++;
+        }else if(
+              (is_agg && (pNC->ncFlags & NC_AllowAgg)==0)
+           || (is_agg && (pDef->funcFlags&SQLITE_FUNC_WINDOW) && !pWin)
+           || (is_agg && pWin && (pNC->ncFlags & NC_AllowWin)==0)
+        ){
+          const char *zType;
+          if( (pDef->funcFlags & SQLITE_FUNC_WINDOW) || pWin ){
+            zType = "window";
+          }else{
+            zType = "aggregate";
+          }
+          sqlite3ErrorMsg(pParse, "misuse of %s function %#T()",zType,pExpr);
+          pNC->nNcErr++;
+          is_agg = 0;
+        }
+#else
+        if( (is_agg && (pNC->ncFlags & NC_AllowAgg)==0) ){
+          sqlite3ErrorMsg(pParse,"misuse of aggregate function %#T()",pExpr);
+          pNC->nNcErr++;
+          is_agg = 0;
+        }
+#endif
+        else if( no_such_func && pParse->db->init.busy==0
+#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
+                  && pParse->explain==0
+#endif
+        ){
+          sqlite3ErrorMsg(pParse, "no such function: %#T", pExpr);
+          pNC->nNcErr++;
+        }else if( wrong_num_args ){
+          sqlite3ErrorMsg(pParse,"wrong number of arguments to function %#T()",
+               pExpr);
+          pNC->nNcErr++;
+        }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+        else if( is_agg==0 && ExprHasProperty(pExpr, EP_WinFunc) ){
+          sqlite3ErrorMsg(pParse,
+              "FILTER may not be used with non-aggregate %#T()",
+              pExpr
+          );
+          pNC->nNcErr++;
+        }
+#endif
+        else if( is_agg==0 && pExpr->pLeft ){
+          sqlite3ExprOrderByAggregateError(pParse, pExpr);
+          pNC->nNcErr++;
+        }
+        if( is_agg ){
+          /* Window functions may not be arguments of aggregate functions.
+          ** Or arguments of other window functions. But aggregate functions
+          ** may be arguments for window functions.  */
+#ifndef SQLITE_OMIT_WINDOWFUNC
+          pNC->ncFlags &= ~(NC_AllowWin | (!pWin ? NC_AllowAgg : 0));
+#else
+          pNC->ncFlags &= ~NC_AllowAgg;
+#endif
+        }
+      }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      else if( ExprHasProperty(pExpr, EP_WinFunc) ){
+        is_agg = 1;
+      }
+#endif
+      sqlite3WalkExprList(pWalker, pList);
+      if( is_agg ){
+        if( pExpr->pLeft ){
+          assert( pExpr->pLeft->op==TK_ORDER );
+          assert( ExprUseXList(pExpr->pLeft) );
+          sqlite3WalkExprList(pWalker, pExpr->pLeft->x.pList);
+        }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+        if( pWin ){
+          Select *pSel = pNC->pWinSelect;
+          assert( pWin==0 || (ExprUseYWin(pExpr) && pWin==pExpr->y.pWin) );
+          if( IN_RENAME_OBJECT==0 ){
+            sqlite3WindowUpdate(pParse, pSel ? pSel->pWinDefn : 0, pWin, pDef);
+            if( pParse->db->mallocFailed ) break;
+          }
+          sqlite3WalkExprList(pWalker, pWin->pPartition);
+          sqlite3WalkExprList(pWalker, pWin->pOrderBy);
+          sqlite3WalkExpr(pWalker, pWin->pFilter);
+          sqlite3WindowLink(pSel, pWin);
+          pNC->ncFlags |= NC_HasWin;
+        }else
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+        {
+          NameContext *pNC2;          /* For looping up thru outer contexts */
+          pExpr->op = TK_AGG_FUNCTION;
+          pExpr->op2 = 0;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+          if( ExprHasProperty(pExpr, EP_WinFunc) ){
+            sqlite3WalkExpr(pWalker, pExpr->y.pWin->pFilter);
+          }
+#endif
+          pNC2 = pNC;
+          while( pNC2
+              && sqlite3ReferencesSrcList(pParse, pExpr, pNC2->pSrcList)==0
+          ){
+            pExpr->op2 += (1 + pNC2->nNestedSelect);
+            pNC2 = pNC2->pNext;
+          }
+          assert( pDef!=0 || IN_RENAME_OBJECT );
+          if( pNC2 && pDef ){
+            pExpr->op2 += pNC2->nNestedSelect;
+            assert( SQLITE_FUNC_MINMAX==NC_MinMaxAgg );
+            assert( SQLITE_FUNC_ANYORDER==NC_OrderAgg );
+            testcase( (pDef->funcFlags & SQLITE_FUNC_MINMAX)!=0 );
+            testcase( (pDef->funcFlags & SQLITE_FUNC_ANYORDER)!=0 );
+            pNC2->ncFlags |= NC_HasAgg
+              | ((pDef->funcFlags^SQLITE_FUNC_ANYORDER)
+                  & (SQLITE_FUNC_MINMAX|SQLITE_FUNC_ANYORDER));
+          }
+        }
+        pNC->ncFlags |= savedAllowFlags;
+      }
+      /* FIX ME:  Compute pExpr->affinity based on the expected return
+      ** type of the function
+      */
+      return WRC_Prune;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_SELECT:
+    case TK_EXISTS:  testcase( pExpr->op==TK_EXISTS );
+#endif
+    case TK_IN: {
+      testcase( pExpr->op==TK_IN );
+      if( ExprUseXSelect(pExpr) ){
+        int nRef = pNC->nRef;
+        testcase( pNC->ncFlags & NC_IsCheck );
+        testcase( pNC->ncFlags & NC_PartIdx );
+        testcase( pNC->ncFlags & NC_IdxExpr );
+        testcase( pNC->ncFlags & NC_GenCol );
+        if( pNC->ncFlags & NC_SelfRef ){
+          notValidImpl(pParse, pNC, "subqueries", pExpr, pExpr);
+        }else{
+          sqlite3WalkSelect(pWalker, pExpr->x.pSelect);
+        }
+        assert( pNC->nRef>=nRef );
+        if( nRef!=pNC->nRef ){
+          ExprSetProperty(pExpr, EP_VarSelect);
+        }
+        pNC->ncFlags |= NC_Subquery;
+      }
+      break;
+    }
+    case TK_VARIABLE: {
+      testcase( pNC->ncFlags & NC_IsCheck );
+      testcase( pNC->ncFlags & NC_PartIdx );
+      testcase( pNC->ncFlags & NC_IdxExpr );
+      testcase( pNC->ncFlags & NC_GenCol );
+      sqlite3ResolveNotValid(pParse, pNC, "parameters",
+               NC_IsCheck|NC_PartIdx|NC_IdxExpr|NC_GenCol, pExpr, pExpr);
+      break;
+    }
+    case TK_IS:
+    case TK_ISNOT: {
+      Expr *pRight = sqlite3ExprSkipCollateAndLikely(pExpr->pRight);
+      assert( !ExprHasProperty(pExpr, EP_Reduced) );
+      /* Handle special cases of "x IS TRUE", "x IS FALSE", "x IS NOT TRUE",
+      ** and "x IS NOT FALSE". */
+      if( ALWAYS(pRight) && (pRight->op==TK_ID || pRight->op==TK_TRUEFALSE) ){
+        int rc = resolveExprStep(pWalker, pRight);
+        if( rc==WRC_Abort ) return WRC_Abort;
+        if( pRight->op==TK_TRUEFALSE ){
+          pExpr->op2 = pExpr->op;
+          pExpr->op = TK_TRUTH;
+          return WRC_Continue;
+        }
+      }
+      /* no break */ deliberate_fall_through
+    }
+    case TK_BETWEEN:
+    case TK_EQ:
+    case TK_NE:
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE: {
+      int nLeft, nRight;
+      if( pParse->db->mallocFailed ) break;
+      assert( pExpr->pLeft!=0 );
+      nLeft = sqlite3ExprVectorSize(pExpr->pLeft);
+      if( pExpr->op==TK_BETWEEN ){
+        assert( ExprUseXList(pExpr) );
+        nRight = sqlite3ExprVectorSize(pExpr->x.pList->a[0].pExpr);
+        if( nRight==nLeft ){
+          nRight = sqlite3ExprVectorSize(pExpr->x.pList->a[1].pExpr);
+        }
+      }else{
+        assert( pExpr->pRight!=0 );
+        nRight = sqlite3ExprVectorSize(pExpr->pRight);
+      }
+      if( nLeft!=nRight ){
+        testcase( pExpr->op==TK_EQ );
+        testcase( pExpr->op==TK_NE );
+        testcase( pExpr->op==TK_LT );
+        testcase( pExpr->op==TK_LE );
+        testcase( pExpr->op==TK_GT );
+        testcase( pExpr->op==TK_GE );
+        testcase( pExpr->op==TK_IS );
+        testcase( pExpr->op==TK_ISNOT );
+        testcase( pExpr->op==TK_BETWEEN );
+        sqlite3ErrorMsg(pParse, "row value misused");
+        sqlite3RecordErrorOffsetOfExpr(pParse->db, pExpr);
+      }
+      break;
+    }
+  }
+  assert( pParse->db->mallocFailed==0 || pParse->nErr!=0 );
+  return pParse->nErr ? WRC_Abort : WRC_Continue;
+}
+
+/*
+** pEList is a list of expressions which are really the result set of the
+** a SELECT statement.  pE is a term in an ORDER BY or GROUP BY clause.
+** This routine checks to see if pE is a simple identifier which corresponds
+** to the AS-name of one of the terms of the expression list.  If it is,
+** this routine return an integer between 1 and N where N is the number of
+** elements in pEList, corresponding to the matching entry.  If there is
+** no match, or if pE is not a simple identifier, then this routine
+** return 0.
+**
+** pEList has been resolved.  pE has not.
+*/
+static int resolveAsName(
+  Parse *pParse,     /* Parsing context for error messages */
+  ExprList *pEList,  /* List of expressions to scan */
+  Expr *pE           /* Expression we are trying to match */
+){
+  int i;             /* Loop counter */
+
+  UNUSED_PARAMETER(pParse);
+
+  if( pE->op==TK_ID ){
+    const char *zCol;
+    assert( !ExprHasProperty(pE, EP_IntValue) );
+    zCol = pE->u.zToken;
+    for(i=0; i<pEList->nExpr; i++){
+      if( pEList->a[i].fg.eEName==ENAME_NAME
+       && sqlite3_stricmp(pEList->a[i].zEName, zCol)==0
+      ){
+        return i+1;
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** pE is a pointer to an expression which is a single term in the
+** ORDER BY of a compound SELECT.  The expression has not been
+** name resolved.
+**
+** At the point this routine is called, we already know that the
+** ORDER BY term is not an integer index into the result set.  That
+** case is handled by the calling routine.
+**
+** Attempt to match pE against result set columns in the left-most
+** SELECT statement.  Return the index i of the matching column,
+** as an indication to the caller that it should sort by the i-th column.
+** The left-most column is 1.  In other words, the value returned is the
+** same integer value that would be used in the SQL statement to indicate
+** the column.
+**
+** If there is no match, return 0.  Return -1 if an error occurs.
+*/
+static int resolveOrderByTermToExprList(
+  Parse *pParse,     /* Parsing context for error messages */
+  Select *pSelect,   /* The SELECT statement with the ORDER BY clause */
+  Expr *pE           /* The specific ORDER BY term */
+){
+  int i;             /* Loop counter */
+  ExprList *pEList;  /* The columns of the result set */
+  NameContext nc;    /* Name context for resolving pE */
+  sqlite3 *db;       /* Database connection */
+  int rc;            /* Return code from subprocedures */
+  u8 savedSuppErr;   /* Saved value of db->suppressErr */
+
+  assert( sqlite3ExprIsInteger(pE, &i)==0 );
+  pEList = pSelect->pEList;
+
+  /* Resolve all names in the ORDER BY term expression
+  */
+  memset(&nc, 0, sizeof(nc));
+  nc.pParse = pParse;
+  nc.pSrcList = pSelect->pSrc;
+  nc.uNC.pEList = pEList;
+  nc.ncFlags = NC_AllowAgg|NC_UEList|NC_NoSelect;
+  nc.nNcErr = 0;
+  db = pParse->db;
+  savedSuppErr = db->suppressErr;
+  db->suppressErr = 1;
+  rc = sqlite3ResolveExprNames(&nc, pE);
+  db->suppressErr = savedSuppErr;
+  if( rc ) return 0;
+
+  /* Try to match the ORDER BY expression against an expression
+  ** in the result set.  Return an 1-based index of the matching
+  ** result-set entry.
+  */
+  for(i=0; i<pEList->nExpr; i++){
+    if( sqlite3ExprCompare(0, pEList->a[i].pExpr, pE, -1)<2 ){
+      return i+1;
+    }
+  }
+
+  /* If no match, return 0. */
+  return 0;
+}
+
+/*
+** Generate an ORDER BY or GROUP BY term out-of-range error.
+*/
+static void resolveOutOfRangeError(
+  Parse *pParse,         /* The error context into which to write the error */
+  const char *zType,     /* "ORDER" or "GROUP" */
+  int i,                 /* The index (1-based) of the term out of range */
+  int mx,                /* Largest permissible value of i */
+  Expr *pError           /* Associate the error with the expression */
+){
+  sqlite3ErrorMsg(pParse,
+    "%r %s BY term out of range - should be "
+    "between 1 and %d", i, zType, mx);
+  sqlite3RecordErrorOffsetOfExpr(pParse->db, pError);
+}
+
+/*
+** Analyze the ORDER BY clause in a compound SELECT statement.   Modify
+** each term of the ORDER BY clause is a constant integer between 1
+** and N where N is the number of columns in the compound SELECT.
+**
+** ORDER BY terms that are already an integer between 1 and N are
+** unmodified.  ORDER BY terms that are integers outside the range of
+** 1 through N generate an error.  ORDER BY terms that are expressions
+** are matched against result set expressions of compound SELECT
+** beginning with the left-most SELECT and working toward the right.
+** At the first match, the ORDER BY expression is transformed into
+** the integer column number.
+**
+** Return the number of errors seen.
+*/
+static int resolveCompoundOrderBy(
+  Parse *pParse,        /* Parsing context.  Leave error messages here */
+  Select *pSelect       /* The SELECT statement containing the ORDER BY */
+){
+  int i;
+  ExprList *pOrderBy;
+  ExprList *pEList;
+  sqlite3 *db;
+  int moreToDo = 1;
+
+  pOrderBy = pSelect->pOrderBy;
+  if( pOrderBy==0 ) return 0;
+  db = pParse->db;
+  if( pOrderBy->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many terms in ORDER BY clause");
+    return 1;
+  }
+  for(i=0; i<pOrderBy->nExpr; i++){
+    pOrderBy->a[i].fg.done = 0;
+  }
+  pSelect->pNext = 0;
+  while( pSelect->pPrior ){
+    pSelect->pPrior->pNext = pSelect;
+    pSelect = pSelect->pPrior;
+  }
+  while( pSelect && moreToDo ){
+    struct ExprList_item *pItem;
+    moreToDo = 0;
+    pEList = pSelect->pEList;
+    assert( pEList!=0 );
+    for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
+      int iCol = -1;
+      Expr *pE, *pDup;
+      if( pItem->fg.done ) continue;
+      pE = sqlite3ExprSkipCollateAndLikely(pItem->pExpr);
+      if( NEVER(pE==0) ) continue;
+      if( sqlite3ExprIsInteger(pE, &iCol) ){
+        if( iCol<=0 || iCol>pEList->nExpr ){
+          resolveOutOfRangeError(pParse, "ORDER", i+1, pEList->nExpr, pE);
+          return 1;
+        }
+      }else{
+        iCol = resolveAsName(pParse, pEList, pE);
+        if( iCol==0 ){
+          /* Now test if expression pE matches one of the values returned
+          ** by pSelect. In the usual case this is done by duplicating the
+          ** expression, resolving any symbols in it, and then comparing
+          ** it against each expression returned by the SELECT statement.
+          ** Once the comparisons are finished, the duplicate expression
+          ** is deleted.
+          **
+          ** If this is running as part of an ALTER TABLE operation and
+          ** the symbols resolve successfully, also resolve the symbols in the
+          ** actual expression. This allows the code in alter.c to modify
+          ** column references within the ORDER BY expression as required.  */
+          pDup = sqlite3ExprDup(db, pE, 0);
+          if( !db->mallocFailed ){
+            assert(pDup);
+            iCol = resolveOrderByTermToExprList(pParse, pSelect, pDup);
+            if( IN_RENAME_OBJECT && iCol>0 ){
+              resolveOrderByTermToExprList(pParse, pSelect, pE);
+            }
+          }
+          sqlite3ExprDelete(db, pDup);
+        }
+      }
+      if( iCol>0 ){
+        /* Convert the ORDER BY term into an integer column number iCol,
+        ** taking care to preserve the COLLATE clause if it exists. */
+        if( !IN_RENAME_OBJECT ){
+          Expr *pNew = sqlite3Expr(db, TK_INTEGER, 0);
+          if( pNew==0 ) return 1;
+          pNew->flags |= EP_IntValue;
+          pNew->u.iValue = iCol;
+          if( pItem->pExpr==pE ){
+            pItem->pExpr = pNew;
+          }else{
+            Expr *pParent = pItem->pExpr;
+            assert( pParent->op==TK_COLLATE );
+            while( pParent->pLeft->op==TK_COLLATE ) pParent = pParent->pLeft;
+            assert( pParent->pLeft==pE );
+            pParent->pLeft = pNew;
+          }
+          sqlite3ExprDelete(db, pE);
+          pItem->u.x.iOrderByCol = (u16)iCol;
+        }
+        pItem->fg.done = 1;
+      }else{
+        moreToDo = 1;
+      }
+    }
+    pSelect = pSelect->pNext;
+  }
+  for(i=0; i<pOrderBy->nExpr; i++){
+    if( pOrderBy->a[i].fg.done==0 ){
+      sqlite3ErrorMsg(pParse, "%r ORDER BY term does not match any "
+            "column in the result set", i+1);
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Check every term in the ORDER BY or GROUP BY clause pOrderBy of
+** the SELECT statement pSelect.  If any term is reference to a
+** result set expression (as determined by the ExprList.a.u.x.iOrderByCol
+** field) then convert that term into a copy of the corresponding result set
+** column.
+**
+** If any errors are detected, add an error message to pParse and
+** return non-zero.  Return zero if no errors are seen.
+*/
+int sqlite3ResolveOrderGroupBy(
+  Parse *pParse,        /* Parsing context.  Leave error messages here */
+  Select *pSelect,      /* The SELECT statement containing the clause */
+  ExprList *pOrderBy,   /* The ORDER BY or GROUP BY clause to be processed */
+  const char *zType     /* "ORDER" or "GROUP" */
+){
+  int i;
+  sqlite3 *db = pParse->db;
+  ExprList *pEList;
+  struct ExprList_item *pItem;
+
+  if( pOrderBy==0 || pParse->db->mallocFailed || IN_RENAME_OBJECT ) return 0;
+  if( pOrderBy->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many terms in %s BY clause", zType);
+    return 1;
+  }
+  pEList = pSelect->pEList;
+  assert( pEList!=0 );  /* sqlite3SelectNew() guarantees this */
+  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
+    if( pItem->u.x.iOrderByCol ){
+      if( pItem->u.x.iOrderByCol>pEList->nExpr ){
+        resolveOutOfRangeError(pParse, zType, i+1, pEList->nExpr, 0);
+        return 1;
+      }
+      resolveAlias(pParse, pEList, pItem->u.x.iOrderByCol-1, pItem->pExpr,0);
+    }
+  }
+  return 0;
+}
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+/*
+** Walker callback for windowRemoveExprFromSelect().
+*/
+static int resolveRemoveWindowsCb(Walker *pWalker, Expr *pExpr){
+  UNUSED_PARAMETER(pWalker);
+  if( ExprHasProperty(pExpr, EP_WinFunc) ){
+    Window *pWin = pExpr->y.pWin;
+    sqlite3WindowUnlinkFromSelect(pWin);
+  }
+  return WRC_Continue;
+}
+
+/*
+** Remove any Window objects owned by the expression pExpr from the
+** Select.pWin list of Select object pSelect.
+*/
+static void windowRemoveExprFromSelect(Select *pSelect, Expr *pExpr){
+  if( pSelect->pWin ){
+    Walker sWalker;
+    memset(&sWalker, 0, sizeof(Walker));
+    sWalker.xExprCallback = resolveRemoveWindowsCb;
+    sWalker.u.pSelect = pSelect;
+    sqlite3WalkExpr(&sWalker, pExpr);
+  }
+}
+#else
+# define windowRemoveExprFromSelect(a, b)
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+/*
+** pOrderBy is an ORDER BY or GROUP BY clause in SELECT statement pSelect.
+** The Name context of the SELECT statement is pNC.  zType is either
+** "ORDER" or "GROUP" depending on which type of clause pOrderBy is.
+**
+** This routine resolves each term of the clause into an expression.
+** If the order-by term is an integer I between 1 and N (where N is the
+** number of columns in the result set of the SELECT) then the expression
+** in the resolution is a copy of the I-th result-set expression.  If
+** the order-by term is an identifier that corresponds to the AS-name of
+** a result-set expression, then the term resolves to a copy of the
+** result-set expression.  Otherwise, the expression is resolved in
+** the usual way - using sqlite3ResolveExprNames().
+**
+** This routine returns the number of errors.  If errors occur, then
+** an appropriate error message might be left in pParse.  (OOM errors
+** excepted.)
+*/
+static int resolveOrderGroupBy(
+  NameContext *pNC,     /* The name context of the SELECT statement */
+  Select *pSelect,      /* The SELECT statement holding pOrderBy */
+  ExprList *pOrderBy,   /* An ORDER BY or GROUP BY clause to resolve */
+  const char *zType     /* Either "ORDER" or "GROUP", as appropriate */
+){
+  int i, j;                      /* Loop counters */
+  int iCol;                      /* Column number */
+  struct ExprList_item *pItem;   /* A term of the ORDER BY clause */
+  Parse *pParse;                 /* Parsing context */
+  int nResult;                   /* Number of terms in the result set */
+
+  assert( pOrderBy!=0 );
+  nResult = pSelect->pEList->nExpr;
+  pParse = pNC->pParse;
+  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
+    Expr *pE = pItem->pExpr;
+    Expr *pE2 = sqlite3ExprSkipCollateAndLikely(pE);
+    if( NEVER(pE2==0) ) continue;
+    if( zType[0]!='G' ){
+      iCol = resolveAsName(pParse, pSelect->pEList, pE2);
+      if( iCol>0 ){
+        /* If an AS-name match is found, mark this ORDER BY column as being
+        ** a copy of the iCol-th result-set column.  The subsequent call to
+        ** sqlite3ResolveOrderGroupBy() will convert the expression to a
+        ** copy of the iCol-th result-set expression. */
+        pItem->u.x.iOrderByCol = (u16)iCol;
+        continue;
+      }
+    }
+    if( sqlite3ExprIsInteger(pE2, &iCol) ){
+      /* The ORDER BY term is an integer constant.  Again, set the column
+      ** number so that sqlite3ResolveOrderGroupBy() will convert the
+      ** order-by term to a copy of the result-set expression */
+      if( iCol<1 || iCol>0xffff ){
+        resolveOutOfRangeError(pParse, zType, i+1, nResult, pE2);
+        return 1;
+      }
+      pItem->u.x.iOrderByCol = (u16)iCol;
+      continue;
+    }
+
+    /* Otherwise, treat the ORDER BY term as an ordinary expression */
+    pItem->u.x.iOrderByCol = 0;
+    if( sqlite3ResolveExprNames(pNC, pE) ){
+      return 1;
+    }
+    for(j=0; j<pSelect->pEList->nExpr; j++){
+      if( sqlite3ExprCompare(0, pE, pSelect->pEList->a[j].pExpr, -1)==0 ){
+        /* Since this expression is being changed into a reference
+        ** to an identical expression in the result set, remove all Window
+        ** objects belonging to the expression from the Select.pWin list. */
+        windowRemoveExprFromSelect(pSelect, pE);
+        pItem->u.x.iOrderByCol = j+1;
+      }
+    }
+  }
+  return sqlite3ResolveOrderGroupBy(pParse, pSelect, pOrderBy, zType);
+}
+
+/*
+** Resolve names in the SELECT statement p and all of its descendants.
+*/
+static int resolveSelectStep(Walker *pWalker, Select *p){
+  NameContext *pOuterNC;  /* Context that contains this SELECT */
+  NameContext sNC;        /* Name context of this SELECT */
+  int isCompound;         /* True if p is a compound select */
+  int nCompound;          /* Number of compound terms processed so far */
+  Parse *pParse;          /* Parsing context */
+  int i;                  /* Loop counter */
+  ExprList *pGroupBy;     /* The GROUP BY clause */
+  Select *pLeftmost;      /* Left-most of SELECT of a compound */
+  sqlite3 *db;            /* Database connection */
+ 
+
+  assert( p!=0 );
+  if( p->selFlags & SF_Resolved ){
+    return WRC_Prune;
+  }
+  pOuterNC = pWalker->u.pNC;
+  pParse = pWalker->pParse;
+  db = pParse->db;
+
+  /* Normally sqlite3SelectExpand() will be called first and will have
+  ** already expanded this SELECT.  However, if this is a subquery within
+  ** an expression, sqlite3ResolveExprNames() will be called without a
+  ** prior call to sqlite3SelectExpand().  When that happens, let
+  ** sqlite3SelectPrep() do all of the processing for this SELECT.
+  ** sqlite3SelectPrep() will invoke both sqlite3SelectExpand() and
+  ** this routine in the correct order.
+  */
+  if( (p->selFlags & SF_Expanded)==0 ){
+    sqlite3SelectPrep(pParse, p, pOuterNC);
+    return pParse->nErr ? WRC_Abort : WRC_Prune;
+  }
+
+  isCompound = p->pPrior!=0;
+  nCompound = 0;
+  pLeftmost = p;
+  while( p ){
+    assert( (p->selFlags & SF_Expanded)!=0 );
+    assert( (p->selFlags & SF_Resolved)==0 );
+    p->selFlags |= SF_Resolved;
+
+    /* Resolve the expressions in the LIMIT and OFFSET clauses. These
+    ** are not allowed to refer to any names, so pass an empty NameContext.
+    */
+    memset(&sNC, 0, sizeof(sNC));
+    sNC.pParse = pParse;
+    sNC.pWinSelect = p;
+    if( sqlite3ResolveExprNames(&sNC, p->pLimit) ){
+      return WRC_Abort;
+    }
+
+    /* If the SF_Converted flags is set, then this Select object was
+    ** was created by the convertCompoundSelectToSubquery() function.
+    ** In this case the ORDER BY clause (p->pOrderBy) should be resolved
+    ** as if it were part of the sub-query, not the parent. This block
+    ** moves the pOrderBy down to the sub-query. It will be moved back
+    ** after the names have been resolved.  */
+    if( p->selFlags & SF_Converted ){
+      Select *pSub = p->pSrc->a[0].pSelect;
+      assert( p->pSrc->nSrc==1 && p->pOrderBy );
+      assert( pSub->pPrior && pSub->pOrderBy==0 );
+      pSub->pOrderBy = p->pOrderBy;
+      p->pOrderBy = 0;
+    }
+ 
+    /* Recursively resolve names in all subqueries in the FROM clause
+    */
+    if( pOuterNC ) pOuterNC->nNestedSelect++;
+    for(i=0; i<p->pSrc->nSrc; i++){
+      SrcItem *pItem = &p->pSrc->a[i];
+      if( pItem->pSelect && (pItem->pSelect->selFlags & SF_Resolved)==0 ){
+        int nRef = pOuterNC ? pOuterNC->nRef : 0;
+        const char *zSavedContext = pParse->zAuthContext;
+
+        if( pItem->zName ) pParse->zAuthContext = pItem->zName;
+        sqlite3ResolveSelectNames(pParse, pItem->pSelect, pOuterNC);
+        pParse->zAuthContext = zSavedContext;
+        if( pParse->nErr ) return WRC_Abort;
+        assert( db->mallocFailed==0 );
+
+        /* If the number of references to the outer context changed when
+        ** expressions in the sub-select were resolved, the sub-select
+        ** is correlated. It is not required to check the refcount on any
+        ** but the innermost outer context object, as lookupName() increments
+        ** the refcount on all contexts between the current one and the
+        ** context containing the column when it resolves a name. */
+        if( pOuterNC ){
+          assert( pItem->fg.isCorrelated==0 && pOuterNC->nRef>=nRef );
+          pItem->fg.isCorrelated = (pOuterNC->nRef>nRef);
+        }
+      }
+    }
+    if( pOuterNC && ALWAYS(pOuterNC->nNestedSelect>0) ){
+      pOuterNC->nNestedSelect--;
+    }
+ 
+    /* Set up the local name-context to pass to sqlite3ResolveExprNames() to
+    ** resolve the result-set expression list.
+    */
+    sNC.ncFlags = NC_AllowAgg|NC_AllowWin;
+    sNC.pSrcList = p->pSrc;
+    sNC.pNext = pOuterNC;
+ 
+    /* Resolve names in the result set. */
+    if( sqlite3ResolveExprListNames(&sNC, p->pEList) ) return WRC_Abort;
+    sNC.ncFlags &= ~NC_AllowWin;
+ 
+    /* If there are no aggregate functions in the result-set, and no GROUP BY
+    ** expression, do not allow aggregates in any of the other expressions.
+    */
+    assert( (p->selFlags & SF_Aggregate)==0 );
+    pGroupBy = p->pGroupBy;
+    if( pGroupBy || (sNC.ncFlags & NC_HasAgg)!=0 ){
+      assert( NC_MinMaxAgg==SF_MinMaxAgg );
+      assert( NC_OrderAgg==SF_OrderByReqd );
+      p->selFlags |= SF_Aggregate | (sNC.ncFlags&(NC_MinMaxAgg|NC_OrderAgg));
+    }else{
+      sNC.ncFlags &= ~NC_AllowAgg;
+    }
+ 
+    /* Add the output column list to the name-context before parsing the
+    ** other expressions in the SELECT statement. This is so that
+    ** expressions in the WHERE clause (etc.) can refer to expressions by
+    ** aliases in the result set.
+    **
+    ** Minor point: If this is the case, then the expression will be
+    ** re-evaluated for each reference to it.
+    */
+    assert( (sNC.ncFlags & (NC_UAggInfo|NC_UUpsert|NC_UBaseReg))==0 );
+    sNC.uNC.pEList = p->pEList;
+    sNC.ncFlags |= NC_UEList;
+    if( p->pHaving ){
+      if( (p->selFlags & SF_Aggregate)==0 ){
+        sqlite3ErrorMsg(pParse, "HAVING clause on a non-aggregate query");
+        return WRC_Abort;
+      }
+      if( sqlite3ResolveExprNames(&sNC, p->pHaving) ) return WRC_Abort;
+    }
+    if( sqlite3ResolveExprNames(&sNC, p->pWhere) ) return WRC_Abort;
+
+    /* Resolve names in table-valued-function arguments */
+    for(i=0; i<p->pSrc->nSrc; i++){
+      SrcItem *pItem = &p->pSrc->a[i];
+      if( pItem->fg.isTabFunc
+       && sqlite3ResolveExprListNames(&sNC, pItem->u1.pFuncArg)
+      ){
+        return WRC_Abort;
+      }
+    }
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( IN_RENAME_OBJECT ){
+      Window *pWin;
+      for(pWin=p->pWinDefn; pWin; pWin=pWin->pNextWin){
+        if( sqlite3ResolveExprListNames(&sNC, pWin->pOrderBy)
+         || sqlite3ResolveExprListNames(&sNC, pWin->pPartition)
+        ){
+          return WRC_Abort;
+        }
+      }
+    }
+#endif
+
+    /* The ORDER BY and GROUP BY clauses may not refer to terms in
+    ** outer queries
+    */
+    sNC.pNext = 0;
+    sNC.ncFlags |= NC_AllowAgg|NC_AllowWin;
+
+    /* If this is a converted compound query, move the ORDER BY clause from
+    ** the sub-query back to the parent query. At this point each term
+    ** within the ORDER BY clause has been transformed to an integer value.
+    ** These integers will be replaced by copies of the corresponding result
+    ** set expressions by the call to resolveOrderGroupBy() below.  */
+    if( p->selFlags & SF_Converted ){
+      Select *pSub = p->pSrc->a[0].pSelect;
+      p->pOrderBy = pSub->pOrderBy;
+      pSub->pOrderBy = 0;
+    }
+
+    /* Process the ORDER BY clause for singleton SELECT statements.
+    ** The ORDER BY clause for compounds SELECT statements is handled
+    ** below, after all of the result-sets for all of the elements of
+    ** the compound have been resolved.
+    **
+    ** If there is an ORDER BY clause on a term of a compound-select other
+    ** than the right-most term, then that is a syntax error.  But the error
+    ** is not detected until much later, and so we need to go ahead and
+    ** resolve those symbols on the incorrect ORDER BY for consistency.
+    */
+    if( p->pOrderBy!=0
+     && isCompound<=nCompound  /* Defer right-most ORDER BY of a compound */
+     && resolveOrderGroupBy(&sNC, p, p->pOrderBy, "ORDER")
+    ){
+      return WRC_Abort;
+    }
+    if( db->mallocFailed ){
+      return WRC_Abort;
+    }
+    sNC.ncFlags &= ~NC_AllowWin;
+ 
+    /* Resolve the GROUP BY clause.  At the same time, make sure
+    ** the GROUP BY clause does not contain aggregate functions.
+    */
+    if( pGroupBy ){
+      struct ExprList_item *pItem;
+   
+      if( resolveOrderGroupBy(&sNC, p, pGroupBy, "GROUP") || db->mallocFailed ){
+        return WRC_Abort;
+      }
+      for(i=0, pItem=pGroupBy->a; i<pGroupBy->nExpr; i++, pItem++){
+        if( ExprHasProperty(pItem->pExpr, EP_Agg) ){
+          sqlite3ErrorMsg(pParse, "aggregate functions are not allowed in "
+              "the GROUP BY clause");
+          return WRC_Abort;
+        }
+      }
+    }
+
+    /* If this is part of a compound SELECT, check that it has the right
+    ** number of expressions in the select list. */
+    if( p->pNext && p->pEList->nExpr!=p->pNext->pEList->nExpr ){
+      sqlite3SelectWrongNumTermsError(pParse, p->pNext);
+      return WRC_Abort;
+    }
+
+    /* Advance to the next term of the compound
+    */
+    p = p->pPrior;
+    nCompound++;
+  }
+
+  /* Resolve the ORDER BY on a compound SELECT after all terms of
+  ** the compound have been resolved.
+  */
+  if( isCompound && resolveCompoundOrderBy(pParse, pLeftmost) ){
+    return WRC_Abort;
+  }
+
+  return WRC_Prune;
+}
+
+/*
+** This routine walks an expression tree and resolves references to
+** table columns and result-set columns.  At the same time, do error
+** checking on function usage and set a flag if any aggregate functions
+** are seen.
+**
+** To resolve table columns references we look for nodes (or subtrees) of the
+** form X.Y.Z or Y.Z or just Z where
+**
+**      X:   The name of a database.  Ex:  "main" or "temp" or
+**           the symbolic name assigned to an ATTACH-ed database.
+**
+**      Y:   The name of a table in a FROM clause.  Or in a trigger
+**           one of the special names "old" or "new".
+**
+**      Z:   The name of a column in table Y.
+**
+** The node at the root of the subtree is modified as follows:
+**
+**    Expr.op        Changed to TK_COLUMN
+**    Expr.pTab      Points to the Table object for X.Y
+**    Expr.iColumn   The column index in X.Y.  -1 for the rowid.
+**    Expr.iTable    The VDBE cursor number for X.Y
+**
+**
+** To resolve result-set references, look for expression nodes of the
+** form Z (with no X and Y prefix) where the Z matches the right-hand
+** size of an AS clause in the result-set of a SELECT.  The Z expression
+** is replaced by a copy of the left-hand side of the result-set expression.
+** Table-name and function resolution occurs on the substituted expression
+** tree.  For example, in:
+**
+**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY x;
+**
+** The "x" term of the order by is replaced by "a+b" to render:
+**
+**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY a+b;
+**
+** Function calls are checked to make sure that the function is
+** defined and that the correct number of arguments are specified.
+** If the function is an aggregate function, then the NC_HasAgg flag is
+** set and the opcode is changed from TK_FUNCTION to TK_AGG_FUNCTION.
+** If an expression contains aggregate functions then the EP_Agg
+** property on the expression is set.
+**
+** An error message is left in pParse if anything is amiss.  The number
+** if errors is returned.
+*/
+int sqlite3ResolveExprNames(
+  NameContext *pNC,       /* Namespace to resolve expressions in. */
+  Expr *pExpr             /* The expression to be analyzed. */
+){
+  int savedHasAgg;
+  Walker w;
+
+  if( pExpr==0 ) return SQLITE_OK;
+  savedHasAgg = pNC->ncFlags & (NC_HasAgg|NC_MinMaxAgg|NC_HasWin|NC_OrderAgg);
+  pNC->ncFlags &= ~(NC_HasAgg|NC_MinMaxAgg|NC_HasWin|NC_OrderAgg);
+  w.pParse = pNC->pParse;
+  w.xExprCallback = resolveExprStep;
+  w.xSelectCallback = (pNC->ncFlags & NC_NoSelect) ? 0 : resolveSelectStep;
+  w.xSelectCallback2 = 0;
+  w.u.pNC = pNC;
+#if SQLITE_MAX_EXPR_DEPTH>0
+  w.pParse->nHeight += pExpr->nHeight;
+  if( sqlite3ExprCheckHeight(w.pParse, w.pParse->nHeight) ){
+    return SQLITE_ERROR;
+  }
+#endif
+  assert( pExpr!=0 );
+  sqlite3WalkExprNN(&w, pExpr);
+#if SQLITE_MAX_EXPR_DEPTH>0
+  w.pParse->nHeight -= pExpr->nHeight;
+#endif
+  assert( EP_Agg==NC_HasAgg );
+  assert( EP_Win==NC_HasWin );
+  testcase( pNC->ncFlags & NC_HasAgg );
+  testcase( pNC->ncFlags & NC_HasWin );
+  ExprSetProperty(pExpr, pNC->ncFlags & (NC_HasAgg|NC_HasWin) );
+  pNC->ncFlags |= savedHasAgg;
+  return pNC->nNcErr>0 || w.pParse->nErr>0;
+}
+
+/*
+** Resolve all names for all expression in an expression list.  This is
+** just like sqlite3ResolveExprNames() except that it works for an expression
+** list rather than a single expression.
+*/
+int sqlite3ResolveExprListNames(
+  NameContext *pNC,       /* Namespace to resolve expressions in. */
+  ExprList *pList         /* The expression list to be analyzed. */
+){
+  int i;
+  int savedHasAgg = 0;
+  Walker w;
+  if( pList==0 ) return WRC_Continue;
+  w.pParse = pNC->pParse;
+  w.xExprCallback = resolveExprStep;
+  w.xSelectCallback = resolveSelectStep;
+  w.xSelectCallback2 = 0;
+  w.u.pNC = pNC;
+  savedHasAgg = pNC->ncFlags & (NC_HasAgg|NC_MinMaxAgg|NC_HasWin|NC_OrderAgg);
+  pNC->ncFlags &= ~(NC_HasAgg|NC_MinMaxAgg|NC_HasWin|NC_OrderAgg);
+  for(i=0; i<pList->nExpr; i++){
+    Expr *pExpr = pList->a[i].pExpr;
+    if( pExpr==0 ) continue;
+#if SQLITE_MAX_EXPR_DEPTH>0
+    w.pParse->nHeight += pExpr->nHeight;
+    if( sqlite3ExprCheckHeight(w.pParse, w.pParse->nHeight) ){
+      return WRC_Abort;
+    }
+#endif
+    sqlite3WalkExprNN(&w, pExpr);
+#if SQLITE_MAX_EXPR_DEPTH>0
+    w.pParse->nHeight -= pExpr->nHeight;
+#endif
+    assert( EP_Agg==NC_HasAgg );
+    assert( EP_Win==NC_HasWin );
+    testcase( pNC->ncFlags & NC_HasAgg );
+    testcase( pNC->ncFlags & NC_HasWin );
+    if( pNC->ncFlags & (NC_HasAgg|NC_MinMaxAgg|NC_HasWin|NC_OrderAgg) ){
+      ExprSetProperty(pExpr, pNC->ncFlags & (NC_HasAgg|NC_HasWin) );
+      savedHasAgg |= pNC->ncFlags &
+                          (NC_HasAgg|NC_MinMaxAgg|NC_HasWin|NC_OrderAgg);
+      pNC->ncFlags &= ~(NC_HasAgg|NC_MinMaxAgg|NC_HasWin|NC_OrderAgg);
+    }
+    if( w.pParse->nErr>0 ) return WRC_Abort;
+  }
+  pNC->ncFlags |= savedHasAgg;
+  return WRC_Continue;
+}
+
+/*
+** Resolve all names in all expressions of a SELECT and in all
+** descendants of the SELECT, including compounds off of p->pPrior,
+** subqueries in expressions, and subqueries used as FROM clause
+** terms.
+**
+** See sqlite3ResolveExprNames() for a description of the kinds of
+** transformations that occur.
+**
+** All SELECT statements should have been expanded using
+** sqlite3SelectExpand() prior to invoking this routine.
+*/
+void sqlite3ResolveSelectNames(
+  Parse *pParse,         /* The parser context */
+  Select *p,             /* The SELECT statement being coded. */
+  NameContext *pOuterNC  /* Name context for parent SELECT statement */
+){
+  Walker w;
+
+  assert( p!=0 );
+  w.xExprCallback = resolveExprStep;
+  w.xSelectCallback = resolveSelectStep;
+  w.xSelectCallback2 = 0;
+  w.pParse = pParse;
+  w.u.pNC = pOuterNC;
+  sqlite3WalkSelect(&w, p);
+}
+
+/*
+** Resolve names in expressions that can only reference a single table
+** or which cannot reference any tables at all.  Examples:
+**
+**                                                    "type" flag
+**                                                    ------------
+**    (1)   CHECK constraints                         NC_IsCheck
+**    (2)   WHERE clauses on partial indices          NC_PartIdx
+**    (3)   Expressions in indexes on expressions     NC_IdxExpr
+**    (4)   Expression arguments to VACUUM INTO.      0
+**    (5)   GENERATED ALWAYS as expressions           NC_GenCol
+**
+** In all cases except (4), the Expr.iTable value for Expr.op==TK_COLUMN
+** nodes of the expression is set to -1 and the Expr.iColumn value is
+** set to the column number.  In case (4), TK_COLUMN nodes cause an error.
+**
+** Any errors cause an error message to be set in pParse.
+*/
+int sqlite3ResolveSelfReference(
+  Parse *pParse,   /* Parsing context */
+  Table *pTab,     /* The table being referenced, or NULL */
+  int type,        /* NC_IsCheck, NC_PartIdx, NC_IdxExpr, NC_GenCol, or 0 */
+  Expr *pExpr,     /* Expression to resolve.  May be NULL. */
+  ExprList *pList  /* Expression list to resolve.  May be NULL. */
+){
+  SrcList sSrc;                   /* Fake SrcList for pParse->pNewTable */
+  NameContext sNC;                /* Name context for pParse->pNewTable */
+  int rc;
+
+  assert( type==0 || pTab!=0 );
+  assert( type==NC_IsCheck || type==NC_PartIdx || type==NC_IdxExpr
+          || type==NC_GenCol || pTab==0 );
+  memset(&sNC, 0, sizeof(sNC));
+  memset(&sSrc, 0, sizeof(sSrc));
+  if( pTab ){
+    sSrc.nSrc = 1;
+    sSrc.a[0].zName = pTab->zName;
+    sSrc.a[0].pTab = pTab;
+    sSrc.a[0].iCursor = -1;
+    if( pTab->pSchema!=pParse->db->aDb[1].pSchema ){
+      /* Cause EP_FromDDL to be set on TK_FUNCTION nodes of non-TEMP
+      ** schema elements */
+      type |= NC_FromDDL;
+    }
+  }
+  sNC.pParse = pParse;
+  sNC.pSrcList = &sSrc;
+  sNC.ncFlags = type | NC_IsDDL;
+  if( (rc = sqlite3ResolveExprNames(&sNC, pExpr))!=SQLITE_OK ) return rc;
+  if( pList ) rc = sqlite3ResolveExprListNames(&sNC, pList);
+  return rc;
+}
diff --git a/src/rowset.c b/src/rowset.c
new file mode 100644
index 0000000..5956cb2
--- /dev/null
+++ b/src/rowset.c
@@ -0,0 +1,502 @@
+/*
+** 2008 December 3
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This module implements an object we call a "RowSet".
+**
+** The RowSet object is a collection of rowids.  Rowids
+** are inserted into the RowSet in an arbitrary order.  Inserts
+** can be intermixed with tests to see if a given rowid has been
+** previously inserted into the RowSet.
+**
+** After all inserts are finished, it is possible to extract the
+** elements of the RowSet in sorted order.  Once this extraction
+** process has started, no new elements may be inserted.
+**
+** Hence, the primitive operations for a RowSet are:
+**
+**    CREATE
+**    INSERT
+**    TEST
+**    SMALLEST
+**    DESTROY
+**
+** The CREATE and DESTROY primitives are the constructor and destructor,
+** obviously.  The INSERT primitive adds a new element to the RowSet.
+** TEST checks to see if an element is already in the RowSet.  SMALLEST
+** extracts the least value from the RowSet.
+**
+** The INSERT primitive might allocate additional memory.  Memory is
+** allocated in chunks so most INSERTs do no allocation.  There is an
+** upper bound on the size of allocated memory.  No memory is freed
+** until DESTROY.
+**
+** The TEST primitive includes a "batch" number.  The TEST primitive
+** will only see elements that were inserted before the last change
+** in the batch number.  In other words, if an INSERT occurs between
+** two TESTs where the TESTs have the same batch number, then the
+** value added by the INSERT will not be visible to the second TEST.
+** The initial batch number is zero, so if the very first TEST contains
+** a non-zero batch number, it will see all prior INSERTs.
+**
+** No INSERTs may occurs after a SMALLEST.  An assertion will fail if
+** that is attempted.
+**
+** The cost of an INSERT is roughly constant.  (Sometimes new memory
+** has to be allocated on an INSERT.)  The cost of a TEST with a new
+** batch number is O(NlogN) where N is the number of elements in the RowSet.
+** The cost of a TEST using the same batch number is O(logN).  The cost
+** of the first SMALLEST is O(NlogN).  Second and subsequent SMALLEST
+** primitives are constant time.  The cost of DESTROY is O(N).
+**
+** TEST and SMALLEST may not be used by the same RowSet.  This used to
+** be possible, but the feature was not used, so it was removed in order
+** to simplify the code.
+*/
+#include "sqliteInt.h"
+
+
+/*
+** Target size for allocation chunks.
+*/
+#define ROWSET_ALLOCATION_SIZE 1024
+
+/*
+** The number of rowset entries per allocation chunk.
+*/
+#define ROWSET_ENTRY_PER_CHUNK  \
+                       ((ROWSET_ALLOCATION_SIZE-8)/sizeof(struct RowSetEntry))
+
+/*
+** Each entry in a RowSet is an instance of the following object.
+**
+** This same object is reused to store a linked list of trees of RowSetEntry
+** objects.  In that alternative use, pRight points to the next entry
+** in the list, pLeft points to the tree, and v is unused.  The
+** RowSet.pForest value points to the head of this forest list.
+*/
+struct RowSetEntry {           
+  i64 v;                        /* ROWID value for this entry */
+  struct RowSetEntry *pRight;   /* Right subtree (larger entries) or list */
+  struct RowSetEntry *pLeft;    /* Left subtree (smaller entries) */
+};
+
+/*
+** RowSetEntry objects are allocated in large chunks (instances of the
+** following structure) to reduce memory allocation overhead.  The
+** chunks are kept on a linked list so that they can be deallocated
+** when the RowSet is destroyed.
+*/
+struct RowSetChunk {
+  struct RowSetChunk *pNextChunk;        /* Next chunk on list of them all */
+  struct RowSetEntry aEntry[ROWSET_ENTRY_PER_CHUNK]; /* Allocated entries */
+};
+
+/*
+** A RowSet in an instance of the following structure.
+**
+** A typedef of this structure if found in sqliteInt.h.
+*/
+struct RowSet {
+  struct RowSetChunk *pChunk;    /* List of all chunk allocations */
+  sqlite3 *db;                   /* The database connection */
+  struct RowSetEntry *pEntry;    /* List of entries using pRight */
+  struct RowSetEntry *pLast;     /* Last entry on the pEntry list */
+  struct RowSetEntry *pFresh;    /* Source of new entry objects */
+  struct RowSetEntry *pForest;   /* List of binary trees of entries */
+  u16 nFresh;                    /* Number of objects on pFresh */
+  u16 rsFlags;                   /* Various flags */
+  int iBatch;                    /* Current insert batch */
+};
+
+/*
+** Allowed values for RowSet.rsFlags
+*/
+#define ROWSET_SORTED  0x01   /* True if RowSet.pEntry is sorted */
+#define ROWSET_NEXT    0x02   /* True if sqlite3RowSetNext() has been called */
+
+/*
+** Allocate a RowSet object.  Return NULL if a memory allocation
+** error occurs.
+*/
+RowSet *sqlite3RowSetInit(sqlite3 *db){
+  RowSet *p = sqlite3DbMallocRawNN(db, sizeof(*p));
+  if( p ){
+    int N = sqlite3DbMallocSize(db, p);
+    p->pChunk = 0;
+    p->db = db;
+    p->pEntry = 0;
+    p->pLast = 0;
+    p->pForest = 0;
+    p->pFresh = (struct RowSetEntry*)(ROUND8(sizeof(*p)) + (char*)p);
+    p->nFresh = (u16)((N - ROUND8(sizeof(*p)))/sizeof(struct RowSetEntry));
+    p->rsFlags = ROWSET_SORTED;
+    p->iBatch = 0;
+  }
+  return p;
+}
+
+/*
+** Deallocate all chunks from a RowSet.  This frees all memory that
+** the RowSet has allocated over its lifetime.  This routine is
+** the destructor for the RowSet.
+*/
+void sqlite3RowSetClear(void *pArg){
+  RowSet *p = (RowSet*)pArg;
+  struct RowSetChunk *pChunk, *pNextChunk;
+  for(pChunk=p->pChunk; pChunk; pChunk = pNextChunk){
+    pNextChunk = pChunk->pNextChunk;
+    sqlite3DbFree(p->db, pChunk);
+  }
+  p->pChunk = 0;
+  p->nFresh = 0;
+  p->pEntry = 0;
+  p->pLast = 0;
+  p->pForest = 0;
+  p->rsFlags = ROWSET_SORTED;
+}
+
+/*
+** Deallocate all chunks from a RowSet.  This frees all memory that
+** the RowSet has allocated over its lifetime.  This routine is
+** the destructor for the RowSet.
+*/
+void sqlite3RowSetDelete(void *pArg){
+  sqlite3RowSetClear(pArg);
+  sqlite3DbFree(((RowSet*)pArg)->db, pArg);
+}
+
+/*
+** Allocate a new RowSetEntry object that is associated with the
+** given RowSet.  Return a pointer to the new and completely uninitialized
+** object.
+**
+** In an OOM situation, the RowSet.db->mallocFailed flag is set and this
+** routine returns NULL.
+*/
+static struct RowSetEntry *rowSetEntryAlloc(RowSet *p){
+  assert( p!=0 );
+  if( p->nFresh==0 ){  /*OPTIMIZATION-IF-FALSE*/
+    /* We could allocate a fresh RowSetEntry each time one is needed, but it
+    ** is more efficient to pull a preallocated entry from the pool */
+    struct RowSetChunk *pNew;
+    pNew = sqlite3DbMallocRawNN(p->db, sizeof(*pNew));
+    if( pNew==0 ){
+      return 0;
+    }
+    pNew->pNextChunk = p->pChunk;
+    p->pChunk = pNew;
+    p->pFresh = pNew->aEntry;
+    p->nFresh = ROWSET_ENTRY_PER_CHUNK;
+  }
+  p->nFresh--;
+  return p->pFresh++;
+}
+
+/*
+** Insert a new value into a RowSet.
+**
+** The mallocFailed flag of the database connection is set if a
+** memory allocation fails.
+*/
+void sqlite3RowSetInsert(RowSet *p, i64 rowid){
+  struct RowSetEntry *pEntry;  /* The new entry */
+  struct RowSetEntry *pLast;   /* The last prior entry */
+
+  /* This routine is never called after sqlite3RowSetNext() */
+  assert( p!=0 && (p->rsFlags & ROWSET_NEXT)==0 );
+
+  pEntry = rowSetEntryAlloc(p);
+  if( pEntry==0 ) return;
+  pEntry->v = rowid;
+  pEntry->pRight = 0;
+  pLast = p->pLast;
+  if( pLast ){
+    if( rowid<=pLast->v ){  /*OPTIMIZATION-IF-FALSE*/
+      /* Avoid unnecessary sorts by preserving the ROWSET_SORTED flags
+      ** where possible */
+      p->rsFlags &= ~ROWSET_SORTED;
+    }
+    pLast->pRight = pEntry;
+  }else{
+    p->pEntry = pEntry;
+  }
+  p->pLast = pEntry;
+}
+
+/*
+** Merge two lists of RowSetEntry objects.  Remove duplicates.
+**
+** The input lists are connected via pRight pointers and are
+** assumed to each already be in sorted order.
+*/
+static struct RowSetEntry *rowSetEntryMerge(
+  struct RowSetEntry *pA,    /* First sorted list to be merged */
+  struct RowSetEntry *pB     /* Second sorted list to be merged */
+){
+  struct RowSetEntry head;
+  struct RowSetEntry *pTail;
+
+  pTail = &head;
+  assert( pA!=0 && pB!=0 );
+  for(;;){
+    assert( pA->pRight==0 || pA->v<=pA->pRight->v );
+    assert( pB->pRight==0 || pB->v<=pB->pRight->v );
+    if( pA->v<=pB->v ){
+      if( pA->v<pB->v ) pTail = pTail->pRight = pA;
+      pA = pA->pRight;
+      if( pA==0 ){
+        pTail->pRight = pB;
+        break;
+      }
+    }else{
+      pTail = pTail->pRight = pB;
+      pB = pB->pRight;
+      if( pB==0 ){
+        pTail->pRight = pA;
+        break;
+      }
+    }
+  }
+  return head.pRight;
+}
+
+/*
+** Sort all elements on the list of RowSetEntry objects into order of
+** increasing v.
+*/
+static struct RowSetEntry *rowSetEntrySort(struct RowSetEntry *pIn){
+  unsigned int i;
+  struct RowSetEntry *pNext, *aBucket[40];
+
+  memset(aBucket, 0, sizeof(aBucket));
+  while( pIn ){
+    pNext = pIn->pRight;
+    pIn->pRight = 0;
+    for(i=0; aBucket[i]; i++){
+      pIn = rowSetEntryMerge(aBucket[i], pIn);
+      aBucket[i] = 0;
+    }
+    aBucket[i] = pIn;
+    pIn = pNext;
+  }
+  pIn = aBucket[0];
+  for(i=1; i<sizeof(aBucket)/sizeof(aBucket[0]); i++){
+    if( aBucket[i]==0 ) continue;
+    pIn = pIn ? rowSetEntryMerge(pIn, aBucket[i]) : aBucket[i];
+  }
+  return pIn;
+}
+
+
+/*
+** The input, pIn, is a binary tree (or subtree) of RowSetEntry objects.
+** Convert this tree into a linked list connected by the pRight pointers
+** and return pointers to the first and last elements of the new list.
+*/
+static void rowSetTreeToList(
+  struct RowSetEntry *pIn,         /* Root of the input tree */
+  struct RowSetEntry **ppFirst,    /* Write head of the output list here */
+  struct RowSetEntry **ppLast      /* Write tail of the output list here */
+){
+  assert( pIn!=0 );
+  if( pIn->pLeft ){
+    struct RowSetEntry *p;
+    rowSetTreeToList(pIn->pLeft, ppFirst, &p);
+    p->pRight = pIn;
+  }else{
+    *ppFirst = pIn;
+  }
+  if( pIn->pRight ){
+    rowSetTreeToList(pIn->pRight, &pIn->pRight, ppLast);
+  }else{
+    *ppLast = pIn;
+  }
+  assert( (*ppLast)->pRight==0 );
+}
+
+
+/*
+** Convert a sorted list of elements (connected by pRight) into a binary
+** tree with depth of iDepth.  A depth of 1 means the tree contains a single
+** node taken from the head of *ppList.  A depth of 2 means a tree with
+** three nodes.  And so forth.
+**
+** Use as many entries from the input list as required and update the
+** *ppList to point to the unused elements of the list.  If the input
+** list contains too few elements, then construct an incomplete tree
+** and leave *ppList set to NULL.
+**
+** Return a pointer to the root of the constructed binary tree.
+*/
+static struct RowSetEntry *rowSetNDeepTree(
+  struct RowSetEntry **ppList,
+  int iDepth
+){
+  struct RowSetEntry *p;         /* Root of the new tree */
+  struct RowSetEntry *pLeft;     /* Left subtree */
+  if( *ppList==0 ){ /*OPTIMIZATION-IF-TRUE*/
+    /* Prevent unnecessary deep recursion when we run out of entries */
+    return 0;
+  }
+  if( iDepth>1 ){   /*OPTIMIZATION-IF-TRUE*/
+    /* This branch causes a *balanced* tree to be generated.  A valid tree
+    ** is still generated without this branch, but the tree is wildly
+    ** unbalanced and inefficient. */
+    pLeft = rowSetNDeepTree(ppList, iDepth-1);
+    p = *ppList;
+    if( p==0 ){     /*OPTIMIZATION-IF-FALSE*/
+      /* It is safe to always return here, but the resulting tree
+      ** would be unbalanced */
+      return pLeft;
+    }
+    p->pLeft = pLeft;
+    *ppList = p->pRight;
+    p->pRight = rowSetNDeepTree(ppList, iDepth-1);
+  }else{
+    p = *ppList;
+    *ppList = p->pRight;
+    p->pLeft = p->pRight = 0;
+  }
+  return p;
+}
+
+/*
+** Convert a sorted list of elements into a binary tree. Make the tree
+** as deep as it needs to be in order to contain the entire list.
+*/
+static struct RowSetEntry *rowSetListToTree(struct RowSetEntry *pList){
+  int iDepth;           /* Depth of the tree so far */
+  struct RowSetEntry *p;       /* Current tree root */
+  struct RowSetEntry *pLeft;   /* Left subtree */
+
+  assert( pList!=0 );
+  p = pList;
+  pList = p->pRight;
+  p->pLeft = p->pRight = 0;
+  for(iDepth=1; pList; iDepth++){
+    pLeft = p;
+    p = pList;
+    pList = p->pRight;
+    p->pLeft = pLeft;
+    p->pRight = rowSetNDeepTree(&pList, iDepth);
+  }
+  return p;
+}
+
+/*
+** Extract the smallest element from the RowSet.
+** Write the element into *pRowid.  Return 1 on success.  Return
+** 0 if the RowSet is already empty.
+**
+** After this routine has been called, the sqlite3RowSetInsert()
+** routine may not be called again.
+**
+** This routine may not be called after sqlite3RowSetTest() has
+** been used.  Older versions of RowSet allowed that, but as the
+** capability was not used by the code generator, it was removed
+** for code economy.
+*/
+int sqlite3RowSetNext(RowSet *p, i64 *pRowid){
+  assert( p!=0 );
+  assert( p->pForest==0 );  /* Cannot be used with sqlite3RowSetText() */
+
+  /* Merge the forest into a single sorted list on first call */
+  if( (p->rsFlags & ROWSET_NEXT)==0 ){  /*OPTIMIZATION-IF-FALSE*/
+    if( (p->rsFlags & ROWSET_SORTED)==0 ){  /*OPTIMIZATION-IF-FALSE*/
+      p->pEntry = rowSetEntrySort(p->pEntry);
+    }
+    p->rsFlags |= ROWSET_SORTED|ROWSET_NEXT;
+  }
+
+  /* Return the next entry on the list */
+  if( p->pEntry ){
+    *pRowid = p->pEntry->v;
+    p->pEntry = p->pEntry->pRight;
+    if( p->pEntry==0 ){ /*OPTIMIZATION-IF-TRUE*/
+      /* Free memory immediately, rather than waiting on sqlite3_finalize() */
+      sqlite3RowSetClear(p);
+    }
+    return 1;
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Check to see if element iRowid was inserted into the rowset as
+** part of any insert batch prior to iBatch.  Return 1 or 0.
+**
+** If this is the first test of a new batch and if there exist entries
+** on pRowSet->pEntry, then sort those entries into the forest at
+** pRowSet->pForest so that they can be tested.
+*/
+int sqlite3RowSetTest(RowSet *pRowSet, int iBatch, sqlite3_int64 iRowid){
+  struct RowSetEntry *p, *pTree;
+
+  /* This routine is never called after sqlite3RowSetNext() */
+  assert( pRowSet!=0 && (pRowSet->rsFlags & ROWSET_NEXT)==0 );
+
+  /* Sort entries into the forest on the first test of a new batch.
+  ** To save unnecessary work, only do this when the batch number changes.
+  */
+  if( iBatch!=pRowSet->iBatch ){  /*OPTIMIZATION-IF-FALSE*/
+    p = pRowSet->pEntry;
+    if( p ){
+      struct RowSetEntry **ppPrevTree = &pRowSet->pForest;
+      if( (pRowSet->rsFlags & ROWSET_SORTED)==0 ){ /*OPTIMIZATION-IF-FALSE*/
+        /* Only sort the current set of entries if they need it */
+        p = rowSetEntrySort(p);
+      }
+      for(pTree = pRowSet->pForest; pTree; pTree=pTree->pRight){
+        ppPrevTree = &pTree->pRight;
+        if( pTree->pLeft==0 ){
+          pTree->pLeft = rowSetListToTree(p);
+          break;
+        }else{
+          struct RowSetEntry *pAux, *pTail;
+          rowSetTreeToList(pTree->pLeft, &pAux, &pTail);
+          pTree->pLeft = 0;
+          p = rowSetEntryMerge(pAux, p);
+        }
+      }
+      if( pTree==0 ){
+        *ppPrevTree = pTree = rowSetEntryAlloc(pRowSet);
+        if( pTree ){
+          pTree->v = 0;
+          pTree->pRight = 0;
+          pTree->pLeft = rowSetListToTree(p);
+        }
+      }
+      pRowSet->pEntry = 0;
+      pRowSet->pLast = 0;
+      pRowSet->rsFlags |= ROWSET_SORTED;
+    }
+    pRowSet->iBatch = iBatch;
+  }
+
+  /* Test to see if the iRowid value appears anywhere in the forest.
+  ** Return 1 if it does and 0 if not.
+  */
+  for(pTree = pRowSet->pForest; pTree; pTree=pTree->pRight){
+    p = pTree->pLeft;
+    while( p ){
+      if( p->v<iRowid ){
+        p = p->pRight;
+      }else if( p->v>iRowid ){
+        p = p->pLeft;
+      }else{
+        return 1;
+      }
+    }
+  }
+  return 0;
+}
diff --git a/src/select.c b/src/select.c
new file mode 100644
index 0000000..1215727
--- /dev/null
+++ b/src/select.c
@@ -0,0 +1,8572 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle SELECT statements in SQLite.
+*/
+#include "sqliteInt.h"
+
+/*
+** An instance of the following object is used to record information about
+** how to process the DISTINCT keyword, to simplify passing that information
+** into the selectInnerLoop() routine.
+*/
+typedef struct DistinctCtx DistinctCtx;
+struct DistinctCtx {
+  u8 isTnct;      /* 0: Not distinct. 1: DISTICT  2: DISTINCT and ORDER BY */
+  u8 eTnctType;   /* One of the WHERE_DISTINCT_* operators */
+  int tabTnct;    /* Ephemeral table used for DISTINCT processing */
+  int addrTnct;   /* Address of OP_OpenEphemeral opcode for tabTnct */
+};
+
+/*
+** An instance of the following object is used to record information about
+** the ORDER BY (or GROUP BY) clause of query is being coded.
+**
+** The aDefer[] array is used by the sorter-references optimization. For
+** example, assuming there is no index that can be used for the ORDER BY,
+** for the query:
+**
+**     SELECT a, bigblob FROM t1 ORDER BY a LIMIT 10;
+**
+** it may be more efficient to add just the "a" values to the sorter, and
+** retrieve the associated "bigblob" values directly from table t1 as the
+** 10 smallest "a" values are extracted from the sorter.
+**
+** When the sorter-reference optimization is used, there is one entry in the
+** aDefer[] array for each database table that may be read as values are
+** extracted from the sorter.
+*/
+typedef struct SortCtx SortCtx;
+struct SortCtx {
+  ExprList *pOrderBy;   /* The ORDER BY (or GROUP BY clause) */
+  int nOBSat;           /* Number of ORDER BY terms satisfied by indices */
+  int iECursor;         /* Cursor number for the sorter */
+  int regReturn;        /* Register holding block-output return address */
+  int labelBkOut;       /* Start label for the block-output subroutine */
+  int addrSortIndex;    /* Address of the OP_SorterOpen or OP_OpenEphemeral */
+  int labelDone;        /* Jump here when done, ex: LIMIT reached */
+  int labelOBLopt;      /* Jump here when sorter is full */
+  u8 sortFlags;         /* Zero or more SORTFLAG_* bits */
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+  u8 nDefer;            /* Number of valid entries in aDefer[] */
+  struct DeferredCsr {
+    Table *pTab;        /* Table definition */
+    int iCsr;           /* Cursor number for table */
+    int nKey;           /* Number of PK columns for table pTab (>=1) */
+  } aDefer[4];
+#endif
+  struct RowLoadInfo *pDeferredRowLoad;  /* Deferred row loading info or NULL */
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  int addrPush;         /* First instruction to push data into sorter */
+  int addrPushEnd;      /* Last instruction that pushes data into sorter */
+#endif
+};
+#define SORTFLAG_UseSorter  0x01   /* Use SorterOpen instead of OpenEphemeral */
+
+/*
+** Delete all the content of a Select structure.  Deallocate the structure
+** itself depending on the value of bFree
+**
+** If bFree==1, call sqlite3DbFree() on the p object.
+** If bFree==0, Leave the first Select object unfreed
+*/
+static void clearSelect(sqlite3 *db, Select *p, int bFree){
+  assert( db!=0 );
+  while( p ){
+    Select *pPrior = p->pPrior;
+    sqlite3ExprListDelete(db, p->pEList);
+    sqlite3SrcListDelete(db, p->pSrc);
+    sqlite3ExprDelete(db, p->pWhere);
+    sqlite3ExprListDelete(db, p->pGroupBy);
+    sqlite3ExprDelete(db, p->pHaving);
+    sqlite3ExprListDelete(db, p->pOrderBy);
+    sqlite3ExprDelete(db, p->pLimit);
+    if( OK_IF_ALWAYS_TRUE(p->pWith) ) sqlite3WithDelete(db, p->pWith);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( OK_IF_ALWAYS_TRUE(p->pWinDefn) ){
+      sqlite3WindowListDelete(db, p->pWinDefn);
+    }
+    while( p->pWin ){
+      assert( p->pWin->ppThis==&p->pWin );
+      sqlite3WindowUnlinkFromSelect(p->pWin);
+    }
+#endif
+    if( bFree ) sqlite3DbNNFreeNN(db, p);
+    p = pPrior;
+    bFree = 1;
+  }
+}
+
+/*
+** Initialize a SelectDest structure.
+*/
+void sqlite3SelectDestInit(SelectDest *pDest, int eDest, int iParm){
+  pDest->eDest = (u8)eDest;
+  pDest->iSDParm = iParm;
+  pDest->iSDParm2 = 0;
+  pDest->zAffSdst = 0;
+  pDest->iSdst = 0;
+  pDest->nSdst = 0;
+}
+
+
+/*
+** Allocate a new Select structure and return a pointer to that
+** structure.
+*/
+Select *sqlite3SelectNew(
+  Parse *pParse,        /* Parsing context */
+  ExprList *pEList,     /* which columns to include in the result */
+  SrcList *pSrc,        /* the FROM clause -- which tables to scan */
+  Expr *pWhere,         /* the WHERE clause */
+  ExprList *pGroupBy,   /* the GROUP BY clause */
+  Expr *pHaving,        /* the HAVING clause */
+  ExprList *pOrderBy,   /* the ORDER BY clause */
+  u32 selFlags,         /* Flag parameters, such as SF_Distinct */
+  Expr *pLimit          /* LIMIT value.  NULL means not used */
+){
+  Select *pNew, *pAllocated;
+  Select standin;
+  pAllocated = pNew = sqlite3DbMallocRawNN(pParse->db, sizeof(*pNew) );
+  if( pNew==0 ){
+    assert( pParse->db->mallocFailed );
+    pNew = &standin;
+  }
+  if( pEList==0 ){
+    pEList = sqlite3ExprListAppend(pParse, 0,
+                                   sqlite3Expr(pParse->db,TK_ASTERISK,0));
+  }
+  pNew->pEList = pEList;
+  pNew->op = TK_SELECT;
+  pNew->selFlags = selFlags;
+  pNew->iLimit = 0;
+  pNew->iOffset = 0;
+  pNew->selId = ++pParse->nSelect;
+  pNew->addrOpenEphm[0] = -1;
+  pNew->addrOpenEphm[1] = -1;
+  pNew->nSelectRow = 0;
+  if( pSrc==0 ) pSrc = sqlite3DbMallocZero(pParse->db, sizeof(*pSrc));
+  pNew->pSrc = pSrc;
+  pNew->pWhere = pWhere;
+  pNew->pGroupBy = pGroupBy;
+  pNew->pHaving = pHaving;
+  pNew->pOrderBy = pOrderBy;
+  pNew->pPrior = 0;
+  pNew->pNext = 0;
+  pNew->pLimit = pLimit;
+  pNew->pWith = 0;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  pNew->pWin = 0;
+  pNew->pWinDefn = 0;
+#endif
+  if( pParse->db->mallocFailed ) {
+    clearSelect(pParse->db, pNew, pNew!=&standin);
+    pAllocated = 0;
+  }else{
+    assert( pNew->pSrc!=0 || pParse->nErr>0 );
+  }
+  return pAllocated;
+}
+
+
+/*
+** Delete the given Select structure and all of its substructures.
+*/
+void sqlite3SelectDelete(sqlite3 *db, Select *p){
+  if( OK_IF_ALWAYS_TRUE(p) ) clearSelect(db, p, 1);
+}
+void sqlite3SelectDeleteGeneric(sqlite3 *db, void *p){
+  if( ALWAYS(p) ) clearSelect(db, (Select*)p, 1);
+}
+
+/*
+** Return a pointer to the right-most SELECT statement in a compound.
+*/
+static Select *findRightmost(Select *p){
+  while( p->pNext ) p = p->pNext;
+  return p;
+}
+
+/*
+** Given 1 to 3 identifiers preceding the JOIN keyword, determine the
+** type of join.  Return an integer constant that expresses that type
+** in terms of the following bit values:
+**
+**     JT_INNER
+**     JT_CROSS
+**     JT_OUTER
+**     JT_NATURAL
+**     JT_LEFT
+**     JT_RIGHT
+**
+** A full outer join is the combination of JT_LEFT and JT_RIGHT.
+**
+** If an illegal or unsupported join type is seen, then still return
+** a join type, but put an error in the pParse structure.
+**
+** These are the valid join types:
+**
+**
+**      pA       pB       pC               Return Value
+**     -------  -----    -----             ------------
+**     CROSS      -        -                 JT_CROSS
+**     INNER      -        -                 JT_INNER
+**     LEFT       -        -                 JT_LEFT|JT_OUTER
+**     LEFT     OUTER      -                 JT_LEFT|JT_OUTER
+**     RIGHT      -        -                 JT_RIGHT|JT_OUTER
+**     RIGHT    OUTER      -                 JT_RIGHT|JT_OUTER
+**     FULL       -        -                 JT_LEFT|JT_RIGHT|JT_OUTER
+**     FULL     OUTER      -                 JT_LEFT|JT_RIGHT|JT_OUTER
+**     NATURAL  INNER      -                 JT_NATURAL|JT_INNER
+**     NATURAL  LEFT       -                 JT_NATURAL|JT_LEFT|JT_OUTER
+**     NATURAL  LEFT     OUTER               JT_NATURAL|JT_LEFT|JT_OUTER
+**     NATURAL  RIGHT      -                 JT_NATURAL|JT_RIGHT|JT_OUTER
+**     NATURAL  RIGHT    OUTER               JT_NATURAL|JT_RIGHT|JT_OUTER
+**     NATURAL  FULL       -                 JT_NATURAL|JT_LEFT|JT_RIGHT
+**     NATURAL  FULL     OUTER               JT_NATRUAL|JT_LEFT|JT_RIGHT
+**
+** To preserve historical compatibly, SQLite also accepts a variety
+** of other non-standard and in many cases nonsensical join types.
+** This routine makes as much sense at it can from the nonsense join
+** type and returns a result.  Examples of accepted nonsense join types
+** include but are not limited to:
+**
+**          INNER CROSS JOIN        ->   same as JOIN
+**          NATURAL CROSS JOIN      ->   same as NATURAL JOIN
+**          OUTER LEFT JOIN         ->   same as LEFT JOIN
+**          LEFT NATURAL JOIN       ->   same as NATURAL LEFT JOIN
+**          LEFT RIGHT JOIN         ->   same as FULL JOIN
+**          RIGHT OUTER FULL JOIN   ->   same as FULL JOIN
+**          CROSS CROSS CROSS JOIN  ->   same as JOIN
+**
+** The only restrictions on the join type name are:
+**
+**    *   "INNER" cannot appear together with "OUTER", "LEFT", "RIGHT",
+**        or "FULL".
+**
+**    *   "CROSS" cannot appear together with "OUTER", "LEFT", "RIGHT,
+**        or "FULL".
+**
+**    *   If "OUTER" is present then there must also be one of
+**        "LEFT", "RIGHT", or "FULL"
+*/
+int sqlite3JoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
+  int jointype = 0;
+  Token *apAll[3];
+  Token *p;
+                             /*   0123456789 123456789 123456789 123 */
+  static const char zKeyText[] = "naturaleftouterightfullinnercross";
+  static const struct {
+    u8 i;        /* Beginning of keyword text in zKeyText[] */
+    u8 nChar;    /* Length of the keyword in characters */
+    u8 code;     /* Join type mask */
+  } aKeyword[] = {
+    /* (0) natural */ { 0,  7, JT_NATURAL                },
+    /* (1) left    */ { 6,  4, JT_LEFT|JT_OUTER          },
+    /* (2) outer   */ { 10, 5, JT_OUTER                  },
+    /* (3) right   */ { 14, 5, JT_RIGHT|JT_OUTER         },
+    /* (4) full    */ { 19, 4, JT_LEFT|JT_RIGHT|JT_OUTER },
+    /* (5) inner   */ { 23, 5, JT_INNER                  },
+    /* (6) cross   */ { 28, 5, JT_INNER|JT_CROSS         },
+  };
+  int i, j;
+  apAll[0] = pA;
+  apAll[1] = pB;
+  apAll[2] = pC;
+  for(i=0; i<3 && apAll[i]; i++){
+    p = apAll[i];
+    for(j=0; j<ArraySize(aKeyword); j++){
+      if( p->n==aKeyword[j].nChar
+          && sqlite3StrNICmp((char*)p->z, &zKeyText[aKeyword[j].i], p->n)==0 ){
+        jointype |= aKeyword[j].code;
+        break;
+      }
+    }
+    testcase( j==0 || j==1 || j==2 || j==3 || j==4 || j==5 || j==6 );
+    if( j>=ArraySize(aKeyword) ){
+      jointype |= JT_ERROR;
+      break;
+    }
+  }
+  if(
+     (jointype & (JT_INNER|JT_OUTER))==(JT_INNER|JT_OUTER) ||
+     (jointype & JT_ERROR)!=0 ||
+     (jointype & (JT_OUTER|JT_LEFT|JT_RIGHT))==JT_OUTER
+  ){
+    const char *zSp1 = " ";
+    const char *zSp2 = " ";
+    if( pB==0 ){ zSp1++; }
+    if( pC==0 ){ zSp2++; }
+    sqlite3ErrorMsg(pParse, "unknown join type: "
+       "%T%s%T%s%T", pA, zSp1, pB, zSp2, pC);
+    jointype = JT_INNER;
+  }
+  return jointype;
+}
+
+/*
+** Return the index of a column in a table.  Return -1 if the column
+** is not contained in the table.
+*/
+int sqlite3ColumnIndex(Table *pTab, const char *zCol){
+  int i;
+  u8 h = sqlite3StrIHash(zCol);
+  Column *pCol;
+  for(pCol=pTab->aCol, i=0; i<pTab->nCol; pCol++, i++){
+    if( pCol->hName==h && sqlite3StrICmp(pCol->zCnName, zCol)==0 ) return i;
+  }
+  return -1;
+}
+
+/*
+** Mark a subquery result column as having been used.
+*/
+void sqlite3SrcItemColumnUsed(SrcItem *pItem, int iCol){
+  assert( pItem!=0 );
+  assert( (int)pItem->fg.isNestedFrom == IsNestedFrom(pItem->pSelect) );
+  if( pItem->fg.isNestedFrom ){
+    ExprList *pResults;
+    assert( pItem->pSelect!=0 );
+    pResults = pItem->pSelect->pEList;
+    assert( pResults!=0 );
+    assert( iCol>=0 && iCol<pResults->nExpr );
+    pResults->a[iCol].fg.bUsed = 1;
+  }
+}
+
+/*
+** Search the tables iStart..iEnd (inclusive) in pSrc, looking for a
+** table that has a column named zCol.  The search is left-to-right.
+** The first match found is returned.
+**
+** When found, set *piTab and *piCol to the table index and column index
+** of the matching column and return TRUE.
+**
+** If not found, return FALSE.
+*/
+static int tableAndColumnIndex(
+  SrcList *pSrc,       /* Array of tables to search */
+  int iStart,          /* First member of pSrc->a[] to check */
+  int iEnd,            /* Last member of pSrc->a[] to check */
+  const char *zCol,    /* Name of the column we are looking for */
+  int *piTab,          /* Write index of pSrc->a[] here */
+  int *piCol,          /* Write index of pSrc->a[*piTab].pTab->aCol[] here */
+  int bIgnoreHidden    /* Ignore hidden columns */
+){
+  int i;               /* For looping over tables in pSrc */
+  int iCol;            /* Index of column matching zCol */
+
+  assert( iEnd<pSrc->nSrc );
+  assert( iStart>=0 );
+  assert( (piTab==0)==(piCol==0) );  /* Both or neither are NULL */
+
+  for(i=iStart; i<=iEnd; i++){
+    iCol = sqlite3ColumnIndex(pSrc->a[i].pTab, zCol);
+    if( iCol>=0
+     && (bIgnoreHidden==0 || IsHiddenColumn(&pSrc->a[i].pTab->aCol[iCol])==0)
+    ){
+      if( piTab ){
+        sqlite3SrcItemColumnUsed(&pSrc->a[i], iCol);
+        *piTab = i;
+        *piCol = iCol;
+      }
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Set the EP_OuterON property on all terms of the given expression.
+** And set the Expr.w.iJoin to iTable for every term in the
+** expression.
+**
+** The EP_OuterON property is used on terms of an expression to tell
+** the OUTER JOIN processing logic that this term is part of the
+** join restriction specified in the ON or USING clause and not a part
+** of the more general WHERE clause.  These terms are moved over to the
+** WHERE clause during join processing but we need to remember that they
+** originated in the ON or USING clause.
+**
+** The Expr.w.iJoin tells the WHERE clause processing that the
+** expression depends on table w.iJoin even if that table is not
+** explicitly mentioned in the expression.  That information is needed
+** for cases like this:
+**
+**    SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.b AND t1.x=5
+**
+** The where clause needs to defer the handling of the t1.x=5
+** term until after the t2 loop of the join.  In that way, a
+** NULL t2 row will be inserted whenever t1.x!=5.  If we do not
+** defer the handling of t1.x=5, it will be processed immediately
+** after the t1 loop and rows with t1.x!=5 will never appear in
+** the output, which is incorrect.
+*/
+void sqlite3SetJoinExpr(Expr *p, int iTable, u32 joinFlag){
+  assert( joinFlag==EP_OuterON || joinFlag==EP_InnerON );
+  while( p ){
+    ExprSetProperty(p, joinFlag);
+    assert( !ExprHasProperty(p, EP_TokenOnly|EP_Reduced) );
+    ExprSetVVAProperty(p, EP_NoReduce);
+    p->w.iJoin = iTable;
+    if( p->op==TK_FUNCTION ){
+      assert( ExprUseXList(p) );
+      if( p->x.pList ){
+        int i;
+        for(i=0; i<p->x.pList->nExpr; i++){
+          sqlite3SetJoinExpr(p->x.pList->a[i].pExpr, iTable, joinFlag);
+        }
+      }
+    }
+    sqlite3SetJoinExpr(p->pLeft, iTable, joinFlag);
+    p = p->pRight;
+  }
+}
+
+/* Undo the work of sqlite3SetJoinExpr().  This is used when a LEFT JOIN
+** is simplified into an ordinary JOIN, and when an ON expression is
+** "pushed down" into the WHERE clause of a subquery.
+**
+** Convert every term that is marked with EP_OuterON and w.iJoin==iTable into
+** an ordinary term that omits the EP_OuterON mark.  Or if iTable<0, then
+** just clear every EP_OuterON and EP_InnerON mark from the expression tree.
+**
+** If nullable is true, that means that Expr p might evaluate to NULL even
+** if it is a reference to a NOT NULL column.  This can happen, for example,
+** if the table that p references is on the left side of a RIGHT JOIN.
+** If nullable is true, then take care to not remove the EP_CanBeNull bit.
+** See forum thread https://sqlite.org/forum/forumpost/b40696f50145d21c
+*/
+static void unsetJoinExpr(Expr *p, int iTable, int nullable){
+  while( p ){
+    if( iTable<0 || (ExprHasProperty(p, EP_OuterON) && p->w.iJoin==iTable) ){
+      ExprClearProperty(p, EP_OuterON|EP_InnerON);
+      if( iTable>=0 ) ExprSetProperty(p, EP_InnerON);
+    }
+    if( p->op==TK_COLUMN && p->iTable==iTable && !nullable ){
+      ExprClearProperty(p, EP_CanBeNull);
+    }
+    if( p->op==TK_FUNCTION ){
+      assert( ExprUseXList(p) );
+      assert( p->pLeft==0 );
+      if( p->x.pList ){
+        int i;
+        for(i=0; i<p->x.pList->nExpr; i++){
+          unsetJoinExpr(p->x.pList->a[i].pExpr, iTable, nullable);
+        }
+      }
+    }
+    unsetJoinExpr(p->pLeft, iTable, nullable);
+    p = p->pRight;
+  }
+}
+
+/*
+** This routine processes the join information for a SELECT statement.
+**
+**   *  A NATURAL join is converted into a USING join.  After that, we
+**      do not need to be concerned with NATURAL joins and we only have
+**      think about USING joins.
+**
+**   *  ON and USING clauses result in extra terms being added to the
+**      WHERE clause to enforce the specified constraints.  The extra
+**      WHERE clause terms will be tagged with EP_OuterON or
+**      EP_InnerON so that we know that they originated in ON/USING.
+**
+** The terms of a FROM clause are contained in the Select.pSrc structure.
+** The left most table is the first entry in Select.pSrc.  The right-most
+** table is the last entry.  The join operator is held in the entry to
+** the right.  Thus entry 1 contains the join operator for the join between
+** entries 0 and 1.  Any ON or USING clauses associated with the join are
+** also attached to the right entry.
+**
+** This routine returns the number of errors encountered.
+*/
+static int sqlite3ProcessJoin(Parse *pParse, Select *p){
+  SrcList *pSrc;                  /* All tables in the FROM clause */
+  int i, j;                       /* Loop counters */
+  SrcItem *pLeft;                 /* Left table being joined */
+  SrcItem *pRight;                /* Right table being joined */
+
+  pSrc = p->pSrc;
+  pLeft = &pSrc->a[0];
+  pRight = &pLeft[1];
+  for(i=0; i<pSrc->nSrc-1; i++, pRight++, pLeft++){
+    Table *pRightTab = pRight->pTab;
+    u32 joinType;
+
+    if( NEVER(pLeft->pTab==0 || pRightTab==0) ) continue;
+    joinType = (pRight->fg.jointype & JT_OUTER)!=0 ? EP_OuterON : EP_InnerON;
+
+    /* If this is a NATURAL join, synthesize an appropriate USING clause
+    ** to specify which columns should be joined.
+    */
+    if( pRight->fg.jointype & JT_NATURAL ){
+      IdList *pUsing = 0;
+      if( pRight->fg.isUsing || pRight->u3.pOn ){
+        sqlite3ErrorMsg(pParse, "a NATURAL join may not have "
+           "an ON or USING clause", 0);
+        return 1;
+      }
+      for(j=0; j<pRightTab->nCol; j++){
+        char *zName;   /* Name of column in the right table */
+
+        if( IsHiddenColumn(&pRightTab->aCol[j]) ) continue;
+        zName = pRightTab->aCol[j].zCnName;
+        if( tableAndColumnIndex(pSrc, 0, i, zName, 0, 0, 1) ){
+          pUsing = sqlite3IdListAppend(pParse, pUsing, 0);
+          if( pUsing ){
+            assert( pUsing->nId>0 );
+            assert( pUsing->a[pUsing->nId-1].zName==0 );
+            pUsing->a[pUsing->nId-1].zName = sqlite3DbStrDup(pParse->db, zName);
+          }
+        }
+      }
+      if( pUsing ){
+        pRight->fg.isUsing = 1;
+        pRight->fg.isSynthUsing = 1;
+        pRight->u3.pUsing = pUsing;
+      }
+      if( pParse->nErr ) return 1;
+    }
+
+    /* Create extra terms on the WHERE clause for each column named
+    ** in the USING clause.  Example: If the two tables to be joined are
+    ** A and B and the USING clause names X, Y, and Z, then add this
+    ** to the WHERE clause:    A.X=B.X AND A.Y=B.Y AND A.Z=B.Z
+    ** Report an error if any column mentioned in the USING clause is
+    ** not contained in both tables to be joined.
+    */
+    if( pRight->fg.isUsing ){
+      IdList *pList = pRight->u3.pUsing;
+      sqlite3 *db = pParse->db;
+      assert( pList!=0 );
+      for(j=0; j<pList->nId; j++){
+        char *zName;     /* Name of the term in the USING clause */
+        int iLeft;       /* Table on the left with matching column name */
+        int iLeftCol;    /* Column number of matching column on the left */
+        int iRightCol;   /* Column number of matching column on the right */
+        Expr *pE1;       /* Reference to the column on the LEFT of the join */
+        Expr *pE2;       /* Reference to the column on the RIGHT of the join */
+        Expr *pEq;       /* Equality constraint.  pE1 == pE2 */
+
+        zName = pList->a[j].zName;
+        iRightCol = sqlite3ColumnIndex(pRightTab, zName);
+        if( iRightCol<0
+         || tableAndColumnIndex(pSrc, 0, i, zName, &iLeft, &iLeftCol,
+                                pRight->fg.isSynthUsing)==0
+        ){
+          sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
+            "not present in both tables", zName);
+          return 1;
+        }
+        pE1 = sqlite3CreateColumnExpr(db, pSrc, iLeft, iLeftCol);
+        sqlite3SrcItemColumnUsed(&pSrc->a[iLeft], iLeftCol);
+        if( (pSrc->a[0].fg.jointype & JT_LTORJ)!=0 ){
+          /* This branch runs if the query contains one or more RIGHT or FULL
+          ** JOINs.  If only a single table on the left side of this join
+          ** contains the zName column, then this branch is a no-op.
+          ** But if there are two or more tables on the left side
+          ** of the join, construct a coalesce() function that gathers all
+          ** such tables.  Raise an error if more than one of those references
+          ** to zName is not also within a prior USING clause.
+          **
+          ** We really ought to raise an error if there are two or more
+          ** non-USING references to zName on the left of an INNER or LEFT
+          ** JOIN.  But older versions of SQLite do not do that, so we avoid
+          ** adding a new error so as to not break legacy applications.
+          */
+          ExprList *pFuncArgs = 0;   /* Arguments to the coalesce() */
+          static const Token tkCoalesce = { "coalesce", 8 };
+          while( tableAndColumnIndex(pSrc, iLeft+1, i, zName, &iLeft, &iLeftCol,
+                                     pRight->fg.isSynthUsing)!=0 ){
+            if( pSrc->a[iLeft].fg.isUsing==0
+             || sqlite3IdListIndex(pSrc->a[iLeft].u3.pUsing, zName)<0
+            ){
+              sqlite3ErrorMsg(pParse, "ambiguous reference to %s in USING()",
+                              zName);
+              break;
+            }
+            pFuncArgs = sqlite3ExprListAppend(pParse, pFuncArgs, pE1);
+            pE1 = sqlite3CreateColumnExpr(db, pSrc, iLeft, iLeftCol);
+            sqlite3SrcItemColumnUsed(&pSrc->a[iLeft], iLeftCol);
+          }
+          if( pFuncArgs ){
+            pFuncArgs = sqlite3ExprListAppend(pParse, pFuncArgs, pE1);
+            pE1 = sqlite3ExprFunction(pParse, pFuncArgs, &tkCoalesce, 0);
+          }
+        }
+        pE2 = sqlite3CreateColumnExpr(db, pSrc, i+1, iRightCol);
+        sqlite3SrcItemColumnUsed(pRight, iRightCol);
+        pEq = sqlite3PExpr(pParse, TK_EQ, pE1, pE2);
+        assert( pE2!=0 || pEq==0 );
+        if( pEq ){
+          ExprSetProperty(pEq, joinType);
+          assert( !ExprHasProperty(pEq, EP_TokenOnly|EP_Reduced) );
+          ExprSetVVAProperty(pEq, EP_NoReduce);
+          pEq->w.iJoin = pE2->iTable;
+        }
+        p->pWhere = sqlite3ExprAnd(pParse, p->pWhere, pEq);
+      }
+    }
+
+    /* Add the ON clause to the end of the WHERE clause, connected by
+    ** an AND operator.
+    */
+    else if( pRight->u3.pOn ){
+      sqlite3SetJoinExpr(pRight->u3.pOn, pRight->iCursor, joinType);
+      p->pWhere = sqlite3ExprAnd(pParse, p->pWhere, pRight->u3.pOn);
+      pRight->u3.pOn = 0;
+      pRight->fg.isOn = 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** An instance of this object holds information (beyond pParse and pSelect)
+** needed to load the next result row that is to be added to the sorter.
+*/
+typedef struct RowLoadInfo RowLoadInfo;
+struct RowLoadInfo {
+  int regResult;               /* Store results in array of registers here */
+  u8 ecelFlags;                /* Flag argument to ExprCodeExprList() */
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+  ExprList *pExtra;            /* Extra columns needed by sorter refs */
+  int regExtraResult;          /* Where to load the extra columns */
+#endif
+};
+
+/*
+** This routine does the work of loading query data into an array of
+** registers so that it can be added to the sorter.
+*/
+static void innerLoopLoadRow(
+  Parse *pParse,             /* Statement under construction */
+  Select *pSelect,           /* The query being coded */
+  RowLoadInfo *pInfo         /* Info needed to complete the row load */
+){
+  sqlite3ExprCodeExprList(pParse, pSelect->pEList, pInfo->regResult,
+                          0, pInfo->ecelFlags);
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+  if( pInfo->pExtra ){
+    sqlite3ExprCodeExprList(pParse, pInfo->pExtra, pInfo->regExtraResult, 0, 0);
+    sqlite3ExprListDelete(pParse->db, pInfo->pExtra);
+  }
+#endif
+}
+
+/*
+** Code the OP_MakeRecord instruction that generates the entry to be
+** added into the sorter.
+**
+** Return the register in which the result is stored.
+*/
+static int makeSorterRecord(
+  Parse *pParse,
+  SortCtx *pSort,
+  Select *pSelect,
+  int regBase,
+  int nBase
+){
+  int nOBSat = pSort->nOBSat;
+  Vdbe *v = pParse->pVdbe;
+  int regOut = ++pParse->nMem;
+  if( pSort->pDeferredRowLoad ){
+    innerLoopLoadRow(pParse, pSelect, pSort->pDeferredRowLoad);
+  }
+  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat, regOut);
+  return regOut;
+}
+
+/*
+** Generate code that will push the record in registers regData
+** through regData+nData-1 onto the sorter.
+*/
+static void pushOntoSorter(
+  Parse *pParse,         /* Parser context */
+  SortCtx *pSort,        /* Information about the ORDER BY clause */
+  Select *pSelect,       /* The whole SELECT statement */
+  int regData,           /* First register holding data to be sorted */
+  int regOrigData,       /* First register holding data before packing */
+  int nData,             /* Number of elements in the regData data array */
+  int nPrefixReg         /* No. of reg prior to regData available for use */
+){
+  Vdbe *v = pParse->pVdbe;                         /* Stmt under construction */
+  int bSeq = ((pSort->sortFlags & SORTFLAG_UseSorter)==0);
+  int nExpr = pSort->pOrderBy->nExpr;              /* No. of ORDER BY terms */
+  int nBase = nExpr + bSeq + nData;                /* Fields in sorter record */
+  int regBase;                                     /* Regs for sorter record */
+  int regRecord = 0;                               /* Assembled sorter record */
+  int nOBSat = pSort->nOBSat;                      /* ORDER BY terms to skip */
+  int op;                            /* Opcode to add sorter record to sorter */
+  int iLimit;                        /* LIMIT counter */
+  int iSkip = 0;                     /* End of the sorter insert loop */
+
+  assert( bSeq==0 || bSeq==1 );
+
+  /* Three cases:
+  **   (1) The data to be sorted has already been packed into a Record
+  **       by a prior OP_MakeRecord.  In this case nData==1 and regData
+  **       will be completely unrelated to regOrigData.
+  **   (2) All output columns are included in the sort record.  In that
+  **       case regData==regOrigData.
+  **   (3) Some output columns are omitted from the sort record due to
+  **       the SQLITE_ENABLE_SORTER_REFERENCES optimization, or due to the
+  **       SQLITE_ECEL_OMITREF optimization, or due to the
+  **       SortCtx.pDeferredRowLoad optimization.  In any of these cases
+  **       regOrigData is 0 to prevent this routine from trying to copy
+  **       values that might not yet exist.
+  */
+  assert( nData==1 || regData==regOrigData || regOrigData==0 );
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  pSort->addrPush = sqlite3VdbeCurrentAddr(v);
+#endif
+
+  if( nPrefixReg ){
+    assert( nPrefixReg==nExpr+bSeq );
+    regBase = regData - nPrefixReg;
+  }else{
+    regBase = pParse->nMem + 1;
+    pParse->nMem += nBase;
+  }
+  assert( pSelect->iOffset==0 || pSelect->iLimit!=0 );
+  iLimit = pSelect->iOffset ? pSelect->iOffset+1 : pSelect->iLimit;
+  pSort->labelDone = sqlite3VdbeMakeLabel(pParse);
+  sqlite3ExprCodeExprList(pParse, pSort->pOrderBy, regBase, regOrigData,
+                          SQLITE_ECEL_DUP | (regOrigData? SQLITE_ECEL_REF : 0));
+  if( bSeq ){
+    sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);
+  }
+  if( nPrefixReg==0 && nData>0 ){
+    sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+bSeq, nData);
+  }
+  if( nOBSat>0 ){
+    int regPrevKey;   /* The first nOBSat columns of the previous row */
+    int addrFirst;    /* Address of the OP_IfNot opcode */
+    int addrJmp;      /* Address of the OP_Jump opcode */
+    VdbeOp *pOp;      /* Opcode that opens the sorter */
+    int nKey;         /* Number of sorting key columns, including OP_Sequence */
+    KeyInfo *pKI;     /* Original KeyInfo on the sorter table */
+
+    regRecord = makeSorterRecord(pParse, pSort, pSelect, regBase, nBase);
+    regPrevKey = pParse->nMem+1;
+    pParse->nMem += pSort->nOBSat;
+    nKey = nExpr - pSort->nOBSat + bSeq;
+    if( bSeq ){
+      addrFirst = sqlite3VdbeAddOp1(v, OP_IfNot, regBase+nExpr);
+    }else{
+      addrFirst = sqlite3VdbeAddOp1(v, OP_SequenceTest, pSort->iECursor);
+    }
+    VdbeCoverage(v);
+    sqlite3VdbeAddOp3(v, OP_Compare, regPrevKey, regBase, pSort->nOBSat);
+    pOp = sqlite3VdbeGetOp(v, pSort->addrSortIndex);
+    if( pParse->db->mallocFailed ) return;
+    pOp->p2 = nKey + nData;
+    pKI = pOp->p4.pKeyInfo;
+    memset(pKI->aSortFlags, 0, pKI->nKeyField); /* Makes OP_Jump testable */
+    sqlite3VdbeChangeP4(v, -1, (char*)pKI, P4_KEYINFO);
+    testcase( pKI->nAllField > pKI->nKeyField+2 );
+    pOp->p4.pKeyInfo = sqlite3KeyInfoFromExprList(pParse,pSort->pOrderBy,nOBSat,
+                                           pKI->nAllField-pKI->nKeyField-1);
+    pOp = 0; /* Ensure pOp not used after sqlite3VdbeAddOp3() */
+    addrJmp = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp3(v, OP_Jump, addrJmp+1, 0, addrJmp+1); VdbeCoverage(v);
+    pSort->labelBkOut = sqlite3VdbeMakeLabel(pParse);
+    pSort->regReturn = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Gosub, pSort->regReturn, pSort->labelBkOut);
+    sqlite3VdbeAddOp1(v, OP_ResetSorter, pSort->iECursor);
+    if( iLimit ){
+      sqlite3VdbeAddOp2(v, OP_IfNot, iLimit, pSort->labelDone);
+      VdbeCoverage(v);
+    }
+    sqlite3VdbeJumpHere(v, addrFirst);
+    sqlite3ExprCodeMove(pParse, regBase, regPrevKey, pSort->nOBSat);
+    sqlite3VdbeJumpHere(v, addrJmp);
+  }
+  if( iLimit ){
+    /* At this point the values for the new sorter entry are stored
+    ** in an array of registers. They need to be composed into a record
+    ** and inserted into the sorter if either (a) there are currently
+    ** less than LIMIT+OFFSET items or (b) the new record is smaller than
+    ** the largest record currently in the sorter. If (b) is true and there
+    ** are already LIMIT+OFFSET items in the sorter, delete the largest
+    ** entry before inserting the new one. This way there are never more
+    ** than LIMIT+OFFSET items in the sorter.
+    **
+    ** If the new record does not need to be inserted into the sorter,
+    ** jump to the next iteration of the loop. If the pSort->labelOBLopt
+    ** value is not zero, then it is a label of where to jump.  Otherwise,
+    ** just bypass the row insert logic.  See the header comment on the
+    ** sqlite3WhereOrderByLimitOptLabel() function for additional info.
+    */
+    int iCsr = pSort->iECursor;
+    sqlite3VdbeAddOp2(v, OP_IfNotZero, iLimit, sqlite3VdbeCurrentAddr(v)+4);
+    VdbeCoverage(v);
+    sqlite3VdbeAddOp2(v, OP_Last, iCsr, 0);
+    iSkip = sqlite3VdbeAddOp4Int(v, OP_IdxLE,
+                                 iCsr, 0, regBase+nOBSat, nExpr-nOBSat);
+    VdbeCoverage(v);
+    sqlite3VdbeAddOp1(v, OP_Delete, iCsr);
+  }
+  if( regRecord==0 ){
+    regRecord = makeSorterRecord(pParse, pSort, pSelect, regBase, nBase);
+  }
+  if( pSort->sortFlags & SORTFLAG_UseSorter ){
+    op = OP_SorterInsert;
+  }else{
+    op = OP_IdxInsert;
+  }
+  sqlite3VdbeAddOp4Int(v, op, pSort->iECursor, regRecord,
+                       regBase+nOBSat, nBase-nOBSat);
+  if( iSkip ){
+    sqlite3VdbeChangeP2(v, iSkip,
+         pSort->labelOBLopt ? pSort->labelOBLopt : sqlite3VdbeCurrentAddr(v));
+  }
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  pSort->addrPushEnd = sqlite3VdbeCurrentAddr(v)-1;
+#endif
+}
+
+/*
+** Add code to implement the OFFSET
+*/
+static void codeOffset(
+  Vdbe *v,          /* Generate code into this VM */
+  int iOffset,      /* Register holding the offset counter */
+  int iContinue     /* Jump here to skip the current record */
+){
+  if( iOffset>0 ){
+    sqlite3VdbeAddOp3(v, OP_IfPos, iOffset, iContinue, 1); VdbeCoverage(v);
+    VdbeComment((v, "OFFSET"));
+  }
+}
+
+/*
+** Add code that will check to make sure the array of registers starting at
+** iMem form a distinct entry. This is used by both "SELECT DISTINCT ..." and
+** distinct aggregates ("SELECT count(DISTINCT <expr>) ..."). Three strategies
+** are available. Which is used depends on the value of parameter eTnctType,
+** as follows:
+**
+**   WHERE_DISTINCT_UNORDERED/WHERE_DISTINCT_NOOP:
+**     Build an ephemeral table that contains all entries seen before and
+**     skip entries which have been seen before.
+**
+**     Parameter iTab is the cursor number of an ephemeral table that must
+**     be opened before the VM code generated by this routine is executed.
+**     The ephemeral cursor table is queried for a record identical to the
+**     record formed by the current array of registers. If one is found,
+**     jump to VM address addrRepeat. Otherwise, insert a new record into
+**     the ephemeral cursor and proceed.
+**
+**     The returned value in this case is a copy of parameter iTab.
+**
+**   WHERE_DISTINCT_ORDERED:
+**     In this case rows are being delivered sorted order. The ephemeral
+**     table is not required. Instead, the current set of values
+**     is compared against previous row. If they match, the new row
+**     is not distinct and control jumps to VM address addrRepeat. Otherwise,
+**     the VM program proceeds with processing the new row.
+**
+**     The returned value in this case is the register number of the first
+**     in an array of registers used to store the previous result row so that
+**     it can be compared to the next. The caller must ensure that this
+**     register is initialized to NULL.  (The fixDistinctOpenEph() routine
+**     will take care of this initialization.)
+**
+**   WHERE_DISTINCT_UNIQUE:
+**     In this case it has already been determined that the rows are distinct.
+**     No special action is required. The return value is zero.
+**
+** Parameter pEList is the list of expressions used to generated the
+** contents of each row. It is used by this routine to determine (a)
+** how many elements there are in the array of registers and (b) the
+** collation sequences that should be used for the comparisons if
+** eTnctType is WHERE_DISTINCT_ORDERED.
+*/
+static int codeDistinct(
+  Parse *pParse,     /* Parsing and code generating context */
+  int eTnctType,     /* WHERE_DISTINCT_* value */
+  int iTab,          /* A sorting index used to test for distinctness */
+  int addrRepeat,    /* Jump to here if not distinct */
+  ExprList *pEList,  /* Expression for each element */
+  int regElem        /* First element */
+){
+  int iRet = 0;
+  int nResultCol = pEList->nExpr;
+  Vdbe *v = pParse->pVdbe;
+
+  switch( eTnctType ){
+    case WHERE_DISTINCT_ORDERED: {
+      int i;
+      int iJump;              /* Jump destination */
+      int regPrev;            /* Previous row content */
+
+      /* Allocate space for the previous row */
+      iRet = regPrev = pParse->nMem+1;
+      pParse->nMem += nResultCol;
+
+      iJump = sqlite3VdbeCurrentAddr(v) + nResultCol;
+      for(i=0; i<nResultCol; i++){
+        CollSeq *pColl = sqlite3ExprCollSeq(pParse, pEList->a[i].pExpr);
+        if( i<nResultCol-1 ){
+          sqlite3VdbeAddOp3(v, OP_Ne, regElem+i, iJump, regPrev+i);
+          VdbeCoverage(v);
+        }else{
+          sqlite3VdbeAddOp3(v, OP_Eq, regElem+i, addrRepeat, regPrev+i);
+          VdbeCoverage(v);
+         }
+        sqlite3VdbeChangeP4(v, -1, (const char *)pColl, P4_COLLSEQ);
+        sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
+      }
+      assert( sqlite3VdbeCurrentAddr(v)==iJump || pParse->db->mallocFailed );
+      sqlite3VdbeAddOp3(v, OP_Copy, regElem, regPrev, nResultCol-1);
+      break;
+    }
+
+    case WHERE_DISTINCT_UNIQUE: {
+      /* nothing to do */
+      break;
+    }
+
+    default: {
+      int r1 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp4Int(v, OP_Found, iTab, addrRepeat, regElem, nResultCol);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regElem, nResultCol, r1);
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iTab, r1, regElem, nResultCol);
+      sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+      sqlite3ReleaseTempReg(pParse, r1);
+      iRet = iTab;
+      break;
+    }
+  }
+
+  return iRet;
+}
+
+/*
+** This routine runs after codeDistinct().  It makes necessary
+** adjustments to the OP_OpenEphemeral opcode that the codeDistinct()
+** routine made use of.  This processing must be done separately since
+** sometimes codeDistinct is called before the OP_OpenEphemeral is actually
+** laid down.
+**
+** WHERE_DISTINCT_NOOP:
+** WHERE_DISTINCT_UNORDERED:
+**
+**     No adjustments necessary.  This function is a no-op.
+**
+** WHERE_DISTINCT_UNIQUE:
+**
+**     The ephemeral table is not needed.  So change the
+**     OP_OpenEphemeral opcode into an OP_Noop.
+**
+** WHERE_DISTINCT_ORDERED:
+**
+**     The ephemeral table is not needed.  But we do need register
+**     iVal to be initialized to NULL.  So change the OP_OpenEphemeral
+**     into an OP_Null on the iVal register.
+*/
+static void fixDistinctOpenEph(
+  Parse *pParse,     /* Parsing and code generating context */
+  int eTnctType,     /* WHERE_DISTINCT_* value */
+  int iVal,          /* Value returned by codeDistinct() */
+  int iOpenEphAddr   /* Address of OP_OpenEphemeral instruction for iTab */
+){
+  if( pParse->nErr==0
+   && (eTnctType==WHERE_DISTINCT_UNIQUE || eTnctType==WHERE_DISTINCT_ORDERED)
+  ){
+    Vdbe *v = pParse->pVdbe;
+    sqlite3VdbeChangeToNoop(v, iOpenEphAddr);
+    if( sqlite3VdbeGetOp(v, iOpenEphAddr+1)->opcode==OP_Explain ){
+      sqlite3VdbeChangeToNoop(v, iOpenEphAddr+1);
+    }
+    if( eTnctType==WHERE_DISTINCT_ORDERED ){
+      /* Change the OP_OpenEphemeral to an OP_Null that sets the MEM_Cleared
+      ** bit on the first register of the previous value.  This will cause the
+      ** OP_Ne added in codeDistinct() to always fail on the first iteration of
+      ** the loop even if the first row is all NULLs.  */
+      VdbeOp *pOp = sqlite3VdbeGetOp(v, iOpenEphAddr);
+      pOp->opcode = OP_Null;
+      pOp->p1 = 1;
+      pOp->p2 = iVal;
+    }
+  }
+}
+
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+/*
+** This function is called as part of inner-loop generation for a SELECT
+** statement with an ORDER BY that is not optimized by an index. It
+** determines the expressions, if any, that the sorter-reference
+** optimization should be used for. The sorter-reference optimization
+** is used for SELECT queries like:
+**
+**   SELECT a, bigblob FROM t1 ORDER BY a LIMIT 10
+**
+** If the optimization is used for expression "bigblob", then instead of
+** storing values read from that column in the sorter records, the PK of
+** the row from table t1 is stored instead. Then, as records are extracted from
+** the sorter to return to the user, the required value of bigblob is
+** retrieved directly from table t1. If the values are very large, this
+** can be more efficient than storing them directly in the sorter records.
+**
+** The ExprList_item.fg.bSorterRef flag is set for each expression in pEList
+** for which the sorter-reference optimization should be enabled.
+** Additionally, the pSort->aDefer[] array is populated with entries
+** for all cursors required to evaluate all selected expressions. Finally.
+** output variable (*ppExtra) is set to an expression list containing
+** expressions for all extra PK values that should be stored in the
+** sorter records.
+*/
+static void selectExprDefer(
+  Parse *pParse,                  /* Leave any error here */
+  SortCtx *pSort,                 /* Sorter context */
+  ExprList *pEList,               /* Expressions destined for sorter */
+  ExprList **ppExtra              /* Expressions to append to sorter record */
+){
+  int i;
+  int nDefer = 0;
+  ExprList *pExtra = 0;
+  for(i=0; i<pEList->nExpr; i++){
+    struct ExprList_item *pItem = &pEList->a[i];
+    if( pItem->u.x.iOrderByCol==0 ){
+      Expr *pExpr = pItem->pExpr;
+      Table *pTab;
+      if( pExpr->op==TK_COLUMN
+       && pExpr->iColumn>=0
+       && ALWAYS( ExprUseYTab(pExpr) )
+       && (pTab = pExpr->y.pTab)!=0
+       && IsOrdinaryTable(pTab)
+       && (pTab->aCol[pExpr->iColumn].colFlags & COLFLAG_SORTERREF)!=0
+      ){
+        int j;
+        for(j=0; j<nDefer; j++){
+          if( pSort->aDefer[j].iCsr==pExpr->iTable ) break;
+        }
+        if( j==nDefer ){
+          if( nDefer==ArraySize(pSort->aDefer) ){
+            continue;
+          }else{
+            int nKey = 1;
+            int k;
+            Index *pPk = 0;
+            if( !HasRowid(pTab) ){
+              pPk = sqlite3PrimaryKeyIndex(pTab);
+              nKey = pPk->nKeyCol;
+            }
+            for(k=0; k<nKey; k++){
+              Expr *pNew = sqlite3PExpr(pParse, TK_COLUMN, 0, 0);
+              if( pNew ){
+                pNew->iTable = pExpr->iTable;
+                assert( ExprUseYTab(pNew) );
+                pNew->y.pTab = pExpr->y.pTab;
+                pNew->iColumn = pPk ? pPk->aiColumn[k] : -1;
+                pExtra = sqlite3ExprListAppend(pParse, pExtra, pNew);
+              }
+            }
+            pSort->aDefer[nDefer].pTab = pExpr->y.pTab;
+            pSort->aDefer[nDefer].iCsr = pExpr->iTable;
+            pSort->aDefer[nDefer].nKey = nKey;
+            nDefer++;
+          }
+        }
+        pItem->fg.bSorterRef = 1;
+      }
+    }
+  }
+  pSort->nDefer = (u8)nDefer;
+  *ppExtra = pExtra;
+}
+#endif
+
+/*
+** This routine generates the code for the inside of the inner loop
+** of a SELECT.
+**
+** If srcTab is negative, then the p->pEList expressions
+** are evaluated in order to get the data for this row.  If srcTab is
+** zero or more, then data is pulled from srcTab and p->pEList is used only
+** to get the number of columns and the collation sequence for each column.
+*/
+static void selectInnerLoop(
+  Parse *pParse,          /* The parser context */
+  Select *p,              /* The complete select statement being coded */
+  int srcTab,             /* Pull data from this table if non-negative */
+  SortCtx *pSort,         /* If not NULL, info on how to process ORDER BY */
+  DistinctCtx *pDistinct, /* If not NULL, info on how to process DISTINCT */
+  SelectDest *pDest,      /* How to dispose of the results */
+  int iContinue,          /* Jump here to continue with next row */
+  int iBreak              /* Jump here to break out of the inner loop */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  int hasDistinct;            /* True if the DISTINCT keyword is present */
+  int eDest = pDest->eDest;   /* How to dispose of results */
+  int iParm = pDest->iSDParm; /* First argument to disposal method */
+  int nResultCol;             /* Number of result columns */
+  int nPrefixReg = 0;         /* Number of extra registers before regResult */
+  RowLoadInfo sRowLoadInfo;   /* Info for deferred row loading */
+
+  /* Usually, regResult is the first cell in an array of memory cells
+  ** containing the current result row. In this case regOrig is set to the
+  ** same value. However, if the results are being sent to the sorter, the
+  ** values for any expressions that are also part of the sort-key are omitted
+  ** from this array. In this case regOrig is set to zero.  */
+  int regResult;              /* Start of memory holding current results */
+  int regOrig;                /* Start of memory holding full result (or 0) */
+
+  assert( v );
+  assert( p->pEList!=0 );
+  hasDistinct = pDistinct ? pDistinct->eTnctType : WHERE_DISTINCT_NOOP;
+  if( pSort && pSort->pOrderBy==0 ) pSort = 0;
+  if( pSort==0 && !hasDistinct ){
+    assert( iContinue!=0 );
+    codeOffset(v, p->iOffset, iContinue);
+  }
+
+  /* Pull the requested columns.
+  */
+  nResultCol = p->pEList->nExpr;
+
+  if( pDest->iSdst==0 ){
+    if( pSort ){
+      nPrefixReg = pSort->pOrderBy->nExpr;
+      if( !(pSort->sortFlags & SORTFLAG_UseSorter) ) nPrefixReg++;
+      pParse->nMem += nPrefixReg;
+    }
+    pDest->iSdst = pParse->nMem+1;
+    pParse->nMem += nResultCol;
+  }else if( pDest->iSdst+nResultCol > pParse->nMem ){
+    /* This is an error condition that can result, for example, when a SELECT
+    ** on the right-hand side of an INSERT contains more result columns than
+    ** there are columns in the table on the left.  The error will be caught
+    ** and reported later.  But we need to make sure enough memory is allocated
+    ** to avoid other spurious errors in the meantime. */
+    pParse->nMem += nResultCol;
+  }
+  pDest->nSdst = nResultCol;
+  regOrig = regResult = pDest->iSdst;
+  if( srcTab>=0 ){
+    for(i=0; i<nResultCol; i++){
+      sqlite3VdbeAddOp3(v, OP_Column, srcTab, i, regResult+i);
+      VdbeComment((v, "%s", p->pEList->a[i].zEName));
+    }
+  }else if( eDest!=SRT_Exists ){
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    ExprList *pExtra = 0;
+#endif
+    /* If the destination is an EXISTS(...) expression, the actual
+    ** values returned by the SELECT are not required.
+    */
+    u8 ecelFlags;    /* "ecel" is an abbreviation of "ExprCodeExprList" */
+    ExprList *pEList;
+    if( eDest==SRT_Mem || eDest==SRT_Output || eDest==SRT_Coroutine ){
+      ecelFlags = SQLITE_ECEL_DUP;
+    }else{
+      ecelFlags = 0;
+    }
+    if( pSort && hasDistinct==0 && eDest!=SRT_EphemTab && eDest!=SRT_Table ){
+      /* For each expression in p->pEList that is a copy of an expression in
+      ** the ORDER BY clause (pSort->pOrderBy), set the associated
+      ** iOrderByCol value to one more than the index of the ORDER BY
+      ** expression within the sort-key that pushOntoSorter() will generate.
+      ** This allows the p->pEList field to be omitted from the sorted record,
+      ** saving space and CPU cycles.  */
+      ecelFlags |= (SQLITE_ECEL_OMITREF|SQLITE_ECEL_REF);
+
+      for(i=pSort->nOBSat; i<pSort->pOrderBy->nExpr; i++){
+        int j;
+        if( (j = pSort->pOrderBy->a[i].u.x.iOrderByCol)>0 ){
+          p->pEList->a[j-1].u.x.iOrderByCol = i+1-pSort->nOBSat;
+        }
+      }
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+      selectExprDefer(pParse, pSort, p->pEList, &pExtra);
+      if( pExtra && pParse->db->mallocFailed==0 ){
+        /* If there are any extra PK columns to add to the sorter records,
+        ** allocate extra memory cells and adjust the OpenEphemeral
+        ** instruction to account for the larger records. This is only
+        ** required if there are one or more WITHOUT ROWID tables with
+        ** composite primary keys in the SortCtx.aDefer[] array.  */
+        VdbeOp *pOp = sqlite3VdbeGetOp(v, pSort->addrSortIndex);
+        pOp->p2 += (pExtra->nExpr - pSort->nDefer);
+        pOp->p4.pKeyInfo->nAllField += (pExtra->nExpr - pSort->nDefer);
+        pParse->nMem += pExtra->nExpr;
+      }
+#endif
+
+      /* Adjust nResultCol to account for columns that are omitted
+      ** from the sorter by the optimizations in this branch */
+      pEList = p->pEList;
+      for(i=0; i<pEList->nExpr; i++){
+        if( pEList->a[i].u.x.iOrderByCol>0
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+         || pEList->a[i].fg.bSorterRef
+#endif
+        ){
+          nResultCol--;
+          regOrig = 0;
+        }
+      }
+
+      testcase( regOrig );
+      testcase( eDest==SRT_Set );
+      testcase( eDest==SRT_Mem );
+      testcase( eDest==SRT_Coroutine );
+      testcase( eDest==SRT_Output );
+      assert( eDest==SRT_Set || eDest==SRT_Mem
+           || eDest==SRT_Coroutine || eDest==SRT_Output
+           || eDest==SRT_Upfrom );
+    }
+    sRowLoadInfo.regResult = regResult;
+    sRowLoadInfo.ecelFlags = ecelFlags;
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    sRowLoadInfo.pExtra = pExtra;
+    sRowLoadInfo.regExtraResult = regResult + nResultCol;
+    if( pExtra ) nResultCol += pExtra->nExpr;
+#endif
+    if( p->iLimit
+     && (ecelFlags & SQLITE_ECEL_OMITREF)!=0
+     && nPrefixReg>0
+    ){
+      assert( pSort!=0 );
+      assert( hasDistinct==0 );
+      pSort->pDeferredRowLoad = &sRowLoadInfo;
+      regOrig = 0;
+    }else{
+      innerLoopLoadRow(pParse, p, &sRowLoadInfo);
+    }
+  }
+
+  /* If the DISTINCT keyword was present on the SELECT statement
+  ** and this row has been seen before, then do not make this row
+  ** part of the result.
+  */
+  if( hasDistinct ){
+    int eType = pDistinct->eTnctType;
+    int iTab = pDistinct->tabTnct;
+    assert( nResultCol==p->pEList->nExpr );
+    iTab = codeDistinct(pParse, eType, iTab, iContinue, p->pEList, regResult);
+    fixDistinctOpenEph(pParse, eType, iTab, pDistinct->addrTnct);
+    if( pSort==0 ){
+      codeOffset(v, p->iOffset, iContinue);
+    }
+  }
+
+  switch( eDest ){
+    /* In this mode, write each query result to the key of the temporary
+    ** table iParm.
+    */
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+    case SRT_Union: {
+      int r1;
+      r1 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1);
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, regResult, nResultCol);
+      sqlite3ReleaseTempReg(pParse, r1);
+      break;
+    }
+
+    /* Construct a record from the query result, but instead of
+    ** saving that record, use it as a key to delete elements from
+    ** the temporary table iParm.
+    */
+    case SRT_Except: {
+      sqlite3VdbeAddOp3(v, OP_IdxDelete, iParm, regResult, nResultCol);
+      break;
+    }
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+
+    /* Store the result as data using a unique key.
+    */
+    case SRT_Fifo:
+    case SRT_DistFifo:
+    case SRT_Table:
+    case SRT_EphemTab: {
+      int r1 = sqlite3GetTempRange(pParse, nPrefixReg+1);
+      testcase( eDest==SRT_Table );
+      testcase( eDest==SRT_EphemTab );
+      testcase( eDest==SRT_Fifo );
+      testcase( eDest==SRT_DistFifo );
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1+nPrefixReg);
+#if !defined(SQLITE_ENABLE_NULL_TRIM) && defined(SQLITE_DEBUG)
+      /* A destination of SRT_Table and a non-zero iSDParm2 parameter means
+      ** that this is an "UPDATE ... FROM" on a virtual table or view. In this
+      ** case set the p5 parameter of the OP_MakeRecord to OPFLAG_NOCHNG_MAGIC.
+      ** This does not affect operation in any way - it just allows MakeRecord
+      ** to process OPFLAG_NOCHANGE values without an assert() failing. */
+      if( eDest==SRT_Table && pDest->iSDParm2 ){
+        sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG_MAGIC);
+      }
+#endif
+#ifndef SQLITE_OMIT_CTE
+      if( eDest==SRT_DistFifo ){
+        /* If the destination is DistFifo, then cursor (iParm+1) is open
+        ** on an ephemeral index. If the current row is already present
+        ** in the index, do not write it to the output. If not, add the
+        ** current row to the index and proceed with writing it to the
+        ** output table as well.  */
+        int addr = sqlite3VdbeCurrentAddr(v) + 4;
+        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0);
+        VdbeCoverage(v);
+        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm+1, r1,regResult,nResultCol);
+        assert( pSort==0 );
+      }
+#endif
+      if( pSort ){
+        assert( regResult==regOrig );
+        pushOntoSorter(pParse, pSort, p, r1+nPrefixReg, regOrig, 1, nPrefixReg);
+      }else{
+        int r2 = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
+        sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
+        sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+        sqlite3ReleaseTempReg(pParse, r2);
+      }
+      sqlite3ReleaseTempRange(pParse, r1, nPrefixReg+1);
+      break;
+    }
+
+    case SRT_Upfrom: {
+      if( pSort ){
+        pushOntoSorter(
+            pParse, pSort, p, regResult, regOrig, nResultCol, nPrefixReg);
+      }else{
+        int i2 = pDest->iSDParm2;
+        int r1 = sqlite3GetTempReg(pParse);
+
+        /* If the UPDATE FROM join is an aggregate that matches no rows, it
+        ** might still be trying to return one row, because that is what
+        ** aggregates do.  Don't record that empty row in the output table. */
+        sqlite3VdbeAddOp2(v, OP_IsNull, regResult, iBreak); VdbeCoverage(v);
+
+        sqlite3VdbeAddOp3(v, OP_MakeRecord,
+                          regResult+(i2<0), nResultCol-(i2<0), r1);
+        if( i2<0 ){
+          sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, regResult);
+        }else{
+          sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, regResult, i2);
+        }
+      }
+      break;
+    }
+
+#ifndef SQLITE_OMIT_SUBQUERY
+    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
+    ** then there should be a single item on the stack.  Write this
+    ** item into the set table with bogus data.
+    */
+    case SRT_Set: {
+      if( pSort ){
+        /* At first glance you would think we could optimize out the
+        ** ORDER BY in this case since the order of entries in the set
+        ** does not matter.  But there might be a LIMIT clause, in which
+        ** case the order does matter */
+        pushOntoSorter(
+            pParse, pSort, p, regResult, regOrig, nResultCol, nPrefixReg);
+      }else{
+        int r1 = sqlite3GetTempReg(pParse);
+        assert( sqlite3Strlen30(pDest->zAffSdst)==nResultCol );
+        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult, nResultCol,
+            r1, pDest->zAffSdst, nResultCol);
+        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, regResult, nResultCol);
+        sqlite3ReleaseTempReg(pParse, r1);
+      }
+      break;
+    }
+
+
+    /* If any row exist in the result set, record that fact and abort.
+    */
+    case SRT_Exists: {
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, iParm);
+      /* The LIMIT clause will terminate the loop for us */
+      break;
+    }
+
+    /* If this is a scalar select that is part of an expression, then
+    ** store the results in the appropriate memory cell or array of
+    ** memory cells and break out of the scan loop.
+    */
+    case SRT_Mem: {
+      if( pSort ){
+        assert( nResultCol<=pDest->nSdst );
+        pushOntoSorter(
+            pParse, pSort, p, regResult, regOrig, nResultCol, nPrefixReg);
+      }else{
+        assert( nResultCol==pDest->nSdst );
+        assert( regResult==iParm );
+        /* The LIMIT clause will jump out of the loop for us */
+      }
+      break;
+    }
+#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
+
+    case SRT_Coroutine:       /* Send data to a co-routine */
+    case SRT_Output: {        /* Return the results */
+      testcase( eDest==SRT_Coroutine );
+      testcase( eDest==SRT_Output );
+      if( pSort ){
+        pushOntoSorter(pParse, pSort, p, regResult, regOrig, nResultCol,
+                       nPrefixReg);
+      }else if( eDest==SRT_Coroutine ){
+        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iSDParm);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nResultCol);
+      }
+      break;
+    }
+
+#ifndef SQLITE_OMIT_CTE
+    /* Write the results into a priority queue that is order according to
+    ** pDest->pOrderBy (in pSO).  pDest->iSDParm (in iParm) is the cursor for an
+    ** index with pSO->nExpr+2 columns.  Build a key using pSO for the first
+    ** pSO->nExpr columns, then make sure all keys are unique by adding a
+    ** final OP_Sequence column.  The last column is the record as a blob.
+    */
+    case SRT_DistQueue:
+    case SRT_Queue: {
+      int nKey;
+      int r1, r2, r3;
+      int addrTest = 0;
+      ExprList *pSO;
+      pSO = pDest->pOrderBy;
+      assert( pSO );
+      nKey = pSO->nExpr;
+      r1 = sqlite3GetTempReg(pParse);
+      r2 = sqlite3GetTempRange(pParse, nKey+2);
+      r3 = r2+nKey+1;
+      if( eDest==SRT_DistQueue ){
+        /* If the destination is DistQueue, then cursor (iParm+1) is open
+        ** on a second ephemeral index that holds all values every previously
+        ** added to the queue. */
+        addrTest = sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, 0,
+                                        regResult, nResultCol);
+        VdbeCoverage(v);
+      }
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r3);
+      if( eDest==SRT_DistQueue ){
+        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm+1, r3);
+        sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+      }
+      for(i=0; i<nKey; i++){
+        sqlite3VdbeAddOp2(v, OP_SCopy,
+                          regResult + pSO->a[i].u.x.iOrderByCol - 1,
+                          r2+i);
+      }
+      sqlite3VdbeAddOp2(v, OP_Sequence, iParm, r2+nKey);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, r2, nKey+2, r1);
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, r2, nKey+2);
+      if( addrTest ) sqlite3VdbeJumpHere(v, addrTest);
+      sqlite3ReleaseTempReg(pParse, r1);
+      sqlite3ReleaseTempRange(pParse, r2, nKey+2);
+      break;
+    }
+#endif /* SQLITE_OMIT_CTE */
+
+
+
+#if !defined(SQLITE_OMIT_TRIGGER)
+    /* Discard the results.  This is used for SELECT statements inside
+    ** the body of a TRIGGER.  The purpose of such selects is to call
+    ** user-defined functions that have side effects.  We do not care
+    ** about the actual results of the select.
+    */
+    default: {
+      assert( eDest==SRT_Discard );
+      break;
+    }
+#endif
+  }
+
+  /* Jump to the end of the loop if the LIMIT is reached.  Except, if
+  ** there is a sorter, in which case the sorter has already limited
+  ** the output for us.
+  */
+  if( pSort==0 && p->iLimit ){
+    sqlite3VdbeAddOp2(v, OP_DecrJumpZero, p->iLimit, iBreak); VdbeCoverage(v);
+  }
+}
+
+/*
+** Allocate a KeyInfo object sufficient for an index of N key columns and
+** X extra columns.
+*/
+KeyInfo *sqlite3KeyInfoAlloc(sqlite3 *db, int N, int X){
+  int nExtra = (N+X)*(sizeof(CollSeq*)+1) - sizeof(CollSeq*);
+  KeyInfo *p = sqlite3DbMallocRawNN(db, sizeof(KeyInfo) + nExtra);
+  if( p ){
+    p->aSortFlags = (u8*)&p->aColl[N+X];
+    p->nKeyField = (u16)N;
+    p->nAllField = (u16)(N+X);
+    p->enc = ENC(db);
+    p->db = db;
+    p->nRef = 1;
+    memset(&p[1], 0, nExtra);
+  }else{
+    return (KeyInfo*)sqlite3OomFault(db);
+  }
+  return p;
+}
+
+/*
+** Deallocate a KeyInfo object
+*/
+void sqlite3KeyInfoUnref(KeyInfo *p){
+  if( p ){
+    assert( p->db!=0 );
+    assert( p->nRef>0 );
+    p->nRef--;
+    if( p->nRef==0 ) sqlite3DbNNFreeNN(p->db, p);
+  }
+}
+
+/*
+** Make a new pointer to a KeyInfo object
+*/
+KeyInfo *sqlite3KeyInfoRef(KeyInfo *p){
+  if( p ){
+    assert( p->nRef>0 );
+    p->nRef++;
+  }
+  return p;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Return TRUE if a KeyInfo object can be change.  The KeyInfo object
+** can only be changed if this is just a single reference to the object.
+**
+** This routine is used only inside of assert() statements.
+*/
+int sqlite3KeyInfoIsWriteable(KeyInfo *p){ return p->nRef==1; }
+#endif /* SQLITE_DEBUG */
+
+/*
+** Given an expression list, generate a KeyInfo structure that records
+** the collating sequence for each expression in that expression list.
+**
+** If the ExprList is an ORDER BY or GROUP BY clause then the resulting
+** KeyInfo structure is appropriate for initializing a virtual index to
+** implement that clause.  If the ExprList is the result set of a SELECT
+** then the KeyInfo structure is appropriate for initializing a virtual
+** index to implement a DISTINCT test.
+**
+** Space to hold the KeyInfo structure is obtained from malloc.  The calling
+** function is responsible for seeing that this structure is eventually
+** freed.
+*/
+KeyInfo *sqlite3KeyInfoFromExprList(
+  Parse *pParse,       /* Parsing context */
+  ExprList *pList,     /* Form the KeyInfo object from this ExprList */
+  int iStart,          /* Begin with this column of pList */
+  int nExtra           /* Add this many extra columns to the end */
+){
+  int nExpr;
+  KeyInfo *pInfo;
+  struct ExprList_item *pItem;
+  sqlite3 *db = pParse->db;
+  int i;
+
+  nExpr = pList->nExpr;
+  pInfo = sqlite3KeyInfoAlloc(db, nExpr-iStart, nExtra+1);
+  if( pInfo ){
+    assert( sqlite3KeyInfoIsWriteable(pInfo) );
+    for(i=iStart, pItem=pList->a+iStart; i<nExpr; i++, pItem++){
+      pInfo->aColl[i-iStart] = sqlite3ExprNNCollSeq(pParse, pItem->pExpr);
+      pInfo->aSortFlags[i-iStart] = pItem->fg.sortFlags;
+    }
+  }
+  return pInfo;
+}
+
+/*
+** Name of the connection operator, used for error messages.
+*/
+const char *sqlite3SelectOpName(int id){
+  char *z;
+  switch( id ){
+    case TK_ALL:       z = "UNION ALL";   break;
+    case TK_INTERSECT: z = "INTERSECT";   break;
+    case TK_EXCEPT:    z = "EXCEPT";      break;
+    default:           z = "UNION";       break;
+  }
+  return z;
+}
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** Unless an "EXPLAIN QUERY PLAN" command is being processed, this function
+** is a no-op. Otherwise, it adds a single row of output to the EQP result,
+** where the caption is of the form:
+**
+**   "USE TEMP B-TREE FOR xxx"
+**
+** where xxx is one of "DISTINCT", "ORDER BY" or "GROUP BY". Exactly which
+** is determined by the zUsage argument.
+*/
+static void explainTempTable(Parse *pParse, const char *zUsage){
+  ExplainQueryPlan((pParse, 0, "USE TEMP B-TREE FOR %s", zUsage));
+}
+
+/*
+** Assign expression b to lvalue a. A second, no-op, version of this macro
+** is provided when SQLITE_OMIT_EXPLAIN is defined. This allows the code
+** in sqlite3Select() to assign values to structure member variables that
+** only exist if SQLITE_OMIT_EXPLAIN is not defined without polluting the
+** code with #ifndef directives.
+*/
+# define explainSetInteger(a, b) a = b
+
+#else
+/* No-op versions of the explainXXX() functions and macros. */
+# define explainTempTable(y,z)
+# define explainSetInteger(y,z)
+#endif
+
+
+/*
+** If the inner loop was generated using a non-null pOrderBy argument,
+** then the results were placed in a sorter.  After the loop is terminated
+** we need to run the sorter and output the results.  The following
+** routine generates the code needed to do that.
+*/
+static void generateSortTail(
+  Parse *pParse,    /* Parsing context */
+  Select *p,        /* The SELECT statement */
+  SortCtx *pSort,   /* Information on the ORDER BY clause */
+  int nColumn,      /* Number of columns of data */
+  SelectDest *pDest /* Write the sorted results here */
+){
+  Vdbe *v = pParse->pVdbe;                     /* The prepared statement */
+  int addrBreak = pSort->labelDone;            /* Jump here to exit loop */
+  int addrContinue = sqlite3VdbeMakeLabel(pParse);/* Jump here for next cycle */
+  int addr;                       /* Top of output loop. Jump for Next. */
+  int addrOnce = 0;
+  int iTab;
+  ExprList *pOrderBy = pSort->pOrderBy;
+  int eDest = pDest->eDest;
+  int iParm = pDest->iSDParm;
+  int regRow;
+  int regRowid;
+  int iCol;
+  int nKey;                       /* Number of key columns in sorter record */
+  int iSortTab;                   /* Sorter cursor to read from */
+  int i;
+  int bSeq;                       /* True if sorter record includes seq. no. */
+  int nRefKey = 0;
+  struct ExprList_item *aOutEx = p->pEList->a;
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  int addrExplain;                /* Address of OP_Explain instruction */
+#endif
+
+  ExplainQueryPlan2(addrExplain, (pParse, 0,
+        "USE TEMP B-TREE FOR %sORDER BY", pSort->nOBSat>0?"RIGHT PART OF ":"")
+  );
+  sqlite3VdbeScanStatusRange(v, addrExplain,pSort->addrPush,pSort->addrPushEnd);
+  sqlite3VdbeScanStatusCounters(v, addrExplain, addrExplain, pSort->addrPush);
+
+
+  assert( addrBreak<0 );
+  if( pSort->labelBkOut ){
+    sqlite3VdbeAddOp2(v, OP_Gosub, pSort->regReturn, pSort->labelBkOut);
+    sqlite3VdbeGoto(v, addrBreak);
+    sqlite3VdbeResolveLabel(v, pSort->labelBkOut);
+  }
+
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+  /* Open any cursors needed for sorter-reference expressions */
+  for(i=0; i<pSort->nDefer; i++){
+    Table *pTab = pSort->aDefer[i].pTab;
+    int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+    sqlite3OpenTable(pParse, pSort->aDefer[i].iCsr, iDb, pTab, OP_OpenRead);
+    nRefKey = MAX(nRefKey, pSort->aDefer[i].nKey);
+  }
+#endif
+
+  iTab = pSort->iECursor;
+  if( eDest==SRT_Output || eDest==SRT_Coroutine || eDest==SRT_Mem ){
+    if( eDest==SRT_Mem && p->iOffset ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, pDest->iSdst);
+    }
+    regRowid = 0;
+    regRow = pDest->iSdst;
+  }else{
+    regRowid = sqlite3GetTempReg(pParse);
+    if( eDest==SRT_EphemTab || eDest==SRT_Table ){
+      regRow = sqlite3GetTempReg(pParse);
+      nColumn = 0;
+    }else{
+      regRow = sqlite3GetTempRange(pParse, nColumn);
+    }
+  }
+  nKey = pOrderBy->nExpr - pSort->nOBSat;
+  if( pSort->sortFlags & SORTFLAG_UseSorter ){
+    int regSortOut = ++pParse->nMem;
+    iSortTab = pParse->nTab++;
+    if( pSort->labelBkOut ){
+      addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+    }
+    sqlite3VdbeAddOp3(v, OP_OpenPseudo, iSortTab, regSortOut,
+        nKey+1+nColumn+nRefKey);
+    if( addrOnce ) sqlite3VdbeJumpHere(v, addrOnce);
+    addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
+    VdbeCoverage(v);
+    assert( p->iLimit==0 && p->iOffset==0 );
+    sqlite3VdbeAddOp3(v, OP_SorterData, iTab, regSortOut, iSortTab);
+    bSeq = 0;
+  }else{
+    addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak); VdbeCoverage(v);
+    codeOffset(v, p->iOffset, addrContinue);
+    iSortTab = iTab;
+    bSeq = 1;
+    if( p->iOffset>0 ){
+      sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
+    }
+  }
+  for(i=0, iCol=nKey+bSeq-1; i<nColumn; i++){
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    if( aOutEx[i].fg.bSorterRef ) continue;
+#endif
+    if( aOutEx[i].u.x.iOrderByCol==0 ) iCol++;
+  }
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+  if( pSort->nDefer ){
+    int iKey = iCol+1;
+    int regKey = sqlite3GetTempRange(pParse, nRefKey);
+
+    for(i=0; i<pSort->nDefer; i++){
+      int iCsr = pSort->aDefer[i].iCsr;
+      Table *pTab = pSort->aDefer[i].pTab;
+      int nKey = pSort->aDefer[i].nKey;
+
+      sqlite3VdbeAddOp1(v, OP_NullRow, iCsr);
+      if( HasRowid(pTab) ){
+        sqlite3VdbeAddOp3(v, OP_Column, iSortTab, iKey++, regKey);
+        sqlite3VdbeAddOp3(v, OP_SeekRowid, iCsr,
+            sqlite3VdbeCurrentAddr(v)+1, regKey);
+      }else{
+        int k;
+        int iJmp;
+        assert( sqlite3PrimaryKeyIndex(pTab)->nKeyCol==nKey );
+        for(k=0; k<nKey; k++){
+          sqlite3VdbeAddOp3(v, OP_Column, iSortTab, iKey++, regKey+k);
+        }
+        iJmp = sqlite3VdbeCurrentAddr(v);
+        sqlite3VdbeAddOp4Int(v, OP_SeekGE, iCsr, iJmp+2, regKey, nKey);
+        sqlite3VdbeAddOp4Int(v, OP_IdxLE, iCsr, iJmp+3, regKey, nKey);
+        sqlite3VdbeAddOp1(v, OP_NullRow, iCsr);
+      }
+    }
+    sqlite3ReleaseTempRange(pParse, regKey, nRefKey);
+  }
+#endif
+  for(i=nColumn-1; i>=0; i--){
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    if( aOutEx[i].fg.bSorterRef ){
+      sqlite3ExprCode(pParse, aOutEx[i].pExpr, regRow+i);
+    }else
+#endif
+    {
+      int iRead;
+      if( aOutEx[i].u.x.iOrderByCol ){
+        iRead = aOutEx[i].u.x.iOrderByCol-1;
+      }else{
+        iRead = iCol--;
+      }
+      sqlite3VdbeAddOp3(v, OP_Column, iSortTab, iRead, regRow+i);
+      VdbeComment((v, "%s", aOutEx[i].zEName));
+    }
+  }
+  sqlite3VdbeScanStatusRange(v, addrExplain, addrExplain, -1);
+  switch( eDest ){
+    case SRT_Table:
+    case SRT_EphemTab: {
+      sqlite3VdbeAddOp3(v, OP_Column, iSortTab, nKey+bSeq, regRow);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, regRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, iParm, regRow, regRowid);
+      sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case SRT_Set: {
+      assert( nColumn==sqlite3Strlen30(pDest->zAffSdst) );
+      sqlite3VdbeAddOp4(v, OP_MakeRecord, regRow, nColumn, regRowid,
+                        pDest->zAffSdst, nColumn);
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, regRowid, regRow, nColumn);
+      break;
+    }
+    case SRT_Mem: {
+      /* The LIMIT clause will terminate the loop for us */
+      break;
+    }
+#endif
+    case SRT_Upfrom: {
+      int i2 = pDest->iSDParm2;
+      int r1 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord,regRow+(i2<0),nColumn-(i2<0),r1);
+      if( i2<0 ){
+        sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, regRow);
+      }else{
+        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, regRow, i2);
+      }
+      break;
+    }
+    default: {
+      assert( eDest==SRT_Output || eDest==SRT_Coroutine );
+      testcase( eDest==SRT_Output );
+      testcase( eDest==SRT_Coroutine );
+      if( eDest==SRT_Output ){
+        sqlite3VdbeAddOp2(v, OP_ResultRow, pDest->iSdst, nColumn);
+      }else{
+        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iSDParm);
+      }
+      break;
+    }
+  }
+  if( regRowid ){
+    if( eDest==SRT_Set ){
+      sqlite3ReleaseTempRange(pParse, regRow, nColumn);
+    }else{
+      sqlite3ReleaseTempReg(pParse, regRow);
+    }
+    sqlite3ReleaseTempReg(pParse, regRowid);
+  }
+  /* The bottom of the loop
+  */
+  sqlite3VdbeResolveLabel(v, addrContinue);
+  if( pSort->sortFlags & SORTFLAG_UseSorter ){
+    sqlite3VdbeAddOp2(v, OP_SorterNext, iTab, addr); VdbeCoverage(v);
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Next, iTab, addr); VdbeCoverage(v);
+  }
+  sqlite3VdbeScanStatusRange(v, addrExplain, sqlite3VdbeCurrentAddr(v)-1, -1);
+  if( pSort->regReturn ) sqlite3VdbeAddOp1(v, OP_Return, pSort->regReturn);
+  sqlite3VdbeResolveLabel(v, addrBreak);
+}
+
+/*
+** Return a pointer to a string containing the 'declaration type' of the
+** expression pExpr. The string may be treated as static by the caller.
+**
+** The declaration type is the exact datatype definition extracted from the
+** original CREATE TABLE statement if the expression is a column. The
+** declaration type for a ROWID field is INTEGER. Exactly when an expression
+** is considered a column can be complex in the presence of subqueries. The
+** result-set expression in all of the following SELECT statements is
+** considered a column by this function.
+**
+**   SELECT col FROM tbl;
+**   SELECT (SELECT col FROM tbl;
+**   SELECT (SELECT col FROM tbl);
+**   SELECT abc FROM (SELECT col AS abc FROM tbl);
+**
+** The declaration type for any expression other than a column is NULL.
+**
+** This routine has either 3 or 6 parameters depending on whether or not
+** the SQLITE_ENABLE_COLUMN_METADATA compile-time option is used.
+*/
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+# define columnType(A,B,C,D,E) columnTypeImpl(A,B,C,D,E)
+#else /* if !defined(SQLITE_ENABLE_COLUMN_METADATA) */
+# define columnType(A,B,C,D,E) columnTypeImpl(A,B)
+#endif
+static const char *columnTypeImpl(
+  NameContext *pNC,
+#ifndef SQLITE_ENABLE_COLUMN_METADATA
+  Expr *pExpr
+#else
+  Expr *pExpr,
+  const char **pzOrigDb,
+  const char **pzOrigTab,
+  const char **pzOrigCol
+#endif
+){
+  char const *zType = 0;
+  int j;
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  char const *zOrigDb = 0;
+  char const *zOrigTab = 0;
+  char const *zOrigCol = 0;
+#endif
+
+  assert( pExpr!=0 );
+  assert( pNC->pSrcList!=0 );
+  switch( pExpr->op ){
+    case TK_COLUMN: {
+      /* The expression is a column. Locate the table the column is being
+      ** extracted from in NameContext.pSrcList. This table may be real
+      ** database table or a subquery.
+      */
+      Table *pTab = 0;            /* Table structure column is extracted from */
+      Select *pS = 0;             /* Select the column is extracted from */
+      int iCol = pExpr->iColumn;  /* Index of column in pTab */
+      while( pNC && !pTab ){
+        SrcList *pTabList = pNC->pSrcList;
+        for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
+        if( j<pTabList->nSrc ){
+          pTab = pTabList->a[j].pTab;
+          pS = pTabList->a[j].pSelect;
+        }else{
+          pNC = pNC->pNext;
+        }
+      }
+
+      if( pTab==0 ){
+        /* At one time, code such as "SELECT new.x" within a trigger would
+        ** cause this condition to run.  Since then, we have restructured how
+        ** trigger code is generated and so this condition is no longer
+        ** possible. However, it can still be true for statements like
+        ** the following:
+        **
+        **   CREATE TABLE t1(col INTEGER);
+        **   SELECT (SELECT t1.col) FROM FROM t1;
+        **
+        ** when columnType() is called on the expression "t1.col" in the
+        ** sub-select. In this case, set the column type to NULL, even
+        ** though it should really be "INTEGER".
+        **
+        ** This is not a problem, as the column type of "t1.col" is never
+        ** used. When columnType() is called on the expression
+        ** "(SELECT t1.col)", the correct type is returned (see the TK_SELECT
+        ** branch below.  */
+        break;
+      }
+
+      assert( pTab && ExprUseYTab(pExpr) && pExpr->y.pTab==pTab );
+      if( pS ){
+        /* The "table" is actually a sub-select or a view in the FROM clause
+        ** of the SELECT statement. Return the declaration type and origin
+        ** data for the result-set column of the sub-select.
+        */
+        if( iCol<pS->pEList->nExpr
+#ifdef SQLITE_ALLOW_ROWID_IN_VIEW
+         && iCol>=0
+#else
+         && ALWAYS(iCol>=0)
+#endif
+        ){
+          /* If iCol is less than zero, then the expression requests the
+          ** rowid of the sub-select or view. This expression is legal (see
+          ** test case misc2.2.2) - it always evaluates to NULL.
+          */
+          NameContext sNC;
+          Expr *p = pS->pEList->a[iCol].pExpr;
+          sNC.pSrcList = pS->pSrc;
+          sNC.pNext = pNC;
+          sNC.pParse = pNC->pParse;
+          zType = columnType(&sNC, p,&zOrigDb,&zOrigTab,&zOrigCol);
+        }
+      }else{
+        /* A real table or a CTE table */
+        assert( !pS );
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+        if( iCol<0 ) iCol = pTab->iPKey;
+        assert( iCol==XN_ROWID || (iCol>=0 && iCol<pTab->nCol) );
+        if( iCol<0 ){
+          zType = "INTEGER";
+          zOrigCol = "rowid";
+        }else{
+          zOrigCol = pTab->aCol[iCol].zCnName;
+          zType = sqlite3ColumnType(&pTab->aCol[iCol],0);
+        }
+        zOrigTab = pTab->zName;
+        if( pNC->pParse && pTab->pSchema ){
+          int iDb = sqlite3SchemaToIndex(pNC->pParse->db, pTab->pSchema);
+          zOrigDb = pNC->pParse->db->aDb[iDb].zDbSName;
+        }
+#else
+        assert( iCol==XN_ROWID || (iCol>=0 && iCol<pTab->nCol) );
+        if( iCol<0 ){
+          zType = "INTEGER";
+        }else{
+          zType = sqlite3ColumnType(&pTab->aCol[iCol],0);
+        }
+#endif
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_SELECT: {
+      /* The expression is a sub-select. Return the declaration type and
+      ** origin info for the single column in the result set of the SELECT
+      ** statement.
+      */
+      NameContext sNC;
+      Select *pS;
+      Expr *p;
+      assert( ExprUseXSelect(pExpr) );
+      pS = pExpr->x.pSelect;
+      p = pS->pEList->a[0].pExpr;
+      sNC.pSrcList = pS->pSrc;
+      sNC.pNext = pNC;
+      sNC.pParse = pNC->pParse;
+      zType = columnType(&sNC, p, &zOrigDb, &zOrigTab, &zOrigCol);
+      break;
+    }
+#endif
+  }
+
+#ifdef SQLITE_ENABLE_COLUMN_METADATA 
+  if( pzOrigDb ){
+    assert( pzOrigTab && pzOrigCol );
+    *pzOrigDb = zOrigDb;
+    *pzOrigTab = zOrigTab;
+    *pzOrigCol = zOrigCol;
+  }
+#endif
+  return zType;
+}
+
+/*
+** Generate code that will tell the VDBE the declaration types of columns
+** in the result set.
+*/
+static void generateColumnTypes(
+  Parse *pParse,      /* Parser context */
+  SrcList *pTabList,  /* List of tables */
+  ExprList *pEList    /* Expressions defining the result set */
+){
+#ifndef SQLITE_OMIT_DECLTYPE
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  NameContext sNC;
+  sNC.pSrcList = pTabList;
+  sNC.pParse = pParse;
+  sNC.pNext = 0;
+  for(i=0; i<pEList->nExpr; i++){
+    Expr *p = pEList->a[i].pExpr;
+    const char *zType;
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+    const char *zOrigDb = 0;
+    const char *zOrigTab = 0;
+    const char *zOrigCol = 0;
+    zType = columnType(&sNC, p, &zOrigDb, &zOrigTab, &zOrigCol);
+
+    /* The vdbe must make its own copy of the column-type and other
+    ** column specific strings, in case the schema is reset before this
+    ** virtual machine is deleted.
+    */
+    sqlite3VdbeSetColName(v, i, COLNAME_DATABASE, zOrigDb, SQLITE_TRANSIENT);
+    sqlite3VdbeSetColName(v, i, COLNAME_TABLE, zOrigTab, SQLITE_TRANSIENT);
+    sqlite3VdbeSetColName(v, i, COLNAME_COLUMN, zOrigCol, SQLITE_TRANSIENT);
+#else
+    zType = columnType(&sNC, p, 0, 0, 0);
+#endif
+    sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, SQLITE_TRANSIENT);
+  }
+#endif /* !defined(SQLITE_OMIT_DECLTYPE) */
+}
+
+
+/*
+** Compute the column names for a SELECT statement.
+**
+** The only guarantee that SQLite makes about column names is that if the
+** column has an AS clause assigning it a name, that will be the name used.
+** That is the only documented guarantee.  However, countless applications
+** developed over the years have made baseless assumptions about column names
+** and will break if those assumptions changes.  Hence, use extreme caution
+** when modifying this routine to avoid breaking legacy.
+**
+** See Also: sqlite3ColumnsFromExprList()
+**
+** The PRAGMA short_column_names and PRAGMA full_column_names settings are
+** deprecated.  The default setting is short=ON, full=OFF.  99.9% of all
+** applications should operate this way.  Nevertheless, we need to support the
+** other modes for legacy:
+**
+**    short=OFF, full=OFF:      Column name is the text of the expression has it
+**                              originally appears in the SELECT statement.  In
+**                              other words, the zSpan of the result expression.
+**
+**    short=ON, full=OFF:       (This is the default setting).  If the result
+**                              refers directly to a table column, then the
+**                              result column name is just the table column
+**                              name: COLUMN.  Otherwise use zSpan.
+**
+**    full=ON, short=ANY:       If the result refers directly to a table column,
+**                              then the result column name with the table name
+**                              prefix, ex: TABLE.COLUMN.  Otherwise use zSpan.
+*/
+void sqlite3GenerateColumnNames(
+  Parse *pParse,      /* Parser context */
+  Select *pSelect     /* Generate column names for this SELECT statement */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  Table *pTab;
+  SrcList *pTabList;
+  ExprList *pEList;
+  sqlite3 *db = pParse->db;
+  int fullName;    /* TABLE.COLUMN if no AS clause and is a direct table ref */
+  int srcName;     /* COLUMN or TABLE.COLUMN if no AS clause and is direct */
+
+  if( pParse->colNamesSet ) return;
+  /* Column names are determined by the left-most term of a compound select */
+  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
+  TREETRACE(0x80,pParse,pSelect,("generating column names\n"));
+  pTabList = pSelect->pSrc;
+  pEList = pSelect->pEList;
+  assert( v!=0 );
+  assert( pTabList!=0 );
+  pParse->colNamesSet = 1;
+  fullName = (db->flags & SQLITE_FullColNames)!=0;
+  srcName = (db->flags & SQLITE_ShortColNames)!=0 || fullName;
+  sqlite3VdbeSetNumCols(v, pEList->nExpr);
+  for(i=0; i<pEList->nExpr; i++){
+    Expr *p = pEList->a[i].pExpr;
+
+    assert( p!=0 );
+    assert( p->op!=TK_AGG_COLUMN );  /* Agg processing has not run yet */
+    assert( p->op!=TK_COLUMN
+        || (ExprUseYTab(p) && p->y.pTab!=0) ); /* Covering idx not yet coded */
+    if( pEList->a[i].zEName && pEList->a[i].fg.eEName==ENAME_NAME ){
+      /* An AS clause always takes first priority */
+      char *zName = pEList->a[i].zEName;
+      sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT);
+    }else if( srcName && p->op==TK_COLUMN ){
+      char *zCol;
+      int iCol = p->iColumn;
+      pTab = p->y.pTab;
+      assert( pTab!=0 );
+      if( iCol<0 ) iCol = pTab->iPKey;
+      assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
+      if( iCol<0 ){
+        zCol = "rowid";
+      }else{
+        zCol = pTab->aCol[iCol].zCnName;
+      }
+      if( fullName ){
+        char *zName = 0;
+        zName = sqlite3MPrintf(db, "%s.%s", pTab->zName, zCol);
+        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_DYNAMIC);
+      }else{
+        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, SQLITE_TRANSIENT);
+      }
+    }else{
+      const char *z = pEList->a[i].zEName;
+      z = z==0 ? sqlite3MPrintf(db, "column%d", i+1) : sqlite3DbStrDup(db, z);
+      sqlite3VdbeSetColName(v, i, COLNAME_NAME, z, SQLITE_DYNAMIC);
+    }
+  }
+  generateColumnTypes(pParse, pTabList, pEList);
+}
+
+/*
+** Given an expression list (which is really the list of expressions
+** that form the result set of a SELECT statement) compute appropriate
+** column names for a table that would hold the expression list.
+**
+** All column names will be unique.
+**
+** Only the column names are computed.  Column.zType, Column.zColl,
+** and other fields of Column are zeroed.
+**
+** Return SQLITE_OK on success.  If a memory allocation error occurs,
+** store NULL in *paCol and 0 in *pnCol and return SQLITE_NOMEM.
+**
+** The only guarantee that SQLite makes about column names is that if the
+** column has an AS clause assigning it a name, that will be the name used.
+** That is the only documented guarantee.  However, countless applications
+** developed over the years have made baseless assumptions about column names
+** and will break if those assumptions changes.  Hence, use extreme caution
+** when modifying this routine to avoid breaking legacy.
+**
+** See Also: sqlite3GenerateColumnNames()
+*/
+int sqlite3ColumnsFromExprList(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pEList,       /* Expr list from which to derive column names */
+  i16 *pnCol,             /* Write the number of columns here */
+  Column **paCol          /* Write the new column list here */
+){
+  sqlite3 *db = pParse->db;   /* Database connection */
+  int i, j;                   /* Loop counters */
+  u32 cnt;                    /* Index added to make the name unique */
+  Column *aCol, *pCol;        /* For looping over result columns */
+  int nCol;                   /* Number of columns in the result set */
+  char *zName;                /* Column name */
+  int nName;                  /* Size of name in zName[] */
+  Hash ht;                    /* Hash table of column names */
+  Table *pTab;
+
+  sqlite3HashInit(&ht);
+  if( pEList ){
+    nCol = pEList->nExpr;
+    aCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol);
+    testcase( aCol==0 );
+    if( NEVER(nCol>32767) ) nCol = 32767;
+  }else{
+    nCol = 0;
+    aCol = 0;
+  }
+  assert( nCol==(i16)nCol );
+  *pnCol = nCol;
+  *paCol = aCol;
+
+  for(i=0, pCol=aCol; i<nCol && !pParse->nErr; i++, pCol++){
+    struct ExprList_item *pX = &pEList->a[i];
+    struct ExprList_item *pCollide;
+    /* Get an appropriate name for the column
+    */
+    if( (zName = pX->zEName)!=0 && pX->fg.eEName==ENAME_NAME ){
+      /* If the column contains an "AS <name>" phrase, use <name> as the name */
+    }else{
+      Expr *pColExpr = sqlite3ExprSkipCollateAndLikely(pX->pExpr);
+      while( ALWAYS(pColExpr!=0) && pColExpr->op==TK_DOT ){
+        pColExpr = pColExpr->pRight;
+        assert( pColExpr!=0 );
+      }
+      if( pColExpr->op==TK_COLUMN
+       && ALWAYS( ExprUseYTab(pColExpr) )
+       && ALWAYS( pColExpr->y.pTab!=0 )
+      ){
+        /* For columns use the column name name */
+        int iCol = pColExpr->iColumn;
+        pTab = pColExpr->y.pTab;
+        if( iCol<0 ) iCol = pTab->iPKey;
+        zName = iCol>=0 ? pTab->aCol[iCol].zCnName : "rowid";
+      }else if( pColExpr->op==TK_ID ){
+        assert( !ExprHasProperty(pColExpr, EP_IntValue) );
+        zName = pColExpr->u.zToken;
+      }else{
+        /* Use the original text of the column expression as its name */
+        assert( zName==pX->zEName );  /* pointer comparison intended */
+      }
+    }
+    if( zName && !sqlite3IsTrueOrFalse(zName) ){
+      zName = sqlite3DbStrDup(db, zName);
+    }else{
+      zName = sqlite3MPrintf(db,"column%d",i+1);
+    }
+
+    /* Make sure the column name is unique.  If the name is not unique,
+    ** append an integer to the name so that it becomes unique.
+    */
+    cnt = 0;
+    while( zName && (pCollide = sqlite3HashFind(&ht, zName))!=0 ){
+      if( pCollide->fg.bUsingTerm ){
+        pCol->colFlags |= COLFLAG_NOEXPAND;
+      }
+      nName = sqlite3Strlen30(zName);
+      if( nName>0 ){
+        for(j=nName-1; j>0 && sqlite3Isdigit(zName[j]); j--){}
+        if( zName[j]==':' ) nName = j;
+      }
+      zName = sqlite3MPrintf(db, "%.*z:%u", nName, zName, ++cnt);
+      sqlite3ProgressCheck(pParse);
+      if( cnt>3 ){
+        sqlite3_randomness(sizeof(cnt), &cnt);
+      }
+    }
+    pCol->zCnName = zName;
+    pCol->hName = sqlite3StrIHash(zName);
+    if( pX->fg.bNoExpand ){
+      pCol->colFlags |= COLFLAG_NOEXPAND;
+    }
+    sqlite3ColumnPropertiesFromName(0, pCol);
+    if( zName && sqlite3HashInsert(&ht, zName, pX)==pX ){
+      sqlite3OomFault(db);
+    }
+  }
+  sqlite3HashClear(&ht);
+  if( pParse->nErr ){
+    for(j=0; j<i; j++){
+      sqlite3DbFree(db, aCol[j].zCnName);
+    }
+    sqlite3DbFree(db, aCol);
+    *paCol = 0;
+    *pnCol = 0;
+    return pParse->rc;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** pTab is a transient Table object that represents a subquery of some
+** kind (maybe a parenthesized subquery in the FROM clause of a larger
+** query, or a VIEW, or a CTE).  This routine computes type information
+** for that Table object based on the Select object that implements the
+** subquery.  For the purposes of this routine, "type information" means:
+**
+**    *   The datatype name, as it might appear in a CREATE TABLE statement
+**    *   Which collating sequence to use for the column
+**    *   The affinity of the column
+*/
+void sqlite3SubqueryColumnTypes(
+  Parse *pParse,      /* Parsing contexts */
+  Table *pTab,        /* Add column type information to this table */
+  Select *pSelect,    /* SELECT used to determine types and collations */
+  char aff            /* Default affinity. */
+){
+  sqlite3 *db = pParse->db;
+  Column *pCol;
+  CollSeq *pColl;
+  int i,j;
+  Expr *p;
+  struct ExprList_item *a;
+  NameContext sNC;
+
+  assert( pSelect!=0 );
+  testcase( (pSelect->selFlags & SF_Resolved)==0 );
+  assert( (pSelect->selFlags & SF_Resolved)!=0 || IN_RENAME_OBJECT );
+  assert( pTab->nCol==pSelect->pEList->nExpr || pParse->nErr>0 );
+  assert( aff==SQLITE_AFF_NONE || aff==SQLITE_AFF_BLOB );
+  if( db->mallocFailed || IN_RENAME_OBJECT ) return;
+  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
+  a = pSelect->pEList->a;
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pSrcList = pSelect->pSrc;
+  for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
+    const char *zType;
+    i64 n;
+    pTab->tabFlags |= (pCol->colFlags & COLFLAG_NOINSERT);
+    p = a[i].pExpr;
+    /* pCol->szEst = ... // Column size est for SELECT tables never used */
+    pCol->affinity = sqlite3ExprAffinity(p);
+    if( pCol->affinity<=SQLITE_AFF_NONE ){
+      pCol->affinity = aff;
+    }
+    if( pCol->affinity>=SQLITE_AFF_TEXT && pSelect->pNext ){
+      int m = 0;
+      Select *pS2;
+      for(m=0, pS2=pSelect->pNext; pS2; pS2=pS2->pNext){
+        m |= sqlite3ExprDataType(pS2->pEList->a[i].pExpr);
+      }
+      if( pCol->affinity==SQLITE_AFF_TEXT && (m&0x01)!=0 ){
+        pCol->affinity = SQLITE_AFF_BLOB;
+      }else
+      if( pCol->affinity>=SQLITE_AFF_NUMERIC && (m&0x02)!=0 ){
+        pCol->affinity = SQLITE_AFF_BLOB;
+      }
+      if( pCol->affinity>=SQLITE_AFF_NUMERIC && p->op==TK_CAST ){
+        pCol->affinity = SQLITE_AFF_FLEXNUM;
+      }
+    }
+    zType = columnType(&sNC, p, 0, 0, 0);
+    if( zType==0 || pCol->affinity!=sqlite3AffinityType(zType, 0) ){
+      if( pCol->affinity==SQLITE_AFF_NUMERIC
+       || pCol->affinity==SQLITE_AFF_FLEXNUM
+      ){
+        zType = "NUM";
+      }else{
+        zType = 0;
+        for(j=1; j<SQLITE_N_STDTYPE; j++){
+          if( sqlite3StdTypeAffinity[j]==pCol->affinity ){
+            zType = sqlite3StdType[j];
+            break;
+          }
+        }
+      }
+    }
+    if( zType ){
+      i64 m = sqlite3Strlen30(zType);
+      n = sqlite3Strlen30(pCol->zCnName);
+      pCol->zCnName = sqlite3DbReallocOrFree(db, pCol->zCnName, n+m+2);
+      pCol->colFlags &= ~(COLFLAG_HASTYPE|COLFLAG_HASCOLL);
+      if( pCol->zCnName ){
+        memcpy(&pCol->zCnName[n+1], zType, m+1);
+        pCol->colFlags |= COLFLAG_HASTYPE;
+      }
+    }
+    pColl = sqlite3ExprCollSeq(pParse, p);
+    if( pColl ){
+      assert( pTab->pIndex==0 );
+      sqlite3ColumnSetColl(db, pCol, pColl->zName);
+    }
+  }
+  pTab->szTabRow = 1; /* Any non-zero value works */
+}
+
+/*
+** Given a SELECT statement, generate a Table structure that describes
+** the result set of that SELECT.
+*/
+Table *sqlite3ResultSetOfSelect(Parse *pParse, Select *pSelect, char aff){
+  Table *pTab;
+  sqlite3 *db = pParse->db;
+  u64 savedFlags;
+
+  savedFlags = db->flags;
+  db->flags &= ~(u64)SQLITE_FullColNames;
+  db->flags |= SQLITE_ShortColNames;
+  sqlite3SelectPrep(pParse, pSelect, 0);
+  db->flags = savedFlags;
+  if( pParse->nErr ) return 0;
+  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
+  pTab = sqlite3DbMallocZero(db, sizeof(Table) );
+  if( pTab==0 ){
+    return 0;
+  }
+  pTab->nTabRef = 1;
+  pTab->zName = 0;
+  pTab->nRowLogEst = 200; assert( 200==sqlite3LogEst(1048576) );
+  sqlite3ColumnsFromExprList(pParse, pSelect->pEList, &pTab->nCol, &pTab->aCol);
+  sqlite3SubqueryColumnTypes(pParse, pTab, pSelect, aff);
+  pTab->iPKey = -1;
+  if( db->mallocFailed ){
+    sqlite3DeleteTable(db, pTab);
+    return 0;
+  }
+  return pTab;
+}
+
+/*
+** Get a VDBE for the given parser context.  Create a new one if necessary.
+** If an error occurs, return NULL and leave a message in pParse.
+*/
+Vdbe *sqlite3GetVdbe(Parse *pParse){
+  if( pParse->pVdbe ){
+    return pParse->pVdbe;
+  }
+  if( pParse->pToplevel==0
+   && OptimizationEnabled(pParse->db,SQLITE_FactorOutConst)
+  ){
+    pParse->okConstFactor = 1;
+  }
+  return sqlite3VdbeCreate(pParse);
+}
+
+
+/*
+** Compute the iLimit and iOffset fields of the SELECT based on the
+** pLimit expressions.  pLimit->pLeft and pLimit->pRight hold the expressions
+** that appear in the original SQL statement after the LIMIT and OFFSET
+** keywords.  Or NULL if those keywords are omitted. iLimit and iOffset
+** are the integer memory register numbers for counters used to compute
+** the limit and offset.  If there is no limit and/or offset, then
+** iLimit and iOffset are negative.
+**
+** This routine changes the values of iLimit and iOffset only if
+** a limit or offset is defined by pLimit->pLeft and pLimit->pRight.  iLimit
+** and iOffset should have been preset to appropriate default values (zero)
+** prior to calling this routine.
+**
+** The iOffset register (if it exists) is initialized to the value
+** of the OFFSET.  The iLimit register is initialized to LIMIT.  Register
+** iOffset+1 is initialized to LIMIT+OFFSET.
+**
+** Only if pLimit->pLeft!=0 do the limit registers get
+** redefined.  The UNION ALL operator uses this property to force
+** the reuse of the same limit and offset registers across multiple
+** SELECT statements.
+*/
+static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
+  Vdbe *v = 0;
+  int iLimit = 0;
+  int iOffset;
+  int n;
+  Expr *pLimit = p->pLimit;
+
+  if( p->iLimit ) return;
+
+  /*
+  ** "LIMIT -1" always shows all rows.  There is some
+  ** controversy about what the correct behavior should be.
+  ** The current implementation interprets "LIMIT 0" to mean
+  ** no rows.
+  */
+  if( pLimit ){
+    assert( pLimit->op==TK_LIMIT );
+    assert( pLimit->pLeft!=0 );
+    p->iLimit = iLimit = ++pParse->nMem;
+    v = sqlite3GetVdbe(pParse);
+    assert( v!=0 );
+    if( sqlite3ExprIsInteger(pLimit->pLeft, &n) ){
+      sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
+      VdbeComment((v, "LIMIT counter"));
+      if( n==0 ){
+        sqlite3VdbeGoto(v, iBreak);
+      }else if( n>=0 && p->nSelectRow>sqlite3LogEst((u64)n) ){
+        p->nSelectRow = sqlite3LogEst((u64)n);
+        p->selFlags |= SF_FixedLimit;
+      }
+    }else{
+      sqlite3ExprCode(pParse, pLimit->pLeft, iLimit);
+      sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit); VdbeCoverage(v);
+      VdbeComment((v, "LIMIT counter"));
+      sqlite3VdbeAddOp2(v, OP_IfNot, iLimit, iBreak); VdbeCoverage(v);
+    }
+    if( pLimit->pRight ){
+      p->iOffset = iOffset = ++pParse->nMem;
+      pParse->nMem++;   /* Allocate an extra register for limit+offset */
+      sqlite3ExprCode(pParse, pLimit->pRight, iOffset);
+      sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset); VdbeCoverage(v);
+      VdbeComment((v, "OFFSET counter"));
+      sqlite3VdbeAddOp3(v, OP_OffsetLimit, iLimit, iOffset+1, iOffset);
+      VdbeComment((v, "LIMIT+OFFSET"));
+    }
+  }
+}
+
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/*
+** Return the appropriate collating sequence for the iCol-th column of
+** the result set for the compound-select statement "p".  Return NULL if
+** the column has no default collating sequence.
+**
+** The collating sequence for the compound select is taken from the
+** left-most term of the select that has a collating sequence.
+*/
+static CollSeq *multiSelectCollSeq(Parse *pParse, Select *p, int iCol){
+  CollSeq *pRet;
+  if( p->pPrior ){
+    pRet = multiSelectCollSeq(pParse, p->pPrior, iCol);
+  }else{
+    pRet = 0;
+  }
+  assert( iCol>=0 );
+  /* iCol must be less than p->pEList->nExpr.  Otherwise an error would
+  ** have been thrown during name resolution and we would not have gotten
+  ** this far */
+  if( pRet==0 && ALWAYS(iCol<p->pEList->nExpr) ){
+    pRet = sqlite3ExprCollSeq(pParse, p->pEList->a[iCol].pExpr);
+  }
+  return pRet;
+}
+
+/*
+** The select statement passed as the second parameter is a compound SELECT
+** with an ORDER BY clause. This function allocates and returns a KeyInfo
+** structure suitable for implementing the ORDER BY.
+**
+** Space to hold the KeyInfo structure is obtained from malloc. The calling
+** function is responsible for ensuring that this structure is eventually
+** freed.
+*/
+static KeyInfo *multiSelectOrderByKeyInfo(Parse *pParse, Select *p, int nExtra){
+  ExprList *pOrderBy = p->pOrderBy;
+  int nOrderBy = ALWAYS(pOrderBy!=0) ? pOrderBy->nExpr : 0;
+  sqlite3 *db = pParse->db;
+  KeyInfo *pRet = sqlite3KeyInfoAlloc(db, nOrderBy+nExtra, 1);
+  if( pRet ){
+    int i;
+    for(i=0; i<nOrderBy; i++){
+      struct ExprList_item *pItem = &pOrderBy->a[i];
+      Expr *pTerm = pItem->pExpr;
+      CollSeq *pColl;
+
+      if( pTerm->flags & EP_Collate ){
+        pColl = sqlite3ExprCollSeq(pParse, pTerm);
+      }else{
+        pColl = multiSelectCollSeq(pParse, p, pItem->u.x.iOrderByCol-1);
+        if( pColl==0 ) pColl = db->pDfltColl;
+        pOrderBy->a[i].pExpr =
+          sqlite3ExprAddCollateString(pParse, pTerm, pColl->zName);
+      }
+      assert( sqlite3KeyInfoIsWriteable(pRet) );
+      pRet->aColl[i] = pColl;
+      pRet->aSortFlags[i] = pOrderBy->a[i].fg.sortFlags;
+    }
+  }
+
+  return pRet;
+}
+
+#ifndef SQLITE_OMIT_CTE
+/*
+** This routine generates VDBE code to compute the content of a WITH RECURSIVE
+** query of the form:
+**
+**   <recursive-table> AS (<setup-query> UNION [ALL] <recursive-query>)
+**                         \___________/             \_______________/
+**                           p->pPrior                      p
+**
+**
+** There is exactly one reference to the recursive-table in the FROM clause
+** of recursive-query, marked with the SrcList->a[].fg.isRecursive flag.
+**
+** The setup-query runs once to generate an initial set of rows that go
+** into a Queue table.  Rows are extracted from the Queue table one by
+** one.  Each row extracted from Queue is output to pDest.  Then the single
+** extracted row (now in the iCurrent table) becomes the content of the
+** recursive-table for a recursive-query run.  The output of the recursive-query
+** is added back into the Queue table.  Then another row is extracted from Queue
+** and the iteration continues until the Queue table is empty.
+**
+** If the compound query operator is UNION then no duplicate rows are ever
+** inserted into the Queue table.  The iDistinct table keeps a copy of all rows
+** that have ever been inserted into Queue and causes duplicates to be
+** discarded.  If the operator is UNION ALL, then duplicates are allowed.
+**
+** If the query has an ORDER BY, then entries in the Queue table are kept in
+** ORDER BY order and the first entry is extracted for each cycle.  Without
+** an ORDER BY, the Queue table is just a FIFO.
+**
+** If a LIMIT clause is provided, then the iteration stops after LIMIT rows
+** have been output to pDest.  A LIMIT of zero means to output no rows and a
+** negative LIMIT means to output all rows.  If there is also an OFFSET clause
+** with a positive value, then the first OFFSET outputs are discarded rather
+** than being sent to pDest.  The LIMIT count does not begin until after OFFSET
+** rows have been skipped.
+*/
+static void generateWithRecursiveQuery(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The recursive SELECT to be coded */
+  SelectDest *pDest     /* What to do with query results */
+){
+  SrcList *pSrc = p->pSrc;      /* The FROM clause of the recursive query */
+  int nCol = p->pEList->nExpr;  /* Number of columns in the recursive table */
+  Vdbe *v = pParse->pVdbe;      /* The prepared statement under construction */
+  Select *pSetup;               /* The setup query */
+  Select *pFirstRec;            /* Left-most recursive term */
+  int addrTop;                  /* Top of the loop */
+  int addrCont, addrBreak;      /* CONTINUE and BREAK addresses */
+  int iCurrent = 0;             /* The Current table */
+  int regCurrent;               /* Register holding Current table */
+  int iQueue;                   /* The Queue table */
+  int iDistinct = 0;            /* To ensure unique results if UNION */
+  int eDest = SRT_Fifo;         /* How to write to Queue */
+  SelectDest destQueue;         /* SelectDest targeting the Queue table */
+  int i;                        /* Loop counter */
+  int rc;                       /* Result code */
+  ExprList *pOrderBy;           /* The ORDER BY clause */
+  Expr *pLimit;                 /* Saved LIMIT and OFFSET */
+  int regLimit, regOffset;      /* Registers used by LIMIT and OFFSET */
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( p->pWin ){
+    sqlite3ErrorMsg(pParse, "cannot use window functions in recursive queries");
+    return;
+  }
+#endif
+
+  /* Obtain authorization to do a recursive query */
+  if( sqlite3AuthCheck(pParse, SQLITE_RECURSIVE, 0, 0, 0) ) return;
+
+  /* Process the LIMIT and OFFSET clauses, if they exist */
+  addrBreak = sqlite3VdbeMakeLabel(pParse);
+  p->nSelectRow = 320;  /* 4 billion rows */
+  computeLimitRegisters(pParse, p, addrBreak);
+  pLimit = p->pLimit;
+  regLimit = p->iLimit;
+  regOffset = p->iOffset;
+  p->pLimit = 0;
+  p->iLimit = p->iOffset = 0;
+  pOrderBy = p->pOrderBy;
+
+  /* Locate the cursor number of the Current table */
+  for(i=0; ALWAYS(i<pSrc->nSrc); i++){
+    if( pSrc->a[i].fg.isRecursive ){
+      iCurrent = pSrc->a[i].iCursor;
+      break;
+    }
+  }
+
+  /* Allocate cursors numbers for Queue and Distinct.  The cursor number for
+  ** the Distinct table must be exactly one greater than Queue in order
+  ** for the SRT_DistFifo and SRT_DistQueue destinations to work. */
+  iQueue = pParse->nTab++;
+  if( p->op==TK_UNION ){
+    eDest = pOrderBy ? SRT_DistQueue : SRT_DistFifo;
+    iDistinct = pParse->nTab++;
+  }else{
+    eDest = pOrderBy ? SRT_Queue : SRT_Fifo;
+  }
+  sqlite3SelectDestInit(&destQueue, eDest, iQueue);
+
+  /* Allocate cursors for Current, Queue, and Distinct. */
+  regCurrent = ++pParse->nMem;
+  sqlite3VdbeAddOp3(v, OP_OpenPseudo, iCurrent, regCurrent, nCol);
+  if( pOrderBy ){
+    KeyInfo *pKeyInfo = multiSelectOrderByKeyInfo(pParse, p, 1);
+    sqlite3VdbeAddOp4(v, OP_OpenEphemeral, iQueue, pOrderBy->nExpr+2, 0,
+                      (char*)pKeyInfo, P4_KEYINFO);
+    destQueue.pOrderBy = pOrderBy;
+  }else{
+    sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iQueue, nCol);
+  }
+  VdbeComment((v, "Queue table"));
+  if( iDistinct ){
+    p->addrOpenEphm[0] = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iDistinct, 0);
+    p->selFlags |= SF_UsesEphemeral;
+  }
+
+  /* Detach the ORDER BY clause from the compound SELECT */
+  p->pOrderBy = 0;
+
+  /* Figure out how many elements of the compound SELECT are part of the
+  ** recursive query.  Make sure no recursive elements use aggregate
+  ** functions.  Mark the recursive elements as UNION ALL even if they
+  ** are really UNION because the distinctness will be enforced by the
+  ** iDistinct table.  pFirstRec is left pointing to the left-most
+  ** recursive term of the CTE.
+  */
+  for(pFirstRec=p; ALWAYS(pFirstRec!=0); pFirstRec=pFirstRec->pPrior){
+    if( pFirstRec->selFlags & SF_Aggregate ){
+      sqlite3ErrorMsg(pParse, "recursive aggregate queries not supported");
+      goto end_of_recursive_query;
+    }
+    pFirstRec->op = TK_ALL;
+    if( (pFirstRec->pPrior->selFlags & SF_Recursive)==0 ) break;
+  }
+
+  /* Store the results of the setup-query in Queue. */
+  pSetup = pFirstRec->pPrior;
+  pSetup->pNext = 0;
+  ExplainQueryPlan((pParse, 1, "SETUP"));
+  rc = sqlite3Select(pParse, pSetup, &destQueue);
+  pSetup->pNext = p;
+  if( rc ) goto end_of_recursive_query;
+
+  /* Find the next row in the Queue and output that row */
+  addrTop = sqlite3VdbeAddOp2(v, OP_Rewind, iQueue, addrBreak); VdbeCoverage(v);
+
+  /* Transfer the next row in Queue over to Current */
+  sqlite3VdbeAddOp1(v, OP_NullRow, iCurrent); /* To reset column cache */
+  if( pOrderBy ){
+    sqlite3VdbeAddOp3(v, OP_Column, iQueue, pOrderBy->nExpr+1, regCurrent);
+  }else{
+    sqlite3VdbeAddOp2(v, OP_RowData, iQueue, regCurrent);
+  }
+  sqlite3VdbeAddOp1(v, OP_Delete, iQueue);
+
+  /* Output the single row in Current */
+  addrCont = sqlite3VdbeMakeLabel(pParse);
+  codeOffset(v, regOffset, addrCont);
+  selectInnerLoop(pParse, p, iCurrent,
+      0, 0, pDest, addrCont, addrBreak);
+  if( regLimit ){
+    sqlite3VdbeAddOp2(v, OP_DecrJumpZero, regLimit, addrBreak);
+    VdbeCoverage(v);
+  }
+  sqlite3VdbeResolveLabel(v, addrCont);
+
+  /* Execute the recursive SELECT taking the single row in Current as
+  ** the value for the recursive-table. Store the results in the Queue.
+  */
+  pFirstRec->pPrior = 0;
+  ExplainQueryPlan((pParse, 1, "RECURSIVE STEP"));
+  sqlite3Select(pParse, p, &destQueue);
+  assert( pFirstRec->pPrior==0 );
+  pFirstRec->pPrior = pSetup;
+
+  /* Keep running the loop until the Queue is empty */
+  sqlite3VdbeGoto(v, addrTop);
+  sqlite3VdbeResolveLabel(v, addrBreak);
+
+end_of_recursive_query:
+  sqlite3ExprListDelete(pParse->db, p->pOrderBy);
+  p->pOrderBy = pOrderBy;
+  p->pLimit = pLimit;
+  return;
+}
+#endif /* SQLITE_OMIT_CTE */
+
+/* Forward references */
+static int multiSelectOrderBy(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The right-most of SELECTs to be coded */
+  SelectDest *pDest     /* What to do with query results */
+);
+
+/*
+** Handle the special case of a compound-select that originates from a
+** VALUES clause.  By handling this as a special case, we avoid deep
+** recursion, and thus do not need to enforce the SQLITE_LIMIT_COMPOUND_SELECT
+** on a VALUES clause.
+**
+** Because the Select object originates from a VALUES clause:
+**   (1) There is no LIMIT or OFFSET or else there is a LIMIT of exactly 1
+**   (2) All terms are UNION ALL
+**   (3) There is no ORDER BY clause
+**
+** The "LIMIT of exactly 1" case of condition (1) comes about when a VALUES
+** clause occurs within scalar expression (ex: "SELECT (VALUES(1),(2),(3))").
+** The sqlite3CodeSubselect will have added the LIMIT 1 clause in tht case.
+** Since the limit is exactly 1, we only need to evaluate the left-most VALUES.
+*/
+static int multiSelectValues(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The right-most of SELECTs to be coded */
+  SelectDest *pDest     /* What to do with query results */
+){
+  int nRow = 1;
+  int rc = 0;
+  int bShowAll = p->pLimit==0;
+  assert( p->selFlags & SF_MultiValue );
+  do{
+    assert( p->selFlags & SF_Values );
+    assert( p->op==TK_ALL || (p->op==TK_SELECT && p->pPrior==0) );
+    assert( p->pNext==0 || p->pEList->nExpr==p->pNext->pEList->nExpr );
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( p->pWin ) return -1;
+#endif
+    if( p->pPrior==0 ) break;
+    assert( p->pPrior->pNext==p );
+    p = p->pPrior;
+    nRow += bShowAll;
+  }while(1);
+  ExplainQueryPlan((pParse, 0, "SCAN %d CONSTANT ROW%s", nRow,
+                    nRow==1 ? "" : "S"));
+  while( p ){
+    selectInnerLoop(pParse, p, -1, 0, 0, pDest, 1, 1);
+    if( !bShowAll ) break;
+    p->nSelectRow = nRow;
+    p = p->pNext;
+  }
+  return rc;
+}
+
+/*
+** Return true if the SELECT statement which is known to be the recursive
+** part of a recursive CTE still has its anchor terms attached.  If the
+** anchor terms have already been removed, then return false.
+*/
+static int hasAnchor(Select *p){
+  while( p && (p->selFlags & SF_Recursive)!=0 ){ p = p->pPrior; }
+  return p!=0;
+}
+
+/*
+** This routine is called to process a compound query form from
+** two or more separate queries using UNION, UNION ALL, EXCEPT, or
+** INTERSECT
+**
+** "p" points to the right-most of the two queries.  the query on the
+** left is p->pPrior.  The left query could also be a compound query
+** in which case this routine will be called recursively.
+**
+** The results of the total query are to be written into a destination
+** of type eDest with parameter iParm.
+**
+** Example 1:  Consider a three-way compound SQL statement.
+**
+**     SELECT a FROM t1 UNION SELECT b FROM t2 UNION SELECT c FROM t3
+**
+** This statement is parsed up as follows:
+**
+**     SELECT c FROM t3
+**      |
+**      `----->  SELECT b FROM t2
+**                |
+**                `------>  SELECT a FROM t1
+**
+** The arrows in the diagram above represent the Select.pPrior pointer.
+** So if this routine is called with p equal to the t3 query, then
+** pPrior will be the t2 query.  p->op will be TK_UNION in this case.
+**
+** Notice that because of the way SQLite parses compound SELECTs, the
+** individual selects always group from left to right.
+*/
+static int multiSelect(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The right-most of SELECTs to be coded */
+  SelectDest *pDest     /* What to do with query results */
+){
+  int rc = SQLITE_OK;   /* Success code from a subroutine */
+  Select *pPrior;       /* Another SELECT immediately to our left */
+  Vdbe *v;              /* Generate code to this VDBE */
+  SelectDest dest;      /* Alternative data destination */
+  Select *pDelete = 0;  /* Chain of simple selects to delete */
+  sqlite3 *db;          /* Database connection */
+
+  /* Make sure there is no ORDER BY or LIMIT clause on prior SELECTs.  Only
+  ** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
+  */
+  assert( p && p->pPrior );  /* Calling function guarantees this much */
+  assert( (p->selFlags & SF_Recursive)==0 || p->op==TK_ALL || p->op==TK_UNION );
+  assert( p->selFlags & SF_Compound );
+  db = pParse->db;
+  pPrior = p->pPrior;
+  dest = *pDest;
+  assert( pPrior->pOrderBy==0 );
+  assert( pPrior->pLimit==0 );
+
+  v = sqlite3GetVdbe(pParse);
+  assert( v!=0 );  /* The VDBE already created by calling function */
+
+  /* Create the destination temporary table if necessary
+  */
+  if( dest.eDest==SRT_EphemTab ){
+    assert( p->pEList );
+    sqlite3VdbeAddOp2(v, OP_OpenEphemeral, dest.iSDParm, p->pEList->nExpr);
+    dest.eDest = SRT_Table;
+  }
+
+  /* Special handling for a compound-select that originates as a VALUES clause.
+  */
+  if( p->selFlags & SF_MultiValue ){
+    rc = multiSelectValues(pParse, p, &dest);
+    if( rc>=0 ) goto multi_select_end;
+    rc = SQLITE_OK;
+  }
+
+  /* Make sure all SELECTs in the statement have the same number of elements
+  ** in their result sets.
+  */
+  assert( p->pEList && pPrior->pEList );
+  assert( p->pEList->nExpr==pPrior->pEList->nExpr );
+
+#ifndef SQLITE_OMIT_CTE
+  if( (p->selFlags & SF_Recursive)!=0 && hasAnchor(p) ){
+    generateWithRecursiveQuery(pParse, p, &dest);
+  }else
+#endif
+
+  /* Compound SELECTs that have an ORDER BY clause are handled separately.
+  */
+  if( p->pOrderBy ){
+    return multiSelectOrderBy(pParse, p, pDest);
+  }else{
+
+#ifndef SQLITE_OMIT_EXPLAIN
+    if( pPrior->pPrior==0 ){
+      ExplainQueryPlan((pParse, 1, "COMPOUND QUERY"));
+      ExplainQueryPlan((pParse, 1, "LEFT-MOST SUBQUERY"));
+    }
+#endif
+
+    /* Generate code for the left and right SELECT statements.
+    */
+    switch( p->op ){
+      case TK_ALL: {
+        int addr = 0;
+        int nLimit = 0;  /* Initialize to suppress harmless compiler warning */
+        assert( !pPrior->pLimit );
+        pPrior->iLimit = p->iLimit;
+        pPrior->iOffset = p->iOffset;
+        pPrior->pLimit = p->pLimit;
+        TREETRACE(0x200, pParse, p, ("multiSelect UNION ALL left...\n"));
+        rc = sqlite3Select(pParse, pPrior, &dest);
+        pPrior->pLimit = 0;
+        if( rc ){
+          goto multi_select_end;
+        }
+        p->pPrior = 0;
+        p->iLimit = pPrior->iLimit;
+        p->iOffset = pPrior->iOffset;
+        if( p->iLimit ){
+          addr = sqlite3VdbeAddOp1(v, OP_IfNot, p->iLimit); VdbeCoverage(v);
+          VdbeComment((v, "Jump ahead if LIMIT reached"));
+          if( p->iOffset ){
+            sqlite3VdbeAddOp3(v, OP_OffsetLimit,
+                              p->iLimit, p->iOffset+1, p->iOffset);
+          }
+        }
+        ExplainQueryPlan((pParse, 1, "UNION ALL"));
+        TREETRACE(0x200, pParse, p, ("multiSelect UNION ALL right...\n"));
+        rc = sqlite3Select(pParse, p, &dest);
+        testcase( rc!=SQLITE_OK );
+        pDelete = p->pPrior;
+        p->pPrior = pPrior;
+        p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
+        if( p->pLimit
+         && sqlite3ExprIsInteger(p->pLimit->pLeft, &nLimit)
+         && nLimit>0 && p->nSelectRow > sqlite3LogEst((u64)nLimit)
+        ){
+          p->nSelectRow = sqlite3LogEst((u64)nLimit);
+        }
+        if( addr ){
+          sqlite3VdbeJumpHere(v, addr);
+        }
+        break;
+      }
+      case TK_EXCEPT:
+      case TK_UNION: {
+        int unionTab;    /* Cursor number of the temp table holding result */
+        u8 op = 0;       /* One of the SRT_ operations to apply to self */
+        int priorOp;     /* The SRT_ operation to apply to prior selects */
+        Expr *pLimit;    /* Saved values of p->nLimit  */
+        int addr;
+        SelectDest uniondest;
+ 
+        testcase( p->op==TK_EXCEPT );
+        testcase( p->op==TK_UNION );
+        priorOp = SRT_Union;
+        if( dest.eDest==priorOp ){
+          /* We can reuse a temporary table generated by a SELECT to our
+          ** right.
+          */
+          assert( p->pLimit==0 );      /* Not allowed on leftward elements */
+          unionTab = dest.iSDParm;
+        }else{
+          /* We will need to create our own temporary table to hold the
+          ** intermediate results.
+          */
+          unionTab = pParse->nTab++;
+          assert( p->pOrderBy==0 );
+          addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, unionTab, 0);
+          assert( p->addrOpenEphm[0] == -1 );
+          p->addrOpenEphm[0] = addr;
+          findRightmost(p)->selFlags |= SF_UsesEphemeral;
+          assert( p->pEList );
+        }
+         
+ 
+        /* Code the SELECT statements to our left
+        */
+        assert( !pPrior->pOrderBy );
+        sqlite3SelectDestInit(&uniondest, priorOp, unionTab);
+        TREETRACE(0x200, pParse, p, ("multiSelect EXCEPT/UNION left...\n"));
+        rc = sqlite3Select(pParse, pPrior, &uniondest);
+        if( rc ){
+          goto multi_select_end;
+        }
+ 
+        /* Code the current SELECT statement
+        */
+        if( p->op==TK_EXCEPT ){
+          op = SRT_Except;
+        }else{
+          assert( p->op==TK_UNION );
+          op = SRT_Union;
+        }
+        p->pPrior = 0;
+        pLimit = p->pLimit;
+        p->pLimit = 0;
+        uniondest.eDest = op;
+        ExplainQueryPlan((pParse, 1, "%s USING TEMP B-TREE",
+                          sqlite3SelectOpName(p->op)));
+        TREETRACE(0x200, pParse, p, ("multiSelect EXCEPT/UNION right...\n"));
+        rc = sqlite3Select(pParse, p, &uniondest);
+        testcase( rc!=SQLITE_OK );
+        assert( p->pOrderBy==0 );
+        pDelete = p->pPrior;
+        p->pPrior = pPrior;
+        p->pOrderBy = 0;
+        if( p->op==TK_UNION ){
+          p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
+        }
+        sqlite3ExprDelete(db, p->pLimit);
+        p->pLimit = pLimit;
+        p->iLimit = 0;
+        p->iOffset = 0;
+ 
+        /* Convert the data in the temporary table into whatever form
+        ** it is that we currently need.
+        */
+        assert( unionTab==dest.iSDParm || dest.eDest!=priorOp );
+        assert( p->pEList || db->mallocFailed );
+        if( dest.eDest!=priorOp && db->mallocFailed==0 ){
+          int iCont, iBreak, iStart;
+          iBreak = sqlite3VdbeMakeLabel(pParse);
+          iCont = sqlite3VdbeMakeLabel(pParse);
+          computeLimitRegisters(pParse, p, iBreak);
+          sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak); VdbeCoverage(v);
+          iStart = sqlite3VdbeCurrentAddr(v);
+          selectInnerLoop(pParse, p, unionTab,
+                          0, 0, &dest, iCont, iBreak);
+          sqlite3VdbeResolveLabel(v, iCont);
+          sqlite3VdbeAddOp2(v, OP_Next, unionTab, iStart); VdbeCoverage(v);
+          sqlite3VdbeResolveLabel(v, iBreak);
+          sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
+        }
+        break;
+      }
+      default: assert( p->op==TK_INTERSECT ); {
+        int tab1, tab2;
+        int iCont, iBreak, iStart;
+        Expr *pLimit;
+        int addr;
+        SelectDest intersectdest;
+        int r1;
+ 
+        /* INTERSECT is different from the others since it requires
+        ** two temporary tables.  Hence it has its own case.  Begin
+        ** by allocating the tables we will need.
+        */
+        tab1 = pParse->nTab++;
+        tab2 = pParse->nTab++;
+        assert( p->pOrderBy==0 );
+ 
+        addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab1, 0);
+        assert( p->addrOpenEphm[0] == -1 );
+        p->addrOpenEphm[0] = addr;
+        findRightmost(p)->selFlags |= SF_UsesEphemeral;
+        assert( p->pEList );
+ 
+        /* Code the SELECTs to our left into temporary table "tab1".
+        */
+        sqlite3SelectDestInit(&intersectdest, SRT_Union, tab1);
+        TREETRACE(0x400, pParse, p, ("multiSelect INTERSECT left...\n"));
+        rc = sqlite3Select(pParse, pPrior, &intersectdest);
+        if( rc ){
+          goto multi_select_end;
+        }
+ 
+        /* Code the current SELECT into temporary table "tab2"
+        */
+        addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab2, 0);
+        assert( p->addrOpenEphm[1] == -1 );
+        p->addrOpenEphm[1] = addr;
+        p->pPrior = 0;
+        pLimit = p->pLimit;
+        p->pLimit = 0;
+        intersectdest.iSDParm = tab2;
+        ExplainQueryPlan((pParse, 1, "%s USING TEMP B-TREE",
+                          sqlite3SelectOpName(p->op)));
+        TREETRACE(0x400, pParse, p, ("multiSelect INTERSECT right...\n"));
+        rc = sqlite3Select(pParse, p, &intersectdest);
+        testcase( rc!=SQLITE_OK );
+        pDelete = p->pPrior;
+        p->pPrior = pPrior;
+        if( p->nSelectRow>pPrior->nSelectRow ){
+          p->nSelectRow = pPrior->nSelectRow;
+        }
+        sqlite3ExprDelete(db, p->pLimit);
+        p->pLimit = pLimit;
+ 
+        /* Generate code to take the intersection of the two temporary
+        ** tables.
+        */
+        if( rc ) break;
+        assert( p->pEList );
+        iBreak = sqlite3VdbeMakeLabel(pParse);
+        iCont = sqlite3VdbeMakeLabel(pParse);
+        computeLimitRegisters(pParse, p, iBreak);
+        sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak); VdbeCoverage(v);
+        r1 = sqlite3GetTempReg(pParse);
+        iStart = sqlite3VdbeAddOp2(v, OP_RowData, tab1, r1);
+        sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0);
+        VdbeCoverage(v);
+        sqlite3ReleaseTempReg(pParse, r1);
+        selectInnerLoop(pParse, p, tab1,
+                        0, 0, &dest, iCont, iBreak);
+        sqlite3VdbeResolveLabel(v, iCont);
+        sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart); VdbeCoverage(v);
+        sqlite3VdbeResolveLabel(v, iBreak);
+        sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
+        sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
+        break;
+      }
+    }
+ 
+  #ifndef SQLITE_OMIT_EXPLAIN
+    if( p->pNext==0 ){
+      ExplainQueryPlanPop(pParse);
+    }
+  #endif
+  }
+  if( pParse->nErr ) goto multi_select_end;
+ 
+  /* Compute collating sequences used by
+  ** temporary tables needed to implement the compound select.
+  ** Attach the KeyInfo structure to all temporary tables.
+  **
+  ** This section is run by the right-most SELECT statement only.
+  ** SELECT statements to the left always skip this part.  The right-most
+  ** SELECT might also skip this part if it has no ORDER BY clause and
+  ** no temp tables are required.
+  */
+  if( p->selFlags & SF_UsesEphemeral ){
+    int i;                        /* Loop counter */
+    KeyInfo *pKeyInfo;            /* Collating sequence for the result set */
+    Select *pLoop;                /* For looping through SELECT statements */
+    CollSeq **apColl;             /* For looping through pKeyInfo->aColl[] */
+    int nCol;                     /* Number of columns in result set */
+
+    assert( p->pNext==0 );
+    assert( p->pEList!=0 );
+    nCol = p->pEList->nExpr;
+    pKeyInfo = sqlite3KeyInfoAlloc(db, nCol, 1);
+    if( !pKeyInfo ){
+      rc = SQLITE_NOMEM_BKPT;
+      goto multi_select_end;
+    }
+    for(i=0, apColl=pKeyInfo->aColl; i<nCol; i++, apColl++){
+      *apColl = multiSelectCollSeq(pParse, p, i);
+      if( 0==*apColl ){
+        *apColl = db->pDfltColl;
+      }
+    }
+
+    for(pLoop=p; pLoop; pLoop=pLoop->pPrior){
+      for(i=0; i<2; i++){
+        int addr = pLoop->addrOpenEphm[i];
+        if( addr<0 ){
+          /* If [0] is unused then [1] is also unused.  So we can
+          ** always safely abort as soon as the first unused slot is found */
+          assert( pLoop->addrOpenEphm[1]<0 );
+          break;
+        }
+        sqlite3VdbeChangeP2(v, addr, nCol);
+        sqlite3VdbeChangeP4(v, addr, (char*)sqlite3KeyInfoRef(pKeyInfo),
+                            P4_KEYINFO);
+        pLoop->addrOpenEphm[i] = -1;
+      }
+    }
+    sqlite3KeyInfoUnref(pKeyInfo);
+  }
+
+multi_select_end:
+  pDest->iSdst = dest.iSdst;
+  pDest->nSdst = dest.nSdst;
+  if( pDelete ){
+    sqlite3ParserAddCleanup(pParse, sqlite3SelectDeleteGeneric, pDelete);
+  }
+  return rc;
+}
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+
+/*
+** Error message for when two or more terms of a compound select have different
+** size result sets.
+*/
+void sqlite3SelectWrongNumTermsError(Parse *pParse, Select *p){
+  if( p->selFlags & SF_Values ){
+    sqlite3ErrorMsg(pParse, "all VALUES must have the same number of terms");
+  }else{
+    sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
+      " do not have the same number of result columns",
+      sqlite3SelectOpName(p->op));
+  }
+}
+
+/*
+** Code an output subroutine for a coroutine implementation of a
+** SELECT statement.
+**
+** The data to be output is contained in pIn->iSdst.  There are
+** pIn->nSdst columns to be output.  pDest is where the output should
+** be sent.
+**
+** regReturn is the number of the register holding the subroutine
+** return address.
+**
+** If regPrev>0 then it is the first register in a vector that
+** records the previous output.  mem[regPrev] is a flag that is false
+** if there has been no previous output.  If regPrev>0 then code is
+** generated to suppress duplicates.  pKeyInfo is used for comparing
+** keys.
+**
+** If the LIMIT found in p->iLimit is reached, jump immediately to
+** iBreak.
+*/
+static int generateOutputSubroutine(
+  Parse *pParse,          /* Parsing context */
+  Select *p,              /* The SELECT statement */
+  SelectDest *pIn,        /* Coroutine supplying data */
+  SelectDest *pDest,      /* Where to send the data */
+  int regReturn,          /* The return address register */
+  int regPrev,            /* Previous result register.  No uniqueness if 0 */
+  KeyInfo *pKeyInfo,      /* For comparing with previous entry */
+  int iBreak              /* Jump here if we hit the LIMIT */
+){
+  Vdbe *v = pParse->pVdbe;
+  int iContinue;
+  int addr;
+
+  addr = sqlite3VdbeCurrentAddr(v);
+  iContinue = sqlite3VdbeMakeLabel(pParse);
+
+  /* Suppress duplicates for UNION, EXCEPT, and INTERSECT
+  */
+  if( regPrev ){
+    int addr1, addr2;
+    addr1 = sqlite3VdbeAddOp1(v, OP_IfNot, regPrev); VdbeCoverage(v);
+    addr2 = sqlite3VdbeAddOp4(v, OP_Compare, pIn->iSdst, regPrev+1, pIn->nSdst,
+                              (char*)sqlite3KeyInfoRef(pKeyInfo), P4_KEYINFO);
+    sqlite3VdbeAddOp3(v, OP_Jump, addr2+2, iContinue, addr2+2); VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addr1);
+    sqlite3VdbeAddOp3(v, OP_Copy, pIn->iSdst, regPrev+1, pIn->nSdst-1);
+    sqlite3VdbeAddOp2(v, OP_Integer, 1, regPrev);
+  }
+  if( pParse->db->mallocFailed ) return 0;
+
+  /* Suppress the first OFFSET entries if there is an OFFSET clause
+  */
+  codeOffset(v, p->iOffset, iContinue);
+
+  assert( pDest->eDest!=SRT_Exists );
+  assert( pDest->eDest!=SRT_Table );
+  switch( pDest->eDest ){
+    /* Store the result as data using a unique key.
+    */
+    case SRT_EphemTab: {
+      int r1 = sqlite3GetTempReg(pParse);
+      int r2 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, pIn->iSdst, pIn->nSdst, r1);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, pDest->iSDParm, r2);
+      sqlite3VdbeAddOp3(v, OP_Insert, pDest->iSDParm, r1, r2);
+      sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+      sqlite3ReleaseTempReg(pParse, r2);
+      sqlite3ReleaseTempReg(pParse, r1);
+      break;
+    }
+
+#ifndef SQLITE_OMIT_SUBQUERY
+    /* If we are creating a set for an "expr IN (SELECT ...)".
+    */
+    case SRT_Set: {
+      int r1;
+      testcase( pIn->nSdst>1 );
+      r1 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp4(v, OP_MakeRecord, pIn->iSdst, pIn->nSdst,
+          r1, pDest->zAffSdst, pIn->nSdst);
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, pDest->iSDParm, r1,
+                           pIn->iSdst, pIn->nSdst);
+      sqlite3ReleaseTempReg(pParse, r1);
+      break;
+    }
+
+    /* If this is a scalar select that is part of an expression, then
+    ** store the results in the appropriate memory cell and break out
+    ** of the scan loop.  Note that the select might return multiple columns
+    ** if it is the RHS of a row-value IN operator.
+    */
+    case SRT_Mem: {
+      testcase( pIn->nSdst>1 );
+      sqlite3ExprCodeMove(pParse, pIn->iSdst, pDest->iSDParm, pIn->nSdst);
+      /* The LIMIT clause will jump out of the loop for us */
+      break;
+    }
+#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
+
+    /* The results are stored in a sequence of registers
+    ** starting at pDest->iSdst.  Then the co-routine yields.
+    */
+    case SRT_Coroutine: {
+      if( pDest->iSdst==0 ){
+        pDest->iSdst = sqlite3GetTempRange(pParse, pIn->nSdst);
+        pDest->nSdst = pIn->nSdst;
+      }
+      sqlite3ExprCodeMove(pParse, pIn->iSdst, pDest->iSdst, pIn->nSdst);
+      sqlite3VdbeAddOp1(v, OP_Yield, pDest->iSDParm);
+      break;
+    }
+
+    /* If none of the above, then the result destination must be
+    ** SRT_Output.  This routine is never called with any other
+    ** destination other than the ones handled above or SRT_Output.
+    **
+    ** For SRT_Output, results are stored in a sequence of registers. 
+    ** Then the OP_ResultRow opcode is used to cause sqlite3_step() to
+    ** return the next row of result.
+    */
+    default: {
+      assert( pDest->eDest==SRT_Output );
+      sqlite3VdbeAddOp2(v, OP_ResultRow, pIn->iSdst, pIn->nSdst);
+      break;
+    }
+  }
+
+  /* Jump to the end of the loop if the LIMIT is reached.
+  */
+  if( p->iLimit ){
+    sqlite3VdbeAddOp2(v, OP_DecrJumpZero, p->iLimit, iBreak); VdbeCoverage(v);
+  }
+
+  /* Generate the subroutine return
+  */
+  sqlite3VdbeResolveLabel(v, iContinue);
+  sqlite3VdbeAddOp1(v, OP_Return, regReturn);
+
+  return addr;
+}
+
+/*
+** Alternative compound select code generator for cases when there
+** is an ORDER BY clause.
+**
+** We assume a query of the following form:
+**
+**      <selectA>  <operator>  <selectB>  ORDER BY <orderbylist>
+**
+** <operator> is one of UNION ALL, UNION, EXCEPT, or INTERSECT.  The idea
+** is to code both <selectA> and <selectB> with the ORDER BY clause as
+** co-routines.  Then run the co-routines in parallel and merge the results
+** into the output.  In addition to the two coroutines (called selectA and
+** selectB) there are 7 subroutines:
+**
+**    outA:    Move the output of the selectA coroutine into the output
+**             of the compound query.
+**
+**    outB:    Move the output of the selectB coroutine into the output
+**             of the compound query.  (Only generated for UNION and
+**             UNION ALL.  EXCEPT and INSERTSECT never output a row that
+**             appears only in B.)
+**
+**    AltB:    Called when there is data from both coroutines and A<B.
+**
+**    AeqB:    Called when there is data from both coroutines and A==B.
+**
+**    AgtB:    Called when there is data from both coroutines and A>B.
+**
+**    EofA:    Called when data is exhausted from selectA.
+**
+**    EofB:    Called when data is exhausted from selectB.
+**
+** The implementation of the latter five subroutines depend on which
+** <operator> is used:
+**
+**
+**             UNION ALL         UNION            EXCEPT          INTERSECT
+**          -------------  -----------------  --------------  -----------------
+**   AltB:   outA, nextA      outA, nextA       outA, nextA         nextA
+**
+**   AeqB:   outA, nextA         nextA             nextA         outA, nextA
+**
+**   AgtB:   outB, nextB      outB, nextB          nextB            nextB
+**
+**   EofA:   outB, nextB      outB, nextB          halt             halt
+**
+**   EofB:   outA, nextA      outA, nextA       outA, nextA         halt
+**
+** In the AltB, AeqB, and AgtB subroutines, an EOF on A following nextA
+** causes an immediate jump to EofA and an EOF on B following nextB causes
+** an immediate jump to EofB.  Within EofA and EofB, and EOF on entry or
+** following nextX causes a jump to the end of the select processing.
+**
+** Duplicate removal in the UNION, EXCEPT, and INTERSECT cases is handled
+** within the output subroutine.  The regPrev register set holds the previously
+** output value.  A comparison is made against this value and the output
+** is skipped if the next results would be the same as the previous.
+**
+** The implementation plan is to implement the two coroutines and seven
+** subroutines first, then put the control logic at the bottom.  Like this:
+**
+**          goto Init
+**     coA: coroutine for left query (A)
+**     coB: coroutine for right query (B)
+**    outA: output one row of A
+**    outB: output one row of B (UNION and UNION ALL only)
+**    EofA: ...
+**    EofB: ...
+**    AltB: ...
+**    AeqB: ...
+**    AgtB: ...
+**    Init: initialize coroutine registers
+**          yield coA
+**          if eof(A) goto EofA
+**          yield coB
+**          if eof(B) goto EofB
+**    Cmpr: Compare A, B
+**          Jump AltB, AeqB, AgtB
+**     End: ...
+**
+** We call AltB, AeqB, AgtB, EofA, and EofB "subroutines" but they are not
+** actually called using Gosub and they do not Return.  EofA and EofB loop
+** until all data is exhausted then jump to the "end" label.  AltB, AeqB,
+** and AgtB jump to either L2 or to one of EofA or EofB.
+*/
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+static int multiSelectOrderBy(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The right-most of SELECTs to be coded */
+  SelectDest *pDest     /* What to do with query results */
+){
+  int i, j;             /* Loop counters */
+  Select *pPrior;       /* Another SELECT immediately to our left */
+  Select *pSplit;       /* Left-most SELECT in the right-hand group */
+  int nSelect;          /* Number of SELECT statements in the compound */
+  Vdbe *v;              /* Generate code to this VDBE */
+  SelectDest destA;     /* Destination for coroutine A */
+  SelectDest destB;     /* Destination for coroutine B */
+  int regAddrA;         /* Address register for select-A coroutine */
+  int regAddrB;         /* Address register for select-B coroutine */
+  int addrSelectA;      /* Address of the select-A coroutine */
+  int addrSelectB;      /* Address of the select-B coroutine */
+  int regOutA;          /* Address register for the output-A subroutine */
+  int regOutB;          /* Address register for the output-B subroutine */
+  int addrOutA;         /* Address of the output-A subroutine */
+  int addrOutB = 0;     /* Address of the output-B subroutine */
+  int addrEofA;         /* Address of the select-A-exhausted subroutine */
+  int addrEofA_noB;     /* Alternate addrEofA if B is uninitialized */
+  int addrEofB;         /* Address of the select-B-exhausted subroutine */
+  int addrAltB;         /* Address of the A<B subroutine */
+  int addrAeqB;         /* Address of the A==B subroutine */
+  int addrAgtB;         /* Address of the A>B subroutine */
+  int regLimitA;        /* Limit register for select-A */
+  int regLimitB;        /* Limit register for select-A */
+  int regPrev;          /* A range of registers to hold previous output */
+  int savedLimit;       /* Saved value of p->iLimit */
+  int savedOffset;      /* Saved value of p->iOffset */
+  int labelCmpr;        /* Label for the start of the merge algorithm */
+  int labelEnd;         /* Label for the end of the overall SELECT stmt */
+  int addr1;            /* Jump instructions that get retargeted */
+  int op;               /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
+  KeyInfo *pKeyDup = 0; /* Comparison information for duplicate removal */
+  KeyInfo *pKeyMerge;   /* Comparison information for merging rows */
+  sqlite3 *db;          /* Database connection */
+  ExprList *pOrderBy;   /* The ORDER BY clause */
+  int nOrderBy;         /* Number of terms in the ORDER BY clause */
+  u32 *aPermute;        /* Mapping from ORDER BY terms to result set columns */
+
+  assert( p->pOrderBy!=0 );
+  assert( pKeyDup==0 ); /* "Managed" code needs this.  Ticket #3382. */
+  db = pParse->db;
+  v = pParse->pVdbe;
+  assert( v!=0 );       /* Already thrown the error if VDBE alloc failed */
+  labelEnd = sqlite3VdbeMakeLabel(pParse);
+  labelCmpr = sqlite3VdbeMakeLabel(pParse);
+
+
+  /* Patch up the ORDER BY clause
+  */
+  op = p->op; 
+  assert( p->pPrior->pOrderBy==0 );
+  pOrderBy = p->pOrderBy;
+  assert( pOrderBy );
+  nOrderBy = pOrderBy->nExpr;
+
+  /* For operators other than UNION ALL we have to make sure that
+  ** the ORDER BY clause covers every term of the result set.  Add
+  ** terms to the ORDER BY clause as necessary.
+  */
+  if( op!=TK_ALL ){
+    for(i=1; db->mallocFailed==0 && i<=p->pEList->nExpr; i++){
+      struct ExprList_item *pItem;
+      for(j=0, pItem=pOrderBy->a; j<nOrderBy; j++, pItem++){
+        assert( pItem!=0 );
+        assert( pItem->u.x.iOrderByCol>0 );
+        if( pItem->u.x.iOrderByCol==i ) break;
+      }
+      if( j==nOrderBy ){
+        Expr *pNew = sqlite3Expr(db, TK_INTEGER, 0);
+        if( pNew==0 ) return SQLITE_NOMEM_BKPT;
+        pNew->flags |= EP_IntValue;
+        pNew->u.iValue = i;
+        p->pOrderBy = pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew);
+        if( pOrderBy ) pOrderBy->a[nOrderBy++].u.x.iOrderByCol = (u16)i;
+      }
+    }
+  }
+
+  /* Compute the comparison permutation and keyinfo that is used with
+  ** the permutation used to determine if the next
+  ** row of results comes from selectA or selectB.  Also add explicit
+  ** collations to the ORDER BY clause terms so that when the subqueries
+  ** to the right and the left are evaluated, they use the correct
+  ** collation.
+  */
+  aPermute = sqlite3DbMallocRawNN(db, sizeof(u32)*(nOrderBy + 1));
+  if( aPermute ){
+    struct ExprList_item *pItem;
+    aPermute[0] = nOrderBy;
+    for(i=1, pItem=pOrderBy->a; i<=nOrderBy; i++, pItem++){
+      assert( pItem!=0 );
+      assert( pItem->u.x.iOrderByCol>0 );
+      assert( pItem->u.x.iOrderByCol<=p->pEList->nExpr );
+      aPermute[i] = pItem->u.x.iOrderByCol - 1;
+    }
+    pKeyMerge = multiSelectOrderByKeyInfo(pParse, p, 1);
+  }else{
+    pKeyMerge = 0;
+  }
+
+  /* Allocate a range of temporary registers and the KeyInfo needed
+  ** for the logic that removes duplicate result rows when the
+  ** operator is UNION, EXCEPT, or INTERSECT (but not UNION ALL).
+  */
+  if( op==TK_ALL ){
+    regPrev = 0;
+  }else{
+    int nExpr = p->pEList->nExpr;
+    assert( nOrderBy>=nExpr || db->mallocFailed );
+    regPrev = pParse->nMem+1;
+    pParse->nMem += nExpr+1;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regPrev);
+    pKeyDup = sqlite3KeyInfoAlloc(db, nExpr, 1);
+    if( pKeyDup ){
+      assert( sqlite3KeyInfoIsWriteable(pKeyDup) );
+      for(i=0; i<nExpr; i++){
+        pKeyDup->aColl[i] = multiSelectCollSeq(pParse, p, i);
+        pKeyDup->aSortFlags[i] = 0;
+      }
+    }
+  }
+
+  /* Separate the left and the right query from one another
+  */
+  nSelect = 1;
+  if( (op==TK_ALL || op==TK_UNION)
+   && OptimizationEnabled(db, SQLITE_BalancedMerge)
+  ){
+    for(pSplit=p; pSplit->pPrior!=0 && pSplit->op==op; pSplit=pSplit->pPrior){
+      nSelect++;
+      assert( pSplit->pPrior->pNext==pSplit );
+    }
+  }
+  if( nSelect<=3 ){
+    pSplit = p;
+  }else{
+    pSplit = p;
+    for(i=2; i<nSelect; i+=2){ pSplit = pSplit->pPrior; }
+  }
+  pPrior = pSplit->pPrior;
+  assert( pPrior!=0 );
+  pSplit->pPrior = 0;
+  pPrior->pNext = 0;
+  assert( p->pOrderBy == pOrderBy );
+  assert( pOrderBy!=0 || db->mallocFailed );
+  pPrior->pOrderBy = sqlite3ExprListDup(pParse->db, pOrderBy, 0);
+  sqlite3ResolveOrderGroupBy(pParse, p, p->pOrderBy, "ORDER");
+  sqlite3ResolveOrderGroupBy(pParse, pPrior, pPrior->pOrderBy, "ORDER");
+
+  /* Compute the limit registers */
+  computeLimitRegisters(pParse, p, labelEnd);
+  if( p->iLimit && op==TK_ALL ){
+    regLimitA = ++pParse->nMem;
+    regLimitB = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Copy, p->iOffset ? p->iOffset+1 : p->iLimit,
+                                  regLimitA);
+    sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
+  }else{
+    regLimitA = regLimitB = 0;
+  }
+  sqlite3ExprDelete(db, p->pLimit);
+  p->pLimit = 0;
+
+  regAddrA = ++pParse->nMem;
+  regAddrB = ++pParse->nMem;
+  regOutA = ++pParse->nMem;
+  regOutB = ++pParse->nMem;
+  sqlite3SelectDestInit(&destA, SRT_Coroutine, regAddrA);
+  sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);
+
+  ExplainQueryPlan((pParse, 1, "MERGE (%s)", sqlite3SelectOpName(p->op)));
+
+  /* Generate a coroutine to evaluate the SELECT statement to the
+  ** left of the compound operator - the "A" select.
+  */
+  addrSelectA = sqlite3VdbeCurrentAddr(v) + 1;
+  addr1 = sqlite3VdbeAddOp3(v, OP_InitCoroutine, regAddrA, 0, addrSelectA);
+  VdbeComment((v, "left SELECT"));
+  pPrior->iLimit = regLimitA;
+  ExplainQueryPlan((pParse, 1, "LEFT"));
+  sqlite3Select(pParse, pPrior, &destA);
+  sqlite3VdbeEndCoroutine(v, regAddrA);
+  sqlite3VdbeJumpHere(v, addr1);
+
+  /* Generate a coroutine to evaluate the SELECT statement on
+  ** the right - the "B" select
+  */
+  addrSelectB = sqlite3VdbeCurrentAddr(v) + 1;
+  addr1 = sqlite3VdbeAddOp3(v, OP_InitCoroutine, regAddrB, 0, addrSelectB);
+  VdbeComment((v, "right SELECT"));
+  savedLimit = p->iLimit;
+  savedOffset = p->iOffset;
+  p->iLimit = regLimitB;
+  p->iOffset = 0; 
+  ExplainQueryPlan((pParse, 1, "RIGHT"));
+  sqlite3Select(pParse, p, &destB);
+  p->iLimit = savedLimit;
+  p->iOffset = savedOffset;
+  sqlite3VdbeEndCoroutine(v, regAddrB);
+
+  /* Generate a subroutine that outputs the current row of the A
+  ** select as the next output row of the compound select.
+  */
+  VdbeNoopComment((v, "Output routine for A"));
+  addrOutA = generateOutputSubroutine(pParse,
+                 p, &destA, pDest, regOutA,
+                 regPrev, pKeyDup, labelEnd);
+ 
+  /* Generate a subroutine that outputs the current row of the B
+  ** select as the next output row of the compound select.
+  */
+  if( op==TK_ALL || op==TK_UNION ){
+    VdbeNoopComment((v, "Output routine for B"));
+    addrOutB = generateOutputSubroutine(pParse,
+                 p, &destB, pDest, regOutB,
+                 regPrev, pKeyDup, labelEnd);
+  }
+  sqlite3KeyInfoUnref(pKeyDup);
+
+  /* Generate a subroutine to run when the results from select A
+  ** are exhausted and only data in select B remains.
+  */
+  if( op==TK_EXCEPT || op==TK_INTERSECT ){
+    addrEofA_noB = addrEofA = labelEnd;
+  }else{ 
+    VdbeNoopComment((v, "eof-A subroutine"));
+    addrEofA = sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
+    addrEofA_noB = sqlite3VdbeAddOp2(v, OP_Yield, regAddrB, labelEnd);
+                                     VdbeCoverage(v);
+    sqlite3VdbeGoto(v, addrEofA);
+    p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
+  }
+
+  /* Generate a subroutine to run when the results from select B
+  ** are exhausted and only data in select A remains.
+  */
+  if( op==TK_INTERSECT ){
+    addrEofB = addrEofA;
+    if( p->nSelectRow > pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
+  }else{ 
+    VdbeNoopComment((v, "eof-B subroutine"));
+    addrEofB = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
+    sqlite3VdbeAddOp2(v, OP_Yield, regAddrA, labelEnd); VdbeCoverage(v);
+    sqlite3VdbeGoto(v, addrEofB);
+  }
+
+  /* Generate code to handle the case of A<B
+  */
+  VdbeNoopComment((v, "A-lt-B subroutine"));
+  addrAltB = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
+  sqlite3VdbeAddOp2(v, OP_Yield, regAddrA, addrEofA); VdbeCoverage(v);
+  sqlite3VdbeGoto(v, labelCmpr);
+
+  /* Generate code to handle the case of A==B
+  */
+  if( op==TK_ALL ){
+    addrAeqB = addrAltB;
+  }else if( op==TK_INTERSECT ){
+    addrAeqB = addrAltB;
+    addrAltB++;
+  }else{
+    VdbeNoopComment((v, "A-eq-B subroutine"));
+    addrAeqB =
+    sqlite3VdbeAddOp2(v, OP_Yield, regAddrA, addrEofA); VdbeCoverage(v);
+    sqlite3VdbeGoto(v, labelCmpr);
+  }
+
+  /* Generate code to handle the case of A>B
+  */
+  VdbeNoopComment((v, "A-gt-B subroutine"));
+  addrAgtB = sqlite3VdbeCurrentAddr(v);
+  if( op==TK_ALL || op==TK_UNION ){
+    sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
+  }
+  sqlite3VdbeAddOp2(v, OP_Yield, regAddrB, addrEofB); VdbeCoverage(v);
+  sqlite3VdbeGoto(v, labelCmpr);
+
+  /* This code runs once to initialize everything.
+  */
+  sqlite3VdbeJumpHere(v, addr1);
+  sqlite3VdbeAddOp2(v, OP_Yield, regAddrA, addrEofA_noB); VdbeCoverage(v);
+  sqlite3VdbeAddOp2(v, OP_Yield, regAddrB, addrEofB); VdbeCoverage(v);
+
+  /* Implement the main merge loop
+  */
+  sqlite3VdbeResolveLabel(v, labelCmpr);
+  sqlite3VdbeAddOp4(v, OP_Permutation, 0, 0, 0, (char*)aPermute, P4_INTARRAY);
+  sqlite3VdbeAddOp4(v, OP_Compare, destA.iSdst, destB.iSdst, nOrderBy,
+                         (char*)pKeyMerge, P4_KEYINFO);
+  sqlite3VdbeChangeP5(v, OPFLAG_PERMUTE);
+  sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB); VdbeCoverage(v);
+
+  /* Jump to the this point in order to terminate the query.
+  */
+  sqlite3VdbeResolveLabel(v, labelEnd);
+
+  /* Make arrangements to free the 2nd and subsequent arms of the compound
+  ** after the parse has finished */
+  if( pSplit->pPrior ){
+    sqlite3ParserAddCleanup(pParse, sqlite3SelectDeleteGeneric, pSplit->pPrior);
+  }
+  pSplit->pPrior = pPrior;
+  pPrior->pNext = pSplit;
+  sqlite3ExprListDelete(db, pPrior->pOrderBy);
+  pPrior->pOrderBy = 0;
+
+  /*** TBD:  Insert subroutine calls to close cursors on incomplete
+  **** subqueries ****/
+  ExplainQueryPlanPop(pParse);
+  return pParse->nErr!=0;
+}
+#endif
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+
+/* An instance of the SubstContext object describes an substitution edit
+** to be performed on a parse tree.
+**
+** All references to columns in table iTable are to be replaced by corresponding
+** expressions in pEList.
+**
+** ## About "isOuterJoin":
+**
+** The isOuterJoin column indicates that the replacement will occur into a
+** position in the parent that NULL-able due to an OUTER JOIN.  Either the
+** target slot in the parent is the right operand of a LEFT JOIN, or one of
+** the left operands of a RIGHT JOIN.  In either case, we need to potentially
+** bypass the substituted expression with OP_IfNullRow.
+**
+** Suppose the original expression is an integer constant. Even though the table
+** has the nullRow flag set, because the expression is an integer constant,
+** it will not be NULLed out.  So instead, we insert an OP_IfNullRow opcode
+** that checks to see if the nullRow flag is set on the table.  If the nullRow
+** flag is set, then the value in the register is set to NULL and the original
+** expression is bypassed.  If the nullRow flag is not set, then the original
+** expression runs to populate the register.
+**
+** Example where this is needed:
+**
+**      CREATE TABLE t1(a INTEGER PRIMARY KEY, b INT);
+**      CREATE TABLE t2(x INT UNIQUE);
+**
+**      SELECT a,b,m,x FROM t1 LEFT JOIN (SELECT 59 AS m,x FROM t2) ON b=x;
+**
+** When the subquery on the right side of the LEFT JOIN is flattened, we
+** have to add OP_IfNullRow in front of the OP_Integer that implements the
+** "m" value of the subquery so that a NULL will be loaded instead of 59
+** when processing a non-matched row of the left.
+*/
+typedef struct SubstContext {
+  Parse *pParse;            /* The parsing context */
+  int iTable;               /* Replace references to this table */
+  int iNewTable;            /* New table number */
+  int isOuterJoin;          /* Add TK_IF_NULL_ROW opcodes on each replacement */
+  ExprList *pEList;         /* Replacement expressions */
+  ExprList *pCList;         /* Collation sequences for replacement expr */
+} SubstContext;
+
+/* Forward Declarations */
+static void substExprList(SubstContext*, ExprList*);
+static void substSelect(SubstContext*, Select*, int);
+
+/*
+** Scan through the expression pExpr.  Replace every reference to
+** a column in table number iTable with a copy of the iColumn-th
+** entry in pEList.  (But leave references to the ROWID column
+** unchanged.)
+**
+** This routine is part of the flattening procedure.  A subquery
+** whose result set is defined by pEList appears as entry in the
+** FROM clause of a SELECT such that the VDBE cursor assigned to that
+** FORM clause entry is iTable.  This routine makes the necessary
+** changes to pExpr so that it refers directly to the source table
+** of the subquery rather the result set of the subquery.
+*/
+static Expr *substExpr(
+  SubstContext *pSubst,  /* Description of the substitution */
+  Expr *pExpr            /* Expr in which substitution occurs */
+){
+  if( pExpr==0 ) return 0;
+  if( ExprHasProperty(pExpr, EP_OuterON|EP_InnerON)
+   && pExpr->w.iJoin==pSubst->iTable
+  ){
+    testcase( ExprHasProperty(pExpr, EP_InnerON) );
+    pExpr->w.iJoin = pSubst->iNewTable;
+  }
+  if( pExpr->op==TK_COLUMN
+   && pExpr->iTable==pSubst->iTable
+   && !ExprHasProperty(pExpr, EP_FixedCol)
+  ){
+#ifdef SQLITE_ALLOW_ROWID_IN_VIEW
+    if( pExpr->iColumn<0 ){
+      pExpr->op = TK_NULL;
+    }else
+#endif
+    {
+      Expr *pNew;
+      int iColumn;
+      Expr *pCopy;
+      Expr ifNullRow;
+      iColumn = pExpr->iColumn;
+      assert( iColumn>=0 );
+      assert( pSubst->pEList!=0 && iColumn<pSubst->pEList->nExpr );
+      assert( pExpr->pRight==0 );
+      pCopy = pSubst->pEList->a[iColumn].pExpr;
+      if( sqlite3ExprIsVector(pCopy) ){
+        sqlite3VectorErrorMsg(pSubst->pParse, pCopy);
+      }else{
+        sqlite3 *db = pSubst->pParse->db;
+        if( pSubst->isOuterJoin
+         && (pCopy->op!=TK_COLUMN || pCopy->iTable!=pSubst->iNewTable)
+        ){
+          memset(&ifNullRow, 0, sizeof(ifNullRow));
+          ifNullRow.op = TK_IF_NULL_ROW;
+          ifNullRow.pLeft = pCopy;
+          ifNullRow.iTable = pSubst->iNewTable;
+          ifNullRow.iColumn = -99;
+          ifNullRow.flags = EP_IfNullRow;
+          pCopy = &ifNullRow;
+        }
+        testcase( ExprHasProperty(pCopy, EP_Subquery) );
+        pNew = sqlite3ExprDup(db, pCopy, 0);
+        if( db->mallocFailed ){
+          sqlite3ExprDelete(db, pNew);
+          return pExpr;
+        }
+        if( pSubst->isOuterJoin ){
+          ExprSetProperty(pNew, EP_CanBeNull);
+        }
+        if( ExprHasProperty(pExpr,EP_OuterON|EP_InnerON) ){
+          sqlite3SetJoinExpr(pNew, pExpr->w.iJoin,
+                             pExpr->flags & (EP_OuterON|EP_InnerON));
+        }
+        sqlite3ExprDelete(db, pExpr);
+        pExpr = pNew;
+        if( pExpr->op==TK_TRUEFALSE ){
+          pExpr->u.iValue = sqlite3ExprTruthValue(pExpr);
+          pExpr->op = TK_INTEGER;
+          ExprSetProperty(pExpr, EP_IntValue);
+        }
+
+        /* Ensure that the expression now has an implicit collation sequence,
+        ** just as it did when it was a column of a view or sub-query. */
+        {
+          CollSeq *pNat = sqlite3ExprCollSeq(pSubst->pParse, pExpr);
+          CollSeq *pColl = sqlite3ExprCollSeq(pSubst->pParse,
+                pSubst->pCList->a[iColumn].pExpr
+          );
+          if( pNat!=pColl || (pExpr->op!=TK_COLUMN && pExpr->op!=TK_COLLATE) ){
+            pExpr = sqlite3ExprAddCollateString(pSubst->pParse, pExpr,
+                (pColl ? pColl->zName : "BINARY")
+            );
+          }
+        }
+        ExprClearProperty(pExpr, EP_Collate);
+      }
+    }
+  }else{
+    if( pExpr->op==TK_IF_NULL_ROW && pExpr->iTable==pSubst->iTable ){
+      pExpr->iTable = pSubst->iNewTable;
+    }
+    pExpr->pLeft = substExpr(pSubst, pExpr->pLeft);
+    pExpr->pRight = substExpr(pSubst, pExpr->pRight);
+    if( ExprUseXSelect(pExpr) ){
+      substSelect(pSubst, pExpr->x.pSelect, 1);
+    }else{
+      substExprList(pSubst, pExpr->x.pList);
+    }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( ExprHasProperty(pExpr, EP_WinFunc) ){
+      Window *pWin = pExpr->y.pWin;
+      pWin->pFilter = substExpr(pSubst, pWin->pFilter);
+      substExprList(pSubst, pWin->pPartition);
+      substExprList(pSubst, pWin->pOrderBy);
+    }
+#endif
+  }
+  return pExpr;
+}
+static void substExprList(
+  SubstContext *pSubst, /* Description of the substitution */
+  ExprList *pList       /* List to scan and in which to make substitutes */
+){
+  int i;
+  if( pList==0 ) return;
+  for(i=0; i<pList->nExpr; i++){
+    pList->a[i].pExpr = substExpr(pSubst, pList->a[i].pExpr);
+  }
+}
+static void substSelect(
+  SubstContext *pSubst, /* Description of the substitution */
+  Select *p,            /* SELECT statement in which to make substitutions */
+  int doPrior           /* Do substitutes on p->pPrior too */
+){
+  SrcList *pSrc;
+  SrcItem *pItem;
+  int i;
+  if( !p ) return;
+  do{
+    substExprList(pSubst, p->pEList);
+    substExprList(pSubst, p->pGroupBy);
+    substExprList(pSubst, p->pOrderBy);
+    p->pHaving = substExpr(pSubst, p->pHaving);
+    p->pWhere = substExpr(pSubst, p->pWhere);
+    pSrc = p->pSrc;
+    assert( pSrc!=0 );
+    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
+      substSelect(pSubst, pItem->pSelect, 1);
+      if( pItem->fg.isTabFunc ){
+        substExprList(pSubst, pItem->u1.pFuncArg);
+      }
+    }
+  }while( doPrior && (p = p->pPrior)!=0 );
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** pSelect is a SELECT statement and pSrcItem is one item in the FROM
+** clause of that SELECT.
+**
+** This routine scans the entire SELECT statement and recomputes the
+** pSrcItem->colUsed mask.
+*/
+static int recomputeColumnsUsedExpr(Walker *pWalker, Expr *pExpr){
+  SrcItem *pItem;
+  if( pExpr->op!=TK_COLUMN ) return WRC_Continue;
+  pItem = pWalker->u.pSrcItem;
+  if( pItem->iCursor!=pExpr->iTable ) return WRC_Continue;
+  if( pExpr->iColumn<0 ) return WRC_Continue;
+  pItem->colUsed |= sqlite3ExprColUsed(pExpr);
+  return WRC_Continue;
+}
+static void recomputeColumnsUsed(
+  Select *pSelect,                 /* The complete SELECT statement */
+  SrcItem *pSrcItem                /* Which FROM clause item to recompute */
+){
+  Walker w;
+  if( NEVER(pSrcItem->pTab==0) ) return;
+  memset(&w, 0, sizeof(w));
+  w.xExprCallback = recomputeColumnsUsedExpr;
+  w.xSelectCallback = sqlite3SelectWalkNoop;
+  w.u.pSrcItem = pSrcItem;
+  pSrcItem->colUsed = 0;
+  sqlite3WalkSelect(&w, pSelect);
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** Assign new cursor numbers to each of the items in pSrc. For each
+** new cursor number assigned, set an entry in the aCsrMap[] array
+** to map the old cursor number to the new:
+**
+**     aCsrMap[iOld+1] = iNew;
+**
+** The array is guaranteed by the caller to be large enough for all
+** existing cursor numbers in pSrc.  aCsrMap[0] is the array size.
+**
+** If pSrc contains any sub-selects, call this routine recursively
+** on the FROM clause of each such sub-select, with iExcept set to -1.
+*/
+static void srclistRenumberCursors(
+  Parse *pParse,                  /* Parse context */
+  int *aCsrMap,                   /* Array to store cursor mappings in */
+  SrcList *pSrc,                  /* FROM clause to renumber */
+  int iExcept                     /* FROM clause item to skip */
+){
+  int i;
+  SrcItem *pItem;
+  for(i=0, pItem=pSrc->a; i<pSrc->nSrc; i++, pItem++){
+    if( i!=iExcept ){
+      Select *p;
+      assert( pItem->iCursor < aCsrMap[0] );
+      if( !pItem->fg.isRecursive || aCsrMap[pItem->iCursor+1]==0 ){
+        aCsrMap[pItem->iCursor+1] = pParse->nTab++;
+      }
+      pItem->iCursor = aCsrMap[pItem->iCursor+1];
+      for(p=pItem->pSelect; p; p=p->pPrior){
+        srclistRenumberCursors(pParse, aCsrMap, p->pSrc, -1);
+      }
+    }
+  }
+}
+
+/*
+** *piCursor is a cursor number.  Change it if it needs to be mapped.
+*/
+static void renumberCursorDoMapping(Walker *pWalker, int *piCursor){
+  int *aCsrMap = pWalker->u.aiCol;
+  int iCsr = *piCursor;
+  if( iCsr < aCsrMap[0] && aCsrMap[iCsr+1]>0 ){
+    *piCursor = aCsrMap[iCsr+1];
+  }
+}
+
+/*
+** Expression walker callback used by renumberCursors() to update
+** Expr objects to match newly assigned cursor numbers.
+*/
+static int renumberCursorsCb(Walker *pWalker, Expr *pExpr){
+  int op = pExpr->op;
+  if( op==TK_COLUMN || op==TK_IF_NULL_ROW ){
+    renumberCursorDoMapping(pWalker, &pExpr->iTable);
+  }
+  if( ExprHasProperty(pExpr, EP_OuterON) ){
+    renumberCursorDoMapping(pWalker, &pExpr->w.iJoin);
+  }
+  return WRC_Continue;
+}
+
+/*
+** Assign a new cursor number to each cursor in the FROM clause (Select.pSrc)
+** of the SELECT statement passed as the second argument, and to each
+** cursor in the FROM clause of any FROM clause sub-selects, recursively.
+** Except, do not assign a new cursor number to the iExcept'th element in
+** the FROM clause of (*p). Update all expressions and other references
+** to refer to the new cursor numbers.
+**
+** Argument aCsrMap is an array that may be used for temporary working
+** space. Two guarantees are made by the caller:
+**
+**   * the array is larger than the largest cursor number used within the
+**     select statement passed as an argument, and
+**
+**   * the array entries for all cursor numbers that do *not* appear in
+**     FROM clauses of the select statement as described above are
+**     initialized to zero.
+*/
+static void renumberCursors(
+  Parse *pParse,                  /* Parse context */
+  Select *p,                      /* Select to renumber cursors within */
+  int iExcept,                    /* FROM clause item to skip */
+  int *aCsrMap                    /* Working space */
+){
+  Walker w;
+  srclistRenumberCursors(pParse, aCsrMap, p->pSrc, iExcept);
+  memset(&w, 0, sizeof(w));
+  w.u.aiCol = aCsrMap;
+  w.xExprCallback = renumberCursorsCb;
+  w.xSelectCallback = sqlite3SelectWalkNoop;
+  sqlite3WalkSelect(&w, p);
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+/*
+** If pSel is not part of a compound SELECT, return a pointer to its
+** expression list. Otherwise, return a pointer to the expression list
+** of the leftmost SELECT in the compound.
+*/
+static ExprList *findLeftmostExprlist(Select *pSel){
+  while( pSel->pPrior ){
+    pSel = pSel->pPrior;
+  }
+  return pSel->pEList;
+}
+
+/*
+** Return true if any of the result-set columns in the compound query
+** have incompatible affinities on one or more arms of the compound.
+*/
+static int compoundHasDifferentAffinities(Select *p){
+  int ii;
+  ExprList *pList;
+  assert( p!=0 );
+  assert( p->pEList!=0 );
+  assert( p->pPrior!=0 );
+  pList = p->pEList;
+  for(ii=0; ii<pList->nExpr; ii++){
+    char aff;
+    Select *pSub1;
+    assert( pList->a[ii].pExpr!=0 );
+    aff = sqlite3ExprAffinity(pList->a[ii].pExpr);
+    for(pSub1=p->pPrior; pSub1; pSub1=pSub1->pPrior){
+      assert( pSub1->pEList!=0 );
+      assert( pSub1->pEList->nExpr>ii );
+      assert( pSub1->pEList->a[ii].pExpr!=0 );
+      if( sqlite3ExprAffinity(pSub1->pEList->a[ii].pExpr)!=aff ){
+        return 1;
+      }
+    }
+  }
+  return 0;
+}
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** This routine attempts to flatten subqueries as a performance optimization.
+** This routine returns 1 if it makes changes and 0 if no flattening occurs.
+**
+** To understand the concept of flattening, consider the following
+** query:
+**
+**     SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
+**
+** The default way of implementing this query is to execute the
+** subquery first and store the results in a temporary table, then
+** run the outer query on that temporary table.  This requires two
+** passes over the data.  Furthermore, because the temporary table
+** has no indices, the WHERE clause on the outer query cannot be
+** optimized.
+**
+** This routine attempts to rewrite queries such as the above into
+** a single flat select, like this:
+**
+**     SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
+**
+** The code generated for this simplification gives the same result
+** but only has to scan the data once.  And because indices might
+** exist on the table t1, a complete scan of the data might be
+** avoided.
+**
+** Flattening is subject to the following constraints:
+**
+**  (**)  We no longer attempt to flatten aggregate subqueries. Was:
+**        The subquery and the outer query cannot both be aggregates.
+**
+**  (**)  We no longer attempt to flatten aggregate subqueries. Was:
+**        (2) If the subquery is an aggregate then
+**        (2a) the outer query must not be a join and
+**        (2b) the outer query must not use subqueries
+**             other than the one FROM-clause subquery that is a candidate
+**             for flattening.  (This is due to ticket [2f7170d73bf9abf80]
+**             from 2015-02-09.)
+**
+**   (3)  If the subquery is the right operand of a LEFT JOIN then
+**        (3a) the subquery may not be a join and
+**        (3b) the FROM clause of the subquery may not contain a virtual
+**             table and
+**        (**) Was: "The outer query may not have a GROUP BY." This case
+**             is now managed correctly
+**        (3d) the outer query may not be DISTINCT.
+**        See also (26) for restrictions on RIGHT JOIN.
+**
+**   (4)  The subquery can not be DISTINCT.
+**
+**  (**)  At one point restrictions (4) and (5) defined a subset of DISTINCT
+**        sub-queries that were excluded from this optimization. Restriction
+**        (4) has since been expanded to exclude all DISTINCT subqueries.
+**
+**  (**)  We no longer attempt to flatten aggregate subqueries.  Was:
+**        If the subquery is aggregate, the outer query may not be DISTINCT.
+**
+**   (7)  The subquery must have a FROM clause.  TODO:  For subqueries without
+**        A FROM clause, consider adding a FROM clause with the special
+**        table sqlite_once that consists of a single row containing a
+**        single NULL.
+**
+**   (8)  If the subquery uses LIMIT then the outer query may not be a join.
+**
+**   (9)  If the subquery uses LIMIT then the outer query may not be aggregate.
+**
+**  (**)  Restriction (10) was removed from the code on 2005-02-05 but we
+**        accidentally carried the comment forward until 2014-09-15.  Original
+**        constraint: "If the subquery is aggregate then the outer query
+**        may not use LIMIT."
+**
+**  (11)  The subquery and the outer query may not both have ORDER BY clauses.
+**
+**  (**)  Not implemented.  Subsumed into restriction (3).  Was previously
+**        a separate restriction deriving from ticket #350.
+**
+**  (13)  The subquery and outer query may not both use LIMIT.
+**
+**  (14)  The subquery may not use OFFSET.
+**
+**  (15)  If the outer query is part of a compound select, then the
+**        subquery may not use LIMIT.
+**        (See ticket #2339 and ticket [02a8e81d44]).
+**
+**  (16)  If the outer query is aggregate, then the subquery may not
+**        use ORDER BY.  (Ticket #2942)  This used to not matter
+**        until we introduced the group_concat() function. 
+**
+**  (17)  If the subquery is a compound select, then
+**        (17a) all compound operators must be a UNION ALL, and
+**        (17b) no terms within the subquery compound may be aggregate
+**              or DISTINCT, and
+**        (17c) every term within the subquery compound must have a FROM clause
+**        (17d) the outer query may not be
+**              (17d1) aggregate, or
+**              (17d2) DISTINCT
+**        (17e) the subquery may not contain window functions, and
+**        (17f) the subquery must not be the RHS of a LEFT JOIN.
+**        (17g) either the subquery is the first element of the outer
+**              query or there are no RIGHT or FULL JOINs in any arm
+**              of the subquery.  (This is a duplicate of condition (27b).)
+**        (17h) The corresponding result set expressions in all arms of the
+**              compound must have the same affinity.
+**
+**        The parent and sub-query may contain WHERE clauses. Subject to
+**        rules (11), (13) and (14), they may also contain ORDER BY,
+**        LIMIT and OFFSET clauses.  The subquery cannot use any compound
+**        operator other than UNION ALL because all the other compound
+**        operators have an implied DISTINCT which is disallowed by
+**        restriction (4).
+**
+**        Also, each component of the sub-query must return the same number
+**        of result columns. This is actually a requirement for any compound
+**        SELECT statement, but all the code here does is make sure that no
+**        such (illegal) sub-query is flattened. The caller will detect the
+**        syntax error and return a detailed message.
+**
+**  (18)  If the sub-query is a compound select, then all terms of the
+**        ORDER BY clause of the parent must be copies of a term returned
+**        by the parent query.
+**
+**  (19)  If the subquery uses LIMIT then the outer query may not
+**        have a WHERE clause.
+**
+**  (20)  If the sub-query is a compound select, then it must not use
+**        an ORDER BY clause.  Ticket #3773.  We could relax this constraint
+**        somewhat by saying that the terms of the ORDER BY clause must
+**        appear as unmodified result columns in the outer query.  But we
+**        have other optimizations in mind to deal with that case.
+**
+**  (21)  If the subquery uses LIMIT then the outer query may not be
+**        DISTINCT.  (See ticket [752e1646fc]).
+**
+**  (22)  The subquery may not be a recursive CTE.
+**
+**  (23)  If the outer query is a recursive CTE, then the sub-query may not be
+**        a compound query.  This restriction is because transforming the
+**        parent to a compound query confuses the code that handles
+**        recursive queries in multiSelect().
+**
+**  (**)  We no longer attempt to flatten aggregate subqueries.  Was:
+**        The subquery may not be an aggregate that uses the built-in min() or
+**        or max() functions.  (Without this restriction, a query like:
+**        "SELECT x FROM (SELECT max(y), x FROM t1)" would not necessarily
+**        return the value X for which Y was maximal.)
+**
+**  (25)  If either the subquery or the parent query contains a window
+**        function in the select list or ORDER BY clause, flattening
+**        is not attempted.
+**
+**  (26)  The subquery may not be the right operand of a RIGHT JOIN.
+**        See also (3) for restrictions on LEFT JOIN.
+**
+**  (27)  The subquery may not contain a FULL or RIGHT JOIN unless it
+**        is the first element of the parent query.  Two subcases:
+**        (27a) the subquery is not a compound query.
+**        (27b) the subquery is a compound query and the RIGHT JOIN occurs
+**              in any arm of the compound query.  (See also (17g).)
+**
+**  (28)  The subquery is not a MATERIALIZED CTE.  (This is handled
+**        in the caller before ever reaching this routine.)
+**
+**
+** In this routine, the "p" parameter is a pointer to the outer query.
+** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
+** uses aggregates.
+**
+** If flattening is not attempted, this routine is a no-op and returns 0.
+** If flattening is attempted this routine returns 1.
+**
+** All of the expression analysis must occur on both the outer query and
+** the subquery before this routine runs.
+*/
+static int flattenSubquery(
+  Parse *pParse,       /* Parsing context */
+  Select *p,           /* The parent or outer SELECT statement */
+  int iFrom,           /* Index in p->pSrc->a[] of the inner subquery */
+  int isAgg            /* True if outer SELECT uses aggregate functions */
+){
+  const char *zSavedAuthContext = pParse->zAuthContext;
+  Select *pParent;    /* Current UNION ALL term of the other query */
+  Select *pSub;       /* The inner query or "subquery" */
+  Select *pSub1;      /* Pointer to the rightmost select in sub-query */
+  SrcList *pSrc;      /* The FROM clause of the outer query */
+  SrcList *pSubSrc;   /* The FROM clause of the subquery */
+  int iParent;        /* VDBE cursor number of the pSub result set temp table */
+  int iNewParent = -1;/* Replacement table for iParent */
+  int isOuterJoin = 0; /* True if pSub is the right side of a LEFT JOIN */   
+  int i;              /* Loop counter */
+  Expr *pWhere;                    /* The WHERE clause */
+  SrcItem *pSubitem;               /* The subquery */
+  sqlite3 *db = pParse->db;
+  Walker w;                        /* Walker to persist agginfo data */
+  int *aCsrMap = 0;
+
+  /* Check to see if flattening is permitted.  Return 0 if not.
+  */
+  assert( p!=0 );
+  assert( p->pPrior==0 );
+  if( OptimizationDisabled(db, SQLITE_QueryFlattener) ) return 0;
+  pSrc = p->pSrc;
+  assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
+  pSubitem = &pSrc->a[iFrom];
+  iParent = pSubitem->iCursor;
+  pSub = pSubitem->pSelect;
+  assert( pSub!=0 );
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( p->pWin || pSub->pWin ) return 0;                  /* Restriction (25) */
+#endif
+
+  pSubSrc = pSub->pSrc;
+  assert( pSubSrc );
+  /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
+  ** not arbitrary expressions, we allowed some combining of LIMIT and OFFSET
+  ** because they could be computed at compile-time.  But when LIMIT and OFFSET
+  ** became arbitrary expressions, we were forced to add restrictions (13)
+  ** and (14). */
+  if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
+  if( pSub->pLimit && pSub->pLimit->pRight ) return 0;   /* Restriction (14) */
+  if( (p->selFlags & SF_Compound)!=0 && pSub->pLimit ){
+    return 0;                                            /* Restriction (15) */
+  }
+  if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
+  if( pSub->selFlags & SF_Distinct ) return 0;           /* Restriction (4)  */
+  if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
+     return 0;         /* Restrictions (8)(9) */
+  }
+  if( p->pOrderBy && pSub->pOrderBy ){
+     return 0;                                           /* Restriction (11) */
+  }
+  if( isAgg && pSub->pOrderBy ) return 0;                /* Restriction (16) */
+  if( pSub->pLimit && p->pWhere ) return 0;              /* Restriction (19) */
+  if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
+     return 0;         /* Restriction (21) */
+  }
+  if( pSub->selFlags & (SF_Recursive) ){
+    return 0; /* Restrictions (22) */
+  }
+
+  /*
+  ** If the subquery is the right operand of a LEFT JOIN, then the
+  ** subquery may not be a join itself (3a). Example of why this is not
+  ** allowed:
+  **
+  **         t1 LEFT OUTER JOIN (t2 JOIN t3)
+  **
+  ** If we flatten the above, we would get
+  **
+  **         (t1 LEFT OUTER JOIN t2) JOIN t3
+  **
+  ** which is not at all the same thing.
+  **
+  ** See also tickets #306, #350, and #3300.
+  */
+  if( (pSubitem->fg.jointype & (JT_OUTER|JT_LTORJ))!=0 ){
+    if( pSubSrc->nSrc>1                        /* (3a) */
+     || IsVirtual(pSubSrc->a[0].pTab)          /* (3b) */
+     || (p->selFlags & SF_Distinct)!=0         /* (3d) */
+     || (pSubitem->fg.jointype & JT_RIGHT)!=0  /* (26) */
+    ){
+      return 0;
+    }
+    isOuterJoin = 1;
+  }
+
+  assert( pSubSrc->nSrc>0 );  /* True by restriction (7) */
+  if( iFrom>0 && (pSubSrc->a[0].fg.jointype & JT_LTORJ)!=0 ){
+    return 0;   /* Restriction (27a) */
+  }
+
+  /* Condition (28) is blocked by the caller */
+  assert( !pSubitem->fg.isCte || pSubitem->u2.pCteUse->eM10d!=M10d_Yes );
+
+  /* Restriction (17): If the sub-query is a compound SELECT, then it must
+  ** use only the UNION ALL operator. And none of the simple select queries
+  ** that make up the compound SELECT are allowed to be aggregate or distinct
+  ** queries.
+  */
+  if( pSub->pPrior ){
+    int ii;
+    if( pSub->pOrderBy ){
+      return 0;  /* Restriction (20) */
+    }
+    if( isAgg || (p->selFlags & SF_Distinct)!=0 || isOuterJoin>0 ){
+      return 0; /* (17d1), (17d2), or (17f) */
+    }
+    for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
+      testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
+      testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
+      assert( pSub->pSrc!=0 );
+      assert( (pSub->selFlags & SF_Recursive)==0 );
+      assert( pSub->pEList->nExpr==pSub1->pEList->nExpr );
+      if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0    /* (17b) */
+       || (pSub1->pPrior && pSub1->op!=TK_ALL)                 /* (17a) */
+       || pSub1->pSrc->nSrc<1                                  /* (17c) */
+#ifndef SQLITE_OMIT_WINDOWFUNC
+       || pSub1->pWin                                          /* (17e) */
+#endif
+      ){
+        return 0;
+      }
+      if( iFrom>0 && (pSub1->pSrc->a[0].fg.jointype & JT_LTORJ)!=0 ){
+        /* Without this restriction, the JT_LTORJ flag would end up being
+        ** omitted on left-hand tables of the right join that is being
+        ** flattened. */
+        return 0;   /* Restrictions (17g), (27b) */
+      }
+      testcase( pSub1->pSrc->nSrc>1 );
+    }
+
+    /* Restriction (18). */
+    if( p->pOrderBy ){
+      for(ii=0; ii<p->pOrderBy->nExpr; ii++){
+        if( p->pOrderBy->a[ii].u.x.iOrderByCol==0 ) return 0;
+      }
+    }
+
+    /* Restriction (23) */
+    if( (p->selFlags & SF_Recursive) ) return 0;
+
+    /* Restriction (17h) */
+    if( compoundHasDifferentAffinities(pSub) ) return 0;
+
+    if( pSrc->nSrc>1 ){
+      if( pParse->nSelect>500 ) return 0;
+      if( OptimizationDisabled(db, SQLITE_FlttnUnionAll) ) return 0;
+      aCsrMap = sqlite3DbMallocZero(db, ((i64)pParse->nTab+1)*sizeof(int));
+      if( aCsrMap ) aCsrMap[0] = pParse->nTab;
+    }
+  }
+
+  /***** If we reach this point, flattening is permitted. *****/
+  TREETRACE(0x4,pParse,p,("flatten %u.%p from term %d\n",
+                   pSub->selId, pSub, iFrom));
+
+  /* Authorize the subquery */
+  pParse->zAuthContext = pSubitem->zName;
+  TESTONLY(i =) sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);
+  testcase( i==SQLITE_DENY );
+  pParse->zAuthContext = zSavedAuthContext;
+
+  /* Delete the transient structures associated with the subquery */
+  pSub1 = pSubitem->pSelect;
+  sqlite3DbFree(db, pSubitem->zDatabase);
+  sqlite3DbFree(db, pSubitem->zName);
+  sqlite3DbFree(db, pSubitem->zAlias);
+  pSubitem->zDatabase = 0;
+  pSubitem->zName = 0;
+  pSubitem->zAlias = 0;
+  pSubitem->pSelect = 0;
+  assert( pSubitem->fg.isUsing!=0 || pSubitem->u3.pOn==0 );
+
+  /* If the sub-query is a compound SELECT statement, then (by restrictions
+  ** 17 and 18 above) it must be a UNION ALL and the parent query must
+  ** be of the form:
+  **
+  **     SELECT <expr-list> FROM (<sub-query>) <where-clause>
+  **
+  ** followed by any ORDER BY, LIMIT and/or OFFSET clauses. This block
+  ** creates N-1 copies of the parent query without any ORDER BY, LIMIT or
+  ** OFFSET clauses and joins them to the left-hand-side of the original
+  ** using UNION ALL operators. In this case N is the number of simple
+  ** select statements in the compound sub-query.
+  **
+  ** Example:
+  **
+  **     SELECT a+1 FROM (
+  **        SELECT x FROM tab
+  **        UNION ALL
+  **        SELECT y FROM tab
+  **        UNION ALL
+  **        SELECT abs(z*2) FROM tab2
+  **     ) WHERE a!=5 ORDER BY 1
+  **
+  ** Transformed into:
+  **
+  **     SELECT x+1 FROM tab WHERE x+1!=5
+  **     UNION ALL
+  **     SELECT y+1 FROM tab WHERE y+1!=5
+  **     UNION ALL
+  **     SELECT abs(z*2)+1 FROM tab2 WHERE abs(z*2)+1!=5
+  **     ORDER BY 1
+  **
+  ** We call this the "compound-subquery flattening".
+  */
+  for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
+    Select *pNew;
+    ExprList *pOrderBy = p->pOrderBy;
+    Expr *pLimit = p->pLimit;
+    Select *pPrior = p->pPrior;
+    Table *pItemTab = pSubitem->pTab;
+    pSubitem->pTab = 0;
+    p->pOrderBy = 0;
+    p->pPrior = 0;
+    p->pLimit = 0;
+    pNew = sqlite3SelectDup(db, p, 0);
+    p->pLimit = pLimit;
+    p->pOrderBy = pOrderBy;
+    p->op = TK_ALL;
+    pSubitem->pTab = pItemTab;
+    if( pNew==0 ){
+      p->pPrior = pPrior;
+    }else{
+      pNew->selId = ++pParse->nSelect;
+      if( aCsrMap && ALWAYS(db->mallocFailed==0) ){
+        renumberCursors(pParse, pNew, iFrom, aCsrMap);
+      }
+      pNew->pPrior = pPrior;
+      if( pPrior ) pPrior->pNext = pNew;
+      pNew->pNext = p;
+      p->pPrior = pNew;
+      TREETRACE(0x4,pParse,p,("compound-subquery flattener"
+                              " creates %u as peer\n",pNew->selId));
+    }
+    assert( pSubitem->pSelect==0 );
+  }
+  sqlite3DbFree(db, aCsrMap);
+  if( db->mallocFailed ){
+    pSubitem->pSelect = pSub1;
+    return 1;
+  }
+
+  /* Defer deleting the Table object associated with the
+  ** subquery until code generation is
+  ** complete, since there may still exist Expr.pTab entries that
+  ** refer to the subquery even after flattening.  Ticket #3346.
+  **
+  ** pSubitem->pTab is always non-NULL by test restrictions and tests above.
+  */
+  if( ALWAYS(pSubitem->pTab!=0) ){
+    Table *pTabToDel = pSubitem->pTab;
+    if( pTabToDel->nTabRef==1 ){
+      Parse *pToplevel = sqlite3ParseToplevel(pParse);
+      sqlite3ParserAddCleanup(pToplevel, sqlite3DeleteTableGeneric, pTabToDel);
+      testcase( pToplevel->earlyCleanup );
+    }else{
+      pTabToDel->nTabRef--;
+    }
+    pSubitem->pTab = 0;
+  }
+
+  /* The following loop runs once for each term in a compound-subquery
+  ** flattening (as described above).  If we are doing a different kind
+  ** of flattening - a flattening other than a compound-subquery flattening -
+  ** then this loop only runs once.
+  **
+  ** This loop moves all of the FROM elements of the subquery into the
+  ** the FROM clause of the outer query.  Before doing this, remember
+  ** the cursor number for the original outer query FROM element in
+  ** iParent.  The iParent cursor will never be used.  Subsequent code
+  ** will scan expressions looking for iParent references and replace
+  ** those references with expressions that resolve to the subquery FROM
+  ** elements we are now copying in.
+  */
+  pSub = pSub1;
+  for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
+    int nSubSrc;
+    u8 jointype = 0;
+    u8 ltorj = pSrc->a[iFrom].fg.jointype & JT_LTORJ;
+    assert( pSub!=0 );
+    pSubSrc = pSub->pSrc;     /* FROM clause of subquery */
+    nSubSrc = pSubSrc->nSrc;  /* Number of terms in subquery FROM clause */
+    pSrc = pParent->pSrc;     /* FROM clause of the outer query */
+
+    if( pParent==p ){
+      jointype = pSubitem->fg.jointype;     /* First time through the loop */
+    }
+   
+    /* The subquery uses a single slot of the FROM clause of the outer
+    ** query.  If the subquery has more than one element in its FROM clause,
+    ** then expand the outer query to make space for it to hold all elements
+    ** of the subquery.
+    **
+    ** Example:
+    **
+    **    SELECT * FROM tabA, (SELECT * FROM sub1, sub2), tabB;
+    **
+    ** The outer query has 3 slots in its FROM clause.  One slot of the
+    ** outer query (the middle slot) is used by the subquery.  The next
+    ** block of code will expand the outer query FROM clause to 4 slots.
+    ** The middle slot is expanded to two slots in order to make space
+    ** for the two elements in the FROM clause of the subquery.
+    */
+    if( nSubSrc>1 ){
+      pSrc = sqlite3SrcListEnlarge(pParse, pSrc, nSubSrc-1,iFrom+1);
+      if( pSrc==0 ) break;
+      pParent->pSrc = pSrc;
+    }
+
+    /* Transfer the FROM clause terms from the subquery into the
+    ** outer query.
+    */
+    for(i=0; i<nSubSrc; i++){
+      SrcItem *pItem = &pSrc->a[i+iFrom];
+      if( pItem->fg.isUsing ) sqlite3IdListDelete(db, pItem->u3.pUsing);
+      assert( pItem->fg.isTabFunc==0 );
+      *pItem = pSubSrc->a[i];
+      pItem->fg.jointype |= ltorj;
+      iNewParent = pSubSrc->a[i].iCursor;
+      memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
+    }
+    pSrc->a[iFrom].fg.jointype &= JT_LTORJ;
+    pSrc->a[iFrom].fg.jointype |= jointype | ltorj;
+ 
+    /* Now begin substituting subquery result set expressions for
+    ** references to the iParent in the outer query.
+    **
+    ** Example:
+    **
+    **   SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
+    **   \                     \_____________ subquery __________/          /
+    **    \_____________________ outer query ______________________________/
+    **
+    ** We look at every expression in the outer query and every place we see
+    ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
+    */
+    if( pSub->pOrderBy && (pParent->selFlags & SF_NoopOrderBy)==0 ){
+      /* At this point, any non-zero iOrderByCol values indicate that the
+      ** ORDER BY column expression is identical to the iOrderByCol'th
+      ** expression returned by SELECT statement pSub. Since these values
+      ** do not necessarily correspond to columns in SELECT statement pParent,
+      ** zero them before transferring the ORDER BY clause.
+      **
+      ** Not doing this may cause an error if a subsequent call to this
+      ** function attempts to flatten a compound sub-query into pParent
+      ** (the only way this can happen is if the compound sub-query is
+      ** currently part of pSub->pSrc). See ticket [d11a6e908f].  */
+      ExprList *pOrderBy = pSub->pOrderBy;
+      for(i=0; i<pOrderBy->nExpr; i++){
+        pOrderBy->a[i].u.x.iOrderByCol = 0;
+      }
+      assert( pParent->pOrderBy==0 );
+      pParent->pOrderBy = pOrderBy;
+      pSub->pOrderBy = 0;
+    }
+    pWhere = pSub->pWhere;
+    pSub->pWhere = 0;
+    if( isOuterJoin>0 ){
+      sqlite3SetJoinExpr(pWhere, iNewParent, EP_OuterON);
+    }
+    if( pWhere ){
+      if( pParent->pWhere ){
+        pParent->pWhere = sqlite3PExpr(pParse, TK_AND, pWhere, pParent->pWhere);
+      }else{
+        pParent->pWhere = pWhere;
+      }
+    }
+    if( db->mallocFailed==0 ){
+      SubstContext x;
+      x.pParse = pParse;
+      x.iTable = iParent;
+      x.iNewTable = iNewParent;
+      x.isOuterJoin = isOuterJoin;
+      x.pEList = pSub->pEList;
+      x.pCList = findLeftmostExprlist(pSub);
+      substSelect(&x, pParent, 0);
+    }
+ 
+    /* The flattened query is a compound if either the inner or the
+    ** outer query is a compound. */
+    pParent->selFlags |= pSub->selFlags & SF_Compound;
+    assert( (pSub->selFlags & SF_Distinct)==0 ); /* restriction (17b) */
+ 
+    /*
+    ** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
+    **
+    ** One is tempted to try to add a and b to combine the limits.  But this
+    ** does not work if either limit is negative.
+    */
+    if( pSub->pLimit ){
+      pParent->pLimit = pSub->pLimit;
+      pSub->pLimit = 0;
+    }
+
+    /* Recompute the SrcItem.colUsed masks for the flattened
+    ** tables. */
+    for(i=0; i<nSubSrc; i++){
+      recomputeColumnsUsed(pParent, &pSrc->a[i+iFrom]);
+    }
+  }
+
+  /* Finally, delete what is left of the subquery and return success.
+  */
+  sqlite3AggInfoPersistWalkerInit(&w, pParse);
+  sqlite3WalkSelect(&w,pSub1);
+  sqlite3SelectDelete(db, pSub1);
+
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x4 ){
+    TREETRACE(0x4,pParse,p,("After flattening:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+
+  return 1;
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+/*
+** A structure to keep track of all of the column values that are fixed to
+** a known value due to WHERE clause constraints of the form COLUMN=VALUE.
+*/
+typedef struct WhereConst WhereConst;
+struct WhereConst {
+  Parse *pParse;   /* Parsing context */
+  u8 *pOomFault;   /* Pointer to pParse->db->mallocFailed */
+  int nConst;      /* Number for COLUMN=CONSTANT terms */
+  int nChng;       /* Number of times a constant is propagated */
+  int bHasAffBlob; /* At least one column in apExpr[] as affinity BLOB */
+  u32 mExcludeOn;  /* Which ON expressions to exclude from considertion.
+                   ** Either EP_OuterON or EP_InnerON|EP_OuterON */
+  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
+};
+
+/*
+** Add a new entry to the pConst object.  Except, do not add duplicate
+** pColumn entries.  Also, do not add if doing so would not be appropriate.
+**
+** The caller guarantees the pColumn is a column and pValue is a constant.
+** This routine has to do some additional checks before completing the
+** insert.
+*/
+static void constInsert(
+  WhereConst *pConst,  /* The WhereConst into which we are inserting */
+  Expr *pColumn,       /* The COLUMN part of the constraint */
+  Expr *pValue,        /* The VALUE part of the constraint */
+  Expr *pExpr          /* Overall expression: COLUMN=VALUE or VALUE=COLUMN */
+){
+  int i;
+  assert( pColumn->op==TK_COLUMN );
+  assert( sqlite3ExprIsConstant(pValue) );
+
+  if( ExprHasProperty(pColumn, EP_FixedCol) ) return;
+  if( sqlite3ExprAffinity(pValue)!=0 ) return;
+  if( !sqlite3IsBinary(sqlite3ExprCompareCollSeq(pConst->pParse,pExpr)) ){
+    return;
+  }
+
+  /* 2018-10-25 ticket [cf5ed20f]
+  ** Make sure the same pColumn is not inserted more than once */
+  for(i=0; i<pConst->nConst; i++){
+    const Expr *pE2 = pConst->apExpr[i*2];
+    assert( pE2->op==TK_COLUMN );
+    if( pE2->iTable==pColumn->iTable
+     && pE2->iColumn==pColumn->iColumn
+    ){
+      return;  /* Already present.  Return without doing anything. */
+    }
+  }
+  if( sqlite3ExprAffinity(pColumn)==SQLITE_AFF_BLOB ){
+    pConst->bHasAffBlob = 1;
+  }
+
+  pConst->nConst++;
+  pConst->apExpr = sqlite3DbReallocOrFree(pConst->pParse->db, pConst->apExpr,
+                         pConst->nConst*2*sizeof(Expr*));
+  if( pConst->apExpr==0 ){
+    pConst->nConst = 0;
+  }else{
+    pConst->apExpr[pConst->nConst*2-2] = pColumn;
+    pConst->apExpr[pConst->nConst*2-1] = pValue;
+  }
+}
+
+/*
+** Find all terms of COLUMN=VALUE or VALUE=COLUMN in pExpr where VALUE
+** is a constant expression and where the term must be true because it
+** is part of the AND-connected terms of the expression.  For each term
+** found, add it to the pConst structure.
+*/
+static void findConstInWhere(WhereConst *pConst, Expr *pExpr){
+  Expr *pRight, *pLeft;
+  if( NEVER(pExpr==0) ) return;
+  if( ExprHasProperty(pExpr, pConst->mExcludeOn) ){
+    testcase( ExprHasProperty(pExpr, EP_OuterON) );
+    testcase( ExprHasProperty(pExpr, EP_InnerON) );
+    return;
+  }
+  if( pExpr->op==TK_AND ){
+    findConstInWhere(pConst, pExpr->pRight);
+    findConstInWhere(pConst, pExpr->pLeft);
+    return;
+  }
+  if( pExpr->op!=TK_EQ ) return;
+  pRight = pExpr->pRight;
+  pLeft = pExpr->pLeft;
+  assert( pRight!=0 );
+  assert( pLeft!=0 );
+  if( pRight->op==TK_COLUMN && sqlite3ExprIsConstant(pLeft) ){
+    constInsert(pConst,pRight,pLeft,pExpr);
+  }
+  if( pLeft->op==TK_COLUMN && sqlite3ExprIsConstant(pRight) ){
+    constInsert(pConst,pLeft,pRight,pExpr);
+  }
+}
+
+/*
+** This is a helper function for Walker callback propagateConstantExprRewrite().
+**
+** Argument pExpr is a candidate expression to be replaced by a value. If
+** pExpr is equivalent to one of the columns named in pWalker->u.pConst,
+** then overwrite it with the corresponding value. Except, do not do so
+** if argument bIgnoreAffBlob is non-zero and the affinity of pExpr
+** is SQLITE_AFF_BLOB.
+*/
+static int propagateConstantExprRewriteOne(
+  WhereConst *pConst,
+  Expr *pExpr,
+  int bIgnoreAffBlob
+){
+  int i;
+  if( pConst->pOomFault[0] ) return WRC_Prune;
+  if( pExpr->op!=TK_COLUMN ) return WRC_Continue;
+  if( ExprHasProperty(pExpr, EP_FixedCol|pConst->mExcludeOn) ){
+    testcase( ExprHasProperty(pExpr, EP_FixedCol) );
+    testcase( ExprHasProperty(pExpr, EP_OuterON) );
+    testcase( ExprHasProperty(pExpr, EP_InnerON) );
+    return WRC_Continue;
+  }
+  for(i=0; i<pConst->nConst; i++){
+    Expr *pColumn = pConst->apExpr[i*2];
+    if( pColumn==pExpr ) continue;
+    if( pColumn->iTable!=pExpr->iTable ) continue;
+    if( pColumn->iColumn!=pExpr->iColumn ) continue;
+    if( bIgnoreAffBlob && sqlite3ExprAffinity(pColumn)==SQLITE_AFF_BLOB ){
+      break;
+    }
+    /* A match is found.  Add the EP_FixedCol property */
+    pConst->nChng++;
+    ExprClearProperty(pExpr, EP_Leaf);
+    ExprSetProperty(pExpr, EP_FixedCol);
+    assert( pExpr->pLeft==0 );
+    pExpr->pLeft = sqlite3ExprDup(pConst->pParse->db, pConst->apExpr[i*2+1], 0);
+    if( pConst->pParse->db->mallocFailed ) return WRC_Prune;
+    break;
+  }
+  return WRC_Prune;
+}
+
+/*
+** This is a Walker expression callback. pExpr is a node from the WHERE
+** clause of a SELECT statement. This function examines pExpr to see if
+** any substitutions based on the contents of pWalker->u.pConst should
+** be made to pExpr or its immediate children.
+**
+** A substitution is made if:
+**
+**   + pExpr is a column with an affinity other than BLOB that matches
+**     one of the columns in pWalker->u.pConst, or
+**
+**   + pExpr is a binary comparison operator (=, <=, >=, <, >) that
+**     uses an affinity other than TEXT and one of its immediate
+**     children is a column that matches one of the columns in
+**     pWalker->u.pConst.
+*/
+static int propagateConstantExprRewrite(Walker *pWalker, Expr *pExpr){
+  WhereConst *pConst = pWalker->u.pConst;
+  assert( TK_GT==TK_EQ+1 );
+  assert( TK_LE==TK_EQ+2 );
+  assert( TK_LT==TK_EQ+3 );
+  assert( TK_GE==TK_EQ+4 );
+  if( pConst->bHasAffBlob ){
+    if( (pExpr->op>=TK_EQ && pExpr->op<=TK_GE)
+     || pExpr->op==TK_IS
+    ){
+      propagateConstantExprRewriteOne(pConst, pExpr->pLeft, 0);
+      if( pConst->pOomFault[0] ) return WRC_Prune;
+      if( sqlite3ExprAffinity(pExpr->pLeft)!=SQLITE_AFF_TEXT ){
+        propagateConstantExprRewriteOne(pConst, pExpr->pRight, 0);
+      }
+    }
+  }
+  return propagateConstantExprRewriteOne(pConst, pExpr, pConst->bHasAffBlob);
+}
+
+/*
+** The WHERE-clause constant propagation optimization.
+**
+** If the WHERE clause contains terms of the form COLUMN=CONSTANT or
+** CONSTANT=COLUMN that are top-level AND-connected terms that are not
+** part of a ON clause from a LEFT JOIN, then throughout the query
+** replace all other occurrences of COLUMN with CONSTANT.
+**
+** For example, the query:
+**
+**      SELECT * FROM t1, t2, t3 WHERE t1.a=39 AND t2.b=t1.a AND t3.c=t2.b
+**
+** Is transformed into
+**
+**      SELECT * FROM t1, t2, t3 WHERE t1.a=39 AND t2.b=39 AND t3.c=39
+**
+** Return true if any transformations where made and false if not.
+**
+** Implementation note:  Constant propagation is tricky due to affinity
+** and collating sequence interactions.  Consider this example:
+**
+**    CREATE TABLE t1(a INT,b TEXT);
+**    INSERT INTO t1 VALUES(123,'0123');
+**    SELECT * FROM t1 WHERE a=123 AND b=a;
+**    SELECT * FROM t1 WHERE a=123 AND b=123;
+**
+** The two SELECT statements above should return different answers.  b=a
+** is always true because the comparison uses numeric affinity, but b=123
+** is false because it uses text affinity and '0123' is not the same as '123'.
+** To work around this, the expression tree is not actually changed from
+** "b=a" to "b=123" but rather the "a" in "b=a" is tagged with EP_FixedCol
+** and the "123" value is hung off of the pLeft pointer.  Code generator
+** routines know to generate the constant "123" instead of looking up the
+** column value.  Also, to avoid collation problems, this optimization is
+** only attempted if the "a=123" term uses the default BINARY collation.
+**
+** 2021-05-25 forum post 6a06202608: Another troublesome case is...
+**
+**    CREATE TABLE t1(x);
+**    INSERT INTO t1 VALUES(10.0);
+**    SELECT 1 FROM t1 WHERE x=10 AND x LIKE 10;
+**
+** The query should return no rows, because the t1.x value is '10.0' not '10'
+** and '10.0' is not LIKE '10'.  But if we are not careful, the first WHERE
+** term "x=10" will cause the second WHERE term to become "10 LIKE 10",
+** resulting in a false positive.  To avoid this, constant propagation for
+** columns with BLOB affinity is only allowed if the constant is used with
+** operators ==, <=, <, >=, >, or IS in a way that will cause the correct
+** type conversions to occur.  See logic associated with the bHasAffBlob flag
+** for details.
+*/
+static int propagateConstants(
+  Parse *pParse,   /* The parsing context */
+  Select *p        /* The query in which to propagate constants */
+){
+  WhereConst x;
+  Walker w;
+  int nChng = 0;
+  x.pParse = pParse;
+  x.pOomFault = &pParse->db->mallocFailed;
+  do{
+    x.nConst = 0;
+    x.nChng = 0;
+    x.apExpr = 0;
+    x.bHasAffBlob = 0;
+    if( ALWAYS(p->pSrc!=0)
+     && p->pSrc->nSrc>0
+     && (p->pSrc->a[0].fg.jointype & JT_LTORJ)!=0
+    ){
+      /* Do not propagate constants on any ON clause if there is a
+      ** RIGHT JOIN anywhere in the query */
+      x.mExcludeOn = EP_InnerON | EP_OuterON;
+    }else{
+      /* Do not propagate constants through the ON clause of a LEFT JOIN */
+      x.mExcludeOn = EP_OuterON;
+    }
+    findConstInWhere(&x, p->pWhere);
+    if( x.nConst ){
+      memset(&w, 0, sizeof(w));
+      w.pParse = pParse;
+      w.xExprCallback = propagateConstantExprRewrite;
+      w.xSelectCallback = sqlite3SelectWalkNoop;
+      w.xSelectCallback2 = 0;
+      w.walkerDepth = 0;
+      w.u.pConst = &x;
+      sqlite3WalkExpr(&w, p->pWhere);
+      sqlite3DbFree(x.pParse->db, x.apExpr);
+      nChng += x.nChng;
+    }
+  }while( x.nChng ); 
+  return nChng;
+}
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+# if !defined(SQLITE_OMIT_WINDOWFUNC)
+/*
+** This function is called to determine whether or not it is safe to
+** push WHERE clause expression pExpr down to FROM clause sub-query
+** pSubq, which contains at least one window function. Return 1
+** if it is safe and the expression should be pushed down, or 0
+** otherwise.
+**
+** It is only safe to push the expression down if it consists only
+** of constants and copies of expressions that appear in the PARTITION
+** BY clause of all window function used by the sub-query. It is safe
+** to filter out entire partitions, but not rows within partitions, as
+** this may change the results of the window functions.
+**
+** At the time this function is called it is guaranteed that
+**
+**   * the sub-query uses only one distinct window frame, and
+**   * that the window frame has a PARTITION BY clause.
+*/
+static int pushDownWindowCheck(Parse *pParse, Select *pSubq, Expr *pExpr){
+  assert( pSubq->pWin->pPartition );
+  assert( (pSubq->selFlags & SF_MultiPart)==0 );
+  assert( pSubq->pPrior==0 );
+  return sqlite3ExprIsConstantOrGroupBy(pParse, pExpr, pSubq->pWin->pPartition);
+}
+# endif /* SQLITE_OMIT_WINDOWFUNC */
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** Make copies of relevant WHERE clause terms of the outer query into
+** the WHERE clause of subquery.  Example:
+**
+**    SELECT * FROM (SELECT a AS x, c-d AS y FROM t1) WHERE x=5 AND y=10;
+**
+** Transformed into:
+**
+**    SELECT * FROM (SELECT a AS x, c-d AS y FROM t1 WHERE a=5 AND c-d=10)
+**     WHERE x=5 AND y=10;
+**
+** The hope is that the terms added to the inner query will make it more
+** efficient.
+**
+** Do not attempt this optimization if:
+**
+**   (1) (** This restriction was removed on 2017-09-29.  We used to
+**           disallow this optimization for aggregate subqueries, but now
+**           it is allowed by putting the extra terms on the HAVING clause.
+**           The added HAVING clause is pointless if the subquery lacks
+**           a GROUP BY clause.  But such a HAVING clause is also harmless
+**           so there does not appear to be any reason to add extra logic
+**           to suppress it. **)
+**
+**   (2) The inner query is the recursive part of a common table expression.
+**
+**   (3) The inner query has a LIMIT clause (since the changes to the WHERE
+**       clause would change the meaning of the LIMIT).
+**
+**   (4) The inner query is the right operand of a LEFT JOIN and the
+**       expression to be pushed down does not come from the ON clause
+**       on that LEFT JOIN.
+**
+**   (5) The WHERE clause expression originates in the ON or USING clause
+**       of a LEFT JOIN where iCursor is not the right-hand table of that
+**       left join.  An example:
+**
+**           SELECT *
+**           FROM (SELECT 1 AS a1 UNION ALL SELECT 2) AS aa
+**           JOIN (SELECT 1 AS b2 UNION ALL SELECT 2) AS bb ON (a1=b2)
+**           LEFT JOIN (SELECT 8 AS c3 UNION ALL SELECT 9) AS cc ON (b2=2);
+**
+**       The correct answer is three rows:  (1,1,NULL),(2,2,8),(2,2,9).
+**       But if the (b2=2) term were to be pushed down into the bb subquery,
+**       then the (1,1,NULL) row would be suppressed.
+**
+**   (6) Window functions make things tricky as changes to the WHERE clause
+**       of the inner query could change the window over which window
+**       functions are calculated. Therefore, do not attempt the optimization
+**       if:
+**
+**     (6a) The inner query uses multiple incompatible window partitions.
+**
+**     (6b) The inner query is a compound and uses window-functions.
+**
+**     (6c) The WHERE clause does not consist entirely of constants and
+**          copies of expressions found in the PARTITION BY clause of
+**          all window-functions used by the sub-query. It is safe to
+**          filter out entire partitions, as this does not change the
+**          window over which any window-function is calculated.
+**
+**   (7) The inner query is a Common Table Expression (CTE) that should
+**       be materialized.  (This restriction is implemented in the calling
+**       routine.)
+**
+**   (8) If the subquery is a compound that uses UNION, INTERSECT,
+**       or EXCEPT, then all of the result set columns for all arms of
+**       the compound must use the BINARY collating sequence.
+**
+**   (9) All three of the following are true:
+**
+**       (9a) The WHERE clause expression originates in the ON or USING clause
+**            of a join (either an INNER or an OUTER join), and
+**
+**       (9b) The subquery is to the right of the ON/USING clause
+**
+**       (9c) There is a RIGHT JOIN (or FULL JOIN) in between the ON/USING
+**            clause and the subquery.
+**
+**       Without this restriction, the push-down optimization might move
+**       the ON/USING filter expression from the left side of a RIGHT JOIN
+**       over to the right side, which leads to incorrect answers.  See
+**       also restriction (6) in sqlite3ExprIsSingleTableConstraint().
+**
+**  (10) The inner query is not the right-hand table of a RIGHT JOIN.
+**
+**  (11) The subquery is not a VALUES clause
+**
+** Return 0 if no changes are made and non-zero if one or more WHERE clause
+** terms are duplicated into the subquery.
+*/
+static int pushDownWhereTerms(
+  Parse *pParse,        /* Parse context (for malloc() and error reporting) */
+  Select *pSubq,        /* The subquery whose WHERE clause is to be augmented */
+  Expr *pWhere,         /* The WHERE clause of the outer query */
+  SrcList *pSrcList,    /* The complete from clause of the outer query */
+  int iSrc              /* Which FROM clause term to try to push into  */
+){
+  Expr *pNew;
+  SrcItem *pSrc;        /* The subquery FROM term into which WHERE is pushed */
+  int nChng = 0;
+  pSrc = &pSrcList->a[iSrc];
+  if( pWhere==0 ) return 0;
+  if( pSubq->selFlags & (SF_Recursive|SF_MultiPart) ){
+    return 0;           /* restrictions (2) and (11) */
+  }
+  if( pSrc->fg.jointype & (JT_LTORJ|JT_RIGHT) ){
+    return 0;           /* restrictions (10) */
+  }
+
+  if( pSubq->pPrior ){
+    Select *pSel;
+    int notUnionAll = 0;
+    for(pSel=pSubq; pSel; pSel=pSel->pPrior){
+      u8 op = pSel->op;
+      assert( op==TK_ALL || op==TK_SELECT
+           || op==TK_UNION || op==TK_INTERSECT || op==TK_EXCEPT );
+      if( op!=TK_ALL && op!=TK_SELECT ){
+        notUnionAll = 1;
+      }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      if( pSel->pWin ) return 0;    /* restriction (6b) */
+#endif
+    }
+    if( notUnionAll ){
+      /* If any of the compound arms are connected using UNION, INTERSECT,
+      ** or EXCEPT, then we must ensure that none of the columns use a
+      ** non-BINARY collating sequence. */
+      for(pSel=pSubq; pSel; pSel=pSel->pPrior){
+        int ii;
+        const ExprList *pList = pSel->pEList;
+        assert( pList!=0 );
+        for(ii=0; ii<pList->nExpr; ii++){
+          CollSeq *pColl = sqlite3ExprCollSeq(pParse, pList->a[ii].pExpr);
+          if( !sqlite3IsBinary(pColl) ){
+            return 0;  /* Restriction (8) */
+          }
+        }
+      }
+    }
+  }else{
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( pSubq->pWin && pSubq->pWin->pPartition==0 ) return 0;
+#endif
+  }
+
+#ifdef SQLITE_DEBUG
+  /* Only the first term of a compound can have a WITH clause.  But make
+  ** sure no other terms are marked SF_Recursive in case something changes
+  ** in the future.
+  */
+  {
+    Select *pX; 
+    for(pX=pSubq; pX; pX=pX->pPrior){
+      assert( (pX->selFlags & (SF_Recursive))==0 );
+    }
+  }
+#endif
+
+  if( pSubq->pLimit!=0 ){
+    return 0; /* restriction (3) */
+  }
+  while( pWhere->op==TK_AND ){
+    nChng += pushDownWhereTerms(pParse, pSubq, pWhere->pRight, pSrcList, iSrc);
+    pWhere = pWhere->pLeft;
+  }
+
+#if 0 /* These checks now done by sqlite3ExprIsSingleTableConstraint() */
+  if( ExprHasProperty(pWhere, EP_OuterON|EP_InnerON) /* (9a) */
+   && (pSrcList->a[0].fg.jointype & JT_LTORJ)!=0     /* Fast pre-test of (9c) */
+  ){
+    int jj;
+    for(jj=0; jj<iSrc; jj++){
+      if( pWhere->w.iJoin==pSrcList->a[jj].iCursor ){
+        /* If we reach this point, both (9a) and (9b) are satisfied.
+        ** The following loop checks (9c):
+        */
+        for(jj++; jj<iSrc; jj++){
+          if( (pSrcList->a[jj].fg.jointype & JT_RIGHT)!=0 ){
+            return 0;  /* restriction (9) */
+          }
+        }
+      }
+    }
+  }
+  if( isLeftJoin
+   && (ExprHasProperty(pWhere,EP_OuterON)==0
+         || pWhere->w.iJoin!=iCursor)
+  ){
+    return 0; /* restriction (4) */
+  }
+  if( ExprHasProperty(pWhere,EP_OuterON)
+   && pWhere->w.iJoin!=iCursor
+  ){
+    return 0; /* restriction (5) */
+  }
+#endif
+
+  if( sqlite3ExprIsSingleTableConstraint(pWhere, pSrcList, iSrc) ){
+    nChng++;
+    pSubq->selFlags |= SF_PushDown;
+    while( pSubq ){
+      SubstContext x;
+      pNew = sqlite3ExprDup(pParse->db, pWhere, 0);
+      unsetJoinExpr(pNew, -1, 1);
+      x.pParse = pParse;
+      x.iTable = pSrc->iCursor;
+      x.iNewTable = pSrc->iCursor;
+      x.isOuterJoin = 0;
+      x.pEList = pSubq->pEList;
+      x.pCList = findLeftmostExprlist(pSubq);
+      pNew = substExpr(&x, pNew);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      if( pSubq->pWin && 0==pushDownWindowCheck(pParse, pSubq, pNew) ){
+        /* Restriction 6c has prevented push-down in this case */
+        sqlite3ExprDelete(pParse->db, pNew);
+        nChng--;
+        break;
+      }
+#endif
+      if( pSubq->selFlags & SF_Aggregate ){
+        pSubq->pHaving = sqlite3ExprAnd(pParse, pSubq->pHaving, pNew);
+      }else{
+        pSubq->pWhere = sqlite3ExprAnd(pParse, pSubq->pWhere, pNew);
+      }
+      pSubq = pSubq->pPrior;
+    }
+  }
+  return nChng;
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+/*
+** Check to see if a subquery contains result-set columns that are
+** never used.  If it does, change the value of those result-set columns
+** to NULL so that they do not cause unnecessary work to compute.
+**
+** Return the number of column that were changed to NULL.
+*/
+static int disableUnusedSubqueryResultColumns(SrcItem *pItem){
+  int nCol;
+  Select *pSub;      /* The subquery to be simplified */
+  Select *pX;        /* For looping over compound elements of pSub */
+  Table *pTab;       /* The table that describes the subquery */
+  int j;             /* Column number */
+  int nChng = 0;     /* Number of columns converted to NULL */
+  Bitmask colUsed;   /* Columns that may not be NULLed out */
+
+  assert( pItem!=0 );
+  if( pItem->fg.isCorrelated || pItem->fg.isCte ){
+    return 0;
+  }
+  assert( pItem->pTab!=0 );
+  pTab = pItem->pTab;
+  assert( pItem->pSelect!=0 );
+  pSub = pItem->pSelect;
+  assert( pSub->pEList->nExpr==pTab->nCol );
+  for(pX=pSub; pX; pX=pX->pPrior){
+    if( (pX->selFlags & (SF_Distinct|SF_Aggregate))!=0 ){
+      testcase( pX->selFlags & SF_Distinct );
+      testcase( pX->selFlags & SF_Aggregate );
+      return 0;
+    }
+    if( pX->pPrior && pX->op!=TK_ALL ){
+      /* This optimization does not work for compound subqueries that
+      ** use UNION, INTERSECT, or EXCEPT.  Only UNION ALL is allowed. */
+      return 0;
+    }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( pX->pWin ){
+      /* This optimization does not work for subqueries that use window
+      ** functions. */
+      return 0;
+    }
+#endif
+  }
+  colUsed = pItem->colUsed;
+  if( pSub->pOrderBy ){
+    ExprList *pList = pSub->pOrderBy;
+    for(j=0; j<pList->nExpr; j++){
+      u16 iCol = pList->a[j].u.x.iOrderByCol;
+      if( iCol>0 ){
+        iCol--;
+        colUsed |= ((Bitmask)1)<<(iCol>=BMS ? BMS-1 : iCol);
+      }
+    }
+  }
+  nCol = pTab->nCol;
+  for(j=0; j<nCol; j++){
+    Bitmask m = j<BMS-1 ? MASKBIT(j) : TOPBIT;
+    if( (m & colUsed)!=0 ) continue;
+    for(pX=pSub; pX; pX=pX->pPrior) {
+      Expr *pY = pX->pEList->a[j].pExpr;
+      if( pY->op==TK_NULL ) continue;
+      pY->op = TK_NULL;
+      ExprClearProperty(pY, EP_Skip|EP_Unlikely);
+      pX->selFlags |= SF_PushDown;
+      nChng++;
+    }
+  }
+  return nChng;
+}
+
+
+/*
+** The pFunc is the only aggregate function in the query.  Check to see
+** if the query is a candidate for the min/max optimization.
+**
+** If the query is a candidate for the min/max optimization, then set
+** *ppMinMax to be an ORDER BY clause to be used for the optimization
+** and return either WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX depending on
+** whether pFunc is a min() or max() function.
+**
+** If the query is not a candidate for the min/max optimization, return
+** WHERE_ORDERBY_NORMAL (which must be zero).
+**
+** This routine must be called after aggregate functions have been
+** located but before their arguments have been subjected to aggregate
+** analysis.
+*/
+static u8 minMaxQuery(sqlite3 *db, Expr *pFunc, ExprList **ppMinMax){
+  int eRet = WHERE_ORDERBY_NORMAL;      /* Return value */
+  ExprList *pEList;                     /* Arguments to agg function */
+  const char *zFunc;                    /* Name of aggregate function pFunc */
+  ExprList *pOrderBy;
+  u8 sortFlags = 0;
+
+  assert( *ppMinMax==0 );
+  assert( pFunc->op==TK_AGG_FUNCTION );
+  assert( !IsWindowFunc(pFunc) );
+  assert( ExprUseXList(pFunc) );
+  pEList = pFunc->x.pList;
+  if( pEList==0
+   || pEList->nExpr!=1
+   || ExprHasProperty(pFunc, EP_WinFunc)
+   || OptimizationDisabled(db, SQLITE_MinMaxOpt)
+  ){
+    return eRet;
+  }
+  assert( !ExprHasProperty(pFunc, EP_IntValue) );
+  zFunc = pFunc->u.zToken;
+  if( sqlite3StrICmp(zFunc, "min")==0 ){
+    eRet = WHERE_ORDERBY_MIN;
+    if( sqlite3ExprCanBeNull(pEList->a[0].pExpr) ){
+      sortFlags = KEYINFO_ORDER_BIGNULL;
+    }
+  }else if( sqlite3StrICmp(zFunc, "max")==0 ){
+    eRet = WHERE_ORDERBY_MAX;
+    sortFlags = KEYINFO_ORDER_DESC;
+  }else{
+    return eRet;
+  }
+  *ppMinMax = pOrderBy = sqlite3ExprListDup(db, pEList, 0);
+  assert( pOrderBy!=0 || db->mallocFailed );
+  if( pOrderBy ) pOrderBy->a[0].fg.sortFlags = sortFlags;
+  return eRet;
+}
+
+/*
+** The select statement passed as the first argument is an aggregate query.
+** The second argument is the associated aggregate-info object. This
+** function tests if the SELECT is of the form:
+**
+**   SELECT count(*) FROM <tbl>
+**
+** where table is a database table, not a sub-select or view. If the query
+** does match this pattern, then a pointer to the Table object representing
+** <tbl> is returned. Otherwise, NULL is returned.
+**
+** This routine checks to see if it is safe to use the count optimization.
+** A correct answer is still obtained (though perhaps more slowly) if
+** this routine returns NULL when it could have returned a table pointer.
+** But returning the pointer when NULL should have been returned can
+** result in incorrect answers and/or crashes.  So, when in doubt, return NULL.
+*/
+static Table *isSimpleCount(Select *p, AggInfo *pAggInfo){
+  Table *pTab;
+  Expr *pExpr;
+
+  assert( !p->pGroupBy );
+
+  if( p->pWhere
+   || p->pEList->nExpr!=1
+   || p->pSrc->nSrc!=1
+   || p->pSrc->a[0].pSelect
+   || pAggInfo->nFunc!=1
+   || p->pHaving
+  ){
+    return 0;
+  }
+  pTab = p->pSrc->a[0].pTab;
+  assert( pTab!=0 );
+  assert( !IsView(pTab) );
+  if( !IsOrdinaryTable(pTab) ) return 0;
+  pExpr = p->pEList->a[0].pExpr;
+  assert( pExpr!=0 );
+  if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
+  if( pExpr->pAggInfo!=pAggInfo ) return 0;
+  if( (pAggInfo->aFunc[0].pFunc->funcFlags&SQLITE_FUNC_COUNT)==0 ) return 0;
+  assert( pAggInfo->aFunc[0].pFExpr==pExpr );
+  testcase( ExprHasProperty(pExpr, EP_Distinct) );
+  testcase( ExprHasProperty(pExpr, EP_WinFunc) );
+  if( ExprHasProperty(pExpr, EP_Distinct|EP_WinFunc) ) return 0;
+
+  return pTab;
+}
+
+/*
+** If the source-list item passed as an argument was augmented with an
+** INDEXED BY clause, then try to locate the specified index. If there
+** was such a clause and the named index cannot be found, return
+** SQLITE_ERROR and leave an error in pParse. Otherwise, populate
+** pFrom->pIndex and return SQLITE_OK.
+*/
+int sqlite3IndexedByLookup(Parse *pParse, SrcItem *pFrom){
+  Table *pTab = pFrom->pTab;
+  char *zIndexedBy = pFrom->u1.zIndexedBy;
+  Index *pIdx;
+  assert( pTab!=0 );
+  assert( pFrom->fg.isIndexedBy!=0 );
+
+  for(pIdx=pTab->pIndex;
+      pIdx && sqlite3StrICmp(pIdx->zName, zIndexedBy);
+      pIdx=pIdx->pNext
+  );
+  if( !pIdx ){
+    sqlite3ErrorMsg(pParse, "no such index: %s", zIndexedBy, 0);
+    pParse->checkSchema = 1;
+    return SQLITE_ERROR;
+  }
+  assert( pFrom->fg.isCte==0 );
+  pFrom->u2.pIBIndex = pIdx;
+  return SQLITE_OK;
+}
+
+/*
+** Detect compound SELECT statements that use an ORDER BY clause with
+** an alternative collating sequence.
+**
+**    SELECT ... FROM t1 EXCEPT SELECT ... FROM t2 ORDER BY .. COLLATE ...
+**
+** These are rewritten as a subquery:
+**
+**    SELECT * FROM (SELECT ... FROM t1 EXCEPT SELECT ... FROM t2)
+**     ORDER BY ... COLLATE ...
+**
+** This transformation is necessary because the multiSelectOrderBy() routine
+** above that generates the code for a compound SELECT with an ORDER BY clause
+** uses a merge algorithm that requires the same collating sequence on the
+** result columns as on the ORDER BY clause.  See ticket
+** http://www.sqlite.org/src/info/6709574d2a
+**
+** This transformation is only needed for EXCEPT, INTERSECT, and UNION.
+** The UNION ALL operator works fine with multiSelectOrderBy() even when
+** there are COLLATE terms in the ORDER BY.
+*/
+static int convertCompoundSelectToSubquery(Walker *pWalker, Select *p){
+  int i;
+  Select *pNew;
+  Select *pX;
+  sqlite3 *db;
+  struct ExprList_item *a;
+  SrcList *pNewSrc;
+  Parse *pParse;
+  Token dummy;
+
+  if( p->pPrior==0 ) return WRC_Continue;
+  if( p->pOrderBy==0 ) return WRC_Continue;
+  for(pX=p; pX && (pX->op==TK_ALL || pX->op==TK_SELECT); pX=pX->pPrior){}
+  if( pX==0 ) return WRC_Continue;
+  a = p->pOrderBy->a;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  /* If iOrderByCol is already non-zero, then it has already been matched
+  ** to a result column of the SELECT statement. This occurs when the
+  ** SELECT is rewritten for window-functions processing and then passed
+  ** to sqlite3SelectPrep() and similar a second time. The rewriting done
+  ** by this function is not required in this case. */
+  if( a[0].u.x.iOrderByCol ) return WRC_Continue;
+#endif
+  for(i=p->pOrderBy->nExpr-1; i>=0; i--){
+    if( a[i].pExpr->flags & EP_Collate ) break;
+  }
+  if( i<0 ) return WRC_Continue;
+
+  /* If we reach this point, that means the transformation is required. */
+
+  pParse = pWalker->pParse;
+  db = pParse->db;
+  pNew = sqlite3DbMallocZero(db, sizeof(*pNew) );
+  if( pNew==0 ) return WRC_Abort;
+  memset(&dummy, 0, sizeof(dummy));
+  pNewSrc = sqlite3SrcListAppendFromTerm(pParse,0,0,0,&dummy,pNew,0);
+  if( pNewSrc==0 ) return WRC_Abort;
+  *pNew = *p;
+  p->pSrc = pNewSrc;
+  p->pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ASTERISK, 0));
+  p->op = TK_SELECT;
+  p->pWhere = 0;
+  pNew->pGroupBy = 0;
+  pNew->pHaving = 0;
+  pNew->pOrderBy = 0;
+  p->pPrior = 0;
+  p->pNext = 0;
+  p->pWith = 0;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  p->pWinDefn = 0;
+#endif
+  p->selFlags &= ~SF_Compound;
+  assert( (p->selFlags & SF_Converted)==0 );
+  p->selFlags |= SF_Converted;
+  assert( pNew->pPrior!=0 );
+  pNew->pPrior->pNext = pNew;
+  pNew->pLimit = 0;
+  return WRC_Continue;
+}
+
+/*
+** Check to see if the FROM clause term pFrom has table-valued function
+** arguments.  If it does, leave an error message in pParse and return
+** non-zero, since pFrom is not allowed to be a table-valued function.
+*/
+static int cannotBeFunction(Parse *pParse, SrcItem *pFrom){
+  if( pFrom->fg.isTabFunc ){
+    sqlite3ErrorMsg(pParse, "'%s' is not a function", pFrom->zName);
+    return 1;
+  }
+  return 0;
+}
+
+#ifndef SQLITE_OMIT_CTE
+/*
+** Argument pWith (which may be NULL) points to a linked list of nested
+** WITH contexts, from inner to outermost. If the table identified by
+** FROM clause element pItem is really a common-table-expression (CTE)
+** then return a pointer to the CTE definition for that table. Otherwise
+** return NULL.
+**
+** If a non-NULL value is returned, set *ppContext to point to the With
+** object that the returned CTE belongs to.
+*/
+static struct Cte *searchWith(
+  With *pWith,                    /* Current innermost WITH clause */
+  SrcItem *pItem,                 /* FROM clause element to resolve */
+  With **ppContext                /* OUT: WITH clause return value belongs to */
+){
+  const char *zName = pItem->zName;
+  With *p;
+  assert( pItem->zDatabase==0 );
+  assert( zName!=0 );
+  for(p=pWith; p; p=p->pOuter){
+    int i;
+    for(i=0; i<p->nCte; i++){
+      if( sqlite3StrICmp(zName, p->a[i].zName)==0 ){
+        *ppContext = p;
+        return &p->a[i];
+      }
+    }
+    if( p->bView ) break;
+  }
+  return 0;
+}
+
+/* The code generator maintains a stack of active WITH clauses
+** with the inner-most WITH clause being at the top of the stack.
+**
+** This routine pushes the WITH clause passed as the second argument
+** onto the top of the stack. If argument bFree is true, then this
+** WITH clause will never be popped from the stack but should instead
+** be freed along with the Parse object. In other cases, when
+** bFree==0, the With object will be freed along with the SELECT
+** statement with which it is associated.
+**
+** This routine returns a copy of pWith.  Or, if bFree is true and
+** the pWith object is destroyed immediately due to an OOM condition,
+** then this routine return NULL.
+**
+** If bFree is true, do not continue to use the pWith pointer after
+** calling this routine,  Instead, use only the return value.
+*/
+With *sqlite3WithPush(Parse *pParse, With *pWith, u8 bFree){
+  if( pWith ){
+    if( bFree ){
+      pWith = (With*)sqlite3ParserAddCleanup(pParse, sqlite3WithDeleteGeneric,
+                      pWith);
+      if( pWith==0 ) return 0;
+    }
+    if( pParse->nErr==0 ){
+      assert( pParse->pWith!=pWith );
+      pWith->pOuter = pParse->pWith;
+      pParse->pWith = pWith;
+    }
+  }
+  return pWith;
+}
+
+/*
+** This function checks if argument pFrom refers to a CTE declared by
+** a WITH clause on the stack currently maintained by the parser (on the
+** pParse->pWith linked list).  And if currently processing a CTE
+** CTE expression, through routine checks to see if the reference is
+** a recursive reference to the CTE.
+**
+** If pFrom matches a CTE according to either of these two above, pFrom->pTab
+** and other fields are populated accordingly.
+**
+** Return 0 if no match is found.
+** Return 1 if a match is found.
+** Return 2 if an error condition is detected.
+*/
+static int resolveFromTermToCte(
+  Parse *pParse,                  /* The parsing context */
+  Walker *pWalker,                /* Current tree walker */
+  SrcItem *pFrom                  /* The FROM clause term to check */
+){
+  Cte *pCte;               /* Matched CTE (or NULL if no match) */
+  With *pWith;             /* The matching WITH */
+
+  assert( pFrom->pTab==0 );
+  if( pParse->pWith==0 ){
+    /* There are no WITH clauses in the stack.  No match is possible */
+    return 0;
+  }
+  if( pParse->nErr ){
+    /* Prior errors might have left pParse->pWith in a goofy state, so
+    ** go no further. */
+    return 0;
+  }
+  if( pFrom->zDatabase!=0 ){
+    /* The FROM term contains a schema qualifier (ex: main.t1) and so
+    ** it cannot possibly be a CTE reference. */
+    return 0;
+  }
+  if( pFrom->fg.notCte ){
+    /* The FROM term is specifically excluded from matching a CTE.
+    **   (1)  It is part of a trigger that used to have zDatabase but had
+    **        zDatabase removed by sqlite3FixTriggerStep().
+    **   (2)  This is the first term in the FROM clause of an UPDATE.
+    */
+    return 0;
+  }
+  pCte = searchWith(pParse->pWith, pFrom, &pWith);
+  if( pCte ){
+    sqlite3 *db = pParse->db;
+    Table *pTab;
+    ExprList *pEList;
+    Select *pSel;
+    Select *pLeft;                /* Left-most SELECT statement */
+    Select *pRecTerm;             /* Left-most recursive term */
+    int bMayRecursive;            /* True if compound joined by UNION [ALL] */
+    With *pSavedWith;             /* Initial value of pParse->pWith */
+    int iRecTab = -1;             /* Cursor for recursive table */
+    CteUse *pCteUse;
+
+    /* If pCte->zCteErr is non-NULL at this point, then this is an illegal
+    ** recursive reference to CTE pCte. Leave an error in pParse and return
+    ** early. If pCte->zCteErr is NULL, then this is not a recursive reference.
+    ** In this case, proceed.  */
+    if( pCte->zCteErr ){
+      sqlite3ErrorMsg(pParse, pCte->zCteErr, pCte->zName);
+      return 2;
+    }
+    if( cannotBeFunction(pParse, pFrom) ) return 2;
+
+    assert( pFrom->pTab==0 );
+    pTab = sqlite3DbMallocZero(db, sizeof(Table));
+    if( pTab==0 ) return 2;
+    pCteUse = pCte->pUse;
+    if( pCteUse==0 ){
+      pCte->pUse = pCteUse = sqlite3DbMallocZero(db, sizeof(pCteUse[0]));
+      if( pCteUse==0
+       || sqlite3ParserAddCleanup(pParse,sqlite3DbFree,pCteUse)==0
+      ){
+        sqlite3DbFree(db, pTab);
+        return 2;
+      }
+      pCteUse->eM10d = pCte->eM10d;
+    }
+    pFrom->pTab = pTab;
+    pTab->nTabRef = 1;
+    pTab->zName = sqlite3DbStrDup(db, pCte->zName);
+    pTab->iPKey = -1;
+    pTab->nRowLogEst = 200; assert( 200==sqlite3LogEst(1048576) );
+    pTab->tabFlags |= TF_Ephemeral | TF_NoVisibleRowid;
+    pFrom->pSelect = sqlite3SelectDup(db, pCte->pSelect, 0);
+    if( db->mallocFailed ) return 2;
+    pFrom->pSelect->selFlags |= SF_CopyCte;
+    assert( pFrom->pSelect );
+    if( pFrom->fg.isIndexedBy ){
+      sqlite3ErrorMsg(pParse, "no such index: \"%s\"", pFrom->u1.zIndexedBy);
+      return 2;
+    }
+    pFrom->fg.isCte = 1;
+    pFrom->u2.pCteUse = pCteUse;
+    pCteUse->nUse++;
+
+    /* Check if this is a recursive CTE. */
+    pRecTerm = pSel = pFrom->pSelect;
+    bMayRecursive = ( pSel->op==TK_ALL || pSel->op==TK_UNION );
+    while( bMayRecursive && pRecTerm->op==pSel->op ){
+      int i;
+      SrcList *pSrc = pRecTerm->pSrc;
+      assert( pRecTerm->pPrior!=0 );
+      for(i=0; i<pSrc->nSrc; i++){
+        SrcItem *pItem = &pSrc->a[i];
+        if( pItem->zDatabase==0
+         && pItem->zName!=0
+         && 0==sqlite3StrICmp(pItem->zName, pCte->zName)
+        ){
+          pItem->pTab = pTab;
+          pTab->nTabRef++;
+          pItem->fg.isRecursive = 1;
+          if( pRecTerm->selFlags & SF_Recursive ){
+            sqlite3ErrorMsg(pParse,
+               "multiple references to recursive table: %s", pCte->zName
+            );
+            return 2;
+          }
+          pRecTerm->selFlags |= SF_Recursive;
+          if( iRecTab<0 ) iRecTab = pParse->nTab++;
+          pItem->iCursor = iRecTab;
+        }
+      }
+      if( (pRecTerm->selFlags & SF_Recursive)==0 ) break;
+      pRecTerm = pRecTerm->pPrior;
+    }
+
+    pCte->zCteErr = "circular reference: %s";
+    pSavedWith = pParse->pWith;
+    pParse->pWith = pWith;
+    if( pSel->selFlags & SF_Recursive ){
+      int rc;
+      assert( pRecTerm!=0 );
+      assert( (pRecTerm->selFlags & SF_Recursive)==0 );
+      assert( pRecTerm->pNext!=0 );
+      assert( (pRecTerm->pNext->selFlags & SF_Recursive)!=0 );
+      assert( pRecTerm->pWith==0 );
+      pRecTerm->pWith = pSel->pWith;
+      rc = sqlite3WalkSelect(pWalker, pRecTerm);
+      pRecTerm->pWith = 0;
+      if( rc ){
+        pParse->pWith = pSavedWith;
+        return 2;
+      }
+    }else{
+      if( sqlite3WalkSelect(pWalker, pSel) ){
+        pParse->pWith = pSavedWith;
+        return 2;
+      }
+    }
+    pParse->pWith = pWith;
+
+    for(pLeft=pSel; pLeft->pPrior; pLeft=pLeft->pPrior);
+    pEList = pLeft->pEList;
+    if( pCte->pCols ){
+      if( pEList && pEList->nExpr!=pCte->pCols->nExpr ){
+        sqlite3ErrorMsg(pParse, "table %s has %d values for %d columns",
+            pCte->zName, pEList->nExpr, pCte->pCols->nExpr
+        );
+        pParse->pWith = pSavedWith;
+        return 2;
+      }
+      pEList = pCte->pCols;
+    }
+
+    sqlite3ColumnsFromExprList(pParse, pEList, &pTab->nCol, &pTab->aCol);
+    if( bMayRecursive ){
+      if( pSel->selFlags & SF_Recursive ){
+        pCte->zCteErr = "multiple recursive references: %s";
+      }else{
+        pCte->zCteErr = "recursive reference in a subquery: %s";
+      }
+      sqlite3WalkSelect(pWalker, pSel);
+    }
+    pCte->zCteErr = 0;
+    pParse->pWith = pSavedWith;
+    return 1;  /* Success */
+  }
+  return 0;  /* No match */
+}
+#endif
+
+#ifndef SQLITE_OMIT_CTE
+/*
+** If the SELECT passed as the second argument has an associated WITH
+** clause, pop it from the stack stored as part of the Parse object.
+**
+** This function is used as the xSelectCallback2() callback by
+** sqlite3SelectExpand() when walking a SELECT tree to resolve table
+** names and other FROM clause elements.
+*/
+void sqlite3SelectPopWith(Walker *pWalker, Select *p){
+  Parse *pParse = pWalker->pParse;
+  if( OK_IF_ALWAYS_TRUE(pParse->pWith) && p->pPrior==0 ){
+    With *pWith = findRightmost(p)->pWith;
+    if( pWith!=0 ){
+      assert( pParse->pWith==pWith || pParse->nErr );
+      pParse->pWith = pWith->pOuter;
+    }
+  }
+}
+#endif
+
+/*
+** The SrcItem structure passed as the second argument represents a
+** sub-query in the FROM clause of a SELECT statement. This function
+** allocates and populates the SrcItem.pTab object. If successful,
+** SQLITE_OK is returned. Otherwise, if an OOM error is encountered,
+** SQLITE_NOMEM.
+*/
+int sqlite3ExpandSubquery(Parse *pParse, SrcItem *pFrom){
+  Select *pSel = pFrom->pSelect;
+  Table *pTab;
+
+  assert( pSel );
+  pFrom->pTab = pTab = sqlite3DbMallocZero(pParse->db, sizeof(Table));
+  if( pTab==0 ) return SQLITE_NOMEM;
+  pTab->nTabRef = 1;
+  if( pFrom->zAlias ){
+    pTab->zName = sqlite3DbStrDup(pParse->db, pFrom->zAlias);
+  }else{
+    pTab->zName = sqlite3MPrintf(pParse->db, "%!S", pFrom);
+  }
+  while( pSel->pPrior ){ pSel = pSel->pPrior; }
+  sqlite3ColumnsFromExprList(pParse, pSel->pEList,&pTab->nCol,&pTab->aCol);
+  pTab->iPKey = -1;
+  pTab->nRowLogEst = 200; assert( 200==sqlite3LogEst(1048576) );
+#ifndef SQLITE_ALLOW_ROWID_IN_VIEW
+  /* The usual case - do not allow ROWID on a subquery */
+  pTab->tabFlags |= TF_Ephemeral | TF_NoVisibleRowid;
+#else
+  pTab->tabFlags |= TF_Ephemeral;  /* Legacy compatibility mode */
+#endif
+  return pParse->nErr ? SQLITE_ERROR : SQLITE_OK;
+}
+
+
+/*
+** Check the N SrcItem objects to the right of pBase.  (N might be zero!)
+** If any of those SrcItem objects have a USING clause containing zName
+** then return true.
+**
+** If N is zero, or none of the N SrcItem objects to the right of pBase
+** contains a USING clause, or if none of the USING clauses contain zName,
+** then return false.
+*/
+static int inAnyUsingClause(
+  const char *zName, /* Name we are looking for */
+  SrcItem *pBase,    /* The base SrcItem.  Looking at pBase[1] and following */
+  int N              /* How many SrcItems to check */
+){
+  while( N>0 ){
+    N--;
+    pBase++;
+    if( pBase->fg.isUsing==0 ) continue;
+    if( NEVER(pBase->u3.pUsing==0) ) continue;
+    if( sqlite3IdListIndex(pBase->u3.pUsing, zName)>=0 ) return 1;
+  }
+  return 0;
+}
+
+
+/*
+** This routine is a Walker callback for "expanding" a SELECT statement.
+** "Expanding" means to do the following:
+**
+**    (1)  Make sure VDBE cursor numbers have been assigned to every
+**         element of the FROM clause.
+**
+**    (2)  Fill in the pTabList->a[].pTab fields in the SrcList that
+**         defines FROM clause.  When views appear in the FROM clause,
+**         fill pTabList->a[].pSelect with a copy of the SELECT statement
+**         that implements the view.  A copy is made of the view's SELECT
+**         statement so that we can freely modify or delete that statement
+**         without worrying about messing up the persistent representation
+**         of the view.
+**
+**    (3)  Add terms to the WHERE clause to accommodate the NATURAL keyword
+**         on joins and the ON and USING clause of joins.
+**
+**    (4)  Scan the list of columns in the result set (pEList) looking
+**         for instances of the "*" operator or the TABLE.* operator.
+**         If found, expand each "*" to be every column in every table
+**         and TABLE.* to be every column in TABLE.
+**
+*/
+static int selectExpander(Walker *pWalker, Select *p){
+  Parse *pParse = pWalker->pParse;
+  int i, j, k, rc;
+  SrcList *pTabList;
+  ExprList *pEList;
+  SrcItem *pFrom;
+  sqlite3 *db = pParse->db;
+  Expr *pE, *pRight, *pExpr;
+  u16 selFlags = p->selFlags;
+  u32 elistFlags = 0;
+
+  p->selFlags |= SF_Expanded;
+  if( db->mallocFailed  ){
+    return WRC_Abort;
+  }
+  assert( p->pSrc!=0 );
+  if( (selFlags & SF_Expanded)!=0 ){
+    return WRC_Prune;
+  }
+  if( pWalker->eCode ){
+    /* Renumber selId because it has been copied from a view */
+    p->selId = ++pParse->nSelect;
+  }
+  pTabList = p->pSrc;
+  pEList = p->pEList;
+  if( pParse->pWith && (p->selFlags & SF_View) ){
+    if( p->pWith==0 ){
+      p->pWith = (With*)sqlite3DbMallocZero(db, sizeof(With));
+      if( p->pWith==0 ){
+        return WRC_Abort;
+      }
+    }
+    p->pWith->bView = 1;
+  }
+  sqlite3WithPush(pParse, p->pWith, 0);
+
+  /* Make sure cursor numbers have been assigned to all entries in
+  ** the FROM clause of the SELECT statement.
+  */
+  sqlite3SrcListAssignCursors(pParse, pTabList);
+
+  /* Look up every table named in the FROM clause of the select.  If
+  ** an entry of the FROM clause is a subquery instead of a table or view,
+  ** then create a transient table structure to describe the subquery.
+  */
+  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+    Table *pTab;
+    assert( pFrom->fg.isRecursive==0 || pFrom->pTab!=0 );
+    if( pFrom->pTab ) continue;
+    assert( pFrom->fg.isRecursive==0 );
+    if( pFrom->zName==0 ){
+#ifndef SQLITE_OMIT_SUBQUERY
+      Select *pSel = pFrom->pSelect;
+      /* A sub-query in the FROM clause of a SELECT */
+      assert( pSel!=0 );
+      assert( pFrom->pTab==0 );
+      if( sqlite3WalkSelect(pWalker, pSel) ) return WRC_Abort;
+      if( sqlite3ExpandSubquery(pParse, pFrom) ) return WRC_Abort;
+#endif
+#ifndef SQLITE_OMIT_CTE
+    }else if( (rc = resolveFromTermToCte(pParse, pWalker, pFrom))!=0 ){
+      if( rc>1 ) return WRC_Abort;
+      pTab = pFrom->pTab;
+      assert( pTab!=0 );
+#endif
+    }else{
+      /* An ordinary table or view name in the FROM clause */
+      assert( pFrom->pTab==0 );
+      pFrom->pTab = pTab = sqlite3LocateTableItem(pParse, 0, pFrom);
+      if( pTab==0 ) return WRC_Abort;
+      if( pTab->nTabRef>=0xffff ){
+        sqlite3ErrorMsg(pParse, "too many references to \"%s\": max 65535",
+           pTab->zName);
+        pFrom->pTab = 0;
+        return WRC_Abort;
+      }
+      pTab->nTabRef++;
+      if( !IsVirtual(pTab) && cannotBeFunction(pParse, pFrom) ){
+        return WRC_Abort;
+      }
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+      if( !IsOrdinaryTable(pTab) ){
+        i16 nCol;
+        u8 eCodeOrig = pWalker->eCode;
+        if( sqlite3ViewGetColumnNames(pParse, pTab) ) return WRC_Abort;
+        assert( pFrom->pSelect==0 );
+        if( IsView(pTab) ){
+          if( (db->flags & SQLITE_EnableView)==0
+           && pTab->pSchema!=db->aDb[1].pSchema
+          ){
+            sqlite3ErrorMsg(pParse, "access to view \"%s\" prohibited",
+              pTab->zName);
+          }
+          pFrom->pSelect = sqlite3SelectDup(db, pTab->u.view.pSelect, 0);
+        }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+        else if( ALWAYS(IsVirtual(pTab))
+         && pFrom->fg.fromDDL
+         && ALWAYS(pTab->u.vtab.p!=0)
+         && pTab->u.vtab.p->eVtabRisk > ((db->flags & SQLITE_TrustedSchema)!=0)
+        ){
+          sqlite3ErrorMsg(pParse, "unsafe use of virtual table \"%s\"",
+                                  pTab->zName);
+        }
+        assert( SQLITE_VTABRISK_Normal==1 && SQLITE_VTABRISK_High==2 );
+#endif
+        nCol = pTab->nCol;
+        pTab->nCol = -1;
+        pWalker->eCode = 1;  /* Turn on Select.selId renumbering */
+        sqlite3WalkSelect(pWalker, pFrom->pSelect);
+        pWalker->eCode = eCodeOrig;
+        pTab->nCol = nCol;
+      }
+#endif
+    }
+
+    /* Locate the index named by the INDEXED BY clause, if any. */
+    if( pFrom->fg.isIndexedBy && sqlite3IndexedByLookup(pParse, pFrom) ){
+      return WRC_Abort;
+    }
+  }
+
+  /* Process NATURAL keywords, and ON and USING clauses of joins.
+  */
+  assert( db->mallocFailed==0 || pParse->nErr!=0 );
+  if( pParse->nErr || sqlite3ProcessJoin(pParse, p) ){
+    return WRC_Abort;
+  }
+
+  /* For every "*" that occurs in the column list, insert the names of
+  ** all columns in all tables.  And for every TABLE.* insert the names
+  ** of all columns in TABLE.  The parser inserted a special expression
+  ** with the TK_ASTERISK operator for each "*" that it found in the column
+  ** list.  The following code just has to locate the TK_ASTERISK
+  ** expressions and expand each one to the list of all columns in
+  ** all tables.
+  **
+  ** The first loop just checks to see if there are any "*" operators
+  ** that need expanding.
+  */
+  for(k=0; k<pEList->nExpr; k++){
+    pE = pEList->a[k].pExpr;
+    if( pE->op==TK_ASTERISK ) break;
+    assert( pE->op!=TK_DOT || pE->pRight!=0 );
+    assert( pE->op!=TK_DOT || (pE->pLeft!=0 && pE->pLeft->op==TK_ID) );
+    if( pE->op==TK_DOT && pE->pRight->op==TK_ASTERISK ) break;
+    elistFlags |= pE->flags;
+  }
+  if( k<pEList->nExpr ){
+    /*
+    ** If we get here it means the result set contains one or more "*"
+    ** operators that need to be expanded.  Loop through each expression
+    ** in the result set and expand them one by one.
+    */
+    struct ExprList_item *a = pEList->a;
+    ExprList *pNew = 0;
+    int flags = pParse->db->flags;
+    int longNames = (flags & SQLITE_FullColNames)!=0
+                      && (flags & SQLITE_ShortColNames)==0;
+
+    for(k=0; k<pEList->nExpr; k++){
+      pE = a[k].pExpr;
+      elistFlags |= pE->flags;
+      pRight = pE->pRight;
+      assert( pE->op!=TK_DOT || pRight!=0 );
+      if( pE->op!=TK_ASTERISK
+       && (pE->op!=TK_DOT || pRight->op!=TK_ASTERISK)
+      ){
+        /* This particular expression does not need to be expanded.
+        */
+        pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr);
+        if( pNew ){
+          pNew->a[pNew->nExpr-1].zEName = a[k].zEName;
+          pNew->a[pNew->nExpr-1].fg.eEName = a[k].fg.eEName;
+          a[k].zEName = 0;
+        }
+        a[k].pExpr = 0;
+      }else{
+        /* This expression is a "*" or a "TABLE.*" and needs to be
+        ** expanded. */
+        int tableSeen = 0;      /* Set to 1 when TABLE matches */
+        char *zTName = 0;       /* text of name of TABLE */
+        int iErrOfst;
+        if( pE->op==TK_DOT ){
+          assert( (selFlags & SF_NestedFrom)==0 );
+          assert( pE->pLeft!=0 );
+          assert( !ExprHasProperty(pE->pLeft, EP_IntValue) );
+          zTName = pE->pLeft->u.zToken;
+          assert( ExprUseWOfst(pE->pLeft) );
+          iErrOfst = pE->pRight->w.iOfst;
+        }else{
+          assert( ExprUseWOfst(pE) );
+          iErrOfst = pE->w.iOfst;
+        }
+        for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+          int nAdd;                    /* Number of cols including rowid */
+          Table *pTab = pFrom->pTab;   /* Table for this data source */
+          ExprList *pNestedFrom;       /* Result-set of a nested FROM clause */
+          char *zTabName;              /* AS name for this data source */
+          const char *zSchemaName = 0; /* Schema name for this data source */
+          int iDb;                     /* Schema index for this data src */
+          IdList *pUsing;              /* USING clause for pFrom[1] */
+
+          if( (zTabName = pFrom->zAlias)==0 ){
+            zTabName = pTab->zName;
+          }
+          if( db->mallocFailed ) break;
+          assert( (int)pFrom->fg.isNestedFrom == IsNestedFrom(pFrom->pSelect) );
+          if( pFrom->fg.isNestedFrom ){
+            assert( pFrom->pSelect!=0 );
+            pNestedFrom = pFrom->pSelect->pEList;
+            assert( pNestedFrom!=0 );
+            assert( pNestedFrom->nExpr==pTab->nCol );
+            assert( VisibleRowid(pTab)==0 );
+          }else{
+            if( zTName && sqlite3StrICmp(zTName, zTabName)!=0 ){
+              continue;
+            }
+            pNestedFrom = 0;
+            iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+            zSchemaName = iDb>=0 ? db->aDb[iDb].zDbSName : "*";
+          }
+          if( i+1<pTabList->nSrc
+           && pFrom[1].fg.isUsing
+           && (selFlags & SF_NestedFrom)!=0
+          ){
+            int ii;
+            pUsing = pFrom[1].u3.pUsing;
+            for(ii=0; ii<pUsing->nId; ii++){
+              const char *zUName = pUsing->a[ii].zName;
+              pRight = sqlite3Expr(db, TK_ID, zUName);
+              sqlite3ExprSetErrorOffset(pRight, iErrOfst);
+              pNew = sqlite3ExprListAppend(pParse, pNew, pRight);
+              if( pNew ){
+                struct ExprList_item *pX = &pNew->a[pNew->nExpr-1];
+                assert( pX->zEName==0 );
+                pX->zEName = sqlite3MPrintf(db,"..%s", zUName);
+                pX->fg.eEName = ENAME_TAB;
+                pX->fg.bUsingTerm = 1;
+              }
+            }
+          }else{
+            pUsing = 0;
+          }
+
+          nAdd = pTab->nCol + (VisibleRowid(pTab) && (selFlags&SF_NestedFrom));
+          for(j=0; j<nAdd; j++){
+            const char *zName; 
+            struct ExprList_item *pX; /* Newly added ExprList term */
+
+            if( j==pTab->nCol ){
+              zName = sqlite3RowidAlias(pTab);
+              if( zName==0 ) continue;
+            }else{
+              zName = pTab->aCol[j].zCnName;
+
+              /* If pTab is actually an SF_NestedFrom sub-select, do not
+              ** expand any ENAME_ROWID columns.  */
+              if( pNestedFrom && pNestedFrom->a[j].fg.eEName==ENAME_ROWID ){
+                continue;
+              }
+
+              if( zTName
+               && pNestedFrom
+               && sqlite3MatchEName(&pNestedFrom->a[j], 0, zTName, 0, 0)==0
+              ){
+                continue;
+              }
+
+              /* If a column is marked as 'hidden', omit it from the expanded
+              ** result-set list unless the SELECT has the SF_IncludeHidden
+              ** bit set.
+              */
+              if( (p->selFlags & SF_IncludeHidden)==0
+                && IsHiddenColumn(&pTab->aCol[j])
+              ){
+                continue;
+              }
+              if( (pTab->aCol[j].colFlags & COLFLAG_NOEXPAND)!=0
+               && zTName==0
+               && (selFlags & (SF_NestedFrom))==0
+              ){
+                continue;
+              }
+            }
+            assert( zName );
+            tableSeen = 1;
+
+            if( i>0 && zTName==0 && (selFlags & SF_NestedFrom)==0 ){
+              if( pFrom->fg.isUsing
+               && sqlite3IdListIndex(pFrom->u3.pUsing, zName)>=0
+              ){
+                /* In a join with a USING clause, omit columns in the
+                ** using clause from the table on the right. */
+                continue;
+              }
+            }
+            pRight = sqlite3Expr(db, TK_ID, zName);
+            if( (pTabList->nSrc>1
+                 && (  (pFrom->fg.jointype & JT_LTORJ)==0
+                     || (selFlags & SF_NestedFrom)!=0
+                     || !inAnyUsingClause(zName,pFrom,pTabList->nSrc-i-1)
+                    )
+                )
+             || IN_RENAME_OBJECT
+            ){
+              Expr *pLeft;
+              pLeft = sqlite3Expr(db, TK_ID, zTabName);
+              pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight);
+              if( IN_RENAME_OBJECT && pE->pLeft ){
+                sqlite3RenameTokenRemap(pParse, pLeft, pE->pLeft);
+              }
+              if( zSchemaName ){
+                pLeft = sqlite3Expr(db, TK_ID, zSchemaName);
+                pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pExpr);
+              }
+            }else{
+              pExpr = pRight;
+            }
+            sqlite3ExprSetErrorOffset(pExpr, iErrOfst);
+            pNew = sqlite3ExprListAppend(pParse, pNew, pExpr);
+            if( pNew==0 ){
+              break;  /* OOM */
+            }
+            pX = &pNew->a[pNew->nExpr-1];
+            assert( pX->zEName==0 );
+            if( (selFlags & SF_NestedFrom)!=0 && !IN_RENAME_OBJECT ){
+              if( pNestedFrom ){
+                pX->zEName = sqlite3DbStrDup(db, pNestedFrom->a[j].zEName);
+                testcase( pX->zEName==0 );
+              }else{
+                pX->zEName = sqlite3MPrintf(db, "%s.%s.%s",
+                                           zSchemaName, zTabName, zName);
+                testcase( pX->zEName==0 );
+              }
+              pX->fg.eEName = (j==pTab->nCol ? ENAME_ROWID : ENAME_TAB);
+              if( (pFrom->fg.isUsing
+                   && sqlite3IdListIndex(pFrom->u3.pUsing, zName)>=0)
+               || (pUsing && sqlite3IdListIndex(pUsing, zName)>=0)
+               || (j<pTab->nCol && (pTab->aCol[j].colFlags & COLFLAG_NOEXPAND))
+              ){
+                pX->fg.bNoExpand = 1;
+              }
+            }else if( longNames ){
+              pX->zEName = sqlite3MPrintf(db, "%s.%s", zTabName, zName);
+              pX->fg.eEName = ENAME_NAME;
+            }else{
+              pX->zEName = sqlite3DbStrDup(db, zName);
+              pX->fg.eEName = ENAME_NAME;
+            }
+          }
+        }
+        if( !tableSeen ){
+          if( zTName ){
+            sqlite3ErrorMsg(pParse, "no such table: %s", zTName);
+          }else{
+            sqlite3ErrorMsg(pParse, "no tables specified");
+          }
+        }
+      }
+    }
+    sqlite3ExprListDelete(db, pEList);
+    p->pEList = pNew;
+  }
+  if( p->pEList ){
+    if( p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+      sqlite3ErrorMsg(pParse, "too many columns in result set");
+      return WRC_Abort;
+    }
+    if( (elistFlags & (EP_HasFunc|EP_Subquery))!=0 ){
+      p->selFlags |= SF_ComplexResult;
+    }
+  }
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x8 ){
+    TREETRACE(0x8,pParse,p,("After result-set wildcard expansion:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+  return WRC_Continue;
+}
+
+#if SQLITE_DEBUG
+/*
+** Always assert.  This xSelectCallback2 implementation proves that the
+** xSelectCallback2 is never invoked.
+*/
+void sqlite3SelectWalkAssert2(Walker *NotUsed, Select *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  assert( 0 );
+}
+#endif
+/*
+** This routine "expands" a SELECT statement and all of its subqueries.
+** For additional information on what it means to "expand" a SELECT
+** statement, see the comment on the selectExpand worker callback above.
+**
+** Expanding a SELECT statement is the first step in processing a
+** SELECT statement.  The SELECT statement must be expanded before
+** name resolution is performed.
+**
+** If anything goes wrong, an error message is written into pParse.
+** The calling function can detect the problem by looking at pParse->nErr
+** and/or pParse->db->mallocFailed.
+*/
+static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
+  Walker w;
+  w.xExprCallback = sqlite3ExprWalkNoop;
+  w.pParse = pParse;
+  if( OK_IF_ALWAYS_TRUE(pParse->hasCompound) ){
+    w.xSelectCallback = convertCompoundSelectToSubquery;
+    w.xSelectCallback2 = 0;
+    sqlite3WalkSelect(&w, pSelect);
+  }
+  w.xSelectCallback = selectExpander;
+  w.xSelectCallback2 = sqlite3SelectPopWith;
+  w.eCode = 0;
+  sqlite3WalkSelect(&w, pSelect);
+}
+
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** This is a Walker.xSelectCallback callback for the sqlite3SelectTypeInfo()
+** interface.
+**
+** For each FROM-clause subquery, add Column.zType, Column.zColl, and
+** Column.affinity information to the Table structure that represents
+** the result set of that subquery.
+**
+** The Table structure that represents the result set was constructed
+** by selectExpander() but the type and collation and affinity information
+** was omitted at that point because identifiers had not yet been resolved.
+** This routine is called after identifier resolution.
+*/
+static void selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
+  Parse *pParse;
+  int i;
+  SrcList *pTabList;
+  SrcItem *pFrom;
+
+  if( p->selFlags & SF_HasTypeInfo ) return;
+  p->selFlags |= SF_HasTypeInfo;
+  pParse = pWalker->pParse;
+  testcase( (p->selFlags & SF_Resolved)==0 );
+  assert( (p->selFlags & SF_Resolved) || IN_RENAME_OBJECT );
+  pTabList = p->pSrc;
+  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+    Table *pTab = pFrom->pTab;
+    assert( pTab!=0 );
+    if( (pTab->tabFlags & TF_Ephemeral)!=0 ){
+      /* A sub-query in the FROM clause of a SELECT */
+      Select *pSel = pFrom->pSelect;
+      if( pSel ){
+        sqlite3SubqueryColumnTypes(pParse, pTab, pSel, SQLITE_AFF_NONE);
+      }
+    }
+  }
+}
+#endif
+
+
+/*
+** This routine adds datatype and collating sequence information to
+** the Table structures of all FROM-clause subqueries in a
+** SELECT statement.
+**
+** Use this routine after name resolution.
+*/
+static void sqlite3SelectAddTypeInfo(Parse *pParse, Select *pSelect){
+#ifndef SQLITE_OMIT_SUBQUERY
+  Walker w;
+  w.xSelectCallback = sqlite3SelectWalkNoop;
+  w.xSelectCallback2 = selectAddSubqueryTypeInfo;
+  w.xExprCallback = sqlite3ExprWalkNoop;
+  w.pParse = pParse;
+  sqlite3WalkSelect(&w, pSelect);
+#endif
+}
+
+
+/*
+** This routine sets up a SELECT statement for processing.  The
+** following is accomplished:
+**
+**     *  VDBE Cursor numbers are assigned to all FROM-clause terms.
+**     *  Ephemeral Table objects are created for all FROM-clause subqueries.
+**     *  ON and USING clauses are shifted into WHERE statements
+**     *  Wildcards "*" and "TABLE.*" in result sets are expanded.
+**     *  Identifiers in expression are matched to tables.
+**
+** This routine acts recursively on all subqueries within the SELECT.
+*/
+void sqlite3SelectPrep(
+  Parse *pParse,         /* The parser context */
+  Select *p,             /* The SELECT statement being coded. */
+  NameContext *pOuterNC  /* Name context for container */
+){
+  assert( p!=0 || pParse->db->mallocFailed );
+  assert( pParse->db->pParse==pParse );
+  if( pParse->db->mallocFailed ) return;
+  if( p->selFlags & SF_HasTypeInfo ) return;
+  sqlite3SelectExpand(pParse, p);
+  if( pParse->nErr ) return;
+  sqlite3ResolveSelectNames(pParse, p, pOuterNC);
+  if( pParse->nErr ) return;
+  sqlite3SelectAddTypeInfo(pParse, p);
+}
+
+#if TREETRACE_ENABLED
+/*
+** Display all information about an AggInfo object
+*/
+static void printAggInfo(AggInfo *pAggInfo){
+  int ii;
+  for(ii=0; ii<pAggInfo->nColumn; ii++){
+    struct AggInfo_col *pCol = &pAggInfo->aCol[ii];
+    sqlite3DebugPrintf(
+       "agg-column[%d] pTab=%s iTable=%d iColumn=%d iMem=%d"
+       " iSorterColumn=%d %s\n",
+       ii, pCol->pTab ? pCol->pTab->zName : "NULL",
+       pCol->iTable, pCol->iColumn, pAggInfo->iFirstReg+ii,
+       pCol->iSorterColumn,
+       ii>=pAggInfo->nAccumulator ? "" : " Accumulator");
+    sqlite3TreeViewExpr(0, pAggInfo->aCol[ii].pCExpr, 0);
+  }
+  for(ii=0; ii<pAggInfo->nFunc; ii++){
+    sqlite3DebugPrintf("agg-func[%d]: iMem=%d\n",
+        ii, pAggInfo->iFirstReg+pAggInfo->nColumn+ii);
+    sqlite3TreeViewExpr(0, pAggInfo->aFunc[ii].pFExpr, 0);
+  }
+}
+#endif /* TREETRACE_ENABLED */
+
+/*
+** Analyze the arguments to aggregate functions.  Create new pAggInfo->aCol[]
+** entries for columns that are arguments to aggregate functions but which
+** are not otherwise used.
+**
+** The aCol[] entries in AggInfo prior to nAccumulator are columns that
+** are referenced outside of aggregate functions.  These might be columns
+** that are part of the GROUP by clause, for example.  Other database engines
+** would throw an error if there is a column reference that is not in the
+** GROUP BY clause and that is not part of an aggregate function argument.
+** But SQLite allows this.
+**
+** The aCol[] entries beginning with the aCol[nAccumulator] and following
+** are column references that are used exclusively as arguments to
+** aggregate functions.  This routine is responsible for computing
+** (or recomputing) those aCol[] entries.
+*/
+static void analyzeAggFuncArgs(
+  AggInfo *pAggInfo,
+  NameContext *pNC
+){
+  int i;
+  assert( pAggInfo!=0 );
+  assert( pAggInfo->iFirstReg==0 );
+  pNC->ncFlags |= NC_InAggFunc;
+  for(i=0; i<pAggInfo->nFunc; i++){
+    Expr *pExpr = pAggInfo->aFunc[i].pFExpr;
+    assert( pExpr->op==TK_FUNCTION || pExpr->op==TK_AGG_FUNCTION );
+    assert( ExprUseXList(pExpr) );
+    sqlite3ExprAnalyzeAggList(pNC, pExpr->x.pList);
+    if( pExpr->pLeft ){
+      assert( pExpr->pLeft->op==TK_ORDER );
+      assert( ExprUseXList(pExpr->pLeft) );
+      sqlite3ExprAnalyzeAggList(pNC, pExpr->pLeft->x.pList);
+    }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    assert( !IsWindowFunc(pExpr) );
+    if( ExprHasProperty(pExpr, EP_WinFunc) ){
+      sqlite3ExprAnalyzeAggregates(pNC, pExpr->y.pWin->pFilter);
+    }
+#endif
+  }
+  pNC->ncFlags &= ~NC_InAggFunc;
+}
+
+/*
+** An index on expressions is being used in the inner loop of an
+** aggregate query with a GROUP BY clause.  This routine attempts
+** to adjust the AggInfo object to take advantage of index and to
+** perhaps use the index as a covering index.
+**
+*/
+static void optimizeAggregateUseOfIndexedExpr(
+  Parse *pParse,          /* Parsing context */
+  Select *pSelect,        /* The SELECT statement being processed */
+  AggInfo *pAggInfo,      /* The aggregate info */
+  NameContext *pNC        /* Name context used to resolve agg-func args */
+){
+  assert( pAggInfo->iFirstReg==0 );
+  assert( pSelect!=0 );
+  assert( pSelect->pGroupBy!=0 );
+  pAggInfo->nColumn = pAggInfo->nAccumulator;
+  if( ALWAYS(pAggInfo->nSortingColumn>0) ){
+    int mx = pSelect->pGroupBy->nExpr - 1;
+    int j, k;
+    for(j=0; j<pAggInfo->nColumn; j++){
+      k = pAggInfo->aCol[j].iSorterColumn;
+      if( k>mx ) mx = k;
+    }
+    pAggInfo->nSortingColumn = mx+1;
+  }
+  analyzeAggFuncArgs(pAggInfo, pNC);
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x20 ){
+    IndexedExpr *pIEpr;
+    TREETRACE(0x20, pParse, pSelect,
+        ("AggInfo (possibly) adjusted for Indexed Exprs\n"));
+    sqlite3TreeViewSelect(0, pSelect, 0);
+    for(pIEpr=pParse->pIdxEpr; pIEpr; pIEpr=pIEpr->pIENext){
+      printf("data-cursor=%d index={%d,%d}\n",
+          pIEpr->iDataCur, pIEpr->iIdxCur, pIEpr->iIdxCol);
+      sqlite3TreeViewExpr(0, pIEpr->pExpr, 0);
+    }
+    printAggInfo(pAggInfo);
+  }
+#else
+  UNUSED_PARAMETER(pSelect);
+  UNUSED_PARAMETER(pParse);
+#endif
+}
+
+/*
+** Walker callback for aggregateConvertIndexedExprRefToColumn().
+*/
+static int aggregateIdxEprRefToColCallback(Walker *pWalker, Expr *pExpr){
+  AggInfo *pAggInfo;
+  struct AggInfo_col *pCol;
+  UNUSED_PARAMETER(pWalker);
+  if( pExpr->pAggInfo==0 ) return WRC_Continue;
+  if( pExpr->op==TK_AGG_COLUMN ) return WRC_Continue;
+  if( pExpr->op==TK_AGG_FUNCTION ) return WRC_Continue;
+  if( pExpr->op==TK_IF_NULL_ROW ) return WRC_Continue;
+  pAggInfo = pExpr->pAggInfo;
+  if( NEVER(pExpr->iAgg>=pAggInfo->nColumn) ) return WRC_Continue;
+  assert( pExpr->iAgg>=0 );
+  pCol = &pAggInfo->aCol[pExpr->iAgg];
+  pExpr->op = TK_AGG_COLUMN;
+  pExpr->iTable = pCol->iTable;
+  pExpr->iColumn = pCol->iColumn;
+  ExprClearProperty(pExpr, EP_Skip|EP_Collate|EP_Unlikely);
+  return WRC_Prune;
+}
+
+/*
+** Convert every pAggInfo->aFunc[].pExpr such that any node within
+** those expressions that has pAppInfo set is changed into a TK_AGG_COLUMN
+** opcode.
+*/
+static void aggregateConvertIndexedExprRefToColumn(AggInfo *pAggInfo){
+  int i;
+  Walker w;
+  memset(&w, 0, sizeof(w));
+  w.xExprCallback = aggregateIdxEprRefToColCallback;
+  for(i=0; i<pAggInfo->nFunc; i++){
+    sqlite3WalkExpr(&w, pAggInfo->aFunc[i].pFExpr);
+  }
+}
+
+
+/*
+** Allocate a block of registers so that there is one register for each
+** pAggInfo->aCol[] and pAggInfo->aFunc[] entry in pAggInfo.  The first
+** register in this block is stored in pAggInfo->iFirstReg.
+**
+** This routine may only be called once for each AggInfo object.  Prior
+** to calling this routine:
+**
+**     *  The aCol[] and aFunc[] arrays may be modified
+**     *  The AggInfoColumnReg() and AggInfoFuncReg() macros may not be used
+**
+** After calling this routine:
+**
+**     *  The aCol[] and aFunc[] arrays are fixed
+**     *  The AggInfoColumnReg() and AggInfoFuncReg() macros may be used
+**
+*/
+static void assignAggregateRegisters(Parse *pParse, AggInfo *pAggInfo){
+  assert( pAggInfo!=0 );
+  assert( pAggInfo->iFirstReg==0 );
+  pAggInfo->iFirstReg = pParse->nMem + 1;
+  pParse->nMem += pAggInfo->nColumn + pAggInfo->nFunc;
+}
+
+/*
+** Reset the aggregate accumulator.
+**
+** The aggregate accumulator is a set of memory cells that hold
+** intermediate results while calculating an aggregate.  This
+** routine generates code that stores NULLs in all of those memory
+** cells.
+*/
+static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  struct AggInfo_func *pFunc;
+  int nReg = pAggInfo->nFunc + pAggInfo->nColumn;
+  assert( pAggInfo->iFirstReg>0 );
+  assert( pParse->db->pParse==pParse );
+  assert( pParse->db->mallocFailed==0 || pParse->nErr!=0 );
+  if( nReg==0 ) return;
+  if( pParse->nErr ) return;
+  sqlite3VdbeAddOp3(v, OP_Null, 0, pAggInfo->iFirstReg,
+                    pAggInfo->iFirstReg+nReg-1);
+  for(pFunc=pAggInfo->aFunc, i=0; i<pAggInfo->nFunc; i++, pFunc++){
+    if( pFunc->iDistinct>=0 ){
+      Expr *pE = pFunc->pFExpr;
+      assert( ExprUseXList(pE) );
+      if( pE->x.pList==0 || pE->x.pList->nExpr!=1 ){
+        sqlite3ErrorMsg(pParse, "DISTINCT aggregates must have exactly one "
+           "argument");
+        pFunc->iDistinct = -1;
+      }else{
+        KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pE->x.pList,0,0);
+        pFunc->iDistAddr = sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
+            pFunc->iDistinct, 0, 0, (char*)pKeyInfo, P4_KEYINFO);
+        ExplainQueryPlan((pParse, 0, "USE TEMP B-TREE FOR %s(DISTINCT)",
+                          pFunc->pFunc->zName));
+      }
+    }
+    if( pFunc->iOBTab>=0 ){
+      ExprList *pOBList;
+      KeyInfo *pKeyInfo;
+      int nExtra = 0;
+      assert( pFunc->pFExpr->pLeft!=0 );
+      assert( pFunc->pFExpr->pLeft->op==TK_ORDER );
+      assert( ExprUseXList(pFunc->pFExpr->pLeft) );
+      assert( pFunc->pFunc!=0 );
+      pOBList = pFunc->pFExpr->pLeft->x.pList;
+      if( !pFunc->bOBUnique ){
+        nExtra++;  /* One extra column for the OP_Sequence */
+      }
+      if( pFunc->bOBPayload ){
+        /* extra columns for the function arguments */
+        assert( ExprUseXList(pFunc->pFExpr) );
+        nExtra += pFunc->pFExpr->x.pList->nExpr;
+      }
+      if( pFunc->bUseSubtype ){
+        nExtra += pFunc->pFExpr->x.pList->nExpr;
+      }
+      pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pOBList, 0, nExtra);
+      if( !pFunc->bOBUnique && pParse->nErr==0 ){
+        pKeyInfo->nKeyField++;
+      }
+      sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
+            pFunc->iOBTab, pOBList->nExpr+nExtra, 0,
+            (char*)pKeyInfo, P4_KEYINFO);
+      ExplainQueryPlan((pParse, 0, "USE TEMP B-TREE FOR %s(ORDER BY)",
+                          pFunc->pFunc->zName));
+    }
+  }
+}
+
+/*
+** Invoke the OP_AggFinalize opcode for every aggregate function
+** in the AggInfo structure.
+*/
+static void finalizeAggFunctions(Parse *pParse, AggInfo *pAggInfo){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  struct AggInfo_func *pF;
+  for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
+    ExprList *pList;
+    assert( ExprUseXList(pF->pFExpr) );
+    pList = pF->pFExpr->x.pList;
+    if( pF->iOBTab>=0 ){
+      /* For an ORDER BY aggregate, calls to OP_AggStep were deferred.  Inputs
+      ** were stored in emphermal table pF->iOBTab.  Here, we extract those
+      ** inputs (in ORDER BY order) and make all calls to OP_AggStep
+      ** before doing the OP_AggFinal call. */
+      int iTop;        /* Start of loop for extracting columns */
+      int nArg;        /* Number of columns to extract */
+      int nKey;        /* Key columns to be skipped */
+      int regAgg;      /* Extract into this array */
+      int j;           /* Loop counter */
+     
+      assert( pF->pFunc!=0 );
+      nArg = pList->nExpr;
+      regAgg = sqlite3GetTempRange(pParse, nArg);
+
+      if( pF->bOBPayload==0 ){
+        nKey = 0;
+      }else{
+        assert( pF->pFExpr->pLeft!=0 );
+        assert( ExprUseXList(pF->pFExpr->pLeft) );
+        assert( pF->pFExpr->pLeft->x.pList!=0 );
+        nKey = pF->pFExpr->pLeft->x.pList->nExpr;
+        if( ALWAYS(!pF->bOBUnique) ) nKey++;
+      }
+      iTop = sqlite3VdbeAddOp1(v, OP_Rewind, pF->iOBTab); VdbeCoverage(v);
+      for(j=nArg-1; j>=0; j--){
+        sqlite3VdbeAddOp3(v, OP_Column, pF->iOBTab, nKey+j, regAgg+j);
+      }
+      if( pF->bUseSubtype ){
+        int regSubtype = sqlite3GetTempReg(pParse);
+        int iBaseCol = nKey + nArg + (pF->bOBPayload==0 && pF->bOBUnique==0);
+        for(j=nArg-1; j>=0; j--){
+          sqlite3VdbeAddOp3(v, OP_Column, pF->iOBTab, iBaseCol+j, regSubtype);
+          sqlite3VdbeAddOp2(v, OP_SetSubtype, regSubtype, regAgg+j);
+        }
+        sqlite3ReleaseTempReg(pParse, regSubtype);
+      }
+      sqlite3VdbeAddOp3(v, OP_AggStep, 0, regAgg, AggInfoFuncReg(pAggInfo,i));
+      sqlite3VdbeAppendP4(v, pF->pFunc, P4_FUNCDEF);
+      sqlite3VdbeChangeP5(v, (u8)nArg);
+      sqlite3VdbeAddOp2(v, OP_Next, pF->iOBTab, iTop+1); VdbeCoverage(v);
+      sqlite3VdbeJumpHere(v, iTop);
+      sqlite3ReleaseTempRange(pParse, regAgg, nArg);
+    }
+    sqlite3VdbeAddOp2(v, OP_AggFinal, AggInfoFuncReg(pAggInfo,i),
+                      pList ? pList->nExpr : 0);
+    sqlite3VdbeAppendP4(v, pF->pFunc, P4_FUNCDEF);
+  }
+}
+
+/*
+** Generate code that will update the accumulator memory cells for an
+** aggregate based on the current cursor position.
+**
+** If regAcc is non-zero and there are no min() or max() aggregates
+** in pAggInfo, then only populate the pAggInfo->nAccumulator accumulator
+** registers if register regAcc contains 0. The caller will take care
+** of setting and clearing regAcc.
+**
+** For an ORDER BY aggregate, the actual accumulator memory cell update
+** is deferred until after all input rows have been received, so that they
+** can be run in the requested order.  In that case, instead of invoking
+** OP_AggStep to update the accumulator, just add the arguments that would
+** have been passed into OP_AggStep into the sorting ephemeral table
+** (along with the appropriate sort key).
+*/
+static void updateAccumulator(
+  Parse *pParse,
+  int regAcc,
+  AggInfo *pAggInfo,
+  int eDistinctType
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  int regHit = 0;
+  int addrHitTest = 0;
+  struct AggInfo_func *pF;
+  struct AggInfo_col *pC;
+
+  assert( pAggInfo->iFirstReg>0 );
+  if( pParse->nErr ) return;
+  pAggInfo->directMode = 1;
+  for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
+    int nArg;
+    int addrNext = 0;
+    int regAgg;
+    int regAggSz = 0;
+    int regDistinct = 0;
+    ExprList *pList;
+    assert( ExprUseXList(pF->pFExpr) );
+    assert( !IsWindowFunc(pF->pFExpr) );
+    assert( pF->pFunc!=0 );
+    pList = pF->pFExpr->x.pList;
+    if( ExprHasProperty(pF->pFExpr, EP_WinFunc) ){
+      Expr *pFilter = pF->pFExpr->y.pWin->pFilter;
+      if( pAggInfo->nAccumulator
+       && (pF->pFunc->funcFlags & SQLITE_FUNC_NEEDCOLL)
+       && regAcc
+      ){
+        /* If regAcc==0, there there exists some min() or max() function
+        ** without a FILTER clause that will ensure the magnet registers
+        ** are populated. */
+        if( regHit==0 ) regHit = ++pParse->nMem;
+        /* If this is the first row of the group (regAcc contains 0), clear the
+        ** "magnet" register regHit so that the accumulator registers
+        ** are populated if the FILTER clause jumps over the the
+        ** invocation of min() or max() altogether. Or, if this is not
+        ** the first row (regAcc contains 1), set the magnet register so that
+        ** the accumulators are not populated unless the min()/max() is invoked
+        ** and indicates that they should be.  */
+        sqlite3VdbeAddOp2(v, OP_Copy, regAcc, regHit);
+      }
+      addrNext = sqlite3VdbeMakeLabel(pParse);
+      sqlite3ExprIfFalse(pParse, pFilter, addrNext, SQLITE_JUMPIFNULL);
+    }
+    if( pF->iOBTab>=0 ){
+      /* Instead of invoking AggStep, we must push the arguments that would
+      ** have been passed to AggStep onto the sorting table. */
+      int jj;                /* Registered used so far in building the record */
+      ExprList *pOBList;     /* The ORDER BY clause */
+      assert( pList!=0 );
+      nArg = pList->nExpr;
+      assert( nArg>0 );
+      assert( pF->pFExpr->pLeft!=0 );
+      assert( pF->pFExpr->pLeft->op==TK_ORDER );
+      assert( ExprUseXList(pF->pFExpr->pLeft) );
+      pOBList = pF->pFExpr->pLeft->x.pList;
+      assert( pOBList!=0 );
+      assert( pOBList->nExpr>0 );
+      regAggSz = pOBList->nExpr;
+      if( !pF->bOBUnique ){
+        regAggSz++;   /* One register for OP_Sequence */
+      }
+      if( pF->bOBPayload ){
+        regAggSz += nArg;
+      }
+      if( pF->bUseSubtype ){
+        regAggSz += nArg;
+      }
+      regAggSz++;  /* One extra register to hold result of MakeRecord */
+      regAgg = sqlite3GetTempRange(pParse, regAggSz);
+      regDistinct = regAgg;
+      sqlite3ExprCodeExprList(pParse, pOBList, regAgg, 0, SQLITE_ECEL_DUP);
+      jj = pOBList->nExpr;
+      if( !pF->bOBUnique ){
+        sqlite3VdbeAddOp2(v, OP_Sequence, pF->iOBTab, regAgg+jj);
+        jj++;
+      }
+      if( pF->bOBPayload ){
+        regDistinct = regAgg+jj;
+        sqlite3ExprCodeExprList(pParse, pList, regDistinct, 0, SQLITE_ECEL_DUP);
+        jj += nArg;
+      }
+      if( pF->bUseSubtype ){
+        int kk;
+        int regBase = pF->bOBPayload ? regDistinct : regAgg;
+        for(kk=0; kk<nArg; kk++, jj++){
+          sqlite3VdbeAddOp2(v, OP_GetSubtype, regBase+kk, regAgg+jj);
+        }
+      }
+    }else if( pList ){
+      nArg = pList->nExpr;
+      regAgg = sqlite3GetTempRange(pParse, nArg);
+      regDistinct = regAgg;
+      sqlite3ExprCodeExprList(pParse, pList, regAgg, 0, SQLITE_ECEL_DUP);
+    }else{
+      nArg = 0;
+      regAgg = 0;
+    }
+    if( pF->iDistinct>=0 && pList ){
+      if( addrNext==0 ){
+        addrNext = sqlite3VdbeMakeLabel(pParse);
+      }
+      pF->iDistinct = codeDistinct(pParse, eDistinctType,
+          pF->iDistinct, addrNext, pList, regDistinct);
+    }
+    if( pF->iOBTab>=0 ){
+      /* Insert a new record into the ORDER BY table */
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regAgg, regAggSz-1,
+                        regAgg+regAggSz-1);
+      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, pF->iOBTab, regAgg+regAggSz-1,
+                           regAgg, regAggSz-1);
+      sqlite3ReleaseTempRange(pParse, regAgg, regAggSz);
+    }else{
+      /* Invoke the AggStep function */
+      if( pF->pFunc->funcFlags & SQLITE_FUNC_NEEDCOLL ){
+        CollSeq *pColl = 0;
+        struct ExprList_item *pItem;
+        int j;
+        assert( pList!=0 );  /* pList!=0 if pF->pFunc has NEEDCOLL */
+        for(j=0, pItem=pList->a; !pColl && j<nArg; j++, pItem++){
+          pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
+        }
+        if( !pColl ){
+          pColl = pParse->db->pDfltColl;
+        }
+        if( regHit==0 && pAggInfo->nAccumulator ) regHit = ++pParse->nMem;
+        sqlite3VdbeAddOp4(v, OP_CollSeq, regHit, 0, 0,
+                         (char *)pColl, P4_COLLSEQ);
+      }
+      sqlite3VdbeAddOp3(v, OP_AggStep, 0, regAgg, AggInfoFuncReg(pAggInfo,i));
+      sqlite3VdbeAppendP4(v, pF->pFunc, P4_FUNCDEF);
+      sqlite3VdbeChangeP5(v, (u8)nArg);
+      sqlite3ReleaseTempRange(pParse, regAgg, nArg);
+    }
+    if( addrNext ){
+      sqlite3VdbeResolveLabel(v, addrNext);
+    }
+  }
+  if( regHit==0 && pAggInfo->nAccumulator ){
+    regHit = regAcc;
+  }
+  if( regHit ){
+    addrHitTest = sqlite3VdbeAddOp1(v, OP_If, regHit); VdbeCoverage(v);
+  }
+  for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
+    sqlite3ExprCode(pParse, pC->pCExpr, AggInfoColumnReg(pAggInfo,i));
+  }
+
+  pAggInfo->directMode = 0;
+  if( addrHitTest ){
+    sqlite3VdbeJumpHereOrPopInst(v, addrHitTest);
+  }
+}
+
+/*
+** Add a single OP_Explain instruction to the VDBE to explain a simple
+** count(*) query ("SELECT count(*) FROM pTab").
+*/
+#ifndef SQLITE_OMIT_EXPLAIN
+static void explainSimpleCount(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being queried */
+  Index *pIdx                     /* Index used to optimize scan, or NULL */
+){
+  if( pParse->explain==2 ){
+    int bCover = (pIdx!=0 && (HasRowid(pTab) || !IsPrimaryKeyIndex(pIdx)));
+    sqlite3VdbeExplain(pParse, 0, "SCAN %s%s%s",
+        pTab->zName,
+        bCover ? " USING COVERING INDEX " : "",
+        bCover ? pIdx->zName : ""
+    );
+  }
+}
+#else
+# define explainSimpleCount(a,b,c)
+#endif
+
+/*
+** sqlite3WalkExpr() callback used by havingToWhere().
+**
+** If the node passed to the callback is a TK_AND node, return
+** WRC_Continue to tell sqlite3WalkExpr() to iterate through child nodes.
+**
+** Otherwise, return WRC_Prune. In this case, also check if the
+** sub-expression matches the criteria for being moved to the WHERE
+** clause. If so, add it to the WHERE clause and replace the sub-expression
+** within the HAVING expression with a constant "1".
+*/
+static int havingToWhereExprCb(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op!=TK_AND ){
+    Select *pS = pWalker->u.pSelect;
+    /* This routine is called before the HAVING clause of the current
+    ** SELECT is analyzed for aggregates. So if pExpr->pAggInfo is set
+    ** here, it indicates that the expression is a correlated reference to a
+    ** column from an outer aggregate query, or an aggregate function that
+    ** belongs to an outer query. Do not move the expression to the WHERE
+    ** clause in this obscure case, as doing so may corrupt the outer Select
+    ** statements AggInfo structure.  */
+    if( sqlite3ExprIsConstantOrGroupBy(pWalker->pParse, pExpr, pS->pGroupBy)
+     && ExprAlwaysFalse(pExpr)==0
+     && pExpr->pAggInfo==0
+    ){
+      sqlite3 *db = pWalker->pParse->db;
+      Expr *pNew = sqlite3Expr(db, TK_INTEGER, "1");
+      if( pNew ){
+        Expr *pWhere = pS->pWhere;
+        SWAP(Expr, *pNew, *pExpr);
+        pNew = sqlite3ExprAnd(pWalker->pParse, pWhere, pNew);
+        pS->pWhere = pNew;
+        pWalker->eCode = 1;
+      }
+    }
+    return WRC_Prune;
+  }
+  return WRC_Continue;
+}
+
+/*
+** Transfer eligible terms from the HAVING clause of a query, which is
+** processed after grouping, to the WHERE clause, which is processed before
+** grouping. For example, the query:
+**
+**   SELECT * FROM <tables> WHERE a=? GROUP BY b HAVING b=? AND c=?
+**
+** can be rewritten as:
+**
+**   SELECT * FROM <tables> WHERE a=? AND b=? GROUP BY b HAVING c=?
+**
+** A term of the HAVING expression is eligible for transfer if it consists
+** entirely of constants and expressions that are also GROUP BY terms that
+** use the "BINARY" collation sequence.
+*/
+static void havingToWhere(Parse *pParse, Select *p){
+  Walker sWalker;
+  memset(&sWalker, 0, sizeof(sWalker));
+  sWalker.pParse = pParse;
+  sWalker.xExprCallback = havingToWhereExprCb;
+  sWalker.u.pSelect = p;
+  sqlite3WalkExpr(&sWalker, p->pHaving);
+#if TREETRACE_ENABLED
+  if( sWalker.eCode && (sqlite3TreeTrace & 0x100)!=0 ){
+    TREETRACE(0x100,pParse,p,("Move HAVING terms into WHERE:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+}
+
+/*
+** Check to see if the pThis entry of pTabList is a self-join of another view.
+** Search FROM-clause entries in the range of iFirst..iEnd, including iFirst
+** but stopping before iEnd.
+**
+** If pThis is a self-join, then return the SrcItem for the first other
+** instance of that view found.  If pThis is not a self-join then return 0.
+*/
+static SrcItem *isSelfJoinView(
+  SrcList *pTabList,           /* Search for self-joins in this FROM clause */
+  SrcItem *pThis,              /* Search for prior reference to this subquery */
+  int iFirst, int iEnd        /* Range of FROM-clause entries to search. */
+){
+  SrcItem *pItem;
+  assert( pThis->pSelect!=0 );
+  if( pThis->pSelect->selFlags & SF_PushDown ) return 0;
+  while( iFirst<iEnd ){
+    Select *pS1;
+    pItem = &pTabList->a[iFirst++];
+    if( pItem->pSelect==0 ) continue;
+    if( pItem->fg.viaCoroutine ) continue;
+    if( pItem->zName==0 ) continue;
+    assert( pItem->pTab!=0 );
+    assert( pThis->pTab!=0 );
+    if( pItem->pTab->pSchema!=pThis->pTab->pSchema ) continue;
+    if( sqlite3_stricmp(pItem->zName, pThis->zName)!=0 ) continue;
+    pS1 = pItem->pSelect;
+    if( pItem->pTab->pSchema==0 && pThis->pSelect->selId!=pS1->selId ){
+      /* The query flattener left two different CTE tables with identical
+      ** names in the same FROM clause. */
+      continue;
+    }
+    if( pItem->pSelect->selFlags & SF_PushDown ){
+      /* The view was modified by some other optimization such as
+      ** pushDownWhereTerms() */
+      continue;
+    }
+    return pItem;
+  }
+  return 0;
+}
+
+/*
+** Deallocate a single AggInfo object
+*/
+static void agginfoFree(sqlite3 *db, void *pArg){
+  AggInfo *p = (AggInfo*)pArg;
+  sqlite3DbFree(db, p->aCol);
+  sqlite3DbFree(db, p->aFunc);
+  sqlite3DbFreeNN(db, p);
+}
+
+/*
+** Attempt to transform a query of the form
+**
+**    SELECT count(*) FROM (SELECT x FROM t1 UNION ALL SELECT y FROM t2)
+**
+** Into this:
+**
+**    SELECT (SELECT count(*) FROM t1)+(SELECT count(*) FROM t2)
+**
+** The transformation only works if all of the following are true:
+**
+**   *  The subquery is a UNION ALL of two or more terms
+**   *  The subquery does not have a LIMIT clause
+**   *  There is no WHERE or GROUP BY or HAVING clauses on the subqueries
+**   *  The outer query is a simple count(*) with no WHERE clause or other
+**      extraneous syntax.
+**
+** Return TRUE if the optimization is undertaken.
+*/
+static int countOfViewOptimization(Parse *pParse, Select *p){
+  Select *pSub, *pPrior;
+  Expr *pExpr;
+  Expr *pCount;
+  sqlite3 *db;
+  if( (p->selFlags & SF_Aggregate)==0 ) return 0;   /* This is an aggregate */
+  if( p->pEList->nExpr!=1 ) return 0;               /* Single result column */
+  if( p->pWhere ) return 0;
+  if( p->pHaving ) return 0;
+  if( p->pGroupBy ) return 0;
+  if( p->pOrderBy ) return 0;
+  pExpr = p->pEList->a[0].pExpr;
+  if( pExpr->op!=TK_AGG_FUNCTION ) return 0;        /* Result is an aggregate */
+  assert( ExprUseUToken(pExpr) );
+  if( sqlite3_stricmp(pExpr->u.zToken,"count") ) return 0;  /* Is count() */
+  assert( ExprUseXList(pExpr) );
+  if( pExpr->x.pList!=0 ) return 0;                 /* Must be count(*) */
+  if( p->pSrc->nSrc!=1 ) return 0;                  /* One table in FROM  */
+  if( ExprHasProperty(pExpr, EP_WinFunc) ) return 0;/* Not a window function */
+  pSub = p->pSrc->a[0].pSelect;
+  if( pSub==0 ) return 0;                           /* The FROM is a subquery */
+  if( pSub->pPrior==0 ) return 0;                   /* Must be a compound */
+  if( pSub->selFlags & SF_CopyCte ) return 0;       /* Not a CTE */
+  do{
+    if( pSub->op!=TK_ALL && pSub->pPrior ) return 0;  /* Must be UNION ALL */
+    if( pSub->pWhere ) return 0;                      /* No WHERE clause */
+    if( pSub->pLimit ) return 0;                      /* No LIMIT clause */
+    if( pSub->selFlags & SF_Aggregate ) return 0;     /* Not an aggregate */
+    assert( pSub->pHaving==0 );  /* Due to the previous */
+   pSub = pSub->pPrior;                              /* Repeat over compound */
+  }while( pSub );
+
+  /* If we reach this point then it is OK to perform the transformation */
+
+  db = pParse->db;
+  pCount = pExpr;
+  pExpr = 0;
+  pSub = p->pSrc->a[0].pSelect;
+  p->pSrc->a[0].pSelect = 0;
+  sqlite3SrcListDelete(db, p->pSrc);
+  p->pSrc = sqlite3DbMallocZero(pParse->db, sizeof(*p->pSrc));
+  while( pSub ){
+    Expr *pTerm;
+    pPrior = pSub->pPrior;
+    pSub->pPrior = 0;
+    pSub->pNext = 0;
+    pSub->selFlags |= SF_Aggregate;
+    pSub->selFlags &= ~SF_Compound;
+    pSub->nSelectRow = 0;
+    sqlite3ParserAddCleanup(pParse, sqlite3ExprListDeleteGeneric, pSub->pEList);
+    pTerm = pPrior ? sqlite3ExprDup(db, pCount, 0) : pCount;
+    pSub->pEList = sqlite3ExprListAppend(pParse, 0, pTerm);
+    pTerm = sqlite3PExpr(pParse, TK_SELECT, 0, 0);
+    sqlite3PExprAddSelect(pParse, pTerm, pSub);
+    if( pExpr==0 ){
+      pExpr = pTerm;
+    }else{
+      pExpr = sqlite3PExpr(pParse, TK_PLUS, pTerm, pExpr);
+    }
+    pSub = pPrior;
+  }
+  p->pEList->a[0].pExpr = pExpr;
+  p->selFlags &= ~SF_Aggregate;
+
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x200 ){
+    TREETRACE(0x200,pParse,p,("After count-of-view optimization:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+  return 1;
+}
+
+/*
+** If any term of pSrc, or any SF_NestedFrom sub-query, is not the same
+** as pSrcItem but has the same alias as p0, then return true.
+** Otherwise return false.
+*/
+static int sameSrcAlias(SrcItem *p0, SrcList *pSrc){
+  int i;
+  for(i=0; i<pSrc->nSrc; i++){
+    SrcItem *p1 = &pSrc->a[i];
+    if( p1==p0 ) continue;
+    if( p0->pTab==p1->pTab && 0==sqlite3_stricmp(p0->zAlias, p1->zAlias) ){
+      return 1;
+    }
+    if( p1->pSelect
+     && (p1->pSelect->selFlags & SF_NestedFrom)!=0
+     && sameSrcAlias(p0, p1->pSelect->pSrc)
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Return TRUE (non-zero) if the i-th entry in the pTabList SrcList can
+** be implemented as a co-routine.  The i-th entry is guaranteed to be
+** a subquery.
+**
+** The subquery is implemented as a co-routine if all of the following are
+** true:
+**
+**    (1)  The subquery will likely be implemented in the outer loop of
+**         the query.  This will be the case if any one of the following
+**         conditions hold:
+**         (a)  The subquery is the only term in the FROM clause
+**         (b)  The subquery is the left-most term and a CROSS JOIN or similar
+**              requires it to be the outer loop
+**         (c)  All of the following are true:
+**                (i) The subquery is the left-most subquery in the FROM clause
+**               (ii) There is nothing that would prevent the subquery from
+**                    being used as the outer loop if the sqlite3WhereBegin()
+**                    routine nominates it to that position.
+**              (iii) The query is not a UPDATE ... FROM
+**    (2)  The subquery is not a CTE that should be materialized because
+**         (a) the AS MATERIALIZED keyword is used, or
+**         (b) the CTE is used multiple times and does not have the
+**             NOT MATERIALIZED keyword
+**    (3)  The subquery is not part of a left operand for a RIGHT JOIN
+**    (4)  The SQLITE_Coroutine optimization disable flag is not set
+**    (5)  The subquery is not self-joined
+*/
+static int fromClauseTermCanBeCoroutine(
+  Parse *pParse,          /* Parsing context */
+  SrcList *pTabList,      /* FROM clause */
+  int i,                  /* Which term of the FROM clause holds the subquery */
+  int selFlags            /* Flags on the SELECT statement */
+){
+  SrcItem *pItem = &pTabList->a[i];
+  if( pItem->fg.isCte ){
+    const CteUse *pCteUse = pItem->u2.pCteUse;
+    if( pCteUse->eM10d==M10d_Yes ) return 0;                          /* (2a) */
+    if( pCteUse->nUse>=2 && pCteUse->eM10d!=M10d_No ) return 0;       /* (2b) */
+  }
+  if( pTabList->a[0].fg.jointype & JT_LTORJ ) return 0;               /* (3)  */
+  if( OptimizationDisabled(pParse->db, SQLITE_Coroutines) ) return 0; /* (4)  */
+  if( isSelfJoinView(pTabList, pItem, i+1, pTabList->nSrc)!=0 ){
+    return 0;                                                          /* (5) */
+  }
+  if( i==0 ){
+    if( pTabList->nSrc==1 ) return 1;                             /* (1a) */
+    if( pTabList->a[1].fg.jointype & JT_CROSS ) return 1;         /* (1b) */
+    if( selFlags & SF_UpdateFrom )              return 0;         /* (1c-iii) */
+    return 1;
+  }
+  if( selFlags & SF_UpdateFrom ) return 0;                        /* (1c-iii) */
+  while( 1 /*exit-by-break*/ ){
+    if( pItem->fg.jointype & (JT_OUTER|JT_CROSS)  ) return 0;     /* (1c-ii) */
+    if( i==0 ) break;
+    i--;
+    pItem--;
+    if( pItem->pSelect!=0 ) return 0;                             /* (1c-i) */
+  }
+  return 1;
+}
+
+/*
+** Generate code for the SELECT statement given in the p argument. 
+**
+** The results are returned according to the SelectDest structure.
+** See comments in sqliteInt.h for further information.
+**
+** This routine returns the number of errors.  If any errors are
+** encountered, then an appropriate error message is left in
+** pParse->zErrMsg.
+**
+** This routine does NOT free the Select structure passed in.  The
+** calling function needs to do that.
+*/
+int sqlite3Select(
+  Parse *pParse,         /* The parser context */
+  Select *p,             /* The SELECT statement being coded. */
+  SelectDest *pDest      /* What to do with the query results */
+){
+  int i, j;              /* Loop counters */
+  WhereInfo *pWInfo;     /* Return from sqlite3WhereBegin() */
+  Vdbe *v;               /* The virtual machine under construction */
+  int isAgg;             /* True for select lists like "count(*)" */
+  ExprList *pEList = 0;  /* List of columns to extract. */
+  SrcList *pTabList;     /* List of tables to select from */
+  Expr *pWhere;          /* The WHERE clause.  May be NULL */
+  ExprList *pGroupBy;    /* The GROUP BY clause.  May be NULL */
+  Expr *pHaving;         /* The HAVING clause.  May be NULL */
+  AggInfo *pAggInfo = 0; /* Aggregate information */
+  int rc = 1;            /* Value to return from this function */
+  DistinctCtx sDistinct; /* Info on how to code the DISTINCT keyword */
+  SortCtx sSort;         /* Info on how to code the ORDER BY clause */
+  int iEnd;              /* Address of the end of the query */
+  sqlite3 *db;           /* The database connection */
+  ExprList *pMinMaxOrderBy = 0;  /* Added ORDER BY for min/max queries */
+  u8 minMaxFlag;                 /* Flag for min/max queries */
+
+  db = pParse->db;
+  assert( pParse==db->pParse );
+  v = sqlite3GetVdbe(pParse);
+  if( p==0 || pParse->nErr ){
+    return 1;
+  }
+  assert( db->mallocFailed==0 );
+  if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
+#if TREETRACE_ENABLED
+  TREETRACE(0x1,pParse,p, ("begin processing:\n", pParse->addrExplain));
+  if( sqlite3TreeTrace & 0x10000 ){
+    if( (sqlite3TreeTrace & 0x10001)==0x10000 ){
+      sqlite3TreeViewLine(0, "In sqlite3Select() at %s:%d",
+                           __FILE__, __LINE__);
+    }
+    sqlite3ShowSelect(p);
+  }
+#endif
+
+  assert( p->pOrderBy==0 || pDest->eDest!=SRT_DistFifo );
+  assert( p->pOrderBy==0 || pDest->eDest!=SRT_Fifo );
+  assert( p->pOrderBy==0 || pDest->eDest!=SRT_DistQueue );
+  assert( p->pOrderBy==0 || pDest->eDest!=SRT_Queue );
+  if( IgnorableDistinct(pDest) ){
+    assert(pDest->eDest==SRT_Exists     || pDest->eDest==SRT_Union ||
+           pDest->eDest==SRT_Except     || pDest->eDest==SRT_Discard ||
+           pDest->eDest==SRT_DistQueue  || pDest->eDest==SRT_DistFifo );
+    /* All of these destinations are also able to ignore the ORDER BY clause */
+    if( p->pOrderBy ){
+#if TREETRACE_ENABLED
+      TREETRACE(0x800,pParse,p, ("dropping superfluous ORDER BY:\n"));
+      if( sqlite3TreeTrace & 0x800 ){
+        sqlite3TreeViewExprList(0, p->pOrderBy, 0, "ORDERBY");
+      }
+#endif   
+      sqlite3ParserAddCleanup(pParse, sqlite3ExprListDeleteGeneric,
+                              p->pOrderBy);
+      testcase( pParse->earlyCleanup );
+      p->pOrderBy = 0;
+    }
+    p->selFlags &= ~SF_Distinct;
+    p->selFlags |= SF_NoopOrderBy;
+  }
+  sqlite3SelectPrep(pParse, p, 0);
+  if( pParse->nErr ){
+    goto select_end;
+  }
+  assert( db->mallocFailed==0 );
+  assert( p->pEList!=0 );
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x10 ){
+    TREETRACE(0x10,pParse,p, ("after name resolution:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+
+  /* If the SF_UFSrcCheck flag is set, then this function is being called
+  ** as part of populating the temp table for an UPDATE...FROM statement.
+  ** In this case, it is an error if the target object (pSrc->a[0]) name
+  ** or alias is duplicated within FROM clause (pSrc->a[1..n]). 
+  **
+  ** Postgres disallows this case too. The reason is that some other
+  ** systems handle this case differently, and not all the same way,
+  ** which is just confusing. To avoid this, we follow PG's lead and
+  ** disallow it altogether.  */
+  if( p->selFlags & SF_UFSrcCheck ){
+    SrcItem *p0 = &p->pSrc->a[0];
+    if( sameSrcAlias(p0, p->pSrc) ){
+      sqlite3ErrorMsg(pParse,
+          "target object/alias may not appear in FROM clause: %s",
+          p0->zAlias ? p0->zAlias : p0->pTab->zName
+      );
+      goto select_end;
+    }
+
+    /* Clear the SF_UFSrcCheck flag. The check has already been performed,
+    ** and leaving this flag set can cause errors if a compound sub-query
+    ** in p->pSrc is flattened into this query and this function called
+    ** again as part of compound SELECT processing.  */
+    p->selFlags &= ~SF_UFSrcCheck;
+  }
+
+  if( pDest->eDest==SRT_Output ){
+    sqlite3GenerateColumnNames(pParse, p);
+  }
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( sqlite3WindowRewrite(pParse, p) ){
+    assert( pParse->nErr );
+    goto select_end;
+  }
+#if TREETRACE_ENABLED
+  if( p->pWin && (sqlite3TreeTrace & 0x40)!=0 ){
+    TREETRACE(0x40,pParse,p, ("after window rewrite:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+  pTabList = p->pSrc;
+  isAgg = (p->selFlags & SF_Aggregate)!=0;
+  memset(&sSort, 0, sizeof(sSort));
+  sSort.pOrderBy = p->pOrderBy;
+
+  /* Try to do various optimizations (flattening subqueries, and strength
+  ** reduction of join operators) in the FROM clause up into the main query
+  */
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+  for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
+    SrcItem *pItem = &pTabList->a[i];
+    Select *pSub = pItem->pSelect;
+    Table *pTab = pItem->pTab;
+
+    /* The expander should have already created transient Table objects
+    ** even for FROM clause elements such as subqueries that do not correspond
+    ** to a real table */
+    assert( pTab!=0 );
+
+    /* Try to simplify joins:
+    **
+    **      LEFT JOIN  ->  JOIN
+    **     RIGHT JOIN  ->  JOIN
+    **      FULL JOIN  ->  RIGHT JOIN
+    **
+    ** If terms of the i-th table are used in the WHERE clause in such a
+    ** way that the i-th table cannot be the NULL row of a join, then
+    ** perform the appropriate simplification. This is called
+    ** "OUTER JOIN strength reduction" in the SQLite documentation.
+    */
+    if( (pItem->fg.jointype & (JT_LEFT|JT_LTORJ))!=0
+     && sqlite3ExprImpliesNonNullRow(p->pWhere, pItem->iCursor,
+                                     pItem->fg.jointype & JT_LTORJ)
+     && OptimizationEnabled(db, SQLITE_SimplifyJoin)
+    ){
+      if( pItem->fg.jointype & JT_LEFT ){
+        if( pItem->fg.jointype & JT_RIGHT ){
+          TREETRACE(0x1000,pParse,p,
+                    ("FULL-JOIN simplifies to RIGHT-JOIN on term %d\n",i));
+          pItem->fg.jointype &= ~JT_LEFT;
+        }else{
+          TREETRACE(0x1000,pParse,p,
+                    ("LEFT-JOIN simplifies to JOIN on term %d\n",i));
+          pItem->fg.jointype &= ~(JT_LEFT|JT_OUTER);
+          unsetJoinExpr(p->pWhere, pItem->iCursor, 0);
+        }
+      }
+      if( pItem->fg.jointype & JT_LTORJ ){
+        for(j=i+1; j<pTabList->nSrc; j++){
+          SrcItem *pI2 = &pTabList->a[j];
+          if( pI2->fg.jointype & JT_RIGHT ){
+            if( pI2->fg.jointype & JT_LEFT ){
+              TREETRACE(0x1000,pParse,p,
+                        ("FULL-JOIN simplifies to LEFT-JOIN on term %d\n",j));
+              pI2->fg.jointype &= ~JT_RIGHT;
+            }else{
+              TREETRACE(0x1000,pParse,p,
+                        ("RIGHT-JOIN simplifies to JOIN on term %d\n",j));
+              pI2->fg.jointype &= ~(JT_RIGHT|JT_OUTER);
+              unsetJoinExpr(p->pWhere, pI2->iCursor, 1);
+            }
+          }
+        }
+        for(j=pTabList->nSrc-1; j>=0; j--){
+          pTabList->a[j].fg.jointype &= ~JT_LTORJ;
+          if( pTabList->a[j].fg.jointype & JT_RIGHT ) break;
+        }
+      }
+    }
+
+    /* No further action if this term of the FROM clause is not a subquery */
+    if( pSub==0 ) continue;
+
+    /* Catch mismatch in the declared columns of a view and the number of
+    ** columns in the SELECT on the RHS */
+    if( pTab->nCol!=pSub->pEList->nExpr ){
+      sqlite3ErrorMsg(pParse, "expected %d columns for '%s' but got %d",
+                      pTab->nCol, pTab->zName, pSub->pEList->nExpr);
+      goto select_end;
+    }
+
+    /* Do not attempt the usual optimizations (flattening and ORDER BY
+    ** elimination) on a MATERIALIZED common table expression because
+    ** a MATERIALIZED common table expression is an optimization fence.
+    */
+    if( pItem->fg.isCte && pItem->u2.pCteUse->eM10d==M10d_Yes ){
+      continue;
+    }
+
+    /* Do not try to flatten an aggregate subquery.
+    **
+    ** Flattening an aggregate subquery is only possible if the outer query
+    ** is not a join.  But if the outer query is not a join, then the subquery
+    ** will be implemented as a co-routine and there is no advantage to
+    ** flattening in that case.
+    */
+    if( (pSub->selFlags & SF_Aggregate)!=0 ) continue;
+    assert( pSub->pGroupBy==0 );
+
+    /* If a FROM-clause subquery has an ORDER BY clause that is not
+    ** really doing anything, then delete it now so that it does not
+    ** interfere with query flattening.  See the discussion at
+    ** https://sqlite.org/forum/forumpost/2d76f2bcf65d256a
+    **
+    ** Beware of these cases where the ORDER BY clause may not be safely
+    ** omitted:
+    **
+    **    (1)   There is also a LIMIT clause
+    **    (2)   The subquery was added to help with window-function
+    **          processing
+    **    (3)   The subquery is in the FROM clause of an UPDATE
+    **    (4)   The outer query uses an aggregate function other than
+    **          the built-in count(), min(), or max().
+    **    (5)   The ORDER BY isn't going to accomplish anything because
+    **          one of:
+    **            (a)  The outer query has a different ORDER BY clause
+    **            (b)  The subquery is part of a join
+    **          See forum post 062d576715d277c8
+    **
+    ** Also retain the ORDER BY if the OmitOrderBy optimization is disabled.
+    */
+    if( pSub->pOrderBy!=0
+     && (p->pOrderBy!=0 || pTabList->nSrc>1)      /* Condition (5) */
+     && pSub->pLimit==0                           /* Condition (1) */
+     && (pSub->selFlags & SF_OrderByReqd)==0      /* Condition (2) */
+     && (p->selFlags & SF_OrderByReqd)==0         /* Condition (3) and (4) */
+     && OptimizationEnabled(db, SQLITE_OmitOrderBy)
+    ){
+      TREETRACE(0x800,pParse,p,
+                ("omit superfluous ORDER BY on %r FROM-clause subquery\n",i+1));
+      sqlite3ParserAddCleanup(pParse, sqlite3ExprListDeleteGeneric,
+                              pSub->pOrderBy);
+      pSub->pOrderBy = 0;
+    }
+
+    /* If the outer query contains a "complex" result set (that is,
+    ** if the result set of the outer query uses functions or subqueries)
+    ** and if the subquery contains an ORDER BY clause and if
+    ** it will be implemented as a co-routine, then do not flatten.  This
+    ** restriction allows SQL constructs like this:
+    **
+    **  SELECT expensive_function(x)
+    **    FROM (SELECT x FROM tab ORDER BY y LIMIT 10);
+    **
+    ** The expensive_function() is only computed on the 10 rows that
+    ** are output, rather than every row of the table.
+    **
+    ** The requirement that the outer query have a complex result set
+    ** means that flattening does occur on simpler SQL constraints without
+    ** the expensive_function() like:
+    **
+    **  SELECT x FROM (SELECT x FROM tab ORDER BY y LIMIT 10);
+    */
+    if( pSub->pOrderBy!=0
+     && i==0
+     && (p->selFlags & SF_ComplexResult)!=0
+     && (pTabList->nSrc==1
+         || (pTabList->a[1].fg.jointype&(JT_OUTER|JT_CROSS))!=0)
+    ){
+      continue;
+    }
+
+    if( flattenSubquery(pParse, p, i, isAgg) ){
+      if( pParse->nErr ) goto select_end;
+      /* This subquery can be absorbed into its parent. */
+      i = -1;
+    }
+    pTabList = p->pSrc;
+    if( db->mallocFailed ) goto select_end;
+    if( !IgnorableOrderby(pDest) ){
+      sSort.pOrderBy = p->pOrderBy;
+    }
+  }
+#endif
+
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+  /* Handle compound SELECT statements using the separate multiSelect()
+  ** procedure.
+  */
+  if( p->pPrior ){
+    rc = multiSelect(pParse, p, pDest);
+#if TREETRACE_ENABLED
+    TREETRACE(0x400,pParse,p,("end compound-select processing\n"));
+    if( (sqlite3TreeTrace & 0x400)!=0 && ExplainQueryPlanParent(pParse)==0 ){
+      sqlite3TreeViewSelect(0, p, 0);
+    }
+#endif
+    if( p->pNext==0 ) ExplainQueryPlanPop(pParse);
+    return rc;
+  }
+#endif
+
+  /* Do the WHERE-clause constant propagation optimization if this is
+  ** a join.  No need to speed time on this operation for non-join queries
+  ** as the equivalent optimization will be handled by query planner in
+  ** sqlite3WhereBegin().
+  */
+  if( p->pWhere!=0
+   && p->pWhere->op==TK_AND
+   && OptimizationEnabled(db, SQLITE_PropagateConst)
+   && propagateConstants(pParse, p)
+  ){
+#if TREETRACE_ENABLED
+    if( sqlite3TreeTrace & 0x2000 ){
+      TREETRACE(0x2000,pParse,p,("After constant propagation:\n"));
+      sqlite3TreeViewSelect(0, p, 0);
+    }
+#endif
+  }else{
+    TREETRACE(0x2000,pParse,p,("Constant propagation not helpful\n"));
+  }
+
+  if( OptimizationEnabled(db, SQLITE_QueryFlattener|SQLITE_CountOfView)
+   && countOfViewOptimization(pParse, p)
+  ){
+    if( db->mallocFailed ) goto select_end;
+    pTabList = p->pSrc;
+  }
+
+  /* For each term in the FROM clause, do two things:
+  ** (1) Authorized unreferenced tables
+  ** (2) Generate code for all sub-queries
+  */
+  for(i=0; i<pTabList->nSrc; i++){
+    SrcItem *pItem = &pTabList->a[i];
+    SrcItem *pPrior;
+    SelectDest dest;
+    Select *pSub;
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+    const char *zSavedAuthContext;
+#endif
+
+    /* Issue SQLITE_READ authorizations with a fake column name for any
+    ** tables that are referenced but from which no values are extracted.
+    ** Examples of where these kinds of null SQLITE_READ authorizations
+    ** would occur:
+    **
+    **     SELECT count(*) FROM t1;   -- SQLITE_READ t1.""
+    **     SELECT t1.* FROM t1, t2;   -- SQLITE_READ t2.""
+    **
+    ** The fake column name is an empty string.  It is possible for a table to
+    ** have a column named by the empty string, in which case there is no way to
+    ** distinguish between an unreferenced table and an actual reference to the
+    ** "" column. The original design was for the fake column name to be a NULL,
+    ** which would be unambiguous.  But legacy authorization callbacks might
+    ** assume the column name is non-NULL and segfault.  The use of an empty
+    ** string for the fake column name seems safer.
+    */
+    if( pItem->colUsed==0 && pItem->zName!=0 ){
+      sqlite3AuthCheck(pParse, SQLITE_READ, pItem->zName, "", pItem->zDatabase);
+    }
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+    /* Generate code for all sub-queries in the FROM clause
+    */
+    pSub = pItem->pSelect;
+    if( pSub==0 ) continue;
+
+    /* The code for a subquery should only be generated once. */
+    assert( pItem->addrFillSub==0 );
+
+    /* Increment Parse.nHeight by the height of the largest expression
+    ** tree referred to by this, the parent select. The child select
+    ** may contain expression trees of at most
+    ** (SQLITE_MAX_EXPR_DEPTH-Parse.nHeight) height. This is a bit
+    ** more conservative than necessary, but much easier than enforcing
+    ** an exact limit.
+    */
+    pParse->nHeight += sqlite3SelectExprHeight(p);
+
+    /* Make copies of constant WHERE-clause terms in the outer query down
+    ** inside the subquery.  This can help the subquery to run more efficiently.
+    */
+    if( OptimizationEnabled(db, SQLITE_PushDown)
+     && (pItem->fg.isCte==0
+         || (pItem->u2.pCteUse->eM10d!=M10d_Yes && pItem->u2.pCteUse->nUse<2))
+     && pushDownWhereTerms(pParse, pSub, p->pWhere, pTabList, i)
+    ){
+#if TREETRACE_ENABLED
+      if( sqlite3TreeTrace & 0x4000 ){
+        TREETRACE(0x4000,pParse,p,
+            ("After WHERE-clause push-down into subquery %d:\n", pSub->selId));
+        sqlite3TreeViewSelect(0, p, 0);
+      }
+#endif
+      assert( pItem->pSelect && (pItem->pSelect->selFlags & SF_PushDown)!=0 );
+    }else{
+      TREETRACE(0x4000,pParse,p,("Push-down not possible\n"));
+    }
+
+    /* Convert unused result columns of the subquery into simple NULL
+    ** expressions, to avoid unneeded searching and computation.
+    */
+    if( OptimizationEnabled(db, SQLITE_NullUnusedCols)
+     && disableUnusedSubqueryResultColumns(pItem)
+    ){
+#if TREETRACE_ENABLED
+      if( sqlite3TreeTrace & 0x4000 ){
+        TREETRACE(0x4000,pParse,p,
+            ("Change unused result columns to NULL for subquery %d:\n",
+             pSub->selId));
+        sqlite3TreeViewSelect(0, p, 0);
+      }
+#endif
+    }
+
+    zSavedAuthContext = pParse->zAuthContext;
+    pParse->zAuthContext = pItem->zName;
+
+    /* Generate code to implement the subquery
+    */
+    if( fromClauseTermCanBeCoroutine(pParse, pTabList, i, p->selFlags) ){
+      /* Implement a co-routine that will return a single row of the result
+      ** set on each invocation.
+      */
+      int addrTop = sqlite3VdbeCurrentAddr(v)+1;
+    
+      pItem->regReturn = ++pParse->nMem;
+      sqlite3VdbeAddOp3(v, OP_InitCoroutine, pItem->regReturn, 0, addrTop);
+      VdbeComment((v, "%!S", pItem));
+      pItem->addrFillSub = addrTop;
+      sqlite3SelectDestInit(&dest, SRT_Coroutine, pItem->regReturn);
+      ExplainQueryPlan((pParse, 1, "CO-ROUTINE %!S", pItem));
+      sqlite3Select(pParse, pSub, &dest);
+      pItem->pTab->nRowLogEst = pSub->nSelectRow;
+      pItem->fg.viaCoroutine = 1;
+      pItem->regResult = dest.iSdst;
+      sqlite3VdbeEndCoroutine(v, pItem->regReturn);
+      sqlite3VdbeJumpHere(v, addrTop-1);
+      sqlite3ClearTempRegCache(pParse);
+    }else if( pItem->fg.isCte && pItem->u2.pCteUse->addrM9e>0 ){
+      /* This is a CTE for which materialization code has already been
+      ** generated.  Invoke the subroutine to compute the materialization,
+      ** the make the pItem->iCursor be a copy of the ephemeral table that
+      ** holds the result of the materialization. */
+      CteUse *pCteUse = pItem->u2.pCteUse;
+      sqlite3VdbeAddOp2(v, OP_Gosub, pCteUse->regRtn, pCteUse->addrM9e);
+      if( pItem->iCursor!=pCteUse->iCur ){
+        sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pCteUse->iCur);
+        VdbeComment((v, "%!S", pItem));
+      }
+      pSub->nSelectRow = pCteUse->nRowEst;
+    }else if( (pPrior = isSelfJoinView(pTabList, pItem, 0, i))!=0 ){
+      /* This view has already been materialized by a prior entry in
+      ** this same FROM clause.  Reuse it. */
+      if( pPrior->addrFillSub ){
+        sqlite3VdbeAddOp2(v, OP_Gosub, pPrior->regReturn, pPrior->addrFillSub);
+      }
+      sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pPrior->iCursor);
+      pSub->nSelectRow = pPrior->pSelect->nSelectRow;
+    }else{
+      /* Materialize the view.  If the view is not correlated, generate a
+      ** subroutine to do the materialization so that subsequent uses of
+      ** the same view can reuse the materialization. */
+      int topAddr;
+      int onceAddr = 0;
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+      int addrExplain;
+#endif
+
+      pItem->regReturn = ++pParse->nMem;
+      topAddr = sqlite3VdbeAddOp0(v, OP_Goto);
+      pItem->addrFillSub = topAddr+1;
+      pItem->fg.isMaterialized = 1;
+      if( pItem->fg.isCorrelated==0 ){
+        /* If the subquery is not correlated and if we are not inside of
+        ** a trigger, then we only need to compute the value of the subquery
+        ** once. */
+        onceAddr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+        VdbeComment((v, "materialize %!S", pItem));
+      }else{
+        VdbeNoopComment((v, "materialize %!S", pItem));
+      }
+      sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
+
+      ExplainQueryPlan2(addrExplain, (pParse, 1, "MATERIALIZE %!S", pItem));
+      sqlite3Select(pParse, pSub, &dest);
+      pItem->pTab->nRowLogEst = pSub->nSelectRow;
+      if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
+      sqlite3VdbeAddOp2(v, OP_Return, pItem->regReturn, topAddr+1);
+      VdbeComment((v, "end %!S", pItem));
+      sqlite3VdbeScanStatusRange(v, addrExplain, addrExplain, -1);
+      sqlite3VdbeJumpHere(v, topAddr);
+      sqlite3ClearTempRegCache(pParse);
+      if( pItem->fg.isCte && pItem->fg.isCorrelated==0 ){
+        CteUse *pCteUse = pItem->u2.pCteUse;
+        pCteUse->addrM9e = pItem->addrFillSub;
+        pCteUse->regRtn = pItem->regReturn;
+        pCteUse->iCur = pItem->iCursor;
+        pCteUse->nRowEst = pSub->nSelectRow;
+      }
+    }
+    if( db->mallocFailed ) goto select_end;
+    pParse->nHeight -= sqlite3SelectExprHeight(p);
+    pParse->zAuthContext = zSavedAuthContext;
+#endif
+  }
+
+  /* Various elements of the SELECT copied into local variables for
+  ** convenience */
+  pEList = p->pEList;
+  pWhere = p->pWhere;
+  pGroupBy = p->pGroupBy;
+  pHaving = p->pHaving;
+  sDistinct.isTnct = (p->selFlags & SF_Distinct)!=0;
+
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x8000 ){
+    TREETRACE(0x8000,pParse,p,("After all FROM-clause analysis:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+
+  /* If the query is DISTINCT with an ORDER BY but is not an aggregate, and
+  ** if the select-list is the same as the ORDER BY list, then this query
+  ** can be rewritten as a GROUP BY. In other words, this:
+  **
+  **     SELECT DISTINCT xyz FROM ... ORDER BY xyz
+  **
+  ** is transformed to:
+  **
+  **     SELECT xyz FROM ... GROUP BY xyz ORDER BY xyz
+  **
+  ** The second form is preferred as a single index (or temp-table) may be
+  ** used for both the ORDER BY and DISTINCT processing. As originally
+  ** written the query must use a temp-table for at least one of the ORDER
+  ** BY and DISTINCT, and an index or separate temp-table for the other.
+  */
+  if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct
+   && sqlite3ExprListCompare(sSort.pOrderBy, pEList, -1)==0
+#ifndef SQLITE_OMIT_WINDOWFUNC
+   && p->pWin==0
+#endif
+  ){
+    p->selFlags &= ~SF_Distinct;
+    pGroupBy = p->pGroupBy = sqlite3ExprListDup(db, pEList, 0);
+    p->selFlags |= SF_Aggregate;
+    /* Notice that even thought SF_Distinct has been cleared from p->selFlags,
+    ** the sDistinct.isTnct is still set.  Hence, isTnct represents the
+    ** original setting of the SF_Distinct flag, not the current setting */
+    assert( sDistinct.isTnct );
+    sDistinct.isTnct = 2;
+
+#if TREETRACE_ENABLED
+    if( sqlite3TreeTrace & 0x20000 ){
+      TREETRACE(0x20000,pParse,p,("Transform DISTINCT into GROUP BY:\n"));
+      sqlite3TreeViewSelect(0, p, 0);
+    }
+#endif
+  }
+
+  /* If there is an ORDER BY clause, then create an ephemeral index to
+  ** do the sorting.  But this sorting ephemeral index might end up
+  ** being unused if the data can be extracted in pre-sorted order.
+  ** If that is the case, then the OP_OpenEphemeral instruction will be
+  ** changed to an OP_Noop once we figure out that the sorting index is
+  ** not needed.  The sSort.addrSortIndex variable is used to facilitate
+  ** that change.
+  */
+  if( sSort.pOrderBy ){
+    KeyInfo *pKeyInfo;
+    pKeyInfo = sqlite3KeyInfoFromExprList(
+        pParse, sSort.pOrderBy, 0, pEList->nExpr);
+    sSort.iECursor = pParse->nTab++;
+    sSort.addrSortIndex =
+      sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
+          sSort.iECursor, sSort.pOrderBy->nExpr+1+pEList->nExpr, 0,
+          (char*)pKeyInfo, P4_KEYINFO
+      );
+  }else{
+    sSort.addrSortIndex = -1;
+  }
+
+  /* If the output is destined for a temporary table, open that table.
+  */
+  if( pDest->eDest==SRT_EphemTab ){
+    sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pDest->iSDParm, pEList->nExpr);
+    if( p->selFlags & SF_NestedFrom ){
+      /* Delete or NULL-out result columns that will never be used */
+      int ii;
+      for(ii=pEList->nExpr-1; ii>0 && pEList->a[ii].fg.bUsed==0; ii--){
+        sqlite3ExprDelete(db, pEList->a[ii].pExpr);
+        sqlite3DbFree(db, pEList->a[ii].zEName);
+        pEList->nExpr--;
+      }
+      for(ii=0; ii<pEList->nExpr; ii++){
+        if( pEList->a[ii].fg.bUsed==0 ) pEList->a[ii].pExpr->op = TK_NULL;
+      }
+    }
+  }
+
+  /* Set the limiter.
+  */
+  iEnd = sqlite3VdbeMakeLabel(pParse);
+  if( (p->selFlags & SF_FixedLimit)==0 ){
+    p->nSelectRow = 320;  /* 4 billion rows */
+  }
+  if( p->pLimit ) computeLimitRegisters(pParse, p, iEnd);
+  if( p->iLimit==0 && sSort.addrSortIndex>=0 ){
+    sqlite3VdbeChangeOpcode(v, sSort.addrSortIndex, OP_SorterOpen);
+    sSort.sortFlags |= SORTFLAG_UseSorter;
+  }
+
+  /* Open an ephemeral index to use for the distinct set.
+  */
+  if( p->selFlags & SF_Distinct ){
+    sDistinct.tabTnct = pParse->nTab++;
+    sDistinct.addrTnct = sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
+                       sDistinct.tabTnct, 0, 0,
+                       (char*)sqlite3KeyInfoFromExprList(pParse, p->pEList,0,0),
+                       P4_KEYINFO);
+    sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
+    sDistinct.eTnctType = WHERE_DISTINCT_UNORDERED;
+  }else{
+    sDistinct.eTnctType = WHERE_DISTINCT_NOOP;
+  }
+
+  if( !isAgg && pGroupBy==0 ){
+    /* No aggregate functions and no GROUP BY clause */
+    u16 wctrlFlags = (sDistinct.isTnct ? WHERE_WANT_DISTINCT : 0)
+                   | (p->selFlags & SF_FixedLimit);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    Window *pWin = p->pWin;      /* Main window object (or NULL) */
+    if( pWin ){
+      sqlite3WindowCodeInit(pParse, p);
+    }
+#endif
+    assert( WHERE_USE_LIMIT==SF_FixedLimit );
+
+
+    /* Begin the database scan. */
+    TREETRACE(0x2,pParse,p,("WhereBegin\n"));
+    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, sSort.pOrderBy,
+                               p->pEList, p, wctrlFlags, p->nSelectRow);
+    if( pWInfo==0 ) goto select_end;
+    if( sqlite3WhereOutputRowCount(pWInfo) < p->nSelectRow ){
+      p->nSelectRow = sqlite3WhereOutputRowCount(pWInfo);
+    }
+    if( sDistinct.isTnct && sqlite3WhereIsDistinct(pWInfo) ){
+      sDistinct.eTnctType = sqlite3WhereIsDistinct(pWInfo);
+    }
+    if( sSort.pOrderBy ){
+      sSort.nOBSat = sqlite3WhereIsOrdered(pWInfo);
+      sSort.labelOBLopt = sqlite3WhereOrderByLimitOptLabel(pWInfo);
+      if( sSort.nOBSat==sSort.pOrderBy->nExpr ){
+        sSort.pOrderBy = 0;
+      }
+    }
+    TREETRACE(0x2,pParse,p,("WhereBegin returns\n"));
+
+    /* If sorting index that was created by a prior OP_OpenEphemeral
+    ** instruction ended up not being needed, then change the OP_OpenEphemeral
+    ** into an OP_Noop.
+    */
+    if( sSort.addrSortIndex>=0 && sSort.pOrderBy==0 ){
+      sqlite3VdbeChangeToNoop(v, sSort.addrSortIndex);
+    }
+
+    assert( p->pEList==pEList );
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( pWin ){
+      int addrGosub = sqlite3VdbeMakeLabel(pParse);
+      int iCont = sqlite3VdbeMakeLabel(pParse);
+      int iBreak = sqlite3VdbeMakeLabel(pParse);
+      int regGosub = ++pParse->nMem;
+
+      sqlite3WindowCodeStep(pParse, p, pWInfo, regGosub, addrGosub);
+
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, iBreak);
+      sqlite3VdbeResolveLabel(v, addrGosub);
+      VdbeNoopComment((v, "inner-loop subroutine"));
+      sSort.labelOBLopt = 0;
+      selectInnerLoop(pParse, p, -1, &sSort, &sDistinct, pDest, iCont, iBreak);
+      sqlite3VdbeResolveLabel(v, iCont);
+      sqlite3VdbeAddOp1(v, OP_Return, regGosub);
+      VdbeComment((v, "end inner-loop subroutine"));
+      sqlite3VdbeResolveLabel(v, iBreak);
+    }else
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+    {
+      /* Use the standard inner loop. */
+      selectInnerLoop(pParse, p, -1, &sSort, &sDistinct, pDest,
+          sqlite3WhereContinueLabel(pWInfo),
+          sqlite3WhereBreakLabel(pWInfo));
+
+      /* End the database scan loop.
+      */
+      TREETRACE(0x2,pParse,p,("WhereEnd\n"));
+      sqlite3WhereEnd(pWInfo);
+    }
+  }else{
+    /* This case when there exist aggregate functions or a GROUP BY clause
+    ** or both */
+    NameContext sNC;    /* Name context for processing aggregate information */
+    int iAMem;          /* First Mem address for storing current GROUP BY */
+    int iBMem;          /* First Mem address for previous GROUP BY */
+    int iUseFlag;       /* Mem address holding flag indicating that at least
+                        ** one row of the input to the aggregator has been
+                        ** processed */
+    int iAbortFlag;     /* Mem address which causes query abort if positive */
+    int groupBySort;    /* Rows come from source in GROUP BY order */
+    int addrEnd;        /* End of processing for this SELECT */
+    int sortPTab = 0;   /* Pseudotable used to decode sorting results */
+    int sortOut = 0;    /* Output register from the sorter */
+    int orderByGrp = 0; /* True if the GROUP BY and ORDER BY are the same */
+
+    /* Remove any and all aliases between the result set and the
+    ** GROUP BY clause.
+    */
+    if( pGroupBy ){
+      int k;                        /* Loop counter */
+      struct ExprList_item *pItem;  /* For looping over expression in a list */
+
+      for(k=p->pEList->nExpr, pItem=p->pEList->a; k>0; k--, pItem++){
+        pItem->u.x.iAlias = 0;
+      }
+      for(k=pGroupBy->nExpr, pItem=pGroupBy->a; k>0; k--, pItem++){
+        pItem->u.x.iAlias = 0;
+      }
+      assert( 66==sqlite3LogEst(100) );
+      if( p->nSelectRow>66 ) p->nSelectRow = 66;
+
+      /* If there is both a GROUP BY and an ORDER BY clause and they are
+      ** identical, then it may be possible to disable the ORDER BY clause
+      ** on the grounds that the GROUP BY will cause elements to come out
+      ** in the correct order. It also may not - the GROUP BY might use a
+      ** database index that causes rows to be grouped together as required
+      ** but not actually sorted. Either way, record the fact that the
+      ** ORDER BY and GROUP BY clauses are the same by setting the orderByGrp
+      ** variable.  */
+      if( sSort.pOrderBy && pGroupBy->nExpr==sSort.pOrderBy->nExpr ){
+        int ii;
+        /* The GROUP BY processing doesn't care whether rows are delivered in
+        ** ASC or DESC order - only that each group is returned contiguously.
+        ** So set the ASC/DESC flags in the GROUP BY to match those in the
+        ** ORDER BY to maximize the chances of rows being delivered in an
+        ** order that makes the ORDER BY redundant.  */
+        for(ii=0; ii<pGroupBy->nExpr; ii++){
+          u8 sortFlags;
+          sortFlags = sSort.pOrderBy->a[ii].fg.sortFlags & KEYINFO_ORDER_DESC;
+          pGroupBy->a[ii].fg.sortFlags = sortFlags;
+        }
+        if( sqlite3ExprListCompare(pGroupBy, sSort.pOrderBy, -1)==0 ){
+          orderByGrp = 1;
+        }
+      }
+    }else{
+      assert( 0==sqlite3LogEst(1) );
+      p->nSelectRow = 0;
+    }
+
+    /* Create a label to jump to when we want to abort the query */
+    addrEnd = sqlite3VdbeMakeLabel(pParse);
+
+    /* Convert TK_COLUMN nodes into TK_AGG_COLUMN and make entries in
+    ** sAggInfo for all TK_AGG_FUNCTION nodes in expressions of the
+    ** SELECT statement.
+    */
+    pAggInfo = sqlite3DbMallocZero(db, sizeof(*pAggInfo) );
+    if( pAggInfo ){
+      sqlite3ParserAddCleanup(pParse, agginfoFree, pAggInfo);
+      testcase( pParse->earlyCleanup );
+    }
+    if( db->mallocFailed ){
+      goto select_end;
+    }
+    pAggInfo->selId = p->selId;
+#ifdef SQLITE_DEBUG
+    pAggInfo->pSelect = p;
+#endif
+    memset(&sNC, 0, sizeof(sNC));
+    sNC.pParse = pParse;
+    sNC.pSrcList = pTabList;
+    sNC.uNC.pAggInfo = pAggInfo;
+    VVA_ONLY( sNC.ncFlags = NC_UAggInfo; )
+    pAggInfo->nSortingColumn = pGroupBy ? pGroupBy->nExpr : 0;
+    pAggInfo->pGroupBy = pGroupBy;
+    sqlite3ExprAnalyzeAggList(&sNC, pEList);
+    sqlite3ExprAnalyzeAggList(&sNC, sSort.pOrderBy);
+    if( pHaving ){
+      if( pGroupBy ){
+        assert( pWhere==p->pWhere );
+        assert( pHaving==p->pHaving );
+        assert( pGroupBy==p->pGroupBy );
+        havingToWhere(pParse, p);
+        pWhere = p->pWhere;
+      }
+      sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
+    }
+    pAggInfo->nAccumulator = pAggInfo->nColumn;
+    if( p->pGroupBy==0 && p->pHaving==0 && pAggInfo->nFunc==1 ){
+      minMaxFlag = minMaxQuery(db, pAggInfo->aFunc[0].pFExpr, &pMinMaxOrderBy);
+    }else{
+      minMaxFlag = WHERE_ORDERBY_NORMAL;
+    }
+    analyzeAggFuncArgs(pAggInfo, &sNC);
+    if( db->mallocFailed ) goto select_end;
+#if TREETRACE_ENABLED
+    if( sqlite3TreeTrace & 0x20 ){
+      TREETRACE(0x20,pParse,p,("After aggregate analysis %p:\n", pAggInfo));
+      sqlite3TreeViewSelect(0, p, 0);
+      if( minMaxFlag ){
+        sqlite3DebugPrintf("MIN/MAX Optimization (0x%02x) adds:\n", minMaxFlag);
+        sqlite3TreeViewExprList(0, pMinMaxOrderBy, 0, "ORDERBY");
+      }
+      printAggInfo(pAggInfo);
+    }
+#endif
+
+
+    /* Processing for aggregates with GROUP BY is very different and
+    ** much more complex than aggregates without a GROUP BY.
+    */
+    if( pGroupBy ){
+      KeyInfo *pKeyInfo;  /* Keying information for the group by clause */
+      int addr1;          /* A-vs-B comparison jump */
+      int addrOutputRow;  /* Start of subroutine that outputs a result row */
+      int regOutputRow;   /* Return address register for output subroutine */
+      int addrSetAbort;   /* Set the abort flag and return */
+      int addrTopOfLoop;  /* Top of the input loop */
+      int addrSortingIdx; /* The OP_OpenEphemeral for the sorting index */
+      int addrReset;      /* Subroutine for resetting the accumulator */
+      int regReset;       /* Return address register for reset subroutine */
+      ExprList *pDistinct = 0;
+      u16 distFlag = 0;
+      int eDist = WHERE_DISTINCT_NOOP;
+
+      if( pAggInfo->nFunc==1
+       && pAggInfo->aFunc[0].iDistinct>=0
+       && ALWAYS(pAggInfo->aFunc[0].pFExpr!=0)
+       && ALWAYS(ExprUseXList(pAggInfo->aFunc[0].pFExpr))
+       && pAggInfo->aFunc[0].pFExpr->x.pList!=0
+      ){
+        Expr *pExpr = pAggInfo->aFunc[0].pFExpr->x.pList->a[0].pExpr;
+        pExpr = sqlite3ExprDup(db, pExpr, 0);
+        pDistinct = sqlite3ExprListDup(db, pGroupBy, 0);
+        pDistinct = sqlite3ExprListAppend(pParse, pDistinct, pExpr);
+        distFlag = pDistinct ? (WHERE_WANT_DISTINCT|WHERE_AGG_DISTINCT) : 0;
+      }
+
+      /* If there is a GROUP BY clause we might need a sorting index to
+      ** implement it.  Allocate that sorting index now.  If it turns out
+      ** that we do not need it after all, the OP_SorterOpen instruction
+      ** will be converted into a Noop. 
+      */
+      pAggInfo->sortingIdx = pParse->nTab++;
+      pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pGroupBy,
+                                            0, pAggInfo->nColumn);
+      addrSortingIdx = sqlite3VdbeAddOp4(v, OP_SorterOpen,
+          pAggInfo->sortingIdx, pAggInfo->nSortingColumn,
+          0, (char*)pKeyInfo, P4_KEYINFO);
+
+      /* Initialize memory locations used by GROUP BY aggregate processing
+      */
+      iUseFlag = ++pParse->nMem;
+      iAbortFlag = ++pParse->nMem;
+      regOutputRow = ++pParse->nMem;
+      addrOutputRow = sqlite3VdbeMakeLabel(pParse);
+      regReset = ++pParse->nMem;
+      addrReset = sqlite3VdbeMakeLabel(pParse);
+      iAMem = pParse->nMem + 1;
+      pParse->nMem += pGroupBy->nExpr;
+      iBMem = pParse->nMem + 1;
+      pParse->nMem += pGroupBy->nExpr;
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, iAbortFlag);
+      VdbeComment((v, "clear abort flag"));
+      sqlite3VdbeAddOp3(v, OP_Null, 0, iAMem, iAMem+pGroupBy->nExpr-1);
+
+      /* Begin a loop that will extract all source rows in GROUP BY order.
+      ** This might involve two separate loops with an OP_Sort in between, or
+      ** it might be a single loop that uses an index to extract information
+      ** in the right order to begin with.
+      */
+      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
+      TREETRACE(0x2,pParse,p,("WhereBegin\n"));
+      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pGroupBy, pDistinct,
+          p, (sDistinct.isTnct==2 ? WHERE_DISTINCTBY : WHERE_GROUPBY)
+          |  (orderByGrp ? WHERE_SORTBYGROUP : 0) | distFlag, 0
+      );
+      if( pWInfo==0 ){
+        sqlite3ExprListDelete(db, pDistinct);
+        goto select_end;
+      }
+      if( pParse->pIdxEpr ){
+        optimizeAggregateUseOfIndexedExpr(pParse, p, pAggInfo, &sNC);
+      }
+      assignAggregateRegisters(pParse, pAggInfo);
+      eDist = sqlite3WhereIsDistinct(pWInfo);
+      TREETRACE(0x2,pParse,p,("WhereBegin returns\n"));
+      if( sqlite3WhereIsOrdered(pWInfo)==pGroupBy->nExpr ){
+        /* The optimizer is able to deliver rows in group by order so
+        ** we do not have to sort.  The OP_OpenEphemeral table will be
+        ** cancelled later because we still need to use the pKeyInfo
+        */
+        groupBySort = 0;
+      }else{
+        /* Rows are coming out in undetermined order.  We have to push
+        ** each row into a sorting index, terminate the first loop,
+        ** then loop over the sorting index in order to get the output
+        ** in sorted order
+        */
+        int regBase;
+        int regRecord;
+        int nCol;
+        int nGroupBy;
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+        int addrExp;              /* Address of OP_Explain instruction */
+#endif
+        ExplainQueryPlan2(addrExp, (pParse, 0, "USE TEMP B-TREE FOR %s",
+            (sDistinct.isTnct && (p->selFlags&SF_Distinct)==0) ?
+                    "DISTINCT" : "GROUP BY"
+        ));
+
+        groupBySort = 1;
+        nGroupBy = pGroupBy->nExpr;
+        nCol = nGroupBy;
+        j = nGroupBy;
+        for(i=0; i<pAggInfo->nColumn; i++){
+          if( pAggInfo->aCol[i].iSorterColumn>=j ){
+            nCol++;
+            j++;
+          }
+        }
+        regBase = sqlite3GetTempRange(pParse, nCol);
+        sqlite3ExprCodeExprList(pParse, pGroupBy, regBase, 0, 0);
+        j = nGroupBy;
+        pAggInfo->directMode = 1;
+        for(i=0; i<pAggInfo->nColumn; i++){
+          struct AggInfo_col *pCol = &pAggInfo->aCol[i];
+          if( pCol->iSorterColumn>=j ){
+            sqlite3ExprCode(pParse, pCol->pCExpr, j + regBase);
+            j++;
+          }
+        }
+        pAggInfo->directMode = 0;
+        regRecord = sqlite3GetTempReg(pParse);
+        sqlite3VdbeScanStatusCounters(v, addrExp, 0, sqlite3VdbeCurrentAddr(v));
+        sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
+        sqlite3VdbeAddOp2(v, OP_SorterInsert, pAggInfo->sortingIdx, regRecord);
+        sqlite3VdbeScanStatusRange(v, addrExp, sqlite3VdbeCurrentAddr(v)-2, -1);
+        sqlite3ReleaseTempReg(pParse, regRecord);
+        sqlite3ReleaseTempRange(pParse, regBase, nCol);
+        TREETRACE(0x2,pParse,p,("WhereEnd\n"));
+        sqlite3WhereEnd(pWInfo);
+        pAggInfo->sortingIdxPTab = sortPTab = pParse->nTab++;
+        sortOut = sqlite3GetTempReg(pParse);
+        sqlite3VdbeScanStatusCounters(v, addrExp, sqlite3VdbeCurrentAddr(v), 0);
+        sqlite3VdbeAddOp3(v, OP_OpenPseudo, sortPTab, sortOut, nCol);
+        sqlite3VdbeAddOp2(v, OP_SorterSort, pAggInfo->sortingIdx, addrEnd);
+        VdbeComment((v, "GROUP BY sort")); VdbeCoverage(v);
+        pAggInfo->useSortingIdx = 1;
+        sqlite3VdbeScanStatusRange(v, addrExp, -1, sortPTab);
+        sqlite3VdbeScanStatusRange(v, addrExp, -1, pAggInfo->sortingIdx);
+      }
+
+      /* If there are entries in pAgggInfo->aFunc[] that contain subexpressions
+      ** that are indexed (and that were previously identified and tagged
+      ** in optimizeAggregateUseOfIndexedExpr()) then those subexpressions
+      ** must now be converted into a TK_AGG_COLUMN node so that the value
+      ** is correctly pulled from the index rather than being recomputed. */
+      if( pParse->pIdxEpr ){
+        aggregateConvertIndexedExprRefToColumn(pAggInfo);
+#if TREETRACE_ENABLED
+        if( sqlite3TreeTrace & 0x20 ){
+          TREETRACE(0x20, pParse, p,
+             ("AggInfo function expressions converted to reference index\n"));
+          sqlite3TreeViewSelect(0, p, 0);
+          printAggInfo(pAggInfo);
+        }
+#endif
+      }
+
+      /* If the index or temporary table used by the GROUP BY sort
+      ** will naturally deliver rows in the order required by the ORDER BY
+      ** clause, cancel the ephemeral table open coded earlier.
+      **
+      ** This is an optimization - the correct answer should result regardless.
+      ** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER to
+      ** disable this optimization for testing purposes.  */
+      if( orderByGrp && OptimizationEnabled(db, SQLITE_GroupByOrder)
+       && (groupBySort || sqlite3WhereIsSorted(pWInfo))
+      ){
+        sSort.pOrderBy = 0;
+        sqlite3VdbeChangeToNoop(v, sSort.addrSortIndex);
+      }
+
+      /* Evaluate the current GROUP BY terms and store in b0, b1, b2...
+      ** (b0 is memory location iBMem+0, b1 is iBMem+1, and so forth)
+      ** Then compare the current GROUP BY terms against the GROUP BY terms
+      ** from the previous row currently stored in a0, a1, a2...
+      */
+      addrTopOfLoop = sqlite3VdbeCurrentAddr(v);
+      if( groupBySort ){
+        sqlite3VdbeAddOp3(v, OP_SorterData, pAggInfo->sortingIdx,
+                          sortOut, sortPTab);
+      }
+      for(j=0; j<pGroupBy->nExpr; j++){
+        if( groupBySort ){
+          sqlite3VdbeAddOp3(v, OP_Column, sortPTab, j, iBMem+j);
+        }else{
+          pAggInfo->directMode = 1;
+          sqlite3ExprCode(pParse, pGroupBy->a[j].pExpr, iBMem+j);
+        }
+      }
+      sqlite3VdbeAddOp4(v, OP_Compare, iAMem, iBMem, pGroupBy->nExpr,
+                          (char*)sqlite3KeyInfoRef(pKeyInfo), P4_KEYINFO);
+      addr1 = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp3(v, OP_Jump, addr1+1, 0, addr1+1); VdbeCoverage(v);
+
+      /* Generate code that runs whenever the GROUP BY changes.
+      ** Changes in the GROUP BY are detected by the previous code
+      ** block.  If there were no changes, this block is skipped.
+      **
+      ** This code copies current group by terms in b0,b1,b2,...
+      ** over to a0,a1,a2.  It then calls the output subroutine
+      ** and resets the aggregate accumulator registers in preparation
+      ** for the next GROUP BY batch.
+      */
+      sqlite3ExprCodeMove(pParse, iBMem, iAMem, pGroupBy->nExpr);
+      sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
+      VdbeComment((v, "output one row"));
+      sqlite3VdbeAddOp2(v, OP_IfPos, iAbortFlag, addrEnd); VdbeCoverage(v);
+      VdbeComment((v, "check abort flag"));
+      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
+      VdbeComment((v, "reset accumulator"));
+
+      /* Update the aggregate accumulators based on the content of
+      ** the current row
+      */
+      sqlite3VdbeJumpHere(v, addr1);
+      updateAccumulator(pParse, iUseFlag, pAggInfo, eDist);
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, iUseFlag);
+      VdbeComment((v, "indicate data in accumulator"));
+
+      /* End of the loop
+      */
+      if( groupBySort ){
+        sqlite3VdbeAddOp2(v, OP_SorterNext, pAggInfo->sortingIdx,addrTopOfLoop);
+        VdbeCoverage(v);
+      }else{
+        TREETRACE(0x2,pParse,p,("WhereEnd\n"));
+        sqlite3WhereEnd(pWInfo);
+        sqlite3VdbeChangeToNoop(v, addrSortingIdx);
+      }
+      sqlite3ExprListDelete(db, pDistinct);
+
+      /* Output the final row of result
+      */
+      sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
+      VdbeComment((v, "output final row"));
+
+      /* Jump over the subroutines
+      */
+      sqlite3VdbeGoto(v, addrEnd);
+
+      /* Generate a subroutine that outputs a single row of the result
+      ** set.  This subroutine first looks at the iUseFlag.  If iUseFlag
+      ** is less than or equal to zero, the subroutine is a no-op.  If
+      ** the processing calls for the query to abort, this subroutine
+      ** increments the iAbortFlag memory location before returning in
+      ** order to signal the caller to abort.
+      */
+      addrSetAbort = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, iAbortFlag);
+      VdbeComment((v, "set abort flag"));
+      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+      sqlite3VdbeResolveLabel(v, addrOutputRow);
+      addrOutputRow = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
+      VdbeCoverage(v);
+      VdbeComment((v, "Groupby result generator entry point"));
+      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+      finalizeAggFunctions(pParse, pAggInfo);
+      sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
+      selectInnerLoop(pParse, p, -1, &sSort,
+                      &sDistinct, pDest,
+                      addrOutputRow+1, addrSetAbort);
+      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+      VdbeComment((v, "end groupby result generator"));
+
+      /* Generate a subroutine that will reset the group-by accumulator
+      */
+      sqlite3VdbeResolveLabel(v, addrReset);
+      resetAccumulator(pParse, pAggInfo);
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, iUseFlag);
+      VdbeComment((v, "indicate accumulator empty"));
+      sqlite3VdbeAddOp1(v, OP_Return, regReset);
+
+      if( distFlag!=0 && eDist!=WHERE_DISTINCT_NOOP ){
+        struct AggInfo_func *pF = &pAggInfo->aFunc[0];
+        fixDistinctOpenEph(pParse, eDist, pF->iDistinct, pF->iDistAddr);
+      }
+    } /* endif pGroupBy.  Begin aggregate queries without GROUP BY: */
+    else {
+      Table *pTab;
+      if( (pTab = isSimpleCount(p, pAggInfo))!=0 ){
+        /* If isSimpleCount() returns a pointer to a Table structure, then
+        ** the SQL statement is of the form:
+        **
+        **   SELECT count(*) FROM <tbl>
+        **
+        ** where the Table structure returned represents table <tbl>.
+        **
+        ** This statement is so common that it is optimized specially. The
+        ** OP_Count instruction is executed either on the intkey table that
+        ** contains the data for table <tbl> or on one of its indexes. It
+        ** is better to execute the op on an index, as indexes are almost
+        ** always spread across less pages than their corresponding tables.
+        */
+        const int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+        const int iCsr = pParse->nTab++;     /* Cursor to scan b-tree */
+        Index *pIdx;                         /* Iterator variable */
+        KeyInfo *pKeyInfo = 0;               /* Keyinfo for scanned index */
+        Index *pBest = 0;                    /* Best index found so far */
+        Pgno iRoot = pTab->tnum;             /* Root page of scanned b-tree */
+
+        sqlite3CodeVerifySchema(pParse, iDb);
+        sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+
+        /* Search for the index that has the lowest scan cost.
+        **
+        ** (2011-04-15) Do not do a full scan of an unordered index.
+        **
+        ** (2013-10-03) Do not count the entries in a partial index.
+        **
+        ** In practice the KeyInfo structure will not be used. It is only
+        ** passed to keep OP_OpenRead happy.
+        */
+        if( !HasRowid(pTab) ) pBest = sqlite3PrimaryKeyIndex(pTab);
+        if( !p->pSrc->a[0].fg.notIndexed ){
+          for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+            if( pIdx->bUnordered==0
+             && pIdx->szIdxRow<pTab->szTabRow
+             && pIdx->pPartIdxWhere==0
+             && (!pBest || pIdx->szIdxRow<pBest->szIdxRow)
+            ){
+              pBest = pIdx;
+            }
+          }
+        }
+        if( pBest ){
+          iRoot = pBest->tnum;
+          pKeyInfo = sqlite3KeyInfoOfIndex(pParse, pBest);
+        }
+
+        /* Open a read-only cursor, execute the OP_Count, close the cursor. */
+        sqlite3VdbeAddOp4Int(v, OP_OpenRead, iCsr, (int)iRoot, iDb, 1);
+        if( pKeyInfo ){
+          sqlite3VdbeChangeP4(v, -1, (char *)pKeyInfo, P4_KEYINFO);
+        }
+        assignAggregateRegisters(pParse, pAggInfo);
+        sqlite3VdbeAddOp2(v, OP_Count, iCsr, AggInfoFuncReg(pAggInfo,0));
+        sqlite3VdbeAddOp1(v, OP_Close, iCsr);
+        explainSimpleCount(pParse, pTab, pBest);
+      }else{
+        int regAcc = 0;           /* "populate accumulators" flag */
+        ExprList *pDistinct = 0;
+        u16 distFlag = 0;
+        int eDist;
+
+        /* If there are accumulator registers but no min() or max() functions
+        ** without FILTER clauses, allocate register regAcc. Register regAcc
+        ** will contain 0 the first time the inner loop runs, and 1 thereafter.
+        ** The code generated by updateAccumulator() uses this to ensure
+        ** that the accumulator registers are (a) updated only once if
+        ** there are no min() or max functions or (b) always updated for the
+        ** first row visited by the aggregate, so that they are updated at
+        ** least once even if the FILTER clause means the min() or max()
+        ** function visits zero rows.  */
+        if( pAggInfo->nAccumulator ){
+          for(i=0; i<pAggInfo->nFunc; i++){
+            if( ExprHasProperty(pAggInfo->aFunc[i].pFExpr, EP_WinFunc) ){
+              continue;
+            }
+            if( pAggInfo->aFunc[i].pFunc->funcFlags&SQLITE_FUNC_NEEDCOLL ){
+              break;
+            }
+          }
+          if( i==pAggInfo->nFunc ){
+            regAcc = ++pParse->nMem;
+            sqlite3VdbeAddOp2(v, OP_Integer, 0, regAcc);
+          }
+        }else if( pAggInfo->nFunc==1 && pAggInfo->aFunc[0].iDistinct>=0 ){
+          assert( ExprUseXList(pAggInfo->aFunc[0].pFExpr) );
+          pDistinct = pAggInfo->aFunc[0].pFExpr->x.pList;
+          distFlag = pDistinct ? (WHERE_WANT_DISTINCT|WHERE_AGG_DISTINCT) : 0;
+        }
+        assignAggregateRegisters(pParse, pAggInfo);
+
+        /* This case runs if the aggregate has no GROUP BY clause.  The
+        ** processing is much simpler since there is only a single row
+        ** of output.
+        */
+        assert( p->pGroupBy==0 );
+        resetAccumulator(pParse, pAggInfo);
+
+        /* If this query is a candidate for the min/max optimization, then
+        ** minMaxFlag will have been previously set to either
+        ** WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX and pMinMaxOrderBy will
+        ** be an appropriate ORDER BY expression for the optimization.
+        */
+        assert( minMaxFlag==WHERE_ORDERBY_NORMAL || pMinMaxOrderBy!=0 );
+        assert( pMinMaxOrderBy==0 || pMinMaxOrderBy->nExpr==1 );
+
+        TREETRACE(0x2,pParse,p,("WhereBegin\n"));
+        pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pMinMaxOrderBy,
+                                   pDistinct, p, minMaxFlag|distFlag, 0);
+        if( pWInfo==0 ){
+          goto select_end;
+        }
+        TREETRACE(0x2,pParse,p,("WhereBegin returns\n"));
+        eDist = sqlite3WhereIsDistinct(pWInfo);
+        updateAccumulator(pParse, regAcc, pAggInfo, eDist);
+        if( eDist!=WHERE_DISTINCT_NOOP ){
+          struct AggInfo_func *pF = pAggInfo->aFunc;
+          if( pF ){
+            fixDistinctOpenEph(pParse, eDist, pF->iDistinct, pF->iDistAddr);
+          }
+        }
+
+        if( regAcc ) sqlite3VdbeAddOp2(v, OP_Integer, 1, regAcc);
+        if( minMaxFlag ){
+          sqlite3WhereMinMaxOptEarlyOut(v, pWInfo);
+        }
+        TREETRACE(0x2,pParse,p,("WhereEnd\n"));
+        sqlite3WhereEnd(pWInfo);
+        finalizeAggFunctions(pParse, pAggInfo);
+      }
+
+      sSort.pOrderBy = 0;
+      sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
+      selectInnerLoop(pParse, p, -1, 0, 0,
+                      pDest, addrEnd, addrEnd);
+    }
+    sqlite3VdbeResolveLabel(v, addrEnd);
+
+  } /* endif aggregate query */
+
+  if( sDistinct.eTnctType==WHERE_DISTINCT_UNORDERED ){
+    explainTempTable(pParse, "DISTINCT");
+  }
+
+  /* If there is an ORDER BY clause, then we need to sort the results
+  ** and send them to the callback one by one.
+  */
+  if( sSort.pOrderBy ){
+    assert( p->pEList==pEList );
+    generateSortTail(pParse, p, &sSort, pEList->nExpr, pDest);
+  }
+
+  /* Jump here to skip this query
+  */
+  sqlite3VdbeResolveLabel(v, iEnd);
+
+  /* The SELECT has been coded. If there is an error in the Parse structure,
+  ** set the return code to 1. Otherwise 0. */
+  rc = (pParse->nErr>0);
+
+  /* Control jumps to here if an error is encountered above, or upon
+  ** successful coding of the SELECT.
+  */
+select_end:
+  assert( db->mallocFailed==0 || db->mallocFailed==1 );
+  assert( db->mallocFailed==0 || pParse->nErr!=0 );
+  sqlite3ExprListDelete(db, pMinMaxOrderBy);
+#ifdef SQLITE_DEBUG
+  if( pAggInfo && !db->mallocFailed ){
+    for(i=0; i<pAggInfo->nColumn; i++){
+      Expr *pExpr = pAggInfo->aCol[i].pCExpr;
+      if( pExpr==0 ) continue;
+      assert( pExpr->pAggInfo==pAggInfo );
+      assert( pExpr->iAgg==i );
+    }
+    for(i=0; i<pAggInfo->nFunc; i++){
+      Expr *pExpr = pAggInfo->aFunc[i].pFExpr;
+      assert( pExpr!=0 );
+      assert( pExpr->pAggInfo==pAggInfo );
+      assert( pExpr->iAgg==i );
+    }
+  }
+#endif
+
+#if TREETRACE_ENABLED
+  TREETRACE(0x1,pParse,p,("end processing\n"));
+  if( (sqlite3TreeTrace & 0x40000)!=0 && ExplainQueryPlanParent(pParse)==0 ){
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+  ExplainQueryPlanPop(pParse);
+  return rc;
+}
diff --git a/src/shell.c.in b/src/shell.c.in
new file mode 100644
index 0000000..da3b9f8
--- /dev/null
+++ b/src/shell.c.in
@@ -0,0 +1,12781 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code to implement the "sqlite" command line
+** utility for accessing SQLite databases.
+*/
+#if (defined(_WIN32) || defined(WIN32)) && !defined(_CRT_SECURE_NO_WARNINGS)
+/* This needs to come before any includes for MSVC compiler */
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+typedef unsigned int u32;
+typedef unsigned short int u16;
+
+/*
+** Optionally #include a user-defined header, whereby compilation options
+** may be set prior to where they take effect, but after platform setup.
+** If SQLITE_CUSTOM_INCLUDE=? is defined, its value names the #include
+** file. Note that this macro has a like effect on sqlite3.c compilation.
+*/
+# define SHELL_STRINGIFY_(f) #f
+# define SHELL_STRINGIFY(f) SHELL_STRINGIFY_(f)
+#ifdef SQLITE_CUSTOM_INCLUDE
+# include SHELL_STRINGIFY(SQLITE_CUSTOM_INCLUDE)
+#endif
+
+/*
+** Determine if we are dealing with WinRT, which provides only a subset of
+** the full Win32 API.
+*/
+#if !defined(SQLITE_OS_WINRT)
+# define SQLITE_OS_WINRT 0
+#endif
+
+/*
+** If SQLITE_SHELL_FIDDLE is defined then the shell is modified
+** somewhat for use as a WASM module in a web browser. This flag
+** should only be used when building the "fiddle" web application, as
+** the browser-mode build has much different user input requirements
+** and this build mode rewires the user input subsystem to account for
+** that.
+*/
+
+/*
+** Warning pragmas copied from msvc.h in the core.
+*/
+#if defined(_MSC_VER)
+#pragma warning(disable : 4054)
+#pragma warning(disable : 4055)
+#pragma warning(disable : 4100)
+#pragma warning(disable : 4127)
+#pragma warning(disable : 4130)
+#pragma warning(disable : 4152)
+#pragma warning(disable : 4189)
+#pragma warning(disable : 4206)
+#pragma warning(disable : 4210)
+#pragma warning(disable : 4232)
+#pragma warning(disable : 4244)
+#pragma warning(disable : 4305)
+#pragma warning(disable : 4306)
+#pragma warning(disable : 4702)
+#pragma warning(disable : 4706)
+#endif /* defined(_MSC_VER) */
+
+/*
+** No support for loadable extensions in VxWorks.
+*/
+#if (defined(__RTP__) || defined(_WRS_KERNEL)) && !SQLITE_OMIT_LOAD_EXTENSION
+# define SQLITE_OMIT_LOAD_EXTENSION 1
+#endif
+
+/*
+** Enable large-file support for fopen() and friends on unix.
+*/
+#ifndef SQLITE_DISABLE_LFS
+# define _LARGE_FILE       1
+# ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+# endif
+# define _LARGEFILE_SOURCE 1
+#endif
+
+#if defined(SQLITE_SHELL_FIDDLE) && !defined(_POSIX_SOURCE)
+/*
+** emcc requires _POSIX_SOURCE (or one of several similar defines)
+** to expose strdup().
+*/
+# define _POSIX_SOURCE
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <assert.h>
+#include <math.h>
+#include "sqlite3.h"
+typedef sqlite3_int64 i64;
+typedef sqlite3_uint64 u64;
+typedef unsigned char u8;
+#if SQLITE_USER_AUTHENTICATION
+# include "sqlite3userauth.h"
+#endif
+#include <ctype.h>
+#include <stdarg.h>
+
+#if !defined(_WIN32) && !defined(WIN32)
+# include <signal.h>
+# if !defined(__RTP__) && !defined(_WRS_KERNEL) && !defined(SQLITE_WASI)
+#  include <pwd.h>
+# endif
+#endif
+#if (!defined(_WIN32) && !defined(WIN32)) || defined(__MINGW32__)
+# include <unistd.h>
+# include <dirent.h>
+# define GETPID getpid
+# if defined(__MINGW32__)
+#  define DIRENT dirent
+#  ifndef S_ISLNK
+#   define S_ISLNK(mode) (0)
+#  endif
+# endif
+#else
+# define GETPID (int)GetCurrentProcessId
+#endif
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#if HAVE_READLINE
+# include <readline/readline.h>
+# include <readline/history.h>
+#endif
+
+#if HAVE_EDITLINE
+# include <editline/readline.h>
+#endif
+
+#if HAVE_EDITLINE || HAVE_READLINE
+
+# define shell_add_history(X) add_history(X)
+# define shell_read_history(X) read_history(X)
+# define shell_write_history(X) write_history(X)
+# define shell_stifle_history(X) stifle_history(X)
+# define shell_readline(X) readline(X)
+
+#elif HAVE_LINENOISE
+
+# include "linenoise.h"
+# define shell_add_history(X) linenoiseHistoryAdd(X)
+# define shell_read_history(X) linenoiseHistoryLoad(X)
+# define shell_write_history(X) linenoiseHistorySave(X)
+# define shell_stifle_history(X) linenoiseHistorySetMaxLen(X)
+# define shell_readline(X) linenoise(X)
+
+#else
+
+# define shell_read_history(X)
+# define shell_write_history(X)
+# define shell_stifle_history(X)
+
+# define SHELL_USE_LOCAL_GETLINE 1
+#endif
+
+#ifndef deliberate_fall_through
+/* Quiet some compilers about some of our intentional code. */
+# if defined(GCC_VERSION) && GCC_VERSION>=7000000
+#  define deliberate_fall_through __attribute__((fallthrough));
+# else
+#  define deliberate_fall_through
+# endif
+#endif
+
+#if defined(_WIN32) || defined(WIN32)
+# if SQLITE_OS_WINRT
+#  define SQLITE_OMIT_POPEN 1
+# else
+#  include <io.h>
+#  include <fcntl.h>
+#  define isatty(h) _isatty(h)
+#  ifndef access
+#   define access(f,m) _access((f),(m))
+#  endif
+#  ifndef unlink
+#   define unlink _unlink
+#  endif
+#  ifndef strdup
+#   define strdup _strdup
+#  endif
+#  undef popen
+#  define popen _popen
+#  undef pclose
+#  define pclose _pclose
+# endif
+#else
+ /* Make sure isatty() has a prototype. */
+ extern int isatty(int);
+
+# if !defined(__RTP__) && !defined(_WRS_KERNEL) && !defined(SQLITE_WASI)
+  /* popen and pclose are not C89 functions and so are
+  ** sometimes omitted from the <stdio.h> header */
+   extern FILE *popen(const char*,const char*);
+   extern int pclose(FILE*);
+# else
+#  define SQLITE_OMIT_POPEN 1
+# endif
+#endif
+
+#if defined(_WIN32_WCE)
+/* Windows CE (arm-wince-mingw32ce-gcc) does not provide isatty()
+ * thus we always assume that we have a console. That can be
+ * overridden with the -batch command line option.
+ */
+#define isatty(x) 1
+#endif
+
+/* ctype macros that work with signed characters */
+#define IsSpace(X)  isspace((unsigned char)X)
+#define IsDigit(X)  isdigit((unsigned char)X)
+#define ToLower(X)  (char)tolower((unsigned char)X)
+
+#if defined(_WIN32) || defined(WIN32)
+#if SQLITE_OS_WINRT
+#include <intrin.h>
+#endif
+#undef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+/* string conversion routines only needed on Win32 */
+extern char *sqlite3_win32_unicode_to_utf8(LPCWSTR);
+extern LPWSTR sqlite3_win32_utf8_to_unicode(const char *zText);
+#endif
+
+/* Use console I/O package as a direct INCLUDE. */
+#define SQLITE_INTERNAL_LINKAGE static
+
+#ifdef SQLITE_SHELL_FIDDLE
+/* Deselect most features from the console I/O package for Fiddle. */
+# define SQLITE_CIO_NO_REDIRECT
+# define SQLITE_CIO_NO_CLASSIFY
+# define SQLITE_CIO_NO_TRANSLATE
+# define SQLITE_CIO_NO_SETMODE
+#endif
+INCLUDE ../ext/consio/console_io.h
+INCLUDE ../ext/consio/console_io.c
+
+#ifndef SQLITE_SHELL_FIDDLE
+
+/* From here onward, fgets() is redirected to the console_io library. */
+# define fgets(b,n,f) fGetsUtf8(b,n,f)
+/*
+ * Define macros for emitting output text in various ways:
+ *  sputz(s, z)      => emit 0-terminated string z to given stream s
+ *  sputf(s, f, ...) => emit varargs per format f to given stream s
+ *  oputz(z)         => emit 0-terminated string z to default stream
+ *  oputf(f, ...)    => emit varargs per format f to default stream
+ *  eputz(z)         => emit 0-terminated string z to error stream
+ *  eputf(f, ...)    => emit varargs per format f to error stream
+ *  oputb(b, n)      => emit char buffer b[0..n-1] to default stream
+ *
+ * Note that the default stream is whatever has been last set via:
+ *   setOutputStream(FILE *pf)
+ * This is normally the stream that CLI normal output goes to.
+ * For the stand-alone CLI, it is stdout with no .output redirect.
+ */
+# define sputz(s,z) fPutsUtf8(z,s)
+# define sputf fPrintfUtf8
+# define oputz(z) oPutsUtf8(z)
+# define oputf oPrintfUtf8
+# define eputz(z) ePutsUtf8(z)
+# define eputf ePrintfUtf8
+# define oputb(buf,na) oPutbUtf8(buf,na)
+
+#else
+/* For Fiddle, all console handling and emit redirection is omitted. */
+# define sputz(fp,z) fputs(z,fp)
+# define sputf(fp,fmt, ...) fprintf(fp,fmt,__VA_ARGS__)
+# define oputz(z) fputs(z,stdout)
+# define oputf(fmt, ...) printf(fmt,__VA_ARGS__)
+# define eputz(z) fputs(z,stderr)
+# define eputf(fmt, ...) fprintf(stderr,fmt,__VA_ARGS__)
+# define oputb(buf,na) fwrite(buf,1,na,stdout)
+#endif
+
+/* True if the timer is enabled */
+static int enableTimer = 0;
+
+/* A version of strcmp() that works with NULL values */
+static int cli_strcmp(const char *a, const char *b){
+  if( a==0 ) a = "";
+  if( b==0 ) b = "";
+  return strcmp(a,b);
+}
+static int cli_strncmp(const char *a, const char *b, size_t n){
+  if( a==0 ) a = "";
+  if( b==0 ) b = "";
+  return strncmp(a,b,n);
+}
+
+/* Return the current wall-clock time */
+static sqlite3_int64 timeOfDay(void){
+  static sqlite3_vfs *clockVfs = 0;
+  sqlite3_int64 t;
+  if( clockVfs==0 ) clockVfs = sqlite3_vfs_find(0);
+  if( clockVfs==0 ) return 0;  /* Never actually happens */
+  if( clockVfs->iVersion>=2 && clockVfs->xCurrentTimeInt64!=0 ){
+    clockVfs->xCurrentTimeInt64(clockVfs, &t);
+  }else{
+    double r;
+    clockVfs->xCurrentTime(clockVfs, &r);
+    t = (sqlite3_int64)(r*86400000.0);
+  }
+  return t;
+}
+
+#if !defined(_WIN32) && !defined(WIN32) && !defined(__minux)
+#include <sys/time.h>
+#include <sys/resource.h>
+
+/* VxWorks does not support getrusage() as far as we can determine */
+#if defined(_WRS_KERNEL) || defined(__RTP__)
+struct rusage {
+  struct timeval ru_utime; /* user CPU time used */
+  struct timeval ru_stime; /* system CPU time used */
+};
+#define getrusage(A,B) memset(B,0,sizeof(*B))
+#endif
+
+/* Saved resource information for the beginning of an operation */
+static struct rusage sBegin;  /* CPU time at start */
+static sqlite3_int64 iBegin;  /* Wall-clock time at start */
+
+/*
+** Begin timing an operation
+*/
+static void beginTimer(void){
+  if( enableTimer ){
+    getrusage(RUSAGE_SELF, &sBegin);
+    iBegin = timeOfDay();
+  }
+}
+
+/* Return the difference of two time_structs in seconds */
+static double timeDiff(struct timeval *pStart, struct timeval *pEnd){
+  return (pEnd->tv_usec - pStart->tv_usec)*0.000001 +
+         (double)(pEnd->tv_sec - pStart->tv_sec);
+}
+
+/*
+** Print the timing results.
+*/
+static void endTimer(void){
+  if( enableTimer ){
+    sqlite3_int64 iEnd = timeOfDay();
+    struct rusage sEnd;
+    getrusage(RUSAGE_SELF, &sEnd);
+    sputf(stdout, "Run Time: real %.3f user %f sys %f\n",
+          (iEnd - iBegin)*0.001,
+          timeDiff(&sBegin.ru_utime, &sEnd.ru_utime),
+          timeDiff(&sBegin.ru_stime, &sEnd.ru_stime));
+  }
+}
+
+#define BEGIN_TIMER beginTimer()
+#define END_TIMER endTimer()
+#define HAS_TIMER 1
+
+#elif (defined(_WIN32) || defined(WIN32))
+
+/* Saved resource information for the beginning of an operation */
+static HANDLE hProcess;
+static FILETIME ftKernelBegin;
+static FILETIME ftUserBegin;
+static sqlite3_int64 ftWallBegin;
+typedef BOOL (WINAPI *GETPROCTIMES)(HANDLE, LPFILETIME, LPFILETIME,
+                                    LPFILETIME, LPFILETIME);
+static GETPROCTIMES getProcessTimesAddr = NULL;
+
+/*
+** Check to see if we have timer support.  Return 1 if necessary
+** support found (or found previously).
+*/
+static int hasTimer(void){
+  if( getProcessTimesAddr ){
+    return 1;
+  } else {
+#if !SQLITE_OS_WINRT
+    /* GetProcessTimes() isn't supported in WIN95 and some other Windows
+    ** versions. See if the version we are running on has it, and if it
+    ** does, save off a pointer to it and the current process handle.
+    */
+    hProcess = GetCurrentProcess();
+    if( hProcess ){
+      HINSTANCE hinstLib = LoadLibrary(TEXT("Kernel32.dll"));
+      if( NULL != hinstLib ){
+        getProcessTimesAddr =
+            (GETPROCTIMES) GetProcAddress(hinstLib, "GetProcessTimes");
+        if( NULL != getProcessTimesAddr ){
+          return 1;
+        }
+        FreeLibrary(hinstLib);
+      }
+    }
+#endif
+  }
+  return 0;
+}
+
+/*
+** Begin timing an operation
+*/
+static void beginTimer(void){
+  if( enableTimer && getProcessTimesAddr ){
+    FILETIME ftCreation, ftExit;
+    getProcessTimesAddr(hProcess,&ftCreation,&ftExit,
+                        &ftKernelBegin,&ftUserBegin);
+    ftWallBegin = timeOfDay();
+  }
+}
+
+/* Return the difference of two FILETIME structs in seconds */
+static double timeDiff(FILETIME *pStart, FILETIME *pEnd){
+  sqlite_int64 i64Start = *((sqlite_int64 *) pStart);
+  sqlite_int64 i64End = *((sqlite_int64 *) pEnd);
+  return (double) ((i64End - i64Start) / 10000000.0);
+}
+
+/*
+** Print the timing results.
+*/
+static void endTimer(void){
+  if( enableTimer && getProcessTimesAddr){
+    FILETIME ftCreation, ftExit, ftKernelEnd, ftUserEnd;
+    sqlite3_int64 ftWallEnd = timeOfDay();
+    getProcessTimesAddr(hProcess,&ftCreation,&ftExit,&ftKernelEnd,&ftUserEnd);
+    sputf(stdout, "Run Time: real %.3f user %f sys %f\n",
+          (ftWallEnd - ftWallBegin)*0.001,
+          timeDiff(&ftUserBegin, &ftUserEnd),
+          timeDiff(&ftKernelBegin, &ftKernelEnd));
+  }
+}
+
+#define BEGIN_TIMER beginTimer()
+#define END_TIMER endTimer()
+#define HAS_TIMER hasTimer()
+
+#else
+#define BEGIN_TIMER
+#define END_TIMER
+#define HAS_TIMER 0
+#endif
+
+/*
+** Used to prevent warnings about unused parameters
+*/
+#define UNUSED_PARAMETER(x) (void)(x)
+
+/*
+** Number of elements in an array
+*/
+#define ArraySize(X)  (int)(sizeof(X)/sizeof(X[0]))
+
+/*
+** If the following flag is set, then command execution stops
+** at an error if we are not interactive.
+*/
+static int bail_on_error = 0;
+
+/*
+** Treat stdin as an interactive input if the following variable
+** is true.  Otherwise, assume stdin is connected to a file or pipe.
+*/
+static int stdin_is_interactive = 1;
+
+/*
+** On Windows systems we need to know if standard output is a console
+** in order to show that UTF-16 translation is done in the sign-on
+** banner. The following variable is true if it is the console.
+*/
+static int stdout_is_console = 1;
+
+/*
+** The following is the open SQLite database.  We make a pointer
+** to this database a static variable so that it can be accessed
+** by the SIGINT handler to interrupt database processing.
+*/
+static sqlite3 *globalDb = 0;
+
+/*
+** True if an interrupt (Control-C) has been received.
+*/
+static volatile int seenInterrupt = 0;
+
+/*
+** This is the name of our program. It is set in main(), used
+** in a number of other places, mostly for error messages.
+*/
+static char *Argv0;
+
+/*
+** Prompt strings. Initialized in main. Settable with
+**   .prompt main continue
+*/
+#define PROMPT_LEN_MAX 20
+/* First line prompt.   default: "sqlite> " */
+static char mainPrompt[PROMPT_LEN_MAX];
+/* Continuation prompt. default: "   ...> " */
+static char continuePrompt[PROMPT_LEN_MAX];
+
+/* This is variant of the standard-library strncpy() routine with the
+** one change that the destination string is always zero-terminated, even
+** if there is no zero-terminator in the first n-1 characters of the source
+** string.
+*/
+static char *shell_strncpy(char *dest, const char *src, size_t n){
+  size_t i;
+  for(i=0; i<n-1 && src[i]!=0; i++) dest[i] = src[i];
+  dest[i] = 0;
+  return dest;
+}
+
+/*
+** Optionally disable dynamic continuation prompt.
+** Unless disabled, the continuation prompt shows open SQL lexemes if any,
+** or open parentheses level if non-zero, or continuation prompt as set.
+** This facility interacts with the scanner and process_input() where the
+** below 5 macros are used.
+*/
+#ifdef SQLITE_OMIT_DYNAPROMPT
+# define CONTINUATION_PROMPT continuePrompt
+# define CONTINUE_PROMPT_RESET
+# define CONTINUE_PROMPT_AWAITS(p,s)
+# define CONTINUE_PROMPT_AWAITC(p,c)
+# define CONTINUE_PAREN_INCR(p,n)
+# define CONTINUE_PROMPT_PSTATE 0
+typedef void *t_NoDynaPrompt;
+# define SCAN_TRACKER_REFTYPE t_NoDynaPrompt
+#else
+# define CONTINUATION_PROMPT dynamicContinuePrompt()
+# define CONTINUE_PROMPT_RESET \
+  do {setLexemeOpen(&dynPrompt,0,0); trackParenLevel(&dynPrompt,0);} while(0)
+# define CONTINUE_PROMPT_AWAITS(p,s) \
+  if(p && stdin_is_interactive) setLexemeOpen(p, s, 0)
+# define CONTINUE_PROMPT_AWAITC(p,c) \
+  if(p && stdin_is_interactive) setLexemeOpen(p, 0, c)
+# define CONTINUE_PAREN_INCR(p,n) \
+  if(p && stdin_is_interactive) (trackParenLevel(p,n))
+# define CONTINUE_PROMPT_PSTATE (&dynPrompt)
+typedef struct DynaPrompt *t_DynaPromptRef;
+# define SCAN_TRACKER_REFTYPE t_DynaPromptRef
+
+static struct DynaPrompt {
+  char dynamicPrompt[PROMPT_LEN_MAX];
+  char acAwait[2];
+  int inParenLevel;
+  char *zScannerAwaits;
+} dynPrompt = { {0}, {0}, 0, 0 };
+
+/* Record parenthesis nesting level change, or force level to 0. */
+static void trackParenLevel(struct DynaPrompt *p, int ni){
+  p->inParenLevel += ni;
+  if( ni==0 ) p->inParenLevel = 0;
+  p->zScannerAwaits = 0;
+}
+
+/* Record that a lexeme is opened, or closed with args==0. */
+static void setLexemeOpen(struct DynaPrompt *p, char *s, char c){
+  if( s!=0 || c==0 ){
+    p->zScannerAwaits = s;
+    p->acAwait[0] = 0;
+  }else{
+    p->acAwait[0] = c;
+    p->zScannerAwaits = p->acAwait;
+  }
+}
+
+/* Upon demand, derive the continuation prompt to display. */
+static char *dynamicContinuePrompt(void){
+  if( continuePrompt[0]==0
+      || (dynPrompt.zScannerAwaits==0 && dynPrompt.inParenLevel == 0) ){
+    return continuePrompt;
+  }else{
+    if( dynPrompt.zScannerAwaits ){
+      size_t ncp = strlen(continuePrompt);
+      size_t ndp = strlen(dynPrompt.zScannerAwaits);
+      if( ndp > ncp-3 ) return continuePrompt;
+      strcpy(dynPrompt.dynamicPrompt, dynPrompt.zScannerAwaits);
+      while( ndp<3 ) dynPrompt.dynamicPrompt[ndp++] = ' ';
+      shell_strncpy(dynPrompt.dynamicPrompt+3, continuePrompt+3,
+              PROMPT_LEN_MAX-4);
+    }else{
+      if( dynPrompt.inParenLevel>9 ){
+        shell_strncpy(dynPrompt.dynamicPrompt, "(..", 4);
+      }else if( dynPrompt.inParenLevel<0 ){
+        shell_strncpy(dynPrompt.dynamicPrompt, ")x!", 4);
+      }else{
+        shell_strncpy(dynPrompt.dynamicPrompt, "(x.", 4);
+        dynPrompt.dynamicPrompt[2] = (char)('0'+dynPrompt.inParenLevel);
+      }
+      shell_strncpy(dynPrompt.dynamicPrompt+3, continuePrompt+3,
+                    PROMPT_LEN_MAX-4);
+    }
+  }
+  return dynPrompt.dynamicPrompt;
+}
+#endif /* !defined(SQLITE_OMIT_DYNAPROMPT) */
+
+/* Indicate out-of-memory and exit. */
+static void shell_out_of_memory(void){
+  eputz("Error: out of memory\n");
+  exit(1);
+}
+
+/* Check a pointer to see if it is NULL.  If it is NULL, exit with an
+** out-of-memory error.
+*/
+static void shell_check_oom(const void *p){
+  if( p==0 ) shell_out_of_memory();
+}
+
+/*
+** Write I/O traces to the following stream.
+*/
+#ifdef SQLITE_ENABLE_IOTRACE
+static FILE *iotrace = 0;
+#endif
+
+/*
+** This routine works like printf in that its first argument is a
+** format string and subsequent arguments are values to be substituted
+** in place of % fields.  The result of formatting this string
+** is written to iotrace.
+*/
+#ifdef SQLITE_ENABLE_IOTRACE
+static void SQLITE_CDECL iotracePrintf(const char *zFormat, ...){
+  va_list ap;
+  char *z;
+  if( iotrace==0 ) return;
+  va_start(ap, zFormat);
+  z = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  sputf(iotrace, "%s", z);
+  sqlite3_free(z);
+}
+#endif
+
+/*
+** Output string zUtf to Out stream as w characters.  If w is negative,
+** then right-justify the text.  W is the width in UTF-8 characters, not
+** in bytes.  This is different from the %*.*s specification in printf
+** since with %*.*s the width is measured in bytes, not characters.
+*/
+static void utf8_width_print(int w, const char *zUtf){
+  int i;
+  int n;
+  int aw = w<0 ? -w : w;
+  if( zUtf==0 ) zUtf = "";
+  for(i=n=0; zUtf[i]; i++){
+    if( (zUtf[i]&0xc0)!=0x80 ){
+      n++;
+      if( n==aw ){
+        do{ i++; }while( (zUtf[i]&0xc0)==0x80 );
+        break;
+      }
+    }
+  }
+  if( n>=aw ){
+    oputf("%.*s", i, zUtf);
+  }else if( w<0 ){
+    oputf("%*s%s", aw-n, "", zUtf);
+  }else{
+    oputf("%s%*s", zUtf, aw-n, "");
+  }
+}
+
+
+/*
+** Determines if a string is a number of not.
+*/
+static int isNumber(const char *z, int *realnum){
+  if( *z=='-' || *z=='+' ) z++;
+  if( !IsDigit(*z) ){
+    return 0;
+  }
+  z++;
+  if( realnum ) *realnum = 0;
+  while( IsDigit(*z) ){ z++; }
+  if( *z=='.' ){
+    z++;
+    if( !IsDigit(*z) ) return 0;
+    while( IsDigit(*z) ){ z++; }
+    if( realnum ) *realnum = 1;
+  }
+  if( *z=='e' || *z=='E' ){
+    z++;
+    if( *z=='+' || *z=='-' ) z++;
+    if( !IsDigit(*z) ) return 0;
+    while( IsDigit(*z) ){ z++; }
+    if( realnum ) *realnum = 1;
+  }
+  return *z==0;
+}
+
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+*/
+static int strlen30(const char *z){
+  const char *z2 = z;
+  while( *z2 ){ z2++; }
+  return 0x3fffffff & (int)(z2 - z);
+}
+
+/*
+** Return the length of a string in characters.  Multibyte UTF8 characters
+** count as a single character.
+*/
+static int strlenChar(const char *z){
+  int n = 0;
+  while( *z ){
+    if( (0xc0&*(z++))!=0x80 ) n++;
+  }
+  return n;
+}
+
+/*
+** Return open FILE * if zFile exists, can be opened for read
+** and is an ordinary file or a character stream source.
+** Otherwise return 0.
+*/
+static FILE * openChrSource(const char *zFile){
+#if defined(_WIN32) || defined(WIN32)
+  struct __stat64 x = {0};
+# define STAT_CHR_SRC(mode) ((mode & (_S_IFCHR|_S_IFIFO|_S_IFREG))!=0)
+  /* On Windows, open first, then check the stream nature. This order
+  ** is necessary because _stat() and sibs, when checking a named pipe,
+  ** effectively break the pipe as its supplier sees it. */
+  FILE *rv = fopen(zFile, "rb");
+  if( rv==0 ) return 0;
+  if( _fstat64(_fileno(rv), &x) != 0
+      || !STAT_CHR_SRC(x.st_mode)){
+    fclose(rv);
+    rv = 0;
+  }
+  return rv;
+#else
+  struct stat x = {0};
+  int rc = stat(zFile, &x);
+# define STAT_CHR_SRC(mode) (S_ISREG(mode)||S_ISFIFO(mode)||S_ISCHR(mode))
+  if( rc!=0 ) return 0;
+  if( STAT_CHR_SRC(x.st_mode) ){
+    return fopen(zFile, "rb");
+  }else{
+    return 0;
+  }
+#endif
+#undef STAT_CHR_SRC
+}
+
+/*
+** This routine reads a line of text from FILE in, stores
+** the text in memory obtained from malloc() and returns a pointer
+** to the text.  NULL is returned at end of file, or if malloc()
+** fails.
+**
+** If zLine is not NULL then it is a malloced buffer returned from
+** a previous call to this routine that may be reused.
+*/
+static char *local_getline(char *zLine, FILE *in){
+  int nLine = zLine==0 ? 0 : 100;
+  int n = 0;
+
+  while( 1 ){
+    if( n+100>nLine ){
+      nLine = nLine*2 + 100;
+      zLine = realloc(zLine, nLine);
+      shell_check_oom(zLine);
+    }
+    if( fgets(&zLine[n], nLine - n, in)==0 ){
+      if( n==0 ){
+        free(zLine);
+        return 0;
+      }
+      zLine[n] = 0;
+      break;
+    }
+    while( zLine[n] ) n++;
+    if( n>0 && zLine[n-1]=='\n' ){
+      n--;
+      if( n>0 && zLine[n-1]=='\r' ) n--;
+      zLine[n] = 0;
+      break;
+    }
+  }
+  return zLine;
+}
+
+/*
+** Retrieve a single line of input text.
+**
+** If in==0 then read from standard input and prompt before each line.
+** If isContinuation is true, then a continuation prompt is appropriate.
+** If isContinuation is zero, then the main prompt should be used.
+**
+** If zPrior is not NULL then it is a buffer from a prior call to this
+** routine that can be reused.
+**
+** The result is stored in space obtained from malloc() and must either
+** be freed by the caller or else passed back into this routine via the
+** zPrior argument for reuse.
+*/
+#ifndef SQLITE_SHELL_FIDDLE
+static char *one_input_line(FILE *in, char *zPrior, int isContinuation){
+  char *zPrompt;
+  char *zResult;
+  if( in!=0 ){
+    zResult = local_getline(zPrior, in);
+  }else{
+    zPrompt = isContinuation ? CONTINUATION_PROMPT : mainPrompt;
+#if SHELL_USE_LOCAL_GETLINE
+    sputz(stdout, zPrompt);
+    fflush(stdout);
+    do{
+      zResult = local_getline(zPrior, stdin);
+      zPrior = 0;
+      /* ^C trap creates a false EOF, so let "interrupt" thread catch up. */
+      if( zResult==0 ) sqlite3_sleep(50);
+    }while( zResult==0 && seenInterrupt>0 );
+#else
+    free(zPrior);
+    zResult = shell_readline(zPrompt);
+    while( zResult==0 ){
+      /* ^C trap creates a false EOF, so let "interrupt" thread catch up. */
+      sqlite3_sleep(50);
+      if( seenInterrupt==0 ) break;
+      zResult = shell_readline("");
+    }
+    if( zResult && *zResult ) shell_add_history(zResult);
+#endif
+  }
+  return zResult;
+}
+#endif /* !SQLITE_SHELL_FIDDLE */
+
+/*
+** Return the value of a hexadecimal digit.  Return -1 if the input
+** is not a hex digit.
+*/
+static int hexDigitValue(char c){
+  if( c>='0' && c<='9' ) return c - '0';
+  if( c>='a' && c<='f' ) return c - 'a' + 10;
+  if( c>='A' && c<='F' ) return c - 'A' + 10;
+  return -1;
+}
+
+/*
+** Interpret zArg as an integer value, possibly with suffixes.
+*/
+static sqlite3_int64 integerValue(const char *zArg){
+  sqlite3_int64 v = 0;
+  static const struct { char *zSuffix; int iMult; } aMult[] = {
+    { "KiB", 1024 },
+    { "MiB", 1024*1024 },
+    { "GiB", 1024*1024*1024 },
+    { "KB",  1000 },
+    { "MB",  1000000 },
+    { "GB",  1000000000 },
+    { "K",   1000 },
+    { "M",   1000000 },
+    { "G",   1000000000 },
+  };
+  int i;
+  int isNeg = 0;
+  if( zArg[0]=='-' ){
+    isNeg = 1;
+    zArg++;
+  }else if( zArg[0]=='+' ){
+    zArg++;
+  }
+  if( zArg[0]=='0' && zArg[1]=='x' ){
+    int x;
+    zArg += 2;
+    while( (x = hexDigitValue(zArg[0]))>=0 ){
+      v = (v<<4) + x;
+      zArg++;
+    }
+  }else{
+    while( IsDigit(zArg[0]) ){
+      v = v*10 + zArg[0] - '0';
+      zArg++;
+    }
+  }
+  for(i=0; i<ArraySize(aMult); i++){
+    if( sqlite3_stricmp(aMult[i].zSuffix, zArg)==0 ){
+      v *= aMult[i].iMult;
+      break;
+    }
+  }
+  return isNeg? -v : v;
+}
+
+/*
+** A variable length string to which one can append text.
+*/
+typedef struct ShellText ShellText;
+struct ShellText {
+  char *z;
+  int n;
+  int nAlloc;
+};
+
+/*
+** Initialize and destroy a ShellText object
+*/
+static void initText(ShellText *p){
+  memset(p, 0, sizeof(*p));
+}
+static void freeText(ShellText *p){
+  free(p->z);
+  initText(p);
+}
+
+/* zIn is either a pointer to a NULL-terminated string in memory obtained
+** from malloc(), or a NULL pointer. The string pointed to by zAppend is
+** added to zIn, and the result returned in memory obtained from malloc().
+** zIn, if it was not NULL, is freed.
+**
+** If the third argument, quote, is not '\0', then it is used as a
+** quote character for zAppend.
+*/
+static void appendText(ShellText *p, const char *zAppend, char quote){
+  i64 len;
+  i64 i;
+  i64 nAppend = strlen30(zAppend);
+
+  len = nAppend+p->n+1;
+  if( quote ){
+    len += 2;
+    for(i=0; i<nAppend; i++){
+      if( zAppend[i]==quote ) len++;
+    }
+  }
+
+  if( p->z==0 || p->n+len>=p->nAlloc ){
+    p->nAlloc = p->nAlloc*2 + len + 20;
+    p->z = realloc(p->z, p->nAlloc);
+    shell_check_oom(p->z);
+  }
+
+  if( quote ){
+    char *zCsr = p->z+p->n;
+    *zCsr++ = quote;
+    for(i=0; i<nAppend; i++){
+      *zCsr++ = zAppend[i];
+      if( zAppend[i]==quote ) *zCsr++ = quote;
+    }
+    *zCsr++ = quote;
+    p->n = (int)(zCsr - p->z);
+    *zCsr = '\0';
+  }else{
+    memcpy(p->z+p->n, zAppend, nAppend);
+    p->n += nAppend;
+    p->z[p->n] = '\0';
+  }
+}
+
+/*
+** Attempt to determine if identifier zName needs to be quoted, either
+** because it contains non-alphanumeric characters, or because it is an
+** SQLite keyword.  Be conservative in this estimate:  When in doubt assume
+** that quoting is required.
+**
+** Return '"' if quoting is required.  Return 0 if no quoting is required.
+*/
+static char quoteChar(const char *zName){
+  int i;
+  if( zName==0 ) return '"';
+  if( !isalpha((unsigned char)zName[0]) && zName[0]!='_' ) return '"';
+  for(i=0; zName[i]; i++){
+    if( !isalnum((unsigned char)zName[i]) && zName[i]!='_' ) return '"';
+  }
+  return sqlite3_keyword_check(zName, i) ? '"' : 0;
+}
+
+/*
+** Construct a fake object name and column list to describe the structure
+** of the view, virtual table, or table valued function zSchema.zName.
+*/
+static char *shellFakeSchema(
+  sqlite3 *db,            /* The database connection containing the vtab */
+  const char *zSchema,    /* Schema of the database holding the vtab */
+  const char *zName       /* The name of the virtual table */
+){
+  sqlite3_stmt *pStmt = 0;
+  char *zSql;
+  ShellText s;
+  char cQuote;
+  char *zDiv = "(";
+  int nRow = 0;
+
+  zSql = sqlite3_mprintf("PRAGMA \"%w\".table_info=%Q;",
+                         zSchema ? zSchema : "main", zName);
+  shell_check_oom(zSql);
+  sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+  initText(&s);
+  if( zSchema ){
+    cQuote = quoteChar(zSchema);
+    if( cQuote && sqlite3_stricmp(zSchema,"temp")==0 ) cQuote = 0;
+    appendText(&s, zSchema, cQuote);
+    appendText(&s, ".", 0);
+  }
+  cQuote = quoteChar(zName);
+  appendText(&s, zName, cQuote);
+  while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    const char *zCol = (const char*)sqlite3_column_text(pStmt, 1);
+    nRow++;
+    appendText(&s, zDiv, 0);
+    zDiv = ",";
+    if( zCol==0 ) zCol = "";
+    cQuote = quoteChar(zCol);
+    appendText(&s, zCol, cQuote);
+  }
+  appendText(&s, ")", 0);
+  sqlite3_finalize(pStmt);
+  if( nRow==0 ){
+    freeText(&s);
+    s.z = 0;
+  }
+  return s.z;
+}
+
+/*
+** SQL function:  strtod(X)
+**
+** Use the C-library strtod() function to convert string X into a double.
+** Used for comparing the accuracy of SQLite's internal text-to-float conversion
+** routines against the C-library.
+*/
+static void shellStrtod(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  char *z = (char*)sqlite3_value_text(apVal[0]);
+  UNUSED_PARAMETER(nVal);
+  if( z==0 ) return;
+  sqlite3_result_double(pCtx, strtod(z,0));
+}
+
+/*
+** SQL function:  dtostr(X)
+**
+** Use the C-library printf() function to convert real value X into a string.
+** Used for comparing the accuracy of SQLite's internal float-to-text conversion
+** routines against the C-library.
+*/
+static void shellDtostr(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  double r = sqlite3_value_double(apVal[0]);
+  int n = nVal>=2 ? sqlite3_value_int(apVal[1]) : 26;
+  char z[400];
+  if( n<1 ) n = 1;
+  if( n>350 ) n = 350;
+  sqlite3_snprintf(sizeof(z), z, "%#+.*e", n, r);
+  sqlite3_result_text(pCtx, z, -1, SQLITE_TRANSIENT);
+}
+
+
+/*
+** SQL function:  shell_module_schema(X)
+**
+** Return a fake schema for the table-valued function or eponymous virtual
+** table X.
+*/
+static void shellModuleSchema(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  const char *zName;
+  char *zFake;
+  UNUSED_PARAMETER(nVal);
+  zName = (const char*)sqlite3_value_text(apVal[0]);
+  zFake = zName? shellFakeSchema(sqlite3_context_db_handle(pCtx), 0, zName) : 0;
+  if( zFake ){
+    sqlite3_result_text(pCtx, sqlite3_mprintf("/* %s */", zFake),
+                        -1, sqlite3_free);
+    free(zFake);
+  }
+}
+
+/*
+** SQL function:  shell_add_schema(S,X)
+**
+** Add the schema name X to the CREATE statement in S and return the result.
+** Examples:
+**
+**    CREATE TABLE t1(x)   ->   CREATE TABLE xyz.t1(x);
+**
+** Also works on
+**
+**    CREATE INDEX
+**    CREATE UNIQUE INDEX
+**    CREATE VIEW
+**    CREATE TRIGGER
+**    CREATE VIRTUAL TABLE
+**
+** This UDF is used by the .schema command to insert the schema name of
+** attached databases into the middle of the sqlite_schema.sql field.
+*/
+static void shellAddSchemaName(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  static const char *aPrefix[] = {
+     "TABLE",
+     "INDEX",
+     "UNIQUE INDEX",
+     "VIEW",
+     "TRIGGER",
+     "VIRTUAL TABLE"
+  };
+  int i = 0;
+  const char *zIn = (const char*)sqlite3_value_text(apVal[0]);
+  const char *zSchema = (const char*)sqlite3_value_text(apVal[1]);
+  const char *zName = (const char*)sqlite3_value_text(apVal[2]);
+  sqlite3 *db = sqlite3_context_db_handle(pCtx);
+  UNUSED_PARAMETER(nVal);
+  if( zIn!=0 && cli_strncmp(zIn, "CREATE ", 7)==0 ){
+    for(i=0; i<ArraySize(aPrefix); i++){
+      int n = strlen30(aPrefix[i]);
+      if( cli_strncmp(zIn+7, aPrefix[i], n)==0 && zIn[n+7]==' ' ){
+        char *z = 0;
+        char *zFake = 0;
+        if( zSchema ){
+          char cQuote = quoteChar(zSchema);
+          if( cQuote && sqlite3_stricmp(zSchema,"temp")!=0 ){
+            z = sqlite3_mprintf("%.*s \"%w\".%s", n+7, zIn, zSchema, zIn+n+8);
+          }else{
+            z = sqlite3_mprintf("%.*s %s.%s", n+7, zIn, zSchema, zIn+n+8);
+          }
+        }
+        if( zName
+         && aPrefix[i][0]=='V'
+         && (zFake = shellFakeSchema(db, zSchema, zName))!=0
+        ){
+          if( z==0 ){
+            z = sqlite3_mprintf("%s\n/* %s */", zIn, zFake);
+          }else{
+            z = sqlite3_mprintf("%z\n/* %s */", z, zFake);
+          }
+          free(zFake);
+        }
+        if( z ){
+          sqlite3_result_text(pCtx, z, -1, sqlite3_free);
+          return;
+        }
+      }
+    }
+  }
+  sqlite3_result_value(pCtx, apVal[0]);
+}
+
+/*
+** The source code for several run-time loadable extensions is inserted
+** below by the ../tool/mkshellc.tcl script.  Before processing that included
+** code, we need to override some macros to make the included program code
+** work here in the middle of this regular program.
+*/
+#define SQLITE_EXTENSION_INIT1
+#define SQLITE_EXTENSION_INIT2(X) (void)(X)
+
+#if defined(_WIN32) && defined(_MSC_VER)
+INCLUDE test_windirent.h
+INCLUDE test_windirent.c
+#define dirent DIRENT
+#endif
+INCLUDE ../ext/misc/memtrace.c
+INCLUDE ../ext/misc/pcachetrace.c
+INCLUDE ../ext/misc/shathree.c
+INCLUDE ../ext/misc/uint.c
+INCLUDE ../ext/misc/decimal.c
+#undef sqlite3_base_init
+#define sqlite3_base_init sqlite3_base64_init
+INCLUDE ../ext/misc/base64.c
+#undef sqlite3_base_init
+#define sqlite3_base_init sqlite3_base85_init
+#define OMIT_BASE85_CHECKER
+INCLUDE ../ext/misc/base85.c
+INCLUDE ../ext/misc/ieee754.c
+INCLUDE ../ext/misc/series.c
+INCLUDE ../ext/misc/regexp.c
+#ifndef SQLITE_SHELL_FIDDLE
+INCLUDE ../ext/misc/fileio.c
+INCLUDE ../ext/misc/completion.c
+INCLUDE ../ext/misc/appendvfs.c
+#endif
+#ifdef SQLITE_HAVE_ZLIB
+INCLUDE ../ext/misc/zipfile.c
+INCLUDE ../ext/misc/sqlar.c
+#endif
+INCLUDE ../ext/expert/sqlite3expert.h
+INCLUDE ../ext/expert/sqlite3expert.c
+
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_ENABLE_DBPAGE_VTAB)
+#define SQLITE_SHELL_HAVE_RECOVER 1
+#else
+#define SQLITE_SHELL_HAVE_RECOVER 0
+#endif
+#if SQLITE_SHELL_HAVE_RECOVER
+INCLUDE ../ext/recover/sqlite3recover.h
+# ifndef SQLITE_HAVE_SQLITE3R
+INCLUDE ../ext/recover/dbdata.c
+INCLUDE ../ext/recover/sqlite3recover.c
+# endif /* SQLITE_HAVE_SQLITE3R */
+#endif
+#ifdef SQLITE_SHELL_EXTSRC
+# include SHELL_STRINGIFY(SQLITE_SHELL_EXTSRC)
+#endif
+
+#if defined(SQLITE_ENABLE_SESSION)
+/*
+** State information for a single open session
+*/
+typedef struct OpenSession OpenSession;
+struct OpenSession {
+  char *zName;             /* Symbolic name for this session */
+  int nFilter;             /* Number of xFilter rejection GLOB patterns */
+  char **azFilter;         /* Array of xFilter rejection GLOB patterns */
+  sqlite3_session *p;      /* The open session */
+};
+#endif
+
+typedef struct ExpertInfo ExpertInfo;
+struct ExpertInfo {
+  sqlite3expert *pExpert;
+  int bVerbose;
+};
+
+/* A single line in the EQP output */
+typedef struct EQPGraphRow EQPGraphRow;
+struct EQPGraphRow {
+  int iEqpId;           /* ID for this row */
+  int iParentId;        /* ID of the parent row */
+  EQPGraphRow *pNext;   /* Next row in sequence */
+  char zText[1];        /* Text to display for this row */
+};
+
+/* All EQP output is collected into an instance of the following */
+typedef struct EQPGraph EQPGraph;
+struct EQPGraph {
+  EQPGraphRow *pRow;    /* Linked list of all rows of the EQP output */
+  EQPGraphRow *pLast;   /* Last element of the pRow list */
+  char zPrefix[100];    /* Graph prefix */
+};
+
+/* Parameters affecting columnar mode result display (defaulting together) */
+typedef struct ColModeOpts {
+  int iWrap;            /* In columnar modes, wrap lines reaching this limit */
+  u8 bQuote;            /* Quote results for .mode box and table */
+  u8 bWordWrap;         /* In columnar modes, wrap at word boundaries  */
+} ColModeOpts;
+#define ColModeOpts_default { 60, 0, 0 }
+#define ColModeOpts_default_qbox { 60, 1, 0 }
+
+/*
+** State information about the database connection is contained in an
+** instance of the following structure.
+*/
+typedef struct ShellState ShellState;
+struct ShellState {
+  sqlite3 *db;           /* The database */
+  u8 autoExplain;        /* Automatically turn on .explain mode */
+  u8 autoEQP;            /* Run EXPLAIN QUERY PLAN prior to each SQL stmt */
+  u8 autoEQPtest;        /* autoEQP is in test mode */
+  u8 autoEQPtrace;       /* autoEQP is in trace mode */
+  u8 scanstatsOn;        /* True to display scan stats before each finalize */
+  u8 openMode;           /* SHELL_OPEN_NORMAL, _APPENDVFS, or _ZIPFILE */
+  u8 doXdgOpen;          /* Invoke start/open/xdg-open in output_reset() */
+  u8 nEqpLevel;          /* Depth of the EQP output graph */
+  u8 eTraceType;         /* SHELL_TRACE_* value for type of trace */
+  u8 bSafeMode;          /* True to prohibit unsafe operations */
+  u8 bSafeModePersist;   /* The long-term value of bSafeMode */
+  u8 eRestoreState;      /* See comments above doAutoDetectRestore() */
+  ColModeOpts cmOpts;    /* Option values affecting columnar mode output */
+  unsigned statsOn;      /* True to display memory stats before each finalize */
+  unsigned mEqpLines;    /* Mask of vertical lines in the EQP output graph */
+  int inputNesting;      /* Track nesting level of .read and other redirects */
+  int outCount;          /* Revert to stdout when reaching zero */
+  int cnt;               /* Number of records displayed so far */
+  int lineno;            /* Line number of last line read from in */
+  int openFlags;         /* Additional flags to open.  (SQLITE_OPEN_NOFOLLOW) */
+  FILE *in;              /* Read commands from this stream */
+  FILE *out;             /* Write results here */
+  FILE *traceOut;        /* Output for sqlite3_trace() */
+  int nErr;              /* Number of errors seen */
+  int mode;              /* An output mode setting */
+  int modePrior;         /* Saved mode */
+  int cMode;             /* temporary output mode for the current query */
+  int normalMode;        /* Output mode before ".explain on" */
+  int writableSchema;    /* True if PRAGMA writable_schema=ON */
+  int showHeader;        /* True to show column names in List or Column mode */
+  int nCheck;            /* Number of ".check" commands run */
+  unsigned nProgress;    /* Number of progress callbacks encountered */
+  unsigned mxProgress;   /* Maximum progress callbacks before failing */
+  unsigned flgProgress;  /* Flags for the progress callback */
+  unsigned shellFlgs;    /* Various flags */
+  unsigned priorShFlgs;  /* Saved copy of flags */
+  sqlite3_int64 szMax;   /* --maxsize argument to .open */
+  char *zDestTable;      /* Name of destination table when MODE_Insert */
+  char *zTempFile;       /* Temporary file that might need deleting */
+  char zTestcase[30];    /* Name of current test case */
+  char colSeparator[20]; /* Column separator character for several modes */
+  char rowSeparator[20]; /* Row separator character for MODE_Ascii */
+  char colSepPrior[20];  /* Saved column separator */
+  char rowSepPrior[20];  /* Saved row separator */
+  int *colWidth;         /* Requested width of each column in columnar modes */
+  int *actualWidth;      /* Actual width of each column */
+  int nWidth;            /* Number of slots in colWidth[] and actualWidth[] */
+  char nullValue[20];    /* The text to print when a NULL comes back from
+                         ** the database */
+  char outfile[FILENAME_MAX]; /* Filename for *out */
+  sqlite3_stmt *pStmt;   /* Current statement if any. */
+  FILE *pLog;            /* Write log output here */
+  struct AuxDb {         /* Storage space for auxiliary database connections */
+    sqlite3 *db;               /* Connection pointer */
+    const char *zDbFilename;   /* Filename used to open the connection */
+    char *zFreeOnClose;        /* Free this memory allocation on close */
+#if defined(SQLITE_ENABLE_SESSION)
+    int nSession;              /* Number of active sessions */
+    OpenSession aSession[4];   /* Array of sessions.  [0] is in focus. */
+#endif
+  } aAuxDb[5],           /* Array of all database connections */
+    *pAuxDb;             /* Currently active database connection */
+  int *aiIndent;         /* Array of indents used in MODE_Explain */
+  int nIndent;           /* Size of array aiIndent[] */
+  int iIndent;           /* Index of current op in aiIndent[] */
+  char *zNonce;          /* Nonce for temporary safe-mode escapes */
+  EQPGraph sGraph;       /* Information for the graphical EXPLAIN QUERY PLAN */
+  ExpertInfo expert;     /* Valid if previous command was ".expert OPT..." */
+#ifdef SQLITE_SHELL_FIDDLE
+  struct {
+    const char * zInput; /* Input string from wasm/JS proxy */
+    const char * zPos;   /* Cursor pos into zInput */
+    const char * zDefaultDbName; /* Default name for db file */
+  } wasm;
+#endif
+};
+
+#ifdef SQLITE_SHELL_FIDDLE
+static ShellState shellState;
+#endif
+
+
+/* Allowed values for ShellState.autoEQP
+*/
+#define AUTOEQP_off      0           /* Automatic EXPLAIN QUERY PLAN is off */
+#define AUTOEQP_on       1           /* Automatic EQP is on */
+#define AUTOEQP_trigger  2           /* On and also show plans for triggers */
+#define AUTOEQP_full     3           /* Show full EXPLAIN */
+
+/* Allowed values for ShellState.openMode
+*/
+#define SHELL_OPEN_UNSPEC      0      /* No open-mode specified */
+#define SHELL_OPEN_NORMAL      1      /* Normal database file */
+#define SHELL_OPEN_APPENDVFS   2      /* Use appendvfs */
+#define SHELL_OPEN_ZIPFILE     3      /* Use the zipfile virtual table */
+#define SHELL_OPEN_READONLY    4      /* Open a normal database read-only */
+#define SHELL_OPEN_DESERIALIZE 5      /* Open using sqlite3_deserialize() */
+#define SHELL_OPEN_HEXDB       6      /* Use "dbtotxt" output as data source */
+
+/* Allowed values for ShellState.eTraceType
+*/
+#define SHELL_TRACE_PLAIN      0      /* Show input SQL text */
+#define SHELL_TRACE_EXPANDED   1      /* Show expanded SQL text */
+#define SHELL_TRACE_NORMALIZED 2      /* Show normalized SQL text */
+
+/* Bits in the ShellState.flgProgress variable */
+#define SHELL_PROGRESS_QUIET 0x01  /* Omit announcing every progress callback */
+#define SHELL_PROGRESS_RESET 0x02  /* Reset the count when the progress
+                                   ** callback limit is reached, and for each
+                                   ** top-level SQL statement */
+#define SHELL_PROGRESS_ONCE  0x04  /* Cancel the --limit after firing once */
+
+/*
+** These are the allowed shellFlgs values
+*/
+#define SHFLG_Pagecache      0x00000001 /* The --pagecache option is used */
+#define SHFLG_Lookaside      0x00000002 /* Lookaside memory is used */
+#define SHFLG_Backslash      0x00000004 /* The --backslash option is used */
+#define SHFLG_PreserveRowid  0x00000008 /* .dump preserves rowid values */
+#define SHFLG_Newlines       0x00000010 /* .dump --newline flag */
+#define SHFLG_CountChanges   0x00000020 /* .changes setting */
+#define SHFLG_Echo           0x00000040 /* .echo on/off, or --echo setting */
+#define SHFLG_HeaderSet      0x00000080 /* showHeader has been specified */
+#define SHFLG_DumpDataOnly   0x00000100 /* .dump show data only */
+#define SHFLG_DumpNoSys      0x00000200 /* .dump omits system tables */
+#define SHFLG_TestingMode    0x00000400 /* allow unsafe testing features */
+
+/*
+** Macros for testing and setting shellFlgs
+*/
+#define ShellHasFlag(P,X)    (((P)->shellFlgs & (X))!=0)
+#define ShellSetFlag(P,X)    ((P)->shellFlgs|=(X))
+#define ShellClearFlag(P,X)  ((P)->shellFlgs&=(~(X)))
+
+/*
+** These are the allowed modes.
+*/
+#define MODE_Line     0  /* One column per line.  Blank line between records */
+#define MODE_Column   1  /* One record per line in neat columns */
+#define MODE_List     2  /* One record per line with a separator */
+#define MODE_Semi     3  /* Same as MODE_List but append ";" to each line */
+#define MODE_Html     4  /* Generate an XHTML table */
+#define MODE_Insert   5  /* Generate SQL "insert" statements */
+#define MODE_Quote    6  /* Quote values as for SQL */
+#define MODE_Tcl      7  /* Generate ANSI-C or TCL quoted elements */
+#define MODE_Csv      8  /* Quote strings, numbers are plain */
+#define MODE_Explain  9  /* Like MODE_Column, but do not truncate data */
+#define MODE_Ascii   10  /* Use ASCII unit and record separators (0x1F/0x1E) */
+#define MODE_Pretty  11  /* Pretty-print schemas */
+#define MODE_EQP     12  /* Converts EXPLAIN QUERY PLAN output into a graph */
+#define MODE_Json    13  /* Output JSON */
+#define MODE_Markdown 14 /* Markdown formatting */
+#define MODE_Table   15  /* MySQL-style table formatting */
+#define MODE_Box     16  /* Unicode box-drawing characters */
+#define MODE_Count   17  /* Output only a count of the rows of output */
+#define MODE_Off     18  /* No query output shown */
+#define MODE_ScanExp 19  /* Like MODE_Explain, but for ".scanstats vm" */
+
+static const char *modeDescr[] = {
+  "line",
+  "column",
+  "list",
+  "semi",
+  "html",
+  "insert",
+  "quote",
+  "tcl",
+  "csv",
+  "explain",
+  "ascii",
+  "prettyprint",
+  "eqp",
+  "json",
+  "markdown",
+  "table",
+  "box",
+  "count",
+  "off"
+};
+
+/*
+** These are the column/row/line separators used by the various
+** import/export modes.
+*/
+#define SEP_Column    "|"
+#define SEP_Row       "\n"
+#define SEP_Tab       "\t"
+#define SEP_Space     " "
+#define SEP_Comma     ","
+#define SEP_CrLf      "\r\n"
+#define SEP_Unit      "\x1F"
+#define SEP_Record    "\x1E"
+
+/*
+** Limit input nesting via .read or any other input redirect.
+** It's not too expensive, so a generous allowance can be made.
+*/
+#define MAX_INPUT_NESTING 25
+
+/*
+** A callback for the sqlite3_log() interface.
+*/
+static void shellLog(void *pArg, int iErrCode, const char *zMsg){
+  ShellState *p = (ShellState*)pArg;
+  if( p->pLog==0 ) return;
+  sputf(p->pLog, "(%d) %s\n", iErrCode, zMsg);
+  fflush(p->pLog);
+}
+
+/*
+** SQL function:  shell_putsnl(X)
+**
+** Write the text X to the screen (or whatever output is being directed)
+** adding a newline at the end, and then return X.
+*/
+static void shellPutsFunc(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  /* Unused: (ShellState*)sqlite3_user_data(pCtx); */
+  (void)nVal;
+  oputf("%s\n", sqlite3_value_text(apVal[0]));
+  sqlite3_result_value(pCtx, apVal[0]);
+}
+
+/*
+** If in safe mode, print an error message described by the arguments
+** and exit immediately.
+*/
+static void failIfSafeMode(
+  ShellState *p,
+  const char *zErrMsg,
+  ...
+){
+  if( p->bSafeMode ){
+    va_list ap;
+    char *zMsg;
+    va_start(ap, zErrMsg);
+    zMsg = sqlite3_vmprintf(zErrMsg, ap);
+    va_end(ap);
+    eputf("line %d: %s\n", p->lineno, zMsg);
+    exit(1);
+  }
+}
+
+/*
+** SQL function:   edit(VALUE)
+**                 edit(VALUE,EDITOR)
+**
+** These steps:
+**
+**     (1) Write VALUE into a temporary file.
+**     (2) Run program EDITOR on that temporary file.
+**     (3) Read the temporary file back and return its content as the result.
+**     (4) Delete the temporary file
+**
+** If the EDITOR argument is omitted, use the value in the VISUAL
+** environment variable.  If still there is no EDITOR, through an error.
+**
+** Also throw an error if the EDITOR program returns a non-zero exit code.
+*/
+#ifndef SQLITE_NOHAVE_SYSTEM
+static void editFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zEditor;
+  char *zTempFile = 0;
+  sqlite3 *db;
+  char *zCmd = 0;
+  int bBin;
+  int rc;
+  int hasCRNL = 0;
+  FILE *f = 0;
+  sqlite3_int64 sz;
+  sqlite3_int64 x;
+  unsigned char *p = 0;
+
+  if( argc==2 ){
+    zEditor = (const char*)sqlite3_value_text(argv[1]);
+  }else{
+    zEditor = getenv("VISUAL");
+  }
+  if( zEditor==0 ){
+    sqlite3_result_error(context, "no editor for edit()", -1);
+    return;
+  }
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ){
+    sqlite3_result_error(context, "NULL input to edit()", -1);
+    return;
+  }
+  db = sqlite3_context_db_handle(context);
+  zTempFile = 0;
+  sqlite3_file_control(db, 0, SQLITE_FCNTL_TEMPFILENAME, &zTempFile);
+  if( zTempFile==0 ){
+    sqlite3_uint64 r = 0;
+    sqlite3_randomness(sizeof(r), &r);
+    zTempFile = sqlite3_mprintf("temp%llx", r);
+    if( zTempFile==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }
+  }
+  bBin = sqlite3_value_type(argv[0])==SQLITE_BLOB;
+  /* When writing the file to be edited, do \n to \r\n conversions on systems
+  ** that want \r\n line endings */
+  f = fopen(zTempFile, bBin ? "wb" : "w");
+  if( f==0 ){
+    sqlite3_result_error(context, "edit() cannot open temp file", -1);
+    goto edit_func_end;
+  }
+  sz = sqlite3_value_bytes(argv[0]);
+  if( bBin ){
+    x = fwrite(sqlite3_value_blob(argv[0]), 1, (size_t)sz, f);
+  }else{
+    const char *z = (const char*)sqlite3_value_text(argv[0]);
+    /* Remember whether or not the value originally contained \r\n */
+    if( z && strstr(z,"\r\n")!=0 ) hasCRNL = 1;
+    x = fwrite(sqlite3_value_text(argv[0]), 1, (size_t)sz, f);
+  }
+  fclose(f);
+  f = 0;
+  if( x!=sz ){
+    sqlite3_result_error(context, "edit() could not write the whole file", -1);
+    goto edit_func_end;
+  }
+  zCmd = sqlite3_mprintf("%s \"%s\"", zEditor, zTempFile);
+  if( zCmd==0 ){
+    sqlite3_result_error_nomem(context);
+    goto edit_func_end;
+  }
+  rc = system(zCmd);
+  sqlite3_free(zCmd);
+  if( rc ){
+    sqlite3_result_error(context, "EDITOR returned non-zero", -1);
+    goto edit_func_end;
+  }
+  f = fopen(zTempFile, "rb");
+  if( f==0 ){
+    sqlite3_result_error(context,
+      "edit() cannot reopen temp file after edit", -1);
+    goto edit_func_end;
+  }
+  fseek(f, 0, SEEK_END);
+  sz = ftell(f);
+  rewind(f);
+  p = sqlite3_malloc64( sz+1 );
+  if( p==0 ){
+    sqlite3_result_error_nomem(context);
+    goto edit_func_end;
+  }
+  x = fread(p, 1, (size_t)sz, f);
+  fclose(f);
+  f = 0;
+  if( x!=sz ){
+    sqlite3_result_error(context, "could not read back the whole file", -1);
+    goto edit_func_end;
+  }
+  if( bBin ){
+    sqlite3_result_blob64(context, p, sz, sqlite3_free);
+  }else{
+    sqlite3_int64 i, j;
+    if( hasCRNL ){
+      /* If the original contains \r\n then do no conversions back to \n */
+    }else{
+      /* If the file did not originally contain \r\n then convert any new
+      ** \r\n back into \n */
+      p[sz] = 0;
+      for(i=j=0; i<sz; i++){
+        if( p[i]=='\r' && p[i+1]=='\n' ) i++;
+        p[j++] = p[i];
+      }
+      sz = j;
+      p[sz] = 0;
+    }
+    sqlite3_result_text64(context, (const char*)p, sz,
+                          sqlite3_free, SQLITE_UTF8);
+  }
+  p = 0;
+
+edit_func_end:
+  if( f ) fclose(f);
+  unlink(zTempFile);
+  sqlite3_free(zTempFile);
+  sqlite3_free(p);
+}
+#endif /* SQLITE_NOHAVE_SYSTEM */
+
+/*
+** Save or restore the current output mode
+*/
+static void outputModePush(ShellState *p){
+  p->modePrior = p->mode;
+  p->priorShFlgs = p->shellFlgs;
+  memcpy(p->colSepPrior, p->colSeparator, sizeof(p->colSeparator));
+  memcpy(p->rowSepPrior, p->rowSeparator, sizeof(p->rowSeparator));
+}
+static void outputModePop(ShellState *p){
+  p->mode = p->modePrior;
+  p->shellFlgs = p->priorShFlgs;
+  memcpy(p->colSeparator, p->colSepPrior, sizeof(p->colSeparator));
+  memcpy(p->rowSeparator, p->rowSepPrior, sizeof(p->rowSeparator));
+}
+
+/*
+** Output the given string as a hex-encoded blob (eg. X'1234' )
+*/
+static void output_hex_blob(const void *pBlob, int nBlob){
+  int i;
+  unsigned char *aBlob = (unsigned char*)pBlob;
+
+  char *zStr = sqlite3_malloc(nBlob*2 + 1);
+  shell_check_oom(zStr);
+
+  for(i=0; i<nBlob; i++){
+    static const char aHex[] = {
+        '0', '1', '2', '3', '4', '5', '6', '7',
+        '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+    };
+    zStr[i*2] = aHex[ (aBlob[i] >> 4) ];
+    zStr[i*2+1] = aHex[ (aBlob[i] & 0x0F) ];
+  }
+  zStr[i*2] = '\0';
+
+  oputf("X'%s'", zStr);
+  sqlite3_free(zStr);
+}
+
+/*
+** Find a string that is not found anywhere in z[].  Return a pointer
+** to that string.
+**
+** Try to use zA and zB first.  If both of those are already found in z[]
+** then make up some string and store it in the buffer zBuf.
+*/
+static const char *unused_string(
+  const char *z,                    /* Result must not appear anywhere in z */
+  const char *zA, const char *zB,   /* Try these first */
+  char *zBuf                        /* Space to store a generated string */
+){
+  unsigned i = 0;
+  if( strstr(z, zA)==0 ) return zA;
+  if( strstr(z, zB)==0 ) return zB;
+  do{
+    sqlite3_snprintf(20,zBuf,"(%s%u)", zA, i++);
+  }while( strstr(z,zBuf)!=0 );
+  return zBuf;
+}
+
+/*
+** Output the given string as a quoted string using SQL quoting conventions.
+**
+** See also: output_quoted_escaped_string()
+*/
+static void output_quoted_string(const char *z){
+  int i;
+  char c;
+#ifndef SQLITE_SHELL_FIDDLE
+  FILE *pfO = setOutputStream(invalidFileStream);
+  setBinaryMode(pfO, 1);
+#endif
+  if( z==0 ) return;
+  for(i=0; (c = z[i])!=0 && c!='\''; i++){}
+  if( c==0 ){
+    oputf("'%s'",z);
+  }else{
+    oputz("'");
+    while( *z ){
+      for(i=0; (c = z[i])!=0 && c!='\''; i++){}
+      if( c=='\'' ) i++;
+      if( i ){
+        oputf("%.*s", i, z);
+        z += i;
+      }
+      if( c=='\'' ){
+        oputz("'");
+        continue;
+      }
+      if( c==0 ){
+        break;
+      }
+      z++;
+    }
+    oputz("'");
+  }
+#ifndef SQLITE_SHELL_FIDDLE
+  setTextMode(pfO, 1);
+#else
+  setTextMode(stdout, 1);
+#endif
+}
+
+/*
+** Output the given string as a quoted string using SQL quoting conventions.
+** Additionallly , escape the "\n" and "\r" characters so that they do not
+** get corrupted by end-of-line translation facilities in some operating
+** systems.
+**
+** This is like output_quoted_string() but with the addition of the \r\n
+** escape mechanism.
+*/
+static void output_quoted_escaped_string(const char *z){
+  int i;
+  char c;
+#ifndef SQLITE_SHELL_FIDDLE
+  FILE *pfO = setOutputStream(invalidFileStream);
+  setBinaryMode(pfO, 1);
+#endif
+  for(i=0; (c = z[i])!=0 && c!='\'' && c!='\n' && c!='\r'; i++){}
+  if( c==0 ){
+    oputf("'%s'",z);
+  }else{
+    const char *zNL = 0;
+    const char *zCR = 0;
+    int nNL = 0;
+    int nCR = 0;
+    char zBuf1[20], zBuf2[20];
+    for(i=0; z[i]; i++){
+      if( z[i]=='\n' ) nNL++;
+      if( z[i]=='\r' ) nCR++;
+    }
+    if( nNL ){
+      oputz("replace(");
+      zNL = unused_string(z, "\\n", "\\012", zBuf1);
+    }
+    if( nCR ){
+      oputz("replace(");
+      zCR = unused_string(z, "\\r", "\\015", zBuf2);
+    }
+    oputz("'");
+    while( *z ){
+      for(i=0; (c = z[i])!=0 && c!='\n' && c!='\r' && c!='\''; i++){}
+      if( c=='\'' ) i++;
+      if( i ){
+        oputf("%.*s", i, z);
+        z += i;
+      }
+      if( c=='\'' ){
+        oputz("'");
+        continue;
+      }
+      if( c==0 ){
+        break;
+      }
+      z++;
+      if( c=='\n' ){
+        oputz(zNL);
+        continue;
+      }
+      oputz(zCR);
+    }
+    oputz("'");
+    if( nCR ){
+      oputf(",'%s',char(13))", zCR);
+    }
+    if( nNL ){
+      oputf(",'%s',char(10))", zNL);
+    }
+  }
+#ifndef SQLITE_SHELL_FIDDLE
+  setTextMode(pfO, 1);
+#else
+  setTextMode(stdout, 1);
+#endif
+}
+
+/*
+** Find earliest of chars within s specified in zAny.
+** With ns == ~0, is like strpbrk(s,zAny) and s must be 0-terminated.
+*/
+static const char *anyOfInStr(const char *s, const char *zAny, size_t ns){
+  const char *pcFirst = 0;
+  if( ns == ~(size_t)0 ) ns = strlen(s);
+  while(*zAny){
+    const char *pc = (const char*)memchr(s, *zAny&0xff, ns);
+    if( pc ){
+      pcFirst = pc;
+      ns = pcFirst - s;
+    }
+    ++zAny;
+  }
+  return pcFirst;
+}
+/*
+** Output the given string as a quoted according to C or TCL quoting rules.
+*/
+static void output_c_string(const char *z){
+  char c;
+  static const char *zq = "\"";
+  static long ctrlMask = ~0L;
+  static const char *zDQBSRO = "\"\\\x7f"; /* double-quote, backslash, rubout */
+  char ace[3] = "\\?";
+  char cbsSay;
+  oputz(zq);
+  while( *z!=0 ){
+    const char *pcDQBSRO = anyOfInStr(z, zDQBSRO, ~(size_t)0);
+    const char *pcPast = zSkipValidUtf8(z, INT_MAX, ctrlMask);
+    const char *pcEnd = (pcDQBSRO && pcDQBSRO < pcPast)? pcDQBSRO : pcPast;
+    if( pcEnd > z ) oputb(z, (int)(pcEnd-z));
+    if( (c = *pcEnd)==0 ) break;
+    ++pcEnd;
+    switch( c ){
+    case '\\': case '"':
+      cbsSay = (char)c;
+      break;
+    case '\t': cbsSay = 't'; break;
+    case '\n': cbsSay = 'n'; break;
+    case '\r': cbsSay = 'r'; break;
+    case '\f': cbsSay = 'f'; break;
+    default: cbsSay = 0; break;
+    }
+    if( cbsSay ){
+      ace[1] = cbsSay;
+      oputz(ace);
+    }else if( !isprint(c&0xff) ){
+      oputf("\\%03o", c&0xff);
+    }else{
+      ace[1] = (char)c;
+      oputz(ace+1);
+    }
+    z = pcEnd;
+  }
+  oputz(zq);
+}
+
+/*
+** Output the given string as a quoted according to JSON quoting rules.
+*/
+static void output_json_string(const char *z, i64 n){
+  char c;
+  static const char *zq = "\"";
+  static long ctrlMask = ~0L;
+  static const char *zDQBS = "\"\\";
+  const char *pcLimit;
+  char ace[3] = "\\?";
+  char cbsSay;
+
+  if( z==0 ) z = "";
+  pcLimit = z + ((n<0)? strlen(z) : (size_t)n);
+  oputz(zq);
+  while( z < pcLimit ){
+    const char *pcDQBS = anyOfInStr(z, zDQBS, pcLimit-z);
+    const char *pcPast = zSkipValidUtf8(z, (int)(pcLimit-z), ctrlMask);
+    const char *pcEnd = (pcDQBS && pcDQBS < pcPast)? pcDQBS : pcPast;
+    if( pcEnd > z ){
+      oputb(z, (int)(pcEnd-z));
+      z = pcEnd;
+    }
+    if( z >= pcLimit ) break;
+    c = *(z++);
+    switch( c ){
+    case '"': case '\\':
+      cbsSay = (char)c;
+      break;
+    case '\b': cbsSay = 'b'; break;
+    case '\f': cbsSay = 'f'; break;
+    case '\n': cbsSay = 'n'; break;
+    case '\r': cbsSay = 'r'; break;
+    case '\t': cbsSay = 't'; break;
+    default: cbsSay = 0; break;
+    }
+    if( cbsSay ){
+      ace[1] = cbsSay;
+      oputz(ace);
+    }else if( c<=0x1f ){
+      oputf("u%04x", c);
+    }else{
+      ace[1] = (char)c;
+      oputz(ace+1);
+    }
+  }
+  oputz(zq);
+}
+
+/*
+** Output the given string with characters that are special to
+** HTML escaped.
+*/
+static void output_html_string(const char *z){
+  int i;
+  if( z==0 ) z = "";
+  while( *z ){
+    for(i=0;   z[i]
+            && z[i]!='<'
+            && z[i]!='&'
+            && z[i]!='>'
+            && z[i]!='\"'
+            && z[i]!='\'';
+        i++){}
+    if( i>0 ){
+      oputf("%.*s",i,z);
+    }
+    if( z[i]=='<' ){
+      oputz("&lt;");
+    }else if( z[i]=='&' ){
+      oputz("&amp;");
+    }else if( z[i]=='>' ){
+      oputz("&gt;");
+    }else if( z[i]=='\"' ){
+      oputz("&quot;");
+    }else if( z[i]=='\'' ){
+      oputz("&#39;");
+    }else{
+      break;
+    }
+    z += i + 1;
+  }
+}
+
+/*
+** If a field contains any character identified by a 1 in the following
+** array, then the string must be quoted for CSV.
+*/
+static const char needCsvQuote[] = {
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 0, 1, 0, 0, 0, 0, 1,   0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+};
+
+/*
+** Output a single term of CSV.  Actually, p->colSeparator is used for
+** the separator, which may or may not be a comma.  p->nullValue is
+** the null value.  Strings are quoted if necessary.  The separator
+** is only issued if bSep is true.
+*/
+static void output_csv(ShellState *p, const char *z, int bSep){
+  if( z==0 ){
+    oputf("%s",p->nullValue);
+  }else{
+    unsigned i;
+    for(i=0; z[i]; i++){
+      if( needCsvQuote[((unsigned char*)z)[i]] ){
+        i = 0;
+        break;
+      }
+    }
+    if( i==0 || strstr(z, p->colSeparator)!=0 ){
+      char *zQuoted = sqlite3_mprintf("\"%w\"", z);
+      shell_check_oom(zQuoted);
+      oputz(zQuoted);
+      sqlite3_free(zQuoted);
+    }else{
+      oputz(z);
+    }
+  }
+  if( bSep ){
+    oputz(p->colSeparator);
+  }
+}
+
+/*
+** This routine runs when the user presses Ctrl-C
+*/
+static void interrupt_handler(int NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  if( ++seenInterrupt>1 ) exit(1);
+  if( globalDb ) sqlite3_interrupt(globalDb);
+}
+
+#if (defined(_WIN32) || defined(WIN32)) && !defined(_WIN32_WCE)
+/*
+** This routine runs for console events (e.g. Ctrl-C) on Win32
+*/
+static BOOL WINAPI ConsoleCtrlHandler(
+  DWORD dwCtrlType /* One of the CTRL_*_EVENT constants */
+){
+  if( dwCtrlType==CTRL_C_EVENT ){
+    interrupt_handler(0);
+    return TRUE;
+  }
+  return FALSE;
+}
+#endif
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+/*
+** This authorizer runs in safe mode.
+*/
+static int safeModeAuth(
+  void *pClientData,
+  int op,
+  const char *zA1,
+  const char *zA2,
+  const char *zA3,
+  const char *zA4
+){
+  ShellState *p = (ShellState*)pClientData;
+  static const char *azProhibitedFunctions[] = {
+    "edit",
+    "fts3_tokenizer",
+    "load_extension",
+    "readfile",
+    "writefile",
+    "zipfile",
+    "zipfile_cds",
+  };
+  UNUSED_PARAMETER(zA1);
+  UNUSED_PARAMETER(zA3);
+  UNUSED_PARAMETER(zA4);
+  switch( op ){
+    case SQLITE_ATTACH: {
+#ifndef SQLITE_SHELL_FIDDLE
+      /* In WASM builds the filesystem is a virtual sandbox, so
+      ** there's no harm in using ATTACH. */
+      failIfSafeMode(p, "cannot run ATTACH in safe mode");
+#endif
+      break;
+    }
+    case SQLITE_FUNCTION: {
+      int i;
+      for(i=0; i<ArraySize(azProhibitedFunctions); i++){
+        if( sqlite3_stricmp(zA2, azProhibitedFunctions[i])==0 ){
+          failIfSafeMode(p, "cannot use the %s() function in safe mode",
+                         azProhibitedFunctions[i]);
+        }
+      }
+      break;
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** When the ".auth ON" is set, the following authorizer callback is
+** invoked.  It always returns SQLITE_OK.
+*/
+static int shellAuth(
+  void *pClientData,
+  int op,
+  const char *zA1,
+  const char *zA2,
+  const char *zA3,
+  const char *zA4
+){
+  ShellState *p = (ShellState*)pClientData;
+  static const char *azAction[] = { 0,
+     "CREATE_INDEX",         "CREATE_TABLE",         "CREATE_TEMP_INDEX",
+     "CREATE_TEMP_TABLE",    "CREATE_TEMP_TRIGGER",  "CREATE_TEMP_VIEW",
+     "CREATE_TRIGGER",       "CREATE_VIEW",          "DELETE",
+     "DROP_INDEX",           "DROP_TABLE",           "DROP_TEMP_INDEX",
+     "DROP_TEMP_TABLE",      "DROP_TEMP_TRIGGER",    "DROP_TEMP_VIEW",
+     "DROP_TRIGGER",         "DROP_VIEW",            "INSERT",
+     "PRAGMA",               "READ",                 "SELECT",
+     "TRANSACTION",          "UPDATE",               "ATTACH",
+     "DETACH",               "ALTER_TABLE",          "REINDEX",
+     "ANALYZE",              "CREATE_VTABLE",        "DROP_VTABLE",
+     "FUNCTION",             "SAVEPOINT",            "RECURSIVE"
+  };
+  int i;
+  const char *az[4];
+  az[0] = zA1;
+  az[1] = zA2;
+  az[2] = zA3;
+  az[3] = zA4;
+  oputf("authorizer: %s", azAction[op]);
+  for(i=0; i<4; i++){
+    oputz(" ");
+    if( az[i] ){
+      output_c_string(az[i]);
+    }else{
+      oputz("NULL");
+    }
+  }
+  oputz("\n");
+  if( p->bSafeMode ) (void)safeModeAuth(pClientData, op, zA1, zA2, zA3, zA4);
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Print a schema statement.  Part of MODE_Semi and MODE_Pretty output.
+**
+** This routine converts some CREATE TABLE statements for shadow tables
+** in FTS3/4/5 into CREATE TABLE IF NOT EXISTS statements.
+**
+** If the schema statement in z[] contains a start-of-comment and if
+** sqlite3_complete() returns false, try to terminate the comment before
+** printing the result.  https://sqlite.org/forum/forumpost/d7be961c5c
+*/
+static void printSchemaLine(const char *z, const char *zTail){
+  char *zToFree = 0;
+  if( z==0 ) return;
+  if( zTail==0 ) return;
+  if( zTail[0]==';' && (strstr(z, "/*")!=0 || strstr(z,"--")!=0) ){
+    const char *zOrig = z;
+    static const char *azTerm[] = { "", "*/", "\n" };
+    int i;
+    for(i=0; i<ArraySize(azTerm); i++){
+      char *zNew = sqlite3_mprintf("%s%s;", zOrig, azTerm[i]);
+      shell_check_oom(zNew);
+      if( sqlite3_complete(zNew) ){
+        size_t n = strlen(zNew);
+        zNew[n-1] = 0;
+        zToFree = zNew;
+        z = zNew;
+        break;
+      }
+      sqlite3_free(zNew);
+    }
+  }
+  if( sqlite3_strglob("CREATE TABLE ['\"]*", z)==0 ){
+    oputf("CREATE TABLE IF NOT EXISTS %s%s", z+13, zTail);
+  }else{
+    oputf("%s%s", z, zTail);
+  }
+  sqlite3_free(zToFree);
+}
+static void printSchemaLineN(char *z, int n, const char *zTail){
+  char c = z[n];
+  z[n] = 0;
+  printSchemaLine(z, zTail);
+  z[n] = c;
+}
+
+/*
+** Return true if string z[] has nothing but whitespace and comments to the
+** end of the first line.
+*/
+static int wsToEol(const char *z){
+  int i;
+  for(i=0; z[i]; i++){
+    if( z[i]=='\n' ) return 1;
+    if( IsSpace(z[i]) ) continue;
+    if( z[i]=='-' && z[i+1]=='-' ) return 1;
+    return 0;
+  }
+  return 1;
+}
+
+/*
+** Add a new entry to the EXPLAIN QUERY PLAN data
+*/
+static void eqp_append(ShellState *p, int iEqpId, int p2, const char *zText){
+  EQPGraphRow *pNew;
+  i64 nText;
+  if( zText==0 ) return;
+  nText = strlen(zText);
+  if( p->autoEQPtest ){
+    oputf("%d,%d,%s\n", iEqpId, p2, zText);
+  }
+  pNew = sqlite3_malloc64( sizeof(*pNew) + nText );
+  shell_check_oom(pNew);
+  pNew->iEqpId = iEqpId;
+  pNew->iParentId = p2;
+  memcpy(pNew->zText, zText, nText+1);
+  pNew->pNext = 0;
+  if( p->sGraph.pLast ){
+    p->sGraph.pLast->pNext = pNew;
+  }else{
+    p->sGraph.pRow = pNew;
+  }
+  p->sGraph.pLast = pNew;
+}
+
+/*
+** Free and reset the EXPLAIN QUERY PLAN data that has been collected
+** in p->sGraph.
+*/
+static void eqp_reset(ShellState *p){
+  EQPGraphRow *pRow, *pNext;
+  for(pRow = p->sGraph.pRow; pRow; pRow = pNext){
+    pNext = pRow->pNext;
+    sqlite3_free(pRow);
+  }
+  memset(&p->sGraph, 0, sizeof(p->sGraph));
+}
+
+/* Return the next EXPLAIN QUERY PLAN line with iEqpId that occurs after
+** pOld, or return the first such line if pOld is NULL
+*/
+static EQPGraphRow *eqp_next_row(ShellState *p, int iEqpId, EQPGraphRow *pOld){
+  EQPGraphRow *pRow = pOld ? pOld->pNext : p->sGraph.pRow;
+  while( pRow && pRow->iParentId!=iEqpId ) pRow = pRow->pNext;
+  return pRow;
+}
+
+/* Render a single level of the graph that has iEqpId as its parent.  Called
+** recursively to render sublevels.
+*/
+static void eqp_render_level(ShellState *p, int iEqpId){
+  EQPGraphRow *pRow, *pNext;
+  i64 n = strlen(p->sGraph.zPrefix);
+  char *z;
+  for(pRow = eqp_next_row(p, iEqpId, 0); pRow; pRow = pNext){
+    pNext = eqp_next_row(p, iEqpId, pRow);
+    z = pRow->zText;
+    oputf("%s%s%s\n", p->sGraph.zPrefix, pNext ? "|--" : "`--", z);
+    if( n<(i64)sizeof(p->sGraph.zPrefix)-7 ){
+      memcpy(&p->sGraph.zPrefix[n], pNext ? "|  " : "   ", 4);
+      eqp_render_level(p, pRow->iEqpId);
+      p->sGraph.zPrefix[n] = 0;
+    }
+  }
+}
+
+/*
+** Display and reset the EXPLAIN QUERY PLAN data
+*/
+static void eqp_render(ShellState *p, i64 nCycle){
+  EQPGraphRow *pRow = p->sGraph.pRow;
+  if( pRow ){
+    if( pRow->zText[0]=='-' ){
+      if( pRow->pNext==0 ){
+        eqp_reset(p);
+        return;
+      }
+      oputf("%s\n", pRow->zText+3);
+      p->sGraph.pRow = pRow->pNext;
+      sqlite3_free(pRow);
+    }else if( nCycle>0 ){
+      oputf("QUERY PLAN (cycles=%lld [100%%])\n", nCycle);
+    }else{
+      oputz("QUERY PLAN\n");
+    }
+    p->sGraph.zPrefix[0] = 0;
+    eqp_render_level(p, 0);
+    eqp_reset(p);
+  }
+}
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+/*
+** Progress handler callback.
+*/
+static int progress_handler(void *pClientData) {
+  ShellState *p = (ShellState*)pClientData;
+  p->nProgress++;
+  if( p->nProgress>=p->mxProgress && p->mxProgress>0 ){
+    oputf("Progress limit reached (%u)\n", p->nProgress);
+    if( p->flgProgress & SHELL_PROGRESS_RESET ) p->nProgress = 0;
+    if( p->flgProgress & SHELL_PROGRESS_ONCE ) p->mxProgress = 0;
+    return 1;
+  }
+  if( (p->flgProgress & SHELL_PROGRESS_QUIET)==0 ){
+    oputf("Progress %u\n", p->nProgress);
+  }
+  return 0;
+}
+#endif /* SQLITE_OMIT_PROGRESS_CALLBACK */
+
+/*
+** Print N dashes
+*/
+static void print_dashes(int N){
+  const char zDash[] = "--------------------------------------------------";
+  const int nDash = sizeof(zDash) - 1;
+  while( N>nDash ){
+    oputz(zDash);
+    N -= nDash;
+  }
+  oputf("%.*s", N, zDash);
+}
+
+/*
+** Print a markdown or table-style row separator using ascii-art
+*/
+static void print_row_separator(
+  ShellState *p,
+  int nArg,
+  const char *zSep
+){
+  int i;
+  if( nArg>0 ){
+    oputz(zSep);
+    print_dashes(p->actualWidth[0]+2);
+    for(i=1; i<nArg; i++){
+      oputz(zSep);
+      print_dashes(p->actualWidth[i]+2);
+    }
+    oputz(zSep);
+  }
+  oputz("\n");
+}
+
+/*
+** This is the callback routine that the shell
+** invokes for each row of a query result.
+*/
+static int shell_callback(
+  void *pArg,
+  int nArg,        /* Number of result columns */
+  char **azArg,    /* Text of each result column */
+  char **azCol,    /* Column names */
+  int *aiType      /* Column types.  Might be NULL */
+){
+  int i;
+  ShellState *p = (ShellState*)pArg;
+
+  if( azArg==0 ) return 0;
+  switch( p->cMode ){
+    case MODE_Count:
+    case MODE_Off: {
+      break;
+    }
+    case MODE_Line: {
+      int w = 5;
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        int len = strlen30(azCol[i] ? azCol[i] : "");
+        if( len>w ) w = len;
+      }
+      if( p->cnt++>0 ) oputz(p->rowSeparator);
+      for(i=0; i<nArg; i++){
+        oputf("%*s = %s%s", w, azCol[i],
+              azArg[i] ? azArg[i] : p->nullValue, p->rowSeparator);
+      }
+      break;
+    }
+    case MODE_ScanExp:
+    case MODE_Explain: {
+      static const int aExplainWidth[] = {4,       13, 4, 4, 4, 13, 2, 13};
+      static const int aExplainMap[] =   {0,       1,  2, 3, 4, 5,  6, 7 };
+      static const int aScanExpWidth[] = {4, 6, 6, 13, 4, 4, 4, 13, 2, 13};
+      static const int aScanExpMap[] =   {0, 9, 8, 1,  2, 3, 4, 5,  6, 7 };
+
+      const int *aWidth = aExplainWidth;
+      const int *aMap = aExplainMap;
+      int nWidth = ArraySize(aExplainWidth);
+      int iIndent = 1;
+
+      if( p->cMode==MODE_ScanExp ){
+        aWidth = aScanExpWidth;
+        aMap = aScanExpMap;
+        nWidth = ArraySize(aScanExpWidth);
+        iIndent = 3;
+      }
+      if( nArg>nWidth ) nArg = nWidth;
+
+      /* If this is the first row seen, print out the headers */
+      if( p->cnt++==0 ){
+        for(i=0; i<nArg; i++){
+          utf8_width_print(aWidth[i], azCol[ aMap[i] ]);
+          oputz(i==nArg-1 ? "\n" : "  ");
+        }
+        for(i=0; i<nArg; i++){
+          print_dashes(aWidth[i]);
+          oputz(i==nArg-1 ? "\n" : "  ");
+        }
+      }
+
+      /* If there is no data, exit early. */
+      if( azArg==0 ) break;
+
+      for(i=0; i<nArg; i++){
+        const char *zSep = "  ";
+        int w = aWidth[i];
+        const char *zVal = azArg[ aMap[i] ];
+        if( i==nArg-1 ) w = 0;
+        if( zVal && strlenChar(zVal)>w ){
+          w = strlenChar(zVal);
+          zSep = " ";
+        }
+        if( i==iIndent && p->aiIndent && p->pStmt ){
+          if( p->iIndent<p->nIndent ){
+            oputf("%*.s", p->aiIndent[p->iIndent], "");
+          }
+          p->iIndent++;
+        }
+        utf8_width_print(w, zVal ? zVal : p->nullValue);
+        oputz(i==nArg-1 ? "\n" : zSep);
+      }
+      break;
+    }
+    case MODE_Semi: {   /* .schema and .fullschema output */
+      printSchemaLine(azArg[0], ";\n");
+      break;
+    }
+    case MODE_Pretty: {  /* .schema and .fullschema with --indent */
+      char *z;
+      int j;
+      int nParen = 0;
+      char cEnd = 0;
+      char c;
+      int nLine = 0;
+      assert( nArg==1 );
+      if( azArg[0]==0 ) break;
+      if( sqlite3_strlike("CREATE VIEW%", azArg[0], 0)==0
+       || sqlite3_strlike("CREATE TRIG%", azArg[0], 0)==0
+      ){
+        oputf("%s;\n", azArg[0]);
+        break;
+      }
+      z = sqlite3_mprintf("%s", azArg[0]);
+      shell_check_oom(z);
+      j = 0;
+      for(i=0; IsSpace(z[i]); i++){}
+      for(; (c = z[i])!=0; i++){
+        if( IsSpace(c) ){
+          if( z[j-1]=='\r' ) z[j-1] = '\n';
+          if( IsSpace(z[j-1]) || z[j-1]=='(' ) continue;
+        }else if( (c=='(' || c==')') && j>0 && IsSpace(z[j-1]) ){
+          j--;
+        }
+        z[j++] = c;
+      }
+      while( j>0 && IsSpace(z[j-1]) ){ j--; }
+      z[j] = 0;
+      if( strlen30(z)>=79 ){
+        for(i=j=0; (c = z[i])!=0; i++){ /* Copy from z[i] back to z[j] */
+          if( c==cEnd ){
+            cEnd = 0;
+          }else if( c=='"' || c=='\'' || c=='`' ){
+            cEnd = c;
+          }else if( c=='[' ){
+            cEnd = ']';
+          }else if( c=='-' && z[i+1]=='-' ){
+            cEnd = '\n';
+          }else if( c=='(' ){
+            nParen++;
+          }else if( c==')' ){
+            nParen--;
+            if( nLine>0 && nParen==0 && j>0 ){
+              printSchemaLineN(z, j, "\n");
+              j = 0;
+            }
+          }
+          z[j++] = c;
+          if( nParen==1 && cEnd==0
+           && (c=='(' || c=='\n' || (c==',' && !wsToEol(z+i+1)))
+          ){
+            if( c=='\n' ) j--;
+            printSchemaLineN(z, j, "\n  ");
+            j = 0;
+            nLine++;
+            while( IsSpace(z[i+1]) ){ i++; }
+          }
+        }
+        z[j] = 0;
+      }
+      printSchemaLine(z, ";\n");
+      sqlite3_free(z);
+      break;
+    }
+    case MODE_List: {
+      if( p->cnt++==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          oputf("%s%s",azCol[i], i==nArg-1 ? p->rowSeparator : p->colSeparator);
+        }
+      }
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        char *z = azArg[i];
+        if( z==0 ) z = p->nullValue;
+        oputz(z);
+        oputz((i<nArg-1)? p->colSeparator : p->rowSeparator);
+      }
+      break;
+    }
+    case MODE_Html: {
+      if( p->cnt++==0 && p->showHeader ){
+        oputz("<TR>");
+        for(i=0; i<nArg; i++){
+          oputz("<TH>");
+          output_html_string(azCol[i]);
+          oputz("</TH>\n");
+        }
+        oputz("</TR>\n");
+      }
+      if( azArg==0 ) break;
+      oputz("<TR>");
+      for(i=0; i<nArg; i++){
+        oputz("<TD>");
+        output_html_string(azArg[i] ? azArg[i] : p->nullValue);
+        oputz("</TD>\n");
+      }
+      oputz("</TR>\n");
+      break;
+    }
+    case MODE_Tcl: {
+      if( p->cnt++==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          output_c_string(azCol[i] ? azCol[i] : "");
+          if(i<nArg-1) oputz(p->colSeparator);
+        }
+        oputz(p->rowSeparator);
+      }
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        output_c_string(azArg[i] ? azArg[i] : p->nullValue);
+        if(i<nArg-1) oputz(p->colSeparator);
+      }
+      oputz(p->rowSeparator);
+      break;
+    }
+    case MODE_Csv: {
+      setBinaryMode(p->out, 1);
+      if( p->cnt++==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          output_csv(p, azCol[i] ? azCol[i] : "", i<nArg-1);
+        }
+        oputz(p->rowSeparator);
+      }
+      if( nArg>0 ){
+        for(i=0; i<nArg; i++){
+          output_csv(p, azArg[i], i<nArg-1);
+        }
+        oputz(p->rowSeparator);
+      }
+      setTextMode(p->out, 1);
+      break;
+    }
+    case MODE_Insert: {
+      if( azArg==0 ) break;
+      oputf("INSERT INTO %s",p->zDestTable);
+      if( p->showHeader ){
+        oputz("(");
+        for(i=0; i<nArg; i++){
+          if( i>0 ) oputz(",");
+          if( quoteChar(azCol[i]) ){
+            char *z = sqlite3_mprintf("\"%w\"", azCol[i]);
+            shell_check_oom(z);
+            oputz(z);
+            sqlite3_free(z);
+          }else{
+            oputf("%s", azCol[i]);
+          }
+        }
+        oputz(")");
+      }
+      p->cnt++;
+      for(i=0; i<nArg; i++){
+        oputz(i>0 ? "," : " VALUES(");
+        if( (azArg[i]==0) || (aiType && aiType[i]==SQLITE_NULL) ){
+          oputz("NULL");
+        }else if( aiType && aiType[i]==SQLITE_TEXT ){
+          if( ShellHasFlag(p, SHFLG_Newlines) ){
+            output_quoted_string(azArg[i]);
+          }else{
+            output_quoted_escaped_string(azArg[i]);
+          }
+        }else if( aiType && aiType[i]==SQLITE_INTEGER ){
+          oputz(azArg[i]);
+        }else if( aiType && aiType[i]==SQLITE_FLOAT ){
+          char z[50];
+          double r = sqlite3_column_double(p->pStmt, i);
+          sqlite3_uint64 ur;
+          memcpy(&ur,&r,sizeof(r));
+          if( ur==0x7ff0000000000000LL ){
+            oputz("9.0e+999");
+          }else if( ur==0xfff0000000000000LL ){
+            oputz("-9.0e+999");
+          }else{
+            sqlite3_int64 ir = (sqlite3_int64)r;
+            if( r==(double)ir ){
+              sqlite3_snprintf(50,z,"%lld.0", ir);
+            }else{
+              sqlite3_snprintf(50,z,"%!.20g", r);
+            }
+            oputz(z);
+          }
+        }else if( aiType && aiType[i]==SQLITE_BLOB && p->pStmt ){
+          const void *pBlob = sqlite3_column_blob(p->pStmt, i);
+          int nBlob = sqlite3_column_bytes(p->pStmt, i);
+          output_hex_blob(pBlob, nBlob);
+        }else if( isNumber(azArg[i], 0) ){
+          oputz(azArg[i]);
+        }else if( ShellHasFlag(p, SHFLG_Newlines) ){
+          output_quoted_string(azArg[i]);
+        }else{
+          output_quoted_escaped_string(azArg[i]);
+        }
+      }
+      oputz(");\n");
+      break;
+    }
+    case MODE_Json: {
+      if( azArg==0 ) break;
+      if( p->cnt==0 ){
+        fputs("[{", p->out);
+      }else{
+        fputs(",\n{", p->out);
+      }
+      p->cnt++;
+      for(i=0; i<nArg; i++){
+        output_json_string(azCol[i], -1);
+        oputz(":");
+        if( (azArg[i]==0) || (aiType && aiType[i]==SQLITE_NULL) ){
+          oputz("null");
+        }else if( aiType && aiType[i]==SQLITE_FLOAT ){
+          char z[50];
+          double r = sqlite3_column_double(p->pStmt, i);
+          sqlite3_uint64 ur;
+          memcpy(&ur,&r,sizeof(r));
+          if( ur==0x7ff0000000000000LL ){
+            oputz("9.0e+999");
+          }else if( ur==0xfff0000000000000LL ){
+            oputz("-9.0e+999");
+          }else{
+            sqlite3_snprintf(50,z,"%!.20g", r);
+            oputz(z);
+          }
+        }else if( aiType && aiType[i]==SQLITE_BLOB && p->pStmt ){
+          const void *pBlob = sqlite3_column_blob(p->pStmt, i);
+          int nBlob = sqlite3_column_bytes(p->pStmt, i);
+          output_json_string(pBlob, nBlob);
+        }else if( aiType && aiType[i]==SQLITE_TEXT ){
+          output_json_string(azArg[i], -1);
+        }else{
+          oputz(azArg[i]);
+        }
+        if( i<nArg-1 ){
+          oputz(",");
+        }
+      }
+      oputz("}");
+      break;
+    }
+    case MODE_Quote: {
+      if( azArg==0 ) break;
+      if( p->cnt==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          if( i>0 ) fputs(p->colSeparator, p->out);
+          output_quoted_string(azCol[i]);
+        }
+        fputs(p->rowSeparator, p->out);
+      }
+      p->cnt++;
+      for(i=0; i<nArg; i++){
+        if( i>0 ) fputs(p->colSeparator, p->out);
+        if( (azArg[i]==0) || (aiType && aiType[i]==SQLITE_NULL) ){
+          oputz("NULL");
+        }else if( aiType && aiType[i]==SQLITE_TEXT ){
+          output_quoted_string(azArg[i]);
+        }else if( aiType && aiType[i]==SQLITE_INTEGER ){
+          oputz(azArg[i]);
+        }else if( aiType && aiType[i]==SQLITE_FLOAT ){
+          char z[50];
+          double r = sqlite3_column_double(p->pStmt, i);
+          sqlite3_snprintf(50,z,"%!.20g", r);
+          oputz(z);
+        }else if( aiType && aiType[i]==SQLITE_BLOB && p->pStmt ){
+          const void *pBlob = sqlite3_column_blob(p->pStmt, i);
+          int nBlob = sqlite3_column_bytes(p->pStmt, i);
+          output_hex_blob(pBlob, nBlob);
+        }else if( isNumber(azArg[i], 0) ){
+          oputz(azArg[i]);
+        }else{
+          output_quoted_string(azArg[i]);
+        }
+      }
+      fputs(p->rowSeparator, p->out);
+      break;
+    }
+    case MODE_Ascii: {
+      if( p->cnt++==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          if( i>0 ) oputz(p->colSeparator);
+          oputz(azCol[i] ? azCol[i] : "");
+        }
+        oputz(p->rowSeparator);
+      }
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        if( i>0 ) oputz(p->colSeparator);
+        oputz(azArg[i] ? azArg[i] : p->nullValue);
+      }
+      oputz(p->rowSeparator);
+      break;
+    }
+    case MODE_EQP: {
+      eqp_append(p, atoi(azArg[0]), atoi(azArg[1]), azArg[3]);
+      break;
+    }
+  }
+  return 0;
+}
+
+/*
+** This is the callback routine that the SQLite library
+** invokes for each row of a query result.
+*/
+static int callback(void *pArg, int nArg, char **azArg, char **azCol){
+  /* since we don't have type info, call the shell_callback with a NULL value */
+  return shell_callback(pArg, nArg, azArg, azCol, NULL);
+}
+
+/*
+** This is the callback routine from sqlite3_exec() that appends all
+** output onto the end of a ShellText object.
+*/
+static int captureOutputCallback(void *pArg, int nArg, char **azArg, char **az){
+  ShellText *p = (ShellText*)pArg;
+  int i;
+  UNUSED_PARAMETER(az);
+  if( azArg==0 ) return 0;
+  if( p->n ) appendText(p, "|", 0);
+  for(i=0; i<nArg; i++){
+    if( i ) appendText(p, ",", 0);
+    if( azArg[i] ) appendText(p, azArg[i], 0);
+  }
+  return 0;
+}
+
+/*
+** Generate an appropriate SELFTEST table in the main database.
+*/
+static void createSelftestTable(ShellState *p){
+  char *zErrMsg = 0;
+  sqlite3_exec(p->db,
+    "SAVEPOINT selftest_init;\n"
+    "CREATE TABLE IF NOT EXISTS selftest(\n"
+    "  tno INTEGER PRIMARY KEY,\n"   /* Test number */
+    "  op TEXT,\n"                   /* Operator:  memo run */
+    "  cmd TEXT,\n"                  /* Command text */
+    "  ans TEXT\n"                   /* Desired answer */
+    ");"
+    "CREATE TEMP TABLE [_shell$self](op,cmd,ans);\n"
+    "INSERT INTO [_shell$self](rowid,op,cmd)\n"
+    "  VALUES(coalesce((SELECT (max(tno)+100)/10 FROM selftest),10),\n"
+    "         'memo','Tests generated by --init');\n"
+    "INSERT INTO [_shell$self]\n"
+    "  SELECT 'run',\n"
+    "    'SELECT hex(sha3_query(''SELECT type,name,tbl_name,sql "
+                                 "FROM sqlite_schema ORDER BY 2'',224))',\n"
+    "    hex(sha3_query('SELECT type,name,tbl_name,sql "
+                          "FROM sqlite_schema ORDER BY 2',224));\n"
+    "INSERT INTO [_shell$self]\n"
+    "  SELECT 'run',"
+    "    'SELECT hex(sha3_query(''SELECT * FROM \"' ||"
+    "        printf('%w',name) || '\" NOT INDEXED'',224))',\n"
+    "    hex(sha3_query(printf('SELECT * FROM \"%w\" NOT INDEXED',name),224))\n"
+    "  FROM (\n"
+    "    SELECT name FROM sqlite_schema\n"
+    "     WHERE type='table'\n"
+    "       AND name<>'selftest'\n"
+    "       AND coalesce(rootpage,0)>0\n"
+    "  )\n"
+    " ORDER BY name;\n"
+    "INSERT INTO [_shell$self]\n"
+    "  VALUES('run','PRAGMA integrity_check','ok');\n"
+    "INSERT INTO selftest(tno,op,cmd,ans)"
+    "  SELECT rowid*10,op,cmd,ans FROM [_shell$self];\n"
+    "DROP TABLE [_shell$self];"
+    ,0,0,&zErrMsg);
+  if( zErrMsg ){
+    eputf("SELFTEST initialization failure: %s\n", zErrMsg);
+    sqlite3_free(zErrMsg);
+  }
+  sqlite3_exec(p->db, "RELEASE selftest_init",0,0,0);
+}
+
+
+/*
+** Set the destination table field of the ShellState structure to
+** the name of the table given.  Escape any quote characters in the
+** table name.
+*/
+static void set_table_name(ShellState *p, const char *zName){
+  int i, n;
+  char cQuote;
+  char *z;
+
+  if( p->zDestTable ){
+    free(p->zDestTable);
+    p->zDestTable = 0;
+  }
+  if( zName==0 ) return;
+  cQuote = quoteChar(zName);
+  n = strlen30(zName);
+  if( cQuote ) n += n+2;
+  z = p->zDestTable = malloc( n+1 );
+  shell_check_oom(z);
+  n = 0;
+  if( cQuote ) z[n++] = cQuote;
+  for(i=0; zName[i]; i++){
+    z[n++] = zName[i];
+    if( zName[i]==cQuote ) z[n++] = cQuote;
+  }
+  if( cQuote ) z[n++] = cQuote;
+  z[n] = 0;
+}
+
+/*
+** Maybe construct two lines of text that point out the position of a
+** syntax error.  Return a pointer to the text, in memory obtained from
+** sqlite3_malloc().  Or, if the most recent error does not involve a
+** specific token that we can point to, return an empty string.
+**
+** In all cases, the memory returned is obtained from sqlite3_malloc64()
+** and should be released by the caller invoking sqlite3_free().
+*/
+static char *shell_error_context(const char *zSql, sqlite3 *db){
+  int iOffset;
+  size_t len;
+  char *zCode;
+  char *zMsg;
+  int i;
+  if( db==0
+   || zSql==0
+   || (iOffset = sqlite3_error_offset(db))<0
+   || iOffset>=(int)strlen(zSql)
+  ){
+    return sqlite3_mprintf("");
+  }
+  while( iOffset>50 ){
+    iOffset--;
+    zSql++;
+    while( (zSql[0]&0xc0)==0x80 ){ zSql++; iOffset--; }
+  }
+  len = strlen(zSql);
+  if( len>78 ){
+    len = 78;
+    while( len>0 && (zSql[len]&0xc0)==0x80 ) len--;
+  }
+  zCode = sqlite3_mprintf("%.*s", len, zSql);
+  shell_check_oom(zCode);
+  for(i=0; zCode[i]; i++){ if( IsSpace(zSql[i]) ) zCode[i] = ' '; }
+  if( iOffset<25 ){
+    zMsg = sqlite3_mprintf("\n  %z\n  %*s^--- error here", zCode,iOffset,"");
+  }else{
+    zMsg = sqlite3_mprintf("\n  %z\n  %*serror here ---^", zCode,iOffset-14,"");
+  }
+  return zMsg;
+}
+
+
+/*
+** Execute a query statement that will generate SQL output.  Print
+** the result columns, comma-separated, on a line and then add a
+** semicolon terminator to the end of that line.
+**
+** If the number of columns is 1 and that column contains text "--"
+** then write the semicolon on a separate line.  That way, if a
+** "--" comment occurs at the end of the statement, the comment
+** won't consume the semicolon terminator.
+*/
+static int run_table_dump_query(
+  ShellState *p,           /* Query context */
+  const char *zSelect      /* SELECT statement to extract content */
+){
+  sqlite3_stmt *pSelect;
+  int rc;
+  int nResult;
+  int i;
+  const char *z;
+  rc = sqlite3_prepare_v2(p->db, zSelect, -1, &pSelect, 0);
+  if( rc!=SQLITE_OK || !pSelect ){
+    char *zContext = shell_error_context(zSelect, p->db);
+    oputf("/**** ERROR: (%d) %s *****/\n%s",
+          rc, sqlite3_errmsg(p->db), zContext);
+    sqlite3_free(zContext);
+    if( (rc&0xff)!=SQLITE_CORRUPT ) p->nErr++;
+    return rc;
+  }
+  rc = sqlite3_step(pSelect);
+  nResult = sqlite3_column_count(pSelect);
+  while( rc==SQLITE_ROW ){
+    z = (const char*)sqlite3_column_text(pSelect, 0);
+    oputf("%s", z);
+    for(i=1; i<nResult; i++){
+      oputf(",%s", sqlite3_column_text(pSelect, i));
+    }
+    if( z==0 ) z = "";
+    while( z[0] && (z[0]!='-' || z[1]!='-') ) z++;
+    if( z[0] ){
+      oputz("\n;\n");
+    }else{
+      oputz(";\n");
+    }
+    rc = sqlite3_step(pSelect);
+  }
+  rc = sqlite3_finalize(pSelect);
+  if( rc!=SQLITE_OK ){
+    oputf("/**** ERROR: (%d) %s *****/\n", rc, sqlite3_errmsg(p->db));
+    if( (rc&0xff)!=SQLITE_CORRUPT ) p->nErr++;
+  }
+  return rc;
+}
+
+/*
+** Allocate space and save off string indicating current error.
+*/
+static char *save_err_msg(
+  sqlite3 *db,           /* Database to query */
+  const char *zPhase,    /* When the error occurs */
+  int rc,                /* Error code returned from API */
+  const char *zSql       /* SQL string, or NULL */
+){
+  char *zErr;
+  char *zContext;
+  sqlite3_str *pStr = sqlite3_str_new(0);
+  sqlite3_str_appendf(pStr, "%s, %s", zPhase, sqlite3_errmsg(db));
+  if( rc>1 ){
+    sqlite3_str_appendf(pStr, " (%d)", rc);
+  }
+  zContext = shell_error_context(zSql, db);
+  if( zContext ){
+    sqlite3_str_appendall(pStr, zContext);
+    sqlite3_free(zContext);
+  }
+  zErr = sqlite3_str_finish(pStr);
+  shell_check_oom(zErr);
+  return zErr;
+}
+
+#ifdef __linux__
+/*
+** Attempt to display I/O stats on Linux using /proc/PID/io
+*/
+static void displayLinuxIoStats(void){
+  FILE *in;
+  char z[200];
+  sqlite3_snprintf(sizeof(z), z, "/proc/%d/io", getpid());
+  in = fopen(z, "rb");
+  if( in==0 ) return;
+  while( fgets(z, sizeof(z), in)!=0 ){
+    static const struct {
+      const char *zPattern;
+      const char *zDesc;
+    } aTrans[] = {
+      { "rchar: ",                  "Bytes received by read():" },
+      { "wchar: ",                  "Bytes sent to write():"    },
+      { "syscr: ",                  "Read() system calls:"      },
+      { "syscw: ",                  "Write() system calls:"     },
+      { "read_bytes: ",             "Bytes read from storage:"  },
+      { "write_bytes: ",            "Bytes written to storage:" },
+      { "cancelled_write_bytes: ",  "Cancelled write bytes:"    },
+    };
+    int i;
+    for(i=0; i<ArraySize(aTrans); i++){
+      int n = strlen30(aTrans[i].zPattern);
+      if( cli_strncmp(aTrans[i].zPattern, z, n)==0 ){
+        oputf("%-36s %s", aTrans[i].zDesc, &z[n]);
+        break;
+      }
+    }
+  }
+  fclose(in);
+}
+#endif
+
+/*
+** Display a single line of status using 64-bit values.
+*/
+static void displayStatLine(
+  char *zLabel,             /* Label for this one line */
+  char *zFormat,            /* Format for the result */
+  int iStatusCtrl,          /* Which status to display */
+  int bReset                /* True to reset the stats */
+){
+  sqlite3_int64 iCur = -1;
+  sqlite3_int64 iHiwtr = -1;
+  int i, nPercent;
+  char zLine[200];
+  sqlite3_status64(iStatusCtrl, &iCur, &iHiwtr, bReset);
+  for(i=0, nPercent=0; zFormat[i]; i++){
+    if( zFormat[i]=='%' ) nPercent++;
+  }
+  if( nPercent>1 ){
+    sqlite3_snprintf(sizeof(zLine), zLine, zFormat, iCur, iHiwtr);
+  }else{
+    sqlite3_snprintf(sizeof(zLine), zLine, zFormat, iHiwtr);
+  }
+  oputf("%-36s %s\n", zLabel, zLine);
+}
+
+/*
+** Display memory stats.
+*/
+static int display_stats(
+  sqlite3 *db,                /* Database to query */
+  ShellState *pArg,           /* Pointer to ShellState */
+  int bReset                  /* True to reset the stats */
+){
+  int iCur;
+  int iHiwtr;
+  if( pArg==0 || pArg->out==0 ) return 0;
+
+  if( pArg->pStmt && pArg->statsOn==2 ){
+    int nCol, i, x;
+    sqlite3_stmt *pStmt = pArg->pStmt;
+    char z[100];
+    nCol = sqlite3_column_count(pStmt);
+    oputf("%-36s %d\n", "Number of output columns:", nCol);
+    for(i=0; i<nCol; i++){
+      sqlite3_snprintf(sizeof(z),z,"Column %d %nname:", i, &x);
+      oputf("%-36s %s\n", z, sqlite3_column_name(pStmt,i));
+#ifndef SQLITE_OMIT_DECLTYPE
+      sqlite3_snprintf(30, z+x, "declared type:");
+      oputf("%-36s %s\n", z, sqlite3_column_decltype(pStmt, i));
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+      sqlite3_snprintf(30, z+x, "database name:");
+      oputf("%-36s %s\n", z, sqlite3_column_database_name(pStmt,i));
+      sqlite3_snprintf(30, z+x, "table name:");
+      oputf("%-36s %s\n", z, sqlite3_column_table_name(pStmt,i));
+      sqlite3_snprintf(30, z+x, "origin name:");
+      oputf("%-36s %s\n", z, sqlite3_column_origin_name(pStmt,i));
+#endif
+    }
+  }
+
+  if( pArg->statsOn==3 ){
+    if( pArg->pStmt ){
+      iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_VM_STEP,bReset);
+      oputf("VM-steps: %d\n", iCur);
+    }
+    return 0;
+  }
+
+  displayStatLine("Memory Used:",
+     "%lld (max %lld) bytes", SQLITE_STATUS_MEMORY_USED, bReset);
+  displayStatLine("Number of Outstanding Allocations:",
+     "%lld (max %lld)", SQLITE_STATUS_MALLOC_COUNT, bReset);
+  if( pArg->shellFlgs & SHFLG_Pagecache ){
+    displayStatLine("Number of Pcache Pages Used:",
+       "%lld (max %lld) pages", SQLITE_STATUS_PAGECACHE_USED, bReset);
+  }
+  displayStatLine("Number of Pcache Overflow Bytes:",
+     "%lld (max %lld) bytes", SQLITE_STATUS_PAGECACHE_OVERFLOW, bReset);
+  displayStatLine("Largest Allocation:",
+     "%lld bytes", SQLITE_STATUS_MALLOC_SIZE, bReset);
+  displayStatLine("Largest Pcache Allocation:",
+     "%lld bytes", SQLITE_STATUS_PAGECACHE_SIZE, bReset);
+#ifdef YYTRACKMAXSTACKDEPTH
+  displayStatLine("Deepest Parser Stack:",
+     "%lld (max %lld)", SQLITE_STATUS_PARSER_STACK, bReset);
+#endif
+
+  if( db ){
+    if( pArg->shellFlgs & SHFLG_Lookaside ){
+      iHiwtr = iCur = -1;
+      sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_USED,
+                        &iCur, &iHiwtr, bReset);
+      oputf("Lookaside Slots Used:                %d (max %d)\n", iCur, iHiwtr);
+      sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_HIT,
+                        &iCur, &iHiwtr, bReset);
+      oputf("Successful lookaside attempts:       %d\n", iHiwtr);
+      sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE,
+                        &iCur, &iHiwtr, bReset);
+      oputf("Lookaside failures due to size:      %d\n", iHiwtr);
+      sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL,
+                        &iCur, &iHiwtr, bReset);
+      oputf("Lookaside failures due to OOM:       %d\n", iHiwtr);
+    }
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_USED, &iCur, &iHiwtr, bReset);
+    oputf("Pager Heap Usage:                    %d bytes\n", iCur);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_HIT, &iCur, &iHiwtr, 1);
+    oputf("Page cache hits:                     %d\n", iCur);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_MISS, &iCur, &iHiwtr, 1);
+    oputf("Page cache misses:                   %d\n", iCur);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_WRITE, &iCur, &iHiwtr, 1);
+    oputf("Page cache writes:                   %d\n", iCur);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_SPILL, &iCur, &iHiwtr, 1);
+    oputf("Page cache spills:                   %d\n", iCur);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_SCHEMA_USED, &iCur, &iHiwtr, bReset);
+    oputf("Schema Heap Usage:                   %d bytes\n", iCur);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_STMT_USED, &iCur, &iHiwtr, bReset);
+    oputf("Statement Heap/Lookaside Usage:      %d bytes\n", iCur);
+  }
+
+  if( pArg->pStmt ){
+    int iHit, iMiss;
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_FULLSCAN_STEP,
+                               bReset);
+    oputf("Fullscan Steps:                      %d\n", iCur);
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_SORT, bReset);
+    oputf("Sort Operations:                     %d\n", iCur);
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_AUTOINDEX,bReset);
+    oputf("Autoindex Inserts:                   %d\n", iCur);
+    iHit = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_FILTER_HIT,
+                               bReset);
+    iMiss = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_FILTER_MISS,
+                                bReset);
+    if( iHit || iMiss ){
+      oputf("Bloom filter bypass taken:           %d/%d\n", iHit, iHit+iMiss);
+    }
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_VM_STEP, bReset);
+    oputf("Virtual Machine Steps:               %d\n", iCur);
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_REPREPARE,bReset);
+    oputf("Reprepare operations:                %d\n", iCur);
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_RUN, bReset);
+    oputf("Number of times run:                 %d\n", iCur);
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_MEMUSED, bReset);
+    oputf("Memory used by prepared stmt:        %d\n", iCur);
+  }
+
+#ifdef __linux__
+  displayLinuxIoStats();
+#endif
+
+  /* Do not remove this machine readable comment: extra-stats-output-here */
+
+  return 0;
+}
+
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+static int scanStatsHeight(sqlite3_stmt *p, int iEntry){
+  int iPid = 0;
+  int ret = 1;
+  sqlite3_stmt_scanstatus_v2(p, iEntry,
+      SQLITE_SCANSTAT_SELECTID, SQLITE_SCANSTAT_COMPLEX, (void*)&iPid
+  );
+  while( iPid!=0 ){
+    int ii;
+    for(ii=0; 1; ii++){
+      int iId;
+      int res;
+      res = sqlite3_stmt_scanstatus_v2(p, ii,
+          SQLITE_SCANSTAT_SELECTID, SQLITE_SCANSTAT_COMPLEX, (void*)&iId
+      );
+      if( res ) break;
+      if( iId==iPid ){
+        sqlite3_stmt_scanstatus_v2(p, ii,
+            SQLITE_SCANSTAT_PARENTID, SQLITE_SCANSTAT_COMPLEX, (void*)&iPid
+        );
+      }
+    }
+    ret++;
+  }
+  return ret;
+}
+#endif
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+static void display_explain_scanstats(
+  sqlite3 *db,                    /* Database to query */
+  ShellState *pArg                /* Pointer to ShellState */
+){
+  static const int f = SQLITE_SCANSTAT_COMPLEX;
+  sqlite3_stmt *p = pArg->pStmt;
+  int ii = 0;
+  i64 nTotal = 0;
+  int nWidth = 0;
+  eqp_reset(pArg);
+
+  for(ii=0; 1; ii++){
+    const char *z = 0;
+    int n = 0;
+    if( sqlite3_stmt_scanstatus_v2(p,ii,SQLITE_SCANSTAT_EXPLAIN,f,(void*)&z) ){
+      break;
+    }
+    n = (int)strlen(z) + scanStatsHeight(p, ii)*3;
+    if( n>nWidth ) nWidth = n;
+  }
+  nWidth += 4;
+
+  sqlite3_stmt_scanstatus_v2(p, -1, SQLITE_SCANSTAT_NCYCLE, f, (void*)&nTotal);
+  for(ii=0; 1; ii++){
+    i64 nLoop = 0;
+    i64 nRow = 0;
+    i64 nCycle = 0;
+    int iId = 0;
+    int iPid = 0;
+    const char *zo = 0;
+    const char *zName = 0;
+    char *zText = 0;
+    double rEst = 0.0;
+
+    if( sqlite3_stmt_scanstatus_v2(p,ii,SQLITE_SCANSTAT_EXPLAIN,f,(void*)&zo) ){
+      break;
+    }
+    sqlite3_stmt_scanstatus_v2(p, ii, SQLITE_SCANSTAT_EST,f,(void*)&rEst);
+    sqlite3_stmt_scanstatus_v2(p, ii, SQLITE_SCANSTAT_NLOOP,f,(void*)&nLoop);
+    sqlite3_stmt_scanstatus_v2(p, ii, SQLITE_SCANSTAT_NVISIT,f,(void*)&nRow);
+    sqlite3_stmt_scanstatus_v2(p, ii, SQLITE_SCANSTAT_NCYCLE,f,(void*)&nCycle);
+    sqlite3_stmt_scanstatus_v2(p, ii, SQLITE_SCANSTAT_SELECTID,f,(void*)&iId);
+    sqlite3_stmt_scanstatus_v2(p, ii, SQLITE_SCANSTAT_PARENTID,f,(void*)&iPid);
+    sqlite3_stmt_scanstatus_v2(p, ii, SQLITE_SCANSTAT_NAME,f,(void*)&zName);
+
+    zText = sqlite3_mprintf("%s", zo);
+    if( nCycle>=0 || nLoop>=0 || nRow>=0 ){
+      char *z = 0;
+      if( nCycle>=0 && nTotal>0 ){
+        z = sqlite3_mprintf("%zcycles=%lld [%d%%]", z,
+            nCycle, ((nCycle*100)+nTotal/2) / nTotal
+        );
+      }
+      if( nLoop>=0 ){
+        z = sqlite3_mprintf("%z%sloops=%lld", z, z ? " " : "", nLoop);
+      }
+      if( nRow>=0 ){
+        z = sqlite3_mprintf("%z%srows=%lld", z, z ? " " : "", nRow);
+      }
+
+      if( zName && pArg->scanstatsOn>1 ){
+        double rpl = (double)nRow / (double)nLoop;
+        z = sqlite3_mprintf("%z rpl=%.1f est=%.1f", z, rpl, rEst);
+      }
+
+      zText = sqlite3_mprintf(
+          "% *z (%z)", -1*(nWidth-scanStatsHeight(p, ii)*3), zText, z
+      );
+    }
+
+    eqp_append(pArg, iId, iPid, zText);
+    sqlite3_free(zText);
+  }
+
+  eqp_render(pArg, nTotal);
+}
+#endif
+
+
+/*
+** Parameter azArray points to a zero-terminated array of strings. zStr
+** points to a single nul-terminated string. Return non-zero if zStr
+** is equal, according to strcmp(), to any of the strings in the array.
+** Otherwise, return zero.
+*/
+static int str_in_array(const char *zStr, const char **azArray){
+  int i;
+  for(i=0; azArray[i]; i++){
+    if( 0==cli_strcmp(zStr, azArray[i]) ) return 1;
+  }
+  return 0;
+}
+
+/*
+** If compiled statement pSql appears to be an EXPLAIN statement, allocate
+** and populate the ShellState.aiIndent[] array with the number of
+** spaces each opcode should be indented before it is output.
+**
+** The indenting rules are:
+**
+**     * For each "Next", "Prev", "VNext" or "VPrev" instruction, indent
+**       all opcodes that occur between the p2 jump destination and the opcode
+**       itself by 2 spaces.
+**
+**     * Do the previous for "Return" instructions for when P2 is positive.
+**       See tag-20220407a in wherecode.c and vdbe.c.
+**
+**     * For each "Goto", if the jump destination is earlier in the program
+**       and ends on one of:
+**          Yield  SeekGt  SeekLt  RowSetRead  Rewind
+**       or if the P1 parameter is one instead of zero,
+**       then indent all opcodes between the earlier instruction
+**       and "Goto" by 2 spaces.
+*/
+static void explain_data_prepare(ShellState *p, sqlite3_stmt *pSql){
+  int *abYield = 0;               /* True if op is an OP_Yield */
+  int nAlloc = 0;                 /* Allocated size of p->aiIndent[], abYield */
+  int iOp;                        /* Index of operation in p->aiIndent[] */
+
+  const char *azNext[] = { "Next", "Prev", "VPrev", "VNext", "SorterNext",
+                           "Return", 0 };
+  const char *azYield[] = { "Yield", "SeekLT", "SeekGT", "RowSetRead",
+                            "Rewind", 0 };
+  const char *azGoto[] = { "Goto", 0 };
+
+  /* The caller guarantees that the leftmost 4 columns of the statement
+  ** passed to this function are equivalent to the leftmost 4 columns
+  ** of EXPLAIN statement output. In practice the statement may be
+  ** an EXPLAIN, or it may be a query on the bytecode() virtual table.  */
+  assert( sqlite3_column_count(pSql)>=4 );
+  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 0), "addr" ) );
+  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 1), "opcode" ) );
+  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 2), "p1" ) );
+  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 3), "p2" ) );
+
+  for(iOp=0; SQLITE_ROW==sqlite3_step(pSql); iOp++){
+    int i;
+    int iAddr = sqlite3_column_int(pSql, 0);
+    const char *zOp = (const char*)sqlite3_column_text(pSql, 1);
+    int p1 = sqlite3_column_int(pSql, 2);
+    int p2 = sqlite3_column_int(pSql, 3);
+
+    /* Assuming that p2 is an instruction address, set variable p2op to the
+    ** index of that instruction in the aiIndent[] array. p2 and p2op may be
+    ** different if the current instruction is part of a sub-program generated
+    ** by an SQL trigger or foreign key.  */
+    int p2op = (p2 + (iOp-iAddr));
+
+    /* Grow the p->aiIndent array as required */
+    if( iOp>=nAlloc ){
+      nAlloc += 100;
+      p->aiIndent = (int*)sqlite3_realloc64(p->aiIndent, nAlloc*sizeof(int));
+      shell_check_oom(p->aiIndent);
+      abYield = (int*)sqlite3_realloc64(abYield, nAlloc*sizeof(int));
+      shell_check_oom(abYield);
+    }
+
+    abYield[iOp] = str_in_array(zOp, azYield);
+    p->aiIndent[iOp] = 0;
+    p->nIndent = iOp+1;
+    if( str_in_array(zOp, azNext) && p2op>0 ){
+      for(i=p2op; i<iOp; i++) p->aiIndent[i] += 2;
+    }
+    if( str_in_array(zOp, azGoto) && p2op<iOp && (abYield[p2op] || p1) ){
+      for(i=p2op; i<iOp; i++) p->aiIndent[i] += 2;
+    }
+  }
+
+  p->iIndent = 0;
+  sqlite3_free(abYield);
+  sqlite3_reset(pSql);
+}
+
+/*
+** Free the array allocated by explain_data_prepare().
+*/
+static void explain_data_delete(ShellState *p){
+  sqlite3_free(p->aiIndent);
+  p->aiIndent = 0;
+  p->nIndent = 0;
+  p->iIndent = 0;
+}
+
+static void exec_prepared_stmt(ShellState*, sqlite3_stmt*);
+
+/*
+** Display scan stats.
+*/
+static void display_scanstats(
+  sqlite3 *db,                    /* Database to query */
+  ShellState *pArg                /* Pointer to ShellState */
+){
+#ifndef SQLITE_ENABLE_STMT_SCANSTATUS
+  UNUSED_PARAMETER(db);
+  UNUSED_PARAMETER(pArg);
+#else
+  if( pArg->scanstatsOn==3 ){
+    const char *zSql =
+      "  SELECT addr, opcode, p1, p2, p3, p4, p5, comment, nexec,"
+      "   round(ncycle*100.0 / (sum(ncycle) OVER ()), 2)||'%' AS cycles"
+      "   FROM bytecode(?)";
+
+    int rc = SQLITE_OK;
+    sqlite3_stmt *pStmt = 0;
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_stmt *pSave = pArg->pStmt;
+      pArg->pStmt = pStmt;
+      sqlite3_bind_pointer(pStmt, 1, pSave, "stmt-pointer", 0);
+
+      pArg->cnt = 0;
+      pArg->cMode = MODE_ScanExp;
+      explain_data_prepare(pArg, pStmt);
+      exec_prepared_stmt(pArg, pStmt);
+      explain_data_delete(pArg);
+
+      sqlite3_finalize(pStmt);
+      pArg->pStmt = pSave;
+    }
+  }else{
+    display_explain_scanstats(db, pArg);
+  }
+#endif
+}
+
+/*
+** Disable and restore .wheretrace and .treetrace/.selecttrace settings.
+*/
+static unsigned int savedSelectTrace;
+static unsigned int savedWhereTrace;
+static void disable_debug_trace_modes(void){
+  unsigned int zero = 0;
+  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 0, &savedSelectTrace);
+  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 1, &zero);
+  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 2, &savedWhereTrace);
+  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 3, &zero);
+}
+static void restore_debug_trace_modes(void){
+  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 1, &savedSelectTrace);
+  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 3, &savedWhereTrace);
+}
+
+/* Create the TEMP table used to store parameter bindings */
+static void bind_table_init(ShellState *p){
+  int wrSchema = 0;
+  int defensiveMode = 0;
+  sqlite3_db_config(p->db, SQLITE_DBCONFIG_DEFENSIVE, -1, &defensiveMode);
+  sqlite3_db_config(p->db, SQLITE_DBCONFIG_DEFENSIVE, 0, 0);
+  sqlite3_db_config(p->db, SQLITE_DBCONFIG_WRITABLE_SCHEMA, -1, &wrSchema);
+  sqlite3_db_config(p->db, SQLITE_DBCONFIG_WRITABLE_SCHEMA, 1, 0);
+  sqlite3_exec(p->db,
+    "CREATE TABLE IF NOT EXISTS temp.sqlite_parameters(\n"
+    "  key TEXT PRIMARY KEY,\n"
+    "  value\n"
+    ") WITHOUT ROWID;",
+    0, 0, 0);
+  sqlite3_db_config(p->db, SQLITE_DBCONFIG_WRITABLE_SCHEMA, wrSchema, 0);
+  sqlite3_db_config(p->db, SQLITE_DBCONFIG_DEFENSIVE, defensiveMode, 0);
+}
+
+/*
+** Bind parameters on a prepared statement.
+**
+** Parameter bindings are taken from a TEMP table of the form:
+**
+**    CREATE TEMP TABLE sqlite_parameters(key TEXT PRIMARY KEY, value)
+**    WITHOUT ROWID;
+**
+** No bindings occur if this table does not exist.  The name of the table
+** begins with "sqlite_" so that it will not collide with ordinary application
+** tables.  The table must be in the TEMP schema.
+*/
+static void bind_prepared_stmt(ShellState *pArg, sqlite3_stmt *pStmt){
+  int nVar;
+  int i;
+  int rc;
+  sqlite3_stmt *pQ = 0;
+
+  nVar = sqlite3_bind_parameter_count(pStmt);
+  if( nVar==0 ) return;  /* Nothing to do */
+  if( sqlite3_table_column_metadata(pArg->db, "TEMP", "sqlite_parameters",
+                                    "key", 0, 0, 0, 0, 0)!=SQLITE_OK ){
+    rc = SQLITE_NOTFOUND;
+    pQ = 0;
+  }else{
+    rc = sqlite3_prepare_v2(pArg->db,
+            "SELECT value FROM temp.sqlite_parameters"
+            " WHERE key=?1", -1, &pQ, 0);
+  }
+  for(i=1; i<=nVar; i++){
+    char zNum[30];
+    const char *zVar = sqlite3_bind_parameter_name(pStmt, i);
+    if( zVar==0 ){
+      sqlite3_snprintf(sizeof(zNum),zNum,"?%d",i);
+      zVar = zNum;
+    }
+    sqlite3_bind_text(pQ, 1, zVar, -1, SQLITE_STATIC);
+    if( rc==SQLITE_OK && pQ && sqlite3_step(pQ)==SQLITE_ROW ){
+      sqlite3_bind_value(pStmt, i, sqlite3_column_value(pQ, 0));
+#ifdef NAN
+    }else if( sqlite3_strlike("_NAN", zVar, 0)==0 ){
+      sqlite3_bind_double(pStmt, i, NAN);
+#endif
+#ifdef INFINITY
+    }else if( sqlite3_strlike("_INF", zVar, 0)==0 ){
+      sqlite3_bind_double(pStmt, i, INFINITY);
+#endif
+    }else{
+      sqlite3_bind_null(pStmt, i);
+    }
+    sqlite3_reset(pQ);
+  }
+  sqlite3_finalize(pQ);
+}
+
+/*
+** UTF8 box-drawing characters.  Imagine box lines like this:
+**
+**           1
+**           |
+**       4 --+-- 2
+**           |
+**           3
+**
+** Each box characters has between 2 and 4 of the lines leading from
+** the center.  The characters are here identified by the numbers of
+** their corresponding lines.
+*/
+#define BOX_24   "\342\224\200"  /* U+2500 --- */
+#define BOX_13   "\342\224\202"  /* U+2502  |  */
+#define BOX_23   "\342\224\214"  /* U+250c  ,- */
+#define BOX_34   "\342\224\220"  /* U+2510 -,  */
+#define BOX_12   "\342\224\224"  /* U+2514  '- */
+#define BOX_14   "\342\224\230"  /* U+2518 -'  */
+#define BOX_123  "\342\224\234"  /* U+251c  |- */
+#define BOX_134  "\342\224\244"  /* U+2524 -|  */
+#define BOX_234  "\342\224\254"  /* U+252c -,- */
+#define BOX_124  "\342\224\264"  /* U+2534 -'- */
+#define BOX_1234 "\342\224\274"  /* U+253c -|- */
+
+/* Draw horizontal line N characters long using unicode box
+** characters
+*/
+static void print_box_line(int N){
+  const char zDash[] =
+      BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24
+      BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24 BOX_24;
+  const int nDash = sizeof(zDash) - 1;
+  N *= 3;
+  while( N>nDash ){
+    oputz(zDash);
+    N -= nDash;
+  }
+  oputf("%.*s", N, zDash);
+}
+
+/*
+** Draw a horizontal separator for a MODE_Box table.
+*/
+static void print_box_row_separator(
+  ShellState *p,
+  int nArg,
+  const char *zSep1,
+  const char *zSep2,
+  const char *zSep3
+){
+  int i;
+  if( nArg>0 ){
+    oputz(zSep1);
+    print_box_line(p->actualWidth[0]+2);
+    for(i=1; i<nArg; i++){
+      oputz(zSep2);
+      print_box_line(p->actualWidth[i]+2);
+    }
+    oputz(zSep3);
+  }
+  oputz("\n");
+}
+
+/*
+** z[] is a line of text that is to be displayed the .mode box or table or
+** similar tabular formats.  z[] might contain control characters such
+** as \n, \t, \f, or \r.
+**
+** Compute characters to display on the first line of z[].  Stop at the
+** first \r, \n, or \f.  Expand \t into spaces.  Return a copy (obtained
+** from malloc()) of that first line, which caller should free sometime.
+** Write anything to display on the next line into *pzTail.  If this is
+** the last line, write a NULL into *pzTail. (*pzTail is not allocated.)
+*/
+static char *translateForDisplayAndDup(
+  const unsigned char *z,            /* Input text to be transformed */
+  const unsigned char **pzTail,      /* OUT: Tail of the input for next line */
+  int mxWidth,                       /* Max width.  0 means no limit */
+  u8 bWordWrap                       /* If true, avoid breaking mid-word */
+){
+  int i;                 /* Input bytes consumed */
+  int j;                 /* Output bytes generated */
+  int k;                 /* Input bytes to be displayed */
+  int n;                 /* Output column number */
+  unsigned char *zOut;   /* Output text */
+
+  if( z==0 ){
+    *pzTail = 0;
+    return 0;
+  }
+  if( mxWidth<0 ) mxWidth = -mxWidth;
+  if( mxWidth==0 ) mxWidth = 1000000;
+  i = j = n = 0;
+  while( n<mxWidth ){
+    if( z[i]>=' ' ){
+      n++;
+      do{ i++; j++; }while( (z[i]&0xc0)==0x80 );
+      continue;
+    }
+    if( z[i]=='\t' ){
+      do{
+        n++;
+        j++;
+      }while( (n&7)!=0 && n<mxWidth );
+      i++;
+      continue;
+    }
+    break;
+  }
+  if( n>=mxWidth && bWordWrap  ){
+    /* Perhaps try to back up to a better place to break the line */
+    for(k=i; k>i/2; k--){
+      if( isspace(z[k-1]) ) break;
+    }
+    if( k<=i/2 ){
+      for(k=i; k>i/2; k--){
+        if( isalnum(z[k-1])!=isalnum(z[k]) && (z[k]&0xc0)!=0x80 ) break;
+      }
+    }
+    if( k<=i/2 ){
+      k = i;
+    }else{
+      i = k;
+      while( z[i]==' ' ) i++;
+    }
+  }else{
+    k = i;
+  }
+  if( n>=mxWidth && z[i]>=' ' ){
+   *pzTail = &z[i];
+  }else if( z[i]=='\r' && z[i+1]=='\n' ){
+    *pzTail = z[i+2] ? &z[i+2] : 0;
+  }else if( z[i]==0 || z[i+1]==0 ){
+    *pzTail = 0;
+  }else{
+    *pzTail = &z[i+1];
+  }
+  zOut = malloc( j+1 );
+  shell_check_oom(zOut);
+  i = j = n = 0;
+  while( i<k ){
+    if( z[i]>=' ' ){
+      n++;
+      do{ zOut[j++] = z[i++]; }while( (z[i]&0xc0)==0x80 );
+      continue;
+    }
+    if( z[i]=='\t' ){
+      do{
+        n++;
+        zOut[j++] = ' ';
+      }while( (n&7)!=0 && n<mxWidth );
+      i++;
+      continue;
+    }
+    break;
+  }
+  zOut[j] = 0;
+  return (char*)zOut;
+}
+
+/* Extract the value of the i-th current column for pStmt as an SQL literal
+** value.  Memory is obtained from sqlite3_malloc64() and must be freed by
+** the caller.
+*/
+static char *quoted_column(sqlite3_stmt *pStmt, int i){
+  switch( sqlite3_column_type(pStmt, i) ){
+    case SQLITE_NULL: {
+      return sqlite3_mprintf("NULL");
+    }
+    case SQLITE_INTEGER:
+    case SQLITE_FLOAT: {
+      return sqlite3_mprintf("%s",sqlite3_column_text(pStmt,i));
+    }
+    case SQLITE_TEXT: {
+      return sqlite3_mprintf("%Q",sqlite3_column_text(pStmt,i));
+    }
+    case SQLITE_BLOB: {
+      int j;
+      sqlite3_str *pStr = sqlite3_str_new(0);
+      const unsigned char *a = sqlite3_column_blob(pStmt,i);
+      int n = sqlite3_column_bytes(pStmt,i);
+      sqlite3_str_append(pStr, "x'", 2);
+      for(j=0; j<n; j++){
+        sqlite3_str_appendf(pStr, "%02x", a[j]);
+      }
+      sqlite3_str_append(pStr, "'", 1);
+      return sqlite3_str_finish(pStr);
+    }
+  }
+  return 0; /* Not reached */
+}
+
+/*
+** Run a prepared statement and output the result in one of the
+** table-oriented formats: MODE_Column, MODE_Markdown, MODE_Table,
+** or MODE_Box.
+**
+** This is different from ordinary exec_prepared_stmt() in that
+** it has to run the entire query and gather the results into memory
+** first, in order to determine column widths, before providing
+** any output.
+*/
+static void exec_prepared_stmt_columnar(
+  ShellState *p,                        /* Pointer to ShellState */
+  sqlite3_stmt *pStmt                   /* Statement to run */
+){
+  sqlite3_int64 nRow = 0;
+  int nColumn = 0;
+  char **azData = 0;
+  sqlite3_int64 nAlloc = 0;
+  char *abRowDiv = 0;
+  const unsigned char *uz;
+  const char *z;
+  char **azQuoted = 0;
+  int rc;
+  sqlite3_int64 i, nData;
+  int j, nTotal, w, n;
+  const char *colSep = 0;
+  const char *rowSep = 0;
+  const unsigned char **azNextLine = 0;
+  int bNextLine = 0;
+  int bMultiLineRowExists = 0;
+  int bw = p->cmOpts.bWordWrap;
+  const char *zEmpty = "";
+  const char *zShowNull = p->nullValue;
+
+  rc = sqlite3_step(pStmt);
+  if( rc!=SQLITE_ROW ) return;
+  nColumn = sqlite3_column_count(pStmt);
+  nAlloc = nColumn*4;
+  if( nAlloc<=0 ) nAlloc = 1;
+  azData = sqlite3_malloc64( nAlloc*sizeof(char*) );
+  shell_check_oom(azData);
+  azNextLine = sqlite3_malloc64( nColumn*sizeof(char*) );
+  shell_check_oom(azNextLine);
+  memset((void*)azNextLine, 0, nColumn*sizeof(char*) );
+  if( p->cmOpts.bQuote ){
+    azQuoted = sqlite3_malloc64( nColumn*sizeof(char*) );
+    shell_check_oom(azQuoted);
+    memset(azQuoted, 0, nColumn*sizeof(char*) );
+  }
+  abRowDiv = sqlite3_malloc64( nAlloc/nColumn );
+  shell_check_oom(abRowDiv);
+  if( nColumn>p->nWidth ){
+    p->colWidth = realloc(p->colWidth, (nColumn+1)*2*sizeof(int));
+    shell_check_oom(p->colWidth);
+    for(i=p->nWidth; i<nColumn; i++) p->colWidth[i] = 0;
+    p->nWidth = nColumn;
+    p->actualWidth = &p->colWidth[nColumn];
+  }
+  memset(p->actualWidth, 0, nColumn*sizeof(int));
+  for(i=0; i<nColumn; i++){
+    w = p->colWidth[i];
+    if( w<0 ) w = -w;
+    p->actualWidth[i] = w;
+  }
+  for(i=0; i<nColumn; i++){
+    const unsigned char *zNotUsed;
+    int wx = p->colWidth[i];
+    if( wx==0 ){
+      wx = p->cmOpts.iWrap;
+    }
+    if( wx<0 ) wx = -wx;
+    uz = (const unsigned char*)sqlite3_column_name(pStmt,i);
+    if( uz==0 ) uz = (u8*)"";
+    azData[i] = translateForDisplayAndDup(uz, &zNotUsed, wx, bw);
+  }
+  do{
+    int useNextLine = bNextLine;
+    bNextLine = 0;
+    if( (nRow+2)*nColumn >= nAlloc ){
+      nAlloc *= 2;
+      azData = sqlite3_realloc64(azData, nAlloc*sizeof(char*));
+      shell_check_oom(azData);
+      abRowDiv = sqlite3_realloc64(abRowDiv, nAlloc/nColumn);
+      shell_check_oom(abRowDiv);
+    }
+    abRowDiv[nRow] = 1;
+    nRow++;
+    for(i=0; i<nColumn; i++){
+      int wx = p->colWidth[i];
+      if( wx==0 ){
+        wx = p->cmOpts.iWrap;
+      }
+      if( wx<0 ) wx = -wx;
+      if( useNextLine ){
+        uz = azNextLine[i];
+        if( uz==0 ) uz = (u8*)zEmpty;
+      }else if( p->cmOpts.bQuote ){
+        sqlite3_free(azQuoted[i]);
+        azQuoted[i] = quoted_column(pStmt,i);
+        uz = (const unsigned char*)azQuoted[i];
+      }else{
+        uz = (const unsigned char*)sqlite3_column_text(pStmt,i);
+        if( uz==0 ) uz = (u8*)zShowNull;
+      }
+      azData[nRow*nColumn + i]
+        = translateForDisplayAndDup(uz, &azNextLine[i], wx, bw);
+      if( azNextLine[i] ){
+        bNextLine = 1;
+        abRowDiv[nRow-1] = 0;
+        bMultiLineRowExists = 1;
+      }
+    }
+  }while( bNextLine || sqlite3_step(pStmt)==SQLITE_ROW );
+  nTotal = nColumn*(nRow+1);
+  for(i=0; i<nTotal; i++){
+    z = azData[i];
+    if( z==0 ) z = (char*)zEmpty;
+    n = strlenChar(z);
+    j = i%nColumn;
+    if( n>p->actualWidth[j] ) p->actualWidth[j] = n;
+  }
+  if( seenInterrupt ) goto columnar_end;
+  if( nColumn==0 ) goto columnar_end;
+  switch( p->cMode ){
+    case MODE_Column: {
+      colSep = "  ";
+      rowSep = "\n";
+      if( p->showHeader ){
+        for(i=0; i<nColumn; i++){
+          w = p->actualWidth[i];
+          if( p->colWidth[i]<0 ) w = -w;
+          utf8_width_print(w, azData[i]);
+          fputs(i==nColumn-1?"\n":"  ", p->out);
+        }
+        for(i=0; i<nColumn; i++){
+          print_dashes(p->actualWidth[i]);
+          fputs(i==nColumn-1?"\n":"  ", p->out);
+        }
+      }
+      break;
+    }
+    case MODE_Table: {
+      colSep = " | ";
+      rowSep = " |\n";
+      print_row_separator(p, nColumn, "+");
+      fputs("| ", p->out);
+      for(i=0; i<nColumn; i++){
+        w = p->actualWidth[i];
+        n = strlenChar(azData[i]);
+        oputf("%*s%s%*s", (w-n)/2, "", azData[i], (w-n+1)/2, "");
+        oputz(i==nColumn-1?" |\n":" | ");
+      }
+      print_row_separator(p, nColumn, "+");
+      break;
+    }
+    case MODE_Markdown: {
+      colSep = " | ";
+      rowSep = " |\n";
+      fputs("| ", p->out);
+      for(i=0; i<nColumn; i++){
+        w = p->actualWidth[i];
+        n = strlenChar(azData[i]);
+        oputf("%*s%s%*s", (w-n)/2, "", azData[i], (w-n+1)/2, "");
+        oputz(i==nColumn-1?" |\n":" | ");
+      }
+      print_row_separator(p, nColumn, "|");
+      break;
+    }
+    case MODE_Box: {
+      colSep = " " BOX_13 " ";
+      rowSep = " " BOX_13 "\n";
+      print_box_row_separator(p, nColumn, BOX_23, BOX_234, BOX_34);
+      oputz(BOX_13 " ");
+      for(i=0; i<nColumn; i++){
+        w = p->actualWidth[i];
+        n = strlenChar(azData[i]);
+        oputf("%*s%s%*s%s",
+              (w-n)/2, "", azData[i], (w-n+1)/2, "",
+              i==nColumn-1?" "BOX_13"\n":" "BOX_13" ");
+      }
+      print_box_row_separator(p, nColumn, BOX_123, BOX_1234, BOX_134);
+      break;
+    }
+  }
+  for(i=nColumn, j=0; i<nTotal; i++, j++){
+    if( j==0 && p->cMode!=MODE_Column ){
+      oputz(p->cMode==MODE_Box?BOX_13" ":"| ");
+    }
+    z = azData[i];
+    if( z==0 ) z = p->nullValue;
+    w = p->actualWidth[j];
+    if( p->colWidth[j]<0 ) w = -w;
+    utf8_width_print(w, z);
+    if( j==nColumn-1 ){
+      oputz(rowSep);
+      if( bMultiLineRowExists && abRowDiv[i/nColumn-1] && i+1<nTotal ){
+        if( p->cMode==MODE_Table ){
+          print_row_separator(p, nColumn, "+");
+        }else if( p->cMode==MODE_Box ){
+          print_box_row_separator(p, nColumn, BOX_123, BOX_1234, BOX_134);
+        }else if( p->cMode==MODE_Column ){
+          oputz("\n");
+        }
+      }
+      j = -1;
+      if( seenInterrupt ) goto columnar_end;
+    }else{
+      oputz(colSep);
+    }
+  }
+  if( p->cMode==MODE_Table ){
+    print_row_separator(p, nColumn, "+");
+  }else if( p->cMode==MODE_Box ){
+    print_box_row_separator(p, nColumn, BOX_12, BOX_124, BOX_14);
+  }
+columnar_end:
+  if( seenInterrupt ){
+    oputz("Interrupt\n");
+  }
+  nData = (nRow+1)*nColumn;
+  for(i=0; i<nData; i++){
+    z = azData[i];
+    if( z!=zEmpty && z!=zShowNull ) free(azData[i]);
+  }
+  sqlite3_free(azData);
+  sqlite3_free((void*)azNextLine);
+  sqlite3_free(abRowDiv);
+  if( azQuoted ){
+    for(i=0; i<nColumn; i++) sqlite3_free(azQuoted[i]);
+    sqlite3_free(azQuoted);
+  }
+}
+
+/*
+** Run a prepared statement
+*/
+static void exec_prepared_stmt(
+  ShellState *pArg,                                /* Pointer to ShellState */
+  sqlite3_stmt *pStmt                              /* Statement to run */
+){
+  int rc;
+  sqlite3_uint64 nRow = 0;
+
+  if( pArg->cMode==MODE_Column
+   || pArg->cMode==MODE_Table
+   || pArg->cMode==MODE_Box
+   || pArg->cMode==MODE_Markdown
+  ){
+    exec_prepared_stmt_columnar(pArg, pStmt);
+    return;
+  }
+
+  /* perform the first step.  this will tell us if we
+  ** have a result set or not and how wide it is.
+  */
+  rc = sqlite3_step(pStmt);
+  /* if we have a result set... */
+  if( SQLITE_ROW == rc ){
+    /* allocate space for col name ptr, value ptr, and type */
+    int nCol = sqlite3_column_count(pStmt);
+    void *pData = sqlite3_malloc64(3*nCol*sizeof(const char*) + 1);
+    if( !pData ){
+      shell_out_of_memory();
+    }else{
+      char **azCols = (char **)pData;      /* Names of result columns */
+      char **azVals = &azCols[nCol];       /* Results */
+      int *aiTypes = (int *)&azVals[nCol]; /* Result types */
+      int i, x;
+      assert(sizeof(int) <= sizeof(char *));
+      /* save off ptrs to column names */
+      for(i=0; i<nCol; i++){
+        azCols[i] = (char *)sqlite3_column_name(pStmt, i);
+      }
+      do{
+        nRow++;
+        /* extract the data and data types */
+        for(i=0; i<nCol; i++){
+          aiTypes[i] = x = sqlite3_column_type(pStmt, i);
+          if( x==SQLITE_BLOB
+           && pArg
+           && (pArg->cMode==MODE_Insert || pArg->cMode==MODE_Quote)
+          ){
+            azVals[i] = "";
+          }else{
+            azVals[i] = (char*)sqlite3_column_text(pStmt, i);
+          }
+          if( !azVals[i] && (aiTypes[i]!=SQLITE_NULL) ){
+            rc = SQLITE_NOMEM;
+            break; /* from for */
+          }
+        } /* end for */
+
+        /* if data and types extracted successfully... */
+        if( SQLITE_ROW == rc ){
+          /* call the supplied callback with the result row data */
+          if( shell_callback(pArg, nCol, azVals, azCols, aiTypes) ){
+            rc = SQLITE_ABORT;
+          }else{
+            rc = sqlite3_step(pStmt);
+          }
+        }
+      } while( SQLITE_ROW == rc );
+      sqlite3_free(pData);
+      if( pArg->cMode==MODE_Json ){
+        fputs("]\n", pArg->out);
+      }else if( pArg->cMode==MODE_Count ){
+        char zBuf[200];
+        sqlite3_snprintf(sizeof(zBuf), zBuf, "%llu row%s\n",
+                         nRow, nRow!=1 ? "s" : "");
+        printf("%s", zBuf);
+      }
+    }
+  }
+}
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** This function is called to process SQL if the previous shell command
+** was ".expert". It passes the SQL in the second argument directly to
+** the sqlite3expert object.
+**
+** If successful, SQLITE_OK is returned. Otherwise, an SQLite error
+** code. In this case, (*pzErr) may be set to point to a buffer containing
+** an English language error message. It is the responsibility of the
+** caller to eventually free this buffer using sqlite3_free().
+*/
+static int expertHandleSQL(
+  ShellState *pState,
+  const char *zSql,
+  char **pzErr
+){
+  assert( pState->expert.pExpert );
+  assert( pzErr==0 || *pzErr==0 );
+  return sqlite3_expert_sql(pState->expert.pExpert, zSql, pzErr);
+}
+
+/*
+** This function is called either to silently clean up the object
+** created by the ".expert" command (if bCancel==1), or to generate a
+** report from it and then clean it up (if bCancel==0).
+**
+** If successful, SQLITE_OK is returned. Otherwise, an SQLite error
+** code. In this case, (*pzErr) may be set to point to a buffer containing
+** an English language error message. It is the responsibility of the
+** caller to eventually free this buffer using sqlite3_free().
+*/
+static int expertFinish(
+  ShellState *pState,
+  int bCancel,
+  char **pzErr
+){
+  int rc = SQLITE_OK;
+  sqlite3expert *p = pState->expert.pExpert;
+  assert( p );
+  assert( bCancel || pzErr==0 || *pzErr==0 );
+  if( bCancel==0 ){
+    int bVerbose = pState->expert.bVerbose;
+
+    rc = sqlite3_expert_analyze(p, pzErr);
+    if( rc==SQLITE_OK ){
+      int nQuery = sqlite3_expert_count(p);
+      int i;
+
+      if( bVerbose ){
+        const char *zCand = sqlite3_expert_report(p,0,EXPERT_REPORT_CANDIDATES);
+        oputz("-- Candidates -----------------------------\n");
+        oputf("%s\n", zCand);
+      }
+      for(i=0; i<nQuery; i++){
+        const char *zSql = sqlite3_expert_report(p, i, EXPERT_REPORT_SQL);
+        const char *zIdx = sqlite3_expert_report(p, i, EXPERT_REPORT_INDEXES);
+        const char *zEQP = sqlite3_expert_report(p, i, EXPERT_REPORT_PLAN);
+        if( zIdx==0 ) zIdx = "(no new indexes)\n";
+        if( bVerbose ){
+          oputf("-- Query %d --------------------------------\n",i+1);
+          oputf("%s\n\n", zSql);
+        }
+        oputf("%s\n", zIdx);
+        oputf("%s\n", zEQP);
+      }
+    }
+  }
+  sqlite3_expert_destroy(p);
+  pState->expert.pExpert = 0;
+  return rc;
+}
+
+/*
+** Implementation of ".expert" dot command.
+*/
+static int expertDotCommand(
+  ShellState *pState,             /* Current shell tool state */
+  char **azArg,                   /* Array of arguments passed to dot command */
+  int nArg                        /* Number of entries in azArg[] */
+){
+  int rc = SQLITE_OK;
+  char *zErr = 0;
+  int i;
+  int iSample = 0;
+
+  assert( pState->expert.pExpert==0 );
+  memset(&pState->expert, 0, sizeof(ExpertInfo));
+
+  for(i=1; rc==SQLITE_OK && i<nArg; i++){
+    char *z = azArg[i];
+    int n;
+    if( z[0]=='-' && z[1]=='-' ) z++;
+    n = strlen30(z);
+    if( n>=2 && 0==cli_strncmp(z, "-verbose", n) ){
+      pState->expert.bVerbose = 1;
+    }
+    else if( n>=2 && 0==cli_strncmp(z, "-sample", n) ){
+      if( i==(nArg-1) ){
+        eputf("option requires an argument: %s\n", z);
+        rc = SQLITE_ERROR;
+      }else{
+        iSample = (int)integerValue(azArg[++i]);
+        if( iSample<0 || iSample>100 ){
+          eputf("value out of range: %s\n", azArg[i]);
+          rc = SQLITE_ERROR;
+        }
+      }
+    }
+    else{
+      eputf("unknown option: %s\n", z);
+      rc = SQLITE_ERROR;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    pState->expert.pExpert = sqlite3_expert_new(pState->db, &zErr);
+    if( pState->expert.pExpert==0 ){
+      eputf("sqlite3_expert_new: %s\n", zErr ? zErr : "out of memory");
+      rc = SQLITE_ERROR;
+    }else{
+      sqlite3_expert_config(
+          pState->expert.pExpert, EXPERT_CONFIG_SAMPLE, iSample
+      );
+    }
+  }
+  sqlite3_free(zErr);
+
+  return rc;
+}
+#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** Execute a statement or set of statements.  Print
+** any result rows/columns depending on the current mode
+** set via the supplied callback.
+**
+** This is very similar to SQLite's built-in sqlite3_exec()
+** function except it takes a slightly different callback
+** and callback data argument.
+*/
+static int shell_exec(
+  ShellState *pArg,                         /* Pointer to ShellState */
+  const char *zSql,                         /* SQL to be evaluated */
+  char **pzErrMsg                           /* Error msg written here */
+){
+  sqlite3_stmt *pStmt = NULL;     /* Statement to execute. */
+  int rc = SQLITE_OK;             /* Return Code */
+  int rc2;
+  const char *zLeftover;          /* Tail of unprocessed SQL */
+  sqlite3 *db = pArg->db;
+
+  if( pzErrMsg ){
+    *pzErrMsg = NULL;
+  }
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( pArg->expert.pExpert ){
+    rc = expertHandleSQL(pArg, zSql, pzErrMsg);
+    return expertFinish(pArg, (rc!=SQLITE_OK), pzErrMsg);
+  }
+#endif
+
+  while( zSql[0] && (SQLITE_OK == rc) ){
+    static const char *zStmtSql;
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, &zLeftover);
+    if( SQLITE_OK != rc ){
+      if( pzErrMsg ){
+        *pzErrMsg = save_err_msg(db, "in prepare", rc, zSql);
+      }
+    }else{
+      if( !pStmt ){
+        /* this happens for a comment or white-space */
+        zSql = zLeftover;
+        while( IsSpace(zSql[0]) ) zSql++;
+        continue;
+      }
+      zStmtSql = sqlite3_sql(pStmt);
+      if( zStmtSql==0 ) zStmtSql = "";
+      while( IsSpace(zStmtSql[0]) ) zStmtSql++;
+
+      /* save off the prepared statement handle and reset row count */
+      if( pArg ){
+        pArg->pStmt = pStmt;
+        pArg->cnt = 0;
+      }
+
+      /* Show the EXPLAIN QUERY PLAN if .eqp is on */
+      if( pArg && pArg->autoEQP && sqlite3_stmt_isexplain(pStmt)==0 ){
+        sqlite3_stmt *pExplain;
+        int triggerEQP = 0;
+        disable_debug_trace_modes();
+        sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, -1, &triggerEQP);
+        if( pArg->autoEQP>=AUTOEQP_trigger ){
+          sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, 1, 0);
+        }
+        pExplain = pStmt;
+        sqlite3_reset(pExplain);
+        rc = sqlite3_stmt_explain(pExplain, 2);
+        if( rc==SQLITE_OK ){
+          while( sqlite3_step(pExplain)==SQLITE_ROW ){
+            const char *zEQPLine = (const char*)sqlite3_column_text(pExplain,3);
+            int iEqpId = sqlite3_column_int(pExplain, 0);
+            int iParentId = sqlite3_column_int(pExplain, 1);
+            if( zEQPLine==0 ) zEQPLine = "";
+            if( zEQPLine[0]=='-' ) eqp_render(pArg, 0);
+            eqp_append(pArg, iEqpId, iParentId, zEQPLine);
+          }
+          eqp_render(pArg, 0);
+        }
+        if( pArg->autoEQP>=AUTOEQP_full ){
+          /* Also do an EXPLAIN for ".eqp full" mode */
+          sqlite3_reset(pExplain);
+          rc = sqlite3_stmt_explain(pExplain, 1);
+          if( rc==SQLITE_OK ){
+            pArg->cMode = MODE_Explain;
+            assert( sqlite3_stmt_isexplain(pExplain)==1 );
+            explain_data_prepare(pArg, pExplain);
+            exec_prepared_stmt(pArg, pExplain);
+            explain_data_delete(pArg);
+          }
+        }
+        if( pArg->autoEQP>=AUTOEQP_trigger && triggerEQP==0 ){
+          sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, 0, 0);
+        }
+        sqlite3_reset(pStmt);
+        sqlite3_stmt_explain(pStmt, 0);
+        restore_debug_trace_modes();
+      }
+
+      if( pArg ){
+        int bIsExplain = (sqlite3_stmt_isexplain(pStmt)==1);
+        pArg->cMode = pArg->mode;
+        if( pArg->autoExplain ){
+          if( bIsExplain ){
+            pArg->cMode = MODE_Explain;
+          }
+          if( sqlite3_stmt_isexplain(pStmt)==2 ){
+            pArg->cMode = MODE_EQP;
+          }
+        }
+
+        /* If the shell is currently in ".explain" mode, gather the extra
+        ** data required to add indents to the output.*/
+        if( pArg->cMode==MODE_Explain && bIsExplain ){
+          explain_data_prepare(pArg, pStmt);
+        }
+      }
+
+      bind_prepared_stmt(pArg, pStmt);
+      exec_prepared_stmt(pArg, pStmt);
+      explain_data_delete(pArg);
+      eqp_render(pArg, 0);
+
+      /* print usage stats if stats on */
+      if( pArg && pArg->statsOn ){
+        display_stats(db, pArg, 0);
+      }
+
+      /* print loop-counters if required */
+      if( pArg && pArg->scanstatsOn ){
+        display_scanstats(db, pArg);
+      }
+
+      /* Finalize the statement just executed. If this fails, save a
+      ** copy of the error message. Otherwise, set zSql to point to the
+      ** next statement to execute. */
+      rc2 = sqlite3_finalize(pStmt);
+      if( rc!=SQLITE_NOMEM ) rc = rc2;
+      if( rc==SQLITE_OK ){
+        zSql = zLeftover;
+        while( IsSpace(zSql[0]) ) zSql++;
+      }else if( pzErrMsg ){
+        *pzErrMsg = save_err_msg(db, "stepping", rc, 0);
+      }
+
+      /* clear saved stmt handle */
+      if( pArg ){
+        pArg->pStmt = NULL;
+      }
+    }
+  } /* end while */
+
+  return rc;
+}
+
+/*
+** Release memory previously allocated by tableColumnList().
+*/
+static void freeColumnList(char **azCol){
+  int i;
+  for(i=1; azCol[i]; i++){
+    sqlite3_free(azCol[i]);
+  }
+  /* azCol[0] is a static string */
+  sqlite3_free(azCol);
+}
+
+/*
+** Return a list of pointers to strings which are the names of all
+** columns in table zTab.   The memory to hold the names is dynamically
+** allocated and must be released by the caller using a subsequent call
+** to freeColumnList().
+**
+** The azCol[0] entry is usually NULL.  However, if zTab contains a rowid
+** value that needs to be preserved, then azCol[0] is filled in with the
+** name of the rowid column.
+**
+** The first regular column in the table is azCol[1].  The list is terminated
+** by an entry with azCol[i]==0.
+*/
+static char **tableColumnList(ShellState *p, const char *zTab){
+  char **azCol = 0;
+  sqlite3_stmt *pStmt;
+  char *zSql;
+  int nCol = 0;
+  int nAlloc = 0;
+  int nPK = 0;       /* Number of PRIMARY KEY columns seen */
+  int isIPK = 0;     /* True if one PRIMARY KEY column of type INTEGER */
+  int preserveRowid = ShellHasFlag(p, SHFLG_PreserveRowid);
+  int rc;
+
+  zSql = sqlite3_mprintf("PRAGMA table_info=%Q", zTab);
+  shell_check_oom(zSql);
+  rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+  if( rc ) return 0;
+  while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    if( nCol>=nAlloc-2 ){
+      nAlloc = nAlloc*2 + nCol + 10;
+      azCol = sqlite3_realloc(azCol, nAlloc*sizeof(azCol[0]));
+      shell_check_oom(azCol);
+    }
+    azCol[++nCol] = sqlite3_mprintf("%s", sqlite3_column_text(pStmt, 1));
+    shell_check_oom(azCol[nCol]);
+    if( sqlite3_column_int(pStmt, 5) ){
+      nPK++;
+      if( nPK==1
+       && sqlite3_stricmp((const char*)sqlite3_column_text(pStmt,2),
+                          "INTEGER")==0
+      ){
+        isIPK = 1;
+      }else{
+        isIPK = 0;
+      }
+    }
+  }
+  sqlite3_finalize(pStmt);
+  if( azCol==0 ) return 0;
+  azCol[0] = 0;
+  azCol[nCol+1] = 0;
+
+  /* The decision of whether or not a rowid really needs to be preserved
+  ** is tricky.  We never need to preserve a rowid for a WITHOUT ROWID table
+  ** or a table with an INTEGER PRIMARY KEY.  We are unable to preserve
+  ** rowids on tables where the rowid is inaccessible because there are other
+  ** columns in the table named "rowid", "_rowid_", and "oid".
+  */
+  if( preserveRowid && isIPK ){
+    /* If a single PRIMARY KEY column with type INTEGER was seen, then it
+    ** might be an alias for the ROWID.  But it might also be a WITHOUT ROWID
+    ** table or a INTEGER PRIMARY KEY DESC column, neither of which are
+    ** ROWID aliases.  To distinguish these cases, check to see if
+    ** there is a "pk" entry in "PRAGMA index_list".  There will be
+    ** no "pk" index if the PRIMARY KEY really is an alias for the ROWID.
+    */
+    zSql = sqlite3_mprintf("SELECT 1 FROM pragma_index_list(%Q)"
+                           " WHERE origin='pk'", zTab);
+    shell_check_oom(zSql);
+    rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+    if( rc ){
+      freeColumnList(azCol);
+      return 0;
+    }
+    rc = sqlite3_step(pStmt);
+    sqlite3_finalize(pStmt);
+    preserveRowid = rc==SQLITE_ROW;
+  }
+  if( preserveRowid ){
+    /* Only preserve the rowid if we can find a name to use for the
+    ** rowid */
+    static char *azRowid[] = { "rowid", "_rowid_", "oid" };
+    int i, j;
+    for(j=0; j<3; j++){
+      for(i=1; i<=nCol; i++){
+        if( sqlite3_stricmp(azRowid[j],azCol[i])==0 ) break;
+      }
+      if( i>nCol ){
+        /* At this point, we know that azRowid[j] is not the name of any
+        ** ordinary column in the table.  Verify that azRowid[j] is a valid
+        ** name for the rowid before adding it to azCol[0].  WITHOUT ROWID
+        ** tables will fail this last check */
+        rc = sqlite3_table_column_metadata(p->db,0,zTab,azRowid[j],0,0,0,0,0);
+        if( rc==SQLITE_OK ) azCol[0] = azRowid[j];
+        break;
+      }
+    }
+  }
+  return azCol;
+}
+
+/*
+** Toggle the reverse_unordered_selects setting.
+*/
+static void toggleSelectOrder(sqlite3 *db){
+  sqlite3_stmt *pStmt = 0;
+  int iSetting = 0;
+  char zStmt[100];
+  sqlite3_prepare_v2(db, "PRAGMA reverse_unordered_selects", -1, &pStmt, 0);
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    iSetting = sqlite3_column_int(pStmt, 0);
+  }
+  sqlite3_finalize(pStmt);
+  sqlite3_snprintf(sizeof(zStmt), zStmt,
+       "PRAGMA reverse_unordered_selects(%d)", !iSetting);
+  sqlite3_exec(db, zStmt, 0, 0, 0);
+}
+
+/*
+** This is a different callback routine used for dumping the database.
+** Each row received by this callback consists of a table name,
+** the table type ("index" or "table") and SQL to create the table.
+** This routine should print text sufficient to recreate the table.
+*/
+static int dump_callback(void *pArg, int nArg, char **azArg, char **azNotUsed){
+  int rc;
+  const char *zTable;
+  const char *zType;
+  const char *zSql;
+  ShellState *p = (ShellState *)pArg;
+  int dataOnly;
+  int noSys;
+
+  UNUSED_PARAMETER(azNotUsed);
+  if( nArg!=3 || azArg==0 ) return 0;
+  zTable = azArg[0];
+  zType = azArg[1];
+  zSql = azArg[2];
+  if( zTable==0 ) return 0;
+  if( zType==0 ) return 0;
+  dataOnly = (p->shellFlgs & SHFLG_DumpDataOnly)!=0;
+  noSys    = (p->shellFlgs & SHFLG_DumpNoSys)!=0;
+
+  if( cli_strcmp(zTable, "sqlite_sequence")==0 && !noSys ){
+    if( !dataOnly ) oputz("DELETE FROM sqlite_sequence;\n");
+  }else if( sqlite3_strglob("sqlite_stat?", zTable)==0 && !noSys ){
+    if( !dataOnly ) oputz("ANALYZE sqlite_schema;\n");
+  }else if( cli_strncmp(zTable, "sqlite_", 7)==0 ){
+    return 0;
+  }else if( dataOnly ){
+    /* no-op */
+  }else if( cli_strncmp(zSql, "CREATE VIRTUAL TABLE", 20)==0 ){
+    char *zIns;
+    if( !p->writableSchema ){
+      oputz("PRAGMA writable_schema=ON;\n");
+      p->writableSchema = 1;
+    }
+    zIns = sqlite3_mprintf(
+       "INSERT INTO sqlite_schema(type,name,tbl_name,rootpage,sql)"
+       "VALUES('table','%q','%q',0,'%q');",
+       zTable, zTable, zSql);
+    shell_check_oom(zIns);
+    oputf("%s\n", zIns);
+    sqlite3_free(zIns);
+    return 0;
+  }else{
+    printSchemaLine(zSql, ";\n");
+  }
+
+  if( cli_strcmp(zType, "table")==0 ){
+    ShellText sSelect;
+    ShellText sTable;
+    char **azCol;
+    int i;
+    char *savedDestTable;
+    int savedMode;
+
+    azCol = tableColumnList(p, zTable);
+    if( azCol==0 ){
+      p->nErr++;
+      return 0;
+    }
+
+    /* Always quote the table name, even if it appears to be pure ascii,
+    ** in case it is a keyword. Ex:  INSERT INTO "table" ... */
+    initText(&sTable);
+    appendText(&sTable, zTable, quoteChar(zTable));
+    /* If preserving the rowid, add a column list after the table name.
+    ** In other words:  "INSERT INTO tab(rowid,a,b,c,...) VALUES(...)"
+    ** instead of the usual "INSERT INTO tab VALUES(...)".
+    */
+    if( azCol[0] ){
+      appendText(&sTable, "(", 0);
+      appendText(&sTable, azCol[0], 0);
+      for(i=1; azCol[i]; i++){
+        appendText(&sTable, ",", 0);
+        appendText(&sTable, azCol[i], quoteChar(azCol[i]));
+      }
+      appendText(&sTable, ")", 0);
+    }
+
+    /* Build an appropriate SELECT statement */
+    initText(&sSelect);
+    appendText(&sSelect, "SELECT ", 0);
+    if( azCol[0] ){
+      appendText(&sSelect, azCol[0], 0);
+      appendText(&sSelect, ",", 0);
+    }
+    for(i=1; azCol[i]; i++){
+      appendText(&sSelect, azCol[i], quoteChar(azCol[i]));
+      if( azCol[i+1] ){
+        appendText(&sSelect, ",", 0);
+      }
+    }
+    freeColumnList(azCol);
+    appendText(&sSelect, " FROM ", 0);
+    appendText(&sSelect, zTable, quoteChar(zTable));
+
+    savedDestTable = p->zDestTable;
+    savedMode = p->mode;
+    p->zDestTable = sTable.z;
+    p->mode = p->cMode = MODE_Insert;
+    rc = shell_exec(p, sSelect.z, 0);
+    if( (rc&0xff)==SQLITE_CORRUPT ){
+      oputz("/****** CORRUPTION ERROR *******/\n");
+      toggleSelectOrder(p->db);
+      shell_exec(p, sSelect.z, 0);
+      toggleSelectOrder(p->db);
+    }
+    p->zDestTable = savedDestTable;
+    p->mode = savedMode;
+    freeText(&sTable);
+    freeText(&sSelect);
+    if( rc ) p->nErr++;
+  }
+  return 0;
+}
+
+/*
+** Run zQuery.  Use dump_callback() as the callback routine so that
+** the contents of the query are output as SQL statements.
+**
+** If we get a SQLITE_CORRUPT error, rerun the query after appending
+** "ORDER BY rowid DESC" to the end.
+*/
+static int run_schema_dump_query(
+  ShellState *p,
+  const char *zQuery
+){
+  int rc;
+  char *zErr = 0;
+  rc = sqlite3_exec(p->db, zQuery, dump_callback, p, &zErr);
+  if( rc==SQLITE_CORRUPT ){
+    char *zQ2;
+    int len = strlen30(zQuery);
+    oputz("/****** CORRUPTION ERROR *******/\n");
+    if( zErr ){
+      oputf("/****** %s ******/\n", zErr);
+      sqlite3_free(zErr);
+      zErr = 0;
+    }
+    zQ2 = malloc( len+100 );
+    if( zQ2==0 ) return rc;
+    sqlite3_snprintf(len+100, zQ2, "%s ORDER BY rowid DESC", zQuery);
+    rc = sqlite3_exec(p->db, zQ2, dump_callback, p, &zErr);
+    if( rc ){
+      oputf("/****** ERROR: %s ******/\n", zErr);
+    }else{
+      rc = SQLITE_CORRUPT;
+    }
+    sqlite3_free(zErr);
+    free(zQ2);
+  }
+  return rc;
+}
+
+/*
+** Text of help messages.
+**
+** The help text for each individual command begins with a line that starts
+** with ".".  Subsequent lines are supplemental information.
+**
+** There must be two or more spaces between the end of the command and the
+** start of the description of what that command does.
+*/
+static const char *(azHelp[]) = {
+#if defined(SQLITE_HAVE_ZLIB) && !defined(SQLITE_OMIT_VIRTUALTABLE) \
+  && !defined(SQLITE_SHELL_FIDDLE)
+  ".archive ...             Manage SQL archives",
+  "   Each command must have exactly one of the following options:",
+  "     -c, --create               Create a new archive",
+  "     -u, --update               Add or update files with changed mtime",
+  "     -i, --insert               Like -u but always add even if unchanged",
+  "     -r, --remove               Remove files from archive",
+  "     -t, --list                 List contents of archive",
+  "     -x, --extract              Extract files from archive",
+  "   Optional arguments:",
+  "     -v, --verbose              Print each filename as it is processed",
+  "     -f FILE, --file FILE       Use archive FILE (default is current db)",
+  "     -a FILE, --append FILE     Open FILE using the apndvfs VFS",
+  "     -C DIR, --directory DIR    Read/extract files from directory DIR",
+  "     -g, --glob                 Use glob matching for names in archive",
+  "     -n, --dryrun               Show the SQL that would have occurred",
+  "   Examples:",
+  "     .ar -cf ARCHIVE foo bar  # Create ARCHIVE from files foo and bar",
+  "     .ar -tf ARCHIVE          # List members of ARCHIVE",
+  "     .ar -xvf ARCHIVE         # Verbosely extract files from ARCHIVE",
+  "   See also:",
+  "      http://sqlite.org/cli.html#sqlite_archive_support",
+#endif
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  ".auth ON|OFF             Show authorizer callbacks",
+#endif
+#ifndef SQLITE_SHELL_FIDDLE
+  ".backup ?DB? FILE        Backup DB (default \"main\") to FILE",
+  "   Options:",
+  "       --append            Use the appendvfs",
+  "       --async             Write to FILE without journal and fsync()",
+#endif
+  ".bail on|off             Stop after hitting an error.  Default OFF",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".cd DIRECTORY            Change the working directory to DIRECTORY",
+#endif
+  ".changes on|off          Show number of rows changed by SQL",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".check GLOB              Fail if output since .testcase does not match",
+  ".clone NEWDB             Clone data into NEWDB from the existing database",
+#endif
+  ".connection [close] [#]  Open or close an auxiliary database connection",
+#if defined(_WIN32) || defined(WIN32)
+  ".crnl on|off             Translate \\n to \\r\\n.  Default ON",
+#endif
+  ".databases               List names and files of attached databases",
+  ".dbconfig ?op? ?val?     List or change sqlite3_db_config() options",
+#if SQLITE_SHELL_HAVE_RECOVER
+  ".dbinfo ?DB?             Show status information about the database",
+#endif
+  ".dump ?OBJECTS?          Render database content as SQL",
+  "   Options:",
+  "     --data-only            Output only INSERT statements",
+  "     --newlines             Allow unescaped newline characters in output",
+  "     --nosys                Omit system tables (ex: \"sqlite_stat1\")",
+  "     --preserve-rowids      Include ROWID values in the output",
+  "   OBJECTS is a LIKE pattern for tables, indexes, triggers or views to dump",
+  "   Additional LIKE patterns can be given in subsequent arguments",
+  ".echo on|off             Turn command echo on or off",
+  ".eqp on|off|full|...     Enable or disable automatic EXPLAIN QUERY PLAN",
+  "   Other Modes:",
+#ifdef SQLITE_DEBUG
+  "      test                  Show raw EXPLAIN QUERY PLAN output",
+  "      trace                 Like \"full\" but enable \"PRAGMA vdbe_trace\"",
+#endif
+  "      trigger               Like \"full\" but also show trigger bytecode",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".excel                   Display the output of next command in spreadsheet",
+  "   --bom                   Put a UTF8 byte-order mark on intermediate file",
+#endif
+#ifndef SQLITE_SHELL_FIDDLE
+  ".exit ?CODE?             Exit this program with return-code CODE",
+#endif
+  ".expert                  EXPERIMENTAL. Suggest indexes for queries",
+  ".explain ?on|off|auto?   Change the EXPLAIN formatting mode.  Default: auto",
+  ".filectrl CMD ...        Run various sqlite3_file_control() operations",
+  "   --schema SCHEMA         Use SCHEMA instead of \"main\"",
+  "   --help                  Show CMD details",
+  ".fullschema ?--indent?   Show schema and the content of sqlite_stat tables",
+  ".headers on|off          Turn display of headers on or off",
+  ".help ?-all? ?PATTERN?   Show help text for PATTERN",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".import FILE TABLE       Import data from FILE into TABLE",
+  "   Options:",
+  "     --ascii               Use \\037 and \\036 as column and row separators",
+  "     --csv                 Use , and \\n as column and row separators",
+  "     --skip N              Skip the first N rows of input",
+  "     --schema S            Target table to be S.TABLE",
+  "     -v                    \"Verbose\" - increase auxiliary output",
+  "   Notes:",
+  "     *  If TABLE does not exist, it is created.  The first row of input",
+  "        determines the column names.",
+  "     *  If neither --csv or --ascii are used, the input mode is derived",
+  "        from the \".mode\" output mode",
+  "     *  If FILE begins with \"|\" then it is a command that generates the",
+  "        input text.",
+#endif
+#ifndef SQLITE_OMIT_TEST_CONTROL
+  ",imposter INDEX TABLE    Create imposter table TABLE on index INDEX",
+#endif
+  ".indexes ?TABLE?         Show names of indexes",
+  "                           If TABLE is specified, only show indexes for",
+  "                           tables matching TABLE using the LIKE operator.",
+#ifdef SQLITE_ENABLE_IOTRACE
+  ",iotrace FILE            Enable I/O diagnostic logging to FILE",
+#endif
+  ".limit ?LIMIT? ?VAL?     Display or change the value of an SQLITE_LIMIT",
+  ".lint OPTIONS            Report potential schema issues.",
+  "     Options:",
+  "        fkey-indexes     Find missing foreign key indexes",
+#if !defined(SQLITE_OMIT_LOAD_EXTENSION) && !defined(SQLITE_SHELL_FIDDLE)
+  ".load FILE ?ENTRY?       Load an extension library",
+#endif
+#if !defined(SQLITE_SHELL_FIDDLE)
+  ".log FILE|on|off         Turn logging on or off.  FILE can be stderr/stdout",
+#else
+  ".log on|off              Turn logging on or off.",
+#endif
+  ".mode MODE ?OPTIONS?     Set output mode",
+  "   MODE is one of:",
+  "     ascii       Columns/rows delimited by 0x1F and 0x1E",
+  "     box         Tables using unicode box-drawing characters",
+  "     csv         Comma-separated values",
+  "     column      Output in columns.  (See .width)",
+  "     html        HTML <table> code",
+  "     insert      SQL insert statements for TABLE",
+  "     json        Results in a JSON array",
+  "     line        One value per line",
+  "     list        Values delimited by \"|\"",
+  "     markdown    Markdown table format",
+  "     qbox        Shorthand for \"box --wrap 60 --quote\"",
+  "     quote       Escape answers as for SQL",
+  "     table       ASCII-art table",
+  "     tabs        Tab-separated values",
+  "     tcl         TCL list elements",
+  "   OPTIONS: (for columnar modes or insert mode):",
+  "     --wrap N       Wrap output lines to no longer than N characters",
+  "     --wordwrap B   Wrap or not at word boundaries per B (on/off)",
+  "     --ww           Shorthand for \"--wordwrap 1\"",
+  "     --quote        Quote output text as SQL literals",
+  "     --noquote      Do not quote output text",
+  "     TABLE          The name of SQL table used for \"insert\" mode",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".nonce STRING            Suspend safe mode for one command if nonce matches",
+#endif
+  ".nullvalue STRING        Use STRING in place of NULL values",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".once ?OPTIONS? ?FILE?   Output for the next SQL command only to FILE",
+  "     If FILE begins with '|' then open as a pipe",
+  "       --bom  Put a UTF8 byte-order mark at the beginning",
+  "       -e     Send output to the system text editor",
+  "       -x     Send output as CSV to a spreadsheet (same as \".excel\")",
+  /* Note that .open is (partially) available in WASM builds but is
+  ** currently only intended to be used by the fiddle tool, not
+  ** end users, so is "undocumented." */
+  ".open ?OPTIONS? ?FILE?   Close existing database and reopen FILE",
+  "     Options:",
+  "        --append        Use appendvfs to append database to the end of FILE",
+#endif
+#ifndef SQLITE_OMIT_DESERIALIZE
+  "        --deserialize   Load into memory using sqlite3_deserialize()",
+  "        --hexdb         Load the output of \"dbtotxt\" as an in-memory db",
+  "        --maxsize N     Maximum size for --hexdb or --deserialized database",
+#endif
+  "        --new           Initialize FILE to an empty database",
+  "        --nofollow      Do not follow symbolic links",
+  "        --readonly      Open FILE readonly",
+  "        --zip           FILE is a ZIP archive",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".output ?FILE?           Send output to FILE or stdout if FILE is omitted",
+  "   If FILE begins with '|' then open it as a pipe.",
+  "   Options:",
+  "     --bom                 Prefix output with a UTF8 byte-order mark",
+  "     -e                    Send output to the system text editor",
+  "     -x                    Send output as CSV to a spreadsheet",
+#endif
+  ".parameter CMD ...       Manage SQL parameter bindings",
+  "   clear                   Erase all bindings",
+  "   init                    Initialize the TEMP table that holds bindings",
+  "   list                    List the current parameter bindings",
+  "   set PARAMETER VALUE     Given SQL parameter PARAMETER a value of VALUE",
+  "                           PARAMETER should start with one of: $ : @ ?",
+  "   unset PARAMETER         Remove PARAMETER from the binding table",
+  ".print STRING...         Print literal STRING",
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  ".progress N              Invoke progress handler after every N opcodes",
+  "   --limit N                 Interrupt after N progress callbacks",
+  "   --once                    Do no more than one progress interrupt",
+  "   --quiet|-q                No output except at interrupts",
+  "   --reset                   Reset the count for each input and interrupt",
+#endif
+  ".prompt MAIN CONTINUE    Replace the standard prompts",
+#ifndef SQLITE_SHELL_FIDDLE
+  ".quit                    Stop interpreting input stream, exit if primary.",
+  ".read FILE               Read input from FILE or command output",
+  "    If FILE begins with \"|\", it is a command that generates the input.",
+#endif
+#if SQLITE_SHELL_HAVE_RECOVER
+  ".recover                 Recover as much data as possible from corrupt db.",
+  "   --ignore-freelist        Ignore pages that appear to be on db freelist",
+  "   --lost-and-found TABLE   Alternative name for the lost-and-found table",
+  "   --no-rowids              Do not attempt to recover rowid values",
+  "                            that are not also INTEGER PRIMARY KEYs",
+#endif
+#ifndef SQLITE_SHELL_FIDDLE
+  ".restore ?DB? FILE       Restore content of DB (default \"main\") from FILE",
+  ".save ?OPTIONS? FILE     Write database to FILE (an alias for .backup ...)",
+#endif
+  ".scanstats on|off|est    Turn sqlite3_stmt_scanstatus() metrics on or off",
+  ".schema ?PATTERN?        Show the CREATE statements matching PATTERN",
+  "   Options:",
+  "      --indent             Try to pretty-print the schema",
+  "      --nosys              Omit objects whose names start with \"sqlite_\"",
+  ",selftest ?OPTIONS?      Run tests defined in the SELFTEST table",
+  "    Options:",
+  "       --init               Create a new SELFTEST table",
+  "       -v                   Verbose output",
+  ".separator COL ?ROW?     Change the column and row separators",
+#if defined(SQLITE_ENABLE_SESSION)
+  ".session ?NAME? CMD ...  Create or control sessions",
+  "   Subcommands:",
+  "     attach TABLE             Attach TABLE",
+  "     changeset FILE           Write a changeset into FILE",
+  "     close                    Close one session",
+  "     enable ?BOOLEAN?         Set or query the enable bit",
+  "     filter GLOB...           Reject tables matching GLOBs",
+  "     indirect ?BOOLEAN?       Mark or query the indirect status",
+  "     isempty                  Query whether the session is empty",
+  "     list                     List currently open session names",
+  "     open DB NAME             Open a new session on DB",
+  "     patchset FILE            Write a patchset into FILE",
+  "   If ?NAME? is omitted, the first defined session is used.",
+#endif
+  ".sha3sum ...             Compute a SHA3 hash of database content",
+  "    Options:",
+  "      --schema              Also hash the sqlite_schema table",
+  "      --sha3-224            Use the sha3-224 algorithm",
+  "      --sha3-256            Use the sha3-256 algorithm (default)",
+  "      --sha3-384            Use the sha3-384 algorithm",
+  "      --sha3-512            Use the sha3-512 algorithm",
+  "    Any other argument is a LIKE pattern for tables to hash",
+#if !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE)
+  ".shell CMD ARGS...       Run CMD ARGS... in a system shell",
+#endif
+  ".show                    Show the current values for various settings",
+  ".stats ?ARG?             Show stats or turn stats on or off",
+  "   off                      Turn off automatic stat display",
+  "   on                       Turn on automatic stat display",
+  "   stmt                     Show statement stats",
+  "   vmstep                   Show the virtual machine step count only",
+#if !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE)
+  ".system CMD ARGS...      Run CMD ARGS... in a system shell",
+#endif
+  ".tables ?TABLE?          List names of tables matching LIKE pattern TABLE",
+#ifndef SQLITE_SHELL_FIDDLE
+  ",testcase NAME           Begin redirecting output to 'testcase-out.txt'",
+#endif
+  ",testctrl CMD ...        Run various sqlite3_test_control() operations",
+  "                           Run \".testctrl\" with no arguments for details",
+  ".timeout MS              Try opening locked tables for MS milliseconds",
+  ".timer on|off            Turn SQL timer on or off",
+#ifndef SQLITE_OMIT_TRACE
+  ".trace ?OPTIONS?         Output each SQL statement as it is run",
+  "    FILE                    Send output to FILE",
+  "    stdout                  Send output to stdout",
+  "    stderr                  Send output to stderr",
+  "    off                     Disable tracing",
+  "    --expanded              Expand query parameters",
+#ifdef SQLITE_ENABLE_NORMALIZE
+  "    --normalized            Normal the SQL statements",
+#endif
+  "    --plain                 Show SQL as it is input",
+  "    --stmt                  Trace statement execution (SQLITE_TRACE_STMT)",
+  "    --profile               Profile statements (SQLITE_TRACE_PROFILE)",
+  "    --row                   Trace each row (SQLITE_TRACE_ROW)",
+  "    --close                 Trace connection close (SQLITE_TRACE_CLOSE)",
+#endif /* SQLITE_OMIT_TRACE */
+#ifdef SQLITE_DEBUG
+  ".unmodule NAME ...       Unregister virtual table modules",
+  "    --allexcept             Unregister everything except those named",
+#endif
+  ".version                 Show source, library and compiler versions",
+  ".vfsinfo ?AUX?           Information about the top-level VFS",
+  ".vfslist                 List all available VFSes",
+  ".vfsname ?AUX?           Print the name of the VFS stack",
+  ".width NUM1 NUM2 ...     Set minimum column widths for columnar output",
+  "     Negative values right-justify",
+};
+
+/*
+** Output help text.
+**
+** zPattern describes the set of commands for which help text is provided.
+** If zPattern is NULL, then show all commands, but only give a one-line
+** description of each.
+**
+** Return the number of matches.
+*/
+static int showHelp(FILE *out, const char *zPattern){
+  int i = 0;
+  int j = 0;
+  int n = 0;
+  char *zPat;
+  if( zPattern==0
+   || zPattern[0]=='0'
+   || cli_strcmp(zPattern,"-a")==0
+   || cli_strcmp(zPattern,"-all")==0
+   || cli_strcmp(zPattern,"--all")==0
+  ){
+    enum HelpWanted { HW_NoCull = 0, HW_SummaryOnly = 1, HW_Undoc = 2 };
+    enum HelpHave { HH_Undoc = 2, HH_Summary = 1, HH_More = 0 };
+    /* Show all or most commands
+    ** *zPattern==0   => summary of documented commands only
+    ** *zPattern=='0' => whole help for undocumented commands
+    ** Otherwise      => whole help for documented commands
+    */
+    enum HelpWanted hw = HW_SummaryOnly;
+    enum HelpHave hh = HH_More;
+    if( zPattern!=0 ){
+      hw = (*zPattern=='0')? HW_NoCull|HW_Undoc : HW_NoCull;
+    }
+    for(i=0; i<ArraySize(azHelp); i++){
+      switch( azHelp[i][0] ){
+      case ',':
+        hh = HH_Summary|HH_Undoc;
+        break;
+      case '.':
+        hh = HH_Summary;
+        break;
+      default:
+        hh &= ~HH_Summary;
+        break;
+      }
+      if( ((hw^hh)&HH_Undoc)==0 ){
+        if( (hh&HH_Summary)!=0 ){
+          sputf(out, ".%s\n", azHelp[i]+1);
+          ++n;
+        }else if( (hw&HW_SummaryOnly)==0 ){
+          sputf(out, "%s\n", azHelp[i]);
+        }
+      }
+    }
+  }else{
+    /* Seek documented commands for which zPattern is an exact prefix */
+    zPat = sqlite3_mprintf(".%s*", zPattern);
+    shell_check_oom(zPat);
+    for(i=0; i<ArraySize(azHelp); i++){
+      if( sqlite3_strglob(zPat, azHelp[i])==0 ){
+        sputf(out, "%s\n", azHelp[i]);
+        j = i+1;
+        n++;
+      }
+    }
+    sqlite3_free(zPat);
+    if( n ){
+      if( n==1 ){
+        /* when zPattern is a prefix of exactly one command, then include
+        ** the details of that command, which should begin at offset j */
+        while( j<ArraySize(azHelp)-1 && azHelp[j][0]==' ' ){
+          sputf(out, "%s\n", azHelp[j]);
+          j++;
+        }
+      }
+      return n;
+    }
+    /* Look for documented commands that contain zPattern anywhere.
+    ** Show complete text of all documented commands that match. */
+    zPat = sqlite3_mprintf("%%%s%%", zPattern);
+    shell_check_oom(zPat);
+    for(i=0; i<ArraySize(azHelp); i++){
+      if( azHelp[i][0]==',' ){
+        while( i<ArraySize(azHelp)-1 && azHelp[i+1][0]==' ' ) ++i;
+        continue;
+      }
+      if( azHelp[i][0]=='.' ) j = i;
+      if( sqlite3_strlike(zPat, azHelp[i], 0)==0 ){
+        sputf(out, "%s\n", azHelp[j]);
+        while( j<ArraySize(azHelp)-1 && azHelp[j+1][0]==' ' ){
+          j++;
+          sputf(out, "%s\n", azHelp[j]);
+        }
+        i = j;
+        n++;
+      }
+    }
+    sqlite3_free(zPat);
+  }
+  return n;
+}
+
+/* Forward reference */
+static int process_input(ShellState *p);
+
+/*
+** Read the content of file zName into memory obtained from sqlite3_malloc64()
+** and return a pointer to the buffer. The caller is responsible for freeing
+** the memory.
+**
+** If parameter pnByte is not NULL, (*pnByte) is set to the number of bytes
+** read.
+**
+** For convenience, a nul-terminator byte is always appended to the data read
+** from the file before the buffer is returned. This byte is not included in
+** the final value of (*pnByte), if applicable.
+**
+** NULL is returned if any error is encountered. The final value of *pnByte
+** is undefined in this case.
+*/
+static char *readFile(const char *zName, int *pnByte){
+  FILE *in = fopen(zName, "rb");
+  long nIn;
+  size_t nRead;
+  char *pBuf;
+  int rc;
+  if( in==0 ) return 0;
+  rc = fseek(in, 0, SEEK_END);
+  if( rc!=0 ){
+    eputf("Error: '%s' not seekable\n", zName);
+    fclose(in);
+    return 0;
+  }
+  nIn = ftell(in);
+  rewind(in);
+  pBuf = sqlite3_malloc64( nIn+1 );
+  if( pBuf==0 ){
+    eputz("Error: out of memory\n");
+    fclose(in);
+    return 0;
+  }
+  nRead = fread(pBuf, nIn, 1, in);
+  fclose(in);
+  if( nRead!=1 ){
+    sqlite3_free(pBuf);
+    eputf("Error: cannot read '%s'\n", zName);
+    return 0;
+  }
+  pBuf[nIn] = 0;
+  if( pnByte ) *pnByte = nIn;
+  return pBuf;
+}
+
+#if defined(SQLITE_ENABLE_SESSION)
+/*
+** Close a single OpenSession object and release all of its associated
+** resources.
+*/
+static void session_close(OpenSession *pSession){
+  int i;
+  sqlite3session_delete(pSession->p);
+  sqlite3_free(pSession->zName);
+  for(i=0; i<pSession->nFilter; i++){
+    sqlite3_free(pSession->azFilter[i]);
+  }
+  sqlite3_free(pSession->azFilter);
+  memset(pSession, 0, sizeof(OpenSession));
+}
+#endif
+
+/*
+** Close all OpenSession objects and release all associated resources.
+*/
+#if defined(SQLITE_ENABLE_SESSION)
+static void session_close_all(ShellState *p, int i){
+  int j;
+  struct AuxDb *pAuxDb = i<0 ? p->pAuxDb : &p->aAuxDb[i];
+  for(j=0; j<pAuxDb->nSession; j++){
+    session_close(&pAuxDb->aSession[j]);
+  }
+  pAuxDb->nSession = 0;
+}
+#else
+# define session_close_all(X,Y)
+#endif
+
+/*
+** Implementation of the xFilter function for an open session.  Omit
+** any tables named by ".session filter" but let all other table through.
+*/
+#if defined(SQLITE_ENABLE_SESSION)
+static int session_filter(void *pCtx, const char *zTab){
+  OpenSession *pSession = (OpenSession*)pCtx;
+  int i;
+  for(i=0; i<pSession->nFilter; i++){
+    if( sqlite3_strglob(pSession->azFilter[i], zTab)==0 ) return 0;
+  }
+  return 1;
+}
+#endif
+
+/*
+** Try to deduce the type of file for zName based on its content.  Return
+** one of the SHELL_OPEN_* constants.
+**
+** If the file does not exist or is empty but its name looks like a ZIP
+** archive and the dfltZip flag is true, then assume it is a ZIP archive.
+** Otherwise, assume an ordinary database regardless of the filename if
+** the type cannot be determined from content.
+*/
+int deduceDatabaseType(const char *zName, int dfltZip){
+  FILE *f = fopen(zName, "rb");
+  size_t n;
+  int rc = SHELL_OPEN_UNSPEC;
+  char zBuf[100];
+  if( f==0 ){
+    if( dfltZip && sqlite3_strlike("%.zip",zName,0)==0 ){
+       return SHELL_OPEN_ZIPFILE;
+    }else{
+       return SHELL_OPEN_NORMAL;
+    }
+  }
+  n = fread(zBuf, 16, 1, f);
+  if( n==1 && memcmp(zBuf, "SQLite format 3", 16)==0 ){
+    fclose(f);
+    return SHELL_OPEN_NORMAL;
+  }
+  fseek(f, -25, SEEK_END);
+  n = fread(zBuf, 25, 1, f);
+  if( n==1 && memcmp(zBuf, "Start-Of-SQLite3-", 17)==0 ){
+    rc = SHELL_OPEN_APPENDVFS;
+  }else{
+    fseek(f, -22, SEEK_END);
+    n = fread(zBuf, 22, 1, f);
+    if( n==1 && zBuf[0]==0x50 && zBuf[1]==0x4b && zBuf[2]==0x05
+       && zBuf[3]==0x06 ){
+      rc = SHELL_OPEN_ZIPFILE;
+    }else if( n==0 && dfltZip && sqlite3_strlike("%.zip",zName,0)==0 ){
+      rc = SHELL_OPEN_ZIPFILE;
+    }
+  }
+  fclose(f);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_DESERIALIZE
+/*
+** Reconstruct an in-memory database using the output from the "dbtotxt"
+** program.  Read content from the file in p->aAuxDb[].zDbFilename.
+** If p->aAuxDb[].zDbFilename is 0, then read from standard input.
+*/
+static unsigned char *readHexDb(ShellState *p, int *pnData){
+  unsigned char *a = 0;
+  int nLine;
+  int n = 0;
+  int pgsz = 0;
+  int iOffset = 0;
+  int j, k;
+  int rc;
+  FILE *in;
+  const char *zDbFilename = p->pAuxDb->zDbFilename;
+  unsigned int x[16];
+  char zLine[1000];
+  if( zDbFilename ){
+    in = fopen(zDbFilename, "r");
+    if( in==0 ){
+      eputf("cannot open \"%s\" for reading\n", zDbFilename);
+      return 0;
+    }
+    nLine = 0;
+  }else{
+    in = p->in;
+    nLine = p->lineno;
+    if( in==0 ) in = stdin;
+  }
+  *pnData = 0;
+  nLine++;
+  if( fgets(zLine, sizeof(zLine), in)==0 ) goto readHexDb_error;
+  rc = sscanf(zLine, "| size %d pagesize %d", &n, &pgsz);
+  if( rc!=2 ) goto readHexDb_error;
+  if( n<0 ) goto readHexDb_error;
+  if( pgsz<512 || pgsz>65536 || (pgsz&(pgsz-1))!=0 ) goto readHexDb_error;
+  n = (n+pgsz-1)&~(pgsz-1);  /* Round n up to the next multiple of pgsz */
+  a = sqlite3_malloc( n ? n : 1 );
+  shell_check_oom(a);
+  memset(a, 0, n);
+  if( pgsz<512 || pgsz>65536 || (pgsz & (pgsz-1))!=0 ){
+    eputz("invalid pagesize\n");
+    goto readHexDb_error;
+  }
+  for(nLine++; fgets(zLine, sizeof(zLine), in)!=0; nLine++){
+    rc = sscanf(zLine, "| page %d offset %d", &j, &k);
+    if( rc==2 ){
+      iOffset = k;
+      continue;
+    }
+    if( cli_strncmp(zLine, "| end ", 6)==0 ){
+      break;
+    }
+    rc = sscanf(zLine,"| %d: %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x",
+                &j, &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7],
+                &x[8], &x[9], &x[10], &x[11], &x[12], &x[13], &x[14], &x[15]);
+    if( rc==17 ){
+      k = iOffset+j;
+      if( k+16<=n && k>=0 ){
+        int ii;
+        for(ii=0; ii<16; ii++) a[k+ii] = x[ii]&0xff;
+      }
+    }
+  }
+  *pnData = n;
+  if( in!=p->in ){
+    fclose(in);
+  }else{
+    p->lineno = nLine;
+  }
+  return a;
+
+readHexDb_error:
+  if( in!=p->in ){
+    fclose(in);
+  }else{
+    while( fgets(zLine, sizeof(zLine), p->in)!=0 ){
+      nLine++;
+      if(cli_strncmp(zLine, "| end ", 6)==0 ) break;
+    }
+    p->lineno = nLine;
+  }
+  sqlite3_free(a);
+  eputf("Error on line %d of --hexdb input\n", nLine);
+  return 0;
+}
+#endif /* SQLITE_OMIT_DESERIALIZE */
+
+/*
+** Scalar function "usleep(X)" invokes sqlite3_sleep(X) and returns X.
+*/
+static void shellUSleepFunc(
+  sqlite3_context *context,
+  int argcUnused,
+  sqlite3_value **argv
+){
+  int sleep = sqlite3_value_int(argv[0]);
+  (void)argcUnused;
+  sqlite3_sleep(sleep/1000);
+  sqlite3_result_int(context, sleep);
+}
+
+/* Flags for open_db().
+**
+** The default behavior of open_db() is to exit(1) if the database fails to
+** open.  The OPEN_DB_KEEPALIVE flag changes that so that it prints an error
+** but still returns without calling exit.
+**
+** The OPEN_DB_ZIPFILE flag causes open_db() to prefer to open files as a
+** ZIP archive if the file does not exist or is empty and its name matches
+** the *.zip pattern.
+*/
+#define OPEN_DB_KEEPALIVE   0x001   /* Return after error if true */
+#define OPEN_DB_ZIPFILE     0x002   /* Open as ZIP if name matches *.zip */
+
+/*
+** Make sure the database is open.  If it is not, then open it.  If
+** the database fails to open, print an error message and exit.
+*/
+static void open_db(ShellState *p, int openFlags){
+  if( p->db==0 ){
+    const char *zDbFilename = p->pAuxDb->zDbFilename;
+    if( p->openMode==SHELL_OPEN_UNSPEC ){
+      if( zDbFilename==0 || zDbFilename[0]==0 ){
+        p->openMode = SHELL_OPEN_NORMAL;
+      }else{
+        p->openMode = (u8)deduceDatabaseType(zDbFilename,
+                             (openFlags & OPEN_DB_ZIPFILE)!=0);
+      }
+    }
+    switch( p->openMode ){
+      case SHELL_OPEN_APPENDVFS: {
+        sqlite3_open_v2(zDbFilename, &p->db,
+           SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|p->openFlags, "apndvfs");
+        break;
+      }
+      case SHELL_OPEN_HEXDB:
+      case SHELL_OPEN_DESERIALIZE: {
+        sqlite3_open(0, &p->db);
+        break;
+      }
+      case SHELL_OPEN_ZIPFILE: {
+        sqlite3_open(":memory:", &p->db);
+        break;
+      }
+      case SHELL_OPEN_READONLY: {
+        sqlite3_open_v2(zDbFilename, &p->db,
+            SQLITE_OPEN_READONLY|p->openFlags, 0);
+        break;
+      }
+      case SHELL_OPEN_UNSPEC:
+      case SHELL_OPEN_NORMAL: {
+        sqlite3_open_v2(zDbFilename, &p->db,
+           SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|p->openFlags, 0);
+        break;
+      }
+    }
+    if( p->db==0 || SQLITE_OK!=sqlite3_errcode(p->db) ){
+      eputf("Error: unable to open database \"%s\": %s\n",
+            zDbFilename, sqlite3_errmsg(p->db));
+      if( (openFlags & OPEN_DB_KEEPALIVE)==0 ){
+        exit(1);
+      }
+      sqlite3_close(p->db);
+      sqlite3_open(":memory:", &p->db);
+      if( p->db==0 || SQLITE_OK!=sqlite3_errcode(p->db) ){
+        eputz("Also: unable to open substitute in-memory database.\n");
+        exit(1);
+      }else{
+        eputf("Notice: using substitute in-memory database instead of \"%s\"\n",
+              zDbFilename);
+      }
+    }
+    globalDb = p->db;
+    sqlite3_db_config(p->db, SQLITE_DBCONFIG_STMT_SCANSTATUS, (int)0, (int*)0);
+
+    /* Reflect the use or absence of --unsafe-testing invocation. */
+    {
+      int testmode_on = ShellHasFlag(p,SHFLG_TestingMode);
+      sqlite3_db_config(p->db, SQLITE_DBCONFIG_TRUSTED_SCHEMA, testmode_on,0);
+      sqlite3_db_config(p->db, SQLITE_DBCONFIG_DEFENSIVE, !testmode_on,0);
+    }
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    sqlite3_enable_load_extension(p->db, 1);
+#endif
+    sqlite3_shathree_init(p->db, 0, 0);
+    sqlite3_uint_init(p->db, 0, 0);
+    sqlite3_decimal_init(p->db, 0, 0);
+    sqlite3_base64_init(p->db, 0, 0);
+    sqlite3_base85_init(p->db, 0, 0);
+    sqlite3_regexp_init(p->db, 0, 0);
+    sqlite3_ieee_init(p->db, 0, 0);
+    sqlite3_series_init(p->db, 0, 0);
+#ifndef SQLITE_SHELL_FIDDLE
+    sqlite3_fileio_init(p->db, 0, 0);
+    sqlite3_completion_init(p->db, 0, 0);
+#endif
+#ifdef SQLITE_HAVE_ZLIB
+    if( !p->bSafeModePersist ){
+      sqlite3_zipfile_init(p->db, 0, 0);
+      sqlite3_sqlar_init(p->db, 0, 0);
+    }
+#endif
+#ifdef SQLITE_SHELL_EXTFUNCS
+    /* Create a preprocessing mechanism for extensions to make
+     * their own provisions for being built into the shell.
+     * This is a short-span macro. See further below for usage.
+     */
+#define SHELL_SUB_MACRO(base, variant) base ## _ ## variant
+#define SHELL_SUBMACRO(base, variant) SHELL_SUB_MACRO(base, variant)
+    /* Let custom-included extensions get their ..._init() called.
+     * The WHATEVER_INIT( db, pzErrorMsg, pApi ) macro should cause
+     * the extension's sqlite3_*_init( db, pzErrorMsg, pApi )
+     * initialization routine to be called.
+     */
+    {
+      int irc = SHELL_SUBMACRO(SQLITE_SHELL_EXTFUNCS, INIT)(p->db);
+    /* Let custom-included extensions expose their functionality.
+     * The WHATEVER_EXPOSE( db, pzErrorMsg ) macro should cause
+     * the SQL functions, virtual tables, collating sequences or
+     * VFS's implemented by the extension to be registered.
+     */
+      if( irc==SQLITE_OK
+          || irc==SQLITE_OK_LOAD_PERMANENTLY ){
+        SHELL_SUBMACRO(SQLITE_SHELL_EXTFUNCS, EXPOSE)(p->db, 0);
+      }
+#undef SHELL_SUB_MACRO
+#undef SHELL_SUBMACRO
+    }
+#endif
+
+    sqlite3_create_function(p->db, "strtod", 1, SQLITE_UTF8, 0,
+                            shellStrtod, 0, 0);
+    sqlite3_create_function(p->db, "dtostr", 1, SQLITE_UTF8, 0,
+                            shellDtostr, 0, 0);
+    sqlite3_create_function(p->db, "dtostr", 2, SQLITE_UTF8, 0,
+                            shellDtostr, 0, 0);
+    sqlite3_create_function(p->db, "shell_add_schema", 3, SQLITE_UTF8, 0,
+                            shellAddSchemaName, 0, 0);
+    sqlite3_create_function(p->db, "shell_module_schema", 1, SQLITE_UTF8, 0,
+                            shellModuleSchema, 0, 0);
+    sqlite3_create_function(p->db, "shell_putsnl", 1, SQLITE_UTF8, p,
+                            shellPutsFunc, 0, 0);
+    sqlite3_create_function(p->db, "usleep",1,SQLITE_UTF8,0,
+                            shellUSleepFunc, 0, 0);
+#ifndef SQLITE_NOHAVE_SYSTEM
+    sqlite3_create_function(p->db, "edit", 1, SQLITE_UTF8, 0,
+                            editFunc, 0, 0);
+    sqlite3_create_function(p->db, "edit", 2, SQLITE_UTF8, 0,
+                            editFunc, 0, 0);
+#endif
+
+    if( p->openMode==SHELL_OPEN_ZIPFILE ){
+      char *zSql = sqlite3_mprintf(
+         "CREATE VIRTUAL TABLE zip USING zipfile(%Q);", zDbFilename);
+      shell_check_oom(zSql);
+      sqlite3_exec(p->db, zSql, 0, 0, 0);
+      sqlite3_free(zSql);
+    }
+#ifndef SQLITE_OMIT_DESERIALIZE
+    else
+    if( p->openMode==SHELL_OPEN_DESERIALIZE || p->openMode==SHELL_OPEN_HEXDB ){
+      int rc;
+      int nData = 0;
+      unsigned char *aData;
+      if( p->openMode==SHELL_OPEN_DESERIALIZE ){
+        aData = (unsigned char*)readFile(zDbFilename, &nData);
+      }else{
+        aData = readHexDb(p, &nData);
+      }
+      if( aData==0 ){
+        return;
+      }
+      rc = sqlite3_deserialize(p->db, "main", aData, nData, nData,
+                   SQLITE_DESERIALIZE_RESIZEABLE |
+                   SQLITE_DESERIALIZE_FREEONCLOSE);
+      if( rc ){
+        eputf("Error: sqlite3_deserialize() returns %d\n", rc);
+      }
+      if( p->szMax>0 ){
+        sqlite3_file_control(p->db, "main", SQLITE_FCNTL_SIZE_LIMIT, &p->szMax);
+      }
+    }
+#endif
+  }
+  if( p->db!=0 ){
+    if( p->bSafeModePersist ){
+      sqlite3_set_authorizer(p->db, safeModeAuth, p);
+    }
+    sqlite3_db_config(
+        p->db, SQLITE_DBCONFIG_STMT_SCANSTATUS, p->scanstatsOn, (int*)0
+    );
+  }
+}
+
+/*
+** Attempt to close the database connection.  Report errors.
+*/
+void close_db(sqlite3 *db){
+  int rc = sqlite3_close(db);
+  if( rc ){
+    eputf("Error: sqlite3_close() returns %d: %s\n", rc, sqlite3_errmsg(db));
+  }
+}
+
+#if HAVE_READLINE || HAVE_EDITLINE
+/*
+** Readline completion callbacks
+*/
+static char *readline_completion_generator(const char *text, int state){
+  static sqlite3_stmt *pStmt = 0;
+  char *zRet;
+  if( state==0 ){
+    char *zSql;
+    sqlite3_finalize(pStmt);
+    zSql = sqlite3_mprintf("SELECT DISTINCT candidate COLLATE nocase"
+                           "  FROM completion(%Q) ORDER BY 1", text);
+    shell_check_oom(zSql);
+    sqlite3_prepare_v2(globalDb, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+  }
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    const char *z = (const char*)sqlite3_column_text(pStmt,0);
+    zRet = z ? strdup(z) : 0;
+  }else{
+    sqlite3_finalize(pStmt);
+    pStmt = 0;
+    zRet = 0;
+  }
+  return zRet;
+}
+static char **readline_completion(const char *zText, int iStart, int iEnd){
+  (void)iStart;
+  (void)iEnd;
+  rl_attempted_completion_over = 1;
+  return rl_completion_matches(zText, readline_completion_generator);
+}
+
+#elif HAVE_LINENOISE
+/*
+** Linenoise completion callback
+*/
+static void linenoise_completion(const char *zLine, linenoiseCompletions *lc){
+  i64 nLine = strlen(zLine);
+  i64 i, iStart;
+  sqlite3_stmt *pStmt = 0;
+  char *zSql;
+  char zBuf[1000];
+
+  if( nLine>(i64)sizeof(zBuf)-30 ) return;
+  if( zLine[0]=='.' || zLine[0]=='#') return;
+  for(i=nLine-1; i>=0 && (isalnum(zLine[i]) || zLine[i]=='_'); i--){}
+  if( i==nLine-1 ) return;
+  iStart = i+1;
+  memcpy(zBuf, zLine, iStart);
+  zSql = sqlite3_mprintf("SELECT DISTINCT candidate COLLATE nocase"
+                         "  FROM completion(%Q,%Q) ORDER BY 1",
+                         &zLine[iStart], zLine);
+  shell_check_oom(zSql);
+  sqlite3_prepare_v2(globalDb, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+  sqlite3_exec(globalDb, "PRAGMA page_count", 0, 0, 0); /* Load the schema */
+  while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    const char *zCompletion = (const char*)sqlite3_column_text(pStmt, 0);
+    int nCompletion = sqlite3_column_bytes(pStmt, 0);
+    if( iStart+nCompletion < (i64)sizeof(zBuf)-1 && zCompletion ){
+      memcpy(zBuf+iStart, zCompletion, nCompletion+1);
+      linenoiseAddCompletion(lc, zBuf);
+    }
+  }
+  sqlite3_finalize(pStmt);
+}
+#endif
+
+/*
+** Do C-language style dequoting.
+**
+**    \a    -> alarm
+**    \b    -> backspace
+**    \t    -> tab
+**    \n    -> newline
+**    \v    -> vertical tab
+**    \f    -> form feed
+**    \r    -> carriage return
+**    \s    -> space
+**    \"    -> "
+**    \'    -> '
+**    \\    -> backslash
+**    \NNN  -> ascii character NNN in octal
+**    \xHH  -> ascii character HH in hexadecimal
+*/
+static void resolve_backslashes(char *z){
+  int i, j;
+  char c;
+  while( *z && *z!='\\' ) z++;
+  for(i=j=0; (c = z[i])!=0; i++, j++){
+    if( c=='\\' && z[i+1]!=0 ){
+      c = z[++i];
+      if( c=='a' ){
+        c = '\a';
+      }else if( c=='b' ){
+        c = '\b';
+      }else if( c=='t' ){
+        c = '\t';
+      }else if( c=='n' ){
+        c = '\n';
+      }else if( c=='v' ){
+        c = '\v';
+      }else if( c=='f' ){
+        c = '\f';
+      }else if( c=='r' ){
+        c = '\r';
+      }else if( c=='"' ){
+        c = '"';
+      }else if( c=='\'' ){
+        c = '\'';
+      }else if( c=='\\' ){
+        c = '\\';
+      }else if( c=='x' ){
+        int nhd = 0, hdv;
+        u8 hv = 0;
+        while( nhd<2 && (c=z[i+1+nhd])!=0 && (hdv=hexDigitValue(c))>=0 ){
+          hv = (u8)((hv<<4)|hdv);
+          ++nhd;
+        }
+        i += nhd;
+        c = (u8)hv;
+      }else if( c>='0' && c<='7' ){
+        c -= '0';
+        if( z[i+1]>='0' && z[i+1]<='7' ){
+          i++;
+          c = (c<<3) + z[i] - '0';
+          if( z[i+1]>='0' && z[i+1]<='7' ){
+            i++;
+            c = (c<<3) + z[i] - '0';
+          }
+        }
+      }
+    }
+    z[j] = c;
+  }
+  if( j<i ) z[j] = 0;
+}
+
+/*
+** Interpret zArg as either an integer or a boolean value.  Return 1 or 0
+** for TRUE and FALSE.  Return the integer value if appropriate.
+*/
+static int booleanValue(const char *zArg){
+  int i;
+  if( zArg[0]=='0' && zArg[1]=='x' ){
+    for(i=2; hexDigitValue(zArg[i])>=0; i++){}
+  }else{
+    for(i=0; zArg[i]>='0' && zArg[i]<='9'; i++){}
+  }
+  if( i>0 && zArg[i]==0 ) return (int)(integerValue(zArg) & 0xffffffff);
+  if( sqlite3_stricmp(zArg, "on")==0 || sqlite3_stricmp(zArg,"yes")==0 ){
+    return 1;
+  }
+  if( sqlite3_stricmp(zArg, "off")==0 || sqlite3_stricmp(zArg,"no")==0 ){
+    return 0;
+  }
+  eputf("ERROR: Not a boolean value: \"%s\". Assuming \"no\".\n", zArg);
+  return 0;
+}
+
+/*
+** Set or clear a shell flag according to a boolean value.
+*/
+static void setOrClearFlag(ShellState *p, unsigned mFlag, const char *zArg){
+  if( booleanValue(zArg) ){
+    ShellSetFlag(p, mFlag);
+  }else{
+    ShellClearFlag(p, mFlag);
+  }
+}
+
+/*
+** Close an output file, assuming it is not stderr or stdout
+*/
+static void output_file_close(FILE *f){
+  if( f && f!=stdout && f!=stderr ) fclose(f);
+}
+
+/*
+** Try to open an output file.   The names "stdout" and "stderr" are
+** recognized and do the right thing.  NULL is returned if the output
+** filename is "off".
+*/
+static FILE *output_file_open(const char *zFile, int bTextMode){
+  FILE *f;
+  if( cli_strcmp(zFile,"stdout")==0 ){
+    f = stdout;
+  }else if( cli_strcmp(zFile, "stderr")==0 ){
+    f = stderr;
+  }else if( cli_strcmp(zFile, "off")==0 ){
+    f = 0;
+  }else{
+    f = fopen(zFile, bTextMode ? "w" : "wb");
+    if( f==0 ){
+      eputf("Error: cannot open \"%s\"\n", zFile);
+    }
+  }
+  return f;
+}
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** A routine for handling output from sqlite3_trace().
+*/
+static int sql_trace_callback(
+  unsigned mType,         /* The trace type */
+  void *pArg,             /* The ShellState pointer */
+  void *pP,               /* Usually a pointer to sqlite_stmt */
+  void *pX                /* Auxiliary output */
+){
+  ShellState *p = (ShellState*)pArg;
+  sqlite3_stmt *pStmt;
+  const char *zSql;
+  i64 nSql;
+  if( p->traceOut==0 ) return 0;
+  if( mType==SQLITE_TRACE_CLOSE ){
+    sputz(p->traceOut, "-- closing database connection\n");
+    return 0;
+  }
+  if( mType!=SQLITE_TRACE_ROW && pX!=0 && ((const char*)pX)[0]=='-' ){
+    zSql = (const char*)pX;
+  }else{
+    pStmt = (sqlite3_stmt*)pP;
+    switch( p->eTraceType ){
+      case SHELL_TRACE_EXPANDED: {
+        zSql = sqlite3_expanded_sql(pStmt);
+        break;
+      }
+#ifdef SQLITE_ENABLE_NORMALIZE
+      case SHELL_TRACE_NORMALIZED: {
+        zSql = sqlite3_normalized_sql(pStmt);
+        break;
+      }
+#endif
+      default: {
+        zSql = sqlite3_sql(pStmt);
+        break;
+      }
+    }
+  }
+  if( zSql==0 ) return 0;
+  nSql = strlen(zSql);
+  if( nSql>1000000000 ) nSql = 1000000000;
+  while( nSql>0 && zSql[nSql-1]==';' ){ nSql--; }
+  switch( mType ){
+    case SQLITE_TRACE_ROW:
+    case SQLITE_TRACE_STMT: {
+      sputf(p->traceOut, "%.*s;\n", (int)nSql, zSql);
+      break;
+    }
+    case SQLITE_TRACE_PROFILE: {
+      sqlite3_int64 nNanosec = pX ? *(sqlite3_int64*)pX : 0;
+      sputf(p->traceOut, "%.*s; -- %lld ns\n", (int)nSql, zSql, nNanosec);
+      break;
+    }
+  }
+  return 0;
+}
+#endif
+
+/*
+** A no-op routine that runs with the ".breakpoint" doc-command.  This is
+** a useful spot to set a debugger breakpoint.
+**
+** This routine does not do anything practical.  The code are there simply
+** to prevent the compiler from optimizing this routine out.
+*/
+static void test_breakpoint(void){
+  static unsigned int nCall = 0;
+  if( (nCall++)==0xffffffff ) printf("Many .breakpoints have run\n");
+}
+
+/*
+** An object used to read a CSV and other files for import.
+*/
+typedef struct ImportCtx ImportCtx;
+struct ImportCtx {
+  const char *zFile;  /* Name of the input file */
+  FILE *in;           /* Read the CSV text from this input stream */
+  int (SQLITE_CDECL *xCloser)(FILE*);      /* Func to close in */
+  char *z;            /* Accumulated text for a field */
+  int n;              /* Number of bytes in z */
+  int nAlloc;         /* Space allocated for z[] */
+  int nLine;          /* Current line number */
+  int nRow;           /* Number of rows imported */
+  int nErr;           /* Number of errors encountered */
+  int bNotFirst;      /* True if one or more bytes already read */
+  int cTerm;          /* Character that terminated the most recent field */
+  int cColSep;        /* The column separator character.  (Usually ",") */
+  int cRowSep;        /* The row separator character.  (Usually "\n") */
+};
+
+/* Clean up resourced used by an ImportCtx */
+static void import_cleanup(ImportCtx *p){
+  if( p->in!=0 && p->xCloser!=0 ){
+    p->xCloser(p->in);
+    p->in = 0;
+  }
+  sqlite3_free(p->z);
+  p->z = 0;
+}
+
+/* Append a single byte to z[] */
+static void import_append_char(ImportCtx *p, int c){
+  if( p->n+1>=p->nAlloc ){
+    p->nAlloc += p->nAlloc + 100;
+    p->z = sqlite3_realloc64(p->z, p->nAlloc);
+    shell_check_oom(p->z);
+  }
+  p->z[p->n++] = (char)c;
+}
+
+/* Read a single field of CSV text.  Compatible with rfc4180 and extended
+** with the option of having a separator other than ",".
+**
+**   +  Input comes from p->in.
+**   +  Store results in p->z of length p->n.  Space to hold p->z comes
+**      from sqlite3_malloc64().
+**   +  Use p->cSep as the column separator.  The default is ",".
+**   +  Use p->rSep as the row separator.  The default is "\n".
+**   +  Keep track of the line number in p->nLine.
+**   +  Store the character that terminates the field in p->cTerm.  Store
+**      EOF on end-of-file.
+**   +  Report syntax errors on stderr
+*/
+static char *SQLITE_CDECL csv_read_one_field(ImportCtx *p){
+  int c;
+  int cSep = (u8)p->cColSep;
+  int rSep = (u8)p->cRowSep;
+  p->n = 0;
+  c = fgetc(p->in);
+  if( c==EOF || seenInterrupt ){
+    p->cTerm = EOF;
+    return 0;
+  }
+  if( c=='"' ){
+    int pc, ppc;
+    int startLine = p->nLine;
+    int cQuote = c;
+    pc = ppc = 0;
+    while( 1 ){
+      c = fgetc(p->in);
+      if( c==rSep ) p->nLine++;
+      if( c==cQuote ){
+        if( pc==cQuote ){
+          pc = 0;
+          continue;
+        }
+      }
+      if( (c==cSep && pc==cQuote)
+       || (c==rSep && pc==cQuote)
+       || (c==rSep && pc=='\r' && ppc==cQuote)
+       || (c==EOF && pc==cQuote)
+      ){
+        do{ p->n--; }while( p->z[p->n]!=cQuote );
+        p->cTerm = c;
+        break;
+      }
+      if( pc==cQuote && c!='\r' ){
+        eputf("%s:%d: unescaped %c character\n", p->zFile, p->nLine, cQuote);
+      }
+      if( c==EOF ){
+        eputf("%s:%d: unterminated %c-quoted field\n",
+              p->zFile, startLine, cQuote);
+        p->cTerm = c;
+        break;
+      }
+      import_append_char(p, c);
+      ppc = pc;
+      pc = c;
+    }
+  }else{
+    /* If this is the first field being parsed and it begins with the
+    ** UTF-8 BOM  (0xEF BB BF) then skip the BOM */
+    if( (c&0xff)==0xef && p->bNotFirst==0 ){
+      import_append_char(p, c);
+      c = fgetc(p->in);
+      if( (c&0xff)==0xbb ){
+        import_append_char(p, c);
+        c = fgetc(p->in);
+        if( (c&0xff)==0xbf ){
+          p->bNotFirst = 1;
+          p->n = 0;
+          return csv_read_one_field(p);
+        }
+      }
+    }
+    while( c!=EOF && c!=cSep && c!=rSep ){
+      import_append_char(p, c);
+      c = fgetc(p->in);
+    }
+    if( c==rSep ){
+      p->nLine++;
+      if( p->n>0 && p->z[p->n-1]=='\r' ) p->n--;
+    }
+    p->cTerm = c;
+  }
+  if( p->z ) p->z[p->n] = 0;
+  p->bNotFirst = 1;
+  return p->z;
+}
+
+/* Read a single field of ASCII delimited text.
+**
+**   +  Input comes from p->in.
+**   +  Store results in p->z of length p->n.  Space to hold p->z comes
+**      from sqlite3_malloc64().
+**   +  Use p->cSep as the column separator.  The default is "\x1F".
+**   +  Use p->rSep as the row separator.  The default is "\x1E".
+**   +  Keep track of the row number in p->nLine.
+**   +  Store the character that terminates the field in p->cTerm.  Store
+**      EOF on end-of-file.
+**   +  Report syntax errors on stderr
+*/
+static char *SQLITE_CDECL ascii_read_one_field(ImportCtx *p){
+  int c;
+  int cSep = (u8)p->cColSep;
+  int rSep = (u8)p->cRowSep;
+  p->n = 0;
+  c = fgetc(p->in);
+  if( c==EOF || seenInterrupt ){
+    p->cTerm = EOF;
+    return 0;
+  }
+  while( c!=EOF && c!=cSep && c!=rSep ){
+    import_append_char(p, c);
+    c = fgetc(p->in);
+  }
+  if( c==rSep ){
+    p->nLine++;
+  }
+  p->cTerm = c;
+  if( p->z ) p->z[p->n] = 0;
+  return p->z;
+}
+
+/*
+** Try to transfer data for table zTable.  If an error is seen while
+** moving forward, try to go backwards.  The backwards movement won't
+** work for WITHOUT ROWID tables.
+*/
+static void tryToCloneData(
+  ShellState *p,
+  sqlite3 *newDb,
+  const char *zTable
+){
+  sqlite3_stmt *pQuery = 0;
+  sqlite3_stmt *pInsert = 0;
+  char *zQuery = 0;
+  char *zInsert = 0;
+  int rc;
+  int i, j, n;
+  int nTable = strlen30(zTable);
+  int k = 0;
+  int cnt = 0;
+  const int spinRate = 10000;
+
+  zQuery = sqlite3_mprintf("SELECT * FROM \"%w\"", zTable);
+  shell_check_oom(zQuery);
+  rc = sqlite3_prepare_v2(p->db, zQuery, -1, &pQuery, 0);
+  if( rc ){
+    eputf("Error %d: %s on [%s]\n",
+          sqlite3_extended_errcode(p->db), sqlite3_errmsg(p->db), zQuery);
+    goto end_data_xfer;
+  }
+  n = sqlite3_column_count(pQuery);
+  zInsert = sqlite3_malloc64(200 + nTable + n*3);
+  shell_check_oom(zInsert);
+  sqlite3_snprintf(200+nTable,zInsert,
+                   "INSERT OR IGNORE INTO \"%s\" VALUES(?", zTable);
+  i = strlen30(zInsert);
+  for(j=1; j<n; j++){
+    memcpy(zInsert+i, ",?", 2);
+    i += 2;
+  }
+  memcpy(zInsert+i, ");", 3);
+  rc = sqlite3_prepare_v2(newDb, zInsert, -1, &pInsert, 0);
+  if( rc ){
+    eputf("Error %d: %s on [%s]\n",
+          sqlite3_extended_errcode(newDb), sqlite3_errmsg(newDb), zInsert);
+    goto end_data_xfer;
+  }
+  for(k=0; k<2; k++){
+    while( (rc = sqlite3_step(pQuery))==SQLITE_ROW ){
+      for(i=0; i<n; i++){
+        switch( sqlite3_column_type(pQuery, i) ){
+          case SQLITE_NULL: {
+            sqlite3_bind_null(pInsert, i+1);
+            break;
+          }
+          case SQLITE_INTEGER: {
+            sqlite3_bind_int64(pInsert, i+1, sqlite3_column_int64(pQuery,i));
+            break;
+          }
+          case SQLITE_FLOAT: {
+            sqlite3_bind_double(pInsert, i+1, sqlite3_column_double(pQuery,i));
+            break;
+          }
+          case SQLITE_TEXT: {
+            sqlite3_bind_text(pInsert, i+1,
+                             (const char*)sqlite3_column_text(pQuery,i),
+                             -1, SQLITE_STATIC);
+            break;
+          }
+          case SQLITE_BLOB: {
+            sqlite3_bind_blob(pInsert, i+1, sqlite3_column_blob(pQuery,i),
+                                            sqlite3_column_bytes(pQuery,i),
+                                            SQLITE_STATIC);
+            break;
+          }
+        }
+      } /* End for */
+      rc = sqlite3_step(pInsert);
+      if( rc!=SQLITE_OK && rc!=SQLITE_ROW && rc!=SQLITE_DONE ){
+        eputf("Error %d: %s\n",
+              sqlite3_extended_errcode(newDb), sqlite3_errmsg(newDb));
+      }
+      sqlite3_reset(pInsert);
+      cnt++;
+      if( (cnt%spinRate)==0 ){
+        printf("%c\b", "|/-\\"[(cnt/spinRate)%4]);
+        fflush(stdout);
+      }
+    } /* End while */
+    if( rc==SQLITE_DONE ) break;
+    sqlite3_finalize(pQuery);
+    sqlite3_free(zQuery);
+    zQuery = sqlite3_mprintf("SELECT * FROM \"%w\" ORDER BY rowid DESC;",
+                             zTable);
+    shell_check_oom(zQuery);
+    rc = sqlite3_prepare_v2(p->db, zQuery, -1, &pQuery, 0);
+    if( rc ){
+      eputf("Warning: cannot step \"%s\" backwards", zTable);
+      break;
+    }
+  } /* End for(k=0...) */
+
+end_data_xfer:
+  sqlite3_finalize(pQuery);
+  sqlite3_finalize(pInsert);
+  sqlite3_free(zQuery);
+  sqlite3_free(zInsert);
+}
+
+
+/*
+** Try to transfer all rows of the schema that match zWhere.  For
+** each row, invoke xForEach() on the object defined by that row.
+** If an error is encountered while moving forward through the
+** sqlite_schema table, try again moving backwards.
+*/
+static void tryToCloneSchema(
+  ShellState *p,
+  sqlite3 *newDb,
+  const char *zWhere,
+  void (*xForEach)(ShellState*,sqlite3*,const char*)
+){
+  sqlite3_stmt *pQuery = 0;
+  char *zQuery = 0;
+  int rc;
+  const unsigned char *zName;
+  const unsigned char *zSql;
+  char *zErrMsg = 0;
+
+  zQuery = sqlite3_mprintf("SELECT name, sql FROM sqlite_schema"
+                           " WHERE %s ORDER BY rowid ASC", zWhere);
+  shell_check_oom(zQuery);
+  rc = sqlite3_prepare_v2(p->db, zQuery, -1, &pQuery, 0);
+  if( rc ){
+    eputf("Error: (%d) %s on [%s]\n", sqlite3_extended_errcode(p->db),
+          sqlite3_errmsg(p->db), zQuery);
+    goto end_schema_xfer;
+  }
+  while( (rc = sqlite3_step(pQuery))==SQLITE_ROW ){
+    zName = sqlite3_column_text(pQuery, 0);
+    zSql = sqlite3_column_text(pQuery, 1);
+    if( zName==0 || zSql==0 ) continue;
+    if( sqlite3_stricmp((char*)zName, "sqlite_sequence")!=0 ){
+      sputf(stdout, "%s... ", zName); fflush(stdout);
+      sqlite3_exec(newDb, (const char*)zSql, 0, 0, &zErrMsg);
+      if( zErrMsg ){
+        eputf("Error: %s\nSQL: [%s]\n", zErrMsg, zSql);
+        sqlite3_free(zErrMsg);
+        zErrMsg = 0;
+      }
+    }
+    if( xForEach ){
+      xForEach(p, newDb, (const char*)zName);
+    }
+    sputz(stdout, "done\n");
+  }
+  if( rc!=SQLITE_DONE ){
+    sqlite3_finalize(pQuery);
+    sqlite3_free(zQuery);
+    zQuery = sqlite3_mprintf("SELECT name, sql FROM sqlite_schema"
+                             " WHERE %s ORDER BY rowid DESC", zWhere);
+    shell_check_oom(zQuery);
+    rc = sqlite3_prepare_v2(p->db, zQuery, -1, &pQuery, 0);
+    if( rc ){
+      eputf("Error: (%d) %s on [%s]\n",
+            sqlite3_extended_errcode(p->db), sqlite3_errmsg(p->db), zQuery);
+      goto end_schema_xfer;
+    }
+    while( sqlite3_step(pQuery)==SQLITE_ROW ){
+      zName = sqlite3_column_text(pQuery, 0);
+      zSql = sqlite3_column_text(pQuery, 1);
+      if( zName==0 || zSql==0 ) continue;
+      if( sqlite3_stricmp((char*)zName, "sqlite_sequence")==0 ) continue;
+      sputf(stdout, "%s... ", zName); fflush(stdout);
+      sqlite3_exec(newDb, (const char*)zSql, 0, 0, &zErrMsg);
+      if( zErrMsg ){
+        eputf("Error: %s\nSQL: [%s]\n", zErrMsg, zSql);
+        sqlite3_free(zErrMsg);
+        zErrMsg = 0;
+      }
+      if( xForEach ){
+        xForEach(p, newDb, (const char*)zName);
+      }
+      sputz(stdout, "done\n");
+    }
+  }
+end_schema_xfer:
+  sqlite3_finalize(pQuery);
+  sqlite3_free(zQuery);
+}
+
+/*
+** Open a new database file named "zNewDb".  Try to recover as much information
+** as possible out of the main database (which might be corrupt) and write it
+** into zNewDb.
+*/
+static void tryToClone(ShellState *p, const char *zNewDb){
+  int rc;
+  sqlite3 *newDb = 0;
+  if( access(zNewDb,0)==0 ){
+    eputf("File \"%s\" already exists.\n", zNewDb);
+    return;
+  }
+  rc = sqlite3_open(zNewDb, &newDb);
+  if( rc ){
+    eputf("Cannot create output database: %s\n", sqlite3_errmsg(newDb));
+  }else{
+    sqlite3_exec(p->db, "PRAGMA writable_schema=ON;", 0, 0, 0);
+    sqlite3_exec(newDb, "BEGIN EXCLUSIVE;", 0, 0, 0);
+    tryToCloneSchema(p, newDb, "type='table'", tryToCloneData);
+    tryToCloneSchema(p, newDb, "type!='table'", 0);
+    sqlite3_exec(newDb, "COMMIT;", 0, 0, 0);
+    sqlite3_exec(p->db, "PRAGMA writable_schema=OFF;", 0, 0, 0);
+  }
+  close_db(newDb);
+}
+
+#ifndef SQLITE_SHELL_FIDDLE
+/*
+** Change the output stream (file or pipe or console) to something else.
+*/
+static void output_redir(ShellState *p, FILE *pfNew){
+  if( p->out != stdout ) eputz("Output already redirected.\n");
+  else{
+    p->out = pfNew;
+    setOutputStream(pfNew);
+  }
+}
+
+/*
+** Change the output file back to stdout.
+**
+** If the p->doXdgOpen flag is set, that means the output was being
+** redirected to a temporary file named by p->zTempFile.  In that case,
+** launch start/open/xdg-open on that temporary file.
+*/
+static void output_reset(ShellState *p){
+  if( p->outfile[0]=='|' ){
+#ifndef SQLITE_OMIT_POPEN
+    pclose(p->out);
+#endif
+  }else{
+    output_file_close(p->out);
+#ifndef SQLITE_NOHAVE_SYSTEM
+    if( p->doXdgOpen ){
+      const char *zXdgOpenCmd =
+#if defined(_WIN32)
+      "start";
+#elif defined(__APPLE__)
+      "open";
+#else
+      "xdg-open";
+#endif
+      char *zCmd;
+      zCmd = sqlite3_mprintf("%s %s", zXdgOpenCmd, p->zTempFile);
+      if( system(zCmd) ){
+        eputf("Failed: [%s]\n", zCmd);
+      }else{
+        /* Give the start/open/xdg-open command some time to get
+        ** going before we continue, and potential delete the
+        ** p->zTempFile data file out from under it */
+        sqlite3_sleep(2000);
+      }
+      sqlite3_free(zCmd);
+      outputModePop(p);
+      p->doXdgOpen = 0;
+    }
+#endif /* !defined(SQLITE_NOHAVE_SYSTEM) */
+  }
+  p->outfile[0] = 0;
+  p->out = stdout;
+  setOutputStream(stdout);
+}
+#else
+# define output_redir(SS,pfO)
+# define output_reset(SS)
+#endif
+
+/*
+** Run an SQL command and return the single integer result.
+*/
+static int db_int(sqlite3 *db, const char *zSql){
+  sqlite3_stmt *pStmt;
+  int res = 0;
+  sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( pStmt && sqlite3_step(pStmt)==SQLITE_ROW ){
+    res = sqlite3_column_int(pStmt,0);
+  }
+  sqlite3_finalize(pStmt);
+  return res;
+}
+
+#if SQLITE_SHELL_HAVE_RECOVER
+/*
+** Convert a 2-byte or 4-byte big-endian integer into a native integer
+*/
+static unsigned int get2byteInt(unsigned char *a){
+  return (a[0]<<8) + a[1];
+}
+static unsigned int get4byteInt(unsigned char *a){
+  return (a[0]<<24) + (a[1]<<16) + (a[2]<<8) + a[3];
+}
+
+/*
+** Implementation of the ".dbinfo" command.
+**
+** Return 1 on error, 2 to exit, and 0 otherwise.
+*/
+static int shell_dbinfo_command(ShellState *p, int nArg, char **azArg){
+  static const struct { const char *zName; int ofst; } aField[] = {
+     { "file change counter:",  24  },
+     { "database page count:",  28  },
+     { "freelist page count:",  36  },
+     { "schema cookie:",        40  },
+     { "schema format:",        44  },
+     { "default cache size:",   48  },
+     { "autovacuum top root:",  52  },
+     { "incremental vacuum:",   64  },
+     { "text encoding:",        56  },
+     { "user version:",         60  },
+     { "application id:",       68  },
+     { "software version:",     96  },
+  };
+  static const struct { const char *zName; const char *zSql; } aQuery[] = {
+     { "number of tables:",
+       "SELECT count(*) FROM %s WHERE type='table'" },
+     { "number of indexes:",
+       "SELECT count(*) FROM %s WHERE type='index'" },
+     { "number of triggers:",
+       "SELECT count(*) FROM %s WHERE type='trigger'" },
+     { "number of views:",
+       "SELECT count(*) FROM %s WHERE type='view'" },
+     { "schema size:",
+       "SELECT total(length(sql)) FROM %s" },
+  };
+  int i, rc;
+  unsigned iDataVersion;
+  char *zSchemaTab;
+  char *zDb = nArg>=2 ? azArg[1] : "main";
+  sqlite3_stmt *pStmt = 0;
+  unsigned char aHdr[100];
+  open_db(p, 0);
+  if( p->db==0 ) return 1;
+  rc = sqlite3_prepare_v2(p->db,
+             "SELECT data FROM sqlite_dbpage(?1) WHERE pgno=1",
+             -1, &pStmt, 0);
+  if( rc ){
+    eputf("error: %s\n", sqlite3_errmsg(p->db));
+    sqlite3_finalize(pStmt);
+    return 1;
+  }
+  sqlite3_bind_text(pStmt, 1, zDb, -1, SQLITE_STATIC);
+  if( sqlite3_step(pStmt)==SQLITE_ROW
+   && sqlite3_column_bytes(pStmt,0)>100
+  ){
+    const u8 *pb = sqlite3_column_blob(pStmt,0);
+    shell_check_oom(pb);
+    memcpy(aHdr, pb, 100);
+    sqlite3_finalize(pStmt);
+  }else{
+    eputz("unable to read database header\n");
+    sqlite3_finalize(pStmt);
+    return 1;
+  }
+  i = get2byteInt(aHdr+16);
+  if( i==1 ) i = 65536;
+  oputf("%-20s %d\n", "database page size:", i);
+  oputf("%-20s %d\n", "write format:", aHdr[18]);
+  oputf("%-20s %d\n", "read format:", aHdr[19]);
+  oputf("%-20s %d\n", "reserved bytes:", aHdr[20]);
+  for(i=0; i<ArraySize(aField); i++){
+    int ofst = aField[i].ofst;
+    unsigned int val = get4byteInt(aHdr + ofst);
+    oputf("%-20s %u", aField[i].zName, val);
+    switch( ofst ){
+      case 56: {
+        if( val==1 ) oputz(" (utf8)");
+        if( val==2 ) oputz(" (utf16le)");
+        if( val==3 ) oputz(" (utf16be)");
+      }
+    }
+    oputz("\n");
+  }
+  if( zDb==0 ){
+    zSchemaTab = sqlite3_mprintf("main.sqlite_schema");
+  }else if( cli_strcmp(zDb,"temp")==0 ){
+    zSchemaTab = sqlite3_mprintf("%s", "sqlite_temp_schema");
+  }else{
+    zSchemaTab = sqlite3_mprintf("\"%w\".sqlite_schema", zDb);
+  }
+  for(i=0; i<ArraySize(aQuery); i++){
+    char *zSql = sqlite3_mprintf(aQuery[i].zSql, zSchemaTab);
+    int val = db_int(p->db, zSql);
+    sqlite3_free(zSql);
+    oputf("%-20s %d\n", aQuery[i].zName, val);
+  }
+  sqlite3_free(zSchemaTab);
+  sqlite3_file_control(p->db, zDb, SQLITE_FCNTL_DATA_VERSION, &iDataVersion);
+  oputf("%-20s %u\n", "data version", iDataVersion);
+  return 0;
+}
+#endif /* SQLITE_SHELL_HAVE_RECOVER */
+
+/*
+** Print the current sqlite3_errmsg() value to stderr and return 1.
+*/
+static int shellDatabaseError(sqlite3 *db){
+  const char *zErr = sqlite3_errmsg(db);
+  eputf("Error: %s\n", zErr);
+  return 1;
+}
+
+/*
+** Compare the pattern in zGlob[] against the text in z[].  Return TRUE
+** if they match and FALSE (0) if they do not match.
+**
+** Globbing rules:
+**
+**      '*'       Matches any sequence of zero or more characters.
+**
+**      '?'       Matches exactly one character.
+**
+**     [...]      Matches one character from the enclosed list of
+**                characters.
+**
+**     [^...]     Matches one character not in the enclosed list.
+**
+**      '#'       Matches any sequence of one or more digits with an
+**                optional + or - sign in front
+**
+**      ' '       Any span of whitespace matches any other span of
+**                whitespace.
+**
+** Extra whitespace at the end of z[] is ignored.
+*/
+static int testcase_glob(const char *zGlob, const char *z){
+  int c, c2;
+  int invert;
+  int seen;
+
+  while( (c = (*(zGlob++)))!=0 ){
+    if( IsSpace(c) ){
+      if( !IsSpace(*z) ) return 0;
+      while( IsSpace(*zGlob) ) zGlob++;
+      while( IsSpace(*z) ) z++;
+    }else if( c=='*' ){
+      while( (c=(*(zGlob++))) == '*' || c=='?' ){
+        if( c=='?' && (*(z++))==0 ) return 0;
+      }
+      if( c==0 ){
+        return 1;
+      }else if( c=='[' ){
+        while( *z && testcase_glob(zGlob-1,z)==0 ){
+          z++;
+        }
+        return (*z)!=0;
+      }
+      while( (c2 = (*(z++)))!=0 ){
+        while( c2!=c ){
+          c2 = *(z++);
+          if( c2==0 ) return 0;
+        }
+        if( testcase_glob(zGlob,z) ) return 1;
+      }
+      return 0;
+    }else if( c=='?' ){
+      if( (*(z++))==0 ) return 0;
+    }else if( c=='[' ){
+      int prior_c = 0;
+      seen = 0;
+      invert = 0;
+      c = *(z++);
+      if( c==0 ) return 0;
+      c2 = *(zGlob++);
+      if( c2=='^' ){
+        invert = 1;
+        c2 = *(zGlob++);
+      }
+      if( c2==']' ){
+        if( c==']' ) seen = 1;
+        c2 = *(zGlob++);
+      }
+      while( c2 && c2!=']' ){
+        if( c2=='-' && zGlob[0]!=']' && zGlob[0]!=0 && prior_c>0 ){
+          c2 = *(zGlob++);
+          if( c>=prior_c && c<=c2 ) seen = 1;
+          prior_c = 0;
+        }else{
+          if( c==c2 ){
+            seen = 1;
+          }
+          prior_c = c2;
+        }
+        c2 = *(zGlob++);
+      }
+      if( c2==0 || (seen ^ invert)==0 ) return 0;
+    }else if( c=='#' ){
+      if( (z[0]=='-' || z[0]=='+') && IsDigit(z[1]) ) z++;
+      if( !IsDigit(z[0]) ) return 0;
+      z++;
+      while( IsDigit(z[0]) ){ z++; }
+    }else{
+      if( c!=(*(z++)) ) return 0;
+    }
+  }
+  while( IsSpace(*z) ){ z++; }
+  return *z==0;
+}
+
+
+/*
+** Compare the string as a command-line option with either one or two
+** initial "-" characters.
+*/
+static int optionMatch(const char *zStr, const char *zOpt){
+  if( zStr[0]!='-' ) return 0;
+  zStr++;
+  if( zStr[0]=='-' ) zStr++;
+  return cli_strcmp(zStr, zOpt)==0;
+}
+
+/*
+** Delete a file.
+*/
+int shellDeleteFile(const char *zFilename){
+  int rc;
+#ifdef _WIN32
+  wchar_t *z = sqlite3_win32_utf8_to_unicode(zFilename);
+  rc = _wunlink(z);
+  sqlite3_free(z);
+#else
+  rc = unlink(zFilename);
+#endif
+  return rc;
+}
+
+/*
+** Try to delete the temporary file (if there is one) and free the
+** memory used to hold the name of the temp file.
+*/
+static void clearTempFile(ShellState *p){
+  if( p->zTempFile==0 ) return;
+  if( p->doXdgOpen ) return;
+  if( shellDeleteFile(p->zTempFile) ) return;
+  sqlite3_free(p->zTempFile);
+  p->zTempFile = 0;
+}
+
+/*
+** Create a new temp file name with the given suffix.
+*/
+static void newTempFile(ShellState *p, const char *zSuffix){
+  clearTempFile(p);
+  sqlite3_free(p->zTempFile);
+  p->zTempFile = 0;
+  if( p->db ){
+    sqlite3_file_control(p->db, 0, SQLITE_FCNTL_TEMPFILENAME, &p->zTempFile);
+  }
+  if( p->zTempFile==0 ){
+    /* If p->db is an in-memory database then the TEMPFILENAME file-control
+    ** will not work and we will need to fallback to guessing */
+    char *zTemp;
+    sqlite3_uint64 r;
+    sqlite3_randomness(sizeof(r), &r);
+    zTemp = getenv("TEMP");
+    if( zTemp==0 ) zTemp = getenv("TMP");
+    if( zTemp==0 ){
+#ifdef _WIN32
+      zTemp = "\\tmp";
+#else
+      zTemp = "/tmp";
+#endif
+    }
+    p->zTempFile = sqlite3_mprintf("%s/temp%llx.%s", zTemp, r, zSuffix);
+  }else{
+    p->zTempFile = sqlite3_mprintf("%z.%s", p->zTempFile, zSuffix);
+  }
+  shell_check_oom(p->zTempFile);
+}
+
+
+/*
+** The implementation of SQL scalar function fkey_collate_clause(), used
+** by the ".lint fkey-indexes" command. This scalar function is always
+** called with four arguments - the parent table name, the parent column name,
+** the child table name and the child column name.
+**
+**   fkey_collate_clause('parent-tab', 'parent-col', 'child-tab', 'child-col')
+**
+** If either of the named tables or columns do not exist, this function
+** returns an empty string. An empty string is also returned if both tables
+** and columns exist but have the same default collation sequence. Or,
+** if both exist but the default collation sequences are different, this
+** function returns the string " COLLATE <parent-collation>", where
+** <parent-collation> is the default collation sequence of the parent column.
+*/
+static void shellFkeyCollateClause(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  sqlite3 *db = sqlite3_context_db_handle(pCtx);
+  const char *zParent;
+  const char *zParentCol;
+  const char *zParentSeq;
+  const char *zChild;
+  const char *zChildCol;
+  const char *zChildSeq = 0;  /* Initialize to avoid false-positive warning */
+  int rc;
+
+  assert( nVal==4 );
+  zParent = (const char*)sqlite3_value_text(apVal[0]);
+  zParentCol = (const char*)sqlite3_value_text(apVal[1]);
+  zChild = (const char*)sqlite3_value_text(apVal[2]);
+  zChildCol = (const char*)sqlite3_value_text(apVal[3]);
+
+  sqlite3_result_text(pCtx, "", -1, SQLITE_STATIC);
+  rc = sqlite3_table_column_metadata(
+      db, "main", zParent, zParentCol, 0, &zParentSeq, 0, 0, 0
+  );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_table_column_metadata(
+        db, "main", zChild, zChildCol, 0, &zChildSeq, 0, 0, 0
+    );
+  }
+
+  if( rc==SQLITE_OK && sqlite3_stricmp(zParentSeq, zChildSeq) ){
+    char *z = sqlite3_mprintf(" COLLATE %s", zParentSeq);
+    sqlite3_result_text(pCtx, z, -1, SQLITE_TRANSIENT);
+    sqlite3_free(z);
+  }
+}
+
+
+/*
+** The implementation of dot-command ".lint fkey-indexes".
+*/
+static int lintFkeyIndexes(
+  ShellState *pState,             /* Current shell tool state */
+  char **azArg,                   /* Array of arguments passed to dot command */
+  int nArg                        /* Number of entries in azArg[] */
+){
+  sqlite3 *db = pState->db;       /* Database handle to query "main" db of */
+  int bVerbose = 0;               /* If -verbose is present */
+  int bGroupByParent = 0;         /* If -groupbyparent is present */
+  int i;                          /* To iterate through azArg[] */
+  const char *zIndent = "";       /* How much to indent CREATE INDEX by */
+  int rc;                         /* Return code */
+  sqlite3_stmt *pSql = 0;         /* Compiled version of SQL statement below */
+
+  /*
+  ** This SELECT statement returns one row for each foreign key constraint
+  ** in the schema of the main database. The column values are:
+  **
+  ** 0. The text of an SQL statement similar to:
+  **
+  **      "EXPLAIN QUERY PLAN SELECT 1 FROM child_table WHERE child_key=?"
+  **
+  **    This SELECT is similar to the one that the foreign keys implementation
+  **    needs to run internally on child tables. If there is an index that can
+  **    be used to optimize this query, then it can also be used by the FK
+  **    implementation to optimize DELETE or UPDATE statements on the parent
+  **    table.
+  **
+  ** 1. A GLOB pattern suitable for sqlite3_strglob(). If the plan output by
+  **    the EXPLAIN QUERY PLAN command matches this pattern, then the schema
+  **    contains an index that can be used to optimize the query.
+  **
+  ** 2. Human readable text that describes the child table and columns. e.g.
+  **
+  **       "child_table(child_key1, child_key2)"
+  **
+  ** 3. Human readable text that describes the parent table and columns. e.g.
+  **
+  **       "parent_table(parent_key1, parent_key2)"
+  **
+  ** 4. A full CREATE INDEX statement for an index that could be used to
+  **    optimize DELETE or UPDATE statements on the parent table. e.g.
+  **
+  **       "CREATE INDEX child_table_child_key ON child_table(child_key)"
+  **
+  ** 5. The name of the parent table.
+  **
+  ** These six values are used by the C logic below to generate the report.
+  */
+  const char *zSql =
+  "SELECT "
+    "     'EXPLAIN QUERY PLAN SELECT 1 FROM ' || quote(s.name) || ' WHERE '"
+    "  || group_concat(quote(s.name) || '.' || quote(f.[from]) || '=?' "
+    "  || fkey_collate_clause("
+    "       f.[table], COALESCE(f.[to], p.[name]), s.name, f.[from]),' AND ')"
+    ", "
+    "     'SEARCH ' || s.name || ' USING COVERING INDEX*('"
+    "  || group_concat('*=?', ' AND ') || ')'"
+    ", "
+    "     s.name  || '(' || group_concat(f.[from],  ', ') || ')'"
+    ", "
+    "     f.[table] || '(' || group_concat(COALESCE(f.[to], p.[name])) || ')'"
+    ", "
+    "     'CREATE INDEX ' || quote(s.name ||'_'|| group_concat(f.[from], '_'))"
+    "  || ' ON ' || quote(s.name) || '('"
+    "  || group_concat(quote(f.[from]) ||"
+    "        fkey_collate_clause("
+    "          f.[table], COALESCE(f.[to], p.[name]), s.name, f.[from]), ', ')"
+    "  || ');'"
+    ", "
+    "     f.[table] "
+    "FROM sqlite_schema AS s, pragma_foreign_key_list(s.name) AS f "
+    "LEFT JOIN pragma_table_info AS p ON (pk-1=seq AND p.arg=f.[table]) "
+    "GROUP BY s.name, f.id "
+    "ORDER BY (CASE WHEN ? THEN f.[table] ELSE s.name END)"
+  ;
+  const char *zGlobIPK = "SEARCH * USING INTEGER PRIMARY KEY (rowid=?)";
+
+  for(i=2; i<nArg; i++){
+    int n = strlen30(azArg[i]);
+    if( n>1 && sqlite3_strnicmp("-verbose", azArg[i], n)==0 ){
+      bVerbose = 1;
+    }
+    else if( n>1 && sqlite3_strnicmp("-groupbyparent", azArg[i], n)==0 ){
+      bGroupByParent = 1;
+      zIndent = "    ";
+    }
+    else{
+      eputf("Usage: %s %s ?-verbose? ?-groupbyparent?\n", azArg[0], azArg[1]);
+      return SQLITE_ERROR;
+    }
+  }
+
+  /* Register the fkey_collate_clause() SQL function */
+  rc = sqlite3_create_function(db, "fkey_collate_clause", 4, SQLITE_UTF8,
+      0, shellFkeyCollateClause, 0, 0
+  );
+
+
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pSql, 0);
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int(pSql, 1, bGroupByParent);
+  }
+
+  if( rc==SQLITE_OK ){
+    int rc2;
+    char *zPrev = 0;
+    while( SQLITE_ROW==sqlite3_step(pSql) ){
+      int res = -1;
+      sqlite3_stmt *pExplain = 0;
+      const char *zEQP = (const char*)sqlite3_column_text(pSql, 0);
+      const char *zGlob = (const char*)sqlite3_column_text(pSql, 1);
+      const char *zFrom = (const char*)sqlite3_column_text(pSql, 2);
+      const char *zTarget = (const char*)sqlite3_column_text(pSql, 3);
+      const char *zCI = (const char*)sqlite3_column_text(pSql, 4);
+      const char *zParent = (const char*)sqlite3_column_text(pSql, 5);
+
+      if( zEQP==0 ) continue;
+      if( zGlob==0 ) continue;
+      rc = sqlite3_prepare_v2(db, zEQP, -1, &pExplain, 0);
+      if( rc!=SQLITE_OK ) break;
+      if( SQLITE_ROW==sqlite3_step(pExplain) ){
+        const char *zPlan = (const char*)sqlite3_column_text(pExplain, 3);
+        res = zPlan!=0 && (  0==sqlite3_strglob(zGlob, zPlan)
+                          || 0==sqlite3_strglob(zGlobIPK, zPlan));
+      }
+      rc = sqlite3_finalize(pExplain);
+      if( rc!=SQLITE_OK ) break;
+
+      if( res<0 ){
+        eputz("Error: internal error");
+        break;
+      }else{
+        if( bGroupByParent
+        && (bVerbose || res==0)
+        && (zPrev==0 || sqlite3_stricmp(zParent, zPrev))
+        ){
+          oputf("-- Parent table %s\n", zParent);
+          sqlite3_free(zPrev);
+          zPrev = sqlite3_mprintf("%s", zParent);
+        }
+
+        if( res==0 ){
+          oputf("%s%s --> %s\n", zIndent, zCI, zTarget);
+        }else if( bVerbose ){
+          oputf("%s/* no extra indexes required for %s -> %s */\n",
+                zIndent, zFrom, zTarget
+          );
+        }
+      }
+    }
+    sqlite3_free(zPrev);
+
+    if( rc!=SQLITE_OK ){
+      eputf("%s\n", sqlite3_errmsg(db));
+    }
+
+    rc2 = sqlite3_finalize(pSql);
+    if( rc==SQLITE_OK && rc2!=SQLITE_OK ){
+      rc = rc2;
+      eputf("%s\n", sqlite3_errmsg(db));
+    }
+  }else{
+    eputf("%s\n", sqlite3_errmsg(db));
+  }
+
+  return rc;
+}
+
+/*
+** Implementation of ".lint" dot command.
+*/
+static int lintDotCommand(
+  ShellState *pState,             /* Current shell tool state */
+  char **azArg,                   /* Array of arguments passed to dot command */
+  int nArg                        /* Number of entries in azArg[] */
+){
+  int n;
+  n = (nArg>=2 ? strlen30(azArg[1]) : 0);
+  if( n<1 || sqlite3_strnicmp(azArg[1], "fkey-indexes", n) ) goto usage;
+  return lintFkeyIndexes(pState, azArg, nArg);
+
+ usage:
+  eputf("Usage %s sub-command ?switches...?\n", azArg[0]);
+  eputz("Where sub-commands are:\n");
+  eputz("    fkey-indexes\n");
+  return SQLITE_ERROR;
+}
+
+static void shellPrepare(
+  sqlite3 *db,
+  int *pRc,
+  const char *zSql,
+  sqlite3_stmt **ppStmt
+){
+  *ppStmt = 0;
+  if( *pRc==SQLITE_OK ){
+    int rc = sqlite3_prepare_v2(db, zSql, -1, ppStmt, 0);
+    if( rc!=SQLITE_OK ){
+      eputf("sql error: %s (%d)\n", sqlite3_errmsg(db), sqlite3_errcode(db));
+      *pRc = rc;
+    }
+  }
+}
+
+/*
+** Create a prepared statement using printf-style arguments for the SQL.
+*/
+static void shellPreparePrintf(
+  sqlite3 *db,
+  int *pRc,
+  sqlite3_stmt **ppStmt,
+  const char *zFmt,
+  ...
+){
+  *ppStmt = 0;
+  if( *pRc==SQLITE_OK ){
+    va_list ap;
+    char *z;
+    va_start(ap, zFmt);
+    z = sqlite3_vmprintf(zFmt, ap);
+    va_end(ap);
+    if( z==0 ){
+      *pRc = SQLITE_NOMEM;
+    }else{
+      shellPrepare(db, pRc, z, ppStmt);
+      sqlite3_free(z);
+    }
+  }
+}
+
+/* 
+** Finalize the prepared statement created using shellPreparePrintf().
+*/
+static void shellFinalize(
+  int *pRc,
+  sqlite3_stmt *pStmt
+){
+  if( pStmt ){
+    sqlite3 *db = sqlite3_db_handle(pStmt);
+    int rc = sqlite3_finalize(pStmt);
+    if( *pRc==SQLITE_OK ){
+      if( rc!=SQLITE_OK ){
+        eputf("SQL error: %s\n", sqlite3_errmsg(db));
+      }
+      *pRc = rc;
+    }
+  }
+}
+
+#if !defined SQLITE_OMIT_VIRTUALTABLE
+/* Reset the prepared statement created using shellPreparePrintf().
+**
+** This routine is could be marked "static".  But it is not always used,
+** depending on compile-time options.  By omitting the "static", we avoid
+** nuisance compiler warnings about "defined but not used".
+*/
+void shellReset(
+  int *pRc,
+  sqlite3_stmt *pStmt
+){
+  int rc = sqlite3_reset(pStmt);
+  if( *pRc==SQLITE_OK ){
+    if( rc!=SQLITE_OK ){
+      sqlite3 *db = sqlite3_db_handle(pStmt);
+      eputf("SQL error: %s\n", sqlite3_errmsg(db));
+    }
+    *pRc = rc;
+  }
+}
+#endif /* !defined SQLITE_OMIT_VIRTUALTABLE */
+
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB)
+/******************************************************************************
+** The ".archive" or ".ar" command.
+*/
+/*
+** Structure representing a single ".ar" command.
+*/
+typedef struct ArCommand ArCommand;
+struct ArCommand {
+  u8 eCmd;                        /* An AR_CMD_* value */
+  u8 bVerbose;                    /* True if --verbose */
+  u8 bZip;                        /* True if the archive is a ZIP */
+  u8 bDryRun;                     /* True if --dry-run */
+  u8 bAppend;                     /* True if --append */
+  u8 bGlob;                       /* True if --glob */
+  u8 fromCmdLine;                 /* Run from -A instead of .archive */
+  int nArg;                       /* Number of command arguments */
+  char *zSrcTable;                /* "sqlar", "zipfile($file)" or "zip" */
+  const char *zFile;              /* --file argument, or NULL */
+  const char *zDir;               /* --directory argument, or NULL */
+  char **azArg;                   /* Array of command arguments */
+  ShellState *p;                  /* Shell state */
+  sqlite3 *db;                    /* Database containing the archive */
+};
+
+/*
+** Print a usage message for the .ar command to stderr and return SQLITE_ERROR.
+*/
+static int arUsage(FILE *f){
+  showHelp(f,"archive");
+  return SQLITE_ERROR;
+}
+
+/*
+** Print an error message for the .ar command to stderr and return
+** SQLITE_ERROR.
+*/
+static int arErrorMsg(ArCommand *pAr, const char *zFmt, ...){
+  va_list ap;
+  char *z;
+  va_start(ap, zFmt);
+  z = sqlite3_vmprintf(zFmt, ap);
+  va_end(ap);
+  eputf("Error: %s\n", z);
+  if( pAr->fromCmdLine ){
+    eputz("Use \"-A\" for more help\n");
+  }else{
+    eputz("Use \".archive --help\" for more help\n");
+  }
+  sqlite3_free(z);
+  return SQLITE_ERROR;
+}
+
+/*
+** Values for ArCommand.eCmd.
+*/
+#define AR_CMD_CREATE       1
+#define AR_CMD_UPDATE       2
+#define AR_CMD_INSERT       3
+#define AR_CMD_EXTRACT      4
+#define AR_CMD_LIST         5
+#define AR_CMD_HELP         6
+#define AR_CMD_REMOVE       7
+
+/*
+** Other (non-command) switches.
+*/
+#define AR_SWITCH_VERBOSE     8
+#define AR_SWITCH_FILE        9
+#define AR_SWITCH_DIRECTORY  10
+#define AR_SWITCH_APPEND     11
+#define AR_SWITCH_DRYRUN     12
+#define AR_SWITCH_GLOB       13
+
+static int arProcessSwitch(ArCommand *pAr, int eSwitch, const char *zArg){
+  switch( eSwitch ){
+    case AR_CMD_CREATE:
+    case AR_CMD_EXTRACT:
+    case AR_CMD_LIST:
+    case AR_CMD_REMOVE:
+    case AR_CMD_UPDATE:
+    case AR_CMD_INSERT:
+    case AR_CMD_HELP:
+      if( pAr->eCmd ){
+        return arErrorMsg(pAr, "multiple command options");
+      }
+      pAr->eCmd = eSwitch;
+      break;
+
+    case AR_SWITCH_DRYRUN:
+      pAr->bDryRun = 1;
+      break;
+    case AR_SWITCH_GLOB:
+      pAr->bGlob = 1;
+      break;
+    case AR_SWITCH_VERBOSE:
+      pAr->bVerbose = 1;
+      break;
+    case AR_SWITCH_APPEND:
+      pAr->bAppend = 1;
+      deliberate_fall_through;
+    case AR_SWITCH_FILE:
+      pAr->zFile = zArg;
+      break;
+    case AR_SWITCH_DIRECTORY:
+      pAr->zDir = zArg;
+      break;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Parse the command line for an ".ar" command. The results are written into
+** structure (*pAr). SQLITE_OK is returned if the command line is parsed
+** successfully, otherwise an error message is written to stderr and
+** SQLITE_ERROR returned.
+*/
+static int arParseCommand(
+  char **azArg,                   /* Array of arguments passed to dot command */
+  int nArg,                       /* Number of entries in azArg[] */
+  ArCommand *pAr                  /* Populate this object */
+){
+  struct ArSwitch {
+    const char *zLong;
+    char cShort;
+    u8 eSwitch;
+    u8 bArg;
+  } aSwitch[] = {
+    { "create",    'c', AR_CMD_CREATE,       0 },
+    { "extract",   'x', AR_CMD_EXTRACT,      0 },
+    { "insert",    'i', AR_CMD_INSERT,       0 },
+    { "list",      't', AR_CMD_LIST,         0 },
+    { "remove",    'r', AR_CMD_REMOVE,       0 },
+    { "update",    'u', AR_CMD_UPDATE,       0 },
+    { "help",      'h', AR_CMD_HELP,         0 },
+    { "verbose",   'v', AR_SWITCH_VERBOSE,   0 },
+    { "file",      'f', AR_SWITCH_FILE,      1 },
+    { "append",    'a', AR_SWITCH_APPEND,    1 },
+    { "directory", 'C', AR_SWITCH_DIRECTORY, 1 },
+    { "dryrun",    'n', AR_SWITCH_DRYRUN,    0 },
+    { "glob",      'g', AR_SWITCH_GLOB,      0 },
+  };
+  int nSwitch = sizeof(aSwitch) / sizeof(struct ArSwitch);
+  struct ArSwitch *pEnd = &aSwitch[nSwitch];
+
+  if( nArg<=1 ){
+    eputz("Wrong number of arguments.  Usage:\n");
+    return arUsage(stderr);
+  }else{
+    char *z = azArg[1];
+    if( z[0]!='-' ){
+      /* Traditional style [tar] invocation */
+      int i;
+      int iArg = 2;
+      for(i=0; z[i]; i++){
+        const char *zArg = 0;
+        struct ArSwitch *pOpt;
+        for(pOpt=&aSwitch[0]; pOpt<pEnd; pOpt++){
+          if( z[i]==pOpt->cShort ) break;
+        }
+        if( pOpt==pEnd ){
+          return arErrorMsg(pAr, "unrecognized option: %c", z[i]);
+        }
+        if( pOpt->bArg ){
+          if( iArg>=nArg ){
+            return arErrorMsg(pAr, "option requires an argument: %c",z[i]);
+          }
+          zArg = azArg[iArg++];
+        }
+        if( arProcessSwitch(pAr, pOpt->eSwitch, zArg) ) return SQLITE_ERROR;
+      }
+      pAr->nArg = nArg-iArg;
+      if( pAr->nArg>0 ){
+        pAr->azArg = &azArg[iArg];
+      }
+    }else{
+      /* Non-traditional invocation */
+      int iArg;
+      for(iArg=1; iArg<nArg; iArg++){
+        int n;
+        z = azArg[iArg];
+        if( z[0]!='-' ){
+          /* All remaining command line words are command arguments. */
+          pAr->azArg = &azArg[iArg];
+          pAr->nArg = nArg-iArg;
+          break;
+        }
+        n = strlen30(z);
+
+        if( z[1]!='-' ){
+          int i;
+          /* One or more short options */
+          for(i=1; i<n; i++){
+            const char *zArg = 0;
+            struct ArSwitch *pOpt;
+            for(pOpt=&aSwitch[0]; pOpt<pEnd; pOpt++){
+              if( z[i]==pOpt->cShort ) break;
+            }
+            if( pOpt==pEnd ){
+              return arErrorMsg(pAr, "unrecognized option: %c", z[i]);
+            }
+            if( pOpt->bArg ){
+              if( i<(n-1) ){
+                zArg = &z[i+1];
+                i = n;
+              }else{
+                if( iArg>=(nArg-1) ){
+                  return arErrorMsg(pAr, "option requires an argument: %c",
+                                    z[i]);
+                }
+                zArg = azArg[++iArg];
+              }
+            }
+            if( arProcessSwitch(pAr, pOpt->eSwitch, zArg) ) return SQLITE_ERROR;
+          }
+        }else if( z[2]=='\0' ){
+          /* A -- option, indicating that all remaining command line words
+          ** are command arguments.  */
+          pAr->azArg = &azArg[iArg+1];
+          pAr->nArg = nArg-iArg-1;
+          break;
+        }else{
+          /* A long option */
+          const char *zArg = 0;             /* Argument for option, if any */
+          struct ArSwitch *pMatch = 0;      /* Matching option */
+          struct ArSwitch *pOpt;            /* Iterator */
+          for(pOpt=&aSwitch[0]; pOpt<pEnd; pOpt++){
+            const char *zLong = pOpt->zLong;
+            if( (n-2)<=strlen30(zLong) && 0==memcmp(&z[2], zLong, n-2) ){
+              if( pMatch ){
+                return arErrorMsg(pAr, "ambiguous option: %s",z);
+              }else{
+                pMatch = pOpt;
+              }
+            }
+          }
+
+          if( pMatch==0 ){
+            return arErrorMsg(pAr, "unrecognized option: %s", z);
+          }
+          if( pMatch->bArg ){
+            if( iArg>=(nArg-1) ){
+              return arErrorMsg(pAr, "option requires an argument: %s", z);
+            }
+            zArg = azArg[++iArg];
+          }
+          if( arProcessSwitch(pAr, pMatch->eSwitch, zArg) ) return SQLITE_ERROR;
+        }
+      }
+    }
+  }
+  if( pAr->eCmd==0 ){
+    eputz("Required argument missing.  Usage:\n");
+    return arUsage(stderr);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This function assumes that all arguments within the ArCommand.azArg[]
+** array refer to archive members, as for the --extract, --list or --remove
+** commands. It checks that each of them are "present". If any specified
+** file is not present in the archive, an error is printed to stderr and an
+** error code returned. Otherwise, if all specified arguments are present
+** in the archive, SQLITE_OK is returned. Here, "present" means either an
+** exact equality when pAr->bGlob is false or a "name GLOB pattern" match
+** when pAr->bGlob is true.
+**
+** This function strips any trailing '/' characters from each argument.
+** This is consistent with the way the [tar] command seems to work on
+** Linux.
+*/
+static int arCheckEntries(ArCommand *pAr){
+  int rc = SQLITE_OK;
+  if( pAr->nArg ){
+    int i, j;
+    sqlite3_stmt *pTest = 0;
+    const char *zSel = (pAr->bGlob)
+      ? "SELECT name FROM %s WHERE glob($name,name)"
+      : "SELECT name FROM %s WHERE name=$name";
+
+    shellPreparePrintf(pAr->db, &rc, &pTest, zSel, pAr->zSrcTable);
+    j = sqlite3_bind_parameter_index(pTest, "$name");
+    for(i=0; i<pAr->nArg && rc==SQLITE_OK; i++){
+      char *z = pAr->azArg[i];
+      int n = strlen30(z);
+      int bOk = 0;
+      while( n>0 && z[n-1]=='/' ) n--;
+      z[n] = '\0';
+      sqlite3_bind_text(pTest, j, z, -1, SQLITE_STATIC);
+      if( SQLITE_ROW==sqlite3_step(pTest) ){
+        bOk = 1;
+      }
+      shellReset(&rc, pTest);
+      if( rc==SQLITE_OK && bOk==0 ){
+        eputf("not found in archive: %s\n", z);
+        rc = SQLITE_ERROR;
+      }
+    }
+    shellFinalize(&rc, pTest);
+  }
+  return rc;
+}
+
+/*
+** Format a WHERE clause that can be used against the "sqlar" table to
+** identify all archive members that match the command arguments held
+** in (*pAr). Leave this WHERE clause in (*pzWhere) before returning.
+** The caller is responsible for eventually calling sqlite3_free() on
+** any non-NULL (*pzWhere) value. Here, "match" means strict equality
+** when pAr->bGlob is false and GLOB match when pAr->bGlob is true.
+*/
+static void arWhereClause(
+  int *pRc,
+  ArCommand *pAr,
+  char **pzWhere                  /* OUT: New WHERE clause */
+){
+  char *zWhere = 0;
+  const char *zSameOp = (pAr->bGlob)? "GLOB" : "=";
+  if( *pRc==SQLITE_OK ){
+    if( pAr->nArg==0 ){
+      zWhere = sqlite3_mprintf("1");
+    }else{
+      int i;
+      const char *zSep = "";
+      for(i=0; i<pAr->nArg; i++){
+        const char *z = pAr->azArg[i];
+        zWhere = sqlite3_mprintf(
+          "%z%s name %s '%q' OR substr(name,1,%d) %s '%q/'",
+          zWhere, zSep, zSameOp, z, strlen30(z)+1, zSameOp, z
+        );
+        if( zWhere==0 ){
+          *pRc = SQLITE_NOMEM;
+          break;
+        }
+        zSep = " OR ";
+      }
+    }
+  }
+  *pzWhere = zWhere;
+}
+
+/*
+** Implementation of .ar "lisT" command.
+*/
+static int arListCommand(ArCommand *pAr){
+  const char *zSql = "SELECT %s FROM %s WHERE %s";
+  const char *azCols[] = {
+    "name",
+    "lsmode(mode), sz, datetime(mtime, 'unixepoch'), name"
+  };
+
+  char *zWhere = 0;
+  sqlite3_stmt *pSql = 0;
+  int rc;
+
+  rc = arCheckEntries(pAr);
+  arWhereClause(&rc, pAr, &zWhere);
+
+  shellPreparePrintf(pAr->db, &rc, &pSql, zSql, azCols[pAr->bVerbose],
+                     pAr->zSrcTable, zWhere);
+  if( pAr->bDryRun ){
+    oputf("%s\n", sqlite3_sql(pSql));
+  }else{
+    while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pSql) ){
+      if( pAr->bVerbose ){
+        oputf("%s % 10d  %s  %s\n",
+              sqlite3_column_text(pSql, 0), sqlite3_column_int(pSql, 1),
+              sqlite3_column_text(pSql, 2),sqlite3_column_text(pSql, 3));
+      }else{
+        oputf("%s\n", sqlite3_column_text(pSql, 0));
+      }
+    }
+  }
+  shellFinalize(&rc, pSql);
+  sqlite3_free(zWhere);
+  return rc;
+}
+
+/*
+** Implementation of .ar "Remove" command.
+*/
+static int arRemoveCommand(ArCommand *pAr){
+  int rc = 0;
+  char *zSql = 0;
+  char *zWhere = 0;
+
+  if( pAr->nArg ){
+    /* Verify that args actually exist within the archive before proceeding.
+    ** And formulate a WHERE clause to match them.  */
+    rc = arCheckEntries(pAr);
+    arWhereClause(&rc, pAr, &zWhere);
+  }
+  if( rc==SQLITE_OK ){
+    zSql = sqlite3_mprintf("DELETE FROM %s WHERE %s;",
+                           pAr->zSrcTable, zWhere);
+    if( pAr->bDryRun ){
+      oputf("%s\n", zSql);
+    }else{
+      char *zErr = 0;
+      rc = sqlite3_exec(pAr->db, "SAVEPOINT ar;", 0, 0, 0);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3_exec(pAr->db, zSql, 0, 0, &zErr);
+        if( rc!=SQLITE_OK ){
+          sqlite3_exec(pAr->db, "ROLLBACK TO ar; RELEASE ar;", 0, 0, 0);
+        }else{
+          rc = sqlite3_exec(pAr->db, "RELEASE ar;", 0, 0, 0);
+        }
+      }
+      if( zErr ){
+        sputf(stdout, "ERROR: %s\n", zErr); /* stdout? */
+        sqlite3_free(zErr);
+      }
+    }
+  }
+  sqlite3_free(zWhere);
+  sqlite3_free(zSql);
+  return rc;
+}
+
+/*
+** Implementation of .ar "eXtract" command.
+*/
+static int arExtractCommand(ArCommand *pAr){
+  const char *zSql1 =
+    "SELECT "
+    " ($dir || name),"
+    " writefile(($dir || name), %s, mode, mtime) "
+    "FROM %s WHERE (%s) AND (data IS NULL OR $dirOnly = 0)"
+    " AND name NOT GLOB '*..[/\\]*'";
+
+  const char *azExtraArg[] = {
+    "sqlar_uncompress(data, sz)",
+    "data"
+  };
+
+  sqlite3_stmt *pSql = 0;
+  int rc = SQLITE_OK;
+  char *zDir = 0;
+  char *zWhere = 0;
+  int i, j;
+
+  /* If arguments are specified, check that they actually exist within
+  ** the archive before proceeding. And formulate a WHERE clause to
+  ** match them.  */
+  rc = arCheckEntries(pAr);
+  arWhereClause(&rc, pAr, &zWhere);
+
+  if( rc==SQLITE_OK ){
+    if( pAr->zDir ){
+      zDir = sqlite3_mprintf("%s/", pAr->zDir);
+    }else{
+      zDir = sqlite3_mprintf("");
+    }
+    if( zDir==0 ) rc = SQLITE_NOMEM;
+  }
+
+  shellPreparePrintf(pAr->db, &rc, &pSql, zSql1,
+      azExtraArg[pAr->bZip], pAr->zSrcTable, zWhere
+  );
+
+  if( rc==SQLITE_OK ){
+    j = sqlite3_bind_parameter_index(pSql, "$dir");
+    sqlite3_bind_text(pSql, j, zDir, -1, SQLITE_STATIC);
+
+    /* Run the SELECT statement twice. The first time, writefile() is called
+    ** for all archive members that should be extracted. The second time,
+    ** only for the directories. This is because the timestamps for
+    ** extracted directories must be reset after they are populated (as
+    ** populating them changes the timestamp).  */
+    for(i=0; i<2; i++){
+      j = sqlite3_bind_parameter_index(pSql, "$dirOnly");
+      sqlite3_bind_int(pSql, j, i);
+      if( pAr->bDryRun ){
+        oputf("%s\n", sqlite3_sql(pSql));
+      }else{
+        while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pSql) ){
+          if( i==0 && pAr->bVerbose ){
+            oputf("%s\n", sqlite3_column_text(pSql, 0));
+          }
+        }
+      }
+      shellReset(&rc, pSql);
+    }
+    shellFinalize(&rc, pSql);
+  }
+
+  sqlite3_free(zDir);
+  sqlite3_free(zWhere);
+  return rc;
+}
+
+/*
+** Run the SQL statement in zSql.  Or if doing a --dryrun, merely print it out.
+*/
+static int arExecSql(ArCommand *pAr, const char *zSql){
+  int rc;
+  if( pAr->bDryRun ){
+    oputf("%s\n", zSql);
+    rc = SQLITE_OK;
+  }else{
+    char *zErr = 0;
+    rc = sqlite3_exec(pAr->db, zSql, 0, 0, &zErr);
+    if( zErr ){
+      sputf(stdout, "ERROR: %s\n", zErr);
+      sqlite3_free(zErr);
+    }
+  }
+  return rc;
+}
+
+
+/*
+** Implementation of .ar "create", "insert", and "update" commands.
+**
+**     create    ->     Create a new SQL archive
+**     insert    ->     Insert or reinsert all files listed
+**     update    ->     Insert files that have changed or that were not
+**                      previously in the archive
+**
+** Create the "sqlar" table in the database if it does not already exist.
+** Then add each file in the azFile[] array to the archive. Directories
+** are added recursively. If argument bVerbose is non-zero, a message is
+** printed on stdout for each file archived.
+**
+** The create command is the same as update, except that it drops
+** any existing "sqlar" table before beginning.  The "insert" command
+** always overwrites every file named on the command-line, where as
+** "update" only overwrites if the size or mtime or mode has changed.
+*/
+static int arCreateOrUpdateCommand(
+  ArCommand *pAr,                 /* Command arguments and options */
+  int bUpdate,                    /* true for a --create. */
+  int bOnlyIfChanged              /* Only update if file has changed */
+){
+  const char *zCreate =
+      "CREATE TABLE IF NOT EXISTS sqlar(\n"
+      "  name TEXT PRIMARY KEY,  -- name of the file\n"
+      "  mode INT,               -- access permissions\n"
+      "  mtime INT,              -- last modification time\n"
+      "  sz INT,                 -- original file size\n"
+      "  data BLOB               -- compressed content\n"
+      ")";
+  const char *zDrop = "DROP TABLE IF EXISTS sqlar";
+  const char *zInsertFmt[2] = {
+     "REPLACE INTO %s(name,mode,mtime,sz,data)\n"
+     "  SELECT\n"
+     "    %s,\n"
+     "    mode,\n"
+     "    mtime,\n"
+     "    CASE substr(lsmode(mode),1,1)\n"
+     "      WHEN '-' THEN length(data)\n"
+     "      WHEN 'd' THEN 0\n"
+     "      ELSE -1 END,\n"
+     "    sqlar_compress(data)\n"
+     "  FROM fsdir(%Q,%Q) AS disk\n"
+     "  WHERE lsmode(mode) NOT LIKE '?%%'%s;"
+     ,
+     "REPLACE INTO %s(name,mode,mtime,data)\n"
+     "  SELECT\n"
+     "    %s,\n"
+     "    mode,\n"
+     "    mtime,\n"
+     "    data\n"
+     "  FROM fsdir(%Q,%Q) AS disk\n"
+     "  WHERE lsmode(mode) NOT LIKE '?%%'%s;"
+  };
+  int i;                          /* For iterating through azFile[] */
+  int rc;                         /* Return code */
+  const char *zTab = 0;           /* SQL table into which to insert */
+  char *zSql;
+  char zTemp[50];
+  char *zExists = 0;
+
+  arExecSql(pAr, "PRAGMA page_size=512");
+  rc = arExecSql(pAr, "SAVEPOINT ar;");
+  if( rc!=SQLITE_OK ) return rc;
+  zTemp[0] = 0;
+  if( pAr->bZip ){
+    /* Initialize the zipfile virtual table, if necessary */
+    if( pAr->zFile ){
+      sqlite3_uint64 r;
+      sqlite3_randomness(sizeof(r),&r);
+      sqlite3_snprintf(sizeof(zTemp),zTemp,"zip%016llx",r);
+      zTab = zTemp;
+      zSql = sqlite3_mprintf(
+         "CREATE VIRTUAL TABLE temp.%s USING zipfile(%Q)",
+         zTab, pAr->zFile
+      );
+      rc = arExecSql(pAr, zSql);
+      sqlite3_free(zSql);
+    }else{
+      zTab = "zip";
+    }
+  }else{
+    /* Initialize the table for an SQLAR */
+    zTab = "sqlar";
+    if( bUpdate==0 ){
+      rc = arExecSql(pAr, zDrop);
+      if( rc!=SQLITE_OK ) goto end_ar_transaction;
+    }
+    rc = arExecSql(pAr, zCreate);
+  }
+  if( bOnlyIfChanged ){
+    zExists = sqlite3_mprintf(
+      " AND NOT EXISTS("
+          "SELECT 1 FROM %s AS mem"
+          " WHERE mem.name=disk.name"
+          " AND mem.mtime=disk.mtime"
+          " AND mem.mode=disk.mode)", zTab);
+  }else{
+    zExists = sqlite3_mprintf("");
+  }
+  if( zExists==0 ) rc = SQLITE_NOMEM;
+  for(i=0; i<pAr->nArg && rc==SQLITE_OK; i++){
+    char *zSql2 = sqlite3_mprintf(zInsertFmt[pAr->bZip], zTab,
+        pAr->bVerbose ? "shell_putsnl(name)" : "name",
+        pAr->azArg[i], pAr->zDir, zExists);
+    rc = arExecSql(pAr, zSql2);
+    sqlite3_free(zSql2);
+  }
+end_ar_transaction:
+  if( rc!=SQLITE_OK ){
+    sqlite3_exec(pAr->db, "ROLLBACK TO ar; RELEASE ar;", 0, 0, 0);
+  }else{
+    rc = arExecSql(pAr, "RELEASE ar;");
+    if( pAr->bZip && pAr->zFile ){
+      zSql = sqlite3_mprintf("DROP TABLE %s", zTemp);
+      arExecSql(pAr, zSql);
+      sqlite3_free(zSql);
+    }
+  }
+  sqlite3_free(zExists);
+  return rc;
+}
+
+/*
+** Implementation of ".ar" dot command.
+*/
+static int arDotCommand(
+  ShellState *pState,          /* Current shell tool state */
+  int fromCmdLine,             /* True if -A command-line option, not .ar cmd */
+  char **azArg,                /* Array of arguments passed to dot command */
+  int nArg                     /* Number of entries in azArg[] */
+){
+  ArCommand cmd;
+  int rc;
+  memset(&cmd, 0, sizeof(cmd));
+  cmd.fromCmdLine = fromCmdLine;
+  rc = arParseCommand(azArg, nArg, &cmd);
+  if( rc==SQLITE_OK ){
+    int eDbType = SHELL_OPEN_UNSPEC;
+    cmd.p = pState;
+    cmd.db = pState->db;
+    if( cmd.zFile ){
+      eDbType = deduceDatabaseType(cmd.zFile, 1);
+    }else{
+      eDbType = pState->openMode;
+    }
+    if( eDbType==SHELL_OPEN_ZIPFILE ){
+      if( cmd.eCmd==AR_CMD_EXTRACT || cmd.eCmd==AR_CMD_LIST ){
+        if( cmd.zFile==0 ){
+          cmd.zSrcTable = sqlite3_mprintf("zip");
+        }else{
+          cmd.zSrcTable = sqlite3_mprintf("zipfile(%Q)", cmd.zFile);
+        }
+      }
+      cmd.bZip = 1;
+    }else if( cmd.zFile ){
+      int flags;
+      if( cmd.bAppend ) eDbType = SHELL_OPEN_APPENDVFS;
+      if( cmd.eCmd==AR_CMD_CREATE || cmd.eCmd==AR_CMD_INSERT
+           || cmd.eCmd==AR_CMD_REMOVE || cmd.eCmd==AR_CMD_UPDATE ){
+        flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE;
+      }else{
+        flags = SQLITE_OPEN_READONLY;
+      }
+      cmd.db = 0;
+      if( cmd.bDryRun ){
+        oputf("-- open database '%s'%s\n", cmd.zFile,
+              eDbType==SHELL_OPEN_APPENDVFS ? " using 'apndvfs'" : "");
+      }
+      rc = sqlite3_open_v2(cmd.zFile, &cmd.db, flags,
+             eDbType==SHELL_OPEN_APPENDVFS ? "apndvfs" : 0);
+      if( rc!=SQLITE_OK ){
+        eputf("cannot open file: %s (%s)\n", cmd.zFile, sqlite3_errmsg(cmd.db));
+        goto end_ar_command;
+      }
+      sqlite3_fileio_init(cmd.db, 0, 0);
+      sqlite3_sqlar_init(cmd.db, 0, 0);
+      sqlite3_create_function(cmd.db, "shell_putsnl", 1, SQLITE_UTF8, cmd.p,
+                              shellPutsFunc, 0, 0);
+
+    }
+    if( cmd.zSrcTable==0 && cmd.bZip==0 && cmd.eCmd!=AR_CMD_HELP ){
+      if( cmd.eCmd!=AR_CMD_CREATE
+       && sqlite3_table_column_metadata(cmd.db,0,"sqlar","name",0,0,0,0,0)
+      ){
+        eputz("database does not contain an 'sqlar' table\n");
+        rc = SQLITE_ERROR;
+        goto end_ar_command;
+      }
+      cmd.zSrcTable = sqlite3_mprintf("sqlar");
+    }
+
+    switch( cmd.eCmd ){
+      case AR_CMD_CREATE:
+        rc = arCreateOrUpdateCommand(&cmd, 0, 0);
+        break;
+
+      case AR_CMD_EXTRACT:
+        rc = arExtractCommand(&cmd);
+        break;
+
+      case AR_CMD_LIST:
+        rc = arListCommand(&cmd);
+        break;
+
+      case AR_CMD_HELP:
+        arUsage(pState->out);
+        break;
+
+      case AR_CMD_INSERT:
+        rc = arCreateOrUpdateCommand(&cmd, 1, 0);
+        break;
+
+      case AR_CMD_REMOVE:
+        rc = arRemoveCommand(&cmd);
+        break;
+
+      default:
+        assert( cmd.eCmd==AR_CMD_UPDATE );
+        rc = arCreateOrUpdateCommand(&cmd, 1, 1);
+        break;
+    }
+  }
+end_ar_command:
+  if( cmd.db!=pState->db ){
+    close_db(cmd.db);
+  }
+  sqlite3_free(cmd.zSrcTable);
+
+  return rc;
+}
+/* End of the ".archive" or ".ar" command logic
+*******************************************************************************/
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB) */
+
+#if SQLITE_SHELL_HAVE_RECOVER
+
+/*
+** This function is used as a callback by the recover extension. Simply
+** print the supplied SQL statement to stdout.
+*/
+static int recoverSqlCb(void *pCtx, const char *zSql){
+  ShellState *pState = (ShellState*)pCtx;
+  sputf(pState->out, "%s;\n", zSql);
+  return SQLITE_OK;
+}
+
+/*
+** This function is called to recover data from the database. A script
+** to construct a new database containing all recovered data is output
+** on stream pState->out.
+*/
+static int recoverDatabaseCmd(ShellState *pState, int nArg, char **azArg){
+  int rc = SQLITE_OK;
+  const char *zRecoveryDb = "";   /* Name of "recovery" database.  Debug only */
+  const char *zLAF = "lost_and_found";
+  int bFreelist = 1;              /* 0 if --ignore-freelist is specified */
+  int bRowids = 1;                /* 0 if --no-rowids */
+  sqlite3_recover *p = 0;
+  int i = 0;
+
+  for(i=1; i<nArg; i++){
+    char *z = azArg[i];
+    int n;
+    if( z[0]=='-' && z[1]=='-' ) z++;
+    n = strlen30(z);
+    if( n<=17 && memcmp("-ignore-freelist", z, n)==0 ){
+      bFreelist = 0;
+    }else
+    if( n<=12 && memcmp("-recovery-db", z, n)==0 && i<(nArg-1) ){
+      /* This option determines the name of the ATTACH-ed database used
+      ** internally by the recovery extension.  The default is "" which
+      ** means to use a temporary database that is automatically deleted
+      ** when closed.  This option is undocumented and might disappear at
+      ** any moment. */
+      i++;
+      zRecoveryDb = azArg[i];
+    }else
+    if( n<=15 && memcmp("-lost-and-found", z, n)==0 && i<(nArg-1) ){
+      i++;
+      zLAF = azArg[i];
+    }else
+    if( n<=10 && memcmp("-no-rowids", z, n)==0 ){
+      bRowids = 0;
+    }
+    else{
+      eputf("unexpected option: %s\n", azArg[i]);
+      showHelp(pState->out, azArg[0]);
+      return 1;
+    }
+  }
+
+  p = sqlite3_recover_init_sql(
+      pState->db, "main", recoverSqlCb, (void*)pState
+  );
+
+  sqlite3_recover_config(p, 789, (void*)zRecoveryDb);  /* Debug use only */
+  sqlite3_recover_config(p, SQLITE_RECOVER_LOST_AND_FOUND, (void*)zLAF);
+  sqlite3_recover_config(p, SQLITE_RECOVER_ROWIDS, (void*)&bRowids);
+  sqlite3_recover_config(p, SQLITE_RECOVER_FREELIST_CORRUPT,(void*)&bFreelist);
+
+  sqlite3_recover_run(p);
+  if( sqlite3_recover_errcode(p)!=SQLITE_OK ){
+    const char *zErr = sqlite3_recover_errmsg(p);
+    int errCode = sqlite3_recover_errcode(p);
+    eputf("sql error: %s (%d)\n", zErr, errCode);
+  }
+  rc = sqlite3_recover_finish(p);
+  return rc;
+}
+#endif /* SQLITE_SHELL_HAVE_RECOVER */
+
+
+/*
+ * zAutoColumn(zCol, &db, ?) => Maybe init db, add column zCol to it.
+ * zAutoColumn(0, &db, ?) => (db!=0) Form columns spec for CREATE TABLE,
+ *   close db and set it to 0, and return the columns spec, to later
+ *   be sqlite3_free()'ed by the caller.
+ * The return is 0 when either:
+ *   (a) The db was not initialized and zCol==0 (There are no columns.)
+ *   (b) zCol!=0  (Column was added, db initialized as needed.)
+ * The 3rd argument, pRenamed, references an out parameter. If the
+ * pointer is non-zero, its referent will be set to a summary of renames
+ * done if renaming was necessary, or set to 0 if none was done. The out
+ * string (if any) must be sqlite3_free()'ed by the caller.
+ */
+#ifdef SHELL_DEBUG
+#define rc_err_oom_die(rc) \
+  if( rc==SQLITE_NOMEM ) shell_check_oom(0); \
+  else if(!(rc==SQLITE_OK||rc==SQLITE_DONE)) \
+    eputf("E:%d\n",rc), assert(0)
+#else
+static void rc_err_oom_die(int rc){
+  if( rc==SQLITE_NOMEM ) shell_check_oom(0);
+  assert(rc==SQLITE_OK||rc==SQLITE_DONE);
+}
+#endif
+
+#ifdef SHELL_COLFIX_DB /* If this is set, the DB can be in a file. */
+static char zCOL_DB[] = SHELL_STRINGIFY(SHELL_COLFIX_DB);
+#else  /* Otherwise, memory is faster/better for the transient DB. */
+static const char *zCOL_DB = ":memory:";
+#endif
+
+/* Define character (as C string) to separate generated column ordinal
+ * from protected part of incoming column names. This defaults to "_"
+ * so that incoming column identifiers that did not need not be quoted
+ * remain usable without being quoted. It must be one character.
+ */
+#ifndef SHELL_AUTOCOLUMN_SEP
+# define AUTOCOLUMN_SEP "_"
+#else
+# define AUTOCOLUMN_SEP SHELL_STRINGIFY(SHELL_AUTOCOLUMN_SEP)
+#endif
+
+static char *zAutoColumn(const char *zColNew, sqlite3 **pDb, char **pzRenamed){
+  /* Queries and D{D,M}L used here */
+  static const char * const zTabMake = "\
+CREATE TABLE ColNames(\
+ cpos INTEGER PRIMARY KEY,\
+ name TEXT, nlen INT, chop INT, reps INT, suff TEXT);\
+CREATE VIEW RepeatedNames AS \
+SELECT DISTINCT t.name FROM ColNames t \
+WHERE t.name COLLATE NOCASE IN (\
+ SELECT o.name FROM ColNames o WHERE o.cpos<>t.cpos\
+);\
+";
+  static const char * const zTabFill = "\
+INSERT INTO ColNames(name,nlen,chop,reps,suff)\
+ VALUES(iif(length(?1)>0,?1,'?'),max(length(?1),1),0,0,'')\
+";
+  static const char * const zHasDupes = "\
+SELECT count(DISTINCT (substring(name,1,nlen-chop)||suff) COLLATE NOCASE)\
+ <count(name) FROM ColNames\
+";
+#ifdef SHELL_COLUMN_RENAME_CLEAN
+  static const char * const zDedoctor = "\
+UPDATE ColNames SET chop=iif(\
+  (substring(name,nlen,1) BETWEEN '0' AND '9')\
+  AND (rtrim(name,'0123456790') glob '*"AUTOCOLUMN_SEP"'),\
+ nlen-length(rtrim(name, '"AUTOCOLUMN_SEP"0123456789')),\
+ 0\
+)\
+";
+#endif
+  static const char * const zSetReps = "\
+UPDATE ColNames AS t SET reps=\
+(SELECT count(*) FROM ColNames d \
+ WHERE substring(t.name,1,t.nlen-t.chop)=substring(d.name,1,d.nlen-d.chop)\
+ COLLATE NOCASE\
+)\
+";
+#ifdef SQLITE_ENABLE_MATH_FUNCTIONS
+  static const char * const zColDigits = "\
+SELECT CAST(ceil(log(count(*)+0.5)) AS INT) FROM ColNames \
+";
+#else
+  /* Counting on SQLITE_MAX_COLUMN < 100,000 here. (32767 is the hard limit.) */
+  static const char * const zColDigits = "\
+SELECT CASE WHEN (nc < 10) THEN 1 WHEN (nc < 100) THEN 2 \
+ WHEN (nc < 1000) THEN 3 WHEN (nc < 10000) THEN 4 \
+ ELSE 5 FROM (SELECT count(*) AS nc FROM ColNames) \
+";
+#endif
+  static const char * const zRenameRank =
+#ifdef SHELL_COLUMN_RENAME_CLEAN
+    "UPDATE ColNames AS t SET suff="
+    "iif(reps>1, printf('%c%0*d', '"AUTOCOLUMN_SEP"', $1, cpos), '')"
+#else /* ...RENAME_MINIMAL_ONE_PASS */
+"WITH Lzn(nlz) AS (" /* Find minimum extraneous leading 0's for uniqueness */
+"  SELECT 0 AS nlz"
+"  UNION"
+"  SELECT nlz+1 AS nlz FROM Lzn"
+"  WHERE EXISTS("
+"   SELECT 1"
+"   FROM ColNames t, ColNames o"
+"   WHERE"
+"    iif(t.name IN (SELECT * FROM RepeatedNames),"
+"     printf('%s"AUTOCOLUMN_SEP"%s',"
+"      t.name, substring(printf('%.*c%0.*d',nlz+1,'0',$1,t.cpos),2)),"
+"     t.name"
+"    )"
+"    ="
+"    iif(o.name IN (SELECT * FROM RepeatedNames),"
+"     printf('%s"AUTOCOLUMN_SEP"%s',"
+"      o.name, substring(printf('%.*c%0.*d',nlz+1,'0',$1,o.cpos),2)),"
+"     o.name"
+"    )"
+"    COLLATE NOCASE"
+"    AND o.cpos<>t.cpos"
+"   GROUP BY t.cpos"
+"  )"
+") UPDATE Colnames AS t SET"
+" chop = 0," /* No chopping, never touch incoming names. */
+" suff = iif(name IN (SELECT * FROM RepeatedNames),"
+"  printf('"AUTOCOLUMN_SEP"%s', substring("
+"   printf('%.*c%0.*d',(SELECT max(nlz) FROM Lzn)+1,'0',1,t.cpos),2)),"
+"  ''"
+" )"
+#endif
+    ;
+  static const char * const zCollectVar = "\
+SELECT\
+ '('||x'0a'\
+ || group_concat(\
+  cname||' TEXT',\
+  ','||iif((cpos-1)%4>0, ' ', x'0a'||' '))\
+ ||')' AS ColsSpec \
+FROM (\
+ SELECT cpos, printf('\"%w\"',printf('%!.*s%s', nlen-chop,name,suff)) AS cname \
+ FROM ColNames ORDER BY cpos\
+)";
+  static const char * const zRenamesDone =
+    "SELECT group_concat("
+    " printf('\"%w\" to \"%w\"',name,printf('%!.*s%s', nlen-chop, name, suff)),"
+    " ','||x'0a')"
+    "FROM ColNames WHERE suff<>'' OR chop!=0"
+    ;
+  int rc;
+  sqlite3_stmt *pStmt = 0;
+  assert(pDb!=0);
+  if( zColNew ){
+    /* Add initial or additional column. Init db if necessary. */
+    if( *pDb==0 ){
+      if( SQLITE_OK!=sqlite3_open(zCOL_DB, pDb) ) return 0;
+#ifdef SHELL_COLFIX_DB
+      if(*zCOL_DB!=':')
+        sqlite3_exec(*pDb,"drop table if exists ColNames;"
+                     "drop view if exists RepeatedNames;",0,0,0);
+#endif
+#undef SHELL_COLFIX_DB
+      rc = sqlite3_exec(*pDb, zTabMake, 0, 0, 0);
+      rc_err_oom_die(rc);
+    }
+    assert(*pDb!=0);
+    rc = sqlite3_prepare_v2(*pDb, zTabFill, -1, &pStmt, 0);
+    rc_err_oom_die(rc);
+    rc = sqlite3_bind_text(pStmt, 1, zColNew, -1, 0);
+    rc_err_oom_die(rc);
+    rc = sqlite3_step(pStmt);
+    rc_err_oom_die(rc);
+    sqlite3_finalize(pStmt);
+    return 0;
+  }else if( *pDb==0 ){
+    return 0;
+  }else{
+    /* Formulate the columns spec, close the DB, zero *pDb. */
+    char *zColsSpec = 0;
+    int hasDupes = db_int(*pDb, zHasDupes);
+    int nDigits = (hasDupes)? db_int(*pDb, zColDigits) : 0;
+    if( hasDupes ){
+#ifdef SHELL_COLUMN_RENAME_CLEAN
+      rc = sqlite3_exec(*pDb, zDedoctor, 0, 0, 0);
+      rc_err_oom_die(rc);
+#endif
+      rc = sqlite3_exec(*pDb, zSetReps, 0, 0, 0);
+      rc_err_oom_die(rc);
+      rc = sqlite3_prepare_v2(*pDb, zRenameRank, -1, &pStmt, 0);
+      rc_err_oom_die(rc);
+      sqlite3_bind_int(pStmt, 1, nDigits);
+      rc = sqlite3_step(pStmt);
+      sqlite3_finalize(pStmt);
+      if( rc!=SQLITE_DONE ) rc_err_oom_die(SQLITE_NOMEM);
+    }
+    assert(db_int(*pDb, zHasDupes)==0); /* Consider: remove this */
+    rc = sqlite3_prepare_v2(*pDb, zCollectVar, -1, &pStmt, 0);
+    rc_err_oom_die(rc);
+    rc = sqlite3_step(pStmt);
+    if( rc==SQLITE_ROW ){
+      zColsSpec = sqlite3_mprintf("%s", sqlite3_column_text(pStmt, 0));
+    }else{
+      zColsSpec = 0;
+    }
+    if( pzRenamed!=0 ){
+      if( !hasDupes ) *pzRenamed = 0;
+      else{
+        sqlite3_finalize(pStmt);
+        if( SQLITE_OK==sqlite3_prepare_v2(*pDb, zRenamesDone, -1, &pStmt, 0)
+            && SQLITE_ROW==sqlite3_step(pStmt) ){
+          *pzRenamed = sqlite3_mprintf("%s", sqlite3_column_text(pStmt, 0));
+        }else
+          *pzRenamed = 0;
+      }
+    }
+    sqlite3_finalize(pStmt);
+    sqlite3_close(*pDb);
+    *pDb = 0;
+    return zColsSpec;
+  }
+}
+
+/*
+** Check if the sqlite_schema table contains one or more virtual tables. If
+** parameter zLike is not NULL, then it is an SQL expression that the
+** sqlite_schema row must also match. If one or more such rows are found,
+** print the following warning to the output:
+**
+** WARNING: Script requires that SQLITE_DBCONFIG_DEFENSIVE be disabled
+*/
+static int outputDumpWarning(ShellState *p, const char *zLike){
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pStmt = 0;
+  shellPreparePrintf(p->db, &rc, &pStmt,
+    "SELECT 1 FROM sqlite_schema o WHERE "
+    "sql LIKE 'CREATE VIRTUAL TABLE%%' AND %s", zLike ? zLike : "true"
+  );
+  if( rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
+    oputz("/* WARNING: "
+          "Script requires that SQLITE_DBCONFIG_DEFENSIVE be disabled */\n"
+    );
+  }
+  shellFinalize(&rc, pStmt);
+  return rc;
+}
+
+/*
+** If an input line begins with "." then invoke this routine to
+** process that line.
+**
+** Return 1 on error, 2 to exit, and 0 otherwise.
+*/
+static int do_meta_command(char *zLine, ShellState *p){
+  int h = 1;
+  int nArg = 0;
+  int n, c;
+  int rc = 0;
+  char *azArg[52];
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( p->expert.pExpert ){
+    expertFinish(p, 1, 0);
+  }
+#endif
+
+  /* Parse the input line into tokens.
+  */
+  while( zLine[h] && nArg<ArraySize(azArg)-1 ){
+    while( IsSpace(zLine[h]) ){ h++; }
+    if( zLine[h]==0 ) break;
+    if( zLine[h]=='\'' || zLine[h]=='"' ){
+      int delim = zLine[h++];
+      azArg[nArg++] = &zLine[h];
+      while( zLine[h] && zLine[h]!=delim ){
+        if( zLine[h]=='\\' && delim=='"' && zLine[h+1]!=0 ) h++;
+        h++;
+      }
+      if( zLine[h]==delim ){
+        zLine[h++] = 0;
+      }
+      if( delim=='"' ) resolve_backslashes(azArg[nArg-1]);
+    }else{
+      azArg[nArg++] = &zLine[h];
+      while( zLine[h] && !IsSpace(zLine[h]) ){ h++; }
+      if( zLine[h] ) zLine[h++] = 0;
+    }
+  }
+  azArg[nArg] = 0;
+
+  /* Process the input line.
+  */
+  if( nArg==0 ) return 0; /* no tokens, no error */
+  n = strlen30(azArg[0]);
+  c = azArg[0][0];
+  clearTempFile(p);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( c=='a' && cli_strncmp(azArg[0], "auth", n)==0 ){
+    if( nArg!=2 ){
+      eputz("Usage: .auth ON|OFF\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    open_db(p, 0);
+    if( booleanValue(azArg[1]) ){
+      sqlite3_set_authorizer(p->db, shellAuth, p);
+    }else if( p->bSafeModePersist ){
+      sqlite3_set_authorizer(p->db, safeModeAuth, p);
+    }else{
+      sqlite3_set_authorizer(p->db, 0, 0);
+    }
+  }else
+#endif
+
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB) \
+  && !defined(SQLITE_SHELL_FIDDLE)
+  if( c=='a' && cli_strncmp(azArg[0], "archive", n)==0 ){
+    open_db(p, 0);
+    failIfSafeMode(p, "cannot run .archive in safe mode");
+    rc = arDotCommand(p, 0, azArg, nArg);
+  }else
+#endif
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( (c=='b' && n>=3 && cli_strncmp(azArg[0], "backup", n)==0)
+   || (c=='s' && n>=3 && cli_strncmp(azArg[0], "save", n)==0)
+  ){
+    const char *zDestFile = 0;
+    const char *zDb = 0;
+    sqlite3 *pDest;
+    sqlite3_backup *pBackup;
+    int j;
+    int bAsync = 0;
+    const char *zVfs = 0;
+    failIfSafeMode(p, "cannot run .%s in safe mode", azArg[0]);
+    for(j=1; j<nArg; j++){
+      const char *z = azArg[j];
+      if( z[0]=='-' ){
+        if( z[1]=='-' ) z++;
+        if( cli_strcmp(z, "-append")==0 ){
+          zVfs = "apndvfs";
+        }else
+        if( cli_strcmp(z, "-async")==0 ){
+          bAsync = 1;
+        }else
+        {
+          eputf("unknown option: %s\n", azArg[j]);
+          return 1;
+        }
+      }else if( zDestFile==0 ){
+        zDestFile = azArg[j];
+      }else if( zDb==0 ){
+        zDb = zDestFile;
+        zDestFile = azArg[j];
+      }else{
+        eputz("Usage: .backup ?DB? ?OPTIONS? FILENAME\n");
+        return 1;
+      }
+    }
+    if( zDestFile==0 ){
+      eputz("missing FILENAME argument on .backup\n");
+      return 1;
+    }
+    if( zDb==0 ) zDb = "main";
+    rc = sqlite3_open_v2(zDestFile, &pDest,
+                  SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE, zVfs);
+    if( rc!=SQLITE_OK ){
+      eputf("Error: cannot open \"%s\"\n", zDestFile);
+      close_db(pDest);
+      return 1;
+    }
+    if( bAsync ){
+      sqlite3_exec(pDest, "PRAGMA synchronous=OFF; PRAGMA journal_mode=OFF;",
+                   0, 0, 0);
+    }
+    open_db(p, 0);
+    pBackup = sqlite3_backup_init(pDest, "main", p->db, zDb);
+    if( pBackup==0 ){
+      eputf("Error: %s\n", sqlite3_errmsg(pDest));
+      close_db(pDest);
+      return 1;
+    }
+    while(  (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK ){}
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = 0;
+    }else{
+      eputf("Error: %s\n", sqlite3_errmsg(pDest));
+      rc = 1;
+    }
+    close_db(pDest);
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+  if( c=='b' && n>=3 && cli_strncmp(azArg[0], "bail", n)==0 ){
+    if( nArg==2 ){
+      bail_on_error = booleanValue(azArg[1]);
+    }else{
+      eputz("Usage: .bail on|off\n");
+      rc = 1;
+    }
+  }else
+
+  /* Undocumented.  Legacy only.  See "crnl" below */
+  if( c=='b' && n>=3 && cli_strncmp(azArg[0], "binary", n)==0 ){
+    if( nArg==2 ){
+      if( booleanValue(azArg[1]) ){
+        setBinaryMode(p->out, 1);
+      }else{
+        setTextMode(p->out, 1);
+      }
+    }else{
+      eputz("The \".binary\" command is deprecated. Use \".crnl\" instead.\n"
+            "Usage: .binary on|off\n");
+      rc = 1;
+    }
+  }else
+
+  /* The undocumented ".breakpoint" command causes a call to the no-op
+  ** routine named test_breakpoint().
+  */
+  if( c=='b' && n>=3 && cli_strncmp(azArg[0], "breakpoint", n)==0 ){
+    test_breakpoint();
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='c' && cli_strcmp(azArg[0],"cd")==0 ){
+    failIfSafeMode(p, "cannot run .cd in safe mode");
+    if( nArg==2 ){
+#if defined(_WIN32) || defined(WIN32)
+      wchar_t *z = sqlite3_win32_utf8_to_unicode(azArg[1]);
+      rc = !SetCurrentDirectoryW(z);
+      sqlite3_free(z);
+#else
+      rc = chdir(azArg[1]);
+#endif
+      if( rc ){
+        eputf("Cannot change to directory \"%s\"\n", azArg[1]);
+        rc = 1;
+      }
+    }else{
+      eputz("Usage: .cd DIRECTORY\n");
+      rc = 1;
+    }
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+  if( c=='c' && n>=3 && cli_strncmp(azArg[0], "changes", n)==0 ){
+    if( nArg==2 ){
+      setOrClearFlag(p, SHFLG_CountChanges, azArg[1]);
+    }else{
+      eputz("Usage: .changes on|off\n");
+      rc = 1;
+    }
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  /* Cancel output redirection, if it is currently set (by .testcase)
+  ** Then read the content of the testcase-out.txt file and compare against
+  ** azArg[1].  If there are differences, report an error and exit.
+  */
+  if( c=='c' && n>=3 && cli_strncmp(azArg[0], "check", n)==0 ){
+    char *zRes = 0;
+    output_reset(p);
+    if( nArg!=2 ){
+      eputz("Usage: .check GLOB-PATTERN\n");
+      rc = 2;
+    }else if( (zRes = readFile("testcase-out.txt", 0))==0 ){
+      rc = 2;
+    }else if( testcase_glob(azArg[1],zRes)==0 ){
+      eputf("testcase-%s FAILED\n Expected: [%s]\n      Got: [%s]\n",
+            p->zTestcase, azArg[1], zRes);
+      rc = 1;
+    }else{
+      oputf("testcase-%s ok\n", p->zTestcase);
+      p->nCheck++;
+    }
+    sqlite3_free(zRes);
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='c' && cli_strncmp(azArg[0], "clone", n)==0 ){
+    failIfSafeMode(p, "cannot run .clone in safe mode");
+    if( nArg==2 ){
+      tryToClone(p, azArg[1]);
+    }else{
+      eputz("Usage: .clone FILENAME\n");
+      rc = 1;
+    }
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+  if( c=='c' && cli_strncmp(azArg[0], "connection", n)==0 ){
+    if( nArg==1 ){
+      /* List available connections */
+      int i;
+      for(i=0; i<ArraySize(p->aAuxDb); i++){
+        const char *zFile = p->aAuxDb[i].zDbFilename;
+        if( p->aAuxDb[i].db==0 && p->pAuxDb!=&p->aAuxDb[i] ){
+          zFile = "(not open)";
+        }else if( zFile==0 ){
+          zFile = "(memory)";
+        }else if( zFile[0]==0 ){
+          zFile = "(temporary-file)";
+        }
+        if( p->pAuxDb == &p->aAuxDb[i] ){
+          sputf(stdout, "ACTIVE %d: %s\n", i, zFile);
+        }else if( p->aAuxDb[i].db!=0 ){
+          sputf(stdout, "       %d: %s\n", i, zFile);
+        }
+      }
+    }else if( nArg==2 && IsDigit(azArg[1][0]) && azArg[1][1]==0 ){
+      int i = azArg[1][0] - '0';
+      if( p->pAuxDb != &p->aAuxDb[i] && i>=0 && i<ArraySize(p->aAuxDb) ){
+        p->pAuxDb->db = p->db;
+        p->pAuxDb = &p->aAuxDb[i];
+        globalDb = p->db = p->pAuxDb->db;
+        p->pAuxDb->db = 0;
+      }
+    }else if( nArg==3 && cli_strcmp(azArg[1], "close")==0
+           && IsDigit(azArg[2][0]) && azArg[2][1]==0 ){
+      int i = azArg[2][0] - '0';
+      if( i<0 || i>=ArraySize(p->aAuxDb) ){
+        /* No-op */
+      }else if( p->pAuxDb == &p->aAuxDb[i] ){
+        eputz("cannot close the active database connection\n");
+        rc = 1;
+      }else if( p->aAuxDb[i].db ){
+        session_close_all(p, i);
+        close_db(p->aAuxDb[i].db);
+        p->aAuxDb[i].db = 0;
+      }
+    }else{
+      eputz("Usage: .connection [close] [CONNECTION-NUMBER]\n");
+      rc = 1;
+    }
+  }else
+
+  if( c=='c' && n==4 && cli_strncmp(azArg[0], "crnl", n)==0 ){
+    if( nArg==2 ){
+      if( booleanValue(azArg[1]) ){
+        setTextMode(p->out, 1);
+      }else{
+        setBinaryMode(p->out, 1);
+      }
+    }else{
+#if !defined(_WIN32) && !defined(WIN32)
+      eputz("The \".crnl\" is a no-op on non-Windows machines.\n");
+#endif
+      eputz("Usage: .crnl on|off\n");
+      rc = 1;
+    }
+  }else
+
+  if( c=='d' && n>1 && cli_strncmp(azArg[0], "databases", n)==0 ){
+    char **azName = 0;
+    int nName = 0;
+    sqlite3_stmt *pStmt;
+    int i;
+    open_db(p, 0);
+    rc = sqlite3_prepare_v2(p->db, "PRAGMA database_list", -1, &pStmt, 0);
+    if( rc ){
+      eputf("Error: %s\n", sqlite3_errmsg(p->db));
+      rc = 1;
+    }else{
+      while( sqlite3_step(pStmt)==SQLITE_ROW ){
+        const char *zSchema = (const char *)sqlite3_column_text(pStmt,1);
+        const char *zFile = (const char*)sqlite3_column_text(pStmt,2);
+        if( zSchema==0 || zFile==0 ) continue;
+        azName = sqlite3_realloc(azName, (nName+1)*2*sizeof(char*));
+        shell_check_oom(azName);
+        azName[nName*2] = strdup(zSchema);
+        azName[nName*2+1] = strdup(zFile);
+        nName++;
+      }
+    }
+    sqlite3_finalize(pStmt);
+    for(i=0; i<nName; i++){
+      int eTxn = sqlite3_txn_state(p->db, azName[i*2]);
+      int bRdonly = sqlite3_db_readonly(p->db, azName[i*2]);
+      const char *z = azName[i*2+1];
+      oputf("%s: %s %s%s\n",
+            azName[i*2], z && z[0] ? z : "\"\"", bRdonly ? "r/o" : "r/w",
+            eTxn==SQLITE_TXN_NONE ? "" :
+            eTxn==SQLITE_TXN_READ ? " read-txn" : " write-txn");
+      free(azName[i*2]);
+      free(azName[i*2+1]);
+    }
+    sqlite3_free(azName);
+  }else
+
+  if( c=='d' && n>=3 && cli_strncmp(azArg[0], "dbconfig", n)==0 ){
+    static const struct DbConfigChoices {
+      const char *zName;
+      int op;
+    } aDbConfig[] = {
+        { "defensive",          SQLITE_DBCONFIG_DEFENSIVE             },
+        { "dqs_ddl",            SQLITE_DBCONFIG_DQS_DDL               },
+        { "dqs_dml",            SQLITE_DBCONFIG_DQS_DML               },
+        { "enable_fkey",        SQLITE_DBCONFIG_ENABLE_FKEY           },
+        { "enable_qpsg",        SQLITE_DBCONFIG_ENABLE_QPSG           },
+        { "enable_trigger",     SQLITE_DBCONFIG_ENABLE_TRIGGER        },
+        { "enable_view",        SQLITE_DBCONFIG_ENABLE_VIEW           },
+        { "fts3_tokenizer",     SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER },
+        { "legacy_alter_table", SQLITE_DBCONFIG_LEGACY_ALTER_TABLE    },
+        { "legacy_file_format", SQLITE_DBCONFIG_LEGACY_FILE_FORMAT    },
+        { "load_extension",     SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION },
+        { "no_ckpt_on_close",   SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE      },
+        { "reset_database",     SQLITE_DBCONFIG_RESET_DATABASE        },
+        { "reverse_scanorder",  SQLITE_DBCONFIG_REVERSE_SCANORDER     },
+        { "stmt_scanstatus",    SQLITE_DBCONFIG_STMT_SCANSTATUS       },
+        { "trigger_eqp",        SQLITE_DBCONFIG_TRIGGER_EQP           },
+        { "trusted_schema",     SQLITE_DBCONFIG_TRUSTED_SCHEMA        },
+        { "writable_schema",    SQLITE_DBCONFIG_WRITABLE_SCHEMA       },
+    };
+    int ii, v;
+    open_db(p, 0);
+    for(ii=0; ii<ArraySize(aDbConfig); ii++){
+      if( nArg>1 && cli_strcmp(azArg[1], aDbConfig[ii].zName)!=0 ) continue;
+      if( nArg>=3 ){
+        sqlite3_db_config(p->db, aDbConfig[ii].op, booleanValue(azArg[2]), 0);
+      }
+      sqlite3_db_config(p->db, aDbConfig[ii].op, -1, &v);
+      oputf("%19s %s\n", aDbConfig[ii].zName, v ? "on" : "off");
+      if( nArg>1 ) break;
+    }
+    if( nArg>1 && ii==ArraySize(aDbConfig) ){
+      eputf("Error: unknown dbconfig \"%s\"\n", azArg[1]);
+      eputz("Enter \".dbconfig\" with no arguments for a list\n");
+    }
+  }else
+
+#if SQLITE_SHELL_HAVE_RECOVER
+  if( c=='d' && n>=3 && cli_strncmp(azArg[0], "dbinfo", n)==0 ){
+    rc = shell_dbinfo_command(p, nArg, azArg);
+  }else
+
+  if( c=='r' && cli_strncmp(azArg[0], "recover", n)==0 ){
+    open_db(p, 0);
+    rc = recoverDatabaseCmd(p, nArg, azArg);
+  }else
+#endif /* SQLITE_SHELL_HAVE_RECOVER */
+
+  if( c=='d' && cli_strncmp(azArg[0], "dump", n)==0 ){
+    char *zLike = 0;
+    char *zSql;
+    int i;
+    int savedShowHeader = p->showHeader;
+    int savedShellFlags = p->shellFlgs;
+    ShellClearFlag(p,
+       SHFLG_PreserveRowid|SHFLG_Newlines|SHFLG_Echo
+       |SHFLG_DumpDataOnly|SHFLG_DumpNoSys);
+    for(i=1; i<nArg; i++){
+      if( azArg[i][0]=='-' ){
+        const char *z = azArg[i]+1;
+        if( z[0]=='-' ) z++;
+        if( cli_strcmp(z,"preserve-rowids")==0 ){
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+          eputz("The --preserve-rowids option is not compatible"
+                " with SQLITE_OMIT_VIRTUALTABLE\n");
+          rc = 1;
+          sqlite3_free(zLike);
+          goto meta_command_exit;
+#else
+          ShellSetFlag(p, SHFLG_PreserveRowid);
+#endif
+        }else
+        if( cli_strcmp(z,"newlines")==0 ){
+          ShellSetFlag(p, SHFLG_Newlines);
+        }else
+        if( cli_strcmp(z,"data-only")==0 ){
+          ShellSetFlag(p, SHFLG_DumpDataOnly);
+        }else
+        if( cli_strcmp(z,"nosys")==0 ){
+          ShellSetFlag(p, SHFLG_DumpNoSys);
+        }else
+        {
+          eputf("Unknown option \"%s\" on \".dump\"\n", azArg[i]);
+          rc = 1;
+          sqlite3_free(zLike);
+          goto meta_command_exit;
+        }
+      }else{
+        /* azArg[i] contains a LIKE pattern. This ".dump" request should
+        ** only dump data for tables for which either the table name matches
+        ** the LIKE pattern, or the table appears to be a shadow table of
+        ** a virtual table for which the name matches the LIKE pattern.
+        */
+        char *zExpr = sqlite3_mprintf(
+            "name LIKE %Q ESCAPE '\\' OR EXISTS ("
+            "  SELECT 1 FROM sqlite_schema WHERE "
+            "    name LIKE %Q ESCAPE '\\' AND"
+            "    sql LIKE 'CREATE VIRTUAL TABLE%%' AND"
+            "    substr(o.name, 1, length(name)+1) == (name||'_')"
+            ")", azArg[i], azArg[i]
+        );
+
+        if( zLike ){
+          zLike = sqlite3_mprintf("%z OR %z", zLike, zExpr);
+        }else{
+          zLike = zExpr;
+        }
+      }
+    }
+
+    open_db(p, 0);
+
+    outputDumpWarning(p, zLike);
+    if( (p->shellFlgs & SHFLG_DumpDataOnly)==0 ){
+      /* When playing back a "dump", the content might appear in an order
+      ** which causes immediate foreign key constraints to be violated.
+      ** So disable foreign-key constraint enforcement to prevent problems. */
+      oputz("PRAGMA foreign_keys=OFF;\n");
+      oputz("BEGIN TRANSACTION;\n");
+    }
+    p->writableSchema = 0;
+    p->showHeader = 0;
+    /* Set writable_schema=ON since doing so forces SQLite to initialize
+    ** as much of the schema as it can even if the sqlite_schema table is
+    ** corrupt. */
+    sqlite3_exec(p->db, "SAVEPOINT dump; PRAGMA writable_schema=ON", 0, 0, 0);
+    p->nErr = 0;
+    if( zLike==0 ) zLike = sqlite3_mprintf("true");
+    zSql = sqlite3_mprintf(
+      "SELECT name, type, sql FROM sqlite_schema AS o "
+      "WHERE (%s) AND type=='table'"
+      "  AND sql NOT NULL"
+      " ORDER BY tbl_name='sqlite_sequence', rowid",
+      zLike
+    );
+    run_schema_dump_query(p,zSql);
+    sqlite3_free(zSql);
+    if( (p->shellFlgs & SHFLG_DumpDataOnly)==0 ){
+      zSql = sqlite3_mprintf(
+        "SELECT sql FROM sqlite_schema AS o "
+        "WHERE (%s) AND sql NOT NULL"
+        "  AND type IN ('index','trigger','view')",
+        zLike
+      );
+      run_table_dump_query(p, zSql);
+      sqlite3_free(zSql);
+    }
+    sqlite3_free(zLike);
+    if( p->writableSchema ){
+      oputz("PRAGMA writable_schema=OFF;\n");
+      p->writableSchema = 0;
+    }
+    sqlite3_exec(p->db, "PRAGMA writable_schema=OFF;", 0, 0, 0);
+    sqlite3_exec(p->db, "RELEASE dump;", 0, 0, 0);
+    if( (p->shellFlgs & SHFLG_DumpDataOnly)==0 ){
+      oputz(p->nErr?"ROLLBACK; -- due to errors\n":"COMMIT;\n");
+    }
+    p->showHeader = savedShowHeader;
+    p->shellFlgs = savedShellFlags;
+  }else
+
+  if( c=='e' && cli_strncmp(azArg[0], "echo", n)==0 ){
+    if( nArg==2 ){
+      setOrClearFlag(p, SHFLG_Echo, azArg[1]);
+    }else{
+      eputz("Usage: .echo on|off\n");
+      rc = 1;
+    }
+  }else
+
+  if( c=='e' && cli_strncmp(azArg[0], "eqp", n)==0 ){
+    if( nArg==2 ){
+      p->autoEQPtest = 0;
+      if( p->autoEQPtrace ){
+        if( p->db ) sqlite3_exec(p->db, "PRAGMA vdbe_trace=OFF;", 0, 0, 0);
+        p->autoEQPtrace = 0;
+      }
+      if( cli_strcmp(azArg[1],"full")==0 ){
+        p->autoEQP = AUTOEQP_full;
+      }else if( cli_strcmp(azArg[1],"trigger")==0 ){
+        p->autoEQP = AUTOEQP_trigger;
+#ifdef SQLITE_DEBUG
+      }else if( cli_strcmp(azArg[1],"test")==0 ){
+        p->autoEQP = AUTOEQP_on;
+        p->autoEQPtest = 1;
+      }else if( cli_strcmp(azArg[1],"trace")==0 ){
+        p->autoEQP = AUTOEQP_full;
+        p->autoEQPtrace = 1;
+        open_db(p, 0);
+        sqlite3_exec(p->db, "SELECT name FROM sqlite_schema LIMIT 1", 0, 0, 0);
+        sqlite3_exec(p->db, "PRAGMA vdbe_trace=ON;", 0, 0, 0);
+#endif
+      }else{
+        p->autoEQP = (u8)booleanValue(azArg[1]);
+      }
+    }else{
+      eputz("Usage: .eqp off|on|trace|trigger|full\n");
+      rc = 1;
+    }
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='e' && cli_strncmp(azArg[0], "exit", n)==0 ){
+    if( nArg>1 && (rc = (int)integerValue(azArg[1]))!=0 ) exit(rc);
+    rc = 2;
+  }else
+#endif
+
+  /* The ".explain" command is automatic now.  It is largely pointless.  It
+  ** retained purely for backwards compatibility */
+  if( c=='e' && cli_strncmp(azArg[0], "explain", n)==0 ){
+    int val = 1;
+    if( nArg>=2 ){
+      if( cli_strcmp(azArg[1],"auto")==0 ){
+        val = 99;
+      }else{
+        val =  booleanValue(azArg[1]);
+      }
+    }
+    if( val==1 && p->mode!=MODE_Explain ){
+      p->normalMode = p->mode;
+      p->mode = MODE_Explain;
+      p->autoExplain = 0;
+    }else if( val==0 ){
+      if( p->mode==MODE_Explain ) p->mode = p->normalMode;
+      p->autoExplain = 0;
+    }else if( val==99 ){
+      if( p->mode==MODE_Explain ) p->mode = p->normalMode;
+      p->autoExplain = 1;
+    }
+  }else
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( c=='e' && cli_strncmp(azArg[0], "expert", n)==0 ){
+    if( p->bSafeMode ){
+      eputf("Cannot run experimental commands such as \"%s\" in safe mode\n",
+            azArg[0]);
+      rc = 1;
+    }else{
+      open_db(p, 0);
+      expertDotCommand(p, azArg, nArg);
+    }
+  }else
+#endif
+
+  if( c=='f' && cli_strncmp(azArg[0], "filectrl", n)==0 ){
+    static const struct {
+       const char *zCtrlName;   /* Name of a test-control option */
+       int ctrlCode;            /* Integer code for that option */
+       const char *zUsage;      /* Usage notes */
+    } aCtrl[] = {
+      { "chunk_size",     SQLITE_FCNTL_CHUNK_SIZE,      "SIZE"           },
+      { "data_version",   SQLITE_FCNTL_DATA_VERSION,    ""               },
+      { "has_moved",      SQLITE_FCNTL_HAS_MOVED,       ""               },
+      { "lock_timeout",   SQLITE_FCNTL_LOCK_TIMEOUT,    "MILLISEC"       },
+      { "persist_wal",    SQLITE_FCNTL_PERSIST_WAL,     "[BOOLEAN]"      },
+   /* { "pragma",         SQLITE_FCNTL_PRAGMA,          "NAME ARG"       },*/
+      { "psow",       SQLITE_FCNTL_POWERSAFE_OVERWRITE, "[BOOLEAN]"      },
+      { "reserve_bytes",  SQLITE_FCNTL_RESERVE_BYTES,   "[N]"            },
+      { "size_limit",     SQLITE_FCNTL_SIZE_LIMIT,      "[LIMIT]"        },
+      { "tempfilename",   SQLITE_FCNTL_TEMPFILENAME,    ""               },
+   /* { "win32_av_retry", SQLITE_FCNTL_WIN32_AV_RETRY,  "COUNT DELAY"    },*/
+    };
+    int filectrl = -1;
+    int iCtrl = -1;
+    sqlite3_int64 iRes = 0;  /* Integer result to display if rc2==1 */
+    int isOk = 0;            /* 0: usage  1: %lld  2: no-result */
+    int n2, i;
+    const char *zCmd = 0;
+    const char *zSchema = 0;
+
+    open_db(p, 0);
+    zCmd = nArg>=2 ? azArg[1] : "help";
+
+    if( zCmd[0]=='-'
+     && (cli_strcmp(zCmd,"--schema")==0 || cli_strcmp(zCmd,"-schema")==0)
+     && nArg>=4
+    ){
+      zSchema = azArg[2];
+      for(i=3; i<nArg; i++) azArg[i-2] = azArg[i];
+      nArg -= 2;
+      zCmd = azArg[1];
+    }
+
+    /* The argument can optionally begin with "-" or "--" */
+    if( zCmd[0]=='-' && zCmd[1] ){
+      zCmd++;
+      if( zCmd[0]=='-' && zCmd[1] ) zCmd++;
+    }
+
+    /* --help lists all file-controls */
+    if( cli_strcmp(zCmd,"help")==0 ){
+      oputz("Available file-controls:\n");
+      for(i=0; i<ArraySize(aCtrl); i++){
+        oputf("  .filectrl %s %s\n", aCtrl[i].zCtrlName, aCtrl[i].zUsage);
+      }
+      rc = 1;
+      goto meta_command_exit;
+    }
+
+    /* convert filectrl text option to value. allow any unique prefix
+    ** of the option name, or a numerical value. */
+    n2 = strlen30(zCmd);
+    for(i=0; i<ArraySize(aCtrl); i++){
+      if( cli_strncmp(zCmd, aCtrl[i].zCtrlName, n2)==0 ){
+        if( filectrl<0 ){
+          filectrl = aCtrl[i].ctrlCode;
+          iCtrl = i;
+        }else{
+          eputf("Error: ambiguous file-control: \"%s\"\n"
+                "Use \".filectrl --help\" for help\n", zCmd);
+          rc = 1;
+          goto meta_command_exit;
+        }
+      }
+    }
+    if( filectrl<0 ){
+      eputf("Error: unknown file-control: %s\n"
+            "Use \".filectrl --help\" for help\n", zCmd);
+    }else{
+      switch(filectrl){
+        case SQLITE_FCNTL_SIZE_LIMIT: {
+          if( nArg!=2 && nArg!=3 ) break;
+          iRes = nArg==3 ? integerValue(azArg[2]) : -1;
+          sqlite3_file_control(p->db, zSchema, SQLITE_FCNTL_SIZE_LIMIT, &iRes);
+          isOk = 1;
+          break;
+        }
+        case SQLITE_FCNTL_LOCK_TIMEOUT:
+        case SQLITE_FCNTL_CHUNK_SIZE: {
+          int x;
+          if( nArg!=3 ) break;
+          x = (int)integerValue(azArg[2]);
+          sqlite3_file_control(p->db, zSchema, filectrl, &x);
+          isOk = 2;
+          break;
+        }
+        case SQLITE_FCNTL_PERSIST_WAL:
+        case SQLITE_FCNTL_POWERSAFE_OVERWRITE: {
+          int x;
+          if( nArg!=2 && nArg!=3 ) break;
+          x = nArg==3 ? booleanValue(azArg[2]) : -1;
+          sqlite3_file_control(p->db, zSchema, filectrl, &x);
+          iRes = x;
+          isOk = 1;
+          break;
+        }
+        case SQLITE_FCNTL_DATA_VERSION:
+        case SQLITE_FCNTL_HAS_MOVED: {
+          int x;
+          if( nArg!=2 ) break;
+          sqlite3_file_control(p->db, zSchema, filectrl, &x);
+          iRes = x;
+          isOk = 1;
+          break;
+        }
+        case SQLITE_FCNTL_TEMPFILENAME: {
+          char *z = 0;
+          if( nArg!=2 ) break;
+          sqlite3_file_control(p->db, zSchema, filectrl, &z);
+          if( z ){
+            oputf("%s\n", z);
+            sqlite3_free(z);
+          }
+          isOk = 2;
+          break;
+        }
+        case SQLITE_FCNTL_RESERVE_BYTES: {
+          int x;
+          if( nArg>=3 ){
+            x = atoi(azArg[2]);
+            sqlite3_file_control(p->db, zSchema, filectrl, &x);
+          }
+          x = -1;
+          sqlite3_file_control(p->db, zSchema, filectrl, &x);
+          oputf("%d\n", x);
+          isOk = 2;
+          break;
+        }
+      }
+    }
+    if( isOk==0 && iCtrl>=0 ){
+      oputf("Usage: .filectrl %s %s\n", zCmd,aCtrl[iCtrl].zUsage);
+      rc = 1;
+    }else if( isOk==1 ){
+      char zBuf[100];
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "%lld", iRes);
+      oputf("%s\n", zBuf);
+    }
+  }else
+
+  if( c=='f' && cli_strncmp(azArg[0], "fullschema", n)==0 ){
+    ShellState data;
+    int doStats = 0;
+    memcpy(&data, p, sizeof(data));
+    data.showHeader = 0;
+    data.cMode = data.mode = MODE_Semi;
+    if( nArg==2 && optionMatch(azArg[1], "indent") ){
+      data.cMode = data.mode = MODE_Pretty;
+      nArg = 1;
+    }
+    if( nArg!=1 ){
+      eputz("Usage: .fullschema ?--indent?\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    open_db(p, 0);
+    rc = sqlite3_exec(p->db,
+       "SELECT sql FROM"
+       "  (SELECT sql sql, type type, tbl_name tbl_name, name name, rowid x"
+       "     FROM sqlite_schema UNION ALL"
+       "   SELECT sql, type, tbl_name, name, rowid FROM sqlite_temp_schema) "
+       "WHERE type!='meta' AND sql NOTNULL AND name NOT LIKE 'sqlite_%' "
+       "ORDER BY x",
+       callback, &data, 0
+    );
+    if( rc==SQLITE_OK ){
+      sqlite3_stmt *pStmt;
+      rc = sqlite3_prepare_v2(p->db,
+               "SELECT rowid FROM sqlite_schema"
+               " WHERE name GLOB 'sqlite_stat[134]'",
+               -1, &pStmt, 0);
+      if( rc==SQLITE_OK ){
+        doStats = sqlite3_step(pStmt)==SQLITE_ROW;
+        sqlite3_finalize(pStmt);
+      }
+    }
+    if( doStats==0 ){
+      oputz("/* No STAT tables available */\n");
+    }else{
+      oputz("ANALYZE sqlite_schema;\n");
+      data.cMode = data.mode = MODE_Insert;
+      data.zDestTable = "sqlite_stat1";
+      shell_exec(&data, "SELECT * FROM sqlite_stat1", 0);
+      data.zDestTable = "sqlite_stat4";
+      shell_exec(&data, "SELECT * FROM sqlite_stat4", 0);
+      oputz("ANALYZE sqlite_schema;\n");
+    }
+  }else
+
+  if( c=='h' && cli_strncmp(azArg[0], "headers", n)==0 ){
+    if( nArg==2 ){
+      p->showHeader = booleanValue(azArg[1]);
+      p->shellFlgs |= SHFLG_HeaderSet;
+    }else{
+      eputz("Usage: .headers on|off\n");
+      rc = 1;
+    }
+  }else
+
+  if( c=='h' && cli_strncmp(azArg[0], "help", n)==0 ){
+    if( nArg>=2 ){
+      n = showHelp(p->out, azArg[1]);
+      if( n==0 ){
+        oputf("Nothing matches '%s'\n", azArg[1]);
+      }
+    }else{
+      showHelp(p->out, 0);
+    }
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='i' && cli_strncmp(azArg[0], "import", n)==0 ){
+    char *zTable = 0;           /* Insert data into this table */
+    char *zSchema = 0;          /* within this schema (may default to "main") */
+    char *zFile = 0;            /* Name of file to extra content from */
+    sqlite3_stmt *pStmt = NULL; /* A statement */
+    int nCol;                   /* Number of columns in the table */
+    int nByte;                  /* Number of bytes in an SQL string */
+    int i, j;                   /* Loop counters */
+    int needCommit;             /* True to COMMIT or ROLLBACK at end */
+    int nSep;                   /* Number of bytes in p->colSeparator[] */
+    char *zSql;                 /* An SQL statement */
+    char *zFullTabName;         /* Table name with schema if applicable */
+    ImportCtx sCtx;             /* Reader context */
+    char *(SQLITE_CDECL *xRead)(ImportCtx*); /* Func to read one value */
+    int eVerbose = 0;           /* Larger for more console output */
+    int nSkip = 0;              /* Initial lines to skip */
+    int useOutputMode = 1;      /* Use output mode to determine separators */
+    char *zCreate = 0;          /* CREATE TABLE statement text */
+
+    failIfSafeMode(p, "cannot run .import in safe mode");
+    memset(&sCtx, 0, sizeof(sCtx));
+    if( p->mode==MODE_Ascii ){
+      xRead = ascii_read_one_field;
+    }else{
+      xRead = csv_read_one_field;
+    }
+    rc = 1;
+    for(i=1; i<nArg; i++){
+      char *z = azArg[i];
+      if( z[0]=='-' && z[1]=='-' ) z++;
+      if( z[0]!='-' ){
+        if( zFile==0 ){
+          zFile = z;
+        }else if( zTable==0 ){
+          zTable = z;
+        }else{
+          oputf("ERROR: extra argument: \"%s\".  Usage:\n", z);
+          showHelp(p->out, "import");
+          goto meta_command_exit;
+        }
+      }else if( cli_strcmp(z,"-v")==0 ){
+        eVerbose++;
+      }else if( cli_strcmp(z,"-schema")==0 && i<nArg-1 ){
+        zSchema = azArg[++i];
+      }else if( cli_strcmp(z,"-skip")==0 && i<nArg-1 ){
+        nSkip = integerValue(azArg[++i]);
+      }else if( cli_strcmp(z,"-ascii")==0 ){
+        sCtx.cColSep = SEP_Unit[0];
+        sCtx.cRowSep = SEP_Record[0];
+        xRead = ascii_read_one_field;
+        useOutputMode = 0;
+      }else if( cli_strcmp(z,"-csv")==0 ){
+        sCtx.cColSep = ',';
+        sCtx.cRowSep = '\n';
+        xRead = csv_read_one_field;
+        useOutputMode = 0;
+      }else{
+        oputf("ERROR: unknown option: \"%s\".  Usage:\n", z);
+        showHelp(p->out, "import");
+        goto meta_command_exit;
+      }
+    }
+    if( zTable==0 ){
+      oputf("ERROR: missing %s argument. Usage:\n",
+            zFile==0 ? "FILE" : "TABLE");
+      showHelp(p->out, "import");
+      goto meta_command_exit;
+    }
+    seenInterrupt = 0;
+    open_db(p, 0);
+    if( useOutputMode ){
+      /* If neither the --csv or --ascii options are specified, then set
+      ** the column and row separator characters from the output mode. */
+      nSep = strlen30(p->colSeparator);
+      if( nSep==0 ){
+        eputz("Error: non-null column separator required for import\n");
+        goto meta_command_exit;
+      }
+      if( nSep>1 ){
+        eputz("Error: multi-character column separators not allowed"
+              " for import\n");
+        goto meta_command_exit;
+      }
+      nSep = strlen30(p->rowSeparator);
+      if( nSep==0 ){
+        eputz("Error: non-null row separator required for import\n");
+        goto meta_command_exit;
+      }
+      if( nSep==2 && p->mode==MODE_Csv
+       && cli_strcmp(p->rowSeparator,SEP_CrLf)==0
+      ){
+        /* When importing CSV (only), if the row separator is set to the
+        ** default output row separator, change it to the default input
+        ** row separator.  This avoids having to maintain different input
+        ** and output row separators. */
+        sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_Row);
+        nSep = strlen30(p->rowSeparator);
+      }
+      if( nSep>1 ){
+        eputz("Error: multi-character row separators not allowed"
+              " for import\n");
+        goto meta_command_exit;
+      }
+      sCtx.cColSep = (u8)p->colSeparator[0];
+      sCtx.cRowSep = (u8)p->rowSeparator[0];
+    }
+    sCtx.zFile = zFile;
+    sCtx.nLine = 1;
+    if( sCtx.zFile[0]=='|' ){
+#ifdef SQLITE_OMIT_POPEN
+      eputz("Error: pipes are not supported in this OS\n");
+      goto meta_command_exit;
+#else
+      sCtx.in = popen(sCtx.zFile+1, "r");
+      sCtx.zFile = "<pipe>";
+      sCtx.xCloser = pclose;
+#endif
+    }else{
+      sCtx.in = fopen(sCtx.zFile, "rb");
+      sCtx.xCloser = fclose;
+    }
+    if( sCtx.in==0 ){
+      eputf("Error: cannot open \"%s\"\n", zFile);
+      goto meta_command_exit;
+    }
+    if( eVerbose>=2 || (eVerbose>=1 && useOutputMode) ){
+      char zSep[2];
+      zSep[1] = 0;
+      zSep[0] = sCtx.cColSep;
+      oputz("Column separator ");
+      output_c_string(zSep);
+      oputz(", row separator ");
+      zSep[0] = sCtx.cRowSep;
+      output_c_string(zSep);
+      oputz("\n");
+    }
+    sCtx.z = sqlite3_malloc64(120);
+    if( sCtx.z==0 ){
+      import_cleanup(&sCtx);
+      shell_out_of_memory();
+    }
+    /* Below, resources must be freed before exit. */
+    while( (nSkip--)>0 ){
+      while( xRead(&sCtx) && sCtx.cTerm==sCtx.cColSep ){}
+    }
+    if( zSchema!=0 ){
+      zFullTabName = sqlite3_mprintf("\"%w\".\"%w\"", zSchema, zTable);
+    }else{
+      zFullTabName = sqlite3_mprintf("\"%w\"", zTable);
+    }
+    zSql = sqlite3_mprintf("SELECT * FROM %s", zFullTabName);
+    if( zSql==0 || zFullTabName==0 ){
+      import_cleanup(&sCtx);
+      shell_out_of_memory();
+    }
+    nByte = strlen30(zSql);
+    rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    import_append_char(&sCtx, 0);    /* To ensure sCtx.z is allocated */
+    if( rc && sqlite3_strglob("no such table: *", sqlite3_errmsg(p->db))==0 ){
+      sqlite3 *dbCols = 0;
+      char *zRenames = 0;
+      char *zColDefs;
+      zCreate = sqlite3_mprintf("CREATE TABLE %s", zFullTabName);
+      while( xRead(&sCtx) ){
+        zAutoColumn(sCtx.z, &dbCols, 0);
+        if( sCtx.cTerm!=sCtx.cColSep ) break;
+      }
+      zColDefs = zAutoColumn(0, &dbCols, &zRenames);
+      if( zRenames!=0 ){
+        sputf((stdin_is_interactive && p->in==stdin)? p->out : stderr,
+              "Columns renamed during .import %s due to duplicates:\n"
+              "%s\n", sCtx.zFile, zRenames);
+        sqlite3_free(zRenames);
+      }
+      assert(dbCols==0);
+      if( zColDefs==0 ){
+        eputf("%s: empty file\n", sCtx.zFile);
+      import_fail:
+        sqlite3_free(zCreate);
+        sqlite3_free(zSql);
+        sqlite3_free(zFullTabName);
+        import_cleanup(&sCtx);
+        rc = 1;
+        goto meta_command_exit;
+      }
+      zCreate = sqlite3_mprintf("%z%z\n", zCreate, zColDefs);
+      if( eVerbose>=1 ){
+        oputf("%s\n", zCreate);
+      }
+      rc = sqlite3_exec(p->db, zCreate, 0, 0, 0);
+      if( rc ){
+        eputf("%s failed:\n%s\n", zCreate, sqlite3_errmsg(p->db));
+        goto import_fail;
+      }
+      sqlite3_free(zCreate);
+      zCreate = 0;
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    }
+    if( rc ){
+      if (pStmt) sqlite3_finalize(pStmt);
+      eputf("Error: %s\n", sqlite3_errmsg(p->db));
+      goto import_fail;
+    }
+    sqlite3_free(zSql);
+    nCol = sqlite3_column_count(pStmt);
+    sqlite3_finalize(pStmt);
+    pStmt = 0;
+    if( nCol==0 ) return 0; /* no columns, no error */
+    zSql = sqlite3_malloc64( nByte*2 + 20 + nCol*2 );
+    if( zSql==0 ){
+      import_cleanup(&sCtx);
+      shell_out_of_memory();
+    }
+    sqlite3_snprintf(nByte+20, zSql, "INSERT INTO %s VALUES(?", zFullTabName);
+    j = strlen30(zSql);
+    for(i=1; i<nCol; i++){
+      zSql[j++] = ',';
+      zSql[j++] = '?';
+    }
+    zSql[j++] = ')';
+    zSql[j] = 0;
+    if( eVerbose>=2 ){
+      oputf("Insert using: %s\n", zSql);
+    }
+    rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    if( rc ){
+      eputf("Error: %s\n", sqlite3_errmsg(p->db));
+      if (pStmt) sqlite3_finalize(pStmt);
+      goto import_fail;
+    }
+    sqlite3_free(zSql);
+    sqlite3_free(zFullTabName);
+    needCommit = sqlite3_get_autocommit(p->db);
+    if( needCommit ) sqlite3_exec(p->db, "BEGIN", 0, 0, 0);
+    do{
+      int startLine = sCtx.nLine;
+      for(i=0; i<nCol; i++){
+        char *z = xRead(&sCtx);
+        /*
+        ** Did we reach end-of-file before finding any columns?
+        ** If so, stop instead of NULL filling the remaining columns.
+        */
+        if( z==0 && i==0 ) break;
+        /*
+        ** Did we reach end-of-file OR end-of-line before finding any
+        ** columns in ASCII mode?  If so, stop instead of NULL filling
+        ** the remaining columns.
+        */
+        if( p->mode==MODE_Ascii && (z==0 || z[0]==0) && i==0 ) break;
+        /*
+        ** For CSV mode, per RFC 4180, accept EOF in lieu of final
+        ** record terminator but only for last field of multi-field row.
+        ** (If there are too few fields, it's not valid CSV anyway.)
+        */
+        if( z==0 && (xRead==csv_read_one_field) && i==nCol-1 && i>0 ){
+          z = "";
+        }
+        sqlite3_bind_text(pStmt, i+1, z, -1, SQLITE_TRANSIENT);
+        if( i<nCol-1 && sCtx.cTerm!=sCtx.cColSep ){
+          eputf("%s:%d: expected %d columns but found %d"
+                " - filling the rest with NULL\n",
+                sCtx.zFile, startLine, nCol, i+1);
+          i += 2;
+          while( i<=nCol ){ sqlite3_bind_null(pStmt, i); i++; }
+        }
+      }
+      if( sCtx.cTerm==sCtx.cColSep ){
+        do{
+          xRead(&sCtx);
+          i++;
+        }while( sCtx.cTerm==sCtx.cColSep );
+        eputf("%s:%d: expected %d columns but found %d - extras ignored\n",
+              sCtx.zFile, startLine, nCol, i);
+      }
+      if( i>=nCol ){
+        sqlite3_step(pStmt);
+        rc = sqlite3_reset(pStmt);
+        if( rc!=SQLITE_OK ){
+          eputf("%s:%d: INSERT failed: %s\n",
+                sCtx.zFile, startLine, sqlite3_errmsg(p->db));
+          sCtx.nErr++;
+        }else{
+          sCtx.nRow++;
+        }
+      }
+    }while( sCtx.cTerm!=EOF );
+
+    import_cleanup(&sCtx);
+    sqlite3_finalize(pStmt);
+    if( needCommit ) sqlite3_exec(p->db, "COMMIT", 0, 0, 0);
+    if( eVerbose>0 ){
+      oputf("Added %d rows with %d errors using %d lines of input\n",
+            sCtx.nRow, sCtx.nErr, sCtx.nLine-1);
+    }
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+#ifndef SQLITE_UNTESTABLE
+  if( c=='i' && cli_strncmp(azArg[0], "imposter", n)==0 ){
+    char *zSql;
+    char *zCollist = 0;
+    sqlite3_stmt *pStmt;
+    int tnum = 0;
+    int isWO = 0;  /* True if making an imposter of a WITHOUT ROWID table */
+    int lenPK = 0; /* Length of the PRIMARY KEY string for isWO tables */
+    int i;
+    if( !ShellHasFlag(p,SHFLG_TestingMode) ){
+      eputf(".%s unavailable without --unsafe-testing\n",
+            "imposter");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    if( !(nArg==3 || (nArg==2 && sqlite3_stricmp(azArg[1],"off")==0)) ){
+      eputz("Usage: .imposter INDEX IMPOSTER\n"
+            "       .imposter off\n");
+      /* Also allowed, but not documented:
+      **
+      **    .imposter TABLE IMPOSTER
+      **
+      ** where TABLE is a WITHOUT ROWID table.  In that case, the
+      ** imposter is another WITHOUT ROWID table with the columns in
+      ** storage order. */
+      rc = 1;
+      goto meta_command_exit;
+    }
+    open_db(p, 0);
+    if( nArg==2 ){
+      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->db, "main", 0, 1);
+      goto meta_command_exit;
+    }
+    zSql = sqlite3_mprintf(
+      "SELECT rootpage, 0 FROM sqlite_schema"
+      " WHERE name='%q' AND type='index'"
+      "UNION ALL "
+      "SELECT rootpage, 1 FROM sqlite_schema"
+      " WHERE name='%q' AND type='table'"
+      "   AND sql LIKE '%%without%%rowid%%'",
+      azArg[1], azArg[1]
+    );
+    sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+    if( sqlite3_step(pStmt)==SQLITE_ROW ){
+      tnum = sqlite3_column_int(pStmt, 0);
+      isWO = sqlite3_column_int(pStmt, 1);
+    }
+    sqlite3_finalize(pStmt);
+    zSql = sqlite3_mprintf("PRAGMA index_xinfo='%q'", azArg[1]);
+    rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+    i = 0;
+    while( rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
+      char zLabel[20];
+      const char *zCol = (const char*)sqlite3_column_text(pStmt,2);
+      i++;
+      if( zCol==0 ){
+        if( sqlite3_column_int(pStmt,1)==-1 ){
+          zCol = "_ROWID_";
+        }else{
+          sqlite3_snprintf(sizeof(zLabel),zLabel,"expr%d",i);
+          zCol = zLabel;
+        }
+      }
+      if( isWO && lenPK==0 && sqlite3_column_int(pStmt,5)==0 && zCollist ){
+        lenPK = (int)strlen(zCollist);
+      }
+      if( zCollist==0 ){
+        zCollist = sqlite3_mprintf("\"%w\"", zCol);
+      }else{
+        zCollist = sqlite3_mprintf("%z,\"%w\"", zCollist, zCol);
+      }
+    }
+    sqlite3_finalize(pStmt);
+    if( i==0 || tnum==0 ){
+      eputf("no such index: \"%s\"\n", azArg[1]);
+      rc = 1;
+      sqlite3_free(zCollist);
+      goto meta_command_exit;
+    }
+    if( lenPK==0 ) lenPK = 100000;
+    zSql = sqlite3_mprintf(
+          "CREATE TABLE \"%w\"(%s,PRIMARY KEY(%.*s))WITHOUT ROWID",
+          azArg[2], zCollist, lenPK, zCollist);
+    sqlite3_free(zCollist);
+    rc = sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->db, "main", 1, tnum);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
+      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->db, "main", 0, 0);
+      if( rc ){
+        eputf("Error in [%s]: %s\n", zSql, sqlite3_errmsg(p->db));
+      }else{
+        sputf(stdout, "%s;\n", zSql);
+        sputf(stdout, "WARNING: writing to an imposter table will corrupt"
+              " the \"%s\" %s!\n", azArg[1], isWO ? "table" : "index");
+      }
+    }else{
+      eputf("SQLITE_TESTCTRL_IMPOSTER returns %d\n", rc);
+      rc = 1;
+    }
+    sqlite3_free(zSql);
+  }else
+#endif /* !defined(SQLITE_OMIT_TEST_CONTROL) */
+
+#ifdef SQLITE_ENABLE_IOTRACE
+  if( c=='i' && cli_strncmp(azArg[0], "iotrace", n)==0 ){
+    SQLITE_API extern void (SQLITE_CDECL *sqlite3IoTrace)(const char*, ...);
+    if( iotrace && iotrace!=stdout ) fclose(iotrace);
+    iotrace = 0;
+    if( nArg<2 ){
+      sqlite3IoTrace = 0;
+    }else if( cli_strcmp(azArg[1], "-")==0 ){
+      sqlite3IoTrace = iotracePrintf;
+      iotrace = stdout;
+    }else{
+      iotrace = fopen(azArg[1], "w");
+      if( iotrace==0 ){
+        eputf("Error: cannot open \"%s\"\n", azArg[1]);
+        sqlite3IoTrace = 0;
+        rc = 1;
+      }else{
+        sqlite3IoTrace = iotracePrintf;
+      }
+    }
+  }else
+#endif
+
+  if( c=='l' && n>=5 && cli_strncmp(azArg[0], "limits", n)==0 ){
+    static const struct {
+       const char *zLimitName;   /* Name of a limit */
+       int limitCode;            /* Integer code for that limit */
+    } aLimit[] = {
+      { "length",                SQLITE_LIMIT_LENGTH                    },
+      { "sql_length",            SQLITE_LIMIT_SQL_LENGTH                },
+      { "column",                SQLITE_LIMIT_COLUMN                    },
+      { "expr_depth",            SQLITE_LIMIT_EXPR_DEPTH                },
+      { "compound_select",       SQLITE_LIMIT_COMPOUND_SELECT           },
+      { "vdbe_op",               SQLITE_LIMIT_VDBE_OP                   },
+      { "function_arg",          SQLITE_LIMIT_FUNCTION_ARG              },
+      { "attached",              SQLITE_LIMIT_ATTACHED                  },
+      { "like_pattern_length",   SQLITE_LIMIT_LIKE_PATTERN_LENGTH       },
+      { "variable_number",       SQLITE_LIMIT_VARIABLE_NUMBER           },
+      { "trigger_depth",         SQLITE_LIMIT_TRIGGER_DEPTH             },
+      { "worker_threads",        SQLITE_LIMIT_WORKER_THREADS            },
+    };
+    int i, n2;
+    open_db(p, 0);
+    if( nArg==1 ){
+      for(i=0; i<ArraySize(aLimit); i++){
+        sputf(stdout, "%20s %d\n", aLimit[i].zLimitName,
+              sqlite3_limit(p->db, aLimit[i].limitCode, -1));
+      }
+    }else if( nArg>3 ){
+      eputz("Usage: .limit NAME ?NEW-VALUE?\n");
+      rc = 1;
+      goto meta_command_exit;
+    }else{
+      int iLimit = -1;
+      n2 = strlen30(azArg[1]);
+      for(i=0; i<ArraySize(aLimit); i++){
+        if( sqlite3_strnicmp(aLimit[i].zLimitName, azArg[1], n2)==0 ){
+          if( iLimit<0 ){
+            iLimit = i;
+          }else{
+            eputf("ambiguous limit: \"%s\"\n", azArg[1]);
+            rc = 1;
+            goto meta_command_exit;
+          }
+        }
+      }
+      if( iLimit<0 ){
+        eputf("unknown limit: \"%s\"\n"
+              "enter \".limits\" with no arguments for a list.\n",
+              azArg[1]);
+        rc = 1;
+        goto meta_command_exit;
+      }
+      if( nArg==3 ){
+        sqlite3_limit(p->db, aLimit[iLimit].limitCode,
+                      (int)integerValue(azArg[2]));
+      }
+      sputf(stdout, "%20s %d\n", aLimit[iLimit].zLimitName,
+            sqlite3_limit(p->db, aLimit[iLimit].limitCode, -1));
+    }
+  }else
+
+  if( c=='l' && n>2 && cli_strncmp(azArg[0], "lint", n)==0 ){
+    open_db(p, 0);
+    lintDotCommand(p, azArg, nArg);
+  }else
+
+#if !defined(SQLITE_OMIT_LOAD_EXTENSION) && !defined(SQLITE_SHELL_FIDDLE)
+  if( c=='l' && cli_strncmp(azArg[0], "load", n)==0 ){
+    const char *zFile, *zProc;
+    char *zErrMsg = 0;
+    failIfSafeMode(p, "cannot run .load in safe mode");
+    if( nArg<2 || azArg[1][0]==0 ){
+      /* Must have a non-empty FILE. (Will not load self.) */
+      eputz("Usage: .load FILE ?ENTRYPOINT?\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    zFile = azArg[1];
+    zProc = nArg>=3 ? azArg[2] : 0;
+    open_db(p, 0);
+    rc = sqlite3_load_extension(p->db, zFile, zProc, &zErrMsg);
+    if( rc!=SQLITE_OK ){
+      eputf("Error: %s\n", zErrMsg);
+      sqlite3_free(zErrMsg);
+      rc = 1;
+    }
+  }else
+#endif
+
+  if( c=='l' && cli_strncmp(azArg[0], "log", n)==0 ){
+    if( nArg!=2 ){
+      eputz("Usage: .log FILENAME\n");
+      rc = 1;
+    }else{
+      const char *zFile = azArg[1];
+      if( p->bSafeMode
+       && cli_strcmp(zFile,"on")!=0
+       && cli_strcmp(zFile,"off")!=0
+      ){
+        sputz(stdout, "cannot set .log to anything other"
+              " than \"on\" or \"off\"\n");
+        zFile = "off";
+      }
+      output_file_close(p->pLog);
+      if( cli_strcmp(zFile,"on")==0 ) zFile = "stdout";
+      p->pLog = output_file_open(zFile, 0);
+    }
+  }else
+
+  if( c=='m' && cli_strncmp(azArg[0], "mode", n)==0 ){
+    const char *zMode = 0;
+    const char *zTabname = 0;
+    int i, n2;
+    ColModeOpts cmOpts = ColModeOpts_default;
+    for(i=1; i<nArg; i++){
+      const char *z = azArg[i];
+      if( optionMatch(z,"wrap") && i+1<nArg ){
+        cmOpts.iWrap = integerValue(azArg[++i]);
+      }else if( optionMatch(z,"ww") ){
+        cmOpts.bWordWrap = 1;
+      }else if( optionMatch(z,"wordwrap") && i+1<nArg ){
+        cmOpts.bWordWrap = (u8)booleanValue(azArg[++i]);
+      }else if( optionMatch(z,"quote") ){
+        cmOpts.bQuote = 1;
+      }else if( optionMatch(z,"noquote") ){
+        cmOpts.bQuote = 0;
+      }else if( zMode==0 ){
+        zMode = z;
+        /* Apply defaults for qbox pseudo-mode.  If that
+         * overwrites already-set values, user was informed of this.
+         */
+        if( cli_strcmp(z, "qbox")==0 ){
+          ColModeOpts cmo = ColModeOpts_default_qbox;
+          zMode = "box";
+          cmOpts = cmo;
+        }
+      }else if( zTabname==0 ){
+        zTabname = z;
+      }else if( z[0]=='-' ){
+        eputf("unknown option: %s\n", z);
+        eputz("options:\n"
+              "  --noquote\n"
+              "  --quote\n"
+              "  --wordwrap on/off\n"
+              "  --wrap N\n"
+              "  --ww\n");
+        rc = 1;
+        goto meta_command_exit;
+      }else{
+        eputf("extra argument: \"%s\"\n", z);
+        rc = 1;
+        goto meta_command_exit;
+      }
+    }
+    if( zMode==0 ){
+      if( p->mode==MODE_Column
+       || (p->mode>=MODE_Markdown && p->mode<=MODE_Box)
+      ){
+        oputf("current output mode: %s --wrap %d --wordwrap %s --%squote\n",
+              modeDescr[p->mode], p->cmOpts.iWrap,
+              p->cmOpts.bWordWrap ? "on" : "off",
+              p->cmOpts.bQuote ? "" : "no");
+      }else{
+        oputf("current output mode: %s\n", modeDescr[p->mode]);
+      }
+      zMode = modeDescr[p->mode];
+    }
+    n2 = strlen30(zMode);
+    if( cli_strncmp(zMode,"lines",n2)==0 ){
+      p->mode = MODE_Line;
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_Row);
+    }else if( cli_strncmp(zMode,"columns",n2)==0 ){
+      p->mode = MODE_Column;
+      if( (p->shellFlgs & SHFLG_HeaderSet)==0 ){
+        p->showHeader = 1;
+      }
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_Row);
+      p->cmOpts = cmOpts;
+    }else if( cli_strncmp(zMode,"list",n2)==0 ){
+      p->mode = MODE_List;
+      sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator, SEP_Column);
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_Row);
+    }else if( cli_strncmp(zMode,"html",n2)==0 ){
+      p->mode = MODE_Html;
+    }else if( cli_strncmp(zMode,"tcl",n2)==0 ){
+      p->mode = MODE_Tcl;
+      sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator, SEP_Space);
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_Row);
+    }else if( cli_strncmp(zMode,"csv",n2)==0 ){
+      p->mode = MODE_Csv;
+      sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator, SEP_Comma);
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_CrLf);
+    }else if( cli_strncmp(zMode,"tabs",n2)==0 ){
+      p->mode = MODE_List;
+      sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator, SEP_Tab);
+    }else if( cli_strncmp(zMode,"insert",n2)==0 ){
+      p->mode = MODE_Insert;
+      set_table_name(p, zTabname ? zTabname : "table");
+    }else if( cli_strncmp(zMode,"quote",n2)==0 ){
+      p->mode = MODE_Quote;
+      sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator, SEP_Comma);
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_Row);
+    }else if( cli_strncmp(zMode,"ascii",n2)==0 ){
+      p->mode = MODE_Ascii;
+      sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator, SEP_Unit);
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_Record);
+    }else if( cli_strncmp(zMode,"markdown",n2)==0 ){
+      p->mode = MODE_Markdown;
+      p->cmOpts = cmOpts;
+    }else if( cli_strncmp(zMode,"table",n2)==0 ){
+      p->mode = MODE_Table;
+      p->cmOpts = cmOpts;
+    }else if( cli_strncmp(zMode,"box",n2)==0 ){
+      p->mode = MODE_Box;
+      p->cmOpts = cmOpts;
+    }else if( cli_strncmp(zMode,"count",n2)==0 ){
+      p->mode = MODE_Count;
+    }else if( cli_strncmp(zMode,"off",n2)==0 ){
+      p->mode = MODE_Off;
+    }else if( cli_strncmp(zMode,"json",n2)==0 ){
+      p->mode = MODE_Json;
+    }else{
+      eputz("Error: mode should be one of: "
+            "ascii box column csv html insert json line list markdown "
+            "qbox quote table tabs tcl\n");
+      rc = 1;
+    }
+    p->cMode = p->mode;
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='n' && cli_strcmp(azArg[0], "nonce")==0 ){
+    if( nArg!=2 ){
+      eputz("Usage: .nonce NONCE\n");
+      rc = 1;
+    }else if( p->zNonce==0 || cli_strcmp(azArg[1],p->zNonce)!=0 ){
+      eputf("line %d: incorrect nonce: \"%s\"\n",
+            p->lineno, azArg[1]);
+      exit(1);
+    }else{
+      p->bSafeMode = 0;
+      return 0;  /* Return immediately to bypass the safe mode reset
+                 ** at the end of this procedure */
+    }
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+  if( c=='n' && cli_strncmp(azArg[0], "nullvalue", n)==0 ){
+    if( nArg==2 ){
+      sqlite3_snprintf(sizeof(p->nullValue), p->nullValue,
+                       "%.*s", (int)ArraySize(p->nullValue)-1, azArg[1]);
+    }else{
+      eputz("Usage: .nullvalue STRING\n");
+      rc = 1;
+    }
+  }else
+
+  if( c=='o' && cli_strncmp(azArg[0], "open", n)==0 && n>=2 ){
+    const char *zFN = 0;     /* Pointer to constant filename */
+    char *zNewFilename = 0;  /* Name of the database file to open */
+    int iName = 1;           /* Index in azArg[] of the filename */
+    int newFlag = 0;         /* True to delete file before opening */
+    int openMode = SHELL_OPEN_UNSPEC;
+
+    /* Check for command-line arguments */
+    for(iName=1; iName<nArg; iName++){
+      const char *z = azArg[iName];
+#ifndef SQLITE_SHELL_FIDDLE
+      if( optionMatch(z,"new") ){
+        newFlag = 1;
+#ifdef SQLITE_HAVE_ZLIB
+      }else if( optionMatch(z, "zip") ){
+        openMode = SHELL_OPEN_ZIPFILE;
+#endif
+      }else if( optionMatch(z, "append") ){
+        openMode = SHELL_OPEN_APPENDVFS;
+      }else if( optionMatch(z, "readonly") ){
+        openMode = SHELL_OPEN_READONLY;
+      }else if( optionMatch(z, "nofollow") ){
+        p->openFlags |= SQLITE_OPEN_NOFOLLOW;
+#ifndef SQLITE_OMIT_DESERIALIZE
+      }else if( optionMatch(z, "deserialize") ){
+        openMode = SHELL_OPEN_DESERIALIZE;
+      }else if( optionMatch(z, "hexdb") ){
+        openMode = SHELL_OPEN_HEXDB;
+      }else if( optionMatch(z, "maxsize") && iName+1<nArg ){
+        p->szMax = integerValue(azArg[++iName]);
+#endif /* SQLITE_OMIT_DESERIALIZE */
+      }else
+#endif /* !SQLITE_SHELL_FIDDLE */
+      if( z[0]=='-' ){
+        eputf("unknown option: %s\n", z);
+        rc = 1;
+        goto meta_command_exit;
+      }else if( zFN ){
+        eputf("extra argument: \"%s\"\n", z);
+        rc = 1;
+        goto meta_command_exit;
+      }else{
+        zFN = z;
+      }
+    }
+
+    /* Close the existing database */
+    session_close_all(p, -1);
+    close_db(p->db);
+    p->db = 0;
+    p->pAuxDb->zDbFilename = 0;
+    sqlite3_free(p->pAuxDb->zFreeOnClose);
+    p->pAuxDb->zFreeOnClose = 0;
+    p->openMode = openMode;
+    p->openFlags = 0;
+    p->szMax = 0;
+
+    /* If a filename is specified, try to open it first */
+    if( zFN || p->openMode==SHELL_OPEN_HEXDB ){
+      if( newFlag && zFN && !p->bSafeMode ) shellDeleteFile(zFN);
+#ifndef SQLITE_SHELL_FIDDLE
+      if( p->bSafeMode
+       && p->openMode!=SHELL_OPEN_HEXDB
+       && zFN
+       && cli_strcmp(zFN,":memory:")!=0
+      ){
+        failIfSafeMode(p, "cannot open disk-based database files in safe mode");
+      }
+#else
+      /* WASM mode has its own sandboxed pseudo-filesystem. */
+#endif
+      if( zFN ){
+        zNewFilename = sqlite3_mprintf("%s", zFN);
+        shell_check_oom(zNewFilename);
+      }else{
+        zNewFilename = 0;
+      }
+      p->pAuxDb->zDbFilename = zNewFilename;
+      open_db(p, OPEN_DB_KEEPALIVE);
+      if( p->db==0 ){
+        eputf("Error: cannot open '%s'\n", zNewFilename);
+        sqlite3_free(zNewFilename);
+      }else{
+        p->pAuxDb->zFreeOnClose = zNewFilename;
+      }
+    }
+    if( p->db==0 ){
+      /* As a fall-back open a TEMP database */
+      p->pAuxDb->zDbFilename = 0;
+      open_db(p, 0);
+    }
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( (c=='o'
+        && (cli_strncmp(azArg[0], "output", n)==0
+            || cli_strncmp(azArg[0], "once", n)==0))
+   || (c=='e' && n==5 && cli_strcmp(azArg[0],"excel")==0)
+  ){
+    char *zFile = 0;
+    int bTxtMode = 0;
+    int i;
+    int eMode = 0;
+    int bOnce = 0;            /* 0: .output, 1: .once, 2: .excel */
+    static const char *zBomUtf8 = "\xef\xbb\xbf";
+    const char *zBom = 0;
+
+    failIfSafeMode(p, "cannot run .%s in safe mode", azArg[0]);
+    if( c=='e' ){
+      eMode = 'x';
+      bOnce = 2;
+    }else if( cli_strncmp(azArg[0],"once",n)==0 ){
+      bOnce = 1;
+    }
+    for(i=1; i<nArg; i++){
+      char *z = azArg[i];
+      if( z[0]=='-' ){
+        if( z[1]=='-' ) z++;
+        if( cli_strcmp(z,"-bom")==0 ){
+          zBom = zBomUtf8;
+        }else if( c!='e' && cli_strcmp(z,"-x")==0 ){
+          eMode = 'x';  /* spreadsheet */
+        }else if( c!='e' && cli_strcmp(z,"-e")==0 ){
+          eMode = 'e';  /* text editor */
+        }else{
+          oputf("ERROR: unknown option: \"%s\".  Usage:\n", azArg[i]);
+          showHelp(p->out, azArg[0]);
+          rc = 1;
+          goto meta_command_exit;
+        }
+      }else if( zFile==0 && eMode!='e' && eMode!='x' ){
+        zFile = sqlite3_mprintf("%s", z);
+        if( zFile && zFile[0]=='|' ){
+          while( i+1<nArg ) zFile = sqlite3_mprintf("%z %s", zFile, azArg[++i]);
+          break;
+        }
+      }else{
+        oputf("ERROR: extra parameter: \"%s\".  Usage:\n", azArg[i]);
+        showHelp(p->out, azArg[0]);
+        rc = 1;
+        sqlite3_free(zFile);
+        goto meta_command_exit;
+      }
+    }
+    if( zFile==0 ){
+      zFile = sqlite3_mprintf("stdout");
+    }
+    if( bOnce ){
+      p->outCount = 2;
+    }else{
+      p->outCount = 0;
+    }
+    output_reset(p);
+#ifndef SQLITE_NOHAVE_SYSTEM
+    if( eMode=='e' || eMode=='x' ){
+      p->doXdgOpen = 1;
+      outputModePush(p);
+      if( eMode=='x' ){
+        /* spreadsheet mode.  Output as CSV. */
+        newTempFile(p, "csv");
+        ShellClearFlag(p, SHFLG_Echo);
+        p->mode = MODE_Csv;
+        sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator, SEP_Comma);
+        sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator, SEP_CrLf);
+      }else{
+        /* text editor mode */
+        newTempFile(p, "txt");
+        bTxtMode = 1;
+      }
+      sqlite3_free(zFile);
+      zFile = sqlite3_mprintf("%s", p->zTempFile);
+    }
+#endif /* SQLITE_NOHAVE_SYSTEM */
+    shell_check_oom(zFile);
+    if( zFile[0]=='|' ){
+#ifdef SQLITE_OMIT_POPEN
+      eputz("Error: pipes are not supported in this OS\n");
+      rc = 1;
+      output_redir(p, stdout);
+#else
+      FILE *pfPipe = popen(zFile + 1, "w");
+      if( pfPipe==0 ){
+        eputf("Error: cannot open pipe \"%s\"\n", zFile + 1);
+        rc = 1;
+      }else{
+        output_redir(p, pfPipe);
+        if( zBom ) oputz(zBom);
+        sqlite3_snprintf(sizeof(p->outfile), p->outfile, "%s", zFile);
+      }
+#endif
+    }else{
+      FILE *pfFile = output_file_open(zFile, bTxtMode);
+      if( pfFile==0 ){
+        if( cli_strcmp(zFile,"off")!=0 ){
+          eputf("Error: cannot write to \"%s\"\n", zFile);
+        }
+        rc = 1;
+      } else {
+        output_redir(p, pfFile);
+        if( zBom ) oputz(zBom);
+        sqlite3_snprintf(sizeof(p->outfile), p->outfile, "%s", zFile);
+      }
+    }
+    sqlite3_free(zFile);
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+  if( c=='p' && n>=3 && cli_strncmp(azArg[0], "parameter", n)==0 ){
+    open_db(p,0);
+    if( nArg<=1 ) goto parameter_syntax_error;
+
+    /* .parameter clear
+    ** Clear all bind parameters by dropping the TEMP table that holds them.
+    */
+    if( nArg==2 && cli_strcmp(azArg[1],"clear")==0 ){
+      sqlite3_exec(p->db, "DROP TABLE IF EXISTS temp.sqlite_parameters;",
+                   0, 0, 0);
+    }else
+
+    /* .parameter list
+    ** List all bind parameters.
+    */
+    if( nArg==2 && cli_strcmp(azArg[1],"list")==0 ){
+      sqlite3_stmt *pStmt = 0;
+      int rx;
+      int len = 0;
+      rx = sqlite3_prepare_v2(p->db,
+             "SELECT max(length(key)) "
+             "FROM temp.sqlite_parameters;", -1, &pStmt, 0);
+      if( rx==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
+        len = sqlite3_column_int(pStmt, 0);
+        if( len>40 ) len = 40;
+      }
+      sqlite3_finalize(pStmt);
+      pStmt = 0;
+      if( len ){
+        rx = sqlite3_prepare_v2(p->db,
+             "SELECT key, quote(value) "
+             "FROM temp.sqlite_parameters;", -1, &pStmt, 0);
+        while( rx==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
+          oputf("%-*s %s\n", len, sqlite3_column_text(pStmt,0),
+                sqlite3_column_text(pStmt,1));
+        }
+        sqlite3_finalize(pStmt);
+      }
+    }else
+
+    /* .parameter init
+    ** Make sure the TEMP table used to hold bind parameters exists.
+    ** Create it if necessary.
+    */
+    if( nArg==2 && cli_strcmp(azArg[1],"init")==0 ){
+      bind_table_init(p);
+    }else
+
+    /* .parameter set NAME VALUE
+    ** Set or reset a bind parameter.  NAME should be the full parameter
+    ** name exactly as it appears in the query.  (ex: $abc, @def).  The
+    ** VALUE can be in either SQL literal notation, or if not it will be
+    ** understood to be a text string.
+    */
+    if( nArg==4 && cli_strcmp(azArg[1],"set")==0 ){
+      int rx;
+      char *zSql;
+      sqlite3_stmt *pStmt;
+      const char *zKey = azArg[2];
+      const char *zValue = azArg[3];
+      bind_table_init(p);
+      zSql = sqlite3_mprintf(
+                  "REPLACE INTO temp.sqlite_parameters(key,value)"
+                  "VALUES(%Q,%s);", zKey, zValue);
+      shell_check_oom(zSql);
+      pStmt = 0;
+      rx = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+      sqlite3_free(zSql);
+      if( rx!=SQLITE_OK ){
+        sqlite3_finalize(pStmt);
+        pStmt = 0;
+        zSql = sqlite3_mprintf(
+                   "REPLACE INTO temp.sqlite_parameters(key,value)"
+                   "VALUES(%Q,%Q);", zKey, zValue);
+        shell_check_oom(zSql);
+        rx = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+        sqlite3_free(zSql);
+        if( rx!=SQLITE_OK ){
+          oputf("Error: %s\n", sqlite3_errmsg(p->db));
+          sqlite3_finalize(pStmt);
+          pStmt = 0;
+          rc = 1;
+        }
+      }
+      sqlite3_step(pStmt);
+      sqlite3_finalize(pStmt);
+    }else
+
+    /* .parameter unset NAME
+    ** Remove the NAME binding from the parameter binding table, if it
+    ** exists.
+    */
+    if( nArg==3 && cli_strcmp(azArg[1],"unset")==0 ){
+      char *zSql = sqlite3_mprintf(
+          "DELETE FROM temp.sqlite_parameters WHERE key=%Q", azArg[2]);
+      shell_check_oom(zSql);
+      sqlite3_exec(p->db, zSql, 0, 0, 0);
+      sqlite3_free(zSql);
+    }else
+    /* If no command name matches, show a syntax error */
+    parameter_syntax_error:
+    showHelp(p->out, "parameter");
+  }else
+
+  if( c=='p' && n>=3 && cli_strncmp(azArg[0], "print", n)==0 ){
+    int i;
+    for(i=1; i<nArg; i++){
+      if( i>1 ) oputz(" ");
+      oputz(azArg[i]);
+    }
+    oputz("\n");
+  }else
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  if( c=='p' && n>=3 && cli_strncmp(azArg[0], "progress", n)==0 ){
+    int i;
+    int nn = 0;
+    p->flgProgress = 0;
+    p->mxProgress = 0;
+    p->nProgress = 0;
+    for(i=1; i<nArg; i++){
+      const char *z = azArg[i];
+      if( z[0]=='-' ){
+        z++;
+        if( z[0]=='-' ) z++;
+        if( cli_strcmp(z,"quiet")==0 || cli_strcmp(z,"q")==0 ){
+          p->flgProgress |= SHELL_PROGRESS_QUIET;
+          continue;
+        }
+        if( cli_strcmp(z,"reset")==0 ){
+          p->flgProgress |= SHELL_PROGRESS_RESET;
+          continue;
+        }
+        if( cli_strcmp(z,"once")==0 ){
+          p->flgProgress |= SHELL_PROGRESS_ONCE;
+          continue;
+        }
+        if( cli_strcmp(z,"limit")==0 ){
+          if( i+1>=nArg ){
+            eputz("Error: missing argument on --limit\n");
+            rc = 1;
+            goto meta_command_exit;
+          }else{
+            p->mxProgress = (int)integerValue(azArg[++i]);
+          }
+          continue;
+        }
+        eputf("Error: unknown option: \"%s\"\n", azArg[i]);
+        rc = 1;
+        goto meta_command_exit;
+      }else{
+        nn = (int)integerValue(z);
+      }
+    }
+    open_db(p, 0);
+    sqlite3_progress_handler(p->db, nn, progress_handler, p);
+  }else
+#endif /* SQLITE_OMIT_PROGRESS_CALLBACK */
+
+  if( c=='p' && cli_strncmp(azArg[0], "prompt", n)==0 ){
+    if( nArg >= 2) {
+      shell_strncpy(mainPrompt,azArg[1],(int)ArraySize(mainPrompt)-1);
+    }
+    if( nArg >= 3) {
+      shell_strncpy(continuePrompt,azArg[2],(int)ArraySize(continuePrompt)-1);
+    }
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='q' && cli_strncmp(azArg[0], "quit", n)==0 ){
+    rc = 2;
+  }else
+#endif
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='r' && n>=3 && cli_strncmp(azArg[0], "read", n)==0 ){
+    FILE *inSaved = p->in;
+    int savedLineno = p->lineno;
+    failIfSafeMode(p, "cannot run .read in safe mode");
+    if( nArg!=2 ){
+      eputz("Usage: .read FILE\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    if( azArg[1][0]=='|' ){
+#ifdef SQLITE_OMIT_POPEN
+      eputz("Error: pipes are not supported in this OS\n");
+      rc = 1;
+      p->out = stdout;
+#else
+      p->in = popen(azArg[1]+1, "r");
+      if( p->in==0 ){
+        eputf("Error: cannot open \"%s\"\n", azArg[1]);
+        rc = 1;
+      }else{
+        rc = process_input(p);
+        pclose(p->in);
+      }
+#endif
+    }else if( (p->in = openChrSource(azArg[1]))==0 ){
+      eputf("Error: cannot open \"%s\"\n", azArg[1]);
+      rc = 1;
+    }else{
+      rc = process_input(p);
+      fclose(p->in);
+    }
+    p->in = inSaved;
+    p->lineno = savedLineno;
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+#ifndef SQLITE_SHELL_FIDDLE
+  if( c=='r' && n>=3 && cli_strncmp(azArg[0], "restore", n)==0 ){
+    const char *zSrcFile;
+    const char *zDb;
+    sqlite3 *pSrc;
+    sqlite3_backup *pBackup;
+    int nTimeout = 0;
+
+    failIfSafeMode(p, "cannot run .restore in safe mode");
+    if( nArg==2 ){
+      zSrcFile = azArg[1];
+      zDb = "main";
+    }else if( nArg==3 ){
+      zSrcFile = azArg[2];
+      zDb = azArg[1];
+    }else{
+      eputz("Usage: .restore ?DB? FILE\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    rc = sqlite3_open(zSrcFile, &pSrc);
+    if( rc!=SQLITE_OK ){
+      eputf("Error: cannot open \"%s\"\n", zSrcFile);
+      close_db(pSrc);
+      return 1;
+    }
+    open_db(p, 0);
+    pBackup = sqlite3_backup_init(p->db, zDb, pSrc, "main");
+    if( pBackup==0 ){
+      eputf("Error: %s\n", sqlite3_errmsg(p->db));
+      close_db(pSrc);
+      return 1;
+    }
+    while( (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK
+          || rc==SQLITE_BUSY  ){
+      if( rc==SQLITE_BUSY ){
+        if( nTimeout++ >= 3 ) break;
+        sqlite3_sleep(100);
+      }
+    }
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = 0;
+    }else if( rc==SQLITE_BUSY || rc==SQLITE_LOCKED ){
+      eputz("Error: source database is busy\n");
+      rc = 1;
+    }else{
+      eputf("Error: %s\n", sqlite3_errmsg(p->db));
+      rc = 1;
+    }
+    close_db(pSrc);
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+  if( c=='s' && cli_strncmp(azArg[0], "scanstats", n)==0 ){
+    if( nArg==2 ){
+      if( cli_strcmp(azArg[1], "vm")==0 ){
+        p->scanstatsOn = 3;
+      }else
+      if( cli_strcmp(azArg[1], "est")==0 ){
+        p->scanstatsOn = 2;
+      }else{
+        p->scanstatsOn = (u8)booleanValue(azArg[1]);
+      }
+      open_db(p, 0);
+      sqlite3_db_config(
+          p->db, SQLITE_DBCONFIG_STMT_SCANSTATUS, p->scanstatsOn, (int*)0
+      );
+#if !defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+      eputz("Warning: .scanstats not available in this build.\n");
+#elif !defined(SQLITE_ENABLE_BYTECODE_VTAB)
+      if( p->scanstatsOn==3 ){
+        eputz("Warning: \".scanstats vm\" not available in this build.\n");
+      }
+#endif
+    }else{
+      eputz("Usage: .scanstats on|off|est\n");
+      rc = 1;
+    }
+  }else
+
+  if( c=='s' && cli_strncmp(azArg[0], "schema", n)==0 ){
+    ShellText sSelect;
+    ShellState data;
+    char *zErrMsg = 0;
+    const char *zDiv = "(";
+    const char *zName = 0;
+    int iSchema = 0;
+    int bDebug = 0;
+    int bNoSystemTabs = 0;
+    int ii;
+
+    open_db(p, 0);
+    memcpy(&data, p, sizeof(data));
+    data.showHeader = 0;
+    data.cMode = data.mode = MODE_Semi;
+    initText(&sSelect);
+    for(ii=1; ii<nArg; ii++){
+      if( optionMatch(azArg[ii],"indent") ){
+        data.cMode = data.mode = MODE_Pretty;
+      }else if( optionMatch(azArg[ii],"debug") ){
+        bDebug = 1;
+      }else if( optionMatch(azArg[ii],"nosys") ){
+        bNoSystemTabs = 1;
+      }else if( azArg[ii][0]=='-' ){
+        eputf("Unknown option: \"%s\"\n", azArg[ii]);
+        rc = 1;
+        goto meta_command_exit;
+      }else if( zName==0 ){
+        zName = azArg[ii];
+      }else{
+        eputz("Usage: .schema ?--indent? ?--nosys? ?LIKE-PATTERN?\n");
+        rc = 1;
+        goto meta_command_exit;
+      }
+    }
+    if( zName!=0 ){
+      int isSchema = sqlite3_strlike(zName, "sqlite_master", '\\')==0
+                  || sqlite3_strlike(zName, "sqlite_schema", '\\')==0
+                  || sqlite3_strlike(zName,"sqlite_temp_master", '\\')==0
+                  || sqlite3_strlike(zName,"sqlite_temp_schema", '\\')==0;
+      if( isSchema ){
+        char *new_argv[2], *new_colv[2];
+        new_argv[0] = sqlite3_mprintf(
+                      "CREATE TABLE %s (\n"
+                      "  type text,\n"
+                      "  name text,\n"
+                      "  tbl_name text,\n"
+                      "  rootpage integer,\n"
+                      "  sql text\n"
+                      ")", zName);
+        shell_check_oom(new_argv[0]);
+        new_argv[1] = 0;
+        new_colv[0] = "sql";
+        new_colv[1] = 0;
+        callback(&data, 1, new_argv, new_colv);
+        sqlite3_free(new_argv[0]);
+      }
+    }
+    if( zDiv ){
+      sqlite3_stmt *pStmt = 0;
+      rc = sqlite3_prepare_v2(p->db, "SELECT name FROM pragma_database_list",
+                              -1, &pStmt, 0);
+      if( rc ){
+        eputf("Error: %s\n", sqlite3_errmsg(p->db));
+        sqlite3_finalize(pStmt);
+        rc = 1;
+        goto meta_command_exit;
+      }
+      appendText(&sSelect, "SELECT sql FROM", 0);
+      iSchema = 0;
+      while( sqlite3_step(pStmt)==SQLITE_ROW ){
+        const char *zDb = (const char*)sqlite3_column_text(pStmt, 0);
+        char zScNum[30];
+        sqlite3_snprintf(sizeof(zScNum), zScNum, "%d", ++iSchema);
+        appendText(&sSelect, zDiv, 0);
+        zDiv = " UNION ALL ";
+        appendText(&sSelect, "SELECT shell_add_schema(sql,", 0);
+        if( sqlite3_stricmp(zDb, "main")!=0 ){
+          appendText(&sSelect, zDb, '\'');
+        }else{
+          appendText(&sSelect, "NULL", 0);
+        }
+        appendText(&sSelect, ",name) AS sql, type, tbl_name, name, rowid,", 0);
+        appendText(&sSelect, zScNum, 0);
+        appendText(&sSelect, " AS snum, ", 0);
+        appendText(&sSelect, zDb, '\'');
+        appendText(&sSelect, " AS sname FROM ", 0);
+        appendText(&sSelect, zDb, quoteChar(zDb));
+        appendText(&sSelect, ".sqlite_schema", 0);
+      }
+      sqlite3_finalize(pStmt);
+#ifndef SQLITE_OMIT_INTROSPECTION_PRAGMAS
+      if( zName ){
+        appendText(&sSelect,
+           " UNION ALL SELECT shell_module_schema(name),"
+           " 'table', name, name, name, 9e+99, 'main' FROM pragma_module_list",
+        0);
+      }
+#endif
+      appendText(&sSelect, ") WHERE ", 0);
+      if( zName ){
+        char *zQarg = sqlite3_mprintf("%Q", zName);
+        int bGlob;
+        shell_check_oom(zQarg);
+        bGlob = strchr(zName, '*') != 0 || strchr(zName, '?') != 0 ||
+                strchr(zName, '[') != 0;
+        if( strchr(zName, '.') ){
+          appendText(&sSelect, "lower(printf('%s.%s',sname,tbl_name))", 0);
+        }else{
+          appendText(&sSelect, "lower(tbl_name)", 0);
+        }
+        appendText(&sSelect, bGlob ? " GLOB " : " LIKE ", 0);
+        appendText(&sSelect, zQarg, 0);
+        if( !bGlob ){
+          appendText(&sSelect, " ESCAPE '\\' ", 0);
+        }
+        appendText(&sSelect, " AND ", 0);
+        sqlite3_free(zQarg);
+      }
+      if( bNoSystemTabs ){
+        appendText(&sSelect, "name NOT LIKE 'sqlite_%%' AND ", 0);
+      }
+      appendText(&sSelect, "sql IS NOT NULL"
+                           " ORDER BY snum, rowid", 0);
+      if( bDebug ){
+        oputf("SQL: %s;\n", sSelect.z);
+      }else{
+        rc = sqlite3_exec(p->db, sSelect.z, callback, &data, &zErrMsg);
+      }
+      freeText(&sSelect);
+    }
+    if( zErrMsg ){
+      eputf("Error: %s\n", zErrMsg);
+      sqlite3_free(zErrMsg);
+      rc = 1;
+    }else if( rc != SQLITE_OK ){
+      eputz("Error: querying schema information\n");
+      rc = 1;
+    }else{
+      rc = 0;
+    }
+  }else
+
+  if( (c=='s' && n==11 && cli_strncmp(azArg[0], "selecttrace", n)==0)
+   || (c=='t' && n==9  && cli_strncmp(azArg[0], "treetrace", n)==0)
+  ){
+    unsigned int x = nArg>=2? (unsigned int)integerValue(azArg[1]) : 0xffffffff;
+    sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 1, &x);
+  }else
+
+#if defined(SQLITE_ENABLE_SESSION)
+  if( c=='s' && cli_strncmp(azArg[0],"session",n)==0 && n>=3 ){
+    struct AuxDb *pAuxDb = p->pAuxDb;
+    OpenSession *pSession = &pAuxDb->aSession[0];
+    char **azCmd = &azArg[1];
+    int iSes = 0;
+    int nCmd = nArg - 1;
+    int i;
+    if( nArg<=1 ) goto session_syntax_error;
+    open_db(p, 0);
+    if( nArg>=3 ){
+      for(iSes=0; iSes<pAuxDb->nSession; iSes++){
+        if( cli_strcmp(pAuxDb->aSession[iSes].zName, azArg[1])==0 ) break;
+      }
+      if( iSes<pAuxDb->nSession ){
+        pSession = &pAuxDb->aSession[iSes];
+        azCmd++;
+        nCmd--;
+      }else{
+        pSession = &pAuxDb->aSession[0];
+        iSes = 0;
+      }
+    }
+
+    /* .session attach TABLE
+    ** Invoke the sqlite3session_attach() interface to attach a particular
+    ** table so that it is never filtered.
+    */
+    if( cli_strcmp(azCmd[0],"attach")==0 ){
+      if( nCmd!=2 ) goto session_syntax_error;
+      if( pSession->p==0 ){
+        session_not_open:
+        eputz("ERROR: No sessions are open\n");
+      }else{
+        rc = sqlite3session_attach(pSession->p, azCmd[1]);
+        if( rc ){
+          eputf("ERROR: sqlite3session_attach() returns %d\n",rc);
+          rc = 0;
+        }
+      }
+    }else
+
+    /* .session changeset FILE
+    ** .session patchset FILE
+    ** Write a changeset or patchset into a file.  The file is overwritten.
+    */
+    if( cli_strcmp(azCmd[0],"changeset")==0
+     || cli_strcmp(azCmd[0],"patchset")==0
+    ){
+      FILE *out = 0;
+      failIfSafeMode(p, "cannot run \".session %s\" in safe mode", azCmd[0]);
+      if( nCmd!=2 ) goto session_syntax_error;
+      if( pSession->p==0 ) goto session_not_open;
+      out = fopen(azCmd[1], "wb");
+      if( out==0 ){
+        eputf("ERROR: cannot open \"%s\" for writing\n",
+              azCmd[1]);
+      }else{
+        int szChng;
+        void *pChng;
+        if( azCmd[0][0]=='c' ){
+          rc = sqlite3session_changeset(pSession->p, &szChng, &pChng);
+        }else{
+          rc = sqlite3session_patchset(pSession->p, &szChng, &pChng);
+        }
+        if( rc ){
+          sputf(stdout, "Error: error code %d\n", rc);
+          rc = 0;
+        }
+        if( pChng
+          && fwrite(pChng, szChng, 1, out)!=1 ){
+          eputf("ERROR: Failed to write entire %d-byte output\n", szChng);
+        }
+        sqlite3_free(pChng);
+        fclose(out);
+      }
+    }else
+
+    /* .session close
+    ** Close the identified session
+    */
+    if( cli_strcmp(azCmd[0], "close")==0 ){
+      if( nCmd!=1 ) goto session_syntax_error;
+      if( pAuxDb->nSession ){
+        session_close(pSession);
+        pAuxDb->aSession[iSes] = pAuxDb->aSession[--pAuxDb->nSession];
+      }
+    }else
+
+    /* .session enable ?BOOLEAN?
+    ** Query or set the enable flag
+    */
+    if( cli_strcmp(azCmd[0], "enable")==0 ){
+      int ii;
+      if( nCmd>2 ) goto session_syntax_error;
+      ii = nCmd==1 ? -1 : booleanValue(azCmd[1]);
+      if( pAuxDb->nSession ){
+        ii = sqlite3session_enable(pSession->p, ii);
+        oputf("session %s enable flag = %d\n", pSession->zName, ii);
+      }
+    }else
+
+    /* .session filter GLOB ....
+    ** Set a list of GLOB patterns of table names to be excluded.
+    */
+    if( cli_strcmp(azCmd[0], "filter")==0 ){
+      int ii, nByte;
+      if( nCmd<2 ) goto session_syntax_error;
+      if( pAuxDb->nSession ){
+        for(ii=0; ii<pSession->nFilter; ii++){
+          sqlite3_free(pSession->azFilter[ii]);
+        }
+        sqlite3_free(pSession->azFilter);
+        nByte = sizeof(pSession->azFilter[0])*(nCmd-1);
+        pSession->azFilter = sqlite3_malloc( nByte );
+        shell_check_oom( pSession->azFilter );
+        for(ii=1; ii<nCmd; ii++){
+          char *x = pSession->azFilter[ii-1] = sqlite3_mprintf("%s", azCmd[ii]);
+          shell_check_oom(x);
+        }
+        pSession->nFilter = ii-1;
+      }
+    }else
+
+    /* .session indirect ?BOOLEAN?
+    ** Query or set the indirect flag
+    */
+    if( cli_strcmp(azCmd[0], "indirect")==0 ){
+      int ii;
+      if( nCmd>2 ) goto session_syntax_error;
+      ii = nCmd==1 ? -1 : booleanValue(azCmd[1]);
+      if( pAuxDb->nSession ){
+        ii = sqlite3session_indirect(pSession->p, ii);
+        oputf("session %s indirect flag = %d\n", pSession->zName, ii);
+      }
+    }else
+
+    /* .session isempty
+    ** Determine if the session is empty
+    */
+    if( cli_strcmp(azCmd[0], "isempty")==0 ){
+      int ii;
+      if( nCmd!=1 ) goto session_syntax_error;
+      if( pAuxDb->nSession ){
+        ii = sqlite3session_isempty(pSession->p);
+        oputf("session %s isempty flag = %d\n", pSession->zName, ii);
+      }
+    }else
+
+    /* .session list
+    ** List all currently open sessions
+    */
+    if( cli_strcmp(azCmd[0],"list")==0 ){
+      for(i=0; i<pAuxDb->nSession; i++){
+        oputf("%d %s\n", i, pAuxDb->aSession[i].zName);
+      }
+    }else
+
+    /* .session open DB NAME
+    ** Open a new session called NAME on the attached database DB.
+    ** DB is normally "main".
+    */
+    if( cli_strcmp(azCmd[0],"open")==0 ){
+      char *zName;
+      if( nCmd!=3 ) goto session_syntax_error;
+      zName = azCmd[2];
+      if( zName[0]==0 ) goto session_syntax_error;
+      for(i=0; i<pAuxDb->nSession; i++){
+        if( cli_strcmp(pAuxDb->aSession[i].zName,zName)==0 ){
+          eputf("Session \"%s\" already exists\n", zName);
+          goto meta_command_exit;
+        }
+      }
+      if( pAuxDb->nSession>=ArraySize(pAuxDb->aSession) ){
+        eputf("Maximum of %d sessions\n", ArraySize(pAuxDb->aSession));
+        goto meta_command_exit;
+      }
+      pSession = &pAuxDb->aSession[pAuxDb->nSession];
+      rc = sqlite3session_create(p->db, azCmd[1], &pSession->p);
+      if( rc ){
+        eputf("Cannot open session: error code=%d\n", rc);
+        rc = 0;
+        goto meta_command_exit;
+      }
+      pSession->nFilter = 0;
+      sqlite3session_table_filter(pSession->p, session_filter, pSession);
+      pAuxDb->nSession++;
+      pSession->zName = sqlite3_mprintf("%s", zName);
+      shell_check_oom(pSession->zName);
+    }else
+    /* If no command name matches, show a syntax error */
+    session_syntax_error:
+    showHelp(p->out, "session");
+  }else
+#endif
+
+#ifdef SQLITE_DEBUG
+  /* Undocumented commands for internal testing.  Subject to change
+  ** without notice. */
+  if( c=='s' && n>=10 && cli_strncmp(azArg[0], "selftest-", 9)==0 ){
+    if( cli_strncmp(azArg[0]+9, "boolean", n-9)==0 ){
+      int i, v;
+      for(i=1; i<nArg; i++){
+        v = booleanValue(azArg[i]);
+        oputf("%s: %d 0x%x\n", azArg[i], v, v);
+      }
+    }
+    if( cli_strncmp(azArg[0]+9, "integer", n-9)==0 ){
+      int i; sqlite3_int64 v;
+      for(i=1; i<nArg; i++){
+        char zBuf[200];
+        v = integerValue(azArg[i]);
+        sqlite3_snprintf(sizeof(zBuf),zBuf,"%s: %lld 0x%llx\n", azArg[i],v,v);
+        oputz(zBuf);
+      }
+    }
+  }else
+#endif
+
+  if( c=='s' && n>=4 && cli_strncmp(azArg[0],"selftest",n)==0 ){
+    int bIsInit = 0;         /* True to initialize the SELFTEST table */
+    int bVerbose = 0;        /* Verbose output */
+    int bSelftestExists;     /* True if SELFTEST already exists */
+    int i, k;                /* Loop counters */
+    int nTest = 0;           /* Number of tests runs */
+    int nErr = 0;            /* Number of errors seen */
+    ShellText str;           /* Answer for a query */
+    sqlite3_stmt *pStmt = 0; /* Query against the SELFTEST table */
+
+    open_db(p,0);
+    for(i=1; i<nArg; i++){
+      const char *z = azArg[i];
+      if( z[0]=='-' && z[1]=='-' ) z++;
+      if( cli_strcmp(z,"-init")==0 ){
+        bIsInit = 1;
+      }else
+      if( cli_strcmp(z,"-v")==0 ){
+        bVerbose++;
+      }else
+      {
+        eputf("Unknown option \"%s\" on \"%s\"\n", azArg[i], azArg[0]);
+        eputz("Should be one of: --init -v\n");
+        rc = 1;
+        goto meta_command_exit;
+      }
+    }
+    if( sqlite3_table_column_metadata(p->db,"main","selftest",0,0,0,0,0,0)
+           != SQLITE_OK ){
+      bSelftestExists = 0;
+    }else{
+      bSelftestExists = 1;
+    }
+    if( bIsInit ){
+      createSelftestTable(p);
+      bSelftestExists = 1;
+    }
+    initText(&str);
+    appendText(&str, "x", 0);
+    for(k=bSelftestExists; k>=0; k--){
+      if( k==1 ){
+        rc = sqlite3_prepare_v2(p->db,
+            "SELECT tno,op,cmd,ans FROM selftest ORDER BY tno",
+            -1, &pStmt, 0);
+      }else{
+        rc = sqlite3_prepare_v2(p->db,
+          "VALUES(0,'memo','Missing SELFTEST table - default checks only',''),"
+          "      (1,'run','PRAGMA integrity_check','ok')",
+          -1, &pStmt, 0);
+      }
+      if( rc ){
+        eputz("Error querying the selftest table\n");
+        rc = 1;
+        sqlite3_finalize(pStmt);
+        goto meta_command_exit;
+      }
+      for(i=1; sqlite3_step(pStmt)==SQLITE_ROW; i++){
+        int tno = sqlite3_column_int(pStmt, 0);
+        const char *zOp = (const char*)sqlite3_column_text(pStmt, 1);
+        const char *zSql = (const char*)sqlite3_column_text(pStmt, 2);
+        const char *zAns = (const char*)sqlite3_column_text(pStmt, 3);
+
+        if( zOp==0 ) continue;
+        if( zSql==0 ) continue;
+        if( zAns==0 ) continue;
+        k = 0;
+        if( bVerbose>0 ){
+          sputf(stdout, "%d: %s %s\n", tno, zOp, zSql);
+        }
+        if( cli_strcmp(zOp,"memo")==0 ){
+          oputf("%s\n", zSql);
+        }else
+        if( cli_strcmp(zOp,"run")==0 ){
+          char *zErrMsg = 0;
+          str.n = 0;
+          str.z[0] = 0;
+          rc = sqlite3_exec(p->db, zSql, captureOutputCallback, &str, &zErrMsg);
+          nTest++;
+          if( bVerbose ){
+            oputf("Result: %s\n", str.z);
+          }
+          if( rc || zErrMsg ){
+            nErr++;
+            rc = 1;
+            oputf("%d: error-code-%d: %s\n", tno, rc, zErrMsg);
+            sqlite3_free(zErrMsg);
+          }else if( cli_strcmp(zAns,str.z)!=0 ){
+            nErr++;
+            rc = 1;
+            oputf("%d: Expected: [%s]\n", tno, zAns);
+            oputf("%d:      Got: [%s]\n", tno, str.z);
+          }
+        }
+        else{
+          eputf("Unknown operation \"%s\" on selftest line %d\n", zOp, tno);
+          rc = 1;
+          break;
+        }
+      } /* End loop over rows of content from SELFTEST */
+      sqlite3_finalize(pStmt);
+    } /* End loop over k */
+    freeText(&str);
+    oputf("%d errors out of %d tests\n", nErr, nTest);
+  }else
+
+  if( c=='s' && cli_strncmp(azArg[0], "separator", n)==0 ){
+    if( nArg<2 || nArg>3 ){
+      eputz("Usage: .separator COL ?ROW?\n");
+      rc = 1;
+    }
+    if( nArg>=2 ){
+      sqlite3_snprintf(sizeof(p->colSeparator), p->colSeparator,
+                       "%.*s", (int)ArraySize(p->colSeparator)-1, azArg[1]);
+    }
+    if( nArg>=3 ){
+      sqlite3_snprintf(sizeof(p->rowSeparator), p->rowSeparator,
+                       "%.*s", (int)ArraySize(p->rowSeparator)-1, azArg[2]);
+    }
+  }else
+
+  if( c=='s' && n>=4 && cli_strncmp(azArg[0],"sha3sum",n)==0 ){
+    const char *zLike = 0;   /* Which table to checksum. 0 means everything */
+    int i;                   /* Loop counter */
+    int bSchema = 0;         /* Also hash the schema */
+    int bSeparate = 0;       /* Hash each table separately */
+    int iSize = 224;         /* Hash algorithm to use */
+    int bDebug = 0;          /* Only show the query that would have run */
+    sqlite3_stmt *pStmt;     /* For querying tables names */
+    char *zSql;              /* SQL to be run */
+    char *zSep;              /* Separator */
+    ShellText sSql;          /* Complete SQL for the query to run the hash */
+    ShellText sQuery;        /* Set of queries used to read all content */
+    open_db(p, 0);
+    for(i=1; i<nArg; i++){
+      const char *z = azArg[i];
+      if( z[0]=='-' ){
+        z++;
+        if( z[0]=='-' ) z++;
+        if( cli_strcmp(z,"schema")==0 ){
+          bSchema = 1;
+        }else
+        if( cli_strcmp(z,"sha3-224")==0 || cli_strcmp(z,"sha3-256")==0
+         || cli_strcmp(z,"sha3-384")==0 || cli_strcmp(z,"sha3-512")==0
+        ){
+          iSize = atoi(&z[5]);
+        }else
+        if( cli_strcmp(z,"debug")==0 ){
+          bDebug = 1;
+        }else
+        {
+          eputf("Unknown option \"%s\" on \"%s\"\n", azArg[i], azArg[0]);
+          showHelp(p->out, azArg[0]);
+          rc = 1;
+          goto meta_command_exit;
+        }
+      }else if( zLike ){
+        eputz("Usage: .sha3sum ?OPTIONS? ?LIKE-PATTERN?\n");
+        rc = 1;
+        goto meta_command_exit;
+      }else{
+        zLike = z;
+        bSeparate = 1;
+        if( sqlite3_strlike("sqlite\\_%", zLike, '\\')==0 ) bSchema = 1;
+      }
+    }
+    if( bSchema ){
+      zSql = "SELECT lower(name) as tname FROM sqlite_schema"
+             " WHERE type='table' AND coalesce(rootpage,0)>1"
+             " UNION ALL SELECT 'sqlite_schema'"
+             " ORDER BY 1 collate nocase";
+    }else{
+      zSql = "SELECT lower(name) as tname FROM sqlite_schema"
+             " WHERE type='table' AND coalesce(rootpage,0)>1"
+             " AND name NOT LIKE 'sqlite_%'"
+             " ORDER BY 1 collate nocase";
+    }
+    sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    initText(&sQuery);
+    initText(&sSql);
+    appendText(&sSql, "WITH [sha3sum$query](a,b) AS(",0);
+    zSep = "VALUES(";
+    while( SQLITE_ROW==sqlite3_step(pStmt) ){
+      const char *zTab = (const char*)sqlite3_column_text(pStmt,0);
+      if( zTab==0 ) continue;
+      if( zLike && sqlite3_strlike(zLike, zTab, 0)!=0 ) continue;
+      if( cli_strncmp(zTab, "sqlite_",7)!=0 ){
+        appendText(&sQuery,"SELECT * FROM ", 0);
+        appendText(&sQuery,zTab,'"');
+        appendText(&sQuery," NOT INDEXED;", 0);
+      }else if( cli_strcmp(zTab, "sqlite_schema")==0 ){
+        appendText(&sQuery,"SELECT type,name,tbl_name,sql FROM sqlite_schema"
+                           " ORDER BY name;", 0);
+      }else if( cli_strcmp(zTab, "sqlite_sequence")==0 ){
+        appendText(&sQuery,"SELECT name,seq FROM sqlite_sequence"
+                           " ORDER BY name;", 0);
+      }else if( cli_strcmp(zTab, "sqlite_stat1")==0 ){
+        appendText(&sQuery,"SELECT tbl,idx,stat FROM sqlite_stat1"
+                           " ORDER BY tbl,idx;", 0);
+      }else if( cli_strcmp(zTab, "sqlite_stat4")==0 ){
+        appendText(&sQuery, "SELECT * FROM ", 0);
+        appendText(&sQuery, zTab, 0);
+        appendText(&sQuery, " ORDER BY tbl, idx, rowid;\n", 0);
+      }
+      appendText(&sSql, zSep, 0);
+      appendText(&sSql, sQuery.z, '\'');
+      sQuery.n = 0;
+      appendText(&sSql, ",", 0);
+      appendText(&sSql, zTab, '\'');
+      zSep = "),(";
+    }
+    sqlite3_finalize(pStmt);
+    if( bSeparate ){
+      zSql = sqlite3_mprintf(
+          "%s))"
+          " SELECT lower(hex(sha3_query(a,%d))) AS hash, b AS label"
+          "   FROM [sha3sum$query]",
+          sSql.z, iSize);
+    }else{
+      zSql = sqlite3_mprintf(
+          "%s))"
+          " SELECT lower(hex(sha3_query(group_concat(a,''),%d))) AS hash"
+          "   FROM [sha3sum$query]",
+          sSql.z, iSize);
+    }
+    shell_check_oom(zSql);
+    freeText(&sQuery);
+    freeText(&sSql);
+    if( bDebug ){
+      oputf("%s\n", zSql);
+    }else{
+      shell_exec(p, zSql, 0);
+    }
+#if !defined(SQLITE_OMIT_SCHEMA_PRAGMAS) && !defined(SQLITE_OMIT_VIRTUALTABLE)
+    {
+      int lrc;
+      char *zRevText = /* Query for reversible to-blob-to-text check */
+        "SELECT lower(name) as tname FROM sqlite_schema\n"
+        "WHERE type='table' AND coalesce(rootpage,0)>1\n"
+        "AND name NOT LIKE 'sqlite_%%'%s\n"
+        "ORDER BY 1 collate nocase";
+      zRevText = sqlite3_mprintf(zRevText, zLike? " AND name LIKE $tspec" : "");
+      zRevText = sqlite3_mprintf(
+          /* lower-case query is first run, producing upper-case query. */
+          "with tabcols as materialized(\n"
+          "select tname, cname\n"
+          "from ("
+          " select printf('\"%%w\"',ss.tname) as tname,"
+          " printf('\"%%w\"',ti.name) as cname\n"
+          " from (%z) ss\n inner join pragma_table_info(tname) ti))\n"
+          "select 'SELECT total(bad_text_count) AS bad_text_count\n"
+          "FROM ('||group_concat(query, ' UNION ALL ')||')' as btc_query\n"
+          " from (select 'SELECT COUNT(*) AS bad_text_count\n"
+          "FROM '||tname||' WHERE '\n"
+          "||group_concat('CAST(CAST('||cname||' AS BLOB) AS TEXT)<>'||cname\n"
+          "|| ' AND typeof('||cname||')=''text'' ',\n"
+          "' OR ') as query, tname from tabcols group by tname)"
+          , zRevText);
+      shell_check_oom(zRevText);
+      if( bDebug ) oputf("%s\n", zRevText);
+      lrc = sqlite3_prepare_v2(p->db, zRevText, -1, &pStmt, 0);
+      if( lrc!=SQLITE_OK ){
+        /* assert(lrc==SQLITE_NOMEM); // might also be SQLITE_ERROR if the
+        ** user does cruel and unnatural things like ".limit expr_depth 0". */
+        rc = 1;
+      }else{
+        if( zLike ) sqlite3_bind_text(pStmt,1,zLike,-1,SQLITE_STATIC);
+        lrc = SQLITE_ROW==sqlite3_step(pStmt);
+        if( lrc ){
+          const char *zGenQuery = (char*)sqlite3_column_text(pStmt,0);
+          sqlite3_stmt *pCheckStmt;
+          lrc = sqlite3_prepare_v2(p->db, zGenQuery, -1, &pCheckStmt, 0);
+          if( bDebug ) oputf("%s\n", zGenQuery);
+          if( lrc!=SQLITE_OK ){
+            rc = 1;
+          }else{
+            if( SQLITE_ROW==sqlite3_step(pCheckStmt) ){
+              double countIrreversible = sqlite3_column_double(pCheckStmt, 0);
+              if( countIrreversible>0 ){
+                int sz = (int)(countIrreversible + 0.5);
+                eputf("Digest includes %d invalidly encoded text field%s.\n",
+                      sz, (sz>1)? "s": "");
+              }
+            }
+            sqlite3_finalize(pCheckStmt);
+          }
+          sqlite3_finalize(pStmt);
+        }
+      }
+      if( rc ) eputz(".sha3sum failed.\n");
+      sqlite3_free(zRevText);
+    }
+#endif /* !defined(*_OMIT_SCHEMA_PRAGMAS) && !defined(*_OMIT_VIRTUALTABLE) */
+    sqlite3_free(zSql);
+  }else
+
+#if !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE)
+  if( c=='s'
+   && (cli_strncmp(azArg[0], "shell", n)==0
+       || cli_strncmp(azArg[0],"system",n)==0)
+  ){
+    char *zCmd;
+    int i, x;
+    failIfSafeMode(p, "cannot run .%s in safe mode", azArg[0]);
+    if( nArg<2 ){
+      eputz("Usage: .system COMMAND\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    zCmd = sqlite3_mprintf(strchr(azArg[1],' ')==0?"%s":"\"%s\"", azArg[1]);
+    for(i=2; i<nArg && zCmd!=0; i++){
+      zCmd = sqlite3_mprintf(strchr(azArg[i],' ')==0?"%z %s":"%z \"%s\"",
+                             zCmd, azArg[i]);
+    }
+    consoleRestore();
+    x = zCmd!=0 ? system(zCmd) : 1;
+    consoleRenewSetup();
+    sqlite3_free(zCmd);
+    if( x ) eputf("System command returns %d\n", x);
+  }else
+#endif /* !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE) */
+
+  if( c=='s' && cli_strncmp(azArg[0], "show", n)==0 ){
+    static const char *azBool[] = { "off", "on", "trigger", "full"};
+    const char *zOut;
+    int i;
+    if( nArg!=1 ){
+      eputz("Usage: .show\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    oputf("%12.12s: %s\n","echo",
+          azBool[ShellHasFlag(p, SHFLG_Echo)]);
+    oputf("%12.12s: %s\n","eqp", azBool[p->autoEQP&3]);
+    oputf("%12.12s: %s\n","explain",
+          p->mode==MODE_Explain ? "on" : p->autoExplain ? "auto" : "off");
+    oputf("%12.12s: %s\n","headers", azBool[p->showHeader!=0]);
+    if( p->mode==MODE_Column
+     || (p->mode>=MODE_Markdown && p->mode<=MODE_Box)
+    ){
+      oputf("%12.12s: %s --wrap %d --wordwrap %s --%squote\n", "mode",
+            modeDescr[p->mode], p->cmOpts.iWrap,
+            p->cmOpts.bWordWrap ? "on" : "off",
+            p->cmOpts.bQuote ? "" : "no");
+    }else{
+      oputf("%12.12s: %s\n","mode", modeDescr[p->mode]);
+    }
+    oputf("%12.12s: ", "nullvalue");
+    output_c_string(p->nullValue);
+    oputz("\n");
+    oputf("%12.12s: %s\n","output",
+          strlen30(p->outfile) ? p->outfile : "stdout");
+    oputf("%12.12s: ", "colseparator");
+     output_c_string(p->colSeparator);
+     oputz("\n");
+    oputf("%12.12s: ", "rowseparator");
+     output_c_string(p->rowSeparator);
+     oputz("\n");
+    switch( p->statsOn ){
+      case 0:  zOut = "off";     break;
+      default: zOut = "on";      break;
+      case 2:  zOut = "stmt";    break;
+      case 3:  zOut = "vmstep";  break;
+    }
+    oputf("%12.12s: %s\n","stats", zOut);
+    oputf("%12.12s: ", "width");
+    for (i=0;i<p->nWidth;i++) {
+      oputf("%d ", p->colWidth[i]);
+    }
+    oputz("\n");
+    oputf("%12.12s: %s\n", "filename",
+          p->pAuxDb->zDbFilename ? p->pAuxDb->zDbFilename : "");
+  }else
+
+  if( c=='s' && cli_strncmp(azArg[0], "stats", n)==0 ){
+    if( nArg==2 ){
+      if( cli_strcmp(azArg[1],"stmt")==0 ){
+        p->statsOn = 2;
+      }else if( cli_strcmp(azArg[1],"vmstep")==0 ){
+        p->statsOn = 3;
+      }else{
+        p->statsOn = (u8)booleanValue(azArg[1]);
+      }
+    }else if( nArg==1 ){
+      display_stats(p->db, p, 0);
+    }else{
+      eputz("Usage: .stats ?on|off|stmt|vmstep?\n");
+      rc = 1;
+    }
+  }else
+
+  if( (c=='t' && n>1 && cli_strncmp(azArg[0], "tables", n)==0)
+   || (c=='i' && (cli_strncmp(azArg[0], "indices", n)==0
+                 || cli_strncmp(azArg[0], "indexes", n)==0) )
+  ){
+    sqlite3_stmt *pStmt;
+    char **azResult;
+    int nRow, nAlloc;
+    int ii;
+    ShellText s;
+    initText(&s);
+    open_db(p, 0);
+    rc = sqlite3_prepare_v2(p->db, "PRAGMA database_list", -1, &pStmt, 0);
+    if( rc ){
+      sqlite3_finalize(pStmt);
+      return shellDatabaseError(p->db);
+    }
+
+    if( nArg>2 && c=='i' ){
+      /* It is an historical accident that the .indexes command shows an error
+      ** when called with the wrong number of arguments whereas the .tables
+      ** command does not. */
+      eputz("Usage: .indexes ?LIKE-PATTERN?\n");
+      rc = 1;
+      sqlite3_finalize(pStmt);
+      goto meta_command_exit;
+    }
+    for(ii=0; sqlite3_step(pStmt)==SQLITE_ROW; ii++){
+      const char *zDbName = (const char*)sqlite3_column_text(pStmt, 1);
+      if( zDbName==0 ) continue;
+      if( s.z && s.z[0] ) appendText(&s, " UNION ALL ", 0);
+      if( sqlite3_stricmp(zDbName, "main")==0 ){
+        appendText(&s, "SELECT name FROM ", 0);
+      }else{
+        appendText(&s, "SELECT ", 0);
+        appendText(&s, zDbName, '\'');
+        appendText(&s, "||'.'||name FROM ", 0);
+      }
+      appendText(&s, zDbName, '"');
+      appendText(&s, ".sqlite_schema ", 0);
+      if( c=='t' ){
+        appendText(&s," WHERE type IN ('table','view')"
+                      "   AND name NOT LIKE 'sqlite_%'"
+                      "   AND name LIKE ?1", 0);
+      }else{
+        appendText(&s," WHERE type='index'"
+                      "   AND tbl_name LIKE ?1", 0);
+      }
+    }
+    rc = sqlite3_finalize(pStmt);
+    if( rc==SQLITE_OK ){
+      appendText(&s, " ORDER BY 1", 0);
+      rc = sqlite3_prepare_v2(p->db, s.z, -1, &pStmt, 0);
+    }
+    freeText(&s);
+    if( rc ) return shellDatabaseError(p->db);
+
+    /* Run the SQL statement prepared by the above block. Store the results
+    ** as an array of nul-terminated strings in azResult[].  */
+    nRow = nAlloc = 0;
+    azResult = 0;
+    if( nArg>1 ){
+      sqlite3_bind_text(pStmt, 1, azArg[1], -1, SQLITE_TRANSIENT);
+    }else{
+      sqlite3_bind_text(pStmt, 1, "%", -1, SQLITE_STATIC);
+    }
+    while( sqlite3_step(pStmt)==SQLITE_ROW ){
+      if( nRow>=nAlloc ){
+        char **azNew;
+        int n2 = nAlloc*2 + 10;
+        azNew = sqlite3_realloc64(azResult, sizeof(azResult[0])*n2);
+        shell_check_oom(azNew);
+        nAlloc = n2;
+        azResult = azNew;
+      }
+      azResult[nRow] = sqlite3_mprintf("%s", sqlite3_column_text(pStmt, 0));
+      shell_check_oom(azResult[nRow]);
+      nRow++;
+    }
+    if( sqlite3_finalize(pStmt)!=SQLITE_OK ){
+      rc = shellDatabaseError(p->db);
+    }
+
+    /* Pretty-print the contents of array azResult[] to the output */
+    if( rc==0 && nRow>0 ){
+      int len, maxlen = 0;
+      int i, j;
+      int nPrintCol, nPrintRow;
+      for(i=0; i<nRow; i++){
+        len = strlen30(azResult[i]);
+        if( len>maxlen ) maxlen = len;
+      }
+      nPrintCol = 80/(maxlen+2);
+      if( nPrintCol<1 ) nPrintCol = 1;
+      nPrintRow = (nRow + nPrintCol - 1)/nPrintCol;
+      for(i=0; i<nPrintRow; i++){
+        for(j=i; j<nRow; j+=nPrintRow){
+          char *zSp = j<nPrintRow ? "" : "  ";
+          oputf("%s%-*s", zSp, maxlen, azResult[j] ? azResult[j]:"");
+        }
+        oputz("\n");
+      }
+    }
+
+    for(ii=0; ii<nRow; ii++) sqlite3_free(azResult[ii]);
+    sqlite3_free(azResult);
+  }else
+
+#ifndef SQLITE_SHELL_FIDDLE
+  /* Begin redirecting output to the file "testcase-out.txt" */
+  if( c=='t' && cli_strcmp(azArg[0],"testcase")==0 ){
+    output_reset(p);
+    p->out = output_file_open("testcase-out.txt", 0);
+    if( p->out==0 ){
+      eputz("Error: cannot open 'testcase-out.txt'\n");
+    }
+    if( nArg>=2 ){
+      sqlite3_snprintf(sizeof(p->zTestcase), p->zTestcase, "%s", azArg[1]);
+    }else{
+      sqlite3_snprintf(sizeof(p->zTestcase), p->zTestcase, "?");
+    }
+  }else
+#endif /* !defined(SQLITE_SHELL_FIDDLE) */
+
+#ifndef SQLITE_UNTESTABLE
+  if( c=='t' && n>=8 && cli_strncmp(azArg[0], "testctrl", n)==0 ){
+    static const struct {
+       const char *zCtrlName;   /* Name of a test-control option */
+       int ctrlCode;            /* Integer code for that option */
+       int unSafe;              /* Not valid unless --unsafe-testing */
+       const char *zUsage;      /* Usage notes */
+    } aCtrl[] = {
+    {"always",             SQLITE_TESTCTRL_ALWAYS, 1,     "BOOLEAN"         },
+    {"assert",             SQLITE_TESTCTRL_ASSERT, 1,     "BOOLEAN"         },
+  /*{"benign_malloc_hooks",SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS,1, ""        },*/
+  /*{"bitvec_test",        SQLITE_TESTCTRL_BITVEC_TEST, 1,  ""              },*/
+    {"byteorder",          SQLITE_TESTCTRL_BYTEORDER, 0,  ""                },
+    {"extra_schema_checks",SQLITE_TESTCTRL_EXTRA_SCHEMA_CHECKS,0,"BOOLEAN"  },
+  /*{"fault_install",      SQLITE_TESTCTRL_FAULT_INSTALL, 1,""              },*/
+    {"fk_no_action",       SQLITE_TESTCTRL_FK_NO_ACTION, 0, "BOOLEAN"       },
+    {"imposter",         SQLITE_TESTCTRL_IMPOSTER,1,"SCHEMA ON/OFF ROOTPAGE"},
+    {"internal_functions", SQLITE_TESTCTRL_INTERNAL_FUNCTIONS,0,""          },
+    {"json_selfcheck",     SQLITE_TESTCTRL_JSON_SELFCHECK ,0,"BOOLEAN"      },
+    {"localtime_fault",    SQLITE_TESTCTRL_LOCALTIME_FAULT,0,"BOOLEAN"      },
+    {"never_corrupt",      SQLITE_TESTCTRL_NEVER_CORRUPT,1, "BOOLEAN"       },
+    {"optimizations",      SQLITE_TESTCTRL_OPTIMIZATIONS,0,"DISABLE-MASK"   },
+#ifdef YYCOVERAGE
+    {"parser_coverage",    SQLITE_TESTCTRL_PARSER_COVERAGE,0,""             },
+#endif
+    {"pending_byte",       SQLITE_TESTCTRL_PENDING_BYTE,0, "OFFSET  "       },
+    {"prng_restore",       SQLITE_TESTCTRL_PRNG_RESTORE,0, ""               },
+    {"prng_save",          SQLITE_TESTCTRL_PRNG_SAVE,   0, ""               },
+    {"prng_seed",          SQLITE_TESTCTRL_PRNG_SEED,   0, "SEED ?db?"      },
+    {"seek_count",         SQLITE_TESTCTRL_SEEK_COUNT,  0, ""               },
+    {"sorter_mmap",        SQLITE_TESTCTRL_SORTER_MMAP, 0, "NMAX"           },
+    {"tune",               SQLITE_TESTCTRL_TUNE,        1, "ID VALUE"       },
+    {"uselongdouble",  SQLITE_TESTCTRL_USELONGDOUBLE,0,"?BOOLEAN|\"default\"?"},
+    };
+    int testctrl = -1;
+    int iCtrl = -1;
+    int rc2 = 0;    /* 0: usage.  1: %d  2: %x  3: no-output */
+    int isOk = 0;
+    int i, n2;
+    const char *zCmd = 0;
+
+    open_db(p, 0);
+    zCmd = nArg>=2 ? azArg[1] : "help";
+
+    /* The argument can optionally begin with "-" or "--" */
+    if( zCmd[0]=='-' && zCmd[1] ){
+      zCmd++;
+      if( zCmd[0]=='-' && zCmd[1] ) zCmd++;
+    }
+
+    /* --help lists all test-controls */
+    if( cli_strcmp(zCmd,"help")==0 ){
+      oputz("Available test-controls:\n");
+      for(i=0; i<ArraySize(aCtrl); i++){
+        if( aCtrl[i].unSafe && !ShellHasFlag(p,SHFLG_TestingMode) ) continue;
+        oputf("  .testctrl %s %s\n",
+              aCtrl[i].zCtrlName, aCtrl[i].zUsage);
+      }
+      rc = 1;
+      goto meta_command_exit;
+    }
+
+    /* convert testctrl text option to value. allow any unique prefix
+    ** of the option name, or a numerical value. */
+    n2 = strlen30(zCmd);
+    for(i=0; i<ArraySize(aCtrl); i++){
+      if( aCtrl[i].unSafe && !ShellHasFlag(p,SHFLG_TestingMode) ) continue;
+      if( cli_strncmp(zCmd, aCtrl[i].zCtrlName, n2)==0 ){
+        if( testctrl<0 ){
+          testctrl = aCtrl[i].ctrlCode;
+          iCtrl = i;
+        }else{
+          eputf("Error: ambiguous test-control: \"%s\"\n"
+                "Use \".testctrl --help\" for help\n", zCmd);
+          rc = 1;
+          goto meta_command_exit;
+        }
+      }
+    }
+    if( testctrl<0 ){
+      eputf("Error: unknown test-control: %s\n"
+            "Use \".testctrl --help\" for help\n", zCmd);
+    }else{
+      switch(testctrl){
+
+        /* sqlite3_test_control(int, db, int) */
+        case SQLITE_TESTCTRL_OPTIMIZATIONS:
+        case SQLITE_TESTCTRL_FK_NO_ACTION:
+          if( nArg==3 ){
+            unsigned int opt = (unsigned int)strtol(azArg[2], 0, 0);
+            rc2 = sqlite3_test_control(testctrl, p->db, opt);
+            isOk = 3;
+          }
+          break;
+
+        /* sqlite3_test_control(int) */
+        case SQLITE_TESTCTRL_PRNG_SAVE:
+        case SQLITE_TESTCTRL_PRNG_RESTORE:
+        case SQLITE_TESTCTRL_BYTEORDER:
+          if( nArg==2 ){
+            rc2 = sqlite3_test_control(testctrl);
+            isOk = testctrl==SQLITE_TESTCTRL_BYTEORDER ? 1 : 3;
+          }
+          break;
+
+        /* sqlite3_test_control(int, uint) */
+        case SQLITE_TESTCTRL_PENDING_BYTE:
+          if( nArg==3 ){
+            unsigned int opt = (unsigned int)integerValue(azArg[2]);
+            rc2 = sqlite3_test_control(testctrl, opt);
+            isOk = 3;
+          }
+          break;
+
+        /* sqlite3_test_control(int, int, sqlite3*) */
+        case SQLITE_TESTCTRL_PRNG_SEED:
+          if( nArg==3 || nArg==4 ){
+            int ii = (int)integerValue(azArg[2]);
+            sqlite3 *db;
+            if( ii==0 && cli_strcmp(azArg[2],"random")==0 ){
+              sqlite3_randomness(sizeof(ii),&ii);
+              sputf(stdout, "-- random seed: %d\n", ii);
+            }
+            if( nArg==3 ){
+              db = 0;
+            }else{
+              db = p->db;
+              /* Make sure the schema has been loaded */
+              sqlite3_table_column_metadata(db, 0, "x", 0, 0, 0, 0, 0, 0);
+            }
+            rc2 = sqlite3_test_control(testctrl, ii, db);
+            isOk = 3;
+          }
+          break;
+
+        /* sqlite3_test_control(int, int) */
+        case SQLITE_TESTCTRL_ASSERT:
+        case SQLITE_TESTCTRL_ALWAYS:
+          if( nArg==3 ){
+            int opt = booleanValue(azArg[2]);
+            rc2 = sqlite3_test_control(testctrl, opt);
+            isOk = 1;
+          }
+          break;
+
+        /* sqlite3_test_control(int, int) */
+        case SQLITE_TESTCTRL_LOCALTIME_FAULT:
+        case SQLITE_TESTCTRL_NEVER_CORRUPT:
+          if( nArg==3 ){
+            int opt = booleanValue(azArg[2]);
+            rc2 = sqlite3_test_control(testctrl, opt);
+            isOk = 3;
+          }
+          break;
+
+        /* sqlite3_test_control(int, int) */
+        case SQLITE_TESTCTRL_USELONGDOUBLE: {
+          int opt = -1;
+          if( nArg==3 ){
+            if( cli_strcmp(azArg[2],"default")==0 ){
+              opt = 2;
+            }else{
+              opt = booleanValue(azArg[2]);
+            }
+          }
+          rc2 = sqlite3_test_control(testctrl, opt);
+          isOk = 1;
+          break;
+        }
+
+        /* sqlite3_test_control(sqlite3*) */
+        case SQLITE_TESTCTRL_INTERNAL_FUNCTIONS:
+          rc2 = sqlite3_test_control(testctrl, p->db);
+          isOk = 3;
+          break;
+
+        case SQLITE_TESTCTRL_IMPOSTER:
+          if( nArg==5 ){
+            rc2 = sqlite3_test_control(testctrl, p->db,
+                          azArg[2],
+                          integerValue(azArg[3]),
+                          integerValue(azArg[4]));
+            isOk = 3;
+          }
+          break;
+
+        case SQLITE_TESTCTRL_SEEK_COUNT: {
+          u64 x = 0;
+          rc2 = sqlite3_test_control(testctrl, p->db, &x);
+          oputf("%llu\n", x);
+          isOk = 3;
+          break;
+        }
+
+#ifdef YYCOVERAGE
+        case SQLITE_TESTCTRL_PARSER_COVERAGE: {
+          if( nArg==2 ){
+            sqlite3_test_control(testctrl, p->out);
+            isOk = 3;
+          }
+          break;
+        }
+#endif
+#ifdef SQLITE_DEBUG
+        case SQLITE_TESTCTRL_TUNE: {
+          if( nArg==4 ){
+            int id = (int)integerValue(azArg[2]);
+            int val = (int)integerValue(azArg[3]);
+            sqlite3_test_control(testctrl, id, &val);
+            isOk = 3;
+          }else if( nArg==3 ){
+            int id = (int)integerValue(azArg[2]);
+            sqlite3_test_control(testctrl, -id, &rc2);
+            isOk = 1;
+          }else if( nArg==2 ){
+            int id = 1;
+            while(1){
+              int val = 0;
+              rc2 = sqlite3_test_control(testctrl, -id, &val);
+              if( rc2!=SQLITE_OK ) break;
+              if( id>1 ) oputz("  ");
+              oputf("%d: %d", id, val);
+              id++;
+            }
+            if( id>1 ) oputz("\n");
+            isOk = 3;
+          }
+          break;
+        }
+#endif
+        case SQLITE_TESTCTRL_SORTER_MMAP:
+          if( nArg==3 ){
+            int opt = (unsigned int)integerValue(azArg[2]);
+            rc2 = sqlite3_test_control(testctrl, p->db, opt);
+            isOk = 3;
+          }
+          break;
+        case SQLITE_TESTCTRL_JSON_SELFCHECK:
+          if( nArg==2 ){
+            rc2 = -1;
+            isOk = 1;
+          }else{
+            rc2 = booleanValue(azArg[2]);
+            isOk = 3;
+          }
+          sqlite3_test_control(testctrl, &rc2);
+          break;
+      }
+    }
+    if( isOk==0 && iCtrl>=0 ){
+      oputf("Usage: .testctrl %s %s\n", zCmd,aCtrl[iCtrl].zUsage);
+      rc = 1;
+    }else if( isOk==1 ){
+      oputf("%d\n", rc2);
+    }else if( isOk==2 ){
+      oputf("0x%08x\n", rc2);
+    }
+  }else
+#endif /* !defined(SQLITE_UNTESTABLE) */
+
+  if( c=='t' && n>4 && cli_strncmp(azArg[0], "timeout", n)==0 ){
+    open_db(p, 0);
+    sqlite3_busy_timeout(p->db, nArg>=2 ? (int)integerValue(azArg[1]) : 0);
+  }else
+
+  if( c=='t' && n>=5 && cli_strncmp(azArg[0], "timer", n)==0 ){
+    if( nArg==2 ){
+      enableTimer = booleanValue(azArg[1]);
+      if( enableTimer && !HAS_TIMER ){
+        eputz("Error: timer not available on this system.\n");
+        enableTimer = 0;
+      }
+    }else{
+      eputz("Usage: .timer on|off\n");
+      rc = 1;
+    }
+  }else
+
+#ifndef SQLITE_OMIT_TRACE
+  if( c=='t' && cli_strncmp(azArg[0], "trace", n)==0 ){
+    int mType = 0;
+    int jj;
+    open_db(p, 0);
+    for(jj=1; jj<nArg; jj++){
+      const char *z = azArg[jj];
+      if( z[0]=='-' ){
+        if( optionMatch(z, "expanded") ){
+          p->eTraceType = SHELL_TRACE_EXPANDED;
+        }
+#ifdef SQLITE_ENABLE_NORMALIZE
+        else if( optionMatch(z, "normalized") ){
+          p->eTraceType = SHELL_TRACE_NORMALIZED;
+        }
+#endif
+        else if( optionMatch(z, "plain") ){
+          p->eTraceType = SHELL_TRACE_PLAIN;
+        }
+        else if( optionMatch(z, "profile") ){
+          mType |= SQLITE_TRACE_PROFILE;
+        }
+        else if( optionMatch(z, "row") ){
+          mType |= SQLITE_TRACE_ROW;
+        }
+        else if( optionMatch(z, "stmt") ){
+          mType |= SQLITE_TRACE_STMT;
+        }
+        else if( optionMatch(z, "close") ){
+          mType |= SQLITE_TRACE_CLOSE;
+        }
+        else {
+          eputf("Unknown option \"%s\" on \".trace\"\n", z);
+          rc = 1;
+          goto meta_command_exit;
+        }
+      }else{
+        output_file_close(p->traceOut);
+        p->traceOut = output_file_open(z, 0);
+      }
+    }
+    if( p->traceOut==0 ){
+      sqlite3_trace_v2(p->db, 0, 0, 0);
+    }else{
+      if( mType==0 ) mType = SQLITE_TRACE_STMT;
+      sqlite3_trace_v2(p->db, mType, sql_trace_callback, p);
+    }
+  }else
+#endif /* !defined(SQLITE_OMIT_TRACE) */
+
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_OMIT_VIRTUALTABLE)
+  if( c=='u' && cli_strncmp(azArg[0], "unmodule", n)==0 ){
+    int ii;
+    int lenOpt;
+    char *zOpt;
+    if( nArg<2 ){
+      eputz("Usage: .unmodule [--allexcept] NAME ...\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    open_db(p, 0);
+    zOpt = azArg[1];
+    if( zOpt[0]=='-' && zOpt[1]=='-' && zOpt[2]!=0 ) zOpt++;
+    lenOpt = (int)strlen(zOpt);
+    if( lenOpt>=3 && cli_strncmp(zOpt, "-allexcept",lenOpt)==0 ){
+      assert( azArg[nArg]==0 );
+      sqlite3_drop_modules(p->db, nArg>2 ? (const char**)(azArg+2) : 0);
+    }else{
+      for(ii=1; ii<nArg; ii++){
+        sqlite3_create_module(p->db, azArg[ii], 0, 0);
+      }
+    }
+  }else
+#endif
+
+#if SQLITE_USER_AUTHENTICATION
+  if( c=='u' && cli_strncmp(azArg[0], "user", n)==0 ){
+    if( nArg<2 ){
+      eputz("Usage: .user SUBCOMMAND ...\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+    open_db(p, 0);
+    if( cli_strcmp(azArg[1],"login")==0 ){
+      if( nArg!=4 ){
+        eputz("Usage: .user login USER PASSWORD\n");
+        rc = 1;
+        goto meta_command_exit;
+      }
+      rc = sqlite3_user_authenticate(p->db, azArg[2], azArg[3],
+                                     strlen30(azArg[3]));
+      if( rc ){
+        eputf("Authentication failed for user %s\n", azArg[2]);
+        rc = 1;
+      }
+    }else if( cli_strcmp(azArg[1],"add")==0 ){
+      if( nArg!=5 ){
+        eputz("Usage: .user add USER PASSWORD ISADMIN\n");
+        rc = 1;
+        goto meta_command_exit;
+      }
+      rc = sqlite3_user_add(p->db, azArg[2], azArg[3], strlen30(azArg[3]),
+                            booleanValue(azArg[4]));
+      if( rc ){
+        eputf("User-Add failed: %d\n", rc);
+        rc = 1;
+      }
+    }else if( cli_strcmp(azArg[1],"edit")==0 ){
+      if( nArg!=5 ){
+        eputz("Usage: .user edit USER PASSWORD ISADMIN\n");
+        rc = 1;
+        goto meta_command_exit;
+      }
+      rc = sqlite3_user_change(p->db, azArg[2], azArg[3], strlen30(azArg[3]),
+                              booleanValue(azArg[4]));
+      if( rc ){
+        eputf("User-Edit failed: %d\n", rc);
+        rc = 1;
+      }
+    }else if( cli_strcmp(azArg[1],"delete")==0 ){
+      if( nArg!=3 ){
+        eputz("Usage: .user delete USER\n");
+        rc = 1;
+        goto meta_command_exit;
+      }
+      rc = sqlite3_user_delete(p->db, azArg[2]);
+      if( rc ){
+        eputf("User-Delete failed: %d\n", rc);
+        rc = 1;
+      }
+    }else{
+      eputz("Usage: .user login|add|edit|delete ...\n");
+      rc = 1;
+      goto meta_command_exit;
+    }
+  }else
+#endif /* SQLITE_USER_AUTHENTICATION */
+
+  if( c=='v' && cli_strncmp(azArg[0], "version", n)==0 ){
+    char *zPtrSz = sizeof(void*)==8 ? "64-bit" : "32-bit";
+    oputf("SQLite %s %s\n" /*extra-version-info*/,
+          sqlite3_libversion(), sqlite3_sourceid());
+#if SQLITE_HAVE_ZLIB
+    oputf("zlib version %s\n", zlibVersion());
+#endif
+#define CTIMEOPT_VAL_(opt) #opt
+#define CTIMEOPT_VAL(opt) CTIMEOPT_VAL_(opt)
+#if defined(__clang__) && defined(__clang_major__)
+    oputf("clang-" CTIMEOPT_VAL(__clang_major__) "."
+          CTIMEOPT_VAL(__clang_minor__) "."
+          CTIMEOPT_VAL(__clang_patchlevel__) " (%s)\n", zPtrSz);
+#elif defined(_MSC_VER)
+    oputf("msvc-" CTIMEOPT_VAL(_MSC_VER) " (%s)\n", zPtrSz);
+#elif defined(__GNUC__) && defined(__VERSION__)
+    oputf("gcc-" __VERSION__ " (%s)\n", zPtrSz);
+#endif
+  }else
+
+  if( c=='v' && cli_strncmp(azArg[0], "vfsinfo", n)==0 ){
+    const char *zDbName = nArg==2 ? azArg[1] : "main";
+    sqlite3_vfs *pVfs = 0;
+    if( p->db ){
+      sqlite3_file_control(p->db, zDbName, SQLITE_FCNTL_VFS_POINTER, &pVfs);
+      if( pVfs ){
+        oputf("vfs.zName      = \"%s\"\n", pVfs->zName);
+        oputf("vfs.iVersion   = %d\n", pVfs->iVersion);
+        oputf("vfs.szOsFile   = %d\n", pVfs->szOsFile);
+        oputf("vfs.mxPathname = %d\n", pVfs->mxPathname);
+      }
+    }
+  }else
+
+  if( c=='v' && cli_strncmp(azArg[0], "vfslist", n)==0 ){
+    sqlite3_vfs *pVfs;
+    sqlite3_vfs *pCurrent = 0;
+    if( p->db ){
+      sqlite3_file_control(p->db, "main", SQLITE_FCNTL_VFS_POINTER, &pCurrent);
+    }
+    for(pVfs=sqlite3_vfs_find(0); pVfs; pVfs=pVfs->pNext){
+      oputf("vfs.zName      = \"%s\"%s\n", pVfs->zName,
+            pVfs==pCurrent ? "  <--- CURRENT" : "");
+      oputf("vfs.iVersion   = %d\n", pVfs->iVersion);
+      oputf("vfs.szOsFile   = %d\n", pVfs->szOsFile);
+      oputf("vfs.mxPathname = %d\n", pVfs->mxPathname);
+      if( pVfs->pNext ){
+        oputz("-----------------------------------\n");
+      }
+    }
+  }else
+
+  if( c=='v' && cli_strncmp(azArg[0], "vfsname", n)==0 ){
+    const char *zDbName = nArg==2 ? azArg[1] : "main";
+    char *zVfsName = 0;
+    if( p->db ){
+      sqlite3_file_control(p->db, zDbName, SQLITE_FCNTL_VFSNAME, &zVfsName);
+      if( zVfsName ){
+        oputf("%s\n", zVfsName);
+        sqlite3_free(zVfsName);
+      }
+    }
+  }else
+
+  if( c=='w' && cli_strncmp(azArg[0], "wheretrace", n)==0 ){
+    unsigned int x = nArg>=2? (unsigned int)integerValue(azArg[1]) : 0xffffffff;
+    sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 3, &x);
+  }else
+
+  if( c=='w' && cli_strncmp(azArg[0], "width", n)==0 ){
+    int j;
+    assert( nArg<=ArraySize(azArg) );
+    p->nWidth = nArg-1;
+    p->colWidth = realloc(p->colWidth, (p->nWidth+1)*sizeof(int)*2);
+    if( p->colWidth==0 && p->nWidth>0 ) shell_out_of_memory();
+    if( p->nWidth ) p->actualWidth = &p->colWidth[p->nWidth];
+    for(j=1; j<nArg; j++){
+      p->colWidth[j-1] = (int)integerValue(azArg[j]);
+    }
+  }else
+
+  {
+    eputf("Error: unknown command or invalid arguments: "
+          " \"%s\". Enter \".help\" for help\n", azArg[0]);
+    rc = 1;
+  }
+
+meta_command_exit:
+  if( p->outCount ){
+    p->outCount--;
+    if( p->outCount==0 ) output_reset(p);
+  }
+  p->bSafeMode = p->bSafeModePersist;
+  return rc;
+}
+
+/* Line scan result and intermediate states (supporting scan resumption)
+*/
+#ifndef CHAR_BIT
+# define CHAR_BIT 8
+#endif
+typedef enum {
+  QSS_HasDark = 1<<CHAR_BIT, QSS_EndingSemi = 2<<CHAR_BIT,
+  QSS_CharMask = (1<<CHAR_BIT)-1, QSS_ScanMask = 3<<CHAR_BIT,
+  QSS_Start = 0
+} QuickScanState;
+#define QSS_SETV(qss, newst) ((newst) | ((qss) & QSS_ScanMask))
+#define QSS_INPLAIN(qss) (((qss)&QSS_CharMask)==QSS_Start)
+#define QSS_PLAINWHITE(qss) (((qss)&~QSS_EndingSemi)==QSS_Start)
+#define QSS_PLAINDARK(qss) (((qss)&~QSS_EndingSemi)==QSS_HasDark)
+#define QSS_SEMITERM(qss) (((qss)&~QSS_HasDark)==QSS_EndingSemi)
+
+/*
+** Scan line for classification to guide shell's handling.
+** The scan is resumable for subsequent lines when prior
+** return values are passed as the 2nd argument.
+*/
+static QuickScanState quickscan(char *zLine, QuickScanState qss,
+                                SCAN_TRACKER_REFTYPE pst){
+  char cin;
+  char cWait = (char)qss; /* intentional narrowing loss */
+  if( cWait==0 ){
+  PlainScan:
+    assert( cWait==0 );
+    while( (cin = *zLine++)!=0 ){
+      if( IsSpace(cin) )
+        continue;
+      switch (cin){
+      case '-':
+        if( *zLine!='-' )
+          break;
+        while((cin = *++zLine)!=0 )
+          if( cin=='\n')
+            goto PlainScan;
+        return qss;
+      case ';':
+        qss |= QSS_EndingSemi;
+        continue;
+      case '/':
+        if( *zLine=='*' ){
+          ++zLine;
+          cWait = '*';
+          CONTINUE_PROMPT_AWAITS(pst, "/*");
+          qss = QSS_SETV(qss, cWait);
+          goto TermScan;
+        }
+        break;
+      case '[':
+        cin = ']';
+        deliberate_fall_through;
+      case '`': case '\'': case '"':
+        cWait = cin;
+        qss = QSS_HasDark | cWait;
+        CONTINUE_PROMPT_AWAITC(pst, cin);
+        goto TermScan;
+      case '(':
+        CONTINUE_PAREN_INCR(pst, 1);
+        break;
+      case ')':
+        CONTINUE_PAREN_INCR(pst, -1);
+        break;
+      default:
+        break;
+      }
+      qss = (qss & ~QSS_EndingSemi) | QSS_HasDark;
+    }
+  }else{
+  TermScan:
+    while( (cin = *zLine++)!=0 ){
+      if( cin==cWait ){
+        switch( cWait ){
+        case '*':
+          if( *zLine != '/' )
+            continue;
+          ++zLine;
+          cWait = 0;
+          CONTINUE_PROMPT_AWAITC(pst, 0);
+          qss = QSS_SETV(qss, 0);
+          goto PlainScan;
+        case '`': case '\'': case '"':
+          if(*zLine==cWait){
+            /* Swallow doubled end-delimiter.*/
+            ++zLine;
+            continue;
+          }
+          deliberate_fall_through;
+        case ']':
+          cWait = 0;
+          CONTINUE_PROMPT_AWAITC(pst, 0);
+          qss = QSS_SETV(qss, 0);
+          goto PlainScan;
+        default: assert(0);
+        }
+      }
+    }
+  }
+  return qss;
+}
+
+/*
+** Return TRUE if the line typed in is an SQL command terminator other
+** than a semi-colon.  The SQL Server style "go" command is understood
+** as is the Oracle "/".
+*/
+static int line_is_command_terminator(char *zLine){
+  while( IsSpace(zLine[0]) ){ zLine++; };
+  if( zLine[0]=='/' )
+    zLine += 1; /* Oracle */
+  else if ( ToLower(zLine[0])=='g' && ToLower(zLine[1])=='o' )
+    zLine += 2; /* SQL Server */
+  else
+    return 0;
+  return quickscan(zLine, QSS_Start, 0)==QSS_Start;
+}
+
+/*
+** The CLI needs a working sqlite3_complete() to work properly.  So error
+** out of the build if compiling with SQLITE_OMIT_COMPLETE.
+*/
+#ifdef SQLITE_OMIT_COMPLETE
+# error the CLI application is imcompatable with SQLITE_OMIT_COMPLETE.
+#endif
+
+/*
+** Return true if zSql is a complete SQL statement.  Return false if it
+** ends in the middle of a string literal or C-style comment.
+*/
+static int line_is_complete(char *zSql, int nSql){
+  int rc;
+  if( zSql==0 ) return 1;
+  zSql[nSql] = ';';
+  zSql[nSql+1] = 0;
+  rc = sqlite3_complete(zSql);
+  zSql[nSql] = 0;
+  return rc;
+}
+
+/*
+** This function is called after processing each line of SQL in the
+** runOneSqlLine() function. Its purpose is to detect scenarios where
+** defensive mode should be automatically turned off. Specifically, when
+**
+**   1. The first line of input is "PRAGMA foreign_keys=OFF;",
+**   2. The second line of input is "BEGIN TRANSACTION;",
+**   3. The database is empty, and
+**   4. The shell is not running in --safe mode.
+** 
+** The implementation uses the ShellState.eRestoreState to maintain state:
+**
+**    0: Have not seen any SQL.
+**    1: Have seen "PRAGMA foreign_keys=OFF;".
+**    2-6: Currently running .dump transaction. If the "2" bit is set,
+**         disable DEFENSIVE when done. If "4" is set, disable DQS_DDL.
+**    7: Nothing left to do. This function becomes a no-op.
+*/
+static int doAutoDetectRestore(ShellState *p, const char *zSql){
+  int rc = SQLITE_OK;
+
+  if( p->eRestoreState<7 ){
+    switch( p->eRestoreState ){
+      case 0: {
+        const char *zExpect = "PRAGMA foreign_keys=OFF;";
+        assert( strlen(zExpect)==24 );
+        if( p->bSafeMode==0 && memcmp(zSql, zExpect, 25)==0 ){
+          p->eRestoreState = 1;
+        }else{
+          p->eRestoreState = 7;
+        }
+        break;
+      };
+  
+      case 1: {
+        int bIsDump = 0;
+        const char *zExpect = "BEGIN TRANSACTION;";
+        assert( strlen(zExpect)==18 );
+        if( memcmp(zSql, zExpect, 19)==0 ){
+          /* Now check if the database is empty. */
+          const char *zQuery = "SELECT 1 FROM sqlite_schema LIMIT 1";
+          sqlite3_stmt *pStmt = 0;
+  
+          bIsDump = 1;
+          shellPrepare(p->db, &rc, zQuery, &pStmt);
+          if( rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
+            bIsDump = 0;
+          }
+          shellFinalize(&rc, pStmt);
+        }
+        if( bIsDump && rc==SQLITE_OK ){
+          int bDefense = 0;
+          int bDqsDdl = 0;
+          sqlite3_db_config(p->db, SQLITE_DBCONFIG_DEFENSIVE, -1, &bDefense);
+          sqlite3_db_config(p->db, SQLITE_DBCONFIG_DQS_DDL, -1, &bDqsDdl);
+          sqlite3_db_config(p->db, SQLITE_DBCONFIG_DEFENSIVE, 0, 0);
+          sqlite3_db_config(p->db, SQLITE_DBCONFIG_DQS_DDL, 1, 0);
+          p->eRestoreState = (bDefense ? 2 : 0) + (bDqsDdl ? 4 : 0);
+        }else{
+          p->eRestoreState = 7;
+        }
+        break;
+      }
+  
+      default: {
+        if( sqlite3_get_autocommit(p->db) ){
+          if( (p->eRestoreState & 2) ){
+            sqlite3_db_config(p->db, SQLITE_DBCONFIG_DEFENSIVE, 1, 0);
+          }
+          if( (p->eRestoreState & 4) ){
+            sqlite3_db_config(p->db, SQLITE_DBCONFIG_DQS_DDL, 0, 0);
+          }
+          p->eRestoreState = 7;
+        }
+        break;
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Run a single line of SQL.  Return the number of errors.
+*/
+static int runOneSqlLine(ShellState *p, char *zSql, FILE *in, int startline){
+  int rc;
+  char *zErrMsg = 0;
+
+  open_db(p, 0);
+  if( ShellHasFlag(p,SHFLG_Backslash) ) resolve_backslashes(zSql);
+  if( p->flgProgress & SHELL_PROGRESS_RESET ) p->nProgress = 0;
+  BEGIN_TIMER;
+  rc = shell_exec(p, zSql, &zErrMsg);
+  END_TIMER;
+  if( rc || zErrMsg ){
+    char zPrefix[100];
+    const char *zErrorTail;
+    const char *zErrorType;
+    if( zErrMsg==0 ){
+      zErrorType = "Error";
+      zErrorTail = sqlite3_errmsg(p->db);
+    }else if( cli_strncmp(zErrMsg, "in prepare, ",12)==0 ){
+      zErrorType = "Parse error";
+      zErrorTail = &zErrMsg[12];
+    }else if( cli_strncmp(zErrMsg, "stepping, ", 10)==0 ){
+      zErrorType = "Runtime error";
+      zErrorTail = &zErrMsg[10];
+    }else{
+      zErrorType = "Error";
+      zErrorTail = zErrMsg;
+    }
+    if( in!=0 || !stdin_is_interactive ){
+      sqlite3_snprintf(sizeof(zPrefix), zPrefix,
+                       "%s near line %d:", zErrorType, startline);
+    }else{
+      sqlite3_snprintf(sizeof(zPrefix), zPrefix, "%s:", zErrorType);
+    }
+    eputf("%s %s\n", zPrefix, zErrorTail);
+    sqlite3_free(zErrMsg);
+    zErrMsg = 0;
+    return 1;
+  }else if( ShellHasFlag(p, SHFLG_CountChanges) ){
+    char zLineBuf[2000];
+    sqlite3_snprintf(sizeof(zLineBuf), zLineBuf,
+            "changes: %lld   total_changes: %lld",
+            sqlite3_changes64(p->db), sqlite3_total_changes64(p->db));
+    oputf("%s\n", zLineBuf);
+  }
+
+  if( doAutoDetectRestore(p, zSql) ) return 1;
+  return 0;
+}
+
+static void echo_group_input(ShellState *p, const char *zDo){
+  if( ShellHasFlag(p, SHFLG_Echo) ) oputf("%s\n", zDo);
+}
+
+#ifdef SQLITE_SHELL_FIDDLE
+/*
+** Alternate one_input_line() impl for wasm mode. This is not in the primary
+** impl because we need the global shellState and cannot access it from that
+** function without moving lots of code around (creating a larger/messier diff).
+*/
+static char *one_input_line(FILE *in, char *zPrior, int isContinuation){
+  /* Parse the next line from shellState.wasm.zInput. */
+  const char *zBegin = shellState.wasm.zPos;
+  const char *z = zBegin;
+  char *zLine = 0;
+  i64 nZ = 0;
+
+  UNUSED_PARAMETER(in);
+  UNUSED_PARAMETER(isContinuation);
+  if(!z || !*z){
+    return 0;
+  }
+  while(*z && isspace(*z)) ++z;
+  zBegin = z;
+  for(; *z && '\n'!=*z; ++nZ, ++z){}
+  if(nZ>0 && '\r'==zBegin[nZ-1]){
+    --nZ;
+  }
+  shellState.wasm.zPos = z;
+  zLine = realloc(zPrior, nZ+1);
+  shell_check_oom(zLine);
+  memcpy(zLine, zBegin, nZ);
+  zLine[nZ] = 0;
+  return zLine;
+}
+#endif /* SQLITE_SHELL_FIDDLE */
+
+/*
+** Read input from *in and process it.  If *in==0 then input
+** is interactive - the user is typing it it.  Otherwise, input
+** is coming from a file or device.  A prompt is issued and history
+** is saved only if input is interactive.  An interrupt signal will
+** cause this routine to exit immediately, unless input is interactive.
+**
+** Return the number of errors.
+*/
+static int process_input(ShellState *p){
+  char *zLine = 0;          /* A single input line */
+  char *zSql = 0;           /* Accumulated SQL text */
+  i64 nLine;                /* Length of current line */
+  i64 nSql = 0;             /* Bytes of zSql[] used */
+  i64 nAlloc = 0;           /* Allocated zSql[] space */
+  int rc;                   /* Error code */
+  int errCnt = 0;           /* Number of errors seen */
+  i64 startline = 0;        /* Line number for start of current input */
+  QuickScanState qss = QSS_Start; /* Accumulated line status (so far) */
+
+  if( p->inputNesting==MAX_INPUT_NESTING ){
+    /* This will be more informative in a later version. */
+    eputf("Input nesting limit (%d) reached at line %d."
+          " Check recursion.\n", MAX_INPUT_NESTING, p->lineno);
+    return 1;
+  }
+  ++p->inputNesting;
+  p->lineno = 0;
+  CONTINUE_PROMPT_RESET;
+  while( errCnt==0 || !bail_on_error || (p->in==0 && stdin_is_interactive) ){
+    fflush(p->out);
+    zLine = one_input_line(p->in, zLine, nSql>0);
+    if( zLine==0 ){
+      /* End of input */
+      if( p->in==0 && stdin_is_interactive ) oputz("\n");
+      break;
+    }
+    if( seenInterrupt ){
+      if( p->in!=0 ) break;
+      seenInterrupt = 0;
+    }
+    p->lineno++;
+    if( QSS_INPLAIN(qss)
+        && line_is_command_terminator(zLine)
+        && line_is_complete(zSql, nSql) ){
+      memcpy(zLine,";",2);
+    }
+    qss = quickscan(zLine, qss, CONTINUE_PROMPT_PSTATE);
+    if( QSS_PLAINWHITE(qss) && nSql==0 ){
+      /* Just swallow single-line whitespace */
+      echo_group_input(p, zLine);
+      qss = QSS_Start;
+      continue;
+    }
+    if( zLine && (zLine[0]=='.' || zLine[0]=='#') && nSql==0 ){
+      CONTINUE_PROMPT_RESET;
+      echo_group_input(p, zLine);
+      if( zLine[0]=='.' ){
+        rc = do_meta_command(zLine, p);
+        if( rc==2 ){ /* exit requested */
+          break;
+        }else if( rc ){
+          errCnt++;
+        }
+      }
+      qss = QSS_Start;
+      continue;
+    }
+    /* No single-line dispositions remain; accumulate line(s). */
+    nLine = strlen(zLine);
+    if( nSql+nLine+2>=nAlloc ){
+      /* Grow buffer by half-again increments when big. */
+      nAlloc = nSql+(nSql>>1)+nLine+100;
+      zSql = realloc(zSql, nAlloc);
+      shell_check_oom(zSql);
+    }
+    if( nSql==0 ){
+      i64 i;
+      for(i=0; zLine[i] && IsSpace(zLine[i]); i++){}
+      assert( nAlloc>0 && zSql!=0 );
+      memcpy(zSql, zLine+i, nLine+1-i);
+      startline = p->lineno;
+      nSql = nLine-i;
+    }else{
+      zSql[nSql++] = '\n';
+      memcpy(zSql+nSql, zLine, nLine+1);
+      nSql += nLine;
+    }
+    if( nSql && QSS_SEMITERM(qss) && sqlite3_complete(zSql) ){
+      echo_group_input(p, zSql);
+      errCnt += runOneSqlLine(p, zSql, p->in, startline);
+      CONTINUE_PROMPT_RESET;
+      nSql = 0;
+      if( p->outCount ){
+        output_reset(p);
+        p->outCount = 0;
+      }else{
+        clearTempFile(p);
+      }
+      p->bSafeMode = p->bSafeModePersist;
+      qss = QSS_Start;
+    }else if( nSql && QSS_PLAINWHITE(qss) ){
+      echo_group_input(p, zSql);
+      nSql = 0;
+      qss = QSS_Start;
+    }
+  }
+  if( nSql ){
+    /* This may be incomplete. Let the SQL parser deal with that. */
+    echo_group_input(p, zSql);
+    errCnt += runOneSqlLine(p, zSql, p->in, startline);
+    CONTINUE_PROMPT_RESET;
+  }
+  free(zSql);
+  free(zLine);
+  --p->inputNesting;
+  return errCnt>0;
+}
+
+/*
+** Return a pathname which is the user's home directory.  A
+** 0 return indicates an error of some kind.
+*/
+static char *find_home_dir(int clearFlag){
+  static char *home_dir = NULL;
+  if( clearFlag ){
+    free(home_dir);
+    home_dir = 0;
+    return 0;
+  }
+  if( home_dir ) return home_dir;
+
+#if !defined(_WIN32) && !defined(WIN32) && !defined(_WIN32_WCE) \
+     && !defined(__RTP__) && !defined(_WRS_KERNEL) && !defined(SQLITE_WASI)
+  {
+    struct passwd *pwent;
+    uid_t uid = getuid();
+    if( (pwent=getpwuid(uid)) != NULL) {
+      home_dir = pwent->pw_dir;
+    }
+  }
+#endif
+
+#if defined(_WIN32_WCE)
+  /* Windows CE (arm-wince-mingw32ce-gcc) does not provide getenv()
+   */
+  home_dir = "/";
+#else
+
+#if defined(_WIN32) || defined(WIN32)
+  if (!home_dir) {
+    home_dir = getenv("USERPROFILE");
+  }
+#endif
+
+  if (!home_dir) {
+    home_dir = getenv("HOME");
+  }
+
+#if defined(_WIN32) || defined(WIN32)
+  if (!home_dir) {
+    char *zDrive, *zPath;
+    int n;
+    zDrive = getenv("HOMEDRIVE");
+    zPath = getenv("HOMEPATH");
+    if( zDrive && zPath ){
+      n = strlen30(zDrive) + strlen30(zPath) + 1;
+      home_dir = malloc( n );
+      if( home_dir==0 ) return 0;
+      sqlite3_snprintf(n, home_dir, "%s%s", zDrive, zPath);
+      return home_dir;
+    }
+    home_dir = "c:\\";
+  }
+#endif
+
+#endif /* !_WIN32_WCE */
+
+  if( home_dir ){
+    i64 n = strlen(home_dir) + 1;
+    char *z = malloc( n );
+    if( z ) memcpy(z, home_dir, n);
+    home_dir = z;
+  }
+
+  return home_dir;
+}
+
+/*
+** On non-Windows platforms, look for $XDG_CONFIG_HOME.
+** If ${XDG_CONFIG_HOME}/sqlite3/sqliterc is found, return
+** the path to it, else return 0. The result is cached for
+** subsequent calls.
+*/
+static const char *find_xdg_config(void){
+#if defined(_WIN32) || defined(WIN32) || defined(_WIN32_WCE) \
+     || defined(__RTP__) || defined(_WRS_KERNEL)
+  return 0;
+#else
+  static int alreadyTried = 0;
+  static char *zConfig = 0;
+  const char *zXdgHome;
+
+  if( alreadyTried!=0 ){
+    return zConfig;
+  }
+  alreadyTried = 1;
+  zXdgHome = getenv("XDG_CONFIG_HOME");
+  if( zXdgHome==0 ){
+    return 0;
+  }
+  zConfig = sqlite3_mprintf("%s/sqlite3/sqliterc", zXdgHome);
+  shell_check_oom(zConfig);
+  if( access(zConfig,0)!=0 ){
+    sqlite3_free(zConfig);
+    zConfig = 0;
+  }
+  return zConfig;
+#endif
+}
+
+/*
+** Read input from the file given by sqliterc_override.  Or if that
+** parameter is NULL, take input from the first of find_xdg_config()
+** or ~/.sqliterc which is found.
+**
+** Returns the number of errors.
+*/
+static void process_sqliterc(
+  ShellState *p,                  /* Configuration data */
+  const char *sqliterc_override   /* Name of config file. NULL to use default */
+){
+  char *home_dir = NULL;
+  const char *sqliterc = sqliterc_override;
+  char *zBuf = 0;
+  FILE *inSaved = p->in;
+  int savedLineno = p->lineno;
+
+  if( sqliterc == NULL ){
+    sqliterc = find_xdg_config();
+  }
+  if( sqliterc == NULL ){
+    home_dir = find_home_dir(0);
+    if( home_dir==0 ){
+      eputz("-- warning: cannot find home directory;"
+            " cannot read ~/.sqliterc\n");
+      return;
+    }
+    zBuf = sqlite3_mprintf("%s/.sqliterc",home_dir);
+    shell_check_oom(zBuf);
+    sqliterc = zBuf;
+  }
+  p->in = fopen(sqliterc,"rb");
+  if( p->in ){
+    if( stdin_is_interactive ){
+      eputf("-- Loading resources from %s\n", sqliterc);
+    }
+    if( process_input(p) && bail_on_error ) exit(1);
+    fclose(p->in);
+  }else if( sqliterc_override!=0 ){
+    eputf("cannot open: \"%s\"\n", sqliterc);
+    if( bail_on_error ) exit(1);
+  }
+  p->in = inSaved;
+  p->lineno = savedLineno;
+  sqlite3_free(zBuf);
+}
+
+/*
+** Show available command line options
+*/
+static const char zOptions[] =
+  "   --                   treat no subsequent arguments as options\n"
+#if defined(SQLITE_HAVE_ZLIB) && !defined(SQLITE_OMIT_VIRTUALTABLE)
+  "   -A ARGS...           run \".archive ARGS\" and exit\n"
+#endif
+  "   -append              append the database to the end of the file\n"
+  "   -ascii               set output mode to 'ascii'\n"
+  "   -bail                stop after hitting an error\n"
+  "   -batch               force batch I/O\n"
+  "   -box                 set output mode to 'box'\n"
+  "   -column              set output mode to 'column'\n"
+  "   -cmd COMMAND         run \"COMMAND\" before reading stdin\n"
+  "   -csv                 set output mode to 'csv'\n"
+#if !defined(SQLITE_OMIT_DESERIALIZE)
+  "   -deserialize         open the database using sqlite3_deserialize()\n"
+#endif
+  "   -echo                print inputs before execution\n"
+  "   -init FILENAME       read/process named file\n"
+  "   -[no]header          turn headers on or off\n"
+#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
+  "   -heap SIZE           Size of heap for memsys3 or memsys5\n"
+#endif
+  "   -help                show this message\n"
+  "   -html                set output mode to HTML\n"
+  "   -interactive         force interactive I/O\n"
+  "   -json                set output mode to 'json'\n"
+  "   -line                set output mode to 'line'\n"
+  "   -list                set output mode to 'list'\n"
+  "   -lookaside SIZE N    use N entries of SZ bytes for lookaside memory\n"
+  "   -markdown            set output mode to 'markdown'\n"
+#if !defined(SQLITE_OMIT_DESERIALIZE)
+  "   -maxsize N           maximum size for a --deserialize database\n"
+#endif
+  "   -memtrace            trace all memory allocations and deallocations\n"
+  "   -mmap N              default mmap size set to N\n"
+#ifdef SQLITE_ENABLE_MULTIPLEX
+  "   -multiplex           enable the multiplexor VFS\n"
+#endif
+  "   -newline SEP         set output row separator. Default: '\\n'\n"
+  "   -nofollow            refuse to open symbolic links to database files\n"
+  "   -nonce STRING        set the safe-mode escape nonce\n"
+  "   -nullvalue TEXT      set text string for NULL values. Default ''\n"
+  "   -pagecache SIZE N    use N slots of SZ bytes each for page cache memory\n"
+  "   -pcachetrace         trace all page cache operations\n"
+  "   -quote               set output mode to 'quote'\n"
+  "   -readonly            open the database read-only\n"
+  "   -safe                enable safe-mode\n"
+  "   -separator SEP       set output column separator. Default: '|'\n"
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+  "   -sorterref SIZE      sorter references threshold size\n"
+#endif
+  "   -stats               print memory stats before each finalize\n"
+  "   -table               set output mode to 'table'\n"
+  "   -tabs                set output mode to 'tabs'\n"
+  "   -unsafe-testing      allow unsafe commands and modes for testing\n"
+  "   -version             show SQLite version\n"
+  "   -vfs NAME            use NAME as the default VFS\n"
+#ifdef SQLITE_ENABLE_VFSTRACE
+  "   -vfstrace            enable tracing of all VFS calls\n"
+#endif
+#ifdef SQLITE_HAVE_ZLIB
+  "   -zip                 open the file as a ZIP Archive\n"
+#endif
+;
+static void usage(int showDetail){
+  eputf("Usage: %s [OPTIONS] [FILENAME [SQL]]\n"
+       "FILENAME is the name of an SQLite database. A new database is created\n"
+       "if the file does not previously exist. Defaults to :memory:.\n", Argv0);
+  if( showDetail ){
+    eputf("OPTIONS include:\n%s", zOptions);
+  }else{
+    eputz("Use the -help option for additional information\n");
+  }
+  exit(1);
+}
+
+/*
+** Internal check:  Verify that the SQLite is uninitialized.  Print a
+** error message if it is initialized.
+*/
+static void verify_uninitialized(void){
+  if( sqlite3_config(-1)==SQLITE_MISUSE ){
+    sputz(stdout, "WARNING: attempt to configure SQLite after"
+          " initialization.\n");
+  }
+}
+
+/*
+** Initialize the state information in data
+*/
+static void main_init(ShellState *data) {
+  memset(data, 0, sizeof(*data));
+  data->normalMode = data->cMode = data->mode = MODE_List;
+  data->autoExplain = 1;
+  data->pAuxDb = &data->aAuxDb[0];
+  memcpy(data->colSeparator,SEP_Column, 2);
+  memcpy(data->rowSeparator,SEP_Row, 2);
+  data->showHeader = 0;
+  data->shellFlgs = SHFLG_Lookaside;
+  sqlite3_config(SQLITE_CONFIG_LOG, shellLog, data);
+#if !defined(SQLITE_SHELL_FIDDLE)
+  verify_uninitialized();
+#endif
+  sqlite3_config(SQLITE_CONFIG_URI, 1);
+  sqlite3_config(SQLITE_CONFIG_MULTITHREAD);
+  sqlite3_snprintf(sizeof(mainPrompt), mainPrompt,"sqlite> ");
+  sqlite3_snprintf(sizeof(continuePrompt), continuePrompt,"   ...> ");
+}
+
+/*
+** Output text to the console in a font that attracts extra attention.
+*/
+#if defined(_WIN32) || defined(WIN32)
+static void printBold(const char *zText){
+#if !SQLITE_OS_WINRT
+  HANDLE out = GetStdHandle(STD_OUTPUT_HANDLE);
+  CONSOLE_SCREEN_BUFFER_INFO defaultScreenInfo;
+  GetConsoleScreenBufferInfo(out, &defaultScreenInfo);
+  SetConsoleTextAttribute(out,
+         FOREGROUND_RED|FOREGROUND_INTENSITY
+  );
+#endif
+  sputz(stdout, zText);
+#if !SQLITE_OS_WINRT
+  SetConsoleTextAttribute(out, defaultScreenInfo.wAttributes);
+#endif
+}
+#else
+static void printBold(const char *zText){
+  sputf(stdout, "\033[1m%s\033[0m", zText);
+}
+#endif
+
+/*
+** Get the argument to an --option.  Throw an error and die if no argument
+** is available.
+*/
+static char *cmdline_option_value(int argc, char **argv, int i){
+  if( i==argc ){
+    eputf("%s: Error: missing argument to %s\n", argv[0], argv[argc-1]);
+    exit(1);
+  }
+  return argv[i];
+}
+
+static void sayAbnormalExit(void){
+  if( seenInterrupt ) eputz("Program interrupted.\n");
+}
+
+#ifndef SQLITE_SHELL_IS_UTF8
+#  if (defined(_WIN32) || defined(WIN32)) \
+   && (defined(_MSC_VER) || (defined(UNICODE) && defined(__GNUC__)))
+#    define SQLITE_SHELL_IS_UTF8          (0)
+#  else
+#    define SQLITE_SHELL_IS_UTF8          (1)
+#  endif
+#endif
+
+#ifdef SQLITE_SHELL_FIDDLE
+#  define main fiddle_main
+#endif
+
+#if SQLITE_SHELL_IS_UTF8
+int SQLITE_CDECL main(int argc, char **argv){
+#else
+int SQLITE_CDECL wmain(int argc, wchar_t **wargv){
+  char **argv;
+#endif
+#ifdef SQLITE_DEBUG
+  sqlite3_int64 mem_main_enter = 0;
+#endif
+  char *zErrMsg = 0;
+#ifdef SQLITE_SHELL_FIDDLE
+#  define data shellState
+#else
+  ShellState data;
+  StreamsAreConsole consStreams = SAC_NoConsole;
+#endif
+  const char *zInitFile = 0;
+  int i;
+  int rc = 0;
+  int warnInmemoryDb = 0;
+  int readStdin = 1;
+  int nCmd = 0;
+  int nOptsEnd = argc;
+  char **azCmd = 0;
+  const char *zVfs = 0;           /* Value of -vfs command-line option */
+#if !SQLITE_SHELL_IS_UTF8
+  char **argvToFree = 0;
+  int argcToFree = 0;
+#endif
+  setvbuf(stderr, 0, _IONBF, 0); /* Make sure stderr is unbuffered */
+
+#ifdef SQLITE_SHELL_FIDDLE
+  stdin_is_interactive = 0;
+  stdout_is_console = 1;
+  data.wasm.zDefaultDbName = "/fiddle.sqlite3";
+#else
+  consStreams = consoleClassifySetup(stdin, stdout, stderr);
+  stdin_is_interactive = (consStreams & SAC_InConsole)!=0;
+  stdout_is_console = (consStreams & SAC_OutConsole)!=0;
+  atexit(consoleRestore);
+#endif
+  atexit(sayAbnormalExit);
+#ifdef SQLITE_DEBUG
+  mem_main_enter = sqlite3_memory_used();
+#endif
+#if !defined(_WIN32_WCE)
+  if( getenv("SQLITE_DEBUG_BREAK") ){
+    if( isatty(0) && isatty(2) ){
+      eputf("attach debugger to process %d and press any key to continue.\n",
+            GETPID());
+      fgetc(stdin);
+    }else{
+#if defined(_WIN32) || defined(WIN32)
+#if SQLITE_OS_WINRT
+      __debugbreak();
+#else
+      DebugBreak();
+#endif
+#elif defined(SIGTRAP)
+      raise(SIGTRAP);
+#endif
+    }
+  }
+#endif
+  /* Register a valid signal handler early, before much else is done. */
+#ifdef SIGINT
+  signal(SIGINT, interrupt_handler);
+#elif (defined(_WIN32) || defined(WIN32)) && !defined(_WIN32_WCE)
+  if( !SetConsoleCtrlHandler(ConsoleCtrlHandler, TRUE) ){
+    eputz("No ^C handler.\n");
+  }
+#endif
+
+#if USE_SYSTEM_SQLITE+0!=1
+  if( cli_strncmp(sqlite3_sourceid(),SQLITE_SOURCE_ID,60)!=0 ){
+    eputf("SQLite header and source version mismatch\n%s\n%s\n",
+          sqlite3_sourceid(), SQLITE_SOURCE_ID);
+    exit(1);
+  }
+#endif
+  main_init(&data);
+
+  /* On Windows, we must translate command-line arguments into UTF-8.
+  ** The SQLite memory allocator subsystem has to be enabled in order to
+  ** do this.  But we want to run an sqlite3_shutdown() afterwards so that
+  ** subsequent sqlite3_config() calls will work.  So copy all results into
+  ** memory that does not come from the SQLite memory allocator.
+  */
+#if !SQLITE_SHELL_IS_UTF8
+  sqlite3_initialize();
+  argvToFree = malloc(sizeof(argv[0])*argc*2);
+  shell_check_oom(argvToFree);
+  argcToFree = argc;
+  argv = argvToFree + argc;
+  for(i=0; i<argc; i++){
+    char *z = sqlite3_win32_unicode_to_utf8(wargv[i]);
+    i64 n;
+    shell_check_oom(z);
+    n = strlen(z);
+    argv[i] = malloc( n+1 );
+    shell_check_oom(argv[i]);
+    memcpy(argv[i], z, n+1);
+    argvToFree[i] = argv[i];
+    sqlite3_free(z);
+  }
+  sqlite3_shutdown();
+#endif
+
+  assert( argc>=1 && argv && argv[0] );
+  Argv0 = argv[0];
+
+#ifdef SQLITE_SHELL_DBNAME_PROC
+  {
+    /* If the SQLITE_SHELL_DBNAME_PROC macro is defined, then it is the name
+    ** of a C-function that will provide the name of the database file.  Use
+    ** this compile-time option to embed this shell program in larger
+    ** applications. */
+    extern void SQLITE_SHELL_DBNAME_PROC(const char**);
+    SQLITE_SHELL_DBNAME_PROC(&data.pAuxDb->zDbFilename);
+    warnInmemoryDb = 0;
+  }
+#endif
+
+  /* Do an initial pass through the command-line argument to locate
+  ** the name of the database file, the name of the initialization file,
+  ** the size of the alternative malloc heap, options affecting commands
+  ** or SQL run from the command line, and the first command to execute.
+  */
+#ifndef SQLITE_SHELL_FIDDLE
+  verify_uninitialized();
+#endif
+  for(i=1; i<argc; i++){
+    char *z;
+    z = argv[i];
+    if( z[0]!='-' || i>nOptsEnd ){
+      if( data.aAuxDb->zDbFilename==0 ){
+        data.aAuxDb->zDbFilename = z;
+      }else{
+        /* Excess arguments are interpreted as SQL (or dot-commands) and
+        ** mean that nothing is read from stdin */
+        readStdin = 0;
+        nCmd++;
+        azCmd = realloc(azCmd, sizeof(azCmd[0])*nCmd);
+        shell_check_oom(azCmd);
+        azCmd[nCmd-1] = z;
+      }
+      continue;
+    }
+    if( z[1]=='-' ) z++;
+    if( cli_strcmp(z, "-")==0 ){
+      nOptsEnd = i;
+      continue;
+    }else if( cli_strcmp(z,"-separator")==0
+     || cli_strcmp(z,"-nullvalue")==0
+     || cli_strcmp(z,"-newline")==0
+     || cli_strcmp(z,"-cmd")==0
+    ){
+      (void)cmdline_option_value(argc, argv, ++i);
+    }else if( cli_strcmp(z,"-init")==0 ){
+      zInitFile = cmdline_option_value(argc, argv, ++i);
+    }else if( cli_strcmp(z,"-interactive")==0 ){
+    }else if( cli_strcmp(z,"-batch")==0 ){
+      /* Need to check for batch mode here to so we can avoid printing
+      ** informational messages (like from process_sqliterc) before
+      ** we do the actual processing of arguments later in a second pass.
+      */
+      stdin_is_interactive = 0;
+    }else if( cli_strcmp(z,"-utf8")==0 ){
+    }else if( cli_strcmp(z,"-no-utf8")==0 ){
+    }else if( cli_strcmp(z,"-heap")==0 ){
+#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
+      const char *zSize;
+      sqlite3_int64 szHeap;
+
+      zSize = cmdline_option_value(argc, argv, ++i);
+      szHeap = integerValue(zSize);
+      if( szHeap>0x7fff0000 ) szHeap = 0x7fff0000;
+      verify_uninitialized();
+      sqlite3_config(SQLITE_CONFIG_HEAP, malloc((int)szHeap), (int)szHeap, 64);
+#else
+      (void)cmdline_option_value(argc, argv, ++i);
+#endif
+    }else if( cli_strcmp(z,"-pagecache")==0 ){
+      sqlite3_int64 n, sz;
+      sz = integerValue(cmdline_option_value(argc,argv,++i));
+      if( sz>70000 ) sz = 70000;
+      if( sz<0 ) sz = 0;
+      n = integerValue(cmdline_option_value(argc,argv,++i));
+      if( sz>0 && n>0 && 0xffffffffffffLL/sz<n ){
+        n = 0xffffffffffffLL/sz;
+      }
+      verify_uninitialized();
+      sqlite3_config(SQLITE_CONFIG_PAGECACHE,
+                    (n>0 && sz>0) ? malloc(n*sz) : 0, sz, n);
+      data.shellFlgs |= SHFLG_Pagecache;
+    }else if( cli_strcmp(z,"-lookaside")==0 ){
+      int n, sz;
+      sz = (int)integerValue(cmdline_option_value(argc,argv,++i));
+      if( sz<0 ) sz = 0;
+      n = (int)integerValue(cmdline_option_value(argc,argv,++i));
+      if( n<0 ) n = 0;
+      verify_uninitialized();
+      sqlite3_config(SQLITE_CONFIG_LOOKASIDE, sz, n);
+      if( sz*n==0 ) data.shellFlgs &= ~SHFLG_Lookaside;
+    }else if( cli_strcmp(z,"-threadsafe")==0 ){
+      int n;
+      n = (int)integerValue(cmdline_option_value(argc,argv,++i));
+      verify_uninitialized();
+      switch( n ){
+         case 0:  sqlite3_config(SQLITE_CONFIG_SINGLETHREAD);  break;
+         case 2:  sqlite3_config(SQLITE_CONFIG_MULTITHREAD);   break;
+         default: sqlite3_config(SQLITE_CONFIG_SERIALIZED);    break;
+      }
+#ifdef SQLITE_ENABLE_VFSTRACE
+    }else if( cli_strcmp(z,"-vfstrace")==0 ){
+      extern int vfstrace_register(
+         const char *zTraceName,
+         const char *zOldVfsName,
+         int (*xOut)(const char*,void*),
+         void *pOutArg,
+         int makeDefault
+      );
+      vfstrace_register("trace",0,(int(*)(const char*,void*))fputs,stderr,1);
+#endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+    }else if( cli_strcmp(z,"-multiplex")==0 ){
+      extern int sqlite3_multiplex_initialize(const char*,int);
+      sqlite3_multiplex_initialize(0, 1);
+#endif
+    }else if( cli_strcmp(z,"-mmap")==0 ){
+      sqlite3_int64 sz = integerValue(cmdline_option_value(argc,argv,++i));
+      verify_uninitialized();
+      sqlite3_config(SQLITE_CONFIG_MMAP_SIZE, sz, sz);
+#if defined(SQLITE_ENABLE_SORTER_REFERENCES)
+    }else if( cli_strcmp(z,"-sorterref")==0 ){
+      sqlite3_int64 sz = integerValue(cmdline_option_value(argc,argv,++i));
+      verify_uninitialized();
+      sqlite3_config(SQLITE_CONFIG_SORTERREF_SIZE, (int)sz);
+#endif
+    }else if( cli_strcmp(z,"-vfs")==0 ){
+      zVfs = cmdline_option_value(argc, argv, ++i);
+#ifdef SQLITE_HAVE_ZLIB
+    }else if( cli_strcmp(z,"-zip")==0 ){
+      data.openMode = SHELL_OPEN_ZIPFILE;
+#endif
+    }else if( cli_strcmp(z,"-append")==0 ){
+      data.openMode = SHELL_OPEN_APPENDVFS;
+#ifndef SQLITE_OMIT_DESERIALIZE
+    }else if( cli_strcmp(z,"-deserialize")==0 ){
+      data.openMode = SHELL_OPEN_DESERIALIZE;
+    }else if( cli_strcmp(z,"-maxsize")==0 && i+1<argc ){
+      data.szMax = integerValue(argv[++i]);
+#endif
+    }else if( cli_strcmp(z,"-readonly")==0 ){
+      data.openMode = SHELL_OPEN_READONLY;
+    }else if( cli_strcmp(z,"-nofollow")==0 ){
+      data.openFlags = SQLITE_OPEN_NOFOLLOW;
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB)
+    }else if( cli_strncmp(z, "-A",2)==0 ){
+      /* All remaining command-line arguments are passed to the ".archive"
+      ** command, so ignore them */
+      break;
+#endif
+    }else if( cli_strcmp(z, "-memtrace")==0 ){
+      sqlite3MemTraceActivate(stderr);
+    }else if( cli_strcmp(z, "-pcachetrace")==0 ){
+      sqlite3PcacheTraceActivate(stderr);
+    }else if( cli_strcmp(z,"-bail")==0 ){
+      bail_on_error = 1;
+    }else if( cli_strcmp(z,"-nonce")==0 ){
+      free(data.zNonce);
+      data.zNonce = strdup(cmdline_option_value(argc, argv, ++i));
+    }else if( cli_strcmp(z,"-unsafe-testing")==0 ){
+      ShellSetFlag(&data,SHFLG_TestingMode);
+    }else if( cli_strcmp(z,"-safe")==0 ){
+      /* no-op - catch this on the second pass */
+    }
+  }
+#ifndef SQLITE_SHELL_FIDDLE
+  verify_uninitialized();
+#endif
+
+
+#ifdef SQLITE_SHELL_INIT_PROC
+  {
+    /* If the SQLITE_SHELL_INIT_PROC macro is defined, then it is the name
+    ** of a C-function that will perform initialization actions on SQLite that
+    ** occur just before or after sqlite3_initialize(). Use this compile-time
+    ** option to embed this shell program in larger applications. */
+    extern void SQLITE_SHELL_INIT_PROC(void);
+    SQLITE_SHELL_INIT_PROC();
+  }
+#else
+  /* All the sqlite3_config() calls have now been made. So it is safe
+  ** to call sqlite3_initialize() and process any command line -vfs option. */
+  sqlite3_initialize();
+#endif
+
+  if( zVfs ){
+    sqlite3_vfs *pVfs = sqlite3_vfs_find(zVfs);
+    if( pVfs ){
+      sqlite3_vfs_register(pVfs, 1);
+    }else{
+      eputf("no such VFS: \"%s\"\n", zVfs);
+      exit(1);
+    }
+  }
+
+  if( data.pAuxDb->zDbFilename==0 ){
+#ifndef SQLITE_OMIT_MEMORYDB
+    data.pAuxDb->zDbFilename = ":memory:";
+    warnInmemoryDb = argc==1;
+#else
+    eputf("%s: Error: no database filename specified\n", Argv0);
+    return 1;
+#endif
+  }
+  data.out = stdout;
+#ifndef SQLITE_SHELL_FIDDLE
+  sqlite3_appendvfs_init(0,0,0);
+#endif
+
+  /* Go ahead and open the database file if it already exists.  If the
+  ** file does not exist, delay opening it.  This prevents empty database
+  ** files from being created if a user mistypes the database name argument
+  ** to the sqlite command-line tool.
+  */
+  if( access(data.pAuxDb->zDbFilename, 0)==0 ){
+    open_db(&data, 0);
+  }
+
+  /* Process the initialization file if there is one.  If no -init option
+  ** is given on the command line, look for a file named ~/.sqliterc and
+  ** try to process it.
+  */
+  process_sqliterc(&data,zInitFile);
+
+  /* Make a second pass through the command-line argument and set
+  ** options.  This second pass is delayed until after the initialization
+  ** file is processed so that the command-line arguments will override
+  ** settings in the initialization file.
+  */
+  for(i=1; i<argc; i++){
+    char *z = argv[i];
+    if( z[0]!='-' || i>=nOptsEnd ) continue;
+    if( z[1]=='-' ){ z++; }
+    if( cli_strcmp(z,"-init")==0 ){
+      i++;
+    }else if( cli_strcmp(z,"-html")==0 ){
+      data.mode = MODE_Html;
+    }else if( cli_strcmp(z,"-list")==0 ){
+      data.mode = MODE_List;
+    }else if( cli_strcmp(z,"-quote")==0 ){
+      data.mode = MODE_Quote;
+      sqlite3_snprintf(sizeof(data.colSeparator), data.colSeparator, SEP_Comma);
+      sqlite3_snprintf(sizeof(data.rowSeparator), data.rowSeparator, SEP_Row);
+    }else if( cli_strcmp(z,"-line")==0 ){
+      data.mode = MODE_Line;
+    }else if( cli_strcmp(z,"-column")==0 ){
+      data.mode = MODE_Column;
+    }else if( cli_strcmp(z,"-json")==0 ){
+      data.mode = MODE_Json;
+    }else if( cli_strcmp(z,"-markdown")==0 ){
+      data.mode = MODE_Markdown;
+    }else if( cli_strcmp(z,"-table")==0 ){
+      data.mode = MODE_Table;
+    }else if( cli_strcmp(z,"-box")==0 ){
+      data.mode = MODE_Box;
+    }else if( cli_strcmp(z,"-csv")==0 ){
+      data.mode = MODE_Csv;
+      memcpy(data.colSeparator,",",2);
+#ifdef SQLITE_HAVE_ZLIB
+    }else if( cli_strcmp(z,"-zip")==0 ){
+      data.openMode = SHELL_OPEN_ZIPFILE;
+#endif
+    }else if( cli_strcmp(z,"-append")==0 ){
+      data.openMode = SHELL_OPEN_APPENDVFS;
+#ifndef SQLITE_OMIT_DESERIALIZE
+    }else if( cli_strcmp(z,"-deserialize")==0 ){
+      data.openMode = SHELL_OPEN_DESERIALIZE;
+    }else if( cli_strcmp(z,"-maxsize")==0 && i+1<argc ){
+      data.szMax = integerValue(argv[++i]);
+#endif
+    }else if( cli_strcmp(z,"-readonly")==0 ){
+      data.openMode = SHELL_OPEN_READONLY;
+    }else if( cli_strcmp(z,"-nofollow")==0 ){
+      data.openFlags |= SQLITE_OPEN_NOFOLLOW;
+    }else if( cli_strcmp(z,"-ascii")==0 ){
+      data.mode = MODE_Ascii;
+      sqlite3_snprintf(sizeof(data.colSeparator), data.colSeparator,SEP_Unit);
+      sqlite3_snprintf(sizeof(data.rowSeparator), data.rowSeparator,SEP_Record);
+    }else if( cli_strcmp(z,"-tabs")==0 ){
+      data.mode = MODE_List;
+      sqlite3_snprintf(sizeof(data.colSeparator), data.colSeparator,SEP_Tab);
+      sqlite3_snprintf(sizeof(data.rowSeparator), data.rowSeparator,SEP_Row);
+    }else if( cli_strcmp(z,"-separator")==0 ){
+      sqlite3_snprintf(sizeof(data.colSeparator), data.colSeparator,
+                       "%s",cmdline_option_value(argc,argv,++i));
+    }else if( cli_strcmp(z,"-newline")==0 ){
+      sqlite3_snprintf(sizeof(data.rowSeparator), data.rowSeparator,
+                       "%s",cmdline_option_value(argc,argv,++i));
+    }else if( cli_strcmp(z,"-nullvalue")==0 ){
+      sqlite3_snprintf(sizeof(data.nullValue), data.nullValue,
+                       "%s",cmdline_option_value(argc,argv,++i));
+    }else if( cli_strcmp(z,"-header")==0 ){
+      data.showHeader = 1;
+      ShellSetFlag(&data, SHFLG_HeaderSet);
+     }else if( cli_strcmp(z,"-noheader")==0 ){
+      data.showHeader = 0;
+      ShellSetFlag(&data, SHFLG_HeaderSet);
+    }else if( cli_strcmp(z,"-echo")==0 ){
+      ShellSetFlag(&data, SHFLG_Echo);
+    }else if( cli_strcmp(z,"-eqp")==0 ){
+      data.autoEQP = AUTOEQP_on;
+    }else if( cli_strcmp(z,"-eqpfull")==0 ){
+      data.autoEQP = AUTOEQP_full;
+    }else if( cli_strcmp(z,"-stats")==0 ){
+      data.statsOn = 1;
+    }else if( cli_strcmp(z,"-scanstats")==0 ){
+      data.scanstatsOn = 1;
+    }else if( cli_strcmp(z,"-backslash")==0 ){
+      /* Undocumented command-line option: -backslash
+      ** Causes C-style backslash escapes to be evaluated in SQL statements
+      ** prior to sending the SQL into SQLite.  Useful for injecting
+      ** crazy bytes in the middle of SQL statements for testing and debugging.
+      */
+      ShellSetFlag(&data, SHFLG_Backslash);
+    }else if( cli_strcmp(z,"-bail")==0 ){
+      /* No-op.  The bail_on_error flag should already be set. */
+    }else if( cli_strcmp(z,"-version")==0 ){
+      sputf(stdout, "%s %s (%d-bit)\n",
+            sqlite3_libversion(), sqlite3_sourceid(), 8*(int)sizeof(char*));
+      return 0;
+    }else if( cli_strcmp(z,"-interactive")==0 ){
+      /* Need to check for interactive override here to so that it can
+      ** affect console setup (for Windows only) and testing thereof.
+      */
+      stdin_is_interactive = 1;
+    }else if( cli_strcmp(z,"-batch")==0 ){
+      /* already handled */
+    }else if( cli_strcmp(z,"-utf8")==0 ){
+      /* already handled */
+    }else if( cli_strcmp(z,"-no-utf8")==0 ){
+      /* already handled */
+    }else if( cli_strcmp(z,"-heap")==0 ){
+      i++;
+    }else if( cli_strcmp(z,"-pagecache")==0 ){
+      i+=2;
+    }else if( cli_strcmp(z,"-lookaside")==0 ){
+      i+=2;
+    }else if( cli_strcmp(z,"-threadsafe")==0 ){
+      i+=2;
+    }else if( cli_strcmp(z,"-nonce")==0 ){
+      i += 2;
+    }else if( cli_strcmp(z,"-mmap")==0 ){
+      i++;
+    }else if( cli_strcmp(z,"-memtrace")==0 ){
+      i++;
+    }else if( cli_strcmp(z,"-pcachetrace")==0 ){
+      i++;
+#ifdef SQLITE_ENABLE_SORTER_REFERENCES
+    }else if( cli_strcmp(z,"-sorterref")==0 ){
+      i++;
+#endif
+    }else if( cli_strcmp(z,"-vfs")==0 ){
+      i++;
+#ifdef SQLITE_ENABLE_VFSTRACE
+    }else if( cli_strcmp(z,"-vfstrace")==0 ){
+      i++;
+#endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+    }else if( cli_strcmp(z,"-multiplex")==0 ){
+      i++;
+#endif
+    }else if( cli_strcmp(z,"-help")==0 ){
+      usage(1);
+    }else if( cli_strcmp(z,"-cmd")==0 ){
+      /* Run commands that follow -cmd first and separately from commands
+      ** that simply appear on the command-line.  This seems goofy.  It would
+      ** be better if all commands ran in the order that they appear.  But
+      ** we retain the goofy behavior for historical compatibility. */
+      if( i==argc-1 ) break;
+      z = cmdline_option_value(argc,argv,++i);
+      if( z[0]=='.' ){
+        rc = do_meta_command(z, &data);
+        if( rc && bail_on_error ) return rc==2 ? 0 : rc;
+      }else{
+        open_db(&data, 0);
+        rc = shell_exec(&data, z, &zErrMsg);
+        if( zErrMsg!=0 ){
+          eputf("Error: %s\n", zErrMsg);
+          if( bail_on_error ) return rc!=0 ? rc : 1;
+        }else if( rc!=0 ){
+          eputf("Error: unable to process SQL \"%s\"\n", z);
+          if( bail_on_error ) return rc;
+        }
+      }
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB)
+    }else if( cli_strncmp(z, "-A", 2)==0 ){
+      if( nCmd>0 ){
+        eputf("Error: cannot mix regular SQL or dot-commands"
+              " with \"%s\"\n", z);
+        return 1;
+      }
+      open_db(&data, OPEN_DB_ZIPFILE);
+      if( z[2] ){
+        argv[i] = &z[2];
+        arDotCommand(&data, 1, argv+(i-1), argc-(i-1));
+      }else{
+        arDotCommand(&data, 1, argv+i, argc-i);
+      }
+      readStdin = 0;
+      break;
+#endif
+    }else if( cli_strcmp(z,"-safe")==0 ){
+      data.bSafeMode = data.bSafeModePersist = 1;
+    }else if( cli_strcmp(z,"-unsafe-testing")==0 ){
+      /* Acted upon in first pass. */
+    }else{
+      eputf("%s: Error: unknown option: %s\n", Argv0, z);
+      eputz("Use -help for a list of options.\n");
+      return 1;
+    }
+    data.cMode = data.mode;
+  }
+
+  if( !readStdin ){
+    /* Run all arguments that do not begin with '-' as if they were separate
+    ** command-line inputs, except for the argToSkip argument which contains
+    ** the database filename.
+    */
+    for(i=0; i<nCmd; i++){
+      if( azCmd[i][0]=='.' ){
+        rc = do_meta_command(azCmd[i], &data);
+        if( rc ){
+          free(azCmd);
+          return rc==2 ? 0 : rc;
+        }
+      }else{
+        open_db(&data, 0);
+        echo_group_input(&data, azCmd[i]);
+        rc = shell_exec(&data, azCmd[i], &zErrMsg);
+        if( zErrMsg || rc ){
+          if( zErrMsg!=0 ){
+            eputf("Error: %s\n", zErrMsg);
+          }else{
+            eputf("Error: unable to process SQL: %s\n", azCmd[i]);
+          }
+          sqlite3_free(zErrMsg);
+          free(azCmd);
+          return rc!=0 ? rc : 1;
+        }
+      }
+    }
+  }else{
+    /* Run commands received from standard input
+    */
+    if( stdin_is_interactive ){
+      char *zHome;
+      char *zHistory;
+      int nHistory;
+#if CIO_WIN_WC_XLATE
+# define SHELL_CIO_CHAR_SET (stdout_is_console? " (UTF-16 console I/O)" : "")
+#else
+# define SHELL_CIO_CHAR_SET ""
+#endif
+      sputf(stdout, "SQLite version %s %.19s%s\n" /*extra-version-info*/
+            "Enter \".help\" for usage hints.\n",
+            sqlite3_libversion(), sqlite3_sourceid(), SHELL_CIO_CHAR_SET);
+      if( warnInmemoryDb ){
+        sputz(stdout, "Connected to a ");
+        printBold("transient in-memory database");
+        sputz(stdout, ".\nUse \".open FILENAME\" to reopen on a"
+              " persistent database.\n");
+      }
+      zHistory = getenv("SQLITE_HISTORY");
+      if( zHistory ){
+        zHistory = strdup(zHistory);
+      }else if( (zHome = find_home_dir(0))!=0 ){
+        nHistory = strlen30(zHome) + 20;
+        if( (zHistory = malloc(nHistory))!=0 ){
+          sqlite3_snprintf(nHistory, zHistory,"%s/.sqlite_history", zHome);
+        }
+      }
+      if( zHistory ){ shell_read_history(zHistory); }
+#if HAVE_READLINE || HAVE_EDITLINE
+      rl_attempted_completion_function = readline_completion;
+#elif HAVE_LINENOISE
+      linenoiseSetCompletionCallback(linenoise_completion);
+#endif
+      data.in = 0;
+      rc = process_input(&data);
+      if( zHistory ){
+        shell_stifle_history(2000);
+        shell_write_history(zHistory);
+        free(zHistory);
+      }
+    }else{
+      data.in = stdin;
+      rc = process_input(&data);
+    }
+  }
+#ifndef SQLITE_SHELL_FIDDLE
+  /* In WASM mode we have to leave the db state in place so that
+  ** client code can "push" SQL into it after this call returns. */
+  free(azCmd);
+  set_table_name(&data, 0);
+  if( data.db ){
+    session_close_all(&data, -1);
+    close_db(data.db);
+  }
+  for(i=0; i<ArraySize(data.aAuxDb); i++){
+    sqlite3_free(data.aAuxDb[i].zFreeOnClose);
+    if( data.aAuxDb[i].db ){
+      session_close_all(&data, i);
+      close_db(data.aAuxDb[i].db);
+    }
+  }
+  find_home_dir(1);
+  output_reset(&data);
+  data.doXdgOpen = 0;
+  clearTempFile(&data);
+#if !SQLITE_SHELL_IS_UTF8
+  for(i=0; i<argcToFree; i++) free(argvToFree[i]);
+  free(argvToFree);
+#endif
+  free(data.colWidth);
+  free(data.zNonce);
+  /* Clear the global data structure so that valgrind will detect memory
+  ** leaks */
+  memset(&data, 0, sizeof(data));
+#ifdef SQLITE_DEBUG
+  if( sqlite3_memory_used()>mem_main_enter ){
+    eputf("Memory leaked: %u bytes\n",
+          (unsigned int)(sqlite3_memory_used()-mem_main_enter));
+  }
+#endif
+#endif /* !SQLITE_SHELL_FIDDLE */
+  return rc;
+}
+
+
+#ifdef SQLITE_SHELL_FIDDLE
+/* Only for emcc experimentation purposes. */
+int fiddle_experiment(int a,int b){
+  return a + b;
+}
+
+/*
+** Returns a pointer to the current DB handle.
+*/
+sqlite3 * fiddle_db_handle(){
+  return globalDb;
+}
+
+/*
+** Returns a pointer to the given DB name's VFS. If zDbName is 0 then
+** "main" is assumed. Returns 0 if no db with the given name is
+** open.
+*/
+sqlite3_vfs * fiddle_db_vfs(const char *zDbName){
+  sqlite3_vfs * pVfs = 0;
+  if(globalDb){
+    sqlite3_file_control(globalDb, zDbName ? zDbName : "main",
+                         SQLITE_FCNTL_VFS_POINTER, &pVfs);
+  }
+  return pVfs;
+}
+
+/* Only for emcc experimentation purposes. */
+sqlite3 * fiddle_db_arg(sqlite3 *arg){
+    printf("fiddle_db_arg(%p)\n", (const void*)arg);
+    return arg;
+}
+
+/*
+** Intended to be called via a SharedWorker() while a separate
+** SharedWorker() (which manages the wasm module) is performing work
+** which should be interrupted. Unfortunately, SharedWorker is not
+** portable enough to make real use of.
+*/
+void fiddle_interrupt(void){
+  if( globalDb ) sqlite3_interrupt(globalDb);
+}
+
+/*
+** Returns the filename of the given db name, assuming "main" if
+** zDbName is NULL. Returns NULL if globalDb is not opened.
+*/
+const char * fiddle_db_filename(const char * zDbName){
+    return globalDb
+      ? sqlite3_db_filename(globalDb, zDbName ? zDbName : "main")
+      : NULL;
+}
+
+/*
+** Completely wipes out the contents of the currently-opened database
+** but leaves its storage intact for reuse.
+*/
+void fiddle_reset_db(void){
+  if( globalDb ){
+    int rc = sqlite3_db_config(globalDb, SQLITE_DBCONFIG_RESET_DATABASE, 1, 0);
+    if( 0==rc ) rc = sqlite3_exec(globalDb, "VACUUM", 0, 0, 0);
+    sqlite3_db_config(globalDb, SQLITE_DBCONFIG_RESET_DATABASE, 0, 0);
+  }
+}
+
+/*
+** Uses the current database's VFS xRead to stream the db file's
+** contents out to the given callback. The callback gets a single
+** chunk of size n (its 2nd argument) on each call and must return 0
+** on success, non-0 on error. This function returns 0 on success,
+** SQLITE_NOTFOUND if no db is open, or propagates any other non-0
+** code from the callback. Note that this is not thread-friendly: it
+** expects that it will be the only thread reading the db file and
+** takes no measures to ensure that is the case.
+*/
+int fiddle_export_db( int (*xCallback)(unsigned const char *zOut, int n) ){
+  sqlite3_int64 nSize = 0;
+  sqlite3_int64 nPos = 0;
+  sqlite3_file * pFile = 0;
+  unsigned char buf[1024 * 8];
+  int nBuf = (int)sizeof(buf);
+  int rc = shellState.db
+    ? sqlite3_file_control(shellState.db, "main",
+                           SQLITE_FCNTL_FILE_POINTER, &pFile)
+    : SQLITE_NOTFOUND;
+  if( rc ) return rc;
+  rc = pFile->pMethods->xFileSize(pFile, &nSize);
+  if( rc ) return rc;
+  if(nSize % nBuf){
+    /* DB size is not an even multiple of the buffer size. Reduce
+    ** buffer size so that we do not unduly inflate the db size when
+    ** exporting. */
+    if(0 == nSize % 4096) nBuf = 4096;
+    else if(0 == nSize % 2048) nBuf = 2048;
+    else if(0 == nSize % 1024) nBuf = 1024;
+    else nBuf = 512;
+  }
+  for( ; 0==rc && nPos<nSize; nPos += nBuf ){
+    rc = pFile->pMethods->xRead(pFile, buf, nBuf, nPos);
+    if(SQLITE_IOERR_SHORT_READ == rc){
+      rc = (nPos + nBuf) < nSize ? rc : 0/*assume EOF*/;
+    }
+    if( 0==rc ) rc = xCallback(buf, nBuf);
+  }
+  return rc;
+}
+
+/*
+** Trivial exportable function for emscripten. It processes zSql as if
+** it were input to the sqlite3 shell and redirects all output to the
+** wasm binding. fiddle_main() must have been called before this
+** is called, or results are undefined.
+*/
+void fiddle_exec(const char * zSql){
+  if(zSql && *zSql){
+    if('.'==*zSql) puts(zSql);
+    shellState.wasm.zInput = zSql;
+    shellState.wasm.zPos = zSql;
+    process_input(&shellState);
+    shellState.wasm.zInput = shellState.wasm.zPos = 0;
+  }
+}
+#endif /* SQLITE_SHELL_FIDDLE */
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
new file mode 100644
index 0000000..4a19fe9
--- /dev/null
+++ b/src/sqlite.h.in
@@ -0,0 +1,10802 @@
+/*
+** 2001-09-15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the SQLite library
+** presents to client programs.  If a C-function, structure, datatype,
+** or constant definition does not appear in this file, then it is
+** not a published API of SQLite, is subject to change without
+** notice, and should not be referenced by programs that use SQLite.
+**
+** Some of the definitions that are in this file are marked as
+** "experimental".  Experimental interfaces are normally new
+** features recently added to SQLite.  We do not anticipate changes
+** to experimental interfaces but reserve the right to make minor changes
+** if experience from use "in the wild" suggest such changes are prudent.
+**
+** The official C-language API documentation for SQLite is derived
+** from comments in this file.  This file is the authoritative source
+** on how SQLite interfaces are supposed to operate.
+**
+** The name of this file under configuration management is "sqlite.h.in".
+** The makefile makes some minor changes to this file (such as inserting
+** the version number) and changes its name to "sqlite3.h" as
+** part of the build process.
+*/
+#ifndef SQLITE3_H
+#define SQLITE3_H
+#include <stdarg.h>     /* Needed for the definition of va_list */
+
+/*
+** Make sure we can call this stuff from C++.
+*/
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/*
+** Facilitate override of interface linkage and calling conventions.
+** Be aware that these macros may not be used within this particular
+** translation of the amalgamation and its associated header file.
+**
+** The SQLITE_EXTERN and SQLITE_API macros are used to instruct the
+** compiler that the target identifier should have external linkage.
+**
+** The SQLITE_CDECL macro is used to set the calling convention for
+** public functions that accept a variable number of arguments.
+**
+** The SQLITE_APICALL macro is used to set the calling convention for
+** public functions that accept a fixed number of arguments.
+**
+** The SQLITE_STDCALL macro is no longer used and is now deprecated.
+**
+** The SQLITE_CALLBACK macro is used to set the calling convention for
+** function pointers.
+**
+** The SQLITE_SYSAPI macro is used to set the calling convention for
+** functions provided by the operating system.
+**
+** Currently, the SQLITE_CDECL, SQLITE_APICALL, SQLITE_CALLBACK, and
+** SQLITE_SYSAPI macros are used only when building for environments
+** that require non-default calling conventions.
+*/
+#ifndef SQLITE_EXTERN
+# define SQLITE_EXTERN extern
+#endif
+#ifndef SQLITE_API
+# define SQLITE_API
+#endif
+#ifndef SQLITE_CDECL
+# define SQLITE_CDECL
+#endif
+#ifndef SQLITE_APICALL
+# define SQLITE_APICALL
+#endif
+#ifndef SQLITE_STDCALL
+# define SQLITE_STDCALL SQLITE_APICALL
+#endif
+#ifndef SQLITE_CALLBACK
+# define SQLITE_CALLBACK
+#endif
+#ifndef SQLITE_SYSAPI
+# define SQLITE_SYSAPI
+#endif
+
+/*
+** These no-op macros are used in front of interfaces to mark those
+** interfaces as either deprecated or experimental.  New applications
+** should not use deprecated interfaces - they are supported for backwards
+** compatibility only.  Application writers should be aware that
+** experimental interfaces are subject to change in point releases.
+**
+** These macros used to resolve to various kinds of compiler magic that
+** would generate warning messages when they were used.  But that
+** compiler magic ended up generating such a flurry of bug reports
+** that we have taken it all out and gone back to using simple
+** noop macros.
+*/
+#define SQLITE_DEPRECATED
+#define SQLITE_EXPERIMENTAL
+
+/*
+** Ensure these symbols were not defined by some previous header file.
+*/
+#ifdef SQLITE_VERSION
+# undef SQLITE_VERSION
+#endif
+#ifdef SQLITE_VERSION_NUMBER
+# undef SQLITE_VERSION_NUMBER
+#endif
+
+/*
+** CAPI3REF: Compile-Time Library Version Numbers
+**
+** ^(The [SQLITE_VERSION] C preprocessor macro in the sqlite3.h header
+** evaluates to a string literal that is the SQLite version in the
+** format "X.Y.Z" where X is the major version number (always 3 for
+** SQLite3) and Y is the minor version number and Z is the release number.)^
+** ^(The [SQLITE_VERSION_NUMBER] C preprocessor macro resolves to an integer
+** with the value (X*1000000 + Y*1000 + Z) where X, Y, and Z are the same
+** numbers used in [SQLITE_VERSION].)^
+** The SQLITE_VERSION_NUMBER for any given release of SQLite will also
+** be larger than the release from which it is derived.  Either Y will
+** be held constant and Z will be incremented or else Y will be incremented
+** and Z will be reset to zero.
+**
+** Since [version 3.6.18] ([dateof:3.6.18]),
+** SQLite source code has been stored in the
+** <a href="http://www.fossil-scm.org/">Fossil configuration management
+** system</a>.  ^The SQLITE_SOURCE_ID macro evaluates to
+** a string which identifies a particular check-in of SQLite
+** within its configuration management system.  ^The SQLITE_SOURCE_ID
+** string contains the date and time of the check-in (UTC) and a SHA1
+** or SHA3-256 hash of the entire source tree.  If the source code has
+** been edited in any way since it was last checked in, then the last
+** four hexadecimal digits of the hash may be modified.
+**
+** See also: [sqlite3_libversion()],
+** [sqlite3_libversion_number()], [sqlite3_sourceid()],
+** [sqlite_version()] and [sqlite_source_id()].
+*/
+#define SQLITE_VERSION        "--VERS--"
+#define SQLITE_VERSION_NUMBER --VERSION-NUMBER--
+#define SQLITE_SOURCE_ID      "--SOURCE-ID--"
+
+/*
+** CAPI3REF: Run-Time Library Version Numbers
+** KEYWORDS: sqlite3_version sqlite3_sourceid
+**
+** These interfaces provide the same information as the [SQLITE_VERSION],
+** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
+** but are associated with the library instead of the header file.  ^(Cautious
+** programmers might include assert() statements in their application to
+** verify that values returned by these interfaces match the macros in
+** the header, and thus ensure that the application is
+** compiled with matching library and header files.
+**
+** <blockquote><pre>
+** assert( sqlite3_libversion_number()==SQLITE_VERSION_NUMBER );
+** assert( strncmp(sqlite3_sourceid(),SQLITE_SOURCE_ID,80)==0 );
+** assert( strcmp(sqlite3_libversion(),SQLITE_VERSION)==0 );
+** </pre></blockquote>)^
+**
+** ^The sqlite3_version[] string constant contains the text of [SQLITE_VERSION]
+** macro.  ^The sqlite3_libversion() function returns a pointer to the
+** to the sqlite3_version[] string constant.  The sqlite3_libversion()
+** function is provided for use in DLLs since DLL users usually do not have
+** direct access to string constants within the DLL.  ^The
+** sqlite3_libversion_number() function returns an integer equal to
+** [SQLITE_VERSION_NUMBER].  ^(The sqlite3_sourceid() function returns
+** a pointer to a string constant whose value is the same as the
+** [SQLITE_SOURCE_ID] C preprocessor macro.  Except if SQLite is built
+** using an edited copy of [the amalgamation], then the last four characters
+** of the hash might be different from [SQLITE_SOURCE_ID].)^
+**
+** See also: [sqlite_version()] and [sqlite_source_id()].
+*/
+SQLITE_EXTERN const char sqlite3_version[];
+const char *sqlite3_libversion(void);
+const char *sqlite3_sourceid(void);
+int sqlite3_libversion_number(void);
+
+/*
+** CAPI3REF: Run-Time Library Compilation Options Diagnostics
+**
+** ^The sqlite3_compileoption_used() function returns 0 or 1
+** indicating whether the specified option was defined at
+** compile time.  ^The SQLITE_ prefix may be omitted from the
+** option name passed to sqlite3_compileoption_used().
+**
+** ^The sqlite3_compileoption_get() function allows iterating
+** over the list of options that were defined at compile time by
+** returning the N-th compile time option string.  ^If N is out of range,
+** sqlite3_compileoption_get() returns a NULL pointer.  ^The SQLITE_
+** prefix is omitted from any strings returned by
+** sqlite3_compileoption_get().
+**
+** ^Support for the diagnostic functions sqlite3_compileoption_used()
+** and sqlite3_compileoption_get() may be omitted by specifying the
+** [SQLITE_OMIT_COMPILEOPTION_DIAGS] option at compile time.
+**
+** See also: SQL functions [sqlite_compileoption_used()] and
+** [sqlite_compileoption_get()] and the [compile_options pragma].
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+int sqlite3_compileoption_used(const char *zOptName);
+const char *sqlite3_compileoption_get(int N);
+#else
+# define sqlite3_compileoption_used(X) 0
+# define sqlite3_compileoption_get(X)  ((void*)0)
+#endif
+
+/*
+** CAPI3REF: Test To See If The Library Is Threadsafe
+**
+** ^The sqlite3_threadsafe() function returns zero if and only if
+** SQLite was compiled with mutexing code omitted due to the
+** [SQLITE_THREADSAFE] compile-time option being set to 0.
+**
+** SQLite can be compiled with or without mutexes.  When
+** the [SQLITE_THREADSAFE] C preprocessor macro is 1 or 2, mutexes
+** are enabled and SQLite is threadsafe.  When the
+** [SQLITE_THREADSAFE] macro is 0,
+** the mutexes are omitted.  Without the mutexes, it is not safe
+** to use SQLite concurrently from more than one thread.
+**
+** Enabling mutexes incurs a measurable performance penalty.
+** So if speed is of utmost importance, it makes sense to disable
+** the mutexes.  But for maximum safety, mutexes should be enabled.
+** ^The default behavior is for mutexes to be enabled.
+**
+** This interface can be used by an application to make sure that the
+** version of SQLite that it is linking against was compiled with
+** the desired setting of the [SQLITE_THREADSAFE] macro.
+**
+** This interface only reports on the compile-time mutex setting
+** of the [SQLITE_THREADSAFE] flag.  If SQLite is compiled with
+** SQLITE_THREADSAFE=1 or =2 then mutexes are enabled by default but
+** can be fully or partially disabled using a call to [sqlite3_config()]
+** with the verbs [SQLITE_CONFIG_SINGLETHREAD], [SQLITE_CONFIG_MULTITHREAD],
+** or [SQLITE_CONFIG_SERIALIZED].  ^(The return value of the
+** sqlite3_threadsafe() function shows only the compile-time setting of
+** thread safety, not any run-time changes to that setting made by
+** sqlite3_config(). In other words, the return value from sqlite3_threadsafe()
+** is unchanged by calls to sqlite3_config().)^
+**
+** See the [threading mode] documentation for additional information.
+*/
+int sqlite3_threadsafe(void);
+
+/*
+** CAPI3REF: Database Connection Handle
+** KEYWORDS: {database connection} {database connections}
+**
+** Each open SQLite database is represented by a pointer to an instance of
+** the opaque structure named "sqlite3".  It is useful to think of an sqlite3
+** pointer as an object.  The [sqlite3_open()], [sqlite3_open16()], and
+** [sqlite3_open_v2()] interfaces are its constructors, and [sqlite3_close()]
+** and [sqlite3_close_v2()] are its destructors.  There are many other
+** interfaces (such as
+** [sqlite3_prepare_v2()], [sqlite3_create_function()], and
+** [sqlite3_busy_timeout()] to name but three) that are methods on an
+** sqlite3 object.
+*/
+typedef struct sqlite3 sqlite3;
+
+/*
+** CAPI3REF: 64-Bit Integer Types
+** KEYWORDS: sqlite_int64 sqlite_uint64
+**
+** Because there is no cross-platform way to specify 64-bit integer types
+** SQLite includes typedefs for 64-bit signed and unsigned integers.
+**
+** The sqlite3_int64 and sqlite3_uint64 are the preferred type definitions.
+** The sqlite_int64 and sqlite_uint64 types are supported for backwards
+** compatibility only.
+**
+** ^The sqlite3_int64 and sqlite_int64 types can store integer values
+** between -9223372036854775808 and +9223372036854775807 inclusive.  ^The
+** sqlite3_uint64 and sqlite_uint64 types can store integer values
+** between 0 and +18446744073709551615 inclusive.
+*/
+#ifdef SQLITE_INT64_TYPE
+  typedef SQLITE_INT64_TYPE sqlite_int64;
+# ifdef SQLITE_UINT64_TYPE
+    typedef SQLITE_UINT64_TYPE sqlite_uint64;
+# else
+    typedef unsigned SQLITE_INT64_TYPE sqlite_uint64;
+# endif
+#elif defined(_MSC_VER) || defined(__BORLANDC__)
+  typedef __int64 sqlite_int64;
+  typedef unsigned __int64 sqlite_uint64;
+#else
+  typedef long long int sqlite_int64;
+  typedef unsigned long long int sqlite_uint64;
+#endif
+typedef sqlite_int64 sqlite3_int64;
+typedef sqlite_uint64 sqlite3_uint64;
+
+/*
+** If compiling for a processor that lacks floating point support,
+** substitute integer for floating-point.
+*/
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define double sqlite3_int64
+#endif
+
+/*
+** CAPI3REF: Closing A Database Connection
+** DESTRUCTOR: sqlite3
+**
+** ^The sqlite3_close() and sqlite3_close_v2() routines are destructors
+** for the [sqlite3] object.
+** ^Calls to sqlite3_close() and sqlite3_close_v2() return [SQLITE_OK] if
+** the [sqlite3] object is successfully destroyed and all associated
+** resources are deallocated.
+**
+** Ideally, applications should [sqlite3_finalize | finalize] all
+** [prepared statements], [sqlite3_blob_close | close] all [BLOB handles], and
+** [sqlite3_backup_finish | finish] all [sqlite3_backup] objects associated
+** with the [sqlite3] object prior to attempting to close the object.
+** ^If the database connection is associated with unfinalized prepared
+** statements, BLOB handlers, and/or unfinished sqlite3_backup objects then
+** sqlite3_close() will leave the database connection open and return
+** [SQLITE_BUSY]. ^If sqlite3_close_v2() is called with unfinalized prepared
+** statements, unclosed BLOB handlers, and/or unfinished sqlite3_backups,
+** it returns [SQLITE_OK] regardless, but instead of deallocating the database
+** connection immediately, it marks the database connection as an unusable
+** "zombie" and makes arrangements to automatically deallocate the database
+** connection after all prepared statements are finalized, all BLOB handles
+** are closed, and all backups have finished. The sqlite3_close_v2() interface
+** is intended for use with host languages that are garbage collected, and
+** where the order in which destructors are called is arbitrary.
+**
+** ^If an [sqlite3] object is destroyed while a transaction is open,
+** the transaction is automatically rolled back.
+**
+** The C parameter to [sqlite3_close(C)] and [sqlite3_close_v2(C)]
+** must be either a NULL
+** pointer or an [sqlite3] object pointer obtained
+** from [sqlite3_open()], [sqlite3_open16()], or
+** [sqlite3_open_v2()], and not previously closed.
+** ^Calling sqlite3_close() or sqlite3_close_v2() with a NULL pointer
+** argument is a harmless no-op.
+*/
+int sqlite3_close(sqlite3*);
+int sqlite3_close_v2(sqlite3*);
+
+/*
+** The type for a callback function.
+** This is legacy and deprecated.  It is included for historical
+** compatibility and is not documented.
+*/
+typedef int (*sqlite3_callback)(void*,int,char**, char**);
+
+/*
+** CAPI3REF: One-Step Query Execution Interface
+** METHOD: sqlite3
+**
+** The sqlite3_exec() interface is a convenience wrapper around
+** [sqlite3_prepare_v2()], [sqlite3_step()], and [sqlite3_finalize()],
+** that allows an application to run multiple statements of SQL
+** without having to use a lot of C code.
+**
+** ^The sqlite3_exec() interface runs zero or more UTF-8 encoded,
+** semicolon-separate SQL statements passed into its 2nd argument,
+** in the context of the [database connection] passed in as its 1st
+** argument.  ^If the callback function of the 3rd argument to
+** sqlite3_exec() is not NULL, then it is invoked for each result row
+** coming out of the evaluated SQL statements.  ^The 4th argument to
+** sqlite3_exec() is relayed through to the 1st argument of each
+** callback invocation.  ^If the callback pointer to sqlite3_exec()
+** is NULL, then no callback is ever invoked and result rows are
+** ignored.
+**
+** ^If an error occurs while evaluating the SQL statements passed into
+** sqlite3_exec(), then execution of the current statement stops and
+** subsequent statements are skipped.  ^If the 5th parameter to sqlite3_exec()
+** is not NULL then any error message is written into memory obtained
+** from [sqlite3_malloc()] and passed back through the 5th parameter.
+** To avoid memory leaks, the application should invoke [sqlite3_free()]
+** on error message strings returned through the 5th parameter of
+** sqlite3_exec() after the error message string is no longer needed.
+** ^If the 5th parameter to sqlite3_exec() is not NULL and no errors
+** occur, then sqlite3_exec() sets the pointer in its 5th parameter to
+** NULL before returning.
+**
+** ^If an sqlite3_exec() callback returns non-zero, the sqlite3_exec()
+** routine returns SQLITE_ABORT without invoking the callback again and
+** without running any subsequent SQL statements.
+**
+** ^The 2nd argument to the sqlite3_exec() callback function is the
+** number of columns in the result.  ^The 3rd argument to the sqlite3_exec()
+** callback is an array of pointers to strings obtained as if from
+** [sqlite3_column_text()], one for each column.  ^If an element of a
+** result row is NULL then the corresponding string pointer for the
+** sqlite3_exec() callback is a NULL pointer.  ^The 4th argument to the
+** sqlite3_exec() callback is an array of pointers to strings where each
+** entry represents the name of corresponding result column as obtained
+** from [sqlite3_column_name()].
+**
+** ^If the 2nd parameter to sqlite3_exec() is a NULL pointer, a pointer
+** to an empty string, or a pointer that contains only whitespace and/or
+** SQL comments, then no SQL statements are evaluated and the database
+** is not changed.
+**
+** Restrictions:
+**
+** <ul>
+** <li> The application must ensure that the 1st parameter to sqlite3_exec()
+**      is a valid and open [database connection].
+** <li> The application must not close the [database connection] specified by
+**      the 1st parameter to sqlite3_exec() while sqlite3_exec() is running.
+** <li> The application must not modify the SQL statement text passed into
+**      the 2nd parameter of sqlite3_exec() while sqlite3_exec() is running.
+** </ul>
+*/
+int sqlite3_exec(
+  sqlite3*,                                  /* An open database */
+  const char *sql,                           /* SQL to be evaluated */
+  int (*callback)(void*,int,char**,char**),  /* Callback function */
+  void *,                                    /* 1st argument to callback */
+  char **errmsg                              /* Error msg written here */
+);
+
+/*
+** CAPI3REF: Result Codes
+** KEYWORDS: {result code definitions}
+**
+** Many SQLite functions return an integer result code from the set shown
+** here in order to indicate success or failure.
+**
+** New error codes may be added in future versions of SQLite.
+**
+** See also: [extended result code definitions]
+*/
+#define SQLITE_OK           0   /* Successful result */
+/* beginning-of-error-codes */
+#define SQLITE_ERROR        1   /* Generic error */
+#define SQLITE_INTERNAL     2   /* Internal logic error in SQLite */
+#define SQLITE_PERM         3   /* Access permission denied */
+#define SQLITE_ABORT        4   /* Callback routine requested an abort */
+#define SQLITE_BUSY         5   /* The database file is locked */
+#define SQLITE_LOCKED       6   /* A table in the database is locked */
+#define SQLITE_NOMEM        7   /* A malloc() failed */
+#define SQLITE_READONLY     8   /* Attempt to write a readonly database */
+#define SQLITE_INTERRUPT    9   /* Operation terminated by sqlite3_interrupt()*/
+#define SQLITE_IOERR       10   /* Some kind of disk I/O error occurred */
+#define SQLITE_CORRUPT     11   /* The database disk image is malformed */
+#define SQLITE_NOTFOUND    12   /* Unknown opcode in sqlite3_file_control() */
+#define SQLITE_FULL        13   /* Insertion failed because database is full */
+#define SQLITE_CANTOPEN    14   /* Unable to open the database file */
+#define SQLITE_PROTOCOL    15   /* Database lock protocol error */
+#define SQLITE_EMPTY       16   /* Internal use only */
+#define SQLITE_SCHEMA      17   /* The database schema changed */
+#define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
+#define SQLITE_CONSTRAINT  19   /* Abort due to constraint violation */
+#define SQLITE_MISMATCH    20   /* Data type mismatch */
+#define SQLITE_MISUSE      21   /* Library used incorrectly */
+#define SQLITE_NOLFS       22   /* Uses OS features not supported on host */
+#define SQLITE_AUTH        23   /* Authorization denied */
+#define SQLITE_FORMAT      24   /* Not used */
+#define SQLITE_RANGE       25   /* 2nd parameter to sqlite3_bind out of range */
+#define SQLITE_NOTADB      26   /* File opened that is not a database file */
+#define SQLITE_NOTICE      27   /* Notifications from sqlite3_log() */
+#define SQLITE_WARNING     28   /* Warnings from sqlite3_log() */
+#define SQLITE_ROW         100  /* sqlite3_step() has another row ready */
+#define SQLITE_DONE        101  /* sqlite3_step() has finished executing */
+/* end-of-error-codes */
+
+/*
+** CAPI3REF: Extended Result Codes
+** KEYWORDS: {extended result code definitions}
+**
+** In its default configuration, SQLite API routines return one of 30 integer
+** [result codes].  However, experience has shown that many of
+** these result codes are too coarse-grained.  They do not provide as
+** much information about problems as programmers might like.  In an effort to
+** address this, newer versions of SQLite (version 3.3.8 [dateof:3.3.8]
+** and later) include
+** support for additional result codes that provide more detailed information
+** about errors. These [extended result codes] are enabled or disabled
+** on a per database connection basis using the
+** [sqlite3_extended_result_codes()] API.  Or, the extended code for
+** the most recent error can be obtained using
+** [sqlite3_extended_errcode()].
+*/
+#define SQLITE_ERROR_MISSING_COLLSEQ   (SQLITE_ERROR | (1<<8))
+#define SQLITE_ERROR_RETRY             (SQLITE_ERROR | (2<<8))
+#define SQLITE_ERROR_SNAPSHOT          (SQLITE_ERROR | (3<<8))
+#define SQLITE_IOERR_READ              (SQLITE_IOERR | (1<<8))
+#define SQLITE_IOERR_SHORT_READ        (SQLITE_IOERR | (2<<8))
+#define SQLITE_IOERR_WRITE             (SQLITE_IOERR | (3<<8))
+#define SQLITE_IOERR_FSYNC             (SQLITE_IOERR | (4<<8))
+#define SQLITE_IOERR_DIR_FSYNC         (SQLITE_IOERR | (5<<8))
+#define SQLITE_IOERR_TRUNCATE          (SQLITE_IOERR | (6<<8))
+#define SQLITE_IOERR_FSTAT             (SQLITE_IOERR | (7<<8))
+#define SQLITE_IOERR_UNLOCK            (SQLITE_IOERR | (8<<8))
+#define SQLITE_IOERR_RDLOCK            (SQLITE_IOERR | (9<<8))
+#define SQLITE_IOERR_DELETE            (SQLITE_IOERR | (10<<8))
+#define SQLITE_IOERR_BLOCKED           (SQLITE_IOERR | (11<<8))
+#define SQLITE_IOERR_NOMEM             (SQLITE_IOERR | (12<<8))
+#define SQLITE_IOERR_ACCESS            (SQLITE_IOERR | (13<<8))
+#define SQLITE_IOERR_CHECKRESERVEDLOCK (SQLITE_IOERR | (14<<8))
+#define SQLITE_IOERR_LOCK              (SQLITE_IOERR | (15<<8))
+#define SQLITE_IOERR_CLOSE             (SQLITE_IOERR | (16<<8))
+#define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
+#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
+#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
+#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
+#define SQLITE_IOERR_SHMMAP            (SQLITE_IOERR | (21<<8))
+#define SQLITE_IOERR_SEEK              (SQLITE_IOERR | (22<<8))
+#define SQLITE_IOERR_DELETE_NOENT      (SQLITE_IOERR | (23<<8))
+#define SQLITE_IOERR_MMAP              (SQLITE_IOERR | (24<<8))
+#define SQLITE_IOERR_GETTEMPPATH       (SQLITE_IOERR | (25<<8))
+#define SQLITE_IOERR_CONVPATH          (SQLITE_IOERR | (26<<8))
+#define SQLITE_IOERR_VNODE             (SQLITE_IOERR | (27<<8))
+#define SQLITE_IOERR_AUTH              (SQLITE_IOERR | (28<<8))
+#define SQLITE_IOERR_BEGIN_ATOMIC      (SQLITE_IOERR | (29<<8))
+#define SQLITE_IOERR_COMMIT_ATOMIC     (SQLITE_IOERR | (30<<8))
+#define SQLITE_IOERR_ROLLBACK_ATOMIC   (SQLITE_IOERR | (31<<8))
+#define SQLITE_IOERR_DATA              (SQLITE_IOERR | (32<<8))
+#define SQLITE_IOERR_CORRUPTFS         (SQLITE_IOERR | (33<<8))
+#define SQLITE_IOERR_IN_PAGE           (SQLITE_IOERR | (34<<8))
+#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
+#define SQLITE_LOCKED_VTAB             (SQLITE_LOCKED |  (2<<8))
+#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
+#define SQLITE_BUSY_SNAPSHOT           (SQLITE_BUSY   |  (2<<8))
+#define SQLITE_BUSY_TIMEOUT            (SQLITE_BUSY   |  (3<<8))
+#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
+#define SQLITE_CANTOPEN_ISDIR          (SQLITE_CANTOPEN | (2<<8))
+#define SQLITE_CANTOPEN_FULLPATH       (SQLITE_CANTOPEN | (3<<8))
+#define SQLITE_CANTOPEN_CONVPATH       (SQLITE_CANTOPEN | (4<<8))
+#define SQLITE_CANTOPEN_DIRTYWAL       (SQLITE_CANTOPEN | (5<<8)) /* Not Used */
+#define SQLITE_CANTOPEN_SYMLINK        (SQLITE_CANTOPEN | (6<<8))
+#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
+#define SQLITE_CORRUPT_SEQUENCE        (SQLITE_CORRUPT | (2<<8))
+#define SQLITE_CORRUPT_INDEX           (SQLITE_CORRUPT | (3<<8))
+#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))
+#define SQLITE_READONLY_CANTLOCK       (SQLITE_READONLY | (2<<8))
+#define SQLITE_READONLY_ROLLBACK       (SQLITE_READONLY | (3<<8))
+#define SQLITE_READONLY_DBMOVED        (SQLITE_READONLY | (4<<8))
+#define SQLITE_READONLY_CANTINIT       (SQLITE_READONLY | (5<<8))
+#define SQLITE_READONLY_DIRECTORY      (SQLITE_READONLY | (6<<8))
+#define SQLITE_ABORT_ROLLBACK          (SQLITE_ABORT | (2<<8))
+#define SQLITE_CONSTRAINT_CHECK        (SQLITE_CONSTRAINT | (1<<8))
+#define SQLITE_CONSTRAINT_COMMITHOOK   (SQLITE_CONSTRAINT | (2<<8))
+#define SQLITE_CONSTRAINT_FOREIGNKEY   (SQLITE_CONSTRAINT | (3<<8))
+#define SQLITE_CONSTRAINT_FUNCTION     (SQLITE_CONSTRAINT | (4<<8))
+#define SQLITE_CONSTRAINT_NOTNULL      (SQLITE_CONSTRAINT | (5<<8))
+#define SQLITE_CONSTRAINT_PRIMARYKEY   (SQLITE_CONSTRAINT | (6<<8))
+#define SQLITE_CONSTRAINT_TRIGGER      (SQLITE_CONSTRAINT | (7<<8))
+#define SQLITE_CONSTRAINT_UNIQUE       (SQLITE_CONSTRAINT | (8<<8))
+#define SQLITE_CONSTRAINT_VTAB         (SQLITE_CONSTRAINT | (9<<8))
+#define SQLITE_CONSTRAINT_ROWID        (SQLITE_CONSTRAINT |(10<<8))
+#define SQLITE_CONSTRAINT_PINNED       (SQLITE_CONSTRAINT |(11<<8))
+#define SQLITE_CONSTRAINT_DATATYPE     (SQLITE_CONSTRAINT |(12<<8))
+#define SQLITE_NOTICE_RECOVER_WAL      (SQLITE_NOTICE | (1<<8))
+#define SQLITE_NOTICE_RECOVER_ROLLBACK (SQLITE_NOTICE | (2<<8))
+#define SQLITE_NOTICE_RBU              (SQLITE_NOTICE | (3<<8))
+#define SQLITE_WARNING_AUTOINDEX       (SQLITE_WARNING | (1<<8))
+#define SQLITE_AUTH_USER               (SQLITE_AUTH | (1<<8))
+#define SQLITE_OK_LOAD_PERMANENTLY     (SQLITE_OK | (1<<8))
+#define SQLITE_OK_SYMLINK              (SQLITE_OK | (2<<8)) /* internal use only */
+
+/*
+** CAPI3REF: Flags For File Open Operations
+**
+** These bit values are intended for use in the
+** 3rd parameter to the [sqlite3_open_v2()] interface and
+** in the 4th parameter to the [sqlite3_vfs.xOpen] method.
+**
+** Only those flags marked as "Ok for sqlite3_open_v2()" may be
+** used as the third argument to the [sqlite3_open_v2()] interface.
+** The other flags have historically been ignored by sqlite3_open_v2(),
+** though future versions of SQLite might change so that an error is
+** raised if any of the disallowed bits are passed into sqlite3_open_v2().
+** Applications should not depend on the historical behavior.
+**
+** Note in particular that passing the SQLITE_OPEN_EXCLUSIVE flag into
+** [sqlite3_open_v2()] does *not* cause the underlying database file
+** to be opened using O_EXCL.  Passing SQLITE_OPEN_EXCLUSIVE into
+** [sqlite3_open_v2()] has historically be a no-op and might become an
+** error in future versions of SQLite.
+*/
+#define SQLITE_OPEN_READONLY         0x00000001  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_READWRITE        0x00000002  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_CREATE           0x00000004  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_DELETEONCLOSE    0x00000008  /* VFS only */
+#define SQLITE_OPEN_EXCLUSIVE        0x00000010  /* VFS only */
+#define SQLITE_OPEN_AUTOPROXY        0x00000020  /* VFS only */
+#define SQLITE_OPEN_URI              0x00000040  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_MEMORY           0x00000080  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_MAIN_DB          0x00000100  /* VFS only */
+#define SQLITE_OPEN_TEMP_DB          0x00000200  /* VFS only */
+#define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
+#define SQLITE_OPEN_MAIN_JOURNAL     0x00000800  /* VFS only */
+#define SQLITE_OPEN_TEMP_JOURNAL     0x00001000  /* VFS only */
+#define SQLITE_OPEN_SUBJOURNAL       0x00002000  /* VFS only */
+#define SQLITE_OPEN_SUPER_JOURNAL    0x00004000  /* VFS only */
+#define SQLITE_OPEN_NOMUTEX          0x00008000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_FULLMUTEX        0x00010000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_SHAREDCACHE      0x00020000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_PRIVATECACHE     0x00040000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_WAL              0x00080000  /* VFS only */
+#define SQLITE_OPEN_NOFOLLOW         0x01000000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_EXRESCODE        0x02000000  /* Extended result codes */
+
+/* Reserved:                         0x00F00000 */
+/* Legacy compatibility: */
+#define SQLITE_OPEN_MASTER_JOURNAL   0x00004000  /* VFS only */
+
+
+/*
+** CAPI3REF: Device Characteristics
+**
+** The xDeviceCharacteristics method of the [sqlite3_io_methods]
+** object returns an integer which is a vector of these
+** bit values expressing I/O characteristics of the mass storage
+** device that holds the file that the [sqlite3_io_methods]
+** refers to.
+**
+** The SQLITE_IOCAP_ATOMIC property means that all writes of
+** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
+** mean that writes of blocks that are nnn bytes in size and
+** are aligned to an address which is an integer multiple of
+** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
+** that when data is appended to a file, the data is appended
+** first then the size of the file is extended, never the other
+** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
+** information is written to disk in the same order as calls
+** to xWrite().  The SQLITE_IOCAP_POWERSAFE_OVERWRITE property means that
+** after reboot following a crash or power loss, the only bytes in a
+** file that were written at the application level might have changed
+** and that adjacent bytes, even bytes within the same sector are
+** guaranteed to be unchanged.  The SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
+** flag indicates that a file cannot be deleted when open.  The
+** SQLITE_IOCAP_IMMUTABLE flag indicates that the file is on
+** read-only media and cannot be changed even by processes with
+** elevated privileges.
+**
+** The SQLITE_IOCAP_BATCH_ATOMIC property means that the underlying
+** filesystem supports doing multiple write operations atomically when those
+** write operations are bracketed by [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] and
+** [SQLITE_FCNTL_COMMIT_ATOMIC_WRITE].
+*/
+#define SQLITE_IOCAP_ATOMIC                 0x00000001
+#define SQLITE_IOCAP_ATOMIC512              0x00000002
+#define SQLITE_IOCAP_ATOMIC1K               0x00000004
+#define SQLITE_IOCAP_ATOMIC2K               0x00000008
+#define SQLITE_IOCAP_ATOMIC4K               0x00000010
+#define SQLITE_IOCAP_ATOMIC8K               0x00000020
+#define SQLITE_IOCAP_ATOMIC16K              0x00000040
+#define SQLITE_IOCAP_ATOMIC32K              0x00000080
+#define SQLITE_IOCAP_ATOMIC64K              0x00000100
+#define SQLITE_IOCAP_SAFE_APPEND            0x00000200
+#define SQLITE_IOCAP_SEQUENTIAL             0x00000400
+#define SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN  0x00000800
+#define SQLITE_IOCAP_POWERSAFE_OVERWRITE    0x00001000
+#define SQLITE_IOCAP_IMMUTABLE              0x00002000
+#define SQLITE_IOCAP_BATCH_ATOMIC           0x00004000
+
+/*
+** CAPI3REF: File Locking Levels
+**
+** SQLite uses one of these integer values as the second
+** argument to calls it makes to the xLock() and xUnlock() methods
+** of an [sqlite3_io_methods] object.  These values are ordered from
+** lest restrictive to most restrictive.
+**
+** The argument to xLock() is always SHARED or higher.  The argument to
+** xUnlock is either SHARED or NONE.
+*/
+#define SQLITE_LOCK_NONE          0       /* xUnlock() only */
+#define SQLITE_LOCK_SHARED        1       /* xLock() or xUnlock() */
+#define SQLITE_LOCK_RESERVED      2       /* xLock() only */
+#define SQLITE_LOCK_PENDING       3       /* xLock() only */
+#define SQLITE_LOCK_EXCLUSIVE     4       /* xLock() only */
+
+/*
+** CAPI3REF: Synchronization Type Flags
+**
+** When SQLite invokes the xSync() method of an
+** [sqlite3_io_methods] object it uses a combination of
+** these integer values as the second argument.
+**
+** When the SQLITE_SYNC_DATAONLY flag is used, it means that the
+** sync operation only needs to flush data to mass storage.  Inode
+** information need not be flushed. If the lower four bits of the flag
+** equal SQLITE_SYNC_NORMAL, that means to use normal fsync() semantics.
+** If the lower four bits equal SQLITE_SYNC_FULL, that means
+** to use Mac OS X style fullsync instead of fsync().
+**
+** Do not confuse the SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL flags
+** with the [PRAGMA synchronous]=NORMAL and [PRAGMA synchronous]=FULL
+** settings.  The [synchronous pragma] determines when calls to the
+** xSync VFS method occur and applies uniformly across all platforms.
+** The SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL flags determine how
+** energetic or rigorous or forceful the sync operations are and
+** only make a difference on Mac OSX for the default SQLite code.
+** (Third-party VFS implementations might also make the distinction
+** between SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL, but among the
+** operating systems natively supported by SQLite, only Mac OSX
+** cares about the difference.)
+*/
+#define SQLITE_SYNC_NORMAL        0x00002
+#define SQLITE_SYNC_FULL          0x00003
+#define SQLITE_SYNC_DATAONLY      0x00010
+
+/*
+** CAPI3REF: OS Interface Open File Handle
+**
+** An [sqlite3_file] object represents an open file in the
+** [sqlite3_vfs | OS interface layer].  Individual OS interface
+** implementations will
+** want to subclass this object by appending additional fields
+** for their own use.  The pMethods entry is a pointer to an
+** [sqlite3_io_methods] object that defines methods for performing
+** I/O operations on the open file.
+*/
+typedef struct sqlite3_file sqlite3_file;
+struct sqlite3_file {
+  const struct sqlite3_io_methods *pMethods;  /* Methods for an open file */
+};
+
+/*
+** CAPI3REF: OS Interface File Virtual Methods Object
+**
+** Every file opened by the [sqlite3_vfs.xOpen] method populates an
+** [sqlite3_file] object (or, more commonly, a subclass of the
+** [sqlite3_file] object) with a pointer to an instance of this object.
+** This object defines the methods used to perform various operations
+** against the open file represented by the [sqlite3_file] object.
+**
+** If the [sqlite3_vfs.xOpen] method sets the sqlite3_file.pMethods element
+** to a non-NULL pointer, then the sqlite3_io_methods.xClose method
+** may be invoked even if the [sqlite3_vfs.xOpen] reported that it failed.  The
+** only way to prevent a call to xClose following a failed [sqlite3_vfs.xOpen]
+** is for the [sqlite3_vfs.xOpen] to set the sqlite3_file.pMethods element
+** to NULL.
+**
+** The flags argument to xSync may be one of [SQLITE_SYNC_NORMAL] or
+** [SQLITE_SYNC_FULL].  The first choice is the normal fsync().
+** The second choice is a Mac OS X style fullsync.  The [SQLITE_SYNC_DATAONLY]
+** flag may be ORed in to indicate that only the data of the file
+** and not its inode needs to be synced.
+**
+** The integer values to xLock() and xUnlock() are one of
+** <ul>
+** <li> [SQLITE_LOCK_NONE],
+** <li> [SQLITE_LOCK_SHARED],
+** <li> [SQLITE_LOCK_RESERVED],
+** <li> [SQLITE_LOCK_PENDING], or
+** <li> [SQLITE_LOCK_EXCLUSIVE].
+** </ul>
+** xLock() upgrades the database file lock.  In other words, xLock() moves the
+** database file lock in the direction NONE toward EXCLUSIVE. The argument to
+** xLock() is always on of SHARED, RESERVED, PENDING, or EXCLUSIVE, never
+** SQLITE_LOCK_NONE.  If the database file lock is already at or above the
+** requested lock, then the call to xLock() is a no-op.
+** xUnlock() downgrades the database file lock to either SHARED or NONE.
+*  If the lock is already at or below the requested lock state, then the call
+** to xUnlock() is a no-op.
+** The xCheckReservedLock() method checks whether any database connection,
+** either in this process or in some other process, is holding a RESERVED,
+** PENDING, or EXCLUSIVE lock on the file.  It returns true
+** if such a lock exists and false otherwise.
+**
+** The xFileControl() method is a generic interface that allows custom
+** VFS implementations to directly control an open file using the
+** [sqlite3_file_control()] interface.  The second "op" argument is an
+** integer opcode.  The third argument is a generic pointer intended to
+** point to a structure that may contain arguments or space in which to
+** write return values.  Potential uses for xFileControl() might be
+** functions to enable blocking locks with timeouts, to change the
+** locking strategy (for example to use dot-file locks), to inquire
+** about the status of a lock, or to break stale locks.  The SQLite
+** core reserves all opcodes less than 100 for its own use.
+** A [file control opcodes | list of opcodes] less than 100 is available.
+** Applications that define a custom xFileControl method should use opcodes
+** greater than 100 to avoid conflicts.  VFS implementations should
+** return [SQLITE_NOTFOUND] for file control opcodes that they do not
+** recognize.
+**
+** The xSectorSize() method returns the sector size of the
+** device that underlies the file.  The sector size is the
+** minimum write that can be performed without disturbing
+** other bytes in the file.  The xDeviceCharacteristics()
+** method returns a bit vector describing behaviors of the
+** underlying device:
+**
+** <ul>
+** <li> [SQLITE_IOCAP_ATOMIC]
+** <li> [SQLITE_IOCAP_ATOMIC512]
+** <li> [SQLITE_IOCAP_ATOMIC1K]
+** <li> [SQLITE_IOCAP_ATOMIC2K]
+** <li> [SQLITE_IOCAP_ATOMIC4K]
+** <li> [SQLITE_IOCAP_ATOMIC8K]
+** <li> [SQLITE_IOCAP_ATOMIC16K]
+** <li> [SQLITE_IOCAP_ATOMIC32K]
+** <li> [SQLITE_IOCAP_ATOMIC64K]
+** <li> [SQLITE_IOCAP_SAFE_APPEND]
+** <li> [SQLITE_IOCAP_SEQUENTIAL]
+** <li> [SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN]
+** <li> [SQLITE_IOCAP_POWERSAFE_OVERWRITE]
+** <li> [SQLITE_IOCAP_IMMUTABLE]
+** <li> [SQLITE_IOCAP_BATCH_ATOMIC]
+** </ul>
+**
+** The SQLITE_IOCAP_ATOMIC property means that all writes of
+** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
+** mean that writes of blocks that are nnn bytes in size and
+** are aligned to an address which is an integer multiple of
+** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
+** that when data is appended to a file, the data is appended
+** first then the size of the file is extended, never the other
+** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
+** information is written to disk in the same order as calls
+** to xWrite().
+**
+** If xRead() returns SQLITE_IOERR_SHORT_READ it must also fill
+** in the unread portions of the buffer with zeros.  A VFS that
+** fails to zero-fill short reads might seem to work.  However,
+** failure to zero-fill short reads will eventually lead to
+** database corruption.
+*/
+typedef struct sqlite3_io_methods sqlite3_io_methods;
+struct sqlite3_io_methods {
+  int iVersion;
+  int (*xClose)(sqlite3_file*);
+  int (*xRead)(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
+  int (*xTruncate)(sqlite3_file*, sqlite3_int64 size);
+  int (*xSync)(sqlite3_file*, int flags);
+  int (*xFileSize)(sqlite3_file*, sqlite3_int64 *pSize);
+  int (*xLock)(sqlite3_file*, int);
+  int (*xUnlock)(sqlite3_file*, int);
+  int (*xCheckReservedLock)(sqlite3_file*, int *pResOut);
+  int (*xFileControl)(sqlite3_file*, int op, void *pArg);
+  int (*xSectorSize)(sqlite3_file*);
+  int (*xDeviceCharacteristics)(sqlite3_file*);
+  /* Methods above are valid for version 1 */
+  int (*xShmMap)(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
+  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
+  void (*xShmBarrier)(sqlite3_file*);
+  int (*xShmUnmap)(sqlite3_file*, int deleteFlag);
+  /* Methods above are valid for version 2 */
+  int (*xFetch)(sqlite3_file*, sqlite3_int64 iOfst, int iAmt, void **pp);
+  int (*xUnfetch)(sqlite3_file*, sqlite3_int64 iOfst, void *p);
+  /* Methods above are valid for version 3 */
+  /* Additional methods may be added in future releases */
+};
+
+/*
+** CAPI3REF: Standard File Control Opcodes
+** KEYWORDS: {file control opcodes} {file control opcode}
+**
+** These integer constants are opcodes for the xFileControl method
+** of the [sqlite3_io_methods] object and for the [sqlite3_file_control()]
+** interface.
+**
+** <ul>
+** <li>[[SQLITE_FCNTL_LOCKSTATE]]
+** The [SQLITE_FCNTL_LOCKSTATE] opcode is used for debugging.  This
+** opcode causes the xFileControl method to write the current state of
+** the lock (one of [SQLITE_LOCK_NONE], [SQLITE_LOCK_SHARED],
+** [SQLITE_LOCK_RESERVED], [SQLITE_LOCK_PENDING], or [SQLITE_LOCK_EXCLUSIVE])
+** into an integer that the pArg argument points to.
+** This capability is only available if SQLite is compiled with [SQLITE_DEBUG].
+**
+** <li>[[SQLITE_FCNTL_SIZE_HINT]]
+** The [SQLITE_FCNTL_SIZE_HINT] opcode is used by SQLite to give the VFS
+** layer a hint of how large the database file will grow to be during the
+** current transaction.  This hint is not guaranteed to be accurate but it
+** is often close.  The underlying VFS might choose to preallocate database
+** file space based on this hint in order to help writes to the database
+** file run faster.
+**
+** <li>[[SQLITE_FCNTL_SIZE_LIMIT]]
+** The [SQLITE_FCNTL_SIZE_LIMIT] opcode is used by in-memory VFS that
+** implements [sqlite3_deserialize()] to set an upper bound on the size
+** of the in-memory database.  The argument is a pointer to a [sqlite3_int64].
+** If the integer pointed to is negative, then it is filled in with the
+** current limit.  Otherwise the limit is set to the larger of the value
+** of the integer pointed to and the current database size.  The integer
+** pointed to is set to the new limit.
+**
+** <li>[[SQLITE_FCNTL_CHUNK_SIZE]]
+** The [SQLITE_FCNTL_CHUNK_SIZE] opcode is used to request that the VFS
+** extends and truncates the database file in chunks of a size specified
+** by the user. The fourth argument to [sqlite3_file_control()] should
+** point to an integer (type int) containing the new chunk-size to use
+** for the nominated database. Allocating database file space in large
+** chunks (say 1MB at a time), may reduce file-system fragmentation and
+** improve performance on some systems.
+**
+** <li>[[SQLITE_FCNTL_FILE_POINTER]]
+** The [SQLITE_FCNTL_FILE_POINTER] opcode is used to obtain a pointer
+** to the [sqlite3_file] object associated with a particular database
+** connection.  See also [SQLITE_FCNTL_JOURNAL_POINTER].
+**
+** <li>[[SQLITE_FCNTL_JOURNAL_POINTER]]
+** The [SQLITE_FCNTL_JOURNAL_POINTER] opcode is used to obtain a pointer
+** to the [sqlite3_file] object associated with the journal file (either
+** the [rollback journal] or the [write-ahead log]) for a particular database
+** connection.  See also [SQLITE_FCNTL_FILE_POINTER].
+**
+** <li>[[SQLITE_FCNTL_SYNC_OMITTED]]
+** No longer in use.
+**
+** <li>[[SQLITE_FCNTL_SYNC]]
+** The [SQLITE_FCNTL_SYNC] opcode is generated internally by SQLite and
+** sent to the VFS immediately before the xSync method is invoked on a
+** database file descriptor. Or, if the xSync method is not invoked
+** because the user has configured SQLite with
+** [PRAGMA synchronous | PRAGMA synchronous=OFF] it is invoked in place
+** of the xSync method. In most cases, the pointer argument passed with
+** this file-control is NULL. However, if the database file is being synced
+** as part of a multi-database commit, the argument points to a nul-terminated
+** string containing the transactions super-journal file name. VFSes that
+** do not need this signal should silently ignore this opcode. Applications
+** should not call [sqlite3_file_control()] with this opcode as doing so may
+** disrupt the operation of the specialized VFSes that do require it.
+**
+** <li>[[SQLITE_FCNTL_COMMIT_PHASETWO]]
+** The [SQLITE_FCNTL_COMMIT_PHASETWO] opcode is generated internally by SQLite
+** and sent to the VFS after a transaction has been committed immediately
+** but before the database is unlocked. VFSes that do not need this signal
+** should silently ignore this opcode. Applications should not call
+** [sqlite3_file_control()] with this opcode as doing so may disrupt the
+** operation of the specialized VFSes that do require it.
+**
+** <li>[[SQLITE_FCNTL_WIN32_AV_RETRY]]
+** ^The [SQLITE_FCNTL_WIN32_AV_RETRY] opcode is used to configure automatic
+** retry counts and intervals for certain disk I/O operations for the
+** windows [VFS] in order to provide robustness in the presence of
+** anti-virus programs.  By default, the windows VFS will retry file read,
+** file write, and file delete operations up to 10 times, with a delay
+** of 25 milliseconds before the first retry and with the delay increasing
+** by an additional 25 milliseconds with each subsequent retry.  This
+** opcode allows these two values (10 retries and 25 milliseconds of delay)
+** to be adjusted.  The values are changed for all database connections
+** within the same process.  The argument is a pointer to an array of two
+** integers where the first integer is the new retry count and the second
+** integer is the delay.  If either integer is negative, then the setting
+** is not changed but instead the prior value of that setting is written
+** into the array entry, allowing the current retry settings to be
+** interrogated.  The zDbName parameter is ignored.
+**
+** <li>[[SQLITE_FCNTL_PERSIST_WAL]]
+** ^The [SQLITE_FCNTL_PERSIST_WAL] opcode is used to set or query the
+** persistent [WAL | Write Ahead Log] setting.  By default, the auxiliary
+** write ahead log ([WAL file]) and shared memory
+** files used for transaction control
+** are automatically deleted when the latest connection to the database
+** closes.  Setting persistent WAL mode causes those files to persist after
+** close.  Persisting the files is useful when other processes that do not
+** have write permission on the directory containing the database file want
+** to read the database file, as the WAL and shared memory files must exist
+** in order for the database to be readable.  The fourth parameter to
+** [sqlite3_file_control()] for this opcode should be a pointer to an integer.
+** That integer is 0 to disable persistent WAL mode or 1 to enable persistent
+** WAL mode.  If the integer is -1, then it is overwritten with the current
+** WAL persistence setting.
+**
+** <li>[[SQLITE_FCNTL_POWERSAFE_OVERWRITE]]
+** ^The [SQLITE_FCNTL_POWERSAFE_OVERWRITE] opcode is used to set or query the
+** persistent "powersafe-overwrite" or "PSOW" setting.  The PSOW setting
+** determines the [SQLITE_IOCAP_POWERSAFE_OVERWRITE] bit of the
+** xDeviceCharacteristics methods. The fourth parameter to
+** [sqlite3_file_control()] for this opcode should be a pointer to an integer.
+** That integer is 0 to disable zero-damage mode or 1 to enable zero-damage
+** mode.  If the integer is -1, then it is overwritten with the current
+** zero-damage mode setting.
+**
+** <li>[[SQLITE_FCNTL_OVERWRITE]]
+** ^The [SQLITE_FCNTL_OVERWRITE] opcode is invoked by SQLite after opening
+** a write transaction to indicate that, unless it is rolled back for some
+** reason, the entire database file will be overwritten by the current
+** transaction. This is used by VACUUM operations.
+**
+** <li>[[SQLITE_FCNTL_VFSNAME]]
+** ^The [SQLITE_FCNTL_VFSNAME] opcode can be used to obtain the names of
+** all [VFSes] in the VFS stack.  The names are of all VFS shims and the
+** final bottom-level VFS are written into memory obtained from
+** [sqlite3_malloc()] and the result is stored in the char* variable
+** that the fourth parameter of [sqlite3_file_control()] points to.
+** The caller is responsible for freeing the memory when done.  As with
+** all file-control actions, there is no guarantee that this will actually
+** do anything.  Callers should initialize the char* variable to a NULL
+** pointer in case this file-control is not implemented.  This file-control
+** is intended for diagnostic use only.
+**
+** <li>[[SQLITE_FCNTL_VFS_POINTER]]
+** ^The [SQLITE_FCNTL_VFS_POINTER] opcode finds a pointer to the top-level
+** [VFSes] currently in use.  ^(The argument X in
+** sqlite3_file_control(db,SQLITE_FCNTL_VFS_POINTER,X) must be
+** of type "[sqlite3_vfs] **".  This opcodes will set *X
+** to a pointer to the top-level VFS.)^
+** ^When there are multiple VFS shims in the stack, this opcode finds the
+** upper-most shim only.
+**
+** <li>[[SQLITE_FCNTL_PRAGMA]]
+** ^Whenever a [PRAGMA] statement is parsed, an [SQLITE_FCNTL_PRAGMA]
+** file control is sent to the open [sqlite3_file] object corresponding
+** to the database file to which the pragma statement refers. ^The argument
+** to the [SQLITE_FCNTL_PRAGMA] file control is an array of
+** pointers to strings (char**) in which the second element of the array
+** is the name of the pragma and the third element is the argument to the
+** pragma or NULL if the pragma has no argument.  ^The handler for an
+** [SQLITE_FCNTL_PRAGMA] file control can optionally make the first element
+** of the char** argument point to a string obtained from [sqlite3_mprintf()]
+** or the equivalent and that string will become the result of the pragma or
+** the error message if the pragma fails. ^If the
+** [SQLITE_FCNTL_PRAGMA] file control returns [SQLITE_NOTFOUND], then normal
+** [PRAGMA] processing continues.  ^If the [SQLITE_FCNTL_PRAGMA]
+** file control returns [SQLITE_OK], then the parser assumes that the
+** VFS has handled the PRAGMA itself and the parser generates a no-op
+** prepared statement if result string is NULL, or that returns a copy
+** of the result string if the string is non-NULL.
+** ^If the [SQLITE_FCNTL_PRAGMA] file control returns
+** any result code other than [SQLITE_OK] or [SQLITE_NOTFOUND], that means
+** that the VFS encountered an error while handling the [PRAGMA] and the
+** compilation of the PRAGMA fails with an error.  ^The [SQLITE_FCNTL_PRAGMA]
+** file control occurs at the beginning of pragma statement analysis and so
+** it is able to override built-in [PRAGMA] statements.
+**
+** <li>[[SQLITE_FCNTL_BUSYHANDLER]]
+** ^The [SQLITE_FCNTL_BUSYHANDLER]
+** file-control may be invoked by SQLite on the database file handle
+** shortly after it is opened in order to provide a custom VFS with access
+** to the connection's busy-handler callback. The argument is of type (void**)
+** - an array of two (void *) values. The first (void *) actually points
+** to a function of type (int (*)(void *)). In order to invoke the connection's
+** busy-handler, this function should be invoked with the second (void *) in
+** the array as the only argument. If it returns non-zero, then the operation
+** should be retried. If it returns zero, the custom VFS should abandon the
+** current operation.
+**
+** <li>[[SQLITE_FCNTL_TEMPFILENAME]]
+** ^Applications can invoke the [SQLITE_FCNTL_TEMPFILENAME] file-control
+** to have SQLite generate a
+** temporary filename using the same algorithm that is followed to generate
+** temporary filenames for TEMP tables and other internal uses.  The
+** argument should be a char** which will be filled with the filename
+** written into memory obtained from [sqlite3_malloc()].  The caller should
+** invoke [sqlite3_free()] on the result to avoid a memory leak.
+**
+** <li>[[SQLITE_FCNTL_MMAP_SIZE]]
+** The [SQLITE_FCNTL_MMAP_SIZE] file control is used to query or set the
+** maximum number of bytes that will be used for memory-mapped I/O.
+** The argument is a pointer to a value of type sqlite3_int64 that
+** is an advisory maximum number of bytes in the file to memory map.  The
+** pointer is overwritten with the old value.  The limit is not changed if
+** the value originally pointed to is negative, and so the current limit
+** can be queried by passing in a pointer to a negative number.  This
+** file-control is used internally to implement [PRAGMA mmap_size].
+**
+** <li>[[SQLITE_FCNTL_TRACE]]
+** The [SQLITE_FCNTL_TRACE] file control provides advisory information
+** to the VFS about what the higher layers of the SQLite stack are doing.
+** This file control is used by some VFS activity tracing [shims].
+** The argument is a zero-terminated string.  Higher layers in the
+** SQLite stack may generate instances of this file control if
+** the [SQLITE_USE_FCNTL_TRACE] compile-time option is enabled.
+**
+** <li>[[SQLITE_FCNTL_HAS_MOVED]]
+** The [SQLITE_FCNTL_HAS_MOVED] file control interprets its argument as a
+** pointer to an integer and it writes a boolean into that integer depending
+** on whether or not the file has been renamed, moved, or deleted since it
+** was first opened.
+**
+** <li>[[SQLITE_FCNTL_WIN32_GET_HANDLE]]
+** The [SQLITE_FCNTL_WIN32_GET_HANDLE] opcode can be used to obtain the
+** underlying native file handle associated with a file handle.  This file
+** control interprets its argument as a pointer to a native file handle and
+** writes the resulting value there.
+**
+** <li>[[SQLITE_FCNTL_WIN32_SET_HANDLE]]
+** The [SQLITE_FCNTL_WIN32_SET_HANDLE] opcode is used for debugging.  This
+** opcode causes the xFileControl method to swap the file handle with the one
+** pointed to by the pArg argument.  This capability is used during testing
+** and only needs to be supported when SQLITE_TEST is defined.
+**
+** <li>[[SQLITE_FCNTL_WAL_BLOCK]]
+** The [SQLITE_FCNTL_WAL_BLOCK] is a signal to the VFS layer that it might
+** be advantageous to block on the next WAL lock if the lock is not immediately
+** available.  The WAL subsystem issues this signal during rare
+** circumstances in order to fix a problem with priority inversion.
+** Applications should <em>not</em> use this file-control.
+**
+** <li>[[SQLITE_FCNTL_ZIPVFS]]
+** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
+** VFS should return SQLITE_NOTFOUND for this opcode.
+**
+** <li>[[SQLITE_FCNTL_RBU]]
+** The [SQLITE_FCNTL_RBU] opcode is implemented by the special VFS used by
+** the RBU extension only.  All other VFS should return SQLITE_NOTFOUND for
+** this opcode.
+**
+** <li>[[SQLITE_FCNTL_BEGIN_ATOMIC_WRITE]]
+** If the [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] opcode returns SQLITE_OK, then
+** the file descriptor is placed in "batch write mode", which
+** means all subsequent write operations will be deferred and done
+** atomically at the next [SQLITE_FCNTL_COMMIT_ATOMIC_WRITE].  Systems
+** that do not support batch atomic writes will return SQLITE_NOTFOUND.
+** ^Following a successful SQLITE_FCNTL_BEGIN_ATOMIC_WRITE and prior to
+** the closing [SQLITE_FCNTL_COMMIT_ATOMIC_WRITE] or
+** [SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE], SQLite will make
+** no VFS interface calls on the same [sqlite3_file] file descriptor
+** except for calls to the xWrite method and the xFileControl method
+** with [SQLITE_FCNTL_SIZE_HINT].
+**
+** <li>[[SQLITE_FCNTL_COMMIT_ATOMIC_WRITE]]
+** The [SQLITE_FCNTL_COMMIT_ATOMIC_WRITE] opcode causes all write
+** operations since the previous successful call to
+** [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] to be performed atomically.
+** This file control returns [SQLITE_OK] if and only if the writes were
+** all performed successfully and have been committed to persistent storage.
+** ^Regardless of whether or not it is successful, this file control takes
+** the file descriptor out of batch write mode so that all subsequent
+** write operations are independent.
+** ^SQLite will never invoke SQLITE_FCNTL_COMMIT_ATOMIC_WRITE without
+** a prior successful call to [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE].
+**
+** <li>[[SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE]]
+** The [SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE] opcode causes all write
+** operations since the previous successful call to
+** [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] to be rolled back.
+** ^This file control takes the file descriptor out of batch write mode
+** so that all subsequent write operations are independent.
+** ^SQLite will never invoke SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE without
+** a prior successful call to [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE].
+**
+** <li>[[SQLITE_FCNTL_LOCK_TIMEOUT]]
+** The [SQLITE_FCNTL_LOCK_TIMEOUT] opcode is used to configure a VFS
+** to block for up to M milliseconds before failing when attempting to
+** obtain a file lock using the xLock or xShmLock methods of the VFS.
+** The parameter is a pointer to a 32-bit signed integer that contains
+** the value that M is to be set to. Before returning, the 32-bit signed
+** integer is overwritten with the previous value of M.
+**
+** <li>[[SQLITE_FCNTL_DATA_VERSION]]
+** The [SQLITE_FCNTL_DATA_VERSION] opcode is used to detect changes to
+** a database file.  The argument is a pointer to a 32-bit unsigned integer.
+** The "data version" for the pager is written into the pointer.  The
+** "data version" changes whenever any change occurs to the corresponding
+** database file, either through SQL statements on the same database
+** connection or through transactions committed by separate database
+** connections possibly in other processes. The [sqlite3_total_changes()]
+** interface can be used to find if any database on the connection has changed,
+** but that interface responds to changes on TEMP as well as MAIN and does
+** not provide a mechanism to detect changes to MAIN only.  Also, the
+** [sqlite3_total_changes()] interface responds to internal changes only and
+** omits changes made by other database connections.  The
+** [PRAGMA data_version] command provides a mechanism to detect changes to
+** a single attached database that occur due to other database connections,
+** but omits changes implemented by the database connection on which it is
+** called.  This file control is the only mechanism to detect changes that
+** happen either internally or externally and that are associated with
+** a particular attached database.
+**
+** <li>[[SQLITE_FCNTL_CKPT_START]]
+** The [SQLITE_FCNTL_CKPT_START] opcode is invoked from within a checkpoint
+** in wal mode before the client starts to copy pages from the wal
+** file to the database file.
+**
+** <li>[[SQLITE_FCNTL_CKPT_DONE]]
+** The [SQLITE_FCNTL_CKPT_DONE] opcode is invoked from within a checkpoint
+** in wal mode after the client has finished copying pages from the wal
+** file to the database file, but before the *-shm file is updated to
+** record the fact that the pages have been checkpointed.
+**
+** <li>[[SQLITE_FCNTL_EXTERNAL_READER]]
+** The EXPERIMENTAL [SQLITE_FCNTL_EXTERNAL_READER] opcode is used to detect
+** whether or not there is a database client in another process with a wal-mode
+** transaction open on the database or not. It is only available on unix.The
+** (void*) argument passed with this file-control should be a pointer to a
+** value of type (int). The integer value is set to 1 if the database is a wal
+** mode database and there exists at least one client in another process that
+** currently has an SQL transaction open on the database. It is set to 0 if
+** the database is not a wal-mode db, or if there is no such connection in any
+** other process. This opcode cannot be used to detect transactions opened
+** by clients within the current process, only within other processes.
+**
+** <li>[[SQLITE_FCNTL_CKSM_FILE]]
+** The [SQLITE_FCNTL_CKSM_FILE] opcode is for use internally by the
+** [checksum VFS shim] only.
+**
+** <li>[[SQLITE_FCNTL_RESET_CACHE]]
+** If there is currently no transaction open on the database, and the
+** database is not a temp db, then the [SQLITE_FCNTL_RESET_CACHE] file-control
+** purges the contents of the in-memory page cache. If there is an open
+** transaction, or if the db is a temp-db, this opcode is a no-op, not an error.
+** </ul>
+*/
+#define SQLITE_FCNTL_LOCKSTATE               1
+#define SQLITE_FCNTL_GET_LOCKPROXYFILE       2
+#define SQLITE_FCNTL_SET_LOCKPROXYFILE       3
+#define SQLITE_FCNTL_LAST_ERRNO              4
+#define SQLITE_FCNTL_SIZE_HINT               5
+#define SQLITE_FCNTL_CHUNK_SIZE              6
+#define SQLITE_FCNTL_FILE_POINTER            7
+#define SQLITE_FCNTL_SYNC_OMITTED            8
+#define SQLITE_FCNTL_WIN32_AV_RETRY          9
+#define SQLITE_FCNTL_PERSIST_WAL            10
+#define SQLITE_FCNTL_OVERWRITE              11
+#define SQLITE_FCNTL_VFSNAME                12
+#define SQLITE_FCNTL_POWERSAFE_OVERWRITE    13
+#define SQLITE_FCNTL_PRAGMA                 14
+#define SQLITE_FCNTL_BUSYHANDLER            15
+#define SQLITE_FCNTL_TEMPFILENAME           16
+#define SQLITE_FCNTL_MMAP_SIZE              18
+#define SQLITE_FCNTL_TRACE                  19
+#define SQLITE_FCNTL_HAS_MOVED              20
+#define SQLITE_FCNTL_SYNC                   21
+#define SQLITE_FCNTL_COMMIT_PHASETWO        22
+#define SQLITE_FCNTL_WIN32_SET_HANDLE       23
+#define SQLITE_FCNTL_WAL_BLOCK              24
+#define SQLITE_FCNTL_ZIPVFS                 25
+#define SQLITE_FCNTL_RBU                    26
+#define SQLITE_FCNTL_VFS_POINTER            27
+#define SQLITE_FCNTL_JOURNAL_POINTER        28
+#define SQLITE_FCNTL_WIN32_GET_HANDLE       29
+#define SQLITE_FCNTL_PDB                    30
+#define SQLITE_FCNTL_BEGIN_ATOMIC_WRITE     31
+#define SQLITE_FCNTL_COMMIT_ATOMIC_WRITE    32
+#define SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE  33
+#define SQLITE_FCNTL_LOCK_TIMEOUT           34
+#define SQLITE_FCNTL_DATA_VERSION           35
+#define SQLITE_FCNTL_SIZE_LIMIT             36
+#define SQLITE_FCNTL_CKPT_DONE              37
+#define SQLITE_FCNTL_RESERVE_BYTES          38
+#define SQLITE_FCNTL_CKPT_START             39
+#define SQLITE_FCNTL_EXTERNAL_READER        40
+#define SQLITE_FCNTL_CKSM_FILE              41
+#define SQLITE_FCNTL_RESET_CACHE            42
+
+/* deprecated names */
+#define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
+#define SQLITE_SET_LOCKPROXYFILE      SQLITE_FCNTL_SET_LOCKPROXYFILE
+#define SQLITE_LAST_ERRNO             SQLITE_FCNTL_LAST_ERRNO
+
+
+/*
+** CAPI3REF: Mutex Handle
+**
+** The mutex module within SQLite defines [sqlite3_mutex] to be an
+** abstract type for a mutex object.  The SQLite core never looks
+** at the internal representation of an [sqlite3_mutex].  It only
+** deals with pointers to the [sqlite3_mutex] object.
+**
+** Mutexes are created using [sqlite3_mutex_alloc()].
+*/
+typedef struct sqlite3_mutex sqlite3_mutex;
+
+/*
+** CAPI3REF: Loadable Extension Thunk
+**
+** A pointer to the opaque sqlite3_api_routines structure is passed as
+** the third parameter to entry points of [loadable extensions].  This
+** structure must be typedefed in order to work around compiler warnings
+** on some platforms.
+*/
+typedef struct sqlite3_api_routines sqlite3_api_routines;
+
+/*
+** CAPI3REF: File Name
+**
+** Type [sqlite3_filename] is used by SQLite to pass filenames to the
+** xOpen method of a [VFS]. It may be cast to (const char*) and treated
+** as a normal, nul-terminated, UTF-8 buffer containing the filename, but
+** may also be passed to special APIs such as:
+**
+** <ul>
+** <li>  sqlite3_filename_database()
+** <li>  sqlite3_filename_journal()
+** <li>  sqlite3_filename_wal()
+** <li>  sqlite3_uri_parameter()
+** <li>  sqlite3_uri_boolean()
+** <li>  sqlite3_uri_int64()
+** <li>  sqlite3_uri_key()
+** </ul>
+*/
+typedef const char *sqlite3_filename;
+
+/*
+** CAPI3REF: OS Interface Object
+**
+** An instance of the sqlite3_vfs object defines the interface between
+** the SQLite core and the underlying operating system.  The "vfs"
+** in the name of the object stands for "virtual file system".  See
+** the [VFS | VFS documentation] for further information.
+**
+** The VFS interface is sometimes extended by adding new methods onto
+** the end.  Each time such an extension occurs, the iVersion field
+** is incremented.  The iVersion value started out as 1 in
+** SQLite [version 3.5.0] on [dateof:3.5.0], then increased to 2
+** with SQLite [version 3.7.0] on [dateof:3.7.0], and then increased
+** to 3 with SQLite [version 3.7.6] on [dateof:3.7.6].  Additional fields
+** may be appended to the sqlite3_vfs object and the iVersion value
+** may increase again in future versions of SQLite.
+** Note that due to an oversight, the structure
+** of the sqlite3_vfs object changed in the transition from
+** SQLite [version 3.5.9] to [version 3.6.0] on [dateof:3.6.0]
+** and yet the iVersion field was not increased.
+**
+** The szOsFile field is the size of the subclassed [sqlite3_file]
+** structure used by this VFS.  mxPathname is the maximum length of
+** a pathname in this VFS.
+**
+** Registered sqlite3_vfs objects are kept on a linked list formed by
+** the pNext pointer.  The [sqlite3_vfs_register()]
+** and [sqlite3_vfs_unregister()] interfaces manage this list
+** in a thread-safe way.  The [sqlite3_vfs_find()] interface
+** searches the list.  Neither the application code nor the VFS
+** implementation should use the pNext pointer.
+**
+** The pNext field is the only field in the sqlite3_vfs
+** structure that SQLite will ever modify.  SQLite will only access
+** or modify this field while holding a particular static mutex.
+** The application should never modify anything within the sqlite3_vfs
+** object once the object has been registered.
+**
+** The zName field holds the name of the VFS module.  The name must
+** be unique across all VFS modules.
+**
+** [[sqlite3_vfs.xOpen]]
+** ^SQLite guarantees that the zFilename parameter to xOpen
+** is either a NULL pointer or string obtained
+** from xFullPathname() with an optional suffix added.
+** ^If a suffix is added to the zFilename parameter, it will
+** consist of a single "-" character followed by no more than
+** 11 alphanumeric and/or "-" characters.
+** ^SQLite further guarantees that
+** the string will be valid and unchanged until xClose() is
+** called. Because of the previous sentence,
+** the [sqlite3_file] can safely store a pointer to the
+** filename if it needs to remember the filename for some reason.
+** If the zFilename parameter to xOpen is a NULL pointer then xOpen
+** must invent its own temporary name for the file.  ^Whenever the
+** xFilename parameter is NULL it will also be the case that the
+** flags parameter will include [SQLITE_OPEN_DELETEONCLOSE].
+**
+** The flags argument to xOpen() includes all bits set in
+** the flags argument to [sqlite3_open_v2()].  Or if [sqlite3_open()]
+** or [sqlite3_open16()] is used, then flags includes at least
+** [SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE].
+** If xOpen() opens a file read-only then it sets *pOutFlags to
+** include [SQLITE_OPEN_READONLY].  Other bits in *pOutFlags may be set.
+**
+** ^(SQLite will also add one of the following flags to the xOpen()
+** call, depending on the object being opened:
+**
+** <ul>
+** <li>  [SQLITE_OPEN_MAIN_DB]
+** <li>  [SQLITE_OPEN_MAIN_JOURNAL]
+** <li>  [SQLITE_OPEN_TEMP_DB]
+** <li>  [SQLITE_OPEN_TEMP_JOURNAL]
+** <li>  [SQLITE_OPEN_TRANSIENT_DB]
+** <li>  [SQLITE_OPEN_SUBJOURNAL]
+** <li>  [SQLITE_OPEN_SUPER_JOURNAL]
+** <li>  [SQLITE_OPEN_WAL]
+** </ul>)^
+**
+** The file I/O implementation can use the object type flags to
+** change the way it deals with files.  For example, an application
+** that does not care about crash recovery or rollback might make
+** the open of a journal file a no-op.  Writes to this journal would
+** also be no-ops, and any attempt to read the journal would return
+** SQLITE_IOERR.  Or the implementation might recognize that a database
+** file will be doing page-aligned sector reads and writes in a random
+** order and set up its I/O subsystem accordingly.
+**
+** SQLite might also add one of the following flags to the xOpen method:
+**
+** <ul>
+** <li> [SQLITE_OPEN_DELETEONCLOSE]
+** <li> [SQLITE_OPEN_EXCLUSIVE]
+** </ul>
+**
+** The [SQLITE_OPEN_DELETEONCLOSE] flag means the file should be
+** deleted when it is closed.  ^The [SQLITE_OPEN_DELETEONCLOSE]
+** will be set for TEMP databases and their journals, transient
+** databases, and subjournals.
+**
+** ^The [SQLITE_OPEN_EXCLUSIVE] flag is always used in conjunction
+** with the [SQLITE_OPEN_CREATE] flag, which are both directly
+** analogous to the O_EXCL and O_CREAT flags of the POSIX open()
+** API.  The SQLITE_OPEN_EXCLUSIVE flag, when paired with the
+** SQLITE_OPEN_CREATE, is used to indicate that file should always
+** be created, and that it is an error if it already exists.
+** It is <i>not</i> used to indicate the file should be opened
+** for exclusive access.
+**
+** ^At least szOsFile bytes of memory are allocated by SQLite
+** to hold the [sqlite3_file] structure passed as the third
+** argument to xOpen.  The xOpen method does not have to
+** allocate the structure; it should just fill it in.  Note that
+** the xOpen method must set the sqlite3_file.pMethods to either
+** a valid [sqlite3_io_methods] object or to NULL.  xOpen must do
+** this even if the open fails.  SQLite expects that the sqlite3_file.pMethods
+** element will be valid after xOpen returns regardless of the success
+** or failure of the xOpen call.
+**
+** [[sqlite3_vfs.xAccess]]
+** ^The flags argument to xAccess() may be [SQLITE_ACCESS_EXISTS]
+** to test for the existence of a file, or [SQLITE_ACCESS_READWRITE] to
+** test whether a file is readable and writable, or [SQLITE_ACCESS_READ]
+** to test whether a file is at least readable.  The SQLITE_ACCESS_READ
+** flag is never actually used and is not implemented in the built-in
+** VFSes of SQLite.  The file is named by the second argument and can be a
+** directory. The xAccess method returns [SQLITE_OK] on success or some
+** non-zero error code if there is an I/O error or if the name of
+** the file given in the second argument is illegal.  If SQLITE_OK
+** is returned, then non-zero or zero is written into *pResOut to indicate
+** whether or not the file is accessible.
+**
+** ^SQLite will always allocate at least mxPathname+1 bytes for the
+** output buffer xFullPathname.  The exact size of the output buffer
+** is also passed as a parameter to both  methods. If the output buffer
+** is not large enough, [SQLITE_CANTOPEN] should be returned. Since this is
+** handled as a fatal error by SQLite, vfs implementations should endeavor
+** to prevent this by setting mxPathname to a sufficiently large value.
+**
+** The xRandomness(), xSleep(), xCurrentTime(), and xCurrentTimeInt64()
+** interfaces are not strictly a part of the filesystem, but they are
+** included in the VFS structure for completeness.
+** The xRandomness() function attempts to return nBytes bytes
+** of good-quality randomness into zOut.  The return value is
+** the actual number of bytes of randomness obtained.
+** The xSleep() method causes the calling thread to sleep for at
+** least the number of microseconds given.  ^The xCurrentTime()
+** method returns a Julian Day Number for the current date and time as
+** a floating point value.
+** ^The xCurrentTimeInt64() method returns, as an integer, the Julian
+** Day Number multiplied by 86400000 (the number of milliseconds in
+** a 24-hour day).
+** ^SQLite will use the xCurrentTimeInt64() method to get the current
+** date and time if that method is available (if iVersion is 2 or
+** greater and the function pointer is not NULL) and will fall back
+** to xCurrentTime() if xCurrentTimeInt64() is unavailable.
+**
+** ^The xSetSystemCall(), xGetSystemCall(), and xNestSystemCall() interfaces
+** are not used by the SQLite core.  These optional interfaces are provided
+** by some VFSes to facilitate testing of the VFS code. By overriding
+** system calls with functions under its control, a test program can
+** simulate faults and error conditions that would otherwise be difficult
+** or impossible to induce.  The set of system calls that can be overridden
+** varies from one VFS to another, and from one version of the same VFS to the
+** next.  Applications that use these interfaces must be prepared for any
+** or all of these interfaces to be NULL or for their behavior to change
+** from one release to the next.  Applications must not attempt to access
+** any of these methods if the iVersion of the VFS is less than 3.
+*/
+typedef struct sqlite3_vfs sqlite3_vfs;
+typedef void (*sqlite3_syscall_ptr)(void);
+struct sqlite3_vfs {
+  int iVersion;            /* Structure version number (currently 3) */
+  int szOsFile;            /* Size of subclassed sqlite3_file */
+  int mxPathname;          /* Maximum file pathname length */
+  sqlite3_vfs *pNext;      /* Next registered VFS */
+  const char *zName;       /* Name of this virtual file system */
+  void *pAppData;          /* Pointer to application-specific data */
+  int (*xOpen)(sqlite3_vfs*, sqlite3_filename zName, sqlite3_file*,
+               int flags, int *pOutFlags);
+  int (*xDelete)(sqlite3_vfs*, const char *zName, int syncDir);
+  int (*xAccess)(sqlite3_vfs*, const char *zName, int flags, int *pResOut);
+  int (*xFullPathname)(sqlite3_vfs*, const char *zName, int nOut, char *zOut);
+  void *(*xDlOpen)(sqlite3_vfs*, const char *zFilename);
+  void (*xDlError)(sqlite3_vfs*, int nByte, char *zErrMsg);
+  void (*(*xDlSym)(sqlite3_vfs*,void*, const char *zSymbol))(void);
+  void (*xDlClose)(sqlite3_vfs*, void*);
+  int (*xRandomness)(sqlite3_vfs*, int nByte, char *zOut);
+  int (*xSleep)(sqlite3_vfs*, int microseconds);
+  int (*xCurrentTime)(sqlite3_vfs*, double*);
+  int (*xGetLastError)(sqlite3_vfs*, int, char *);
+  /*
+  ** The methods above are in version 1 of the sqlite_vfs object
+  ** definition.  Those that follow are added in version 2 or later
+  */
+  int (*xCurrentTimeInt64)(sqlite3_vfs*, sqlite3_int64*);
+  /*
+  ** The methods above are in versions 1 and 2 of the sqlite_vfs object.
+  ** Those below are for version 3 and greater.
+  */
+  int (*xSetSystemCall)(sqlite3_vfs*, const char *zName, sqlite3_syscall_ptr);
+  sqlite3_syscall_ptr (*xGetSystemCall)(sqlite3_vfs*, const char *zName);
+  const char *(*xNextSystemCall)(sqlite3_vfs*, const char *zName);
+  /*
+  ** The methods above are in versions 1 through 3 of the sqlite_vfs object.
+  ** New fields may be appended in future versions.  The iVersion
+  ** value will increment whenever this happens.
+  */
+};
+
+/*
+** CAPI3REF: Flags for the xAccess VFS method
+**
+** These integer constants can be used as the third parameter to
+** the xAccess method of an [sqlite3_vfs] object.  They determine
+** what kind of permissions the xAccess method is looking for.
+** With SQLITE_ACCESS_EXISTS, the xAccess method
+** simply checks whether the file exists.
+** With SQLITE_ACCESS_READWRITE, the xAccess method
+** checks whether the named directory is both readable and writable
+** (in other words, if files can be added, removed, and renamed within
+** the directory).
+** The SQLITE_ACCESS_READWRITE constant is currently used only by the
+** [temp_store_directory pragma], though this could change in a future
+** release of SQLite.
+** With SQLITE_ACCESS_READ, the xAccess method
+** checks whether the file is readable.  The SQLITE_ACCESS_READ constant is
+** currently unused, though it might be used in a future release of
+** SQLite.
+*/
+#define SQLITE_ACCESS_EXISTS    0
+#define SQLITE_ACCESS_READWRITE 1   /* Used by PRAGMA temp_store_directory */
+#define SQLITE_ACCESS_READ      2   /* Unused */
+
+/*
+** CAPI3REF: Flags for the xShmLock VFS method
+**
+** These integer constants define the various locking operations
+** allowed by the xShmLock method of [sqlite3_io_methods].  The
+** following are the only legal combinations of flags to the
+** xShmLock method:
+**
+** <ul>
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
+** </ul>
+**
+** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
+** was given on the corresponding lock.
+**
+** The xShmLock method can transition between unlocked and SHARED or
+** between unlocked and EXCLUSIVE.  It cannot transition between SHARED
+** and EXCLUSIVE.
+*/
+#define SQLITE_SHM_UNLOCK       1
+#define SQLITE_SHM_LOCK         2
+#define SQLITE_SHM_SHARED       4
+#define SQLITE_SHM_EXCLUSIVE    8
+
+/*
+** CAPI3REF: Maximum xShmLock index
+**
+** The xShmLock method on [sqlite3_io_methods] may use values
+** between 0 and this upper bound as its "offset" argument.
+** The SQLite core will never attempt to acquire or release a
+** lock outside of this range
+*/
+#define SQLITE_SHM_NLOCK        8
+
+
+/*
+** CAPI3REF: Initialize The SQLite Library
+**
+** ^The sqlite3_initialize() routine initializes the
+** SQLite library.  ^The sqlite3_shutdown() routine
+** deallocates any resources that were allocated by sqlite3_initialize().
+** These routines are designed to aid in process initialization and
+** shutdown on embedded systems.  Workstation applications using
+** SQLite normally do not need to invoke either of these routines.
+**
+** A call to sqlite3_initialize() is an "effective" call if it is
+** the first time sqlite3_initialize() is invoked during the lifetime of
+** the process, or if it is the first time sqlite3_initialize() is invoked
+** following a call to sqlite3_shutdown().  ^(Only an effective call
+** of sqlite3_initialize() does any initialization.  All other calls
+** are harmless no-ops.)^
+**
+** A call to sqlite3_shutdown() is an "effective" call if it is the first
+** call to sqlite3_shutdown() since the last sqlite3_initialize().  ^(Only
+** an effective call to sqlite3_shutdown() does any deinitialization.
+** All other valid calls to sqlite3_shutdown() are harmless no-ops.)^
+**
+** The sqlite3_initialize() interface is threadsafe, but sqlite3_shutdown()
+** is not.  The sqlite3_shutdown() interface must only be called from a
+** single thread.  All open [database connections] must be closed and all
+** other SQLite resources must be deallocated prior to invoking
+** sqlite3_shutdown().
+**
+** Among other things, ^sqlite3_initialize() will invoke
+** sqlite3_os_init().  Similarly, ^sqlite3_shutdown()
+** will invoke sqlite3_os_end().
+**
+** ^The sqlite3_initialize() routine returns [SQLITE_OK] on success.
+** ^If for some reason, sqlite3_initialize() is unable to initialize
+** the library (perhaps it is unable to allocate a needed resource such
+** as a mutex) it returns an [error code] other than [SQLITE_OK].
+**
+** ^The sqlite3_initialize() routine is called internally by many other
+** SQLite interfaces so that an application usually does not need to
+** invoke sqlite3_initialize() directly.  For example, [sqlite3_open()]
+** calls sqlite3_initialize() so the SQLite library will be automatically
+** initialized when [sqlite3_open()] is called if it has not be initialized
+** already.  ^However, if SQLite is compiled with the [SQLITE_OMIT_AUTOINIT]
+** compile-time option, then the automatic calls to sqlite3_initialize()
+** are omitted and the application must call sqlite3_initialize() directly
+** prior to using any other SQLite interface.  For maximum portability,
+** it is recommended that applications always invoke sqlite3_initialize()
+** directly prior to using any other SQLite interface.  Future releases
+** of SQLite may require this.  In other words, the behavior exhibited
+** when SQLite is compiled with [SQLITE_OMIT_AUTOINIT] might become the
+** default behavior in some future release of SQLite.
+**
+** The sqlite3_os_init() routine does operating-system specific
+** initialization of the SQLite library.  The sqlite3_os_end()
+** routine undoes the effect of sqlite3_os_init().  Typical tasks
+** performed by these routines include allocation or deallocation
+** of static resources, initialization of global variables,
+** setting up a default [sqlite3_vfs] module, or setting up
+** a default configuration using [sqlite3_config()].
+**
+** The application should never invoke either sqlite3_os_init()
+** or sqlite3_os_end() directly.  The application should only invoke
+** sqlite3_initialize() and sqlite3_shutdown().  The sqlite3_os_init()
+** interface is called automatically by sqlite3_initialize() and
+** sqlite3_os_end() is called by sqlite3_shutdown().  Appropriate
+** implementations for sqlite3_os_init() and sqlite3_os_end()
+** are built into SQLite when it is compiled for Unix, Windows, or OS/2.
+** When [custom builds | built for other platforms]
+** (using the [SQLITE_OS_OTHER=1] compile-time
+** option) the application must supply a suitable implementation for
+** sqlite3_os_init() and sqlite3_os_end().  An application-supplied
+** implementation of sqlite3_os_init() or sqlite3_os_end()
+** must return [SQLITE_OK] on success and some other [error code] upon
+** failure.
+*/
+int sqlite3_initialize(void);
+int sqlite3_shutdown(void);
+int sqlite3_os_init(void);
+int sqlite3_os_end(void);
+
+/*
+** CAPI3REF: Configuring The SQLite Library
+**
+** The sqlite3_config() interface is used to make global configuration
+** changes to SQLite in order to tune SQLite to the specific needs of
+** the application.  The default configuration is recommended for most
+** applications and so this routine is usually not necessary.  It is
+** provided to support rare applications with unusual needs.
+**
+** <b>The sqlite3_config() interface is not threadsafe. The application
+** must ensure that no other SQLite interfaces are invoked by other
+** threads while sqlite3_config() is running.</b>
+**
+** The first argument to sqlite3_config() is an integer
+** [configuration option] that determines
+** what property of SQLite is to be configured.  Subsequent arguments
+** vary depending on the [configuration option]
+** in the first argument.
+**
+** For most configuration options, the sqlite3_config() interface
+** may only be invoked prior to library initialization using
+** [sqlite3_initialize()] or after shutdown by [sqlite3_shutdown()].
+** The exceptional configuration options that may be invoked at any time
+** are called "anytime configuration options".
+** ^If sqlite3_config() is called after [sqlite3_initialize()] and before
+** [sqlite3_shutdown()] with a first argument that is not an anytime
+** configuration option, then the sqlite3_config() call will return SQLITE_MISUSE.
+** Note, however, that ^sqlite3_config() can be called as part of the
+** implementation of an application-defined [sqlite3_os_init()].
+**
+** ^When a configuration option is set, sqlite3_config() returns [SQLITE_OK].
+** ^If the option is unknown or SQLite is unable to set the option
+** then this routine returns a non-zero [error code].
+*/
+int sqlite3_config(int, ...);
+
+/*
+** CAPI3REF: Configure database connections
+** METHOD: sqlite3
+**
+** The sqlite3_db_config() interface is used to make configuration
+** changes to a [database connection].  The interface is similar to
+** [sqlite3_config()] except that the changes apply to a single
+** [database connection] (specified in the first argument).
+**
+** The second argument to sqlite3_db_config(D,V,...)  is the
+** [SQLITE_DBCONFIG_LOOKASIDE | configuration verb] - an integer code
+** that indicates what aspect of the [database connection] is being configured.
+** Subsequent arguments vary depending on the configuration verb.
+**
+** ^Calls to sqlite3_db_config() return SQLITE_OK if and only if
+** the call is considered successful.
+*/
+int sqlite3_db_config(sqlite3*, int op, ...);
+
+/*
+** CAPI3REF: Memory Allocation Routines
+**
+** An instance of this object defines the interface between SQLite
+** and low-level memory allocation routines.
+**
+** This object is used in only one place in the SQLite interface.
+** A pointer to an instance of this object is the argument to
+** [sqlite3_config()] when the configuration option is
+** [SQLITE_CONFIG_MALLOC] or [SQLITE_CONFIG_GETMALLOC].
+** By creating an instance of this object
+** and passing it to [sqlite3_config]([SQLITE_CONFIG_MALLOC])
+** during configuration, an application can specify an alternative
+** memory allocation subsystem for SQLite to use for all of its
+** dynamic memory needs.
+**
+** Note that SQLite comes with several [built-in memory allocators]
+** that are perfectly adequate for the overwhelming majority of applications
+** and that this object is only useful to a tiny minority of applications
+** with specialized memory allocation requirements.  This object is
+** also used during testing of SQLite in order to specify an alternative
+** memory allocator that simulates memory out-of-memory conditions in
+** order to verify that SQLite recovers gracefully from such
+** conditions.
+**
+** The xMalloc, xRealloc, and xFree methods must work like the
+** malloc(), realloc() and free() functions from the standard C library.
+** ^SQLite guarantees that the second argument to
+** xRealloc is always a value returned by a prior call to xRoundup.
+**
+** xSize should return the allocated size of a memory allocation
+** previously obtained from xMalloc or xRealloc.  The allocated size
+** is always at least as big as the requested size but may be larger.
+**
+** The xRoundup method returns what would be the allocated size of
+** a memory allocation given a particular requested size.  Most memory
+** allocators round up memory allocations at least to the next multiple
+** of 8.  Some allocators round up to a larger multiple or to a power of 2.
+** Every memory allocation request coming in through [sqlite3_malloc()]
+** or [sqlite3_realloc()] first calls xRoundup.  If xRoundup returns 0,
+** that causes the corresponding memory allocation to fail.
+**
+** The xInit method initializes the memory allocator.  For example,
+** it might allocate any required mutexes or initialize internal data
+** structures.  The xShutdown method is invoked (indirectly) by
+** [sqlite3_shutdown()] and should deallocate any resources acquired
+** by xInit.  The pAppData pointer is used as the only parameter to
+** xInit and xShutdown.
+**
+** SQLite holds the [SQLITE_MUTEX_STATIC_MAIN] mutex when it invokes
+** the xInit method, so the xInit method need not be threadsafe.  The
+** xShutdown method is only called from [sqlite3_shutdown()] so it does
+** not need to be threadsafe either.  For all other methods, SQLite
+** holds the [SQLITE_MUTEX_STATIC_MEM] mutex as long as the
+** [SQLITE_CONFIG_MEMSTATUS] configuration option is turned on (which
+** it is by default) and so the methods are automatically serialized.
+** However, if [SQLITE_CONFIG_MEMSTATUS] is disabled, then the other
+** methods must be threadsafe or else make their own arrangements for
+** serialization.
+**
+** SQLite will never invoke xInit() more than once without an intervening
+** call to xShutdown().
+*/
+typedef struct sqlite3_mem_methods sqlite3_mem_methods;
+struct sqlite3_mem_methods {
+  void *(*xMalloc)(int);         /* Memory allocation function */
+  void (*xFree)(void*);          /* Free a prior allocation */
+  void *(*xRealloc)(void*,int);  /* Resize an allocation */
+  int (*xSize)(void*);           /* Return the size of an allocation */
+  int (*xRoundup)(int);          /* Round up request size to allocation size */
+  int (*xInit)(void*);           /* Initialize the memory allocator */
+  void (*xShutdown)(void*);      /* Deinitialize the memory allocator */
+  void *pAppData;                /* Argument to xInit() and xShutdown() */
+};
+
+/*
+** CAPI3REF: Configuration Options
+** KEYWORDS: {configuration option}
+**
+** These constants are the available integer configuration options that
+** can be passed as the first argument to the [sqlite3_config()] interface.
+**
+** Most of the configuration options for sqlite3_config()
+** will only work if invoked prior to [sqlite3_initialize()] or after
+** [sqlite3_shutdown()].  The few exceptions to this rule are called
+** "anytime configuration options".
+** ^Calling [sqlite3_config()] with a first argument that is not an
+** anytime configuration option in between calls to [sqlite3_initialize()] and
+** [sqlite3_shutdown()] is a no-op that returns SQLITE_MISUSE.
+**
+** The set of anytime configuration options can change (by insertions
+** and/or deletions) from one release of SQLite to the next.
+** As of SQLite version 3.42.0, the complete set of anytime configuration
+** options is:
+** <ul>
+** <li> SQLITE_CONFIG_LOG
+** <li> SQLITE_CONFIG_PCACHE_HDRSZ
+** </ul>
+**
+** New configuration options may be added in future releases of SQLite.
+** Existing configuration options might be discontinued.  Applications
+** should check the return code from [sqlite3_config()] to make sure that
+** the call worked.  The [sqlite3_config()] interface will return a
+** non-zero [error code] if a discontinued or unsupported configuration option
+** is invoked.
+**
+** <dl>
+** [[SQLITE_CONFIG_SINGLETHREAD]] <dt>SQLITE_CONFIG_SINGLETHREAD</dt>
+** <dd>There are no arguments to this option.  ^This option sets the
+** [threading mode] to Single-thread.  In other words, it disables
+** all mutexing and puts SQLite into a mode where it can only be used
+** by a single thread.   ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** it is not possible to change the [threading mode] from its default
+** value of Single-thread and so [sqlite3_config()] will return
+** [SQLITE_ERROR] if called with the SQLITE_CONFIG_SINGLETHREAD
+** configuration option.</dd>
+**
+** [[SQLITE_CONFIG_MULTITHREAD]] <dt>SQLITE_CONFIG_MULTITHREAD</dt>
+** <dd>There are no arguments to this option.  ^This option sets the
+** [threading mode] to Multi-thread.  In other words, it disables
+** mutexing on [database connection] and [prepared statement] objects.
+** The application is responsible for serializing access to
+** [database connections] and [prepared statements].  But other mutexes
+** are enabled so that SQLite will be safe to use in a multi-threaded
+** environment as long as no two threads attempt to use the same
+** [database connection] at the same time.  ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** it is not possible to set the Multi-thread [threading mode] and
+** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
+** SQLITE_CONFIG_MULTITHREAD configuration option.</dd>
+**
+** [[SQLITE_CONFIG_SERIALIZED]] <dt>SQLITE_CONFIG_SERIALIZED</dt>
+** <dd>There are no arguments to this option.  ^This option sets the
+** [threading mode] to Serialized. In other words, this option enables
+** all mutexes including the recursive
+** mutexes on [database connection] and [prepared statement] objects.
+** In this mode (which is the default when SQLite is compiled with
+** [SQLITE_THREADSAFE=1]) the SQLite library will itself serialize access
+** to [database connections] and [prepared statements] so that the
+** application is free to use the same [database connection] or the
+** same [prepared statement] in different threads at the same time.
+** ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** it is not possible to set the Serialized [threading mode] and
+** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
+** SQLITE_CONFIG_SERIALIZED configuration option.</dd>
+**
+** [[SQLITE_CONFIG_MALLOC]] <dt>SQLITE_CONFIG_MALLOC</dt>
+** <dd> ^(The SQLITE_CONFIG_MALLOC option takes a single argument which is
+** a pointer to an instance of the [sqlite3_mem_methods] structure.
+** The argument specifies
+** alternative low-level memory allocation routines to be used in place of
+** the memory allocation routines built into SQLite.)^ ^SQLite makes
+** its own private copy of the content of the [sqlite3_mem_methods] structure
+** before the [sqlite3_config()] call returns.</dd>
+**
+** [[SQLITE_CONFIG_GETMALLOC]] <dt>SQLITE_CONFIG_GETMALLOC</dt>
+** <dd> ^(The SQLITE_CONFIG_GETMALLOC option takes a single argument which
+** is a pointer to an instance of the [sqlite3_mem_methods] structure.
+** The [sqlite3_mem_methods]
+** structure is filled with the currently defined memory allocation routines.)^
+** This option can be used to overload the default memory allocation
+** routines with a wrapper that simulations memory allocation failure or
+** tracks memory usage, for example. </dd>
+**
+** [[SQLITE_CONFIG_SMALL_MALLOC]] <dt>SQLITE_CONFIG_SMALL_MALLOC</dt>
+** <dd> ^The SQLITE_CONFIG_SMALL_MALLOC option takes single argument of
+** type int, interpreted as a boolean, which if true provides a hint to
+** SQLite that it should avoid large memory allocations if possible.
+** SQLite will run faster if it is free to make large memory allocations,
+** but some application might prefer to run slower in exchange for
+** guarantees about memory fragmentation that are possible if large
+** allocations are avoided.  This hint is normally off.
+** </dd>
+**
+** [[SQLITE_CONFIG_MEMSTATUS]] <dt>SQLITE_CONFIG_MEMSTATUS</dt>
+** <dd> ^The SQLITE_CONFIG_MEMSTATUS option takes single argument of type int,
+** interpreted as a boolean, which enables or disables the collection of
+** memory allocation statistics. ^(When memory allocation statistics are
+** disabled, the following SQLite interfaces become non-operational:
+**   <ul>
+**   <li> [sqlite3_hard_heap_limit64()]
+**   <li> [sqlite3_memory_used()]
+**   <li> [sqlite3_memory_highwater()]
+**   <li> [sqlite3_soft_heap_limit64()]
+**   <li> [sqlite3_status64()]
+**   </ul>)^
+** ^Memory allocation statistics are enabled by default unless SQLite is
+** compiled with [SQLITE_DEFAULT_MEMSTATUS]=0 in which case memory
+** allocation statistics are disabled by default.
+** </dd>
+**
+** [[SQLITE_CONFIG_SCRATCH]] <dt>SQLITE_CONFIG_SCRATCH</dt>
+** <dd> The SQLITE_CONFIG_SCRATCH option is no longer used.
+** </dd>
+**
+** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt>
+** <dd> ^The SQLITE_CONFIG_PAGECACHE option specifies a memory pool
+** that SQLite can use for the database page cache with the default page
+** cache implementation.
+** This configuration option is a no-op if an application-defined page
+** cache implementation is loaded using the [SQLITE_CONFIG_PCACHE2].
+** ^There are three arguments to SQLITE_CONFIG_PAGECACHE: A pointer to
+** 8-byte aligned memory (pMem), the size of each page cache line (sz),
+** and the number of cache lines (N).
+** The sz argument should be the size of the largest database page
+** (a power of two between 512 and 65536) plus some extra bytes for each
+** page header.  ^The number of extra bytes needed by the page header
+** can be determined using [SQLITE_CONFIG_PCACHE_HDRSZ].
+** ^It is harmless, apart from the wasted memory,
+** for the sz parameter to be larger than necessary.  The pMem
+** argument must be either a NULL pointer or a pointer to an 8-byte
+** aligned block of memory of at least sz*N bytes, otherwise
+** subsequent behavior is undefined.
+** ^When pMem is not NULL, SQLite will strive to use the memory provided
+** to satisfy page cache needs, falling back to [sqlite3_malloc()] if
+** a page cache line is larger than sz bytes or if all of the pMem buffer
+** is exhausted.
+** ^If pMem is NULL and N is non-zero, then each database connection
+** does an initial bulk allocation for page cache memory
+** from [sqlite3_malloc()] sufficient for N cache lines if N is positive or
+** of -1024*N bytes if N is negative, . ^If additional
+** page cache memory is needed beyond what is provided by the initial
+** allocation, then SQLite goes to [sqlite3_malloc()] separately for each
+** additional cache line. </dd>
+**
+** [[SQLITE_CONFIG_HEAP]] <dt>SQLITE_CONFIG_HEAP</dt>
+** <dd> ^The SQLITE_CONFIG_HEAP option specifies a static memory buffer
+** that SQLite will use for all of its dynamic memory allocation needs
+** beyond those provided for by [SQLITE_CONFIG_PAGECACHE].
+** ^The SQLITE_CONFIG_HEAP option is only available if SQLite is compiled
+** with either [SQLITE_ENABLE_MEMSYS3] or [SQLITE_ENABLE_MEMSYS5] and returns
+** [SQLITE_ERROR] if invoked otherwise.
+** ^There are three arguments to SQLITE_CONFIG_HEAP:
+** An 8-byte aligned pointer to the memory,
+** the number of bytes in the memory buffer, and the minimum allocation size.
+** ^If the first pointer (the memory pointer) is NULL, then SQLite reverts
+** to using its default memory allocator (the system malloc() implementation),
+** undoing any prior invocation of [SQLITE_CONFIG_MALLOC].  ^If the
+** memory pointer is not NULL then the alternative memory
+** allocator is engaged to handle all of SQLites memory allocation needs.
+** The first pointer (the memory pointer) must be aligned to an 8-byte
+** boundary or subsequent behavior of SQLite will be undefined.
+** The minimum allocation size is capped at 2**12. Reasonable values
+** for the minimum allocation size are 2**5 through 2**8.</dd>
+**
+** [[SQLITE_CONFIG_MUTEX]] <dt>SQLITE_CONFIG_MUTEX</dt>
+** <dd> ^(The SQLITE_CONFIG_MUTEX option takes a single argument which is a
+** pointer to an instance of the [sqlite3_mutex_methods] structure.
+** The argument specifies alternative low-level mutex routines to be used
+** in place the mutex routines built into SQLite.)^  ^SQLite makes a copy of
+** the content of the [sqlite3_mutex_methods] structure before the call to
+** [sqlite3_config()] returns. ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** the entire mutexing subsystem is omitted from the build and hence calls to
+** [sqlite3_config()] with the SQLITE_CONFIG_MUTEX configuration option will
+** return [SQLITE_ERROR].</dd>
+**
+** [[SQLITE_CONFIG_GETMUTEX]] <dt>SQLITE_CONFIG_GETMUTEX</dt>
+** <dd> ^(The SQLITE_CONFIG_GETMUTEX option takes a single argument which
+** is a pointer to an instance of the [sqlite3_mutex_methods] structure.  The
+** [sqlite3_mutex_methods]
+** structure is filled with the currently defined mutex routines.)^
+** This option can be used to overload the default mutex allocation
+** routines with a wrapper used to track mutex usage for performance
+** profiling or testing, for example.   ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** the entire mutexing subsystem is omitted from the build and hence calls to
+** [sqlite3_config()] with the SQLITE_CONFIG_GETMUTEX configuration option will
+** return [SQLITE_ERROR].</dd>
+**
+** [[SQLITE_CONFIG_LOOKASIDE]] <dt>SQLITE_CONFIG_LOOKASIDE</dt>
+** <dd> ^(The SQLITE_CONFIG_LOOKASIDE option takes two arguments that determine
+** the default size of lookaside memory on each [database connection].
+** The first argument is the
+** size of each lookaside buffer slot and the second is the number of
+** slots allocated to each database connection.)^  ^(SQLITE_CONFIG_LOOKASIDE
+** sets the <i>default</i> lookaside size. The [SQLITE_DBCONFIG_LOOKASIDE]
+** option to [sqlite3_db_config()] can be used to change the lookaside
+** configuration on individual connections.)^ </dd>
+**
+** [[SQLITE_CONFIG_PCACHE2]] <dt>SQLITE_CONFIG_PCACHE2</dt>
+** <dd> ^(The SQLITE_CONFIG_PCACHE2 option takes a single argument which is
+** a pointer to an [sqlite3_pcache_methods2] object.  This object specifies
+** the interface to a custom page cache implementation.)^
+** ^SQLite makes a copy of the [sqlite3_pcache_methods2] object.</dd>
+**
+** [[SQLITE_CONFIG_GETPCACHE2]] <dt>SQLITE_CONFIG_GETPCACHE2</dt>
+** <dd> ^(The SQLITE_CONFIG_GETPCACHE2 option takes a single argument which
+** is a pointer to an [sqlite3_pcache_methods2] object.  SQLite copies of
+** the current page cache implementation into that object.)^ </dd>
+**
+** [[SQLITE_CONFIG_LOG]] <dt>SQLITE_CONFIG_LOG</dt>
+** <dd> The SQLITE_CONFIG_LOG option is used to configure the SQLite
+** global [error log].
+** (^The SQLITE_CONFIG_LOG option takes two arguments: a pointer to a
+** function with a call signature of void(*)(void*,int,const char*),
+** and a pointer to void. ^If the function pointer is not NULL, it is
+** invoked by [sqlite3_log()] to process each logging event.  ^If the
+** function pointer is NULL, the [sqlite3_log()] interface becomes a no-op.
+** ^The void pointer that is the second argument to SQLITE_CONFIG_LOG is
+** passed through as the first parameter to the application-defined logger
+** function whenever that function is invoked.  ^The second parameter to
+** the logger function is a copy of the first parameter to the corresponding
+** [sqlite3_log()] call and is intended to be a [result code] or an
+** [extended result code].  ^The third parameter passed to the logger is
+** log message after formatting via [sqlite3_snprintf()].
+** The SQLite logging interface is not reentrant; the logger function
+** supplied by the application must not invoke any SQLite interface.
+** In a multi-threaded application, the application-defined logger
+** function must be threadsafe. </dd>
+**
+** [[SQLITE_CONFIG_URI]] <dt>SQLITE_CONFIG_URI
+** <dd>^(The SQLITE_CONFIG_URI option takes a single argument of type int.
+** If non-zero, then URI handling is globally enabled. If the parameter is zero,
+** then URI handling is globally disabled.)^ ^If URI handling is globally
+** enabled, all filenames passed to [sqlite3_open()], [sqlite3_open_v2()],
+** [sqlite3_open16()] or
+** specified as part of [ATTACH] commands are interpreted as URIs, regardless
+** of whether or not the [SQLITE_OPEN_URI] flag is set when the database
+** connection is opened. ^If it is globally disabled, filenames are
+** only interpreted as URIs if the SQLITE_OPEN_URI flag is set when the
+** database connection is opened. ^(By default, URI handling is globally
+** disabled. The default value may be changed by compiling with the
+** [SQLITE_USE_URI] symbol defined.)^
+**
+** [[SQLITE_CONFIG_COVERING_INDEX_SCAN]] <dt>SQLITE_CONFIG_COVERING_INDEX_SCAN
+** <dd>^The SQLITE_CONFIG_COVERING_INDEX_SCAN option takes a single integer
+** argument which is interpreted as a boolean in order to enable or disable
+** the use of covering indices for full table scans in the query optimizer.
+** ^The default setting is determined
+** by the [SQLITE_ALLOW_COVERING_INDEX_SCAN] compile-time option, or is "on"
+** if that compile-time option is omitted.
+** The ability to disable the use of covering indices for full table scans
+** is because some incorrectly coded legacy applications might malfunction
+** when the optimization is enabled.  Providing the ability to
+** disable the optimization allows the older, buggy application code to work
+** without change even with newer versions of SQLite.
+**
+** [[SQLITE_CONFIG_PCACHE]] [[SQLITE_CONFIG_GETPCACHE]]
+** <dt>SQLITE_CONFIG_PCACHE and SQLITE_CONFIG_GETPCACHE
+** <dd> These options are obsolete and should not be used by new code.
+** They are retained for backwards compatibility but are now no-ops.
+** </dd>
+**
+** [[SQLITE_CONFIG_SQLLOG]]
+** <dt>SQLITE_CONFIG_SQLLOG
+** <dd>This option is only available if sqlite is compiled with the
+** [SQLITE_ENABLE_SQLLOG] pre-processor macro defined. The first argument should
+** be a pointer to a function of type void(*)(void*,sqlite3*,const char*, int).
+** The second should be of type (void*). The callback is invoked by the library
+** in three separate circumstances, identified by the value passed as the
+** fourth parameter. If the fourth parameter is 0, then the database connection
+** passed as the second argument has just been opened. The third argument
+** points to a buffer containing the name of the main database file. If the
+** fourth parameter is 1, then the SQL statement that the third parameter
+** points to has just been executed. Or, if the fourth parameter is 2, then
+** the connection being passed as the second parameter is being closed. The
+** third parameter is passed NULL In this case.  An example of using this
+** configuration option can be seen in the "test_sqllog.c" source file in
+** the canonical SQLite source tree.</dd>
+**
+** [[SQLITE_CONFIG_MMAP_SIZE]]
+** <dt>SQLITE_CONFIG_MMAP_SIZE
+** <dd>^SQLITE_CONFIG_MMAP_SIZE takes two 64-bit integer (sqlite3_int64) values
+** that are the default mmap size limit (the default setting for
+** [PRAGMA mmap_size]) and the maximum allowed mmap size limit.
+** ^The default setting can be overridden by each database connection using
+** either the [PRAGMA mmap_size] command, or by using the
+** [SQLITE_FCNTL_MMAP_SIZE] file control.  ^(The maximum allowed mmap size
+** will be silently truncated if necessary so that it does not exceed the
+** compile-time maximum mmap size set by the
+** [SQLITE_MAX_MMAP_SIZE] compile-time option.)^
+** ^If either argument to this option is negative, then that argument is
+** changed to its compile-time default.
+**
+** [[SQLITE_CONFIG_WIN32_HEAPSIZE]]
+** <dt>SQLITE_CONFIG_WIN32_HEAPSIZE
+** <dd>^The SQLITE_CONFIG_WIN32_HEAPSIZE option is only available if SQLite is
+** compiled for Windows with the [SQLITE_WIN32_MALLOC] pre-processor macro
+** defined. ^SQLITE_CONFIG_WIN32_HEAPSIZE takes a 32-bit unsigned integer value
+** that specifies the maximum size of the created heap.
+**
+** [[SQLITE_CONFIG_PCACHE_HDRSZ]]
+** <dt>SQLITE_CONFIG_PCACHE_HDRSZ
+** <dd>^The SQLITE_CONFIG_PCACHE_HDRSZ option takes a single parameter which
+** is a pointer to an integer and writes into that integer the number of extra
+** bytes per page required for each page in [SQLITE_CONFIG_PAGECACHE].
+** The amount of extra space required can change depending on the compiler,
+** target platform, and SQLite version.
+**
+** [[SQLITE_CONFIG_PMASZ]]
+** <dt>SQLITE_CONFIG_PMASZ
+** <dd>^The SQLITE_CONFIG_PMASZ option takes a single parameter which
+** is an unsigned integer and sets the "Minimum PMA Size" for the multithreaded
+** sorter to that integer.  The default minimum PMA Size is set by the
+** [SQLITE_SORTER_PMASZ] compile-time option.  New threads are launched
+** to help with sort operations when multithreaded sorting
+** is enabled (using the [PRAGMA threads] command) and the amount of content
+** to be sorted exceeds the page size times the minimum of the
+** [PRAGMA cache_size] setting and this value.
+**
+** [[SQLITE_CONFIG_STMTJRNL_SPILL]]
+** <dt>SQLITE_CONFIG_STMTJRNL_SPILL
+** <dd>^The SQLITE_CONFIG_STMTJRNL_SPILL option takes a single parameter which
+** becomes the [statement journal] spill-to-disk threshold.
+** [Statement journals] are held in memory until their size (in bytes)
+** exceeds this threshold, at which point they are written to disk.
+** Or if the threshold is -1, statement journals are always held
+** exclusively in memory.
+** Since many statement journals never become large, setting the spill
+** threshold to a value such as 64KiB can greatly reduce the amount of
+** I/O required to support statement rollback.
+** The default value for this setting is controlled by the
+** [SQLITE_STMTJRNL_SPILL] compile-time option.
+**
+** [[SQLITE_CONFIG_SORTERREF_SIZE]]
+** <dt>SQLITE_CONFIG_SORTERREF_SIZE
+** <dd>The SQLITE_CONFIG_SORTERREF_SIZE option accepts a single parameter
+** of type (int) - the new value of the sorter-reference size threshold.
+** Usually, when SQLite uses an external sort to order records according
+** to an ORDER BY clause, all fields required by the caller are present in the
+** sorted records. However, if SQLite determines based on the declared type
+** of a table column that its values are likely to be very large - larger
+** than the configured sorter-reference size threshold - then a reference
+** is stored in each sorted record and the required column values loaded
+** from the database as records are returned in sorted order. The default
+** value for this option is to never use this optimization. Specifying a
+** negative value for this option restores the default behavior.
+** This option is only available if SQLite is compiled with the
+** [SQLITE_ENABLE_SORTER_REFERENCES] compile-time option.
+**
+** [[SQLITE_CONFIG_MEMDB_MAXSIZE]]
+** <dt>SQLITE_CONFIG_MEMDB_MAXSIZE
+** <dd>The SQLITE_CONFIG_MEMDB_MAXSIZE option accepts a single parameter
+** [sqlite3_int64] parameter which is the default maximum size for an in-memory
+** database created using [sqlite3_deserialize()].  This default maximum
+** size can be adjusted up or down for individual databases using the
+** [SQLITE_FCNTL_SIZE_LIMIT] [sqlite3_file_control|file-control].  If this
+** configuration setting is never used, then the default maximum is determined
+** by the [SQLITE_MEMDB_DEFAULT_MAXSIZE] compile-time option.  If that
+** compile-time option is not set, then the default maximum is 1073741824.
+** </dl>
+*/
+#define SQLITE_CONFIG_SINGLETHREAD         1  /* nil */
+#define SQLITE_CONFIG_MULTITHREAD          2  /* nil */
+#define SQLITE_CONFIG_SERIALIZED           3  /* nil */
+#define SQLITE_CONFIG_MALLOC               4  /* sqlite3_mem_methods* */
+#define SQLITE_CONFIG_GETMALLOC            5  /* sqlite3_mem_methods* */
+#define SQLITE_CONFIG_SCRATCH              6  /* No longer used */
+#define SQLITE_CONFIG_PAGECACHE            7  /* void*, int sz, int N */
+#define SQLITE_CONFIG_HEAP                 8  /* void*, int nByte, int min */
+#define SQLITE_CONFIG_MEMSTATUS            9  /* boolean */
+#define SQLITE_CONFIG_MUTEX               10  /* sqlite3_mutex_methods* */
+#define SQLITE_CONFIG_GETMUTEX            11  /* sqlite3_mutex_methods* */
+/* previously SQLITE_CONFIG_CHUNKALLOC    12 which is now unused. */
+#define SQLITE_CONFIG_LOOKASIDE           13  /* int int */
+#define SQLITE_CONFIG_PCACHE              14  /* no-op */
+#define SQLITE_CONFIG_GETPCACHE           15  /* no-op */
+#define SQLITE_CONFIG_LOG                 16  /* xFunc, void* */
+#define SQLITE_CONFIG_URI                 17  /* int */
+#define SQLITE_CONFIG_PCACHE2             18  /* sqlite3_pcache_methods2* */
+#define SQLITE_CONFIG_GETPCACHE2          19  /* sqlite3_pcache_methods2* */
+#define SQLITE_CONFIG_COVERING_INDEX_SCAN 20  /* int */
+#define SQLITE_CONFIG_SQLLOG              21  /* xSqllog, void* */
+#define SQLITE_CONFIG_MMAP_SIZE           22  /* sqlite3_int64, sqlite3_int64 */
+#define SQLITE_CONFIG_WIN32_HEAPSIZE      23  /* int nByte */
+#define SQLITE_CONFIG_PCACHE_HDRSZ        24  /* int *psz */
+#define SQLITE_CONFIG_PMASZ               25  /* unsigned int szPma */
+#define SQLITE_CONFIG_STMTJRNL_SPILL      26  /* int nByte */
+#define SQLITE_CONFIG_SMALL_MALLOC        27  /* boolean */
+#define SQLITE_CONFIG_SORTERREF_SIZE      28  /* int nByte */
+#define SQLITE_CONFIG_MEMDB_MAXSIZE       29  /* sqlite3_int64 */
+
+/*
+** CAPI3REF: Database Connection Configuration Options
+**
+** These constants are the available integer configuration options that
+** can be passed as the second argument to the [sqlite3_db_config()] interface.
+**
+** New configuration options may be added in future releases of SQLite.
+** Existing configuration options might be discontinued.  Applications
+** should check the return code from [sqlite3_db_config()] to make sure that
+** the call worked.  ^The [sqlite3_db_config()] interface will return a
+** non-zero [error code] if a discontinued or unsupported configuration option
+** is invoked.
+**
+** <dl>
+** [[SQLITE_DBCONFIG_LOOKASIDE]]
+** <dt>SQLITE_DBCONFIG_LOOKASIDE</dt>
+** <dd> ^This option takes three additional arguments that determine the
+** [lookaside memory allocator] configuration for the [database connection].
+** ^The first argument (the third parameter to [sqlite3_db_config()] is a
+** pointer to a memory buffer to use for lookaside memory.
+** ^The first argument after the SQLITE_DBCONFIG_LOOKASIDE verb
+** may be NULL in which case SQLite will allocate the
+** lookaside buffer itself using [sqlite3_malloc()]. ^The second argument is the
+** size of each lookaside buffer slot.  ^The third argument is the number of
+** slots.  The size of the buffer in the first argument must be greater than
+** or equal to the product of the second and third arguments.  The buffer
+** must be aligned to an 8-byte boundary.  ^If the second argument to
+** SQLITE_DBCONFIG_LOOKASIDE is not a multiple of 8, it is internally
+** rounded down to the next smaller multiple of 8.  ^(The lookaside memory
+** configuration for a database connection can only be changed when that
+** connection is not currently using lookaside memory, or in other words
+** when the "current value" returned by
+** [sqlite3_db_status](D,[SQLITE_DBSTATUS_LOOKASIDE_USED],...) is zero.
+** Any attempt to change the lookaside memory configuration when lookaside
+** memory is in use leaves the configuration unchanged and returns
+** [SQLITE_BUSY].)^</dd>
+**
+** [[SQLITE_DBCONFIG_ENABLE_FKEY]]
+** <dt>SQLITE_DBCONFIG_ENABLE_FKEY</dt>
+** <dd> ^This option is used to enable or disable the enforcement of
+** [foreign key constraints].  There should be two additional arguments.
+** The first argument is an integer which is 0 to disable FK enforcement,
+** positive to enable FK enforcement or negative to leave FK enforcement
+** unchanged.  The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether FK enforcement is off or on
+** following this call.  The second parameter may be a NULL pointer, in
+** which case the FK enforcement setting is not reported back. </dd>
+**
+** [[SQLITE_DBCONFIG_ENABLE_TRIGGER]]
+** <dt>SQLITE_DBCONFIG_ENABLE_TRIGGER</dt>
+** <dd> ^This option is used to enable or disable [CREATE TRIGGER | triggers].
+** There should be two additional arguments.
+** The first argument is an integer which is 0 to disable triggers,
+** positive to enable triggers or negative to leave the setting unchanged.
+** The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether triggers are disabled or enabled
+** following this call.  The second parameter may be a NULL pointer, in
+** which case the trigger setting is not reported back.
+**
+** <p>Originally this option disabled all triggers.  ^(However, since
+** SQLite version 3.35.0, TEMP triggers are still allowed even if
+** this option is off.  So, in other words, this option now only disables
+** triggers in the main database schema or in the schemas of ATTACH-ed
+** databases.)^ </dd>
+**
+** [[SQLITE_DBCONFIG_ENABLE_VIEW]]
+** <dt>SQLITE_DBCONFIG_ENABLE_VIEW</dt>
+** <dd> ^This option is used to enable or disable [CREATE VIEW | views].
+** There should be two additional arguments.
+** The first argument is an integer which is 0 to disable views,
+** positive to enable views or negative to leave the setting unchanged.
+** The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether views are disabled or enabled
+** following this call.  The second parameter may be a NULL pointer, in
+** which case the view setting is not reported back.
+**
+** <p>Originally this option disabled all views.  ^(However, since
+** SQLite version 3.35.0, TEMP views are still allowed even if
+** this option is off.  So, in other words, this option now only disables
+** views in the main database schema or in the schemas of ATTACH-ed
+** databases.)^ </dd>
+**
+** [[SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER]]
+** <dt>SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER</dt>
+** <dd> ^This option is used to enable or disable the
+** [fts3_tokenizer()] function which is part of the
+** [FTS3] full-text search engine extension.
+** There should be two additional arguments.
+** The first argument is an integer which is 0 to disable fts3_tokenizer() or
+** positive to enable fts3_tokenizer() or negative to leave the setting
+** unchanged.
+** The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether fts3_tokenizer is disabled or enabled
+** following this call.  The second parameter may be a NULL pointer, in
+** which case the new setting is not reported back. </dd>
+**
+** [[SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION]]
+** <dt>SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION</dt>
+** <dd> ^This option is used to enable or disable the [sqlite3_load_extension()]
+** interface independently of the [load_extension()] SQL function.
+** The [sqlite3_enable_load_extension()] API enables or disables both the
+** C-API [sqlite3_load_extension()] and the SQL function [load_extension()].
+** There should be two additional arguments.
+** When the first argument to this interface is 1, then only the C-API is
+** enabled and the SQL function remains disabled.  If the first argument to
+** this interface is 0, then both the C-API and the SQL function are disabled.
+** If the first argument is -1, then no changes are made to state of either the
+** C-API or the SQL function.
+** The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether [sqlite3_load_extension()] interface
+** is disabled or enabled following this call.  The second parameter may
+** be a NULL pointer, in which case the new setting is not reported back.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_MAINDBNAME]] <dt>SQLITE_DBCONFIG_MAINDBNAME</dt>
+** <dd> ^This option is used to change the name of the "main" database
+** schema.  ^The sole argument is a pointer to a constant UTF8 string
+** which will become the new schema name in place of "main".  ^SQLite
+** does not make a copy of the new main schema name string, so the application
+** must ensure that the argument passed into this DBCONFIG option is unchanged
+** until after the database connection closes.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE]]
+** <dt>SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE</dt>
+** <dd> Usually, when a database in wal mode is closed or detached from a
+** database handle, SQLite checks if this will mean that there are now no
+** connections at all to the database. If so, it performs a checkpoint
+** operation before closing the connection. This option may be used to
+** override this behavior. The first parameter passed to this operation
+** is an integer - positive to disable checkpoints-on-close, or zero (the
+** default) to enable them, and negative to leave the setting unchanged.
+** The second parameter is a pointer to an integer
+** into which is written 0 or 1 to indicate whether checkpoints-on-close
+** have been disabled - 0 if they are not disabled, 1 if they are.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_ENABLE_QPSG]] <dt>SQLITE_DBCONFIG_ENABLE_QPSG</dt>
+** <dd>^(The SQLITE_DBCONFIG_ENABLE_QPSG option activates or deactivates
+** the [query planner stability guarantee] (QPSG).  When the QPSG is active,
+** a single SQL query statement will always use the same algorithm regardless
+** of values of [bound parameters].)^ The QPSG disables some query optimizations
+** that look at the values of bound parameters, which can make some queries
+** slower.  But the QPSG has the advantage of more predictable behavior.  With
+** the QPSG active, SQLite will always use the same query plan in the field as
+** was used during testing in the lab.
+** The first argument to this setting is an integer which is 0 to disable
+** the QPSG, positive to enable QPSG, or negative to leave the setting
+** unchanged. The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether the QPSG is disabled or enabled
+** following this call.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_TRIGGER_EQP]] <dt>SQLITE_DBCONFIG_TRIGGER_EQP</dt>
+** <dd> By default, the output of EXPLAIN QUERY PLAN commands does not
+** include output for any operations performed by trigger programs. This
+** option is used to set or clear (the default) a flag that governs this
+** behavior. The first parameter passed to this operation is an integer -
+** positive to enable output for trigger programs, or zero to disable it,
+** or negative to leave the setting unchanged.
+** The second parameter is a pointer to an integer into which is written
+** 0 or 1 to indicate whether output-for-triggers has been disabled - 0 if
+** it is not disabled, 1 if it is. 
+** </dd>
+**
+** [[SQLITE_DBCONFIG_RESET_DATABASE]] <dt>SQLITE_DBCONFIG_RESET_DATABASE</dt>
+** <dd> Set the SQLITE_DBCONFIG_RESET_DATABASE flag and then run
+** [VACUUM] in order to reset a database back to an empty database
+** with no schema and no content. The following process works even for
+** a badly corrupted database file:
+** <ol>
+** <li> If the database connection is newly opened, make sure it has read the
+**      database schema by preparing then discarding some query against the
+**      database, or calling sqlite3_table_column_metadata(), ignoring any
+**      errors.  This step is only necessary if the application desires to keep
+**      the database in WAL mode after the reset if it was in WAL mode before
+**      the reset. 
+** <li> sqlite3_db_config(db, SQLITE_DBCONFIG_RESET_DATABASE, 1, 0);
+** <li> [sqlite3_exec](db, "[VACUUM]", 0, 0, 0);
+** <li> sqlite3_db_config(db, SQLITE_DBCONFIG_RESET_DATABASE, 0, 0);
+** </ol>
+** Because resetting a database is destructive and irreversible, the
+** process requires the use of this obscure API and multiple steps to
+** help ensure that it does not happen by accident. Because this
+** feature must be capable of resetting corrupt databases, and
+** shutting down virtual tables may require access to that corrupt
+** storage, the library must abandon any installed virtual tables
+** without calling their xDestroy() methods.
+**
+** [[SQLITE_DBCONFIG_DEFENSIVE]] <dt>SQLITE_DBCONFIG_DEFENSIVE</dt>
+** <dd>The SQLITE_DBCONFIG_DEFENSIVE option activates or deactivates the
+** "defensive" flag for a database connection.  When the defensive
+** flag is enabled, language features that allow ordinary SQL to
+** deliberately corrupt the database file are disabled.  The disabled
+** features include but are not limited to the following:
+** <ul>
+** <li> The [PRAGMA writable_schema=ON] statement.
+** <li> The [PRAGMA journal_mode=OFF] statement.
+** <li> The [PRAGMA schema_version=N] statement.
+** <li> Writes to the [sqlite_dbpage] virtual table.
+** <li> Direct writes to [shadow tables].
+** </ul>
+** </dd>
+**
+** [[SQLITE_DBCONFIG_WRITABLE_SCHEMA]] <dt>SQLITE_DBCONFIG_WRITABLE_SCHEMA</dt>
+** <dd>The SQLITE_DBCONFIG_WRITABLE_SCHEMA option activates or deactivates the
+** "writable_schema" flag. This has the same effect and is logically equivalent
+** to setting [PRAGMA writable_schema=ON] or [PRAGMA writable_schema=OFF].
+** The first argument to this setting is an integer which is 0 to disable
+** the writable_schema, positive to enable writable_schema, or negative to
+** leave the setting unchanged. The second parameter is a pointer to an
+** integer into which is written 0 or 1 to indicate whether the writable_schema
+** is enabled or disabled following this call.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_LEGACY_ALTER_TABLE]]
+** <dt>SQLITE_DBCONFIG_LEGACY_ALTER_TABLE</dt>
+** <dd>The SQLITE_DBCONFIG_LEGACY_ALTER_TABLE option activates or deactivates
+** the legacy behavior of the [ALTER TABLE RENAME] command such it
+** behaves as it did prior to [version 3.24.0] (2018-06-04).  See the
+** "Compatibility Notice" on the [ALTER TABLE RENAME documentation] for
+** additional information. This feature can also be turned on and off
+** using the [PRAGMA legacy_alter_table] statement.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_DQS_DML]]
+** <dt>SQLITE_DBCONFIG_DQS_DML</dt>
+** <dd>The SQLITE_DBCONFIG_DQS_DML option activates or deactivates
+** the legacy [double-quoted string literal] misfeature for DML statements
+** only, that is DELETE, INSERT, SELECT, and UPDATE statements. The
+** default value of this setting is determined by the [-DSQLITE_DQS]
+** compile-time option.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_DQS_DDL]]
+** <dt>SQLITE_DBCONFIG_DQS_DDL</dt>
+** <dd>The SQLITE_DBCONFIG_DQS option activates or deactivates
+** the legacy [double-quoted string literal] misfeature for DDL statements,
+** such as CREATE TABLE and CREATE INDEX. The
+** default value of this setting is determined by the [-DSQLITE_DQS]
+** compile-time option.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_TRUSTED_SCHEMA]]
+** <dt>SQLITE_DBCONFIG_TRUSTED_SCHEMA</dt>
+** <dd>The SQLITE_DBCONFIG_TRUSTED_SCHEMA option tells SQLite to
+** assume that database schemas are untainted by malicious content.
+** When the SQLITE_DBCONFIG_TRUSTED_SCHEMA option is disabled, SQLite
+** takes additional defensive steps to protect the application from harm
+** including:
+** <ul>
+** <li> Prohibit the use of SQL functions inside triggers, views,
+** CHECK constraints, DEFAULT clauses, expression indexes,
+** partial indexes, or generated columns
+** unless those functions are tagged with [SQLITE_INNOCUOUS].
+** <li> Prohibit the use of virtual tables inside of triggers or views
+** unless those virtual tables are tagged with [SQLITE_VTAB_INNOCUOUS].
+** </ul>
+** This setting defaults to "on" for legacy compatibility, however
+** all applications are advised to turn it off if possible. This setting
+** can also be controlled using the [PRAGMA trusted_schema] statement.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_LEGACY_FILE_FORMAT]]
+** <dt>SQLITE_DBCONFIG_LEGACY_FILE_FORMAT</dt>
+** <dd>The SQLITE_DBCONFIG_LEGACY_FILE_FORMAT option activates or deactivates
+** the legacy file format flag.  When activated, this flag causes all newly
+** created database file to have a schema format version number (the 4-byte
+** integer found at offset 44 into the database header) of 1.  This in turn
+** means that the resulting database file will be readable and writable by
+** any SQLite version back to 3.0.0 ([dateof:3.0.0]).  Without this setting,
+** newly created databases are generally not understandable by SQLite versions
+** prior to 3.3.0 ([dateof:3.3.0]).  As these words are written, there
+** is now scarcely any need to generate database files that are compatible
+** all the way back to version 3.0.0, and so this setting is of little
+** practical use, but is provided so that SQLite can continue to claim the
+** ability to generate new database files that are compatible with  version
+** 3.0.0.
+** <p>Note that when the SQLITE_DBCONFIG_LEGACY_FILE_FORMAT setting is on,
+** the [VACUUM] command will fail with an obscure error when attempting to
+** process a table with generated columns and a descending index.  This is
+** not considered a bug since SQLite versions 3.3.0 and earlier do not support
+** either generated columns or descending indexes.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_STMT_SCANSTATUS]]
+** <dt>SQLITE_DBCONFIG_STMT_SCANSTATUS</dt>
+** <dd>The SQLITE_DBCONFIG_STMT_SCANSTATUS option is only useful in
+** SQLITE_ENABLE_STMT_SCANSTATUS builds. In this case, it sets or clears
+** a flag that enables collection of the sqlite3_stmt_scanstatus_v2()
+** statistics. For statistics to be collected, the flag must be set on
+** the database handle both when the SQL statement is prepared and when it
+** is stepped. The flag is set (collection of statistics is enabled)
+** by default.  This option takes two arguments: an integer and a pointer to
+** an integer..  The first argument is 1, 0, or -1 to enable, disable, or
+** leave unchanged the statement scanstatus option.  If the second argument
+** is not NULL, then the value of the statement scanstatus setting after
+** processing the first argument is written into the integer that the second
+** argument points to.
+** </dd>
+**
+** [[SQLITE_DBCONFIG_REVERSE_SCANORDER]]
+** <dt>SQLITE_DBCONFIG_REVERSE_SCANORDER</dt>
+** <dd>The SQLITE_DBCONFIG_REVERSE_SCANORDER option changes the default order
+** in which tables and indexes are scanned so that the scans start at the end
+** and work toward the beginning rather than starting at the beginning and
+** working toward the end. Setting SQLITE_DBCONFIG_REVERSE_SCANORDER is the
+** same as setting [PRAGMA reverse_unordered_selects].  This option takes
+** two arguments which are an integer and a pointer to an integer.  The first
+** argument is 1, 0, or -1 to enable, disable, or leave unchanged the
+** reverse scan order flag, respectively.  If the second argument is not NULL,
+** then 0 or 1 is written into the integer that the second argument points to
+** depending on if the reverse scan order flag is set after processing the
+** first argument.
+** </dd>
+**
+** </dl>
+*/
+#define SQLITE_DBCONFIG_MAINDBNAME            1000 /* const char* */
+#define SQLITE_DBCONFIG_LOOKASIDE             1001 /* void* int int */
+#define SQLITE_DBCONFIG_ENABLE_FKEY           1002 /* int int* */
+#define SQLITE_DBCONFIG_ENABLE_TRIGGER        1003 /* int int* */
+#define SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER 1004 /* int int* */
+#define SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION 1005 /* int int* */
+#define SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE      1006 /* int int* */
+#define SQLITE_DBCONFIG_ENABLE_QPSG           1007 /* int int* */
+#define SQLITE_DBCONFIG_TRIGGER_EQP           1008 /* int int* */
+#define SQLITE_DBCONFIG_RESET_DATABASE        1009 /* int int* */
+#define SQLITE_DBCONFIG_DEFENSIVE             1010 /* int int* */
+#define SQLITE_DBCONFIG_WRITABLE_SCHEMA       1011 /* int int* */
+#define SQLITE_DBCONFIG_LEGACY_ALTER_TABLE    1012 /* int int* */
+#define SQLITE_DBCONFIG_DQS_DML               1013 /* int int* */
+#define SQLITE_DBCONFIG_DQS_DDL               1014 /* int int* */
+#define SQLITE_DBCONFIG_ENABLE_VIEW           1015 /* int int* */
+#define SQLITE_DBCONFIG_LEGACY_FILE_FORMAT    1016 /* int int* */
+#define SQLITE_DBCONFIG_TRUSTED_SCHEMA        1017 /* int int* */
+#define SQLITE_DBCONFIG_STMT_SCANSTATUS       1018 /* int int* */
+#define SQLITE_DBCONFIG_REVERSE_SCANORDER     1019 /* int int* */
+#define SQLITE_DBCONFIG_MAX                   1019 /* Largest DBCONFIG */
+
+/*
+** CAPI3REF: Enable Or Disable Extended Result Codes
+** METHOD: sqlite3
+**
+** ^The sqlite3_extended_result_codes() routine enables or disables the
+** [extended result codes] feature of SQLite. ^The extended result
+** codes are disabled by default for historical compatibility.
+*/
+int sqlite3_extended_result_codes(sqlite3*, int onoff);
+
+/*
+** CAPI3REF: Last Insert Rowid
+** METHOD: sqlite3
+**
+** ^Each entry in most SQLite tables (except for [WITHOUT ROWID] tables)
+** has a unique 64-bit signed
+** integer key called the [ROWID | "rowid"]. ^The rowid is always available
+** as an undeclared column named ROWID, OID, or _ROWID_ as long as those
+** names are not also used by explicitly declared columns. ^If
+** the table has a column of type [INTEGER PRIMARY KEY] then that column
+** is another alias for the rowid.
+**
+** ^The sqlite3_last_insert_rowid(D) interface usually returns the [rowid] of
+** the most recent successful [INSERT] into a rowid table or [virtual table]
+** on database connection D. ^Inserts into [WITHOUT ROWID] tables are not
+** recorded. ^If no successful [INSERT]s into rowid tables have ever occurred
+** on the database connection D, then sqlite3_last_insert_rowid(D) returns
+** zero.
+**
+** As well as being set automatically as rows are inserted into database
+** tables, the value returned by this function may be set explicitly by
+** [sqlite3_set_last_insert_rowid()]
+**
+** Some virtual table implementations may INSERT rows into rowid tables as
+** part of committing a transaction (e.g. to flush data accumulated in memory
+** to disk). In this case subsequent calls to this function return the rowid
+** associated with these internal INSERT operations, which leads to
+** unintuitive results. Virtual table implementations that do write to rowid
+** tables in this way can avoid this problem by restoring the original
+** rowid value using [sqlite3_set_last_insert_rowid()] before returning
+** control to the user.
+**
+** ^(If an [INSERT] occurs within a trigger then this routine will
+** return the [rowid] of the inserted row as long as the trigger is
+** running. Once the trigger program ends, the value returned
+** by this routine reverts to what it was before the trigger was fired.)^
+**
+** ^An [INSERT] that fails due to a constraint violation is not a
+** successful [INSERT] and does not change the value returned by this
+** routine.  ^Thus INSERT OR FAIL, INSERT OR IGNORE, INSERT OR ROLLBACK,
+** and INSERT OR ABORT make no changes to the return value of this
+** routine when their insertion fails.  ^(When INSERT OR REPLACE
+** encounters a constraint violation, it does not fail.  The
+** INSERT continues to completion after deleting rows that caused
+** the constraint problem so INSERT OR REPLACE will always change
+** the return value of this interface.)^
+**
+** ^For the purposes of this routine, an [INSERT] is considered to
+** be successful even if it is subsequently rolled back.
+**
+** This function is accessible to SQL statements via the
+** [last_insert_rowid() SQL function].
+**
+** If a separate thread performs a new [INSERT] on the same
+** database connection while the [sqlite3_last_insert_rowid()]
+** function is running and thus changes the last insert [rowid],
+** then the value returned by [sqlite3_last_insert_rowid()] is
+** unpredictable and might not equal either the old or the new
+** last insert [rowid].
+*/
+sqlite3_int64 sqlite3_last_insert_rowid(sqlite3*);
+
+/*
+** CAPI3REF: Set the Last Insert Rowid value.
+** METHOD: sqlite3
+**
+** The sqlite3_set_last_insert_rowid(D, R) method allows the application to
+** set the value returned by calling sqlite3_last_insert_rowid(D) to R
+** without inserting a row into the database.
+*/
+void sqlite3_set_last_insert_rowid(sqlite3*,sqlite3_int64);
+
+/*
+** CAPI3REF: Count The Number Of Rows Modified
+** METHOD: sqlite3
+**
+** ^These functions return the number of rows modified, inserted or
+** deleted by the most recently completed INSERT, UPDATE or DELETE
+** statement on the database connection specified by the only parameter.
+** The two functions are identical except for the type of the return value
+** and that if the number of rows modified by the most recent INSERT, UPDATE
+** or DELETE is greater than the maximum value supported by type "int", then
+** the return value of sqlite3_changes() is undefined. ^Executing any other
+** type of SQL statement does not modify the value returned by these functions.
+**
+** ^Only changes made directly by the INSERT, UPDATE or DELETE statement are
+** considered - auxiliary changes caused by [CREATE TRIGGER | triggers],
+** [foreign key actions] or [REPLACE] constraint resolution are not counted.
+**
+** Changes to a view that are intercepted by
+** [INSTEAD OF trigger | INSTEAD OF triggers] are not counted. ^The value
+** returned by sqlite3_changes() immediately after an INSERT, UPDATE or
+** DELETE statement run on a view is always zero. Only changes made to real
+** tables are counted.
+**
+** Things are more complicated if the sqlite3_changes() function is
+** executed while a trigger program is running. This may happen if the
+** program uses the [changes() SQL function], or if some other callback
+** function invokes sqlite3_changes() directly. Essentially:
+**
+** <ul>
+**   <li> ^(Before entering a trigger program the value returned by
+**        sqlite3_changes() function is saved. After the trigger program
+**        has finished, the original value is restored.)^
+**
+**   <li> ^(Within a trigger program each INSERT, UPDATE and DELETE
+**        statement sets the value returned by sqlite3_changes()
+**        upon completion as normal. Of course, this value will not include
+**        any changes performed by sub-triggers, as the sqlite3_changes()
+**        value will be saved and restored after each sub-trigger has run.)^
+** </ul>
+**
+** ^This means that if the changes() SQL function (or similar) is used
+** by the first INSERT, UPDATE or DELETE statement within a trigger, it
+** returns the value as set when the calling statement began executing.
+** ^If it is used by the second or subsequent such statement within a trigger
+** program, the value returned reflects the number of rows modified by the
+** previous INSERT, UPDATE or DELETE statement within the same trigger.
+**
+** If a separate thread makes changes on the same database connection
+** while [sqlite3_changes()] is running then the value returned
+** is unpredictable and not meaningful.
+**
+** See also:
+** <ul>
+** <li> the [sqlite3_total_changes()] interface
+** <li> the [count_changes pragma]
+** <li> the [changes() SQL function]
+** <li> the [data_version pragma]
+** </ul>
+*/
+int sqlite3_changes(sqlite3*);
+sqlite3_int64 sqlite3_changes64(sqlite3*);
+
+/*
+** CAPI3REF: Total Number Of Rows Modified
+** METHOD: sqlite3
+**
+** ^These functions return the total number of rows inserted, modified or
+** deleted by all [INSERT], [UPDATE] or [DELETE] statements completed
+** since the database connection was opened, including those executed as
+** part of trigger programs. The two functions are identical except for the
+** type of the return value and that if the number of rows modified by the
+** connection exceeds the maximum value supported by type "int", then
+** the return value of sqlite3_total_changes() is undefined. ^Executing
+** any other type of SQL statement does not affect the value returned by
+** sqlite3_total_changes().
+**
+** ^Changes made as part of [foreign key actions] are included in the
+** count, but those made as part of REPLACE constraint resolution are
+** not. ^Changes to a view that are intercepted by INSTEAD OF triggers
+** are not counted.
+**
+** The [sqlite3_total_changes(D)] interface only reports the number
+** of rows that changed due to SQL statement run against database
+** connection D.  Any changes by other database connections are ignored.
+** To detect changes against a database file from other database
+** connections use the [PRAGMA data_version] command or the
+** [SQLITE_FCNTL_DATA_VERSION] [file control].
+**
+** If a separate thread makes changes on the same database connection
+** while [sqlite3_total_changes()] is running then the value
+** returned is unpredictable and not meaningful.
+**
+** See also:
+** <ul>
+** <li> the [sqlite3_changes()] interface
+** <li> the [count_changes pragma]
+** <li> the [changes() SQL function]
+** <li> the [data_version pragma]
+** <li> the [SQLITE_FCNTL_DATA_VERSION] [file control]
+** </ul>
+*/
+int sqlite3_total_changes(sqlite3*);
+sqlite3_int64 sqlite3_total_changes64(sqlite3*);
+
+/*
+** CAPI3REF: Interrupt A Long-Running Query
+** METHOD: sqlite3
+**
+** ^This function causes any pending database operation to abort and
+** return at its earliest opportunity. This routine is typically
+** called in response to a user action such as pressing "Cancel"
+** or Ctrl-C where the user wants a long query operation to halt
+** immediately.
+**
+** ^It is safe to call this routine from a thread different from the
+** thread that is currently running the database operation.  But it
+** is not safe to call this routine with a [database connection] that
+** is closed or might close before sqlite3_interrupt() returns.
+**
+** ^If an SQL operation is very nearly finished at the time when
+** sqlite3_interrupt() is called, then it might not have an opportunity
+** to be interrupted and might continue to completion.
+**
+** ^An SQL operation that is interrupted will return [SQLITE_INTERRUPT].
+** ^If the interrupted SQL operation is an INSERT, UPDATE, or DELETE
+** that is inside an explicit transaction, then the entire transaction
+** will be rolled back automatically.
+**
+** ^The sqlite3_interrupt(D) call is in effect until all currently running
+** SQL statements on [database connection] D complete.  ^Any new SQL statements
+** that are started after the sqlite3_interrupt() call and before the
+** running statement count reaches zero are interrupted as if they had been
+** running prior to the sqlite3_interrupt() call.  ^New SQL statements
+** that are started after the running statement count reaches zero are
+** not effected by the sqlite3_interrupt().
+** ^A call to sqlite3_interrupt(D) that occurs when there are no running
+** SQL statements is a no-op and has no effect on SQL statements
+** that are started after the sqlite3_interrupt() call returns.
+**
+** ^The [sqlite3_is_interrupted(D)] interface can be used to determine whether
+** or not an interrupt is currently in effect for [database connection] D.
+** It returns 1 if an interrupt is currently in effect, or 0 otherwise.
+*/
+void sqlite3_interrupt(sqlite3*);
+int sqlite3_is_interrupted(sqlite3*);
+
+/*
+** CAPI3REF: Determine If An SQL Statement Is Complete
+**
+** These routines are useful during command-line input to determine if the
+** currently entered text seems to form a complete SQL statement or
+** if additional input is needed before sending the text into
+** SQLite for parsing.  ^These routines return 1 if the input string
+** appears to be a complete SQL statement.  ^A statement is judged to be
+** complete if it ends with a semicolon token and is not a prefix of a
+** well-formed CREATE TRIGGER statement.  ^Semicolons that are embedded within
+** string literals or quoted identifier names or comments are not
+** independent tokens (they are part of the token in which they are
+** embedded) and thus do not count as a statement terminator.  ^Whitespace
+** and comments that follow the final semicolon are ignored.
+**
+** ^These routines return 0 if the statement is incomplete.  ^If a
+** memory allocation fails, then SQLITE_NOMEM is returned.
+**
+** ^These routines do not parse the SQL statements thus
+** will not detect syntactically incorrect SQL.
+**
+** ^(If SQLite has not been initialized using [sqlite3_initialize()] prior
+** to invoking sqlite3_complete16() then sqlite3_initialize() is invoked
+** automatically by sqlite3_complete16().  If that initialization fails,
+** then the return value from sqlite3_complete16() will be non-zero
+** regardless of whether or not the input SQL is complete.)^
+**
+** The input to [sqlite3_complete()] must be a zero-terminated
+** UTF-8 string.
+**
+** The input to [sqlite3_complete16()] must be a zero-terminated
+** UTF-16 string in native byte order.
+*/
+int sqlite3_complete(const char *sql);
+int sqlite3_complete16(const void *sql);
+
+/*
+** CAPI3REF: Register A Callback To Handle SQLITE_BUSY Errors
+** KEYWORDS: {busy-handler callback} {busy handler}
+** METHOD: sqlite3
+**
+** ^The sqlite3_busy_handler(D,X,P) routine sets a callback function X
+** that might be invoked with argument P whenever
+** an attempt is made to access a database table associated with
+** [database connection] D when another thread
+** or process has the table locked.
+** The sqlite3_busy_handler() interface is used to implement
+** [sqlite3_busy_timeout()] and [PRAGMA busy_timeout].
+**
+** ^If the busy callback is NULL, then [SQLITE_BUSY]
+** is returned immediately upon encountering the lock.  ^If the busy callback
+** is not NULL, then the callback might be invoked with two arguments.
+**
+** ^The first argument to the busy handler is a copy of the void* pointer which
+** is the third argument to sqlite3_busy_handler().  ^The second argument to
+** the busy handler callback is the number of times that the busy handler has
+** been invoked previously for the same locking event.  ^If the
+** busy callback returns 0, then no additional attempts are made to
+** access the database and [SQLITE_BUSY] is returned
+** to the application.
+** ^If the callback returns non-zero, then another attempt
+** is made to access the database and the cycle repeats.
+**
+** The presence of a busy handler does not guarantee that it will be invoked
+** when there is lock contention. ^If SQLite determines that invoking the busy
+** handler could result in a deadlock, it will go ahead and return [SQLITE_BUSY]
+** to the application instead of invoking the
+** busy handler.
+** Consider a scenario where one process is holding a read lock that
+** it is trying to promote to a reserved lock and
+** a second process is holding a reserved lock that it is trying
+** to promote to an exclusive lock.  The first process cannot proceed
+** because it is blocked by the second and the second process cannot
+** proceed because it is blocked by the first.  If both processes
+** invoke the busy handlers, neither will make any progress.  Therefore,
+** SQLite returns [SQLITE_BUSY] for the first process, hoping that this
+** will induce the first process to release its read lock and allow
+** the second process to proceed.
+**
+** ^The default busy callback is NULL.
+**
+** ^(There can only be a single busy handler defined for each
+** [database connection].  Setting a new busy handler clears any
+** previously set handler.)^  ^Note that calling [sqlite3_busy_timeout()]
+** or evaluating [PRAGMA busy_timeout=N] will change the
+** busy handler and thus clear any previously set busy handler.
+**
+** The busy callback should not take any actions which modify the
+** database connection that invoked the busy handler.  In other words,
+** the busy handler is not reentrant.  Any such actions
+** result in undefined behavior.
+**
+** A busy handler must not close the database connection
+** or [prepared statement] that invoked the busy handler.
+*/
+int sqlite3_busy_handler(sqlite3*,int(*)(void*,int),void*);
+
+/*
+** CAPI3REF: Set A Busy Timeout
+** METHOD: sqlite3
+**
+** ^This routine sets a [sqlite3_busy_handler | busy handler] that sleeps
+** for a specified amount of time when a table is locked.  ^The handler
+** will sleep multiple times until at least "ms" milliseconds of sleeping
+** have accumulated.  ^After at least "ms" milliseconds of sleeping,
+** the handler returns 0 which causes [sqlite3_step()] to return
+** [SQLITE_BUSY].
+**
+** ^Calling this routine with an argument less than or equal to zero
+** turns off all busy handlers.
+**
+** ^(There can only be a single busy handler for a particular
+** [database connection] at any given moment.  If another busy handler
+** was defined  (using [sqlite3_busy_handler()]) prior to calling
+** this routine, that other busy handler is cleared.)^
+**
+** See also:  [PRAGMA busy_timeout]
+*/
+int sqlite3_busy_timeout(sqlite3*, int ms);
+
+/*
+** CAPI3REF: Convenience Routines For Running Queries
+** METHOD: sqlite3
+**
+** This is a legacy interface that is preserved for backwards compatibility.
+** Use of this interface is not recommended.
+**
+** Definition: A <b>result table</b> is memory data structure created by the
+** [sqlite3_get_table()] interface.  A result table records the
+** complete query results from one or more queries.
+**
+** The table conceptually has a number of rows and columns.  But
+** these numbers are not part of the result table itself.  These
+** numbers are obtained separately.  Let N be the number of rows
+** and M be the number of columns.
+**
+** A result table is an array of pointers to zero-terminated UTF-8 strings.
+** There are (N+1)*M elements in the array.  The first M pointers point
+** to zero-terminated strings that  contain the names of the columns.
+** The remaining entries all point to query results.  NULL values result
+** in NULL pointers.  All other values are in their UTF-8 zero-terminated
+** string representation as returned by [sqlite3_column_text()].
+**
+** A result table might consist of one or more memory allocations.
+** It is not safe to pass a result table directly to [sqlite3_free()].
+** A result table should be deallocated using [sqlite3_free_table()].
+**
+** ^(As an example of the result table format, suppose a query result
+** is as follows:
+**
+** <blockquote><pre>
+**        Name        | Age
+**        -----------------------
+**        Alice       | 43
+**        Bob         | 28
+**        Cindy       | 21
+** </pre></blockquote>
+**
+** There are two columns (M==2) and three rows (N==3).  Thus the
+** result table has 8 entries.  Suppose the result table is stored
+** in an array named azResult.  Then azResult holds this content:
+**
+** <blockquote><pre>
+**        azResult&#91;0] = "Name";
+**        azResult&#91;1] = "Age";
+**        azResult&#91;2] = "Alice";
+**        azResult&#91;3] = "43";
+**        azResult&#91;4] = "Bob";
+**        azResult&#91;5] = "28";
+**        azResult&#91;6] = "Cindy";
+**        azResult&#91;7] = "21";
+** </pre></blockquote>)^
+**
+** ^The sqlite3_get_table() function evaluates one or more
+** semicolon-separated SQL statements in the zero-terminated UTF-8
+** string of its 2nd parameter and returns a result table to the
+** pointer given in its 3rd parameter.
+**
+** After the application has finished with the result from sqlite3_get_table(),
+** it must pass the result table pointer to sqlite3_free_table() in order to
+** release the memory that was malloced.  Because of the way the
+** [sqlite3_malloc()] happens within sqlite3_get_table(), the calling
+** function must not try to call [sqlite3_free()] directly.  Only
+** [sqlite3_free_table()] is able to release the memory properly and safely.
+**
+** The sqlite3_get_table() interface is implemented as a wrapper around
+** [sqlite3_exec()].  The sqlite3_get_table() routine does not have access
+** to any internal data structures of SQLite.  It uses only the public
+** interface defined here.  As a consequence, errors that occur in the
+** wrapper layer outside of the internal [sqlite3_exec()] call are not
+** reflected in subsequent calls to [sqlite3_errcode()] or
+** [sqlite3_errmsg()].
+*/
+int sqlite3_get_table(
+  sqlite3 *db,          /* An open database */
+  const char *zSql,     /* SQL to be evaluated */
+  char ***pazResult,    /* Results of the query */
+  int *pnRow,           /* Number of result rows written here */
+  int *pnColumn,        /* Number of result columns written here */
+  char **pzErrmsg       /* Error msg written here */
+);
+void sqlite3_free_table(char **result);
+
+/*
+** CAPI3REF: Formatted String Printing Functions
+**
+** These routines are work-alikes of the "printf()" family of functions
+** from the standard C library.
+** These routines understand most of the common formatting options from
+** the standard library printf()
+** plus some additional non-standard formats ([%q], [%Q], [%w], and [%z]).
+** See the [built-in printf()] documentation for details.
+**
+** ^The sqlite3_mprintf() and sqlite3_vmprintf() routines write their
+** results into memory obtained from [sqlite3_malloc64()].
+** The strings returned by these two routines should be
+** released by [sqlite3_free()].  ^Both routines return a
+** NULL pointer if [sqlite3_malloc64()] is unable to allocate enough
+** memory to hold the resulting string.
+**
+** ^(The sqlite3_snprintf() routine is similar to "snprintf()" from
+** the standard C library.  The result is written into the
+** buffer supplied as the second parameter whose size is given by
+** the first parameter. Note that the order of the
+** first two parameters is reversed from snprintf().)^  This is an
+** historical accident that cannot be fixed without breaking
+** backwards compatibility.  ^(Note also that sqlite3_snprintf()
+** returns a pointer to its buffer instead of the number of
+** characters actually written into the buffer.)^  We admit that
+** the number of characters written would be a more useful return
+** value but we cannot change the implementation of sqlite3_snprintf()
+** now without breaking compatibility.
+**
+** ^As long as the buffer size is greater than zero, sqlite3_snprintf()
+** guarantees that the buffer is always zero-terminated.  ^The first
+** parameter "n" is the total size of the buffer, including space for
+** the zero terminator.  So the longest string that can be completely
+** written will be n-1 characters.
+**
+** ^The sqlite3_vsnprintf() routine is a varargs version of sqlite3_snprintf().
+**
+** See also:  [built-in printf()], [printf() SQL function]
+*/
+char *sqlite3_mprintf(const char*,...);
+char *sqlite3_vmprintf(const char*, va_list);
+char *sqlite3_snprintf(int,char*,const char*, ...);
+char *sqlite3_vsnprintf(int,char*,const char*, va_list);
+
+/*
+** CAPI3REF: Memory Allocation Subsystem
+**
+** The SQLite core uses these three routines for all of its own
+** internal memory allocation needs. "Core" in the previous sentence
+** does not include operating-system specific [VFS] implementation.  The
+** Windows VFS uses native malloc() and free() for some operations.
+**
+** ^The sqlite3_malloc() routine returns a pointer to a block
+** of memory at least N bytes in length, where N is the parameter.
+** ^If sqlite3_malloc() is unable to obtain sufficient free
+** memory, it returns a NULL pointer.  ^If the parameter N to
+** sqlite3_malloc() is zero or negative then sqlite3_malloc() returns
+** a NULL pointer.
+**
+** ^The sqlite3_malloc64(N) routine works just like
+** sqlite3_malloc(N) except that N is an unsigned 64-bit integer instead
+** of a signed 32-bit integer.
+**
+** ^Calling sqlite3_free() with a pointer previously returned
+** by sqlite3_malloc() or sqlite3_realloc() releases that memory so
+** that it might be reused.  ^The sqlite3_free() routine is
+** a no-op if is called with a NULL pointer.  Passing a NULL pointer
+** to sqlite3_free() is harmless.  After being freed, memory
+** should neither be read nor written.  Even reading previously freed
+** memory might result in a segmentation fault or other severe error.
+** Memory corruption, a segmentation fault, or other severe error
+** might result if sqlite3_free() is called with a non-NULL pointer that
+** was not obtained from sqlite3_malloc() or sqlite3_realloc().
+**
+** ^The sqlite3_realloc(X,N) interface attempts to resize a
+** prior memory allocation X to be at least N bytes.
+** ^If the X parameter to sqlite3_realloc(X,N)
+** is a NULL pointer then its behavior is identical to calling
+** sqlite3_malloc(N).
+** ^If the N parameter to sqlite3_realloc(X,N) is zero or
+** negative then the behavior is exactly the same as calling
+** sqlite3_free(X).
+** ^sqlite3_realloc(X,N) returns a pointer to a memory allocation
+** of at least N bytes in size or NULL if insufficient memory is available.
+** ^If M is the size of the prior allocation, then min(N,M) bytes
+** of the prior allocation are copied into the beginning of buffer returned
+** by sqlite3_realloc(X,N) and the prior allocation is freed.
+** ^If sqlite3_realloc(X,N) returns NULL and N is positive, then the
+** prior allocation is not freed.
+**
+** ^The sqlite3_realloc64(X,N) interfaces works the same as
+** sqlite3_realloc(X,N) except that N is a 64-bit unsigned integer instead
+** of a 32-bit signed integer.
+**
+** ^If X is a memory allocation previously obtained from sqlite3_malloc(),
+** sqlite3_malloc64(), sqlite3_realloc(), or sqlite3_realloc64(), then
+** sqlite3_msize(X) returns the size of that memory allocation in bytes.
+** ^The value returned by sqlite3_msize(X) might be larger than the number
+** of bytes requested when X was allocated.  ^If X is a NULL pointer then
+** sqlite3_msize(X) returns zero.  If X points to something that is not
+** the beginning of memory allocation, or if it points to a formerly
+** valid memory allocation that has now been freed, then the behavior
+** of sqlite3_msize(X) is undefined and possibly harmful.
+**
+** ^The memory returned by sqlite3_malloc(), sqlite3_realloc(),
+** sqlite3_malloc64(), and sqlite3_realloc64()
+** is always aligned to at least an 8 byte boundary, or to a
+** 4 byte boundary if the [SQLITE_4_BYTE_ALIGNED_MALLOC] compile-time
+** option is used.
+**
+** The pointer arguments to [sqlite3_free()] and [sqlite3_realloc()]
+** must be either NULL or else pointers obtained from a prior
+** invocation of [sqlite3_malloc()] or [sqlite3_realloc()] that have
+** not yet been released.
+**
+** The application must not read or write any part of
+** a block of memory after it has been released using
+** [sqlite3_free()] or [sqlite3_realloc()].
+*/
+void *sqlite3_malloc(int);
+void *sqlite3_malloc64(sqlite3_uint64);
+void *sqlite3_realloc(void*, int);
+void *sqlite3_realloc64(void*, sqlite3_uint64);
+void sqlite3_free(void*);
+sqlite3_uint64 sqlite3_msize(void*);
+
+/*
+** CAPI3REF: Memory Allocator Statistics
+**
+** SQLite provides these two interfaces for reporting on the status
+** of the [sqlite3_malloc()], [sqlite3_free()], and [sqlite3_realloc()]
+** routines, which form the built-in memory allocation subsystem.
+**
+** ^The [sqlite3_memory_used()] routine returns the number of bytes
+** of memory currently outstanding (malloced but not freed).
+** ^The [sqlite3_memory_highwater()] routine returns the maximum
+** value of [sqlite3_memory_used()] since the high-water mark
+** was last reset.  ^The values returned by [sqlite3_memory_used()] and
+** [sqlite3_memory_highwater()] include any overhead
+** added by SQLite in its implementation of [sqlite3_malloc()],
+** but not overhead added by the any underlying system library
+** routines that [sqlite3_malloc()] may call.
+**
+** ^The memory high-water mark is reset to the current value of
+** [sqlite3_memory_used()] if and only if the parameter to
+** [sqlite3_memory_highwater()] is true.  ^The value returned
+** by [sqlite3_memory_highwater(1)] is the high-water mark
+** prior to the reset.
+*/
+sqlite3_int64 sqlite3_memory_used(void);
+sqlite3_int64 sqlite3_memory_highwater(int resetFlag);
+
+/*
+** CAPI3REF: Pseudo-Random Number Generator
+**
+** SQLite contains a high-quality pseudo-random number generator (PRNG) used to
+** select random [ROWID | ROWIDs] when inserting new records into a table that
+** already uses the largest possible [ROWID].  The PRNG is also used for
+** the built-in random() and randomblob() SQL functions.  This interface allows
+** applications to access the same PRNG for other purposes.
+**
+** ^A call to this routine stores N bytes of randomness into buffer P.
+** ^The P parameter can be a NULL pointer.
+**
+** ^If this routine has not been previously called or if the previous
+** call had N less than one or a NULL pointer for P, then the PRNG is
+** seeded using randomness obtained from the xRandomness method of
+** the default [sqlite3_vfs] object.
+** ^If the previous call to this routine had an N of 1 or more and a
+** non-NULL P then the pseudo-randomness is generated
+** internally and without recourse to the [sqlite3_vfs] xRandomness
+** method.
+*/
+void sqlite3_randomness(int N, void *P);
+
+/*
+** CAPI3REF: Compile-Time Authorization Callbacks
+** METHOD: sqlite3
+** KEYWORDS: {authorizer callback}
+**
+** ^This routine registers an authorizer callback with a particular
+** [database connection], supplied in the first argument.
+** ^The authorizer callback is invoked as SQL statements are being compiled
+** by [sqlite3_prepare()] or its variants [sqlite3_prepare_v2()],
+** [sqlite3_prepare_v3()], [sqlite3_prepare16()], [sqlite3_prepare16_v2()],
+** and [sqlite3_prepare16_v3()].  ^At various
+** points during the compilation process, as logic is being created
+** to perform various actions, the authorizer callback is invoked to
+** see if those actions are allowed.  ^The authorizer callback should
+** return [SQLITE_OK] to allow the action, [SQLITE_IGNORE] to disallow the
+** specific action but allow the SQL statement to continue to be
+** compiled, or [SQLITE_DENY] to cause the entire SQL statement to be
+** rejected with an error.  ^If the authorizer callback returns
+** any value other than [SQLITE_IGNORE], [SQLITE_OK], or [SQLITE_DENY]
+** then the [sqlite3_prepare_v2()] or equivalent call that triggered
+** the authorizer will fail with an error message.
+**
+** When the callback returns [SQLITE_OK], that means the operation
+** requested is ok.  ^When the callback returns [SQLITE_DENY], the
+** [sqlite3_prepare_v2()] or equivalent call that triggered the
+** authorizer will fail with an error message explaining that
+** access is denied.
+**
+** ^The first parameter to the authorizer callback is a copy of the third
+** parameter to the sqlite3_set_authorizer() interface. ^The second parameter
+** to the callback is an integer [SQLITE_COPY | action code] that specifies
+** the particular action to be authorized. ^The third through sixth parameters
+** to the callback are either NULL pointers or zero-terminated strings
+** that contain additional details about the action to be authorized.
+** Applications must always be prepared to encounter a NULL pointer in any
+** of the third through the sixth parameters of the authorization callback.
+**
+** ^If the action code is [SQLITE_READ]
+** and the callback returns [SQLITE_IGNORE] then the
+** [prepared statement] statement is constructed to substitute
+** a NULL value in place of the table column that would have
+** been read if [SQLITE_OK] had been returned.  The [SQLITE_IGNORE]
+** return can be used to deny an untrusted user access to individual
+** columns of a table.
+** ^When a table is referenced by a [SELECT] but no column values are
+** extracted from that table (for example in a query like
+** "SELECT count(*) FROM tab") then the [SQLITE_READ] authorizer callback
+** is invoked once for that table with a column name that is an empty string.
+** ^If the action code is [SQLITE_DELETE] and the callback returns
+** [SQLITE_IGNORE] then the [DELETE] operation proceeds but the
+** [truncate optimization] is disabled and all rows are deleted individually.
+**
+** An authorizer is used when [sqlite3_prepare | preparing]
+** SQL statements from an untrusted source, to ensure that the SQL statements
+** do not try to access data they are not allowed to see, or that they do not
+** try to execute malicious statements that damage the database.  For
+** example, an application may allow a user to enter arbitrary
+** SQL queries for evaluation by a database.  But the application does
+** not want the user to be able to make arbitrary changes to the
+** database.  An authorizer could then be put in place while the
+** user-entered SQL is being [sqlite3_prepare | prepared] that
+** disallows everything except [SELECT] statements.
+**
+** Applications that need to process SQL from untrusted sources
+** might also consider lowering resource limits using [sqlite3_limit()]
+** and limiting database size using the [max_page_count] [PRAGMA]
+** in addition to using an authorizer.
+**
+** ^(Only a single authorizer can be in place on a database connection
+** at a time.  Each call to sqlite3_set_authorizer overrides the
+** previous call.)^  ^Disable the authorizer by installing a NULL callback.
+** The authorizer is disabled by default.
+**
+** The authorizer callback must not do anything that will modify
+** the database connection that invoked the authorizer callback.
+** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
+** database connections for the meaning of "modify" in this paragraph.
+**
+** ^When [sqlite3_prepare_v2()] is used to prepare a statement, the
+** statement might be re-prepared during [sqlite3_step()] due to a
+** schema change.  Hence, the application should ensure that the
+** correct authorizer callback remains in place during the [sqlite3_step()].
+**
+** ^Note that the authorizer callback is invoked only during
+** [sqlite3_prepare()] or its variants.  Authorization is not
+** performed during statement evaluation in [sqlite3_step()], unless
+** as stated in the previous paragraph, sqlite3_step() invokes
+** sqlite3_prepare_v2() to reprepare a statement after a schema change.
+*/
+int sqlite3_set_authorizer(
+  sqlite3*,
+  int (*xAuth)(void*,int,const char*,const char*,const char*,const char*),
+  void *pUserData
+);
+
+/*
+** CAPI3REF: Authorizer Return Codes
+**
+** The [sqlite3_set_authorizer | authorizer callback function] must
+** return either [SQLITE_OK] or one of these two constants in order
+** to signal SQLite whether or not the action is permitted.  See the
+** [sqlite3_set_authorizer | authorizer documentation] for additional
+** information.
+**
+** Note that SQLITE_IGNORE is also used as a [conflict resolution mode]
+** returned from the [sqlite3_vtab_on_conflict()] interface.
+*/
+#define SQLITE_DENY   1   /* Abort the SQL statement with an error */
+#define SQLITE_IGNORE 2   /* Don't allow access, but don't generate an error */
+
+/*
+** CAPI3REF: Authorizer Action Codes
+**
+** The [sqlite3_set_authorizer()] interface registers a callback function
+** that is invoked to authorize certain SQL statement actions.  The
+** second parameter to the callback is an integer code that specifies
+** what action is being authorized.  These are the integer action codes that
+** the authorizer callback may be passed.
+**
+** These action code values signify what kind of operation is to be
+** authorized.  The 3rd and 4th parameters to the authorization
+** callback function will be parameters or NULL depending on which of these
+** codes is used as the second parameter.  ^(The 5th parameter to the
+** authorizer callback is the name of the database ("main", "temp",
+** etc.) if applicable.)^  ^The 6th parameter to the authorizer callback
+** is the name of the inner-most trigger or view that is responsible for
+** the access attempt or NULL if this access attempt is directly from
+** top-level SQL code.
+*/
+/******************************************* 3rd ************ 4th ***********/
+#define SQLITE_CREATE_INDEX          1   /* Index Name      Table Name      */
+#define SQLITE_CREATE_TABLE          2   /* Table Name      NULL            */
+#define SQLITE_CREATE_TEMP_INDEX     3   /* Index Name      Table Name      */
+#define SQLITE_CREATE_TEMP_TABLE     4   /* Table Name      NULL            */
+#define SQLITE_CREATE_TEMP_TRIGGER   5   /* Trigger Name    Table Name      */
+#define SQLITE_CREATE_TEMP_VIEW      6   /* View Name       NULL            */
+#define SQLITE_CREATE_TRIGGER        7   /* Trigger Name    Table Name      */
+#define SQLITE_CREATE_VIEW           8   /* View Name       NULL            */
+#define SQLITE_DELETE                9   /* Table Name      NULL            */
+#define SQLITE_DROP_INDEX           10   /* Index Name      Table Name      */
+#define SQLITE_DROP_TABLE           11   /* Table Name      NULL            */
+#define SQLITE_DROP_TEMP_INDEX      12   /* Index Name      Table Name      */
+#define SQLITE_DROP_TEMP_TABLE      13   /* Table Name      NULL            */
+#define SQLITE_DROP_TEMP_TRIGGER    14   /* Trigger Name    Table Name      */
+#define SQLITE_DROP_TEMP_VIEW       15   /* View Name       NULL            */
+#define SQLITE_DROP_TRIGGER         16   /* Trigger Name    Table Name      */
+#define SQLITE_DROP_VIEW            17   /* View Name       NULL            */
+#define SQLITE_INSERT               18   /* Table Name      NULL            */
+#define SQLITE_PRAGMA               19   /* Pragma Name     1st arg or NULL */
+#define SQLITE_READ                 20   /* Table Name      Column Name     */
+#define SQLITE_SELECT               21   /* NULL            NULL            */
+#define SQLITE_TRANSACTION          22   /* Operation       NULL            */
+#define SQLITE_UPDATE               23   /* Table Name      Column Name     */
+#define SQLITE_ATTACH               24   /* Filename        NULL            */
+#define SQLITE_DETACH               25   /* Database Name   NULL            */
+#define SQLITE_ALTER_TABLE          26   /* Database Name   Table Name      */
+#define SQLITE_REINDEX              27   /* Index Name      NULL            */
+#define SQLITE_ANALYZE              28   /* Table Name      NULL            */
+#define SQLITE_CREATE_VTABLE        29   /* Table Name      Module Name     */
+#define SQLITE_DROP_VTABLE          30   /* Table Name      Module Name     */
+#define SQLITE_FUNCTION             31   /* NULL            Function Name   */
+#define SQLITE_SAVEPOINT            32   /* Operation       Savepoint Name  */
+#define SQLITE_COPY                  0   /* No longer used */
+#define SQLITE_RECURSIVE            33   /* NULL            NULL            */
+
+/*
+** CAPI3REF: Tracing And Profiling Functions
+** METHOD: sqlite3
+**
+** These routines are deprecated. Use the [sqlite3_trace_v2()] interface
+** instead of the routines described here.
+**
+** These routines register callback functions that can be used for
+** tracing and profiling the execution of SQL statements.
+**
+** ^The callback function registered by sqlite3_trace() is invoked at
+** various times when an SQL statement is being run by [sqlite3_step()].
+** ^The sqlite3_trace() callback is invoked with a UTF-8 rendering of the
+** SQL statement text as the statement first begins executing.
+** ^(Additional sqlite3_trace() callbacks might occur
+** as each triggered subprogram is entered.  The callbacks for triggers
+** contain a UTF-8 SQL comment that identifies the trigger.)^
+**
+** The [SQLITE_TRACE_SIZE_LIMIT] compile-time option can be used to limit
+** the length of [bound parameter] expansion in the output of sqlite3_trace().
+**
+** ^The callback function registered by sqlite3_profile() is invoked
+** as each SQL statement finishes.  ^The profile callback contains
+** the original statement text and an estimate of wall-clock time
+** of how long that statement took to run.  ^The profile callback
+** time is in units of nanoseconds, however the current implementation
+** is only capable of millisecond resolution so the six least significant
+** digits in the time are meaningless.  Future versions of SQLite
+** might provide greater resolution on the profiler callback.  Invoking
+** either [sqlite3_trace()] or [sqlite3_trace_v2()] will cancel the
+** profile callback.
+*/
+SQLITE_DEPRECATED void *sqlite3_trace(sqlite3*,
+   void(*xTrace)(void*,const char*), void*);
+SQLITE_DEPRECATED void *sqlite3_profile(sqlite3*,
+   void(*xProfile)(void*,const char*,sqlite3_uint64), void*);
+
+/*
+** CAPI3REF: SQL Trace Event Codes
+** KEYWORDS: SQLITE_TRACE
+**
+** These constants identify classes of events that can be monitored
+** using the [sqlite3_trace_v2()] tracing logic.  The M argument
+** to [sqlite3_trace_v2(D,M,X,P)] is an OR-ed combination of one or more of
+** the following constants.  ^The first argument to the trace callback
+** is one of the following constants.
+**
+** New tracing constants may be added in future releases.
+**
+** ^A trace callback has four arguments: xCallback(T,C,P,X).
+** ^The T argument is one of the integer type codes above.
+** ^The C argument is a copy of the context pointer passed in as the
+** fourth argument to [sqlite3_trace_v2()].
+** The P and X arguments are pointers whose meanings depend on T.
+**
+** <dl>
+** [[SQLITE_TRACE_STMT]] <dt>SQLITE_TRACE_STMT</dt>
+** <dd>^An SQLITE_TRACE_STMT callback is invoked when a prepared statement
+** first begins running and possibly at other times during the
+** execution of the prepared statement, such as at the start of each
+** trigger subprogram. ^The P argument is a pointer to the
+** [prepared statement]. ^The X argument is a pointer to a string which
+** is the unexpanded SQL text of the prepared statement or an SQL comment
+** that indicates the invocation of a trigger.  ^The callback can compute
+** the same text that would have been returned by the legacy [sqlite3_trace()]
+** interface by using the X argument when X begins with "--" and invoking
+** [sqlite3_expanded_sql(P)] otherwise.
+**
+** [[SQLITE_TRACE_PROFILE]] <dt>SQLITE_TRACE_PROFILE</dt>
+** <dd>^An SQLITE_TRACE_PROFILE callback provides approximately the same
+** information as is provided by the [sqlite3_profile()] callback.
+** ^The P argument is a pointer to the [prepared statement] and the
+** X argument points to a 64-bit integer which is approximately
+** the number of nanoseconds that the prepared statement took to run.
+** ^The SQLITE_TRACE_PROFILE callback is invoked when the statement finishes.
+**
+** [[SQLITE_TRACE_ROW]] <dt>SQLITE_TRACE_ROW</dt>
+** <dd>^An SQLITE_TRACE_ROW callback is invoked whenever a prepared
+** statement generates a single row of result.
+** ^The P argument is a pointer to the [prepared statement] and the
+** X argument is unused.
+**
+** [[SQLITE_TRACE_CLOSE]] <dt>SQLITE_TRACE_CLOSE</dt>
+** <dd>^An SQLITE_TRACE_CLOSE callback is invoked when a database
+** connection closes.
+** ^The P argument is a pointer to the [database connection] object
+** and the X argument is unused.
+** </dl>
+*/
+#define SQLITE_TRACE_STMT       0x01
+#define SQLITE_TRACE_PROFILE    0x02
+#define SQLITE_TRACE_ROW        0x04
+#define SQLITE_TRACE_CLOSE      0x08
+
+/*
+** CAPI3REF: SQL Trace Hook
+** METHOD: sqlite3
+**
+** ^The sqlite3_trace_v2(D,M,X,P) interface registers a trace callback
+** function X against [database connection] D, using property mask M
+** and context pointer P.  ^If the X callback is
+** NULL or if the M mask is zero, then tracing is disabled.  The
+** M argument should be the bitwise OR-ed combination of
+** zero or more [SQLITE_TRACE] constants.
+**
+** ^Each call to either sqlite3_trace(D,X,P) or sqlite3_trace_v2(D,M,X,P)
+** overrides (cancels) all prior calls to sqlite3_trace(D,X,P) or
+** sqlite3_trace_v2(D,M,X,P) for the [database connection] D.  Each
+** database connection may have at most one trace callback.
+**
+** ^The X callback is invoked whenever any of the events identified by
+** mask M occur.  ^The integer return value from the callback is currently
+** ignored, though this may change in future releases.  Callback
+** implementations should return zero to ensure future compatibility.
+**
+** ^A trace callback is invoked with four arguments: callback(T,C,P,X).
+** ^The T argument is one of the [SQLITE_TRACE]
+** constants to indicate why the callback was invoked.
+** ^The C argument is a copy of the context pointer.
+** The P and X arguments are pointers whose meanings depend on T.
+**
+** The sqlite3_trace_v2() interface is intended to replace the legacy
+** interfaces [sqlite3_trace()] and [sqlite3_profile()], both of which
+** are deprecated.
+*/
+int sqlite3_trace_v2(
+  sqlite3*,
+  unsigned uMask,
+  int(*xCallback)(unsigned,void*,void*,void*),
+  void *pCtx
+);
+
+/*
+** CAPI3REF: Query Progress Callbacks
+** METHOD: sqlite3
+**
+** ^The sqlite3_progress_handler(D,N,X,P) interface causes the callback
+** function X to be invoked periodically during long running calls to
+** [sqlite3_step()] and [sqlite3_prepare()] and similar for
+** database connection D.  An example use for this
+** interface is to keep a GUI updated during a large query.
+**
+** ^The parameter P is passed through as the only parameter to the
+** callback function X.  ^The parameter N is the approximate number of
+** [virtual machine instructions] that are evaluated between successive
+** invocations of the callback X.  ^If N is less than one then the progress
+** handler is disabled.
+**
+** ^Only a single progress handler may be defined at one time per
+** [database connection]; setting a new progress handler cancels the
+** old one.  ^Setting parameter X to NULL disables the progress handler.
+** ^The progress handler is also disabled by setting N to a value less
+** than 1.
+**
+** ^If the progress callback returns non-zero, the operation is
+** interrupted.  This feature can be used to implement a
+** "Cancel" button on a GUI progress dialog box.
+**
+** The progress handler callback must not do anything that will modify
+** the database connection that invoked the progress handler.
+** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
+** database connections for the meaning of "modify" in this paragraph.
+**
+** The progress handler callback would originally only be invoked from the
+** bytecode engine.  It still might be invoked during [sqlite3_prepare()]
+** and similar because those routines might force a reparse of the schema
+** which involves running the bytecode engine.  However, beginning with
+** SQLite version 3.41.0, the progress handler callback might also be
+** invoked directly from [sqlite3_prepare()] while analyzing and generating
+** code for complex queries.
+*/
+void sqlite3_progress_handler(sqlite3*, int, int(*)(void*), void*);
+
+/*
+** CAPI3REF: Opening A New Database Connection
+** CONSTRUCTOR: sqlite3
+**
+** ^These routines open an SQLite database file as specified by the
+** filename argument. ^The filename argument is interpreted as UTF-8 for
+** sqlite3_open() and sqlite3_open_v2() and as UTF-16 in the native byte
+** order for sqlite3_open16(). ^(A [database connection] handle is usually
+** returned in *ppDb, even if an error occurs.  The only exception is that
+** if SQLite is unable to allocate memory to hold the [sqlite3] object,
+** a NULL will be written into *ppDb instead of a pointer to the [sqlite3]
+** object.)^ ^(If the database is opened (and/or created) successfully, then
+** [SQLITE_OK] is returned.  Otherwise an [error code] is returned.)^ ^The
+** [sqlite3_errmsg()] or [sqlite3_errmsg16()] routines can be used to obtain
+** an English language description of the error following a failure of any
+** of the sqlite3_open() routines.
+**
+** ^The default encoding will be UTF-8 for databases created using
+** sqlite3_open() or sqlite3_open_v2().  ^The default encoding for databases
+** created using sqlite3_open16() will be UTF-16 in the native byte order.
+**
+** Whether or not an error occurs when it is opened, resources
+** associated with the [database connection] handle should be released by
+** passing it to [sqlite3_close()] when it is no longer required.
+**
+** The sqlite3_open_v2() interface works like sqlite3_open()
+** except that it accepts two additional parameters for additional control
+** over the new database connection.  ^(The flags parameter to
+** sqlite3_open_v2() must include, at a minimum, one of the following
+** three flag combinations:)^
+**
+** <dl>
+** ^(<dt>[SQLITE_OPEN_READONLY]</dt>
+** <dd>The database is opened in read-only mode.  If the database does
+** not already exist, an error is returned.</dd>)^
+**
+** ^(<dt>[SQLITE_OPEN_READWRITE]</dt>
+** <dd>The database is opened for reading and writing if possible, or
+** reading only if the file is write protected by the operating
+** system.  In either case the database must already exist, otherwise
+** an error is returned.  For historical reasons, if opening in
+** read-write mode fails due to OS-level permissions, an attempt is
+** made to open it in read-only mode. [sqlite3_db_readonly()] can be
+** used to determine whether the database is actually
+** read-write.</dd>)^
+**
+** ^(<dt>[SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]</dt>
+** <dd>The database is opened for reading and writing, and is created if
+** it does not already exist. This is the behavior that is always used for
+** sqlite3_open() and sqlite3_open16().</dd>)^
+** </dl>
+**
+** In addition to the required flags, the following optional flags are
+** also supported:
+**
+** <dl>
+** ^(<dt>[SQLITE_OPEN_URI]</dt>
+** <dd>The filename can be interpreted as a URI if this flag is set.</dd>)^
+**
+** ^(<dt>[SQLITE_OPEN_MEMORY]</dt>
+** <dd>The database will be opened as an in-memory database.  The database
+** is named by the "filename" argument for the purposes of cache-sharing,
+** if shared cache mode is enabled, but the "filename" is otherwise ignored.
+** </dd>)^
+**
+** ^(<dt>[SQLITE_OPEN_NOMUTEX]</dt>
+** <dd>The new database connection will use the "multi-thread"
+** [threading mode].)^  This means that separate threads are allowed
+** to use SQLite at the same time, as long as each thread is using
+** a different [database connection].
+**
+** ^(<dt>[SQLITE_OPEN_FULLMUTEX]</dt>
+** <dd>The new database connection will use the "serialized"
+** [threading mode].)^  This means the multiple threads can safely
+** attempt to use the same database connection at the same time.
+** (Mutexes will block any actual concurrency, but in this mode
+** there is no harm in trying.)
+**
+** ^(<dt>[SQLITE_OPEN_SHAREDCACHE]</dt>
+** <dd>The database is opened [shared cache] enabled, overriding
+** the default shared cache setting provided by
+** [sqlite3_enable_shared_cache()].)^
+** The [use of shared cache mode is discouraged] and hence shared cache
+** capabilities may be omitted from many builds of SQLite.  In such cases,
+** this option is a no-op.
+**
+** ^(<dt>[SQLITE_OPEN_PRIVATECACHE]</dt>
+** <dd>The database is opened [shared cache] disabled, overriding
+** the default shared cache setting provided by
+** [sqlite3_enable_shared_cache()].)^
+**
+** [[OPEN_EXRESCODE]] ^(<dt>[SQLITE_OPEN_EXRESCODE]</dt>
+** <dd>The database connection comes up in "extended result code mode".
+** In other words, the database behaves has if
+** [sqlite3_extended_result_codes(db,1)] where called on the database
+** connection as soon as the connection is created. In addition to setting
+** the extended result code mode, this flag also causes [sqlite3_open_v2()]
+** to return an extended result code.</dd>
+**
+** [[OPEN_NOFOLLOW]] ^(<dt>[SQLITE_OPEN_NOFOLLOW]</dt>
+** <dd>The database filename is not allowed to contain a symbolic link</dd>
+** </dl>)^
+**
+** If the 3rd parameter to sqlite3_open_v2() is not one of the
+** required combinations shown above optionally combined with other
+** [SQLITE_OPEN_READONLY | SQLITE_OPEN_* bits]
+** then the behavior is undefined.  Historic versions of SQLite
+** have silently ignored surplus bits in the flags parameter to
+** sqlite3_open_v2(), however that behavior might not be carried through
+** into future versions of SQLite and so applications should not rely
+** upon it.  Note in particular that the SQLITE_OPEN_EXCLUSIVE flag is a no-op
+** for sqlite3_open_v2().  The SQLITE_OPEN_EXCLUSIVE does *not* cause
+** the open to fail if the database already exists.  The SQLITE_OPEN_EXCLUSIVE
+** flag is intended for use by the [sqlite3_vfs|VFS interface] only, and not
+** by sqlite3_open_v2().
+**
+** ^The fourth parameter to sqlite3_open_v2() is the name of the
+** [sqlite3_vfs] object that defines the operating system interface that
+** the new database connection should use.  ^If the fourth parameter is
+** a NULL pointer then the default [sqlite3_vfs] object is used.
+**
+** ^If the filename is ":memory:", then a private, temporary in-memory database
+** is created for the connection.  ^This in-memory database will vanish when
+** the database connection is closed.  Future versions of SQLite might
+** make use of additional special filenames that begin with the ":" character.
+** It is recommended that when a database filename actually does begin with
+** a ":" character you should prefix the filename with a pathname such as
+** "./" to avoid ambiguity.
+**
+** ^If the filename is an empty string, then a private, temporary
+** on-disk database will be created.  ^This private database will be
+** automatically deleted as soon as the database connection is closed.
+**
+** [[URI filenames in sqlite3_open()]] <h3>URI Filenames</h3>
+**
+** ^If [URI filename] interpretation is enabled, and the filename argument
+** begins with "file:", then the filename is interpreted as a URI. ^URI
+** filename interpretation is enabled if the [SQLITE_OPEN_URI] flag is
+** set in the third argument to sqlite3_open_v2(), or if it has
+** been enabled globally using the [SQLITE_CONFIG_URI] option with the
+** [sqlite3_config()] method or by the [SQLITE_USE_URI] compile-time option.
+** URI filename interpretation is turned off
+** by default, but future releases of SQLite might enable URI filename
+** interpretation by default.  See "[URI filenames]" for additional
+** information.
+**
+** URI filenames are parsed according to RFC 3986. ^If the URI contains an
+** authority, then it must be either an empty string or the string
+** "localhost". ^If the authority is not an empty string or "localhost", an
+** error is returned to the caller. ^The fragment component of a URI, if
+** present, is ignored.
+**
+** ^SQLite uses the path component of the URI as the name of the disk file
+** which contains the database. ^If the path begins with a '/' character,
+** then it is interpreted as an absolute path. ^If the path does not begin
+** with a '/' (meaning that the authority section is omitted from the URI)
+** then the path is interpreted as a relative path.
+** ^(On windows, the first component of an absolute path
+** is a drive specification (e.g. "C:").)^
+**
+** [[core URI query parameters]]
+** The query component of a URI may contain parameters that are interpreted
+** either by SQLite itself, or by a [VFS | custom VFS implementation].
+** SQLite and its built-in [VFSes] interpret the
+** following query parameters:
+**
+** <ul>
+**   <li> <b>vfs</b>: ^The "vfs" parameter may be used to specify the name of
+**     a VFS object that provides the operating system interface that should
+**     be used to access the database file on disk. ^If this option is set to
+**     an empty string the default VFS object is used. ^Specifying an unknown
+**     VFS is an error. ^If sqlite3_open_v2() is used and the vfs option is
+**     present, then the VFS specified by the option takes precedence over
+**     the value passed as the fourth parameter to sqlite3_open_v2().
+**
+**   <li> <b>mode</b>: ^(The mode parameter may be set to either "ro", "rw",
+**     "rwc", or "memory". Attempting to set it to any other value is
+**     an error)^.
+**     ^If "ro" is specified, then the database is opened for read-only
+**     access, just as if the [SQLITE_OPEN_READONLY] flag had been set in the
+**     third argument to sqlite3_open_v2(). ^If the mode option is set to
+**     "rw", then the database is opened for read-write (but not create)
+**     access, as if SQLITE_OPEN_READWRITE (but not SQLITE_OPEN_CREATE) had
+**     been set. ^Value "rwc" is equivalent to setting both
+**     SQLITE_OPEN_READWRITE and SQLITE_OPEN_CREATE.  ^If the mode option is
+**     set to "memory" then a pure [in-memory database] that never reads
+**     or writes from disk is used. ^It is an error to specify a value for
+**     the mode parameter that is less restrictive than that specified by
+**     the flags passed in the third parameter to sqlite3_open_v2().
+**
+**   <li> <b>cache</b>: ^The cache parameter may be set to either "shared" or
+**     "private". ^Setting it to "shared" is equivalent to setting the
+**     SQLITE_OPEN_SHAREDCACHE bit in the flags argument passed to
+**     sqlite3_open_v2(). ^Setting the cache parameter to "private" is
+**     equivalent to setting the SQLITE_OPEN_PRIVATECACHE bit.
+**     ^If sqlite3_open_v2() is used and the "cache" parameter is present in
+**     a URI filename, its value overrides any behavior requested by setting
+**     SQLITE_OPEN_PRIVATECACHE or SQLITE_OPEN_SHAREDCACHE flag.
+**
+**  <li> <b>psow</b>: ^The psow parameter indicates whether or not the
+**     [powersafe overwrite] property does or does not apply to the
+**     storage media on which the database file resides.
+**
+**  <li> <b>nolock</b>: ^The nolock parameter is a boolean query parameter
+**     which if set disables file locking in rollback journal modes.  This
+**     is useful for accessing a database on a filesystem that does not
+**     support locking.  Caution:  Database corruption might result if two
+**     or more processes write to the same database and any one of those
+**     processes uses nolock=1.
+**
+**  <li> <b>immutable</b>: ^The immutable parameter is a boolean query
+**     parameter that indicates that the database file is stored on
+**     read-only media.  ^When immutable is set, SQLite assumes that the
+**     database file cannot be changed, even by a process with higher
+**     privilege, and so the database is opened read-only and all locking
+**     and change detection is disabled.  Caution: Setting the immutable
+**     property on a database file that does in fact change can result
+**     in incorrect query results and/or [SQLITE_CORRUPT] errors.
+**     See also: [SQLITE_IOCAP_IMMUTABLE].
+**      
+** </ul>
+**
+** ^Specifying an unknown parameter in the query component of a URI is not an
+** error.  Future versions of SQLite might understand additional query
+** parameters.  See "[query parameters with special meaning to SQLite]" for
+** additional information.
+**
+** [[URI filename examples]] <h3>URI filename examples</h3>
+**
+** <table border="1" align=center cellpadding=5>
+** <tr><th> URI filenames <th> Results
+** <tr><td> file:data.db <td>
+**          Open the file "data.db" in the current directory.
+** <tr><td> file:/home/fred/data.db<br>
+**          file:///home/fred/data.db <br>
+**          file://localhost/home/fred/data.db <br> <td>
+**          Open the database file "/home/fred/data.db".
+** <tr><td> file://darkstar/home/fred/data.db <td>
+**          An error. "darkstar" is not a recognized authority.
+** <tr><td style="white-space:nowrap">
+**          file:///C:/Documents%20and%20Settings/fred/Desktop/data.db
+**     <td> Windows only: Open the file "data.db" on fred's desktop on drive
+**          C:. Note that the %20 escaping in this example is not strictly
+**          necessary - space characters can be used literally
+**          in URI filenames.
+** <tr><td> file:data.db?mode=ro&cache=private <td>
+**          Open file "data.db" in the current directory for read-only access.
+**          Regardless of whether or not shared-cache mode is enabled by
+**          default, use a private cache.
+** <tr><td> file:/home/fred/data.db?vfs=unix-dotfile <td>
+**          Open file "/home/fred/data.db". Use the special VFS "unix-dotfile"
+**          that uses dot-files in place of posix advisory locking.
+** <tr><td> file:data.db?mode=readonly <td>
+**          An error. "readonly" is not a valid option for the "mode" parameter.
+**          Use "ro" instead:  "file:data.db?mode=ro".
+** </table>
+**
+** ^URI hexadecimal escape sequences (%HH) are supported within the path and
+** query components of a URI. A hexadecimal escape sequence consists of a
+** percent sign - "%" - followed by exactly two hexadecimal digits
+** specifying an octet value. ^Before the path or query components of a
+** URI filename are interpreted, they are encoded using UTF-8 and all
+** hexadecimal escape sequences replaced by a single byte containing the
+** corresponding octet. If this process generates an invalid UTF-8 encoding,
+** the results are undefined.
+**
+** <b>Note to Windows users:</b>  The encoding used for the filename argument
+** of sqlite3_open() and sqlite3_open_v2() must be UTF-8, not whatever
+** codepage is currently defined.  Filenames containing international
+** characters must be converted to UTF-8 prior to passing them into
+** sqlite3_open() or sqlite3_open_v2().
+**
+** <b>Note to Windows Runtime users:</b>  The temporary directory must be set
+** prior to calling sqlite3_open() or sqlite3_open_v2().  Otherwise, various
+** features that require the use of temporary files may fail.
+**
+** See also: [sqlite3_temp_directory]
+*/
+int sqlite3_open(
+  const char *filename,   /* Database filename (UTF-8) */
+  sqlite3 **ppDb          /* OUT: SQLite db handle */
+);
+int sqlite3_open16(
+  const void *filename,   /* Database filename (UTF-16) */
+  sqlite3 **ppDb          /* OUT: SQLite db handle */
+);
+int sqlite3_open_v2(
+  const char *filename,   /* Database filename (UTF-8) */
+  sqlite3 **ppDb,         /* OUT: SQLite db handle */
+  int flags,              /* Flags */
+  const char *zVfs        /* Name of VFS module to use */
+);
+
+/*
+** CAPI3REF: Obtain Values For URI Parameters
+**
+** These are utility routines, useful to [VFS|custom VFS implementations],
+** that check if a database file was a URI that contained a specific query
+** parameter, and if so obtains the value of that query parameter.
+**
+** The first parameter to these interfaces (hereafter referred to
+** as F) must be one of:
+** <ul>
+** <li> A database filename pointer created by the SQLite core and
+** passed into the xOpen() method of a VFS implementation, or
+** <li> A filename obtained from [sqlite3_db_filename()], or
+** <li> A new filename constructed using [sqlite3_create_filename()].
+** </ul>
+** If the F parameter is not one of the above, then the behavior is
+** undefined and probably undesirable.  Older versions of SQLite were
+** more tolerant of invalid F parameters than newer versions.
+**
+** If F is a suitable filename (as described in the previous paragraph)
+** and if P is the name of the query parameter, then
+** sqlite3_uri_parameter(F,P) returns the value of the P
+** parameter if it exists or a NULL pointer if P does not appear as a
+** query parameter on F.  If P is a query parameter of F and it
+** has no explicit value, then sqlite3_uri_parameter(F,P) returns
+** a pointer to an empty string.
+**
+** The sqlite3_uri_boolean(F,P,B) routine assumes that P is a boolean
+** parameter and returns true (1) or false (0) according to the value
+** of P.  The sqlite3_uri_boolean(F,P,B) routine returns true (1) if the
+** value of query parameter P is one of "yes", "true", or "on" in any
+** case or if the value begins with a non-zero number.  The
+** sqlite3_uri_boolean(F,P,B) routines returns false (0) if the value of
+** query parameter P is one of "no", "false", or "off" in any case or
+** if the value begins with a numeric zero.  If P is not a query
+** parameter on F or if the value of P does not match any of the
+** above, then sqlite3_uri_boolean(F,P,B) returns (B!=0).
+**
+** The sqlite3_uri_int64(F,P,D) routine converts the value of P into a
+** 64-bit signed integer and returns that integer, or D if P does not
+** exist.  If the value of P is something other than an integer, then
+** zero is returned.
+**
+** The sqlite3_uri_key(F,N) returns a pointer to the name (not
+** the value) of the N-th query parameter for filename F, or a NULL
+** pointer if N is less than zero or greater than the number of query
+** parameters minus 1.  The N value is zero-based so N should be 0 to obtain
+** the name of the first query parameter, 1 for the second parameter, and
+** so forth.
+**
+** If F is a NULL pointer, then sqlite3_uri_parameter(F,P) returns NULL and
+** sqlite3_uri_boolean(F,P,B) returns B.  If F is not a NULL pointer and
+** is not a database file pathname pointer that the SQLite core passed
+** into the xOpen VFS method, then the behavior of this routine is undefined
+** and probably undesirable.
+**
+** Beginning with SQLite [version 3.31.0] ([dateof:3.31.0]) the input F
+** parameter can also be the name of a rollback journal file or WAL file
+** in addition to the main database file.  Prior to version 3.31.0, these
+** routines would only work if F was the name of the main database file.
+** When the F parameter is the name of the rollback journal or WAL file,
+** it has access to all the same query parameters as were found on the
+** main database file.
+**
+** See the [URI filename] documentation for additional information.
+*/
+const char *sqlite3_uri_parameter(sqlite3_filename z, const char *zParam);
+int sqlite3_uri_boolean(sqlite3_filename z, const char *zParam, int bDefault);
+sqlite3_int64 sqlite3_uri_int64(sqlite3_filename, const char*, sqlite3_int64);
+const char *sqlite3_uri_key(sqlite3_filename z, int N);
+
+/*
+** CAPI3REF:  Translate filenames
+**
+** These routines are available to [VFS|custom VFS implementations] for
+** translating filenames between the main database file, the journal file,
+** and the WAL file.
+**
+** If F is the name of an sqlite database file, journal file, or WAL file
+** passed by the SQLite core into the VFS, then sqlite3_filename_database(F)
+** returns the name of the corresponding database file.
+**
+** If F is the name of an sqlite database file, journal file, or WAL file
+** passed by the SQLite core into the VFS, or if F is a database filename
+** obtained from [sqlite3_db_filename()], then sqlite3_filename_journal(F)
+** returns the name of the corresponding rollback journal file.
+**
+** If F is the name of an sqlite database file, journal file, or WAL file
+** that was passed by the SQLite core into the VFS, or if F is a database
+** filename obtained from [sqlite3_db_filename()], then
+** sqlite3_filename_wal(F) returns the name of the corresponding
+** WAL file.
+**
+** In all of the above, if F is not the name of a database, journal or WAL
+** filename passed into the VFS from the SQLite core and F is not the
+** return value from [sqlite3_db_filename()], then the result is
+** undefined and is likely a memory access violation.
+*/
+const char *sqlite3_filename_database(sqlite3_filename);
+const char *sqlite3_filename_journal(sqlite3_filename);
+const char *sqlite3_filename_wal(sqlite3_filename);
+
+/*
+** CAPI3REF:  Database File Corresponding To A Journal
+**
+** ^If X is the name of a rollback or WAL-mode journal file that is
+** passed into the xOpen method of [sqlite3_vfs], then
+** sqlite3_database_file_object(X) returns a pointer to the [sqlite3_file]
+** object that represents the main database file.
+**
+** This routine is intended for use in custom [VFS] implementations
+** only.  It is not a general-purpose interface.
+** The argument sqlite3_file_object(X) must be a filename pointer that
+** has been passed into [sqlite3_vfs].xOpen method where the
+** flags parameter to xOpen contains one of the bits
+** [SQLITE_OPEN_MAIN_JOURNAL] or [SQLITE_OPEN_WAL].  Any other use
+** of this routine results in undefined and probably undesirable
+** behavior.
+*/
+sqlite3_file *sqlite3_database_file_object(const char*);
+
+/*
+** CAPI3REF: Create and Destroy VFS Filenames
+**
+** These interfaces are provided for use by [VFS shim] implementations and
+** are not useful outside of that context.
+**
+** The sqlite3_create_filename(D,J,W,N,P) allocates memory to hold a version of
+** database filename D with corresponding journal file J and WAL file W and
+** with N URI parameters key/values pairs in the array P.  The result from
+** sqlite3_create_filename(D,J,W,N,P) is a pointer to a database filename that
+** is safe to pass to routines like:
+** <ul>
+** <li> [sqlite3_uri_parameter()],
+** <li> [sqlite3_uri_boolean()],
+** <li> [sqlite3_uri_int64()],
+** <li> [sqlite3_uri_key()],
+** <li> [sqlite3_filename_database()],
+** <li> [sqlite3_filename_journal()], or
+** <li> [sqlite3_filename_wal()].
+** </ul>
+** If a memory allocation error occurs, sqlite3_create_filename() might
+** return a NULL pointer.  The memory obtained from sqlite3_create_filename(X)
+** must be released by a corresponding call to sqlite3_free_filename(Y).
+**
+** The P parameter in sqlite3_create_filename(D,J,W,N,P) should be an array
+** of 2*N pointers to strings.  Each pair of pointers in this array corresponds
+** to a key and value for a query parameter.  The P parameter may be a NULL
+** pointer if N is zero.  None of the 2*N pointers in the P array may be
+** NULL pointers and key pointers should not be empty strings.
+** None of the D, J, or W parameters to sqlite3_create_filename(D,J,W,N,P) may
+** be NULL pointers, though they can be empty strings.
+**
+** The sqlite3_free_filename(Y) routine releases a memory allocation
+** previously obtained from sqlite3_create_filename().  Invoking
+** sqlite3_free_filename(Y) where Y is a NULL pointer is a harmless no-op.
+**
+** If the Y parameter to sqlite3_free_filename(Y) is anything other
+** than a NULL pointer or a pointer previously acquired from
+** sqlite3_create_filename(), then bad things such as heap
+** corruption or segfaults may occur. The value Y should not be
+** used again after sqlite3_free_filename(Y) has been called.  This means
+** that if the [sqlite3_vfs.xOpen()] method of a VFS has been called using Y,
+** then the corresponding [sqlite3_module.xClose() method should also be
+** invoked prior to calling sqlite3_free_filename(Y).
+*/
+sqlite3_filename sqlite3_create_filename(
+  const char *zDatabase,
+  const char *zJournal,
+  const char *zWal,
+  int nParam,
+  const char **azParam
+);
+void sqlite3_free_filename(sqlite3_filename);
+
+/*
+** CAPI3REF: Error Codes And Messages
+** METHOD: sqlite3
+**
+** ^If the most recent sqlite3_* API call associated with
+** [database connection] D failed, then the sqlite3_errcode(D) interface
+** returns the numeric [result code] or [extended result code] for that
+** API call.
+** ^The sqlite3_extended_errcode()
+** interface is the same except that it always returns the
+** [extended result code] even when extended result codes are
+** disabled.
+**
+** The values returned by sqlite3_errcode() and/or
+** sqlite3_extended_errcode() might change with each API call.
+** Except, there are some interfaces that are guaranteed to never
+** change the value of the error code.  The error-code preserving
+** interfaces include the following:
+**
+** <ul>
+** <li> sqlite3_errcode()
+** <li> sqlite3_extended_errcode()
+** <li> sqlite3_errmsg()
+** <li> sqlite3_errmsg16()
+** <li> sqlite3_error_offset()
+** </ul>
+**
+** ^The sqlite3_errmsg() and sqlite3_errmsg16() return English-language
+** text that describes the error, as either UTF-8 or UTF-16 respectively,
+** or NULL if no error message is available.
+** (See how SQLite handles [invalid UTF] for exceptions to this rule.)
+** ^(Memory to hold the error message string is managed internally.
+** The application does not need to worry about freeing the result.
+** However, the error string might be overwritten or deallocated by
+** subsequent calls to other SQLite interface functions.)^
+**
+** ^The sqlite3_errstr(E) interface returns the English-language text
+** that describes the [result code] E, as UTF-8, or NULL if E is not an
+** result code for which a text error message is available.
+** ^(Memory to hold the error message string is managed internally
+** and must not be freed by the application)^.
+**
+** ^If the most recent error references a specific token in the input
+** SQL, the sqlite3_error_offset() interface returns the byte offset
+** of the start of that token.  ^The byte offset returned by
+** sqlite3_error_offset() assumes that the input SQL is UTF8.
+** ^If the most recent error does not reference a specific token in the input
+** SQL, then the sqlite3_error_offset() function returns -1.
+**
+** When the serialized [threading mode] is in use, it might be the
+** case that a second error occurs on a separate thread in between
+** the time of the first error and the call to these interfaces.
+** When that happens, the second error will be reported since these
+** interfaces always report the most recent result.  To avoid
+** this, each thread can obtain exclusive use of the [database connection] D
+** by invoking [sqlite3_mutex_enter]([sqlite3_db_mutex](D)) before beginning
+** to use D and invoking [sqlite3_mutex_leave]([sqlite3_db_mutex](D)) after
+** all calls to the interfaces listed here are completed.
+**
+** If an interface fails with SQLITE_MISUSE, that means the interface
+** was invoked incorrectly by the application.  In that case, the
+** error code and message may or may not be set.
+*/
+int sqlite3_errcode(sqlite3 *db);
+int sqlite3_extended_errcode(sqlite3 *db);
+const char *sqlite3_errmsg(sqlite3*);
+const void *sqlite3_errmsg16(sqlite3*);
+const char *sqlite3_errstr(int);
+int sqlite3_error_offset(sqlite3 *db);
+
+/*
+** CAPI3REF: Prepared Statement Object
+** KEYWORDS: {prepared statement} {prepared statements}
+**
+** An instance of this object represents a single SQL statement that
+** has been compiled into binary form and is ready to be evaluated.
+**
+** Think of each SQL statement as a separate computer program.  The
+** original SQL text is source code.  A prepared statement object
+** is the compiled object code.  All SQL must be converted into a
+** prepared statement before it can be run.
+**
+** The life-cycle of a prepared statement object usually goes like this:
+**
+** <ol>
+** <li> Create the prepared statement object using [sqlite3_prepare_v2()].
+** <li> Bind values to [parameters] using the sqlite3_bind_*()
+**      interfaces.
+** <li> Run the SQL by calling [sqlite3_step()] one or more times.
+** <li> Reset the prepared statement using [sqlite3_reset()] then go back
+**      to step 2.  Do this zero or more times.
+** <li> Destroy the object using [sqlite3_finalize()].
+** </ol>
+*/
+typedef struct sqlite3_stmt sqlite3_stmt;
+
+/*
+** CAPI3REF: Run-time Limits
+** METHOD: sqlite3
+**
+** ^(This interface allows the size of various constructs to be limited
+** on a connection by connection basis.  The first parameter is the
+** [database connection] whose limit is to be set or queried.  The
+** second parameter is one of the [limit categories] that define a
+** class of constructs to be size limited.  The third parameter is the
+** new limit for that construct.)^
+**
+** ^If the new limit is a negative number, the limit is unchanged.
+** ^(For each limit category SQLITE_LIMIT_<i>NAME</i> there is a
+** [limits | hard upper bound]
+** set at compile-time by a C preprocessor macro called
+** [limits | SQLITE_MAX_<i>NAME</i>].
+** (The "_LIMIT_" in the name is changed to "_MAX_".))^
+** ^Attempts to increase a limit above its hard upper bound are
+** silently truncated to the hard upper bound.
+**
+** ^Regardless of whether or not the limit was changed, the
+** [sqlite3_limit()] interface returns the prior value of the limit.
+** ^Hence, to find the current value of a limit without changing it,
+** simply invoke this interface with the third parameter set to -1.
+**
+** Run-time limits are intended for use in applications that manage
+** both their own internal database and also databases that are controlled
+** by untrusted external sources.  An example application might be a
+** web browser that has its own databases for storing history and
+** separate databases controlled by JavaScript applications downloaded
+** off the Internet.  The internal databases can be given the
+** large, default limits.  Databases managed by external sources can
+** be given much smaller limits designed to prevent a denial of service
+** attack.  Developers might also want to use the [sqlite3_set_authorizer()]
+** interface to further control untrusted SQL.  The size of the database
+** created by an untrusted script can be contained using the
+** [max_page_count] [PRAGMA].
+**
+** New run-time limit categories may be added in future releases.
+*/
+int sqlite3_limit(sqlite3*, int id, int newVal);
+
+/*
+** CAPI3REF: Run-Time Limit Categories
+** KEYWORDS: {limit category} {*limit categories}
+**
+** These constants define various performance limits
+** that can be lowered at run-time using [sqlite3_limit()].
+** The synopsis of the meanings of the various limits is shown below.
+** Additional information is available at [limits | Limits in SQLite].
+**
+** <dl>
+** [[SQLITE_LIMIT_LENGTH]] ^(<dt>SQLITE_LIMIT_LENGTH</dt>
+** <dd>The maximum size of any string or BLOB or table row, in bytes.<dd>)^
+**
+** [[SQLITE_LIMIT_SQL_LENGTH]] ^(<dt>SQLITE_LIMIT_SQL_LENGTH</dt>
+** <dd>The maximum length of an SQL statement, in bytes.</dd>)^
+**
+** [[SQLITE_LIMIT_COLUMN]] ^(<dt>SQLITE_LIMIT_COLUMN</dt>
+** <dd>The maximum number of columns in a table definition or in the
+** result set of a [SELECT] or the maximum number of columns in an index
+** or in an ORDER BY or GROUP BY clause.</dd>)^
+**
+** [[SQLITE_LIMIT_EXPR_DEPTH]] ^(<dt>SQLITE_LIMIT_EXPR_DEPTH</dt>
+** <dd>The maximum depth of the parse tree on any expression.</dd>)^
+**
+** [[SQLITE_LIMIT_COMPOUND_SELECT]] ^(<dt>SQLITE_LIMIT_COMPOUND_SELECT</dt>
+** <dd>The maximum number of terms in a compound SELECT statement.</dd>)^
+**
+** [[SQLITE_LIMIT_VDBE_OP]] ^(<dt>SQLITE_LIMIT_VDBE_OP</dt>
+** <dd>The maximum number of instructions in a virtual machine program
+** used to implement an SQL statement.  If [sqlite3_prepare_v2()] or
+** the equivalent tries to allocate space for more than this many opcodes
+** in a single prepared statement, an SQLITE_NOMEM error is returned.</dd>)^
+**
+** [[SQLITE_LIMIT_FUNCTION_ARG]] ^(<dt>SQLITE_LIMIT_FUNCTION_ARG</dt>
+** <dd>The maximum number of arguments on a function.</dd>)^
+**
+** [[SQLITE_LIMIT_ATTACHED]] ^(<dt>SQLITE_LIMIT_ATTACHED</dt>
+** <dd>The maximum number of [ATTACH | attached databases].)^</dd>
+**
+** [[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]]
+** ^(<dt>SQLITE_LIMIT_LIKE_PATTERN_LENGTH</dt>
+** <dd>The maximum length of the pattern argument to the [LIKE] or
+** [GLOB] operators.</dd>)^
+**
+** [[SQLITE_LIMIT_VARIABLE_NUMBER]]
+** ^(<dt>SQLITE_LIMIT_VARIABLE_NUMBER</dt>
+** <dd>The maximum index number of any [parameter] in an SQL statement.)^
+**
+** [[SQLITE_LIMIT_TRIGGER_DEPTH]] ^(<dt>SQLITE_LIMIT_TRIGGER_DEPTH</dt>
+** <dd>The maximum depth of recursion for triggers.</dd>)^
+**
+** [[SQLITE_LIMIT_WORKER_THREADS]] ^(<dt>SQLITE_LIMIT_WORKER_THREADS</dt>
+** <dd>The maximum number of auxiliary worker threads that a single
+** [prepared statement] may start.</dd>)^
+** </dl>
+*/
+#define SQLITE_LIMIT_LENGTH                    0
+#define SQLITE_LIMIT_SQL_LENGTH                1
+#define SQLITE_LIMIT_COLUMN                    2
+#define SQLITE_LIMIT_EXPR_DEPTH                3
+#define SQLITE_LIMIT_COMPOUND_SELECT           4
+#define SQLITE_LIMIT_VDBE_OP                   5
+#define SQLITE_LIMIT_FUNCTION_ARG              6
+#define SQLITE_LIMIT_ATTACHED                  7
+#define SQLITE_LIMIT_LIKE_PATTERN_LENGTH       8
+#define SQLITE_LIMIT_VARIABLE_NUMBER           9
+#define SQLITE_LIMIT_TRIGGER_DEPTH            10
+#define SQLITE_LIMIT_WORKER_THREADS           11
+
+/*
+** CAPI3REF: Prepare Flags
+**
+** These constants define various flags that can be passed into
+** "prepFlags" parameter of the [sqlite3_prepare_v3()] and
+** [sqlite3_prepare16_v3()] interfaces.
+**
+** New flags may be added in future releases of SQLite.
+**
+** <dl>
+** [[SQLITE_PREPARE_PERSISTENT]] ^(<dt>SQLITE_PREPARE_PERSISTENT</dt>
+** <dd>The SQLITE_PREPARE_PERSISTENT flag is a hint to the query planner
+** that the prepared statement will be retained for a long time and
+** probably reused many times.)^ ^Without this flag, [sqlite3_prepare_v3()]
+** and [sqlite3_prepare16_v3()] assume that the prepared statement will
+** be used just once or at most a few times and then destroyed using
+** [sqlite3_finalize()] relatively soon. The current implementation acts
+** on this hint by avoiding the use of [lookaside memory] so as not to
+** deplete the limited store of lookaside memory. Future versions of
+** SQLite may act on this hint differently.
+**
+** [[SQLITE_PREPARE_NORMALIZE]] <dt>SQLITE_PREPARE_NORMALIZE</dt>
+** <dd>The SQLITE_PREPARE_NORMALIZE flag is a no-op. This flag used
+** to be required for any prepared statement that wanted to use the
+** [sqlite3_normalized_sql()] interface.  However, the
+** [sqlite3_normalized_sql()] interface is now available to all
+** prepared statements, regardless of whether or not they use this
+** flag.
+**
+** [[SQLITE_PREPARE_NO_VTAB]] <dt>SQLITE_PREPARE_NO_VTAB</dt>
+** <dd>The SQLITE_PREPARE_NO_VTAB flag causes the SQL compiler
+** to return an error (error code SQLITE_ERROR) if the statement uses
+** any virtual tables.
+** </dl>
+*/
+#define SQLITE_PREPARE_PERSISTENT              0x01
+#define SQLITE_PREPARE_NORMALIZE               0x02
+#define SQLITE_PREPARE_NO_VTAB                 0x04
+
+/*
+** CAPI3REF: Compiling An SQL Statement
+** KEYWORDS: {SQL statement compiler}
+** METHOD: sqlite3
+** CONSTRUCTOR: sqlite3_stmt
+**
+** To execute an SQL statement, it must first be compiled into a byte-code
+** program using one of these routines.  Or, in other words, these routines
+** are constructors for the [prepared statement] object.
+**
+** The preferred routine to use is [sqlite3_prepare_v2()].  The
+** [sqlite3_prepare()] interface is legacy and should be avoided.
+** [sqlite3_prepare_v3()] has an extra "prepFlags" option that is used
+** for special purposes.
+**
+** The use of the UTF-8 interfaces is preferred, as SQLite currently
+** does all parsing using UTF-8.  The UTF-16 interfaces are provided
+** as a convenience.  The UTF-16 interfaces work by converting the
+** input text into UTF-8, then invoking the corresponding UTF-8 interface.
+**
+** The first argument, "db", is a [database connection] obtained from a
+** prior successful call to [sqlite3_open()], [sqlite3_open_v2()] or
+** [sqlite3_open16()].  The database connection must not have been closed.
+**
+** The second argument, "zSql", is the statement to be compiled, encoded
+** as either UTF-8 or UTF-16.  The sqlite3_prepare(), sqlite3_prepare_v2(),
+** and sqlite3_prepare_v3()
+** interfaces use UTF-8, and sqlite3_prepare16(), sqlite3_prepare16_v2(),
+** and sqlite3_prepare16_v3() use UTF-16.
+**
+** ^If the nByte argument is negative, then zSql is read up to the
+** first zero terminator. ^If nByte is positive, then it is the
+** number of bytes read from zSql.  ^If nByte is zero, then no prepared
+** statement is generated.
+** If the caller knows that the supplied string is nul-terminated, then
+** there is a small performance advantage to passing an nByte parameter that
+** is the number of bytes in the input string <i>including</i>
+** the nul-terminator.
+**
+** ^If pzTail is not NULL then *pzTail is made to point to the first byte
+** past the end of the first SQL statement in zSql.  These routines only
+** compile the first statement in zSql, so *pzTail is left pointing to
+** what remains uncompiled.
+**
+** ^*ppStmt is left pointing to a compiled [prepared statement] that can be
+** executed using [sqlite3_step()].  ^If there is an error, *ppStmt is set
+** to NULL.  ^If the input text contains no SQL (if the input is an empty
+** string or a comment) then *ppStmt is set to NULL.
+** The calling procedure is responsible for deleting the compiled
+** SQL statement using [sqlite3_finalize()] after it has finished with it.
+** ppStmt may not be NULL.
+**
+** ^On success, the sqlite3_prepare() family of routines return [SQLITE_OK];
+** otherwise an [error code] is returned.
+**
+** The sqlite3_prepare_v2(), sqlite3_prepare_v3(), sqlite3_prepare16_v2(),
+** and sqlite3_prepare16_v3() interfaces are recommended for all new programs.
+** The older interfaces (sqlite3_prepare() and sqlite3_prepare16())
+** are retained for backwards compatibility, but their use is discouraged.
+** ^In the "vX" interfaces, the prepared statement
+** that is returned (the [sqlite3_stmt] object) contains a copy of the
+** original SQL text. This causes the [sqlite3_step()] interface to
+** behave differently in three ways:
+**
+** <ol>
+** <li>
+** ^If the database schema changes, instead of returning [SQLITE_SCHEMA] as it
+** always used to do, [sqlite3_step()] will automatically recompile the SQL
+** statement and try to run it again. As many as [SQLITE_MAX_SCHEMA_RETRY]
+** retries will occur before sqlite3_step() gives up and returns an error.
+** </li>
+**
+** <li>
+** ^When an error occurs, [sqlite3_step()] will return one of the detailed
+** [error codes] or [extended error codes].  ^The legacy behavior was that
+** [sqlite3_step()] would only return a generic [SQLITE_ERROR] result code
+** and the application would have to make a second call to [sqlite3_reset()]
+** in order to find the underlying cause of the problem. With the "v2" prepare
+** interfaces, the underlying reason for the error is returned immediately.
+** </li>
+**
+** <li>
+** ^If the specific value bound to a [parameter | host parameter] in the
+** WHERE clause might influence the choice of query plan for a statement,
+** then the statement will be automatically recompiled, as if there had been
+** a schema change, on the first [sqlite3_step()] call following any change
+** to the [sqlite3_bind_text | bindings] of that [parameter].
+** ^The specific value of a WHERE-clause [parameter] might influence the
+** choice of query plan if the parameter is the left-hand side of a [LIKE]
+** or [GLOB] operator or if the parameter is compared to an indexed column
+** and the [SQLITE_ENABLE_STAT4] compile-time option is enabled.
+** </li>
+** </ol>
+**
+** <p>^sqlite3_prepare_v3() differs from sqlite3_prepare_v2() only in having
+** the extra prepFlags parameter, which is a bit array consisting of zero or
+** more of the [SQLITE_PREPARE_PERSISTENT|SQLITE_PREPARE_*] flags.  ^The
+** sqlite3_prepare_v2() interface works exactly the same as
+** sqlite3_prepare_v3() with a zero prepFlags parameter.
+*/
+int sqlite3_prepare(
+  sqlite3 *db,            /* Database handle */
+  const char *zSql,       /* SQL statement, UTF-8 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const char **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare_v2(
+  sqlite3 *db,            /* Database handle */
+  const char *zSql,       /* SQL statement, UTF-8 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const char **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare_v3(
+  sqlite3 *db,            /* Database handle */
+  const char *zSql,       /* SQL statement, UTF-8 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  unsigned int prepFlags, /* Zero or more SQLITE_PREPARE_ flags */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const char **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare16(
+  sqlite3 *db,            /* Database handle */
+  const void *zSql,       /* SQL statement, UTF-16 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const void **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare16_v2(
+  sqlite3 *db,            /* Database handle */
+  const void *zSql,       /* SQL statement, UTF-16 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const void **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare16_v3(
+  sqlite3 *db,            /* Database handle */
+  const void *zSql,       /* SQL statement, UTF-16 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  unsigned int prepFlags, /* Zero or more SQLITE_PREPARE_ flags */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const void **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+
+/*
+** CAPI3REF: Retrieving Statement SQL
+** METHOD: sqlite3_stmt
+**
+** ^The sqlite3_sql(P) interface returns a pointer to a copy of the UTF-8
+** SQL text used to create [prepared statement] P if P was
+** created by [sqlite3_prepare_v2()], [sqlite3_prepare_v3()],
+** [sqlite3_prepare16_v2()], or [sqlite3_prepare16_v3()].
+** ^The sqlite3_expanded_sql(P) interface returns a pointer to a UTF-8
+** string containing the SQL text of prepared statement P with
+** [bound parameters] expanded.
+** ^The sqlite3_normalized_sql(P) interface returns a pointer to a UTF-8
+** string containing the normalized SQL text of prepared statement P.  The
+** semantics used to normalize a SQL statement are unspecified and subject
+** to change.  At a minimum, literal values will be replaced with suitable
+** placeholders.
+**
+** ^(For example, if a prepared statement is created using the SQL
+** text "SELECT $abc,:xyz" and if parameter $abc is bound to integer 2345
+** and parameter :xyz is unbound, then sqlite3_sql() will return
+** the original string, "SELECT $abc,:xyz" but sqlite3_expanded_sql()
+** will return "SELECT 2345,NULL".)^
+**
+** ^The sqlite3_expanded_sql() interface returns NULL if insufficient memory
+** is available to hold the result, or if the result would exceed the
+** the maximum string length determined by the [SQLITE_LIMIT_LENGTH].
+**
+** ^The [SQLITE_TRACE_SIZE_LIMIT] compile-time option limits the size of
+** bound parameter expansions.  ^The [SQLITE_OMIT_TRACE] compile-time
+** option causes sqlite3_expanded_sql() to always return NULL.
+**
+** ^The strings returned by sqlite3_sql(P) and sqlite3_normalized_sql(P)
+** are managed by SQLite and are automatically freed when the prepared
+** statement is finalized.
+** ^The string returned by sqlite3_expanded_sql(P), on the other hand,
+** is obtained from [sqlite3_malloc()] and must be freed by the application
+** by passing it to [sqlite3_free()].
+**
+** ^The sqlite3_normalized_sql() interface is only available if
+** the [SQLITE_ENABLE_NORMALIZE] compile-time option is defined.
+*/
+const char *sqlite3_sql(sqlite3_stmt *pStmt);
+char *sqlite3_expanded_sql(sqlite3_stmt *pStmt);
+#ifdef SQLITE_ENABLE_NORMALIZE
+const char *sqlite3_normalized_sql(sqlite3_stmt *pStmt);
+#endif
+
+/*
+** CAPI3REF: Determine If An SQL Statement Writes The Database
+** METHOD: sqlite3_stmt
+**
+** ^The sqlite3_stmt_readonly(X) interface returns true (non-zero) if
+** and only if the [prepared statement] X makes no direct changes to
+** the content of the database file.
+**
+** Note that [application-defined SQL functions] or
+** [virtual tables] might change the database indirectly as a side effect. 
+** ^(For example, if an application defines a function "eval()" that
+** calls [sqlite3_exec()], then the following SQL statement would
+** change the database file through side-effects:
+**
+** <blockquote><pre>
+**    SELECT eval('DELETE FROM t1') FROM t2;
+** </pre></blockquote>
+**
+** But because the [SELECT] statement does not change the database file
+** directly, sqlite3_stmt_readonly() would still return true.)^
+**
+** ^Transaction control statements such as [BEGIN], [COMMIT], [ROLLBACK],
+** [SAVEPOINT], and [RELEASE] cause sqlite3_stmt_readonly() to return true,
+** since the statements themselves do not actually modify the database but
+** rather they control the timing of when other statements modify the
+** database.  ^The [ATTACH] and [DETACH] statements also cause
+** sqlite3_stmt_readonly() to return true since, while those statements
+** change the configuration of a database connection, they do not make
+** changes to the content of the database files on disk.
+** ^The sqlite3_stmt_readonly() interface returns true for [BEGIN] since
+** [BEGIN] merely sets internal flags, but the [BEGIN|BEGIN IMMEDIATE] and
+** [BEGIN|BEGIN EXCLUSIVE] commands do touch the database and so
+** sqlite3_stmt_readonly() returns false for those commands.
+**
+** ^This routine returns false if there is any possibility that the
+** statement might change the database file.  ^A false return does
+** not guarantee that the statement will change the database file.
+** ^For example, an UPDATE statement might have a WHERE clause that
+** makes it a no-op, but the sqlite3_stmt_readonly() result would still
+** be false.  ^Similarly, a CREATE TABLE IF NOT EXISTS statement is a
+** read-only no-op if the table already exists, but
+** sqlite3_stmt_readonly() still returns false for such a statement.
+**
+** ^If prepared statement X is an [EXPLAIN] or [EXPLAIN QUERY PLAN]
+** statement, then sqlite3_stmt_readonly(X) returns the same value as
+** if the EXPLAIN or EXPLAIN QUERY PLAN prefix were omitted.
+*/
+int sqlite3_stmt_readonly(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Query The EXPLAIN Setting For A Prepared Statement
+** METHOD: sqlite3_stmt
+**
+** ^The sqlite3_stmt_isexplain(S) interface returns 1 if the
+** prepared statement S is an EXPLAIN statement, or 2 if the
+** statement S is an EXPLAIN QUERY PLAN.
+** ^The sqlite3_stmt_isexplain(S) interface returns 0 if S is
+** an ordinary statement or a NULL pointer.
+*/
+int sqlite3_stmt_isexplain(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Change The EXPLAIN Setting For A Prepared Statement
+** METHOD: sqlite3_stmt
+**
+** The sqlite3_stmt_explain(S,E) interface changes the EXPLAIN
+** setting for [prepared statement] S.  If E is zero, then S becomes
+** a normal prepared statement.  If E is 1, then S behaves as if
+** its SQL text began with "[EXPLAIN]".  If E is 2, then S behaves as if
+** its SQL text began with "[EXPLAIN QUERY PLAN]".
+**
+** Calling sqlite3_stmt_explain(S,E) might cause S to be reprepared.
+** SQLite tries to avoid a reprepare, but a reprepare might be necessary
+** on the first transition into EXPLAIN or EXPLAIN QUERY PLAN mode.
+**
+** Because of the potential need to reprepare, a call to
+** sqlite3_stmt_explain(S,E) will fail with SQLITE_ERROR if S cannot be
+** reprepared because it was created using [sqlite3_prepare()] instead of
+** the newer [sqlite3_prepare_v2()] or [sqlite3_prepare_v3()] interfaces and
+** hence has no saved SQL text with which to reprepare.
+**
+** Changing the explain setting for a prepared statement does not change
+** the original SQL text for the statement.  Hence, if the SQL text originally
+** began with EXPLAIN or EXPLAIN QUERY PLAN, but sqlite3_stmt_explain(S,0)
+** is called to convert the statement into an ordinary statement, the EXPLAIN
+** or EXPLAIN QUERY PLAN keywords will still appear in the sqlite3_sql(S)
+** output, even though the statement now acts like a normal SQL statement.
+**
+** This routine returns SQLITE_OK if the explain mode is successfully
+** changed, or an error code if the explain mode could not be changed.
+** The explain mode cannot be changed while a statement is active.
+** Hence, it is good practice to call [sqlite3_reset(S)]
+** immediately prior to calling sqlite3_stmt_explain(S,E).
+*/
+int sqlite3_stmt_explain(sqlite3_stmt *pStmt, int eMode);
+
+/*
+** CAPI3REF: Determine If A Prepared Statement Has Been Reset
+** METHOD: sqlite3_stmt
+**
+** ^The sqlite3_stmt_busy(S) interface returns true (non-zero) if the
+** [prepared statement] S has been stepped at least once using
+** [sqlite3_step(S)] but has neither run to completion (returned
+** [SQLITE_DONE] from [sqlite3_step(S)]) nor
+** been reset using [sqlite3_reset(S)].  ^The sqlite3_stmt_busy(S)
+** interface returns false if S is a NULL pointer.  If S is not a
+** NULL pointer and is not a pointer to a valid [prepared statement]
+** object, then the behavior is undefined and probably undesirable.
+**
+** This interface can be used in combination [sqlite3_next_stmt()]
+** to locate all prepared statements associated with a database
+** connection that are in need of being reset.  This can be used,
+** for example, in diagnostic routines to search for prepared
+** statements that are holding a transaction open.
+*/
+int sqlite3_stmt_busy(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Dynamically Typed Value Object
+** KEYWORDS: {protected sqlite3_value} {unprotected sqlite3_value}
+**
+** SQLite uses the sqlite3_value object to represent all values
+** that can be stored in a database table. SQLite uses dynamic typing
+** for the values it stores.  ^Values stored in sqlite3_value objects
+** can be integers, floating point values, strings, BLOBs, or NULL.
+**
+** An sqlite3_value object may be either "protected" or "unprotected".
+** Some interfaces require a protected sqlite3_value.  Other interfaces
+** will accept either a protected or an unprotected sqlite3_value.
+** Every interface that accepts sqlite3_value arguments specifies
+** whether or not it requires a protected sqlite3_value.  The
+** [sqlite3_value_dup()] interface can be used to construct a new
+** protected sqlite3_value from an unprotected sqlite3_value.
+**
+** The terms "protected" and "unprotected" refer to whether or not
+** a mutex is held.  An internal mutex is held for a protected
+** sqlite3_value object but no mutex is held for an unprotected
+** sqlite3_value object.  If SQLite is compiled to be single-threaded
+** (with [SQLITE_THREADSAFE=0] and with [sqlite3_threadsafe()] returning 0)
+** or if SQLite is run in one of reduced mutex modes
+** [SQLITE_CONFIG_SINGLETHREAD] or [SQLITE_CONFIG_MULTITHREAD]
+** then there is no distinction between protected and unprotected
+** sqlite3_value objects and they can be used interchangeably.  However,
+** for maximum code portability it is recommended that applications
+** still make the distinction between protected and unprotected
+** sqlite3_value objects even when not strictly required.
+**
+** ^The sqlite3_value objects that are passed as parameters into the
+** implementation of [application-defined SQL functions] are protected.
+** ^The sqlite3_value objects returned by [sqlite3_vtab_rhs_value()]
+** are protected.
+** ^The sqlite3_value object returned by
+** [sqlite3_column_value()] is unprotected.
+** Unprotected sqlite3_value objects may only be used as arguments
+** to [sqlite3_result_value()], [sqlite3_bind_value()], and
+** [sqlite3_value_dup()].
+** The [sqlite3_value_blob | sqlite3_value_type()] family of
+** interfaces require protected sqlite3_value objects.
+*/
+typedef struct sqlite3_value sqlite3_value;
+
+/*
+** CAPI3REF: SQL Function Context Object
+**
+** The context in which an SQL function executes is stored in an
+** sqlite3_context object.  ^A pointer to an sqlite3_context object
+** is always first parameter to [application-defined SQL functions].
+** The application-defined SQL function implementation will pass this
+** pointer through into calls to [sqlite3_result_int | sqlite3_result()],
+** [sqlite3_aggregate_context()], [sqlite3_user_data()],
+** [sqlite3_context_db_handle()], [sqlite3_get_auxdata()],
+** and/or [sqlite3_set_auxdata()].
+*/
+typedef struct sqlite3_context sqlite3_context;
+
+/*
+** CAPI3REF: Binding Values To Prepared Statements
+** KEYWORDS: {host parameter} {host parameters} {host parameter name}
+** KEYWORDS: {SQL parameter} {SQL parameters} {parameter binding}
+** METHOD: sqlite3_stmt
+**
+** ^(In the SQL statement text input to [sqlite3_prepare_v2()] and its variants,
+** literals may be replaced by a [parameter] that matches one of following
+** templates:
+**
+** <ul>
+** <li>  ?
+** <li>  ?NNN
+** <li>  :VVV
+** <li>  @VVV
+** <li>  $VVV
+** </ul>
+**
+** In the templates above, NNN represents an integer literal,
+** and VVV represents an alphanumeric identifier.)^  ^The values of these
+** parameters (also called "host parameter names" or "SQL parameters")
+** can be set using the sqlite3_bind_*() routines defined here.
+**
+** ^The first argument to the sqlite3_bind_*() routines is always
+** a pointer to the [sqlite3_stmt] object returned from
+** [sqlite3_prepare_v2()] or its variants.
+**
+** ^The second argument is the index of the SQL parameter to be set.
+** ^The leftmost SQL parameter has an index of 1.  ^When the same named
+** SQL parameter is used more than once, second and subsequent
+** occurrences have the same index as the first occurrence.
+** ^The index for named parameters can be looked up using the
+** [sqlite3_bind_parameter_index()] API if desired.  ^The index
+** for "?NNN" parameters is the value of NNN.
+** ^The NNN value must be between 1 and the [sqlite3_limit()]
+** parameter [SQLITE_LIMIT_VARIABLE_NUMBER] (default value: 32766).
+**
+** ^The third argument is the value to bind to the parameter.
+** ^If the third parameter to sqlite3_bind_text() or sqlite3_bind_text16()
+** or sqlite3_bind_blob() is a NULL pointer then the fourth parameter
+** is ignored and the end result is the same as sqlite3_bind_null().
+** ^If the third parameter to sqlite3_bind_text() is not NULL, then
+** it should be a pointer to well-formed UTF8 text.
+** ^If the third parameter to sqlite3_bind_text16() is not NULL, then
+** it should be a pointer to well-formed UTF16 text.
+** ^If the third parameter to sqlite3_bind_text64() is not NULL, then
+** it should be a pointer to a well-formed unicode string that is
+** either UTF8 if the sixth parameter is SQLITE_UTF8, or UTF16
+** otherwise.
+**
+** [[byte-order determination rules]] ^The byte-order of
+** UTF16 input text is determined by the byte-order mark (BOM, U+FEFF)
+** found in first character, which is removed, or in the absence of a BOM
+** the byte order is the native byte order of the host
+** machine for sqlite3_bind_text16() or the byte order specified in
+** the 6th parameter for sqlite3_bind_text64().)^
+** ^If UTF16 input text contains invalid unicode
+** characters, then SQLite might change those invalid characters
+** into the unicode replacement character: U+FFFD.
+**
+** ^(In those routines that have a fourth argument, its value is the
+** number of bytes in the parameter.  To be clear: the value is the
+** number of <u>bytes</u> in the value, not the number of characters.)^
+** ^If the fourth parameter to sqlite3_bind_text() or sqlite3_bind_text16()
+** is negative, then the length of the string is
+** the number of bytes up to the first zero terminator.
+** If the fourth parameter to sqlite3_bind_blob() is negative, then
+** the behavior is undefined.
+** If a non-negative fourth parameter is provided to sqlite3_bind_text()
+** or sqlite3_bind_text16() or sqlite3_bind_text64() then
+** that parameter must be the byte offset
+** where the NUL terminator would occur assuming the string were NUL
+** terminated.  If any NUL characters occurs at byte offsets less than
+** the value of the fourth parameter then the resulting string value will
+** contain embedded NULs.  The result of expressions involving strings
+** with embedded NULs is undefined.
+**
+** ^The fifth argument to the BLOB and string binding interfaces controls
+** or indicates the lifetime of the object referenced by the third parameter.
+** These three options exist:
+** ^ (1) A destructor to dispose of the BLOB or string after SQLite has finished
+** with it may be passed. ^It is called to dispose of the BLOB or string even
+** if the call to the bind API fails, except the destructor is not called if
+** the third parameter is a NULL pointer or the fourth parameter is negative.
+** ^ (2) The special constant, [SQLITE_STATIC], may be passed to indicate that
+** the application remains responsible for disposing of the object. ^In this
+** case, the object and the provided pointer to it must remain valid until
+** either the prepared statement is finalized or the same SQL parameter is
+** bound to something else, whichever occurs sooner.
+** ^ (3) The constant, [SQLITE_TRANSIENT], may be passed to indicate that the
+** object is to be copied prior to the return from sqlite3_bind_*(). ^The
+** object and pointer to it must remain valid until then. ^SQLite will then
+** manage the lifetime of its private copy.
+**
+** ^The sixth argument to sqlite3_bind_text64() must be one of
+** [SQLITE_UTF8], [SQLITE_UTF16], [SQLITE_UTF16BE], or [SQLITE_UTF16LE]
+** to specify the encoding of the text in the third parameter.  If
+** the sixth argument to sqlite3_bind_text64() is not one of the
+** allowed values shown above, or if the text encoding is different
+** from the encoding specified by the sixth parameter, then the behavior
+** is undefined.
+**
+** ^The sqlite3_bind_zeroblob() routine binds a BLOB of length N that
+** is filled with zeroes.  ^A zeroblob uses a fixed amount of memory
+** (just an integer to hold its size) while it is being processed.
+** Zeroblobs are intended to serve as placeholders for BLOBs whose
+** content is later written using
+** [sqlite3_blob_open | incremental BLOB I/O] routines.
+** ^A negative value for the zeroblob results in a zero-length BLOB.
+**
+** ^The sqlite3_bind_pointer(S,I,P,T,D) routine causes the I-th parameter in
+** [prepared statement] S to have an SQL value of NULL, but to also be
+** associated with the pointer P of type T.  ^D is either a NULL pointer or
+** a pointer to a destructor function for P. ^SQLite will invoke the
+** destructor D with a single argument of P when it is finished using
+** P.  The T parameter should be a static string, preferably a string
+** literal. The sqlite3_bind_pointer() routine is part of the
+** [pointer passing interface] added for SQLite 3.20.0.
+**
+** ^If any of the sqlite3_bind_*() routines are called with a NULL pointer
+** for the [prepared statement] or with a prepared statement for which
+** [sqlite3_step()] has been called more recently than [sqlite3_reset()],
+** then the call will return [SQLITE_MISUSE].  If any sqlite3_bind_()
+** routine is passed a [prepared statement] that has been finalized, the
+** result is undefined and probably harmful.
+**
+** ^Bindings are not cleared by the [sqlite3_reset()] routine.
+** ^Unbound parameters are interpreted as NULL.
+**
+** ^The sqlite3_bind_* routines return [SQLITE_OK] on success or an
+** [error code] if anything goes wrong.
+** ^[SQLITE_TOOBIG] might be returned if the size of a string or BLOB
+** exceeds limits imposed by [sqlite3_limit]([SQLITE_LIMIT_LENGTH]) or
+** [SQLITE_MAX_LENGTH].
+** ^[SQLITE_RANGE] is returned if the parameter
+** index is out of range.  ^[SQLITE_NOMEM] is returned if malloc() fails.
+**
+** See also: [sqlite3_bind_parameter_count()],
+** [sqlite3_bind_parameter_name()], and [sqlite3_bind_parameter_index()].
+*/
+int sqlite3_bind_blob(sqlite3_stmt*, int, const void*, int n, void(*)(void*));
+int sqlite3_bind_blob64(sqlite3_stmt*, int, const void*, sqlite3_uint64,
+                        void(*)(void*));
+int sqlite3_bind_double(sqlite3_stmt*, int, double);
+int sqlite3_bind_int(sqlite3_stmt*, int, int);
+int sqlite3_bind_int64(sqlite3_stmt*, int, sqlite3_int64);
+int sqlite3_bind_null(sqlite3_stmt*, int);
+int sqlite3_bind_text(sqlite3_stmt*,int,const char*,int,void(*)(void*));
+int sqlite3_bind_text16(sqlite3_stmt*, int, const void*, int, void(*)(void*));
+int sqlite3_bind_text64(sqlite3_stmt*, int, const char*, sqlite3_uint64,
+                         void(*)(void*), unsigned char encoding);
+int sqlite3_bind_value(sqlite3_stmt*, int, const sqlite3_value*);
+int sqlite3_bind_pointer(sqlite3_stmt*, int, void*, const char*,void(*)(void*));
+int sqlite3_bind_zeroblob(sqlite3_stmt*, int, int n);
+int sqlite3_bind_zeroblob64(sqlite3_stmt*, int, sqlite3_uint64);
+
+/*
+** CAPI3REF: Number Of SQL Parameters
+** METHOD: sqlite3_stmt
+**
+** ^This routine can be used to find the number of [SQL parameters]
+** in a [prepared statement].  SQL parameters are tokens of the
+** form "?", "?NNN", ":AAA", "$AAA", or "@AAA" that serve as
+** placeholders for values that are [sqlite3_bind_blob | bound]
+** to the parameters at a later time.
+**
+** ^(This routine actually returns the index of the largest (rightmost)
+** parameter. For all forms except ?NNN, this will correspond to the
+** number of unique parameters.  If parameters of the ?NNN form are used,
+** there may be gaps in the list.)^
+**
+** See also: [sqlite3_bind_blob|sqlite3_bind()],
+** [sqlite3_bind_parameter_name()], and
+** [sqlite3_bind_parameter_index()].
+*/
+int sqlite3_bind_parameter_count(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Name Of A Host Parameter
+** METHOD: sqlite3_stmt
+**
+** ^The sqlite3_bind_parameter_name(P,N) interface returns
+** the name of the N-th [SQL parameter] in the [prepared statement] P.
+** ^(SQL parameters of the form "?NNN" or ":AAA" or "@AAA" or "$AAA"
+** have a name which is the string "?NNN" or ":AAA" or "@AAA" or "$AAA"
+** respectively.
+** In other words, the initial ":" or "$" or "@" or "?"
+** is included as part of the name.)^
+** ^Parameters of the form "?" without a following integer have no name
+** and are referred to as "nameless" or "anonymous parameters".
+**
+** ^The first host parameter has an index of 1, not 0.
+**
+** ^If the value N is out of range or if the N-th parameter is
+** nameless, then NULL is returned.  ^The returned string is
+** always in UTF-8 encoding even if the named parameter was
+** originally specified as UTF-16 in [sqlite3_prepare16()],
+** [sqlite3_prepare16_v2()], or [sqlite3_prepare16_v3()].
+**
+** See also: [sqlite3_bind_blob|sqlite3_bind()],
+** [sqlite3_bind_parameter_count()], and
+** [sqlite3_bind_parameter_index()].
+*/
+const char *sqlite3_bind_parameter_name(sqlite3_stmt*, int);
+
+/*
+** CAPI3REF: Index Of A Parameter With A Given Name
+** METHOD: sqlite3_stmt
+**
+** ^Return the index of an SQL parameter given its name.  ^The
+** index value returned is suitable for use as the second
+** parameter to [sqlite3_bind_blob|sqlite3_bind()].  ^A zero
+** is returned if no matching parameter is found.  ^The parameter
+** name must be given in UTF-8 even if the original statement
+** was prepared from UTF-16 text using [sqlite3_prepare16_v2()] or
+** [sqlite3_prepare16_v3()].
+**
+** See also: [sqlite3_bind_blob|sqlite3_bind()],
+** [sqlite3_bind_parameter_count()], and
+** [sqlite3_bind_parameter_name()].
+*/
+int sqlite3_bind_parameter_index(sqlite3_stmt*, const char *zName);
+
+/*
+** CAPI3REF: Reset All Bindings On A Prepared Statement
+** METHOD: sqlite3_stmt
+**
+** ^Contrary to the intuition of many, [sqlite3_reset()] does not reset
+** the [sqlite3_bind_blob | bindings] on a [prepared statement].
+** ^Use this routine to reset all host parameters to NULL.
+*/
+int sqlite3_clear_bindings(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Number Of Columns In A Result Set
+** METHOD: sqlite3_stmt
+**
+** ^Return the number of columns in the result set returned by the
+** [prepared statement]. ^If this routine returns 0, that means the
+** [prepared statement] returns no data (for example an [UPDATE]).
+** ^However, just because this routine returns a positive number does not
+** mean that one or more rows of data will be returned.  ^A SELECT statement
+** will always have a positive sqlite3_column_count() but depending on the
+** WHERE clause constraints and the table content, it might return no rows.
+**
+** See also: [sqlite3_data_count()]
+*/
+int sqlite3_column_count(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Column Names In A Result Set
+** METHOD: sqlite3_stmt
+**
+** ^These routines return the name assigned to a particular column
+** in the result set of a [SELECT] statement.  ^The sqlite3_column_name()
+** interface returns a pointer to a zero-terminated UTF-8 string
+** and sqlite3_column_name16() returns a pointer to a zero-terminated
+** UTF-16 string.  ^The first parameter is the [prepared statement]
+** that implements the [SELECT] statement. ^The second parameter is the
+** column number.  ^The leftmost column is number 0.
+**
+** ^The returned string pointer is valid until either the [prepared statement]
+** is destroyed by [sqlite3_finalize()] or until the statement is automatically
+** reprepared by the first call to [sqlite3_step()] for a particular run
+** or until the next call to
+** sqlite3_column_name() or sqlite3_column_name16() on the same column.
+**
+** ^If sqlite3_malloc() fails during the processing of either routine
+** (for example during a conversion from UTF-8 to UTF-16) then a
+** NULL pointer is returned.
+**
+** ^The name of a result column is the value of the "AS" clause for
+** that column, if there is an AS clause.  If there is no AS clause
+** then the name of the column is unspecified and may change from
+** one release of SQLite to the next.
+*/
+const char *sqlite3_column_name(sqlite3_stmt*, int N);
+const void *sqlite3_column_name16(sqlite3_stmt*, int N);
+
+/*
+** CAPI3REF: Source Of Data In A Query Result
+** METHOD: sqlite3_stmt
+**
+** ^These routines provide a means to determine the database, table, and
+** table column that is the origin of a particular result column in
+** [SELECT] statement.
+** ^The name of the database or table or column can be returned as
+** either a UTF-8 or UTF-16 string.  ^The _database_ routines return
+** the database name, the _table_ routines return the table name, and
+** the origin_ routines return the column name.
+** ^The returned string is valid until the [prepared statement] is destroyed
+** using [sqlite3_finalize()] or until the statement is automatically
+** reprepared by the first call to [sqlite3_step()] for a particular run
+** or until the same information is requested
+** again in a different encoding.
+**
+** ^The names returned are the original un-aliased names of the
+** database, table, and column.
+**
+** ^The first argument to these interfaces is a [prepared statement].
+** ^These functions return information about the Nth result column returned by
+** the statement, where N is the second function argument.
+** ^The left-most column is column 0 for these routines.
+**
+** ^If the Nth column returned by the statement is an expression or
+** subquery and is not a column value, then all of these functions return
+** NULL.  ^These routines might also return NULL if a memory allocation error
+** occurs.  ^Otherwise, they return the name of the attached database, table,
+** or column that query result column was extracted from.
+**
+** ^As with all other SQLite APIs, those whose names end with "16" return
+** UTF-16 encoded strings and the other functions return UTF-8.
+**
+** ^These APIs are only available if the library was compiled with the
+** [SQLITE_ENABLE_COLUMN_METADATA] C-preprocessor symbol.
+**
+** If two or more threads call one or more
+** [sqlite3_column_database_name | column metadata interfaces]
+** for the same [prepared statement] and result column
+** at the same time then the results are undefined.
+*/
+const char *sqlite3_column_database_name(sqlite3_stmt*,int);
+const void *sqlite3_column_database_name16(sqlite3_stmt*,int);
+const char *sqlite3_column_table_name(sqlite3_stmt*,int);
+const void *sqlite3_column_table_name16(sqlite3_stmt*,int);
+const char *sqlite3_column_origin_name(sqlite3_stmt*,int);
+const void *sqlite3_column_origin_name16(sqlite3_stmt*,int);
+
+/*
+** CAPI3REF: Declared Datatype Of A Query Result
+** METHOD: sqlite3_stmt
+**
+** ^(The first parameter is a [prepared statement].
+** If this statement is a [SELECT] statement and the Nth column of the
+** returned result set of that [SELECT] is a table column (not an
+** expression or subquery) then the declared type of the table
+** column is returned.)^  ^If the Nth column of the result set is an
+** expression or subquery, then a NULL pointer is returned.
+** ^The returned string is always UTF-8 encoded.
+**
+** ^(For example, given the database schema:
+**
+** CREATE TABLE t1(c1 VARIANT);
+**
+** and the following statement to be compiled:
+**
+** SELECT c1 + 1, c1 FROM t1;
+**
+** this routine would return the string "VARIANT" for the second result
+** column (i==1), and a NULL pointer for the first result column (i==0).)^
+**
+** ^SQLite uses dynamic run-time typing.  ^So just because a column
+** is declared to contain a particular type does not mean that the
+** data stored in that column is of the declared type.  SQLite is
+** strongly typed, but the typing is dynamic not static.  ^Type
+** is associated with individual values, not with the containers
+** used to hold those values.
+*/
+const char *sqlite3_column_decltype(sqlite3_stmt*,int);
+const void *sqlite3_column_decltype16(sqlite3_stmt*,int);
+
+/*
+** CAPI3REF: Evaluate An SQL Statement
+** METHOD: sqlite3_stmt
+**
+** After a [prepared statement] has been prepared using any of
+** [sqlite3_prepare_v2()], [sqlite3_prepare_v3()], [sqlite3_prepare16_v2()],
+** or [sqlite3_prepare16_v3()] or one of the legacy
+** interfaces [sqlite3_prepare()] or [sqlite3_prepare16()], this function
+** must be called one or more times to evaluate the statement.
+**
+** The details of the behavior of the sqlite3_step() interface depend
+** on whether the statement was prepared using the newer "vX" interfaces
+** [sqlite3_prepare_v3()], [sqlite3_prepare_v2()], [sqlite3_prepare16_v3()],
+** [sqlite3_prepare16_v2()] or the older legacy
+** interfaces [sqlite3_prepare()] and [sqlite3_prepare16()].  The use of the
+** new "vX" interface is recommended for new applications but the legacy
+** interface will continue to be supported.
+**
+** ^In the legacy interface, the return value will be either [SQLITE_BUSY],
+** [SQLITE_DONE], [SQLITE_ROW], [SQLITE_ERROR], or [SQLITE_MISUSE].
+** ^With the "v2" interface, any of the other [result codes] or
+** [extended result codes] might be returned as well.
+**
+** ^[SQLITE_BUSY] means that the database engine was unable to acquire the
+** database locks it needs to do its job.  ^If the statement is a [COMMIT]
+** or occurs outside of an explicit transaction, then you can retry the
+** statement.  If the statement is not a [COMMIT] and occurs within an
+** explicit transaction then you should rollback the transaction before
+** continuing.
+**
+** ^[SQLITE_DONE] means that the statement has finished executing
+** successfully.  sqlite3_step() should not be called again on this virtual
+** machine without first calling [sqlite3_reset()] to reset the virtual
+** machine back to its initial state.
+**
+** ^If the SQL statement being executed returns any data, then [SQLITE_ROW]
+** is returned each time a new row of data is ready for processing by the
+** caller. The values may be accessed using the [column access functions].
+** sqlite3_step() is called again to retrieve the next row of data.
+**
+** ^[SQLITE_ERROR] means that a run-time error (such as a constraint
+** violation) has occurred.  sqlite3_step() should not be called again on
+** the VM. More information may be found by calling [sqlite3_errmsg()].
+** ^With the legacy interface, a more specific error code (for example,
+** [SQLITE_INTERRUPT], [SQLITE_SCHEMA], [SQLITE_CORRUPT], and so forth)
+** can be obtained by calling [sqlite3_reset()] on the
+** [prepared statement].  ^In the "v2" interface,
+** the more specific error code is returned directly by sqlite3_step().
+**
+** [SQLITE_MISUSE] means that the this routine was called inappropriately.
+** Perhaps it was called on a [prepared statement] that has
+** already been [sqlite3_finalize | finalized] or on one that had
+** previously returned [SQLITE_ERROR] or [SQLITE_DONE].  Or it could
+** be the case that the same database connection is being used by two or
+** more threads at the same moment in time.
+**
+** For all versions of SQLite up to and including 3.6.23.1, a call to
+** [sqlite3_reset()] was required after sqlite3_step() returned anything
+** other than [SQLITE_ROW] before any subsequent invocation of
+** sqlite3_step().  Failure to reset the prepared statement using
+** [sqlite3_reset()] would result in an [SQLITE_MISUSE] return from
+** sqlite3_step().  But after [version 3.6.23.1] ([dateof:3.6.23.1],
+** sqlite3_step() began
+** calling [sqlite3_reset()] automatically in this circumstance rather
+** than returning [SQLITE_MISUSE].  This is not considered a compatibility
+** break because any application that ever receives an SQLITE_MISUSE error
+** is broken by definition.  The [SQLITE_OMIT_AUTORESET] compile-time option
+** can be used to restore the legacy behavior.
+**
+** <b>Goofy Interface Alert:</b> In the legacy interface, the sqlite3_step()
+** API always returns a generic error code, [SQLITE_ERROR], following any
+** error other than [SQLITE_BUSY] and [SQLITE_MISUSE].  You must call
+** [sqlite3_reset()] or [sqlite3_finalize()] in order to find one of the
+** specific [error codes] that better describes the error.
+** We admit that this is a goofy design.  The problem has been fixed
+** with the "v2" interface.  If you prepare all of your SQL statements
+** using [sqlite3_prepare_v3()] or [sqlite3_prepare_v2()]
+** or [sqlite3_prepare16_v2()] or [sqlite3_prepare16_v3()] instead
+** of the legacy [sqlite3_prepare()] and [sqlite3_prepare16()] interfaces,
+** then the more specific [error codes] are returned directly
+** by sqlite3_step().  The use of the "vX" interfaces is recommended.
+*/
+int sqlite3_step(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Number of columns in a result set
+** METHOD: sqlite3_stmt
+**
+** ^The sqlite3_data_count(P) interface returns the number of columns in the
+** current row of the result set of [prepared statement] P.
+** ^If prepared statement P does not have results ready to return
+** (via calls to the [sqlite3_column_int | sqlite3_column()] family of
+** interfaces) then sqlite3_data_count(P) returns 0.
+** ^The sqlite3_data_count(P) routine also returns 0 if P is a NULL pointer.
+** ^The sqlite3_data_count(P) routine returns 0 if the previous call to
+** [sqlite3_step](P) returned [SQLITE_DONE].  ^The sqlite3_data_count(P)
+** will return non-zero if previous call to [sqlite3_step](P) returned
+** [SQLITE_ROW], except in the case of the [PRAGMA incremental_vacuum]
+** where it always returns zero since each step of that multi-step
+** pragma returns 0 columns of data.
+**
+** See also: [sqlite3_column_count()]
+*/
+int sqlite3_data_count(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Fundamental Datatypes
+** KEYWORDS: SQLITE_TEXT
+**
+** ^(Every value in SQLite has one of five fundamental datatypes:
+**
+** <ul>
+** <li> 64-bit signed integer
+** <li> 64-bit IEEE floating point number
+** <li> string
+** <li> BLOB
+** <li> NULL
+** </ul>)^
+**
+** These constants are codes for each of those types.
+**
+** Note that the SQLITE_TEXT constant was also used in SQLite version 2
+** for a completely different meaning.  Software that links against both
+** SQLite version 2 and SQLite version 3 should use SQLITE3_TEXT, not
+** SQLITE_TEXT.
+*/
+#define SQLITE_INTEGER  1
+#define SQLITE_FLOAT    2
+#define SQLITE_BLOB     4
+#define SQLITE_NULL     5
+#ifdef SQLITE_TEXT
+# undef SQLITE_TEXT
+#else
+# define SQLITE_TEXT     3
+#endif
+#define SQLITE3_TEXT     3
+
+/*
+** CAPI3REF: Result Values From A Query
+** KEYWORDS: {column access functions}
+** METHOD: sqlite3_stmt
+**
+** <b>Summary:</b>
+** <blockquote><table border=0 cellpadding=0 cellspacing=0>
+** <tr><td><b>sqlite3_column_blob</b><td>&rarr;<td>BLOB result
+** <tr><td><b>sqlite3_column_double</b><td>&rarr;<td>REAL result
+** <tr><td><b>sqlite3_column_int</b><td>&rarr;<td>32-bit INTEGER result
+** <tr><td><b>sqlite3_column_int64</b><td>&rarr;<td>64-bit INTEGER result
+** <tr><td><b>sqlite3_column_text</b><td>&rarr;<td>UTF-8 TEXT result
+** <tr><td><b>sqlite3_column_text16</b><td>&rarr;<td>UTF-16 TEXT result
+** <tr><td><b>sqlite3_column_value</b><td>&rarr;<td>The result as an
+** [sqlite3_value|unprotected sqlite3_value] object.
+** <tr><td>&nbsp;<td>&nbsp;<td>&nbsp;
+** <tr><td><b>sqlite3_column_bytes</b><td>&rarr;<td>Size of a BLOB
+** or a UTF-8 TEXT result in bytes
+** <tr><td><b>sqlite3_column_bytes16&nbsp;&nbsp;</b>
+** <td>&rarr;&nbsp;&nbsp;<td>Size of UTF-16
+** TEXT in bytes
+** <tr><td><b>sqlite3_column_type</b><td>&rarr;<td>Default
+** datatype of the result
+** </table></blockquote>
+**
+** <b>Details:</b>
+**
+** ^These routines return information about a single column of the current
+** result row of a query.  ^In every case the first argument is a pointer
+** to the [prepared statement] that is being evaluated (the [sqlite3_stmt*]
+** that was returned from [sqlite3_prepare_v2()] or one of its variants)
+** and the second argument is the index of the column for which information
+** should be returned. ^The leftmost column of the result set has the index 0.
+** ^The number of columns in the result can be determined using
+** [sqlite3_column_count()].
+**
+** If the SQL statement does not currently point to a valid row, or if the
+** column index is out of range, the result is undefined.
+** These routines may only be called when the most recent call to
+** [sqlite3_step()] has returned [SQLITE_ROW] and neither
+** [sqlite3_reset()] nor [sqlite3_finalize()] have been called subsequently.
+** If any of these routines are called after [sqlite3_reset()] or
+** [sqlite3_finalize()] or after [sqlite3_step()] has returned
+** something other than [SQLITE_ROW], the results are undefined.
+** If [sqlite3_step()] or [sqlite3_reset()] or [sqlite3_finalize()]
+** are called from a different thread while any of these routines
+** are pending, then the results are undefined.
+**
+** The first six interfaces (_blob, _double, _int, _int64, _text, and _text16)
+** each return the value of a result column in a specific data format.  If
+** the result column is not initially in the requested format (for example,
+** if the query returns an integer but the sqlite3_column_text() interface
+** is used to extract the value) then an automatic type conversion is performed.
+**
+** ^The sqlite3_column_type() routine returns the
+** [SQLITE_INTEGER | datatype code] for the initial data type
+** of the result column.  ^The returned value is one of [SQLITE_INTEGER],
+** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].
+** The return value of sqlite3_column_type() can be used to decide which
+** of the first six interface should be used to extract the column value.
+** The value returned by sqlite3_column_type() is only meaningful if no
+** automatic type conversions have occurred for the value in question. 
+** After a type conversion, the result of calling sqlite3_column_type()
+** is undefined, though harmless.  Future
+** versions of SQLite may change the behavior of sqlite3_column_type()
+** following a type conversion.
+**
+** If the result is a BLOB or a TEXT string, then the sqlite3_column_bytes()
+** or sqlite3_column_bytes16() interfaces can be used to determine the size
+** of that BLOB or string.
+**
+** ^If the result is a BLOB or UTF-8 string then the sqlite3_column_bytes()
+** routine returns the number of bytes in that BLOB or string.
+** ^If the result is a UTF-16 string, then sqlite3_column_bytes() converts
+** the string to UTF-8 and then returns the number of bytes.
+** ^If the result is a numeric value then sqlite3_column_bytes() uses
+** [sqlite3_snprintf()] to convert that value to a UTF-8 string and returns
+** the number of bytes in that string.
+** ^If the result is NULL, then sqlite3_column_bytes() returns zero.
+**
+** ^If the result is a BLOB or UTF-16 string then the sqlite3_column_bytes16()
+** routine returns the number of bytes in that BLOB or string.
+** ^If the result is a UTF-8 string, then sqlite3_column_bytes16() converts
+** the string to UTF-16 and then returns the number of bytes.
+** ^If the result is a numeric value then sqlite3_column_bytes16() uses
+** [sqlite3_snprintf()] to convert that value to a UTF-16 string and returns
+** the number of bytes in that string.
+** ^If the result is NULL, then sqlite3_column_bytes16() returns zero.
+**
+** ^The values returned by [sqlite3_column_bytes()] and
+** [sqlite3_column_bytes16()] do not include the zero terminators at the end
+** of the string.  ^For clarity: the values returned by
+** [sqlite3_column_bytes()] and [sqlite3_column_bytes16()] are the number of
+** bytes in the string, not the number of characters.
+**
+** ^Strings returned by sqlite3_column_text() and sqlite3_column_text16(),
+** even empty strings, are always zero-terminated.  ^The return
+** value from sqlite3_column_blob() for a zero-length BLOB is a NULL pointer.
+**
+** ^Strings returned by sqlite3_column_text16() always have the endianness
+** which is native to the platform, regardless of the text encoding set
+** for the database.
+**
+** <b>Warning:</b> ^The object returned by [sqlite3_column_value()] is an
+** [unprotected sqlite3_value] object.  In a multithreaded environment,
+** an unprotected sqlite3_value object may only be used safely with
+** [sqlite3_bind_value()] and [sqlite3_result_value()].
+** If the [unprotected sqlite3_value] object returned by
+** [sqlite3_column_value()] is used in any other way, including calls
+** to routines like [sqlite3_value_int()], [sqlite3_value_text()],
+** or [sqlite3_value_bytes()], the behavior is not threadsafe.
+** Hence, the sqlite3_column_value() interface
+** is normally only useful within the implementation of
+** [application-defined SQL functions] or [virtual tables], not within
+** top-level application code.
+**
+** These routines may attempt to convert the datatype of the result.
+** ^For example, if the internal representation is FLOAT and a text result
+** is requested, [sqlite3_snprintf()] is used internally to perform the
+** conversion automatically.  ^(The following table details the conversions
+** that are applied:
+**
+** <blockquote>
+** <table border="1">
+** <tr><th> Internal<br>Type <th> Requested<br>Type <th>  Conversion
+**
+** <tr><td>  NULL    <td> INTEGER   <td> Result is 0
+** <tr><td>  NULL    <td>  FLOAT    <td> Result is 0.0
+** <tr><td>  NULL    <td>   TEXT    <td> Result is a NULL pointer
+** <tr><td>  NULL    <td>   BLOB    <td> Result is a NULL pointer
+** <tr><td> INTEGER  <td>  FLOAT    <td> Convert from integer to float
+** <tr><td> INTEGER  <td>   TEXT    <td> ASCII rendering of the integer
+** <tr><td> INTEGER  <td>   BLOB    <td> Same as INTEGER->TEXT
+** <tr><td>  FLOAT   <td> INTEGER   <td> [CAST] to INTEGER
+** <tr><td>  FLOAT   <td>   TEXT    <td> ASCII rendering of the float
+** <tr><td>  FLOAT   <td>   BLOB    <td> [CAST] to BLOB
+** <tr><td>  TEXT    <td> INTEGER   <td> [CAST] to INTEGER
+** <tr><td>  TEXT    <td>  FLOAT    <td> [CAST] to REAL
+** <tr><td>  TEXT    <td>   BLOB    <td> No change
+** <tr><td>  BLOB    <td> INTEGER   <td> [CAST] to INTEGER
+** <tr><td>  BLOB    <td>  FLOAT    <td> [CAST] to REAL
+** <tr><td>  BLOB    <td>   TEXT    <td> [CAST] to TEXT, ensure zero terminator
+** </table>
+** </blockquote>)^
+**
+** Note that when type conversions occur, pointers returned by prior
+** calls to sqlite3_column_blob(), sqlite3_column_text(), and/or
+** sqlite3_column_text16() may be invalidated.
+** Type conversions and pointer invalidations might occur
+** in the following cases:
+**
+** <ul>
+** <li> The initial content is a BLOB and sqlite3_column_text() or
+**      sqlite3_column_text16() is called.  A zero-terminator might
+**      need to be added to the string.</li>
+** <li> The initial content is UTF-8 text and sqlite3_column_bytes16() or
+**      sqlite3_column_text16() is called.  The content must be converted
+**      to UTF-16.</li>
+** <li> The initial content is UTF-16 text and sqlite3_column_bytes() or
+**      sqlite3_column_text() is called.  The content must be converted
+**      to UTF-8.</li>
+** </ul>
+**
+** ^Conversions between UTF-16be and UTF-16le are always done in place and do
+** not invalidate a prior pointer, though of course the content of the buffer
+** that the prior pointer references will have been modified.  Other kinds
+** of conversion are done in place when it is possible, but sometimes they
+** are not possible and in those cases prior pointers are invalidated.
+**
+** The safest policy is to invoke these routines
+** in one of the following ways:
+**
+** <ul>
+**  <li>sqlite3_column_text() followed by sqlite3_column_bytes()</li>
+**  <li>sqlite3_column_blob() followed by sqlite3_column_bytes()</li>
+**  <li>sqlite3_column_text16() followed by sqlite3_column_bytes16()</li>
+** </ul>
+**
+** In other words, you should call sqlite3_column_text(),
+** sqlite3_column_blob(), or sqlite3_column_text16() first to force the result
+** into the desired format, then invoke sqlite3_column_bytes() or
+** sqlite3_column_bytes16() to find the size of the result.  Do not mix calls
+** to sqlite3_column_text() or sqlite3_column_blob() with calls to
+** sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16()
+** with calls to sqlite3_column_bytes().
+**
+** ^The pointers returned are valid until a type conversion occurs as
+** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
+** [sqlite3_finalize()] is called.  ^The memory space used to hold strings
+** and BLOBs is freed automatically.  Do not pass the pointers returned
+** from [sqlite3_column_blob()], [sqlite3_column_text()], etc. into
+** [sqlite3_free()].
+**
+** As long as the input parameters are correct, these routines will only
+** fail if an out-of-memory error occurs during a format conversion.
+** Only the following subset of interfaces are subject to out-of-memory
+** errors:
+**
+** <ul>
+** <li> sqlite3_column_blob()
+** <li> sqlite3_column_text()
+** <li> sqlite3_column_text16()
+** <li> sqlite3_column_bytes()
+** <li> sqlite3_column_bytes16()
+** </ul>
+**
+** If an out-of-memory error occurs, then the return value from these
+** routines is the same as if the column had contained an SQL NULL value.
+** Valid SQL NULL returns can be distinguished from out-of-memory errors
+** by invoking the [sqlite3_errcode()] immediately after the suspect
+** return value is obtained and before any
+** other SQLite interface is called on the same [database connection].
+*/
+const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
+double sqlite3_column_double(sqlite3_stmt*, int iCol);
+int sqlite3_column_int(sqlite3_stmt*, int iCol);
+sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
+const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
+const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);
+sqlite3_value *sqlite3_column_value(sqlite3_stmt*, int iCol);
+int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
+int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
+int sqlite3_column_type(sqlite3_stmt*, int iCol);
+
+/*
+** CAPI3REF: Destroy A Prepared Statement Object
+** DESTRUCTOR: sqlite3_stmt
+**
+** ^The sqlite3_finalize() function is called to delete a [prepared statement].
+** ^If the most recent evaluation of the statement encountered no errors
+** or if the statement is never been evaluated, then sqlite3_finalize() returns
+** SQLITE_OK.  ^If the most recent evaluation of statement S failed, then
+** sqlite3_finalize(S) returns the appropriate [error code] or
+** [extended error code].
+**
+** ^The sqlite3_finalize(S) routine can be called at any point during
+** the life cycle of [prepared statement] S:
+** before statement S is ever evaluated, after
+** one or more calls to [sqlite3_reset()], or after any call
+** to [sqlite3_step()] regardless of whether or not the statement has
+** completed execution.
+**
+** ^Invoking sqlite3_finalize() on a NULL pointer is a harmless no-op.
+**
+** The application must finalize every [prepared statement] in order to avoid
+** resource leaks.  It is a grievous error for the application to try to use
+** a prepared statement after it has been finalized.  Any use of a prepared
+** statement after it has been finalized can result in undefined and
+** undesirable behavior such as segfaults and heap corruption.
+*/
+int sqlite3_finalize(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Reset A Prepared Statement Object
+** METHOD: sqlite3_stmt
+**
+** The sqlite3_reset() function is called to reset a [prepared statement]
+** object back to its initial state, ready to be re-executed.
+** ^Any SQL statement variables that had values bound to them using
+** the [sqlite3_bind_blob | sqlite3_bind_*() API] retain their values.
+** Use [sqlite3_clear_bindings()] to reset the bindings.
+**
+** ^The [sqlite3_reset(S)] interface resets the [prepared statement] S
+** back to the beginning of its program.
+**
+** ^The return code from [sqlite3_reset(S)] indicates whether or not
+** the previous evaluation of prepared statement S completed successfully.
+** ^If [sqlite3_step(S)] has never before been called on S or if
+** [sqlite3_step(S)] has not been called since the previous call
+** to [sqlite3_reset(S)], then [sqlite3_reset(S)] will return
+** [SQLITE_OK].
+**
+** ^If the most recent call to [sqlite3_step(S)] for the
+** [prepared statement] S indicated an error, then
+** [sqlite3_reset(S)] returns an appropriate [error code].
+** ^The [sqlite3_reset(S)] interface might also return an [error code]
+** if there were no prior errors but the process of resetting
+** the prepared statement caused a new error. ^For example, if an
+** [INSERT] statement with a [RETURNING] clause is only stepped one time,
+** that one call to [sqlite3_step(S)] might return SQLITE_ROW but
+** the overall statement might still fail and the [sqlite3_reset(S)] call
+** might return SQLITE_BUSY if locking constraints prevent the
+** database change from committing.  Therefore, it is important that
+** applications check the return code from [sqlite3_reset(S)] even if
+** no prior call to [sqlite3_step(S)] indicated a problem.
+**
+** ^The [sqlite3_reset(S)] interface does not change the values
+** of any [sqlite3_bind_blob|bindings] on the [prepared statement] S.
+*/
+int sqlite3_reset(sqlite3_stmt *pStmt);
+
+
+/*
+** CAPI3REF: Create Or Redefine SQL Functions
+** KEYWORDS: {function creation routines}
+** METHOD: sqlite3
+**
+** ^These functions (collectively known as "function creation routines")
+** are used to add SQL functions or aggregates or to redefine the behavior
+** of existing SQL functions or aggregates. The only differences between
+** the three "sqlite3_create_function*" routines are the text encoding
+** expected for the second parameter (the name of the function being
+** created) and the presence or absence of a destructor callback for
+** the application data pointer. Function sqlite3_create_window_function()
+** is similar, but allows the user to supply the extra callback functions
+** needed by [aggregate window functions].
+**
+** ^The first parameter is the [database connection] to which the SQL
+** function is to be added.  ^If an application uses more than one database
+** connection then application-defined SQL functions must be added
+** to each database connection separately.
+**
+** ^The second parameter is the name of the SQL function to be created or
+** redefined.  ^The length of the name is limited to 255 bytes in a UTF-8
+** representation, exclusive of the zero-terminator.  ^Note that the name
+** length limit is in UTF-8 bytes, not characters nor UTF-16 bytes. 
+** ^Any attempt to create a function with a longer name
+** will result in [SQLITE_MISUSE] being returned.
+**
+** ^The third parameter (nArg)
+** is the number of arguments that the SQL function or
+** aggregate takes. ^If this parameter is -1, then the SQL function or
+** aggregate may take any number of arguments between 0 and the limit
+** set by [sqlite3_limit]([SQLITE_LIMIT_FUNCTION_ARG]).  If the third
+** parameter is less than -1 or greater than 127 then the behavior is
+** undefined.
+**
+** ^The fourth parameter, eTextRep, specifies what
+** [SQLITE_UTF8 | text encoding] this SQL function prefers for
+** its parameters.  The application should set this parameter to
+** [SQLITE_UTF16LE] if the function implementation invokes
+** [sqlite3_value_text16le()] on an input, or [SQLITE_UTF16BE] if the
+** implementation invokes [sqlite3_value_text16be()] on an input, or
+** [SQLITE_UTF16] if [sqlite3_value_text16()] is used, or [SQLITE_UTF8]
+** otherwise.  ^The same SQL function may be registered multiple times using
+** different preferred text encodings, with different implementations for
+** each encoding.
+** ^When multiple implementations of the same function are available, SQLite
+** will pick the one that involves the least amount of data conversion.
+**
+** ^The fourth parameter may optionally be ORed with [SQLITE_DETERMINISTIC]
+** to signal that the function will always return the same result given
+** the same inputs within a single SQL statement.  Most SQL functions are
+** deterministic.  The built-in [random()] SQL function is an example of a
+** function that is not deterministic.  The SQLite query planner is able to
+** perform additional optimizations on deterministic functions, so use
+** of the [SQLITE_DETERMINISTIC] flag is recommended where possible.
+**
+** ^The fourth parameter may also optionally include the [SQLITE_DIRECTONLY]
+** flag, which if present prevents the function from being invoked from
+** within VIEWs, TRIGGERs, CHECK constraints, generated column expressions,
+** index expressions, or the WHERE clause of partial indexes.
+**
+** For best security, the [SQLITE_DIRECTONLY] flag is recommended for
+** all application-defined SQL functions that do not need to be
+** used inside of triggers, view, CHECK constraints, or other elements of
+** the database schema.  This flags is especially recommended for SQL
+** functions that have side effects or reveal internal application state.
+** Without this flag, an attacker might be able to modify the schema of
+** a database file to include invocations of the function with parameters
+** chosen by the attacker, which the application will then execute when
+** the database file is opened and read.
+**
+** ^(The fifth parameter is an arbitrary pointer.  The implementation of the
+** function can gain access to this pointer using [sqlite3_user_data()].)^
+**
+** ^The sixth, seventh and eighth parameters passed to the three
+** "sqlite3_create_function*" functions, xFunc, xStep and xFinal, are
+** pointers to C-language functions that implement the SQL function or
+** aggregate. ^A scalar SQL function requires an implementation of the xFunc
+** callback only; NULL pointers must be passed as the xStep and xFinal
+** parameters. ^An aggregate SQL function requires an implementation of xStep
+** and xFinal and NULL pointer must be passed for xFunc. ^To delete an existing
+** SQL function or aggregate, pass NULL pointers for all three function
+** callbacks.
+**
+** ^The sixth, seventh, eighth and ninth parameters (xStep, xFinal, xValue
+** and xInverse) passed to sqlite3_create_window_function are pointers to
+** C-language callbacks that implement the new function. xStep and xFinal
+** must both be non-NULL. xValue and xInverse may either both be NULL, in
+** which case a regular aggregate function is created, or must both be
+** non-NULL, in which case the new function may be used as either an aggregate
+** or aggregate window function. More details regarding the implementation
+** of aggregate window functions are
+** [user-defined window functions|available here].
+**
+** ^(If the final parameter to sqlite3_create_function_v2() or
+** sqlite3_create_window_function() is not NULL, then it is destructor for
+** the application data pointer. The destructor is invoked when the function
+** is deleted, either by being overloaded or when the database connection
+** closes.)^ ^The destructor is also invoked if the call to
+** sqlite3_create_function_v2() fails.  ^When the destructor callback is
+** invoked, it is passed a single argument which is a copy of the application
+** data pointer which was the fifth parameter to sqlite3_create_function_v2().
+**
+** ^It is permitted to register multiple implementations of the same
+** functions with the same name but with either differing numbers of
+** arguments or differing preferred text encodings.  ^SQLite will use
+** the implementation that most closely matches the way in which the
+** SQL function is used.  ^A function implementation with a non-negative
+** nArg parameter is a better match than a function implementation with
+** a negative nArg.  ^A function where the preferred text encoding
+** matches the database encoding is a better
+** match than a function where the encoding is different. 
+** ^A function where the encoding difference is between UTF16le and UTF16be
+** is a closer match than a function where the encoding difference is
+** between UTF8 and UTF16.
+**
+** ^Built-in functions may be overloaded by new application-defined functions.
+**
+** ^An application-defined function is permitted to call other
+** SQLite interfaces.  However, such calls must not
+** close the database connection nor finalize or reset the prepared
+** statement in which the function is running.
+*/
+int sqlite3_create_function(
+  sqlite3 *db,
+  const char *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *pApp,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*)
+);
+int sqlite3_create_function16(
+  sqlite3 *db,
+  const void *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *pApp,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*)
+);
+int sqlite3_create_function_v2(
+  sqlite3 *db,
+  const char *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *pApp,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*),
+  void(*xDestroy)(void*)
+);
+int sqlite3_create_window_function(
+  sqlite3 *db,
+  const char *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *pApp,
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*),
+  void (*xValue)(sqlite3_context*),
+  void (*xInverse)(sqlite3_context*,int,sqlite3_value**),
+  void(*xDestroy)(void*)
+);
+
+/*
+** CAPI3REF: Text Encodings
+**
+** These constant define integer codes that represent the various
+** text encodings supported by SQLite.
+*/
+#define SQLITE_UTF8           1    /* IMP: R-37514-35566 */
+#define SQLITE_UTF16LE        2    /* IMP: R-03371-37637 */
+#define SQLITE_UTF16BE        3    /* IMP: R-51971-34154 */
+#define SQLITE_UTF16          4    /* Use native byte order */
+#define SQLITE_ANY            5    /* Deprecated */
+#define SQLITE_UTF16_ALIGNED  8    /* sqlite3_create_collation only */
+
+/*
+** CAPI3REF: Function Flags
+**
+** These constants may be ORed together with the
+** [SQLITE_UTF8 | preferred text encoding] as the fourth argument
+** to [sqlite3_create_function()], [sqlite3_create_function16()], or
+** [sqlite3_create_function_v2()].
+**
+** <dl>
+** [[SQLITE_DETERMINISTIC]] <dt>SQLITE_DETERMINISTIC</dt><dd>
+** The SQLITE_DETERMINISTIC flag means that the new function always gives
+** the same output when the input parameters are the same.
+** The [abs|abs() function] is deterministic, for example, but
+** [randomblob|randomblob()] is not.  Functions must
+** be deterministic in order to be used in certain contexts such as
+** with the WHERE clause of [partial indexes] or in [generated columns].
+** SQLite might also optimize deterministic functions by factoring them
+** out of inner loops.
+** </dd>
+**
+** [[SQLITE_DIRECTONLY]] <dt>SQLITE_DIRECTONLY</dt><dd>
+** The SQLITE_DIRECTONLY flag means that the function may only be invoked
+** from top-level SQL, and cannot be used in VIEWs or TRIGGERs nor in
+** schema structures such as [CHECK constraints], [DEFAULT clauses],
+** [expression indexes], [partial indexes], or [generated columns].
+** <p>
+** The SQLITE_DIRECTONLY flag is recommended for any
+** [application-defined SQL function]
+** that has side-effects or that could potentially leak sensitive information.
+** This will prevent attacks in which an application is tricked
+** into using a database file that has had its schema surreptitiously
+** modified to invoke the application-defined function in ways that are
+** harmful.
+** <p>
+** Some people say it is good practice to set SQLITE_DIRECTONLY on all
+** [application-defined SQL functions], regardless of whether or not they
+** are security sensitive, as doing so prevents those functions from being used
+** inside of the database schema, and thus ensures that the database
+** can be inspected and modified using generic tools (such as the [CLI])
+** that do not have access to the application-defined functions.
+** </dd>
+**
+** [[SQLITE_INNOCUOUS]] <dt>SQLITE_INNOCUOUS</dt><dd>
+** The SQLITE_INNOCUOUS flag means that the function is unlikely
+** to cause problems even if misused.  An innocuous function should have
+** no side effects and should not depend on any values other than its
+** input parameters. The [abs|abs() function] is an example of an
+** innocuous function.
+** The [load_extension() SQL function] is not innocuous because of its
+** side effects.
+** <p> SQLITE_INNOCUOUS is similar to SQLITE_DETERMINISTIC, but is not
+** exactly the same.  The [random|random() function] is an example of a
+** function that is innocuous but not deterministic.
+** <p>Some heightened security settings
+** ([SQLITE_DBCONFIG_TRUSTED_SCHEMA] and [PRAGMA trusted_schema=OFF])
+** disable the use of SQL functions inside views and triggers and in
+** schema structures such as [CHECK constraints], [DEFAULT clauses],
+** [expression indexes], [partial indexes], and [generated columns] unless
+** the function is tagged with SQLITE_INNOCUOUS.  Most built-in functions
+** are innocuous.  Developers are advised to avoid using the
+** SQLITE_INNOCUOUS flag for application-defined functions unless the
+** function has been carefully audited and found to be free of potentially
+** security-adverse side-effects and information-leaks.
+** </dd>
+**
+** [[SQLITE_SUBTYPE]] <dt>SQLITE_SUBTYPE</dt><dd>
+** The SQLITE_SUBTYPE flag indicates to SQLite that a function might call
+** [sqlite3_value_subtype()] to inspect the sub-types of its arguments.
+** This flag instructs SQLite to omit some corner-case optimizations that
+** might disrupt the operation of the [sqlite3_value_subtype()] function,
+** causing it to return zero rather than the correct subtype().
+** SQL functions that invokes [sqlite3_value_subtype()] should have this
+** property.  If the SQLITE_SUBTYPE property is omitted, then the return
+** value from [sqlite3_value_subtype()] might sometimes be zero even though
+** a non-zero subtype was specified by the function argument expression.
+**
+** [[SQLITE_RESULT_SUBTYPE]] <dt>SQLITE_RESULT_SUBTYPE</dt><dd>
+** The SQLITE_RESULT_SUBTYPE flag indicates to SQLite that a function might call
+** [sqlite3_result_subtype()] to cause a sub-type to be associated with its
+** result.
+** Every function that invokes [sqlite3_result_subtype()] should have this
+** property.  If it does not, then the call to [sqlite3_result_subtype()]
+** might become a no-op if the function is used as term in an
+** [expression index].  On the other hand, SQL functions that never invoke
+** [sqlite3_result_subtype()] should avoid setting this property, as the
+** purpose of this property is to disable certain optimizations that are
+** incompatible with subtypes.
+** </dd>
+** </dl>
+*/
+#define SQLITE_DETERMINISTIC    0x000000800
+#define SQLITE_DIRECTONLY       0x000080000
+#define SQLITE_SUBTYPE          0x000100000
+#define SQLITE_INNOCUOUS        0x000200000
+#define SQLITE_RESULT_SUBTYPE   0x001000000
+
+/*
+** CAPI3REF: Deprecated Functions
+** DEPRECATED
+**
+** These functions are [deprecated].  In order to maintain
+** backwards compatibility with older code, these functions continue
+** to be supported.  However, new applications should avoid
+** the use of these functions.  To encourage programmers to avoid
+** these functions, we will not explain what they do.
+*/
+#ifndef SQLITE_OMIT_DEPRECATED
+SQLITE_DEPRECATED int sqlite3_aggregate_count(sqlite3_context*);
+SQLITE_DEPRECATED int sqlite3_expired(sqlite3_stmt*);
+SQLITE_DEPRECATED int sqlite3_transfer_bindings(sqlite3_stmt*, sqlite3_stmt*);
+SQLITE_DEPRECATED int sqlite3_global_recover(void);
+SQLITE_DEPRECATED void sqlite3_thread_cleanup(void);
+SQLITE_DEPRECATED int sqlite3_memory_alarm(void(*)(void*,sqlite3_int64,int),
+                      void*,sqlite3_int64);
+#endif
+
+/*
+** CAPI3REF: Obtaining SQL Values
+** METHOD: sqlite3_value
+**
+** <b>Summary:</b>
+** <blockquote><table border=0 cellpadding=0 cellspacing=0>
+** <tr><td><b>sqlite3_value_blob</b><td>&rarr;<td>BLOB value
+** <tr><td><b>sqlite3_value_double</b><td>&rarr;<td>REAL value
+** <tr><td><b>sqlite3_value_int</b><td>&rarr;<td>32-bit INTEGER value
+** <tr><td><b>sqlite3_value_int64</b><td>&rarr;<td>64-bit INTEGER value
+** <tr><td><b>sqlite3_value_pointer</b><td>&rarr;<td>Pointer value
+** <tr><td><b>sqlite3_value_text</b><td>&rarr;<td>UTF-8 TEXT value
+** <tr><td><b>sqlite3_value_text16</b><td>&rarr;<td>UTF-16 TEXT value in
+** the native byteorder
+** <tr><td><b>sqlite3_value_text16be</b><td>&rarr;<td>UTF-16be TEXT value
+** <tr><td><b>sqlite3_value_text16le</b><td>&rarr;<td>UTF-16le TEXT value
+** <tr><td>&nbsp;<td>&nbsp;<td>&nbsp;
+** <tr><td><b>sqlite3_value_bytes</b><td>&rarr;<td>Size of a BLOB
+** or a UTF-8 TEXT in bytes
+** <tr><td><b>sqlite3_value_bytes16&nbsp;&nbsp;</b>
+** <td>&rarr;&nbsp;&nbsp;<td>Size of UTF-16
+** TEXT in bytes
+** <tr><td><b>sqlite3_value_type</b><td>&rarr;<td>Default
+** datatype of the value
+** <tr><td><b>sqlite3_value_numeric_type&nbsp;&nbsp;</b>
+** <td>&rarr;&nbsp;&nbsp;<td>Best numeric datatype of the value
+** <tr><td><b>sqlite3_value_nochange&nbsp;&nbsp;</b>
+** <td>&rarr;&nbsp;&nbsp;<td>True if the column is unchanged in an UPDATE
+** against a virtual table.
+** <tr><td><b>sqlite3_value_frombind&nbsp;&nbsp;</b>
+** <td>&rarr;&nbsp;&nbsp;<td>True if value originated from a [bound parameter]
+** </table></blockquote>
+**
+** <b>Details:</b>
+**
+** These routines extract type, size, and content information from
+** [protected sqlite3_value] objects.  Protected sqlite3_value objects
+** are used to pass parameter information into the functions that
+** implement [application-defined SQL functions] and [virtual tables].
+**
+** These routines work only with [protected sqlite3_value] objects.
+** Any attempt to use these routines on an [unprotected sqlite3_value]
+** is not threadsafe.
+**
+** ^These routines work just like the corresponding [column access functions]
+** except that these routines take a single [protected sqlite3_value] object
+** pointer instead of a [sqlite3_stmt*] pointer and an integer column number.
+**
+** ^The sqlite3_value_text16() interface extracts a UTF-16 string
+** in the native byte-order of the host machine.  ^The
+** sqlite3_value_text16be() and sqlite3_value_text16le() interfaces
+** extract UTF-16 strings as big-endian and little-endian respectively.
+**
+** ^If [sqlite3_value] object V was initialized
+** using [sqlite3_bind_pointer(S,I,P,X,D)] or [sqlite3_result_pointer(C,P,X,D)]
+** and if X and Y are strings that compare equal according to strcmp(X,Y),
+** then sqlite3_value_pointer(V,Y) will return the pointer P.  ^Otherwise,
+** sqlite3_value_pointer(V,Y) returns a NULL. The sqlite3_bind_pointer()
+** routine is part of the [pointer passing interface] added for SQLite 3.20.0.
+**
+** ^(The sqlite3_value_type(V) interface returns the
+** [SQLITE_INTEGER | datatype code] for the initial datatype of the
+** [sqlite3_value] object V. The returned value is one of [SQLITE_INTEGER],
+** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].)^
+** Other interfaces might change the datatype for an sqlite3_value object.
+** For example, if the datatype is initially SQLITE_INTEGER and
+** sqlite3_value_text(V) is called to extract a text value for that
+** integer, then subsequent calls to sqlite3_value_type(V) might return
+** SQLITE_TEXT.  Whether or not a persistent internal datatype conversion
+** occurs is undefined and may change from one release of SQLite to the next.
+**
+** ^(The sqlite3_value_numeric_type() interface attempts to apply
+** numeric affinity to the value.  This means that an attempt is
+** made to convert the value to an integer or floating point.  If
+** such a conversion is possible without loss of information (in other
+** words, if the value is a string that looks like a number)
+** then the conversion is performed.  Otherwise no conversion occurs.
+** The [SQLITE_INTEGER | datatype] after conversion is returned.)^
+**
+** ^Within the [xUpdate] method of a [virtual table], the
+** sqlite3_value_nochange(X) interface returns true if and only if
+** the column corresponding to X is unchanged by the UPDATE operation
+** that the xUpdate method call was invoked to implement and if
+** and the prior [xColumn] method call that was invoked to extracted
+** the value for that column returned without setting a result (probably
+** because it queried [sqlite3_vtab_nochange()] and found that the column
+** was unchanging).  ^Within an [xUpdate] method, any value for which
+** sqlite3_value_nochange(X) is true will in all other respects appear
+** to be a NULL value.  If sqlite3_value_nochange(X) is invoked anywhere other
+** than within an [xUpdate] method call for an UPDATE statement, then
+** the return value is arbitrary and meaningless.
+**
+** ^The sqlite3_value_frombind(X) interface returns non-zero if the
+** value X originated from one of the [sqlite3_bind_int|sqlite3_bind()]
+** interfaces.  ^If X comes from an SQL literal value, or a table column,
+** or an expression, then sqlite3_value_frombind(X) returns zero.
+**
+** Please pay particular attention to the fact that the pointer returned
+** from [sqlite3_value_blob()], [sqlite3_value_text()], or
+** [sqlite3_value_text16()] can be invalidated by a subsequent call to
+** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
+** or [sqlite3_value_text16()].
+**
+** These routines must be called from the same thread as
+** the SQL function that supplied the [sqlite3_value*] parameters.
+**
+** As long as the input parameter is correct, these routines can only
+** fail if an out-of-memory error occurs during a format conversion.
+** Only the following subset of interfaces are subject to out-of-memory
+** errors:
+**
+** <ul>
+** <li> sqlite3_value_blob()
+** <li> sqlite3_value_text()
+** <li> sqlite3_value_text16()
+** <li> sqlite3_value_text16le()
+** <li> sqlite3_value_text16be()
+** <li> sqlite3_value_bytes()
+** <li> sqlite3_value_bytes16()
+** </ul>
+**
+** If an out-of-memory error occurs, then the return value from these
+** routines is the same as if the column had contained an SQL NULL value.
+** Valid SQL NULL returns can be distinguished from out-of-memory errors
+** by invoking the [sqlite3_errcode()] immediately after the suspect
+** return value is obtained and before any
+** other SQLite interface is called on the same [database connection].
+*/
+const void *sqlite3_value_blob(sqlite3_value*);
+double sqlite3_value_double(sqlite3_value*);
+int sqlite3_value_int(sqlite3_value*);
+sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
+void *sqlite3_value_pointer(sqlite3_value*, const char*);
+const unsigned char *sqlite3_value_text(sqlite3_value*);
+const void *sqlite3_value_text16(sqlite3_value*);
+const void *sqlite3_value_text16le(sqlite3_value*);
+const void *sqlite3_value_text16be(sqlite3_value*);
+int sqlite3_value_bytes(sqlite3_value*);
+int sqlite3_value_bytes16(sqlite3_value*);
+int sqlite3_value_type(sqlite3_value*);
+int sqlite3_value_numeric_type(sqlite3_value*);
+int sqlite3_value_nochange(sqlite3_value*);
+int sqlite3_value_frombind(sqlite3_value*);
+
+/*
+** CAPI3REF: Report the internal text encoding state of an sqlite3_value object
+** METHOD: sqlite3_value
+**
+** ^(The sqlite3_value_encoding(X) interface returns one of [SQLITE_UTF8],
+** [SQLITE_UTF16BE], or [SQLITE_UTF16LE] according to the current text encoding
+** of the value X, assuming that X has type TEXT.)^  If sqlite3_value_type(X)
+** returns something other than SQLITE_TEXT, then the return value from
+** sqlite3_value_encoding(X) is meaningless.  ^Calls to
+** [sqlite3_value_text(X)], [sqlite3_value_text16(X)], [sqlite3_value_text16be(X)],
+** [sqlite3_value_text16le(X)], [sqlite3_value_bytes(X)], or
+** [sqlite3_value_bytes16(X)] might change the encoding of the value X and
+** thus change the return from subsequent calls to sqlite3_value_encoding(X).
+**
+** This routine is intended for used by applications that test and validate
+** the SQLite implementation.  This routine is inquiring about the opaque
+** internal state of an [sqlite3_value] object.  Ordinary applications should
+** not need to know what the internal state of an sqlite3_value object is and
+** hence should not need to use this interface.
+*/
+int sqlite3_value_encoding(sqlite3_value*);
+
+/*
+** CAPI3REF: Finding The Subtype Of SQL Values
+** METHOD: sqlite3_value
+**
+** The sqlite3_value_subtype(V) function returns the subtype for
+** an [application-defined SQL function] argument V.  The subtype
+** information can be used to pass a limited amount of context from
+** one SQL function to another.  Use the [sqlite3_result_subtype()]
+** routine to set the subtype for the return value of an SQL function.
+**
+** Every [application-defined SQL function] that invoke this interface
+** should include the [SQLITE_SUBTYPE] property in the text
+** encoding argument when the function is [sqlite3_create_function|registered].
+** If the [SQLITE_SUBTYPE] property is omitted, then sqlite3_value_subtype()
+** might return zero instead of the upstream subtype in some corner cases.
+*/
+unsigned int sqlite3_value_subtype(sqlite3_value*);
+
+/*
+** CAPI3REF: Copy And Free SQL Values
+** METHOD: sqlite3_value
+**
+** ^The sqlite3_value_dup(V) interface makes a copy of the [sqlite3_value]
+** object D and returns a pointer to that copy.  ^The [sqlite3_value] returned
+** is a [protected sqlite3_value] object even if the input is not.
+** ^The sqlite3_value_dup(V) interface returns NULL if V is NULL or if a
+** memory allocation fails. ^If V is a [pointer value], then the result
+** of sqlite3_value_dup(V) is a NULL value.
+**
+** ^The sqlite3_value_free(V) interface frees an [sqlite3_value] object
+** previously obtained from [sqlite3_value_dup()].  ^If V is a NULL pointer
+** then sqlite3_value_free(V) is a harmless no-op.
+*/
+sqlite3_value *sqlite3_value_dup(const sqlite3_value*);
+void sqlite3_value_free(sqlite3_value*);
+
+/*
+** CAPI3REF: Obtain Aggregate Function Context
+** METHOD: sqlite3_context
+**
+** Implementations of aggregate SQL functions use this
+** routine to allocate memory for storing their state.
+**
+** ^The first time the sqlite3_aggregate_context(C,N) routine is called
+** for a particular aggregate function, SQLite allocates
+** N bytes of memory, zeroes out that memory, and returns a pointer
+** to the new memory. ^On second and subsequent calls to
+** sqlite3_aggregate_context() for the same aggregate function instance,
+** the same buffer is returned.  Sqlite3_aggregate_context() is normally
+** called once for each invocation of the xStep callback and then one
+** last time when the xFinal callback is invoked.  ^(When no rows match
+** an aggregate query, the xStep() callback of the aggregate function
+** implementation is never called and xFinal() is called exactly once.
+** In those cases, sqlite3_aggregate_context() might be called for the
+** first time from within xFinal().)^
+**
+** ^The sqlite3_aggregate_context(C,N) routine returns a NULL pointer
+** when first called if N is less than or equal to zero or if a memory
+** allocation error occurs.
+**
+** ^(The amount of space allocated by sqlite3_aggregate_context(C,N) is
+** determined by the N parameter on first successful call.  Changing the
+** value of N in any subsequent call to sqlite3_aggregate_context() within
+** the same aggregate function instance will not resize the memory
+** allocation.)^  Within the xFinal callback, it is customary to set
+** N=0 in calls to sqlite3_aggregate_context(C,N) so that no
+** pointless memory allocations occur.
+**
+** ^SQLite automatically frees the memory allocated by
+** sqlite3_aggregate_context() when the aggregate query concludes.
+**
+** The first parameter must be a copy of the
+** [sqlite3_context | SQL function context] that is the first parameter
+** to the xStep or xFinal callback routine that implements the aggregate
+** function.
+**
+** This routine must be called from the same thread in which
+** the aggregate SQL function is running.
+*/
+void *sqlite3_aggregate_context(sqlite3_context*, int nBytes);
+
+/*
+** CAPI3REF: User Data For Functions
+** METHOD: sqlite3_context
+**
+** ^The sqlite3_user_data() interface returns a copy of
+** the pointer that was the pUserData parameter (the 5th parameter)
+** of the [sqlite3_create_function()]
+** and [sqlite3_create_function16()] routines that originally
+** registered the application defined function.
+**
+** This routine must be called from the same thread in which
+** the application-defined function is running.
+*/
+void *sqlite3_user_data(sqlite3_context*);
+
+/*
+** CAPI3REF: Database Connection For Functions
+** METHOD: sqlite3_context
+**
+** ^The sqlite3_context_db_handle() interface returns a copy of
+** the pointer to the [database connection] (the 1st parameter)
+** of the [sqlite3_create_function()]
+** and [sqlite3_create_function16()] routines that originally
+** registered the application defined function.
+*/
+sqlite3 *sqlite3_context_db_handle(sqlite3_context*);
+
+/*
+** CAPI3REF: Function Auxiliary Data
+** METHOD: sqlite3_context
+**
+** These functions may be used by (non-aggregate) SQL functions to
+** associate auxiliary data with argument values. If the same argument
+** value is passed to multiple invocations of the same SQL function during
+** query execution, under some circumstances the associated auxiliary data
+** might be preserved.  An example of where this might be useful is in a
+** regular-expression matching function. The compiled version of the regular
+** expression can be stored as auxiliary data associated with the pattern string. 
+** Then as long as the pattern string remains the same,
+** the compiled regular expression can be reused on multiple
+** invocations of the same function.
+**
+** ^The sqlite3_get_auxdata(C,N) interface returns a pointer to the auxiliary data
+** associated by the sqlite3_set_auxdata(C,N,P,X) function with the Nth argument
+** value to the application-defined function.  ^N is zero for the left-most
+** function argument.  ^If there is no auxiliary data
+** associated with the function argument, the sqlite3_get_auxdata(C,N) interface
+** returns a NULL pointer.
+**
+** ^The sqlite3_set_auxdata(C,N,P,X) interface saves P as auxiliary data for the
+** N-th argument of the application-defined function.  ^Subsequent
+** calls to sqlite3_get_auxdata(C,N) return P from the most recent
+** sqlite3_set_auxdata(C,N,P,X) call if the auxiliary data is still valid or
+** NULL if the auxiliary data has been discarded.
+** ^After each call to sqlite3_set_auxdata(C,N,P,X) where X is not NULL,
+** SQLite will invoke the destructor function X with parameter P exactly
+** once, when the auxiliary data is discarded.
+** SQLite is free to discard the auxiliary data at any time, including: <ul>
+** <li> ^(when the corresponding function parameter changes)^, or
+** <li> ^(when [sqlite3_reset()] or [sqlite3_finalize()] is called for the
+**      SQL statement)^, or
+** <li> ^(when sqlite3_set_auxdata() is invoked again on the same
+**       parameter)^, or
+** <li> ^(during the original sqlite3_set_auxdata() call when a memory
+**      allocation error occurs.)^
+** <li> ^(during the original sqlite3_set_auxdata() call if the function
+**      is evaluated during query planning instead of during query execution,
+**      as sometimes happens with [SQLITE_ENABLE_STAT4].)^ </ul>
+**
+** Note the last two bullets in particular.  The destructor X in
+** sqlite3_set_auxdata(C,N,P,X) might be called immediately, before the
+** sqlite3_set_auxdata() interface even returns.  Hence sqlite3_set_auxdata()
+** should be called near the end of the function implementation and the
+** function implementation should not make any use of P after
+** sqlite3_set_auxdata() has been called.  Furthermore, a call to
+** sqlite3_get_auxdata() that occurs immediately after a corresponding call
+** to sqlite3_set_auxdata() might still return NULL if an out-of-memory
+** condition occurred during the sqlite3_set_auxdata() call or if the
+** function is being evaluated during query planning rather than during
+** query execution.
+**
+** ^(In practice, auxiliary data is preserved between function calls for
+** function parameters that are compile-time constants, including literal
+** values and [parameters] and expressions composed from the same.)^
+**
+** The value of the N parameter to these interfaces should be non-negative.
+** Future enhancements may make use of negative N values to define new
+** kinds of function caching behavior.
+**
+** These routines must be called from the same thread in which
+** the SQL function is running.
+**
+** See also: [sqlite3_get_clientdata()] and [sqlite3_set_clientdata()].
+*/
+void *sqlite3_get_auxdata(sqlite3_context*, int N);
+void sqlite3_set_auxdata(sqlite3_context*, int N, void*, void (*)(void*));
+
+/*
+** CAPI3REF: Database Connection Client Data
+** METHOD: sqlite3
+**
+** These functions are used to associate one or more named pointers
+** with a [database connection].
+** A call to sqlite3_set_clientdata(D,N,P,X) causes the pointer P
+** to be attached to [database connection] D using name N.  Subsequent
+** calls to sqlite3_get_clientdata(D,N) will return a copy of pointer P
+** or a NULL pointer if there were no prior calls to
+** sqlite3_set_clientdata() with the same values of D and N.
+** Names are compared using strcmp() and are thus case sensitive.
+**
+** If P and X are both non-NULL, then the destructor X is invoked with
+** argument P on the first of the following occurrences:
+** <ul>
+** <li> An out-of-memory error occurs during the call to
+**      sqlite3_set_clientdata() which attempts to register pointer P.
+** <li> A subsequent call to sqlite3_set_clientdata(D,N,P,X) is made
+**      with the same D and N parameters.
+** <li> The database connection closes.  SQLite does not make any guarantees
+**      about the order in which destructors are called, only that all
+**      destructors will be called exactly once at some point during the
+**      database connection closing process.
+** </ul>
+**
+** SQLite does not do anything with client data other than invoke
+** destructors on the client data at the appropriate time.  The intended
+** use for client data is to provide a mechanism for wrapper libraries
+** to store additional information about an SQLite database connection.
+**
+** There is no limit (other than available memory) on the number of different
+** client data pointers (with different names) that can be attached to a
+** single database connection.  However, the implementation is optimized
+** for the case of having only one or two different client data names.
+** Applications and wrapper libraries are discouraged from using more than
+** one client data name each.
+**
+** There is no way to enumerate the client data pointers
+** associated with a database connection.  The N parameter can be thought
+** of as a secret key such that only code that knows the secret key is able
+** to access the associated data.
+**
+** Security Warning:  These interfaces should not be exposed in scripting
+** languages or in other circumstances where it might be possible for an
+** an attacker to invoke them.  Any agent that can invoke these interfaces
+** can probably also take control of the process.
+** 
+** Database connection client data is only available for SQLite
+** version 3.44.0 ([dateof:3.44.0]) and later.
+**
+** See also: [sqlite3_set_auxdata()] and [sqlite3_get_auxdata()].
+*/
+void *sqlite3_get_clientdata(sqlite3*,const char*);
+int sqlite3_set_clientdata(sqlite3*, const char*, void*, void(*)(void*));
+
+/*
+** CAPI3REF: Constants Defining Special Destructor Behavior
+**
+** These are special values for the destructor that is passed in as the
+** final argument to routines like [sqlite3_result_blob()].  ^If the destructor
+** argument is SQLITE_STATIC, it means that the content pointer is constant
+** and will never change.  It does not need to be destroyed.  ^The
+** SQLITE_TRANSIENT value means that the content will likely change in
+** the near future and that SQLite should make its own private copy of
+** the content before returning.
+**
+** The typedef is necessary to work around problems in certain
+** C++ compilers.
+*/
+typedef void (*sqlite3_destructor_type)(void*);
+#define SQLITE_STATIC      ((sqlite3_destructor_type)0)
+#define SQLITE_TRANSIENT   ((sqlite3_destructor_type)-1)
+
+/*
+** CAPI3REF: Setting The Result Of An SQL Function
+** METHOD: sqlite3_context
+**
+** These routines are used by the xFunc or xFinal callbacks that
+** implement SQL functions and aggregates.  See
+** [sqlite3_create_function()] and [sqlite3_create_function16()]
+** for additional information.
+**
+** These functions work very much like the [parameter binding] family of
+** functions used to bind values to host parameters in prepared statements.
+** Refer to the [SQL parameter] documentation for additional information.
+**
+** ^The sqlite3_result_blob() interface sets the result from
+** an application-defined function to be the BLOB whose content is pointed
+** to by the second parameter and which is N bytes long where N is the
+** third parameter.
+**
+** ^The sqlite3_result_zeroblob(C,N) and sqlite3_result_zeroblob64(C,N)
+** interfaces set the result of the application-defined function to be
+** a BLOB containing all zero bytes and N bytes in size.
+**
+** ^The sqlite3_result_double() interface sets the result from
+** an application-defined function to be a floating point value specified
+** by its 2nd argument.
+**
+** ^The sqlite3_result_error() and sqlite3_result_error16() functions
+** cause the implemented SQL function to throw an exception.
+** ^SQLite uses the string pointed to by the
+** 2nd parameter of sqlite3_result_error() or sqlite3_result_error16()
+** as the text of an error message.  ^SQLite interprets the error
+** message string from sqlite3_result_error() as UTF-8. ^SQLite
+** interprets the string from sqlite3_result_error16() as UTF-16 using
+** the same [byte-order determination rules] as [sqlite3_bind_text16()].
+** ^If the third parameter to sqlite3_result_error()
+** or sqlite3_result_error16() is negative then SQLite takes as the error
+** message all text up through the first zero character.
+** ^If the third parameter to sqlite3_result_error() or
+** sqlite3_result_error16() is non-negative then SQLite takes that many
+** bytes (not characters) from the 2nd parameter as the error message.
+** ^The sqlite3_result_error() and sqlite3_result_error16()
+** routines make a private copy of the error message text before
+** they return.  Hence, the calling function can deallocate or
+** modify the text after they return without harm.
+** ^The sqlite3_result_error_code() function changes the error code
+** returned by SQLite as a result of an error in a function.  ^By default,
+** the error code is SQLITE_ERROR.  ^A subsequent call to sqlite3_result_error()
+** or sqlite3_result_error16() resets the error code to SQLITE_ERROR.
+**
+** ^The sqlite3_result_error_toobig() interface causes SQLite to throw an
+** error indicating that a string or BLOB is too long to represent.
+**
+** ^The sqlite3_result_error_nomem() interface causes SQLite to throw an
+** error indicating that a memory allocation failed.
+**
+** ^The sqlite3_result_int() interface sets the return value
+** of the application-defined function to be the 32-bit signed integer
+** value given in the 2nd argument.
+** ^The sqlite3_result_int64() interface sets the return value
+** of the application-defined function to be the 64-bit signed integer
+** value given in the 2nd argument.
+**
+** ^The sqlite3_result_null() interface sets the return value
+** of the application-defined function to be NULL.
+**
+** ^The sqlite3_result_text(), sqlite3_result_text16(),
+** sqlite3_result_text16le(), and sqlite3_result_text16be() interfaces
+** set the return value of the application-defined function to be
+** a text string which is represented as UTF-8, UTF-16 native byte order,
+** UTF-16 little endian, or UTF-16 big endian, respectively.
+** ^The sqlite3_result_text64() interface sets the return value of an
+** application-defined function to be a text string in an encoding
+** specified by the fifth (and last) parameter, which must be one
+** of [SQLITE_UTF8], [SQLITE_UTF16], [SQLITE_UTF16BE], or [SQLITE_UTF16LE].
+** ^SQLite takes the text result from the application from
+** the 2nd parameter of the sqlite3_result_text* interfaces.
+** ^If the 3rd parameter to any of the sqlite3_result_text* interfaces
+** other than sqlite3_result_text64() is negative, then SQLite computes
+** the string length itself by searching the 2nd parameter for the first
+** zero character.
+** ^If the 3rd parameter to the sqlite3_result_text* interfaces
+** is non-negative, then as many bytes (not characters) of the text
+** pointed to by the 2nd parameter are taken as the application-defined
+** function result.  If the 3rd parameter is non-negative, then it
+** must be the byte offset into the string where the NUL terminator would
+** appear if the string where NUL terminated.  If any NUL characters occur
+** in the string at a byte offset that is less than the value of the 3rd
+** parameter, then the resulting string will contain embedded NULs and the
+** result of expressions operating on strings with embedded NULs is undefined.
+** ^If the 4th parameter to the sqlite3_result_text* interfaces
+** or sqlite3_result_blob is a non-NULL pointer, then SQLite calls that
+** function as the destructor on the text or BLOB result when it has
+** finished using that result.
+** ^If the 4th parameter to the sqlite3_result_text* interfaces or to
+** sqlite3_result_blob is the special constant SQLITE_STATIC, then SQLite
+** assumes that the text or BLOB result is in constant space and does not
+** copy the content of the parameter nor call a destructor on the content
+** when it has finished using that result.
+** ^If the 4th parameter to the sqlite3_result_text* interfaces
+** or sqlite3_result_blob is the special constant SQLITE_TRANSIENT
+** then SQLite makes a copy of the result into space obtained
+** from [sqlite3_malloc()] before it returns.
+**
+** ^For the sqlite3_result_text16(), sqlite3_result_text16le(), and
+** sqlite3_result_text16be() routines, and for sqlite3_result_text64()
+** when the encoding is not UTF8, if the input UTF16 begins with a
+** byte-order mark (BOM, U+FEFF) then the BOM is removed from the
+** string and the rest of the string is interpreted according to the
+** byte-order specified by the BOM.  ^The byte-order specified by
+** the BOM at the beginning of the text overrides the byte-order
+** specified by the interface procedure.  ^So, for example, if
+** sqlite3_result_text16le() is invoked with text that begins
+** with bytes 0xfe, 0xff (a big-endian byte-order mark) then the
+** first two bytes of input are skipped and the remaining input
+** is interpreted as UTF16BE text.
+**
+** ^For UTF16 input text to the sqlite3_result_text16(),
+** sqlite3_result_text16be(), sqlite3_result_text16le(), and
+** sqlite3_result_text64() routines, if the text contains invalid
+** UTF16 characters, the invalid characters might be converted
+** into the unicode replacement character, U+FFFD.
+**
+** ^The sqlite3_result_value() interface sets the result of
+** the application-defined function to be a copy of the
+** [unprotected sqlite3_value] object specified by the 2nd parameter.  ^The
+** sqlite3_result_value() interface makes a copy of the [sqlite3_value]
+** so that the [sqlite3_value] specified in the parameter may change or
+** be deallocated after sqlite3_result_value() returns without harm.
+** ^A [protected sqlite3_value] object may always be used where an
+** [unprotected sqlite3_value] object is required, so either
+** kind of [sqlite3_value] object can be used with this interface.
+**
+** ^The sqlite3_result_pointer(C,P,T,D) interface sets the result to an
+** SQL NULL value, just like [sqlite3_result_null(C)], except that it
+** also associates the host-language pointer P or type T with that
+** NULL value such that the pointer can be retrieved within an
+** [application-defined SQL function] using [sqlite3_value_pointer()].
+** ^If the D parameter is not NULL, then it is a pointer to a destructor
+** for the P parameter.  ^SQLite invokes D with P as its only argument
+** when SQLite is finished with P.  The T parameter should be a static
+** string and preferably a string literal. The sqlite3_result_pointer()
+** routine is part of the [pointer passing interface] added for SQLite 3.20.0.
+**
+** If these routines are called from within the different thread
+** than the one containing the application-defined function that received
+** the [sqlite3_context] pointer, the results are undefined.
+*/
+void sqlite3_result_blob(sqlite3_context*, const void*, int, void(*)(void*));
+void sqlite3_result_blob64(sqlite3_context*,const void*,
+                           sqlite3_uint64,void(*)(void*));
+void sqlite3_result_double(sqlite3_context*, double);
+void sqlite3_result_error(sqlite3_context*, const char*, int);
+void sqlite3_result_error16(sqlite3_context*, const void*, int);
+void sqlite3_result_error_toobig(sqlite3_context*);
+void sqlite3_result_error_nomem(sqlite3_context*);
+void sqlite3_result_error_code(sqlite3_context*, int);
+void sqlite3_result_int(sqlite3_context*, int);
+void sqlite3_result_int64(sqlite3_context*, sqlite3_int64);
+void sqlite3_result_null(sqlite3_context*);
+void sqlite3_result_text(sqlite3_context*, const char*, int, void(*)(void*));
+void sqlite3_result_text64(sqlite3_context*, const char*,sqlite3_uint64,
+                           void(*)(void*), unsigned char encoding);
+void sqlite3_result_text16(sqlite3_context*, const void*, int, void(*)(void*));
+void sqlite3_result_text16le(sqlite3_context*, const void*, int,void(*)(void*));
+void sqlite3_result_text16be(sqlite3_context*, const void*, int,void(*)(void*));
+void sqlite3_result_value(sqlite3_context*, sqlite3_value*);
+void sqlite3_result_pointer(sqlite3_context*, void*,const char*,void(*)(void*));
+void sqlite3_result_zeroblob(sqlite3_context*, int n);
+int sqlite3_result_zeroblob64(sqlite3_context*, sqlite3_uint64 n);
+
+
+/*
+** CAPI3REF: Setting The Subtype Of An SQL Function
+** METHOD: sqlite3_context
+**
+** The sqlite3_result_subtype(C,T) function causes the subtype of
+** the result from the [application-defined SQL function] with
+** [sqlite3_context] C to be the value T.  Only the lower 8 bits
+** of the subtype T are preserved in current versions of SQLite;
+** higher order bits are discarded.
+** The number of subtype bytes preserved by SQLite might increase
+** in future releases of SQLite.
+**
+** Every [application-defined SQL function] that invokes this interface
+** should include the [SQLITE_RESULT_SUBTYPE] property in its
+** text encoding argument when the SQL function is
+** [sqlite3_create_function|registered].  If the [SQLITE_RESULT_SUBTYPE]
+** property is omitted from the function that invokes sqlite3_result_subtype(),
+** then in some cases the sqlite3_result_subtype() might fail to set
+** the result subtype.
+**
+** If SQLite is compiled with -DSQLITE_STRICT_SUBTYPE=1, then any
+** SQL function that invokes the sqlite3_result_subtype() interface
+** and that does not have the SQLITE_RESULT_SUBTYPE property will raise
+** an error.  Future versions of SQLite might enable -DSQLITE_STRICT_SUBTYPE=1
+** by default.
+*/
+void sqlite3_result_subtype(sqlite3_context*,unsigned int);
+
+/*
+** CAPI3REF: Define New Collating Sequences
+** METHOD: sqlite3
+**
+** ^These functions add, remove, or modify a [collation] associated
+** with the [database connection] specified as the first argument.
+**
+** ^The name of the collation is a UTF-8 string
+** for sqlite3_create_collation() and sqlite3_create_collation_v2()
+** and a UTF-16 string in native byte order for sqlite3_create_collation16().
+** ^Collation names that compare equal according to [sqlite3_strnicmp()] are
+** considered to be the same name.
+**
+** ^(The third argument (eTextRep) must be one of the constants:
+** <ul>
+** <li> [SQLITE_UTF8],
+** <li> [SQLITE_UTF16LE],
+** <li> [SQLITE_UTF16BE],
+** <li> [SQLITE_UTF16], or
+** <li> [SQLITE_UTF16_ALIGNED].
+** </ul>)^
+** ^The eTextRep argument determines the encoding of strings passed
+** to the collating function callback, xCompare.
+** ^The [SQLITE_UTF16] and [SQLITE_UTF16_ALIGNED] values for eTextRep
+** force strings to be UTF16 with native byte order.
+** ^The [SQLITE_UTF16_ALIGNED] value for eTextRep forces strings to begin
+** on an even byte address.
+**
+** ^The fourth argument, pArg, is an application data pointer that is passed
+** through as the first argument to the collating function callback.
+**
+** ^The fifth argument, xCompare, is a pointer to the collating function.
+** ^Multiple collating functions can be registered using the same name but
+** with different eTextRep parameters and SQLite will use whichever
+** function requires the least amount of data transformation.
+** ^If the xCompare argument is NULL then the collating function is
+** deleted.  ^When all collating functions having the same name are deleted,
+** that collation is no longer usable.
+**
+** ^The collating function callback is invoked with a copy of the pArg
+** application data pointer and with two strings in the encoding specified
+** by the eTextRep argument.  The two integer parameters to the collating
+** function callback are the length of the two strings, in bytes. The collating
+** function must return an integer that is negative, zero, or positive
+** if the first string is less than, equal to, or greater than the second,
+** respectively.  A collating function must always return the same answer
+** given the same inputs.  If two or more collating functions are registered
+** to the same collation name (using different eTextRep values) then all
+** must give an equivalent answer when invoked with equivalent strings.
+** The collating function must obey the following properties for all
+** strings A, B, and C:
+**
+** <ol>
+** <li> If A==B then B==A.
+** <li> If A==B and B==C then A==C.
+** <li> If A&lt;B THEN B&gt;A.
+** <li> If A&lt;B and B&lt;C then A&lt;C.
+** </ol>
+**
+** If a collating function fails any of the above constraints and that
+** collating function is registered and used, then the behavior of SQLite
+** is undefined.
+**
+** ^The sqlite3_create_collation_v2() works like sqlite3_create_collation()
+** with the addition that the xDestroy callback is invoked on pArg when
+** the collating function is deleted.
+** ^Collating functions are deleted when they are overridden by later
+** calls to the collation creation functions or when the
+** [database connection] is closed using [sqlite3_close()].
+**
+** ^The xDestroy callback is <u>not</u> called if the
+** sqlite3_create_collation_v2() function fails.  Applications that invoke
+** sqlite3_create_collation_v2() with a non-NULL xDestroy argument should
+** check the return code and dispose of the application data pointer
+** themselves rather than expecting SQLite to deal with it for them.
+** This is different from every other SQLite interface.  The inconsistency
+** is unfortunate but cannot be changed without breaking backwards
+** compatibility.
+**
+** See also:  [sqlite3_collation_needed()] and [sqlite3_collation_needed16()].
+*/
+int sqlite3_create_collation(
+  sqlite3*,
+  const char *zName,
+  int eTextRep,
+  void *pArg,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+);
+int sqlite3_create_collation_v2(
+  sqlite3*,
+  const char *zName,
+  int eTextRep,
+  void *pArg,
+  int(*xCompare)(void*,int,const void*,int,const void*),
+  void(*xDestroy)(void*)
+);
+int sqlite3_create_collation16(
+  sqlite3*,
+  const void *zName,
+  int eTextRep,
+  void *pArg,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+);
+
+/*
+** CAPI3REF: Collation Needed Callbacks
+** METHOD: sqlite3
+**
+** ^To avoid having to register all collation sequences before a database
+** can be used, a single callback function may be registered with the
+** [database connection] to be invoked whenever an undefined collation
+** sequence is required.
+**
+** ^If the function is registered using the sqlite3_collation_needed() API,
+** then it is passed the names of undefined collation sequences as strings
+** encoded in UTF-8. ^If sqlite3_collation_needed16() is used,
+** the names are passed as UTF-16 in machine native byte order.
+** ^A call to either function replaces the existing collation-needed callback.
+**
+** ^(When the callback is invoked, the first argument passed is a copy
+** of the second argument to sqlite3_collation_needed() or
+** sqlite3_collation_needed16().  The second argument is the database
+** connection.  The third argument is one of [SQLITE_UTF8], [SQLITE_UTF16BE],
+** or [SQLITE_UTF16LE], indicating the most desirable form of the collation
+** sequence function required.  The fourth parameter is the name of the
+** required collation sequence.)^
+**
+** The callback function should register the desired collation using
+** [sqlite3_create_collation()], [sqlite3_create_collation16()], or
+** [sqlite3_create_collation_v2()].
+*/
+int sqlite3_collation_needed(
+  sqlite3*,
+  void*,
+  void(*)(void*,sqlite3*,int eTextRep,const char*)
+);
+int sqlite3_collation_needed16(
+  sqlite3*,
+  void*,
+  void(*)(void*,sqlite3*,int eTextRep,const void*)
+);
+
+#ifdef SQLITE_ENABLE_CEROD
+/*
+** Specify the activation key for a CEROD database.  Unless
+** activated, none of the CEROD routines will work.
+*/
+void sqlite3_activate_cerod(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+/*
+** CAPI3REF: Suspend Execution For A Short Time
+**
+** The sqlite3_sleep() function causes the current thread to suspend execution
+** for at least a number of milliseconds specified in its parameter.
+**
+** If the operating system does not support sleep requests with
+** millisecond time resolution, then the time will be rounded up to
+** the nearest second. The number of milliseconds of sleep actually
+** requested from the operating system is returned.
+**
+** ^SQLite implements this interface by calling the xSleep()
+** method of the default [sqlite3_vfs] object.  If the xSleep() method
+** of the default VFS is not implemented correctly, or not implemented at
+** all, then the behavior of sqlite3_sleep() may deviate from the description
+** in the previous paragraphs.
+**
+** If a negative argument is passed to sqlite3_sleep() the results vary by
+** VFS and operating system.  Some system treat a negative argument as an
+** instruction to sleep forever.  Others understand it to mean do not sleep
+** at all. ^In SQLite version 3.42.0 and later, a negative
+** argument passed into sqlite3_sleep() is changed to zero before it is relayed
+** down into the xSleep method of the VFS.
+*/
+int sqlite3_sleep(int);
+
+/*
+** CAPI3REF: Name Of The Folder Holding Temporary Files
+**
+** ^(If this global variable is made to point to a string which is
+** the name of a folder (a.k.a. directory), then all temporary files
+** created by SQLite when using a built-in [sqlite3_vfs | VFS]
+** will be placed in that directory.)^  ^If this variable
+** is a NULL pointer, then SQLite performs a search for an appropriate
+** temporary file directory.
+**
+** Applications are strongly discouraged from using this global variable.
+** It is required to set a temporary folder on Windows Runtime (WinRT).
+** But for all other platforms, it is highly recommended that applications
+** neither read nor write this variable.  This global variable is a relic
+** that exists for backwards compatibility of legacy applications and should
+** be avoided in new projects.
+**
+** It is not safe to read or modify this variable in more than one
+** thread at a time.  It is not safe to read or modify this variable
+** if a [database connection] is being used at the same time in a separate
+** thread.
+** It is intended that this variable be set once
+** as part of process initialization and before any SQLite interface
+** routines have been called and that this variable remain unchanged
+** thereafter.
+**
+** ^The [temp_store_directory pragma] may modify this variable and cause
+** it to point to memory obtained from [sqlite3_malloc].  ^Furthermore,
+** the [temp_store_directory pragma] always assumes that any string
+** that this variable points to is held in memory obtained from
+** [sqlite3_malloc] and the pragma may attempt to free that memory
+** using [sqlite3_free].
+** Hence, if this variable is modified directly, either it should be
+** made NULL or made to point to memory obtained from [sqlite3_malloc]
+** or else the use of the [temp_store_directory pragma] should be avoided.
+** Except when requested by the [temp_store_directory pragma], SQLite
+** does not free the memory that sqlite3_temp_directory points to.  If
+** the application wants that memory to be freed, it must do
+** so itself, taking care to only do so after all [database connection]
+** objects have been destroyed.
+**
+** <b>Note to Windows Runtime users:</b>  The temporary directory must be set
+** prior to calling [sqlite3_open] or [sqlite3_open_v2].  Otherwise, various
+** features that require the use of temporary files may fail.  Here is an
+** example of how to do this using C++ with the Windows Runtime:
+**
+** <blockquote><pre>
+** LPCWSTR zPath = Windows::Storage::ApplicationData::Current->
+** &nbsp;     TemporaryFolder->Path->Data();
+** char zPathBuf&#91;MAX_PATH + 1&#93;;
+** memset(zPathBuf, 0, sizeof(zPathBuf));
+** WideCharToMultiByte(CP_UTF8, 0, zPath, -1, zPathBuf, sizeof(zPathBuf),
+** &nbsp;     NULL, NULL);
+** sqlite3_temp_directory = sqlite3_mprintf("%s", zPathBuf);
+** </pre></blockquote>
+*/
+SQLITE_EXTERN char *sqlite3_temp_directory;
+
+/*
+** CAPI3REF: Name Of The Folder Holding Database Files
+**
+** ^(If this global variable is made to point to a string which is
+** the name of a folder (a.k.a. directory), then all database files
+** specified with a relative pathname and created or accessed by
+** SQLite when using a built-in windows [sqlite3_vfs | VFS] will be assumed
+** to be relative to that directory.)^ ^If this variable is a NULL
+** pointer, then SQLite assumes that all database files specified
+** with a relative pathname are relative to the current directory
+** for the process.  Only the windows VFS makes use of this global
+** variable; it is ignored by the unix VFS.
+**
+** Changing the value of this variable while a database connection is
+** open can result in a corrupt database.
+**
+** It is not safe to read or modify this variable in more than one
+** thread at a time.  It is not safe to read or modify this variable
+** if a [database connection] is being used at the same time in a separate
+** thread.
+** It is intended that this variable be set once
+** as part of process initialization and before any SQLite interface
+** routines have been called and that this variable remain unchanged
+** thereafter.
+**
+** ^The [data_store_directory pragma] may modify this variable and cause
+** it to point to memory obtained from [sqlite3_malloc].  ^Furthermore,
+** the [data_store_directory pragma] always assumes that any string
+** that this variable points to is held in memory obtained from
+** [sqlite3_malloc] and the pragma may attempt to free that memory
+** using [sqlite3_free].
+** Hence, if this variable is modified directly, either it should be
+** made NULL or made to point to memory obtained from [sqlite3_malloc]
+** or else the use of the [data_store_directory pragma] should be avoided.
+*/
+SQLITE_EXTERN char *sqlite3_data_directory;
+
+/*
+** CAPI3REF: Win32 Specific Interface
+**
+** These interfaces are available only on Windows.  The
+** [sqlite3_win32_set_directory] interface is used to set the value associated
+** with the [sqlite3_temp_directory] or [sqlite3_data_directory] variable, to
+** zValue, depending on the value of the type parameter.  The zValue parameter
+** should be NULL to cause the previous value to be freed via [sqlite3_free];
+** a non-NULL value will be copied into memory obtained from [sqlite3_malloc]
+** prior to being used.  The [sqlite3_win32_set_directory] interface returns
+** [SQLITE_OK] to indicate success, [SQLITE_ERROR] if the type is unsupported,
+** or [SQLITE_NOMEM] if memory could not be allocated.  The value of the
+** [sqlite3_data_directory] variable is intended to act as a replacement for
+** the current directory on the sub-platforms of Win32 where that concept is
+** not present, e.g. WinRT and UWP.  The [sqlite3_win32_set_directory8] and
+** [sqlite3_win32_set_directory16] interfaces behave exactly the same as the
+** sqlite3_win32_set_directory interface except the string parameter must be
+** UTF-8 or UTF-16, respectively.
+*/
+int sqlite3_win32_set_directory(
+  unsigned long type, /* Identifier for directory being set or reset */
+  void *zValue        /* New value for directory being set or reset */
+);
+int sqlite3_win32_set_directory8(unsigned long type, const char *zValue);
+int sqlite3_win32_set_directory16(unsigned long type, const void *zValue);
+
+/*
+** CAPI3REF: Win32 Directory Types
+**
+** These macros are only available on Windows.  They define the allowed values
+** for the type argument to the [sqlite3_win32_set_directory] interface.
+*/
+#define SQLITE_WIN32_DATA_DIRECTORY_TYPE  1
+#define SQLITE_WIN32_TEMP_DIRECTORY_TYPE  2
+
+/*
+** CAPI3REF: Test For Auto-Commit Mode
+** KEYWORDS: {autocommit mode}
+** METHOD: sqlite3
+**
+** ^The sqlite3_get_autocommit() interface returns non-zero or
+** zero if the given database connection is or is not in autocommit mode,
+** respectively.  ^Autocommit mode is on by default.
+** ^Autocommit mode is disabled by a [BEGIN] statement.
+** ^Autocommit mode is re-enabled by a [COMMIT] or [ROLLBACK].
+**
+** If certain kinds of errors occur on a statement within a multi-statement
+** transaction (errors including [SQLITE_FULL], [SQLITE_IOERR],
+** [SQLITE_NOMEM], [SQLITE_BUSY], and [SQLITE_INTERRUPT]) then the
+** transaction might be rolled back automatically.  The only way to
+** find out whether SQLite automatically rolled back the transaction after
+** an error is to use this function.
+**
+** If another thread changes the autocommit status of the database
+** connection while this routine is running, then the return value
+** is undefined.
+*/
+int sqlite3_get_autocommit(sqlite3*);
+
+/*
+** CAPI3REF: Find The Database Handle Of A Prepared Statement
+** METHOD: sqlite3_stmt
+**
+** ^The sqlite3_db_handle interface returns the [database connection] handle
+** to which a [prepared statement] belongs.  ^The [database connection]
+** returned by sqlite3_db_handle is the same [database connection]
+** that was the first argument
+** to the [sqlite3_prepare_v2()] call (or its variants) that was used to
+** create the statement in the first place.
+*/
+sqlite3 *sqlite3_db_handle(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Return The Schema Name For A Database Connection
+** METHOD: sqlite3
+**
+** ^The sqlite3_db_name(D,N) interface returns a pointer to the schema name
+** for the N-th database on database connection D, or a NULL pointer of N is
+** out of range.  An N value of 0 means the main database file.  An N of 1 is
+** the "temp" schema.  Larger values of N correspond to various ATTACH-ed
+** databases.
+**
+** Space to hold the string that is returned by sqlite3_db_name() is managed
+** by SQLite itself.  The string might be deallocated by any operation that
+** changes the schema, including [ATTACH] or [DETACH] or calls to
+** [sqlite3_serialize()] or [sqlite3_deserialize()], even operations that
+** occur on a different thread.  Applications that need to
+** remember the string long-term should make their own copy.  Applications that
+** are accessing the same database connection simultaneously on multiple
+** threads should mutex-protect calls to this API and should make their own
+** private copy of the result prior to releasing the mutex.
+*/
+const char *sqlite3_db_name(sqlite3 *db, int N);
+
+/*
+** CAPI3REF: Return The Filename For A Database Connection
+** METHOD: sqlite3
+**
+** ^The sqlite3_db_filename(D,N) interface returns a pointer to the filename
+** associated with database N of connection D.
+** ^If there is no attached database N on the database
+** connection D, or if database N is a temporary or in-memory database, then
+** this function will return either a NULL pointer or an empty string.
+**
+** ^The string value returned by this routine is owned and managed by
+** the database connection.  ^The value will be valid until the database N
+** is [DETACH]-ed or until the database connection closes.
+**
+** ^The filename returned by this function is the output of the
+** xFullPathname method of the [VFS].  ^In other words, the filename
+** will be an absolute pathname, even if the filename used
+** to open the database originally was a URI or relative pathname.
+**
+** If the filename pointer returned by this routine is not NULL, then it
+** can be used as the filename input parameter to these routines:
+** <ul>
+** <li> [sqlite3_uri_parameter()]
+** <li> [sqlite3_uri_boolean()]
+** <li> [sqlite3_uri_int64()]
+** <li> [sqlite3_filename_database()]
+** <li> [sqlite3_filename_journal()]
+** <li> [sqlite3_filename_wal()]
+** </ul>
+*/
+sqlite3_filename sqlite3_db_filename(sqlite3 *db, const char *zDbName);
+
+/*
+** CAPI3REF: Determine if a database is read-only
+** METHOD: sqlite3
+**
+** ^The sqlite3_db_readonly(D,N) interface returns 1 if the database N
+** of connection D is read-only, 0 if it is read/write, or -1 if N is not
+** the name of a database on connection D.
+*/
+int sqlite3_db_readonly(sqlite3 *db, const char *zDbName);
+
+/*
+** CAPI3REF: Determine the transaction state of a database
+** METHOD: sqlite3
+**
+** ^The sqlite3_txn_state(D,S) interface returns the current
+** [transaction state] of schema S in database connection D.  ^If S is NULL,
+** then the highest transaction state of any schema on database connection D
+** is returned.  Transaction states are (in order of lowest to highest):
+** <ol>
+** <li value="0"> SQLITE_TXN_NONE
+** <li value="1"> SQLITE_TXN_READ
+** <li value="2"> SQLITE_TXN_WRITE
+** </ol>
+** ^If the S argument to sqlite3_txn_state(D,S) is not the name of
+** a valid schema, then -1 is returned.
+*/
+int sqlite3_txn_state(sqlite3*,const char *zSchema);
+
+/*
+** CAPI3REF: Allowed return values from sqlite3_txn_state()
+** KEYWORDS: {transaction state}
+**
+** These constants define the current transaction state of a database file.
+** ^The [sqlite3_txn_state(D,S)] interface returns one of these
+** constants in order to describe the transaction state of schema S
+** in [database connection] D.
+**
+** <dl>
+** [[SQLITE_TXN_NONE]] <dt>SQLITE_TXN_NONE</dt>
+** <dd>The SQLITE_TXN_NONE state means that no transaction is currently
+** pending.</dd>
+**
+** [[SQLITE_TXN_READ]] <dt>SQLITE_TXN_READ</dt>
+** <dd>The SQLITE_TXN_READ state means that the database is currently
+** in a read transaction.  Content has been read from the database file
+** but nothing in the database file has changed.  The transaction state
+** will advanced to SQLITE_TXN_WRITE if any changes occur and there are
+** no other conflicting concurrent write transactions.  The transaction
+** state will revert to SQLITE_TXN_NONE following a [ROLLBACK] or
+** [COMMIT].</dd>
+**
+** [[SQLITE_TXN_WRITE]] <dt>SQLITE_TXN_WRITE</dt>
+** <dd>The SQLITE_TXN_WRITE state means that the database is currently
+** in a write transaction.  Content has been written to the database file
+** but has not yet committed.  The transaction state will change to
+** to SQLITE_TXN_NONE at the next [ROLLBACK] or [COMMIT].</dd>
+*/
+#define SQLITE_TXN_NONE  0
+#define SQLITE_TXN_READ  1
+#define SQLITE_TXN_WRITE 2
+
+/*
+** CAPI3REF: Find the next prepared statement
+** METHOD: sqlite3
+**
+** ^This interface returns a pointer to the next [prepared statement] after
+** pStmt associated with the [database connection] pDb.  ^If pStmt is NULL
+** then this interface returns a pointer to the first prepared statement
+** associated with the database connection pDb.  ^If no prepared statement
+** satisfies the conditions of this routine, it returns NULL.
+**
+** The [database connection] pointer D in a call to
+** [sqlite3_next_stmt(D,S)] must refer to an open database
+** connection and in particular must not be a NULL pointer.
+*/
+sqlite3_stmt *sqlite3_next_stmt(sqlite3 *pDb, sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Commit And Rollback Notification Callbacks
+** METHOD: sqlite3
+**
+** ^The sqlite3_commit_hook() interface registers a callback
+** function to be invoked whenever a transaction is [COMMIT | committed].
+** ^Any callback set by a previous call to sqlite3_commit_hook()
+** for the same database connection is overridden.
+** ^The sqlite3_rollback_hook() interface registers a callback
+** function to be invoked whenever a transaction is [ROLLBACK | rolled back].
+** ^Any callback set by a previous call to sqlite3_rollback_hook()
+** for the same database connection is overridden.
+** ^The pArg argument is passed through to the callback.
+** ^If the callback on a commit hook function returns non-zero,
+** then the commit is converted into a rollback.
+**
+** ^The sqlite3_commit_hook(D,C,P) and sqlite3_rollback_hook(D,C,P) functions
+** return the P argument from the previous call of the same function
+** on the same [database connection] D, or NULL for
+** the first call for each function on D.
+**
+** The commit and rollback hook callbacks are not reentrant.
+** The callback implementation must not do anything that will modify
+** the database connection that invoked the callback.  Any actions
+** to modify the database connection must be deferred until after the
+** completion of the [sqlite3_step()] call that triggered the commit
+** or rollback hook in the first place.
+** Note that running any other SQL statements, including SELECT statements,
+** or merely calling [sqlite3_prepare_v2()] and [sqlite3_step()] will modify
+** the database connections for the meaning of "modify" in this paragraph.
+**
+** ^Registering a NULL function disables the callback.
+**
+** ^When the commit hook callback routine returns zero, the [COMMIT]
+** operation is allowed to continue normally.  ^If the commit hook
+** returns non-zero, then the [COMMIT] is converted into a [ROLLBACK].
+** ^The rollback hook is invoked on a rollback that results from a commit
+** hook returning non-zero, just as it would be with any other rollback.
+**
+** ^For the purposes of this API, a transaction is said to have been
+** rolled back if an explicit "ROLLBACK" statement is executed, or
+** an error or constraint causes an implicit rollback to occur.
+** ^The rollback callback is not invoked if a transaction is
+** automatically rolled back because the database connection is closed.
+**
+** See also the [sqlite3_update_hook()] interface.
+*/
+void *sqlite3_commit_hook(sqlite3*, int(*)(void*), void*);
+void *sqlite3_rollback_hook(sqlite3*, void(*)(void *), void*);
+
+/*
+** CAPI3REF: Autovacuum Compaction Amount Callback
+** METHOD: sqlite3
+**
+** ^The sqlite3_autovacuum_pages(D,C,P,X) interface registers a callback
+** function C that is invoked prior to each autovacuum of the database
+** file.  ^The callback is passed a copy of the generic data pointer (P),
+** the schema-name of the attached database that is being autovacuumed,
+** the size of the database file in pages, the number of free pages,
+** and the number of bytes per page, respectively.  The callback should
+** return the number of free pages that should be removed by the
+** autovacuum.  ^If the callback returns zero, then no autovacuum happens.
+** ^If the value returned is greater than or equal to the number of
+** free pages, then a complete autovacuum happens.
+**
+** <p>^If there are multiple ATTACH-ed database files that are being
+** modified as part of a transaction commit, then the autovacuum pages
+** callback is invoked separately for each file.
+**
+** <p><b>The callback is not reentrant.</b> The callback function should
+** not attempt to invoke any other SQLite interface.  If it does, bad
+** things may happen, including segmentation faults and corrupt database
+** files.  The callback function should be a simple function that
+** does some arithmetic on its input parameters and returns a result.
+**
+** ^The X parameter to sqlite3_autovacuum_pages(D,C,P,X) is an optional
+** destructor for the P parameter.  ^If X is not NULL, then X(P) is
+** invoked whenever the database connection closes or when the callback
+** is overwritten by another invocation of sqlite3_autovacuum_pages().
+**
+** <p>^There is only one autovacuum pages callback per database connection.
+** ^Each call to the sqlite3_autovacuum_pages() interface overrides all
+** previous invocations for that database connection.  ^If the callback
+** argument (C) to sqlite3_autovacuum_pages(D,C,P,X) is a NULL pointer,
+** then the autovacuum steps callback is canceled.  The return value
+** from sqlite3_autovacuum_pages() is normally SQLITE_OK, but might
+** be some other error code if something goes wrong.  The current
+** implementation will only return SQLITE_OK or SQLITE_MISUSE, but other
+** return codes might be added in future releases.
+**
+** <p>If no autovacuum pages callback is specified (the usual case) or
+** a NULL pointer is provided for the callback,
+** then the default behavior is to vacuum all free pages.  So, in other
+** words, the default behavior is the same as if the callback function
+** were something like this:
+**
+** <blockquote><pre>
+** &nbsp;   unsigned int demonstration_autovac_pages_callback(
+** &nbsp;     void *pClientData,
+** &nbsp;     const char *zSchema,
+** &nbsp;     unsigned int nDbPage,
+** &nbsp;     unsigned int nFreePage,
+** &nbsp;     unsigned int nBytePerPage
+** &nbsp;   ){
+** &nbsp;     return nFreePage;
+** &nbsp;   }
+** </pre></blockquote>
+*/
+int sqlite3_autovacuum_pages(
+  sqlite3 *db,
+  unsigned int(*)(void*,const char*,unsigned int,unsigned int,unsigned int),
+  void*,
+  void(*)(void*)
+);
+
+
+/*
+** CAPI3REF: Data Change Notification Callbacks
+** METHOD: sqlite3
+**
+** ^The sqlite3_update_hook() interface registers a callback function
+** with the [database connection] identified by the first argument
+** to be invoked whenever a row is updated, inserted or deleted in
+** a [rowid table].
+** ^Any callback set by a previous call to this function
+** for the same database connection is overridden.
+**
+** ^The second argument is a pointer to the function to invoke when a
+** row is updated, inserted or deleted in a rowid table.
+** ^The first argument to the callback is a copy of the third argument
+** to sqlite3_update_hook().
+** ^The second callback argument is one of [SQLITE_INSERT], [SQLITE_DELETE],
+** or [SQLITE_UPDATE], depending on the operation that caused the callback
+** to be invoked.
+** ^The third and fourth arguments to the callback contain pointers to the
+** database and table name containing the affected row.
+** ^The final callback parameter is the [rowid] of the row.
+** ^In the case of an update, this is the [rowid] after the update takes place.
+**
+** ^(The update hook is not invoked when internal system tables are
+** modified (i.e. sqlite_sequence).)^
+** ^The update hook is not invoked when [WITHOUT ROWID] tables are modified.
+**
+** ^In the current implementation, the update hook
+** is not invoked when conflicting rows are deleted because of an
+** [ON CONFLICT | ON CONFLICT REPLACE] clause.  ^Nor is the update hook
+** invoked when rows are deleted using the [truncate optimization].
+** The exceptions defined in this paragraph might change in a future
+** release of SQLite.
+**
+** The update hook implementation must not do anything that will modify
+** the database connection that invoked the update hook.  Any actions
+** to modify the database connection must be deferred until after the
+** completion of the [sqlite3_step()] call that triggered the update hook.
+** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
+** database connections for the meaning of "modify" in this paragraph.
+**
+** ^The sqlite3_update_hook(D,C,P) function
+** returns the P argument from the previous call
+** on the same [database connection] D, or NULL for
+** the first call on D.
+**
+** See also the [sqlite3_commit_hook()], [sqlite3_rollback_hook()],
+** and [sqlite3_preupdate_hook()] interfaces.
+*/
+void *sqlite3_update_hook(
+  sqlite3*,
+  void(*)(void *,int ,char const *,char const *,sqlite3_int64),
+  void*
+);
+
+/*
+** CAPI3REF: Enable Or Disable Shared Pager Cache
+**
+** ^(This routine enables or disables the sharing of the database cache
+** and schema data structures between [database connection | connections]
+** to the same database. Sharing is enabled if the argument is true
+** and disabled if the argument is false.)^
+**
+** This interface is omitted if SQLite is compiled with
+** [-DSQLITE_OMIT_SHARED_CACHE].  The [-DSQLITE_OMIT_SHARED_CACHE]
+** compile-time option is recommended because the
+** [use of shared cache mode is discouraged].
+**
+** ^Cache sharing is enabled and disabled for an entire process.
+** This is a change as of SQLite [version 3.5.0] ([dateof:3.5.0]).
+** In prior versions of SQLite,
+** sharing was enabled or disabled for each thread separately.
+**
+** ^(The cache sharing mode set by this interface effects all subsequent
+** calls to [sqlite3_open()], [sqlite3_open_v2()], and [sqlite3_open16()].
+** Existing database connections continue to use the sharing mode
+** that was in effect at the time they were opened.)^
+**
+** ^(This routine returns [SQLITE_OK] if shared cache was enabled or disabled
+** successfully.  An [error code] is returned otherwise.)^
+**
+** ^Shared cache is disabled by default. It is recommended that it stay
+** that way.  In other words, do not use this routine.  This interface
+** continues to be provided for historical compatibility, but its use is
+** discouraged.  Any use of shared cache is discouraged.  If shared cache
+** must be used, it is recommended that shared cache only be enabled for
+** individual database connections using the [sqlite3_open_v2()] interface
+** with the [SQLITE_OPEN_SHAREDCACHE] flag.
+**
+** Note: This method is disabled on MacOS X 10.7 and iOS version 5.0
+** and will always return SQLITE_MISUSE. On those systems,
+** shared cache mode should be enabled per-database connection via
+** [sqlite3_open_v2()] with [SQLITE_OPEN_SHAREDCACHE].
+**
+** This interface is threadsafe on processors where writing a
+** 32-bit integer is atomic.
+**
+** See Also:  [SQLite Shared-Cache Mode]
+*/
+int sqlite3_enable_shared_cache(int);
+
+/*
+** CAPI3REF: Attempt To Free Heap Memory
+**
+** ^The sqlite3_release_memory() interface attempts to free N bytes
+** of heap memory by deallocating non-essential memory allocations
+** held by the database library.   Memory used to cache database
+** pages to improve performance is an example of non-essential memory.
+** ^sqlite3_release_memory() returns the number of bytes actually freed,
+** which might be more or less than the amount requested.
+** ^The sqlite3_release_memory() routine is a no-op returning zero
+** if SQLite is not compiled with [SQLITE_ENABLE_MEMORY_MANAGEMENT].
+**
+** See also: [sqlite3_db_release_memory()]
+*/
+int sqlite3_release_memory(int);
+
+/*
+** CAPI3REF: Free Memory Used By A Database Connection
+** METHOD: sqlite3
+**
+** ^The sqlite3_db_release_memory(D) interface attempts to free as much heap
+** memory as possible from database connection D. Unlike the
+** [sqlite3_release_memory()] interface, this interface is in effect even
+** when the [SQLITE_ENABLE_MEMORY_MANAGEMENT] compile-time option is
+** omitted.
+**
+** See also: [sqlite3_release_memory()]
+*/
+int sqlite3_db_release_memory(sqlite3*);
+
+/*
+** CAPI3REF: Impose A Limit On Heap Size
+**
+** These interfaces impose limits on the amount of heap memory that will be
+** by all database connections within a single process.
+**
+** ^The sqlite3_soft_heap_limit64() interface sets and/or queries the
+** soft limit on the amount of heap memory that may be allocated by SQLite.
+** ^SQLite strives to keep heap memory utilization below the soft heap
+** limit by reducing the number of pages held in the page cache
+** as heap memory usages approaches the limit.
+** ^The soft heap limit is "soft" because even though SQLite strives to stay
+** below the limit, it will exceed the limit rather than generate
+** an [SQLITE_NOMEM] error.  In other words, the soft heap limit
+** is advisory only.
+**
+** ^The sqlite3_hard_heap_limit64(N) interface sets a hard upper bound of
+** N bytes on the amount of memory that will be allocated.  ^The
+** sqlite3_hard_heap_limit64(N) interface is similar to
+** sqlite3_soft_heap_limit64(N) except that memory allocations will fail
+** when the hard heap limit is reached.
+**
+** ^The return value from both sqlite3_soft_heap_limit64() and
+** sqlite3_hard_heap_limit64() is the size of
+** the heap limit prior to the call, or negative in the case of an
+** error.  ^If the argument N is negative
+** then no change is made to the heap limit.  Hence, the current
+** size of heap limits can be determined by invoking
+** sqlite3_soft_heap_limit64(-1) or sqlite3_hard_heap_limit(-1).
+**
+** ^Setting the heap limits to zero disables the heap limiter mechanism.
+**
+** ^The soft heap limit may not be greater than the hard heap limit.
+** ^If the hard heap limit is enabled and if sqlite3_soft_heap_limit(N)
+** is invoked with a value of N that is greater than the hard heap limit,
+** the soft heap limit is set to the value of the hard heap limit.
+** ^The soft heap limit is automatically enabled whenever the hard heap
+** limit is enabled. ^When sqlite3_hard_heap_limit64(N) is invoked and
+** the soft heap limit is outside the range of 1..N, then the soft heap
+** limit is set to N.  ^Invoking sqlite3_soft_heap_limit64(0) when the
+** hard heap limit is enabled makes the soft heap limit equal to the
+** hard heap limit.
+**
+** The memory allocation limits can also be adjusted using
+** [PRAGMA soft_heap_limit] and [PRAGMA hard_heap_limit].
+**
+** ^(The heap limits are not enforced in the current implementation
+** if one or more of following conditions are true:
+**
+** <ul>
+** <li> The limit value is set to zero.
+** <li> Memory accounting is disabled using a combination of the
+**      [sqlite3_config]([SQLITE_CONFIG_MEMSTATUS],...) start-time option and
+**      the [SQLITE_DEFAULT_MEMSTATUS] compile-time option.
+** <li> An alternative page cache implementation is specified using
+**      [sqlite3_config]([SQLITE_CONFIG_PCACHE2],...).
+** <li> The page cache allocates from its own memory pool supplied
+**      by [sqlite3_config]([SQLITE_CONFIG_PAGECACHE],...) rather than
+**      from the heap.
+** </ul>)^
+**
+** The circumstances under which SQLite will enforce the heap limits may
+** changes in future releases of SQLite.
+*/
+sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 N);
+sqlite3_int64 sqlite3_hard_heap_limit64(sqlite3_int64 N);
+
+/*
+** CAPI3REF: Deprecated Soft Heap Limit Interface
+** DEPRECATED
+**
+** This is a deprecated version of the [sqlite3_soft_heap_limit64()]
+** interface.  This routine is provided for historical compatibility
+** only.  All new applications should use the
+** [sqlite3_soft_heap_limit64()] interface rather than this one.
+*/
+SQLITE_DEPRECATED void sqlite3_soft_heap_limit(int N);
+
+
+/*
+** CAPI3REF: Extract Metadata About A Column Of A Table
+** METHOD: sqlite3
+**
+** ^(The sqlite3_table_column_metadata(X,D,T,C,....) routine returns
+** information about column C of table T in database D
+** on [database connection] X.)^  ^The sqlite3_table_column_metadata()
+** interface returns SQLITE_OK and fills in the non-NULL pointers in
+** the final five arguments with appropriate values if the specified
+** column exists.  ^The sqlite3_table_column_metadata() interface returns
+** SQLITE_ERROR if the specified column does not exist.
+** ^If the column-name parameter to sqlite3_table_column_metadata() is a
+** NULL pointer, then this routine simply checks for the existence of the
+** table and returns SQLITE_OK if the table exists and SQLITE_ERROR if it
+** does not.  If the table name parameter T in a call to
+** sqlite3_table_column_metadata(X,D,T,C,...) is NULL then the result is
+** undefined behavior.
+**
+** ^The column is identified by the second, third and fourth parameters to
+** this function. ^(The second parameter is either the name of the database
+** (i.e. "main", "temp", or an attached database) containing the specified
+** table or NULL.)^ ^If it is NULL, then all attached databases are searched
+** for the table using the same algorithm used by the database engine to
+** resolve unqualified table references.
+**
+** ^The third and fourth parameters to this function are the table and column
+** name of the desired column, respectively.
+**
+** ^Metadata is returned by writing to the memory locations passed as the 5th
+** and subsequent parameters to this function. ^Any of these arguments may be
+** NULL, in which case the corresponding element of metadata is omitted.
+**
+** ^(<blockquote>
+** <table border="1">
+** <tr><th> Parameter <th> Output<br>Type <th>  Description
+**
+** <tr><td> 5th <td> const char* <td> Data type
+** <tr><td> 6th <td> const char* <td> Name of default collation sequence
+** <tr><td> 7th <td> int         <td> True if column has a NOT NULL constraint
+** <tr><td> 8th <td> int         <td> True if column is part of the PRIMARY KEY
+** <tr><td> 9th <td> int         <td> True if column is [AUTOINCREMENT]
+** </table>
+** </blockquote>)^
+**
+** ^The memory pointed to by the character pointers returned for the
+** declaration type and collation sequence is valid until the next
+** call to any SQLite API function.
+**
+** ^If the specified table is actually a view, an [error code] is returned.
+**
+** ^If the specified column is "rowid", "oid" or "_rowid_" and the table
+** is not a [WITHOUT ROWID] table and an
+** [INTEGER PRIMARY KEY] column has been explicitly declared, then the output
+** parameters are set for the explicitly declared column. ^(If there is no
+** [INTEGER PRIMARY KEY] column, then the outputs
+** for the [rowid] are set as follows:
+**
+** <pre>
+**     data type: "INTEGER"
+**     collation sequence: "BINARY"
+**     not null: 0
+**     primary key: 1
+**     auto increment: 0
+** </pre>)^
+**
+** ^This function causes all database schemas to be read from disk and
+** parsed, if that has not already been done, and returns an error if
+** any errors are encountered while loading the schema.
+*/
+int sqlite3_table_column_metadata(
+  sqlite3 *db,                /* Connection handle */
+  const char *zDbName,        /* Database name or NULL */
+  const char *zTableName,     /* Table name */
+  const char *zColumnName,    /* Column name */
+  char const **pzDataType,    /* OUTPUT: Declared data type */
+  char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
+  int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
+  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
+  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
+);
+
+/*
+** CAPI3REF: Load An Extension
+** METHOD: sqlite3
+**
+** ^This interface loads an SQLite extension library from the named file.
+**
+** ^The sqlite3_load_extension() interface attempts to load an
+** [SQLite extension] library contained in the file zFile.  If
+** the file cannot be loaded directly, attempts are made to load
+** with various operating-system specific extensions added.
+** So for example, if "samplelib" cannot be loaded, then names like
+** "samplelib.so" or "samplelib.dylib" or "samplelib.dll" might
+** be tried also.
+**
+** ^The entry point is zProc.
+** ^(zProc may be 0, in which case SQLite will try to come up with an
+** entry point name on its own.  It first tries "sqlite3_extension_init".
+** If that does not work, it constructs a name "sqlite3_X_init" where the
+** X is consists of the lower-case equivalent of all ASCII alphabetic
+** characters in the filename from the last "/" to the first following
+** "." and omitting any initial "lib".)^
+** ^The sqlite3_load_extension() interface returns
+** [SQLITE_OK] on success and [SQLITE_ERROR] if something goes wrong.
+** ^If an error occurs and pzErrMsg is not 0, then the
+** [sqlite3_load_extension()] interface shall attempt to
+** fill *pzErrMsg with error message text stored in memory
+** obtained from [sqlite3_malloc()]. The calling function
+** should free this memory by calling [sqlite3_free()].
+**
+** ^Extension loading must be enabled using
+** [sqlite3_enable_load_extension()] or
+** [sqlite3_db_config](db,[SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION],1,NULL)
+** prior to calling this API,
+** otherwise an error will be returned.
+**
+** <b>Security warning:</b> It is recommended that the
+** [SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION] method be used to enable only this
+** interface.  The use of the [sqlite3_enable_load_extension()] interface
+** should be avoided.  This will keep the SQL function [load_extension()]
+** disabled and prevent SQL injections from giving attackers
+** access to extension loading capabilities.
+**
+** See also the [load_extension() SQL function].
+*/
+int sqlite3_load_extension(
+  sqlite3 *db,          /* Load the extension into this database connection */
+  const char *zFile,    /* Name of the shared library containing extension */
+  const char *zProc,    /* Entry point.  Derived from zFile if 0 */
+  char **pzErrMsg       /* Put error message here if not 0 */
+);
+
+/*
+** CAPI3REF: Enable Or Disable Extension Loading
+** METHOD: sqlite3
+**
+** ^So as not to open security holes in older applications that are
+** unprepared to deal with [extension loading], and as a means of disabling
+** [extension loading] while evaluating user-entered SQL, the following API
+** is provided to turn the [sqlite3_load_extension()] mechanism on and off.
+**
+** ^Extension loading is off by default.
+** ^Call the sqlite3_enable_load_extension() routine with onoff==1
+** to turn extension loading on and call it with onoff==0 to turn
+** it back off again.
+**
+** ^This interface enables or disables both the C-API
+** [sqlite3_load_extension()] and the SQL function [load_extension()].
+** ^(Use [sqlite3_db_config](db,[SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION],..)
+** to enable or disable only the C-API.)^
+**
+** <b>Security warning:</b> It is recommended that extension loading
+** be enabled using the [SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION] method
+** rather than this interface, so the [load_extension()] SQL function
+** remains disabled. This will prevent SQL injections from giving attackers
+** access to extension loading capabilities.
+*/
+int sqlite3_enable_load_extension(sqlite3 *db, int onoff);
+
+/*
+** CAPI3REF: Automatically Load Statically Linked Extensions
+**
+** ^This interface causes the xEntryPoint() function to be invoked for
+** each new [database connection] that is created.  The idea here is that
+** xEntryPoint() is the entry point for a statically linked [SQLite extension]
+** that is to be automatically loaded into all new database connections.
+**
+** ^(Even though the function prototype shows that xEntryPoint() takes
+** no arguments and returns void, SQLite invokes xEntryPoint() with three
+** arguments and expects an integer result as if the signature of the
+** entry point where as follows:
+**
+** <blockquote><pre>
+** &nbsp;  int xEntryPoint(
+** &nbsp;    sqlite3 *db,
+** &nbsp;    const char **pzErrMsg,
+** &nbsp;    const struct sqlite3_api_routines *pThunk
+** &nbsp;  );
+** </pre></blockquote>)^
+**
+** If the xEntryPoint routine encounters an error, it should make *pzErrMsg
+** point to an appropriate error message (obtained from [sqlite3_mprintf()])
+** and return an appropriate [error code].  ^SQLite ensures that *pzErrMsg
+** is NULL before calling the xEntryPoint().  ^SQLite will invoke
+** [sqlite3_free()] on *pzErrMsg after xEntryPoint() returns.  ^If any
+** xEntryPoint() returns an error, the [sqlite3_open()], [sqlite3_open16()],
+** or [sqlite3_open_v2()] call that provoked the xEntryPoint() will fail.
+**
+** ^Calling sqlite3_auto_extension(X) with an entry point X that is already
+** on the list of automatic extensions is a harmless no-op. ^No entry point
+** will be called more than once for each database connection that is opened.
+**
+** See also: [sqlite3_reset_auto_extension()]
+** and [sqlite3_cancel_auto_extension()]
+*/
+int sqlite3_auto_extension(void(*xEntryPoint)(void));
+
+/*
+** CAPI3REF: Cancel Automatic Extension Loading
+**
+** ^The [sqlite3_cancel_auto_extension(X)] interface unregisters the
+** initialization routine X that was registered using a prior call to
+** [sqlite3_auto_extension(X)].  ^The [sqlite3_cancel_auto_extension(X)]
+** routine returns 1 if initialization routine X was successfully
+** unregistered and it returns 0 if X was not on the list of initialization
+** routines.
+*/
+int sqlite3_cancel_auto_extension(void(*xEntryPoint)(void));
+
+/*
+** CAPI3REF: Reset Automatic Extension Loading
+**
+** ^This interface disables all automatic extensions previously
+** registered using [sqlite3_auto_extension()].
+*/
+void sqlite3_reset_auto_extension(void);
+
+/*
+** Structures used by the virtual table interface
+*/
+typedef struct sqlite3_vtab sqlite3_vtab;
+typedef struct sqlite3_index_info sqlite3_index_info;
+typedef struct sqlite3_vtab_cursor sqlite3_vtab_cursor;
+typedef struct sqlite3_module sqlite3_module;
+
+/*
+** CAPI3REF: Virtual Table Object
+** KEYWORDS: sqlite3_module {virtual table module}
+**
+** This structure, sometimes called a "virtual table module",
+** defines the implementation of a [virtual table]. 
+** This structure consists mostly of methods for the module.
+**
+** ^A virtual table module is created by filling in a persistent
+** instance of this structure and passing a pointer to that instance
+** to [sqlite3_create_module()] or [sqlite3_create_module_v2()].
+** ^The registration remains valid until it is replaced by a different
+** module or until the [database connection] closes.  The content
+** of this structure must not change while it is registered with
+** any database connection.
+*/
+struct sqlite3_module {
+  int iVersion;
+  int (*xCreate)(sqlite3*, void *pAux,
+               int argc, const char *const*argv,
+               sqlite3_vtab **ppVTab, char**);
+  int (*xConnect)(sqlite3*, void *pAux,
+               int argc, const char *const*argv,
+               sqlite3_vtab **ppVTab, char**);
+  int (*xBestIndex)(sqlite3_vtab *pVTab, sqlite3_index_info*);
+  int (*xDisconnect)(sqlite3_vtab *pVTab);
+  int (*xDestroy)(sqlite3_vtab *pVTab);
+  int (*xOpen)(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor);
+  int (*xClose)(sqlite3_vtab_cursor*);
+  int (*xFilter)(sqlite3_vtab_cursor*, int idxNum, const char *idxStr,
+                int argc, sqlite3_value **argv);
+  int (*xNext)(sqlite3_vtab_cursor*);
+  int (*xEof)(sqlite3_vtab_cursor*);
+  int (*xColumn)(sqlite3_vtab_cursor*, sqlite3_context*, int);
+  int (*xRowid)(sqlite3_vtab_cursor*, sqlite3_int64 *pRowid);
+  int (*xUpdate)(sqlite3_vtab *, int, sqlite3_value **, sqlite3_int64 *);
+  int (*xBegin)(sqlite3_vtab *pVTab);
+  int (*xSync)(sqlite3_vtab *pVTab);
+  int (*xCommit)(sqlite3_vtab *pVTab);
+  int (*xRollback)(sqlite3_vtab *pVTab);
+  int (*xFindFunction)(sqlite3_vtab *pVtab, int nArg, const char *zName,
+                       void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
+                       void **ppArg);
+  int (*xRename)(sqlite3_vtab *pVtab, const char *zNew);
+  /* The methods above are in version 1 of the sqlite_module object. Those
+  ** below are for version 2 and greater. */
+  int (*xSavepoint)(sqlite3_vtab *pVTab, int);
+  int (*xRelease)(sqlite3_vtab *pVTab, int);
+  int (*xRollbackTo)(sqlite3_vtab *pVTab, int);
+  /* The methods above are in versions 1 and 2 of the sqlite_module object.
+  ** Those below are for version 3 and greater. */
+  int (*xShadowName)(const char*);
+  /* The methods above are in versions 1 through 3 of the sqlite_module object.
+  ** Those below are for version 4 and greater. */
+  int (*xIntegrity)(sqlite3_vtab *pVTab, const char *zSchema,
+                    const char *zTabName, int mFlags, char **pzErr);
+};
+
+/*
+** CAPI3REF: Virtual Table Indexing Information
+** KEYWORDS: sqlite3_index_info
+**
+** The sqlite3_index_info structure and its substructures is used as part
+** of the [virtual table] interface to
+** pass information into and receive the reply from the [xBestIndex]
+** method of a [virtual table module].  The fields under **Inputs** are the
+** inputs to xBestIndex and are read-only.  xBestIndex inserts its
+** results into the **Outputs** fields.
+**
+** ^(The aConstraint[] array records WHERE clause constraints of the form:
+**
+** <blockquote>column OP expr</blockquote>
+**
+** where OP is =, &lt;, &lt;=, &gt;, or &gt;=.)^  ^(The particular operator is
+** stored in aConstraint[].op using one of the
+** [SQLITE_INDEX_CONSTRAINT_EQ | SQLITE_INDEX_CONSTRAINT_ values].)^
+** ^(The index of the column is stored in
+** aConstraint[].iColumn.)^  ^(aConstraint[].usable is TRUE if the
+** expr on the right-hand side can be evaluated (and thus the constraint
+** is usable) and false if it cannot.)^
+**
+** ^The optimizer automatically inverts terms of the form "expr OP column"
+** and makes other simplifications to the WHERE clause in an attempt to
+** get as many WHERE clause terms into the form shown above as possible.
+** ^The aConstraint[] array only reports WHERE clause terms that are
+** relevant to the particular virtual table being queried.
+**
+** ^Information about the ORDER BY clause is stored in aOrderBy[].
+** ^Each term of aOrderBy records a column of the ORDER BY clause.
+**
+** The colUsed field indicates which columns of the virtual table may be
+** required by the current scan. Virtual table columns are numbered from
+** zero in the order in which they appear within the CREATE TABLE statement
+** passed to sqlite3_declare_vtab(). For the first 63 columns (columns 0-62),
+** the corresponding bit is set within the colUsed mask if the column may be
+** required by SQLite. If the table has at least 64 columns and any column
+** to the right of the first 63 is required, then bit 63 of colUsed is also
+** set. In other words, column iCol may be required if the expression
+** (colUsed & ((sqlite3_uint64)1 << (iCol>=63 ? 63 : iCol))) evaluates to
+** non-zero.
+**
+** The [xBestIndex] method must fill aConstraintUsage[] with information
+** about what parameters to pass to xFilter.  ^If argvIndex>0 then
+** the right-hand side of the corresponding aConstraint[] is evaluated
+** and becomes the argvIndex-th entry in argv.  ^(If aConstraintUsage[].omit
+** is true, then the constraint is assumed to be fully handled by the
+** virtual table and might not be checked again by the byte code.)^ ^(The
+** aConstraintUsage[].omit flag is an optimization hint. When the omit flag
+** is left in its default setting of false, the constraint will always be
+** checked separately in byte code.  If the omit flag is change to true, then
+** the constraint may or may not be checked in byte code.  In other words,
+** when the omit flag is true there is no guarantee that the constraint will
+** not be checked again using byte code.)^
+**
+** ^The idxNum and idxStr values are recorded and passed into the
+** [xFilter] method.
+** ^[sqlite3_free()] is used to free idxStr if and only if
+** needToFreeIdxStr is true.
+**
+** ^The orderByConsumed means that output from [xFilter]/[xNext] will occur in
+** the correct order to satisfy the ORDER BY clause so that no separate
+** sorting step is required.
+**
+** ^The estimatedCost value is an estimate of the cost of a particular
+** strategy. A cost of N indicates that the cost of the strategy is similar
+** to a linear scan of an SQLite table with N rows. A cost of log(N)
+** indicates that the expense of the operation is similar to that of a
+** binary search on a unique indexed field of an SQLite table with N rows.
+**
+** ^The estimatedRows value is an estimate of the number of rows that
+** will be returned by the strategy.
+**
+** The xBestIndex method may optionally populate the idxFlags field with a
+** mask of SQLITE_INDEX_SCAN_* flags. Currently there is only one such flag -
+** SQLITE_INDEX_SCAN_UNIQUE. If the xBestIndex method sets this flag, SQLite
+** assumes that the strategy may visit at most one row.
+**
+** Additionally, if xBestIndex sets the SQLITE_INDEX_SCAN_UNIQUE flag, then
+** SQLite also assumes that if a call to the xUpdate() method is made as
+** part of the same statement to delete or update a virtual table row and the
+** implementation returns SQLITE_CONSTRAINT, then there is no need to rollback
+** any database changes. In other words, if the xUpdate() returns
+** SQLITE_CONSTRAINT, the database contents must be exactly as they were
+** before xUpdate was called. By contrast, if SQLITE_INDEX_SCAN_UNIQUE is not
+** set and xUpdate returns SQLITE_CONSTRAINT, any database changes made by
+** the xUpdate method are automatically rolled back by SQLite.
+**
+** IMPORTANT: The estimatedRows field was added to the sqlite3_index_info
+** structure for SQLite [version 3.8.2] ([dateof:3.8.2]).
+** If a virtual table extension is
+** used with an SQLite version earlier than 3.8.2, the results of attempting
+** to read or write the estimatedRows field are undefined (but are likely
+** to include crashing the application). The estimatedRows field should
+** therefore only be used if [sqlite3_libversion_number()] returns a
+** value greater than or equal to 3008002. Similarly, the idxFlags field
+** was added for [version 3.9.0] ([dateof:3.9.0]).
+** It may therefore only be used if
+** sqlite3_libversion_number() returns a value greater than or equal to
+** 3009000.
+*/
+struct sqlite3_index_info {
+  /* Inputs */
+  int nConstraint;           /* Number of entries in aConstraint */
+  struct sqlite3_index_constraint {
+     int iColumn;              /* Column constrained.  -1 for ROWID */
+     unsigned char op;         /* Constraint operator */
+     unsigned char usable;     /* True if this constraint is usable */
+     int iTermOffset;          /* Used internally - xBestIndex should ignore */
+  } *aConstraint;            /* Table of WHERE clause constraints */
+  int nOrderBy;              /* Number of terms in the ORDER BY clause */
+  struct sqlite3_index_orderby {
+     int iColumn;              /* Column number */
+     unsigned char desc;       /* True for DESC.  False for ASC. */
+  } *aOrderBy;               /* The ORDER BY clause */
+  /* Outputs */
+  struct sqlite3_index_constraint_usage {
+    int argvIndex;           /* if >0, constraint is part of argv to xFilter */
+    unsigned char omit;      /* Do not code a test for this constraint */
+  } *aConstraintUsage;
+  int idxNum;                /* Number used to identify the index */
+  char *idxStr;              /* String, possibly obtained from sqlite3_malloc */
+  int needToFreeIdxStr;      /* Free idxStr using sqlite3_free() if true */
+  int orderByConsumed;       /* True if output is already ordered */
+  double estimatedCost;           /* Estimated cost of using this index */
+  /* Fields below are only available in SQLite 3.8.2 and later */
+  sqlite3_int64 estimatedRows;    /* Estimated number of rows returned */
+  /* Fields below are only available in SQLite 3.9.0 and later */
+  int idxFlags;              /* Mask of SQLITE_INDEX_SCAN_* flags */
+  /* Fields below are only available in SQLite 3.10.0 and later */
+  sqlite3_uint64 colUsed;    /* Input: Mask of columns used by statement */
+};
+
+/*
+** CAPI3REF: Virtual Table Scan Flags
+**
+** Virtual table implementations are allowed to set the
+** [sqlite3_index_info].idxFlags field to some combination of
+** these bits.
+*/
+#define SQLITE_INDEX_SCAN_UNIQUE      1     /* Scan visits at most 1 row */
+
+/*
+** CAPI3REF: Virtual Table Constraint Operator Codes
+**
+** These macros define the allowed values for the
+** [sqlite3_index_info].aConstraint[].op field.  Each value represents
+** an operator that is part of a constraint term in the WHERE clause of
+** a query that uses a [virtual table].
+**
+** ^The left-hand operand of the operator is given by the corresponding
+** aConstraint[].iColumn field.  ^An iColumn of -1 indicates the left-hand
+** operand is the rowid.
+** The SQLITE_INDEX_CONSTRAINT_LIMIT and SQLITE_INDEX_CONSTRAINT_OFFSET
+** operators have no left-hand operand, and so for those operators the
+** corresponding aConstraint[].iColumn is meaningless and should not be
+** used.
+**
+** All operator values from SQLITE_INDEX_CONSTRAINT_FUNCTION through
+** value 255 are reserved to represent functions that are overloaded
+** by the [xFindFunction|xFindFunction method] of the virtual table
+** implementation.
+**
+** The right-hand operands for each constraint might be accessible using
+** the [sqlite3_vtab_rhs_value()] interface.  Usually the right-hand
+** operand is only available if it appears as a single constant literal
+** in the input SQL.  If the right-hand operand is another column or an
+** expression (even a constant expression) or a parameter, then the
+** sqlite3_vtab_rhs_value() probably will not be able to extract it.
+** ^The SQLITE_INDEX_CONSTRAINT_ISNULL and
+** SQLITE_INDEX_CONSTRAINT_ISNOTNULL operators have no right-hand operand
+** and hence calls to sqlite3_vtab_rhs_value() for those operators will
+** always return SQLITE_NOTFOUND.
+**
+** The collating sequence to be used for comparison can be found using
+** the [sqlite3_vtab_collation()] interface.  For most real-world virtual
+** tables, the collating sequence of constraints does not matter (for example
+** because the constraints are numeric) and so the sqlite3_vtab_collation()
+** interface is not commonly needed.
+*/
+#define SQLITE_INDEX_CONSTRAINT_EQ          2
+#define SQLITE_INDEX_CONSTRAINT_GT          4
+#define SQLITE_INDEX_CONSTRAINT_LE          8
+#define SQLITE_INDEX_CONSTRAINT_LT         16
+#define SQLITE_INDEX_CONSTRAINT_GE         32
+#define SQLITE_INDEX_CONSTRAINT_MATCH      64
+#define SQLITE_INDEX_CONSTRAINT_LIKE       65
+#define SQLITE_INDEX_CONSTRAINT_GLOB       66
+#define SQLITE_INDEX_CONSTRAINT_REGEXP     67
+#define SQLITE_INDEX_CONSTRAINT_NE         68
+#define SQLITE_INDEX_CONSTRAINT_ISNOT      69
+#define SQLITE_INDEX_CONSTRAINT_ISNOTNULL  70
+#define SQLITE_INDEX_CONSTRAINT_ISNULL     71
+#define SQLITE_INDEX_CONSTRAINT_IS         72
+#define SQLITE_INDEX_CONSTRAINT_LIMIT      73
+#define SQLITE_INDEX_CONSTRAINT_OFFSET     74
+#define SQLITE_INDEX_CONSTRAINT_FUNCTION  150
+
+/*
+** CAPI3REF: Register A Virtual Table Implementation
+** METHOD: sqlite3
+**
+** ^These routines are used to register a new [virtual table module] name.
+** ^Module names must be registered before
+** creating a new [virtual table] using the module and before using a
+** preexisting [virtual table] for the module.
+**
+** ^The module name is registered on the [database connection] specified
+** by the first parameter.  ^The name of the module is given by the
+** second parameter.  ^The third parameter is a pointer to
+** the implementation of the [virtual table module].   ^The fourth
+** parameter is an arbitrary client data pointer that is passed through
+** into the [xCreate] and [xConnect] methods of the virtual table module
+** when a new virtual table is be being created or reinitialized.
+**
+** ^The sqlite3_create_module_v2() interface has a fifth parameter which
+** is a pointer to a destructor for the pClientData.  ^SQLite will
+** invoke the destructor function (if it is not NULL) when SQLite
+** no longer needs the pClientData pointer.  ^The destructor will also
+** be invoked if the call to sqlite3_create_module_v2() fails.
+** ^The sqlite3_create_module()
+** interface is equivalent to sqlite3_create_module_v2() with a NULL
+** destructor.
+**
+** ^If the third parameter (the pointer to the sqlite3_module object) is
+** NULL then no new module is created and any existing modules with the
+** same name are dropped.
+**
+** See also: [sqlite3_drop_modules()]
+*/
+int sqlite3_create_module(
+  sqlite3 *db,               /* SQLite connection to register module with */
+  const char *zName,         /* Name of the module */
+  const sqlite3_module *p,   /* Methods for the module */
+  void *pClientData          /* Client data for xCreate/xConnect */
+);
+int sqlite3_create_module_v2(
+  sqlite3 *db,               /* SQLite connection to register module with */
+  const char *zName,         /* Name of the module */
+  const sqlite3_module *p,   /* Methods for the module */
+  void *pClientData,         /* Client data for xCreate/xConnect */
+  void(*xDestroy)(void*)     /* Module destructor function */
+);
+
+/*
+** CAPI3REF: Remove Unnecessary Virtual Table Implementations
+** METHOD: sqlite3
+**
+** ^The sqlite3_drop_modules(D,L) interface removes all virtual
+** table modules from database connection D except those named on list L.
+** The L parameter must be either NULL or a pointer to an array of pointers
+** to strings where the array is terminated by a single NULL pointer.
+** ^If the L parameter is NULL, then all virtual table modules are removed.
+**
+** See also: [sqlite3_create_module()]
+*/
+int sqlite3_drop_modules(
+  sqlite3 *db,                /* Remove modules from this connection */
+  const char **azKeep         /* Except, do not remove the ones named here */
+);
+
+/*
+** CAPI3REF: Virtual Table Instance Object
+** KEYWORDS: sqlite3_vtab
+**
+** Every [virtual table module] implementation uses a subclass
+** of this object to describe a particular instance
+** of the [virtual table].  Each subclass will
+** be tailored to the specific needs of the module implementation.
+** The purpose of this superclass is to define certain fields that are
+** common to all module implementations.
+**
+** ^Virtual tables methods can set an error message by assigning a
+** string obtained from [sqlite3_mprintf()] to zErrMsg.  The method should
+** take care that any prior string is freed by a call to [sqlite3_free()]
+** prior to assigning a new string to zErrMsg.  ^After the error message
+** is delivered up to the client application, the string will be automatically
+** freed by sqlite3_free() and the zErrMsg field will be zeroed.
+*/
+struct sqlite3_vtab {
+  const sqlite3_module *pModule;  /* The module for this virtual table */
+  int nRef;                       /* Number of open cursors */
+  char *zErrMsg;                  /* Error message from sqlite3_mprintf() */
+  /* Virtual table implementations will typically add additional fields */
+};
+
+/*
+** CAPI3REF: Virtual Table Cursor Object
+** KEYWORDS: sqlite3_vtab_cursor {virtual table cursor}
+**
+** Every [virtual table module] implementation uses a subclass of the
+** following structure to describe cursors that point into the
+** [virtual table] and are used
+** to loop through the virtual table.  Cursors are created using the
+** [sqlite3_module.xOpen | xOpen] method of the module and are destroyed
+** by the [sqlite3_module.xClose | xClose] method.  Cursors are used
+** by the [xFilter], [xNext], [xEof], [xColumn], and [xRowid] methods
+** of the module.  Each module implementation will define
+** the content of a cursor structure to suit its own needs.
+**
+** This superclass exists in order to define fields of the cursor that
+** are common to all implementations.
+*/
+struct sqlite3_vtab_cursor {
+  sqlite3_vtab *pVtab;      /* Virtual table of this cursor */
+  /* Virtual table implementations will typically add additional fields */
+};
+
+/*
+** CAPI3REF: Declare The Schema Of A Virtual Table
+**
+** ^The [xCreate] and [xConnect] methods of a
+** [virtual table module] call this interface
+** to declare the format (the names and datatypes of the columns) of
+** the virtual tables they implement.
+*/
+int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
+
+/*
+** CAPI3REF: Overload A Function For A Virtual Table
+** METHOD: sqlite3
+**
+** ^(Virtual tables can provide alternative implementations of functions
+** using the [xFindFunction] method of the [virtual table module]. 
+** But global versions of those functions
+** must exist in order to be overloaded.)^
+**
+** ^(This API makes sure a global version of a function with a particular
+** name and number of parameters exists.  If no such function exists
+** before this API is called, a new function is created.)^  ^The implementation
+** of the new function always causes an exception to be thrown.  So
+** the new function is not good for anything by itself.  Its only
+** purpose is to be a placeholder function that can be overloaded
+** by a [virtual table].
+*/
+int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
+
+/*
+** CAPI3REF: A Handle To An Open BLOB
+** KEYWORDS: {BLOB handle} {BLOB handles}
+**
+** An instance of this object represents an open BLOB on which
+** [sqlite3_blob_open | incremental BLOB I/O] can be performed.
+** ^Objects of this type are created by [sqlite3_blob_open()]
+** and destroyed by [sqlite3_blob_close()].
+** ^The [sqlite3_blob_read()] and [sqlite3_blob_write()] interfaces
+** can be used to read or write small subsections of the BLOB.
+** ^The [sqlite3_blob_bytes()] interface returns the size of the BLOB in bytes.
+*/
+typedef struct sqlite3_blob sqlite3_blob;
+
+/*
+** CAPI3REF: Open A BLOB For Incremental I/O
+** METHOD: sqlite3
+** CONSTRUCTOR: sqlite3_blob
+**
+** ^(This interfaces opens a [BLOB handle | handle] to the BLOB located
+** in row iRow, column zColumn, table zTable in database zDb;
+** in other words, the same BLOB that would be selected by:
+**
+** <pre>
+**     SELECT zColumn FROM zDb.zTable WHERE [rowid] = iRow;
+** </pre>)^
+**
+** ^(Parameter zDb is not the filename that contains the database, but
+** rather the symbolic name of the database. For attached databases, this is
+** the name that appears after the AS keyword in the [ATTACH] statement.
+** For the main database file, the database name is "main". For TEMP
+** tables, the database name is "temp".)^
+**
+** ^If the flags parameter is non-zero, then the BLOB is opened for read
+** and write access. ^If the flags parameter is zero, the BLOB is opened for
+** read-only access.
+**
+** ^(On success, [SQLITE_OK] is returned and the new [BLOB handle] is stored
+** in *ppBlob. Otherwise an [error code] is returned and, unless the error
+** code is SQLITE_MISUSE, *ppBlob is set to NULL.)^ ^This means that, provided
+** the API is not misused, it is always safe to call [sqlite3_blob_close()]
+** on *ppBlob after this function it returns.
+**
+** This function fails with SQLITE_ERROR if any of the following are true:
+** <ul>
+**   <li> ^(Database zDb does not exist)^,
+**   <li> ^(Table zTable does not exist within database zDb)^,
+**   <li> ^(Table zTable is a WITHOUT ROWID table)^,
+**   <li> ^(Column zColumn does not exist)^,
+**   <li> ^(Row iRow is not present in the table)^,
+**   <li> ^(The specified column of row iRow contains a value that is not
+**         a TEXT or BLOB value)^,
+**   <li> ^(Column zColumn is part of an index, PRIMARY KEY or UNIQUE
+**         constraint and the blob is being opened for read/write access)^,
+**   <li> ^([foreign key constraints | Foreign key constraints] are enabled,
+**         column zColumn is part of a [child key] definition and the blob is
+**         being opened for read/write access)^.
+** </ul>
+**
+** ^Unless it returns SQLITE_MISUSE, this function sets the
+** [database connection] error code and message accessible via
+** [sqlite3_errcode()] and [sqlite3_errmsg()] and related functions.
+**
+** A BLOB referenced by sqlite3_blob_open() may be read using the
+** [sqlite3_blob_read()] interface and modified by using
+** [sqlite3_blob_write()].  The [BLOB handle] can be moved to a
+** different row of the same table using the [sqlite3_blob_reopen()]
+** interface.  However, the column, table, or database of a [BLOB handle]
+** cannot be changed after the [BLOB handle] is opened.
+**
+** ^(If the row that a BLOB handle points to is modified by an
+** [UPDATE], [DELETE], or by [ON CONFLICT] side-effects
+** then the BLOB handle is marked as "expired".
+** This is true if any column of the row is changed, even a column
+** other than the one the BLOB handle is open on.)^
+** ^Calls to [sqlite3_blob_read()] and [sqlite3_blob_write()] for
+** an expired BLOB handle fail with a return code of [SQLITE_ABORT].
+** ^(Changes written into a BLOB prior to the BLOB expiring are not
+** rolled back by the expiration of the BLOB.  Such changes will eventually
+** commit if the transaction continues to completion.)^
+**
+** ^Use the [sqlite3_blob_bytes()] interface to determine the size of
+** the opened blob.  ^The size of a blob may not be changed by this
+** interface.  Use the [UPDATE] SQL command to change the size of a
+** blob.
+**
+** ^The [sqlite3_bind_zeroblob()] and [sqlite3_result_zeroblob()] interfaces
+** and the built-in [zeroblob] SQL function may be used to create a
+** zero-filled blob to read or write using the incremental-blob interface.
+**
+** To avoid a resource leak, every open [BLOB handle] should eventually
+** be released by a call to [sqlite3_blob_close()].
+**
+** See also: [sqlite3_blob_close()],
+** [sqlite3_blob_reopen()], [sqlite3_blob_read()],
+** [sqlite3_blob_bytes()], [sqlite3_blob_write()].
+*/
+int sqlite3_blob_open(
+  sqlite3*,
+  const char *zDb,
+  const char *zTable,
+  const char *zColumn,
+  sqlite3_int64 iRow,
+  int flags,
+  sqlite3_blob **ppBlob
+);
+
+/*
+** CAPI3REF: Move a BLOB Handle to a New Row
+** METHOD: sqlite3_blob
+**
+** ^This function is used to move an existing [BLOB handle] so that it points
+** to a different row of the same database table. ^The new row is identified
+** by the rowid value passed as the second argument. Only the row can be
+** changed. ^The database, table and column on which the blob handle is open
+** remain the same. Moving an existing [BLOB handle] to a new row is
+** faster than closing the existing handle and opening a new one.
+**
+** ^(The new row must meet the same criteria as for [sqlite3_blob_open()] -
+** it must exist and there must be either a blob or text value stored in
+** the nominated column.)^ ^If the new row is not present in the table, or if
+** it does not contain a blob or text value, or if another error occurs, an
+** SQLite error code is returned and the blob handle is considered aborted.
+** ^All subsequent calls to [sqlite3_blob_read()], [sqlite3_blob_write()] or
+** [sqlite3_blob_reopen()] on an aborted blob handle immediately return
+** SQLITE_ABORT. ^Calling [sqlite3_blob_bytes()] on an aborted blob handle
+** always returns zero.
+**
+** ^This function sets the database handle error code and message.
+*/
+int sqlite3_blob_reopen(sqlite3_blob *, sqlite3_int64);
+
+/*
+** CAPI3REF: Close A BLOB Handle
+** DESTRUCTOR: sqlite3_blob
+**
+** ^This function closes an open [BLOB handle]. ^(The BLOB handle is closed
+** unconditionally.  Even if this routine returns an error code, the
+** handle is still closed.)^
+**
+** ^If the blob handle being closed was opened for read-write access, and if
+** the database is in auto-commit mode and there are no other open read-write
+** blob handles or active write statements, the current transaction is
+** committed. ^If an error occurs while committing the transaction, an error
+** code is returned and the transaction rolled back.
+**
+** Calling this function with an argument that is not a NULL pointer or an
+** open blob handle results in undefined behavior. ^Calling this routine
+** with a null pointer (such as would be returned by a failed call to
+** [sqlite3_blob_open()]) is a harmless no-op. ^Otherwise, if this function
+** is passed a valid open blob handle, the values returned by the
+** sqlite3_errcode() and sqlite3_errmsg() functions are set before returning.
+*/
+int sqlite3_blob_close(sqlite3_blob *);
+
+/*
+** CAPI3REF: Return The Size Of An Open BLOB
+** METHOD: sqlite3_blob
+**
+** ^Returns the size in bytes of the BLOB accessible via the
+** successfully opened [BLOB handle] in its only argument.  ^The
+** incremental blob I/O routines can only read or overwriting existing
+** blob content; they cannot change the size of a blob.
+**
+** This routine only works on a [BLOB handle] which has been created
+** by a prior successful call to [sqlite3_blob_open()] and which has not
+** been closed by [sqlite3_blob_close()].  Passing any other pointer in
+** to this routine results in undefined and probably undesirable behavior.
+*/
+int sqlite3_blob_bytes(sqlite3_blob *);
+
+/*
+** CAPI3REF: Read Data From A BLOB Incrementally
+** METHOD: sqlite3_blob
+**
+** ^(This function is used to read data from an open [BLOB handle] into a
+** caller-supplied buffer. N bytes of data are copied into buffer Z
+** from the open BLOB, starting at offset iOffset.)^
+**
+** ^If offset iOffset is less than N bytes from the end of the BLOB,
+** [SQLITE_ERROR] is returned and no data is read.  ^If N or iOffset is
+** less than zero, [SQLITE_ERROR] is returned and no data is read.
+** ^The size of the blob (and hence the maximum value of N+iOffset)
+** can be determined using the [sqlite3_blob_bytes()] interface.
+**
+** ^An attempt to read from an expired [BLOB handle] fails with an
+** error code of [SQLITE_ABORT].
+**
+** ^(On success, sqlite3_blob_read() returns SQLITE_OK.
+** Otherwise, an [error code] or an [extended error code] is returned.)^
+**
+** This routine only works on a [BLOB handle] which has been created
+** by a prior successful call to [sqlite3_blob_open()] and which has not
+** been closed by [sqlite3_blob_close()].  Passing any other pointer in
+** to this routine results in undefined and probably undesirable behavior.
+**
+** See also: [sqlite3_blob_write()].
+*/
+int sqlite3_blob_read(sqlite3_blob *, void *Z, int N, int iOffset);
+
+/*
+** CAPI3REF: Write Data Into A BLOB Incrementally
+** METHOD: sqlite3_blob
+**
+** ^(This function is used to write data into an open [BLOB handle] from a
+** caller-supplied buffer. N bytes of data are copied from the buffer Z
+** into the open BLOB, starting at offset iOffset.)^
+**
+** ^(On success, sqlite3_blob_write() returns SQLITE_OK.
+** Otherwise, an  [error code] or an [extended error code] is returned.)^
+** ^Unless SQLITE_MISUSE is returned, this function sets the
+** [database connection] error code and message accessible via
+** [sqlite3_errcode()] and [sqlite3_errmsg()] and related functions.
+**
+** ^If the [BLOB handle] passed as the first argument was not opened for
+** writing (the flags parameter to [sqlite3_blob_open()] was zero),
+** this function returns [SQLITE_READONLY].
+**
+** This function may only modify the contents of the BLOB; it is
+** not possible to increase the size of a BLOB using this API.
+** ^If offset iOffset is less than N bytes from the end of the BLOB,
+** [SQLITE_ERROR] is returned and no data is written. The size of the
+** BLOB (and hence the maximum value of N+iOffset) can be determined
+** using the [sqlite3_blob_bytes()] interface. ^If N or iOffset are less
+** than zero [SQLITE_ERROR] is returned and no data is written.
+**
+** ^An attempt to write to an expired [BLOB handle] fails with an
+** error code of [SQLITE_ABORT].  ^Writes to the BLOB that occurred
+** before the [BLOB handle] expired are not rolled back by the
+** expiration of the handle, though of course those changes might
+** have been overwritten by the statement that expired the BLOB handle
+** or by other independent statements.
+**
+** This routine only works on a [BLOB handle] which has been created
+** by a prior successful call to [sqlite3_blob_open()] and which has not
+** been closed by [sqlite3_blob_close()].  Passing any other pointer in
+** to this routine results in undefined and probably undesirable behavior.
+**
+** See also: [sqlite3_blob_read()].
+*/
+int sqlite3_blob_write(sqlite3_blob *, const void *z, int n, int iOffset);
+
+/*
+** CAPI3REF: Virtual File System Objects
+**
+** A virtual filesystem (VFS) is an [sqlite3_vfs] object
+** that SQLite uses to interact
+** with the underlying operating system.  Most SQLite builds come with a
+** single default VFS that is appropriate for the host computer.
+** New VFSes can be registered and existing VFSes can be unregistered.
+** The following interfaces are provided.
+**
+** ^The sqlite3_vfs_find() interface returns a pointer to a VFS given its name.
+** ^Names are case sensitive.
+** ^Names are zero-terminated UTF-8 strings.
+** ^If there is no match, a NULL pointer is returned.
+** ^If zVfsName is NULL then the default VFS is returned.
+**
+** ^New VFSes are registered with sqlite3_vfs_register().
+** ^Each new VFS becomes the default VFS if the makeDflt flag is set.
+** ^The same VFS can be registered multiple times without injury.
+** ^To make an existing VFS into the default VFS, register it again
+** with the makeDflt flag set.  If two different VFSes with the
+** same name are registered, the behavior is undefined.  If a
+** VFS is registered with a name that is NULL or an empty string,
+** then the behavior is undefined.
+**
+** ^Unregister a VFS with the sqlite3_vfs_unregister() interface.
+** ^(If the default VFS is unregistered, another VFS is chosen as
+** the default.  The choice for the new VFS is arbitrary.)^
+*/
+sqlite3_vfs *sqlite3_vfs_find(const char *zVfsName);
+int sqlite3_vfs_register(sqlite3_vfs*, int makeDflt);
+int sqlite3_vfs_unregister(sqlite3_vfs*);
+
+/*
+** CAPI3REF: Mutexes
+**
+** The SQLite core uses these routines for thread
+** synchronization. Though they are intended for internal
+** use by SQLite, code that links against SQLite is
+** permitted to use any of these routines.
+**
+** The SQLite source code contains multiple implementations
+** of these mutex routines.  An appropriate implementation
+** is selected automatically at compile-time.  The following
+** implementations are available in the SQLite core:
+**
+** <ul>
+** <li>   SQLITE_MUTEX_PTHREADS
+** <li>   SQLITE_MUTEX_W32
+** <li>   SQLITE_MUTEX_NOOP
+** </ul>
+**
+** The SQLITE_MUTEX_NOOP implementation is a set of routines
+** that does no real locking and is appropriate for use in
+** a single-threaded application.  The SQLITE_MUTEX_PTHREADS and
+** SQLITE_MUTEX_W32 implementations are appropriate for use on Unix
+** and Windows.
+**
+** If SQLite is compiled with the SQLITE_MUTEX_APPDEF preprocessor
+** macro defined (with "-DSQLITE_MUTEX_APPDEF=1"), then no mutex
+** implementation is included with the library. In this case the
+** application must supply a custom mutex implementation using the
+** [SQLITE_CONFIG_MUTEX] option of the sqlite3_config() function
+** before calling sqlite3_initialize() or any other public sqlite3_
+** function that calls sqlite3_initialize().
+**
+** ^The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it. ^The sqlite3_mutex_alloc()
+** routine returns NULL if it is unable to allocate the requested
+** mutex.  The argument to sqlite3_mutex_alloc() must one of these
+** integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST
+** <li>  SQLITE_MUTEX_RECURSIVE
+** <li>  SQLITE_MUTEX_STATIC_MAIN
+** <li>  SQLITE_MUTEX_STATIC_MEM
+** <li>  SQLITE_MUTEX_STATIC_OPEN
+** <li>  SQLITE_MUTEX_STATIC_PRNG
+** <li>  SQLITE_MUTEX_STATIC_LRU
+** <li>  SQLITE_MUTEX_STATIC_PMEM
+** <li>  SQLITE_MUTEX_STATIC_APP1
+** <li>  SQLITE_MUTEX_STATIC_APP2
+** <li>  SQLITE_MUTEX_STATIC_APP3
+** <li>  SQLITE_MUTEX_STATIC_VFS1
+** <li>  SQLITE_MUTEX_STATIC_VFS2
+** <li>  SQLITE_MUTEX_STATIC_VFS3
+** </ul>
+**
+** ^The first two constants (SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE)
+** cause sqlite3_mutex_alloc() to create
+** a new mutex.  ^The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  SQLite will only request a recursive mutex in
+** cases where it really needs one.  If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** ^The other allowed parameters to sqlite3_mutex_alloc() (anything other
+** than SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE) each return
+** a pointer to a static preexisting mutex.  ^Nine static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** ^Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  ^For the static
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+**
+** ^The sqlite3_mutex_free() routine deallocates a previously
+** allocated dynamic mutex.  Attempting to deallocate a static
+** mutex results in undefined behavior.
+**
+** ^The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  ^If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  ^The sqlite3_mutex_try() interface returns [SQLITE_OK]
+** upon successful entry.  ^(Mutexes created using
+** SQLITE_MUTEX_RECURSIVE can be entered multiple times by the same thread.
+** In such cases, the
+** mutex must be exited an equal number of times before another thread
+** can enter.)^  If the same thread tries to enter any mutex other
+** than an SQLITE_MUTEX_RECURSIVE more than once, the behavior is undefined.
+**
+** ^(Some systems (for example, Windows 95) do not support the operation
+** implemented by sqlite3_mutex_try().  On those systems, sqlite3_mutex_try()
+** will always return SQLITE_BUSY. In most cases the SQLite core only uses
+** sqlite3_mutex_try() as an optimization, so this is acceptable
+** behavior. The exceptions are unix builds that set the 
+** SQLITE_ENABLE_SETLK_TIMEOUT build option. In that case a working
+** sqlite3_mutex_try() is required.)^
+**
+** ^The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.   The behavior
+** is undefined if the mutex is not currently entered by the
+** calling thread or is not currently allocated.
+**
+** ^If the argument to sqlite3_mutex_enter(), sqlite3_mutex_try(),
+** sqlite3_mutex_leave(), or sqlite3_mutex_free() is a NULL pointer,
+** then any of the four routines behaves as a no-op.
+**
+** See also: [sqlite3_mutex_held()] and [sqlite3_mutex_notheld()].
+*/
+sqlite3_mutex *sqlite3_mutex_alloc(int);
+void sqlite3_mutex_free(sqlite3_mutex*);
+void sqlite3_mutex_enter(sqlite3_mutex*);
+int sqlite3_mutex_try(sqlite3_mutex*);
+void sqlite3_mutex_leave(sqlite3_mutex*);
+
+/*
+** CAPI3REF: Mutex Methods Object
+**
+** An instance of this structure defines the low-level routines
+** used to allocate and use mutexes.
+**
+** Usually, the default mutex implementations provided by SQLite are
+** sufficient, however the application has the option of substituting a custom
+** implementation for specialized deployments or systems for which SQLite
+** does not provide a suitable implementation. In this case, the application
+** creates and populates an instance of this structure to pass
+** to sqlite3_config() along with the [SQLITE_CONFIG_MUTEX] option.
+** Additionally, an instance of this structure can be used as an
+** output variable when querying the system for the current mutex
+** implementation, using the [SQLITE_CONFIG_GETMUTEX] option.
+**
+** ^The xMutexInit method defined by this structure is invoked as
+** part of system initialization by the sqlite3_initialize() function.
+** ^The xMutexInit routine is called by SQLite exactly once for each
+** effective call to [sqlite3_initialize()].
+**
+** ^The xMutexEnd method defined by this structure is invoked as
+** part of system shutdown by the sqlite3_shutdown() function. The
+** implementation of this method is expected to release all outstanding
+** resources obtained by the mutex methods implementation, especially
+** those obtained by the xMutexInit method.  ^The xMutexEnd()
+** interface is invoked exactly once for each call to [sqlite3_shutdown()].
+**
+** ^(The remaining seven methods defined by this structure (xMutexAlloc,
+** xMutexFree, xMutexEnter, xMutexTry, xMutexLeave, xMutexHeld and
+** xMutexNotheld) implement the following interfaces (respectively):
+**
+** <ul>
+**   <li>  [sqlite3_mutex_alloc()] </li>
+**   <li>  [sqlite3_mutex_free()] </li>
+**   <li>  [sqlite3_mutex_enter()] </li>
+**   <li>  [sqlite3_mutex_try()] </li>
+**   <li>  [sqlite3_mutex_leave()] </li>
+**   <li>  [sqlite3_mutex_held()] </li>
+**   <li>  [sqlite3_mutex_notheld()] </li>
+** </ul>)^
+**
+** The only difference is that the public sqlite3_XXX functions enumerated
+** above silently ignore any invocations that pass a NULL pointer instead
+** of a valid mutex handle. The implementations of the methods defined
+** by this structure are not required to handle this case. The results
+** of passing a NULL pointer instead of a valid mutex handle are undefined
+** (i.e. it is acceptable to provide an implementation that segfaults if
+** it is passed a NULL pointer).
+**
+** The xMutexInit() method must be threadsafe.  It must be harmless to
+** invoke xMutexInit() multiple times within the same process and without
+** intervening calls to xMutexEnd().  Second and subsequent calls to
+** xMutexInit() must be no-ops.
+**
+** xMutexInit() must not use SQLite memory allocation ([sqlite3_malloc()]
+** and its associates).  Similarly, xMutexAlloc() must not use SQLite memory
+** allocation for a static mutex.  ^However xMutexAlloc() may use SQLite
+** memory allocation for a fast or recursive mutex.
+**
+** ^SQLite will invoke the xMutexEnd() method when [sqlite3_shutdown()] is
+** called, but only if the prior call to xMutexInit returned SQLITE_OK.
+** If xMutexInit fails in any way, it is expected to clean up after itself
+** prior to returning.
+*/
+typedef struct sqlite3_mutex_methods sqlite3_mutex_methods;
+struct sqlite3_mutex_methods {
+  int (*xMutexInit)(void);
+  int (*xMutexEnd)(void);
+  sqlite3_mutex *(*xMutexAlloc)(int);
+  void (*xMutexFree)(sqlite3_mutex *);
+  void (*xMutexEnter)(sqlite3_mutex *);
+  int (*xMutexTry)(sqlite3_mutex *);
+  void (*xMutexLeave)(sqlite3_mutex *);
+  int (*xMutexHeld)(sqlite3_mutex *);
+  int (*xMutexNotheld)(sqlite3_mutex *);
+};
+
+/*
+** CAPI3REF: Mutex Verification Routines
+**
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routines
+** are intended for use inside assert() statements.  The SQLite core
+** never uses these routines except inside an assert() and applications
+** are advised to follow the lead of the core.  The SQLite core only
+** provides implementations for these routines when it is compiled
+** with the SQLITE_DEBUG flag.  External mutex implementations
+** are only required to provide these routines if SQLITE_DEBUG is
+** defined and if NDEBUG is not defined.
+**
+** These routines should return true if the mutex in their argument
+** is held or not held, respectively, by the calling thread.
+**
+** The implementation is not required to provide versions of these
+** routines that actually work. If the implementation does not provide working
+** versions of these routines, it should at least provide stubs that always
+** return true so that one does not get spurious assertion failures.
+**
+** If the argument to sqlite3_mutex_held() is a NULL pointer then
+** the routine should return 1.   This seems counter-intuitive since
+** clearly the mutex cannot be held if it does not exist.  But
+** the reason the mutex does not exist is because the build is not
+** using mutexes.  And we do not want the assert() containing the
+** call to sqlite3_mutex_held() to fail, so a non-zero return is
+** the appropriate thing to do.  The sqlite3_mutex_notheld()
+** interface should also return 1 when given a NULL pointer.
+*/
+#ifndef NDEBUG
+int sqlite3_mutex_held(sqlite3_mutex*);
+int sqlite3_mutex_notheld(sqlite3_mutex*);
+#endif
+
+/*
+** CAPI3REF: Mutex Types
+**
+** The [sqlite3_mutex_alloc()] interface takes a single argument
+** which is one of these integer constants.
+**
+** The set of static mutexes may change from one SQLite release to the
+** next.  Applications that override the built-in mutex logic must be
+** prepared to accommodate additional static mutexes.
+*/
+#define SQLITE_MUTEX_FAST             0
+#define SQLITE_MUTEX_RECURSIVE        1
+#define SQLITE_MUTEX_STATIC_MAIN      2
+#define SQLITE_MUTEX_STATIC_MEM       3  /* sqlite3_malloc() */
+#define SQLITE_MUTEX_STATIC_MEM2      4  /* NOT USED */
+#define SQLITE_MUTEX_STATIC_OPEN      4  /* sqlite3BtreeOpen() */
+#define SQLITE_MUTEX_STATIC_PRNG      5  /* sqlite3_randomness() */
+#define SQLITE_MUTEX_STATIC_LRU       6  /* lru page list */
+#define SQLITE_MUTEX_STATIC_LRU2      7  /* NOT USED */
+#define SQLITE_MUTEX_STATIC_PMEM      7  /* sqlite3PageMalloc() */
+#define SQLITE_MUTEX_STATIC_APP1      8  /* For use by application */
+#define SQLITE_MUTEX_STATIC_APP2      9  /* For use by application */
+#define SQLITE_MUTEX_STATIC_APP3     10  /* For use by application */
+#define SQLITE_MUTEX_STATIC_VFS1     11  /* For use by built-in VFS */
+#define SQLITE_MUTEX_STATIC_VFS2     12  /* For use by extension VFS */
+#define SQLITE_MUTEX_STATIC_VFS3     13  /* For use by application VFS */
+
+/* Legacy compatibility: */
+#define SQLITE_MUTEX_STATIC_MASTER    2
+
+
+/*
+** CAPI3REF: Retrieve the mutex for a database connection
+** METHOD: sqlite3
+**
+** ^This interface returns a pointer the [sqlite3_mutex] object that
+** serializes access to the [database connection] given in the argument
+** when the [threading mode] is Serialized.
+** ^If the [threading mode] is Single-thread or Multi-thread then this
+** routine returns a NULL pointer.
+*/
+sqlite3_mutex *sqlite3_db_mutex(sqlite3*);
+
+/*
+** CAPI3REF: Low-Level Control Of Database Files
+** METHOD: sqlite3
+** KEYWORDS: {file control}
+**
+** ^The [sqlite3_file_control()] interface makes a direct call to the
+** xFileControl method for the [sqlite3_io_methods] object associated
+** with a particular database identified by the second argument. ^The
+** name of the database is "main" for the main database or "temp" for the
+** TEMP database, or the name that appears after the AS keyword for
+** databases that are added using the [ATTACH] SQL command.
+** ^A NULL pointer can be used in place of "main" to refer to the
+** main database file.
+** ^The third and fourth parameters to this routine
+** are passed directly through to the second and third parameters of
+** the xFileControl method.  ^The return value of the xFileControl
+** method becomes the return value of this routine.
+**
+** A few opcodes for [sqlite3_file_control()] are handled directly
+** by the SQLite core and never invoke the
+** sqlite3_io_methods.xFileControl method.
+** ^The [SQLITE_FCNTL_FILE_POINTER] value for the op parameter causes
+** a pointer to the underlying [sqlite3_file] object to be written into
+** the space pointed to by the 4th parameter.  The
+** [SQLITE_FCNTL_JOURNAL_POINTER] works similarly except that it returns
+** the [sqlite3_file] object associated with the journal file instead of
+** the main database.  The [SQLITE_FCNTL_VFS_POINTER] opcode returns
+** a pointer to the underlying [sqlite3_vfs] object for the file.
+** The [SQLITE_FCNTL_DATA_VERSION] returns the data version counter
+** from the pager.
+**
+** ^If the second parameter (zDbName) does not match the name of any
+** open database file, then SQLITE_ERROR is returned.  ^This error
+** code is not remembered and will not be recalled by [sqlite3_errcode()]
+** or [sqlite3_errmsg()].  The underlying xFileControl method might
+** also return SQLITE_ERROR.  There is no way to distinguish between
+** an incorrect zDbName and an SQLITE_ERROR return from the underlying
+** xFileControl method.
+**
+** See also: [file control opcodes]
+*/
+int sqlite3_file_control(sqlite3*, const char *zDbName, int op, void*);
+
+/*
+** CAPI3REF: Testing Interface
+**
+** ^The sqlite3_test_control() interface is used to read out internal
+** state of SQLite and to inject faults into SQLite for testing
+** purposes.  ^The first parameter is an operation code that determines
+** the number, meaning, and operation of all subsequent parameters.
+**
+** This interface is not for use by applications.  It exists solely
+** for verifying the correct operation of the SQLite library.  Depending
+** on how the SQLite library is compiled, this interface might not exist.
+**
+** The details of the operation codes, their meanings, the parameters
+** they take, and what they do are all subject to change without notice.
+** Unlike most of the SQLite API, this function is not guaranteed to
+** operate consistently from one release to the next.
+*/
+int sqlite3_test_control(int op, ...);
+
+/*
+** CAPI3REF: Testing Interface Operation Codes
+**
+** These constants are the valid operation code parameters used
+** as the first argument to [sqlite3_test_control()].
+**
+** These parameters and their meanings are subject to change
+** without notice.  These values are for testing purposes only.
+** Applications should not use any of these parameters or the
+** [sqlite3_test_control()] interface.
+*/
+#define SQLITE_TESTCTRL_FIRST                    5
+#define SQLITE_TESTCTRL_PRNG_SAVE                5
+#define SQLITE_TESTCTRL_PRNG_RESTORE             6
+#define SQLITE_TESTCTRL_PRNG_RESET               7  /* NOT USED */
+#define SQLITE_TESTCTRL_FK_NO_ACTION             7
+#define SQLITE_TESTCTRL_BITVEC_TEST              8
+#define SQLITE_TESTCTRL_FAULT_INSTALL            9
+#define SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS     10
+#define SQLITE_TESTCTRL_PENDING_BYTE            11
+#define SQLITE_TESTCTRL_ASSERT                  12
+#define SQLITE_TESTCTRL_ALWAYS                  13
+#define SQLITE_TESTCTRL_RESERVE                 14  /* NOT USED */
+#define SQLITE_TESTCTRL_JSON_SELFCHECK          14
+#define SQLITE_TESTCTRL_OPTIMIZATIONS           15
+#define SQLITE_TESTCTRL_ISKEYWORD               16  /* NOT USED */
+#define SQLITE_TESTCTRL_SCRATCHMALLOC           17  /* NOT USED */
+#define SQLITE_TESTCTRL_INTERNAL_FUNCTIONS      17
+#define SQLITE_TESTCTRL_LOCALTIME_FAULT         18
+#define SQLITE_TESTCTRL_EXPLAIN_STMT            19  /* NOT USED */
+#define SQLITE_TESTCTRL_ONCE_RESET_THRESHOLD    19
+#define SQLITE_TESTCTRL_NEVER_CORRUPT           20
+#define SQLITE_TESTCTRL_VDBE_COVERAGE           21
+#define SQLITE_TESTCTRL_BYTEORDER               22
+#define SQLITE_TESTCTRL_ISINIT                  23
+#define SQLITE_TESTCTRL_SORTER_MMAP             24
+#define SQLITE_TESTCTRL_IMPOSTER                25
+#define SQLITE_TESTCTRL_PARSER_COVERAGE         26
+#define SQLITE_TESTCTRL_RESULT_INTREAL          27
+#define SQLITE_TESTCTRL_PRNG_SEED               28
+#define SQLITE_TESTCTRL_EXTRA_SCHEMA_CHECKS     29
+#define SQLITE_TESTCTRL_SEEK_COUNT              30
+#define SQLITE_TESTCTRL_TRACEFLAGS              31
+#define SQLITE_TESTCTRL_TUNE                    32
+#define SQLITE_TESTCTRL_LOGEST                  33
+#define SQLITE_TESTCTRL_USELONGDOUBLE           34
+#define SQLITE_TESTCTRL_LAST                    34  /* Largest TESTCTRL */
+
+/*
+** CAPI3REF: SQL Keyword Checking
+**
+** These routines provide access to the set of SQL language keywords
+** recognized by SQLite.  Applications can uses these routines to determine
+** whether or not a specific identifier needs to be escaped (for example,
+** by enclosing in double-quotes) so as not to confuse the parser.
+**
+** The sqlite3_keyword_count() interface returns the number of distinct
+** keywords understood by SQLite.
+**
+** The sqlite3_keyword_name(N,Z,L) interface finds the N-th keyword and
+** makes *Z point to that keyword expressed as UTF8 and writes the number
+** of bytes in the keyword into *L.  The string that *Z points to is not
+** zero-terminated.  The sqlite3_keyword_name(N,Z,L) routine returns
+** SQLITE_OK if N is within bounds and SQLITE_ERROR if not. If either Z
+** or L are NULL or invalid pointers then calls to
+** sqlite3_keyword_name(N,Z,L) result in undefined behavior.
+**
+** The sqlite3_keyword_check(Z,L) interface checks to see whether or not
+** the L-byte UTF8 identifier that Z points to is a keyword, returning non-zero
+** if it is and zero if not.
+**
+** The parser used by SQLite is forgiving.  It is often possible to use
+** a keyword as an identifier as long as such use does not result in a
+** parsing ambiguity.  For example, the statement
+** "CREATE TABLE BEGIN(REPLACE,PRAGMA,END);" is accepted by SQLite, and
+** creates a new table named "BEGIN" with three columns named
+** "REPLACE", "PRAGMA", and "END".  Nevertheless, best practice is to avoid
+** using keywords as identifiers.  Common techniques used to avoid keyword
+** name collisions include:
+** <ul>
+** <li> Put all identifier names inside double-quotes.  This is the official
+**      SQL way to escape identifier names.
+** <li> Put identifier names inside &#91;...&#93;.  This is not standard SQL,
+**      but it is what SQL Server does and so lots of programmers use this
+**      technique.
+** <li> Begin every identifier with the letter "Z" as no SQL keywords start
+**      with "Z".
+** <li> Include a digit somewhere in every identifier name.
+** </ul>
+**
+** Note that the number of keywords understood by SQLite can depend on
+** compile-time options.  For example, "VACUUM" is not a keyword if
+** SQLite is compiled with the [-DSQLITE_OMIT_VACUUM] option.  Also,
+** new keywords may be added to future releases of SQLite.
+*/
+int sqlite3_keyword_count(void);
+int sqlite3_keyword_name(int,const char**,int*);
+int sqlite3_keyword_check(const char*,int);
+
+/*
+** CAPI3REF: Dynamic String Object
+** KEYWORDS: {dynamic string}
+**
+** An instance of the sqlite3_str object contains a dynamically-sized
+** string under construction.
+**
+** The lifecycle of an sqlite3_str object is as follows:
+** <ol>
+** <li> ^The sqlite3_str object is created using [sqlite3_str_new()].
+** <li> ^Text is appended to the sqlite3_str object using various
+** methods, such as [sqlite3_str_appendf()].
+** <li> ^The sqlite3_str object is destroyed and the string it created
+** is returned using the [sqlite3_str_finish()] interface.
+** </ol>
+*/
+typedef struct sqlite3_str sqlite3_str;
+
+/*
+** CAPI3REF: Create A New Dynamic String Object
+** CONSTRUCTOR: sqlite3_str
+**
+** ^The [sqlite3_str_new(D)] interface allocates and initializes
+** a new [sqlite3_str] object.  To avoid memory leaks, the object returned by
+** [sqlite3_str_new()] must be freed by a subsequent call to
+** [sqlite3_str_finish(X)].
+**
+** ^The [sqlite3_str_new(D)] interface always returns a pointer to a
+** valid [sqlite3_str] object, though in the event of an out-of-memory
+** error the returned object might be a special singleton that will
+** silently reject new text, always return SQLITE_NOMEM from
+** [sqlite3_str_errcode()], always return 0 for
+** [sqlite3_str_length()], and always return NULL from
+** [sqlite3_str_finish(X)].  It is always safe to use the value
+** returned by [sqlite3_str_new(D)] as the sqlite3_str parameter
+** to any of the other [sqlite3_str] methods.
+**
+** The D parameter to [sqlite3_str_new(D)] may be NULL.  If the
+** D parameter in [sqlite3_str_new(D)] is not NULL, then the maximum
+** length of the string contained in the [sqlite3_str] object will be
+** the value set for [sqlite3_limit](D,[SQLITE_LIMIT_LENGTH]) instead
+** of [SQLITE_MAX_LENGTH].
+*/
+sqlite3_str *sqlite3_str_new(sqlite3*);
+
+/*
+** CAPI3REF: Finalize A Dynamic String
+** DESTRUCTOR: sqlite3_str
+**
+** ^The [sqlite3_str_finish(X)] interface destroys the sqlite3_str object X
+** and returns a pointer to a memory buffer obtained from [sqlite3_malloc64()]
+** that contains the constructed string.  The calling application should
+** pass the returned value to [sqlite3_free()] to avoid a memory leak.
+** ^The [sqlite3_str_finish(X)] interface may return a NULL pointer if any
+** errors were encountered during construction of the string.  ^The
+** [sqlite3_str_finish(X)] interface will also return a NULL pointer if the
+** string in [sqlite3_str] object X is zero bytes long.
+*/
+char *sqlite3_str_finish(sqlite3_str*);
+
+/*
+** CAPI3REF: Add Content To A Dynamic String
+** METHOD: sqlite3_str
+**
+** These interfaces add content to an sqlite3_str object previously obtained
+** from [sqlite3_str_new()].
+**
+** ^The [sqlite3_str_appendf(X,F,...)] and
+** [sqlite3_str_vappendf(X,F,V)] interfaces uses the [built-in printf]
+** functionality of SQLite to append formatted text onto the end of
+** [sqlite3_str] object X.
+**
+** ^The [sqlite3_str_append(X,S,N)] method appends exactly N bytes from string S
+** onto the end of the [sqlite3_str] object X.  N must be non-negative.
+** S must contain at least N non-zero bytes of content.  To append a
+** zero-terminated string in its entirety, use the [sqlite3_str_appendall()]
+** method instead.
+**
+** ^The [sqlite3_str_appendall(X,S)] method appends the complete content of
+** zero-terminated string S onto the end of [sqlite3_str] object X.
+**
+** ^The [sqlite3_str_appendchar(X,N,C)] method appends N copies of the
+** single-byte character C onto the end of [sqlite3_str] object X.
+** ^This method can be used, for example, to add whitespace indentation.
+**
+** ^The [sqlite3_str_reset(X)] method resets the string under construction
+** inside [sqlite3_str] object X back to zero bytes in length. 
+**
+** These methods do not return a result code.  ^If an error occurs, that fact
+** is recorded in the [sqlite3_str] object and can be recovered by a
+** subsequent call to [sqlite3_str_errcode(X)].
+*/
+void sqlite3_str_appendf(sqlite3_str*, const char *zFormat, ...);
+void sqlite3_str_vappendf(sqlite3_str*, const char *zFormat, va_list);
+void sqlite3_str_append(sqlite3_str*, const char *zIn, int N);
+void sqlite3_str_appendall(sqlite3_str*, const char *zIn);
+void sqlite3_str_appendchar(sqlite3_str*, int N, char C);
+void sqlite3_str_reset(sqlite3_str*);
+
+/*
+** CAPI3REF: Status Of A Dynamic String
+** METHOD: sqlite3_str
+**
+** These interfaces return the current status of an [sqlite3_str] object.
+**
+** ^If any prior errors have occurred while constructing the dynamic string
+** in sqlite3_str X, then the [sqlite3_str_errcode(X)] method will return
+** an appropriate error code.  ^The [sqlite3_str_errcode(X)] method returns
+** [SQLITE_NOMEM] following any out-of-memory error, or
+** [SQLITE_TOOBIG] if the size of the dynamic string exceeds
+** [SQLITE_MAX_LENGTH], or [SQLITE_OK] if there have been no errors.
+**
+** ^The [sqlite3_str_length(X)] method returns the current length, in bytes,
+** of the dynamic string under construction in [sqlite3_str] object X.
+** ^The length returned by [sqlite3_str_length(X)] does not include the
+** zero-termination byte.
+**
+** ^The [sqlite3_str_value(X)] method returns a pointer to the current
+** content of the dynamic string under construction in X.  The value
+** returned by [sqlite3_str_value(X)] is managed by the sqlite3_str object X
+** and might be freed or altered by any subsequent method on the same
+** [sqlite3_str] object.  Applications must not used the pointer returned
+** [sqlite3_str_value(X)] after any subsequent method call on the same
+** object.  ^Applications may change the content of the string returned
+** by [sqlite3_str_value(X)] as long as they do not write into any bytes
+** outside the range of 0 to [sqlite3_str_length(X)] and do not read or
+** write any byte after any subsequent sqlite3_str method call.
+*/
+int sqlite3_str_errcode(sqlite3_str*);
+int sqlite3_str_length(sqlite3_str*);
+char *sqlite3_str_value(sqlite3_str*);
+
+/*
+** CAPI3REF: SQLite Runtime Status
+**
+** ^These interfaces are used to retrieve runtime status information
+** about the performance of SQLite, and optionally to reset various
+** highwater marks.  ^The first argument is an integer code for
+** the specific parameter to measure.  ^(Recognized integer codes
+** are of the form [status parameters | SQLITE_STATUS_...].)^
+** ^The current value of the parameter is returned into *pCurrent.
+** ^The highest recorded value is returned in *pHighwater.  ^If the
+** resetFlag is true, then the highest record value is reset after
+** *pHighwater is written.  ^(Some parameters do not record the highest
+** value.  For those parameters
+** nothing is written into *pHighwater and the resetFlag is ignored.)^
+** ^(Other parameters record only the highwater mark and not the current
+** value.  For these latter parameters nothing is written into *pCurrent.)^
+**
+** ^The sqlite3_status() and sqlite3_status64() routines return
+** SQLITE_OK on success and a non-zero [error code] on failure.
+**
+** If either the current value or the highwater mark is too large to
+** be represented by a 32-bit integer, then the values returned by
+** sqlite3_status() are undefined.
+**
+** See also: [sqlite3_db_status()]
+*/
+int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
+int sqlite3_status64(
+  int op,
+  sqlite3_int64 *pCurrent,
+  sqlite3_int64 *pHighwater,
+  int resetFlag
+);
+
+
+/*
+** CAPI3REF: Status Parameters
+** KEYWORDS: {status parameters}
+**
+** These integer constants designate various run-time status parameters
+** that can be returned by [sqlite3_status()].
+**
+** <dl>
+** [[SQLITE_STATUS_MEMORY_USED]] ^(<dt>SQLITE_STATUS_MEMORY_USED</dt>
+** <dd>This parameter is the current amount of memory checked out
+** using [sqlite3_malloc()], either directly or indirectly.  The
+** figure includes calls made to [sqlite3_malloc()] by the application
+** and internal memory usage by the SQLite library.  Auxiliary page-cache
+** memory controlled by [SQLITE_CONFIG_PAGECACHE] is not included in
+** this parameter.  The amount returned is the sum of the allocation
+** sizes as reported by the xSize method in [sqlite3_mem_methods].</dd>)^
+**
+** [[SQLITE_STATUS_MALLOC_SIZE]] ^(<dt>SQLITE_STATUS_MALLOC_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to [sqlite3_malloc()] or [sqlite3_realloc()] (or their
+** internal equivalents).  Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest. 
+** The value written into the *pCurrent parameter is undefined.</dd>)^
+**
+** [[SQLITE_STATUS_MALLOC_COUNT]] ^(<dt>SQLITE_STATUS_MALLOC_COUNT</dt>
+** <dd>This parameter records the number of separate memory allocations
+** currently checked out.</dd>)^
+**
+** [[SQLITE_STATUS_PAGECACHE_USED]] ^(<dt>SQLITE_STATUS_PAGECACHE_USED</dt>
+** <dd>This parameter returns the number of pages used out of the
+** [pagecache memory allocator] that was configured using
+** [SQLITE_CONFIG_PAGECACHE].  The
+** value returned is in pages, not in bytes.</dd>)^
+**
+** [[SQLITE_STATUS_PAGECACHE_OVERFLOW]]
+** ^(<dt>SQLITE_STATUS_PAGECACHE_OVERFLOW</dt>
+** <dd>This parameter returns the number of bytes of page cache
+** allocation which could not be satisfied by the [SQLITE_CONFIG_PAGECACHE]
+** buffer and where forced to overflow to [sqlite3_malloc()].  The
+** returned value includes allocations that overflowed because they
+** where too large (they were larger than the "sz" parameter to
+** [SQLITE_CONFIG_PAGECACHE]) and allocations that overflowed because
+** no space was left in the page cache.</dd>)^
+**
+** [[SQLITE_STATUS_PAGECACHE_SIZE]] ^(<dt>SQLITE_STATUS_PAGECACHE_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to the [pagecache memory allocator].  Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest. 
+** The value written into the *pCurrent parameter is undefined.</dd>)^
+**
+** [[SQLITE_STATUS_SCRATCH_USED]] <dt>SQLITE_STATUS_SCRATCH_USED</dt>
+** <dd>No longer used.</dd>
+**
+** [[SQLITE_STATUS_SCRATCH_OVERFLOW]] ^(<dt>SQLITE_STATUS_SCRATCH_OVERFLOW</dt>
+** <dd>No longer used.</dd>
+**
+** [[SQLITE_STATUS_SCRATCH_SIZE]] <dt>SQLITE_STATUS_SCRATCH_SIZE</dt>
+** <dd>No longer used.</dd>
+**
+** [[SQLITE_STATUS_PARSER_STACK]] ^(<dt>SQLITE_STATUS_PARSER_STACK</dt>
+** <dd>The *pHighwater parameter records the deepest parser stack.
+** The *pCurrent value is undefined.  The *pHighwater value is only
+** meaningful if SQLite is compiled with [YYTRACKMAXSTACKDEPTH].</dd>)^
+** </dl>
+**
+** New status parameters may be added from time to time.
+*/
+#define SQLITE_STATUS_MEMORY_USED          0
+#define SQLITE_STATUS_PAGECACHE_USED       1
+#define SQLITE_STATUS_PAGECACHE_OVERFLOW   2
+#define SQLITE_STATUS_SCRATCH_USED         3  /* NOT USED */
+#define SQLITE_STATUS_SCRATCH_OVERFLOW     4  /* NOT USED */
+#define SQLITE_STATUS_MALLOC_SIZE          5
+#define SQLITE_STATUS_PARSER_STACK         6
+#define SQLITE_STATUS_PAGECACHE_SIZE       7
+#define SQLITE_STATUS_SCRATCH_SIZE         8  /* NOT USED */
+#define SQLITE_STATUS_MALLOC_COUNT         9
+
+/*
+** CAPI3REF: Database Connection Status
+** METHOD: sqlite3
+**
+** ^This interface is used to retrieve runtime status information
+** about a single [database connection].  ^The first argument is the
+** database connection object to be interrogated.  ^The second argument
+** is an integer constant, taken from the set of
+** [SQLITE_DBSTATUS options], that
+** determines the parameter to interrogate.  The set of
+** [SQLITE_DBSTATUS options] is likely
+** to grow in future releases of SQLite.
+**
+** ^The current value of the requested parameter is written into *pCur
+** and the highest instantaneous value is written into *pHiwtr.  ^If
+** the resetFlg is true, then the highest instantaneous value is
+** reset back down to the current value.
+**
+** ^The sqlite3_db_status() routine returns SQLITE_OK on success and a
+** non-zero [error code] on failure.
+**
+** See also: [sqlite3_status()] and [sqlite3_stmt_status()].
+*/
+int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
+
+/*
+** CAPI3REF: Status Parameters for database connections
+** KEYWORDS: {SQLITE_DBSTATUS options}
+**
+** These constants are the available integer "verbs" that can be passed as
+** the second argument to the [sqlite3_db_status()] interface.
+**
+** New verbs may be added in future releases of SQLite. Existing verbs
+** might be discontinued. Applications should check the return code from
+** [sqlite3_db_status()] to make sure that the call worked.
+** The [sqlite3_db_status()] interface will return a non-zero error code
+** if a discontinued or unsupported verb is invoked.
+**
+** <dl>
+** [[SQLITE_DBSTATUS_LOOKASIDE_USED]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
+** <dd>This parameter returns the number of lookaside memory slots currently
+** checked out.</dd>)^
+**
+** [[SQLITE_DBSTATUS_LOOKASIDE_HIT]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_HIT</dt>
+** <dd>This parameter returns the number of malloc attempts that were
+** satisfied using lookaside memory. Only the high-water value is meaningful;
+** the current value is always zero.)^
+**
+** [[SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE]]
+** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE</dt>
+** <dd>This parameter returns the number malloc attempts that might have
+** been satisfied using lookaside memory but failed due to the amount of
+** memory requested being larger than the lookaside slot size.
+** Only the high-water value is meaningful;
+** the current value is always zero.)^
+**
+** [[SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL]]
+** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL</dt>
+** <dd>This parameter returns the number malloc attempts that might have
+** been satisfied using lookaside memory but failed due to all lookaside
+** memory already being in use.
+** Only the high-water value is meaningful;
+** the current value is always zero.)^
+**
+** [[SQLITE_DBSTATUS_CACHE_USED]] ^(<dt>SQLITE_DBSTATUS_CACHE_USED</dt>
+** <dd>This parameter returns the approximate number of bytes of heap
+** memory used by all pager caches associated with the database connection.)^
+** ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always 0.
+**
+** [[SQLITE_DBSTATUS_CACHE_USED_SHARED]]
+** ^(<dt>SQLITE_DBSTATUS_CACHE_USED_SHARED</dt>
+** <dd>This parameter is similar to DBSTATUS_CACHE_USED, except that if a
+** pager cache is shared between two or more connections the bytes of heap
+** memory used by that pager cache is divided evenly between the attached
+** connections.)^  In other words, if none of the pager caches associated
+** with the database connection are shared, this request returns the same
+** value as DBSTATUS_CACHE_USED. Or, if one or more or the pager caches are
+** shared, the value returned by this call will be smaller than that returned
+** by DBSTATUS_CACHE_USED. ^The highwater mark associated with
+** SQLITE_DBSTATUS_CACHE_USED_SHARED is always 0.
+**
+** [[SQLITE_DBSTATUS_SCHEMA_USED]] ^(<dt>SQLITE_DBSTATUS_SCHEMA_USED</dt>
+** <dd>This parameter returns the approximate number of bytes of heap
+** memory used to store the schema for all databases associated
+** with the connection - main, temp, and any [ATTACH]-ed databases.)^
+** ^The full amount of memory used by the schemas is reported, even if the
+** schema memory is shared with other database connections due to
+** [shared cache mode] being enabled.
+** ^The highwater mark associated with SQLITE_DBSTATUS_SCHEMA_USED is always 0.
+**
+** [[SQLITE_DBSTATUS_STMT_USED]] ^(<dt>SQLITE_DBSTATUS_STMT_USED</dt>
+** <dd>This parameter returns the approximate number of bytes of heap
+** and lookaside memory used by all prepared statements associated with
+** the database connection.)^
+** ^The highwater mark associated with SQLITE_DBSTATUS_STMT_USED is always 0.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_HIT]] ^(<dt>SQLITE_DBSTATUS_CACHE_HIT</dt>
+** <dd>This parameter returns the number of pager cache hits that have
+** occurred.)^ ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_HIT
+** is always 0.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_MISS]] ^(<dt>SQLITE_DBSTATUS_CACHE_MISS</dt>
+** <dd>This parameter returns the number of pager cache misses that have
+** occurred.)^ ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_MISS
+** is always 0.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_WRITE]] ^(<dt>SQLITE_DBSTATUS_CACHE_WRITE</dt>
+** <dd>This parameter returns the number of dirty cache entries that have
+** been written to disk. Specifically, the number of pages written to the
+** wal file in wal mode databases, or the number of pages written to the
+** database file in rollback mode databases. Any pages written as part of
+** transaction rollback or database recovery operations are not included.
+** If an IO or other error occurs while writing a page to disk, the effect
+** on subsequent SQLITE_DBSTATUS_CACHE_WRITE requests is undefined.)^ ^The
+** highwater mark associated with SQLITE_DBSTATUS_CACHE_WRITE is always 0.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_SPILL]] ^(<dt>SQLITE_DBSTATUS_CACHE_SPILL</dt>
+** <dd>This parameter returns the number of dirty cache entries that have
+** been written to disk in the middle of a transaction due to the page
+** cache overflowing. Transactions are more efficient if they are written
+** to disk all at once. When pages spill mid-transaction, that introduces
+** additional overhead. This parameter can be used help identify
+** inefficiencies that can be resolved by increasing the cache size.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_DEFERRED_FKS]] ^(<dt>SQLITE_DBSTATUS_DEFERRED_FKS</dt>
+** <dd>This parameter returns zero for the current value if and only if
+** all foreign key constraints (deferred or immediate) have been
+** resolved.)^  ^The highwater mark is always 0.
+** </dd>
+** </dl>
+*/
+#define SQLITE_DBSTATUS_LOOKASIDE_USED       0
+#define SQLITE_DBSTATUS_CACHE_USED           1
+#define SQLITE_DBSTATUS_SCHEMA_USED          2
+#define SQLITE_DBSTATUS_STMT_USED            3
+#define SQLITE_DBSTATUS_LOOKASIDE_HIT        4
+#define SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE  5
+#define SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL  6
+#define SQLITE_DBSTATUS_CACHE_HIT            7
+#define SQLITE_DBSTATUS_CACHE_MISS           8
+#define SQLITE_DBSTATUS_CACHE_WRITE          9
+#define SQLITE_DBSTATUS_DEFERRED_FKS        10
+#define SQLITE_DBSTATUS_CACHE_USED_SHARED   11
+#define SQLITE_DBSTATUS_CACHE_SPILL         12
+#define SQLITE_DBSTATUS_MAX                 12   /* Largest defined DBSTATUS */
+
+
+/*
+** CAPI3REF: Prepared Statement Status
+** METHOD: sqlite3_stmt
+**
+** ^(Each prepared statement maintains various
+** [SQLITE_STMTSTATUS counters] that measure the number
+** of times it has performed specific operations.)^  These counters can
+** be used to monitor the performance characteristics of the prepared
+** statements.  For example, if the number of table steps greatly exceeds
+** the number of table searches or result rows, that would tend to indicate
+** that the prepared statement is using a full table scan rather than
+** an index. 
+**
+** ^(This interface is used to retrieve and reset counter values from
+** a [prepared statement].  The first argument is the prepared statement
+** object to be interrogated.  The second argument
+** is an integer code for a specific [SQLITE_STMTSTATUS counter]
+** to be interrogated.)^
+** ^The current value of the requested counter is returned.
+** ^If the resetFlg is true, then the counter is reset to zero after this
+** interface call returns.
+**
+** See also: [sqlite3_status()] and [sqlite3_db_status()].
+*/
+int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
+
+/*
+** CAPI3REF: Status Parameters for prepared statements
+** KEYWORDS: {SQLITE_STMTSTATUS counter} {SQLITE_STMTSTATUS counters}
+**
+** These preprocessor macros define integer codes that name counter
+** values associated with the [sqlite3_stmt_status()] interface.
+** The meanings of the various counters are as follows:
+**
+** <dl>
+** [[SQLITE_STMTSTATUS_FULLSCAN_STEP]] <dt>SQLITE_STMTSTATUS_FULLSCAN_STEP</dt>
+** <dd>^This is the number of times that SQLite has stepped forward in
+** a table as part of a full table scan.  Large numbers for this counter
+** may indicate opportunities for performance improvement through
+** careful use of indices.</dd>
+**
+** [[SQLITE_STMTSTATUS_SORT]] <dt>SQLITE_STMTSTATUS_SORT</dt>
+** <dd>^This is the number of sort operations that have occurred.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance through careful use of indices.</dd>
+**
+** [[SQLITE_STMTSTATUS_AUTOINDEX]] <dt>SQLITE_STMTSTATUS_AUTOINDEX</dt>
+** <dd>^This is the number of rows inserted into transient indices that
+** were created automatically in order to help joins run faster.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance by adding permanent indices that do not
+** need to be reinitialized each time the statement is run.</dd>
+**
+** [[SQLITE_STMTSTATUS_VM_STEP]] <dt>SQLITE_STMTSTATUS_VM_STEP</dt>
+** <dd>^This is the number of virtual machine operations executed
+** by the prepared statement if that number is less than or equal
+** to 2147483647.  The number of virtual machine operations can be
+** used as a proxy for the total work done by the prepared statement.
+** If the number of virtual machine operations exceeds 2147483647
+** then the value returned by this statement status code is undefined.
+**
+** [[SQLITE_STMTSTATUS_REPREPARE]] <dt>SQLITE_STMTSTATUS_REPREPARE</dt>
+** <dd>^This is the number of times that the prepare statement has been
+** automatically regenerated due to schema changes or changes to
+** [bound parameters] that might affect the query plan.
+**
+** [[SQLITE_STMTSTATUS_RUN]] <dt>SQLITE_STMTSTATUS_RUN</dt>
+** <dd>^This is the number of times that the prepared statement has
+** been run.  A single "run" for the purposes of this counter is one
+** or more calls to [sqlite3_step()] followed by a call to [sqlite3_reset()].
+** The counter is incremented on the first [sqlite3_step()] call of each
+** cycle.
+**
+** [[SQLITE_STMTSTATUS_FILTER_MISS]]
+** [[SQLITE_STMTSTATUS_FILTER HIT]]
+** <dt>SQLITE_STMTSTATUS_FILTER_HIT<br>
+** SQLITE_STMTSTATUS_FILTER_MISS</dt>
+** <dd>^SQLITE_STMTSTATUS_FILTER_HIT is the number of times that a join
+** step was bypassed because a Bloom filter returned not-found.  The
+** corresponding SQLITE_STMTSTATUS_FILTER_MISS value is the number of
+** times that the Bloom filter returned a find, and thus the join step
+** had to be processed as normal.
+**
+** [[SQLITE_STMTSTATUS_MEMUSED]] <dt>SQLITE_STMTSTATUS_MEMUSED</dt>
+** <dd>^This is the approximate number of bytes of heap memory
+** used to store the prepared statement.  ^This value is not actually
+** a counter, and so the resetFlg parameter to sqlite3_stmt_status()
+** is ignored when the opcode is SQLITE_STMTSTATUS_MEMUSED.
+** </dd>
+** </dl>
+*/
+#define SQLITE_STMTSTATUS_FULLSCAN_STEP     1
+#define SQLITE_STMTSTATUS_SORT              2
+#define SQLITE_STMTSTATUS_AUTOINDEX         3
+#define SQLITE_STMTSTATUS_VM_STEP           4
+#define SQLITE_STMTSTATUS_REPREPARE         5
+#define SQLITE_STMTSTATUS_RUN               6
+#define SQLITE_STMTSTATUS_FILTER_MISS       7
+#define SQLITE_STMTSTATUS_FILTER_HIT        8
+#define SQLITE_STMTSTATUS_MEMUSED           99
+
+/*
+** CAPI3REF: Custom Page Cache Object
+**
+** The sqlite3_pcache type is opaque.  It is implemented by
+** the pluggable module.  The SQLite core has no knowledge of
+** its size or internal structure and never deals with the
+** sqlite3_pcache object except by holding and passing pointers
+** to the object.
+**
+** See [sqlite3_pcache_methods2] for additional information.
+*/
+typedef struct sqlite3_pcache sqlite3_pcache;
+
+/*
+** CAPI3REF: Custom Page Cache Object
+**
+** The sqlite3_pcache_page object represents a single page in the
+** page cache.  The page cache will allocate instances of this
+** object.  Various methods of the page cache use pointers to instances
+** of this object as parameters or as their return value.
+**
+** See [sqlite3_pcache_methods2] for additional information.
+*/
+typedef struct sqlite3_pcache_page sqlite3_pcache_page;
+struct sqlite3_pcache_page {
+  void *pBuf;        /* The content of the page */
+  void *pExtra;      /* Extra information associated with the page */
+};
+
+/*
+** CAPI3REF: Application Defined Page Cache.
+** KEYWORDS: {page cache}
+**
+** ^(The [sqlite3_config]([SQLITE_CONFIG_PCACHE2], ...) interface can
+** register an alternative page cache implementation by passing in an
+** instance of the sqlite3_pcache_methods2 structure.)^
+** In many applications, most of the heap memory allocated by
+** SQLite is used for the page cache.
+** By implementing a
+** custom page cache using this API, an application can better control
+** the amount of memory consumed by SQLite, the way in which
+** that memory is allocated and released, and the policies used to
+** determine exactly which parts of a database file are cached and for
+** how long.
+**
+** The alternative page cache mechanism is an
+** extreme measure that is only needed by the most demanding applications.
+** The built-in page cache is recommended for most uses.
+**
+** ^(The contents of the sqlite3_pcache_methods2 structure are copied to an
+** internal buffer by SQLite within the call to [sqlite3_config].  Hence
+** the application may discard the parameter after the call to
+** [sqlite3_config()] returns.)^
+**
+** [[the xInit() page cache method]]
+** ^(The xInit() method is called once for each effective
+** call to [sqlite3_initialize()])^
+** (usually only once during the lifetime of the process). ^(The xInit()
+** method is passed a copy of the sqlite3_pcache_methods2.pArg value.)^
+** The intent of the xInit() method is to set up global data structures
+** required by the custom page cache implementation.
+** ^(If the xInit() method is NULL, then the
+** built-in default page cache is used instead of the application defined
+** page cache.)^
+**
+** [[the xShutdown() page cache method]]
+** ^The xShutdown() method is called by [sqlite3_shutdown()].
+** It can be used to clean up
+** any outstanding resources before process shutdown, if required.
+** ^The xShutdown() method may be NULL.
+**
+** ^SQLite automatically serializes calls to the xInit method,
+** so the xInit method need not be threadsafe.  ^The
+** xShutdown method is only called from [sqlite3_shutdown()] so it does
+** not need to be threadsafe either.  All other methods must be threadsafe
+** in multithreaded applications.
+**
+** ^SQLite will never invoke xInit() more than once without an intervening
+** call to xShutdown().
+**
+** [[the xCreate() page cache methods]]
+** ^SQLite invokes the xCreate() method to construct a new cache instance.
+** SQLite will typically create one cache instance for each open database file,
+** though this is not guaranteed. ^The
+** first parameter, szPage, is the size in bytes of the pages that must
+** be allocated by the cache.  ^szPage will always a power of two.  ^The
+** second parameter szExtra is a number of bytes of extra storage
+** associated with each page cache entry.  ^The szExtra parameter will
+** a number less than 250.  SQLite will use the
+** extra szExtra bytes on each page to store metadata about the underlying
+** database page on disk.  The value passed into szExtra depends
+** on the SQLite version, the target platform, and how SQLite was compiled.
+** ^The third argument to xCreate(), bPurgeable, is true if the cache being
+** created will be used to cache database pages of a file stored on disk, or
+** false if it is used for an in-memory database. The cache implementation
+** does not have to do anything special based with the value of bPurgeable;
+** it is purely advisory.  ^On a cache where bPurgeable is false, SQLite will
+** never invoke xUnpin() except to deliberately delete a page.
+** ^In other words, calls to xUnpin() on a cache with bPurgeable set to
+** false will always have the "discard" flag set to true. 
+** ^Hence, a cache created with bPurgeable false will
+** never contain any unpinned pages.
+**
+** [[the xCachesize() page cache method]]
+** ^(The xCachesize() method may be called at any time by SQLite to set the
+** suggested maximum cache-size (number of pages stored by) the cache
+** instance passed as the first argument. This is the value configured using
+** the SQLite "[PRAGMA cache_size]" command.)^  As with the bPurgeable
+** parameter, the implementation is not required to do anything with this
+** value; it is advisory only.
+**
+** [[the xPagecount() page cache methods]]
+** The xPagecount() method must return the number of pages currently
+** stored in the cache, both pinned and unpinned.
+**
+** [[the xFetch() page cache methods]]
+** The xFetch() method locates a page in the cache and returns a pointer to
+** an sqlite3_pcache_page object associated with that page, or a NULL pointer.
+** The pBuf element of the returned sqlite3_pcache_page object will be a
+** pointer to a buffer of szPage bytes used to store the content of a
+** single database page.  The pExtra element of sqlite3_pcache_page will be
+** a pointer to the szExtra bytes of extra storage that SQLite has requested
+** for each entry in the page cache.
+**
+** The page to be fetched is determined by the key. ^The minimum key value
+** is 1.  After it has been retrieved using xFetch, the page is considered
+** to be "pinned".
+**
+** If the requested page is already in the page cache, then the page cache
+** implementation must return a pointer to the page buffer with its content
+** intact.  If the requested page is not already in the cache, then the
+** cache implementation should use the value of the createFlag
+** parameter to help it determined what action to take:
+**
+** <table border=1 width=85% align=center>
+** <tr><th> createFlag <th> Behavior when page is not already in cache
+** <tr><td> 0 <td> Do not allocate a new page.  Return NULL.
+** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so.
+**                 Otherwise return NULL.
+** <tr><td> 2 <td> Make every effort to allocate a new page.  Only return
+**                 NULL if allocating a new page is effectively impossible.
+** </table>
+**
+** ^(SQLite will normally invoke xFetch() with a createFlag of 0 or 1.  SQLite
+** will only use a createFlag of 2 after a prior call with a createFlag of 1
+** failed.)^  In between the xFetch() calls, SQLite may
+** attempt to unpin one or more cache pages by spilling the content of
+** pinned pages to disk and synching the operating system disk cache.
+**
+** [[the xUnpin() page cache method]]
+** ^xUnpin() is called by SQLite with a pointer to a currently pinned page
+** as its second argument.  If the third parameter, discard, is non-zero,
+** then the page must be evicted from the cache.
+** ^If the discard parameter is
+** zero, then the page may be discarded or retained at the discretion of
+** page cache implementation. ^The page cache implementation
+** may choose to evict unpinned pages at any time.
+**
+** The cache must not perform any reference counting. A single
+** call to xUnpin() unpins the page regardless of the number of prior calls
+** to xFetch().
+**
+** [[the xRekey() page cache methods]]
+** The xRekey() method is used to change the key value associated with the
+** page passed as the second argument. If the cache
+** previously contains an entry associated with newKey, it must be
+** discarded. ^Any prior cache entry associated with newKey is guaranteed not
+** to be pinned.
+**
+** When SQLite calls the xTruncate() method, the cache must discard all
+** existing cache entries with page numbers (keys) greater than or equal
+** to the value of the iLimit parameter passed to xTruncate(). If any
+** of these pages are pinned, they are implicitly unpinned, meaning that
+** they can be safely discarded.
+**
+** [[the xDestroy() page cache method]]
+** ^The xDestroy() method is used to delete a cache allocated by xCreate().
+** All resources associated with the specified cache should be freed. ^After
+** calling the xDestroy() method, SQLite considers the [sqlite3_pcache*]
+** handle invalid, and will not use it with any other sqlite3_pcache_methods2
+** functions.
+**
+** [[the xShrink() page cache method]]
+** ^SQLite invokes the xShrink() method when it wants the page cache to
+** free up as much of heap memory as possible.  The page cache implementation
+** is not obligated to free any memory, but well-behaved implementations should
+** do their best.
+*/
+typedef struct sqlite3_pcache_methods2 sqlite3_pcache_methods2;
+struct sqlite3_pcache_methods2 {
+  int iVersion;
+  void *pArg;
+  int (*xInit)(void*);
+  void (*xShutdown)(void*);
+  sqlite3_pcache *(*xCreate)(int szPage, int szExtra, int bPurgeable);
+  void (*xCachesize)(sqlite3_pcache*, int nCachesize);
+  int (*xPagecount)(sqlite3_pcache*);
+  sqlite3_pcache_page *(*xFetch)(sqlite3_pcache*, unsigned key, int createFlag);
+  void (*xUnpin)(sqlite3_pcache*, sqlite3_pcache_page*, int discard);
+  void (*xRekey)(sqlite3_pcache*, sqlite3_pcache_page*,
+      unsigned oldKey, unsigned newKey);
+  void (*xTruncate)(sqlite3_pcache*, unsigned iLimit);
+  void (*xDestroy)(sqlite3_pcache*);
+  void (*xShrink)(sqlite3_pcache*);
+};
+
+/*
+** This is the obsolete pcache_methods object that has now been replaced
+** by sqlite3_pcache_methods2.  This object is not used by SQLite.  It is
+** retained in the header file for backwards compatibility only.
+*/
+typedef struct sqlite3_pcache_methods sqlite3_pcache_methods;
+struct sqlite3_pcache_methods {
+  void *pArg;
+  int (*xInit)(void*);
+  void (*xShutdown)(void*);
+  sqlite3_pcache *(*xCreate)(int szPage, int bPurgeable);
+  void (*xCachesize)(sqlite3_pcache*, int nCachesize);
+  int (*xPagecount)(sqlite3_pcache*);
+  void *(*xFetch)(sqlite3_pcache*, unsigned key, int createFlag);
+  void (*xUnpin)(sqlite3_pcache*, void*, int discard);
+  void (*xRekey)(sqlite3_pcache*, void*, unsigned oldKey, unsigned newKey);
+  void (*xTruncate)(sqlite3_pcache*, unsigned iLimit);
+  void (*xDestroy)(sqlite3_pcache*);
+};
+
+
+/*
+** CAPI3REF: Online Backup Object
+**
+** The sqlite3_backup object records state information about an ongoing
+** online backup operation.  ^The sqlite3_backup object is created by
+** a call to [sqlite3_backup_init()] and is destroyed by a call to
+** [sqlite3_backup_finish()].
+**
+** See Also: [Using the SQLite Online Backup API]
+*/
+typedef struct sqlite3_backup sqlite3_backup;
+
+/*
+** CAPI3REF: Online Backup API.
+**
+** The backup API copies the content of one database into another.
+** It is useful either for creating backups of databases or
+** for copying in-memory databases to or from persistent files.
+**
+** See Also: [Using the SQLite Online Backup API]
+**
+** ^SQLite holds a write transaction open on the destination database file
+** for the duration of the backup operation.
+** ^The source database is read-locked only while it is being read;
+** it is not locked continuously for the entire backup operation.
+** ^Thus, the backup may be performed on a live source database without
+** preventing other database connections from
+** reading or writing to the source database while the backup is underway.
+**
+** ^(To perform a backup operation:
+**   <ol>
+**     <li><b>sqlite3_backup_init()</b> is called once to initialize the
+**         backup,
+**     <li><b>sqlite3_backup_step()</b> is called one or more times to transfer
+**         the data between the two databases, and finally
+**     <li><b>sqlite3_backup_finish()</b> is called to release all resources
+**         associated with the backup operation.
+**   </ol>)^
+** There should be exactly one call to sqlite3_backup_finish() for each
+** successful call to sqlite3_backup_init().
+**
+** [[sqlite3_backup_init()]] <b>sqlite3_backup_init()</b>
+**
+** ^The D and N arguments to sqlite3_backup_init(D,N,S,M) are the
+** [database connection] associated with the destination database
+** and the database name, respectively.
+** ^The database name is "main" for the main database, "temp" for the
+** temporary database, or the name specified after the AS keyword in
+** an [ATTACH] statement for an attached database.
+** ^The S and M arguments passed to
+** sqlite3_backup_init(D,N,S,M) identify the [database connection]
+** and database name of the source database, respectively.
+** ^The source and destination [database connections] (parameters S and D)
+** must be different or else sqlite3_backup_init(D,N,S,M) will fail with
+** an error.
+**
+** ^A call to sqlite3_backup_init() will fail, returning NULL, if
+** there is already a read or read-write transaction open on the
+** destination database.
+**
+** ^If an error occurs within sqlite3_backup_init(D,N,S,M), then NULL is
+** returned and an error code and error message are stored in the
+** destination [database connection] D.
+** ^The error code and message for the failed call to sqlite3_backup_init()
+** can be retrieved using the [sqlite3_errcode()], [sqlite3_errmsg()], and/or
+** [sqlite3_errmsg16()] functions.
+** ^A successful call to sqlite3_backup_init() returns a pointer to an
+** [sqlite3_backup] object.
+** ^The [sqlite3_backup] object may be used with the sqlite3_backup_step() and
+** sqlite3_backup_finish() functions to perform the specified backup
+** operation.
+**
+** [[sqlite3_backup_step()]] <b>sqlite3_backup_step()</b>
+**
+** ^Function sqlite3_backup_step(B,N) will copy up to N pages between
+** the source and destination databases specified by [sqlite3_backup] object B.
+** ^If N is negative, all remaining source pages are copied.
+** ^If sqlite3_backup_step(B,N) successfully copies N pages and there
+** are still more pages to be copied, then the function returns [SQLITE_OK].
+** ^If sqlite3_backup_step(B,N) successfully finishes copying all pages
+** from source to destination, then it returns [SQLITE_DONE].
+** ^If an error occurs while running sqlite3_backup_step(B,N),
+** then an [error code] is returned. ^As well as [SQLITE_OK] and
+** [SQLITE_DONE], a call to sqlite3_backup_step() may return [SQLITE_READONLY],
+** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
+** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
+**
+** ^(The sqlite3_backup_step() might return [SQLITE_READONLY] if
+** <ol>
+** <li> the destination database was opened read-only, or
+** <li> the destination database is using write-ahead-log journaling
+** and the destination and source page sizes differ, or
+** <li> the destination database is an in-memory database and the
+** destination and source page sizes differ.
+** </ol>)^
+**
+** ^If sqlite3_backup_step() cannot obtain a required file-system lock, then
+** the [sqlite3_busy_handler | busy-handler function]
+** is invoked (if one is specified). ^If the
+** busy-handler returns non-zero before the lock is available, then
+** [SQLITE_BUSY] is returned to the caller. ^In this case the call to
+** sqlite3_backup_step() can be retried later. ^If the source
+** [database connection]
+** is being used to write to the source database when sqlite3_backup_step()
+** is called, then [SQLITE_LOCKED] is returned immediately. ^Again, in this
+** case the call to sqlite3_backup_step() can be retried later on. ^(If
+** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX], [SQLITE_NOMEM], or
+** [SQLITE_READONLY] is returned, then
+** there is no point in retrying the call to sqlite3_backup_step(). These
+** errors are considered fatal.)^  The application must accept
+** that the backup operation has failed and pass the backup operation handle
+** to the sqlite3_backup_finish() to release associated resources.
+**
+** ^The first call to sqlite3_backup_step() obtains an exclusive lock
+** on the destination file. ^The exclusive lock is not released until either
+** sqlite3_backup_finish() is called or the backup operation is complete
+** and sqlite3_backup_step() returns [SQLITE_DONE].  ^Every call to
+** sqlite3_backup_step() obtains a [shared lock] on the source database that
+** lasts for the duration of the sqlite3_backup_step() call.
+** ^Because the source database is not locked between calls to
+** sqlite3_backup_step(), the source database may be modified mid-way
+** through the backup process.  ^If the source database is modified by an
+** external process or via a database connection other than the one being
+** used by the backup operation, then the backup will be automatically
+** restarted by the next call to sqlite3_backup_step(). ^If the source
+** database is modified by the using the same database connection as is used
+** by the backup operation, then the backup database is automatically
+** updated at the same time.
+**
+** [[sqlite3_backup_finish()]] <b>sqlite3_backup_finish()</b>
+**
+** When sqlite3_backup_step() has returned [SQLITE_DONE], or when the
+** application wishes to abandon the backup operation, the application
+** should destroy the [sqlite3_backup] by passing it to sqlite3_backup_finish().
+** ^The sqlite3_backup_finish() interfaces releases all
+** resources associated with the [sqlite3_backup] object.
+** ^If sqlite3_backup_step() has not yet returned [SQLITE_DONE], then any
+** active write-transaction on the destination database is rolled back.
+** The [sqlite3_backup] object is invalid
+** and may not be used following a call to sqlite3_backup_finish().
+**
+** ^The value returned by sqlite3_backup_finish is [SQLITE_OK] if no
+** sqlite3_backup_step() errors occurred, regardless or whether or not
+** sqlite3_backup_step() completed.
+** ^If an out-of-memory condition or IO error occurred during any prior
+** sqlite3_backup_step() call on the same [sqlite3_backup] object, then
+** sqlite3_backup_finish() returns the corresponding [error code].
+**
+** ^A return of [SQLITE_BUSY] or [SQLITE_LOCKED] from sqlite3_backup_step()
+** is not a permanent error and does not affect the return value of
+** sqlite3_backup_finish().
+**
+** [[sqlite3_backup_remaining()]] [[sqlite3_backup_pagecount()]]
+** <b>sqlite3_backup_remaining() and sqlite3_backup_pagecount()</b>
+**
+** ^The sqlite3_backup_remaining() routine returns the number of pages still
+** to be backed up at the conclusion of the most recent sqlite3_backup_step().
+** ^The sqlite3_backup_pagecount() routine returns the total number of pages
+** in the source database at the conclusion of the most recent
+** sqlite3_backup_step().
+** ^(The values returned by these functions are only updated by
+** sqlite3_backup_step(). If the source database is modified in a way that
+** changes the size of the source database or the number of pages remaining,
+** those changes are not reflected in the output of sqlite3_backup_pagecount()
+** and sqlite3_backup_remaining() until after the next
+** sqlite3_backup_step().)^
+**
+** <b>Concurrent Usage of Database Handles</b>
+**
+** ^The source [database connection] may be used by the application for other
+** purposes while a backup operation is underway or being initialized.
+** ^If SQLite is compiled and configured to support threadsafe database
+** connections, then the source database connection may be used concurrently
+** from within other threads.
+**
+** However, the application must guarantee that the destination
+** [database connection] is not passed to any other API (by any thread) after
+** sqlite3_backup_init() is called and before the corresponding call to
+** sqlite3_backup_finish().  SQLite does not currently check to see
+** if the application incorrectly accesses the destination [database connection]
+** and so no error code is reported, but the operations may malfunction
+** nevertheless.  Use of the destination database connection while a
+** backup is in progress might also cause a mutex deadlock.
+**
+** If running in [shared cache mode], the application must
+** guarantee that the shared cache used by the destination database
+** is not accessed while the backup is running. In practice this means
+** that the application must guarantee that the disk file being
+** backed up to is not accessed by any connection within the process,
+** not just the specific connection that was passed to sqlite3_backup_init().
+**
+** The [sqlite3_backup] object itself is partially threadsafe. Multiple
+** threads may safely make multiple concurrent calls to sqlite3_backup_step().
+** However, the sqlite3_backup_remaining() and sqlite3_backup_pagecount()
+** APIs are not strictly speaking threadsafe. If they are invoked at the
+** same time as another thread is invoking sqlite3_backup_step() it is
+** possible that they return invalid values.
+*/
+sqlite3_backup *sqlite3_backup_init(
+  sqlite3 *pDest,                        /* Destination database handle */
+  const char *zDestName,                 /* Destination database name */
+  sqlite3 *pSource,                      /* Source database handle */
+  const char *zSourceName                /* Source database name */
+);
+int sqlite3_backup_step(sqlite3_backup *p, int nPage);
+int sqlite3_backup_finish(sqlite3_backup *p);
+int sqlite3_backup_remaining(sqlite3_backup *p);
+int sqlite3_backup_pagecount(sqlite3_backup *p);
+
+/*
+** CAPI3REF: Unlock Notification
+** METHOD: sqlite3
+**
+** ^When running in shared-cache mode, a database operation may fail with
+** an [SQLITE_LOCKED] error if the required locks on the shared-cache or
+** individual tables within the shared-cache cannot be obtained. See
+** [SQLite Shared-Cache Mode] for a description of shared-cache locking.
+** ^This API may be used to register a callback that SQLite will invoke
+** when the connection currently holding the required lock relinquishes it.
+** ^This API is only available if the library was compiled with the
+** [SQLITE_ENABLE_UNLOCK_NOTIFY] C-preprocessor symbol defined.
+**
+** See Also: [Using the SQLite Unlock Notification Feature].
+**
+** ^Shared-cache locks are released when a database connection concludes
+** its current transaction, either by committing it or rolling it back.
+**
+** ^When a connection (known as the blocked connection) fails to obtain a
+** shared-cache lock and SQLITE_LOCKED is returned to the caller, the
+** identity of the database connection (the blocking connection) that
+** has locked the required resource is stored internally. ^After an
+** application receives an SQLITE_LOCKED error, it may call the
+** sqlite3_unlock_notify() method with the blocked connection handle as
+** the first argument to register for a callback that will be invoked
+** when the blocking connections current transaction is concluded. ^The
+** callback is invoked from within the [sqlite3_step] or [sqlite3_close]
+** call that concludes the blocking connection's transaction.
+**
+** ^(If sqlite3_unlock_notify() is called in a multi-threaded application,
+** there is a chance that the blocking connection will have already
+** concluded its transaction by the time sqlite3_unlock_notify() is invoked.
+** If this happens, then the specified callback is invoked immediately,
+** from within the call to sqlite3_unlock_notify().)^
+**
+** ^If the blocked connection is attempting to obtain a write-lock on a
+** shared-cache table, and more than one other connection currently holds
+** a read-lock on the same table, then SQLite arbitrarily selects one of
+** the other connections to use as the blocking connection.
+**
+** ^(There may be at most one unlock-notify callback registered by a
+** blocked connection. If sqlite3_unlock_notify() is called when the
+** blocked connection already has a registered unlock-notify callback,
+** then the new callback replaces the old.)^ ^If sqlite3_unlock_notify() is
+** called with a NULL pointer as its second argument, then any existing
+** unlock-notify callback is canceled. ^The blocked connections
+** unlock-notify callback may also be canceled by closing the blocked
+** connection using [sqlite3_close()].
+**
+** The unlock-notify callback is not reentrant. If an application invokes
+** any sqlite3_xxx API functions from within an unlock-notify callback, a
+** crash or deadlock may be the result.
+**
+** ^Unless deadlock is detected (see below), sqlite3_unlock_notify() always
+** returns SQLITE_OK.
+**
+** <b>Callback Invocation Details</b>
+**
+** When an unlock-notify callback is registered, the application provides a
+** single void* pointer that is passed to the callback when it is invoked.
+** However, the signature of the callback function allows SQLite to pass
+** it an array of void* context pointers. The first argument passed to
+** an unlock-notify callback is a pointer to an array of void* pointers,
+** and the second is the number of entries in the array.
+**
+** When a blocking connection's transaction is concluded, there may be
+** more than one blocked connection that has registered for an unlock-notify
+** callback. ^If two or more such blocked connections have specified the
+** same callback function, then instead of invoking the callback function
+** multiple times, it is invoked once with the set of void* context pointers
+** specified by the blocked connections bundled together into an array.
+** This gives the application an opportunity to prioritize any actions
+** related to the set of unblocked database connections.
+**
+** <b>Deadlock Detection</b>
+**
+** Assuming that after registering for an unlock-notify callback a
+** database waits for the callback to be issued before taking any further
+** action (a reasonable assumption), then using this API may cause the
+** application to deadlock. For example, if connection X is waiting for
+** connection Y's transaction to be concluded, and similarly connection
+** Y is waiting on connection X's transaction, then neither connection
+** will proceed and the system may remain deadlocked indefinitely.
+**
+** To avoid this scenario, the sqlite3_unlock_notify() performs deadlock
+** detection. ^If a given call to sqlite3_unlock_notify() would put the
+** system in a deadlocked state, then SQLITE_LOCKED is returned and no
+** unlock-notify callback is registered. The system is said to be in
+** a deadlocked state if connection A has registered for an unlock-notify
+** callback on the conclusion of connection B's transaction, and connection
+** B has itself registered for an unlock-notify callback when connection
+** A's transaction is concluded. ^Indirect deadlock is also detected, so
+** the system is also considered to be deadlocked if connection B has
+** registered for an unlock-notify callback on the conclusion of connection
+** C's transaction, where connection C is waiting on connection A. ^Any
+** number of levels of indirection are allowed.
+**
+** <b>The "DROP TABLE" Exception</b>
+**
+** When a call to [sqlite3_step()] returns SQLITE_LOCKED, it is almost
+** always appropriate to call sqlite3_unlock_notify(). There is however,
+** one exception. When executing a "DROP TABLE" or "DROP INDEX" statement,
+** SQLite checks if there are any currently executing SELECT statements
+** that belong to the same connection. If there are, SQLITE_LOCKED is
+** returned. In this case there is no "blocking connection", so invoking
+** sqlite3_unlock_notify() results in the unlock-notify callback being
+** invoked immediately. If the application then re-attempts the "DROP TABLE"
+** or "DROP INDEX" query, an infinite loop might be the result.
+**
+** One way around this problem is to check the extended error code returned
+** by an sqlite3_step() call. ^(If there is a blocking connection, then the
+** extended error code is set to SQLITE_LOCKED_SHAREDCACHE. Otherwise, in
+** the special "DROP TABLE/INDEX" case, the extended error code is just
+** SQLITE_LOCKED.)^
+*/
+int sqlite3_unlock_notify(
+  sqlite3 *pBlocked,                          /* Waiting connection */
+  void (*xNotify)(void **apArg, int nArg),    /* Callback function to invoke */
+  void *pNotifyArg                            /* Argument to pass to xNotify */
+);
+
+
+/*
+** CAPI3REF: String Comparison
+**
+** ^The [sqlite3_stricmp()] and [sqlite3_strnicmp()] APIs allow applications
+** and extensions to compare the contents of two buffers containing UTF-8
+** strings in a case-independent fashion, using the same definition of "case
+** independence" that SQLite uses internally when comparing identifiers.
+*/
+int sqlite3_stricmp(const char *, const char *);
+int sqlite3_strnicmp(const char *, const char *, int);
+
+/*
+** CAPI3REF: String Globbing
+*
+** ^The [sqlite3_strglob(P,X)] interface returns zero if and only if
+** string X matches the [GLOB] pattern P.
+** ^The definition of [GLOB] pattern matching used in
+** [sqlite3_strglob(P,X)] is the same as for the "X GLOB P" operator in the
+** SQL dialect understood by SQLite.  ^The [sqlite3_strglob(P,X)] function
+** is case sensitive.
+**
+** Note that this routine returns zero on a match and non-zero if the strings
+** do not match, the same as [sqlite3_stricmp()] and [sqlite3_strnicmp()].
+**
+** See also: [sqlite3_strlike()].
+*/
+int sqlite3_strglob(const char *zGlob, const char *zStr);
+
+/*
+** CAPI3REF: String LIKE Matching
+*
+** ^The [sqlite3_strlike(P,X,E)] interface returns zero if and only if
+** string X matches the [LIKE] pattern P with escape character E.
+** ^The definition of [LIKE] pattern matching used in
+** [sqlite3_strlike(P,X,E)] is the same as for the "X LIKE P ESCAPE E"
+** operator in the SQL dialect understood by SQLite.  ^For "X LIKE P" without
+** the ESCAPE clause, set the E parameter of [sqlite3_strlike(P,X,E)] to 0.
+** ^As with the LIKE operator, the [sqlite3_strlike(P,X,E)] function is case
+** insensitive - equivalent upper and lower case ASCII characters match
+** one another.
+**
+** ^The [sqlite3_strlike(P,X,E)] function matches Unicode characters, though
+** only ASCII characters are case folded.
+**
+** Note that this routine returns zero on a match and non-zero if the strings
+** do not match, the same as [sqlite3_stricmp()] and [sqlite3_strnicmp()].
+**
+** See also: [sqlite3_strglob()].
+*/
+int sqlite3_strlike(const char *zGlob, const char *zStr, unsigned int cEsc);
+
+/*
+** CAPI3REF: Error Logging Interface
+**
+** ^The [sqlite3_log()] interface writes a message into the [error log]
+** established by the [SQLITE_CONFIG_LOG] option to [sqlite3_config()].
+** ^If logging is enabled, the zFormat string and subsequent arguments are
+** used with [sqlite3_snprintf()] to generate the final output string.
+**
+** The sqlite3_log() interface is intended for use by extensions such as
+** virtual tables, collating functions, and SQL functions.  While there is
+** nothing to prevent an application from calling sqlite3_log(), doing so
+** is considered bad form.
+**
+** The zFormat string must not be NULL.
+**
+** To avoid deadlocks and other threading problems, the sqlite3_log() routine
+** will not use dynamically allocated memory.  The log message is stored in
+** a fixed-length buffer on the stack.  If the log message is longer than
+** a few hundred characters, it will be truncated to the length of the
+** buffer.
+*/
+void sqlite3_log(int iErrCode, const char *zFormat, ...);
+
+/*
+** CAPI3REF: Write-Ahead Log Commit Hook
+** METHOD: sqlite3
+**
+** ^The [sqlite3_wal_hook()] function is used to register a callback that
+** is invoked each time data is committed to a database in wal mode.
+**
+** ^(The callback is invoked by SQLite after the commit has taken place and
+** the associated write-lock on the database released)^, so the implementation
+** may read, write or [checkpoint] the database as required.
+**
+** ^The first parameter passed to the callback function when it is invoked
+** is a copy of the third parameter passed to sqlite3_wal_hook() when
+** registering the callback. ^The second is a copy of the database handle.
+** ^The third parameter is the name of the database that was written to -
+** either "main" or the name of an [ATTACH]-ed database. ^The fourth parameter
+** is the number of pages currently in the write-ahead log file,
+** including those that were just committed.
+**
+** The callback function should normally return [SQLITE_OK].  ^If an error
+** code is returned, that error will propagate back up through the
+** SQLite code base to cause the statement that provoked the callback
+** to report an error, though the commit will have still occurred. If the
+** callback returns [SQLITE_ROW] or [SQLITE_DONE], or if it returns a value
+** that does not correspond to any valid SQLite error code, the results
+** are undefined.
+**
+** A single database handle may have at most a single write-ahead log callback
+** registered at one time. ^Calling [sqlite3_wal_hook()] replaces any
+** previously registered write-ahead log callback. ^The return value is
+** a copy of the third parameter from the previous call, if any, or 0.
+** ^Note that the [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] both invoke [sqlite3_wal_hook()] and will
+** overwrite any prior [sqlite3_wal_hook()] settings.
+*/
+void *sqlite3_wal_hook(
+  sqlite3*,
+  int(*)(void *,sqlite3*,const char*,int),
+  void*
+);
+
+/*
+** CAPI3REF: Configure an auto-checkpoint
+** METHOD: sqlite3
+**
+** ^The [sqlite3_wal_autocheckpoint(D,N)] is a wrapper around
+** [sqlite3_wal_hook()] that causes any database on [database connection] D
+** to automatically [checkpoint]
+** after committing a transaction if there are N or
+** more frames in the [write-ahead log] file.  ^Passing zero or
+** a negative value as the nFrame parameter disables automatic
+** checkpoints entirely.
+**
+** ^The callback registered by this function replaces any existing callback
+** registered using [sqlite3_wal_hook()].  ^Likewise, registering a callback
+** using [sqlite3_wal_hook()] disables the automatic checkpoint mechanism
+** configured by this function.
+**
+** ^The [wal_autocheckpoint pragma] can be used to invoke this interface
+** from SQL.
+**
+** ^Checkpoints initiated by this mechanism are
+** [sqlite3_wal_checkpoint_v2|PASSIVE].
+**
+** ^Every new [database connection] defaults to having the auto-checkpoint
+** enabled with a threshold of 1000 or [SQLITE_DEFAULT_WAL_AUTOCHECKPOINT]
+** pages.  The use of this interface
+** is only necessary if the default setting is found to be suboptimal
+** for a particular application.
+*/
+int sqlite3_wal_autocheckpoint(sqlite3 *db, int N);
+
+/*
+** CAPI3REF: Checkpoint a database
+** METHOD: sqlite3
+**
+** ^(The sqlite3_wal_checkpoint(D,X) is equivalent to
+** [sqlite3_wal_checkpoint_v2](D,X,[SQLITE_CHECKPOINT_PASSIVE],0,0).)^
+**
+** In brief, sqlite3_wal_checkpoint(D,X) causes the content in the
+** [write-ahead log] for database X on [database connection] D to be
+** transferred into the database file and for the write-ahead log to
+** be reset.  See the [checkpointing] documentation for addition
+** information.
+**
+** This interface used to be the only way to cause a checkpoint to
+** occur.  But then the newer and more powerful [sqlite3_wal_checkpoint_v2()]
+** interface was added.  This interface is retained for backwards
+** compatibility and as a convenience for applications that need to manually
+** start a callback but which do not need the full power (and corresponding
+** complication) of [sqlite3_wal_checkpoint_v2()].
+*/
+int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb);
+
+/*
+** CAPI3REF: Checkpoint a database
+** METHOD: sqlite3
+**
+** ^(The sqlite3_wal_checkpoint_v2(D,X,M,L,C) interface runs a checkpoint
+** operation on database X of [database connection] D in mode M.  Status
+** information is written back into integers pointed to by L and C.)^
+** ^(The M parameter must be a valid [checkpoint mode]:)^
+**
+** <dl>
+** <dt>SQLITE_CHECKPOINT_PASSIVE<dd>
+**   ^Checkpoint as many frames as possible without waiting for any database
+**   readers or writers to finish, then sync the database file if all frames
+**   in the log were checkpointed. ^The [busy-handler callback]
+**   is never invoked in the SQLITE_CHECKPOINT_PASSIVE mode. 
+**   ^On the other hand, passive mode might leave the checkpoint unfinished
+**   if there are concurrent readers or writers.
+**
+** <dt>SQLITE_CHECKPOINT_FULL<dd>
+**   ^This mode blocks (it invokes the
+**   [sqlite3_busy_handler|busy-handler callback]) until there is no
+**   database writer and all readers are reading from the most recent database
+**   snapshot. ^It then checkpoints all frames in the log file and syncs the
+**   database file. ^This mode blocks new database writers while it is pending,
+**   but new database readers are allowed to continue unimpeded.
+**
+** <dt>SQLITE_CHECKPOINT_RESTART<dd>
+**   ^This mode works the same way as SQLITE_CHECKPOINT_FULL with the addition
+**   that after checkpointing the log file it blocks (calls the
+**   [busy-handler callback])
+**   until all readers are reading from the database file only. ^This ensures
+**   that the next writer will restart the log file from the beginning.
+**   ^Like SQLITE_CHECKPOINT_FULL, this mode blocks new
+**   database writer attempts while it is pending, but does not impede readers.
+**
+** <dt>SQLITE_CHECKPOINT_TRUNCATE<dd>
+**   ^This mode works the same way as SQLITE_CHECKPOINT_RESTART with the
+**   addition that it also truncates the log file to zero bytes just prior
+**   to a successful return.
+** </dl>
+**
+** ^If pnLog is not NULL, then *pnLog is set to the total number of frames in
+** the log file or to -1 if the checkpoint could not run because
+** of an error or because the database is not in [WAL mode]. ^If pnCkpt is not
+** NULL,then *pnCkpt is set to the total number of checkpointed frames in the
+** log file (including any that were already checkpointed before the function
+** was called) or to -1 if the checkpoint could not run due to an error or
+** because the database is not in WAL mode. ^Note that upon successful
+** completion of an SQLITE_CHECKPOINT_TRUNCATE, the log file will have been
+** truncated to zero bytes and so both *pnLog and *pnCkpt will be set to zero.
+**
+** ^All calls obtain an exclusive "checkpoint" lock on the database file. ^If
+** any other process is running a checkpoint operation at the same time, the
+** lock cannot be obtained and SQLITE_BUSY is returned. ^Even if there is a
+** busy-handler configured, it will not be invoked in this case.
+**
+** ^The SQLITE_CHECKPOINT_FULL, RESTART and TRUNCATE modes also obtain the
+** exclusive "writer" lock on the database file. ^If the writer lock cannot be
+** obtained immediately, and a busy-handler is configured, it is invoked and
+** the writer lock retried until either the busy-handler returns 0 or the lock
+** is successfully obtained. ^The busy-handler is also invoked while waiting for
+** database readers as described above. ^If the busy-handler returns 0 before
+** the writer lock is obtained or while waiting for database readers, the
+** checkpoint operation proceeds from that point in the same way as
+** SQLITE_CHECKPOINT_PASSIVE - checkpointing as many frames as possible
+** without blocking any further. ^SQLITE_BUSY is returned in this case.
+**
+** ^If parameter zDb is NULL or points to a zero length string, then the
+** specified operation is attempted on all WAL databases [attached] to
+** [database connection] db.  In this case the
+** values written to output parameters *pnLog and *pnCkpt are undefined. ^If
+** an SQLITE_BUSY error is encountered when processing one or more of the
+** attached WAL databases, the operation is still attempted on any remaining
+** attached databases and SQLITE_BUSY is returned at the end. ^If any other
+** error occurs while processing an attached database, processing is abandoned
+** and the error code is returned to the caller immediately. ^If no error
+** (SQLITE_BUSY or otherwise) is encountered while processing the attached
+** databases, SQLITE_OK is returned.
+**
+** ^If database zDb is the name of an attached database that is not in WAL
+** mode, SQLITE_OK is returned and both *pnLog and *pnCkpt set to -1. ^If
+** zDb is not NULL (or a zero length string) and is not the name of any
+** attached database, SQLITE_ERROR is returned to the caller.
+**
+** ^Unless it returns SQLITE_MISUSE,
+** the sqlite3_wal_checkpoint_v2() interface
+** sets the error information that is queried by
+** [sqlite3_errcode()] and [sqlite3_errmsg()].
+**
+** ^The [PRAGMA wal_checkpoint] command can be used to invoke this interface
+** from SQL.
+*/
+int sqlite3_wal_checkpoint_v2(
+  sqlite3 *db,                    /* Database handle */
+  const char *zDb,                /* Name of attached database (or NULL) */
+  int eMode,                      /* SQLITE_CHECKPOINT_* value */
+  int *pnLog,                     /* OUT: Size of WAL log in frames */
+  int *pnCkpt                     /* OUT: Total number of frames checkpointed */
+);
+
+/*
+** CAPI3REF: Checkpoint Mode Values
+** KEYWORDS: {checkpoint mode}
+**
+** These constants define all valid values for the "checkpoint mode" passed
+** as the third parameter to the [sqlite3_wal_checkpoint_v2()] interface.
+** See the [sqlite3_wal_checkpoint_v2()] documentation for details on the
+** meaning of each of these checkpoint modes.
+*/
+#define SQLITE_CHECKPOINT_PASSIVE  0  /* Do as much as possible w/o blocking */
+#define SQLITE_CHECKPOINT_FULL     1  /* Wait for writers, then checkpoint */
+#define SQLITE_CHECKPOINT_RESTART  2  /* Like FULL but wait for readers */
+#define SQLITE_CHECKPOINT_TRUNCATE 3  /* Like RESTART but also truncate WAL */
+
+/*
+** CAPI3REF: Virtual Table Interface Configuration
+**
+** This function may be called by either the [xConnect] or [xCreate] method
+** of a [virtual table] implementation to configure
+** various facets of the virtual table interface.
+**
+** If this interface is invoked outside the context of an xConnect or
+** xCreate virtual table method then the behavior is undefined.
+**
+** In the call sqlite3_vtab_config(D,C,...) the D parameter is the
+** [database connection] in which the virtual table is being created and
+** which is passed in as the first argument to the [xConnect] or [xCreate]
+** method that is invoking sqlite3_vtab_config().  The C parameter is one
+** of the [virtual table configuration options].  The presence and meaning
+** of parameters after C depend on which [virtual table configuration option]
+** is used.
+*/
+int sqlite3_vtab_config(sqlite3*, int op, ...);
+
+/*
+** CAPI3REF: Virtual Table Configuration Options
+** KEYWORDS: {virtual table configuration options}
+** KEYWORDS: {virtual table configuration option}
+**
+** These macros define the various options to the
+** [sqlite3_vtab_config()] interface that [virtual table] implementations
+** can use to customize and optimize their behavior.
+**
+** <dl>
+** [[SQLITE_VTAB_CONSTRAINT_SUPPORT]]
+** <dt>SQLITE_VTAB_CONSTRAINT_SUPPORT</dt>
+** <dd>Calls of the form
+** [sqlite3_vtab_config](db,SQLITE_VTAB_CONSTRAINT_SUPPORT,X) are supported,
+** where X is an integer.  If X is zero, then the [virtual table] whose
+** [xCreate] or [xConnect] method invoked [sqlite3_vtab_config()] does not
+** support constraints.  In this configuration (which is the default) if
+** a call to the [xUpdate] method returns [SQLITE_CONSTRAINT], then the entire
+** statement is rolled back as if [ON CONFLICT | OR ABORT] had been
+** specified as part of the users SQL statement, regardless of the actual
+** ON CONFLICT mode specified.
+**
+** If X is non-zero, then the virtual table implementation guarantees
+** that if [xUpdate] returns [SQLITE_CONSTRAINT], it will do so before
+** any modifications to internal or persistent data structures have been made.
+** If the [ON CONFLICT] mode is ABORT, FAIL, IGNORE or ROLLBACK, SQLite
+** is able to roll back a statement or database transaction, and abandon
+** or continue processing the current SQL statement as appropriate.
+** If the ON CONFLICT mode is REPLACE and the [xUpdate] method returns
+** [SQLITE_CONSTRAINT], SQLite handles this as if the ON CONFLICT mode
+** had been ABORT.
+**
+** Virtual table implementations that are required to handle OR REPLACE
+** must do so within the [xUpdate] method. If a call to the
+** [sqlite3_vtab_on_conflict()] function indicates that the current ON
+** CONFLICT policy is REPLACE, the virtual table implementation should
+** silently replace the appropriate rows within the xUpdate callback and
+** return SQLITE_OK. Or, if this is not possible, it may return
+** SQLITE_CONSTRAINT, in which case SQLite falls back to OR ABORT
+** constraint handling.
+** </dd>
+**
+** [[SQLITE_VTAB_DIRECTONLY]]<dt>SQLITE_VTAB_DIRECTONLY</dt>
+** <dd>Calls of the form
+** [sqlite3_vtab_config](db,SQLITE_VTAB_DIRECTONLY) from within the
+** the [xConnect] or [xCreate] methods of a [virtual table] implementation
+** prohibits that virtual table from being used from within triggers and
+** views.
+** </dd>
+**
+** [[SQLITE_VTAB_INNOCUOUS]]<dt>SQLITE_VTAB_INNOCUOUS</dt>
+** <dd>Calls of the form
+** [sqlite3_vtab_config](db,SQLITE_VTAB_INNOCUOUS) from within the
+** the [xConnect] or [xCreate] methods of a [virtual table] implementation
+** identify that virtual table as being safe to use from within triggers
+** and views.  Conceptually, the SQLITE_VTAB_INNOCUOUS tag means that the
+** virtual table can do no serious harm even if it is controlled by a
+** malicious hacker.  Developers should avoid setting the SQLITE_VTAB_INNOCUOUS
+** flag unless absolutely necessary.
+** </dd>
+**
+** [[SQLITE_VTAB_USES_ALL_SCHEMAS]]<dt>SQLITE_VTAB_USES_ALL_SCHEMAS</dt>
+** <dd>Calls of the form
+** [sqlite3_vtab_config](db,SQLITE_VTAB_USES_ALL_SCHEMA) from within the
+** the [xConnect] or [xCreate] methods of a [virtual table] implementation
+** instruct the query planner to begin at least a read transaction on
+** all schemas ("main", "temp", and any ATTACH-ed databases) whenever the
+** virtual table is used.
+** </dd>
+** </dl>
+*/
+#define SQLITE_VTAB_CONSTRAINT_SUPPORT 1
+#define SQLITE_VTAB_INNOCUOUS          2
+#define SQLITE_VTAB_DIRECTONLY         3
+#define SQLITE_VTAB_USES_ALL_SCHEMAS   4
+
+/*
+** CAPI3REF: Determine The Virtual Table Conflict Policy
+**
+** This function may only be called from within a call to the [xUpdate] method
+** of a [virtual table] implementation for an INSERT or UPDATE operation. ^The
+** value returned is one of [SQLITE_ROLLBACK], [SQLITE_IGNORE], [SQLITE_FAIL],
+** [SQLITE_ABORT], or [SQLITE_REPLACE], according to the [ON CONFLICT] mode
+** of the SQL statement that triggered the call to the [xUpdate] method of the
+** [virtual table].
+*/
+int sqlite3_vtab_on_conflict(sqlite3 *);
+
+/*
+** CAPI3REF: Determine If Virtual Table Column Access Is For UPDATE
+**
+** If the sqlite3_vtab_nochange(X) routine is called within the [xColumn]
+** method of a [virtual table], then it might return true if the
+** column is being fetched as part of an UPDATE operation during which the
+** column value will not change.  The virtual table implementation can use
+** this hint as permission to substitute a return value that is less
+** expensive to compute and that the corresponding
+** [xUpdate] method understands as a "no-change" value.
+**
+** If the [xColumn] method calls sqlite3_vtab_nochange() and finds that
+** the column is not changed by the UPDATE statement, then the xColumn
+** method can optionally return without setting a result, without calling
+** any of the [sqlite3_result_int|sqlite3_result_xxxxx() interfaces].
+** In that case, [sqlite3_value_nochange(X)] will return true for the
+** same column in the [xUpdate] method.
+**
+** The sqlite3_vtab_nochange() routine is an optimization.  Virtual table
+** implementations should continue to give a correct answer even if the
+** sqlite3_vtab_nochange() interface were to always return false.  In the
+** current implementation, the sqlite3_vtab_nochange() interface does always
+** returns false for the enhanced [UPDATE FROM] statement.
+*/
+int sqlite3_vtab_nochange(sqlite3_context*);
+
+/*
+** CAPI3REF: Determine The Collation For a Virtual Table Constraint
+** METHOD: sqlite3_index_info
+**
+** This function may only be called from within a call to the [xBestIndex]
+** method of a [virtual table].  This function returns a pointer to a string
+** that is the name of the appropriate collation sequence to use for text
+** comparisons on the constraint identified by its arguments.
+**
+** The first argument must be the pointer to the [sqlite3_index_info] object
+** that is the first parameter to the xBestIndex() method. The second argument
+** must be an index into the aConstraint[] array belonging to the
+** sqlite3_index_info structure passed to xBestIndex.
+**
+** Important:
+** The first parameter must be the same pointer that is passed into the
+** xBestMethod() method.  The first parameter may not be a pointer to a
+** different [sqlite3_index_info] object, even an exact copy.
+**
+** The return value is computed as follows:
+**
+** <ol>
+** <li><p> If the constraint comes from a WHERE clause expression that contains
+**         a [COLLATE operator], then the name of the collation specified by
+**         that COLLATE operator is returned.
+** <li><p> If there is no COLLATE operator, but the column that is the subject
+**         of the constraint specifies an alternative collating sequence via
+**         a [COLLATE clause] on the column definition within the CREATE TABLE
+**         statement that was passed into [sqlite3_declare_vtab()], then the
+**         name of that alternative collating sequence is returned.
+** <li><p> Otherwise, "BINARY" is returned.
+** </ol>
+*/
+const char *sqlite3_vtab_collation(sqlite3_index_info*,int);
+
+/*
+** CAPI3REF: Determine if a virtual table query is DISTINCT
+** METHOD: sqlite3_index_info
+**
+** This API may only be used from within an [xBestIndex|xBestIndex method]
+** of a [virtual table] implementation. The result of calling this
+** interface from outside of xBestIndex() is undefined and probably harmful.
+**
+** ^The sqlite3_vtab_distinct() interface returns an integer between 0 and
+** 3.  The integer returned by sqlite3_vtab_distinct()
+** gives the virtual table additional information about how the query
+** planner wants the output to be ordered. As long as the virtual table
+** can meet the ordering requirements of the query planner, it may set
+** the "orderByConsumed" flag.
+**
+** <ol><li value="0"><p>
+** ^If the sqlite3_vtab_distinct() interface returns 0, that means
+** that the query planner needs the virtual table to return all rows in the
+** sort order defined by the "nOrderBy" and "aOrderBy" fields of the
+** [sqlite3_index_info] object.  This is the default expectation.  If the
+** virtual table outputs all rows in sorted order, then it is always safe for
+** the xBestIndex method to set the "orderByConsumed" flag, regardless of
+** the return value from sqlite3_vtab_distinct().
+** <li value="1"><p>
+** ^(If the sqlite3_vtab_distinct() interface returns 1, that means
+** that the query planner does not need the rows to be returned in sorted order
+** as long as all rows with the same values in all columns identified by the
+** "aOrderBy" field are adjacent.)^  This mode is used when the query planner
+** is doing a GROUP BY.
+** <li value="2"><p>
+** ^(If the sqlite3_vtab_distinct() interface returns 2, that means
+** that the query planner does not need the rows returned in any particular
+** order, as long as rows with the same values in all "aOrderBy" columns
+** are adjacent.)^  ^(Furthermore, only a single row for each particular
+** combination of values in the columns identified by the "aOrderBy" field
+** needs to be returned.)^  ^It is always ok for two or more rows with the same
+** values in all "aOrderBy" columns to be returned, as long as all such rows
+** are adjacent.  ^The virtual table may, if it chooses, omit extra rows
+** that have the same value for all columns identified by "aOrderBy".
+** ^However omitting the extra rows is optional.
+** This mode is used for a DISTINCT query.
+** <li value="3"><p>
+** ^(If the sqlite3_vtab_distinct() interface returns 3, that means
+** that the query planner needs only distinct rows but it does need the
+** rows to be sorted.)^ ^The virtual table implementation is free to omit
+** rows that are identical in all aOrderBy columns, if it wants to, but
+** it is not required to omit any rows.  This mode is used for queries
+** that have both DISTINCT and ORDER BY clauses.
+** </ol>
+**
+** ^For the purposes of comparing virtual table output values to see if the
+** values are same value for sorting purposes, two NULL values are considered
+** to be the same.  In other words, the comparison operator is "IS"
+** (or "IS NOT DISTINCT FROM") and not "==".
+**
+** If a virtual table implementation is unable to meet the requirements
+** specified above, then it must not set the "orderByConsumed" flag in the
+** [sqlite3_index_info] object or an incorrect answer may result.
+**
+** ^A virtual table implementation is always free to return rows in any order
+** it wants, as long as the "orderByConsumed" flag is not set.  ^When the
+** the "orderByConsumed" flag is unset, the query planner will add extra
+** [bytecode] to ensure that the final results returned by the SQL query are
+** ordered correctly.  The use of the "orderByConsumed" flag and the
+** sqlite3_vtab_distinct() interface is merely an optimization.  ^Careful
+** use of the sqlite3_vtab_distinct() interface and the "orderByConsumed"
+** flag might help queries against a virtual table to run faster.  Being
+** overly aggressive and setting the "orderByConsumed" flag when it is not
+** valid to do so, on the other hand, might cause SQLite to return incorrect
+** results.
+*/
+int sqlite3_vtab_distinct(sqlite3_index_info*);
+
+/*
+** CAPI3REF: Identify and handle IN constraints in xBestIndex
+**
+** This interface may only be used from within an
+** [xBestIndex|xBestIndex() method] of a [virtual table] implementation.
+** The result of invoking this interface from any other context is
+** undefined and probably harmful.
+**
+** ^(A constraint on a virtual table of the form
+** "[IN operator|column IN (...)]" is
+** communicated to the xBestIndex method as a
+** [SQLITE_INDEX_CONSTRAINT_EQ] constraint.)^  If xBestIndex wants to use
+** this constraint, it must set the corresponding
+** aConstraintUsage[].argvIndex to a positive integer.  ^(Then, under
+** the usual mode of handling IN operators, SQLite generates [bytecode]
+** that invokes the [xFilter|xFilter() method] once for each value
+** on the right-hand side of the IN operator.)^  Thus the virtual table
+** only sees a single value from the right-hand side of the IN operator
+** at a time.
+**
+** In some cases, however, it would be advantageous for the virtual
+** table to see all values on the right-hand of the IN operator all at
+** once.  The sqlite3_vtab_in() interfaces facilitates this in two ways:
+**
+** <ol>
+** <li><p>
+**   ^A call to sqlite3_vtab_in(P,N,-1) will return true (non-zero)
+**   if and only if the [sqlite3_index_info|P->aConstraint][N] constraint
+**   is an [IN operator] that can be processed all at once.  ^In other words,
+**   sqlite3_vtab_in() with -1 in the third argument is a mechanism
+**   by which the virtual table can ask SQLite if all-at-once processing
+**   of the IN operator is even possible.
+**
+** <li><p>
+**   ^A call to sqlite3_vtab_in(P,N,F) with F==1 or F==0 indicates
+**   to SQLite that the virtual table does or does not want to process
+**   the IN operator all-at-once, respectively.  ^Thus when the third
+**   parameter (F) is non-negative, this interface is the mechanism by
+**   which the virtual table tells SQLite how it wants to process the
+**   IN operator.
+** </ol>
+**
+** ^The sqlite3_vtab_in(P,N,F) interface can be invoked multiple times
+** within the same xBestIndex method call.  ^For any given P,N pair,
+** the return value from sqlite3_vtab_in(P,N,F) will always be the same
+** within the same xBestIndex call.  ^If the interface returns true
+** (non-zero), that means that the constraint is an IN operator
+** that can be processed all-at-once.  ^If the constraint is not an IN
+** operator or cannot be processed all-at-once, then the interface returns
+** false.
+**
+** ^(All-at-once processing of the IN operator is selected if both of the
+** following conditions are met:
+**
+** <ol>
+** <li><p> The P->aConstraintUsage[N].argvIndex value is set to a positive
+** integer.  This is how the virtual table tells SQLite that it wants to
+** use the N-th constraint.
+**
+** <li><p> The last call to sqlite3_vtab_in(P,N,F) for which F was
+** non-negative had F>=1.
+** </ol>)^
+**
+** ^If either or both of the conditions above are false, then SQLite uses
+** the traditional one-at-a-time processing strategy for the IN constraint.
+** ^If both conditions are true, then the argvIndex-th parameter to the
+** xFilter method will be an [sqlite3_value] that appears to be NULL,
+** but which can be passed to [sqlite3_vtab_in_first()] and
+** [sqlite3_vtab_in_next()] to find all values on the right-hand side
+** of the IN constraint.
+*/
+int sqlite3_vtab_in(sqlite3_index_info*, int iCons, int bHandle);
+
+/*
+** CAPI3REF: Find all elements on the right-hand side of an IN constraint.
+**
+** These interfaces are only useful from within the
+** [xFilter|xFilter() method] of a [virtual table] implementation.
+** The result of invoking these interfaces from any other context
+** is undefined and probably harmful.
+**
+** The X parameter in a call to sqlite3_vtab_in_first(X,P) or
+** sqlite3_vtab_in_next(X,P) should be one of the parameters to the
+** xFilter method which invokes these routines, and specifically
+** a parameter that was previously selected for all-at-once IN constraint
+** processing use the [sqlite3_vtab_in()] interface in the
+** [xBestIndex|xBestIndex method].  ^(If the X parameter is not
+** an xFilter argument that was selected for all-at-once IN constraint
+** processing, then these routines return [SQLITE_ERROR].)^
+**
+** ^(Use these routines to access all values on the right-hand side
+** of the IN constraint using code like the following:
+**
+** <blockquote><pre>
+** &nbsp;  for(rc=sqlite3_vtab_in_first(pList, &pVal);
+** &nbsp;      rc==SQLITE_OK && pVal;
+** &nbsp;      rc=sqlite3_vtab_in_next(pList, &pVal)
+** &nbsp;  ){
+** &nbsp;    // do something with pVal
+** &nbsp;  }
+** &nbsp;  if( rc!=SQLITE_OK ){
+** &nbsp;    // an error has occurred
+** &nbsp;  }
+** </pre></blockquote>)^
+**
+** ^On success, the sqlite3_vtab_in_first(X,P) and sqlite3_vtab_in_next(X,P)
+** routines return SQLITE_OK and set *P to point to the first or next value
+** on the RHS of the IN constraint.  ^If there are no more values on the
+** right hand side of the IN constraint, then *P is set to NULL and these
+** routines return [SQLITE_DONE].  ^The return value might be
+** some other value, such as SQLITE_NOMEM, in the event of a malfunction.
+**
+** The *ppOut values returned by these routines are only valid until the
+** next call to either of these routines or until the end of the xFilter
+** method from which these routines were called.  If the virtual table
+** implementation needs to retain the *ppOut values for longer, it must make
+** copies.  The *ppOut values are [protected sqlite3_value|protected].
+*/
+int sqlite3_vtab_in_first(sqlite3_value *pVal, sqlite3_value **ppOut);
+int sqlite3_vtab_in_next(sqlite3_value *pVal, sqlite3_value **ppOut);
+
+/*
+** CAPI3REF: Constraint values in xBestIndex()
+** METHOD: sqlite3_index_info
+**
+** This API may only be used from within the [xBestIndex|xBestIndex method]
+** of a [virtual table] implementation. The result of calling this interface
+** from outside of an xBestIndex method are undefined and probably harmful.
+**
+** ^When the sqlite3_vtab_rhs_value(P,J,V) interface is invoked from within
+** the [xBestIndex] method of a [virtual table] implementation, with P being
+** a copy of the [sqlite3_index_info] object pointer passed into xBestIndex and
+** J being a 0-based index into P->aConstraint[], then this routine
+** attempts to set *V to the value of the right-hand operand of
+** that constraint if the right-hand operand is known.  ^If the
+** right-hand operand is not known, then *V is set to a NULL pointer.
+** ^The sqlite3_vtab_rhs_value(P,J,V) interface returns SQLITE_OK if
+** and only if *V is set to a value.  ^The sqlite3_vtab_rhs_value(P,J,V)
+** inteface returns SQLITE_NOTFOUND if the right-hand side of the J-th
+** constraint is not available.  ^The sqlite3_vtab_rhs_value() interface
+** can return an result code other than SQLITE_OK or SQLITE_NOTFOUND if
+** something goes wrong.
+**
+** The sqlite3_vtab_rhs_value() interface is usually only successful if
+** the right-hand operand of a constraint is a literal value in the original
+** SQL statement.  If the right-hand operand is an expression or a reference
+** to some other column or a [host parameter], then sqlite3_vtab_rhs_value()
+** will probably return [SQLITE_NOTFOUND].
+**
+** ^(Some constraints, such as [SQLITE_INDEX_CONSTRAINT_ISNULL] and
+** [SQLITE_INDEX_CONSTRAINT_ISNOTNULL], have no right-hand operand.  For such
+** constraints, sqlite3_vtab_rhs_value() always returns SQLITE_NOTFOUND.)^
+**
+** ^The [sqlite3_value] object returned in *V is a protected sqlite3_value
+** and remains valid for the duration of the xBestIndex method call.
+** ^When xBestIndex returns, the sqlite3_value object returned by
+** sqlite3_vtab_rhs_value() is automatically deallocated.
+**
+** The "_rhs_" in the name of this routine is an abbreviation for
+** "Right-Hand Side".
+*/
+int sqlite3_vtab_rhs_value(sqlite3_index_info*, int, sqlite3_value **ppVal);
+
+/*
+** CAPI3REF: Conflict resolution modes
+** KEYWORDS: {conflict resolution mode}
+**
+** These constants are returned by [sqlite3_vtab_on_conflict()] to
+** inform a [virtual table] implementation what the [ON CONFLICT] mode
+** is for the SQL statement being evaluated.
+**
+** Note that the [SQLITE_IGNORE] constant is also used as a potential
+** return value from the [sqlite3_set_authorizer()] callback and that
+** [SQLITE_ABORT] is also a [result code].
+*/
+#define SQLITE_ROLLBACK 1
+/* #define SQLITE_IGNORE 2 // Also used by sqlite3_authorizer() callback */
+#define SQLITE_FAIL     3
+/* #define SQLITE_ABORT 4  // Also an error code */
+#define SQLITE_REPLACE  5
+
+/*
+** CAPI3REF: Prepared Statement Scan Status Opcodes
+** KEYWORDS: {scanstatus options}
+**
+** The following constants can be used for the T parameter to the
+** [sqlite3_stmt_scanstatus(S,X,T,V)] interface.  Each constant designates a
+** different metric for sqlite3_stmt_scanstatus() to return.
+**
+** When the value returned to V is a string, space to hold that string is
+** managed by the prepared statement S and will be automatically freed when
+** S is finalized.
+**
+** Not all values are available for all query elements. When a value is
+** not available, the output variable is set to -1 if the value is numeric,
+** or to NULL if it is a string (SQLITE_SCANSTAT_NAME).
+**
+** <dl>
+** [[SQLITE_SCANSTAT_NLOOP]] <dt>SQLITE_SCANSTAT_NLOOP</dt>
+** <dd>^The [sqlite3_int64] variable pointed to by the V parameter will be
+** set to the total number of times that the X-th loop has run.</dd>
+**
+** [[SQLITE_SCANSTAT_NVISIT]] <dt>SQLITE_SCANSTAT_NVISIT</dt>
+** <dd>^The [sqlite3_int64] variable pointed to by the V parameter will be set
+** to the total number of rows examined by all iterations of the X-th loop.</dd>
+**
+** [[SQLITE_SCANSTAT_EST]] <dt>SQLITE_SCANSTAT_EST</dt>
+** <dd>^The "double" variable pointed to by the V parameter will be set to the
+** query planner's estimate for the average number of rows output from each
+** iteration of the X-th loop.  If the query planner's estimates was accurate,
+** then this value will approximate the quotient NVISIT/NLOOP and the
+** product of this value for all prior loops with the same SELECTID will
+** be the NLOOP value for the current loop.
+**
+** [[SQLITE_SCANSTAT_NAME]] <dt>SQLITE_SCANSTAT_NAME</dt>
+** <dd>^The "const char *" variable pointed to by the V parameter will be set
+** to a zero-terminated UTF-8 string containing the name of the index or table
+** used for the X-th loop.
+**
+** [[SQLITE_SCANSTAT_EXPLAIN]] <dt>SQLITE_SCANSTAT_EXPLAIN</dt>
+** <dd>^The "const char *" variable pointed to by the V parameter will be set
+** to a zero-terminated UTF-8 string containing the [EXPLAIN QUERY PLAN]
+** description for the X-th loop.
+**
+** [[SQLITE_SCANSTAT_SELECTID]] <dt>SQLITE_SCANSTAT_SELECTID</dt>
+** <dd>^The "int" variable pointed to by the V parameter will be set to the
+** id for the X-th query plan element. The id value is unique within the
+** statement. The select-id is the same value as is output in the first
+** column of an [EXPLAIN QUERY PLAN] query.
+**
+** [[SQLITE_SCANSTAT_PARENTID]] <dt>SQLITE_SCANSTAT_PARENTID</dt>
+** <dd>The "int" variable pointed to by the V parameter will be set to the
+** the id of the parent of the current query element, if applicable, or
+** to zero if the query element has no parent. This is the same value as
+** returned in the second column of an [EXPLAIN QUERY PLAN] query.
+**
+** [[SQLITE_SCANSTAT_NCYCLE]] <dt>SQLITE_SCANSTAT_NCYCLE</dt>
+** <dd>The sqlite3_int64 output value is set to the number of cycles,
+** according to the processor time-stamp counter, that elapsed while the
+** query element was being processed. This value is not available for
+** all query elements - if it is unavailable the output variable is
+** set to -1.
+** </dl>
+*/
+#define SQLITE_SCANSTAT_NLOOP    0
+#define SQLITE_SCANSTAT_NVISIT   1
+#define SQLITE_SCANSTAT_EST      2
+#define SQLITE_SCANSTAT_NAME     3
+#define SQLITE_SCANSTAT_EXPLAIN  4
+#define SQLITE_SCANSTAT_SELECTID 5
+#define SQLITE_SCANSTAT_PARENTID 6
+#define SQLITE_SCANSTAT_NCYCLE   7
+
+/*
+** CAPI3REF: Prepared Statement Scan Status
+** METHOD: sqlite3_stmt
+**
+** These interfaces return information about the predicted and measured
+** performance for pStmt.  Advanced applications can use this
+** interface to compare the predicted and the measured performance and
+** issue warnings and/or rerun [ANALYZE] if discrepancies are found.
+**
+** Since this interface is expected to be rarely used, it is only
+** available if SQLite is compiled using the [SQLITE_ENABLE_STMT_SCANSTATUS]
+** compile-time option.
+**
+** The "iScanStatusOp" parameter determines which status information to return.
+** The "iScanStatusOp" must be one of the [scanstatus options] or the behavior
+** of this interface is undefined. ^The requested measurement is written into
+** a variable pointed to by the "pOut" parameter.
+**
+** The "flags" parameter must be passed a mask of flags. At present only
+** one flag is defined - SQLITE_SCANSTAT_COMPLEX. If SQLITE_SCANSTAT_COMPLEX
+** is specified, then status information is available for all elements
+** of a query plan that are reported by "EXPLAIN QUERY PLAN" output. If
+** SQLITE_SCANSTAT_COMPLEX is not specified, then only query plan elements
+** that correspond to query loops (the "SCAN..." and "SEARCH..." elements of
+** the EXPLAIN QUERY PLAN output) are available. Invoking API
+** sqlite3_stmt_scanstatus() is equivalent to calling
+** sqlite3_stmt_scanstatus_v2() with a zeroed flags parameter.
+**
+** Parameter "idx" identifies the specific query element to retrieve statistics
+** for. Query elements are numbered starting from zero. A value of -1 may be
+** to query for statistics regarding the entire query. ^If idx is out of range
+** - less than -1 or greater than or equal to the total number of query
+** elements used to implement the statement - a non-zero value is returned and
+** the variable that pOut points to is unchanged.
+**
+** See also: [sqlite3_stmt_scanstatus_reset()]
+*/
+int sqlite3_stmt_scanstatus(
+  sqlite3_stmt *pStmt,      /* Prepared statement for which info desired */
+  int idx,                  /* Index of loop to report on */
+  int iScanStatusOp,        /* Information desired.  SQLITE_SCANSTAT_* */
+  void *pOut                /* Result written here */
+);    
+int sqlite3_stmt_scanstatus_v2(
+  sqlite3_stmt *pStmt,      /* Prepared statement for which info desired */
+  int idx,                  /* Index of loop to report on */
+  int iScanStatusOp,        /* Information desired.  SQLITE_SCANSTAT_* */
+  int flags,                /* Mask of flags defined below */
+  void *pOut                /* Result written here */
+);    
+
+/*
+** CAPI3REF: Prepared Statement Scan Status
+** KEYWORDS: {scan status flags}
+*/
+#define SQLITE_SCANSTAT_COMPLEX 0x0001
+
+/*
+** CAPI3REF: Zero Scan-Status Counters
+** METHOD: sqlite3_stmt
+**
+** ^Zero all [sqlite3_stmt_scanstatus()] related event counters.
+**
+** This API is only available if the library is built with pre-processor
+** symbol [SQLITE_ENABLE_STMT_SCANSTATUS] defined.
+*/
+void sqlite3_stmt_scanstatus_reset(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Flush caches to disk mid-transaction
+** METHOD: sqlite3
+**
+** ^If a write-transaction is open on [database connection] D when the
+** [sqlite3_db_cacheflush(D)] interface invoked, any dirty
+** pages in the pager-cache that are not currently in use are written out
+** to disk. A dirty page may be in use if a database cursor created by an
+** active SQL statement is reading from it, or if it is page 1 of a database
+** file (page 1 is always "in use").  ^The [sqlite3_db_cacheflush(D)]
+** interface flushes caches for all schemas - "main", "temp", and
+** any [attached] databases.
+**
+** ^If this function needs to obtain extra database locks before dirty pages
+** can be flushed to disk, it does so. ^If those locks cannot be obtained
+** immediately and there is a busy-handler callback configured, it is invoked
+** in the usual manner. ^If the required lock still cannot be obtained, then
+** the database is skipped and an attempt made to flush any dirty pages
+** belonging to the next (if any) database. ^If any databases are skipped
+** because locks cannot be obtained, but no other error occurs, this
+** function returns SQLITE_BUSY.
+**
+** ^If any other error occurs while flushing dirty pages to disk (for
+** example an IO error or out-of-memory condition), then processing is
+** abandoned and an SQLite [error code] is returned to the caller immediately.
+**
+** ^Otherwise, if no error occurs, [sqlite3_db_cacheflush()] returns SQLITE_OK.
+**
+** ^This function does not set the database handle error code or message
+** returned by the [sqlite3_errcode()] and [sqlite3_errmsg()] functions.
+*/
+int sqlite3_db_cacheflush(sqlite3*);
+
+/*
+** CAPI3REF: The pre-update hook.
+** METHOD: sqlite3
+**
+** ^These interfaces are only available if SQLite is compiled using the
+** [SQLITE_ENABLE_PREUPDATE_HOOK] compile-time option.
+**
+** ^The [sqlite3_preupdate_hook()] interface registers a callback function
+** that is invoked prior to each [INSERT], [UPDATE], and [DELETE] operation
+** on a database table.
+** ^At most one preupdate hook may be registered at a time on a single
+** [database connection]; each call to [sqlite3_preupdate_hook()] overrides
+** the previous setting.
+** ^The preupdate hook is disabled by invoking [sqlite3_preupdate_hook()]
+** with a NULL pointer as the second parameter.
+** ^The third parameter to [sqlite3_preupdate_hook()] is passed through as
+** the first parameter to callbacks.
+**
+** ^The preupdate hook only fires for changes to real database tables; the
+** preupdate hook is not invoked for changes to [virtual tables] or to
+** system tables like sqlite_sequence or sqlite_stat1.
+**
+** ^The second parameter to the preupdate callback is a pointer to
+** the [database connection] that registered the preupdate hook.
+** ^The third parameter to the preupdate callback is one of the constants
+** [SQLITE_INSERT], [SQLITE_DELETE], or [SQLITE_UPDATE] to identify the
+** kind of update operation that is about to occur.
+** ^(The fourth parameter to the preupdate callback is the name of the
+** database within the database connection that is being modified.  This
+** will be "main" for the main database or "temp" for TEMP tables or
+** the name given after the AS keyword in the [ATTACH] statement for attached
+** databases.)^
+** ^The fifth parameter to the preupdate callback is the name of the
+** table that is being modified.
+**
+** For an UPDATE or DELETE operation on a [rowid table], the sixth
+** parameter passed to the preupdate callback is the initial [rowid] of the
+** row being modified or deleted. For an INSERT operation on a rowid table,
+** or any operation on a WITHOUT ROWID table, the value of the sixth
+** parameter is undefined. For an INSERT or UPDATE on a rowid table the
+** seventh parameter is the final rowid value of the row being inserted
+** or updated. The value of the seventh parameter passed to the callback
+** function is not defined for operations on WITHOUT ROWID tables, or for
+** DELETE operations on rowid tables.
+**
+** ^The sqlite3_preupdate_hook(D,C,P) function returns the P argument from
+** the previous call on the same [database connection] D, or NULL for
+** the first call on D.
+**
+** The [sqlite3_preupdate_old()], [sqlite3_preupdate_new()],
+** [sqlite3_preupdate_count()], and [sqlite3_preupdate_depth()] interfaces
+** provide additional information about a preupdate event. These routines
+** may only be called from within a preupdate callback.  Invoking any of
+** these routines from outside of a preupdate callback or with a
+** [database connection] pointer that is different from the one supplied
+** to the preupdate callback results in undefined and probably undesirable
+** behavior.
+**
+** ^The [sqlite3_preupdate_count(D)] interface returns the number of columns
+** in the row that is being inserted, updated, or deleted.
+**
+** ^The [sqlite3_preupdate_old(D,N,P)] interface writes into P a pointer to
+** a [protected sqlite3_value] that contains the value of the Nth column of
+** the table row before it is updated.  The N parameter must be between 0
+** and one less than the number of columns or the behavior will be
+** undefined. This must only be used within SQLITE_UPDATE and SQLITE_DELETE
+** preupdate callbacks; if it is used by an SQLITE_INSERT callback then the
+** behavior is undefined.  The [sqlite3_value] that P points to
+** will be destroyed when the preupdate callback returns.
+**
+** ^The [sqlite3_preupdate_new(D,N,P)] interface writes into P a pointer to
+** a [protected sqlite3_value] that contains the value of the Nth column of
+** the table row after it is updated.  The N parameter must be between 0
+** and one less than the number of columns or the behavior will be
+** undefined. This must only be used within SQLITE_INSERT and SQLITE_UPDATE
+** preupdate callbacks; if it is used by an SQLITE_DELETE callback then the
+** behavior is undefined.  The [sqlite3_value] that P points to
+** will be destroyed when the preupdate callback returns.
+**
+** ^The [sqlite3_preupdate_depth(D)] interface returns 0 if the preupdate
+** callback was invoked as a result of a direct insert, update, or delete
+** operation; or 1 for inserts, updates, or deletes invoked by top-level
+** triggers; or 2 for changes resulting from triggers called by top-level
+** triggers; and so forth.
+**
+** When the [sqlite3_blob_write()] API is used to update a blob column,
+** the pre-update hook is invoked with SQLITE_DELETE. This is because the
+** in this case the new values are not available. In this case, when a
+** callback made with op==SQLITE_DELETE is actually a write using the
+** sqlite3_blob_write() API, the [sqlite3_preupdate_blobwrite()] returns
+** the index of the column being written. In other cases, where the
+** pre-update hook is being invoked for some other reason, including a
+** regular DELETE, sqlite3_preupdate_blobwrite() returns -1.
+**
+** See also:  [sqlite3_update_hook()]
+*/
+#if defined(SQLITE_ENABLE_PREUPDATE_HOOK)
+void *sqlite3_preupdate_hook(
+  sqlite3 *db,
+  void(*xPreUpdate)(
+    void *pCtx,                   /* Copy of third arg to preupdate_hook() */
+    sqlite3 *db,                  /* Database handle */
+    int op,                       /* SQLITE_UPDATE, DELETE or INSERT */
+    char const *zDb,              /* Database name */
+    char const *zName,            /* Table name */
+    sqlite3_int64 iKey1,          /* Rowid of row about to be deleted/updated */
+    sqlite3_int64 iKey2           /* New rowid value (for a rowid UPDATE) */
+  ),
+  void*
+);
+int sqlite3_preupdate_old(sqlite3 *, int, sqlite3_value **);
+int sqlite3_preupdate_count(sqlite3 *);
+int sqlite3_preupdate_depth(sqlite3 *);
+int sqlite3_preupdate_new(sqlite3 *, int, sqlite3_value **);
+int sqlite3_preupdate_blobwrite(sqlite3 *);
+#endif
+
+/*
+** CAPI3REF: Low-level system error code
+** METHOD: sqlite3
+**
+** ^Attempt to return the underlying operating system error code or error
+** number that caused the most recent I/O error or failure to open a file.
+** The return value is OS-dependent.  For example, on unix systems, after
+** [sqlite3_open_v2()] returns [SQLITE_CANTOPEN], this interface could be
+** called to get back the underlying "errno" that caused the problem, such
+** as ENOSPC, EAUTH, EISDIR, and so forth. 
+*/
+int sqlite3_system_errno(sqlite3*);
+
+/*
+** CAPI3REF: Database Snapshot
+** KEYWORDS: {snapshot} {sqlite3_snapshot}
+**
+** An instance of the snapshot object records the state of a [WAL mode]
+** database for some specific point in history.
+**
+** In [WAL mode], multiple [database connections] that are open on the
+** same database file can each be reading a different historical version
+** of the database file.  When a [database connection] begins a read
+** transaction, that connection sees an unchanging copy of the database
+** as it existed for the point in time when the transaction first started.
+** Subsequent changes to the database from other connections are not seen
+** by the reader until a new read transaction is started.
+**
+** The sqlite3_snapshot object records state information about an historical
+** version of the database file so that it is possible to later open a new read
+** transaction that sees that historical version of the database rather than
+** the most recent version.
+*/
+typedef struct sqlite3_snapshot {
+  unsigned char hidden[48];
+} sqlite3_snapshot;
+
+/*
+** CAPI3REF: Record A Database Snapshot
+** CONSTRUCTOR: sqlite3_snapshot
+**
+** ^The [sqlite3_snapshot_get(D,S,P)] interface attempts to make a
+** new [sqlite3_snapshot] object that records the current state of
+** schema S in database connection D.  ^On success, the
+** [sqlite3_snapshot_get(D,S,P)] interface writes a pointer to the newly
+** created [sqlite3_snapshot] object into *P and returns SQLITE_OK.
+** If there is not already a read-transaction open on schema S when
+** this function is called, one is opened automatically.
+**
+** The following must be true for this function to succeed. If any of
+** the following statements are false when sqlite3_snapshot_get() is
+** called, SQLITE_ERROR is returned. The final value of *P is undefined
+** in this case.
+**
+** <ul>
+**   <li> The database handle must not be in [autocommit mode].
+**
+**   <li> Schema S of [database connection] D must be a [WAL mode] database.
+**
+**   <li> There must not be a write transaction open on schema S of database
+**        connection D.
+**
+**   <li> One or more transactions must have been written to the current wal
+**        file since it was created on disk (by any connection). This means
+**        that a snapshot cannot be taken on a wal mode database with no wal
+**        file immediately after it is first opened. At least one transaction
+**        must be written to it first.
+** </ul>
+**
+** This function may also return SQLITE_NOMEM.  If it is called with the
+** database handle in autocommit mode but fails for some other reason,
+** whether or not a read transaction is opened on schema S is undefined.
+**
+** The [sqlite3_snapshot] object returned from a successful call to
+** [sqlite3_snapshot_get()] must be freed using [sqlite3_snapshot_free()]
+** to avoid a memory leak.
+**
+** The [sqlite3_snapshot_get()] interface is only available when the
+** [SQLITE_ENABLE_SNAPSHOT] compile-time option is used.
+*/
+SQLITE_EXPERIMENTAL int sqlite3_snapshot_get(
+  sqlite3 *db,
+  const char *zSchema,
+  sqlite3_snapshot **ppSnapshot
+);
+
+/*
+** CAPI3REF: Start a read transaction on an historical snapshot
+** METHOD: sqlite3_snapshot
+**
+** ^The [sqlite3_snapshot_open(D,S,P)] interface either starts a new read
+** transaction or upgrades an existing one for schema S of
+** [database connection] D such that the read transaction refers to
+** historical [snapshot] P, rather than the most recent change to the
+** database. ^The [sqlite3_snapshot_open()] interface returns SQLITE_OK
+** on success or an appropriate [error code] if it fails.
+**
+** ^In order to succeed, the database connection must not be in
+** [autocommit mode] when [sqlite3_snapshot_open(D,S,P)] is called. If there
+** is already a read transaction open on schema S, then the database handle
+** must have no active statements (SELECT statements that have been passed
+** to sqlite3_step() but not sqlite3_reset() or sqlite3_finalize()).
+** SQLITE_ERROR is returned if either of these conditions is violated, or
+** if schema S does not exist, or if the snapshot object is invalid.
+**
+** ^A call to sqlite3_snapshot_open() will fail to open if the specified
+** snapshot has been overwritten by a [checkpoint]. In this case
+** SQLITE_ERROR_SNAPSHOT is returned.
+**
+** If there is already a read transaction open when this function is
+** invoked, then the same read transaction remains open (on the same
+** database snapshot) if SQLITE_ERROR, SQLITE_BUSY or SQLITE_ERROR_SNAPSHOT
+** is returned. If another error code - for example SQLITE_PROTOCOL or an
+** SQLITE_IOERR error code - is returned, then the final state of the
+** read transaction is undefined. If SQLITE_OK is returned, then the
+** read transaction is now open on database snapshot P.
+**
+** ^(A call to [sqlite3_snapshot_open(D,S,P)] will fail if the
+** database connection D does not know that the database file for
+** schema S is in [WAL mode].  A database connection might not know
+** that the database file is in [WAL mode] if there has been no prior
+** I/O on that database connection, or if the database entered [WAL mode]
+** after the most recent I/O on the database connection.)^
+** (Hint: Run "[PRAGMA application_id]" against a newly opened
+** database connection in order to make it ready to use snapshots.)
+**
+** The [sqlite3_snapshot_open()] interface is only available when the
+** [SQLITE_ENABLE_SNAPSHOT] compile-time option is used.
+*/
+SQLITE_EXPERIMENTAL int sqlite3_snapshot_open(
+  sqlite3 *db,
+  const char *zSchema,
+  sqlite3_snapshot *pSnapshot
+);
+
+/*
+** CAPI3REF: Destroy a snapshot
+** DESTRUCTOR: sqlite3_snapshot
+**
+** ^The [sqlite3_snapshot_free(P)] interface destroys [sqlite3_snapshot] P.
+** The application must eventually free every [sqlite3_snapshot] object
+** using this routine to avoid a memory leak.
+**
+** The [sqlite3_snapshot_free()] interface is only available when the
+** [SQLITE_ENABLE_SNAPSHOT] compile-time option is used.
+*/
+SQLITE_EXPERIMENTAL void sqlite3_snapshot_free(sqlite3_snapshot*);
+
+/*
+** CAPI3REF: Compare the ages of two snapshot handles.
+** METHOD: sqlite3_snapshot
+**
+** The sqlite3_snapshot_cmp(P1, P2) interface is used to compare the ages
+** of two valid snapshot handles.
+**
+** If the two snapshot handles are not associated with the same database
+** file, the result of the comparison is undefined.
+**
+** Additionally, the result of the comparison is only valid if both of the
+** snapshot handles were obtained by calling sqlite3_snapshot_get() since the
+** last time the wal file was deleted. The wal file is deleted when the
+** database is changed back to rollback mode or when the number of database
+** clients drops to zero. If either snapshot handle was obtained before the
+** wal file was last deleted, the value returned by this function
+** is undefined.
+**
+** Otherwise, this API returns a negative value if P1 refers to an older
+** snapshot than P2, zero if the two handles refer to the same database
+** snapshot, and a positive value if P1 is a newer snapshot than P2.
+**
+** This interface is only available if SQLite is compiled with the
+** [SQLITE_ENABLE_SNAPSHOT] option.
+*/
+SQLITE_EXPERIMENTAL int sqlite3_snapshot_cmp(
+  sqlite3_snapshot *p1,
+  sqlite3_snapshot *p2
+);
+
+/*
+** CAPI3REF: Recover snapshots from a wal file
+** METHOD: sqlite3_snapshot
+**
+** If a [WAL file] remains on disk after all database connections close
+** (either through the use of the [SQLITE_FCNTL_PERSIST_WAL] [file control]
+** or because the last process to have the database opened exited without
+** calling [sqlite3_close()]) and a new connection is subsequently opened
+** on that database and [WAL file], the [sqlite3_snapshot_open()] interface
+** will only be able to open the last transaction added to the WAL file
+** even though the WAL file contains other valid transactions.
+**
+** This function attempts to scan the WAL file associated with database zDb
+** of database handle db and make all valid snapshots available to
+** sqlite3_snapshot_open(). It is an error if there is already a read
+** transaction open on the database, or if the database is not a WAL mode
+** database.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+**
+** This interface is only available if SQLite is compiled with the
+** [SQLITE_ENABLE_SNAPSHOT] option.
+*/
+SQLITE_EXPERIMENTAL int sqlite3_snapshot_recover(sqlite3 *db, const char *zDb);
+
+/*
+** CAPI3REF: Serialize a database
+**
+** The sqlite3_serialize(D,S,P,F) interface returns a pointer to memory
+** that is a serialization of the S database on [database connection] D.
+** If P is not a NULL pointer, then the size of the database in bytes
+** is written into *P.
+**
+** For an ordinary on-disk database file, the serialization is just a
+** copy of the disk file.  For an in-memory database or a "TEMP" database,
+** the serialization is the same sequence of bytes which would be written
+** to disk if that database where backed up to disk.
+**
+** The usual case is that sqlite3_serialize() copies the serialization of
+** the database into memory obtained from [sqlite3_malloc64()] and returns
+** a pointer to that memory.  The caller is responsible for freeing the
+** returned value to avoid a memory leak.  However, if the F argument
+** contains the SQLITE_SERIALIZE_NOCOPY bit, then no memory allocations
+** are made, and the sqlite3_serialize() function will return a pointer
+** to the contiguous memory representation of the database that SQLite
+** is currently using for that database, or NULL if the no such contiguous
+** memory representation of the database exists.  A contiguous memory
+** representation of the database will usually only exist if there has
+** been a prior call to [sqlite3_deserialize(D,S,...)] with the same
+** values of D and S.
+** The size of the database is written into *P even if the
+** SQLITE_SERIALIZE_NOCOPY bit is set but no contiguous copy
+** of the database exists.
+**
+** After the call, if the SQLITE_SERIALIZE_NOCOPY bit had been set,
+** the returned buffer content will remain accessible and unchanged
+** until either the next write operation on the connection or when
+** the connection is closed, and applications must not modify the
+** buffer. If the bit had been clear, the returned buffer will not
+** be accessed by SQLite after the call.
+**
+** A call to sqlite3_serialize(D,S,P,F) might return NULL even if the
+** SQLITE_SERIALIZE_NOCOPY bit is omitted from argument F if a memory
+** allocation error occurs.
+**
+** This interface is omitted if SQLite is compiled with the
+** [SQLITE_OMIT_DESERIALIZE] option.
+*/
+unsigned char *sqlite3_serialize(
+  sqlite3 *db,           /* The database connection */
+  const char *zSchema,   /* Which DB to serialize. ex: "main", "temp", ... */
+  sqlite3_int64 *piSize, /* Write size of the DB here, if not NULL */
+  unsigned int mFlags    /* Zero or more SQLITE_SERIALIZE_* flags */
+);
+
+/*
+** CAPI3REF: Flags for sqlite3_serialize
+**
+** Zero or more of the following constants can be OR-ed together for
+** the F argument to [sqlite3_serialize(D,S,P,F)].
+**
+** SQLITE_SERIALIZE_NOCOPY means that [sqlite3_serialize()] will return
+** a pointer to contiguous in-memory database that it is currently using,
+** without making a copy of the database.  If SQLite is not currently using
+** a contiguous in-memory database, then this option causes
+** [sqlite3_serialize()] to return a NULL pointer.  SQLite will only be
+** using a contiguous in-memory database if it has been initialized by a
+** prior call to [sqlite3_deserialize()].
+*/
+#define SQLITE_SERIALIZE_NOCOPY 0x001   /* Do no memory allocations */
+
+/*
+** CAPI3REF: Deserialize a database
+**
+** The sqlite3_deserialize(D,S,P,N,M,F) interface causes the
+** [database connection] D to disconnect from database S and then
+** reopen S as an in-memory database based on the serialization contained
+** in P.  The serialized database P is N bytes in size.  M is the size of
+** the buffer P, which might be larger than N.  If M is larger than N, and
+** the SQLITE_DESERIALIZE_READONLY bit is not set in F, then SQLite is
+** permitted to add content to the in-memory database as long as the total
+** size does not exceed M bytes.
+**
+** If the SQLITE_DESERIALIZE_FREEONCLOSE bit is set in F, then SQLite will
+** invoke sqlite3_free() on the serialization buffer when the database
+** connection closes.  If the SQLITE_DESERIALIZE_RESIZEABLE bit is set, then
+** SQLite will try to increase the buffer size using sqlite3_realloc64()
+** if writes on the database cause it to grow larger than M bytes.
+**
+** Applications must not modify the buffer P or invalidate it before
+** the database connection D is closed.
+**
+** The sqlite3_deserialize() interface will fail with SQLITE_BUSY if the
+** database is currently in a read transaction or is involved in a backup
+** operation.
+**
+** It is not possible to deserialized into the TEMP database.  If the
+** S argument to sqlite3_deserialize(D,S,P,N,M,F) is "temp" then the
+** function returns SQLITE_ERROR.
+**
+** The deserialized database should not be in [WAL mode].  If the database
+** is in WAL mode, then any attempt to use the database file will result
+** in an [SQLITE_CANTOPEN] error.  The application can set the
+** [file format version numbers] (bytes 18 and 19) of the input database P
+** to 0x01 prior to invoking sqlite3_deserialize(D,S,P,N,M,F) to force the
+** database file into rollback mode and work around this limitation.
+**
+** If sqlite3_deserialize(D,S,P,N,M,F) fails for any reason and if the
+** SQLITE_DESERIALIZE_FREEONCLOSE bit is set in argument F, then
+** [sqlite3_free()] is invoked on argument P prior to returning.
+**
+** This interface is omitted if SQLite is compiled with the
+** [SQLITE_OMIT_DESERIALIZE] option.
+*/
+int sqlite3_deserialize(
+  sqlite3 *db,            /* The database connection */
+  const char *zSchema,    /* Which DB to reopen with the deserialization */
+  unsigned char *pData,   /* The serialized database content */
+  sqlite3_int64 szDb,     /* Number bytes in the deserialization */
+  sqlite3_int64 szBuf,    /* Total size of buffer pData[] */
+  unsigned mFlags         /* Zero or more SQLITE_DESERIALIZE_* flags */
+);
+
+/*
+** CAPI3REF: Flags for sqlite3_deserialize()
+**
+** The following are allowed values for 6th argument (the F argument) to
+** the [sqlite3_deserialize(D,S,P,N,M,F)] interface.
+**
+** The SQLITE_DESERIALIZE_FREEONCLOSE means that the database serialization
+** in the P argument is held in memory obtained from [sqlite3_malloc64()]
+** and that SQLite should take ownership of this memory and automatically
+** free it when it has finished using it.  Without this flag, the caller
+** is responsible for freeing any dynamically allocated memory.
+**
+** The SQLITE_DESERIALIZE_RESIZEABLE flag means that SQLite is allowed to
+** grow the size of the database using calls to [sqlite3_realloc64()].  This
+** flag should only be used if SQLITE_DESERIALIZE_FREEONCLOSE is also used.
+** Without this flag, the deserialized database cannot increase in size beyond
+** the number of bytes specified by the M parameter.
+**
+** The SQLITE_DESERIALIZE_READONLY flag means that the deserialized database
+** should be treated as read-only.
+*/
+#define SQLITE_DESERIALIZE_FREEONCLOSE 1 /* Call sqlite3_free() on close */
+#define SQLITE_DESERIALIZE_RESIZEABLE  2 /* Resize using sqlite3_realloc64() */
+#define SQLITE_DESERIALIZE_READONLY    4 /* Database is read-only */
+
+/*
+** Undo the hack that converts floating point types to integer for
+** builds on processors without floating point support.
+*/
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# undef double
+#endif
+
+#if defined(__wasi__)
+# undef SQLITE_WASI
+# define SQLITE_WASI 1
+# undef SQLITE_OMIT_WAL
+# define SQLITE_OMIT_WAL 1/* because it requires shared memory APIs */
+# ifndef SQLITE_OMIT_LOAD_EXTENSION
+#  define SQLITE_OMIT_LOAD_EXTENSION
+# endif
+# ifndef SQLITE_THREADSAFE
+#  define SQLITE_THREADSAFE 0
+# endif
+#endif
+
+#ifdef __cplusplus
+}  /* End of the 'extern "C"' block */
+#endif
+#endif /* SQLITE3_H */
diff --git a/src/sqlite3.rc b/src/sqlite3.rc
new file mode 100644
index 0000000..5a85649
--- /dev/null
+++ b/src/sqlite3.rc
@@ -0,0 +1,83 @@
+/*
+** 2012 September 2
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code and resources that are specific to Windows.
+*/
+
+#if !defined(_WIN32_WCE)
+#include "winresrc.h"
+#else
+#include "windows.h"
+#endif /* !defined(_WIN32_WCE) */
+
+#if !defined(VS_FF_NONE)
+#  define VS_FF_NONE            0x00000000L
+#endif /* !defined(VS_FF_NONE) */
+
+#include "sqlite3.h"
+#include "sqlite3rc.h"
+
+/*
+ * English (U.S.) resources
+ */
+
+#if defined(_WIN32)
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+#pragma code_page(1252)
+#endif /* defined(_WIN32) */
+
+/*
+ * Icon
+ */
+
+#if !defined(RC_VERONLY)
+#define IDI_SQLITE 101
+
+IDI_SQLITE ICON "..\\art\\sqlite370.ico"
+#endif /* !defined(RC_VERONLY) */
+
+/*
+ * Version
+ */
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION SQLITE_RESOURCE_VERSION
+  PRODUCTVERSION SQLITE_RESOURCE_VERSION
+  FILEFLAGSMASK VS_FFI_FILEFLAGSMASK
+#if defined(_DEBUG)
+  FILEFLAGS VS_FF_DEBUG
+#else
+  FILEFLAGS VS_FF_NONE
+#endif /* defined(_DEBUG) */
+  FILEOS VOS__WINDOWS32
+  FILETYPE VFT_DLL
+  FILESUBTYPE VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0"
+    BEGIN
+      VALUE "CompanyName", "SQLite Development Team"
+      VALUE "FileDescription", "SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine."
+      VALUE "FileVersion", SQLITE_VERSION
+      VALUE "InternalName", "sqlite3"
+      VALUE "LegalCopyright", "http://www.sqlite.org/copyright.html"
+      VALUE "ProductName", "SQLite"
+      VALUE "ProductVersion", SQLITE_VERSION
+      VALUE "SourceId", SQLITE_SOURCE_ID
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 0x4b0
+  END
+END
diff --git a/src/sqlite3ext.h b/src/sqlite3ext.h
new file mode 100644
index 0000000..ae0949b
--- /dev/null
+++ b/src/sqlite3ext.h
@@ -0,0 +1,719 @@
+/*
+** 2006 June 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the SQLite interface for use by
+** shared libraries that want to be imported as extensions into
+** an SQLite instance.  Shared libraries that intend to be loaded
+** as extensions by SQLite should #include this file instead of 
+** sqlite3.h.
+*/
+#ifndef SQLITE3EXT_H
+#define SQLITE3EXT_H
+#include "sqlite3.h"
+
+/*
+** The following structure holds pointers to all of the SQLite API
+** routines.
+**
+** WARNING:  In order to maintain backwards compatibility, add new
+** interfaces to the end of this structure only.  If you insert new
+** interfaces in the middle of this structure, then older different
+** versions of SQLite will not be able to load each other's shared
+** libraries!
+*/
+struct sqlite3_api_routines {
+  void * (*aggregate_context)(sqlite3_context*,int nBytes);
+  int  (*aggregate_count)(sqlite3_context*);
+  int  (*bind_blob)(sqlite3_stmt*,int,const void*,int n,void(*)(void*));
+  int  (*bind_double)(sqlite3_stmt*,int,double);
+  int  (*bind_int)(sqlite3_stmt*,int,int);
+  int  (*bind_int64)(sqlite3_stmt*,int,sqlite_int64);
+  int  (*bind_null)(sqlite3_stmt*,int);
+  int  (*bind_parameter_count)(sqlite3_stmt*);
+  int  (*bind_parameter_index)(sqlite3_stmt*,const char*zName);
+  const char * (*bind_parameter_name)(sqlite3_stmt*,int);
+  int  (*bind_text)(sqlite3_stmt*,int,const char*,int n,void(*)(void*));
+  int  (*bind_text16)(sqlite3_stmt*,int,const void*,int,void(*)(void*));
+  int  (*bind_value)(sqlite3_stmt*,int,const sqlite3_value*);
+  int  (*busy_handler)(sqlite3*,int(*)(void*,int),void*);
+  int  (*busy_timeout)(sqlite3*,int ms);
+  int  (*changes)(sqlite3*);
+  int  (*close)(sqlite3*);
+  int  (*collation_needed)(sqlite3*,void*,void(*)(void*,sqlite3*,
+                           int eTextRep,const char*));
+  int  (*collation_needed16)(sqlite3*,void*,void(*)(void*,sqlite3*,
+                             int eTextRep,const void*));
+  const void * (*column_blob)(sqlite3_stmt*,int iCol);
+  int  (*column_bytes)(sqlite3_stmt*,int iCol);
+  int  (*column_bytes16)(sqlite3_stmt*,int iCol);
+  int  (*column_count)(sqlite3_stmt*pStmt);
+  const char * (*column_database_name)(sqlite3_stmt*,int);
+  const void * (*column_database_name16)(sqlite3_stmt*,int);
+  const char * (*column_decltype)(sqlite3_stmt*,int i);
+  const void * (*column_decltype16)(sqlite3_stmt*,int);
+  double  (*column_double)(sqlite3_stmt*,int iCol);
+  int  (*column_int)(sqlite3_stmt*,int iCol);
+  sqlite_int64  (*column_int64)(sqlite3_stmt*,int iCol);
+  const char * (*column_name)(sqlite3_stmt*,int);
+  const void * (*column_name16)(sqlite3_stmt*,int);
+  const char * (*column_origin_name)(sqlite3_stmt*,int);
+  const void * (*column_origin_name16)(sqlite3_stmt*,int);
+  const char * (*column_table_name)(sqlite3_stmt*,int);
+  const void * (*column_table_name16)(sqlite3_stmt*,int);
+  const unsigned char * (*column_text)(sqlite3_stmt*,int iCol);
+  const void * (*column_text16)(sqlite3_stmt*,int iCol);
+  int  (*column_type)(sqlite3_stmt*,int iCol);
+  sqlite3_value* (*column_value)(sqlite3_stmt*,int iCol);
+  void * (*commit_hook)(sqlite3*,int(*)(void*),void*);
+  int  (*complete)(const char*sql);
+  int  (*complete16)(const void*sql);
+  int  (*create_collation)(sqlite3*,const char*,int,void*,
+                           int(*)(void*,int,const void*,int,const void*));
+  int  (*create_collation16)(sqlite3*,const void*,int,void*,
+                             int(*)(void*,int,const void*,int,const void*));
+  int  (*create_function)(sqlite3*,const char*,int,int,void*,
+                          void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+                          void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+                          void (*xFinal)(sqlite3_context*));
+  int  (*create_function16)(sqlite3*,const void*,int,int,void*,
+                            void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xFinal)(sqlite3_context*));
+  int (*create_module)(sqlite3*,const char*,const sqlite3_module*,void*);
+  int  (*data_count)(sqlite3_stmt*pStmt);
+  sqlite3 * (*db_handle)(sqlite3_stmt*);
+  int (*declare_vtab)(sqlite3*,const char*);
+  int  (*enable_shared_cache)(int);
+  int  (*errcode)(sqlite3*db);
+  const char * (*errmsg)(sqlite3*);
+  const void * (*errmsg16)(sqlite3*);
+  int  (*exec)(sqlite3*,const char*,sqlite3_callback,void*,char**);
+  int  (*expired)(sqlite3_stmt*);
+  int  (*finalize)(sqlite3_stmt*pStmt);
+  void  (*free)(void*);
+  void  (*free_table)(char**result);
+  int  (*get_autocommit)(sqlite3*);
+  void * (*get_auxdata)(sqlite3_context*,int);
+  int  (*get_table)(sqlite3*,const char*,char***,int*,int*,char**);
+  int  (*global_recover)(void);
+  void  (*interruptx)(sqlite3*);
+  sqlite_int64  (*last_insert_rowid)(sqlite3*);
+  const char * (*libversion)(void);
+  int  (*libversion_number)(void);
+  void *(*malloc)(int);
+  char * (*mprintf)(const char*,...);
+  int  (*open)(const char*,sqlite3**);
+  int  (*open16)(const void*,sqlite3**);
+  int  (*prepare)(sqlite3*,const char*,int,sqlite3_stmt**,const char**);
+  int  (*prepare16)(sqlite3*,const void*,int,sqlite3_stmt**,const void**);
+  void * (*profile)(sqlite3*,void(*)(void*,const char*,sqlite_uint64),void*);
+  void  (*progress_handler)(sqlite3*,int,int(*)(void*),void*);
+  void *(*realloc)(void*,int);
+  int  (*reset)(sqlite3_stmt*pStmt);
+  void  (*result_blob)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_double)(sqlite3_context*,double);
+  void  (*result_error)(sqlite3_context*,const char*,int);
+  void  (*result_error16)(sqlite3_context*,const void*,int);
+  void  (*result_int)(sqlite3_context*,int);
+  void  (*result_int64)(sqlite3_context*,sqlite_int64);
+  void  (*result_null)(sqlite3_context*);
+  void  (*result_text)(sqlite3_context*,const char*,int,void(*)(void*));
+  void  (*result_text16)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_text16be)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_text16le)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_value)(sqlite3_context*,sqlite3_value*);
+  void * (*rollback_hook)(sqlite3*,void(*)(void*),void*);
+  int  (*set_authorizer)(sqlite3*,int(*)(void*,int,const char*,const char*,
+                         const char*,const char*),void*);
+  void  (*set_auxdata)(sqlite3_context*,int,void*,void (*)(void*));
+  char * (*xsnprintf)(int,char*,const char*,...);
+  int  (*step)(sqlite3_stmt*);
+  int  (*table_column_metadata)(sqlite3*,const char*,const char*,const char*,
+                                char const**,char const**,int*,int*,int*);
+  void  (*thread_cleanup)(void);
+  int  (*total_changes)(sqlite3*);
+  void * (*trace)(sqlite3*,void(*xTrace)(void*,const char*),void*);
+  int  (*transfer_bindings)(sqlite3_stmt*,sqlite3_stmt*);
+  void * (*update_hook)(sqlite3*,void(*)(void*,int ,char const*,char const*,
+                                         sqlite_int64),void*);
+  void * (*user_data)(sqlite3_context*);
+  const void * (*value_blob)(sqlite3_value*);
+  int  (*value_bytes)(sqlite3_value*);
+  int  (*value_bytes16)(sqlite3_value*);
+  double  (*value_double)(sqlite3_value*);
+  int  (*value_int)(sqlite3_value*);
+  sqlite_int64  (*value_int64)(sqlite3_value*);
+  int  (*value_numeric_type)(sqlite3_value*);
+  const unsigned char * (*value_text)(sqlite3_value*);
+  const void * (*value_text16)(sqlite3_value*);
+  const void * (*value_text16be)(sqlite3_value*);
+  const void * (*value_text16le)(sqlite3_value*);
+  int  (*value_type)(sqlite3_value*);
+  char *(*vmprintf)(const char*,va_list);
+  /* Added ??? */
+  int (*overload_function)(sqlite3*, const char *zFuncName, int nArg);
+  /* Added by 3.3.13 */
+  int (*prepare_v2)(sqlite3*,const char*,int,sqlite3_stmt**,const char**);
+  int (*prepare16_v2)(sqlite3*,const void*,int,sqlite3_stmt**,const void**);
+  int (*clear_bindings)(sqlite3_stmt*);
+  /* Added by 3.4.1 */
+  int (*create_module_v2)(sqlite3*,const char*,const sqlite3_module*,void*,
+                          void (*xDestroy)(void *));
+  /* Added by 3.5.0 */
+  int (*bind_zeroblob)(sqlite3_stmt*,int,int);
+  int (*blob_bytes)(sqlite3_blob*);
+  int (*blob_close)(sqlite3_blob*);
+  int (*blob_open)(sqlite3*,const char*,const char*,const char*,sqlite3_int64,
+                   int,sqlite3_blob**);
+  int (*blob_read)(sqlite3_blob*,void*,int,int);
+  int (*blob_write)(sqlite3_blob*,const void*,int,int);
+  int (*create_collation_v2)(sqlite3*,const char*,int,void*,
+                             int(*)(void*,int,const void*,int,const void*),
+                             void(*)(void*));
+  int (*file_control)(sqlite3*,const char*,int,void*);
+  sqlite3_int64 (*memory_highwater)(int);
+  sqlite3_int64 (*memory_used)(void);
+  sqlite3_mutex *(*mutex_alloc)(int);
+  void (*mutex_enter)(sqlite3_mutex*);
+  void (*mutex_free)(sqlite3_mutex*);
+  void (*mutex_leave)(sqlite3_mutex*);
+  int (*mutex_try)(sqlite3_mutex*);
+  int (*open_v2)(const char*,sqlite3**,int,const char*);
+  int (*release_memory)(int);
+  void (*result_error_nomem)(sqlite3_context*);
+  void (*result_error_toobig)(sqlite3_context*);
+  int (*sleep)(int);
+  void (*soft_heap_limit)(int);
+  sqlite3_vfs *(*vfs_find)(const char*);
+  int (*vfs_register)(sqlite3_vfs*,int);
+  int (*vfs_unregister)(sqlite3_vfs*);
+  int (*xthreadsafe)(void);
+  void (*result_zeroblob)(sqlite3_context*,int);
+  void (*result_error_code)(sqlite3_context*,int);
+  int (*test_control)(int, ...);
+  void (*randomness)(int,void*);
+  sqlite3 *(*context_db_handle)(sqlite3_context*);
+  int (*extended_result_codes)(sqlite3*,int);
+  int (*limit)(sqlite3*,int,int);
+  sqlite3_stmt *(*next_stmt)(sqlite3*,sqlite3_stmt*);
+  const char *(*sql)(sqlite3_stmt*);
+  int (*status)(int,int*,int*,int);
+  int (*backup_finish)(sqlite3_backup*);
+  sqlite3_backup *(*backup_init)(sqlite3*,const char*,sqlite3*,const char*);
+  int (*backup_pagecount)(sqlite3_backup*);
+  int (*backup_remaining)(sqlite3_backup*);
+  int (*backup_step)(sqlite3_backup*,int);
+  const char *(*compileoption_get)(int);
+  int (*compileoption_used)(const char*);
+  int (*create_function_v2)(sqlite3*,const char*,int,int,void*,
+                            void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xFinal)(sqlite3_context*),
+                            void(*xDestroy)(void*));
+  int (*db_config)(sqlite3*,int,...);
+  sqlite3_mutex *(*db_mutex)(sqlite3*);
+  int (*db_status)(sqlite3*,int,int*,int*,int);
+  int (*extended_errcode)(sqlite3*);
+  void (*log)(int,const char*,...);
+  sqlite3_int64 (*soft_heap_limit64)(sqlite3_int64);
+  const char *(*sourceid)(void);
+  int (*stmt_status)(sqlite3_stmt*,int,int);
+  int (*strnicmp)(const char*,const char*,int);
+  int (*unlock_notify)(sqlite3*,void(*)(void**,int),void*);
+  int (*wal_autocheckpoint)(sqlite3*,int);
+  int (*wal_checkpoint)(sqlite3*,const char*);
+  void *(*wal_hook)(sqlite3*,int(*)(void*,sqlite3*,const char*,int),void*);
+  int (*blob_reopen)(sqlite3_blob*,sqlite3_int64);
+  int (*vtab_config)(sqlite3*,int op,...);
+  int (*vtab_on_conflict)(sqlite3*);
+  /* Version 3.7.16 and later */
+  int (*close_v2)(sqlite3*);
+  const char *(*db_filename)(sqlite3*,const char*);
+  int (*db_readonly)(sqlite3*,const char*);
+  int (*db_release_memory)(sqlite3*);
+  const char *(*errstr)(int);
+  int (*stmt_busy)(sqlite3_stmt*);
+  int (*stmt_readonly)(sqlite3_stmt*);
+  int (*stricmp)(const char*,const char*);
+  int (*uri_boolean)(const char*,const char*,int);
+  sqlite3_int64 (*uri_int64)(const char*,const char*,sqlite3_int64);
+  const char *(*uri_parameter)(const char*,const char*);
+  char *(*xvsnprintf)(int,char*,const char*,va_list);
+  int (*wal_checkpoint_v2)(sqlite3*,const char*,int,int*,int*);
+  /* Version 3.8.7 and later */
+  int (*auto_extension)(void(*)(void));
+  int (*bind_blob64)(sqlite3_stmt*,int,const void*,sqlite3_uint64,
+                     void(*)(void*));
+  int (*bind_text64)(sqlite3_stmt*,int,const char*,sqlite3_uint64,
+                      void(*)(void*),unsigned char);
+  int (*cancel_auto_extension)(void(*)(void));
+  int (*load_extension)(sqlite3*,const char*,const char*,char**);
+  void *(*malloc64)(sqlite3_uint64);
+  sqlite3_uint64 (*msize)(void*);
+  void *(*realloc64)(void*,sqlite3_uint64);
+  void (*reset_auto_extension)(void);
+  void (*result_blob64)(sqlite3_context*,const void*,sqlite3_uint64,
+                        void(*)(void*));
+  void (*result_text64)(sqlite3_context*,const char*,sqlite3_uint64,
+                         void(*)(void*), unsigned char);
+  int (*strglob)(const char*,const char*);
+  /* Version 3.8.11 and later */
+  sqlite3_value *(*value_dup)(const sqlite3_value*);
+  void (*value_free)(sqlite3_value*);
+  int (*result_zeroblob64)(sqlite3_context*,sqlite3_uint64);
+  int (*bind_zeroblob64)(sqlite3_stmt*, int, sqlite3_uint64);
+  /* Version 3.9.0 and later */
+  unsigned int (*value_subtype)(sqlite3_value*);
+  void (*result_subtype)(sqlite3_context*,unsigned int);
+  /* Version 3.10.0 and later */
+  int (*status64)(int,sqlite3_int64*,sqlite3_int64*,int);
+  int (*strlike)(const char*,const char*,unsigned int);
+  int (*db_cacheflush)(sqlite3*);
+  /* Version 3.12.0 and later */
+  int (*system_errno)(sqlite3*);
+  /* Version 3.14.0 and later */
+  int (*trace_v2)(sqlite3*,unsigned,int(*)(unsigned,void*,void*,void*),void*);
+  char *(*expanded_sql)(sqlite3_stmt*);
+  /* Version 3.18.0 and later */
+  void (*set_last_insert_rowid)(sqlite3*,sqlite3_int64);
+  /* Version 3.20.0 and later */
+  int (*prepare_v3)(sqlite3*,const char*,int,unsigned int,
+                    sqlite3_stmt**,const char**);
+  int (*prepare16_v3)(sqlite3*,const void*,int,unsigned int,
+                      sqlite3_stmt**,const void**);
+  int (*bind_pointer)(sqlite3_stmt*,int,void*,const char*,void(*)(void*));
+  void (*result_pointer)(sqlite3_context*,void*,const char*,void(*)(void*));
+  void *(*value_pointer)(sqlite3_value*,const char*);
+  int (*vtab_nochange)(sqlite3_context*);
+  int (*value_nochange)(sqlite3_value*);
+  const char *(*vtab_collation)(sqlite3_index_info*,int);
+  /* Version 3.24.0 and later */
+  int (*keyword_count)(void);
+  int (*keyword_name)(int,const char**,int*);
+  int (*keyword_check)(const char*,int);
+  sqlite3_str *(*str_new)(sqlite3*);
+  char *(*str_finish)(sqlite3_str*);
+  void (*str_appendf)(sqlite3_str*, const char *zFormat, ...);
+  void (*str_vappendf)(sqlite3_str*, const char *zFormat, va_list);
+  void (*str_append)(sqlite3_str*, const char *zIn, int N);
+  void (*str_appendall)(sqlite3_str*, const char *zIn);
+  void (*str_appendchar)(sqlite3_str*, int N, char C);
+  void (*str_reset)(sqlite3_str*);
+  int (*str_errcode)(sqlite3_str*);
+  int (*str_length)(sqlite3_str*);
+  char *(*str_value)(sqlite3_str*);
+  /* Version 3.25.0 and later */
+  int (*create_window_function)(sqlite3*,const char*,int,int,void*,
+                            void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xFinal)(sqlite3_context*),
+                            void (*xValue)(sqlite3_context*),
+                            void (*xInv)(sqlite3_context*,int,sqlite3_value**),
+                            void(*xDestroy)(void*));
+  /* Version 3.26.0 and later */
+  const char *(*normalized_sql)(sqlite3_stmt*);
+  /* Version 3.28.0 and later */
+  int (*stmt_isexplain)(sqlite3_stmt*);
+  int (*value_frombind)(sqlite3_value*);
+  /* Version 3.30.0 and later */
+  int (*drop_modules)(sqlite3*,const char**);
+  /* Version 3.31.0 and later */
+  sqlite3_int64 (*hard_heap_limit64)(sqlite3_int64);
+  const char *(*uri_key)(const char*,int);
+  const char *(*filename_database)(const char*);
+  const char *(*filename_journal)(const char*);
+  const char *(*filename_wal)(const char*);
+  /* Version 3.32.0 and later */
+  const char *(*create_filename)(const char*,const char*,const char*,
+                           int,const char**);
+  void (*free_filename)(const char*);
+  sqlite3_file *(*database_file_object)(const char*);
+  /* Version 3.34.0 and later */
+  int (*txn_state)(sqlite3*,const char*);
+  /* Version 3.36.1 and later */
+  sqlite3_int64 (*changes64)(sqlite3*);
+  sqlite3_int64 (*total_changes64)(sqlite3*);
+  /* Version 3.37.0 and later */
+  int (*autovacuum_pages)(sqlite3*,
+     unsigned int(*)(void*,const char*,unsigned int,unsigned int,unsigned int),
+     void*, void(*)(void*));
+  /* Version 3.38.0 and later */
+  int (*error_offset)(sqlite3*);
+  int (*vtab_rhs_value)(sqlite3_index_info*,int,sqlite3_value**);
+  int (*vtab_distinct)(sqlite3_index_info*);
+  int (*vtab_in)(sqlite3_index_info*,int,int);
+  int (*vtab_in_first)(sqlite3_value*,sqlite3_value**);
+  int (*vtab_in_next)(sqlite3_value*,sqlite3_value**);
+  /* Version 3.39.0 and later */
+  int (*deserialize)(sqlite3*,const char*,unsigned char*,
+                     sqlite3_int64,sqlite3_int64,unsigned);
+  unsigned char *(*serialize)(sqlite3*,const char *,sqlite3_int64*,
+                              unsigned int);
+  const char *(*db_name)(sqlite3*,int);
+  /* Version 3.40.0 and later */
+  int (*value_encoding)(sqlite3_value*);
+  /* Version 3.41.0 and later */
+  int (*is_interrupted)(sqlite3*);
+  /* Version 3.43.0 and later */
+  int (*stmt_explain)(sqlite3_stmt*,int);
+  /* Version 3.44.0 and later */
+  void *(*get_clientdata)(sqlite3*,const char*);
+  int (*set_clientdata)(sqlite3*, const char*, void*, void(*)(void*));
+};
+
+/*
+** This is the function signature used for all extension entry points.  It
+** is also defined in the file "loadext.c".
+*/
+typedef int (*sqlite3_loadext_entry)(
+  sqlite3 *db,                       /* Handle to the database. */
+  char **pzErrMsg,                   /* Used to set error string on failure. */
+  const sqlite3_api_routines *pThunk /* Extension API function pointers. */
+);
+
+/*
+** The following macros redefine the API routines so that they are
+** redirected through the global sqlite3_api structure.
+**
+** This header file is also used by the loadext.c source file
+** (part of the main SQLite library - not an extension) so that
+** it can get access to the sqlite3_api_routines structure
+** definition.  But the main library does not want to redefine
+** the API.  So the redefinition macros are only valid if the
+** SQLITE_CORE macros is undefined.
+*/
+#if !defined(SQLITE_CORE) && !defined(SQLITE_OMIT_LOAD_EXTENSION)
+#define sqlite3_aggregate_context      sqlite3_api->aggregate_context
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_aggregate_count        sqlite3_api->aggregate_count
+#endif
+#define sqlite3_bind_blob              sqlite3_api->bind_blob
+#define sqlite3_bind_double            sqlite3_api->bind_double
+#define sqlite3_bind_int               sqlite3_api->bind_int
+#define sqlite3_bind_int64             sqlite3_api->bind_int64
+#define sqlite3_bind_null              sqlite3_api->bind_null
+#define sqlite3_bind_parameter_count   sqlite3_api->bind_parameter_count
+#define sqlite3_bind_parameter_index   sqlite3_api->bind_parameter_index
+#define sqlite3_bind_parameter_name    sqlite3_api->bind_parameter_name
+#define sqlite3_bind_text              sqlite3_api->bind_text
+#define sqlite3_bind_text16            sqlite3_api->bind_text16
+#define sqlite3_bind_value             sqlite3_api->bind_value
+#define sqlite3_busy_handler           sqlite3_api->busy_handler
+#define sqlite3_busy_timeout           sqlite3_api->busy_timeout
+#define sqlite3_changes                sqlite3_api->changes
+#define sqlite3_close                  sqlite3_api->close
+#define sqlite3_collation_needed       sqlite3_api->collation_needed
+#define sqlite3_collation_needed16     sqlite3_api->collation_needed16
+#define sqlite3_column_blob            sqlite3_api->column_blob
+#define sqlite3_column_bytes           sqlite3_api->column_bytes
+#define sqlite3_column_bytes16         sqlite3_api->column_bytes16
+#define sqlite3_column_count           sqlite3_api->column_count
+#define sqlite3_column_database_name   sqlite3_api->column_database_name
+#define sqlite3_column_database_name16 sqlite3_api->column_database_name16
+#define sqlite3_column_decltype        sqlite3_api->column_decltype
+#define sqlite3_column_decltype16      sqlite3_api->column_decltype16
+#define sqlite3_column_double          sqlite3_api->column_double
+#define sqlite3_column_int             sqlite3_api->column_int
+#define sqlite3_column_int64           sqlite3_api->column_int64
+#define sqlite3_column_name            sqlite3_api->column_name
+#define sqlite3_column_name16          sqlite3_api->column_name16
+#define sqlite3_column_origin_name     sqlite3_api->column_origin_name
+#define sqlite3_column_origin_name16   sqlite3_api->column_origin_name16
+#define sqlite3_column_table_name      sqlite3_api->column_table_name
+#define sqlite3_column_table_name16    sqlite3_api->column_table_name16
+#define sqlite3_column_text            sqlite3_api->column_text
+#define sqlite3_column_text16          sqlite3_api->column_text16
+#define sqlite3_column_type            sqlite3_api->column_type
+#define sqlite3_column_value           sqlite3_api->column_value
+#define sqlite3_commit_hook            sqlite3_api->commit_hook
+#define sqlite3_complete               sqlite3_api->complete
+#define sqlite3_complete16             sqlite3_api->complete16
+#define sqlite3_create_collation       sqlite3_api->create_collation
+#define sqlite3_create_collation16     sqlite3_api->create_collation16
+#define sqlite3_create_function        sqlite3_api->create_function
+#define sqlite3_create_function16      sqlite3_api->create_function16
+#define sqlite3_create_module          sqlite3_api->create_module
+#define sqlite3_create_module_v2       sqlite3_api->create_module_v2
+#define sqlite3_data_count             sqlite3_api->data_count
+#define sqlite3_db_handle              sqlite3_api->db_handle
+#define sqlite3_declare_vtab           sqlite3_api->declare_vtab
+#define sqlite3_enable_shared_cache    sqlite3_api->enable_shared_cache
+#define sqlite3_errcode                sqlite3_api->errcode
+#define sqlite3_errmsg                 sqlite3_api->errmsg
+#define sqlite3_errmsg16               sqlite3_api->errmsg16
+#define sqlite3_exec                   sqlite3_api->exec
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_expired                sqlite3_api->expired
+#endif
+#define sqlite3_finalize               sqlite3_api->finalize
+#define sqlite3_free                   sqlite3_api->free
+#define sqlite3_free_table             sqlite3_api->free_table
+#define sqlite3_get_autocommit         sqlite3_api->get_autocommit
+#define sqlite3_get_auxdata            sqlite3_api->get_auxdata
+#define sqlite3_get_table              sqlite3_api->get_table
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_global_recover         sqlite3_api->global_recover
+#endif
+#define sqlite3_interrupt              sqlite3_api->interruptx
+#define sqlite3_last_insert_rowid      sqlite3_api->last_insert_rowid
+#define sqlite3_libversion             sqlite3_api->libversion
+#define sqlite3_libversion_number      sqlite3_api->libversion_number
+#define sqlite3_malloc                 sqlite3_api->malloc
+#define sqlite3_mprintf                sqlite3_api->mprintf
+#define sqlite3_open                   sqlite3_api->open
+#define sqlite3_open16                 sqlite3_api->open16
+#define sqlite3_prepare                sqlite3_api->prepare
+#define sqlite3_prepare16              sqlite3_api->prepare16
+#define sqlite3_prepare_v2             sqlite3_api->prepare_v2
+#define sqlite3_prepare16_v2           sqlite3_api->prepare16_v2
+#define sqlite3_profile                sqlite3_api->profile
+#define sqlite3_progress_handler       sqlite3_api->progress_handler
+#define sqlite3_realloc                sqlite3_api->realloc
+#define sqlite3_reset                  sqlite3_api->reset
+#define sqlite3_result_blob            sqlite3_api->result_blob
+#define sqlite3_result_double          sqlite3_api->result_double
+#define sqlite3_result_error           sqlite3_api->result_error
+#define sqlite3_result_error16         sqlite3_api->result_error16
+#define sqlite3_result_int             sqlite3_api->result_int
+#define sqlite3_result_int64           sqlite3_api->result_int64
+#define sqlite3_result_null            sqlite3_api->result_null
+#define sqlite3_result_text            sqlite3_api->result_text
+#define sqlite3_result_text16          sqlite3_api->result_text16
+#define sqlite3_result_text16be        sqlite3_api->result_text16be
+#define sqlite3_result_text16le        sqlite3_api->result_text16le
+#define sqlite3_result_value           sqlite3_api->result_value
+#define sqlite3_rollback_hook          sqlite3_api->rollback_hook
+#define sqlite3_set_authorizer         sqlite3_api->set_authorizer
+#define sqlite3_set_auxdata            sqlite3_api->set_auxdata
+#define sqlite3_snprintf               sqlite3_api->xsnprintf
+#define sqlite3_step                   sqlite3_api->step
+#define sqlite3_table_column_metadata  sqlite3_api->table_column_metadata
+#define sqlite3_thread_cleanup         sqlite3_api->thread_cleanup
+#define sqlite3_total_changes          sqlite3_api->total_changes
+#define sqlite3_trace                  sqlite3_api->trace
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_transfer_bindings      sqlite3_api->transfer_bindings
+#endif
+#define sqlite3_update_hook            sqlite3_api->update_hook
+#define sqlite3_user_data              sqlite3_api->user_data
+#define sqlite3_value_blob             sqlite3_api->value_blob
+#define sqlite3_value_bytes            sqlite3_api->value_bytes
+#define sqlite3_value_bytes16          sqlite3_api->value_bytes16
+#define sqlite3_value_double           sqlite3_api->value_double
+#define sqlite3_value_int              sqlite3_api->value_int
+#define sqlite3_value_int64            sqlite3_api->value_int64
+#define sqlite3_value_numeric_type     sqlite3_api->value_numeric_type
+#define sqlite3_value_text             sqlite3_api->value_text
+#define sqlite3_value_text16           sqlite3_api->value_text16
+#define sqlite3_value_text16be         sqlite3_api->value_text16be
+#define sqlite3_value_text16le         sqlite3_api->value_text16le
+#define sqlite3_value_type             sqlite3_api->value_type
+#define sqlite3_vmprintf               sqlite3_api->vmprintf
+#define sqlite3_vsnprintf              sqlite3_api->xvsnprintf
+#define sqlite3_overload_function      sqlite3_api->overload_function
+#define sqlite3_prepare_v2             sqlite3_api->prepare_v2
+#define sqlite3_prepare16_v2           sqlite3_api->prepare16_v2
+#define sqlite3_clear_bindings         sqlite3_api->clear_bindings
+#define sqlite3_bind_zeroblob          sqlite3_api->bind_zeroblob
+#define sqlite3_blob_bytes             sqlite3_api->blob_bytes
+#define sqlite3_blob_close             sqlite3_api->blob_close
+#define sqlite3_blob_open              sqlite3_api->blob_open
+#define sqlite3_blob_read              sqlite3_api->blob_read
+#define sqlite3_blob_write             sqlite3_api->blob_write
+#define sqlite3_create_collation_v2    sqlite3_api->create_collation_v2
+#define sqlite3_file_control           sqlite3_api->file_control
+#define sqlite3_memory_highwater       sqlite3_api->memory_highwater
+#define sqlite3_memory_used            sqlite3_api->memory_used
+#define sqlite3_mutex_alloc            sqlite3_api->mutex_alloc
+#define sqlite3_mutex_enter            sqlite3_api->mutex_enter
+#define sqlite3_mutex_free             sqlite3_api->mutex_free
+#define sqlite3_mutex_leave            sqlite3_api->mutex_leave
+#define sqlite3_mutex_try              sqlite3_api->mutex_try
+#define sqlite3_open_v2                sqlite3_api->open_v2
+#define sqlite3_release_memory         sqlite3_api->release_memory
+#define sqlite3_result_error_nomem     sqlite3_api->result_error_nomem
+#define sqlite3_result_error_toobig    sqlite3_api->result_error_toobig
+#define sqlite3_sleep                  sqlite3_api->sleep
+#define sqlite3_soft_heap_limit        sqlite3_api->soft_heap_limit
+#define sqlite3_vfs_find               sqlite3_api->vfs_find
+#define sqlite3_vfs_register           sqlite3_api->vfs_register
+#define sqlite3_vfs_unregister         sqlite3_api->vfs_unregister
+#define sqlite3_threadsafe             sqlite3_api->xthreadsafe
+#define sqlite3_result_zeroblob        sqlite3_api->result_zeroblob
+#define sqlite3_result_error_code      sqlite3_api->result_error_code
+#define sqlite3_test_control           sqlite3_api->test_control
+#define sqlite3_randomness             sqlite3_api->randomness
+#define sqlite3_context_db_handle      sqlite3_api->context_db_handle
+#define sqlite3_extended_result_codes  sqlite3_api->extended_result_codes
+#define sqlite3_limit                  sqlite3_api->limit
+#define sqlite3_next_stmt              sqlite3_api->next_stmt
+#define sqlite3_sql                    sqlite3_api->sql
+#define sqlite3_status                 sqlite3_api->status
+#define sqlite3_backup_finish          sqlite3_api->backup_finish
+#define sqlite3_backup_init            sqlite3_api->backup_init
+#define sqlite3_backup_pagecount       sqlite3_api->backup_pagecount
+#define sqlite3_backup_remaining       sqlite3_api->backup_remaining
+#define sqlite3_backup_step            sqlite3_api->backup_step
+#define sqlite3_compileoption_get      sqlite3_api->compileoption_get
+#define sqlite3_compileoption_used     sqlite3_api->compileoption_used
+#define sqlite3_create_function_v2     sqlite3_api->create_function_v2
+#define sqlite3_db_config              sqlite3_api->db_config
+#define sqlite3_db_mutex               sqlite3_api->db_mutex
+#define sqlite3_db_status              sqlite3_api->db_status
+#define sqlite3_extended_errcode       sqlite3_api->extended_errcode
+#define sqlite3_log                    sqlite3_api->log
+#define sqlite3_soft_heap_limit64      sqlite3_api->soft_heap_limit64
+#define sqlite3_sourceid               sqlite3_api->sourceid
+#define sqlite3_stmt_status            sqlite3_api->stmt_status
+#define sqlite3_strnicmp               sqlite3_api->strnicmp
+#define sqlite3_unlock_notify          sqlite3_api->unlock_notify
+#define sqlite3_wal_autocheckpoint     sqlite3_api->wal_autocheckpoint
+#define sqlite3_wal_checkpoint         sqlite3_api->wal_checkpoint
+#define sqlite3_wal_hook               sqlite3_api->wal_hook
+#define sqlite3_blob_reopen            sqlite3_api->blob_reopen
+#define sqlite3_vtab_config            sqlite3_api->vtab_config
+#define sqlite3_vtab_on_conflict       sqlite3_api->vtab_on_conflict
+/* Version 3.7.16 and later */
+#define sqlite3_close_v2               sqlite3_api->close_v2
+#define sqlite3_db_filename            sqlite3_api->db_filename
+#define sqlite3_db_readonly            sqlite3_api->db_readonly
+#define sqlite3_db_release_memory      sqlite3_api->db_release_memory
+#define sqlite3_errstr                 sqlite3_api->errstr
+#define sqlite3_stmt_busy              sqlite3_api->stmt_busy
+#define sqlite3_stmt_readonly          sqlite3_api->stmt_readonly
+#define sqlite3_stricmp                sqlite3_api->stricmp
+#define sqlite3_uri_boolean            sqlite3_api->uri_boolean
+#define sqlite3_uri_int64              sqlite3_api->uri_int64
+#define sqlite3_uri_parameter          sqlite3_api->uri_parameter
+#define sqlite3_uri_vsnprintf          sqlite3_api->xvsnprintf
+#define sqlite3_wal_checkpoint_v2      sqlite3_api->wal_checkpoint_v2
+/* Version 3.8.7 and later */
+#define sqlite3_auto_extension         sqlite3_api->auto_extension
+#define sqlite3_bind_blob64            sqlite3_api->bind_blob64
+#define sqlite3_bind_text64            sqlite3_api->bind_text64
+#define sqlite3_cancel_auto_extension  sqlite3_api->cancel_auto_extension
+#define sqlite3_load_extension         sqlite3_api->load_extension
+#define sqlite3_malloc64               sqlite3_api->malloc64
+#define sqlite3_msize                  sqlite3_api->msize
+#define sqlite3_realloc64              sqlite3_api->realloc64
+#define sqlite3_reset_auto_extension   sqlite3_api->reset_auto_extension
+#define sqlite3_result_blob64          sqlite3_api->result_blob64
+#define sqlite3_result_text64          sqlite3_api->result_text64
+#define sqlite3_strglob                sqlite3_api->strglob
+/* Version 3.8.11 and later */
+#define sqlite3_value_dup              sqlite3_api->value_dup
+#define sqlite3_value_free             sqlite3_api->value_free
+#define sqlite3_result_zeroblob64      sqlite3_api->result_zeroblob64
+#define sqlite3_bind_zeroblob64        sqlite3_api->bind_zeroblob64
+/* Version 3.9.0 and later */
+#define sqlite3_value_subtype          sqlite3_api->value_subtype
+#define sqlite3_result_subtype         sqlite3_api->result_subtype
+/* Version 3.10.0 and later */
+#define sqlite3_status64               sqlite3_api->status64
+#define sqlite3_strlike                sqlite3_api->strlike
+#define sqlite3_db_cacheflush          sqlite3_api->db_cacheflush
+/* Version 3.12.0 and later */
+#define sqlite3_system_errno           sqlite3_api->system_errno
+/* Version 3.14.0 and later */
+#define sqlite3_trace_v2               sqlite3_api->trace_v2
+#define sqlite3_expanded_sql           sqlite3_api->expanded_sql
+/* Version 3.18.0 and later */
+#define sqlite3_set_last_insert_rowid  sqlite3_api->set_last_insert_rowid
+/* Version 3.20.0 and later */
+#define sqlite3_prepare_v3             sqlite3_api->prepare_v3
+#define sqlite3_prepare16_v3           sqlite3_api->prepare16_v3
+#define sqlite3_bind_pointer           sqlite3_api->bind_pointer
+#define sqlite3_result_pointer         sqlite3_api->result_pointer
+#define sqlite3_value_pointer          sqlite3_api->value_pointer
+/* Version 3.22.0 and later */
+#define sqlite3_vtab_nochange          sqlite3_api->vtab_nochange
+#define sqlite3_value_nochange         sqlite3_api->value_nochange
+#define sqlite3_vtab_collation         sqlite3_api->vtab_collation
+/* Version 3.24.0 and later */
+#define sqlite3_keyword_count          sqlite3_api->keyword_count
+#define sqlite3_keyword_name           sqlite3_api->keyword_name
+#define sqlite3_keyword_check          sqlite3_api->keyword_check
+#define sqlite3_str_new                sqlite3_api->str_new
+#define sqlite3_str_finish             sqlite3_api->str_finish
+#define sqlite3_str_appendf            sqlite3_api->str_appendf
+#define sqlite3_str_vappendf           sqlite3_api->str_vappendf
+#define sqlite3_str_append             sqlite3_api->str_append
+#define sqlite3_str_appendall          sqlite3_api->str_appendall
+#define sqlite3_str_appendchar         sqlite3_api->str_appendchar
+#define sqlite3_str_reset              sqlite3_api->str_reset
+#define sqlite3_str_errcode            sqlite3_api->str_errcode
+#define sqlite3_str_length             sqlite3_api->str_length
+#define sqlite3_str_value              sqlite3_api->str_value
+/* Version 3.25.0 and later */
+#define sqlite3_create_window_function sqlite3_api->create_window_function
+/* Version 3.26.0 and later */
+#define sqlite3_normalized_sql         sqlite3_api->normalized_sql
+/* Version 3.28.0 and later */
+#define sqlite3_stmt_isexplain         sqlite3_api->stmt_isexplain
+#define sqlite3_value_frombind         sqlite3_api->value_frombind
+/* Version 3.30.0 and later */
+#define sqlite3_drop_modules           sqlite3_api->drop_modules
+/* Version 3.31.0 and later */
+#define sqlite3_hard_heap_limit64      sqlite3_api->hard_heap_limit64
+#define sqlite3_uri_key                sqlite3_api->uri_key
+#define sqlite3_filename_database      sqlite3_api->filename_database
+#define sqlite3_filename_journal       sqlite3_api->filename_journal
+#define sqlite3_filename_wal           sqlite3_api->filename_wal
+/* Version 3.32.0 and later */
+#define sqlite3_create_filename        sqlite3_api->create_filename
+#define sqlite3_free_filename          sqlite3_api->free_filename
+#define sqlite3_database_file_object   sqlite3_api->database_file_object
+/* Version 3.34.0 and later */
+#define sqlite3_txn_state              sqlite3_api->txn_state
+/* Version 3.36.1 and later */
+#define sqlite3_changes64              sqlite3_api->changes64
+#define sqlite3_total_changes64        sqlite3_api->total_changes64
+/* Version 3.37.0 and later */
+#define sqlite3_autovacuum_pages       sqlite3_api->autovacuum_pages
+/* Version 3.38.0 and later */
+#define sqlite3_error_offset           sqlite3_api->error_offset
+#define sqlite3_vtab_rhs_value         sqlite3_api->vtab_rhs_value
+#define sqlite3_vtab_distinct          sqlite3_api->vtab_distinct
+#define sqlite3_vtab_in                sqlite3_api->vtab_in
+#define sqlite3_vtab_in_first          sqlite3_api->vtab_in_first
+#define sqlite3_vtab_in_next           sqlite3_api->vtab_in_next
+/* Version 3.39.0 and later */
+#ifndef SQLITE_OMIT_DESERIALIZE
+#define sqlite3_deserialize            sqlite3_api->deserialize
+#define sqlite3_serialize              sqlite3_api->serialize
+#endif
+#define sqlite3_db_name                sqlite3_api->db_name
+/* Version 3.40.0 and later */
+#define sqlite3_value_encoding         sqlite3_api->value_encoding
+/* Version 3.41.0 and later */
+#define sqlite3_is_interrupted         sqlite3_api->is_interrupted
+/* Version 3.43.0 and later */
+#define sqlite3_stmt_explain           sqlite3_api->stmt_explain
+/* Version 3.44.0 and later */
+#define sqlite3_get_clientdata         sqlite3_api->get_clientdata
+#define sqlite3_set_clientdata         sqlite3_api->set_clientdata
+#endif /* !defined(SQLITE_CORE) && !defined(SQLITE_OMIT_LOAD_EXTENSION) */
+
+#if !defined(SQLITE_CORE) && !defined(SQLITE_OMIT_LOAD_EXTENSION)
+  /* This case when the file really is being compiled as a loadable 
+  ** extension */
+# define SQLITE_EXTENSION_INIT1     const sqlite3_api_routines *sqlite3_api=0;
+# define SQLITE_EXTENSION_INIT2(v)  sqlite3_api=v;
+# define SQLITE_EXTENSION_INIT3     \
+    extern const sqlite3_api_routines *sqlite3_api;
+#else
+  /* This case when the file is being statically linked into the 
+  ** application */
+# define SQLITE_EXTENSION_INIT1     /*no-op*/
+# define SQLITE_EXTENSION_INIT2(v)  (void)v; /* unused parameter */
+# define SQLITE_EXTENSION_INIT3     /*no-op*/
+#endif
+
+#endif /* SQLITE3EXT_H */
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
new file mode 100644
index 0000000..79a36e0
--- /dev/null
+++ b/src/sqliteInt.h
@@ -0,0 +1,5766 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Internal interface definitions for SQLite.
+**
+*/
+#ifndef SQLITEINT_H
+#define SQLITEINT_H
+
+/* Special Comments:
+**
+** Some comments have special meaning to the tools that measure test
+** coverage:
+**
+**    NO_TEST                     - The branches on this line are not
+**                                  measured by branch coverage.  This is
+**                                  used on lines of code that actually
+**                                  implement parts of coverage testing.
+**
+**    OPTIMIZATION-IF-TRUE        - This branch is allowed to always be false
+**                                  and the correct answer is still obtained,
+**                                  though perhaps more slowly.
+**
+**    OPTIMIZATION-IF-FALSE       - This branch is allowed to always be true
+**                                  and the correct answer is still obtained,
+**                                  though perhaps more slowly.
+**
+**    PREVENTS-HARMLESS-OVERREAD  - This branch prevents a buffer overread
+**                                  that would be harmless and undetectable
+**                                  if it did occur.
+**
+** In all cases, the special comment must be enclosed in the usual
+** slash-asterisk...asterisk-slash comment marks, with no spaces between the
+** asterisks and the comment text.
+*/
+
+/*
+** Make sure the Tcl calling convention macro is defined.  This macro is
+** only used by test code and Tcl integration code.
+*/
+#ifndef SQLITE_TCLAPI
+#  define SQLITE_TCLAPI
+#endif
+
+/*
+** Include the header file used to customize the compiler options for MSVC.
+** This should be done first so that it can successfully prevent spurious
+** compiler warnings due to subsequent content in this file and other files
+** that are included by this file.
+*/
+#include "msvc.h"
+
+/*
+** Special setup for VxWorks
+*/
+#include "vxworks.h"
+
+/*
+** These #defines should enable >2GB file support on POSIX if the
+** underlying operating system supports it.  If the OS lacks
+** large file support, or if the OS is windows, these should be no-ops.
+**
+** Ticket #2739:  The _LARGEFILE_SOURCE macro must appear before any
+** system #includes.  Hence, this block of code must be the very first
+** code in all source files.
+**
+** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
+** on the compiler command line.  This is necessary if you are compiling
+** on a recent machine (ex: Red Hat 7.2) but you want your code to work
+** on an older machine (ex: Red Hat 6.0).  If you compile on Red Hat 7.2
+** without this option, LFS is enable.  But LFS does not exist in the kernel
+** in Red Hat 6.0, so the code won't work.  Hence, for maximum binary
+** portability you should omit LFS.
+**
+** The previous paragraph was written in 2005.  (This paragraph is written
+** on 2008-11-28.) These days, all Linux kernels support large files, so
+** you should probably leave LFS enabled.  But some embedded platforms might
+** lack LFS in which case the SQLITE_DISABLE_LFS macro might still be useful.
+**
+** Similar is true for Mac OS X.  LFS is only supported on Mac OS X 9 and later.
+*/
+#ifndef SQLITE_DISABLE_LFS
+# define _LARGE_FILE       1
+# ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+# endif
+# define _LARGEFILE_SOURCE 1
+#endif
+
+/* The GCC_VERSION and MSVC_VERSION macros are used to
+** conditionally include optimizations for each of these compilers.  A
+** value of 0 means that compiler is not being used.  The
+** SQLITE_DISABLE_INTRINSIC macro means do not use any compiler-specific
+** optimizations, and hence set all compiler macros to 0
+**
+** There was once also a CLANG_VERSION macro.  However, we learn that the
+** version numbers in clang are for "marketing" only and are inconsistent
+** and unreliable.  Fortunately, all versions of clang also recognize the
+** gcc version numbers and have reasonable settings for gcc version numbers,
+** so the GCC_VERSION macro will be set to a correct non-zero value even
+** when compiling with clang.
+*/
+#if defined(__GNUC__) && !defined(SQLITE_DISABLE_INTRINSIC)
+# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
+#else
+# define GCC_VERSION 0
+#endif
+#if defined(_MSC_VER) && !defined(SQLITE_DISABLE_INTRINSIC)
+# define MSVC_VERSION _MSC_VER
+#else
+# define MSVC_VERSION 0
+#endif
+
+/*
+** Some C99 functions in "math.h" are only present for MSVC when its version
+** is associated with Visual Studio 2013 or higher.
+*/
+#ifndef SQLITE_HAVE_C99_MATH_FUNCS
+# if MSVC_VERSION==0 || MSVC_VERSION>=1800
+#  define SQLITE_HAVE_C99_MATH_FUNCS (1)
+# else
+#  define SQLITE_HAVE_C99_MATH_FUNCS (0)
+# endif
+#endif
+
+/* Needed for various definitions... */
+#if defined(__GNUC__) && !defined(_GNU_SOURCE)
+# define _GNU_SOURCE
+#endif
+
+#if defined(__OpenBSD__) && !defined(_BSD_SOURCE)
+# define _BSD_SOURCE
+#endif
+
+/*
+** Macro to disable warnings about missing "break" at the end of a "case".
+*/
+#if GCC_VERSION>=7000000
+# define deliberate_fall_through __attribute__((fallthrough));
+#else
+# define deliberate_fall_through
+#endif
+
+/*
+** For MinGW, check to see if we can include the header file containing its
+** version information, among other things.  Normally, this internal MinGW
+** header file would [only] be included automatically by other MinGW header
+** files; however, the contained version information is now required by this
+** header file to work around binary compatibility issues (see below) and
+** this is the only known way to reliably obtain it.  This entire #if block
+** would be completely unnecessary if there was any other way of detecting
+** MinGW via their preprocessor (e.g. if they customized their GCC to define
+** some MinGW-specific macros).  When compiling for MinGW, either the
+** _HAVE_MINGW_H or _HAVE__MINGW_H (note the extra underscore) macro must be
+** defined; otherwise, detection of conditions specific to MinGW will be
+** disabled.
+*/
+#if defined(_HAVE_MINGW_H)
+# include "mingw.h"
+#elif defined(_HAVE__MINGW_H)
+# include "_mingw.h"
+#endif
+
+/*
+** For MinGW version 4.x (and higher), check to see if the _USE_32BIT_TIME_T
+** define is required to maintain binary compatibility with the MSVC runtime
+** library in use (e.g. for Windows XP).
+*/
+#if !defined(_USE_32BIT_TIME_T) && !defined(_USE_64BIT_TIME_T) && \
+    defined(_WIN32) && !defined(_WIN64) && \
+    defined(__MINGW_MAJOR_VERSION) && __MINGW_MAJOR_VERSION >= 4 && \
+    defined(__MSVCRT__)
+# define _USE_32BIT_TIME_T
+#endif
+
+/* Optionally #include a user-defined header, whereby compilation options
+** may be set prior to where they take effect, but after platform setup.
+** If SQLITE_CUSTOM_INCLUDE=? is defined, its value names the #include
+** file.
+*/
+#ifdef SQLITE_CUSTOM_INCLUDE
+# define INC_STRINGIFY_(f) #f
+# define INC_STRINGIFY(f) INC_STRINGIFY_(f)
+# include INC_STRINGIFY(SQLITE_CUSTOM_INCLUDE)
+#endif
+
+/* The public SQLite interface.  The _FILE_OFFSET_BITS macro must appear
+** first in QNX.  Also, the _USE_32BIT_TIME_T macro must appear first for
+** MinGW.
+*/
+#include "sqlite3.h"
+
+/*
+** Reuse the STATIC_LRU for mutex access to sqlite3_temp_directory.
+*/
+#define SQLITE_MUTEX_STATIC_TEMPDIR SQLITE_MUTEX_STATIC_VFS1
+
+/*
+** Include the configuration header output by 'configure' if we're using the
+** autoconf-based build
+*/
+#if defined(_HAVE_SQLITE_CONFIG_H) && !defined(SQLITECONFIG_H)
+#include "sqlite_cfg.h"
+#define SQLITECONFIG_H 1
+#endif
+
+#include "sqliteLimit.h"
+
+/* Disable nuisance warnings on Borland compilers */
+#if defined(__BORLANDC__)
+#pragma warn -rch /* unreachable code */
+#pragma warn -ccc /* Condition is always true or false */
+#pragma warn -aus /* Assigned value is never used */
+#pragma warn -csu /* Comparing signed and unsigned */
+#pragma warn -spa /* Suspicious pointer arithmetic */
+#endif
+
+/*
+** A few places in the code require atomic load/store of aligned
+** integer values.
+*/
+#ifndef __has_extension
+# define __has_extension(x) 0     /* compatibility with non-clang compilers */
+#endif
+#if GCC_VERSION>=4007000 || __has_extension(c_atomic)
+# define SQLITE_ATOMIC_INTRINSICS 1
+# define AtomicLoad(PTR)       __atomic_load_n((PTR),__ATOMIC_RELAXED)
+# define AtomicStore(PTR,VAL)  __atomic_store_n((PTR),(VAL),__ATOMIC_RELAXED)
+#else
+# define SQLITE_ATOMIC_INTRINSICS 0
+# define AtomicLoad(PTR)       (*(PTR))
+# define AtomicStore(PTR,VAL)  (*(PTR) = (VAL))
+#endif
+
+/*
+** Include standard header files as necessary
+*/
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#ifdef HAVE_INTTYPES_H
+#include <inttypes.h>
+#endif
+
+/*
+** The following macros are used to cast pointers to integers and
+** integers to pointers.  The way you do this varies from one compiler
+** to the next, so we have developed the following set of #if statements
+** to generate appropriate macros for a wide range of compilers.
+**
+** The correct "ANSI" way to do this is to use the intptr_t type.
+** Unfortunately, that typedef is not available on all compilers, or
+** if it is available, it requires an #include of specific headers
+** that vary from one machine to the next.
+**
+** Ticket #3860:  The llvm-gcc-4.2 compiler from Apple chokes on
+** the ((void*)&((char*)0)[X]) construct.  But MSVC chokes on ((void*)(X)).
+** So we have to define the macros in different ways depending on the
+** compiler.
+*/
+#if defined(HAVE_STDINT_H)   /* Use this case if we have ANSI headers */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
+#elif defined(__PTRDIFF_TYPE__)  /* This case should work for GCC */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(__PTRDIFF_TYPE__)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(__PTRDIFF_TYPE__)(X))
+#elif !defined(__GNUC__)       /* Works for compilers other than LLVM */
+# define SQLITE_INT_TO_PTR(X)  ((void*)&((char*)0)[X])
+# define SQLITE_PTR_TO_INT(X)  ((int)(((char*)X)-(char*)0))
+#else                          /* Generates a warning - but it always works */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(X))
+#endif
+
+/*
+** Macros to hint to the compiler that a function should or should not be
+** inlined.
+*/
+#if defined(__GNUC__)
+#  define SQLITE_NOINLINE  __attribute__((noinline))
+#  define SQLITE_INLINE    __attribute__((always_inline)) inline
+#elif defined(_MSC_VER) && _MSC_VER>=1310
+#  define SQLITE_NOINLINE  __declspec(noinline)
+#  define SQLITE_INLINE    __forceinline
+#else
+#  define SQLITE_NOINLINE
+#  define SQLITE_INLINE
+#endif
+#if defined(SQLITE_COVERAGE_TEST) || defined(__STRICT_ANSI__)
+# undef SQLITE_INLINE
+# define SQLITE_INLINE
+#endif
+
+/*
+** Make sure that the compiler intrinsics we desire are enabled when
+** compiling with an appropriate version of MSVC unless prevented by
+** the SQLITE_DISABLE_INTRINSIC define.
+*/
+#if !defined(SQLITE_DISABLE_INTRINSIC)
+#  if defined(_MSC_VER) && _MSC_VER>=1400
+#    if !defined(_WIN32_WCE)
+#      include <intrin.h>
+#      pragma intrinsic(_byteswap_ushort)
+#      pragma intrinsic(_byteswap_ulong)
+#      pragma intrinsic(_byteswap_uint64)
+#      pragma intrinsic(_ReadWriteBarrier)
+#    else
+#      include <cmnintrin.h>
+#    endif
+#  endif
+#endif
+
+/*
+** Enable SQLITE_USE_SEH by default on MSVC builds.  Only omit
+** SEH support if the -DSQLITE_OMIT_SEH option is given.
+*/
+#if defined(_MSC_VER) && !defined(SQLITE_OMIT_SEH)
+# define SQLITE_USE_SEH 1
+#else
+# undef SQLITE_USE_SEH
+#endif
+
+/*
+** Enable SQLITE_DIRECT_OVERFLOW_READ, unless the build explicitly
+** disables it using -DSQLITE_DIRECT_OVERFLOW_READ=0
+*/
+#if defined(SQLITE_DIRECT_OVERFLOW_READ) && SQLITE_DIRECT_OVERFLOW_READ+1==1
+  /* Disable if -DSQLITE_DIRECT_OVERFLOW_READ=0 */
+# undef SQLITE_DIRECT_OVERFLOW_READ
+#else
+  /* In all other cases, enable */
+# define SQLITE_DIRECT_OVERFLOW_READ 1
+#endif
+
+
+/*
+** The SQLITE_THREADSAFE macro must be defined as 0, 1, or 2.
+** 0 means mutexes are permanently disable and the library is never
+** threadsafe.  1 means the library is serialized which is the highest
+** level of threadsafety.  2 means the library is multithreaded - multiple
+** threads can use SQLite as long as no two threads try to use the same
+** database connection at the same time.
+**
+** Older versions of SQLite used an optional THREADSAFE macro.
+** We support that for legacy.
+**
+** To ensure that the correct value of "THREADSAFE" is reported when querying
+** for compile-time options at runtime (e.g. "PRAGMA compile_options"), this
+** logic is partially replicated in ctime.c. If it is updated here, it should
+** also be updated there.
+*/
+#if !defined(SQLITE_THREADSAFE)
+# if defined(THREADSAFE)
+#   define SQLITE_THREADSAFE THREADSAFE
+# else
+#   define SQLITE_THREADSAFE 1 /* IMP: R-07272-22309 */
+# endif
+#endif
+
+/*
+** Powersafe overwrite is on by default.  But can be turned off using
+** the -DSQLITE_POWERSAFE_OVERWRITE=0 command-line option.
+*/
+#ifndef SQLITE_POWERSAFE_OVERWRITE
+# define SQLITE_POWERSAFE_OVERWRITE 1
+#endif
+
+/*
+** EVIDENCE-OF: R-25715-37072 Memory allocation statistics are enabled by
+** default unless SQLite is compiled with SQLITE_DEFAULT_MEMSTATUS=0 in
+** which case memory allocation statistics are disabled by default.
+*/
+#if !defined(SQLITE_DEFAULT_MEMSTATUS)
+# define SQLITE_DEFAULT_MEMSTATUS 1
+#endif
+
+/*
+** Exactly one of the following macros must be defined in order to
+** specify which memory allocation subsystem to use.
+**
+**     SQLITE_SYSTEM_MALLOC          // Use normal system malloc()
+**     SQLITE_WIN32_MALLOC           // Use Win32 native heap API
+**     SQLITE_ZERO_MALLOC            // Use a stub allocator that always fails
+**     SQLITE_MEMDEBUG               // Debugging version of system malloc()
+**
+** On Windows, if the SQLITE_WIN32_MALLOC_VALIDATE macro is defined and the
+** assert() macro is enabled, each call into the Win32 native heap subsystem
+** will cause HeapValidate to be called.  If heap validation should fail, an
+** assertion will be triggered.
+**
+** If none of the above are defined, then set SQLITE_SYSTEM_MALLOC as
+** the default.
+*/
+#if defined(SQLITE_SYSTEM_MALLOC) \
+  + defined(SQLITE_WIN32_MALLOC) \
+  + defined(SQLITE_ZERO_MALLOC) \
+  + defined(SQLITE_MEMDEBUG)>1
+# error "Two or more of the following compile-time configuration options\
+ are defined but at most one is allowed:\
+ SQLITE_SYSTEM_MALLOC, SQLITE_WIN32_MALLOC, SQLITE_MEMDEBUG,\
+ SQLITE_ZERO_MALLOC"
+#endif
+#if defined(SQLITE_SYSTEM_MALLOC) \
+  + defined(SQLITE_WIN32_MALLOC) \
+  + defined(SQLITE_ZERO_MALLOC) \
+  + defined(SQLITE_MEMDEBUG)==0
+# define SQLITE_SYSTEM_MALLOC 1
+#endif
+
+/*
+** If SQLITE_MALLOC_SOFT_LIMIT is not zero, then try to keep the
+** sizes of memory allocations below this value where possible.
+*/
+#if !defined(SQLITE_MALLOC_SOFT_LIMIT)
+# define SQLITE_MALLOC_SOFT_LIMIT 1024
+#endif
+
+/*
+** We need to define _XOPEN_SOURCE as follows in order to enable
+** recursive mutexes on most Unix systems and fchmod() on OpenBSD.
+** But _XOPEN_SOURCE define causes problems for Mac OS X, so omit
+** it.
+*/
+#if !defined(_XOPEN_SOURCE) && !defined(__DARWIN__) && !defined(__APPLE__)
+#  define _XOPEN_SOURCE 600
+#endif
+
+/*
+** NDEBUG and SQLITE_DEBUG are opposites.  It should always be true that
+** defined(NDEBUG)==!defined(SQLITE_DEBUG).  If this is not currently true,
+** make it true by defining or undefining NDEBUG.
+**
+** Setting NDEBUG makes the code smaller and faster by disabling the
+** assert() statements in the code.  So we want the default action
+** to be for NDEBUG to be set and NDEBUG to be undefined only if SQLITE_DEBUG
+** is set.  Thus NDEBUG becomes an opt-in rather than an opt-out
+** feature.
+*/
+#if !defined(NDEBUG) && !defined(SQLITE_DEBUG)
+# define NDEBUG 1
+#endif
+#if defined(NDEBUG) && defined(SQLITE_DEBUG)
+# undef NDEBUG
+#endif
+
+/*
+** Enable SQLITE_ENABLE_EXPLAIN_COMMENTS if SQLITE_DEBUG is turned on.
+*/
+#if !defined(SQLITE_ENABLE_EXPLAIN_COMMENTS) && defined(SQLITE_DEBUG)
+# define SQLITE_ENABLE_EXPLAIN_COMMENTS 1
+#endif
+
+/*
+** The testcase() macro is used to aid in coverage testing.  When
+** doing coverage testing, the condition inside the argument to
+** testcase() must be evaluated both true and false in order to
+** get full branch coverage.  The testcase() macro is inserted
+** to help ensure adequate test coverage in places where simple
+** condition/decision coverage is inadequate.  For example, testcase()
+** can be used to make sure boundary values are tested.  For
+** bitmask tests, testcase() can be used to make sure each bit
+** is significant and used at least once.  On switch statements
+** where multiple cases go to the same block of code, testcase()
+** can insure that all cases are evaluated.
+*/
+#if defined(SQLITE_COVERAGE_TEST) || defined(SQLITE_DEBUG)
+# ifndef SQLITE_AMALGAMATION
+    extern unsigned int sqlite3CoverageCounter;
+# endif
+# define testcase(X)  if( X ){ sqlite3CoverageCounter += (unsigned)__LINE__; }
+#else
+# define testcase(X)
+#endif
+
+/*
+** The TESTONLY macro is used to enclose variable declarations or
+** other bits of code that are needed to support the arguments
+** within testcase() and assert() macros.
+*/
+#if !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST)
+# define TESTONLY(X)  X
+#else
+# define TESTONLY(X)
+#endif
+
+/*
+** Sometimes we need a small amount of code such as a variable initialization
+** to setup for a later assert() statement.  We do not want this code to
+** appear when assert() is disabled.  The following macro is therefore
+** used to contain that setup code.  The "VVA" acronym stands for
+** "Verification, Validation, and Accreditation".  In other words, the
+** code within VVA_ONLY() will only run during verification processes.
+*/
+#ifndef NDEBUG
+# define VVA_ONLY(X)  X
+#else
+# define VVA_ONLY(X)
+#endif
+
+/*
+** Disable ALWAYS() and NEVER() (make them pass-throughs) for coverage
+** and mutation testing
+*/
+#if defined(SQLITE_COVERAGE_TEST) || defined(SQLITE_MUTATION_TEST)
+# define SQLITE_OMIT_AUXILIARY_SAFETY_CHECKS  1
+#endif
+
+/*
+** The ALWAYS and NEVER macros surround boolean expressions which
+** are intended to always be true or false, respectively.  Such
+** expressions could be omitted from the code completely.  But they
+** are included in a few cases in order to enhance the resilience
+** of SQLite to unexpected behavior - to make the code "self-healing"
+** or "ductile" rather than being "brittle" and crashing at the first
+** hint of unplanned behavior.
+**
+** In other words, ALWAYS and NEVER are added for defensive code.
+**
+** When doing coverage testing ALWAYS and NEVER are hard-coded to
+** be true and false so that the unreachable code they specify will
+** not be counted as untested code.
+*/
+#if defined(SQLITE_OMIT_AUXILIARY_SAFETY_CHECKS)
+# define ALWAYS(X)      (1)
+# define NEVER(X)       (0)
+#elif !defined(NDEBUG)
+# define ALWAYS(X)      ((X)?1:(assert(0),0))
+# define NEVER(X)       ((X)?(assert(0),1):0)
+#else
+# define ALWAYS(X)      (X)
+# define NEVER(X)       (X)
+#endif
+
+/*
+** Some conditionals are optimizations only.  In other words, if the
+** conditionals are replaced with a constant 1 (true) or 0 (false) then
+** the correct answer is still obtained, though perhaps not as quickly.
+**
+** The following macros mark these optimizations conditionals.
+*/
+#if defined(SQLITE_MUTATION_TEST)
+# define OK_IF_ALWAYS_TRUE(X)  (1)
+# define OK_IF_ALWAYS_FALSE(X) (0)
+#else
+# define OK_IF_ALWAYS_TRUE(X)  (X)
+# define OK_IF_ALWAYS_FALSE(X) (X)
+#endif
+
+/*
+** Some malloc failures are only possible if SQLITE_TEST_REALLOC_STRESS is
+** defined.  We need to defend against those failures when testing with
+** SQLITE_TEST_REALLOC_STRESS, but we don't want the unreachable branches
+** during a normal build.  The following macro can be used to disable tests
+** that are always false except when SQLITE_TEST_REALLOC_STRESS is set.
+*/
+#if defined(SQLITE_TEST_REALLOC_STRESS)
+# define ONLY_IF_REALLOC_STRESS(X)  (X)
+#elif !defined(NDEBUG)
+# define ONLY_IF_REALLOC_STRESS(X)  ((X)?(assert(0),1):0)
+#else
+# define ONLY_IF_REALLOC_STRESS(X)  (0)
+#endif
+
+/*
+** Declarations used for tracing the operating system interfaces.
+*/
+#if defined(SQLITE_FORCE_OS_TRACE) || defined(SQLITE_TEST) || \
+    (defined(SQLITE_DEBUG) && SQLITE_OS_WIN)
+  extern int sqlite3OSTrace;
+# define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
+# define SQLITE_HAVE_OS_TRACE
+#else
+# define OSTRACE(X)
+# undef  SQLITE_HAVE_OS_TRACE
+#endif
+
+/*
+** Is the sqlite3ErrName() function needed in the build?  Currently,
+** it is needed by "mutex_w32.c" (when debugging), "os_win.c" (when
+** OSTRACE is enabled), and by several "test*.c" files (which are
+** compiled using SQLITE_TEST).
+*/
+#if defined(SQLITE_HAVE_OS_TRACE) || defined(SQLITE_TEST) || \
+    (defined(SQLITE_DEBUG) && SQLITE_OS_WIN)
+# define SQLITE_NEED_ERR_NAME
+#else
+# undef  SQLITE_NEED_ERR_NAME
+#endif
+
+/*
+** SQLITE_ENABLE_EXPLAIN_COMMENTS is incompatible with SQLITE_OMIT_EXPLAIN
+*/
+#ifdef SQLITE_OMIT_EXPLAIN
+# undef SQLITE_ENABLE_EXPLAIN_COMMENTS
+#endif
+
+/*
+** SQLITE_OMIT_VIRTUALTABLE implies SQLITE_OMIT_ALTERTABLE
+*/
+#if defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_ALTERTABLE)
+# define SQLITE_OMIT_ALTERTABLE
+#endif
+
+/*
+** Return true (non-zero) if the input is an integer that is too large
+** to fit in 32-bits.  This macro is used inside of various testcase()
+** macros to verify that we have tested SQLite for large-file support.
+*/
+#define IS_BIG_INT(X)  (((X)&~(i64)0xffffffff)!=0)
+
+/*
+** The macro unlikely() is a hint that surrounds a boolean
+** expression that is usually false.  Macro likely() surrounds
+** a boolean expression that is usually true.  These hints could,
+** in theory, be used by the compiler to generate better code, but
+** currently they are just comments for human readers.
+*/
+#define likely(X)    (X)
+#define unlikely(X)  (X)
+
+#include "hash.h"
+#include "parse.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <stddef.h>
+
+/*
+** Use a macro to replace memcpy() if compiled with SQLITE_INLINE_MEMCPY.
+** This allows better measurements of where memcpy() is used when running
+** cachegrind.  But this macro version of memcpy() is very slow so it
+** should not be used in production.  This is a performance measurement
+** hack only.
+*/
+#ifdef SQLITE_INLINE_MEMCPY
+# define memcpy(D,S,N) {char*xxd=(char*)(D);const char*xxs=(const char*)(S);\
+                        int xxn=(N);while(xxn-->0)*(xxd++)=*(xxs++);}
+#endif
+
+/*
+** If compiling for a processor that lacks floating point support,
+** substitute integer for floating-point
+*/
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define double sqlite_int64
+# define float sqlite_int64
+# define LONGDOUBLE_TYPE sqlite_int64
+# ifndef SQLITE_BIG_DBL
+#   define SQLITE_BIG_DBL (((sqlite3_int64)1)<<50)
+# endif
+# define SQLITE_OMIT_DATETIME_FUNCS 1
+# define SQLITE_OMIT_TRACE 1
+# undef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+# undef SQLITE_HAVE_ISNAN
+#endif
+#ifndef SQLITE_BIG_DBL
+# define SQLITE_BIG_DBL (1e99)
+#endif
+
+/*
+** OMIT_TEMPDB is set to 1 if SQLITE_OMIT_TEMPDB is defined, or 0
+** afterward. Having this macro allows us to cause the C compiler
+** to omit code used by TEMP tables without messy #ifndef statements.
+*/
+#ifdef SQLITE_OMIT_TEMPDB
+#define OMIT_TEMPDB 1
+#else
+#define OMIT_TEMPDB 0
+#endif
+
+/*
+** The "file format" number is an integer that is incremented whenever
+** the VDBE-level file format changes.  The following macros define the
+** the default file format for new databases and the maximum file format
+** that the library can read.
+*/
+#define SQLITE_MAX_FILE_FORMAT 4
+#ifndef SQLITE_DEFAULT_FILE_FORMAT
+# define SQLITE_DEFAULT_FILE_FORMAT 4
+#endif
+
+/*
+** Determine whether triggers are recursive by default.  This can be
+** changed at run-time using a pragma.
+*/
+#ifndef SQLITE_DEFAULT_RECURSIVE_TRIGGERS
+# define SQLITE_DEFAULT_RECURSIVE_TRIGGERS 0
+#endif
+
+/*
+** Provide a default value for SQLITE_TEMP_STORE in case it is not specified
+** on the command-line
+*/
+#ifndef SQLITE_TEMP_STORE
+# define SQLITE_TEMP_STORE 1
+#endif
+
+/*
+** If no value has been provided for SQLITE_MAX_WORKER_THREADS, or if
+** SQLITE_TEMP_STORE is set to 3 (never use temporary files), set it
+** to zero.
+*/
+#if SQLITE_TEMP_STORE==3 || SQLITE_THREADSAFE==0
+# undef SQLITE_MAX_WORKER_THREADS
+# define SQLITE_MAX_WORKER_THREADS 0
+#endif
+#ifndef SQLITE_MAX_WORKER_THREADS
+# define SQLITE_MAX_WORKER_THREADS 8
+#endif
+#ifndef SQLITE_DEFAULT_WORKER_THREADS
+# define SQLITE_DEFAULT_WORKER_THREADS 0
+#endif
+#if SQLITE_DEFAULT_WORKER_THREADS>SQLITE_MAX_WORKER_THREADS
+# undef SQLITE_MAX_WORKER_THREADS
+# define SQLITE_MAX_WORKER_THREADS SQLITE_DEFAULT_WORKER_THREADS
+#endif
+
+/*
+** The default initial allocation for the pagecache when using separate
+** pagecaches for each database connection.  A positive number is the
+** number of pages.  A negative number N translations means that a buffer
+** of -1024*N bytes is allocated and used for as many pages as it will hold.
+**
+** The default value of "20" was chosen to minimize the run-time of the
+** speedtest1 test program with options: --shrink-memory --reprepare
+*/
+#ifndef SQLITE_DEFAULT_PCACHE_INITSZ
+# define SQLITE_DEFAULT_PCACHE_INITSZ 20
+#endif
+
+/*
+** Default value for the SQLITE_CONFIG_SORTERREF_SIZE option.
+*/
+#ifndef SQLITE_DEFAULT_SORTERREF_SIZE
+# define SQLITE_DEFAULT_SORTERREF_SIZE 0x7fffffff
+#endif
+
+/*
+** The compile-time options SQLITE_MMAP_READWRITE and
+** SQLITE_ENABLE_BATCH_ATOMIC_WRITE are not compatible with one another.
+** You must choose one or the other (or neither) but not both.
+*/
+#if defined(SQLITE_MMAP_READWRITE) && defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+#error Cannot use both SQLITE_MMAP_READWRITE and SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+#endif
+
+/*
+** GCC does not define the offsetof() macro so we'll have to do it
+** ourselves.
+*/
+#ifndef offsetof
+#define offsetof(STRUCTURE,FIELD) ((int)((char*)&((STRUCTURE*)0)->FIELD))
+#endif
+
+/*
+** Macros to compute minimum and maximum of two numbers.
+*/
+#ifndef MIN
+# define MIN(A,B) ((A)<(B)?(A):(B))
+#endif
+#ifndef MAX
+# define MAX(A,B) ((A)>(B)?(A):(B))
+#endif
+
+/*
+** Swap two objects of type TYPE.
+*/
+#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
+
+/*
+** Check to see if this machine uses EBCDIC.  (Yes, believe it or
+** not, there are still machines out there that use EBCDIC.)
+*/
+#if 'A' == '\301'
+# define SQLITE_EBCDIC 1
+#else
+# define SQLITE_ASCII 1
+#endif
+
+/*
+** Integers of known sizes.  These typedefs might change for architectures
+** where the sizes very.  Preprocessor macros are available so that the
+** types can be conveniently redefined at compile-type.  Like this:
+**
+**         cc '-DUINTPTR_TYPE=long long int' ...
+*/
+#ifndef UINT32_TYPE
+# ifdef HAVE_UINT32_T
+#  define UINT32_TYPE uint32_t
+# else
+#  define UINT32_TYPE unsigned int
+# endif
+#endif
+#ifndef UINT16_TYPE
+# ifdef HAVE_UINT16_T
+#  define UINT16_TYPE uint16_t
+# else
+#  define UINT16_TYPE unsigned short int
+# endif
+#endif
+#ifndef INT16_TYPE
+# ifdef HAVE_INT16_T
+#  define INT16_TYPE int16_t
+# else
+#  define INT16_TYPE short int
+# endif
+#endif
+#ifndef UINT8_TYPE
+# ifdef HAVE_UINT8_T
+#  define UINT8_TYPE uint8_t
+# else
+#  define UINT8_TYPE unsigned char
+# endif
+#endif
+#ifndef INT8_TYPE
+# ifdef HAVE_INT8_T
+#  define INT8_TYPE int8_t
+# else
+#  define INT8_TYPE signed char
+# endif
+#endif
+#ifndef LONGDOUBLE_TYPE
+# define LONGDOUBLE_TYPE long double
+#endif
+typedef sqlite_int64 i64;          /* 8-byte signed integer */
+typedef sqlite_uint64 u64;         /* 8-byte unsigned integer */
+typedef UINT32_TYPE u32;           /* 4-byte unsigned integer */
+typedef UINT16_TYPE u16;           /* 2-byte unsigned integer */
+typedef INT16_TYPE i16;            /* 2-byte signed integer */
+typedef UINT8_TYPE u8;             /* 1-byte unsigned integer */
+typedef INT8_TYPE i8;              /* 1-byte signed integer */
+
+/*
+** SQLITE_MAX_U32 is a u64 constant that is the maximum u64 value
+** that can be stored in a u32 without loss of data.  The value
+** is 0x00000000ffffffff.  But because of quirks of some compilers, we
+** have to specify the value in the less intuitive manner shown:
+*/
+#define SQLITE_MAX_U32  ((((u64)1)<<32)-1)
+
+/*
+** The datatype used to store estimates of the number of rows in a
+** table or index.
+*/
+typedef u64 tRowcnt;
+
+/*
+** Estimated quantities used for query planning are stored as 16-bit
+** logarithms.  For quantity X, the value stored is 10*log2(X).  This
+** gives a possible range of values of approximately 1.0e986 to 1e-986.
+** But the allowed values are "grainy".  Not every value is representable.
+** For example, quantities 16 and 17 are both represented by a LogEst
+** of 40.  However, since LogEst quantities are suppose to be estimates,
+** not exact values, this imprecision is not a problem.
+**
+** "LogEst" is short for "Logarithmic Estimate".
+**
+** Examples:
+**      1 -> 0              20 -> 43          10000 -> 132
+**      2 -> 10             25 -> 46          25000 -> 146
+**      3 -> 16            100 -> 66        1000000 -> 199
+**      4 -> 20           1000 -> 99        1048576 -> 200
+**     10 -> 33           1024 -> 100    4294967296 -> 320
+**
+** The LogEst can be negative to indicate fractional values.
+** Examples:
+**
+**    0.5 -> -10           0.1 -> -33        0.0625 -> -40
+*/
+typedef INT16_TYPE LogEst;
+
+/*
+** Set the SQLITE_PTRSIZE macro to the number of bytes in a pointer
+*/
+#ifndef SQLITE_PTRSIZE
+# if defined(__SIZEOF_POINTER__)
+#   define SQLITE_PTRSIZE __SIZEOF_POINTER__
+# elif defined(i386)     || defined(__i386__)   || defined(_M_IX86) ||    \
+       defined(_M_ARM)   || defined(__arm__)    || defined(__x86)   ||    \
+      (defined(__APPLE__) && defined(__POWERPC__)) ||                     \
+      (defined(__TOS_AIX__) && !defined(__64BIT__))
+#   define SQLITE_PTRSIZE 4
+# else
+#   define SQLITE_PTRSIZE 8
+# endif
+#endif
+
+/* The uptr type is an unsigned integer large enough to hold a pointer
+*/
+#if defined(HAVE_STDINT_H)
+  typedef uintptr_t uptr;
+#elif SQLITE_PTRSIZE==4
+  typedef u32 uptr;
+#else
+  typedef u64 uptr;
+#endif
+
+/*
+** The SQLITE_WITHIN(P,S,E) macro checks to see if pointer P points to
+** something between S (inclusive) and E (exclusive).
+**
+** In other words, S is a buffer and E is a pointer to the first byte after
+** the end of buffer S.  This macro returns true if P points to something
+** contained within the buffer S.
+*/
+#define SQLITE_WITHIN(P,S,E)   (((uptr)(P)>=(uptr)(S))&&((uptr)(P)<(uptr)(E)))
+
+/*
+** P is one byte past the end of a large buffer. Return true if a span of bytes
+** between S..E crosses the end of that buffer.  In other words, return true
+** if the sub-buffer S..E-1 overflows the buffer whose last byte is P-1.
+**
+** S is the start of the span.  E is one byte past the end of end of span.
+**
+**                        P
+**     |-----------------|                FALSE
+**               |-------|
+**               S        E
+**
+**                        P
+**     |-----------------|
+**                    |-------|           TRUE
+**                    S        E
+**
+**                        P
+**     |-----------------|               
+**                        |-------|       FALSE
+**                        S        E
+*/
+#define SQLITE_OVERFLOW(P,S,E) (((uptr)(S)<(uptr)(P))&&((uptr)(E)>(uptr)(P)))
+
+/*
+** Macros to determine whether the machine is big or little endian,
+** and whether or not that determination is run-time or compile-time.
+**
+** For best performance, an attempt is made to guess at the byte-order
+** using C-preprocessor macros.  If that is unsuccessful, or if
+** -DSQLITE_BYTEORDER=0 is set, then byte-order is determined
+** at run-time.
+**
+** If you are building SQLite on some obscure platform for which the
+** following ifdef magic does not work, you can always include either:
+**
+**    -DSQLITE_BYTEORDER=1234
+**
+** or
+**
+**    -DSQLITE_BYTEORDER=4321
+**
+** to cause the build to work for little-endian or big-endian processors,
+** respectively.
+*/
+#ifndef SQLITE_BYTEORDER  /* Replicate changes at tag-20230904a */
+# if defined(__BYTE_ORDER__) && __BYTE_ORDER__==__ORDER_BIG_ENDIAN__
+#   define SQLITE_BYTEORDER 4321
+# elif defined(__BYTE_ORDER__) && __BYTE_ORDER__==__ORDER_LITTLE_ENDIAN__
+#   define SQLITE_BYTEORDER 1234
+# elif defined(__BIG_ENDIAN__) && __BIG_ENDIAN__==1
+#   define SQLITE_BYTEORDER 4321
+# elif defined(i386)    || defined(__i386__)      || defined(_M_IX86) ||    \
+     defined(__x86_64)  || defined(__x86_64__)    || defined(_M_X64)  ||    \
+     defined(_M_AMD64)  || defined(_M_ARM)        || defined(__x86)   ||    \
+     defined(__ARMEL__) || defined(__AARCH64EL__) || defined(_M_ARM64)
+#   define SQLITE_BYTEORDER 1234
+# elif defined(sparc)   || defined(__ARMEB__)     || defined(__AARCH64EB__)
+#   define SQLITE_BYTEORDER 4321
+# else
+#   define SQLITE_BYTEORDER 0
+# endif
+#endif
+#if SQLITE_BYTEORDER==4321
+# define SQLITE_BIGENDIAN    1
+# define SQLITE_LITTLEENDIAN 0
+# define SQLITE_UTF16NATIVE  SQLITE_UTF16BE
+#elif SQLITE_BYTEORDER==1234
+# define SQLITE_BIGENDIAN    0
+# define SQLITE_LITTLEENDIAN 1
+# define SQLITE_UTF16NATIVE  SQLITE_UTF16LE
+#else
+# ifdef SQLITE_AMALGAMATION
+  const int sqlite3one = 1;
+# else
+  extern const int sqlite3one;
+# endif
+# define SQLITE_BIGENDIAN    (*(char *)(&sqlite3one)==0)
+# define SQLITE_LITTLEENDIAN (*(char *)(&sqlite3one)==1)
+# define SQLITE_UTF16NATIVE  (SQLITE_BIGENDIAN?SQLITE_UTF16BE:SQLITE_UTF16LE)
+#endif
+
+/*
+** Constants for the largest and smallest possible 64-bit signed integers.
+** These macros are designed to work correctly on both 32-bit and 64-bit
+** compilers.
+*/
+#define LARGEST_INT64  (0xffffffff|(((i64)0x7fffffff)<<32))
+#define LARGEST_UINT64 (0xffffffff|(((u64)0xffffffff)<<32))
+#define SMALLEST_INT64 (((i64)-1) - LARGEST_INT64)
+
+/*
+** Round up a number to the next larger multiple of 8.  This is used
+** to force 8-byte alignment on 64-bit architectures.
+**
+** ROUND8() always does the rounding, for any argument.
+**
+** ROUND8P() assumes that the argument is already an integer number of
+** pointers in size, and so it is a no-op on systems where the pointer
+** size is 8.
+*/
+#define ROUND8(x)     (((x)+7)&~7)
+#if SQLITE_PTRSIZE==8
+# define ROUND8P(x)   (x)
+#else
+# define ROUND8P(x)   (((x)+7)&~7)
+#endif
+
+/*
+** Round down to the nearest multiple of 8
+*/
+#define ROUNDDOWN8(x) ((x)&~7)
+
+/*
+** Assert that the pointer X is aligned to an 8-byte boundary.  This
+** macro is used only within assert() to verify that the code gets
+** all alignment restrictions correct.
+**
+** Except, if SQLITE_4_BYTE_ALIGNED_MALLOC is defined, then the
+** underlying malloc() implementation might return us 4-byte aligned
+** pointers.  In that case, only verify 4-byte alignment.
+*/
+#ifdef SQLITE_4_BYTE_ALIGNED_MALLOC
+# define EIGHT_BYTE_ALIGNMENT(X)   ((((uptr)(X) - (uptr)0)&3)==0)
+#else
+# define EIGHT_BYTE_ALIGNMENT(X)   ((((uptr)(X) - (uptr)0)&7)==0)
+#endif
+
+/*
+** Disable MMAP on platforms where it is known to not work
+*/
+#if defined(__OpenBSD__) || defined(__QNXNTO__)
+# undef SQLITE_MAX_MMAP_SIZE
+# define SQLITE_MAX_MMAP_SIZE 0
+#endif
+
+/*
+** Default maximum size of memory used by memory-mapped I/O in the VFS
+*/
+#ifdef __APPLE__
+# include <TargetConditionals.h>
+#endif
+#ifndef SQLITE_MAX_MMAP_SIZE
+# if defined(__linux__) \
+  || defined(_WIN32) \
+  || (defined(__APPLE__) && defined(__MACH__)) \
+  || defined(__sun) \
+  || defined(__FreeBSD__) \
+  || defined(__DragonFly__)
+#   define SQLITE_MAX_MMAP_SIZE 0x7fff0000  /* 2147418112 */
+# else
+#   define SQLITE_MAX_MMAP_SIZE 0
+# endif
+#endif
+
+/*
+** The default MMAP_SIZE is zero on all platforms.  Or, even if a larger
+** default MMAP_SIZE is specified at compile-time, make sure that it does
+** not exceed the maximum mmap size.
+*/
+#ifndef SQLITE_DEFAULT_MMAP_SIZE
+# define SQLITE_DEFAULT_MMAP_SIZE 0
+#endif
+#if SQLITE_DEFAULT_MMAP_SIZE>SQLITE_MAX_MMAP_SIZE
+# undef SQLITE_DEFAULT_MMAP_SIZE
+# define SQLITE_DEFAULT_MMAP_SIZE SQLITE_MAX_MMAP_SIZE
+#endif
+
+/*
+** TREETRACE_ENABLED will be either 1 or 0 depending on whether or not
+** the Abstract Syntax Tree tracing logic is turned on.
+*/
+#if !defined(SQLITE_AMALGAMATION)
+extern u32 sqlite3TreeTrace;
+#endif
+#if defined(SQLITE_DEBUG) \
+    && (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_SELECTTRACE) \
+                             || defined(SQLITE_ENABLE_TREETRACE))
+# define TREETRACE_ENABLED 1
+# define TREETRACE(K,P,S,X)  \
+  if(sqlite3TreeTrace&(K))   \
+    sqlite3DebugPrintf("%u/%d/%p: ",(S)->selId,(P)->addrExplain,(S)),\
+    sqlite3DebugPrintf X
+#else
+# define TREETRACE(K,P,S,X)
+# define TREETRACE_ENABLED 0
+#endif
+
+/* TREETRACE flag meanings:
+**
+**   0x00000001     Beginning and end of SELECT processing
+**   0x00000002     WHERE clause processing
+**   0x00000004     Query flattener
+**   0x00000008     Result-set wildcard expansion
+**   0x00000010     Query name resolution
+**   0x00000020     Aggregate analysis
+**   0x00000040     Window functions
+**   0x00000080     Generated column names
+**   0x00000100     Move HAVING terms into WHERE
+**   0x00000200     Count-of-view optimization
+**   0x00000400     Compound SELECT processing
+**   0x00000800     Drop superfluous ORDER BY
+**   0x00001000     LEFT JOIN simplifies to JOIN
+**   0x00002000     Constant propagation
+**   0x00004000     Push-down optimization
+**   0x00008000     After all FROM-clause analysis
+**   0x00010000     Beginning of DELETE/INSERT/UPDATE processing
+**   0x00020000     Transform DISTINCT into GROUP BY
+**   0x00040000     SELECT tree dump after all code has been generated
+*/
+
+/*
+** Macros for "wheretrace"
+*/
+extern u32 sqlite3WhereTrace;
+#if defined(SQLITE_DEBUG) \
+    && (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_WHERETRACE))
+# define WHERETRACE(K,X)  if(sqlite3WhereTrace&(K)) sqlite3DebugPrintf X
+# define WHERETRACE_ENABLED 1
+#else
+# define WHERETRACE(K,X)
+#endif
+
+/*
+** Bits for the sqlite3WhereTrace mask:
+**
+** (---any--)   Top-level block structure
+** 0x-------F   High-level debug messages
+** 0x----FFF-   More detail
+** 0xFFFF----   Low-level debug messages
+**
+** 0x00000001   Code generation
+** 0x00000002   Solver
+** 0x00000004   Solver costs
+** 0x00000008   WhereLoop inserts
+**
+** 0x00000010   Display sqlite3_index_info xBestIndex calls
+** 0x00000020   Range an equality scan metrics
+** 0x00000040   IN operator decisions
+** 0x00000080   WhereLoop cost adjustements
+** 0x00000100
+** 0x00000200   Covering index decisions
+** 0x00000400   OR optimization
+** 0x00000800   Index scanner
+** 0x00001000   More details associated with code generation
+** 0x00002000
+** 0x00004000   Show all WHERE terms at key points
+** 0x00008000   Show the full SELECT statement at key places
+**
+** 0x00010000   Show more detail when printing WHERE terms
+** 0x00020000   Show WHERE terms returned from whereScanNext()
+*/
+
+
+/*
+** An instance of the following structure is used to store the busy-handler
+** callback for a given sqlite handle.
+**
+** The sqlite.busyHandler member of the sqlite struct contains the busy
+** callback for the database handle. Each pager opened via the sqlite
+** handle is passed a pointer to sqlite.busyHandler. The busy-handler
+** callback is currently invoked only from within pager.c.
+*/
+typedef struct BusyHandler BusyHandler;
+struct BusyHandler {
+  int (*xBusyHandler)(void *,int);  /* The busy callback */
+  void *pBusyArg;                   /* First arg to busy callback */
+  int nBusy;                        /* Incremented with each busy call */
+};
+
+/*
+** Name of table that holds the database schema.
+**
+** The PREFERRED names are used wherever possible.  But LEGACY is also
+** used for backwards compatibility.
+**
+**  1.  Queries can use either the PREFERRED or the LEGACY names
+**  2.  The sqlite3_set_authorizer() callback uses the LEGACY name
+**  3.  The PRAGMA table_list statement uses the PREFERRED name
+**
+** The LEGACY names are stored in the internal symbol hash table
+** in support of (2).  Names are translated using sqlite3PreferredTableName()
+** for (3).  The sqlite3FindTable() function takes care of translating
+** names for (1).
+**
+** Note that "sqlite_temp_schema" can also be called "temp.sqlite_schema".
+*/
+#define LEGACY_SCHEMA_TABLE          "sqlite_master"
+#define LEGACY_TEMP_SCHEMA_TABLE     "sqlite_temp_master"
+#define PREFERRED_SCHEMA_TABLE       "sqlite_schema"
+#define PREFERRED_TEMP_SCHEMA_TABLE  "sqlite_temp_schema"
+
+
+/*
+** The root-page of the schema table.
+*/
+#define SCHEMA_ROOT    1
+
+/*
+** The name of the schema table.  The name is different for TEMP.
+*/
+#define SCHEMA_TABLE(x) \
+    ((!OMIT_TEMPDB)&&(x==1)?LEGACY_TEMP_SCHEMA_TABLE:LEGACY_SCHEMA_TABLE)
+
+/*
+** A convenience macro that returns the number of elements in
+** an array.
+*/
+#define ArraySize(X)    ((int)(sizeof(X)/sizeof(X[0])))
+
+/*
+** Determine if the argument is a power of two
+*/
+#define IsPowerOfTwo(X) (((X)&((X)-1))==0)
+
+/*
+** The following value as a destructor means to use sqlite3DbFree().
+** The sqlite3DbFree() routine requires two parameters instead of the
+** one parameter that destructors normally want.  So we have to introduce
+** this magic value that the code knows to handle differently.  Any
+** pointer will work here as long as it is distinct from SQLITE_STATIC
+** and SQLITE_TRANSIENT.
+*/
+#define SQLITE_DYNAMIC   ((sqlite3_destructor_type)sqlite3OomClear)
+
+/*
+** When SQLITE_OMIT_WSD is defined, it means that the target platform does
+** not support Writable Static Data (WSD) such as global and static variables.
+** All variables must either be on the stack or dynamically allocated from
+** the heap.  When WSD is unsupported, the variable declarations scattered
+** throughout the SQLite code must become constants instead.  The SQLITE_WSD
+** macro is used for this purpose.  And instead of referencing the variable
+** directly, we use its constant as a key to lookup the run-time allocated
+** buffer that holds real variable.  The constant is also the initializer
+** for the run-time allocated buffer.
+**
+** In the usual case where WSD is supported, the SQLITE_WSD and GLOBAL
+** macros become no-ops and have zero performance impact.
+*/
+#ifdef SQLITE_OMIT_WSD
+  #define SQLITE_WSD const
+  #define GLOBAL(t,v) (*(t*)sqlite3_wsd_find((void*)&(v), sizeof(v)))
+  #define sqlite3GlobalConfig GLOBAL(struct Sqlite3Config, sqlite3Config)
+  int sqlite3_wsd_init(int N, int J);
+  void *sqlite3_wsd_find(void *K, int L);
+#else
+  #define SQLITE_WSD
+  #define GLOBAL(t,v) v
+  #define sqlite3GlobalConfig sqlite3Config
+#endif
+
+/*
+** The following macros are used to suppress compiler warnings and to
+** make it clear to human readers when a function parameter is deliberately
+** left unused within the body of a function. This usually happens when
+** a function is called via a function pointer. For example the
+** implementation of an SQL aggregate step callback may not use the
+** parameter indicating the number of arguments passed to the aggregate,
+** if it knows that this is enforced elsewhere.
+**
+** When a function parameter is not used at all within the body of a function,
+** it is generally named "NotUsed" or "NotUsed2" to make things even clearer.
+** However, these macros may also be used to suppress warnings related to
+** parameters that may or may not be used depending on compilation options.
+** For example those parameters only used in assert() statements. In these
+** cases the parameters are named as per the usual conventions.
+*/
+#define UNUSED_PARAMETER(x) (void)(x)
+#define UNUSED_PARAMETER2(x,y) UNUSED_PARAMETER(x),UNUSED_PARAMETER(y)
+
+/*
+** Forward references to structures
+*/
+typedef struct AggInfo AggInfo;
+typedef struct AuthContext AuthContext;
+typedef struct AutoincInfo AutoincInfo;
+typedef struct Bitvec Bitvec;
+typedef struct CollSeq CollSeq;
+typedef struct Column Column;
+typedef struct Cte Cte;
+typedef struct CteUse CteUse;
+typedef struct Db Db;
+typedef struct DbClientData DbClientData;
+typedef struct DbFixer DbFixer;
+typedef struct Schema Schema;
+typedef struct Expr Expr;
+typedef struct ExprList ExprList;
+typedef struct FKey FKey;
+typedef struct FpDecode FpDecode;
+typedef struct FuncDestructor FuncDestructor;
+typedef struct FuncDef FuncDef;
+typedef struct FuncDefHash FuncDefHash;
+typedef struct IdList IdList;
+typedef struct Index Index;
+typedef struct IndexedExpr IndexedExpr;
+typedef struct IndexSample IndexSample;
+typedef struct KeyClass KeyClass;
+typedef struct KeyInfo KeyInfo;
+typedef struct Lookaside Lookaside;
+typedef struct LookasideSlot LookasideSlot;
+typedef struct Module Module;
+typedef struct NameContext NameContext;
+typedef struct OnOrUsing OnOrUsing;
+typedef struct Parse Parse;
+typedef struct ParseCleanup ParseCleanup;
+typedef struct PreUpdate PreUpdate;
+typedef struct PrintfArguments PrintfArguments;
+typedef struct RCStr RCStr;
+typedef struct RenameToken RenameToken;
+typedef struct Returning Returning;
+typedef struct RowSet RowSet;
+typedef struct Savepoint Savepoint;
+typedef struct Select Select;
+typedef struct SQLiteThread SQLiteThread;
+typedef struct SelectDest SelectDest;
+typedef struct SrcItem SrcItem;
+typedef struct SrcList SrcList;
+typedef struct sqlite3_str StrAccum; /* Internal alias for sqlite3_str */
+typedef struct Table Table;
+typedef struct TableLock TableLock;
+typedef struct Token Token;
+typedef struct TreeView TreeView;
+typedef struct Trigger Trigger;
+typedef struct TriggerPrg TriggerPrg;
+typedef struct TriggerStep TriggerStep;
+typedef struct UnpackedRecord UnpackedRecord;
+typedef struct Upsert Upsert;
+typedef struct VTable VTable;
+typedef struct VtabCtx VtabCtx;
+typedef struct Walker Walker;
+typedef struct WhereInfo WhereInfo;
+typedef struct Window Window;
+typedef struct With With;
+
+
+/*
+** The bitmask datatype defined below is used for various optimizations.
+**
+** Changing this from a 64-bit to a 32-bit type limits the number of
+** tables in a join to 32 instead of 64.  But it also reduces the size
+** of the library by 738 bytes on ix86.
+*/
+#ifdef SQLITE_BITMASK_TYPE
+  typedef SQLITE_BITMASK_TYPE Bitmask;
+#else
+  typedef u64 Bitmask;
+#endif
+
+/*
+** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
+*/
+#define BMS  ((int)(sizeof(Bitmask)*8))
+
+/*
+** A bit in a Bitmask
+*/
+#define MASKBIT(n)    (((Bitmask)1)<<(n))
+#define MASKBIT64(n)  (((u64)1)<<(n))
+#define MASKBIT32(n)  (((unsigned int)1)<<(n))
+#define SMASKBIT32(n) ((n)<=31?((unsigned int)1)<<(n):0)
+#define ALLBITS       ((Bitmask)-1)
+#define TOPBIT        (((Bitmask)1)<<(BMS-1))
+
+/* A VList object records a mapping between parameters/variables/wildcards
+** in the SQL statement (such as $abc, @pqr, or :xyz) and the integer
+** variable number associated with that parameter.  See the format description
+** on the sqlite3VListAdd() routine for more information.  A VList is really
+** just an array of integers.
+*/
+typedef int VList;
+
+/*
+** Defer sourcing vdbe.h and btree.h until after the "u8" and
+** "BusyHandler" typedefs. vdbe.h also requires a few of the opaque
+** pointer types (i.e. FuncDef) defined above.
+*/
+#include "os.h"
+#include "pager.h"
+#include "btree.h"
+#include "vdbe.h"
+#include "pcache.h"
+#include "mutex.h"
+
+/* The SQLITE_EXTRA_DURABLE compile-time option used to set the default
+** synchronous setting to EXTRA.  It is no longer supported.
+*/
+#ifdef SQLITE_EXTRA_DURABLE
+# warning Use SQLITE_DEFAULT_SYNCHRONOUS=3 instead of SQLITE_EXTRA_DURABLE
+# define SQLITE_DEFAULT_SYNCHRONOUS 3
+#endif
+
+/*
+** Default synchronous levels.
+**
+** Note that (for historical reasons) the PAGER_SYNCHRONOUS_* macros differ
+** from the SQLITE_DEFAULT_SYNCHRONOUS value by 1.
+**
+**           PAGER_SYNCHRONOUS       DEFAULT_SYNCHRONOUS
+**   OFF           1                         0
+**   NORMAL        2                         1
+**   FULL          3                         2
+**   EXTRA         4                         3
+**
+** The "PRAGMA synchronous" statement also uses the zero-based numbers.
+** In other words, the zero-based numbers are used for all external interfaces
+** and the one-based values are used internally.
+*/
+#ifndef SQLITE_DEFAULT_SYNCHRONOUS
+# define SQLITE_DEFAULT_SYNCHRONOUS 2
+#endif
+#ifndef SQLITE_DEFAULT_WAL_SYNCHRONOUS
+# define SQLITE_DEFAULT_WAL_SYNCHRONOUS SQLITE_DEFAULT_SYNCHRONOUS
+#endif
+
+/*
+** Each database file to be accessed by the system is an instance
+** of the following structure.  There are normally two of these structures
+** in the sqlite.aDb[] array.  aDb[0] is the main database file and
+** aDb[1] is the database file used to hold temporary tables.  Additional
+** databases may be attached.
+*/
+struct Db {
+  char *zDbSName;      /* Name of this database. (schema name, not filename) */
+  Btree *pBt;          /* The B*Tree structure for this database file */
+  u8 safety_level;     /* How aggressive at syncing data to disk */
+  u8 bSyncSet;         /* True if "PRAGMA synchronous=N" has been run */
+  Schema *pSchema;     /* Pointer to database schema (possibly shared) */
+};
+
+/*
+** An instance of the following structure stores a database schema.
+**
+** Most Schema objects are associated with a Btree.  The exception is
+** the Schema for the TEMP database (sqlite3.aDb[1]) which is free-standing.
+** In shared cache mode, a single Schema object can be shared by multiple
+** Btrees that refer to the same underlying BtShared object.
+**
+** Schema objects are automatically deallocated when the last Btree that
+** references them is destroyed.   The TEMP Schema is manually freed by
+** sqlite3_close().
+*
+** A thread must be holding a mutex on the corresponding Btree in order
+** to access Schema content.  This implies that the thread must also be
+** holding a mutex on the sqlite3 connection pointer that owns the Btree.
+** For a TEMP Schema, only the connection mutex is required.
+*/
+struct Schema {
+  int schema_cookie;   /* Database schema version number for this file */
+  int iGeneration;     /* Generation counter.  Incremented with each change */
+  Hash tblHash;        /* All tables indexed by name */
+  Hash idxHash;        /* All (named) indices indexed by name */
+  Hash trigHash;       /* All triggers indexed by name */
+  Hash fkeyHash;       /* All foreign keys by referenced table name */
+  Table *pSeqTab;      /* The sqlite_sequence table used by AUTOINCREMENT */
+  u8 file_format;      /* Schema format version for this file */
+  u8 enc;              /* Text encoding used by this database */
+  u16 schemaFlags;     /* Flags associated with this schema */
+  int cache_size;      /* Number of pages to use in the cache */
+};
+
+/*
+** These macros can be used to test, set, or clear bits in the
+** Db.pSchema->flags field.
+*/
+#define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->schemaFlags&(P))==(P))
+#define DbHasAnyProperty(D,I,P)  (((D)->aDb[I].pSchema->schemaFlags&(P))!=0)
+#define DbSetProperty(D,I,P)     (D)->aDb[I].pSchema->schemaFlags|=(P)
+#define DbClearProperty(D,I,P)   (D)->aDb[I].pSchema->schemaFlags&=~(P)
+
+/*
+** Allowed values for the DB.pSchema->flags field.
+**
+** The DB_SchemaLoaded flag is set after the database schema has been
+** read into internal hash tables.
+**
+** DB_UnresetViews means that one or more views have column names that
+** have been filled out.  If the schema changes, these column names might
+** changes and so the view will need to be reset.
+*/
+#define DB_SchemaLoaded    0x0001  /* The schema has been loaded */
+#define DB_UnresetViews    0x0002  /* Some views have defined column names */
+#define DB_ResetWanted     0x0008  /* Reset the schema when nSchemaLock==0 */
+
+/*
+** The number of different kinds of things that can be limited
+** using the sqlite3_limit() interface.
+*/
+#define SQLITE_N_LIMIT (SQLITE_LIMIT_WORKER_THREADS+1)
+
+/*
+** Lookaside malloc is a set of fixed-size buffers that can be used
+** to satisfy small transient memory allocation requests for objects
+** associated with a particular database connection.  The use of
+** lookaside malloc provides a significant performance enhancement
+** (approx 10%) by avoiding numerous malloc/free requests while parsing
+** SQL statements.
+**
+** The Lookaside structure holds configuration information about the
+** lookaside malloc subsystem.  Each available memory allocation in
+** the lookaside subsystem is stored on a linked list of LookasideSlot
+** objects.
+**
+** Lookaside allocations are only allowed for objects that are associated
+** with a particular database connection.  Hence, schema information cannot
+** be stored in lookaside because in shared cache mode the schema information
+** is shared by multiple database connections.  Therefore, while parsing
+** schema information, the Lookaside.bEnabled flag is cleared so that
+** lookaside allocations are not used to construct the schema objects.
+**
+** New lookaside allocations are only allowed if bDisable==0.  When
+** bDisable is greater than zero, sz is set to zero which effectively
+** disables lookaside without adding a new test for the bDisable flag
+** in a performance-critical path.  sz should be set by to szTrue whenever
+** bDisable changes back to zero.
+**
+** Lookaside buffers are initially held on the pInit list.  As they are
+** used and freed, they are added back to the pFree list.  New allocations
+** come off of pFree first, then pInit as a fallback.  This dual-list
+** allows use to compute a high-water mark - the maximum number of allocations
+** outstanding at any point in the past - by subtracting the number of
+** allocations on the pInit list from the total number of allocations.
+**
+** Enhancement on 2019-12-12:  Two-size-lookaside
+** The default lookaside configuration is 100 slots of 1200 bytes each.
+** The larger slot sizes are important for performance, but they waste
+** a lot of space, as most lookaside allocations are less than 128 bytes.
+** The two-size-lookaside enhancement breaks up the lookaside allocation
+** into two pools:  One of 128-byte slots and the other of the default size
+** (1200-byte) slots.   Allocations are filled from the small-pool first,
+** failing over to the full-size pool if that does not work.  Thus more
+** lookaside slots are available while also using less memory.
+** This enhancement can be omitted by compiling with
+** SQLITE_OMIT_TWOSIZE_LOOKASIDE.
+*/
+struct Lookaside {
+  u32 bDisable;           /* Only operate the lookaside when zero */
+  u16 sz;                 /* Size of each buffer in bytes */
+  u16 szTrue;             /* True value of sz, even if disabled */
+  u8 bMalloced;           /* True if pStart obtained from sqlite3_malloc() */
+  u32 nSlot;              /* Number of lookaside slots allocated */
+  u32 anStat[3];          /* 0: hits.  1: size misses.  2: full misses */
+  LookasideSlot *pInit;   /* List of buffers not previously used */
+  LookasideSlot *pFree;   /* List of available buffers */
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+  LookasideSlot *pSmallInit; /* List of small buffers not previously used */
+  LookasideSlot *pSmallFree; /* List of available small buffers */
+  void *pMiddle;          /* First byte past end of full-size buffers and
+                          ** the first byte of LOOKASIDE_SMALL buffers */
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+  void *pStart;           /* First byte of available memory space */
+  void *pEnd;             /* First byte past end of available space */
+  void *pTrueEnd;         /* True value of pEnd, when db->pnBytesFreed!=0 */
+};
+struct LookasideSlot {
+  LookasideSlot *pNext;    /* Next buffer in the list of free buffers */
+};
+
+#define DisableLookaside  db->lookaside.bDisable++;db->lookaside.sz=0
+#define EnableLookaside   db->lookaside.bDisable--;\
+   db->lookaside.sz=db->lookaside.bDisable?0:db->lookaside.szTrue
+
+/* Size of the smaller allocations in two-size lookaside */
+#ifdef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+#  define LOOKASIDE_SMALL           0
+#else
+#  define LOOKASIDE_SMALL         128
+#endif
+
+/*
+** A hash table for built-in function definitions.  (Application-defined
+** functions use a regular table table from hash.h.)
+**
+** Hash each FuncDef structure into one of the FuncDefHash.a[] slots.
+** Collisions are on the FuncDef.u.pHash chain.  Use the SQLITE_FUNC_HASH()
+** macro to compute a hash on the function name.
+*/
+#define SQLITE_FUNC_HASH_SZ 23
+struct FuncDefHash {
+  FuncDef *a[SQLITE_FUNC_HASH_SZ];       /* Hash table for functions */
+};
+#define SQLITE_FUNC_HASH(C,L) (((C)+(L))%SQLITE_FUNC_HASH_SZ)
+
+#ifdef SQLITE_USER_AUTHENTICATION
+/*
+** Information held in the "sqlite3" database connection object and used
+** to manage user authentication.
+*/
+typedef struct sqlite3_userauth sqlite3_userauth;
+struct sqlite3_userauth {
+  u8 authLevel;                 /* Current authentication level */
+  int nAuthPW;                  /* Size of the zAuthPW in bytes */
+  char *zAuthPW;                /* Password used to authenticate */
+  char *zAuthUser;              /* User name used to authenticate */
+};
+
+/* Allowed values for sqlite3_userauth.authLevel */
+#define UAUTH_Unknown     0     /* Authentication not yet checked */
+#define UAUTH_Fail        1     /* User authentication failed */
+#define UAUTH_User        2     /* Authenticated as a normal user */
+#define UAUTH_Admin       3     /* Authenticated as an administrator */
+
+/* Functions used only by user authorization logic */
+int sqlite3UserAuthTable(const char*);
+int sqlite3UserAuthCheckLogin(sqlite3*,const char*,u8*);
+void sqlite3UserAuthInit(sqlite3*);
+void sqlite3CryptFunc(sqlite3_context*,int,sqlite3_value**);
+
+#endif /* SQLITE_USER_AUTHENTICATION */
+
+/*
+** typedef for the authorization callback function.
+*/
+#ifdef SQLITE_USER_AUTHENTICATION
+  typedef int (*sqlite3_xauth)(void*,int,const char*,const char*,const char*,
+                               const char*, const char*);
+#else
+  typedef int (*sqlite3_xauth)(void*,int,const char*,const char*,const char*,
+                               const char*);
+#endif
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/* This is an extra SQLITE_TRACE macro that indicates "legacy" tracing
+** in the style of sqlite3_trace()
+*/
+#define SQLITE_TRACE_LEGACY          0x40     /* Use the legacy xTrace */
+#define SQLITE_TRACE_XPROFILE        0x80     /* Use the legacy xProfile */
+#else
+#define SQLITE_TRACE_LEGACY          0
+#define SQLITE_TRACE_XPROFILE        0
+#endif /* SQLITE_OMIT_DEPRECATED */
+#define SQLITE_TRACE_NONLEGACY_MASK  0x0f     /* Normal flags */
+
+/*
+** Maximum number of sqlite3.aDb[] entries.  This is the number of attached
+** databases plus 2 for "main" and "temp".
+*/
+#define SQLITE_MAX_DB (SQLITE_MAX_ATTACHED+2)
+
+/*
+** Each database connection is an instance of the following structure.
+*/
+struct sqlite3 {
+  sqlite3_vfs *pVfs;            /* OS Interface */
+  struct Vdbe *pVdbe;           /* List of active virtual machines */
+  CollSeq *pDfltColl;           /* BINARY collseq for the database encoding */
+  sqlite3_mutex *mutex;         /* Connection mutex */
+  Db *aDb;                      /* All backends */
+  int nDb;                      /* Number of backends currently in use */
+  u32 mDbFlags;                 /* flags recording internal state */
+  u64 flags;                    /* flags settable by pragmas. See below */
+  i64 lastRowid;                /* ROWID of most recent insert (see above) */
+  i64 szMmap;                   /* Default mmap_size setting */
+  u32 nSchemaLock;              /* Do not reset the schema when non-zero */
+  unsigned int openFlags;       /* Flags passed to sqlite3_vfs.xOpen() */
+  int errCode;                  /* Most recent error code (SQLITE_*) */
+  int errByteOffset;            /* Byte offset of error in SQL statement */
+  int errMask;                  /* & result codes with this before returning */
+  int iSysErrno;                /* Errno value from last system error */
+  u32 dbOptFlags;               /* Flags to enable/disable optimizations */
+  u8 enc;                       /* Text encoding */
+  u8 autoCommit;                /* The auto-commit flag. */
+  u8 temp_store;                /* 1: file 2: memory 0: default */
+  u8 mallocFailed;              /* True if we have seen a malloc failure */
+  u8 bBenignMalloc;             /* Do not require OOMs if true */
+  u8 dfltLockMode;              /* Default locking-mode for attached dbs */
+  signed char nextAutovac;      /* Autovac setting after VACUUM if >=0 */
+  u8 suppressErr;               /* Do not issue error messages if true */
+  u8 vtabOnConflict;            /* Value to return for s3_vtab_on_conflict() */
+  u8 isTransactionSavepoint;    /* True if the outermost savepoint is a TS */
+  u8 mTrace;                    /* zero or more SQLITE_TRACE flags */
+  u8 noSharedCache;             /* True if no shared-cache backends */
+  u8 nSqlExec;                  /* Number of pending OP_SqlExec opcodes */
+  u8 eOpenState;                /* Current condition of the connection */
+  int nextPagesize;             /* Pagesize after VACUUM if >0 */
+  i64 nChange;                  /* Value returned by sqlite3_changes() */
+  i64 nTotalChange;             /* Value returned by sqlite3_total_changes() */
+  int aLimit[SQLITE_N_LIMIT];   /* Limits */
+  int nMaxSorterMmap;           /* Maximum size of regions mapped by sorter */
+  struct sqlite3InitInfo {      /* Information used during initialization */
+    Pgno newTnum;               /* Rootpage of table being initialized */
+    u8 iDb;                     /* Which db file is being initialized */
+    u8 busy;                    /* TRUE if currently initializing */
+    unsigned orphanTrigger : 1; /* Last statement is orphaned TEMP trigger */
+    unsigned imposterTable : 1; /* Building an imposter table */
+    unsigned reopenMemdb : 1;   /* ATTACH is really a reopen using MemDB */
+    const char **azInit;        /* "type", "name", and "tbl_name" columns */
+  } init;
+  int nVdbeActive;              /* Number of VDBEs currently running */
+  int nVdbeRead;                /* Number of active VDBEs that read or write */
+  int nVdbeWrite;               /* Number of active VDBEs that read and write */
+  int nVdbeExec;                /* Number of nested calls to VdbeExec() */
+  int nVDestroy;                /* Number of active OP_VDestroy operations */
+  int nExtension;               /* Number of loaded extensions */
+  void **aExtension;            /* Array of shared library handles */
+  union {
+    void (*xLegacy)(void*,const char*);   /* mTrace==SQLITE_TRACE_LEGACY */
+    int (*xV2)(u32,void*,void*,void*);    /* All other mTrace values */
+  } trace;
+  void *pTraceArg;                        /* Argument to the trace function */
+#ifndef SQLITE_OMIT_DEPRECATED
+  void (*xProfile)(void*,const char*,u64);  /* Profiling function */
+  void *pProfileArg;                        /* Argument to profile function */
+#endif
+  void *pCommitArg;                 /* Argument to xCommitCallback() */
+  int (*xCommitCallback)(void*);    /* Invoked at every commit. */
+  void *pRollbackArg;               /* Argument to xRollbackCallback() */
+  void (*xRollbackCallback)(void*); /* Invoked at every commit. */
+  void *pUpdateArg;
+  void (*xUpdateCallback)(void*,int, const char*,const char*,sqlite_int64);
+  void *pAutovacPagesArg;           /* Client argument to autovac_pages */
+  void (*xAutovacDestr)(void*);     /* Destructor for pAutovacPAgesArg */
+  unsigned int (*xAutovacPages)(void*,const char*,u32,u32,u32);
+  Parse *pParse;                /* Current parse */
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  void *pPreUpdateArg;          /* First argument to xPreUpdateCallback */
+  void (*xPreUpdateCallback)(   /* Registered using sqlite3_preupdate_hook() */
+    void*,sqlite3*,int,char const*,char const*,sqlite3_int64,sqlite3_int64
+  );
+  PreUpdate *pPreUpdate;        /* Context for active pre-update callback */
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+#ifndef SQLITE_OMIT_WAL
+  int (*xWalCallback)(void *, sqlite3 *, const char *, int);
+  void *pWalArg;
+#endif
+  void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*);
+  void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*);
+  void *pCollNeededArg;
+  sqlite3_value *pErr;          /* Most recent error message */
+  union {
+    volatile int isInterrupted; /* True if sqlite3_interrupt has been called */
+    double notUsed1;            /* Spacer */
+  } u1;
+  Lookaside lookaside;          /* Lookaside malloc configuration */
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  sqlite3_xauth xAuth;          /* Access authorization function */
+  void *pAuthArg;               /* 1st argument to the access auth function */
+#endif
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  int (*xProgress)(void *);     /* The progress callback */
+  void *pProgressArg;           /* Argument to the progress callback */
+  unsigned nProgressOps;        /* Number of opcodes for progress callback */
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  int nVTrans;                  /* Allocated size of aVTrans */
+  Hash aModule;                 /* populated by sqlite3_create_module() */
+  VtabCtx *pVtabCtx;            /* Context for active vtab connect/create */
+  VTable **aVTrans;             /* Virtual tables with open transactions */
+  VTable *pDisconnect;          /* Disconnect these in next sqlite3_prepare() */
+#endif
+  Hash aFunc;                   /* Hash table of connection functions */
+  Hash aCollSeq;                /* All collating sequences */
+  BusyHandler busyHandler;      /* Busy callback */
+  Db aDbStatic[2];              /* Static space for the 2 default backends */
+  Savepoint *pSavepoint;        /* List of active savepoints */
+  int nAnalysisLimit;           /* Number of index rows to ANALYZE */
+  int busyTimeout;              /* Busy handler timeout, in msec */
+  int nSavepoint;               /* Number of non-transaction savepoints */
+  int nStatement;               /* Number of nested statement-transactions  */
+  i64 nDeferredCons;            /* Net deferred constraints this transaction. */
+  i64 nDeferredImmCons;         /* Net deferred immediate constraints */
+  int *pnBytesFreed;            /* If not NULL, increment this in DbFree() */
+  DbClientData *pDbData;        /* sqlite3_set_clientdata() content */
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  /* The following variables are all protected by the STATIC_MAIN
+  ** mutex, not by sqlite3.mutex. They are used by code in notify.c.
+  **
+  ** When X.pUnlockConnection==Y, that means that X is waiting for Y to
+  ** unlock so that it can proceed.
+  **
+  ** When X.pBlockingConnection==Y, that means that something that X tried
+  ** tried to do recently failed with an SQLITE_LOCKED error due to locks
+  ** held by Y.
+  */
+  sqlite3 *pBlockingConnection; /* Connection that caused SQLITE_LOCKED */
+  sqlite3 *pUnlockConnection;           /* Connection to watch for unlock */
+  void *pUnlockArg;                     /* Argument to xUnlockNotify */
+  void (*xUnlockNotify)(void **, int);  /* Unlock notify callback */
+  sqlite3 *pNextBlocked;        /* Next in list of all blocked connections */
+#endif
+#ifdef SQLITE_USER_AUTHENTICATION
+  sqlite3_userauth auth;        /* User authentication information */
+#endif
+};
+
+/*
+** A macro to discover the encoding of a database.
+*/
+#define SCHEMA_ENC(db) ((db)->aDb[0].pSchema->enc)
+#define ENC(db)        ((db)->enc)
+
+/*
+** A u64 constant where the lower 32 bits are all zeros.  Only the
+** upper 32 bits are included in the argument.  Necessary because some
+** C-compilers still do not accept LL integer literals.
+*/
+#define HI(X)  ((u64)(X)<<32)
+
+/*
+** Possible values for the sqlite3.flags.
+**
+** Value constraints (enforced via assert()):
+**      SQLITE_FullFSync     == PAGER_FULLFSYNC
+**      SQLITE_CkptFullFSync == PAGER_CKPT_FULLFSYNC
+**      SQLITE_CacheSpill    == PAGER_CACHE_SPILL
+*/
+#define SQLITE_WriteSchema    0x00000001  /* OK to update SQLITE_SCHEMA */
+#define SQLITE_LegacyFileFmt  0x00000002  /* Create new databases in format 1 */
+#define SQLITE_FullColNames   0x00000004  /* Show full column names on SELECT */
+#define SQLITE_FullFSync      0x00000008  /* Use full fsync on the backend */
+#define SQLITE_CkptFullFSync  0x00000010  /* Use full fsync for checkpoint */
+#define SQLITE_CacheSpill     0x00000020  /* OK to spill pager cache */
+#define SQLITE_ShortColNames  0x00000040  /* Show short columns names */
+#define SQLITE_TrustedSchema  0x00000080  /* Allow unsafe functions and
+                                          ** vtabs in the schema definition */
+#define SQLITE_NullCallback   0x00000100  /* Invoke the callback once if the */
+                                          /*   result set is empty */
+#define SQLITE_IgnoreChecks   0x00000200  /* Do not enforce check constraints */
+#define SQLITE_StmtScanStatus 0x00000400  /* Enable stmt_scanstats() counters */
+#define SQLITE_NoCkptOnClose  0x00000800  /* No checkpoint on close()/DETACH */
+#define SQLITE_ReverseOrder   0x00001000  /* Reverse unordered SELECTs */
+#define SQLITE_RecTriggers    0x00002000  /* Enable recursive triggers */
+#define SQLITE_ForeignKeys    0x00004000  /* Enforce foreign key constraints  */
+#define SQLITE_AutoIndex      0x00008000  /* Enable automatic indexes */
+#define SQLITE_LoadExtension  0x00010000  /* Enable load_extension */
+#define SQLITE_LoadExtFunc    0x00020000  /* Enable load_extension() SQL func */
+#define SQLITE_EnableTrigger  0x00040000  /* True to enable triggers */
+#define SQLITE_DeferFKs       0x00080000  /* Defer all FK constraints */
+#define SQLITE_QueryOnly      0x00100000  /* Disable database changes */
+#define SQLITE_CellSizeCk     0x00200000  /* Check btree cell sizes on load */
+#define SQLITE_Fts3Tokenizer  0x00400000  /* Enable fts3_tokenizer(2) */
+#define SQLITE_EnableQPSG     0x00800000  /* Query Planner Stability Guarantee*/
+#define SQLITE_TriggerEQP     0x01000000  /* Show trigger EXPLAIN QUERY PLAN */
+#define SQLITE_ResetDatabase  0x02000000  /* Reset the database */
+#define SQLITE_LegacyAlter    0x04000000  /* Legacy ALTER TABLE behaviour */
+#define SQLITE_NoSchemaError  0x08000000  /* Do not report schema parse errors*/
+#define SQLITE_Defensive      0x10000000  /* Input SQL is likely hostile */
+#define SQLITE_DqsDDL         0x20000000  /* dbl-quoted strings allowed in DDL*/
+#define SQLITE_DqsDML         0x40000000  /* dbl-quoted strings allowed in DML*/
+#define SQLITE_EnableView     0x80000000  /* Enable the use of views */
+#define SQLITE_CountRows      HI(0x00001) /* Count rows changed by INSERT, */
+                                          /*   DELETE, or UPDATE and return */
+                                          /*   the count using a callback. */
+#define SQLITE_CorruptRdOnly  HI(0x00002) /* Prohibit writes due to error */
+#define SQLITE_ReadUncommit   HI(0x00004) /* READ UNCOMMITTED in shared-cache */
+#define SQLITE_FkNoAction     HI(0x00008) /* Treat all FK as NO ACTION */
+
+/* Flags used only if debugging */
+#ifdef SQLITE_DEBUG
+#define SQLITE_SqlTrace       HI(0x0100000) /* Debug print SQL as it executes */
+#define SQLITE_VdbeListing    HI(0x0200000) /* Debug listings of VDBE progs */
+#define SQLITE_VdbeTrace      HI(0x0400000) /* True to trace VDBE execution */
+#define SQLITE_VdbeAddopTrace HI(0x0800000) /* Trace sqlite3VdbeAddOp() calls */
+#define SQLITE_VdbeEQP        HI(0x1000000) /* Debug EXPLAIN QUERY PLAN */
+#define SQLITE_ParserTrace    HI(0x2000000) /* PRAGMA parser_trace=ON */
+#endif
+
+/*
+** Allowed values for sqlite3.mDbFlags
+*/
+#define DBFLAG_SchemaChange   0x0001  /* Uncommitted Hash table changes */
+#define DBFLAG_PreferBuiltin  0x0002  /* Preference to built-in funcs */
+#define DBFLAG_Vacuum         0x0004  /* Currently in a VACUUM */
+#define DBFLAG_VacuumInto     0x0008  /* Currently running VACUUM INTO */
+#define DBFLAG_SchemaKnownOk  0x0010  /* Schema is known to be valid */
+#define DBFLAG_InternalFunc   0x0020  /* Allow use of internal functions */
+#define DBFLAG_EncodingFixed  0x0040  /* No longer possible to change enc. */
+
+/*
+** Bits of the sqlite3.dbOptFlags field that are used by the
+** sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS,...) interface to
+** selectively disable various optimizations.
+*/
+#define SQLITE_QueryFlattener 0x00000001 /* Query flattening */
+#define SQLITE_WindowFunc     0x00000002 /* Use xInverse for window functions */
+#define SQLITE_GroupByOrder   0x00000004 /* GROUPBY cover of ORDERBY */
+#define SQLITE_FactorOutConst 0x00000008 /* Constant factoring */
+#define SQLITE_DistinctOpt    0x00000010 /* DISTINCT using indexes */
+#define SQLITE_CoverIdxScan   0x00000020 /* Covering index scans */
+#define SQLITE_OrderByIdxJoin 0x00000040 /* ORDER BY of joins via index */
+#define SQLITE_Transitive     0x00000080 /* Transitive constraints */
+#define SQLITE_OmitNoopJoin   0x00000100 /* Omit unused tables in joins */
+#define SQLITE_CountOfView    0x00000200 /* The count-of-view optimization */
+#define SQLITE_CursorHints    0x00000400 /* Add OP_CursorHint opcodes */
+#define SQLITE_Stat4          0x00000800 /* Use STAT4 data */
+   /* TH3 expects this value  ^^^^^^^^^^ to be 0x0000800. Don't change it */
+#define SQLITE_PushDown       0x00001000 /* The push-down optimization */
+#define SQLITE_SimplifyJoin   0x00002000 /* Convert LEFT JOIN to JOIN */
+#define SQLITE_SkipScan       0x00004000 /* Skip-scans */
+#define SQLITE_PropagateConst 0x00008000 /* The constant propagation opt */
+#define SQLITE_MinMaxOpt      0x00010000 /* The min/max optimization */
+#define SQLITE_SeekScan       0x00020000 /* The OP_SeekScan optimization */
+#define SQLITE_OmitOrderBy    0x00040000 /* Omit pointless ORDER BY */
+   /* TH3 expects this value  ^^^^^^^^^^ to be 0x40000. Coordinate any change */
+#define SQLITE_BloomFilter    0x00080000 /* Use a Bloom filter on searches */
+#define SQLITE_BloomPulldown  0x00100000 /* Run Bloom filters early */
+#define SQLITE_BalancedMerge  0x00200000 /* Balance multi-way merges */
+#define SQLITE_ReleaseReg     0x00400000 /* Use OP_ReleaseReg for testing */
+#define SQLITE_FlttnUnionAll  0x00800000 /* Disable the UNION ALL flattener */
+   /* TH3 expects this value  ^^^^^^^^^^ See flatten04.test */
+#define SQLITE_IndexedExpr    0x01000000 /* Pull exprs from index when able */
+#define SQLITE_Coroutines     0x02000000 /* Co-routines for subqueries */
+#define SQLITE_NullUnusedCols 0x04000000 /* NULL unused columns in subqueries */
+#define SQLITE_OnePass        0x08000000 /* Single-pass DELETE and UPDATE */
+#define SQLITE_AllOpts        0xffffffff /* All optimizations */
+
+/*
+** Macros for testing whether or not optimizations are enabled or disabled.
+*/
+#define OptimizationDisabled(db, mask)  (((db)->dbOptFlags&(mask))!=0)
+#define OptimizationEnabled(db, mask)   (((db)->dbOptFlags&(mask))==0)
+
+/*
+** Return true if it OK to factor constant expressions into the initialization
+** code. The argument is a Parse object for the code generator.
+*/
+#define ConstFactorOk(P) ((P)->okConstFactor)
+
+/* Possible values for the sqlite3.eOpenState field.
+** The numbers are randomly selected such that a minimum of three bits must
+** change to convert any number to another or to zero
+*/
+#define SQLITE_STATE_OPEN     0x76  /* Database is open */
+#define SQLITE_STATE_CLOSED   0xce  /* Database is closed */
+#define SQLITE_STATE_SICK     0xba  /* Error and awaiting close */
+#define SQLITE_STATE_BUSY     0x6d  /* Database currently in use */
+#define SQLITE_STATE_ERROR    0xd5  /* An SQLITE_MISUSE error occurred */
+#define SQLITE_STATE_ZOMBIE   0xa7  /* Close with last statement close */
+
+/*
+** Each SQL function is defined by an instance of the following
+** structure.  For global built-in functions (ex: substr(), max(), count())
+** a pointer to this structure is held in the sqlite3BuiltinFunctions object.
+** For per-connection application-defined functions, a pointer to this
+** structure is held in the db->aHash hash table.
+**
+** The u.pHash field is used by the global built-ins.  The u.pDestructor
+** field is used by per-connection app-def functions.
+*/
+struct FuncDef {
+  i8 nArg;             /* Number of arguments.  -1 means unlimited */
+  u32 funcFlags;       /* Some combination of SQLITE_FUNC_* */
+  void *pUserData;     /* User data parameter */
+  FuncDef *pNext;      /* Next function with same name */
+  void (*xSFunc)(sqlite3_context*,int,sqlite3_value**); /* func or agg-step */
+  void (*xFinalize)(sqlite3_context*);                  /* Agg finalizer */
+  void (*xValue)(sqlite3_context*);                     /* Current agg value */
+  void (*xInverse)(sqlite3_context*,int,sqlite3_value**); /* inverse agg-step */
+  const char *zName;   /* SQL name of the function. */
+  union {
+    FuncDef *pHash;      /* Next with a different name but the same hash */
+    FuncDestructor *pDestructor;   /* Reference counted destructor function */
+  } u; /* pHash if SQLITE_FUNC_BUILTIN, pDestructor otherwise */
+};
+
+/*
+** This structure encapsulates a user-function destructor callback (as
+** configured using create_function_v2()) and a reference counter. When
+** create_function_v2() is called to create a function with a destructor,
+** a single object of this type is allocated. FuncDestructor.nRef is set to
+** the number of FuncDef objects created (either 1 or 3, depending on whether
+** or not the specified encoding is SQLITE_ANY). The FuncDef.pDestructor
+** member of each of the new FuncDef objects is set to point to the allocated
+** FuncDestructor.
+**
+** Thereafter, when one of the FuncDef objects is deleted, the reference
+** count on this object is decremented. When it reaches 0, the destructor
+** is invoked and the FuncDestructor structure freed.
+*/
+struct FuncDestructor {
+  int nRef;
+  void (*xDestroy)(void *);
+  void *pUserData;
+};
+
+/*
+** Possible values for FuncDef.flags.  Note that the _LENGTH and _TYPEOF
+** values must correspond to OPFLAG_LENGTHARG and OPFLAG_TYPEOFARG.  And
+** SQLITE_FUNC_CONSTANT must be the same as SQLITE_DETERMINISTIC.  There
+** are assert() statements in the code to verify this.
+**
+** Value constraints (enforced via assert()):
+**     SQLITE_FUNC_MINMAX      ==  NC_MinMaxAgg      == SF_MinMaxAgg
+**     SQLITE_FUNC_ANYORDER    ==  NC_OrderAgg       == SF_OrderByReqd
+**     SQLITE_FUNC_LENGTH      ==  OPFLAG_LENGTHARG
+**     SQLITE_FUNC_TYPEOF      ==  OPFLAG_TYPEOFARG
+**     SQLITE_FUNC_BYTELEN     ==  OPFLAG_BYTELENARG
+**     SQLITE_FUNC_CONSTANT    ==  SQLITE_DETERMINISTIC from the API
+**     SQLITE_FUNC_DIRECT      ==  SQLITE_DIRECTONLY from the API
+**     SQLITE_FUNC_UNSAFE      ==  SQLITE_INNOCUOUS  -- opposite meanings!!!
+**     SQLITE_FUNC_ENCMASK   depends on SQLITE_UTF* macros in the API
+**
+** Note that even though SQLITE_FUNC_UNSAFE and SQLITE_INNOCUOUS have the
+** same bit value, their meanings are inverted.  SQLITE_FUNC_UNSAFE is
+** used internally and if set means that the function has side effects.
+** SQLITE_INNOCUOUS is used by application code and means "not unsafe".
+** See multiple instances of tag-20230109-1.
+*/
+#define SQLITE_FUNC_ENCMASK  0x0003 /* SQLITE_UTF8, SQLITE_UTF16BE or UTF16LE */
+#define SQLITE_FUNC_LIKE     0x0004 /* Candidate for the LIKE optimization */
+#define SQLITE_FUNC_CASE     0x0008 /* Case-sensitive LIKE-type function */
+#define SQLITE_FUNC_EPHEM    0x0010 /* Ephemeral.  Delete with VDBE */
+#define SQLITE_FUNC_NEEDCOLL 0x0020 /* sqlite3GetFuncCollSeq() might be called*/
+#define SQLITE_FUNC_LENGTH   0x0040 /* Built-in length() function */
+#define SQLITE_FUNC_TYPEOF   0x0080 /* Built-in typeof() function */
+#define SQLITE_FUNC_BYTELEN  0x00c0 /* Built-in octet_length() function */
+#define SQLITE_FUNC_COUNT    0x0100 /* Built-in count(*) aggregate */
+/*                           0x0200 -- available for reuse */
+#define SQLITE_FUNC_UNLIKELY 0x0400 /* Built-in unlikely() function */
+#define SQLITE_FUNC_CONSTANT 0x0800 /* Constant inputs give a constant output */
+#define SQLITE_FUNC_MINMAX   0x1000 /* True for min() and max() aggregates */
+#define SQLITE_FUNC_SLOCHNG  0x2000 /* "Slow Change". Value constant during a
+                                    ** single query - might change over time */
+#define SQLITE_FUNC_TEST     0x4000 /* Built-in testing functions */
+#define SQLITE_FUNC_RUNONLY  0x8000 /* Cannot be used by valueFromFunction */
+#define SQLITE_FUNC_WINDOW   0x00010000 /* Built-in window-only function */
+#define SQLITE_FUNC_INTERNAL 0x00040000 /* For use by NestedParse() only */
+#define SQLITE_FUNC_DIRECT   0x00080000 /* Not for use in TRIGGERs or VIEWs */
+/* SQLITE_SUBTYPE            0x00100000 // Consumer of subtypes */
+#define SQLITE_FUNC_UNSAFE   0x00200000 /* Function has side effects */
+#define SQLITE_FUNC_INLINE   0x00400000 /* Functions implemented in-line */
+#define SQLITE_FUNC_BUILTIN  0x00800000 /* This is a built-in function */
+/*  SQLITE_RESULT_SUBTYPE    0x01000000 // Generator of subtypes */
+#define SQLITE_FUNC_ANYORDER 0x08000000 /* count/min/max aggregate */
+
+/* Identifier numbers for each in-line function */
+#define INLINEFUNC_coalesce             0
+#define INLINEFUNC_implies_nonnull_row  1
+#define INLINEFUNC_expr_implies_expr    2
+#define INLINEFUNC_expr_compare         3
+#define INLINEFUNC_affinity             4
+#define INLINEFUNC_iif                  5
+#define INLINEFUNC_sqlite_offset        6
+#define INLINEFUNC_unlikely            99  /* Default case */
+
+/*
+** The following three macros, FUNCTION(), LIKEFUNC() and AGGREGATE() are
+** used to create the initializers for the FuncDef structures.
+**
+**   FUNCTION(zName, nArg, iArg, bNC, xFunc)
+**     Used to create a scalar function definition of a function zName
+**     implemented by C function xFunc that accepts nArg arguments. The
+**     value passed as iArg is cast to a (void*) and made available
+**     as the user-data (sqlite3_user_data()) for the function. If
+**     argument bNC is true, then the SQLITE_FUNC_NEEDCOLL flag is set.
+**
+**   VFUNCTION(zName, nArg, iArg, bNC, xFunc)
+**     Like FUNCTION except it omits the SQLITE_FUNC_CONSTANT flag.
+**
+**   SFUNCTION(zName, nArg, iArg, bNC, xFunc)
+**     Like FUNCTION except it omits the SQLITE_FUNC_CONSTANT flag and
+**     adds the SQLITE_DIRECTONLY flag.
+**
+**   INLINE_FUNC(zName, nArg, iFuncId, mFlags)
+**     zName is the name of a function that is implemented by in-line
+**     byte code rather than by the usual callbacks. The iFuncId
+**     parameter determines the function id.  The mFlags parameter is
+**     optional SQLITE_FUNC_ flags for this function.
+**
+**   TEST_FUNC(zName, nArg, iFuncId, mFlags)
+**     zName is the name of a test-only function implemented by in-line
+**     byte code rather than by the usual callbacks. The iFuncId
+**     parameter determines the function id.  The mFlags parameter is
+**     optional SQLITE_FUNC_ flags for this function.
+**
+**   DFUNCTION(zName, nArg, iArg, bNC, xFunc)
+**     Like FUNCTION except it omits the SQLITE_FUNC_CONSTANT flag and
+**     adds the SQLITE_FUNC_SLOCHNG flag.  Used for date & time functions
+**     and functions like sqlite_version() that can change, but not during
+**     a single query.  The iArg is ignored.  The user-data is always set
+**     to a NULL pointer.  The bNC parameter is not used.
+**
+**   MFUNCTION(zName, nArg, xPtr, xFunc)
+**     For math-library functions.  xPtr is an arbitrary pointer.
+**
+**   PURE_DATE(zName, nArg, iArg, bNC, xFunc)
+**     Used for "pure" date/time functions, this macro is like DFUNCTION
+**     except that it does set the SQLITE_FUNC_CONSTANT flags.  iArg is
+**     ignored and the user-data for these functions is set to an
+**     arbitrary non-NULL pointer.  The bNC parameter is not used.
+**
+**   AGGREGATE(zName, nArg, iArg, bNC, xStep, xFinal)
+**     Used to create an aggregate function definition implemented by
+**     the C functions xStep and xFinal. The first four parameters
+**     are interpreted in the same way as the first 4 parameters to
+**     FUNCTION().
+**
+**   WAGGREGATE(zName, nArg, iArg, xStep, xFinal, xValue, xInverse)
+**     Used to create an aggregate function definition implemented by
+**     the C functions xStep and xFinal. The first four parameters
+**     are interpreted in the same way as the first 4 parameters to
+**     FUNCTION().
+**
+**   LIKEFUNC(zName, nArg, pArg, flags)
+**     Used to create a scalar function definition of a function zName
+**     that accepts nArg arguments and is implemented by a call to C
+**     function likeFunc. Argument pArg is cast to a (void *) and made
+**     available as the function user-data (sqlite3_user_data()). The
+**     FuncDef.flags variable is set to the value passed as the flags
+**     parameter.
+*/
+#define FUNCTION(zName, nArg, iArg, bNC, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|\
+   SQLITE_FUNC_CONSTANT|SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL), \
+   SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, 0, 0, #zName, {0} }
+#define VFUNCTION(zName, nArg, iArg, bNC, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL), \
+   SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, 0, 0, #zName, {0} }
+#define SFUNCTION(zName, nArg, iArg, bNC, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|SQLITE_UTF8|SQLITE_DIRECTONLY|SQLITE_FUNC_UNSAFE, \
+   SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, 0, 0, #zName, {0} }
+#define MFUNCTION(zName, nArg, xPtr, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|SQLITE_FUNC_CONSTANT|SQLITE_UTF8, \
+   xPtr, 0, xFunc, 0, 0, 0, #zName, {0} }
+#define JFUNCTION(zName, nArg, bUseCache, bWS, bRS, bJsonB, iArg, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|SQLITE_DETERMINISTIC|SQLITE_FUNC_CONSTANT|\
+   SQLITE_UTF8|((bUseCache)*SQLITE_FUNC_RUNONLY)|\
+   ((bRS)*SQLITE_SUBTYPE)|((bWS)*SQLITE_RESULT_SUBTYPE), \
+   SQLITE_INT_TO_PTR(iArg|((bJsonB)*JSON_BLOB)),0,xFunc,0, 0, 0, #zName, {0} }
+#define INLINE_FUNC(zName, nArg, iArg, mFlags) \
+  {nArg, SQLITE_FUNC_BUILTIN|\
+   SQLITE_UTF8|SQLITE_FUNC_INLINE|SQLITE_FUNC_CONSTANT|(mFlags), \
+   SQLITE_INT_TO_PTR(iArg), 0, noopFunc, 0, 0, 0, #zName, {0} }
+#define TEST_FUNC(zName, nArg, iArg, mFlags) \
+  {nArg, SQLITE_FUNC_BUILTIN|\
+         SQLITE_UTF8|SQLITE_FUNC_INTERNAL|SQLITE_FUNC_TEST| \
+         SQLITE_FUNC_INLINE|SQLITE_FUNC_CONSTANT|(mFlags), \
+   SQLITE_INT_TO_PTR(iArg), 0, noopFunc, 0, 0, 0, #zName, {0} }
+#define DFUNCTION(zName, nArg, iArg, bNC, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|SQLITE_FUNC_SLOCHNG|SQLITE_UTF8, \
+   0, 0, xFunc, 0, 0, 0, #zName, {0} }
+#define PURE_DATE(zName, nArg, iArg, bNC, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|\
+         SQLITE_FUNC_SLOCHNG|SQLITE_UTF8|SQLITE_FUNC_CONSTANT, \
+   (void*)&sqlite3Config, 0, xFunc, 0, 0, 0, #zName, {0} }
+#define FUNCTION2(zName, nArg, iArg, bNC, xFunc, extraFlags) \
+  {nArg, SQLITE_FUNC_BUILTIN|\
+   SQLITE_FUNC_CONSTANT|SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL)|extraFlags,\
+   SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, 0, 0, #zName, {0} }
+#define STR_FUNCTION(zName, nArg, pArg, bNC, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|\
+   SQLITE_FUNC_SLOCHNG|SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL), \
+   pArg, 0, xFunc, 0, 0, 0, #zName, }
+#define LIKEFUNC(zName, nArg, arg, flags) \
+  {nArg, SQLITE_FUNC_BUILTIN|SQLITE_FUNC_CONSTANT|SQLITE_UTF8|flags, \
+   (void *)arg, 0, likeFunc, 0, 0, 0, #zName, {0} }
+#define WAGGREGATE(zName, nArg, arg, nc, xStep, xFinal, xValue, xInverse, f) \
+  {nArg, SQLITE_FUNC_BUILTIN|SQLITE_UTF8|(nc*SQLITE_FUNC_NEEDCOLL)|f, \
+   SQLITE_INT_TO_PTR(arg), 0, xStep,xFinal,xValue,xInverse,#zName, {0}}
+#define INTERNAL_FUNCTION(zName, nArg, xFunc) \
+  {nArg, SQLITE_FUNC_BUILTIN|\
+   SQLITE_FUNC_INTERNAL|SQLITE_UTF8|SQLITE_FUNC_CONSTANT, \
+   0, 0, xFunc, 0, 0, 0, #zName, {0} }
+
+
+/*
+** All current savepoints are stored in a linked list starting at
+** sqlite3.pSavepoint. The first element in the list is the most recently
+** opened savepoint. Savepoints are added to the list by the vdbe
+** OP_Savepoint instruction.
+*/
+struct Savepoint {
+  char *zName;                        /* Savepoint name (nul-terminated) */
+  i64 nDeferredCons;                  /* Number of deferred fk violations */
+  i64 nDeferredImmCons;               /* Number of deferred imm fk. */
+  Savepoint *pNext;                   /* Parent savepoint (if any) */
+};
+
+/*
+** The following are used as the second parameter to sqlite3Savepoint(),
+** and as the P1 argument to the OP_Savepoint instruction.
+*/
+#define SAVEPOINT_BEGIN      0
+#define SAVEPOINT_RELEASE    1
+#define SAVEPOINT_ROLLBACK   2
+
+
+/*
+** Each SQLite module (virtual table definition) is defined by an
+** instance of the following structure, stored in the sqlite3.aModule
+** hash table.
+*/
+struct Module {
+  const sqlite3_module *pModule;       /* Callback pointers */
+  const char *zName;                   /* Name passed to create_module() */
+  int nRefModule;                      /* Number of pointers to this object */
+  void *pAux;                          /* pAux passed to create_module() */
+  void (*xDestroy)(void *);            /* Module destructor function */
+  Table *pEpoTab;                      /* Eponymous table for this module */
+};
+
+/*
+** Information about each column of an SQL table is held in an instance
+** of the Column structure, in the Table.aCol[] array.
+**
+** Definitions:
+**
+**   "table column index"     This is the index of the column in the
+**                            Table.aCol[] array, and also the index of
+**                            the column in the original CREATE TABLE stmt.
+**
+**   "storage column index"   This is the index of the column in the
+**                            record BLOB generated by the OP_MakeRecord
+**                            opcode.  The storage column index is less than
+**                            or equal to the table column index.  It is
+**                            equal if and only if there are no VIRTUAL
+**                            columns to the left.
+**
+** Notes on zCnName:
+** The zCnName field stores the name of the column, the datatype of the
+** column, and the collating sequence for the column, in that order, all in
+** a single allocation.  Each string is 0x00 terminated.  The datatype
+** is only included if the COLFLAG_HASTYPE bit of colFlags is set and the
+** collating sequence name is only included if the COLFLAG_HASCOLL bit is
+** set.
+*/
+struct Column {
+  char *zCnName;        /* Name of this column */
+  unsigned notNull :4;  /* An OE_ code for handling a NOT NULL constraint */
+  unsigned eCType :4;   /* One of the standard types */
+  char affinity;        /* One of the SQLITE_AFF_... values */
+  u8 szEst;             /* Est size of value in this column. sizeof(INT)==1 */
+  u8 hName;             /* Column name hash for faster lookup */
+  u16 iDflt;            /* 1-based index of DEFAULT.  0 means "none" */
+  u16 colFlags;         /* Boolean properties.  See COLFLAG_ defines below */
+};
+
+/* Allowed values for Column.eCType.
+**
+** Values must match entries in the global constant arrays
+** sqlite3StdTypeLen[] and sqlite3StdType[].  Each value is one more
+** than the offset into these arrays for the corresponding name.
+** Adjust the SQLITE_N_STDTYPE value if adding or removing entries.
+*/
+#define COLTYPE_CUSTOM      0   /* Type appended to zName */
+#define COLTYPE_ANY         1
+#define COLTYPE_BLOB        2
+#define COLTYPE_INT         3
+#define COLTYPE_INTEGER     4
+#define COLTYPE_REAL        5
+#define COLTYPE_TEXT        6
+#define SQLITE_N_STDTYPE    6  /* Number of standard types */
+
+/* Allowed values for Column.colFlags.
+**
+** Constraints:
+**         TF_HasVirtual == COLFLAG_VIRTUAL
+**         TF_HasStored  == COLFLAG_STORED
+**         TF_HasHidden  == COLFLAG_HIDDEN
+*/
+#define COLFLAG_PRIMKEY   0x0001   /* Column is part of the primary key */
+#define COLFLAG_HIDDEN    0x0002   /* A hidden column in a virtual table */
+#define COLFLAG_HASTYPE   0x0004   /* Type name follows column name */
+#define COLFLAG_UNIQUE    0x0008   /* Column def contains "UNIQUE" or "PK" */
+#define COLFLAG_SORTERREF 0x0010   /* Use sorter-refs with this column */
+#define COLFLAG_VIRTUAL   0x0020   /* GENERATED ALWAYS AS ... VIRTUAL */
+#define COLFLAG_STORED    0x0040   /* GENERATED ALWAYS AS ... STORED */
+#define COLFLAG_NOTAVAIL  0x0080   /* STORED column not yet calculated */
+#define COLFLAG_BUSY      0x0100   /* Blocks recursion on GENERATED columns */
+#define COLFLAG_HASCOLL   0x0200   /* Has collating sequence name in zCnName */
+#define COLFLAG_NOEXPAND  0x0400   /* Omit this column when expanding "*" */
+#define COLFLAG_GENERATED 0x0060   /* Combo: _STORED, _VIRTUAL */
+#define COLFLAG_NOINSERT  0x0062   /* Combo: _HIDDEN, _STORED, _VIRTUAL */
+
+/*
+** A "Collating Sequence" is defined by an instance of the following
+** structure. Conceptually, a collating sequence consists of a name and
+** a comparison routine that defines the order of that sequence.
+**
+** If CollSeq.xCmp is NULL, it means that the
+** collating sequence is undefined.  Indices built on an undefined
+** collating sequence may not be read or written.
+*/
+struct CollSeq {
+  char *zName;          /* Name of the collating sequence, UTF-8 encoded */
+  u8 enc;               /* Text encoding handled by xCmp() */
+  void *pUser;          /* First argument to xCmp() */
+  int (*xCmp)(void*,int, const void*, int, const void*);
+  void (*xDel)(void*);  /* Destructor for pUser */
+};
+
+/*
+** A sort order can be either ASC or DESC.
+*/
+#define SQLITE_SO_ASC       0  /* Sort in ascending order */
+#define SQLITE_SO_DESC      1  /* Sort in ascending order */
+#define SQLITE_SO_UNDEFINED -1 /* No sort order specified */
+
+/*
+** Column affinity types.
+**
+** These used to have mnemonic name like 'i' for SQLITE_AFF_INTEGER and
+** 't' for SQLITE_AFF_TEXT.  But we can save a little space and improve
+** the speed a little by numbering the values consecutively.
+**
+** But rather than start with 0 or 1, we begin with 'A'.  That way,
+** when multiple affinity types are concatenated into a string and
+** used as the P4 operand, they will be more readable.
+**
+** Note also that the numeric types are grouped together so that testing
+** for a numeric type is a single comparison.  And the BLOB type is first.
+*/
+#define SQLITE_AFF_NONE     0x40  /* '@' */
+#define SQLITE_AFF_BLOB     0x41  /* 'A' */
+#define SQLITE_AFF_TEXT     0x42  /* 'B' */
+#define SQLITE_AFF_NUMERIC  0x43  /* 'C' */
+#define SQLITE_AFF_INTEGER  0x44  /* 'D' */
+#define SQLITE_AFF_REAL     0x45  /* 'E' */
+#define SQLITE_AFF_FLEXNUM  0x46  /* 'F' */
+
+#define sqlite3IsNumericAffinity(X)  ((X)>=SQLITE_AFF_NUMERIC)
+
+/*
+** The SQLITE_AFF_MASK values masks off the significant bits of an
+** affinity value.
+*/
+#define SQLITE_AFF_MASK     0x47
+
+/*
+** Additional bit values that can be ORed with an affinity without
+** changing the affinity.
+**
+** The SQLITE_NOTNULL flag is a combination of NULLEQ and JUMPIFNULL.
+** It causes an assert() to fire if either operand to a comparison
+** operator is NULL.  It is added to certain comparison operators to
+** prove that the operands are always NOT NULL.
+*/
+#define SQLITE_JUMPIFNULL   0x10  /* jumps if either operand is NULL */
+#define SQLITE_NULLEQ       0x80  /* NULL=NULL */
+#define SQLITE_NOTNULL      0x90  /* Assert that operands are never NULL */
+
+/*
+** An object of this type is created for each virtual table present in
+** the database schema.
+**
+** If the database schema is shared, then there is one instance of this
+** structure for each database connection (sqlite3*) that uses the shared
+** schema. This is because each database connection requires its own unique
+** instance of the sqlite3_vtab* handle used to access the virtual table
+** implementation. sqlite3_vtab* handles can not be shared between
+** database connections, even when the rest of the in-memory database
+** schema is shared, as the implementation often stores the database
+** connection handle passed to it via the xConnect() or xCreate() method
+** during initialization internally. This database connection handle may
+** then be used by the virtual table implementation to access real tables
+** within the database. So that they appear as part of the callers
+** transaction, these accesses need to be made via the same database
+** connection as that used to execute SQL operations on the virtual table.
+**
+** All VTable objects that correspond to a single table in a shared
+** database schema are initially stored in a linked-list pointed to by
+** the Table.pVTable member variable of the corresponding Table object.
+** When an sqlite3_prepare() operation is required to access the virtual
+** table, it searches the list for the VTable that corresponds to the
+** database connection doing the preparing so as to use the correct
+** sqlite3_vtab* handle in the compiled query.
+**
+** When an in-memory Table object is deleted (for example when the
+** schema is being reloaded for some reason), the VTable objects are not
+** deleted and the sqlite3_vtab* handles are not xDisconnect()ed
+** immediately. Instead, they are moved from the Table.pVTable list to
+** another linked list headed by the sqlite3.pDisconnect member of the
+** corresponding sqlite3 structure. They are then deleted/xDisconnected
+** next time a statement is prepared using said sqlite3*. This is done
+** to avoid deadlock issues involving multiple sqlite3.mutex mutexes.
+** Refer to comments above function sqlite3VtabUnlockList() for an
+** explanation as to why it is safe to add an entry to an sqlite3.pDisconnect
+** list without holding the corresponding sqlite3.mutex mutex.
+**
+** The memory for objects of this type is always allocated by
+** sqlite3DbMalloc(), using the connection handle stored in VTable.db as
+** the first argument.
+*/
+struct VTable {
+  sqlite3 *db;              /* Database connection associated with this table */
+  Module *pMod;             /* Pointer to module implementation */
+  sqlite3_vtab *pVtab;      /* Pointer to vtab instance */
+  int nRef;                 /* Number of pointers to this structure */
+  u8 bConstraint;           /* True if constraints are supported */
+  u8 bAllSchemas;           /* True if might use any attached schema */
+  u8 eVtabRisk;             /* Riskiness of allowing hacker access */
+  int iSavepoint;           /* Depth of the SAVEPOINT stack */
+  VTable *pNext;            /* Next in linked list (see above) */
+};
+
+/* Allowed values for VTable.eVtabRisk
+*/
+#define SQLITE_VTABRISK_Low          0
+#define SQLITE_VTABRISK_Normal       1
+#define SQLITE_VTABRISK_High         2
+
+/*
+** The schema for each SQL table, virtual table, and view is represented
+** in memory by an instance of the following structure.
+*/
+struct Table {
+  char *zName;         /* Name of the table or view */
+  Column *aCol;        /* Information about each column */
+  Index *pIndex;       /* List of SQL indexes on this table. */
+  char *zColAff;       /* String defining the affinity of each column */
+  ExprList *pCheck;    /* All CHECK constraints */
+                       /*   ... also used as column name list in a VIEW */
+  Pgno tnum;           /* Root BTree page for this table */
+  u32 nTabRef;         /* Number of pointers to this Table */
+  u32 tabFlags;        /* Mask of TF_* values */
+  i16 iPKey;           /* If not negative, use aCol[iPKey] as the rowid */
+  i16 nCol;            /* Number of columns in this table */
+  i16 nNVCol;          /* Number of columns that are not VIRTUAL */
+  LogEst nRowLogEst;   /* Estimated rows in table - from sqlite_stat1 table */
+  LogEst szTabRow;     /* Estimated size of each table row in bytes */
+#ifdef SQLITE_ENABLE_COSTMULT
+  LogEst costMult;     /* Cost multiplier for using this table */
+#endif
+  u8 keyConf;          /* What to do in case of uniqueness conflict on iPKey */
+  u8 eTabType;         /* 0: normal, 1: virtual, 2: view */
+  union {
+    struct {             /* Used by ordinary tables: */
+      int addColOffset;    /* Offset in CREATE TABLE stmt to add a new column */
+      FKey *pFKey;         /* Linked list of all foreign keys in this table */
+      ExprList *pDfltList; /* DEFAULT clauses on various columns.
+                           ** Or the AS clause for generated columns. */
+    } tab;
+    struct {             /* Used by views: */
+      Select *pSelect;     /* View definition */
+    } view;
+    struct {             /* Used by virtual tables only: */
+      int nArg;            /* Number of arguments to the module */
+      char **azArg;        /* 0: module 1: schema 2: vtab name 3...: args */
+      VTable *p;           /* List of VTable objects. */
+    } vtab;
+  } u;
+  Trigger *pTrigger;   /* List of triggers on this object */
+  Schema *pSchema;     /* Schema that contains this table */
+};
+
+/*
+** Allowed values for Table.tabFlags.
+**
+** TF_OOOHidden applies to tables or view that have hidden columns that are
+** followed by non-hidden columns.  Example:  "CREATE VIRTUAL TABLE x USING
+** vtab1(a HIDDEN, b);".  Since "b" is a non-hidden column but "a" is hidden,
+** the TF_OOOHidden attribute would apply in this case.  Such tables require
+** special handling during INSERT processing. The "OOO" means "Out Of Order".
+**
+** Constraints:
+**
+**         TF_HasVirtual == COLFLAG_VIRTUAL
+**         TF_HasStored  == COLFLAG_STORED
+**         TF_HasHidden  == COLFLAG_HIDDEN
+*/
+#define TF_Readonly       0x00000001 /* Read-only system table */
+#define TF_HasHidden      0x00000002 /* Has one or more hidden columns */
+#define TF_HasPrimaryKey  0x00000004 /* Table has a primary key */
+#define TF_Autoincrement  0x00000008 /* Integer primary key is autoincrement */
+#define TF_HasStat1       0x00000010 /* nRowLogEst set from sqlite_stat1 */
+#define TF_HasVirtual     0x00000020 /* Has one or more VIRTUAL columns */
+#define TF_HasStored      0x00000040 /* Has one or more STORED columns */
+#define TF_HasGenerated   0x00000060 /* Combo: HasVirtual + HasStored */
+#define TF_WithoutRowid   0x00000080 /* No rowid.  PRIMARY KEY is the key */
+#define TF_StatsUsed      0x00000100 /* Query planner decisions affected by
+                                     ** Index.aiRowLogEst[] values */
+#define TF_NoVisibleRowid 0x00000200 /* No user-visible "rowid" column */
+#define TF_OOOHidden      0x00000400 /* Out-of-Order hidden columns */
+#define TF_HasNotNull     0x00000800 /* Contains NOT NULL constraints */
+#define TF_Shadow         0x00001000 /* True for a shadow table */
+#define TF_HasStat4       0x00002000 /* STAT4 info available for this table */
+#define TF_Ephemeral      0x00004000 /* An ephemeral table */
+#define TF_Eponymous      0x00008000 /* An eponymous virtual table */
+#define TF_Strict         0x00010000 /* STRICT mode */
+
+/*
+** Allowed values for Table.eTabType
+*/
+#define TABTYP_NORM      0     /* Ordinary table */
+#define TABTYP_VTAB      1     /* Virtual table */
+#define TABTYP_VIEW      2     /* A view */
+
+#define IsView(X)           ((X)->eTabType==TABTYP_VIEW)
+#define IsOrdinaryTable(X)  ((X)->eTabType==TABTYP_NORM)
+
+/*
+** Test to see whether or not a table is a virtual table.  This is
+** done as a macro so that it will be optimized out when virtual
+** table support is omitted from the build.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+#  define IsVirtual(X)      ((X)->eTabType==TABTYP_VTAB)
+#  define ExprIsVtab(X)  \
+   ((X)->op==TK_COLUMN && (X)->y.pTab->eTabType==TABTYP_VTAB)
+#else
+#  define IsVirtual(X)      0
+#  define ExprIsVtab(X)     0
+#endif
+
+/*
+** Macros to determine if a column is hidden.  IsOrdinaryHiddenColumn()
+** only works for non-virtual tables (ordinary tables and views) and is
+** always false unless SQLITE_ENABLE_HIDDEN_COLUMNS is defined.  The
+** IsHiddenColumn() macro is general purpose.
+*/
+#if defined(SQLITE_ENABLE_HIDDEN_COLUMNS)
+#  define IsHiddenColumn(X)         (((X)->colFlags & COLFLAG_HIDDEN)!=0)
+#  define IsOrdinaryHiddenColumn(X) (((X)->colFlags & COLFLAG_HIDDEN)!=0)
+#elif !defined(SQLITE_OMIT_VIRTUALTABLE)
+#  define IsHiddenColumn(X)         (((X)->colFlags & COLFLAG_HIDDEN)!=0)
+#  define IsOrdinaryHiddenColumn(X) 0
+#else
+#  define IsHiddenColumn(X)         0
+#  define IsOrdinaryHiddenColumn(X) 0
+#endif
+
+
+/* Does the table have a rowid */
+#define HasRowid(X)     (((X)->tabFlags & TF_WithoutRowid)==0)
+#define VisibleRowid(X) (((X)->tabFlags & TF_NoVisibleRowid)==0)
+
+/*
+** Each foreign key constraint is an instance of the following structure.
+**
+** A foreign key is associated with two tables.  The "from" table is
+** the table that contains the REFERENCES clause that creates the foreign
+** key.  The "to" table is the table that is named in the REFERENCES clause.
+** Consider this example:
+**
+**     CREATE TABLE ex1(
+**       a INTEGER PRIMARY KEY,
+**       b INTEGER CONSTRAINT fk1 REFERENCES ex2(x)
+**     );
+**
+** For foreign key "fk1", the from-table is "ex1" and the to-table is "ex2".
+** Equivalent names:
+**
+**     from-table == child-table
+**       to-table == parent-table
+**
+** Each REFERENCES clause generates an instance of the following structure
+** which is attached to the from-table.  The to-table need not exist when
+** the from-table is created.  The existence of the to-table is not checked.
+**
+** The list of all parents for child Table X is held at X.pFKey.
+**
+** A list of all children for a table named Z (which might not even exist)
+** is held in Schema.fkeyHash with a hash key of Z.
+*/
+struct FKey {
+  Table *pFrom;     /* Table containing the REFERENCES clause (aka: Child) */
+  FKey *pNextFrom;  /* Next FKey with the same in pFrom. Next parent of pFrom */
+  char *zTo;        /* Name of table that the key points to (aka: Parent) */
+  FKey *pNextTo;    /* Next with the same zTo. Next child of zTo. */
+  FKey *pPrevTo;    /* Previous with the same zTo */
+  int nCol;         /* Number of columns in this key */
+  /* EV: R-30323-21917 */
+  u8 isDeferred;       /* True if constraint checking is deferred till COMMIT */
+  u8 aAction[2];        /* ON DELETE and ON UPDATE actions, respectively */
+  Trigger *apTrigger[2];/* Triggers for aAction[] actions */
+  struct sColMap {      /* Mapping of columns in pFrom to columns in zTo */
+    int iFrom;            /* Index of column in pFrom */
+    char *zCol;           /* Name of column in zTo.  If NULL use PRIMARY KEY */
+  } aCol[1];            /* One entry for each of nCol columns */
+};
+
+/*
+** SQLite supports many different ways to resolve a constraint
+** error.  ROLLBACK processing means that a constraint violation
+** causes the operation in process to fail and for the current transaction
+** to be rolled back.  ABORT processing means the operation in process
+** fails and any prior changes from that one operation are backed out,
+** but the transaction is not rolled back.  FAIL processing means that
+** the operation in progress stops and returns an error code.  But prior
+** changes due to the same operation are not backed out and no rollback
+** occurs.  IGNORE means that the particular row that caused the constraint
+** error is not inserted or updated.  Processing continues and no error
+** is returned.  REPLACE means that preexisting database rows that caused
+** a UNIQUE constraint violation are removed so that the new insert or
+** update can proceed.  Processing continues and no error is reported.
+** UPDATE applies to insert operations only and means that the insert
+** is omitted and the DO UPDATE clause of an upsert is run instead.
+**
+** RESTRICT, SETNULL, SETDFLT, and CASCADE actions apply only to foreign keys.
+** RESTRICT is the same as ABORT for IMMEDIATE foreign keys and the
+** same as ROLLBACK for DEFERRED keys.  SETNULL means that the foreign
+** key is set to NULL.  SETDFLT means that the foreign key is set
+** to its default value.  CASCADE means that a DELETE or UPDATE of the
+** referenced table row is propagated into the row that holds the
+** foreign key.
+**
+** The OE_Default value is a place holder that means to use whatever
+** conflict resolution algorithm is required from context.
+**
+** The following symbolic values are used to record which type
+** of conflict resolution action to take.
+*/
+#define OE_None     0   /* There is no constraint to check */
+#define OE_Rollback 1   /* Fail the operation and rollback the transaction */
+#define OE_Abort    2   /* Back out changes but do no rollback transaction */
+#define OE_Fail     3   /* Stop the operation but leave all prior changes */
+#define OE_Ignore   4   /* Ignore the error. Do not do the INSERT or UPDATE */
+#define OE_Replace  5   /* Delete existing record, then do INSERT or UPDATE */
+#define OE_Update   6   /* Process as a DO UPDATE in an upsert */
+#define OE_Restrict 7   /* OE_Abort for IMMEDIATE, OE_Rollback for DEFERRED */
+#define OE_SetNull  8   /* Set the foreign key value to NULL */
+#define OE_SetDflt  9   /* Set the foreign key value to its default */
+#define OE_Cascade  10  /* Cascade the changes */
+#define OE_Default  11  /* Do whatever the default action is */
+
+
+/*
+** An instance of the following structure is passed as the first
+** argument to sqlite3VdbeKeyCompare and is used to control the
+** comparison of the two index keys.
+**
+** Note that aSortOrder[] and aColl[] have nField+1 slots.  There
+** are nField slots for the columns of an index then one extra slot
+** for the rowid at the end.
+*/
+struct KeyInfo {
+  u32 nRef;           /* Number of references to this KeyInfo object */
+  u8 enc;             /* Text encoding - one of the SQLITE_UTF* values */
+  u16 nKeyField;      /* Number of key columns in the index */
+  u16 nAllField;      /* Total columns, including key plus others */
+  sqlite3 *db;        /* The database connection */
+  u8 *aSortFlags;     /* Sort order for each column. */
+  CollSeq *aColl[1];  /* Collating sequence for each term of the key */
+};
+
+/*
+** Allowed bit values for entries in the KeyInfo.aSortFlags[] array.
+*/
+#define KEYINFO_ORDER_DESC    0x01    /* DESC sort order */
+#define KEYINFO_ORDER_BIGNULL 0x02    /* NULL is larger than any other value */
+
+/*
+** This object holds a record which has been parsed out into individual
+** fields, for the purposes of doing a comparison.
+**
+** A record is an object that contains one or more fields of data.
+** Records are used to store the content of a table row and to store
+** the key of an index.  A blob encoding of a record is created by
+** the OP_MakeRecord opcode of the VDBE and is disassembled by the
+** OP_Column opcode.
+**
+** An instance of this object serves as a "key" for doing a search on
+** an index b+tree. The goal of the search is to find the entry that
+** is closed to the key described by this object.  This object might hold
+** just a prefix of the key.  The number of fields is given by
+** pKeyInfo->nField.
+**
+** The r1 and r2 fields are the values to return if this key is less than
+** or greater than a key in the btree, respectively.  These are normally
+** -1 and +1 respectively, but might be inverted to +1 and -1 if the b-tree
+** is in DESC order.
+**
+** The key comparison functions actually return default_rc when they find
+** an equals comparison.  default_rc can be -1, 0, or +1.  If there are
+** multiple entries in the b-tree with the same key (when only looking
+** at the first pKeyInfo->nFields,) then default_rc can be set to -1 to
+** cause the search to find the last match, or +1 to cause the search to
+** find the first match.
+**
+** The key comparison functions will set eqSeen to true if they ever
+** get and equal results when comparing this structure to a b-tree record.
+** When default_rc!=0, the search might end up on the record immediately
+** before the first match or immediately after the last match.  The
+** eqSeen field will indicate whether or not an exact match exists in the
+** b-tree.
+*/
+struct UnpackedRecord {
+  KeyInfo *pKeyInfo;  /* Collation and sort-order information */
+  Mem *aMem;          /* Values */
+  union {
+    char *z;            /* Cache of aMem[0].z for vdbeRecordCompareString() */
+    i64 i;              /* Cache of aMem[0].u.i for vdbeRecordCompareInt() */
+  } u;
+  int n;              /* Cache of aMem[0].n used by vdbeRecordCompareString() */
+  u16 nField;         /* Number of entries in apMem[] */
+  i8 default_rc;      /* Comparison result if keys are equal */
+  u8 errCode;         /* Error detected by xRecordCompare (CORRUPT or NOMEM) */
+  i8 r1;              /* Value to return if (lhs < rhs) */
+  i8 r2;              /* Value to return if (lhs > rhs) */
+  u8 eqSeen;          /* True if an equality comparison has been seen */
+};
+
+
+/*
+** Each SQL index is represented in memory by an
+** instance of the following structure.
+**
+** The columns of the table that are to be indexed are described
+** by the aiColumn[] field of this structure.  For example, suppose
+** we have the following table and index:
+**
+**     CREATE TABLE Ex1(c1 int, c2 int, c3 text);
+**     CREATE INDEX Ex2 ON Ex1(c3,c1);
+**
+** In the Table structure describing Ex1, nCol==3 because there are
+** three columns in the table.  In the Index structure describing
+** Ex2, nColumn==2 since 2 of the 3 columns of Ex1 are indexed.
+** The value of aiColumn is {2, 0}.  aiColumn[0]==2 because the
+** first column to be indexed (c3) has an index of 2 in Ex1.aCol[].
+** The second column to be indexed (c1) has an index of 0 in
+** Ex1.aCol[], hence Ex2.aiColumn[1]==0.
+**
+** The Index.onError field determines whether or not the indexed columns
+** must be unique and what to do if they are not.  When Index.onError=OE_None,
+** it means this is not a unique index.  Otherwise it is a unique index
+** and the value of Index.onError indicates which conflict resolution
+** algorithm to employ when an attempt is made to insert a non-unique
+** element.
+**
+** The colNotIdxed bitmask is used in combination with SrcItem.colUsed
+** for a fast test to see if an index can serve as a covering index.
+** colNotIdxed has a 1 bit for every column of the original table that
+** is *not* available in the index.  Thus the expression
+** "colUsed & colNotIdxed" will be non-zero if the index is not a
+** covering index.  The most significant bit of of colNotIdxed will always
+** be true (note-20221022-a).  If a column beyond the 63rd column of the
+** table is used, the "colUsed & colNotIdxed" test will always be non-zero
+** and we have to assume either that the index is not covering, or use
+** an alternative (slower) algorithm to determine whether or not
+** the index is covering.
+**
+** While parsing a CREATE TABLE or CREATE INDEX statement in order to
+** generate VDBE code (as opposed to parsing one read from an sqlite_schema
+** table as part of parsing an existing database schema), transient instances
+** of this structure may be created. In this case the Index.tnum variable is
+** used to store the address of a VDBE instruction, not a database page
+** number (it cannot - the database page is not allocated until the VDBE
+** program is executed). See convertToWithoutRowidTable() for details.
+*/
+struct Index {
+  char *zName;             /* Name of this index */
+  i16 *aiColumn;           /* Which columns are used by this index.  1st is 0 */
+  LogEst *aiRowLogEst;     /* From ANALYZE: Est. rows selected by each column */
+  Table *pTable;           /* The SQL table being indexed */
+  char *zColAff;           /* String defining the affinity of each column */
+  Index *pNext;            /* The next index associated with the same table */
+  Schema *pSchema;         /* Schema containing this index */
+  u8 *aSortOrder;          /* for each column: True==DESC, False==ASC */
+  const char **azColl;     /* Array of collation sequence names for index */
+  Expr *pPartIdxWhere;     /* WHERE clause for partial indices */
+  ExprList *aColExpr;      /* Column expressions */
+  Pgno tnum;               /* DB Page containing root of this index */
+  LogEst szIdxRow;         /* Estimated average row size in bytes */
+  u16 nKeyCol;             /* Number of columns forming the key */
+  u16 nColumn;             /* Number of columns stored in the index */
+  u8 onError;              /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
+  unsigned idxType:2;      /* 0:Normal 1:UNIQUE, 2:PRIMARY KEY, 3:IPK */
+  unsigned bUnordered:1;   /* Use this index for == or IN queries only */
+  unsigned uniqNotNull:1;  /* True if UNIQUE and NOT NULL for all columns */
+  unsigned isResized:1;    /* True if resizeIndexObject() has been called */
+  unsigned isCovering:1;   /* True if this is a covering index */
+  unsigned noSkipScan:1;   /* Do not try to use skip-scan if true */
+  unsigned hasStat1:1;     /* aiRowLogEst values come from sqlite_stat1 */
+  unsigned bLowQual:1;     /* sqlite_stat1 says this is a low-quality index */
+  unsigned bNoQuery:1;     /* Do not use this index to optimize queries */
+  unsigned bAscKeyBug:1;   /* True if the bba7b69f9849b5bf bug applies */
+  unsigned bHasVCol:1;     /* Index references one or more VIRTUAL columns */
+  unsigned bHasExpr:1;     /* Index contains an expression, either a literal
+                           ** expression, or a reference to a VIRTUAL column */
+#ifdef SQLITE_ENABLE_STAT4
+  int nSample;             /* Number of elements in aSample[] */
+  int mxSample;            /* Number of slots allocated to aSample[] */
+  int nSampleCol;          /* Size of IndexSample.anEq[] and so on */
+  tRowcnt *aAvgEq;         /* Average nEq values for keys not in aSample */
+  IndexSample *aSample;    /* Samples of the left-most key */
+  tRowcnt *aiRowEst;       /* Non-logarithmic stat1 data for this index */
+  tRowcnt nRowEst0;        /* Non-logarithmic number of rows in the index */
+#endif
+  Bitmask colNotIdxed;     /* Unindexed columns in pTab */
+};
+
+/*
+** Allowed values for Index.idxType
+*/
+#define SQLITE_IDXTYPE_APPDEF      0   /* Created using CREATE INDEX */
+#define SQLITE_IDXTYPE_UNIQUE      1   /* Implements a UNIQUE constraint */
+#define SQLITE_IDXTYPE_PRIMARYKEY  2   /* Is the PRIMARY KEY for the table */
+#define SQLITE_IDXTYPE_IPK         3   /* INTEGER PRIMARY KEY index */
+
+/* Return true if index X is a PRIMARY KEY index */
+#define IsPrimaryKeyIndex(X)  ((X)->idxType==SQLITE_IDXTYPE_PRIMARYKEY)
+
+/* Return true if index X is a UNIQUE index */
+#define IsUniqueIndex(X)      ((X)->onError!=OE_None)
+
+/* The Index.aiColumn[] values are normally positive integer.  But
+** there are some negative values that have special meaning:
+*/
+#define XN_ROWID     (-1)     /* Indexed column is the rowid */
+#define XN_EXPR      (-2)     /* Indexed column is an expression */
+
+/*
+** Each sample stored in the sqlite_stat4 table is represented in memory
+** using a structure of this type.  See documentation at the top of the
+** analyze.c source file for additional information.
+*/
+struct IndexSample {
+  void *p;          /* Pointer to sampled record */
+  int n;            /* Size of record in bytes */
+  tRowcnt *anEq;    /* Est. number of rows where the key equals this sample */
+  tRowcnt *anLt;    /* Est. number of rows where key is less than this sample */
+  tRowcnt *anDLt;   /* Est. number of distinct keys less than this sample */
+};
+
+/*
+** Possible values to use within the flags argument to sqlite3GetToken().
+*/
+#define SQLITE_TOKEN_QUOTED    0x1 /* Token is a quoted identifier. */
+#define SQLITE_TOKEN_KEYWORD   0x2 /* Token is a keyword. */
+
+/*
+** Each token coming out of the lexer is an instance of
+** this structure.  Tokens are also used as part of an expression.
+**
+** The memory that "z" points to is owned by other objects.  Take care
+** that the owner of the "z" string does not deallocate the string before
+** the Token goes out of scope!  Very often, the "z" points to some place
+** in the middle of the Parse.zSql text.  But it might also point to a
+** static string.
+*/
+struct Token {
+  const char *z;     /* Text of the token.  Not NULL-terminated! */
+  unsigned int n;    /* Number of characters in this token */
+};
+
+/*
+** An instance of this structure contains information needed to generate
+** code for a SELECT that contains aggregate functions.
+**
+** If Expr.op==TK_AGG_COLUMN or TK_AGG_FUNCTION then Expr.pAggInfo is a
+** pointer to this structure.  The Expr.iAgg field is the index in
+** AggInfo.aCol[] or AggInfo.aFunc[] of information needed to generate
+** code for that node.
+**
+** AggInfo.pGroupBy and AggInfo.aFunc.pExpr point to fields within the
+** original Select structure that describes the SELECT statement.  These
+** fields do not need to be freed when deallocating the AggInfo structure.
+*/
+struct AggInfo {
+  u8 directMode;          /* Direct rendering mode means take data directly
+                          ** from source tables rather than from accumulators */
+  u8 useSortingIdx;       /* In direct mode, reference the sorting index rather
+                          ** than the source table */
+  u16 nSortingColumn;     /* Number of columns in the sorting index */
+  int sortingIdx;         /* Cursor number of the sorting index */
+  int sortingIdxPTab;     /* Cursor number of pseudo-table */
+  int iFirstReg;          /* First register in range for aCol[] and aFunc[] */
+  ExprList *pGroupBy;     /* The group by clause */
+  struct AggInfo_col {    /* For each column used in source tables */
+    Table *pTab;             /* Source table */
+    Expr *pCExpr;            /* The original expression */
+    int iTable;              /* Cursor number of the source table */
+    i16 iColumn;             /* Column number within the source table */
+    i16 iSorterColumn;       /* Column number in the sorting index */
+  } *aCol;
+  int nColumn;            /* Number of used entries in aCol[] */
+  int nAccumulator;       /* Number of columns that show through to the output.
+                          ** Additional columns are used only as parameters to
+                          ** aggregate functions */
+  struct AggInfo_func {   /* For each aggregate function */
+    Expr *pFExpr;            /* Expression encoding the function */
+    FuncDef *pFunc;          /* The aggregate function implementation */
+    int iDistinct;           /* Ephemeral table used to enforce DISTINCT */
+    int iDistAddr;           /* Address of OP_OpenEphemeral */
+    int iOBTab;              /* Ephemeral table to implement ORDER BY */
+    u8 bOBPayload;           /* iOBTab has payload columns separate from key */
+    u8 bOBUnique;            /* Enforce uniqueness on iOBTab keys */
+    u8 bUseSubtype;          /* Transfer subtype info through sorter */
+  } *aFunc;
+  int nFunc;              /* Number of entries in aFunc[] */
+  u32 selId;              /* Select to which this AggInfo belongs */
+#ifdef SQLITE_DEBUG
+  Select *pSelect;        /* SELECT statement that this AggInfo supports */
+#endif
+};
+
+/*
+** Macros to compute aCol[] and aFunc[] register numbers.
+**
+** These macros should not be used prior to the call to
+** assignAggregateRegisters() that computes the value of pAggInfo->iFirstReg.
+** The assert()s that are part of this macro verify that constraint.
+*/
+#define AggInfoColumnReg(A,I)  (assert((A)->iFirstReg),(A)->iFirstReg+(I))
+#define AggInfoFuncReg(A,I)    \
+                      (assert((A)->iFirstReg),(A)->iFirstReg+(A)->nColumn+(I))
+
+/*
+** The datatype ynVar is a signed integer, either 16-bit or 32-bit.
+** Usually it is 16-bits.  But if SQLITE_MAX_VARIABLE_NUMBER is greater
+** than 32767 we have to make it 32-bit.  16-bit is preferred because
+** it uses less memory in the Expr object, which is a big memory user
+** in systems with lots of prepared statements.  And few applications
+** need more than about 10 or 20 variables.  But some extreme users want
+** to have prepared statements with over 32766 variables, and for them
+** the option is available (at compile-time).
+*/
+#if SQLITE_MAX_VARIABLE_NUMBER<32767
+typedef i16 ynVar;
+#else
+typedef int ynVar;
+#endif
+
+/*
+** Each node of an expression in the parse tree is an instance
+** of this structure.
+**
+** Expr.op is the opcode. The integer parser token codes are reused
+** as opcodes here. For example, the parser defines TK_GE to be an integer
+** code representing the ">=" operator. This same integer code is reused
+** to represent the greater-than-or-equal-to operator in the expression
+** tree.
+**
+** If the expression is an SQL literal (TK_INTEGER, TK_FLOAT, TK_BLOB,
+** or TK_STRING), then Expr.u.zToken contains the text of the SQL literal. If
+** the expression is a variable (TK_VARIABLE), then Expr.u.zToken contains the
+** variable name. Finally, if the expression is an SQL function (TK_FUNCTION),
+** then Expr.u.zToken contains the name of the function.
+**
+** Expr.pRight and Expr.pLeft are the left and right subexpressions of a
+** binary operator. Either or both may be NULL.
+**
+** Expr.x.pList is a list of arguments if the expression is an SQL function,
+** a CASE expression or an IN expression of the form "<lhs> IN (<y>, <z>...)".
+** Expr.x.pSelect is used if the expression is a sub-select or an expression of
+** the form "<lhs> IN (SELECT ...)". If the EP_xIsSelect bit is set in the
+** Expr.flags mask, then Expr.x.pSelect is valid. Otherwise, Expr.x.pList is
+** valid.
+**
+** An expression of the form ID or ID.ID refers to a column in a table.
+** For such expressions, Expr.op is set to TK_COLUMN and Expr.iTable is
+** the integer cursor number of a VDBE cursor pointing to that table and
+** Expr.iColumn is the column number for the specific column.  If the
+** expression is used as a result in an aggregate SELECT, then the
+** value is also stored in the Expr.iAgg column in the aggregate so that
+** it can be accessed after all aggregates are computed.
+**
+** If the expression is an unbound variable marker (a question mark
+** character '?' in the original SQL) then the Expr.iTable holds the index
+** number for that variable.
+**
+** If the expression is a subquery then Expr.iColumn holds an integer
+** register number containing the result of the subquery.  If the
+** subquery gives a constant result, then iTable is -1.  If the subquery
+** gives a different answer at different times during statement processing
+** then iTable is the address of a subroutine that computes the subquery.
+**
+** If the Expr is of type OP_Column, and the table it is selecting from
+** is a disk table or the "old.*" pseudo-table, then pTab points to the
+** corresponding table definition.
+**
+** ALLOCATION NOTES:
+**
+** Expr objects can use a lot of memory space in database schema.  To
+** help reduce memory requirements, sometimes an Expr object will be
+** truncated.  And to reduce the number of memory allocations, sometimes
+** two or more Expr objects will be stored in a single memory allocation,
+** together with Expr.u.zToken strings.
+**
+** If the EP_Reduced and EP_TokenOnly flags are set when
+** an Expr object is truncated.  When EP_Reduced is set, then all
+** the child Expr objects in the Expr.pLeft and Expr.pRight subtrees
+** are contained within the same memory allocation.  Note, however, that
+** the subtrees in Expr.x.pList or Expr.x.pSelect are always separately
+** allocated, regardless of whether or not EP_Reduced is set.
+*/
+struct Expr {
+  u8 op;                 /* Operation performed by this node */
+  char affExpr;          /* affinity, or RAISE type */
+  u8 op2;                /* TK_REGISTER/TK_TRUTH: original value of Expr.op
+                         ** TK_COLUMN: the value of p5 for OP_Column
+                         ** TK_AGG_FUNCTION: nesting depth
+                         ** TK_FUNCTION: NC_SelfRef flag if needs OP_PureFunc */
+#ifdef SQLITE_DEBUG
+  u8 vvaFlags;           /* Verification flags. */
+#endif
+  u32 flags;             /* Various flags.  EP_* See below */
+  union {
+    char *zToken;          /* Token value. Zero terminated and dequoted */
+    int iValue;            /* Non-negative integer value if EP_IntValue */
+  } u;
+
+  /* If the EP_TokenOnly flag is set in the Expr.flags mask, then no
+  ** space is allocated for the fields below this point. An attempt to
+  ** access them will result in a segfault or malfunction.
+  *********************************************************************/
+
+  Expr *pLeft;           /* Left subnode */
+  Expr *pRight;          /* Right subnode */
+  union {
+    ExprList *pList;     /* op = IN, EXISTS, SELECT, CASE, FUNCTION, BETWEEN */
+    Select *pSelect;     /* EP_xIsSelect and op = IN, EXISTS, SELECT */
+  } x;
+
+  /* If the EP_Reduced flag is set in the Expr.flags mask, then no
+  ** space is allocated for the fields below this point. An attempt to
+  ** access them will result in a segfault or malfunction.
+  *********************************************************************/
+
+#if SQLITE_MAX_EXPR_DEPTH>0
+  int nHeight;           /* Height of the tree headed by this node */
+#endif
+  int iTable;            /* TK_COLUMN: cursor number of table holding column
+                         ** TK_REGISTER: register number
+                         ** TK_TRIGGER: 1 -> new, 0 -> old
+                         ** EP_Unlikely:  134217728 times likelihood
+                         ** TK_IN: ephemeral table holding RHS
+                         ** TK_SELECT_COLUMN: Number of columns on the LHS
+                         ** TK_SELECT: 1st register of result vector */
+  ynVar iColumn;         /* TK_COLUMN: column index.  -1 for rowid.
+                         ** TK_VARIABLE: variable number (always >= 1).
+                         ** TK_SELECT_COLUMN: column of the result vector */
+  i16 iAgg;              /* Which entry in pAggInfo->aCol[] or ->aFunc[] */
+  union {
+    int iJoin;             /* If EP_OuterON or EP_InnerON, the right table */
+    int iOfst;             /* else: start of token from start of statement */
+  } w;
+  AggInfo *pAggInfo;     /* Used by TK_AGG_COLUMN and TK_AGG_FUNCTION */
+  union {
+    Table *pTab;           /* TK_COLUMN: Table containing column. Can be NULL
+                           ** for a column of an index on an expression */
+    Window *pWin;          /* EP_WinFunc: Window/Filter defn for a function */
+    struct {               /* TK_IN, TK_SELECT, and TK_EXISTS */
+      int iAddr;             /* Subroutine entry address */
+      int regReturn;         /* Register used to hold return address */
+    } sub;
+  } y;
+};
+
+/* The following are the meanings of bits in the Expr.flags field.
+** Value restrictions:
+**
+**          EP_Agg == NC_HasAgg == SF_HasAgg
+**          EP_Win == NC_HasWin
+*/
+#define EP_OuterON    0x000001 /* Originates in ON/USING clause of outer join */
+#define EP_InnerON    0x000002 /* Originates in ON/USING of an inner join */
+#define EP_Distinct   0x000004 /* Aggregate function with DISTINCT keyword */
+#define EP_HasFunc    0x000008 /* Contains one or more functions of any kind */
+#define EP_Agg        0x000010 /* Contains one or more aggregate functions */
+#define EP_FixedCol   0x000020 /* TK_Column with a known fixed value */
+#define EP_VarSelect  0x000040 /* pSelect is correlated, not constant */
+#define EP_DblQuoted  0x000080 /* token.z was originally in "..." */
+#define EP_InfixFunc  0x000100 /* True for an infix function: LIKE, GLOB, etc */
+#define EP_Collate    0x000200 /* Tree contains a TK_COLLATE operator */
+#define EP_Commuted   0x000400 /* Comparison operator has been commuted */
+#define EP_IntValue   0x000800 /* Integer value contained in u.iValue */
+#define EP_xIsSelect  0x001000 /* x.pSelect is valid (otherwise x.pList is) */
+#define EP_Skip       0x002000 /* Operator does not contribute to affinity */
+#define EP_Reduced    0x004000 /* Expr struct EXPR_REDUCEDSIZE bytes only */
+#define EP_Win        0x008000 /* Contains window functions */
+#define EP_TokenOnly  0x010000 /* Expr struct EXPR_TOKENONLYSIZE bytes only */
+#define EP_FullSize   0x020000 /* Expr structure must remain full sized */
+#define EP_IfNullRow  0x040000 /* The TK_IF_NULL_ROW opcode */
+#define EP_Unlikely   0x080000 /* unlikely() or likelihood() function */
+#define EP_ConstFunc  0x100000 /* A SQLITE_FUNC_CONSTANT or _SLOCHNG function */
+#define EP_CanBeNull  0x200000 /* Can be null despite NOT NULL constraint */
+#define EP_Subquery   0x400000 /* Tree contains a TK_SELECT operator */
+#define EP_Leaf       0x800000 /* Expr.pLeft, .pRight, .u.pSelect all NULL */
+#define EP_WinFunc   0x1000000 /* TK_FUNCTION with Expr.y.pWin set */
+#define EP_Subrtn    0x2000000 /* Uses Expr.y.sub. TK_IN, _SELECT, or _EXISTS */
+#define EP_Quoted    0x4000000 /* TK_ID was originally quoted */
+#define EP_Static    0x8000000 /* Held in memory not obtained from malloc() */
+#define EP_IsTrue   0x10000000 /* Always has boolean value of TRUE */
+#define EP_IsFalse  0x20000000 /* Always has boolean value of FALSE */
+#define EP_FromDDL  0x40000000 /* Originates from sqlite_schema */
+               /*   0x80000000 // Available */
+
+/* The EP_Propagate mask is a set of properties that automatically propagate
+** upwards into parent nodes.
+*/
+#define EP_Propagate (EP_Collate|EP_Subquery|EP_HasFunc)
+
+/* Macros can be used to test, set, or clear bits in the
+** Expr.flags field.
+*/
+#define ExprHasProperty(E,P)     (((E)->flags&(P))!=0)
+#define ExprHasAllProperty(E,P)  (((E)->flags&(P))==(P))
+#define ExprSetProperty(E,P)     (E)->flags|=(P)
+#define ExprClearProperty(E,P)   (E)->flags&=~(P)
+#define ExprAlwaysTrue(E)   (((E)->flags&(EP_OuterON|EP_IsTrue))==EP_IsTrue)
+#define ExprAlwaysFalse(E)  (((E)->flags&(EP_OuterON|EP_IsFalse))==EP_IsFalse)
+#define ExprIsFullSize(E)   (((E)->flags&(EP_Reduced|EP_TokenOnly))==0)
+
+/* Macros used to ensure that the correct members of unions are accessed
+** in Expr.
+*/
+#define ExprUseUToken(E)    (((E)->flags&EP_IntValue)==0)
+#define ExprUseUValue(E)    (((E)->flags&EP_IntValue)!=0)
+#define ExprUseWOfst(E)     (((E)->flags&(EP_InnerON|EP_OuterON))==0)
+#define ExprUseWJoin(E)     (((E)->flags&(EP_InnerON|EP_OuterON))!=0)
+#define ExprUseXList(E)     (((E)->flags&EP_xIsSelect)==0)
+#define ExprUseXSelect(E)   (((E)->flags&EP_xIsSelect)!=0)
+#define ExprUseYTab(E)      (((E)->flags&(EP_WinFunc|EP_Subrtn))==0)
+#define ExprUseYWin(E)      (((E)->flags&EP_WinFunc)!=0)
+#define ExprUseYSub(E)      (((E)->flags&EP_Subrtn)!=0)
+
+/* Flags for use with Expr.vvaFlags
+*/
+#define EP_NoReduce   0x01  /* Cannot EXPRDUP_REDUCE this Expr */
+#define EP_Immutable  0x02  /* Do not change this Expr node */
+
+/* The ExprSetVVAProperty() macro is used for Verification, Validation,
+** and Accreditation only.  It works like ExprSetProperty() during VVA
+** processes but is a no-op for delivery.
+*/
+#ifdef SQLITE_DEBUG
+# define ExprSetVVAProperty(E,P)   (E)->vvaFlags|=(P)
+# define ExprHasVVAProperty(E,P)   (((E)->vvaFlags&(P))!=0)
+# define ExprClearVVAProperties(E) (E)->vvaFlags = 0
+#else
+# define ExprSetVVAProperty(E,P)
+# define ExprHasVVAProperty(E,P)   0
+# define ExprClearVVAProperties(E)
+#endif
+
+/*
+** Macros to determine the number of bytes required by a normal Expr
+** struct, an Expr struct with the EP_Reduced flag set in Expr.flags
+** and an Expr struct with the EP_TokenOnly flag set.
+*/
+#define EXPR_FULLSIZE           sizeof(Expr)           /* Full size */
+#define EXPR_REDUCEDSIZE        offsetof(Expr,iTable)  /* Common features */
+#define EXPR_TOKENONLYSIZE      offsetof(Expr,pLeft)   /* Fewer features */
+
+/*
+** Flags passed to the sqlite3ExprDup() function. See the header comment
+** above sqlite3ExprDup() for details.
+*/
+#define EXPRDUP_REDUCE         0x0001  /* Used reduced-size Expr nodes */
+
+/*
+** True if the expression passed as an argument was a function with
+** an OVER() clause (a window function).
+*/
+#ifdef SQLITE_OMIT_WINDOWFUNC
+# define IsWindowFunc(p) 0
+#else
+# define IsWindowFunc(p) ( \
+    ExprHasProperty((p), EP_WinFunc) && p->y.pWin->eFrmType!=TK_FILTER \
+ )
+#endif
+
+/*
+** A list of expressions.  Each expression may optionally have a
+** name.  An expr/name combination can be used in several ways, such
+** as the list of "expr AS ID" fields following a "SELECT" or in the
+** list of "ID = expr" items in an UPDATE.  A list of expressions can
+** also be used as the argument to a function, in which case the a.zName
+** field is not used.
+**
+** In order to try to keep memory usage down, the Expr.a.zEName field
+** is used for multiple purposes:
+**
+**     eEName          Usage
+**    ----------       -------------------------
+**    ENAME_NAME       (1) the AS of result set column
+**                     (2) COLUMN= of an UPDATE
+**
+**    ENAME_TAB        DB.TABLE.NAME used to resolve names
+**                     of subqueries
+**
+**    ENAME_SPAN       Text of the original result set
+**                     expression.
+*/
+struct ExprList {
+  int nExpr;             /* Number of expressions on the list */
+  int nAlloc;            /* Number of a[] slots allocated */
+  struct ExprList_item { /* For each expression in the list */
+    Expr *pExpr;            /* The parse tree for this expression */
+    char *zEName;           /* Token associated with this expression */
+    struct {
+      u8 sortFlags;           /* Mask of KEYINFO_ORDER_* flags */
+      unsigned eEName :2;     /* Meaning of zEName */
+      unsigned done :1;       /* Indicates when processing is finished */
+      unsigned reusable :1;   /* Constant expression is reusable */
+      unsigned bSorterRef :1; /* Defer evaluation until after sorting */
+      unsigned bNulls :1;     /* True if explicit "NULLS FIRST/LAST" */
+      unsigned bUsed :1;      /* This column used in a SF_NestedFrom subquery */
+      unsigned bUsingTerm:1;  /* Term from the USING clause of a NestedFrom */
+      unsigned bNoExpand: 1;  /* Term is an auxiliary in NestedFrom and should
+                              ** not be expanded by "*" in parent queries */
+    } fg;
+    union {
+      struct {             /* Used by any ExprList other than Parse.pConsExpr */
+        u16 iOrderByCol;      /* For ORDER BY, column number in result set */
+        u16 iAlias;           /* Index into Parse.aAlias[] for zName */
+      } x;
+      int iConstExprReg;   /* Register in which Expr value is cached. Used only
+                           ** by Parse.pConstExpr */
+    } u;
+  } a[1];                  /* One slot for each expression in the list */
+};
+
+/*
+** Allowed values for Expr.a.eEName
+*/
+#define ENAME_NAME  0       /* The AS clause of a result set */
+#define ENAME_SPAN  1       /* Complete text of the result set expression */
+#define ENAME_TAB   2       /* "DB.TABLE.NAME" for the result set */
+#define ENAME_ROWID 3       /* "DB.TABLE._rowid_" for * expansion of rowid */
+
+/*
+** An instance of this structure can hold a simple list of identifiers,
+** such as the list "a,b,c" in the following statements:
+**
+**      INSERT INTO t(a,b,c) VALUES ...;
+**      CREATE INDEX idx ON t(a,b,c);
+**      CREATE TRIGGER trig BEFORE UPDATE ON t(a,b,c) ...;
+**
+** The IdList.a.idx field is used when the IdList represents the list of
+** column names after a table name in an INSERT statement.  In the statement
+**
+**     INSERT INTO t(a,b,c) ...
+**
+** If "a" is the k-th column of table "t", then IdList.a[0].idx==k.
+*/
+struct IdList {
+  int nId;         /* Number of identifiers on the list */
+  u8 eU4;          /* Which element of a.u4 is valid */
+  struct IdList_item {
+    char *zName;      /* Name of the identifier */
+    union {
+      int idx;          /* Index in some Table.aCol[] of a column named zName */
+      Expr *pExpr;      /* Expr to implement a USING variable -- NOT USED */
+    } u4;
+  } a[1];
+};
+
+/*
+** Allowed values for IdList.eType, which determines which value of the a.u4
+** is valid.
+*/
+#define EU4_NONE   0   /* Does not use IdList.a.u4 */
+#define EU4_IDX    1   /* Uses IdList.a.u4.idx */
+#define EU4_EXPR   2   /* Uses IdList.a.u4.pExpr -- NOT CURRENTLY USED */
+
+/*
+** The SrcItem object represents a single term in the FROM clause of a query.
+** The SrcList object is mostly an array of SrcItems.
+**
+** The jointype starts out showing the join type between the current table
+** and the next table on the list.  The parser builds the list this way.
+** But sqlite3SrcListShiftJoinType() later shifts the jointypes so that each
+** jointype expresses the join between the table and the previous table.
+**
+** In the colUsed field, the high-order bit (bit 63) is set if the table
+** contains more than 63 columns and the 64-th or later column is used.
+**
+** Union member validity:
+**
+**    u1.zIndexedBy          fg.isIndexedBy && !fg.isTabFunc
+**    u1.pFuncArg            fg.isTabFunc   && !fg.isIndexedBy
+**    u2.pIBIndex            fg.isIndexedBy && !fg.isCte
+**    u2.pCteUse             fg.isCte       && !fg.isIndexedBy
+*/
+struct SrcItem {
+  Schema *pSchema;  /* Schema to which this item is fixed */
+  char *zDatabase;  /* Name of database holding this table */
+  char *zName;      /* Name of the table */
+  char *zAlias;     /* The "B" part of a "A AS B" phrase.  zName is the "A" */
+  Table *pTab;      /* An SQL table corresponding to zName */
+  Select *pSelect;  /* A SELECT statement used in place of a table name */
+  int addrFillSub;  /* Address of subroutine to manifest a subquery */
+  int regReturn;    /* Register holding return address of addrFillSub */
+  int regResult;    /* Registers holding results of a co-routine */
+  struct {
+    u8 jointype;      /* Type of join between this table and the previous */
+    unsigned notIndexed :1;    /* True if there is a NOT INDEXED clause */
+    unsigned isIndexedBy :1;   /* True if there is an INDEXED BY clause */
+    unsigned isTabFunc :1;     /* True if table-valued-function syntax */
+    unsigned isCorrelated :1;  /* True if sub-query is correlated */
+    unsigned isMaterialized:1; /* This is a materialized view */
+    unsigned viaCoroutine :1;  /* Implemented as a co-routine */
+    unsigned isRecursive :1;   /* True for recursive reference in WITH */
+    unsigned fromDDL :1;       /* Comes from sqlite_schema */
+    unsigned isCte :1;         /* This is a CTE */
+    unsigned notCte :1;        /* This item may not match a CTE */
+    unsigned isUsing :1;       /* u3.pUsing is valid */
+    unsigned isOn :1;          /* u3.pOn was once valid and non-NULL */
+    unsigned isSynthUsing :1;  /* u3.pUsing is synthesized from NATURAL */
+    unsigned isNestedFrom :1;  /* pSelect is a SF_NestedFrom subquery */
+  } fg;
+  int iCursor;      /* The VDBE cursor number used to access this table */
+  union {
+    Expr *pOn;        /* fg.isUsing==0 =>  The ON clause of a join */
+    IdList *pUsing;   /* fg.isUsing==1 =>  The USING clause of a join */
+  } u3;
+  Bitmask colUsed;  /* Bit N set if column N used. Details above for N>62 */
+  union {
+    char *zIndexedBy;    /* Identifier from "INDEXED BY <zIndex>" clause */
+    ExprList *pFuncArg;  /* Arguments to table-valued-function */
+  } u1;
+  union {
+    Index *pIBIndex;  /* Index structure corresponding to u1.zIndexedBy */
+    CteUse *pCteUse;  /* CTE Usage info when fg.isCte is true */
+  } u2;
+};
+
+/*
+** The OnOrUsing object represents either an ON clause or a USING clause.
+** It can never be both at the same time, but it can be neither.
+*/
+struct OnOrUsing {
+  Expr *pOn;         /* The ON clause of a join */
+  IdList *pUsing;    /* The USING clause of a join */
+};
+
+/*
+** This object represents one or more tables that are the source of
+** content for an SQL statement.  For example, a single SrcList object
+** is used to hold the FROM clause of a SELECT statement.  SrcList also
+** represents the target tables for DELETE, INSERT, and UPDATE statements.
+**
+*/
+struct SrcList {
+  int nSrc;        /* Number of tables or subqueries in the FROM clause */
+  u32 nAlloc;      /* Number of entries allocated in a[] below */
+  SrcItem a[1];    /* One entry for each identifier on the list */
+};
+
+/*
+** Permitted values of the SrcList.a.jointype field
+*/
+#define JT_INNER     0x01    /* Any kind of inner or cross join */
+#define JT_CROSS     0x02    /* Explicit use of the CROSS keyword */
+#define JT_NATURAL   0x04    /* True for a "natural" join */
+#define JT_LEFT      0x08    /* Left outer join */
+#define JT_RIGHT     0x10    /* Right outer join */
+#define JT_OUTER     0x20    /* The "OUTER" keyword is present */
+#define JT_LTORJ     0x40    /* One of the LEFT operands of a RIGHT JOIN
+                             ** Mnemonic: Left Table Of Right Join */
+#define JT_ERROR     0x80    /* unknown or unsupported join type */
+
+/*
+** Flags appropriate for the wctrlFlags parameter of sqlite3WhereBegin()
+** and the WhereInfo.wctrlFlags member.
+**
+** Value constraints (enforced via assert()):
+**     WHERE_USE_LIMIT  == SF_FixedLimit
+*/
+#define WHERE_ORDERBY_NORMAL   0x0000 /* No-op */
+#define WHERE_ORDERBY_MIN      0x0001 /* ORDER BY processing for min() func */
+#define WHERE_ORDERBY_MAX      0x0002 /* ORDER BY processing for max() func */
+#define WHERE_ONEPASS_DESIRED  0x0004 /* Want to do one-pass UPDATE/DELETE */
+#define WHERE_ONEPASS_MULTIROW 0x0008 /* ONEPASS is ok with multiple rows */
+#define WHERE_DUPLICATES_OK    0x0010 /* Ok to return a row more than once */
+#define WHERE_OR_SUBCLAUSE     0x0020 /* Processing a sub-WHERE as part of
+                                      ** the OR optimization  */
+#define WHERE_GROUPBY          0x0040 /* pOrderBy is really a GROUP BY */
+#define WHERE_DISTINCTBY       0x0080 /* pOrderby is really a DISTINCT clause */
+#define WHERE_WANT_DISTINCT    0x0100 /* All output needs to be distinct */
+#define WHERE_SORTBYGROUP      0x0200 /* Support sqlite3WhereIsSorted() */
+#define WHERE_AGG_DISTINCT     0x0400 /* Query is "SELECT agg(DISTINCT ...)" */
+#define WHERE_ORDERBY_LIMIT    0x0800 /* ORDERBY+LIMIT on the inner loop */
+#define WHERE_RIGHT_JOIN       0x1000 /* Processing a RIGHT JOIN */
+                        /*     0x2000    not currently used */
+#define WHERE_USE_LIMIT        0x4000 /* Use the LIMIT in cost estimates */
+                        /*     0x8000    not currently used */
+
+/* Allowed return values from sqlite3WhereIsDistinct()
+*/
+#define WHERE_DISTINCT_NOOP      0  /* DISTINCT keyword not used */
+#define WHERE_DISTINCT_UNIQUE    1  /* No duplicates */
+#define WHERE_DISTINCT_ORDERED   2  /* All duplicates are adjacent */
+#define WHERE_DISTINCT_UNORDERED 3  /* Duplicates are scattered */
+
+/*
+** A NameContext defines a context in which to resolve table and column
+** names.  The context consists of a list of tables (the pSrcList) field and
+** a list of named expression (pEList).  The named expression list may
+** be NULL.  The pSrc corresponds to the FROM clause of a SELECT or
+** to the table being operated on by INSERT, UPDATE, or DELETE.  The
+** pEList corresponds to the result set of a SELECT and is NULL for
+** other statements.
+**
+** NameContexts can be nested.  When resolving names, the inner-most
+** context is searched first.  If no match is found, the next outer
+** context is checked.  If there is still no match, the next context
+** is checked.  This process continues until either a match is found
+** or all contexts are check.  When a match is found, the nRef member of
+** the context containing the match is incremented.
+**
+** Each subquery gets a new NameContext.  The pNext field points to the
+** NameContext in the parent query.  Thus the process of scanning the
+** NameContext list corresponds to searching through successively outer
+** subqueries looking for a match.
+*/
+struct NameContext {
+  Parse *pParse;       /* The parser */
+  SrcList *pSrcList;   /* One or more tables used to resolve names */
+  union {
+    ExprList *pEList;    /* Optional list of result-set columns */
+    AggInfo *pAggInfo;   /* Information about aggregates at this level */
+    Upsert *pUpsert;     /* ON CONFLICT clause information from an upsert */
+    int iBaseReg;        /* For TK_REGISTER when parsing RETURNING */
+  } uNC;
+  NameContext *pNext;  /* Next outer name context.  NULL for outermost */
+  int nRef;            /* Number of names resolved by this context */
+  int nNcErr;          /* Number of errors encountered while resolving names */
+  int ncFlags;         /* Zero or more NC_* flags defined below */
+  u32 nNestedSelect;   /* Number of nested selects using this NC */
+  Select *pWinSelect;  /* SELECT statement for any window functions */
+};
+
+/*
+** Allowed values for the NameContext, ncFlags field.
+**
+** Value constraints (all checked via assert()):
+**    NC_HasAgg    == SF_HasAgg       == EP_Agg
+**    NC_MinMaxAgg == SF_MinMaxAgg    == SQLITE_FUNC_MINMAX
+**    NC_OrderAgg  == SF_OrderByReqd  == SQLITE_FUNC_ANYORDER
+**    NC_HasWin    == EP_Win
+**
+*/
+#define NC_AllowAgg  0x000001 /* Aggregate functions are allowed here */
+#define NC_PartIdx   0x000002 /* True if resolving a partial index WHERE */
+#define NC_IsCheck   0x000004 /* True if resolving a CHECK constraint */
+#define NC_GenCol    0x000008 /* True for a GENERATED ALWAYS AS clause */
+#define NC_HasAgg    0x000010 /* One or more aggregate functions seen */
+#define NC_IdxExpr   0x000020 /* True if resolving columns of CREATE INDEX */
+#define NC_SelfRef   0x00002e /* Combo: PartIdx, isCheck, GenCol, and IdxExpr */
+#define NC_Subquery  0x000040 /* A subquery has been seen */
+#define NC_UEList    0x000080 /* True if uNC.pEList is used */
+#define NC_UAggInfo  0x000100 /* True if uNC.pAggInfo is used */
+#define NC_UUpsert   0x000200 /* True if uNC.pUpsert is used */
+#define NC_UBaseReg  0x000400 /* True if uNC.iBaseReg is used */
+#define NC_MinMaxAgg 0x001000 /* min/max aggregates seen.  See note above */
+#define NC_Complex   0x002000 /* True if a function or subquery seen */
+#define NC_AllowWin  0x004000 /* Window functions are allowed here */
+#define NC_HasWin    0x008000 /* One or more window functions seen */
+#define NC_IsDDL     0x010000 /* Resolving names in a CREATE statement */
+#define NC_InAggFunc 0x020000 /* True if analyzing arguments to an agg func */
+#define NC_FromDDL   0x040000 /* SQL text comes from sqlite_schema */
+#define NC_NoSelect  0x080000 /* Do not descend into sub-selects */
+#define NC_OrderAgg 0x8000000 /* Has an aggregate other than count/min/max */
+
+/*
+** An instance of the following object describes a single ON CONFLICT
+** clause in an upsert.
+**
+** The pUpsertTarget field is only set if the ON CONFLICT clause includes
+** conflict-target clause.  (In "ON CONFLICT(a,b)" the "(a,b)" is the
+** conflict-target clause.)  The pUpsertTargetWhere is the optional
+** WHERE clause used to identify partial unique indexes.
+**
+** pUpsertSet is the list of column=expr terms of the UPDATE statement.
+** The pUpsertSet field is NULL for a ON CONFLICT DO NOTHING.  The
+** pUpsertWhere is the WHERE clause for the UPDATE and is NULL if the
+** WHERE clause is omitted.
+*/
+struct Upsert {
+  ExprList *pUpsertTarget;  /* Optional description of conflict target */
+  Expr *pUpsertTargetWhere; /* WHERE clause for partial index targets */
+  ExprList *pUpsertSet;     /* The SET clause from an ON CONFLICT UPDATE */
+  Expr *pUpsertWhere;       /* WHERE clause for the ON CONFLICT UPDATE */
+  Upsert *pNextUpsert;      /* Next ON CONFLICT clause in the list */
+  u8 isDoUpdate;            /* True for DO UPDATE.  False for DO NOTHING */
+  /* Above this point is the parse tree for the ON CONFLICT clauses.
+  ** The next group of fields stores intermediate data. */
+  void *pToFree;            /* Free memory when deleting the Upsert object */
+  /* All fields above are owned by the Upsert object and must be freed
+  ** when the Upsert is destroyed.  The fields below are used to transfer
+  ** information from the INSERT processing down into the UPDATE processing
+  ** while generating code.  The fields below are owned by the INSERT
+  ** statement and will be freed by INSERT processing. */
+  Index *pUpsertIdx;        /* UNIQUE constraint specified by pUpsertTarget */
+  SrcList *pUpsertSrc;      /* Table to be updated */
+  int regData;              /* First register holding array of VALUES */
+  int iDataCur;             /* Index of the data cursor */
+  int iIdxCur;              /* Index of the first index cursor */
+};
+
+/*
+** An instance of the following structure contains all information
+** needed to generate code for a single SELECT statement.
+**
+** See the header comment on the computeLimitRegisters() routine for a
+** detailed description of the meaning of the iLimit and iOffset fields.
+**
+** addrOpenEphm[] entries contain the address of OP_OpenEphemeral opcodes.
+** These addresses must be stored so that we can go back and fill in
+** the P4_KEYINFO and P2 parameters later.  Neither the KeyInfo nor
+** the number of columns in P2 can be computed at the same time
+** as the OP_OpenEphm instruction is coded because not
+** enough information about the compound query is known at that point.
+** The KeyInfo for addrOpenTran[0] and [1] contains collating sequences
+** for the result set.  The KeyInfo for addrOpenEphm[2] contains collating
+** sequences for the ORDER BY clause.
+*/
+struct Select {
+  u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
+  LogEst nSelectRow;     /* Estimated number of result rows */
+  u32 selFlags;          /* Various SF_* values */
+  int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
+  u32 selId;             /* Unique identifier number for this SELECT */
+  int addrOpenEphm[2];   /* OP_OpenEphem opcodes related to this select */
+  ExprList *pEList;      /* The fields of the result */
+  SrcList *pSrc;         /* The FROM clause */
+  Expr *pWhere;          /* The WHERE clause */
+  ExprList *pGroupBy;    /* The GROUP BY clause */
+  Expr *pHaving;         /* The HAVING clause */
+  ExprList *pOrderBy;    /* The ORDER BY clause */
+  Select *pPrior;        /* Prior select in a compound select statement */
+  Select *pNext;         /* Next select to the left in a compound */
+  Expr *pLimit;          /* LIMIT expression. NULL means not used. */
+  With *pWith;           /* WITH clause attached to this select. Or NULL. */
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  Window *pWin;          /* List of window functions */
+  Window *pWinDefn;      /* List of named window definitions */
+#endif
+};
+
+/*
+** Allowed values for Select.selFlags.  The "SF" prefix stands for
+** "Select Flag".
+**
+** Value constraints (all checked via assert())
+**     SF_HasAgg      == NC_HasAgg
+**     SF_MinMaxAgg   == NC_MinMaxAgg     == SQLITE_FUNC_MINMAX
+**     SF_OrderByReqd == NC_OrderAgg      == SQLITE_FUNC_ANYORDER
+**     SF_FixedLimit  == WHERE_USE_LIMIT
+*/
+#define SF_Distinct      0x0000001 /* Output should be DISTINCT */
+#define SF_All           0x0000002 /* Includes the ALL keyword */
+#define SF_Resolved      0x0000004 /* Identifiers have been resolved */
+#define SF_Aggregate     0x0000008 /* Contains agg functions or a GROUP BY */
+#define SF_HasAgg        0x0000010 /* Contains aggregate functions */
+#define SF_UsesEphemeral 0x0000020 /* Uses the OpenEphemeral opcode */
+#define SF_Expanded      0x0000040 /* sqlite3SelectExpand() called on this */
+#define SF_HasTypeInfo   0x0000080 /* FROM subqueries have Table metadata */
+#define SF_Compound      0x0000100 /* Part of a compound query */
+#define SF_Values        0x0000200 /* Synthesized from VALUES clause */
+#define SF_MultiValue    0x0000400 /* Single VALUES term with multiple rows */
+#define SF_NestedFrom    0x0000800 /* Part of a parenthesized FROM clause */
+#define SF_MinMaxAgg     0x0001000 /* Aggregate containing min() or max() */
+#define SF_Recursive     0x0002000 /* The recursive part of a recursive CTE */
+#define SF_FixedLimit    0x0004000 /* nSelectRow set by a constant LIMIT */
+#define SF_MaybeConvert  0x0008000 /* Need convertCompoundSelectToSubquery() */
+#define SF_Converted     0x0010000 /* By convertCompoundSelectToSubquery() */
+#define SF_IncludeHidden 0x0020000 /* Include hidden columns in output */
+#define SF_ComplexResult 0x0040000 /* Result contains subquery or function */
+#define SF_WhereBegin    0x0080000 /* Really a WhereBegin() call.  Debug Only */
+#define SF_WinRewrite    0x0100000 /* Window function rewrite accomplished */
+#define SF_View          0x0200000 /* SELECT statement is a view */
+#define SF_NoopOrderBy   0x0400000 /* ORDER BY is ignored for this query */
+#define SF_UFSrcCheck    0x0800000 /* Check pSrc as required by UPDATE...FROM */
+#define SF_PushDown      0x1000000 /* SELECT has be modified by push-down opt */
+#define SF_MultiPart     0x2000000 /* Has multiple incompatible PARTITIONs */
+#define SF_CopyCte       0x4000000 /* SELECT statement is a copy of a CTE */
+#define SF_OrderByReqd   0x8000000 /* The ORDER BY clause may not be omitted */
+#define SF_UpdateFrom   0x10000000 /* Query originates with UPDATE FROM */
+
+/* True if S exists and has SF_NestedFrom */
+#define IsNestedFrom(S) ((S)!=0 && ((S)->selFlags&SF_NestedFrom)!=0)
+
+/*
+** The results of a SELECT can be distributed in several ways, as defined
+** by one of the following macros.  The "SRT" prefix means "SELECT Result
+** Type".
+**
+**     SRT_Union       Store results as a key in a temporary index
+**                     identified by pDest->iSDParm.
+**
+**     SRT_Except      Remove results from the temporary index pDest->iSDParm.
+**
+**     SRT_Exists      Store a 1 in memory cell pDest->iSDParm if the result
+**                     set is not empty.
+**
+**     SRT_Discard     Throw the results away.  This is used by SELECT
+**                     statements within triggers whose only purpose is
+**                     the side-effects of functions.
+**
+**     SRT_Output      Generate a row of output (using the OP_ResultRow
+**                     opcode) for each row in the result set.
+**
+**     SRT_Mem         Only valid if the result is a single column.
+**                     Store the first column of the first result row
+**                     in register pDest->iSDParm then abandon the rest
+**                     of the query.  This destination implies "LIMIT 1".
+**
+**     SRT_Set         The result must be a single column.  Store each
+**                     row of result as the key in table pDest->iSDParm.
+**                     Apply the affinity pDest->affSdst before storing
+**                     results.  Used to implement "IN (SELECT ...)".
+**
+**     SRT_EphemTab    Create an temporary table pDest->iSDParm and store
+**                     the result there. The cursor is left open after
+**                     returning.  This is like SRT_Table except that
+**                     this destination uses OP_OpenEphemeral to create
+**                     the table first.
+**
+**     SRT_Coroutine   Generate a co-routine that returns a new row of
+**                     results each time it is invoked.  The entry point
+**                     of the co-routine is stored in register pDest->iSDParm
+**                     and the result row is stored in pDest->nDest registers
+**                     starting with pDest->iSdst.
+**
+**     SRT_Table       Store results in temporary table pDest->iSDParm.
+**     SRT_Fifo        This is like SRT_EphemTab except that the table
+**                     is assumed to already be open.  SRT_Fifo has
+**                     the additional property of being able to ignore
+**                     the ORDER BY clause.
+**
+**     SRT_DistFifo    Store results in a temporary table pDest->iSDParm.
+**                     But also use temporary table pDest->iSDParm+1 as
+**                     a record of all prior results and ignore any duplicate
+**                     rows.  Name means:  "Distinct Fifo".
+**
+**     SRT_Queue       Store results in priority queue pDest->iSDParm (really
+**                     an index).  Append a sequence number so that all entries
+**                     are distinct.
+**
+**     SRT_DistQueue   Store results in priority queue pDest->iSDParm only if
+**                     the same record has never been stored before.  The
+**                     index at pDest->iSDParm+1 hold all prior stores.
+**
+**     SRT_Upfrom      Store results in the temporary table already opened by
+**                     pDest->iSDParm. If (pDest->iSDParm<0), then the temp
+**                     table is an intkey table - in this case the first
+**                     column returned by the SELECT is used as the integer
+**                     key. If (pDest->iSDParm>0), then the table is an index
+**                     table. (pDest->iSDParm) is the number of key columns in
+**                     each index record in this case.
+*/
+#define SRT_Union        1  /* Store result as keys in an index */
+#define SRT_Except       2  /* Remove result from a UNION index */
+#define SRT_Exists       3  /* Store 1 if the result is not empty */
+#define SRT_Discard      4  /* Do not save the results anywhere */
+#define SRT_DistFifo     5  /* Like SRT_Fifo, but unique results only */
+#define SRT_DistQueue    6  /* Like SRT_Queue, but unique results only */
+
+/* The DISTINCT clause is ignored for all of the above.  Not that
+** IgnorableDistinct() implies IgnorableOrderby() */
+#define IgnorableDistinct(X) ((X->eDest)<=SRT_DistQueue)
+
+#define SRT_Queue        7  /* Store result in an queue */
+#define SRT_Fifo         8  /* Store result as data with an automatic rowid */
+
+/* The ORDER BY clause is ignored for all of the above */
+#define IgnorableOrderby(X) ((X->eDest)<=SRT_Fifo)
+
+#define SRT_Output       9  /* Output each row of result */
+#define SRT_Mem         10  /* Store result in a memory cell */
+#define SRT_Set         11  /* Store results as keys in an index */
+#define SRT_EphemTab    12  /* Create transient tab and store like SRT_Table */
+#define SRT_Coroutine   13  /* Generate a single row of result */
+#define SRT_Table       14  /* Store result as data with an automatic rowid */
+#define SRT_Upfrom      15  /* Store result as data with rowid */
+
+/*
+** An instance of this object describes where to put of the results of
+** a SELECT statement.
+*/
+struct SelectDest {
+  u8 eDest;            /* How to dispose of the results.  One of SRT_* above. */
+  int iSDParm;         /* A parameter used by the eDest disposal method */
+  int iSDParm2;        /* A second parameter for the eDest disposal method */
+  int iSdst;           /* Base register where results are written */
+  int nSdst;           /* Number of registers allocated */
+  char *zAffSdst;      /* Affinity used for SRT_Set */
+  ExprList *pOrderBy;  /* Key columns for SRT_Queue and SRT_DistQueue */
+};
+
+/*
+** During code generation of statements that do inserts into AUTOINCREMENT
+** tables, the following information is attached to the Table.u.autoInc.p
+** pointer of each autoincrement table to record some side information that
+** the code generator needs.  We have to keep per-table autoincrement
+** information in case inserts are done within triggers.  Triggers do not
+** normally coordinate their activities, but we do need to coordinate the
+** loading and saving of autoincrement information.
+*/
+struct AutoincInfo {
+  AutoincInfo *pNext;   /* Next info block in a list of them all */
+  Table *pTab;          /* Table this info block refers to */
+  int iDb;              /* Index in sqlite3.aDb[] of database holding pTab */
+  int regCtr;           /* Memory register holding the rowid counter */
+};
+
+/*
+** At least one instance of the following structure is created for each
+** trigger that may be fired while parsing an INSERT, UPDATE or DELETE
+** statement. All such objects are stored in the linked list headed at
+** Parse.pTriggerPrg and deleted once statement compilation has been
+** completed.
+**
+** A Vdbe sub-program that implements the body and WHEN clause of trigger
+** TriggerPrg.pTrigger, assuming a default ON CONFLICT clause of
+** TriggerPrg.orconf, is stored in the TriggerPrg.pProgram variable.
+** The Parse.pTriggerPrg list never contains two entries with the same
+** values for both pTrigger and orconf.
+**
+** The TriggerPrg.aColmask[0] variable is set to a mask of old.* columns
+** accessed (or set to 0 for triggers fired as a result of INSERT
+** statements). Similarly, the TriggerPrg.aColmask[1] variable is set to
+** a mask of new.* columns used by the program.
+*/
+struct TriggerPrg {
+  Trigger *pTrigger;      /* Trigger this program was coded from */
+  TriggerPrg *pNext;      /* Next entry in Parse.pTriggerPrg list */
+  SubProgram *pProgram;   /* Program implementing pTrigger/orconf */
+  int orconf;             /* Default ON CONFLICT policy */
+  u32 aColmask[2];        /* Masks of old.*, new.* columns accessed */
+};
+
+/*
+** The yDbMask datatype for the bitmask of all attached databases.
+*/
+#if SQLITE_MAX_ATTACHED>30
+  typedef unsigned char yDbMask[(SQLITE_MAX_ATTACHED+9)/8];
+# define DbMaskTest(M,I)    (((M)[(I)/8]&(1<<((I)&7)))!=0)
+# define DbMaskZero(M)      memset((M),0,sizeof(M))
+# define DbMaskSet(M,I)     (M)[(I)/8]|=(1<<((I)&7))
+# define DbMaskAllZero(M)   sqlite3DbMaskAllZero(M)
+# define DbMaskNonZero(M)   (sqlite3DbMaskAllZero(M)==0)
+#else
+  typedef unsigned int yDbMask;
+# define DbMaskTest(M,I)    (((M)&(((yDbMask)1)<<(I)))!=0)
+# define DbMaskZero(M)      ((M)=0)
+# define DbMaskSet(M,I)     ((M)|=(((yDbMask)1)<<(I)))
+# define DbMaskAllZero(M)   ((M)==0)
+# define DbMaskNonZero(M)   ((M)!=0)
+#endif
+
+/*
+** For each index X that has as one of its arguments either an expression
+** or the name of a virtual generated column, and if X is in scope such that
+** the value of the expression can simply be read from the index, then
+** there is an instance of this object on the Parse.pIdxExpr list.
+**
+** During code generation, while generating code to evaluate expressions,
+** this list is consulted and if a matching expression is found, the value
+** is read from the index rather than being recomputed.
+*/
+struct IndexedExpr {
+  Expr *pExpr;            /* The expression contained in the index */
+  int iDataCur;           /* The data cursor associated with the index */
+  int iIdxCur;            /* The index cursor */
+  int iIdxCol;            /* The index column that contains value of pExpr */
+  u8 bMaybeNullRow;       /* True if we need an OP_IfNullRow check */
+  u8 aff;                 /* Affinity of the pExpr expression */
+  IndexedExpr *pIENext;   /* Next in a list of all indexed expressions */
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  const char *zIdxName;   /* Name of index, used only for bytecode comments */
+#endif
+};
+
+/*
+** An instance of the ParseCleanup object specifies an operation that
+** should be performed after parsing to deallocation resources obtained
+** during the parse and which are no longer needed.
+*/
+struct ParseCleanup {
+  ParseCleanup *pNext;               /* Next cleanup task */
+  void *pPtr;                        /* Pointer to object to deallocate */
+  void (*xCleanup)(sqlite3*,void*);  /* Deallocation routine */
+};
+
+/*
+** An SQL parser context.  A copy of this structure is passed through
+** the parser and down into all the parser action routine in order to
+** carry around information that is global to the entire parse.
+**
+** The structure is divided into two parts.  When the parser and code
+** generate call themselves recursively, the first part of the structure
+** is constant but the second part is reset at the beginning and end of
+** each recursion.
+**
+** The nTableLock and aTableLock variables are only used if the shared-cache
+** feature is enabled (if sqlite3Tsd()->useSharedData is true). They are
+** used to store the set of table-locks required by the statement being
+** compiled. Function sqlite3TableLock() is used to add entries to the
+** list.
+*/
+struct Parse {
+  sqlite3 *db;         /* The main database structure */
+  char *zErrMsg;       /* An error message */
+  Vdbe *pVdbe;         /* An engine for executing database bytecode */
+  int rc;              /* Return code from execution */
+  u8 colNamesSet;      /* TRUE after OP_ColumnName has been issued to pVdbe */
+  u8 checkSchema;      /* Causes schema cookie check after an error */
+  u8 nested;           /* Number of nested calls to the parser/code generator */
+  u8 nTempReg;         /* Number of temporary registers in aTempReg[] */
+  u8 isMultiWrite;     /* True if statement may modify/insert multiple rows */
+  u8 mayAbort;         /* True if statement may throw an ABORT exception */
+  u8 hasCompound;      /* Need to invoke convertCompoundSelectToSubquery() */
+  u8 okConstFactor;    /* OK to factor out constants */
+  u8 disableLookaside; /* Number of times lookaside has been disabled */
+  u8 prepFlags;        /* SQLITE_PREPARE_* flags */
+  u8 withinRJSubrtn;   /* Nesting level for RIGHT JOIN body subroutines */
+#if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
+  u8 earlyCleanup;     /* OOM inside sqlite3ParserAddCleanup() */
+#endif
+#ifdef SQLITE_DEBUG
+  u8 ifNotExists;      /* Might be true if IF NOT EXISTS.  Assert()s only */
+#endif
+  int nRangeReg;       /* Size of the temporary register block */
+  int iRangeReg;       /* First register in temporary register block */
+  int nErr;            /* Number of errors seen */
+  int nTab;            /* Number of previously allocated VDBE cursors */
+  int nMem;            /* Number of memory cells used so far */
+  int szOpAlloc;       /* Bytes of memory space allocated for Vdbe.aOp[] */
+  int iSelfTab;        /* Table associated with an index on expr, or negative
+                       ** of the base register during check-constraint eval */
+  int nLabel;          /* The *negative* of the number of labels used */
+  int nLabelAlloc;     /* Number of slots in aLabel */
+  int *aLabel;         /* Space to hold the labels */
+  ExprList *pConstExpr;/* Constant expressions */
+  IndexedExpr *pIdxEpr;/* List of expressions used by active indexes */
+  IndexedExpr *pIdxPartExpr; /* Exprs constrained by index WHERE clauses */
+  Token constraintName;/* Name of the constraint currently being parsed */
+  yDbMask writeMask;   /* Start a write transaction on these databases */
+  yDbMask cookieMask;  /* Bitmask of schema verified databases */
+  int regRowid;        /* Register holding rowid of CREATE TABLE entry */
+  int regRoot;         /* Register holding root page number for new objects */
+  int nMaxArg;         /* Max args passed to user function by sub-program */
+  int nSelect;         /* Number of SELECT stmts. Counter for Select.selId */
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  u32 nProgressSteps;  /* xProgress steps taken during sqlite3_prepare() */
+#endif
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  int nTableLock;        /* Number of locks in aTableLock */
+  TableLock *aTableLock; /* Required table locks for shared-cache mode */
+#endif
+  AutoincInfo *pAinc;  /* Information about AUTOINCREMENT counters */
+  Parse *pToplevel;    /* Parse structure for main program (or NULL) */
+  Table *pTriggerTab;  /* Table triggers are being coded for */
+  TriggerPrg *pTriggerPrg;  /* Linked list of coded triggers */
+  ParseCleanup *pCleanup;   /* List of cleanup operations to run after parse */
+  union {
+    int addrCrTab;         /* Address of OP_CreateBtree on CREATE TABLE */
+    Returning *pReturning; /* The RETURNING clause */
+  } u1;
+  u32 oldmask;         /* Mask of old.* columns referenced */
+  u32 newmask;         /* Mask of new.* columns referenced */
+  LogEst nQueryLoop;   /* Est number of iterations of a query (10*log2(N)) */
+  u8 eTriggerOp;       /* TK_UPDATE, TK_INSERT or TK_DELETE */
+  u8 bReturning;       /* Coding a RETURNING trigger */
+  u8 eOrconf;          /* Default ON CONFLICT policy for trigger steps */
+  u8 disableTriggers;  /* True to disable triggers */
+
+  /**************************************************************************
+  ** Fields above must be initialized to zero.  The fields that follow,
+  ** down to the beginning of the recursive section, do not need to be
+  ** initialized as they will be set before being used.  The boundary is
+  ** determined by offsetof(Parse,aTempReg).
+  **************************************************************************/
+
+  int aTempReg[8];        /* Holding area for temporary registers */
+  Parse *pOuterParse;     /* Outer Parse object when nested */
+  Token sNameToken;       /* Token with unqualified schema object name */
+
+  /************************************************************************
+  ** Above is constant between recursions.  Below is reset before and after
+  ** each recursion.  The boundary between these two regions is determined
+  ** using offsetof(Parse,sLastToken) so the sLastToken field must be the
+  ** first field in the recursive region.
+  ************************************************************************/
+
+  Token sLastToken;       /* The last token parsed */
+  ynVar nVar;               /* Number of '?' variables seen in the SQL so far */
+  u8 iPkSortOrder;          /* ASC or DESC for INTEGER PRIMARY KEY */
+  u8 explain;               /* True if the EXPLAIN flag is found on the query */
+  u8 eParseMode;            /* PARSE_MODE_XXX constant */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  int nVtabLock;            /* Number of virtual tables to lock */
+#endif
+  int nHeight;              /* Expression tree height of current sub-select */
+#ifndef SQLITE_OMIT_EXPLAIN
+  int addrExplain;          /* Address of current OP_Explain opcode */
+#endif
+  VList *pVList;            /* Mapping between variable names and numbers */
+  Vdbe *pReprepare;         /* VM being reprepared (sqlite3Reprepare()) */
+  const char *zTail;        /* All SQL text past the last semicolon parsed */
+  Table *pNewTable;         /* A table being constructed by CREATE TABLE */
+  Index *pNewIndex;         /* An index being constructed by CREATE INDEX.
+                            ** Also used to hold redundant UNIQUE constraints
+                            ** during a RENAME COLUMN */
+  Trigger *pNewTrigger;     /* Trigger under construct by a CREATE TRIGGER */
+  const char *zAuthContext; /* The 6th parameter to db->xAuth callbacks */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  Token sArg;               /* Complete text of a module argument */
+  Table **apVtabLock;       /* Pointer to virtual tables needing locking */
+#endif
+  With *pWith;              /* Current WITH clause, or NULL */
+#ifndef SQLITE_OMIT_ALTERTABLE
+  RenameToken *pRename;     /* Tokens subject to renaming by ALTER TABLE */
+#endif
+};
+
+/* Allowed values for Parse.eParseMode
+*/
+#define PARSE_MODE_NORMAL        0
+#define PARSE_MODE_DECLARE_VTAB  1
+#define PARSE_MODE_RENAME        2
+#define PARSE_MODE_UNMAP         3
+
+/*
+** Sizes and pointers of various parts of the Parse object.
+*/
+#define PARSE_HDR(X)  (((char*)(X))+offsetof(Parse,zErrMsg))
+#define PARSE_HDR_SZ (offsetof(Parse,aTempReg)-offsetof(Parse,zErrMsg)) /* Recursive part w/o aColCache*/
+#define PARSE_RECURSE_SZ offsetof(Parse,sLastToken)    /* Recursive part */
+#define PARSE_TAIL_SZ (sizeof(Parse)-PARSE_RECURSE_SZ) /* Non-recursive part */
+#define PARSE_TAIL(X) (((char*)(X))+PARSE_RECURSE_SZ)  /* Pointer to tail */
+
+/*
+** Return true if currently inside an sqlite3_declare_vtab() call.
+*/
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  #define IN_DECLARE_VTAB 0
+#else
+  #define IN_DECLARE_VTAB (pParse->eParseMode==PARSE_MODE_DECLARE_VTAB)
+#endif
+
+#if defined(SQLITE_OMIT_ALTERTABLE)
+  #define IN_RENAME_OBJECT 0
+#else
+  #define IN_RENAME_OBJECT (pParse->eParseMode>=PARSE_MODE_RENAME)
+#endif
+
+#if defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_OMIT_ALTERTABLE)
+  #define IN_SPECIAL_PARSE 0
+#else
+  #define IN_SPECIAL_PARSE (pParse->eParseMode!=PARSE_MODE_NORMAL)
+#endif
+
+/*
+** An instance of the following structure can be declared on a stack and used
+** to save the Parse.zAuthContext value so that it can be restored later.
+*/
+struct AuthContext {
+  const char *zAuthContext;   /* Put saved Parse.zAuthContext here */
+  Parse *pParse;              /* The Parse structure */
+};
+
+/*
+** Bitfield flags for P5 value in various opcodes.
+**
+** Value constraints (enforced via assert()):
+**    OPFLAG_LENGTHARG    == SQLITE_FUNC_LENGTH
+**    OPFLAG_TYPEOFARG    == SQLITE_FUNC_TYPEOF
+**    OPFLAG_BULKCSR      == BTREE_BULKLOAD
+**    OPFLAG_SEEKEQ       == BTREE_SEEK_EQ
+**    OPFLAG_FORDELETE    == BTREE_FORDELETE
+**    OPFLAG_SAVEPOSITION == BTREE_SAVEPOSITION
+**    OPFLAG_AUXDELETE    == BTREE_AUXDELETE
+*/
+#define OPFLAG_NCHANGE       0x01    /* OP_Insert: Set to update db->nChange */
+                                     /* Also used in P2 (not P5) of OP_Delete */
+#define OPFLAG_NOCHNG        0x01    /* OP_VColumn nochange for UPDATE */
+#define OPFLAG_EPHEM         0x01    /* OP_Column: Ephemeral output is ok */
+#define OPFLAG_LASTROWID     0x20    /* Set to update db->lastRowid */
+#define OPFLAG_ISUPDATE      0x04    /* This OP_Insert is an sql UPDATE */
+#define OPFLAG_APPEND        0x08    /* This is likely to be an append */
+#define OPFLAG_USESEEKRESULT 0x10    /* Try to avoid a seek in BtreeInsert() */
+#define OPFLAG_ISNOOP        0x40    /* OP_Delete does pre-update-hook only */
+#define OPFLAG_LENGTHARG     0x40    /* OP_Column only used for length() */
+#define OPFLAG_TYPEOFARG     0x80    /* OP_Column only used for typeof() */
+#define OPFLAG_BYTELENARG    0xc0    /* OP_Column only for octet_length() */
+#define OPFLAG_BULKCSR       0x01    /* OP_Open** used to open bulk cursor */
+#define OPFLAG_SEEKEQ        0x02    /* OP_Open** cursor uses EQ seek only */
+#define OPFLAG_FORDELETE     0x08    /* OP_Open should use BTREE_FORDELETE */
+#define OPFLAG_P2ISREG       0x10    /* P2 to OP_Open** is a register number */
+#define OPFLAG_PERMUTE       0x01    /* OP_Compare: use the permutation */
+#define OPFLAG_SAVEPOSITION  0x02    /* OP_Delete/Insert: save cursor pos */
+#define OPFLAG_AUXDELETE     0x04    /* OP_Delete: index in a DELETE op */
+#define OPFLAG_NOCHNG_MAGIC  0x6d    /* OP_MakeRecord: serialtype 10 is ok */
+#define OPFLAG_PREFORMAT     0x80    /* OP_Insert uses preformatted cell */
+
+/*
+** Each trigger present in the database schema is stored as an instance of
+** struct Trigger.
+**
+** Pointers to instances of struct Trigger are stored in two ways.
+** 1. In the "trigHash" hash table (part of the sqlite3* that represents the
+**    database). This allows Trigger structures to be retrieved by name.
+** 2. All triggers associated with a single table form a linked list, using the
+**    pNext member of struct Trigger. A pointer to the first element of the
+**    linked list is stored as the "pTrigger" member of the associated
+**    struct Table.
+**
+** The "step_list" member points to the first element of a linked list
+** containing the SQL statements specified as the trigger program.
+*/
+struct Trigger {
+  char *zName;            /* The name of the trigger                        */
+  char *table;            /* The table or view to which the trigger applies */
+  u8 op;                  /* One of TK_DELETE, TK_UPDATE, TK_INSERT         */
+  u8 tr_tm;               /* One of TRIGGER_BEFORE, TRIGGER_AFTER */
+  u8 bReturning;          /* This trigger implements a RETURNING clause */
+  Expr *pWhen;            /* The WHEN clause of the expression (may be NULL) */
+  IdList *pColumns;       /* If this is an UPDATE OF <column-list> trigger,
+                             the <column-list> is stored here */
+  Schema *pSchema;        /* Schema containing the trigger */
+  Schema *pTabSchema;     /* Schema containing the table */
+  TriggerStep *step_list; /* Link list of trigger program steps             */
+  Trigger *pNext;         /* Next trigger associated with the table */
+};
+
+/*
+** A trigger is either a BEFORE or an AFTER trigger.  The following constants
+** determine which.
+**
+** If there are multiple triggers, you might of some BEFORE and some AFTER.
+** In that cases, the constants below can be ORed together.
+*/
+#define TRIGGER_BEFORE  1
+#define TRIGGER_AFTER   2
+
+/*
+** An instance of struct TriggerStep is used to store a single SQL statement
+** that is a part of a trigger-program.
+**
+** Instances of struct TriggerStep are stored in a singly linked list (linked
+** using the "pNext" member) referenced by the "step_list" member of the
+** associated struct Trigger instance. The first element of the linked list is
+** the first step of the trigger-program.
+**
+** The "op" member indicates whether this is a "DELETE", "INSERT", "UPDATE" or
+** "SELECT" statement. The meanings of the other members is determined by the
+** value of "op" as follows:
+**
+** (op == TK_INSERT)
+** orconf    -> stores the ON CONFLICT algorithm
+** pSelect   -> The content to be inserted - either a SELECT statement or
+**              a VALUES clause.
+** zTarget   -> Dequoted name of the table to insert into.
+** pIdList   -> If this is an INSERT INTO ... (<column-names>) VALUES ...
+**              statement, then this stores the column-names to be
+**              inserted into.
+** pUpsert   -> The ON CONFLICT clauses for an Upsert
+**
+** (op == TK_DELETE)
+** zTarget   -> Dequoted name of the table to delete from.
+** pWhere    -> The WHERE clause of the DELETE statement if one is specified.
+**              Otherwise NULL.
+**
+** (op == TK_UPDATE)
+** zTarget   -> Dequoted name of the table to update.
+** pWhere    -> The WHERE clause of the UPDATE statement if one is specified.
+**              Otherwise NULL.
+** pExprList -> A list of the columns to update and the expressions to update
+**              them to. See sqlite3Update() documentation of "pChanges"
+**              argument.
+**
+** (op == TK_SELECT)
+** pSelect   -> The SELECT statement
+**
+** (op == TK_RETURNING)
+** pExprList -> The list of expressions that follow the RETURNING keyword.
+**
+*/
+struct TriggerStep {
+  u8 op;               /* One of TK_DELETE, TK_UPDATE, TK_INSERT, TK_SELECT,
+                       ** or TK_RETURNING */
+  u8 orconf;           /* OE_Rollback etc. */
+  Trigger *pTrig;      /* The trigger that this step is a part of */
+  Select *pSelect;     /* SELECT statement or RHS of INSERT INTO SELECT ... */
+  char *zTarget;       /* Target table for DELETE, UPDATE, INSERT */
+  SrcList *pFrom;      /* FROM clause for UPDATE statement (if any) */
+  Expr *pWhere;        /* The WHERE clause for DELETE or UPDATE steps */
+  ExprList *pExprList; /* SET clause for UPDATE, or RETURNING clause */
+  IdList *pIdList;     /* Column names for INSERT */
+  Upsert *pUpsert;     /* Upsert clauses on an INSERT */
+  char *zSpan;         /* Original SQL text of this command */
+  TriggerStep *pNext;  /* Next in the link-list */
+  TriggerStep *pLast;  /* Last element in link-list. Valid for 1st elem only */
+};
+
+/*
+** Information about a RETURNING clause
+*/
+struct Returning {
+  Parse *pParse;        /* The parse that includes the RETURNING clause */
+  ExprList *pReturnEL;  /* List of expressions to return */
+  Trigger retTrig;      /* The transient trigger that implements RETURNING */
+  TriggerStep retTStep; /* The trigger step */
+  int iRetCur;          /* Transient table holding RETURNING results */
+  int nRetCol;          /* Number of in pReturnEL after expansion */
+  int iRetReg;          /* Register array for holding a row of RETURNING */
+  char zName[40];       /* Name of trigger: "sqlite_returning_%p" */
+};
+
+/*
+** An objected used to accumulate the text of a string where we
+** do not necessarily know how big the string will be in the end.
+*/
+struct sqlite3_str {
+  sqlite3 *db;         /* Optional database for lookaside.  Can be NULL */
+  char *zText;         /* The string collected so far */
+  u32  nAlloc;         /* Amount of space allocated in zText */
+  u32  mxAlloc;        /* Maximum allowed allocation.  0 for no malloc usage */
+  u32  nChar;          /* Length of the string so far */
+  u8   accError;       /* SQLITE_NOMEM or SQLITE_TOOBIG */
+  u8   printfFlags;    /* SQLITE_PRINTF flags below */
+};
+#define SQLITE_PRINTF_INTERNAL 0x01  /* Internal-use-only converters allowed */
+#define SQLITE_PRINTF_SQLFUNC  0x02  /* SQL function arguments to VXPrintf */
+#define SQLITE_PRINTF_MALLOCED 0x04  /* True if xText is allocated space */
+
+#define isMalloced(X)  (((X)->printfFlags & SQLITE_PRINTF_MALLOCED)!=0)
+
+/*
+** The following object is the header for an "RCStr" or "reference-counted
+** string".  An RCStr is passed around and used like any other char*
+** that has been dynamically allocated.  The important interface
+** differences:
+**
+**   1.  RCStr strings are reference counted.  They are deallocated
+**       when the reference count reaches zero.
+**
+**   2.  Use sqlite3RCStrUnref() to free an RCStr string rather than
+**       sqlite3_free()
+**
+**   3.  Make a (read-only) copy of a read-only RCStr string using
+**       sqlite3RCStrRef().
+**
+** "String" is in the name, but an RCStr object can also be used to hold
+** binary data.
+*/
+struct RCStr {
+  u64 nRCRef;            /* Number of references */
+  /* Total structure size should be a multiple of 8 bytes for alignment */
+};
+
+/*
+** A pointer to this structure is used to communicate information
+** from sqlite3Init and OP_ParseSchema into the sqlite3InitCallback.
+*/
+typedef struct {
+  sqlite3 *db;        /* The database being initialized */
+  char **pzErrMsg;    /* Error message stored here */
+  int iDb;            /* 0 for main database.  1 for TEMP, 2.. for ATTACHed */
+  int rc;             /* Result code stored here */
+  u32 mInitFlags;     /* Flags controlling error messages */
+  u32 nInitRow;       /* Number of rows processed */
+  Pgno mxPage;        /* Maximum page number.  0 for no limit. */
+} InitData;
+
+/*
+** Allowed values for mInitFlags
+*/
+#define INITFLAG_AlterMask     0x0003  /* Types of ALTER */
+#define INITFLAG_AlterRename   0x0001  /* Reparse after a RENAME */
+#define INITFLAG_AlterDrop     0x0002  /* Reparse after a DROP COLUMN */
+#define INITFLAG_AlterAdd      0x0003  /* Reparse after an ADD COLUMN */
+
+/* Tuning parameters are set using SQLITE_TESTCTRL_TUNE and are controlled
+** on debug-builds of the CLI using ".testctrl tune ID VALUE".  Tuning
+** parameters are for temporary use during development, to help find
+** optimal values for parameters in the query planner.  The should not
+** be used on trunk check-ins.  They are a temporary mechanism available
+** for transient development builds only.
+**
+** Tuning parameters are numbered starting with 1.
+*/
+#define SQLITE_NTUNE  6             /* Should be zero for all trunk check-ins */
+#ifdef SQLITE_DEBUG
+# define Tuning(X)  (sqlite3Config.aTune[(X)-1])
+#else
+# define Tuning(X)  0
+#endif
+
+/*
+** Structure containing global configuration data for the SQLite library.
+**
+** This structure also contains some state information.
+*/
+struct Sqlite3Config {
+  int bMemstat;                     /* True to enable memory status */
+  u8 bCoreMutex;                    /* True to enable core mutexing */
+  u8 bFullMutex;                    /* True to enable full mutexing */
+  u8 bOpenUri;                      /* True to interpret filenames as URIs */
+  u8 bUseCis;                       /* Use covering indices for full-scans */
+  u8 bSmallMalloc;                  /* Avoid large memory allocations if true */
+  u8 bExtraSchemaChecks;            /* Verify type,name,tbl_name in schema */
+  u8 bUseLongDouble;                /* Make use of long double */
+#ifdef SQLITE_DEBUG
+  u8 bJsonSelfcheck;                /* Double-check JSON parsing */
+#endif
+  int mxStrlen;                     /* Maximum string length */
+  int neverCorrupt;                 /* Database is always well-formed */
+  int szLookaside;                  /* Default lookaside buffer size */
+  int nLookaside;                   /* Default lookaside buffer count */
+  int nStmtSpill;                   /* Stmt-journal spill-to-disk threshold */
+  sqlite3_mem_methods m;            /* Low-level memory allocation interface */
+  sqlite3_mutex_methods mutex;      /* Low-level mutex interface */
+  sqlite3_pcache_methods2 pcache2;  /* Low-level page-cache interface */
+  void *pHeap;                      /* Heap storage space */
+  int nHeap;                        /* Size of pHeap[] */
+  int mnReq, mxReq;                 /* Min and max heap requests sizes */
+  sqlite3_int64 szMmap;             /* mmap() space per open file */
+  sqlite3_int64 mxMmap;             /* Maximum value for szMmap */
+  void *pPage;                      /* Page cache memory */
+  int szPage;                       /* Size of each page in pPage[] */
+  int nPage;                        /* Number of pages in pPage[] */
+  int mxParserStack;                /* maximum depth of the parser stack */
+  int sharedCacheEnabled;           /* true if shared-cache mode enabled */
+  u32 szPma;                        /* Maximum Sorter PMA size */
+  /* The above might be initialized to non-zero.  The following need to always
+  ** initially be zero, however. */
+  int isInit;                       /* True after initialization has finished */
+  int inProgress;                   /* True while initialization in progress */
+  int isMutexInit;                  /* True after mutexes are initialized */
+  int isMallocInit;                 /* True after malloc is initialized */
+  int isPCacheInit;                 /* True after malloc is initialized */
+  int nRefInitMutex;                /* Number of users of pInitMutex */
+  sqlite3_mutex *pInitMutex;        /* Mutex used by sqlite3_initialize() */
+  void (*xLog)(void*,int,const char*); /* Function for logging */
+  void *pLogArg;                       /* First argument to xLog() */
+#ifdef SQLITE_ENABLE_SQLLOG
+  void(*xSqllog)(void*,sqlite3*,const char*, int);
+  void *pSqllogArg;
+#endif
+#ifdef SQLITE_VDBE_COVERAGE
+  /* The following callback (if not NULL) is invoked on every VDBE branch
+  ** operation.  Set the callback using SQLITE_TESTCTRL_VDBE_COVERAGE.
+  */
+  void (*xVdbeBranch)(void*,unsigned iSrcLine,u8 eThis,u8 eMx);  /* Callback */
+  void *pVdbeBranchArg;                                     /* 1st argument */
+#endif
+#ifndef SQLITE_OMIT_DESERIALIZE
+  sqlite3_int64 mxMemdbSize;        /* Default max memdb size */
+#endif
+#ifndef SQLITE_UNTESTABLE
+  int (*xTestCallback)(int);        /* Invoked by sqlite3FaultSim() */
+#endif
+  int bLocaltimeFault;              /* True to fail localtime() calls */
+  int (*xAltLocaltime)(const void*,void*); /* Alternative localtime() routine */
+  int iOnceResetThreshold;          /* When to reset OP_Once counters */
+  u32 szSorterRef;                  /* Min size in bytes to use sorter-refs */
+  unsigned int iPrngSeed;           /* Alternative fixed seed for the PRNG */
+  /* vvvv--- must be last ---vvv */
+#ifdef SQLITE_DEBUG
+  sqlite3_int64 aTune[SQLITE_NTUNE]; /* Tuning parameters */
+#endif
+};
+
+/*
+** This macro is used inside of assert() statements to indicate that
+** the assert is only valid on a well-formed database.  Instead of:
+**
+**     assert( X );
+**
+** One writes:
+**
+**     assert( X || CORRUPT_DB );
+**
+** CORRUPT_DB is true during normal operation.  CORRUPT_DB does not indicate
+** that the database is definitely corrupt, only that it might be corrupt.
+** For most test cases, CORRUPT_DB is set to false using a special
+** sqlite3_test_control().  This enables assert() statements to prove
+** things that are always true for well-formed databases.
+*/
+#define CORRUPT_DB  (sqlite3Config.neverCorrupt==0)
+
+/*
+** Context pointer passed down through the tree-walk.
+*/
+struct Walker {
+  Parse *pParse;                            /* Parser context.  */
+  int (*xExprCallback)(Walker*, Expr*);     /* Callback for expressions */
+  int (*xSelectCallback)(Walker*,Select*);  /* Callback for SELECTs */
+  void (*xSelectCallback2)(Walker*,Select*);/* Second callback for SELECTs */
+  int walkerDepth;                          /* Number of subqueries */
+  u16 eCode;                                /* A small processing code */
+  u16 mWFlags;                              /* Use-dependent flags */
+  union {                                   /* Extra data for callback */
+    NameContext *pNC;                         /* Naming context */
+    int n;                                    /* A counter */
+    int iCur;                                 /* A cursor number */
+    SrcList *pSrcList;                        /* FROM clause */
+    struct CCurHint *pCCurHint;               /* Used by codeCursorHint() */
+    struct RefSrcList *pRefSrcList;           /* sqlite3ReferencesSrcList() */
+    int *aiCol;                               /* array of column indexes */
+    struct IdxCover *pIdxCover;               /* Check for index coverage */
+    ExprList *pGroupBy;                       /* GROUP BY clause */
+    Select *pSelect;                          /* HAVING to WHERE clause ctx */
+    struct WindowRewrite *pRewrite;           /* Window rewrite context */
+    struct WhereConst *pConst;                /* WHERE clause constants */
+    struct RenameCtx *pRename;                /* RENAME COLUMN context */
+    struct Table *pTab;                       /* Table of generated column */
+    struct CoveringIndexCheck *pCovIdxCk;     /* Check for covering index */
+    SrcItem *pSrcItem;                        /* A single FROM clause item */
+    DbFixer *pFix;                            /* See sqlite3FixSelect() */
+    Mem *aMem;                                /* See sqlite3BtreeCursorHint() */
+  } u;
+};
+
+/*
+** The following structure contains information used by the sqliteFix...
+** routines as they walk the parse tree to make database references
+** explicit.
+*/
+struct DbFixer {
+  Parse *pParse;      /* The parsing context.  Error messages written here */
+  Walker w;           /* Walker object */
+  Schema *pSchema;    /* Fix items to this schema */
+  u8 bTemp;           /* True for TEMP schema entries */
+  const char *zDb;    /* Make sure all objects are contained in this database */
+  const char *zType;  /* Type of the container - used for error messages */
+  const Token *pName; /* Name of the container - used for error messages */
+};
+
+/* Forward declarations */
+int sqlite3WalkExpr(Walker*, Expr*);
+int sqlite3WalkExprNN(Walker*, Expr*);
+int sqlite3WalkExprList(Walker*, ExprList*);
+int sqlite3WalkSelect(Walker*, Select*);
+int sqlite3WalkSelectExpr(Walker*, Select*);
+int sqlite3WalkSelectFrom(Walker*, Select*);
+int sqlite3ExprWalkNoop(Walker*, Expr*);
+int sqlite3SelectWalkNoop(Walker*, Select*);
+int sqlite3SelectWalkFail(Walker*, Select*);
+int sqlite3WalkerDepthIncrease(Walker*,Select*);
+void sqlite3WalkerDepthDecrease(Walker*,Select*);
+void sqlite3WalkWinDefnDummyCallback(Walker*,Select*);
+
+#ifdef SQLITE_DEBUG
+void sqlite3SelectWalkAssert2(Walker*, Select*);
+#endif
+
+#ifndef SQLITE_OMIT_CTE
+void sqlite3SelectPopWith(Walker*, Select*);
+#else
+# define sqlite3SelectPopWith 0
+#endif
+
+/*
+** Return code from the parse-tree walking primitives and their
+** callbacks.
+*/
+#define WRC_Continue    0   /* Continue down into children */
+#define WRC_Prune       1   /* Omit children but continue walking siblings */
+#define WRC_Abort       2   /* Abandon the tree walk */
+
+/*
+** A single common table expression
+*/
+struct Cte {
+  char *zName;            /* Name of this CTE */
+  ExprList *pCols;        /* List of explicit column names, or NULL */
+  Select *pSelect;        /* The definition of this CTE */
+  const char *zCteErr;    /* Error message for circular references */
+  CteUse *pUse;           /* Usage information for this CTE */
+  u8 eM10d;               /* The MATERIALIZED flag */
+};
+
+/*
+** Allowed values for the materialized flag (eM10d):
+*/
+#define M10d_Yes       0  /* AS MATERIALIZED */
+#define M10d_Any       1  /* Not specified.  Query planner's choice */
+#define M10d_No        2  /* AS NOT MATERIALIZED */
+
+/*
+** An instance of the With object represents a WITH clause containing
+** one or more CTEs (common table expressions).
+*/
+struct With {
+  int nCte;               /* Number of CTEs in the WITH clause */
+  int bView;              /* Belongs to the outermost Select of a view */
+  With *pOuter;           /* Containing WITH clause, or NULL */
+  Cte a[1];               /* For each CTE in the WITH clause.... */
+};
+
+/*
+** The Cte object is not guaranteed to persist for the entire duration
+** of code generation.  (The query flattener or other parser tree
+** edits might delete it.)  The following object records information
+** about each Common Table Expression that must be preserved for the
+** duration of the parse.
+**
+** The CteUse objects are freed using sqlite3ParserAddCleanup() rather
+** than sqlite3SelectDelete(), which is what enables them to persist
+** until the end of code generation.
+*/
+struct CteUse {
+  int nUse;              /* Number of users of this CTE */
+  int addrM9e;           /* Start of subroutine to compute materialization */
+  int regRtn;            /* Return address register for addrM9e subroutine */
+  int iCur;              /* Ephemeral table holding the materialization */
+  LogEst nRowEst;        /* Estimated number of rows in the table */
+  u8 eM10d;              /* The MATERIALIZED flag */
+};
+
+
+/* Client data associated with sqlite3_set_clientdata() and
+** sqlite3_get_clientdata().
+*/
+struct DbClientData {
+  DbClientData *pNext;        /* Next in a linked list */
+  void *pData;                /* The data */
+  void (*xDestructor)(void*); /* Destructor.  Might be NULL */
+  char zName[1];              /* Name of this client data. MUST BE LAST */
+};
+
+#ifdef SQLITE_DEBUG
+/*
+** An instance of the TreeView object is used for printing the content of
+** data structures on sqlite3DebugPrintf() using a tree-like view.
+*/
+struct TreeView {
+  int iLevel;             /* Which level of the tree we are on */
+  u8  bLine[100];         /* Draw vertical in column i if bLine[i] is true */
+};
+#endif /* SQLITE_DEBUG */
+
+/*
+** This object is used in various ways, most (but not all) related to window
+** functions.
+**
+**   (1) A single instance of this structure is attached to the
+**       the Expr.y.pWin field for each window function in an expression tree.
+**       This object holds the information contained in the OVER clause,
+**       plus additional fields used during code generation.
+**
+**   (2) All window functions in a single SELECT form a linked-list
+**       attached to Select.pWin.  The Window.pFunc and Window.pExpr
+**       fields point back to the expression that is the window function.
+**
+**   (3) The terms of the WINDOW clause of a SELECT are instances of this
+**       object on a linked list attached to Select.pWinDefn.
+**
+**   (4) For an aggregate function with a FILTER clause, an instance
+**       of this object is stored in Expr.y.pWin with eFrmType set to
+**       TK_FILTER. In this case the only field used is Window.pFilter.
+**
+** The uses (1) and (2) are really the same Window object that just happens
+** to be accessible in two different ways.  Use case (3) are separate objects.
+*/
+struct Window {
+  char *zName;            /* Name of window (may be NULL) */
+  char *zBase;            /* Name of base window for chaining (may be NULL) */
+  ExprList *pPartition;   /* PARTITION BY clause */
+  ExprList *pOrderBy;     /* ORDER BY clause */
+  u8 eFrmType;            /* TK_RANGE, TK_GROUPS, TK_ROWS, or 0 */
+  u8 eStart;              /* UNBOUNDED, CURRENT, PRECEDING or FOLLOWING */
+  u8 eEnd;                /* UNBOUNDED, CURRENT, PRECEDING or FOLLOWING */
+  u8 bImplicitFrame;      /* True if frame was implicitly specified */
+  u8 eExclude;            /* TK_NO, TK_CURRENT, TK_TIES, TK_GROUP, or 0 */
+  Expr *pStart;           /* Expression for "<expr> PRECEDING" */
+  Expr *pEnd;             /* Expression for "<expr> FOLLOWING" */
+  Window **ppThis;        /* Pointer to this object in Select.pWin list */
+  Window *pNextWin;       /* Next window function belonging to this SELECT */
+  Expr *pFilter;          /* The FILTER expression */
+  FuncDef *pWFunc;        /* The function */
+  int iEphCsr;            /* Partition buffer or Peer buffer */
+  int regAccum;           /* Accumulator */
+  int regResult;          /* Interim result */
+  int csrApp;             /* Function cursor (used by min/max) */
+  int regApp;             /* Function register (also used by min/max) */
+  int regPart;            /* Array of registers for PARTITION BY values */
+  Expr *pOwner;           /* Expression object this window is attached to */
+  int nBufferCol;         /* Number of columns in buffer table */
+  int iArgCol;            /* Offset of first argument for this function */
+  int regOne;             /* Register containing constant value 1 */
+  int regStartRowid;
+  int regEndRowid;
+  u8 bExprArgs;           /* Defer evaluation of window function arguments
+                          ** due to the SQLITE_SUBTYPE flag */
+};
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+void sqlite3WindowDelete(sqlite3*, Window*);
+void sqlite3WindowUnlinkFromSelect(Window*);
+void sqlite3WindowListDelete(sqlite3 *db, Window *p);
+Window *sqlite3WindowAlloc(Parse*, int, int, Expr*, int , Expr*, u8);
+void sqlite3WindowAttach(Parse*, Expr*, Window*);
+void sqlite3WindowLink(Select *pSel, Window *pWin);
+int sqlite3WindowCompare(const Parse*, const Window*, const Window*, int);
+void sqlite3WindowCodeInit(Parse*, Select*);
+void sqlite3WindowCodeStep(Parse*, Select*, WhereInfo*, int, int);
+int sqlite3WindowRewrite(Parse*, Select*);
+void sqlite3WindowUpdate(Parse*, Window*, Window*, FuncDef*);
+Window *sqlite3WindowDup(sqlite3 *db, Expr *pOwner, Window *p);
+Window *sqlite3WindowListDup(sqlite3 *db, Window *p);
+void sqlite3WindowFunctions(void);
+void sqlite3WindowChain(Parse*, Window*, Window*);
+Window *sqlite3WindowAssemble(Parse*, Window*, ExprList*, ExprList*, Token*);
+#else
+# define sqlite3WindowDelete(a,b)
+# define sqlite3WindowFunctions()
+# define sqlite3WindowAttach(a,b,c)
+#endif
+
+/*
+** Assuming zIn points to the first byte of a UTF-8 character,
+** advance zIn to point to the first byte of the next UTF-8 character.
+*/
+#define SQLITE_SKIP_UTF8(zIn) {                        \
+  if( (*(zIn++))>=0xc0 ){                              \
+    while( (*zIn & 0xc0)==0x80 ){ zIn++; }             \
+  }                                                    \
+}
+
+/*
+** The SQLITE_*_BKPT macros are substitutes for the error codes with
+** the same name but without the _BKPT suffix.  These macros invoke
+** routines that report the line-number on which the error originated
+** using sqlite3_log().  The routines also provide a convenient place
+** to set a debugger breakpoint.
+*/
+int sqlite3ReportError(int iErr, int lineno, const char *zType);
+int sqlite3CorruptError(int);
+int sqlite3MisuseError(int);
+int sqlite3CantopenError(int);
+#define SQLITE_CORRUPT_BKPT sqlite3CorruptError(__LINE__)
+#define SQLITE_MISUSE_BKPT sqlite3MisuseError(__LINE__)
+#define SQLITE_CANTOPEN_BKPT sqlite3CantopenError(__LINE__)
+#ifdef SQLITE_DEBUG
+  int sqlite3NomemError(int);
+  int sqlite3IoerrnomemError(int);
+# define SQLITE_NOMEM_BKPT sqlite3NomemError(__LINE__)
+# define SQLITE_IOERR_NOMEM_BKPT sqlite3IoerrnomemError(__LINE__)
+#else
+# define SQLITE_NOMEM_BKPT SQLITE_NOMEM
+# define SQLITE_IOERR_NOMEM_BKPT SQLITE_IOERR_NOMEM
+#endif
+#if defined(SQLITE_DEBUG) || defined(SQLITE_ENABLE_CORRUPT_PGNO)
+  int sqlite3CorruptPgnoError(int,Pgno);
+# define SQLITE_CORRUPT_PGNO(P) sqlite3CorruptPgnoError(__LINE__,(P))
+#else
+# define SQLITE_CORRUPT_PGNO(P) sqlite3CorruptError(__LINE__)
+#endif
+
+/*
+** FTS3 and FTS4 both require virtual table support
+*/
+#if defined(SQLITE_OMIT_VIRTUALTABLE)
+# undef SQLITE_ENABLE_FTS3
+# undef SQLITE_ENABLE_FTS4
+#endif
+
+/*
+** FTS4 is really an extension for FTS3.  It is enabled using the
+** SQLITE_ENABLE_FTS3 macro.  But to avoid confusion we also call
+** the SQLITE_ENABLE_FTS4 macro to serve as an alias for SQLITE_ENABLE_FTS3.
+*/
+#if defined(SQLITE_ENABLE_FTS4) && !defined(SQLITE_ENABLE_FTS3)
+# define SQLITE_ENABLE_FTS3 1
+#endif
+
+/*
+** The ctype.h header is needed for non-ASCII systems.  It is also
+** needed by FTS3 when FTS3 is included in the amalgamation.
+*/
+#if !defined(SQLITE_ASCII) || \
+    (defined(SQLITE_ENABLE_FTS3) && defined(SQLITE_AMALGAMATION))
+# include <ctype.h>
+#endif
+
+/*
+** The following macros mimic the standard library functions toupper(),
+** isspace(), isalnum(), isdigit() and isxdigit(), respectively. The
+** sqlite versions only work for ASCII characters, regardless of locale.
+*/
+#ifdef SQLITE_ASCII
+# define sqlite3Toupper(x)  ((x)&~(sqlite3CtypeMap[(unsigned char)(x)]&0x20))
+# define sqlite3Isspace(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x01)
+# define sqlite3Isalnum(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x06)
+# define sqlite3Isalpha(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x02)
+# define sqlite3Isdigit(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x04)
+# define sqlite3Isxdigit(x)  (sqlite3CtypeMap[(unsigned char)(x)]&0x08)
+# define sqlite3Tolower(x)   (sqlite3UpperToLower[(unsigned char)(x)])
+# define sqlite3Isquote(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x80)
+# define sqlite3JsonId1(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x42)
+# define sqlite3JsonId2(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x46)
+#else
+# define sqlite3Toupper(x)   toupper((unsigned char)(x))
+# define sqlite3Isspace(x)   isspace((unsigned char)(x))
+# define sqlite3Isalnum(x)   isalnum((unsigned char)(x))
+# define sqlite3Isalpha(x)   isalpha((unsigned char)(x))
+# define sqlite3Isdigit(x)   isdigit((unsigned char)(x))
+# define sqlite3Isxdigit(x)  isxdigit((unsigned char)(x))
+# define sqlite3Tolower(x)   tolower((unsigned char)(x))
+# define sqlite3Isquote(x)   ((x)=='"'||(x)=='\''||(x)=='['||(x)=='`')
+# define sqlite3JsonId1(x)   (sqlite3IsIdChar(x)&&(x)<'0')
+# define sqlite3JsonId2(x)   sqlite3IsIdChar(x)
+#endif
+int sqlite3IsIdChar(u8);
+
+/*
+** Internal function prototypes
+*/
+int sqlite3StrICmp(const char*,const char*);
+int sqlite3Strlen30(const char*);
+#define sqlite3Strlen30NN(C) (strlen(C)&0x3fffffff)
+char *sqlite3ColumnType(Column*,char*);
+#define sqlite3StrNICmp sqlite3_strnicmp
+
+int sqlite3MallocInit(void);
+void sqlite3MallocEnd(void);
+void *sqlite3Malloc(u64);
+void *sqlite3MallocZero(u64);
+void *sqlite3DbMallocZero(sqlite3*, u64);
+void *sqlite3DbMallocRaw(sqlite3*, u64);
+void *sqlite3DbMallocRawNN(sqlite3*, u64);
+char *sqlite3DbStrDup(sqlite3*,const char*);
+char *sqlite3DbStrNDup(sqlite3*,const char*, u64);
+char *sqlite3DbSpanDup(sqlite3*,const char*,const char*);
+void *sqlite3Realloc(void*, u64);
+void *sqlite3DbReallocOrFree(sqlite3 *, void *, u64);
+void *sqlite3DbRealloc(sqlite3 *, void *, u64);
+void sqlite3DbFree(sqlite3*, void*);
+void sqlite3DbFreeNN(sqlite3*, void*);
+void sqlite3DbNNFreeNN(sqlite3*, void*);
+int sqlite3MallocSize(const void*);
+int sqlite3DbMallocSize(sqlite3*, const void*);
+void *sqlite3PageMalloc(int);
+void sqlite3PageFree(void*);
+void sqlite3MemSetDefault(void);
+#ifndef SQLITE_UNTESTABLE
+void sqlite3BenignMallocHooks(void (*)(void), void (*)(void));
+#endif
+int sqlite3HeapNearlyFull(void);
+
+/*
+** On systems with ample stack space and that support alloca(), make
+** use of alloca() to obtain space for large automatic objects.  By default,
+** obtain space from malloc().
+**
+** The alloca() routine never returns NULL.  This will cause code paths
+** that deal with sqlite3StackAlloc() failures to be unreachable.
+*/
+#ifdef SQLITE_USE_ALLOCA
+# define sqlite3StackAllocRaw(D,N)   alloca(N)
+# define sqlite3StackAllocRawNN(D,N) alloca(N)
+# define sqlite3StackFree(D,P)
+# define sqlite3StackFreeNN(D,P)
+#else
+# define sqlite3StackAllocRaw(D,N)   sqlite3DbMallocRaw(D,N)
+# define sqlite3StackAllocRawNN(D,N) sqlite3DbMallocRawNN(D,N)
+# define sqlite3StackFree(D,P)       sqlite3DbFree(D,P)
+# define sqlite3StackFreeNN(D,P)     sqlite3DbFreeNN(D,P)
+#endif
+
+/* Do not allow both MEMSYS5 and MEMSYS3 to be defined together.  If they
+** are, disable MEMSYS3
+*/
+#ifdef SQLITE_ENABLE_MEMSYS5
+const sqlite3_mem_methods *sqlite3MemGetMemsys5(void);
+#undef SQLITE_ENABLE_MEMSYS3
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS3
+const sqlite3_mem_methods *sqlite3MemGetMemsys3(void);
+#endif
+
+
+#ifndef SQLITE_MUTEX_OMIT
+  sqlite3_mutex_methods const *sqlite3DefaultMutex(void);
+  sqlite3_mutex_methods const *sqlite3NoopMutex(void);
+  sqlite3_mutex *sqlite3MutexAlloc(int);
+  int sqlite3MutexInit(void);
+  int sqlite3MutexEnd(void);
+#endif
+#if !defined(SQLITE_MUTEX_OMIT) && !defined(SQLITE_MUTEX_NOOP)
+  void sqlite3MemoryBarrier(void);
+#else
+# define sqlite3MemoryBarrier()
+#endif
+
+sqlite3_int64 sqlite3StatusValue(int);
+void sqlite3StatusUp(int, int);
+void sqlite3StatusDown(int, int);
+void sqlite3StatusHighwater(int, int);
+int sqlite3LookasideUsed(sqlite3*,int*);
+
+/* Access to mutexes used by sqlite3_status() */
+sqlite3_mutex *sqlite3Pcache1Mutex(void);
+sqlite3_mutex *sqlite3MallocMutex(void);
+
+#if defined(SQLITE_ENABLE_MULTITHREADED_CHECKS) && !defined(SQLITE_MUTEX_OMIT)
+void sqlite3MutexWarnOnContention(sqlite3_mutex*);
+#else
+# define sqlite3MutexWarnOnContention(x)
+#endif
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+# define EXP754 (((u64)0x7ff)<<52)
+# define MAN754 ((((u64)1)<<52)-1)
+# define IsNaN(X) (((X)&EXP754)==EXP754 && ((X)&MAN754)!=0)
+  int sqlite3IsNaN(double);
+#else
+# define IsNaN(X)         0
+# define sqlite3IsNaN(X)  0
+#endif
+
+/*
+** An instance of the following structure holds information about SQL
+** functions arguments that are the parameters to the printf() function.
+*/
+struct PrintfArguments {
+  int nArg;                /* Total number of arguments */
+  int nUsed;               /* Number of arguments used so far */
+  sqlite3_value **apArg;   /* The argument values */
+};
+
+/*
+** An instance of this object receives the decoding of a floating point
+** value into an approximate decimal representation.
+*/
+struct FpDecode {
+  char sign;           /* '+' or '-' */
+  char isSpecial;      /* 1: Infinity  2: NaN */
+  int n;               /* Significant digits in the decode */
+  int iDP;             /* Location of the decimal point */
+  char *z;             /* Start of significant digits */
+  char zBuf[24];       /* Storage for significant digits */
+};
+
+void sqlite3FpDecode(FpDecode*,double,int,int);
+char *sqlite3MPrintf(sqlite3*,const char*, ...);
+char *sqlite3VMPrintf(sqlite3*,const char*, va_list);
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
+  void sqlite3DebugPrintf(const char*, ...);
+#endif
+#if defined(SQLITE_TEST)
+  void *sqlite3TestTextToPtr(const char*);
+#endif
+
+#if defined(SQLITE_DEBUG)
+  void sqlite3TreeViewLine(TreeView*, const char *zFormat, ...);
+  void sqlite3TreeViewExpr(TreeView*, const Expr*, u8);
+  void sqlite3TreeViewBareExprList(TreeView*, const ExprList*, const char*);
+  void sqlite3TreeViewExprList(TreeView*, const ExprList*, u8, const char*);
+  void sqlite3TreeViewBareIdList(TreeView*, const IdList*, const char*);
+  void sqlite3TreeViewIdList(TreeView*, const IdList*, u8, const char*);
+  void sqlite3TreeViewColumnList(TreeView*, const Column*, int, u8);
+  void sqlite3TreeViewSrcList(TreeView*, const SrcList*);
+  void sqlite3TreeViewSelect(TreeView*, const Select*, u8);
+  void sqlite3TreeViewWith(TreeView*, const With*, u8);
+  void sqlite3TreeViewUpsert(TreeView*, const Upsert*, u8);
+#if TREETRACE_ENABLED
+  void sqlite3TreeViewDelete(const With*, const SrcList*, const Expr*,
+                             const ExprList*,const Expr*, const Trigger*);
+  void sqlite3TreeViewInsert(const With*, const SrcList*,
+                             const IdList*, const Select*, const ExprList*,
+                             int, const Upsert*, const Trigger*);
+  void sqlite3TreeViewUpdate(const With*, const SrcList*, const ExprList*,
+                             const Expr*, int, const ExprList*, const Expr*,
+                             const Upsert*, const Trigger*);
+#endif
+#ifndef SQLITE_OMIT_TRIGGER
+  void sqlite3TreeViewTriggerStep(TreeView*, const TriggerStep*, u8, u8);
+  void sqlite3TreeViewTrigger(TreeView*, const Trigger*, u8, u8);
+#endif
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  void sqlite3TreeViewWindow(TreeView*, const Window*, u8);
+  void sqlite3TreeViewWinFunc(TreeView*, const Window*, u8);
+#endif
+  void sqlite3ShowExpr(const Expr*);
+  void sqlite3ShowExprList(const ExprList*);
+  void sqlite3ShowIdList(const IdList*);
+  void sqlite3ShowSrcList(const SrcList*);
+  void sqlite3ShowSelect(const Select*);
+  void sqlite3ShowWith(const With*);
+  void sqlite3ShowUpsert(const Upsert*);
+#ifndef SQLITE_OMIT_TRIGGER
+  void sqlite3ShowTriggerStep(const TriggerStep*);
+  void sqlite3ShowTriggerStepList(const TriggerStep*);
+  void sqlite3ShowTrigger(const Trigger*);
+  void sqlite3ShowTriggerList(const Trigger*);
+#endif
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  void sqlite3ShowWindow(const Window*);
+  void sqlite3ShowWinFunc(const Window*);
+#endif
+#endif
+
+void sqlite3SetString(char **, sqlite3*, const char*);
+void sqlite3ProgressCheck(Parse*);
+void sqlite3ErrorMsg(Parse*, const char*, ...);
+int sqlite3ErrorToParser(sqlite3*,int);
+void sqlite3Dequote(char*);
+void sqlite3DequoteExpr(Expr*);
+void sqlite3DequoteToken(Token*);
+void sqlite3TokenInit(Token*,char*);
+int sqlite3KeywordCode(const unsigned char*, int);
+int sqlite3RunParser(Parse*, const char*);
+void sqlite3FinishCoding(Parse*);
+int sqlite3GetTempReg(Parse*);
+void sqlite3ReleaseTempReg(Parse*,int);
+int sqlite3GetTempRange(Parse*,int);
+void sqlite3ReleaseTempRange(Parse*,int,int);
+void sqlite3ClearTempRegCache(Parse*);
+void sqlite3TouchRegister(Parse*,int);
+#if defined(SQLITE_ENABLE_STAT4) || defined(SQLITE_DEBUG)
+int sqlite3FirstAvailableRegister(Parse*,int);
+#endif
+#ifdef SQLITE_DEBUG
+int sqlite3NoTempsInRange(Parse*,int,int);
+#endif
+Expr *sqlite3ExprAlloc(sqlite3*,int,const Token*,int);
+Expr *sqlite3Expr(sqlite3*,int,const char*);
+void sqlite3ExprAttachSubtrees(sqlite3*,Expr*,Expr*,Expr*);
+Expr *sqlite3PExpr(Parse*, int, Expr*, Expr*);
+void sqlite3PExprAddSelect(Parse*, Expr*, Select*);
+Expr *sqlite3ExprAnd(Parse*,Expr*, Expr*);
+Expr *sqlite3ExprSimplifiedAndOr(Expr*);
+Expr *sqlite3ExprFunction(Parse*,ExprList*, const Token*, int);
+void sqlite3ExprAddFunctionOrderBy(Parse*,Expr*,ExprList*);
+void sqlite3ExprOrderByAggregateError(Parse*,Expr*);
+void sqlite3ExprFunctionUsable(Parse*,const Expr*,const FuncDef*);
+void sqlite3ExprAssignVarNumber(Parse*, Expr*, u32);
+void sqlite3ExprDelete(sqlite3*, Expr*);
+void sqlite3ExprDeleteGeneric(sqlite3*,void*);
+void sqlite3ExprDeferredDelete(Parse*, Expr*);
+void sqlite3ExprUnmapAndDelete(Parse*, Expr*);
+ExprList *sqlite3ExprListAppend(Parse*,ExprList*,Expr*);
+ExprList *sqlite3ExprListAppendVector(Parse*,ExprList*,IdList*,Expr*);
+Select *sqlite3ExprListToValues(Parse*, int, ExprList*);
+void sqlite3ExprListSetSortOrder(ExprList*,int,int);
+void sqlite3ExprListSetName(Parse*,ExprList*,const Token*,int);
+void sqlite3ExprListSetSpan(Parse*,ExprList*,const char*,const char*);
+void sqlite3ExprListDelete(sqlite3*, ExprList*);
+void sqlite3ExprListDeleteGeneric(sqlite3*,void*);
+u32 sqlite3ExprListFlags(const ExprList*);
+int sqlite3IndexHasDuplicateRootPage(Index*);
+int sqlite3Init(sqlite3*, char**);
+int sqlite3InitCallback(void*, int, char**, char**);
+int sqlite3InitOne(sqlite3*, int, char**, u32);
+void sqlite3Pragma(Parse*,Token*,Token*,Token*,int);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+Module *sqlite3PragmaVtabRegister(sqlite3*,const char *zName);
+#endif
+void sqlite3ResetAllSchemasOfConnection(sqlite3*);
+void sqlite3ResetOneSchema(sqlite3*,int);
+void sqlite3CollapseDatabaseArray(sqlite3*);
+void sqlite3CommitInternalChanges(sqlite3*);
+void sqlite3ColumnSetExpr(Parse*,Table*,Column*,Expr*);
+Expr *sqlite3ColumnExpr(Table*,Column*);
+void sqlite3ColumnSetColl(sqlite3*,Column*,const char*zColl);
+const char *sqlite3ColumnColl(Column*);
+void sqlite3DeleteColumnNames(sqlite3*,Table*);
+void sqlite3GenerateColumnNames(Parse *pParse, Select *pSelect);
+int sqlite3ColumnsFromExprList(Parse*,ExprList*,i16*,Column**);
+void sqlite3SubqueryColumnTypes(Parse*,Table*,Select*,char);
+Table *sqlite3ResultSetOfSelect(Parse*,Select*,char);
+void sqlite3OpenSchemaTable(Parse *, int);
+Index *sqlite3PrimaryKeyIndex(Table*);
+i16 sqlite3TableColumnToIndex(Index*, i16);
+#ifdef SQLITE_OMIT_GENERATED_COLUMNS
+# define sqlite3TableColumnToStorage(T,X) (X)  /* No-op pass-through */
+# define sqlite3StorageColumnToTable(T,X) (X)  /* No-op pass-through */
+#else
+  i16 sqlite3TableColumnToStorage(Table*, i16);
+  i16 sqlite3StorageColumnToTable(Table*, i16);
+#endif
+void sqlite3StartTable(Parse*,Token*,Token*,int,int,int,int);
+#if SQLITE_ENABLE_HIDDEN_COLUMNS
+  void sqlite3ColumnPropertiesFromName(Table*, Column*);
+#else
+# define sqlite3ColumnPropertiesFromName(T,C) /* no-op */
+#endif
+void sqlite3AddColumn(Parse*,Token,Token);
+void sqlite3AddNotNull(Parse*, int);
+void sqlite3AddPrimaryKey(Parse*, ExprList*, int, int, int);
+void sqlite3AddCheckConstraint(Parse*, Expr*, const char*, const char*);
+void sqlite3AddDefaultValue(Parse*,Expr*,const char*,const char*);
+void sqlite3AddCollateType(Parse*, Token*);
+void sqlite3AddGenerated(Parse*,Expr*,Token*);
+void sqlite3EndTable(Parse*,Token*,Token*,u32,Select*);
+void sqlite3AddReturning(Parse*,ExprList*);
+int sqlite3ParseUri(const char*,const char*,unsigned int*,
+                    sqlite3_vfs**,char**,char **);
+#define sqlite3CodecQueryParameters(A,B,C) 0
+Btree *sqlite3DbNameToBtree(sqlite3*,const char*);
+
+#ifdef SQLITE_UNTESTABLE
+# define sqlite3FaultSim(X) SQLITE_OK
+#else
+  int sqlite3FaultSim(int);
+#endif
+
+Bitvec *sqlite3BitvecCreate(u32);
+int sqlite3BitvecTest(Bitvec*, u32);
+int sqlite3BitvecTestNotNull(Bitvec*, u32);
+int sqlite3BitvecSet(Bitvec*, u32);
+void sqlite3BitvecClear(Bitvec*, u32, void*);
+void sqlite3BitvecDestroy(Bitvec*);
+u32 sqlite3BitvecSize(Bitvec*);
+#ifndef SQLITE_UNTESTABLE
+int sqlite3BitvecBuiltinTest(int,int*);
+#endif
+
+RowSet *sqlite3RowSetInit(sqlite3*);
+void sqlite3RowSetDelete(void*);
+void sqlite3RowSetClear(void*);
+void sqlite3RowSetInsert(RowSet*, i64);
+int sqlite3RowSetTest(RowSet*, int iBatch, i64);
+int sqlite3RowSetNext(RowSet*, i64*);
+
+void sqlite3CreateView(Parse*,Token*,Token*,Token*,ExprList*,Select*,int,int);
+
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+  int sqlite3ViewGetColumnNames(Parse*,Table*);
+#else
+# define sqlite3ViewGetColumnNames(A,B) 0
+#endif
+
+#if SQLITE_MAX_ATTACHED>30
+  int sqlite3DbMaskAllZero(yDbMask);
+#endif
+void sqlite3DropTable(Parse*, SrcList*, int, int);
+void sqlite3CodeDropTable(Parse*, Table*, int, int);
+void sqlite3DeleteTable(sqlite3*, Table*);
+void sqlite3DeleteTableGeneric(sqlite3*, void*);
+void sqlite3FreeIndex(sqlite3*, Index*);
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  void sqlite3AutoincrementBegin(Parse *pParse);
+  void sqlite3AutoincrementEnd(Parse *pParse);
+#else
+# define sqlite3AutoincrementBegin(X)
+# define sqlite3AutoincrementEnd(X)
+#endif
+void sqlite3Insert(Parse*, SrcList*, Select*, IdList*, int, Upsert*);
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  void sqlite3ComputeGeneratedColumns(Parse*, int, Table*);
+#endif
+void *sqlite3ArrayAllocate(sqlite3*,void*,int,int*,int*);
+IdList *sqlite3IdListAppend(Parse*, IdList*, Token*);
+int sqlite3IdListIndex(IdList*,const char*);
+SrcList *sqlite3SrcListEnlarge(Parse*, SrcList*, int, int);
+SrcList *sqlite3SrcListAppendList(Parse *pParse, SrcList *p1, SrcList *p2);
+SrcList *sqlite3SrcListAppend(Parse*, SrcList*, Token*, Token*);
+SrcList *sqlite3SrcListAppendFromTerm(Parse*, SrcList*, Token*, Token*,
+                                      Token*, Select*, OnOrUsing*);
+void sqlite3SrcListIndexedBy(Parse *, SrcList *, Token *);
+void sqlite3SrcListFuncArgs(Parse*, SrcList*, ExprList*);
+int sqlite3IndexedByLookup(Parse *, SrcItem *);
+void sqlite3SrcListShiftJoinType(Parse*,SrcList*);
+void sqlite3SrcListAssignCursors(Parse*, SrcList*);
+void sqlite3IdListDelete(sqlite3*, IdList*);
+void sqlite3ClearOnOrUsing(sqlite3*, OnOrUsing*);
+void sqlite3SrcListDelete(sqlite3*, SrcList*);
+Index *sqlite3AllocateIndexObject(sqlite3*,i16,int,char**);
+void sqlite3CreateIndex(Parse*,Token*,Token*,SrcList*,ExprList*,int,Token*,
+                          Expr*, int, int, u8);
+void sqlite3DropIndex(Parse*, SrcList*, int);
+int sqlite3Select(Parse*, Select*, SelectDest*);
+Select *sqlite3SelectNew(Parse*,ExprList*,SrcList*,Expr*,ExprList*,
+                         Expr*,ExprList*,u32,Expr*);
+void sqlite3SelectDelete(sqlite3*, Select*);
+void sqlite3SelectDeleteGeneric(sqlite3*,void*);
+Table *sqlite3SrcListLookup(Parse*, SrcList*);
+int sqlite3IsReadOnly(Parse*, Table*, Trigger*);
+void sqlite3OpenTable(Parse*, int iCur, int iDb, Table*, int);
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
+Expr *sqlite3LimitWhere(Parse*,SrcList*,Expr*,ExprList*,Expr*,char*);
+#endif
+void sqlite3CodeChangeCount(Vdbe*,int,const char*);
+void sqlite3DeleteFrom(Parse*, SrcList*, Expr*, ExprList*, Expr*);
+void sqlite3Update(Parse*, SrcList*, ExprList*,Expr*,int,ExprList*,Expr*,
+                   Upsert*);
+WhereInfo *sqlite3WhereBegin(Parse*,SrcList*,Expr*,ExprList*,
+                             ExprList*,Select*,u16,int);
+void sqlite3WhereEnd(WhereInfo*);
+LogEst sqlite3WhereOutputRowCount(WhereInfo*);
+int sqlite3WhereIsDistinct(WhereInfo*);
+int sqlite3WhereIsOrdered(WhereInfo*);
+int sqlite3WhereOrderByLimitOptLabel(WhereInfo*);
+void sqlite3WhereMinMaxOptEarlyOut(Vdbe*,WhereInfo*);
+int sqlite3WhereIsSorted(WhereInfo*);
+int sqlite3WhereContinueLabel(WhereInfo*);
+int sqlite3WhereBreakLabel(WhereInfo*);
+int sqlite3WhereOkOnePass(WhereInfo*, int*);
+#define ONEPASS_OFF      0        /* Use of ONEPASS not allowed */
+#define ONEPASS_SINGLE   1        /* ONEPASS valid for a single row update */
+#define ONEPASS_MULTI    2        /* ONEPASS is valid for multiple rows */
+int sqlite3WhereUsesDeferredSeek(WhereInfo*);
+void sqlite3ExprCodeLoadIndexColumn(Parse*, Index*, int, int, int);
+int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int, u8);
+void sqlite3ExprCodeGetColumnOfTable(Vdbe*, Table*, int, int, int);
+void sqlite3ExprCodeMove(Parse*, int, int, int);
+void sqlite3ExprCode(Parse*, Expr*, int);
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+void sqlite3ExprCodeGeneratedColumn(Parse*, Table*, Column*, int);
+#endif
+void sqlite3ExprCodeCopy(Parse*, Expr*, int);
+void sqlite3ExprCodeFactorable(Parse*, Expr*, int);
+int sqlite3ExprCodeRunJustOnce(Parse*, Expr*, int);
+int sqlite3ExprCodeTemp(Parse*, Expr*, int*);
+int sqlite3ExprCodeTarget(Parse*, Expr*, int);
+int sqlite3ExprCodeExprList(Parse*, ExprList*, int, int, u8);
+#define SQLITE_ECEL_DUP      0x01  /* Deep, not shallow copies */
+#define SQLITE_ECEL_FACTOR   0x02  /* Factor out constant terms */
+#define SQLITE_ECEL_REF      0x04  /* Use ExprList.u.x.iOrderByCol */
+#define SQLITE_ECEL_OMITREF  0x08  /* Omit if ExprList.u.x.iOrderByCol */
+void sqlite3ExprIfTrue(Parse*, Expr*, int, int);
+void sqlite3ExprIfFalse(Parse*, Expr*, int, int);
+void sqlite3ExprIfFalseDup(Parse*, Expr*, int, int);
+Table *sqlite3FindTable(sqlite3*,const char*, const char*);
+#define LOCATE_VIEW    0x01
+#define LOCATE_NOERR   0x02
+Table *sqlite3LocateTable(Parse*,u32 flags,const char*, const char*);
+const char *sqlite3PreferredTableName(const char*);
+Table *sqlite3LocateTableItem(Parse*,u32 flags,SrcItem *);
+Index *sqlite3FindIndex(sqlite3*,const char*, const char*);
+void sqlite3UnlinkAndDeleteTable(sqlite3*,int,const char*);
+void sqlite3UnlinkAndDeleteIndex(sqlite3*,int,const char*);
+void sqlite3Vacuum(Parse*,Token*,Expr*);
+int sqlite3RunVacuum(char**, sqlite3*, int, sqlite3_value*);
+char *sqlite3NameFromToken(sqlite3*, const Token*);
+int sqlite3ExprCompare(const Parse*,const Expr*,const Expr*, int);
+int sqlite3ExprCompareSkip(Expr*,Expr*,int);
+int sqlite3ExprListCompare(const ExprList*,const ExprList*, int);
+int sqlite3ExprImpliesExpr(const Parse*,const Expr*,const Expr*, int);
+int sqlite3ExprImpliesNonNullRow(Expr*,int,int);
+void sqlite3AggInfoPersistWalkerInit(Walker*,Parse*);
+void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
+void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
+int sqlite3ExprCoveredByIndex(Expr*, int iCur, Index *pIdx);
+int sqlite3ReferencesSrcList(Parse*, Expr*, SrcList*);
+Vdbe *sqlite3GetVdbe(Parse*);
+#ifndef SQLITE_UNTESTABLE
+void sqlite3PrngSaveState(void);
+void sqlite3PrngRestoreState(void);
+#endif
+void sqlite3RollbackAll(sqlite3*,int);
+void sqlite3CodeVerifySchema(Parse*, int);
+void sqlite3CodeVerifyNamedSchema(Parse*, const char *zDb);
+void sqlite3BeginTransaction(Parse*, int);
+void sqlite3EndTransaction(Parse*,int);
+void sqlite3Savepoint(Parse*, int, Token*);
+void sqlite3CloseSavepoints(sqlite3 *);
+void sqlite3LeaveMutexAndCloseZombie(sqlite3*);
+u32 sqlite3IsTrueOrFalse(const char*);
+int sqlite3ExprIdToTrueFalse(Expr*);
+int sqlite3ExprTruthValue(const Expr*);
+int sqlite3ExprIsConstant(Expr*);
+int sqlite3ExprIsConstantNotJoin(Expr*);
+int sqlite3ExprIsConstantOrFunction(Expr*, u8);
+int sqlite3ExprIsConstantOrGroupBy(Parse*, Expr*, ExprList*);
+int sqlite3ExprIsTableConstant(Expr*,int);
+int sqlite3ExprIsSingleTableConstraint(Expr*,const SrcList*,int);
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+int sqlite3ExprContainsSubquery(Expr*);
+#endif
+int sqlite3ExprIsInteger(const Expr*, int*);
+int sqlite3ExprCanBeNull(const Expr*);
+int sqlite3ExprNeedsNoAffinityChange(const Expr*, char);
+int sqlite3IsRowid(const char*);
+const char *sqlite3RowidAlias(Table *pTab);
+void sqlite3GenerateRowDelete(
+    Parse*,Table*,Trigger*,int,int,int,i16,u8,u8,u8,int);
+void sqlite3GenerateRowIndexDelete(Parse*, Table*, int, int, int*, int);
+int sqlite3GenerateIndexKey(Parse*, Index*, int, int, int, int*,Index*,int);
+void sqlite3ResolvePartIdxLabel(Parse*,int);
+int sqlite3ExprReferencesUpdatedColumn(Expr*,int*,int);
+void sqlite3GenerateConstraintChecks(Parse*,Table*,int*,int,int,int,int,
+                                     u8,u8,int,int*,int*,Upsert*);
+#ifdef SQLITE_ENABLE_NULL_TRIM
+  void sqlite3SetMakeRecordP5(Vdbe*,Table*);
+#else
+# define sqlite3SetMakeRecordP5(A,B)
+#endif
+void sqlite3CompleteInsertion(Parse*,Table*,int,int,int,int*,int,int,int);
+int sqlite3OpenTableAndIndices(Parse*, Table*, int, u8, int, u8*, int*, int*);
+void sqlite3BeginWriteOperation(Parse*, int, int);
+void sqlite3MultiWrite(Parse*);
+void sqlite3MayAbort(Parse*);
+void sqlite3HaltConstraint(Parse*, int, int, char*, i8, u8);
+void sqlite3UniqueConstraint(Parse*, int, Index*);
+void sqlite3RowidConstraint(Parse*, int, Table*);
+Expr *sqlite3ExprDup(sqlite3*,const Expr*,int);
+ExprList *sqlite3ExprListDup(sqlite3*,const ExprList*,int);
+SrcList *sqlite3SrcListDup(sqlite3*,const SrcList*,int);
+IdList *sqlite3IdListDup(sqlite3*,const IdList*);
+Select *sqlite3SelectDup(sqlite3*,const Select*,int);
+FuncDef *sqlite3FunctionSearch(int,const char*);
+void sqlite3InsertBuiltinFuncs(FuncDef*,int);
+FuncDef *sqlite3FindFunction(sqlite3*,const char*,int,u8,u8);
+void sqlite3QuoteValue(StrAccum*,sqlite3_value*);
+void sqlite3RegisterBuiltinFunctions(void);
+void sqlite3RegisterDateTimeFunctions(void);
+void sqlite3RegisterJsonFunctions(void);
+void sqlite3RegisterPerConnectionBuiltinFunctions(sqlite3*);
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_JSON)
+  int sqlite3JsonTableFunctions(sqlite3*);
+#endif
+int sqlite3SafetyCheckOk(sqlite3*);
+int sqlite3SafetyCheckSickOrOk(sqlite3*);
+void sqlite3ChangeCookie(Parse*, int);
+With *sqlite3WithDup(sqlite3 *db, With *p);
+
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+void sqlite3MaterializeView(Parse*, Table*, Expr*, ExprList*,Expr*,int);
+#endif
+
+#ifndef SQLITE_OMIT_TRIGGER
+  void sqlite3BeginTrigger(Parse*, Token*,Token*,int,int,IdList*,SrcList*,
+                           Expr*,int, int);
+  void sqlite3FinishTrigger(Parse*, TriggerStep*, Token*);
+  void sqlite3DropTrigger(Parse*, SrcList*, int);
+  void sqlite3DropTriggerPtr(Parse*, Trigger*);
+  Trigger *sqlite3TriggersExist(Parse *, Table*, int, ExprList*, int *pMask);
+  Trigger *sqlite3TriggerList(Parse *, Table *);
+  void sqlite3CodeRowTrigger(Parse*, Trigger *, int, ExprList*, int, Table *,
+                            int, int, int);
+  void sqlite3CodeRowTriggerDirect(Parse *, Trigger *, Table *, int, int, int);
+  void sqliteViewTriggers(Parse*, Table*, Expr*, int, ExprList*);
+  void sqlite3DeleteTriggerStep(sqlite3*, TriggerStep*);
+  TriggerStep *sqlite3TriggerSelectStep(sqlite3*,Select*,
+                                        const char*,const char*);
+  TriggerStep *sqlite3TriggerInsertStep(Parse*,Token*, IdList*,
+                                        Select*,u8,Upsert*,
+                                        const char*,const char*);
+  TriggerStep *sqlite3TriggerUpdateStep(Parse*,Token*,SrcList*,ExprList*,
+                                        Expr*, u8, const char*,const char*);
+  TriggerStep *sqlite3TriggerDeleteStep(Parse*,Token*, Expr*,
+                                        const char*,const char*);
+  void sqlite3DeleteTrigger(sqlite3*, Trigger*);
+  void sqlite3UnlinkAndDeleteTrigger(sqlite3*,int,const char*);
+  u32 sqlite3TriggerColmask(Parse*,Trigger*,ExprList*,int,int,Table*,int);
+  SrcList *sqlite3TriggerStepSrc(Parse*, TriggerStep*);
+# define sqlite3ParseToplevel(p) ((p)->pToplevel ? (p)->pToplevel : (p))
+# define sqlite3IsToplevel(p) ((p)->pToplevel==0)
+#else
+# define sqlite3TriggersExist(B,C,D,E,F) 0
+# define sqlite3DeleteTrigger(A,B)
+# define sqlite3DropTriggerPtr(A,B)
+# define sqlite3UnlinkAndDeleteTrigger(A,B,C)
+# define sqlite3CodeRowTrigger(A,B,C,D,E,F,G,H,I)
+# define sqlite3CodeRowTriggerDirect(A,B,C,D,E,F)
+# define sqlite3TriggerList(X, Y) 0
+# define sqlite3ParseToplevel(p) p
+# define sqlite3IsToplevel(p) 1
+# define sqlite3TriggerColmask(A,B,C,D,E,F,G) 0
+# define sqlite3TriggerStepSrc(A,B) 0
+#endif
+
+int sqlite3JoinType(Parse*, Token*, Token*, Token*);
+int sqlite3ColumnIndex(Table *pTab, const char *zCol);
+void sqlite3SrcItemColumnUsed(SrcItem*,int);
+void sqlite3SetJoinExpr(Expr*,int,u32);
+void sqlite3CreateForeignKey(Parse*, ExprList*, Token*, ExprList*, int);
+void sqlite3DeferForeignKey(Parse*, int);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  void sqlite3AuthRead(Parse*,Expr*,Schema*,SrcList*);
+  int sqlite3AuthCheck(Parse*,int, const char*, const char*, const char*);
+  void sqlite3AuthContextPush(Parse*, AuthContext*, const char*);
+  void sqlite3AuthContextPop(AuthContext*);
+  int sqlite3AuthReadCol(Parse*, const char *, const char *, int);
+#else
+# define sqlite3AuthRead(a,b,c,d)
+# define sqlite3AuthCheck(a,b,c,d,e)    SQLITE_OK
+# define sqlite3AuthContextPush(a,b,c)
+# define sqlite3AuthContextPop(a)  ((void)(a))
+#endif
+int sqlite3DbIsNamed(sqlite3 *db, int iDb, const char *zName);
+void sqlite3Attach(Parse*, Expr*, Expr*, Expr*);
+void sqlite3Detach(Parse*, Expr*);
+void sqlite3FixInit(DbFixer*, Parse*, int, const char*, const Token*);
+int sqlite3FixSrcList(DbFixer*, SrcList*);
+int sqlite3FixSelect(DbFixer*, Select*);
+int sqlite3FixExpr(DbFixer*, Expr*);
+int sqlite3FixTriggerStep(DbFixer*, TriggerStep*);
+
+int sqlite3RealSameAsInt(double,sqlite3_int64);
+i64 sqlite3RealToI64(double);
+int sqlite3Int64ToText(i64,char*);
+int sqlite3AtoF(const char *z, double*, int, u8);
+int sqlite3GetInt32(const char *, int*);
+int sqlite3GetUInt32(const char*, u32*);
+int sqlite3Atoi(const char*);
+#ifndef SQLITE_OMIT_UTF16
+int sqlite3Utf16ByteLen(const void *pData, int nChar);
+#endif
+int sqlite3Utf8CharLen(const char *pData, int nByte);
+u32 sqlite3Utf8Read(const u8**);
+int sqlite3Utf8ReadLimited(const u8*, int, u32*);
+LogEst sqlite3LogEst(u64);
+LogEst sqlite3LogEstAdd(LogEst,LogEst);
+LogEst sqlite3LogEstFromDouble(double);
+u64 sqlite3LogEstToInt(LogEst);
+VList *sqlite3VListAdd(sqlite3*,VList*,const char*,int,int);
+const char *sqlite3VListNumToName(VList*,int);
+int sqlite3VListNameToNum(VList*,const char*,int);
+
+/*
+** Routines to read and write variable-length integers.  These used to
+** be defined locally, but now we use the varint routines in the util.c
+** file.
+*/
+int sqlite3PutVarint(unsigned char*, u64);
+u8 sqlite3GetVarint(const unsigned char *, u64 *);
+u8 sqlite3GetVarint32(const unsigned char *, u32 *);
+int sqlite3VarintLen(u64 v);
+
+/*
+** The common case is for a varint to be a single byte.  They following
+** macros handle the common case without a procedure call, but then call
+** the procedure for larger varints.
+*/
+#define getVarint32(A,B)  \
+  (u8)((*(A)<(u8)0x80)?((B)=(u32)*(A)),1:sqlite3GetVarint32((A),(u32 *)&(B)))
+#define getVarint32NR(A,B) \
+  B=(u32)*(A);if(B>=0x80)sqlite3GetVarint32((A),(u32*)&(B))
+#define putVarint32(A,B)  \
+  (u8)(((u32)(B)<(u32)0x80)?(*(A)=(unsigned char)(B)),1:\
+  sqlite3PutVarint((A),(B)))
+#define getVarint    sqlite3GetVarint
+#define putVarint    sqlite3PutVarint
+
+
+const char *sqlite3IndexAffinityStr(sqlite3*, Index*);
+char *sqlite3TableAffinityStr(sqlite3*,const Table*);
+void sqlite3TableAffinity(Vdbe*, Table*, int);
+char sqlite3CompareAffinity(const Expr *pExpr, char aff2);
+int sqlite3IndexAffinityOk(const Expr *pExpr, char idx_affinity);
+char sqlite3TableColumnAffinity(const Table*,int);
+char sqlite3ExprAffinity(const Expr *pExpr);
+int sqlite3ExprDataType(const Expr *pExpr);
+int sqlite3Atoi64(const char*, i64*, int, u8);
+int sqlite3DecOrHexToI64(const char*, i64*);
+void sqlite3ErrorWithMsg(sqlite3*, int, const char*,...);
+void sqlite3Error(sqlite3*,int);
+void sqlite3ErrorClear(sqlite3*);
+void sqlite3SystemError(sqlite3*,int);
+void *sqlite3HexToBlob(sqlite3*, const char *z, int n);
+u8 sqlite3HexToInt(int h);
+int sqlite3TwoPartName(Parse *, Token *, Token *, Token **);
+
+#if defined(SQLITE_NEED_ERR_NAME)
+const char *sqlite3ErrName(int);
+#endif
+
+#ifndef SQLITE_OMIT_DESERIALIZE
+int sqlite3MemdbInit(void);
+int sqlite3IsMemdb(const sqlite3_vfs*);
+#else
+# define sqlite3IsMemdb(X) 0
+#endif
+
+const char *sqlite3ErrStr(int);
+int sqlite3ReadSchema(Parse *pParse);
+CollSeq *sqlite3FindCollSeq(sqlite3*,u8 enc, const char*,int);
+int sqlite3IsBinary(const CollSeq*);
+CollSeq *sqlite3LocateCollSeq(Parse *pParse, const char*zName);
+void sqlite3SetTextEncoding(sqlite3 *db, u8);
+CollSeq *sqlite3ExprCollSeq(Parse *pParse, const Expr *pExpr);
+CollSeq *sqlite3ExprNNCollSeq(Parse *pParse, const Expr *pExpr);
+int sqlite3ExprCollSeqMatch(Parse*,const Expr*,const Expr*);
+Expr *sqlite3ExprAddCollateToken(const Parse *pParse, Expr*, const Token*, int);
+Expr *sqlite3ExprAddCollateString(const Parse*,Expr*,const char*);
+Expr *sqlite3ExprSkipCollate(Expr*);
+Expr *sqlite3ExprSkipCollateAndLikely(Expr*);
+int sqlite3CheckCollSeq(Parse *, CollSeq *);
+int sqlite3WritableSchema(sqlite3*);
+int sqlite3CheckObjectName(Parse*, const char*,const char*,const char*);
+void sqlite3VdbeSetChanges(sqlite3 *, i64);
+int sqlite3AddInt64(i64*,i64);
+int sqlite3SubInt64(i64*,i64);
+int sqlite3MulInt64(i64*,i64);
+int sqlite3AbsInt32(int);
+#ifdef SQLITE_ENABLE_8_3_NAMES
+void sqlite3FileSuffix3(const char*, char*);
+#else
+# define sqlite3FileSuffix3(X,Y)
+#endif
+u8 sqlite3GetBoolean(const char *z,u8);
+
+const void *sqlite3ValueText(sqlite3_value*, u8);
+int sqlite3ValueIsOfClass(const sqlite3_value*, void(*)(void*));
+int sqlite3ValueBytes(sqlite3_value*, u8);
+void sqlite3ValueSetStr(sqlite3_value*, int, const void *,u8,
+                        void(*)(void*));
+void sqlite3ValueSetNull(sqlite3_value*);
+void sqlite3ValueFree(sqlite3_value*);
+#ifndef SQLITE_UNTESTABLE
+void sqlite3ResultIntReal(sqlite3_context*);
+#endif
+sqlite3_value *sqlite3ValueNew(sqlite3 *);
+#ifndef SQLITE_OMIT_UTF16
+char *sqlite3Utf16to8(sqlite3 *, const void*, int, u8);
+#endif
+int sqlite3ValueFromExpr(sqlite3 *, const Expr *, u8, u8, sqlite3_value **);
+void sqlite3ValueApplyAffinity(sqlite3_value *, u8, u8);
+#ifndef SQLITE_AMALGAMATION
+extern const unsigned char sqlite3OpcodeProperty[];
+extern const char sqlite3StrBINARY[];
+extern const unsigned char sqlite3StdTypeLen[];
+extern const char sqlite3StdTypeAffinity[];
+extern const char *sqlite3StdType[];
+extern const unsigned char sqlite3UpperToLower[];
+extern const unsigned char *sqlite3aLTb;
+extern const unsigned char *sqlite3aEQb;
+extern const unsigned char *sqlite3aGTb;
+extern const unsigned char sqlite3CtypeMap[];
+extern SQLITE_WSD struct Sqlite3Config sqlite3Config;
+extern FuncDefHash sqlite3BuiltinFunctions;
+#ifndef SQLITE_OMIT_WSD
+extern int sqlite3PendingByte;
+#endif
+#endif /* SQLITE_AMALGAMATION */
+#ifdef VDBE_PROFILE
+extern sqlite3_uint64 sqlite3NProfileCnt;
+#endif
+void sqlite3RootPageMoved(sqlite3*, int, Pgno, Pgno);
+void sqlite3Reindex(Parse*, Token*, Token*);
+void sqlite3AlterFunctions(void);
+void sqlite3AlterRenameTable(Parse*, SrcList*, Token*);
+void sqlite3AlterRenameColumn(Parse*, SrcList*, Token*, Token*);
+int sqlite3GetToken(const unsigned char *, int *);
+void sqlite3NestedParse(Parse*, const char*, ...);
+void sqlite3ExpirePreparedStatements(sqlite3*, int);
+void sqlite3CodeRhsOfIN(Parse*, Expr*, int);
+int sqlite3CodeSubselect(Parse*, Expr*);
+void sqlite3SelectPrep(Parse*, Select*, NameContext*);
+int sqlite3ExpandSubquery(Parse*, SrcItem*);
+void sqlite3SelectWrongNumTermsError(Parse *pParse, Select *p);
+int sqlite3MatchEName(
+  const struct ExprList_item*,
+  const char*,
+  const char*,
+  const char*,
+  int*
+);
+Bitmask sqlite3ExprColUsed(Expr*);
+u8 sqlite3StrIHash(const char*);
+int sqlite3ResolveExprNames(NameContext*, Expr*);
+int sqlite3ResolveExprListNames(NameContext*, ExprList*);
+void sqlite3ResolveSelectNames(Parse*, Select*, NameContext*);
+int sqlite3ResolveSelfReference(Parse*,Table*,int,Expr*,ExprList*);
+int sqlite3ResolveOrderGroupBy(Parse*, Select*, ExprList*, const char*);
+void sqlite3ColumnDefault(Vdbe *, Table *, int, int);
+void sqlite3AlterFinishAddColumn(Parse *, Token *);
+void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
+void sqlite3AlterDropColumn(Parse*, SrcList*, const Token*);
+const void *sqlite3RenameTokenMap(Parse*, const void*, const Token*);
+void sqlite3RenameTokenRemap(Parse*, const void *pTo, const void *pFrom);
+void sqlite3RenameExprUnmap(Parse*, Expr*);
+void sqlite3RenameExprlistUnmap(Parse*, ExprList*);
+CollSeq *sqlite3GetCollSeq(Parse*, u8, CollSeq *, const char*);
+char sqlite3AffinityType(const char*, Column*);
+void sqlite3Analyze(Parse*, Token*, Token*);
+int sqlite3InvokeBusyHandler(BusyHandler*);
+int sqlite3FindDb(sqlite3*, Token*);
+int sqlite3FindDbName(sqlite3 *, const char *);
+int sqlite3AnalysisLoad(sqlite3*,int iDB);
+void sqlite3DeleteIndexSamples(sqlite3*,Index*);
+void sqlite3DefaultRowEst(Index*);
+void sqlite3RegisterLikeFunctions(sqlite3*, int);
+int sqlite3IsLikeFunction(sqlite3*,Expr*,int*,char*);
+void sqlite3SchemaClear(void *);
+Schema *sqlite3SchemaGet(sqlite3 *, Btree *);
+int sqlite3SchemaToIndex(sqlite3 *db, Schema *);
+KeyInfo *sqlite3KeyInfoAlloc(sqlite3*,int,int);
+void sqlite3KeyInfoUnref(KeyInfo*);
+KeyInfo *sqlite3KeyInfoRef(KeyInfo*);
+KeyInfo *sqlite3KeyInfoOfIndex(Parse*, Index*);
+KeyInfo *sqlite3KeyInfoFromExprList(Parse*, ExprList*, int, int);
+const char *sqlite3SelectOpName(int);
+int sqlite3HasExplicitNulls(Parse*, ExprList*);
+
+#ifdef SQLITE_DEBUG
+int sqlite3KeyInfoIsWriteable(KeyInfo*);
+#endif
+int sqlite3CreateFunc(sqlite3 *, const char *, int, int, void *,
+  void (*)(sqlite3_context*,int,sqlite3_value **),
+  void (*)(sqlite3_context*,int,sqlite3_value **),
+  void (*)(sqlite3_context*),
+  void (*)(sqlite3_context*),
+  void (*)(sqlite3_context*,int,sqlite3_value **),
+  FuncDestructor *pDestructor
+);
+void sqlite3NoopDestructor(void*);
+void *sqlite3OomFault(sqlite3*);
+void sqlite3OomClear(sqlite3*);
+int sqlite3ApiExit(sqlite3 *db, int);
+int sqlite3OpenTempDatabase(Parse *);
+
+char *sqlite3RCStrRef(char*);
+void sqlite3RCStrUnref(void*);
+char *sqlite3RCStrNew(u64);
+char *sqlite3RCStrResize(char*,u64);
+
+void sqlite3StrAccumInit(StrAccum*, sqlite3*, char*, int, int);
+int sqlite3StrAccumEnlarge(StrAccum*, i64);
+char *sqlite3StrAccumFinish(StrAccum*);
+void sqlite3StrAccumSetError(StrAccum*, u8);
+void sqlite3ResultStrAccum(sqlite3_context*,StrAccum*);
+void sqlite3SelectDestInit(SelectDest*,int,int);
+Expr *sqlite3CreateColumnExpr(sqlite3 *, SrcList *, int, int);
+void sqlite3RecordErrorByteOffset(sqlite3*,const char*);
+void sqlite3RecordErrorOffsetOfExpr(sqlite3*,const Expr*);
+
+void sqlite3BackupRestart(sqlite3_backup *);
+void sqlite3BackupUpdate(sqlite3_backup *, Pgno, const u8 *);
+
+#ifndef SQLITE_OMIT_SUBQUERY
+int sqlite3ExprCheckIN(Parse*, Expr*);
+#else
+# define sqlite3ExprCheckIN(x,y) SQLITE_OK
+#endif
+
+#ifdef SQLITE_ENABLE_STAT4
+int sqlite3Stat4ProbeSetValue(
+    Parse*,Index*,UnpackedRecord**,Expr*,int,int,int*);
+int sqlite3Stat4ValueFromExpr(Parse*, Expr*, u8, sqlite3_value**);
+void sqlite3Stat4ProbeFree(UnpackedRecord*);
+int sqlite3Stat4Column(sqlite3*, const void*, int, int, sqlite3_value**);
+char sqlite3IndexColumnAffinity(sqlite3*, Index*, int);
+#endif
+
+/*
+** The interface to the LEMON-generated parser
+*/
+#ifndef SQLITE_AMALGAMATION
+  void *sqlite3ParserAlloc(void*(*)(u64), Parse*);
+  void sqlite3ParserFree(void*, void(*)(void*));
+#endif
+void sqlite3Parser(void*, int, Token);
+int sqlite3ParserFallback(int);
+#ifdef YYTRACKMAXSTACKDEPTH
+  int sqlite3ParserStackPeak(void*);
+#endif
+
+void sqlite3AutoLoadExtensions(sqlite3*);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  void sqlite3CloseExtensions(sqlite3*);
+#else
+# define sqlite3CloseExtensions(X)
+#endif
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  void sqlite3TableLock(Parse *, int, Pgno, u8, const char *);
+#else
+  #define sqlite3TableLock(v,w,x,y,z)
+#endif
+
+#ifdef SQLITE_TEST
+  int sqlite3Utf8To8(unsigned char*);
+#endif
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+#  define sqlite3VtabClear(D,T)
+#  define sqlite3VtabSync(X,Y) SQLITE_OK
+#  define sqlite3VtabRollback(X)
+#  define sqlite3VtabCommit(X)
+#  define sqlite3VtabInSync(db) 0
+#  define sqlite3VtabLock(X)
+#  define sqlite3VtabUnlock(X)
+#  define sqlite3VtabModuleUnref(D,X)
+#  define sqlite3VtabUnlockList(X)
+#  define sqlite3VtabSavepoint(X, Y, Z) SQLITE_OK
+#  define sqlite3GetVTable(X,Y)  ((VTable*)0)
+#else
+   void sqlite3VtabClear(sqlite3 *db, Table*);
+   void sqlite3VtabDisconnect(sqlite3 *db, Table *p);
+   int sqlite3VtabSync(sqlite3 *db, Vdbe*);
+   int sqlite3VtabRollback(sqlite3 *db);
+   int sqlite3VtabCommit(sqlite3 *db);
+   void sqlite3VtabLock(VTable *);
+   void sqlite3VtabUnlock(VTable *);
+   void sqlite3VtabModuleUnref(sqlite3*,Module*);
+   void sqlite3VtabUnlockList(sqlite3*);
+   int sqlite3VtabSavepoint(sqlite3 *, int, int);
+   void sqlite3VtabImportErrmsg(Vdbe*, sqlite3_vtab*);
+   VTable *sqlite3GetVTable(sqlite3*, Table*);
+   Module *sqlite3VtabCreateModule(
+     sqlite3*,
+     const char*,
+     const sqlite3_module*,
+     void*,
+     void(*)(void*)
+   );
+#  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
+#endif
+int sqlite3ReadOnlyShadowTables(sqlite3 *db);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  int sqlite3ShadowTableName(sqlite3 *db, const char *zName);
+  int sqlite3IsShadowTableOf(sqlite3*,Table*,const char*);
+  void sqlite3MarkAllShadowTablesOf(sqlite3*, Table*);
+#else
+# define sqlite3ShadowTableName(A,B) 0
+# define sqlite3IsShadowTableOf(A,B,C) 0
+# define sqlite3MarkAllShadowTablesOf(A,B)
+#endif
+int sqlite3VtabEponymousTableInit(Parse*,Module*);
+void sqlite3VtabEponymousTableClear(sqlite3*,Module*);
+void sqlite3VtabMakeWritable(Parse*,Table*);
+void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*, int);
+void sqlite3VtabFinishParse(Parse*, Token*);
+void sqlite3VtabArgInit(Parse*);
+void sqlite3VtabArgExtend(Parse*, Token*);
+int sqlite3VtabCallCreate(sqlite3*, int, const char *, char **);
+int sqlite3VtabCallConnect(Parse*, Table*);
+int sqlite3VtabCallDestroy(sqlite3*, int, const char *);
+int sqlite3VtabBegin(sqlite3 *, VTable *);
+
+FuncDef *sqlite3VtabOverloadFunction(sqlite3 *,FuncDef*, int nArg, Expr*);
+void sqlite3VtabUsesAllSchemas(Parse*);
+sqlite3_int64 sqlite3StmtCurrentTime(sqlite3_context*);
+int sqlite3VdbeParameterIndex(Vdbe*, const char*, int);
+int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
+void sqlite3ParseObjectInit(Parse*,sqlite3*);
+void sqlite3ParseObjectReset(Parse*);
+void *sqlite3ParserAddCleanup(Parse*,void(*)(sqlite3*,void*),void*);
+#ifdef SQLITE_ENABLE_NORMALIZE
+char *sqlite3Normalize(Vdbe*, const char*);
+#endif
+int sqlite3Reprepare(Vdbe*);
+void sqlite3ExprListCheckLength(Parse*, ExprList*, const char*);
+CollSeq *sqlite3ExprCompareCollSeq(Parse*,const Expr*);
+CollSeq *sqlite3BinaryCompareCollSeq(Parse *, const Expr*, const Expr*);
+int sqlite3TempInMemory(const sqlite3*);
+const char *sqlite3JournalModename(int);
+#ifndef SQLITE_OMIT_WAL
+  int sqlite3Checkpoint(sqlite3*, int, int, int*, int*);
+  int sqlite3WalDefaultHook(void*,sqlite3*,const char*,int);
+#endif
+#ifndef SQLITE_OMIT_CTE
+  Cte *sqlite3CteNew(Parse*,Token*,ExprList*,Select*,u8);
+  void sqlite3CteDelete(sqlite3*,Cte*);
+  With *sqlite3WithAdd(Parse*,With*,Cte*);
+  void sqlite3WithDelete(sqlite3*,With*);
+  void sqlite3WithDeleteGeneric(sqlite3*,void*);
+  With *sqlite3WithPush(Parse*, With*, u8);
+#else
+# define sqlite3CteNew(P,T,E,S)   ((void*)0)
+# define sqlite3CteDelete(D,C)
+# define sqlite3CteWithAdd(P,W,C) ((void*)0)
+# define sqlite3WithDelete(x,y)
+# define sqlite3WithPush(x,y,z) ((void*)0)
+#endif
+#ifndef SQLITE_OMIT_UPSERT
+  Upsert *sqlite3UpsertNew(sqlite3*,ExprList*,Expr*,ExprList*,Expr*,Upsert*);
+  void sqlite3UpsertDelete(sqlite3*,Upsert*);
+  Upsert *sqlite3UpsertDup(sqlite3*,Upsert*);
+  int sqlite3UpsertAnalyzeTarget(Parse*,SrcList*,Upsert*);
+  void sqlite3UpsertDoUpdate(Parse*,Upsert*,Table*,Index*,int);
+  Upsert *sqlite3UpsertOfIndex(Upsert*,Index*);
+  int sqlite3UpsertNextIsIPK(Upsert*);
+#else
+#define sqlite3UpsertNew(u,v,w,x,y,z) ((Upsert*)0)
+#define sqlite3UpsertDelete(x,y)
+#define sqlite3UpsertDup(x,y)         ((Upsert*)0)
+#define sqlite3UpsertOfIndex(x,y)     ((Upsert*)0)
+#define sqlite3UpsertNextIsIPK(x)     0
+#endif
+
+
+/* Declarations for functions in fkey.c. All of these are replaced by
+** no-op macros if OMIT_FOREIGN_KEY is defined. In this case no foreign
+** key functionality is available. If OMIT_TRIGGER is defined but
+** OMIT_FOREIGN_KEY is not, only some of the functions are no-oped. In
+** this case foreign keys are parsed, but no other functionality is
+** provided (enforcement of FK constraints requires the triggers sub-system).
+*/
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+  void sqlite3FkCheck(Parse*, Table*, int, int, int*, int);
+  void sqlite3FkDropTable(Parse*, SrcList *, Table*);
+  void sqlite3FkActions(Parse*, Table*, ExprList*, int, int*, int);
+  int sqlite3FkRequired(Parse*, Table*, int*, int);
+  u32 sqlite3FkOldmask(Parse*, Table*);
+  FKey *sqlite3FkReferences(Table *);
+  void sqlite3FkClearTriggerCache(sqlite3*,int);
+#else
+  #define sqlite3FkActions(a,b,c,d,e,f)
+  #define sqlite3FkCheck(a,b,c,d,e,f)
+  #define sqlite3FkDropTable(a,b,c)
+  #define sqlite3FkOldmask(a,b)         0
+  #define sqlite3FkRequired(a,b,c,d)    0
+  #define sqlite3FkReferences(a)        0
+  #define sqlite3FkClearTriggerCache(a,b)
+#endif
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  void sqlite3FkDelete(sqlite3 *, Table*);
+  int sqlite3FkLocateIndex(Parse*,Table*,FKey*,Index**,int**);
+#else
+  #define sqlite3FkDelete(a,b)
+  #define sqlite3FkLocateIndex(a,b,c,d,e)
+#endif
+
+
+/*
+** Available fault injectors.  Should be numbered beginning with 0.
+*/
+#define SQLITE_FAULTINJECTOR_MALLOC     0
+#define SQLITE_FAULTINJECTOR_COUNT      1
+
+/*
+** The interface to the code in fault.c used for identifying "benign"
+** malloc failures. This is only present if SQLITE_UNTESTABLE
+** is not defined.
+*/
+#ifndef SQLITE_UNTESTABLE
+  void sqlite3BeginBenignMalloc(void);
+  void sqlite3EndBenignMalloc(void);
+#else
+  #define sqlite3BeginBenignMalloc()
+  #define sqlite3EndBenignMalloc()
+#endif
+
+/*
+** Allowed return values from sqlite3FindInIndex()
+*/
+#define IN_INDEX_ROWID        1   /* Search the rowid of the table */
+#define IN_INDEX_EPH          2   /* Search an ephemeral b-tree */
+#define IN_INDEX_INDEX_ASC    3   /* Existing index ASCENDING */
+#define IN_INDEX_INDEX_DESC   4   /* Existing index DESCENDING */
+#define IN_INDEX_NOOP         5   /* No table available. Use comparisons */
+/*
+** Allowed flags for the 3rd parameter to sqlite3FindInIndex().
+*/
+#define IN_INDEX_NOOP_OK     0x0001  /* OK to return IN_INDEX_NOOP */
+#define IN_INDEX_MEMBERSHIP  0x0002  /* IN operator used for membership test */
+#define IN_INDEX_LOOP        0x0004  /* IN operator used as a loop */
+int sqlite3FindInIndex(Parse *, Expr *, u32, int*, int*, int*);
+
+int sqlite3JournalOpen(sqlite3_vfs *, const char *, sqlite3_file *, int, int);
+int sqlite3JournalSize(sqlite3_vfs *);
+#if defined(SQLITE_ENABLE_ATOMIC_WRITE) \
+ || defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+  int sqlite3JournalCreate(sqlite3_file *);
+#endif
+
+int sqlite3JournalIsInMemory(sqlite3_file *p);
+void sqlite3MemJournalOpen(sqlite3_file *);
+
+void sqlite3ExprSetHeightAndFlags(Parse *pParse, Expr *p);
+#if SQLITE_MAX_EXPR_DEPTH>0
+  int sqlite3SelectExprHeight(const Select *);
+  int sqlite3ExprCheckHeight(Parse*, int);
+#else
+  #define sqlite3SelectExprHeight(x) 0
+  #define sqlite3ExprCheckHeight(x,y)
+#endif
+void sqlite3ExprSetErrorOffset(Expr*,int);
+
+u32 sqlite3Get4byte(const u8*);
+void sqlite3Put4byte(u8*, u32);
+
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  void sqlite3ConnectionBlocked(sqlite3 *, sqlite3 *);
+  void sqlite3ConnectionUnlocked(sqlite3 *db);
+  void sqlite3ConnectionClosed(sqlite3 *db);
+#else
+  #define sqlite3ConnectionBlocked(x,y)
+  #define sqlite3ConnectionUnlocked(x)
+  #define sqlite3ConnectionClosed(x)
+#endif
+
+#ifdef SQLITE_DEBUG
+  void sqlite3ParserTrace(FILE*, char *);
+#endif
+#if defined(YYCOVERAGE)
+  int sqlite3ParserCoverage(FILE*);
+#endif
+
+/*
+** If the SQLITE_ENABLE IOTRACE exists then the global variable
+** sqlite3IoTrace is a pointer to a printf-like routine used to
+** print I/O tracing messages.
+*/
+#ifdef SQLITE_ENABLE_IOTRACE
+# define IOTRACE(A)  if( sqlite3IoTrace ){ sqlite3IoTrace A; }
+  void sqlite3VdbeIOTraceSql(Vdbe*);
+SQLITE_API SQLITE_EXTERN void (SQLITE_CDECL *sqlite3IoTrace)(const char*,...);
+#else
+# define IOTRACE(A)
+# define sqlite3VdbeIOTraceSql(X)
+#endif
+
+/*
+** These routines are available for the mem2.c debugging memory allocator
+** only.  They are used to verify that different "types" of memory
+** allocations are properly tracked by the system.
+**
+** sqlite3MemdebugSetType() sets the "type" of an allocation to one of
+** the MEMTYPE_* macros defined below.  The type must be a bitmask with
+** a single bit set.
+**
+** sqlite3MemdebugHasType() returns true if any of the bits in its second
+** argument match the type set by the previous sqlite3MemdebugSetType().
+** sqlite3MemdebugHasType() is intended for use inside assert() statements.
+**
+** sqlite3MemdebugNoType() returns true if none of the bits in its second
+** argument match the type set by the previous sqlite3MemdebugSetType().
+**
+** Perhaps the most important point is the difference between MEMTYPE_HEAP
+** and MEMTYPE_LOOKASIDE.  If an allocation is MEMTYPE_LOOKASIDE, that means
+** it might have been allocated by lookaside, except the allocation was
+** too large or lookaside was already full.  It is important to verify
+** that allocations that might have been satisfied by lookaside are not
+** passed back to non-lookaside free() routines.  Asserts such as the
+** example above are placed on the non-lookaside free() routines to verify
+** this constraint.
+**
+** All of this is no-op for a production build.  It only comes into
+** play when the SQLITE_MEMDEBUG compile-time option is used.
+*/
+#ifdef SQLITE_MEMDEBUG
+  void sqlite3MemdebugSetType(void*,u8);
+  int sqlite3MemdebugHasType(const void*,u8);
+  int sqlite3MemdebugNoType(const void*,u8);
+#else
+# define sqlite3MemdebugSetType(X,Y)  /* no-op */
+# define sqlite3MemdebugHasType(X,Y)  1
+# define sqlite3MemdebugNoType(X,Y)   1
+#endif
+#define MEMTYPE_HEAP       0x01  /* General heap allocations */
+#define MEMTYPE_LOOKASIDE  0x02  /* Heap that might have been lookaside */
+#define MEMTYPE_PCACHE     0x04  /* Page cache allocations */
+
+/*
+** Threading interface
+*/
+#if SQLITE_MAX_WORKER_THREADS>0
+int sqlite3ThreadCreate(SQLiteThread**,void*(*)(void*),void*);
+int sqlite3ThreadJoin(SQLiteThread*, void**);
+#endif
+
+#if defined(SQLITE_ENABLE_DBPAGE_VTAB) || defined(SQLITE_TEST)
+int sqlite3DbpageRegister(sqlite3*);
+#endif
+#if defined(SQLITE_ENABLE_DBSTAT_VTAB) || defined(SQLITE_TEST)
+int sqlite3DbstatRegister(sqlite3*);
+#endif
+
+int sqlite3ExprVectorSize(const Expr *pExpr);
+int sqlite3ExprIsVector(const Expr *pExpr);
+Expr *sqlite3VectorFieldSubexpr(Expr*, int);
+Expr *sqlite3ExprForVectorField(Parse*,Expr*,int,int);
+void sqlite3VectorErrorMsg(Parse*, Expr*);
+
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+const char **sqlite3CompileOptions(int *pnOpt);
+#endif
+
+#if SQLITE_OS_UNIX && defined(SQLITE_OS_KV_OPTIONAL)
+int sqlite3KvvfsInit(void);
+#endif
+
+#if defined(VDBE_PROFILE) \
+ || defined(SQLITE_PERFORMANCE_TRACE) \
+ || defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+sqlite3_uint64 sqlite3Hwtime(void);
+#endif
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+# define IS_STMT_SCANSTATUS(db) (db->flags & SQLITE_StmtScanStatus)
+#else
+# define IS_STMT_SCANSTATUS(db) 0
+#endif
+
+#endif /* SQLITEINT_H */
diff --git a/src/sqliteLimit.h b/src/sqliteLimit.h
new file mode 100644
index 0000000..abf59e1
--- /dev/null
+++ b/src/sqliteLimit.h
@@ -0,0 +1,210 @@
+/*
+** 2007 May 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file defines various limits of what SQLite can process.
+*/
+
+/*
+** The maximum length of a TEXT or BLOB in bytes.   This also
+** limits the size of a row in a table or index.
+**
+** The hard limit is the ability of a 32-bit signed integer
+** to count the size: 2^31-1 or 2147483647.
+*/
+#ifndef SQLITE_MAX_LENGTH
+# define SQLITE_MAX_LENGTH 1000000000
+#endif
+
+/*
+** This is the maximum number of
+**
+**    * Columns in a table
+**    * Columns in an index
+**    * Columns in a view
+**    * Terms in the SET clause of an UPDATE statement
+**    * Terms in the result set of a SELECT statement
+**    * Terms in the GROUP BY or ORDER BY clauses of a SELECT statement.
+**    * Terms in the VALUES clause of an INSERT statement
+**
+** The hard upper limit here is 32676.  Most database people will
+** tell you that in a well-normalized database, you usually should
+** not have more than a dozen or so columns in any table.  And if
+** that is the case, there is no point in having more than a few
+** dozen values in any of the other situations described above.
+*/
+#ifndef SQLITE_MAX_COLUMN
+# define SQLITE_MAX_COLUMN 2000
+#endif
+
+/*
+** The maximum length of a single SQL statement in bytes.
+**
+** It used to be the case that setting this value to zero would
+** turn the limit off.  That is no longer true.  It is not possible
+** to turn this limit off.
+*/
+#ifndef SQLITE_MAX_SQL_LENGTH
+# define SQLITE_MAX_SQL_LENGTH 1000000000
+#endif
+
+/*
+** The maximum depth of an expression tree. This is limited to
+** some extent by SQLITE_MAX_SQL_LENGTH. But sometime you might
+** want to place more severe limits on the complexity of an
+** expression. A value of 0 means that there is no limit.
+*/
+#ifndef SQLITE_MAX_EXPR_DEPTH
+# define SQLITE_MAX_EXPR_DEPTH 1000
+#endif
+
+/*
+** The maximum number of terms in a compound SELECT statement.
+** The code generator for compound SELECT statements does one
+** level of recursion for each term.  A stack overflow can result
+** if the number of terms is too large.  In practice, most SQL
+** never has more than 3 or 4 terms.  Use a value of 0 to disable
+** any limit on the number of terms in a compound SELECT.
+*/
+#ifndef SQLITE_MAX_COMPOUND_SELECT
+# define SQLITE_MAX_COMPOUND_SELECT 500
+#endif
+
+/*
+** The maximum number of opcodes in a VDBE program.
+** Not currently enforced.
+*/
+#ifndef SQLITE_MAX_VDBE_OP
+# define SQLITE_MAX_VDBE_OP 250000000
+#endif
+
+/*
+** The maximum number of arguments to an SQL function.
+*/
+#ifndef SQLITE_MAX_FUNCTION_ARG
+# define SQLITE_MAX_FUNCTION_ARG 127
+#endif
+
+/*
+** The suggested maximum number of in-memory pages to use for
+** the main database table and for temporary tables.
+**
+** IMPLEMENTATION-OF: R-30185-15359 The default suggested cache size is -2000,
+** which means the cache size is limited to 2048000 bytes of memory.
+** IMPLEMENTATION-OF: R-48205-43578 The default suggested cache size can be
+** altered using the SQLITE_DEFAULT_CACHE_SIZE compile-time options.
+*/
+#ifndef SQLITE_DEFAULT_CACHE_SIZE
+# define SQLITE_DEFAULT_CACHE_SIZE  -2000
+#endif
+
+/*
+** The default number of frames to accumulate in the log file before
+** checkpointing the database in WAL mode.
+*/
+#ifndef SQLITE_DEFAULT_WAL_AUTOCHECKPOINT
+# define SQLITE_DEFAULT_WAL_AUTOCHECKPOINT  1000
+#endif
+
+/*
+** The maximum number of attached databases.  This must be between 0
+** and 125.  The upper bound of 125 is because the attached databases are
+** counted using a signed 8-bit integer which has a maximum value of 127
+** and we have to allow 2 extra counts for the "main" and "temp" databases.
+*/
+#ifndef SQLITE_MAX_ATTACHED
+# define SQLITE_MAX_ATTACHED 10
+#endif
+
+
+/*
+** The maximum value of a ?nnn wildcard that the parser will accept.
+** If the value exceeds 32767 then extra space is required for the Expr
+** structure.  But otherwise, we believe that the number can be as large
+** as a signed 32-bit integer can hold.
+*/
+#ifndef SQLITE_MAX_VARIABLE_NUMBER
+# define SQLITE_MAX_VARIABLE_NUMBER 32766
+#endif
+
+/* Maximum page size.  The upper bound on this value is 65536.  This a limit
+** imposed by the use of 16-bit offsets within each page.
+**
+** Earlier versions of SQLite allowed the user to change this value at
+** compile time. This is no longer permitted, on the grounds that it creates
+** a library that is technically incompatible with an SQLite library
+** compiled with a different limit. If a process operating on a database
+** with a page-size of 65536 bytes crashes, then an instance of SQLite
+** compiled with the default page-size limit will not be able to rollback
+** the aborted transaction. This could lead to database corruption.
+*/
+#ifdef SQLITE_MAX_PAGE_SIZE
+# undef SQLITE_MAX_PAGE_SIZE
+#endif
+#define SQLITE_MAX_PAGE_SIZE 65536
+
+
+/*
+** The default size of a database page.
+*/
+#ifndef SQLITE_DEFAULT_PAGE_SIZE
+# define SQLITE_DEFAULT_PAGE_SIZE 4096
+#endif
+#if SQLITE_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
+# undef SQLITE_DEFAULT_PAGE_SIZE
+# define SQLITE_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
+#endif
+
+/*
+** Ordinarily, if no value is explicitly provided, SQLite creates databases
+** with page size SQLITE_DEFAULT_PAGE_SIZE. However, based on certain
+** device characteristics (sector-size and atomic write() support),
+** SQLite may choose a larger value. This constant is the maximum value
+** SQLite will choose on its own.
+*/
+#ifndef SQLITE_MAX_DEFAULT_PAGE_SIZE
+# define SQLITE_MAX_DEFAULT_PAGE_SIZE 8192
+#endif
+#if SQLITE_MAX_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
+# undef SQLITE_MAX_DEFAULT_PAGE_SIZE
+# define SQLITE_MAX_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
+#endif
+
+
+/*
+** Maximum number of pages in one database file.
+**
+** This is really just the default value for the max_page_count pragma.
+** This value can be lowered (or raised) at run-time using that the
+** max_page_count macro.
+*/
+#ifndef SQLITE_MAX_PAGE_COUNT
+# define SQLITE_MAX_PAGE_COUNT 0xfffffffe /* 4294967294 */
+#endif
+
+/*
+** Maximum length (in bytes) of the pattern in a LIKE or GLOB
+** operator.
+*/
+#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
+# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
+#endif
+
+/*
+** Maximum depth of recursion for triggers.
+**
+** A value of 1 means that a trigger program will not be able to itself
+** fire any triggers. A value of 0 means that no trigger programs at all
+** may be executed.
+*/
+#ifndef SQLITE_MAX_TRIGGER_DEPTH
+# define SQLITE_MAX_TRIGGER_DEPTH 1000
+#endif
diff --git a/src/status.c b/src/status.c
new file mode 100644
index 0000000..a462c94
--- /dev/null
+++ b/src/status.c
@@ -0,0 +1,398 @@
+/*
+** 2008 June 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This module implements the sqlite3_status() interface and related
+** functionality.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/*
+** Variables in which to record status information.
+*/
+#if SQLITE_PTRSIZE>4
+typedef sqlite3_int64 sqlite3StatValueType;
+#else
+typedef u32 sqlite3StatValueType;
+#endif
+typedef struct sqlite3StatType sqlite3StatType;
+static SQLITE_WSD struct sqlite3StatType {
+  sqlite3StatValueType nowValue[10];  /* Current value */
+  sqlite3StatValueType mxValue[10];   /* Maximum value */
+} sqlite3Stat = { {0,}, {0,} };
+
+/*
+** Elements of sqlite3Stat[] are protected by either the memory allocator
+** mutex, or by the pcache1 mutex.  The following array determines which.
+*/
+static const char statMutex[] = {
+  0,  /* SQLITE_STATUS_MEMORY_USED */
+  1,  /* SQLITE_STATUS_PAGECACHE_USED */
+  1,  /* SQLITE_STATUS_PAGECACHE_OVERFLOW */
+  0,  /* SQLITE_STATUS_SCRATCH_USED */
+  0,  /* SQLITE_STATUS_SCRATCH_OVERFLOW */
+  0,  /* SQLITE_STATUS_MALLOC_SIZE */
+  0,  /* SQLITE_STATUS_PARSER_STACK */
+  1,  /* SQLITE_STATUS_PAGECACHE_SIZE */
+  0,  /* SQLITE_STATUS_SCRATCH_SIZE */
+  0,  /* SQLITE_STATUS_MALLOC_COUNT */
+};
+
+
+/* The "wsdStat" macro will resolve to the status information
+** state vector.  If writable static data is unsupported on the target,
+** we have to locate the state vector at run-time.  In the more common
+** case where writable static data is supported, wsdStat can refer directly
+** to the "sqlite3Stat" state vector declared above.
+*/
+#ifdef SQLITE_OMIT_WSD
+# define wsdStatInit  sqlite3StatType *x = &GLOBAL(sqlite3StatType,sqlite3Stat)
+# define wsdStat x[0]
+#else
+# define wsdStatInit
+# define wsdStat sqlite3Stat
+#endif
+
+/*
+** Return the current value of a status parameter.  The caller must
+** be holding the appropriate mutex.
+*/
+sqlite3_int64 sqlite3StatusValue(int op){
+  wsdStatInit;
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+  assert( op>=0 && op<ArraySize(statMutex) );
+  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
+                                           : sqlite3MallocMutex()) );
+  return wsdStat.nowValue[op];
+}
+
+/*
+** Add N to the value of a status record.  The caller must hold the
+** appropriate mutex.  (Locking is checked by assert()).
+**
+** The StatusUp() routine can accept positive or negative values for N.
+** The value of N is added to the current status value and the high-water
+** mark is adjusted if necessary.
+**
+** The StatusDown() routine lowers the current value by N.  The highwater
+** mark is unchanged.  N must be non-negative for StatusDown().
+*/
+void sqlite3StatusUp(int op, int N){
+  wsdStatInit;
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+  assert( op>=0 && op<ArraySize(statMutex) );
+  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
+                                           : sqlite3MallocMutex()) );
+  wsdStat.nowValue[op] += N;
+  if( wsdStat.nowValue[op]>wsdStat.mxValue[op] ){
+    wsdStat.mxValue[op] = wsdStat.nowValue[op];
+  }
+}
+void sqlite3StatusDown(int op, int N){
+  wsdStatInit;
+  assert( N>=0 );
+  assert( op>=0 && op<ArraySize(statMutex) );
+  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
+                                           : sqlite3MallocMutex()) );
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+  wsdStat.nowValue[op] -= N;
+}
+
+/*
+** Adjust the highwater mark if necessary.
+** The caller must hold the appropriate mutex.
+*/
+void sqlite3StatusHighwater(int op, int X){
+  sqlite3StatValueType newValue;
+  wsdStatInit;
+  assert( X>=0 );
+  newValue = (sqlite3StatValueType)X;
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+  assert( op>=0 && op<ArraySize(statMutex) );
+  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
+                                           : sqlite3MallocMutex()) );
+  assert( op==SQLITE_STATUS_MALLOC_SIZE
+          || op==SQLITE_STATUS_PAGECACHE_SIZE
+          || op==SQLITE_STATUS_PARSER_STACK );
+  if( newValue>wsdStat.mxValue[op] ){
+    wsdStat.mxValue[op] = newValue;
+  }
+}
+
+/*
+** Query status information.
+*/
+int sqlite3_status64(
+  int op,
+  sqlite3_int64 *pCurrent,
+  sqlite3_int64 *pHighwater,
+  int resetFlag
+){
+  sqlite3_mutex *pMutex;
+  wsdStatInit;
+  if( op<0 || op>=ArraySize(wsdStat.nowValue) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCurrent==0 || pHighwater==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  pMutex = statMutex[op] ? sqlite3Pcache1Mutex() : sqlite3MallocMutex();
+  sqlite3_mutex_enter(pMutex);
+  *pCurrent = wsdStat.nowValue[op];
+  *pHighwater = wsdStat.mxValue[op];
+  if( resetFlag ){
+    wsdStat.mxValue[op] = wsdStat.nowValue[op];
+  }
+  sqlite3_mutex_leave(pMutex);
+  (void)pMutex;  /* Prevent warning when SQLITE_THREADSAFE=0 */
+  return SQLITE_OK;
+}
+int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag){
+  sqlite3_int64 iCur = 0, iHwtr = 0;
+  int rc;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCurrent==0 || pHighwater==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  rc = sqlite3_status64(op, &iCur, &iHwtr, resetFlag);
+  if( rc==0 ){
+    *pCurrent = (int)iCur;
+    *pHighwater = (int)iHwtr;
+  }
+  return rc;
+}
+
+/*
+** Return the number of LookasideSlot elements on the linked list
+*/
+static u32 countLookasideSlots(LookasideSlot *p){
+  u32 cnt = 0;
+  while( p ){
+    p = p->pNext;
+    cnt++;
+  }
+  return cnt;
+}
+
+/*
+** Count the number of slots of lookaside memory that are outstanding
+*/
+int sqlite3LookasideUsed(sqlite3 *db, int *pHighwater){
+  u32 nInit = countLookasideSlots(db->lookaside.pInit);
+  u32 nFree = countLookasideSlots(db->lookaside.pFree);
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+  nInit += countLookasideSlots(db->lookaside.pSmallInit);
+  nFree += countLookasideSlots(db->lookaside.pSmallFree);
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+  if( pHighwater ) *pHighwater = db->lookaside.nSlot - nInit;
+  return db->lookaside.nSlot - (nInit+nFree);
+}
+
+/*
+** Query status information for a single database connection
+*/
+int sqlite3_db_status(
+  sqlite3 *db,          /* The database connection whose status is desired */
+  int op,               /* Status verb */
+  int *pCurrent,        /* Write current value here */
+  int *pHighwater,      /* Write high-water mark here */
+  int resetFlag         /* Reset high-water mark if true */
+){
+  int rc = SQLITE_OK;   /* Return code */
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || pCurrent==0|| pHighwater==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  switch( op ){
+    case SQLITE_DBSTATUS_LOOKASIDE_USED: {
+      *pCurrent = sqlite3LookasideUsed(db, pHighwater);
+      if( resetFlag ){
+        LookasideSlot *p = db->lookaside.pFree;
+        if( p ){
+          while( p->pNext ) p = p->pNext;
+          p->pNext = db->lookaside.pInit;
+          db->lookaside.pInit = db->lookaside.pFree;
+          db->lookaside.pFree = 0;
+        }
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+        p = db->lookaside.pSmallFree;
+        if( p ){
+          while( p->pNext ) p = p->pNext;
+          p->pNext = db->lookaside.pSmallInit;
+          db->lookaside.pSmallInit = db->lookaside.pSmallFree;
+          db->lookaside.pSmallFree = 0;
+        }
+#endif
+      }
+      break;
+    }
+
+    case SQLITE_DBSTATUS_LOOKASIDE_HIT:
+    case SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE:
+    case SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL: {
+      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_HIT );
+      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE );
+      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL );
+      assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)>=0 );
+      assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)<3 );
+      *pCurrent = 0;
+      *pHighwater = db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT];
+      if( resetFlag ){
+        db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT] = 0;
+      }
+      break;
+    }
+
+    /* 
+    ** Return an approximation for the amount of memory currently used
+    ** by all pagers associated with the given database connection.  The
+    ** highwater mark is meaningless and is returned as zero.
+    */
+    case SQLITE_DBSTATUS_CACHE_USED_SHARED:
+    case SQLITE_DBSTATUS_CACHE_USED: {
+      int totalUsed = 0;
+      int i;
+      sqlite3BtreeEnterAll(db);
+      for(i=0; i<db->nDb; i++){
+        Btree *pBt = db->aDb[i].pBt;
+        if( pBt ){
+          Pager *pPager = sqlite3BtreePager(pBt);
+          int nByte = sqlite3PagerMemUsed(pPager);
+          if( op==SQLITE_DBSTATUS_CACHE_USED_SHARED ){
+            nByte = nByte / sqlite3BtreeConnectionCount(pBt);
+          }
+          totalUsed += nByte;
+        }
+      }
+      sqlite3BtreeLeaveAll(db);
+      *pCurrent = totalUsed;
+      *pHighwater = 0;
+      break;
+    }
+
+    /*
+    ** *pCurrent gets an accurate estimate of the amount of memory used
+    ** to store the schema for all databases (main, temp, and any ATTACHed
+    ** databases.  *pHighwater is set to zero.
+    */
+    case SQLITE_DBSTATUS_SCHEMA_USED: {
+      int i;                      /* Used to iterate through schemas */
+      int nByte = 0;              /* Used to accumulate return value */
+
+      sqlite3BtreeEnterAll(db);
+      db->pnBytesFreed = &nByte;
+      assert( db->lookaside.pEnd==db->lookaside.pTrueEnd );
+      db->lookaside.pEnd = db->lookaside.pStart;
+      for(i=0; i<db->nDb; i++){
+        Schema *pSchema = db->aDb[i].pSchema;
+        if( ALWAYS(pSchema!=0) ){
+          HashElem *p;
+
+          nByte += sqlite3GlobalConfig.m.xRoundup(sizeof(HashElem)) * (
+              pSchema->tblHash.count 
+            + pSchema->trigHash.count
+            + pSchema->idxHash.count
+            + pSchema->fkeyHash.count
+          );
+          nByte += sqlite3_msize(pSchema->tblHash.ht);
+          nByte += sqlite3_msize(pSchema->trigHash.ht);
+          nByte += sqlite3_msize(pSchema->idxHash.ht);
+          nByte += sqlite3_msize(pSchema->fkeyHash.ht);
+
+          for(p=sqliteHashFirst(&pSchema->trigHash); p; p=sqliteHashNext(p)){
+            sqlite3DeleteTrigger(db, (Trigger*)sqliteHashData(p));
+          }
+          for(p=sqliteHashFirst(&pSchema->tblHash); p; p=sqliteHashNext(p)){
+            sqlite3DeleteTable(db, (Table *)sqliteHashData(p));
+          }
+        }
+      }
+      db->pnBytesFreed = 0;
+      db->lookaside.pEnd = db->lookaside.pTrueEnd;
+      sqlite3BtreeLeaveAll(db);
+
+      *pHighwater = 0;
+      *pCurrent = nByte;
+      break;
+    }
+
+    /*
+    ** *pCurrent gets an accurate estimate of the amount of memory used
+    ** to store all prepared statements.
+    ** *pHighwater is set to zero.
+    */
+    case SQLITE_DBSTATUS_STMT_USED: {
+      struct Vdbe *pVdbe;         /* Used to iterate through VMs */
+      int nByte = 0;              /* Used to accumulate return value */
+
+      db->pnBytesFreed = &nByte;
+      assert( db->lookaside.pEnd==db->lookaside.pTrueEnd );
+      db->lookaside.pEnd = db->lookaside.pStart;
+      for(pVdbe=db->pVdbe; pVdbe; pVdbe=pVdbe->pVNext){
+        sqlite3VdbeDelete(pVdbe);
+      }
+      db->lookaside.pEnd = db->lookaside.pTrueEnd;
+      db->pnBytesFreed = 0;
+
+      *pHighwater = 0;  /* IMP: R-64479-57858 */
+      *pCurrent = nByte;
+
+      break;
+    }
+
+    /*
+    ** Set *pCurrent to the total cache hits or misses encountered by all
+    ** pagers the database handle is connected to. *pHighwater is always set 
+    ** to zero.
+    */
+    case SQLITE_DBSTATUS_CACHE_SPILL:
+      op = SQLITE_DBSTATUS_CACHE_WRITE+1;
+      /* no break */ deliberate_fall_through
+    case SQLITE_DBSTATUS_CACHE_HIT:
+    case SQLITE_DBSTATUS_CACHE_MISS:
+    case SQLITE_DBSTATUS_CACHE_WRITE:{
+      int i;
+      u64 nRet = 0;
+      assert( SQLITE_DBSTATUS_CACHE_MISS==SQLITE_DBSTATUS_CACHE_HIT+1 );
+      assert( SQLITE_DBSTATUS_CACHE_WRITE==SQLITE_DBSTATUS_CACHE_HIT+2 );
+
+      for(i=0; i<db->nDb; i++){
+        if( db->aDb[i].pBt ){
+          Pager *pPager = sqlite3BtreePager(db->aDb[i].pBt);
+          sqlite3PagerCacheStat(pPager, op, resetFlag, &nRet);
+        }
+      }
+      *pHighwater = 0; /* IMP: R-42420-56072 */
+                       /* IMP: R-54100-20147 */
+                       /* IMP: R-29431-39229 */
+      *pCurrent = (int)nRet & 0x7fffffff;
+      break;
+    }
+
+    /* Set *pCurrent to non-zero if there are unresolved deferred foreign
+    ** key constraints.  Set *pCurrent to zero if all foreign key constraints
+    ** have been satisfied.  The *pHighwater is always set to zero.
+    */
+    case SQLITE_DBSTATUS_DEFERRED_FKS: {
+      *pHighwater = 0;  /* IMP: R-11967-56545 */
+      *pCurrent = db->nDeferredImmCons>0 || db->nDeferredCons>0;
+      break;
+    }
+
+    default: {
+      rc = SQLITE_ERROR;
+    }
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
diff --git a/src/table.c b/src/table.c
new file mode 100644
index 0000000..db60a82
--- /dev/null
+++ b/src/table.c
@@ -0,0 +1,198 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the sqlite3_get_table() and sqlite3_free_table()
+** interface routines.  These are just wrappers around the main
+** interface routine of sqlite3_exec().
+**
+** These routines are in a separate files so that they will not be linked
+** if they are not used.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_GET_TABLE
+
+/*
+** This structure is used to pass data from sqlite3_get_table() through
+** to the callback function is uses to build the result.
+*/
+typedef struct TabResult {
+  char **azResult;   /* Accumulated output */
+  char *zErrMsg;     /* Error message text, if an error occurs */
+  u32 nAlloc;        /* Slots allocated for azResult[] */
+  u32 nRow;          /* Number of rows in the result */
+  u32 nColumn;       /* Number of columns in the result */
+  u32 nData;         /* Slots used in azResult[].  (nRow+1)*nColumn */
+  int rc;            /* Return code from sqlite3_exec() */
+} TabResult;
+
+/*
+** This routine is called once for each row in the result table.  Its job
+** is to fill in the TabResult structure appropriately, allocating new
+** memory as necessary.
+*/
+static int sqlite3_get_table_cb(void *pArg, int nCol, char **argv, char **colv){
+  TabResult *p = (TabResult*)pArg;  /* Result accumulator */
+  int need;                         /* Slots needed in p->azResult[] */
+  int i;                            /* Loop counter */
+  char *z;                          /* A single column of result */
+
+  /* Make sure there is enough space in p->azResult to hold everything
+  ** we need to remember from this invocation of the callback.
+  */
+  if( p->nRow==0 && argv!=0 ){
+    need = nCol*2;
+  }else{
+    need = nCol;
+  }
+  if( p->nData + need > p->nAlloc ){
+    char **azNew;
+    p->nAlloc = p->nAlloc*2 + need;
+    azNew = sqlite3Realloc( p->azResult, sizeof(char*)*p->nAlloc );
+    if( azNew==0 ) goto malloc_failed;
+    p->azResult = azNew;
+  }
+
+  /* If this is the first row, then generate an extra row containing
+  ** the names of all columns.
+  */
+  if( p->nRow==0 ){
+    p->nColumn = nCol;
+    for(i=0; i<nCol; i++){
+      z = sqlite3_mprintf("%s", colv[i]);
+      if( z==0 ) goto malloc_failed;
+      p->azResult[p->nData++] = z;
+    }
+  }else if( (int)p->nColumn!=nCol ){
+    sqlite3_free(p->zErrMsg);
+    p->zErrMsg = sqlite3_mprintf(
+       "sqlite3_get_table() called with two or more incompatible queries"
+    );
+    p->rc = SQLITE_ERROR;
+    return 1;
+  }
+
+  /* Copy over the row data
+  */
+  if( argv!=0 ){
+    for(i=0; i<nCol; i++){
+      if( argv[i]==0 ){
+        z = 0;
+      }else{
+        int n = sqlite3Strlen30(argv[i])+1;
+        z = sqlite3_malloc64( n );
+        if( z==0 ) goto malloc_failed;
+        memcpy(z, argv[i], n);
+      }
+      p->azResult[p->nData++] = z;
+    }
+    p->nRow++;
+  }
+  return 0;
+
+malloc_failed:
+  p->rc = SQLITE_NOMEM_BKPT;
+  return 1;
+}
+
+/*
+** Query the database.  But instead of invoking a callback for each row,
+** malloc() for space to hold the result and return the entire results
+** at the conclusion of the call.
+**
+** The result that is written to ***pazResult is held in memory obtained
+** from malloc().  But the caller cannot free this memory directly.  
+** Instead, the entire table should be passed to sqlite3_free_table() when
+** the calling procedure is finished using it.
+*/
+int sqlite3_get_table(
+  sqlite3 *db,                /* The database on which the SQL executes */
+  const char *zSql,           /* The SQL to be executed */
+  char ***pazResult,          /* Write the result table here */
+  int *pnRow,                 /* Write the number of rows in the result here */
+  int *pnColumn,              /* Write the number of columns of result here */
+  char **pzErrMsg             /* Write error messages here */
+){
+  int rc;
+  TabResult res;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || pazResult==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  *pazResult = 0;
+  if( pnColumn ) *pnColumn = 0;
+  if( pnRow ) *pnRow = 0;
+  if( pzErrMsg ) *pzErrMsg = 0;
+  res.zErrMsg = 0;
+  res.nRow = 0;
+  res.nColumn = 0;
+  res.nData = 1;
+  res.nAlloc = 20;
+  res.rc = SQLITE_OK;
+  res.azResult = sqlite3_malloc64(sizeof(char*)*res.nAlloc );
+  if( res.azResult==0 ){
+     db->errCode = SQLITE_NOMEM;
+     return SQLITE_NOMEM_BKPT;
+  }
+  res.azResult[0] = 0;
+  rc = sqlite3_exec(db, zSql, sqlite3_get_table_cb, &res, pzErrMsg);
+  assert( sizeof(res.azResult[0])>= sizeof(res.nData) );
+  res.azResult[0] = SQLITE_INT_TO_PTR(res.nData);
+  if( (rc&0xff)==SQLITE_ABORT ){
+    sqlite3_free_table(&res.azResult[1]);
+    if( res.zErrMsg ){
+      if( pzErrMsg ){
+        sqlite3_free(*pzErrMsg);
+        *pzErrMsg = sqlite3_mprintf("%s",res.zErrMsg);
+      }
+      sqlite3_free(res.zErrMsg);
+    }
+    db->errCode = res.rc;  /* Assume 32-bit assignment is atomic */
+    return res.rc;
+  }
+  sqlite3_free(res.zErrMsg);
+  if( rc!=SQLITE_OK ){
+    sqlite3_free_table(&res.azResult[1]);
+    return rc;
+  }
+  if( res.nAlloc>res.nData ){
+    char **azNew;
+    azNew = sqlite3Realloc( res.azResult, sizeof(char*)*res.nData );
+    if( azNew==0 ){
+      sqlite3_free_table(&res.azResult[1]);
+      db->errCode = SQLITE_NOMEM;
+      return SQLITE_NOMEM_BKPT;
+    }
+    res.azResult = azNew;
+  }
+  *pazResult = &res.azResult[1];
+  if( pnColumn ) *pnColumn = res.nColumn;
+  if( pnRow ) *pnRow = res.nRow;
+  return rc;
+}
+
+/*
+** This routine frees the space the sqlite3_get_table() malloced.
+*/
+void sqlite3_free_table(
+  char **azResult            /* Result returned from sqlite3_get_table() */
+){
+  if( azResult ){
+    int i, n;
+    azResult--;
+    assert( azResult!=0 );
+    n = SQLITE_PTR_TO_INT(azResult[0]);
+    for(i=1; i<n; i++){ if( azResult[i] ) sqlite3_free(azResult[i]); }
+    sqlite3_free(azResult);
+  }
+}
+
+#endif /* SQLITE_OMIT_GET_TABLE */
diff --git a/src/tclsqlite.c b/src/tclsqlite.c
new file mode 100644
index 0000000..d91b2fa
--- /dev/null
+++ b/src/tclsqlite.c
@@ -0,0 +1,4075 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** A TCL Interface to SQLite.  Append this file to sqlite3.c and
+** compile the whole thing to build a TCL-enabled version of SQLite.
+**
+** Compile-time options:
+**
+**  -DTCLSH         Add a "main()" routine that works as a tclsh.
+**
+**  -DTCLSH_INIT_PROC=name
+**
+**                  Invoke name(interp) to initialize the Tcl interpreter.
+**                  If name(interp) returns a non-NULL string, then run
+**                  that string as a Tcl script to launch the application.
+**                  If name(interp) returns NULL, then run the regular
+**                  tclsh-emulator code.
+*/
+#ifdef TCLSH_INIT_PROC
+# define TCLSH 1
+#endif
+
+/*
+** If requested, include the SQLite compiler options file for MSVC.
+*/
+#if defined(INCLUDE_MSVC_H)
+# include "msvc.h"
+#endif
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+# include "sqlite_tcl.h"
+#else
+# include "tcl.h"
+# ifndef SQLITE_TCLAPI
+#  define SQLITE_TCLAPI
+# endif
+#endif
+#include <errno.h>
+
+/*
+** Some additional include files are needed if this file is not
+** appended to the amalgamation.
+*/
+#ifndef SQLITE_AMALGAMATION
+# include "sqlite3.h"
+# include <stdlib.h>
+# include <string.h>
+# include <assert.h>
+  typedef unsigned char u8;
+# ifndef SQLITE_PTRSIZE
+#   if defined(__SIZEOF_POINTER__)
+#     define SQLITE_PTRSIZE __SIZEOF_POINTER__
+#   elif defined(i386)     || defined(__i386__)   || defined(_M_IX86) ||    \
+         defined(_M_ARM)   || defined(__arm__)    || defined(__x86)   ||    \
+        (defined(__APPLE__) && defined(__POWERPC__)) ||                     \
+        (defined(__TOS_AIX__) && !defined(__64BIT__))
+#     define SQLITE_PTRSIZE 4
+#   else
+#     define SQLITE_PTRSIZE 8
+#   endif
+# endif /* SQLITE_PTRSIZE */
+# if defined(HAVE_STDINT_H)
+    typedef uintptr_t uptr;
+# elif SQLITE_PTRSIZE==4
+    typedef unsigned int uptr;
+# else
+    typedef sqlite3_uint64 uptr;
+# endif
+#endif
+#include <ctype.h>
+
+/* Used to get the current process ID */
+#if !defined(_WIN32)
+# include <signal.h>
+# include <unistd.h>
+# define GETPID getpid
+#elif !defined(_WIN32_WCE)
+# ifndef SQLITE_AMALGAMATION
+#  ifndef WIN32_LEAN_AND_MEAN
+#   define WIN32_LEAN_AND_MEAN
+#  endif
+#  include <windows.h>
+# endif
+# include <io.h>
+# define isatty(h) _isatty(h)
+# define GETPID (int)GetCurrentProcessId
+#endif
+
+/*
+ * Windows needs to know which symbols to export.  Unix does not.
+ * BUILD_sqlite should be undefined for Unix.
+ */
+#ifdef BUILD_sqlite
+#undef TCL_STORAGE_CLASS
+#define TCL_STORAGE_CLASS DLLEXPORT
+#endif /* BUILD_sqlite */
+
+#define NUM_PREPARED_STMTS 10
+#define MAX_PREPARED_STMTS 100
+
+/* Forward declaration */
+typedef struct SqliteDb SqliteDb;
+
+/*
+** New SQL functions can be created as TCL scripts.  Each such function
+** is described by an instance of the following structure.
+**
+** Variable eType may be set to SQLITE_INTEGER, SQLITE_FLOAT, SQLITE_TEXT,
+** SQLITE_BLOB or SQLITE_NULL. If it is SQLITE_NULL, then the implementation
+** attempts to determine the type of the result based on the Tcl object.
+** If it is SQLITE_TEXT or SQLITE_BLOB, then a text (sqlite3_result_text())
+** or blob (sqlite3_result_blob()) is returned. If it is SQLITE_INTEGER
+** or SQLITE_FLOAT, then an attempt is made to return an integer or float
+** value, falling back to float and then text if this is not possible.
+*/
+typedef struct SqlFunc SqlFunc;
+struct SqlFunc {
+  Tcl_Interp *interp;   /* The TCL interpret to execute the function */
+  Tcl_Obj *pScript;     /* The Tcl_Obj representation of the script */
+  SqliteDb *pDb;        /* Database connection that owns this function */
+  int useEvalObjv;      /* True if it is safe to use Tcl_EvalObjv */
+  int eType;            /* Type of value to return */
+  char *zName;          /* Name of this function */
+  SqlFunc *pNext;       /* Next function on the list of them all */
+};
+
+/*
+** New collation sequences function can be created as TCL scripts.  Each such
+** function is described by an instance of the following structure.
+*/
+typedef struct SqlCollate SqlCollate;
+struct SqlCollate {
+  Tcl_Interp *interp;   /* The TCL interpret to execute the function */
+  char *zScript;        /* The script to be run */
+  SqlCollate *pNext;    /* Next function on the list of them all */
+};
+
+/*
+** Prepared statements are cached for faster execution.  Each prepared
+** statement is described by an instance of the following structure.
+*/
+typedef struct SqlPreparedStmt SqlPreparedStmt;
+struct SqlPreparedStmt {
+  SqlPreparedStmt *pNext;  /* Next in linked list */
+  SqlPreparedStmt *pPrev;  /* Previous on the list */
+  sqlite3_stmt *pStmt;     /* The prepared statement */
+  int nSql;                /* chars in zSql[] */
+  const char *zSql;        /* Text of the SQL statement */
+  int nParm;               /* Size of apParm array */
+  Tcl_Obj **apParm;        /* Array of referenced object pointers */
+};
+
+typedef struct IncrblobChannel IncrblobChannel;
+
+/*
+** There is one instance of this structure for each SQLite database
+** that has been opened by the SQLite TCL interface.
+**
+** If this module is built with SQLITE_TEST defined (to create the SQLite
+** testfixture executable), then it may be configured to use either
+** sqlite3_prepare_v2() or sqlite3_prepare() to prepare SQL statements.
+** If SqliteDb.bLegacyPrepare is true, sqlite3_prepare() is used.
+*/
+struct SqliteDb {
+  sqlite3 *db;               /* The "real" database structure. MUST BE FIRST */
+  Tcl_Interp *interp;        /* The interpreter used for this database */
+  char *zBusy;               /* The busy callback routine */
+  char *zCommit;             /* The commit hook callback routine */
+  char *zTrace;              /* The trace callback routine */
+  char *zTraceV2;            /* The trace_v2 callback routine */
+  char *zProfile;            /* The profile callback routine */
+  char *zProgress;           /* The progress callback routine */
+  char *zBindFallback;       /* Callback to invoke on a binding miss */
+  char *zAuth;               /* The authorization callback routine */
+  int disableAuth;           /* Disable the authorizer if it exists */
+  char *zNull;               /* Text to substitute for an SQL NULL value */
+  SqlFunc *pFunc;            /* List of SQL functions */
+  Tcl_Obj *pUpdateHook;      /* Update hook script (if any) */
+  Tcl_Obj *pPreUpdateHook;   /* Pre-update hook script (if any) */
+  Tcl_Obj *pRollbackHook;    /* Rollback hook script (if any) */
+  Tcl_Obj *pWalHook;         /* WAL hook script (if any) */
+  Tcl_Obj *pUnlockNotify;    /* Unlock notify script (if any) */
+  SqlCollate *pCollate;      /* List of SQL collation functions */
+  int rc;                    /* Return code of most recent sqlite3_exec() */
+  Tcl_Obj *pCollateNeeded;   /* Collation needed script */
+  SqlPreparedStmt *stmtList; /* List of prepared statements*/
+  SqlPreparedStmt *stmtLast; /* Last statement in the list */
+  int maxStmt;               /* The next maximum number of stmtList */
+  int nStmt;                 /* Number of statements in stmtList */
+  IncrblobChannel *pIncrblob;/* Linked list of open incrblob channels */
+  int nStep, nSort, nIndex;  /* Statistics for most recent operation */
+  int nVMStep;               /* Another statistic for most recent operation */
+  int nTransaction;          /* Number of nested [transaction] methods */
+  int openFlags;             /* Flags used to open.  (SQLITE_OPEN_URI) */
+  int nRef;                  /* Delete object when this reaches 0 */
+#ifdef SQLITE_TEST
+  int bLegacyPrepare;        /* True to use sqlite3_prepare() */
+#endif
+};
+
+struct IncrblobChannel {
+  sqlite3_blob *pBlob;      /* sqlite3 blob handle */
+  SqliteDb *pDb;            /* Associated database connection */
+  int iSeek;                /* Current seek offset */
+  Tcl_Channel channel;      /* Channel identifier */
+  IncrblobChannel *pNext;   /* Linked list of all open incrblob channels */
+  IncrblobChannel *pPrev;   /* Linked list of all open incrblob channels */
+};
+
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+*/
+static int strlen30(const char *z){
+  const char *z2 = z;
+  while( *z2 ){ z2++; }
+  return 0x3fffffff & (int)(z2 - z);
+}
+
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Close all incrblob channels opened using database connection pDb.
+** This is called when shutting down the database connection.
+*/
+static void closeIncrblobChannels(SqliteDb *pDb){
+  IncrblobChannel *p;
+  IncrblobChannel *pNext;
+
+  for(p=pDb->pIncrblob; p; p=pNext){
+    pNext = p->pNext;
+
+    /* Note: Calling unregister here call Tcl_Close on the incrblob channel,
+    ** which deletes the IncrblobChannel structure at *p. So do not
+    ** call Tcl_Free() here.
+    */
+    Tcl_UnregisterChannel(pDb->interp, p->channel);
+  }
+}
+
+/*
+** Close an incremental blob channel.
+*/
+static int SQLITE_TCLAPI incrblobClose(
+  ClientData instanceData,
+  Tcl_Interp *interp
+){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+  int rc = sqlite3_blob_close(p->pBlob);
+  sqlite3 *db = p->pDb->db;
+
+  /* Remove the channel from the SqliteDb.pIncrblob list. */
+  if( p->pNext ){
+    p->pNext->pPrev = p->pPrev;
+  }
+  if( p->pPrev ){
+    p->pPrev->pNext = p->pNext;
+  }
+  if( p->pDb->pIncrblob==p ){
+    p->pDb->pIncrblob = p->pNext;
+  }
+
+  /* Free the IncrblobChannel structure */
+  Tcl_Free((char *)p);
+
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3_errmsg(db), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Read data from an incremental blob channel.
+*/
+static int SQLITE_TCLAPI incrblobInput(
+  ClientData instanceData,
+  char *buf,
+  int bufSize,
+  int *errorCodePtr
+){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+  int nRead = bufSize;         /* Number of bytes to read */
+  int nBlob;                   /* Total size of the blob */
+  int rc;                      /* sqlite error code */
+
+  nBlob = sqlite3_blob_bytes(p->pBlob);
+  if( (p->iSeek+nRead)>nBlob ){
+    nRead = nBlob-p->iSeek;
+  }
+  if( nRead<=0 ){
+    return 0;
+  }
+
+  rc = sqlite3_blob_read(p->pBlob, (void *)buf, nRead, p->iSeek);
+  if( rc!=SQLITE_OK ){
+    *errorCodePtr = rc;
+    return -1;
+  }
+
+  p->iSeek += nRead;
+  return nRead;
+}
+
+/*
+** Write data to an incremental blob channel.
+*/
+static int SQLITE_TCLAPI incrblobOutput(
+  ClientData instanceData,
+  CONST char *buf,
+  int toWrite,
+  int *errorCodePtr
+){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+  int nWrite = toWrite;        /* Number of bytes to write */
+  int nBlob;                   /* Total size of the blob */
+  int rc;                      /* sqlite error code */
+
+  nBlob = sqlite3_blob_bytes(p->pBlob);
+  if( (p->iSeek+nWrite)>nBlob ){
+    *errorCodePtr = EINVAL;
+    return -1;
+  }
+  if( nWrite<=0 ){
+    return 0;
+  }
+
+  rc = sqlite3_blob_write(p->pBlob, (void *)buf, nWrite, p->iSeek);
+  if( rc!=SQLITE_OK ){
+    *errorCodePtr = EIO;
+    return -1;
+  }
+
+  p->iSeek += nWrite;
+  return nWrite;
+}
+
+/*
+** Seek an incremental blob channel.
+*/
+static int SQLITE_TCLAPI incrblobSeek(
+  ClientData instanceData,
+  long offset,
+  int seekMode,
+  int *errorCodePtr
+){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+
+  switch( seekMode ){
+    case SEEK_SET:
+      p->iSeek = offset;
+      break;
+    case SEEK_CUR:
+      p->iSeek += offset;
+      break;
+    case SEEK_END:
+      p->iSeek = sqlite3_blob_bytes(p->pBlob) + offset;
+      break;
+
+    default: assert(!"Bad seekMode");
+  }
+
+  return p->iSeek;
+}
+
+
+static void SQLITE_TCLAPI incrblobWatch(
+  ClientData instanceData,
+  int mode
+){
+  /* NO-OP */
+}
+static int SQLITE_TCLAPI incrblobHandle(
+  ClientData instanceData,
+  int dir,
+  ClientData *hPtr
+){
+  return TCL_ERROR;
+}
+
+static Tcl_ChannelType IncrblobChannelType = {
+  "incrblob",                        /* typeName                             */
+  TCL_CHANNEL_VERSION_2,             /* version                              */
+  incrblobClose,                     /* closeProc                            */
+  incrblobInput,                     /* inputProc                            */
+  incrblobOutput,                    /* outputProc                           */
+  incrblobSeek,                      /* seekProc                             */
+  0,                                 /* setOptionProc                        */
+  0,                                 /* getOptionProc                        */
+  incrblobWatch,                     /* watchProc (this is a no-op)          */
+  incrblobHandle,                    /* getHandleProc (always returns error) */
+  0,                                 /* close2Proc                           */
+  0,                                 /* blockModeProc                        */
+  0,                                 /* flushProc                            */
+  0,                                 /* handlerProc                          */
+  0,                                 /* wideSeekProc                         */
+};
+
+/*
+** Create a new incrblob channel.
+*/
+static int createIncrblobChannel(
+  Tcl_Interp *interp,
+  SqliteDb *pDb,
+  const char *zDb,
+  const char *zTable,
+  const char *zColumn,
+  sqlite_int64 iRow,
+  int isReadonly
+){
+  IncrblobChannel *p;
+  sqlite3 *db = pDb->db;
+  sqlite3_blob *pBlob;
+  int rc;
+  int flags = TCL_READABLE|(isReadonly ? 0 : TCL_WRITABLE);
+
+  /* This variable is used to name the channels: "incrblob_[incr count]" */
+  static int count = 0;
+  char zChannel[64];
+
+  rc = sqlite3_blob_open(db, zDb, zTable, zColumn, iRow, !isReadonly, &pBlob);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3_errmsg(pDb->db), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+
+  p = (IncrblobChannel *)Tcl_Alloc(sizeof(IncrblobChannel));
+  p->iSeek = 0;
+  p->pBlob = pBlob;
+
+  sqlite3_snprintf(sizeof(zChannel), zChannel, "incrblob_%d", ++count);
+  p->channel = Tcl_CreateChannel(&IncrblobChannelType, zChannel, p, flags);
+  Tcl_RegisterChannel(interp, p->channel);
+
+  /* Link the new channel into the SqliteDb.pIncrblob list. */
+  p->pNext = pDb->pIncrblob;
+  p->pPrev = 0;
+  if( p->pNext ){
+    p->pNext->pPrev = p;
+  }
+  pDb->pIncrblob = p;
+  p->pDb = pDb;
+
+  Tcl_SetResult(interp, (char *)Tcl_GetChannelName(p->channel), TCL_VOLATILE);
+  return TCL_OK;
+}
+#else  /* else clause for "#ifndef SQLITE_OMIT_INCRBLOB" */
+  #define closeIncrblobChannels(pDb)
+#endif
+
+/*
+** Look at the script prefix in pCmd.  We will be executing this script
+** after first appending one or more arguments.  This routine analyzes
+** the script to see if it is safe to use Tcl_EvalObjv() on the script
+** rather than the more general Tcl_EvalEx().  Tcl_EvalObjv() is much
+** faster.
+**
+** Scripts that are safe to use with Tcl_EvalObjv() consists of a
+** command name followed by zero or more arguments with no [...] or $
+** or {...} or ; to be seen anywhere.  Most callback scripts consist
+** of just a single procedure name and they meet this requirement.
+*/
+static int safeToUseEvalObjv(Tcl_Interp *interp, Tcl_Obj *pCmd){
+  /* We could try to do something with Tcl_Parse().  But we will instead
+  ** just do a search for forbidden characters.  If any of the forbidden
+  ** characters appear in pCmd, we will report the string as unsafe.
+  */
+  const char *z;
+  int n;
+  z = Tcl_GetStringFromObj(pCmd, &n);
+  while( n-- > 0 ){
+    int c = *(z++);
+    if( c=='$' || c=='[' || c==';' ) return 0;
+  }
+  return 1;
+}
+
+/*
+** Find an SqlFunc structure with the given name.  Or create a new
+** one if an existing one cannot be found.  Return a pointer to the
+** structure.
+*/
+static SqlFunc *findSqlFunc(SqliteDb *pDb, const char *zName){
+  SqlFunc *p, *pNew;
+  int nName = strlen30(zName);
+  pNew = (SqlFunc*)Tcl_Alloc( sizeof(*pNew) + nName + 1 );
+  pNew->zName = (char*)&pNew[1];
+  memcpy(pNew->zName, zName, nName+1);
+  for(p=pDb->pFunc; p; p=p->pNext){
+    if( sqlite3_stricmp(p->zName, pNew->zName)==0 ){
+      Tcl_Free((char*)pNew);
+      return p;
+    }
+  }
+  pNew->interp = pDb->interp;
+  pNew->pDb = pDb;
+  pNew->pScript = 0;
+  pNew->pNext = pDb->pFunc;
+  pDb->pFunc = pNew;
+  return pNew;
+}
+
+/*
+** Free a single SqlPreparedStmt object.
+*/
+static void dbFreeStmt(SqlPreparedStmt *pStmt){
+#ifdef SQLITE_TEST
+  if( sqlite3_sql(pStmt->pStmt)==0 ){
+    Tcl_Free((char *)pStmt->zSql);
+  }
+#endif
+  sqlite3_finalize(pStmt->pStmt);
+  Tcl_Free((char *)pStmt);
+}
+
+/*
+** Finalize and free a list of prepared statements
+*/
+static void flushStmtCache(SqliteDb *pDb){
+  SqlPreparedStmt *pPreStmt;
+  SqlPreparedStmt *pNext;
+
+  for(pPreStmt = pDb->stmtList; pPreStmt; pPreStmt=pNext){
+    pNext = pPreStmt->pNext;
+    dbFreeStmt(pPreStmt);
+  }
+  pDb->nStmt = 0;
+  pDb->stmtLast = 0;
+  pDb->stmtList = 0;
+}
+
+/*
+** Increment the reference counter on the SqliteDb object. The reference
+** should be released by calling delDatabaseRef().
+*/
+static void addDatabaseRef(SqliteDb *pDb){
+  pDb->nRef++;
+}
+
+/*
+** Decrement the reference counter associated with the SqliteDb object.
+** If it reaches zero, delete the object.
+*/
+static void delDatabaseRef(SqliteDb *pDb){
+  assert( pDb->nRef>0 );
+  pDb->nRef--;
+  if( pDb->nRef==0 ){
+    flushStmtCache(pDb);
+    closeIncrblobChannels(pDb);
+    sqlite3_close(pDb->db);
+    while( pDb->pFunc ){
+      SqlFunc *pFunc = pDb->pFunc;
+      pDb->pFunc = pFunc->pNext;
+      assert( pFunc->pDb==pDb );
+      Tcl_DecrRefCount(pFunc->pScript);
+      Tcl_Free((char*)pFunc);
+    }
+    while( pDb->pCollate ){
+      SqlCollate *pCollate = pDb->pCollate;
+      pDb->pCollate = pCollate->pNext;
+      Tcl_Free((char*)pCollate);
+    }
+    if( pDb->zBusy ){
+      Tcl_Free(pDb->zBusy);
+    }
+    if( pDb->zTrace ){
+      Tcl_Free(pDb->zTrace);
+    }
+    if( pDb->zTraceV2 ){
+      Tcl_Free(pDb->zTraceV2);
+    }
+    if( pDb->zProfile ){
+      Tcl_Free(pDb->zProfile);
+    }
+    if( pDb->zBindFallback ){
+      Tcl_Free(pDb->zBindFallback);
+    }
+    if( pDb->zAuth ){
+      Tcl_Free(pDb->zAuth);
+    }
+    if( pDb->zNull ){
+      Tcl_Free(pDb->zNull);
+    }
+    if( pDb->pUpdateHook ){
+      Tcl_DecrRefCount(pDb->pUpdateHook);
+    }
+    if( pDb->pPreUpdateHook ){
+      Tcl_DecrRefCount(pDb->pPreUpdateHook);
+    }
+    if( pDb->pRollbackHook ){
+      Tcl_DecrRefCount(pDb->pRollbackHook);
+    }
+    if( pDb->pWalHook ){
+      Tcl_DecrRefCount(pDb->pWalHook);
+    }
+    if( pDb->pCollateNeeded ){
+      Tcl_DecrRefCount(pDb->pCollateNeeded);
+    }
+    Tcl_Free((char*)pDb);
+  }
+}
+
+/*
+** TCL calls this procedure when an sqlite3 database command is
+** deleted.
+*/
+static void SQLITE_TCLAPI DbDeleteCmd(void *db){
+  SqliteDb *pDb = (SqliteDb*)db;
+  delDatabaseRef(pDb);
+}
+
+/*
+** This routine is called when a database file is locked while trying
+** to execute SQL.
+*/
+static int DbBusyHandler(void *cd, int nTries){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int rc;
+  char zVal[30];
+
+  sqlite3_snprintf(sizeof(zVal), zVal, "%d", nTries);
+  rc = Tcl_VarEval(pDb->interp, pDb->zBusy, " ", zVal, (char*)0);
+  if( rc!=TCL_OK || atoi(Tcl_GetStringResult(pDb->interp)) ){
+    return 0;
+  }
+  return 1;
+}
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+/*
+** This routine is invoked as the 'progress callback' for the database.
+*/
+static int DbProgressHandler(void *cd){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int rc;
+
+  assert( pDb->zProgress );
+  rc = Tcl_Eval(pDb->interp, pDb->zProgress);
+  if( rc!=TCL_OK || atoi(Tcl_GetStringResult(pDb->interp)) ){
+    return 1;
+  }
+  return 0;
+}
+#endif
+
+#if !defined(SQLITE_OMIT_TRACE) && !defined(SQLITE_OMIT_FLOATING_POINT) && \
+    !defined(SQLITE_OMIT_DEPRECATED)
+/*
+** This routine is called by the SQLite trace handler whenever a new
+** block of SQL is executed.  The TCL script in pDb->zTrace is executed.
+*/
+static void DbTraceHandler(void *cd, const char *zSql){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  Tcl_DString str;
+
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppend(&str, pDb->zTrace, -1);
+  Tcl_DStringAppendElement(&str, zSql);
+  Tcl_Eval(pDb->interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  Tcl_ResetResult(pDb->interp);
+}
+#endif
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** This routine is called by the SQLite trace_v2 handler whenever a new
+** supported event is generated.  Unsupported event types are ignored.
+** The TCL script in pDb->zTraceV2 is executed, with the arguments for
+** the event appended to it (as list elements).
+*/
+static int DbTraceV2Handler(
+  unsigned type, /* One of the SQLITE_TRACE_* event types. */
+  void *cd,      /* The original context data pointer. */
+  void *pd,      /* Primary event data, depends on event type. */
+  void *xd       /* Extra event data, depends on event type. */
+){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  Tcl_Obj *pCmd;
+
+  switch( type ){
+    case SQLITE_TRACE_STMT: {
+      sqlite3_stmt *pStmt = (sqlite3_stmt *)pd;
+      char *zSql = (char *)xd;
+
+      pCmd = Tcl_NewStringObj(pDb->zTraceV2, -1);
+      Tcl_IncrRefCount(pCmd);
+      Tcl_ListObjAppendElement(pDb->interp, pCmd,
+                               Tcl_NewWideIntObj((Tcl_WideInt)(uptr)pStmt));
+      Tcl_ListObjAppendElement(pDb->interp, pCmd,
+                               Tcl_NewStringObj(zSql, -1));
+      Tcl_EvalObjEx(pDb->interp, pCmd, TCL_EVAL_DIRECT);
+      Tcl_DecrRefCount(pCmd);
+      Tcl_ResetResult(pDb->interp);
+      break;
+    }
+    case SQLITE_TRACE_PROFILE: {
+      sqlite3_stmt *pStmt = (sqlite3_stmt *)pd;
+      sqlite3_int64 ns = *(sqlite3_int64*)xd;
+
+      pCmd = Tcl_NewStringObj(pDb->zTraceV2, -1);
+      Tcl_IncrRefCount(pCmd);
+      Tcl_ListObjAppendElement(pDb->interp, pCmd,
+                               Tcl_NewWideIntObj((Tcl_WideInt)(uptr)pStmt));
+      Tcl_ListObjAppendElement(pDb->interp, pCmd,
+                               Tcl_NewWideIntObj((Tcl_WideInt)ns));
+      Tcl_EvalObjEx(pDb->interp, pCmd, TCL_EVAL_DIRECT);
+      Tcl_DecrRefCount(pCmd);
+      Tcl_ResetResult(pDb->interp);
+      break;
+    }
+    case SQLITE_TRACE_ROW: {
+      sqlite3_stmt *pStmt = (sqlite3_stmt *)pd;
+
+      pCmd = Tcl_NewStringObj(pDb->zTraceV2, -1);
+      Tcl_IncrRefCount(pCmd);
+      Tcl_ListObjAppendElement(pDb->interp, pCmd,
+                               Tcl_NewWideIntObj((Tcl_WideInt)(uptr)pStmt));
+      Tcl_EvalObjEx(pDb->interp, pCmd, TCL_EVAL_DIRECT);
+      Tcl_DecrRefCount(pCmd);
+      Tcl_ResetResult(pDb->interp);
+      break;
+    }
+    case SQLITE_TRACE_CLOSE: {
+      sqlite3 *db = (sqlite3 *)pd;
+
+      pCmd = Tcl_NewStringObj(pDb->zTraceV2, -1);
+      Tcl_IncrRefCount(pCmd);
+      Tcl_ListObjAppendElement(pDb->interp, pCmd,
+                               Tcl_NewWideIntObj((Tcl_WideInt)(uptr)db));
+      Tcl_EvalObjEx(pDb->interp, pCmd, TCL_EVAL_DIRECT);
+      Tcl_DecrRefCount(pCmd);
+      Tcl_ResetResult(pDb->interp);
+      break;
+    }
+  }
+  return SQLITE_OK;
+}
+#endif
+
+#if !defined(SQLITE_OMIT_TRACE) && !defined(SQLITE_OMIT_FLOATING_POINT) && \
+    !defined(SQLITE_OMIT_DEPRECATED)
+/*
+** This routine is called by the SQLite profile handler after a statement
+** SQL has executed.  The TCL script in pDb->zProfile is evaluated.
+*/
+static void DbProfileHandler(void *cd, const char *zSql, sqlite_uint64 tm){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  Tcl_DString str;
+  char zTm[100];
+
+  sqlite3_snprintf(sizeof(zTm)-1, zTm, "%lld", tm);
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppend(&str, pDb->zProfile, -1);
+  Tcl_DStringAppendElement(&str, zSql);
+  Tcl_DStringAppendElement(&str, zTm);
+  Tcl_Eval(pDb->interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  Tcl_ResetResult(pDb->interp);
+}
+#endif
+
+/*
+** This routine is called when a transaction is committed.  The
+** TCL script in pDb->zCommit is executed.  If it returns non-zero or
+** if it throws an exception, the transaction is rolled back instead
+** of being committed.
+*/
+static int DbCommitHandler(void *cd){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int rc;
+
+  rc = Tcl_Eval(pDb->interp, pDb->zCommit);
+  if( rc!=TCL_OK || atoi(Tcl_GetStringResult(pDb->interp)) ){
+    return 1;
+  }
+  return 0;
+}
+
+static void DbRollbackHandler(void *clientData){
+  SqliteDb *pDb = (SqliteDb*)clientData;
+  assert(pDb->pRollbackHook);
+  if( TCL_OK!=Tcl_EvalObjEx(pDb->interp, pDb->pRollbackHook, 0) ){
+    Tcl_BackgroundError(pDb->interp);
+  }
+}
+
+/*
+** This procedure handles wal_hook callbacks.
+*/
+static int DbWalHandler(
+  void *clientData,
+  sqlite3 *db,
+  const char *zDb,
+  int nEntry
+){
+  int ret = SQLITE_OK;
+  Tcl_Obj *p;
+  SqliteDb *pDb = (SqliteDb*)clientData;
+  Tcl_Interp *interp = pDb->interp;
+  assert(pDb->pWalHook);
+
+  assert( db==pDb->db );
+  p = Tcl_DuplicateObj(pDb->pWalHook);
+  Tcl_IncrRefCount(p);
+  Tcl_ListObjAppendElement(interp, p, Tcl_NewStringObj(zDb, -1));
+  Tcl_ListObjAppendElement(interp, p, Tcl_NewIntObj(nEntry));
+  if( TCL_OK!=Tcl_EvalObjEx(interp, p, 0)
+   || TCL_OK!=Tcl_GetIntFromObj(interp, Tcl_GetObjResult(interp), &ret)
+  ){
+    Tcl_BackgroundError(interp);
+  }
+  Tcl_DecrRefCount(p);
+
+  return ret;
+}
+
+#if defined(SQLITE_TEST) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+static void setTestUnlockNotifyVars(Tcl_Interp *interp, int iArg, int nArg){
+  char zBuf[64];
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", iArg);
+  Tcl_SetVar(interp, "sqlite_unlock_notify_arg", zBuf, TCL_GLOBAL_ONLY);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", nArg);
+  Tcl_SetVar(interp, "sqlite_unlock_notify_argcount", zBuf, TCL_GLOBAL_ONLY);
+}
+#else
+# define setTestUnlockNotifyVars(x,y,z)
+#endif
+
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+static void DbUnlockNotify(void **apArg, int nArg){
+  int i;
+  for(i=0; i<nArg; i++){
+    const int flags = (TCL_EVAL_GLOBAL|TCL_EVAL_DIRECT);
+    SqliteDb *pDb = (SqliteDb *)apArg[i];
+    setTestUnlockNotifyVars(pDb->interp, i, nArg);
+    assert( pDb->pUnlockNotify);
+    Tcl_EvalObjEx(pDb->interp, pDb->pUnlockNotify, flags);
+    Tcl_DecrRefCount(pDb->pUnlockNotify);
+    pDb->pUnlockNotify = 0;
+  }
+}
+#endif
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** Pre-update hook callback.
+*/
+static void DbPreUpdateHandler(
+  void *p,
+  sqlite3 *db,
+  int op,
+  const char *zDb,
+  const char *zTbl,
+  sqlite_int64 iKey1,
+  sqlite_int64 iKey2
+){
+  SqliteDb *pDb = (SqliteDb *)p;
+  Tcl_Obj *pCmd;
+  static const char *azStr[] = {"DELETE", "INSERT", "UPDATE"};
+
+  assert( (SQLITE_DELETE-1)/9 == 0 );
+  assert( (SQLITE_INSERT-1)/9 == 1 );
+  assert( (SQLITE_UPDATE-1)/9 == 2 );
+  assert( pDb->pPreUpdateHook );
+  assert( db==pDb->db );
+  assert( op==SQLITE_INSERT || op==SQLITE_UPDATE || op==SQLITE_DELETE );
+
+  pCmd = Tcl_DuplicateObj(pDb->pPreUpdateHook);
+  Tcl_IncrRefCount(pCmd);
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(azStr[(op-1)/9], -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(zDb, -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(zTbl, -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewWideIntObj(iKey1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewWideIntObj(iKey2));
+  Tcl_EvalObjEx(pDb->interp, pCmd, TCL_EVAL_DIRECT);
+  Tcl_DecrRefCount(pCmd);
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+
+static void DbUpdateHandler(
+  void *p,
+  int op,
+  const char *zDb,
+  const char *zTbl,
+  sqlite_int64 rowid
+){
+  SqliteDb *pDb = (SqliteDb *)p;
+  Tcl_Obj *pCmd;
+  static const char *azStr[] = {"DELETE", "INSERT", "UPDATE"};
+
+  assert( (SQLITE_DELETE-1)/9 == 0 );
+  assert( (SQLITE_INSERT-1)/9 == 1 );
+  assert( (SQLITE_UPDATE-1)/9 == 2 );
+
+  assert( pDb->pUpdateHook );
+  assert( op==SQLITE_INSERT || op==SQLITE_UPDATE || op==SQLITE_DELETE );
+
+  pCmd = Tcl_DuplicateObj(pDb->pUpdateHook);
+  Tcl_IncrRefCount(pCmd);
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(azStr[(op-1)/9], -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(zDb, -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(zTbl, -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewWideIntObj(rowid));
+  Tcl_EvalObjEx(pDb->interp, pCmd, TCL_EVAL_DIRECT);
+  Tcl_DecrRefCount(pCmd);
+}
+
+static void tclCollateNeeded(
+  void *pCtx,
+  sqlite3 *db,
+  int enc,
+  const char *zName
+){
+  SqliteDb *pDb = (SqliteDb *)pCtx;
+  Tcl_Obj *pScript = Tcl_DuplicateObj(pDb->pCollateNeeded);
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj(zName, -1));
+  Tcl_EvalObjEx(pDb->interp, pScript, 0);
+  Tcl_DecrRefCount(pScript);
+}
+
+/*
+** This routine is called to evaluate an SQL collation function implemented
+** using TCL script.
+*/
+static int tclSqlCollate(
+  void *pCtx,
+  int nA,
+  const void *zA,
+  int nB,
+  const void *zB
+){
+  SqlCollate *p = (SqlCollate *)pCtx;
+  Tcl_Obj *pCmd;
+
+  pCmd = Tcl_NewStringObj(p->zScript, -1);
+  Tcl_IncrRefCount(pCmd);
+  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zA, nA));
+  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zB, nB));
+  Tcl_EvalObjEx(p->interp, pCmd, TCL_EVAL_DIRECT);
+  Tcl_DecrRefCount(pCmd);
+  return (atoi(Tcl_GetStringResult(p->interp)));
+}
+
+/*
+** This routine is called to evaluate an SQL function implemented
+** using TCL script.
+*/
+static void tclSqlFunc(sqlite3_context *context, int argc, sqlite3_value**argv){
+  SqlFunc *p = sqlite3_user_data(context);
+  Tcl_Obj *pCmd;
+  int i;
+  int rc;
+
+  if( argc==0 ){
+    /* If there are no arguments to the function, call Tcl_EvalObjEx on the
+    ** script object directly.  This allows the TCL compiler to generate
+    ** bytecode for the command on the first invocation and thus make
+    ** subsequent invocations much faster. */
+    pCmd = p->pScript;
+    Tcl_IncrRefCount(pCmd);
+    rc = Tcl_EvalObjEx(p->interp, pCmd, 0);
+    Tcl_DecrRefCount(pCmd);
+  }else{
+    /* If there are arguments to the function, make a shallow copy of the
+    ** script object, lappend the arguments, then evaluate the copy.
+    **
+    ** By "shallow" copy, we mean only the outer list Tcl_Obj is duplicated.
+    ** The new Tcl_Obj contains pointers to the original list elements.
+    ** That way, when Tcl_EvalObjv() is run and shimmers the first element
+    ** of the list to tclCmdNameType, that alternate representation will
+    ** be preserved and reused on the next invocation.
+    */
+    Tcl_Obj **aArg;
+    int nArg;
+    if( Tcl_ListObjGetElements(p->interp, p->pScript, &nArg, &aArg) ){
+      sqlite3_result_error(context, Tcl_GetStringResult(p->interp), -1);
+      return;
+    }
+    pCmd = Tcl_NewListObj(nArg, aArg);
+    Tcl_IncrRefCount(pCmd);
+    for(i=0; i<argc; i++){
+      sqlite3_value *pIn = argv[i];
+      Tcl_Obj *pVal;
+
+      /* Set pVal to contain the i'th column of this row. */
+      switch( sqlite3_value_type(pIn) ){
+        case SQLITE_BLOB: {
+          int bytes = sqlite3_value_bytes(pIn);
+          pVal = Tcl_NewByteArrayObj(sqlite3_value_blob(pIn), bytes);
+          break;
+        }
+        case SQLITE_INTEGER: {
+          sqlite_int64 v = sqlite3_value_int64(pIn);
+          if( v>=-2147483647 && v<=2147483647 ){
+            pVal = Tcl_NewIntObj((int)v);
+          }else{
+            pVal = Tcl_NewWideIntObj(v);
+          }
+          break;
+        }
+        case SQLITE_FLOAT: {
+          double r = sqlite3_value_double(pIn);
+          pVal = Tcl_NewDoubleObj(r);
+          break;
+        }
+        case SQLITE_NULL: {
+          pVal = Tcl_NewStringObj(p->pDb->zNull, -1);
+          break;
+        }
+        default: {
+          int bytes = sqlite3_value_bytes(pIn);
+          pVal = Tcl_NewStringObj((char *)sqlite3_value_text(pIn), bytes);
+          break;
+        }
+      }
+      rc = Tcl_ListObjAppendElement(p->interp, pCmd, pVal);
+      if( rc ){
+        Tcl_DecrRefCount(pCmd);
+        sqlite3_result_error(context, Tcl_GetStringResult(p->interp), -1);
+        return;
+      }
+    }
+    if( !p->useEvalObjv ){
+      /* Tcl_EvalObjEx() will automatically call Tcl_EvalObjv() if pCmd
+      ** is a list without a string representation.  To prevent this from
+      ** happening, make sure pCmd has a valid string representation */
+      Tcl_GetString(pCmd);
+    }
+    rc = Tcl_EvalObjEx(p->interp, pCmd, TCL_EVAL_DIRECT);
+    Tcl_DecrRefCount(pCmd);
+  }
+
+  if( rc && rc!=TCL_RETURN ){
+    sqlite3_result_error(context, Tcl_GetStringResult(p->interp), -1);
+  }else{
+    Tcl_Obj *pVar = Tcl_GetObjResult(p->interp);
+    int n;
+    u8 *data;
+    const char *zType = (pVar->typePtr ? pVar->typePtr->name : "");
+    char c = zType[0];
+    int eType = p->eType;
+
+    if( eType==SQLITE_NULL ){
+      if( c=='b' && strcmp(zType,"bytearray")==0 && pVar->bytes==0 ){
+        /* Only return a BLOB type if the Tcl variable is a bytearray and
+        ** has no string representation. */
+        eType = SQLITE_BLOB;
+      }else if( (c=='b' && strcmp(zType,"boolean")==0)
+             || (c=='w' && strcmp(zType,"wideInt")==0)
+             || (c=='i' && strcmp(zType,"int")==0) 
+      ){
+        eType = SQLITE_INTEGER;
+      }else if( c=='d' && strcmp(zType,"double")==0 ){
+        eType = SQLITE_FLOAT;
+      }else{
+        eType = SQLITE_TEXT;
+      }
+    }
+
+    switch( eType ){
+      case SQLITE_BLOB: {
+        data = Tcl_GetByteArrayFromObj(pVar, &n);
+        sqlite3_result_blob(context, data, n, SQLITE_TRANSIENT);
+        break;
+      }
+      case SQLITE_INTEGER: {
+        Tcl_WideInt v;
+        if( TCL_OK==Tcl_GetWideIntFromObj(0, pVar, &v) ){
+          sqlite3_result_int64(context, v);
+          break;
+        }
+        /* fall-through */
+      }
+      case SQLITE_FLOAT: {
+        double r;
+        if( TCL_OK==Tcl_GetDoubleFromObj(0, pVar, &r) ){
+          sqlite3_result_double(context, r);
+          break;
+        }
+        /* fall-through */
+      }
+      default: {
+        data = (unsigned char *)Tcl_GetStringFromObj(pVar, &n);
+        sqlite3_result_text(context, (char *)data, n, SQLITE_TRANSIENT);
+        break;
+      }
+    }
+
+  }
+}
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+/*
+** This is the authentication function.  It appends the authentication
+** type code and the two arguments to zCmd[] then invokes the result
+** on the interpreter.  The reply is examined to determine if the
+** authentication fails or succeeds.
+*/
+static int auth_callback(
+  void *pArg,
+  int code,
+  const char *zArg1,
+  const char *zArg2,
+  const char *zArg3,
+  const char *zArg4
+#ifdef SQLITE_USER_AUTHENTICATION
+  ,const char *zArg5
+#endif
+){
+  const char *zCode;
+  Tcl_DString str;
+  int rc;
+  const char *zReply;
+  /* EVIDENCE-OF: R-38590-62769 The first parameter to the authorizer
+  ** callback is a copy of the third parameter to the
+  ** sqlite3_set_authorizer() interface.
+  */
+  SqliteDb *pDb = (SqliteDb*)pArg;
+  if( pDb->disableAuth ) return SQLITE_OK;
+
+  /* EVIDENCE-OF: R-56518-44310 The second parameter to the callback is an
+  ** integer action code that specifies the particular action to be
+  ** authorized. */
+  switch( code ){
+    case SQLITE_COPY              : zCode="SQLITE_COPY"; break;
+    case SQLITE_CREATE_INDEX      : zCode="SQLITE_CREATE_INDEX"; break;
+    case SQLITE_CREATE_TABLE      : zCode="SQLITE_CREATE_TABLE"; break;
+    case SQLITE_CREATE_TEMP_INDEX : zCode="SQLITE_CREATE_TEMP_INDEX"; break;
+    case SQLITE_CREATE_TEMP_TABLE : zCode="SQLITE_CREATE_TEMP_TABLE"; break;
+    case SQLITE_CREATE_TEMP_TRIGGER: zCode="SQLITE_CREATE_TEMP_TRIGGER"; break;
+    case SQLITE_CREATE_TEMP_VIEW  : zCode="SQLITE_CREATE_TEMP_VIEW"; break;
+    case SQLITE_CREATE_TRIGGER    : zCode="SQLITE_CREATE_TRIGGER"; break;
+    case SQLITE_CREATE_VIEW       : zCode="SQLITE_CREATE_VIEW"; break;
+    case SQLITE_DELETE            : zCode="SQLITE_DELETE"; break;
+    case SQLITE_DROP_INDEX        : zCode="SQLITE_DROP_INDEX"; break;
+    case SQLITE_DROP_TABLE        : zCode="SQLITE_DROP_TABLE"; break;
+    case SQLITE_DROP_TEMP_INDEX   : zCode="SQLITE_DROP_TEMP_INDEX"; break;
+    case SQLITE_DROP_TEMP_TABLE   : zCode="SQLITE_DROP_TEMP_TABLE"; break;
+    case SQLITE_DROP_TEMP_TRIGGER : zCode="SQLITE_DROP_TEMP_TRIGGER"; break;
+    case SQLITE_DROP_TEMP_VIEW    : zCode="SQLITE_DROP_TEMP_VIEW"; break;
+    case SQLITE_DROP_TRIGGER      : zCode="SQLITE_DROP_TRIGGER"; break;
+    case SQLITE_DROP_VIEW         : zCode="SQLITE_DROP_VIEW"; break;
+    case SQLITE_INSERT            : zCode="SQLITE_INSERT"; break;
+    case SQLITE_PRAGMA            : zCode="SQLITE_PRAGMA"; break;
+    case SQLITE_READ              : zCode="SQLITE_READ"; break;
+    case SQLITE_SELECT            : zCode="SQLITE_SELECT"; break;
+    case SQLITE_TRANSACTION       : zCode="SQLITE_TRANSACTION"; break;
+    case SQLITE_UPDATE            : zCode="SQLITE_UPDATE"; break;
+    case SQLITE_ATTACH            : zCode="SQLITE_ATTACH"; break;
+    case SQLITE_DETACH            : zCode="SQLITE_DETACH"; break;
+    case SQLITE_ALTER_TABLE       : zCode="SQLITE_ALTER_TABLE"; break;
+    case SQLITE_REINDEX           : zCode="SQLITE_REINDEX"; break;
+    case SQLITE_ANALYZE           : zCode="SQLITE_ANALYZE"; break;
+    case SQLITE_CREATE_VTABLE     : zCode="SQLITE_CREATE_VTABLE"; break;
+    case SQLITE_DROP_VTABLE       : zCode="SQLITE_DROP_VTABLE"; break;
+    case SQLITE_FUNCTION          : zCode="SQLITE_FUNCTION"; break;
+    case SQLITE_SAVEPOINT         : zCode="SQLITE_SAVEPOINT"; break;
+    case SQLITE_RECURSIVE         : zCode="SQLITE_RECURSIVE"; break;
+    default                       : zCode="????"; break;
+  }
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppend(&str, pDb->zAuth, -1);
+  Tcl_DStringAppendElement(&str, zCode);
+  Tcl_DStringAppendElement(&str, zArg1 ? zArg1 : "");
+  Tcl_DStringAppendElement(&str, zArg2 ? zArg2 : "");
+  Tcl_DStringAppendElement(&str, zArg3 ? zArg3 : "");
+  Tcl_DStringAppendElement(&str, zArg4 ? zArg4 : "");
+#ifdef SQLITE_USER_AUTHENTICATION
+  Tcl_DStringAppendElement(&str, zArg5 ? zArg5 : "");
+#endif
+  rc = Tcl_GlobalEval(pDb->interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  zReply = rc==TCL_OK ? Tcl_GetStringResult(pDb->interp) : "SQLITE_DENY";
+  if( strcmp(zReply,"SQLITE_OK")==0 ){
+    rc = SQLITE_OK;
+  }else if( strcmp(zReply,"SQLITE_DENY")==0 ){
+    rc = SQLITE_DENY;
+  }else if( strcmp(zReply,"SQLITE_IGNORE")==0 ){
+    rc = SQLITE_IGNORE;
+  }else{
+    rc = 999;
+  }
+  return rc;
+}
+#endif /* SQLITE_OMIT_AUTHORIZATION */
+
+/*
+** This routine reads a line of text from FILE in, stores
+** the text in memory obtained from malloc() and returns a pointer
+** to the text.  NULL is returned at end of file, or if malloc()
+** fails.
+**
+** The interface is like "readline" but no command-line editing
+** is done.
+**
+** copied from shell.c from '.import' command
+*/
+static char *local_getline(char *zPrompt, FILE *in){
+  char *zLine;
+  int nLine;
+  int n;
+
+  nLine = 100;
+  zLine = malloc( nLine );
+  if( zLine==0 ) return 0;
+  n = 0;
+  while( 1 ){
+    if( n+100>nLine ){
+      nLine = nLine*2 + 100;
+      zLine = realloc(zLine, nLine);
+      if( zLine==0 ) return 0;
+    }
+    if( fgets(&zLine[n], nLine - n, in)==0 ){
+      if( n==0 ){
+        free(zLine);
+        return 0;
+      }
+      zLine[n] = 0;
+      break;
+    }
+    while( zLine[n] ){ n++; }
+    if( n>0 && zLine[n-1]=='\n' ){
+      n--;
+      zLine[n] = 0;
+      break;
+    }
+  }
+  zLine = realloc( zLine, n+1 );
+  return zLine;
+}
+
+
+/*
+** This function is part of the implementation of the command:
+**
+**   $db transaction [-deferred|-immediate|-exclusive] SCRIPT
+**
+** It is invoked after evaluating the script SCRIPT to commit or rollback
+** the transaction or savepoint opened by the [transaction] command.
+*/
+static int SQLITE_TCLAPI DbTransPostCmd(
+  ClientData data[],                   /* data[0] is the Sqlite3Db* for $db */
+  Tcl_Interp *interp,                  /* Tcl interpreter */
+  int result                           /* Result of evaluating SCRIPT */
+){
+  static const char *const azEnd[] = {
+    "RELEASE _tcl_transaction",        /* rc==TCL_ERROR, nTransaction!=0 */
+    "COMMIT",                          /* rc!=TCL_ERROR, nTransaction==0 */
+    "ROLLBACK TO _tcl_transaction ; RELEASE _tcl_transaction",
+    "ROLLBACK"                         /* rc==TCL_ERROR, nTransaction==0 */
+  };
+  SqliteDb *pDb = (SqliteDb*)data[0];
+  int rc = result;
+  const char *zEnd;
+
+  pDb->nTransaction--;
+  zEnd = azEnd[(rc==TCL_ERROR)*2 + (pDb->nTransaction==0)];
+
+  pDb->disableAuth++;
+  if( sqlite3_exec(pDb->db, zEnd, 0, 0, 0) ){
+      /* This is a tricky scenario to handle. The most likely cause of an
+      ** error is that the exec() above was an attempt to commit the
+      ** top-level transaction that returned SQLITE_BUSY. Or, less likely,
+      ** that an IO-error has occurred. In either case, throw a Tcl exception
+      ** and try to rollback the transaction.
+      **
+      ** But it could also be that the user executed one or more BEGIN,
+      ** COMMIT, SAVEPOINT, RELEASE or ROLLBACK commands that are confusing
+      ** this method's logic. Not clear how this would be best handled.
+      */
+    if( rc!=TCL_ERROR ){
+      Tcl_AppendResult(interp, sqlite3_errmsg(pDb->db), (char*)0);
+      rc = TCL_ERROR;
+    }
+    sqlite3_exec(pDb->db, "ROLLBACK", 0, 0, 0);
+  }
+  pDb->disableAuth--;
+
+  delDatabaseRef(pDb);
+  return rc;
+}
+
+/*
+** Unless SQLITE_TEST is defined, this function is a simple wrapper around
+** sqlite3_prepare_v2(). If SQLITE_TEST is defined, then it uses either
+** sqlite3_prepare_v2() or legacy interface sqlite3_prepare(), depending
+** on whether or not the [db_use_legacy_prepare] command has been used to
+** configure the connection.
+*/
+static int dbPrepare(
+  SqliteDb *pDb,                  /* Database object */
+  const char *zSql,               /* SQL to compile */
+  sqlite3_stmt **ppStmt,          /* OUT: Prepared statement */
+  const char **pzOut              /* OUT: Pointer to next SQL statement */
+){
+  unsigned int prepFlags = 0;
+#ifdef SQLITE_TEST
+  if( pDb->bLegacyPrepare ){
+    return sqlite3_prepare(pDb->db, zSql, -1, ppStmt, pzOut);
+  }
+#endif
+  /* If the statement cache is large, use the SQLITE_PREPARE_PERSISTENT
+  ** flags, which uses less lookaside memory.  But if the cache is small,
+  ** omit that flag to make full use of lookaside */
+  if( pDb->maxStmt>5 ) prepFlags = SQLITE_PREPARE_PERSISTENT;
+
+  return sqlite3_prepare_v3(pDb->db, zSql, -1, prepFlags, ppStmt, pzOut);
+}
+
+/*
+** Search the cache for a prepared-statement object that implements the
+** first SQL statement in the buffer pointed to by parameter zIn. If
+** no such prepared-statement can be found, allocate and prepare a new
+** one. In either case, bind the current values of the relevant Tcl
+** variables to any $var, :var or @var variables in the statement. Before
+** returning, set *ppPreStmt to point to the prepared-statement object.
+**
+** Output parameter *pzOut is set to point to the next SQL statement in
+** buffer zIn, or to the '\0' byte at the end of zIn if there is no
+** next statement.
+**
+** If successful, TCL_OK is returned. Otherwise, TCL_ERROR is returned
+** and an error message loaded into interpreter pDb->interp.
+*/
+static int dbPrepareAndBind(
+  SqliteDb *pDb,                  /* Database object */
+  char const *zIn,                /* SQL to compile */
+  char const **pzOut,             /* OUT: Pointer to next SQL statement */
+  SqlPreparedStmt **ppPreStmt     /* OUT: Object used to cache statement */
+){
+  const char *zSql = zIn;         /* Pointer to first SQL statement in zIn */
+  sqlite3_stmt *pStmt = 0;        /* Prepared statement object */
+  SqlPreparedStmt *pPreStmt;      /* Pointer to cached statement */
+  int nSql;                       /* Length of zSql in bytes */
+  int nVar = 0;                   /* Number of variables in statement */
+  int iParm = 0;                  /* Next free entry in apParm */
+  char c;
+  int i;
+  int needResultReset = 0;        /* Need to invoke Tcl_ResetResult() */
+  int rc = SQLITE_OK;             /* Value to return */
+  Tcl_Interp *interp = pDb->interp;
+
+  *ppPreStmt = 0;
+
+  /* Trim spaces from the start of zSql and calculate the remaining length. */
+  while( (c = zSql[0])==' ' || c=='\t' || c=='\r' || c=='\n' ){ zSql++; }
+  nSql = strlen30(zSql);
+
+  for(pPreStmt = pDb->stmtList; pPreStmt; pPreStmt=pPreStmt->pNext){
+    int n = pPreStmt->nSql;
+    if( nSql>=n
+        && memcmp(pPreStmt->zSql, zSql, n)==0
+        && (zSql[n]==0 || zSql[n-1]==';')
+    ){
+      pStmt = pPreStmt->pStmt;
+      *pzOut = &zSql[pPreStmt->nSql];
+
+      /* When a prepared statement is found, unlink it from the
+      ** cache list.  It will later be added back to the beginning
+      ** of the cache list in order to implement LRU replacement.
+      */
+      if( pPreStmt->pPrev ){
+        pPreStmt->pPrev->pNext = pPreStmt->pNext;
+      }else{
+        pDb->stmtList = pPreStmt->pNext;
+      }
+      if( pPreStmt->pNext ){
+        pPreStmt->pNext->pPrev = pPreStmt->pPrev;
+      }else{
+        pDb->stmtLast = pPreStmt->pPrev;
+      }
+      pDb->nStmt--;
+      nVar = sqlite3_bind_parameter_count(pStmt);
+      break;
+    }
+  }
+
+  /* If no prepared statement was found. Compile the SQL text. Also allocate
+  ** a new SqlPreparedStmt structure.  */
+  if( pPreStmt==0 ){
+    int nByte;
+
+    if( SQLITE_OK!=dbPrepare(pDb, zSql, &pStmt, pzOut) ){
+      Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3_errmsg(pDb->db), -1));
+      return TCL_ERROR;
+    }
+    if( pStmt==0 ){
+      if( SQLITE_OK!=sqlite3_errcode(pDb->db) ){
+        /* A compile-time error in the statement. */
+        Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3_errmsg(pDb->db), -1));
+        return TCL_ERROR;
+      }else{
+        /* The statement was a no-op.  Continue to the next statement
+        ** in the SQL string.
+        */
+        return TCL_OK;
+      }
+    }
+
+    assert( pPreStmt==0 );
+    nVar = sqlite3_bind_parameter_count(pStmt);
+    nByte = sizeof(SqlPreparedStmt) + nVar*sizeof(Tcl_Obj *);
+    pPreStmt = (SqlPreparedStmt*)Tcl_Alloc(nByte);
+    memset(pPreStmt, 0, nByte);
+
+    pPreStmt->pStmt = pStmt;
+    pPreStmt->nSql = (int)(*pzOut - zSql);
+    pPreStmt->zSql = sqlite3_sql(pStmt);
+    pPreStmt->apParm = (Tcl_Obj **)&pPreStmt[1];
+#ifdef SQLITE_TEST
+    if( pPreStmt->zSql==0 ){
+      char *zCopy = Tcl_Alloc(pPreStmt->nSql + 1);
+      memcpy(zCopy, zSql, pPreStmt->nSql);
+      zCopy[pPreStmt->nSql] = '\0';
+      pPreStmt->zSql = zCopy;
+    }
+#endif
+  }
+  assert( pPreStmt );
+  assert( strlen30(pPreStmt->zSql)==pPreStmt->nSql );
+  assert( 0==memcmp(pPreStmt->zSql, zSql, pPreStmt->nSql) );
+
+  /* Bind values to parameters that begin with $ or : */
+  for(i=1; i<=nVar; i++){
+    const char *zVar = sqlite3_bind_parameter_name(pStmt, i);
+    if( zVar!=0 && (zVar[0]=='$' || zVar[0]==':' || zVar[0]=='@') ){
+      Tcl_Obj *pVar = Tcl_GetVar2Ex(interp, &zVar[1], 0, 0);
+      if( pVar==0 && pDb->zBindFallback!=0 ){
+        Tcl_Obj *pCmd;
+        int rx;
+        pCmd = Tcl_NewStringObj(pDb->zBindFallback, -1);
+        Tcl_IncrRefCount(pCmd);
+        Tcl_ListObjAppendElement(interp, pCmd, Tcl_NewStringObj(zVar,-1));
+        if( needResultReset ) Tcl_ResetResult(interp);
+        needResultReset = 1;
+        rx = Tcl_EvalObjEx(interp, pCmd, TCL_EVAL_DIRECT);
+        Tcl_DecrRefCount(pCmd);
+        if( rx==TCL_OK ){
+          pVar = Tcl_GetObjResult(interp);
+        }else if( rx==TCL_ERROR ){
+          rc = TCL_ERROR;
+          break;
+        }else{
+          pVar = 0;
+        }
+      }
+      if( pVar ){
+        int n;
+        u8 *data;
+        const char *zType = (pVar->typePtr ? pVar->typePtr->name : "");
+        c = zType[0];
+        if( zVar[0]=='@' ||
+           (c=='b' && strcmp(zType,"bytearray")==0 && pVar->bytes==0) ){
+          /* Load a BLOB type if the Tcl variable is a bytearray and
+          ** it has no string representation or the host
+          ** parameter name begins with "@". */
+          data = Tcl_GetByteArrayFromObj(pVar, &n);
+          sqlite3_bind_blob(pStmt, i, data, n, SQLITE_STATIC);
+          Tcl_IncrRefCount(pVar);
+          pPreStmt->apParm[iParm++] = pVar;
+        }else if( c=='b' && strcmp(zType,"boolean")==0 ){
+          Tcl_GetIntFromObj(interp, pVar, &n);
+          sqlite3_bind_int(pStmt, i, n);
+        }else if( c=='d' && strcmp(zType,"double")==0 ){
+          double r;
+          Tcl_GetDoubleFromObj(interp, pVar, &r);
+          sqlite3_bind_double(pStmt, i, r);
+        }else if( (c=='w' && strcmp(zType,"wideInt")==0) ||
+              (c=='i' && strcmp(zType,"int")==0) ){
+          Tcl_WideInt v;
+          Tcl_GetWideIntFromObj(interp, pVar, &v);
+          sqlite3_bind_int64(pStmt, i, v);
+        }else{
+          data = (unsigned char *)Tcl_GetStringFromObj(pVar, &n);
+          sqlite3_bind_text(pStmt, i, (char *)data, n, SQLITE_STATIC);
+          Tcl_IncrRefCount(pVar);
+          pPreStmt->apParm[iParm++] = pVar;
+        }
+      }else{
+        sqlite3_bind_null(pStmt, i);
+      }
+      if( needResultReset ) Tcl_ResetResult(pDb->interp);
+    }
+  }
+  pPreStmt->nParm = iParm;
+  *ppPreStmt = pPreStmt;
+  if( needResultReset && rc==TCL_OK ) Tcl_ResetResult(pDb->interp);
+
+  return rc;
+}
+
+/*
+** Release a statement reference obtained by calling dbPrepareAndBind().
+** There should be exactly one call to this function for each call to
+** dbPrepareAndBind().
+**
+** If the discard parameter is non-zero, then the statement is deleted
+** immediately. Otherwise it is added to the LRU list and may be returned
+** by a subsequent call to dbPrepareAndBind().
+*/
+static void dbReleaseStmt(
+  SqliteDb *pDb,                  /* Database handle */
+  SqlPreparedStmt *pPreStmt,      /* Prepared statement handle to release */
+  int discard                     /* True to delete (not cache) the pPreStmt */
+){
+  int i;
+
+  /* Free the bound string and blob parameters */
+  for(i=0; i<pPreStmt->nParm; i++){
+    Tcl_DecrRefCount(pPreStmt->apParm[i]);
+  }
+  pPreStmt->nParm = 0;
+
+  if( pDb->maxStmt<=0 || discard ){
+    /* If the cache is turned off, deallocated the statement */
+    dbFreeStmt(pPreStmt);
+  }else{
+    /* Add the prepared statement to the beginning of the cache list. */
+    pPreStmt->pNext = pDb->stmtList;
+    pPreStmt->pPrev = 0;
+    if( pDb->stmtList ){
+     pDb->stmtList->pPrev = pPreStmt;
+    }
+    pDb->stmtList = pPreStmt;
+    if( pDb->stmtLast==0 ){
+      assert( pDb->nStmt==0 );
+      pDb->stmtLast = pPreStmt;
+    }else{
+      assert( pDb->nStmt>0 );
+    }
+    pDb->nStmt++;
+
+    /* If we have too many statement in cache, remove the surplus from
+    ** the end of the cache list.  */
+    while( pDb->nStmt>pDb->maxStmt ){
+      SqlPreparedStmt *pLast = pDb->stmtLast;
+      pDb->stmtLast = pLast->pPrev;
+      pDb->stmtLast->pNext = 0;
+      pDb->nStmt--;
+      dbFreeStmt(pLast);
+    }
+  }
+}
+
+/*
+** Structure used with dbEvalXXX() functions:
+**
+**   dbEvalInit()
+**   dbEvalStep()
+**   dbEvalFinalize()
+**   dbEvalRowInfo()
+**   dbEvalColumnValue()
+*/
+typedef struct DbEvalContext DbEvalContext;
+struct DbEvalContext {
+  SqliteDb *pDb;                  /* Database handle */
+  Tcl_Obj *pSql;                  /* Object holding string zSql */
+  const char *zSql;               /* Remaining SQL to execute */
+  SqlPreparedStmt *pPreStmt;      /* Current statement */
+  int nCol;                       /* Number of columns returned by pStmt */
+  int evalFlags;                  /* Flags used */
+  Tcl_Obj *pArray;                /* Name of array variable */
+  Tcl_Obj **apColName;            /* Array of column names */
+};
+
+#define SQLITE_EVAL_WITHOUTNULLS  0x00001  /* Unset array(*) for NULL */
+
+/*
+** Release any cache of column names currently held as part of
+** the DbEvalContext structure passed as the first argument.
+*/
+static void dbReleaseColumnNames(DbEvalContext *p){
+  if( p->apColName ){
+    int i;
+    for(i=0; i<p->nCol; i++){
+      Tcl_DecrRefCount(p->apColName[i]);
+    }
+    Tcl_Free((char *)p->apColName);
+    p->apColName = 0;
+  }
+  p->nCol = 0;
+}
+
+/*
+** Initialize a DbEvalContext structure.
+**
+** If pArray is not NULL, then it contains the name of a Tcl array
+** variable. The "*" member of this array is set to a list containing
+** the names of the columns returned by the statement as part of each
+** call to dbEvalStep(), in order from left to right. e.g. if the names
+** of the returned columns are a, b and c, it does the equivalent of the
+** tcl command:
+**
+**     set ${pArray}(*) {a b c}
+*/
+static void dbEvalInit(
+  DbEvalContext *p,               /* Pointer to structure to initialize */
+  SqliteDb *pDb,                  /* Database handle */
+  Tcl_Obj *pSql,                  /* Object containing SQL script */
+  Tcl_Obj *pArray,                /* Name of Tcl array to set (*) element of */
+  int evalFlags                   /* Flags controlling evaluation */
+){
+  memset(p, 0, sizeof(DbEvalContext));
+  p->pDb = pDb;
+  p->zSql = Tcl_GetString(pSql);
+  p->pSql = pSql;
+  Tcl_IncrRefCount(pSql);
+  if( pArray ){
+    p->pArray = pArray;
+    Tcl_IncrRefCount(pArray);
+  }
+  p->evalFlags = evalFlags;
+  addDatabaseRef(p->pDb);
+}
+
+/*
+** Obtain information about the row that the DbEvalContext passed as the
+** first argument currently points to.
+*/
+static void dbEvalRowInfo(
+  DbEvalContext *p,               /* Evaluation context */
+  int *pnCol,                     /* OUT: Number of column names */
+  Tcl_Obj ***papColName           /* OUT: Array of column names */
+){
+  /* Compute column names */
+  if( 0==p->apColName ){
+    sqlite3_stmt *pStmt = p->pPreStmt->pStmt;
+    int i;                        /* Iterator variable */
+    int nCol;                     /* Number of columns returned by pStmt */
+    Tcl_Obj **apColName = 0;      /* Array of column names */
+
+    p->nCol = nCol = sqlite3_column_count(pStmt);
+    if( nCol>0 && (papColName || p->pArray) ){
+      apColName = (Tcl_Obj**)Tcl_Alloc( sizeof(Tcl_Obj*)*nCol );
+      for(i=0; i<nCol; i++){
+        apColName[i] = Tcl_NewStringObj(sqlite3_column_name(pStmt,i), -1);
+        Tcl_IncrRefCount(apColName[i]);
+      }
+      p->apColName = apColName;
+    }
+
+    /* If results are being stored in an array variable, then create
+    ** the array(*) entry for that array
+    */
+    if( p->pArray ){
+      Tcl_Interp *interp = p->pDb->interp;
+      Tcl_Obj *pColList = Tcl_NewObj();
+      Tcl_Obj *pStar = Tcl_NewStringObj("*", -1);
+
+      for(i=0; i<nCol; i++){
+        Tcl_ListObjAppendElement(interp, pColList, apColName[i]);
+      }
+      Tcl_IncrRefCount(pStar);
+      Tcl_ObjSetVar2(interp, p->pArray, pStar, pColList, 0);
+      Tcl_DecrRefCount(pStar);
+    }
+  }
+
+  if( papColName ){
+    *papColName = p->apColName;
+  }
+  if( pnCol ){
+    *pnCol = p->nCol;
+  }
+}
+
+/*
+** Return one of TCL_OK, TCL_BREAK or TCL_ERROR. If TCL_ERROR is
+** returned, then an error message is stored in the interpreter before
+** returning.
+**
+** A return value of TCL_OK means there is a row of data available. The
+** data may be accessed using dbEvalRowInfo() and dbEvalColumnValue(). This
+** is analogous to a return of SQLITE_ROW from sqlite3_step(). If TCL_BREAK
+** is returned, then the SQL script has finished executing and there are
+** no further rows available. This is similar to SQLITE_DONE.
+*/
+static int dbEvalStep(DbEvalContext *p){
+  const char *zPrevSql = 0;       /* Previous value of p->zSql */
+
+  while( p->zSql[0] || p->pPreStmt ){
+    int rc;
+    if( p->pPreStmt==0 ){
+      zPrevSql = (p->zSql==zPrevSql ? 0 : p->zSql);
+      rc = dbPrepareAndBind(p->pDb, p->zSql, &p->zSql, &p->pPreStmt);
+      if( rc!=TCL_OK ) return rc;
+    }else{
+      int rcs;
+      SqliteDb *pDb = p->pDb;
+      SqlPreparedStmt *pPreStmt = p->pPreStmt;
+      sqlite3_stmt *pStmt = pPreStmt->pStmt;
+
+      rcs = sqlite3_step(pStmt);
+      if( rcs==SQLITE_ROW ){
+        return TCL_OK;
+      }
+      if( p->pArray ){
+        dbEvalRowInfo(p, 0, 0);
+      }
+      rcs = sqlite3_reset(pStmt);
+
+      pDb->nStep = sqlite3_stmt_status(pStmt,SQLITE_STMTSTATUS_FULLSCAN_STEP,1);
+      pDb->nSort = sqlite3_stmt_status(pStmt,SQLITE_STMTSTATUS_SORT,1);
+      pDb->nIndex = sqlite3_stmt_status(pStmt,SQLITE_STMTSTATUS_AUTOINDEX,1);
+      pDb->nVMStep = sqlite3_stmt_status(pStmt,SQLITE_STMTSTATUS_VM_STEP,1);
+      dbReleaseColumnNames(p);
+      p->pPreStmt = 0;
+
+      if( rcs!=SQLITE_OK ){
+        /* If a run-time error occurs, report the error and stop reading
+        ** the SQL.  */
+        dbReleaseStmt(pDb, pPreStmt, 1);
+#if SQLITE_TEST
+        if( p->pDb->bLegacyPrepare && rcs==SQLITE_SCHEMA && zPrevSql ){
+          /* If the runtime error was an SQLITE_SCHEMA, and the database
+          ** handle is configured to use the legacy sqlite3_prepare()
+          ** interface, retry prepare()/step() on the same SQL statement.
+          ** This only happens once. If there is a second SQLITE_SCHEMA
+          ** error, the error will be returned to the caller. */
+          p->zSql = zPrevSql;
+          continue;
+        }
+#endif
+        Tcl_SetObjResult(pDb->interp,
+                         Tcl_NewStringObj(sqlite3_errmsg(pDb->db), -1));
+        return TCL_ERROR;
+      }else{
+        dbReleaseStmt(pDb, pPreStmt, 0);
+      }
+    }
+  }
+
+  /* Finished */
+  return TCL_BREAK;
+}
+
+/*
+** Free all resources currently held by the DbEvalContext structure passed
+** as the first argument. There should be exactly one call to this function
+** for each call to dbEvalInit().
+*/
+static void dbEvalFinalize(DbEvalContext *p){
+  if( p->pPreStmt ){
+    sqlite3_reset(p->pPreStmt->pStmt);
+    dbReleaseStmt(p->pDb, p->pPreStmt, 0);
+    p->pPreStmt = 0;
+  }
+  if( p->pArray ){
+    Tcl_DecrRefCount(p->pArray);
+    p->pArray = 0;
+  }
+  Tcl_DecrRefCount(p->pSql);
+  dbReleaseColumnNames(p);
+  delDatabaseRef(p->pDb);
+}
+
+/*
+** Return a pointer to a Tcl_Obj structure with ref-count 0 that contains
+** the value for the iCol'th column of the row currently pointed to by
+** the DbEvalContext structure passed as the first argument.
+*/
+static Tcl_Obj *dbEvalColumnValue(DbEvalContext *p, int iCol){
+  sqlite3_stmt *pStmt = p->pPreStmt->pStmt;
+  switch( sqlite3_column_type(pStmt, iCol) ){
+    case SQLITE_BLOB: {
+      int bytes = sqlite3_column_bytes(pStmt, iCol);
+      const char *zBlob = sqlite3_column_blob(pStmt, iCol);
+      if( !zBlob ) bytes = 0;
+      return Tcl_NewByteArrayObj((u8*)zBlob, bytes);
+    }
+    case SQLITE_INTEGER: {
+      sqlite_int64 v = sqlite3_column_int64(pStmt, iCol);
+      if( v>=-2147483647 && v<=2147483647 ){
+        return Tcl_NewIntObj((int)v);
+      }else{
+        return Tcl_NewWideIntObj(v);
+      }
+    }
+    case SQLITE_FLOAT: {
+      return Tcl_NewDoubleObj(sqlite3_column_double(pStmt, iCol));
+    }
+    case SQLITE_NULL: {
+      return Tcl_NewStringObj(p->pDb->zNull, -1);
+    }
+  }
+
+  return Tcl_NewStringObj((char*)sqlite3_column_text(pStmt, iCol), -1);
+}
+
+/*
+** If using Tcl version 8.6 or greater, use the NR functions to avoid
+** recursive evaluation of scripts by the [db eval] and [db trans]
+** commands. Even if the headers used while compiling the extension
+** are 8.6 or newer, the code still tests the Tcl version at runtime.
+** This allows stubs-enabled builds to be used with older Tcl libraries.
+*/
+#if TCL_MAJOR_VERSION>8 || (TCL_MAJOR_VERSION==8 && TCL_MINOR_VERSION>=6)
+# define SQLITE_TCL_NRE 1
+static int DbUseNre(void){
+  int major, minor;
+  Tcl_GetVersion(&major, &minor, 0, 0);
+  return( (major==8 && minor>=6) || major>8 );
+}
+#else
+/*
+** Compiling using headers earlier than 8.6. In this case NR cannot be
+** used, so DbUseNre() to always return zero. Add #defines for the other
+** Tcl_NRxxx() functions to prevent them from causing compilation errors,
+** even though the only invocations of them are within conditional blocks
+** of the form:
+**
+**   if( DbUseNre() ) { ... }
+*/
+# define SQLITE_TCL_NRE 0
+# define DbUseNre() 0
+# define Tcl_NRAddCallback(a,b,c,d,e,f) (void)0
+# define Tcl_NREvalObj(a,b,c) 0
+# define Tcl_NRCreateCommand(a,b,c,d,e,f) (void)0
+#endif
+
+/*
+** This function is part of the implementation of the command:
+**
+**   $db eval SQL ?ARRAYNAME? SCRIPT
+*/
+static int SQLITE_TCLAPI DbEvalNextCmd(
+  ClientData data[],                   /* data[0] is the (DbEvalContext*) */
+  Tcl_Interp *interp,                  /* Tcl interpreter */
+  int result                           /* Result so far */
+){
+  int rc = result;                     /* Return code */
+
+  /* The first element of the data[] array is a pointer to a DbEvalContext
+  ** structure allocated using Tcl_Alloc(). The second element of data[]
+  ** is a pointer to a Tcl_Obj containing the script to run for each row
+  ** returned by the queries encapsulated in data[0]. */
+  DbEvalContext *p = (DbEvalContext *)data[0];
+  Tcl_Obj *pScript = (Tcl_Obj *)data[1];
+  Tcl_Obj *pArray = p->pArray;
+
+  while( (rc==TCL_OK || rc==TCL_CONTINUE) && TCL_OK==(rc = dbEvalStep(p)) ){
+    int i;
+    int nCol;
+    Tcl_Obj **apColName;
+    dbEvalRowInfo(p, &nCol, &apColName);
+    for(i=0; i<nCol; i++){
+      if( pArray==0 ){
+        Tcl_ObjSetVar2(interp, apColName[i], 0, dbEvalColumnValue(p,i), 0);
+      }else if( (p->evalFlags & SQLITE_EVAL_WITHOUTNULLS)!=0
+             && sqlite3_column_type(p->pPreStmt->pStmt, i)==SQLITE_NULL 
+      ){
+        Tcl_UnsetVar2(interp, Tcl_GetString(pArray), 
+                      Tcl_GetString(apColName[i]), 0);
+      }else{
+        Tcl_ObjSetVar2(interp, pArray, apColName[i], dbEvalColumnValue(p,i), 0);
+      }
+    }
+
+    /* The required interpreter variables are now populated with the data
+    ** from the current row. If using NRE, schedule callbacks to evaluate
+    ** script pScript, then to invoke this function again to fetch the next
+    ** row (or clean up if there is no next row or the script throws an
+    ** exception). After scheduling the callbacks, return control to the
+    ** caller.
+    **
+    ** If not using NRE, evaluate pScript directly and continue with the
+    ** next iteration of this while(...) loop.  */
+    if( DbUseNre() ){
+      Tcl_NRAddCallback(interp, DbEvalNextCmd, (void*)p, (void*)pScript, 0, 0);
+      return Tcl_NREvalObj(interp, pScript, 0);
+    }else{
+      rc = Tcl_EvalObjEx(interp, pScript, 0);
+    }
+  }
+
+  Tcl_DecrRefCount(pScript);
+  dbEvalFinalize(p);
+  Tcl_Free((char *)p);
+
+  if( rc==TCL_OK || rc==TCL_BREAK ){
+    Tcl_ResetResult(interp);
+    rc = TCL_OK;
+  }
+  return rc;
+}
+
+/*
+** This function is used by the implementations of the following database
+** handle sub-commands:
+**
+**   $db update_hook ?SCRIPT?
+**   $db wal_hook ?SCRIPT?
+**   $db commit_hook ?SCRIPT?
+**   $db preupdate hook ?SCRIPT?
+*/
+static void DbHookCmd(
+  Tcl_Interp *interp,             /* Tcl interpreter */
+  SqliteDb *pDb,                  /* Database handle */
+  Tcl_Obj *pArg,                  /* SCRIPT argument (or NULL) */
+  Tcl_Obj **ppHook                /* Pointer to member of SqliteDb */
+){
+  sqlite3 *db = pDb->db;
+
+  if( *ppHook ){
+    Tcl_SetObjResult(interp, *ppHook);
+    if( pArg ){
+      Tcl_DecrRefCount(*ppHook);
+      *ppHook = 0;
+    }
+  }
+  if( pArg ){
+    assert( !(*ppHook) );
+    if( Tcl_GetCharLength(pArg)>0 ){
+      *ppHook = pArg;
+      Tcl_IncrRefCount(*ppHook);
+    }
+  }
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  sqlite3_preupdate_hook(db, (pDb->pPreUpdateHook?DbPreUpdateHandler:0), pDb);
+#endif
+  sqlite3_update_hook(db, (pDb->pUpdateHook?DbUpdateHandler:0), pDb);
+  sqlite3_rollback_hook(db, (pDb->pRollbackHook?DbRollbackHandler:0), pDb);
+  sqlite3_wal_hook(db, (pDb->pWalHook?DbWalHandler:0), pDb);
+}
+
+/*
+** The "sqlite" command below creates a new Tcl command for each
+** connection it opens to an SQLite database.  This routine is invoked
+** whenever one of those connection-specific commands is executed
+** in Tcl.  For example, if you run Tcl code like this:
+**
+**       sqlite3 db1  "my_database"
+**       db1 close
+**
+** The first command opens a connection to the "my_database" database
+** and calls that connection "db1".  The second command causes this
+** subroutine to be invoked.
+*/
+static int SQLITE_TCLAPI DbObjCmd(
+  void *cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *const*objv
+){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int choice;
+  int rc = TCL_OK;
+  static const char *DB_strs[] = {
+    "authorizer",             "backup",                "bind_fallback",
+    "busy",                   "cache",                 "changes",
+    "close",                  "collate",               "collation_needed",
+    "commit_hook",            "complete",              "config",
+    "copy",                   "deserialize",           "enable_load_extension",
+    "errorcode",              "erroroffset",           "eval",
+    "exists",                 "function",              "incrblob",
+    "interrupt",              "last_insert_rowid",     "nullvalue",
+    "onecolumn",              "preupdate",             "profile",
+    "progress",               "rekey",                 "restore",
+    "rollback_hook",          "serialize",             "status",
+    "timeout",                "total_changes",         "trace",
+    "trace_v2",               "transaction",           "unlock_notify",
+    "update_hook",            "version",               "wal_hook",
+    0                        
+  };
+  enum DB_enum {
+    DB_AUTHORIZER,            DB_BACKUP,               DB_BIND_FALLBACK,
+    DB_BUSY,                  DB_CACHE,                DB_CHANGES,
+    DB_CLOSE,                 DB_COLLATE,              DB_COLLATION_NEEDED,
+    DB_COMMIT_HOOK,           DB_COMPLETE,             DB_CONFIG,
+    DB_COPY,                  DB_DESERIALIZE,          DB_ENABLE_LOAD_EXTENSION,
+    DB_ERRORCODE,             DB_ERROROFFSET,          DB_EVAL,
+    DB_EXISTS,                DB_FUNCTION,             DB_INCRBLOB,
+    DB_INTERRUPT,             DB_LAST_INSERT_ROWID,    DB_NULLVALUE,
+    DB_ONECOLUMN,             DB_PREUPDATE,            DB_PROFILE,
+    DB_PROGRESS,              DB_REKEY,                DB_RESTORE,
+    DB_ROLLBACK_HOOK,         DB_SERIALIZE,            DB_STATUS,
+    DB_TIMEOUT,               DB_TOTAL_CHANGES,        DB_TRACE,
+    DB_TRACE_V2,              DB_TRANSACTION,          DB_UNLOCK_NOTIFY,
+    DB_UPDATE_HOOK,           DB_VERSION,              DB_WAL_HOOK,
+  };
+  /* don't leave trailing commas on DB_enum, it confuses the AIX xlc compiler */
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], DB_strs, "option", 0, &choice) ){
+    return TCL_ERROR;
+  }
+
+  switch( (enum DB_enum)choice ){
+
+  /*    $db authorizer ?CALLBACK?
+  **
+  ** Invoke the given callback to authorize each SQL operation as it is
+  ** compiled.  5 arguments are appended to the callback before it is
+  ** invoked:
+  **
+  **   (1) The authorization type (ex: SQLITE_CREATE_TABLE, SQLITE_INSERT, ...)
+  **   (2) First descriptive name (depends on authorization type)
+  **   (3) Second descriptive name
+  **   (4) Name of the database (ex: "main", "temp")
+  **   (5) Name of trigger that is doing the access
+  **
+  ** The callback should return on of the following strings: SQLITE_OK,
+  ** SQLITE_IGNORE, or SQLITE_DENY.  Any other return value is an error.
+  **
+  ** If this method is invoked with no arguments, the current authorization
+  ** callback string is returned.
+  */
+  case DB_AUTHORIZER: {
+#ifdef SQLITE_OMIT_AUTHORIZATION
+    Tcl_AppendResult(interp, "authorization not available in this build",
+                     (char*)0);
+    return TCL_ERROR;
+#else
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zAuth ){
+        Tcl_AppendResult(interp, pDb->zAuth, (char*)0);
+      }
+    }else{
+      char *zAuth;
+      int len;
+      if( pDb->zAuth ){
+        Tcl_Free(pDb->zAuth);
+      }
+      zAuth = Tcl_GetStringFromObj(objv[2], &len);
+      if( zAuth && len>0 ){
+        pDb->zAuth = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zAuth, zAuth, len+1);
+      }else{
+        pDb->zAuth = 0;
+      }
+      if( pDb->zAuth ){
+        typedef int (*sqlite3_auth_cb)(
+           void*,int,const char*,const char*,
+           const char*,const char*);
+        pDb->interp = interp;
+        sqlite3_set_authorizer(pDb->db,(sqlite3_auth_cb)auth_callback,pDb);
+      }else{
+        sqlite3_set_authorizer(pDb->db, 0, 0);
+      }
+    }
+#endif
+    break;
+  }
+
+  /*    $db backup ?DATABASE? FILENAME
+  **
+  ** Open or create a database file named FILENAME.  Transfer the
+  ** content of local database DATABASE (default: "main") into the
+  ** FILENAME database.
+  */
+  case DB_BACKUP: {
+    const char *zDestFile;
+    const char *zSrcDb;
+    sqlite3 *pDest;
+    sqlite3_backup *pBackup;
+
+    if( objc==3 ){
+      zSrcDb = "main";
+      zDestFile = Tcl_GetString(objv[2]);
+    }else if( objc==4 ){
+      zSrcDb = Tcl_GetString(objv[2]);
+      zDestFile = Tcl_GetString(objv[3]);
+    }else{
+      Tcl_WrongNumArgs(interp, 2, objv, "?DATABASE? FILENAME");
+      return TCL_ERROR;
+    }
+    rc = sqlite3_open_v2(zDestFile, &pDest,
+               SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE| pDb->openFlags, 0);
+    if( rc!=SQLITE_OK ){
+      Tcl_AppendResult(interp, "cannot open target database: ",
+           sqlite3_errmsg(pDest), (char*)0);
+      sqlite3_close(pDest);
+      return TCL_ERROR;
+    }
+    pBackup = sqlite3_backup_init(pDest, "main", pDb->db, zSrcDb);
+    if( pBackup==0 ){
+      Tcl_AppendResult(interp, "backup failed: ",
+           sqlite3_errmsg(pDest), (char*)0);
+      sqlite3_close(pDest);
+      return TCL_ERROR;
+    }
+    while(  (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK ){}
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = TCL_OK;
+    }else{
+      Tcl_AppendResult(interp, "backup failed: ",
+           sqlite3_errmsg(pDest), (char*)0);
+      rc = TCL_ERROR;
+    }
+    sqlite3_close(pDest);
+    break;
+  }
+
+  /*    $db bind_fallback ?CALLBACK?
+  **
+  ** When resolving bind parameters in an SQL statement, if the parameter
+  ** cannot be associated with a TCL variable then invoke CALLBACK with a
+  ** single argument that is the name of the parameter and use the return
+  ** value of the CALLBACK as the binding.  If CALLBACK returns something
+  ** other than TCL_OK or TCL_ERROR then bind a NULL.
+  **
+  ** If CALLBACK is an empty string, then revert to the default behavior 
+  ** which is to set the binding to NULL.
+  **
+  ** If CALLBACK returns an error, that causes the statement execution to
+  ** abort.  Hence, to configure a connection so that it throws an error
+  ** on an attempt to bind an unknown variable, do something like this:
+  **
+  **     proc bind_error {name} {error "no such variable: $name"}
+  **     db bind_fallback bind_error
+  */
+  case DB_BIND_FALLBACK: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zBindFallback ){
+        Tcl_AppendResult(interp, pDb->zBindFallback, (char*)0);
+      }
+    }else{
+      char *zCallback;
+      int len;
+      if( pDb->zBindFallback ){
+        Tcl_Free(pDb->zBindFallback);
+      }
+      zCallback = Tcl_GetStringFromObj(objv[2], &len);
+      if( zCallback && len>0 ){
+        pDb->zBindFallback = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zBindFallback, zCallback, len+1);
+      }else{
+        pDb->zBindFallback = 0;
+      }
+    }
+    break;
+  }
+
+  /*    $db busy ?CALLBACK?
+  **
+  ** Invoke the given callback if an SQL statement attempts to open
+  ** a locked database file.
+  */
+  case DB_BUSY: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "CALLBACK");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zBusy ){
+        Tcl_AppendResult(interp, pDb->zBusy, (char*)0);
+      }
+    }else{
+      char *zBusy;
+      int len;
+      if( pDb->zBusy ){
+        Tcl_Free(pDb->zBusy);
+      }
+      zBusy = Tcl_GetStringFromObj(objv[2], &len);
+      if( zBusy && len>0 ){
+        pDb->zBusy = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zBusy, zBusy, len+1);
+      }else{
+        pDb->zBusy = 0;
+      }
+      if( pDb->zBusy ){
+        pDb->interp = interp;
+        sqlite3_busy_handler(pDb->db, DbBusyHandler, pDb);
+      }else{
+        sqlite3_busy_handler(pDb->db, 0, 0);
+      }
+    }
+    break;
+  }
+
+  /*     $db cache flush
+  **     $db cache size n
+  **
+  ** Flush the prepared statement cache, or set the maximum number of
+  ** cached statements.
+  */
+  case DB_CACHE: {
+    char *subCmd;
+    int n;
+
+    if( objc<=2 ){
+      Tcl_WrongNumArgs(interp, 1, objv, "cache option ?arg?");
+      return TCL_ERROR;
+    }
+    subCmd = Tcl_GetStringFromObj( objv[2], 0 );
+    if( *subCmd=='f' && strcmp(subCmd,"flush")==0 ){
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "flush");
+        return TCL_ERROR;
+      }else{
+        flushStmtCache( pDb );
+      }
+    }else if( *subCmd=='s' && strcmp(subCmd,"size")==0 ){
+      if( objc!=4 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "size n");
+        return TCL_ERROR;
+      }else{
+        if( TCL_ERROR==Tcl_GetIntFromObj(interp, objv[3], &n) ){
+          Tcl_AppendResult( interp, "cannot convert \"",
+               Tcl_GetStringFromObj(objv[3],0), "\" to integer", (char*)0);
+          return TCL_ERROR;
+        }else{
+          if( n<0 ){
+            flushStmtCache( pDb );
+            n = 0;
+          }else if( n>MAX_PREPARED_STMTS ){
+            n = MAX_PREPARED_STMTS;
+          }
+          pDb->maxStmt = n;
+        }
+      }
+    }else{
+      Tcl_AppendResult( interp, "bad option \"",
+          Tcl_GetStringFromObj(objv[2],0), "\": must be flush or size",
+          (char*)0);
+      return TCL_ERROR;
+    }
+    break;
+  }
+
+  /*     $db changes
+  **
+  ** Return the number of rows that were modified, inserted, or deleted by
+  ** the most recent INSERT, UPDATE or DELETE statement, not including
+  ** any changes made by trigger programs.
+  */
+  case DB_CHANGES: {
+    Tcl_Obj *pResult;
+    if( objc!=2 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "");
+      return TCL_ERROR;
+    }
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetWideIntObj(pResult, sqlite3_changes64(pDb->db));
+    break;
+  }
+
+  /*    $db close
+  **
+  ** Shutdown the database
+  */
+  case DB_CLOSE: {
+    Tcl_DeleteCommand(interp, Tcl_GetStringFromObj(objv[0], 0));
+    break;
+  }
+
+  /*
+  **     $db collate NAME SCRIPT
+  **
+  ** Create a new SQL collation function called NAME.  Whenever
+  ** that function is called, invoke SCRIPT to evaluate the function.
+  */
+  case DB_COLLATE: {
+    SqlCollate *pCollate;
+    char *zName;
+    char *zScript;
+    int nScript;
+    if( objc!=4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "NAME SCRIPT");
+      return TCL_ERROR;
+    }
+    zName = Tcl_GetStringFromObj(objv[2], 0);
+    zScript = Tcl_GetStringFromObj(objv[3], &nScript);
+    pCollate = (SqlCollate*)Tcl_Alloc( sizeof(*pCollate) + nScript + 1 );
+    if( pCollate==0 ) return TCL_ERROR;
+    pCollate->interp = interp;
+    pCollate->pNext = pDb->pCollate;
+    pCollate->zScript = (char*)&pCollate[1];
+    pDb->pCollate = pCollate;
+    memcpy(pCollate->zScript, zScript, nScript+1);
+    if( sqlite3_create_collation(pDb->db, zName, SQLITE_UTF8,
+        pCollate, tclSqlCollate) ){
+      Tcl_SetResult(interp, (char *)sqlite3_errmsg(pDb->db), TCL_VOLATILE);
+      return TCL_ERROR;
+    }
+    break;
+  }
+
+  /*
+  **     $db collation_needed SCRIPT
+  **
+  ** Create a new SQL collation function called NAME.  Whenever
+  ** that function is called, invoke SCRIPT to evaluate the function.
+  */
+  case DB_COLLATION_NEEDED: {
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SCRIPT");
+      return TCL_ERROR;
+    }
+    if( pDb->pCollateNeeded ){
+      Tcl_DecrRefCount(pDb->pCollateNeeded);
+    }
+    pDb->pCollateNeeded = Tcl_DuplicateObj(objv[2]);
+    Tcl_IncrRefCount(pDb->pCollateNeeded);
+    sqlite3_collation_needed(pDb->db, pDb, tclCollateNeeded);
+    break;
+  }
+
+  /*    $db commit_hook ?CALLBACK?
+  **
+  ** Invoke the given callback just before committing every SQL transaction.
+  ** If the callback throws an exception or returns non-zero, then the
+  ** transaction is aborted.  If CALLBACK is an empty string, the callback
+  ** is disabled.
+  */
+  case DB_COMMIT_HOOK: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zCommit ){
+        Tcl_AppendResult(interp, pDb->zCommit, (char*)0);
+      }
+    }else{
+      const char *zCommit;
+      int len;
+      if( pDb->zCommit ){
+        Tcl_Free(pDb->zCommit);
+      }
+      zCommit = Tcl_GetStringFromObj(objv[2], &len);
+      if( zCommit && len>0 ){
+        pDb->zCommit = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zCommit, zCommit, len+1);
+      }else{
+        pDb->zCommit = 0;
+      }
+      if( pDb->zCommit ){
+        pDb->interp = interp;
+        sqlite3_commit_hook(pDb->db, DbCommitHandler, pDb);
+      }else{
+        sqlite3_commit_hook(pDb->db, 0, 0);
+      }
+    }
+    break;
+  }
+
+  /*    $db complete SQL
+  **
+  ** Return TRUE if SQL is a complete SQL statement.  Return FALSE if
+  ** additional lines of input are needed.  This is similar to the
+  ** built-in "info complete" command of Tcl.
+  */
+  case DB_COMPLETE: {
+#ifndef SQLITE_OMIT_COMPLETE
+    Tcl_Obj *pResult;
+    int isComplete;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SQL");
+      return TCL_ERROR;
+    }
+    isComplete = sqlite3_complete( Tcl_GetStringFromObj(objv[2], 0) );
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetBooleanObj(pResult, isComplete);
+#endif
+    break;
+  }
+
+  /*    $db config ?OPTION? ?BOOLEAN?
+  **
+  ** Configure the database connection using the sqlite3_db_config()
+  ** interface.
+  */
+  case DB_CONFIG: {
+    static const struct DbConfigChoices {
+      const char *zName;
+      int op;
+    } aDbConfig[] = {
+        { "defensive",          SQLITE_DBCONFIG_DEFENSIVE             },
+        { "dqs_ddl",            SQLITE_DBCONFIG_DQS_DDL               },
+        { "dqs_dml",            SQLITE_DBCONFIG_DQS_DML               },
+        { "enable_fkey",        SQLITE_DBCONFIG_ENABLE_FKEY           },
+        { "enable_qpsg",        SQLITE_DBCONFIG_ENABLE_QPSG           },
+        { "enable_trigger",     SQLITE_DBCONFIG_ENABLE_TRIGGER        },
+        { "enable_view",        SQLITE_DBCONFIG_ENABLE_VIEW           },
+        { "fts3_tokenizer",     SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER },
+        { "legacy_alter_table", SQLITE_DBCONFIG_LEGACY_ALTER_TABLE    },
+        { "legacy_file_format", SQLITE_DBCONFIG_LEGACY_FILE_FORMAT    },
+        { "load_extension",     SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION },
+        { "no_ckpt_on_close",   SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE      },
+        { "reset_database",     SQLITE_DBCONFIG_RESET_DATABASE        },
+        { "trigger_eqp",        SQLITE_DBCONFIG_TRIGGER_EQP           },
+        { "trusted_schema",     SQLITE_DBCONFIG_TRUSTED_SCHEMA        },
+        { "writable_schema",    SQLITE_DBCONFIG_WRITABLE_SCHEMA       },
+    };
+    Tcl_Obj *pResult;
+    int ii;
+    if( objc>4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?OPTION? ?BOOLEAN?");
+      return TCL_ERROR;
+    }
+    if( objc==2 ){
+      /* With no arguments, list all configuration options and with the
+      ** current value */
+      pResult = Tcl_NewListObj(0,0);
+      for(ii=0; ii<sizeof(aDbConfig)/sizeof(aDbConfig[0]); ii++){
+        int v = 0;
+        sqlite3_db_config(pDb->db, aDbConfig[ii].op, -1, &v);
+        Tcl_ListObjAppendElement(interp, pResult,
+           Tcl_NewStringObj(aDbConfig[ii].zName,-1));
+        Tcl_ListObjAppendElement(interp, pResult,
+           Tcl_NewIntObj(v));
+      }
+    }else{
+      const char *zOpt = Tcl_GetString(objv[2]);
+      int onoff = -1;
+      int v = 0;
+      if( zOpt[0]=='-' ) zOpt++;
+      for(ii=0; ii<sizeof(aDbConfig)/sizeof(aDbConfig[0]); ii++){
+        if( strcmp(aDbConfig[ii].zName, zOpt)==0 ) break;
+      }
+      if( ii>=sizeof(aDbConfig)/sizeof(aDbConfig[0]) ){
+        Tcl_AppendResult(interp, "unknown config option: \"", zOpt,
+                                "\"", (void*)0);
+        return TCL_ERROR;
+      }
+      if( objc==4 ){
+        if( Tcl_GetBooleanFromObj(interp, objv[3], &onoff) ){
+          return TCL_ERROR;
+        }
+      }
+      sqlite3_db_config(pDb->db, aDbConfig[ii].op, onoff, &v);
+      pResult = Tcl_NewIntObj(v);
+    }
+    Tcl_SetObjResult(interp, pResult);
+    break;
+  }
+
+  /*    $db copy conflict-algorithm table filename ?SEPARATOR? ?NULLINDICATOR?
+  **
+  ** Copy data into table from filename, optionally using SEPARATOR
+  ** as column separators.  If a column contains a null string, or the
+  ** value of NULLINDICATOR, a NULL is inserted for the column.
+  ** conflict-algorithm is one of the sqlite conflict algorithms:
+  **    rollback, abort, fail, ignore, replace
+  ** On success, return the number of lines processed, not necessarily same
+  ** as 'db changes' due to conflict-algorithm selected.
+  **
+  ** This code is basically an implementation/enhancement of
+  ** the sqlite3 shell.c ".import" command.
+  **
+  ** This command usage is equivalent to the sqlite2.x COPY statement,
+  ** which imports file data into a table using the PostgreSQL COPY file format:
+  **   $db copy $conflict_algorithm $table_name $filename \t \\N
+  */
+  case DB_COPY: {
+    char *zTable;               /* Insert data into this table */
+    char *zFile;                /* The file from which to extract data */
+    char *zConflict;            /* The conflict algorithm to use */
+    sqlite3_stmt *pStmt;        /* A statement */
+    int nCol;                   /* Number of columns in the table */
+    int nByte;                  /* Number of bytes in an SQL string */
+    int i, j;                   /* Loop counters */
+    int nSep;                   /* Number of bytes in zSep[] */
+    int nNull;                  /* Number of bytes in zNull[] */
+    char *zSql;                 /* An SQL statement */
+    char *zLine;                /* A single line of input from the file */
+    char **azCol;               /* zLine[] broken up into columns */
+    const char *zCommit;        /* How to commit changes */
+    FILE *in;                   /* The input file */
+    int lineno = 0;             /* Line number of input file */
+    char zLineNum[80];          /* Line number print buffer */
+    Tcl_Obj *pResult;           /* interp result */
+
+    const char *zSep;
+    const char *zNull;
+    if( objc<5 || objc>7 ){
+      Tcl_WrongNumArgs(interp, 2, objv,
+         "CONFLICT-ALGORITHM TABLE FILENAME ?SEPARATOR? ?NULLINDICATOR?");
+      return TCL_ERROR;
+    }
+    if( objc>=6 ){
+      zSep = Tcl_GetStringFromObj(objv[5], 0);
+    }else{
+      zSep = "\t";
+    }
+    if( objc>=7 ){
+      zNull = Tcl_GetStringFromObj(objv[6], 0);
+    }else{
+      zNull = "";
+    }
+    zConflict = Tcl_GetStringFromObj(objv[2], 0);
+    zTable = Tcl_GetStringFromObj(objv[3], 0);
+    zFile = Tcl_GetStringFromObj(objv[4], 0);
+    nSep = strlen30(zSep);
+    nNull = strlen30(zNull);
+    if( nSep==0 ){
+      Tcl_AppendResult(interp,"Error: non-null separator required for copy",
+                       (char*)0);
+      return TCL_ERROR;
+    }
+    if(strcmp(zConflict, "rollback") != 0 &&
+       strcmp(zConflict, "abort"   ) != 0 &&
+       strcmp(zConflict, "fail"    ) != 0 &&
+       strcmp(zConflict, "ignore"  ) != 0 &&
+       strcmp(zConflict, "replace" ) != 0 ) {
+      Tcl_AppendResult(interp, "Error: \"", zConflict,
+            "\", conflict-algorithm must be one of: rollback, "
+            "abort, fail, ignore, or replace", (char*)0);
+      return TCL_ERROR;
+    }
+    zSql = sqlite3_mprintf("SELECT * FROM '%q'", zTable);
+    if( zSql==0 ){
+      Tcl_AppendResult(interp, "Error: no such table: ", zTable, (char*)0);
+      return TCL_ERROR;
+    }
+    nByte = strlen30(zSql);
+    rc = sqlite3_prepare(pDb->db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+    if( rc ){
+      Tcl_AppendResult(interp, "Error: ", sqlite3_errmsg(pDb->db), (char*)0);
+      nCol = 0;
+    }else{
+      nCol = sqlite3_column_count(pStmt);
+    }
+    sqlite3_finalize(pStmt);
+    if( nCol==0 ) {
+      return TCL_ERROR;
+    }
+    zSql = malloc( nByte + 50 + nCol*2 );
+    if( zSql==0 ) {
+      Tcl_AppendResult(interp, "Error: can't malloc()", (char*)0);
+      return TCL_ERROR;
+    }
+    sqlite3_snprintf(nByte+50, zSql, "INSERT OR %q INTO '%q' VALUES(?",
+         zConflict, zTable);
+    j = strlen30(zSql);
+    for(i=1; i<nCol; i++){
+      zSql[j++] = ',';
+      zSql[j++] = '?';
+    }
+    zSql[j++] = ')';
+    zSql[j] = 0;
+    rc = sqlite3_prepare(pDb->db, zSql, -1, &pStmt, 0);
+    free(zSql);
+    if( rc ){
+      Tcl_AppendResult(interp, "Error: ", sqlite3_errmsg(pDb->db), (char*)0);
+      sqlite3_finalize(pStmt);
+      return TCL_ERROR;
+    }
+    in = fopen(zFile, "rb");
+    if( in==0 ){
+      Tcl_AppendResult(interp, "Error: cannot open file: ", zFile, (char*)0);
+      sqlite3_finalize(pStmt);
+      return TCL_ERROR;
+    }
+    azCol = malloc( sizeof(azCol[0])*(nCol+1) );
+    if( azCol==0 ) {
+      Tcl_AppendResult(interp, "Error: can't malloc()", (char*)0);
+      fclose(in);
+      return TCL_ERROR;
+    }
+    (void)sqlite3_exec(pDb->db, "BEGIN", 0, 0, 0);
+    zCommit = "COMMIT";
+    while( (zLine = local_getline(0, in))!=0 ){
+      char *z;
+      lineno++;
+      azCol[0] = zLine;
+      for(i=0, z=zLine; *z; z++){
+        if( *z==zSep[0] && strncmp(z, zSep, nSep)==0 ){
+          *z = 0;
+          i++;
+          if( i<nCol ){
+            azCol[i] = &z[nSep];
+            z += nSep-1;
+          }
+        }
+      }
+      if( i+1!=nCol ){
+        char *zErr;
+        int nErr = strlen30(zFile) + 200;
+        zErr = malloc(nErr);
+        if( zErr ){
+          sqlite3_snprintf(nErr, zErr,
+             "Error: %s line %d: expected %d columns of data but found %d",
+             zFile, lineno, nCol, i+1);
+          Tcl_AppendResult(interp, zErr, (char*)0);
+          free(zErr);
+        }
+        zCommit = "ROLLBACK";
+        break;
+      }
+      for(i=0; i<nCol; i++){
+        /* check for null data, if so, bind as null */
+        if( (nNull>0 && strcmp(azCol[i], zNull)==0)
+          || strlen30(azCol[i])==0
+        ){
+          sqlite3_bind_null(pStmt, i+1);
+        }else{
+          sqlite3_bind_text(pStmt, i+1, azCol[i], -1, SQLITE_STATIC);
+        }
+      }
+      sqlite3_step(pStmt);
+      rc = sqlite3_reset(pStmt);
+      free(zLine);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp,"Error: ", sqlite3_errmsg(pDb->db), (char*)0);
+        zCommit = "ROLLBACK";
+        break;
+      }
+    }
+    free(azCol);
+    fclose(in);
+    sqlite3_finalize(pStmt);
+    (void)sqlite3_exec(pDb->db, zCommit, 0, 0, 0);
+
+    if( zCommit[0] == 'C' ){
+      /* success, set result as number of lines processed */
+      pResult = Tcl_GetObjResult(interp);
+      Tcl_SetIntObj(pResult, lineno);
+      rc = TCL_OK;
+    }else{
+      /* failure, append lineno where failed */
+      sqlite3_snprintf(sizeof(zLineNum), zLineNum,"%d",lineno);
+      Tcl_AppendResult(interp,", failed while processing line: ",zLineNum,
+                       (char*)0);
+      rc = TCL_ERROR;
+    }
+    break;
+  }
+
+  /*
+  **     $db deserialize ?-maxsize N? ?-readonly BOOL? ?DATABASE? VALUE
+  **
+  ** Reopen DATABASE (default "main") using the content in $VALUE
+  */
+  case DB_DESERIALIZE: {
+#ifdef SQLITE_OMIT_DESERIALIZE
+    Tcl_AppendResult(interp, "MEMDB not available in this build",
+                     (char*)0);
+    rc = TCL_ERROR;
+#else
+    const char *zSchema = 0;
+    Tcl_Obj *pValue = 0;
+    unsigned char *pBA;
+    unsigned char *pData;
+    int len, xrc;
+    sqlite3_int64 mxSize = 0;
+    int i;
+    int isReadonly = 0;
+
+
+    if( objc<3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?DATABASE? VALUE");
+      rc = TCL_ERROR;
+      break;
+    }
+    for(i=2; i<objc-1; i++){
+      const char *z = Tcl_GetString(objv[i]);
+      if( strcmp(z,"-maxsize")==0 && i<objc-2 ){
+        Tcl_WideInt x;
+        rc = Tcl_GetWideIntFromObj(interp, objv[++i], &x);
+        if( rc ) goto deserialize_error;
+        mxSize = x;
+        continue;
+      }
+      if( strcmp(z,"-readonly")==0 && i<objc-2 ){
+        rc = Tcl_GetBooleanFromObj(interp, objv[++i], &isReadonly);
+        if( rc ) goto deserialize_error;
+        continue;
+      }
+      if( zSchema==0 && i==objc-2 && z[0]!='-' ){
+        zSchema = z;
+        continue;
+      }
+      Tcl_AppendResult(interp, "unknown option: ", z, (char*)0);
+      rc = TCL_ERROR;
+      goto deserialize_error;
+    }
+    pValue = objv[objc-1];
+    pBA = Tcl_GetByteArrayFromObj(pValue, &len);
+    pData = sqlite3_malloc64( len );
+    if( pData==0 && len>0 ){
+      Tcl_AppendResult(interp, "out of memory", (char*)0);
+      rc = TCL_ERROR;
+    }else{
+      int flags;
+      if( len>0 ) memcpy(pData, pBA, len);
+      if( isReadonly ){
+        flags = SQLITE_DESERIALIZE_FREEONCLOSE | SQLITE_DESERIALIZE_READONLY;
+      }else{
+        flags = SQLITE_DESERIALIZE_FREEONCLOSE | SQLITE_DESERIALIZE_RESIZEABLE;
+      }
+      xrc = sqlite3_deserialize(pDb->db, zSchema, pData, len, len, flags);
+      if( xrc ){
+        Tcl_AppendResult(interp, "unable to set MEMDB content", (char*)0);
+        rc = TCL_ERROR;
+      }
+      if( mxSize>0 ){
+        sqlite3_file_control(pDb->db, zSchema,SQLITE_FCNTL_SIZE_LIMIT,&mxSize);
+      }
+    }
+deserialize_error:
+#endif
+    break; 
+  }
+
+  /*
+  **    $db enable_load_extension BOOLEAN
+  **
+  ** Turn the extension loading feature on or off.  It if off by
+  ** default.
+  */
+  case DB_ENABLE_LOAD_EXTENSION: {
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    int onoff;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "BOOLEAN");
+      return TCL_ERROR;
+    }
+    if( Tcl_GetBooleanFromObj(interp, objv[2], &onoff) ){
+      return TCL_ERROR;
+    }
+    sqlite3_enable_load_extension(pDb->db, onoff);
+    break;
+#else
+    Tcl_AppendResult(interp, "extension loading is turned off at compile-time",
+                     (char*)0);
+    return TCL_ERROR;
+#endif
+  }
+
+  /*
+  **    $db errorcode
+  **
+  ** Return the numeric error code that was returned by the most recent
+  ** call to sqlite3_exec().
+  */
+  case DB_ERRORCODE: {
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_errcode(pDb->db)));
+    break;
+  }
+
+  /*
+  **    $db erroroffset
+  **
+  ** Return the numeric error code that was returned by the most recent
+  ** call to sqlite3_exec().
+  */
+  case DB_ERROROFFSET: {
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_error_offset(pDb->db)));
+    break;
+  }
+
+  /*
+  **    $db exists $sql
+  **    $db onecolumn $sql
+  **
+  ** The onecolumn method is the equivalent of:
+  **     lindex [$db eval $sql] 0
+  */
+  case DB_EXISTS:
+  case DB_ONECOLUMN: {
+    Tcl_Obj *pResult = 0;
+    DbEvalContext sEval;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SQL");
+      return TCL_ERROR;
+    }
+
+    dbEvalInit(&sEval, pDb, objv[2], 0, 0);
+    rc = dbEvalStep(&sEval);
+    if( choice==DB_ONECOLUMN ){
+      if( rc==TCL_OK ){
+        pResult = dbEvalColumnValue(&sEval, 0);
+      }else if( rc==TCL_BREAK ){
+        Tcl_ResetResult(interp);
+      }
+    }else if( rc==TCL_BREAK || rc==TCL_OK ){
+      pResult = Tcl_NewBooleanObj(rc==TCL_OK);
+    }
+    dbEvalFinalize(&sEval);
+    if( pResult ) Tcl_SetObjResult(interp, pResult);
+
+    if( rc==TCL_BREAK ){
+      rc = TCL_OK;
+    }
+    break;
+  }
+
+  /*
+  **    $db eval ?options? $sql ?array? ?{  ...code... }?
+  **
+  ** The SQL statement in $sql is evaluated.  For each row, the values are
+  ** placed in elements of the array named "array" and ...code... is executed.
+  ** If "array" and "code" are omitted, then no callback is every invoked.
+  ** If "array" is an empty string, then the values are placed in variables
+  ** that have the same name as the fields extracted by the query.
+  */
+  case DB_EVAL: {
+    int evalFlags = 0;
+    const char *zOpt;
+    while( objc>3 && (zOpt = Tcl_GetString(objv[2]))!=0 && zOpt[0]=='-' ){
+      if( strcmp(zOpt, "-withoutnulls")==0 ){
+        evalFlags |= SQLITE_EVAL_WITHOUTNULLS;
+      }
+      else{
+        Tcl_AppendResult(interp, "unknown option: \"", zOpt, "\"", (void*)0);
+        return TCL_ERROR;
+      }
+      objc--;
+      objv++;
+    }
+    if( objc<3 || objc>5 ){
+      Tcl_WrongNumArgs(interp, 2, objv, 
+          "?OPTIONS? SQL ?ARRAY-NAME? ?SCRIPT?");
+      return TCL_ERROR;
+    }
+
+    if( objc==3 ){
+      DbEvalContext sEval;
+      Tcl_Obj *pRet = Tcl_NewObj();
+      Tcl_IncrRefCount(pRet);
+      dbEvalInit(&sEval, pDb, objv[2], 0, 0);
+      while( TCL_OK==(rc = dbEvalStep(&sEval)) ){
+        int i;
+        int nCol;
+        dbEvalRowInfo(&sEval, &nCol, 0);
+        for(i=0; i<nCol; i++){
+          Tcl_ListObjAppendElement(interp, pRet, dbEvalColumnValue(&sEval, i));
+        }
+      }
+      dbEvalFinalize(&sEval);
+      if( rc==TCL_BREAK ){
+        Tcl_SetObjResult(interp, pRet);
+        rc = TCL_OK;
+      }
+      Tcl_DecrRefCount(pRet);
+    }else{
+      ClientData cd2[2];
+      DbEvalContext *p;
+      Tcl_Obj *pArray = 0;
+      Tcl_Obj *pScript;
+
+      if( objc>=5 && *(char *)Tcl_GetString(objv[3]) ){
+        pArray = objv[3];
+      }
+      pScript = objv[objc-1];
+      Tcl_IncrRefCount(pScript);
+
+      p = (DbEvalContext *)Tcl_Alloc(sizeof(DbEvalContext));
+      dbEvalInit(p, pDb, objv[2], pArray, evalFlags);
+
+      cd2[0] = (void *)p;
+      cd2[1] = (void *)pScript;
+      rc = DbEvalNextCmd(cd2, interp, TCL_OK);
+    }
+    break;
+  }
+
+  /*
+  **     $db function NAME [OPTIONS] SCRIPT
+  **
+  ** Create a new SQL function called NAME.  Whenever that function is
+  ** called, invoke SCRIPT to evaluate the function.
+  **
+  ** Options:
+  **         --argcount N           Function has exactly N arguments
+  **         --deterministic        The function is pure
+  **         --directonly           Prohibit use inside triggers and views
+  **         --innocuous            Has no side effects or information leaks
+  **         --returntype TYPE      Specify the return type of the function
+  */
+  case DB_FUNCTION: {
+    int flags = SQLITE_UTF8;
+    SqlFunc *pFunc;
+    Tcl_Obj *pScript;
+    char *zName;
+    int nArg = -1;
+    int i;
+    int eType = SQLITE_NULL;
+    if( objc<4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "NAME ?SWITCHES? SCRIPT");
+      return TCL_ERROR;
+    }
+    for(i=3; i<(objc-1); i++){
+      const char *z = Tcl_GetString(objv[i]);
+      int n = strlen30(z);
+      if( n>1 && strncmp(z, "-argcount",n)==0 ){
+        if( i==(objc-2) ){
+          Tcl_AppendResult(interp, "option requires an argument: ", z,(char*)0);
+          return TCL_ERROR;
+        }
+        if( Tcl_GetIntFromObj(interp, objv[i+1], &nArg) ) return TCL_ERROR;
+        if( nArg<0 ){
+          Tcl_AppendResult(interp, "number of arguments must be non-negative",
+                           (char*)0);
+          return TCL_ERROR;
+        }
+        i++;
+      }else
+      if( n>1 && strncmp(z, "-deterministic",n)==0 ){
+        flags |= SQLITE_DETERMINISTIC;
+      }else
+      if( n>1 && strncmp(z, "-directonly",n)==0 ){
+        flags |= SQLITE_DIRECTONLY;
+      }else
+      if( n>1 && strncmp(z, "-innocuous",n)==0 ){
+        flags |= SQLITE_INNOCUOUS;
+      }else
+      if( n>1 && strncmp(z, "-returntype", n)==0 ){
+        const char *azType[] = {"integer", "real", "text", "blob", "any", 0};
+        assert( SQLITE_INTEGER==1 && SQLITE_FLOAT==2 && SQLITE_TEXT==3 );
+        assert( SQLITE_BLOB==4 && SQLITE_NULL==5 );
+        if( i==(objc-2) ){
+          Tcl_AppendResult(interp, "option requires an argument: ", z,(char*)0);
+          return TCL_ERROR;
+        }
+        i++;
+        if( Tcl_GetIndexFromObj(interp, objv[i], azType, "type", 0, &eType) ){
+          return TCL_ERROR;
+        }
+        eType++;
+      }else{
+        Tcl_AppendResult(interp, "bad option \"", z,
+            "\": must be -argcount, -deterministic, -directonly,"
+            " -innocuous, or -returntype", (char*)0
+        );
+        return TCL_ERROR;
+      }
+    }
+
+    pScript = objv[objc-1];
+    zName = Tcl_GetStringFromObj(objv[2], 0);
+    pFunc = findSqlFunc(pDb, zName);
+    if( pFunc==0 ) return TCL_ERROR;
+    if( pFunc->pScript ){
+      Tcl_DecrRefCount(pFunc->pScript);
+    }
+    pFunc->pScript = pScript;
+    Tcl_IncrRefCount(pScript);
+    pFunc->useEvalObjv = safeToUseEvalObjv(interp, pScript);
+    pFunc->eType = eType;
+    rc = sqlite3_create_function(pDb->db, zName, nArg, flags,
+        pFunc, tclSqlFunc, 0, 0);
+    if( rc!=SQLITE_OK ){
+      rc = TCL_ERROR;
+      Tcl_SetResult(interp, (char *)sqlite3_errmsg(pDb->db), TCL_VOLATILE);
+    }
+    break;
+  }
+
+  /*
+  **     $db incrblob ?-readonly? ?DB? TABLE COLUMN ROWID
+  */
+  case DB_INCRBLOB: {
+#ifdef SQLITE_OMIT_INCRBLOB
+    Tcl_AppendResult(interp, "incrblob not available in this build", (char*)0);
+    return TCL_ERROR;
+#else
+    int isReadonly = 0;
+    const char *zDb = "main";
+    const char *zTable;
+    const char *zColumn;
+    Tcl_WideInt iRow;
+
+    /* Check for the -readonly option */
+    if( objc>3 && strcmp(Tcl_GetString(objv[2]), "-readonly")==0 ){
+      isReadonly = 1;
+    }
+
+    if( objc!=(5+isReadonly) && objc!=(6+isReadonly) ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?-readonly? ?DB? TABLE COLUMN ROWID");
+      return TCL_ERROR;
+    }
+
+    if( objc==(6+isReadonly) ){
+      zDb = Tcl_GetString(objv[2+isReadonly]);
+    }
+    zTable = Tcl_GetString(objv[objc-3]);
+    zColumn = Tcl_GetString(objv[objc-2]);
+    rc = Tcl_GetWideIntFromObj(interp, objv[objc-1], &iRow);
+
+    if( rc==TCL_OK ){
+      rc = createIncrblobChannel(
+          interp, pDb, zDb, zTable, zColumn, (sqlite3_int64)iRow, isReadonly
+      );
+    }
+#endif
+    break;
+  }
+
+  /*
+  **     $db interrupt
+  **
+  ** Interrupt the execution of the inner-most SQL interpreter.  This
+  ** causes the SQL statement to return an error of SQLITE_INTERRUPT.
+  */
+  case DB_INTERRUPT: {
+    sqlite3_interrupt(pDb->db);
+    break;
+  }
+
+  /*
+  **     $db nullvalue ?STRING?
+  **
+  ** Change text used when a NULL comes back from the database. If ?STRING?
+  ** is not present, then the current string used for NULL is returned.
+  ** If STRING is present, then STRING is returned.
+  **
+  */
+  case DB_NULLVALUE: {
+    if( objc!=2 && objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "NULLVALUE");
+      return TCL_ERROR;
+    }
+    if( objc==3 ){
+      int len;
+      char *zNull = Tcl_GetStringFromObj(objv[2], &len);
+      if( pDb->zNull ){
+        Tcl_Free(pDb->zNull);
+      }
+      if( zNull && len>0 ){
+        pDb->zNull = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zNull, zNull, len);
+        pDb->zNull[len] = '\0';
+      }else{
+        pDb->zNull = 0;
+      }
+    }
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(pDb->zNull, -1));
+    break;
+  }
+
+  /*
+  **     $db last_insert_rowid
+  **
+  ** Return an integer which is the ROWID for the most recent insert.
+  */
+  case DB_LAST_INSERT_ROWID: {
+    Tcl_Obj *pResult;
+    Tcl_WideInt rowid;
+    if( objc!=2 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "");
+      return TCL_ERROR;
+    }
+    rowid = sqlite3_last_insert_rowid(pDb->db);
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetWideIntObj(pResult, rowid);
+    break;
+  }
+
+  /*
+  ** The DB_ONECOLUMN method is implemented together with DB_EXISTS.
+  */
+
+  /*    $db progress ?N CALLBACK?
+  **
+  ** Invoke the given callback every N virtual machine opcodes while executing
+  ** queries.
+  */
+  case DB_PROGRESS: {
+    if( objc==2 ){
+      if( pDb->zProgress ){
+        Tcl_AppendResult(interp, pDb->zProgress, (char*)0);
+      }
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+      sqlite3_progress_handler(pDb->db, 0, 0, 0);
+#endif
+    }else if( objc==4 ){
+      char *zProgress;
+      int len;
+      int N;
+      if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &N) ){
+        return TCL_ERROR;
+      };
+      if( pDb->zProgress ){
+        Tcl_Free(pDb->zProgress);
+      }
+      zProgress = Tcl_GetStringFromObj(objv[3], &len);
+      if( zProgress && len>0 ){
+        pDb->zProgress = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zProgress, zProgress, len+1);
+      }else{
+        pDb->zProgress = 0;
+      }
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+      if( pDb->zProgress ){
+        pDb->interp = interp;
+        sqlite3_progress_handler(pDb->db, N, DbProgressHandler, pDb);
+      }else{
+        sqlite3_progress_handler(pDb->db, 0, 0, 0);
+      }
+#endif
+    }else{
+      Tcl_WrongNumArgs(interp, 2, objv, "N CALLBACK");
+      return TCL_ERROR;
+    }
+    break;
+  }
+
+  /*    $db profile ?CALLBACK?
+  **
+  ** Make arrangements to invoke the CALLBACK routine after each SQL statement
+  ** that has run.  The text of the SQL and the amount of elapse time are
+  ** appended to CALLBACK before the script is run.
+  */
+  case DB_PROFILE: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zProfile ){
+        Tcl_AppendResult(interp, pDb->zProfile, (char*)0);
+      }
+    }else{
+      char *zProfile;
+      int len;
+      if( pDb->zProfile ){
+        Tcl_Free(pDb->zProfile);
+      }
+      zProfile = Tcl_GetStringFromObj(objv[2], &len);
+      if( zProfile && len>0 ){
+        pDb->zProfile = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zProfile, zProfile, len+1);
+      }else{
+        pDb->zProfile = 0;
+      }
+#if !defined(SQLITE_OMIT_TRACE) && !defined(SQLITE_OMIT_FLOATING_POINT) && \
+    !defined(SQLITE_OMIT_DEPRECATED)
+      if( pDb->zProfile ){
+        pDb->interp = interp;
+        sqlite3_profile(pDb->db, DbProfileHandler, pDb);
+      }else{
+        sqlite3_profile(pDb->db, 0, 0);
+      }
+#endif
+    }
+    break;
+  }
+
+  /*
+  **     $db rekey KEY
+  **
+  ** Change the encryption key on the currently open database.
+  */
+  case DB_REKEY: {
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "KEY");
+      return TCL_ERROR;
+    }
+    break;
+  }
+
+  /*    $db restore ?DATABASE? FILENAME
+  **
+  ** Open a database file named FILENAME.  Transfer the content
+  ** of FILENAME into the local database DATABASE (default: "main").
+  */
+  case DB_RESTORE: {
+    const char *zSrcFile;
+    const char *zDestDb;
+    sqlite3 *pSrc;
+    sqlite3_backup *pBackup;
+    int nTimeout = 0;
+
+    if( objc==3 ){
+      zDestDb = "main";
+      zSrcFile = Tcl_GetString(objv[2]);
+    }else if( objc==4 ){
+      zDestDb = Tcl_GetString(objv[2]);
+      zSrcFile = Tcl_GetString(objv[3]);
+    }else{
+      Tcl_WrongNumArgs(interp, 2, objv, "?DATABASE? FILENAME");
+      return TCL_ERROR;
+    }
+    rc = sqlite3_open_v2(zSrcFile, &pSrc,
+                         SQLITE_OPEN_READONLY | pDb->openFlags, 0);
+    if( rc!=SQLITE_OK ){
+      Tcl_AppendResult(interp, "cannot open source database: ",
+           sqlite3_errmsg(pSrc), (char*)0);
+      sqlite3_close(pSrc);
+      return TCL_ERROR;
+    }
+    pBackup = sqlite3_backup_init(pDb->db, zDestDb, pSrc, "main");
+    if( pBackup==0 ){
+      Tcl_AppendResult(interp, "restore failed: ",
+           sqlite3_errmsg(pDb->db), (char*)0);
+      sqlite3_close(pSrc);
+      return TCL_ERROR;
+    }
+    while( (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK
+              || rc==SQLITE_BUSY ){
+      if( rc==SQLITE_BUSY ){
+        if( nTimeout++ >= 3 ) break;
+        sqlite3_sleep(100);
+      }
+    }
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = TCL_OK;
+    }else if( rc==SQLITE_BUSY || rc==SQLITE_LOCKED ){
+      Tcl_AppendResult(interp, "restore failed: source database busy",
+                       (char*)0);
+      rc = TCL_ERROR;
+    }else{
+      Tcl_AppendResult(interp, "restore failed: ",
+           sqlite3_errmsg(pDb->db), (char*)0);
+      rc = TCL_ERROR;
+    }
+    sqlite3_close(pSrc);
+    break;
+  }
+
+  /*
+  **     $db serialize ?DATABASE?
+  **
+  ** Return a serialization of a database.  
+  */
+  case DB_SERIALIZE: {
+#ifdef SQLITE_OMIT_DESERIALIZE
+    Tcl_AppendResult(interp, "MEMDB not available in this build",
+                     (char*)0);
+    rc = TCL_ERROR;
+#else
+    const char *zSchema = objc>=3 ? Tcl_GetString(objv[2]) : "main";
+    sqlite3_int64 sz = 0;
+    unsigned char *pData;
+    if( objc!=2 && objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?DATABASE?");
+      rc = TCL_ERROR;
+    }else{
+      int needFree;
+      pData = sqlite3_serialize(pDb->db, zSchema, &sz, SQLITE_SERIALIZE_NOCOPY);
+      if( pData ){
+        needFree = 0;
+      }else{
+        pData = sqlite3_serialize(pDb->db, zSchema, &sz, 0);
+        needFree = 1;
+      }
+      Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(pData,sz));
+      if( needFree ) sqlite3_free(pData);
+    }
+#endif
+    break;
+  }
+
+  /*
+  **     $db status (step|sort|autoindex|vmstep)
+  **
+  ** Display SQLITE_STMTSTATUS_FULLSCAN_STEP or
+  ** SQLITE_STMTSTATUS_SORT for the most recent eval.
+  */
+  case DB_STATUS: {
+    int v;
+    const char *zOp;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "(step|sort|autoindex)");
+      return TCL_ERROR;
+    }
+    zOp = Tcl_GetString(objv[2]);
+    if( strcmp(zOp, "step")==0 ){
+      v = pDb->nStep;
+    }else if( strcmp(zOp, "sort")==0 ){
+      v = pDb->nSort;
+    }else if( strcmp(zOp, "autoindex")==0 ){
+      v = pDb->nIndex;
+    }else if( strcmp(zOp, "vmstep")==0 ){
+      v = pDb->nVMStep;
+    }else{
+      Tcl_AppendResult(interp,
+            "bad argument: should be autoindex, step, sort or vmstep",
+            (char*)0);
+      return TCL_ERROR;
+    }
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(v));
+    break;
+  }
+
+  /*
+  **     $db timeout MILLESECONDS
+  **
+  ** Delay for the number of milliseconds specified when a file is locked.
+  */
+  case DB_TIMEOUT: {
+    int ms;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "MILLISECONDS");
+      return TCL_ERROR;
+    }
+    if( Tcl_GetIntFromObj(interp, objv[2], &ms) ) return TCL_ERROR;
+    sqlite3_busy_timeout(pDb->db, ms);
+    break;
+  }
+
+  /*
+  **     $db total_changes
+  **
+  ** Return the number of rows that were modified, inserted, or deleted
+  ** since the database handle was created.
+  */
+  case DB_TOTAL_CHANGES: {
+    Tcl_Obj *pResult;
+    if( objc!=2 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "");
+      return TCL_ERROR;
+    }
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetWideIntObj(pResult, sqlite3_total_changes64(pDb->db));
+    break;
+  }
+
+  /*    $db trace ?CALLBACK?
+  **
+  ** Make arrangements to invoke the CALLBACK routine for each SQL statement
+  ** that is executed.  The text of the SQL is appended to CALLBACK before
+  ** it is executed.
+  */
+  case DB_TRACE: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zTrace ){
+        Tcl_AppendResult(interp, pDb->zTrace, (char*)0);
+      }
+    }else{
+      char *zTrace;
+      int len;
+      if( pDb->zTrace ){
+        Tcl_Free(pDb->zTrace);
+      }
+      zTrace = Tcl_GetStringFromObj(objv[2], &len);
+      if( zTrace && len>0 ){
+        pDb->zTrace = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zTrace, zTrace, len+1);
+      }else{
+        pDb->zTrace = 0;
+      }
+#if !defined(SQLITE_OMIT_TRACE) && !defined(SQLITE_OMIT_FLOATING_POINT) && \
+    !defined(SQLITE_OMIT_DEPRECATED)
+      if( pDb->zTrace ){
+        pDb->interp = interp;
+        sqlite3_trace(pDb->db, DbTraceHandler, pDb);
+      }else{
+        sqlite3_trace(pDb->db, 0, 0);
+      }
+#endif
+    }
+    break;
+  }
+
+  /*    $db trace_v2 ?CALLBACK? ?MASK?
+  **
+  ** Make arrangements to invoke the CALLBACK routine for each trace event
+  ** matching the mask that is generated.  The parameters are appended to
+  ** CALLBACK before it is executed.
+  */
+  case DB_TRACE_V2: {
+    if( objc>4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK? ?MASK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zTraceV2 ){
+        Tcl_AppendResult(interp, pDb->zTraceV2, (char*)0);
+      }
+    }else{
+      char *zTraceV2;
+      int len;
+      Tcl_WideInt wMask = 0;
+      if( objc==4 ){
+        static const char *TTYPE_strs[] = {
+          "statement", "profile", "row", "close", 0
+        };
+        enum TTYPE_enum {
+          TTYPE_STMT, TTYPE_PROFILE, TTYPE_ROW, TTYPE_CLOSE
+        };
+        int i;
+        if( TCL_OK!=Tcl_ListObjLength(interp, objv[3], &len) ){
+          return TCL_ERROR;
+        }
+        for(i=0; i<len; i++){
+          Tcl_Obj *pObj;
+          int ttype;
+          if( TCL_OK!=Tcl_ListObjIndex(interp, objv[3], i, &pObj) ){
+            return TCL_ERROR;
+          }
+          if( Tcl_GetIndexFromObj(interp, pObj, TTYPE_strs, "trace type",
+                                  0, &ttype)!=TCL_OK ){
+            Tcl_WideInt wType;
+            Tcl_Obj *pError = Tcl_DuplicateObj(Tcl_GetObjResult(interp));
+            Tcl_IncrRefCount(pError);
+            if( TCL_OK==Tcl_GetWideIntFromObj(interp, pObj, &wType) ){
+              Tcl_DecrRefCount(pError);
+              wMask |= wType;
+            }else{
+              Tcl_SetObjResult(interp, pError);
+              Tcl_DecrRefCount(pError);
+              return TCL_ERROR;
+            }
+          }else{
+            switch( (enum TTYPE_enum)ttype ){
+              case TTYPE_STMT:    wMask |= SQLITE_TRACE_STMT;    break;
+              case TTYPE_PROFILE: wMask |= SQLITE_TRACE_PROFILE; break;
+              case TTYPE_ROW:     wMask |= SQLITE_TRACE_ROW;     break;
+              case TTYPE_CLOSE:   wMask |= SQLITE_TRACE_CLOSE;   break;
+            }
+          }
+        }
+      }else{
+        wMask = SQLITE_TRACE_STMT; /* use the "legacy" default */
+      }
+      if( pDb->zTraceV2 ){
+        Tcl_Free(pDb->zTraceV2);
+      }
+      zTraceV2 = Tcl_GetStringFromObj(objv[2], &len);
+      if( zTraceV2 && len>0 ){
+        pDb->zTraceV2 = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zTraceV2, zTraceV2, len+1);
+      }else{
+        pDb->zTraceV2 = 0;
+      }
+#if !defined(SQLITE_OMIT_TRACE) && !defined(SQLITE_OMIT_FLOATING_POINT)
+      if( pDb->zTraceV2 ){
+        pDb->interp = interp;
+        sqlite3_trace_v2(pDb->db, (unsigned)wMask, DbTraceV2Handler, pDb);
+      }else{
+        sqlite3_trace_v2(pDb->db, 0, 0, 0);
+      }
+#endif
+    }
+    break;
+  }
+
+  /*    $db transaction [-deferred|-immediate|-exclusive] SCRIPT
+  **
+  ** Start a new transaction (if we are not already in the midst of a
+  ** transaction) and execute the TCL script SCRIPT.  After SCRIPT
+  ** completes, either commit the transaction or roll it back if SCRIPT
+  ** throws an exception.  Or if no new transaction was started, do nothing.
+  ** pass the exception on up the stack.
+  **
+  ** This command was inspired by Dave Thomas's talk on Ruby at the
+  ** 2005 O'Reilly Open Source Convention (OSCON).
+  */
+  case DB_TRANSACTION: {
+    Tcl_Obj *pScript;
+    const char *zBegin = "SAVEPOINT _tcl_transaction";
+    if( objc!=3 && objc!=4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "[TYPE] SCRIPT");
+      return TCL_ERROR;
+    }
+
+    if( pDb->nTransaction==0 && objc==4 ){
+      static const char *TTYPE_strs[] = {
+        "deferred",   "exclusive",  "immediate", 0
+      };
+      enum TTYPE_enum {
+        TTYPE_DEFERRED, TTYPE_EXCLUSIVE, TTYPE_IMMEDIATE
+      };
+      int ttype;
+      if( Tcl_GetIndexFromObj(interp, objv[2], TTYPE_strs, "transaction type",
+                              0, &ttype) ){
+        return TCL_ERROR;
+      }
+      switch( (enum TTYPE_enum)ttype ){
+        case TTYPE_DEFERRED:    /* no-op */;                 break;
+        case TTYPE_EXCLUSIVE:   zBegin = "BEGIN EXCLUSIVE";  break;
+        case TTYPE_IMMEDIATE:   zBegin = "BEGIN IMMEDIATE";  break;
+      }
+    }
+    pScript = objv[objc-1];
+
+    /* Run the SQLite BEGIN command to open a transaction or savepoint. */
+    pDb->disableAuth++;
+    rc = sqlite3_exec(pDb->db, zBegin, 0, 0, 0);
+    pDb->disableAuth--;
+    if( rc!=SQLITE_OK ){
+      Tcl_AppendResult(interp, sqlite3_errmsg(pDb->db), (char*)0);
+      return TCL_ERROR;
+    }
+    pDb->nTransaction++;
+
+    /* If using NRE, schedule a callback to invoke the script pScript, then
+    ** a second callback to commit (or rollback) the transaction or savepoint
+    ** opened above. If not using NRE, evaluate the script directly, then
+    ** call function DbTransPostCmd() to commit (or rollback) the transaction
+    ** or savepoint.  */
+    addDatabaseRef(pDb);          /* DbTransPostCmd() calls delDatabaseRef() */
+    if( DbUseNre() ){
+      Tcl_NRAddCallback(interp, DbTransPostCmd, cd, 0, 0, 0);
+      (void)Tcl_NREvalObj(interp, pScript, 0);
+    }else{
+      rc = DbTransPostCmd(&cd, interp, Tcl_EvalObjEx(interp, pScript, 0));
+    }
+    break;
+  }
+
+  /*
+  **    $db unlock_notify ?script?
+  */
+  case DB_UNLOCK_NOTIFY: {
+#ifndef SQLITE_ENABLE_UNLOCK_NOTIFY
+    Tcl_AppendResult(interp, "unlock_notify not available in this build",
+                     (char*)0);
+    rc = TCL_ERROR;
+#else
+    if( objc!=2 && objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
+      rc = TCL_ERROR;
+    }else{
+      void (*xNotify)(void **, int) = 0;
+      void *pNotifyArg = 0;
+
+      if( pDb->pUnlockNotify ){
+        Tcl_DecrRefCount(pDb->pUnlockNotify);
+        pDb->pUnlockNotify = 0;
+      }
+
+      if( objc==3 ){
+        xNotify = DbUnlockNotify;
+        pNotifyArg = (void *)pDb;
+        pDb->pUnlockNotify = objv[2];
+        Tcl_IncrRefCount(pDb->pUnlockNotify);
+      }
+
+      if( sqlite3_unlock_notify(pDb->db, xNotify, pNotifyArg) ){
+        Tcl_AppendResult(interp, sqlite3_errmsg(pDb->db), (char*)0);
+        rc = TCL_ERROR;
+      }
+    }
+#endif
+    break;
+  }
+
+  /*
+  **    $db preupdate_hook count
+  **    $db preupdate_hook hook ?SCRIPT?
+  **    $db preupdate_hook new INDEX
+  **    $db preupdate_hook old INDEX
+  */
+  case DB_PREUPDATE: {
+#ifndef SQLITE_ENABLE_PREUPDATE_HOOK
+    Tcl_AppendResult(interp, "preupdate_hook was omitted at compile-time", 
+                     (char*)0);
+    rc = TCL_ERROR;
+#else
+    static const char *azSub[] = {"count", "depth", "hook", "new", "old", 0};
+    enum DbPreupdateSubCmd {
+      PRE_COUNT, PRE_DEPTH, PRE_HOOK, PRE_NEW, PRE_OLD
+    };
+    int iSub;
+
+    if( objc<3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SUB-COMMAND ?ARGS?");
+    }
+    if( Tcl_GetIndexFromObj(interp, objv[2], azSub, "sub-command", 0, &iSub) ){
+      return TCL_ERROR;
+    }
+
+    switch( (enum DbPreupdateSubCmd)iSub ){
+      case PRE_COUNT: {
+        int nCol = sqlite3_preupdate_count(pDb->db);
+        Tcl_SetObjResult(interp, Tcl_NewIntObj(nCol));
+        break;
+      }
+
+      case PRE_HOOK: {
+        if( objc>4 ){
+          Tcl_WrongNumArgs(interp, 2, objv, "hook ?SCRIPT?");
+          return TCL_ERROR;
+        }
+        DbHookCmd(interp, pDb, (objc==4 ? objv[3] : 0), &pDb->pPreUpdateHook);
+        break;
+      }
+
+      case PRE_DEPTH: {
+        Tcl_Obj *pRet;
+        if( objc!=3 ){
+          Tcl_WrongNumArgs(interp, 3, objv, "");
+          return TCL_ERROR;
+        }
+        pRet = Tcl_NewIntObj(sqlite3_preupdate_depth(pDb->db));
+        Tcl_SetObjResult(interp, pRet);
+        break;
+      }
+
+      case PRE_NEW:
+      case PRE_OLD: {
+        int iIdx;
+        sqlite3_value *pValue;
+        if( objc!=4 ){
+          Tcl_WrongNumArgs(interp, 3, objv, "INDEX");
+          return TCL_ERROR;
+        }
+        if( Tcl_GetIntFromObj(interp, objv[3], &iIdx) ){
+          return TCL_ERROR;
+        }
+
+        if( iSub==PRE_OLD ){
+          rc = sqlite3_preupdate_old(pDb->db, iIdx, &pValue);
+        }else{
+          assert( iSub==PRE_NEW );
+          rc = sqlite3_preupdate_new(pDb->db, iIdx, &pValue);
+        }
+
+        if( rc==SQLITE_OK ){
+          Tcl_Obj *pObj;
+          pObj = Tcl_NewStringObj((char*)sqlite3_value_text(pValue), -1);
+          Tcl_SetObjResult(interp, pObj);
+        }else{
+          Tcl_AppendResult(interp, sqlite3_errmsg(pDb->db), (char*)0);
+          return TCL_ERROR;
+        }
+      }
+    }
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+    break;
+  }
+
+  /*
+  **    $db wal_hook ?script?
+  **    $db update_hook ?script?
+  **    $db rollback_hook ?script?
+  */
+  case DB_WAL_HOOK:
+  case DB_UPDATE_HOOK:
+  case DB_ROLLBACK_HOOK: {
+    /* set ppHook to point at pUpdateHook or pRollbackHook, depending on
+    ** whether [$db update_hook] or [$db rollback_hook] was invoked.
+    */
+    Tcl_Obj **ppHook = 0;
+    if( choice==DB_WAL_HOOK ) ppHook = &pDb->pWalHook;
+    if( choice==DB_UPDATE_HOOK ) ppHook = &pDb->pUpdateHook;
+    if( choice==DB_ROLLBACK_HOOK ) ppHook = &pDb->pRollbackHook;
+    if( objc>3 ){
+       Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
+       return TCL_ERROR;
+    }
+
+    DbHookCmd(interp, pDb, (objc==3 ? objv[2] : 0), ppHook);
+    break;
+  }
+
+  /*    $db version
+  **
+  ** Return the version string for this database.
+  */
+  case DB_VERSION: {
+    int i;
+    for(i=2; i<objc; i++){
+      const char *zArg = Tcl_GetString(objv[i]);
+      /* Optional arguments to $db version are used for testing purpose */
+#ifdef SQLITE_TEST
+      /* $db version -use-legacy-prepare BOOLEAN
+      **
+      ** Turn the use of legacy sqlite3_prepare() on or off.
+      */
+      if( strcmp(zArg, "-use-legacy-prepare")==0 && i+1<objc ){
+        i++;
+        if( Tcl_GetBooleanFromObj(interp, objv[i], &pDb->bLegacyPrepare) ){
+          return TCL_ERROR;
+        }
+      }else
+
+      /* $db version -last-stmt-ptr
+      **
+      ** Return a string which is a hex encoding of the pointer to the
+      ** most recent sqlite3_stmt in the statement cache.
+      */
+      if( strcmp(zArg, "-last-stmt-ptr")==0 ){
+        char zBuf[100];
+        sqlite3_snprintf(sizeof(zBuf), zBuf, "%p",
+                         pDb->stmtList ? pDb->stmtList->pStmt: 0);
+        Tcl_SetResult(interp, zBuf, TCL_VOLATILE);
+      }else
+#endif /* SQLITE_TEST */
+      {
+        Tcl_AppendResult(interp, "unknown argument: ", zArg, (char*)0);
+        return TCL_ERROR;
+      }
+    }
+    if( i==2 ){   
+      Tcl_SetResult(interp, (char *)sqlite3_libversion(), TCL_STATIC);
+    }
+    break;
+  }
+
+
+  } /* End of the SWITCH statement */
+  return rc;
+}
+
+#if SQLITE_TCL_NRE
+/*
+** Adaptor that provides an objCmd interface to the NRE-enabled
+** interface implementation.
+*/
+static int SQLITE_TCLAPI DbObjCmdAdaptor(
+  void *cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *const*objv
+){
+  return Tcl_NRCallObjProc(interp, DbObjCmd, cd, objc, objv);
+}
+#endif /* SQLITE_TCL_NRE */
+
+/*
+** Issue the usage message when the "sqlite3" command arguments are
+** incorrect.
+*/
+static int sqliteCmdUsage(
+  Tcl_Interp *interp,
+  Tcl_Obj *const*objv
+){
+  Tcl_WrongNumArgs(interp, 1, objv,
+    "HANDLE ?FILENAME? ?-vfs VFSNAME? ?-readonly BOOLEAN? ?-create BOOLEAN?"
+    " ?-nofollow BOOLEAN?"
+    " ?-nomutex BOOLEAN? ?-fullmutex BOOLEAN? ?-uri BOOLEAN?"
+  );
+  return TCL_ERROR;
+}
+
+/*
+**   sqlite3 DBNAME FILENAME ?-vfs VFSNAME? ?-key KEY? ?-readonly BOOLEAN?
+**                           ?-create BOOLEAN? ?-nomutex BOOLEAN?
+**                           ?-nofollow BOOLEAN?
+**
+** This is the main Tcl command.  When the "sqlite" Tcl command is
+** invoked, this routine runs to process that command.
+**
+** The first argument, DBNAME, is an arbitrary name for a new
+** database connection.  This command creates a new command named
+** DBNAME that is used to control that connection.  The database
+** connection is deleted when the DBNAME command is deleted.
+**
+** The second argument is the name of the database file.
+**
+*/
+static int SQLITE_TCLAPI DbMain(
+  void *cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *const*objv
+){
+  SqliteDb *p;
+  const char *zArg;
+  char *zErrMsg;
+  int i;
+  const char *zFile = 0;
+  const char *zVfs = 0;
+  int flags;
+  int bTranslateFileName = 1;
+  Tcl_DString translatedFilename;
+  int rc;
+
+  /* In normal use, each TCL interpreter runs in a single thread.  So
+  ** by default, we can turn off mutexing on SQLite database connections.
+  ** However, for testing purposes it is useful to have mutexes turned
+  ** on.  So, by default, mutexes default off.  But if compiled with
+  ** SQLITE_TCL_DEFAULT_FULLMUTEX then mutexes default on.
+  */
+#ifdef SQLITE_TCL_DEFAULT_FULLMUTEX
+  flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX;
+#else
+  flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_NOMUTEX;
+#endif
+
+  if( objc==1 ) return sqliteCmdUsage(interp, objv);
+  if( objc==2 ){
+    zArg = Tcl_GetStringFromObj(objv[1], 0);
+    if( strcmp(zArg,"-version")==0 ){
+      Tcl_AppendResult(interp,sqlite3_libversion(), (char*)0);
+      return TCL_OK;
+    }
+    if( strcmp(zArg,"-sourceid")==0 ){
+      Tcl_AppendResult(interp,sqlite3_sourceid(), (char*)0);
+      return TCL_OK;
+    }
+    if( strcmp(zArg,"-has-codec")==0 ){
+      Tcl_AppendResult(interp,"0",(char*)0);
+      return TCL_OK;
+    }
+    if( zArg[0]=='-' ) return sqliteCmdUsage(interp, objv);
+  }
+  for(i=2; i<objc; i++){
+    zArg = Tcl_GetString(objv[i]);
+    if( zArg[0]!='-' ){
+      if( zFile!=0 ) return sqliteCmdUsage(interp, objv);
+      zFile = zArg;
+      continue;
+    }
+    if( i==objc-1 ) return sqliteCmdUsage(interp, objv);
+    i++;
+    if( strcmp(zArg,"-key")==0 ){
+      /* no-op */
+    }else if( strcmp(zArg, "-vfs")==0 ){
+      zVfs = Tcl_GetString(objv[i]);
+    }else if( strcmp(zArg, "-readonly")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
+      if( b ){
+        flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
+        flags |= SQLITE_OPEN_READONLY;
+      }else{
+        flags &= ~SQLITE_OPEN_READONLY;
+        flags |= SQLITE_OPEN_READWRITE;
+      }
+    }else if( strcmp(zArg, "-create")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
+      if( b && (flags & SQLITE_OPEN_READONLY)==0 ){
+        flags |= SQLITE_OPEN_CREATE;
+      }else{
+        flags &= ~SQLITE_OPEN_CREATE;
+      }
+    }else if( strcmp(zArg, "-nofollow")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
+      if( b ){
+        flags |= SQLITE_OPEN_NOFOLLOW;
+      }else{
+        flags &= ~SQLITE_OPEN_NOFOLLOW;
+      }
+    }else if( strcmp(zArg, "-nomutex")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
+      if( b ){
+        flags |= SQLITE_OPEN_NOMUTEX;
+        flags &= ~SQLITE_OPEN_FULLMUTEX;
+      }else{
+        flags &= ~SQLITE_OPEN_NOMUTEX;
+      }
+    }else if( strcmp(zArg, "-fullmutex")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
+      if( b ){
+        flags |= SQLITE_OPEN_FULLMUTEX;
+        flags &= ~SQLITE_OPEN_NOMUTEX;
+      }else{
+        flags &= ~SQLITE_OPEN_FULLMUTEX;
+      }
+    }else if( strcmp(zArg, "-uri")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
+      if( b ){
+        flags |= SQLITE_OPEN_URI;
+      }else{
+        flags &= ~SQLITE_OPEN_URI;
+      }
+    }else if( strcmp(zArg, "-translatefilename")==0 ){
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &bTranslateFileName) ){
+        return TCL_ERROR;
+      }
+    }else{
+      Tcl_AppendResult(interp, "unknown option: ", zArg, (char*)0);
+      return TCL_ERROR;
+    }
+  }
+  zErrMsg = 0;
+  p = (SqliteDb*)Tcl_Alloc( sizeof(*p) );
+  memset(p, 0, sizeof(*p));
+  if( zFile==0 ) zFile = "";
+  if( bTranslateFileName ){
+    zFile = Tcl_TranslateFileName(interp, zFile, &translatedFilename);
+  }
+  rc = sqlite3_open_v2(zFile, &p->db, flags, zVfs);
+  if( bTranslateFileName ){
+    Tcl_DStringFree(&translatedFilename);
+  }
+  if( p->db ){
+    if( SQLITE_OK!=sqlite3_errcode(p->db) ){
+      zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(p->db));
+      sqlite3_close(p->db);
+      p->db = 0;
+    }
+  }else{
+    zErrMsg = sqlite3_mprintf("%s", sqlite3_errstr(rc));
+  }
+  if( p->db==0 ){
+    Tcl_SetResult(interp, zErrMsg, TCL_VOLATILE);
+    Tcl_Free((char*)p);
+    sqlite3_free(zErrMsg);
+    return TCL_ERROR;
+  }
+  p->maxStmt = NUM_PREPARED_STMTS;
+  p->openFlags = flags & SQLITE_OPEN_URI;
+  p->interp = interp;
+  zArg = Tcl_GetStringFromObj(objv[1], 0);
+  if( DbUseNre() ){
+    Tcl_NRCreateCommand(interp, zArg, DbObjCmdAdaptor, DbObjCmd,
+                        (char*)p, DbDeleteCmd);
+  }else{
+    Tcl_CreateObjCommand(interp, zArg, DbObjCmd, (char*)p, DbDeleteCmd);
+  }
+  p->nRef = 1;
+  return TCL_OK;
+}
+
+/*
+** Provide a dummy Tcl_InitStubs if we are using this as a static
+** library.
+*/
+#ifndef USE_TCL_STUBS
+# undef  Tcl_InitStubs
+# define Tcl_InitStubs(a,b,c) TCL_VERSION
+#endif
+
+/*
+** Make sure we have a PACKAGE_VERSION macro defined.  This will be
+** defined automatically by the TEA makefile.  But other makefiles
+** do not define it.
+*/
+#ifndef PACKAGE_VERSION
+# define PACKAGE_VERSION SQLITE_VERSION
+#endif
+
+/*
+** Initialize this module.
+**
+** This Tcl module contains only a single new Tcl command named "sqlite".
+** (Hence there is no namespace.  There is no point in using a namespace
+** if the extension only supplies one new name!)  The "sqlite" command is
+** used to open a new SQLite database.  See the DbMain() routine above
+** for additional information.
+**
+** The EXTERN macros are required by TCL in order to work on windows.
+*/
+EXTERN int Sqlite3_Init(Tcl_Interp *interp){
+  int rc = Tcl_InitStubs(interp, "8.4", 0) ? TCL_OK : TCL_ERROR;
+  if( rc==TCL_OK ){
+    Tcl_CreateObjCommand(interp, "sqlite3", (Tcl_ObjCmdProc*)DbMain, 0, 0);
+#ifndef SQLITE_3_SUFFIX_ONLY
+    /* The "sqlite" alias is undocumented.  It is here only to support
+    ** legacy scripts.  All new scripts should use only the "sqlite3"
+    ** command. */
+    Tcl_CreateObjCommand(interp, "sqlite", (Tcl_ObjCmdProc*)DbMain, 0, 0);
+#endif
+    rc = Tcl_PkgProvide(interp, "sqlite3", PACKAGE_VERSION);
+  }
+  return rc;
+}
+EXTERN int Tclsqlite3_Init(Tcl_Interp *interp){ return Sqlite3_Init(interp); }
+EXTERN int Sqlite3_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+EXTERN int Tclsqlite3_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+
+/* Because it accesses the file-system and uses persistent state, SQLite
+** is not considered appropriate for safe interpreters.  Hence, we cause
+** the _SafeInit() interfaces return TCL_ERROR.
+*/
+EXTERN int Sqlite3_SafeInit(Tcl_Interp *interp){ return TCL_ERROR; }
+EXTERN int Sqlite3_SafeUnload(Tcl_Interp *interp, int flags){return TCL_ERROR;}
+
+
+
+#ifndef SQLITE_3_SUFFIX_ONLY
+int Sqlite_Init(Tcl_Interp *interp){ return Sqlite3_Init(interp); }
+int Tclsqlite_Init(Tcl_Interp *interp){ return Sqlite3_Init(interp); }
+int Sqlite_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+int Tclsqlite_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+#endif
+
+/*
+** If the TCLSH macro is defined, add code to make a stand-alone program.
+*/
+#if defined(TCLSH)
+
+/* This is the main routine for an ordinary TCL shell.  If there are
+** are arguments, run the first argument as a script.  Otherwise,
+** read TCL commands from standard input
+*/
+static const char *tclsh_main_loop(void){
+  static const char zMainloop[] =
+    "if {[llength $argv]>=1} {\n"
+      "set argv0 [lindex $argv 0]\n"
+      "set argv [lrange $argv 1 end]\n"
+      "source $argv0\n"
+    "} else {\n"
+      "set line {}\n"
+      "while {![eof stdin]} {\n"
+        "if {$line!=\"\"} {\n"
+          "puts -nonewline \"> \"\n"
+        "} else {\n"
+          "puts -nonewline \"% \"\n"
+        "}\n"
+        "flush stdout\n"
+        "append line [gets stdin]\n"
+        "if {[info complete $line]} {\n"
+          "if {[catch {uplevel #0 $line} result]} {\n"
+            "puts stderr \"Error: $result\"\n"
+          "} elseif {$result!=\"\"} {\n"
+            "puts $result\n"
+          "}\n"
+          "set line {}\n"
+        "} else {\n"
+          "append line \\n\n"
+        "}\n"
+      "}\n"
+    "}\n"
+  ;
+  return zMainloop;
+}
+
+#ifndef TCLSH_MAIN
+# define TCLSH_MAIN main
+#endif
+int SQLITE_CDECL TCLSH_MAIN(int argc, char **argv){
+  Tcl_Interp *interp;
+  int i;
+  const char *zScript = 0;
+  char zArgc[32];
+#if defined(TCLSH_INIT_PROC)
+  extern const char *TCLSH_INIT_PROC(Tcl_Interp*);
+#endif
+
+#if !defined(_WIN32_WCE)
+  if( getenv("SQLITE_DEBUG_BREAK") ){
+    if( isatty(0) && isatty(2) ){
+      fprintf(stderr,
+          "attach debugger to process %d and press any key to continue.\n",
+          GETPID());
+      fgetc(stdin);
+    }else{
+#if defined(_WIN32) || defined(WIN32)
+      DebugBreak();
+#elif defined(SIGTRAP)
+      raise(SIGTRAP);
+#endif
+    }
+  }
+#endif
+
+  /* Call sqlite3_shutdown() once before doing anything else. This is to
+  ** test that sqlite3_shutdown() can be safely called by a process before
+  ** sqlite3_initialize() is. */
+  sqlite3_shutdown();
+
+  Tcl_FindExecutable(argv[0]);
+  Tcl_SetSystemEncoding(NULL, "utf-8");
+  interp = Tcl_CreateInterp();
+  Sqlite3_Init(interp);
+
+  sqlite3_snprintf(sizeof(zArgc), zArgc, "%d", argc-1);
+  Tcl_SetVar(interp,"argc", zArgc, TCL_GLOBAL_ONLY);
+  Tcl_SetVar(interp,"argv0",argv[0],TCL_GLOBAL_ONLY);
+  Tcl_SetVar(interp,"argv", "", TCL_GLOBAL_ONLY);
+  for(i=1; i<argc; i++){
+    Tcl_SetVar(interp, "argv", argv[i],
+        TCL_GLOBAL_ONLY | TCL_LIST_ELEMENT | TCL_APPEND_VALUE);
+  }
+#if defined(TCLSH_INIT_PROC)
+  zScript = TCLSH_INIT_PROC(interp);
+#endif
+  if( zScript==0 ){
+    zScript = tclsh_main_loop();
+  }
+  if( Tcl_GlobalEval(interp, zScript)!=TCL_OK ){
+    const char *zInfo = Tcl_GetVar(interp, "errorInfo", TCL_GLOBAL_ONLY);
+    if( zInfo==0 ) zInfo = Tcl_GetStringResult(interp);
+    fprintf(stderr,"%s: %s\n", *argv, zInfo);
+    return 1;
+  }
+  return 0;
+}
+#endif /* TCLSH */
diff --git a/src/test1.c b/src/test1.c
new file mode 100644
index 0000000..9c28259
--- /dev/null
+++ b/src/test1.c
@@ -0,0 +1,9373 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#if SQLITE_OS_WIN
+#  include "os_win.h"
+#  include <windows.h>
+#else
+#  include <unistd.h>
+#  if defined(__APPLE__)
+#    include <sys/param.h>
+#    include <sys/sysctl.h>
+#  endif
+#endif
+
+#include "vdbeInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** This is a copy of the first part of the SqliteDb structure in 
+** tclsqlite.c.  We need it here so that the get_sqlite_pointer routine
+** can extract the sqlite3* pointer from an existing Tcl SQLite
+** connection.
+*/
+struct SqliteDb {
+  sqlite3 *db;
+};
+
+/*
+** Convert text generated by the "%p" conversion format back into
+** a pointer.
+*/
+static int testHexToInt(int h){
+  if( h>='0' && h<='9' ){
+    return h - '0';
+  }else if( h>='a' && h<='f' ){
+    return h - 'a' + 10;
+  }else{
+    assert( h>='A' && h<='F' );
+    return h - 'A' + 10;
+  }
+}
+void *sqlite3TestTextToPtr(const char *z){
+  void *p;
+  u64 v;
+  u32 v2;
+  if( z[0]=='0' && z[1]=='x' ){
+    z += 2;
+  }
+  v = 0;
+  while( *z ){
+    v = (v<<4) + testHexToInt(*z);
+    z++;
+  }
+  if( sizeof(p)==sizeof(v) ){
+    memcpy(&p, &v, sizeof(p));
+  }else{
+    assert( sizeof(p)==sizeof(v2) );
+    v2 = (u32)v;
+    memcpy(&p, &v2, sizeof(p));
+  }
+  return p;
+}
+
+
+/*
+** A TCL command that returns the address of the sqlite* pointer
+** for an sqlite connection instance.  Bad things happen if the
+** input is not an sqlite connection.
+*/
+static int SQLITE_TCLAPI get_sqlite_pointer(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SqliteDb *p;
+  Tcl_CmdInfo cmdInfo;
+  char zBuf[100];
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SQLITE-CONNECTION");
+    return TCL_ERROR;
+  }
+  if( !Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ",
+           Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  p = (struct SqliteDb*)cmdInfo.objClientData;
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%p", p->db);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb){
+  struct SqliteDb *p;
+  Tcl_CmdInfo cmdInfo;
+  if( Tcl_GetCommandInfo(interp, zA, &cmdInfo) ){
+    p = (struct SqliteDb*)cmdInfo.objClientData;
+    *ppDb = p->db;
+  }else{
+    *ppDb = (sqlite3*)sqlite3TestTextToPtr(zA);
+  }
+  return TCL_OK;
+}
+
+#if SQLITE_OS_WIN
+/*
+** Decode a Win32 HANDLE object.
+*/
+int getWin32Handle(Tcl_Interp *interp, const char *zA, LPHANDLE phFile){
+  *phFile = (HANDLE)sqlite3TestTextToPtr(zA);
+  return TCL_OK;
+}
+#endif
+
+extern const char *sqlite3ErrName(int);
+#define t1ErrorName sqlite3ErrName
+
+/*
+** Convert an sqlite3_stmt* into an sqlite3*.  This depends on the
+** fact that the sqlite3* is the first field in the Vdbe structure.
+*/
+#define StmtToDb(X)   sqlite3_db_handle(X)
+
+/*
+** Check a return value to make sure it agrees with the results
+** from sqlite3_errcode.
+*/
+int sqlite3TestErrCode(Tcl_Interp *interp, sqlite3 *db, int rc){
+  if( sqlite3_threadsafe()==0 && rc!=SQLITE_MISUSE && rc!=SQLITE_OK
+   && sqlite3_errcode(db)!=rc ){
+    char zBuf[200];
+    int r2 = sqlite3_errcode(db);
+    sqlite3_snprintf(sizeof(zBuf), zBuf,
+       "error code %s (%d) does not match sqlite3_errcode %s (%d)",
+       t1ErrorName(rc), rc, t1ErrorName(r2), r2);
+    Tcl_ResetResult(interp);
+    Tcl_AppendResult(interp, zBuf, 0);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Decode a pointer to an sqlite3_stmt object.
+*/
+static int getStmtPointer(
+  Tcl_Interp *interp, 
+  const char *zArg,  
+  sqlite3_stmt **ppStmt
+){
+  *ppStmt = (sqlite3_stmt*)sqlite3TestTextToPtr(zArg);
+  return TCL_OK;
+}
+
+/*
+** Generate a text representation of a pointer that can be understood
+** by the getDbPointer and getVmPointer routines above.
+**
+** The problem is, on some machines (Solaris) if you do a printf with
+** "%p" you cannot turn around and do a scanf with the same "%p" and
+** get your pointer back.  You have to prepend a "0x" before it will
+** work.  Or at least that is what is reported to me (drh).  But this
+** behavior varies from machine to machine.  The solution used her is
+** to test the string right after it is generated to see if it can be
+** understood by scanf, and if not, try prepending an "0x" to see if
+** that helps.  If nothing works, a fatal error is generated.
+*/
+int sqlite3TestMakePointerStr(Tcl_Interp *interp, char *zPtr, void *p){
+  sqlite3_snprintf(100, zPtr, "%p", p);
+  return TCL_OK;
+}
+
+/*
+** The callback routine for sqlite3_exec_printf().
+*/
+static int exec_printf_cb(void *pArg, int argc, char **argv, char **name){
+  Tcl_DString *str = (Tcl_DString*)pArg;
+  int i;
+
+  if( Tcl_DStringLength(str)==0 ){
+    for(i=0; i<argc; i++){
+      Tcl_DStringAppendElement(str, name[i] ? name[i] : "NULL");
+    }
+  }
+  for(i=0; i<argc; i++){
+    Tcl_DStringAppendElement(str, argv[i] ? argv[i] : "NULL");
+  }
+  return 0;
+}
+
+/*
+** The I/O tracing callback.
+*/
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+static FILE *iotrace_file = 0;
+static void io_trace_callback(const char *zFormat, ...){
+  va_list ap;
+  va_start(ap, zFormat);
+  vfprintf(iotrace_file, zFormat, ap);
+  va_end(ap);
+  fflush(iotrace_file);
+}
+#endif
+
+/*
+** Usage:  io_trace FILENAME
+**
+** Turn I/O tracing on or off.  If FILENAME is not an empty string,
+** I/O tracing begins going into FILENAME. If FILENAME is an empty
+** string, I/O tracing is turned off.
+*/
+static int SQLITE_TCLAPI test_io_trace(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+          " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( iotrace_file ){
+    if( iotrace_file!=stdout && iotrace_file!=stderr ){
+      fclose(iotrace_file);
+    }
+    iotrace_file = 0;
+    sqlite3IoTrace = 0;
+  }
+  if( argv[1][0] ){
+    if( strcmp(argv[1],"stdout")==0 ){
+      iotrace_file = stdout;
+    }else if( strcmp(argv[1],"stderr")==0 ){
+      iotrace_file = stderr;
+    }else{
+      iotrace_file = fopen(argv[1], "w");
+    }
+    sqlite3IoTrace = io_trace_callback;
+  }
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  clang_sanitize_address 
+**
+** Returns true if the program was compiled using clang with the 
+** -fsanitize=address switch on the command line. False otherwise.
+**
+** Also return true if the OMIT_MISUSE environment variable exists.
+*/
+static int SQLITE_TCLAPI clang_sanitize_address(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int res = 0;
+#if defined(__has_feature)
+# if __has_feature(address_sanitizer)
+  res = 1;
+# endif
+#endif
+#ifdef __SANITIZE_ADDRESS__
+  res = 1;
+#endif
+  if( res==0 && getenv("OMIT_MISUSE")!=0 ) res = 1;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
+  return TCL_OK;
+}
+  
+/*
+** Usage:  sqlite3_exec_printf  DB  FORMAT  STRING
+**
+** Invoke the sqlite3_exec_printf() interface using the open database
+** DB.  The SQL is the string FORMAT.  The format string should contain
+** one %s or %q.  STRING is the value inserted into %s or %q.
+*/
+static int SQLITE_TCLAPI test_exec_printf(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc;
+  char *zErr = 0;
+  char *zSql;
+  char zBuf[30];
+  if( argc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB FORMAT STRING", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  Tcl_DStringInit(&str);
+  zSql = sqlite3_mprintf(argv[2], argv[3]);
+  rc = sqlite3_exec(db, zSql, exec_printf_cb, &str, &zErr);
+  sqlite3_free(zSql);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
+  Tcl_DStringFree(&str);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_exec_hex  DB  HEX
+**
+** Invoke the sqlite3_exec() on a string that is obtained by translating
+** HEX into ASCII.  Most characters are translated as is.  %HH becomes
+** a hex character.
+*/
+static int SQLITE_TCLAPI test_exec_hex(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc, i, j;
+  char *zErr = 0;
+  char *zHex;
+  char zSql[501];
+  char zBuf[30];
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB HEX", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  zHex = argv[2];
+  for(i=j=0; i<(sizeof(zSql)-1) && zHex[j]; i++, j++){
+    if( zHex[j]=='%' && zHex[j+2] && zHex[j+2] ){
+      zSql[i] = (testHexToInt(zHex[j+1])<<4) + testHexToInt(zHex[j+2]);
+      j += 2;
+    }else{
+      zSql[i] = zHex[j];
+    }
+  }
+  zSql[i] = 0;
+  Tcl_DStringInit(&str);
+  rc = sqlite3_exec(db, zSql, exec_printf_cb, &str, &zErr);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
+  Tcl_DStringFree(&str);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  db_enter DB
+**         db_leave DB
+**
+** Enter or leave the mutex on a database connection.
+*/
+static int SQLITE_TCLAPI db_enter(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_mutex_enter(db->mutex);
+  return TCL_OK;
+}
+static int SQLITE_TCLAPI db_leave(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_mutex_leave(db->mutex);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_exec  DB  SQL
+**
+** Invoke the sqlite3_exec interface using the open database DB
+*/
+static int SQLITE_TCLAPI test_exec(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc;
+  char *zErr = 0;
+  char *zSql;
+  int i, j;
+  char zBuf[30];
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB SQL", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  Tcl_DStringInit(&str);
+  zSql = sqlite3_mprintf("%s", argv[2]);
+  for(i=j=0; zSql[i];){
+    if( zSql[i]=='%' ){
+      zSql[j++] = (testHexToInt(zSql[i+1])<<4) + testHexToInt(zSql[i+2]);
+      i += 3;
+    }else{
+      zSql[j++] = zSql[i++];
+    }
+  }
+  zSql[j] = 0;
+  rc = sqlite3_exec(db, zSql, exec_printf_cb, &str, &zErr);
+  sqlite3_free(zSql);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
+  Tcl_DStringFree(&str);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_exec_nr  DB  SQL
+**
+** Invoke the sqlite3_exec interface using the open database DB.  Discard
+** all results
+*/
+static int SQLITE_TCLAPI test_exec_nr(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  char *zErr = 0;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB SQL", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_z_test  SEPARATOR  ARG0  ARG1 ...
+**
+** Test the %z format of sqlite_mprintf().  Use multiple mprintf() calls to 
+** concatenate arg0 through argn using separator as the separator.
+** Return the result.
+*/
+static int SQLITE_TCLAPI test_mprintf_z(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *zResult = 0;
+  int i;
+
+  for(i=2; i<argc && (i==2 || zResult); i++){
+    zResult = sqlite3_mprintf("%z%s%s", zResult, argv[1], argv[i]);
+  }
+  Tcl_AppendResult(interp, zResult, 0);
+  sqlite3_free(zResult);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_n_test  STRING
+**
+** Test the %n format of sqlite_mprintf().  Return the length of the
+** input string.
+*/
+static int SQLITE_TCLAPI test_mprintf_n(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *zStr;
+  int n = 0;
+  zStr = sqlite3_mprintf("%s%n", argv[1], &n);
+  sqlite3_free(zStr);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(n));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_snprintf_int  SIZE FORMAT  INT
+**
+** Test the of sqlite3_snprintf() routine.  SIZE is the size of the
+** output buffer in bytes.  The maximum size is 100.  FORMAT is the
+** format string.  INT is a single integer argument.  The FORMAT
+** string must require no more than this one integer argument.  If
+** You pass in a format string that requires more than one argument,
+** bad things will happen.
+*/
+static int SQLITE_TCLAPI test_snprintf_int(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char zStr[100];
+  int n = atoi(argv[1]);
+  const char *zFormat = argv[2];
+  int a1 = atoi(argv[3]);
+  if( n>sizeof(zStr) ) n = sizeof(zStr);
+  sqlite3_snprintf(sizeof(zStr), zStr, "abcdefghijklmnopqrstuvwxyz");
+  sqlite3_snprintf(n, zStr, zFormat, a1);
+  Tcl_AppendResult(interp, zStr, 0);
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_GET_TABLE
+
+/*
+** Usage:  sqlite3_get_table_printf  DB  FORMAT  STRING  ?--no-counts?
+**
+** Invoke the sqlite3_get_table_printf() interface using the open database
+** DB.  The SQL is the string FORMAT.  The format string should contain
+** one %s or %q.  STRING is the value inserted into %s or %q.
+*/
+static int SQLITE_TCLAPI test_get_table_printf(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc;
+  char *zErr = 0;
+  int nRow = 0, nCol = 0;
+  char **aResult;
+  int i;
+  char zBuf[30];
+  char *zSql;
+  int resCount = -1;
+  if( argc==5 ){
+    if( Tcl_GetInt(interp, argv[4], &resCount) ) return TCL_ERROR;
+  }
+  if( argc!=4 && argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB FORMAT STRING ?COUNT?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  Tcl_DStringInit(&str);
+  zSql = sqlite3_mprintf(argv[2],argv[3]);
+  if( argc==5 ){
+    rc = sqlite3_get_table(db, zSql, &aResult, 0, 0, &zErr);
+  }else{
+    rc = sqlite3_get_table(db, zSql, &aResult, &nRow, &nCol, &zErr);
+    resCount = (nRow+1)*nCol;
+  }
+  sqlite3_free(zSql);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  if( rc==SQLITE_OK ){
+    if( argc==4 ){
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", nRow);
+      Tcl_AppendElement(interp, zBuf);
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", nCol);
+      Tcl_AppendElement(interp, zBuf);
+    }
+    for(i=0; i<resCount; i++){
+      Tcl_AppendElement(interp, aResult[i] ? aResult[i] : "NULL");
+    }
+  }else{
+    Tcl_AppendElement(interp, zErr);
+  }
+  sqlite3_free_table(aResult);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+#endif /* SQLITE_OMIT_GET_TABLE */
+
+
+/*
+** Usage:  sqlite3_last_insert_rowid DB
+**
+** Returns the integer ROWID of the most recent insert.
+*/
+static int SQLITE_TCLAPI test_last_rowid(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  char zBuf[30];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], " DB\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%lld", sqlite3_last_insert_rowid(db));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:  sqlite3_key DB KEY
+**
+** Set the codec key.
+*/
+static int SQLITE_TCLAPI test_key(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_rekey DB KEY
+**
+** Change the codec key.
+*/
+static int SQLITE_TCLAPI test_rekey(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_close DB
+**
+** Closes the database opened by sqlite3_open.
+*/
+static int SQLITE_TCLAPI sqlite_test_close(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_close(db);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_close_v2 DB
+**
+** Closes the database opened by sqlite3_open.
+*/
+static int SQLITE_TCLAPI sqlite_test_close_v2(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_close_v2(db);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Implementation of the x_coalesce() function.
+** Return the first argument non-NULL argument.
+*/
+static void t1_ifnullFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+  for(i=0; i<argc; i++){
+    if( SQLITE_NULL!=sqlite3_value_type(argv[i]) ){
+      int n = sqlite3_value_bytes(argv[i]);
+      sqlite3_result_text(context, (char*)sqlite3_value_text(argv[i]),
+          n, SQLITE_TRANSIENT);
+      break;
+    }
+  }
+}
+
+/*
+** These are test functions.    hex8() interprets its argument as
+** UTF8 and returns a hex encoding.  hex16le() interprets its argument
+** as UTF16le and returns a hex encoding.
+*/
+static void hex8Func(sqlite3_context *p, int argc, sqlite3_value **argv){
+  const unsigned char *z;
+  int i;
+  char zBuf[200];
+  z = sqlite3_value_text(argv[0]);
+  for(i=0; i<sizeof(zBuf)/2 - 2 && z[i]; i++){
+    sqlite3_snprintf(sizeof(zBuf)-i*2, &zBuf[i*2], "%02x", z[i]);
+  }
+  zBuf[i*2] = 0;
+  sqlite3_result_text(p, (char*)zBuf, -1, SQLITE_TRANSIENT);
+}
+#ifndef SQLITE_OMIT_UTF16
+static void hex16Func(sqlite3_context *p, int argc, sqlite3_value **argv){
+  const unsigned short int *z;
+  int i;
+  char zBuf[400];
+  z = sqlite3_value_text16(argv[0]);
+  for(i=0; i<sizeof(zBuf)/4 - 4 && z[i]; i++){
+    sqlite3_snprintf(sizeof(zBuf)-i*4, &zBuf[i*4],"%04x", z[i]&0xff);
+  }
+  zBuf[i*4] = 0;
+  sqlite3_result_text(p, (char*)zBuf, -1, SQLITE_TRANSIENT);
+}
+#endif
+
+/*
+** A structure into which to accumulate text.
+*/
+struct dstr {
+  int nAlloc;  /* Space allocated */
+  int nUsed;   /* Space used */
+  char *z;     /* The space */
+};
+
+/*
+** Append text to a dstr
+*/
+static void dstrAppend(struct dstr *p, const char *z, int divider){
+  int n = (int)strlen(z);
+  if( p->nUsed + n + 2 > p->nAlloc ){
+    char *zNew;
+    p->nAlloc = p->nAlloc*2 + n + 200;
+    zNew = sqlite3_realloc(p->z, p->nAlloc);
+    if( zNew==0 ){
+      sqlite3_free(p->z);
+      memset(p, 0, sizeof(*p));
+      return;
+    }
+    p->z = zNew;
+  }
+  if( divider && p->nUsed>0 ){
+    p->z[p->nUsed++] = divider;
+  }
+  memcpy(&p->z[p->nUsed], z, n+1);
+  p->nUsed += n;
+}
+
+/*
+** Invoked for each callback from sqlite3ExecFunc
+*/
+static int execFuncCallback(void *pData, int argc, char **argv, char **NotUsed){
+  struct dstr *p = (struct dstr*)pData;
+  int i;
+  for(i=0; i<argc; i++){
+    if( argv[i]==0 ){
+      dstrAppend(p, "NULL", ' ');
+    }else{
+      dstrAppend(p, argv[i], ' ');
+    }
+  }
+  return 0;
+}
+
+/*
+** Implementation of the x_sqlite_exec() function.  This function takes
+** a single argument and attempts to execute that argument as SQL code.
+** This is illegal and should set the SQLITE_MISUSE flag on the database.
+**
+** 2004-Jan-07:  We have changed this to make it legal to call sqlite3_exec()
+** from within a function call.  
+** 
+** This routine simulates the effect of having two threads attempt to
+** use the same database at the same time.
+*/
+static void sqlite3ExecFunc(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  struct dstr x;
+  memset(&x, 0, sizeof(x));
+  (void)sqlite3_exec((sqlite3*)sqlite3_user_data(context),
+      (char*)sqlite3_value_text(argv[0]),
+      execFuncCallback, &x, 0);
+  sqlite3_result_text(context, x.z, x.nUsed, SQLITE_TRANSIENT);
+  sqlite3_free(x.z);
+}
+
+/*
+** Implementation of tkt2213func(), a scalar function that takes exactly
+** one argument. It has two interesting features:
+**
+** * It calls sqlite3_value_text() 3 times on the argument sqlite3_value*.
+**   If the three pointers returned are not the same an SQL error is raised.
+**
+** * Otherwise it returns a copy of the text representation of its 
+**   argument in such a way as the VDBE representation is a Mem* cell 
+**   with the MEM_Term flag clear. 
+**
+** Ticket #2213 can therefore be tested by evaluating the following
+** SQL expression:
+**
+**   tkt2213func(tkt2213func('a string'));
+*/
+static void tkt2213Function(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  int nText;
+  unsigned char const *zText1;
+  unsigned char const *zText2;
+  unsigned char const *zText3;
+
+  nText = sqlite3_value_bytes(argv[0]);
+  zText1 = sqlite3_value_text(argv[0]);
+  zText2 = sqlite3_value_text(argv[0]);
+  zText3 = sqlite3_value_text(argv[0]);
+
+  if( zText1!=zText2 || zText2!=zText3 ){
+    sqlite3_result_error(context, "tkt2213 is not fixed", -1);
+  }else{
+    char *zCopy = (char *)sqlite3_malloc(nText);
+    memcpy(zCopy, zText1, nText);
+    sqlite3_result_text(context, zCopy, nText, sqlite3_free);
+  }
+}
+
+/*
+** The following SQL function takes 4 arguments.  The 2nd and
+** 4th argument must be one of these strings:  'text', 'text16',
+** or 'blob' corresponding to API functions
+**
+**      sqlite3_value_text()
+**      sqlite3_value_text16()
+**      sqlite3_value_blob()
+**
+** The third argument is a string, either 'bytes' or 'bytes16' or 'noop',
+** corresponding to APIs:
+**
+**      sqlite3_value_bytes()
+**      sqlite3_value_bytes16()
+**      noop
+**
+** The APIs designated by the 2nd through 4th arguments are applied
+** to the first argument in order.  If the pointers returned by the
+** second and fourth are different, this routine returns 1.  Otherwise,
+** this routine returns 0.
+**
+** This function is used to test to see when returned pointers from
+** the _text(), _text16() and _blob() APIs become invalidated.
+*/
+static void ptrChngFunction(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  const void *p1, *p2;
+  const char *zCmd;
+  if( argc!=4 ) return;
+  zCmd = (const char*)sqlite3_value_text(argv[1]);
+  if( zCmd==0 ) return;
+  if( strcmp(zCmd,"text")==0 ){
+    p1 = (const void*)sqlite3_value_text(argv[0]);
+#ifndef SQLITE_OMIT_UTF16
+  }else if( strcmp(zCmd, "text16")==0 ){
+    p1 = (const void*)sqlite3_value_text16(argv[0]);
+#endif
+  }else if( strcmp(zCmd, "blob")==0 ){
+    p1 = (const void*)sqlite3_value_blob(argv[0]);
+  }else{
+    return;
+  }
+  zCmd = (const char*)sqlite3_value_text(argv[2]);
+  if( zCmd==0 ) return;
+  if( strcmp(zCmd,"bytes")==0 ){
+    sqlite3_value_bytes(argv[0]);
+#ifndef SQLITE_OMIT_UTF16
+  }else if( strcmp(zCmd, "bytes16")==0 ){
+    sqlite3_value_bytes16(argv[0]);
+#endif
+  }else if( strcmp(zCmd, "noop")==0 ){
+    /* do nothing */
+  }else{
+    return;
+  }
+  zCmd = (const char*)sqlite3_value_text(argv[3]);
+  if( zCmd==0 ) return;
+  if( strcmp(zCmd,"text")==0 ){
+    p2 = (const void*)sqlite3_value_text(argv[0]);
+#ifndef SQLITE_OMIT_UTF16
+  }else if( strcmp(zCmd, "text16")==0 ){
+    p2 = (const void*)sqlite3_value_text16(argv[0]);
+#endif
+  }else if( strcmp(zCmd, "blob")==0 ){
+    p2 = (const void*)sqlite3_value_blob(argv[0]);
+  }else{
+    return;
+  }
+  sqlite3_result_int(context, p1!=p2);
+}
+
+/*
+** This SQL function returns a different answer each time it is called, even if
+** the arguments are the same.
+*/
+static void nondeterministicFunction(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  static int cnt = 0;
+  sqlite3_result_int(context, cnt++);
+}
+
+/*
+** This SQL function returns the integer value of its argument as a MEM_IntReal
+** value.
+*/
+static void intrealFunction(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  sqlite3_int64 v = sqlite3_value_int64(argv[0]);
+  sqlite3_result_int64(context, v);
+  sqlite3_test_control(SQLITE_TESTCTRL_RESULT_INTREAL, context);
+}
+
+/*
+** SQL function:  strtod(X)
+**
+** Use the C-library strtod() function to convert string X into a double.
+** Used for comparing the accuracy of SQLite's internal text-to-float conversion
+** routines against the C-library.
+*/
+static void shellStrtod(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  char *z = (char*)sqlite3_value_text(apVal[0]);
+  UNUSED_PARAMETER(nVal);
+  if( z==0 ) return;
+  sqlite3_result_double(pCtx, strtod(z,0));
+}
+
+/*
+** SQL function:  dtostr(X)
+**
+** Use the C-library printf() function to convert real value X into a string.
+** Used for comparing the accuracy of SQLite's internal float-to-text conversion
+** routines against the C-library.
+*/
+static void shellDtostr(
+  sqlite3_context *pCtx,
+  int nVal,
+  sqlite3_value **apVal
+){
+  double r = sqlite3_value_double(apVal[0]);
+  int n = nVal>=2 ? sqlite3_value_int(apVal[1]) : 26;
+  char z[400];
+  if( n<1 ) n = 1;
+  if( n>350 ) n = 350;
+  sprintf(z, "%#+.*e", n, r);
+  sqlite3_result_text(pCtx, z, -1, SQLITE_TRANSIENT);
+}
+
+
+/*
+** Usage:  sqlite3_create_function DB
+**
+** Call the sqlite3_create_function API on the given database in order
+** to create a function named "x_coalesce".  This function does the same thing
+** as the "coalesce" function.  This function also registers an SQL function
+** named "x_sqlite_exec" that invokes sqlite3_exec().  Invoking sqlite3_exec()
+** in this way is illegal recursion and should raise an SQLITE_MISUSE error.
+** The effect is similar to trying to use the same database connection from
+** two threads at the same time.
+**
+** The original motivation for this routine was to be able to call the
+** sqlite3_create_function function while a query is in progress in order
+** to test the SQLITE_MISUSE detection logic.
+*/
+static int SQLITE_TCLAPI test_create_function(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int rc;
+  sqlite3 *db;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " DB\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, "x_coalesce", -1, SQLITE_UTF8, 0, 
+        t1_ifnullFunc, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "hex8", 1, SQLITE_UTF8 | SQLITE_DETERMINISTIC,
+          0, hex8Func, 0, 0);
+  }
+#ifndef SQLITE_OMIT_UTF16
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "hex16", 1, SQLITE_UTF16 | SQLITE_DETERMINISTIC,
+          0, hex16Func, 0, 0);
+  }
+#endif
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "tkt2213func", 1, SQLITE_ANY, 0, 
+          tkt2213Function, 0, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "pointer_change", 4, SQLITE_ANY, 0, 
+          ptrChngFunction, 0, 0);
+  }
+
+  /* Functions counter1() and counter2() have the same implementation - they
+  ** both return an ascending integer with each call.  But counter1() is marked
+  ** as non-deterministic and counter2() is marked as deterministic.
+  */
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "counter1", -1, SQLITE_UTF8,
+          0, nondeterministicFunction, 0, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "counter2", -1, SQLITE_UTF8|SQLITE_DETERMINISTIC,
+          0, nondeterministicFunction, 0, 0);
+  }
+
+  /* The intreal() function converts its argument to an integer and returns
+  ** it as a MEM_IntReal.
+  */
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "intreal", 1, SQLITE_UTF8,
+          0, intrealFunction, 0, 0);
+  }
+
+  /* Functions strtod() and dtostr() work as in the shell.  These routines
+  ** use the standard C library to convert between floating point and
+  ** text.  This is used to compare SQLite's internal conversion routines
+  ** against the standard library conversion routines.
+  **
+  ** Both routines copy/pasted from the shell.c.in implementation
+  ** on 2023-07-03.
+  */
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "strtod", 1, SQLITE_UTF8, 0,
+                                 shellStrtod, 0, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "dtostr", 1, SQLITE_UTF8, 0,
+                                 shellDtostr, 0, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "dtostr", 2, SQLITE_UTF8, 0,
+                                 shellDtostr, 0, 0);
+  }
+
+#ifndef SQLITE_OMIT_UTF16
+  /* Use the sqlite3_create_function16() API here. Mainly for fun, but also 
+  ** because it is not tested anywhere else. */
+  if( rc==SQLITE_OK ){
+    const void *zUtf16;
+    sqlite3_value *pVal;
+    sqlite3_mutex_enter(db->mutex);
+    pVal = sqlite3ValueNew(db);
+    sqlite3ValueSetStr(pVal, -1, "x_sqlite_exec", SQLITE_UTF8, SQLITE_STATIC);
+    zUtf16 = sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);
+    if( db->mallocFailed ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_create_function16(db, zUtf16, 
+                1, SQLITE_UTF16, db, sqlite3ExecFunc, 0, 0);
+    }
+    sqlite3ValueFree(pVal);
+    sqlite3_mutex_leave(db->mutex);
+  }
+#endif
+
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_drop_modules DB ?NAME ...?
+**
+** Invoke the sqlite3_drop_modules(D,L) interface on database
+** connection DB, in order to drop all modules except those named in
+** the argument.
+*/
+static int SQLITE_TCLAPI test_drop_modules(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+
+  if( argc<2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " DB\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_drop_modules(db, argc>2 ? (const char**)(argv+2) : 0);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Routines to implement the x_count() aggregate function.
+**
+** x_count() counts the number of non-null arguments.  But there are
+** some twists for testing purposes.
+**
+** If the argument to x_count() is 40 then a UTF-8 error is reported
+** on the step function.  If x_count(41) is seen, then a UTF-16 error
+** is reported on the step function.  If the total count is 42, then
+** a UTF-8 error is reported on the finalize function.
+*/
+typedef struct t1CountCtx t1CountCtx;
+struct t1CountCtx {
+  int n;
+};
+static void t1CountStep(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  t1CountCtx *p;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( (argc==0 || SQLITE_NULL!=sqlite3_value_type(argv[0]) ) && p ){
+    p->n++;
+  }
+  if( argc>0 ){
+    int v = sqlite3_value_int(argv[0]);
+    if( v==40 ){
+      sqlite3_result_error(context, "value of 40 handed to x_count", -1);
+#ifndef SQLITE_OMIT_UTF16
+    }else if( v==41 ){
+      const char zUtf16ErrMsg[] = { 0, 0x61, 0, 0x62, 0, 0x63, 0, 0, 0};
+      sqlite3_result_error16(context, &zUtf16ErrMsg[1-SQLITE_BIGENDIAN], -1);
+#endif
+    }
+  }
+}   
+static void t1CountFinalize(sqlite3_context *context){
+  t1CountCtx *p;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( p ){
+    if( p->n==42 ){
+      sqlite3_result_error(context, "x_count totals to 42", -1);
+    }else{
+      sqlite3_result_int(context, p ? p->n : 0);
+    }
+  }
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+static void legacyCountStep(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  /* no-op */
+}
+
+static void legacyCountFinalize(sqlite3_context *context){
+  sqlite3_result_int(context, sqlite3_aggregate_count(context));
+}
+#endif
+
+/*
+** Usage:  sqlite3_create_aggregate DB
+**
+** Call the sqlite3_create_function API on the given database in order
+** to create a function named "x_count".  This function is similar
+** to the built-in count() function, with a few special quirks
+** for testing the sqlite3_result_error() APIs.
+**
+** The original motivation for this routine was to be able to call the
+** sqlite3_create_aggregate function while a query is in progress in order
+** to test the SQLITE_MISUSE detection logic.  See misuse.test.
+**
+** This routine was later extended to test the use of sqlite3_result_error()
+** within aggregate functions.
+**
+** Later: It is now also extended to register the aggregate function
+** "legacy_count()" with the supplied database handle. This is used
+** to test the deprecated sqlite3_aggregate_count() API.
+*/
+static int SQLITE_TCLAPI test_create_aggregate(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, "x_count", 0, SQLITE_UTF8, 0, 0,
+      t1CountStep,t1CountFinalize);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "x_count", 1, SQLITE_UTF8, 0, 0,
+        t1CountStep,t1CountFinalize);
+  }
+#ifndef SQLITE_OMIT_DEPRECATED
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "legacy_count", 0, SQLITE_ANY, 0, 0,
+        legacyCountStep, legacyCountFinalize
+    );
+  }
+#endif
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:  printf TEXT
+**
+** Send output to printf.  Use this rather than puts to merge the output
+** in the correct sequence with debugging printfs inserted into C code.
+** Puts uses a separate buffer and debugging statements will be out of
+** sequence if it is used.
+*/
+static int SQLITE_TCLAPI test_printf(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " TEXT\"", 0);
+    return TCL_ERROR;
+  }
+  printf("%s\n", argv[1]);
+  return TCL_OK;
+}
+
+
+
+/*
+** Usage:  sqlite3_mprintf_int FORMAT INTEGER INTEGER INTEGER
+**
+** Call mprintf with three integer arguments
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_int(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT INT\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<5; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-2]) ) return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], a[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_int64 FORMAT INTEGER INTEGER INTEGER
+**
+** Call mprintf with three 64-bit integer arguments
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_int64(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int i;
+  sqlite_int64 a[3];
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT INT\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<5; i++){
+    if( sqlite3Atoi64(argv[i], &a[i-2], sqlite3Strlen30(argv[i]), SQLITE_UTF8) ){
+      Tcl_AppendResult(interp, "argument is not a valid 64-bit integer", 0);
+      return TCL_ERROR;
+    }
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], a[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_long FORMAT INTEGER INTEGER INTEGER
+**
+** Call mprintf with three long integer arguments.   This might be the
+** same as sqlite3_mprintf_int or sqlite3_mprintf_int64, depending on
+** platform.
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_long(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int i;
+  long int a[3];
+  int b[3];
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT INT\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<5; i++){
+    if( Tcl_GetInt(interp, argv[i], &b[i-2]) ) return TCL_ERROR;
+    a[i-2] = (long int)b[i-2];
+    a[i-2] &= (((u64)1)<<(sizeof(int)*8))-1;
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], a[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_str FORMAT INTEGER INTEGER STRING
+**
+** Call mprintf with two integer arguments and one string argument
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_str(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  char *z;
+  if( argc<4 || argc>5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT ?STRING?\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<4; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-2]) ) return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], argc>4 ? argv[4] : NULL);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_snprintf_str INTEGER FORMAT INTEGER INTEGER STRING
+**
+** Call mprintf with two integer arguments and one string argument
+*/
+static int SQLITE_TCLAPI sqlite3_snprintf_str(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  int n;
+  char *z;
+  if( argc<5 || argc>6 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " INT FORMAT INT INT ?STRING?\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], &n) ) return TCL_ERROR;
+  if( n<0 ){
+    Tcl_AppendResult(interp, "N must be non-negative", 0);
+    return TCL_ERROR;
+  }
+  for(i=3; i<5; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-3]) ) return TCL_ERROR;
+  }
+  z = sqlite3_malloc( n+1 );
+  sqlite3_snprintf(n, z, argv[2], a[0], a[1], argc>4 ? argv[5] : NULL);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_double FORMAT INTEGER INTEGER DOUBLE
+**
+** Call mprintf with two integer arguments and one double argument
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_double(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  double r;
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT DOUBLE\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<4; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-2]) ) return TCL_ERROR;
+  }
+  if( Tcl_GetDouble(interp, argv[4], &r) ) return TCL_ERROR;
+  z = sqlite3_mprintf(argv[1], a[0], a[1], r);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_scaled FORMAT DOUBLE DOUBLE
+**
+** Call mprintf with a single double argument which is the product of the
+** two arguments given above.  This is used to generate overflow and underflow
+** doubles to test that they are converted properly.
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_scaled(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int i;
+  double r[2];
+  char *z;
+  if( argc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT DOUBLE DOUBLE\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<4; i++){
+    if( Tcl_GetDouble(interp, argv[i], &r[i-2]) ) return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], r[0]*r[1]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_stronly FORMAT STRING
+**
+** Call mprintf with a single double argument which is the product of the
+** two arguments given above.  This is used to generate overflow and underflow
+** doubles to test that they are converted properly.
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_stronly(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *z;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT STRING\"", 0);
+    return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], argv[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_hexdouble FORMAT HEX
+**
+** Call mprintf with a single double argument which is derived from the
+** hexadecimal encoding of an IEEE double.
+*/
+static int SQLITE_TCLAPI sqlite3_mprintf_hexdouble(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *z;
+  double r;
+  unsigned int x1, x2;
+  sqlite_uint64 d;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT STRING\"", 0);
+    return TCL_ERROR;
+  }
+  if( sscanf(argv[2], "%08x%08x", &x2, &x1)!=2 ){
+    Tcl_AppendResult(interp, "2nd argument should be 16-characters of hex", 0);
+    return TCL_ERROR;
+  }
+  d = x2;
+  d = (d<<32) + x1;
+  memcpy(&r, &d, sizeof(r));
+  z = sqlite3_mprintf(argv[1], r);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_enable_shared_cache ?BOOLEAN?
+**
+*/
+#if !defined(SQLITE_OMIT_SHARED_CACHE)
+static int SQLITE_TCLAPI test_enable_shared(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int rc;
+  int enable;
+  int ret = 0;
+
+  if( objc!=2 && objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?BOOLEAN?");
+    return TCL_ERROR;
+  }
+  ret = sqlite3GlobalConfig.sharedCacheEnabled;
+
+  if( objc==2 ){
+    if( Tcl_GetBooleanFromObj(interp, objv[1], &enable) ){
+      return TCL_ERROR;
+    }
+    rc = sqlite3_enable_shared_cache(enable);
+    if( rc!=SQLITE_OK ){
+      Tcl_SetResult(interp, (char *)sqlite3ErrStr(rc), TCL_STATIC);
+      return TCL_ERROR;
+    }
+  }
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(ret));
+  return TCL_OK;
+}
+#endif
+
+
+
+/*
+** Usage: sqlite3_extended_result_codes   DB    BOOLEAN
+**
+*/
+static int SQLITE_TCLAPI test_extended_result_codes(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int enable;
+  sqlite3 *db;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &enable) ) return TCL_ERROR;
+  sqlite3_extended_result_codes(db, enable);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_libversion_number
+**
+*/
+static int SQLITE_TCLAPI test_libversion_number(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_libversion_number()));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_table_column_metadata DB dbname tblname colname
+**
+*/
+static int SQLITE_TCLAPI test_table_column_metadata(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zDb;
+  const char *zTbl;
+  const char *zCol;
+  int rc;
+  Tcl_Obj *pRet;
+
+  const char *zDatatype;
+  const char *zCollseq;
+  int notnull;
+  int primarykey;
+  int autoincrement;
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB dbname tblname colname");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zDb = Tcl_GetString(objv[2]);
+  zTbl = Tcl_GetString(objv[3]);
+  zCol = objc==5 ? Tcl_GetString(objv[4]) : 0;
+
+  if( strlen(zDb)==0 ) zDb = 0;
+
+  rc = sqlite3_table_column_metadata(db, zDb, zTbl, zCol, 
+      &zDatatype, &zCollseq, &notnull, &primarykey, &autoincrement);
+
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zDatatype, -1));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zCollseq, -1));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(notnull));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(primarykey));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(autoincrement));
+  Tcl_SetObjResult(interp, pRet);
+
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_INCRBLOB
+
+static int SQLITE_TCLAPI blobHandleFromObj(
+  Tcl_Interp *interp, 
+  Tcl_Obj *pObj,
+  sqlite3_blob **ppBlob
+){
+  char *z;
+  int n;
+
+  z = Tcl_GetStringFromObj(pObj, &n);
+  if( n==0 ){
+    *ppBlob = 0;
+  }else{
+    int notUsed;
+    Tcl_Channel channel;
+    ClientData instanceData;
+    
+    channel = Tcl_GetChannel(interp, z, &notUsed);
+    if( !channel ) return TCL_ERROR;
+
+    Tcl_Flush(channel);
+    Tcl_Seek(channel, 0, SEEK_SET);
+
+    instanceData = Tcl_GetChannelInstanceData(channel);
+    *ppBlob = *((sqlite3_blob **)instanceData);
+  }
+
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_blob_reopen(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_WideInt iRowid;
+  sqlite3_blob *pBlob;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "CHANNEL ROWID");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  if( Tcl_GetWideIntFromObj(interp, objv[2], &iRowid) ) return TCL_ERROR;
+
+  rc = sqlite3_blob_reopen(pBlob, iRowid);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  }
+
+  return (rc==SQLITE_OK ? TCL_OK : TCL_ERROR);
+}
+
+#endif
+
+/*
+** Usage: sqlite3_create_collation_v2 DB-HANDLE NAME CMP-PROC DEL-PROC
+**
+**   This Tcl proc is used for testing the experimental
+**   sqlite3_create_collation_v2() interface.
+*/
+struct TestCollationX {
+  Tcl_Interp *interp;
+  Tcl_Obj *pCmp;
+  Tcl_Obj *pDel;
+};
+typedef struct TestCollationX TestCollationX;
+static void testCreateCollationDel(void *pCtx){
+  TestCollationX *p = (TestCollationX *)pCtx;
+
+  int rc = Tcl_EvalObjEx(p->interp, p->pDel, TCL_EVAL_DIRECT|TCL_EVAL_GLOBAL);
+  if( rc!=TCL_OK ){
+    Tcl_BackgroundError(p->interp);
+  }
+
+  Tcl_DecrRefCount(p->pCmp);
+  Tcl_DecrRefCount(p->pDel);
+  sqlite3_free((void *)p);
+}
+static int testCreateCollationCmp(
+  void *pCtx,
+  int nLeft,
+  const void *zLeft,
+  int nRight,
+  const void *zRight
+){
+  TestCollationX *p = (TestCollationX *)pCtx;
+  Tcl_Obj *pScript = Tcl_DuplicateObj(p->pCmp);
+  int iRes = 0;
+
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zLeft, nLeft));
+  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zRight,nRight));
+
+  if( TCL_OK!=Tcl_EvalObjEx(p->interp, pScript, TCL_EVAL_DIRECT|TCL_EVAL_GLOBAL)
+   || TCL_OK!=Tcl_GetIntFromObj(p->interp, Tcl_GetObjResult(p->interp), &iRes)
+  ){
+    Tcl_BackgroundError(p->interp);
+  }
+  Tcl_DecrRefCount(pScript);
+
+  return iRes;
+}
+static int SQLITE_TCLAPI test_create_collation_v2(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  TestCollationX *p;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB-HANDLE NAME CMP-PROC DEL-PROC");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  p = (TestCollationX *)sqlite3_malloc(sizeof(TestCollationX));
+  p->pCmp = objv[3];
+  p->pDel = objv[4];
+  p->interp = interp;
+  Tcl_IncrRefCount(p->pCmp);
+  Tcl_IncrRefCount(p->pDel);
+
+  rc = sqlite3_create_collation_v2(db, Tcl_GetString(objv[2]), 16, 
+      (void *)p, testCreateCollationCmp, testCreateCollationDel
+  );
+  if( rc!=SQLITE_MISUSE ){
+    Tcl_AppendResult(interp, "sqlite3_create_collate_v2() failed to detect "
+      "an invalid encoding", (char*)0);
+    return TCL_ERROR;
+  }
+  rc = sqlite3_create_collation_v2(db, Tcl_GetString(objv[2]), SQLITE_UTF8, 
+      (void *)p, testCreateCollationCmp, testCreateCollationDel
+  );
+  return TCL_OK;
+}
+
+/*
+** USAGE: sqlite3_create_function_v2 DB NAME NARG ENC ?SWITCHES?
+**
+** Available switches are:
+**
+**   -func    SCRIPT
+**   -step    SCRIPT
+**   -final   SCRIPT
+**   -destroy SCRIPT
+*/
+typedef struct CreateFunctionV2 CreateFunctionV2;
+struct CreateFunctionV2 {
+  Tcl_Interp *interp;
+  Tcl_Obj *pFunc;                 /* Script for function invocation */
+  Tcl_Obj *pStep;                 /* Script for agg. step invocation */
+  Tcl_Obj *pFinal;                /* Script for agg. finalization invocation */
+  Tcl_Obj *pDestroy;              /* Destructor script */
+};
+static void cf2Func(sqlite3_context *ctx, int nArg, sqlite3_value **aArg){
+}
+static void cf2Step(sqlite3_context *ctx, int nArg, sqlite3_value **aArg){
+}
+static void cf2Final(sqlite3_context *ctx){
+}
+static void cf2Destroy(void *pUser){
+  CreateFunctionV2 *p = (CreateFunctionV2 *)pUser;
+
+  if( p->interp && p->pDestroy ){
+    int rc = Tcl_EvalObjEx(p->interp, p->pDestroy, 0);
+    if( rc!=TCL_OK ) Tcl_BackgroundError(p->interp);
+  }
+
+  if( p->pFunc ) Tcl_DecrRefCount(p->pFunc); 
+  if( p->pStep ) Tcl_DecrRefCount(p->pStep); 
+  if( p->pFinal ) Tcl_DecrRefCount(p->pFinal); 
+  if( p->pDestroy ) Tcl_DecrRefCount(p->pDestroy); 
+  sqlite3_free(p);
+}
+static int SQLITE_TCLAPI test_create_function_v2(
+  ClientData clientData,          /* Not used */
+  Tcl_Interp *interp,             /* The invoking TCL interpreter */
+  int objc,                       /* Number of arguments */
+  Tcl_Obj *CONST objv[]           /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zFunc;
+  int nArg;
+  int enc;
+  CreateFunctionV2 *p;
+  int i;
+  int rc;
+
+  struct EncTable {
+    const char *zEnc;
+    int enc;
+  } aEnc[] = {
+    {"utf8",    SQLITE_UTF8 },
+    {"utf16",   SQLITE_UTF16 },
+    {"utf16le", SQLITE_UTF16LE },
+    {"utf16be", SQLITE_UTF16BE },
+    {"any",     SQLITE_ANY },
+    {"0", 0 },
+    {0, 0 }
+  };
+
+  if( objc<5 || (objc%2)==0 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB NAME NARG ENC SWITCHES...");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zFunc = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &nArg) ) return TCL_ERROR;
+  if( Tcl_GetIndexFromObjStruct(interp, objv[4], aEnc, sizeof(aEnc[0]), 
+          "encoding", 0, &enc)
+  ){
+    return TCL_ERROR;
+  }
+  enc = aEnc[enc].enc;
+
+  p = sqlite3_malloc(sizeof(CreateFunctionV2));
+  assert( p );
+  memset(p, 0, sizeof(CreateFunctionV2));
+  p->interp = interp;
+
+  for(i=5; i<objc; i+=2){
+    int iSwitch;
+    const char *azSwitch[] = {"-func", "-step", "-final", "-destroy", 0};
+    if( Tcl_GetIndexFromObj(interp, objv[i], azSwitch, "switch", 0, &iSwitch) ){
+      sqlite3_free(p);
+      return TCL_ERROR;
+    }
+
+    switch( iSwitch ){
+      case 0: p->pFunc = objv[i+1];      break;
+      case 1: p->pStep = objv[i+1];      break;
+      case 2: p->pFinal = objv[i+1];     break;
+      case 3: p->pDestroy = objv[i+1];   break;
+    }
+  }
+  if( p->pFunc ) p->pFunc = Tcl_DuplicateObj(p->pFunc); 
+  if( p->pStep ) p->pStep = Tcl_DuplicateObj(p->pStep); 
+  if( p->pFinal ) p->pFinal = Tcl_DuplicateObj(p->pFinal); 
+  if( p->pDestroy ) p->pDestroy = Tcl_DuplicateObj(p->pDestroy); 
+
+  if( p->pFunc ) Tcl_IncrRefCount(p->pFunc); 
+  if( p->pStep ) Tcl_IncrRefCount(p->pStep); 
+  if( p->pFinal ) Tcl_IncrRefCount(p->pFinal); 
+  if( p->pDestroy ) Tcl_IncrRefCount(p->pDestroy); 
+
+  rc = sqlite3_create_function_v2(db, zFunc, nArg, enc, (void *)p, 
+      (p->pFunc ? cf2Func : 0),
+      (p->pStep ? cf2Step : 0),
+      (p->pFinal ? cf2Final : 0),
+      cf2Destroy
+  );
+  if( rc!=SQLITE_OK ){
+    Tcl_ResetResult(interp);
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_load_extension DB-HANDLE FILE ?PROC?
+*/
+static int SQLITE_TCLAPI test_load_extension(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_CmdInfo cmdInfo;
+  sqlite3 *db;
+  int rc;
+  char *zDb;
+  char *zFile;
+  char *zProc = 0;
+  char *zErr = 0;
+
+  if( objc!=4 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB-HANDLE FILE ?PROC?");
+    return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[1]);
+  zFile = Tcl_GetString(objv[2]);
+  if( objc==4 ){
+    zProc = Tcl_GetString(objv[3]);
+  }
+
+  /* Extract the C database handle from the Tcl command name */
+  if( !Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ", zDb, (char*)0);
+    return TCL_ERROR;
+  }
+  db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+  assert(db);
+
+  /* Call the underlying C function. If an error occurs, set rc to 
+  ** TCL_ERROR and load any error string into the interpreter. If no 
+  ** error occurs, set rc to TCL_OK.
+  */
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  rc = SQLITE_ERROR;
+  zErr = sqlite3_mprintf("this build omits sqlite3_load_extension()");
+  (void)zProc;
+  (void)zFile;
+#else
+  rc = sqlite3_load_extension(db, zFile, zProc, &zErr);
+#endif
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, zErr ? zErr : "", TCL_VOLATILE);
+    rc = TCL_ERROR;
+  }else{
+    rc = TCL_OK;
+  }
+  sqlite3_free(zErr);
+
+  return rc;
+}
+
+/*
+** Usage: sqlite3_enable_load_extension DB-HANDLE ONOFF
+*/
+static int SQLITE_TCLAPI test_enable_load(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_CmdInfo cmdInfo;
+  sqlite3 *db;
+  char *zDb;
+  int onoff;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB-HANDLE ONOFF");
+    return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[1]);
+
+  /* Extract the C database handle from the Tcl command name */
+  if( !Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ", zDb, (char*)0);
+    return TCL_ERROR;
+  }
+  db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+  assert(db);
+
+  /* Get the onoff parameter */
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &onoff) ){
+    return TCL_ERROR;
+  }
+
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  Tcl_AppendResult(interp, "this build omits sqlite3_load_extension()");
+  return TCL_ERROR;
+#else
+  sqlite3_enable_load_extension(db, onoff);
+  return TCL_OK;
+#endif
+}
+
+/*
+** Usage:  sqlite_abort
+**
+** Shutdown the process immediately.  This is not a clean shutdown.
+** This command is used to test the recoverability of a database in
+** the event of a program crash.
+*/
+static int SQLITE_TCLAPI sqlite_abort(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+#if defined(_MSC_VER)
+  /* We do this, otherwise the test will halt with a popup message
+   * that we have to click away before the test will continue.
+   */
+  _set_abort_behavior( 0, _CALL_REPORTFAULT );
+#endif
+  exit(255);
+  assert( interp==0 );   /* This will always fail */
+  return TCL_OK;
+}
+
+/*
+** The following routine is a user-defined SQL function whose purpose
+** is to test the sqlite_set_result() API.
+*/
+static void testFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  while( argc>=2 ){
+    const char *zArg0 = (char*)sqlite3_value_text(argv[0]);
+    if( zArg0 ){
+      if( 0==sqlite3StrICmp(zArg0, "int") ){
+        sqlite3_result_int(context, sqlite3_value_int(argv[1]));
+      }else if( sqlite3StrICmp(zArg0,"int64")==0 ){
+        sqlite3_result_int64(context, sqlite3_value_int64(argv[1]));
+      }else if( sqlite3StrICmp(zArg0,"string")==0 ){
+        sqlite3_result_text(context, (char*)sqlite3_value_text(argv[1]), -1,
+            SQLITE_TRANSIENT);
+      }else if( sqlite3StrICmp(zArg0,"double")==0 ){
+        sqlite3_result_double(context, sqlite3_value_double(argv[1]));
+      }else if( sqlite3StrICmp(zArg0,"null")==0 ){
+        sqlite3_result_null(context);
+      }else if( sqlite3StrICmp(zArg0,"value")==0 ){
+        sqlite3_result_value(context, argv[sqlite3_value_int(argv[1])]);
+      }else{
+        goto error_out;
+      }
+    }else{
+      goto error_out;
+    }
+    argc -= 2;
+    argv += 2;
+  }
+  return;
+
+error_out:
+  sqlite3_result_error(context,"first argument should be one of: "
+      "int int64 string double null value", -1);
+}
+
+/*
+** Usage:   sqlite_register_test_function  DB  NAME
+**
+** Register the test SQL function on the database DB under the name NAME.
+*/
+static int SQLITE_TCLAPI test_register_func(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB FUNCTION-NAME", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, argv[2], -1, SQLITE_UTF8, 0, 
+      testFunc, 0, 0);
+  if( rc!=0 ){
+    Tcl_AppendResult(interp, sqlite3ErrStr(rc), 0);
+    return TCL_ERROR;
+  }
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_finalize  STMT 
+**
+** Finalize a statement handle.
+*/
+static int SQLITE_TCLAPI test_finalize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  sqlite3 *db = 0;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <STMT>", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  if( pStmt ){
+    db = StmtToDb(pStmt);
+  }
+  rc = sqlite3_finalize(pStmt);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  if( db && sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_status  STMT  CODE  RESETFLAG
+**
+** Get the value of a status counter from a statement.
+*/
+static int SQLITE_TCLAPI test_stmt_status(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iValue;
+  int i, op = 0, resetFlag;
+  const char *zOpName;
+  sqlite3_stmt *pStmt;
+
+  static const struct {
+    const char *zName;
+    int op;
+  } aOp[] = {
+    { "SQLITE_STMTSTATUS_FULLSCAN_STEP",   SQLITE_STMTSTATUS_FULLSCAN_STEP   },
+    { "SQLITE_STMTSTATUS_SORT",            SQLITE_STMTSTATUS_SORT            },
+    { "SQLITE_STMTSTATUS_AUTOINDEX",       SQLITE_STMTSTATUS_AUTOINDEX       },
+    { "SQLITE_STMTSTATUS_VM_STEP",         SQLITE_STMTSTATUS_VM_STEP         },
+    { "SQLITE_STMTSTATUS_REPREPARE",       SQLITE_STMTSTATUS_REPREPARE       },
+    { "SQLITE_STMTSTATUS_RUN",             SQLITE_STMTSTATUS_RUN             },
+    { "SQLITE_STMTSTATUS_MEMUSED",         SQLITE_STMTSTATUS_MEMUSED         },
+  };
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT PARAMETER RESETFLAG");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  zOpName = Tcl_GetString(objv[2]);
+  for(i=0; i<ArraySize(aOp); i++){
+    if( strcmp(aOp[i].zName, zOpName)==0 ){
+      op = aOp[i].op;
+      break;
+    }
+  }
+  if( i>=ArraySize(aOp) ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &op) ) return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[3], &resetFlag) ) return TCL_ERROR;
+  iValue = sqlite3_stmt_status(pStmt, op, resetFlag);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(iValue));
+  return TCL_OK;
+}
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+/*
+** Usage:  sqlite3_stmt_scanstatus ?-flags FLAGS? STMT IDX
+*/
+static int SQLITE_TCLAPI test_stmt_scanstatus(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;            /* First argument */
+  int idx;                        /* Second argument */
+
+  const char *zName;
+  const char *zExplain;
+  sqlite3_int64 nLoop;
+  sqlite3_int64 nVisit;
+  sqlite3_int64 nCycle;
+  double rEst;
+  int res;
+  int flags = 0;
+  int iSelectId = 0;
+  int iParentId = 0;
+  int bDebug = 0;
+
+  if( objc==5 ){
+    struct Flag {
+      const char *zFlag;
+      int flag;
+    } aTbl[] = {
+      {"complex", SQLITE_SCANSTAT_COMPLEX},
+      {"debug", -1},
+      {0, 0}
+    };
+
+    Tcl_Obj **aFlag = 0;
+    int nFlag = 0;
+    int ii;
+
+    if( Tcl_ListObjGetElements(interp, objv[2], &nFlag, &aFlag) ){
+      return TCL_ERROR;
+    }
+    for(ii=0; ii<nFlag; ii++){
+      int iVal = 0;
+      int res = Tcl_GetIndexFromObjStruct(
+          interp, aFlag[ii], aTbl, sizeof(aTbl[0]), "flag", 0, &iVal
+      );
+      if( res ) return TCL_ERROR;
+      if( aTbl[iVal].flag==-1 ){
+        bDebug = 1;
+      }else{
+        flags |= aTbl[iVal].flag;
+      }
+    }
+  }
+
+  if( objc!=3 && objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "-flags FLAGS STMT IDX");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[objc-2]), &pStmt) 
+   || Tcl_GetIntFromObj(interp, objv[objc-1], &idx)
+  ){
+    return TCL_ERROR;
+  }
+
+  if( bDebug && 0==(flags & SQLITE_SCANSTAT_COMPLEX) ){
+    Tcl_SetObjResult(interp, 
+        Tcl_NewStringObj("may not specify debug without complex", -1)
+    );
+    return TCL_ERROR;
+  }
+
+  if( idx<0 ){
+    Tcl_Obj *pRet = Tcl_NewObj();
+    res = sqlite3_stmt_scanstatus_v2(
+        pStmt, -1, SQLITE_SCANSTAT_NCYCLE, flags, (void*)&nCycle
+    );
+    sqlite3_stmt_scanstatus_v2(
+        pStmt, idx, SQLITE_SCANSTAT_NCYCLE, flags, (void*)&nCycle);
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("nCycle", -1));
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewWideIntObj(nCycle));
+    Tcl_SetObjResult(interp, pRet);
+  }else{
+    res = sqlite3_stmt_scanstatus_v2(
+        pStmt, idx, SQLITE_SCANSTAT_NLOOP, flags, (void*)&nLoop
+    );
+    if( res==0 ){
+      Tcl_Obj *pRet = Tcl_NewObj();
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("nLoop", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewWideIntObj(nLoop));
+      sqlite3_stmt_scanstatus_v2(
+          pStmt, idx, SQLITE_SCANSTAT_NVISIT, flags, (void*)&nVisit);
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("nVisit", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewWideIntObj(nVisit));
+      sqlite3_stmt_scanstatus_v2(
+          pStmt, idx, SQLITE_SCANSTAT_EST, flags, (void*)&rEst);
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("nEst", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewDoubleObj(rEst));
+      sqlite3_stmt_scanstatus_v2(
+          pStmt, idx, SQLITE_SCANSTAT_NAME, flags, (void*)&zName);
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("zName", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zName, -1));
+      sqlite3_stmt_scanstatus_v2(
+          pStmt, idx, SQLITE_SCANSTAT_EXPLAIN, flags, (void*)&zExplain);
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("zExplain", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zExplain, -1));
+      sqlite3_stmt_scanstatus_v2(
+          pStmt, idx, SQLITE_SCANSTAT_SELECTID, flags, (void*)&iSelectId);
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("iSelectId", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(iSelectId));
+      sqlite3_stmt_scanstatus_v2(
+          pStmt, idx, SQLITE_SCANSTAT_PARENTID, flags, (void*)&iParentId);
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("iParentId", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(iParentId));
+      sqlite3_stmt_scanstatus_v2(
+          pStmt, idx, SQLITE_SCANSTAT_NCYCLE, flags, (void*)&nCycle);
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("nCycle", -1));
+      Tcl_ListObjAppendElement(0, pRet, Tcl_NewWideIntObj(nCycle));
+
+      if( bDebug ){
+        int ii;
+        ScanStatus *pScan = &((Vdbe*)pStmt)->aScan[idx];
+        Tcl_Obj *pRange = Tcl_NewObj();
+        Tcl_Obj *pCsr = Tcl_NewObj();
+
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("debug_loop", -1));
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(pScan->addrLoop));
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("debug_visit", -1));
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(pScan->addrVisit));
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("debug_explain",-1));
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(pScan->addrExplain));
+        for(ii=0; ii<ArraySize(pScan->aAddrRange)/2; ii++){
+          int iStart = pScan->aAddrRange[ii*2];
+          int iEnd = pScan->aAddrRange[ii*2+1];
+          if( iStart>0 ){
+            Tcl_ListObjAppendElement(0, pRange, Tcl_NewIntObj(iStart));
+            Tcl_ListObjAppendElement(0, pRange, Tcl_NewIntObj(iEnd));
+          }else if( iStart<0 ){
+            Tcl_ListObjAppendElement(0, pCsr, Tcl_NewIntObj(iEnd));
+          }
+        }
+
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("debug_range", -1));
+        Tcl_ListObjAppendElement(0, pRet, pRange);
+        Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj("debug_csr", -1));
+        Tcl_ListObjAppendElement(0, pRet, pCsr);
+      }
+
+      Tcl_SetObjResult(interp, pRet);
+    }else{
+      Tcl_ResetResult(interp);
+    }
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_scanstatus_reset  STMT
+*/
+static int SQLITE_TCLAPI test_stmt_scanstatus_reset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;            /* First argument */
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  sqlite3_stmt_scanstatus_reset(pStmt);
+  return TCL_OK;
+}
+#endif
+
+#ifdef SQLITE_ENABLE_SQLLOG
+/*
+** Usage:  sqlite3_config_sqllog
+**
+** Zero the SQLITE_CONFIG_SQLLOG configuration
+*/
+static int SQLITE_TCLAPI test_config_sqllog(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  sqlite3_config(SQLITE_CONFIG_SQLLOG, 0, 0);
+  return TCL_OK;
+}
+#endif
+
+/*
+** Usage:  sqlite3_config_sorterref
+**
+** Set the SQLITE_CONFIG_SORTERREF_SIZE configuration option
+*/
+static int SQLITE_TCLAPI test_config_sorterref(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iVal;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NBYTE");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &iVal) ) return TCL_ERROR;
+  sqlite3_config(SQLITE_CONFIG_SORTERREF_SIZE, iVal);
+  return TCL_OK;
+}
+
+/*
+** Usage: vfs_current_time_int64
+**
+** Return the value returned by the default VFS's xCurrentTimeInt64 method.
+*/
+static int SQLITE_TCLAPI vfsCurrentTimeInt64(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  i64 t;
+  sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  pVfs->xCurrentTimeInt64(pVfs, &t);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(t));
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Usage: create_null_module DB NAME
+*/
+static int SQLITE_TCLAPI test_create_null_module(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  char *zName;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+
+  sqlite3_create_module(db, zName, 0, 0);
+  return TCL_OK;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Usage: sqlite3_snapshot_get DB DBNAME
+*/
+static int SQLITE_TCLAPI test_snapshot_get(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3 *db;
+  char *zName;
+  sqlite3_snapshot *pSnapshot = 0;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+
+  rc = sqlite3_snapshot_get(db, zName, &pSnapshot);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }else{
+    char zBuf[100];
+    if( sqlite3TestMakePointerStr(interp, zBuf, pSnapshot) ) return TCL_ERROR;
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(zBuf, -1));
+  }
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Usage: sqlite3_snapshot_recover DB DBNAME
+*/
+static int SQLITE_TCLAPI test_snapshot_recover(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3 *db;
+  char *zName;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+
+  rc = sqlite3_snapshot_recover(db, zName);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }else{
+    Tcl_ResetResult(interp);
+  }
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Usage: sqlite3_snapshot_open DB DBNAME SNAPSHOT
+*/
+static int SQLITE_TCLAPI test_snapshot_open(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3 *db;
+  char *zName;
+  sqlite3_snapshot *pSnapshot;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SNAPSHOT");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+  pSnapshot = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[3]));
+
+  rc = sqlite3_snapshot_open(db, zName, pSnapshot);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }else{
+    Tcl_ResetResult(interp);
+  }
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Usage: sqlite3_snapshot_free SNAPSHOT
+*/
+static int SQLITE_TCLAPI test_snapshot_free(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_snapshot *pSnapshot;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SNAPSHOT");
+    return TCL_ERROR;
+  }
+  pSnapshot = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  sqlite3_snapshot_free(pSnapshot);
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Usage: sqlite3_snapshot_cmp SNAPSHOT1 SNAPSHOT2
+*/
+static int SQLITE_TCLAPI test_snapshot_cmp(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int res;
+  sqlite3_snapshot *p1;
+  sqlite3_snapshot *p2;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SNAPSHOT1 SNAPSHOT2");
+    return TCL_ERROR;
+  }
+  p1 = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  p2 = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[2]));
+  res = sqlite3_snapshot_cmp(p1, p2);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Usage: sqlite3_snapshot_get_blob DB DBNAME
+*/
+static int SQLITE_TCLAPI test_snapshot_get_blob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3 *db;
+  char *zName;
+  sqlite3_snapshot *pSnapshot = 0;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+
+  rc = sqlite3_snapshot_get(db, zName, &pSnapshot);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }else{
+    Tcl_SetObjResult(interp, 
+        Tcl_NewByteArrayObj((unsigned char*)pSnapshot, sizeof(sqlite3_snapshot))
+    );
+    sqlite3_snapshot_free(pSnapshot);
+  }
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  /*
+  ** Usage: sqlite3_snapshot_open_blob DB DBNAME SNAPSHOT
+*/
+static int SQLITE_TCLAPI test_snapshot_open_blob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3 *db;
+  char *zName;
+  unsigned char *pBlob;
+  int nBlob;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SNAPSHOT");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+  pBlob = Tcl_GetByteArrayFromObj(objv[3], &nBlob);
+  if( nBlob!=sizeof(sqlite3_snapshot) ){
+    Tcl_AppendResult(interp, "bad SNAPSHOT", 0);
+    return TCL_ERROR;
+  }
+  rc = sqlite3_snapshot_open(db, zName, (sqlite3_snapshot*)pBlob);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** Usage: sqlite3_snapshot_cmp_blob SNAPSHOT1 SNAPSHOT2
+*/
+static int SQLITE_TCLAPI test_snapshot_cmp_blob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int res;
+  unsigned char *p1;
+  unsigned char *p2;
+  int n1;
+  int n2;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SNAPSHOT1 SNAPSHOT2");
+    return TCL_ERROR;
+  }
+
+  p1 = Tcl_GetByteArrayFromObj(objv[1], &n1);
+  p2 = Tcl_GetByteArrayFromObj(objv[2], &n2);
+
+  if( n1!=sizeof(sqlite3_snapshot) || n1!=n2 ){
+    Tcl_AppendResult(interp, "bad SNAPSHOT", 0);
+    return TCL_ERROR;
+  }
+
+  res = sqlite3_snapshot_cmp((sqlite3_snapshot*)p1, (sqlite3_snapshot*)p2);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+/*
+** Usage: sqlite3_delete_database FILENAME
+*/
+int sqlite3_delete_database(const char*);   /* in test_delete.c */
+static int SQLITE_TCLAPI test_delete_database(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  const char *zFile;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILE");
+    return TCL_ERROR;
+  }
+  zFile = (const char*)Tcl_GetString(objv[1]);
+  rc = sqlite3_delete_database(zFile);
+
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+  return TCL_OK;
+}
+
+/*
+** Usage: atomic_batch_write PATH
+*/
+static int SQLITE_TCLAPI test_atomic_batch_write(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  char *zFile = 0;                /* Path to file to test */
+  sqlite3 *db = 0;                /* Database handle */
+  sqlite3_file *pFd = 0;          /* SQLite fd open on zFile */
+  int bRes = 0;                   /* Integer result of this command */
+  int dc = 0;                     /* Device-characteristics mask */
+  int rc;                         /* sqlite3_open() return code */
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PATH");
+    return TCL_ERROR;
+  }
+  zFile = Tcl_GetString(objv[1]);
+
+  rc = sqlite3_open(zFile, &db);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3_errmsg(db), 0);
+    sqlite3_close(db);
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_file_control(db, "main", SQLITE_FCNTL_FILE_POINTER, (void*)&pFd);
+  dc = pFd->pMethods->xDeviceCharacteristics(pFd);
+  if( dc & SQLITE_IOCAP_BATCH_ATOMIC ){
+    bRes = 1;
+  }
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(bRes));
+  sqlite3_close(db);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_next_stmt  DB  STMT
+**
+** Return the next statement in sequence after STMT.
+*/
+static int SQLITE_TCLAPI test_next_stmt(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  sqlite3 *db = 0;
+  char zBuf[50];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( getStmtPointer(interp, Tcl_GetString(objv[2]), &pStmt) ) return TCL_ERROR;
+  pStmt = sqlite3_next_stmt(db, pStmt);
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_readonly  STMT
+**
+** Return true if STMT is a NULL pointer or a pointer to a statement
+** that is guaranteed to leave the database unmodified.
+*/
+static int SQLITE_TCLAPI test_stmt_readonly(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = sqlite3_stmt_readonly(pStmt);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_isexplain  STMT
+**
+** Return 1, 2, or 0 respectively if STMT is an EXPLAIN statement, an
+** EXPLAIN QUERY PLAN statement or an ordinary statement or NULL pointer.
+*/
+static int SQLITE_TCLAPI test_stmt_isexplain(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = sqlite3_stmt_isexplain(pStmt);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_explain  STMT  INT
+**
+** Set the explain to normal (0), EXPLAIN (1) or EXPLAIN QUERY PLAN (2).
+*/
+static int SQLITE_TCLAPI test_stmt_explain(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int eMode = 0;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT INT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &eMode) ) return TCL_ERROR;
+  rc = sqlite3_stmt_explain(pStmt, eMode);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_busy  STMT
+**
+** Return true if STMT is a non-NULL pointer to a statement
+** that has been stepped but not to completion.
+*/
+static int SQLITE_TCLAPI test_stmt_busy(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = sqlite3_stmt_busy(pStmt);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:  uses_stmt_journal  STMT
+**
+** Return true if STMT uses a statement journal.
+*/
+static int SQLITE_TCLAPI uses_stmt_journal(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  sqlite3_stmt_readonly(pStmt);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(((Vdbe *)pStmt)->usesStmtJournal));
+  return TCL_OK;
+}
+
+
+/*
+** Usage:  sqlite3_reset  STMT 
+**
+** Reset a statement handle.
+*/
+static int SQLITE_TCLAPI test_reset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <STMT>", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  rc = sqlite3_reset(pStmt);
+  if( pStmt && sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ){
+    return TCL_ERROR;
+  }
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+/*
+  if( rc ){
+    return TCL_ERROR;
+  }
+*/
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_expired STMT 
+**
+** Return TRUE if a recompilation of the statement is recommended.
+*/
+static int SQLITE_TCLAPI test_expired(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_stmt *pStmt;
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <STMT>", 0);
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(sqlite3_expired(pStmt)));
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_transfer_bindings FROMSTMT TOSTMT
+**
+** Transfer all bindings from FROMSTMT over to TOSTMT
+*/
+static int SQLITE_TCLAPI test_transfer_bind(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_stmt *pStmt1, *pStmt2;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " FROM-STMT TO-STMT", 0);
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt1)) return TCL_ERROR;
+  if( getStmtPointer(interp, Tcl_GetString(objv[2]), &pStmt2)) return TCL_ERROR;
+  Tcl_SetObjResult(interp, 
+     Tcl_NewIntObj(sqlite3_transfer_bindings(pStmt1,pStmt2)));
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_changes DB
+**
+** Return the number of changes made to the database by the last SQL
+** execution.
+*/
+static int SQLITE_TCLAPI test_changes(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_changes(db)));
+  return TCL_OK;
+}
+
+/*
+** This is the "static_bind_value" that variables are bound to when
+** the FLAG option of sqlite3_bind is "static"
+*/
+static char *sqlite_static_bind_value = 0;
+static int sqlite_static_bind_nbyte = 0;
+
+/*
+** Usage:  sqlite3_bind  VM  IDX  VALUE  FLAGS
+**
+** Sets the value of the IDX-th occurrence of "?" in the original SQL
+** string.  VALUE is the new value.  If FLAGS=="null" then VALUE is
+** ignored and the value is set to NULL.  If FLAGS=="static" then
+** the value is set to the value of a static variable named
+** "sqlite_static_bind_value".  If FLAGS=="normal" then a copy
+** of the VALUE is made.  If FLAGS=="blob10" then a VALUE is ignored
+** an a 10-byte blob "abc\000xyz\000pq" is inserted.
+*/
+static int SQLITE_TCLAPI test_bind(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  int idx;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " VM IDX VALUE (null|static|normal)\"", 0);
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, argv[1], &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[2], &idx) ) return TCL_ERROR;
+  if( strcmp(argv[4],"null")==0 ){
+    rc = sqlite3_bind_null(pStmt, idx);
+  }else if( strcmp(argv[4],"static")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, sqlite_static_bind_value, -1, 0);
+  }else if( strcmp(argv[4],"static-nbytes")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, sqlite_static_bind_value,
+                                       sqlite_static_bind_nbyte, 0);
+  }else if( strcmp(argv[4],"normal")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, argv[3], -1, SQLITE_TRANSIENT);
+  }else if( strcmp(argv[4],"blob10")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, "abc\000xyz\000pq", 10, SQLITE_STATIC);
+  }else{
+    Tcl_AppendResult(interp, "4th argument should be "
+        "\"null\" or \"static\" or \"normal\"", 0);
+    return TCL_ERROR;
+  }
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc ){
+    char zBuf[50];
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3ErrStr(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Usage: add_test_collate <db ptr> <utf8> <utf16le> <utf16be>
+**
+** This function is used to test that SQLite selects the correct collation
+** sequence callback when multiple versions (for different text encodings)
+** are available.
+**
+** Calling this routine registers the collation sequence "test_collate"
+** with database handle <db>. The second argument must be a list of three
+** boolean values. If the first is true, then a version of test_collate is
+** registered for UTF-8, if the second is true, a version is registered for
+** UTF-16le, if the third is true, a UTF-16be version is available.
+** Previous versions of test_collate are deleted.
+**
+** The collation sequence test_collate is implemented by calling the
+** following TCL script:
+**
+**   "test_collate <enc> <lhs> <rhs>"
+**
+** The <lhs> and <rhs> are the two values being compared, encoded in UTF-8.
+** The <enc> parameter is the encoding of the collation function that
+** SQLite selected to call. The TCL test script implements the
+** "test_collate" proc.
+**
+** Note that this will only work with one interpreter at a time, as the
+** interp pointer to use when evaluating the TCL script is stored in
+** pTestCollateInterp.
+*/
+static Tcl_Interp* pTestCollateInterp;
+static int test_collate_func(
+  void *pCtx, 
+  int nA, const void *zA,
+  int nB, const void *zB
+){
+  Tcl_Interp *i = pTestCollateInterp;
+  int encin = SQLITE_PTR_TO_INT(pCtx);
+  int res;
+  int n;
+
+  sqlite3_value *pVal;
+  Tcl_Obj *pX;
+
+  pX = Tcl_NewStringObj("test_collate", -1);
+  Tcl_IncrRefCount(pX);
+
+  switch( encin ){
+    case SQLITE_UTF8:
+      Tcl_ListObjAppendElement(i,pX,Tcl_NewStringObj("UTF-8",-1));
+      break;
+    case SQLITE_UTF16LE:
+      Tcl_ListObjAppendElement(i,pX,Tcl_NewStringObj("UTF-16LE",-1));
+      break;
+    case SQLITE_UTF16BE:
+      Tcl_ListObjAppendElement(i,pX,Tcl_NewStringObj("UTF-16BE",-1));
+      break;
+    default:
+      assert(0);
+  }
+
+  sqlite3BeginBenignMalloc();
+  pVal = sqlite3ValueNew(0);
+  if( pVal ){
+    sqlite3ValueSetStr(pVal, nA, zA, encin, SQLITE_STATIC);
+    n = sqlite3_value_bytes(pVal);
+    Tcl_ListObjAppendElement(i,pX,
+        Tcl_NewStringObj((char*)sqlite3_value_text(pVal),n));
+    sqlite3ValueSetStr(pVal, nB, zB, encin, SQLITE_STATIC);
+    n = sqlite3_value_bytes(pVal);
+    Tcl_ListObjAppendElement(i,pX,
+        Tcl_NewStringObj((char*)sqlite3_value_text(pVal),n));
+    sqlite3ValueFree(pVal);
+  }
+  sqlite3EndBenignMalloc();
+
+  Tcl_EvalObjEx(i, pX, 0);
+  Tcl_DecrRefCount(pX);
+  Tcl_GetIntFromObj(i, Tcl_GetObjResult(i), &res);
+  return res;
+}
+static int SQLITE_TCLAPI test_collate(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int val;
+  sqlite3_value *pVal;
+  int rc;
+
+  if( objc!=5 ) goto bad_args;
+  pTestCollateInterp = interp;
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
+  rc = sqlite3_create_collation(db, "test_collate", SQLITE_UTF8, 
+          (void *)SQLITE_UTF8, val?test_collate_func:0);
+  if( rc==SQLITE_OK ){
+    const void *zUtf16;
+    if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+    rc = sqlite3_create_collation(db, "test_collate", SQLITE_UTF16LE, 
+            (void *)SQLITE_UTF16LE, val?test_collate_func:0);
+    if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[4], &val) ) return TCL_ERROR;
+
+#if 0
+    if( sqlite3_iMallocFail>0 ){
+      sqlite3_iMallocFail++;
+    }
+#endif
+    sqlite3_mutex_enter(db->mutex);
+    pVal = sqlite3ValueNew(db);
+    sqlite3ValueSetStr(pVal, -1, "test_collate", SQLITE_UTF8, SQLITE_STATIC);
+    zUtf16 = sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);
+    if( db->mallocFailed ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_create_collation16(db, zUtf16, SQLITE_UTF16BE, 
+          (void *)SQLITE_UTF16BE, val?test_collate_func:0);
+    }
+    sqlite3ValueFree(pVal);
+    sqlite3_mutex_leave(db->mutex);
+  }
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+
+bad_args:
+  Tcl_AppendResult(interp, "wrong # args: should be \"",
+      Tcl_GetStringFromObj(objv[0], 0), " <DB> <utf8> <utf16le> <utf16be>", 0);
+  return TCL_ERROR;
+}
+
+/*
+** Usage: add_test_utf16bin_collate <db ptr>
+**
+** Add a utf-16 collation sequence named "utf16bin" to the database
+** handle. This collation sequence compares arguments in the same way as the
+** built-in collation "binary".
+*/
+static int test_utf16bin_collate_func(
+  void *pCtx, 
+  int nA, const void *zA,
+  int nB, const void *zB
+){
+  int nCmp = (nA>nB ? nB : nA);
+  int res = memcmp(zA, zB, nCmp);
+  if( res==0 ) res = nA - nB;
+  return res;
+}
+static int SQLITE_TCLAPI test_utf16bin_collate(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ) goto bad_args;
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  rc = sqlite3_create_collation(db, "utf16bin", SQLITE_UTF16, 0, 
+      test_utf16bin_collate_func
+  );
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+
+bad_args:
+  Tcl_WrongNumArgs(interp, 1, objv, "DB");
+  return TCL_ERROR;
+}
+
+/*
+** When the collation needed callback is invoked, record the name of 
+** the requested collating function here.  The recorded name is linked
+** to a TCL variable and used to make sure that the requested collation
+** name is correct.
+*/
+static char zNeededCollation[200];
+static char *pzNeededCollation = zNeededCollation;
+
+
+/*
+** Called when a collating sequence is needed.  Registered using
+** sqlite3_collation_needed16().
+*/
+static void test_collate_needed_cb(
+  void *pCtx, 
+  sqlite3 *db,
+  int eTextRep,
+  const void *pName
+){
+  int enc = ENC(db);
+  int i;
+  char *z;
+  for(z = (char*)pName, i=0; *z || z[1]; z++){
+    if( *z ) zNeededCollation[i++] = *z;
+  }
+  zNeededCollation[i] = 0;
+  sqlite3_create_collation(
+      db, "test_collate", ENC(db), SQLITE_INT_TO_PTR(enc), test_collate_func);
+}
+
+/*
+** Usage: add_test_collate_needed DB
+*/
+static int SQLITE_TCLAPI test_collate_needed(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ) goto bad_args;
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_collation_needed16(db, 0, test_collate_needed_cb);
+  zNeededCollation[0] = 0;
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+
+bad_args:
+  Tcl_WrongNumArgs(interp, 1, objv, "DB");
+  return TCL_ERROR;
+}
+
+/*
+** tclcmd:   add_alignment_test_collations  DB
+**
+** Add two new collating sequences to the database DB
+**
+**     utf16_aligned
+**     utf16_unaligned
+**
+** Both collating sequences use the same sort order as BINARY.
+** The only difference is that the utf16_aligned collating
+** sequence is declared with the SQLITE_UTF16_ALIGNED flag.
+** Both collating functions increment the unaligned utf16 counter
+** whenever they see a string that begins on an odd byte boundary.
+*/
+static int unaligned_string_counter = 0;
+static int alignmentCollFunc(
+  void *NotUsed,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  int rc, n;
+  n = nKey1<nKey2 ? nKey1 : nKey2;
+  if( nKey1>0 && 1==(1&(SQLITE_PTR_TO_INT(pKey1))) ) unaligned_string_counter++;
+  if( nKey2>0 && 1==(1&(SQLITE_PTR_TO_INT(pKey2))) ) unaligned_string_counter++;
+  rc = memcmp(pKey1, pKey2, n);
+  if( rc==0 ){
+    rc = nKey1 - nKey2;
+  }
+  return rc;
+}
+static int SQLITE_TCLAPI add_alignment_test_collations(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc>=2 ){
+    if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+    sqlite3_create_collation(db, "utf16_unaligned", SQLITE_UTF16, 
+        0, alignmentCollFunc);
+    sqlite3_create_collation(db, "utf16_aligned", SQLITE_UTF16_ALIGNED, 
+        0, alignmentCollFunc);
+  }
+  return SQLITE_OK;
+}
+#endif /* !defined(SQLITE_OMIT_UTF16) */
+
+/*
+** Usage: add_test_function <db ptr> <utf8> <utf16le> <utf16be>
+**
+** This function is used to test that SQLite selects the correct user
+** function callback when multiple versions (for different text encodings)
+** are available.
+**
+** Calling this routine registers up to three versions of the user function
+** "test_function" with database handle <db>.  If the second argument is
+** true, then a version of test_function is registered for UTF-8, if the
+** third is true, a version is registered for UTF-16le, if the fourth is
+** true, a UTF-16be version is available.  Previous versions of
+** test_function are deleted.
+**
+** The user function is implemented by calling the following TCL script:
+**
+**   "test_function <enc> <arg>"
+**
+** Where <enc> is one of UTF-8, UTF-16LE or UTF16BE, and <arg> is the
+** single argument passed to the SQL function. The value returned by
+** the TCL script is used as the return value of the SQL function. It
+** is passed to SQLite using UTF-16BE for a UTF-8 test_function(), UTF-8
+** for a UTF-16LE test_function(), and UTF-16LE for an implementation that
+** prefers UTF-16BE.
+*/
+#ifndef SQLITE_OMIT_UTF16
+static void test_function_utf8(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  Tcl_Interp *interp;
+  Tcl_Obj *pX;
+  sqlite3_value *pVal;
+  interp = (Tcl_Interp *)sqlite3_user_data(pCtx);
+  pX = Tcl_NewStringObj("test_function", -1);
+  Tcl_IncrRefCount(pX);
+  Tcl_ListObjAppendElement(interp, pX, Tcl_NewStringObj("UTF-8", -1));
+  Tcl_ListObjAppendElement(interp, pX, 
+      Tcl_NewStringObj((char*)sqlite3_value_text(argv[0]), -1));
+  Tcl_EvalObjEx(interp, pX, 0);
+  Tcl_DecrRefCount(pX);
+  sqlite3_result_text(pCtx, Tcl_GetStringResult(interp), -1, SQLITE_TRANSIENT);
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, Tcl_GetStringResult(interp), 
+      SQLITE_UTF8, SQLITE_STATIC);
+  sqlite3_result_text16be(pCtx, sqlite3_value_text16be(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3ValueFree(pVal);
+}
+static void test_function_utf16le(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  Tcl_Interp *interp;
+  Tcl_Obj *pX;
+  sqlite3_value *pVal;
+  interp = (Tcl_Interp *)sqlite3_user_data(pCtx);
+  pX = Tcl_NewStringObj("test_function", -1);
+  Tcl_IncrRefCount(pX);
+  Tcl_ListObjAppendElement(interp, pX, Tcl_NewStringObj("UTF-16LE", -1));
+  Tcl_ListObjAppendElement(interp, pX, 
+      Tcl_NewStringObj((char*)sqlite3_value_text(argv[0]), -1));
+  Tcl_EvalObjEx(interp, pX, 0);
+  Tcl_DecrRefCount(pX);
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, Tcl_GetStringResult(interp), 
+      SQLITE_UTF8, SQLITE_STATIC);
+  sqlite3_result_text(pCtx,(char*)sqlite3_value_text(pVal),-1,SQLITE_TRANSIENT);
+  sqlite3ValueFree(pVal);
+}
+static void test_function_utf16be(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  Tcl_Interp *interp;
+  Tcl_Obj *pX;
+  sqlite3_value *pVal;
+  interp = (Tcl_Interp *)sqlite3_user_data(pCtx);
+  pX = Tcl_NewStringObj("test_function", -1);
+  Tcl_IncrRefCount(pX);
+  Tcl_ListObjAppendElement(interp, pX, Tcl_NewStringObj("UTF-16BE", -1));
+  Tcl_ListObjAppendElement(interp, pX, 
+      Tcl_NewStringObj((char*)sqlite3_value_text(argv[0]), -1));
+  Tcl_EvalObjEx(interp, pX, 0);
+  Tcl_DecrRefCount(pX);
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, Tcl_GetStringResult(interp), 
+      SQLITE_UTF8, SQLITE_STATIC);
+  sqlite3_result_text16(pCtx, sqlite3_value_text16le(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3_result_text16be(pCtx, sqlite3_value_text16le(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3_result_text16le(pCtx, sqlite3_value_text16le(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3ValueFree(pVal);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+static int SQLITE_TCLAPI test_function(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  int val;
+
+  if( objc!=5 ) goto bad_args;
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
+  if( val ){
+    sqlite3_create_function(db, "test_function", 1, SQLITE_UTF8, 
+        interp, test_function_utf8, 0, 0);
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+  if( val ){
+    sqlite3_create_function(db, "test_function", 1, SQLITE_UTF16LE, 
+        interp, test_function_utf16le, 0, 0);
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[4], &val) ) return TCL_ERROR;
+  if( val ){
+    sqlite3_create_function(db, "test_function", 1, SQLITE_UTF16BE, 
+        interp, test_function_utf16be, 0, 0);
+  }
+
+  return TCL_OK;
+bad_args:
+  Tcl_AppendResult(interp, "wrong # args: should be \"",
+      Tcl_GetStringFromObj(objv[0], 0), " <DB> <utf8> <utf16le> <utf16be>", 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_ERROR;
+}
+
+/*
+** Usage:         sqlite3_test_errstr <err code>
+**
+** Test that the English language string equivalents for sqlite error codes
+** are sane. The parameter is an integer representing an sqlite error code.
+** The result is a list of two elements, the string representation of the
+** error code and the English language explanation.
+*/
+static int SQLITE_TCLAPI test_errstr(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  char *zCode;
+  int i;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "<error code>");
+  }
+
+  zCode = Tcl_GetString(objv[1]);
+  for(i=0; i<200; i++){
+    if( 0==strcmp(t1ErrorName(i), zCode) ) break;
+  }
+  Tcl_SetResult(interp, (char *)sqlite3ErrStr(i), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:    breakpoint
+**
+** This routine exists for one purpose - to provide a place to put a
+** breakpoint with GDB that can be triggered using TCL code.  The use
+** for this is when a particular test fails on (say) the 1485th iteration.
+** In the TCL test script, we can add code like this:
+**
+**     if {$i==1485} breakpoint
+**
+** Then run testfixture in the debugger and wait for the breakpoint to
+** fire.  Then additional breakpoints can be set to trace down the bug.
+*/
+static int SQLITE_TCLAPI test_breakpoint(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  return TCL_OK;         /* Do nothing */
+}
+
+/*
+** Usage:   sqlite3_bind_zeroblob  STMT IDX N
+**
+** Test the sqlite3_bind_zeroblob interface.  STMT is a prepared statement.
+** IDX is the index of a wildcard in the prepared statement.  This command
+** binds a N-byte zero-filled BLOB to the wildcard.
+*/
+static int SQLITE_TCLAPI test_bind_zeroblob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int n;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT IDX N");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &n) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_zeroblob(pStmt, idx, n);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_zeroblob64  STMT IDX N
+**
+** Test the sqlite3_bind_zeroblob64 interface.  STMT is a prepared statement.
+** IDX is the index of a wildcard in the prepared statement.  This command
+** binds a N-byte zero-filled BLOB to the wildcard.
+*/
+static int SQLITE_TCLAPI test_bind_zeroblob64(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  Tcl_WideInt n;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT IDX N");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetWideIntFromObj(interp, objv[3], &n) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_zeroblob64(pStmt, idx, n);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_int  STMT N VALUE
+**
+** Test the sqlite3_bind_int interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a 32-bit integer VALUE to that wildcard.
+*/
+static int SQLITE_TCLAPI test_bind_int(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int value;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &value) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_int(pStmt, idx, value);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   intarray_addr  INT  ...
+**
+** Return the address of a C-language array of 32-bit integers.
+**
+** Space to hold the array is obtained from malloc().  Call this procedure once
+** with no arguments in order to release memory.  Each call to this procedure
+** overwrites the previous array.
+*/
+static int SQLITE_TCLAPI test_intarray_addr(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int i;
+  static int *p = 0;
+
+  sqlite3_free(p);
+  p = 0;
+  if( objc>1 ){
+    p = sqlite3_malloc( sizeof(p[0])*(objc-1) );
+    if( p==0 ) return TCL_ERROR;
+    for(i=0; i<objc-1; i++){
+      if( Tcl_GetIntFromObj(interp, objv[1+i], &p[i]) ){
+        sqlite3_free(p);
+        p = 0;
+        return TCL_ERROR;
+      }
+    }
+  }  
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj((uptr)p));
+  return TCL_OK;
+}
+/*
+** Usage:   intarray_addr  INT  ...
+**
+** Return the address of a C-language array of 32-bit integers.
+**
+** Space to hold the array is obtained from malloc().  Call this procedure once
+** with no arguments in order to release memory.  Each call to this procedure
+** overwrites the previous array.
+*/
+static int SQLITE_TCLAPI test_int64array_addr(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int i;
+  static sqlite3_int64 *p = 0;
+
+  sqlite3_free(p);
+  p = 0;
+  if( objc>1 ){
+    p = sqlite3_malloc( sizeof(p[0])*(objc-1) );
+    if( p==0 ) return TCL_ERROR;
+    for(i=0; i<objc-1; i++){
+      Tcl_WideInt v;
+      if( Tcl_GetWideIntFromObj(interp, objv[1+i], &v) ){
+        sqlite3_free(p);
+        p = 0;
+        return TCL_ERROR;
+      }
+      p[i] = v;
+    }
+  }  
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj((uptr)p));
+  return TCL_OK;
+}
+/*
+** Usage:   doublearray_addr  INT  ...
+**
+** Return the address of a C-language array of doubles.
+**
+** Space to hold the array is obtained from malloc().  Call this procedure once
+** with no arguments in order to release memory.  Each call to this procedure
+** overwrites the previous array.
+*/
+static int SQLITE_TCLAPI test_doublearray_addr(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int i;
+  static double *p = 0;
+
+  sqlite3_free(p);
+  p = 0;
+  if( objc>1 ){
+    p = sqlite3_malloc( sizeof(p[0])*(objc-1) );
+    if( p==0 ) return TCL_ERROR;
+    for(i=0; i<objc-1; i++){
+      if( Tcl_GetDoubleFromObj(interp, objv[1+i], &p[i]) ){
+        sqlite3_free(p);
+        p = 0;
+        return TCL_ERROR;
+      }
+    }
+  }  
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj((uptr)p));
+  return TCL_OK;
+}
+/*
+** Usage:   textarray_addr  TEXT ...
+**
+** Return the address of a C-language array of strings.
+**
+** Space to hold the array is obtained from malloc().  Call this procedure once
+** with no arguments in order to release memory.  Each call to this procedure
+** overwrites the previous array.
+*/
+static int SQLITE_TCLAPI test_textarray_addr(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int i;
+  static int n = 0;
+  static char **p = 0;
+
+  for(i=0; i<n; i++) sqlite3_free(p[i]);
+  sqlite3_free(p);
+  p = 0;
+  if( objc>1 ){
+    p = sqlite3_malloc( sizeof(p[0])*(objc-1) );
+    if( p==0 ) return TCL_ERROR;
+    for(i=0; i<objc-1; i++){
+      p[i] = sqlite3_mprintf("%s", Tcl_GetString(objv[1+i]));
+    }
+  }
+  n = objc-1;
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj((uptr)p));
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   sqlite3_bind_int64  STMT N VALUE
+**
+** Test the sqlite3_bind_int64 interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a 64-bit integer VALUE to that wildcard.
+*/
+static int SQLITE_TCLAPI test_bind_int64(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  Tcl_WideInt value;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetWideIntFromObj(interp, objv[3], &value) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_int64(pStmt, idx, value);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   sqlite3_bind_double  STMT N VALUE
+**
+** Test the sqlite3_bind_double interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a 64-bit integer VALUE to that wildcard.
+*/
+static int SQLITE_TCLAPI test_bind_double(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  double value = 0;
+  int rc;
+  const char *zVal;
+  int i;
+  static const struct {
+    const char *zName;     /* Name of the special floating point value */
+    unsigned int iUpper;   /* Upper 32 bits */
+    unsigned int iLower;   /* Lower 32 bits */
+  } aSpecialFp[] = {
+    {  "NaN",      0x7fffffff, 0xffffffff },
+    {  "SNaN",     0x7ff7ffff, 0xffffffff },
+    {  "-NaN",     0xffffffff, 0xffffffff },
+    {  "-SNaN",    0xfff7ffff, 0xffffffff },
+    {  "+Inf",     0x7ff00000, 0x00000000 },
+    {  "-Inf",     0xfff00000, 0x00000000 },
+    {  "Epsilon",  0x00000000, 0x00000001 },
+    {  "-Epsilon", 0x80000000, 0x00000001 },
+    {  "NaN0",     0x7ff80000, 0x00000000 },
+    {  "-NaN0",    0xfff80000, 0x00000000 },
+  };
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+
+  /* Intercept the string "NaN" and generate a NaN value for it.
+  ** All other strings are passed through to Tcl_GetDoubleFromObj().
+  ** Tcl_GetDoubleFromObj() should understand "NaN" but some versions
+  ** contain a bug.
+  */
+  zVal = Tcl_GetString(objv[3]);
+  for(i=0; i<sizeof(aSpecialFp)/sizeof(aSpecialFp[0]); i++){
+    if( strcmp(aSpecialFp[i].zName, zVal)==0 ){
+      sqlite3_uint64 x;
+      x = aSpecialFp[i].iUpper;
+      x <<= 32;
+      x |= aSpecialFp[i].iLower;
+      assert( sizeof(value)==8 );
+      assert( sizeof(x)==8 );
+      memcpy(&value, &x, 8);
+      break;
+    }
+  }
+  if( i>=sizeof(aSpecialFp)/sizeof(aSpecialFp[0]) &&
+         Tcl_GetDoubleFromObj(interp, objv[3], &value) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_bind_double(pStmt, idx, value);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_null  STMT N
+**
+** Test the sqlite3_bind_null interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a NULL to the wildcard.
+*/
+static int SQLITE_TCLAPI test_bind_null(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_null(pStmt, idx);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_text  STMT N STRING BYTES
+**
+** Test the sqlite3_bind_text interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a UTF-8 string STRING to the wildcard.  The string is BYTES bytes
+** long.
+*/
+static int SQLITE_TCLAPI test_bind_text(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int trueLength = 0;
+  int bytes;
+  char *value;
+  int rc;
+  char *toFree = 0;
+
+  if( objc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE BYTES", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  value = (char*)Tcl_GetByteArrayFromObj(objv[3], &trueLength);
+  if( Tcl_GetIntFromObj(interp, objv[4], &bytes) ) return TCL_ERROR;
+  if( bytes<0 ){
+    toFree = malloc( trueLength + 1 );
+    if( toFree==0 ){
+      Tcl_AppendResult(interp, "out of memory", (void*)0);
+      return TCL_ERROR;
+    }
+    memcpy(toFree, value, trueLength);
+    toFree[trueLength] = 0;
+    value = toFree;
+  }
+  rc = sqlite3_bind_text(pStmt, idx, value, bytes, SQLITE_TRANSIENT);
+  free(toFree);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), (void*)0);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_text16 ?-static? STMT N STRING BYTES
+**
+** Test the sqlite3_bind_text16 interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a UTF-16 string STRING to the wildcard.  The string is BYTES bytes
+** long.
+*/
+static int SQLITE_TCLAPI test_bind_text16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3_stmt *pStmt;
+  int idx;
+  int bytes;
+  char *value;
+  char *toFree = 0;
+  int rc;
+  int trueLength = 0;
+
+  void (*xDel)(void*) = (objc==6?SQLITE_STATIC:SQLITE_TRANSIENT);
+  Tcl_Obj *oStmt    = objv[objc-4];
+  Tcl_Obj *oN       = objv[objc-3];
+  Tcl_Obj *oString  = objv[objc-2];
+  Tcl_Obj *oBytes   = objv[objc-1];
+
+  if( objc!=5 && objc!=6){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE BYTES", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(oStmt), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, oN, &idx) ) return TCL_ERROR;
+  value = (char*)Tcl_GetByteArrayFromObj(oString, &trueLength);
+  if( Tcl_GetIntFromObj(interp, oBytes, &bytes) ) return TCL_ERROR;
+  if( bytes<0 && xDel==SQLITE_TRANSIENT ){
+    toFree = malloc( trueLength + 3 );
+    if( toFree==0 ){
+      Tcl_AppendResult(interp, "out of memory", (void*)0);
+      return TCL_ERROR;
+    }
+    memcpy(toFree, value, trueLength);
+    memset(toFree+trueLength, 0, 3);
+    value = toFree;
+  }
+  rc = sqlite3_bind_text16(pStmt, idx, (void *)value, bytes, xDel);
+  free(toFree);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_blob ?-static? STMT N DATA BYTES
+**
+** Test the sqlite3_bind_blob interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a BLOB to the wildcard.  The BLOB is BYTES bytes in size.
+*/
+static int SQLITE_TCLAPI test_bind_blob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int len, idx;
+  int bytes;
+  char *value;
+  int rc;
+  sqlite3_destructor_type xDestructor = SQLITE_TRANSIENT;
+
+  if( objc!=5 && objc!=6 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N DATA BYTES", 0);
+    return TCL_ERROR;
+  }
+
+  if( objc==6 ){
+    xDestructor = SQLITE_STATIC;
+    objv++;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+
+  value = (char*)Tcl_GetByteArrayFromObj(objv[3], &len);
+  if( Tcl_GetIntFromObj(interp, objv[4], &bytes) ) return TCL_ERROR;
+
+  if( bytes>len ){
+    char zBuf[200];
+    sqlite3_snprintf(sizeof(zBuf), zBuf,
+                     "cannot use %d blob bytes, have %d", bytes, len);
+    Tcl_AppendResult(interp, zBuf, (char*)0);
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_bind_blob(pStmt, idx, value, bytes, xDestructor);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_value_from_preupdate STMT N NEW|OLD IDX
+**
+** Test the sqlite3_bind_value interface using sqlite3_value objects
+** obtained from either sqlite3_preupdate_new() (if arg[3]=="new") or
+** sqlite3_preupdate_old() if (arg[3]=="old"). IDX is the index to
+** pass to the sqlite3_preupdate_xxx() function.
+*/
+static int SQLITE_TCLAPI test_bind_value_from_preupdate(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int bidx;
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  const char *z3 = 0;
+  sqlite3 *db = 0;
+  sqlite3_value *pVal = 0;
+#endif
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT N NEW|OLD IDX");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[4], &bidx) ) return TCL_ERROR;
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  z3 = Tcl_GetString(objv[3]);
+  db = sqlite3_db_handle(pStmt);
+  if( z3[0]=='n' ){
+    sqlite3_preupdate_new(db, bidx, &pVal);
+  }else if( z3[0]=='o' ){
+    sqlite3_preupdate_old(db, bidx, &pVal);
+  }else{
+    Tcl_AppendResult(interp, "expected new or old, got: ", z3, (char*)0);
+    return TCL_ERROR;
+  }
+  sqlite3_bind_value(pStmt, idx, pVal);
+#endif
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_value_from_select STMT N SELECT
+**
+** Test the sqlite3_bind_value interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement. 
+*/
+static int SQLITE_TCLAPI test_bind_value_from_select(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  sqlite3_stmt *pStmt2;
+  int idx;
+  const char *zSql = 0;
+  sqlite3 *db = 0;
+  int rc = SQLITE_OK;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT N SELECT");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[3]);
+  db = sqlite3_db_handle(pStmt);
+
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt2, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, "error in SQL: ", sqlite3_errmsg(db), (char*)0);
+    return TCL_ERROR;
+  }
+  if( sqlite3_step(pStmt2)==SQLITE_ROW ){
+    sqlite3_value *pVal = sqlite3_column_value(pStmt2, 0);
+    sqlite3_bind_value(pStmt, idx, pVal);
+  }
+  rc = sqlite3_finalize(pStmt2);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, 
+        "error runnning SQL: ", sqlite3_errmsg(db), (char*)0
+    );
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+#ifdef _WIN32
+  struct iovec {
+    void *iov_base;
+    size_t iov_len;
+  };
+#else
+# include <sys/uio.h>
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** sqlite3_carray_bind [options...] STMT NAME VALUE ...
+**
+** Options:
+**    -transient
+**    -static
+**    -int32
+**    -int64
+**    -double
+**    -text
+**    -blob
+**
+** Each call clears static data.  Called with no options does nothing
+** but clear static data.
+*/
+static int SQLITE_TCLAPI test_carray_bind(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int eType = 0;   /* CARRAY_INT32 */
+  int nData = 0;
+  void *aData = 0;
+  int isTransient = 0;
+  int isStatic = 0;
+  int idx;
+  int i, j;
+  int rc;
+  void (*xDel)(void*) = sqlite3_free;
+  static void *aStaticData = 0;
+  static int nStaticData = 0;
+  static int eStaticType = 0;
+  extern int sqlite3_carray_bind(
+    sqlite3_stmt *pStmt,
+    int i,
+    void *aData,
+    int nData,
+    int mFlags,
+    void (*xDestroy)(void*)
+  );
+  
+  if( aStaticData ){
+    /* Always clear preexisting static data on every call */
+    if( eStaticType==3 ){
+      for(i=0; i<nStaticData; i++){
+        sqlite3_free(((char**)aStaticData)[i]);
+      }
+    }
+    if( eStaticType==4 ){
+      for(i=0; i<nStaticData; i++){
+        sqlite3_free(((struct iovec*)aStaticData)[i].iov_base);
+      }
+    } 
+    sqlite3_free(aStaticData);
+    aStaticData = 0;
+    nStaticData = 0;
+    eStaticType = 0;
+  }
+  if( objc==1 ) return TCL_OK;
+
+  for(i=1; i<objc && Tcl_GetString(objv[i])[0]=='-'; i++){
+    const char *z = Tcl_GetString(objv[i]);
+    if( strcmp(z, "-transient")==0 ){
+      isTransient = 1;
+      xDel = SQLITE_TRANSIENT;
+    }else
+    if( strcmp(z, "-static")==0 ){
+      isStatic = 1;
+      xDel = SQLITE_STATIC;
+    }else
+    if( strcmp(z, "-int32")==0 ){
+      eType = 0;  /* CARRAY_INT32 */
+    }else
+    if( strcmp(z, "-int64")==0 ){
+      eType = 1;  /* CARRAY_INT64 */
+    }else
+    if( strcmp(z, "-double")==0 ){
+      eType = 2;  /* CARRAY_DOUBLE */
+    }else
+    if( strcmp(z, "-text")==0 ){
+      eType = 3;  /* CARRAY_TEXT */
+    }else
+    if( strcmp(z, "-blob")==0 ){
+      eType = 4;  /* CARRAY_BLOB */
+    }else
+    if( strcmp(z, "--")==0 ){
+      break;
+    }else
+    {
+      Tcl_AppendResult(interp, "unknown option: ", z, (char*)0);
+      return TCL_ERROR;
+    }
+  }
+  if( eType==3 && !isStatic && !isTransient ){
+    Tcl_AppendResult(interp, "text data must be either -static or -transient",
+                     (char*)0);
+    return TCL_ERROR;
+  }
+  if( eType==4 && !isStatic && !isTransient ){
+    Tcl_AppendResult(interp, "blob data must be either -static or -transient",
+                     (char*)0);
+    return TCL_ERROR;
+  }
+  if( isStatic && isTransient ){
+    Tcl_AppendResult(interp, "cannot be both -static and -transient",
+                     (char*)0);
+    return TCL_ERROR;
+  }
+  if( objc-i < 2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "[OPTIONS] STMT IDX VALUE ...");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[i]), &pStmt) ) return TCL_ERROR;
+  i++;
+  if( Tcl_GetIntFromObj(interp, objv[i], &idx) ) return TCL_ERROR;
+  i++;
+  nData = objc - i;
+  switch( eType + 5*(nData<=0) ){
+    case 0: { /* INT32 */
+      int *a = sqlite3_malloc( sizeof(int)*nData );
+      if( a==0 ){ rc = SQLITE_NOMEM; goto carray_bind_done; }
+      for(j=0; j<nData; j++){
+        int v;
+        if( Tcl_GetIntFromObj(interp, objv[i+j], &v) ){
+          sqlite3_free(a);
+          return TCL_ERROR;
+        }
+        a[j] = v;
+      }
+      aData = a;
+      break;
+    }
+    case 1: { /* INT64 */
+      sqlite3_int64 *a = sqlite3_malloc( sizeof(sqlite3_int64)*nData );
+      if( a==0 ){ rc = SQLITE_NOMEM; goto carray_bind_done; }
+      for(j=0; j<nData; j++){
+        Tcl_WideInt v;
+        if( Tcl_GetWideIntFromObj(interp, objv[i+j], &v) ){
+          sqlite3_free(a);
+          return TCL_ERROR;
+        }
+        a[j] = v;
+      }
+      aData = a;
+      break;
+    }
+    case 2: { /* DOUBLE */
+      double *a = sqlite3_malloc( sizeof(double)*nData );
+      if( a==0 ){ rc = SQLITE_NOMEM; goto carray_bind_done; }
+      for(j=0; j<nData; j++){
+        double v;
+        if( Tcl_GetDoubleFromObj(interp, objv[i+j], &v) ){
+          sqlite3_free(a);
+          return TCL_ERROR;
+        }
+        a[j] = v;
+      }
+      aData = a;
+      break;
+    }
+    case 3: { /* TEXT */
+      char **a = sqlite3_malloc( sizeof(char*)*nData );
+      if( a==0 ){ rc = SQLITE_NOMEM; goto carray_bind_done; }
+      for(j=0; j<nData; j++){
+        const char *v = Tcl_GetString(objv[i+j]);
+        a[j] = sqlite3_mprintf("%s", v);
+      }
+      aData = a;
+      break;
+    }
+    case 4: { /* BLOB */
+      struct iovec *a = sqlite3_malloc( sizeof(struct iovec)*nData );
+      if( a==0 ){ rc = SQLITE_NOMEM; goto carray_bind_done; }
+      for(j=0; j<nData; j++){
+        int n = 0;
+        unsigned char *v = Tcl_GetByteArrayFromObj(objv[i+i], &n);
+        a[j].iov_len = n;
+        a[j].iov_base = sqlite3_malloc64( n );
+        if( a[j].iov_base==0 ){
+          a[j].iov_len = 0;
+        }else{
+          memcpy(a[j].iov_base, v, n);
+        }
+      }
+      aData = a;
+      break;
+    }
+    case 5: { /* nData==0 */
+      aData = "";
+      xDel = SQLITE_STATIC;
+      isTransient = 0;
+      isStatic = 0;
+      break;
+    }
+  }
+  if( isStatic ){
+    aStaticData = aData;
+    nStaticData = nData;
+    eStaticType = eType;
+  }
+  rc = sqlite3_carray_bind(pStmt, idx, aData, nData, eType, xDel);
+  if( isTransient ){
+    if( eType==3 ){
+      for(i=0; i<nData; i++) sqlite3_free(((char**)aData)[i]);
+    }
+    if( eType==4 ){
+      for(i=0; i<nData; i++) sqlite3_free(((struct iovec*)aData)[i].iov_base);
+    }
+    sqlite3_free(aData);
+  }
+carray_bind_done:
+  if( rc ){
+    Tcl_AppendResult(interp, sqlite3_errstr(rc), (char*)0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** Usage:   sqlite3_bind_parameter_count  STMT
+**
+** Return the number of wildcards in the given statement.
+*/
+static int SQLITE_TCLAPI test_bind_parameter_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_bind_parameter_count(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_parameter_name  STMT  N
+**
+** Return the name of the Nth wildcard.  The first wildcard is 1.
+** An empty string is returned if N is out of range or if the wildcard
+** is nameless.
+*/
+static int SQLITE_TCLAPI test_bind_parameter_name(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int i;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT N");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &i) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, 
+     Tcl_NewStringObj(sqlite3_bind_parameter_name(pStmt,i),-1)
+  );
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_parameter_index  STMT  NAME
+**
+** Return the index of the wildcard called NAME.  Return 0 if there is
+** no such wildcard.
+*/
+static int SQLITE_TCLAPI test_bind_parameter_index(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT NAME");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, 
+     Tcl_NewIntObj(
+       sqlite3_bind_parameter_index(pStmt,Tcl_GetString(objv[2]))
+     )
+  );
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_clear_bindings STMT
+**
+*/
+static int SQLITE_TCLAPI test_clear_bindings(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_clear_bindings(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_sleep MILLISECONDS
+*/
+static int SQLITE_TCLAPI test_sleep(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int ms;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "MILLISECONDS");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &ms) ){
+    return TCL_ERROR;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_sleep(ms)));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_extended_errcode DB
+**
+** Return the string representation of the most recent sqlite3_* API
+** error code. e.g. "SQLITE_ERROR".
+*/
+static int SQLITE_TCLAPI test_ex_errcode(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_extended_errcode(db);
+  Tcl_AppendResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+
+/*
+** Usage: sqlite3_errcode DB
+**
+** Return the string representation of the most recent sqlite3_* API
+** error code. e.g. "SQLITE_ERROR".
+*/
+static int SQLITE_TCLAPI test_errcode(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_errcode(db);
+  Tcl_AppendResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_errmsg DB
+**
+** Returns the UTF-8 representation of the error message string for the
+** most recent sqlite3_* API call.
+*/
+static int SQLITE_TCLAPI test_errmsg(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zErr;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  zErr = sqlite3_errmsg(db);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(zErr, -1));
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   sqlite3_error_offset DB
+**
+** Return the byte offset into the input UTF8 SQL for the most recent
+** error, or -1 of the error does not refer to a specific token.
+*/
+static int SQLITE_TCLAPI test_error_offset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int iByteOffset;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  iByteOffset = sqlite3_error_offset(db);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(iByteOffset));
+  return TCL_OK;
+}
+
+/*
+** Usage:   test_errmsg16 DB
+**
+** Returns the UTF-16 representation of the error message string for the
+** most recent sqlite3_* API call. This is a byte array object at the TCL 
+** level, and it includes the 0x00 0x00 terminator bytes at the end of the
+** UTF-16 string.
+*/
+static int SQLITE_TCLAPI test_errmsg16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  const void *zErr;
+  const char *z;
+  int bytes = 0;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  zErr = sqlite3_errmsg16(db);
+  if( zErr ){
+    z = zErr;
+    for(bytes=0; z[bytes] || z[bytes+1]; bytes+=2){}
+  }
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(zErr, bytes));
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare DB sql bytes ?tailvar?
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int SQLITE_TCLAPI test_prepare(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSql;
+  int bytes;
+  const char *zTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes ?tailvar?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_prepare(db, zSql, bytes, &pStmt, objc>=5 ? &zTail : 0);
+  Tcl_ResetResult(interp);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( zTail && objc>=5 ){
+    if( bytes>=0 ){
+      bytes = bytes - (int)(zTail-zSql);
+    }
+    if( (int)strlen(zTail)<bytes ){
+      bytes = (int)strlen(zTail);
+    }
+    Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
+  }
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare_v2 DB sql bytes ?tailvar?
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int SQLITE_TCLAPI test_prepare_v2(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSql;
+  char *zCopy = 0;                /* malloc() copy of zSql */
+  int bytes;
+  const char *zTail = 0;
+  const char **pzTail;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  /* Instead of using zSql directly, make a copy into a buffer obtained
+  ** directly from malloc(). The idea is to make it easier for valgrind
+  ** to spot buffer overreads.  */
+  if( bytes>=0 ){
+    zCopy = malloc(bytes);
+    memcpy(zCopy, zSql, bytes);
+  }else{
+    int n = (int)strlen(zSql) + 1;
+    zCopy = malloc(n);
+    memcpy(zCopy, zSql, n);
+  }
+  pzTail = objc>=5 ? &zTail : 0;
+  rc = sqlite3_prepare_v2(db, zCopy, bytes, &pStmt, pzTail);
+  if( objc>=5 ){
+    zTail = &zSql[(zTail - zCopy)];
+  }
+  free(zCopy);
+
+  assert(rc==SQLITE_OK || pStmt==0);
+  Tcl_ResetResult(interp);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc==SQLITE_OK && objc>=5 && zTail ){
+    if( bytes>=0 ){
+      bytes = bytes - (int)(zTail-zSql);
+    }
+    Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
+  }
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare_v3 DB sql bytes flags ?tailvar?
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB> and flags <flags>. The parameter <tailval> is
+** the name of a global variable that is set to the unused portion of
+** <sql> (if any). A STMT handle is returned.
+*/
+static int SQLITE_TCLAPI test_prepare_v3(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSql;
+  char *zCopy = 0;                /* malloc() copy of zSql */
+  int bytes, flags;
+  const char *zTail = 0;
+  const char **pzTail;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+
+  if( objc!=6 && objc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes flags tailvar", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[4], &flags) ) return TCL_ERROR;
+
+  /* Instead of using zSql directly, make a copy into a buffer obtained
+  ** directly from malloc(). The idea is to make it easier for valgrind
+  ** to spot buffer overreads.  */
+  if( bytes>=0 ){
+    zCopy = malloc(bytes);
+    memcpy(zCopy, zSql, bytes);
+  }else{
+    int n = (int)strlen(zSql) + 1;
+    zCopy = malloc(n);
+    memcpy(zCopy, zSql, n);
+  }
+  pzTail = objc>=6 ? &zTail : 0;
+  rc = sqlite3_prepare_v3(db, zCopy, bytes, (unsigned int)flags,&pStmt,pzTail);
+  free(zCopy);
+  zTail = &zSql[(zTail - zCopy)];
+
+  assert(rc==SQLITE_OK || pStmt==0);
+  Tcl_ResetResult(interp);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc==SQLITE_OK && zTail && objc>=6 ){
+    if( bytes>=0 ){
+      bytes = bytes - (int)(zTail-zSql);
+    }
+    Tcl_ObjSetVar2(interp, objv[5], 0, Tcl_NewStringObj(zTail, bytes), 0);
+  }
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare_tkt3134 DB
+**
+** Generate a prepared statement for a zero-byte string as a test
+** for ticket #3134.  The string should be preceded by a zero byte.
+*/
+static int SQLITE_TCLAPI test_prepare_tkt3134(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  static const char zSql[] = "\000SELECT 1";
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_prepare_v2(db, &zSql[1], 0, &pStmt, 0);
+  assert(rc==SQLITE_OK || pStmt==0);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare16 DB sql bytes tailvar
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int SQLITE_TCLAPI test_prepare16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  const void *zSql;
+  const void *zTail = 0;
+  Tcl_Obj *pTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50]; 
+  int rc;
+  int bytes;                /* The integer specified as arg 3 */
+  int objlen;               /* The byte-array length of arg 2 */
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes ?tailvar?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetByteArrayFromObj(objv[2], &objlen);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_prepare16(db, zSql, bytes, &pStmt, objc>=5 ? &zTail : 0);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc ){
+    return TCL_ERROR;
+  }
+
+  if( objc>=5 ){
+    if( zTail ){
+      objlen = objlen - (int)((u8 *)zTail-(u8 *)zSql);
+    }else{
+      objlen = 0;
+    }
+    pTail = Tcl_NewByteArrayObj((u8 *)zTail, objlen);
+    Tcl_IncrRefCount(pTail);
+    Tcl_ObjSetVar2(interp, objv[4], 0, pTail, 0);
+    Tcl_DecrRefCount(pTail);
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, zBuf, 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare16_v2 DB sql bytes ?tailvar?
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int SQLITE_TCLAPI test_prepare16_v2(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  const void *zSql;
+  const void *zTail = 0;
+  Tcl_Obj *pTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50]; 
+  int rc;
+  int bytes;                /* The integer specified as arg 3 */
+  int objlen;               /* The byte-array length of arg 2 */
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes ?tailvar?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetByteArrayFromObj(objv[2], &objlen);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_prepare16_v2(db, zSql, bytes, &pStmt, objc>=5 ? &zTail : 0);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc ){
+    return TCL_ERROR;
+  }
+
+  if( objc>=5 ){
+    if( zTail ){
+      objlen = objlen - (int)((u8 *)zTail-(u8 *)zSql);
+    }else{
+      objlen = 0;
+    }
+    pTail = Tcl_NewByteArrayObj((u8 *)zTail, objlen);
+    Tcl_IncrRefCount(pTail);
+    Tcl_ObjSetVar2(interp, objv[4], 0, pTail, 0);
+    Tcl_DecrRefCount(pTail);
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, zBuf, 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_open filename ?options-list?
+*/
+static int SQLITE_TCLAPI test_open(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;
+  sqlite3 *db;
+  char zBuf[100];
+
+  if( objc!=3 && objc!=2 && objc!=1 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " filename options-list", 0);
+    return TCL_ERROR;
+  }
+
+  zFilename = objc>1 ? Tcl_GetString(objv[1]) : 0;
+  sqlite3_open(zFilename, &db);
+  
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_open_v2 FILENAME FLAGS VFS
+*/
+static int SQLITE_TCLAPI test_open_v2(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;
+  const char *zVfs;
+  int flags = 0;
+  sqlite3 *db;
+  int rc;
+  char zBuf[100];
+
+  int nFlag;
+  Tcl_Obj **apFlag;
+  int i;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME FLAGS VFS");
+    return TCL_ERROR;
+  }
+  zFilename = Tcl_GetString(objv[1]);
+  zVfs = Tcl_GetString(objv[3]);
+  if( zVfs[0]==0x00 ) zVfs = 0;
+
+  rc = Tcl_ListObjGetElements(interp, objv[2], &nFlag, &apFlag);
+  if( rc!=TCL_OK ) return rc;
+  for(i=0; i<nFlag; i++){
+    int iFlag;
+    struct OpenFlag {
+      const char *zFlag;
+      int flag;
+    } aFlag[] = {
+      { "SQLITE_OPEN_READONLY", SQLITE_OPEN_READONLY },
+      { "SQLITE_OPEN_READWRITE", SQLITE_OPEN_READWRITE },
+      { "SQLITE_OPEN_CREATE", SQLITE_OPEN_CREATE },
+      { "SQLITE_OPEN_DELETEONCLOSE", SQLITE_OPEN_DELETEONCLOSE },
+      { "SQLITE_OPEN_EXCLUSIVE", SQLITE_OPEN_EXCLUSIVE },
+      { "SQLITE_OPEN_AUTOPROXY", SQLITE_OPEN_AUTOPROXY },
+      { "SQLITE_OPEN_MAIN_DB", SQLITE_OPEN_MAIN_DB },
+      { "SQLITE_OPEN_TEMP_DB", SQLITE_OPEN_TEMP_DB },
+      { "SQLITE_OPEN_TRANSIENT_DB", SQLITE_OPEN_TRANSIENT_DB },
+      { "SQLITE_OPEN_MAIN_JOURNAL", SQLITE_OPEN_MAIN_JOURNAL },
+      { "SQLITE_OPEN_TEMP_JOURNAL", SQLITE_OPEN_TEMP_JOURNAL },
+      { "SQLITE_OPEN_SUBJOURNAL", SQLITE_OPEN_SUBJOURNAL },
+      { "SQLITE_OPEN_SUPER_JOURNAL", SQLITE_OPEN_SUPER_JOURNAL },
+      { "SQLITE_OPEN_NOMUTEX", SQLITE_OPEN_NOMUTEX },
+      { "SQLITE_OPEN_FULLMUTEX", SQLITE_OPEN_FULLMUTEX },
+      { "SQLITE_OPEN_SHAREDCACHE", SQLITE_OPEN_SHAREDCACHE },
+      { "SQLITE_OPEN_PRIVATECACHE", SQLITE_OPEN_PRIVATECACHE },
+      { "SQLITE_OPEN_WAL", SQLITE_OPEN_WAL },
+      { "SQLITE_OPEN_URI", SQLITE_OPEN_URI },
+      { "SQLITE_OPEN_EXRESCODE", SQLITE_OPEN_EXRESCODE },
+      { 0, 0 }
+    };
+    rc = Tcl_GetIndexFromObjStruct(interp, apFlag[i], aFlag, sizeof(aFlag[0]), 
+        "flag", 0, &iFlag
+    );
+    if( rc!=TCL_OK ) return rc;
+    flags |= aFlag[iFlag].flag;
+  }
+
+  rc = sqlite3_open_v2(zFilename, &db, flags, zVfs);
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_open16 filename options
+*/
+static int SQLITE_TCLAPI test_open16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  const void *zFilename;
+  sqlite3 *db;
+  char zBuf[100];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " filename options-list", 0);
+    return TCL_ERROR;
+  }
+
+  zFilename = Tcl_GetByteArrayFromObj(objv[1], 0);
+  sqlite3_open16(zFilename, &db);
+  
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_complete16 <UTF-16 string>
+**
+** Return 1 if the supplied argument is a complete SQL statement, or zero
+** otherwise.
+*/
+static int SQLITE_TCLAPI test_complete16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#if !defined(SQLITE_OMIT_COMPLETE) && !defined(SQLITE_OMIT_UTF16)
+  char *zBuf;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "<utf-16 sql>");
+    return TCL_ERROR;
+  }
+
+  zBuf = (char*)Tcl_GetByteArrayFromObj(objv[1], 0);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_complete16(zBuf)));
+#endif /* SQLITE_OMIT_COMPLETE && SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_normalize SQL
+**
+** Return the normalized value for an SQL statement.
+*/
+static int SQLITE_TCLAPI test_normalize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  char *zSql;
+  char *zNorm;
+  extern char *sqlite3_normalize(const char*);
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SQL");
+    return TCL_ERROR;
+  }
+
+  zSql = (char*)Tcl_GetString(objv[1]);
+  zNorm = sqlite3_normalize(zSql);
+  if( zNorm ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(zNorm, -1));
+    sqlite3_free(zNorm);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_step STMT
+**
+** Advance the statement to the next row.
+*/
+static int SQLITE_TCLAPI test_step(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = sqlite3_step(pStmt);
+
+  /* if( rc!=SQLITE_DONE && rc!=SQLITE_ROW ) return TCL_ERROR; */
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_sql(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetResult(interp, (char *)sqlite3_sql(pStmt), TCL_VOLATILE);
+  return TCL_OK;
+}
+static int SQLITE_TCLAPI test_ex_sql(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  char *z;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  z = sqlite3_expanded_sql(pStmt);
+  Tcl_SetResult(interp, z, TCL_VOLATILE);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+#ifdef SQLITE_ENABLE_NORMALIZE
+static int SQLITE_TCLAPI test_norm_sql(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetResult(interp, (char *)sqlite3_normalized_sql(pStmt), TCL_VOLATILE);
+  return TCL_OK;
+}
+#endif /* SQLITE_ENABLE_NORMALIZE */
+
+/*
+** Usage: sqlite3_column_count STMT 
+**
+** Return the number of columns returned by the sql statement STMT.
+*/
+static int SQLITE_TCLAPI test_column_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_column_count(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_type STMT column
+**
+** Return the type of the data in column 'column' of the current row.
+*/
+static int SQLITE_TCLAPI test_column_type(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  int tp;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  tp = sqlite3_column_type(pStmt, col);
+  switch( tp ){
+    case SQLITE_INTEGER: 
+      Tcl_SetResult(interp, "INTEGER", TCL_STATIC); 
+      break;
+    case SQLITE_NULL:
+      Tcl_SetResult(interp, "NULL", TCL_STATIC); 
+      break;
+    case SQLITE_FLOAT:
+      Tcl_SetResult(interp, "FLOAT", TCL_STATIC); 
+      break;
+    case SQLITE_TEXT:
+      Tcl_SetResult(interp, "TEXT", TCL_STATIC); 
+      break;
+    case SQLITE_BLOB:
+      Tcl_SetResult(interp, "BLOB", TCL_STATIC); 
+      break;
+    default:
+      assert(0);
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_int64 STMT column
+**
+** Return the data in column 'column' of the current row cast as an
+** wide (64-bit) integer.
+*/
+static int SQLITE_TCLAPI test_column_int64(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  i64 iVal;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  iVal = sqlite3_column_int64(pStmt, col);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(iVal));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_blob STMT column
+*/
+static int SQLITE_TCLAPI test_column_blob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+
+  int len;
+  const void *pBlob;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  len = sqlite3_column_bytes(pStmt, col);
+  pBlob = sqlite3_column_blob(pStmt, col);
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(pBlob, len));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_double STMT column
+**
+** Return the data in column 'column' of the current row cast as a double.
+*/
+static int SQLITE_TCLAPI test_column_double(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  double rVal;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  rVal = sqlite3_column_double(pStmt, col);
+  Tcl_SetObjResult(interp, Tcl_NewDoubleObj(rVal));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_data_count STMT 
+**
+** Return the number of columns returned by the sql statement STMT.
+*/
+static int SQLITE_TCLAPI test_data_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_data_count(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_text STMT column
+**
+** Usage: sqlite3_column_decltype STMT column
+**
+** Usage: sqlite3_column_name STMT column
+*/
+static int SQLITE_TCLAPI test_stmt_utf8(
+  void * clientData,        /* Pointer to SQLite API function to be invoke */
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  const char *(*xFunc)(sqlite3_stmt*, int);
+  const char *zRet;
+
+  xFunc = (const char *(*)(sqlite3_stmt*, int))clientData;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+  zRet = xFunc(pStmt, col);
+  if( zRet ){
+    Tcl_SetResult(interp, (char *)zRet, 0);
+  }
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_global_recover(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  int rc;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  rc = sqlite3_global_recover();
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_text STMT column
+**
+** Usage: sqlite3_column_decltype STMT column
+**
+** Usage: sqlite3_column_name STMT column
+*/
+static int SQLITE_TCLAPI test_stmt_utf16(
+  void * clientData,     /* Pointer to SQLite API function to be invoked */
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3_stmt *pStmt;
+  int col;
+  Tcl_Obj *pRet;
+  const void *zName16;
+  const void *(*xFunc)(sqlite3_stmt*, int);
+
+  xFunc = (const void *(*)(sqlite3_stmt*, int))clientData;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  zName16 = xFunc(pStmt, col);
+  if( zName16 ){
+    int n;
+    const char *z = zName16;
+    for(n=0; z[n] || z[n+1]; n+=2){}
+    pRet = Tcl_NewByteArrayObj(zName16, n+2);
+    Tcl_SetObjResult(interp, pRet);
+  }
+#endif /* SQLITE_OMIT_UTF16 */
+
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_int STMT column
+**
+** Usage: sqlite3_column_bytes STMT column
+**
+** Usage: sqlite3_column_bytes16 STMT column
+**
+*/
+static int SQLITE_TCLAPI test_stmt_int(
+  void * clientData,    /* Pointer to SQLite API function to be invoked */
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  int (*xFunc)(sqlite3_stmt*, int);
+
+  xFunc = (int (*)(sqlite3_stmt*, int))clientData;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(xFunc(pStmt, col)));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_interrupt  DB 
+**
+** Trigger an interrupt on DB
+*/
+static int SQLITE_TCLAPI test_interrupt(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_interrupt(db);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_is_interrupted  DB 
+**
+** return true if an interrupt is current in effect on DB
+*/
+static int SQLITE_TCLAPI test_is_interrupted(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_is_interrupted(db);
+  Tcl_AppendResult(interp, rc ? "1" : "0", (void*)0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite_delete_function DB function-name
+**
+** Delete the user function 'function-name' from database handle DB. It
+** is assumed that the user function was created as UTF8, any number of
+** arguments (the way the TCL interface does it).
+*/
+static int SQLITE_TCLAPI delete_function(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  int rc;
+  sqlite3 *db;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB function-name", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, argv[2], -1, SQLITE_UTF8, 0, 0, 0, 0);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite_delete_collation DB collation-name
+**
+** Delete the collation sequence 'collation-name' from database handle 
+** DB. It is assumed that the collation sequence was created as UTF8 (the 
+** way the TCL interface does it).
+*/
+static int SQLITE_TCLAPI delete_collation(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  int rc;
+  sqlite3 *db;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB function-name", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_collation(db, argv[2], SQLITE_UTF8, 0, 0);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_get_autocommit DB
+**
+** Return true if the database DB is currently in auto-commit mode.
+** Return false if not.
+*/
+static int SQLITE_TCLAPI get_autocommit(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  char zBuf[30];
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", sqlite3_get_autocommit(db));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_busy_timeout DB MS
+**
+** Set the busy timeout.  This is more easily done using the timeout
+** method of the TCL interface.  But we need a way to test the case
+** where it returns SQLITE_MISUSE.
+*/
+static int SQLITE_TCLAPI test_busy_timeout(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  int rc, ms;
+  sqlite3 *db;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[2], &ms) ) return TCL_ERROR;
+  rc = sqlite3_busy_timeout(db, ms);
+  Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:  tcl_variable_type VARIABLENAME
+**
+** Return the name of the internal representation for the
+** value of the given variable.
+*/
+static int SQLITE_TCLAPI tcl_variable_type(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj *pVar;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "VARIABLE");
+    return TCL_ERROR;
+  }
+  pVar = Tcl_GetVar2Ex(interp, Tcl_GetString(objv[1]), 0, TCL_LEAVE_ERR_MSG);
+  if( pVar==0 ) return TCL_ERROR;
+  if( pVar->typePtr ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(pVar->typePtr->name, -1));
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_release_memory ?N?
+**
+** Attempt to release memory currently held but not actually required.
+** The integer N is the number of bytes we are trying to release.  The 
+** return value is the amount of memory actually released.
+*/
+static int SQLITE_TCLAPI test_release_memory(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
+  int N;
+  int amt;
+  if( objc!=1 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?N?");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( Tcl_GetIntFromObj(interp, objv[1], &N) ) return TCL_ERROR;
+  }else{
+    N = -1;
+  }
+  amt = sqlite3_release_memory(N);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(amt));
+#endif
+  return TCL_OK;
+}
+
+
+/*
+** Usage:  sqlite3_db_release_memory DB
+**
+** Attempt to release memory currently held by database DB.  Return the
+** result code (which in the current implementation is always zero).
+*/
+static int SQLITE_TCLAPI test_db_release_memory(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_db_release_memory(db);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_db_cacheflush DB
+**
+** Attempt to flush any dirty pages to disk.
+*/
+static int SQLITE_TCLAPI test_db_cacheflush(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_db_cacheflush(db);
+  if( rc ){
+    Tcl_SetResult(interp, (char *)sqlite3ErrStr(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_system_errno DB
+**
+** Return the low-level system errno value.
+*/
+static int SQLITE_TCLAPI test_system_errno(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int iErrno;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  iErrno = sqlite3_system_errno(db);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(iErrno));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_db_filename DB DBNAME
+**
+** Return the name of a file associated with a database.
+*/
+static int SQLITE_TCLAPI test_db_filename(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zDbName;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zDbName = Tcl_GetString(objv[2]);
+  Tcl_AppendResult(interp, sqlite3_db_filename(db, zDbName), (void*)0);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_db_readonly DB DBNAME
+**
+** Return 1 or 0 if DBNAME is readonly or not.  Return -1 if DBNAME does
+** not exist.
+*/
+static int SQLITE_TCLAPI test_db_readonly(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zDbName;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zDbName = Tcl_GetString(objv[2]);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_db_readonly(db, zDbName)));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_soft_heap_limit ?N?
+**
+** Query or set the soft heap limit for the current thread.  The
+** limit is only changed if the N is present.  The previous limit
+** is returned.
+*/
+static int SQLITE_TCLAPI test_soft_heap_limit(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_int64 amt;
+  Tcl_WideInt N = -1;
+  if( objc!=1 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?N?");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( Tcl_GetWideIntFromObj(interp, objv[1], &N) ) return TCL_ERROR;
+  }
+  amt = sqlite3_soft_heap_limit64(N);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(amt));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_hard_heap_limit ?N?
+**
+** Query or set the hard heap limit for the current thread.  The
+** limit is only changed if the N is present.  The previous limit
+** is returned.
+*/
+static int SQLITE_TCLAPI test_hard_heap_limit(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_int64 amt;
+  Tcl_WideInt N = -1;
+  if( objc!=1 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?N?");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( Tcl_GetWideIntFromObj(interp, objv[1], &N) ) return TCL_ERROR;
+  }
+  amt = sqlite3_hard_heap_limit64(N);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(amt));
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_thread_cleanup
+**
+** Call the sqlite3_thread_cleanup API.
+*/
+static int SQLITE_TCLAPI test_thread_cleanup(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_thread_cleanup();
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_pager_refcounts  DB
+**
+** Return a list of numbers which are the PagerRefcount for all
+** pagers on each database connection.
+*/
+static int SQLITE_TCLAPI test_pager_refcounts(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int i;
+  int v, *a;
+  Tcl_Obj *pResult;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  pResult = Tcl_NewObj();
+  for(i=0; i<db->nDb; i++){
+    if( db->aDb[i].pBt==0 ){
+      v = -1;
+    }else{
+      sqlite3_mutex_enter(db->mutex);
+      a = sqlite3PagerStats(sqlite3BtreePager(db->aDb[i].pBt));
+      v = a[0];
+      sqlite3_mutex_leave(db->mutex);
+    }
+    Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(v));
+  }
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   working_64bit_int
+**
+** Some TCL builds (ex: cygwin) do not support 64-bit integers.  This
+** leads to a number of test failures.  The present command checks the
+** TCL build to see whether or not it supports 64-bit integers.  It
+** returns TRUE if it does and FALSE if not.
+**
+** This command is used to warn users that their TCL build is defective
+** and that the errors they are seeing in the test scripts might be
+** a result of their defective TCL rather than problems in SQLite.
+*/
+static int SQLITE_TCLAPI working_64bit_int(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_Obj *pTestObj;
+  int working = 0;
+
+  pTestObj = Tcl_NewWideIntObj(1000000*(i64)1234567890);
+  working = strcmp(Tcl_GetString(pTestObj), "1234567890000000")==0;
+  Tcl_DecrRefCount(pTestObj);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(working));
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   vfs_unlink_test
+**
+** This TCL command unregisters the primary VFS and then registers
+** it back again.  This is used to test the ability to register a
+** VFS when none are previously registered, and the ability to 
+** unregister the only available VFS.  Ticket #2738
+*/
+static int SQLITE_TCLAPI vfs_unlink_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  sqlite3_vfs *pMain;
+  sqlite3_vfs *apVfs[20];
+  sqlite3_vfs one, two;
+
+  sqlite3_vfs_unregister(0);   /* Unregister of NULL is harmless */
+  one.zName = "__one";
+  two.zName = "__two";
+
+  /* Calling sqlite3_vfs_register with 2nd argument of 0 does not
+  ** change the default VFS
+  */
+  pMain = sqlite3_vfs_find(0);
+  sqlite3_vfs_register(&one, 0);
+  assert( pMain==0 || pMain==sqlite3_vfs_find(0) );
+  sqlite3_vfs_register(&two, 0);
+  assert( pMain==0 || pMain==sqlite3_vfs_find(0) );
+
+  /* We can find a VFS by its name */
+  assert( sqlite3_vfs_find("__one")==&one );
+  assert( sqlite3_vfs_find("__two")==&two );
+
+  /* Calling sqlite_vfs_register with non-zero second parameter changes the
+  ** default VFS, even if the 1st parameter is an existing VFS that is
+  ** previously registered as the non-default.
+  */
+  sqlite3_vfs_register(&one, 1);
+  assert( sqlite3_vfs_find("__one")==&one );
+  assert( sqlite3_vfs_find("__two")==&two );
+  assert( sqlite3_vfs_find(0)==&one );
+  sqlite3_vfs_register(&two, 1);
+  assert( sqlite3_vfs_find("__one")==&one );
+  assert( sqlite3_vfs_find("__two")==&two );
+  assert( sqlite3_vfs_find(0)==&two );
+  if( pMain ){
+    sqlite3_vfs_register(pMain, 1);
+    assert( sqlite3_vfs_find("__one")==&one );
+    assert( sqlite3_vfs_find("__two")==&two );
+    assert( sqlite3_vfs_find(0)==pMain );
+  }
+  
+  /* Unlink the default VFS.  Repeat until there are no more VFSes
+  ** registered.
+  */
+  for(i=0; i<sizeof(apVfs)/sizeof(apVfs[0]); i++){
+    apVfs[i] = sqlite3_vfs_find(0);
+    if( apVfs[i] ){
+      assert( apVfs[i]==sqlite3_vfs_find(apVfs[i]->zName) );
+      sqlite3_vfs_unregister(apVfs[i]);
+      assert( 0==sqlite3_vfs_find(apVfs[i]->zName) );
+    }
+  }
+  assert( 0==sqlite3_vfs_find(0) );
+  
+  /* Register the main VFS as non-default (will be made default, since
+  ** it'll be the only one in existence).
+  */
+  sqlite3_vfs_register(pMain, 0);
+  assert( sqlite3_vfs_find(0)==pMain );
+  
+  /* Un-register the main VFS again to restore an empty VFS list */
+  sqlite3_vfs_unregister(pMain);
+  assert( 0==sqlite3_vfs_find(0) );
+
+  /* Relink all VFSes in reverse order. */  
+  for(i=sizeof(apVfs)/sizeof(apVfs[0])-1; i>=0; i--){
+    if( apVfs[i] ){
+      sqlite3_vfs_register(apVfs[i], 1);
+      assert( apVfs[i]==sqlite3_vfs_find(0) );
+      assert( apVfs[i]==sqlite3_vfs_find(apVfs[i]->zName) );
+    }
+  }
+
+  /* Unregister out sample VFSes. */
+  sqlite3_vfs_unregister(&one);
+  sqlite3_vfs_unregister(&two);
+
+  /* Unregistering a VFS that is not currently registered is harmless */
+  sqlite3_vfs_unregister(&one);
+  sqlite3_vfs_unregister(&two);
+  assert( sqlite3_vfs_find("__one")==0 );
+  assert( sqlite3_vfs_find("__two")==0 );
+
+  /* We should be left with the original default VFS back as the
+  ** original */
+  assert( sqlite3_vfs_find(0)==pMain );
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   vfs_initfail_test
+**
+** This TCL command attempts to vfs_find and vfs_register when the
+** sqlite3_initialize() interface is failing.  All calls should fail.
+*/
+static int SQLITE_TCLAPI vfs_initfail_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs one;
+  one.zName = "__one";
+
+  if( sqlite3_vfs_find(0) ) return TCL_ERROR;
+  sqlite3_vfs_register(&one, 0);
+  if( sqlite3_vfs_find(0) ) return TCL_ERROR;
+  sqlite3_vfs_register(&one, 1);
+  if( sqlite3_vfs_find(0) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Saved VFSes
+*/
+static sqlite3_vfs *apVfs[20];
+static int nVfs = 0;
+
+/*
+** tclcmd:   vfs_unregister_all
+**
+** Unregister all VFSes.
+*/
+static int SQLITE_TCLAPI vfs_unregister_all(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  for(i=0; i<ArraySize(apVfs); i++){
+    apVfs[i] = sqlite3_vfs_find(0);
+    if( apVfs[i]==0 ) break;
+    sqlite3_vfs_unregister(apVfs[i]);
+  }
+  nVfs = i;
+  return TCL_OK;
+}
+/*
+** tclcmd:   vfs_reregister_all
+**
+** Restore all VFSes that were removed using vfs_unregister_all. Taking
+** care to put the linked list back together in the same order as it was
+** in before vfs_unregister_all was invoked.
+*/
+static int SQLITE_TCLAPI vfs_reregister_all(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  for(i=nVfs-1; i>=0; i--){
+    sqlite3_vfs_register(apVfs[i], 1);
+  }
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   file_control_test DB
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the same.
+*/
+static int SQLITE_TCLAPI file_control_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int iArg = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_file_control(db, 0, 0, &iArg);
+  assert( rc==SQLITE_NOTFOUND );
+  rc = sqlite3_file_control(db, "notadatabase", SQLITE_FCNTL_LOCKSTATE, &iArg);
+  assert( rc==SQLITE_ERROR );
+  rc = sqlite3_file_control(db, "main", -1, &iArg);
+  assert( rc==SQLITE_NOTFOUND );
+  rc = sqlite3_file_control(db, "temp", -1, &iArg);
+  assert( rc==SQLITE_NOTFOUND || rc==SQLITE_ERROR );
+
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   file_control_lasterrno_test DB
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the SQLITE_LAST_ERRNO verb.
+*/
+static int SQLITE_TCLAPI file_control_lasterrno_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int iArg = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_file_control(db, NULL, SQLITE_LAST_ERRNO, &iArg);
+  if( rc ){ 
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(rc)); 
+    return TCL_ERROR; 
+  }
+  if( iArg!=0 ) {
+    Tcl_AppendResult(interp, "Unexpected non-zero errno: ",
+                     Tcl_GetStringFromObj(Tcl_NewIntObj(iArg), 0), " ", 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_data_version DB DBNAME
+**
+** This TCL command runs the sqlite3_file_control with the
+** SQLITE_FCNTL_DATA_VERSION opcode, returning the result.
+*/
+static int SQLITE_TCLAPI file_control_data_version(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  unsigned int iVers;             /* data version */
+  char *zDb;                      /* Db name ("main", "temp" etc.) */
+  sqlite3 *db;                    /* Database handle */
+  int rc;                         /* file_control() return code */
+  char zBuf[100];
+
+  if( objc!=3 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB [DBNAME]");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+   return TCL_ERROR;
+  }
+  zDb = objc==3 ? Tcl_GetString(objv[2]) : NULL;
+
+  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_DATA_VERSION, (void *)&iVers);
+  if( rc ){
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }else{
+    sqlite3_snprintf(sizeof(zBuf),zBuf,"%u",iVers);
+    Tcl_SetResult(interp, (char *)zBuf, TCL_VOLATILE);
+    return TCL_OK;
+  }
+}
+
+/*
+** tclcmd:   file_control_chunksize_test DB DBNAME SIZE
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the SQLITE_GET_LOCKPROXYFILE and
+** SQLITE_SET_LOCKPROXYFILE verbs.
+*/
+static int SQLITE_TCLAPI file_control_chunksize_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int nSize;                      /* New chunk size */
+  char *zDb;                      /* Db name ("main", "temp" etc.) */
+  sqlite3 *db;                    /* Database handle */
+  int rc;                         /* file_control() return code */
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SIZE");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetIntFromObj(interp, objv[3], &nSize)
+  ){
+   return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[2]);
+  if( zDb[0]=='\0' ) zDb = NULL;
+
+  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_CHUNK_SIZE, (void *)&nSize);
+  if( rc ){
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   file_control_sizehint_test DB DBNAME SIZE
+**
+** This TCL command runs the sqlite3_file_control interface 
+** with SQLITE_FCNTL_SIZE_HINT
+*/
+static int SQLITE_TCLAPI file_control_sizehint_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_WideInt nSize;              /* Hinted size */
+  char *zDb;                      /* Db name ("main", "temp" etc.) */
+  sqlite3 *db;                    /* Database handle */
+  int rc;                         /* file_control() return code */
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SIZE");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetWideIntFromObj(interp, objv[3], &nSize)
+  ){
+   return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[2]);
+  if( zDb[0]=='\0' ) zDb = NULL;
+
+  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_SIZE_HINT, (void *)&nSize);
+  if( rc ){
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   file_control_lockproxy_test DB PWD
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the SQLITE_GET_LOCKPROXYFILE and
+** SQLITE_SET_LOCKPROXYFILE verbs.
+*/
+static int SQLITE_TCLAPI file_control_lockproxy_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+                     Tcl_GetStringFromObj(objv[0], 0), " DB PWD", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+   return TCL_ERROR;
+  }
+  
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+  {
+    char *testPath;
+    int rc;
+    int nPwd;
+    const char *zPwd;
+    char proxyPath[400];
+    
+    zPwd = Tcl_GetStringFromObj(objv[2], &nPwd);
+    if( sizeof(proxyPath)<nPwd+20 ){
+      Tcl_AppendResult(interp, "PWD too big", (void*)0);
+      return TCL_ERROR;
+    }
+    sqlite3_snprintf(sizeof(proxyPath), proxyPath, "%s/test.proxy", zPwd);
+    rc = sqlite3_file_control(db, NULL, SQLITE_SET_LOCKPROXYFILE, proxyPath);
+    if( rc ){
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(rc)); 
+      return TCL_ERROR;
+    }
+    rc = sqlite3_file_control(db, NULL, SQLITE_GET_LOCKPROXYFILE, &testPath);
+    if( strncmp(proxyPath,testPath,11) ){
+      Tcl_AppendResult(interp, "Lock proxy file did not match the "
+                               "previously assigned value", 0);
+      return TCL_ERROR;
+    }
+    if( rc ){
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+      return TCL_ERROR;
+    }
+    rc = sqlite3_file_control(db, NULL, SQLITE_SET_LOCKPROXYFILE, proxyPath);
+    if( rc ){
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+      return TCL_ERROR;
+    }
+  }
+#endif
+  return TCL_OK;  
+}
+
+#if SQLITE_OS_WIN
+/*
+** tclcmd:   file_control_win32_av_retry DB  NRETRY  DELAY
+**
+** This TCL command runs the sqlite3_file_control interface with
+** the SQLITE_FCNTL_WIN32_AV_RETRY opcode.
+*/
+static int SQLITE_TCLAPI file_control_win32_av_retry(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  int a[2];
+  char z[100];
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB NRETRY DELAY", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &a[0]) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &a[1]) ) return TCL_ERROR;
+  rc = sqlite3_file_control(db, NULL, SQLITE_FCNTL_WIN32_AV_RETRY, (void*)a);
+  sqlite3_snprintf(sizeof(z), z, "%d %d %d", rc, a[0], a[1]);
+  Tcl_AppendResult(interp, z, (char*)0);
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_win32_get_handle DB
+**
+** This TCL command runs the sqlite3_file_control interface with
+** the SQLITE_FCNTL_WIN32_GET_HANDLE opcode.
+*/
+static int file_control_win32_get_handle(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  HANDLE hFile = NULL;
+  char z[100];
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_file_control(db, NULL, SQLITE_FCNTL_WIN32_GET_HANDLE,
+                            (void*)&hFile);
+  sqlite3_snprintf(sizeof(z), z, "%d %p", rc, (void*)hFile);
+  Tcl_AppendResult(interp, z, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   file_control_win32_set_handle DB HANDLE
+**
+** This TCL command runs the sqlite3_file_control interface with
+** the SQLITE_FCNTL_WIN32_SET_HANDLE opcode.
+*/
+static int SQLITE_TCLAPI file_control_win32_set_handle(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  HANDLE hFile = NULL;
+  char z[100];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB HANDLE", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( getWin32Handle(interp, Tcl_GetString(objv[2]), &hFile) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_file_control(db, NULL, SQLITE_FCNTL_WIN32_SET_HANDLE,
+                            (void*)&hFile);
+  sqlite3_snprintf(sizeof(z), z, "%d %p", rc, (void*)hFile);
+  Tcl_AppendResult(interp, z, (char*)0);
+  return TCL_OK;  
+}
+#endif
+
+/*
+** tclcmd:   file_control_persist_wal DB PERSIST-FLAG
+**
+** This TCL command runs the sqlite3_file_control interface with
+** the SQLITE_FCNTL_PERSIST_WAL opcode.
+*/
+static int SQLITE_TCLAPI file_control_persist_wal(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  int bPersist;
+  char z[100];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB FLAG", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &bPersist) ) return TCL_ERROR;
+  rc = sqlite3_file_control(db, NULL, SQLITE_FCNTL_PERSIST_WAL, (void*)&bPersist);
+  sqlite3_snprintf(sizeof(z), z, "%d %d", rc, bPersist);
+  Tcl_AppendResult(interp, z, (char*)0);
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_powersafe_overwrite DB PSOW-FLAG
+**
+** This TCL command runs the sqlite3_file_control interface with
+** the SQLITE_FCNTL_POWERSAFE_OVERWRITE opcode.
+*/
+static int SQLITE_TCLAPI file_control_powersafe_overwrite(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  int b;
+  char z[100];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB FLAG", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &b) ) return TCL_ERROR;
+  rc = sqlite3_file_control(db,NULL,SQLITE_FCNTL_POWERSAFE_OVERWRITE,(void*)&b);
+  sqlite3_snprintf(sizeof(z), z, "%d %d", rc, b);
+  Tcl_AppendResult(interp, z, (char*)0);
+  return TCL_OK;  
+}
+
+
+/*
+** tclcmd:   file_control_vfsname DB ?AUXDB?
+**
+** Return a string that describes the stack of VFSes.
+*/
+static int SQLITE_TCLAPI file_control_vfsname(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zDbName = "main";
+  char *zVfsName = 0;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB ?AUXDB?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( objc==3 ){
+    zDbName = Tcl_GetString(objv[2]);
+  }
+  sqlite3_file_control(db, zDbName, SQLITE_FCNTL_VFSNAME,(void*)&zVfsName);
+  Tcl_AppendResult(interp, zVfsName, (char*)0);
+  sqlite3_free(zVfsName);
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_reservebytes DB N
+*/
+static int SQLITE_TCLAPI file_control_reservebytes(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zDbName = "main";
+  int n = 0;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB N");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db)
+   || Tcl_GetIntFromObj(interp, objv[2], &n) 
+  ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_file_control(db, zDbName, SQLITE_FCNTL_RESERVE_BYTES, (void*)&n);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+  return TCL_OK;  
+}
+
+
+/*
+** tclcmd:   file_control_tempfilename DB ?AUXDB?
+**
+** Return a string that is a temporary filename
+*/
+static int SQLITE_TCLAPI file_control_tempfilename(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zDbName = "main";
+  char *zTName = 0;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB ?AUXDB?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( objc==3 ){
+    zDbName = Tcl_GetString(objv[2]);
+  }
+  sqlite3_file_control(db, zDbName, SQLITE_FCNTL_TEMPFILENAME, (void*)&zTName);
+  Tcl_AppendResult(interp, zTName, (char*)0);
+  sqlite3_free(zTName);
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_external_reader DB ?AUXDB?
+**
+** Return a string that is a temporary filename
+*/
+static int SQLITE_TCLAPI file_control_external_reader(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zName = "main";
+  int iRes = 0;
+  int rc = SQLITE_OK;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB ?AUXDB?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( objc==3 ){
+    zName = Tcl_GetString(objv[2]);
+  }
+  rc = sqlite3_file_control(db, zName, SQLITE_FCNTL_EXTERNAL_READER, &iRes);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(iRes));
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   sqlite3_vfs_list
+**
+**   Return a tcl list containing the names of all registered vfs's.
+*/
+static int SQLITE_TCLAPI vfs_list(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs *pVfs;
+  Tcl_Obj *pRet = Tcl_NewObj();
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  for(pVfs=sqlite3_vfs_find(0); pVfs; pVfs=pVfs->pNext){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj(pVfs->zName, -1));
+  }
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   sqlite3_limit DB ID VALUE
+**
+** This TCL command runs the sqlite3_limit interface and
+** verifies correct operation of the same.
+*/
+static int SQLITE_TCLAPI test_limit(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  static const struct {
+     char *zName;
+     int id;
+  } aId[] = {
+    { "SQLITE_LIMIT_LENGTH",              SQLITE_LIMIT_LENGTH               },
+    { "SQLITE_LIMIT_SQL_LENGTH",          SQLITE_LIMIT_SQL_LENGTH           },
+    { "SQLITE_LIMIT_COLUMN",              SQLITE_LIMIT_COLUMN               },
+    { "SQLITE_LIMIT_EXPR_DEPTH",          SQLITE_LIMIT_EXPR_DEPTH           },
+    { "SQLITE_LIMIT_COMPOUND_SELECT",     SQLITE_LIMIT_COMPOUND_SELECT      },
+    { "SQLITE_LIMIT_VDBE_OP",             SQLITE_LIMIT_VDBE_OP              },
+    { "SQLITE_LIMIT_FUNCTION_ARG",        SQLITE_LIMIT_FUNCTION_ARG         },
+    { "SQLITE_LIMIT_ATTACHED",            SQLITE_LIMIT_ATTACHED             },
+    { "SQLITE_LIMIT_LIKE_PATTERN_LENGTH", SQLITE_LIMIT_LIKE_PATTERN_LENGTH  },
+    { "SQLITE_LIMIT_VARIABLE_NUMBER",     SQLITE_LIMIT_VARIABLE_NUMBER      },
+    { "SQLITE_LIMIT_TRIGGER_DEPTH",       SQLITE_LIMIT_TRIGGER_DEPTH        },
+    { "SQLITE_LIMIT_WORKER_THREADS",      SQLITE_LIMIT_WORKER_THREADS       },
+    
+    /* Out of range test cases */
+    { "SQLITE_LIMIT_TOOSMALL",            -1,                               },
+    { "SQLITE_LIMIT_TOOBIG",              SQLITE_LIMIT_WORKER_THREADS+1     },
+  };
+  int i, id = 0;
+  int val;
+  const char *zId;
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB ID VALUE", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zId = Tcl_GetString(objv[2]);
+  for(i=0; i<sizeof(aId)/sizeof(aId[0]); i++){
+    if( strcmp(zId, aId[i].zName)==0 ){
+      id = aId[i].id;
+      break;
+    }
+  }
+  if( i>=sizeof(aId)/sizeof(aId[0]) ){
+    Tcl_AppendResult(interp, "unknown limit type: ", zId, (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+  rc = sqlite3_limit(db, id, val);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:  save_prng_state
+**
+** Save the state of the pseudo-random number generator.
+** At the same time, verify that sqlite3_test_control works even when
+** called with an out-of-range opcode.
+*/
+static int SQLITE_TCLAPI save_prng_state(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int rc = sqlite3_test_control(9999);
+  assert( rc==0 );
+  rc = sqlite3_test_control(-1);
+  assert( rc==0 );
+  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_SAVE);
+  return TCL_OK;
+}
+/*
+** tclcmd:  restore_prng_state
+*/
+static int SQLITE_TCLAPI restore_prng_state(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_RESTORE);
+  return TCL_OK;
+}
+/*
+** tclcmd:  reset_prng_state
+*/
+static int SQLITE_TCLAPI reset_prng_state(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_randomness(0,0);
+  return TCL_OK;
+}
+/*
+** tclcmd:  prng_seed INT ?DB?
+**
+** Set up the SQLITE_TESTCTRL_PRNG_SEED pragma with parameter INT and DB.
+** INT is an integer.  DB is a database connection, or a NULL pointer if
+** omitted.
+**
+** When INT!=0 and DB!=0, set the PRNG seed to the value of the schema
+** cookie for DB, or to INT if the schema cookie happens to be zero.
+**
+** When INT!=0 and DB==0, set the PRNG seed to just INT.
+**
+** If INT==0 and DB==0 then use the default procedure of calling the
+** xRandomness method on the default VFS to get the PRNG seed.
+*/
+static int SQLITE_TCLAPI prng_seed(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i = 0;
+  sqlite3 *db = 0;
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SEED ?DB?");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp,objv[1],&i) ) return TCL_ERROR;
+  if( objc==3 && getDbPointer(interp, Tcl_GetString(objv[2]), &db) ){
+    return TCL_ERROR;
+  }
+  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_SEED, i, db);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  extra_schema_checks BOOLEAN
+**
+** Enable or disable schema checks when parsing the sqlite_schema file.
+** This is always enabled in production, but it is sometimes useful to
+** disable the checks in order to make some internal error states reachable
+** for testing.
+*/
+static int SQLITE_TCLAPI extra_schema_checks(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i = 0;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp,objv[1],&i) ) return TCL_ERROR;
+  sqlite3_test_control(SQLITE_TESTCTRL_EXTRA_SCHEMA_CHECKS, i);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  use_long_double BOOLEAN|"default"
+**
+** If no argument, report the current value of the use-long-double flag.
+**
+** If argument is "default", set the use-long-double flag to the default
+** value for this build, based on the size of LONGDOUBLE_TYPE.
+**
+** If argument is a boolean, set the use-long-double flag accordingly.
+**
+** Return the new setting.
+*/
+static int SQLITE_TCLAPI use_long_double(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i = -1;
+  if( objc==2 ){
+    if( strcmp(Tcl_GetString(objv[1]),"default")==0 ){
+      i = 2;
+    }else{
+      if( Tcl_GetBooleanFromObj(interp,objv[1],&i) ) return TCL_ERROR;
+    }
+  }
+  i = sqlite3_test_control(SQLITE_TESTCTRL_USELONGDOUBLE, i);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(i));
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  database_may_be_corrupt
+**
+** Indicate that database files might be corrupt. In other words, set the normal
+** state of operation.
+*/
+static int SQLITE_TCLAPI database_may_be_corrupt(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_test_control(SQLITE_TESTCTRL_NEVER_CORRUPT, 0);
+  return TCL_OK;
+}
+/*
+** tclcmd:  database_never_corrupt
+**
+** Indicate that database files are always well-formed. This enables
+** extra assert() statements that test conditions that are always true
+** for well-formed databases.
+*/
+static int SQLITE_TCLAPI database_never_corrupt(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_test_control(SQLITE_TESTCTRL_NEVER_CORRUPT, 1);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  pcache_stats
+*/
+static int SQLITE_TCLAPI test_pcache_stats(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int nMin;
+  int nMax;
+  int nCurrent;
+  int nRecyclable;
+  Tcl_Obj *pRet;
+
+  sqlite3PcacheStats(&nCurrent, &nMax, &nMin, &nRecyclable);
+
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("current", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nCurrent));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("max", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nMax));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("min", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nMin));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("recyclable", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nRecyclable));
+
+  Tcl_SetObjResult(interp, pRet);
+
+  return TCL_OK;
+}
+
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+static void test_unlock_notify_cb(void **aArg, int nArg){
+  int ii;
+  for(ii=0; ii<nArg; ii++){
+    Tcl_EvalEx((Tcl_Interp *)aArg[ii], "unlock_notify", -1, TCL_EVAL_GLOBAL);
+  }
+}
+#endif /* SQLITE_ENABLE_UNLOCK_NOTIFY */
+
+/*
+** tclcmd:  sqlite3_unlock_notify db
+*/
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+static int SQLITE_TCLAPI test_unlock_notify(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_unlock_notify(db, test_unlock_notify_cb, (void *)interp);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+#endif
+
+/*
+** tclcmd:  sqlite3_wal_checkpoint db ?NAME?
+*/
+static int SQLITE_TCLAPI test_wal_checkpoint(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zDb = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=3 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB ?NAME?");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( objc==3 ){
+    zDb = Tcl_GetString(objv[2]);
+  }
+  rc = sqlite3_wal_checkpoint(db, zDb);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  sqlite3_wal_checkpoint_v2 db MODE ?NAME?
+**
+** This command calls the wal_checkpoint_v2() function with the specified
+** mode argument (passive, full or restart). If present, the database name
+** NAME is passed as the second argument to wal_checkpoint_v2(). If it the
+** NAME argument is not present, a NULL pointer is passed instead.
+**
+** If wal_checkpoint_v2() returns any value other than SQLITE_BUSY or
+** SQLITE_OK, then this command returns TCL_ERROR. The Tcl result is set
+** to the error message obtained from sqlite3_errmsg().
+**
+** Otherwise, this command returns a list of three integers. The first integer
+** is 1 if SQLITE_BUSY was returned, or 0 otherwise. The following two integers
+** are the values returned via the output parameters by wal_checkpoint_v2() -
+** the number of frames in the log and the number of frames in the log
+** that have been checkpointed.
+*/
+static int SQLITE_TCLAPI test_wal_checkpoint_v2(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zDb = 0;
+  sqlite3 *db;
+  int rc;
+
+  int eMode;
+  int nLog = -555;
+  int nCkpt = -555;
+  Tcl_Obj *pRet;
+
+  const char * aMode[] = { "passive", "full", "restart", "truncate", 0 };
+  assert( SQLITE_CHECKPOINT_PASSIVE==0 );
+  assert( SQLITE_CHECKPOINT_FULL==1 );
+  assert( SQLITE_CHECKPOINT_RESTART==2 );
+  assert( SQLITE_CHECKPOINT_TRUNCATE==3 );
+
+  if( objc!=3 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB MODE ?NAME?");
+    return TCL_ERROR;
+  }
+
+  if( objc==4 ){
+    zDb = Tcl_GetString(objv[3]);
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) || (
+      TCL_OK!=Tcl_GetIntFromObj(0, objv[2], &eMode)
+   && TCL_OK!=Tcl_GetIndexFromObj(interp, objv[2], aMode, "mode", 0, &eMode) 
+  )){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_wal_checkpoint_v2(db, zDb, eMode, &nLog, &nCkpt);
+  if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
+    const char *zErrCode = sqlite3ErrName(rc);
+    Tcl_ResetResult(interp);
+    Tcl_AppendResult(interp, zErrCode, " - ", (char *)sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(rc==SQLITE_BUSY?1:0));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nLog));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nCkpt));
+  Tcl_SetObjResult(interp, pRet);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  sqlite3_wal_autocheckpoint db VALUE
+*/
+static int SQLITE_TCLAPI test_wal_autocheckpoint(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  int iVal;
+
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB VALUE");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetIntFromObj(0, objv[2], &iVal)
+  ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_wal_autocheckpoint(db, iVal);
+  Tcl_ResetResult(interp);
+  if( rc!=SQLITE_OK ){
+    const char *zErrCode = sqlite3ErrName(rc);
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(zErrCode, -1));
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:  test_sqlite3_log ?SCRIPT?
+*/
+static struct LogCallback {
+  Tcl_Interp *pInterp;
+  Tcl_Obj *pObj;
+} logcallback = {0, 0};
+static void xLogcallback(void *unused, int err, char *zMsg){
+  Tcl_Obj *pNew = Tcl_DuplicateObj(logcallback.pObj);
+  Tcl_IncrRefCount(pNew);
+  Tcl_ListObjAppendElement(
+      0, pNew, Tcl_NewStringObj(sqlite3ErrName(err), -1)
+  );
+  Tcl_ListObjAppendElement(0, pNew, Tcl_NewStringObj(zMsg, -1));
+  Tcl_EvalObjEx(logcallback.pInterp, pNew, TCL_EVAL_GLOBAL|TCL_EVAL_DIRECT);
+  Tcl_DecrRefCount(pNew);
+}
+static int SQLITE_TCLAPI test_sqlite3_log(
+  ClientData clientData,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  if( objc>2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SCRIPT");
+    return TCL_ERROR;
+  }
+  if( logcallback.pObj ){
+    Tcl_DecrRefCount(logcallback.pObj);
+    logcallback.pObj = 0;
+    logcallback.pInterp = 0;
+    sqlite3_config(SQLITE_CONFIG_LOG, (void*)0, (void*)0);
+  }
+  if( objc>1 ){
+    logcallback.pObj = objv[1];
+    Tcl_IncrRefCount(logcallback.pObj);
+    logcallback.pInterp = interp;
+    sqlite3_config(SQLITE_CONFIG_LOG, xLogcallback, (void*)0);
+  }
+  return TCL_OK;
+}
+
+/*
+**     tcl_objproc COMMANDNAME ARGS...
+**
+** Run a TCL command using its objProc interface.  Throw an error if
+** the command has no objProc interface.
+*/
+static int SQLITE_TCLAPI runAsObjProc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_CmdInfo cmdInfo;
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "COMMAND ...");
+    return TCL_ERROR;
+  }
+  if( !Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ",
+           Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  if( cmdInfo.objProc==0 ){
+    Tcl_AppendResult(interp, "command has no objProc: ",
+           Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  return cmdInfo.objProc(cmdInfo.objClientData, interp, objc-1, objv+1);
+}
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** WARNING: The following function, printExplainQueryPlan() is an exact
+** copy of example code from eqp.in (eqp.html). If this code is modified,
+** then the documentation copy needs to be modified as well.
+*/
+/*
+** Argument pStmt is a prepared SQL statement. This function compiles
+** an EXPLAIN QUERY PLAN command to report on the prepared statement,
+** and prints the report to stdout using printf().
+*/
+int printExplainQueryPlan(sqlite3_stmt *pStmt){
+  const char *zSql;               /* Input SQL */
+  char *zExplain;                 /* SQL with EXPLAIN QUERY PLAN prepended */
+  sqlite3_stmt *pExplain;         /* Compiled EXPLAIN QUERY PLAN command */
+  int rc;                         /* Return code from sqlite3_prepare_v2() */
+
+  zSql = sqlite3_sql(pStmt);
+  if( zSql==0 ) return SQLITE_ERROR;
+
+  zExplain = sqlite3_mprintf("EXPLAIN QUERY PLAN %s", zSql);
+  if( zExplain==0 ) return SQLITE_NOMEM;
+
+  rc = sqlite3_prepare_v2(sqlite3_db_handle(pStmt), zExplain, -1, &pExplain, 0);
+  sqlite3_free(zExplain);
+  if( rc!=SQLITE_OK ) return rc;
+
+  while( SQLITE_ROW==sqlite3_step(pExplain) ){
+    int iSelectid = sqlite3_column_int(pExplain, 0);
+    int iOrder = sqlite3_column_int(pExplain, 1);
+    int iFrom = sqlite3_column_int(pExplain, 2);
+    const char *zDetail = (const char *)sqlite3_column_text(pExplain, 3);
+
+    printf("%d %d %d %s\n", iSelectid, iOrder, iFrom, zDetail);
+  }
+
+  return sqlite3_finalize(pExplain);
+}
+
+static int SQLITE_TCLAPI test_print_eqp(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = printExplainQueryPlan(pStmt);
+  /* This is needed on Windows so that a test case using this 
+  ** function can open a read pipe and get the output of
+  ** printExplainQueryPlan() immediately.
+  */
+  fflush(stdout);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+#endif /* SQLITE_OMIT_EXPLAIN */
+
+#include <time.h>
+/*
+** This is an alternative localtime_r() implementation used for testing
+** the 'localtime' and 'utc' modifiers of date-time functions.  Because
+** the OS-supplied localtime_r() is locale-dependent, this alternative is
+** provided as a stable test platform.
+**
+** Operation:
+**
+**     (1)  Localtime is 30 minutes earlier than (west of) UTC on
+**          even days (counting from 1970-01-01)
+**
+**     (2)  Localtime is 30 minutes later than (east of) UTC on odd days.
+**
+**     (3)  The function fails for the specific date/time value
+**          of 2000-05-29 14:16:00 in order to test the ability of
+**          SQLite to deal with localtime_r() failures.
+*/
+static int testLocaltime(const void *aliasT, void *aliasTM){
+  const time_t t = *(const time_t*)aliasT;
+  struct tm *pTm = (struct tm *)aliasTM;
+  time_t altT;
+  sqlite3_int64 iJD;
+  int Z, A, B, C, D, E, X1, S;
+
+  if( (t/86400) & 1 ){
+    altT = t + 1800;  /* 30 minutes later on odd days */
+  }else{
+    altT = t - 1800;  /* 30 minutes earlier on even days */
+  }
+  iJD = (sqlite3_int64)(altT + 210866760000);
+  Z = (int)((iJD + 43200)/86400);
+  A = (int)((Z - 1867216.25)/36524.25);
+  A = Z + 1 + A - (A/4);
+  B = A + 1524;
+  C = (int)((B - 122.1)/365.25);
+  D = (36525*(C&32767))/100;
+  E = (int)((B-D)/30.6001);
+  X1 = (int)(30.6001*E);
+  pTm->tm_mday = B - D - X1;
+  pTm->tm_mon = E<14 ? E-2 : E-14;
+  pTm->tm_year = (pTm->tm_mon>1 ? C - 4716 : C - 4715) - 1900;
+  S = (int)((iJD + 43200)%86400);
+  pTm->tm_hour = S/3600;
+  pTm->tm_min = (S/60)%60;
+  pTm->tm_sec = S % 60;
+  return t==959609760; /* Special case: 2000-05-29 14:16:00 fails */
+}
+
+/*
+** TCLCMD:  strftime FORMAT UNIXTIMESTAMP
+**
+** Access to the C-library strftime() routine, so that its results
+** can be compared against SQLite's internal strftime() SQL function
+** implementation.
+*/
+static int SQLITE_TCLAPI strftime_cmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_WideInt ts;
+  time_t t;
+  struct tm *pTm;
+  const char *zFmt;
+  size_t n;
+  char zBuf[1000];
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FORMAT UNIXTIMESTAMP");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetWideIntFromObj(interp,  objv[2], &ts) ) return TCL_ERROR;
+  zFmt = Tcl_GetString(objv[1]);
+  t = (time_t)ts;
+  pTm = gmtime(&t);
+  n = strftime(zBuf, sizeof(zBuf)-1, zFmt, pTm);
+  if( n>=0 && n<sizeof(zBuf) ){
+    zBuf[n] = 0;
+    Tcl_SetResult(interp, zBuf, TCL_VOLATILE);
+  }
+  return TCL_OK;
+}
+
+/*
+** .treetrace N
+*/
+static int SQLITE_TCLAPI test_treetrace(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  unsigned int v = 0;
+  if( objc>=2 ){
+    if( Tcl_GetIntFromObj(interp, objv[1], (int*)&v)==TCL_OK ){
+      sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 1, &v);
+    }
+  }
+  sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 0, &v);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj((int)v));
+  return TCL_OK;
+}
+
+/*
+** sqlite3_test_control VERB ARGS...
+*/
+static int SQLITE_TCLAPI test_test_control(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct Verb {
+    const char *zName;
+    int i;
+  } aVerb[] = {
+    { "SQLITE_TESTCTRL_LOCALTIME_FAULT",    SQLITE_TESTCTRL_LOCALTIME_FAULT }, 
+    { "SQLITE_TESTCTRL_SORTER_MMAP",        SQLITE_TESTCTRL_SORTER_MMAP     }, 
+    { "SQLITE_TESTCTRL_IMPOSTER",           SQLITE_TESTCTRL_IMPOSTER        },
+    { "SQLITE_TESTCTRL_INTERNAL_FUNCTIONS", SQLITE_TESTCTRL_INTERNAL_FUNCTIONS},
+    { "SQLITE_TESTCTRL_FK_NO_ACTION",       SQLITE_TESTCTRL_FK_NO_ACTION},
+    { 0, 0 }
+  };
+  int iVerb;
+  int iFlag;
+  int rc;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "VERB ARGS...");
+    return TCL_ERROR;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[1], aVerb, sizeof(aVerb[0]), "VERB", 0, &iVerb
+  );
+  if( rc!=TCL_OK ) return rc;
+
+  iFlag = aVerb[iVerb].i;
+  switch( iFlag ){
+    case SQLITE_TESTCTRL_INTERNAL_FUNCTIONS: {
+      sqlite3 *db = 0;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "DB");
+        return TCL_ERROR;
+      }
+      if( getDbPointer(interp, Tcl_GetString(objv[2]), &db) ) return TCL_ERROR;
+      sqlite3_test_control(SQLITE_TESTCTRL_INTERNAL_FUNCTIONS, db);
+      break;
+    }
+    case SQLITE_TESTCTRL_LOCALTIME_FAULT: {
+      int val;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "0|1|2");
+        return TCL_ERROR;
+      }
+      if( Tcl_GetIntFromObj(interp, objv[2], &val) ) return TCL_ERROR;
+      sqlite3_test_control(iFlag, val, testLocaltime);
+      break;
+    }
+
+    case SQLITE_TESTCTRL_FK_NO_ACTION: {
+      int val = 0;
+      sqlite3 *db = 0;
+      if( objc!=4 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "DB BOOLEAN");
+        return TCL_ERROR;
+      }
+      if( getDbPointer(interp, Tcl_GetString(objv[2]), &db) ) return TCL_ERROR;
+      if( Tcl_GetBooleanFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+
+      sqlite3_test_control(SQLITE_TESTCTRL_FK_NO_ACTION, db, val);
+      break;
+    }
+
+    case SQLITE_TESTCTRL_SORTER_MMAP: {
+      int val;
+      sqlite3 *db;
+      if( objc!=4 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "DB LIMIT");
+        return TCL_ERROR;
+      }
+      if( getDbPointer(interp, Tcl_GetString(objv[2]), &db) ) return TCL_ERROR;
+      if( Tcl_GetIntFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+      sqlite3_test_control(SQLITE_TESTCTRL_SORTER_MMAP, db, val);
+      break;
+    }
+
+    case SQLITE_TESTCTRL_IMPOSTER: {
+      int onOff, tnum;
+      const char *zDbName;
+      sqlite3 *db;
+      if( objc!=6 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "DB dbName onOff tnum");
+        return TCL_ERROR;
+      }
+      if( getDbPointer(interp, Tcl_GetString(objv[2]), &db) ) return TCL_ERROR;
+      zDbName = Tcl_GetString(objv[3]);
+      if( Tcl_GetIntFromObj(interp, objv[4], &onOff) ) return TCL_ERROR;
+      if( Tcl_GetIntFromObj(interp, objv[5], &tnum) ) return TCL_ERROR;
+      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, db, zDbName, onOff, tnum);
+      break;
+    }
+  }
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+#if SQLITE_OS_UNIX
+#include <sys/time.h>
+#include <sys/resource.h>
+
+static int SQLITE_TCLAPI test_getrusage(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  char buf[1024];
+  struct rusage r;
+  memset(&r, 0, sizeof(r));
+  getrusage(RUSAGE_SELF, &r);
+
+  sqlite3_snprintf(sizeof(buf), buf,
+    "ru_utime=%d.%06d ru_stime=%d.%06d ru_minflt=%d ru_majflt=%d", 
+    (int)r.ru_utime.tv_sec, (int)r.ru_utime.tv_usec, 
+    (int)r.ru_stime.tv_sec, (int)r.ru_stime.tv_usec, 
+    (int)r.ru_minflt, (int)r.ru_majflt
+  );
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(buf, -1));
+  return TCL_OK;
+}
+#endif
+
+#if SQLITE_OS_WIN
+/*
+** Information passed from the main thread into the windows file locker
+** background thread.
+*/
+struct win32FileLocker {
+  char *evName;       /* Name of event to signal thread startup */
+  HANDLE h;           /* Handle of the file to be locked */
+  int delay1;         /* Delay before locking */
+  int delay2;         /* Delay before unlocking */
+  int ok;             /* Finished ok */
+  int err;            /* True if an error occurs */
+};
+#endif
+
+
+#if SQLITE_OS_WIN
+#include <process.h>
+/*
+** The background thread that does file locking.
+*/
+static void SQLITE_CDECL win32_file_locker(void *pAppData){
+  struct win32FileLocker *p = (struct win32FileLocker*)pAppData;
+  if( p->evName ){
+    HANDLE ev = OpenEvent(EVENT_MODIFY_STATE, FALSE, p->evName);
+    if ( ev ){
+      SetEvent(ev);
+      CloseHandle(ev);
+    }
+  }
+  if( p->delay1 ) Sleep(p->delay1);
+  if( LockFile(p->h, 0, 0, 100000000, 0) ){
+    Sleep(p->delay2);
+    UnlockFile(p->h, 0, 0, 100000000, 0);
+    p->ok = 1;
+  }else{
+    p->err = 1;
+  }
+  CloseHandle(p->h);
+  p->h = 0;
+  p->delay1 = 0;
+  p->delay2 = 0;
+}
+#endif
+
+#if SQLITE_OS_WIN
+/*
+**      lock_win32_file FILENAME DELAY1 DELAY2
+**
+** Get an exclusive manditory lock on file for DELAY2 milliseconds.
+** Wait DELAY1 milliseconds before acquiring the lock.
+*/
+static int SQLITE_TCLAPI win32_file_lock(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static struct win32FileLocker x = { "win32_file_lock", 0, 0, 0, 0, 0 };
+  const char *zFilename;
+  char zBuf[200];
+  int retry = 0;
+  HANDLE ev;
+  DWORD wResult;
+  
+  if( objc!=4 && objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME DELAY1 DELAY2");
+    return TCL_ERROR;
+  }
+  if( objc==1 ){
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "%d %d %d %d %d",
+                     x.ok, x.err, x.delay1, x.delay2, x.h);
+    Tcl_AppendResult(interp, zBuf, (char*)0);
+    return TCL_OK;
+  }
+  while( x.h && retry<30 ){
+    retry++;
+    Sleep(100);
+  }
+  if( x.h ){
+    Tcl_AppendResult(interp, "busy", (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &x.delay1) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &x.delay2) ) return TCL_ERROR;
+  zFilename = Tcl_GetString(objv[1]);
+  x.h = CreateFile(zFilename, GENERIC_READ|GENERIC_WRITE,
+              FILE_SHARE_READ|FILE_SHARE_WRITE, 0, OPEN_ALWAYS,
+              FILE_ATTRIBUTE_NORMAL, 0);
+  if( !x.h ){
+    Tcl_AppendResult(interp, "cannot open file: ", zFilename, (char*)0);
+    return TCL_ERROR;
+  }
+  ev = CreateEvent(NULL, TRUE, FALSE, x.evName);
+  if ( !ev ){
+    Tcl_AppendResult(interp, "cannot create event: ", x.evName, (char*)0);
+    return TCL_ERROR;
+  }
+  _beginthread(win32_file_locker, 0, (void*)&x);
+  Sleep(0);
+  if ( (wResult = WaitForSingleObject(ev, 10000))!=WAIT_OBJECT_0 ){
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "0x%x", wResult);
+    Tcl_AppendResult(interp, "wait failed: ", zBuf, (char*)0);
+    CloseHandle(ev);
+    return TCL_ERROR;
+  }
+  CloseHandle(ev);
+  return TCL_OK;
+}
+
+/*
+**      exists_win32_path PATH
+**
+** Returns non-zero if the specified path exists, whose fully qualified name
+** may exceed 260 characters if it is prefixed with "\\?\".
+*/
+static int SQLITE_TCLAPI win32_exists_path(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PATH");
+    return TCL_ERROR;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(
+      GetFileAttributesW( Tcl_GetUnicode(objv[1]))!=INVALID_FILE_ATTRIBUTES ));
+  return TCL_OK;
+}
+
+/*
+**      find_win32_file PATTERN
+**
+** Returns a list of entries in a directory that match the specified pattern,
+** whose fully qualified name may exceed 248 characters if it is prefixed with
+** "\\?\".
+*/
+static int SQLITE_TCLAPI win32_find_file(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  HANDLE hFindFile = INVALID_HANDLE_VALUE;
+  WIN32_FIND_DATAW findData;
+  Tcl_Obj *listObj;
+  DWORD lastErrno;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PATTERN");
+    return TCL_ERROR;
+  }
+  hFindFile = FindFirstFileW(Tcl_GetUnicode(objv[1]), &findData);
+  if( hFindFile==INVALID_HANDLE_VALUE ){
+    Tcl_SetObjResult(interp, Tcl_NewWideIntObj(GetLastError()));
+    return TCL_ERROR;
+  }
+  listObj = Tcl_NewObj();
+  Tcl_IncrRefCount(listObj);
+  do {
+    Tcl_ListObjAppendElement(interp, listObj, Tcl_NewUnicodeObj(
+        findData.cFileName, -1));
+    Tcl_ListObjAppendElement(interp, listObj, Tcl_NewWideIntObj(
+        findData.dwFileAttributes));
+  } while( FindNextFileW(hFindFile, &findData) );
+  lastErrno = GetLastError();
+  if( lastErrno!=NO_ERROR && lastErrno!=ERROR_NO_MORE_FILES ){
+    FindClose(hFindFile);
+    Tcl_DecrRefCount(listObj);
+    Tcl_SetObjResult(interp, Tcl_NewWideIntObj(GetLastError()));
+    return TCL_ERROR;
+  }
+  FindClose(hFindFile);
+  Tcl_SetObjResult(interp, listObj);
+  return TCL_OK;
+}
+
+/*
+**      delete_win32_file FILENAME
+**
+** Deletes the specified file, whose fully qualified name may exceed 260
+** characters if it is prefixed with "\\?\".
+*/
+static int SQLITE_TCLAPI win32_delete_file(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+  if( !DeleteFileW(Tcl_GetUnicode(objv[1])) ){
+    Tcl_SetObjResult(interp, Tcl_NewWideIntObj(GetLastError()));
+    return TCL_ERROR;
+  }
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+/*
+**      make_win32_dir DIRECTORY
+**
+** Creates the specified directory, whose fully qualified name may exceed 248
+** characters if it is prefixed with "\\?\".
+*/
+static int SQLITE_TCLAPI win32_mkdir(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DIRECTORY");
+    return TCL_ERROR;
+  }
+  if( !CreateDirectoryW(Tcl_GetUnicode(objv[1]), NULL) ){
+    Tcl_SetObjResult(interp, Tcl_NewWideIntObj(GetLastError()));
+    return TCL_ERROR;
+  }
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+/*
+**      remove_win32_dir DIRECTORY
+**
+** Removes the specified directory, whose fully qualified name may exceed 248
+** characters if it is prefixed with "\\?\".
+*/
+static int SQLITE_TCLAPI win32_rmdir(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DIRECTORY");
+    return TCL_ERROR;
+  }
+  if( !RemoveDirectoryW(Tcl_GetUnicode(objv[1])) ){
+    Tcl_SetObjResult(interp, Tcl_NewWideIntObj(GetLastError()));
+    return TCL_ERROR;
+  }
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+#endif
+
+
+/*
+**      optimization_control DB OPT BOOLEAN
+**
+** Enable or disable query optimizations using the sqlite3_test_control()
+** interface.  Disable if BOOLEAN is false and enable if BOOLEAN is true.
+** OPT is the name of the optimization to be disabled.  OPT can also be a
+** list or optimizations names, in which case all optimizations named are
+** enabled or disabled.
+**
+** Each invocation of this control overrides all prior invocations.  The
+** changes are not cumulative.
+*/
+static int SQLITE_TCLAPI optimization_control(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int i;
+  sqlite3 *db;
+  const char *zOpt;
+  int onoff;
+  int mask = 0;
+  int cnt = 0;
+  static const struct {
+    const char *zOptName;
+    int mask;
+  } aOpt[] = {
+    { "all",                 SQLITE_AllOpts        },
+    { "none",                0                     },
+    { "query-flattener",     SQLITE_QueryFlattener },
+    { "groupby-order",       SQLITE_GroupByOrder   },
+    { "factor-constants",    SQLITE_FactorOutConst },
+    { "distinct-opt",        SQLITE_DistinctOpt    },
+    { "cover-idx-scan",      SQLITE_CoverIdxScan   },
+    { "order-by-idx-join",   SQLITE_OrderByIdxJoin },
+    { "transitive",          SQLITE_Transitive     },
+    { "omit-noop-join",      SQLITE_OmitNoopJoin   },
+    { "stat4",               SQLITE_Stat4          },
+    { "skip-scan",           SQLITE_SkipScan       },
+    { "push-down",           SQLITE_PushDown       },
+    { "balanced-merge",      SQLITE_BalancedMerge  },
+    { "propagate-const",     SQLITE_PropagateConst },
+    { "one-pass",            SQLITE_OnePass        },
+  };
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB OPT BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetBooleanFromObj(interp, objv[3], &onoff) ) return TCL_ERROR;
+  zOpt = Tcl_GetString(objv[2]);
+  for(i=0; i<sizeof(aOpt)/sizeof(aOpt[0]); i++){
+    if( strstr(zOpt, aOpt[i].zOptName)!=0 ){
+      mask |= aOpt[i].mask;
+      cnt++;
+    }
+  }
+  if( onoff ) mask = ~mask;
+  if( cnt==0 ){
+    Tcl_AppendResult(interp, "unknown optimization - should be one of:",
+                     (char*)0);
+    for(i=0; i<sizeof(aOpt)/sizeof(aOpt[0]); i++){
+      Tcl_AppendResult(interp, " ", aOpt[i].zOptName, (char*)0);
+    }
+    return TCL_ERROR;
+  }
+  sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS, db, mask);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(mask));
+  return TCL_OK;
+}
+
+/*
+**     load_static_extension DB NAME ...
+**
+** Load one or more statically linked extensions.
+*/
+static int SQLITE_TCLAPI tclLoadStaticExtensionCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int sqlite3_amatch_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_appendvfs_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_basexx_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_carray_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_closure_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_csv_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_eval_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_explain_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_fileio_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_decimal_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_fuzzer_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_ieee_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_nextchar_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_percentile_init(sqlite3*,char**,const sqlite3_api_routines*);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  extern int sqlite3_prefixes_init(sqlite3*,char**,const sqlite3_api_routines*);
+#endif
+  extern int sqlite3_qpvtab_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_randomjson_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_regexp_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_remember_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_series_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_spellfix_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_totype_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_wholenumber_init(sqlite3*,char**,const sqlite3_api_routines*);
+  extern int sqlite3_unionvtab_init(sqlite3*,char**,const sqlite3_api_routines*);
+#ifdef SQLITE_HAVE_ZLIB
+  extern int sqlite3_zipfile_init(sqlite3*,char**,const sqlite3_api_routines*);
+#endif
+  static const struct {
+    const char *zExtName;
+    int (*pInit)(sqlite3*,char**,const sqlite3_api_routines*);
+  } aExtension[] = {
+    { "amatch",                sqlite3_amatch_init               },
+    { "appendvfs",             sqlite3_appendvfs_init            },
+    { "basexx",                sqlite3_basexx_init               },
+    { "carray",                sqlite3_carray_init               },
+    { "closure",               sqlite3_closure_init              },
+    { "csv",                   sqlite3_csv_init                  },
+    { "decimal",               sqlite3_decimal_init              },
+    { "eval",                  sqlite3_eval_init                 },
+    { "explain",               sqlite3_explain_init              },
+    { "fileio",                sqlite3_fileio_init               },
+    { "fuzzer",                sqlite3_fuzzer_init               },
+    { "ieee754",               sqlite3_ieee_init                 },
+    { "nextchar",              sqlite3_nextchar_init             },
+    { "percentile",            sqlite3_percentile_init           },
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    { "prefixes",              sqlite3_prefixes_init             },
+#endif
+    { "qpvtab",                sqlite3_qpvtab_init               },
+    { "randomjson",            sqlite3_randomjson_init           },
+    { "regexp",                sqlite3_regexp_init               },
+    { "remember",              sqlite3_remember_init             },
+    { "series",                sqlite3_series_init               },
+    { "spellfix",              sqlite3_spellfix_init             },
+    { "totype",                sqlite3_totype_init               },
+    { "unionvtab",             sqlite3_unionvtab_init            },
+    { "wholenumber",           sqlite3_wholenumber_init          },
+#ifdef SQLITE_HAVE_ZLIB
+    { "zipfile",               sqlite3_zipfile_init              },
+#endif
+  };
+  sqlite3 *db;
+  const char *zName;
+  int i, j, rc;
+  char *zErrMsg = 0;
+  if( objc<3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB NAME ...");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  for(j=2; j<objc; j++){
+    zName = Tcl_GetString(objv[j]);
+    for(i=0; i<ArraySize(aExtension); i++){
+      if( strcmp(zName, aExtension[i].zExtName)==0 ) break;
+    }
+    if( i>=ArraySize(aExtension) ){
+      Tcl_AppendResult(interp, "no such extension: ", zName, (char*)0);
+      return TCL_ERROR;
+    }
+    if( aExtension[i].pInit ){
+      rc = aExtension[i].pInit(db, &zErrMsg, 0);
+    }else{
+      rc = SQLITE_OK;
+    }
+    if( (rc!=SQLITE_OK && rc!=SQLITE_OK_LOAD_PERMANENTLY) || zErrMsg ){
+      Tcl_AppendResult(interp, "initialization of ", zName, " failed: ", zErrMsg,
+                       (char*)0);
+      sqlite3_free(zErrMsg);
+      return TCL_ERROR;
+    }
+  }
+  return TCL_OK;
+}
+
+/*
+**     sorter_test_fakeheap BOOL
+**
+*/
+static int SQLITE_TCLAPI sorter_test_fakeheap(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int bArg;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOL");
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &bArg) ){
+    return TCL_ERROR;
+  }
+
+  if( bArg ){
+    if( sqlite3GlobalConfig.pHeap==0 ){
+      sqlite3GlobalConfig.pHeap = SQLITE_INT_TO_PTR(-1);
+    }
+  }else{
+    if( sqlite3GlobalConfig.pHeap==SQLITE_INT_TO_PTR(-1) ){
+      sqlite3GlobalConfig.pHeap = 0;
+    }
+  }
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+/*
+**     sorter_test_sort4_helper DB SQL1 NSTEP SQL2
+**
+** Compile SQL statement $SQL1 and step it $NSTEP times. For each row, 
+** check that the leftmost and rightmost columns returned are both integers,
+** and that both contain the same value.
+**
+** Then execute statement $SQL2. Check that the statement returns the same
+** set of integers in the same order as in the previous step (using $SQL1).
+*/
+static int SQLITE_TCLAPI sorter_test_sort4_helper(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zSql1;
+  const char *zSql2;
+  int nStep; 
+  int iStep; 
+  unsigned int iCksum1 = 0; 
+  unsigned int iCksum2 = 0; 
+  int rc;
+  int iB;
+  sqlite3 *db;
+  sqlite3_stmt *pStmt;
+  
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB SQL1 NSTEP SQL2");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql1 = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &nStep) ) return TCL_ERROR;
+  zSql2 = Tcl_GetString(objv[4]);
+
+  rc = sqlite3_prepare_v2(db, zSql1, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) goto sql_error;
+
+  iB = sqlite3_column_count(pStmt)-1;
+  for(iStep=0; iStep<nStep && SQLITE_ROW==sqlite3_step(pStmt); iStep++){
+    int a = sqlite3_column_int(pStmt, 0);
+    if( a!=sqlite3_column_int(pStmt, iB) ){
+      Tcl_AppendResult(interp, "data error: (a!=b)", 0);
+      return TCL_ERROR;
+    }
+
+    iCksum1 += (iCksum1 << 3) + (unsigned int)a;
+  }
+  rc = sqlite3_finalize(pStmt);
+  if( rc!=SQLITE_OK ) goto sql_error;
+
+  rc = sqlite3_prepare_v2(db, zSql2, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) goto sql_error;
+  for(iStep=0; SQLITE_ROW==sqlite3_step(pStmt); iStep++){
+    int a = sqlite3_column_int(pStmt, 0);
+    iCksum2 += (iCksum2 << 3) + (unsigned int)a;
+  }
+  rc = sqlite3_finalize(pStmt);
+  if( rc!=SQLITE_OK ) goto sql_error;
+
+  if( iCksum1!=iCksum2 ){
+    Tcl_AppendResult(interp, "checksum mismatch", 0);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+ sql_error:
+  Tcl_AppendResult(interp, "sql error: ", sqlite3_errmsg(db), 0);
+  return TCL_ERROR;
+}
+
+
+#ifdef SQLITE_USER_AUTHENTICATION
+#include "sqlite3userauth.h"
+/*
+** tclcmd:  sqlite3_user_authenticate DB USERNAME PASSWORD
+*/
+static int SQLITE_TCLAPI test_user_authenticate(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zUser = 0;
+  char *zPasswd = 0;
+  int nPasswd = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB USERNAME PASSWORD");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  zUser = Tcl_GetString(objv[2]);
+  zPasswd = Tcl_GetStringFromObj(objv[3], &nPasswd);
+  rc = sqlite3_user_authenticate(db, zUser, zPasswd, nPasswd);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+#endif /* SQLITE_USER_AUTHENTICATION */
+
+#ifdef SQLITE_USER_AUTHENTICATION
+/*
+** tclcmd:  sqlite3_user_add DB USERNAME PASSWORD ISADMIN
+*/
+static int SQLITE_TCLAPI test_user_add(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zUser = 0;
+  char *zPasswd = 0;
+  int nPasswd = 0;
+  int isAdmin = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB USERNAME PASSWORD ISADMIN");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  zUser = Tcl_GetString(objv[2]);
+  zPasswd = Tcl_GetStringFromObj(objv[3], &nPasswd);
+  Tcl_GetBooleanFromObj(interp, objv[4], &isAdmin);
+  rc = sqlite3_user_add(db, zUser, zPasswd, nPasswd, isAdmin);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+#endif /* SQLITE_USER_AUTHENTICATION */
+
+#ifdef SQLITE_USER_AUTHENTICATION
+/*
+** tclcmd:  sqlite3_user_change DB USERNAME PASSWORD ISADMIN
+*/
+static int SQLITE_TCLAPI test_user_change(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zUser = 0;
+  char *zPasswd = 0;
+  int nPasswd = 0;
+  int isAdmin = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB USERNAME PASSWORD ISADMIN");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  zUser = Tcl_GetString(objv[2]);
+  zPasswd = Tcl_GetStringFromObj(objv[3], &nPasswd);
+  Tcl_GetBooleanFromObj(interp, objv[4], &isAdmin);
+  rc = sqlite3_user_change(db, zUser, zPasswd, nPasswd, isAdmin);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+#endif /* SQLITE_USER_AUTHENTICATION */
+
+#ifdef SQLITE_USER_AUTHENTICATION
+/*
+** tclcmd:  sqlite3_user_delete DB USERNAME
+*/
+static int SQLITE_TCLAPI test_user_delete(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zUser = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB USERNAME");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  zUser = Tcl_GetString(objv[2]);
+  rc = sqlite3_user_delete(db, zUser);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+#endif /* SQLITE_USER_AUTHENTICATION */
+
+/*
+** tclcmd: bad_behavior TYPE
+**
+** Do some things that should trigger a valgrind or -fsanitize=undefined
+** warning.  This is used to verify that errors and warnings output by those
+** tools are detected by the test scripts.
+**
+**       TYPE       BEHAVIOR
+**       1          Overflow a signed integer
+**       2          Jump based on an uninitialized variable
+**       3          Read after free
+**       4          Panic
+*/
+static int SQLITE_TCLAPI test_bad_behavior(
+  ClientData clientData, /* Pointer to an integer containing zero */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int iType;
+  int xyz;
+  int i = *(int*)clientData;
+  int j;
+  int w[10];
+  int *a;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "TYPE");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &iType) ) return TCL_ERROR;
+  switch( iType ){
+    case 1: {
+      xyz = 0x7fffff00 - i;
+      xyz += 0x100;
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(xyz));
+      break;
+    }
+    case 2: {
+      w[1] = 5;
+      if( w[i]>0 ) w[1]++;
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(w[1]));
+      break;
+    }
+    case 3: {
+      a = malloc( sizeof(int)*10 );
+      for(j=0; j<10; j++) a[j] = j;
+      free(a);
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(a[i]));
+      break;
+    }
+    case 4: {
+      Tcl_Panic("Deliberate panic");
+      break;
+    }
+  }
+  return TCL_OK;
+}  
+
+/*
+** tclcmd:   register_dbstat_vtab DB
+**
+** Cause the dbstat virtual table to be available on the connection DB
+*/
+static int SQLITE_TCLAPI test_register_dbstat_vtab(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  Tcl_AppendResult(interp, "dbstat not available because of "
+                           "SQLITE_OMIT_VIRTUALTABLE", (void*)0);
+  return TCL_ERROR;
+#else
+  struct SqliteDb { sqlite3 *db; };
+  char *zDb;
+  Tcl_CmdInfo cmdInfo;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+
+  zDb = Tcl_GetString(objv[1]);
+  if( Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+    sqlite3* db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+    sqlite3DbstatRegister(db);
+  }
+  return TCL_OK;
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+}
+
+/*
+** tclcmd:   sqlite3_db_config DB SETTING VALUE
+**
+** Invoke sqlite3_db_config() for one of the setting values.
+*/
+static int SQLITE_TCLAPI test_sqlite3_db_config(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static const struct {
+    const char *zName;
+    int eVal;
+  } aSetting[] = {
+    { "FKEY",               SQLITE_DBCONFIG_ENABLE_FKEY },
+    { "TRIGGER",            SQLITE_DBCONFIG_ENABLE_TRIGGER },
+    { "FTS3_TOKENIZER",     SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER },
+    { "LOAD_EXTENSION",     SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION },
+    { "NO_CKPT_ON_CLOSE",   SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE },
+    { "QPSG",               SQLITE_DBCONFIG_ENABLE_QPSG },
+    { "TRIGGER_EQP",        SQLITE_DBCONFIG_TRIGGER_EQP },
+    { "RESET_DB",           SQLITE_DBCONFIG_RESET_DATABASE },
+    { "DEFENSIVE",          SQLITE_DBCONFIG_DEFENSIVE },
+    { "WRITABLE_SCHEMA",    SQLITE_DBCONFIG_WRITABLE_SCHEMA },
+    { "LEGACY_ALTER_TABLE", SQLITE_DBCONFIG_LEGACY_ALTER_TABLE },
+    { "DQS_DML",            SQLITE_DBCONFIG_DQS_DML },
+    { "DQS_DDL",            SQLITE_DBCONFIG_DQS_DDL },
+    { "LEGACY_FILE_FORMAT", SQLITE_DBCONFIG_LEGACY_FILE_FORMAT },
+    { "STMT_SCANSTATUS",    SQLITE_DBCONFIG_STMT_SCANSTATUS },
+  };
+  int i;
+  int v = 0;
+  const char *zSetting;
+  sqlite3 *db;
+
+  if( objc!=4 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB SETTING [VALUE]");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSetting = Tcl_GetString(objv[2]);
+  if( sqlite3_strglob("SQLITE_*", zSetting)==0 ) zSetting += 7;
+  if( sqlite3_strglob("DBCONFIG_*", zSetting)==0 ) zSetting += 9;
+  if( sqlite3_strglob("ENABLE_*", zSetting)==0 ) zSetting += 7;
+  for(i=0; i<ArraySize(aSetting); i++){
+    if( strcmp(zSetting, aSetting[i].zName)==0 ) break;
+  }
+  if( i>=ArraySize(aSetting) ){
+    Tcl_SetObjResult(interp,
+      Tcl_NewStringObj("unknown sqlite3_db_config setting", -1));
+    return TCL_ERROR;
+  }
+  if( objc==4 ){
+    if( Tcl_GetIntFromObj(interp, objv[3], &v) ) return TCL_ERROR;
+  }else{
+    v = -1;
+  }
+  sqlite3_db_config(db, aSetting[i].eVal, v, &v);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(v));
+  return TCL_OK;
+}
+/*
+** tclcmd:   sqlite3_txn_state DB ?SCHEMA?
+**
+** Invoke sqlite3_txn_state(DB,SCHEMA) and return the
+** numeric value that results.  Use NULL for SCHEMA if the 3 argument
+** is omitted.
+*/
+static int SQLITE_TCLAPI test_sqlite3_txn_state(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSchema;
+  int iTxn;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB ?SCHEMA?");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSchema = objc==3 ? Tcl_GetString(objv[2]) : 0;
+  iTxn = sqlite3_txn_state(db, zSchema);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(iTxn));
+  return TCL_OK;
+}
+
+/*
+** Change the name of the main database schema from "main" to "icecube".
+*/
+static int SQLITE_TCLAPI test_dbconfig_maindbname_icecube(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3 *db;
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }else{
+    if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+    rc = sqlite3_db_config(db, SQLITE_DBCONFIG_MAINDBNAME, "icecube");
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+    return TCL_OK;
+  }
+}
+
+/*
+** Usage: sqlite3_mmap_warm DB DBNAME
+*/
+static int SQLITE_TCLAPI test_mmap_warm(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  extern int sqlite3_mmap_warm(sqlite3 *db, const char *);
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB ?DBNAME?");
+    return TCL_ERROR;
+  }else{
+    int rc;
+    sqlite3 *db;
+    const char *zDb = 0;
+    if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+    if( objc==3 ){
+      zDb = Tcl_GetString(objv[2]);
+    }
+    rc = sqlite3_mmap_warm(db, zDb);
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_OK;
+  }
+}
+
+/*
+** Usage:  test_write_db DB OFFSET DATA
+**
+** Obtain the sqlite3_file* object for the database file for the "main" db
+** of handle DB. Then invoke its xWrite method to write data DATA to offset
+** OFFSET.
+*/
+static int SQLITE_TCLAPI test_write_db(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db = 0;
+  Tcl_WideInt iOff = 0;
+  const unsigned char *aData = 0;
+  int nData = 0;
+  sqlite3_file *pFile = 0;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB OFFSET DATA");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetWideIntFromObj(interp, objv[2], &iOff) ) return TCL_ERROR;
+  aData = Tcl_GetByteArrayFromObj(objv[3], &nData);
+
+  sqlite3_file_control(db, "main", SQLITE_FCNTL_FILE_POINTER, (void*)&pFile);
+  rc = pFile->pMethods->xWrite(pFile, aData, nData, iOff);
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_register_cksumvfs
+**
+*/
+static int SQLITE_TCLAPI test_register_cksumvfs(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }else{
+    extern int sqlite3_register_cksumvfs(const char*);
+    int rc = sqlite3_register_cksumvfs(0);
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_unregister_cksumvfs
+**
+*/
+static int SQLITE_TCLAPI test_unregister_cksumvfs(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }else{
+    extern int sqlite3_unregister_cksumvfs(void);
+    int rc = sqlite3_unregister_cksumvfs();
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  decode_hexdb TEXT
+**
+** Example:   db deserialize [decode_hexdb $output_of_dbtotxt]
+**
+** This routine returns a byte-array for an SQLite database file that
+** is constructed from a text input which is the output of the "dbtotxt"
+** utility.
+*/
+static int SQLITE_TCLAPI test_decode_hexdb(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zIn = 0;
+  unsigned char *a = 0;
+  int n = 0;
+  int lineno = 0;
+  int i, iNext;
+  int iOffset = 0;
+  int j, k;
+  int rc;
+  unsigned int x[16];
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HEXDB");
+    return TCL_ERROR;
+  }
+  zIn = Tcl_GetString(objv[1]);
+  for(i=0; zIn[i]; i=iNext){
+    lineno++;
+    for(iNext=i; zIn[iNext] && zIn[iNext]!='\n'; iNext++){}
+    if( zIn[iNext]=='\n' ) iNext++;
+    while( zIn[i]==' ' || zIn[i]=='\t' ){ i++; }
+    if( a==0 ){
+      int pgsz;
+      rc = sscanf(zIn+i, "| size %d pagesize %d", &n, &pgsz);
+      if( rc!=2 ) continue;
+      if( pgsz<512 || pgsz>65536 || (pgsz&(pgsz-1))!=0 ){
+        Tcl_AppendResult(interp, "bad 'pagesize' field", (void*)0);
+        return TCL_ERROR;
+      }
+      n = (n+pgsz-1)&~(pgsz-1);  /* Round n up to the next multiple of pgsz */
+      if( n<512 ){
+        Tcl_AppendResult(interp, "bad 'size' field", (void*)0);
+        return TCL_ERROR;
+      }
+      a = malloc( n );
+      if( a==0 ){
+        Tcl_AppendResult(interp, "out of memory", (void*)0);
+        return TCL_ERROR;
+      }
+      memset(a, 0, n);
+      continue;
+    }
+    rc = sscanf(zIn+i, "| page %d offset %d", &j, &k);
+    if( rc==2 ){
+      iOffset = k;
+      continue;
+    }
+    rc = sscanf(zIn+i,"| %d: %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x",
+                &j, &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7],
+                &x[8], &x[9], &x[10], &x[11], &x[12], &x[13], &x[14], &x[15]);
+    if( rc==17 ){
+      k = iOffset+j;
+      if( k+16<=n ){
+        int ii;
+        for(ii=0; ii<16; ii++) a[k+ii] = x[ii]&0xff;
+      }
+      continue;
+    }
+  }
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(a, n));
+  free(a);
+  return TCL_OK;
+}
+
+/*
+** Client data for the autovacuum_pages callback.
+*/
+struct AutovacPageData {
+  Tcl_Interp *interp;
+  char *zScript;
+};
+typedef struct AutovacPageData AutovacPageData;
+
+/*
+** Callback functions for sqlite3_autovacuum_pages
+*/
+static unsigned int test_autovacuum_pages_callback(
+  void *pClientData,
+  const char *zSchema,
+  unsigned int nFilePages,
+  unsigned int nFreePages,
+  unsigned int nBytePerPage
+){
+  AutovacPageData *pData = (AutovacPageData*)pClientData;
+  Tcl_DString str;
+  unsigned int x;
+  char zBuf[100];
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppend(&str, pData->zScript, -1);
+  Tcl_DStringAppendElement(&str, zSchema);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%u", nFilePages);
+  Tcl_DStringAppendElement(&str, zBuf);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%u", nFreePages);
+  Tcl_DStringAppendElement(&str, zBuf);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%u", nBytePerPage);
+  Tcl_DStringAppendElement(&str, zBuf);
+  Tcl_ResetResult(pData->interp);
+  Tcl_Eval(pData->interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  x = nFreePages;
+  (void)Tcl_GetIntFromObj(0, Tcl_GetObjResult(pData->interp), (int*)&x);
+  return x;
+}
+
+/*
+** Usage:  sqlite3_autovacuum_pages DB SCRIPT
+**
+** Add an autovacuum-pages callback to database connection DB.  The callback
+** will invoke SCRIPT, after appending parameters.
+**
+** If SCRIPT is an empty string or is omitted, then the callback is
+** cancelled.
+*/
+static int SQLITE_TCLAPI test_autovacuum_pages(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  AutovacPageData *pData;
+  sqlite3 *db;
+  int rc;
+  const char *zScript;
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB ?SCRIPT?");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zScript = objc==3 ? Tcl_GetString(objv[2]) : 0;
+  if( zScript ){
+    size_t nScript = strlen(zScript);
+    pData = sqlite3_malloc64( sizeof(*pData) + nScript + 1 );
+    if( pData==0 ){
+      Tcl_AppendResult(interp, "out of memory", (void*)0);
+      return TCL_ERROR;
+    }
+    pData->interp = interp;
+    pData->zScript = (char*)&pData[1];
+    memcpy(pData->zScript, zScript, nScript+1);
+    rc = sqlite3_autovacuum_pages(db,test_autovacuum_pages_callback,
+                                  pData, sqlite3_free);
+  }else{
+    rc = sqlite3_autovacuum_pages(db, 0, 0, 0);
+  }
+  if( rc ){
+    char zBuf[1000];
+    sqlite3_snprintf(sizeof(zBuf), zBuf,
+       "sqlite3_autovacuum_pages() returns %d", rc);
+    Tcl_AppendResult(interp, zBuf, (void*)0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  number_of_cores
+**
+** Return a guess at the number of available cores available on the
+** processor on which this process is running.
+*/
+static int SQLITE_TCLAPI guess_number_of_cores(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  unsigned int nCore = 1;
+#if SQLITE_OS_WIN
+  SYSTEM_INFO sysinfo;
+  GetSystemInfo(&sysinfo);
+  nCore = (unsigned int)sysinfo.dwNumberOfProcessors;
+#elif defined(__APPLE__)
+  int nm[2];
+  size_t len = 4;
+  nm[0] = CTL_HW; nm[1] = HW_AVAILCPU;
+  sysctl(nm, 2, &nCore, &len, NULL, 0);
+  if( nCore<1 ){
+    nm[1] = HW_NCPU;
+    sysctl(nm, 2, &nCore, &len, NULL, 0);
+  }
+#else
+  nCore = sysconf(_SC_NPROCESSORS_ONLN);
+#endif
+  if( nCore<=0 ) nCore = 1;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj((int)nCore));
+  return SQLITE_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest1_Init(Tcl_Interp *interp){
+  extern int sqlite3_search_count;
+  extern int sqlite3_found_count;
+  extern int sqlite3_interrupt_count;
+  extern int sqlite3_open_file_count;
+  extern int sqlite3_sort_count;
+  extern int sqlite3_current_time;
+#if SQLITE_OS_UNIX && defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+  extern int sqlite3_hostid_num;
+#endif
+  extern int sqlite3_max_blobsize;
+  extern int SQLITE_TCLAPI sqlite3BtreeSharedCacheReport(void*,
+                                          Tcl_Interp*,int,Tcl_Obj*CONST*);
+  static int iZero = 0;
+  static struct {
+     char *zName;
+     Tcl_CmdProc *xProc;
+  } aCmd[] = {
+     { "db_enter",                      (Tcl_CmdProc*)db_enter               },
+     { "db_leave",                      (Tcl_CmdProc*)db_leave               },
+     { "sqlite3_mprintf_int",           (Tcl_CmdProc*)sqlite3_mprintf_int    },
+     { "sqlite3_mprintf_int64",         (Tcl_CmdProc*)sqlite3_mprintf_int64  },
+     { "sqlite3_mprintf_long",          (Tcl_CmdProc*)sqlite3_mprintf_long   },
+     { "sqlite3_mprintf_str",           (Tcl_CmdProc*)sqlite3_mprintf_str    },
+     { "sqlite3_snprintf_str",          (Tcl_CmdProc*)sqlite3_snprintf_str   },
+     { "sqlite3_mprintf_stronly",       (Tcl_CmdProc*)sqlite3_mprintf_stronly},
+     { "sqlite3_mprintf_double",        (Tcl_CmdProc*)sqlite3_mprintf_double },
+     { "sqlite3_mprintf_scaled",        (Tcl_CmdProc*)sqlite3_mprintf_scaled },
+     { "sqlite3_mprintf_hexdouble",   (Tcl_CmdProc*)sqlite3_mprintf_hexdouble},
+     { "sqlite3_mprintf_z_test",        (Tcl_CmdProc*)test_mprintf_z        },
+     { "sqlite3_mprintf_n_test",        (Tcl_CmdProc*)test_mprintf_n        },
+     { "sqlite3_snprintf_int",          (Tcl_CmdProc*)test_snprintf_int     },
+     { "sqlite3_last_insert_rowid",     (Tcl_CmdProc*)test_last_rowid       },
+     { "sqlite3_exec_printf",           (Tcl_CmdProc*)test_exec_printf      },
+     { "sqlite3_exec_hex",              (Tcl_CmdProc*)test_exec_hex         },
+     { "sqlite3_exec",                  (Tcl_CmdProc*)test_exec             },
+     { "sqlite3_exec_nr",               (Tcl_CmdProc*)test_exec_nr          },
+#ifndef SQLITE_OMIT_GET_TABLE
+     { "sqlite3_get_table_printf",      (Tcl_CmdProc*)test_get_table_printf },
+#endif
+     { "sqlite3_close",                 (Tcl_CmdProc*)sqlite_test_close     },
+     { "sqlite3_close_v2",              (Tcl_CmdProc*)sqlite_test_close_v2  },
+     { "sqlite3_create_function",       (Tcl_CmdProc*)test_create_function  },
+     { "sqlite3_create_aggregate",      (Tcl_CmdProc*)test_create_aggregate },
+     { "sqlite3_drop_modules",          (Tcl_CmdProc*)test_drop_modules     },
+     { "sqlite_register_test_function", (Tcl_CmdProc*)test_register_func    },
+     { "sqlite_abort",                  (Tcl_CmdProc*)sqlite_abort          },
+     { "sqlite_bind",                   (Tcl_CmdProc*)test_bind             },
+     { "breakpoint",                    (Tcl_CmdProc*)test_breakpoint       },
+     { "sqlite3_key",                   (Tcl_CmdProc*)test_key              },
+     { "sqlite3_rekey",                 (Tcl_CmdProc*)test_rekey            },
+     { "sqlite3_interrupt",             (Tcl_CmdProc*)test_interrupt        },
+     { "sqlite3_is_interrupted",        (Tcl_CmdProc*)test_is_interrupted   },
+     { "sqlite_delete_function",        (Tcl_CmdProc*)delete_function       },
+     { "sqlite_delete_collation",       (Tcl_CmdProc*)delete_collation      },
+     { "sqlite3_get_autocommit",        (Tcl_CmdProc*)get_autocommit        },
+     { "sqlite3_busy_timeout",          (Tcl_CmdProc*)test_busy_timeout     },
+     { "printf",                        (Tcl_CmdProc*)test_printf           },
+     { "sqlite3IoTrace",              (Tcl_CmdProc*)test_io_trace         },
+     { "clang_sanitize_address",        (Tcl_CmdProc*)clang_sanitize_address },
+  };
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "sqlite3_db_config",             test_sqlite3_db_config, 0 },
+     { "sqlite3_txn_state",             test_sqlite3_txn_state, 0 },
+     { "bad_behavior",                  test_bad_behavior,  (void*)&iZero },
+     { "register_dbstat_vtab",          test_register_dbstat_vtab  },
+     { "sqlite3_connection_pointer",    get_sqlite_pointer, 0 },
+     { "intarray_addr",                 test_intarray_addr, 0 },
+     { "int64array_addr",               test_int64array_addr, 0 },
+     { "doublearray_addr",              test_doublearray_addr, 0 },
+     { "textarray_addr",                test_textarray_addr, 0 },
+     { "sqlite3_bind_int",              test_bind_int,      0 },
+     { "sqlite3_bind_zeroblob",         test_bind_zeroblob, 0 },
+     { "sqlite3_bind_zeroblob64",       test_bind_zeroblob64, 0 },
+     { "sqlite3_bind_int64",            test_bind_int64,    0 },
+     { "sqlite3_bind_double",           test_bind_double,   0 },
+     { "sqlite3_bind_null",             test_bind_null     ,0 },
+     { "sqlite3_bind_text",             test_bind_text     ,0 },
+     { "sqlite3_bind_text16",           test_bind_text16   ,0 },
+     { "sqlite3_bind_blob",             test_bind_blob     ,0 },
+     { "sqlite3_bind_value_from_select",test_bind_value_from_select ,0 },
+     { "sqlite3_bind_value_from_preupdate",test_bind_value_from_preupdate ,0 },
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+     { "sqlite3_carray_bind",           test_carray_bind   ,0 },
+#endif
+     { "sqlite3_bind_parameter_count",  test_bind_parameter_count, 0},
+     { "sqlite3_bind_parameter_name",   test_bind_parameter_name,  0},
+     { "sqlite3_bind_parameter_index",  test_bind_parameter_index, 0},
+     { "sqlite3_clear_bindings",        test_clear_bindings, 0},
+     { "sqlite3_sleep",                 test_sleep,          0},
+     { "sqlite3_errcode",               test_errcode       ,0 },
+     { "sqlite3_extended_errcode",      test_ex_errcode    ,0 },
+     { "sqlite3_errmsg",                test_errmsg        ,0 },
+     { "sqlite3_error_offset",          test_error_offset  ,0 },
+     { "sqlite3_errmsg16",              test_errmsg16      ,0 },
+     { "sqlite3_open",                  test_open          ,0 },
+     { "sqlite3_open16",                test_open16        ,0 },
+     { "sqlite3_open_v2",               test_open_v2       ,0 },
+     { "sqlite3_complete16",            test_complete16    ,0 },
+     { "sqlite3_normalize",             test_normalize     ,0 },
+
+     { "sqlite3_prepare",               test_prepare       ,0 },
+     { "sqlite3_prepare16",             test_prepare16     ,0 },
+     { "sqlite3_prepare_v2",            test_prepare_v2    ,0 },
+     { "sqlite3_prepare_v3",            test_prepare_v3    ,0 },
+     { "sqlite3_prepare_tkt3134",       test_prepare_tkt3134, 0},
+     { "sqlite3_prepare16_v2",          test_prepare16_v2  ,0 },
+     { "sqlite3_finalize",              test_finalize      ,0 },
+     { "sqlite3_stmt_status",           test_stmt_status   ,0 },
+     { "sqlite3_reset",                 test_reset         ,0 },
+     { "sqlite3_expired",               test_expired       ,0 },
+     { "sqlite3_transfer_bindings",     test_transfer_bind ,0 },
+     { "sqlite3_changes",               test_changes       ,0 },
+     { "sqlite3_step",                  test_step          ,0 },
+     { "sqlite3_sql",                   test_sql           ,0 },
+     { "sqlite3_expanded_sql",          test_ex_sql        ,0 },
+#ifdef SQLITE_ENABLE_NORMALIZE
+     { "sqlite3_normalized_sql",        test_norm_sql      ,0 },
+#endif
+     { "sqlite3_next_stmt",             test_next_stmt     ,0 },
+     { "sqlite3_stmt_readonly",         test_stmt_readonly ,0 },
+     { "sqlite3_stmt_isexplain",        test_stmt_isexplain,0 },
+     { "sqlite3_stmt_explain",          test_stmt_explain  ,0 },
+     { "sqlite3_stmt_busy",             test_stmt_busy     ,0 },
+     { "uses_stmt_journal",             uses_stmt_journal ,0 },
+
+     { "sqlite3_release_memory",        test_release_memory,     0},
+     { "sqlite3_db_release_memory",     test_db_release_memory,  0},
+     { "sqlite3_db_cacheflush",         test_db_cacheflush,      0},
+     { "sqlite3_system_errno",          test_system_errno,       0},
+     { "sqlite3_db_filename",           test_db_filename,        0},
+     { "sqlite3_db_readonly",           test_db_readonly,        0},
+     { "sqlite3_soft_heap_limit",       test_soft_heap_limit,    0},
+     { "sqlite3_soft_heap_limit64",     test_soft_heap_limit,    0},
+     { "sqlite3_hard_heap_limit64",     test_hard_heap_limit,    0},
+     { "sqlite3_thread_cleanup",        test_thread_cleanup,     0},
+     { "sqlite3_pager_refcounts",       test_pager_refcounts,    0},
+
+     { "sqlite3_load_extension",        test_load_extension,     0},
+     { "sqlite3_enable_load_extension", test_enable_load,        0},
+     { "sqlite3_extended_result_codes", test_extended_result_codes, 0},
+     { "sqlite3_limit",                 test_limit,                 0},
+     { "dbconfig_maindbname_icecube",   test_dbconfig_maindbname_icecube },
+
+     { "save_prng_state",               save_prng_state,    0 },
+     { "restore_prng_state",            restore_prng_state, 0 },
+     { "reset_prng_state",              reset_prng_state,   0 },
+     { "prng_seed",                     prng_seed,          0 },
+     { "extra_schema_checks",           extra_schema_checks,    0},
+     { "use_long_double",               use_long_double,        0},
+     { "database_never_corrupt",        database_never_corrupt, 0},
+     { "database_may_be_corrupt",       database_may_be_corrupt, 0},
+     { "optimization_control",          optimization_control,0},
+#if SQLITE_OS_WIN
+     { "lock_win32_file",               win32_file_lock,    0 },
+     { "exists_win32_path",             win32_exists_path,  0 },
+     { "find_win32_file",               win32_find_file,    0 },
+     { "delete_win32_file",             win32_delete_file,  0 },
+     { "make_win32_dir",                win32_mkdir,        0 },
+     { "remove_win32_dir",              win32_rmdir,        0 },
+#endif
+     { "tcl_objproc",                   runAsObjProc,       0 },
+
+     /* sqlite3_column_*() API */
+     { "sqlite3_column_count",          test_column_count  ,0 },
+     { "sqlite3_data_count",            test_data_count    ,0 },
+     { "sqlite3_column_type",           test_column_type   ,0 },
+     { "sqlite3_column_blob",           test_column_blob   ,0 },
+     { "sqlite3_column_double",         test_column_double ,0 },
+     { "sqlite3_column_int64",          test_column_int64  ,0 },
+     { "sqlite3_column_text",   test_stmt_utf8,  (void*)sqlite3_column_text },
+     { "sqlite3_column_name",   test_stmt_utf8,  (void*)sqlite3_column_name },
+     { "sqlite3_column_int",    test_stmt_int,   (void*)sqlite3_column_int  },
+     { "sqlite3_column_bytes",  test_stmt_int,   (void*)sqlite3_column_bytes},
+#ifndef SQLITE_OMIT_DECLTYPE
+     { "sqlite3_column_decltype",test_stmt_utf8,(void*)sqlite3_column_decltype},
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+{ "sqlite3_column_database_name",test_stmt_utf8,(void*)sqlite3_column_database_name},
+{ "sqlite3_column_table_name",test_stmt_utf8,(void*)sqlite3_column_table_name},
+{ "sqlite3_column_origin_name",test_stmt_utf8,(void*)sqlite3_column_origin_name},
+#endif
+
+#ifndef SQLITE_OMIT_UTF16
+     { "sqlite3_column_bytes16", test_stmt_int, (void*)sqlite3_column_bytes16 },
+     { "sqlite3_column_text16",  test_stmt_utf16, (void*)sqlite3_column_text16},
+     { "sqlite3_column_name16",  test_stmt_utf16, (void*)sqlite3_column_name16},
+     { "add_alignment_test_collations", add_alignment_test_collations, 0      },
+#ifndef SQLITE_OMIT_DECLTYPE
+     { "sqlite3_column_decltype16",test_stmt_utf16,(void*)sqlite3_column_decltype16},
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+{"sqlite3_column_database_name16",
+  test_stmt_utf16, (void*)sqlite3_column_database_name16},
+{"sqlite3_column_table_name16", test_stmt_utf16, (void*)sqlite3_column_table_name16},
+{"sqlite3_column_origin_name16", test_stmt_utf16, (void*)sqlite3_column_origin_name16},
+#endif
+#endif
+     { "sqlite3_create_collation_v2", test_create_collation_v2, 0 },
+     { "sqlite3_global_recover",     test_global_recover, 0   },
+     { "working_64bit_int",          working_64bit_int,   0   },
+     { "vfs_unlink_test",            vfs_unlink_test,     0   },
+     { "vfs_initfail_test",          vfs_initfail_test,   0   },
+     { "vfs_unregister_all",         vfs_unregister_all,  0   },
+     { "vfs_reregister_all",         vfs_reregister_all,  0   },
+     { "file_control_test",          file_control_test,   0   },
+     { "file_control_lasterrno_test", file_control_lasterrno_test,  0   },
+     { "file_control_lockproxy_test", file_control_lockproxy_test,  0   },
+     { "file_control_chunksize_test", file_control_chunksize_test,  0   },
+     { "file_control_sizehint_test",  file_control_sizehint_test,   0   },
+     { "file_control_data_version",   file_control_data_version,    0   },
+#if SQLITE_OS_WIN
+     { "file_control_win32_av_retry", file_control_win32_av_retry,  0   },
+     { "file_control_win32_get_handle", file_control_win32_get_handle, 0  },
+     { "file_control_win32_set_handle", file_control_win32_set_handle, 0  },
+#endif
+     { "file_control_persist_wal",    file_control_persist_wal,     0   },
+     { "file_control_powersafe_overwrite",file_control_powersafe_overwrite,0},
+     { "file_control_vfsname",        file_control_vfsname,         0   },
+     { "file_control_reservebytes",   file_control_reservebytes,    0   },
+     { "file_control_tempfilename",   file_control_tempfilename,    0   },
+     { "file_control_external_reader",   file_control_external_reader,    0   },
+     { "sqlite3_vfs_list",           vfs_list,     0   },
+     { "sqlite3_create_function_v2", test_create_function_v2, 0 },
+
+     /* Functions from os.h */
+#ifndef SQLITE_OMIT_UTF16
+     { "add_test_collate",        test_collate, 0            },
+     { "add_test_collate_needed", test_collate_needed, 0     },
+     { "add_test_function",       test_function, 0           },
+     { "add_test_utf16bin_collate",    test_utf16bin_collate, 0        },
+#endif
+     { "sqlite3_test_errstr",     test_errstr, 0             },
+     { "tcl_variable_type",       tcl_variable_type, 0       },
+#ifndef SQLITE_OMIT_SHARED_CACHE
+     { "sqlite3_enable_shared_cache", test_enable_shared, 0  },
+     { "sqlite3_shared_cache_report", sqlite3BtreeSharedCacheReport, 0},
+#endif
+     { "sqlite3_libversion_number", test_libversion_number, 0  },
+     { "sqlite3_table_column_metadata", test_table_column_metadata, 0  },
+#ifndef SQLITE_OMIT_INCRBLOB
+     { "sqlite3_blob_reopen", test_blob_reopen, 0  },
+#endif
+     { "pcache_stats",       test_pcache_stats, 0  },
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+     { "sqlite3_unlock_notify", test_unlock_notify, 0  },
+#endif
+     { "sqlite3_wal_checkpoint",   test_wal_checkpoint, 0  },
+     { "sqlite3_wal_checkpoint_v2",test_wal_checkpoint_v2, 0  },
+     { "sqlite3_wal_autocheckpoint",test_wal_autocheckpoint, 0  },
+     { "test_sqlite3_log",         test_sqlite3_log, 0  },
+#ifndef SQLITE_OMIT_EXPLAIN
+     { "print_explain_query_plan", test_print_eqp, 0  },
+#endif
+     { "strftime",             strftime_cmd      },
+     { "sqlite3_test_control", test_test_control },
+     { ".treetrace",           test_treetrace    },
+#if SQLITE_OS_UNIX
+     { "getrusage", test_getrusage },
+#endif
+     { "load_static_extension", tclLoadStaticExtensionCmd },
+     { "sorter_test_fakeheap", sorter_test_fakeheap },
+     { "sorter_test_sort4_helper", sorter_test_sort4_helper },
+#ifdef SQLITE_USER_AUTHENTICATION
+     { "sqlite3_user_authenticate", test_user_authenticate, 0 },
+     { "sqlite3_user_add",          test_user_add,          0 },
+     { "sqlite3_user_change",       test_user_change,       0 },
+     { "sqlite3_user_delete",       test_user_delete,       0 },
+#endif
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+     { "sqlite3_stmt_scanstatus",       test_stmt_scanstatus,   0 },
+     { "sqlite3_stmt_scanstatus_reset", test_stmt_scanstatus_reset,   0 },
+#endif
+#ifdef SQLITE_ENABLE_SQLLOG
+     { "sqlite3_config_sqllog",         test_config_sqllog,   0 },
+#endif
+     { "vfs_current_time_int64",           vfsCurrentTimeInt64,   0 },
+#ifdef SQLITE_ENABLE_SNAPSHOT
+     { "sqlite3_snapshot_get", test_snapshot_get, 0 },
+     { "sqlite3_snapshot_open", test_snapshot_open, 0 },
+     { "sqlite3_snapshot_free", test_snapshot_free, 0 },
+     { "sqlite3_snapshot_cmp", test_snapshot_cmp, 0 },
+     { "sqlite3_snapshot_recover", test_snapshot_recover, 0 },
+     { "sqlite3_snapshot_get_blob", test_snapshot_get_blob, 0 },
+     { "sqlite3_snapshot_open_blob", test_snapshot_open_blob, 0 },
+     { "sqlite3_snapshot_cmp_blob", test_snapshot_cmp_blob, 0 },
+#endif
+     { "sqlite3_delete_database", test_delete_database,    0 },
+     { "atomic_batch_write",      test_atomic_batch_write, 0 },
+     { "sqlite3_mmap_warm",       test_mmap_warm,          0 },
+     { "sqlite3_config_sorterref", test_config_sorterref,   0 },
+     { "sqlite3_autovacuum_pages", test_autovacuum_pages,   0 },
+     { "decode_hexdb",             test_decode_hexdb,       0 },
+     { "test_write_db",            test_write_db,           0 },
+     { "sqlite3_register_cksumvfs", test_register_cksumvfs,  0 },
+     { "sqlite3_unregister_cksumvfs", test_unregister_cksumvfs,  0 },
+     { "number_of_cores",             guess_number_of_cores,     0 },
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+     { "create_null_module",       test_create_null_module,     0 },
+#endif
+  };
+  static int bitmask_size = sizeof(Bitmask)*8;
+  static int longdouble_size = sizeof(LONGDOUBLE_TYPE);
+  int i;
+  extern int sqlite3_sync_count, sqlite3_fullsync_count;
+  extern int sqlite3_opentemp_count;
+  extern int sqlite3_like_count;
+  extern int sqlite3_xferopt_count;
+  extern int sqlite3_pager_readdb_count;
+  extern int sqlite3_pager_writedb_count;
+  extern int sqlite3_pager_writej_count;
+#if SQLITE_OS_WIN
+  extern LONG volatile sqlite3_os_type;
+#endif
+#ifdef SQLITE_DEBUG
+  extern u32 sqlite3WhereTrace;
+  extern int sqlite3OSTrace;
+  extern int sqlite3WalTrace;
+#endif
+#ifdef SQLITE_TEST
+#ifdef SQLITE_ENABLE_FTS3
+  extern int sqlite3_fts3_enable_parentheses;
+#endif
+#endif
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  Tcl_LinkVar(interp, "sqlite_search_count", 
+      (char*)&sqlite3_search_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_found_count", 
+      (char*)&sqlite3_found_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_sort_count", 
+      (char*)&sqlite3_sort_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_max_blobsize", 
+      (char*)&sqlite3_max_blobsize, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_like_count", 
+      (char*)&sqlite3_like_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_interrupt_count", 
+      (char*)&sqlite3_interrupt_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_open_file_count", 
+      (char*)&sqlite3_open_file_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_current_time", 
+      (char*)&sqlite3_current_time, TCL_LINK_INT);
+#if SQLITE_OS_UNIX && defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+  Tcl_LinkVar(interp, "sqlite_hostid_num", 
+      (char*)&sqlite3_hostid_num, TCL_LINK_INT);
+#endif
+  Tcl_LinkVar(interp, "sqlite3_xferopt_count",
+      (char*)&sqlite3_xferopt_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_pager_readdb_count",
+      (char*)&sqlite3_pager_readdb_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_pager_writedb_count",
+      (char*)&sqlite3_pager_writedb_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_pager_writej_count",
+      (char*)&sqlite3_pager_writej_count, TCL_LINK_INT);
+#ifndef SQLITE_OMIT_UTF16
+  Tcl_LinkVar(interp, "unaligned_string_counter",
+      (char*)&unaligned_string_counter, TCL_LINK_INT);
+#endif
+#ifndef SQLITE_OMIT_UTF16
+  Tcl_LinkVar(interp, "sqlite_last_needed_collation",
+      (char*)&pzNeededCollation, TCL_LINK_STRING|TCL_LINK_READ_ONLY);
+#endif
+#if SQLITE_OS_WIN
+  Tcl_LinkVar(interp, "sqlite_os_type",
+      (char*)&sqlite3_os_type, TCL_LINK_LONG);
+#endif
+#ifdef SQLITE_TEST
+  {
+    static const char *query_plan = "*** OBSOLETE VARIABLE ***";
+    Tcl_LinkVar(interp, "sqlite_query_plan",
+       (char*)&query_plan, TCL_LINK_STRING|TCL_LINK_READ_ONLY);
+  }
+#endif
+#ifdef SQLITE_DEBUG
+  Tcl_LinkVar(interp, "sqlite_where_trace",
+      (char*)&sqlite3WhereTrace, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_os_trace",
+      (char*)&sqlite3OSTrace, TCL_LINK_INT);
+#ifndef SQLITE_OMIT_WAL
+  Tcl_LinkVar(interp, "sqlite_wal_trace",
+      (char*)&sqlite3WalTrace, TCL_LINK_INT);
+#endif
+#endif
+#ifndef SQLITE_OMIT_DISKIO
+  Tcl_LinkVar(interp, "sqlite_opentemp_count",
+      (char*)&sqlite3_opentemp_count, TCL_LINK_INT);
+#endif
+  Tcl_LinkVar(interp, "sqlite_static_bind_value",
+      (char*)&sqlite_static_bind_value, TCL_LINK_STRING);
+  Tcl_LinkVar(interp, "sqlite_static_bind_nbyte",
+      (char*)&sqlite_static_bind_nbyte, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_temp_directory",
+      (char*)&sqlite3_temp_directory, TCL_LINK_STRING);
+  Tcl_LinkVar(interp, "sqlite_data_directory",
+      (char*)&sqlite3_data_directory, TCL_LINK_STRING);
+  Tcl_LinkVar(interp, "bitmask_size",
+      (char*)&bitmask_size, TCL_LINK_INT|TCL_LINK_READ_ONLY);
+  Tcl_LinkVar(interp, "longdouble_size",
+      (char*)&longdouble_size, TCL_LINK_INT|TCL_LINK_READ_ONLY);
+  Tcl_LinkVar(interp, "sqlite_sync_count",
+      (char*)&sqlite3_sync_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_fullsync_count",
+      (char*)&sqlite3_fullsync_count, TCL_LINK_INT);
+#if defined(SQLITE_ENABLE_TREETRACE)
+  Tcl_LinkVar(interp, "sqlite3_unsupported_treetrace",
+      (char*)&sqlite3TreeTrace, TCL_LINK_INT);
+#endif
+#if defined(SQLITE_ENABLE_FTS3) && defined(SQLITE_TEST)
+  Tcl_LinkVar(interp, "sqlite_fts3_enable_parentheses",
+      (char*)&sqlite3_fts3_enable_parentheses, TCL_LINK_INT);
+#endif
+  return TCL_OK;
+}
diff --git a/src/test2.c b/src/test2.c
new file mode 100644
index 0000000..c75fa2e
--- /dev/null
+++ b/src/test2.c
@@ -0,0 +1,760 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the pager.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+extern const char *sqlite3ErrName(int);
+
+/*
+** Page size and reserved size used for testing.
+*/
+static int test_pagesize = 1024;
+
+/*
+** Dummy page reinitializer
+*/
+static void pager_test_reiniter(DbPage *pNotUsed){
+  return;
+}
+
+/*
+** Usage:   pager_open FILENAME N-PAGE
+**
+** Open a new pager
+*/
+static int SQLITE_TCLAPI pager_open(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  u32 pageSize;
+  Pager *pPager;
+  int nPage;
+  int rc;
+  char zBuf[100];
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME N-PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &nPage) ) return TCL_ERROR;
+  rc = sqlite3PagerOpen(sqlite3_vfs_find(0), &pPager, argv[1], 0, 0,
+      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB,
+      pager_test_reiniter);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3PagerSetCachesize(pPager, nPage);
+  pageSize = test_pagesize;
+  sqlite3PagerSetPagesize(pPager, &pageSize, -1);
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPager);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_close ID
+**
+** Close the given pager.
+*/
+static int SQLITE_TCLAPI pager_close(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerClose(pPager, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_rollback ID
+**
+** Rollback changes
+*/
+static int SQLITE_TCLAPI pager_rollback(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerRollback(pPager);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_commit ID
+**
+** Commit all changes
+*/
+static int SQLITE_TCLAPI pager_commit(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerCommitPhaseOne(pPager, 0, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  rc = sqlite3PagerCommitPhaseTwo(pPager);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stmt_begin ID
+**
+** Start a new checkpoint.
+*/
+static int SQLITE_TCLAPI pager_stmt_begin(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerOpenSavepoint(pPager, 1);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stmt_rollback ID
+**
+** Rollback changes to a checkpoint
+*/
+static int SQLITE_TCLAPI pager_stmt_rollback(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, 0);
+  sqlite3PagerSavepoint(pPager, SAVEPOINT_RELEASE, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stmt_commit ID
+**
+** Commit changes to a checkpoint
+*/
+static int SQLITE_TCLAPI pager_stmt_commit(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_RELEASE, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stats ID
+**
+** Return pager statistics.
+*/
+static int SQLITE_TCLAPI pager_stats(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int i, *a;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  a = sqlite3PagerStats(pPager);
+  for(i=0; i<9; i++){
+    static char *zName[] = {
+      "ref", "page", "max", "size", "state", "err",
+      "hit", "miss", "ovfl",
+    };
+    char zBuf[100];
+    Tcl_AppendElement(interp, zName[i]);
+    sqlite3_snprintf(sizeof(zBuf),zBuf,"%d",a[i]);
+    Tcl_AppendElement(interp, zBuf);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_pagecount ID
+**
+** Return the size of the database file.
+*/
+static int SQLITE_TCLAPI pager_pagecount(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  char zBuf[100];
+  int nPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  sqlite3PagerPagecount(pPager, &nPage);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", nPage);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_get ID PGNO
+**
+** Return a pointer to a page from the database.
+*/
+static int SQLITE_TCLAPI page_get(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  char zBuf[100];
+  DbPage *pPage = 0;
+  int pgno;
+  int rc;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID PGNO\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
+  rc = sqlite3PagerSharedLock(pPager);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3PagerGet(pPager, pgno, &pPage, 0);
+  }
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPage);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_lookup ID PGNO
+**
+** Return a pointer to a page if the page is already in cache.
+** If not in cache, return an empty string.
+*/
+static int SQLITE_TCLAPI page_lookup(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  char zBuf[100];
+  DbPage *pPage;
+  int pgno;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID PGNO\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
+  pPage = sqlite3PagerLookup(pPager, pgno);
+  if( pPage ){
+    sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPage);
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_truncate ID PGNO
+*/
+static int SQLITE_TCLAPI pager_truncate(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int pgno;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID PGNO\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
+  sqlite3PagerTruncateImage(pPager, pgno);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   page_unref PAGE
+**
+** Drop a pointer to a page.
+*/
+static int SQLITE_TCLAPI page_unref(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  DbPage *pPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = (DbPage *)sqlite3TestTextToPtr(argv[1]);
+  sqlite3PagerUnref(pPage);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_read PAGE
+**
+** Return the content of a page
+*/
+static int SQLITE_TCLAPI page_read(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  char zBuf[100];
+  DbPage *pPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = sqlite3TestTextToPtr(argv[1]);
+  memcpy(zBuf, sqlite3PagerGetData(pPage), sizeof(zBuf));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_number PAGE
+**
+** Return the page number for a page.
+*/
+static int SQLITE_TCLAPI page_number(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  char zBuf[100];
+  DbPage *pPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = (DbPage *)sqlite3TestTextToPtr(argv[1]);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", sqlite3PagerPagenumber(pPage));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_write PAGE DATA
+**
+** Write something into a page.
+*/
+static int SQLITE_TCLAPI page_write(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  DbPage *pPage;
+  char *pData;
+  int rc;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE DATA\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = (DbPage *)sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerWrite(pPage);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  pData = sqlite3PagerGetData(pPage);
+  strncpy(pData, argv[2], test_pagesize-1);
+  pData[test_pagesize-1] = 0;
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_DISKIO
+/*
+** Usage:   fake_big_file  N  FILENAME
+**
+** Write a few bytes at the N megabyte point of FILENAME.  This will
+** create a large file.  If the file was a valid SQLite database, then
+** the next time the database is opened, SQLite will begin allocating
+** new pages after N.  If N is 2096 or bigger, this will test the
+** ability of SQLite to write to large files.
+*/
+static int SQLITE_TCLAPI fake_big_file(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  sqlite3_vfs *pVfs;
+  sqlite3_file *fd = 0;
+  int rc;
+  int n;
+  i64 offset;
+  char *zFile;
+  int nFile;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " N-MEGABYTES FILE\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], &n) ) return TCL_ERROR;
+#if defined(_WIN32)
+  if( n>2 ){
+    Tcl_AppendResult(interp, "cannot create ", argv[1],
+       "MB file because Windows "
+       "does not support sparse files", (void*)0);
+    return TCL_ERROR;
+  }
+#endif
+
+  pVfs = sqlite3_vfs_find(0);
+  nFile = (int)strlen(argv[2]);
+  zFile = sqlite3_malloc( nFile+2 );
+  if( zFile==0 ) return TCL_ERROR;
+  memcpy(zFile, argv[2], nFile+1);
+  zFile[nFile+1] = 0;
+  rc = sqlite3OsOpenMalloc(pVfs, zFile, &fd, 
+      (SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_DB), 0
+  );
+  if( rc ){
+    Tcl_AppendResult(interp, "open failed: ", sqlite3ErrName(rc), 0);
+    sqlite3_free(zFile);
+    return TCL_ERROR;
+  }
+  offset = n;
+  offset *= 1024*1024;
+  rc = sqlite3OsWrite(fd, "Hello, World!", 14, offset);
+  sqlite3OsCloseFree(fd);
+  sqlite3_free(zFile);
+  if( rc ){
+    Tcl_AppendResult(interp, "write failed: ", sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+#endif
+
+
+/*
+** test_control_pending_byte  PENDING_BYTE
+**
+** Set the PENDING_BYTE using the sqlite3_test_control() interface.
+*/
+static int SQLITE_TCLAPI testPendingByte(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int pbyte;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+                     " PENDING-BYTE\"", (void*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], &pbyte) ) return TCL_ERROR;
+  rc = sqlite3_test_control(SQLITE_TESTCTRL_PENDING_BYTE, pbyte);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** The sqlite3FaultSim() callback:
+*/
+static Tcl_Interp *faultSimInterp = 0;
+static int faultSimScriptSize = 0;
+static char *faultSimScript;
+static int faultSimCallback(int x){
+  char zInt[30];
+  int i;
+  int isNeg;
+  int rc;
+  if( x==0 ){
+    memcpy(faultSimScript+faultSimScriptSize, "0", 2);
+  }else{
+    /* Convert x to text without using any sqlite3 routines */
+    if( x<0 ){
+      isNeg = 1;
+      x = -x;
+    }else{
+      isNeg = 0;
+    }
+    zInt[sizeof(zInt)-1] = 0;
+    for(i=sizeof(zInt)-2; i>0 && x>0; i--, x /= 10){
+      zInt[i] = (x%10) + '0';
+    }
+    if( isNeg ) zInt[i--] = '-';
+    memcpy(faultSimScript+faultSimScriptSize, zInt+i+1, sizeof(zInt)-i-1);
+  }
+  rc = Tcl_Eval(faultSimInterp, faultSimScript);
+  if( rc ){
+    fprintf(stderr, "fault simulator script failed: [%s]", faultSimScript);
+    rc = SQLITE_ERROR;
+  }else{
+    rc = atoi(Tcl_GetStringResult(faultSimInterp));
+  }
+  Tcl_ResetResult(faultSimInterp);
+  return rc;
+}
+
+/*
+** sqlite3_test_control_fault_install SCRIPT
+**
+** Arrange to invoke SCRIPT with the integer argument to sqlite3FaultSim()
+** appended, whenever sqlite3FaultSim() is called.  Or, if SCRIPT is the
+** empty string, cancel the sqlite3FaultSim() callback.
+*/
+static int SQLITE_TCLAPI faultInstallCmd(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  const char *zScript;
+  int nScript;
+  int rc;
+  if( argc!=1 && argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+                     " SCRIPT\"", (void*)0);
+  }
+  zScript = argc==2 ? argv[1] : "";
+  nScript = (int)strlen(zScript);
+  if( faultSimScript ){
+    free(faultSimScript);
+    faultSimScript = 0;
+  }
+  if( nScript==0 ){
+    rc = sqlite3_test_control(SQLITE_TESTCTRL_FAULT_INSTALL, 0);
+  }else{
+    faultSimScript = malloc( nScript+100 );
+    if( faultSimScript==0 ){
+      Tcl_AppendResult(interp, "out of memory", (void*)0);
+      return SQLITE_ERROR;
+    }
+    memcpy(faultSimScript, zScript, nScript);
+    faultSimScript[nScript] = ' ';
+    faultSimScriptSize = nScript+1;
+    faultSimInterp = interp;
+    rc = sqlite3_test_control(SQLITE_TESTCTRL_FAULT_INSTALL, faultSimCallback);
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** sqlite3BitvecBuiltinTest SIZE PROGRAM
+**
+** Invoke the SQLITE_TESTCTRL_BITVEC_TEST operator on test_control.
+** See comments on sqlite3BitvecBuiltinTest() for additional information.
+*/
+static int SQLITE_TCLAPI testBitvecBuiltinTest(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int sz, rc;
+  int nProg = 0;
+  int aProg[100];
+  const char *z;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+                     " SIZE PROGRAM\"", (void*)0);
+  }
+  if( Tcl_GetInt(interp, argv[1], &sz) ) return TCL_ERROR;
+  z = argv[2];
+  while( nProg<99 && *z ){
+    while( *z && !sqlite3Isdigit(*z) ){ z++; }
+    if( *z==0 ) break;
+    aProg[nProg++] = atoi(z);
+    while( sqlite3Isdigit(*z) ){ z++; }
+  }
+  aProg[nProg] = 0;
+  rc = sqlite3_test_control(SQLITE_TESTCTRL_BITVEC_TEST, sz, aProg);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}  
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest2_Init(Tcl_Interp *interp){
+  extern int sqlite3_io_error_persist;
+  extern int sqlite3_io_error_pending;
+  extern int sqlite3_io_error_hit;
+  extern int sqlite3_io_error_hardhit;
+  extern int sqlite3_diskfull_pending;
+  extern int sqlite3_diskfull;
+  static struct {
+    char *zName;
+    Tcl_CmdProc *xProc;
+  } aCmd[] = {
+    { "pager_open",              (Tcl_CmdProc*)pager_open          },
+    { "pager_close",             (Tcl_CmdProc*)pager_close         },
+    { "pager_commit",            (Tcl_CmdProc*)pager_commit        },
+    { "pager_rollback",          (Tcl_CmdProc*)pager_rollback      },
+    { "pager_stmt_begin",        (Tcl_CmdProc*)pager_stmt_begin    },
+    { "pager_stmt_commit",       (Tcl_CmdProc*)pager_stmt_commit   },
+    { "pager_stmt_rollback",     (Tcl_CmdProc*)pager_stmt_rollback },
+    { "pager_stats",             (Tcl_CmdProc*)pager_stats         },
+    { "pager_pagecount",         (Tcl_CmdProc*)pager_pagecount     },
+    { "page_get",                (Tcl_CmdProc*)page_get            },
+    { "page_lookup",             (Tcl_CmdProc*)page_lookup         },
+    { "page_unref",              (Tcl_CmdProc*)page_unref          },
+    { "page_read",               (Tcl_CmdProc*)page_read           },
+    { "page_write",              (Tcl_CmdProc*)page_write          },
+    { "page_number",             (Tcl_CmdProc*)page_number         },
+    { "pager_truncate",          (Tcl_CmdProc*)pager_truncate      },
+#ifndef SQLITE_OMIT_DISKIO
+    { "fake_big_file",           (Tcl_CmdProc*)fake_big_file       },
+#endif
+    { "sqlite3BitvecBuiltinTest",(Tcl_CmdProc*)testBitvecBuiltinTest     },
+    { "sqlite3_test_control_pending_byte",  (Tcl_CmdProc*)testPendingByte },
+    { "sqlite3_test_control_fault_install", (Tcl_CmdProc*)faultInstallCmd },
+  };
+  int i;
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  Tcl_LinkVar(interp, "sqlite_io_error_pending",
+     (char*)&sqlite3_io_error_pending, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_io_error_persist",
+     (char*)&sqlite3_io_error_persist, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_io_error_hit",
+     (char*)&sqlite3_io_error_hit, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_io_error_hardhit",
+     (char*)&sqlite3_io_error_hardhit, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_diskfull_pending",
+     (char*)&sqlite3_diskfull_pending, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_diskfull",
+     (char*)&sqlite3_diskfull, TCL_LINK_INT);
+#ifndef SQLITE_OMIT_WSD
+  Tcl_LinkVar(interp, "sqlite_pending_byte",
+     (char*)&sqlite3PendingByte, TCL_LINK_INT | TCL_LINK_READ_ONLY);
+#endif
+  return TCL_OK;
+}
diff --git a/src/test3.c b/src/test3.c
new file mode 100644
index 0000000..7fd7662
--- /dev/null
+++ b/src/test3.c
@@ -0,0 +1,690 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the btree.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#include "btreeInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+
+extern const char *sqlite3ErrName(int);
+
+/*
+** A bogus sqlite3 connection structure for use in the btree
+** tests.
+*/
+static sqlite3 sDb;
+static int nRefSqlite3 = 0;
+
+/*
+** Usage:   btree_open FILENAME NCACHE
+**
+** Open a new database
+*/
+static int SQLITE_TCLAPI btree_open(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int rc, nCache;
+  char zBuf[100];
+  int n;
+  char *zFilename;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME NCACHE FLAGS\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
+  nRefSqlite3++;
+  if( nRefSqlite3==1 ){
+    sDb.pVfs = sqlite3_vfs_find(0);
+    sDb.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
+    sqlite3_mutex_enter(sDb.mutex);
+  }
+  n = (int)strlen(argv[1]);
+  zFilename = sqlite3_malloc( n+2 );
+  if( zFilename==0 ) return TCL_ERROR;
+  memcpy(zFilename, argv[1], n+1);
+  zFilename[n+1] = 0;
+  rc = sqlite3BtreeOpen(sDb.pVfs, zFilename, &sDb, &pBt, 0, 
+     SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB);
+  sqlite3_free(zFilename);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3BtreeSetCacheSize(pBt, nCache);
+  sqlite3_snprintf(sizeof(zBuf), zBuf,"%p", pBt);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_close ID
+**
+** Close the given database.
+*/
+static int SQLITE_TCLAPI btree_close(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3BtreeClose(pBt);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  nRefSqlite3--;
+  if( nRefSqlite3==0 ){
+    sqlite3_mutex_leave(sDb.mutex);
+    sqlite3_mutex_free(sDb.mutex);
+    sDb.mutex = 0;
+    sDb.pVfs = 0;
+  }
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   btree_begin_transaction ID
+**
+** Start a new transaction
+*/
+static int SQLITE_TCLAPI btree_begin_transaction(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
+  rc = sqlite3BtreeBeginTrans(pBt, 1, 0);
+  sqlite3BtreeLeave(pBt);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_pager_stats ID
+**
+** Returns pager statistics
+*/
+static int SQLITE_TCLAPI btree_pager_stats(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int i;
+  int *a;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+ 
+  /* Normally in this file, with a b-tree handle opened using the 
+  ** [btree_open] command it is safe to call sqlite3BtreeEnter() directly.
+  ** But this function is sometimes called with a btree handle obtained
+  ** from an open SQLite connection (using [btree_from_db]). In this case
+  ** we need to obtain the mutex for the controlling SQLite handle before
+  ** it is safe to call sqlite3BtreeEnter().
+  */
+  sqlite3_mutex_enter(pBt->db->mutex);
+
+  sqlite3BtreeEnter(pBt);
+  a = sqlite3PagerStats(sqlite3BtreePager(pBt));
+  for(i=0; i<11; i++){
+    static char *zName[] = {
+      "ref", "page", "max", "size", "state", "err",
+      "hit", "miss", "ovfl", "read", "write"
+    };
+    char zBuf[100];
+    Tcl_AppendElement(interp, zName[i]);
+    sqlite3_snprintf(sizeof(zBuf), zBuf,"%d",a[i]);
+    Tcl_AppendElement(interp, zBuf);
+  }
+  sqlite3BtreeLeave(pBt);
+
+  /* Release the mutex on the SQLite handle that controls this b-tree */
+  sqlite3_mutex_leave(pBt->db->mutex);
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_cursor ID TABLENUM WRITEABLE
+**
+** Create a new cursor.  Return the ID for the cursor.
+*/
+static int SQLITE_TCLAPI btree_cursor(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int iTable;
+  BtCursor *pCur;
+  int rc = SQLITE_OK;
+  int wrFlag;
+  char zBuf[30];
+
+  if( argc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID TABLENUM WRITEABLE\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &iTable) ) return TCL_ERROR;
+  if( Tcl_GetBoolean(interp, argv[3], &wrFlag) ) return TCL_ERROR;
+  if( wrFlag ) wrFlag = BTREE_WRCSR;
+  pCur = (BtCursor *)ckalloc(sqlite3BtreeCursorSize());
+  memset(pCur, 0, sqlite3BtreeCursorSize());
+  sqlite3_mutex_enter(pBt->db->mutex);
+  sqlite3BtreeEnter(pBt);
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  rc = sqlite3BtreeLockTable(pBt, iTable, !!wrFlag);
+#endif
+  if( rc==SQLITE_OK ){
+    rc = sqlite3BtreeCursor(pBt, iTable, wrFlag, 0, pCur);
+  }
+  sqlite3BtreeLeave(pBt);
+  sqlite3_mutex_leave(pBt->db->mutex);
+  if( rc ){
+    ckfree((char *)pCur);
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf), zBuf,"%p", pCur);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_close_cursor ID
+**
+** Close a cursor opened using btree_cursor.
+*/
+static int SQLITE_TCLAPI btree_close_cursor(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int rc;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+#if SQLITE_THREADSAFE>0
+  {
+    Btree *pBt = pCur->pBtree;
+    sqlite3_mutex_enter(pBt->db->mutex);
+    sqlite3BtreeEnter(pBt);
+    rc = sqlite3BtreeCloseCursor(pCur);
+    sqlite3BtreeLeave(pBt);
+    sqlite3_mutex_leave(pBt->db->mutex);
+  }
+#else
+  rc = sqlite3BtreeCloseCursor(pCur);
+#endif
+  ckfree((char *)pCur);
+  if( rc ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_next ID
+**
+** Move the cursor to the next entry in the table.  Return 0 on success
+** or 1 if the cursor was already on the last entry in the table or if
+** the table is empty.
+*/
+static int SQLITE_TCLAPI btree_next(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int rc;
+  int res = 0;
+  char zBuf[100];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeNext(pCur, 0);
+  if( rc==SQLITE_DONE ){
+    res = 1;
+    rc = SQLITE_OK;
+  }
+  sqlite3BtreeLeave(pCur->pBtree);
+  if( rc ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%d",res);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_first ID
+**
+** Move the cursor to the first entry in the table.  Return 0 if the
+** cursor was left point to something and 1 if the table is empty.
+*/
+static int SQLITE_TCLAPI btree_first(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int rc;
+  int res = 0;
+  char zBuf[100];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeFirst(pCur, &res);
+  sqlite3BtreeLeave(pCur->pBtree);
+  if( rc ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%d",res);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_eof ID
+**
+** Return TRUE if the given cursor is not pointing at a valid entry.
+** Return FALSE if the cursor does point to a valid entry.
+*/
+static int SQLITE_TCLAPI btree_eof(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int rc;
+  char zBuf[50];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeEof(pCur);
+  sqlite3BtreeLeave(pCur->pBtree);
+  sqlite3_snprintf(sizeof(zBuf),zBuf, "%d", rc);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_payload_size ID
+**
+** Return the number of bytes of payload
+*/
+static int SQLITE_TCLAPI btree_payload_size(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  u32 n;
+  char zBuf[50];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+  n = sqlite3BtreePayloadSize(pCur);
+  sqlite3BtreeLeave(pCur->pBtree);
+  sqlite3_snprintf(sizeof(zBuf),zBuf, "%u", n);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** usage:   varint_test  START  MULTIPLIER  COUNT  INCREMENT
+**
+** This command tests the putVarint() and getVarint()
+** routines, both for accuracy and for speed.
+**
+** An integer is written using putVarint() and read back with
+** getVarint() and verified to be unchanged.  This repeats COUNT
+** times.  The first integer is START*MULTIPLIER.  Each iteration
+** increases the integer by INCREMENT.
+**
+** This command returns nothing if it works.  It returns an error message
+** if something goes wrong.
+*/
+static int SQLITE_TCLAPI btree_varint_test(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  u32 start, mult, count, incr;
+  u64 in, out;
+  int n1, n2, i, j;
+  unsigned char zBuf[100];
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " START MULTIPLIER COUNT INCREMENT\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], (int*)&start) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[2], (int*)&mult) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[3], (int*)&count) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[4], (int*)&incr) ) return TCL_ERROR;
+  in = start;
+  in *= mult;
+  for(i=0; i<(int)count; i++){
+    char zErr[200];
+    n1 = putVarint(zBuf, in);
+    if( n1>9 || n1<1 ){
+      sqlite3_snprintf(sizeof(zErr), zErr,
+         "putVarint returned %d - should be between 1 and 9", n1);
+      Tcl_AppendResult(interp, zErr, 0);
+      return TCL_ERROR;
+    }
+    n2 = getVarint(zBuf, &out);
+    if( n1!=n2 ){
+      sqlite3_snprintf(sizeof(zErr), zErr,
+          "putVarint returned %d and getVarint returned %d", n1, n2);
+      Tcl_AppendResult(interp, zErr, 0);
+      return TCL_ERROR;
+    }
+    if( in!=out ){
+      sqlite3_snprintf(sizeof(zErr), zErr,
+          "Wrote 0x%016llx and got back 0x%016llx", in, out);
+      Tcl_AppendResult(interp, zErr, 0);
+      return TCL_ERROR;
+    }
+    if( (in & 0xffffffff)==in ){
+      u32 out32;
+      n2 = getVarint32(zBuf, out32);
+      out = out32;
+      if( n1!=n2 ){
+        sqlite3_snprintf(sizeof(zErr), zErr,
+          "putVarint returned %d and GetVarint32 returned %d", 
+                  n1, n2);
+        Tcl_AppendResult(interp, zErr, 0);
+        return TCL_ERROR;
+      }
+      if( in!=out ){
+        sqlite3_snprintf(sizeof(zErr), zErr,
+          "Wrote 0x%016llx and got back 0x%016llx from GetVarint32",
+            in, out);
+        Tcl_AppendResult(interp, zErr, 0);
+        return TCL_ERROR;
+      }
+    }
+
+    /* In order to get realistic timings, run getVarint 19 more times.
+    ** This is because getVarint is called about 20 times more often
+    ** than putVarint.
+    */
+    for(j=0; j<19; j++){
+      getVarint(zBuf, &out);
+    }
+    in += incr;
+  }
+  return TCL_OK;
+}
+
+/*
+** usage:   btree_from_db  DB-HANDLE
+**
+** This command returns the btree handle for the main database associated
+** with the database-handle passed as the argument. Example usage:
+**
+** sqlite3 db test.db
+** set bt [btree_from_db db]
+*/
+static int SQLITE_TCLAPI btree_from_db(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  char zBuf[100];
+  Tcl_CmdInfo info;
+  sqlite3 *db;
+  Btree *pBt;
+  int iDb = 0;
+
+  if( argc!=2 && argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " DB-HANDLE ?N?\"", 0);
+    return TCL_ERROR;
+  }
+
+  if( 1!=Tcl_GetCommandInfo(interp, argv[1], &info) ){
+    Tcl_AppendResult(interp, "No such db-handle: \"", argv[1], "\"", 0);
+    return TCL_ERROR;
+  }
+  if( argc==3 ){
+    iDb = atoi(argv[2]);
+  }
+
+  db = *((sqlite3 **)info.objClientData);
+  assert( db );
+
+  pBt = db->aDb[iDb].pBt;
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%p", pBt);
+  Tcl_SetResult(interp, zBuf, TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_ismemdb ID
+**
+** Return true if the B-Tree is currently stored entirely in memory.
+*/
+static int SQLITE_TCLAPI btree_ismemdb(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int res;
+  sqlite3_file *pFile;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  sqlite3_mutex_enter(pBt->db->mutex);
+  sqlite3BtreeEnter(pBt);
+  pFile = sqlite3PagerFile(sqlite3BtreePager(pBt));
+  res = (pFile->pMethods==0);
+  sqlite3BtreeLeave(pBt);
+  sqlite3_mutex_leave(pBt->db->mutex);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(res));
+  return SQLITE_OK;
+}
+
+/*
+** usage:   btree_set_cache_size ID NCACHE
+**
+** Set the size of the cache used by btree $ID.
+*/
+static int SQLITE_TCLAPI btree_set_cache_size(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int nCache;
+  Btree *pBt;
+  
+  if( argc!=3 ){
+    Tcl_AppendResult(
+        interp, "wrong # args: should be \"", argv[0], " BT NCACHE\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
+
+  sqlite3_mutex_enter(pBt->db->mutex);
+  sqlite3BtreeEnter(pBt);
+  sqlite3BtreeSetCacheSize(pBt, nCache);
+  sqlite3BtreeLeave(pBt);
+  sqlite3_mutex_leave(pBt->db->mutex);
+  return TCL_OK;
+}      
+
+/*
+** usage:   btree_insert CSR ?KEY? VALUE
+**
+** Set the size of the cache used by btree $ID.
+*/
+static int SQLITE_TCLAPI btree_insert(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *const objv[]
+){
+  BtCursor *pCur;
+  int rc;
+  BtreePayload x;
+
+  if( objc!=4 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?-intkey? CSR KEY VALUE");
+    return TCL_ERROR;
+  }
+
+  memset(&x, 0, sizeof(x));
+  if( objc==4 ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &rc) ) return TCL_ERROR;
+    x.nKey = rc;
+    x.pData = (void*)Tcl_GetByteArrayFromObj(objv[3], &x.nData);
+  }else{
+    x.pKey = (void*)Tcl_GetByteArrayFromObj(objv[2], &rc);
+    x.nKey = rc;
+  }
+  pCur = (BtCursor*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+
+  sqlite3_mutex_enter(pCur->pBtree->db->mutex);
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeInsert(pCur, &x, 0, 0);
+  sqlite3BtreeLeave(pCur->pBtree);
+  sqlite3_mutex_leave(pCur->pBtree->db->mutex);
+
+  Tcl_ResetResult(interp);
+  if( rc ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest3_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_CmdProc *xProc;
+  } aCmd[] = {
+     { "btree_open",               (Tcl_CmdProc*)btree_open               },
+     { "btree_close",              (Tcl_CmdProc*)btree_close              },
+     { "btree_begin_transaction",  (Tcl_CmdProc*)btree_begin_transaction  },
+     { "btree_pager_stats",        (Tcl_CmdProc*)btree_pager_stats        },
+     { "btree_cursor",             (Tcl_CmdProc*)btree_cursor             },
+     { "btree_close_cursor",       (Tcl_CmdProc*)btree_close_cursor       },
+     { "btree_next",               (Tcl_CmdProc*)btree_next               },
+     { "btree_eof",                (Tcl_CmdProc*)btree_eof                },
+     { "btree_payload_size",       (Tcl_CmdProc*)btree_payload_size       },
+     { "btree_first",              (Tcl_CmdProc*)btree_first              },
+     { "btree_varint_test",        (Tcl_CmdProc*)btree_varint_test        },
+     { "btree_from_db",            (Tcl_CmdProc*)btree_from_db            },
+     { "btree_ismemdb",            (Tcl_CmdProc*)btree_ismemdb            },
+     { "btree_set_cache_size",     (Tcl_CmdProc*)btree_set_cache_size     }
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  Tcl_CreateObjCommand(interp, "btree_insert", btree_insert, 0, 0);
+
+  return TCL_OK;
+}
diff --git a/src/test4.c b/src/test4.c
new file mode 100644
index 0000000..2043a33
--- /dev/null
+++ b/src/test4.c
@@ -0,0 +1,741 @@
+/*
+** 2003 December 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the SQLite library in a multithreaded environment.
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#if SQLITE_OS_UNIX && SQLITE_THREADSAFE
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+#include <sched.h>
+#include <ctype.h>
+
+extern const char *sqlite3ErrName(int);
+
+/*
+** Each thread is controlled by an instance of the following
+** structure.
+*/
+typedef struct Thread Thread;
+struct Thread {
+  /* The first group of fields are writable by the leader and read-only
+  ** to the thread. */
+  char *zFilename;       /* Name of database file */
+  void (*xOp)(Thread*);  /* next operation to do */
+  char *zArg;            /* argument usable by xOp */
+  int opnum;             /* Operation number */
+  int busy;              /* True if this thread is in use */
+
+  /* The next group of fields are writable by the thread but read-only to the
+  ** leader. */
+  int completed;        /* Number of operations completed */
+  sqlite3 *db;           /* Open database */
+  sqlite3_stmt *pStmt;     /* Pending operation */
+  char *zErr;           /* operation error */
+  char *zStaticErr;     /* Static error message */
+  int rc;               /* operation return code */
+  int argc;             /* number of columns in result */
+  const char *argv[100];    /* result columns */
+  const char *colv[100];    /* result column names */
+};
+
+/*
+** There can be as many as 26 threads running at once.  Each is named
+** by a capital letter: A, B, C, ..., Y, Z.
+*/
+#define N_THREAD 26
+static Thread threadset[N_THREAD];
+
+static void test_barrier(){
+  sqlite3_mutex *pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_APP1);
+  sqlite3_mutex_enter(pMutex);
+  sqlite3_mutex_leave(pMutex);
+}
+
+/*
+** The main loop for a thread.  Threads use busy waiting. 
+*/
+static void *test_thread_main(void *pArg){
+  Thread *p = (Thread*)pArg;
+  if( p->db ){
+    sqlite3_close(p->db);
+  }
+  sqlite3_open(p->zFilename, &p->db);
+  if( SQLITE_OK!=sqlite3_errcode(p->db) ){
+    p->zErr = strdup(sqlite3_errmsg(p->db));
+    sqlite3_close(p->db);
+    p->db = 0;
+  }
+  p->pStmt = 0;
+  test_barrier();
+  p->completed = 1;
+  while( p->opnum<=p->completed ) sched_yield();
+  test_barrier();
+  while( p->xOp ){
+    if( p->zErr && p->zErr!=p->zStaticErr ){
+      sqlite3_free(p->zErr);
+      p->zErr = 0;
+    }
+    (*p->xOp)(p);
+    test_barrier();
+    p->completed++;
+    while( p->opnum<=p->completed ) sched_yield();
+    test_barrier();
+  }
+  if( p->pStmt ){
+    sqlite3_finalize(p->pStmt);
+    p->pStmt = 0;
+  }
+  if( p->db ){
+    sqlite3_close(p->db);
+    p->db = 0;
+  }
+  if( p->zErr && p->zErr!=p->zStaticErr ){
+    sqlite3_free(p->zErr);
+    p->zErr = 0;
+  }
+  test_barrier();
+  p->completed++;
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_thread_cleanup();
+#endif
+  return 0;
+}
+
+/*
+** Get a thread ID which is an upper case letter.  Return the index.
+** If the argument is not a valid thread ID put an error message in
+** the interpreter and return -1.
+*/
+static int parse_thread_id(Tcl_Interp *interp, const char *zArg){
+  if( zArg==0 || zArg[0]==0 || zArg[1]!=0 || !isupper((unsigned char)zArg[0]) ){
+    Tcl_AppendResult(interp, "thread ID must be an upper case letter", 0);
+    return -1;
+  }
+  return zArg[0] - 'A';
+}
+
+/*
+** Usage:    thread_create NAME  FILENAME
+**
+** NAME should be an upper case letter.  Start the thread running with
+** an open connection to the given database.
+*/
+static int SQLITE_TCLAPI tcl_thread_create(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  pthread_t x;
+  int rc;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID FILENAME", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( threadset[i].busy ){
+    Tcl_AppendResult(interp, "thread ", argv[1], " is already running", 0);
+    return TCL_ERROR;
+  }
+  threadset[i].busy = 1;
+  sqlite3_free(threadset[i].zFilename);
+  threadset[i].zFilename = sqlite3_mprintf("%s", argv[2]);
+  threadset[i].opnum = 1;
+  threadset[i].completed = 0;
+  rc = pthread_create(&x, 0, test_thread_main, &threadset[i]);
+  if( rc ){
+    Tcl_AppendResult(interp, "failed to create the thread", 0);
+    sqlite3_free(threadset[i].zFilename);
+    threadset[i].busy = 0;
+    return TCL_ERROR;
+  }
+  pthread_detach(x);
+  return TCL_OK;
+}
+
+/*
+** Wait for a thread to reach its idle state.
+*/
+static void test_thread_wait(Thread *p){
+  test_barrier();
+  while( p->opnum>p->completed ) sched_yield();
+  test_barrier();
+}
+
+/*
+** Usage:  thread_wait ID
+**
+** Wait on thread ID to reach its idle state.
+*/
+static int SQLITE_TCLAPI tcl_thread_wait(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  return TCL_OK;
+}
+
+/*
+** Stop a thread.
+*/
+static void test_stop_thread(Thread *p){
+  test_thread_wait(p);
+  p->xOp = 0;
+  p->opnum++;
+  test_thread_wait(p);
+  sqlite3_free(p->zArg);
+  p->zArg = 0;
+  sqlite3_free(p->zFilename);
+  p->zFilename = 0;
+  p->busy = 0;
+}
+
+/*
+** Usage:  thread_halt ID
+**
+** Cause a thread to shut itself down.  Wait for the shutdown to be
+** completed.  If ID is "*" then stop all threads.
+*/
+static int SQLITE_TCLAPI tcl_thread_halt(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  if( argv[1][0]=='*' && argv[1][1]==0 ){
+    for(i=0; i<N_THREAD; i++){
+      if( threadset[i].busy ) test_stop_thread(&threadset[i]);
+    }
+  }else{
+    i = parse_thread_id(interp, argv[1]);
+    if( i<0 ) return TCL_ERROR;
+    if( !threadset[i].busy ){
+      Tcl_AppendResult(interp, "no such thread", 0);
+      return TCL_ERROR;
+    }
+    test_stop_thread(&threadset[i]);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_argc  ID
+**
+** Wait on the most recent thread_step to complete, then return the
+** number of columns in the result set.
+*/
+static int SQLITE_TCLAPI tcl_thread_argc(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  char zBuf[100];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", threadset[i].argc);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_argv  ID   N
+**
+** Wait on the most recent thread_step to complete, then return the
+** value of the N-th columns in the result set.
+*/
+static int SQLITE_TCLAPI tcl_thread_argv(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  int n;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID N", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  test_thread_wait(&threadset[i]);
+  if( n<0 || n>=threadset[i].argc ){
+    Tcl_AppendResult(interp, "column number out of range", 0);
+    return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, threadset[i].argv[n], 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_colname  ID   N
+**
+** Wait on the most recent thread_step to complete, then return the
+** name of the N-th columns in the result set.
+*/
+static int SQLITE_TCLAPI tcl_thread_colname(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  int n;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID N", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  test_thread_wait(&threadset[i]);
+  if( n<0 || n>=threadset[i].argc ){
+    Tcl_AppendResult(interp, "column number out of range", 0);
+    return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, threadset[i].colv[n], 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_result  ID
+**
+** Wait on the most recent operation to complete, then return the
+** result code from that operation.
+*/
+static int SQLITE_TCLAPI tcl_thread_result(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  const char *zName;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  zName = sqlite3ErrName(threadset[i].rc);
+  Tcl_AppendResult(interp, zName, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_error  ID
+**
+** Wait on the most recent operation to complete, then return the
+** error string.
+*/
+static int SQLITE_TCLAPI tcl_thread_error(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  Tcl_AppendResult(interp, threadset[i].zErr, 0);
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to compile an SQL statement.
+*/
+static void do_compile(Thread *p){
+  if( p->db==0 ){
+    p->zErr = p->zStaticErr = "no database is open";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  if( p->pStmt ){
+    sqlite3_finalize(p->pStmt);
+    p->pStmt = 0;
+  }
+  p->rc = sqlite3_prepare(p->db, p->zArg, -1, &p->pStmt, 0);
+}
+
+/*
+** Usage: thread_compile ID SQL
+**
+** Compile a new virtual machine.
+*/
+static int SQLITE_TCLAPI tcl_thread_compile(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID SQL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  threadset[i].xOp = do_compile;
+  sqlite3_free(threadset[i].zArg);
+  threadset[i].zArg = sqlite3_mprintf("%s", argv[2]);
+  test_barrier();
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to step the virtual machine.
+*/
+static void do_step(Thread *p){
+  int i;
+  if( p->pStmt==0 ){
+    p->zErr = p->zStaticErr = "no virtual machine available";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  p->rc = sqlite3_step(p->pStmt);
+  if( p->rc==SQLITE_ROW ){
+    p->argc = sqlite3_column_count(p->pStmt);
+    for(i=0; i<sqlite3_data_count(p->pStmt); i++){
+      p->argv[i] = (char*)sqlite3_column_text(p->pStmt, i);
+    }
+    for(i=0; i<p->argc; i++){
+      p->colv[i] = sqlite3_column_name(p->pStmt, i);
+    }
+  }
+}
+
+/*
+** Usage: thread_step ID
+**
+** Advance the virtual machine by one step
+*/
+static int SQLITE_TCLAPI tcl_thread_step(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " IDL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  threadset[i].xOp = do_step;
+  test_barrier();
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to finalize a virtual machine.
+*/
+static void do_finalize(Thread *p){
+  if( p->pStmt==0 ){
+    p->zErr = p->zStaticErr = "no virtual machine available";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  p->rc = sqlite3_finalize(p->pStmt);
+  p->pStmt = 0;
+}
+
+/*
+** Usage: thread_finalize ID
+**
+** Finalize the virtual machine.
+*/
+static int SQLITE_TCLAPI tcl_thread_finalize(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " IDL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  threadset[i].xOp = do_finalize;
+  sqlite3_free(threadset[i].zArg);
+  threadset[i].zArg = 0;
+  test_barrier();
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_swap ID ID
+**
+** Interchange the sqlite* pointer between two threads.
+*/
+static int SQLITE_TCLAPI tcl_thread_swap(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i, j;
+  sqlite3 *temp;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID1 ID2", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  j = parse_thread_id(interp, argv[2]);
+  if( j<0 ) return TCL_ERROR;
+  if( !threadset[j].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[j]);
+  temp = threadset[i].db;
+  threadset[i].db = threadset[j].db;
+  threadset[j].db = temp;
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_db_get ID
+**
+** Return the database connection pointer for the given thread.  Then
+** remove the pointer from the thread itself.  Afterwards, the thread
+** can be stopped and the connection can be used by the main thread.
+*/
+static int SQLITE_TCLAPI tcl_thread_db_get(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  char zBuf[100];
+  extern int sqlite3TestMakePointerStr(Tcl_Interp*, char*, void*);
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  sqlite3TestMakePointerStr(interp, zBuf, threadset[i].db);
+  threadset[i].db = 0;
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_db_put ID DB
+**
+*/
+static int SQLITE_TCLAPI tcl_thread_db_put(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  extern int sqlite3TestMakePointerStr(Tcl_Interp*, char*, void*);
+  extern void *sqlite3TestTextToPtr(const char *);
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID DB", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  assert( !threadset[i].db );
+  threadset[i].db = (sqlite3*)sqlite3TestTextToPtr(argv[2]);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_stmt_get ID
+**
+** Return the database stmt pointer for the given thread.  Then
+** remove the pointer from the thread itself. 
+*/
+static int SQLITE_TCLAPI tcl_thread_stmt_get(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  char zBuf[100];
+  extern int sqlite3TestMakePointerStr(Tcl_Interp*, char*, void*);
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  test_thread_wait(&threadset[i]);
+  sqlite3TestMakePointerStr(interp, zBuf, threadset[i].pStmt);
+  threadset[i].pStmt = 0;
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest4_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_CmdProc *xProc;
+  } aCmd[] = {
+     { "thread_create",     (Tcl_CmdProc*)tcl_thread_create     },
+     { "thread_wait",       (Tcl_CmdProc*)tcl_thread_wait       },
+     { "thread_halt",       (Tcl_CmdProc*)tcl_thread_halt       },
+     { "thread_argc",       (Tcl_CmdProc*)tcl_thread_argc       },
+     { "thread_argv",       (Tcl_CmdProc*)tcl_thread_argv       },
+     { "thread_colname",    (Tcl_CmdProc*)tcl_thread_colname    },
+     { "thread_result",     (Tcl_CmdProc*)tcl_thread_result     },
+     { "thread_error",      (Tcl_CmdProc*)tcl_thread_error      },
+     { "thread_compile",    (Tcl_CmdProc*)tcl_thread_compile    },
+     { "thread_step",       (Tcl_CmdProc*)tcl_thread_step       },
+     { "thread_finalize",   (Tcl_CmdProc*)tcl_thread_finalize   },
+     { "thread_swap",       (Tcl_CmdProc*)tcl_thread_swap       },
+     { "thread_db_get",     (Tcl_CmdProc*)tcl_thread_db_get     },
+     { "thread_db_put",     (Tcl_CmdProc*)tcl_thread_db_put     },
+     { "thread_stmt_get",   (Tcl_CmdProc*)tcl_thread_stmt_get   },
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  return TCL_OK;
+}
+#else
+int Sqlitetest4_Init(Tcl_Interp *interp){ return TCL_OK; }
+#endif /* SQLITE_OS_UNIX */
diff --git a/src/test5.c b/src/test5.c
new file mode 100644
index 0000000..0d92428
--- /dev/null
+++ b/src/test5.c
@@ -0,0 +1,220 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the utf.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library. Specifically, the code in this file
+** is used for testing the SQLite routines for converting between
+** the various supported unicode encodings.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** The first argument is a TCL UTF-8 string. Return the byte array
+** object with the encoded representation of the string, including
+** the NULL terminator.
+*/
+static int SQLITE_TCLAPI binarize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int len;
+  char *bytes;
+  Tcl_Obj *pRet;
+  assert(objc==2);
+
+  bytes = Tcl_GetStringFromObj(objv[1], &len);
+  pRet = Tcl_NewByteArrayObj((u8*)bytes, len+1);
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;
+}
+
+/*
+** Usage: test_value_overhead <repeat-count> <do-calls>.
+**
+** This routine is used to test the overhead of calls to
+** sqlite3_value_text(), on a value that contains a UTF-8 string. The idea
+** is to figure out whether or not it is a problem to use sqlite3_value
+** structures with collation sequence functions.
+**
+** If <do-calls> is 0, then the calls to sqlite3_value_text() are not
+** actually made.
+*/
+static int SQLITE_TCLAPI test_value_overhead(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int do_calls;
+  int repeat_count;
+  int i;
+  Mem val;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <repeat-count> <do-calls>", 0);
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetIntFromObj(interp, objv[1], &repeat_count) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &do_calls) ) return TCL_ERROR;
+
+  val.flags = MEM_Str|MEM_Term|MEM_Static;
+  val.z = "hello world";
+  val.enc = SQLITE_UTF8;
+
+  for(i=0; i<repeat_count; i++){
+    if( do_calls ){
+      sqlite3_value_text(&val);
+    }
+  }
+
+  return TCL_OK;
+}
+
+static u8 name_to_enc(Tcl_Interp *interp, Tcl_Obj *pObj){
+  struct EncName {
+    char *zName;
+    u8 enc;
+  } encnames[] = {
+    { "UTF8", SQLITE_UTF8 },
+    { "UTF16LE", SQLITE_UTF16LE },
+    { "UTF16BE", SQLITE_UTF16BE },
+    { "UTF16", SQLITE_UTF16 },
+    { 0, 0 }
+  };
+  struct EncName *pEnc;
+  char *z = Tcl_GetString(pObj);
+  for(pEnc=&encnames[0]; pEnc->zName; pEnc++){
+    if( 0==sqlite3StrICmp(z, pEnc->zName) ){
+      break;
+    }
+  }
+  if( !pEnc->enc ){
+    Tcl_AppendResult(interp, "No such encoding: ", z, 0);
+  }
+  if( pEnc->enc==SQLITE_UTF16 ){
+    return SQLITE_UTF16NATIVE;
+  }
+  return pEnc->enc;
+}
+
+/*
+** Usage:   test_translate <string/blob> <from enc> <to enc> ?<transient>?
+**
+*/
+static int SQLITE_TCLAPI test_translate(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  u8 enc_from;
+  u8 enc_to;
+  sqlite3_value *pVal;
+
+  char *z;
+  int len;
+  void (*xDel)(void *p) = SQLITE_STATIC;
+
+  if( objc!=4 && objc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), 
+        " <string/blob> <from enc> <to enc>", 0
+    );
+    return TCL_ERROR;
+  }
+  if( objc==5 ){
+    xDel = sqlite3_free;
+  }
+
+  enc_from = name_to_enc(interp, objv[2]);
+  if( !enc_from ) return TCL_ERROR;
+  enc_to = name_to_enc(interp, objv[3]);
+  if( !enc_to ) return TCL_ERROR;
+
+  pVal = sqlite3ValueNew(0);
+
+  if( enc_from==SQLITE_UTF8 ){
+    z = Tcl_GetString(objv[1]);
+    if( objc==5 ){
+      z = sqlite3_mprintf("%s", z);
+    }
+    sqlite3ValueSetStr(pVal, -1, z, enc_from, xDel);
+  }else{
+    z = (char*)Tcl_GetByteArrayFromObj(objv[1], &len);
+    if( objc==5 ){
+      char *zTmp = z;
+      z = sqlite3_malloc(len);
+      memcpy(z, zTmp, len);
+    }
+    sqlite3ValueSetStr(pVal, -1, z, enc_from, xDel);
+  }
+
+  z = (char *)sqlite3ValueText(pVal, enc_to);
+  len = sqlite3ValueBytes(pVal, enc_to) + (enc_to==SQLITE_UTF8?1:2);
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj((u8*)z, len));
+
+  sqlite3ValueFree(pVal);
+
+  return TCL_OK;
+}
+
+/*
+** Usage: translate_selftest
+**
+** Call sqlite3UtfSelfTest() to run the internal tests for unicode
+** translation. If there is a problem an assert() will fail.
+**/
+void sqlite3UtfSelfTest(void);
+static int SQLITE_TCLAPI test_translate_selftest(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3UtfSelfTest();
+#endif
+  return SQLITE_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest5_Init(Tcl_Interp *interp){
+  static struct {
+    char *zName;
+    Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "binarize",                (Tcl_ObjCmdProc*)binarize },
+    { "test_value_overhead",     (Tcl_ObjCmdProc*)test_value_overhead },
+    { "test_translate",          (Tcl_ObjCmdProc*)test_translate     },
+    { "translate_selftest",      (Tcl_ObjCmdProc*)test_translate_selftest},
+  };
+  int i;
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  return SQLITE_OK;
+}
diff --git a/src/test6.c b/src/test6.c
new file mode 100644
index 0000000..5d8e6b9
--- /dev/null
+++ b/src/test6.c
@@ -0,0 +1,1107 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that modified the OS layer in order to simulate
+** the effect on the database file of an OS crash or power failure.  This
+** is used to test the ability of SQLite to recover from those situations.
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+#ifndef SQLITE_OMIT_DISKIO  /* This file is a no-op if disk I/O is disabled */
+
+/* #define TRACE_CRASHTEST */
+
+typedef struct CrashFile CrashFile;
+typedef struct CrashGlobal CrashGlobal;
+typedef struct WriteBuffer WriteBuffer;
+
+/*
+** Method:
+**
+**   This layer is implemented as a wrapper around the "real"
+**   sqlite3_file object for the host system. Each time data is
+**   written to the file object, instead of being written to the
+**   underlying file, the write operation is stored in an in-memory
+**   structure (type WriteBuffer). This structure is placed at the
+**   end of a global ordered list (the write-list).
+**
+**   When data is read from a file object, the requested region is
+**   first retrieved from the real file. The write-list is then
+**   traversed and data copied from any overlapping WriteBuffer
+**   structures to the output buffer. i.e. a read() operation following
+**   one or more write() operations works as expected, even if no
+**   data has actually been written out to the real file.
+**
+**   When a fsync() operation is performed, an operating system crash
+**   may be simulated, in which case exit(-1) is called (the call to
+**   xSync() never returns). Whether or not a crash is simulated,
+**   the data associated with a subset of the WriteBuffer structures
+**   stored in the write-list is written to the real underlying files
+**   and the entries removed from the write-list. If a crash is simulated,
+**   a subset of the buffers may be corrupted before the data is written.
+**
+**   The exact subset of the write-list written and/or corrupted is
+**   determined by the simulated device characteristics and sector-size.
+**
+** "Normal" mode:
+**
+**   Normal mode is used when the simulated device has none of the
+**   SQLITE_IOCAP_XXX flags set.
+**
+**   In normal mode, if the fsync() is not a simulated crash, the
+**   write-list is traversed from beginning to end. Each WriteBuffer
+**   structure associated with the file handle used to call xSync()
+**   is written to the real file and removed from the write-list.
+**
+**   If a crash is simulated, one of the following takes place for
+**   each WriteBuffer in the write-list, regardless of which
+**   file-handle it is associated with:
+**
+**     1. The buffer is correctly written to the file, just as if
+**        a crash were not being simulated.
+**
+**     2. Nothing is done.
+**
+**     3. Garbage data is written to all sectors of the file that
+**        overlap the region specified by the WriteBuffer. Or garbage
+**        data is written to some contiguous section within the
+**        overlapped sectors.
+**
+** Device Characteristic flag handling:
+**
+**   If the IOCAP_ATOMIC flag is set, then option (3) above is
+**   never selected.
+**
+**   If the IOCAP_ATOMIC512 flag is set, and the WriteBuffer represents
+**   an aligned write() of an integer number of 512 byte regions, then
+**   option (3) above is never selected. Instead, each 512 byte region
+**   is either correctly written or left completely untouched. Similar
+**   logic governs the behavior if any of the other ATOMICXXX flags
+**   is set.
+**
+**   If either the IOCAP_SAFEAPPEND or IOCAP_SEQUENTIAL flags are set
+**   and a crash is being simulated, then an entry of the write-list is
+**   selected at random. Everything in the list after the selected entry
+**   is discarded before processing begins.
+**
+**   If IOCAP_SEQUENTIAL is set and a crash is being simulated, option
+**   (1) is selected for all write-list entries except the last. If a
+**   crash is not being simulated, then all entries in the write-list
+**   that occur before at least one write() on the file-handle specified
+**   as part of the xSync() are written to their associated real files.
+**
+**   If IOCAP_SAFEAPPEND is set and the first byte written by the write()
+**   operation is one byte past the current end of the file, then option
+**   (1) is always selected.
+*/
+
+/*
+** Each write operation in the write-list is represented by an instance
+** of the following structure.
+**
+** If zBuf is 0, then this structure represents a call to xTruncate(),
+** not xWrite(). In that case, iOffset is the size that the file is
+** truncated to.
+*/
+struct WriteBuffer {
+  i64 iOffset;                 /* Byte offset of the start of this write() */
+  int nBuf;                    /* Number of bytes written */
+  u8 *zBuf;                    /* Pointer to copy of written data */
+  CrashFile *pFile;            /* File this write() applies to */
+
+  WriteBuffer *pNext;          /* Next in CrashGlobal.pWriteList */
+};
+
+struct CrashFile {
+  const sqlite3_io_methods *pMethod;   /* Must be first */
+  sqlite3_file *pRealFile;             /* Underlying "real" file handle */
+  char *zName;
+  int flags;                           /* Flags the file was opened with */
+
+  /* Cache of the entire file. This is used to speed up OsRead() and
+  ** OsFileSize() calls. Although both could be done by traversing the
+  ** write-list, in practice this is impractically slow.
+  */
+  u8 *zData;                           /* Buffer containing file contents */
+  int nData;                           /* Size of buffer allocated at zData */
+  i64 iSize;                           /* Size of file in bytes */
+};
+
+struct CrashGlobal {
+  WriteBuffer *pWriteList;     /* Head of write-list */
+  WriteBuffer *pWriteListEnd;  /* End of write-list */
+
+  int iSectorSize;             /* Value of simulated sector size */
+  int iDeviceCharacteristics;  /* Value of simulated device characteristics */
+
+  int iCrash;                  /* Crash on the iCrash'th call to xSync() */
+  char zCrashFile[500];        /* Crash during an xSync() on this file */
+};
+
+static CrashGlobal g = {0, 0, SQLITE_DEFAULT_SECTOR_SIZE, 0, 0};
+
+/*
+** Set this global variable to 1 to enable crash testing.
+*/
+static int sqlite3CrashTestEnable = 0;
+
+static void *crash_malloc(int nByte){
+  return (void *)Tcl_AttemptAlloc((size_t)nByte);
+}
+static void crash_free(void *p){
+  Tcl_Free(p);
+}
+static void *crash_realloc(void *p, int n){
+  return (void *)Tcl_AttemptRealloc(p, (size_t)n);
+}
+
+/*
+** Wrapper around the sqlite3OsWrite() function that avoids writing to the
+** 512 byte block beginning at offset PENDING_BYTE.
+*/
+static int writeDbFile(CrashFile *p, u8 *z, i64 iAmt, i64 iOff){
+  int rc = SQLITE_OK;
+  int iSkip = 0;
+  if( (iAmt-iSkip)>0 ){
+    rc = sqlite3OsWrite(p->pRealFile, &z[iSkip], (int)(iAmt-iSkip), iOff+iSkip);
+  }
+  return rc;
+}
+
+/*
+** Flush the write-list as if xSync() had been called on file handle
+** pFile. If isCrash is true, simulate a crash.
+*/
+static int writeListSync(CrashFile *pFile, int isCrash){
+  int rc = SQLITE_OK;
+  int iDc = g.iDeviceCharacteristics;
+
+  WriteBuffer *pWrite;
+  WriteBuffer **ppPtr;
+
+  /* If this is not a crash simulation, set pFinal to point to the
+  ** last element of the write-list that is associated with file handle
+  ** pFile.
+  **
+  ** If this is a crash simulation, set pFinal to an arbitrarily selected
+  ** element of the write-list.
+  */
+  WriteBuffer *pFinal = 0;
+  if( !isCrash ){
+    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext){
+      if( pWrite->pFile==pFile ){
+        pFinal = pWrite;
+      }
+    }
+  }else if( iDc&(SQLITE_IOCAP_SEQUENTIAL|SQLITE_IOCAP_SAFE_APPEND) ){
+    int nWrite = 0;
+    int iFinal;
+    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext) nWrite++;
+    sqlite3_randomness(sizeof(int), &iFinal);
+    iFinal = ((iFinal<0)?-1*iFinal:iFinal)%nWrite;
+    for(pWrite=g.pWriteList; iFinal>0; pWrite=pWrite->pNext) iFinal--;
+    pFinal = pWrite;
+  }
+
+#ifdef TRACE_CRASHTEST
+  if( pFile ){
+    printf("Sync %s (is %s crash)\n", pFile->zName, (isCrash?"a":"not a"));
+  }
+#endif
+
+  ppPtr = &g.pWriteList;
+  for(pWrite=*ppPtr; rc==SQLITE_OK && pWrite; pWrite=*ppPtr){
+    sqlite3_file *pRealFile = pWrite->pFile->pRealFile;
+
+    /* (eAction==1)      -> write block out normally,
+    ** (eAction==2)      -> do nothing,
+    ** (eAction==3)      -> trash sectors.
+    */
+    int eAction = 0;
+    if( !isCrash ){
+      eAction = 2;
+      if( (pWrite->pFile==pFile || iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+        eAction = 1;
+      }
+    }else{
+      char random;
+      sqlite3_randomness(1, &random);
+
+      /* Do not select option 3 (sector trashing) if the IOCAP_ATOMIC flag
+      ** is set or this is an OsTruncate(), not an Oswrite().
+      */
+      if( (iDc&SQLITE_IOCAP_ATOMIC) || (pWrite->zBuf==0) ){
+        random &= 0x01;
+      }
+
+      /* If IOCAP_SEQUENTIAL is set and this is not the final entry
+      ** in the truncated write-list, always select option 1 (write
+      ** out correctly).
+      */
+      if( (iDc&SQLITE_IOCAP_SEQUENTIAL && pWrite!=pFinal) ){
+        random = 0;
+      }
+
+      /* If IOCAP_SAFE_APPEND is set and this OsWrite() operation is
+      ** an append (first byte of the written region is 1 byte past the
+      ** current EOF), always select option 1 (write out correctly).
+      */
+      if( iDc&SQLITE_IOCAP_SAFE_APPEND && pWrite->zBuf ){
+        i64 iSize;
+        sqlite3OsFileSize(pRealFile, &iSize);
+        if( iSize==pWrite->iOffset ){
+          random = 0;
+        }
+      }
+
+      if( (random&0x06)==0x06 ){
+        eAction = 3;
+      }else{
+        eAction = ((random&0x01)?2:1);
+      }
+    }
+
+    switch( eAction ){
+      case 1: {               /* Write out correctly */
+        if( pWrite->zBuf ){
+          rc = writeDbFile(
+              pWrite->pFile, pWrite->zBuf, pWrite->nBuf, pWrite->iOffset
+          );
+        }else{
+          rc = sqlite3OsTruncate(pRealFile, pWrite->iOffset);
+        }
+        *ppPtr = pWrite->pNext;
+#ifdef TRACE_CRASHTEST
+        if( isCrash ){
+          printf("Writing %d bytes @ %d (%s)\n",
+            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
+          );
+        }
+#endif
+        crash_free(pWrite);
+        break;
+      }
+      case 2: {               /* Do nothing */
+        ppPtr = &pWrite->pNext;
+#ifdef TRACE_CRASHTEST
+        if( isCrash ){
+          printf("Omiting %d bytes @ %d (%s)\n",
+            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
+          );
+        }
+#endif
+        break;
+      }
+      case 3: {               /* Trash sectors */
+        u8 *zGarbage;
+        int iFirst = (int)(pWrite->iOffset/g.iSectorSize);
+        int iLast = (int)((pWrite->iOffset+pWrite->nBuf-1)/g.iSectorSize);
+
+        assert(pWrite->zBuf);
+
+#ifdef TRACE_CRASHTEST
+        printf("Trashing %d sectors (%d bytes) @ %lld (sector %d) (%s)\n",
+            1+iLast-iFirst, (1+iLast-iFirst)*g.iSectorSize,
+            pWrite->iOffset, iFirst, pWrite->pFile->zName
+        );
+#endif
+
+        zGarbage = crash_malloc(g.iSectorSize);
+        if( zGarbage ){
+          sqlite3_int64 i;
+          for(i=iFirst; rc==SQLITE_OK && i<=iLast; i++){
+            sqlite3_randomness(g.iSectorSize, zGarbage);
+            rc = writeDbFile(
+              pWrite->pFile, zGarbage, g.iSectorSize, i*g.iSectorSize
+            );
+          }
+          crash_free(zGarbage);
+        }else{
+          rc = SQLITE_NOMEM;
+        }
+
+        ppPtr = &pWrite->pNext;
+        break;
+      }
+
+      default:
+        assert(!"Cannot happen");
+    }
+
+    if( pWrite==pFinal ) break;
+  }
+
+  if( rc==SQLITE_OK && isCrash ){
+    exit(-1);
+  }
+
+  for(pWrite=g.pWriteList; pWrite && pWrite->pNext; pWrite=pWrite->pNext);
+  g.pWriteListEnd = pWrite;
+
+  return rc;
+}
+
+/*
+** Add an entry to the end of the write-list.
+*/
+static int writeListAppend(
+  sqlite3_file *pFile,
+  sqlite3_int64 iOffset,
+  const u8 *zBuf,
+  int nBuf
+){
+  WriteBuffer *pNew;
+
+  assert((zBuf && nBuf) || (!nBuf && !zBuf));
+
+  pNew = (WriteBuffer *)crash_malloc(sizeof(WriteBuffer) + nBuf);
+  if( pNew==0 ){
+    fprintf(stderr, "out of memory in the crash simulator\n");
+  }
+  memset(pNew, 0, sizeof(WriteBuffer)+nBuf);
+  pNew->iOffset = iOffset;
+  pNew->nBuf = nBuf;
+  pNew->pFile = (CrashFile *)pFile;
+  if( zBuf ){
+    pNew->zBuf = (u8 *)&pNew[1];
+    memcpy(pNew->zBuf, zBuf, nBuf);
+  }
+
+  if( g.pWriteList ){
+    assert(g.pWriteListEnd);
+    g.pWriteListEnd->pNext = pNew;
+  }else{
+    g.pWriteList = pNew;
+  }
+  g.pWriteListEnd = pNew;
+ 
+  return SQLITE_OK;
+}
+
+/*
+** Close a crash-file.
+*/
+static int cfClose(sqlite3_file *pFile){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  writeListSync(pCrash, 0);
+  sqlite3OsClose(pCrash->pRealFile);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from a crash-file.
+*/
+static int cfRead(
+  sqlite3_file *pFile,
+  void *zBuf,
+  int iAmt,
+  sqlite_int64 iOfst
+){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  int nCopy = (int)MIN((i64)iAmt, (pCrash->iSize - iOfst));
+
+  if( nCopy>0 ){
+    memcpy(zBuf, &pCrash->zData[iOfst], nCopy);
+  }
+
+  /* Check the file-size to see if this is a short-read */
+  if( nCopy<iAmt ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Write data to a crash-file.
+*/
+static int cfWrite(
+  sqlite3_file *pFile,
+  const void *zBuf,
+  int iAmt,
+  sqlite_int64 iOfst
+){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  if( iAmt+iOfst>pCrash->iSize ){
+    pCrash->iSize = (int)(iAmt+iOfst);
+  }
+  while( pCrash->iSize>pCrash->nData ){
+    u8 *zNew;
+    int nNew = (pCrash->nData*2) + 4096;
+    zNew = crash_realloc(pCrash->zData, nNew);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    memset(&zNew[pCrash->nData], 0, nNew-pCrash->nData);
+    pCrash->nData = nNew;
+    pCrash->zData = zNew;
+  }
+  memcpy(&pCrash->zData[iOfst], zBuf, iAmt);
+  return writeListAppend(pFile, iOfst, zBuf, iAmt);
+}
+
+/*
+** Truncate a crash-file.
+*/
+static int cfTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  assert(size>=0);
+  if( pCrash->iSize>size ){
+    pCrash->iSize = (int)size;
+  }
+  return writeListAppend(pFile, size, 0, 0);
+}
+
+/*
+** Sync a crash-file.
+*/
+static int cfSync(sqlite3_file *pFile, int flags){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  int isCrash = 0;
+
+  const char *zName = pCrash->zName;
+  const char *zCrashFile = g.zCrashFile;
+  int nName = (int)strlen(zName);
+  int nCrashFile = (int)strlen(zCrashFile);
+
+  if( nCrashFile>0 && zCrashFile[nCrashFile-1]=='*' ){
+    nCrashFile--;
+    if( nName>nCrashFile ) nName = nCrashFile;
+  }
+
+#ifdef TRACE_CRASHTEST
+  printf("cfSync(): nName = %d, nCrashFile = %d, zName = %s, zCrashFile = %s\n",
+         nName, nCrashFile, zName, zCrashFile);
+#endif
+
+  if( nName==nCrashFile && 0==memcmp(zName, zCrashFile, nName) ){
+#ifdef TRACE_CRASHTEST
+    printf("cfSync(): name matched, g.iCrash = %d\n", g.iCrash);
+#endif
+    if( (--g.iCrash)==0 ) isCrash = 1;
+  }
+
+  return writeListSync(pCrash, isCrash);
+}
+
+/*
+** Return the current file-size of the crash-file.
+*/
+static int cfFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  *pSize = (i64)pCrash->iSize;
+  return SQLITE_OK;
+}
+
+/*
+** Calls related to file-locks are passed on to the real file handle.
+*/
+static int cfLock(sqlite3_file *pFile, int eLock){
+  return sqlite3OsLock(((CrashFile *)pFile)->pRealFile, eLock);
+}
+static int cfUnlock(sqlite3_file *pFile, int eLock){
+  return sqlite3OsUnlock(((CrashFile *)pFile)->pRealFile, eLock);
+}
+static int cfCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  return sqlite3OsCheckReservedLock(((CrashFile *)pFile)->pRealFile, pResOut);
+}
+static int cfFileControl(sqlite3_file *pFile, int op, void *pArg){
+  if( op==SQLITE_FCNTL_SIZE_HINT ){
+    CrashFile *pCrash = (CrashFile *)pFile;
+    i64 nByte = *(i64 *)pArg;
+    if( nByte>pCrash->iSize ){
+      if( SQLITE_OK==writeListAppend(pFile, nByte, 0, 0) ){
+        pCrash->iSize = (int)nByte;
+      }
+    }
+    return SQLITE_OK;
+  }
+  return sqlite3OsFileControl(((CrashFile *)pFile)->pRealFile, op, pArg);
+}
+
+/*
+** The xSectorSize() and xDeviceCharacteristics() functions return
+** the global values configured by the [sqlite_crashparams] tcl
+*  interface.
+*/
+static int cfSectorSize(sqlite3_file *pFile){
+  return g.iSectorSize;
+}
+static int cfDeviceCharacteristics(sqlite3_file *pFile){
+  return g.iDeviceCharacteristics;
+}
+
+/*
+** Pass-throughs for WAL support.
+*/
+static int cfShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
+  return pReal->pMethods->xShmLock(pReal, ofst, n, flags);
+}
+static void cfShmBarrier(sqlite3_file *pFile){
+  sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
+  pReal->pMethods->xShmBarrier(pReal);
+}
+static int cfShmUnmap(sqlite3_file *pFile, int delFlag){
+  sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
+  return pReal->pMethods->xShmUnmap(pReal, delFlag);
+}
+static int cfShmMap(
+  sqlite3_file *pFile,            /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int sz,                         /* Size of regions */
+  int w,                          /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  sqlite3_file *pReal = ((CrashFile*)pFile)->pRealFile;
+  return pReal->pMethods->xShmMap(pReal, iRegion, sz, w, pp);
+}
+
+static const sqlite3_io_methods CrashFileVtab = {
+  2,                            /* iVersion */
+  cfClose,                      /* xClose */
+  cfRead,                       /* xRead */
+  cfWrite,                      /* xWrite */
+  cfTruncate,                   /* xTruncate */
+  cfSync,                       /* xSync */
+  cfFileSize,                   /* xFileSize */
+  cfLock,                       /* xLock */
+  cfUnlock,                     /* xUnlock */
+  cfCheckReservedLock,          /* xCheckReservedLock */
+  cfFileControl,                /* xFileControl */
+  cfSectorSize,                 /* xSectorSize */
+  cfDeviceCharacteristics,      /* xDeviceCharacteristics */
+  cfShmMap,                     /* xShmMap */
+  cfShmLock,                    /* xShmLock */
+  cfShmBarrier,                 /* xShmBarrier */
+  cfShmUnmap                    /* xShmUnmap */
+};
+
+/*
+** Application data for the crash VFS
+*/
+struct crashAppData {
+  sqlite3_vfs *pOrig;                   /* Wrapped vfs structure */
+};
+
+/*
+** Open a crash-file file handle.
+**
+** The caller will have allocated pVfs->szOsFile bytes of space
+** at pFile. This file uses this space for the CrashFile structure
+** and allocates space for the "real" file structure using
+** sqlite3_malloc(). The assumption here is (pVfs->szOsFile) is
+** equal or greater than sizeof(CrashFile).
+*/
+static int cfOpen(
+  sqlite3_vfs *pCfVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  int rc;
+  CrashFile *pWrapper = (CrashFile *)pFile;
+  sqlite3_file *pReal = (sqlite3_file*)&pWrapper[1];
+
+  memset(pWrapper, 0, sizeof(CrashFile));
+  rc = sqlite3OsOpen(pVfs, zName, pReal, flags, pOutFlags);
+
+  if( rc==SQLITE_OK ){
+    i64 iSize;
+    pWrapper->pMethod = &CrashFileVtab;
+    pWrapper->zName = (char *)zName;
+    pWrapper->pRealFile = pReal;
+    rc = sqlite3OsFileSize(pReal, &iSize);
+    pWrapper->iSize = (int)iSize;
+    pWrapper->flags = flags;
+  }
+  if( rc==SQLITE_OK ){
+    pWrapper->nData = (int)(4096 + pWrapper->iSize);
+    pWrapper->zData = crash_malloc(pWrapper->nData);
+    if( pWrapper->zData ){
+      /* os_unix.c contains an assert() that fails if the caller attempts
+      ** to read data from the 512-byte locking region of a file opened
+      ** with the SQLITE_OPEN_MAIN_DB flag. This region of a database file
+      ** never contains valid data anyhow. So avoid doing such a read here.
+      **
+      ** UPDATE: It also contains an assert() verifying that each call
+      ** to the xRead() method reads less than 128KB of data.
+      */
+      i64 iOff;
+
+      memset(pWrapper->zData, 0, pWrapper->nData);
+      for(iOff=0; iOff<pWrapper->iSize; iOff += 512){
+        int nRead = (int)(pWrapper->iSize - iOff);
+        if( nRead>512 ) nRead = 512;
+        rc = sqlite3OsRead(pReal, &pWrapper->zData[iOff], nRead, iOff);
+      }
+    }else{
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc!=SQLITE_OK && pWrapper->pMethod ){
+    sqlite3OsClose(pFile);
+  }
+  return rc;
+}
+
+static int cfDelete(sqlite3_vfs *pCfVfs, const char *zPath, int dirSync){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xDelete(pVfs, zPath, dirSync);
+}
+static int cfAccess(
+  sqlite3_vfs *pCfVfs,
+  const char *zPath,
+  int flags,
+  int *pResOut
+){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xAccess(pVfs, zPath, flags, pResOut);
+}
+static int cfFullPathname(
+  sqlite3_vfs *pCfVfs,
+  const char *zPath,
+  int nPathOut,
+  char *zPathOut
+){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut);
+}
+static void *cfDlOpen(sqlite3_vfs *pCfVfs, const char *zPath){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xDlOpen(pVfs, zPath);
+}
+static void cfDlError(sqlite3_vfs *pCfVfs, int nByte, char *zErrMsg){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  pVfs->xDlError(pVfs, nByte, zErrMsg);
+}
+static void (*cfDlSym(sqlite3_vfs *pCfVfs, void *pH, const char *zSym))(void){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xDlSym(pVfs, pH, zSym);
+}
+static void cfDlClose(sqlite3_vfs *pCfVfs, void *pHandle){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  pVfs->xDlClose(pVfs, pHandle);
+}
+static int cfRandomness(sqlite3_vfs *pCfVfs, int nByte, char *zBufOut){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xRandomness(pVfs, nByte, zBufOut);
+}
+static int cfSleep(sqlite3_vfs *pCfVfs, int nMicro){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xSleep(pVfs, nMicro);
+}
+static int cfCurrentTime(sqlite3_vfs *pCfVfs, double *pTimeOut){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xCurrentTime(pVfs, pTimeOut);
+}
+static int cfGetLastError(sqlite3_vfs *pCfVfs, int n, char *z){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xGetLastError(pVfs, n, z);
+}
+
+static int processDevSymArgs(
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[],
+  int *piDeviceChar,
+  int *piSectorSize
+){
+  struct DeviceFlag {
+    char *zName;
+    int iValue;
+  } aFlag[] = {
+    { "atomic",              SQLITE_IOCAP_ATOMIC                },
+    { "atomic512",           SQLITE_IOCAP_ATOMIC512             },
+    { "atomic1k",            SQLITE_IOCAP_ATOMIC1K              },
+    { "atomic2k",            SQLITE_IOCAP_ATOMIC2K              },
+    { "atomic4k",            SQLITE_IOCAP_ATOMIC4K              },
+    { "atomic8k",            SQLITE_IOCAP_ATOMIC8K              },
+    { "atomic16k",           SQLITE_IOCAP_ATOMIC16K             },
+    { "atomic32k",           SQLITE_IOCAP_ATOMIC32K             },
+    { "atomic64k",           SQLITE_IOCAP_ATOMIC64K             },
+    { "sequential",          SQLITE_IOCAP_SEQUENTIAL            },
+    { "safe_append",         SQLITE_IOCAP_SAFE_APPEND           },
+    { "powersafe_overwrite", SQLITE_IOCAP_POWERSAFE_OVERWRITE   },
+    { "batch-atomic",        SQLITE_IOCAP_BATCH_ATOMIC          },
+    { 0, 0 }
+  };
+
+  int i;
+  int iDc = 0;
+  int iSectorSize = 0;
+  int setSectorsize = 0;
+  int setDeviceChar = 0;
+
+  for(i=0; i<objc; i+=2){
+    int nOpt;
+    char *zOpt = Tcl_GetStringFromObj(objv[i], &nOpt);
+
+    if( (nOpt>11 || nOpt<2 || strncmp("-sectorsize", zOpt, nOpt))
+     && (nOpt>16 || nOpt<2 || strncmp("-characteristics", zOpt, nOpt))
+    ){
+      Tcl_AppendResult(interp,
+        "Bad option: \"", zOpt,
+        "\" - must be \"-characteristics\" or \"-sectorsize\"", 0
+      );
+      return TCL_ERROR;
+    }
+    if( i==objc-1 ){
+      Tcl_AppendResult(interp, "Option requires an argument: \"", zOpt, "\"",0);
+      return TCL_ERROR;
+    }
+
+    if( zOpt[1]=='s' ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &iSectorSize) ){
+        return TCL_ERROR;
+      }
+      setSectorsize = 1;
+    }else{
+      int j;
+      Tcl_Obj **apObj;
+      int nObj;
+      if( Tcl_ListObjGetElements(interp, objv[i+1], &nObj, &apObj) ){
+        return TCL_ERROR;
+      }
+      for(j=0; j<nObj; j++){
+        int rc;
+        int iChoice;
+        Tcl_Obj *pFlag = Tcl_DuplicateObj(apObj[j]);
+        Tcl_IncrRefCount(pFlag);
+        Tcl_UtfToLower(Tcl_GetString(pFlag));
+
+        rc = Tcl_GetIndexFromObjStruct(
+            interp, pFlag, aFlag, sizeof(aFlag[0]), "no such flag", 0, &iChoice
+        );
+        Tcl_DecrRefCount(pFlag);
+        if( rc ){
+          return TCL_ERROR;
+        }
+
+        iDc |= aFlag[iChoice].iValue;
+      }
+      setDeviceChar = 1;
+    }
+  }
+
+  if( setDeviceChar ){
+    *piDeviceChar = iDc;
+  }
+  if( setSectorsize ){
+    *piSectorSize = iSectorSize;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   sqlite3_crash_now
+**
+** Simulate a crash immediately. This function does not return
+** (writeListSync() calls exit(-1)).
+*/
+static int SQLITE_TCLAPI crashNowCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  writeListSync(0, 1);
+  assert( 0 );
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   sqlite_crash_enable ENABLE ?DEFAULT?
+**
+** Parameter ENABLE must be a boolean value. If true, then the "crash"
+** vfs is added to the system. If false, it is removed.
+*/
+static int SQLITE_TCLAPI crashEnableCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int isEnable;
+  int isDefault = 0;
+  static sqlite3_vfs crashVfs = {
+    2,                  /* iVersion */
+    0,                  /* szOsFile */
+    0,                  /* mxPathname */
+    0,                  /* pNext */
+    "crash",            /* zName */
+    0,                  /* pAppData */
+ 
+    cfOpen,               /* xOpen */
+    cfDelete,             /* xDelete */
+    cfAccess,             /* xAccess */
+    cfFullPathname,       /* xFullPathname */
+    cfDlOpen,             /* xDlOpen */
+    cfDlError,            /* xDlError */
+    cfDlSym,              /* xDlSym */
+    cfDlClose,            /* xDlClose */
+    cfRandomness,         /* xRandomness */
+    cfSleep,              /* xSleep */
+    cfCurrentTime,        /* xCurrentTime */
+    cfGetLastError,       /* xGetLastError */
+    0,                    /* xCurrentTimeInt64 */
+  };
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "ENABLE ?DEFAULT?");
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &isEnable) ){
+    return TCL_ERROR;
+  }
+  if( objc==3 && Tcl_GetBooleanFromObj(interp, objv[2], &isDefault) ){
+    return TCL_ERROR;
+  }
+
+  if( (isEnable && crashVfs.pAppData) || (!isEnable && !crashVfs.pAppData) ){
+    return TCL_OK;
+  }
+
+  if( crashVfs.pAppData==0 ){
+    sqlite3_vfs *pOriginalVfs = sqlite3_vfs_find(0);
+    crashVfs.mxPathname = pOriginalVfs->mxPathname;
+    crashVfs.pAppData = (void *)pOriginalVfs;
+    crashVfs.szOsFile = sizeof(CrashFile) + pOriginalVfs->szOsFile;
+    sqlite3_vfs_register(&crashVfs, isDefault);
+  }else{
+    crashVfs.pAppData = 0;
+    sqlite3_vfs_unregister(&crashVfs);
+  }
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   sqlite_crashparams ?OPTIONS? DELAY CRASHFILE
+**
+** This procedure implements a TCL command that enables crash testing
+** in testfixture.  Once enabled, crash testing cannot be disabled.
+**
+** Available options are "-characteristics" and "-sectorsize". Both require
+** an argument. For -sectorsize, this is the simulated sector size in
+** bytes. For -characteristics, the argument must be a list of io-capability
+** flags to simulate. Valid flags are "atomic", "atomic512", "atomic1K",
+** "atomic2K", "atomic4K", "atomic8K", "atomic16K", "atomic32K",
+** "atomic64K", "sequential" and "safe_append".
+**
+** Example:
+**
+**   sqlite_crashparams -sect 1024 -char {atomic sequential} ./test.db 1
+**
+*/
+static int SQLITE_TCLAPI crashParamsObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iDelay;
+  const char *zCrashFile;
+  int nCrashFile, iDc, iSectorSize;
+
+  iDc = -1;
+  iSectorSize = -1;
+
+  if( objc<3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?OPTIONS? DELAY CRASHFILE");
+    goto error;
+  }
+
+  zCrashFile = Tcl_GetStringFromObj(objv[objc-1], &nCrashFile);
+  if( nCrashFile>=sizeof(g.zCrashFile) ){
+    Tcl_AppendResult(interp, "Filename is too long: \"", zCrashFile, "\"", 0);
+    goto error;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[objc-2], &iDelay) ){
+    goto error;
+  }
+
+  if( processDevSymArgs(interp, objc-3, &objv[1], &iDc, &iSectorSize) ){
+    return TCL_ERROR;
+  }
+
+  if( iDc>=0 ){
+    g.iDeviceCharacteristics = iDc;
+  }
+  if( iSectorSize>=0 ){
+    g.iSectorSize = iSectorSize;
+  }
+
+  g.iCrash = iDelay;
+  memcpy(g.zCrashFile, zCrashFile, nCrashFile+1);
+  sqlite3CrashTestEnable = 1;
+  return TCL_OK;
+
+error:
+  return TCL_ERROR;
+}
+
+static int SQLITE_TCLAPI devSymObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void devsym_register(int iDeviceChar, int iSectorSize);
+
+  int iDc = -1;
+  int iSectorSize = -1;
+
+  if( processDevSymArgs(interp, objc-1, &objv[1], &iDc, &iSectorSize) ){
+    return TCL_ERROR;
+  }
+  devsym_register(iDc, iSectorSize);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_crash_on_write N
+*/
+static int SQLITE_TCLAPI writeCrashObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void devsym_crash_on_write(int);
+  int nWrite = 0;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NWRITE");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &nWrite) ){
+    return TCL_ERROR;
+  }
+
+  devsym_crash_on_write(nWrite);
+  return TCL_OK;
+}
+
+/*
+** tclcmd: unregister_devsim
+*/
+static int SQLITE_TCLAPI dsUnregisterObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void devsym_unregister(void);
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  devsym_unregister();
+  return TCL_OK;
+}
+
+/*
+** tclcmd: register_jt_vfs ?-default? PARENT-VFS
+*/
+static int SQLITE_TCLAPI jtObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int jt_register(char *, int);
+  char *zParent = 0;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?-default? PARENT-VFS");
+    return TCL_ERROR;
+  }
+  zParent = Tcl_GetString(objv[1]);
+  if( objc==3 ){
+    if( strcmp(zParent, "-default") ){
+      Tcl_AppendResult(interp,
+          "bad option \"", zParent, "\": must be -default", 0
+      );
+      return TCL_ERROR;
+    }
+    zParent = Tcl_GetString(objv[2]);
+  }
+
+  if( !(*zParent) ){
+    zParent = 0;
+  }
+  if( jt_register(zParent, objc==3) ){
+    Tcl_AppendResult(interp, "Error in jt_register", 0);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: unregister_jt_vfs
+*/
+static int SQLITE_TCLAPI jtUnregisterObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void jt_unregister(void);
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  jt_unregister();
+  return TCL_OK;
+}
+
+#endif /* SQLITE_OMIT_DISKIO */
+
+/*
+** This procedure registers the TCL procedures defined in this file.
+*/
+int Sqlitetest6_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_DISKIO
+  Tcl_CreateObjCommand(interp, "sqlite3_crash_enable", crashEnableCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_crashparams", crashParamsObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_crash_now", crashNowCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_simulate_device", devSymObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_crash_on_write", writeCrashObjCmd,0,0);
+  Tcl_CreateObjCommand(interp, "unregister_devsim", dsUnregisterObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "register_jt_vfs", jtObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "unregister_jt_vfs", jtUnregisterObjCmd, 0, 0);
+#endif
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test8.c b/src/test8.c
new file mode 100644
index 0000000..4aeb555
--- /dev/null
+++ b/src/test8.c
@@ -0,0 +1,1457 @@
+/*
+** 2006 June 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+typedef struct echo_vtab echo_vtab;
+typedef struct echo_cursor echo_cursor;
+
+/*
+** The test module defined in this file uses four global Tcl variables to
+** communicate with test-scripts:
+**
+**     $::echo_module
+**     $::echo_module_sync_fail
+**     $::echo_module_begin_fail
+**     $::echo_module_cost
+**
+** The variable ::echo_module is a list. Each time one of the following
+** methods is called, one or more elements are appended to the list.
+** This is used for automated testing of virtual table modules.
+**
+** The ::echo_module_sync_fail variable is set by test scripts and read
+** by code in this file. If it is set to the name of a real table in the
+** the database, then all xSync operations on echo virtual tables that
+** use the named table as a backing store will fail.
+*/
+
+/*
+** Errors can be provoked within the following echo virtual table methods:
+**
+**   xBestIndex   xOpen     xFilter   xNext   
+**   xColumn      xRowid    xUpdate   xSync   
+**   xBegin       xRename
+**
+** This is done by setting the global tcl variable:
+**
+**   echo_module_fail($method,$tbl)
+**
+** where $method is set to the name of the virtual table method to fail
+** (i.e. "xBestIndex") and $tbl is the name of the table being echoed (not
+** the name of the virtual table, the name of the underlying real table).
+*/
+
+/* 
+** An echo virtual-table object.
+**
+** echo.vtab.aIndex is an array of booleans. The nth entry is true if 
+** the nth column of the real table is the left-most column of an index
+** (implicit or otherwise). In other words, if SQLite can optimize
+** a query like "SELECT * FROM real_table WHERE col = ?".
+**
+** Member variable aCol[] contains copies of the column names of the real
+** table.
+*/
+struct echo_vtab {
+  sqlite3_vtab base;
+  Tcl_Interp *interp;     /* Tcl interpreter containing debug variables */
+  sqlite3 *db;            /* Database connection */
+
+  int isPattern;
+  int inTransaction;      /* True if within a transaction */
+  char *zThis;            /* Name of the echo table */
+  char *zTableName;       /* Name of the real table */
+  char *zLogName;         /* Name of the log table */
+  int nCol;               /* Number of columns in the real table */
+  int *aIndex;            /* Array of size nCol. True if column has an index */
+  char **aCol;            /* Array of size nCol. Column names */
+};
+
+/* An echo cursor object */
+struct echo_cursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pStmt;
+};
+
+static int simulateVtabError(echo_vtab *p, const char *zMethod){
+  const char *zErr;
+  char zVarname[128];
+  zVarname[127] = '\0';
+  sqlite3_snprintf(127, zVarname, "echo_module_fail(%s,%s)", zMethod, p->zTableName);
+  zErr = Tcl_GetVar(p->interp, zVarname, TCL_GLOBAL_ONLY);
+  if( zErr ){
+    p->base.zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", zErr);
+  }
+  return (zErr!=0);
+}
+
+/*
+** Convert an SQL-style quoted string into a normal string by removing
+** the quote characters.  The conversion is done in-place.  If the
+** input does not begin with a quote character, then this routine
+** is a no-op.
+**
+** Examples:
+**
+**     "abc"   becomes   abc
+**     'xyz'   becomes   xyz
+**     [pqr]   becomes   pqr
+**     `mno`   becomes   mno
+*/
+static void dequoteString(char *z){
+  int quote;
+  int i, j;
+  if( z==0 ) return;
+  quote = z[0];
+  switch( quote ){
+    case '\'':  break;
+    case '"':   break;
+    case '`':   break;                /* For MySQL compatibility */
+    case '[':   quote = ']';  break;  /* For MS SqlServer compatibility */
+    default:    return;
+  }
+  for(i=1, j=0; z[i]; i++){
+    if( z[i]==quote ){
+      if( z[i+1]==quote ){
+        z[j++] = quote;
+        i++;
+      }else{
+        z[j++] = 0;
+        break;
+      }
+    }else{
+      z[j++] = z[i];
+    }
+  }
+}
+
+/*
+** Retrieve the column names for the table named zTab via database
+** connection db. SQLITE_OK is returned on success, or an sqlite error
+** code otherwise.
+**
+** If successful, the number of columns is written to *pnCol. *paCol is
+** set to point at sqlite3_malloc()'d space containing the array of
+** nCol column names. The caller is responsible for calling sqlite3_free
+** on *paCol.
+*/
+static int getColumnNames(
+  sqlite3 *db, 
+  const char *zTab,
+  char ***paCol, 
+  int *pnCol
+){
+  char **aCol = 0;
+  char *zSql;
+  sqlite3_stmt *pStmt = 0;
+  int rc = SQLITE_OK;
+  int nCol = 0;
+
+  /* Prepare the statement "SELECT * FROM <tbl>". The column names
+  ** of the result set of the compiled SELECT will be the same as
+  ** the column names of table <tbl>.
+  */
+  zSql = sqlite3_mprintf("SELECT * FROM %Q", zTab);
+  if( !zSql ){
+    rc = SQLITE_NOMEM;
+    goto out;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+
+  if( rc==SQLITE_OK ){
+    int ii;
+    int nBytes;
+    char *zSpace;
+    nCol = sqlite3_column_count(pStmt);
+
+    /* Figure out how much space to allocate for the array of column names 
+    ** (including space for the strings themselves). Then allocate it.
+    */
+    nBytes = sizeof(char *) * nCol;
+    for(ii=0; ii<nCol; ii++){
+      const char *zName = sqlite3_column_name(pStmt, ii);
+      if( !zName ){
+        rc = SQLITE_NOMEM;
+        goto out;
+      }
+      nBytes += (int)strlen(zName)+1;
+    }
+    aCol = (char **)sqlite3MallocZero(nBytes);
+    if( !aCol ){
+      rc = SQLITE_NOMEM;
+      goto out;
+    }
+
+    /* Copy the column names into the allocated space and set up the
+    ** pointers in the aCol[] array.
+    */
+    zSpace = (char *)(&aCol[nCol]);
+    for(ii=0; ii<nCol; ii++){
+      aCol[ii] = zSpace;
+      sqlite3_snprintf(nBytes, zSpace, "%s", sqlite3_column_name(pStmt,ii));
+      zSpace += (int)strlen(zSpace) + 1;
+    }
+    assert( (zSpace-nBytes)==(char *)aCol );
+  }
+
+  *paCol = aCol;
+  *pnCol = nCol;
+
+out:
+  sqlite3_finalize(pStmt);
+  return rc;
+}
+
+/*
+** Parameter zTab is the name of a table in database db with nCol 
+** columns. This function allocates an array of integers nCol in 
+** size and populates it according to any implicit or explicit 
+** indices on table zTab.
+**
+** If successful, SQLITE_OK is returned and *paIndex set to point 
+** at the allocated array. Otherwise, an error code is returned.
+**
+** See comments associated with the member variable aIndex above 
+** "struct echo_vtab" for details of the contents of the array.
+*/
+static int getIndexArray(
+  sqlite3 *db,             /* Database connection */
+  const char *zTab,        /* Name of table in database db */
+  int nCol,
+  int **paIndex
+){
+  sqlite3_stmt *pStmt = 0;
+  int *aIndex = 0;
+  int rc;
+  char *zSql;
+
+  /* Allocate space for the index array */
+  aIndex = (int *)sqlite3MallocZero(sizeof(int) * nCol);
+  if( !aIndex ){
+    rc = SQLITE_NOMEM;
+    goto get_index_array_out;
+  }
+
+  /* Compile an sqlite pragma to loop through all indices on table zTab */
+  zSql = sqlite3_mprintf("PRAGMA index_list(%s)", zTab);
+  if( !zSql ){
+    rc = SQLITE_NOMEM;
+    goto get_index_array_out;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+
+  /* For each index, figure out the left-most column and set the 
+  ** corresponding entry in aIndex[] to 1.
+  */
+  while( pStmt && sqlite3_step(pStmt)==SQLITE_ROW ){
+    const char *zIdx = (const char *)sqlite3_column_text(pStmt, 1);
+    sqlite3_stmt *pStmt2 = 0;
+    if( zIdx==0 ) continue;
+    zSql = sqlite3_mprintf("PRAGMA index_info(%s)", zIdx);
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+      goto get_index_array_out;
+    }
+    rc = sqlite3_prepare(db, zSql, -1, &pStmt2, 0);
+    sqlite3_free(zSql);
+    if( pStmt2 && sqlite3_step(pStmt2)==SQLITE_ROW ){
+      int cid = sqlite3_column_int(pStmt2, 1);
+      assert( cid>=0 && cid<nCol );
+      aIndex[cid] = 1;
+    }
+    if( pStmt2 ){
+      rc = sqlite3_finalize(pStmt2);
+    }
+    if( rc!=SQLITE_OK ){
+      goto get_index_array_out;
+    }
+  }
+
+
+get_index_array_out:
+  if( pStmt ){
+    int rc2 = sqlite3_finalize(pStmt);
+    if( rc==SQLITE_OK ){
+      rc = rc2;
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(aIndex);
+    aIndex = 0;
+  }
+  *paIndex = aIndex;
+  return rc;
+}
+
+/*
+** Global Tcl variable $echo_module is a list. This routine appends
+** the string element zArg to that list in interpreter interp.
+*/
+static void appendToEchoModule(Tcl_Interp *interp, const char *zArg){
+  int flags = (TCL_APPEND_VALUE | TCL_LIST_ELEMENT | TCL_GLOBAL_ONLY);
+  Tcl_SetVar(interp, "echo_module", (zArg?zArg:""), flags);
+}
+
+/*
+** This function is called from within the echo-modules xCreate and
+** xConnect methods. The argc and argv arguments are copies of those 
+** passed to the calling method. This function is responsible for
+** calling sqlite3_declare_vtab() to declare the schema of the virtual
+** table being created or connected.
+**
+** If the constructor was passed just one argument, i.e.:
+**
+**   CREATE TABLE t1 AS echo(t2);
+**
+** Then t2 is assumed to be the name of a *real* database table. The
+** schema of the virtual table is declared by passing a copy of the 
+** CREATE TABLE statement for the real table to sqlite3_declare_vtab().
+** Hence, the virtual table should have exactly the same column names and 
+** types as the real table.
+*/
+static int echoDeclareVtab(
+  echo_vtab *pVtab, 
+  sqlite3 *db 
+){
+  int rc = SQLITE_OK;
+
+  if( pVtab->zTableName ){
+    sqlite3_stmt *pStmt = 0;
+    rc = sqlite3_prepare(db, 
+        "SELECT sql FROM sqlite_schema WHERE type = 'table' AND name = ?",
+        -1, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_text(pStmt, 1, pVtab->zTableName, -1, 0);
+      if( sqlite3_step(pStmt)==SQLITE_ROW ){
+        int rc2;
+        const char *zCreateTable = (const char *)sqlite3_column_text(pStmt, 0);
+        rc = sqlite3_declare_vtab(db, zCreateTable);
+        rc2 = sqlite3_finalize(pStmt);
+        if( rc==SQLITE_OK ){
+          rc = rc2;
+        }
+      } else {
+        rc = sqlite3_finalize(pStmt);
+        if( rc==SQLITE_OK ){ 
+          rc = SQLITE_ERROR;
+        }
+      }
+      if( rc==SQLITE_OK ){
+        rc = getColumnNames(db, pVtab->zTableName, &pVtab->aCol, &pVtab->nCol);
+      }
+      if( rc==SQLITE_OK ){
+        rc = getIndexArray(db, pVtab->zTableName, pVtab->nCol, &pVtab->aIndex);
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function frees all runtime structures associated with the virtual
+** table pVtab.
+*/
+static int echoDestructor(sqlite3_vtab *pVtab){
+  echo_vtab *p = (echo_vtab*)pVtab;
+  sqlite3_free(p->aIndex);
+  sqlite3_free(p->aCol);
+  sqlite3_free(p->zThis);
+  sqlite3_free(p->zTableName);
+  sqlite3_free(p->zLogName);
+  sqlite3_free(p);
+  return 0;
+}
+
+typedef struct EchoModule EchoModule;
+struct EchoModule {
+  Tcl_Interp *interp;
+  sqlite3 *db;
+};
+
+/*
+** This function is called to do the work of the xConnect() method -
+** to allocate the required in-memory structures for a newly connected
+** virtual table.
+*/
+static int echoConstructor(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc;
+  int i;
+  echo_vtab *pVtab;
+
+  /* Allocate the sqlite3_vtab/echo_vtab structure itself */
+  pVtab = sqlite3MallocZero( sizeof(*pVtab) );
+  if( !pVtab ){
+    return SQLITE_NOMEM;
+  }
+  pVtab->interp = ((EchoModule *)pAux)->interp;
+  pVtab->db = db;
+
+  /* Allocate echo_vtab.zThis */
+  pVtab->zThis = sqlite3_mprintf("%s", argv[2]);
+  if( !pVtab->zThis ){
+    echoDestructor((sqlite3_vtab *)pVtab);
+    return SQLITE_NOMEM;
+  }
+
+  /* Allocate echo_vtab.zTableName */
+  if( argc>3 ){
+    pVtab->zTableName = sqlite3_mprintf("%s", argv[3]);
+    dequoteString(pVtab->zTableName);
+    if( pVtab->zTableName && pVtab->zTableName[0]=='*' ){
+      char *z = sqlite3_mprintf("%s%s", argv[2], &(pVtab->zTableName[1]));
+      sqlite3_free(pVtab->zTableName);
+      pVtab->zTableName = z;
+      pVtab->isPattern = 1;
+    }
+    if( !pVtab->zTableName ){
+      echoDestructor((sqlite3_vtab *)pVtab);
+      return SQLITE_NOMEM;
+    }
+  }
+
+  /* Log the arguments to this function to Tcl var ::echo_module */
+  for(i=0; i<argc; i++){
+    appendToEchoModule(pVtab->interp, argv[i]);
+  }
+
+  /* Invoke sqlite3_declare_vtab and set up other members of the echo_vtab
+  ** structure. If an error occurs, delete the sqlite3_vtab structure and
+  ** return an error code.
+  */
+  rc = echoDeclareVtab(pVtab, db);
+  if( rc!=SQLITE_OK ){
+    echoDestructor((sqlite3_vtab *)pVtab);
+    return rc;
+  }
+
+  /* Success. Set *ppVtab and return */
+  *ppVtab = &pVtab->base;
+  return SQLITE_OK;
+}
+
+/* 
+** Echo virtual table module xCreate method.
+*/
+static int echoCreate(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc = SQLITE_OK;
+  appendToEchoModule(((EchoModule *)pAux)->interp, "xCreate");
+  rc = echoConstructor(db, pAux, argc, argv, ppVtab, pzErr);
+
+  /* If there were two arguments passed to the module at the SQL level 
+  ** (i.e. "CREATE VIRTUAL TABLE tbl USING echo(arg1, arg2)"), then 
+  ** the second argument is used as a table name. Attempt to create
+  ** such a table with a single column, "logmsg". This table will
+  ** be used to log calls to the xUpdate method. It will be deleted
+  ** when the virtual table is DROPed.
+  **
+  ** Note: The main point of this is to test that we can drop tables
+  ** from within an xDestroy method call.
+  */
+  if( rc==SQLITE_OK && argc==5 ){
+    char *zSql;
+    echo_vtab *pVtab = *(echo_vtab **)ppVtab;
+    pVtab->zLogName = sqlite3_mprintf("%s", argv[4]);
+    zSql = sqlite3_mprintf("CREATE TABLE %Q(logmsg)", pVtab->zLogName);
+    rc = sqlite3_exec(db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+    if( rc!=SQLITE_OK ){
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }
+  }
+
+  if( *ppVtab && rc!=SQLITE_OK ){
+    echoDestructor(*ppVtab);
+    *ppVtab = 0;
+  }
+
+  if( rc==SQLITE_OK ){
+    (*(echo_vtab**)ppVtab)->inTransaction = 1;
+  }
+
+  return rc;
+}
+
+/* 
+** Echo virtual table module xConnect method.
+*/
+static int echoConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  appendToEchoModule(((EchoModule *)pAux)->interp, "xConnect");
+  return echoConstructor(db, pAux, argc, argv, ppVtab, pzErr);
+}
+
+/* 
+** Echo virtual table module xDisconnect method.
+*/
+static int echoDisconnect(sqlite3_vtab *pVtab){
+  appendToEchoModule(((echo_vtab *)pVtab)->interp, "xDisconnect");
+  return echoDestructor(pVtab);
+}
+
+/* 
+** Echo virtual table module xDestroy method.
+*/
+static int echoDestroy(sqlite3_vtab *pVtab){
+  int rc = SQLITE_OK;
+  echo_vtab *p = (echo_vtab *)pVtab;
+  appendToEchoModule(((echo_vtab *)pVtab)->interp, "xDestroy");
+
+  /* Drop the "log" table, if one exists (see echoCreate() for details) */
+  if( p && p->zLogName ){
+    char *zSql;
+    zSql = sqlite3_mprintf("DROP TABLE %Q", p->zLogName);
+    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = echoDestructor(pVtab);
+  }
+  return rc;
+}
+
+/* 
+** Echo virtual table module xOpen method.
+*/
+static int echoOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  echo_cursor *pCur;
+  if( simulateVtabError((echo_vtab *)pVTab, "xOpen") ){
+    return SQLITE_ERROR;
+  }
+  pCur = sqlite3MallocZero(sizeof(echo_cursor));
+  *ppCursor = (sqlite3_vtab_cursor *)pCur;
+  return (pCur ? SQLITE_OK : SQLITE_NOMEM);
+}
+
+/* 
+** Echo virtual table module xClose method.
+*/
+static int echoClose(sqlite3_vtab_cursor *cur){
+  int rc;
+  echo_cursor *pCur = (echo_cursor *)cur;
+  sqlite3_stmt *pStmt = pCur->pStmt;
+  pCur->pStmt = 0;
+  sqlite3_free(pCur);
+  rc = sqlite3_finalize(pStmt);
+  return rc;
+}
+
+/*
+** Return non-zero if the cursor does not currently point to a valid record
+** (i.e if the scan has finished), or zero otherwise.
+*/
+static int echoEof(sqlite3_vtab_cursor *cur){
+  return (((echo_cursor *)cur)->pStmt ? 0 : 1);
+}
+
+/* 
+** Echo virtual table module xNext method.
+*/
+static int echoNext(sqlite3_vtab_cursor *cur){
+  int rc = SQLITE_OK;
+  echo_cursor *pCur = (echo_cursor *)cur;
+
+  if( simulateVtabError((echo_vtab *)(cur->pVtab), "xNext") ){
+    return SQLITE_ERROR;
+  }
+
+  if( pCur->pStmt ){
+    rc = sqlite3_step(pCur->pStmt);
+    if( rc==SQLITE_ROW ){
+      rc = SQLITE_OK;
+    }else{
+      rc = sqlite3_finalize(pCur->pStmt);
+      pCur->pStmt = 0;
+    }
+  }
+
+  return rc;
+}
+
+/* 
+** Echo virtual table module xColumn method.
+*/
+static int echoColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  int iCol = i + 1;
+  sqlite3_stmt *pStmt = ((echo_cursor *)cur)->pStmt;
+
+  if( simulateVtabError((echo_vtab *)(cur->pVtab), "xColumn") ){
+    return SQLITE_ERROR;
+  }
+
+  if( !pStmt ){
+    sqlite3_result_null(ctx);
+  }else{
+    assert( sqlite3_data_count(pStmt)>iCol );
+    sqlite3_result_value(ctx, sqlite3_column_value(pStmt, iCol));
+  }
+  return SQLITE_OK;
+}
+
+/* 
+** Echo virtual table module xRowid method.
+*/
+static int echoRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  sqlite3_stmt *pStmt = ((echo_cursor *)cur)->pStmt;
+
+  if( simulateVtabError((echo_vtab *)(cur->pVtab), "xRowid") ){
+    return SQLITE_ERROR;
+  }
+
+  *pRowid = sqlite3_column_int64(pStmt, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Compute a simple hash of the null terminated string zString.
+**
+** This module uses only sqlite3_index_info.idxStr, not 
+** sqlite3_index_info.idxNum. So to test idxNum, when idxStr is set
+** in echoBestIndex(), idxNum is set to the corresponding hash value.
+** In echoFilter(), code assert()s that the supplied idxNum value is
+** indeed the hash of the supplied idxStr.
+*/
+static int hashString(const char *zString){
+  u32 val = 0;
+  int ii;
+  for(ii=0; zString[ii]; ii++){
+    val = (val << 3) + (int)zString[ii];
+  }
+  return (int)(val&0x7fffffff);
+}
+
+/* 
+** Echo virtual table module xFilter method.
+*/
+static int echoFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  int rc;
+  int i;
+
+  echo_cursor *pCur = (echo_cursor *)pVtabCursor;
+  echo_vtab *pVtab = (echo_vtab *)pVtabCursor->pVtab;
+  sqlite3 *db = pVtab->db;
+
+  if( simulateVtabError(pVtab, "xFilter") ){
+    return SQLITE_ERROR;
+  }
+
+  /* Check that idxNum matches idxStr */
+  assert( idxNum==hashString(idxStr) );
+
+  /* Log arguments to the ::echo_module Tcl variable */
+  appendToEchoModule(pVtab->interp, "xFilter");
+  appendToEchoModule(pVtab->interp, idxStr);
+  for(i=0; i<argc; i++){
+    appendToEchoModule(pVtab->interp, (const char*)sqlite3_value_text(argv[i]));
+  }
+
+  sqlite3_finalize(pCur->pStmt);
+  pCur->pStmt = 0;
+
+  /* Prepare the SQL statement created by echoBestIndex and bind the
+  ** runtime parameters passed to this function to it.
+  */
+  rc = sqlite3_prepare(db, idxStr, -1, &pCur->pStmt, 0);
+  assert( pCur->pStmt || rc!=SQLITE_OK );
+  for(i=0; rc==SQLITE_OK && i<argc; i++){
+    rc = sqlite3_bind_value(pCur->pStmt, i+1, argv[i]);
+  }
+
+  /* If everything was successful, advance to the first row of the scan */
+  if( rc==SQLITE_OK ){
+    rc = echoNext(pVtabCursor);
+  }
+
+  return rc;
+}
+
+
+/*
+** A helper function used by echoUpdate() and echoBestIndex() for
+** manipulating strings in concert with the sqlite3_mprintf() function.
+**
+** Parameter pzStr points to a pointer to a string allocated with
+** sqlite3_mprintf. The second parameter, zAppend, points to another
+** string. The two strings are concatenated together and *pzStr
+** set to point at the result. The initial buffer pointed to by *pzStr
+** is deallocated via sqlite3_free().
+**
+** If the third argument, doFree, is true, then sqlite3_free() is
+** also called to free the buffer pointed to by zAppend.
+*/
+static void string_concat(char **pzStr, char *zAppend, int doFree, int *pRc){
+  char *zIn = *pzStr;
+  if( !zAppend && doFree && *pRc==SQLITE_OK ){
+    *pRc = SQLITE_NOMEM;
+  }
+  if( *pRc!=SQLITE_OK ){
+    sqlite3_free(zIn);
+    zIn = 0;
+  }else{
+    if( zIn ){
+      char *zTemp = zIn;
+      zIn = sqlite3_mprintf("%s%s", zIn, zAppend);
+      sqlite3_free(zTemp);
+    }else{
+      zIn = sqlite3_mprintf("%s", zAppend);
+    }
+    if( !zIn ){
+      *pRc = SQLITE_NOMEM;
+    }
+  }
+  *pzStr = zIn;
+  if( doFree ){
+    sqlite3_free(zAppend);
+  }
+}
+
+/*
+** This function returns a pointer to an sqlite3_malloc()ed buffer 
+** containing the select-list (the thing between keywords SELECT and FROM)
+** to query the underlying real table with for the scan described by
+** argument pIdxInfo.
+**
+** If the current SQLite version is earlier than 3.10.0, this is just "*"
+** (select all columns). Or, for version 3.10.0 and greater, the list of
+** columns identified by the pIdxInfo->colUsed mask.
+*/
+static char *echoSelectList(echo_vtab *pTab, sqlite3_index_info *pIdxInfo){
+  char *zRet = 0;
+  if( sqlite3_libversion_number()<3010000 ){
+    zRet = sqlite3_mprintf(", *");
+  }else{
+    int i;
+    for(i=0; i<pTab->nCol; i++){
+      if( pIdxInfo->colUsed & ((sqlite3_uint64)1 << (i>=63 ? 63 : i)) ){
+        zRet = sqlite3_mprintf("%z, %s", zRet, pTab->aCol[i]);
+      }else{
+        zRet = sqlite3_mprintf("%z, NULL", zRet);
+      }
+      if( !zRet ) break;
+    }
+  }
+  return zRet;
+}
+
+/*
+** The echo module implements the subset of query constraints and sort
+** orders that may take advantage of SQLite indices on the underlying
+** real table. For example, if the real table is declared as:
+**
+**     CREATE TABLE real(a, b, c);
+**     CREATE INDEX real_index ON real(b);
+**
+** then the echo module handles WHERE or ORDER BY clauses that refer
+** to the column "b", but not "a" or "c". If a multi-column index is
+** present, only its left most column is considered. 
+**
+** This xBestIndex method encodes the proposed search strategy as
+** an SQL query on the real table underlying the virtual echo module 
+** table and stores the query in sqlite3_index_info.idxStr. The SQL
+** statement is of the form:
+**
+**   SELECT rowid, * FROM <real-table> ?<where-clause>? ?<order-by-clause>?
+**
+** where the <where-clause> and <order-by-clause> are determined
+** by the contents of the structure pointed to by the pIdxInfo argument.
+*/
+static int echoBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int ii;
+  char *zQuery = 0;
+  char *zCol = 0;
+  char *zNew;
+  int nArg = 0;
+  const char *zSep = "WHERE";
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  sqlite3_stmt *pStmt = 0;
+  Tcl_Interp *interp = pVtab->interp;
+
+  int nRow = 0;
+  int useIdx = 0;
+  int rc = SQLITE_OK;
+  int useCost = 0;
+  double cost = 0;
+  int isIgnoreUsable = 0;
+  if( Tcl_GetVar(interp, "echo_module_ignore_usable", TCL_GLOBAL_ONLY) ){
+    isIgnoreUsable = 1;
+  }
+
+  if( simulateVtabError(pVtab, "xBestIndex") ){
+    return SQLITE_ERROR;
+  }
+
+  /* Determine the number of rows in the table and store this value in local
+  ** variable nRow. The 'estimated-cost' of the scan will be the number of
+  ** rows in the table for a linear scan, or the log (base 2) of the 
+  ** number of rows if the proposed scan uses an index.  
+  */
+  if( Tcl_GetVar(interp, "echo_module_cost", TCL_GLOBAL_ONLY) ){
+    cost = atof(Tcl_GetVar(interp, "echo_module_cost", TCL_GLOBAL_ONLY));
+    useCost = 1;
+  } else {
+    zQuery = sqlite3_mprintf("SELECT count(*) FROM %Q", pVtab->zTableName);
+    if( !zQuery ){
+      return SQLITE_NOMEM;
+    }
+    rc = sqlite3_prepare(pVtab->db, zQuery, -1, &pStmt, 0);
+    sqlite3_free(zQuery);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    sqlite3_step(pStmt);
+    nRow = sqlite3_column_int(pStmt, 0);
+    rc = sqlite3_finalize(pStmt);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }
+
+  zCol = echoSelectList(pVtab, pIdxInfo);
+  if( !zCol ) return SQLITE_NOMEM;
+  zQuery = sqlite3_mprintf("SELECT rowid%z FROM %Q", zCol, pVtab->zTableName);
+  if( !zQuery ) return SQLITE_NOMEM;
+
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    const struct sqlite3_index_constraint *pConstraint;
+    struct sqlite3_index_constraint_usage *pUsage;
+    int iCol;
+
+    pConstraint = &pIdxInfo->aConstraint[ii];
+    pUsage = &pIdxInfo->aConstraintUsage[ii];
+
+    if( !isIgnoreUsable && !pConstraint->usable ) continue;
+
+    iCol = pConstraint->iColumn;
+    if( iCol<0 || pVtab->aIndex[iCol] ){
+      char *zNewCol = iCol>=0 ? pVtab->aCol[iCol] : "rowid";
+      char *zOp = 0;
+      useIdx = 1;
+      switch( pConstraint->op ){
+        case SQLITE_INDEX_CONSTRAINT_EQ:
+          zOp = "="; break;
+        case SQLITE_INDEX_CONSTRAINT_LT:
+          zOp = "<"; break;
+        case SQLITE_INDEX_CONSTRAINT_GT:
+          zOp = ">"; break;
+        case SQLITE_INDEX_CONSTRAINT_LE:
+          zOp = "<="; break;
+        case SQLITE_INDEX_CONSTRAINT_GE:
+          zOp = ">="; break;
+        case SQLITE_INDEX_CONSTRAINT_MATCH:
+          /* Purposely translate the MATCH operator into a LIKE, which
+          ** will be used by the next block of code to construct a new
+          ** query.  It should also be noted here that the next block
+          ** of code requires the first letter of this operator to be
+          ** in upper-case to trigger the special MATCH handling (i.e.
+          ** wrapping the bound parameter with literal '%'s).
+          */
+          zOp = "LIKE"; break;
+        case SQLITE_INDEX_CONSTRAINT_LIKE:
+          zOp = "like"; break;
+        case SQLITE_INDEX_CONSTRAINT_GLOB:
+          zOp = "glob"; break;
+        case SQLITE_INDEX_CONSTRAINT_REGEXP:
+          zOp = "regexp"; break;
+      }
+      if( zOp ){
+        if( zOp[0]=='L' ){
+          zNew = sqlite3_mprintf(" %s %s LIKE (SELECT '%%'||?||'%%')", 
+              zSep, zNewCol);
+        } else {
+          zNew = sqlite3_mprintf(" %s %s %s ?", zSep, zNewCol, zOp);
+        }
+        string_concat(&zQuery, zNew, 1, &rc);
+        zSep = "AND";
+        pUsage->argvIndex = ++nArg;
+        pUsage->omit = 1;
+      }
+    }
+  }
+
+  /* If there is only one term in the ORDER BY clause, and it is
+  ** on a column that this virtual table has an index for, then consume 
+  ** the ORDER BY clause.
+  */
+  if( pIdxInfo->nOrderBy==1 && (
+        pIdxInfo->aOrderBy->iColumn<0 ||
+        pVtab->aIndex[pIdxInfo->aOrderBy->iColumn]) ){
+    int iCol = pIdxInfo->aOrderBy->iColumn;
+    char *zNewCol = iCol>=0 ? pVtab->aCol[iCol] : "rowid";
+    char *zDir = pIdxInfo->aOrderBy->desc?"DESC":"ASC";
+    zNew = sqlite3_mprintf(" ORDER BY %s %s", zNewCol, zDir);
+    string_concat(&zQuery, zNew, 1, &rc);
+    pIdxInfo->orderByConsumed = 1;
+  }
+
+  appendToEchoModule(pVtab->interp, "xBestIndex");;
+  appendToEchoModule(pVtab->interp, zQuery);
+
+  if( !zQuery ){
+    return rc;
+  }
+  pIdxInfo->idxNum = hashString(zQuery);
+  pIdxInfo->idxStr = zQuery;
+  pIdxInfo->needToFreeIdxStr = 1;
+  if( useCost ){
+    pIdxInfo->estimatedCost = cost;
+  }else if( useIdx ){
+    /* Approximation of log2(nRow). */
+    for( ii=0; ii<(sizeof(int)*8)-1; ii++ ){
+      if( nRow & (1<<ii) ){
+        pIdxInfo->estimatedCost = (double)ii;
+      }
+    }
+  }else{
+    pIdxInfo->estimatedCost = (double)nRow;
+  }
+  return rc;
+}
+
+/*
+** The xUpdate method for echo module virtual tables.
+** 
+**    apData[0]  apData[1]  apData[2..]
+**
+**    INTEGER                              DELETE            
+**
+**    INTEGER    NULL       (nCol args)    UPDATE (do not set rowid)
+**    INTEGER    INTEGER    (nCol args)    UPDATE (with SET rowid = <arg1>)
+**
+**    NULL       NULL       (nCol args)    INSERT INTO (automatic rowid value)
+**    NULL       INTEGER    (nCol args)    INSERT (incl. rowid value)
+**
+*/
+int echoUpdate(
+  sqlite3_vtab *tab, 
+  int nData, 
+  sqlite3_value **apData, 
+  sqlite_int64 *pRowid
+){
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  sqlite3 *db = pVtab->db;
+  int rc = SQLITE_OK;
+
+  sqlite3_stmt *pStmt = 0;
+  char *z = 0;               /* SQL statement to execute */
+  int bindArgZero = 0;       /* True to bind apData[0] to sql var no. nData */
+  int bindArgOne = 0;        /* True to bind apData[1] to sql var no. 1 */
+  int i;                     /* Counter variable used by for loops */
+
+  assert( nData==pVtab->nCol+2 || nData==1 );
+
+  /* Ticket #3083 - make sure we always start a transaction prior to
+  ** making any changes to a virtual table */
+  assert( pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xUpdate") ){
+    return SQLITE_ERROR;
+  }
+
+  /* If apData[0] is an integer and nData>1 then do an UPDATE */
+  if( nData>1 && sqlite3_value_type(apData[0])==SQLITE_INTEGER ){
+    char *zSep = " SET";
+    z = sqlite3_mprintf("UPDATE %Q", pVtab->zTableName);
+    if( !z ){
+      rc = SQLITE_NOMEM;
+    }
+
+    bindArgOne = (apData[1] && sqlite3_value_type(apData[1])==SQLITE_INTEGER);
+    bindArgZero = 1;
+
+    if( bindArgOne ){
+       string_concat(&z, " SET rowid=?1 ", 0, &rc);
+       zSep = ",";
+    }
+    for(i=2; i<nData; i++){
+      if( apData[i]==0 ) continue;
+      string_concat(&z, sqlite3_mprintf(
+          "%s %Q=?%d", zSep, pVtab->aCol[i-2], i), 1, &rc);
+      zSep = ",";
+    }
+    string_concat(&z, sqlite3_mprintf(" WHERE rowid=?%d", nData), 1, &rc);
+  }
+
+  /* If apData[0] is an integer and nData==1 then do a DELETE */
+  else if( nData==1 && sqlite3_value_type(apData[0])==SQLITE_INTEGER ){
+    z = sqlite3_mprintf("DELETE FROM %Q WHERE rowid = ?1", pVtab->zTableName);
+    if( !z ){
+      rc = SQLITE_NOMEM;
+    }
+    bindArgZero = 1;
+  }
+
+  /* If the first argument is NULL and there are more than two args, INSERT */
+  else if( nData>2 && sqlite3_value_type(apData[0])==SQLITE_NULL ){
+    int ii;
+    char *zInsert = 0;
+    char *zValues = 0;
+  
+    zInsert = sqlite3_mprintf("INSERT INTO %Q (", pVtab->zTableName);
+    if( !zInsert ){
+      rc = SQLITE_NOMEM;
+    }
+    if( sqlite3_value_type(apData[1])==SQLITE_INTEGER ){
+      bindArgOne = 1;
+      zValues = sqlite3_mprintf("?");
+      string_concat(&zInsert, "rowid", 0, &rc);
+    }
+
+    assert((pVtab->nCol+2)==nData);
+    for(ii=2; ii<nData; ii++){
+      string_concat(&zInsert, 
+          sqlite3_mprintf("%s%Q", zValues?", ":"", pVtab->aCol[ii-2]), 1, &rc);
+      string_concat(&zValues, 
+          sqlite3_mprintf("%s?%d", zValues?", ":"", ii), 1, &rc);
+    }
+
+    string_concat(&z, zInsert, 1, &rc);
+    string_concat(&z, ") VALUES(", 0, &rc);
+    string_concat(&z, zValues, 1, &rc);
+    string_concat(&z, ")", 0, &rc);
+  }
+
+  /* Anything else is an error */
+  else{
+    assert(0);
+    return SQLITE_ERROR;
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_prepare(db, z, -1, &pStmt, 0);
+  }
+  assert( rc!=SQLITE_OK || pStmt );
+  sqlite3_free(z);
+  if( rc==SQLITE_OK ) {
+    if( bindArgZero ){
+      sqlite3_bind_value(pStmt, nData, apData[0]);
+    }
+    if( bindArgOne ){
+      sqlite3_bind_value(pStmt, 1, apData[1]);
+    }
+    for(i=2; i<nData && rc==SQLITE_OK; i++){
+      if( apData[i] ) rc = sqlite3_bind_value(pStmt, i, apData[i]);
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3_step(pStmt);
+      rc = sqlite3_finalize(pStmt);
+    }else{
+      sqlite3_finalize(pStmt);
+    }
+  }
+
+  if( pRowid && rc==SQLITE_OK ){
+    *pRowid = sqlite3_last_insert_rowid(db);
+  }
+  if( rc!=SQLITE_OK ){
+    tab->zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", sqlite3_errmsg(db));
+  }
+
+  return rc;
+}
+
+/*
+** xBegin, xSync, xCommit and xRollback callbacks for echo module
+** virtual tables. Do nothing other than add the name of the callback
+** to the $::echo_module Tcl variable.
+*/
+static int echoTransactionCall(sqlite3_vtab *tab, const char *zCall){
+  char *z;
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  z = sqlite3_mprintf("echo(%s)", pVtab->zTableName);
+  if( z==0 ) return SQLITE_NOMEM;
+  appendToEchoModule(pVtab->interp, zCall);
+  appendToEchoModule(pVtab->interp, z);
+  sqlite3_free(z);
+  return SQLITE_OK;
+}
+static int echoBegin(sqlite3_vtab *tab){
+  int rc;
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  Tcl_Interp *interp = pVtab->interp;
+  const char *zVal; 
+
+  /* Ticket #3083 - do not start a transaction if we are already in
+  ** a transaction */
+  assert( !pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xBegin") ){
+    return SQLITE_ERROR;
+  }
+
+  rc = echoTransactionCall(tab, "xBegin");
+
+  if( rc==SQLITE_OK ){
+    /* Check if the $::echo_module_begin_fail variable is defined. If it is,
+    ** and it is set to the name of the real table underlying this virtual
+    ** echo module table, then cause this xSync operation to fail.
+    */
+    zVal = Tcl_GetVar(interp, "echo_module_begin_fail", TCL_GLOBAL_ONLY);
+    if( zVal && 0==strcmp(zVal, pVtab->zTableName) ){
+      rc = SQLITE_ERROR;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    pVtab->inTransaction = 1;
+  }
+  return rc;
+}
+static int echoSync(sqlite3_vtab *tab){
+  int rc;
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  Tcl_Interp *interp = pVtab->interp;
+  const char *zVal; 
+
+  /* Ticket #3083 - Only call xSync if we have previously started a
+  ** transaction */
+  assert( pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xSync") ){
+    return SQLITE_ERROR;
+  }
+
+  rc = echoTransactionCall(tab, "xSync");
+
+  if( rc==SQLITE_OK ){
+    /* Check if the $::echo_module_sync_fail variable is defined. If it is,
+    ** and it is set to the name of the real table underlying this virtual
+    ** echo module table, then cause this xSync operation to fail.
+    */
+    zVal = Tcl_GetVar(interp, "echo_module_sync_fail", TCL_GLOBAL_ONLY);
+    if( zVal && 0==strcmp(zVal, pVtab->zTableName) ){
+      rc = -1;
+    }
+  }
+  return rc;
+}
+static int echoCommit(sqlite3_vtab *tab){
+  echo_vtab *pVtab = (echo_vtab*)tab;
+  int rc;
+
+  /* Ticket #3083 - Only call xCommit if we have previously started
+  ** a transaction */
+  assert( pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xCommit") ){
+    return SQLITE_ERROR;
+  }
+
+  sqlite3BeginBenignMalloc();
+  rc = echoTransactionCall(tab, "xCommit");
+  sqlite3EndBenignMalloc();
+  pVtab->inTransaction = 0;
+  return rc;
+}
+static int echoRollback(sqlite3_vtab *tab){
+  int rc;
+  echo_vtab *pVtab = (echo_vtab*)tab;
+
+  /* Ticket #3083 - Only call xRollback if we have previously started
+  ** a transaction */
+  assert( pVtab->inTransaction );
+
+  rc = echoTransactionCall(tab, "xRollback");
+  pVtab->inTransaction = 0;
+  return rc;
+}
+
+/*
+** Implementation of "GLOB" function on the echo module.  Pass
+** all arguments to the ::echo_glob_overload procedure of TCL
+** and return the result of that procedure as a string.
+*/
+static void overloadedGlobFunction(
+  sqlite3_context *pContext,
+  int nArg,
+  sqlite3_value **apArg
+){
+  Tcl_Interp *interp = sqlite3_user_data(pContext);
+  Tcl_DString str;
+  int i;
+  int rc;
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppendElement(&str, "::echo_glob_overload");
+  for(i=0; i<nArg; i++){
+    Tcl_DStringAppendElement(&str, (char*)sqlite3_value_text(apArg[i]));
+  }
+  rc = Tcl_Eval(interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  if( rc ){
+    sqlite3_result_error(pContext, Tcl_GetStringResult(interp), -1);
+  }else{
+    sqlite3_result_text(pContext, Tcl_GetStringResult(interp),
+                        -1, SQLITE_TRANSIENT);
+  }
+  Tcl_ResetResult(interp);
+}
+
+/*
+** This is the xFindFunction implementation for the echo module.
+** SQLite calls this routine when the first argument of a function
+** is a column of an echo virtual table.  This routine can optionally
+** override the implementation of that function.  It will choose to
+** do so if the function is named "glob", and a TCL command named
+** ::echo_glob_overload exists.
+*/
+static int echoFindFunction(
+  sqlite3_vtab *vtab,
+  int nArg,
+  const char *zFuncName,
+  void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
+  void **ppArg
+){
+  echo_vtab *pVtab = (echo_vtab *)vtab;
+  Tcl_Interp *interp = pVtab->interp;
+  Tcl_CmdInfo info;
+  if( strcmp(zFuncName,"glob")!=0 ){
+    return 0;
+  }
+  if( Tcl_GetCommandInfo(interp, "::echo_glob_overload", &info)==0 ){
+    return 0;
+  }
+  *pxFunc = overloadedGlobFunction;
+  *ppArg = interp;
+  return 1;
+}
+
+static int echoRename(sqlite3_vtab *vtab, const char *zNewName){
+  int rc = SQLITE_OK;
+  echo_vtab *p = (echo_vtab *)vtab;
+
+  if( simulateVtabError(p, "xRename") ){
+    return SQLITE_ERROR;
+  }
+
+  if( p->isPattern ){
+    int nThis = (int)strlen(p->zThis);
+    char *zSql = sqlite3_mprintf("ALTER TABLE %s RENAME TO %s%s", 
+        p->zTableName, zNewName, &p->zTableName[nThis]
+    );
+    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+
+  return rc;
+}
+
+static int echoSavepoint(sqlite3_vtab *pVTab, int iSavepoint){
+  assert( pVTab );
+  return SQLITE_OK;
+}
+
+static int echoRelease(sqlite3_vtab *pVTab, int iSavepoint){
+  assert( pVTab );
+  return SQLITE_OK;
+}
+
+static int echoRollbackTo(sqlite3_vtab *pVTab, int iSavepoint){
+  assert( pVTab );
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that merely "echos" the contents of another
+** table (like an SQL VIEW).
+*/
+static sqlite3_module echoModule = {
+  1,                         /* iVersion */
+  echoCreate,
+  echoConnect,
+  echoBestIndex,
+  echoDisconnect, 
+  echoDestroy,
+  echoOpen,                  /* xOpen - open a cursor */
+  echoClose,                 /* xClose - close a cursor */
+  echoFilter,                /* xFilter - configure scan constraints */
+  echoNext,                  /* xNext - advance a cursor */
+  echoEof,                   /* xEof */
+  echoColumn,                /* xColumn - read data */
+  echoRowid,                 /* xRowid - read data */
+  echoUpdate,                /* xUpdate - write data */
+  echoBegin,                 /* xBegin - begin transaction */
+  echoSync,                  /* xSync - sync transaction */
+  echoCommit,                /* xCommit - commit transaction */
+  echoRollback,              /* xRollback - rollback transaction */
+  echoFindFunction,          /* xFindFunction - function overloading */
+  echoRename,                /* xRename - rename the table */
+  0,                         /* xSavepoint */
+  0,                         /* xRelease */
+  0,                         /* xRollbackTo */
+  0,                         /* xShadowName */
+  0                          /* xIntegrity */
+};
+
+static sqlite3_module echoModuleV2 = {
+  2,                         /* iVersion */
+  echoCreate,
+  echoConnect,
+  echoBestIndex,
+  echoDisconnect, 
+  echoDestroy,
+  echoOpen,                  /* xOpen - open a cursor */
+  echoClose,                 /* xClose - close a cursor */
+  echoFilter,                /* xFilter - configure scan constraints */
+  echoNext,                  /* xNext - advance a cursor */
+  echoEof,                   /* xEof */
+  echoColumn,                /* xColumn - read data */
+  echoRowid,                 /* xRowid - read data */
+  echoUpdate,                /* xUpdate - write data */
+  echoBegin,                 /* xBegin - begin transaction */
+  echoSync,                  /* xSync - sync transaction */
+  echoCommit,                /* xCommit - commit transaction */
+  echoRollback,              /* xRollback - rollback transaction */
+  echoFindFunction,          /* xFindFunction - function overloading */
+  echoRename,                /* xRename - rename the table */
+  echoSavepoint,
+  echoRelease,
+  echoRollbackTo,
+  0,                         /* xShadowName */
+  0                          /* xIntegrity  */
+};
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+extern const char *sqlite3ErrName(int);
+
+static void moduleDestroy(void *p){
+  EchoModule *pMod = (EchoModule*)p;
+  sqlite3_create_function(pMod->db, "function_that_does_not_exist_0982ma98",
+                          SQLITE_ANY, 1, 0, 0, 0, 0);
+  sqlite3_free(p);
+}
+
+/*
+** Register the echo virtual table module.
+*/
+static int SQLITE_TCLAPI register_echo_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int rc;
+  sqlite3 *db;
+  EchoModule *pMod;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  /* Virtual table module "echo" */
+  pMod = sqlite3_malloc(sizeof(EchoModule));
+  pMod->interp = interp;
+  pMod->db = db;
+  rc = sqlite3_create_module_v2(
+      db, "echo", &echoModule, (void*)pMod, moduleDestroy
+  );
+
+  /* Virtual table module "echo_v2" */
+  if( rc==SQLITE_OK ){
+    pMod = sqlite3_malloc(sizeof(EchoModule));
+    pMod->interp = interp;
+    pMod->db = db;
+    rc = sqlite3_create_module_v2(db, "echo_v2", 
+        &echoModuleV2, (void*)pMod, moduleDestroy
+    );
+  }
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Tcl interface to sqlite3_declare_vtab, invoked as follows from Tcl:
+**
+** sqlite3_declare_vtab DB SQL
+*/
+static int SQLITE_TCLAPI declare_vtab(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB SQL");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_declare_vtab(db, Tcl_GetString(objv[2]));
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3_errmsg(db), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest8_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_echo_module",       register_echo_module, 0 },
+     { "sqlite3_declare_vtab",       declare_vtab, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+#endif
+  return TCL_OK;
+}
diff --git a/src/test9.c b/src/test9.c
new file mode 100644
index 0000000..5b139e8
--- /dev/null
+++ b/src/test9.c
@@ -0,0 +1,204 @@
+/*
+** 2007 March 29
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains obscure tests of the C-interface required
+** for completeness. Test code is written in C for these cases
+** as there is not much point in binding to Tcl.
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** c_collation_test
+*/
+static int SQLITE_TCLAPI c_collation_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  const char *zErrFunction = "N/A";
+  sqlite3 *db;
+
+  int rc;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  /* Open a database. */
+  rc = sqlite3_open(":memory:", &db);
+  if( rc!=SQLITE_OK ){
+    zErrFunction = "sqlite3_open";
+    goto error_out;
+  }
+
+  rc = sqlite3_create_collation(db, "collate", 456, 0, 0);
+  if( rc!=SQLITE_MISUSE ){
+    sqlite3_close(db);
+    zErrFunction = "sqlite3_create_collation";
+    goto error_out;
+  }
+
+  sqlite3_close(db);
+  return TCL_OK;
+
+error_out:
+  Tcl_ResetResult(interp);
+  Tcl_AppendResult(interp, "Error testing function: ", zErrFunction, 0);
+  return TCL_ERROR;
+}
+
+/*
+** c_realloc_test
+*/
+static int SQLITE_TCLAPI c_realloc_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  void *p;
+  const char *zErrFunction = "N/A";
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  p = sqlite3_malloc(5);
+  if( !p ){
+    zErrFunction = "sqlite3_malloc";
+    goto error_out;
+  }
+
+  /* Test that realloc()ing a block of memory to a negative size is
+  ** the same as free()ing that memory.
+  */
+  p = sqlite3_realloc(p, -1);
+  if( p ){
+    zErrFunction = "sqlite3_realloc";
+    goto error_out;
+  }
+
+  return TCL_OK;
+
+error_out:
+  Tcl_ResetResult(interp);
+  Tcl_AppendResult(interp, "Error testing function: ", zErrFunction, 0);
+  return TCL_ERROR;
+}
+
+
+/*
+** c_misuse_test
+*/
+static int SQLITE_TCLAPI c_misuse_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  const char *zErrFunction = "N/A";
+  sqlite3 *db = 0;
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  /* Open a database. Then close it again. We need to do this so that
+  ** we have a "closed database handle" to pass to various API functions.
+  */
+  rc = sqlite3_open(":memory:", &db);
+  if( rc!=SQLITE_OK ){
+    zErrFunction = "sqlite3_open";
+    goto error_out;
+  }
+  sqlite3_close(db);
+
+
+  rc = sqlite3_errcode(db);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_errcode";
+    goto error_out;
+  }
+
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare";
+    goto error_out;
+  }
+  assert( pStmt==0 ); /* Verify that pStmt is zeroed even on a MISUSE error */
+
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare_v2(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare_v2";
+    goto error_out;
+  }
+  assert( pStmt==0 );
+
+#ifndef SQLITE_OMIT_UTF16
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare16(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare16";
+    goto error_out;
+  }
+  assert( pStmt==0 );
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare16_v2(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare16_v2";
+    goto error_out;
+  }
+  assert( pStmt==0 );
+#endif
+
+  return TCL_OK;
+
+error_out:
+  Tcl_ResetResult(interp);
+  Tcl_AppendResult(interp, "Error testing function: ", zErrFunction, 0);
+  return TCL_ERROR;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest9_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "c_misuse_test",    c_misuse_test, 0 },
+     { "c_realloc_test",   c_realloc_test, 0 },
+     { "c_collation_test", c_collation_test, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
diff --git a/src/test_async.c b/src/test_async.c
new file mode 100644
index 0000000..c32c74c
--- /dev/null
+++ b/src/test_async.c
@@ -0,0 +1,248 @@
+/*
+** 2005 December 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a binding of the asynchronous IO extension interface
+** (defined in ext/async/sqlite3async.h) to Tcl.
+*/
+
+#define TCL_THREADS 
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+
+#ifdef SQLITE_ENABLE_ASYNCIO
+
+#include "sqlite3async.h"
+#include "sqlite3.h"
+#include <assert.h>
+
+/* From main.c */
+extern const char *sqlite3ErrName(int);
+
+
+struct TestAsyncGlobal {
+  int isInstalled;                     /* True when async VFS is installed */
+} testasync_g = { 0 };
+
+TCL_DECLARE_MUTEX(testasync_g_writerMutex);
+
+/*
+** sqlite3async_initialize PARENT-VFS ISDEFAULT
+*/
+static int SQLITE_TCLAPI testAsyncInit(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zParent;
+  int isDefault;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PARENT-VFS ISDEFAULT");
+    return TCL_ERROR;
+  }
+  zParent = Tcl_GetString(objv[1]);
+  if( !*zParent ) {
+    zParent = 0;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &isDefault) ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3async_initialize(zParent, isDefault);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** sqlite3async_shutdown
+*/
+static int SQLITE_TCLAPI testAsyncShutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3async_shutdown();
+  return TCL_OK;
+}
+
+static Tcl_ThreadCreateType tclWriterThread(ClientData pIsStarted){
+  Tcl_MutexLock(&testasync_g_writerMutex);
+  *((int *)pIsStarted) = 1;
+  sqlite3async_run();
+  Tcl_MutexUnlock(&testasync_g_writerMutex);
+  Tcl_ExitThread(0);
+  TCL_THREAD_CREATE_RETURN;
+}
+
+/*
+** sqlite3async_start
+**
+** Start a new writer thread.
+*/
+static int SQLITE_TCLAPI testAsyncStart(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  volatile int isStarted = 0;
+  ClientData threadData = (ClientData)&isStarted;
+
+  Tcl_ThreadId x;
+  const int nStack = TCL_THREAD_STACK_DEFAULT;
+  const int flags = TCL_THREAD_NOFLAGS;
+  int rc;
+
+  rc = Tcl_CreateThread(&x, tclWriterThread, threadData, nStack, flags);
+  if( rc!=TCL_OK ){
+    Tcl_AppendResult(interp, "Tcl_CreateThread() failed", 0);
+    return TCL_ERROR;
+  }
+
+  while( isStarted==0 ) { /* Busy loop */ }
+  return TCL_OK;
+}
+
+/*
+** sqlite3async_wait
+**
+** Wait for the current writer thread to terminate.
+**
+** If the current writer thread is set to run forever then this
+** command would block forever.  To prevent that, an error is returned. 
+*/
+static int SQLITE_TCLAPI testAsyncWait(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int eCond;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  sqlite3async_control(SQLITEASYNC_GET_HALT, &eCond);
+  if( eCond==SQLITEASYNC_HALT_NEVER ){
+    Tcl_AppendResult(interp, "would block forever", (char*)0);
+    return TCL_ERROR;
+  }
+
+  Tcl_MutexLock(&testasync_g_writerMutex);
+  Tcl_MutexUnlock(&testasync_g_writerMutex);
+  return TCL_OK;
+}
+
+/*
+** sqlite3async_control OPTION ?VALUE?
+*/
+static int SQLITE_TCLAPI testAsyncControl(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = SQLITE_OK;
+  int aeOpt[] = { SQLITEASYNC_HALT, SQLITEASYNC_DELAY, SQLITEASYNC_LOCKFILES };
+  const char *azOpt[] = { "halt", "delay", "lockfiles", 0 };
+  const char *az[] = { "never", "now", "idle", 0 };
+  int iVal;
+  int eOpt;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "OPTION ?VALUE?");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], azOpt, "option", 0, &eOpt) ){
+    return TCL_ERROR;
+  }
+  eOpt = aeOpt[eOpt];
+
+  if( objc==3 ){
+    switch( eOpt ){
+      case SQLITEASYNC_HALT: {
+        assert( SQLITEASYNC_HALT_NEVER==0 );
+        assert( SQLITEASYNC_HALT_NOW==1 );
+        assert( SQLITEASYNC_HALT_IDLE==2 );
+        if( Tcl_GetIndexFromObj(interp, objv[2], az, "value", 0, &iVal) ){
+          return TCL_ERROR;
+        }
+        break;
+      }
+      case SQLITEASYNC_DELAY:
+        if( Tcl_GetIntFromObj(interp, objv[2], &iVal) ){
+          return TCL_ERROR;
+        }
+        break;
+
+      case SQLITEASYNC_LOCKFILES:
+        if( Tcl_GetBooleanFromObj(interp, objv[2], &iVal) ){
+          return TCL_ERROR;
+        }
+        break;
+    }
+
+    rc = sqlite3async_control(eOpt, iVal);
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = sqlite3async_control(
+        eOpt==SQLITEASYNC_HALT ? SQLITEASYNC_GET_HALT :
+        eOpt==SQLITEASYNC_DELAY ? SQLITEASYNC_GET_DELAY :
+        SQLITEASYNC_GET_LOCKFILES, &iVal);
+  }
+
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+
+  if( eOpt==SQLITEASYNC_HALT ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(az[iVal], -1));
+  }else{
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(iVal));
+  }
+
+  return TCL_OK;
+}
+
+#endif  /* SQLITE_ENABLE_ASYNCIO */
+
+/*
+** This routine registers the custom TCL commands defined in this
+** module.  This should be the only procedure visible from outside
+** of this module.
+*/
+int Sqlitetestasync_Init(Tcl_Interp *interp){
+#ifdef SQLITE_ENABLE_ASYNCIO
+  Tcl_CreateObjCommand(interp,"sqlite3async_start",testAsyncStart,0,0);
+  Tcl_CreateObjCommand(interp,"sqlite3async_wait",testAsyncWait,0,0);
+
+  Tcl_CreateObjCommand(interp,"sqlite3async_control",testAsyncControl,0,0);
+  Tcl_CreateObjCommand(interp,"sqlite3async_initialize",testAsyncInit,0,0);
+  Tcl_CreateObjCommand(interp,"sqlite3async_shutdown",testAsyncShutdown,0,0);
+#endif  /* SQLITE_ENABLE_ASYNCIO */
+  return TCL_OK;
+}
diff --git a/src/test_autoext.c b/src/test_autoext.c
new file mode 100644
index 0000000..e23e41a
--- /dev/null
+++ b/src/test_autoext.c
@@ -0,0 +1,228 @@
+/*
+** 2006 August 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Test extension for testing the sqlite3_auto_extension() function.
+*/
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+#include "sqlite3ext.h"
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+SQLITE_EXTENSION_INIT1
+
+/*
+** The sqr() SQL function returns the square of its input value.
+*/
+static void sqrFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  double r = sqlite3_value_double(argv[0]);
+  sqlite3_result_double(context, r*r);
+}
+
+/*
+** This is the entry point to register the extension for the sqr() function.
+*/
+static int sqr_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi);
+  sqlite3_create_function(db, "sqr", 1, SQLITE_ANY, 0, sqrFunc, 0, 0);
+  return 0;
+}
+
+/*
+** The cube() SQL function returns the cube of its input value.
+*/
+static void cubeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  double r = sqlite3_value_double(argv[0]);
+  sqlite3_result_double(context, r*r*r);
+}
+
+/*
+** This is the entry point to register the extension for the cube() function.
+*/
+static int cube_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi);
+  sqlite3_create_function(db, "cube", 1, SQLITE_ANY, 0, cubeFunc, 0, 0);
+  return 0;
+}
+
+/*
+** This is a broken extension entry point
+*/
+static int broken_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  char *zErr;
+  SQLITE_EXTENSION_INIT2(pApi);
+  zErr = sqlite3_mprintf("broken autoext!");
+  *pzErrMsg = zErr;
+  return 1;
+}
+
+/*
+** tclcmd:   sqlite3_auto_extension_sqr
+**
+** Register the "sqr" extension to be loaded automatically.
+*/
+static int SQLITE_TCLAPI autoExtSqrObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_auto_extension((void(*)(void))sqr_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** tclcmd:   sqlite3_cancel_auto_extension_sqr
+**
+** Unregister the "sqr" extension.
+*/
+static int SQLITE_TCLAPI cancelAutoExtSqrObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_cancel_auto_extension((void(*)(void))sqr_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** tclcmd:   sqlite3_auto_extension_cube
+**
+** Register the "cube" extension to be loaded automatically.
+*/
+static int SQLITE_TCLAPI autoExtCubeObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_auto_extension((void(*)(void))cube_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** tclcmd:   sqlite3_cancel_auto_extension_cube
+**
+** Unregister the "cube" extension.
+*/
+static int SQLITE_TCLAPI cancelAutoExtCubeObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_cancel_auto_extension((void(*)(void))cube_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** tclcmd:   sqlite3_auto_extension_broken
+**
+** Register the broken extension to be loaded automatically.
+*/
+static int SQLITE_TCLAPI autoExtBrokenObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_auto_extension((void(*)(void))broken_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** tclcmd:   sqlite3_cancel_auto_extension_broken
+**
+** Unregister the broken extension.
+*/
+static int SQLITE_TCLAPI cancelAutoExtBrokenObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_cancel_auto_extension((void(*)(void))broken_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+
+
+/*
+** tclcmd:   sqlite3_reset_auto_extension
+**
+** Reset all auto-extensions
+*/
+static int SQLITE_TCLAPI resetAutoExtObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_reset_auto_extension();
+  return SQLITE_OK;
+}
+
+
+/*
+** This procedure registers the TCL procs defined in this file.
+*/
+int Sqlitetest_autoext_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  Tcl_CreateObjCommand(interp, "sqlite3_auto_extension_sqr",
+          autoExtSqrObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_auto_extension_cube",
+          autoExtCubeObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_auto_extension_broken",
+          autoExtBrokenObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_cancel_auto_extension_sqr",
+          cancelAutoExtSqrObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_cancel_auto_extension_cube",
+          cancelAutoExtCubeObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_cancel_auto_extension_broken",
+          cancelAutoExtBrokenObjCmd, 0, 0);
+#endif
+  Tcl_CreateObjCommand(interp, "sqlite3_reset_auto_extension",
+          resetAutoExtObjCmd, 0, 0);
+  return TCL_OK;
+}
diff --git a/src/test_backup.c b/src/test_backup.c
new file mode 100644
index 0000000..9b684a2
--- /dev/null
+++ b/src/test_backup.c
@@ -0,0 +1,157 @@
+/*
+** 2009 January 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains test logic for the sqlite3_backup() interface.
+**
+*/
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+#include "sqlite3.h"
+#include <assert.h>
+
+/* These functions are implemented in main.c. */
+extern const char *sqlite3ErrName(int);
+
+/* These functions are implemented in test1.c. */
+extern int getDbPointer(Tcl_Interp *, const char *, sqlite3 **);
+
+static int SQLITE_TCLAPI backupTestCmd(
+  ClientData clientData, 
+  Tcl_Interp *interp, 
+  int objc,
+  Tcl_Obj *const*objv
+){
+  enum BackupSubCommandEnum {
+    BACKUP_STEP, BACKUP_FINISH, BACKUP_REMAINING, BACKUP_PAGECOUNT
+  };
+  struct BackupSubCommand {
+    const char *zCmd;
+    enum BackupSubCommandEnum eCmd;
+    int nArg;
+    const char *zArg;
+  } aSub[] = {
+    {"step",      BACKUP_STEP      , 1, "npage" },
+    {"finish",    BACKUP_FINISH    , 0, ""      },
+    {"remaining", BACKUP_REMAINING , 0, ""      },
+    {"pagecount", BACKUP_PAGECOUNT , 0, ""      },
+    {0, 0, 0, 0}
+  };
+
+  sqlite3_backup *p = (sqlite3_backup *)clientData;
+  int iCmd;
+  int rc;
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[1], aSub, sizeof(aSub[0]), "option", 0, &iCmd
+  );
+  if( rc!=TCL_OK ){
+    return rc;
+  }
+  if( objc!=(2 + aSub[iCmd].nArg) ){
+    Tcl_WrongNumArgs(interp, 2, objv, aSub[iCmd].zArg);
+    return TCL_ERROR;
+  }
+
+  switch( aSub[iCmd].eCmd ){
+
+    case BACKUP_FINISH: {
+      const char *zCmdName;
+      Tcl_CmdInfo cmdInfo;
+      zCmdName = Tcl_GetString(objv[0]);
+      Tcl_GetCommandInfo(interp, zCmdName, &cmdInfo);
+      cmdInfo.deleteProc = 0;
+      Tcl_SetCommandInfo(interp, zCmdName, &cmdInfo);
+      Tcl_DeleteCommand(interp, zCmdName);
+
+      rc = sqlite3_backup_finish(p);
+      Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+      break;
+    }
+
+    case BACKUP_STEP: {
+      int nPage;
+      if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &nPage) ){
+        return TCL_ERROR;
+      }
+      rc = sqlite3_backup_step(p, nPage);
+      Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+      break;
+    }
+
+    case BACKUP_REMAINING:
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_backup_remaining(p)));
+      break;
+
+    case BACKUP_PAGECOUNT:
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_backup_pagecount(p)));
+      break;
+  }
+
+  return TCL_OK;
+}
+
+static void SQLITE_TCLAPI backupTestFinish(ClientData clientData){
+  sqlite3_backup *pBackup = (sqlite3_backup *)clientData;
+  sqlite3_backup_finish(pBackup);
+}
+
+/*
+**     sqlite3_backup CMDNAME DESTHANDLE DESTNAME SRCHANDLE SRCNAME
+**
+*/
+static int SQLITE_TCLAPI backupTestInit(
+  ClientData clientData, 
+  Tcl_Interp *interp, 
+  int objc,
+  Tcl_Obj *const*objv
+){
+  sqlite3_backup *pBackup;
+  sqlite3 *pDestDb;
+  sqlite3 *pSrcDb;
+  const char *zDestName;
+  const char *zSrcName;
+  const char *zCmd;
+
+  if( objc!=6 ){
+    Tcl_WrongNumArgs(
+      interp, 1, objv, "CMDNAME DESTHANDLE DESTNAME SRCHANDLE SRCNAME"
+    );
+    return TCL_ERROR;
+  }
+
+  zCmd = Tcl_GetString(objv[1]);
+  getDbPointer(interp, Tcl_GetString(objv[2]), &pDestDb);
+  zDestName = Tcl_GetString(objv[3]);
+  getDbPointer(interp, Tcl_GetString(objv[4]), &pSrcDb);
+  zSrcName = Tcl_GetString(objv[5]);
+
+  pBackup = sqlite3_backup_init(pDestDb, zDestName, pSrcDb, zSrcName);
+  if( !pBackup ){
+    Tcl_AppendResult(interp, "sqlite3_backup_init() failed", 0);
+    return TCL_ERROR;
+  }
+
+  Tcl_CreateObjCommand(interp, zCmd, backupTestCmd, pBackup, backupTestFinish);
+  Tcl_SetObjResult(interp, objv[1]);
+  return TCL_OK;
+}
+
+int Sqlitetestbackup_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "sqlite3_backup", backupTestInit, 0, 0);
+  return TCL_OK;
+}
diff --git a/src/test_bestindex.c b/src/test_bestindex.c
new file mode 100644
index 0000000..8128530
--- /dev/null
+++ b/src/test_bestindex.c
@@ -0,0 +1,872 @@
+/*
+** 2016-03-01
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table xBestIndex method and the query
+** planner.
+*/
+
+
+/*
+** INSTRUCTIONS
+**
+** This module exports a single tcl command - [register_tcl_module]. When
+** invoked, it registers a special virtual table module with a database
+** connection.
+**
+** The virtual table is currently read-only. And always returns zero rows.
+** It is created with a single argument - the name of a Tcl command - as
+** follows:
+**
+**   CREATE VIRTUAL TABLE x1 USING tcl(tcl_command);
+**
+** The command [tcl_command] is invoked when the table is first created (or
+** connected), when the xBestIndex() method is invoked and when the xFilter()
+** method is called. When it is created (or connected), it is invoked as
+** follows:
+**
+**   tcl_command xConnect
+**
+** In this case the return value of the script is passed to the
+** sqlite3_declare_vtab() function to create the virtual table schema.
+**
+** When the xBestIndex() method is called by SQLite, the Tcl command is
+** invoked as:
+**
+**   tcl_command xBestIndex CONSTRAINTS ORDERBY MASK
+**
+** where CONSTRAINTS is a tcl representation of the aConstraints[] array,
+** ORDERBY is a representation of the contents of the aOrderBy[] array and
+** MASK is a copy of sqlite3_index_info.colUsed. For example if the virtual
+** table is declared as:
+**
+**   CREATE TABLE x1(a, b, c)
+**
+** and the query is:
+**
+**   SELECT * FROM x1 WHERE a=? AND c<? ORDER BY b, c;
+**
+** then the Tcl command is:
+**
+**   tcl_command xBestIndex                                  \
+**     {{op eq column 0 usable 1} {op lt column 2 usable 1}} \
+**     {{column 1 desc 0} {column 2 desc 0}}                 \
+**     7
+**
+** The return value of the script is a list of key-value pairs used to
+** populate the output fields of the sqlite3_index_info structure. Possible
+** keys and the usage of the accompanying values are:
+** 
+**   "orderby"          (value of orderByConsumed flag)
+**   "cost"             (value of estimatedCost field)
+**   "rows"             (value of estimatedRows field)
+**   "use"              (index of used constraint in aConstraint[])
+**   "omit"             (like "use", but also sets omit flag)
+**   "idxnum"           (value of idxNum field)
+**   "idxstr"           (value of idxStr field)
+**
+** Refer to code below for further details.
+**
+** When SQLite calls the xFilter() method, this module invokes the following
+** Tcl script:
+**
+**   tcl_command xFilter IDXNUM IDXSTR ARGLIST
+**
+** IDXNUM and IDXSTR are the values of the idxNum and idxStr parameters
+** passed to xFilter. ARGLIST is a Tcl list containing each of the arguments
+** passed to xFilter in text form.
+**
+** As with xBestIndex(), the return value of the script is interpreted as a
+** list of key-value pairs. There is currently only one key defined - "sql".
+** The value must be the full text of an SQL statement that returns the data
+** for the current scan. The leftmost column returned by the SELECT is assumed
+** to contain the rowid. Other columns must follow, in order from left to
+** right.
+*/
+
+
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+
+typedef struct tcl_vtab tcl_vtab;
+typedef struct tcl_cursor tcl_cursor;
+typedef struct TestFindFunction TestFindFunction;
+
+/* 
+** A fs virtual-table object 
+*/
+struct tcl_vtab {
+  sqlite3_vtab base;
+  Tcl_Interp *interp;
+  Tcl_Obj *pCmd;
+  TestFindFunction *pFindFunctionList;
+  sqlite3 *db;
+};
+
+/* A tcl cursor object */
+struct tcl_cursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pStmt;            /* Read data from here */
+};
+
+struct TestFindFunction {
+  tcl_vtab *pTab;
+  const char *zName;
+  TestFindFunction *pNext;
+};
+
+
+/*
+** Dequote string z in place.
+*/
+static void tclDequote(char *z){
+  char q = z[0];
+
+  /* Set stack variable q to the close-quote character */
+  if( q=='[' || q=='\'' || q=='"' || q=='`' ){
+    int iIn = 1;
+    int iOut = 0;
+    if( q=='[' ) q = ']';  
+
+    while( ALWAYS(z[iIn]) ){
+      if( z[iIn]==q ){
+        if( z[iIn+1]!=q ){
+          /* Character iIn was the close quote. */
+          iIn++;
+          break;
+        }else{
+          /* Character iIn and iIn+1 form an escaped quote character. Skip
+          ** the input cursor past both and copy a single quote character 
+          ** to the output buffer. */
+          iIn += 2;
+          z[iOut++] = q;
+        }
+      }else{
+        z[iOut++] = z[iIn++];
+      }
+    }
+
+    z[iOut] = '\0';
+  }
+}
+
+/*
+** This function is the implementation of both the xConnect and xCreate
+** methods of the fs virtual table.
+**
+** The argv[] array contains the following:
+**
+**   argv[0]   -> module name  ("fs")
+**   argv[1]   -> database name
+**   argv[2]   -> table name
+**   argv[...] -> other module argument fields.
+*/
+static int tclConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  Tcl_Interp *interp = (Tcl_Interp*)pAux;
+  tcl_vtab *pTab = 0;
+  char *zCmd = 0;
+  Tcl_Obj *pScript = 0;
+  int rc = SQLITE_OK;
+
+  if( argc!=4 ){
+    *pzErr = sqlite3_mprintf("wrong number of arguments");
+    return SQLITE_ERROR;
+  }
+
+  zCmd = sqlite3_malloc64(strlen(argv[3])+1);
+  pTab = (tcl_vtab*)sqlite3_malloc64(sizeof(tcl_vtab));
+  if( zCmd && pTab ){
+    memcpy(zCmd, argv[3], strlen(argv[3])+1);
+    tclDequote(zCmd);
+    memset(pTab, 0, sizeof(tcl_vtab));
+
+    pTab->pCmd = Tcl_NewStringObj(zCmd, -1);
+    pTab->interp = interp;
+    pTab->db = db;
+    Tcl_IncrRefCount(pTab->pCmd);
+
+    pScript = Tcl_DuplicateObj(pTab->pCmd);
+    Tcl_IncrRefCount(pScript);
+    Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("xConnect", -1));
+
+    rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
+    if( rc!=TCL_OK ){
+      *pzErr = sqlite3_mprintf("%s", Tcl_GetStringResult(interp));
+      rc = SQLITE_ERROR;
+    }else{
+      rc = sqlite3_declare_vtab(db, Tcl_GetStringResult(interp));
+    }
+
+    if( rc!=SQLITE_OK ){
+      sqlite3_free(pTab);
+      pTab = 0;
+    }
+  }else{
+    rc = SQLITE_NOMEM;
+  }
+
+  sqlite3_free(zCmd);
+  *ppVtab = &pTab->base;
+  return rc;
+}
+
+/* The xDisconnect and xDestroy methods are also the same */
+static int tclDisconnect(sqlite3_vtab *pVtab){
+  tcl_vtab *pTab = (tcl_vtab*)pVtab;
+  while( pTab->pFindFunctionList ){
+    TestFindFunction *p = pTab->pFindFunctionList;
+    pTab->pFindFunctionList = p->pNext;
+    sqlite3_free(p);
+  }
+  Tcl_DecrRefCount(pTab->pCmd);
+  sqlite3_free(pTab);
+  return SQLITE_OK;
+}
+
+/*
+** Open a new tcl cursor.
+*/
+static int tclOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  tcl_cursor *pCur;
+  pCur = sqlite3_malloc(sizeof(tcl_cursor));
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(tcl_cursor));
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a tcl cursor.
+*/
+static int tclClose(sqlite3_vtab_cursor *cur){
+  tcl_cursor *pCur = (tcl_cursor *)cur;
+  if( pCur ){
+    sqlite3_finalize(pCur->pStmt);
+    sqlite3_free(pCur);
+  }
+  return SQLITE_OK;
+}
+
+static int tclNext(sqlite3_vtab_cursor *pVtabCursor){
+  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
+  if( pCsr->pStmt ){
+    tcl_vtab *pTab = (tcl_vtab*)(pVtabCursor->pVtab);
+    int rc = sqlite3_step(pCsr->pStmt);
+    if( rc!=SQLITE_ROW ){
+      const char *zErr;
+      rc = sqlite3_finalize(pCsr->pStmt);
+      pCsr->pStmt = 0;
+      if( rc!=SQLITE_OK ){
+        zErr = sqlite3_errmsg(pTab->db);
+        pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
+      }
+    }
+  }
+  return SQLITE_OK;
+}
+
+static int tclFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
+  tcl_vtab *pTab = (tcl_vtab*)(pVtabCursor->pVtab);
+  Tcl_Interp *interp = pTab->interp;
+  Tcl_Obj *pScript;
+  Tcl_Obj *pArg;
+  int ii;
+  int rc;
+
+  pScript = Tcl_DuplicateObj(pTab->pCmd);
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("xFilter", -1));
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewIntObj(idxNum));
+  if( idxStr ){
+    Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj(idxStr, -1));
+  }else{
+    Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("", -1));
+  }
+
+  pArg = Tcl_NewObj();
+  Tcl_IncrRefCount(pArg);
+  for(ii=0; ii<argc; ii++){
+    const char *zVal = (const char*)sqlite3_value_text(argv[ii]);
+    Tcl_Obj *pVal;
+    if( zVal==0 ){
+      sqlite3_value *pMem;
+      pVal = Tcl_NewObj();
+      for(rc=sqlite3_vtab_in_first(argv[ii], &pMem); 
+          rc==SQLITE_OK && pMem;
+          rc=sqlite3_vtab_in_next(argv[ii], &pMem)
+      ){
+        Tcl_Obj *pVal2 = 0;
+        zVal = (const char*)sqlite3_value_text(pMem);
+        if( zVal ){
+          pVal2 = Tcl_NewStringObj(zVal, -1);
+        }else{
+          pVal2 = Tcl_NewObj();
+        }
+        Tcl_ListObjAppendElement(interp, pVal, pVal2);
+      }
+    }else{
+      pVal = Tcl_NewStringObj(zVal, -1);
+    }
+    Tcl_ListObjAppendElement(interp, pArg, pVal);
+  }
+  Tcl_ListObjAppendElement(interp, pScript, pArg);
+  Tcl_DecrRefCount(pArg);
+
+  rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
+  if( rc!=TCL_OK ){
+    const char *zErr = Tcl_GetStringResult(interp);
+    rc = SQLITE_ERROR;
+    pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
+  }else{
+    /* Analyze the scripts return value. The return value should be a tcl 
+    ** list object with an even number of elements. The first element of each
+    ** pair must be one of:
+    ** 
+    **   "sql"          (SQL statement to return data)
+    */
+    Tcl_Obj *pRes = Tcl_GetObjResult(interp);
+    Tcl_Obj **apElem = 0;
+    int nElem;
+    rc = Tcl_ListObjGetElements(interp, pRes, &nElem, &apElem);
+    if( rc!=TCL_OK ){
+      const char *zErr = Tcl_GetStringResult(interp);
+      rc = SQLITE_ERROR;
+      pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
+    }else{
+      for(ii=0; rc==SQLITE_OK && ii<nElem; ii+=2){
+        const char *zCmd = Tcl_GetString(apElem[ii]);
+        Tcl_Obj *p = apElem[ii+1];
+        if( sqlite3_stricmp("sql", zCmd)==0 ){
+          const char *zSql = Tcl_GetString(p);
+          rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pStmt, 0);
+          if( rc!=SQLITE_OK ){
+            const char *zErr = sqlite3_errmsg(pTab->db);
+            pTab->base.zErrMsg = sqlite3_mprintf("unexpected: %s", zErr);
+          }
+        }else{
+          rc = SQLITE_ERROR;
+          pTab->base.zErrMsg = sqlite3_mprintf("unexpected: %s", zCmd);
+        }
+      }
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = tclNext(pVtabCursor);
+  }
+  return rc;
+}
+
+static int tclColumn(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  sqlite3_context *ctx, 
+  int i
+){
+  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
+  sqlite3_result_value(ctx, sqlite3_column_value(pCsr->pStmt, i+1));
+  return SQLITE_OK;
+}
+
+static int tclRowid(sqlite3_vtab_cursor *pVtabCursor, sqlite_int64 *pRowid){
+  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
+  *pRowid = sqlite3_column_int64(pCsr->pStmt, 0);
+  return SQLITE_OK;
+}
+
+static int tclEof(sqlite3_vtab_cursor *pVtabCursor){
+  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
+  return (pCsr->pStmt==0);
+}
+
+static void testBestIndexObjConstraints(
+  Tcl_Interp *interp, 
+  sqlite3_index_info *pIdxInfo
+){
+  int ii;
+  Tcl_Obj *pRes = Tcl_NewObj();
+  Tcl_IncrRefCount(pRes);
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    struct sqlite3_index_constraint const *pCons = &pIdxInfo->aConstraint[ii];
+    Tcl_Obj *pElem = Tcl_NewObj();
+    const char *zOp = 0;
+
+    Tcl_IncrRefCount(pElem);
+
+    switch( pCons->op ){
+      case SQLITE_INDEX_CONSTRAINT_EQ:
+        zOp = "eq"; break;
+      case SQLITE_INDEX_CONSTRAINT_GT:
+        zOp = "gt"; break;
+      case SQLITE_INDEX_CONSTRAINT_LE:
+        zOp = "le"; break;
+      case SQLITE_INDEX_CONSTRAINT_LT:
+        zOp = "lt"; break;
+      case SQLITE_INDEX_CONSTRAINT_GE:
+        zOp = "ge"; break;
+      case SQLITE_INDEX_CONSTRAINT_MATCH:
+        zOp = "match"; break;
+      case SQLITE_INDEX_CONSTRAINT_LIKE:
+        zOp = "like"; break;
+      case SQLITE_INDEX_CONSTRAINT_GLOB:
+        zOp = "glob"; break;
+      case SQLITE_INDEX_CONSTRAINT_REGEXP:
+        zOp = "regexp"; break;
+      case SQLITE_INDEX_CONSTRAINT_NE:
+        zOp = "ne"; break;
+      case SQLITE_INDEX_CONSTRAINT_ISNOT:
+        zOp = "isnot"; break;
+      case SQLITE_INDEX_CONSTRAINT_ISNOTNULL:
+        zOp = "isnotnull"; break;
+      case SQLITE_INDEX_CONSTRAINT_ISNULL:
+        zOp = "isnull"; break;
+      case SQLITE_INDEX_CONSTRAINT_IS:
+        zOp = "is"; break;
+      case SQLITE_INDEX_CONSTRAINT_LIMIT:
+        zOp = "limit"; break;
+      case SQLITE_INDEX_CONSTRAINT_OFFSET:
+        zOp = "offset"; break;
+    }
+
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewStringObj("op", -1));
+    if( zOp ){
+      Tcl_ListObjAppendElement(0, pElem, Tcl_NewStringObj(zOp, -1));
+    }else{
+      Tcl_ListObjAppendElement(0, pElem, Tcl_NewIntObj(pCons->op));
+    }
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewStringObj("column", -1));
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewIntObj(pCons->iColumn));
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewStringObj("usable", -1));
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewIntObj(pCons->usable));
+
+    Tcl_ListObjAppendElement(0, pRes, pElem);
+    Tcl_DecrRefCount(pElem);
+  }
+
+  Tcl_SetObjResult(interp, pRes);
+  Tcl_DecrRefCount(pRes);
+}
+
+static void testBestIndexObjOrderby(
+  Tcl_Interp *interp, 
+  sqlite3_index_info *pIdxInfo
+){
+  int ii;
+  Tcl_Obj *pRes = Tcl_NewObj();
+  Tcl_IncrRefCount(pRes);
+  for(ii=0; ii<pIdxInfo->nOrderBy; ii++){
+    struct sqlite3_index_orderby const *pOrder = &pIdxInfo->aOrderBy[ii];
+    Tcl_Obj *pElem = Tcl_NewObj();
+    Tcl_IncrRefCount(pElem);
+
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewStringObj("column", -1));
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewIntObj(pOrder->iColumn));
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewStringObj("desc", -1));
+    Tcl_ListObjAppendElement(0, pElem, Tcl_NewIntObj(pOrder->desc));
+
+    Tcl_ListObjAppendElement(0, pRes, pElem);
+    Tcl_DecrRefCount(pElem);
+  }
+
+  Tcl_SetObjResult(interp, pRes);
+  Tcl_DecrRefCount(pRes);
+}
+
+/*
+** Implementation of the handle passed to each xBestIndex callback. This
+** object features the following sub-commands:
+**
+**    $hdl constraints
+**    $hdl orderby
+**    $hdl mask
+**
+**    $hdl distinct
+**      Return the result (an integer) of calling sqlite3_vtab_distinct()
+**      on the index-info structure.
+**
+**    $hdl in IDX BOOLEAN
+**      Wrapper around sqlite3_vtab_in(). Returns an integer.
+**
+**    $hdl rhs_value IDX ?DEFAULT?
+**      Wrapper around sqlite3_vtab_rhs_value().
+*/
+static int SQLITE_TCLAPI testBestIndexObj(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  const char *azSub[] = {
+    "constraints",                /* 0 */
+    "orderby",                    /* 1 */
+    "mask",                       /* 2 */
+    "distinct",                   /* 3 */
+    "in",                         /* 4 */
+    "rhs_value",                  /* 5 */
+    0
+  };
+  int ii;
+  sqlite3_index_info *pIdxInfo = (sqlite3_index_info*)clientData;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], azSub, "sub-command", 0, &ii) ){
+    return TCL_ERROR;
+  }
+
+  if( ii<4 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+  if( ii==4 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "INDEX BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( ii==5 && objc!=3 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "INDEX ?DEFAULT?");
+    return TCL_ERROR;
+  }
+
+  switch( ii ){
+    case 0: assert( sqlite3_stricmp(azSub[ii], "constraints")==0 );
+      testBestIndexObjConstraints(interp, pIdxInfo);
+      break;
+
+    case 1: assert( sqlite3_stricmp(azSub[ii], "orderby")==0 );
+      testBestIndexObjOrderby(interp, pIdxInfo);
+      break;
+
+    case 2: assert( sqlite3_stricmp(azSub[ii], "mask")==0 );
+      Tcl_SetObjResult(interp, Tcl_NewWideIntObj(pIdxInfo->colUsed));
+      break;
+
+    case 3: assert( sqlite3_stricmp(azSub[ii], "distinct")==0 ); {
+      int bDistinct = sqlite3_vtab_distinct(pIdxInfo);
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(bDistinct));
+      break;
+    }
+
+    case 4: assert( sqlite3_stricmp(azSub[ii], "in")==0 ); {
+      int iCons;
+      int bHandle;
+      if( Tcl_GetIntFromObj(interp, objv[2], &iCons) 
+       || Tcl_GetBooleanFromObj(interp, objv[3], &bHandle) 
+      ){
+        return TCL_ERROR;
+      }
+      Tcl_SetObjResult(interp, 
+          Tcl_NewIntObj(sqlite3_vtab_in(pIdxInfo, iCons, bHandle))
+      );
+      break;
+    }
+
+    case 5: assert( sqlite3_stricmp(azSub[ii], "rhs_value")==0 ); {
+      int iCons = 0;
+      int rc;
+      sqlite3_value *pVal = 0;
+      const char *zVal = "";
+      if( Tcl_GetIntFromObj(interp, objv[2], &iCons) ){
+        return TCL_ERROR;
+      }
+      rc = sqlite3_vtab_rhs_value(pIdxInfo, iCons, &pVal);
+      if( rc!=SQLITE_OK && rc!=SQLITE_NOTFOUND ){
+        Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+        return TCL_ERROR;
+      }
+      if( pVal ){
+        zVal = (const char*)sqlite3_value_text(pVal);
+      }else if( objc==4 ){
+        zVal = Tcl_GetString(objv[3]);
+      }
+      Tcl_SetObjResult(interp, Tcl_NewStringObj(zVal, -1));
+      break;
+    }
+  }
+
+  return TCL_OK;
+}
+
+static int tclBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  tcl_vtab *pTab = (tcl_vtab*)tab;
+  Tcl_Interp *interp = pTab->interp;
+  int rc = SQLITE_OK;
+
+  static int iNext = 43;
+  char zHdl[24];
+  Tcl_Obj *pScript;
+
+  pScript = Tcl_DuplicateObj(pTab->pCmd);
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("xBestIndex", -1));
+
+  sqlite3_snprintf(sizeof(zHdl), zHdl, "bestindex%d", iNext++);
+  Tcl_CreateObjCommand(interp, zHdl, testBestIndexObj, pIdxInfo, 0);
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj(zHdl, -1));
+  rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
+  Tcl_DeleteCommand(interp, zHdl);
+  Tcl_DecrRefCount(pScript);
+
+  if( rc!=TCL_OK ){
+    const char *zErr = Tcl_GetStringResult(interp);
+    rc = SQLITE_ERROR;
+    pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
+  }else{
+    /* Analyze the scripts return value. The return value should be a tcl 
+    ** list object with an even number of elements. The first element of each
+    ** pair must be one of:
+    ** 
+    **   "orderby"          (value of orderByConsumed flag)
+    **   "cost"             (value of estimatedCost field)
+    **   "rows"             (value of estimatedRows field)
+    **   "use"              (index of used constraint in aConstraint[])
+    **   "idxnum"           (value of idxNum field)
+    **   "idxstr"           (value of idxStr field)
+    **   "omit"             (index of omitted constraint in aConstraint[])
+    */
+    Tcl_Obj *pRes = Tcl_GetObjResult(interp);
+    Tcl_Obj **apElem = 0;
+    int nElem;
+    rc = Tcl_ListObjGetElements(interp, pRes, &nElem, &apElem);
+    if( rc!=TCL_OK ){
+      const char *zErr = Tcl_GetStringResult(interp);
+      rc = SQLITE_ERROR;
+      pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
+    }else{
+      int ii;
+      int iArgv = 1;
+      for(ii=0; rc==SQLITE_OK && ii<nElem; ii+=2){
+        const char *zCmd = Tcl_GetString(apElem[ii]);
+        Tcl_Obj *p = apElem[ii+1];
+        if( sqlite3_stricmp("cost", zCmd)==0 ){
+          rc = Tcl_GetDoubleFromObj(interp, p, &pIdxInfo->estimatedCost);
+        }else
+        if( sqlite3_stricmp("orderby", zCmd)==0 ){
+          rc = Tcl_GetIntFromObj(interp, p, &pIdxInfo->orderByConsumed);
+        }else
+        if( sqlite3_stricmp("idxnum", zCmd)==0 ){
+          rc = Tcl_GetIntFromObj(interp, p, &pIdxInfo->idxNum);
+        }else
+        if( sqlite3_stricmp("idxstr", zCmd)==0 ){
+          sqlite3_free(pIdxInfo->idxStr);
+          pIdxInfo->idxStr = sqlite3_mprintf("%s", Tcl_GetString(p));
+          pIdxInfo->needToFreeIdxStr = 1;
+        }else
+        if( sqlite3_stricmp("rows", zCmd)==0 ){
+          Tcl_WideInt x = 0;
+          rc = Tcl_GetWideIntFromObj(interp, p, &x);
+          pIdxInfo->estimatedRows = (tRowcnt)x;
+        }else
+        if( sqlite3_stricmp("use", zCmd)==0 
+         || sqlite3_stricmp("omit", zCmd)==0 
+        ){
+          int iCons;
+          rc = Tcl_GetIntFromObj(interp, p, &iCons);
+          if( rc==SQLITE_OK ){
+            if( iCons<0 || iCons>=pIdxInfo->nConstraint ){
+              rc = SQLITE_ERROR;
+              pTab->base.zErrMsg = sqlite3_mprintf("unexpected: %d", iCons);
+            }else{
+              int bOmit = (zCmd[0]=='o' || zCmd[0]=='O');
+              pIdxInfo->aConstraintUsage[iCons].argvIndex = iArgv++;
+              pIdxInfo->aConstraintUsage[iCons].omit = bOmit;
+            }
+          }
+        }else{
+          rc = SQLITE_ERROR;
+          pTab->base.zErrMsg = sqlite3_mprintf("unexpected: %s", zCmd);
+        }
+        if( rc!=SQLITE_OK && pTab->base.zErrMsg==0 ){
+          const char *zErr = Tcl_GetStringResult(interp);
+          pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
+        }
+      }
+    }
+  }
+
+  return rc;
+}
+
+static void tclFunction(sqlite3_context *pCtx, int nArg, sqlite3_value **apArg){
+  TestFindFunction *p = (TestFindFunction*)sqlite3_user_data(pCtx);
+  Tcl_Interp *interp = p->pTab->interp;
+  Tcl_Obj *pScript = 0;
+  Tcl_Obj *pRet = 0;
+  int ii;
+
+  pScript = Tcl_DuplicateObj(p->pTab->pCmd);
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("function", -1));
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj(p->zName, -1));
+
+  for(ii=0; ii<nArg; ii++){
+    const char *zArg = (const char*)sqlite3_value_text(apArg[ii]);
+    Tcl_ListObjAppendElement(interp, pScript,
+        (zArg ? Tcl_NewStringObj(zArg, -1) : Tcl_NewObj())
+    );
+  }
+  Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
+  Tcl_DecrRefCount(pScript);
+
+  pRet = Tcl_GetObjResult(interp);
+  sqlite3_result_text(pCtx, Tcl_GetString(pRet), -1, SQLITE_TRANSIENT);
+}
+
+static int tclFindFunction(
+  sqlite3_vtab *tab, 
+  int nArg, 
+  const char *zName,
+  void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),   /* OUT */
+  void **ppArg                                             /* OUT */
+){
+  int iRet = 0;
+  tcl_vtab *pTab = (tcl_vtab*)tab;
+  Tcl_Interp *interp = pTab->interp;
+  Tcl_Obj *pScript = 0;
+  int rc = SQLITE_OK;
+
+  pScript = Tcl_DuplicateObj(pTab->pCmd);
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(
+      interp, pScript, Tcl_NewStringObj("xFindFunction", -1)
+  );
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewIntObj(nArg));
+  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj(zName, -1));
+  rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
+  Tcl_DecrRefCount(pScript);
+
+  if( rc==SQLITE_OK ){
+    Tcl_Obj *pObj = Tcl_GetObjResult(interp);
+
+    if( Tcl_GetIntFromObj(interp, pObj, &iRet) ){
+      rc = SQLITE_ERROR;
+    }else if( iRet>0 ){
+      sqlite3_int64 nName = strlen(zName);
+      sqlite3_int64 nByte = nName + 1 + sizeof(TestFindFunction);
+      TestFindFunction *pNew = 0;
+
+      pNew = (TestFindFunction*)sqlite3_malloc64(nByte);
+      if( pNew==0 ){
+        iRet = 0;
+      }else{
+        memset(pNew, 0, nByte);
+        pNew->zName = (const char*)&pNew[1];
+        memcpy((char*)pNew->zName, zName, nName);
+        pNew->pTab = pTab;
+        pNew->pNext = pTab->pFindFunctionList;
+        pTab->pFindFunctionList = pNew;
+        *ppArg = (void*)pNew;
+        *pxFunc = tclFunction;
+      }
+    }
+  }
+
+  return iRet;
+}
+
+/*
+** A virtual table module that provides read-only access to a
+** Tcl global variable namespace.
+*/
+static sqlite3_module tclModule = {
+  0,                         /* iVersion */
+  tclConnect,
+  tclConnect,
+  tclBestIndex,
+  tclDisconnect, 
+  tclDisconnect,
+  tclOpen,                      /* xOpen - open a cursor */
+  tclClose,                     /* xClose - close a cursor */
+  tclFilter,                    /* xFilter - configure scan constraints */
+  tclNext,                      /* xNext - advance a cursor */
+  tclEof,                       /* xEof - check for end of scan */
+  tclColumn,                    /* xColumn - read data */
+  tclRowid,                     /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  tclFindFunction,             /* xFindFunction */
+  0,                           /* xRename */
+  0,                           /* xSavepoint */
+  0,                           /* xRelease */
+  0,                           /* xRollbackTo */
+  0,                           /* xShadowName */
+  0                            /* xIntegrity */
+};
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the echo virtual table module.
+*/
+static int SQLITE_TCLAPI register_tcl_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "tcl", &tclModule, (void *)interp);
+#endif
+  return TCL_OK;
+}
+
+#endif
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetesttcl_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_tcl_module",   register_tcl_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+#endif
+  return TCL_OK;
+}
diff --git a/src/test_blob.c b/src/test_blob.c
new file mode 100644
index 0000000..cbdf9f0
--- /dev/null
+++ b/src/test_blob.c
@@ -0,0 +1,330 @@
+/*
+** 2014 October 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#ifndef SQLITE_OMIT_INCRBLOB
+
+/* These functions are implemented in main.c. */
+extern const char *sqlite3ErrName(int);
+
+/* From test1.c: */
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+extern void *sqlite3TestTextToPtr(const char *z);
+
+/*
+** Return a pointer to a buffer containing a text representation of the
+** pointer passed as the only argument. The original pointer may be extracted
+** from the text using sqlite3TestTextToPtr().
+*/
+static char *ptrToText(void *p){
+  static char buf[100];
+  sqlite3_snprintf(sizeof(buf)-1, buf, "%p", p);
+  return buf;
+}
+
+/*
+** Attempt to extract a blob handle (type sqlite3_blob*) from the Tcl
+** object passed as the second argument. If successful, set *ppBlob to
+** point to the blob handle and return TCL_OK. Otherwise, store an error
+** message in the tcl interpreter and return TCL_ERROR. The final value
+** of *ppBlob is undefined in this case.
+**
+** If the object contains a string that begins with "incrblob_", then it
+** is assumed to be the name of a Tcl channel opened using the [db incrblob] 
+** command (see tclsqlite.c). Otherwise, it is assumed to be a pointer 
+** encoded using the ptrToText() routine or similar.
+*/
+static int blobHandleFromObj(
+  Tcl_Interp *interp, 
+  Tcl_Obj *pObj,
+  sqlite3_blob **ppBlob
+){
+  char *z;
+  int n;
+
+  z = Tcl_GetStringFromObj(pObj, &n);
+  if( n==0 ){
+    *ppBlob = 0;
+  }else if( n>9 && 0==memcmp("incrblob_", z, 9) ){
+    int notUsed;
+    Tcl_Channel channel;
+    ClientData instanceData;
+    
+    channel = Tcl_GetChannel(interp, z, &notUsed);
+    if( !channel ) return TCL_ERROR;
+
+    Tcl_Flush(channel);
+    Tcl_Seek(channel, 0, SEEK_SET);
+
+    instanceData = Tcl_GetChannelInstanceData(channel);
+    *ppBlob = *((sqlite3_blob **)instanceData);
+  }else{
+    *ppBlob = (sqlite3_blob*)sqlite3TestTextToPtr(z);
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Like Tcl_GetString(), except that if the string is 0 bytes in size, a
+** NULL Pointer is returned.
+*/
+static char *blobStringFromObj(Tcl_Obj *pObj){
+  int n;
+  char *z;
+  z = Tcl_GetStringFromObj(pObj, &n);
+  return (n ? z : 0);
+}
+
+/*
+** sqlite3_blob_open DB DATABASE TABLE COLUMN ROWID FLAGS VARNAME
+**
+** Tcl test harness for the sqlite3_blob_open() function.
+*/
+static int SQLITE_TCLAPI test_blob_open(
+  ClientData clientData,          /* Not used */
+  Tcl_Interp *interp,             /* Calling TCL interpreter */
+  int objc,                       /* Number of arguments */
+  Tcl_Obj *CONST objv[]           /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zDb;
+  const char *zTable;
+  const char *zColumn;
+  Tcl_WideInt iRowid;
+  int flags;
+  const char *zVarname;
+  int nVarname;
+
+  sqlite3_blob *pBlob = (sqlite3_blob*)&flags;   /* Non-zero initialization */
+  int rc;
+
+  if( objc!=8 ){
+    const char *zUsage = "DB DATABASE TABLE COLUMN ROWID FLAGS VARNAME";
+    Tcl_WrongNumArgs(interp, 1, objv, zUsage);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zDb = Tcl_GetString(objv[2]);
+  zTable = blobStringFromObj(objv[3]);
+  zColumn = Tcl_GetString(objv[4]);
+  if( Tcl_GetWideIntFromObj(interp, objv[5], &iRowid) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[6], &flags) ) return TCL_ERROR;
+  zVarname = Tcl_GetStringFromObj(objv[7], &nVarname);
+
+  if( nVarname>0 ){
+    rc = sqlite3_blob_open(db, zDb, zTable, zColumn, iRowid, flags, &pBlob);
+    Tcl_SetVar(interp, zVarname, ptrToText(pBlob), 0);
+  }else{
+    rc = sqlite3_blob_open(db, zDb, zTable, zColumn, iRowid, flags, 0);
+  }
+
+  if( rc==SQLITE_OK ){
+    Tcl_ResetResult(interp);
+  }else{
+    Tcl_SetResult(interp, (char*)sqlite3ErrName(rc), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+
+/*
+** sqlite3_blob_close  HANDLE
+*/
+static int SQLITE_TCLAPI test_blob_close(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  int rc;
+  
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  rc = sqlite3_blob_close(pBlob);
+
+  if( rc ){
+    Tcl_SetResult(interp, (char*)sqlite3ErrName(rc), TCL_VOLATILE);
+  }else{
+    Tcl_ResetResult(interp);
+  }
+  return TCL_OK;
+}
+
+/*
+** sqlite3_blob_bytes  HANDLE
+*/
+static int SQLITE_TCLAPI test_blob_bytes(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  int nByte;
+  
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  nByte = sqlite3_blob_bytes(pBlob);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nByte));
+
+  return TCL_OK;
+}
+
+/*
+** sqlite3_blob_read  CHANNEL OFFSET N
+**
+**   This command is used to test the sqlite3_blob_read() in ways that
+**   the Tcl channel interface does not. The first argument should
+**   be the name of a valid channel created by the [incrblob] method
+**   of a database handle. This function calls sqlite3_blob_read()
+**   to read N bytes from offset OFFSET from the underlying SQLite
+**   blob handle.
+**
+**   On success, a byte-array object containing the read data is 
+**   returned. On failure, the interpreter result is set to the
+**   text representation of the returned error code (i.e. "SQLITE_NOMEM")
+**   and a Tcl exception is thrown.
+*/
+static int SQLITE_TCLAPI test_blob_read(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  int nByte;
+  int iOffset;
+  unsigned char *zBuf = 0;
+  int rc;
+  
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "CHANNEL OFFSET N");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &iOffset)
+   || TCL_OK!=Tcl_GetIntFromObj(interp, objv[3], &nByte)
+  ){ 
+    return TCL_ERROR;
+  }
+
+  if( nByte>0 ){
+    zBuf = (unsigned char *)Tcl_AttemptAlloc(nByte);
+    if( zBuf==0 ){
+      Tcl_AppendResult(interp, "out of memory in " __FILE__, 0);
+      return TCL_ERROR;
+    }
+  }
+  rc = sqlite3_blob_read(pBlob, zBuf, nByte, iOffset);
+  if( rc==SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(zBuf, nByte));
+  }else{
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  }
+  Tcl_Free((char *)zBuf);
+
+  return (rc==SQLITE_OK ? TCL_OK : TCL_ERROR);
+}
+
+/*
+** sqlite3_blob_write HANDLE OFFSET DATA ?NDATA?
+**
+**   This command is used to test the sqlite3_blob_write() in ways that
+**   the Tcl channel interface does not. The first argument should
+**   be the name of a valid channel created by the [incrblob] method
+**   of a database handle. This function calls sqlite3_blob_write()
+**   to write the DATA byte-array to the underlying SQLite blob handle.
+**   at offset OFFSET.
+**
+**   On success, an empty string is returned. On failure, the interpreter
+**   result is set to the text representation of the returned error code 
+**   (i.e. "SQLITE_NOMEM") and a Tcl exception is thrown.
+*/
+static int SQLITE_TCLAPI test_blob_write(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  int iOffset;
+  int rc;
+
+  unsigned char *zBuf;
+  int nBuf;
+  
+  if( objc!=4 && objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE OFFSET DATA ?NDATA?");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &iOffset) ){ 
+    return TCL_ERROR;
+  }
+
+  zBuf = Tcl_GetByteArrayFromObj(objv[3], &nBuf);
+  if( objc==5 && Tcl_GetIntFromObj(interp, objv[4], &nBuf) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_blob_write(pBlob, zBuf, nBuf, iOffset);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  }
+
+  return (rc==SQLITE_OK ? TCL_OK : TCL_ERROR);
+}
+#endif /* SQLITE_OMIT_INCRBLOB */
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_blob_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_INCRBLOB
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aObjCmd[] = {
+     { "sqlite3_blob_open",            test_blob_open        },
+     { "sqlite3_blob_close",           test_blob_close       },
+     { "sqlite3_blob_bytes",           test_blob_bytes       },
+     { "sqlite3_blob_read",            test_blob_read        },
+     { "sqlite3_blob_write",           test_blob_write       },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, 0, 0);
+  }
+#endif /* SQLITE_OMIT_INCRBLOB */
+  return TCL_OK;
+}
diff --git a/src/test_btree.c b/src/test_btree.c
new file mode 100644
index 0000000..03b8b20
--- /dev/null
+++ b/src/test_btree.c
@@ -0,0 +1,66 @@
+/*
+** 2007 May 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the btree.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "btreeInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+/*
+** Usage: sqlite3_shared_cache_report
+**
+** Return a list of file that are shared and the number of
+** references to each file.
+*/
+int SQLITE_TCLAPI sqlite3BtreeSharedCacheReport(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  extern BtShared *sqlite3SharedCacheList;
+  BtShared *pBt;
+  Tcl_Obj *pRet = Tcl_NewObj();
+  for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
+    const char *zFile = sqlite3PagerFilename(pBt->pPager, 1);
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj(zFile, -1));
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(pBt->nRef));
+  }
+  Tcl_SetObjResult(interp, pRet);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Print debugging information about all cursors to standard output.
+*/
+void sqlite3BtreeCursorList(Btree *p){
+#ifdef SQLITE_DEBUG
+  BtCursor *pCur;
+  BtShared *pBt = p->pBt;
+  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
+    MemPage *pPage = pCur->apPage[pCur->iPage];
+    char *zMode = (pCur->curFlags & BTCF_WriteFlag) ? "rw" : "ro";
+    sqlite3DebugPrintf("CURSOR %p rooted at %4d(%s) currently at %d.%d%s\n",
+       pCur, pCur->pgnoRoot, zMode,
+       pPage ? pPage->pgno : 0, pCur->aiIdx[pCur->iPage],
+       (pCur->eState==CURSOR_VALID) ? "" : " eof"
+    );
+  }
+#endif
+}
diff --git a/src/test_config.c b/src/test_config.c
new file mode 100644
index 0000000..ee766a2
--- /dev/null
+++ b/src/test_config.c
@@ -0,0 +1,829 @@
+/*
+** 2007 May 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** 
+** This file contains code used for testing the SQLite system.
+** None of the code in this file goes into a deliverable build.
+** 
+** The focus of this file is providing the TCL testing layer
+** access to compile-time constants.
+*/
+
+#include "sqliteLimit.h"
+
+#include "sqliteInt.h"
+#if SQLITE_OS_WIN
+#  include "os_win.h"
+#endif
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** Macro to stringify the results of the evaluation a pre-processor
+** macro. i.e. so that STRINGVALUE(SQLITE_NOMEM) -> "7".
+*/
+#define STRINGVALUE2(x) #x
+#define STRINGVALUE(x) STRINGVALUE2(x)
+
+/*
+** This routine sets entries in the global ::sqlite_options() array variable
+** according to the compile-time configuration of the database.  Test
+** procedures use this to determine when tests should be omitted.
+*/
+static void set_options(Tcl_Interp *interp){
+#if HAVE_MALLOC_USABLE_SIZE
+  Tcl_SetVar2(interp, "sqlite_options", "malloc_usable_size", "1",
+              TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "malloc_usable_size", "0",
+              TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_32BIT_ROWID
+  Tcl_SetVar2(interp, "sqlite_options", "rowid32", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "rowid32", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_CASE_SENSITIVE_LIKE
+  Tcl_SetVar2(interp, "sqlite_options","casesensitivelike","1",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options","casesensitivelike","0",TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef CONFIG_SLOWDOWN_FACTOR
+  Tcl_SetVar2(interp, "sqlite_options","configslower",
+              STRINGVALUE(CONFIG_SLOWDOWN_FACTOR),TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options","configslower","1.0",TCL_GLOBAL_ONLY);
+#endif
+
+#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
+  Tcl_SetVar2(interp, "sqlite_options", "curdir", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "curdir", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_WIN32_MALLOC
+  Tcl_SetVar2(interp, "sqlite_options", "win32malloc", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "win32malloc", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DEBUG
+  Tcl_SetVar2(interp, "sqlite_options", "debug", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "debug", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DEFAULT_CKPTFULLFSYNC
+  Tcl_SetVar2(interp, "sqlite_options", "default_ckptfullfsync", 
+              SQLITE_DEFAULT_CKPTFULLFSYNC ? "1" : "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "default_ckptfullfsync", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+  Tcl_SetVar2(interp, "sqlite_options", "direct_read", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "direct_read", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DISABLE_DIRSYNC
+  Tcl_SetVar2(interp, "sqlite_options", "dirsync", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "dirsync", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DISABLE_LFS
+  Tcl_SetVar2(interp, "sqlite_options", "lfs", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "lfs", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
+  Tcl_SetVar2(interp, "sqlite_options", "pagecache_overflow_stats","0",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "pagecache_overflow_stats","1",TCL_GLOBAL_ONLY);
+#endif
+
+#if SQLITE_MAX_MMAP_SIZE>0
+  Tcl_SetVar2(interp, "sqlite_options", "mmap", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mmap", "0", TCL_GLOBAL_ONLY);
+#endif
+
+  Tcl_SetVar2(interp, "sqlite_options", "worker_threads", 
+      STRINGVALUE(SQLITE_MAX_WORKER_THREADS), TCL_GLOBAL_ONLY
+  );
+
+#ifdef SQLITE_MEMDEBUG 
+  Tcl_SetVar2(interp, "sqlite_options", "memdebug", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "memdebug", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_8_3_NAMES
+  Tcl_SetVar2(interp, "sqlite_options", "8_3_names", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "8_3_names", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+  Tcl_SetVar2(interp, "sqlite_options", "cursorhints", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "cursorhints", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_HIDDEN_COLUMNS
+  Tcl_SetVar2(interp, "sqlite_options", "hiddencolumns", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "hiddencolumns", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifndef SQLITE_OMIT_DESERIALIZE
+  Tcl_SetVar2(interp, "sqlite_options", "deserialize", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "deserialize", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_MATH_FUNCTIONS
+  Tcl_SetVar2(interp, "sqlite_options", "mathlib", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mathlib", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_MEMSYS3
+  Tcl_SetVar2(interp, "sqlite_options", "mem3", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mem3", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_MEMSYS5
+  Tcl_SetVar2(interp, "sqlite_options", "mem5", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mem5", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+  Tcl_SetVar2(interp, "sqlite_options", "offset_sql_func","1",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "offset_sql_func","0",TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  Tcl_SetVar2(interp, "sqlite_options", "preupdate", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "preupdate", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  Tcl_SetVar2(interp, "sqlite_options", "snapshot", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "snapshot", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_MUTEX_OMIT
+  Tcl_SetVar2(interp, "sqlite_options", "mutex", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mutex", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_MUTEX_NOOP
+  Tcl_SetVar2(interp, "sqlite_options", "mutex_noop", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mutex_noop", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_ALTERTABLE
+  Tcl_SetVar2(interp, "sqlite_options", "altertable", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "altertable", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_ANALYZE
+  Tcl_SetVar2(interp, "sqlite_options", "analyze", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "analyze", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  Tcl_SetVar2(interp, "sqlite_options", "api_armor", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "api_armor", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  Tcl_SetVar2(interp, "sqlite_options", "atomicwrite", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "atomicwrite", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_GEOPOLY
+  Tcl_SetVar2(interp, "sqlite_options", "geopoly", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "geopoly", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifndef SQLITE_OMIT_JSON
+  Tcl_SetVar2(interp, "sqlite_options", "json1", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "json1", "0", TCL_GLOBAL_ONLY);
+#endif
+
+  Tcl_SetVar2(interp, "sqlite_options", "has_codec", "0", TCL_GLOBAL_ONLY);
+
+#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+  Tcl_SetVar2(interp, "sqlite_options", "like_match_blobs", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "like_match_blobs", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_ATTACH
+  Tcl_SetVar2(interp, "sqlite_options", "attach", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "attach", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTHORIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "auth", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "auth", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTOINCREMENT
+  Tcl_SetVar2(interp, "sqlite_options", "autoinc", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autoinc", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTOMATIC_INDEX
+  Tcl_SetVar2(interp, "sqlite_options", "autoindex", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autoindex", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTORESET
+  Tcl_SetVar2(interp, "sqlite_options", "autoreset", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autoreset", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  Tcl_SetVar2(interp, "sqlite_options", "autovacuum", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autovacuum", "1", TCL_GLOBAL_ONLY);
+#endif /* SQLITE_OMIT_AUTOVACUUM */
+#if !defined(SQLITE_DEFAULT_AUTOVACUUM)
+  Tcl_SetVar2(interp,"sqlite_options","default_autovacuum","0",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "default_autovacuum", 
+      STRINGVALUE(SQLITE_DEFAULT_AUTOVACUUM), TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "between_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "between_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_UNTESTABLE
+  Tcl_SetVar2(interp, "sqlite_options", "builtin_test", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "builtin_test", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_BLOB_LITERAL
+  Tcl_SetVar2(interp, "sqlite_options", "bloblit", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "bloblit", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_CAST
+  Tcl_SetVar2(interp, "sqlite_options", "cast", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "cast", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_CHECK
+  Tcl_SetVar2(interp, "sqlite_options", "check", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "check", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_CTE
+  Tcl_SetVar2(interp, "sqlite_options", "cte", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "cte", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  Tcl_SetVar2(interp, "sqlite_options", "columnmetadata", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "columnmetadata", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_OVERSIZE_CELL_CHECK
+  Tcl_SetVar2(interp, "sqlite_options", "oversize_cell_check", "1",
+              TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "oversize_cell_check", "0",
+              TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  Tcl_SetVar2(interp, "sqlite_options", "compileoption_diags", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "compileoption_diags", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_COMPLETE
+  Tcl_SetVar2(interp, "sqlite_options", "complete", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "complete", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_COMPOUND_SELECT
+  Tcl_SetVar2(interp, "sqlite_options", "compound", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "compound", "1", TCL_GLOBAL_ONLY);
+#endif
+
+  Tcl_SetVar2(interp, "sqlite_options", "conflict", "1", TCL_GLOBAL_ONLY);
+  Tcl_SetVar2(interp, "sqlite_options", "crashtest", "1", TCL_GLOBAL_ONLY);
+
+#ifdef SQLITE_OMIT_DATETIME_FUNCS
+  Tcl_SetVar2(interp, "sqlite_options", "datetime", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "datetime", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_DECLTYPE
+  Tcl_SetVar2(interp, "sqlite_options", "decltype", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "decltype", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_DEPRECATED
+  Tcl_SetVar2(interp, "sqlite_options", "deprecated", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "deprecated", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_DISKIO
+  Tcl_SetVar2(interp, "sqlite_options", "diskio", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "diskio", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_EXPLAIN
+  Tcl_SetVar2(interp, "sqlite_options", "explain", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "explain", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  Tcl_SetVar2(interp, "sqlite_options", "floatingpoint", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "floatingpoint", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_FOREIGN_KEY
+  Tcl_SetVar2(interp, "sqlite_options", "foreignkey", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "foreignkey", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_FTS3
+  Tcl_SetVar2(interp, "sqlite_options", "fts3", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fts3", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_FTS5
+  Tcl_SetVar2(interp, "sqlite_options", "fts5", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fts5", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_ENABLE_FTS3) && !defined(SQLITE_DISABLE_FTS3_UNICODE)
+  Tcl_SetVar2(interp, "sqlite_options", "fts3_unicode", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fts3_unicode", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DISABLE_FTS4_DEFERRED
+  Tcl_SetVar2(interp, "sqlite_options", "fts4_deferred", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fts4_deferred", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_GET_TABLE
+  Tcl_SetVar2(interp, "sqlite_options", "gettable", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "gettable", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_ICU
+  Tcl_SetVar2(interp, "sqlite_options", "icu", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "icu", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_ICU_COLLATIONS
+  Tcl_SetVar2(interp, "sqlite_options", "icu_collations", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "icu_collations", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_INCRBLOB
+  Tcl_SetVar2(interp, "sqlite_options", "incrblob", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "incrblob", "1", TCL_GLOBAL_ONLY);
+#endif /* SQLITE_OMIT_AUTOVACUUM */
+
+#ifdef SQLITE_OMIT_INTEGRITY_CHECK
+  Tcl_SetVar2(interp, "sqlite_options", "integrityck", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "integrityck", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_DEFAULT_FILE_FORMAT) && SQLITE_DEFAULT_FILE_FORMAT==1
+  Tcl_SetVar2(interp, "sqlite_options", "legacyformat", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "legacyformat", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "like_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "like_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  Tcl_SetVar2(interp, "sqlite_options", "load_ext", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "load_ext", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LOCALTIME
+  Tcl_SetVar2(interp, "sqlite_options", "localtime", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "localtime", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LOOKASIDE
+  Tcl_SetVar2(interp, "sqlite_options", "lookaside", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "lookaside", "1", TCL_GLOBAL_ONLY);
+#endif
+
+Tcl_SetVar2(interp, "sqlite_options", "long_double",
+              sizeof(LONGDOUBLE_TYPE)>sizeof(double) ? "1" : "0",
+              TCL_GLOBAL_ONLY);
+
+#ifdef SQLITE_OMIT_MEMORYDB
+  Tcl_SetVar2(interp, "sqlite_options", "memorydb", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "memorydb", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  Tcl_SetVar2(interp, "sqlite_options", "memorymanage", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "memorymanage", "0", TCL_GLOBAL_ONLY);
+#endif
+
+Tcl_SetVar2(interp, "sqlite_options", "mergesort", "1", TCL_GLOBAL_ONLY);
+
+#ifdef SQLITE_ENABLE_NULL_TRIM
+  Tcl_SetVar2(interp, "sqlite_options", "null_trim", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "null_trim", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_OR_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "or_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "or_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_RBU
+  Tcl_SetVar2(interp, "sqlite_options", "rbu", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "rbu", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_PAGER_PRAGMAS
+  Tcl_SetVar2(interp, "sqlite_options", "pager_pragmas", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "pager_pragmas", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_OMIT_PRAGMA) || defined(SQLITE_OMIT_FLAG_PRAGMAS)
+  Tcl_SetVar2(interp, "sqlite_options", "pragma", "0", TCL_GLOBAL_ONLY);
+  Tcl_SetVar2(interp, "sqlite_options", "integrityck", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "pragma", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+  Tcl_SetVar2(interp, "sqlite_options", "progress", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "progress", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_REINDEX
+  Tcl_SetVar2(interp, "sqlite_options", "reindex", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "reindex", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_RTREE
+  Tcl_SetVar2(interp, "sqlite_options", "rtree", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "rtree", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_RTREE_INT_ONLY
+  Tcl_SetVar2(interp, "sqlite_options", "rtree_int_only", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "rtree_int_only", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_SCHEMA_PRAGMAS
+  Tcl_SetVar2(interp, "sqlite_options", "schema_pragmas", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "schema_pragmas", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_ENABLE_SESSION) && defined(SQLITE_ENABLE_PREUPDATE_HOOK)
+  Tcl_SetVar2(interp, "sqlite_options", "session", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "session", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_STAT4
+  Tcl_SetVar2(interp, "sqlite_options", "stat4", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "stat4", "0", TCL_GLOBAL_ONLY);
+#endif
+#if defined(SQLITE_ENABLE_STMTVTAB) && !defined(SQLITE_OMIT_VIRTUALTABLE)
+  Tcl_SetVar2(interp, "sqlite_options", "stmtvtab", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "stmtvtab", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  Tcl_SetVar2(interp, "sqlite_options", "scanstatus", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "scanstatus", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+  Tcl_SetVar2(interp,"sqlite_options","lock_proxy_pragmas","1",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp,"sqlite_options","lock_proxy_pragmas","0",TCL_GLOBAL_ONLY);
+#endif
+#if defined(SQLITE_PREFER_PROXY_LOCKING) && defined(__APPLE__)
+  Tcl_SetVar2(interp,"sqlite_options","prefer_proxy_locking","1",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp,"sqlite_options","prefer_proxy_locking","0",TCL_GLOBAL_ONLY);
+#endif
+    
+    
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  Tcl_SetVar2(interp, "sqlite_options", "shared_cache", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "shared_cache", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_SUBQUERY
+  Tcl_SetVar2(interp, "sqlite_options", "subquery", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "subquery", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TCL_VARIABLE
+  Tcl_SetVar2(interp, "sqlite_options", "tclvar", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "tclvar", "1", TCL_GLOBAL_ONLY);
+#endif
+
+  Tcl_SetVar2(interp, "sqlite_options", "threadsafe", 
+      SQLITE_THREADSAFE ? "1" : "0", TCL_GLOBAL_ONLY);
+  Tcl_SetVar2(interp, "sqlite_options", "threadsafe1", 
+      SQLITE_THREADSAFE==1 ? "1" : "0", TCL_GLOBAL_ONLY);
+  Tcl_SetVar2(interp, "sqlite_options", "threadsafe2", 
+      SQLITE_THREADSAFE==2 ? "1" : "0", TCL_GLOBAL_ONLY);
+  assert( sqlite3_threadsafe()==SQLITE_THREADSAFE );
+
+#ifdef SQLITE_OMIT_TEMPDB
+  Tcl_SetVar2(interp, "sqlite_options", "tempdb", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "tempdb", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TRACE
+  Tcl_SetVar2(interp, "sqlite_options", "trace", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "trace", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TRIGGER
+  Tcl_SetVar2(interp, "sqlite_options", "trigger", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "trigger", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "truncate_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "truncate_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_UTF16
+  Tcl_SetVar2(interp, "sqlite_options", "utf16", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "utf16", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_OMIT_VACUUM) || defined(SQLITE_OMIT_ATTACH)
+  Tcl_SetVar2(interp, "sqlite_options", "vacuum", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "vacuum", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_VIEW
+  Tcl_SetVar2(interp, "sqlite_options", "view", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "view", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  Tcl_SetVar2(interp, "sqlite_options", "vtab", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "vtab", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_WAL
+  Tcl_SetVar2(interp, "sqlite_options", "wal", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "wal", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_WSD
+  Tcl_SetVar2(interp, "sqlite_options", "wsd", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "wsd", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
+  Tcl_SetVar2(interp, "sqlite_options", "update_delete_limit", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "update_delete_limit", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+  Tcl_SetVar2(interp, "sqlite_options", "unlock_notify", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "unlock_notify", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_FAST_SECURE_DELETE
+  Tcl_SetVar2(interp, "sqlite_options", "fast_secure_delete", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fast_secure_delete", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_SECURE_DELETE
+  Tcl_SetVar2(interp, "sqlite_options", "secure_delete", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "secure_delete", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_USER_AUTHENTICATION
+  Tcl_SetVar2(interp, "sqlite_options", "userauth", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "userauth", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_MULTIPLEX_EXT_OVWR
+  Tcl_SetVar2(interp, "sqlite_options", "multiplex_ext_overwrite", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "multiplex_ext_overwrite", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef YYTRACKMAXSTACKDEPTH
+  Tcl_SetVar2(interp, "sqlite_options", "yytrackmaxstackdepth", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "yytrackmaxstackdepth", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_SQLLOG
+  Tcl_SetVar2(interp, "sqlite_options", "sqllog", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "sqllog", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_URI_00_ERROR
+  Tcl_SetVar2(interp, "sqlite_options", "uri_00_error", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "uri_00_error", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_ENABLE_NORMALIZE)
+  Tcl_SetVar2(interp, "sqlite_options", "normalize", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "normalize", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_WINDOWFUNC
+  Tcl_SetVar2(interp, "sqlite_options", "windowfunc", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "windowfunc", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#define LINKVAR(x) { \
+    static const int cv_ ## x = SQLITE_ ## x; \
+    Tcl_LinkVar(interp, "SQLITE_" #x, (char *)&(cv_ ## x), \
+                TCL_LINK_INT | TCL_LINK_READ_ONLY); }
+
+  LINKVAR( MAX_LENGTH );
+  LINKVAR( MAX_COLUMN );
+  LINKVAR( MAX_SQL_LENGTH );
+  LINKVAR( MAX_EXPR_DEPTH );
+  LINKVAR( MAX_COMPOUND_SELECT );
+  LINKVAR( MAX_VDBE_OP );
+  LINKVAR( MAX_FUNCTION_ARG );
+  LINKVAR( MAX_VARIABLE_NUMBER );
+  LINKVAR( MAX_PAGE_SIZE );
+  LINKVAR( MAX_PAGE_COUNT );
+  LINKVAR( MAX_LIKE_PATTERN_LENGTH );
+  LINKVAR( MAX_TRIGGER_DEPTH );
+  LINKVAR( DEFAULT_CACHE_SIZE );
+  LINKVAR( DEFAULT_PAGE_SIZE );
+  LINKVAR( DEFAULT_FILE_FORMAT );
+  LINKVAR( DEFAULT_SYNCHRONOUS );
+  LINKVAR( DEFAULT_WAL_SYNCHRONOUS );
+  LINKVAR( MAX_ATTACHED );
+  LINKVAR( MAX_DEFAULT_PAGE_SIZE );
+  LINKVAR( MAX_WORKER_THREADS );
+
+  {
+    static const int cv_TEMP_STORE = SQLITE_TEMP_STORE;
+    Tcl_LinkVar(interp, "TEMP_STORE", (char *)&(cv_TEMP_STORE),
+                TCL_LINK_INT | TCL_LINK_READ_ONLY);
+  }
+
+#ifdef _MSC_VER
+  {
+    static const int cv__MSC_VER = 1;
+    Tcl_LinkVar(interp, "_MSC_VER", (char *)&(cv__MSC_VER),
+                TCL_LINK_INT | TCL_LINK_READ_ONLY);
+  }
+#endif
+#ifdef __GNUC__
+  {
+    static const int cv___GNUC__ = 1;
+    Tcl_LinkVar(interp, "__GNUC__", (char *)&(cv___GNUC__),
+                TCL_LINK_INT | TCL_LINK_READ_ONLY);
+  }
+#endif
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqliteconfig_Init(Tcl_Interp *interp){
+  set_options(interp);
+  return TCL_OK;
+}
diff --git a/src/test_delete.c b/src/test_delete.c
new file mode 100644
index 0000000..68fdbc6
--- /dev/null
+++ b/src/test_delete.c
@@ -0,0 +1,156 @@
+/*
+** 2016 September 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains test code to delete an SQLite database and all
+** of its associated files. Associated files include:
+**
+**   * The journal file.
+**   * The wal file.
+**   * The SQLITE_ENABLE_8_3_NAMES version of the db, journal or wal files.
+**   * Files created by the test_multiplex.c module to extend any of the 
+**     above.
+*/
+
+#ifndef SQLITE_OS_WIN
+#  include <unistd.h>
+#  include <errno.h>
+#endif
+#include <string.h>
+#include <assert.h>
+#include "sqlite3.h"
+
+/* The following #defines are copied from test_multiplex.c */
+#ifndef MX_CHUNK_NUMBER 
+# define MX_CHUNK_NUMBER 299
+#endif
+#ifndef SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET
+# define SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET 400
+#endif
+#ifndef SQLITE_MULTIPLEX_WAL_8_3_OFFSET
+# define SQLITE_MULTIPLEX_WAL_8_3_OFFSET 700
+#endif
+
+/*
+** This routine is a copy of (most of) the code from SQLite function
+** sqlite3FileSuffix3(). It modifies the filename in buffer z in the
+** same way as SQLite does when in 8.3 filenames mode.
+*/
+static void sqlite3Delete83Name(char *z){
+  int i, sz;
+  sz = (int)strlen(z);
+  for(i=sz-1; i>0 && z[i]!='/' && z[i]!='.'; i--){}
+  if( z[i]=='.' && (sz>i+4) ) memmove(&z[i+1], &z[sz-3], 4);
+}
+
+/*
+** zFile is a filename. Assuming no error occurs, if this file exists, 
+** set *pbExists to true and unlink it. Or, if the file does not exist,
+** set *pbExists to false before returning.
+**
+** If an error occurs, non-zero is returned. Or, if no error occurs, zero.
+*/
+static int sqlite3DeleteUnlinkIfExists(
+  sqlite3_vfs *pVfs,
+  const char *zFile, 
+  int *pbExists
+){
+  int rc = SQLITE_ERROR;
+#if SQLITE_OS_WIN
+  if( pVfs ){
+    if( pbExists ) *pbExists = 1;
+    rc = pVfs->xDelete(pVfs, zFile, 0);
+    if( rc==SQLITE_IOERR_DELETE_NOENT ){
+      if( pbExists ) *pbExists = 0;
+      rc = SQLITE_OK;
+    }
+  }
+#else
+  assert( pVfs==0 );
+  rc = access(zFile, F_OK);
+  if( rc ){
+    if( errno==ENOENT ){ 
+      if( pbExists ) *pbExists = 0;
+      rc = SQLITE_OK; 
+    }
+  }else{
+    if( pbExists ) *pbExists = 1;
+    rc = unlink(zFile);
+  }
+#endif
+  return rc;
+}
+
+/*
+** Delete the database file identified by the string argument passed to this
+** function. The string must contain a filename, not an SQLite URI.
+*/
+SQLITE_API int sqlite3_delete_database(
+  const char *zFile               /* File to delete */
+){
+  char *zBuf;                     /* Buffer to sprintf() filenames to */
+  int nBuf;                       /* Size of buffer in bytes */
+  int rc = 0;                     /* System error code */
+  int i;                          /* Iterate through azFmt[] and aMFile[] */
+
+  const char *azFmt[] = { "%s", "%s-journal", "%s-wal", "%s-shm" };
+
+  struct MFile {
+    const char *zFmt;
+    int iOffset;
+    int b83;
+  } aMFile[] = {
+    { "%s%03d",         0,   0 },
+    { "%s-journal%03d", 0,   0 },
+    { "%s-wal%03d",     0,   0 },
+    { "%s%03d",         0,   1 },
+    { "%s-journal%03d", SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET, 1 },
+    { "%s-wal%03d",     SQLITE_MULTIPLEX_WAL_8_3_OFFSET, 1 },
+  };
+
+#ifdef SQLITE_OS_WIN
+  sqlite3_vfs *pVfs = sqlite3_vfs_find("win32");
+#else
+  sqlite3_vfs *pVfs = 0;
+#endif
+
+  /* Allocate a buffer large enough for any of the files that need to be
+  ** deleted.  */
+  nBuf = (int)strlen(zFile) + 100;
+  zBuf = (char*)sqlite3_malloc(nBuf);
+  if( zBuf==0 ) return SQLITE_NOMEM;
+
+  /* Delete both the regular and 8.3 filenames versions of the database,
+  ** journal, wal and shm files.  */
+  for(i=0; rc==0 && i<sizeof(azFmt)/sizeof(azFmt[0]); i++){
+    sqlite3_snprintf(nBuf, zBuf, azFmt[i], zFile);
+    rc = sqlite3DeleteUnlinkIfExists(pVfs, zBuf, 0);
+    if( rc==0 && i!=0 ){
+      sqlite3Delete83Name(zBuf);
+      rc = sqlite3DeleteUnlinkIfExists(pVfs, zBuf, 0);
+    }
+  }
+
+  /* Delete any multiplexor files */
+  for(i=0; rc==0 && i<sizeof(aMFile)/sizeof(aMFile[0]); i++){
+    struct MFile *p = &aMFile[i];
+    int iChunk;
+    for(iChunk=1; iChunk<=MX_CHUNK_NUMBER; iChunk++){
+      int bExists;
+      sqlite3_snprintf(nBuf, zBuf, p->zFmt, zFile, iChunk+p->iOffset);
+      if( p->b83 ) sqlite3Delete83Name(zBuf);
+      rc = sqlite3DeleteUnlinkIfExists(pVfs, zBuf, &bExists);
+      if( bExists==0 || rc!=0 ) break;
+    }
+  }
+
+  sqlite3_free(zBuf);
+  return (rc ? SQLITE_ERROR : SQLITE_OK);
+}
diff --git a/src/test_demovfs.c b/src/test_demovfs.c
new file mode 100644
index 0000000..e990e98
--- /dev/null
+++ b/src/test_demovfs.c
@@ -0,0 +1,690 @@
+/*
+** 2010 April 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements an example of a simple VFS implementation that 
+** omits complex features often not required or not possible on embedded
+** platforms.  Code is included to buffer writes to the journal file, 
+** which can be a significant performance improvement on some embedded
+** platforms.
+**
+** OVERVIEW
+**
+**   The code in this file implements a minimal SQLite VFS that can be 
+**   used on Linux and other posix-like operating systems. The following 
+**   system calls are used:
+**
+**    File-system: access(), unlink(), getcwd()
+**    File IO:     open(), read(), write(), fsync(), close(), fstat()
+**    Other:       sleep(), usleep(), time()
+**
+**   The following VFS features are omitted:
+**
+**     1. File locking. The user must ensure that there is at most one
+**        connection to each database when using this VFS. Multiple
+**        connections to a single shared-cache count as a single connection
+**        for the purposes of the previous statement.
+**
+**     2. The loading of dynamic extensions (shared libraries).
+**
+**     3. Temporary files. The user must configure SQLite to use in-memory
+**        temp files when using this VFS. The easiest way to do this is to
+**        compile with:
+**
+**          -DSQLITE_TEMP_STORE=3
+**
+**     4. File truncation. As of version 3.6.24, SQLite may run without
+**        a working xTruncate() call, providing the user does not configure
+**        SQLite to use "journal_mode=truncate", or use both
+**        "journal_mode=persist" and ATTACHed databases.
+**
+**   It is assumed that the system uses UNIX-like path-names. Specifically,
+**   that '/' characters are used to separate path components and that
+**   a path-name is a relative path unless it begins with a '/'. And that
+**   no UTF-8 encoded paths are greater than 512 bytes in length.
+**
+** JOURNAL WRITE-BUFFERING
+**
+**   To commit a transaction to the database, SQLite first writes rollback
+**   information into the journal file. This usually consists of 4 steps:
+**
+**     1. The rollback information is sequentially written into the journal
+**        file, starting at the start of the file.
+**     2. The journal file is synced to disk.
+**     3. A modification is made to the first few bytes of the journal file.
+**     4. The journal file is synced to disk again.
+**
+**   Most of the data is written in step 1 using a series of calls to the
+**   VFS xWrite() method. The buffers passed to the xWrite() calls are of
+**   various sizes. For example, as of version 3.6.24, when committing a 
+**   transaction that modifies 3 pages of a database file that uses 4096 
+**   byte pages residing on a media with 512 byte sectors, SQLite makes 
+**   eleven calls to the xWrite() method to create the rollback journal, 
+**   as follows:
+**
+**             Write offset | Bytes written
+**             ----------------------------
+**                        0            512
+**                      512              4
+**                      516           4096
+**                     4612              4
+**                     4616              4
+**                     4620           4096
+**                     8716              4
+**                     8720              4
+**                     8724           4096
+**                    12820              4
+**             ++++++++++++SYNC+++++++++++
+**                        0             12
+**             ++++++++++++SYNC+++++++++++
+**
+**   On many operating systems, this is an efficient way to write to a file.
+**   However, on some embedded systems that do not cache writes in OS 
+**   buffers it is much more efficient to write data in blocks that are
+**   an integer multiple of the sector-size in size and aligned at the
+**   start of a sector.
+**
+**   To work around this, the code in this file allocates a fixed size
+**   buffer of SQLITE_DEMOVFS_BUFFERSZ using sqlite3_malloc() whenever a 
+**   journal file is opened. It uses the buffer to coalesce sequential
+**   writes into aligned SQLITE_DEMOVFS_BUFFERSZ blocks. When SQLite
+**   invokes the xSync() method to sync the contents of the file to disk,
+**   all accumulated data is written out, even if it does not constitute
+**   a complete block. This means the actual IO to create the rollback 
+**   journal for the example transaction above is this:
+**
+**             Write offset | Bytes written
+**             ----------------------------
+**                        0           8192
+**                     8192           4632
+**             ++++++++++++SYNC+++++++++++
+**                        0             12
+**             ++++++++++++SYNC+++++++++++
+**
+**   Much more efficient if the underlying OS is not caching write 
+**   operations.
+*/
+
+#if !defined(SQLITE_TEST) || SQLITE_OS_UNIX
+
+#include "sqlite3.h"
+
+#include <assert.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/file.h>
+#include <sys/param.h>
+#include <unistd.h>
+#include <time.h>
+#include <errno.h>
+#include <fcntl.h>
+
+/*
+** Size of the write buffer used by journal files in bytes.
+*/
+#ifndef SQLITE_DEMOVFS_BUFFERSZ
+# define SQLITE_DEMOVFS_BUFFERSZ 8192
+#endif
+
+/*
+** The maximum pathname length supported by this VFS.
+*/
+#define MAXPATHNAME 512
+
+/*
+** When using this VFS, the sqlite3_file* handles that SQLite uses are
+** actually pointers to instances of type DemoFile.
+*/
+typedef struct DemoFile DemoFile;
+struct DemoFile {
+  sqlite3_file base;              /* Base class. Must be first. */
+  int fd;                         /* File descriptor */
+
+  char *aBuffer;                  /* Pointer to malloc'd buffer */
+  int nBuffer;                    /* Valid bytes of data in zBuffer */
+  sqlite3_int64 iBufferOfst;      /* Offset in file of zBuffer[0] */
+};
+
+/*
+** Write directly to the file passed as the first argument. Even if the
+** file has a write-buffer (DemoFile.aBuffer), ignore it.
+*/
+static int demoDirectWrite(
+  DemoFile *p,                    /* File handle */
+  const void *zBuf,               /* Buffer containing data to write */
+  int iAmt,                       /* Size of data to write in bytes */
+  sqlite_int64 iOfst              /* File offset to write to */
+){
+  off_t ofst;                     /* Return value from lseek() */
+  size_t nWrite;                  /* Return value from write() */
+
+  ofst = lseek(p->fd, iOfst, SEEK_SET);
+  if( ofst!=iOfst ){
+    return SQLITE_IOERR_WRITE;
+  }
+
+  nWrite = write(p->fd, zBuf, iAmt);
+  if( nWrite!=iAmt ){
+    return SQLITE_IOERR_WRITE;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Flush the contents of the DemoFile.aBuffer buffer to disk. This is a
+** no-op if this particular file does not have a buffer (i.e. it is not
+** a journal file) or if the buffer is currently empty.
+*/
+static int demoFlushBuffer(DemoFile *p){
+  int rc = SQLITE_OK;
+  if( p->nBuffer ){
+    rc = demoDirectWrite(p, p->aBuffer, p->nBuffer, p->iBufferOfst);
+    p->nBuffer = 0;
+  }
+  return rc;
+}
+
+/*
+** Close a file.
+*/
+static int demoClose(sqlite3_file *pFile){
+  int rc;
+  DemoFile *p = (DemoFile*)pFile;
+  rc = demoFlushBuffer(p);
+  sqlite3_free(p->aBuffer);
+  close(p->fd);
+  return rc;
+}
+
+/*
+** Read data from a file.
+*/
+static int demoRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  DemoFile *p = (DemoFile*)pFile;
+  off_t ofst;                     /* Return value from lseek() */
+  int nRead;                      /* Return value from read() */
+  int rc;                         /* Return code from demoFlushBuffer() */
+
+  /* Flush any data in the write buffer to disk in case this operation
+  ** is trying to read data the file-region currently cached in the buffer.
+  ** It would be possible to detect this case and possibly save an 
+  ** unnecessary write here, but in practice SQLite will rarely read from
+  ** a journal file when there is data cached in the write-buffer.
+  */
+  rc = demoFlushBuffer(p);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  ofst = lseek(p->fd, iOfst, SEEK_SET);
+  if( ofst!=iOfst ){
+    return SQLITE_IOERR_READ;
+  }
+  nRead = read(p->fd, zBuf, iAmt);
+
+  if( nRead==iAmt ){
+    return SQLITE_OK;
+  }else if( nRead>=0 ){
+    if( nRead<iAmt ){
+      memset(&((char*)zBuf)[nRead], 0, iAmt-nRead);
+    }
+    return SQLITE_IOERR_SHORT_READ;
+  }
+
+  return SQLITE_IOERR_READ;
+}
+
+/*
+** Write data to a crash-file.
+*/
+static int demoWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  DemoFile *p = (DemoFile*)pFile;
+  
+  if( p->aBuffer ){
+    char *z = (char *)zBuf;       /* Pointer to remaining data to write */
+    int n = iAmt;                 /* Number of bytes at z */
+    sqlite3_int64 i = iOfst;      /* File offset to write to */
+
+    while( n>0 ){
+      int nCopy;                  /* Number of bytes to copy into buffer */
+
+      /* If the buffer is full, or if this data is not being written directly
+      ** following the data already buffered, flush the buffer. Flushing
+      ** the buffer is a no-op if it is empty.  
+      */
+      if( p->nBuffer==SQLITE_DEMOVFS_BUFFERSZ || p->iBufferOfst+p->nBuffer!=i ){
+        int rc = demoFlushBuffer(p);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+      }
+      assert( p->nBuffer==0 || p->iBufferOfst+p->nBuffer==i );
+      p->iBufferOfst = i - p->nBuffer;
+
+      /* Copy as much data as possible into the buffer. */
+      nCopy = SQLITE_DEMOVFS_BUFFERSZ - p->nBuffer;
+      if( nCopy>n ){
+        nCopy = n;
+      }
+      memcpy(&p->aBuffer[p->nBuffer], z, nCopy);
+      p->nBuffer += nCopy;
+
+      n -= nCopy;
+      i += nCopy;
+      z += nCopy;
+    }
+  }else{
+    return demoDirectWrite(p, zBuf, iAmt, iOfst);
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Truncate a file. This is a no-op for this VFS (see header comments at
+** the top of the file).
+*/
+static int demoTruncate(sqlite3_file *pFile, sqlite_int64 size){
+#if 0
+  if( ftruncate(((DemoFile *)pFile)->fd, size) ) return SQLITE_IOERR_TRUNCATE;
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Sync the contents of the file to the persistent media.
+*/
+static int demoSync(sqlite3_file *pFile, int flags){
+  DemoFile *p = (DemoFile*)pFile;
+  int rc;
+
+  rc = demoFlushBuffer(p);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  rc = fsync(p->fd);
+  return (rc==0 ? SQLITE_OK : SQLITE_IOERR_FSYNC);
+}
+
+/*
+** Write the size of the file in bytes to *pSize.
+*/
+static int demoFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  DemoFile *p = (DemoFile*)pFile;
+  int rc;                         /* Return code from fstat() call */
+  struct stat sStat;              /* Output of fstat() call */
+
+  /* Flush the contents of the buffer to disk. As with the flush in the
+  ** demoRead() method, it would be possible to avoid this and save a write
+  ** here and there. But in practice this comes up so infrequently it is
+  ** not worth the trouble.
+  */
+  rc = demoFlushBuffer(p);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  rc = fstat(p->fd, &sStat);
+  if( rc!=0 ) return SQLITE_IOERR_FSTAT;
+  *pSize = sStat.st_size;
+  return SQLITE_OK;
+}
+
+/*
+** Locking functions. The xLock() and xUnlock() methods are both no-ops.
+** The xCheckReservedLock() always indicates that no other process holds
+** a reserved lock on the database file. This ensures that if a hot-journal
+** file is found in the file-system it is rolled back.
+*/
+static int demoLock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+static int demoUnlock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+static int demoCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** No xFileControl() verbs are implemented by this VFS.
+*/
+static int demoFileControl(sqlite3_file *pFile, int op, void *pArg){
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** The xSectorSize() and xDeviceCharacteristics() methods. These two
+** may return special values allowing SQLite to optimize file-system 
+** access to some extent. But it is also safe to simply return 0.
+*/
+static int demoSectorSize(sqlite3_file *pFile){
+  return 0;
+}
+static int demoDeviceCharacteristics(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Open a file handle.
+*/
+static int demoOpen(
+  sqlite3_vfs *pVfs,              /* VFS */
+  const char *zName,              /* File to open, or 0 for a temp file */
+  sqlite3_file *pFile,            /* Pointer to DemoFile struct to populate */
+  int flags,                      /* Input SQLITE_OPEN_XXX flags */
+  int *pOutFlags                  /* Output SQLITE_OPEN_XXX flags (or NULL) */
+){
+  static const sqlite3_io_methods demoio = {
+    1,                            /* iVersion */
+    demoClose,                    /* xClose */
+    demoRead,                     /* xRead */
+    demoWrite,                    /* xWrite */
+    demoTruncate,                 /* xTruncate */
+    demoSync,                     /* xSync */
+    demoFileSize,                 /* xFileSize */
+    demoLock,                     /* xLock */
+    demoUnlock,                   /* xUnlock */
+    demoCheckReservedLock,        /* xCheckReservedLock */
+    demoFileControl,              /* xFileControl */
+    demoSectorSize,               /* xSectorSize */
+    demoDeviceCharacteristics     /* xDeviceCharacteristics */
+  };
+
+  DemoFile *p = (DemoFile*)pFile; /* Populate this structure */
+  int oflags = 0;                 /* flags to pass to open() call */
+  char *aBuf = 0;
+
+  if( zName==0 ){
+    return SQLITE_IOERR;
+  }
+
+  if( flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    aBuf = (char *)sqlite3_malloc(SQLITE_DEMOVFS_BUFFERSZ);
+    if( !aBuf ){
+      return SQLITE_NOMEM;
+    }
+  }
+
+  if( flags&SQLITE_OPEN_EXCLUSIVE ) oflags |= O_EXCL;
+  if( flags&SQLITE_OPEN_CREATE )    oflags |= O_CREAT;
+  if( flags&SQLITE_OPEN_READONLY )  oflags |= O_RDONLY;
+  if( flags&SQLITE_OPEN_READWRITE ) oflags |= O_RDWR;
+
+  memset(p, 0, sizeof(DemoFile));
+  p->fd = open(zName, oflags, 0600);
+  if( p->fd<0 ){
+    sqlite3_free(aBuf);
+    return SQLITE_CANTOPEN;
+  }
+  p->aBuffer = aBuf;
+
+  if( pOutFlags ){
+    *pOutFlags = flags;
+  }
+  p->base.pMethods = &demoio;
+  return SQLITE_OK;
+}
+
+/*
+** Delete the file identified by argument zPath. If the dirSync parameter
+** is non-zero, then ensure the file-system modification to delete the
+** file has been synced to disk before returning.
+*/
+static int demoDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc;                         /* Return code */
+
+  rc = unlink(zPath);
+  if( rc!=0 && errno==ENOENT ) return SQLITE_OK;
+
+  if( rc==0 && dirSync ){
+    int dfd;                      /* File descriptor open on directory */
+    char *zSlash;
+    char zDir[MAXPATHNAME+1];     /* Name of directory containing file zPath */
+
+    /* Figure out the directory name from the path of the file deleted. */
+    sqlite3_snprintf(MAXPATHNAME, zDir, "%s", zPath);
+    zDir[MAXPATHNAME] = '\0';
+    zSlash = strrchr(zDir,'/');
+    if( zSlash ){
+      /* Open a file-descriptor on the directory. Sync. Close. */
+      zSlash[0] = 0;
+      dfd = open(zDir, O_RDONLY, 0);
+      if( dfd<0 ){
+        rc = -1;
+      }else{
+        rc = fsync(dfd);
+        close(dfd);
+      }
+    }
+  }
+  return (rc==0 ? SQLITE_OK : SQLITE_IOERR_DELETE);
+}
+
+#ifndef F_OK
+# define F_OK 0
+#endif
+#ifndef R_OK
+# define R_OK 4
+#endif
+#ifndef W_OK
+# define W_OK 2
+#endif
+
+/*
+** Query the file-system to see if the named file exists, is readable or
+** is both readable and writable.
+*/
+static int demoAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  int rc;                         /* access() return code */
+  int eAccess = F_OK;             /* Second argument to access() */
+
+  assert( flags==SQLITE_ACCESS_EXISTS       /* access(zPath, F_OK) */
+       || flags==SQLITE_ACCESS_READ         /* access(zPath, R_OK) */
+       || flags==SQLITE_ACCESS_READWRITE    /* access(zPath, R_OK|W_OK) */
+  );
+
+  if( flags==SQLITE_ACCESS_READWRITE ) eAccess = R_OK|W_OK;
+  if( flags==SQLITE_ACCESS_READ )      eAccess = R_OK;
+
+  rc = access(zPath, eAccess);
+  *pResOut = (rc==0);
+  return SQLITE_OK;
+}
+
+/*
+** Argument zPath points to a nul-terminated string containing a file path.
+** If zPath is an absolute path, then it is copied as is into the output 
+** buffer. Otherwise, if it is a relative path, then the equivalent full
+** path is written to the output buffer.
+**
+** This function assumes that paths are UNIX style. Specifically, that:
+**
+**   1. Path components are separated by a '/'. and 
+**   2. Full paths begin with a '/' character.
+*/
+static int demoFullPathname(
+  sqlite3_vfs *pVfs,              /* VFS */
+  const char *zPath,              /* Input path (possibly a relative path) */
+  int nPathOut,                   /* Size of output buffer in bytes */
+  char *zPathOut                  /* Pointer to output buffer */
+){
+  char zDir[MAXPATHNAME+1];
+  if( zPath[0]=='/' ){
+    zDir[0] = '\0';
+  }else{
+    if( getcwd(zDir, sizeof(zDir))==0 ) return SQLITE_IOERR;
+  }
+  zDir[MAXPATHNAME] = '\0';
+
+  sqlite3_snprintf(nPathOut, zPathOut, "%s/%s", zDir, zPath);
+  zPathOut[nPathOut-1] = '\0';
+
+  return SQLITE_OK;
+}
+
+/*
+** The following four VFS methods:
+**
+**   xDlOpen
+**   xDlError
+**   xDlSym
+**   xDlClose
+**
+** are supposed to implement the functionality needed by SQLite to load
+** extensions compiled as shared objects. This simple VFS does not support
+** this functionality, so the following functions are no-ops.
+*/
+static void *demoDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return 0;
+}
+static void demoDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3_snprintf(nByte, zErrMsg, "Loadable extensions are not supported");
+  zErrMsg[nByte-1] = '\0';
+}
+static void (*demoDlSym(sqlite3_vfs *pVfs, void *pH, const char *z))(void){
+  return 0;
+}
+static void demoDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  return;
+}
+
+/*
+** Parameter zByte points to a buffer nByte bytes in size. Populate this
+** buffer with pseudo-random data.
+*/
+static int demoRandomness(sqlite3_vfs *pVfs, int nByte, char *zByte){
+  return SQLITE_OK;
+}
+
+/*
+** Sleep for at least nMicro microseconds. Return the (approximate) number 
+** of microseconds slept for.
+*/
+static int demoSleep(sqlite3_vfs *pVfs, int nMicro){
+  sleep(nMicro / 1000000);
+  usleep(nMicro % 1000000);
+  return nMicro;
+}
+
+/*
+** Set *pTime to the current UTC time expressed as a Julian day. Return
+** SQLITE_OK if successful, or an error code otherwise.
+**
+**   http://en.wikipedia.org/wiki/Julian_day
+**
+** This implementation is not very good. The current time is rounded to
+** an integer number of seconds. Also, assuming time_t is a signed 32-bit 
+** value, it will stop working some time in the year 2038 AD (the so-called
+** "year 2038" problem that afflicts systems that store time this way). 
+*/
+static int demoCurrentTime(sqlite3_vfs *pVfs, double *pTime){
+  time_t t = time(0);
+  *pTime = t/86400.0 + 2440587.5; 
+  return SQLITE_OK;
+}
+
+/*
+** This function returns a pointer to the VFS implemented in this file.
+** To make the VFS available to SQLite:
+**
+**   sqlite3_vfs_register(sqlite3_demovfs(), 0);
+*/
+sqlite3_vfs *sqlite3_demovfs(void){
+  static sqlite3_vfs demovfs = {
+    1,                            /* iVersion */
+    sizeof(DemoFile),             /* szOsFile */
+    MAXPATHNAME,                  /* mxPathname */
+    0,                            /* pNext */
+    "demo",                       /* zName */
+    0,                            /* pAppData */
+    demoOpen,                     /* xOpen */
+    demoDelete,                   /* xDelete */
+    demoAccess,                   /* xAccess */
+    demoFullPathname,             /* xFullPathname */
+    demoDlOpen,                   /* xDlOpen */
+    demoDlError,                  /* xDlError */
+    demoDlSym,                    /* xDlSym */
+    demoDlClose,                  /* xDlClose */
+    demoRandomness,               /* xRandomness */
+    demoSleep,                    /* xSleep */
+    demoCurrentTime,              /* xCurrentTime */
+  };
+  return &demovfs;
+}
+
+#endif /* !defined(SQLITE_TEST) || SQLITE_OS_UNIX */
+
+
+#ifdef SQLITE_TEST
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+
+#if SQLITE_OS_UNIX
+static int SQLITE_TCLAPI register_demovfs(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs_register(sqlite3_demovfs(), 1);
+  return TCL_OK;
+}
+static int SQLITE_TCLAPI unregister_demovfs(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs_unregister(sqlite3_demovfs());
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_demovfs_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "register_demovfs", register_demovfs, 0, 0);
+  Tcl_CreateObjCommand(interp, "unregister_demovfs", unregister_demovfs, 0, 0);
+  return TCL_OK;
+}
+
+#else
+int Sqlitetest_demovfs_Init(Tcl_Interp *interp){ return TCL_OK; }
+#endif
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_devsym.c b/src/test_devsym.c
new file mode 100644
index 0000000..86b78f1
--- /dev/null
+++ b/src/test_devsym.c
@@ -0,0 +1,525 @@
+/*
+** 2008 Jan 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that modified the OS layer in order to simulate
+** different device types (by overriding the return values of the 
+** xDeviceCharacteristics() and xSectorSize() methods).
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+
+/*
+** Maximum pathname length supported by the devsym backend.
+*/
+#define DEVSYM_MAX_PATHNAME 512
+
+/*
+** Name used to identify this VFS.
+*/
+#define DEVSYM_VFS_NAME "devsym"
+#define WRITECRASH_NAME "writecrash"
+
+typedef struct devsym_file devsym_file;
+struct devsym_file {
+  sqlite3_file base;
+  sqlite3_file *pReal;
+};
+
+/*
+** Method declarations for devsym_file.
+*/
+static int devsymClose(sqlite3_file*);
+static int devsymRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int devsymWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int devsymTruncate(sqlite3_file*, sqlite3_int64 size);
+static int devsymSync(sqlite3_file*, int flags);
+static int devsymFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int devsymLock(sqlite3_file*, int);
+static int devsymUnlock(sqlite3_file*, int);
+static int devsymCheckReservedLock(sqlite3_file*, int *);
+static int devsymFileControl(sqlite3_file*, int op, void *pArg);
+static int devsymSectorSize(sqlite3_file*);
+static int devsymDeviceCharacteristics(sqlite3_file*);
+static int devsymShmLock(sqlite3_file*,int,int,int);
+static int devsymShmMap(sqlite3_file*,int,int,int, void volatile **);
+static void devsymShmBarrier(sqlite3_file*);
+static int devsymShmUnmap(sqlite3_file*,int);
+
+/*
+** Method declarations for devsym_vfs.
+*/
+static int devsymOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int devsymDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int devsymAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int devsymFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+static void *devsymDlOpen(sqlite3_vfs*, const char *zFilename);
+static void devsymDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*devsymDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void devsymDlClose(sqlite3_vfs*, void*);
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+static int devsymRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int devsymSleep(sqlite3_vfs*, int microseconds);
+static int devsymCurrentTime(sqlite3_vfs*, double*);
+
+struct DevsymGlobal {
+  sqlite3_vfs *pVfs;
+  int iDeviceChar;
+  int iSectorSize;
+  int nWriteCrash;
+};
+struct DevsymGlobal g = {0, 0, 512, 0};
+
+/*
+** Close an devsym-file.
+*/
+static int devsymClose(sqlite3_file *pFile){
+  devsym_file *p = (devsym_file *)pFile;
+  sqlite3OsClose(p->pReal);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from an devsym-file.
+*/
+static int devsymRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Write data to an devsym-file.
+*/
+static int devsymWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Truncate an devsym-file.
+*/
+static int devsymTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsTruncate(p->pReal, size);
+}
+
+/*
+** Sync an devsym-file.
+*/
+static int devsymSync(sqlite3_file *pFile, int flags){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsSync(p->pReal, flags);
+}
+
+/*
+** Return the current file-size of an devsym-file.
+*/
+static int devsymFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsFileSize(p->pReal, pSize);
+}
+
+/*
+** Lock an devsym-file.
+*/
+static int devsymLock(sqlite3_file *pFile, int eLock){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsLock(p->pReal, eLock);
+}
+
+/*
+** Unlock an devsym-file.
+*/
+static int devsymUnlock(sqlite3_file *pFile, int eLock){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsUnlock(p->pReal, eLock);
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an devsym-file.
+*/
+static int devsymCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsCheckReservedLock(p->pReal, pResOut);
+}
+
+/*
+** File control method. For custom operations on an devsym-file.
+*/
+static int devsymFileControl(sqlite3_file *pFile, int op, void *pArg){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsFileControl(p->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an devsym-file.
+*/
+static int devsymSectorSize(sqlite3_file *pFile){
+  return g.iSectorSize;
+}
+
+/*
+** Return the device characteristic flags supported by an devsym-file.
+*/
+static int devsymDeviceCharacteristics(sqlite3_file *pFile){
+  return g.iDeviceChar;
+}
+
+/*
+** Shared-memory methods are all pass-throughs.
+*/
+static int devsymShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  devsym_file *p = (devsym_file *)pFile;
+  return p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
+}
+static int devsymShmMap(
+  sqlite3_file *pFile, 
+  int iRegion, 
+  int szRegion, 
+  int isWrite, 
+  void volatile **pp
+){
+  devsym_file *p = (devsym_file *)pFile;
+  return p->pReal->pMethods->xShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
+}
+static void devsymShmBarrier(sqlite3_file *pFile){
+  devsym_file *p = (devsym_file *)pFile;
+  p->pReal->pMethods->xShmBarrier(p->pReal);
+}
+static int devsymShmUnmap(sqlite3_file *pFile, int delFlag){
+  devsym_file *p = (devsym_file *)pFile;
+  return p->pReal->pMethods->xShmUnmap(p->pReal, delFlag);
+}
+
+
+
+/*
+** Open an devsym file handle.
+*/
+static int devsymOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+static sqlite3_io_methods devsym_io_methods = {
+  2,                                /* iVersion */
+  devsymClose,                      /* xClose */
+  devsymRead,                       /* xRead */
+  devsymWrite,                      /* xWrite */
+  devsymTruncate,                   /* xTruncate */
+  devsymSync,                       /* xSync */
+  devsymFileSize,                   /* xFileSize */
+  devsymLock,                       /* xLock */
+  devsymUnlock,                     /* xUnlock */
+  devsymCheckReservedLock,          /* xCheckReservedLock */
+  devsymFileControl,                /* xFileControl */
+  devsymSectorSize,                 /* xSectorSize */
+  devsymDeviceCharacteristics,      /* xDeviceCharacteristics */
+  devsymShmMap,                     /* xShmMap */
+  devsymShmLock,                    /* xShmLock */
+  devsymShmBarrier,                 /* xShmBarrier */
+  devsymShmUnmap                    /* xShmUnmap */
+};
+
+  int rc;
+  devsym_file *p = (devsym_file *)pFile;
+  p->pReal = (sqlite3_file *)&p[1];
+  rc = sqlite3OsOpen(g.pVfs, zName, p->pReal, flags, pOutFlags);
+  if( p->pReal->pMethods ){
+    pFile->pMethods = &devsym_io_methods;
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int devsymDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  return sqlite3OsDelete(g.pVfs, zPath, dirSync);
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int devsymAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  return sqlite3OsAccess(g.pVfs, zPath, flags, pResOut);
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
+*/
+static int devsymFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  return sqlite3OsFullPathname(g.pVfs, zPath, nOut, zOut);
+}
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *devsymDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return sqlite3OsDlOpen(g.pVfs, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void devsymDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3OsDlError(g.pVfs, nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*devsymDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return sqlite3OsDlSym(g.pVfs, p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void devsymDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  sqlite3OsDlClose(g.pVfs, pHandle);
+}
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int devsymRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return sqlite3OsRandomness(g.pVfs, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int devsymSleep(sqlite3_vfs *pVfs, int nMicro){
+  return sqlite3OsSleep(g.pVfs, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int devsymCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return g.pVfs->xCurrentTime(g.pVfs, pTimeOut);
+}
+
+/*
+** Return the sector-size in bytes for an writecrash-file.
+*/
+static int writecrashSectorSize(sqlite3_file *pFile){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsSectorSize(p->pReal);
+}
+
+/*
+** Return the device characteristic flags supported by an writecrash-file.
+*/
+static int writecrashDeviceCharacteristics(sqlite3_file *pFile){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsDeviceCharacteristics(p->pReal);
+}
+
+/*
+** Write data to an writecrash-file.
+*/
+static int writecrashWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  devsym_file *p = (devsym_file *)pFile;
+  if( g.nWriteCrash>0 ){
+    g.nWriteCrash--;
+    if( g.nWriteCrash==0 ) abort();
+  }
+  return sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Open an writecrash file handle.
+*/
+static int writecrashOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+static sqlite3_io_methods writecrash_io_methods = {
+  2,                                /* iVersion */
+  devsymClose,                      /* xClose */
+  devsymRead,                       /* xRead */
+  writecrashWrite,                  /* xWrite */
+  devsymTruncate,                   /* xTruncate */
+  devsymSync,                       /* xSync */
+  devsymFileSize,                   /* xFileSize */
+  devsymLock,                       /* xLock */
+  devsymUnlock,                     /* xUnlock */
+  devsymCheckReservedLock,          /* xCheckReservedLock */
+  devsymFileControl,                /* xFileControl */
+  writecrashSectorSize,             /* xSectorSize */
+  writecrashDeviceCharacteristics,  /* xDeviceCharacteristics */
+  devsymShmMap,                     /* xShmMap */
+  devsymShmLock,                    /* xShmLock */
+  devsymShmBarrier,                 /* xShmBarrier */
+  devsymShmUnmap                    /* xShmUnmap */
+};
+
+  int rc;
+  devsym_file *p = (devsym_file *)pFile;
+  p->pReal = (sqlite3_file *)&p[1];
+  rc = sqlite3OsOpen(g.pVfs, zName, p->pReal, flags, pOutFlags);
+  if( p->pReal->pMethods ){
+    pFile->pMethods = &writecrash_io_methods;
+  }
+  return rc;
+}
+
+static sqlite3_vfs devsym_vfs = {
+  2,                     /* iVersion */
+  sizeof(devsym_file),      /* szOsFile */
+  DEVSYM_MAX_PATHNAME,      /* mxPathname */
+  0,                     /* pNext */
+  DEVSYM_VFS_NAME,          /* zName */
+  0,                     /* pAppData */
+  devsymOpen,               /* xOpen */
+  devsymDelete,             /* xDelete */
+  devsymAccess,             /* xAccess */
+  devsymFullPathname,       /* xFullPathname */
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  devsymDlOpen,             /* xDlOpen */
+  devsymDlError,            /* xDlError */
+  devsymDlSym,              /* xDlSym */
+  devsymDlClose,            /* xDlClose */
+#else
+  0,                        /* xDlOpen */
+  0,                        /* xDlError */
+  0,                        /* xDlSym */
+  0,                        /* xDlClose */
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+  devsymRandomness,         /* xRandomness */
+  devsymSleep,              /* xSleep */
+  devsymCurrentTime,        /* xCurrentTime */
+  0,                        /* xGetLastError */
+  0                         /* xCurrentTimeInt64 */
+};
+
+static sqlite3_vfs writecrash_vfs = {
+  2,                     /* iVersion */
+  sizeof(devsym_file),      /* szOsFile */
+  DEVSYM_MAX_PATHNAME,      /* mxPathname */
+  0,                     /* pNext */
+  WRITECRASH_NAME,          /* zName */
+  0,                     /* pAppData */
+  writecrashOpen,           /* xOpen */
+  devsymDelete,             /* xDelete */
+  devsymAccess,             /* xAccess */
+  devsymFullPathname,       /* xFullPathname */
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  devsymDlOpen,             /* xDlOpen */
+  devsymDlError,            /* xDlError */
+  devsymDlSym,              /* xDlSym */
+  devsymDlClose,            /* xDlClose */
+#else
+  0,                        /* xDlOpen */
+  0,                        /* xDlError */
+  0,                        /* xDlSym */
+  0,                        /* xDlClose */
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+  devsymRandomness,         /* xRandomness */
+  devsymSleep,              /* xSleep */
+  devsymCurrentTime,        /* xCurrentTime */
+  0,                        /* xGetLastError */
+  0                         /* xCurrentTimeInt64 */
+};
+
+
+/*
+** This procedure registers the devsym vfs with SQLite. If the argument is
+** true, the devsym vfs becomes the new default vfs. It is the only publicly
+** available function in this file.
+*/
+void devsym_register(int iDeviceChar, int iSectorSize){
+
+  if( g.pVfs==0 ){
+    g.pVfs = sqlite3_vfs_find(0);
+    devsym_vfs.szOsFile += g.pVfs->szOsFile;
+    writecrash_vfs.szOsFile += g.pVfs->szOsFile;
+    sqlite3_vfs_register(&devsym_vfs, 0);
+    sqlite3_vfs_register(&writecrash_vfs, 0);
+  }
+  if( iDeviceChar>=0 ){
+    g.iDeviceChar = iDeviceChar;
+  }else{
+    g.iDeviceChar = 0;
+  }
+  if( iSectorSize>=0 ){
+    g.iSectorSize = iSectorSize;
+  }else{
+    g.iSectorSize = 512;
+  }
+}
+
+void devsym_unregister(){
+  sqlite3_vfs_unregister(&devsym_vfs);
+  sqlite3_vfs_unregister(&writecrash_vfs);
+  g.pVfs = 0;
+  g.iDeviceChar = 0;
+  g.iSectorSize = 0;
+}
+
+void devsym_crash_on_write(int nWrite){
+  if( g.pVfs==0 ){
+    g.pVfs = sqlite3_vfs_find(0);
+    devsym_vfs.szOsFile += g.pVfs->szOsFile;
+    writecrash_vfs.szOsFile += g.pVfs->szOsFile;
+    sqlite3_vfs_register(&devsym_vfs, 0);
+    sqlite3_vfs_register(&writecrash_vfs, 0);
+  }
+  g.nWriteCrash = nWrite;
+}
+
+#endif
diff --git a/src/test_fs.c b/src/test_fs.c
new file mode 100644
index 0000000..f88f3a9
--- /dev/null
+++ b/src/test_fs.c
@@ -0,0 +1,932 @@
+/*
+** 2013 Jan 11
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+**
+** The FS virtual table is created as follows:
+**
+**   CREATE VIRTUAL TABLE tbl USING fs(idx);
+**
+** where idx is the name of a table in the db with 2 columns.  The virtual
+** table also has two columns - file path and file contents.
+**
+** The first column of table idx must be an IPK, and the second contains file
+** paths. For example:
+**
+**   CREATE TABLE idx(id INTEGER PRIMARY KEY, path TEXT);
+**   INSERT INTO idx VALUES(4, '/etc/passwd');
+**
+** Adding the row to the idx table automatically creates a row in the 
+** virtual table with rowid=4, path=/etc/passwd and a text field that 
+** contains data read from file /etc/passwd on disk.
+**
+*************************************************************************
+** Virtual table module "fsdir"
+**
+** This module is designed to be used as a read-only eponymous virtual table.
+** Its schema is as follows:
+**
+**   CREATE TABLE fsdir(dir TEXT, name TEXT);
+**
+** When queried, a WHERE term of the form "dir = $dir" must be provided. The
+** virtual table then appears to have one row for each entry in file-system
+** directory $dir. Column dir contains a copy of $dir, and column "name"
+** contains the name of the directory entry.
+**
+** If the specified $dir cannot be opened or is not a directory, it is not
+** an error. The virtual table appears to be empty in this case.
+**
+*************************************************************************
+** Virtual table module "fstree"
+**
+** This module is also a read-only eponymous virtual table with the 
+** following schema:
+**
+**   CREATE TABLE fstree(path TEXT, size INT, data BLOB);
+**
+** Running a "SELECT * FROM fstree" query on this table returns the entire
+** contents of the file-system, starting at "/". To restrict the search
+** space, the virtual table supports LIKE and GLOB constraints on the
+** 'path' column. For example:
+**
+**   SELECT * FROM fstree WHERE path LIKE '/home/dan/sqlite/%'
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#if SQLITE_OS_UNIX || defined(__MINGW_H)
+# include <unistd.h>
+# include <dirent.h>
+# ifndef DIRENT
+#  define DIRENT dirent
+# endif
+#endif
+#if SQLITE_OS_WIN
+# include <io.h>
+# if !defined(__MINGW_H)
+#  include "test_windirent.h"
+# endif
+# ifndef S_ISREG
+#  define S_ISREG(mode) (((mode) & S_IFMT) == S_IFREG)
+# endif
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+typedef struct fs_vtab fs_vtab;
+typedef struct fs_cursor fs_cursor;
+
+/* 
+** A fs virtual-table object 
+*/
+struct fs_vtab {
+  sqlite3_vtab base;
+  sqlite3 *db;
+  char *zDb;                      /* Name of db containing zTbl */
+  char *zTbl;                     /* Name of docid->file map table */
+};
+
+/* A fs cursor object */
+struct fs_cursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pStmt;
+  char *zBuf;
+  int nBuf;
+  int nAlloc;
+};
+
+/*************************************************************************
+** Start of fsdir implementation.
+*/
+typedef struct FsdirVtab FsdirVtab;
+typedef struct FsdirCsr FsdirCsr;
+struct FsdirVtab {
+  sqlite3_vtab base;
+};
+
+struct FsdirCsr {
+  sqlite3_vtab_cursor base;
+  char *zDir;                     /* Buffer containing directory scanned */
+  DIR *pDir;                      /* Open directory */
+  sqlite3_int64 iRowid;
+  struct DIRENT *pEntry;
+};
+
+/*
+** This function is the implementation of both the xConnect and xCreate
+** methods of the fsdir virtual table.
+**
+** The argv[] array contains the following:
+**
+**   argv[0]   -> module name  ("fs")
+**   argv[1]   -> database name
+**   argv[2]   -> table name
+**   argv[...] -> other module argument fields.
+*/
+static int fsdirConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  FsdirVtab *pTab;
+
+  if( argc!=3 ){
+    *pzErr = sqlite3_mprintf("wrong number of arguments");
+    return SQLITE_ERROR;
+  }
+
+  pTab = (FsdirVtab *)sqlite3_malloc(sizeof(FsdirVtab));
+  if( !pTab ) return SQLITE_NOMEM;
+  memset(pTab, 0, sizeof(FsdirVtab));
+
+  *ppVtab = &pTab->base;
+  sqlite3_declare_vtab(db, "CREATE TABLE xyz(dir, name);");
+
+  return SQLITE_OK;
+}
+
+/*
+** xDestroy/xDisconnect implementation.
+*/
+static int fsdirDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+
+/*
+** xBestIndex implementation. The only constraint supported is:
+**
+**   (dir = ?)
+*/
+static int fsdirBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int ii;
+
+  pIdxInfo->estimatedCost = 1000000000.0;
+
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    struct sqlite3_index_constraint const *p = &pIdxInfo->aConstraint[ii];
+    if( p->iColumn==0 && p->usable && p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      struct sqlite3_index_constraint_usage *pUsage;
+      pUsage = &pIdxInfo->aConstraintUsage[ii];
+      pUsage->omit = 1;
+      pUsage->argvIndex = 1;
+      pIdxInfo->idxNum = 1;
+      pIdxInfo->estimatedCost = 1.0;
+      break;
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** xOpen implementation.
+**
+** Open a new fsdir cursor.
+*/
+static int fsdirOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  FsdirCsr *pCur;
+  /* Allocate an extra 256 bytes because it is undefined how big dirent.d_name
+  ** is and we need enough space.  Linux provides plenty already, but
+  ** Solaris only provides one byte. */
+  pCur = (FsdirCsr*)sqlite3_malloc(sizeof(FsdirCsr)+256);
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(FsdirCsr));
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a fsdir cursor.
+*/
+static int fsdirClose(sqlite3_vtab_cursor *cur){
+  FsdirCsr *pCur = (FsdirCsr*)cur;
+  if( pCur->pDir ) closedir(pCur->pDir);
+  sqlite3_free(pCur->zDir);
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Skip the cursor to the next entry.
+*/
+static int fsdirNext(sqlite3_vtab_cursor *cur){
+  FsdirCsr *pCsr = (FsdirCsr*)cur;
+
+  if( pCsr->pDir ){
+    pCsr->pEntry = readdir(pCsr->pDir);
+    if( pCsr->pEntry==0 ){
+      closedir(pCsr->pDir);
+      pCsr->pDir = 0;
+    }
+    pCsr->iRowid++;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** xFilter method implementation.
+*/
+static int fsdirFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  FsdirCsr *pCsr = (FsdirCsr*)pVtabCursor;
+  const char *zDir;
+  int nDir;
+
+
+  if( idxNum!=1 || argc!=1 ){
+    return SQLITE_ERROR;
+  }
+
+  pCsr->iRowid = 0;
+  sqlite3_free(pCsr->zDir);
+  if( pCsr->pDir ){
+    closedir(pCsr->pDir);
+    pCsr->pDir = 0;
+  }
+
+  zDir = (const char*)sqlite3_value_text(argv[0]);
+  nDir = sqlite3_value_bytes(argv[0]);
+  pCsr->zDir = sqlite3_malloc(nDir+1);
+  if( pCsr->zDir==0 ) return SQLITE_NOMEM;
+  memcpy(pCsr->zDir, zDir, nDir+1);
+
+  pCsr->pDir = opendir(pCsr->zDir);
+  return fsdirNext(pVtabCursor); 
+}
+
+/*
+** xEof method implementation.
+*/
+static int fsdirEof(sqlite3_vtab_cursor *cur){
+  FsdirCsr *pCsr = (FsdirCsr*)cur;
+  return pCsr->pDir==0;
+}
+
+/*
+** xColumn method implementation.
+*/
+static int fsdirColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  FsdirCsr *pCsr = (FsdirCsr*)cur;
+  switch( i ){
+    case 0: /* dir */
+      sqlite3_result_text(ctx, pCsr->zDir, -1, SQLITE_STATIC);
+      break;
+
+    case 1: /* name */
+      sqlite3_result_text(ctx, pCsr->pEntry->d_name, -1, SQLITE_TRANSIENT);
+      break;
+
+    default:
+      assert( 0 );
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** xRowid method implementation.
+*/
+static int fsdirRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  FsdirCsr *pCsr = (FsdirCsr*)cur;
+  *pRowid = pCsr->iRowid;
+  return SQLITE_OK;
+}
+/*
+** End of fsdir implementation.
+*************************************************************************/
+
+/*************************************************************************
+** Start of fstree implementation.
+*/
+typedef struct FstreeVtab FstreeVtab;
+typedef struct FstreeCsr FstreeCsr;
+struct FstreeVtab {
+  sqlite3_vtab base;
+  sqlite3 *db;
+};
+
+struct FstreeCsr {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pStmt;            /* Statement to list paths */
+  int fd;                         /* File descriptor open on current path */
+};
+
+/*
+** This function is the implementation of both the xConnect and xCreate
+** methods of the fstree virtual table.
+**
+** The argv[] array contains the following:
+**
+**   argv[0]   -> module name  ("fs")
+**   argv[1]   -> database name
+**   argv[2]   -> table name
+**   argv[...] -> other module argument fields.
+*/
+static int fstreeConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  FstreeVtab *pTab;
+
+  if( argc!=3 ){
+    *pzErr = sqlite3_mprintf("wrong number of arguments");
+    return SQLITE_ERROR;
+  }
+
+  pTab = (FstreeVtab *)sqlite3_malloc(sizeof(FstreeVtab));
+  if( !pTab ) return SQLITE_NOMEM;
+  memset(pTab, 0, sizeof(FstreeVtab));
+  pTab->db = db;
+
+  *ppVtab = &pTab->base;
+  sqlite3_declare_vtab(db, "CREATE TABLE xyz(path, size, data);");
+
+  return SQLITE_OK;
+}
+
+/*
+** xDestroy/xDisconnect implementation.
+*/
+static int fstreeDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+
+/*
+** xBestIndex implementation. The only constraint supported is:
+**
+**   (dir = ?)
+*/
+static int fstreeBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int ii;
+
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    struct sqlite3_index_constraint const *p = &pIdxInfo->aConstraint[ii];
+    if( p->iColumn==0 && p->usable && (
+          p->op==SQLITE_INDEX_CONSTRAINT_GLOB
+       || p->op==SQLITE_INDEX_CONSTRAINT_LIKE
+       || p->op==SQLITE_INDEX_CONSTRAINT_EQ
+    )){
+      struct sqlite3_index_constraint_usage *pUsage;
+      pUsage = &pIdxInfo->aConstraintUsage[ii];
+      pIdxInfo->idxNum = p->op;
+      pUsage->argvIndex = 1;
+      pIdxInfo->estimatedCost = 100000.0;
+      return SQLITE_OK;
+    }
+  }
+
+  pIdxInfo->estimatedCost = 1000000000.0;
+  return SQLITE_OK;
+}
+
+/*
+** xOpen implementation.
+**
+** Open a new fstree cursor.
+*/
+static int fstreeOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  FstreeCsr *pCur;
+  pCur = (FstreeCsr*)sqlite3_malloc(sizeof(FstreeCsr));
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(FstreeCsr));
+  pCur->fd = -1;
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+static void fstreeCloseFd(FstreeCsr *pCsr){
+  if( pCsr->fd>=0 ){
+    close(pCsr->fd);
+    pCsr->fd = -1;
+  }
+}
+
+/*
+** Close a fstree cursor.
+*/
+static int fstreeClose(sqlite3_vtab_cursor *cur){
+  FstreeCsr *pCsr = (FstreeCsr*)cur;
+  sqlite3_finalize(pCsr->pStmt);
+  fstreeCloseFd(pCsr);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/*
+** Skip the cursor to the next entry.
+*/
+static int fstreeNext(sqlite3_vtab_cursor *cur){
+  FstreeCsr *pCsr = (FstreeCsr*)cur;
+  int rc;
+
+  fstreeCloseFd(pCsr);
+  rc = sqlite3_step(pCsr->pStmt);
+  if( rc!=SQLITE_ROW ){
+    rc = sqlite3_finalize(pCsr->pStmt);
+    pCsr->pStmt = 0;
+  }else{
+    rc = SQLITE_OK;
+    pCsr->fd = open((const char*)sqlite3_column_text(pCsr->pStmt, 0), O_RDONLY);
+  }
+
+  return rc;
+}
+
+/*
+** xFilter method implementation.
+*/
+static int fstreeFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  FstreeCsr *pCsr = (FstreeCsr*)pVtabCursor;
+  FstreeVtab *pTab = (FstreeVtab*)(pCsr->base.pVtab);
+  int rc;
+  const char *zSql = 
+"WITH r(d) AS ("
+"  SELECT CASE WHEN dir=?2 THEN ?3 ELSE dir END || '/' || name "
+"    FROM fsdir WHERE dir=?1 AND name NOT LIKE '.%'"
+"  UNION ALL"
+"  SELECT dir || '/' || name FROM r, fsdir WHERE dir=d AND name NOT LIKE '.%'"
+") SELECT d FROM r;";
+
+  char *zRoot;
+  int nRoot;
+  char *zPrefix;
+  int nPrefix;
+  const char *zDir;
+  int nDir;
+  char aWild[2] = { '\0', '\0' };
+
+#if SQLITE_OS_WIN
+  const char *zDrive = windirent_getenv("fstreeDrive");
+  if( zDrive==0 ){
+    zDrive = windirent_getenv("SystemDrive");
+  }
+  zRoot = sqlite3_mprintf("%s%c", zDrive, '/');
+  nRoot = sqlite3Strlen30(zRoot);
+  zPrefix = sqlite3_mprintf("%s", zDrive);
+  nPrefix = sqlite3Strlen30(zPrefix);
+#else
+  zRoot = "/";
+  nRoot = 1;
+  zPrefix = "";
+  nPrefix = 0;
+#endif
+
+  zDir = zRoot;
+  nDir = nRoot;
+
+  fstreeCloseFd(pCsr);
+  sqlite3_finalize(pCsr->pStmt);
+  pCsr->pStmt = 0;
+  rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  if( idxNum ){
+    const char *zQuery = (const char*)sqlite3_value_text(argv[0]);
+    switch( idxNum ){
+      case SQLITE_INDEX_CONSTRAINT_GLOB:
+        aWild[0] = '*';
+        aWild[1] = '?';
+        break;
+      case SQLITE_INDEX_CONSTRAINT_LIKE:
+        aWild[0] = '_';
+        aWild[1] = '%';
+        break;
+    }
+
+    if( sqlite3_strnicmp(zQuery, zPrefix, nPrefix)==0 ){
+      int i;
+      for(i=nPrefix; zQuery[i]; i++){
+        if( zQuery[i]==aWild[0] || zQuery[i]==aWild[1] ) break;
+        if( zQuery[i]=='/' ) nDir = i;
+      }
+      zDir = zQuery;
+    }
+  }
+  if( nDir==0 ) nDir = 1;
+
+  sqlite3_bind_text(pCsr->pStmt, 1, zDir, nDir, SQLITE_TRANSIENT);
+  sqlite3_bind_text(pCsr->pStmt, 2, zRoot, nRoot, SQLITE_TRANSIENT);
+  sqlite3_bind_text(pCsr->pStmt, 3, zPrefix, nPrefix, SQLITE_TRANSIENT);
+
+#if SQLITE_OS_WIN
+  sqlite3_free(zPrefix);
+  sqlite3_free(zRoot);
+#endif
+
+  return fstreeNext(pVtabCursor); 
+}
+
+/*
+** xEof method implementation.
+*/
+static int fstreeEof(sqlite3_vtab_cursor *cur){
+  FstreeCsr *pCsr = (FstreeCsr*)cur;
+  return pCsr->pStmt==0;
+}
+
+/*
+** xColumn method implementation.
+*/
+static int fstreeColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  FstreeCsr *pCsr = (FstreeCsr*)cur;
+  if( i==0 ){      /* path */
+    sqlite3_result_value(ctx, sqlite3_column_value(pCsr->pStmt, 0));
+  }else{
+    struct stat sBuf;
+    fstat(pCsr->fd, &sBuf);
+
+    if( S_ISREG(sBuf.st_mode) ){
+      if( i==1 ){
+        sqlite3_result_int64(ctx, sBuf.st_size);
+      }else{
+        int nRead;
+        char *aBuf = sqlite3_malloc(sBuf.st_mode+1);
+        if( !aBuf ) return SQLITE_NOMEM;
+        nRead = read(pCsr->fd, aBuf, sBuf.st_mode);
+        if( nRead!=sBuf.st_mode ){
+          return SQLITE_IOERR;
+        }
+        sqlite3_result_blob(ctx, aBuf, nRead, SQLITE_TRANSIENT);
+        sqlite3_free(aBuf);
+      }
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** xRowid method implementation.
+*/
+static int fstreeRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  *pRowid = 0;
+  return SQLITE_OK;
+}
+/*
+** End of fstree implementation.
+*************************************************************************/
+
+
+
+
+/*
+** This function is the implementation of both the xConnect and xCreate
+** methods of the fs virtual table.
+**
+** The argv[] array contains the following:
+**
+**   argv[0]   -> module name  ("fs")
+**   argv[1]   -> database name
+**   argv[2]   -> table name
+**   argv[...] -> other module argument fields.
+*/
+static int fsConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  fs_vtab *pVtab;
+  int nByte;
+  const char *zTbl;
+  const char *zDb = argv[1];
+
+  if( argc!=4 ){
+    *pzErr = sqlite3_mprintf("wrong number of arguments");
+    return SQLITE_ERROR;
+  }
+  zTbl = argv[3];
+
+  nByte = sizeof(fs_vtab) + (int)strlen(zTbl) + 1 + (int)strlen(zDb) + 1;
+  pVtab = (fs_vtab *)sqlite3MallocZero( nByte );
+  if( !pVtab ) return SQLITE_NOMEM;
+
+  pVtab->zTbl = (char *)&pVtab[1];
+  pVtab->zDb = &pVtab->zTbl[strlen(zTbl)+1];
+  pVtab->db = db;
+  memcpy(pVtab->zTbl, zTbl, strlen(zTbl));
+  memcpy(pVtab->zDb, zDb, strlen(zDb));
+  *ppVtab = &pVtab->base;
+  sqlite3_declare_vtab(db, "CREATE TABLE x(path TEXT, data TEXT)");
+
+  return SQLITE_OK;
+}
+/* Note that for this virtual table, the xCreate and xConnect
+** methods are identical. */
+
+static int fsDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+/* The xDisconnect and xDestroy methods are also the same */
+
+/*
+** Open a new fs cursor.
+*/
+static int fsOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  fs_cursor *pCur;
+  pCur = sqlite3MallocZero(sizeof(fs_cursor));
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a fs cursor.
+*/
+static int fsClose(sqlite3_vtab_cursor *cur){
+  fs_cursor *pCur = (fs_cursor *)cur;
+  sqlite3_finalize(pCur->pStmt);
+  sqlite3_free(pCur->zBuf);
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+static int fsNext(sqlite3_vtab_cursor *cur){
+  fs_cursor *pCur = (fs_cursor *)cur;
+  int rc;
+
+  rc = sqlite3_step(pCur->pStmt);
+  if( rc==SQLITE_ROW || rc==SQLITE_DONE ) rc = SQLITE_OK;
+
+  return rc;
+}
+
+static int fsFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  int rc;
+  fs_cursor *pCur = (fs_cursor *)pVtabCursor;
+  fs_vtab *p = (fs_vtab *)(pVtabCursor->pVtab);
+
+  assert( (idxNum==0 && argc==0) || (idxNum==1 && argc==1) );
+  if( idxNum==1 ){
+    char *zStmt = sqlite3_mprintf(
+        "SELECT * FROM %Q.%Q WHERE rowid=?", p->zDb, p->zTbl);
+    if( !zStmt ) return SQLITE_NOMEM;
+    rc = sqlite3_prepare_v2(p->db, zStmt, -1, &pCur->pStmt, 0);
+    sqlite3_free(zStmt);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_value(pCur->pStmt, 1, argv[0]);
+    }
+  }else{
+    char *zStmt = sqlite3_mprintf("SELECT * FROM %Q.%Q", p->zDb, p->zTbl);
+    if( !zStmt ) return SQLITE_NOMEM;
+    rc = sqlite3_prepare_v2(p->db, zStmt, -1, &pCur->pStmt, 0);
+    sqlite3_free(zStmt);
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = fsNext(pVtabCursor); 
+  }
+  return rc;
+}
+
+static int fsColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  fs_cursor *pCur = (fs_cursor*)cur;
+
+  assert( i==0 || i==1 || i==2 );
+  if( i==0 ){
+    sqlite3_result_value(ctx, sqlite3_column_value(pCur->pStmt, 0));
+  }else{
+    const char *zFile = (const char *)sqlite3_column_text(pCur->pStmt, 1);
+    struct stat sbuf;
+    int fd;
+
+    int n;
+    fd = open(zFile, O_RDONLY);
+    if( fd<0 ) return SQLITE_IOERR;
+    fstat(fd, &sbuf);
+
+    if( sbuf.st_size>=pCur->nAlloc ){
+      sqlite3_int64 nNew = sbuf.st_size*2;
+      char *zNew;
+      if( nNew<1024 ) nNew = 1024;
+
+      zNew = sqlite3Realloc(pCur->zBuf, nNew);
+      if( zNew==0 ){
+        close(fd);
+        return SQLITE_NOMEM;
+      }
+      pCur->zBuf = zNew;
+      pCur->nAlloc = nNew;
+    }
+
+    n = (int)read(fd, pCur->zBuf, sbuf.st_size);
+    close(fd);
+    if( n!=sbuf.st_size ) return SQLITE_ERROR;
+    pCur->nBuf = sbuf.st_size;
+    pCur->zBuf[pCur->nBuf] = '\0';
+
+    sqlite3_result_text(ctx, pCur->zBuf, -1, SQLITE_TRANSIENT);
+  }
+  return SQLITE_OK;
+}
+
+static int fsRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  fs_cursor *pCur = (fs_cursor*)cur;
+  *pRowid = sqlite3_column_int64(pCur->pStmt, 0);
+  return SQLITE_OK;
+}
+
+static int fsEof(sqlite3_vtab_cursor *cur){
+  fs_cursor *pCur = (fs_cursor*)cur;
+  return (sqlite3_data_count(pCur->pStmt)==0);
+}
+
+static int fsBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int ii;
+
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    struct sqlite3_index_constraint const *pCons = &pIdxInfo->aConstraint[ii];
+    if( pCons->iColumn<0 && pCons->usable
+           && pCons->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      struct sqlite3_index_constraint_usage *pUsage;
+      pUsage = &pIdxInfo->aConstraintUsage[ii];
+      pUsage->omit = 0;
+      pUsage->argvIndex = 1;
+      pIdxInfo->idxNum = 1;
+      pIdxInfo->estimatedCost = 1.0;
+      break;
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that provides read-only access to a
+** Tcl global variable namespace.
+*/
+static sqlite3_module fsModule = {
+  0,                         /* iVersion */
+  fsConnect,
+  fsConnect,
+  fsBestIndex,
+  fsDisconnect, 
+  fsDisconnect,
+  fsOpen,                      /* xOpen - open a cursor */
+  fsClose,                     /* xClose - close a cursor */
+  fsFilter,                    /* xFilter - configure scan constraints */
+  fsNext,                      /* xNext - advance a cursor */
+  fsEof,                       /* xEof - check for end of scan */
+  fsColumn,                    /* xColumn - read data */
+  fsRowid,                     /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+  0,                           /* xSavepoint */
+  0,                           /* xRelease */
+  0,                           /* xRollbackTo */
+  0,                           /* xShadowName */
+  0                            /* xIntegrity */
+};
+
+static sqlite3_module fsdirModule = {
+  0,                              /* iVersion */
+  fsdirConnect,                   /* xCreate */
+  fsdirConnect,                   /* xConnect */
+  fsdirBestIndex,                 /* xBestIndex */
+  fsdirDisconnect,                /* xDisconnect */
+  fsdirDisconnect,                /* xDestroy */
+  fsdirOpen,                      /* xOpen - open a cursor */
+  fsdirClose,                     /* xClose - close a cursor */
+  fsdirFilter,                    /* xFilter - configure scan constraints */
+  fsdirNext,                      /* xNext - advance a cursor */
+  fsdirEof,                       /* xEof - check for end of scan */
+  fsdirColumn,                    /* xColumn - read data */
+  fsdirRowid,                     /* xRowid - read data */
+  0,                              /* xUpdate */
+  0,                              /* xBegin */
+  0,                              /* xSync */
+  0,                              /* xCommit */
+  0,                              /* xRollback */
+  0,                              /* xFindMethod */
+  0,                              /* xRename */
+  0,                              /* xSavepoint */
+  0,                              /* xRelease */
+  0,                              /* xRollbackTo */
+  0,                              /* xShadowName */
+  0                               /* xIntegrity */
+};
+
+static sqlite3_module fstreeModule = {
+  0,                              /* iVersion */
+  fstreeConnect,                  /* xCreate */
+  fstreeConnect,                  /* xConnect */
+  fstreeBestIndex,                /* xBestIndex */
+  fstreeDisconnect,               /* xDisconnect */
+  fstreeDisconnect,               /* xDestroy */
+  fstreeOpen,                     /* xOpen - open a cursor */
+  fstreeClose,                    /* xClose - close a cursor */
+  fstreeFilter,                   /* xFilter - configure scan constraints */
+  fstreeNext,                     /* xNext - advance a cursor */
+  fstreeEof,                      /* xEof - check for end of scan */
+  fstreeColumn,                   /* xColumn - read data */
+  fstreeRowid,                    /* xRowid - read data */
+  0,                              /* xUpdate */
+  0,                              /* xBegin */
+  0,                              /* xSync */
+  0,                              /* xCommit */
+  0,                              /* xRollback */
+  0,                              /* xFindMethod */
+  0,                              /* xRename */
+  0,                              /* xSavepoint */
+  0,                              /* xRelease */
+  0,                              /* xRollbackTo */
+  0,                              /* xShadowName */
+  0                               /* xIntegrity */
+};
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the echo virtual table module.
+*/
+static int SQLITE_TCLAPI register_fs_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "fs", &fsModule, (void *)interp);
+  sqlite3_create_module(db, "fsdir", &fsdirModule, 0);
+  sqlite3_create_module(db, "fstree", &fstreeModule, 0);
+#endif
+  return TCL_OK;
+}
+
+#endif
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestfs_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_fs_module",   register_fs_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+#endif
+  return TCL_OK;
+}
diff --git a/src/test_func.c b/src/test_func.c
new file mode 100644
index 0000000..80df488
--- /dev/null
+++ b/src/test_func.c
@@ -0,0 +1,955 @@
+/*
+** 2008 March 19
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces.  This code
+** implements new SQL functions used by the test scripts.
+*/
+#include "sqlite3.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/*
+** Allocate nByte bytes of space using sqlite3_malloc(). If the
+** allocation fails, call sqlite3_result_error_nomem() to notify
+** the database handle that malloc() has failed.
+*/
+static void *testContextMalloc(sqlite3_context *context, int nByte){
+  char *z = sqlite3_malloc(nByte);
+  if( !z && nByte>0 ){
+    sqlite3_result_error_nomem(context);
+  }
+  return z;
+}
+
+/*
+** This function generates a string of random characters.  Used for
+** generating test data.
+*/
+static void randStr(sqlite3_context *context, int argc, sqlite3_value **argv){
+  static const unsigned char zSrc[] = 
+     "abcdefghijklmnopqrstuvwxyz"
+     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+     "0123456789"
+     ".-!,:*^+=_|?/<> ";
+  int iMin, iMax, n, r, i;
+  unsigned char zBuf[1000];
+
+  /* It used to be possible to call randstr() with any number of arguments,
+  ** but now it is registered with SQLite as requiring exactly 2.
+  */
+  assert(argc==2);
+
+  iMin = sqlite3_value_int(argv[0]);
+  if( iMin<0 ) iMin = 0;
+  if( iMin>=sizeof(zBuf) ) iMin = sizeof(zBuf)-1;
+  iMax = sqlite3_value_int(argv[1]);
+  if( iMax<iMin ) iMax = iMin;
+  if( iMax>=sizeof(zBuf) ) iMax = sizeof(zBuf)-1;
+  n = iMin;
+  if( iMax>iMin ){
+    sqlite3_randomness(sizeof(r), &r);
+    r &= 0x7fffffff;
+    n += r%(iMax + 1 - iMin);
+  }
+  assert( n<sizeof(zBuf) );
+  sqlite3_randomness(n, zBuf);
+  for(i=0; i<n; i++){
+    zBuf[i] = zSrc[zBuf[i]%(sizeof(zSrc)-1)];
+  }
+  zBuf[n] = 0;
+  sqlite3_result_text(context, (char*)zBuf, n, SQLITE_TRANSIENT);
+}
+
+/*
+** The following two SQL functions are used to test returning a text
+** result with a destructor. Function 'test_destructor' takes one argument
+** and returns the same argument interpreted as TEXT. A destructor is
+** passed with the sqlite3_result_text() call.
+**
+** SQL function 'test_destructor_count' returns the number of outstanding 
+** allocations made by 'test_destructor';
+**
+** WARNING: Not threadsafe.
+*/
+static int test_destructor_count_var = 0;
+static void destructor(void *p){
+  char *zVal = (char *)p;
+  assert(zVal);
+  zVal--;
+  sqlite3_free(zVal);
+  test_destructor_count_var--;
+}
+static void test_destructor(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  char *zVal;
+  int len;
+  
+  test_destructor_count_var++;
+  assert( nArg==1 );
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  len = sqlite3_value_bytes(argv[0]); 
+  zVal = testContextMalloc(pCtx, len+3);
+  if( !zVal ){
+    return;
+  }
+  zVal[len+1] = 0;
+  zVal[len+2] = 0;
+  zVal++;
+  memcpy(zVal, sqlite3_value_text(argv[0]), len);
+  sqlite3_result_text(pCtx, zVal, -1, destructor);
+}
+#ifndef SQLITE_OMIT_UTF16
+static void test_destructor16(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  char *zVal;
+  int len;
+  
+  test_destructor_count_var++;
+  assert( nArg==1 );
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  len = sqlite3_value_bytes16(argv[0]); 
+  zVal = testContextMalloc(pCtx, len+3);
+  if( !zVal ){
+    return;
+  }
+  zVal[len+1] = 0;
+  zVal[len+2] = 0;
+  zVal++;
+  memcpy(zVal, sqlite3_value_text16(argv[0]), len);
+  sqlite3_result_text16(pCtx, zVal, -1, destructor);
+}
+#endif
+static void test_destructor_count(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  sqlite3_result_int(pCtx, test_destructor_count_var);
+}
+
+/*
+** The following aggregate function, test_agg_errmsg16(), takes zero 
+** arguments. It returns the text value returned by the sqlite3_errmsg16()
+** API function.
+*/
+#ifndef SQLITE_UNTESTABLE
+void sqlite3BeginBenignMalloc(void);
+void sqlite3EndBenignMalloc(void);
+#else
+  #define sqlite3BeginBenignMalloc()
+  #define sqlite3EndBenignMalloc()
+#endif
+static void test_agg_errmsg16_step(sqlite3_context *a, int b,sqlite3_value **c){
+}
+static void test_agg_errmsg16_final(sqlite3_context *ctx){
+#ifndef SQLITE_OMIT_UTF16
+  const void *z;
+  sqlite3 * db = sqlite3_context_db_handle(ctx);
+  sqlite3_aggregate_context(ctx, 2048);
+  z = sqlite3_errmsg16(db);
+  sqlite3_result_text16(ctx, z, -1, SQLITE_TRANSIENT);
+#endif
+}
+
+/*
+** Routines for testing the sqlite3_get_auxdata() and sqlite3_set_auxdata()
+** interface.
+**
+** The test_auxdata() SQL function attempts to register each of its arguments
+** as auxiliary data.  If there are no prior registrations of aux data for
+** that argument (meaning the argument is not a constant or this is its first
+** call) then the result for that argument is 0.  If there is a prior
+** registration, the result for that argument is 1.  The overall result
+** is the individual argument results separated by spaces.
+*/
+static void free_test_auxdata(void *p) {sqlite3_free(p);}
+static void test_auxdata(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int i;
+  char *zRet = testContextMalloc(pCtx, nArg*2);
+  if( !zRet ) return;
+  memset(zRet, 0, nArg*2);
+  for(i=0; i<nArg; i++){
+    char const *z = (char*)sqlite3_value_text(argv[i]);
+    if( z ){
+      int n;
+      char *zAux = sqlite3_get_auxdata(pCtx, i);
+      if( zAux ){
+        zRet[i*2] = '1';
+        assert( strcmp(zAux,z)==0 );
+      }else {
+        zRet[i*2] = '0';
+      }
+      n = (int)strlen(z) + 1;
+      zAux = testContextMalloc(pCtx, n);
+      if( zAux ){
+        memcpy(zAux, z, n);
+        sqlite3_set_auxdata(pCtx, i, zAux, free_test_auxdata);
+      }
+      zRet[i*2+1] = ' ';
+    }
+  }
+  sqlite3_result_text(pCtx, zRet, 2*nArg-1, free_test_auxdata);
+}
+
+/*
+** A function to test error reporting from user functions. This function
+** returns a copy of its first argument as the error message.  If the
+** second argument exists, it becomes the error code.
+*/
+static void test_error(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  sqlite3_result_error(pCtx, (char*)sqlite3_value_text(argv[0]), -1);
+  if( nArg==2 ){
+    sqlite3_result_error_code(pCtx, sqlite3_value_int(argv[1]));
+  }
+}
+
+/*
+** Implementation of the counter(X) function.  If X is an integer
+** constant, then the first invocation will return X.  The second X+1.
+** and so forth.  Can be used (for example) to provide a sequence number
+** in a result set.
+*/
+static void counterFunc(
+  sqlite3_context *pCtx,   /* Function context */
+  int nArg,                /* Number of function arguments */
+  sqlite3_value **argv     /* Values for all function arguments */
+){
+  int *pCounter = (int*)sqlite3_get_auxdata(pCtx, 0);
+  if( pCounter==0 ){
+    pCounter = sqlite3_malloc( sizeof(*pCounter) );
+    if( pCounter==0 ){
+      sqlite3_result_error_nomem(pCtx);
+      return;
+    }
+    *pCounter = sqlite3_value_int(argv[0]);
+    sqlite3_set_auxdata(pCtx, 0, pCounter, sqlite3_free);
+  }else{
+    ++*pCounter;
+  }
+  sqlite3_result_int(pCtx, *pCounter);
+}
+
+
+/*
+** This function takes two arguments.  It performance UTF-8/16 type
+** conversions on the first argument then returns a copy of the second
+** argument.
+**
+** This function is used in cases such as the following:
+**
+**      SELECT test_isolation(x,x) FROM t1;
+**
+** We want to verify that the type conversions that occur on the
+** first argument do not invalidate the second argument.
+*/
+static void test_isolation(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3_value_text16(argv[0]);
+  sqlite3_value_text(argv[0]);
+  sqlite3_value_text16(argv[0]);
+  sqlite3_value_text(argv[0]);
+#endif
+  sqlite3_result_value(pCtx, argv[1]);
+}
+
+/*
+** Invoke an SQL statement recursively.  The function result is the 
+** first column of the first row of the result set.
+*/
+static void test_eval(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  sqlite3 *db = sqlite3_context_db_handle(pCtx);
+  const char *zSql;
+
+  zSql = (char*)sqlite3_value_text(argv[0]);
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_step(pStmt);
+    if( rc==SQLITE_ROW ){
+      sqlite3_result_value(pCtx, sqlite3_column_value(pStmt, 0));
+    }
+    rc = sqlite3_finalize(pStmt);
+  }
+  if( rc ){
+    char *zErr;
+    assert( pStmt==0 );
+    zErr = sqlite3_mprintf("sqlite3_prepare_v2() error: %s",sqlite3_errmsg(db));
+    sqlite3_result_text(pCtx, zErr, -1, sqlite3_free);
+    sqlite3_result_error_code(pCtx, rc);
+  }
+}
+
+
+/*
+** convert one character from hex to binary
+*/
+static int testHexChar(char c){
+  if( c>='0' && c<='9' ){
+    return c - '0';
+  }else if( c>='a' && c<='f' ){
+    return c - 'a' + 10;
+  }else if( c>='A' && c<='F' ){
+    return c - 'A' + 10;
+  }
+  return 0;
+}
+
+/*
+** Convert hex to binary.
+*/
+static void testHexToBin(const char *zIn, char *zOut){
+  while( zIn[0] && zIn[1] ){
+    *(zOut++) = (testHexChar(zIn[0])<<4) + testHexChar(zIn[1]);
+    zIn += 2;
+  }
+}
+
+/*
+**      hex_to_utf16be(HEX)
+**
+** Convert the input string from HEX into binary.  Then return the
+** result using sqlite3_result_text16le().
+*/
+#ifndef SQLITE_OMIT_UTF16
+static void testHexToUtf16be(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int n;
+  const char *zIn;
+  char *zOut;
+  assert( nArg==1 );
+  n = sqlite3_value_bytes(argv[0]);
+  zIn = (const char*)sqlite3_value_text(argv[0]);
+  zOut = sqlite3_malloc( n/2 );
+  if( zOut==0 ){
+    sqlite3_result_error_nomem(pCtx);
+  }else{
+    testHexToBin(zIn, zOut);
+    sqlite3_result_text16be(pCtx, zOut, n/2, sqlite3_free);
+  }
+}
+#endif
+
+/*
+**      hex_to_utf8(HEX)
+**
+** Convert the input string from HEX into binary.  Then return the
+** result using sqlite3_result_text16le().
+*/
+static void testHexToUtf8(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int n;
+  const char *zIn;
+  char *zOut;
+  assert( nArg==1 );
+  n = sqlite3_value_bytes(argv[0]);
+  zIn = (const char*)sqlite3_value_text(argv[0]);
+  zOut = sqlite3_malloc( n/2 );
+  if( zOut==0 ){
+    sqlite3_result_error_nomem(pCtx);
+  }else{
+    testHexToBin(zIn, zOut);
+    sqlite3_result_text(pCtx, zOut, n/2, sqlite3_free);
+  }
+}
+
+/*
+**      hex_to_utf16le(HEX)
+**
+** Convert the input string from HEX into binary.  Then return the
+** result using sqlite3_result_text16le().
+*/
+#ifndef SQLITE_OMIT_UTF16
+static void testHexToUtf16le(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int n;
+  const char *zIn;
+  char *zOut;
+  assert( nArg==1 );
+  n = sqlite3_value_bytes(argv[0]);
+  zIn = (const char*)sqlite3_value_text(argv[0]);
+  zOut = sqlite3_malloc( n/2 );
+  if( zOut==0 ){
+    sqlite3_result_error_nomem(pCtx);
+  }else{
+    testHexToBin(zIn, zOut);
+    sqlite3_result_text16le(pCtx, zOut, n/2, sqlite3_free);
+  }
+}
+#endif
+
+/*
+** SQL function:   real2hex(X)
+**
+** If argument X is a real number, then convert it into a string which is
+** the big-endian hexadecimal representation of the ieee754 encoding of
+** that number.  If X is not a real number, return NULL.
+*/
+static void real2hex(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  union {
+    sqlite3_uint64 i;
+    double r;
+    unsigned char x[8];
+  } v;
+  char zOut[20];
+  int i;
+  int bigEndian;
+  v.i = 1;
+  bigEndian = v.x[0]==0;
+  v.r = sqlite3_value_double(argv[0]);
+  for(i=0; i<8; i++){
+    if( bigEndian ){
+      zOut[i*2]   = "0123456789abcdef"[v.x[i]>>4];
+      zOut[i*2+1] = "0123456789abcdef"[v.x[i]&0xf];
+    }else{
+      zOut[14-i*2]   = "0123456789abcdef"[v.x[i]>>4];
+      zOut[14-i*2+1] = "0123456789abcdef"[v.x[i]&0xf];
+    }
+  }
+  zOut[16] = 0;
+  sqlite3_result_text(context, zOut, -1, SQLITE_TRANSIENT);
+}
+
+/*
+**     test_extract(record, field)
+**
+** This function implements an SQL user-function that accepts a blob
+** containing a formatted database record as the first argument. The
+** second argument is the index of the field within that record to
+** extract and return.
+*/
+static void test_extract(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  u8 *pRec;
+  u8 *pEndHdr;                    /* Points to one byte past record header */
+  u8 *pHdr;                       /* Current point in record header */
+  u8 *pBody;                      /* Current point in record data */
+  u64 nHdr;                       /* Bytes in record header */
+  int iIdx;                       /* Required field */
+  int iCurrent = 0;               /* Current field */
+
+  assert( argc==2 );
+  pRec = (u8*)sqlite3_value_blob(argv[0]);
+  iIdx = sqlite3_value_int(argv[1]);
+
+  pHdr = pRec + sqlite3GetVarint(pRec, &nHdr);
+  pBody = pEndHdr = &pRec[nHdr];
+
+  for(iCurrent=0; pHdr<pEndHdr && iCurrent<=iIdx; iCurrent++){
+    u64 iSerialType;
+    Mem mem;
+
+    memset(&mem, 0, sizeof(mem));
+    mem.db = db;
+    mem.enc = ENC(db);
+    pHdr += sqlite3GetVarint(pHdr, &iSerialType);
+    sqlite3VdbeSerialGet(pBody, (u32)iSerialType, &mem);
+    pBody += sqlite3VdbeSerialTypeLen((u32)iSerialType);
+
+    if( iCurrent==iIdx ){
+      sqlite3_result_value(context, &mem);
+    }
+
+    if( mem.szMalloc ) sqlite3DbFree(db, mem.zMalloc);
+  }
+}
+
+/*
+**      test_decode(record)
+**
+** This function implements an SQL user-function that accepts a blob
+** containing a formatted database record as its only argument. It returns
+** a tcl list (type SQLITE_TEXT) containing each of the values stored
+** in the record.
+*/
+static void test_decode(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  u8 *pRec;
+  u8 *pEndHdr;                    /* Points to one byte past record header */
+  u8 *pHdr;                       /* Current point in record header */
+  u8 *pBody;                      /* Current point in record data */
+  u64 nHdr;                       /* Bytes in record header */
+  Tcl_Obj *pRet;                  /* Return value */
+
+  pRet = Tcl_NewObj();
+  Tcl_IncrRefCount(pRet);
+
+  assert( argc==1 );
+  pRec = (u8*)sqlite3_value_blob(argv[0]);
+
+  pHdr = pRec + sqlite3GetVarint(pRec, &nHdr);
+  pBody = pEndHdr = &pRec[nHdr];
+  while( pHdr<pEndHdr ){
+    Tcl_Obj *pVal = 0;
+    u64 iSerialType;
+    Mem mem;
+
+    memset(&mem, 0, sizeof(mem));
+    mem.db = db;
+    mem.enc = ENC(db);
+    pHdr += sqlite3GetVarint(pHdr, &iSerialType);
+    sqlite3VdbeSerialGet(pBody, (u32)iSerialType, &mem);
+    pBody += sqlite3VdbeSerialTypeLen((u32)iSerialType);
+
+    switch( sqlite3_value_type(&mem) ){
+      case SQLITE_TEXT:
+        pVal = Tcl_NewStringObj((const char*)sqlite3_value_text(&mem), -1);
+        break;
+
+      case SQLITE_BLOB: {
+        char hexdigit[] = {
+          '0', '1', '2', '3', '4', '5', '6', '7',
+          '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+        };
+        int n = sqlite3_value_bytes(&mem);
+        u8 *z = (u8*)sqlite3_value_blob(&mem);
+        int i;
+        pVal = Tcl_NewStringObj("x'", -1);
+        for(i=0; i<n; i++){
+          char hex[3];
+          hex[0] = hexdigit[((z[i] >> 4) & 0x0F)];
+          hex[1] = hexdigit[(z[i] & 0x0F)];
+          hex[2] = '\0';
+          Tcl_AppendStringsToObj(pVal, hex, 0);
+        }
+        Tcl_AppendStringsToObj(pVal, "'", 0);
+        break;
+      }
+
+      case SQLITE_FLOAT:
+        pVal = Tcl_NewDoubleObj(sqlite3_value_double(&mem));
+        break;
+
+      case SQLITE_INTEGER:
+        pVal = Tcl_NewWideIntObj(sqlite3_value_int64(&mem));
+        break;
+
+      case SQLITE_NULL:
+        pVal = Tcl_NewStringObj("NULL", -1);
+        break;
+
+      default:
+        assert( 0 );
+    }
+
+    Tcl_ListObjAppendElement(0, pRet, pVal);
+
+    if( mem.szMalloc ){
+      sqlite3DbFree(db, mem.zMalloc);
+    }
+  }
+
+  sqlite3_result_text(context, Tcl_GetString(pRet), -1, SQLITE_TRANSIENT);
+  Tcl_DecrRefCount(pRet);
+}
+
+/*
+**       test_zeroblob(N)
+**
+** The implementation of scalar SQL function "test_zeroblob()". This is
+** similar to the built-in zeroblob() function, except that it does not
+** check that the integer parameter is within range before passing it
+** to sqlite3_result_zeroblob().
+*/
+static void test_zeroblob(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int nZero = sqlite3_value_int(argv[0]);
+  sqlite3_result_zeroblob(context, nZero);
+}
+
+/*         test_getsubtype(V)
+**
+** Return the subtype for value V.
+*/
+static void test_getsubtype(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_result_int(context, (int)sqlite3_value_subtype(argv[0]));
+}
+
+/*         test_frombind(A,B,C,...)
+**
+** Return an integer bitmask that has a bit set for every argument
+** (up to the first 63 arguments) that originates from a bind a parameter.
+*/
+static void test_frombind(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_uint64 m = 0;
+  int i;
+  for(i=0; i<argc && i<63; i++){
+    if( sqlite3_value_frombind(argv[i]) ) m |= ((sqlite3_uint64)1)<<i;
+  }
+  sqlite3_result_int64(context, (sqlite3_int64)m);
+}
+
+/*         test_setsubtype(V, T)
+**
+** Return the value V with its subtype changed to T
+*/
+static void test_setsubtype(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_result_value(context, argv[0]);
+  sqlite3_result_subtype(context, (unsigned int)sqlite3_value_int(argv[1]));
+}
+
+static int registerTestFunctions(
+  sqlite3 *db,
+  char **pzErrMsg,
+  const sqlite3_api_routines *pThunk
+){
+  static const struct {
+     char *zName;
+     signed char nArg;
+     unsigned int eTextRep; /* 1: UTF-16.  0: UTF-8 */
+     void (*xFunc)(sqlite3_context*,int,sqlite3_value **);
+  } aFuncs[] = {
+    { "randstr",               2, SQLITE_UTF8, randStr    },
+    { "test_destructor",       1, SQLITE_UTF8, test_destructor},
+#ifndef SQLITE_OMIT_UTF16
+    { "test_destructor16",     1, SQLITE_UTF8, test_destructor16},
+    { "hex_to_utf16be",        1, SQLITE_UTF8, testHexToUtf16be},
+    { "hex_to_utf16le",        1, SQLITE_UTF8, testHexToUtf16le},
+#endif
+    { "hex_to_utf8",           1, SQLITE_UTF8, testHexToUtf8},
+    { "test_destructor_count", 0, SQLITE_UTF8, test_destructor_count},
+    { "test_auxdata",         -1, SQLITE_UTF8, test_auxdata},
+    { "test_error",            1, SQLITE_UTF8, test_error},
+    { "test_error",            2, SQLITE_UTF8, test_error},
+    { "test_eval",             1, SQLITE_UTF8, test_eval},
+    { "test_isolation",        2, SQLITE_UTF8, test_isolation},
+    { "test_counter",          1, SQLITE_UTF8, counterFunc},
+    { "real2hex",              1, SQLITE_UTF8, real2hex},
+    { "test_decode",           1, SQLITE_UTF8, test_decode},
+    { "test_extract",          2, SQLITE_UTF8, test_extract},
+    { "test_zeroblob",  1, SQLITE_UTF8|SQLITE_DETERMINISTIC, test_zeroblob},
+    { "test_getsubtype",       1, SQLITE_UTF8, test_getsubtype},
+    { "test_setsubtype",       2, SQLITE_UTF8|SQLITE_RESULT_SUBTYPE,
+                                               test_setsubtype},
+    { "test_frombind",        -1, SQLITE_UTF8, test_frombind},
+  };
+  int i;
+
+  for(i=0; i<sizeof(aFuncs)/sizeof(aFuncs[0]); i++){
+    sqlite3_create_function(db, aFuncs[i].zName, aFuncs[i].nArg,
+        aFuncs[i].eTextRep, 0, aFuncs[i].xFunc, 0, 0);
+  }
+
+  sqlite3_create_function(db, "test_agg_errmsg16", 0, SQLITE_ANY, 0, 0, 
+      test_agg_errmsg16_step, test_agg_errmsg16_final);
+      
+  return SQLITE_OK;
+}
+
+/*
+** TCLCMD:  autoinstall_test_functions
+**
+** Invoke this TCL command to use sqlite3_auto_extension() to cause
+** the standard set of test functions to be loaded into each new
+** database connection.
+*/
+static int SQLITE_TCLAPI autoinstall_test_funcs(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int Md5_Register(sqlite3 *, char **, const sqlite3_api_routines *);
+  int rc = sqlite3_auto_extension((void(*)(void))registerTestFunctions);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_auto_extension((void(*)(void))Md5_Register);
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** A bogus step function and finalizer function.
+*/
+static void tStep(sqlite3_context *a, int b, sqlite3_value **c){}
+static void tFinal(sqlite3_context *a){}
+
+
+/*
+** tclcmd:  abuse_create_function
+**
+** Make various calls to sqlite3_create_function that do not have valid
+** parameters.  Verify that the error condition is detected and reported.
+*/
+static int SQLITE_TCLAPI abuse_create_function(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  sqlite3 *db;
+  int rc;
+  int mxArg;
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, tStep,tStep,tFinal);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, tStep, tStep, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, tStep, 0, tFinal);
+  if( rc!=SQLITE_MISUSE) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, 0, 0, tFinal);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, 0, tStep, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", -2, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 128, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "funcxx"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789",
+       1, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  /* This last function registration should actually work.  Generate
+  ** a no-op function (that always returns NULL) and which has the
+  ** maximum-length function name and the maximum number of parameters.
+  */
+  sqlite3_limit(db, SQLITE_LIMIT_FUNCTION_ARG, 10000);
+  mxArg = sqlite3_limit(db, SQLITE_LIMIT_FUNCTION_ARG, -1);
+  rc = sqlite3_create_function(db, "nullx"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789",
+       mxArg, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_OK ) goto abuse_err;
+                                
+  return TCL_OK;
+
+abuse_err:
+  Tcl_AppendResult(interp, "sqlite3_create_function abused test failed", 
+                   (char*)0);
+  return TCL_ERROR;
+}
+
+
+/*
+** SQLite user defined function to use with matchinfo() to calculate the
+** relevancy of an FTS match. The value returned is the relevancy score
+** (a real value greater than or equal to zero). A larger value indicates 
+** a more relevant document.
+**
+** The overall relevancy returned is the sum of the relevancies of each 
+** column value in the FTS table. The relevancy of a column value is the
+** sum of the following for each reportable phrase in the FTS query:
+**
+**   (<hit count> / <global hit count>) * <column weight>
+**
+** where <hit count> is the number of instances of the phrase in the
+** column value of the current row and <global hit count> is the number
+** of instances of the phrase in the same column of all rows in the FTS
+** table. The <column weight> is a weighting factor assigned to each
+** column by the caller (see below).
+**
+** The first argument to this function must be the return value of the FTS 
+** matchinfo() function. Following this must be one argument for each column 
+** of the FTS table containing a numeric weight factor for the corresponding 
+** column. Example:
+**
+**     CREATE VIRTUAL TABLE documents USING fts3(title, content)
+**
+** The following query returns the docids of documents that match the full-text
+** query <query> sorted from most to least relevant. When calculating
+** relevance, query term instances in the 'title' column are given twice the
+** weighting of those in the 'content' column.
+**
+**     SELECT docid FROM documents 
+**     WHERE documents MATCH <query> 
+**     ORDER BY rank(matchinfo(documents), 1.0, 0.5) DESC
+*/
+static void rankfunc(sqlite3_context *pCtx, int nVal, sqlite3_value **apVal){
+  int *aMatchinfo;                /* Return value of matchinfo() */
+  int nMatchinfo;                 /* Number of elements in aMatchinfo[] */
+  int nCol = 0;                   /* Number of columns in the table */
+  int nPhrase = 0;                /* Number of phrases in the query */
+  int iPhrase;                    /* Current phrase */
+  double score = 0.0;             /* Value to return */
+
+  assert( sizeof(int)==4 );
+
+  /* Check that the number of arguments passed to this function is correct.
+  ** If not, jump to wrong_number_args. Set aMatchinfo to point to the array
+  ** of unsigned integer values returned by FTS function matchinfo. Set
+  ** nPhrase to contain the number of reportable phrases in the users full-text
+  ** query, and nCol to the number of columns in the table. Then check that the
+  ** size of the matchinfo blob is as expected. Return an error if it is not.
+  */
+  if( nVal<1 ) goto wrong_number_args;
+  aMatchinfo = (int*)sqlite3_value_blob(apVal[0]);
+  nMatchinfo = sqlite3_value_bytes(apVal[0]) / sizeof(int);
+  if( nMatchinfo>=2 ){
+    nPhrase = aMatchinfo[0];
+    nCol = aMatchinfo[1];
+  }
+  if( nMatchinfo!=(2+3*nCol*nPhrase) ){
+    sqlite3_result_error(pCtx,
+        "invalid matchinfo blob passed to function rank()", -1);
+    return;
+  }
+  if( nVal!=(1+nCol) ) goto wrong_number_args;
+
+  /* Iterate through each phrase in the users query. */
+  for(iPhrase=0; iPhrase<nPhrase; iPhrase++){
+    int iCol;                     /* Current column */
+
+    /* Now iterate through each column in the users query. For each column,
+    ** increment the relevancy score by:
+    **
+    **   (<hit count> / <global hit count>) * <column weight>
+    **
+    ** aPhraseinfo[] points to the start of the data for phrase iPhrase. So
+    ** the hit count and global hit counts for each column are found in 
+    ** aPhraseinfo[iCol*3] and aPhraseinfo[iCol*3+1], respectively.
+    */
+    int *aPhraseinfo = &aMatchinfo[2 + iPhrase*nCol*3];
+    for(iCol=0; iCol<nCol; iCol++){
+      int nHitCount = aPhraseinfo[3*iCol];
+      int nGlobalHitCount = aPhraseinfo[3*iCol+1];
+      double weight = sqlite3_value_double(apVal[iCol+1]);
+      if( nHitCount>0 ){
+        score += ((double)nHitCount / (double)nGlobalHitCount) * weight;
+      }
+    }
+  }
+
+  sqlite3_result_double(pCtx, score);
+  return;
+
+  /* Jump here if the wrong number of arguments are passed to this function */
+wrong_number_args:
+  sqlite3_result_error(pCtx, "wrong number of arguments to function rank()", -1);
+}
+
+static int SQLITE_TCLAPI install_fts3_rank_function(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  sqlite3 *db;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  sqlite3_create_function(db, "rank", -1, SQLITE_UTF8, 0, rankfunc, 0, 0);
+  return TCL_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_func_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aObjCmd[] = {
+     { "autoinstall_test_functions",    autoinstall_test_funcs },
+     { "abuse_create_function",         abuse_create_function  },
+     { "install_fts3_rank_function",    install_fts3_rank_function  },
+  };
+  int i;
+  extern int Md5_Register(sqlite3 *, char **, const sqlite3_api_routines *);
+
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, 0, 0);
+  }
+  sqlite3_initialize();
+  sqlite3_auto_extension((void(*)(void))registerTestFunctions);
+  sqlite3_auto_extension((void(*)(void))Md5_Register);
+  return TCL_OK;
+}
diff --git a/src/test_hexio.c b/src/test_hexio.c
new file mode 100644
index 0000000..61a41d5
--- /dev/null
+++ b/src/test_hexio.c
@@ -0,0 +1,465 @@
+/*
+** 2007 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces.  This code
+** implements TCL commands for reading and writing the binary
+** database files and displaying the content of those files as
+** hexadecimal.  We could, in theory, use the built-in "binary"
+** command of TCL to do a lot of this, but there are some issues
+** with historical versions of the "binary" command.  So it seems
+** easier and safer to build our own mechanism.
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+
+/*
+** Convert binary to hex.  The input zBuf[] contains N bytes of
+** binary data.  zBuf[] is 2*n+1 bytes long.  Overwrite zBuf[]
+** with a hexadecimal representation of its original binary input.
+*/
+void sqlite3TestBinToHex(unsigned char *zBuf, int N){
+  const unsigned char zHex[] = "0123456789ABCDEF";
+  int i, j;
+  unsigned char c;
+  i = N*2;
+  zBuf[i--] = 0;
+  for(j=N-1; j>=0; j--){
+    c = zBuf[j];
+    zBuf[i--] = zHex[c&0xf];
+    zBuf[i--] = zHex[c>>4];
+  }
+  assert( i==-1 );
+}
+
+/*
+** Convert hex to binary.  The input zIn[] contains N bytes of
+** hexadecimal.  Convert this into binary and write aOut[] with
+** the binary data.  Spaces in the original input are ignored.
+** Return the number of bytes of binary rendered.
+*/
+int sqlite3TestHexToBin(const unsigned char *zIn, int N, unsigned char *aOut){
+  const unsigned char aMap[] = {
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     1, 2, 3, 4, 5, 6, 7, 8,  9,10, 0, 0, 0, 0, 0, 0,
+     0,11,12,13,14,15,16, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0,11,12,13,14,15,16, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  };
+  int i, j;
+  int hi=1;
+  unsigned char c;
+
+  for(i=j=0; i<N; i++){
+    c = aMap[zIn[i]];
+    if( c==0 ) continue;
+    if( hi ){
+      aOut[j] = (c-1)<<4;
+      hi = 0;
+    }else{
+      aOut[j++] |= c-1;
+      hi = 1;
+    }
+  }
+  return j;
+}
+
+
+/*
+** Usage:   hexio_read  FILENAME  OFFSET  AMT
+**
+** Read AMT bytes from file FILENAME beginning at OFFSET from the
+** beginning of the file.  Convert that information to hexadecimal
+** and return the resulting HEX string.
+*/
+static int SQLITE_TCLAPI hexio_read(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int offset;
+  int amt, got;
+  const char *zFile;
+  unsigned char *zBuf;
+  FILE *in;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME OFFSET AMT");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &offset) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &amt) ) return TCL_ERROR;
+  zFile = Tcl_GetString(objv[1]);
+  zBuf = sqlite3_malloc( amt*2+1 );
+  if( zBuf==0 ){
+    return TCL_ERROR;
+  }
+  in = fopen(zFile, "rb");
+  if( in==0 ){
+    in = fopen(zFile, "r");
+  }
+  if( in==0 ){
+    Tcl_AppendResult(interp, "cannot open input file ", zFile, 0);
+    return TCL_ERROR;
+  }
+  fseek(in, offset, SEEK_SET);
+  got = (int)fread(zBuf, 1, amt, in);
+  fclose(in);
+  if( got<0 ){
+    got = 0;
+  }
+  sqlite3TestBinToHex(zBuf, got);
+  Tcl_AppendResult(interp, zBuf, 0);
+  sqlite3_free(zBuf);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   hexio_write  FILENAME  OFFSET  DATA
+**
+** Write DATA into file FILENAME beginning at OFFSET from the
+** beginning of the file.  DATA is expressed in hexadecimal.
+*/
+static int SQLITE_TCLAPI hexio_write(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int offset;
+  int nIn, nOut, written;
+  const char *zFile;
+  const unsigned char *zIn;
+  unsigned char *aOut;
+  FILE *out;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME OFFSET HEXDATA");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &offset) ) return TCL_ERROR;
+  zFile = Tcl_GetString(objv[1]);
+  zIn = (const unsigned char *)Tcl_GetStringFromObj(objv[3], &nIn);
+  aOut = sqlite3_malloc( 1 + nIn/2 );
+  if( aOut==0 ){
+    return TCL_ERROR;
+  }
+  nOut = sqlite3TestHexToBin(zIn, nIn, aOut);
+  out = fopen(zFile, "r+b");
+  if( out==0 ){
+    out = fopen(zFile, "r+");
+  }
+  if( out==0 ){
+    Tcl_AppendResult(interp, "cannot open output file ", zFile, 0);
+    return TCL_ERROR;
+  }
+  fseek(out, offset, SEEK_SET);
+  written = (int)fwrite(aOut, 1, nOut, out);
+  sqlite3_free(aOut);
+  fclose(out);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(written));
+  return TCL_OK;
+}
+
+/*
+** USAGE:   hexio_get_int   HEXDATA
+**
+** Interpret the HEXDATA argument as a big-endian integer.  Return
+** the value of that integer.  HEXDATA can contain between 2 and 8
+** hexadecimal digits.
+*/
+static int SQLITE_TCLAPI hexio_get_int(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int val;
+  int nIn, nOut;
+  const unsigned char *zIn;
+  unsigned char *aOut;
+  unsigned char aNum[4];
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HEXDATA");
+    return TCL_ERROR;
+  }
+  zIn = (const unsigned char *)Tcl_GetStringFromObj(objv[1], &nIn);
+  aOut = sqlite3_malloc( 1 + nIn/2 );
+  if( aOut==0 ){
+    return TCL_ERROR;
+  }
+  nOut = sqlite3TestHexToBin(zIn, nIn, aOut);
+  if( nOut>=4 ){
+    memcpy(aNum, aOut, 4);
+  }else{
+    memset(aNum, 0, sizeof(aNum));
+    memcpy(&aNum[4-nOut], aOut, nOut);
+  }
+  sqlite3_free(aOut);
+  val = (aNum[0]<<24) | (aNum[1]<<16) | (aNum[2]<<8) | aNum[3];
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(val));
+  return TCL_OK;
+}
+
+
+/*
+** USAGE:   hexio_render_int16   INTEGER
+**
+** Render INTEGER has a 16-bit big-endian integer in hexadecimal.
+*/
+static int SQLITE_TCLAPI hexio_render_int16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int val;
+  unsigned char aNum[10];
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "INTEGER");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &val) ) return TCL_ERROR;
+  aNum[0] = val>>8;
+  aNum[1] = val;
+  sqlite3TestBinToHex(aNum, 2);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj((char*)aNum, 4));
+  return TCL_OK;
+}
+
+
+/*
+** USAGE:   hexio_render_int32   INTEGER
+**
+** Render INTEGER has a 32-bit big-endian integer in hexadecimal.
+*/
+static int SQLITE_TCLAPI hexio_render_int32(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int val;
+  unsigned char aNum[10];
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "INTEGER");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &val) ) return TCL_ERROR;
+  aNum[0] = val>>24;
+  aNum[1] = val>>16;
+  aNum[2] = val>>8;
+  aNum[3] = val;
+  sqlite3TestBinToHex(aNum, 4);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj((char*)aNum, 8));
+  return TCL_OK;
+}
+
+/*
+** USAGE:  utf8_to_utf8  HEX
+**
+** The argument is a UTF8 string represented in hexadecimal.
+** The UTF8 might not be well-formed.  Run this string through
+** sqlite3Utf8to8() convert it back to hex and return the result.
+*/
+static int SQLITE_TCLAPI utf8_to_utf8(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifdef SQLITE_DEBUG
+  int n;
+  int nOut;
+  const unsigned char *zOrig;
+  unsigned char *z;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HEX");
+    return TCL_ERROR;
+  }
+  zOrig = (unsigned char *)Tcl_GetStringFromObj(objv[1], &n);
+  z = sqlite3_malloc( n+4 );
+  n = sqlite3TestHexToBin(zOrig, n, z);
+  z[n] = 0;
+  nOut = sqlite3Utf8To8(z);
+  sqlite3TestBinToHex(z,nOut);
+  Tcl_AppendResult(interp, (char*)z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+#else
+  Tcl_AppendResult(interp, 
+      "[utf8_to_utf8] unavailable - SQLITE_DEBUG not defined", 0
+  );
+  return TCL_ERROR;
+#endif
+}
+
+static int getFts3Varint(const char *p, sqlite_int64 *v){
+  const unsigned char *q = (const unsigned char *) p;
+  sqlite_uint64 x = 0, y = 1;
+  while( (*q & 0x80) == 0x80 ){
+    x += y * (*q++ & 0x7f);
+    y <<= 7;
+  }
+  x += y * (*q++);
+  *v = (sqlite_int64) x;
+  return (int) (q - (unsigned char *)p);
+}
+
+static int putFts3Varint(char *p, sqlite_int64 v){
+  unsigned char *q = (unsigned char *) p;
+  sqlite_uint64 vu = v;
+  do{
+    *q++ = (unsigned char) ((vu & 0x7f) | 0x80);
+    vu >>= 7;
+  }while( vu!=0 );
+  q[-1] &= 0x7f;  /* turn off high bit in final byte */
+  assert( q - (unsigned char *)p <= 10 );
+  return (int) (q - (unsigned char *)p);
+}
+
+/*
+** USAGE:  read_fts3varint BLOB VARNAME
+**
+** Read a varint from the start of BLOB. Set variable VARNAME to contain
+** the interpreted value. Return the number of bytes of BLOB consumed.
+*/
+static int SQLITE_TCLAPI read_fts3varint(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nBlob;
+  unsigned char *zBlob;
+  sqlite3_int64 iVal;
+  int nVal;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BLOB VARNAME");
+    return TCL_ERROR;
+  }
+  zBlob = Tcl_GetByteArrayFromObj(objv[1], &nBlob);
+
+  nVal = getFts3Varint((char*)zBlob, (sqlite3_int64 *)(&iVal));
+  Tcl_ObjSetVar2(interp, objv[2], 0, Tcl_NewWideIntObj(iVal), 0);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nVal));
+  return TCL_OK;
+}
+
+/*
+** USAGE:  make_fts3record ARGLIST
+*/
+static int SQLITE_TCLAPI make_fts3record(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj **aArg = 0;
+  int nArg = 0;
+  unsigned char *aOut = 0;
+  int nOut = 0;
+  int nAlloc = 0;
+  int i;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "LIST");
+    return TCL_ERROR;
+  }
+  if( Tcl_ListObjGetElements(interp, objv[1], &nArg, &aArg) ){
+    return TCL_ERROR;
+  }
+
+  for(i=0; i<nArg; i++){
+    sqlite3_int64 iVal;
+    if( TCL_OK==Tcl_GetWideIntFromObj(0, aArg[i], &iVal) ){
+      if( nOut+10>nAlloc ){
+        int nNew = nAlloc?nAlloc*2:128;
+        unsigned char *aNew = sqlite3_realloc(aOut, nNew);
+        if( aNew==0 ){
+          sqlite3_free(aOut);
+          return TCL_ERROR;
+        }
+        aOut = aNew;
+        nAlloc = nNew;
+      }
+      nOut += putFts3Varint((char*)&aOut[nOut], iVal);
+    }else{
+      int nVal = 0;
+      char *zVal = Tcl_GetStringFromObj(aArg[i], &nVal);
+      while( (nOut + nVal)>nAlloc ){
+        int nNew = nAlloc?nAlloc*2:128;
+        unsigned char *aNew = sqlite3_realloc(aOut, nNew);
+        if( aNew==0 ){
+          sqlite3_free(aOut);
+          return TCL_ERROR;
+        }
+        aOut = aNew;
+        nAlloc = nNew;
+      }
+      memcpy(&aOut[nOut], zVal, nVal);
+      nOut += nVal;
+    }
+  }
+
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(aOut, nOut));
+  sqlite3_free(aOut);
+  return TCL_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_hexio_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aObjCmd[] = {
+     { "hexio_read",                   hexio_read            },
+     { "hexio_write",                  hexio_write           },
+     { "hexio_get_int",                hexio_get_int         },
+     { "hexio_render_int16",           hexio_render_int16    },
+     { "hexio_render_int32",           hexio_render_int32    },
+     { "utf8_to_utf8",                 utf8_to_utf8          },
+     { "read_fts3varint",              read_fts3varint       },
+     { "make_fts3record",              make_fts3record       },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, 0, 0);
+  }
+  return TCL_OK;
+}
diff --git a/src/test_init.c b/src/test_init.c
new file mode 100644
index 0000000..400ab9a
--- /dev/null
+++ b/src/test_init.c
@@ -0,0 +1,295 @@
+/*
+** 2009 August 17
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** The code in this file is used for testing SQLite. It is not part of
+** the source code used in production systems.
+**
+** Specifically, this file tests the effect of errors while initializing
+** the various pluggable sub-systems from within sqlite3_initialize().
+** If an error occurs in sqlite3_initialize() the following should be
+** true:
+**
+**   1) An error code is returned to the user, and
+**   2) A subsequent call to sqlite3_shutdown() calls the shutdown method
+**      of those subsystems that were initialized, and
+**   3) A subsequent call to sqlite3_initialize() attempts to initialize
+**      the remaining, uninitialized, subsystems.
+*/
+
+#include "sqliteInt.h"
+#include <string.h>
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+static struct Wrapped {
+  sqlite3_pcache_methods2 pcache;
+  sqlite3_mem_methods     mem;
+  sqlite3_mutex_methods   mutex;
+
+  int mem_init;              /* True if mem subsystem is initialized */
+  int mem_fail;              /* True to fail mem subsystem initialization */
+  int mutex_init;            /* True if mutex subsystem is initialized */
+  int mutex_fail;            /* True to fail mutex subsystem initialization */
+  int pcache_init;           /* True if pcache subsystem is initialized */
+  int pcache_fail;           /* True to fail pcache subsystem initialization */
+} wrapped;
+
+static int wrMemInit(void *pAppData){
+  int rc;
+  if( wrapped.mem_fail ){
+    rc = SQLITE_ERROR;
+  }else{
+    rc = wrapped.mem.xInit(wrapped.mem.pAppData);
+  }
+  if( rc==SQLITE_OK ){
+    wrapped.mem_init = 1;
+  }
+  return rc;
+}
+static void wrMemShutdown(void *pAppData){
+  wrapped.mem.xShutdown(wrapped.mem.pAppData);
+  wrapped.mem_init = 0;
+}
+static void *wrMemMalloc(int n)           {return wrapped.mem.xMalloc(n);}
+static void wrMemFree(void *p)            {wrapped.mem.xFree(p);}
+static void *wrMemRealloc(void *p, int n) {return wrapped.mem.xRealloc(p, n);}
+static int wrMemSize(void *p)             {return wrapped.mem.xSize(p);}
+static int wrMemRoundup(int n)            {return wrapped.mem.xRoundup(n);}
+
+
+static int wrMutexInit(void){
+  int rc;
+  if( wrapped.mutex_fail ){
+    rc = SQLITE_ERROR;
+  }else{
+    rc = wrapped.mutex.xMutexInit();
+  }
+  if( rc==SQLITE_OK ){
+    wrapped.mutex_init = 1;
+  }
+  return rc;
+}
+static int wrMutexEnd(void){
+  wrapped.mutex.xMutexEnd();
+  wrapped.mutex_init = 0;
+  return SQLITE_OK;
+}
+static sqlite3_mutex *wrMutexAlloc(int e){
+  return wrapped.mutex.xMutexAlloc(e);
+}
+static void wrMutexFree(sqlite3_mutex *p){
+  wrapped.mutex.xMutexFree(p);
+}
+static void wrMutexEnter(sqlite3_mutex *p){
+  wrapped.mutex.xMutexEnter(p);
+}
+static int wrMutexTry(sqlite3_mutex *p){
+  return wrapped.mutex.xMutexTry(p);
+}
+static void wrMutexLeave(sqlite3_mutex *p){
+  wrapped.mutex.xMutexLeave(p);
+}
+static int wrMutexHeld(sqlite3_mutex *p){
+  return wrapped.mutex.xMutexHeld(p);
+}
+static int wrMutexNotheld(sqlite3_mutex *p){
+  return wrapped.mutex.xMutexNotheld(p);
+}
+
+
+
+static int wrPCacheInit(void *pArg){
+  int rc;
+  if( wrapped.pcache_fail ){
+    rc = SQLITE_ERROR;
+  }else{
+    rc = wrapped.pcache.xInit(wrapped.pcache.pArg);
+  }
+  if( rc==SQLITE_OK ){
+    wrapped.pcache_init = 1;
+  }
+  return rc;
+}
+static void wrPCacheShutdown(void *pArg){
+  wrapped.pcache.xShutdown(wrapped.pcache.pArg);
+  wrapped.pcache_init = 0;
+}
+
+static sqlite3_pcache *wrPCacheCreate(int a, int b, int c){
+  return wrapped.pcache.xCreate(a, b, c);
+}  
+static void wrPCacheCachesize(sqlite3_pcache *p, int n){
+  wrapped.pcache.xCachesize(p, n);
+}  
+static int wrPCachePagecount(sqlite3_pcache *p){
+  return wrapped.pcache.xPagecount(p);
+}  
+static sqlite3_pcache_page *wrPCacheFetch(sqlite3_pcache *p, unsigned a, int b){
+  return wrapped.pcache.xFetch(p, a, b);
+}  
+static void wrPCacheUnpin(sqlite3_pcache *p, sqlite3_pcache_page *a, int b){
+  wrapped.pcache.xUnpin(p, a, b);
+}  
+static void wrPCacheRekey(
+  sqlite3_pcache *p, 
+  sqlite3_pcache_page *a, 
+  unsigned b, 
+  unsigned c
+){
+  wrapped.pcache.xRekey(p, a, b, c);
+}  
+static void wrPCacheTruncate(sqlite3_pcache *p, unsigned a){
+  wrapped.pcache.xTruncate(p, a);
+}  
+static void wrPCacheDestroy(sqlite3_pcache *p){
+  wrapped.pcache.xDestroy(p);
+}  
+
+static void installInitWrappers(void){
+  sqlite3_mutex_methods mutexmethods = {
+    wrMutexInit,  wrMutexEnd,   wrMutexAlloc,
+    wrMutexFree,  wrMutexEnter, wrMutexTry,
+    wrMutexLeave, wrMutexHeld,  wrMutexNotheld
+  };
+  sqlite3_pcache_methods2 pcachemethods = {
+    1, 0,
+    wrPCacheInit,      wrPCacheShutdown,  wrPCacheCreate, 
+    wrPCacheCachesize, wrPCachePagecount, wrPCacheFetch,
+    wrPCacheUnpin,     wrPCacheRekey,     wrPCacheTruncate,  
+    wrPCacheDestroy
+  };
+  sqlite3_mem_methods memmethods = {
+    wrMemMalloc,   wrMemFree,    wrMemRealloc,
+    wrMemSize,     wrMemRoundup, wrMemInit,
+    wrMemShutdown,
+    0
+  };
+
+  memset(&wrapped, 0, sizeof(wrapped));
+
+  sqlite3_shutdown();
+  sqlite3_config(SQLITE_CONFIG_GETMUTEX, &wrapped.mutex);
+  sqlite3_config(SQLITE_CONFIG_GETMALLOC, &wrapped.mem);
+  sqlite3_config(SQLITE_CONFIG_GETPCACHE2, &wrapped.pcache);
+  sqlite3_config(SQLITE_CONFIG_MUTEX, &mutexmethods);
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &memmethods);
+  sqlite3_config(SQLITE_CONFIG_PCACHE2, &pcachemethods);
+}
+
+static int SQLITE_TCLAPI init_wrapper_install(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  installInitWrappers();
+  for(i=1; i<objc; i++){
+    char *z = Tcl_GetString(objv[i]);
+    if( strcmp(z, "mem")==0 ){
+      wrapped.mem_fail = 1;
+    }else if( strcmp(z, "mutex")==0 ){
+      wrapped.mutex_fail = 1;
+    }else if( strcmp(z, "pcache")==0 ){
+      wrapped.pcache_fail = 1;
+    }else{
+      Tcl_AppendResult(interp, "Unknown argument: \"", z, "\"");
+      return TCL_ERROR;
+    }
+  }
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI init_wrapper_uninstall(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  sqlite3_shutdown();
+  sqlite3_config(SQLITE_CONFIG_MUTEX, &wrapped.mutex);
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &wrapped.mem);
+  sqlite3_config(SQLITE_CONFIG_PCACHE2, &wrapped.pcache);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI init_wrapper_clear(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  wrapped.mem_fail = 0;
+  wrapped.mutex_fail = 0;
+  wrapped.pcache_fail = 0;
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI init_wrapper_query(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_Obj *pRet;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  if( wrapped.mutex_init ){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("mutex", -1));
+  }
+  if( wrapped.mem_init ){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("mem", -1));
+  }
+  if( wrapped.pcache_init ){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("pcache", -1));
+  }
+
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;
+}
+
+int Sqlitetest_init_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aObjCmd[] = {
+    {"init_wrapper_install",   init_wrapper_install},
+    {"init_wrapper_query",     init_wrapper_query  },
+    {"init_wrapper_uninstall", init_wrapper_uninstall},
+    {"init_wrapper_clear",     init_wrapper_clear}
+  };
+  int i;
+
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, 0, 0);
+  }
+
+  return TCL_OK;
+}
diff --git a/src/test_intarray.c b/src/test_intarray.c
new file mode 100644
index 0000000..a978ed5
--- /dev/null
+++ b/src/test_intarray.c
@@ -0,0 +1,397 @@
+/*
+** 2009 November 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements a read-only VIRTUAL TABLE that contains the
+** content of a C-language array of integer values.  See the corresponding
+** header file for full details.
+**
+** This virtual table is used for internal testing of SQLite only.  It is
+** not recommended for use in production.  For a similar virtual table that
+** is production-ready, see the "carray" virtual table over in ext/misc.
+*/
+#include "test_intarray.h"
+#include <string.h>
+#include <assert.h>
+
+
+/*
+** Definition of the sqlite3_intarray object.
+**
+** The internal representation of an intarray object is subject
+** to change, is not externally visible, and should be used by
+** the implementation of intarray only.  This object is opaque
+** to users.
+*/
+struct sqlite3_intarray {
+  int n;                    /* Number of elements in the array */
+  sqlite3_int64 *a;         /* Contents of the array */
+  void (*xFree)(void*);     /* Function used to free a[] */
+};
+
+/* Objects used internally by the virtual table implementation */
+typedef struct intarray_vtab intarray_vtab;
+typedef struct intarray_cursor intarray_cursor;
+
+/* An intarray table object */
+struct intarray_vtab {
+  sqlite3_vtab base;            /* Base class */
+  sqlite3_intarray *pContent;   /* Content of the integer array */
+};
+
+/* An intarray cursor object */
+struct intarray_cursor {
+  sqlite3_vtab_cursor base;    /* Base class */
+  int i;                       /* Current cursor position */
+};
+
+/*
+** None of this works unless we have virtual tables.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Free an sqlite3_intarray object.
+*/
+static void intarrayFree(sqlite3_intarray *p){
+  if( p->xFree ){
+    p->xFree(p->a);
+  }
+  sqlite3_free(p);
+}
+
+/*
+** Table destructor for the intarray module.
+*/
+static int intarrayDestroy(sqlite3_vtab *p){
+  intarray_vtab *pVtab = (intarray_vtab*)p;
+  sqlite3_free(pVtab);
+  return 0;
+}
+
+/*
+** Table constructor for the intarray module.
+*/
+static int intarrayCreate(
+  sqlite3 *db,              /* Database where module is created */
+  void *pAux,               /* clientdata for the module */
+  int argc,                 /* Number of arguments */
+  const char *const*argv,   /* Value for all arguments */
+  sqlite3_vtab **ppVtab,    /* Write the new virtual table object here */
+  char **pzErr              /* Put error message text here */
+){
+  int rc = SQLITE_NOMEM;
+  intarray_vtab *pVtab = sqlite3_malloc64(sizeof(intarray_vtab));
+
+  if( pVtab ){
+    memset(pVtab, 0, sizeof(intarray_vtab));
+    pVtab->pContent = (sqlite3_intarray*)pAux;
+    rc = sqlite3_declare_vtab(db, "CREATE TABLE x(value INTEGER PRIMARY KEY)");
+  }
+  *ppVtab = (sqlite3_vtab *)pVtab;
+  return rc;
+}
+
+/*
+** Open a new cursor on the intarray table.
+*/
+static int intarrayOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  int rc = SQLITE_NOMEM;
+  intarray_cursor *pCur;
+  pCur = sqlite3_malloc64(sizeof(intarray_cursor));
+  if( pCur ){
+    memset(pCur, 0, sizeof(intarray_cursor));
+    *ppCursor = (sqlite3_vtab_cursor *)pCur;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Close a intarray table cursor.
+*/
+static int intarrayClose(sqlite3_vtab_cursor *cur){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve a column of data.
+*/
+static int intarrayColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  intarray_cursor *pCur = (intarray_cursor*)cur;
+  intarray_vtab *pVtab = (intarray_vtab*)cur->pVtab;
+  if( pCur->i>=0 && pCur->i<pVtab->pContent->n ){
+    sqlite3_result_int64(ctx, pVtab->pContent->a[pCur->i]);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve the current rowid.
+*/
+static int intarrayRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  *pRowid = pCur->i;
+  return SQLITE_OK;
+}
+
+static int intarrayEof(sqlite3_vtab_cursor *cur){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  intarray_vtab *pVtab = (intarray_vtab *)cur->pVtab;
+  return pCur->i>=pVtab->pContent->n;
+}
+
+/*
+** Advance the cursor to the next row.
+*/
+static int intarrayNext(sqlite3_vtab_cursor *cur){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  pCur->i++;
+  return SQLITE_OK;
+}
+
+/*
+** Reset a intarray table cursor.
+*/
+static int intarrayFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  intarray_cursor *pCur = (intarray_cursor *)pVtabCursor;
+  pCur->i = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Analyse the WHERE condition.
+*/
+static int intarrayBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that merely echos method calls into TCL
+** variables.
+*/
+static sqlite3_module intarrayModule = {
+  0,                           /* iVersion */
+  intarrayCreate,              /* xCreate - create a new virtual table */
+  intarrayCreate,              /* xConnect - connect to an existing vtab */
+  intarrayBestIndex,           /* xBestIndex - find the best query index */
+  intarrayDestroy,             /* xDisconnect - disconnect a vtab */
+  intarrayDestroy,             /* xDestroy - destroy a vtab */
+  intarrayOpen,                /* xOpen - open a cursor */
+  intarrayClose,               /* xClose - close a cursor */
+  intarrayFilter,              /* xFilter - configure scan constraints */
+  intarrayNext,                /* xNext - advance a cursor */
+  intarrayEof,                 /* xEof */
+  intarrayColumn,              /* xColumn - read data */
+  intarrayRowid,               /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+  0,                           /* xSavepoint */
+  0,                           /* xRelease */
+  0,                           /* xRollbackTo */
+  0,                           /* xShadowName */
+  0                            /* xIntegrity */
+};
+
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
+
+/*
+** Invoke this routine to create a specific instance of an intarray object.
+** The new intarray object is returned by the 3rd parameter.
+**
+** Each intarray object corresponds to a virtual table in the TEMP table
+** with a name of zName.
+**
+** Destroy the intarray object by dropping the virtual table.  If not done
+** explicitly by the application, the virtual table will be dropped implicitly
+** by the system when the database connection is closed.
+*/
+SQLITE_API int sqlite3_intarray_create(
+  sqlite3 *db,
+  const char *zName,
+  sqlite3_intarray **ppReturn
+){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_intarray *p;
+
+  *ppReturn = p = sqlite3_malloc64( sizeof(*p) );
+  if( p==0 ){
+    return SQLITE_NOMEM;
+  }
+  memset(p, 0, sizeof(*p));
+  rc = sqlite3_create_module_v2(db, zName, &intarrayModule, p,
+                                (void(*)(void*))intarrayFree);
+  if( rc==SQLITE_OK ){
+    char *zSql;
+    zSql = sqlite3_mprintf("CREATE VIRTUAL TABLE temp.%Q USING %Q",
+                           zName, zName);
+    rc = sqlite3_exec(db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+#endif
+  return rc;
+}
+
+/*
+** Bind a new array array of integers to a specific intarray object.
+**
+** The array of integers bound must be unchanged for the duration of
+** any query against the corresponding virtual table.  If the integer
+** array does change or is deallocated undefined behavior will result.
+*/
+SQLITE_API int sqlite3_intarray_bind(
+  sqlite3_intarray *pIntArray,   /* The intarray object to bind to */
+  int nElements,                 /* Number of elements in the intarray */
+  sqlite3_int64 *aElements,      /* Content of the intarray */
+  void (*xFree)(void*)           /* How to dispose of the intarray when done */
+){
+  if( pIntArray->xFree ){
+    pIntArray->xFree(pIntArray->a);
+  }
+  pIntArray->n = nElements;
+  pIntArray->a = aElements;
+  pIntArray->xFree = xFree;
+  return SQLITE_OK;
+}
+
+
+/*****************************************************************************
+** Everything below is interface for testing this module.
+*/
+#ifdef SQLITE_TEST
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+
+/*
+** Routines to encode and decode pointers
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+extern void *sqlite3TestTextToPtr(const char*);
+extern int sqlite3TestMakePointerStr(Tcl_Interp*, char *zPtr, void*);
+extern const char *sqlite3ErrName(int);
+
+/*
+**    sqlite3_intarray_create  DB  NAME
+**
+** Invoke the sqlite3_intarray_create interface.  A string that becomes
+** the first parameter to sqlite3_intarray_bind.
+*/
+static int SQLITE_TCLAPI test_intarray_create(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zName;
+  sqlite3_intarray *pArray;
+  int rc = SQLITE_OK;
+  char zPtr[100];
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  rc = sqlite3_intarray_create(db, zName, &pArray);
+#endif
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), (char*)0);
+    return TCL_ERROR;
+  }
+  sqlite3TestMakePointerStr(interp, zPtr, pArray);
+  Tcl_AppendResult(interp, zPtr, (char*)0);
+  return TCL_OK;
+}
+
+/*
+**    sqlite3_intarray_bind  INTARRAY  ?VALUE ...?
+**
+** Invoke the sqlite3_intarray_bind interface on the given array of integers.
+*/
+static int SQLITE_TCLAPI test_intarray_bind(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_intarray *pArray;
+  int rc = SQLITE_OK;
+  int i, n;
+  sqlite3_int64 *a;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "INTARRAY");
+    return TCL_ERROR;
+  }
+  pArray = (sqlite3_intarray*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  n = objc - 2;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  a = sqlite3_malloc64( sizeof(a[0])*n );
+  if( a==0 ){
+    Tcl_AppendResult(interp, "SQLITE_NOMEM", (char*)0);
+    return TCL_ERROR;
+  }
+  for(i=0; i<n; i++){
+    Tcl_WideInt x = 0;
+    Tcl_GetWideIntFromObj(0, objv[i+2], &x);
+    a[i] = x;
+  }
+  rc = sqlite3_intarray_bind(pArray, n, a, sqlite3_free);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3ErrName(rc), (char*)0);
+    return TCL_ERROR;
+  }
+#endif
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestintarray_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "sqlite3_intarray_create", test_intarray_create, 0 },
+     { "sqlite3_intarray_bind", test_intarray_bind, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_intarray.h b/src/test_intarray.h
new file mode 100644
index 0000000..b68233b
--- /dev/null
+++ b/src/test_intarray.h
@@ -0,0 +1,135 @@
+/*
+** 2009 November 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This is the C-language interface definition for the "intarray" or
+** integer array virtual table for SQLite.
+**
+** This virtual table is used for internal testing of SQLite only.  It is
+** not recommended for use in production.  For a similar virtual table that
+** is production-ready, see the "carray" virtual table over in ext/misc.
+**
+** The intarray virtual table is designed to facilitate using an
+** array of integers as the right-hand side of an IN operator.  So
+** instead of doing a prepared statement like this:
+**
+**     SELECT * FROM table WHERE x IN (?,?,?,...,?);
+**
+** And then binding individual integers to each of ? slots, a C-language
+** application can create an intarray object (named "ex1" in the following
+** example), prepare a statement like this:
+**
+**     SELECT * FROM table WHERE x IN ex1;
+**
+** Then bind an ordinary C/C++ array of integer values to the ex1 object
+** to run the statement.
+**
+** USAGE:
+**
+** One or more intarray objects can be created as follows:
+**
+**      sqlite3_intarray *p1, *p2, *p3;
+**      sqlite3_intarray_create(db, "ex1", &p1);
+**      sqlite3_intarray_create(db, "ex2", &p2);
+**      sqlite3_intarray_create(db, "ex3", &p3);
+**
+** Each call to sqlite3_intarray_create() generates a new virtual table
+** module and a singleton of that virtual table module in the TEMP
+** database.  Both the module and the virtual table instance use the
+** name given by the second parameter.  The virtual tables can then be
+** used in prepared statements:
+**
+**      SELECT * FROM t1, t2, t3
+**       WHERE t1.x IN ex1
+**         AND t2.y IN ex2
+**         AND t3.z IN ex3;
+**
+** Each integer array is initially empty.  New arrays can be bound to
+** an integer array as follows:
+**
+**     sqlite3_int64 a1[] = { 1, 2, 3, 4 };
+**     sqlite3_int64 a2[] = { 5, 6, 7, 8, 9, 10, 11 };
+**     sqlite3_int64 *a3 = sqlite3_malloc( 100*sizeof(sqlite3_int64) );
+**     // Fill in content of a3[]
+**     sqlite3_intarray_bind(p1, 4, a1, 0);
+**     sqlite3_intarray_bind(p2, 7, a2, 0);
+**     sqlite3_intarray_bind(p3, 100, a3, sqlite3_free);
+**
+** A single intarray object can be rebound multiple times.  But do not
+** attempt to change the bindings of an intarray while it is in the middle
+** of a query.
+**
+** The array that holds the integers is automatically freed by the function
+** in the fourth parameter to sqlite3_intarray_bind() when the array is no
+** longer needed.  The application must not change the intarray values
+** while an intarray is in the middle of a query.
+**
+** The intarray object is automatically destroyed when its corresponding
+** virtual table is dropped.  Since the virtual tables are created in the
+** TEMP database, they are automatically dropped when the database connection
+** closes so the application does not normally need to take any special
+** action to free the intarray objects.  Because of the way virtual tables
+** work and the (somewhat goofy) way that the intarray virtual table is
+** implemented, it is not allowed to invoke sqlite3_intarray_create(D,N,P)
+** more than once with the same D and N values.
+*/
+#include "sqlite3.h"
+#ifndef SQLITE_INTARRAY_H
+#define SQLITE_INTARRAY_H
+
+/*
+** Make sure we can call this stuff from C++.
+*/
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+** An sqlite3_intarray is an abstract type to stores an instance of
+** an integer array.
+*/
+typedef struct sqlite3_intarray sqlite3_intarray;
+
+/*
+** Invoke this routine to create a specific instance of an intarray object.
+** The new intarray object is returned by the 3rd parameter.
+**
+** Each intarray object corresponds to a virtual table in the TEMP table
+** with a name of zName.
+**
+** Destroy the intarray object by dropping the virtual table.  If not done
+** explicitly by the application, the virtual table will be dropped implicitly
+** by the system when the database connection is closed.
+*/
+SQLITE_API int sqlite3_intarray_create(
+  sqlite3 *db,
+  const char *zName,
+  sqlite3_intarray **ppReturn
+);
+
+/*
+** Bind a new array array of integers to a specific intarray object.
+**
+** The array of integers bound must be unchanged for the duration of
+** any query against the corresponding virtual table.  If the integer
+** array does change or is deallocated undefined behavior will result.
+*/
+SQLITE_API int sqlite3_intarray_bind(
+  sqlite3_intarray *pIntArray,   /* The intarray object to bind to */
+  int nElements,                 /* Number of elements in the intarray */
+  sqlite3_int64 *aElements,      /* Content of the intarray */
+  void (*xFree)(void*)           /* How to dispose of the intarray when done */
+);
+
+#ifdef __cplusplus
+}  /* End of the 'extern "C"' block */
+#endif
+#endif /* SQLITE_INTARRAY_H */
diff --git a/src/test_journal.c b/src/test_journal.c
new file mode 100644
index 0000000..6a040ea
--- /dev/null
+++ b/src/test_journal.c
@@ -0,0 +1,869 @@
+/*
+** 2008 Jan 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code for a VFS layer that acts as a wrapper around
+** an existing VFS. The code in this file attempts to verify that SQLite
+** correctly populates and syncs a journal file before writing to a
+** corresponding database file.
+**
+** INTERFACE
+**
+**   The public interface to this wrapper VFS is two functions:
+**
+**     jt_register()
+**     jt_unregister()
+**
+**   See header comments associated with those two functions below for 
+**   details.
+**
+** LIMITATIONS
+**
+**   This wrapper will not work if "PRAGMA synchronous = off" is used.
+**
+** OPERATION
+**
+**  Starting a Transaction:
+**
+**   When a write-transaction is started, the contents of the database is
+**   inspected and the following data stored as part of the database file 
+**   handle (type struct jt_file):
+**
+**     a) The page-size of the database file.
+**     b) The number of pages that are in the database file.
+**     c) The set of page numbers corresponding to free-list leaf pages.
+**     d) A check-sum for every page in the database file.
+**
+**   The start of a write-transaction is deemed to have occurred when a 
+**   28-byte journal header is written to byte offset 0 of the journal 
+**   file.
+**
+**  Syncing the Journal File:
+**
+**   Whenever the xSync method is invoked to sync a journal-file, the
+**   contents of the journal file are read. For each page written to
+**   the journal file, a check-sum is calculated and compared to the  
+**   check-sum calculated for the corresponding database page when the
+**   write-transaction was initialized. The success of the comparison
+**   is assert()ed. So if SQLite has written something other than the
+**   original content to the database file, an assert() will fail.
+**
+**   Additionally, the set of page numbers for which records exist in
+**   the journal file is added to (unioned with) the set of page numbers
+**   corresponding to free-list leaf pages collected when the 
+**   write-transaction was initialized. This set comprises the page-numbers 
+**   corresponding to those pages that SQLite may now safely modify.
+**
+**  Writing to the Database File:
+**
+**   When a block of data is written to a database file, the following
+**   invariants are asserted:
+**
+**     a) That the block of data is an aligned block of page-size bytes.
+**
+**     b) That if the page being written did not exist when the 
+**        transaction was started (i.e. the database file is growing), then
+**        the journal-file must have been synced at least once since
+**        the start of the transaction.
+**
+**     c) That if the page being written did exist when the transaction 
+**        was started, then the page must have either been a free-list
+**        leaf page at the start of the transaction, or else must have
+**        been stored in the journal file prior to the most recent sync.
+**
+**  Closing a Transaction:
+**
+**   When a transaction is closed, all data collected at the start of
+**   the transaction, or following an xSync of a journal-file, is 
+**   discarded. The end of a transaction is recognized when any one 
+**   of the following occur:
+**
+**     a) A block of zeroes (or anything else that is not a valid 
+**        journal-header) is written to the start of the journal file.
+**
+**     b) A journal file is truncated to zero bytes in size using xTruncate.
+**
+**     c) The journal file is deleted using xDelete.
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+
+/*
+** Maximum pathname length supported by the jt backend.
+*/
+#define JT_MAX_PATHNAME 512
+
+/*
+** Name used to identify this VFS.
+*/
+#define JT_VFS_NAME "jt"
+
+typedef struct jt_file jt_file;
+struct jt_file {
+  sqlite3_file base;
+  const char *zName;       /* Name of open file */
+  int flags;               /* Flags the file was opened with */
+
+  /* The following are only used by database file file handles */
+  int eLock;               /* Current lock held on the file */
+  u32 nPage;               /* Size of file in pages when transaction started */
+  u32 nPagesize;           /* Page size when transaction started */
+  Bitvec *pWritable;       /* Bitvec of pages that may be written to the file */
+  u32 *aCksum;             /* Checksum for first nPage pages */
+  int nSync;               /* Number of times journal file has been synced */
+
+  /* Only used by journal file-handles */
+  sqlite3_int64 iMaxOff;   /* Maximum offset written to this transaction */
+
+  jt_file *pNext;          /* All files are stored in a linked list */
+  sqlite3_file *pReal;     /* The file handle for the underlying vfs */
+};
+
+/*
+** Method declarations for jt_file.
+*/
+static int jtClose(sqlite3_file*);
+static int jtRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int jtWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int jtTruncate(sqlite3_file*, sqlite3_int64 size);
+static int jtSync(sqlite3_file*, int flags);
+static int jtFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int jtLock(sqlite3_file*, int);
+static int jtUnlock(sqlite3_file*, int);
+static int jtCheckReservedLock(sqlite3_file*, int *);
+static int jtFileControl(sqlite3_file*, int op, void *pArg);
+static int jtSectorSize(sqlite3_file*);
+static int jtDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for jt_vfs.
+*/
+static int jtOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int jtDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int jtAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int jtFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *jtDlOpen(sqlite3_vfs*, const char *zFilename);
+static void jtDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*jtDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void jtDlClose(sqlite3_vfs*, void*);
+static int jtRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int jtSleep(sqlite3_vfs*, int microseconds);
+static int jtCurrentTime(sqlite3_vfs*, double*);
+static int jtCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+static int jtGetLastError(sqlite3_vfs*, int, char*);
+
+static sqlite3_vfs jt_vfs = {
+  2,                             /* iVersion */
+  sizeof(jt_file),               /* szOsFile */
+  JT_MAX_PATHNAME,               /* mxPathname */
+  0,                             /* pNext */
+  JT_VFS_NAME,                   /* zName */
+  0,                             /* pAppData */
+  jtOpen,                        /* xOpen */
+  jtDelete,                      /* xDelete */
+  jtAccess,                      /* xAccess */
+  jtFullPathname,                /* xFullPathname */
+  jtDlOpen,                      /* xDlOpen */
+  jtDlError,                     /* xDlError */
+  jtDlSym,                       /* xDlSym */
+  jtDlClose,                     /* xDlClose */
+  jtRandomness,                  /* xRandomness */
+  jtSleep,                       /* xSleep */
+  jtCurrentTime,                 /* xCurrentTime */
+  jtGetLastError,                /* xGetLastError */
+  jtCurrentTimeInt64             /* xCurrentTimeInt64 */
+};
+
+static sqlite3_io_methods jt_io_methods = {
+  1,                             /* iVersion */
+  jtClose,                       /* xClose */
+  jtRead,                        /* xRead */
+  jtWrite,                       /* xWrite */
+  jtTruncate,                    /* xTruncate */
+  jtSync,                        /* xSync */
+  jtFileSize,                    /* xFileSize */
+  jtLock,                        /* xLock */
+  jtUnlock,                      /* xUnlock */
+  jtCheckReservedLock,           /* xCheckReservedLock */
+  jtFileControl,                 /* xFileControl */
+  jtSectorSize,                  /* xSectorSize */
+  jtDeviceCharacteristics        /* xDeviceCharacteristics */
+};
+
+struct JtGlobal {
+  sqlite3_vfs *pVfs;             /* Parent VFS */
+  jt_file *pList;                /* List of all open files */
+};
+static struct JtGlobal g = {0, 0};
+
+/*
+** Functions to obtain and relinquish a mutex to protect g.pList. The
+** STATIC_PRNG mutex is reused, purely for the sake of convenience.
+*/
+static void enterJtMutex(void){
+  sqlite3_mutex_enter(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
+}
+static void leaveJtMutex(void){
+  sqlite3_mutex_leave(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
+}
+
+extern int sqlite3_io_error_pending;
+extern int sqlite3_io_error_hit;
+static void stop_ioerr_simulation(int *piSave, int *piSave2){
+  *piSave = sqlite3_io_error_pending;
+  *piSave2 = sqlite3_io_error_hit;
+  sqlite3_io_error_pending = -1;
+  sqlite3_io_error_hit = 0;
+}
+static void start_ioerr_simulation(int iSave, int iSave2){
+  sqlite3_io_error_pending = iSave;
+  sqlite3_io_error_hit = iSave2;
+}
+
+/*
+** The jt_file pointed to by the argument may or may not be a file-handle
+** open on a main database file. If it is, and a transaction is currently
+** opened on the file, then discard all transaction related data.
+*/
+static void closeTransaction(jt_file *p){
+  sqlite3BitvecDestroy(p->pWritable);
+  sqlite3_free(p->aCksum);
+  p->pWritable = 0;
+  p->aCksum = 0;
+  p->nSync = 0;
+}
+
+/*
+** Close an jt-file.
+*/
+static int jtClose(sqlite3_file *pFile){
+  jt_file **pp;
+  jt_file *p = (jt_file *)pFile;
+
+  closeTransaction(p);
+  enterJtMutex();
+  if( p->zName ){
+    for(pp=&g.pList; *pp!=p; pp=&(*pp)->pNext);
+    *pp = p->pNext;
+  }
+  leaveJtMutex();
+  sqlite3OsClose(p->pReal);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from an jt-file.
+*/
+static int jtRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Parameter zJournal is the name of a journal file that is currently 
+** open. This function locates and returns the handle opened on the
+** corresponding database file by the pager that currently has the
+** journal file opened. This file-handle is identified by the 
+** following properties:
+**
+**   a) SQLITE_OPEN_MAIN_DB was specified when the file was opened.
+**
+**   b) The file-name specified when the file was opened matches
+**      all but the final 8 characters of the journal file name.
+**
+**   c) There is currently a reserved lock on the file. This 
+**      condition is waived if the noLock argument is non-zero.
+**/
+static jt_file *locateDatabaseHandle(const char *zJournal, int noLock){
+  jt_file *pMain = 0;
+  enterJtMutex();
+  for(pMain=g.pList; pMain; pMain=pMain->pNext){
+    int nName = (int)(strlen(zJournal) - strlen("-journal"));
+    if( (pMain->flags&SQLITE_OPEN_MAIN_DB)
+     && ((int)strlen(pMain->zName)==nName)
+     && 0==memcmp(pMain->zName, zJournal, nName)
+     && ((pMain->eLock>=SQLITE_LOCK_RESERVED) || noLock)
+    ){
+      break;
+    }
+  }
+  leaveJtMutex();
+  return pMain;
+}
+
+/*
+** Parameter z points to a buffer of 4 bytes in size containing a 
+** unsigned 32-bit integer stored in big-endian format. Decode the 
+** integer and return its value.
+*/
+static u32 decodeUint32(const unsigned char *z){
+  return (z[0]<<24) + (z[1]<<16) + (z[2]<<8) + z[3];
+}
+
+/*
+** Calculate a checksum from the buffer of length n bytes pointed to
+** by parameter z.
+*/
+static u32 genCksum(const unsigned char *z, int n){
+  int i;
+  u32 cksum = 0;
+  for(i=0; i<n; i++){
+    cksum = cksum + z[i] + (cksum<<3);
+  }
+  return cksum;
+}
+
+/*
+** The first argument, zBuf, points to a buffer containing a 28 byte
+** serialized journal header. This function deserializes four of the
+** integer fields contained in the journal header and writes their
+** values to the output variables.
+**
+** SQLITE_OK is returned if the journal-header is successfully 
+** decoded. Otherwise, SQLITE_ERROR.
+*/
+static int decodeJournalHdr(
+  const unsigned char *zBuf,         /* Input: 28 byte journal header */
+  u32 *pnRec,                        /* Out: Number of journalled records */
+  u32 *pnPage,                       /* Out: Original database page count */
+  u32 *pnSector,                     /* Out: Sector size in bytes */
+  u32 *pnPagesize                    /* Out: Page size in bytes */
+){
+  unsigned char aMagic[] = { 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7 };
+  if( memcmp(aMagic, zBuf, 8) ) return SQLITE_ERROR;
+  if( pnRec ) *pnRec = decodeUint32(&zBuf[8]);
+  if( pnPage ) *pnPage = decodeUint32(&zBuf[16]);
+  if( pnSector ) *pnSector = decodeUint32(&zBuf[20]);
+  if( pnPagesize ) *pnPagesize = decodeUint32(&zBuf[24]);
+  return SQLITE_OK;
+}
+
+/*
+** This function is called when a new transaction is opened, just after
+** the first journal-header is written to the journal file.
+*/
+static int openTransaction(jt_file *pMain, jt_file *pJournal){
+  unsigned char *aData;
+  sqlite3_file *p = pMain->pReal;
+  int rc = SQLITE_OK;
+
+  closeTransaction(pMain);
+  aData = sqlite3_malloc(pMain->nPagesize);
+  pMain->pWritable = sqlite3BitvecCreate(pMain->nPage);
+  pMain->aCksum = sqlite3_malloc(sizeof(u32) * (pMain->nPage + 1));
+  pJournal->iMaxOff = 0;
+
+  if( !pMain->pWritable || !pMain->aCksum || !aData ){
+    rc = SQLITE_IOERR_NOMEM;
+  }else if( pMain->nPage>0 ){
+    u32 iTrunk;
+    int iSave;
+    int iSave2;
+
+    stop_ioerr_simulation(&iSave, &iSave2);
+
+    /* Read the database free-list. Add the page-number for each free-list
+    ** leaf to the jt_file.pWritable bitvec.
+    */
+    rc = sqlite3OsRead(p, aData, pMain->nPagesize, 0);
+    if( rc==SQLITE_OK ){
+      u32 nDbsize = decodeUint32(&aData[28]);
+      if( nDbsize>0 && memcmp(&aData[24], &aData[92], 4)==0 ){
+        u32 iPg;
+        for(iPg=nDbsize+1; iPg<=pMain->nPage; iPg++){
+          sqlite3BitvecSet(pMain->pWritable, iPg);
+        }
+      }
+    }
+    iTrunk = decodeUint32(&aData[32]);
+    while( rc==SQLITE_OK && iTrunk>0 ){
+      u32 nLeaf;
+      u32 iLeaf;
+      sqlite3_int64 iOff = (i64)(iTrunk-1)*pMain->nPagesize;
+      rc = sqlite3OsRead(p, aData, pMain->nPagesize, iOff);
+      nLeaf = decodeUint32(&aData[4]);
+      for(iLeaf=0; rc==SQLITE_OK && iLeaf<nLeaf; iLeaf++){
+        u32 pgno = decodeUint32(&aData[8+4*iLeaf]);
+        sqlite3BitvecSet(pMain->pWritable, pgno);
+      }
+      iTrunk = decodeUint32(aData);
+    }
+
+    /* Calculate and store a checksum for each page in the database file. */
+    if( rc==SQLITE_OK ){
+      int ii;
+      for(ii=0; rc==SQLITE_OK && ii<(int)pMain->nPage; ii++){
+        i64 iOff = (i64)(pMain->nPagesize) * (i64)ii;
+        if( iOff==PENDING_BYTE ) continue;
+        rc = sqlite3OsRead(pMain->pReal, aData, pMain->nPagesize, iOff);
+        pMain->aCksum[ii] = genCksum(aData, pMain->nPagesize);
+        if( ii+1==(int)pMain->nPage && rc==SQLITE_IOERR_SHORT_READ ){
+          rc = SQLITE_OK;
+        }
+      }
+    }
+
+    start_ioerr_simulation(iSave, iSave2);
+  }
+
+  sqlite3_free(aData);
+  return rc;
+}
+
+/*
+** The first argument to this function is a handle open on a journal file.
+** This function reads the journal file and adds the page number for each
+** page in the journal to the Bitvec object passed as the second argument.
+*/
+static int readJournalFile(jt_file *p, jt_file *pMain){
+  int rc = SQLITE_OK;
+  unsigned char zBuf[28];
+  sqlite3_file *pReal = p->pReal;
+  sqlite3_int64 iOff = 0;
+  sqlite3_int64 iSize = p->iMaxOff;
+  unsigned char *aPage;
+  int iSave;
+  int iSave2;
+
+  aPage = sqlite3_malloc(pMain->nPagesize);
+  if( !aPage ){
+    return SQLITE_IOERR_NOMEM;
+  }
+
+  stop_ioerr_simulation(&iSave, &iSave2);
+
+  while( rc==SQLITE_OK && iOff<iSize ){
+    u32 nRec, nPage, nSector, nPagesize;
+    u32 ii;
+
+    /* Read and decode the next journal-header from the journal file. */
+    rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
+    if( rc!=SQLITE_OK 
+     || decodeJournalHdr(zBuf, &nRec, &nPage, &nSector, &nPagesize) 
+    ){
+      goto finish_rjf;
+    }
+    iOff += nSector;
+
+    if( nRec==0 ){
+      /* A trick. There might be another journal-header immediately 
+      ** following this one. In this case, 0 records means 0 records, 
+      ** not "read until the end of the file". See also ticket #2565.
+      */
+      if( iSize>=(iOff+nSector) ){
+        rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
+        if( rc!=SQLITE_OK || 0==decodeJournalHdr(zBuf, 0, 0, 0, 0) ){
+          continue;
+        }
+      }
+      nRec = (u32)((iSize-iOff) / (pMain->nPagesize+8));
+    }
+
+    /* Read all the records that follow the journal-header just read. */
+    for(ii=0; rc==SQLITE_OK && ii<nRec && iOff<iSize; ii++){
+      u32 pgno;
+      rc = sqlite3OsRead(pReal, zBuf, 4, iOff);
+      if( rc==SQLITE_OK ){
+        pgno = decodeUint32(zBuf);
+        if( pgno>0 && pgno<=pMain->nPage ){
+          if( 0==sqlite3BitvecTest(pMain->pWritable, pgno) ){
+            rc = sqlite3OsRead(pReal, aPage, pMain->nPagesize, iOff+4);
+            if( rc==SQLITE_OK ){
+              u32 cksum = genCksum(aPage, pMain->nPagesize);
+              assert( cksum==pMain->aCksum[pgno-1] );
+            }
+          }
+          sqlite3BitvecSet(pMain->pWritable, pgno);
+        }
+        iOff += (8 + pMain->nPagesize);
+      }
+    }
+
+    iOff = ((iOff + (nSector-1)) / nSector) * nSector;
+  }
+
+finish_rjf:
+  start_ioerr_simulation(iSave, iSave2);
+  sqlite3_free(aPage);
+  if( rc==SQLITE_IOERR_SHORT_READ ){
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Write data to an jt-file.
+*/
+static int jtWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    if( iOfst==0 ){
+      jt_file *pMain = locateDatabaseHandle(p->zName, 0);
+      assert( pMain );
+  
+      if( iAmt==28 ){
+        /* Zeroing the first journal-file header. This is the end of a
+        ** transaction. */
+        closeTransaction(pMain);
+      }else if( iAmt!=12 ){
+        /* Writing the first journal header to a journal file. This happens
+        ** when a transaction is first started.  */
+        u8 *z = (u8 *)zBuf;
+        pMain->nPage = decodeUint32(&z[16]);
+        pMain->nPagesize = decodeUint32(&z[24]);
+        if( SQLITE_OK!=(rc=openTransaction(pMain, p)) ){
+          return rc;
+        }
+      }
+    }
+    if( p->iMaxOff<(iOfst + iAmt) ){
+      p->iMaxOff = iOfst + iAmt;
+    }
+  }
+
+  if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
+    if( iAmt<(int)p->nPagesize 
+     && p->nPagesize%iAmt==0 
+     && iOfst>=(PENDING_BYTE+512) 
+     && iOfst+iAmt<=PENDING_BYTE+p->nPagesize
+    ){
+      /* No-op. This special case is hit when the backup code is copying a
+      ** to a database with a larger page-size than the source database and
+      ** it needs to fill in the non-locking-region part of the original
+      ** pending-byte page.
+      */
+    }else{
+      u32 pgno = (u32)(iOfst/p->nPagesize + 1);
+      assert( (iAmt==1||iAmt==(int)p->nPagesize) &&
+              ((iOfst+iAmt)%p->nPagesize)==0 );
+      /* The following assert() statements may fail if this layer is used
+      ** with a connection in "PRAGMA synchronous=off" mode. If they
+      ** fail with sync=normal or sync=full, this may indicate problem.  */
+      assert( p->nPage==0 || pgno<=p->nPage || p->nSync>0 );
+      assert( pgno>p->nPage || sqlite3BitvecTest(p->pWritable, pgno) );
+    }
+  }
+
+  rc = sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
+  if( (p->flags&SQLITE_OPEN_MAIN_JOURNAL) && iAmt==12 ){
+    jt_file *pMain = locateDatabaseHandle(p->zName, 0);
+    int rc2 = readJournalFile(p, pMain);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+  return rc;
+}
+
+/*
+** Truncate an jt-file.
+*/
+static int jtTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  jt_file *p = (jt_file *)pFile;
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL && size==0 ){
+    /* Truncating a journal file. This is the end of a transaction. */
+    jt_file *pMain = locateDatabaseHandle(p->zName, 0);
+    closeTransaction(pMain);
+  }
+  if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
+    u32 pgno;
+    u32 locking_page = (u32)(PENDING_BYTE/p->nPagesize+1);
+    for(pgno=(u32)(size/p->nPagesize+1); pgno<=p->nPage; pgno++){
+      assert( pgno==locking_page || sqlite3BitvecTest(p->pWritable, pgno) );
+    }
+  }
+  return sqlite3OsTruncate(p->pReal, size);
+}
+
+/*
+** Sync an jt-file.
+*/
+static int jtSync(sqlite3_file *pFile, int flags){
+  jt_file *p = (jt_file *)pFile;
+
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    int rc;
+    jt_file *pMain;                   /* The associated database file */
+
+    /* The journal file is being synced. At this point, we inspect the 
+    ** contents of the file up to this point and set each bit in the 
+    ** jt_file.pWritable bitvec of the main database file associated with
+    ** this journal file.
+    */
+    pMain = locateDatabaseHandle(p->zName, 0);
+
+    /* Set the bitvec values */
+    if( pMain && pMain->pWritable ){
+      pMain->nSync++;
+      rc = readJournalFile(p, pMain);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+  }
+
+  return sqlite3OsSync(p->pReal, flags);
+}
+
+/*
+** Return the current file-size of an jt-file.
+*/
+static int jtFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsFileSize(p->pReal, pSize);
+}
+
+/*
+** Lock an jt-file.
+*/
+static int jtLock(sqlite3_file *pFile, int eLock){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  rc = sqlite3OsLock(p->pReal, eLock);
+  if( rc==SQLITE_OK && eLock>p->eLock ){
+    p->eLock = eLock;
+  }
+  return rc;
+}
+
+/*
+** Unlock an jt-file.
+*/
+static int jtUnlock(sqlite3_file *pFile, int eLock){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  rc = sqlite3OsUnlock(p->pReal, eLock);
+  if( rc==SQLITE_OK && eLock<p->eLock ){
+    p->eLock = eLock;
+  }
+  return rc;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an jt-file.
+*/
+static int jtCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsCheckReservedLock(p->pReal, pResOut);
+}
+
+/*
+** File control method. For custom operations on an jt-file.
+*/
+static int jtFileControl(sqlite3_file *pFile, int op, void *pArg){
+  jt_file *p = (jt_file *)pFile;
+  return p->pReal->pMethods->xFileControl(p->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an jt-file.
+*/
+static int jtSectorSize(sqlite3_file *pFile){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsSectorSize(p->pReal);
+}
+
+/*
+** Return the device characteristic flags supported by an jt-file.
+*/
+static int jtDeviceCharacteristics(sqlite3_file *pFile){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsDeviceCharacteristics(p->pReal);
+}
+
+/*
+** Open an jt file handle.
+*/
+static int jtOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  pFile->pMethods = 0;
+  p->pReal = (sqlite3_file *)&p[1];
+  p->pReal->pMethods = 0;
+  rc = sqlite3OsOpen(g.pVfs, zName, p->pReal, flags, pOutFlags);
+  assert( rc==SQLITE_OK || p->pReal->pMethods==0 );
+  if( rc==SQLITE_OK ){
+    pFile->pMethods = &jt_io_methods;
+    p->eLock = 0;
+    p->zName = zName;
+    p->flags = flags;
+    p->pNext = 0;
+    p->pWritable = 0;
+    p->aCksum = 0;
+    enterJtMutex();
+    if( zName ){
+      p->pNext = g.pList;
+      g.pList = p;
+    }
+    leaveJtMutex();
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int jtDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int nPath = (int)strlen(zPath);
+  if( nPath>8 && 0==strcmp("-journal", &zPath[nPath-8]) ){
+    /* Deleting a journal file. The end of a transaction. */
+    jt_file *pMain = locateDatabaseHandle(zPath, 0);
+    if( pMain ){
+      closeTransaction(pMain);
+    }
+  }
+
+  return sqlite3OsDelete(g.pVfs, zPath, dirSync);
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int jtAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  return sqlite3OsAccess(g.pVfs, zPath, flags, pResOut);
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (JT_MAX_PATHNAME+1) bytes.
+*/
+static int jtFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  return sqlite3OsFullPathname(g.pVfs, zPath, nOut, zOut);
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *jtDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return g.pVfs->xDlOpen(g.pVfs, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void jtDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  g.pVfs->xDlError(g.pVfs, nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*jtDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return g.pVfs->xDlSym(g.pVfs, p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void jtDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  g.pVfs->xDlClose(g.pVfs, pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int jtRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return sqlite3OsRandomness(g.pVfs, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int jtSleep(sqlite3_vfs *pVfs, int nMicro){
+  return sqlite3OsSleep(g.pVfs, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int jtCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return g.pVfs->xCurrentTime(g.pVfs, pTimeOut);
+}
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int jtCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  return g.pVfs->xCurrentTimeInt64(g.pVfs, pTimeOut);
+}
+
+static int jtGetLastError(sqlite3_vfs *pVfs, int n, char *z){
+  return g.pVfs->xGetLastError(g.pVfs, n, z);
+}
+
+/**************************************************************************
+** Start of public API.
+*/
+
+/*
+** Configure the jt VFS as a wrapper around the VFS named by parameter 
+** zWrap. If the isDefault parameter is true, then the jt VFS is installed
+** as the new default VFS for SQLite connections. If isDefault is not
+** true, then the jt VFS is installed as non-default. In this case it
+** is available via its name, "jt".
+*/
+int jt_register(char *zWrap, int isDefault){
+  g.pVfs = sqlite3_vfs_find(zWrap);
+  if( g.pVfs==0 ){
+    return SQLITE_ERROR;
+  }
+  jt_vfs.szOsFile = sizeof(jt_file) + g.pVfs->szOsFile;
+  if( g.pVfs->iVersion==1 ){
+    jt_vfs.iVersion = 1;
+  }else if( g.pVfs->xCurrentTimeInt64==0 ){
+    jt_vfs.xCurrentTimeInt64 = 0;
+  }
+  sqlite3_vfs_register(&jt_vfs, isDefault);
+  return SQLITE_OK;
+}
+
+/*
+** Uninstall the jt VFS, if it is installed.
+*/
+void jt_unregister(void){
+  sqlite3_vfs_unregister(&jt_vfs);
+}
+
+#endif
diff --git a/src/test_loadext.c b/src/test_loadext.c
new file mode 100644
index 0000000..6404a69
--- /dev/null
+++ b/src/test_loadext.c
@@ -0,0 +1,128 @@
+/*
+** 2006 June 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Test extension for testing the sqlite3_load_extension() function.
+*/
+#include <string.h>
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+
+/*
+** The half() SQL function returns half of its input value.
+*/
+static void halfFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_result_double(context, 0.5*sqlite3_value_double(argv[0]));
+}
+
+/*
+** SQL functions to call the sqlite3_status function and return results.
+*/
+static void statusFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int op = 0, mx, cur, resetFlag, rc;
+  if( sqlite3_value_type(argv[0])==SQLITE_INTEGER ){
+    op = sqlite3_value_int(argv[0]);
+  }else if( sqlite3_value_type(argv[0])==SQLITE_TEXT ){
+    int i;
+    const char *zName;
+    static const struct {
+      const char *zName;
+      int op;
+    } aOp[] = {
+      { "MEMORY_USED",         SQLITE_STATUS_MEMORY_USED         },
+      { "PAGECACHE_USED",      SQLITE_STATUS_PAGECACHE_USED      },
+      { "PAGECACHE_OVERFLOW",  SQLITE_STATUS_PAGECACHE_OVERFLOW  },
+      { "SCRATCH_USED",        SQLITE_STATUS_SCRATCH_USED        },
+      { "SCRATCH_OVERFLOW",    SQLITE_STATUS_SCRATCH_OVERFLOW    },
+      { "MALLOC_SIZE",         SQLITE_STATUS_MALLOC_SIZE         },
+    };
+    int nOp = sizeof(aOp)/sizeof(aOp[0]);
+    zName = (const char*)sqlite3_value_text(argv[0]);
+    for(i=0; i<nOp; i++){
+      if( strcmp(aOp[i].zName, zName)==0 ){
+        op = aOp[i].op;
+        break;
+      }
+    }
+    if( i>=nOp ){
+      char *zMsg = sqlite3_mprintf("unknown status property: %s", zName);
+      sqlite3_result_error(context, zMsg, -1);
+      sqlite3_free(zMsg);
+      return;
+    }
+  }else{
+    sqlite3_result_error(context, "unknown status type", -1);
+    return;
+  }
+  if( argc==2 ){
+    resetFlag = sqlite3_value_int(argv[1]);
+  }else{
+    resetFlag = 0;
+  }
+  rc = sqlite3_status(op, &cur, &mx, resetFlag);
+  if( rc!=SQLITE_OK ){
+    char *zMsg = sqlite3_mprintf("sqlite3_status(%d,...) returns %d", op, rc);
+    sqlite3_result_error(context, zMsg, -1);
+    sqlite3_free(zMsg);
+    return;
+  } 
+  if( argc==2 ){
+    sqlite3_result_int(context, mx);
+  }else{
+    sqlite3_result_int(context, cur);
+  }
+}
+
+/*
+** Extension load function.
+*/
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int testloadext_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  int nErr = 0;
+  SQLITE_EXTENSION_INIT2(pApi);
+  nErr |= sqlite3_create_function(db, "half", 1, SQLITE_ANY, 0, halfFunc, 0, 0);
+  nErr |= sqlite3_create_function(db, "sqlite3_status", 1, SQLITE_ANY, 0,
+                          statusFunc, 0, 0);
+  nErr |= sqlite3_create_function(db, "sqlite3_status", 2, SQLITE_ANY, 0,
+                          statusFunc, 0, 0);
+  return nErr ? SQLITE_ERROR : SQLITE_OK;
+}
+
+/*
+** Another extension entry point. This one always fails.
+*/
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int testbrokenext_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  char *zErr;
+  SQLITE_EXTENSION_INIT2(pApi);
+  zErr = sqlite3_mprintf("broken!");
+  *pzErrMsg = zErr;
+  return 1;
+}
diff --git a/src/test_malloc.c b/src/test_malloc.c
new file mode 100644
index 0000000..8146501
--- /dev/null
+++ b/src/test_malloc.c
@@ -0,0 +1,1513 @@
+/*
+** 2007 August 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to implement test interfaces to the
+** memory allocation subsystem.
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+/*
+** This structure is used to encapsulate the global state variables used 
+** by malloc() fault simulation.
+*/
+static struct MemFault {
+  int iCountdown;         /* Number of pending successes before a failure */
+  int nRepeat;            /* Number of times to repeat the failure */
+  int nBenign;            /* Number of benign failures seen since last config */
+  int nFail;              /* Number of failures seen since last config */
+  int nOkBefore;          /* Successful allocations prior to the first fault */
+  int nOkAfter;           /* Successful allocations after a fault */
+  u8 enable;              /* True if enabled */
+  int isInstalled;        /* True if the fault simulation layer is installed */
+  int isBenignMode;       /* True if malloc failures are considered benign */
+  sqlite3_mem_methods m;  /* 'Real' malloc implementation */
+} memfault;
+
+/*
+** This routine exists as a place to set a breakpoint that will
+** fire on any simulated malloc() failure.
+*/
+static void sqlite3Fault(void){
+  static int cnt = 0;
+  cnt++;
+}
+
+/*
+** This routine exists as a place to set a breakpoint that will
+** fire the first time any malloc() fails on a single test case.
+** The sqlite3Fault() routine above runs on every malloc() failure.
+** This routine only runs on the first such failure.
+*/
+static void sqlite3FirstFault(void){
+  static int cnt2 = 0;
+  cnt2++;
+}
+
+/*
+** Check to see if a fault should be simulated.  Return true to simulate
+** the fault.  Return false if the fault should not be simulated.
+*/
+static int faultsimStep(void){
+  if( likely(!memfault.enable) ){
+    memfault.nOkAfter++;
+    return 0;
+  }
+  if( memfault.iCountdown>0 ){
+    memfault.iCountdown--;
+    memfault.nOkBefore++;
+    return 0;
+  }
+  if( memfault.nFail==0 ) sqlite3FirstFault();
+  sqlite3Fault();
+  memfault.nFail++;
+  if( memfault.isBenignMode>0 ){
+    memfault.nBenign++;
+  }
+  memfault.nRepeat--;
+  if( memfault.nRepeat<=0 ){
+    memfault.enable = 0;
+  }
+  return 1;  
+}
+
+/*
+** A version of sqlite3_mem_methods.xMalloc() that includes fault simulation
+** logic.
+*/
+static void *faultsimMalloc(int n){
+  void *p = 0;
+  if( !faultsimStep() ){
+    p = memfault.m.xMalloc(n);
+  }
+  return p;
+}
+
+
+/*
+** A version of sqlite3_mem_methods.xRealloc() that includes fault simulation
+** logic.
+*/
+static void *faultsimRealloc(void *pOld, int n){
+  void *p = 0;
+  if( !faultsimStep() ){
+    p = memfault.m.xRealloc(pOld, n);
+  }
+  return p;
+}
+
+/*
+** This routine configures the malloc failure simulation.  After
+** calling this routine, the next nDelay mallocs will succeed, followed
+** by a block of nRepeat failures, after which malloc() calls will begin
+** to succeed again.
+*/
+static void faultsimConfig(int nDelay, int nRepeat){
+  memfault.iCountdown = nDelay;
+  memfault.nRepeat = nRepeat;
+  memfault.nBenign = 0;
+  memfault.nFail = 0;
+  memfault.nOkBefore = 0;
+  memfault.nOkAfter = 0;
+  memfault.enable = nDelay>=0;
+
+  /* Sometimes, when running multi-threaded tests, the isBenignMode 
+  ** variable is not properly incremented/decremented so that it is
+  ** 0 when not inside a benign malloc block. This doesn't affect
+  ** the multi-threaded tests, as they do not use this system. But
+  ** it does affect OOM tests run later in the same process. So
+  ** zero the variable here, just to be sure.
+  */
+  memfault.isBenignMode = 0;
+}
+
+/*
+** Return the number of faults (both hard and benign faults) that have
+** occurred since the injector was last configured.
+*/
+static int faultsimFailures(void){
+  return memfault.nFail;
+}
+
+/*
+** Return the number of benign faults that have occurred since the
+** injector was last configured.
+*/
+static int faultsimBenignFailures(void){
+  return memfault.nBenign;
+}
+
+/*
+** Return the number of successes that will occur before the next failure.
+** If no failures are scheduled, return -1.
+*/
+static int faultsimPending(void){
+  if( memfault.enable ){
+    return memfault.iCountdown;
+  }else{
+    return -1;
+  }
+}
+
+
+static void faultsimBeginBenign(void){
+  memfault.isBenignMode++;
+}
+static void faultsimEndBenign(void){
+  memfault.isBenignMode--;
+}
+
+/*
+** Add or remove the fault-simulation layer using sqlite3_config(). If
+** the argument is non-zero, the 
+*/
+static int faultsimInstall(int install){
+  int rc;
+
+  install = (install ? 1 : 0);
+  assert(memfault.isInstalled==1 || memfault.isInstalled==0);
+
+  if( install==memfault.isInstalled ){
+    return SQLITE_ERROR;
+  }
+
+  if( install ){
+    rc = sqlite3_config(SQLITE_CONFIG_GETMALLOC, &memfault.m);
+    assert(memfault.m.xMalloc);
+    if( rc==SQLITE_OK ){
+      sqlite3_mem_methods m = memfault.m;
+      m.xMalloc = faultsimMalloc;
+      m.xRealloc = faultsimRealloc;
+      rc = sqlite3_config(SQLITE_CONFIG_MALLOC, &m);
+    }
+    sqlite3_test_control(SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS, 
+        faultsimBeginBenign, faultsimEndBenign
+    );
+  }else{
+    sqlite3_mem_methods m2;
+    assert(memfault.m.xMalloc);
+
+    /* One should be able to reset the default memory allocator by storing
+    ** a zeroed allocator then calling GETMALLOC. */
+    memset(&m2, 0, sizeof(m2));
+    sqlite3_config(SQLITE_CONFIG_MALLOC, &m2);
+    sqlite3_config(SQLITE_CONFIG_GETMALLOC, &m2);
+    assert( memcmp(&m2, &memfault.m, sizeof(m2))==0 );
+
+    rc = sqlite3_config(SQLITE_CONFIG_MALLOC, &memfault.m);
+    sqlite3_test_control(SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS,
+        (void*)0, (void*)0);
+  }
+
+  if( rc==SQLITE_OK ){
+    memfault.isInstalled = 1;
+  }
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+
+/*
+** This function is implemented in main.c. Returns a pointer to a static
+** buffer containing the symbolic SQLite error code that corresponds to
+** the least-significant 8-bits of the integer passed as an argument.
+** For example:
+**
+**   sqlite3ErrName(1) -> "SQLITE_ERROR"
+*/
+extern const char *sqlite3ErrName(int);
+
+/*
+** Transform pointers to text and back again
+*/
+static void pointerToText(void *p, char *z){
+  static const char zHex[] = "0123456789abcdef";
+  int i, k;
+  unsigned int u;
+  sqlite3_uint64 n;
+  if( p==0 ){
+    strcpy(z, "0");
+    return;
+  }
+  if( sizeof(n)==sizeof(p) ){
+    memcpy(&n, &p, sizeof(p));
+  }else if( sizeof(u)==sizeof(p) ){
+    memcpy(&u, &p, sizeof(u));
+    n = u;
+  }else{
+    assert( 0 );
+  }
+  for(i=0, k=sizeof(p)*2-1; i<sizeof(p)*2; i++, k--){
+    z[k] = zHex[n&0xf];
+    n >>= 4;
+  }
+  z[sizeof(p)*2] = 0;
+}
+static int hexToInt(int h){
+  if( h>='0' && h<='9' ){
+    return h - '0';
+  }else if( h>='a' && h<='f' ){
+    return h - 'a' + 10;
+  }else{
+    return -1;
+  }
+}
+static int textToPointer(const char *z, void **pp){
+  sqlite3_uint64 n = 0;
+  int i;
+  unsigned int u;
+  for(i=0; i<sizeof(void*)*2 && z[0]; i++){
+    int v;
+    v = hexToInt(*z++);
+    if( v<0 ) return TCL_ERROR;
+    n = n*16 + v;
+  }
+  if( *z!=0 ) return TCL_ERROR;
+  if( sizeof(n)==sizeof(*pp) ){
+    memcpy(pp, &n, sizeof(n));
+  }else if( sizeof(u)==sizeof(*pp) ){
+    u = (unsigned int)n;
+    memcpy(pp, &u, sizeof(u));
+  }else{
+    assert( 0 );
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_malloc  NBYTES
+**
+** Raw test interface for sqlite3_malloc().
+*/
+static int SQLITE_TCLAPI test_malloc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nByte;
+  void *p;
+  char zOut[100];
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NBYTES");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &nByte) ) return TCL_ERROR;
+  p = sqlite3_malloc((unsigned)nByte);
+  pointerToText(p, zOut);
+  Tcl_AppendResult(interp, zOut, NULL);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_realloc  PRIOR  NBYTES
+**
+** Raw test interface for sqlite3_realloc().
+*/
+static int SQLITE_TCLAPI test_realloc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nByte;
+  void *pPrior, *p;
+  char zOut[100];
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PRIOR NBYTES");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &nByte) ) return TCL_ERROR;
+  if( textToPointer(Tcl_GetString(objv[1]), &pPrior) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  p = sqlite3_realloc(pPrior, (unsigned)nByte);
+  pointerToText(p, zOut);
+  Tcl_AppendResult(interp, zOut, NULL);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_free  PRIOR
+**
+** Raw test interface for sqlite3_free().
+*/
+static int SQLITE_TCLAPI test_free(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *pPrior;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PRIOR");
+    return TCL_ERROR;
+  }
+  if( textToPointer(Tcl_GetString(objv[1]), &pPrior) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  sqlite3_free(pPrior);
+  return TCL_OK;
+}
+
+/*
+** These routines are in test_hexio.c
+*/
+int sqlite3TestHexToBin(const char *, int, char *);
+int sqlite3TestBinToHex(char*,int);
+
+/*
+** Usage:    memset  ADDRESS  SIZE  HEX
+**
+** Set a chunk of memory (obtained from malloc, probably) to a
+** specified hex pattern.
+*/
+static int SQLITE_TCLAPI test_memset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *p;
+  int size, n, i;
+  char *zHex;
+  char *zOut;
+  char zBin[100];
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "ADDRESS SIZE HEX");
+    return TCL_ERROR;
+  }
+  if( textToPointer(Tcl_GetString(objv[1]), &p) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &size) ){
+    return TCL_ERROR;
+  }
+  if( size<=0 ){
+    Tcl_AppendResult(interp, "size must be positive", (char*)0);
+    return TCL_ERROR;
+  }
+  zHex = Tcl_GetStringFromObj(objv[3], &n);
+  if( n>sizeof(zBin)*2 ) n = sizeof(zBin)*2;
+  n = sqlite3TestHexToBin(zHex, n, zBin);
+  if( n==0 ){
+    Tcl_AppendResult(interp, "no data", (char*)0);
+    return TCL_ERROR;
+  }
+  zOut = p;
+  for(i=0; i<size; i++){
+    zOut[i] = zBin[i%n];
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    memget  ADDRESS  SIZE
+**
+** Return memory as hexadecimal text.
+*/
+static int SQLITE_TCLAPI test_memget(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *p;
+  int size, n;
+  char *zBin;
+  char zHex[100];
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "ADDRESS SIZE");
+    return TCL_ERROR;
+  }
+  if( textToPointer(Tcl_GetString(objv[1]), &p) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &size) ){
+    return TCL_ERROR;
+  }
+  if( size<=0 ){
+    Tcl_AppendResult(interp, "size must be positive", (char*)0);
+    return TCL_ERROR;
+  }
+  zBin = p;
+  while( size>0 ){
+    if( size>(sizeof(zHex)-1)/2 ){
+      n = (sizeof(zHex)-1)/2;
+    }else{
+      n = size;
+    }
+    memcpy(zHex, zBin, n);
+    zBin += n;
+    size -= n;
+    sqlite3TestBinToHex(zHex, n);
+    Tcl_AppendResult(interp, zHex, (char*)0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memory_used
+**
+** Raw test interface for sqlite3_memory_used().
+*/
+static int SQLITE_TCLAPI test_memory_used(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(sqlite3_memory_used()));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memory_highwater ?RESETFLAG?
+**
+** Raw test interface for sqlite3_memory_highwater().
+*/
+static int SQLITE_TCLAPI test_memory_highwater(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int resetFlag = 0;
+  if( objc!=1 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?RESET?");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( Tcl_GetBooleanFromObj(interp, objv[1], &resetFlag) ) return TCL_ERROR;
+  } 
+  Tcl_SetObjResult(interp, 
+     Tcl_NewWideIntObj(sqlite3_memory_highwater(resetFlag)));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_backtrace DEPTH
+**
+** Set the depth of backtracing.  If SQLITE_MEMDEBUG is not defined
+** then this routine is a no-op.
+*/
+static int SQLITE_TCLAPI test_memdebug_backtrace(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int depth;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DEPT");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &depth) ) return TCL_ERROR;
+#ifdef SQLITE_MEMDEBUG
+  {
+    extern void sqlite3MemdebugBacktrace(int);
+    sqlite3MemdebugBacktrace(depth);
+  }
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_dump  FILENAME
+**
+** Write a summary of unfreed memory to FILENAME.
+*/
+static int SQLITE_TCLAPI test_memdebug_dump(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+#if defined(SQLITE_MEMDEBUG) || defined(SQLITE_MEMORY_SIZE) \
+     || defined(SQLITE_POW2_MEMORY_SIZE)
+  {
+    extern void sqlite3MemdebugDump(const char*);
+    sqlite3MemdebugDump(Tcl_GetString(objv[1]));
+  }
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_malloc_count
+**
+** Return the total number of times malloc() has been called.
+*/
+static int SQLITE_TCLAPI test_memdebug_malloc_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nMalloc = -1;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+#if defined(SQLITE_MEMDEBUG)
+  {
+    extern int sqlite3MemdebugMallocCount();
+    nMalloc = sqlite3MemdebugMallocCount();
+  }
+#endif
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nMalloc));
+  return TCL_OK;
+}
+
+
+/*
+** Usage:    sqlite3_memdebug_fail  COUNTER  ?OPTIONS?
+**
+** where options are:
+**
+**     -repeat    <count>
+**     -benigncnt <varname>
+**
+** Arrange for a simulated malloc() failure after COUNTER successes.
+** If a repeat count is specified, the fault is repeated that many
+** times.
+**
+** Each call to this routine overrides the prior counter value.
+** This routine returns the number of simulated failures that have
+** happened since the previous call to this routine.
+**
+** To disable simulated failures, use a COUNTER of -1.
+*/
+static int SQLITE_TCLAPI test_memdebug_fail(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int ii;
+  int iFail;
+  int nRepeat = 1;
+  Tcl_Obj *pBenignCnt = 0;
+  int nBenign;
+  int nFail = 0;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "COUNTER ?OPTIONS?");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &iFail) ) return TCL_ERROR;
+
+  for(ii=2; ii<objc; ii+=2){
+    int nOption;
+    char *zOption = Tcl_GetStringFromObj(objv[ii], &nOption);
+    char *zErr = 0;
+
+    if( nOption>1 && strncmp(zOption, "-repeat", nOption)==0 ){
+      if( ii==(objc-1) ){
+        zErr = "option requires an argument: ";
+      }else{
+        if( Tcl_GetIntFromObj(interp, objv[ii+1], &nRepeat) ){
+          return TCL_ERROR;
+        }
+      }
+    }else if( nOption>1 && strncmp(zOption, "-benigncnt", nOption)==0 ){
+      if( ii==(objc-1) ){
+        zErr = "option requires an argument: ";
+      }else{
+        pBenignCnt = objv[ii+1];
+      }
+    }else{
+      zErr = "unknown option: ";
+    }
+
+    if( zErr ){
+      Tcl_AppendResult(interp, zErr, zOption, 0);
+      return TCL_ERROR;
+    }
+  }
+  
+  nBenign = faultsimBenignFailures();
+  nFail = faultsimFailures();
+  faultsimConfig(iFail, nRepeat);
+
+  if( pBenignCnt ){
+    Tcl_ObjSetVar2(interp, pBenignCnt, 0, Tcl_NewIntObj(nBenign), 0);
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nFail));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_pending
+**
+** Return the number of malloc() calls that will succeed before a 
+** simulated failure occurs. A negative return value indicates that
+** no malloc() failure is scheduled.
+*/
+static int SQLITE_TCLAPI test_memdebug_pending(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nPending;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  nPending = faultsimPending();
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nPending));
+  return TCL_OK;
+}
+
+/*
+** The following global variable keeps track of the number of tests
+** that have run.  This variable is only useful when running in the
+** debugger.
+*/
+static int sqlite3_memdebug_title_count = 0;
+
+/*
+** Usage:    sqlite3_memdebug_settitle TITLE
+**
+** Set a title string stored with each allocation.  The TITLE is
+** typically the name of the test that was running when the
+** allocation occurred.  The TITLE is stored with the allocation
+** and can be used to figure out which tests are leaking memory.
+**
+** Each title overwrite the previous.
+*/
+static int SQLITE_TCLAPI test_memdebug_settitle(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_memdebug_title_count++;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "TITLE");
+    return TCL_ERROR;
+  }
+#ifdef SQLITE_MEMDEBUG
+  {
+    const char *zTitle;
+    extern int sqlite3MemdebugSettitle(const char*);
+    zTitle = Tcl_GetString(objv[1]);
+    sqlite3MemdebugSettitle(zTitle);
+  }
+#endif
+  return TCL_OK;
+}
+
+#define MALLOC_LOG_FRAMES  10 
+#define MALLOC_LOG_KEYINTS (                                              \
+    10 * ((sizeof(int)>=sizeof(void*)) ? 1 : sizeof(void*)/sizeof(int))   \
+)
+static Tcl_HashTable aMallocLog;
+static int mallocLogEnabled = 0;
+
+typedef struct MallocLog MallocLog;
+struct MallocLog {
+  int nCall;
+  int nByte;
+};
+
+#ifdef SQLITE_MEMDEBUG
+static void test_memdebug_callback(int nByte, int nFrame, void **aFrame){
+  if( mallocLogEnabled ){
+    MallocLog *pLog;
+    Tcl_HashEntry *pEntry;
+    int isNew;
+
+    int aKey[MALLOC_LOG_KEYINTS];
+    unsigned int nKey = sizeof(int)*MALLOC_LOG_KEYINTS;
+
+    memset(aKey, 0, nKey);
+    if( (sizeof(void*)*nFrame)<nKey ){
+      nKey = nFrame*sizeof(void*);
+    }
+    memcpy(aKey, aFrame, nKey);
+
+    pEntry = Tcl_CreateHashEntry(&aMallocLog, (const char *)aKey, &isNew);
+    if( isNew ){
+      pLog = (MallocLog *)Tcl_Alloc(sizeof(MallocLog));
+      memset(pLog, 0, sizeof(MallocLog));
+      Tcl_SetHashValue(pEntry, (ClientData)pLog);
+    }else{
+      pLog = (MallocLog *)Tcl_GetHashValue(pEntry);
+    }
+
+    pLog->nCall++;
+    pLog->nByte += nByte;
+  }
+}
+#endif /* SQLITE_MEMDEBUG */
+
+static void test_memdebug_log_clear(void){
+  Tcl_HashSearch search;
+  Tcl_HashEntry *pEntry;
+  for(
+    pEntry=Tcl_FirstHashEntry(&aMallocLog, &search);
+    pEntry;
+    pEntry=Tcl_NextHashEntry(&search)
+  ){
+    MallocLog *pLog = (MallocLog *)Tcl_GetHashValue(pEntry);
+    Tcl_Free((char *)pLog);
+  }
+  Tcl_DeleteHashTable(&aMallocLog);
+  Tcl_InitHashTable(&aMallocLog, MALLOC_LOG_KEYINTS);
+}
+
+static int SQLITE_TCLAPI test_memdebug_log(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static int isInit = 0;
+  int iSub;
+
+  static const char *MB_strs[] = { "start", "stop", "dump", "clear", "sync" };
+  enum MB_enum { 
+      MB_LOG_START, MB_LOG_STOP, MB_LOG_DUMP, MB_LOG_CLEAR, MB_LOG_SYNC 
+  };
+
+  if( !isInit ){
+#ifdef SQLITE_MEMDEBUG
+    extern void sqlite3MemdebugBacktraceCallback(
+        void (*xBacktrace)(int, int, void **));
+    sqlite3MemdebugBacktraceCallback(test_memdebug_callback);
+#endif
+    Tcl_InitHashTable(&aMallocLog, MALLOC_LOG_KEYINTS);
+    isInit = 1;
+  }
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], MB_strs, "sub-command", 0, &iSub) ){
+    return TCL_ERROR;
+  }
+
+  switch( (enum MB_enum)iSub ){
+    case MB_LOG_START:
+      mallocLogEnabled = 1;
+      break;
+    case MB_LOG_STOP:
+      mallocLogEnabled = 0;
+      break;
+    case MB_LOG_DUMP: {
+      Tcl_HashSearch search;
+      Tcl_HashEntry *pEntry;
+      Tcl_Obj *pRet = Tcl_NewObj();
+
+      assert(sizeof(Tcl_WideInt)>=sizeof(void*));
+
+      for(
+        pEntry=Tcl_FirstHashEntry(&aMallocLog, &search);
+        pEntry;
+        pEntry=Tcl_NextHashEntry(&search)
+      ){
+        Tcl_Obj *apElem[MALLOC_LOG_FRAMES+2];
+        MallocLog *pLog = (MallocLog *)Tcl_GetHashValue(pEntry);
+        Tcl_WideInt *aKey = (Tcl_WideInt *)Tcl_GetHashKey(&aMallocLog, pEntry);
+        int ii;
+  
+        apElem[0] = Tcl_NewIntObj(pLog->nCall);
+        apElem[1] = Tcl_NewIntObj(pLog->nByte);
+        for(ii=0; ii<MALLOC_LOG_FRAMES; ii++){
+          apElem[ii+2] = Tcl_NewWideIntObj(aKey[ii]);
+        }
+
+        Tcl_ListObjAppendElement(interp, pRet,
+            Tcl_NewListObj(MALLOC_LOG_FRAMES+2, apElem)
+        );
+      }
+
+      Tcl_SetObjResult(interp, pRet);
+      break;
+    }
+    case MB_LOG_CLEAR: {
+      test_memdebug_log_clear();
+      break;
+    }
+
+    case MB_LOG_SYNC: {
+#ifdef SQLITE_MEMDEBUG
+      extern void sqlite3MemdebugSync();
+      test_memdebug_log_clear();
+      mallocLogEnabled = 1;
+      sqlite3MemdebugSync();
+#endif
+      break;
+    }
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_pagecache SIZE N
+**
+** Set the page-cache memory buffer using SQLITE_CONFIG_PAGECACHE.
+** The buffer is static and is of limited size.  N might be
+** adjusted downward as needed to accommodate the requested size.
+** The revised value of N is returned.
+**
+** A negative SIZE causes the buffer pointer to be NULL.
+*/
+static int SQLITE_TCLAPI test_config_pagecache(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int sz, N;
+  Tcl_Obj *pRes;
+  static char *buf = 0;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SIZE N");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &N) ) return TCL_ERROR;
+  free(buf);
+  buf = 0;
+
+  /* Set the return value */
+  pRes = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pRes, Tcl_NewIntObj(sqlite3GlobalConfig.szPage));
+  Tcl_ListObjAppendElement(0, pRes, Tcl_NewIntObj(sqlite3GlobalConfig.nPage));
+  Tcl_SetObjResult(interp, pRes);
+
+  if( sz<0 ){
+    sqlite3_config(SQLITE_CONFIG_PAGECACHE, (void*)0, 0, 0);
+  }else{
+    buf = malloc( sz*N );
+    sqlite3_config(SQLITE_CONFIG_PAGECACHE, buf, sz, N);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_alt_pcache INSTALL_FLAG DISCARD_CHANCE PRNG_SEED
+**
+** Set up the alternative test page cache.  Install if INSTALL_FLAG is
+** true and uninstall (reverting to the default page cache) if INSTALL_FLAG
+** is false.  DISCARD_CHANGE is an integer between 0 and 100 inclusive
+** which determines the chance of discarding a page when unpinned.  100
+** is certainty.  0 is never.  PRNG_SEED is the pseudo-random number generator
+** seed.
+*/
+static int SQLITE_TCLAPI test_alt_pcache(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int installFlag;
+  int discardChance = 0;
+  int prngSeed = 0;
+  int highStress = 0;
+  extern void installTestPCache(int,unsigned,unsigned,unsigned);
+  if( objc<2 || objc>5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, 
+        "INSTALLFLAG DISCARDCHANCE PRNGSEEED HIGHSTRESS");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &installFlag) ) return TCL_ERROR;
+  if( objc>=3 && Tcl_GetIntFromObj(interp, objv[2], &discardChance) ){
+     return TCL_ERROR;
+  }
+  if( objc>=4 && Tcl_GetIntFromObj(interp, objv[3], &prngSeed) ){
+     return TCL_ERROR;
+  }
+  if( objc>=5 && Tcl_GetIntFromObj(interp, objv[4], &highStress) ){
+    return TCL_ERROR;
+  }
+  if( discardChance<0 || discardChance>100 ){
+    Tcl_AppendResult(interp, "discard-chance should be between 0 and 100",
+                     (char*)0);
+    return TCL_ERROR;
+  }
+  installTestPCache(installFlag, (unsigned)discardChance, (unsigned)prngSeed,
+                    (unsigned)highStress);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_memstatus BOOLEAN
+**
+** Enable or disable memory status reporting using SQLITE_CONFIG_MEMSTATUS.
+*/
+static int SQLITE_TCLAPI test_config_memstatus(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int enable, rc;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &enable) ) return TCL_ERROR;
+  rc = sqlite3_config(SQLITE_CONFIG_MEMSTATUS, enable);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_lookaside  SIZE  COUNT
+**
+*/
+static int SQLITE_TCLAPI test_config_lookaside(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int sz, cnt;
+  Tcl_Obj *pRet;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SIZE COUNT");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &cnt) ) return TCL_ERROR;
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(
+      interp, pRet, Tcl_NewIntObj(sqlite3GlobalConfig.szLookaside)
+  );
+  Tcl_ListObjAppendElement(
+      interp, pRet, Tcl_NewIntObj(sqlite3GlobalConfig.nLookaside)
+  );
+  sqlite3_config(SQLITE_CONFIG_LOOKASIDE, sz, cnt);
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:    sqlite3_db_config_lookaside  CONNECTION  BUFID  SIZE  COUNT
+**
+** There are two static buffers with BUFID 1 and 2.   Each static buffer
+** is 10KB in size.  A BUFID of 0 indicates that the buffer should be NULL
+** which will cause sqlite3_db_config() to allocate space on its own.
+*/
+static int SQLITE_TCLAPI test_db_config_lookaside(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int sz, cnt;
+  sqlite3 *db;
+  int bufid;
+  static char azBuf[2][10000];
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BUFID SIZE COUNT");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &bufid) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[4], &cnt) ) return TCL_ERROR;
+  if( bufid==0 ){
+    rc = sqlite3_db_config(db, SQLITE_DBCONFIG_LOOKASIDE, (void*)0, sz, cnt);
+  }else if( bufid>=1 && bufid<=2 && sz*cnt<=sizeof(azBuf[0]) ){
+    rc = sqlite3_db_config(db, SQLITE_DBCONFIG_LOOKASIDE, azBuf[bufid], sz,cnt);
+  }else{
+    Tcl_AppendResult(interp, "illegal arguments - see documentation", (char*)0);
+    return TCL_ERROR;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_heap NBYTE NMINALLOC
+*/
+static int SQLITE_TCLAPI test_config_heap(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static char *zBuf; /* Use this memory */
+  int nByte;         /* Size of buffer to pass to sqlite3_config() */
+  int nMinAlloc;     /* Size of minimum allocation */
+  int rc;            /* Return code of sqlite3_config() */
+
+  Tcl_Obj * CONST *aArg = &objv[1];
+  int nArg = objc-1;
+
+  if( nArg!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NBYTE NMINALLOC");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, aArg[0], &nByte) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, aArg[1], &nMinAlloc) ) return TCL_ERROR;
+
+  if( nByte==0 ){
+    free( zBuf );
+    zBuf = 0;
+    rc = sqlite3_config(SQLITE_CONFIG_HEAP, (void*)0, 0, 0);
+  }else{
+    zBuf = realloc(zBuf, nByte);
+    rc = sqlite3_config(SQLITE_CONFIG_HEAP, zBuf, nByte, nMinAlloc);
+  }
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_heap_size NBYTE
+*/
+static int SQLITE_TCLAPI test_config_heap_size(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nByte;         /* Size to pass to sqlite3_config() */
+  int rc;            /* Return code of sqlite3_config() */
+
+  Tcl_Obj * CONST *aArg = &objv[1];
+  int nArg = objc-1;
+
+  if( nArg!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NBYTE");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, aArg[0], &nByte) ) return TCL_ERROR;
+
+  rc = sqlite3_config(SQLITE_CONFIG_WIN32_HEAPSIZE, nByte);
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_error  [DB]
+**
+** Invoke sqlite3_config() or sqlite3_db_config() with invalid
+** opcodes and verify that they return errors.
+*/
+static int SQLITE_TCLAPI test_config_error(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+
+  if( objc!=2 && objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "[DB]");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+    if( sqlite3_db_config(db, 99999)!=SQLITE_ERROR ){
+      Tcl_AppendResult(interp, 
+            "sqlite3_db_config(db, 99999) does not return SQLITE_ERROR",
+            (char*)0);
+      return TCL_ERROR;
+    }
+  }else{
+    if( sqlite3_config(99999)!=SQLITE_ERROR ){
+      Tcl_AppendResult(interp, 
+          "sqlite3_config(99999) does not return SQLITE_ERROR",
+          (char*)0);
+      return TCL_ERROR;
+    }
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_uri  BOOLEAN
+**
+** Enables or disables interpretation of URI parameters by default using
+** SQLITE_CONFIG_URI.
+*/
+static int SQLITE_TCLAPI test_config_uri(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int bOpenUri;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOL");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &bOpenUri) ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_config(SQLITE_CONFIG_URI, bOpenUri);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_cis  BOOLEAN
+**
+** Enables or disables the use of the covering-index scan optimization.
+** SQLITE_CONFIG_COVERING_INDEX_SCAN.
+*/
+static int SQLITE_TCLAPI test_config_cis(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int bUseCis;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOL");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &bUseCis) ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_config(SQLITE_CONFIG_COVERING_INDEX_SCAN, bUseCis);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_pmasz  INTEGER
+**
+** Set the minimum PMA size.
+*/
+static int SQLITE_TCLAPI test_config_pmasz(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int iPmaSz;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOL");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &iPmaSz) ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_config(SQLITE_CONFIG_PMASZ, iPmaSz);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+
+  return TCL_OK;
+}
+
+
+/*
+** Usage:    sqlite3_dump_memsys3  FILENAME
+**           sqlite3_dump_memsys5  FILENAME
+**
+** Write a summary of unfreed memsys3 allocations to FILENAME.
+*/
+static int SQLITE_TCLAPI test_dump_memsys3(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+
+  switch( SQLITE_PTR_TO_INT(clientData) ){
+    case 3: {
+#ifdef SQLITE_ENABLE_MEMSYS3
+      extern void sqlite3Memsys3Dump(const char*);
+      sqlite3Memsys3Dump(Tcl_GetString(objv[1]));
+      break;
+#endif
+    }
+    case 5: {
+#ifdef SQLITE_ENABLE_MEMSYS5
+      extern void sqlite3Memsys5Dump(const char*);
+      sqlite3Memsys5Dump(Tcl_GetString(objv[1]));
+      break;
+#endif
+    }
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_status  OPCODE  RESETFLAG
+**
+** Return a list of three elements which are the sqlite3_status() return
+** code, the current value, and the high-water mark value.
+*/
+static int SQLITE_TCLAPI test_status(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc, iValue, mxValue;
+  int i, op = 0, resetFlag;
+  const char *zOpName;
+  static const struct {
+    const char *zName;
+    int op;
+  } aOp[] = {
+    { "SQLITE_STATUS_MEMORY_USED",         SQLITE_STATUS_MEMORY_USED         },
+    { "SQLITE_STATUS_MALLOC_SIZE",         SQLITE_STATUS_MALLOC_SIZE         },
+    { "SQLITE_STATUS_PAGECACHE_USED",      SQLITE_STATUS_PAGECACHE_USED      },
+    { "SQLITE_STATUS_PAGECACHE_OVERFLOW",  SQLITE_STATUS_PAGECACHE_OVERFLOW  },
+    { "SQLITE_STATUS_PAGECACHE_SIZE",      SQLITE_STATUS_PAGECACHE_SIZE      },
+    { "SQLITE_STATUS_SCRATCH_USED",        SQLITE_STATUS_SCRATCH_USED        },
+    { "SQLITE_STATUS_SCRATCH_OVERFLOW",    SQLITE_STATUS_SCRATCH_OVERFLOW    },
+    { "SQLITE_STATUS_SCRATCH_SIZE",        SQLITE_STATUS_SCRATCH_SIZE        },
+    { "SQLITE_STATUS_PARSER_STACK",        SQLITE_STATUS_PARSER_STACK        },
+    { "SQLITE_STATUS_MALLOC_COUNT",        SQLITE_STATUS_MALLOC_COUNT        },
+  };
+  Tcl_Obj *pResult;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PARAMETER RESETFLAG");
+    return TCL_ERROR;
+  }
+  zOpName = Tcl_GetString(objv[1]);
+  for(i=0; i<ArraySize(aOp); i++){
+    if( strcmp(aOp[i].zName, zOpName)==0 ){
+      op = aOp[i].op;
+      break;
+    }
+  }
+  if( i>=ArraySize(aOp) ){
+    if( Tcl_GetIntFromObj(interp, objv[1], &op) ) return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &resetFlag) ) return TCL_ERROR;
+  iValue = 0;
+  mxValue = 0;
+  rc = sqlite3_status(op, &iValue, &mxValue, resetFlag);
+  pResult = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(rc));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(iValue));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(mxValue));
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_db_status  DATABASE  OPCODE  RESETFLAG
+**
+** Return a list of three elements which are the sqlite3_db_status() return
+** code, the current value, and the high-water mark value.
+*/
+static int SQLITE_TCLAPI test_db_status(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc, iValue, mxValue;
+  int i, op = 0, resetFlag;
+  const char *zOpName;
+  sqlite3 *db;
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  static const struct {
+    const char *zName;
+    int op;
+  } aOp[] = {
+    { "LOOKASIDE_USED",      SQLITE_DBSTATUS_LOOKASIDE_USED      },
+    { "CACHE_USED",          SQLITE_DBSTATUS_CACHE_USED          },
+    { "SCHEMA_USED",         SQLITE_DBSTATUS_SCHEMA_USED         },
+    { "STMT_USED",           SQLITE_DBSTATUS_STMT_USED           },
+    { "LOOKASIDE_HIT",       SQLITE_DBSTATUS_LOOKASIDE_HIT       },
+    { "LOOKASIDE_MISS_SIZE", SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE },
+    { "LOOKASIDE_MISS_FULL", SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL },
+    { "CACHE_HIT",           SQLITE_DBSTATUS_CACHE_HIT           },
+    { "CACHE_MISS",          SQLITE_DBSTATUS_CACHE_MISS          },
+    { "CACHE_WRITE",         SQLITE_DBSTATUS_CACHE_WRITE         },
+    { "DEFERRED_FKS",        SQLITE_DBSTATUS_DEFERRED_FKS        },
+    { "CACHE_USED_SHARED",   SQLITE_DBSTATUS_CACHE_USED_SHARED   },
+    { "CACHE_SPILL",         SQLITE_DBSTATUS_CACHE_SPILL         },
+  };
+  Tcl_Obj *pResult;
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB PARAMETER RESETFLAG");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zOpName = Tcl_GetString(objv[2]);
+  if( memcmp(zOpName, "SQLITE_", 7)==0 ) zOpName += 7;
+  if( memcmp(zOpName, "DBSTATUS_", 9)==0 ) zOpName += 9;
+  for(i=0; i<ArraySize(aOp); i++){
+    if( strcmp(aOp[i].zName, zOpName)==0 ){
+      op = aOp[i].op;
+      break;
+    }
+  }
+  if( i>=ArraySize(aOp) ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &op) ) return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[3], &resetFlag) ) return TCL_ERROR;
+  iValue = 0;
+  mxValue = 0;
+  rc = sqlite3_db_status(db, op, &iValue, &mxValue, resetFlag);
+  pResult = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(rc));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(iValue));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(mxValue));
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** install_malloc_faultsim BOOLEAN
+*/
+static int SQLITE_TCLAPI test_install_malloc_faultsim(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int isInstall;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[1], &isInstall) ){
+    return TCL_ERROR;
+  }
+  rc = faultsimInstall(isInstall);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** sqlite3_install_memsys3
+*/
+static int SQLITE_TCLAPI test_install_memsys3(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = SQLITE_MISUSE;
+#ifdef SQLITE_ENABLE_MEMSYS3
+  const sqlite3_mem_methods *sqlite3MemGetMemsys3(void);
+  rc = sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetMemsys3());
+#endif
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_vfs_oom_test(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int sqlite3_memdebug_vfs_oom_test;
+  if( objc>2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?INTEGER?");
+    return TCL_ERROR;
+  }else if( objc==2 ){
+    int iNew;
+    if( Tcl_GetIntFromObj(interp, objv[1], &iNew) ) return TCL_ERROR;
+    sqlite3_memdebug_vfs_oom_test = iNew;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_memdebug_vfs_oom_test));
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_malloc_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     int clientData;
+  } aObjCmd[] = {
+     { "sqlite3_malloc",             test_malloc                   ,0 },
+     { "sqlite3_realloc",            test_realloc                  ,0 },
+     { "sqlite3_free",               test_free                     ,0 },
+     { "memset",                     test_memset                   ,0 },
+     { "memget",                     test_memget                   ,0 },
+     { "sqlite3_memory_used",        test_memory_used              ,0 },
+     { "sqlite3_memory_highwater",   test_memory_highwater         ,0 },
+     { "sqlite3_memdebug_backtrace", test_memdebug_backtrace       ,0 },
+     { "sqlite3_memdebug_dump",      test_memdebug_dump            ,0 },
+     { "sqlite3_memdebug_fail",      test_memdebug_fail            ,0 },
+     { "sqlite3_memdebug_pending",   test_memdebug_pending         ,0 },
+     { "sqlite3_memdebug_settitle",  test_memdebug_settitle        ,0 },
+     { "sqlite3_memdebug_malloc_count", test_memdebug_malloc_count ,0 },
+     { "sqlite3_memdebug_log",       test_memdebug_log             ,0 },
+     { "sqlite3_config_pagecache",   test_config_pagecache         ,0 },
+     { "sqlite3_config_alt_pcache",  test_alt_pcache               ,0 },
+     { "sqlite3_status",             test_status                   ,0 },
+     { "sqlite3_db_status",          test_db_status                ,0 },
+     { "install_malloc_faultsim",    test_install_malloc_faultsim  ,0 },
+     { "sqlite3_config_heap",        test_config_heap              ,0 },
+     { "sqlite3_config_heap_size",   test_config_heap_size         ,0 },
+     { "sqlite3_config_memstatus",   test_config_memstatus         ,0 },
+     { "sqlite3_config_lookaside",   test_config_lookaside         ,0 },
+     { "sqlite3_config_error",       test_config_error             ,0 },
+     { "sqlite3_config_uri",         test_config_uri               ,0 },
+     { "sqlite3_config_cis",         test_config_cis               ,0 },
+     { "sqlite3_config_pmasz",       test_config_pmasz             ,0 },
+     { "sqlite3_db_config_lookaside",test_db_config_lookaside      ,0 },
+     { "sqlite3_dump_memsys3",       test_dump_memsys3             ,3 },
+     { "sqlite3_dump_memsys5",       test_dump_memsys3             ,5 },
+     { "sqlite3_install_memsys3",    test_install_memsys3          ,0 },
+     { "sqlite3_memdebug_vfs_oom_test", test_vfs_oom_test          ,0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    ClientData c = (ClientData)SQLITE_INT_TO_PTR(aObjCmd[i].clientData);
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, c, 0);
+  }
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_md5.c b/src/test_md5.c
new file mode 100644
index 0000000..7903797
--- /dev/null
+++ b/src/test_md5.c
@@ -0,0 +1,450 @@
+/*
+** 2017-10-13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code to implement an MD5 extension to TCL.
+*/
+#include "sqlite3.h"
+#include <stdlib.h>
+#include <string.h>
+#include "sqlite3.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+# include "sqlite_tcl.h"
+#else
+# include "tcl.h"
+# ifndef SQLITE_TCLAPI
+#  define SQLITE_TCLAPI
+# endif
+#endif
+
+/*
+ * This code implements the MD5 message-digest algorithm.
+ * The algorithm is due to Ron Rivest.  This code was
+ * written by Colin Plumb in 1993, no copyright is claimed.
+ * This code is in the public domain; do with it what you wish.
+ *
+ * Equivalent code is available from RSA Data Security, Inc.
+ * This code has been tested against that, and is equivalent,
+ * except that you don't need to include two pages of legalese
+ * with every copy.
+ *
+ * To compute the message digest of a chunk of bytes, declare an
+ * MD5Context structure, pass it to MD5Init, call MD5Update as
+ * needed on buffers full of bytes, and then call MD5Final, which
+ * will fill a supplied 16-byte array with the digest.
+ */
+
+/*
+ * If compiled on a machine that doesn't have a 32-bit integer,
+ * you just set "uint32" to the appropriate datatype for an
+ * unsigned 32-bit integer.  For example:
+ *
+ *       cc -Duint32='unsigned long' md5.c
+ *
+ */
+#ifndef uint32
+#  define uint32 unsigned int
+#endif
+
+struct MD5Context {
+  int isInit;
+  uint32 buf[4];
+  uint32 bits[2];
+  unsigned char in[64];
+};
+typedef struct MD5Context MD5Context;
+
+/*
+ * Note: this code is harmless on little-endian machines.
+ */
+static void byteReverse (unsigned char *buf, unsigned longs){
+        uint32 t;
+        do {
+                t = (uint32)((unsigned)buf[3]<<8 | buf[2]) << 16 |
+                            ((unsigned)buf[1]<<8 | buf[0]);
+                *(uint32 *)buf = t;
+                buf += 4;
+        } while (--longs);
+}
+/* The four core functions - F1 is optimized somewhat */
+
+/* #define F1(x, y, z) (x & y | ~x & z) */
+#define F1(x, y, z) (z ^ (x & (y ^ z)))
+#define F2(x, y, z) F1(z, x, y)
+#define F3(x, y, z) (x ^ y ^ z)
+#define F4(x, y, z) (y ^ (x | ~z))
+
+/* This is the central step in the MD5 algorithm. */
+#define MD5STEP(f, w, x, y, z, data, s) \
+        ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )
+
+/*
+ * The core of the MD5 algorithm, this alters an existing MD5 hash to
+ * reflect the addition of 16 longwords of new data.  MD5Update blocks
+ * the data and converts bytes into longwords for this routine.
+ */
+static void MD5Transform(uint32 buf[4], const uint32 in[16]){
+        register uint32 a, b, c, d;
+
+        a = buf[0];
+        b = buf[1];
+        c = buf[2];
+        d = buf[3];
+
+        MD5STEP(F1, a, b, c, d, in[ 0]+0xd76aa478,  7);
+        MD5STEP(F1, d, a, b, c, in[ 1]+0xe8c7b756, 12);
+        MD5STEP(F1, c, d, a, b, in[ 2]+0x242070db, 17);
+        MD5STEP(F1, b, c, d, a, in[ 3]+0xc1bdceee, 22);
+        MD5STEP(F1, a, b, c, d, in[ 4]+0xf57c0faf,  7);
+        MD5STEP(F1, d, a, b, c, in[ 5]+0x4787c62a, 12);
+        MD5STEP(F1, c, d, a, b, in[ 6]+0xa8304613, 17);
+        MD5STEP(F1, b, c, d, a, in[ 7]+0xfd469501, 22);
+        MD5STEP(F1, a, b, c, d, in[ 8]+0x698098d8,  7);
+        MD5STEP(F1, d, a, b, c, in[ 9]+0x8b44f7af, 12);
+        MD5STEP(F1, c, d, a, b, in[10]+0xffff5bb1, 17);
+        MD5STEP(F1, b, c, d, a, in[11]+0x895cd7be, 22);
+        MD5STEP(F1, a, b, c, d, in[12]+0x6b901122,  7);
+        MD5STEP(F1, d, a, b, c, in[13]+0xfd987193, 12);
+        MD5STEP(F1, c, d, a, b, in[14]+0xa679438e, 17);
+        MD5STEP(F1, b, c, d, a, in[15]+0x49b40821, 22);
+
+        MD5STEP(F2, a, b, c, d, in[ 1]+0xf61e2562,  5);
+        MD5STEP(F2, d, a, b, c, in[ 6]+0xc040b340,  9);
+        MD5STEP(F2, c, d, a, b, in[11]+0x265e5a51, 14);
+        MD5STEP(F2, b, c, d, a, in[ 0]+0xe9b6c7aa, 20);
+        MD5STEP(F2, a, b, c, d, in[ 5]+0xd62f105d,  5);
+        MD5STEP(F2, d, a, b, c, in[10]+0x02441453,  9);
+        MD5STEP(F2, c, d, a, b, in[15]+0xd8a1e681, 14);
+        MD5STEP(F2, b, c, d, a, in[ 4]+0xe7d3fbc8, 20);
+        MD5STEP(F2, a, b, c, d, in[ 9]+0x21e1cde6,  5);
+        MD5STEP(F2, d, a, b, c, in[14]+0xc33707d6,  9);
+        MD5STEP(F2, c, d, a, b, in[ 3]+0xf4d50d87, 14);
+        MD5STEP(F2, b, c, d, a, in[ 8]+0x455a14ed, 20);
+        MD5STEP(F2, a, b, c, d, in[13]+0xa9e3e905,  5);
+        MD5STEP(F2, d, a, b, c, in[ 2]+0xfcefa3f8,  9);
+        MD5STEP(F2, c, d, a, b, in[ 7]+0x676f02d9, 14);
+        MD5STEP(F2, b, c, d, a, in[12]+0x8d2a4c8a, 20);
+
+        MD5STEP(F3, a, b, c, d, in[ 5]+0xfffa3942,  4);
+        MD5STEP(F3, d, a, b, c, in[ 8]+0x8771f681, 11);
+        MD5STEP(F3, c, d, a, b, in[11]+0x6d9d6122, 16);
+        MD5STEP(F3, b, c, d, a, in[14]+0xfde5380c, 23);
+        MD5STEP(F3, a, b, c, d, in[ 1]+0xa4beea44,  4);
+        MD5STEP(F3, d, a, b, c, in[ 4]+0x4bdecfa9, 11);
+        MD5STEP(F3, c, d, a, b, in[ 7]+0xf6bb4b60, 16);
+        MD5STEP(F3, b, c, d, a, in[10]+0xbebfbc70, 23);
+        MD5STEP(F3, a, b, c, d, in[13]+0x289b7ec6,  4);
+        MD5STEP(F3, d, a, b, c, in[ 0]+0xeaa127fa, 11);
+        MD5STEP(F3, c, d, a, b, in[ 3]+0xd4ef3085, 16);
+        MD5STEP(F3, b, c, d, a, in[ 6]+0x04881d05, 23);
+        MD5STEP(F3, a, b, c, d, in[ 9]+0xd9d4d039,  4);
+        MD5STEP(F3, d, a, b, c, in[12]+0xe6db99e5, 11);
+        MD5STEP(F3, c, d, a, b, in[15]+0x1fa27cf8, 16);
+        MD5STEP(F3, b, c, d, a, in[ 2]+0xc4ac5665, 23);
+
+        MD5STEP(F4, a, b, c, d, in[ 0]+0xf4292244,  6);
+        MD5STEP(F4, d, a, b, c, in[ 7]+0x432aff97, 10);
+        MD5STEP(F4, c, d, a, b, in[14]+0xab9423a7, 15);
+        MD5STEP(F4, b, c, d, a, in[ 5]+0xfc93a039, 21);
+        MD5STEP(F4, a, b, c, d, in[12]+0x655b59c3,  6);
+        MD5STEP(F4, d, a, b, c, in[ 3]+0x8f0ccc92, 10);
+        MD5STEP(F4, c, d, a, b, in[10]+0xffeff47d, 15);
+        MD5STEP(F4, b, c, d, a, in[ 1]+0x85845dd1, 21);
+        MD5STEP(F4, a, b, c, d, in[ 8]+0x6fa87e4f,  6);
+        MD5STEP(F4, d, a, b, c, in[15]+0xfe2ce6e0, 10);
+        MD5STEP(F4, c, d, a, b, in[ 6]+0xa3014314, 15);
+        MD5STEP(F4, b, c, d, a, in[13]+0x4e0811a1, 21);
+        MD5STEP(F4, a, b, c, d, in[ 4]+0xf7537e82,  6);
+        MD5STEP(F4, d, a, b, c, in[11]+0xbd3af235, 10);
+        MD5STEP(F4, c, d, a, b, in[ 2]+0x2ad7d2bb, 15);
+        MD5STEP(F4, b, c, d, a, in[ 9]+0xeb86d391, 21);
+
+        buf[0] += a;
+        buf[1] += b;
+        buf[2] += c;
+        buf[3] += d;
+}
+
+/*
+ * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
+ * initialization constants.
+ */
+static void MD5Init(MD5Context *ctx){
+        ctx->isInit = 1;
+        ctx->buf[0] = 0x67452301;
+        ctx->buf[1] = 0xefcdab89;
+        ctx->buf[2] = 0x98badcfe;
+        ctx->buf[3] = 0x10325476;
+        ctx->bits[0] = 0;
+        ctx->bits[1] = 0;
+}
+
+/*
+ * Update context to reflect the concatenation of another buffer full
+ * of bytes.
+ */
+static
+void MD5Update(MD5Context *ctx, const unsigned char *buf, unsigned int len){
+        uint32 t;
+
+        /* Update bitcount */
+
+        t = ctx->bits[0];
+        if ((ctx->bits[0] = t + ((uint32)len << 3)) < t)
+                ctx->bits[1]++; /* Carry from low to high */
+        ctx->bits[1] += len >> 29;
+
+        t = (t >> 3) & 0x3f;    /* Bytes already in shsInfo->data */
+
+        /* Handle any leading odd-sized chunks */
+
+        if ( t ) {
+                unsigned char *p = (unsigned char *)ctx->in + t;
+
+                t = 64-t;
+                if (len < t) {
+                        memcpy(p, buf, len);
+                        return;
+                }
+                memcpy(p, buf, t);
+                byteReverse(ctx->in, 16);
+                MD5Transform(ctx->buf, (uint32 *)ctx->in);
+                buf += t;
+                len -= t;
+        }
+
+        /* Process data in 64-byte chunks */
+
+        while (len >= 64) {
+                memcpy(ctx->in, buf, 64);
+                byteReverse(ctx->in, 16);
+                MD5Transform(ctx->buf, (uint32 *)ctx->in);
+                buf += 64;
+                len -= 64;
+        }
+
+        /* Handle any remaining bytes of data. */
+
+        memcpy(ctx->in, buf, len);
+}
+
+/*
+ * Final wrapup - pad to 64-byte boundary with the bit pattern
+ * 1 0* (64-bit count of bits processed, MSB-first)
+ */
+static void MD5Final(unsigned char digest[16], MD5Context *ctx){
+        unsigned count;
+        unsigned char *p;
+
+        /* Compute number of bytes mod 64 */
+        count = (ctx->bits[0] >> 3) & 0x3F;
+
+        /* Set the first char of padding to 0x80.  This is safe since there is
+           always at least one byte free */
+        p = ctx->in + count;
+        *p++ = 0x80;
+
+        /* Bytes of padding needed to make 64 bytes */
+        count = 64 - 1 - count;
+
+        /* Pad out to 56 mod 64 */
+        if (count < 8) {
+                /* Two lots of padding:  Pad the first block to 64 bytes */
+                memset(p, 0, count);
+                byteReverse(ctx->in, 16);
+                MD5Transform(ctx->buf, (uint32 *)ctx->in);
+
+                /* Now fill the next block with 56 bytes */
+                memset(ctx->in, 0, 56);
+        } else {
+                /* Pad block to 56 bytes */
+                memset(p, 0, count-8);
+        }
+        byteReverse(ctx->in, 14);
+
+        /* Append length in bits and transform */
+        memcpy(ctx->in + 14*4, ctx->bits, 8);
+
+        MD5Transform(ctx->buf, (uint32 *)ctx->in);
+        byteReverse((unsigned char *)ctx->buf, 4);
+        memcpy(digest, ctx->buf, 16);
+}
+
+/*
+** Convert a 128-bit MD5 digest into a 32-digit base-16 number.
+*/
+static void MD5DigestToBase16(unsigned char *digest, char *zBuf){
+  static char const zEncode[] = "0123456789abcdef";
+  int i, j;
+
+  for(j=i=0; i<16; i++){
+    int a = digest[i];
+    zBuf[j++] = zEncode[(a>>4)&0xf];
+    zBuf[j++] = zEncode[a & 0xf];
+  }
+  zBuf[j] = 0;
+}
+
+
+/*
+** Convert a 128-bit MD5 digest into sequences of eight 5-digit integers
+** each representing 16 bits of the digest and separated from each
+** other by a "-" character.
+*/
+static void MD5DigestToBase10x8(unsigned char digest[16], char zDigest[50]){
+  int i, j;
+  unsigned int x;
+  for(i=j=0; i<16; i+=2){
+    x = digest[i]*256 + digest[i+1];
+    if( i>0 ) zDigest[j++] = '-';
+    sqlite3_snprintf(50-j, &zDigest[j], "%05u", x);
+    j += 5;
+  }
+  zDigest[j] = 0;
+}
+
+/*
+** A TCL command for md5.  The argument is the text to be hashed.  The
+** Result is the hash in base64.
+*/
+static int SQLITE_TCLAPI md5_cmd(
+  void*cd,
+  Tcl_Interp *interp,
+  int argc,
+  const char **argv
+){
+  MD5Context ctx;
+  unsigned char digest[16];
+  char zBuf[50];
+  void (*converter)(unsigned char*, char*);
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp,"wrong # args: should be \"", argv[0],
+        " TEXT\"", (char*)0);
+    return TCL_ERROR;
+  }
+  MD5Init(&ctx);
+  MD5Update(&ctx, (unsigned char*)argv[1], (unsigned)strlen(argv[1]));
+  MD5Final(digest, &ctx);
+  converter = (void(*)(unsigned char*,char*))cd;
+  converter(digest, zBuf);
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** A TCL command to take the md5 hash of a file.  The argument is the
+** name of the file.
+*/
+static int SQLITE_TCLAPI md5file_cmd(
+  void*cd,
+  Tcl_Interp *interp,
+  int argc,
+  const char **argv
+){
+  FILE *in;
+  int ofst;
+  int amt;
+  MD5Context ctx;
+  void (*converter)(unsigned char*, char*);
+  unsigned char digest[16];
+  char zBuf[10240];
+
+  if( argc!=2 && argc!=4 ){
+    Tcl_AppendResult(interp,"wrong # args: should be \"", argv[0],
+        " FILENAME [OFFSET AMT]\"", (char*)0);
+    return TCL_ERROR;
+  }
+  if( argc==4 ){
+    ofst = atoi(argv[2]);
+    amt = atoi(argv[3]);
+  }else{
+    ofst = 0;
+    amt = 2147483647;
+  }
+  in = fopen(argv[1],"rb");
+  if( in==0 ){
+    Tcl_AppendResult(interp,"unable to open file \"", argv[1],
+         "\" for reading", (char*)0);
+    return TCL_ERROR;
+  }
+  fseek(in, ofst, SEEK_SET);
+  MD5Init(&ctx);
+  while( amt>0 ){
+    int n;
+    n = (int)fread(zBuf, 1, sizeof(zBuf)<=amt ? sizeof(zBuf) : amt, in);
+    if( n<=0 ) break;
+    MD5Update(&ctx, (unsigned char*)zBuf, (unsigned)n);
+    amt -= n;
+  }
+  fclose(in);
+  MD5Final(digest, &ctx);
+  converter = (void(*)(unsigned char*,char*))cd;
+  converter(digest, zBuf);
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** Register the four new TCL commands for generating MD5 checksums
+** with the TCL interpreter.
+*/
+int Md5_Init(Tcl_Interp *interp){
+  Tcl_CreateCommand(interp, "md5", (Tcl_CmdProc*)md5_cmd,
+                    MD5DigestToBase16, 0);
+  Tcl_CreateCommand(interp, "md5-10x8", (Tcl_CmdProc*)md5_cmd,
+                    MD5DigestToBase10x8, 0);
+  Tcl_CreateCommand(interp, "md5file", (Tcl_CmdProc*)md5file_cmd,
+                    MD5DigestToBase16, 0);
+  Tcl_CreateCommand(interp, "md5file-10x8", (Tcl_CmdProc*)md5file_cmd,
+                    MD5DigestToBase10x8, 0);
+  return TCL_OK;
+}
+
+/*
+** During testing, the special md5sum() aggregate function is available.
+** inside SQLite.  The following routines implement that function.
+*/
+static void md5step(sqlite3_context *context, int argc, sqlite3_value **argv){
+  MD5Context *p;
+  int i;
+  if( argc<1 ) return;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( p==0 ) return;
+  if( !p->isInit ){
+    MD5Init(p);
+  }
+  for(i=0; i<argc; i++){
+    const char *zData = (char*)sqlite3_value_text(argv[i]);
+    if( zData ){
+      MD5Update(p, (unsigned char*)zData, (int)strlen(zData));
+    }
+  }
+}
+static void md5finalize(sqlite3_context *context){
+  MD5Context *p;
+  unsigned char digest[16];
+  char zBuf[33];
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  MD5Final(digest,p);
+  MD5DigestToBase16(digest, zBuf);
+  sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+}
+int Md5_Register(
+  sqlite3 *db,
+  char **pzErrMsg,
+  const sqlite3_api_routines *pThunk
+){
+  int rc = sqlite3_create_function(db, "md5sum", -1, SQLITE_UTF8, 0, 0,
+                                 md5step, md5finalize);
+  sqlite3_overload_function(db, "md5sum", -1);  /* To exercise this API */
+  return rc;
+}
diff --git a/src/test_multiplex.c b/src/test_multiplex.c
new file mode 100644
index 0000000..d06ed2f
--- /dev/null
+++ b/src/test_multiplex.c
@@ -0,0 +1,1376 @@
+/*
+** 2010 October 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a VFS "shim" - a layer that sits in between the
+** pager and the real VFS - that breaks up a very large database file
+** into two or more smaller files on disk.  This is useful, for example,
+** in order to support large, multi-gigabyte databases on older filesystems
+** that limit the maximum file size to 2 GiB.
+**
+** USAGE:
+**
+** Compile this source file and link it with your application.  Then
+** at start-time, invoke the following procedure:
+**
+**   int sqlite3_multiplex_initialize(
+**      const char *zOrigVfsName,    // The underlying real VFS
+**      int makeDefault              // True to make multiplex the default VFS
+**   );
+**
+** The procedure call above will create and register a new VFS shim named
+** "multiplex".  The multiplex VFS will use the VFS named by zOrigVfsName to
+** do the actual disk I/O.  (The zOrigVfsName parameter may be NULL, in
+** which case the default VFS at the moment sqlite3_multiplex_initialize()
+** is called will be used as the underlying real VFS.)
+**
+** If the makeDefault parameter is TRUE then multiplex becomes the new
+** default VFS.  Otherwise, you can use the multiplex VFS by specifying
+** "multiplex" as the 4th parameter to sqlite3_open_v2() or by employing
+** URI filenames and adding "vfs=multiplex" as a parameter to the filename
+** URI.
+**
+** The multiplex VFS allows databases up to 32 GiB in size.  But it splits
+** the files up into smaller pieces, so that they will work even on
+** filesystems that do not support large files.  The default chunk size
+** is 2147418112 bytes (which is 64KiB less than 2GiB) but this can be
+** changed at compile-time by defining the SQLITE_MULTIPLEX_CHUNK_SIZE
+** macro.  Use the "chunksize=NNNN" query parameter with a URI filename
+** in order to select an alternative chunk size for individual connections
+** at run-time.
+*/
+#include "sqlite3.h"
+#include <string.h>
+#include <assert.h>
+#include <stdlib.h>
+#include "test_multiplex.h"
+
+#ifndef SQLITE_CORE
+  #define SQLITE_CORE 1  /* Disable the API redefinition in sqlite3ext.h */
+#endif
+#include "sqlite3ext.h"
+
+/*
+** These should be defined to be the same as the values in
+** sqliteInt.h.  They are defined separately here so that
+** the multiplex VFS shim can be built as a loadable
+** module.
+*/
+#define UNUSED_PARAMETER(x) (void)(x)
+#define MAX_PAGE_SIZE       0x10000
+#define DEFAULT_SECTOR_SIZE 0x1000
+
+/* Maximum chunk number */
+#define MX_CHUNK_NUMBER 299
+
+/* First chunk for rollback journal files */
+#define SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET 400
+#define SQLITE_MULTIPLEX_WAL_8_3_OFFSET 700
+
+
+/************************ Shim Definitions ******************************/
+
+#ifndef SQLITE_MULTIPLEX_VFS_NAME
+# define SQLITE_MULTIPLEX_VFS_NAME "multiplex"
+#endif
+
+/* This is the limit on the chunk size.  It may be changed by calling
+** the xFileControl() interface.  It will be rounded up to a
+** multiple of MAX_PAGE_SIZE.  We default it here to 2GiB less 64KiB.
+*/
+#ifndef SQLITE_MULTIPLEX_CHUNK_SIZE
+# define SQLITE_MULTIPLEX_CHUNK_SIZE 2147418112
+#endif
+
+/* This used to be the default limit on number of chunks, but
+** it is no longer enforced. There is currently no limit to the
+** number of chunks.
+**
+** May be changed by calling the xFileControl() interface.
+*/
+#ifndef SQLITE_MULTIPLEX_MAX_CHUNKS
+# define SQLITE_MULTIPLEX_MAX_CHUNKS 12
+#endif
+
+/************************ Object Definitions ******************************/
+
+/* Forward declaration of all object types */
+typedef struct multiplexGroup multiplexGroup;
+typedef struct multiplexConn multiplexConn;
+
+/*
+** A "multiplex group" is a collection of files that collectively
+** makeup a single SQLite DB file.  This allows the size of the DB
+** to exceed the limits imposed by the file system.
+**
+** There is an instance of the following object for each defined multiplex
+** group.
+*/
+struct multiplexGroup {
+  struct multiplexReal {           /* For each chunk */
+    sqlite3_file *p;                  /* Handle for the chunk */
+    char *z;                          /* Name of this chunk */
+  } *aReal;                        /* list of all chunks */
+  int nReal;                       /* Number of chunks */
+  char *zName;                     /* Base filename of this group */
+  int nName;                       /* Length of base filename */
+  int flags;                       /* Flags used for original opening */
+  unsigned int szChunk;            /* Chunk size used for this group */
+  unsigned char bEnabled;          /* TRUE to use Multiplex VFS for this file */
+  unsigned char bTruncate;         /* TRUE to enable truncation of databases */
+};
+
+/*
+** An instance of the following object represents each open connection
+** to a file that is multiplex'ed.  This object is a
+** subclass of sqlite3_file.  The sqlite3_file object for the underlying
+** VFS is appended to this structure.
+*/
+struct multiplexConn {
+  sqlite3_file base;              /* Base class - must be first */
+  multiplexGroup *pGroup;         /* The underlying group of files */
+};
+
+/************************* Global Variables **********************************/
+/*
+** All global variables used by this file are containing within the following
+** gMultiplex structure.
+*/
+static struct {
+  /* The pOrigVfs is the real, original underlying VFS implementation.
+  ** Most operations pass-through to the real VFS.  This value is read-only
+  ** during operation.  It is only modified at start-time and thus does not
+  ** require a mutex.
+  */
+  sqlite3_vfs *pOrigVfs;
+
+  /* The sThisVfs is the VFS structure used by this shim.  It is initialized
+  ** at start-time and thus does not require a mutex
+  */
+  sqlite3_vfs sThisVfs;
+
+  /* The sIoMethods defines the methods used by sqlite3_file objects
+  ** associated with this shim.  It is initialized at start-time and does
+  ** not require a mutex.
+  **
+  ** When the underlying VFS is called to open a file, it might return
+  ** either a version 1 or a version 2 sqlite3_file object.  This shim
+  ** has to create a wrapper sqlite3_file of the same version.  Hence
+  ** there are two I/O method structures, one for version 1 and the other
+  ** for version 2.
+  */
+  sqlite3_io_methods sIoMethodsV1;
+  sqlite3_io_methods sIoMethodsV2;
+
+  /* True when this shim has been initialized.
+  */
+  int isInitialized;
+} gMultiplex;
+
+/************************* Utility Routines *********************************/
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+**
+** The value returned will never be negative.  Nor will it ever be greater
+** than the actual length of the string.  For very long strings (greater
+** than 1GiB) the value returned might be less than the true string length.
+*/
+static int multiplexStrlen30(const char *z){
+  const char *z2 = z;
+  if( z==0 ) return 0;
+  while( *z2 ){ z2++; }
+  return 0x3fffffff & (int)(z2 - z);
+}
+
+/*
+** Generate the file-name for chunk iChunk of the group with base name
+** zBase. The file-name is written to buffer zOut before returning. Buffer
+** zOut must be allocated by the caller so that it is at least (nBase+5)
+** bytes in size, where nBase is the length of zBase, not including the
+** nul-terminator.
+**
+** If iChunk is 0 (or 400 - the number for the first journal file chunk),
+** the output is a copy of the input string. Otherwise, if
+** SQLITE_ENABLE_8_3_NAMES is not defined or the input buffer does not contain
+** a "." character, then the output is a copy of the input string with the
+** three-digit zero-padded decimal representation if iChunk appended to it.
+** For example:
+**
+**   zBase="test.db", iChunk=4  ->  zOut="test.db004"
+**
+** Or, if SQLITE_ENABLE_8_3_NAMES is defined and the input buffer contains
+** a "." character, then everything after the "." is replaced by the
+** three-digit representation of iChunk.
+**
+**   zBase="test.db", iChunk=4  ->  zOut="test.004"
+**
+** The output buffer string is terminated by 2 0x00 bytes. This makes it safe
+** to pass to sqlite3_uri_parameter() and similar.
+*/
+static void multiplexFilename(
+  const char *zBase,              /* Filename for chunk 0 */
+  int nBase,                      /* Size of zBase in bytes (without \0) */
+  int flags,                      /* Flags used to open file */
+  int iChunk,                     /* Chunk to generate filename for */
+  char *zOut                      /* Buffer to write generated name to */
+){
+  int n = nBase;
+  memcpy(zOut, zBase, n+1);
+  if( iChunk!=0 && iChunk<=MX_CHUNK_NUMBER ){
+#ifdef SQLITE_ENABLE_8_3_NAMES
+    int i;
+    for(i=n-1; i>0 && i>=n-4 && zOut[i]!='.'; i--){}
+    if( i>=n-4 ) n = i+1;
+    if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
+      /* The extensions on overflow files for main databases are 001, 002,
+      ** 003 and so forth.  To avoid name collisions, add 400 to the
+      ** extensions of journal files so that they are 401, 402, 403, ....
+      */
+      iChunk += SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET;
+    }else if( flags & SQLITE_OPEN_WAL ){
+      /* To avoid name collisions, add 700 to the
+      ** extensions of WAL files so that they are 701, 702, 703, ....
+      */
+      iChunk += SQLITE_MULTIPLEX_WAL_8_3_OFFSET;
+    }
+#endif
+    sqlite3_snprintf(4,&zOut[n],"%03d",iChunk);
+    n += 3;
+  }
+
+  assert( zOut[n]=='\0' );
+  zOut[n+1] = '\0';
+}
+
+/* Compute the filename for the iChunk-th chunk
+*/
+static int multiplexSubFilename(multiplexGroup *pGroup, int iChunk){
+  if( iChunk>=pGroup->nReal ){
+    struct multiplexReal *p;
+    p = sqlite3_realloc64(pGroup->aReal, (iChunk+1)*sizeof(*p));
+    if( p==0 ){
+      return SQLITE_NOMEM;
+    }
+    memset(&p[pGroup->nReal], 0, sizeof(p[0])*(iChunk+1-pGroup->nReal));
+    pGroup->aReal = p;
+    pGroup->nReal = iChunk+1;
+  }
+  if( pGroup->zName && pGroup->aReal[iChunk].z==0 ){
+    char *z;
+    int n = pGroup->nName;
+    z = sqlite3_malloc64( n+5 );
+    if( z==0 ){
+      return SQLITE_NOMEM;
+    }
+    multiplexFilename(pGroup->zName, pGroup->nName, pGroup->flags, iChunk, z);
+    pGroup->aReal[iChunk].z = (char*)sqlite3_create_filename(z,"","",0,0);
+    sqlite3_free(z);
+    if( pGroup->aReal[iChunk].z==0 ) return SQLITE_NOMEM;
+  }
+  return SQLITE_OK;
+}
+
+/* Translate an sqlite3_file* that is really a multiplexGroup* into
+** the sqlite3_file* for the underlying original VFS.
+**
+** For chunk 0, the pGroup->flags determines whether or not a new file
+** is created if it does not already exist.  For chunks 1 and higher, the
+** file is created only if createFlag is 1.
+*/
+static sqlite3_file *multiplexSubOpen(
+  multiplexGroup *pGroup,    /* The multiplexor group */
+  int iChunk,                /* Which chunk to open.  0==original file */
+  int *rc,                   /* Result code in and out */
+  int *pOutFlags,            /* Output flags */
+  int createFlag             /* True to create if iChunk>0 */
+){
+  sqlite3_file *pSubOpen = 0;
+  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;        /* Real VFS */
+
+#ifdef SQLITE_ENABLE_8_3_NAMES
+  /* If JOURNAL_8_3_OFFSET is set to (say) 400, then any overflow files are
+  ** part of a database journal are named db.401, db.402, and so on. A
+  ** database may therefore not grow to larger than 400 chunks. Attempting
+  ** to open chunk 401 indicates the database is full. */
+  if( iChunk>=SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET ){
+    sqlite3_log(SQLITE_FULL, "multiplexed chunk overflow: %s", pGroup->zName);
+    *rc = SQLITE_FULL;
+    return 0;
+  }
+#endif
+
+  *rc = multiplexSubFilename(pGroup, iChunk);
+  if( (*rc)==SQLITE_OK && (pSubOpen = pGroup->aReal[iChunk].p)==0 ){
+    int flags, bExists;
+    flags = pGroup->flags;
+    if( createFlag ){
+      flags |= SQLITE_OPEN_CREATE;
+    }else if( iChunk==0 ){
+      /* Fall through */
+    }else if( pGroup->aReal[iChunk].z==0 ){
+      return 0;
+    }else{
+      *rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[iChunk].z,
+                              SQLITE_ACCESS_EXISTS, &bExists);
+     if( *rc || !bExists ){
+        if( *rc ){
+          sqlite3_log(*rc, "multiplexor.xAccess failure on %s",
+                      pGroup->aReal[iChunk].z);
+        }
+        return 0;
+      }
+      flags &= ~SQLITE_OPEN_CREATE;
+    }
+    pSubOpen = sqlite3_malloc64( pOrigVfs->szOsFile );
+    if( pSubOpen==0 ){
+      *rc = SQLITE_IOERR_NOMEM;
+      return 0;
+    }
+    pGroup->aReal[iChunk].p = pSubOpen;
+    *rc = pOrigVfs->xOpen(pOrigVfs, pGroup->aReal[iChunk].z, pSubOpen,
+                          flags, pOutFlags);
+    if( (*rc)!=SQLITE_OK ){
+      sqlite3_log(*rc, "multiplexor.xOpen failure on %s",
+                  pGroup->aReal[iChunk].z);
+      sqlite3_free(pSubOpen);
+      pGroup->aReal[iChunk].p = 0;
+      return 0;
+    }
+  }
+  return pSubOpen;
+}
+
+/*
+** Return the size, in bytes, of chunk number iChunk.  If that chunk
+** does not exist, then return 0.  This function does not distinguish between
+** non-existent files and zero-length files.
+*/
+static sqlite3_int64 multiplexSubSize(
+  multiplexGroup *pGroup,    /* The multiplexor group */
+  int iChunk,                /* Which chunk to open.  0==original file */
+  int *rc                    /* Result code in and out */
+){
+  sqlite3_file *pSub;
+  sqlite3_int64 sz = 0;
+
+  if( *rc ) return 0;
+  pSub = multiplexSubOpen(pGroup, iChunk, rc, NULL, 0);
+  if( pSub==0 ) return 0;
+  *rc = pSub->pMethods->xFileSize(pSub, &sz);
+  return sz;
+}  
+
+/*
+** This is the implementation of the multiplex_control() SQL function.
+*/
+static void multiplexControlFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int rc = SQLITE_OK;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  int op = 0;
+  int iVal;
+
+  if( !db || argc!=2 ){
+    rc = SQLITE_ERROR;
+  }else{
+    /* extract params */
+    op = sqlite3_value_int(argv[0]);
+    iVal = sqlite3_value_int(argv[1]);
+    /* map function op to file_control op */
+    switch( op ){
+      case 1:
+        op = MULTIPLEX_CTRL_ENABLE;
+        break;
+      case 2:
+        op = MULTIPLEX_CTRL_SET_CHUNK_SIZE;
+        break;
+      case 3:
+        op = MULTIPLEX_CTRL_SET_MAX_CHUNKS;
+        break;
+      default:
+        rc = SQLITE_NOTFOUND;
+        break;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_file_control(db, 0, op, &iVal);
+  }
+  sqlite3_result_error_code(context, rc);
+}
+
+/*
+** This is the entry point to register the auto-extension for the
+** multiplex_control() function.
+*/
+static int multiplexFuncInit(
+  sqlite3 *db,
+  char **pzErrMsg,
+  const sqlite3_api_routines *pApi
+){
+  int rc;
+  rc = sqlite3_create_function(db, "multiplex_control", 2, SQLITE_ANY,
+      0, multiplexControlFunc, 0, 0);
+  return rc;
+}
+
+/*
+** Close a single sub-file in the connection group.
+*/
+static void multiplexSubClose(
+  multiplexGroup *pGroup,
+  int iChunk,
+  sqlite3_vfs *pOrigVfs
+){
+  sqlite3_file *pSubOpen = pGroup->aReal[iChunk].p;
+  if( pSubOpen ){
+    pSubOpen->pMethods->xClose(pSubOpen);
+    if( pOrigVfs && pGroup->aReal[iChunk].z ){
+      pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
+    }
+    sqlite3_free(pGroup->aReal[iChunk].p);
+  }
+  sqlite3_free_filename(pGroup->aReal[iChunk].z);
+  memset(&pGroup->aReal[iChunk], 0, sizeof(pGroup->aReal[iChunk]));
+}
+
+/*
+** Deallocate memory held by a multiplexGroup
+*/
+static void multiplexFreeComponents(multiplexGroup *pGroup){
+  int i;
+  for(i=0; i<pGroup->nReal; i++){ multiplexSubClose(pGroup, i, 0); }
+  sqlite3_free(pGroup->aReal);
+  pGroup->aReal = 0;
+  pGroup->nReal = 0;
+}
+
+
+/************************* VFS Method Wrappers *****************************/
+
+/*
+** This is the xOpen method used for the "multiplex" VFS.
+**
+** Most of the work is done by the underlying original VFS.  This method
+** simply links the new file into the appropriate multiplex group if it is a
+** file that needs to be tracked.
+*/
+static int multiplexOpen(
+  sqlite3_vfs *pVfs,         /* The multiplex VFS */
+  const char *zName,         /* Name of file to be opened */
+  sqlite3_file *pConn,       /* Fill in this file descriptor */
+  int flags,                 /* Flags to control the opening */
+  int *pOutFlags             /* Flags showing results of opening */
+){
+  int rc = SQLITE_OK;                  /* Result code */
+  multiplexConn *pMultiplexOpen;       /* The new multiplex file descriptor */
+  multiplexGroup *pGroup = 0;          /* Corresponding multiplexGroup object */
+  sqlite3_file *pSubOpen = 0;                    /* Real file descriptor */
+  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
+  int nName = 0;
+  int sz = 0;
+  char *zToFree = 0;
+
+  UNUSED_PARAMETER(pVfs);
+  memset(pConn, 0, pVfs->szOsFile);
+  assert( zName || (flags & SQLITE_OPEN_DELETEONCLOSE) );
+
+  /* We need to create a group structure and manage
+  ** access to this group of files.
+  */
+  pMultiplexOpen = (multiplexConn*)pConn;
+
+  if( rc==SQLITE_OK ){
+    /* allocate space for group */
+    nName = zName ? multiplexStrlen30(zName) : 0;
+    sz = sizeof(multiplexGroup)                             /* multiplexGroup */
+       + nName + 1;                                         /* zName */
+    pGroup = sqlite3_malloc64( sz );
+    if( pGroup==0 ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    const char *zUri = (flags & SQLITE_OPEN_URI) ? zName : 0;
+    /* assign pointers to extra space allocated */
+    memset(pGroup, 0, sz);
+    pMultiplexOpen->pGroup = pGroup;
+    pGroup->bEnabled = (unsigned char)-1;
+    pGroup->bTruncate = (unsigned char)sqlite3_uri_boolean(zUri, "truncate",
+                                   (flags & SQLITE_OPEN_MAIN_DB)==0);
+    pGroup->szChunk = (int)sqlite3_uri_int64(zUri, "chunksize",
+                                        SQLITE_MULTIPLEX_CHUNK_SIZE);
+    pGroup->szChunk = (pGroup->szChunk+0xffff)&~0xffff;
+    if( zName ){
+      char *p = (char *)&pGroup[1];
+      pGroup->zName = p;
+      memcpy(pGroup->zName, zName, nName+1);
+      pGroup->nName = nName;
+    }
+    if( pGroup->bEnabled ){
+      /* Make sure that the chunksize is such that the pending byte does not
+      ** falls at the end of a chunk.  A region of up to 64K following
+      ** the pending byte is never written, so if the pending byte occurs
+      ** near the end of a chunk, that chunk will be too small. */
+#ifndef SQLITE_OMIT_WSD
+      extern int sqlite3PendingByte;
+#else
+      int sqlite3PendingByte = 0x40000000;
+#endif
+      while( (sqlite3PendingByte % pGroup->szChunk)>=(pGroup->szChunk-65536) ){
+        pGroup->szChunk += 65536;
+      }
+    }
+    pGroup->flags = (flags & ~SQLITE_OPEN_URI);
+    rc = multiplexSubFilename(pGroup, 1);
+    if( rc==SQLITE_OK ){
+      pSubOpen = multiplexSubOpen(pGroup, 0, &rc, pOutFlags, 0);
+      if( pSubOpen==0 && rc==SQLITE_OK ) rc = SQLITE_CANTOPEN;
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3_int64 sz64;
+
+      rc = pSubOpen->pMethods->xFileSize(pSubOpen, &sz64);
+      if( rc==SQLITE_OK && zName ){
+        int bExists;
+        if( flags & SQLITE_OPEN_SUPER_JOURNAL ){
+          pGroup->bEnabled = 0;
+        }else
+        if( sz64==0 ){
+          if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
+            /* If opening a main journal file and the first chunk is zero
+            ** bytes in size, delete any subsequent chunks from the
+            ** file-system. */
+            int iChunk = 1;
+            do {
+              rc = pOrigVfs->xAccess(pOrigVfs,
+                  pGroup->aReal[iChunk].z, SQLITE_ACCESS_EXISTS, &bExists
+              );
+              if( rc==SQLITE_OK && bExists ){
+                rc = pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
+                if( rc==SQLITE_OK ){
+                  rc = multiplexSubFilename(pGroup, ++iChunk);
+                }
+              }
+            }while( rc==SQLITE_OK && bExists );
+          }
+        }else{
+          /* If the first overflow file exists and if the size of the main file
+          ** is different from the chunk size, that means the chunk size is set
+          ** set incorrectly.  So fix it.
+          **
+          ** Or, if the first overflow file does not exist and the main file is
+          ** larger than the chunk size, that means the chunk size is too small.
+          ** But we have no way of determining the intended chunk size, so
+          ** just disable the multiplexor all together.
+          */
+          rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[1].z,
+              SQLITE_ACCESS_EXISTS, &bExists);
+          bExists = multiplexSubSize(pGroup, 1, &rc)>0;
+          if( rc==SQLITE_OK && bExists && sz64==(sz64&0xffff0000) && sz64>0
+              && sz64!=pGroup->szChunk ){
+            pGroup->szChunk = (int)sz64;
+          }else if( rc==SQLITE_OK && !bExists && sz64>pGroup->szChunk ){
+            pGroup->bEnabled = 0;
+          }
+        }
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      if( pSubOpen->pMethods->iVersion==1 ){
+        pConn->pMethods = &gMultiplex.sIoMethodsV1;
+      }else{
+        pConn->pMethods = &gMultiplex.sIoMethodsV2;
+      }
+    }else{
+      multiplexFreeComponents(pGroup);
+      sqlite3_free(pGroup);
+    }
+  }
+  sqlite3_free(zToFree);
+  return rc;
+}
+
+/*
+** This is the xDelete method used for the "multiplex" VFS.
+** It attempts to delete the filename specified.
+*/
+static int multiplexDelete(
+  sqlite3_vfs *pVfs,         /* The multiplex VFS */
+  const char *zName,         /* Name of file to delete */
+  int syncDir
+){
+  int rc;
+  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
+  rc = pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
+  if( rc==SQLITE_OK ){
+    /* If the main chunk was deleted successfully, also delete any subsequent
+    ** chunks - starting with the last (highest numbered).
+    */
+    int nName = (int)strlen(zName);
+    char *z;
+    z = sqlite3_malloc64(nName + 5);
+    if( z==0 ){
+      rc = SQLITE_IOERR_NOMEM;
+    }else{
+      int iChunk = 0;
+      int bExists;
+      do{
+        multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, ++iChunk, z);
+        rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
+      }while( rc==SQLITE_OK && bExists );
+      while( rc==SQLITE_OK && iChunk>1 ){
+        multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, --iChunk, z);
+        rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
+      }
+      if( rc==SQLITE_OK ){
+        iChunk = 0;
+        do{
+          multiplexFilename(zName, nName, SQLITE_OPEN_WAL, ++iChunk, z);
+          rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
+        }while( rc==SQLITE_OK && bExists );
+        while( rc==SQLITE_OK && iChunk>1 ){
+          multiplexFilename(zName, nName, SQLITE_OPEN_WAL, --iChunk, z);
+          rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
+        }
+      }
+    }
+    sqlite3_free(z);
+  }
+  return rc;
+}
+
+static int multiplexAccess(sqlite3_vfs *a, const char *b, int c, int *d){
+  return gMultiplex.pOrigVfs->xAccess(gMultiplex.pOrigVfs, b, c, d);
+}
+static int multiplexFullPathname(sqlite3_vfs *a, const char *b, int c, char *d){
+  return gMultiplex.pOrigVfs->xFullPathname(gMultiplex.pOrigVfs, b, c, d);
+}
+static void *multiplexDlOpen(sqlite3_vfs *a, const char *b){
+  return gMultiplex.pOrigVfs->xDlOpen(gMultiplex.pOrigVfs, b);
+}
+static void multiplexDlError(sqlite3_vfs *a, int b, char *c){
+  gMultiplex.pOrigVfs->xDlError(gMultiplex.pOrigVfs, b, c);
+}
+static void (*multiplexDlSym(sqlite3_vfs *a, void *b, const char *c))(void){
+  return gMultiplex.pOrigVfs->xDlSym(gMultiplex.pOrigVfs, b, c);
+}
+static void multiplexDlClose(sqlite3_vfs *a, void *b){
+  gMultiplex.pOrigVfs->xDlClose(gMultiplex.pOrigVfs, b);
+}
+static int multiplexRandomness(sqlite3_vfs *a, int b, char *c){
+  return gMultiplex.pOrigVfs->xRandomness(gMultiplex.pOrigVfs, b, c);
+}
+static int multiplexSleep(sqlite3_vfs *a, int b){
+  return gMultiplex.pOrigVfs->xSleep(gMultiplex.pOrigVfs, b);
+}
+static int multiplexCurrentTime(sqlite3_vfs *a, double *b){
+  return gMultiplex.pOrigVfs->xCurrentTime(gMultiplex.pOrigVfs, b);
+}
+static int multiplexGetLastError(sqlite3_vfs *a, int b, char *c){
+  if( gMultiplex.pOrigVfs->xGetLastError ){
+    return gMultiplex.pOrigVfs->xGetLastError(gMultiplex.pOrigVfs, b, c);
+  }else{
+    return 0;
+  }
+}
+static int multiplexCurrentTimeInt64(sqlite3_vfs *a, sqlite3_int64 *b){
+  return gMultiplex.pOrigVfs->xCurrentTimeInt64(gMultiplex.pOrigVfs, b);
+}
+
+/************************ I/O Method Wrappers *******************************/
+
+/* xClose requests get passed through to the original VFS.
+** We loop over all open chunk handles and close them.
+** The group structure for this file is unlinked from
+** our list of groups and freed.
+*/
+static int multiplexClose(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  multiplexFreeComponents(pGroup);
+  sqlite3_free(pGroup);
+  return rc;
+}
+
+/* Pass xRead requests thru to the original VFS after
+** determining the correct chunk to operate on.
+** Break up reads across chunk boundaries.
+*/
+static int multiplexRead(
+  sqlite3_file *pConn,
+  void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_READ;
+    }else{
+      rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
+    }
+  }else{
+    while( iAmt > 0 ){
+      int i = (int)(iOfst / pGroup->szChunk);
+      sqlite3_file *pSubOpen;
+      pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
+      if( pSubOpen ){
+        int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) - pGroup->szChunk;
+        if( extra<0 ) extra = 0;
+        iAmt -= extra;
+        rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt,
+                                       iOfst % pGroup->szChunk);
+        if( rc!=SQLITE_OK ) break;
+        pBuf = (char *)pBuf + iAmt;
+        iOfst += iAmt;
+        iAmt = extra;
+      }else{
+        rc = SQLITE_IOERR_READ;
+        break;
+      }
+    }
+  }
+
+  return rc;
+}
+
+/* Pass xWrite requests thru to the original VFS after
+** determining the correct chunk to operate on.
+** Break up writes across chunk boundaries.
+*/
+static int multiplexWrite(
+  sqlite3_file *pConn,
+  const void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_WRITE;
+    }else{
+      rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
+    }
+  }else{
+    while( rc==SQLITE_OK && iAmt>0 ){
+      int i = (int)(iOfst / pGroup->szChunk);
+      sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
+      if( pSubOpen ){
+        int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) -
+                    pGroup->szChunk;
+        if( extra<0 ) extra = 0;
+        iAmt -= extra;
+        rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt,
+                                        iOfst % pGroup->szChunk);
+        pBuf = (char *)pBuf + iAmt;
+        iOfst += iAmt;
+        iAmt = extra;
+      }
+    }
+  }
+  return rc;
+}
+
+/* Pass xTruncate requests thru to the original VFS after
+** determining the correct chunk to operate on.  Delete any
+** chunks above the truncate mark.
+*/
+static int multiplexTruncate(sqlite3_file *pConn, sqlite3_int64 size){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_TRUNCATE;
+    }else{
+      rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
+    }
+  }else{
+    int i;
+    int iBaseGroup = (int)(size / pGroup->szChunk);
+    sqlite3_file *pSubOpen;
+    sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
+    /* delete the chunks above the truncate limit */
+    for(i = pGroup->nReal-1; i>iBaseGroup && rc==SQLITE_OK; i--){
+      if( pGroup->bTruncate ){
+        multiplexSubClose(pGroup, i, pOrigVfs);
+      }else{
+        pSubOpen = multiplexSubOpen(pGroup, i, &rc, 0, 0);
+        if( pSubOpen ){
+          rc = pSubOpen->pMethods->xTruncate(pSubOpen, 0);
+        }
+      }
+    }
+    if( rc==SQLITE_OK ){
+      pSubOpen = multiplexSubOpen(pGroup, iBaseGroup, &rc, 0, 0);
+      if( pSubOpen ){
+        rc = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->szChunk);
+      }
+    }
+    if( rc ) rc = SQLITE_IOERR_TRUNCATE;
+  }
+  return rc;
+}
+
+/* Pass xSync requests through to the original VFS without change
+*/
+static int multiplexSync(sqlite3_file *pConn, int flags){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  int i;
+  for(i=0; i<pGroup->nReal; i++){
+    sqlite3_file *pSubOpen = pGroup->aReal[i].p;
+    if( pSubOpen ){
+      int rc2 = pSubOpen->pMethods->xSync(pSubOpen, flags);
+      if( rc2!=SQLITE_OK ) rc = rc2;
+    }
+  }
+  return rc;
+}
+
+/* Pass xFileSize requests through to the original VFS.
+** Aggregate the size of all the chunks before returning.
+*/
+static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  int i;
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_FSTAT;
+    }else{
+      rc = pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
+    }
+  }else{
+    *pSize = 0;
+    for(i=0; rc==SQLITE_OK; i++){
+      sqlite3_int64 sz = multiplexSubSize(pGroup, i, &rc);
+      if( sz==0 ) break;
+      *pSize = i*(sqlite3_int64)pGroup->szChunk + sz;
+    }
+  }
+  return rc;
+}
+
+/* Pass xLock requests through to the original VFS unchanged.
+*/
+static int multiplexLock(sqlite3_file *pConn, int lock){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xLock(pSubOpen, lock);
+  }
+  return SQLITE_BUSY;
+}
+
+/* Pass xUnlock requests through to the original VFS unchanged.
+*/
+static int multiplexUnlock(sqlite3_file *pConn, int lock){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
+  }
+  return SQLITE_IOERR_UNLOCK;
+}
+
+/* Pass xCheckReservedLock requests through to the original VFS unchanged.
+*/
+static int multiplexCheckReservedLock(sqlite3_file *pConn, int *pResOut){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
+  }
+  return SQLITE_IOERR_CHECKRESERVEDLOCK;
+}
+
+/* Pass xFileControl requests through to the original VFS unchanged,
+** except for any MULTIPLEX_CTRL_* requests here.
+*/
+static int multiplexFileControl(sqlite3_file *pConn, int op, void *pArg){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_ERROR;
+  sqlite3_file *pSubOpen;
+
+  if( !gMultiplex.isInitialized ) return SQLITE_MISUSE;
+  switch( op ){
+    case MULTIPLEX_CTRL_ENABLE:
+      if( pArg ) {
+        int bEnabled = *(int *)pArg;
+        pGroup->bEnabled = (unsigned char)bEnabled;
+        rc = SQLITE_OK;
+      }
+      break;
+    case MULTIPLEX_CTRL_SET_CHUNK_SIZE:
+      if( pArg ) {
+        unsigned int szChunk = *(unsigned*)pArg;
+        if( szChunk<1 ){
+          rc = SQLITE_MISUSE;
+        }else{
+          /* Round up to nearest multiple of MAX_PAGE_SIZE. */
+          szChunk = (szChunk + (MAX_PAGE_SIZE-1));
+          szChunk &= ~(MAX_PAGE_SIZE-1);
+          pGroup->szChunk = szChunk;
+          rc = SQLITE_OK;
+        }
+      }
+      break;
+    case MULTIPLEX_CTRL_SET_MAX_CHUNKS:
+      rc = SQLITE_OK;
+      break;
+    case SQLITE_FCNTL_SIZE_HINT:
+    case SQLITE_FCNTL_CHUNK_SIZE:
+      /* no-op these */
+      rc = SQLITE_OK;
+      break;
+    case SQLITE_FCNTL_PRAGMA: {
+      char **aFcntl = (char**)pArg;
+      /*
+      ** EVIDENCE-OF: R-29875-31678 The argument to the SQLITE_FCNTL_PRAGMA
+      ** file control is an array of pointers to strings (char**) in which the
+      ** second element of the array is the name of the pragma and the third
+      ** element is the argument to the pragma or NULL if the pragma has no
+      ** argument.
+      */
+      if( aFcntl[1] && sqlite3_strnicmp(aFcntl[1],"multiplex_",10)==0 ){
+        sqlite3_int64 sz = 0;
+        (void)multiplexFileSize(pConn, &sz);
+        /*
+        ** PRAGMA multiplex_truncate=BOOLEAN;
+        ** PRAGMA multiplex_truncate;
+        **
+        ** Turn the multiplexor truncate feature on or off.  Return either
+        ** "on" or "off" to indicate the new setting.  If the BOOLEAN argument
+        ** is omitted, just return the current value for the truncate setting.
+        */
+        if( sqlite3_stricmp(aFcntl[1],"multiplex_truncate")==0 ){
+          if( aFcntl[2] && aFcntl[2][0] ){
+            if( sqlite3_stricmp(aFcntl[2], "on")==0
+             || sqlite3_stricmp(aFcntl[2], "1")==0 ){
+              pGroup->bTruncate = 1;
+            }else
+            if( sqlite3_stricmp(aFcntl[2], "off")==0
+             || sqlite3_stricmp(aFcntl[2], "0")==0 ){
+              pGroup->bTruncate = 0;
+            }
+          }
+          /* EVIDENCE-OF: R-27806-26076 The handler for an SQLITE_FCNTL_PRAGMA
+          ** file control can optionally make the first element of the char**
+          ** argument point to a string obtained from sqlite3_mprintf() or the
+          ** equivalent and that string will become the result of the pragma
+          ** or the error message if the pragma fails.
+          */
+          aFcntl[0] = sqlite3_mprintf(pGroup->bTruncate ? "on" : "off");
+          rc = SQLITE_OK;
+          break;
+        }
+        /*
+        ** PRAGMA multiplex_enabled;
+        **
+        ** Return 0 or 1 depending on whether the multiplexor is enabled or
+        ** disabled, respectively.
+        */
+        if( sqlite3_stricmp(aFcntl[1],"multiplex_enabled")==0 ){
+          aFcntl[0] = sqlite3_mprintf("%d", pGroup->bEnabled!=0);
+          rc = SQLITE_OK;
+          break;
+        }
+        /*
+        ** PRAGMA multiplex_chunksize;
+        **
+        ** Return the chunksize for the multiplexor, or no-op if the
+        ** multiplexor is not active.
+        */
+        if( sqlite3_stricmp(aFcntl[1],"multiplex_chunksize")==0
+         && pGroup->bEnabled
+        ){
+          aFcntl[0] = sqlite3_mprintf("%u", pGroup->szChunk);
+          rc = SQLITE_OK;
+          break;
+        }
+        /*
+        ** PRAGMA multiplex_filecount;
+        **
+        ** Return the number of disk files currently in use by the
+        ** multiplexor.  This should be the total database size size
+        ** divided by the chunksize and rounded up.
+        */
+        if( sqlite3_stricmp(aFcntl[1],"multiplex_filecount")==0 ){
+          int n = 0;
+          int ii;
+          for(ii=0; ii<pGroup->nReal; ii++){
+            if( pGroup->aReal[ii].p!=0 ) n++;
+          }
+          aFcntl[0] = sqlite3_mprintf("%d", n);
+          rc = SQLITE_OK;
+          break;
+        }
+      }
+      /* If the multiplexor does not handle the pragma, pass it through
+      ** into the default case. */
+    }
+    default:
+      pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+      if( pSubOpen ){
+        rc = pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
+        if( op==SQLITE_FCNTL_VFSNAME && rc==SQLITE_OK ){
+         *(char**)pArg = sqlite3_mprintf("multiplex/%z", *(char**)pArg);
+        }
+      }
+      break;
+  }
+  return rc;
+}
+
+/* Pass xSectorSize requests through to the original VFS unchanged.
+*/
+static int multiplexSectorSize(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen && pSubOpen->pMethods->xSectorSize ){
+    return pSubOpen->pMethods->xSectorSize(pSubOpen);
+  }
+  return DEFAULT_SECTOR_SIZE;
+}
+
+/* Pass xDeviceCharacteristics requests through to the original VFS unchanged.
+*/
+static int multiplexDeviceCharacteristics(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
+  }
+  return 0;
+}
+
+/* Pass xShmMap requests through to the original VFS unchanged.
+*/
+static int multiplexShmMap(
+  sqlite3_file *pConn,            /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend,pp);
+  }
+  return SQLITE_IOERR;
+}
+
+/* Pass xShmLock requests through to the original VFS unchanged.
+*/
+static int multiplexShmLock(
+  sqlite3_file *pConn,       /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
+  }
+  return SQLITE_BUSY;
+}
+
+/* Pass xShmBarrier requests through to the original VFS unchanged.
+*/
+static void multiplexShmBarrier(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    pSubOpen->pMethods->xShmBarrier(pSubOpen);
+  }
+}
+
+/* Pass xShmUnmap requests through to the original VFS unchanged.
+*/
+static int multiplexShmUnmap(sqlite3_file *pConn, int deleteFlag){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
+  }
+  return SQLITE_OK;
+}
+
+/************************** Public Interfaces *****************************/
+/*
+** CAPI: Initialize the multiplex VFS shim - sqlite3_multiplex_initialize()
+**
+** Use the VFS named zOrigVfsName as the VFS that does the actual work.
+** Use the default if zOrigVfsName==NULL.
+**
+** The multiplex VFS shim is named "multiplex".  It will become the default
+** VFS if makeDefault is non-zero.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
+** during start-up.
+*/
+int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
+  sqlite3_vfs *pOrigVfs;
+  if( gMultiplex.isInitialized ) return SQLITE_MISUSE;
+  pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
+  if( pOrigVfs==0 ) return SQLITE_ERROR;
+  assert( pOrigVfs!=&gMultiplex.sThisVfs );
+  gMultiplex.isInitialized = 1;
+  gMultiplex.pOrigVfs = pOrigVfs;
+  gMultiplex.sThisVfs = *pOrigVfs;
+  gMultiplex.sThisVfs.szOsFile += sizeof(multiplexConn);
+  gMultiplex.sThisVfs.zName = SQLITE_MULTIPLEX_VFS_NAME;
+  gMultiplex.sThisVfs.xOpen = multiplexOpen;
+  gMultiplex.sThisVfs.xDelete = multiplexDelete;
+  gMultiplex.sThisVfs.xAccess = multiplexAccess;
+  gMultiplex.sThisVfs.xFullPathname = multiplexFullPathname;
+  gMultiplex.sThisVfs.xDlOpen = multiplexDlOpen;
+  gMultiplex.sThisVfs.xDlError = multiplexDlError;
+  gMultiplex.sThisVfs.xDlSym = multiplexDlSym;
+  gMultiplex.sThisVfs.xDlClose = multiplexDlClose;
+  gMultiplex.sThisVfs.xRandomness = multiplexRandomness;
+  gMultiplex.sThisVfs.xSleep = multiplexSleep;
+  gMultiplex.sThisVfs.xCurrentTime = multiplexCurrentTime;
+  gMultiplex.sThisVfs.xGetLastError = multiplexGetLastError;
+  gMultiplex.sThisVfs.xCurrentTimeInt64 = multiplexCurrentTimeInt64;
+
+  gMultiplex.sIoMethodsV1.iVersion = 1;
+  gMultiplex.sIoMethodsV1.xClose = multiplexClose;
+  gMultiplex.sIoMethodsV1.xRead = multiplexRead;
+  gMultiplex.sIoMethodsV1.xWrite = multiplexWrite;
+  gMultiplex.sIoMethodsV1.xTruncate = multiplexTruncate;
+  gMultiplex.sIoMethodsV1.xSync = multiplexSync;
+  gMultiplex.sIoMethodsV1.xFileSize = multiplexFileSize;
+  gMultiplex.sIoMethodsV1.xLock = multiplexLock;
+  gMultiplex.sIoMethodsV1.xUnlock = multiplexUnlock;
+  gMultiplex.sIoMethodsV1.xCheckReservedLock = multiplexCheckReservedLock;
+  gMultiplex.sIoMethodsV1.xFileControl = multiplexFileControl;
+  gMultiplex.sIoMethodsV1.xSectorSize = multiplexSectorSize;
+  gMultiplex.sIoMethodsV1.xDeviceCharacteristics =
+                                            multiplexDeviceCharacteristics;
+  gMultiplex.sIoMethodsV2 = gMultiplex.sIoMethodsV1;
+  gMultiplex.sIoMethodsV2.iVersion = 2;
+  gMultiplex.sIoMethodsV2.xShmMap = multiplexShmMap;
+  gMultiplex.sIoMethodsV2.xShmLock = multiplexShmLock;
+  gMultiplex.sIoMethodsV2.xShmBarrier = multiplexShmBarrier;
+  gMultiplex.sIoMethodsV2.xShmUnmap = multiplexShmUnmap;
+  sqlite3_vfs_register(&gMultiplex.sThisVfs, makeDefault);
+
+  sqlite3_auto_extension((void(*)(void))multiplexFuncInit);
+
+  return SQLITE_OK;
+}
+
+/*
+** CAPI: Shutdown the multiplex system - sqlite3_multiplex_shutdown()
+**
+** All SQLite database connections must be closed before calling this
+** routine.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
+** shutting down in order to free all remaining multiplex groups.
+*/
+int sqlite3_multiplex_shutdown(int eForce){
+  int rc = SQLITE_OK;
+  if( gMultiplex.isInitialized==0 ) return SQLITE_MISUSE;
+  gMultiplex.isInitialized = 0;
+  sqlite3_vfs_unregister(&gMultiplex.sThisVfs);
+  memset(&gMultiplex, 0, sizeof(gMultiplex));
+  return rc;
+}
+
+/***************************** Test Code ***********************************/
+#ifdef SQLITE_TEST
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+extern const char *sqlite3ErrName(int);
+
+
+/*
+** tclcmd: sqlite3_multiplex_initialize NAME MAKEDEFAULT
+*/
+static int SQLITE_TCLAPI test_multiplex_initialize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zName;              /* Name of new multiplex VFS */
+  int makeDefault;                /* True to make the new VFS the default */
+  int rc;                         /* Value returned by multiplex_initialize() */
+
+  UNUSED_PARAMETER(clientData);
+
+  /* Process arguments */
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NAME MAKEDEFAULT");
+    return TCL_ERROR;
+  }
+  zName = Tcl_GetString(objv[1]);
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &makeDefault) ) return TCL_ERROR;
+  if( zName[0]=='\0' ) zName = 0;
+
+  /* Call sqlite3_multiplex_initialize() */
+  rc = sqlite3_multiplex_initialize(zName, makeDefault);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_multiplex_shutdown
+*/
+static int SQLITE_TCLAPI test_multiplex_shutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;                         /* Value returned by multiplex_shutdown() */
+
+  UNUSED_PARAMETER(clientData);
+
+  if( objc==2 && strcmp(Tcl_GetString(objv[1]),"-force")!=0 ){
+    objc = 3;
+  }
+  if( (objc!=1 && objc!=2) ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?-force?");
+    return TCL_ERROR;
+  }
+
+  /* Call sqlite3_multiplex_shutdown() */
+  rc = sqlite3_multiplex_shutdown(objc==2);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** Tclcmd: test_multiplex_control HANDLE DBNAME SUB-COMMAND ?INT-VALUE?
+*/
+static int SQLITE_TCLAPI test_multiplex_control(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;                         /* Return code from file_control() */
+  int idx;                        /* Index in aSub[] */
+  Tcl_CmdInfo cmdInfo;            /* Command info structure for HANDLE */
+  sqlite3 *db;                    /* Underlying db handle for HANDLE */
+  int iValue = 0;
+  void *pArg = 0;
+
+  struct SubCommand {
+    const char *zName;
+    int op;
+    int argtype;
+  } aSub[] = {
+    { "enable",       MULTIPLEX_CTRL_ENABLE,           1 },
+    { "chunk_size",   MULTIPLEX_CTRL_SET_CHUNK_SIZE,   1 },
+    { "max_chunks",   MULTIPLEX_CTRL_SET_MAX_CHUNKS,   1 },
+    { 0, 0, 0 }
+  };
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE DBNAME SUB-COMMAND INT-VALUE");
+    return TCL_ERROR;
+  }
+
+  if( 0==Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
+    Tcl_AppendResult(interp, "expected database handle, got \"", 0);
+    Tcl_AppendResult(interp, Tcl_GetString(objv[1]), "\"", 0);
+    return TCL_ERROR;
+  }else{
+    db = *(sqlite3 **)cmdInfo.objClientData;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[3], aSub, sizeof(aSub[0]), "sub-command", 0, &idx
+  );
+  if( rc!=TCL_OK ) return rc;
+
+  switch( aSub[idx].argtype ){
+    case 1:
+      if( Tcl_GetIntFromObj(interp, objv[4], &iValue) ){
+        return TCL_ERROR;
+      }
+      pArg = (void *)&iValue;
+      break;
+    default:
+      Tcl_WrongNumArgs(interp, 4, objv, "SUB-COMMAND");
+      return TCL_ERROR;
+  }
+
+  rc = sqlite3_file_control(db, Tcl_GetString(objv[2]), aSub[idx].op, pArg);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+  return (rc==SQLITE_OK) ? TCL_OK : TCL_ERROR;
+}
+
+/*
+** This routine registers the custom TCL commands defined in this
+** module.  This should be the only procedure visible from outside
+** of this module.
+*/
+int Sqlitemultiplex_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "sqlite3_multiplex_initialize", test_multiplex_initialize },
+    { "sqlite3_multiplex_shutdown", test_multiplex_shutdown },
+    { "sqlite3_multiplex_control", test_multiplex_control },
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_multiplex.h b/src/test_multiplex.h
new file mode 100644
index 0000000..065fac7
--- /dev/null
+++ b/src/test_multiplex.h
@@ -0,0 +1,99 @@
+/*
+** 2011 March 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a VFS "shim" - a layer that sits in between the
+** pager and the real VFS.
+**
+** This particular shim enforces a multiplex system on DB files. 
+** This shim shards/partitions a single DB file into smaller
+** "chunks" such that the total DB file size may exceed the maximum
+** file size of the underlying file system.
+**
+*/
+
+#ifndef SQLITE_TEST_MULTIPLEX_H
+#define SQLITE_TEST_MULTIPLEX_H
+
+/*
+** CAPI: File-control Operations Supported by Multiplex VFS
+**
+** Values interpreted by the xFileControl method of a Multiplex VFS db file-handle.
+**
+** MULTIPLEX_CTRL_ENABLE:
+**   This file control is used to enable or disable the multiplex
+**   shim.
+**
+** MULTIPLEX_CTRL_SET_CHUNK_SIZE:
+**   This file control is used to set the maximum allowed chunk
+**   size for a multiplex file set.  The chunk size should be
+**   a multiple of SQLITE_MAX_PAGE_SIZE, and will be rounded up
+**   if not.
+**
+** MULTIPLEX_CTRL_SET_MAX_CHUNKS:
+**   This file control is used to set the maximum number of chunks
+**   allowed to be used for a multiplex file set.
+*/
+#define MULTIPLEX_CTRL_ENABLE          214014
+#define MULTIPLEX_CTRL_SET_CHUNK_SIZE  214015
+#define MULTIPLEX_CTRL_SET_MAX_CHUNKS  214016
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+** CAPI: Initialize the multiplex VFS shim - sqlite3_multiplex_initialize()
+**
+** Use the VFS named zOrigVfsName as the VFS that does the actual work. 
+** Use the default if zOrigVfsName==NULL. 
+**
+** The multiplex VFS shim is named "multiplex".  It will become the default
+** VFS if makeDefault is non-zero.
+**
+** An auto-extension is registered which will make the function
+** multiplex_control() available to database connections.  This
+** function gives access to the xFileControl interface of the
+** multiplex VFS shim.
+**
+** SELECT multiplex_control(<op>,<val>);
+**
+**   <op>=1 MULTIPLEX_CTRL_ENABLE
+**   <val>=0 disable
+**   <val>=1 enable
+**
+**   <op>=2 MULTIPLEX_CTRL_SET_CHUNK_SIZE
+**   <val> int, chunk size
+**
+**   <op>=3 MULTIPLEX_CTRL_SET_MAX_CHUNKS
+**   <val> int, max chunks
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
+** during start-up.
+*/
+extern int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault);
+
+/*
+** CAPI: Shutdown the multiplex system - sqlite3_multiplex_shutdown()
+**
+** All SQLite database connections must be closed before calling this
+** routine.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
+** shutting down in order to free all remaining multiplex groups.
+*/
+extern int sqlite3_multiplex_shutdown(int eForce);
+
+#ifdef __cplusplus
+}  /* End of the 'extern "C"' block */
+#endif
+
+#endif /* SQLITE_TEST_MULTIPLEX_H */
diff --git a/src/test_mutex.c b/src/test_mutex.c
new file mode 100644
index 0000000..a203208
--- /dev/null
+++ b/src/test_mutex.c
@@ -0,0 +1,510 @@
+/*
+** 2008 June 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains test logic for the sqlite3_mutex interfaces.
+*/
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include "sqlite3.h"
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <assert.h>
+#include <string.h>
+
+#define MAX_MUTEXES        (SQLITE_MUTEX_STATIC_VFS3+1)
+#define STATIC_MUTEXES     (MAX_MUTEXES-(SQLITE_MUTEX_RECURSIVE+1))
+
+/* defined in main.c */
+extern const char *sqlite3ErrName(int);
+
+static const char *aName[MAX_MUTEXES+1] = {
+  "fast",        "recursive",   "static_main",   "static_mem",
+  "static_open", "static_prng", "static_lru",    "static_pmem",
+  "static_app1", "static_app2", "static_app3",   "static_vfs1",
+  "static_vfs2", "static_vfs3", 0
+};
+
+/* A countable mutex */
+struct sqlite3_mutex {
+  sqlite3_mutex *pReal;
+  int eType;
+};
+
+/* State variables */
+static struct test_mutex_globals {
+  int isInstalled;           /* True if installed */
+  int disableInit;           /* True to cause sqlite3_initialize() to fail */
+  int disableTry;            /* True to force sqlite3_mutex_try() to fail */
+  int isInit;                /* True if initialized */
+  sqlite3_mutex_methods m;   /* Interface to "real" mutex system */
+  int aCounter[MAX_MUTEXES]; /* Number of grabs of each type of mutex */
+  sqlite3_mutex aStatic[STATIC_MUTEXES]; /* The static mutexes */
+} g = {0};
+
+/* Return true if the countable mutex is currently held */
+static int counterMutexHeld(sqlite3_mutex *p){
+  return g.m.xMutexHeld(p->pReal);
+}
+
+/* Return true if the countable mutex is not currently held */
+static int counterMutexNotheld(sqlite3_mutex *p){
+  return g.m.xMutexNotheld(p->pReal);
+}
+
+/* Initialize the countable mutex interface
+** Or, if g.disableInit is non-zero, then do not initialize but instead
+** return the value of g.disableInit as the result code.  This can be used
+** to simulate an initialization failure.
+*/
+static int counterMutexInit(void){ 
+  int rc;
+  if( g.disableInit ) return g.disableInit;
+  rc = g.m.xMutexInit();
+  g.isInit = 1;
+  return rc;
+}
+
+/*
+** Uninitialize the mutex subsystem
+*/
+static int counterMutexEnd(void){ 
+  g.isInit = 0;
+  return g.m.xMutexEnd();
+}
+
+/*
+** Allocate a countable mutex
+*/
+static sqlite3_mutex *counterMutexAlloc(int eType){
+  sqlite3_mutex *pReal;
+  sqlite3_mutex *pRet = 0;
+
+  assert( g.isInit );
+  assert( eType>=SQLITE_MUTEX_FAST );
+  assert( eType<=SQLITE_MUTEX_STATIC_VFS3 );
+
+  pReal = g.m.xMutexAlloc(eType);
+  if( !pReal ) return 0;
+
+  if( eType==SQLITE_MUTEX_FAST || eType==SQLITE_MUTEX_RECURSIVE ){
+    pRet = (sqlite3_mutex *)malloc(sizeof(sqlite3_mutex));
+  }else{
+    int eStaticType = eType - (MAX_MUTEXES - STATIC_MUTEXES);
+    assert( eStaticType>=0 );
+    assert( eStaticType<STATIC_MUTEXES );
+    pRet = &g.aStatic[eStaticType];
+  }
+
+  pRet->eType = eType;
+  pRet->pReal = pReal;
+  return pRet;
+}
+
+/*
+** Free a countable mutex
+*/
+static void counterMutexFree(sqlite3_mutex *p){
+  assert( g.isInit );
+  g.m.xMutexFree(p->pReal);
+  if( p->eType==SQLITE_MUTEX_FAST || p->eType==SQLITE_MUTEX_RECURSIVE ){
+    free(p);
+  }
+}
+
+/*
+** Enter a countable mutex.  Block until entry is safe.
+*/
+static void counterMutexEnter(sqlite3_mutex *p){
+  assert( g.isInit );
+  assert( p->eType>=0 );
+  assert( p->eType<MAX_MUTEXES );
+  g.aCounter[p->eType]++;
+  g.m.xMutexEnter(p->pReal);
+}
+
+/*
+** Try to enter a mutex.  Return true on success.
+*/
+static int counterMutexTry(sqlite3_mutex *p){
+  assert( g.isInit );
+  assert( p->eType>=0 );
+  assert( p->eType<MAX_MUTEXES );
+  g.aCounter[p->eType]++;
+  if( g.disableTry ) return SQLITE_BUSY;
+  return g.m.xMutexTry(p->pReal);
+}
+
+/* Leave a mutex
+*/
+static void counterMutexLeave(sqlite3_mutex *p){
+  assert( g.isInit );
+  g.m.xMutexLeave(p->pReal);
+}
+
+/*
+** sqlite3_shutdown
+*/
+static int SQLITE_TCLAPI test_shutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_shutdown();
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** sqlite3_initialize
+*/
+static int SQLITE_TCLAPI test_initialize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_initialize();
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** install_mutex_counters BOOLEAN
+*/
+static int SQLITE_TCLAPI test_install_mutex_counters(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = SQLITE_OK;
+  int isInstall;
+
+  sqlite3_mutex_methods counter_methods = {
+    counterMutexInit,
+    counterMutexEnd,
+    counterMutexAlloc,
+    counterMutexFree,
+    counterMutexEnter,
+    counterMutexTry,
+    counterMutexLeave,
+    counterMutexHeld,
+    counterMutexNotheld
+  };
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[1], &isInstall) ){
+    return TCL_ERROR;
+  }
+
+  assert(isInstall==0 || isInstall==1);
+  assert(g.isInstalled==0 || g.isInstalled==1);
+  if( isInstall==g.isInstalled ){
+    Tcl_AppendResult(interp, "mutex counters are ", 0);
+    Tcl_AppendResult(interp, isInstall?"already installed":"not installed", 0);
+    return TCL_ERROR;
+  }
+
+  if( isInstall ){
+    assert( g.m.xMutexAlloc==0 );
+    rc = sqlite3_config(SQLITE_CONFIG_GETMUTEX, &g.m);
+    if( rc==SQLITE_OK ){
+      sqlite3_config(SQLITE_CONFIG_MUTEX, &counter_methods);
+    }
+    g.disableTry = 0;
+  }else{
+    assert( g.m.xMutexAlloc );
+    rc = sqlite3_config(SQLITE_CONFIG_MUTEX, &g.m);
+    memset(&g.m, 0, sizeof(sqlite3_mutex_methods));
+  }
+
+  if( rc==SQLITE_OK ){
+    g.isInstalled = isInstall;
+  }
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** read_mutex_counters
+*/
+static int SQLITE_TCLAPI test_read_mutex_counters(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj *pRet;
+  int ii;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_IncrRefCount(pRet);
+  for(ii=0; ii<MAX_MUTEXES; ii++){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj(aName[ii], -1));
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(g.aCounter[ii]));
+  }
+  Tcl_SetObjResult(interp, pRet);
+  Tcl_DecrRefCount(pRet);
+
+  return TCL_OK;
+}
+
+/*
+** clear_mutex_counters
+*/
+static int SQLITE_TCLAPI test_clear_mutex_counters(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int ii;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  for(ii=0; ii<MAX_MUTEXES; ii++){
+    g.aCounter[ii] = 0;
+  }
+  return TCL_OK;
+}
+
+/*
+** Create and free a mutex.  Return the mutex pointer.  The pointer
+** will be invalid since the mutex has already been freed.  The
+** return pointer just checks to see if the mutex really was allocated.
+*/
+static int SQLITE_TCLAPI test_alloc_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *p = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+  char zBuf[100];
+  sqlite3_mutex_free(p);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%p", p);
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+#endif
+  return TCL_OK;
+}
+
+/*
+** sqlite3_config OPTION
+**
+** OPTION can be either one of the keywords:
+**
+**            SQLITE_CONFIG_SINGLETHREAD
+**            SQLITE_CONFIG_MULTITHREAD
+**            SQLITE_CONFIG_SERIALIZED
+**
+** Or OPTION can be an raw integer.
+*/
+static int SQLITE_TCLAPI test_config(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct ConfigOption {
+    const char *zName;
+    int iValue;
+  } aOpt[] = {
+    {"singlethread", SQLITE_CONFIG_SINGLETHREAD},
+    {"multithread",  SQLITE_CONFIG_MULTITHREAD},
+    {"serialized",   SQLITE_CONFIG_SERIALIZED},
+    {0, 0}
+  };
+  int s = sizeof(struct ConfigOption);
+  int i;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetIndexFromObjStruct(interp, objv[1], aOpt, s, "flag", 0, &i) ){
+    if( Tcl_GetIntFromObj(interp, objv[1], &i) ){
+      return TCL_ERROR;
+    }
+  }else{
+    i = aOpt[i].iValue;
+  }
+
+  rc = sqlite3_config(i);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+static sqlite3 *getDbPointer(Tcl_Interp *pInterp, Tcl_Obj *pObj){
+  sqlite3 *db;
+  Tcl_CmdInfo info;
+  char *zCmd = Tcl_GetString(pObj);
+  if( Tcl_GetCommandInfo(pInterp, zCmd, &info) ){
+    db = *((sqlite3 **)info.objClientData);
+  }else{
+    db = (sqlite3*)sqlite3TestTextToPtr(zCmd);
+  }
+  assert( db );
+  return db;
+}
+
+static sqlite3_mutex *getStaticMutexPointer(
+  Tcl_Interp *pInterp,
+  Tcl_Obj *pObj
+){
+  int iMutex;
+  if( Tcl_GetIndexFromObj(pInterp, pObj, aName, "mutex name", 0, &iMutex) ){
+    return 0;
+  }
+  assert( iMutex!=SQLITE_MUTEX_FAST && iMutex!=SQLITE_MUTEX_RECURSIVE );
+  return counterMutexAlloc(iMutex);
+}
+
+static int SQLITE_TCLAPI test_enter_static_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_mutex *pMutex;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NAME");
+    return TCL_ERROR;
+  }
+  pMutex = getStaticMutexPointer(interp, objv[1]);
+  if( !pMutex ){
+    return TCL_ERROR;
+  }
+  sqlite3_mutex_enter(pMutex);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_leave_static_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_mutex *pMutex;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NAME");
+    return TCL_ERROR;
+  }
+  pMutex = getStaticMutexPointer(interp, objv[1]);
+  if( !pMutex ){
+    return TCL_ERROR;
+  }
+  sqlite3_mutex_leave(pMutex);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_enter_db_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  db = getDbPointer(interp, objv[1]);
+  if( !db ){
+    return TCL_ERROR;
+  }
+  sqlite3_mutex_enter(sqlite3_db_mutex(db));
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_leave_db_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  db = getDbPointer(interp, objv[1]);
+  if( !db ){
+    return TCL_ERROR;
+  }
+  sqlite3_mutex_leave(sqlite3_db_mutex(db));
+  return TCL_OK;
+}
+
+int Sqlitetest_mutex_Init(Tcl_Interp *interp){
+  static struct {
+    char *zName;
+    Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "sqlite3_shutdown",        (Tcl_ObjCmdProc*)test_shutdown },
+    { "sqlite3_initialize",      (Tcl_ObjCmdProc*)test_initialize },
+    { "sqlite3_config",          (Tcl_ObjCmdProc*)test_config },
+
+    { "enter_static_mutex",      (Tcl_ObjCmdProc*)test_enter_static_mutex },
+    { "leave_static_mutex",      (Tcl_ObjCmdProc*)test_leave_static_mutex },
+
+    { "enter_db_mutex",          (Tcl_ObjCmdProc*)test_enter_db_mutex },
+    { "leave_db_mutex",          (Tcl_ObjCmdProc*)test_leave_db_mutex },
+
+    { "alloc_dealloc_mutex",     (Tcl_ObjCmdProc*)test_alloc_mutex },
+    { "install_mutex_counters",  (Tcl_ObjCmdProc*)test_install_mutex_counters },
+    { "read_mutex_counters",     (Tcl_ObjCmdProc*)test_read_mutex_counters },
+    { "clear_mutex_counters",    (Tcl_ObjCmdProc*)test_clear_mutex_counters },
+  };
+  int i;
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  Tcl_LinkVar(interp, "disable_mutex_init", 
+              (char*)&g.disableInit, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "disable_mutex_try", 
+              (char*)&g.disableTry, TCL_LINK_INT);
+  return SQLITE_OK;
+}
diff --git a/src/test_onefile.c b/src/test_onefile.c
new file mode 100644
index 0000000..037f4fb
--- /dev/null
+++ b/src/test_onefile.c
@@ -0,0 +1,831 @@
+/*
+** 2007 September 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** OVERVIEW:
+**
+**   This file contains some example code demonstrating how the SQLite 
+**   vfs feature can be used to have SQLite operate directly on an 
+**   embedded media, without using an intermediate file system.
+**
+**   Because this is only a demo designed to run on a workstation, the
+**   underlying media is simulated using a regular file-system file. The
+**   size of the file is fixed when it is first created (default size 10 MB).
+**   From SQLite's point of view, this space is used to store a single
+**   database file and the journal file. 
+**
+**   Any statement journal created is stored in volatile memory obtained 
+**   from sqlite3_malloc(). Any attempt to create a temporary database file 
+**   will fail (SQLITE_IOERR). To prevent SQLite from attempting this,
+**   it should be configured to store all temporary database files in 
+**   main memory (see pragma "temp_store" or the SQLITE_TEMP_STORE compile 
+**   time option).
+**
+** ASSUMPTIONS:
+**
+**   After it has been created, the blob file is accessed using the
+**   following three functions only:
+**
+**       mediaRead();            - Read a 512 byte block from the file.
+**       mediaWrite();           - Write a 512 byte block to the file.
+**       mediaSync();            - Tell the media hardware to sync.
+**
+**   It is assumed that these can be easily implemented by any "real"
+**   media vfs driver adapting this code.
+**
+** FILE FORMAT:
+**
+**   The basic principle is that the "database file" is stored at the
+**   beginning of the 10 MB blob and grows in a forward direction. The 
+**   "journal file" is stored at the end of the 10MB blob and grows
+**   in the reverse direction. If, during a transaction, insufficient
+**   space is available to expand either the journal or database file,
+**   an SQLITE_FULL error is returned. The database file is never allowed
+**   to consume more than 90% of the blob space. If SQLite tries to
+**   create a file larger than this, SQLITE_FULL is returned.
+**
+**   No allowance is made for "wear-leveling", as is required by.
+**   embedded devices in the absence of equivalent hardware features.
+**
+**   The first 512 block byte of the file is reserved for storing the
+**   size of the "database file". It is updated as part of the sync()
+**   operation. On startup, it can only be trusted if no journal file
+**   exists. If a journal-file does exist, then it stores the real size
+**   of the database region. The second and subsequent blocks store the 
+**   actual database content.
+**
+**   The size of the "journal file" is not stored persistently in the 
+**   file. When the system is running, the size of the journal file is
+**   stored in volatile memory. When recovering from a crash, this vfs
+**   reports a very large size for the journal file. The normal journal
+**   header and checksum mechanisms serve to prevent SQLite from 
+**   processing any data that lies past the logical end of the journal.
+**
+**   When SQLite calls OsDelete() to delete the journal file, the final
+**   512 bytes of the blob (the area containing the first journal header)
+**   are zeroed.
+**
+** LOCKING:
+**
+**   File locking is a no-op. Only one connection may be open at any one
+**   time using this demo vfs.
+*/
+
+#include "sqlite3.h"
+#include <assert.h>
+#include <string.h>
+
+/*
+** Maximum pathname length supported by the fs backend.
+*/
+#define BLOCKSIZE 512
+#define BLOBSIZE 10485760
+
+/*
+** Name used to identify this VFS.
+*/
+#define FS_VFS_NAME "fs"
+
+typedef struct fs_real_file fs_real_file;
+struct fs_real_file {
+  sqlite3_file *pFile;
+  const char *zName;
+  int nDatabase;              /* Current size of database region */
+  int nJournal;               /* Current size of journal region */
+  int nBlob;                  /* Total size of allocated blob */
+  int nRef;                   /* Number of pointers to this structure */
+  fs_real_file *pNext;
+  fs_real_file **ppThis;
+};
+
+typedef struct fs_file fs_file;
+struct fs_file {
+  sqlite3_file base;
+  int eType;
+  fs_real_file *pReal;
+};
+
+typedef struct tmp_file tmp_file;
+struct tmp_file {
+  sqlite3_file base;
+  int nSize;
+  int nAlloc;
+  char *zAlloc;
+};
+
+/* Values for fs_file.eType. */
+#define DATABASE_FILE   1
+#define JOURNAL_FILE    2
+
+/*
+** Method declarations for fs_file.
+*/
+static int fsClose(sqlite3_file*);
+static int fsRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int fsWrite(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
+static int fsTruncate(sqlite3_file*, sqlite3_int64 size);
+static int fsSync(sqlite3_file*, int flags);
+static int fsFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int fsLock(sqlite3_file*, int);
+static int fsUnlock(sqlite3_file*, int);
+static int fsCheckReservedLock(sqlite3_file*, int *pResOut);
+static int fsFileControl(sqlite3_file*, int op, void *pArg);
+static int fsSectorSize(sqlite3_file*);
+static int fsDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for tmp_file.
+*/
+static int tmpClose(sqlite3_file*);
+static int tmpRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int tmpWrite(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
+static int tmpTruncate(sqlite3_file*, sqlite3_int64 size);
+static int tmpSync(sqlite3_file*, int flags);
+static int tmpFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int tmpLock(sqlite3_file*, int);
+static int tmpUnlock(sqlite3_file*, int);
+static int tmpCheckReservedLock(sqlite3_file*, int *pResOut);
+static int tmpFileControl(sqlite3_file*, int op, void *pArg);
+static int tmpSectorSize(sqlite3_file*);
+static int tmpDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for fs_vfs.
+*/
+static int fsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int fsDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int fsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int fsFullPathname(sqlite3_vfs*, const char *zName, int nOut,char *zOut);
+static void *fsDlOpen(sqlite3_vfs*, const char *zFilename);
+static void fsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*fsDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void fsDlClose(sqlite3_vfs*, void*);
+static int fsRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int fsSleep(sqlite3_vfs*, int microseconds);
+static int fsCurrentTime(sqlite3_vfs*, double*);
+
+
+typedef struct fs_vfs_t fs_vfs_t;
+struct fs_vfs_t {
+  sqlite3_vfs base;
+  fs_real_file *pFileList;
+  sqlite3_vfs *pParent;
+};
+
+static fs_vfs_t fs_vfs = {
+  {
+    1,                                          /* iVersion */
+    0,                                          /* szOsFile */
+    0,                                          /* mxPathname */
+    0,                                          /* pNext */
+    FS_VFS_NAME,                                /* zName */
+    0,                                          /* pAppData */
+    fsOpen,                                     /* xOpen */
+    fsDelete,                                   /* xDelete */
+    fsAccess,                                   /* xAccess */
+    fsFullPathname,                             /* xFullPathname */
+    fsDlOpen,                                   /* xDlOpen */
+    fsDlError,                                  /* xDlError */
+    fsDlSym,                                    /* xDlSym */
+    fsDlClose,                                  /* xDlClose */
+    fsRandomness,                               /* xRandomness */
+    fsSleep,                                    /* xSleep */
+    fsCurrentTime,                              /* xCurrentTime */
+    0                                           /* xCurrentTimeInt64 */
+  }, 
+  0,                                            /* pFileList */
+  0                                             /* pParent */
+};
+
+static sqlite3_io_methods fs_io_methods = {
+  1,                            /* iVersion */
+  fsClose,                      /* xClose */
+  fsRead,                       /* xRead */
+  fsWrite,                      /* xWrite */
+  fsTruncate,                   /* xTruncate */
+  fsSync,                       /* xSync */
+  fsFileSize,                   /* xFileSize */
+  fsLock,                       /* xLock */
+  fsUnlock,                     /* xUnlock */
+  fsCheckReservedLock,          /* xCheckReservedLock */
+  fsFileControl,                /* xFileControl */
+  fsSectorSize,                 /* xSectorSize */
+  fsDeviceCharacteristics,      /* xDeviceCharacteristics */
+  0,                            /* xShmMap */
+  0,                            /* xShmLock */
+  0,                            /* xShmBarrier */
+  0                             /* xShmUnmap */
+};
+
+
+static sqlite3_io_methods tmp_io_methods = {
+  1,                            /* iVersion */
+  tmpClose,                     /* xClose */
+  tmpRead,                      /* xRead */
+  tmpWrite,                     /* xWrite */
+  tmpTruncate,                  /* xTruncate */
+  tmpSync,                      /* xSync */
+  tmpFileSize,                  /* xFileSize */
+  tmpLock,                      /* xLock */
+  tmpUnlock,                    /* xUnlock */
+  tmpCheckReservedLock,         /* xCheckReservedLock */
+  tmpFileControl,               /* xFileControl */
+  tmpSectorSize,                /* xSectorSize */
+  tmpDeviceCharacteristics,     /* xDeviceCharacteristics */
+  0,                            /* xShmMap */
+  0,                            /* xShmLock */
+  0,                            /* xShmBarrier */
+  0                             /* xShmUnmap */
+};
+
+/* Useful macros used in several places */
+#define MIN(x,y) ((x)<(y)?(x):(y))
+#define MAX(x,y) ((x)>(y)?(x):(y))
+
+
+/*
+** Close a tmp-file.
+*/
+static int tmpClose(sqlite3_file *pFile){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  sqlite3_free(pTmp->zAlloc);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from a tmp-file.
+*/
+static int tmpRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  if( (iAmt+iOfst)>pTmp->nSize ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  memcpy(zBuf, &pTmp->zAlloc[iOfst], iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Write data to a tmp-file.
+*/
+static int tmpWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  if( (iAmt+iOfst)>pTmp->nAlloc ){
+    int nNew = (int)(2*(iAmt+iOfst+pTmp->nAlloc));
+    char *zNew = sqlite3_realloc(pTmp->zAlloc, nNew);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    pTmp->zAlloc = zNew;
+    pTmp->nAlloc = nNew;
+  }
+  memcpy(&pTmp->zAlloc[iOfst], zBuf, iAmt);
+  pTmp->nSize = (int)MAX(pTmp->nSize, iOfst+iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Truncate a tmp-file.
+*/
+static int tmpTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  pTmp->nSize = (int)MIN(pTmp->nSize, size);
+  return SQLITE_OK;
+}
+
+/*
+** Sync a tmp-file.
+*/
+static int tmpSync(sqlite3_file *pFile, int flags){
+  return SQLITE_OK;
+}
+
+/*
+** Return the current file-size of a tmp-file.
+*/
+static int tmpFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  *pSize = pTmp->nSize;
+  return SQLITE_OK;
+}
+
+/*
+** Lock a tmp-file.
+*/
+static int tmpLock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Unlock a tmp-file.
+*/
+static int tmpUnlock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on a tmp-file.
+*/
+static int tmpCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** File control method. For custom operations on a tmp-file.
+*/
+static int tmpFileControl(sqlite3_file *pFile, int op, void *pArg){
+  return SQLITE_OK;
+}
+
+/*
+** Return the sector-size in bytes for a tmp-file.
+*/
+static int tmpSectorSize(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Return the device characteristic flags supported by a tmp-file.
+*/
+static int tmpDeviceCharacteristics(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Close an fs-file.
+*/
+static int fsClose(sqlite3_file *pFile){
+  int rc = SQLITE_OK;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+
+  /* Decrement the real_file ref-count. */
+  pReal->nRef--;
+  assert(pReal->nRef>=0);
+
+  /* When the ref-count reaches 0, destroy the structure */
+  if( pReal->nRef==0 ){
+    *pReal->ppThis = pReal->pNext;
+    if( pReal->pNext ){
+      pReal->pNext->ppThis = pReal->ppThis;
+    }
+    rc = pReal->pFile->pMethods->xClose(pReal->pFile);
+    sqlite3_free(pReal);
+  }
+
+  return rc;
+}
+
+/*
+** Read data from an fs-file.
+*/
+static int fsRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  sqlite3_file *pF = pReal->pFile;
+
+  if( (p->eType==DATABASE_FILE && (iAmt+iOfst)>pReal->nDatabase)
+   || (p->eType==JOURNAL_FILE && (iAmt+iOfst)>pReal->nJournal)
+  ){
+    rc = SQLITE_IOERR_SHORT_READ;
+  }else if( p->eType==DATABASE_FILE ){
+    rc = pF->pMethods->xRead(pF, zBuf, iAmt, iOfst+BLOCKSIZE);
+  }else{
+    /* Journal file. */
+    int iRem = iAmt;
+    int iBuf = 0;
+    int ii = (int)iOfst;
+    while( iRem>0 && rc==SQLITE_OK ){
+      int iRealOff = pReal->nBlob - BLOCKSIZE*((ii/BLOCKSIZE)+1) + ii%BLOCKSIZE;
+      int iRealAmt = MIN(iRem, BLOCKSIZE - (iRealOff%BLOCKSIZE));
+
+      rc = pF->pMethods->xRead(pF, &((char *)zBuf)[iBuf], iRealAmt, iRealOff);
+      ii += iRealAmt;
+      iBuf += iRealAmt;
+      iRem -= iRealAmt;
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Write data to an fs-file.
+*/
+static int fsWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  sqlite3_file *pF = pReal->pFile;
+
+  if( p->eType==DATABASE_FILE ){
+    if( (iAmt+iOfst+BLOCKSIZE)>(pReal->nBlob-pReal->nJournal) ){
+      rc = SQLITE_FULL;
+    }else{
+      rc = pF->pMethods->xWrite(pF, zBuf, iAmt, iOfst+BLOCKSIZE);
+      if( rc==SQLITE_OK ){
+        pReal->nDatabase = (int)MAX(pReal->nDatabase, iAmt+iOfst);
+      }
+    }
+  }else{
+    /* Journal file. */
+    int iRem = iAmt;
+    int iBuf = 0;
+    int ii = (int)iOfst;
+    while( iRem>0 && rc==SQLITE_OK ){
+      int iRealOff = pReal->nBlob - BLOCKSIZE*((ii/BLOCKSIZE)+1) + ii%BLOCKSIZE;
+      int iRealAmt = MIN(iRem, BLOCKSIZE - (iRealOff%BLOCKSIZE));
+
+      if( iRealOff<(pReal->nDatabase+BLOCKSIZE) ){
+        rc = SQLITE_FULL;
+      }else{
+        rc = pF->pMethods->xWrite(pF, &((char *)zBuf)[iBuf], iRealAmt,iRealOff);
+        ii += iRealAmt;
+        iBuf += iRealAmt;
+        iRem -= iRealAmt;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      pReal->nJournal = (int)MAX(pReal->nJournal, iAmt+iOfst);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Truncate an fs-file.
+*/
+static int fsTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  if( p->eType==DATABASE_FILE ){
+    pReal->nDatabase = (int)MIN(pReal->nDatabase, size);
+  }else{
+    pReal->nJournal = (int)MIN(pReal->nJournal, size);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Sync an fs-file.
+*/
+static int fsSync(sqlite3_file *pFile, int flags){
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  sqlite3_file *pRealFile = pReal->pFile;
+  int rc = SQLITE_OK;
+
+  if( p->eType==DATABASE_FILE ){
+    unsigned char zSize[4];
+    zSize[0] = (pReal->nDatabase&0xFF000000)>>24;
+    zSize[1] = (unsigned char)((pReal->nDatabase&0x00FF0000)>>16);
+    zSize[2] = (pReal->nDatabase&0x0000FF00)>>8;
+    zSize[3] = (pReal->nDatabase&0x000000FF);
+    rc = pRealFile->pMethods->xWrite(pRealFile, zSize, 4, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = pRealFile->pMethods->xSync(pRealFile, flags&(~SQLITE_SYNC_DATAONLY));
+  }
+
+  return rc;
+}
+
+/*
+** Return the current file-size of an fs-file.
+*/
+static int fsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  if( p->eType==DATABASE_FILE ){
+    *pSize = pReal->nDatabase;
+  }else{
+    *pSize = pReal->nJournal;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Lock an fs-file.
+*/
+static int fsLock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Unlock an fs-file.
+*/
+static int fsUnlock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an fs-file.
+*/
+static int fsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** File control method. For custom operations on an fs-file.
+*/
+static int fsFileControl(sqlite3_file *pFile, int op, void *pArg){
+  if( op==SQLITE_FCNTL_PRAGMA ) return SQLITE_NOTFOUND;
+  return SQLITE_OK;
+}
+
+/*
+** Return the sector-size in bytes for an fs-file.
+*/
+static int fsSectorSize(sqlite3_file *pFile){
+  return BLOCKSIZE;
+}
+
+/*
+** Return the device characteristic flags supported by an fs-file.
+*/
+static int fsDeviceCharacteristics(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Open an fs file handle.
+*/
+static int fsOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = 0;
+  int eType;
+  int nName;
+  int rc = SQLITE_OK;
+
+  if( 0==(flags&(SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_MAIN_JOURNAL)) ){
+    tmp_file *p2 = (tmp_file *)pFile;
+    memset(p2, 0, sizeof(*p2));
+    p2->base.pMethods = &tmp_io_methods;
+    return SQLITE_OK;
+  }
+
+  eType = ((flags&(SQLITE_OPEN_MAIN_DB))?DATABASE_FILE:JOURNAL_FILE);
+  p->base.pMethods = &fs_io_methods;
+  p->eType = eType;
+
+  assert(strlen("-journal")==8);
+  nName = (int)strlen(zName)-((eType==JOURNAL_FILE)?8:0);
+  pReal=pFsVfs->pFileList; 
+  for(; pReal && strncmp(pReal->zName, zName, nName); pReal=pReal->pNext);
+
+  if( !pReal ){
+    int real_flags = (flags&~(SQLITE_OPEN_MAIN_DB))|SQLITE_OPEN_TEMP_DB;
+    sqlite3_int64 size;
+    sqlite3_file *pRealFile;
+    sqlite3_vfs *pParent = pFsVfs->pParent;
+    assert(eType==DATABASE_FILE);
+
+    pReal = (fs_real_file *)sqlite3_malloc(sizeof(*pReal)+pParent->szOsFile);
+    if( !pReal ){
+      rc = SQLITE_NOMEM;
+      goto open_out;
+    }
+    memset(pReal, 0, sizeof(*pReal)+pParent->szOsFile);
+    pReal->zName = zName;
+    pReal->pFile = (sqlite3_file *)(&pReal[1]);
+
+    rc = pParent->xOpen(pParent, zName, pReal->pFile, real_flags, pOutFlags);
+    if( rc!=SQLITE_OK ){
+      goto open_out;
+    }
+    pRealFile = pReal->pFile;
+
+    rc = pRealFile->pMethods->xFileSize(pRealFile, &size);
+    if( rc!=SQLITE_OK ){
+      goto open_out;
+    }
+    if( size==0 ){
+      rc = pRealFile->pMethods->xWrite(pRealFile, "\0", 1, BLOBSIZE-1);
+      pReal->nBlob = BLOBSIZE;
+    }else{
+      unsigned char zS[4];
+      pReal->nBlob = (int)size;
+      rc = pRealFile->pMethods->xRead(pRealFile, zS, 4, 0);
+      pReal->nDatabase = (zS[0]<<24)+(zS[1]<<16)+(zS[2]<<8)+zS[3];
+      if( rc==SQLITE_OK ){
+        rc = pRealFile->pMethods->xRead(pRealFile, zS, 4, pReal->nBlob-4);
+        if( zS[0] || zS[1] || zS[2] || zS[3] ){
+          pReal->nJournal = pReal->nBlob;
+        }
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      pReal->pNext = pFsVfs->pFileList;
+      if( pReal->pNext ){
+        pReal->pNext->ppThis = &pReal->pNext;
+      }
+      pReal->ppThis = &pFsVfs->pFileList;
+      pFsVfs->pFileList = pReal;
+    }
+  }
+
+open_out:
+  if( pReal ){
+    if( rc==SQLITE_OK ){
+      p->pReal = pReal;
+      pReal->nRef++;
+    }else{
+      if( pReal->pFile->pMethods ){
+        pReal->pFile->pMethods->xClose(pReal->pFile);
+      }
+      sqlite3_free(pReal);
+    }
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int fsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc = SQLITE_OK;
+  fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
+  fs_real_file *pReal;
+  sqlite3_file *pF;
+  int nName = (int)strlen(zPath) - 8;
+
+  assert(strlen("-journal")==8);
+  assert(strcmp("-journal", &zPath[nName])==0);
+
+  pReal = pFsVfs->pFileList; 
+  for(; pReal && strncmp(pReal->zName, zPath, nName); pReal=pReal->pNext);
+  if( pReal ){
+    pF = pReal->pFile;
+    rc = pF->pMethods->xWrite(pF, "\0\0\0\0", 4, pReal->nBlob-BLOCKSIZE);
+    if( rc==SQLITE_OK ){
+      pReal->nJournal = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int fsAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
+  fs_real_file *pReal;
+  int isJournal = 0;
+  int nName = (int)strlen(zPath);
+
+  if( flags!=SQLITE_ACCESS_EXISTS ){
+    sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+    return pParent->xAccess(pParent, zPath, flags, pResOut);
+  }
+
+  assert(strlen("-journal")==8);
+  if( nName>8 && strcmp("-journal", &zPath[nName-8])==0 ){
+    nName -= 8;
+    isJournal = 1;
+  }
+
+  pReal = pFsVfs->pFileList; 
+  for(; pReal && strncmp(pReal->zName, zPath, nName); pReal=pReal->pNext);
+
+  *pResOut = (pReal && (!isJournal || pReal->nJournal>0));
+  return SQLITE_OK;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (FS_MAX_PATHNAME+1) bytes.
+*/
+static int fsFullPathname(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zPath,            /* Possibly relative input path */
+  int nOut,                     /* Size of output buffer in bytes */
+  char *zOut                    /* Output buffer */
+){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xFullPathname(pParent, zPath, nOut, zOut);
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *fsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xDlOpen(pParent, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void fsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  pParent->xDlError(pParent, nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*fsDlSym(sqlite3_vfs *pVfs, void *pH, const char *zSym))(void){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xDlSym(pParent, pH, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void fsDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  pParent->xDlClose(pParent, pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int fsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xRandomness(pParent, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int fsSleep(sqlite3_vfs *pVfs, int nMicro){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xSleep(pParent, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int fsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xCurrentTime(pParent, pTimeOut);
+}
+
+/*
+** This procedure registers the fs vfs with SQLite. If the argument is
+** true, the fs vfs becomes the new default vfs. It is the only publicly
+** available function in this file.
+*/
+int fs_register(void){
+  if( fs_vfs.pParent ) return SQLITE_OK;
+  fs_vfs.pParent = sqlite3_vfs_find(0);
+  fs_vfs.base.mxPathname = fs_vfs.pParent->mxPathname;
+  fs_vfs.base.szOsFile = MAX(sizeof(tmp_file), sizeof(fs_file));
+  return sqlite3_vfs_register(&fs_vfs.base, 0);
+}
+
+#ifdef SQLITE_TEST
+  int SqlitetestOnefile_Init() {return fs_register();}
+#endif
diff --git a/src/test_osinst.c b/src/test_osinst.c
new file mode 100644
index 0000000..062e831
--- /dev/null
+++ b/src/test_osinst.c
@@ -0,0 +1,1229 @@
+/*
+** 2008 April 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains the implementation of an SQLite vfs wrapper that
+** adds instrumentation to all vfs and file methods. C and Tcl interfaces
+** are provided to control the instrumentation.
+*/
+
+/*
+** This module contains code for a wrapper VFS that causes a log of
+** most VFS calls to be written into a nominated file on disk. The log 
+** is stored in a compressed binary format to reduce the amount of IO 
+** overhead introduced into the application by logging.
+**
+** All calls on sqlite3_file objects except xFileControl() are logged.
+** Additionally, calls to the xAccess(), xOpen(), and xDelete()
+** methods are logged. The other sqlite3_vfs object methods (xDlXXX,
+** xRandomness, xSleep, xCurrentTime, xGetLastError and xCurrentTimeInt64) 
+** are not logged.
+**
+** The binary log files are read using a virtual table implementation
+** also contained in this file. 
+**
+** CREATING LOG FILES:
+**
+**       int sqlite3_vfslog_new(
+**         const char *zVfs,          // Name of new VFS
+**         const char *zParentVfs,    // Name of parent VFS (or NULL)
+**         const char *zLog           // Name of log file to write to
+**       );
+**
+**       int sqlite3_vfslog_finalize(const char *zVfs);
+**
+** ANNOTATING LOG FILES:
+**
+**   To write an arbitrary message into a log file:
+**
+**       int sqlite3_vfslog_annotate(const char *zVfs, const char *zMsg);
+**
+** READING LOG FILES:
+**
+**   Log files are read using the "vfslog" virtual table implementation
+**   in this file. To register the virtual table with SQLite, use:
+**
+**       int sqlite3_vfslog_register(sqlite3 *db);
+**
+**   Then, if the log file is named "vfs.log", the following SQL command:
+**
+**       CREATE VIRTUAL TABLE v USING vfslog('vfs.log');
+**
+**   creates a virtual table with 6 columns, as follows:
+**
+**       CREATE TABLE v(
+**         event    TEXT,             // "xOpen", "xRead" etc.
+**         file     TEXT,             // Name of file this call applies to
+**         clicks   INTEGER,          // Time spent in call
+**         rc       INTEGER,          // Return value
+**         size     INTEGER,          // Bytes read or written
+**         offset   INTEGER           // File offset read or written
+**       );
+*/
+
+#include "sqlite3.h"
+
+#include "os_setup.h"
+#if SQLITE_OS_WIN
+#  include "os_win.h"
+#endif
+
+#include <string.h>
+#include <assert.h>
+
+
+/*
+** Maximum pathname length supported by the vfslog backend.
+*/
+#define INST_MAX_PATHNAME 512
+
+#define OS_ACCESS            1
+#define OS_CHECKRESERVEDLOCK 2
+#define OS_CLOSE             3
+#define OS_CURRENTTIME       4
+#define OS_DELETE            5
+#define OS_DEVCHAR           6
+#define OS_FILECONTROL       7
+#define OS_FILESIZE          8
+#define OS_FULLPATHNAME      9
+#define OS_LOCK              11
+#define OS_OPEN              12
+#define OS_RANDOMNESS        13
+#define OS_READ              14 
+#define OS_SECTORSIZE        15
+#define OS_SLEEP             16
+#define OS_SYNC              17
+#define OS_TRUNCATE          18
+#define OS_UNLOCK            19
+#define OS_WRITE             20
+#define OS_SHMUNMAP          22
+#define OS_SHMMAP            23
+#define OS_SHMLOCK           25
+#define OS_SHMBARRIER        26
+#define OS_ANNOTATE          28
+
+#define OS_NUMEVENTS         29
+
+#define VFSLOG_BUFFERSIZE 8192
+
+typedef struct VfslogVfs VfslogVfs;
+typedef struct VfslogFile VfslogFile;
+
+struct VfslogVfs {
+  sqlite3_vfs base;               /* VFS methods */
+  sqlite3_vfs *pVfs;              /* Parent VFS */
+  int iNextFileId;                /* Next file id */
+  sqlite3_file *pLog;             /* Log file handle */
+  sqlite3_int64 iOffset;          /* Log file offset of start of write buffer */
+  int nBuf;                       /* Number of valid bytes in aBuf[] */
+  char aBuf[VFSLOG_BUFFERSIZE];   /* Write buffer */
+};
+
+struct VfslogFile {
+  sqlite3_file base;              /* IO methods */
+  sqlite3_file *pReal;            /* Underlying file handle */
+  sqlite3_vfs *pVfslog;           /* Associated VsflogVfs object */
+  int iFileId;                    /* File id number */
+};
+
+#define REALVFS(p) (((VfslogVfs *)(p))->pVfs)
+
+
+
+/*
+** Method declarations for vfslog_file.
+*/
+static int vfslogClose(sqlite3_file*);
+static int vfslogRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int vfslogWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int vfslogTruncate(sqlite3_file*, sqlite3_int64 size);
+static int vfslogSync(sqlite3_file*, int flags);
+static int vfslogFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int vfslogLock(sqlite3_file*, int);
+static int vfslogUnlock(sqlite3_file*, int);
+static int vfslogCheckReservedLock(sqlite3_file*, int *pResOut);
+static int vfslogFileControl(sqlite3_file*, int op, void *pArg);
+static int vfslogSectorSize(sqlite3_file*);
+static int vfslogDeviceCharacteristics(sqlite3_file*);
+
+static int vfslogShmLock(sqlite3_file *pFile, int ofst, int n, int flags);
+static int vfslogShmMap(sqlite3_file *pFile,int,int,int,volatile void **);
+static void vfslogShmBarrier(sqlite3_file*);
+static int vfslogShmUnmap(sqlite3_file *pFile, int deleteFlag);
+
+/*
+** Method declarations for vfslog_vfs.
+*/
+static int vfslogOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int vfslogDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int vfslogAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int vfslogFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *vfslogDlOpen(sqlite3_vfs*, const char *zFilename);
+static void vfslogDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*vfslogDlSym(sqlite3_vfs *pVfs, void *p, const char*zSym))(void);
+static void vfslogDlClose(sqlite3_vfs*, void*);
+static int vfslogRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int vfslogSleep(sqlite3_vfs*, int microseconds);
+static int vfslogCurrentTime(sqlite3_vfs*, double*);
+
+static int vfslogGetLastError(sqlite3_vfs*, int, char *);
+static int vfslogCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+
+static sqlite3_vfs vfslog_vfs = {
+  1,                              /* iVersion */
+  sizeof(VfslogFile),             /* szOsFile */
+  INST_MAX_PATHNAME,              /* mxPathname */
+  0,                              /* pNext */
+  0,                              /* zName */
+  0,                              /* pAppData */
+  vfslogOpen,                     /* xOpen */
+  vfslogDelete,                   /* xDelete */
+  vfslogAccess,                   /* xAccess */
+  vfslogFullPathname,             /* xFullPathname */
+  vfslogDlOpen,                   /* xDlOpen */
+  vfslogDlError,                  /* xDlError */
+  vfslogDlSym,                    /* xDlSym */
+  vfslogDlClose,                  /* xDlClose */
+  vfslogRandomness,               /* xRandomness */
+  vfslogSleep,                    /* xSleep */
+  vfslogCurrentTime,              /* xCurrentTime */
+  vfslogGetLastError,             /* xGetLastError */
+  vfslogCurrentTimeInt64          /* xCurrentTime */
+};
+
+static sqlite3_io_methods vfslog_io_methods = {
+  2,                              /* iVersion */
+  vfslogClose,                    /* xClose */
+  vfslogRead,                     /* xRead */
+  vfslogWrite,                    /* xWrite */
+  vfslogTruncate,                 /* xTruncate */
+  vfslogSync,                     /* xSync */
+  vfslogFileSize,                 /* xFileSize */
+  vfslogLock,                     /* xLock */
+  vfslogUnlock,                   /* xUnlock */
+  vfslogCheckReservedLock,        /* xCheckReservedLock */
+  vfslogFileControl,              /* xFileControl */
+  vfslogSectorSize,               /* xSectorSize */
+  vfslogDeviceCharacteristics,    /* xDeviceCharacteristics */
+  vfslogShmMap,                   /* xShmMap */
+  vfslogShmLock,                  /* xShmLock */
+  vfslogShmBarrier,               /* xShmBarrier */
+  vfslogShmUnmap                  /* xShmUnmap */
+};
+
+#if SQLITE_OS_UNIX && !defined(NO_GETTOD)
+#include <sys/time.h>
+static sqlite3_uint64 vfslog_time(){
+  struct timeval sTime;
+  gettimeofday(&sTime, 0);
+  return sTime.tv_usec + (sqlite3_uint64)sTime.tv_sec * 1000000;
+}
+#elif SQLITE_OS_WIN
+#include <time.h>
+static sqlite3_uint64 vfslog_time(){
+  FILETIME ft;
+  sqlite3_uint64 u64time = 0;
+ 
+  GetSystemTimeAsFileTime(&ft);
+
+  u64time |= ft.dwHighDateTime;
+  u64time <<= 32;
+  u64time |= ft.dwLowDateTime;
+
+  /* ft is 100-nanosecond intervals, we want microseconds */
+  return u64time /(sqlite3_uint64)10;
+}
+#else
+static sqlite3_uint64 vfslog_time(){
+  return 0;
+}
+#endif
+
+static void vfslog_call(sqlite3_vfs *, int, int, sqlite3_int64, int, int, int);
+static void vfslog_string(sqlite3_vfs *, const char *);
+
+/*
+** Close an vfslog-file.
+*/
+static int vfslogClose(sqlite3_file *pFile){
+  sqlite3_uint64 t;
+  int rc = SQLITE_OK;
+  VfslogFile *p = (VfslogFile *)pFile;
+
+  t = vfslog_time();
+  if( p->pReal->pMethods ){
+    rc = p->pReal->pMethods->xClose(p->pReal);
+  }
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_CLOSE, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+/*
+** Read data from an vfslog-file.
+*/
+static int vfslogRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_READ, p->iFileId, t, rc, iAmt, (int)iOfst);
+  return rc;
+}
+
+/*
+** Write data to an vfslog-file.
+*/
+static int vfslogWrite(
+  sqlite3_file *pFile,
+  const void *z,
+  int iAmt,
+  sqlite_int64 iOfst
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xWrite(p->pReal, z, iAmt, iOfst);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_WRITE, p->iFileId, t, rc, iAmt, (int)iOfst);
+  return rc;
+}
+
+/*
+** Truncate an vfslog-file.
+*/
+static int vfslogTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xTruncate(p->pReal, size);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_TRUNCATE, p->iFileId, t, rc, 0, (int)size);
+  return rc;
+}
+
+/*
+** Sync an vfslog-file.
+*/
+static int vfslogSync(sqlite3_file *pFile, int flags){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xSync(p->pReal, flags);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SYNC, p->iFileId, t, rc, flags, 0);
+  return rc;
+}
+
+/*
+** Return the current file-size of an vfslog-file.
+*/
+static int vfslogFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xFileSize(p->pReal, pSize);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_FILESIZE, p->iFileId, t, rc, 0, (int)*pSize);
+  return rc;
+}
+
+/*
+** Lock an vfslog-file.
+*/
+static int vfslogLock(sqlite3_file *pFile, int eLock){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xLock(p->pReal, eLock);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_LOCK, p->iFileId, t, rc, eLock, 0);
+  return rc;
+}
+
+/*
+** Unlock an vfslog-file.
+*/
+static int vfslogUnlock(sqlite3_file *pFile, int eLock){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xUnlock(p->pReal, eLock);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_UNLOCK, p->iFileId, t, rc, eLock, 0);
+  return rc;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an vfslog-file.
+*/
+static int vfslogCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_CHECKRESERVEDLOCK, p->iFileId, t, rc, *pResOut, 0);
+  return rc;
+}
+
+/*
+** File control method. For custom operations on an vfslog-file.
+*/
+static int vfslogFileControl(sqlite3_file *pFile, int op, void *pArg){
+  VfslogFile *p = (VfslogFile *)pFile;
+  int rc = p->pReal->pMethods->xFileControl(p->pReal, op, pArg);
+  if( op==SQLITE_FCNTL_VFSNAME && rc==SQLITE_OK ){
+    *(char**)pArg = sqlite3_mprintf("vfslog/%z", *(char**)pArg);
+  }
+  return rc;
+}
+
+/*
+** Return the sector-size in bytes for an vfslog-file.
+*/
+static int vfslogSectorSize(sqlite3_file *pFile){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xSectorSize(p->pReal);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SECTORSIZE, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+/*
+** Return the device characteristic flags supported by an vfslog-file.
+*/
+static int vfslogDeviceCharacteristics(sqlite3_file *pFile){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_DEVCHAR, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+static int vfslogShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMLOCK, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+static int vfslogShmMap(
+  sqlite3_file *pFile, 
+  int iRegion, 
+  int szRegion, 
+  int isWrite, 
+  volatile void **pp
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMMAP, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+static void vfslogShmBarrier(sqlite3_file *pFile){
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  p->pReal->pMethods->xShmBarrier(p->pReal);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMBARRIER, p->iFileId, t, SQLITE_OK, 0, 0);
+}
+static int vfslogShmUnmap(sqlite3_file *pFile, int deleteFlag){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xShmUnmap(p->pReal, deleteFlag);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMUNMAP, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+
+/*
+** Open an vfslog file handle.
+*/
+static int vfslogOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  VfslogVfs *pLog = (VfslogVfs *)pVfs;
+
+  pFile->pMethods = &vfslog_io_methods;
+  p->pReal = (sqlite3_file *)&p[1];
+  p->pVfslog = pVfs;
+  p->iFileId = ++pLog->iNextFileId;
+
+  t = vfslog_time();
+  rc = REALVFS(pVfs)->xOpen(REALVFS(pVfs), zName, p->pReal, flags, pOutFlags);
+  t = vfslog_time() - t;
+
+  vfslog_call(pVfs, OS_OPEN, p->iFileId, t, rc, 0, 0);
+  vfslog_string(pVfs, zName);
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int vfslogDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc;
+  sqlite3_uint64 t;
+  t = vfslog_time();
+  rc = REALVFS(pVfs)->xDelete(REALVFS(pVfs), zPath, dirSync);
+  t = vfslog_time() - t;
+  vfslog_call(pVfs, OS_DELETE, 0, t, rc, dirSync, 0);
+  vfslog_string(pVfs, zPath);
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int vfslogAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  int rc;
+  sqlite3_uint64 t;
+  t = vfslog_time();
+  rc = REALVFS(pVfs)->xAccess(REALVFS(pVfs), zPath, flags, pResOut);
+  t = vfslog_time() - t;
+  vfslog_call(pVfs, OS_ACCESS, 0, t, rc, flags, *pResOut);
+  vfslog_string(pVfs, zPath);
+  return rc;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (INST_MAX_PATHNAME+1) bytes.
+*/
+static int vfslogFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  return REALVFS(pVfs)->xFullPathname(REALVFS(pVfs), zPath, nOut, zOut);
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *vfslogDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return REALVFS(pVfs)->xDlOpen(REALVFS(pVfs), zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void vfslogDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  REALVFS(pVfs)->xDlError(REALVFS(pVfs), nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*vfslogDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return REALVFS(pVfs)->xDlSym(REALVFS(pVfs), p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void vfslogDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  REALVFS(pVfs)->xDlClose(REALVFS(pVfs), pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int vfslogRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return REALVFS(pVfs)->xRandomness(REALVFS(pVfs), nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int vfslogSleep(sqlite3_vfs *pVfs, int nMicro){
+  return REALVFS(pVfs)->xSleep(REALVFS(pVfs), nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int vfslogCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return REALVFS(pVfs)->xCurrentTime(REALVFS(pVfs), pTimeOut);
+}
+
+static int vfslogGetLastError(sqlite3_vfs *pVfs, int a, char *b){
+  return REALVFS(pVfs)->xGetLastError(REALVFS(pVfs), a, b);
+}
+static int vfslogCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){
+  return REALVFS(pVfs)->xCurrentTimeInt64(REALVFS(pVfs), p);
+}
+
+static void vfslog_flush(VfslogVfs *p){
+#ifdef SQLITE_TEST
+  extern int sqlite3_io_error_pending;
+  extern int sqlite3_io_error_persist;
+  extern int sqlite3_diskfull_pending;
+
+  int pending = sqlite3_io_error_pending;
+  int persist = sqlite3_io_error_persist;
+  int diskfull = sqlite3_diskfull_pending;
+
+  sqlite3_io_error_pending = 0;
+  sqlite3_io_error_persist = 0;
+  sqlite3_diskfull_pending = 0;
+#endif
+
+  if( p->nBuf ){
+    p->pLog->pMethods->xWrite(p->pLog, p->aBuf, p->nBuf, p->iOffset);
+    p->iOffset += p->nBuf;
+    p->nBuf = 0;
+  }
+
+#ifdef SQLITE_TEST
+  sqlite3_io_error_pending = pending;
+  sqlite3_io_error_persist = persist;
+  sqlite3_diskfull_pending = diskfull;
+#endif
+}
+
+static void put32bits(unsigned char *p, unsigned int v){
+  p[0] = v>>24;
+  p[1] = (unsigned char)(v>>16);
+  p[2] = (unsigned char)(v>>8);
+  p[3] = (unsigned char)v;
+}
+
+static void vfslog_call(
+  sqlite3_vfs *pVfs,
+  int eEvent,
+  int iFileid,
+  sqlite3_int64 nClick,
+  int return_code,
+  int size,
+  int offset
+){
+  VfslogVfs *p = (VfslogVfs *)pVfs;
+  unsigned char *zRec;
+  if( (24+p->nBuf)>sizeof(p->aBuf) ){
+    vfslog_flush(p);
+  }
+  zRec = (unsigned char *)&p->aBuf[p->nBuf];
+  put32bits(&zRec[0], eEvent);
+  put32bits(&zRec[4], iFileid);
+  put32bits(&zRec[8], (unsigned int)(nClick&0xffff));
+  put32bits(&zRec[12], return_code);
+  put32bits(&zRec[16], size);
+  put32bits(&zRec[20], offset);
+  p->nBuf += 24;
+}
+
+static void vfslog_string(sqlite3_vfs *pVfs, const char *zStr){
+  VfslogVfs *p = (VfslogVfs *)pVfs;
+  unsigned char *zRec;
+  int nStr = zStr ? (int)strlen(zStr) : 0;
+  if( (4+nStr+p->nBuf)>sizeof(p->aBuf) ){
+    vfslog_flush(p);
+  }
+  zRec = (unsigned char *)&p->aBuf[p->nBuf];
+  put32bits(&zRec[0], nStr);
+  if( zStr ){
+    memcpy(&zRec[4], zStr, nStr);
+  }
+  p->nBuf += (4 + nStr);
+}
+
+static void vfslog_finalize(VfslogVfs *p){
+  if( p->pLog->pMethods ){
+    vfslog_flush(p);
+    p->pLog->pMethods->xClose(p->pLog);
+  }
+  sqlite3_free(p);
+}
+
+int sqlite3_vfslog_finalize(const char *zVfs){
+  sqlite3_vfs *pVfs;
+  pVfs = sqlite3_vfs_find(zVfs);
+  if( !pVfs || pVfs->xOpen!=vfslogOpen ){
+    return SQLITE_ERROR;
+  } 
+  sqlite3_vfs_unregister(pVfs);
+  vfslog_finalize((VfslogVfs *)pVfs);
+  return SQLITE_OK;
+}
+
+int sqlite3_vfslog_new(
+  const char *zVfs,               /* New VFS name */
+  const char *zParentVfs,         /* Parent VFS name (or NULL) */
+  const char *zLog                /* Log file name */
+){
+  VfslogVfs *p;
+  sqlite3_vfs *pParent;
+  int nByte;
+  int flags;
+  int rc;
+  char *zFile;
+  int nVfs;
+
+  pParent = sqlite3_vfs_find(zParentVfs);
+  if( !pParent ){
+    return SQLITE_ERROR;
+  }
+
+  nVfs = (int)strlen(zVfs);
+  nByte = sizeof(VfslogVfs) + pParent->szOsFile + nVfs+1+pParent->mxPathname+1;
+  p = (VfslogVfs *)sqlite3_malloc(nByte);
+  memset(p, 0, nByte);
+
+  p->pVfs = pParent;
+  p->pLog = (sqlite3_file *)&p[1];
+  memcpy(&p->base, &vfslog_vfs, sizeof(sqlite3_vfs));
+  p->base.zName = &((char *)p->pLog)[pParent->szOsFile];
+  p->base.szOsFile += pParent->szOsFile;
+  memcpy((char *)p->base.zName, zVfs, nVfs);
+
+  zFile = (char *)&p->base.zName[nVfs+1];
+  pParent->xFullPathname(pParent, zLog, pParent->mxPathname, zFile);
+
+  flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_SUPER_JOURNAL;
+  pParent->xDelete(pParent, zFile, 0);
+  rc = pParent->xOpen(pParent, zFile, p->pLog, flags, &flags);
+  if( rc==SQLITE_OK ){
+    memcpy(p->aBuf, "sqlite_ostrace1.....", 20);
+    p->iOffset = 0;
+    p->nBuf = 20;
+    rc = sqlite3_vfs_register((sqlite3_vfs *)p, 1);
+  }
+  if( rc ){
+    vfslog_finalize(p);
+  }
+  return rc;
+}
+
+int sqlite3_vfslog_annotate(const char *zVfs, const char *zMsg){
+  sqlite3_vfs *pVfs;
+  pVfs = sqlite3_vfs_find(zVfs);
+  if( !pVfs || pVfs->xOpen!=vfslogOpen ){
+    return SQLITE_ERROR;
+  } 
+  vfslog_call(pVfs, OS_ANNOTATE, 0, 0, 0, 0, 0);
+  vfslog_string(pVfs, zMsg);
+  return SQLITE_OK;
+}
+
+static const char *vfslog_eventname(int eEvent){
+  const char *zEvent = 0;
+
+  switch( eEvent ){
+    case OS_CLOSE:             zEvent = "xClose"; break;
+    case OS_READ:              zEvent = "xRead"; break;
+    case OS_WRITE:             zEvent = "xWrite"; break;
+    case OS_TRUNCATE:          zEvent = "xTruncate"; break;
+    case OS_SYNC:              zEvent = "xSync"; break;
+    case OS_FILESIZE:          zEvent = "xFilesize"; break;
+    case OS_LOCK:              zEvent = "xLock"; break;
+    case OS_UNLOCK:            zEvent = "xUnlock"; break;
+    case OS_CHECKRESERVEDLOCK: zEvent = "xCheckResLock"; break;
+    case OS_FILECONTROL:       zEvent = "xFileControl"; break;
+    case OS_SECTORSIZE:        zEvent = "xSectorSize"; break;
+    case OS_DEVCHAR:           zEvent = "xDeviceChar"; break;
+    case OS_OPEN:              zEvent = "xOpen"; break;
+    case OS_DELETE:            zEvent = "xDelete"; break;
+    case OS_ACCESS:            zEvent = "xAccess"; break;
+    case OS_FULLPATHNAME:      zEvent = "xFullPathname"; break;
+    case OS_RANDOMNESS:        zEvent = "xRandomness"; break;
+    case OS_SLEEP:             zEvent = "xSleep"; break;
+    case OS_CURRENTTIME:       zEvent = "xCurrentTime"; break;
+
+    case OS_SHMUNMAP:          zEvent = "xShmUnmap"; break;
+    case OS_SHMLOCK:           zEvent = "xShmLock"; break;
+    case OS_SHMBARRIER:        zEvent = "xShmBarrier"; break;
+    case OS_SHMMAP:            zEvent = "xShmMap"; break;
+
+    case OS_ANNOTATE:          zEvent = "annotation"; break;
+  }
+
+  return zEvent;
+}
+
+typedef struct VfslogVtab VfslogVtab;
+typedef struct VfslogCsr VfslogCsr;
+
+/*
+** Virtual table type for the vfslog reader module.
+*/
+struct VfslogVtab {
+  sqlite3_vtab base;              /* Base class */
+  sqlite3_file *pFd;              /* File descriptor open on vfslog file */
+  sqlite3_int64 nByte;            /* Size of file in bytes */
+  char *zFile;                    /* File name for pFd */
+};
+
+/*
+** Virtual table cursor type for the vfslog reader module.
+*/
+struct VfslogCsr {
+  sqlite3_vtab_cursor base;       /* Base class */
+  sqlite3_int64 iRowid;           /* Current rowid. */
+  sqlite3_int64 iOffset;          /* Offset of next record in file */
+  char *zTransient;               /* Transient 'file' string */
+  int nFile;                      /* Size of array azFile[] */
+  char **azFile;                  /* File strings */
+  unsigned char aBuf[1024];       /* Current vfs log entry (read from file) */
+};
+
+static unsigned int get32bits(unsigned char *p){
+  return (p[0]<<24) + (p[1]<<16) + (p[2]<<8) + p[3];
+}
+
+/*
+** The argument must point to a buffer containing a nul-terminated string.
+** If the string begins with an SQL quote character it is overwritten by
+** the dequoted version. Otherwise the buffer is left unmodified.
+*/
+static void dequote(char *z){
+  char quote;                     /* Quote character (if any ) */
+  quote = z[0];
+  if( quote=='[' || quote=='\'' || quote=='"' || quote=='`' ){
+    int iIn = 1;                  /* Index of next byte to read from input */
+    int iOut = 0;                 /* Index of next byte to write to output */
+    if( quote=='[' ) quote = ']';  
+    while( z[iIn] ){
+      if( z[iIn]==quote ){
+        if( z[iIn+1]!=quote ) break;
+        z[iOut++] = quote;
+        iIn += 2;
+      }else{
+        z[iOut++] = z[iIn++];
+      }
+    }
+    z[iOut] = '\0';
+  }
+}
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Connect to or create a vfslog virtual table.
+*/
+static int vlogConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  sqlite3_vfs *pVfs;              /* VFS used to read log file */
+  int flags;                      /* flags passed to pVfs->xOpen() */
+  VfslogVtab *p;
+  int rc;
+  int nByte;
+  char *zFile;
+
+  *ppVtab = 0;
+  pVfs = sqlite3_vfs_find(0);
+  nByte = sizeof(VfslogVtab) + pVfs->szOsFile + pVfs->mxPathname;
+  p = sqlite3_malloc(nByte);
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, nByte);
+
+  p->pFd = (sqlite3_file *)&p[1];
+  p->zFile = &((char *)p->pFd)[pVfs->szOsFile];
+
+  zFile = sqlite3_mprintf("%s", argv[3]);
+  if( !zFile ){
+    sqlite3_free(p);
+    return SQLITE_NOMEM;
+  }
+  dequote(zFile);
+  pVfs->xFullPathname(pVfs, zFile, pVfs->mxPathname, p->zFile);
+  sqlite3_free(zFile);
+
+  flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_SUPER_JOURNAL;
+  rc = pVfs->xOpen(pVfs, p->zFile, p->pFd, flags, &flags);
+
+  if( rc==SQLITE_OK ){
+    p->pFd->pMethods->xFileSize(p->pFd, &p->nByte);
+    sqlite3_declare_vtab(db, 
+        "CREATE TABLE xxx(event, file, click, rc, size, offset)"
+    );
+    *ppVtab = &p->base;
+  }else{
+    sqlite3_free(p);
+  }
+
+  return rc;
+}
+
+/*
+** There is no "best-index". This virtual table always does a linear
+** scan of the binary VFS log file.
+*/
+static int vlogBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  pIdxInfo->estimatedCost = 10.0;
+  return SQLITE_OK;
+}
+
+/*
+** Disconnect from or destroy a vfslog virtual table.
+*/
+static int vlogDisconnect(sqlite3_vtab *pVtab){
+  VfslogVtab *p = (VfslogVtab *)pVtab;
+  if( p->pFd->pMethods ){
+    p->pFd->pMethods->xClose(p->pFd);
+    p->pFd->pMethods = 0;
+  }
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Open a new vfslog cursor.
+*/
+static int vlogOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  VfslogCsr *pCsr;                /* Newly allocated cursor object */
+
+  pCsr = sqlite3_malloc(sizeof(VfslogCsr));
+  if( !pCsr ) return SQLITE_NOMEM;
+  memset(pCsr, 0, sizeof(VfslogCsr));
+  *ppCursor = &pCsr->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a vfslog cursor.
+*/
+static int vlogClose(sqlite3_vtab_cursor *pCursor){
+  VfslogCsr *p = (VfslogCsr *)pCursor;
+  int i;
+  for(i=0; i<p->nFile; i++){
+    sqlite3_free(p->azFile[i]);
+  }
+  sqlite3_free(p->azFile);
+  sqlite3_free(p->zTransient);
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Move a vfslog cursor to the next entry in the file.
+*/
+static int vlogNext(sqlite3_vtab_cursor *pCursor){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  VfslogVtab *p = (VfslogVtab *)pCursor->pVtab;
+  int rc = SQLITE_OK;
+  int nRead;
+
+  sqlite3_free(pCsr->zTransient);
+  pCsr->zTransient = 0;
+
+  nRead = 24;
+  if( pCsr->iOffset+nRead<=p->nByte ){
+    int eEvent;
+    rc = p->pFd->pMethods->xRead(p->pFd, pCsr->aBuf, nRead, pCsr->iOffset);
+
+    eEvent = get32bits(pCsr->aBuf);
+    if( (rc==SQLITE_OK)
+     && (eEvent==OS_OPEN || eEvent==OS_DELETE || eEvent==OS_ACCESS) 
+    ){
+      char buf[4];
+      rc = p->pFd->pMethods->xRead(p->pFd, buf, 4, pCsr->iOffset+nRead);
+      nRead += 4;
+      if( rc==SQLITE_OK ){
+        int nStr = get32bits((unsigned char *)buf);
+        char *zStr = sqlite3_malloc(nStr+1);
+        rc = p->pFd->pMethods->xRead(p->pFd, zStr, nStr, pCsr->iOffset+nRead);
+        zStr[nStr] = '\0';
+        nRead += nStr;
+
+        if( eEvent==OS_OPEN ){
+          int iFileid = get32bits(&pCsr->aBuf[4]);
+          if( iFileid>=pCsr->nFile ){
+            int nNew = sizeof(pCsr->azFile[0])*(iFileid+1);
+            pCsr->azFile = (char **)sqlite3_realloc(pCsr->azFile, nNew);
+            nNew -= sizeof(pCsr->azFile[0])*pCsr->nFile;
+            memset(&pCsr->azFile[pCsr->nFile], 0, nNew);
+            pCsr->nFile = iFileid+1;
+          }
+          sqlite3_free(pCsr->azFile[iFileid]);
+          pCsr->azFile[iFileid] = zStr;
+        }else{
+          pCsr->zTransient = zStr;
+        }
+      }
+    }
+  }
+
+  pCsr->iRowid += 1;
+  pCsr->iOffset += nRead;
+  return rc;
+}
+
+static int vlogEof(sqlite3_vtab_cursor *pCursor){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  VfslogVtab *p = (VfslogVtab *)pCursor->pVtab;
+  return (pCsr->iOffset>=p->nByte);
+}
+
+static int vlogFilter(
+  sqlite3_vtab_cursor *pCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  pCsr->iRowid = 0;
+  pCsr->iOffset = 20;
+  return vlogNext(pCursor);
+}
+
+static int vlogColumn(
+  sqlite3_vtab_cursor *pCursor, 
+  sqlite3_context *ctx, 
+  int i
+){
+  unsigned int val;
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+
+  assert( i<7 );
+  val = get32bits(&pCsr->aBuf[4*i]);
+
+  switch( i ){
+    case 0: {
+      sqlite3_result_text(ctx, vfslog_eventname(val), -1, SQLITE_STATIC);
+      break;
+    }
+    case 1: {
+      char *zStr = pCsr->zTransient;
+      if( val!=0 && val<(unsigned)pCsr->nFile ){
+        zStr = pCsr->azFile[val];
+      }
+      sqlite3_result_text(ctx, zStr, -1, SQLITE_TRANSIENT);
+      break;
+    }
+    default:
+      sqlite3_result_int(ctx, val);
+      break;
+  }
+
+  return SQLITE_OK;
+}
+
+static int vlogRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  *pRowid = pCsr->iRowid;
+  return SQLITE_OK;
+}
+
+int sqlite3_vfslog_register(sqlite3 *db){
+  static sqlite3_module vfslog_module = {
+    0,                            /* iVersion */
+    vlogConnect,                /* xCreate */
+    vlogConnect,                /* xConnect */
+    vlogBestIndex,              /* xBestIndex */
+    vlogDisconnect,             /* xDisconnect */
+    vlogDisconnect,             /* xDestroy */
+    vlogOpen,                   /* xOpen - open a cursor */
+    vlogClose,                  /* xClose - close a cursor */
+    vlogFilter,                 /* xFilter - configure scan constraints */
+    vlogNext,                   /* xNext - advance a cursor */
+    vlogEof,                    /* xEof - check for end of scan */
+    vlogColumn,                 /* xColumn - read data */
+    vlogRowid,                  /* xRowid - read data */
+    0,                            /* xUpdate */
+    0,                            /* xBegin */
+    0,                            /* xSync */
+    0,                            /* xCommit */
+    0,                            /* xRollback */
+    0,                            /* xFindMethod */
+    0,                            /* xRename */
+    0,                            /* xSavepoint */
+    0,                            /* xRelease */
+    0,                            /* xRollbackTo */
+    0,                            /* xShadowName */
+    0                             /* xIntegrity */
+ };
+
+  sqlite3_create_module(db, "vfslog", &vfslog_module, 0);
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/**************************************************************************
+***************************************************************************
+** Tcl interface starts here.
+*/
+
+#if defined(SQLITE_TEST) || defined(TCLSH)
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+
+static int SQLITE_TCLAPI test_vfslog(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SqliteDb { sqlite3 *db; };
+  sqlite3 *db;
+  Tcl_CmdInfo cmdInfo;
+  int rc = SQLITE_ERROR;
+
+  static const char *strs[] = { "annotate", "finalize", "new",  "register", 0 };
+  enum VL_enum { VL_ANNOTATE, VL_FINALIZE, VL_NEW, VL_REGISTER };
+  int iSub;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], strs, "sub-command", 0, &iSub) ){
+    return TCL_ERROR;
+  }
+
+  switch( (enum VL_enum)iSub ){
+    case VL_ANNOTATE: {
+      char *zVfs;
+      char *zMsg;
+      if( objc!=4 ){
+        Tcl_WrongNumArgs(interp, 3, objv, "VFS");
+        return TCL_ERROR;
+      }
+      zVfs = Tcl_GetString(objv[2]);
+      zMsg = Tcl_GetString(objv[3]);
+      rc = sqlite3_vfslog_annotate(zVfs, zMsg);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "failed", 0);
+        return TCL_ERROR;
+      }
+      break;
+    }
+    case VL_FINALIZE: {
+      char *zVfs;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "VFS");
+        return TCL_ERROR;
+      }
+      zVfs = Tcl_GetString(objv[2]);
+      rc = sqlite3_vfslog_finalize(zVfs);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "failed", 0);
+        return TCL_ERROR;
+      }
+      break;
+    };
+
+    case VL_NEW: {
+      char *zVfs;
+      char *zParent;
+      char *zLog;
+      if( objc!=5 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "VFS PARENT LOGFILE");
+        return TCL_ERROR;
+      }
+      zVfs = Tcl_GetString(objv[2]);
+      zParent = Tcl_GetString(objv[3]);
+      zLog = Tcl_GetString(objv[4]);
+      if( *zParent=='\0' ) zParent = 0;
+      rc = sqlite3_vfslog_new(zVfs, zParent, zLog);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "failed", 0);
+        return TCL_ERROR;
+      }
+      break;
+    };
+
+    case VL_REGISTER: {
+      char *zDb;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "DB");
+        return TCL_ERROR;
+      }
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+      Tcl_AppendResult(interp, "vfslog not available because of "
+                               "SQLITE_OMIT_VIRTUALTABLE", (void*)0);
+      return TCL_ERROR;
+#else
+      zDb = Tcl_GetString(objv[2]);
+      if( Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+        db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+        rc = sqlite3_vfslog_register(db);
+      }
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "bad sqlite3 handle: ", zDb, (void*)0);
+        return TCL_ERROR;
+      }
+      break;
+#endif
+    }
+  }
+
+  return TCL_OK;
+}
+
+int SqlitetestOsinst_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "vfslog", test_vfslog, 0, 0);
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_pcache.c b/src/test_pcache.c
new file mode 100644
index 0000000..5266d67
--- /dev/null
+++ b/src/test_pcache.c
@@ -0,0 +1,467 @@
+/*
+** 2008 November 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used for testing the SQLite system.
+** None of the code in this file goes into a deliverable build.
+**
+** This file contains an application-defined pager cache
+** implementation that can be plugged in in place of the
+** default pcache.  This alternative pager cache will throw
+** some errors that the default cache does not.
+**
+** This pagecache implementation is designed for simplicity
+** not speed.
+*/
+#include "sqlite3.h"
+#include <string.h>
+#include <assert.h>
+
+/*
+** Global data used by this test implementation.  There is no
+** mutexing, which means this page cache will not work in a
+** multi-threaded test.
+*/
+typedef struct testpcacheGlobalType testpcacheGlobalType;
+struct testpcacheGlobalType {
+  void *pDummy;             /* Dummy allocation to simulate failures */
+  int nInstance;            /* Number of current instances */
+  unsigned discardChance;   /* Chance of discarding on an unpin (0-100) */
+  unsigned prngSeed;        /* Seed for the PRNG */
+  unsigned highStress;      /* Call xStress aggressively */
+};
+static testpcacheGlobalType testpcacheGlobal;
+
+/*
+** Initializer.
+**
+** Verify that the initializer is only called when the system is
+** uninitialized.  Allocate some memory and report SQLITE_NOMEM if
+** the allocation fails.  This provides a means to test the recovery
+** from a failed initialization attempt.  It also verifies that the
+** the destructor always gets call - otherwise there would be a
+** memory leak.
+*/
+static int testpcacheInit(void *pArg){
+  assert( pArg==(void*)&testpcacheGlobal );
+  assert( testpcacheGlobal.pDummy==0 );
+  assert( testpcacheGlobal.nInstance==0 );
+  testpcacheGlobal.pDummy = sqlite3_malloc(10);
+  return testpcacheGlobal.pDummy==0 ? SQLITE_NOMEM : SQLITE_OK;
+}
+
+/*
+** Destructor
+**
+** Verify that this is only called after initialization.
+** Free the memory allocated by the initializer.
+*/
+static void testpcacheShutdown(void *pArg){
+  assert( pArg==(void*)&testpcacheGlobal );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance==0 );
+  sqlite3_free( testpcacheGlobal.pDummy );
+  testpcacheGlobal.pDummy = 0;
+}
+
+/*
+** Number of pages in a cache.
+**
+** The number of pages is a hard upper bound in this test module.
+** If more pages are requested, sqlite3PcacheFetch() returns NULL.
+**
+** If testing with in-memory temp tables, provide a larger pcache.
+** Some of the test cases need this.
+*/
+#if defined(SQLITE_TEMP_STORE) && SQLITE_TEMP_STORE>=2
+# define TESTPCACHE_NPAGE    499
+#else
+# define TESTPCACHE_NPAGE    217
+#endif
+#define TESTPCACHE_RESERVE   17
+
+/*
+** Magic numbers used to determine validity of the page cache.
+*/
+#define TESTPCACHE_VALID  0x364585fd
+#define TESTPCACHE_CLEAR  0xd42670d4
+
+/*
+** Private implementation of a page cache.
+*/
+typedef struct testpcache testpcache;
+struct testpcache {
+  int szPage;               /* Size of each page.  Multiple of 8. */
+  int szExtra;              /* Size of extra data that accompanies each page */
+  int bPurgeable;           /* True if the page cache is purgeable */
+  int nFree;                /* Number of unused slots in a[] */
+  int nPinned;              /* Number of pinned slots in a[] */
+  unsigned iRand;           /* State of the PRNG */
+  unsigned iMagic;          /* Magic number for sanity checking */
+  struct testpcachePage {
+    sqlite3_pcache_page page;  /* Base class */
+    unsigned key;              /* The key for this page. 0 means unallocated */
+    int isPinned;              /* True if the page is pinned */
+  } a[TESTPCACHE_NPAGE];    /* All pages in the cache */
+};
+
+/*
+** Get a random number using the PRNG in the given page cache.
+*/
+static unsigned testpcacheRandom(testpcache *p){
+  unsigned x = 0;
+  int i;
+  for(i=0; i<4; i++){
+    p->iRand = (p->iRand*69069 + 5);
+    x = (x<<8) | ((p->iRand>>16)&0xff);
+  }
+  return x;
+}
+
+
+/*
+** Allocate a new page cache instance.
+*/
+static sqlite3_pcache *testpcacheCreate(
+  int szPage,
+  int szExtra,
+  int bPurgeable
+){
+  int nMem;
+  char *x;
+  testpcache *p;
+  int i;
+  assert( testpcacheGlobal.pDummy!=0 );
+  szPage = (szPage+7)&~7;
+  nMem = sizeof(testpcache) + TESTPCACHE_NPAGE*(szPage+szExtra);
+  p = sqlite3_malloc( nMem );
+  if( p==0 ) return 0;
+  x = (char*)&p[1];
+  p->szPage = szPage;
+  p->szExtra = szExtra;
+  p->nFree = TESTPCACHE_NPAGE;
+  p->nPinned = 0;
+  p->iRand = testpcacheGlobal.prngSeed;
+  p->bPurgeable = bPurgeable;
+  p->iMagic = TESTPCACHE_VALID;
+  for(i=0; i<TESTPCACHE_NPAGE; i++, x += (szPage+szExtra)){
+    p->a[i].key = 0;
+    p->a[i].isPinned = 0;
+    p->a[i].page.pBuf = (void*)x;
+    p->a[i].page.pExtra = (void*)&x[szPage];
+  }
+  testpcacheGlobal.nInstance++;
+  return (sqlite3_pcache*)p;
+}
+
+/*
+** Set the cache size
+*/
+static void testpcacheCachesize(sqlite3_pcache *pCache, int newSize){
+  testpcache *p = (testpcache*)pCache;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+}
+
+/*
+** Return the number of pages in the cache that are being used.
+** This includes both pinned and unpinned pages.
+*/
+static int testpcachePagecount(sqlite3_pcache *pCache){
+  testpcache *p = (testpcache*)pCache;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+  return TESTPCACHE_NPAGE - p->nFree;
+}
+
+/*
+** Fetch a page.
+*/
+static sqlite3_pcache_page *testpcacheFetch(
+  sqlite3_pcache *pCache,
+  unsigned key,
+  int createFlag
+){
+  testpcache *p = (testpcache*)pCache;
+  int i, j;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+
+  /* See if the page is already in cache.  Return immediately if it is */
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key==key ){
+      if( !p->a[i].isPinned ){
+        p->nPinned++;
+        assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
+        p->a[i].isPinned = 1;
+      }
+      return &p->a[i].page;
+    }
+  }
+
+  /* If createFlag is 0, never allocate a new page */
+  if( createFlag==0 ){
+    return 0;
+  }
+
+  /* If no pages are available, always fail */
+  if( p->nPinned==TESTPCACHE_NPAGE ){
+    return 0;
+  }
+
+  /* Do not allocate the last TESTPCACHE_RESERVE pages unless createFlag is 2 */
+  if( p->nPinned>=TESTPCACHE_NPAGE-TESTPCACHE_RESERVE && createFlag<2 ){
+    return 0;
+  }
+
+  /* Do not allocate if highStress is enabled and createFlag is not 2.
+  **
+  ** The highStress setting causes pagerStress() to be called much more
+  ** often, which exercises the pager logic more intensely.
+  */
+  if( testpcacheGlobal.highStress && createFlag<2 ){
+    return 0;
+  }
+
+  /* Find a free page to allocate if there are any free pages.
+  ** Withhold TESTPCACHE_RESERVE free pages until createFlag is 2.
+  */
+  if( p->nFree>TESTPCACHE_RESERVE || (createFlag==2 && p->nFree>0) ){
+    j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
+    for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
+      if( p->a[j].key==0 ){
+        p->a[j].key = key;
+        p->a[j].isPinned = 1;
+        memset(p->a[j].page.pBuf, 0, p->szPage);
+        memset(p->a[j].page.pExtra, 0, p->szExtra);
+        p->nPinned++;
+        p->nFree--;
+        assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
+        return &p->a[j].page;
+      }
+    }
+
+    /* The prior loop always finds a freepage to allocate */
+    assert( 0 );
+  }
+
+  /* If this cache is not purgeable then we have to fail.
+  */
+  if( p->bPurgeable==0 ){
+    return 0;
+  }
+
+  /* If there are no free pages, recycle a page.  The page to
+  ** recycle is selected at random from all unpinned pages.
+  */
+  j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
+  for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
+    if( p->a[j].key>0 && p->a[j].isPinned==0 ){
+      p->a[j].key = key;
+      p->a[j].isPinned = 1;
+      memset(p->a[j].page.pBuf, 0, p->szPage);
+      memset(p->a[j].page.pExtra, 0, p->szExtra);
+      p->nPinned++;
+      assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
+      return &p->a[j].page;
+    }
+  }
+
+  /* The previous loop always finds a page to recycle. */
+  assert(0);
+  return 0;
+}
+
+/*
+** Unpin a page.
+*/
+static void testpcacheUnpin(
+  sqlite3_pcache *pCache,
+  sqlite3_pcache_page *pOldPage,
+  int discard
+){
+  testpcache *p = (testpcache*)pCache;
+  int i;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+
+  /* Randomly discard pages as they are unpinned according to the
+  ** discardChance setting.  If discardChance is 0, the random discard
+  ** never happens.  If discardChance is 100, it always happens.
+  */
+  if( p->bPurgeable
+  && (100-testpcacheGlobal.discardChance) <= (testpcacheRandom(p)%100)
+  ){
+    discard = 1;
+  }
+
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( &p->a[i].page==pOldPage ){
+      /* The pOldPage pointer always points to a pinned page */
+      assert( p->a[i].isPinned );
+      p->a[i].isPinned = 0;
+      p->nPinned--;
+      assert( p->nPinned>=0 );
+      if( discard ){
+        p->a[i].key = 0;
+        p->nFree++;
+        assert( p->nFree<=TESTPCACHE_NPAGE );
+      }
+      return;
+    }
+  }
+
+  /* The pOldPage pointer always points to a valid page */
+  assert( 0 );
+}
+
+
+/*
+** Rekey a single page.
+*/
+static void testpcacheRekey(
+  sqlite3_pcache *pCache,
+  sqlite3_pcache_page *pOldPage,
+  unsigned oldKey,
+  unsigned newKey
+){
+  testpcache *p = (testpcache*)pCache;
+  int i;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+
+  /* If there already exists another page at newKey, verify that
+  ** the other page is unpinned and discard it.
+  */
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key==newKey ){
+      /* The new key is never a page that is already pinned */
+      assert( p->a[i].isPinned==0 );
+      p->a[i].key = 0;
+      p->nFree++;
+      assert( p->nFree<=TESTPCACHE_NPAGE );
+      break;
+    }
+  }
+
+  /* Find the page to be rekeyed and rekey it.
+  */
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key==oldKey ){
+      /* The oldKey and pOldPage parameters match */
+      assert( &p->a[i].page==pOldPage );
+      /* Page to be rekeyed must be pinned */
+      assert( p->a[i].isPinned );
+      p->a[i].key = newKey;
+      return;
+    }
+  }
+
+  /* Rekey is always given a valid page to work with */
+  assert( 0 );
+}
+
+
+/*
+** Truncate the page cache.  Every page with a key of iLimit or larger
+** is discarded.
+*/
+static void testpcacheTruncate(sqlite3_pcache *pCache, unsigned iLimit){
+  testpcache *p = (testpcache*)pCache;
+  unsigned int i;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key>=iLimit ){
+      p->a[i].key = 0;
+      if( p->a[i].isPinned ){
+        p->nPinned--;
+        assert( p->nPinned>=0 );
+      }
+      p->nFree++;
+      assert( p->nFree<=TESTPCACHE_NPAGE );
+    }
+  }
+}
+
+/*
+** Destroy a page cache.
+*/
+static void testpcacheDestroy(sqlite3_pcache *pCache){
+  testpcache *p = (testpcache*)pCache;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+  p->iMagic = TESTPCACHE_CLEAR;
+  sqlite3_free(p);
+  testpcacheGlobal.nInstance--;
+}
+
+
+/*
+** Invoke this routine to register or unregister the testing pager cache
+** implemented by this file.
+**
+** Install the test pager cache if installFlag is 1 and uninstall it if
+** installFlag is 0.
+**
+** When installing, discardChance is a number between 0 and 100 that
+** indicates the probability of discarding a page when unpinning the
+** page.  0 means never discard (unless the discard flag is set).
+** 100 means always discard.
+*/
+void installTestPCache(
+  int installFlag,            /* True to install.  False to uninstall. */
+  unsigned discardChance,     /* 0-100.  Chance to discard on unpin */
+  unsigned prngSeed,          /* Seed for the PRNG */
+  unsigned highStress         /* Call xStress aggressively */
+){
+  static const sqlite3_pcache_methods2 testPcache = {
+    1,
+    (void*)&testpcacheGlobal,
+    testpcacheInit,
+    testpcacheShutdown,
+    testpcacheCreate,
+    testpcacheCachesize,
+    testpcachePagecount,
+    testpcacheFetch,
+    testpcacheUnpin,
+    testpcacheRekey,
+    testpcacheTruncate,
+    testpcacheDestroy,
+  };
+  static sqlite3_pcache_methods2 defaultPcache;
+  static int isInstalled = 0;
+
+  assert( testpcacheGlobal.nInstance==0 );
+  assert( testpcacheGlobal.pDummy==0 );
+  assert( discardChance<=100 );
+  testpcacheGlobal.discardChance = discardChance;
+  testpcacheGlobal.prngSeed = prngSeed ^ (prngSeed<<16);
+  testpcacheGlobal.highStress = highStress;
+  if( installFlag!=isInstalled ){
+    if( installFlag ){
+      sqlite3_config(SQLITE_CONFIG_GETPCACHE2, &defaultPcache);
+      assert( defaultPcache.xCreate!=testpcacheCreate );
+      sqlite3_config(SQLITE_CONFIG_PCACHE2, &testPcache);
+    }else{
+      assert( defaultPcache.xCreate!=0 );
+      sqlite3_config(SQLITE_CONFIG_PCACHE2, &defaultPcache);
+    }
+    isInstalled = installFlag;
+  }
+}
diff --git a/src/test_quota.c b/src/test_quota.c
new file mode 100644
index 0000000..b436de4
--- /dev/null
+++ b/src/test_quota.c
@@ -0,0 +1,1979 @@
+/*
+** 2010 September 31
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a VFS "shim" - a layer that sits in between the
+** pager and the real VFS.
+**
+** This particular shim enforces a quota system on files.  One or more
+** database files are in a "quota group" that is defined by a GLOB
+** pattern.  A quota is set for the combined size of all files in the
+** the group.  A quota of zero means "no limit".  If the total size
+** of all files in the quota group is greater than the limit, then
+** write requests that attempt to enlarge a file fail with SQLITE_FULL.
+**
+** However, before returning SQLITE_FULL, the write requests invoke
+** a callback function that is configurable for each quota group.
+** This callback has the opportunity to enlarge the quota.  If the
+** callback does enlarge the quota such that the total size of all
+** files within the group is less than the new quota, then the write
+** continues as if nothing had happened.
+*/
+#include "test_quota.h"
+#include <string.h>
+#include <assert.h>
+
+/*
+** For an build without mutexes, no-op the mutex calls.
+*/
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE==0
+#define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
+#define sqlite3_mutex_free(X)
+#define sqlite3_mutex_enter(X)
+#define sqlite3_mutex_try(X)      SQLITE_OK
+#define sqlite3_mutex_leave(X)
+#define sqlite3_mutex_held(X)     ((void)(X),1)
+#define sqlite3_mutex_notheld(X)  ((void)(X),1)
+#endif /* SQLITE_THREADSAFE==0 */
+
+#include "os_setup.h"
+
+#if SQLITE_OS_UNIX
+# include <unistd.h>
+#endif
+#if SQLITE_OS_WIN
+# include "os_win.h"
+# include <io.h>
+#endif
+
+
+/************************ Object Definitions ******************************/
+
+/* Forward declaration of all object types */
+typedef struct quotaGroup quotaGroup;
+typedef struct quotaConn quotaConn;
+typedef struct quotaFile quotaFile;
+
+/*
+** A "quota group" is a collection of files whose collective size we want
+** to limit.  Each quota group is defined by a GLOB pattern.
+**
+** There is an instance of the following object for each defined quota
+** group.  This object records the GLOB pattern that defines which files
+** belong to the quota group.  The object also remembers the size limit
+** for the group (the quota) and the callback to be invoked when the
+** sum of the sizes of the files within the group goes over the limit.
+**
+** A quota group must be established (using sqlite3_quota_set(...))
+** prior to opening any of the database connections that access files
+** within the quota group.
+*/
+struct quotaGroup {
+  const char *zPattern;          /* Filename pattern to be quotaed */
+  sqlite3_int64 iLimit;          /* Upper bound on total file size */
+  sqlite3_int64 iSize;           /* Current size of all files */
+  void (*xCallback)(             /* Callback invoked when going over quota */
+     const char *zFilename,         /* Name of file whose size increases */
+     sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
+     sqlite3_int64 iSize,           /* Total size of all files in the group */
+     void *pArg                     /* Client data */
+  );
+  void *pArg;                    /* Third argument to the xCallback() */
+  void (*xDestroy)(void*);       /* Optional destructor for pArg */
+  quotaGroup *pNext, **ppPrev;   /* Doubly linked list of all quota objects */
+  quotaFile *pFiles;             /* Files within this group */
+};
+
+/*
+** An instance of this structure represents a single file that is part
+** of a quota group.  A single file can be opened multiple times.  In
+** order keep multiple openings of the same file from causing the size
+** of the file to count against the quota multiple times, each file
+** has a unique instance of this object and multiple open connections
+** to the same file each point to a single instance of this object.
+*/
+struct quotaFile {
+  char *zFilename;                /* Name of this file */
+  quotaGroup *pGroup;             /* Quota group to which this file belongs */
+  sqlite3_int64 iSize;            /* Current size of this file */
+  int nRef;                       /* Number of times this file is open */
+  int deleteOnClose;              /* True to delete this file when it closes */
+  quotaFile *pNext, **ppPrev;     /* Linked list of files in the same group */
+};
+
+/*
+** An instance of the following object represents each open connection
+** to a file that participates in quota tracking.  This object is a
+** subclass of sqlite3_file.  The sqlite3_file object for the underlying
+** VFS is appended to this structure.
+*/
+struct quotaConn {
+  sqlite3_file base;              /* Base class - must be first */
+  quotaFile *pFile;               /* The underlying file */
+  /* The underlying VFS sqlite3_file is appended to this object */
+};
+
+/*
+** An instance of the following object records the state of an
+** open file.  This object is opaque to all users - the internal
+** structure is only visible to the functions below.
+*/
+struct quota_FILE {
+  FILE *f;                /* Open stdio file pointer */
+  sqlite3_int64 iOfst;    /* Current offset into the file */
+  quotaFile *pFile;       /* The file record in the quota system */
+#if SQLITE_OS_WIN
+  char *zMbcsName;        /* Full MBCS pathname of the file */
+#endif
+};
+
+
+/************************* Global Variables **********************************/
+/*
+** All global variables used by this file are containing within the following
+** gQuota structure.
+*/
+static struct {
+  /* The pOrigVfs is the real, original underlying VFS implementation.
+  ** Most operations pass-through to the real VFS.  This value is read-only
+  ** during operation.  It is only modified at start-time and thus does not
+  ** require a mutex.
+  */
+  sqlite3_vfs *pOrigVfs;
+
+  /* The sThisVfs is the VFS structure used by this shim.  It is initialized
+  ** at start-time and thus does not require a mutex
+  */
+  sqlite3_vfs sThisVfs;
+
+  /* The sIoMethods defines the methods used by sqlite3_file objects
+  ** associated with this shim.  It is initialized at start-time and does
+  ** not require a mutex.
+  **
+  ** When the underlying VFS is called to open a file, it might return
+  ** either a version 1 or a version 2 sqlite3_file object.  This shim
+  ** has to create a wrapper sqlite3_file of the same version.  Hence
+  ** there are two I/O method structures, one for version 1 and the other
+  ** for version 2.
+  */
+  sqlite3_io_methods sIoMethodsV1;
+  sqlite3_io_methods sIoMethodsV2;
+
+  /* True when this shim as been initialized.
+  */
+  int isInitialized;
+
+  /* For run-time access any of the other global data structures in this
+  ** shim, the following mutex must be held.
+  */
+  sqlite3_mutex *pMutex;
+
+  /* List of quotaGroup objects.
+  */
+  quotaGroup *pGroup;
+
+} gQuota;
+
+/************************* Utility Routines *********************************/
+/*
+** Acquire and release the mutex used to serialize access to the
+** list of quotaGroups.
+*/
+static void quotaEnter(void){ sqlite3_mutex_enter(gQuota.pMutex); }
+static void quotaLeave(void){ sqlite3_mutex_leave(gQuota.pMutex); }
+
+/* Count the number of open files in a quotaGroup
+*/
+static int quotaGroupOpenFileCount(quotaGroup *pGroup){
+  int N = 0;
+  quotaFile *pFile = pGroup->pFiles;
+  while( pFile ){
+    if( pFile->nRef ) N++;
+    pFile = pFile->pNext;
+  }
+  return N;
+}
+
+/* Remove a file from a quota group.
+*/
+static void quotaRemoveFile(quotaFile *pFile){
+  quotaGroup *pGroup = pFile->pGroup;
+  pGroup->iSize -= pFile->iSize;
+  *pFile->ppPrev = pFile->pNext;
+  if( pFile->pNext ) pFile->pNext->ppPrev = pFile->ppPrev;
+  sqlite3_free(pFile);
+}
+
+/* Remove all files from a quota group.  It is always the case that
+** all files will be closed when this routine is called.
+*/
+static void quotaRemoveAllFiles(quotaGroup *pGroup){
+  while( pGroup->pFiles ){
+    assert( pGroup->pFiles->nRef==0 );
+    quotaRemoveFile(pGroup->pFiles);
+  }
+}
+
+
+/* If the reference count and threshold for a quotaGroup are both
+** zero, then destroy the quotaGroup.
+*/
+static void quotaGroupDeref(quotaGroup *pGroup){
+  if( pGroup->iLimit==0 && quotaGroupOpenFileCount(pGroup)==0 ){
+    quotaRemoveAllFiles(pGroup);
+    *pGroup->ppPrev = pGroup->pNext;
+    if( pGroup->pNext ) pGroup->pNext->ppPrev = pGroup->ppPrev;
+    if( pGroup->xDestroy ) pGroup->xDestroy(pGroup->pArg);
+    sqlite3_free(pGroup);
+  }
+}
+
+/*
+** Return TRUE if string z matches glob pattern zGlob.
+**
+** Globbing rules:
+**
+**      '*'       Matches any sequence of zero or more characters.
+**
+**      '?'       Matches exactly one character.
+**
+**     [...]      Matches one character from the enclosed list of
+**                characters.
+**
+**     [^...]     Matches one character not in the enclosed list.
+**
+**     /          Matches "/" or "\\"
+**
+*/
+static int quotaStrglob(const char *zGlob, const char *z){
+  int c, c2, cx;
+  int invert;
+  int seen;
+
+  while( (c = (*(zGlob++)))!=0 ){
+    if( c=='*' ){
+      while( (c=(*(zGlob++))) == '*' || c=='?' ){
+        if( c=='?' && (*(z++))==0 ) return 0;
+      }
+      if( c==0 ){
+        return 1;
+      }else if( c=='[' ){
+        while( *z && quotaStrglob(zGlob-1,z)==0 ){
+          z++;
+        }
+        return (*z)!=0;
+      }
+      cx = (c=='/') ? '\\' : c;
+      while( (c2 = (*(z++)))!=0 ){
+        while( c2!=c && c2!=cx ){
+          c2 = *(z++);
+          if( c2==0 ) return 0;
+        }
+        if( quotaStrglob(zGlob,z) ) return 1;
+      }
+      return 0;
+    }else if( c=='?' ){
+      if( (*(z++))==0 ) return 0;
+    }else if( c=='[' ){
+      int prior_c = 0;
+      seen = 0;
+      invert = 0;
+      c = *(z++);
+      if( c==0 ) return 0;
+      c2 = *(zGlob++);
+      if( c2=='^' ){
+        invert = 1;
+        c2 = *(zGlob++);
+      }
+      if( c2==']' ){
+        if( c==']' ) seen = 1;
+        c2 = *(zGlob++);
+      }
+      while( c2 && c2!=']' ){
+        if( c2=='-' && zGlob[0]!=']' && zGlob[0]!=0 && prior_c>0 ){
+          c2 = *(zGlob++);
+          if( c>=prior_c && c<=c2 ) seen = 1;
+          prior_c = 0;
+        }else{
+          if( c==c2 ){
+            seen = 1;
+          }
+          prior_c = c2;
+        }
+        c2 = *(zGlob++);
+      }
+      if( c2==0 || (seen ^ invert)==0 ) return 0;
+    }else if( c=='/' ){
+      if( z[0]!='/' && z[0]!='\\' ) return 0;
+      z++;
+    }else{
+      if( c!=(*(z++)) ) return 0;
+    }
+  }
+  return *z==0;
+}
+
+
+/* Find a quotaGroup given the filename.
+**
+** Return a pointer to the quotaGroup object. Return NULL if not found.
+*/
+static quotaGroup *quotaGroupFind(const char *zFilename){
+  quotaGroup *p;
+  for(p=gQuota.pGroup; p && quotaStrglob(p->zPattern, zFilename)==0;
+      p=p->pNext){}
+  return p;
+}
+
+/* Translate an sqlite3_file* that is really a quotaConn* into
+** the sqlite3_file* for the underlying original VFS.
+*/
+static sqlite3_file *quotaSubOpen(sqlite3_file *pConn){
+  quotaConn *p = (quotaConn*)pConn;
+  return (sqlite3_file*)&p[1];
+}
+
+/* Find a file in a quota group and return a pointer to that file.
+** Return NULL if the file is not in the group.
+*/
+static quotaFile *quotaFindFile(
+  quotaGroup *pGroup,     /* Group in which to look for the file */
+  const char *zName,      /* Full pathname of the file */
+  int createFlag          /* Try to create the file if not found */
+){
+  quotaFile *pFile = pGroup->pFiles;
+  while( pFile && strcmp(pFile->zFilename, zName)!=0 ){
+    pFile = pFile->pNext;
+  }
+  if( pFile==0 && createFlag ){
+    int nName = (int)(strlen(zName) & 0x3fffffff);
+    pFile = (quotaFile *)sqlite3_malloc( sizeof(*pFile) + nName + 1 );
+    if( pFile ){
+      memset(pFile, 0, sizeof(*pFile));
+      pFile->zFilename = (char*)&pFile[1];
+      memcpy(pFile->zFilename, zName, nName+1);
+      pFile->pNext = pGroup->pFiles;
+      if( pGroup->pFiles ) pGroup->pFiles->ppPrev = &pFile->pNext;
+      pFile->ppPrev = &pGroup->pFiles;
+      pGroup->pFiles = pFile;
+      pFile->pGroup = pGroup;
+    }
+  }
+  return pFile;
+}
+/*
+** Translate UTF8 to MBCS for use in fopen() calls.  Return a pointer to the
+** translated text..  Call quota_mbcs_free() to deallocate any memory
+** used to store the returned pointer when done.
+*/
+static char *quota_utf8_to_mbcs(const char *zUtf8){
+#if SQLITE_OS_WIN
+  size_t n;          /* Bytes in zUtf8 */
+  int nWide;         /* number of UTF-16 characters */
+  int nMbcs;         /* Bytes of MBCS */
+  LPWSTR zTmpWide;   /* The UTF16 text */
+  char *zMbcs;       /* The MBCS text */
+  int codepage;      /* Code page used by fopen() */
+
+  n = strlen(zUtf8);
+  nWide = MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, NULL, 0);
+  if( nWide==0 ) return 0;
+  zTmpWide = (LPWSTR)sqlite3_malloc( (nWide+1)*sizeof(zTmpWide[0]) );
+  if( zTmpWide==0 ) return 0;
+  MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, zTmpWide, nWide);
+  codepage = AreFileApisANSI() ? CP_ACP : CP_OEMCP;
+  nMbcs = WideCharToMultiByte(codepage, 0, zTmpWide, nWide, 0, 0, 0, 0);
+  zMbcs = nMbcs ? (char*)sqlite3_malloc( nMbcs+1 ) : 0;
+  if( zMbcs ){
+    WideCharToMultiByte(codepage, 0, zTmpWide, nWide, zMbcs, nMbcs, 0, 0);
+  }
+  sqlite3_free(zTmpWide);
+  return zMbcs;
+#else
+  return (char*)zUtf8;  /* No-op on unix */
+#endif
+}
+
+/*
+** Deallocate any memory allocated by quota_utf8_to_mbcs().
+*/
+static void quota_mbcs_free(char *zOld){
+#if SQLITE_OS_WIN
+  sqlite3_free(zOld);
+#else
+  /* No-op on unix */
+#endif
+}
+
+/************************* VFS Method Wrappers *****************************/
+/*
+** This is the xOpen method used for the "quota" VFS.
+**
+** Most of the work is done by the underlying original VFS.  This method
+** simply links the new file into the appropriate quota group if it is a
+** file that needs to be tracked.
+*/
+static int quotaOpen(
+  sqlite3_vfs *pVfs,          /* The quota VFS */
+  const char *zName,          /* Name of file to be opened */
+  sqlite3_file *pConn,        /* Fill in this file descriptor */
+  int flags,                  /* Flags to control the opening */
+  int *pOutFlags              /* Flags showing results of opening */
+){
+  int rc;                                    /* Result code */
+  quotaConn *pQuotaOpen;                     /* The new quota file descriptor */
+  quotaFile *pFile;                          /* Corresponding quotaFile obj */
+  quotaGroup *pGroup;                        /* The group file belongs to */
+  sqlite3_file *pSubOpen;                    /* Real file descriptor */
+  sqlite3_vfs *pOrigVfs = gQuota.pOrigVfs;   /* Real VFS */
+
+  /* If the file is not a main database file or a WAL, then use the
+  ** normal xOpen method.
+  */
+  if( (flags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_WAL))==0 ){
+    return pOrigVfs->xOpen(pOrigVfs, zName, pConn, flags, pOutFlags);
+  }
+
+  /* If the name of the file does not match any quota group, then
+  ** use the normal xOpen method.
+  */
+  quotaEnter();
+  pGroup = quotaGroupFind(zName);
+  if( pGroup==0 ){
+    rc = pOrigVfs->xOpen(pOrigVfs, zName, pConn, flags, pOutFlags);
+  }else{
+    /* If we get to this point, it means the file needs to be quota tracked.
+    */
+    pQuotaOpen = (quotaConn*)pConn;
+    pSubOpen = quotaSubOpen(pConn);
+    rc = pOrigVfs->xOpen(pOrigVfs, zName, pSubOpen, flags, pOutFlags);
+    if( rc==SQLITE_OK ){
+      pFile = quotaFindFile(pGroup, zName, 1);
+      if( pFile==0 ){
+        quotaLeave();
+        pSubOpen->pMethods->xClose(pSubOpen);
+        return SQLITE_NOMEM;
+      }
+      pFile->deleteOnClose = (flags & SQLITE_OPEN_DELETEONCLOSE)!=0;
+      pFile->nRef++;
+      pQuotaOpen->pFile = pFile;
+      if( pSubOpen->pMethods->iVersion==1 ){
+        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV1;
+      }else{
+        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV2;
+      }
+    }
+  }
+  quotaLeave();
+  return rc;
+}
+
+/*
+** This is the xDelete method used for the "quota" VFS.
+**
+** If the file being deleted is part of the quota group, then reduce
+** the size of the quota group accordingly.  And remove the file from
+** the set of files in the quota group.
+*/
+static int quotaDelete(
+  sqlite3_vfs *pVfs,          /* The quota VFS */
+  const char *zName,          /* Name of file to be deleted */
+  int syncDir                 /* Do a directory sync after deleting */
+){
+  int rc;                                    /* Result code */
+  quotaFile *pFile;                          /* Files in the quota */
+  quotaGroup *pGroup;                        /* The group file belongs to */
+  sqlite3_vfs *pOrigVfs = gQuota.pOrigVfs;   /* Real VFS */
+
+  /* Do the actual file delete */
+  rc = pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
+
+  /* If the file just deleted is a member of a quota group, then remove
+  ** it from that quota group.
+  */
+  if( rc==SQLITE_OK ){
+    quotaEnter();
+    pGroup = quotaGroupFind(zName);
+    if( pGroup ){
+      pFile = quotaFindFile(pGroup, zName, 0);
+      if( pFile ){
+        if( pFile->nRef ){
+          pFile->deleteOnClose = 1;
+        }else{
+          quotaRemoveFile(pFile);
+          quotaGroupDeref(pGroup);
+        }
+      }
+    }
+    quotaLeave();
+  }
+  return rc;
+}
+
+
+/************************ I/O Method Wrappers *******************************/
+
+/* xClose requests get passed through to the original VFS.  But we
+** also have to unlink the quotaConn from the quotaFile and quotaGroup.
+** The quotaFile and/or quotaGroup are freed if they are no longer in use.
+*/
+static int quotaClose(sqlite3_file *pConn){
+  quotaConn *p = (quotaConn*)pConn;
+  quotaFile *pFile = p->pFile;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  int rc;
+  rc = pSubOpen->pMethods->xClose(pSubOpen);
+  quotaEnter();
+  pFile->nRef--;
+  if( pFile->nRef==0 ){
+    quotaGroup *pGroup = pFile->pGroup;
+    if( pFile->deleteOnClose ){
+      gQuota.pOrigVfs->xDelete(gQuota.pOrigVfs, pFile->zFilename, 0);
+      quotaRemoveFile(pFile);
+    }
+    quotaGroupDeref(pGroup);
+  }
+  quotaLeave();
+  return rc;
+}
+
+/* Pass xRead requests directory thru to the original VFS without
+** further processing.
+*/
+static int quotaRead(
+  sqlite3_file *pConn,
+  void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
+}
+
+/* Check xWrite requests to see if they expand the file.  If they do,
+** the perform a quota check before passing them through to the
+** original VFS.
+*/
+static int quotaWrite(
+  sqlite3_file *pConn,
+  const void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  quotaConn *p = (quotaConn*)pConn;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  sqlite3_int64 iEnd = iOfst+iAmt;
+  quotaGroup *pGroup;
+  quotaFile *pFile = p->pFile;
+  sqlite3_int64 szNew;
+
+  if( pFile->iSize<iEnd ){
+    pGroup = pFile->pGroup;
+    quotaEnter();
+    szNew = pGroup->iSize - pFile->iSize + iEnd;
+    if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
+      if( pGroup->xCallback ){
+        pGroup->xCallback(pFile->zFilename, &pGroup->iLimit, szNew,
+                          pGroup->pArg);
+      }
+      if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
+        quotaLeave();
+        return SQLITE_FULL;
+      }
+    }
+    pGroup->iSize = szNew;
+    pFile->iSize = iEnd;
+    quotaLeave();
+  }
+  return pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
+}
+
+/* Pass xTruncate requests thru to the original VFS.  If the
+** success, update the file size.
+*/
+static int quotaTruncate(sqlite3_file *pConn, sqlite3_int64 size){
+  quotaConn *p = (quotaConn*)pConn;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  int rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
+  quotaFile *pFile = p->pFile;
+  quotaGroup *pGroup;
+  if( rc==SQLITE_OK ){
+    quotaEnter();
+    pGroup = pFile->pGroup;
+    pGroup->iSize -= pFile->iSize;
+    pFile->iSize = size;
+    pGroup->iSize += size;
+    quotaLeave();
+  }
+  return rc;
+}
+
+/* Pass xSync requests through to the original VFS without change
+*/
+static int quotaSync(sqlite3_file *pConn, int flags){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xSync(pSubOpen, flags);
+}
+
+/* Pass xFileSize requests through to the original VFS but then
+** update the quotaGroup with the new size before returning.
+*/
+static int quotaFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
+  quotaConn *p = (quotaConn*)pConn;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  quotaFile *pFile = p->pFile;
+  quotaGroup *pGroup;
+  sqlite3_int64 sz;
+  int rc;
+
+  rc = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
+  if( rc==SQLITE_OK ){
+    quotaEnter();
+    pGroup = pFile->pGroup;
+    pGroup->iSize -= pFile->iSize;
+    pFile->iSize = sz;
+    pGroup->iSize += sz;
+    quotaLeave();
+    *pSize = sz;
+  }
+  return rc;
+}
+
+/* Pass xLock requests through to the original VFS unchanged.
+*/
+static int quotaLock(sqlite3_file *pConn, int lock){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xLock(pSubOpen, lock);
+}
+
+/* Pass xUnlock requests through to the original VFS unchanged.
+*/
+static int quotaUnlock(sqlite3_file *pConn, int lock){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
+}
+
+/* Pass xCheckReservedLock requests through to the original VFS unchanged.
+*/
+static int quotaCheckReservedLock(sqlite3_file *pConn, int *pResOut){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
+}
+
+/* Pass xFileControl requests through to the original VFS unchanged.
+*/
+static int quotaFileControl(sqlite3_file *pConn, int op, void *pArg){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  int rc = pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
+#if defined(SQLITE_FCNTL_VFSNAME)
+  if( op==SQLITE_FCNTL_VFSNAME && rc==SQLITE_OK ){
+    *(char**)pArg = sqlite3_mprintf("quota/%z", *(char**)pArg);
+  }
+#endif
+  return rc;
+}
+
+/* Pass xSectorSize requests through to the original VFS unchanged.
+*/
+static int quotaSectorSize(sqlite3_file *pConn){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xSectorSize(pSubOpen);
+}
+
+/* Pass xDeviceCharacteristics requests through to the original VFS unchanged.
+*/
+static int quotaDeviceCharacteristics(sqlite3_file *pConn){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
+}
+
+/* Pass xShmMap requests through to the original VFS unchanged.
+*/
+static int quotaShmMap(
+  sqlite3_file *pConn,            /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend, pp);
+}
+
+/* Pass xShmLock requests through to the original VFS unchanged.
+*/
+static int quotaShmLock(
+  sqlite3_file *pConn,       /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
+}
+
+/* Pass xShmBarrier requests through to the original VFS unchanged.
+*/
+static void quotaShmBarrier(sqlite3_file *pConn){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  pSubOpen->pMethods->xShmBarrier(pSubOpen);
+}
+
+/* Pass xShmUnmap requests through to the original VFS unchanged.
+*/
+static int quotaShmUnmap(sqlite3_file *pConn, int deleteFlag){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
+}
+
+/************************** Public Interfaces *****************************/
+/*
+** Initialize the quota VFS shim.  Use the VFS named zOrigVfsName
+** as the VFS that does the actual work.  Use the default if
+** zOrigVfsName==NULL.
+**
+** The quota VFS shim is named "quota".  It will become the default
+** VFS if makeDefault is non-zero.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
+** during start-up.
+*/
+int sqlite3_quota_initialize(const char *zOrigVfsName, int makeDefault){
+  sqlite3_vfs *pOrigVfs;
+  if( gQuota.isInitialized ) return SQLITE_MISUSE;
+  pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
+  if( pOrigVfs==0 ) return SQLITE_ERROR;
+  assert( pOrigVfs!=&gQuota.sThisVfs );
+  gQuota.pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+  if( !gQuota.pMutex ){
+    return SQLITE_NOMEM;
+  }
+  gQuota.isInitialized = 1;
+  gQuota.pOrigVfs = pOrigVfs;
+  gQuota.sThisVfs = *pOrigVfs;
+  gQuota.sThisVfs.xOpen = quotaOpen;
+  gQuota.sThisVfs.xDelete = quotaDelete;
+  gQuota.sThisVfs.szOsFile += sizeof(quotaConn);
+  gQuota.sThisVfs.zName = "quota";
+  gQuota.sIoMethodsV1.iVersion = 1;
+  gQuota.sIoMethodsV1.xClose = quotaClose;
+  gQuota.sIoMethodsV1.xRead = quotaRead;
+  gQuota.sIoMethodsV1.xWrite = quotaWrite;
+  gQuota.sIoMethodsV1.xTruncate = quotaTruncate;
+  gQuota.sIoMethodsV1.xSync = quotaSync;
+  gQuota.sIoMethodsV1.xFileSize = quotaFileSize;
+  gQuota.sIoMethodsV1.xLock = quotaLock;
+  gQuota.sIoMethodsV1.xUnlock = quotaUnlock;
+  gQuota.sIoMethodsV1.xCheckReservedLock = quotaCheckReservedLock;
+  gQuota.sIoMethodsV1.xFileControl = quotaFileControl;
+  gQuota.sIoMethodsV1.xSectorSize = quotaSectorSize;
+  gQuota.sIoMethodsV1.xDeviceCharacteristics = quotaDeviceCharacteristics;
+  gQuota.sIoMethodsV2 = gQuota.sIoMethodsV1;
+  gQuota.sIoMethodsV2.iVersion = 2;
+  gQuota.sIoMethodsV2.xShmMap = quotaShmMap;
+  gQuota.sIoMethodsV2.xShmLock = quotaShmLock;
+  gQuota.sIoMethodsV2.xShmBarrier = quotaShmBarrier;
+  gQuota.sIoMethodsV2.xShmUnmap = quotaShmUnmap;
+  sqlite3_vfs_register(&gQuota.sThisVfs, makeDefault);
+  return SQLITE_OK;
+}
+
+/*
+** Shutdown the quota system.
+**
+** All SQLite database connections must be closed before calling this
+** routine.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
+** shutting down in order to free all remaining quota groups.
+*/
+int sqlite3_quota_shutdown(void){
+  quotaGroup *pGroup;
+  if( gQuota.isInitialized==0 ) return SQLITE_MISUSE;
+  for(pGroup=gQuota.pGroup; pGroup; pGroup=pGroup->pNext){
+    if( quotaGroupOpenFileCount(pGroup)>0 ) return SQLITE_MISUSE;
+  }
+  while( gQuota.pGroup ){
+    pGroup = gQuota.pGroup;
+    gQuota.pGroup = pGroup->pNext;
+    pGroup->iLimit = 0;
+    assert( quotaGroupOpenFileCount(pGroup)==0 );
+    quotaGroupDeref(pGroup);
+  }
+  gQuota.isInitialized = 0;
+  sqlite3_mutex_free(gQuota.pMutex);
+  sqlite3_vfs_unregister(&gQuota.sThisVfs);
+  memset(&gQuota, 0, sizeof(gQuota));
+  return SQLITE_OK;
+}
+
+/*
+** Create or destroy a quota group.
+**
+** The quota group is defined by the zPattern.  When calling this routine
+** with a zPattern for a quota group that already exists, this routine
+** merely updates the iLimit, xCallback, and pArg values for that quota
+** group.  If zPattern is new, then a new quota group is created.
+**
+** If the iLimit for a quota group is set to zero, then the quota group
+** is disabled and will be deleted when the last database connection using
+** the quota group is closed.
+**
+** Calling this routine on a zPattern that does not exist and with a
+** zero iLimit is a no-op.
+**
+** A quota group must exist with a non-zero iLimit prior to opening
+** database connections if those connections are to participate in the
+** quota group.  Creating a quota group does not affect database connections
+** that are already open.
+*/
+int sqlite3_quota_set(
+  const char *zPattern,           /* The filename pattern */
+  sqlite3_int64 iLimit,           /* New quota to set for this quota group */
+  void (*xCallback)(              /* Callback invoked when going over quota */
+     const char *zFilename,         /* Name of file whose size increases */
+     sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
+     sqlite3_int64 iSize,           /* Total size of all files in the group */
+     void *pArg                     /* Client data */
+  ),
+  void *pArg,                     /* client data passed thru to callback */
+  void (*xDestroy)(void*)         /* Optional destructor for pArg */
+){
+  quotaGroup *pGroup;
+  quotaEnter();
+  pGroup = gQuota.pGroup;
+  while( pGroup && strcmp(pGroup->zPattern, zPattern)!=0 ){
+    pGroup = pGroup->pNext;
+  }
+  if( pGroup==0 ){
+    int nPattern = (int)(strlen(zPattern) & 0x3fffffff);
+    if( iLimit<=0 ){
+      quotaLeave();
+      return SQLITE_OK;
+    }
+    pGroup = (quotaGroup *)sqlite3_malloc( sizeof(*pGroup) + nPattern + 1 );
+    if( pGroup==0 ){
+      quotaLeave();
+      return SQLITE_NOMEM;
+    }
+    memset(pGroup, 0, sizeof(*pGroup));
+    pGroup->zPattern = (char*)&pGroup[1];
+    memcpy((char *)pGroup->zPattern, zPattern, nPattern+1);
+    if( gQuota.pGroup ) gQuota.pGroup->ppPrev = &pGroup->pNext;
+    pGroup->pNext = gQuota.pGroup;
+    pGroup->ppPrev = &gQuota.pGroup;
+    gQuota.pGroup = pGroup;
+  }
+  pGroup->iLimit = iLimit;
+  pGroup->xCallback = xCallback;
+  if( pGroup->xDestroy && pGroup->pArg!=pArg ){
+    pGroup->xDestroy(pGroup->pArg);
+  }
+  pGroup->pArg = pArg;
+  pGroup->xDestroy = xDestroy;
+  quotaGroupDeref(pGroup);
+  quotaLeave();
+  return SQLITE_OK;
+}
+
+/*
+** Bring the named file under quota management.  Or if it is already under
+** management, update its size.
+*/
+int sqlite3_quota_file(const char *zFilename){
+  char *zFull = 0;
+  sqlite3_file *fd;
+  int rc;
+  int outFlags = 0;
+  sqlite3_int64 iSize;
+  int nAlloc = gQuota.sThisVfs.szOsFile + gQuota.sThisVfs.mxPathname+2;
+
+  /* Allocate space for a file-handle and the full path for file zFilename */
+  fd = (sqlite3_file *)sqlite3_malloc(nAlloc);
+  if( fd==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    zFull = &((char *)fd)[gQuota.sThisVfs.szOsFile];
+    rc = gQuota.pOrigVfs->xFullPathname(gQuota.pOrigVfs, zFilename,
+        gQuota.sThisVfs.mxPathname+1, zFull);
+  }
+
+  if( rc==SQLITE_OK ){
+    zFull[strlen(zFull)+1] = '\0';
+    rc = quotaOpen(&gQuota.sThisVfs, zFull, fd,
+                   SQLITE_OPEN_READONLY | SQLITE_OPEN_MAIN_DB, &outFlags);
+    if( rc==SQLITE_OK ){
+      fd->pMethods->xFileSize(fd, &iSize);
+      fd->pMethods->xClose(fd);
+    }else if( rc==SQLITE_CANTOPEN ){
+      quotaGroup *pGroup;
+      quotaFile *pFile;
+      quotaEnter();
+      pGroup = quotaGroupFind(zFull);
+      if( pGroup ){
+        pFile = quotaFindFile(pGroup, zFull, 0);
+        if( pFile ) quotaRemoveFile(pFile);
+      }
+      quotaLeave();
+    }
+  }
+
+  sqlite3_free(fd);
+  return rc;
+}
+
+/*
+** Open a potentially quotaed file for I/O.
+*/
+quota_FILE *sqlite3_quota_fopen(const char *zFilename, const char *zMode){
+  quota_FILE *p = 0;
+  char *zFull = 0;
+  char *zFullTranslated = 0;
+  int rc;
+  quotaGroup *pGroup;
+  quotaFile *pFile;
+
+  zFull = (char*)sqlite3_malloc(gQuota.sThisVfs.mxPathname + 1);
+  if( zFull==0 ) return 0;
+  rc = gQuota.pOrigVfs->xFullPathname(gQuota.pOrigVfs, zFilename,
+                                      gQuota.sThisVfs.mxPathname+1, zFull);
+  if( rc ) goto quota_fopen_error;
+  p = (quota_FILE*)sqlite3_malloc(sizeof(*p));
+  if( p==0 ) goto quota_fopen_error;
+  memset(p, 0, sizeof(*p));
+  zFullTranslated = quota_utf8_to_mbcs(zFull);
+  if( zFullTranslated==0 ) goto quota_fopen_error;
+  p->f = fopen(zFullTranslated, zMode);
+  if( p->f==0 ) goto quota_fopen_error;
+  quotaEnter();
+  pGroup = quotaGroupFind(zFull);
+  if( pGroup ){
+    pFile = quotaFindFile(pGroup, zFull, 1);
+    if( pFile==0 ){
+      quotaLeave();
+      goto quota_fopen_error;
+    }
+    pFile->nRef++;
+    p->pFile = pFile;
+  }
+  quotaLeave();
+  sqlite3_free(zFull);
+#if SQLITE_OS_WIN
+  p->zMbcsName = zFullTranslated;
+#endif
+  return p;
+
+quota_fopen_error:
+  quota_mbcs_free(zFullTranslated);
+  sqlite3_free(zFull);
+  if( p && p->f ) fclose(p->f);
+  sqlite3_free(p);
+  return 0;
+}
+
+/*
+** Read content from a quota_FILE
+*/
+size_t sqlite3_quota_fread(
+  void *pBuf,            /* Store the content here */
+  size_t size,           /* Size of each element */
+  size_t nmemb,          /* Number of elements to read */
+  quota_FILE *p          /* Read from this quota_FILE object */
+){
+  return fread(pBuf, size, nmemb, p->f);
+}
+
+/*
+** Write content into a quota_FILE.  Invoke the quota callback and block
+** the write if we exceed quota.
+*/
+size_t sqlite3_quota_fwrite(
+  const void *pBuf,      /* Take content to write from here */
+  size_t size,           /* Size of each element */
+  size_t nmemb,          /* Number of elements */
+  quota_FILE *p          /* Write to this quota_FILE object */
+){
+  sqlite3_int64 iOfst;
+  sqlite3_int64 iEnd;
+  sqlite3_int64 szNew;
+  quotaFile *pFile;
+  size_t rc;
+
+  iOfst = ftell(p->f);
+  iEnd = iOfst + size*nmemb;
+  pFile = p->pFile;
+  if( pFile && pFile->iSize<iEnd ){
+    quotaGroup *pGroup = pFile->pGroup;
+    quotaEnter();
+    szNew = pGroup->iSize - pFile->iSize + iEnd;
+    if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
+      if( pGroup->xCallback ){
+        pGroup->xCallback(pFile->zFilename, &pGroup->iLimit, szNew,
+                          pGroup->pArg);
+      }
+      if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
+        iEnd = pGroup->iLimit - pGroup->iSize + pFile->iSize;
+        nmemb = (size_t)((iEnd - iOfst)/size);
+        iEnd = iOfst + size*nmemb;
+        szNew = pGroup->iSize - pFile->iSize + iEnd;
+      }
+    }
+    pGroup->iSize = szNew;
+    pFile->iSize = iEnd;
+    quotaLeave();
+  }else{
+    pFile = 0;
+  }
+  rc = fwrite(pBuf, size, nmemb, p->f);
+
+  /* If the write was incomplete, adjust the file size and group size
+  ** downward */
+  if( rc<nmemb && pFile ){
+    size_t nWritten = rc;
+    sqlite3_int64 iNewEnd = iOfst + size*nWritten;
+    if( iNewEnd<iEnd ) iNewEnd = iEnd;
+    quotaEnter();
+    pFile->pGroup->iSize += iNewEnd - pFile->iSize;
+    pFile->iSize = iNewEnd;
+    quotaLeave();
+  }
+  return rc;
+}
+
+/*
+** Close an open quota_FILE stream.
+*/
+int sqlite3_quota_fclose(quota_FILE *p){
+  int rc;
+  quotaFile *pFile;
+  rc = fclose(p->f);
+  pFile = p->pFile;
+  if( pFile ){
+    quotaEnter();
+    pFile->nRef--;
+    if( pFile->nRef==0 ){
+      quotaGroup *pGroup = pFile->pGroup;
+      if( pFile->deleteOnClose ){
+        gQuota.pOrigVfs->xDelete(gQuota.pOrigVfs, pFile->zFilename, 0);
+        quotaRemoveFile(pFile);
+      }
+      quotaGroupDeref(pGroup);
+    }
+    quotaLeave();
+  }
+#if SQLITE_OS_WIN
+  quota_mbcs_free(p->zMbcsName);
+#endif
+  sqlite3_free(p);
+  return rc;
+}
+
+/*
+** Flush memory buffers for a quota_FILE to disk.
+*/
+int sqlite3_quota_fflush(quota_FILE *p, int doFsync){
+  int rc;
+  rc = fflush(p->f);
+  if( rc==0 && doFsync ){
+#if SQLITE_OS_UNIX
+    rc = fsync(fileno(p->f));
+#endif
+#if SQLITE_OS_WIN
+    rc = _commit(_fileno(p->f));
+#endif
+  }
+  return rc!=0;
+}
+
+/*
+** Seek on a quota_FILE stream.
+*/
+int sqlite3_quota_fseek(quota_FILE *p, long offset, int whence){
+  return fseek(p->f, offset, whence);
+}
+
+/*
+** rewind a quota_FILE stream.
+*/
+void sqlite3_quota_rewind(quota_FILE *p){
+  rewind(p->f);
+}
+
+/*
+** Tell the current location of a quota_FILE stream.
+*/
+long sqlite3_quota_ftell(quota_FILE *p){
+  return ftell(p->f);
+}
+
+/*
+** Test the error indicator for the given file.
+*/
+int sqlite3_quota_ferror(quota_FILE *p){
+  return ferror(p->f);
+}
+
+/*
+** Truncate a file to szNew bytes.
+*/
+int sqlite3_quota_ftruncate(quota_FILE *p, sqlite3_int64 szNew){
+  quotaFile *pFile = p->pFile;
+  int rc;
+  if( (pFile = p->pFile)!=0 && pFile->iSize<szNew ){
+    quotaGroup *pGroup;
+    if( pFile->iSize<szNew ){
+      /* This routine cannot be used to extend a file that is under
+      ** quota management.  Only true truncation is allowed. */
+      return -1;
+    }
+    pGroup = pFile->pGroup;
+    quotaEnter();
+    pGroup->iSize += szNew - pFile->iSize;
+    quotaLeave();
+  }
+#if SQLITE_OS_UNIX
+  rc = ftruncate(fileno(p->f), szNew);
+#endif
+#if SQLITE_OS_WIN
+#  if defined(__MINGW32__) && defined(SQLITE_TEST)
+     /* _chsize_s() is missing from MingW (as of 2012-11-06).  Use
+     ** _chsize() as a work-around for testing purposes. */
+     rc = _chsize(_fileno(p->f), (long)szNew);
+#  else
+     rc = _chsize_s(_fileno(p->f), szNew);
+#  endif
+#endif
+  if( pFile && rc==0 ){
+    quotaGroup *pGroup = pFile->pGroup;
+    quotaEnter();
+    pGroup->iSize += szNew - pFile->iSize;
+    pFile->iSize = szNew;
+    quotaLeave();
+  }
+  return rc;
+}
+
+/*
+** Determine the time that the given file was last modified, in
+** seconds size 1970.  Write the result into *pTime.  Return 0 on
+** success and non-zero on any kind of error.
+*/
+int sqlite3_quota_file_mtime(quota_FILE *p, time_t *pTime){
+  int rc;
+#if SQLITE_OS_UNIX
+  struct stat buf;
+  rc = fstat(fileno(p->f), &buf);
+#endif
+#if SQLITE_OS_WIN
+  struct _stati64 buf;
+  rc = _stati64(p->zMbcsName, &buf);
+#endif
+  if( rc==0 ) *pTime = buf.st_mtime;
+  return rc;
+}
+
+/*
+** Return the true size of the file, as reported by the operating
+** system.
+*/
+sqlite3_int64 sqlite3_quota_file_truesize(quota_FILE *p){
+  int rc;
+#if SQLITE_OS_UNIX
+  struct stat buf;
+  rc = fstat(fileno(p->f), &buf);
+#endif
+#if SQLITE_OS_WIN
+  struct _stati64 buf;
+  rc = _stati64(p->zMbcsName, &buf);
+#endif
+  return rc==0 ? buf.st_size : -1;
+}
+
+/*
+** Return the size of the file, as it is known to the quota subsystem.
+*/
+sqlite3_int64 sqlite3_quota_file_size(quota_FILE *p){
+  return p->pFile ? p->pFile->iSize : -1;
+}
+
+/*
+** Determine the amount of data in bytes available for reading
+** in the given file.
+*/
+long sqlite3_quota_file_available(quota_FILE *p){
+  FILE* f = p->f;
+  long pos1, pos2;
+  int rc;
+  pos1 = ftell(f);
+  if ( pos1 < 0 ) return -1;
+  rc = fseek(f, 0, SEEK_END);
+  if ( rc != 0 ) return -1;
+  pos2 = ftell(f);
+  if ( pos2 < 0 ) return -1;
+  rc = fseek(f, pos1, SEEK_SET);
+  if ( rc != 0 ) return -1;
+  return pos2 - pos1;
+}
+
+/*
+** Remove a managed file.  Update quotas accordingly.
+*/
+int sqlite3_quota_remove(const char *zFilename){
+  char *zFull;            /* Full pathname for zFilename */
+  size_t nFull;           /* Number of bytes in zFilename */
+  int rc;                 /* Result code */
+  quotaGroup *pGroup;     /* Group containing zFilename */
+  quotaFile *pFile;       /* A file in the group */
+  quotaFile *pNextFile;   /* next file in the group */
+  int diff;               /* Difference between filenames */
+  char c;                 /* First character past end of pattern */
+
+  zFull = (char*)sqlite3_malloc(gQuota.sThisVfs.mxPathname + 1);
+  if( zFull==0 ) return SQLITE_NOMEM;
+  rc = gQuota.pOrigVfs->xFullPathname(gQuota.pOrigVfs, zFilename,
+                                      gQuota.sThisVfs.mxPathname+1, zFull);
+  if( rc ){
+    sqlite3_free(zFull);
+    return rc;
+  }
+
+  /* Figure out the length of the full pathname.  If the name ends with
+  ** / (or \ on windows) then remove the trailing /.
+  */
+  nFull = strlen(zFull);
+  if( nFull>0 && (zFull[nFull-1]=='/' || zFull[nFull-1]=='\\') ){
+    nFull--;
+    zFull[nFull] = 0;
+  }
+
+  quotaEnter();
+  pGroup = quotaGroupFind(zFull);
+  if( pGroup ){
+    for(pFile=pGroup->pFiles; pFile && rc==SQLITE_OK; pFile=pNextFile){
+      pNextFile = pFile->pNext;
+      diff = strncmp(zFull, pFile->zFilename, nFull);
+      if( diff==0 && ((c = pFile->zFilename[nFull])==0 || c=='/' || c=='\\') ){
+        if( pFile->nRef ){
+          pFile->deleteOnClose = 1;
+        }else{
+          rc = gQuota.pOrigVfs->xDelete(gQuota.pOrigVfs, pFile->zFilename, 0);
+          quotaRemoveFile(pFile);
+          quotaGroupDeref(pGroup);
+        }
+      }
+    }
+  }
+  quotaLeave();
+  sqlite3_free(zFull);
+  return rc;
+}
+
+/***************************** Test Code ***********************************/
+#ifdef SQLITE_TEST
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+
+/*
+** Argument passed to a TCL quota-over-limit callback.
+*/
+typedef struct TclQuotaCallback TclQuotaCallback;
+struct TclQuotaCallback {
+  Tcl_Interp *interp;    /* Interpreter in which to run the script */
+  Tcl_Obj *pScript;      /* Script to be run */
+};
+
+extern const char *sqlite3ErrName(int);
+
+
+/*
+** This is the callback from a quota-over-limit.
+*/
+static void tclQuotaCallback(
+  const char *zFilename,          /* Name of file whose size increases */
+  sqlite3_int64 *piLimit,         /* IN/OUT: The current limit */
+  sqlite3_int64 iSize,            /* Total size of all files in the group */
+  void *pArg                      /* Client data */
+){
+  TclQuotaCallback *p;            /* Callback script object */
+  Tcl_Obj *pEval;                 /* Script to evaluate */
+  Tcl_Obj *pVarname;              /* Name of variable to pass as 2nd arg */
+  unsigned int rnd;               /* Random part of pVarname */
+  int rc;                         /* Tcl error code */
+
+  p = (TclQuotaCallback *)pArg;
+  if( p==0 ) return;
+
+  pVarname = Tcl_NewStringObj("::piLimit_", -1);
+  Tcl_IncrRefCount(pVarname);
+  sqlite3_randomness(sizeof(rnd), (void *)&rnd);
+  Tcl_AppendObjToObj(pVarname, Tcl_NewIntObj((int)(rnd&0x7FFFFFFF)));
+  Tcl_ObjSetVar2(p->interp, pVarname, 0, Tcl_NewWideIntObj(*piLimit), 0);
+
+  pEval = Tcl_DuplicateObj(p->pScript);
+  Tcl_IncrRefCount(pEval);
+  Tcl_ListObjAppendElement(0, pEval, Tcl_NewStringObj(zFilename, -1));
+  Tcl_ListObjAppendElement(0, pEval, pVarname);
+  Tcl_ListObjAppendElement(0, pEval, Tcl_NewWideIntObj(iSize));
+  rc = Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+
+  if( rc==TCL_OK ){
+    Tcl_WideInt x;
+    Tcl_Obj *pLimit = Tcl_ObjGetVar2(p->interp, pVarname, 0, 0);
+    rc = Tcl_GetWideIntFromObj(p->interp, pLimit, &x);
+    *piLimit = x;
+    Tcl_UnsetVar(p->interp, Tcl_GetString(pVarname), 0);
+  }
+
+  Tcl_DecrRefCount(pEval);
+  Tcl_DecrRefCount(pVarname);
+  if( rc!=TCL_OK ) Tcl_BackgroundError(p->interp);
+}
+
+/*
+** Destructor for a TCL quota-over-limit callback.
+*/
+static void tclCallbackDestructor(void *pObj){
+  TclQuotaCallback *p = (TclQuotaCallback*)pObj;
+  if( p ){
+    Tcl_DecrRefCount(p->pScript);
+    sqlite3_free((char *)p);
+  }
+}
+
+/*
+** tclcmd: sqlite3_quota_initialize NAME MAKEDEFAULT
+*/
+static int SQLITE_TCLAPI test_quota_initialize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zName;              /* Name of new quota VFS */
+  int makeDefault;                /* True to make the new VFS the default */
+  int rc;                         /* Value returned by quota_initialize() */
+
+  /* Process arguments */
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NAME MAKEDEFAULT");
+    return TCL_ERROR;
+  }
+  zName = Tcl_GetString(objv[1]);
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &makeDefault) ) return TCL_ERROR;
+  if( zName[0]=='\0' ) zName = 0;
+
+  /* Call sqlite3_quota_initialize() */
+  rc = sqlite3_quota_initialize(zName, makeDefault);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_shutdown
+*/
+static int SQLITE_TCLAPI test_quota_shutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;                         /* Value returned by quota_shutdown() */
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  /* Call sqlite3_quota_shutdown() */
+  rc = sqlite3_quota_shutdown();
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_set PATTERN LIMIT SCRIPT
+*/
+static int SQLITE_TCLAPI test_quota_set(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zPattern;           /* File pattern to configure */
+  Tcl_WideInt iLimit;             /* Initial quota in bytes */
+  Tcl_Obj *pScript;               /* Tcl script to invoke to increase quota */
+  int rc;                         /* Value returned by quota_set() */
+  TclQuotaCallback *p;            /* Callback object */
+  int nScript;                    /* Length of callback script */
+  void (*xDestroy)(void*);        /* Optional destructor for pArg */
+  void (*xCallback)(const char *, sqlite3_int64 *, sqlite3_int64, void *);
+
+  /* Process arguments */
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PATTERN LIMIT SCRIPT");
+    return TCL_ERROR;
+  }
+  zPattern = Tcl_GetString(objv[1]);
+  if( Tcl_GetWideIntFromObj(interp, objv[2], &iLimit) ) return TCL_ERROR;
+  pScript = objv[3];
+  Tcl_GetStringFromObj(pScript, &nScript);
+
+  if( nScript>0 ){
+    /* Allocate a TclQuotaCallback object */
+    p = (TclQuotaCallback *)sqlite3_malloc(sizeof(TclQuotaCallback));
+    if( !p ){
+      Tcl_SetResult(interp, (char *)"SQLITE_NOMEM", TCL_STATIC);
+      return TCL_OK;
+    }
+    memset(p, 0, sizeof(TclQuotaCallback));
+    p->interp = interp;
+    Tcl_IncrRefCount(pScript);
+    p->pScript = pScript;
+    xDestroy = tclCallbackDestructor;
+    xCallback = tclQuotaCallback;
+  }else{
+    p = 0;
+    xDestroy = 0;
+    xCallback = 0;
+  }
+
+  /* Invoke sqlite3_quota_set() */
+  rc = sqlite3_quota_set(zPattern, iLimit, xCallback, (void*)p, xDestroy);
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_file FILENAME
+*/
+static int SQLITE_TCLAPI test_quota_file(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;          /* File pattern to configure */
+  int rc;                         /* Value returned by quota_file() */
+
+  /* Process arguments */
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+  zFilename = Tcl_GetString(objv[1]);
+
+  /* Invoke sqlite3_quota_file() */
+  rc = sqlite3_quota_file(zFilename);
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  sqlite3_quota_dump
+*/
+static int SQLITE_TCLAPI test_quota_dump(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj *pResult;
+  Tcl_Obj *pGroupTerm;
+  Tcl_Obj *pFileTerm;
+  quotaGroup *pGroup;
+  quotaFile *pFile;
+
+  pResult = Tcl_NewObj();
+  quotaEnter();
+  for(pGroup=gQuota.pGroup; pGroup; pGroup=pGroup->pNext){
+    pGroupTerm = Tcl_NewObj();
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewStringObj(pGroup->zPattern, -1));
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewWideIntObj(pGroup->iLimit));
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewWideIntObj(pGroup->iSize));
+    for(pFile=pGroup->pFiles; pFile; pFile=pFile->pNext){
+      int i;
+      char zTemp[1000];
+      pFileTerm = Tcl_NewObj();
+      sqlite3_snprintf(sizeof(zTemp), zTemp, "%s", pFile->zFilename);
+      for(i=0; zTemp[i]; i++){ if( zTemp[i]=='\\' ) zTemp[i] = '/'; }
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewStringObj(zTemp, -1));
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewWideIntObj(pFile->iSize));
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewWideIntObj(pFile->nRef));
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewWideIntObj(pFile->deleteOnClose));
+      Tcl_ListObjAppendElement(interp, pGroupTerm, pFileTerm);
+    }
+    Tcl_ListObjAppendElement(interp, pResult, pGroupTerm);
+  }
+  quotaLeave();
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_fopen FILENAME MODE
+*/
+static int SQLITE_TCLAPI test_quota_fopen(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;          /* File pattern to configure */
+  const char *zMode;              /* Mode string */
+  quota_FILE *p;                  /* Open string object */
+  char zReturn[50];               /* Name of pointer to return */
+
+  /* Process arguments */
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME MODE");
+    return TCL_ERROR;
+  }
+  zFilename = Tcl_GetString(objv[1]);
+  zMode = Tcl_GetString(objv[2]);
+  p = sqlite3_quota_fopen(zFilename, zMode);
+  sqlite3_snprintf(sizeof(zReturn), zReturn, "%p", p);
+  Tcl_SetResult(interp, zReturn, TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/* Defined in test1.c */
+extern void *sqlite3TestTextToPtr(const char*);
+
+/*
+** tclcmd: sqlite3_quota_fread HANDLE SIZE NELEM
+*/
+static int SQLITE_TCLAPI test_quota_fread(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  char *zBuf;
+  int sz;
+  int nElem;
+  size_t got;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE SIZE NELEM");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  if( Tcl_GetIntFromObj(interp, objv[2], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &nElem) ) return TCL_ERROR;
+  zBuf = (char*)sqlite3_malloc( sz*nElem + 1 );
+  if( zBuf==0 ){
+    Tcl_SetResult(interp, "out of memory", TCL_STATIC);
+    return TCL_ERROR;
+  }
+  got = sqlite3_quota_fread(zBuf, sz, nElem, p);
+  zBuf[got*sz] = 0;
+  Tcl_SetResult(interp, zBuf, TCL_VOLATILE);
+  sqlite3_free(zBuf);
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_fwrite HANDLE SIZE NELEM CONTENT
+*/
+static int SQLITE_TCLAPI test_quota_fwrite(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  char *zBuf;
+  int sz;
+  int nElem;
+  size_t got;
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE SIZE NELEM CONTENT");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  if( Tcl_GetIntFromObj(interp, objv[2], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &nElem) ) return TCL_ERROR;
+  zBuf = Tcl_GetString(objv[4]);
+  got = sqlite3_quota_fwrite(zBuf, sz, nElem, p);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(got));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_fclose HANDLE
+*/
+static int SQLITE_TCLAPI test_quota_fclose(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  rc = sqlite3_quota_fclose(p);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_fflush HANDLE ?HARDSYNC?
+*/
+static int SQLITE_TCLAPI test_quota_fflush(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  int rc;
+  int doSync = 0;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE ?HARDSYNC?");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  if( objc==3 ){
+    if( Tcl_GetBooleanFromObj(interp, objv[2], &doSync) ) return TCL_ERROR;
+  }
+  rc = sqlite3_quota_fflush(p, doSync);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_fseek HANDLE OFFSET WHENCE
+*/
+static int SQLITE_TCLAPI test_quota_fseek(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  int ofst;
+  const char *zWhence;
+  int whence;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE OFFSET WHENCE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  if( Tcl_GetIntFromObj(interp, objv[2], &ofst) ) return TCL_ERROR;
+  zWhence = Tcl_GetString(objv[3]);
+  if( strcmp(zWhence, "SEEK_SET")==0 ){
+    whence = SEEK_SET;
+  }else if( strcmp(zWhence, "SEEK_CUR")==0 ){
+    whence = SEEK_CUR;
+  }else if( strcmp(zWhence, "SEEK_END")==0 ){
+    whence = SEEK_END;
+  }else{
+    Tcl_AppendResult(interp,
+           "WHENCE should be SEEK_SET, SEEK_CUR, or SEEK_END", (char*)0);
+    return TCL_ERROR;
+  }
+  rc = sqlite3_quota_fseek(p, ofst, whence);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_rewind HANDLE
+*/
+static int SQLITE_TCLAPI test_quota_rewind(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  sqlite3_quota_rewind(p);
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_ftell HANDLE
+*/
+static int SQLITE_TCLAPI test_quota_ftell(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  sqlite3_int64 x;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  x = sqlite3_quota_ftell(p);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(x));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_ftruncate HANDLE SIZE
+*/
+static int SQLITE_TCLAPI test_quota_ftruncate(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  sqlite3_int64 x;
+  Tcl_WideInt w;
+  int rc;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE SIZE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  if( Tcl_GetWideIntFromObj(interp, objv[2], &w) ) return TCL_ERROR;
+  x = (sqlite3_int64)w;
+  rc = sqlite3_quota_ftruncate(p, x);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_file_size HANDLE
+*/
+static int SQLITE_TCLAPI test_quota_file_size(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  sqlite3_int64 x;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  x = sqlite3_quota_file_size(p);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(x));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_file_truesize HANDLE
+*/
+static int SQLITE_TCLAPI test_quota_file_truesize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  sqlite3_int64 x;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  x = sqlite3_quota_file_truesize(p);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(x));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_file_mtime HANDLE
+*/
+static int SQLITE_TCLAPI test_quota_file_mtime(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  time_t t;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  t = 0;
+  sqlite3_quota_file_mtime(p, &t);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(t));
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd: sqlite3_quota_remove FILENAME
+*/
+static int SQLITE_TCLAPI test_quota_remove(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;          /* File pattern to configure */
+  int rc;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+  zFilename = Tcl_GetString(objv[1]);
+  rc = sqlite3_quota_remove(zFilename);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_glob PATTERN TEXT
+**
+** Test the glob pattern matching.  Return 1 if TEXT matches PATTERN
+** and return 0 if it does not.
+*/
+static int SQLITE_TCLAPI test_quota_glob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zPattern;          /* The glob pattern */
+  const char *zText;             /* Text to compare against the pattern */
+  int rc;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PATTERN TEXT");
+    return TCL_ERROR;
+  }
+  zPattern = Tcl_GetString(objv[1]);
+  zText = Tcl_GetString(objv[2]);
+  rc = quotaStrglob(zPattern, zText);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_file_available HANDLE
+**
+** Return the number of bytes from the current file point to the end of
+** the file.
+*/
+static int SQLITE_TCLAPI test_quota_file_available(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  sqlite3_int64 x;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  x = sqlite3_quota_file_available(p);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(x));
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_ferror HANDLE
+**
+** Return true if the file handle is in the error state.
+*/
+static int SQLITE_TCLAPI test_quota_ferror(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  quota_FILE *p;
+  int x;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE");
+    return TCL_ERROR;
+  }
+  p = sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  x = sqlite3_quota_ferror(p);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(x));
+  return TCL_OK;
+}
+
+/*
+** This routine registers the custom TCL commands defined in this
+** module.  This should be the only procedure visible from outside
+** of this module.
+*/
+int Sqlitequota_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "sqlite3_quota_initialize",    test_quota_initialize },
+    { "sqlite3_quota_shutdown",      test_quota_shutdown },
+    { "sqlite3_quota_set",           test_quota_set },
+    { "sqlite3_quota_file",          test_quota_file },
+    { "sqlite3_quota_dump",          test_quota_dump },
+    { "sqlite3_quota_fopen",         test_quota_fopen },
+    { "sqlite3_quota_fread",         test_quota_fread },
+    { "sqlite3_quota_fwrite",        test_quota_fwrite },
+    { "sqlite3_quota_fclose",        test_quota_fclose },
+    { "sqlite3_quota_fflush",        test_quota_fflush },
+    { "sqlite3_quota_fseek",         test_quota_fseek },
+    { "sqlite3_quota_rewind",        test_quota_rewind },
+    { "sqlite3_quota_ftell",         test_quota_ftell },
+    { "sqlite3_quota_ftruncate",     test_quota_ftruncate },
+    { "sqlite3_quota_file_size",     test_quota_file_size },
+    { "sqlite3_quota_file_truesize", test_quota_file_truesize },
+    { "sqlite3_quota_file_mtime",    test_quota_file_mtime },
+    { "sqlite3_quota_remove",        test_quota_remove },
+    { "sqlite3_quota_glob",          test_quota_glob },
+    { "sqlite3_quota_file_available",test_quota_file_available },
+    { "sqlite3_quota_ferror",        test_quota_ferror },
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_quota.h b/src/test_quota.h
new file mode 100644
index 0000000..c17e15a
--- /dev/null
+++ b/src/test_quota.h
@@ -0,0 +1,268 @@
+/*
+** 2011 December 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the interface definition for the quota a VFS shim.
+**
+** This particular shim enforces a quota system on files.  One or more
+** database files are in a "quota group" that is defined by a GLOB
+** pattern.  A quota is set for the combined size of all files in the
+** the group.  A quota of zero means "no limit".  If the total size
+** of all files in the quota group is greater than the limit, then
+** write requests that attempt to enlarge a file fail with SQLITE_FULL.
+**
+** However, before returning SQLITE_FULL, the write requests invoke
+** a callback function that is configurable for each quota group.
+** This callback has the opportunity to enlarge the quota.  If the
+** callback does enlarge the quota such that the total size of all
+** files within the group is less than the new quota, then the write
+** continues as if nothing had happened.
+*/
+#ifndef _QUOTA_H_
+#include "sqlite3.h"
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+/* Make this callable from C++ */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+** Initialize the quota VFS shim.  Use the VFS named zOrigVfsName
+** as the VFS that does the actual work.  Use the default if
+** zOrigVfsName==NULL.  
+**
+** The quota VFS shim is named "quota".  It will become the default
+** VFS if makeDefault is non-zero.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
+** during start-up.
+*/
+int sqlite3_quota_initialize(const char *zOrigVfsName, int makeDefault);
+
+/*
+** Shutdown the quota system.
+**
+** All SQLite database connections must be closed before calling this
+** routine.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
+** shutting down in order to free all remaining quota groups.
+*/
+int sqlite3_quota_shutdown(void);
+
+/*
+** Create or destroy a quota group.
+**
+** The quota group is defined by the zPattern.  When calling this routine
+** with a zPattern for a quota group that already exists, this routine
+** merely updates the iLimit, xCallback, and pArg values for that quota
+** group.  If zPattern is new, then a new quota group is created.
+**
+** The zPattern is always compared against the full pathname of the file.
+** Even if APIs are called with relative pathnames, SQLite converts the
+** name to a full pathname before comparing it against zPattern.  zPattern
+** is a glob pattern with the following matching rules:
+**
+**      '*'       Matches any sequence of zero or more characters.
+**
+**      '?'       Matches exactly one character.
+**
+**     [...]      Matches one character from the enclosed list of
+**                characters.  "]" can be part of the list if it is
+**                the first character.  Within the list "X-Y" matches
+**                characters X or Y or any character in between the
+**                two.  Ex:  "[0-9]" matches any digit.
+**
+**     [^...]     Matches one character not in the enclosed list.
+**
+**     /          Matches either / or \.  This allows glob patterns
+**                containing / to work on both unix and windows.
+**
+** Note that, unlike unix shell globbing, the directory separator "/"
+** can match a wildcard.  So, for example, the pattern "/abc/xyz/" "*"
+** matches any files anywhere in the directory hierarchy beneath
+** /abc/xyz.
+**
+** The glob algorithm works on bytes.  Multi-byte UTF8 characters are
+** matched as if each byte were a separate character.
+**
+** If the iLimit for a quota group is set to zero, then the quota group
+** is disabled and will be deleted when the last database connection using
+** the quota group is closed.
+**
+** Calling this routine on a zPattern that does not exist and with a
+** zero iLimit is a no-op.
+**
+** A quota group must exist with a non-zero iLimit prior to opening
+** database connections if those connections are to participate in the
+** quota group.  Creating a quota group does not affect database connections
+** that are already open.
+**
+** The patterns that define the various quota groups should be distinct.
+** If the same filename matches more than one quota group pattern, then
+** the behavior of this package is undefined.
+*/
+int sqlite3_quota_set(
+  const char *zPattern,           /* The filename pattern */
+  sqlite3_int64 iLimit,           /* New quota to set for this quota group */
+  void (*xCallback)(              /* Callback invoked when going over quota */
+     const char *zFilename,         /* Name of file whose size increases */
+     sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
+     sqlite3_int64 iSize,           /* Total size of all files in the group */
+     void *pArg                     /* Client data */
+  ),
+  void *pArg,                     /* client data passed thru to callback */
+  void (*xDestroy)(void*)         /* Optional destructor for pArg */
+);
+
+/*
+** Bring the named file under quota management, assuming its name matches
+** the glob pattern of some quota group.  Or if it is already under
+** management, update its size.  If zFilename does not match the glob
+** pattern of any quota group, this routine is a no-op.
+*/
+int sqlite3_quota_file(const char *zFilename);
+
+/*
+** The following object serves the same role as FILE in the standard C
+** library.  It represents an open connection to a file on disk for I/O.
+**
+** A single quota_FILE should not be used by two or more threads at the
+** same time.  Multiple threads can be using different quota_FILE objects
+** simultaneously, but not the same quota_FILE object.
+*/
+typedef struct quota_FILE quota_FILE;
+
+/*
+** Create a new quota_FILE object used to read and/or write to the
+** file zFilename.  The zMode parameter is as with standard library zMode.
+*/
+quota_FILE *sqlite3_quota_fopen(const char *zFilename, const char *zMode);
+
+/*
+** Perform I/O against a quota_FILE object.  When doing writes, the
+** quota mechanism may result in a short write, in order to prevent
+** the sum of sizes of all files from going over quota.
+*/
+size_t sqlite3_quota_fread(void*, size_t, size_t, quota_FILE*);
+size_t sqlite3_quota_fwrite(const void*, size_t, size_t, quota_FILE*);
+
+/*
+** Flush all written content held in memory buffers out to disk.
+** This is the equivalent of fflush() in the standard library.
+**
+** If the hardSync parameter is true (non-zero) then this routine
+** also forces OS buffers to disk - the equivalent of fsync().
+**
+** This routine return zero on success and non-zero if something goes
+** wrong.
+*/
+int sqlite3_quota_fflush(quota_FILE*, int hardSync);
+
+/*
+** Close a quota_FILE object and free all associated resources.  The
+** file remains under quota management.
+*/
+int sqlite3_quota_fclose(quota_FILE*);
+
+/*
+** Move the read/write pointer for a quota_FILE object.  Or tell the
+** current location of the read/write pointer.
+*/
+int sqlite3_quota_fseek(quota_FILE*, long, int);
+void sqlite3_quota_rewind(quota_FILE*);
+long sqlite3_quota_ftell(quota_FILE*);
+
+/*
+** Test the error indicator for the given file.
+**
+** Return non-zero if the error indicator is set.
+*/
+int sqlite3_quota_ferror(quota_FILE*);
+
+/*
+** Truncate a file previously opened by sqlite3_quota_fopen().  Return
+** zero on success and non-zero on any kind of failure.
+**
+** The newSize argument must be less than or equal to the current file size.
+** Any attempt to "truncate" a file to a larger size results in 
+** undefined behavior.
+*/
+int sqlite3_quota_ftruncate(quota_FILE*, sqlite3_int64 newSize);
+
+/*
+** Return the last modification time of the opened file, in seconds
+** since 1970.
+*/
+int sqlite3_quota_file_mtime(quota_FILE*, time_t *pTime);
+
+/*
+** Return the size of the file as it is known to the quota system.
+**
+** This size might be different from the true size of the file on
+** disk if some outside process has modified the file without using the
+** quota mechanism, or if calls to sqlite3_quota_fwrite() have occurred
+** which have increased the file size, but those writes have not yet been
+** forced to disk using sqlite3_quota_fflush().
+**
+** Return -1 if the file is not participating in quota management.
+*/
+sqlite3_int64 sqlite3_quota_file_size(quota_FILE*);
+
+/*
+** Return the true size of the file.
+**
+** The true size should be the same as the size of the file as known
+** to the quota system, however the sizes might be different if the
+** file has been extended or truncated via some outside process or if
+** pending writes have not yet been flushed to disk.
+**
+** Return -1 if the file does not exist or if the size of the file
+** cannot be determined for some reason.
+*/
+sqlite3_int64 sqlite3_quota_file_truesize(quota_FILE*);
+
+/*
+** Determine the amount of data in bytes available for reading
+** in the given file.
+**
+** Return -1 if the amount cannot be determined for some reason.
+*/
+long sqlite3_quota_file_available(quota_FILE*);
+
+/*
+** Delete a file from the disk, if that file is under quota management.
+** Adjust quotas accordingly.
+**
+** If zFilename is the name of a directory that matches one of the
+** quota glob patterns, then all files under quota management that
+** are contained within that directory are deleted.
+**
+** A standard SQLite result code is returned (SQLITE_OK, SQLITE_NOMEM, etc.)
+** When deleting a directory of files, if the deletion of any one
+** file fails (for example due to an I/O error), then this routine
+** returns immediately, with the error code, and does not try to 
+** delete any of the other files in the specified directory.
+**
+** All files are removed from quota management and deleted from disk.
+** However, no attempt is made to remove empty directories.
+**
+** This routine is a no-op for files that are not under quota management.
+*/
+int sqlite3_quota_remove(const char *zFilename);
+
+#ifdef __cplusplus
+}  /* end of the 'extern "C"' block */
+#endif
+#endif /* _QUOTA_H_ */
diff --git a/src/test_rtree.c b/src/test_rtree.c
new file mode 100644
index 0000000..0c6dbf3
--- /dev/null
+++ b/src/test_rtree.c
@@ -0,0 +1,511 @@
+/*
+** 2010 August 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces. This code
+** is not included in the SQLite library. 
+*/
+
+#include "sqlite3.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+/* Solely for the UNUSED_PARAMETER() macro. */
+#include "sqliteInt.h"
+
+#ifdef SQLITE_ENABLE_RTREE
+/* 
+** Type used to cache parameter information for the "circle" r-tree geometry
+** callback.
+*/
+typedef struct Circle Circle;
+struct Circle {
+  struct Box {
+    double xmin;
+    double xmax;
+    double ymin;
+    double ymax;
+  } aBox[2];
+  double centerx;
+  double centery;
+  double radius;
+  double mxArea;
+  int eScoreType;
+};
+
+/*
+** Destructor function for Circle objects allocated by circle_geom().
+*/
+static void circle_del(void *p){
+  sqlite3_free(p);
+}
+
+/*
+** Implementation of "circle" r-tree geometry callback.
+*/
+static int circle_geom(
+  sqlite3_rtree_geometry *p,
+  int nCoord, 
+  sqlite3_rtree_dbl *aCoord,
+  int *pRes
+){
+  int i;                          /* Iterator variable */
+  Circle *pCircle;                /* Structure defining circular region */
+  double xmin, xmax;              /* X dimensions of box being tested */
+  double ymin, ymax;              /* X dimensions of box being tested */
+
+  xmin = aCoord[0];
+  xmax = aCoord[1];
+  ymin = aCoord[2];
+  ymax = aCoord[3];
+  pCircle = (Circle *)p->pUser;
+  if( pCircle==0 ){
+    /* If pUser is still 0, then the parameter values have not been tested
+    ** for correctness or stored into a Circle structure yet. Do this now. */
+
+    /* This geometry callback is for use with a 2-dimensional r-tree table.
+    ** Return an error if the table does not have exactly 2 dimensions. */
+    if( nCoord!=4 ) return SQLITE_ERROR;
+
+    /* Test that the correct number of parameters (3) have been supplied,
+    ** and that the parameters are in range (that the radius of the circle 
+    ** radius is greater than zero). */
+    if( p->nParam!=3 || p->aParam[2]<0.0 ) return SQLITE_ERROR;
+
+    /* Allocate a structure to cache parameter data in. Return SQLITE_NOMEM
+    ** if the allocation fails. */
+    pCircle = (Circle *)(p->pUser = sqlite3_malloc(sizeof(Circle)));
+    if( !pCircle ) return SQLITE_NOMEM;
+    p->xDelUser = circle_del;
+
+    /* Record the center and radius of the circular region. One way that
+    ** tested bounding boxes that intersect the circular region are detected
+    ** is by testing if each corner of the bounding box lies within radius
+    ** units of the center of the circle. */
+    pCircle->centerx = p->aParam[0];
+    pCircle->centery = p->aParam[1];
+    pCircle->radius = p->aParam[2];
+
+    /* Define two bounding box regions. The first, aBox[0], extends to
+    ** infinity in the X dimension. It covers the same range of the Y dimension
+    ** as the circular region. The second, aBox[1], extends to infinity in
+    ** the Y dimension and is constrained to the range of the circle in the
+    ** X dimension.
+    **
+    ** Then imagine each box is split in half along its short axis by a line
+    ** that intersects the center of the circular region. A bounding box
+    ** being tested can be said to intersect the circular region if it contains
+    ** points from each half of either of the two infinite bounding boxes.
+    */
+    pCircle->aBox[0].xmin = pCircle->centerx;
+    pCircle->aBox[0].xmax = pCircle->centerx;
+    pCircle->aBox[0].ymin = pCircle->centery + pCircle->radius;
+    pCircle->aBox[0].ymax = pCircle->centery - pCircle->radius;
+    pCircle->aBox[1].xmin = pCircle->centerx + pCircle->radius;
+    pCircle->aBox[1].xmax = pCircle->centerx - pCircle->radius;
+    pCircle->aBox[1].ymin = pCircle->centery;
+    pCircle->aBox[1].ymax = pCircle->centery;
+    pCircle->mxArea = (xmax - xmin)*(ymax - ymin) + 1.0;
+  }
+
+  /* Check if any of the 4 corners of the bounding-box being tested lie 
+  ** inside the circular region. If they do, then the bounding-box does
+  ** intersect the region of interest. Set the output variable to true and
+  ** return SQLITE_OK in this case. */
+  for(i=0; i<4; i++){
+    double x = (i&0x01) ? xmax : xmin;
+    double y = (i&0x02) ? ymax : ymin;
+    double d2;
+    
+    d2  = (x-pCircle->centerx)*(x-pCircle->centerx);
+    d2 += (y-pCircle->centery)*(y-pCircle->centery);
+    if( d2<(pCircle->radius*pCircle->radius) ){
+      *pRes = 1;
+      return SQLITE_OK;
+    }
+  }
+
+  /* Check if the bounding box covers any other part of the circular region.
+  ** See comments above for a description of how this test works. If it does
+  ** cover part of the circular region, set the output variable to true
+  ** and return SQLITE_OK. */
+  for(i=0; i<2; i++){
+    if( xmin<=pCircle->aBox[i].xmin 
+     && xmax>=pCircle->aBox[i].xmax 
+     && ymin<=pCircle->aBox[i].ymin 
+     && ymax>=pCircle->aBox[i].ymax 
+    ){
+      *pRes = 1;
+      return SQLITE_OK;
+    }
+  }
+
+  /* The specified bounding box does not intersect the circular region. Set
+  ** the output variable to zero and return SQLITE_OK. */
+  *pRes = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of "circle" r-tree geometry callback using the 
+** 2nd-generation interface that allows scoring.
+**
+** Two calling forms:
+**
+**          Qcircle(X,Y,Radius,eType)        -- All values are doubles
+**          Qcircle('x:X y:Y r:R e:ETYPE')   -- Single string parameter
+*/
+static int circle_query_func(sqlite3_rtree_query_info *p){
+  int i;                          /* Iterator variable */
+  Circle *pCircle;                /* Structure defining circular region */
+  double xmin, xmax;              /* X dimensions of box being tested */
+  double ymin, ymax;              /* X dimensions of box being tested */
+  int nWithin = 0;                /* Number of corners inside the circle */
+
+  xmin = p->aCoord[0];
+  xmax = p->aCoord[1];
+  ymin = p->aCoord[2];
+  ymax = p->aCoord[3];
+  pCircle = (Circle *)p->pUser;
+  if( pCircle==0 ){
+    /* If pUser is still 0, then the parameter values have not been tested
+    ** for correctness or stored into a Circle structure yet. Do this now. */
+
+    /* This geometry callback is for use with a 2-dimensional r-tree table.
+    ** Return an error if the table does not have exactly 2 dimensions. */
+    if( p->nCoord!=4 ) return SQLITE_ERROR;
+
+    /* Test that the correct number of parameters (1 or 4) have been supplied.
+    */
+    if( p->nParam!=4 && p->nParam!=1 ) return SQLITE_ERROR;
+
+    /* Allocate a structure to cache parameter data in. Return SQLITE_NOMEM
+    ** if the allocation fails. */
+    pCircle = (Circle *)(p->pUser = sqlite3_malloc(sizeof(Circle)));
+    if( !pCircle ) return SQLITE_NOMEM;
+    p->xDelUser = circle_del;
+
+    /* Record the center and radius of the circular region. One way that
+    ** tested bounding boxes that intersect the circular region are detected
+    ** is by testing if each corner of the bounding box lies within radius
+    ** units of the center of the circle. */
+    if( p->nParam==4 ){
+      pCircle->centerx = p->aParam[0];
+      pCircle->centery = p->aParam[1];
+      pCircle->radius = p->aParam[2];
+      pCircle->eScoreType = (int)p->aParam[3];
+    }else{
+      const char *z = (const char*)sqlite3_value_text(p->apSqlParam[0]);
+      pCircle->centerx = 0.0;
+      pCircle->centery = 0.0;
+      pCircle->radius = 0.0;
+      pCircle->eScoreType = 0;
+      while( z && z[0] ){
+        if( z[0]=='r' && z[1]==':' ){
+          pCircle->radius = atof(&z[2]);
+        }else if( z[0]=='x' && z[1]==':' ){
+          pCircle->centerx = atof(&z[2]);
+        }else if( z[0]=='y' && z[1]==':' ){
+          pCircle->centery = atof(&z[2]);
+        }else if( z[0]=='e' && z[1]==':' ){
+          pCircle->eScoreType = (int)atof(&z[2]);
+        }else if( z[0]==' ' ){
+          z++;
+          continue;
+        }
+        while( z[0]!=0 && z[0]!=' ' ) z++;
+        while( z[0]==' ' ) z++;
+      }
+    }
+    if( pCircle->radius<0.0 ){
+      sqlite3_free(pCircle);
+      return SQLITE_NOMEM;
+    }
+
+    /* Define two bounding box regions. The first, aBox[0], extends to
+    ** infinity in the X dimension. It covers the same range of the Y dimension
+    ** as the circular region. The second, aBox[1], extends to infinity in
+    ** the Y dimension and is constrained to the range of the circle in the
+    ** X dimension.
+    **
+    ** Then imagine each box is split in half along its short axis by a line
+    ** that intersects the center of the circular region. A bounding box
+    ** being tested can be said to intersect the circular region if it contains
+    ** points from each half of either of the two infinite bounding boxes.
+    */
+    pCircle->aBox[0].xmin = pCircle->centerx;
+    pCircle->aBox[0].xmax = pCircle->centerx;
+    pCircle->aBox[0].ymin = pCircle->centery + pCircle->radius;
+    pCircle->aBox[0].ymax = pCircle->centery - pCircle->radius;
+    pCircle->aBox[1].xmin = pCircle->centerx + pCircle->radius;
+    pCircle->aBox[1].xmax = pCircle->centerx - pCircle->radius;
+    pCircle->aBox[1].ymin = pCircle->centery;
+    pCircle->aBox[1].ymax = pCircle->centery;
+    pCircle->mxArea = 200.0*200.0;
+  }
+
+  /* Check if any of the 4 corners of the bounding-box being tested lie 
+  ** inside the circular region. If they do, then the bounding-box does
+  ** intersect the region of interest. Set the output variable to true and
+  ** return SQLITE_OK in this case. */
+  for(i=0; i<4; i++){
+    double x = (i&0x01) ? xmax : xmin;
+    double y = (i&0x02) ? ymax : ymin;
+    double d2;
+    
+    d2  = (x-pCircle->centerx)*(x-pCircle->centerx);
+    d2 += (y-pCircle->centery)*(y-pCircle->centery);
+    if( d2<(pCircle->radius*pCircle->radius) ) nWithin++;
+  }
+
+  /* Check if the bounding box covers any other part of the circular region.
+  ** See comments above for a description of how this test works. If it does
+  ** cover part of the circular region, set the output variable to true
+  ** and return SQLITE_OK. */
+  if( nWithin==0 ){
+    for(i=0; i<2; i++){
+      if( xmin<=pCircle->aBox[i].xmin 
+       && xmax>=pCircle->aBox[i].xmax 
+       && ymin<=pCircle->aBox[i].ymin 
+       && ymax>=pCircle->aBox[i].ymax 
+      ){
+        nWithin = 1;
+        break;
+      }
+    }
+  }
+
+  if( pCircle->eScoreType==1 ){
+    /* Depth first search */
+    p->rScore = p->iLevel;
+  }else if( pCircle->eScoreType==2 ){
+    /* Breadth first search */
+    p->rScore = 100 - p->iLevel;
+  }else if( pCircle->eScoreType==3 ){
+    /* Depth-first search, except sort the leaf nodes by area with
+    ** the largest area first */
+    if( p->iLevel==1 ){
+      p->rScore = 1.0 - (xmax-xmin)*(ymax-ymin)/pCircle->mxArea;
+      if( p->rScore<0.01 ) p->rScore = 0.01;
+    }else{
+      p->rScore = 0.0;
+    }
+  }else if( pCircle->eScoreType==4 ){
+    /* Depth-first search, except exclude odd rowids */
+    p->rScore = p->iLevel;
+    if( p->iRowid&1 ) nWithin = 0;
+  }else{
+    /* Breadth-first search, except exclude odd rowids */
+    p->rScore = 100 - p->iLevel;
+    if( p->iRowid&1 ) nWithin = 0;
+  }
+  if( nWithin==0 ){
+    p->eWithin = NOT_WITHIN;
+  }else if( nWithin>=4 ){
+    p->eWithin = FULLY_WITHIN;
+  }else{
+    p->eWithin = PARTLY_WITHIN;
+  }
+  return SQLITE_OK;
+}
+/*
+** Implementation of "breadthfirstsearch" r-tree geometry callback using the 
+** 2nd-generation interface that allows scoring.
+**
+**     ... WHERE id MATCH breadthfirstsearch($x0,$x1,$y0,$y1) ...
+**
+** It returns all entries whose bounding boxes overlap with $x0,$x1,$y0,$y1.
+*/
+static int bfs_query_func(sqlite3_rtree_query_info *p){
+  double x0,x1,y0,y1;        /* Dimensions of box being tested */
+  double bx0,bx1,by0,by1;    /* Boundary of the query function */
+
+  if( p->nParam!=4 ) return SQLITE_ERROR;
+  x0 = p->aCoord[0];
+  x1 = p->aCoord[1];
+  y0 = p->aCoord[2];
+  y1 = p->aCoord[3];
+  bx0 = p->aParam[0];
+  bx1 = p->aParam[1];
+  by0 = p->aParam[2];
+  by1 = p->aParam[3];
+  p->rScore = 100 - p->iLevel;
+  if( p->eParentWithin==FULLY_WITHIN ){
+    p->eWithin = FULLY_WITHIN;
+  }else if( x0>=bx0 && x1<=bx1 && y0>=by0 && y1<=by1 ){
+    p->eWithin = FULLY_WITHIN;
+  }else if( x1>=bx0 && x0<=bx1 && y1>=by0 && y0<=by1 ){
+    p->eWithin = PARTLY_WITHIN;
+  }else{
+    p->eWithin = NOT_WITHIN;
+  }
+  return SQLITE_OK;
+}
+
+/* END of implementation of "circle" geometry callback.
+**************************************************************************
+*************************************************************************/
+
+#include <assert.h>
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+typedef struct Cube Cube;
+struct Cube {
+  double x;
+  double y;
+  double z;
+  double width;
+  double height;
+  double depth;
+};
+
+static void cube_context_free(void *p){
+  sqlite3_free(p);
+}
+
+/*
+** The context pointer registered along with the 'cube' callback is
+** always ((void *)&gHere). This is just to facilitate testing, it is not
+** actually used for anything.
+*/
+static int gHere = 42;
+
+/*
+** Implementation of a simple r-tree geom callback to test for intersection
+** of r-tree rows with a "cube" shape. Cubes are defined by six scalar
+** coordinates as follows:
+**
+**   cube(x, y, z, width, height, depth)
+**
+** The width, height and depth parameters must all be greater than zero.
+*/
+static int cube_geom(
+  sqlite3_rtree_geometry *p,
+  int nCoord,
+  sqlite3_rtree_dbl *aCoord,
+  int *piRes
+){
+  Cube *pCube = (Cube *)p->pUser;
+
+  assert( p->pContext==(void *)&gHere );
+
+  if( pCube==0 ){
+    if( p->nParam!=6 || nCoord!=6
+     || p->aParam[3]<=0.0 || p->aParam[4]<=0.0 || p->aParam[5]<=0.0
+    ){
+      return SQLITE_ERROR;
+    }
+    pCube = (Cube *)sqlite3_malloc(sizeof(Cube));
+    if( !pCube ){
+      return SQLITE_NOMEM;
+    }
+    pCube->x = p->aParam[0];
+    pCube->y = p->aParam[1];
+    pCube->z = p->aParam[2];
+    pCube->width = p->aParam[3];
+    pCube->height = p->aParam[4];
+    pCube->depth = p->aParam[5];
+
+    p->pUser = (void *)pCube;
+    p->xDelUser = cube_context_free;
+  }
+
+  assert( nCoord==6 );
+  *piRes = 0;
+  if( aCoord[0]<=(pCube->x+pCube->width)
+   && aCoord[1]>=pCube->x
+   && aCoord[2]<=(pCube->y+pCube->height)
+   && aCoord[3]>=pCube->y
+   && aCoord[4]<=(pCube->z+pCube->depth)
+   && aCoord[5]>=pCube->z
+  ){
+    *piRes = 1;
+  }
+
+  return SQLITE_OK;
+}
+#endif /* SQLITE_ENABLE_RTREE */
+
+static int SQLITE_TCLAPI register_cube_geom(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_ENABLE_RTREE
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(interp);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+#else
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  extern const char *sqlite3ErrName(int);
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_rtree_geometry_callback(db, "cube", cube_geom, (void *)&gHere);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+#endif
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI register_circle_geom(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_ENABLE_RTREE
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(interp);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+#else
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  extern const char *sqlite3ErrName(int);
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_rtree_geometry_callback(db, "circle", circle_geom, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_rtree_query_callback(db, "Qcircle",
+                                      circle_query_func, 0, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_rtree_query_callback(db, "breadthfirstsearch",
+                                      bfs_query_func, 0, 0);
+  }
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
+#endif
+  return TCL_OK;
+}
+
+int Sqlitetestrtree_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "register_cube_geom", register_cube_geom, 0, 0);
+  Tcl_CreateObjCommand(interp, "register_circle_geom",register_circle_geom,0,0);
+  return TCL_OK;
+}
diff --git a/src/test_schema.c b/src/test_schema.c
new file mode 100644
index 0000000..2cbc18e
--- /dev/null
+++ b/src/test_schema.c
@@ -0,0 +1,371 @@
+/*
+** 2006 June 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+
+/* The code in this file defines a sqlite3 virtual-table module that
+** provides a read-only view of the current database schema. There is one
+** row in the schema table for each column in the database schema.
+*/
+#define SCHEMA \
+"CREATE TABLE x("                                                            \
+  "database,"          /* Name of database (i.e. main, temp etc.) */         \
+  "tablename,"         /* Name of table */                                   \
+  "cid,"               /* Column number (from left-to-right, 0 upward) */    \
+  "name,"              /* Column name */                                     \
+  "type,"              /* Specified type (i.e. VARCHAR(32)) */               \
+  "not_null,"          /* Boolean. True if NOT NULL was specified */         \
+  "dflt_value,"        /* Default value for this column */                   \
+  "pk"                 /* True if this column is part of the primary key */  \
+")"
+
+/* If SQLITE_TEST is defined this code is preprocessed for use as part
+** of the sqlite test binary "testfixture". Otherwise it is preprocessed
+** to be compiled into an sqlite dynamic extension.
+*/
+#ifdef SQLITE_TEST
+#  include "sqliteInt.h"
+#  if defined(INCLUDE_SQLITE_TCL_H)
+#    include "sqlite_tcl.h"
+#  else
+#    include "tcl.h"
+#  endif
+#else
+#  include "sqlite3ext.h"
+  SQLITE_EXTENSION_INIT1
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+typedef struct schema_vtab schema_vtab;
+typedef struct schema_cursor schema_cursor;
+
+/* A schema table object */
+struct schema_vtab {
+  sqlite3_vtab base;
+  sqlite3 *db;
+};
+
+/* A schema table cursor object */
+struct schema_cursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pDbList;
+  sqlite3_stmt *pTableList;
+  sqlite3_stmt *pColumnList;
+  int rowid;
+};
+
+/*
+** None of this works unless we have virtual tables.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Table destructor for the schema module.
+*/
+static int schemaDestroy(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return 0;
+}
+
+/*
+** Table constructor for the schema module.
+*/
+static int schemaCreate(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc = SQLITE_NOMEM;
+  schema_vtab *pVtab = sqlite3_malloc(sizeof(schema_vtab));
+  if( pVtab ){
+    memset(pVtab, 0, sizeof(schema_vtab));
+    pVtab->db = db;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    rc = sqlite3_declare_vtab(db, SCHEMA);
+#endif
+  }
+  *ppVtab = (sqlite3_vtab *)pVtab;
+  return rc;
+}
+
+/*
+** Open a new cursor on the schema table.
+*/
+static int schemaOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  int rc = SQLITE_NOMEM;
+  schema_cursor *pCur;
+  pCur = sqlite3_malloc(sizeof(schema_cursor));
+  if( pCur ){
+    memset(pCur, 0, sizeof(schema_cursor));
+    *ppCursor = (sqlite3_vtab_cursor *)pCur;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Close a schema table cursor.
+*/
+static int schemaClose(sqlite3_vtab_cursor *cur){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  sqlite3_finalize(pCur->pDbList);
+  sqlite3_finalize(pCur->pTableList);
+  sqlite3_finalize(pCur->pColumnList);
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve a column of data.
+*/
+static int schemaColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  switch( i ){
+    case 0:
+      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pDbList, 1));
+      break;
+    case 1:
+      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pTableList, 0));
+      break;
+    default:
+      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pColumnList, i-2));
+      break;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve the current rowid.
+*/
+static int schemaRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  *pRowid = pCur->rowid;
+  return SQLITE_OK;
+}
+
+static int finalize(sqlite3_stmt **ppStmt){
+  int rc = sqlite3_finalize(*ppStmt);
+  *ppStmt = 0;
+  return rc;
+}
+
+static int schemaEof(sqlite3_vtab_cursor *cur){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  return (pCur->pDbList ? 0 : 1);
+}
+
+/*
+** Advance the cursor to the next row.
+*/
+static int schemaNext(sqlite3_vtab_cursor *cur){
+  int rc = SQLITE_OK;
+  schema_cursor *pCur = (schema_cursor *)cur;
+  schema_vtab *pVtab = (schema_vtab *)(cur->pVtab);
+  char *zSql = 0;
+
+  while( !pCur->pColumnList || SQLITE_ROW!=sqlite3_step(pCur->pColumnList) ){
+    if( SQLITE_OK!=(rc = finalize(&pCur->pColumnList)) ) goto next_exit;
+
+    while( !pCur->pTableList || SQLITE_ROW!=sqlite3_step(pCur->pTableList) ){
+      if( SQLITE_OK!=(rc = finalize(&pCur->pTableList)) ) goto next_exit;
+
+      assert(pCur->pDbList);
+      while( SQLITE_ROW!=sqlite3_step(pCur->pDbList) ){
+        rc = finalize(&pCur->pDbList);
+        goto next_exit;
+      }
+
+      /* Set zSql to the SQL to pull the list of tables from the 
+      ** sqlite_schema (or sqlite_temp_schema) table of the database
+      ** identified by the row pointed to by the SQL statement pCur->pDbList
+      ** (iterating through a "PRAGMA database_list;" statement).
+      */
+      if( sqlite3_column_int(pCur->pDbList, 0)==1 ){
+        zSql = sqlite3_mprintf(
+            "SELECT name FROM sqlite_temp_schema WHERE type='table'"
+        );
+      }else{
+        sqlite3_stmt *pDbList = pCur->pDbList;
+        zSql = sqlite3_mprintf(
+            "SELECT name FROM %Q.sqlite_schema WHERE type='table'",
+             sqlite3_column_text(pDbList, 1)
+        );
+      }
+      if( !zSql ){
+        rc = SQLITE_NOMEM;
+        goto next_exit;
+      }
+
+      rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pTableList, 0);
+      sqlite3_free(zSql);
+      if( rc!=SQLITE_OK ) goto next_exit;
+    }
+
+    /* Set zSql to the SQL to the table_info pragma for the table currently
+    ** identified by the rows pointed to by statements pCur->pDbList and
+    ** pCur->pTableList.
+    */
+    zSql = sqlite3_mprintf("PRAGMA %Q.table_info(%Q)", 
+        sqlite3_column_text(pCur->pDbList, 1),
+        sqlite3_column_text(pCur->pTableList, 0)
+    );
+
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+      goto next_exit;
+    }
+    rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pColumnList, 0);
+    sqlite3_free(zSql);
+    if( rc!=SQLITE_OK ) goto next_exit;
+  }
+  pCur->rowid++;
+
+next_exit:
+  /* TODO: Handle rc */
+  return rc;
+}
+
+/*
+** Reset a schema table cursor.
+*/
+static int schemaFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  int rc;
+  schema_vtab *pVtab = (schema_vtab *)(pVtabCursor->pVtab);
+  schema_cursor *pCur = (schema_cursor *)pVtabCursor;
+  pCur->rowid = 0;
+  finalize(&pCur->pTableList);
+  finalize(&pCur->pColumnList);
+  finalize(&pCur->pDbList);
+  rc = sqlite3_prepare(pVtab->db,"PRAGMA database_list", -1, &pCur->pDbList, 0);
+  return (rc==SQLITE_OK ? schemaNext(pVtabCursor) : rc);
+}
+
+/*
+** Analyse the WHERE condition.
+*/
+static int schemaBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that merely echos method calls into TCL
+** variables.
+*/
+static sqlite3_module schemaModule = {
+  0,                           /* iVersion */
+  schemaCreate,
+  schemaCreate,
+  schemaBestIndex,
+  schemaDestroy,
+  schemaDestroy,
+  schemaOpen,                  /* xOpen - open a cursor */
+  schemaClose,                 /* xClose - close a cursor */
+  schemaFilter,                /* xFilter - configure scan constraints */
+  schemaNext,                  /* xNext - advance a cursor */
+  schemaEof,                   /* xEof */
+  schemaColumn,                /* xColumn - read data */
+  schemaRowid,                 /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+  0,                           /* xSavepoint */
+  0,                           /* xRelease */
+  0,                           /* xRollbackTo */
+  0,                           /* xShadowName */
+  0                            /* xIntegrity */
+};
+
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
+
+#ifdef SQLITE_TEST
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the schema virtual table module.
+*/
+static int SQLITE_TCLAPI register_schema_module(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "schema", &schemaModule, 0);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestschema_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_schema_module", register_schema_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
+
+#else
+
+/*
+** Extension load function.
+*/
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_schema_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "schema", &schemaModule, 0);
+#endif
+  return 0;
+}
+
+#endif
diff --git a/src/test_sqllog.c b/src/test_sqllog.c
new file mode 100644
index 0000000..9ae0e50
--- /dev/null
+++ b/src/test_sqllog.c
@@ -0,0 +1,556 @@
+/*
+** 2012 November 26
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** OVERVIEW
+**
+**   This file contains experimental code used to record data from live
+**   SQLite applications that may be useful for offline analysis. 
+**   Specifically, this module can be used to capture the following
+**   information:
+**
+**     1) The initial contents of all database files opened by the 
+**        application, and
+**
+**     2) All SQL statements executed by the application.
+**
+**   The captured information can then be used to run (for example)
+**   performance analysis looking for slow queries or to look for
+**   optimization opportunities in either the application or in SQLite
+**   itself.
+**
+** USAGE
+**
+**   To use this module, SQLite must be compiled with the SQLITE_ENABLE_SQLLOG
+**   pre-processor symbol defined and this file linked into the application.
+**   One way to link this file into the application is to append the content
+**   of this file onto the end of the "sqlite3.c" amalgamation and then 
+**   recompile the application as normal except with the addition  of the
+**   -DSQLITE_ENABLE_SQLLOG option.
+**
+**   At runtime, logging is enabled by setting environment variable
+**   SQLITE_SQLLOG_DIR to the name of a directory in which to store logged 
+**   data. The logging directory must already exist.
+**
+**   Usually, if the application opens the same database file more than once
+**   (either by attaching it or by using more than one database handle), only
+**   a single copy is made. This behavior may be overridden (so that a 
+**   separate copy is taken each time the database file is opened or attached)
+**   by setting the environment variable SQLITE_SQLLOG_REUSE_FILES to 0.
+**
+**   If the environment variable SQLITE_SQLLOG_CONDITIONAL is defined, then
+**   logging is only done for database connections if a file named
+**   "<database>-sqllog" exists in the same directly as the main database
+**   file when it is first opened ("<database>" is replaced by the actual 
+**   name of the main database file).
+**
+** OUTPUT:
+**
+**   The SQLITE_SQLLOG_DIR is populated with three types of files:
+**
+**      sqllog_N.db   - Copies of database files. N may be any integer.
+**
+**      sqllog_N.sql  - A list of SQL statements executed by a single
+**                      connection. N may be any integer.
+**
+**      sqllog.idx    - An index mapping from integer N to a database
+**                      file name - indicating the full path of the
+**                      database from which sqllog_N.db was copied.
+**
+** ERROR HANDLING:
+**
+**   This module attempts to make a best effort to continue logging if an
+**   IO or other error is encountered. For example, if a log file cannot 
+**   be opened logs are not collected for that connection, but other
+**   logging proceeds as expected. Errors are logged by calling sqlite3_log().
+*/
+
+#ifndef _SQLITE3_H_
+#include "sqlite3.h"
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include <sys/types.h>
+#include <unistd.h>
+static int getProcessId(void){
+#if SQLITE_OS_WIN
+  return (int)_getpid();
+#else
+  return (int)getpid();
+#endif
+}
+
+/* Names of environment variables to be used */
+#define ENVIRONMENT_VARIABLE1_NAME "SQLITE_SQLLOG_DIR"
+#define ENVIRONMENT_VARIABLE2_NAME "SQLITE_SQLLOG_REUSE_FILES"
+#define ENVIRONMENT_VARIABLE3_NAME "SQLITE_SQLLOG_CONDITIONAL"
+
+/* Assume that all database and database file names are shorted than this. */
+#define SQLLOG_NAMESZ 512
+
+/* Maximum number of simultaneous database connections the process may
+** open (if any more are opened an error is logged using sqlite3_log()
+** and processing is halted).
+*/
+#define MAX_CONNECTIONS 256
+
+/* There is one instance of this object for each SQLite database connection
+** that is being logged.
+*/
+struct SLConn {
+  int isErr;                      /* True if an error has occurred */
+  sqlite3 *db;                    /* Connection handle */
+  int iLog;                       /* First integer value used in file names */
+  FILE *fd;                       /* File descriptor for log file */
+};
+
+/* This object is a singleton that keeps track of all data loggers.
+*/
+static struct SLGlobal {
+  /* Protected by MUTEX_STATIC_MAIN */
+  sqlite3_mutex *mutex;           /* Recursive mutex */
+  int nConn;                      /* Size of aConn[] array */
+
+  /* Protected by SLGlobal.mutex */
+  int bConditional;               /* Only trace if *-sqllog file is present */
+  int bReuse;                     /* True to avoid extra copies of db files */
+  char zPrefix[SQLLOG_NAMESZ];    /* Prefix for all created files */
+  char zIdx[SQLLOG_NAMESZ];       /* Full path to *.idx file */
+  int iNextLog;                   /* Used to allocate file names */
+  int iNextDb;                    /* Used to allocate database file names */
+  int bRec;                       /* True if testSqllog() is called rec. */
+  int iClock;                     /* Clock value */
+  struct SLConn aConn[MAX_CONNECTIONS];
+} sqllogglobal;
+
+/*
+** Return true if c is an ASCII whitespace character.
+*/
+static int sqllog_isspace(char c){
+  return (c==' ' || c=='\t' || c=='\n' || c=='\v' || c=='\f' || c=='\r');
+}
+
+/*
+** The first argument points to a nul-terminated string containing an SQL
+** command. Before returning, this function sets *pz to point to the start
+** of the first token in this command, and *pn to the number of bytes in 
+** the token. This is used to check if the SQL command is an "ATTACH" or 
+** not.
+*/
+static void sqllogTokenize(const char *z, const char **pz, int *pn){
+  const char *p = z;
+  int n;
+
+  /* Skip past any whitespace */
+  while( sqllog_isspace(*p) ){
+    p++;
+  }
+
+  /* Figure out how long the first token is */
+  *pz = p;
+  n = 0;
+  while( (p[n]>='a' && p[n]<='z') || (p[n]>='A' && p[n]<='Z') ) n++;
+  *pn = n;
+}
+
+/*
+** Check if the logs directory already contains a copy of database file 
+** zFile. If so, return a pointer to the full path of the copy. Otherwise,
+** return NULL.
+**
+** If a non-NULL value is returned, then the caller must arrange to 
+** eventually free it using sqlite3_free().
+*/
+static char *sqllogFindFile(const char *zFile){
+  char *zRet = 0;
+  FILE *fd = 0;
+
+  /* Open the index file for reading */
+  fd = fopen(sqllogglobal.zIdx, "r");
+  if( fd==0 ){
+    sqlite3_log(SQLITE_IOERR, "sqllogFindFile(): error in fopen()");
+    return 0;
+  }
+
+  /* Loop through each entry in the index file. If zFile is not NULL and the
+  ** entry is a match, then set zRet to point to the filename of the existing
+  ** copy and break out of the loop.  */
+  while( feof(fd)==0 ){
+    char zLine[SQLLOG_NAMESZ*2+5];
+    if( fgets(zLine, sizeof(zLine), fd) ){
+      int n;
+      char *z;
+
+      zLine[sizeof(zLine)-1] = '\0';
+      z = zLine;
+      while( *z>='0' && *z<='9' ) z++;
+      while( *z==' ' ) z++;
+
+      n = strlen(z);
+      while( n>0 && sqllog_isspace(z[n-1]) ) n--;
+
+      if( n==strlen(zFile) && 0==memcmp(zFile, z, n) ){
+        char zBuf[16];
+        memset(zBuf, 0, sizeof(zBuf));
+        z = zLine;
+        while( *z>='0' && *z<='9' ){
+          zBuf[z-zLine] = *z;
+          z++;
+        }
+        zRet = sqlite3_mprintf("%s_%s.db", sqllogglobal.zPrefix, zBuf);
+        break;
+      }
+    }
+  }
+
+  if( ferror(fd) ){
+    sqlite3_log(SQLITE_IOERR, "sqllogFindFile(): error reading index file");
+  }
+
+  fclose(fd);
+  return zRet;
+}
+
+static int sqllogFindAttached(
+  sqlite3 *db,                    /* Database connection */
+  const char *zSearch,            /* Name to search for (or NULL) */
+  char *zName,                    /* OUT: Name of attached database */
+  char *zFile                     /* OUT: Name of attached file */
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  /* The "PRAGMA database_list" command returns a list of databases in the
+  ** order that they were attached. So a newly attached database is 
+  ** described by the last row returned.  */
+  assert( sqllogglobal.bRec==0 );
+  sqllogglobal.bRec = 1;
+  rc = sqlite3_prepare_v2(db, "PRAGMA database_list", -1, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    while( SQLITE_ROW==sqlite3_step(pStmt) ){
+      const char *zVal1; int nVal1;
+      const char *zVal2; int nVal2;
+
+      zVal1 = (const char*)sqlite3_column_text(pStmt, 1);
+      nVal1 = sqlite3_column_bytes(pStmt, 1);
+      if( zName ){
+        memcpy(zName, zVal1, nVal1+1);
+      }
+
+      zVal2 = (const char*)sqlite3_column_text(pStmt, 2);
+      nVal2 = sqlite3_column_bytes(pStmt, 2);
+      memcpy(zFile, zVal2, nVal2+1);
+
+      if( zSearch && strlen(zSearch)==nVal1 
+       && 0==sqlite3_strnicmp(zSearch, zVal1, nVal1)
+      ){
+        break;
+      }
+    }
+    rc = sqlite3_finalize(pStmt);
+  }
+  sqllogglobal.bRec = 0;
+
+  if( rc!=SQLITE_OK ){
+    sqlite3_log(rc, "sqllogFindAttached(): error in \"PRAGMA database_list\"");
+  }
+  return rc;
+}
+
+
+/*
+** Parameter zSearch is the name of a database attached to the database 
+** connection associated with the first argument. This function creates
+** a backup of this database in the logs directory.
+**
+** The name used for the backup file is automatically generated. Call
+** it zFile.
+**
+** If the bLog parameter is true, then a statement of the following form
+** is written to the log file associated with *p:
+**
+**    ATTACH 'zFile' AS 'zName';
+**
+** Otherwise, if bLog is false, a comment is added to the log file:
+**
+**    -- Main database file is 'zFile'
+**
+** The SLGlobal.mutex mutex is always held when this function is called.
+*/
+static void sqllogCopydb(struct SLConn *p, const char *zSearch, int bLog){
+  char zName[SQLLOG_NAMESZ];      /* Attached database name */
+  char zFile[SQLLOG_NAMESZ];      /* Database file name */
+  char *zFree;
+  char *zInit = 0;
+  int rc;
+
+  rc = sqllogFindAttached(p->db, zSearch, zName, zFile);
+  if( rc!=SQLITE_OK ) return;
+
+  if( zFile[0]=='\0' ){
+    zInit = sqlite3_mprintf("");
+  }else{
+    if( sqllogglobal.bReuse ){
+      zInit = sqllogFindFile(zFile);
+    }else{
+      zInit = 0;
+    }
+    if( zInit==0 ){
+      int rc;
+      sqlite3 *copy = 0;
+      int iDb;
+
+      /* Generate a file-name to use for the copy of this database */
+      iDb = sqllogglobal.iNextDb++;
+      zInit = sqlite3_mprintf("%s_%02d.db", sqllogglobal.zPrefix, iDb);
+
+      /* Create the backup */
+      assert( sqllogglobal.bRec==0 );
+      sqllogglobal.bRec = 1;
+      rc = sqlite3_open(zInit, &copy);
+      if( rc==SQLITE_OK ){
+        sqlite3_backup *pBak;
+        sqlite3_exec(copy, "PRAGMA synchronous = 0", 0, 0, 0);
+        pBak = sqlite3_backup_init(copy, "main", p->db, zName);
+        if( pBak ){
+          sqlite3_backup_step(pBak, -1);
+          rc = sqlite3_backup_finish(pBak);
+        }else{
+          rc = sqlite3_errcode(copy);
+        }
+        sqlite3_close(copy);
+      }
+      sqllogglobal.bRec = 0;
+
+      if( rc==SQLITE_OK ){
+        /* Write an entry into the database index file */
+        FILE *fd = fopen(sqllogglobal.zIdx, "a");
+        if( fd ){
+          fprintf(fd, "%d %s\n", iDb, zFile);
+          fclose(fd);
+        }
+      }else{
+        sqlite3_log(rc, "sqllogCopydb(): error backing up database");
+      }
+    }
+  }
+
+  if( bLog ){
+    zFree = sqlite3_mprintf("ATTACH '%q' AS '%q'; -- clock=%d\n", 
+        zInit, zName, sqllogglobal.iClock++
+    );
+  }else{
+    zFree = sqlite3_mprintf("-- Main database is '%q'\n", zInit);
+  }
+  fprintf(p->fd, "%s", zFree);
+  sqlite3_free(zFree);
+
+  sqlite3_free(zInit);
+}
+
+/*
+** If it is not already open, open the log file for connection *p. 
+**
+** The SLGlobal.mutex mutex is always held when this function is called.
+*/
+static void sqllogOpenlog(struct SLConn *p){
+  /* If the log file has not yet been opened, open it now. */
+  if( p->fd==0 ){
+    char *zLog;
+
+    /* If it is still NULL, have global.zPrefix point to a copy of 
+    ** environment variable $ENVIRONMENT_VARIABLE1_NAME.  */
+    if( sqllogglobal.zPrefix[0]==0 ){
+      FILE *fd;
+      char *zVar = getenv(ENVIRONMENT_VARIABLE1_NAME);
+      if( zVar==0 || strlen(zVar)+10>=(sizeof(sqllogglobal.zPrefix)) ) return;
+      sqlite3_snprintf(sizeof(sqllogglobal.zPrefix), sqllogglobal.zPrefix,
+                        "%s/sqllog_%05d", zVar, getProcessId());
+      sqlite3_snprintf(sizeof(sqllogglobal.zIdx), sqllogglobal.zIdx,
+                        "%s.idx", sqllogglobal.zPrefix);
+      if( getenv(ENVIRONMENT_VARIABLE2_NAME) ){
+        sqllogglobal.bReuse = atoi(getenv(ENVIRONMENT_VARIABLE2_NAME));
+      }
+      fd = fopen(sqllogglobal.zIdx, "w");
+      if( fd ) fclose(fd);
+    }
+
+    /* Open the log file */
+    zLog = sqlite3_mprintf("%s_%05d.sql", sqllogglobal.zPrefix, p->iLog);
+    p->fd = fopen(zLog, "w");
+    sqlite3_free(zLog);
+    if( p->fd==0 ){
+      sqlite3_log(SQLITE_IOERR, "sqllogOpenlog(): Failed to open log file");
+    }
+  }
+}
+
+/*
+** This function is called if the SQLLOG callback is invoked to report
+** execution of an SQL statement. Parameter p is the connection the statement
+** was executed by and parameter zSql is the text of the statement itself.
+*/
+static void testSqllogStmt(struct SLConn *p, const char *zSql){
+  const char *zFirst;             /* Pointer to first token in zSql */
+  int nFirst;                     /* Size of token zFirst in bytes */
+
+  sqllogTokenize(zSql, &zFirst, &nFirst);
+  if( nFirst!=6 || 0!=sqlite3_strnicmp("ATTACH", zFirst, 6) ){
+    /* Not an ATTACH statement. Write this directly to the log. */
+    fprintf(p->fd, "%s; -- clock=%d\n", zSql, sqllogglobal.iClock++);
+  }else{
+    /* This is an ATTACH statement. Copy the database. */
+    sqllogCopydb(p, 0, 1);
+  }
+}
+
+/*
+** The database handle passed as the only argument has just been opened.
+** Return true if this module should log initial databases and SQL 
+** statements for this connection, or false otherwise.
+**
+** If an error occurs, sqlite3_log() is invoked to report it to the user
+** and zero returned.
+*/
+static int sqllogTraceDb(sqlite3 *db){
+  int bRet = 1;
+  if( sqllogglobal.bConditional ){
+    char zFile[SQLLOG_NAMESZ];      /* Attached database name */
+    int rc = sqllogFindAttached(db, "main", 0, zFile);
+    if( rc==SQLITE_OK ){
+      int nFile = strlen(zFile);
+      if( (SQLLOG_NAMESZ-nFile)<8 ){
+        sqlite3_log(SQLITE_IOERR, 
+            "sqllogTraceDb(): database name too long (%d bytes)", nFile
+        );
+        bRet = 0;
+      }else{
+        memcpy(&zFile[nFile], "-sqllog", 8);
+        bRet = !access(zFile, F_OK);
+      }
+    }
+  }
+  return bRet;
+}
+
+/*
+** The SQLITE_CONFIG_SQLLOG callback registered by sqlite3_init_sqllog().
+**
+** The eType parameter has the following values:
+**
+**    0:  Opening a new database connection.  zSql is the name of the
+**        file being opened.  db is a pointer to the newly created database
+**        connection.
+**
+**    1:  An SQL statement has run to completion.  zSql is the text of the
+**        SQL statement with all parameters expanded to their actual values.
+**
+**    2:  Closing a database connection.  zSql is NULL.  The db pointer to
+**        the database connection being closed has already been shut down
+**        and cannot be used for any further SQL.
+**
+** The pCtx parameter is a copy of the pointer that was originally passed
+** into the sqlite3_config(SQLITE_CONFIG_SQLLOG) statement.  In this
+** particular implementation, pCtx is always a pointer to the 
+** sqllogglobal global variable define above.
+*/
+static void testSqllog(void *pCtx, sqlite3 *db, const char *zSql, int eType){
+  struct SLConn *p = 0;
+  sqlite3_mutex *mainmtx = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MAIN);
+
+  assert( eType==0 || eType==1 || eType==2 );
+  assert( (eType==2)==(zSql==0) );
+
+  /* This is a database open command. */
+  if( eType==0 ){
+    sqlite3_mutex_enter(mainmtx);
+    if( sqllogglobal.mutex==0 ){
+      sqllogglobal.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);
+    }
+    sqlite3_mutex_leave(mainmtx);
+
+    sqlite3_mutex_enter(sqllogglobal.mutex);
+    if( sqllogglobal.bRec==0 && sqllogTraceDb(db) ){
+
+      sqlite3_mutex_enter(mainmtx);
+      p = &sqllogglobal.aConn[sqllogglobal.nConn++];
+      p->fd = 0;
+      p->db = db;
+      p->iLog = sqllogglobal.iNextLog++;
+      sqlite3_mutex_leave(mainmtx);
+
+      /* Open the log and take a copy of the main database file */
+      sqllogOpenlog(p);
+      if( p->fd ) sqllogCopydb(p, "main", 0);
+    }
+    sqlite3_mutex_leave(sqllogglobal.mutex);
+  }
+
+  else{
+
+    int i;
+    for(i=0; i<sqllogglobal.nConn; i++){
+      p = &sqllogglobal.aConn[i];
+      if( p->db==db ) break;
+    }
+
+    /* A database handle close command */
+    if( eType==2 ){
+      sqlite3_mutex_enter(mainmtx);
+      if( i<sqllogglobal.nConn ){
+        if( p->fd ) fclose(p->fd);
+        p->db = 0;
+        p->fd = 0;
+        sqllogglobal.nConn--;
+      }
+
+      if( sqllogglobal.nConn==0 ){
+        sqlite3_mutex_free(sqllogglobal.mutex);
+        sqllogglobal.mutex = 0;
+      }else if( i<sqllogglobal.nConn ){
+        int nShift = &sqllogglobal.aConn[sqllogglobal.nConn] - p;
+        if( nShift>0 ){
+          memmove(p, &p[1], nShift*sizeof(struct SLConn));
+        }
+      }
+      sqlite3_mutex_leave(mainmtx);
+
+    /* An ordinary SQL command. */
+    }else if( i<sqllogglobal.nConn && p->fd ){
+      sqlite3_mutex_enter(sqllogglobal.mutex);
+      if( sqllogglobal.bRec==0 ){
+        testSqllogStmt(p, zSql);
+      }
+      sqlite3_mutex_leave(sqllogglobal.mutex);
+    }
+  }
+}
+
+/*
+** This function is called either before sqlite3_initialized() or by it.
+** It checks if the SQLITE_SQLLOG_DIR variable is defined, and if so 
+** registers an SQLITE_CONFIG_SQLLOG callback to record the applications
+** database activity.
+*/
+void sqlite3_init_sqllog(void){
+  if( getenv(ENVIRONMENT_VARIABLE1_NAME) ){
+    if( SQLITE_OK==sqlite3_config(SQLITE_CONFIG_SQLLOG, testSqllog, 0) ){
+      memset(&sqllogglobal, 0, sizeof(sqllogglobal));
+      sqllogglobal.bReuse = 1;
+      if( getenv(ENVIRONMENT_VARIABLE3_NAME) ){
+        sqllogglobal.bConditional = 1;
+      }
+    }
+  }
+}
diff --git a/src/test_superlock.c b/src/test_superlock.c
new file mode 100644
index 0000000..45d0d62
--- /dev/null
+++ b/src/test_superlock.c
@@ -0,0 +1,363 @@
+/*
+** 2010 November 19
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Example code for obtaining an exclusive lock on an SQLite database
+** file. This method is complicated, but works for both WAL and rollback
+** mode database files. The interface to the example code in this file 
+** consists of the following two functions:
+**
+**   sqlite3demo_superlock()
+**   sqlite3demo_superunlock()
+*/
+
+#include "sqlite3.h"
+#include <string.h>               /* memset(), strlen() */
+#include <assert.h>               /* assert() */
+
+/*
+** A structure to collect a busy-handler callback and argument and a count
+** of the number of times it has been invoked.
+*/
+struct SuperlockBusy {
+  int (*xBusy)(void*,int);        /* Pointer to busy-handler function */
+  void *pBusyArg;                 /* First arg to pass to xBusy */
+  int nBusy;                      /* Number of times xBusy has been invoked */
+};
+typedef struct SuperlockBusy SuperlockBusy;
+
+/*
+** An instance of the following structure is allocated for each active
+** superlock. The opaque handle returned by sqlite3demo_superlock() is
+** actually a pointer to an instance of this structure.
+*/
+struct Superlock {
+  sqlite3 *db;                    /* Database handle used to lock db */
+  int bWal;                       /* True if db is a WAL database */
+};
+typedef struct Superlock Superlock;
+
+/*
+** The pCtx pointer passed to this function is actually a pointer to a
+** SuperlockBusy structure. Invoke the busy-handler function encapsulated
+** by the structure and return the result.
+*/
+static int superlockBusyHandler(void *pCtx, int UNUSED){
+  SuperlockBusy *pBusy = (SuperlockBusy *)pCtx;
+  if( pBusy->xBusy==0 ) return 0;
+  return pBusy->xBusy(pBusy->pBusyArg, pBusy->nBusy++);
+}
+
+/*
+** This function is used to determine if the main database file for 
+** connection db is open in WAL mode or not. If no error occurs and the
+** database file is in WAL mode, set *pbWal to true and return SQLITE_OK.
+** If it is not in WAL mode, set *pbWal to false.
+**
+** If an error occurs, return an SQLite error code. The value of *pbWal
+** is undefined in this case.
+*/
+static int superlockIsWal(Superlock *pLock){
+  int rc;                         /* Return Code */
+  sqlite3_stmt *pStmt;            /* Compiled PRAGMA journal_mode statement */
+
+  rc = sqlite3_prepare(pLock->db, "PRAGMA main.journal_mode", -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  pLock->bWal = 0;
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    const char *zMode = (const char *)sqlite3_column_text(pStmt, 0);
+    if( zMode && strlen(zMode)==3 && sqlite3_strnicmp("wal", zMode, 3)==0 ){
+      pLock->bWal = 1;
+    }
+  }
+
+  return sqlite3_finalize(pStmt);
+}
+
+/*
+** Obtain an exclusive shm-lock on nByte bytes starting at offset idx
+** of the file fd. If the lock cannot be obtained immediately, invoke
+** the busy-handler until either it is obtained or the busy-handler
+** callback returns 0.
+*/
+static int superlockShmLock(
+  sqlite3_file *fd,               /* Database file handle */
+  int idx,                        /* Offset of shm-lock to obtain */
+  int nByte,                      /* Number of consective bytes to lock */
+  SuperlockBusy *pBusy            /* Busy-handler wrapper object */
+){
+  int rc;
+  int (*xShmLock)(sqlite3_file*, int, int, int) = fd->pMethods->xShmLock;
+  do {
+    rc = xShmLock(fd, idx, nByte, SQLITE_SHM_LOCK|SQLITE_SHM_EXCLUSIVE);
+  }while( rc==SQLITE_BUSY && superlockBusyHandler((void *)pBusy, 0) );
+  return rc;
+}
+
+/*
+** Obtain the extra locks on the database file required for WAL databases.
+** Invoke the supplied busy-handler as required.
+*/
+static int superlockWalLock(
+  sqlite3 *db,                    /* Database handle open on WAL database */
+  SuperlockBusy *pBusy            /* Busy handler wrapper object */
+){
+  int rc;                         /* Return code */
+  sqlite3_file *fd = 0;           /* Main database file handle */
+  void volatile *p = 0;           /* Pointer to first page of shared memory */
+
+  /* Obtain a pointer to the sqlite3_file object open on the main db file. */
+  rc = sqlite3_file_control(db, "main", SQLITE_FCNTL_FILE_POINTER, (void *)&fd);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Obtain the "recovery" lock. Normally, this lock is only obtained by
+  ** clients running database recovery.  
+  */
+  rc = superlockShmLock(fd, 2, 1, pBusy);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Zero the start of the first shared-memory page. This means that any
+  ** clients that open read or write transactions from this point on will
+  ** have to run recovery before proceeding. Since they need the "recovery"
+  ** lock that this process is holding to do that, no new read or write
+  ** transactions may now be opened. Nor can a checkpoint be run, for the
+  ** same reason.
+  */
+  rc = fd->pMethods->xShmMap(fd, 0, 32*1024, 1, &p);
+  if( rc!=SQLITE_OK ) return rc;
+  memset((void *)p, 0, 32);
+
+  /* Obtain exclusive locks on all the "read-lock" slots. Once these locks
+  ** are held, it is guaranteed that there are no active reader, writer or 
+  ** checkpointer clients.
+  */
+  rc = superlockShmLock(fd, 3, SQLITE_SHM_NLOCK-3, pBusy);
+  return rc;
+}
+
+/*
+** Release a superlock held on a database file. The argument passed to 
+** this function must have been obtained from a successful call to
+** sqlite3demo_superlock().
+*/
+void sqlite3demo_superunlock(void *pLock){
+  Superlock *p = (Superlock *)pLock;
+  if( p->bWal ){
+    int rc;                         /* Return code */
+    int flags = SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE;
+    sqlite3_file *fd = 0;
+    rc = sqlite3_file_control(p->db, "main", SQLITE_FCNTL_FILE_POINTER, (void *)&fd);
+    if( rc==SQLITE_OK ){
+      fd->pMethods->xShmLock(fd, 2, 1, flags);
+      fd->pMethods->xShmLock(fd, 3, SQLITE_SHM_NLOCK-3, flags);
+    }
+  }
+  sqlite3_close(p->db);
+  sqlite3_free(p);
+}
+
+/*
+** Obtain a superlock on the database file identified by zPath, using the
+** locking primitives provided by VFS zVfs. If successful, SQLITE_OK is
+** returned and output variable *ppLock is populated with an opaque handle
+** that may be used with sqlite3demo_superunlock() to release the lock.
+**
+** If an error occurs, *ppLock is set to 0 and an SQLite error code 
+** (e.g. SQLITE_BUSY) is returned.
+**
+** If a required lock cannot be obtained immediately and the xBusy parameter
+** to this function is not NULL, then xBusy is invoked in the same way
+** as a busy-handler registered with SQLite (using sqlite3_busy_handler())
+** until either the lock can be obtained or the busy-handler function returns
+** 0 (indicating "give up").
+*/
+int sqlite3demo_superlock(
+  const char *zPath,              /* Path to database file to lock */
+  const char *zVfs,               /* VFS to use to access database file */
+  int (*xBusy)(void*,int),        /* Busy handler callback */
+  void *pBusyArg,                 /* Context arg for busy handler */
+  void **ppLock                   /* OUT: Context to pass to superunlock() */
+){
+  SuperlockBusy busy = {0, 0, 0}; /* Busy handler wrapper object */
+  int rc;                         /* Return code */
+  Superlock *pLock;
+
+  pLock = sqlite3_malloc(sizeof(Superlock));
+  if( !pLock ) return SQLITE_NOMEM;
+  memset(pLock, 0, sizeof(Superlock));
+
+  /* Open a database handle on the file to superlock. */
+  rc = sqlite3_open_v2(
+      zPath, &pLock->db, SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE, zVfs
+  );
+
+  /* Install a busy-handler and execute a BEGIN EXCLUSIVE. If this is not
+  ** a WAL database, this is all we need to do.  
+  **
+  ** A wrapper function is used to invoke the busy-handler instead of
+  ** registering the busy-handler function supplied by the user directly
+  ** with SQLite. This is because the same busy-handler function may be
+  ** invoked directly later on when attempting to obtain the extra locks
+  ** required in WAL mode. By using the wrapper, we are able to guarantee
+  ** that the "nBusy" integer parameter passed to the users busy-handler
+  ** represents the total number of busy-handler invocations made within
+  ** this call to sqlite3demo_superlock(), including any made during the
+  ** "BEGIN EXCLUSIVE".
+  */
+  if( rc==SQLITE_OK ){
+    busy.xBusy = xBusy;
+    busy.pBusyArg = pBusyArg;
+    sqlite3_busy_handler(pLock->db, superlockBusyHandler, (void *)&busy);
+    rc = sqlite3_exec(pLock->db, "BEGIN EXCLUSIVE", 0, 0, 0);
+  }
+
+  /* If the BEGIN EXCLUSIVE was executed successfully and this is a WAL
+  ** database, call superlockWalLock() to obtain the extra locks required
+  ** to prevent readers, writers and/or checkpointers from accessing the
+  ** db while this process is holding the superlock.
+  **
+  ** Before attempting any WAL locks, commit the transaction started above
+  ** to drop the WAL read and write locks currently held. Otherwise, the
+  ** new WAL locks may conflict with the old.
+  */
+  if( rc==SQLITE_OK ){
+    if( SQLITE_OK==(rc = superlockIsWal(pLock)) && pLock->bWal ){
+      rc = sqlite3_exec(pLock->db, "COMMIT", 0, 0, 0);
+      if( rc==SQLITE_OK ){
+        rc = superlockWalLock(pLock->db, &busy);
+      }
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3demo_superunlock(pLock);
+    *ppLock = 0;
+  }else{
+    *ppLock = pLock;
+  }
+
+  return rc;
+}
+
+/*
+** End of example code. Everything below here is the test harness.
+**************************************************************************
+**************************************************************************
+*************************************************************************/
+
+
+#ifdef SQLITE_TEST
+
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#  ifndef SQLITE_TCLAPI
+#    define SQLITE_TCLAPI
+#  endif
+#endif
+
+struct InterpAndScript {
+  Tcl_Interp *interp;
+  Tcl_Obj *pScript;
+};
+typedef struct InterpAndScript InterpAndScript;
+
+static void SQLITE_TCLAPI superunlock_del(ClientData cd){
+  sqlite3demo_superunlock((void *)cd);
+}
+
+static int SQLITE_TCLAPI superunlock_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  Tcl_DeleteCommand(interp, Tcl_GetString(objv[0]));
+  return TCL_OK;
+}
+
+static int superlock_busy(void *pCtx, int nBusy){
+  InterpAndScript *p = (InterpAndScript *)pCtx;
+  Tcl_Obj *pEval;                 /* Script to evaluate */
+  int iVal = 0;                   /* Value to return */
+
+  pEval = Tcl_DuplicateObj(p->pScript);
+  Tcl_IncrRefCount(pEval);
+  Tcl_ListObjAppendElement(p->interp, pEval, Tcl_NewIntObj(nBusy));
+  Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+  Tcl_GetIntFromObj(p->interp, Tcl_GetObjResult(p->interp), &iVal);
+  Tcl_DecrRefCount(pEval);
+
+  return iVal;
+}
+
+/*
+** Tclcmd: sqlite3demo_superlock CMDNAME PATH VFS BUSY-HANDLER-SCRIPT
+*/
+static int SQLITE_TCLAPI superlock_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *pLock;                    /* Lock context */
+  char *zPath;
+  char *zVfs = 0;
+  InterpAndScript busy = {0, 0};
+  int (*xBusy)(void*,int) = 0;    /* Busy handler callback */
+  int rc;                         /* Return code from sqlite3demo_superlock() */
+
+  if( objc<3 || objc>5 ){
+    Tcl_WrongNumArgs(
+        interp, 1, objv, "CMDNAME PATH ?VFS? ?BUSY-HANDLER-SCRIPT?");
+    return TCL_ERROR;
+  }
+
+  zPath = Tcl_GetString(objv[2]);
+
+  if( objc>3 ){
+    zVfs = Tcl_GetString(objv[3]);
+    if( strlen(zVfs)==0 ) zVfs = 0;
+  }
+  if( objc>4 ){
+    busy.interp = interp;
+    busy.pScript = objv[4];
+    xBusy = superlock_busy;
+  }
+
+  rc = sqlite3demo_superlock(zPath, zVfs, xBusy, &busy, &pLock);
+  assert( rc==SQLITE_OK || pLock==0 );
+  assert( rc!=SQLITE_OK || pLock!=0 );
+
+  if( rc!=SQLITE_OK ){
+    extern const char *sqlite3ErrStr(int);
+    Tcl_ResetResult(interp);
+    Tcl_AppendResult(interp, sqlite3ErrStr(rc), 0);
+    return TCL_ERROR;
+  }
+
+  Tcl_CreateObjCommand(
+      interp, Tcl_GetString(objv[1]), superunlock_cmd, pLock, superunlock_del
+  );
+  Tcl_SetObjResult(interp, objv[1]);
+  return TCL_OK;
+}
+
+int SqliteSuperlock_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "sqlite3demo_superlock", superlock_cmd, 0, 0);
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_syscall.c b/src/test_syscall.c
new file mode 100644
index 0000000..3cd1034
--- /dev/null
+++ b/src/test_syscall.c
@@ -0,0 +1,765 @@
+/*
+** 2011 March 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** The code in this file implements a Tcl interface used to test error
+** handling in the os_unix.c module. Wrapper functions that support fault
+** injection are registered as the low-level OS functions using the 
+** xSetSystemCall() method of the VFS. The Tcl interface is as follows:
+**
+**
+**   test_syscall install LIST
+**     Install wrapper functions for all system calls in argument LIST.
+**     LIST must be a list consisting of zero or more of the following
+**     literal values:
+**
+**         open        close      access   getcwd   stat      fstat    
+**         ftruncate   fcntl      read     pread    pread64   write
+**         pwrite      pwrite64   fchmod   fallocate mmap
+**
+**   test_syscall uninstall
+**     Uninstall all wrapper functions.
+**
+**   test_syscall fault ?COUNT PERSIST?
+**     If [test_syscall fault] is invoked without the two arguments, fault
+**     injection is disabled. Otherwise, fault injection is configured to
+**     cause a failure on the COUNT'th next call to a system call with a
+**     wrapper function installed. A COUNT value of 1 means fail the next
+**     system call. 
+** 
+**     Argument PERSIST is interpreted as a boolean. If true, the all
+**     system calls following the initial failure also fail. Otherwise, only
+**     the single transient failure is injected.
+**
+**   test_syscall errno CALL ERRNO
+**     Set the value that the global "errno" is set to following a fault
+**     in call CALL. Argument CALL must be one of the system call names
+**     listed above (under [test_syscall install]). ERRNO is a symbolic
+**     name (i.e. "EACCES"). Not all errno codes are supported. Add extra
+**     to the aErrno table in function test_syscall_errno() below as 
+**     required.
+**
+**   test_syscall reset ?SYSTEM-CALL?
+**     With no argument, this is an alias for the [uninstall] command. However,
+**     this command uses a VFS call of the form:
+**
+**       xSetSystemCall(pVfs, 0, 0);
+**
+**     To restore the default system calls. The [uninstall] command restores
+**     each system call individually by calling (i.e.):
+**
+**       xSetSystemCall(pVfs, "open", 0);
+**
+**     With an argument, this command attempts to reset the system call named
+**     by the parameter using the same method as [uninstall].
+**
+**   test_syscall exists SYSTEM-CALL
+**     Return true if the named system call exists. Or false otherwise.
+**
+**   test_syscall list
+**     Return a list of all system calls. The list is constructed using
+**     the xNextSystemCall() VFS method.
+**
+**   test_syscall pagesize PGSZ
+**     If PGSZ is a power of two greater than 256, install a wrapper around
+**     OS function getpagesize() that reports the system page size as PGSZ.
+**     Or, if PGSZ is less than zero, remove any wrapper already installed.
+*/
+
+#include "sqliteInt.h"
+#include "sqlite3.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#if SQLITE_OS_UNIX
+
+/* From main.c */
+extern const char *sqlite3ErrName(int);
+
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <errno.h>
+
+static struct TestSyscallGlobal {
+  int bPersist;                   /* 1 for persistent errors, 0 for transient */
+  int nCount;                     /* Fail after this many more calls */
+  int nFail;                      /* Number of failures that have occurred */
+  int pgsz;
+  sqlite3_syscall_ptr orig_getpagesize;
+} gSyscall = { 0, 0, 0, 0, 0 };
+
+static int ts_open(const char *, int, int);
+static int ts_close(int fd);
+static int ts_access(const char *zPath, int mode);
+static char *ts_getcwd(char *zPath, size_t nPath);
+static int ts_stat(const char *zPath, struct stat *p);
+static int ts_fstat(int fd, struct stat *p);
+static int ts_ftruncate(int fd, off_t n);
+static int ts_fcntl(int fd, int cmd, ... );
+static ssize_t ts_read(int fd, void *aBuf, size_t nBuf);
+static ssize_t ts_pread(int fd, void *aBuf, size_t nBuf, off_t off);
+/* Note:  pread64() and pwrite64() actually use off64_t as the type on their
+** last parameter.  But that datatype is not defined on many systems 
+** (ex: Mac, OpenBSD).  So substitute a likely equivalent: sqlite3_uint64 */
+static ssize_t ts_pread64(int fd, void *aBuf, size_t nBuf, sqlite3_uint64 off);
+static ssize_t ts_write(int fd, const void *aBuf, size_t nBuf);
+static ssize_t ts_pwrite(int fd, const void *aBuf, size_t nBuf, off_t off);
+static ssize_t ts_pwrite64(int fd, const void *aBuf, size_t nBuf, sqlite3_uint64 off);
+static int ts_fchmod(int fd, mode_t mode);
+static int ts_fallocate(int fd, off_t off, off_t len);
+static void *ts_mmap(void *, size_t, int, int, int, off_t);
+static void *ts_mremap(void*, size_t, size_t, int, ...);
+
+struct TestSyscallArray {
+  const char *zName;
+  sqlite3_syscall_ptr xTest;
+  sqlite3_syscall_ptr xOrig;
+  int default_errno;              /* Default value for errno following errors */
+  int custom_errno;               /* Current value for errno if error */
+} aSyscall[] = {
+  /*  0 */ { "open",      (sqlite3_syscall_ptr)ts_open,      0, EACCES, 0 },
+  /*  1 */ { "close",     (sqlite3_syscall_ptr)ts_close,     0, 0, 0 },
+  /*  2 */ { "access",    (sqlite3_syscall_ptr)ts_access,    0, 0, 0 },
+  /*  3 */ { "getcwd",    (sqlite3_syscall_ptr)ts_getcwd,    0, 0, 0 },
+  /*  4 */ { "stat",      (sqlite3_syscall_ptr)ts_stat,      0, 0, 0 },
+  /*  5 */ { "fstat",     (sqlite3_syscall_ptr)ts_fstat,     0, 0, 0 },
+  /*  6 */ { "ftruncate", (sqlite3_syscall_ptr)ts_ftruncate, 0, EIO, 0 },
+  /*  7 */ { "fcntl",     (sqlite3_syscall_ptr)ts_fcntl,     0, EACCES, 0 },
+  /*  8 */ { "read",      (sqlite3_syscall_ptr)ts_read,      0, 0, 0 },
+  /*  9 */ { "pread",     (sqlite3_syscall_ptr)ts_pread,     0, 0, 0 },
+  /* 10 */ { "pread64",   (sqlite3_syscall_ptr)ts_pread64,   0, 0, 0 },
+  /* 11 */ { "write",     (sqlite3_syscall_ptr)ts_write,     0, 0, 0 },
+  /* 12 */ { "pwrite",    (sqlite3_syscall_ptr)ts_pwrite,    0, 0, 0 },
+  /* 13 */ { "pwrite64",  (sqlite3_syscall_ptr)ts_pwrite64,  0, 0, 0 },
+  /* 14 */ { "fchmod",    (sqlite3_syscall_ptr)ts_fchmod,    0, 0, 0 },
+  /* 15 */ { "fallocate", (sqlite3_syscall_ptr)ts_fallocate, 0, 0, 0 },
+  /* 16 */ { "mmap",      (sqlite3_syscall_ptr)ts_mmap,      0, 0, 0 },
+  /* 17 */ { "mremap",    (sqlite3_syscall_ptr)ts_mremap,    0, 0, 0 },
+           { 0, 0, 0, 0, 0 }
+};
+
+#define orig_open      ((int(*)(const char *, int, int))aSyscall[0].xOrig)
+#define orig_close     ((int(*)(int))aSyscall[1].xOrig)
+#define orig_access    ((int(*)(const char*,int))aSyscall[2].xOrig)
+#define orig_getcwd    ((char*(*)(char*,size_t))aSyscall[3].xOrig)
+#define orig_stat      ((int(*)(const char*,struct stat*))aSyscall[4].xOrig)
+#define orig_fstat     ((int(*)(int,struct stat*))aSyscall[5].xOrig)
+#define orig_ftruncate ((int(*)(int,off_t))aSyscall[6].xOrig)
+#define orig_fcntl     ((int(*)(int,int,...))aSyscall[7].xOrig)
+#define orig_read      ((ssize_t(*)(int,void*,size_t))aSyscall[8].xOrig)
+#define orig_pread     ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].xOrig)
+#define orig_pread64   ((ssize_t(*)(int,void*,size_t,sqlite3_uint64))aSyscall[10].xOrig)
+#define orig_write     ((ssize_t(*)(int,const void*,size_t))aSyscall[11].xOrig)
+#define orig_pwrite    ((ssize_t(*)(int,const void*,size_t,off_t))\
+                       aSyscall[12].xOrig)
+#define orig_pwrite64  ((ssize_t(*)(int,const void*,size_t,sqlite3_uint64))\
+                       aSyscall[13].xOrig)
+#define orig_fchmod    ((int(*)(int,mode_t))aSyscall[14].xOrig)
+#define orig_fallocate ((int(*)(int,off_t,off_t))aSyscall[15].xOrig)
+#define orig_mmap      ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[16].xOrig)
+#define orig_mremap    ((void*(*)(void*,size_t,size_t,int,...))aSyscall[17].xOrig)
+
+/*
+** This function is called exactly once from within each invocation of a
+** system call wrapper in this file. It returns 1 if the function should
+** fail, or 0 if it should succeed.
+*/
+static int tsIsFail(void){
+  gSyscall.nCount--;
+  if( gSyscall.nCount==0 || (gSyscall.nFail && gSyscall.bPersist) ){
+    gSyscall.nFail++;
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Return the current error-number value for function zFunc. zFunc must be
+** the name of a system call in the aSyscall[] table.
+**
+** Usually, the current error-number is the value that errno should be set
+** to if the named system call fails. The exception is "fallocate". See 
+** comments above the implementation of ts_fallocate() for details.
+*/
+static int tsErrno(const char *zFunc){
+  int i;
+  int nFunc = strlen(zFunc);
+  for(i=0; aSyscall[i].zName; i++){
+    if( strlen(aSyscall[i].zName)!=nFunc ) continue;
+    if( memcmp(aSyscall[i].zName, zFunc, nFunc) ) continue;
+    return aSyscall[i].custom_errno;
+  }
+
+  assert(0);
+  return 0;
+}
+
+/*
+** A wrapper around tsIsFail(). If tsIsFail() returns non-zero, set the
+** value of errno before returning.
+*/
+static int tsIsFailErrno(const char *zFunc){
+  if( tsIsFail() ){
+    errno = tsErrno(zFunc);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** A wrapper around open().
+*/
+static int ts_open(const char *zFile, int flags, int mode){
+  if( tsIsFailErrno("open") ){
+    return -1;
+  }
+  return orig_open(zFile, flags, mode);
+}
+
+/*
+** A wrapper around close().
+*/
+static int ts_close(int fd){
+  if( tsIsFail() ){
+    /* Even if simulating an error, close the original file-descriptor. 
+    ** This is to stop the test process from running out of file-descriptors
+    ** when running a long test. If a call to close() appears to fail, SQLite
+    ** never attempts to use the file-descriptor afterwards (or even to close
+    ** it a second time).  */
+    orig_close(fd);
+    return -1;
+  }
+  return orig_close(fd);
+}
+
+/*
+** A wrapper around access().
+*/
+static int ts_access(const char *zPath, int mode){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_access(zPath, mode);
+}
+
+/*
+** A wrapper around getcwd().
+*/
+static char *ts_getcwd(char *zPath, size_t nPath){
+  if( tsIsFail() ){
+    return NULL;
+  }
+  return orig_getcwd(zPath, nPath);
+}
+
+/*
+** A wrapper around stat().
+*/
+static int ts_stat(const char *zPath, struct stat *p){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_stat(zPath, p);
+}
+
+/*
+** A wrapper around fstat().
+*/
+static int ts_fstat(int fd, struct stat *p){
+  if( tsIsFailErrno("fstat") ){
+    return -1;
+  }
+  return orig_fstat(fd, p);
+}
+
+/*
+** A wrapper around ftruncate().
+*/
+static int ts_ftruncate(int fd, off_t n){
+  if( tsIsFailErrno("ftruncate") ){
+    return -1;
+  }
+  return orig_ftruncate(fd, n);
+}
+
+/*
+** A wrapper around fcntl().
+*/
+static int ts_fcntl(int fd, int cmd, ... ){
+  va_list ap;
+  void *pArg;
+  if( tsIsFailErrno("fcntl") ){
+    return -1;
+  }
+  va_start(ap, cmd);
+  pArg = va_arg(ap, void *);
+  return orig_fcntl(fd, cmd, pArg);
+}
+
+/*
+** A wrapper around read().
+*/
+static ssize_t ts_read(int fd, void *aBuf, size_t nBuf){
+  if( tsIsFailErrno("read") ){
+    return -1;
+  }
+  return orig_read(fd, aBuf, nBuf);
+}
+
+/*
+** A wrapper around pread().
+*/
+static ssize_t ts_pread(int fd, void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pread") ){
+    return -1;
+  }
+  return orig_pread(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around pread64().
+*/
+static ssize_t ts_pread64(int fd, void *aBuf, size_t nBuf, sqlite3_uint64 off){
+  if( tsIsFailErrno("pread64") ){
+    return -1;
+  }
+  return orig_pread64(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around write().
+*/
+static ssize_t ts_write(int fd, const void *aBuf, size_t nBuf){
+  if( tsIsFailErrno("write") ){
+    if( tsErrno("write")==EINTR ) orig_write(fd, aBuf, nBuf/2);
+    return -1;
+  }
+  return orig_write(fd, aBuf, nBuf);
+}
+
+/*
+** A wrapper around pwrite().
+*/
+static ssize_t ts_pwrite(int fd, const void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pwrite") ){
+    return -1;
+  }
+  return orig_pwrite(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around pwrite64().
+*/
+static ssize_t ts_pwrite64(int fd, const void *aBuf, size_t nBuf, sqlite3_uint64 off){
+  if( tsIsFailErrno("pwrite64") ){
+    return -1;
+  }
+  return orig_pwrite64(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around fchmod().
+*/
+static int ts_fchmod(int fd, mode_t mode){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_fchmod(fd, mode);
+}
+
+/*
+** A wrapper around fallocate().
+**
+** SQLite assumes that the fallocate() function is compatible with
+** posix_fallocate(). According to the Linux man page (2009-09-30):
+**
+**   posix_fallocate() returns  zero on success, or an error number on
+**   failure. Note that errno is not set.
+*/
+static int ts_fallocate(int fd, off_t off, off_t len){
+  if( tsIsFail() ){
+    return tsErrno("fallocate");
+  }
+  return orig_fallocate(fd, off, len);
+}
+
+static void *ts_mmap(
+  void *pAddr, 
+  size_t nByte, 
+  int prot, 
+  int flags, 
+  int fd, 
+  off_t iOff
+){
+  if( tsIsFailErrno("mmap") ){
+    return MAP_FAILED;
+  }
+  return orig_mmap(pAddr, nByte, prot, flags, fd, iOff);
+}
+
+static void *ts_mremap(void *a, size_t b, size_t c, int d, ...){
+  va_list ap;
+  void *pArg;
+  if( tsIsFailErrno("mremap") ){
+    return MAP_FAILED;
+  }
+  va_start(ap, d);
+  pArg = va_arg(ap, void *);
+  return orig_mremap(a, b, c, d, pArg);
+}
+
+static int SQLITE_TCLAPI test_syscall_install(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int nElem;
+  int i;
+  Tcl_Obj **apElem;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "SYSCALL-LIST");
+    return TCL_ERROR;
+  }
+  if( Tcl_ListObjGetElements(interp, objv[2], &nElem, &apElem) ){
+    return TCL_ERROR;
+  }
+  pVfs = sqlite3_vfs_find(0);
+
+  for(i=0; i<nElem; i++){
+    int iCall;
+    int rc = Tcl_GetIndexFromObjStruct(interp, 
+        apElem[i], aSyscall, sizeof(aSyscall[0]), "system-call", 0, &iCall
+    );
+    if( rc ) return rc;
+    if( aSyscall[iCall].xOrig==0 ){
+      aSyscall[iCall].xOrig = pVfs->xGetSystemCall(pVfs, aSyscall[iCall].zName);
+      pVfs->xSetSystemCall(pVfs, aSyscall[iCall].zName, aSyscall[iCall].xTest);
+    }
+    aSyscall[iCall].custom_errno = aSyscall[iCall].default_errno;
+  }
+
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_uninstall(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int i;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  for(i=0; aSyscall[i].zName; i++){
+    if( aSyscall[i].xOrig ){
+      pVfs->xSetSystemCall(pVfs, aSyscall[i].zName, 0);
+      aSyscall[i].xOrig = 0;
+    }
+  }
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_reset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int i;
+  int rc;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  if( objc==2 ){
+    rc = pVfs->xSetSystemCall(pVfs, 0, 0);
+    for(i=0; aSyscall[i].zName; i++) aSyscall[i].xOrig = 0;
+  }else{
+    int nFunc;
+    char *zFunc = Tcl_GetStringFromObj(objv[2], &nFunc);
+    rc = pVfs->xSetSystemCall(pVfs, Tcl_GetString(objv[2]), 0);
+    for(i=0; rc==SQLITE_OK && aSyscall[i].zName; i++){
+      if( strlen(aSyscall[i].zName)!=nFunc ) continue;
+      if( memcmp(aSyscall[i].zName, zFunc, nFunc) ) continue;
+      aSyscall[i].xOrig = 0;
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_exists(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  sqlite3_syscall_ptr x;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  x = pVfs->xGetSystemCall(pVfs, Tcl_GetString(objv[2]));
+
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(x!=0));
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_fault(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nCount = 0;
+  int bPersist = 0;
+
+  if( objc!=2 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "?COUNT PERSIST?");
+    return TCL_ERROR;
+  }
+
+  if( objc==4 ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &nCount)
+     || Tcl_GetBooleanFromObj(interp, objv[3], &bPersist)
+    ){
+      return TCL_ERROR;
+    }
+  }
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(gSyscall.nFail));
+  gSyscall.nCount = nCount;
+  gSyscall.bPersist = bPersist;
+  gSyscall.nFail = 0;
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_errno(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iCall;
+  int iErrno;
+  int rc;
+
+  struct Errno {
+    const char *z;
+    int i;
+  } aErrno[] = {
+    { "EACCES",    EACCES },
+    { "EINTR",     EINTR },
+    { "EIO",       EIO },
+    { "EOVERFLOW", EOVERFLOW },
+    { "ENOMEM",    ENOMEM },
+    { "EAGAIN",    EAGAIN },
+    { "ETIMEDOUT", ETIMEDOUT },
+    { "EBUSY",     EBUSY },
+    { "EPERM",     EPERM },
+    { "EDEADLK",   EDEADLK },
+    { "ENOLCK",    ENOLCK },
+    { 0, 0 }
+  };
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "SYSCALL ERRNO");
+    return TCL_ERROR;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[2], aSyscall, sizeof(aSyscall[0]), "system-call", 0, &iCall
+  );
+  if( rc!=TCL_OK ) return rc;
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[3], aErrno, sizeof(aErrno[0]), "errno", 0, &iErrno
+  );
+  if( rc!=TCL_OK ) return rc;
+
+  aSyscall[iCall].custom_errno = aErrno[iErrno].i;
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_list(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zSys;
+  sqlite3_vfs *pVfs; 
+  Tcl_Obj *pList;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  pList = Tcl_NewObj();
+  Tcl_IncrRefCount(pList);
+  for(zSys = pVfs->xNextSystemCall(pVfs, 0); 
+      zSys!=0;
+      zSys = pVfs->xNextSystemCall(pVfs, zSys)
+  ){
+    Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj(zSys, -1));
+  }
+
+  Tcl_SetObjResult(interp, pList);
+  Tcl_DecrRefCount(pList);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_defaultvfs(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(pVfs->zName, -1));
+  return TCL_OK;
+}
+
+static int ts_getpagesize(void){
+  return gSyscall.pgsz;
+}
+
+static int SQLITE_TCLAPI test_syscall_pagesize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+  int pgsz;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "PGSZ");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &pgsz) ){
+    return TCL_ERROR;
+  }
+
+  if( pgsz<0 ){
+    if( gSyscall.orig_getpagesize ){
+      pVfs->xSetSystemCall(pVfs, "getpagesize", gSyscall.orig_getpagesize);
+    }
+  }else{
+    if( pgsz<512 || (pgsz & (pgsz-1)) ){
+      Tcl_AppendResult(interp, "pgsz out of range", 0);
+      return TCL_ERROR;
+    }
+    gSyscall.orig_getpagesize = pVfs->xGetSystemCall(pVfs, "getpagesize");
+    gSyscall.pgsz = pgsz;
+    pVfs->xSetSystemCall(
+        pVfs, "getpagesize", (sqlite3_syscall_ptr)ts_getpagesize
+    );
+  }
+
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SyscallCmd {
+    const char *zName;
+    Tcl_ObjCmdProc *xCmd;
+  } aCmd[] = {
+    { "fault",      test_syscall_fault },
+    { "install",    test_syscall_install },
+    { "uninstall",  test_syscall_uninstall },
+    { "reset",      test_syscall_reset },
+    { "errno",      test_syscall_errno },
+    { "exists",     test_syscall_exists },
+    { "list",       test_syscall_list },
+    { "defaultvfs", test_syscall_defaultvfs },
+    { "pagesize",   test_syscall_pagesize },
+    { 0, 0 }
+  };
+  int iCmd;
+  int rc;
+  sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");
+    return TCL_ERROR;
+  }
+  if( pVfs->iVersion<3 || pVfs->xSetSystemCall==0 ){
+    Tcl_AppendResult(interp, "VFS does not support xSetSystemCall", 0);
+    rc = TCL_ERROR;
+  }else{
+    rc = Tcl_GetIndexFromObjStruct(interp, 
+        objv[1], aCmd, sizeof(aCmd[0]), "sub-command", 0, &iCmd
+    );
+  }
+  if( rc!=TCL_OK ) return rc;
+  return aCmd[iCmd].xCmd(clientData, interp, objc, objv);
+}
+
+int SqlitetestSyscall_Init(Tcl_Interp *interp){
+  struct SyscallCmd {
+    const char *zName;
+    Tcl_ObjCmdProc *xCmd;
+  } aCmd[] = {
+    { "test_syscall",     test_syscall},
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xCmd, 0, 0);
+  }
+  return TCL_OK;
+}
+#else
+int SqlitetestSyscall_Init(Tcl_Interp *interp){
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_tclsh.c b/src/test_tclsh.c
new file mode 100644
index 0000000..32aee42
--- /dev/null
+++ b/src/test_tclsh.c
@@ -0,0 +1,207 @@
+/*
+** 2017-10-13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains extensions to the the "tclsqlite.c" module used for
+** testing.  Basically, all of the other "test_*.c" modules are linked
+** into the enhanced tclsh used for testing (and named "testfixture" or
+** "testfixture.exe") using logic encoded by this file.
+**
+** The code in this file used to be found in tclsqlite3.c, contained within
+** #if SQLITE_TEST ... #endif.  It is factored out into this separate module
+** in an effort to keep the tclsqlite.c file pure.
+*/
+#include "sqlite3.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+# include "sqlite_tcl.h"
+#else
+# include "tcl.h"
+# ifndef SQLITE_TCLAPI
+#  define SQLITE_TCLAPI
+# endif
+#endif
+
+/* Needed for the setrlimit() system call on unix */
+#if defined(unix)
+#include <sys/resource.h>
+#endif
+
+/* Forward declaration */
+static int SQLITE_TCLAPI load_testfixture_extensions(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+);
+
+/*
+** This routine is the primary export of this file.
+**
+** Configure the interpreter passed as the first argument to have access
+** to the commands and linked variables that make up:
+**
+**   * the [sqlite3] extension itself,
+**
+**   * If SQLITE_TCLMD5 or SQLITE_TEST is defined, the Md5 commands, and
+**
+**   * If SQLITE_TEST is set, the various test interfaces used by the Tcl
+**     test suite.
+*/
+const char *sqlite3TestInit(Tcl_Interp *interp){
+  extern int Sqlite3_Init(Tcl_Interp*);
+  extern int Sqliteconfig_Init(Tcl_Interp*);
+  extern int Sqlitetest1_Init(Tcl_Interp*);
+  extern int Sqlitetest2_Init(Tcl_Interp*);
+  extern int Sqlitetest3_Init(Tcl_Interp*);
+  extern int Sqlitetest4_Init(Tcl_Interp*);
+  extern int Sqlitetest5_Init(Tcl_Interp*);
+  extern int Sqlitetest6_Init(Tcl_Interp*);
+  extern int Sqlitetest8_Init(Tcl_Interp*);
+  extern int Sqlitetest9_Init(Tcl_Interp*);
+  extern int Sqlitetestasync_Init(Tcl_Interp*);
+  extern int Sqlitetest_autoext_Init(Tcl_Interp*);
+  extern int Sqlitetest_blob_Init(Tcl_Interp*);
+  extern int Sqlitetest_demovfs_Init(Tcl_Interp *);
+  extern int Sqlitetest_func_Init(Tcl_Interp*);
+  extern int Sqlitetest_hexio_Init(Tcl_Interp*);
+  extern int Sqlitetest_init_Init(Tcl_Interp*);
+  extern int Sqlitetest_malloc_Init(Tcl_Interp*);
+  extern int Sqlitetest_mutex_Init(Tcl_Interp*);
+  extern int Sqlitetestschema_Init(Tcl_Interp*);
+  extern int Sqlitetestsse_Init(Tcl_Interp*);
+  extern int Sqlitetesttclvar_Init(Tcl_Interp*);
+  extern int Sqlitetestfs_Init(Tcl_Interp*);
+  extern int SqlitetestThread_Init(Tcl_Interp*);
+  extern int SqlitetestOnefile_Init();
+  extern int SqlitetestOsinst_Init(Tcl_Interp*);
+  extern int Sqlitetestbackup_Init(Tcl_Interp*);
+  extern int Sqlitetestintarray_Init(Tcl_Interp*);
+  extern int Sqlitetestvfs_Init(Tcl_Interp *);
+  extern int Sqlitetestrtree_Init(Tcl_Interp*);
+  extern int Sqlitetestrtreedoc_Init(Tcl_Interp*);
+  extern int Sqlitequota_Init(Tcl_Interp*);
+  extern int Sqlitemultiplex_Init(Tcl_Interp*);
+  extern int SqliteSuperlock_Init(Tcl_Interp*);
+  extern int SqlitetestSyscall_Init(Tcl_Interp*);
+#if defined(SQLITE_ENABLE_SESSION) && defined(SQLITE_ENABLE_PREUPDATE_HOOK)
+  extern int TestSession_Init(Tcl_Interp*);
+#endif
+  extern int Md5_Init(Tcl_Interp*);
+  extern int Fts5tcl_Init(Tcl_Interp *);
+  extern int SqliteRbu_Init(Tcl_Interp*);
+  extern int Sqlitetesttcl_Init(Tcl_Interp*);
+#if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
+  extern int Sqlitetestfts3_Init(Tcl_Interp *interp);
+#endif
+#ifdef SQLITE_ENABLE_ZIPVFS
+  extern int Zipvfs_Init(Tcl_Interp*);
+#endif
+  extern int TestExpert_Init(Tcl_Interp*);
+  extern int Sqlitetest_window_Init(Tcl_Interp *);
+  extern int Sqlitetestvdbecov_Init(Tcl_Interp *);
+  extern int TestRecover_Init(Tcl_Interp*);
+
+  Tcl_CmdInfo cmdInfo;
+
+  /* Since the primary use case for this binary is testing of SQLite,
+  ** be sure to generate core files if we crash */
+#if defined(unix)
+  { struct rlimit x;
+    getrlimit(RLIMIT_CORE, &x);
+    x.rlim_cur = x.rlim_max;
+    setrlimit(RLIMIT_CORE, &x);
+  }
+#endif /* unix */
+
+  if( Tcl_GetCommandInfo(interp, "sqlite3", &cmdInfo)==0 ){
+    Sqlite3_Init(interp);
+  }
+#ifdef SQLITE_ENABLE_ZIPVFS
+  Zipvfs_Init(interp);
+#endif
+  Md5_Init(interp);
+  Sqliteconfig_Init(interp);
+  Sqlitetest1_Init(interp);
+  Sqlitetest2_Init(interp);
+  Sqlitetest3_Init(interp);
+  Sqlitetest4_Init(interp);
+  Sqlitetest5_Init(interp);
+  Sqlitetest6_Init(interp);
+  Sqlitetest8_Init(interp);
+  Sqlitetest9_Init(interp);
+  Sqlitetestasync_Init(interp);
+  Sqlitetest_autoext_Init(interp);
+  Sqlitetest_blob_Init(interp);
+  Sqlitetest_demovfs_Init(interp);
+  Sqlitetest_func_Init(interp);
+  Sqlitetest_hexio_Init(interp);
+  Sqlitetest_init_Init(interp);
+  Sqlitetest_malloc_Init(interp);
+  Sqlitetest_mutex_Init(interp);
+  Sqlitetestschema_Init(interp);
+  Sqlitetesttclvar_Init(interp);
+  Sqlitetestfs_Init(interp);
+  SqlitetestThread_Init(interp);
+  SqlitetestOnefile_Init();
+  SqlitetestOsinst_Init(interp);
+  Sqlitetestbackup_Init(interp);
+  Sqlitetestintarray_Init(interp);
+  Sqlitetestvfs_Init(interp);
+  Sqlitetestrtree_Init(interp);
+  Sqlitetestrtreedoc_Init(interp);
+  Sqlitequota_Init(interp);
+  Sqlitemultiplex_Init(interp);
+  SqliteSuperlock_Init(interp);
+  SqlitetestSyscall_Init(interp);
+#if defined(SQLITE_ENABLE_SESSION) && defined(SQLITE_ENABLE_PREUPDATE_HOOK)
+  TestSession_Init(interp);
+#endif
+  Fts5tcl_Init(interp);
+  SqliteRbu_Init(interp);
+  Sqlitetesttcl_Init(interp);
+
+#if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
+  Sqlitetestfts3_Init(interp);
+#endif
+  TestExpert_Init(interp);
+  Sqlitetest_window_Init(interp);
+  Sqlitetestvdbecov_Init(interp);
+  TestRecover_Init(interp);
+
+  Tcl_CreateObjCommand(
+      interp, "load_testfixture_extensions", load_testfixture_extensions,0,0
+  );
+  return 0;
+}
+
+/* tclcmd:   load_testfixture_extensions
+*/
+static int SQLITE_TCLAPI load_testfixture_extensions(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+
+  Tcl_Interp *slave;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SLAVE");
+    return TCL_ERROR;
+  }
+
+  slave = Tcl_GetSlave(interp, Tcl_GetString(objv[1]));
+  if( !slave ){
+    return TCL_ERROR;
+  }
+
+  (void)sqlite3TestInit(slave);
+  return TCL_OK;
+}
diff --git a/src/test_tclvar.c b/src/test_tclvar.c
new file mode 100644
index 0000000..36165bc
--- /dev/null
+++ b/src/test_tclvar.c
@@ -0,0 +1,567 @@
+/*
+** 2006 June 13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+**
+** The emphasis of this file is a virtual table that provides
+** access to TCL variables.
+**
+** The TCLVAR eponymous virtual table has a schema like this:
+**
+**    CREATE TABLE tclvar(
+**       name TEXT,       -- base name of the variable:  "x" in "$x(y)"
+**       arrayname TEXT,  -- array index name: "y" in "$x(y)"
+**       value TEXT,      -- the value of the variable 
+**       fullname TEXT,   -- the full name of the variable
+**       PRIMARY KEY(fullname)
+**    ) WITHOUT ROWID;
+**
+** DELETE, INSERT, and UPDATE operations use the "fullname" field to
+** determine the variable to be modified.  Changing "value" to NULL
+** deletes the variable.
+**
+** For SELECT operations, the "name" and "arrayname" fields will always
+** match the "fullname" field.  For DELETE, INSERT, and UPDATE, the
+** "name" and "arrayname" fields are ignored and the variable is modified
+** according to "fullname" and "value" only.
+*/
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Characters that make up the idxStr created by xBestIndex for xFilter.
+*/
+#define TCLVAR_NAME_EQ      'e'
+#define TCLVAR_NAME_MATCH   'm'
+#define TCLVAR_VALUE_GLOB   'g'
+#define TCLVAR_VALUE_REGEXP 'r'
+#define TCLVAR_VALUE_LIKE   'l'
+
+typedef struct tclvar_vtab tclvar_vtab;
+typedef struct tclvar_cursor tclvar_cursor;
+
+/* 
+** A tclvar virtual-table object 
+*/
+struct tclvar_vtab {
+  sqlite3_vtab base;
+  Tcl_Interp *interp;
+};
+
+/* A tclvar cursor object */
+struct tclvar_cursor {
+  sqlite3_vtab_cursor base;
+
+  Tcl_Obj *pList1;     /* Result of [info vars ?pattern?] */
+  Tcl_Obj *pList2;     /* Result of [array names [lindex $pList1 $i1]] */
+  int i1;              /* Current item in pList1 */
+  int i2;              /* Current item (if any) in pList2 */
+};
+
+/* Methods for the tclvar module */
+static int tclvarConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  tclvar_vtab *pVtab;
+  static const char zSchema[] = 
+     "CREATE TABLE x("
+     "  name TEXT,"                       /* Base name */
+     "  arrayname TEXT,"                  /* Array index */
+     "  value TEXT,"                      /* Value */
+     "  fullname TEXT PRIMARY KEY"        /* base(index) name */
+     ") WITHOUT ROWID";
+  pVtab = sqlite3MallocZero( sizeof(*pVtab) );
+  if( pVtab==0 ) return SQLITE_NOMEM;
+  *ppVtab = &pVtab->base;
+  pVtab->interp = (Tcl_Interp *)pAux;
+  sqlite3_declare_vtab(db, zSchema);
+  return SQLITE_OK;
+}
+/* Note that for this virtual table, the xCreate and xConnect
+** methods are identical. */
+
+static int tclvarDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+/* The xDisconnect and xDestroy methods are also the same */
+
+/*
+** Open a new tclvar cursor.
+*/
+static int tclvarOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  tclvar_cursor *pCur;
+  pCur = sqlite3MallocZero(sizeof(tclvar_cursor));
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a tclvar cursor.
+*/
+static int tclvarClose(sqlite3_vtab_cursor *cur){
+  tclvar_cursor *pCur = (tclvar_cursor *)cur;
+  if( pCur->pList1 ){
+    Tcl_DecrRefCount(pCur->pList1);
+  }
+  if( pCur->pList2 ){
+    Tcl_DecrRefCount(pCur->pList2);
+  }
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Returns 1 if data is ready, or 0 if not.
+*/
+static int next2(Tcl_Interp *interp, tclvar_cursor *pCur, Tcl_Obj *pObj){
+  Tcl_Obj *p;
+
+  if( pObj ){
+    if( !pCur->pList2 ){
+      p = Tcl_NewStringObj("array names", -1);
+      Tcl_IncrRefCount(p);
+      Tcl_ListObjAppendElement(0, p, pObj);
+      Tcl_EvalObjEx(interp, p, TCL_EVAL_GLOBAL);
+      Tcl_DecrRefCount(p);
+      pCur->pList2 = Tcl_GetObjResult(interp);
+      Tcl_IncrRefCount(pCur->pList2);
+      assert( pCur->i2==0 );
+    }else{
+      int n = 0;
+      pCur->i2++;
+      Tcl_ListObjLength(0, pCur->pList2, &n);
+      if( pCur->i2>=n ){
+        Tcl_DecrRefCount(pCur->pList2);
+        pCur->pList2 = 0;
+        pCur->i2 = 0;
+        return 0;
+      }
+    }
+  }
+
+  return 1;
+}
+
+static int tclvarNext(sqlite3_vtab_cursor *cur){
+  Tcl_Obj *pObj;
+  int n = 0;
+  int ok = 0;
+
+  tclvar_cursor *pCur = (tclvar_cursor *)cur;
+  Tcl_Interp *interp = ((tclvar_vtab *)(cur->pVtab))->interp;
+
+  Tcl_ListObjLength(0, pCur->pList1, &n);
+  while( !ok && pCur->i1<n ){
+    Tcl_ListObjIndex(0, pCur->pList1, pCur->i1, &pObj);
+    ok = next2(interp, pCur, pObj);
+    if( !ok ){
+      pCur->i1++;
+    }
+  }
+
+  return 0;
+}
+
+static int tclvarFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  tclvar_cursor *pCur = (tclvar_cursor *)pVtabCursor;
+  Tcl_Interp *interp = ((tclvar_vtab *)(pVtabCursor->pVtab))->interp;
+  Tcl_Obj *p = Tcl_NewStringObj("tclvar_filter_cmd", -1);
+
+  const char *zEq = "";
+  const char *zMatch = "";
+  const char *zGlob = "";
+  const char *zRegexp = "";
+  const char *zLike = "";
+  int i;
+
+  for(i=0; idxStr[i]; i++){
+    switch( idxStr[i] ){
+      case TCLVAR_NAME_EQ:
+        zEq = (const char*)sqlite3_value_text(argv[i]);
+        break;
+      case TCLVAR_NAME_MATCH:
+        zMatch = (const char*)sqlite3_value_text(argv[i]);
+        break;
+      case TCLVAR_VALUE_GLOB:
+        zGlob = (const char*)sqlite3_value_text(argv[i]);
+        break;
+      case TCLVAR_VALUE_REGEXP:
+        zRegexp = (const char*)sqlite3_value_text(argv[i]);
+        break;
+      case TCLVAR_VALUE_LIKE:
+        zLike = (const char*)sqlite3_value_text(argv[i]);
+        break;
+      default:
+        assert( 0 );
+    }
+  }
+
+  Tcl_IncrRefCount(p);
+  Tcl_ListObjAppendElement(0, p, Tcl_NewStringObj(zEq, -1));
+  Tcl_ListObjAppendElement(0, p, Tcl_NewStringObj(zMatch, -1));
+  Tcl_ListObjAppendElement(0, p, Tcl_NewStringObj(zGlob, -1));
+  Tcl_ListObjAppendElement(0, p, Tcl_NewStringObj(zRegexp, -1));
+  Tcl_ListObjAppendElement(0, p, Tcl_NewStringObj(zLike, -1));
+
+  Tcl_EvalObjEx(interp, p, TCL_EVAL_GLOBAL);
+  if( pCur->pList1 ){
+    Tcl_DecrRefCount(pCur->pList1);
+  }
+  if( pCur->pList2 ){
+    Tcl_DecrRefCount(pCur->pList2);
+    pCur->pList2 = 0;
+  }
+  pCur->i1 = 0;
+  pCur->i2 = 0;
+  pCur->pList1 = Tcl_GetObjResult(interp);
+  Tcl_IncrRefCount(pCur->pList1);
+
+  Tcl_DecrRefCount(p);
+  return tclvarNext(pVtabCursor);
+}
+
+static int tclvarColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  Tcl_Obj *p1;
+  Tcl_Obj *p2;
+  const char *z1; 
+  const char *z2 = "";
+  tclvar_cursor *pCur = (tclvar_cursor*)cur;
+  Tcl_Interp *interp = ((tclvar_vtab *)cur->pVtab)->interp;
+
+  Tcl_ListObjIndex(interp, pCur->pList1, pCur->i1, &p1);
+  Tcl_ListObjIndex(interp, pCur->pList2, pCur->i2, &p2);
+  z1 = Tcl_GetString(p1);
+  if( p2 ){
+    z2 = Tcl_GetString(p2);
+  }
+  switch (i) {
+    case 0: {
+      sqlite3_result_text(ctx, z1, -1, SQLITE_TRANSIENT);
+      break;
+    }
+    case 1: {
+      sqlite3_result_text(ctx, z2, -1, SQLITE_TRANSIENT);
+      break;
+    }
+    case 2: {
+      Tcl_Obj *pVal = Tcl_GetVar2Ex(interp, z1, *z2?z2:0, TCL_GLOBAL_ONLY);
+      sqlite3_result_text(ctx, Tcl_GetString(pVal), -1, SQLITE_TRANSIENT);
+      break;
+    }
+    case 3: {
+      char *z3;
+      if( p2 ){
+        z3 = sqlite3_mprintf("%s(%s)", z1, z2);
+        sqlite3_result_text(ctx, z3, -1, sqlite3_free);
+      }else{
+        sqlite3_result_text(ctx, z1, -1, SQLITE_TRANSIENT);
+      }
+      break;
+    }
+  }
+  return SQLITE_OK;
+}
+
+static int tclvarRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  *pRowid = 0;
+  return SQLITE_OK;
+}
+
+static int tclvarEof(sqlite3_vtab_cursor *cur){
+  tclvar_cursor *pCur = (tclvar_cursor*)cur;
+  return (pCur->pList2?0:1);
+}
+
+/*
+** If nul-terminated string zStr does not already contain the character 
+** passed as the second argument, append it and return 0. Or, if there is
+** already an instance of x in zStr, do nothing return 1;
+**
+** There is guaranteed to be enough room in the buffer pointed to by zStr
+** for the new character and nul-terminator.
+*/
+static int tclvarAddToIdxstr(char *zStr, char x){
+  int i;
+  for(i=0; zStr[i]; i++){
+    if( zStr[i]==x ) return 1;
+  }
+  zStr[i] = x;
+  zStr[i+1] = '\0';
+  return 0;
+}
+
+/*
+** Return true if variable $::tclvar_set_omit exists and is set to true.
+** False otherwise.
+*/
+static int tclvarSetOmit(Tcl_Interp *interp){
+  int rc;
+  int res = 0;
+  Tcl_Obj *pRes;
+  rc = Tcl_Eval(interp,
+    "expr {[info exists ::tclvar_set_omit] && $::tclvar_set_omit}"
+  );
+  if( rc==TCL_OK ){
+    pRes = Tcl_GetObjResult(interp);
+    rc = Tcl_GetBooleanFromObj(0, pRes, &res);
+  }
+  return (rc==TCL_OK && res);
+}
+
+/*
+** The xBestIndex() method. This virtual table supports the following
+** operators:
+**
+**     name = ?                    (omit flag clear)
+**     name MATCH ?                (omit flag set)
+**     value GLOB ?                (omit flag set iff $::tclvar_set_omit)
+**     value REGEXP ?              (omit flag set iff $::tclvar_set_omit)
+**     value LIKE ?                (omit flag set iff $::tclvar_set_omit)
+**
+** For each constraint present, the corresponding TCLVAR_XXX character is
+** appended to the idxStr value. 
+*/
+static int tclvarBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  tclvar_vtab *pTab = (tclvar_vtab*)tab;
+  int ii;
+  char *zStr = sqlite3_malloc(32);
+  int iStr = 0;
+
+  if( zStr==0 ) return SQLITE_NOMEM;
+  zStr[0] = '\0';
+
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    struct sqlite3_index_constraint const *pCons = &pIdxInfo->aConstraint[ii];
+    struct sqlite3_index_constraint_usage *pUsage;
+    
+    pUsage = &pIdxInfo->aConstraintUsage[ii];
+    if( pCons->usable ){
+      /* name = ? */
+      if( pCons->op==SQLITE_INDEX_CONSTRAINT_EQ && pCons->iColumn==0 ){
+        if( 0==tclvarAddToIdxstr(zStr, TCLVAR_NAME_EQ) ){
+          pUsage->argvIndex = ++iStr;
+          pUsage->omit = 0;
+        }
+      }
+
+      /* name MATCH ? */
+      if( pCons->op==SQLITE_INDEX_CONSTRAINT_MATCH && pCons->iColumn==0 ){
+        if( 0==tclvarAddToIdxstr(zStr, TCLVAR_NAME_MATCH) ){
+          pUsage->argvIndex = ++iStr;
+          pUsage->omit = 1;
+        }
+      }
+
+      /* value GLOB ? */
+      if( pCons->op==SQLITE_INDEX_CONSTRAINT_GLOB && pCons->iColumn==2 ){
+        if( 0==tclvarAddToIdxstr(zStr, TCLVAR_VALUE_GLOB) ){
+          pUsage->argvIndex = ++iStr;
+          pUsage->omit = tclvarSetOmit(pTab->interp);
+        }
+      }
+
+      /* value REGEXP ? */
+      if( pCons->op==SQLITE_INDEX_CONSTRAINT_REGEXP && pCons->iColumn==2 ){
+        if( 0==tclvarAddToIdxstr(zStr, TCLVAR_VALUE_REGEXP) ){
+          pUsage->argvIndex = ++iStr;
+          pUsage->omit = tclvarSetOmit(pTab->interp);
+        }
+      }
+
+      /* value LIKE ? */
+      if( pCons->op==SQLITE_INDEX_CONSTRAINT_LIKE && pCons->iColumn==2 ){
+        if( 0==tclvarAddToIdxstr(zStr, TCLVAR_VALUE_LIKE) ){
+          pUsage->argvIndex = ++iStr;
+          pUsage->omit = tclvarSetOmit(pTab->interp);
+        }
+      }
+    }
+  }
+  pIdxInfo->idxStr = zStr;
+  pIdxInfo->needToFreeIdxStr = 1;
+
+  return SQLITE_OK;
+}
+
+/*
+** Invoked for any UPDATE, INSERT, or DELETE against a tclvar table
+*/
+static int tclvarUpdate(
+  sqlite3_vtab *tab,
+  int argc,
+  sqlite3_value **argv,
+  sqlite_int64 *pRowid
+){
+  tclvar_vtab *pTab = (tclvar_vtab*)tab;
+  if( argc==1 ){
+    /* A DELETE operation.  The variable to be deleted is stored in argv[0] */
+    const char *zVar = (const char*)sqlite3_value_text(argv[0]);
+    Tcl_UnsetVar(pTab->interp, zVar, TCL_GLOBAL_ONLY);
+    return SQLITE_OK;
+  }
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ){
+    /* An INSERT operation */
+    const char *zValue = (const char*)sqlite3_value_text(argv[4]);
+    const char *zName;
+    if( sqlite3_value_type(argv[5])!=SQLITE_TEXT ){
+      tab->zErrMsg = sqlite3_mprintf("the 'fullname' column must be TEXT");
+      return SQLITE_ERROR;
+    }
+    zName = (const char*)sqlite3_value_text(argv[5]);
+    if( zValue ){
+      Tcl_SetVar(pTab->interp, zName, zValue, TCL_GLOBAL_ONLY);
+    }else{
+      Tcl_UnsetVar(pTab->interp, zName, TCL_GLOBAL_ONLY);
+    }
+    return SQLITE_OK;
+  }
+  if( sqlite3_value_type(argv[0])==SQLITE_TEXT
+   && sqlite3_value_type(argv[1])==SQLITE_TEXT
+  ){
+    /* An UPDATE operation */
+    const char *zOldName = (const char*)sqlite3_value_text(argv[0]);
+    const char *zNewName = (const char*)sqlite3_value_text(argv[1]);
+    const char *zValue = (const char*)sqlite3_value_text(argv[4]);
+
+    if( strcmp(zOldName, zNewName)!=0 || zValue==0 ){
+      Tcl_UnsetVar(pTab->interp, zOldName, TCL_GLOBAL_ONLY);
+    }
+    if( zValue!=0 ){
+      Tcl_SetVar(pTab->interp, zNewName, zValue, TCL_GLOBAL_ONLY);
+    }
+    return SQLITE_OK;
+  }
+  tab->zErrMsg = sqlite3_mprintf("prohibited TCL variable change");
+  return SQLITE_ERROR;
+}
+
+/*
+** A virtual table module that provides read-only access to a
+** Tcl global variable namespace.
+*/
+static sqlite3_module tclvarModule = {
+  0,                         /* iVersion */
+  tclvarConnect,
+  tclvarConnect,
+  tclvarBestIndex,
+  tclvarDisconnect, 
+  tclvarDisconnect,
+  tclvarOpen,                  /* xOpen - open a cursor */
+  tclvarClose,                 /* xClose - close a cursor */
+  tclvarFilter,                /* xFilter - configure scan constraints */
+  tclvarNext,                  /* xNext - advance a cursor */
+  tclvarEof,                   /* xEof - check for end of scan */
+  tclvarColumn,                /* xColumn - read data */
+  tclvarRowid,                 /* xRowid - read data */
+  tclvarUpdate,                /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+  0,                           /* xSavepoint */
+  0,                           /* xRelease */
+  0,                           /* xRollbackTo */
+  0,                           /* xShadowName */
+  0                            /* xIntegrity */
+};
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the echo virtual table module.
+*/
+static int SQLITE_TCLAPI register_tclvar_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int rc = TCL_OK;
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "tclvar", &tclvarModule, (void*)interp);
+  rc = Tcl_Eval(interp, 
+      "proc like {pattern str} {\n"
+      "  set p [string map {% * _ ?} $pattern]\n"
+      "  string match $p $str\n"
+      "}\n"
+      "proc tclvar_filter_cmd {eq match glob regexp like} {\n"
+      "  set res {}\n"
+      "  set pattern $eq\n"
+      "  if {$pattern=={}} { set pattern $match }\n"
+      "  if {$pattern=={}} { set pattern * }\n"
+      "  foreach v [uplevel #0 info vars $pattern] {\n"
+      "    if {($glob=={} || [string match $glob [uplevel #0 set $v]])\n"
+      "     && ($like=={} || [like $like [uplevel #0 set $v]])\n"
+      "     && ($regexp=={} || [regexp $regexp [uplevel #0 set $v]])\n"
+      "    } {\n"
+      "      lappend res $v\n"
+      "    }\n"
+      "  }\n"
+      "  set res\n"
+      "}\n"
+  );
+#endif
+  return rc;
+}
+
+#endif
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetesttclvar_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_tclvar_module",   register_tclvar_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+#endif
+  return TCL_OK;
+}
diff --git a/src/test_thread.c b/src/test_thread.c
new file mode 100644
index 0000000..126fd98
--- /dev/null
+++ b/src/test_thread.c
@@ -0,0 +1,667 @@
+/*
+** 2007 September 9
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of some Tcl commands used to
+** test that sqlite3 database handles may be concurrently accessed by 
+** multiple threads. Right now this only works on unix.
+*/
+
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+#if SQLITE_THREADSAFE
+
+#include <errno.h>
+
+#if !defined(_MSC_VER)
+#include <unistd.h>
+#endif
+
+/*
+** One of these is allocated for each thread created by [sqlthread spawn].
+*/
+typedef struct SqlThread SqlThread;
+struct SqlThread {
+  Tcl_ThreadId parent;     /* Thread id of parent thread */
+  Tcl_Interp *interp;      /* Parent interpreter */
+  char *zScript;           /* The script to execute. */
+  char *zVarname;          /* Varname in parent script */
+};
+
+/*
+** A custom Tcl_Event type used by this module. When the event is
+** handled, script zScript is evaluated in interpreter interp. If
+** the evaluation throws an exception (returns TCL_ERROR), then the
+** error is handled by Tcl_BackgroundError(). If no error occurs,
+** the result is simply discarded.
+*/
+typedef struct EvalEvent EvalEvent;
+struct EvalEvent {
+  Tcl_Event base;          /* Base class of type Tcl_Event */
+  char *zScript;           /* The script to execute. */
+  Tcl_Interp *interp;      /* The interpreter to execute it in. */
+};
+
+static Tcl_ObjCmdProc sqlthread_proc;
+static Tcl_ObjCmdProc clock_seconds_proc;
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+static Tcl_ObjCmdProc blocking_step_proc;
+static Tcl_ObjCmdProc blocking_prepare_v2_proc;
+#endif
+int Sqlitetest1_Init(Tcl_Interp *);
+int Sqlite3_Init(Tcl_Interp *);
+
+/* Functions from main.c */
+extern const char *sqlite3ErrName(int);
+
+/* Functions from test1.c */
+extern void *sqlite3TestTextToPtr(const char *);
+extern int getDbPointer(Tcl_Interp *, const char *, sqlite3 **);
+extern int sqlite3TestMakePointerStr(Tcl_Interp *, char *, void *);
+extern int sqlite3TestErrCode(Tcl_Interp *, sqlite3 *, int);
+
+/*
+** Handler for events of type EvalEvent.
+*/
+static int SQLITE_TCLAPI tclScriptEvent(Tcl_Event *evPtr, int flags){
+  int rc;
+  EvalEvent *p = (EvalEvent *)evPtr;
+  rc = Tcl_Eval(p->interp, p->zScript);
+  if( rc!=TCL_OK ){
+    Tcl_BackgroundError(p->interp);
+  }
+  UNUSED_PARAMETER(flags);
+  return 1;
+}
+
+/*
+** Register an EvalEvent to evaluate the script pScript in the
+** parent interpreter/thread of SqlThread p.
+*/
+static void postToParent(SqlThread *p, Tcl_Obj *pScript){
+  EvalEvent *pEvent;
+  char *zMsg;
+  int nMsg;
+
+  zMsg = Tcl_GetStringFromObj(pScript, &nMsg); 
+  pEvent = (EvalEvent *)ckalloc(sizeof(EvalEvent)+nMsg+1);
+  pEvent->base.nextPtr = 0;
+  pEvent->base.proc = tclScriptEvent;
+  pEvent->zScript = (char *)&pEvent[1];
+  memcpy(pEvent->zScript, zMsg, nMsg+1);
+  pEvent->interp = p->interp;
+
+  Tcl_ThreadQueueEvent(p->parent, (Tcl_Event *)pEvent, TCL_QUEUE_TAIL);
+  Tcl_ThreadAlert(p->parent);
+}
+
+/*
+** The main function for threads created with [sqlthread spawn].
+*/
+static Tcl_ThreadCreateType tclScriptThread(ClientData pSqlThread){
+  Tcl_Interp *interp;
+  Tcl_Obj *pRes;
+  Tcl_Obj *pList;
+  int rc;
+  SqlThread *p = (SqlThread *)pSqlThread;
+  extern int Sqlitetest_mutex_Init(Tcl_Interp*);
+
+  interp = Tcl_CreateInterp();
+  Tcl_CreateObjCommand(interp, "clock_seconds", clock_seconds_proc, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlthread", sqlthread_proc, pSqlThread, 0);
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+  Tcl_CreateObjCommand(interp, "sqlite3_blocking_step", blocking_step_proc,0,0);
+  Tcl_CreateObjCommand(interp, 
+      "sqlite3_blocking_prepare_v2", blocking_prepare_v2_proc, (void *)1, 0);
+  Tcl_CreateObjCommand(interp, 
+      "sqlite3_nonblocking_prepare_v2", blocking_prepare_v2_proc, 0, 0);
+#endif
+  Sqlitetest1_Init(interp);
+  Sqlitetest_mutex_Init(interp);
+  Sqlite3_Init(interp);
+
+  rc = Tcl_Eval(interp, p->zScript);
+  pRes = Tcl_GetObjResult(interp);
+  pList = Tcl_NewObj();
+  Tcl_IncrRefCount(pList);
+  Tcl_IncrRefCount(pRes);
+
+  if( rc!=TCL_OK ){
+    Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj("error", -1));
+    Tcl_ListObjAppendElement(interp, pList, pRes);
+    postToParent(p, pList);
+    Tcl_DecrRefCount(pList);
+    pList = Tcl_NewObj();
+  }
+
+  Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj("set", -1));
+  Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj(p->zVarname, -1));
+  Tcl_ListObjAppendElement(interp, pList, pRes);
+  postToParent(p, pList);
+
+  ckfree((void *)p);
+  Tcl_DecrRefCount(pList);
+  Tcl_DecrRefCount(pRes);
+  Tcl_DeleteInterp(interp);
+  while( Tcl_DoOneEvent(TCL_ALL_EVENTS|TCL_DONT_WAIT) );
+  Tcl_ExitThread(0);
+  TCL_THREAD_CREATE_RETURN;
+}
+
+/*
+** sqlthread spawn VARNAME SCRIPT
+**
+**     Spawn a new thread with its own Tcl interpreter and run the
+**     specified SCRIPT(s) in it. The thread terminates after running
+**     the script. The result of the script is stored in the variable
+**     VARNAME.
+**
+**     The caller can wait for the script to terminate using [vwait VARNAME].
+*/
+static int SQLITE_TCLAPI sqlthread_spawn(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_ThreadId x;
+  SqlThread *pNew;
+  int rc;
+
+  int nVarname; char *zVarname;
+  int nScript; char *zScript;
+
+  /* Parameters for thread creation */
+  const int nStack = TCL_THREAD_STACK_DEFAULT;
+  const int flags = TCL_THREAD_NOFLAGS;
+
+  assert(objc==4);
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+
+  zVarname = Tcl_GetStringFromObj(objv[2], &nVarname);
+  zScript = Tcl_GetStringFromObj(objv[3], &nScript);
+
+  pNew = (SqlThread *)ckalloc(sizeof(SqlThread)+nVarname+nScript+2);
+  pNew->zVarname = (char *)&pNew[1];
+  pNew->zScript = (char *)&pNew->zVarname[nVarname+1];
+  memcpy(pNew->zVarname, zVarname, nVarname+1);
+  memcpy(pNew->zScript, zScript, nScript+1);
+  pNew->parent = Tcl_GetCurrentThread();
+  pNew->interp = interp;
+
+  rc = Tcl_CreateThread(&x, tclScriptThread, (void *)pNew, nStack, flags);
+  if( rc!=TCL_OK ){
+    Tcl_AppendResult(interp, "Error in Tcl_CreateThread()", 0);
+    ckfree((char *)pNew);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** sqlthread parent SCRIPT
+**
+**     This can be called by spawned threads only. It sends the specified
+**     script back to the parent thread for execution. The result of
+**     evaluating the SCRIPT is returned. The parent thread must enter
+**     the event loop for this to work - otherwise the caller will
+**     block indefinitely.
+**
+**     NOTE: At the moment, this doesn't work. FIXME.
+*/
+static int SQLITE_TCLAPI sqlthread_parent(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  EvalEvent *pEvent;
+  char *zMsg;
+  int nMsg;
+  SqlThread *p = (SqlThread *)clientData;
+
+  assert(objc==3);
+  UNUSED_PARAMETER(objc);
+
+  if( p==0 ){
+    Tcl_AppendResult(interp, "no parent thread", 0);
+    return TCL_ERROR;
+  }
+
+  zMsg = Tcl_GetStringFromObj(objv[2], &nMsg);
+  pEvent = (EvalEvent *)ckalloc(sizeof(EvalEvent)+nMsg+1);
+  pEvent->base.nextPtr = 0;
+  pEvent->base.proc = tclScriptEvent;
+  pEvent->zScript = (char *)&pEvent[1];
+  memcpy(pEvent->zScript, zMsg, nMsg+1);
+  pEvent->interp = p->interp;
+  Tcl_ThreadQueueEvent(p->parent, (Tcl_Event *)pEvent, TCL_QUEUE_TAIL);
+  Tcl_ThreadAlert(p->parent);
+
+  return TCL_OK;
+}
+
+static int xBusy(void *pArg, int nBusy){
+  UNUSED_PARAMETER(pArg);
+  UNUSED_PARAMETER(nBusy);
+  sqlite3_sleep(50);
+  return 1;             /* Try again... */
+}
+
+/*
+** sqlthread open
+**
+**     Open a database handle and return the string representation of
+**     the pointer value.
+*/
+static int SQLITE_TCLAPI sqlthread_open(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int sqlite3TestMakePointerStr(Tcl_Interp *interp, char *zPtr, void *p);
+
+  const char *zFilename;
+  sqlite3 *db;
+  char zBuf[100];
+  extern int Md5_Register(sqlite3*,char**,const sqlite3_api_routines*);
+
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+
+  zFilename = Tcl_GetString(objv[2]);
+  sqlite3_open(zFilename, &db);
+  Md5_Register(db, 0, 0);
+  sqlite3_busy_handler(db, xBusy, 0);
+  
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+
+  return TCL_OK;
+}
+
+
+/*
+** sqlthread open
+**
+**     Return the current thread-id (Tcl_GetCurrentThread()) cast to
+**     an integer.
+*/
+static int SQLITE_TCLAPI sqlthread_id(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_ThreadId id = Tcl_GetCurrentThread();
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(SQLITE_PTR_TO_INT(id)));
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+  return TCL_OK;
+}
+
+
+/*
+** Dispatch routine for the sub-commands of [sqlthread].
+*/
+static int SQLITE_TCLAPI sqlthread_proc(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SubCommand {
+    char *zName;
+    Tcl_ObjCmdProc *xProc;
+    int nArg;
+    char *zUsage;
+  } aSub[] = {
+    {"parent", sqlthread_parent, 1, "SCRIPT"},
+    {"spawn",  sqlthread_spawn,  2, "VARNAME SCRIPT"},
+    {"open",   sqlthread_open,   1, "DBNAME"},
+    {"id",     sqlthread_id,     0, ""},
+    {0, 0, 0}
+  };
+  struct SubCommand *pSub;
+  int rc;
+  int iIndex;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND");
+    return TCL_ERROR;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[1], aSub, sizeof(aSub[0]), "sub-command", 0, &iIndex
+  );
+  if( rc!=TCL_OK ) return rc;
+  pSub = &aSub[iIndex];
+
+  if( objc<(pSub->nArg+2) ){
+    Tcl_WrongNumArgs(interp, 2, objv, pSub->zUsage);
+    return TCL_ERROR;
+  }
+
+  return pSub->xProc(clientData, interp, objc, objv);
+}
+
+/*
+** The [clock_seconds] command. This is more or less the same as the
+** regular tcl [clock seconds], except that it is available in testfixture
+** when linked against both Tcl 8.4 and 8.5. Because [clock seconds] is
+** implemented as a script in Tcl 8.5, it is not usually available to
+** testfixture.
+*/ 
+static int SQLITE_TCLAPI clock_seconds_proc(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Time now;
+  Tcl_GetTime(&now);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(now.sec));
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+  return TCL_OK;
+}
+
+/*
+** The [clock_milliseconds] command. This is more or less the same as the
+** regular tcl [clock milliseconds]. 
+*/ 
+static int SQLITE_TCLAPI clock_milliseconds_proc(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Time now;
+  Tcl_GetTime(&now);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(
+    ((Tcl_WideInt)now.sec * 1000) + (now.usec / 1000)
+  ));
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+  return TCL_OK;
+}
+
+/*************************************************************************
+** This block contains the implementation of the [sqlite3_blocking_step]
+** command available to threads created by [sqlthread spawn] commands. It
+** is only available on UNIX for now. This is because pthread condition
+** variables are used.
+**
+** The source code for the C functions sqlite3_blocking_step(),
+** blocking_step_notify() and the structure UnlockNotification is
+** automatically extracted from this file and used as part of the
+** documentation for the sqlite3_unlock_notify() API function. This
+** should be considered if these functions are to be extended (i.e. to 
+** support windows) in the future.
+*/ 
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+
+/* BEGIN_SQLITE_BLOCKING_STEP */
+/* This example uses the pthreads API */
+#include <pthread.h>
+
+/*
+** A pointer to an instance of this structure is passed as the user-context
+** pointer when registering for an unlock-notify callback.
+*/
+typedef struct UnlockNotification UnlockNotification;
+struct UnlockNotification {
+  int fired;                         /* True after unlock event has occurred */
+  pthread_cond_t cond;               /* Condition variable to wait on */
+  pthread_mutex_t mutex;             /* Mutex to protect structure */
+};
+
+/*
+** This function is an unlock-notify callback registered with SQLite.
+*/
+static void unlock_notify_cb(void **apArg, int nArg){
+  int i;
+  for(i=0; i<nArg; i++){
+    UnlockNotification *p = (UnlockNotification *)apArg[i];
+    pthread_mutex_lock(&p->mutex);
+    p->fired = 1;
+    pthread_cond_signal(&p->cond);
+    pthread_mutex_unlock(&p->mutex);
+  }
+}
+
+/*
+** This function assumes that an SQLite API call (either sqlite3_prepare_v2() 
+** or sqlite3_step()) has just returned SQLITE_LOCKED. The argument is the
+** associated database connection.
+**
+** This function calls sqlite3_unlock_notify() to register for an 
+** unlock-notify callback, then blocks until that callback is delivered 
+** and returns SQLITE_OK. The caller should then retry the failed operation.
+**
+** Or, if sqlite3_unlock_notify() indicates that to block would deadlock 
+** the system, then this function returns SQLITE_LOCKED immediately. In 
+** this case the caller should not retry the operation and should roll 
+** back the current transaction (if any).
+*/
+static int wait_for_unlock_notify(sqlite3 *db){
+  int rc;
+  UnlockNotification un;
+
+  /* Initialize the UnlockNotification structure. */
+  un.fired = 0;
+  pthread_mutex_init(&un.mutex, 0);
+  pthread_cond_init(&un.cond, 0);
+
+  /* Register for an unlock-notify callback. */
+  rc = sqlite3_unlock_notify(db, unlock_notify_cb, (void *)&un);
+  assert( rc==SQLITE_LOCKED || rc==SQLITE_OK );
+
+  /* The call to sqlite3_unlock_notify() always returns either SQLITE_LOCKED 
+  ** or SQLITE_OK. 
+  **
+  ** If SQLITE_LOCKED was returned, then the system is deadlocked. In this
+  ** case this function needs to return SQLITE_LOCKED to the caller so 
+  ** that the current transaction can be rolled back. Otherwise, block
+  ** until the unlock-notify callback is invoked, then return SQLITE_OK.
+  */
+  if( rc==SQLITE_OK ){
+    pthread_mutex_lock(&un.mutex);
+    if( !un.fired ){
+      pthread_cond_wait(&un.cond, &un.mutex);
+    }
+    pthread_mutex_unlock(&un.mutex);
+  }
+
+  /* Destroy the mutex and condition variables. */
+  pthread_cond_destroy(&un.cond);
+  pthread_mutex_destroy(&un.mutex);
+
+  return rc;
+}
+
+/*
+** This function is a wrapper around the SQLite function sqlite3_step().
+** It functions in the same way as step(), except that if a required
+** shared-cache lock cannot be obtained, this function may block waiting for
+** the lock to become available. In this scenario the normal API step()
+** function always returns SQLITE_LOCKED.
+**
+** If this function returns SQLITE_LOCKED, the caller should rollback
+** the current transaction (if any) and try again later. Otherwise, the
+** system may become deadlocked.
+*/
+int sqlite3_blocking_step(sqlite3_stmt *pStmt){
+  int rc;
+  while( SQLITE_LOCKED==(rc = sqlite3_step(pStmt)) ){
+    rc = wait_for_unlock_notify(sqlite3_db_handle(pStmt));
+    if( rc!=SQLITE_OK ) break;
+    sqlite3_reset(pStmt);
+  }
+  return rc;
+}
+
+/*
+** This function is a wrapper around the SQLite function sqlite3_prepare_v2().
+** It functions in the same way as prepare_v2(), except that if a required
+** shared-cache lock cannot be obtained, this function may block waiting for
+** the lock to become available. In this scenario the normal API prepare_v2()
+** function always returns SQLITE_LOCKED.
+**
+** If this function returns SQLITE_LOCKED, the caller should rollback
+** the current transaction (if any) and try again later. Otherwise, the
+** system may become deadlocked.
+*/
+int sqlite3_blocking_prepare_v2(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nSql,                 /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pz           /* OUT: End of parsed string */
+){
+  int rc;
+  while( SQLITE_LOCKED==(rc = sqlite3_prepare_v2(db, zSql, nSql, ppStmt, pz)) ){
+    rc = wait_for_unlock_notify(db);
+    if( rc!=SQLITE_OK ) break;
+  }
+  return rc;
+}
+/* END_SQLITE_BLOCKING_STEP */
+
+/*
+** Usage: sqlite3_blocking_step STMT
+**
+** Advance the statement to the next row.
+*/
+static int SQLITE_TCLAPI blocking_step_proc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+
+  pStmt = (sqlite3_stmt*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  rc = sqlite3_blocking_step(pStmt);
+
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_blocking_prepare_v2 DB sql bytes ?tailvar?
+** Usage: sqlite3_nonblocking_prepare_v2 DB sql bytes ?tailvar?
+*/
+static int SQLITE_TCLAPI blocking_prepare_v2_proc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSql;
+  int bytes;
+  const char *zTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+  int isBlocking = !(clientData==0);
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  if( isBlocking ){
+    rc = sqlite3_blocking_prepare_v2(db, zSql, bytes, &pStmt, &zTail);
+  }else{
+    rc = sqlite3_prepare_v2(db, zSql, bytes, &pStmt, &zTail);
+  }
+
+  assert(rc==SQLITE_OK || pStmt==0);
+  if( zTail && objc>=5 ){
+    if( bytes>=0 ){
+      bytes = bytes - (zTail-zSql);
+    }
+    Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
+  }
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "%s ", (char *)sqlite3ErrName(rc));
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+#endif /* SQLITE_OS_UNIX && SQLITE_ENABLE_UNLOCK_NOTIFY */
+/*
+** End of implementation of [sqlite3_blocking_step].
+************************************************************************/
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int SqlitetestThread_Init(Tcl_Interp *interp){
+  struct TclCmd {
+    int (*xProc)(void*, Tcl_Interp*, int, Tcl_Obj*const*);
+    const char *zName;
+    int iCtx;
+  } aCmd[] = {
+    { sqlthread_proc,           "sqlthread",                      0 },
+    { clock_seconds_proc,       "clock_second",                   0 },
+    { clock_milliseconds_proc,  "clock_milliseconds",             0 },
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+    { blocking_step_proc,       "sqlite3_blocking_step",          0 },
+    { blocking_prepare_v2_proc, "sqlite3_blocking_prepare_v2",    1 },
+    { blocking_prepare_v2_proc, "sqlite3_nonblocking_prepare_v2", 0 },
+#endif
+  };
+  int ii;
+
+  for(ii=0; ii<sizeof(aCmd)/sizeof(aCmd[0]); ii++){
+    void *p = SQLITE_INT_TO_PTR(aCmd[ii].iCtx);
+    Tcl_CreateObjCommand(interp, aCmd[ii].zName, aCmd[ii].xProc, p, 0);
+  }
+  return TCL_OK;
+}
+#else
+int SqlitetestThread_Init(Tcl_Interp *interp){
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_vdbecov.c b/src/test_vdbecov.c
new file mode 100644
index 0000000..a001b1d
--- /dev/null
+++ b/src/test_vdbecov.c
@@ -0,0 +1,120 @@
+/*
+** 2019 April 02
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+#ifdef SQLITE_VDBE_COVERAGE
+
+static u8 aBranchArray[200000];
+
+static void test_vdbe_branch(
+  void *pCtx, 
+  unsigned int iSrc, 
+  unsigned char iBranch, 
+  unsigned char iType
+){
+  if( iSrc<sizeof(aBranchArray) ){
+    aBranchArray[iSrc] |= iBranch;
+  }
+}
+
+static void appendToList(
+  Tcl_Obj *pList, 
+  int iLine, 
+  int iPath, 
+  const char *zNever
+){
+  Tcl_Obj *pNew = Tcl_NewObj();
+  Tcl_IncrRefCount(pNew);
+  Tcl_ListObjAppendElement(0, pNew, Tcl_NewIntObj(iLine));
+  Tcl_ListObjAppendElement(0, pNew, Tcl_NewIntObj(iPath));
+  Tcl_ListObjAppendElement(0, pNew, Tcl_NewStringObj(zNever, -1));
+  Tcl_ListObjAppendElement(0, pList, pNew);
+  Tcl_DecrRefCount(pNew);
+}
+
+
+static int SQLITE_TCLAPI test_vdbe_coverage(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *aSub[] = { "start", "report", "stop", 0 };
+  int iSub = -1;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "sub-command");
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetIndexFromObj(interp, objv[1], aSub, "sub-command", 0, &iSub) ){
+    return TCL_ERROR;
+  }
+
+  Tcl_ResetResult(interp);
+  assert( iSub==0 || iSub==1 || iSub==2 );
+  switch( iSub ){
+    case 0:       /* start */
+      memset(aBranchArray, 0, sizeof(aBranchArray));
+      sqlite3_test_control(SQLITE_TESTCTRL_VDBE_COVERAGE, test_vdbe_branch, 0);
+      break;
+    case 1: {     /* report */
+      int i;
+      Tcl_Obj *pRes = Tcl_NewObj();
+      Tcl_IncrRefCount(pRes);
+      for(i=0; i<sizeof(aBranchArray); i++){
+        u8 b = aBranchArray[i];
+        int bFlag = ((b >> 4)==4);
+        if( b ){
+          if( (b & 0x01)==0 ){
+            appendToList(pRes, i, 0, bFlag ? "less than" : "falls through");
+          }
+          if( (b & 0x02)==0 ){
+            appendToList(pRes, i, 1, bFlag ? "equal" : "taken");
+          }
+          if( (b & 0x04)==0 ){
+            appendToList(pRes, i, 2, bFlag ? "greater-than" : "NULL");
+          }
+        }
+      }
+      Tcl_SetObjResult(interp, pRes);
+      Tcl_DecrRefCount(pRes);
+      break;
+    };
+      
+    default:      /* stop */         
+      sqlite3_test_control(SQLITE_TESTCTRL_VDBE_COVERAGE, 0, 0);
+      break;
+  }
+
+  return TCL_OK;
+}
+
+#endif  /* SQLITE_VDBE_COVERAGE */
+
+int Sqlitetestvdbecov_Init(Tcl_Interp *interp){
+#ifdef SQLITE_VDBE_COVERAGE
+  Tcl_CreateObjCommand(interp, "vdbe_coverage", test_vdbe_coverage, 0, 0);
+#endif
+  return TCL_OK;
+}
+
+#endif
diff --git a/src/test_vfs.c b/src/test_vfs.c
new file mode 100644
index 0000000..312e1a1
--- /dev/null
+++ b/src/test_vfs.c
@@ -0,0 +1,1695 @@
+/*
+** 2010 May 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains the implementation of the Tcl [testvfs] command,
+** used to create SQLite VFS implementations with various properties and
+** instrumentation to support testing SQLite.
+**
+**   testvfs VFSNAME ?OPTIONS?
+**
+** Available options are:
+**
+**   -noshm      BOOLEAN        (True to omit shm methods. Default false)
+**   -default    BOOLEAN        (True to make the vfs default. Default false)
+**   -szosfile   INTEGER        (Value for sqlite3_vfs.szOsFile)
+**   -mxpathname INTEGER        (Value for sqlite3_vfs.mxPathname)
+**   -iversion   INTEGER        (Value for sqlite3_vfs.iVersion)
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+typedef struct Testvfs Testvfs;
+typedef struct TestvfsShm TestvfsShm;
+typedef struct TestvfsBuffer TestvfsBuffer;
+typedef struct TestvfsFile TestvfsFile;
+typedef struct TestvfsFd TestvfsFd;
+
+/*
+** An open file handle.
+*/
+struct TestvfsFile {
+  sqlite3_file base;              /* Base class.  Must be first */
+  TestvfsFd *pFd;                 /* File data */
+};
+#define tvfsGetFd(pFile) (((TestvfsFile *)pFile)->pFd)
+
+struct TestvfsFd {
+  sqlite3_vfs *pVfs;              /* The VFS */
+  const char *zFilename;          /* Filename as passed to xOpen() */
+  sqlite3_file *pReal;            /* The real, underlying file descriptor */
+  Tcl_Obj *pShmId;                /* Shared memory id for Tcl callbacks */
+
+  TestvfsBuffer *pShm;            /* Shared memory buffer */
+  u32 excllock;                   /* Mask of exclusive locks */
+  u32 sharedlock;                 /* Mask of shared locks */
+  TestvfsFd *pNext;               /* Next handle opened on the same file */
+};
+
+
+#define FAULT_INJECT_NONE       0
+#define FAULT_INJECT_TRANSIENT  1
+#define FAULT_INJECT_PERSISTENT 2
+
+typedef struct TestFaultInject TestFaultInject;
+struct TestFaultInject {
+  int iCnt;                       /* Remaining calls before fault injection */
+  int eFault;                     /* A FAULT_INJECT_* value */
+  int nFail;                      /* Number of faults injected */
+};
+
+/*
+** An instance of this structure is allocated for each VFS created. The
+** sqlite3_vfs.pAppData field of the VFS structure registered with SQLite
+** is set to point to it.
+*/
+struct Testvfs {
+  char *zName;                    /* Name of this VFS */
+  sqlite3_vfs *pParent;           /* The VFS to use for file IO */
+  sqlite3_vfs *pVfs;              /* The testvfs registered with SQLite */
+  Tcl_Interp *interp;             /* Interpreter to run script in */
+  Tcl_Obj *pScript;               /* Script to execute */
+  TestvfsBuffer *pBuffer;         /* List of shared buffers */
+  int isNoshm;
+  int isFullshm;
+
+  int mask;                       /* Mask controlling [script] and [ioerr] */
+
+  TestFaultInject ioerr_err;
+  TestFaultInject full_err;
+  TestFaultInject cantopen_err;
+
+#if 0
+  int iIoerrCnt;
+  int ioerr;
+  int nIoerrFail;
+  int iFullCnt;
+  int fullerr;
+  int nFullFail;
+#endif
+
+  int iDevchar;
+  int iSectorsize;
+};
+
+/*
+** The Testvfs.mask variable is set to a combination of the following.
+** If a bit is clear in Testvfs.mask, then calls made by SQLite to the 
+** corresponding VFS method is ignored for purposes of:
+**
+**   + Simulating IO errors, and
+**   + Invoking the Tcl callback script.
+*/
+#define TESTVFS_SHMOPEN_MASK      0x00000001
+#define TESTVFS_SHMLOCK_MASK      0x00000010
+#define TESTVFS_SHMMAP_MASK       0x00000020
+#define TESTVFS_SHMBARRIER_MASK   0x00000040
+#define TESTVFS_SHMCLOSE_MASK     0x00000080
+
+#define TESTVFS_OPEN_MASK         0x00000100
+#define TESTVFS_SYNC_MASK         0x00000200
+#define TESTVFS_DELETE_MASK       0x00000400
+#define TESTVFS_CLOSE_MASK        0x00000800
+#define TESTVFS_WRITE_MASK        0x00001000
+#define TESTVFS_TRUNCATE_MASK     0x00002000
+#define TESTVFS_ACCESS_MASK       0x00004000
+#define TESTVFS_FULLPATHNAME_MASK 0x00008000
+#define TESTVFS_READ_MASK         0x00010000
+#define TESTVFS_UNLOCK_MASK       0x00020000
+#define TESTVFS_LOCK_MASK         0x00040000
+#define TESTVFS_CKLOCK_MASK       0x00080000
+#define TESTVFS_FCNTL_MASK        0x00100000
+
+#define TESTVFS_ALL_MASK          0x001FFFFF
+
+
+#define TESTVFS_MAX_PAGES 1024
+
+/*
+** A shared-memory buffer. There is one of these objects for each shared
+** memory region opened by clients. If two clients open the same file,
+** there are two TestvfsFile structures but only one TestvfsBuffer structure.
+*/
+struct TestvfsBuffer {
+  char *zFile;                    /* Associated file name */
+  int pgsz;                       /* Page size */
+  u8 *aPage[TESTVFS_MAX_PAGES];   /* Array of ckalloc'd pages */
+  TestvfsFd *pFile;               /* List of open handles */
+  TestvfsBuffer *pNext;           /* Next in linked list of all buffers */
+};
+
+
+#define PARENTVFS(x) (((Testvfs *)((x)->pAppData))->pParent)
+
+#define TESTVFS_MAX_ARGS 12
+
+
+/*
+** Method declarations for TestvfsFile.
+*/
+static int tvfsClose(sqlite3_file*);
+static int tvfsRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int tvfsWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int tvfsTruncate(sqlite3_file*, sqlite3_int64 size);
+static int tvfsSync(sqlite3_file*, int flags);
+static int tvfsFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int tvfsLock(sqlite3_file*, int);
+static int tvfsUnlock(sqlite3_file*, int);
+static int tvfsCheckReservedLock(sqlite3_file*, int *);
+static int tvfsFileControl(sqlite3_file*, int op, void *pArg);
+static int tvfsSectorSize(sqlite3_file*);
+static int tvfsDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for tvfs_vfs.
+*/
+static int tvfsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int tvfsDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int tvfsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int tvfsFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+static void *tvfsDlOpen(sqlite3_vfs*, const char *zFilename);
+static void tvfsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*tvfsDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void tvfsDlClose(sqlite3_vfs*, void*);
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+static int tvfsRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int tvfsSleep(sqlite3_vfs*, int microseconds);
+static int tvfsCurrentTime(sqlite3_vfs*, double*);
+
+static int tvfsShmOpen(sqlite3_file*);
+static int tvfsShmLock(sqlite3_file*, int , int, int);
+static int tvfsShmMap(sqlite3_file*,int,int,int, void volatile **);
+static void tvfsShmBarrier(sqlite3_file*);
+static int tvfsShmUnmap(sqlite3_file*, int);
+
+static int tvfsFetch(sqlite3_file*, sqlite3_int64, int, void**);
+static int tvfsUnfetch(sqlite3_file*, sqlite3_int64, void*);
+
+static sqlite3_io_methods tvfs_io_methods = {
+  3,                              /* iVersion */
+  tvfsClose,                      /* xClose */
+  tvfsRead,                       /* xRead */
+  tvfsWrite,                      /* xWrite */
+  tvfsTruncate,                   /* xTruncate */
+  tvfsSync,                       /* xSync */
+  tvfsFileSize,                   /* xFileSize */
+  tvfsLock,                       /* xLock */
+  tvfsUnlock,                     /* xUnlock */
+  tvfsCheckReservedLock,          /* xCheckReservedLock */
+  tvfsFileControl,                /* xFileControl */
+  tvfsSectorSize,                 /* xSectorSize */
+  tvfsDeviceCharacteristics,      /* xDeviceCharacteristics */
+  tvfsShmMap,                     /* xShmMap */
+  tvfsShmLock,                    /* xShmLock */
+  tvfsShmBarrier,                 /* xShmBarrier */
+  tvfsShmUnmap,                   /* xShmUnmap */
+  tvfsFetch,
+  tvfsUnfetch
+};
+
+static int tvfsResultCode(Testvfs *p, int *pRc){
+  struct errcode {
+    int eCode;
+    const char *zCode;
+  } aCode[] = {
+    { SQLITE_OK,       "SQLITE_OK"     },
+    { SQLITE_ERROR,    "SQLITE_ERROR"  },
+    { SQLITE_IOERR,    "SQLITE_IOERR"  },
+    { SQLITE_LOCKED,   "SQLITE_LOCKED" },
+    { SQLITE_BUSY,     "SQLITE_BUSY"   },
+    { SQLITE_READONLY, "SQLITE_READONLY"   },
+    { SQLITE_READONLY_CANTINIT, "SQLITE_READONLY_CANTINIT"   },
+    { SQLITE_NOTFOUND, "SQLITE_NOTFOUND"   },
+    { -1,              "SQLITE_OMIT"   },
+  };
+
+  const char *z;
+  int i;
+
+  z = Tcl_GetStringResult(p->interp);
+  for(i=0; i<ArraySize(aCode); i++){
+    if( 0==strcmp(z, aCode[i].zCode) ){
+      *pRc = aCode[i].eCode;
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+static int tvfsInjectFault(TestFaultInject *p){
+  int ret = 0;
+  if( p->eFault ){
+    p->iCnt--;
+    if( p->iCnt==0 || (p->iCnt<0 && p->eFault==FAULT_INJECT_PERSISTENT ) ){
+      ret = 1;
+      p->nFail++;
+    }
+  }
+  return ret;
+}
+
+
+static int tvfsInjectIoerr(Testvfs *p){
+  return tvfsInjectFault(&p->ioerr_err);
+}
+
+static int tvfsInjectFullerr(Testvfs *p){
+  return tvfsInjectFault(&p->full_err);
+}
+static int tvfsInjectCantopenerr(Testvfs *p){
+  return tvfsInjectFault(&p->cantopen_err);
+}
+
+
+static void tvfsExecTcl(
+  Testvfs *p, 
+  const char *zMethod,
+  Tcl_Obj *arg1,
+  Tcl_Obj *arg2,
+  Tcl_Obj *arg3,
+  Tcl_Obj *arg4
+){
+  int rc;                         /* Return code from Tcl_EvalObj() */
+  Tcl_Obj *pEval;
+  assert( p->pScript );
+
+  assert( zMethod );
+  assert( p );
+  assert( arg2==0 || arg1!=0 );
+  assert( arg3==0 || arg2!=0 );
+
+  pEval = Tcl_DuplicateObj(p->pScript);
+  Tcl_IncrRefCount(p->pScript);
+  Tcl_ListObjAppendElement(p->interp, pEval, Tcl_NewStringObj(zMethod, -1));
+  if( arg1 ) Tcl_ListObjAppendElement(p->interp, pEval, arg1);
+  if( arg2 ) Tcl_ListObjAppendElement(p->interp, pEval, arg2);
+  if( arg3 ) Tcl_ListObjAppendElement(p->interp, pEval, arg3);
+  if( arg4 ) Tcl_ListObjAppendElement(p->interp, pEval, arg4);
+
+  rc = Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+  if( rc!=TCL_OK ){
+    Tcl_BackgroundError(p->interp);
+    Tcl_ResetResult(p->interp);
+  }
+}
+
+
+/*
+** Close an tvfs-file.
+*/
+static int tvfsClose(sqlite3_file *pFile){
+  TestvfsFile *pTestfile = (TestvfsFile *)pFile;
+  TestvfsFd *pFd = pTestfile->pFd;
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_CLOSE_MASK ){
+    tvfsExecTcl(p, "xClose", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0, 0
+    );
+  }
+
+  if( pFd->pShmId ){
+    Tcl_DecrRefCount(pFd->pShmId);
+    pFd->pShmId = 0;
+  }
+  if( pFile->pMethods ){
+    ckfree((char *)pFile->pMethods);
+  }
+  sqlite3OsClose(pFd->pReal);
+  ckfree((char *)pFd);
+  pTestfile->pFd = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Read data from an tvfs-file.
+*/
+static int tvfsRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_READ_MASK ){
+    tvfsExecTcl(p, "xRead", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+  if( rc==SQLITE_OK && p->mask&TESTVFS_READ_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsRead(pFd->pReal, zBuf, iAmt, iOfst);
+  }
+  return rc;
+}
+
+/*
+** Write data to an tvfs-file.
+*/
+static int tvfsWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_WRITE_MASK ){
+    tvfsExecTcl(p, "xWrite", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 
+        Tcl_NewWideIntObj(iOfst), Tcl_NewIntObj(iAmt)
+    );
+    tvfsResultCode(p, &rc);
+    if( rc<0 ) return SQLITE_OK;
+  }
+
+  if( rc==SQLITE_OK && tvfsInjectFullerr(p) ){
+    rc = SQLITE_FULL;
+  }
+  if( rc==SQLITE_OK && p->mask&TESTVFS_WRITE_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+  
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsWrite(pFd->pReal, zBuf, iAmt, iOfst);
+  }
+  return rc;
+}
+
+/*
+** Truncate an tvfs-file.
+*/
+static int tvfsTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_TRUNCATE_MASK ){
+    tvfsExecTcl(p, "xTruncate", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+  
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsTruncate(pFd->pReal, size);
+  }
+  return rc;
+}
+
+/*
+** Sync an tvfs-file.
+*/
+static int tvfsSync(sqlite3_file *pFile, int flags){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_SYNC_MASK ){
+    char *zFlags = 0;
+
+    switch( flags ){
+      case SQLITE_SYNC_NORMAL:
+        zFlags = "normal";
+        break;
+      case SQLITE_SYNC_FULL:
+        zFlags = "full";
+        break;
+      case SQLITE_SYNC_NORMAL|SQLITE_SYNC_DATAONLY:
+        zFlags = "normal|dataonly";
+        break;
+      case SQLITE_SYNC_FULL|SQLITE_SYNC_DATAONLY:
+        zFlags = "full|dataonly";
+        break;
+      default:
+        assert(0);
+    }
+
+    tvfsExecTcl(p, "xSync", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId,
+        Tcl_NewStringObj(zFlags, -1), 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+
+  if( rc==SQLITE_OK && tvfsInjectFullerr(p) ) rc = SQLITE_FULL;
+
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsSync(pFd->pReal, flags);
+  }
+
+  return rc;
+}
+
+/*
+** Return the current file-size of an tvfs-file.
+*/
+static int tvfsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  TestvfsFd *p = tvfsGetFd(pFile);
+  return sqlite3OsFileSize(p->pReal, pSize);
+}
+
+/*
+** Lock an tvfs-file.
+*/
+static int tvfsLock(sqlite3_file *pFile, int eLock){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_LOCK_MASK ){
+    char zLock[30];
+    sqlite3_snprintf(sizeof(zLock),zLock,"%d",eLock);
+    tvfsExecTcl(p, "xLock", Tcl_NewStringObj(pFd->zFilename, -1), 
+                   Tcl_NewStringObj(zLock, -1), 0, 0);
+  }
+  if( p->mask&TESTVFS_LOCK_MASK && tvfsInjectIoerr(p) ){
+    return SQLITE_IOERR_LOCK;
+  }
+  return sqlite3OsLock(pFd->pReal, eLock);
+}
+
+/*
+** Unlock an tvfs-file.
+*/
+static int tvfsUnlock(sqlite3_file *pFile, int eLock){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_UNLOCK_MASK ){
+    char zLock[30];
+    sqlite3_snprintf(sizeof(zLock),zLock,"%d",eLock);
+    tvfsExecTcl(p, "xUnlock", Tcl_NewStringObj(pFd->zFilename, -1), 
+                   Tcl_NewStringObj(zLock, -1), 0, 0);
+  }
+  if( p->mask&TESTVFS_UNLOCK_MASK && tvfsInjectIoerr(p) ){
+    return SQLITE_IOERR_UNLOCK;
+  }
+  return sqlite3OsUnlock(pFd->pReal, eLock);
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an tvfs-file.
+*/
+static int tvfsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_CKLOCK_MASK ){
+    tvfsExecTcl(p, "xCheckReservedLock", Tcl_NewStringObj(pFd->zFilename, -1),
+                   0, 0, 0);
+  }
+  return sqlite3OsCheckReservedLock(pFd->pReal, pResOut);
+}
+
+/*
+** File control method. For custom operations on an tvfs-file.
+*/
+static int tvfsFileControl(sqlite3_file *pFile, int op, void *pArg){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( op==SQLITE_FCNTL_PRAGMA ){
+    char **argv = (char**)pArg;
+    if( sqlite3_stricmp(argv[1],"error")==0 ){
+      int rc = SQLITE_ERROR;
+      if( argv[2] ){
+        const char *z = argv[2];
+        int x = atoi(z);
+        if( x ){
+          rc = x;
+          while( sqlite3Isdigit(z[0]) ){ z++; }
+          while( sqlite3Isspace(z[0]) ){ z++; }
+        }
+        if( z[0] ) argv[0] = sqlite3_mprintf("%s", z);
+      }
+      return rc;
+    }
+    if( sqlite3_stricmp(argv[1], "filename")==0 ){
+      argv[0] = sqlite3_mprintf("%s", pFd->zFilename);
+      return SQLITE_OK;
+    }
+  }
+  if( p->pScript && (p->mask&TESTVFS_FCNTL_MASK) ){
+    struct Fcntl {
+      int iFnctl;
+      const char *zFnctl;
+    } aF[] = {
+      { SQLITE_FCNTL_BEGIN_ATOMIC_WRITE, "BEGIN_ATOMIC_WRITE" },
+      { SQLITE_FCNTL_COMMIT_ATOMIC_WRITE, "COMMIT_ATOMIC_WRITE" },
+      { SQLITE_FCNTL_ZIPVFS, "ZIPVFS" },
+    };
+    int i;
+    for(i=0; i<sizeof(aF)/sizeof(aF[0]); i++){
+      if( op==aF[i].iFnctl ) break;
+    }
+    if( i<sizeof(aF)/sizeof(aF[0]) ){
+      int rc = 0;
+      tvfsExecTcl(p, "xFileControl", 
+          Tcl_NewStringObj(pFd->zFilename, -1), 
+          Tcl_NewStringObj(aF[i].zFnctl, -1),
+          0, 0
+      );
+      tvfsResultCode(p, &rc);
+      if( rc ) return (rc<0 ? SQLITE_OK : rc);
+    }
+  }
+  return sqlite3OsFileControl(pFd->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an tvfs-file.
+*/
+static int tvfsSectorSize(sqlite3_file *pFile){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->iSectorsize>=0 ){
+    return p->iSectorsize;
+  }
+  return sqlite3OsSectorSize(pFd->pReal);
+}
+
+/*
+** Return the device characteristic flags supported by an tvfs-file.
+*/
+static int tvfsDeviceCharacteristics(sqlite3_file *pFile){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->iDevchar>=0 ){
+    return p->iDevchar;
+  }
+  return sqlite3OsDeviceCharacteristics(pFd->pReal);
+}
+
+/*
+** Open an tvfs file handle.
+*/
+static int tvfsOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  TestvfsFile *pTestfile = (TestvfsFile *)pFile;
+  TestvfsFd *pFd;
+  Tcl_Obj *pId = 0;
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+
+  pFd = (TestvfsFd *)ckalloc(sizeof(TestvfsFd) + PARENTVFS(pVfs)->szOsFile);
+  memset(pFd, 0, sizeof(TestvfsFd) + PARENTVFS(pVfs)->szOsFile);
+  pFd->pShm = 0;
+  pFd->pShmId = 0;
+  pFd->zFilename = zName;
+  pFd->pVfs = pVfs;
+  pFd->pReal = (sqlite3_file *)&pFd[1];
+  memset(pTestfile, 0, sizeof(TestvfsFile));
+  pTestfile->pFd = pFd;
+
+  /* Evaluate the Tcl script: 
+  **
+  **   SCRIPT xOpen FILENAME KEY-VALUE-ARGS
+  **
+  ** If the script returns an SQLite error code other than SQLITE_OK, an
+  ** error is returned to the caller. If it returns SQLITE_OK, the new
+  ** connection is named "anon". Otherwise, the value returned by the
+  ** script is used as the connection name.
+  */
+  Tcl_ResetResult(p->interp);
+  if( p->pScript && p->mask&TESTVFS_OPEN_MASK ){
+    Tcl_Obj *pArg = Tcl_NewObj();
+    Tcl_IncrRefCount(pArg);
+    if( flags&SQLITE_OPEN_MAIN_DB ){
+      const char *z = &zName[strlen(zName)+1];
+      while( *z ){
+        Tcl_ListObjAppendElement(0, pArg, Tcl_NewStringObj(z, -1));
+        z += strlen(z) + 1;
+        Tcl_ListObjAppendElement(0, pArg, Tcl_NewStringObj(z, -1));
+        z += strlen(z) + 1;
+      }
+    }
+    tvfsExecTcl(p, "xOpen", Tcl_NewStringObj(pFd->zFilename, -1), pArg, 0, 0);
+    Tcl_DecrRefCount(pArg);
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }else{
+      pId = Tcl_GetObjResult(p->interp);
+    }
+  }
+
+  if( (p->mask&TESTVFS_OPEN_MASK) &&  tvfsInjectIoerr(p) ) return SQLITE_IOERR;
+  if( tvfsInjectCantopenerr(p) ) return SQLITE_CANTOPEN;
+  if( tvfsInjectFullerr(p) ) return SQLITE_FULL;
+
+  if( !pId ){
+    pId = Tcl_NewStringObj("anon", -1);
+  }
+  Tcl_IncrRefCount(pId);
+  pFd->pShmId = pId;
+  Tcl_ResetResult(p->interp);
+
+  rc = sqlite3OsOpen(PARENTVFS(pVfs), zName, pFd->pReal, flags, pOutFlags);
+  if( pFd->pReal->pMethods ){
+    sqlite3_io_methods *pMethods;
+    int nByte;
+
+    if( pVfs->iVersion>1 ){
+      nByte = sizeof(sqlite3_io_methods);
+    }else{
+      nByte = offsetof(sqlite3_io_methods, xShmMap);
+    }
+
+    pMethods = (sqlite3_io_methods *)ckalloc(nByte);
+    memcpy(pMethods, &tvfs_io_methods, nByte);
+    pMethods->iVersion = pFd->pReal->pMethods->iVersion;
+    if( pMethods->iVersion>pVfs->iVersion ){
+      pMethods->iVersion = pVfs->iVersion;
+    }
+    if( pVfs->iVersion>1 && ((Testvfs *)pVfs->pAppData)->isNoshm ){
+      pMethods->xShmUnmap = 0;
+      pMethods->xShmLock = 0;
+      pMethods->xShmBarrier = 0;
+      pMethods->xShmMap = 0;
+    }
+    pFile->pMethods = pMethods;
+  }
+
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int tvfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc = SQLITE_OK;
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_DELETE_MASK ){
+    tvfsExecTcl(p, "xDelete", 
+        Tcl_NewStringObj(zPath, -1), Tcl_NewIntObj(dirSync), 0, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsDelete(PARENTVFS(pVfs), zPath, dirSync);
+  }
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int tvfsAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_ACCESS_MASK ){
+    int rc;
+    char *zArg = 0;
+    if( flags==SQLITE_ACCESS_EXISTS ) zArg = "SQLITE_ACCESS_EXISTS";
+    if( flags==SQLITE_ACCESS_READWRITE ) zArg = "SQLITE_ACCESS_READWRITE";
+    if( flags==SQLITE_ACCESS_READ ) zArg = "SQLITE_ACCESS_READ";
+    tvfsExecTcl(p, "xAccess", 
+        Tcl_NewStringObj(zPath, -1), Tcl_NewStringObj(zArg, -1), 0, 0
+    );
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }else{
+      Tcl_Interp *interp = p->interp;
+      if( TCL_OK==Tcl_GetBooleanFromObj(0, Tcl_GetObjResult(interp), pResOut) ){
+        return SQLITE_OK;
+      }
+    }
+  }
+  return sqlite3OsAccess(PARENTVFS(pVfs), zPath, flags, pResOut);
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
+*/
+static int tvfsFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_FULLPATHNAME_MASK ){
+    int rc;
+    tvfsExecTcl(p, "xFullPathname", Tcl_NewStringObj(zPath, -1), 0, 0, 0);
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }
+  }
+  return sqlite3OsFullPathname(PARENTVFS(pVfs), zPath, nOut, zOut);
+}
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *tvfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return sqlite3OsDlOpen(PARENTVFS(pVfs), zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void tvfsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3OsDlError(PARENTVFS(pVfs), nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*tvfsDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return sqlite3OsDlSym(PARENTVFS(pVfs), p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void tvfsDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  sqlite3OsDlClose(PARENTVFS(pVfs), pHandle);
+}
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int tvfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return sqlite3OsRandomness(PARENTVFS(pVfs), nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int tvfsSleep(sqlite3_vfs *pVfs, int nMicro){
+  return sqlite3OsSleep(PARENTVFS(pVfs), nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int tvfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return PARENTVFS(pVfs)->xCurrentTime(PARENTVFS(pVfs), pTimeOut);
+}
+
+static int tvfsShmOpen(sqlite3_file *pFile){
+  Testvfs *p;
+  int rc = SQLITE_OK;             /* Return code */
+  TestvfsBuffer *pBuffer;         /* Buffer to open connection to */
+  TestvfsFd *pFd;                 /* The testvfs file structure */
+
+  pFd = tvfsGetFd(pFile);
+  p = (Testvfs *)pFd->pVfs->pAppData;
+  assert( 0==p->isFullshm );
+  assert( pFd->pShmId && pFd->pShm==0 && pFd->pNext==0 );
+
+  /* Evaluate the Tcl script: 
+  **
+  **   SCRIPT xShmOpen FILENAME
+  */
+  Tcl_ResetResult(p->interp);
+  if( p->pScript && p->mask&TESTVFS_SHMOPEN_MASK ){
+    tvfsExecTcl(p, "xShmOpen", Tcl_NewStringObj(pFd->zFilename, -1), 0, 0, 0);
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }
+  }
+
+  assert( rc==SQLITE_OK );
+  if( p->mask&TESTVFS_SHMOPEN_MASK && tvfsInjectIoerr(p) ){
+    return SQLITE_IOERR;
+  }
+
+  /* Search for a TestvfsBuffer. Create a new one if required. */
+  for(pBuffer=p->pBuffer; pBuffer; pBuffer=pBuffer->pNext){
+    if( 0==strcmp(pFd->zFilename, pBuffer->zFile) ) break;
+  }
+  if( !pBuffer ){
+    int szName = (int)strlen(pFd->zFilename);
+    int nByte = sizeof(TestvfsBuffer) + szName + 1;
+    pBuffer = (TestvfsBuffer *)ckalloc(nByte);
+    memset(pBuffer, 0, nByte);
+    pBuffer->zFile = (char *)&pBuffer[1];
+    memcpy(pBuffer->zFile, pFd->zFilename, szName+1);
+    pBuffer->pNext = p->pBuffer;
+    p->pBuffer = pBuffer;
+  }
+
+  /* Connect the TestvfsBuffer to the new TestvfsShm handle and return. */
+  pFd->pNext = pBuffer->pFile;
+  pBuffer->pFile = pFd;
+  pFd->pShm = pBuffer;
+  return rc;
+}
+
+static void tvfsAllocPage(TestvfsBuffer *p, int iPage, int pgsz){
+  assert( iPage<TESTVFS_MAX_PAGES );
+  if( p->aPage[iPage]==0 ){
+    p->aPage[iPage] = (u8 *)ckalloc(pgsz);
+    memset(p->aPage[iPage], 0, pgsz);
+    p->pgsz = pgsz;
+  }
+}
+
+static int tvfsShmMap(
+  sqlite3_file *pFile,            /* Handle open on database file */
+  int iPage,                      /* Page to retrieve */
+  int pgsz,                       /* Size of pages */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+
+  if( p->isFullshm ){
+    sqlite3_file *pReal = pFd->pReal;
+    return pReal->pMethods->xShmMap(pReal, iPage, pgsz, isWrite, pp);
+  }
+
+  if( 0==pFd->pShm ){
+    rc = tvfsShmOpen(pFile);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }
+
+  if( p->pScript && p->mask&TESTVFS_SHMMAP_MASK ){
+    Tcl_Obj *pArg = Tcl_NewObj();
+    Tcl_IncrRefCount(pArg);
+    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(iPage));
+    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(pgsz));
+    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(isWrite));
+    tvfsExecTcl(p, "xShmMap", 
+        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId, pArg, 0
+    );
+    tvfsResultCode(p, &rc);
+    Tcl_DecrRefCount(pArg);
+  }
+  if( rc==SQLITE_OK && p->mask&TESTVFS_SHMMAP_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+
+  if( rc==SQLITE_OK && isWrite && !pFd->pShm->aPage[iPage] ){
+    tvfsAllocPage(pFd->pShm, iPage, pgsz);
+  }
+  if( rc==SQLITE_OK || rc==SQLITE_READONLY ){
+    *pp = (void volatile *)pFd->pShm->aPage[iPage];
+  }
+
+  return rc;
+}
+
+
+static int tvfsShmLock(
+  sqlite3_file *pFile,
+  int ofst,
+  int n,
+  int flags
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+  int nLock;
+  char zLock[80];
+
+  if( p->isFullshm ){
+    sqlite3_file *pReal = pFd->pReal;
+    return pReal->pMethods->xShmLock(pReal, ofst, n, flags);
+  }
+
+  if( p->pScript && p->mask&TESTVFS_SHMLOCK_MASK ){
+    sqlite3_snprintf(sizeof(zLock), zLock, "%d %d", ofst, n);
+    nLock = (int)strlen(zLock);
+    if( flags & SQLITE_SHM_LOCK ){
+      strcpy(&zLock[nLock], " lock");
+    }else{
+      strcpy(&zLock[nLock], " unlock");
+    }
+    nLock += (int)strlen(&zLock[nLock]);
+    if( flags & SQLITE_SHM_SHARED ){
+      strcpy(&zLock[nLock], " shared");
+    }else{
+      strcpy(&zLock[nLock], " exclusive");
+    }
+    tvfsExecTcl(p, "xShmLock", 
+        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId,
+        Tcl_NewStringObj(zLock, -1), 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+
+  if( rc==SQLITE_OK && p->mask&TESTVFS_SHMLOCK_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+
+  if( rc==SQLITE_OK ){
+    int isLock = (flags & SQLITE_SHM_LOCK);
+    int isExcl = (flags & SQLITE_SHM_EXCLUSIVE);
+    u32 mask = (((1<<n)-1) << ofst);
+    if( isLock ){
+      TestvfsFd *p2;
+      for(p2=pFd->pShm->pFile; p2; p2=p2->pNext){
+        if( p2==pFd ) continue;
+        if( (p2->excllock&mask) || (isExcl && p2->sharedlock&mask) ){
+          rc = SQLITE_BUSY;
+          break;
+        }
+      }
+      if( rc==SQLITE_OK ){
+        if( isExcl )  pFd->excllock |= mask;
+        if( !isExcl ) pFd->sharedlock |= mask;
+      }
+    }else{
+      if( isExcl )  pFd->excllock &= (~mask);
+      if( !isExcl ) pFd->sharedlock &= (~mask);
+    }
+  }
+
+  return rc;
+}
+
+static void tvfsShmBarrier(sqlite3_file *pFile){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+
+  if( p->pScript && p->mask&TESTVFS_SHMBARRIER_MASK ){
+    const char *z = pFd->pShm ? pFd->pShm->zFile : "";
+    tvfsExecTcl(p, "xShmBarrier", Tcl_NewStringObj(z, -1), pFd->pShmId, 0, 0);
+  }
+
+  if( p->isFullshm ){
+    sqlite3_file *pReal = pFd->pReal;
+    pReal->pMethods->xShmBarrier(pReal);
+    return;
+  }
+}
+
+static int tvfsShmUnmap(
+  sqlite3_file *pFile,
+  int deleteFlag
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+  TestvfsBuffer *pBuffer = pFd->pShm;
+  TestvfsFd **ppFd;
+
+  if( p->isFullshm ){
+    sqlite3_file *pReal = pFd->pReal;
+    return pReal->pMethods->xShmUnmap(pReal, deleteFlag);
+  }
+
+  if( !pBuffer ) return SQLITE_OK;
+  assert( pFd->pShmId && pFd->pShm );
+
+  if( p->pScript && p->mask&TESTVFS_SHMCLOSE_MASK ){
+    tvfsExecTcl(p, "xShmUnmap", 
+        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId, 0, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+
+  for(ppFd=&pBuffer->pFile; *ppFd!=pFd; ppFd=&((*ppFd)->pNext));
+  assert( (*ppFd)==pFd );
+  *ppFd = pFd->pNext;
+  pFd->pNext = 0;
+
+  if( pBuffer->pFile==0 ){
+    int i;
+    TestvfsBuffer **pp;
+    for(pp=&p->pBuffer; *pp!=pBuffer; pp=&((*pp)->pNext));
+    *pp = (*pp)->pNext;
+    for(i=0; pBuffer->aPage[i]; i++){
+      ckfree((char *)pBuffer->aPage[i]);
+    }
+    ckfree((char *)pBuffer);
+  }
+  pFd->pShm = 0;
+
+  return rc;
+}
+
+static int tvfsFetch(
+    sqlite3_file *pFile, 
+    sqlite3_int64 iOfst, 
+    int iAmt, 
+    void **pp
+){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  return sqlite3OsFetch(pFd->pReal, iOfst, iAmt, pp);
+}
+
+static int tvfsUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *p){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  return sqlite3OsUnfetch(pFd->pReal, iOfst, p);
+}
+
+static int SQLITE_TCLAPI testvfs_obj_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Testvfs *p = (Testvfs *)cd;
+
+  enum DB_enum { 
+    CMD_SHM, CMD_DELETE, CMD_FILTER, CMD_IOERR, CMD_SCRIPT, 
+    CMD_DEVCHAR, CMD_SECTORSIZE, CMD_FULLERR, CMD_CANTOPENERR
+  };
+  struct TestvfsSubcmd {
+    char *zName;
+    enum DB_enum eCmd;
+  } aSubcmd[] = {
+    { "shm",         CMD_SHM         },
+    { "delete",      CMD_DELETE      },
+    { "filter",      CMD_FILTER      },
+    { "ioerr",       CMD_IOERR       },
+    { "fullerr",     CMD_FULLERR     },
+    { "cantopenerr", CMD_CANTOPENERR },
+    { "script",      CMD_SCRIPT      },
+    { "devchar",     CMD_DEVCHAR     },
+    { "sectorsize",  CMD_SECTORSIZE  },
+    { 0, 0 }
+  };
+  int i;
+  
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObjStruct(
+        interp, objv[1], aSubcmd, sizeof(aSubcmd[0]), "subcommand", 0, &i) 
+  ){
+    return TCL_ERROR;
+  }
+  Tcl_ResetResult(interp);
+
+  switch( aSubcmd[i].eCmd ){
+    case CMD_SHM: {
+      Tcl_Obj *pObj;
+      int rc;
+      TestvfsBuffer *pBuffer;
+      char *zName;
+      if( objc!=3 && objc!=4 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "FILE ?VALUE?");
+        return TCL_ERROR;
+      }
+      zName = ckalloc(p->pParent->mxPathname);
+      rc = p->pParent->xFullPathname(
+          p->pParent, Tcl_GetString(objv[2]), 
+          p->pParent->mxPathname, zName
+      );
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "failed to get full path: ",
+                         Tcl_GetString(objv[2]), 0);
+        ckfree(zName);
+        return TCL_ERROR;
+      }
+      for(pBuffer=p->pBuffer; pBuffer; pBuffer=pBuffer->pNext){
+        if( 0==strcmp(pBuffer->zFile, zName) ) break;
+      }
+      ckfree(zName);
+      if( !pBuffer ){
+        Tcl_AppendResult(interp, "no such file: ", Tcl_GetString(objv[2]), 0);
+        return TCL_ERROR;
+      }
+      if( objc==4 ){
+        int n;
+        u8 *a = Tcl_GetByteArrayFromObj(objv[3], &n);
+        int pgsz = pBuffer->pgsz;
+        if( pgsz==0 ) pgsz = 65536;
+        for(i=0; i*pgsz<n; i++){
+          int nByte = pgsz;
+          tvfsAllocPage(pBuffer, i, pgsz);
+          if( n-i*pgsz<pgsz ){
+            nByte = n;
+          }
+          memcpy(pBuffer->aPage[i], &a[i*pgsz], nByte);
+        }
+      }
+
+      pObj = Tcl_NewObj();
+      for(i=0; pBuffer->aPage[i]; i++){
+        int pgsz = pBuffer->pgsz;
+        if( pgsz==0 ) pgsz = 65536;
+        Tcl_AppendObjToObj(pObj, Tcl_NewByteArrayObj(pBuffer->aPage[i], pgsz));
+      }
+      Tcl_SetObjResult(interp, pObj);
+      break;
+    }
+
+    /*  TESTVFS filter METHOD-LIST
+    **
+    **     Activate special processing for those methods contained in the list
+    */
+    case CMD_FILTER: {
+      static struct VfsMethod {
+        char *zName;
+        int mask;
+      } vfsmethod [] = {
+        { "xShmOpen",           TESTVFS_SHMOPEN_MASK },
+        { "xShmLock",           TESTVFS_SHMLOCK_MASK },
+        { "xShmBarrier",        TESTVFS_SHMBARRIER_MASK },
+        { "xShmUnmap",          TESTVFS_SHMCLOSE_MASK },
+        { "xShmMap",            TESTVFS_SHMMAP_MASK },
+        { "xSync",              TESTVFS_SYNC_MASK },
+        { "xDelete",            TESTVFS_DELETE_MASK },
+        { "xWrite",             TESTVFS_WRITE_MASK },
+        { "xRead",              TESTVFS_READ_MASK },
+        { "xTruncate",          TESTVFS_TRUNCATE_MASK },
+        { "xOpen",              TESTVFS_OPEN_MASK },
+        { "xClose",             TESTVFS_CLOSE_MASK },
+        { "xAccess",            TESTVFS_ACCESS_MASK },
+        { "xFullPathname",      TESTVFS_FULLPATHNAME_MASK },
+        { "xUnlock",            TESTVFS_UNLOCK_MASK },
+        { "xLock",              TESTVFS_LOCK_MASK },
+        { "xCheckReservedLock", TESTVFS_CKLOCK_MASK },
+        { "xFileControl",       TESTVFS_FCNTL_MASK },
+      };
+      Tcl_Obj **apElem = 0;
+      int nElem = 0;
+      int mask = 0;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "LIST");
+        return TCL_ERROR;
+      }
+      if( Tcl_ListObjGetElements(interp, objv[2], &nElem, &apElem) ){
+        return TCL_ERROR;
+      }
+      Tcl_ResetResult(interp);
+      for(i=0; i<nElem; i++){
+        int iMethod;
+        char *zElem = Tcl_GetString(apElem[i]);
+        for(iMethod=0; iMethod<ArraySize(vfsmethod); iMethod++){
+          if( strcmp(zElem, vfsmethod[iMethod].zName)==0 ){
+            mask |= vfsmethod[iMethod].mask;
+            break;
+          }
+        }
+        if( iMethod==ArraySize(vfsmethod) ){
+          Tcl_AppendResult(interp, "unknown method: ", zElem, 0);
+          return TCL_ERROR;
+        }
+      }
+      p->mask = mask;
+      break;
+    }
+
+    /*
+    **  TESTVFS script ?SCRIPT?
+    **
+    **  Query or set the script to be run when filtered VFS events
+    **  occur.
+    */
+    case CMD_SCRIPT: {
+      if( objc==3 ){
+        int nByte;
+        if( p->pScript ){
+          Tcl_DecrRefCount(p->pScript);
+          p->pScript = 0;
+        }
+        Tcl_GetStringFromObj(objv[2], &nByte);
+        if( nByte>0 ){
+          p->pScript = Tcl_DuplicateObj(objv[2]);
+          Tcl_IncrRefCount(p->pScript);
+        }
+      }else if( objc!=2 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
+        return TCL_ERROR;
+      }
+
+      Tcl_ResetResult(interp);
+      if( p->pScript ) Tcl_SetObjResult(interp, p->pScript);
+
+      break;
+    }
+
+    /*
+    ** TESTVFS ioerr ?IFAIL PERSIST?
+    **
+    **   Where IFAIL is an integer and PERSIST is boolean.
+    */
+    case CMD_CANTOPENERR:
+    case CMD_IOERR:
+    case CMD_FULLERR: {
+      TestFaultInject *pTest = 0;
+      int iRet;
+
+      switch( aSubcmd[i].eCmd ){
+        case CMD_IOERR: pTest = &p->ioerr_err; break;
+        case CMD_FULLERR: pTest = &p->full_err; break;
+        case CMD_CANTOPENERR: pTest = &p->cantopen_err; break;
+        default: assert(0);
+      }
+      iRet = pTest->nFail;
+      pTest->nFail = 0;
+      pTest->eFault = 0;
+      pTest->iCnt = 0;
+
+      if( objc==4 ){
+        int iCnt, iPersist;
+        if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &iCnt)
+         || TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[3], &iPersist)
+        ){
+          return TCL_ERROR;
+        }
+        pTest->eFault = iPersist?FAULT_INJECT_PERSISTENT:FAULT_INJECT_TRANSIENT;
+        pTest->iCnt = iCnt;
+      }else if( objc!=2 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?CNT PERSIST?");
+        return TCL_ERROR;
+      }
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(iRet));
+      break;
+    }
+
+    case CMD_DELETE: {
+      Tcl_DeleteCommand(interp, Tcl_GetString(objv[0]));
+      break;
+    }
+
+    case CMD_DEVCHAR: {
+      struct DeviceFlag {
+        char *zName;
+        int iValue;
+      } aFlag[] = {
+        { "default",               -1 },
+        { "atomic",                SQLITE_IOCAP_ATOMIC                },
+        { "atomic512",             SQLITE_IOCAP_ATOMIC512             },
+        { "atomic1k",              SQLITE_IOCAP_ATOMIC1K              },
+        { "atomic2k",              SQLITE_IOCAP_ATOMIC2K              },
+        { "atomic4k",              SQLITE_IOCAP_ATOMIC4K              },
+        { "atomic8k",              SQLITE_IOCAP_ATOMIC8K              },
+        { "atomic16k",             SQLITE_IOCAP_ATOMIC16K             },
+        { "atomic32k",             SQLITE_IOCAP_ATOMIC32K             },
+        { "atomic64k",             SQLITE_IOCAP_ATOMIC64K             },
+        { "sequential",            SQLITE_IOCAP_SEQUENTIAL            },
+        { "safe_append",           SQLITE_IOCAP_SAFE_APPEND           },
+        { "undeletable_when_open", SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN },
+        { "powersafe_overwrite",   SQLITE_IOCAP_POWERSAFE_OVERWRITE   },
+        { "immutable",             SQLITE_IOCAP_IMMUTABLE             },
+        { 0, 0 }
+      };
+      Tcl_Obj *pRet;
+      int iFlag;
+
+      if( objc>3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?ATTR-LIST?");
+        return TCL_ERROR;
+      }
+      if( objc==3 ){
+        int j;
+        int iNew = 0;
+        Tcl_Obj **flags = 0;
+        int nFlags = 0;
+
+        if( Tcl_ListObjGetElements(interp, objv[2], &nFlags, &flags) ){
+          return TCL_ERROR;
+        }
+
+        for(j=0; j<nFlags; j++){
+          int idx = 0;
+          if( Tcl_GetIndexFromObjStruct(interp, flags[j], aFlag, 
+                sizeof(aFlag[0]), "flag", 0, &idx) 
+          ){
+            return TCL_ERROR;
+          }
+          if( aFlag[idx].iValue<0 && nFlags>1 ){
+            Tcl_AppendResult(interp, "bad flags: ", Tcl_GetString(objv[2]), 0);
+            return TCL_ERROR;
+          }
+          iNew |= aFlag[idx].iValue;
+        }
+
+        p->iDevchar = iNew| 0x10000000;
+      }
+
+      pRet = Tcl_NewObj();
+      for(iFlag=0; iFlag<sizeof(aFlag)/sizeof(aFlag[0]); iFlag++){
+        if( p->iDevchar & aFlag[iFlag].iValue ){
+          Tcl_ListObjAppendElement(
+              interp, pRet, Tcl_NewStringObj(aFlag[iFlag].zName, -1)
+          );
+        }
+      }
+      Tcl_SetObjResult(interp, pRet);
+
+      break;
+    }
+
+    case CMD_SECTORSIZE: {
+      if( objc>3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?VALUE?");
+        return TCL_ERROR;
+      }
+      if( objc==3 ){
+        int iNew = 0;
+        if( Tcl_GetIntFromObj(interp, objv[2], &iNew) ){
+          return TCL_ERROR;
+        }
+        p->iSectorsize = iNew;
+      }
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(p->iSectorsize));
+      break;
+    }
+  }
+
+  return TCL_OK;
+}
+
+static void SQLITE_TCLAPI testvfs_obj_del(ClientData cd){
+  Testvfs *p = (Testvfs *)cd;
+  if( p->pScript ) Tcl_DecrRefCount(p->pScript);
+  sqlite3_vfs_unregister(p->pVfs);
+  memset(p->pVfs, 0, sizeof(sqlite3_vfs));
+  ckfree((char *)p->pVfs);
+  memset(p, 0, sizeof(Testvfs));
+  ckfree((char *)p);
+}
+
+/*
+** Usage:  testvfs VFSNAME ?SWITCHES?
+**
+** Switches are:
+**
+**   -noshm   BOOLEAN             (True to omit shm methods. Default false)
+**   -default BOOLEAN             (True to make the vfs default. Default false)
+**
+** This command creates two things when it is invoked: an SQLite VFS, and
+** a Tcl command. Both are named VFSNAME. The VFS is installed. It is not
+** installed as the default VFS.
+**
+** The VFS passes all file I/O calls through to the underlying VFS.
+**
+** Whenever the xShmMap method of the VFS
+** is invoked, the SCRIPT is executed as follows:
+**
+**   SCRIPT xShmMap    FILENAME ID
+**
+** The value returned by the invocation of SCRIPT above is interpreted as
+** an SQLite error code and returned to SQLite. Either a symbolic 
+** "SQLITE_OK" or numeric "0" value may be returned.
+**
+** The contents of the shared-memory buffer associated with a given file
+** may be read and set using the following command:
+**
+**   VFSNAME shm FILENAME ?NEWVALUE?
+**
+** When the xShmLock method is invoked by SQLite, the following script is
+** run:
+**
+**   SCRIPT xShmLock    FILENAME ID LOCK
+**
+** where LOCK is of the form "OFFSET NBYTE lock/unlock shared/exclusive"
+*/
+static int SQLITE_TCLAPI testvfs_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static sqlite3_vfs tvfs_vfs = {
+    3,                            /* iVersion */
+    0,                            /* szOsFile */
+    0,                            /* mxPathname */
+    0,                            /* pNext */
+    0,                            /* zName */
+    0,                            /* pAppData */
+    tvfsOpen,                     /* xOpen */
+    tvfsDelete,                   /* xDelete */
+    tvfsAccess,                   /* xAccess */
+    tvfsFullPathname,             /* xFullPathname */
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    tvfsDlOpen,                   /* xDlOpen */
+    tvfsDlError,                  /* xDlError */
+    tvfsDlSym,                    /* xDlSym */
+    tvfsDlClose,                  /* xDlClose */
+#else
+    0,                            /* xDlOpen */
+    0,                            /* xDlError */
+    0,                            /* xDlSym */
+    0,                            /* xDlClose */
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+    tvfsRandomness,               /* xRandomness */
+    tvfsSleep,                    /* xSleep */
+    tvfsCurrentTime,              /* xCurrentTime */
+    0,                            /* xGetLastError */
+    0,                            /* xCurrentTimeInt64 */
+    0,                            /* xSetSystemCall */
+    0,                            /* xGetSystemCall */
+    0,                            /* xNextSystemCall */
+  };
+
+  Testvfs *p;                     /* New object */
+  sqlite3_vfs *pVfs;              /* New VFS */
+  char *zVfs;
+  int nByte;                      /* Bytes of space to allocate at p */
+
+  int i;
+  int isNoshm = 0;                /* True if -noshm is passed */
+  int isFullshm = 0;              /* True if -fullshm is passed */
+  int isDefault = 0;              /* True if -default is passed */
+  int szOsFile = 0;               /* Value passed to -szosfile */
+  int mxPathname = -1;            /* Value passed to -mxpathname */
+  int iVersion = 3;               /* Value passed to -iversion */
+
+  if( objc<2 || 0!=(objc%2) ) goto bad_args;
+  for(i=2; i<objc; i += 2){
+    int nSwitch;
+    char *zSwitch;
+    zSwitch = Tcl_GetStringFromObj(objv[i], &nSwitch); 
+
+    if( nSwitch>2 && 0==strncmp("-noshm", zSwitch, nSwitch) ){
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isNoshm) ){
+        return TCL_ERROR;
+      }
+      if( isNoshm ) isFullshm = 0;
+    }
+    else if( nSwitch>2 && 0==strncmp("-default", zSwitch, nSwitch) ){
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isDefault) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-szosfile", zSwitch, nSwitch) ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &szOsFile) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-mxpathname", zSwitch, nSwitch) ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &mxPathname) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-iversion", zSwitch, nSwitch) ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &iVersion) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-fullshm", zSwitch, nSwitch) ){
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isFullshm) ){
+        return TCL_ERROR;
+      }
+      if( isFullshm ) isNoshm = 0;
+    }
+    else{
+      goto bad_args;
+    }
+  }
+
+  if( szOsFile<sizeof(TestvfsFile) ){
+    szOsFile = sizeof(TestvfsFile);
+  }
+
+  zVfs = Tcl_GetString(objv[1]);
+  nByte = sizeof(Testvfs) + (int)strlen(zVfs)+1;
+  p = (Testvfs *)ckalloc(nByte);
+  memset(p, 0, nByte);
+  p->iDevchar = -1;
+  p->iSectorsize = -1;
+
+  /* Create the new object command before querying SQLite for a default VFS
+  ** to use for 'real' IO operations. This is because creating the new VFS
+  ** may delete an existing [testvfs] VFS of the same name. If such a VFS
+  ** is currently the default, the new [testvfs] may end up calling the 
+  ** methods of a deleted object.
+  */
+  Tcl_CreateObjCommand(interp, zVfs, testvfs_obj_cmd, p, testvfs_obj_del);
+  p->pParent = sqlite3_vfs_find(0);
+  p->interp = interp;
+
+  p->zName = (char *)&p[1];
+  memcpy(p->zName, zVfs, strlen(zVfs)+1);
+
+  pVfs = (sqlite3_vfs *)ckalloc(sizeof(sqlite3_vfs));
+  memcpy(pVfs, &tvfs_vfs, sizeof(sqlite3_vfs));
+  pVfs->pAppData = (void *)p;
+  pVfs->iVersion = iVersion;
+  pVfs->zName = p->zName;
+  pVfs->mxPathname = p->pParent->mxPathname;
+  if( mxPathname>=0 && mxPathname<pVfs->mxPathname ){
+    pVfs->mxPathname = mxPathname;
+  }
+  pVfs->szOsFile = szOsFile;
+  p->pVfs = pVfs;
+  p->isNoshm = isNoshm;
+  p->isFullshm = isFullshm;
+  p->mask = TESTVFS_ALL_MASK;
+
+  sqlite3_vfs_register(pVfs, isDefault);
+
+  return TCL_OK;
+
+ bad_args:
+  Tcl_WrongNumArgs(interp, 1, objv, "VFSNAME ?-noshm BOOL? ?-fullshm BOOL? ?-default BOOL? ?-mxpathname INT? ?-szosfile INT? ?-iversion INT?");
+  return TCL_ERROR;
+}
+
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+extern const char *sqlite3ErrName(int);
+
+/*
+** tclcmd: vfs_shmlock DB DBNAME (shared|exclusive) (lock|unlock) OFFSET N
+*/
+static int SQLITE_TCLAPI test_vfs_shmlock(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *azArg1[] = {"shared", "exclusive", 0};
+  const char *azArg2[] = {"lock", "unlock", 0};
+  sqlite3 *db = 0;
+  int rc = SQLITE_OK;
+  const char *zDbname = 0;
+  int iArg1 = 0;
+  int iArg2 = 0;
+  int iOffset = 0;
+  int n = 0;
+  sqlite3_file *pFd;
+
+  if( objc!=7 ){
+    Tcl_WrongNumArgs(interp, 1, objv, 
+        "DB DBNAME (shared|exclusive) (lock|unlock) OFFSET N"
+    );
+    return TCL_ERROR;
+  }
+
+  zDbname = Tcl_GetString(objv[2]);
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetIndexFromObj(interp, objv[3], azArg1, "ARG", 0, &iArg1) 
+   || Tcl_GetIndexFromObj(interp, objv[4], azArg2, "ARG", 0, &iArg2) 
+   || Tcl_GetIntFromObj(interp, objv[5], &iOffset)
+   || Tcl_GetIntFromObj(interp, objv[6], &n)
+  ){
+    return TCL_ERROR;
+  }
+
+  sqlite3_file_control(db, zDbname, SQLITE_FCNTL_FILE_POINTER, (void*)&pFd);
+  if( pFd==0 ){
+    return TCL_ERROR;
+  }
+  rc = pFd->pMethods->xShmLock(pFd, iOffset, n, 
+      (iArg1==0 ? SQLITE_SHM_SHARED : SQLITE_SHM_EXCLUSIVE)
+    | (iArg2==0 ? SQLITE_SHM_LOCK : SQLITE_SHM_UNLOCK)
+  );
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_vfs_set_readmark(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db = 0;
+  int rc = SQLITE_OK;
+  const char *zDbname = 0;
+  int iSlot = 0;
+  int iVal = -1;
+  sqlite3_file *pFd;
+  void volatile *pShm = 0;
+  u32 *aShm;
+  int iOff;
+
+  if( objc!=4 && objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SLOT ?VALUE?");
+    return TCL_ERROR;
+  }
+
+  zDbname = Tcl_GetString(objv[2]);
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetIntFromObj(interp, objv[3], &iSlot)
+   || (objc==5 && Tcl_GetIntFromObj(interp, objv[4], &iVal))
+  ){
+    return TCL_ERROR;
+  }
+
+  sqlite3_file_control(db, zDbname, SQLITE_FCNTL_FILE_POINTER, (void*)&pFd);
+  if( pFd==0 ){
+    return TCL_ERROR;
+  }
+  rc = pFd->pMethods->xShmMap(pFd, 0, 32*1024, 0, &pShm);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+  if( pShm==0 ){
+    Tcl_AppendResult(interp, "*-shm is not yet mapped", 0);
+    return TCL_ERROR;
+  }
+  aShm = (u32*)pShm;
+  iOff = 12*2+1+iSlot;
+
+  if( objc==5 ){
+    aShm[iOff] = iVal;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(aShm[iOff]));
+
+  return TCL_OK;
+}
+
+int Sqlitetestvfs_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "testvfs", testvfs_cmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "vfs_shmlock", test_vfs_shmlock, 0, 0);
+  Tcl_CreateObjCommand(interp, "vfs_set_readmark", test_vfs_set_readmark, 0, 0);
+  return TCL_OK;
+}
+
+#endif
diff --git a/src/test_vfstrace.c b/src/test_vfstrace.c
new file mode 100644
index 0000000..8b7d2fe
--- /dev/null
+++ b/src/test_vfstrace.c
@@ -0,0 +1,892 @@
+/*
+** 2011 March 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code implements a VFS shim that writes diagnostic
+** output for each VFS call, similar to "strace".
+**
+** USAGE:
+**
+** This source file exports a single symbol which is the name of a
+** function:
+**
+**   int vfstrace_register(
+**     const char *zTraceName,         // Name of the newly constructed VFS
+**     const char *zOldVfsName,        // Name of the underlying VFS
+**     int (*xOut)(const char*,void*), // Output routine.  ex: fputs
+**     void *pOutArg,                  // 2nd argument to xOut.  ex: stderr
+**     int makeDefault                 // Make the new VFS the default
+**   );
+**
+** Applications that want to trace their VFS usage must provide a callback
+** function with this prototype:
+**
+**   int traceOutput(const char *zMessage, void *pAppData);
+**
+** This function will "output" the trace messages, where "output" can
+** mean different things to different applications.  The traceOutput function
+** for the command-line shell (see shell.c) is "fputs" from the standard
+** library, which means that all trace output is written on the stream
+** specified by the second argument.  In the case of the command-line shell
+** the second argument is stderr.  Other applications might choose to output
+** trace information to a file, over a socket, or write it into a buffer.
+**
+** The vfstrace_register() function creates a new "shim" VFS named by
+** the zTraceName parameter.  A "shim" VFS is an SQLite backend that does
+** not really perform the duties of a true backend, but simply filters or
+** interprets VFS calls before passing them off to another VFS which does
+** the actual work.  In this case the other VFS - the one that does the
+** real work - is identified by the second parameter, zOldVfsName.  If
+** the 2nd parameter is NULL then the default VFS is used.  The common
+** case is for the 2nd parameter to be NULL.
+**
+** The third and fourth parameters are the pointer to the output function
+** and the second argument to the output function.  For the SQLite
+** command-line shell, when the -vfstrace option is used, these parameters
+** are fputs and stderr, respectively.
+**
+** The fifth argument is true (non-zero) to cause the newly created VFS
+** to become the default VFS.  The common case is for the fifth parameter
+** to be true.
+**
+** The call to vfstrace_register() simply creates the shim VFS that does
+** tracing.  The application must also arrange to use the new VFS for
+** all database connections that are created and for which tracing is 
+** desired.  This can be done by specifying the trace VFS using URI filename
+** notation, or by specifying the trace VFS as the 4th parameter to
+** sqlite3_open_v2() or by making the trace VFS be the default (by setting
+** the 5th parameter of vfstrace_register() to 1).
+**
+**
+** ENABLING VFSTRACE IN A COMMAND-LINE SHELL
+**
+** The SQLite command line shell implemented by the shell.c source file
+** can be used with this module.  To compile in -vfstrace support, first
+** gather this file (test_vfstrace.c), the shell source file (shell.c),
+** and the SQLite amalgamation source files (sqlite3.c, sqlite3.h) into
+** the working directory.  Then compile using a command like the following:
+**
+**    gcc -o sqlite3 -Os -I. -DSQLITE_ENABLE_VFSTRACE \
+**        -DSQLITE_THREADSAFE=0 -DSQLITE_ENABLE_FTS3 -DSQLITE_ENABLE_RTREE \
+**        -DHAVE_READLINE -DHAVE_USLEEP=1 \
+**        shell.c test_vfstrace.c sqlite3.c -ldl -lreadline -lncurses
+**
+** The gcc command above works on Linux and provides (in addition to the
+** -vfstrace option) support for FTS3 and FTS4, RTREE, and command-line
+** editing using the readline library.  The command-line shell does not
+** use threads so we added -DSQLITE_THREADSAFE=0 just to make the code
+** run a little faster.   For compiling on a Mac, you'll probably need
+** to omit the -DHAVE_READLINE, the -lreadline, and the -lncurses options.
+** The compilation could be simplified to just this:
+**
+**    gcc -DSQLITE_ENABLE_VFSTRACE \
+**         shell.c test_vfstrace.c sqlite3.c -ldl -lpthread
+**
+** In this second example, all unnecessary options have been removed
+** Note that since the code is now threadsafe, we had to add the -lpthread
+** option to pull in the pthreads library.
+**
+** To cross-compile for windows using MinGW, a command like this might
+** work:
+**
+**    /opt/mingw/bin/i386-mingw32msvc-gcc -o sqlite3.exe -Os -I \
+**         -DSQLITE_THREADSAFE=0 -DSQLITE_ENABLE_VFSTRACE \
+**         shell.c test_vfstrace.c sqlite3.c
+**
+** Similar compiler commands will work on different systems.  The key
+** invariants are (1) you must have -DSQLITE_ENABLE_VFSTRACE so that
+** the shell.c source file will know to include the -vfstrace command-line
+** option and (2) you must compile and link the three source files
+** shell,c, test_vfstrace.c, and sqlite3.c.  
+*/
+#include <stdlib.h>
+#include <string.h>
+#include "sqlite3.h"
+
+/*
+** An instance of this structure is attached to the each trace VFS to
+** provide auxiliary information.
+*/
+typedef struct vfstrace_info vfstrace_info;
+struct vfstrace_info {
+  sqlite3_vfs *pRootVfs;              /* The underlying real VFS */
+  int (*xOut)(const char*, void*);    /* Send output here */
+  void *pOutArg;                      /* First argument to xOut */
+  const char *zVfsName;               /* Name of this trace-VFS */
+  sqlite3_vfs *pTraceVfs;             /* Pointer back to the trace VFS */
+};
+
+/*
+** The sqlite3_file object for the trace VFS
+*/
+typedef struct vfstrace_file vfstrace_file;
+struct vfstrace_file {
+  sqlite3_file base;        /* Base class.  Must be first */
+  vfstrace_info *pInfo;     /* The trace-VFS to which this file belongs */
+  const char *zFName;       /* Base name of the file */
+  sqlite3_file *pReal;      /* The real underlying file */
+};
+
+/*
+** Method declarations for vfstrace_file.
+*/
+static int vfstraceClose(sqlite3_file*);
+static int vfstraceRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int vfstraceWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64);
+static int vfstraceTruncate(sqlite3_file*, sqlite3_int64 size);
+static int vfstraceSync(sqlite3_file*, int flags);
+static int vfstraceFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int vfstraceLock(sqlite3_file*, int);
+static int vfstraceUnlock(sqlite3_file*, int);
+static int vfstraceCheckReservedLock(sqlite3_file*, int *);
+static int vfstraceFileControl(sqlite3_file*, int op, void *pArg);
+static int vfstraceSectorSize(sqlite3_file*);
+static int vfstraceDeviceCharacteristics(sqlite3_file*);
+static int vfstraceShmLock(sqlite3_file*,int,int,int);
+static int vfstraceShmMap(sqlite3_file*,int,int,int, void volatile **);
+static void vfstraceShmBarrier(sqlite3_file*);
+static int vfstraceShmUnmap(sqlite3_file*,int);
+
+/*
+** Method declarations for vfstrace_vfs.
+*/
+static int vfstraceOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int vfstraceDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int vfstraceAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int vfstraceFullPathname(sqlite3_vfs*, const char *zName, int, char *);
+static void *vfstraceDlOpen(sqlite3_vfs*, const char *zFilename);
+static void vfstraceDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*vfstraceDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void vfstraceDlClose(sqlite3_vfs*, void*);
+static int vfstraceRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int vfstraceSleep(sqlite3_vfs*, int microseconds);
+static int vfstraceCurrentTime(sqlite3_vfs*, double*);
+static int vfstraceGetLastError(sqlite3_vfs*, int, char*);
+static int vfstraceCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+static int vfstraceSetSystemCall(sqlite3_vfs*,const char*, sqlite3_syscall_ptr);
+static sqlite3_syscall_ptr vfstraceGetSystemCall(sqlite3_vfs*, const char *);
+static const char *vfstraceNextSystemCall(sqlite3_vfs*, const char *zName);
+
+/*
+** Return a pointer to the tail of the pathname.  Examples:
+**
+**     /home/drh/xyzzy.txt -> xyzzy.txt
+**     xyzzy.txt           -> xyzzy.txt
+*/
+static const char *fileTail(const char *z){
+  int i;
+  if( z==0 ) return 0;
+  i = strlen(z)-1;
+  while( i>0 && z[i-1]!='/' ){ i--; }
+  return &z[i];
+}
+
+/*
+** Send trace output defined by zFormat and subsequent arguments.
+*/
+static void vfstrace_printf(
+  vfstrace_info *pInfo,
+  const char *zFormat,
+  ...
+){
+  va_list ap;
+  char *zMsg;
+  va_start(ap, zFormat);
+  zMsg = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  pInfo->xOut(zMsg, pInfo->pOutArg);
+  sqlite3_free(zMsg);
+}
+
+/*
+** Convert value rc into a string and print it using zFormat.  zFormat
+** should have exactly one %s
+*/
+static void vfstrace_print_errcode(
+  vfstrace_info *pInfo,
+  const char *zFormat,
+  int rc
+){
+  char zBuf[50];
+  char *zVal;
+  switch( rc ){
+    case SQLITE_OK:         zVal = "SQLITE_OK";          break;
+    case SQLITE_ERROR:      zVal = "SQLITE_ERROR";       break;
+    case SQLITE_PERM:       zVal = "SQLITE_PERM";        break;
+    case SQLITE_ABORT:      zVal = "SQLITE_ABORT";       break;
+    case SQLITE_BUSY:       zVal = "SQLITE_BUSY";        break;
+    case SQLITE_NOMEM:      zVal = "SQLITE_NOMEM";       break;
+    case SQLITE_READONLY:   zVal = "SQLITE_READONLY";    break;
+    case SQLITE_INTERRUPT:  zVal = "SQLITE_INTERRUPT";   break;
+    case SQLITE_IOERR:      zVal = "SQLITE_IOERR";       break;
+    case SQLITE_CORRUPT:    zVal = "SQLITE_CORRUPT";     break;
+    case SQLITE_FULL:       zVal = "SQLITE_FULL";        break;
+    case SQLITE_CANTOPEN:   zVal = "SQLITE_CANTOPEN";    break;
+    case SQLITE_PROTOCOL:   zVal = "SQLITE_PROTOCOL";    break;
+    case SQLITE_EMPTY:      zVal = "SQLITE_EMPTY";       break;
+    case SQLITE_SCHEMA:     zVal = "SQLITE_SCHEMA";      break;
+    case SQLITE_CONSTRAINT: zVal = "SQLITE_CONSTRAINT";  break;
+    case SQLITE_MISMATCH:   zVal = "SQLITE_MISMATCH";    break;
+    case SQLITE_MISUSE:     zVal = "SQLITE_MISUSE";      break;
+    case SQLITE_NOLFS:      zVal = "SQLITE_NOLFS";       break;
+    case SQLITE_IOERR_READ:         zVal = "SQLITE_IOERR_READ";         break;
+    case SQLITE_IOERR_SHORT_READ:   zVal = "SQLITE_IOERR_SHORT_READ";   break;
+    case SQLITE_IOERR_WRITE:        zVal = "SQLITE_IOERR_WRITE";        break;
+    case SQLITE_IOERR_FSYNC:        zVal = "SQLITE_IOERR_FSYNC";        break;
+    case SQLITE_IOERR_DIR_FSYNC:    zVal = "SQLITE_IOERR_DIR_FSYNC";    break;
+    case SQLITE_IOERR_TRUNCATE:     zVal = "SQLITE_IOERR_TRUNCATE";     break;
+    case SQLITE_IOERR_FSTAT:        zVal = "SQLITE_IOERR_FSTAT";        break;
+    case SQLITE_IOERR_UNLOCK:       zVal = "SQLITE_IOERR_UNLOCK";       break;
+    case SQLITE_IOERR_RDLOCK:       zVal = "SQLITE_IOERR_RDLOCK";       break;
+    case SQLITE_IOERR_DELETE:       zVal = "SQLITE_IOERR_DELETE";       break;
+    case SQLITE_IOERR_BLOCKED:      zVal = "SQLITE_IOERR_BLOCKED";      break;
+    case SQLITE_IOERR_NOMEM:        zVal = "SQLITE_IOERR_NOMEM";        break;
+    case SQLITE_IOERR_ACCESS:       zVal = "SQLITE_IOERR_ACCESS";       break;
+    case SQLITE_IOERR_CHECKRESERVEDLOCK:
+                               zVal = "SQLITE_IOERR_CHECKRESERVEDLOCK"; break;
+    case SQLITE_IOERR_LOCK:         zVal = "SQLITE_IOERR_LOCK";         break;
+    case SQLITE_IOERR_CLOSE:        zVal = "SQLITE_IOERR_CLOSE";        break;
+    case SQLITE_IOERR_DIR_CLOSE:    zVal = "SQLITE_IOERR_DIR_CLOSE";    break;
+    case SQLITE_IOERR_SHMOPEN:      zVal = "SQLITE_IOERR_SHMOPEN";      break;
+    case SQLITE_IOERR_SHMSIZE:      zVal = "SQLITE_IOERR_SHMSIZE";      break;
+    case SQLITE_IOERR_SHMLOCK:      zVal = "SQLITE_IOERR_SHMLOCK";      break;
+    case SQLITE_IOERR_SHMMAP:       zVal = "SQLITE_IOERR_SHMMAP";       break;
+    case SQLITE_IOERR_SEEK:         zVal = "SQLITE_IOERR_SEEK";         break;
+    case SQLITE_IOERR_GETTEMPPATH:  zVal = "SQLITE_IOERR_GETTEMPPATH";  break;
+    case SQLITE_IOERR_CONVPATH:     zVal = "SQLITE_IOERR_CONVPATH";     break;
+    case SQLITE_READONLY_DBMOVED:   zVal = "SQLITE_READONLY_DBMOVED";   break;
+    case SQLITE_LOCKED_SHAREDCACHE: zVal = "SQLITE_LOCKED_SHAREDCACHE"; break;
+    case SQLITE_BUSY_RECOVERY:      zVal = "SQLITE_BUSY_RECOVERY";      break;
+    case SQLITE_CANTOPEN_NOTEMPDIR: zVal = "SQLITE_CANTOPEN_NOTEMPDIR"; break;
+    default: {
+       sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
+       zVal = zBuf;
+       break;
+    }
+  }
+  vfstrace_printf(pInfo, zFormat, zVal);
+}
+
+/*
+** Append to a buffer.
+*/
+static void strappend(char *z, int *pI, const char *zAppend){
+  int i = *pI;
+  while( zAppend[0] ){ z[i++] = *(zAppend++); }
+  z[i] = 0;
+  *pI = i;
+}
+
+/*
+** Close an vfstrace-file.
+*/
+static int vfstraceClose(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xClose(%s)", pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xClose(p->pReal);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  if( rc==SQLITE_OK ){
+    sqlite3_free((void*)p->base.pMethods);
+    p->base.pMethods = 0;
+  }
+  return rc;
+}
+
+/*
+** Read data from an vfstrace-file.
+*/
+static int vfstraceRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xRead(%s,n=%d,ofst=%lld)",
+                  pInfo->zVfsName, p->zFName, iAmt, iOfst);
+  rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Write data to an vfstrace-file.
+*/
+static int vfstraceWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xWrite(%s,n=%d,ofst=%lld)",
+                  pInfo->zVfsName, p->zFName, iAmt, iOfst);
+  rc = p->pReal->pMethods->xWrite(p->pReal, zBuf, iAmt, iOfst);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Truncate an vfstrace-file.
+*/
+static int vfstraceTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xTruncate(%s,%lld)", pInfo->zVfsName, p->zFName,
+                  size);
+  rc = p->pReal->pMethods->xTruncate(p->pReal, size);
+  vfstrace_printf(pInfo, " -> %d\n", rc);
+  return rc;
+}
+
+/*
+** Sync an vfstrace-file.
+*/
+static int vfstraceSync(sqlite3_file *pFile, int flags){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  int i;
+  char zBuf[100];
+  memcpy(zBuf, "|0", 3);
+  i = 0;
+  if( flags & SQLITE_SYNC_FULL )        strappend(zBuf, &i, "|FULL");
+  else if( flags & SQLITE_SYNC_NORMAL ) strappend(zBuf, &i, "|NORMAL");
+  if( flags & SQLITE_SYNC_DATAONLY )    strappend(zBuf, &i, "|DATAONLY");
+  if( flags & ~(SQLITE_SYNC_FULL|SQLITE_SYNC_DATAONLY) ){
+    sqlite3_snprintf(sizeof(zBuf)-i, &zBuf[i], "|0x%x", flags);
+  }
+  vfstrace_printf(pInfo, "%s.xSync(%s,%s)", pInfo->zVfsName, p->zFName,
+                  &zBuf[1]);
+  rc = p->pReal->pMethods->xSync(p->pReal, flags);
+  vfstrace_printf(pInfo, " -> %d\n", rc);
+  return rc;
+}
+
+/*
+** Return the current file-size of an vfstrace-file.
+*/
+static int vfstraceFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xFileSize(%s)", pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xFileSize(p->pReal, pSize);
+  vfstrace_print_errcode(pInfo, " -> %s,", rc);
+  vfstrace_printf(pInfo, " size=%lld\n", *pSize);
+  return rc;
+}
+
+/*
+** Return the name of a lock.
+*/
+static const char *lockName(int eLock){
+  const char *azLockNames[] = {
+     "NONE", "SHARED", "RESERVED", "PENDING", "EXCLUSIVE"
+  };
+  if( eLock<0 || eLock>=sizeof(azLockNames)/sizeof(azLockNames[0]) ){
+    return "???";
+  }else{
+    return azLockNames[eLock];
+  }
+}
+
+/*
+** Lock an vfstrace-file.
+*/
+static int vfstraceLock(sqlite3_file *pFile, int eLock){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xLock(%s,%s)", pInfo->zVfsName, p->zFName,
+                  lockName(eLock));
+  rc = p->pReal->pMethods->xLock(p->pReal, eLock);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Unlock an vfstrace-file.
+*/
+static int vfstraceUnlock(sqlite3_file *pFile, int eLock){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xUnlock(%s,%s)", pInfo->zVfsName, p->zFName,
+                  lockName(eLock));
+  rc = p->pReal->pMethods->xUnlock(p->pReal, eLock);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an vfstrace-file.
+*/
+static int vfstraceCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xCheckReservedLock(%s,%d)", 
+                  pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  vfstrace_printf(pInfo, ", out=%d\n", *pResOut);
+  return rc;
+}
+
+/*
+** File control method. For custom operations on an vfstrace-file.
+*/
+static int vfstraceFileControl(sqlite3_file *pFile, int op, void *pArg){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  char zBuf[100];
+  char *zOp;
+  switch( op ){
+    case SQLITE_FCNTL_LOCKSTATE:    zOp = "LOCKSTATE";          break;
+    case SQLITE_GET_LOCKPROXYFILE:  zOp = "GET_LOCKPROXYFILE";  break;
+    case SQLITE_SET_LOCKPROXYFILE:  zOp = "SET_LOCKPROXYFILE";  break;
+    case SQLITE_LAST_ERRNO:         zOp = "LAST_ERRNO";         break;
+    case SQLITE_FCNTL_SIZE_HINT: {
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "SIZE_HINT,%lld",
+                       *(sqlite3_int64*)pArg);
+      zOp = zBuf;
+      break;
+    }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "CHUNK_SIZE,%d", *(int*)pArg);
+      zOp = zBuf;
+      break;
+    }
+    case SQLITE_FCNTL_FILE_POINTER: zOp = "FILE_POINTER";       break;
+    case SQLITE_FCNTL_SYNC_OMITTED: zOp = "SYNC_OMITTED";       break;
+    case SQLITE_FCNTL_WIN32_AV_RETRY: zOp = "WIN32_AV_RETRY";   break;
+    case SQLITE_FCNTL_PERSIST_WAL:  zOp = "PERSIST_WAL";        break;
+    case SQLITE_FCNTL_OVERWRITE:    zOp = "OVERWRITE";          break;
+    case SQLITE_FCNTL_VFSNAME:      zOp = "VFSNAME";            break;
+    case SQLITE_FCNTL_TEMPFILENAME: zOp = "TEMPFILENAME";       break;
+    case 0xca093fa0:                zOp = "DB_UNCHANGED";       break;
+    case SQLITE_FCNTL_PRAGMA: {
+      const char *const* a = (const char*const*)pArg;
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "PRAGMA,[%s,%s]",a[1],a[2]);
+      zOp = zBuf;
+      break;
+    }
+    default: {
+      sqlite3_snprintf(sizeof zBuf, zBuf, "%d", op);
+      zOp = zBuf;
+      break;
+    }
+  }
+  vfstrace_printf(pInfo, "%s.xFileControl(%s,%s)",
+                  pInfo->zVfsName, p->zFName, zOp);
+  rc = p->pReal->pMethods->xFileControl(p->pReal, op, pArg);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  if( op==SQLITE_FCNTL_VFSNAME && rc==SQLITE_OK ){
+    *(char**)pArg = sqlite3_mprintf("vfstrace.%s/%z",
+                                    pInfo->zVfsName, *(char**)pArg);
+  }
+  if( (op==SQLITE_FCNTL_PRAGMA || op==SQLITE_FCNTL_TEMPFILENAME)
+   && rc==SQLITE_OK && *(char**)pArg ){
+    vfstrace_printf(pInfo, "%s.xFileControl(%s,%s) returns %s",
+                    pInfo->zVfsName, p->zFName, zOp, *(char**)pArg);
+  }
+  return rc;
+}
+
+/*
+** Return the sector-size in bytes for an vfstrace-file.
+*/
+static int vfstraceSectorSize(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xSectorSize(%s)", pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xSectorSize(p->pReal);
+  vfstrace_printf(pInfo, " -> %d\n", rc);
+  return rc;
+}
+
+/*
+** Return the device characteristic flags supported by an vfstrace-file.
+*/
+static int vfstraceDeviceCharacteristics(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xDeviceCharacteristics(%s)",
+                  pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
+  vfstrace_printf(pInfo, " -> 0x%08x\n", rc);
+  return rc;
+}
+
+/*
+** Shared-memory operations.
+*/
+static int vfstraceShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  char zLck[100];
+  int i = 0;
+  memcpy(zLck, "|0", 3);
+  if( flags & SQLITE_SHM_UNLOCK )    strappend(zLck, &i, "|UNLOCK");
+  if( flags & SQLITE_SHM_LOCK )      strappend(zLck, &i, "|LOCK");
+  if( flags & SQLITE_SHM_SHARED )    strappend(zLck, &i, "|SHARED");
+  if( flags & SQLITE_SHM_EXCLUSIVE ) strappend(zLck, &i, "|EXCLUSIVE");
+  if( flags & ~(0xf) ){
+     sqlite3_snprintf(sizeof(zLck)-i, &zLck[i], "|0x%x", flags);
+  }
+  vfstrace_printf(pInfo, "%s.xShmLock(%s,ofst=%d,n=%d,%s)",
+                  pInfo->zVfsName, p->zFName, ofst, n, &zLck[1]);
+  rc = p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+static int vfstraceShmMap(
+  sqlite3_file *pFile, 
+  int iRegion, 
+  int szRegion, 
+  int isWrite, 
+  void volatile **pp
+){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xShmMap(%s,iRegion=%d,szRegion=%d,isWrite=%d,*)",
+                  pInfo->zVfsName, p->zFName, iRegion, szRegion, isWrite);
+  rc = p->pReal->pMethods->xShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+static void vfstraceShmBarrier(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  vfstrace_printf(pInfo, "%s.xShmBarrier(%s)\n", pInfo->zVfsName, p->zFName);
+  p->pReal->pMethods->xShmBarrier(p->pReal);
+}
+static int vfstraceShmUnmap(sqlite3_file *pFile, int delFlag){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xShmUnmap(%s,delFlag=%d)",
+                  pInfo->zVfsName, p->zFName, delFlag);
+  rc = p->pReal->pMethods->xShmUnmap(p->pReal, delFlag);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+
+
+/*
+** Open an vfstrace file handle.
+*/
+static int vfstraceOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  p->pInfo = pInfo;
+  p->zFName = zName ? fileTail(zName) : "<temp>";
+  p->pReal = (sqlite3_file *)&p[1];
+  rc = pRoot->xOpen(pRoot, zName, p->pReal, flags, pOutFlags);
+  vfstrace_printf(pInfo, "%s.xOpen(%s,flags=0x%x)",
+                  pInfo->zVfsName, p->zFName, flags);
+  if( p->pReal->pMethods ){
+    sqlite3_io_methods *pNew = sqlite3_malloc( sizeof(*pNew) );
+    const sqlite3_io_methods *pSub = p->pReal->pMethods;
+    memset(pNew, 0, sizeof(*pNew));
+    pNew->iVersion = pSub->iVersion;
+    pNew->xClose = vfstraceClose;
+    pNew->xRead = vfstraceRead;
+    pNew->xWrite = vfstraceWrite;
+    pNew->xTruncate = vfstraceTruncate;
+    pNew->xSync = vfstraceSync;
+    pNew->xFileSize = vfstraceFileSize;
+    pNew->xLock = vfstraceLock;
+    pNew->xUnlock = vfstraceUnlock;
+    pNew->xCheckReservedLock = vfstraceCheckReservedLock;
+    pNew->xFileControl = vfstraceFileControl;
+    pNew->xSectorSize = vfstraceSectorSize;
+    pNew->xDeviceCharacteristics = vfstraceDeviceCharacteristics;
+    if( pNew->iVersion>=2 ){
+      pNew->xShmMap = pSub->xShmMap ? vfstraceShmMap : 0;
+      pNew->xShmLock = pSub->xShmLock ? vfstraceShmLock : 0;
+      pNew->xShmBarrier = pSub->xShmBarrier ? vfstraceShmBarrier : 0;
+      pNew->xShmUnmap = pSub->xShmUnmap ? vfstraceShmUnmap : 0;
+    }
+    pFile->pMethods = pNew;
+  }
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  if( pOutFlags ){
+    vfstrace_printf(pInfo, ", outFlags=0x%x\n", *pOutFlags);
+  }else{
+    vfstrace_printf(pInfo, "\n");
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int vfstraceDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xDelete(\"%s\",%d)",
+                  pInfo->zVfsName, zPath, dirSync);
+  rc = pRoot->xDelete(pRoot, zPath, dirSync);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int vfstraceAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xAccess(\"%s\",%d)",
+                  pInfo->zVfsName, zPath, flags);
+  rc = pRoot->xAccess(pRoot, zPath, flags, pResOut);
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  vfstrace_printf(pInfo, ", out=%d\n", *pResOut);
+  return rc;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
+*/
+static int vfstraceFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xFullPathname(\"%s\")",
+                  pInfo->zVfsName, zPath);
+  rc = pRoot->xFullPathname(pRoot, zPath, nOut, zOut);
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  vfstrace_printf(pInfo, ", out=\"%.*s\"\n", nOut, zOut);
+  return rc;
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *vfstraceDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlOpen(\"%s\")\n", pInfo->zVfsName, zPath);
+  return pRoot->xDlOpen(pRoot, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void vfstraceDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlError(%d)", pInfo->zVfsName, nByte);
+  pRoot->xDlError(pRoot, nByte, zErrMsg);
+  vfstrace_printf(pInfo, " -> \"%s\"", zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*vfstraceDlSym(sqlite3_vfs *pVfs,void *p,const char *zSym))(void){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlSym(\"%s\")\n", pInfo->zVfsName, zSym);
+  return pRoot->xDlSym(pRoot, p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void vfstraceDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlOpen()\n", pInfo->zVfsName);
+  pRoot->xDlClose(pRoot, pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int vfstraceRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xRandomness(%d)\n", pInfo->zVfsName, nByte);
+  return pRoot->xRandomness(pRoot, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int vfstraceSleep(sqlite3_vfs *pVfs, int nMicro){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xSleep(pRoot, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int vfstraceCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xCurrentTime(pRoot, pTimeOut);
+}
+static int vfstraceCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xCurrentTimeInt64(pRoot, pTimeOut);
+}
+
+/*
+** Return th3 most recent error code and message
+*/
+static int vfstraceGetLastError(sqlite3_vfs *pVfs, int iErr, char *zErr){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xGetLastError(pRoot, iErr, zErr);
+}
+
+/*
+** Override system calls.
+*/
+static int vfstraceSetSystemCall(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_syscall_ptr pFunc
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xSetSystemCall(pRoot, zName, pFunc);
+}
+static sqlite3_syscall_ptr vfstraceGetSystemCall(
+  sqlite3_vfs *pVfs,
+  const char *zName
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xGetSystemCall(pRoot, zName);
+}
+static const char *vfstraceNextSystemCall(sqlite3_vfs *pVfs, const char *zName){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xNextSystemCall(pRoot, zName);
+}
+
+
+/*
+** Clients invoke this routine to construct a new trace-vfs shim.
+**
+** Return SQLITE_OK on success.  
+**
+** SQLITE_NOMEM is returned in the case of a memory allocation error.
+** SQLITE_NOTFOUND is returned if zOldVfsName does not exist.
+*/
+int vfstrace_register(
+   const char *zTraceName,           /* Name of the newly constructed VFS */
+   const char *zOldVfsName,          /* Name of the underlying VFS */
+   int (*xOut)(const char*,void*),   /* Output routine.  ex: fputs */
+   void *pOutArg,                    /* 2nd argument to xOut.  ex: stderr */
+   int makeDefault                   /* True to make the new VFS the default */
+){
+  sqlite3_vfs *pNew;
+  sqlite3_vfs *pRoot;
+  vfstrace_info *pInfo;
+  int nName;
+  int nByte;
+
+  pRoot = sqlite3_vfs_find(zOldVfsName);
+  if( pRoot==0 ) return SQLITE_NOTFOUND;
+  nName = strlen(zTraceName);
+  nByte = sizeof(*pNew) + sizeof(*pInfo) + nName + 1;
+  pNew = sqlite3_malloc( nByte );
+  if( pNew==0 ) return SQLITE_NOMEM;
+  memset(pNew, 0, nByte);
+  pInfo = (vfstrace_info*)&pNew[1];
+  pNew->iVersion = pRoot->iVersion;
+  pNew->szOsFile = pRoot->szOsFile + sizeof(vfstrace_file);
+  pNew->mxPathname = pRoot->mxPathname;
+  pNew->zName = (char*)&pInfo[1];
+  memcpy((char*)&pInfo[1], zTraceName, nName+1);
+  pNew->pAppData = pInfo;
+  pNew->xOpen = vfstraceOpen;
+  pNew->xDelete = vfstraceDelete;
+  pNew->xAccess = vfstraceAccess;
+  pNew->xFullPathname = vfstraceFullPathname;
+  pNew->xDlOpen = pRoot->xDlOpen==0 ? 0 : vfstraceDlOpen;
+  pNew->xDlError = pRoot->xDlError==0 ? 0 : vfstraceDlError;
+  pNew->xDlSym = pRoot->xDlSym==0 ? 0 : vfstraceDlSym;
+  pNew->xDlClose = pRoot->xDlClose==0 ? 0 : vfstraceDlClose;
+  pNew->xRandomness = vfstraceRandomness;
+  pNew->xSleep = vfstraceSleep;
+  pNew->xCurrentTime = vfstraceCurrentTime;
+  pNew->xGetLastError = pRoot->xGetLastError==0 ? 0 : vfstraceGetLastError;
+  if( pNew->iVersion>=2 ){
+    pNew->xCurrentTimeInt64 = pRoot->xCurrentTimeInt64==0 ? 0 :
+                                   vfstraceCurrentTimeInt64;
+    if( pNew->iVersion>=3 ){
+      pNew->xSetSystemCall = pRoot->xSetSystemCall==0 ? 0 : 
+                                   vfstraceSetSystemCall;
+      pNew->xGetSystemCall = pRoot->xGetSystemCall==0 ? 0 : 
+                                   vfstraceGetSystemCall;
+      pNew->xNextSystemCall = pRoot->xNextSystemCall==0 ? 0 : 
+                                   vfstraceNextSystemCall;
+    }
+  }
+  pInfo->pRootVfs = pRoot;
+  pInfo->xOut = xOut;
+  pInfo->pOutArg = pOutArg;
+  pInfo->zVfsName = pNew->zName;
+  pInfo->pTraceVfs = pNew;
+  vfstrace_printf(pInfo, "%s.enabled_for(\"%s\")\n",
+       pInfo->zVfsName, pRoot->zName);
+  return sqlite3_vfs_register(pNew, makeDefault);
+}
diff --git a/src/test_windirent.c b/src/test_windirent.c
new file mode 100644
index 0000000..62165c4
--- /dev/null
+++ b/src/test_windirent.c
@@ -0,0 +1,191 @@
+/*
+** 2015 November 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code to implement most of the opendir() family of
+** POSIX functions on Win32 using the MSVCRT.
+*/
+
+#if defined(_WIN32) && defined(_MSC_VER)
+#include "test_windirent.h"
+
+/*
+** Implementation of the POSIX getenv() function using the Win32 API.
+** This function is not thread-safe.
+*/
+const char *windirent_getenv(
+  const char *name
+){
+  static char value[32768]; /* Maximum length, per MSDN */
+  DWORD dwSize = sizeof(value) / sizeof(char); /* Size in chars */
+  DWORD dwRet; /* Value returned by GetEnvironmentVariableA() */
+
+  memset(value, 0, sizeof(value));
+  dwRet = GetEnvironmentVariableA(name, value, dwSize);
+  if( dwRet==0 || dwRet>dwSize ){
+    /*
+    ** The function call to GetEnvironmentVariableA() failed -OR-
+    ** the buffer is not large enough.  Either way, return NULL.
+    */
+    return 0;
+  }else{
+    /*
+    ** The function call to GetEnvironmentVariableA() succeeded
+    ** -AND- the buffer contains the entire value.
+    */
+    return value;
+  }
+}
+
+/*
+** Implementation of the POSIX opendir() function using the MSVCRT.
+*/
+LPDIR opendir(
+  const char *dirname
+){
+  struct _finddata_t data;
+  LPDIR dirp = (LPDIR)sqlite3_malloc(sizeof(DIR));
+  SIZE_T namesize = sizeof(data.name) / sizeof(data.name[0]);
+
+  if( dirp==NULL ) return NULL;
+  memset(dirp, 0, sizeof(DIR));
+
+  /* TODO: Remove this if Unix-style root paths are not used. */
+  if( sqlite3_stricmp(dirname, "/")==0 ){
+    dirname = windirent_getenv("SystemDrive");
+  }
+
+  memset(&data, 0, sizeof(struct _finddata_t));
+  _snprintf(data.name, namesize, "%s\\*", dirname);
+  dirp->d_handle = _findfirst(data.name, &data);
+
+  if( dirp->d_handle==BAD_INTPTR_T ){
+    closedir(dirp);
+    return NULL;
+  }
+
+  /* TODO: Remove this block to allow hidden and/or system files. */
+  if( is_filtered(data) ){
+next:
+
+    memset(&data, 0, sizeof(struct _finddata_t));
+    if( _findnext(dirp->d_handle, &data)==-1 ){
+      closedir(dirp);
+      return NULL;
+    }
+
+    /* TODO: Remove this block to allow hidden and/or system files. */
+    if( is_filtered(data) ) goto next;
+  }
+
+  dirp->d_first.d_attributes = data.attrib;
+  strncpy(dirp->d_first.d_name, data.name, NAME_MAX);
+  dirp->d_first.d_name[NAME_MAX] = '\0';
+
+  return dirp;
+}
+
+/*
+** Implementation of the POSIX readdir() function using the MSVCRT.
+*/
+LPDIRENT readdir(
+  LPDIR dirp
+){
+  struct _finddata_t data;
+
+  if( dirp==NULL ) return NULL;
+
+  if( dirp->d_first.d_ino==0 ){
+    dirp->d_first.d_ino++;
+    dirp->d_next.d_ino++;
+
+    return &dirp->d_first;
+  }
+
+next:
+
+  memset(&data, 0, sizeof(struct _finddata_t));
+  if( _findnext(dirp->d_handle, &data)==-1 ) return NULL;
+
+  /* TODO: Remove this block to allow hidden and/or system files. */
+  if( is_filtered(data) ) goto next;
+
+  dirp->d_next.d_ino++;
+  dirp->d_next.d_attributes = data.attrib;
+  strncpy(dirp->d_next.d_name, data.name, NAME_MAX);
+  dirp->d_next.d_name[NAME_MAX] = '\0';
+
+  return &dirp->d_next;
+}
+
+/*
+** Implementation of the POSIX readdir_r() function using the MSVCRT.
+*/
+INT readdir_r(
+  LPDIR dirp,
+  LPDIRENT entry,
+  LPDIRENT *result
+){
+  struct _finddata_t data;
+
+  if( dirp==NULL ) return EBADF;
+
+  if( dirp->d_first.d_ino==0 ){
+    dirp->d_first.d_ino++;
+    dirp->d_next.d_ino++;
+
+    entry->d_ino = dirp->d_first.d_ino;
+    entry->d_attributes = dirp->d_first.d_attributes;
+    strncpy(entry->d_name, dirp->d_first.d_name, NAME_MAX);
+    entry->d_name[NAME_MAX] = '\0';
+
+    *result = entry;
+    return 0;
+  }
+
+next:
+
+  memset(&data, 0, sizeof(struct _finddata_t));
+  if( _findnext(dirp->d_handle, &data)==-1 ){
+    *result = NULL;
+    return ENOENT;
+  }
+
+  /* TODO: Remove this block to allow hidden and/or system files. */
+  if( is_filtered(data) ) goto next;
+
+  entry->d_ino = (ino_t)-1; /* not available */
+  entry->d_attributes = data.attrib;
+  strncpy(entry->d_name, data.name, NAME_MAX);
+  entry->d_name[NAME_MAX] = '\0';
+
+  *result = entry;
+  return 0;
+}
+
+/*
+** Implementation of the POSIX closedir() function using the MSVCRT.
+*/
+INT closedir(
+  LPDIR dirp
+){
+  INT result = 0;
+
+  if( dirp==NULL ) return EINVAL;
+
+  if( dirp->d_handle!=NULL_INTPTR_T && dirp->d_handle!=BAD_INTPTR_T ){
+    result = _findclose(dirp->d_handle);
+  }
+
+  sqlite3_free(dirp);
+  return result;
+}
+
+#endif /* defined(WIN32) && defined(_MSC_VER) */
diff --git a/src/test_windirent.h b/src/test_windirent.h
new file mode 100644
index 0000000..28ce667
--- /dev/null
+++ b/src/test_windirent.h
@@ -0,0 +1,159 @@
+/*
+** 2015 November 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains declarations for most of the opendir() family of
+** POSIX functions on Win32 using the MSVCRT.
+*/
+
+#if defined(_WIN32) && defined(_MSC_VER) && !defined(SQLITE_WINDIRENT_H)
+#define SQLITE_WINDIRENT_H
+
+/*
+** We need several data types from the Windows SDK header.
+*/
+
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+
+#include "windows.h"
+
+/*
+** We need several support functions from the SQLite core.
+*/
+
+#include "sqlite3.h"
+
+/*
+** We need several things from the ANSI and MSVCRT headers.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <io.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+/*
+** We may need several defines that should have been in "sys/stat.h".
+*/
+
+#ifndef S_ISREG
+#define S_ISREG(mode) (((mode) & S_IFMT) == S_IFREG)
+#endif
+
+#ifndef S_ISDIR
+#define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
+#endif
+
+#ifndef S_ISLNK
+#define S_ISLNK(mode) (0)
+#endif
+
+/*
+** We may need to provide the "mode_t" type.
+*/
+
+#ifndef MODE_T_DEFINED
+  #define MODE_T_DEFINED
+  typedef unsigned short mode_t;
+#endif
+
+/*
+** We may need to provide the "ino_t" type.
+*/
+
+#ifndef INO_T_DEFINED
+  #define INO_T_DEFINED
+  typedef unsigned short ino_t;
+#endif
+
+/*
+** We need to define "NAME_MAX" if it was not present in "limits.h".
+*/
+
+#ifndef NAME_MAX
+#  ifdef FILENAME_MAX
+#    define NAME_MAX (FILENAME_MAX)
+#  else
+#    define NAME_MAX (260)
+#  endif
+#endif
+
+/*
+** We need to define "NULL_INTPTR_T" and "BAD_INTPTR_T".
+*/
+
+#ifndef NULL_INTPTR_T
+#  define NULL_INTPTR_T ((intptr_t)(0))
+#endif
+
+#ifndef BAD_INTPTR_T
+#  define BAD_INTPTR_T ((intptr_t)(-1))
+#endif
+
+/*
+** We need to provide the necessary structures and related types.
+*/
+
+#ifndef DIRENT_DEFINED
+#define DIRENT_DEFINED
+typedef struct DIRENT DIRENT;
+typedef DIRENT *LPDIRENT;
+struct DIRENT {
+  ino_t d_ino;               /* Sequence number, do not use. */
+  unsigned d_attributes;     /* Win32 file attributes. */
+  char d_name[NAME_MAX + 1]; /* Name within the directory. */
+};
+#endif
+
+#ifndef DIR_DEFINED
+#define DIR_DEFINED
+typedef struct DIR DIR;
+typedef DIR *LPDIR;
+struct DIR {
+  intptr_t d_handle; /* Value returned by "_findfirst". */
+  DIRENT d_first;    /* DIRENT constructed based on "_findfirst". */
+  DIRENT d_next;     /* DIRENT constructed based on "_findnext". */
+};
+#endif
+
+/*
+** Provide a macro, for use by the implementation, to determine if a
+** particular directory entry should be skipped over when searching for
+** the next directory entry that should be returned by the readdir() or
+** readdir_r() functions.
+*/
+
+#ifndef is_filtered
+#  define is_filtered(a) ((((a).attrib)&_A_HIDDEN) || (((a).attrib)&_A_SYSTEM))
+#endif
+
+/*
+** Provide the function prototype for the POSIX compatible getenv()
+** function.  This function is not thread-safe.
+*/
+
+extern const char *windirent_getenv(const char *name);
+
+/*
+** Finally, we can provide the function prototypes for the opendir(),
+** readdir(), readdir_r(), and closedir() POSIX functions.
+*/
+
+extern LPDIR opendir(const char *dirname);
+extern LPDIRENT readdir(LPDIR dirp);
+extern INT readdir_r(LPDIR dirp, LPDIRENT entry, LPDIRENT *result);
+extern INT closedir(LPDIR dirp);
+
+#endif /* defined(WIN32) && defined(_MSC_VER) */
diff --git a/src/test_window.c b/src/test_window.c
new file mode 100644
index 0000000..48ab022
--- /dev/null
+++ b/src/test_window.c
@@ -0,0 +1,349 @@
+/*
+** 2018 June 17
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+*/
+
+#include "sqlite3.h"
+
+#ifdef SQLITE_TEST
+
+#include "sqliteInt.h"
+#include <tcl.h>
+
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+extern const char *sqlite3ErrName(int);
+
+typedef struct TestWindow TestWindow;
+struct TestWindow {
+  Tcl_Obj *xStep;
+  Tcl_Obj *xFinal;
+  Tcl_Obj *xValue;
+  Tcl_Obj *xInverse;
+  Tcl_Interp *interp;
+};
+
+typedef struct TestWindowCtx TestWindowCtx;
+struct TestWindowCtx {
+  Tcl_Obj *pVal;
+};
+
+static void doTestWindowStep(
+  int bInverse,
+  sqlite3_context *ctx, 
+  int nArg, 
+  sqlite3_value **apArg
+){
+  int i;
+  TestWindow *p = (TestWindow*)sqlite3_user_data(ctx);
+  Tcl_Obj *pEval = Tcl_DuplicateObj(bInverse ? p->xInverse : p->xStep);
+  TestWindowCtx *pCtx = sqlite3_aggregate_context(ctx, sizeof(TestWindowCtx));
+
+  Tcl_IncrRefCount(pEval);
+  if( pCtx ){
+    const char *zResult;
+    int rc;
+    if( pCtx->pVal ){
+      Tcl_ListObjAppendElement(p->interp, pEval, Tcl_DuplicateObj(pCtx->pVal));
+    }else{
+      Tcl_ListObjAppendElement(p->interp, pEval, Tcl_NewStringObj("", -1));
+    }
+    for(i=0; i<nArg; i++){
+      Tcl_Obj *pArg;
+      pArg = Tcl_NewStringObj((const char*)sqlite3_value_text(apArg[i]), -1);
+      Tcl_ListObjAppendElement(p->interp, pEval, pArg);
+    }
+    rc = Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+    if( rc!=TCL_OK ){
+      zResult = Tcl_GetStringResult(p->interp);
+      sqlite3_result_error(ctx, zResult, -1);
+    }else{
+      if( pCtx->pVal ) Tcl_DecrRefCount(pCtx->pVal);
+      pCtx->pVal = Tcl_DuplicateObj(Tcl_GetObjResult(p->interp));
+      Tcl_IncrRefCount(pCtx->pVal);
+    }
+  }
+  Tcl_DecrRefCount(pEval);
+}
+
+static void doTestWindowFinalize(int bValue, sqlite3_context *ctx){
+  TestWindow *p = (TestWindow*)sqlite3_user_data(ctx);
+  Tcl_Obj *pEval = Tcl_DuplicateObj(bValue ? p->xValue : p->xFinal);
+  TestWindowCtx *pCtx = sqlite3_aggregate_context(ctx, sizeof(TestWindowCtx));
+
+  Tcl_IncrRefCount(pEval);
+  if( pCtx ){
+    const char *zResult;
+    int rc;
+    if( pCtx->pVal ){
+      Tcl_ListObjAppendElement(p->interp, pEval, Tcl_DuplicateObj(pCtx->pVal));
+    }else{
+      Tcl_ListObjAppendElement(p->interp, pEval, Tcl_NewStringObj("", -1));
+    }
+
+    rc = Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+    zResult = Tcl_GetStringResult(p->interp);
+    if( rc!=TCL_OK ){
+      sqlite3_result_error(ctx, zResult, -1);
+    }else{
+      sqlite3_result_text(ctx, zResult, -1, SQLITE_TRANSIENT);
+    }
+
+    if( bValue==0 ){
+      if( pCtx->pVal ) Tcl_DecrRefCount(pCtx->pVal);
+      pCtx->pVal = 0;
+    }
+  }
+  Tcl_DecrRefCount(pEval);
+}
+
+static void testWindowStep(
+  sqlite3_context *ctx, 
+  int nArg, 
+  sqlite3_value **apArg
+){
+  doTestWindowStep(0, ctx, nArg, apArg);
+}
+static void testWindowInverse(
+  sqlite3_context *ctx, 
+  int nArg, 
+  sqlite3_value **apArg
+){
+  doTestWindowStep(1, ctx, nArg, apArg);
+}
+
+static void testWindowFinal(sqlite3_context *ctx){
+  doTestWindowFinalize(0, ctx);
+}
+static void testWindowValue(sqlite3_context *ctx){
+  doTestWindowFinalize(1, ctx);
+}
+
+static void testWindowDestroy(void *pCtx){
+  ckfree(pCtx);
+}
+
+/*
+** Usage: sqlite3_create_window_function DB NAME XSTEP XFINAL XVALUE XINVERSE
+*/
+static int SQLITE_TCLAPI test_create_window(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  TestWindow *pNew;
+  sqlite3 *db;
+  const char *zName;
+  int rc;
+
+  if( objc!=7 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB NAME XSTEP XFINAL XVALUE XINVERSE");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+  pNew = (TestWindow*)ckalloc(sizeof(TestWindow));
+  memset(pNew, 0, sizeof(TestWindow));
+  pNew->xStep = Tcl_DuplicateObj(objv[3]);
+  pNew->xFinal = Tcl_DuplicateObj(objv[4]);
+  pNew->xValue = Tcl_DuplicateObj(objv[5]);
+  pNew->xInverse = Tcl_DuplicateObj(objv[6]);
+  pNew->interp = interp;
+
+  Tcl_IncrRefCount(pNew->xStep);
+  Tcl_IncrRefCount(pNew->xFinal);
+  Tcl_IncrRefCount(pNew->xValue);
+  Tcl_IncrRefCount(pNew->xInverse);
+
+  rc = sqlite3_create_window_function(db, zName, -1, SQLITE_UTF8, (void*)pNew,
+      testWindowStep, testWindowFinal, testWindowValue, testWindowInverse,
+      testWindowDestroy
+  );
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_create_window_misuse(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  rc = sqlite3_create_window_function(db, "fff", -1, SQLITE_UTF8, 0,
+      0, testWindowFinal, testWindowValue, testWindowInverse,
+      0
+  );
+  if( rc!=SQLITE_MISUSE ) goto error;
+  rc = sqlite3_create_window_function(db, "fff", -1, SQLITE_UTF8, 0,
+      testWindowStep, 0, testWindowValue, testWindowInverse,
+      0
+  );
+  if( rc!=SQLITE_MISUSE ) goto error;
+  rc = sqlite3_create_window_function(db, "fff", -1, SQLITE_UTF8, 0,
+      testWindowStep, testWindowFinal, 0, testWindowInverse,
+      0
+  );
+  if( rc!=SQLITE_MISUSE ) goto error;
+  rc = sqlite3_create_window_function(db, "fff", -1, SQLITE_UTF8, 0,
+      testWindowStep, testWindowFinal, testWindowValue, 0,
+      0
+  );
+  if( rc!=SQLITE_MISUSE ) goto error;
+
+  return TCL_OK;
+
+ error:
+  Tcl_SetObjResult(interp, Tcl_NewStringObj("misuse test error", -1));
+  return TCL_ERROR;
+}
+
+/*
+** xStep for sumint().
+*/
+static void sumintStep(
+  sqlite3_context *ctx, 
+  int nArg, 
+  sqlite3_value *apArg[]
+){
+  sqlite3_int64 *pInt;
+
+  assert( nArg==1 );
+  if( sqlite3_value_type(apArg[0])!=SQLITE_INTEGER ){
+    sqlite3_result_error(ctx, "invalid argument", -1);
+    return;
+  }
+  pInt = (sqlite3_int64*)sqlite3_aggregate_context(ctx, sizeof(sqlite3_int64));
+  if( pInt ){
+    *pInt += sqlite3_value_int64(apArg[0]);
+  }
+}
+
+/*
+** xInverse for sumint().
+*/
+static void sumintInverse(
+  sqlite3_context *ctx, 
+  int nArg, 
+  sqlite3_value *apArg[]
+){
+  sqlite3_int64 *pInt;
+  pInt = (sqlite3_int64*)sqlite3_aggregate_context(ctx, sizeof(sqlite3_int64));
+  *pInt -= sqlite3_value_int64(apArg[0]);
+}
+
+/*
+** xFinal for sumint().
+*/
+static void sumintFinal(sqlite3_context *ctx){
+  sqlite3_int64 res = 0;
+  sqlite3_int64 *pInt;
+  pInt = (sqlite3_int64*)sqlite3_aggregate_context(ctx, 0);
+  if( pInt ) res = *pInt;
+  sqlite3_result_int64(ctx, res);
+}
+
+/*
+** xValue for sumint().
+*/
+static void sumintValue(sqlite3_context *ctx){
+  sqlite3_int64 res = 0;
+  sqlite3_int64 *pInt;
+  pInt = (sqlite3_int64*)sqlite3_aggregate_context(ctx, 0);
+  if( pInt ) res = *pInt;
+  sqlite3_result_int64(ctx, res);
+}
+
+static int SQLITE_TCLAPI test_create_sumint(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  rc = sqlite3_create_window_function(db, "sumint", 1, SQLITE_UTF8, 0,
+      sumintStep, sumintFinal, sumintValue, sumintInverse,
+      0
+  );
+
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_override_sum(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  rc = sqlite3_create_function(db, "sum", -1, SQLITE_UTF8, 0,
+      0, sumintStep, sumintFinal
+  );
+
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+int Sqlitetest_window_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     int clientData;
+  } aObjCmd[] = {
+     { "sqlite3_create_window_function", test_create_window, 0 },
+     { "test_create_window_function_misuse", test_create_window_misuse, 0 },
+     { "test_create_sumint", test_create_sumint, 0 },
+     { "test_override_sum", test_override_sum, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    ClientData c = (ClientData)SQLITE_INT_TO_PTR(aObjCmd[i].clientData);
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, c, 0);
+  }
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_wsd.c b/src/test_wsd.c
new file mode 100644
index 0000000..99e4a05
--- /dev/null
+++ b/src/test_wsd.c
@@ -0,0 +1,84 @@
+/*
+** 2008 September 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** The code in this file contains sample implementations of the 
+** sqlite3_wsd_init() and sqlite3_wsd_find() functions required if the
+** SQLITE_OMIT_WSD symbol is defined at build time.
+*/
+
+#if defined(SQLITE_OMIT_WSD) && defined(SQLITE_TEST)
+
+#include "sqliteInt.h"
+
+#define PLS_HASHSIZE 43
+
+typedef struct ProcessLocalStorage ProcessLocalStorage;
+typedef struct ProcessLocalVar ProcessLocalVar;
+
+struct ProcessLocalStorage {
+  ProcessLocalVar *aData[PLS_HASHSIZE];
+  int nFree;
+  u8 *pFree;
+};
+
+struct ProcessLocalVar {
+  void *pKey;
+  ProcessLocalVar *pNext;
+};
+
+static ProcessLocalStorage *pGlobal = 0;
+
+int sqlite3_wsd_init(int N, int J){
+  if( !pGlobal ){
+    int nMalloc = N + sizeof(ProcessLocalStorage) + J*sizeof(ProcessLocalVar);
+    pGlobal = (ProcessLocalStorage *)malloc(nMalloc);
+    if( pGlobal ){
+      memset(pGlobal, 0, sizeof(ProcessLocalStorage));
+      pGlobal->nFree = nMalloc - sizeof(ProcessLocalStorage);
+      pGlobal->pFree = (u8 *)&pGlobal[1];
+    }
+  }
+
+  return pGlobal ? SQLITE_OK : SQLITE_NOMEM;
+}
+
+void *sqlite3_wsd_find(void *K, int L){
+  int i;
+  int iHash = 0;
+  ProcessLocalVar *pVar;
+
+  /* Calculate a hash of K */
+  for(i=0; i<sizeof(void*); i++){
+    iHash = (iHash<<3) + ((unsigned char *)&K)[i];
+  }
+  iHash = iHash%PLS_HASHSIZE;
+
+  /* Search the hash table for K. */
+  for(pVar=pGlobal->aData[iHash]; pVar && pVar->pKey!=K; pVar=pVar->pNext);
+
+  /* If no entry for K was found, create and populate a new one. */
+  if( !pVar ){
+    int nByte = ROUND8(sizeof(ProcessLocalVar) + L);
+    assert( pGlobal->nFree>=nByte );
+    pVar = (ProcessLocalVar *)pGlobal->pFree;
+    pVar->pKey = K;
+    pVar->pNext = pGlobal->aData[iHash];
+    pGlobal->aData[iHash] = pVar;
+    pGlobal->nFree -= nByte;
+    pGlobal->pFree += nByte;
+    memcpy(&pVar[1], K, L);
+  }
+
+  return (void *)&pVar[1];
+}
+
+#endif
diff --git a/src/threads.c b/src/threads.c
new file mode 100644
index 0000000..f128d69
--- /dev/null
+++ b/src/threads.c
@@ -0,0 +1,274 @@
+/*
+** 2012 July 21
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file presents a simple cross-platform threading interface for
+** use internally by SQLite.
+**
+** A "thread" can be created using sqlite3ThreadCreate().  This thread
+** runs independently of its creator until it is joined using
+** sqlite3ThreadJoin(), at which point it terminates.
+**
+** Threads do not have to be real.  It could be that the work of the
+** "thread" is done by the main thread at either the sqlite3ThreadCreate()
+** or sqlite3ThreadJoin() call.  This is, in fact, what happens in
+** single threaded systems.  Nothing in SQLite requires multiple threads.
+** This interface exists so that applications that want to take advantage
+** of multiple cores can do so, while also allowing applications to stay
+** single-threaded if desired.
+*/
+#include "sqliteInt.h"
+#if SQLITE_OS_WIN
+#  include "os_win.h"
+#endif
+
+#if SQLITE_MAX_WORKER_THREADS>0
+
+/********************************* Unix Pthreads ****************************/
+#if SQLITE_OS_UNIX && defined(SQLITE_MUTEX_PTHREADS) && SQLITE_THREADSAFE>0
+
+#define SQLITE_THREADS_IMPLEMENTED 1  /* Prevent the single-thread code below */
+#include <pthread.h>
+
+/* A running thread */
+struct SQLiteThread {
+  pthread_t tid;                 /* Thread ID */
+  int done;                      /* Set to true when thread finishes */
+  void *pOut;                    /* Result returned by the thread */
+  void *(*xTask)(void*);         /* The thread routine */
+  void *pIn;                     /* Argument to the thread */
+};
+
+/* Create a new thread */
+int sqlite3ThreadCreate(
+  SQLiteThread **ppThread,  /* OUT: Write the thread object here */
+  void *(*xTask)(void*),    /* Routine to run in a separate thread */
+  void *pIn                 /* Argument passed into xTask() */
+){
+  SQLiteThread *p;
+  int rc;
+
+  assert( ppThread!=0 );
+  assert( xTask!=0 );
+  /* This routine is never used in single-threaded mode */
+  assert( sqlite3GlobalConfig.bCoreMutex!=0 );
+
+  *ppThread = 0;
+  p = sqlite3Malloc(sizeof(*p));
+  if( p==0 ) return SQLITE_NOMEM_BKPT;
+  memset(p, 0, sizeof(*p));
+  p->xTask = xTask;
+  p->pIn = pIn;
+  /* If the SQLITE_TESTCTRL_FAULT_INSTALL callback is registered to a 
+  ** function that returns SQLITE_ERROR when passed the argument 200, that
+  ** forces worker threads to run sequentially and deterministically 
+  ** for testing purposes. */
+  if( sqlite3FaultSim(200) ){
+    rc = 1;
+  }else{    
+    rc = pthread_create(&p->tid, 0, xTask, pIn);
+  }
+  if( rc ){
+    p->done = 1;
+    p->pOut = xTask(pIn);
+  }
+  *ppThread = p;
+  return SQLITE_OK;
+}
+
+/* Get the results of the thread */
+int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){
+  int rc;
+
+  assert( ppOut!=0 );
+  if( NEVER(p==0) ) return SQLITE_NOMEM_BKPT;
+  if( p->done ){
+    *ppOut = p->pOut;
+    rc = SQLITE_OK;
+  }else{
+    rc = pthread_join(p->tid, ppOut) ? SQLITE_ERROR : SQLITE_OK;
+  }
+  sqlite3_free(p);
+  return rc;
+}
+
+#endif /* SQLITE_OS_UNIX && defined(SQLITE_MUTEX_PTHREADS) */
+/******************************** End Unix Pthreads *************************/
+
+
+/********************************* Win32 Threads ****************************/
+#if SQLITE_OS_WIN_THREADS
+
+#define SQLITE_THREADS_IMPLEMENTED 1  /* Prevent the single-thread code below */
+#include <process.h>
+
+/* A running thread */
+struct SQLiteThread {
+  void *tid;               /* The thread handle */
+  unsigned id;             /* The thread identifier */
+  void *(*xTask)(void*);   /* The routine to run as a thread */
+  void *pIn;               /* Argument to xTask */
+  void *pResult;           /* Result of xTask */
+};
+
+/* Thread procedure Win32 compatibility shim */
+static unsigned __stdcall sqlite3ThreadProc(
+  void *pArg  /* IN: Pointer to the SQLiteThread structure */
+){
+  SQLiteThread *p = (SQLiteThread *)pArg;
+
+  assert( p!=0 );
+#if 0
+  /*
+  ** This assert appears to trigger spuriously on certain
+  ** versions of Windows, possibly due to _beginthreadex()
+  ** and/or CreateThread() not fully setting their thread
+  ** ID parameter before starting the thread.
+  */
+  assert( p->id==GetCurrentThreadId() );
+#endif
+  assert( p->xTask!=0 );
+  p->pResult = p->xTask(p->pIn);
+
+  _endthreadex(0);
+  return 0; /* NOT REACHED */
+}
+
+/* Create a new thread */
+int sqlite3ThreadCreate(
+  SQLiteThread **ppThread,  /* OUT: Write the thread object here */
+  void *(*xTask)(void*),    /* Routine to run in a separate thread */
+  void *pIn                 /* Argument passed into xTask() */
+){
+  SQLiteThread *p;
+
+  assert( ppThread!=0 );
+  assert( xTask!=0 );
+  *ppThread = 0;
+  p = sqlite3Malloc(sizeof(*p));
+  if( p==0 ) return SQLITE_NOMEM_BKPT;
+  /* If the SQLITE_TESTCTRL_FAULT_INSTALL callback is registered to a 
+  ** function that returns SQLITE_ERROR when passed the argument 200, that
+  ** forces worker threads to run sequentially and deterministically 
+  ** (via the sqlite3FaultSim() term of the conditional) for testing
+  ** purposes. */
+  if( sqlite3GlobalConfig.bCoreMutex==0 || sqlite3FaultSim(200) ){
+    memset(p, 0, sizeof(*p));
+  }else{
+    p->xTask = xTask;
+    p->pIn = pIn;
+    p->tid = (void*)_beginthreadex(0, 0, sqlite3ThreadProc, p, 0, &p->id);
+    if( p->tid==0 ){
+      memset(p, 0, sizeof(*p));
+    }
+  }
+  if( p->xTask==0 ){
+    p->id = GetCurrentThreadId();
+    p->pResult = xTask(pIn);
+  }
+  *ppThread = p;
+  return SQLITE_OK;
+}
+
+DWORD sqlite3Win32Wait(HANDLE hObject); /* os_win.c */
+
+/* Get the results of the thread */
+int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){
+  DWORD rc;
+  BOOL bRc;
+
+  assert( ppOut!=0 );
+  if( NEVER(p==0) ) return SQLITE_NOMEM_BKPT;
+  if( p->xTask==0 ){
+    /* assert( p->id==GetCurrentThreadId() ); */
+    rc = WAIT_OBJECT_0;
+    assert( p->tid==0 );
+  }else{
+    assert( p->id!=0 && p->id!=GetCurrentThreadId() );
+    rc = sqlite3Win32Wait((HANDLE)p->tid);
+    assert( rc!=WAIT_IO_COMPLETION );
+    bRc = CloseHandle((HANDLE)p->tid);
+    assert( bRc );
+  }
+  if( rc==WAIT_OBJECT_0 ) *ppOut = p->pResult;
+  sqlite3_free(p);
+  return (rc==WAIT_OBJECT_0) ? SQLITE_OK : SQLITE_ERROR;
+}
+
+#endif /* SQLITE_OS_WIN_THREADS */
+/******************************** End Win32 Threads *************************/
+
+
+/********************************* Single-Threaded **************************/
+#ifndef SQLITE_THREADS_IMPLEMENTED
+/*
+** This implementation does not actually create a new thread.  It does the
+** work of the thread in the main thread, when either the thread is created
+** or when it is joined
+*/
+
+/* A running thread */
+struct SQLiteThread {
+  void *(*xTask)(void*);   /* The routine to run as a thread */
+  void *pIn;               /* Argument to xTask */
+  void *pResult;           /* Result of xTask */
+};
+
+/* Create a new thread */
+int sqlite3ThreadCreate(
+  SQLiteThread **ppThread,  /* OUT: Write the thread object here */
+  void *(*xTask)(void*),    /* Routine to run in a separate thread */
+  void *pIn                 /* Argument passed into xTask() */
+){
+  SQLiteThread *p;
+
+  assert( ppThread!=0 );
+  assert( xTask!=0 );
+  *ppThread = 0;
+  p = sqlite3Malloc(sizeof(*p));
+  if( p==0 ) return SQLITE_NOMEM_BKPT;
+  if( (SQLITE_PTR_TO_INT(p)/17)&1 ){
+    p->xTask = xTask;
+    p->pIn = pIn;
+  }else{
+    p->xTask = 0;
+    p->pResult = xTask(pIn);
+  }
+  *ppThread = p;
+  return SQLITE_OK;
+}
+
+/* Get the results of the thread */
+int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){
+
+  assert( ppOut!=0 );
+  if( NEVER(p==0) ) return SQLITE_NOMEM_BKPT;
+  if( p->xTask ){
+    *ppOut = p->xTask(p->pIn);
+  }else{
+    *ppOut = p->pResult;
+  }
+  sqlite3_free(p);
+
+#if defined(SQLITE_TEST)
+  {
+    void *pTstAlloc = sqlite3Malloc(10);
+    if (!pTstAlloc) return SQLITE_NOMEM_BKPT;
+    sqlite3_free(pTstAlloc);
+  }
+#endif
+
+  return SQLITE_OK;
+}
+
+#endif /* !defined(SQLITE_THREADS_IMPLEMENTED) */
+/****************************** End Single-Threaded *************************/
+#endif /* SQLITE_MAX_WORKER_THREADS>0 */
diff --git a/src/tokenize.c b/src/tokenize.c
new file mode 100644
index 0000000..f4d013d
--- /dev/null
+++ b/src/tokenize.c
@@ -0,0 +1,854 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** An tokenizer for SQL
+**
+** This file contains C code that splits an SQL input string up into
+** individual tokens and sends those tokens one-by-one over to the
+** parser for analysis.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+
+/* Character classes for tokenizing
+**
+** In the sqlite3GetToken() function, a switch() on aiClass[c] is implemented
+** using a lookup table, whereas a switch() directly on c uses a binary search.
+** The lookup table is much faster.  To maximize speed, and to ensure that
+** a lookup table is used, all of the classes need to be small integers and
+** all of them need to be used within the switch.
+*/
+#define CC_X          0    /* The letter 'x', or start of BLOB literal */
+#define CC_KYWD0      1    /* First letter of a keyword */
+#define CC_KYWD       2    /* Alphabetics or '_'.  Usable in a keyword */
+#define CC_DIGIT      3    /* Digits */
+#define CC_DOLLAR     4    /* '$' */
+#define CC_VARALPHA   5    /* '@', '#', ':'.  Alphabetic SQL variables */
+#define CC_VARNUM     6    /* '?'.  Numeric SQL variables */
+#define CC_SPACE      7    /* Space characters */
+#define CC_QUOTE      8    /* '"', '\'', or '`'.  String literals, quoted ids */
+#define CC_QUOTE2     9    /* '['.   [...] style quoted ids */
+#define CC_PIPE      10    /* '|'.   Bitwise OR or concatenate */
+#define CC_MINUS     11    /* '-'.  Minus or SQL-style comment */
+#define CC_LT        12    /* '<'.  Part of < or <= or <> */
+#define CC_GT        13    /* '>'.  Part of > or >= */
+#define CC_EQ        14    /* '='.  Part of = or == */
+#define CC_BANG      15    /* '!'.  Part of != */
+#define CC_SLASH     16    /* '/'.  / or c-style comment */
+#define CC_LP        17    /* '(' */
+#define CC_RP        18    /* ')' */
+#define CC_SEMI      19    /* ';' */
+#define CC_PLUS      20    /* '+' */
+#define CC_STAR      21    /* '*' */
+#define CC_PERCENT   22    /* '%' */
+#define CC_COMMA     23    /* ',' */
+#define CC_AND       24    /* '&' */
+#define CC_TILDA     25    /* '~' */
+#define CC_DOT       26    /* '.' */
+#define CC_ID        27    /* unicode characters usable in IDs */
+#define CC_ILLEGAL   28    /* Illegal character */
+#define CC_NUL       29    /* 0x00 */
+#define CC_BOM       30    /* First byte of UTF8 BOM:  0xEF 0xBB 0xBF */
+
+static const unsigned char aiClass[] = {
+#ifdef SQLITE_ASCII
+/*         x0  x1  x2  x3  x4  x5  x6  x7  x8  x9  xa  xb  xc  xd  xe  xf */
+/* 0x */   29, 28, 28, 28, 28, 28, 28, 28, 28,  7,  7, 28,  7,  7, 28, 28,
+/* 1x */   28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
+/* 2x */    7, 15,  8,  5,  4, 22, 24,  8, 17, 18, 21, 20, 23, 11, 26, 16,
+/* 3x */    3,  3,  3,  3,  3,  3,  3,  3,  3,  3,  5, 19, 12, 14, 13,  6,
+/* 4x */    5,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
+/* 5x */    1,  1,  1,  1,  1,  1,  1,  1,  0,  2,  2,  9, 28, 28, 28,  2,
+/* 6x */    8,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
+/* 7x */    1,  1,  1,  1,  1,  1,  1,  1,  0,  2,  2, 28, 10, 28, 25, 28,
+/* 8x */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
+/* 9x */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
+/* Ax */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
+/* Bx */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
+/* Cx */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
+/* Dx */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
+/* Ex */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 30,
+/* Fx */   27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27
+#endif
+#ifdef SQLITE_EBCDIC
+/*         x0  x1  x2  x3  x4  x5  x6  x7  x8  x9  xa  xb  xc  xd  xe  xf */
+/* 0x */   29, 28, 28, 28, 28,  7, 28, 28, 28, 28, 28, 28,  7,  7, 28, 28,
+/* 1x */   28, 28, 28, 28, 28,  7, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
+/* 2x */   28, 28, 28, 28, 28,  7, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
+/* 3x */   28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
+/* 4x */    7, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 26, 12, 17, 20, 10,
+/* 5x */   24, 28, 28, 28, 28, 28, 28, 28, 28, 28, 15,  4, 21, 18, 19, 28,
+/* 6x */   11, 16, 28, 28, 28, 28, 28, 28, 28, 28, 28, 23, 22,  2, 13,  6,
+/* 7x */   28, 28, 28, 28, 28, 28, 28, 28, 28,  8,  5,  5,  5,  8, 14,  8,
+/* 8x */   28,  1,  1,  1,  1,  1,  1,  1,  1,  1, 28, 28, 28, 28, 28, 28,
+/* 9x */   28,  1,  1,  1,  1,  1,  1,  1,  1,  1, 28, 28, 28, 28, 28, 28,
+/* Ax */   28, 25,  1,  1,  1,  1,  1,  0,  2,  2, 28, 28, 28, 28, 28, 28,
+/* Bx */   28, 28, 28, 28, 28, 28, 28, 28, 28, 28,  9, 28, 28, 28, 28, 28,
+/* Cx */   28,  1,  1,  1,  1,  1,  1,  1,  1,  1, 28, 28, 28, 28, 28, 28,
+/* Dx */   28,  1,  1,  1,  1,  1,  1,  1,  1,  1, 28, 28, 28, 28, 28, 28,
+/* Ex */   28, 28,  1,  1,  1,  1,  1,  0,  2,  2, 28, 28, 28, 28, 28, 28,
+/* Fx */    3,  3,  3,  3,  3,  3,  3,  3,  3,  3, 28, 28, 28, 28, 28, 28,
+#endif
+};
+
+/*
+** The charMap() macro maps alphabetic characters (only) into their
+** lower-case ASCII equivalent.  On ASCII machines, this is just
+** an upper-to-lower case map.  On EBCDIC machines we also need
+** to adjust the encoding.  The mapping is only valid for alphabetics
+** which are the only characters for which this feature is used. 
+**
+** Used by keywordhash.h
+*/
+#ifdef SQLITE_ASCII
+# define charMap(X) sqlite3UpperToLower[(unsigned char)X]
+#endif
+#ifdef SQLITE_EBCDIC
+# define charMap(X) ebcdicToAscii[(unsigned char)X]
+const unsigned char ebcdicToAscii[] = {
+/* 0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 0x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 1x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 2x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 3x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 4x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 5x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 95,  0,  0,  /* 6x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 7x */
+   0, 97, 98, 99,100,101,102,103,104,105,  0,  0,  0,  0,  0,  0,  /* 8x */
+   0,106,107,108,109,110,111,112,113,114,  0,  0,  0,  0,  0,  0,  /* 9x */
+   0,  0,115,116,117,118,119,120,121,122,  0,  0,  0,  0,  0,  0,  /* Ax */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* Bx */
+   0, 97, 98, 99,100,101,102,103,104,105,  0,  0,  0,  0,  0,  0,  /* Cx */
+   0,106,107,108,109,110,111,112,113,114,  0,  0,  0,  0,  0,  0,  /* Dx */
+   0,  0,115,116,117,118,119,120,121,122,  0,  0,  0,  0,  0,  0,  /* Ex */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* Fx */
+};
+#endif
+
+/*
+** The sqlite3KeywordCode function looks up an identifier to determine if
+** it is a keyword.  If it is a keyword, the token code of that keyword is 
+** returned.  If the input is not a keyword, TK_ID is returned.
+**
+** The implementation of this routine was generated by a program,
+** mkkeywordhash.c, located in the tool subdirectory of the distribution.
+** The output of the mkkeywordhash.c program is written into a file
+** named keywordhash.h and then included into this source file by
+** the #include below.
+*/
+#include "keywordhash.h"
+
+
+/*
+** If X is a character that can be used in an identifier then
+** IdChar(X) will be true.  Otherwise it is false.
+**
+** For ASCII, any character with the high-order bit set is
+** allowed in an identifier.  For 7-bit characters, 
+** sqlite3IsIdChar[X] must be 1.
+**
+** For EBCDIC, the rules are more complex but have the same
+** end result.
+**
+** Ticket #1066.  the SQL standard does not allow '$' in the
+** middle of identifiers.  But many SQL implementations do. 
+** SQLite will allow '$' in identifiers for compatibility.
+** But the feature is undocumented.
+*/
+#ifdef SQLITE_ASCII
+#define IdChar(C)  ((sqlite3CtypeMap[(unsigned char)C]&0x46)!=0)
+#endif
+#ifdef SQLITE_EBCDIC
+const char sqlite3IsEbcdicIdChar[] = {
+/* x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF */
+    0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 4x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0,  /* 5x */
+    0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0,  /* 6x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0,  /* 7x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0,  /* 8x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 1, 0,  /* 9x */
+    1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0,  /* Ax */
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* Bx */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,  /* Cx */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,  /* Dx */
+    0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,  /* Ex */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0,  /* Fx */
+};
+#define IdChar(C)  (((c=C)>=0x42 && sqlite3IsEbcdicIdChar[c-0x40]))
+#endif
+
+/* Make the IdChar function accessible from ctime.c and alter.c */
+int sqlite3IsIdChar(u8 c){ return IdChar(c); }
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+/*
+** Return the id of the next token in string (*pz). Before returning, set
+** (*pz) to point to the byte following the parsed token.
+*/
+static int getToken(const unsigned char **pz){
+  const unsigned char *z = *pz;
+  int t;                          /* Token type to return */
+  do {
+    z += sqlite3GetToken(z, &t);
+  }while( t==TK_SPACE );
+  if( t==TK_ID 
+   || t==TK_STRING 
+   || t==TK_JOIN_KW 
+   || t==TK_WINDOW 
+   || t==TK_OVER 
+   || sqlite3ParserFallback(t)==TK_ID 
+  ){
+    t = TK_ID;
+  }
+  *pz = z;
+  return t;
+}
+
+/*
+** The following three functions are called immediately after the tokenizer
+** reads the keywords WINDOW, OVER and FILTER, respectively, to determine
+** whether the token should be treated as a keyword or an SQL identifier.
+** This cannot be handled by the usual lemon %fallback method, due to
+** the ambiguity in some constructions. e.g.
+**
+**   SELECT sum(x) OVER ...
+**
+** In the above, "OVER" might be a keyword, or it might be an alias for the 
+** sum(x) expression. If a "%fallback ID OVER" directive were added to 
+** grammar, then SQLite would always treat "OVER" as an alias, making it
+** impossible to call a window-function without a FILTER clause.
+**
+** WINDOW is treated as a keyword if:
+**
+**   * the following token is an identifier, or a keyword that can fallback
+**     to being an identifier, and
+**   * the token after than one is TK_AS.
+**
+** OVER is a keyword if:
+**
+**   * the previous token was TK_RP, and
+**   * the next token is either TK_LP or an identifier.
+**
+** FILTER is a keyword if:
+**
+**   * the previous token was TK_RP, and
+**   * the next token is TK_LP.
+*/
+static int analyzeWindowKeyword(const unsigned char *z){
+  int t;
+  t = getToken(&z);
+  if( t!=TK_ID ) return TK_ID;
+  t = getToken(&z);
+  if( t!=TK_AS ) return TK_ID;
+  return TK_WINDOW;
+}
+static int analyzeOverKeyword(const unsigned char *z, int lastToken){
+  if( lastToken==TK_RP ){
+    int t = getToken(&z);
+    if( t==TK_LP || t==TK_ID ) return TK_OVER;
+  }
+  return TK_ID;
+}
+static int analyzeFilterKeyword(const unsigned char *z, int lastToken){
+  if( lastToken==TK_RP && getToken(&z)==TK_LP ){
+    return TK_FILTER;
+  }
+  return TK_ID;
+}
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+/*
+** Return the length (in bytes) of the token that begins at z[0]. 
+** Store the token type in *tokenType before returning.
+*/
+int sqlite3GetToken(const unsigned char *z, int *tokenType){
+  int i, c;
+  switch( aiClass[*z] ){  /* Switch on the character-class of the first byte
+                          ** of the token. See the comment on the CC_ defines
+                          ** above. */
+    case CC_SPACE: {
+      testcase( z[0]==' ' );
+      testcase( z[0]=='\t' );
+      testcase( z[0]=='\n' );
+      testcase( z[0]=='\f' );
+      testcase( z[0]=='\r' );
+      for(i=1; sqlite3Isspace(z[i]); i++){}
+      *tokenType = TK_SPACE;
+      return i;
+    }
+    case CC_MINUS: {
+      if( z[1]=='-' ){
+        for(i=2; (c=z[i])!=0 && c!='\n'; i++){}
+        *tokenType = TK_SPACE;   /* IMP: R-22934-25134 */
+        return i;
+      }else if( z[1]=='>' ){
+        *tokenType = TK_PTR;
+        return 2 + (z[2]=='>');
+      }
+      *tokenType = TK_MINUS;
+      return 1;
+    }
+    case CC_LP: {
+      *tokenType = TK_LP;
+      return 1;
+    }
+    case CC_RP: {
+      *tokenType = TK_RP;
+      return 1;
+    }
+    case CC_SEMI: {
+      *tokenType = TK_SEMI;
+      return 1;
+    }
+    case CC_PLUS: {
+      *tokenType = TK_PLUS;
+      return 1;
+    }
+    case CC_STAR: {
+      *tokenType = TK_STAR;
+      return 1;
+    }
+    case CC_SLASH: {
+      if( z[1]!='*' || z[2]==0 ){
+        *tokenType = TK_SLASH;
+        return 1;
+      }
+      for(i=3, c=z[2]; (c!='*' || z[i]!='/') && (c=z[i])!=0; i++){}
+      if( c ) i++;
+      *tokenType = TK_SPACE;   /* IMP: R-22934-25134 */
+      return i;
+    }
+    case CC_PERCENT: {
+      *tokenType = TK_REM;
+      return 1;
+    }
+    case CC_EQ: {
+      *tokenType = TK_EQ;
+      return 1 + (z[1]=='=');
+    }
+    case CC_LT: {
+      if( (c=z[1])=='=' ){
+        *tokenType = TK_LE;
+        return 2;
+      }else if( c=='>' ){
+        *tokenType = TK_NE;
+        return 2;
+      }else if( c=='<' ){
+        *tokenType = TK_LSHIFT;
+        return 2;
+      }else{
+        *tokenType = TK_LT;
+        return 1;
+      }
+    }
+    case CC_GT: {
+      if( (c=z[1])=='=' ){
+        *tokenType = TK_GE;
+        return 2;
+      }else if( c=='>' ){
+        *tokenType = TK_RSHIFT;
+        return 2;
+      }else{
+        *tokenType = TK_GT;
+        return 1;
+      }
+    }
+    case CC_BANG: {
+      if( z[1]!='=' ){
+        *tokenType = TK_ILLEGAL;
+        return 1;
+      }else{
+        *tokenType = TK_NE;
+        return 2;
+      }
+    }
+    case CC_PIPE: {
+      if( z[1]!='|' ){
+        *tokenType = TK_BITOR;
+        return 1;
+      }else{
+        *tokenType = TK_CONCAT;
+        return 2;
+      }
+    }
+    case CC_COMMA: {
+      *tokenType = TK_COMMA;
+      return 1;
+    }
+    case CC_AND: {
+      *tokenType = TK_BITAND;
+      return 1;
+    }
+    case CC_TILDA: {
+      *tokenType = TK_BITNOT;
+      return 1;
+    }
+    case CC_QUOTE: {
+      int delim = z[0];
+      testcase( delim=='`' );
+      testcase( delim=='\'' );
+      testcase( delim=='"' );
+      for(i=1; (c=z[i])!=0; i++){
+        if( c==delim ){
+          if( z[i+1]==delim ){
+            i++;
+          }else{
+            break;
+          }
+        }
+      }
+      if( c=='\'' ){
+        *tokenType = TK_STRING;
+        return i+1;
+      }else if( c!=0 ){
+        *tokenType = TK_ID;
+        return i+1;
+      }else{
+        *tokenType = TK_ILLEGAL;
+        return i;
+      }
+    }
+    case CC_DOT: {
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      if( !sqlite3Isdigit(z[1]) )
+#endif
+      {
+        *tokenType = TK_DOT;
+        return 1;
+      }
+      /* If the next character is a digit, this is a floating point
+      ** number that begins with ".".  Fall thru into the next case */
+      /* no break */ deliberate_fall_through
+    }
+    case CC_DIGIT: {
+      testcase( z[0]=='0' );  testcase( z[0]=='1' );  testcase( z[0]=='2' );
+      testcase( z[0]=='3' );  testcase( z[0]=='4' );  testcase( z[0]=='5' );
+      testcase( z[0]=='6' );  testcase( z[0]=='7' );  testcase( z[0]=='8' );
+      testcase( z[0]=='9' );  testcase( z[0]=='.' );
+      *tokenType = TK_INTEGER;
+#ifndef SQLITE_OMIT_HEX_INTEGER
+      if( z[0]=='0' && (z[1]=='x' || z[1]=='X') && sqlite3Isxdigit(z[2]) ){
+        for(i=3; sqlite3Isxdigit(z[i]); i++){}
+        return i;
+      }
+#endif
+      for(i=0; sqlite3Isdigit(z[i]); i++){}
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      if( z[i]=='.' ){
+        i++;
+        while( sqlite3Isdigit(z[i]) ){ i++; }
+        *tokenType = TK_FLOAT;
+      }
+      if( (z[i]=='e' || z[i]=='E') &&
+           ( sqlite3Isdigit(z[i+1]) 
+            || ((z[i+1]=='+' || z[i+1]=='-') && sqlite3Isdigit(z[i+2]))
+           )
+      ){
+        i += 2;
+        while( sqlite3Isdigit(z[i]) ){ i++; }
+        *tokenType = TK_FLOAT;
+      }
+#endif
+      while( IdChar(z[i]) ){
+        *tokenType = TK_ILLEGAL;
+        i++;
+      }
+      return i;
+    }
+    case CC_QUOTE2: {
+      for(i=1, c=z[0]; c!=']' && (c=z[i])!=0; i++){}
+      *tokenType = c==']' ? TK_ID : TK_ILLEGAL;
+      return i;
+    }
+    case CC_VARNUM: {
+      *tokenType = TK_VARIABLE;
+      for(i=1; sqlite3Isdigit(z[i]); i++){}
+      return i;
+    }
+    case CC_DOLLAR:
+    case CC_VARALPHA: {
+      int n = 0;
+      testcase( z[0]=='$' );  testcase( z[0]=='@' );
+      testcase( z[0]==':' );  testcase( z[0]=='#' );
+      *tokenType = TK_VARIABLE;
+      for(i=1; (c=z[i])!=0; i++){
+        if( IdChar(c) ){
+          n++;
+#ifndef SQLITE_OMIT_TCL_VARIABLE
+        }else if( c=='(' && n>0 ){
+          do{
+            i++;
+          }while( (c=z[i])!=0 && !sqlite3Isspace(c) && c!=')' );
+          if( c==')' ){
+            i++;
+          }else{
+            *tokenType = TK_ILLEGAL;
+          }
+          break;
+        }else if( c==':' && z[i+1]==':' ){
+          i++;
+#endif
+        }else{
+          break;
+        }
+      }
+      if( n==0 ) *tokenType = TK_ILLEGAL;
+      return i;
+    }
+    case CC_KYWD0: {
+      if( aiClass[z[1]]>CC_KYWD ){ i = 1;  break; }
+      for(i=2; aiClass[z[i]]<=CC_KYWD; i++){}
+      if( IdChar(z[i]) ){
+        /* This token started out using characters that can appear in keywords,
+        ** but z[i] is a character not allowed within keywords, so this must
+        ** be an identifier instead */
+        i++;
+        break;
+      }
+      *tokenType = TK_ID;
+      return keywordCode((char*)z, i, tokenType);
+    }
+    case CC_X: {
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+      testcase( z[0]=='x' ); testcase( z[0]=='X' );
+      if( z[1]=='\'' ){
+        *tokenType = TK_BLOB;
+        for(i=2; sqlite3Isxdigit(z[i]); i++){}
+        if( z[i]!='\'' || i%2 ){
+          *tokenType = TK_ILLEGAL;
+          while( z[i] && z[i]!='\'' ){ i++; }
+        }
+        if( z[i] ) i++;
+        return i;
+      }
+#endif
+      /* If it is not a BLOB literal, then it must be an ID, since no
+      ** SQL keywords start with the letter 'x'.  Fall through */
+      /* no break */ deliberate_fall_through
+    }
+    case CC_KYWD:
+    case CC_ID: {
+      i = 1;
+      break;
+    }
+    case CC_BOM: {
+      if( z[1]==0xbb && z[2]==0xbf ){
+        *tokenType = TK_SPACE;
+        return 3;
+      }
+      i = 1;
+      break;
+    }
+    case CC_NUL: {
+      *tokenType = TK_ILLEGAL;
+      return 0;
+    }
+    default: {
+      *tokenType = TK_ILLEGAL;
+      return 1;
+    }
+  }
+  while( IdChar(z[i]) ){ i++; }
+  *tokenType = TK_ID;
+  return i;
+}
+
+/*
+** Run the parser on the given SQL string.
+*/
+int sqlite3RunParser(Parse *pParse, const char *zSql){
+  int nErr = 0;                   /* Number of errors encountered */
+  void *pEngine;                  /* The LEMON-generated LALR(1) parser */
+  int n = 0;                      /* Length of the next token token */
+  int tokenType;                  /* type of the next token */
+  int lastTokenParsed = -1;       /* type of the previous token */
+  sqlite3 *db = pParse->db;       /* The database connection */
+  int mxSqlLen;                   /* Max length of an SQL string */
+  Parse *pParentParse = 0;        /* Outer parse context, if any */
+#ifdef sqlite3Parser_ENGINEALWAYSONSTACK
+  yyParser sEngine;    /* Space to hold the Lemon-generated Parser object */
+#endif
+  VVA_ONLY( u8 startedWithOom = db->mallocFailed );
+
+  assert( zSql!=0 );
+  mxSqlLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
+  if( db->nVdbeActive==0 ){
+    AtomicStore(&db->u1.isInterrupted, 0);
+  }
+  pParse->rc = SQLITE_OK;
+  pParse->zTail = zSql;
+#ifdef SQLITE_DEBUG
+  if( db->flags & SQLITE_ParserTrace ){
+    printf("parser: [[[%s]]]\n", zSql);
+    sqlite3ParserTrace(stdout, "parser: ");
+  }else{
+    sqlite3ParserTrace(0, 0);
+  }
+#endif
+#ifdef sqlite3Parser_ENGINEALWAYSONSTACK
+  pEngine = &sEngine;
+  sqlite3ParserInit(pEngine, pParse);
+#else
+  pEngine = sqlite3ParserAlloc(sqlite3Malloc, pParse);
+  if( pEngine==0 ){
+    sqlite3OomFault(db);
+    return SQLITE_NOMEM_BKPT;
+  }
+#endif
+  assert( pParse->pNewTable==0 );
+  assert( pParse->pNewTrigger==0 );
+  assert( pParse->nVar==0 );
+  assert( pParse->pVList==0 );
+  pParentParse = db->pParse;
+  db->pParse = pParse;
+  while( 1 ){
+    n = sqlite3GetToken((u8*)zSql, &tokenType);
+    mxSqlLen -= n;
+    if( mxSqlLen<0 ){
+      pParse->rc = SQLITE_TOOBIG;
+      pParse->nErr++;
+      break;
+    }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( tokenType>=TK_WINDOW ){
+      assert( tokenType==TK_SPACE || tokenType==TK_OVER || tokenType==TK_FILTER
+           || tokenType==TK_ILLEGAL || tokenType==TK_WINDOW 
+      );
+#else
+    if( tokenType>=TK_SPACE ){
+      assert( tokenType==TK_SPACE || tokenType==TK_ILLEGAL );
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+      if( AtomicLoad(&db->u1.isInterrupted) ){
+        pParse->rc = SQLITE_INTERRUPT;
+        pParse->nErr++;
+        break;
+      }
+      if( tokenType==TK_SPACE ){
+        zSql += n;
+        continue;
+      }
+      if( zSql[0]==0 ){
+        /* Upon reaching the end of input, call the parser two more times
+        ** with tokens TK_SEMI and 0, in that order. */
+        if( lastTokenParsed==TK_SEMI ){
+          tokenType = 0;
+        }else if( lastTokenParsed==0 ){
+          break;
+        }else{
+          tokenType = TK_SEMI;
+        }
+        n = 0;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      }else if( tokenType==TK_WINDOW ){
+        assert( n==6 );
+        tokenType = analyzeWindowKeyword((const u8*)&zSql[6]);
+      }else if( tokenType==TK_OVER ){
+        assert( n==4 );
+        tokenType = analyzeOverKeyword((const u8*)&zSql[4], lastTokenParsed);
+      }else if( tokenType==TK_FILTER ){
+        assert( n==6 );
+        tokenType = analyzeFilterKeyword((const u8*)&zSql[6], lastTokenParsed);
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+      }else{
+        Token x;
+        x.z = zSql;
+        x.n = n;
+        sqlite3ErrorMsg(pParse, "unrecognized token: \"%T\"", &x);
+        break;
+      }
+    }
+    pParse->sLastToken.z = zSql;
+    pParse->sLastToken.n = n;
+    sqlite3Parser(pEngine, tokenType, pParse->sLastToken);
+    lastTokenParsed = tokenType;
+    zSql += n;
+    assert( db->mallocFailed==0 || pParse->rc!=SQLITE_OK || startedWithOom );
+    if( pParse->rc!=SQLITE_OK ) break;
+  }
+  assert( nErr==0 );
+#ifdef YYTRACKMAXSTACKDEPTH
+  sqlite3_mutex_enter(sqlite3MallocMutex());
+  sqlite3StatusHighwater(SQLITE_STATUS_PARSER_STACK,
+      sqlite3ParserStackPeak(pEngine)
+  );
+  sqlite3_mutex_leave(sqlite3MallocMutex());
+#endif /* YYDEBUG */
+#ifdef sqlite3Parser_ENGINEALWAYSONSTACK
+  sqlite3ParserFinalize(pEngine);
+#else
+  sqlite3ParserFree(pEngine, sqlite3_free);
+#endif
+  if( db->mallocFailed ){
+    pParse->rc = SQLITE_NOMEM_BKPT;
+  }
+  if( pParse->zErrMsg || (pParse->rc!=SQLITE_OK && pParse->rc!=SQLITE_DONE) ){
+    if( pParse->zErrMsg==0 ){
+      pParse->zErrMsg = sqlite3MPrintf(db, "%s", sqlite3ErrStr(pParse->rc));
+    }
+    sqlite3_log(pParse->rc, "%s in \"%s\"", pParse->zErrMsg, pParse->zTail);
+    nErr++;
+  }
+  pParse->zTail = zSql;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_free(pParse->apVtabLock);
+#endif
+
+  if( pParse->pNewTable && !IN_SPECIAL_PARSE ){
+    /* If the pParse->declareVtab flag is set, do not delete any table 
+    ** structure built up in pParse->pNewTable. The calling code (see vtab.c)
+    ** will take responsibility for freeing the Table structure.
+    */
+    sqlite3DeleteTable(db, pParse->pNewTable);
+  }
+  if( pParse->pNewTrigger && !IN_RENAME_OBJECT ){
+    sqlite3DeleteTrigger(db, pParse->pNewTrigger);
+  }
+  if( pParse->pVList ) sqlite3DbNNFreeNN(db, pParse->pVList);
+  db->pParse = pParentParse;
+  assert( nErr==0 || pParse->rc!=SQLITE_OK );
+  return nErr;
+}
+
+
+#ifdef SQLITE_ENABLE_NORMALIZE
+/*
+** Insert a single space character into pStr if the current string
+** ends with an identifier
+*/
+static void addSpaceSeparator(sqlite3_str *pStr){
+  if( pStr->nChar && sqlite3IsIdChar(pStr->zText[pStr->nChar-1]) ){
+    sqlite3_str_append(pStr, " ", 1);
+  }
+}
+
+/*
+** Compute a normalization of the SQL given by zSql[0..nSql-1].  Return
+** the normalization in space obtained from sqlite3DbMalloc().  Or return
+** NULL if anything goes wrong or if zSql is NULL.
+*/
+char *sqlite3Normalize(
+  Vdbe *pVdbe,       /* VM being reprepared */
+  const char *zSql   /* The original SQL string */
+){
+  sqlite3 *db;       /* The database connection */
+  int i;             /* Next unread byte of zSql[] */
+  int n;             /* length of current token */
+  int tokenType;     /* type of current token */
+  int prevType = 0;  /* Previous non-whitespace token */
+  int nParen;        /* Number of nested levels of parentheses */
+  int iStartIN;      /* Start of RHS of IN operator in z[] */
+  int nParenAtIN;    /* Value of nParent at start of RHS of IN operator */
+  u32 j;             /* Bytes of normalized SQL generated so far */
+  sqlite3_str *pStr; /* The normalized SQL string under construction */
+
+  db = sqlite3VdbeDb(pVdbe);
+  tokenType = -1;
+  nParen = iStartIN = nParenAtIN = 0;
+  pStr = sqlite3_str_new(db);
+  assert( pStr!=0 );  /* sqlite3_str_new() never returns NULL */
+  for(i=0; zSql[i] && pStr->accError==0; i+=n){
+    if( tokenType!=TK_SPACE ){
+      prevType = tokenType;
+    }
+    n = sqlite3GetToken((unsigned char*)zSql+i, &tokenType);
+    if( NEVER(n<=0) ) break;
+    switch( tokenType ){
+      case TK_SPACE: {
+        break;
+      }
+      case TK_NULL: {
+        if( prevType==TK_IS || prevType==TK_NOT ){
+          sqlite3_str_append(pStr, " NULL", 5);
+          break;
+        }
+        /* Fall through */
+      }
+      case TK_STRING:
+      case TK_INTEGER:
+      case TK_FLOAT:
+      case TK_VARIABLE:
+      case TK_BLOB: {
+        sqlite3_str_append(pStr, "?", 1);
+        break;
+      }
+      case TK_LP: {
+        nParen++;
+        if( prevType==TK_IN ){
+          iStartIN = pStr->nChar;
+          nParenAtIN = nParen;
+        }
+        sqlite3_str_append(pStr, "(", 1);
+        break;
+      }
+      case TK_RP: {
+        if( iStartIN>0 && nParen==nParenAtIN ){
+          assert( pStr->nChar>=(u32)iStartIN );
+          pStr->nChar = iStartIN+1;
+          sqlite3_str_append(pStr, "?,?,?", 5);
+          iStartIN = 0;
+        }
+        nParen--;
+        sqlite3_str_append(pStr, ")", 1);
+        break;
+      }
+      case TK_ID: {
+        iStartIN = 0;
+        j = pStr->nChar;
+        if( sqlite3Isquote(zSql[i]) ){
+          char *zId = sqlite3DbStrNDup(db, zSql+i, n);
+          int nId;
+          int eType = 0;
+          if( zId==0 ) break;
+          sqlite3Dequote(zId);
+          if( zSql[i]=='"' && sqlite3VdbeUsesDoubleQuotedString(pVdbe, zId) ){
+            sqlite3_str_append(pStr, "?", 1);
+            sqlite3DbFree(db, zId);
+            break;
+          }
+          nId = sqlite3Strlen30(zId);
+          if( sqlite3GetToken((u8*)zId, &eType)==nId && eType==TK_ID ){
+            addSpaceSeparator(pStr);
+            sqlite3_str_append(pStr, zId, nId);
+          }else{
+            sqlite3_str_appendf(pStr, "\"%w\"", zId);
+          }
+          sqlite3DbFree(db, zId);
+        }else{
+          addSpaceSeparator(pStr);
+          sqlite3_str_append(pStr, zSql+i, n);
+        }
+        while( j<pStr->nChar ){
+          pStr->zText[j] = sqlite3Tolower(pStr->zText[j]);
+          j++;
+        }
+        break;
+      }
+      case TK_SELECT: {
+        iStartIN = 0;
+        /* fall through */
+      }
+      default: {
+        if( sqlite3IsIdChar(zSql[i]) ) addSpaceSeparator(pStr);
+        j = pStr->nChar;
+        sqlite3_str_append(pStr, zSql+i, n);
+        while( j<pStr->nChar ){
+          pStr->zText[j] = sqlite3Toupper(pStr->zText[j]);
+          j++;
+        }
+        break;
+      }
+    }
+  }
+  if( tokenType!=TK_SEMI ) sqlite3_str_append(pStr, ";", 1);
+  return sqlite3_str_finish(pStr);
+}
+#endif /* SQLITE_ENABLE_NORMALIZE */
diff --git a/src/treeview.c b/src/treeview.c
new file mode 100644
index 0000000..2576532
--- /dev/null
+++ b/src/treeview.c
@@ -0,0 +1,1312 @@
+/*
+** 2015-06-08
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains C code to implement the TreeView debugging routines.
+** These routines print a parse tree to standard output for debugging and
+** analysis. 
+**
+** The interfaces in this file is only available when compiling
+** with SQLITE_DEBUG.
+*/
+#include "sqliteInt.h"
+#ifdef SQLITE_DEBUG
+
+/*
+** Add a new subitem to the tree.  The moreToFollow flag indicates that this
+** is not the last item in the tree.
+*/
+static void sqlite3TreeViewPush(TreeView **pp, u8 moreToFollow){
+  TreeView *p = *pp;
+  if( p==0 ){
+    *pp = p = sqlite3_malloc64( sizeof(*p) );
+    if( p==0 ) return;
+    memset(p, 0, sizeof(*p));
+  }else{
+    p->iLevel++;
+  }
+  assert( moreToFollow==0 || moreToFollow==1 );
+  if( p->iLevel<(int)sizeof(p->bLine) ) p->bLine[p->iLevel] = moreToFollow;
+}
+
+/*
+** Finished with one layer of the tree
+*/
+static void sqlite3TreeViewPop(TreeView **pp){
+  TreeView *p = *pp;
+  if( p==0 ) return;
+  p->iLevel--;
+  if( p->iLevel<0 ){
+    sqlite3_free(p);
+    *pp = 0;
+  }
+}
+
+/*
+** Generate a single line of output for the tree, with a prefix that contains
+** all the appropriate tree lines
+*/
+void sqlite3TreeViewLine(TreeView *p, const char *zFormat, ...){
+  va_list ap;
+  int i;
+  StrAccum acc;
+  char zBuf[1000];
+  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
+  if( p ){
+    for(i=0; i<p->iLevel && i<(int)sizeof(p->bLine)-1; i++){
+      sqlite3_str_append(&acc, p->bLine[i] ? "|   " : "    ", 4);
+    }
+    sqlite3_str_append(&acc, p->bLine[i] ? "|-- " : "'-- ", 4);
+  }
+  if( zFormat!=0 ){
+    va_start(ap, zFormat);
+    sqlite3_str_vappendf(&acc, zFormat, ap);
+    va_end(ap);
+    assert( acc.nChar>0 || acc.accError );
+    sqlite3_str_append(&acc, "\n", 1);
+  }
+  sqlite3StrAccumFinish(&acc);
+  fprintf(stdout,"%s", zBuf);
+  fflush(stdout);
+}
+
+/*
+** Shorthand for starting a new tree item that consists of a single label
+*/
+static void sqlite3TreeViewItem(TreeView *p, const char *zLabel,u8 moreFollows){
+  sqlite3TreeViewPush(&p, moreFollows);
+  sqlite3TreeViewLine(p, "%s", zLabel);
+}
+
+/*
+** Show a list of Column objects in tree format.
+*/
+void sqlite3TreeViewColumnList(
+  TreeView *pView,
+  const Column *aCol,
+  int nCol,
+  u8 moreToFollow
+){
+  int i;
+  sqlite3TreeViewPush(&pView, moreToFollow);
+  sqlite3TreeViewLine(pView, "COLUMNS");
+  for(i=0; i<nCol; i++){
+    u16 flg = aCol[i].colFlags;
+    int colMoreToFollow = i<(nCol - 1);
+    sqlite3TreeViewPush(&pView, colMoreToFollow);
+    sqlite3TreeViewLine(pView, 0);
+    printf(" %s", aCol[i].zCnName);
+    switch( aCol[i].eCType ){
+      case COLTYPE_ANY:      printf(" ANY");        break;
+      case COLTYPE_BLOB:     printf(" BLOB");       break;
+      case COLTYPE_INT:      printf(" INT");        break;
+      case COLTYPE_INTEGER:  printf(" INTEGER");    break;
+      case COLTYPE_REAL:     printf(" REAL");       break;
+      case COLTYPE_TEXT:     printf(" TEXT");       break;
+      case COLTYPE_CUSTOM: {
+        if( flg & COLFLAG_HASTYPE ){
+          const char *z = aCol[i].zCnName;
+          z += strlen(z)+1;
+          printf(" X-%s", z);
+          break;
+        }
+      }
+    }
+    if( flg & COLFLAG_PRIMKEY ) printf(" PRIMARY KEY");
+    if( flg & COLFLAG_HIDDEN ) printf(" HIDDEN");
+#ifdef COLFLAG_NOEXPAND
+    if( flg & COLFLAG_NOEXPAND ) printf(" NO-EXPAND");
+#endif
+    if( flg ) printf(" flags=%04x", flg);
+    printf("\n");      
+    fflush(stdout);
+    sqlite3TreeViewPop(&pView);
+  }
+  sqlite3TreeViewPop(&pView);
+}
+
+/*
+** Generate a human-readable description of a WITH clause.
+*/
+void sqlite3TreeViewWith(TreeView *pView, const With *pWith, u8 moreToFollow){
+  int i;
+  if( pWith==0 ) return;
+  if( pWith->nCte==0 ) return;
+  if( pWith->pOuter ){
+    sqlite3TreeViewLine(pView, "WITH (0x%p, pOuter=0x%p)",pWith,pWith->pOuter);
+  }else{
+    sqlite3TreeViewLine(pView, "WITH (0x%p)", pWith);
+  }
+  if( pWith->nCte>0 ){
+    sqlite3TreeViewPush(&pView, moreToFollow);
+    for(i=0; i<pWith->nCte; i++){
+      StrAccum x;
+      char zLine[1000];
+      const struct Cte *pCte = &pWith->a[i];
+      sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
+      sqlite3_str_appendf(&x, "%s", pCte->zName);
+      if( pCte->pCols && pCte->pCols->nExpr>0 ){
+        char cSep = '(';
+        int j;
+        for(j=0; j<pCte->pCols->nExpr; j++){
+          sqlite3_str_appendf(&x, "%c%s", cSep, pCte->pCols->a[j].zEName);
+          cSep = ',';
+        }
+        sqlite3_str_appendf(&x, ")");
+      }
+      if( pCte->eM10d!=M10d_Any ){
+        sqlite3_str_appendf(&x, " %sMATERIALIZED", 
+           pCte->eM10d==M10d_No ? "NOT " : "");
+      }
+      if( pCte->pUse ){
+        sqlite3_str_appendf(&x, " (pUse=0x%p, nUse=%d)", pCte->pUse,
+                 pCte->pUse->nUse);
+      }
+      sqlite3StrAccumFinish(&x);
+      sqlite3TreeViewItem(pView, zLine, i<pWith->nCte-1);
+      sqlite3TreeViewSelect(pView, pCte->pSelect, 0);
+      sqlite3TreeViewPop(&pView);
+    }
+    sqlite3TreeViewPop(&pView);
+  }
+}
+
+/*
+** Generate a human-readable description of a SrcList object.
+*/
+void sqlite3TreeViewSrcList(TreeView *pView, const SrcList *pSrc){
+  int i;
+  if( pSrc==0 ) return;
+  for(i=0; i<pSrc->nSrc; i++){
+    const SrcItem *pItem = &pSrc->a[i];
+    StrAccum x;
+    int n = 0;
+    char zLine[1000];
+    sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
+    x.printfFlags |= SQLITE_PRINTF_INTERNAL;
+    sqlite3_str_appendf(&x, "{%d:*} %!S", pItem->iCursor, pItem);
+    if( pItem->pTab ){
+      sqlite3_str_appendf(&x, " tab=%Q nCol=%d ptr=%p used=%llx",
+           pItem->pTab->zName, pItem->pTab->nCol, pItem->pTab, pItem->colUsed);
+    }
+    if( (pItem->fg.jointype & (JT_LEFT|JT_RIGHT))==(JT_LEFT|JT_RIGHT) ){
+      sqlite3_str_appendf(&x, " FULL-OUTER-JOIN");
+    }else if( pItem->fg.jointype & JT_LEFT ){
+      sqlite3_str_appendf(&x, " LEFT-JOIN");
+    }else if( pItem->fg.jointype & JT_RIGHT ){
+      sqlite3_str_appendf(&x, " RIGHT-JOIN");
+    }else if( pItem->fg.jointype & JT_CROSS ){
+      sqlite3_str_appendf(&x, " CROSS-JOIN");
+    }
+    if( pItem->fg.jointype & JT_LTORJ ){
+      sqlite3_str_appendf(&x, " LTORJ");
+    }
+    if( pItem->fg.fromDDL ){
+      sqlite3_str_appendf(&x, " DDL");
+    }
+    if( pItem->fg.isCte ){
+      sqlite3_str_appendf(&x, " CteUse=0x%p", pItem->u2.pCteUse);
+    }
+    if( pItem->fg.isOn || (pItem->fg.isUsing==0 && pItem->u3.pOn!=0) ){
+      sqlite3_str_appendf(&x, " ON");
+    }
+    if( pItem->fg.isTabFunc )      sqlite3_str_appendf(&x, " isTabFunc");
+    if( pItem->fg.isCorrelated )   sqlite3_str_appendf(&x, " isCorrelated");
+    if( pItem->fg.isMaterialized ) sqlite3_str_appendf(&x, " isMaterialized");
+    if( pItem->fg.viaCoroutine )   sqlite3_str_appendf(&x, " viaCoroutine");
+    if( pItem->fg.notCte )         sqlite3_str_appendf(&x, " notCte");
+    if( pItem->fg.isNestedFrom )   sqlite3_str_appendf(&x, " isNestedFrom");
+
+    sqlite3StrAccumFinish(&x);
+    sqlite3TreeViewItem(pView, zLine, i<pSrc->nSrc-1);
+    n = 0;
+    if( pItem->pSelect ) n++;
+    if( pItem->fg.isTabFunc ) n++;
+    if( pItem->fg.isUsing ) n++;
+    if( pItem->fg.isUsing ){
+      sqlite3TreeViewIdList(pView, pItem->u3.pUsing, (--n)>0, "USING");
+    }
+    if( pItem->pSelect ){
+      if( pItem->pTab ){
+        Table *pTab = pItem->pTab;
+        sqlite3TreeViewColumnList(pView, pTab->aCol, pTab->nCol, 1);
+      }
+      assert( (int)pItem->fg.isNestedFrom == IsNestedFrom(pItem->pSelect) );
+      sqlite3TreeViewSelect(pView, pItem->pSelect, (--n)>0);
+    }
+    if( pItem->fg.isTabFunc ){
+      sqlite3TreeViewExprList(pView, pItem->u1.pFuncArg, 0, "func-args:");
+    }
+    sqlite3TreeViewPop(&pView);
+  }
+}
+
+/*
+** Generate a human-readable description of a Select object.
+*/
+void sqlite3TreeViewSelect(TreeView *pView, const Select *p, u8 moreToFollow){
+  int n = 0;
+  int cnt = 0;
+  if( p==0 ){
+    sqlite3TreeViewLine(pView, "nil-SELECT");
+    return;
+  } 
+  sqlite3TreeViewPush(&pView, moreToFollow);
+  if( p->pWith ){
+    sqlite3TreeViewWith(pView, p->pWith, 1);
+    cnt = 1;
+    sqlite3TreeViewPush(&pView, 1);
+  }
+  do{
+    if( p->selFlags & SF_WhereBegin ){
+      sqlite3TreeViewLine(pView, "sqlite3WhereBegin()");
+    }else{
+      sqlite3TreeViewLine(pView,
+        "SELECT%s%s (%u/%p) selFlags=0x%x nSelectRow=%d",
+        ((p->selFlags & SF_Distinct) ? " DISTINCT" : ""),
+        ((p->selFlags & SF_Aggregate) ? " agg_flag" : ""),
+        p->selId, p, p->selFlags,
+        (int)p->nSelectRow
+      );
+    }
+    if( cnt++ ) sqlite3TreeViewPop(&pView);
+    if( p->pPrior ){
+      n = 1000;
+    }else{
+      n = 0;
+      if( p->pSrc && p->pSrc->nSrc ) n++;
+      if( p->pWhere ) n++;
+      if( p->pGroupBy ) n++;
+      if( p->pHaving ) n++;
+      if( p->pOrderBy ) n++;
+      if( p->pLimit ) n++;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      if( p->pWin ) n++;
+      if( p->pWinDefn ) n++;
+#endif
+    }
+    if( p->pEList ){
+      sqlite3TreeViewExprList(pView, p->pEList, n>0, "result-set");
+    }
+    n--;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( p->pWin ){
+      Window *pX;
+      sqlite3TreeViewPush(&pView, (n--)>0);
+      sqlite3TreeViewLine(pView, "window-functions");
+      for(pX=p->pWin; pX; pX=pX->pNextWin){
+        sqlite3TreeViewWinFunc(pView, pX, pX->pNextWin!=0);
+      }
+      sqlite3TreeViewPop(&pView);
+    }
+#endif
+    if( p->pSrc && p->pSrc->nSrc ){
+      sqlite3TreeViewPush(&pView, (n--)>0);
+      sqlite3TreeViewLine(pView, "FROM");
+      sqlite3TreeViewSrcList(pView, p->pSrc);
+      sqlite3TreeViewPop(&pView);
+    }
+    if( p->pWhere ){
+      sqlite3TreeViewItem(pView, "WHERE", (n--)>0);
+      sqlite3TreeViewExpr(pView, p->pWhere, 0);
+      sqlite3TreeViewPop(&pView);
+    }
+    if( p->pGroupBy ){
+      sqlite3TreeViewExprList(pView, p->pGroupBy, (n--)>0, "GROUPBY");
+    }
+    if( p->pHaving ){
+      sqlite3TreeViewItem(pView, "HAVING", (n--)>0);
+      sqlite3TreeViewExpr(pView, p->pHaving, 0);
+      sqlite3TreeViewPop(&pView);
+    }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+    if( p->pWinDefn ){
+      Window *pX;
+      sqlite3TreeViewItem(pView, "WINDOW", (n--)>0);
+      for(pX=p->pWinDefn; pX; pX=pX->pNextWin){
+        sqlite3TreeViewWindow(pView, pX, pX->pNextWin!=0);
+      }
+      sqlite3TreeViewPop(&pView);
+    }
+#endif
+    if( p->pOrderBy ){
+      sqlite3TreeViewExprList(pView, p->pOrderBy, (n--)>0, "ORDERBY");
+    }
+    if( p->pLimit ){
+      sqlite3TreeViewItem(pView, "LIMIT", (n--)>0);
+      sqlite3TreeViewExpr(pView, p->pLimit->pLeft, p->pLimit->pRight!=0);
+      if( p->pLimit->pRight ){
+        sqlite3TreeViewItem(pView, "OFFSET", (n--)>0);
+        sqlite3TreeViewExpr(pView, p->pLimit->pRight, 0);
+        sqlite3TreeViewPop(&pView);
+      }
+      sqlite3TreeViewPop(&pView);
+    }
+    if( p->pPrior ){
+      const char *zOp = "UNION";
+      switch( p->op ){
+        case TK_ALL:         zOp = "UNION ALL";  break;
+        case TK_INTERSECT:   zOp = "INTERSECT";  break;
+        case TK_EXCEPT:      zOp = "EXCEPT";     break;
+      }
+      sqlite3TreeViewItem(pView, zOp, 1);
+    }
+    p = p->pPrior;
+  }while( p!=0 );
+  sqlite3TreeViewPop(&pView);
+}
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+/*
+** Generate a description of starting or stopping bounds
+*/
+void sqlite3TreeViewBound(
+  TreeView *pView,        /* View context */
+  u8 eBound,              /* UNBOUNDED, CURRENT, PRECEDING, FOLLOWING */
+  Expr *pExpr,            /* Value for PRECEDING or FOLLOWING */
+  u8 moreToFollow         /* True if more to follow */
+){
+  switch( eBound ){
+    case TK_UNBOUNDED: {
+      sqlite3TreeViewItem(pView, "UNBOUNDED", moreToFollow);
+      sqlite3TreeViewPop(&pView);
+      break;
+    }
+    case TK_CURRENT: {
+      sqlite3TreeViewItem(pView, "CURRENT", moreToFollow);
+      sqlite3TreeViewPop(&pView);
+      break;
+    }
+    case TK_PRECEDING: {
+      sqlite3TreeViewItem(pView, "PRECEDING", moreToFollow);
+      sqlite3TreeViewExpr(pView, pExpr, 0);
+      sqlite3TreeViewPop(&pView);
+      break;
+    }
+    case TK_FOLLOWING: {
+      sqlite3TreeViewItem(pView, "FOLLOWING", moreToFollow);
+      sqlite3TreeViewExpr(pView, pExpr, 0);
+      sqlite3TreeViewPop(&pView);
+      break;
+    }
+  }
+}
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+/*
+** Generate a human-readable explanation for a Window object
+*/
+void sqlite3TreeViewWindow(TreeView *pView, const Window *pWin, u8 more){
+  int nElement = 0;
+  if( pWin==0 ) return;
+  if( pWin->pFilter ){
+    sqlite3TreeViewItem(pView, "FILTER", 1);
+    sqlite3TreeViewExpr(pView, pWin->pFilter, 0);
+    sqlite3TreeViewPop(&pView);
+    if( pWin->eFrmType==TK_FILTER ) return;
+  }
+  sqlite3TreeViewPush(&pView, more);
+  if( pWin->zName ){
+    sqlite3TreeViewLine(pView, "OVER %s (%p)", pWin->zName, pWin);
+  }else{
+    sqlite3TreeViewLine(pView, "OVER (%p)", pWin);
+  }
+  if( pWin->zBase )    nElement++;
+  if( pWin->pOrderBy ) nElement++;
+  if( pWin->eFrmType!=0 && pWin->eFrmType!=TK_FILTER ) nElement++;
+  if( pWin->eExclude ) nElement++;
+  if( pWin->zBase ){
+    sqlite3TreeViewPush(&pView, (--nElement)>0);
+    sqlite3TreeViewLine(pView, "window: %s", pWin->zBase);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pWin->pPartition ){
+    sqlite3TreeViewExprList(pView, pWin->pPartition, nElement>0,"PARTITION-BY");
+  }
+  if( pWin->pOrderBy ){
+    sqlite3TreeViewExprList(pView, pWin->pOrderBy, (--nElement)>0, "ORDER-BY");
+  }
+  if( pWin->eFrmType!=0 && pWin->eFrmType!=TK_FILTER ){
+    char zBuf[30];
+    const char *zFrmType = "ROWS";
+    if( pWin->eFrmType==TK_RANGE ) zFrmType = "RANGE";
+    if( pWin->eFrmType==TK_GROUPS ) zFrmType = "GROUPS";
+    sqlite3_snprintf(sizeof(zBuf),zBuf,"%s%s",zFrmType,
+        pWin->bImplicitFrame ? " (implied)" : "");
+    sqlite3TreeViewItem(pView, zBuf, (--nElement)>0);
+    sqlite3TreeViewBound(pView, pWin->eStart, pWin->pStart, 1);
+    sqlite3TreeViewBound(pView, pWin->eEnd, pWin->pEnd, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pWin->eExclude ){
+    char zBuf[30];
+    const char *zExclude;
+    switch( pWin->eExclude ){
+      case TK_NO:      zExclude = "NO OTHERS";   break;
+      case TK_CURRENT: zExclude = "CURRENT ROW"; break;
+      case TK_GROUP:   zExclude = "GROUP";       break;
+      case TK_TIES:    zExclude = "TIES";        break;
+      default:
+        sqlite3_snprintf(sizeof(zBuf),zBuf,"invalid(%d)", pWin->eExclude);
+        zExclude = zBuf;
+        break;
+    }
+    sqlite3TreeViewPush(&pView, 0);
+    sqlite3TreeViewLine(pView, "EXCLUDE %s", zExclude);
+    sqlite3TreeViewPop(&pView);
+  }
+  sqlite3TreeViewPop(&pView);
+}
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+/*
+** Generate a human-readable explanation for a Window Function object
+*/
+void sqlite3TreeViewWinFunc(TreeView *pView, const Window *pWin, u8 more){
+  if( pWin==0 ) return;
+  sqlite3TreeViewPush(&pView, more);
+  sqlite3TreeViewLine(pView, "WINFUNC %s(%d)",
+                       pWin->pWFunc->zName, pWin->pWFunc->nArg);
+  sqlite3TreeViewWindow(pView, pWin, 0);
+  sqlite3TreeViewPop(&pView);
+}
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+/*
+** Generate a human-readable explanation of an expression tree.
+*/
+void sqlite3TreeViewExpr(TreeView *pView, const Expr *pExpr, u8 moreToFollow){
+  const char *zBinOp = 0;   /* Binary operator */
+  const char *zUniOp = 0;   /* Unary operator */
+  char zFlgs[200];
+  sqlite3TreeViewPush(&pView, moreToFollow);
+  if( pExpr==0 ){
+    sqlite3TreeViewLine(pView, "nil");
+    sqlite3TreeViewPop(&pView);
+    return;
+  }
+  if( pExpr->flags || pExpr->affExpr || pExpr->vvaFlags || pExpr->pAggInfo ){
+    StrAccum x;
+    sqlite3StrAccumInit(&x, 0, zFlgs, sizeof(zFlgs), 0);
+    sqlite3_str_appendf(&x, " fg.af=%x.%c",
+      pExpr->flags, pExpr->affExpr ? pExpr->affExpr : 'n');
+    if( ExprHasProperty(pExpr, EP_OuterON) ){
+      sqlite3_str_appendf(&x, " outer.iJoin=%d", pExpr->w.iJoin);
+    }
+    if( ExprHasProperty(pExpr, EP_InnerON) ){
+      sqlite3_str_appendf(&x, " inner.iJoin=%d", pExpr->w.iJoin);
+    }
+    if( ExprHasProperty(pExpr, EP_FromDDL) ){
+      sqlite3_str_appendf(&x, " DDL");
+    }
+    if( ExprHasVVAProperty(pExpr, EP_Immutable) ){
+      sqlite3_str_appendf(&x, " IMMUTABLE");
+    }
+    if( pExpr->pAggInfo!=0 ){
+      sqlite3_str_appendf(&x, " agg-column[%d]", pExpr->iAgg);
+    }
+    sqlite3StrAccumFinish(&x);
+  }else{
+    zFlgs[0] = 0;
+  }
+  switch( pExpr->op ){
+    case TK_AGG_COLUMN: {
+      sqlite3TreeViewLine(pView, "AGG{%d:%d}%s",
+            pExpr->iTable, pExpr->iColumn, zFlgs);
+      break;
+    }
+    case TK_COLUMN: {
+      if( pExpr->iTable<0 ){
+        /* This only happens when coding check constraints */
+        char zOp2[16];
+        if( pExpr->op2 ){
+          sqlite3_snprintf(sizeof(zOp2),zOp2," op2=0x%02x",pExpr->op2);
+        }else{
+          zOp2[0] = 0;
+        }
+        sqlite3TreeViewLine(pView, "COLUMN(%d)%s%s",
+                                    pExpr->iColumn, zFlgs, zOp2);
+      }else{
+        assert( ExprUseYTab(pExpr) );
+        sqlite3TreeViewLine(pView, "{%d:%d} pTab=%p%s",
+                        pExpr->iTable, pExpr->iColumn,
+                        pExpr->y.pTab, zFlgs);
+      }
+      if( ExprHasProperty(pExpr, EP_FixedCol) ){
+        sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      }
+      break;
+    }
+    case TK_INTEGER: {
+      if( pExpr->flags & EP_IntValue ){
+        sqlite3TreeViewLine(pView, "%d", pExpr->u.iValue);
+      }else{
+        sqlite3TreeViewLine(pView, "%s", pExpr->u.zToken);
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    case TK_FLOAT: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView,"%s", pExpr->u.zToken);
+      break;
+    }
+#endif
+    case TK_STRING: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView,"%Q", pExpr->u.zToken);
+      break;
+    }
+    case TK_NULL: {
+      sqlite3TreeViewLine(pView,"NULL");
+      break;
+    }
+    case TK_TRUEFALSE: {
+      sqlite3TreeViewLine(pView,"%s%s",
+         sqlite3ExprTruthValue(pExpr) ? "TRUE" : "FALSE", zFlgs);
+      break;
+    }
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+    case TK_BLOB: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView,"%s", pExpr->u.zToken);
+      break;
+    }
+#endif
+    case TK_VARIABLE: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView,"VARIABLE(%s,%d)",
+                          pExpr->u.zToken, pExpr->iColumn);
+      break;
+    }
+    case TK_REGISTER: {
+      sqlite3TreeViewLine(pView,"REGISTER(%d)", pExpr->iTable);
+      break;
+    }
+    case TK_ID: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView,"ID \"%w\"", pExpr->u.zToken);
+      break;
+    }
+#ifndef SQLITE_OMIT_CAST
+    case TK_CAST: {
+      /* Expressions of the form:   CAST(pLeft AS token) */
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView,"CAST %Q", pExpr->u.zToken);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
+#endif /* SQLITE_OMIT_CAST */
+    case TK_LT:      zBinOp = "LT";     break;
+    case TK_LE:      zBinOp = "LE";     break;
+    case TK_GT:      zBinOp = "GT";     break;
+    case TK_GE:      zBinOp = "GE";     break;
+    case TK_NE:      zBinOp = "NE";     break;
+    case TK_EQ:      zBinOp = "EQ";     break;
+    case TK_IS:      zBinOp = "IS";     break;
+    case TK_ISNOT:   zBinOp = "ISNOT";  break;
+    case TK_AND:     zBinOp = "AND";    break;
+    case TK_OR:      zBinOp = "OR";     break;
+    case TK_PLUS:    zBinOp = "ADD";    break;
+    case TK_STAR:    zBinOp = "MUL";    break;
+    case TK_MINUS:   zBinOp = "SUB";    break;
+    case TK_REM:     zBinOp = "REM";    break;
+    case TK_BITAND:  zBinOp = "BITAND"; break;
+    case TK_BITOR:   zBinOp = "BITOR";  break;
+    case TK_SLASH:   zBinOp = "DIV";    break;
+    case TK_LSHIFT:  zBinOp = "LSHIFT"; break;
+    case TK_RSHIFT:  zBinOp = "RSHIFT"; break;
+    case TK_CONCAT:  zBinOp = "CONCAT"; break;
+    case TK_DOT:     zBinOp = "DOT";    break;
+    case TK_LIMIT:   zBinOp = "LIMIT";  break;
+
+    case TK_UMINUS:  zUniOp = "UMINUS"; break;
+    case TK_UPLUS:   zUniOp = "UPLUS";  break;
+    case TK_BITNOT:  zUniOp = "BITNOT"; break;
+    case TK_NOT:     zUniOp = "NOT";    break;
+    case TK_ISNULL:  zUniOp = "ISNULL"; break;
+    case TK_NOTNULL: zUniOp = "NOTNULL"; break;
+
+    case TK_TRUTH: {
+      int x;
+      const char *azOp[] = {
+         "IS-FALSE", "IS-TRUE", "IS-NOT-FALSE", "IS-NOT-TRUE"
+      };
+      assert( pExpr->op2==TK_IS || pExpr->op2==TK_ISNOT );
+      assert( pExpr->pRight );
+      assert( sqlite3ExprSkipCollateAndLikely(pExpr->pRight)->op
+                  == TK_TRUEFALSE );
+      x = (pExpr->op2==TK_ISNOT)*2 + sqlite3ExprTruthValue(pExpr->pRight);
+      zUniOp = azOp[x];
+      break;
+    }
+
+    case TK_SPAN: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView, "SPAN %Q", pExpr->u.zToken);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
+
+    case TK_COLLATE: {
+      /* COLLATE operators without the EP_Collate flag are intended to
+      ** emulate collation associated with a table column.  These show
+      ** up in the treeview output as "SOFT-COLLATE".  Explicit COLLATE
+      ** operators that appear in the original SQL always have the
+      ** EP_Collate bit set and appear in treeview output as just "COLLATE" */
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView, "%sCOLLATE %Q%s",
+        !ExprHasProperty(pExpr, EP_Collate) ? "SOFT-" : "",
+        pExpr->u.zToken, zFlgs);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
+
+    case TK_AGG_FUNCTION:
+    case TK_FUNCTION: {
+      ExprList *pFarg;       /* List of function arguments */
+      Window *pWin;
+      if( ExprHasProperty(pExpr, EP_TokenOnly) ){
+        pFarg = 0;
+        pWin = 0;
+      }else{
+        assert( ExprUseXList(pExpr) );
+        pFarg = pExpr->x.pList;
+#ifndef SQLITE_OMIT_WINDOWFUNC
+        pWin = IsWindowFunc(pExpr) ? pExpr->y.pWin : 0;
+#else
+        pWin = 0;
+#endif 
+      }
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      if( pExpr->op==TK_AGG_FUNCTION ){
+        sqlite3TreeViewLine(pView, "AGG_FUNCTION%d %Q%s agg=%d[%d]/%p",
+                             pExpr->op2, pExpr->u.zToken, zFlgs,
+                             pExpr->pAggInfo ? pExpr->pAggInfo->selId : 0,
+                             pExpr->iAgg, pExpr->pAggInfo);
+      }else if( pExpr->op2!=0 ){
+        const char *zOp2;
+        char zBuf[8];
+        sqlite3_snprintf(sizeof(zBuf),zBuf,"0x%02x",pExpr->op2);
+        zOp2 = zBuf;
+        if( pExpr->op2==NC_IsCheck ) zOp2 = "NC_IsCheck";
+        if( pExpr->op2==NC_IdxExpr ) zOp2 = "NC_IdxExpr";
+        if( pExpr->op2==NC_PartIdx ) zOp2 = "NC_PartIdx";
+        if( pExpr->op2==NC_GenCol ) zOp2 = "NC_GenCol";
+        sqlite3TreeViewLine(pView, "FUNCTION %Q%s op2=%s",
+                            pExpr->u.zToken, zFlgs, zOp2);
+      }else{
+        sqlite3TreeViewLine(pView, "FUNCTION %Q%s", pExpr->u.zToken, zFlgs);
+      }
+      if( pFarg ){
+        sqlite3TreeViewExprList(pView, pFarg, pWin!=0 || pExpr->pLeft, 0);
+        if( pExpr->pLeft ){
+          Expr *pOB = pExpr->pLeft;
+          assert( pOB->op==TK_ORDER );
+          assert( ExprUseXList(pOB) );
+          sqlite3TreeViewExprList(pView, pOB->x.pList, pWin!=0, "ORDERBY");
+        }
+      }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      if( pWin ){
+        sqlite3TreeViewWindow(pView, pWin, 0);
+      }
+#endif
+      break;
+    }
+    case TK_ORDER: {
+      sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, "ORDERBY");
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_EXISTS: {
+      assert( ExprUseXSelect(pExpr) );
+      sqlite3TreeViewLine(pView, "EXISTS-expr flags=0x%x", pExpr->flags);
+      sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
+      break;
+    }
+    case TK_SELECT: {
+      assert( ExprUseXSelect(pExpr) );
+      sqlite3TreeViewLine(pView, "subquery-expr flags=0x%x", pExpr->flags);
+      sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
+      break;
+    }
+    case TK_IN: {
+      sqlite3_str *pStr = sqlite3_str_new(0);
+      char *z;
+      sqlite3_str_appendf(pStr, "IN flags=0x%x", pExpr->flags);
+      if( pExpr->iTable ) sqlite3_str_appendf(pStr, " iTable=%d",pExpr->iTable);
+      if( ExprHasProperty(pExpr, EP_Subrtn) ){
+        sqlite3_str_appendf(pStr, " subrtn(%d,%d)",
+            pExpr->y.sub.regReturn, pExpr->y.sub.iAddr);
+      }
+      z = sqlite3_str_finish(pStr);
+      sqlite3TreeViewLine(pView, z);
+      sqlite3_free(z);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
+      if( ExprUseXSelect(pExpr) ){
+        sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
+      }else{
+        sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, 0);
+      }
+      break;
+    }
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+    /*
+    **    x BETWEEN y AND z
+    **
+    ** This is equivalent to
+    **
+    **    x>=y AND x<=z
+    **
+    ** X is stored in pExpr->pLeft.
+    ** Y is stored in pExpr->pList->a[0].pExpr.
+    ** Z is stored in pExpr->pList->a[1].pExpr.
+    */
+    case TK_BETWEEN: {
+      const Expr *pX, *pY, *pZ;
+      pX = pExpr->pLeft;
+      assert( ExprUseXList(pExpr) );
+      assert( pExpr->x.pList->nExpr==2 );
+      pY = pExpr->x.pList->a[0].pExpr;
+      pZ = pExpr->x.pList->a[1].pExpr;
+      sqlite3TreeViewLine(pView, "BETWEEN%s", zFlgs);
+      sqlite3TreeViewExpr(pView, pX, 1);
+      sqlite3TreeViewExpr(pView, pY, 1);
+      sqlite3TreeViewExpr(pView, pZ, 0);
+      break;
+    }
+    case TK_TRIGGER: {
+      /* If the opcode is TK_TRIGGER, then the expression is a reference
+      ** to a column in the new.* or old.* pseudo-tables available to
+      ** trigger programs. In this case Expr.iTable is set to 1 for the
+      ** new.* pseudo-table, or 0 for the old.* pseudo-table. Expr.iColumn
+      ** is set to the column of the pseudo-table to read, or to -1 to
+      ** read the rowid field.
+      */
+      sqlite3TreeViewLine(pView, "%s(%d)", 
+          pExpr->iTable ? "NEW" : "OLD", pExpr->iColumn);
+      break;
+    }
+    case TK_CASE: {
+      sqlite3TreeViewLine(pView, "CASE");
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
+      assert( ExprUseXList(pExpr) );
+      sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, 0);
+      break;
+    }
+#ifndef SQLITE_OMIT_TRIGGER
+    case TK_RAISE: {
+      const char *zType = "unk";
+      switch( pExpr->affExpr ){
+        case OE_Rollback:   zType = "rollback";  break;
+        case OE_Abort:      zType = "abort";     break;
+        case OE_Fail:       zType = "fail";      break;
+        case OE_Ignore:     zType = "ignore";    break;
+      }
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3TreeViewLine(pView, "RAISE %s(%Q)", zType, pExpr->u.zToken);
+      break;
+    }
+#endif
+    case TK_MATCH: {
+      sqlite3TreeViewLine(pView, "MATCH {%d:%d}%s",
+                          pExpr->iTable, pExpr->iColumn, zFlgs);
+      sqlite3TreeViewExpr(pView, pExpr->pRight, 0);
+      break;
+    }
+    case TK_VECTOR: {
+      char *z = sqlite3_mprintf("VECTOR%s",zFlgs);
+      assert( ExprUseXList(pExpr) );
+      sqlite3TreeViewBareExprList(pView, pExpr->x.pList, z);
+      sqlite3_free(z);
+      break;
+    }
+    case TK_SELECT_COLUMN: {
+      sqlite3TreeViewLine(pView, "SELECT-COLUMN %d of [0..%d]%s",
+              pExpr->iColumn, pExpr->iTable-1,
+              pExpr->pRight==pExpr->pLeft ? " (SELECT-owner)" : "");
+      assert( ExprUseXSelect(pExpr->pLeft) );
+      sqlite3TreeViewSelect(pView, pExpr->pLeft->x.pSelect, 0);
+      break;
+    }
+    case TK_IF_NULL_ROW: {
+      sqlite3TreeViewLine(pView, "IF-NULL-ROW %d", pExpr->iTable);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
+    case TK_ERROR: {
+      Expr tmp;
+      sqlite3TreeViewLine(pView, "ERROR");
+      tmp = *pExpr;
+      tmp.op = pExpr->op2;
+      sqlite3TreeViewExpr(pView, &tmp, 0);
+      break;
+    }
+    case TK_ROW: {
+      if( pExpr->iColumn<=0 ){
+        sqlite3TreeViewLine(pView, "First FROM table rowid");
+      }else{
+        sqlite3TreeViewLine(pView, "First FROM table column %d",
+            pExpr->iColumn-1);
+      }
+      break;
+    }
+    default: {
+      sqlite3TreeViewLine(pView, "op=%d", pExpr->op);
+      break;
+    }
+  }
+  if( zBinOp ){
+    sqlite3TreeViewLine(pView, "%s%s", zBinOp, zFlgs);
+    sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
+    sqlite3TreeViewExpr(pView, pExpr->pRight, 0);
+  }else if( zUniOp ){
+    sqlite3TreeViewLine(pView, "%s%s", zUniOp, zFlgs);
+   sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+  }
+  sqlite3TreeViewPop(&pView);
+}
+
+
+/*
+** Generate a human-readable explanation of an expression list.
+*/
+void sqlite3TreeViewBareExprList(
+  TreeView *pView,
+  const ExprList *pList,
+  const char *zLabel
+){
+  if( zLabel==0 || zLabel[0]==0 ) zLabel = "LIST";
+  if( pList==0 ){
+    sqlite3TreeViewLine(pView, "%s (empty)", zLabel);
+  }else{
+    int i;
+    sqlite3TreeViewLine(pView, "%s", zLabel);
+    for(i=0; i<pList->nExpr; i++){
+      int j = pList->a[i].u.x.iOrderByCol;
+      char *zName = pList->a[i].zEName;
+      int moreToFollow = i<pList->nExpr - 1;
+      if( j || zName ){
+        sqlite3TreeViewPush(&pView, moreToFollow);
+        moreToFollow = 0;
+        sqlite3TreeViewLine(pView, 0);
+        if( zName ){
+          switch( pList->a[i].fg.eEName ){
+            default:
+              fprintf(stdout, "AS %s ", zName);
+              break;
+            case ENAME_TAB:
+              fprintf(stdout, "TABLE-ALIAS-NAME(\"%s\") ", zName);
+              if( pList->a[i].fg.bUsed ) fprintf(stdout, "(used) ");
+              if( pList->a[i].fg.bUsingTerm ) fprintf(stdout, "(USING-term) ");
+              if( pList->a[i].fg.bNoExpand ) fprintf(stdout, "(NoExpand) ");
+              break;
+            case ENAME_SPAN:
+              fprintf(stdout, "SPAN(\"%s\") ", zName);
+              break;
+          }
+        }
+        if( j ){
+          fprintf(stdout, "iOrderByCol=%d", j);
+        }
+        fprintf(stdout, "\n");
+        fflush(stdout);
+      }
+      sqlite3TreeViewExpr(pView, pList->a[i].pExpr, moreToFollow);
+      if( j || zName ){
+        sqlite3TreeViewPop(&pView);
+      }
+    }
+  }
+}
+void sqlite3TreeViewExprList(
+  TreeView *pView,
+  const ExprList *pList,
+  u8 moreToFollow,
+  const char *zLabel
+){
+  sqlite3TreeViewPush(&pView, moreToFollow);
+  sqlite3TreeViewBareExprList(pView, pList, zLabel);
+  sqlite3TreeViewPop(&pView);
+}
+
+/*
+** Generate a human-readable explanation of an id-list.
+*/
+void sqlite3TreeViewBareIdList(
+  TreeView *pView,
+  const IdList *pList,
+  const char *zLabel
+){
+  if( zLabel==0 || zLabel[0]==0 ) zLabel = "LIST";
+  if( pList==0 ){
+    sqlite3TreeViewLine(pView, "%s (empty)", zLabel);
+  }else{
+    int i;
+    sqlite3TreeViewLine(pView, "%s", zLabel);
+    for(i=0; i<pList->nId; i++){
+      char *zName = pList->a[i].zName;
+      int moreToFollow = i<pList->nId - 1;
+      if( zName==0 ) zName = "(null)";
+      sqlite3TreeViewPush(&pView, moreToFollow);
+      sqlite3TreeViewLine(pView, 0);
+      if( pList->eU4==EU4_NONE ){
+        fprintf(stdout, "%s\n", zName);
+      }else if( pList->eU4==EU4_IDX ){
+        fprintf(stdout, "%s (%d)\n", zName, pList->a[i].u4.idx);
+      }else{
+        assert( pList->eU4==EU4_EXPR );
+        if( pList->a[i].u4.pExpr==0 ){
+          fprintf(stdout, "%s (pExpr=NULL)\n", zName);
+        }else{
+          fprintf(stdout, "%s\n", zName);
+          sqlite3TreeViewPush(&pView, i<pList->nId-1);
+          sqlite3TreeViewExpr(pView, pList->a[i].u4.pExpr, 0);
+          sqlite3TreeViewPop(&pView);
+        }
+      }
+      sqlite3TreeViewPop(&pView);
+    }
+  }
+}
+void sqlite3TreeViewIdList(
+  TreeView *pView,
+  const IdList *pList,
+  u8 moreToFollow,
+  const char *zLabel
+){
+  sqlite3TreeViewPush(&pView, moreToFollow);
+  sqlite3TreeViewBareIdList(pView, pList, zLabel);
+  sqlite3TreeViewPop(&pView);
+}
+
+/*
+** Generate a human-readable explanation of a list of Upsert objects
+*/
+void sqlite3TreeViewUpsert(
+  TreeView *pView,
+  const Upsert *pUpsert,
+  u8 moreToFollow
+){
+  if( pUpsert==0 ) return;
+  sqlite3TreeViewPush(&pView, moreToFollow);
+  while( pUpsert ){
+    int n;
+    sqlite3TreeViewPush(&pView, pUpsert->pNextUpsert!=0 || moreToFollow);
+    sqlite3TreeViewLine(pView, "ON CONFLICT DO %s", 
+         pUpsert->isDoUpdate ? "UPDATE" : "NOTHING");
+    n = (pUpsert->pUpsertSet!=0) + (pUpsert->pUpsertWhere!=0);
+    sqlite3TreeViewExprList(pView, pUpsert->pUpsertTarget, (n--)>0, "TARGET");
+    sqlite3TreeViewExprList(pView, pUpsert->pUpsertSet, (n--)>0, "SET");
+    if( pUpsert->pUpsertWhere ){
+      sqlite3TreeViewItem(pView, "WHERE", (n--)>0);
+      sqlite3TreeViewExpr(pView, pUpsert->pUpsertWhere, 0);
+      sqlite3TreeViewPop(&pView);
+    }
+    sqlite3TreeViewPop(&pView);
+    pUpsert = pUpsert->pNextUpsert;
+  }
+  sqlite3TreeViewPop(&pView);
+}
+
+#if TREETRACE_ENABLED
+/*
+** Generate a human-readable diagram of the data structure that go
+** into generating an DELETE statement.
+*/
+void sqlite3TreeViewDelete(
+  const With *pWith,
+  const SrcList *pTabList,
+  const Expr *pWhere,
+  const ExprList *pOrderBy,
+  const Expr *pLimit,
+  const Trigger *pTrigger
+){
+  int n = 0;
+  TreeView *pView = 0;
+  sqlite3TreeViewPush(&pView, 0);
+  sqlite3TreeViewLine(pView, "DELETE");
+  if( pWith ) n++;
+  if( pTabList ) n++;
+  if( pWhere ) n++;
+  if( pOrderBy ) n++;
+  if( pLimit ) n++;
+  if( pTrigger ) n++;
+  if( pWith ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewWith(pView, pWith, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pTabList ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "FROM");
+    sqlite3TreeViewSrcList(pView, pTabList);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pWhere ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "WHERE");
+    sqlite3TreeViewExpr(pView, pWhere, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pOrderBy ){
+    sqlite3TreeViewExprList(pView, pOrderBy, (--n)>0, "ORDER-BY");
+  }
+  if( pLimit ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "LIMIT");
+    sqlite3TreeViewExpr(pView, pLimit, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pTrigger ){
+    sqlite3TreeViewTrigger(pView, pTrigger, (--n)>0, 1);
+  }
+  sqlite3TreeViewPop(&pView);
+}
+#endif /* TREETRACE_ENABLED */
+
+#if TREETRACE_ENABLED
+/*
+** Generate a human-readable diagram of the data structure that go
+** into generating an INSERT statement.
+*/
+void sqlite3TreeViewInsert(
+  const With *pWith,
+  const SrcList *pTabList,
+  const IdList *pColumnList,
+  const Select *pSelect,
+  const ExprList *pExprList,
+  int onError,
+  const Upsert *pUpsert,
+  const Trigger *pTrigger
+){
+  TreeView *pView = 0;
+  int n = 0;
+  const char *zLabel = "INSERT";
+  switch( onError ){
+    case OE_Replace:  zLabel = "REPLACE";             break;
+    case OE_Ignore:   zLabel = "INSERT OR IGNORE";    break;
+    case OE_Rollback: zLabel = "INSERT OR ROLLBACK";  break;
+    case OE_Abort:    zLabel = "INSERT OR ABORT";     break;
+    case OE_Fail:     zLabel = "INSERT OR FAIL";      break;
+  }
+  sqlite3TreeViewPush(&pView, 0);
+  sqlite3TreeViewLine(pView, zLabel);
+  if( pWith ) n++;
+  if( pTabList ) n++;
+  if( pColumnList ) n++;
+  if( pSelect ) n++;
+  if( pExprList ) n++;
+  if( pUpsert ) n++;
+  if( pTrigger ) n++;
+  if( pWith ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewWith(pView, pWith, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pTabList ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "INTO");
+    sqlite3TreeViewSrcList(pView, pTabList);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pColumnList ){
+    sqlite3TreeViewIdList(pView, pColumnList, (--n)>0, "COLUMNS");
+  }
+  if( pSelect ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "DATA-SOURCE");
+    sqlite3TreeViewSelect(pView, pSelect, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pExprList ){
+    sqlite3TreeViewExprList(pView, pExprList, (--n)>0, "VALUES");
+  }
+  if( pUpsert ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "UPSERT");
+    sqlite3TreeViewUpsert(pView, pUpsert, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pTrigger ){
+    sqlite3TreeViewTrigger(pView, pTrigger, (--n)>0, 1);
+  }
+  sqlite3TreeViewPop(&pView);
+}
+#endif /* TREETRACE_ENABLED */
+
+#if TREETRACE_ENABLED
+/*
+** Generate a human-readable diagram of the data structure that go
+** into generating an UPDATE statement.
+*/
+void sqlite3TreeViewUpdate(
+  const With *pWith,
+  const SrcList *pTabList,
+  const ExprList *pChanges,
+  const Expr *pWhere,
+  int onError,
+  const ExprList *pOrderBy,
+  const Expr *pLimit,
+  const Upsert *pUpsert,
+  const Trigger *pTrigger
+){
+  int n = 0;
+  TreeView *pView = 0;
+  const char *zLabel = "UPDATE";
+  switch( onError ){
+    case OE_Replace:  zLabel = "UPDATE OR REPLACE";   break;
+    case OE_Ignore:   zLabel = "UPDATE OR IGNORE";    break;
+    case OE_Rollback: zLabel = "UPDATE OR ROLLBACK";  break;
+    case OE_Abort:    zLabel = "UPDATE OR ABORT";     break;
+    case OE_Fail:     zLabel = "UPDATE OR FAIL";      break;
+  }
+  sqlite3TreeViewPush(&pView, 0);
+  sqlite3TreeViewLine(pView, zLabel);
+  if( pWith ) n++;
+  if( pTabList ) n++;
+  if( pChanges ) n++;
+  if( pWhere ) n++;
+  if( pOrderBy ) n++;
+  if( pLimit ) n++;
+  if( pUpsert ) n++;
+  if( pTrigger ) n++;
+  if( pWith ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewWith(pView, pWith, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pTabList ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "FROM");
+    sqlite3TreeViewSrcList(pView, pTabList);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pChanges ){
+    sqlite3TreeViewExprList(pView, pChanges, (--n)>0, "SET");
+  }
+  if( pWhere ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "WHERE");
+    sqlite3TreeViewExpr(pView, pWhere, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pOrderBy ){
+    sqlite3TreeViewExprList(pView, pOrderBy, (--n)>0, "ORDER-BY");
+  }
+  if( pLimit ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "LIMIT");
+    sqlite3TreeViewExpr(pView, pLimit, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pUpsert ){
+    sqlite3TreeViewPush(&pView, (--n)>0);
+    sqlite3TreeViewLine(pView, "UPSERT");
+    sqlite3TreeViewUpsert(pView, pUpsert, 0);
+    sqlite3TreeViewPop(&pView);
+  }
+  if( pTrigger ){
+    sqlite3TreeViewTrigger(pView, pTrigger, (--n)>0, 1);
+  }
+  sqlite3TreeViewPop(&pView);
+}
+#endif /* TREETRACE_ENABLED */
+
+#ifndef SQLITE_OMIT_TRIGGER
+/*
+** Show a human-readable graph of a TriggerStep
+*/
+void sqlite3TreeViewTriggerStep(
+  TreeView *pView,
+  const TriggerStep *pStep,
+  u8 moreToFollow,
+  u8 showFullList
+){
+  int cnt = 0;
+  if( pStep==0 ) return;
+  sqlite3TreeViewPush(&pView, 
+      moreToFollow || (showFullList && pStep->pNext!=0));
+  do{
+    if( cnt++ && pStep->pNext==0 ){
+      sqlite3TreeViewPop(&pView);
+      sqlite3TreeViewPush(&pView, 0);
+    }
+    sqlite3TreeViewLine(pView, "%s", pStep->zSpan ? pStep->zSpan : "RETURNING");
+  }while( showFullList && (pStep = pStep->pNext)!=0 );
+  sqlite3TreeViewPop(&pView);
+}
+  
+/*
+** Show a human-readable graph of a Trigger
+*/
+void sqlite3TreeViewTrigger(
+  TreeView *pView,
+  const Trigger *pTrigger,
+  u8 moreToFollow,
+  u8 showFullList
+){
+  int cnt = 0;
+  if( pTrigger==0 ) return;
+  sqlite3TreeViewPush(&pView,
+     moreToFollow || (showFullList && pTrigger->pNext!=0));
+  do{
+    if( cnt++ && pTrigger->pNext==0 ){
+      sqlite3TreeViewPop(&pView);
+      sqlite3TreeViewPush(&pView, 0);
+    }
+    sqlite3TreeViewLine(pView, "TRIGGER %s", pTrigger->zName);
+    sqlite3TreeViewPush(&pView, 0);
+    sqlite3TreeViewTriggerStep(pView, pTrigger->step_list, 0, 1);
+    sqlite3TreeViewPop(&pView);
+  }while( showFullList && (pTrigger = pTrigger->pNext)!=0 );
+  sqlite3TreeViewPop(&pView);
+}
+#endif /* SQLITE_OMIT_TRIGGER */
+  
+
+/*
+** These simplified versions of the tree-view routines omit unnecessary
+** parameters.  These variants are intended to be used from a symbolic
+** debugger, such as "gdb", during interactive debugging sessions.
+**
+** This routines are given external linkage so that they will always be
+** accessible to the debugging, and to avoid warnings about unused
+** functions.  But these routines only exist in debugging builds, so they
+** do not contaminate the interface.
+*/
+void sqlite3ShowExpr(const Expr *p){ sqlite3TreeViewExpr(0,p,0); }
+void sqlite3ShowExprList(const ExprList *p){ sqlite3TreeViewExprList(0,p,0,0);}
+void sqlite3ShowIdList(const IdList *p){ sqlite3TreeViewIdList(0,p,0,0); }
+void sqlite3ShowSrcList(const SrcList *p){ sqlite3TreeViewSrcList(0,p); }
+void sqlite3ShowSelect(const Select *p){ sqlite3TreeViewSelect(0,p,0); }
+void sqlite3ShowWith(const With *p){ sqlite3TreeViewWith(0,p,0); }
+void sqlite3ShowUpsert(const Upsert *p){ sqlite3TreeViewUpsert(0,p,0); }
+#ifndef SQLITE_OMIT_TRIGGER
+void sqlite3ShowTriggerStep(const TriggerStep *p){
+  sqlite3TreeViewTriggerStep(0,p,0,0);
+}
+void sqlite3ShowTriggerStepList(const TriggerStep *p){
+  sqlite3TreeViewTriggerStep(0,p,0,1);
+}
+void sqlite3ShowTrigger(const Trigger *p){ sqlite3TreeViewTrigger(0,p,0,0); }
+void sqlite3ShowTriggerList(const Trigger *p){ sqlite3TreeViewTrigger(0,p,0,1);}
+#endif
+#ifndef SQLITE_OMIT_WINDOWFUNC
+void sqlite3ShowWindow(const Window *p){ sqlite3TreeViewWindow(0,p,0); }
+void sqlite3ShowWinFunc(const Window *p){ sqlite3TreeViewWinFunc(0,p,0); }
+#endif
+
+#endif /* SQLITE_DEBUG */
diff --git a/src/trigger.c b/src/trigger.c
new file mode 100644
index 0000000..97ca249
--- /dev/null
+++ b/src/trigger.c
@@ -0,0 +1,1490 @@
+/*
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the implementation for TRIGGERs
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_TRIGGER
+/*
+** Delete a linked list of TriggerStep structures.
+*/
+void sqlite3DeleteTriggerStep(sqlite3 *db, TriggerStep *pTriggerStep){
+  while( pTriggerStep ){
+    TriggerStep * pTmp = pTriggerStep;
+    pTriggerStep = pTriggerStep->pNext;
+
+    sqlite3ExprDelete(db, pTmp->pWhere);
+    sqlite3ExprListDelete(db, pTmp->pExprList);
+    sqlite3SelectDelete(db, pTmp->pSelect);
+    sqlite3IdListDelete(db, pTmp->pIdList);
+    sqlite3UpsertDelete(db, pTmp->pUpsert);
+    sqlite3SrcListDelete(db, pTmp->pFrom);
+    sqlite3DbFree(db, pTmp->zSpan);
+
+    sqlite3DbFree(db, pTmp);
+  }
+}
+
+/*
+** Given table pTab, return a list of all the triggers attached to 
+** the table. The list is connected by Trigger.pNext pointers.
+**
+** All of the triggers on pTab that are in the same database as pTab
+** are already attached to pTab->pTrigger.  But there might be additional
+** triggers on pTab in the TEMP schema.  This routine prepends all
+** TEMP triggers on pTab to the beginning of the pTab->pTrigger list
+** and returns the combined list.
+**
+** To state it another way:  This routine returns a list of all triggers
+** that fire off of pTab.  The list will include any TEMP triggers on
+** pTab as well as the triggers lised in pTab->pTrigger.
+*/
+Trigger *sqlite3TriggerList(Parse *pParse, Table *pTab){
+  Schema *pTmpSchema;       /* Schema of the pTab table */
+  Trigger *pList;           /* List of triggers to return */
+  HashElem *p;              /* Loop variable for TEMP triggers */
+
+  assert( pParse->disableTriggers==0 );
+  pTmpSchema = pParse->db->aDb[1].pSchema;
+  p = sqliteHashFirst(&pTmpSchema->trigHash);
+  pList = pTab->pTrigger;
+  while( p ){
+    Trigger *pTrig = (Trigger *)sqliteHashData(p);
+    if( pTrig->pTabSchema==pTab->pSchema
+     && pTrig->table
+     && 0==sqlite3StrICmp(pTrig->table, pTab->zName)
+     && (pTrig->pTabSchema!=pTmpSchema || pTrig->bReturning)
+    ){
+      pTrig->pNext = pList;
+      pList = pTrig;
+    }else if( pTrig->op==TK_RETURNING ){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+      assert( pParse->db->pVtabCtx==0 );
+#endif
+      assert( pParse->bReturning );
+      assert( &(pParse->u1.pReturning->retTrig) == pTrig );
+      pTrig->table = pTab->zName;
+      pTrig->pTabSchema = pTab->pSchema;
+      pTrig->pNext = pList;
+      pList = pTrig;
+    }        
+    p = sqliteHashNext(p);    
+  }
+#if 0
+  if( pList ){
+    Trigger *pX;
+    printf("Triggers for %s:", pTab->zName);
+    for(pX=pList; pX; pX=pX->pNext){
+      printf(" %s", pX->zName);
+    }
+    printf("\n");
+    fflush(stdout);
+  }
+#endif
+  return pList;  
+}
+
+/*
+** This is called by the parser when it sees a CREATE TRIGGER statement
+** up to the point of the BEGIN before the trigger actions.  A Trigger
+** structure is generated based on the information available and stored
+** in pParse->pNewTrigger.  After the trigger actions have been parsed, the
+** sqlite3FinishTrigger() function is called to complete the trigger
+** construction process.
+*/
+void sqlite3BeginTrigger(
+  Parse *pParse,      /* The parse context of the CREATE TRIGGER statement */
+  Token *pName1,      /* The name of the trigger */
+  Token *pName2,      /* The name of the trigger */
+  int tr_tm,          /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD */
+  int op,             /* One of TK_INSERT, TK_UPDATE, TK_DELETE */
+  IdList *pColumns,   /* column list if this is an UPDATE OF trigger */
+  SrcList *pTableName,/* The name of the table/view the trigger applies to */
+  Expr *pWhen,        /* WHEN clause */
+  int isTemp,         /* True if the TEMPORARY keyword is present */
+  int noErr           /* Suppress errors if the trigger already exists */
+){
+  Trigger *pTrigger = 0;  /* The new trigger */
+  Table *pTab;            /* Table that the trigger fires off of */
+  char *zName = 0;        /* Name of the trigger */
+  sqlite3 *db = pParse->db;  /* The database connection */
+  int iDb;                /* The database to store the trigger in */
+  Token *pName;           /* The unqualified db name */
+  DbFixer sFix;           /* State vector for the DB fixer */
+
+  assert( pName1!=0 );   /* pName1->z might be NULL, but not pName1 itself */
+  assert( pName2!=0 );
+  assert( op==TK_INSERT || op==TK_UPDATE || op==TK_DELETE );
+  assert( op>0 && op<0xff );
+  if( isTemp ){
+    /* If TEMP was specified, then the trigger name may not be qualified. */
+    if( pName2->n>0 ){
+      sqlite3ErrorMsg(pParse, "temporary trigger may not have qualified name");
+      goto trigger_cleanup;
+    }
+    iDb = 1;
+    pName = pName1;
+  }else{
+    /* Figure out the db that the trigger will be created in */
+    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+    if( iDb<0 ){
+      goto trigger_cleanup;
+    }
+  }
+  if( !pTableName || db->mallocFailed ){
+    goto trigger_cleanup;
+  }
+
+  /* A long-standing parser bug is that this syntax was allowed:
+  **
+  **    CREATE TRIGGER attached.demo AFTER INSERT ON attached.tab ....
+  **                                                 ^^^^^^^^
+  **
+  ** To maintain backwards compatibility, ignore the database
+  ** name on pTableName if we are reparsing out of the schema table
+  */
+  if( db->init.busy && iDb!=1 ){
+    sqlite3DbFree(db, pTableName->a[0].zDatabase);
+    pTableName->a[0].zDatabase = 0;
+  }
+
+  /* If the trigger name was unqualified, and the table is a temp table,
+  ** then set iDb to 1 to create the trigger in the temporary database.
+  ** If sqlite3SrcListLookup() returns 0, indicating the table does not
+  ** exist, the error is caught by the block below.
+  */
+  pTab = sqlite3SrcListLookup(pParse, pTableName);
+  if( db->init.busy==0 && pName2->n==0 && pTab
+        && pTab->pSchema==db->aDb[1].pSchema ){
+    iDb = 1;
+  }
+
+  /* Ensure the table name matches database name and that the table exists */
+  if( db->mallocFailed ) goto trigger_cleanup;
+  assert( pTableName->nSrc==1 );
+  sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName);
+  if( sqlite3FixSrcList(&sFix, pTableName) ){
+    goto trigger_cleanup;
+  }
+  pTab = sqlite3SrcListLookup(pParse, pTableName);
+  if( !pTab ){
+    /* The table does not exist. */
+    goto trigger_orphan_error;
+  }
+  if( IsVirtual(pTab) ){
+    sqlite3ErrorMsg(pParse, "cannot create triggers on virtual tables");
+    goto trigger_orphan_error;
+  }
+  if( (pTab->tabFlags & TF_Shadow)!=0 && sqlite3ReadOnlyShadowTables(db) ){
+    sqlite3ErrorMsg(pParse, "cannot create triggers on shadow tables");
+    goto trigger_orphan_error;
+  }
+
+  /* Check that the trigger name is not reserved and that no trigger of the
+  ** specified name exists */
+  zName = sqlite3NameFromToken(db, pName);
+  if( zName==0 ){
+    assert( db->mallocFailed );
+    goto trigger_cleanup;
+  }
+  if( sqlite3CheckObjectName(pParse, zName, "trigger", pTab->zName) ){
+    goto trigger_cleanup;
+  }
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  if( !IN_RENAME_OBJECT ){
+    if( sqlite3HashFind(&(db->aDb[iDb].pSchema->trigHash),zName) ){
+      if( !noErr ){
+        sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);
+      }else{
+        assert( !db->init.busy );
+        sqlite3CodeVerifySchema(pParse, iDb);
+        VVA_ONLY( pParse->ifNotExists = 1; )
+      }
+      goto trigger_cleanup;
+    }
+  }
+
+  /* Do not create a trigger on a system table */
+  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
+    sqlite3ErrorMsg(pParse, "cannot create trigger on system table");
+    goto trigger_cleanup;
+  }
+
+  /* INSTEAD of triggers are only for views and views only support INSTEAD
+  ** of triggers.
+  */
+  if( IsView(pTab) && tr_tm!=TK_INSTEAD ){
+    sqlite3ErrorMsg(pParse, "cannot create %s trigger on view: %S", 
+        (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName->a);
+    goto trigger_orphan_error;
+  }
+  if( !IsView(pTab) && tr_tm==TK_INSTEAD ){
+    sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"
+        " trigger on table: %S", pTableName->a);
+    goto trigger_orphan_error;
+  }
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( !IN_RENAME_OBJECT ){
+    int iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    int code = SQLITE_CREATE_TRIGGER;
+    const char *zDb = db->aDb[iTabDb].zDbSName;
+    const char *zDbTrig = isTemp ? db->aDb[1].zDbSName : zDb;
+    if( iTabDb==1 || isTemp ) code = SQLITE_CREATE_TEMP_TRIGGER;
+    if( sqlite3AuthCheck(pParse, code, zName, pTab->zName, zDbTrig) ){
+      goto trigger_cleanup;
+    }
+    if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(iTabDb),0,zDb)){
+      goto trigger_cleanup;
+    }
+  }
+#endif
+
+  /* INSTEAD OF triggers can only appear on views and BEFORE triggers
+  ** cannot appear on views.  So we might as well translate every
+  ** INSTEAD OF trigger into a BEFORE trigger.  It simplifies code
+  ** elsewhere.
+  */
+  if (tr_tm == TK_INSTEAD){
+    tr_tm = TK_BEFORE;
+  }
+
+  /* Build the Trigger object */
+  pTrigger = (Trigger*)sqlite3DbMallocZero(db, sizeof(Trigger));
+  if( pTrigger==0 ) goto trigger_cleanup;
+  pTrigger->zName = zName;
+  zName = 0;
+  pTrigger->table = sqlite3DbStrDup(db, pTableName->a[0].zName);
+  pTrigger->pSchema = db->aDb[iDb].pSchema;
+  pTrigger->pTabSchema = pTab->pSchema;
+  pTrigger->op = (u8)op;
+  pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;
+  if( IN_RENAME_OBJECT ){
+    sqlite3RenameTokenRemap(pParse, pTrigger->table, pTableName->a[0].zName);
+    pTrigger->pWhen = pWhen;
+    pWhen = 0;
+  }else{
+    pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
+  }
+  pTrigger->pColumns = pColumns;
+  pColumns = 0;
+  assert( pParse->pNewTrigger==0 );
+  pParse->pNewTrigger = pTrigger;
+
+trigger_cleanup:
+  sqlite3DbFree(db, zName);
+  sqlite3SrcListDelete(db, pTableName);
+  sqlite3IdListDelete(db, pColumns);
+  sqlite3ExprDelete(db, pWhen);
+  if( !pParse->pNewTrigger ){
+    sqlite3DeleteTrigger(db, pTrigger);
+  }else{
+    assert( pParse->pNewTrigger==pTrigger );
+  }
+  return;
+
+trigger_orphan_error:
+  if( db->init.iDb==1 ){
+    /* Ticket #3810.
+    ** Normally, whenever a table is dropped, all associated triggers are
+    ** dropped too.  But if a TEMP trigger is created on a non-TEMP table
+    ** and the table is dropped by a different database connection, the
+    ** trigger is not visible to the database connection that does the
+    ** drop so the trigger cannot be dropped.  This results in an
+    ** "orphaned trigger" - a trigger whose associated table is missing.
+    **
+    ** 2020-11-05 see also https://sqlite.org/forum/forumpost/157dc791df
+    */
+    db->init.orphanTrigger = 1;
+  }
+  goto trigger_cleanup;
+}
+
+/*
+** This routine is called after all of the trigger actions have been parsed
+** in order to complete the process of building the trigger.
+*/
+void sqlite3FinishTrigger(
+  Parse *pParse,          /* Parser context */
+  TriggerStep *pStepList, /* The triggered program */
+  Token *pAll             /* Token that describes the complete CREATE TRIGGER */
+){
+  Trigger *pTrig = pParse->pNewTrigger;   /* Trigger being finished */
+  char *zName;                            /* Name of trigger */
+  sqlite3 *db = pParse->db;               /* The database */
+  DbFixer sFix;                           /* Fixer object */
+  int iDb;                                /* Database containing the trigger */
+  Token nameToken;                        /* Trigger name for error reporting */
+
+  pParse->pNewTrigger = 0;
+  if( NEVER(pParse->nErr) || !pTrig ) goto triggerfinish_cleanup;
+  zName = pTrig->zName;
+  iDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
+  pTrig->step_list = pStepList;
+  while( pStepList ){
+    pStepList->pTrig = pTrig;
+    pStepList = pStepList->pNext;
+  }
+  sqlite3TokenInit(&nameToken, pTrig->zName);
+  sqlite3FixInit(&sFix, pParse, iDb, "trigger", &nameToken);
+  if( sqlite3FixTriggerStep(&sFix, pTrig->step_list) 
+   || sqlite3FixExpr(&sFix, pTrig->pWhen) 
+  ){
+    goto triggerfinish_cleanup;
+  }
+
+#ifndef SQLITE_OMIT_ALTERTABLE
+  if( IN_RENAME_OBJECT ){
+    assert( !db->init.busy );
+    pParse->pNewTrigger = pTrig;
+    pTrig = 0;
+  }else
+#endif
+
+  /* if we are not initializing,
+  ** build the sqlite_schema entry
+  */
+  if( !db->init.busy ){
+    Vdbe *v;
+    char *z;
+
+    /* If this is a new CREATE TABLE statement, and if shadow tables
+    ** are read-only, and the trigger makes a change to a shadow table,
+    ** then raise an error - do not allow the trigger to be created. */
+    if( sqlite3ReadOnlyShadowTables(db) ){
+      TriggerStep *pStep;
+      for(pStep=pTrig->step_list; pStep; pStep=pStep->pNext){
+        if( pStep->zTarget!=0
+         && sqlite3ShadowTableName(db, pStep->zTarget)
+        ){
+          sqlite3ErrorMsg(pParse, 
+            "trigger \"%s\" may not write to shadow table \"%s\"",
+            pTrig->zName, pStep->zTarget);
+          goto triggerfinish_cleanup;
+        }
+      }
+    }
+
+    /* Make an entry in the sqlite_schema table */
+    v = sqlite3GetVdbe(pParse);
+    if( v==0 ) goto triggerfinish_cleanup;
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    z = sqlite3DbStrNDup(db, (char*)pAll->z, pAll->n);
+    testcase( z==0 );
+    sqlite3NestedParse(pParse,
+       "INSERT INTO %Q." LEGACY_SCHEMA_TABLE
+       " VALUES('trigger',%Q,%Q,0,'CREATE TRIGGER %q')",
+       db->aDb[iDb].zDbSName, zName,
+       pTrig->table, z);
+    sqlite3DbFree(db, z);
+    sqlite3ChangeCookie(pParse, iDb);
+    sqlite3VdbeAddParseSchemaOp(v, iDb,
+        sqlite3MPrintf(db, "type='trigger' AND name='%q'", zName), 0);
+  }
+
+  if( db->init.busy ){
+    Trigger *pLink = pTrig;
+    Hash *pHash = &db->aDb[iDb].pSchema->trigHash;
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    assert( pLink!=0 );
+    pTrig = sqlite3HashInsert(pHash, zName, pTrig);
+    if( pTrig ){
+      sqlite3OomFault(db);
+    }else if( pLink->pSchema==pLink->pTabSchema ){
+      Table *pTab;
+      pTab = sqlite3HashFind(&pLink->pTabSchema->tblHash, pLink->table);
+      assert( pTab!=0 );
+      pLink->pNext = pTab->pTrigger;
+      pTab->pTrigger = pLink;
+    }
+  }
+
+triggerfinish_cleanup:
+  sqlite3DeleteTrigger(db, pTrig);
+  assert( IN_RENAME_OBJECT || !pParse->pNewTrigger );
+  sqlite3DeleteTriggerStep(db, pStepList);
+}
+
+/*
+** Duplicate a range of text from an SQL statement, then convert all
+** whitespace characters into ordinary space characters.
+*/
+static char *triggerSpanDup(sqlite3 *db, const char *zStart, const char *zEnd){
+  char *z = sqlite3DbSpanDup(db, zStart, zEnd);
+  int i;
+  if( z ) for(i=0; z[i]; i++) if( sqlite3Isspace(z[i]) ) z[i] = ' ';
+  return z;
+}    
+
+/*
+** Turn a SELECT statement (that the pSelect parameter points to) into
+** a trigger step.  Return a pointer to a TriggerStep structure.
+**
+** The parser calls this routine when it finds a SELECT statement in
+** body of a TRIGGER.  
+*/
+TriggerStep *sqlite3TriggerSelectStep(
+  sqlite3 *db,                /* Database connection */
+  Select *pSelect,            /* The SELECT statement */
+  const char *zStart,         /* Start of SQL text */
+  const char *zEnd            /* End of SQL text */
+){
+  TriggerStep *pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep));
+  if( pTriggerStep==0 ) {
+    sqlite3SelectDelete(db, pSelect);
+    return 0;
+  }
+  pTriggerStep->op = TK_SELECT;
+  pTriggerStep->pSelect = pSelect;
+  pTriggerStep->orconf = OE_Default;
+  pTriggerStep->zSpan = triggerSpanDup(db, zStart, zEnd);
+  return pTriggerStep;
+}
+
+/*
+** Allocate space to hold a new trigger step.  The allocated space
+** holds both the TriggerStep object and the TriggerStep.target.z string.
+**
+** If an OOM error occurs, NULL is returned and db->mallocFailed is set.
+*/
+static TriggerStep *triggerStepAllocate(
+  Parse *pParse,              /* Parser context */
+  u8 op,                      /* Trigger opcode */
+  Token *pName,               /* The target name */
+  const char *zStart,         /* Start of SQL text */
+  const char *zEnd            /* End of SQL text */
+){
+  sqlite3 *db = pParse->db;
+  TriggerStep *pTriggerStep;
+
+  if( pParse->nErr ) return 0;
+  pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep) + pName->n + 1);
+  if( pTriggerStep ){
+    char *z = (char*)&pTriggerStep[1];
+    memcpy(z, pName->z, pName->n);
+    sqlite3Dequote(z);
+    pTriggerStep->zTarget = z;
+    pTriggerStep->op = op;
+    pTriggerStep->zSpan = triggerSpanDup(db, zStart, zEnd);
+    if( IN_RENAME_OBJECT ){
+      sqlite3RenameTokenMap(pParse, pTriggerStep->zTarget, pName);
+    }
+  }
+  return pTriggerStep;
+}
+
+/*
+** Build a trigger step out of an INSERT statement.  Return a pointer
+** to the new trigger step.
+**
+** The parser calls this routine when it sees an INSERT inside the
+** body of a trigger.
+*/
+TriggerStep *sqlite3TriggerInsertStep(
+  Parse *pParse,      /* Parser */
+  Token *pTableName,  /* Name of the table into which we insert */
+  IdList *pColumn,    /* List of columns in pTableName to insert into */
+  Select *pSelect,    /* A SELECT statement that supplies values */
+  u8 orconf,          /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */
+  Upsert *pUpsert,    /* ON CONFLICT clauses for upsert */
+  const char *zStart, /* Start of SQL text */
+  const char *zEnd    /* End of SQL text */
+){
+  sqlite3 *db = pParse->db;
+  TriggerStep *pTriggerStep;
+
+  assert(pSelect != 0 || db->mallocFailed);
+
+  pTriggerStep = triggerStepAllocate(pParse, TK_INSERT, pTableName,zStart,zEnd);
+  if( pTriggerStep ){
+    if( IN_RENAME_OBJECT ){
+      pTriggerStep->pSelect = pSelect;
+      pSelect = 0;
+    }else{
+      pTriggerStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
+    }
+    pTriggerStep->pIdList = pColumn;
+    pTriggerStep->pUpsert = pUpsert;
+    pTriggerStep->orconf = orconf;
+    if( pUpsert ){
+      sqlite3HasExplicitNulls(pParse, pUpsert->pUpsertTarget);
+    }
+  }else{
+    testcase( pColumn );
+    sqlite3IdListDelete(db, pColumn);
+    testcase( pUpsert );
+    sqlite3UpsertDelete(db, pUpsert);
+  }
+  sqlite3SelectDelete(db, pSelect);
+
+  return pTriggerStep;
+}
+
+/*
+** Construct a trigger step that implements an UPDATE statement and return
+** a pointer to that trigger step.  The parser calls this routine when it
+** sees an UPDATE statement inside the body of a CREATE TRIGGER.
+*/
+TriggerStep *sqlite3TriggerUpdateStep(
+  Parse *pParse,          /* Parser */
+  Token *pTableName,   /* Name of the table to be updated */
+  SrcList *pFrom,      /* FROM clause for an UPDATE-FROM, or NULL */
+  ExprList *pEList,    /* The SET clause: list of column and new values */
+  Expr *pWhere,        /* The WHERE clause */
+  u8 orconf,           /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
+  const char *zStart,  /* Start of SQL text */
+  const char *zEnd     /* End of SQL text */
+){
+  sqlite3 *db = pParse->db;
+  TriggerStep *pTriggerStep;
+
+  pTriggerStep = triggerStepAllocate(pParse, TK_UPDATE, pTableName,zStart,zEnd);
+  if( pTriggerStep ){
+    if( IN_RENAME_OBJECT ){
+      pTriggerStep->pExprList = pEList;
+      pTriggerStep->pWhere = pWhere;
+      pTriggerStep->pFrom = pFrom;
+      pEList = 0;
+      pWhere = 0;
+      pFrom = 0;
+    }else{
+      pTriggerStep->pExprList = sqlite3ExprListDup(db, pEList, EXPRDUP_REDUCE);
+      pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
+      pTriggerStep->pFrom = sqlite3SrcListDup(db, pFrom, EXPRDUP_REDUCE);
+    }
+    pTriggerStep->orconf = orconf;
+  }
+  sqlite3ExprListDelete(db, pEList);
+  sqlite3ExprDelete(db, pWhere);
+  sqlite3SrcListDelete(db, pFrom);
+  return pTriggerStep;
+}
+
+/*
+** Construct a trigger step that implements a DELETE statement and return
+** a pointer to that trigger step.  The parser calls this routine when it
+** sees a DELETE statement inside the body of a CREATE TRIGGER.
+*/
+TriggerStep *sqlite3TriggerDeleteStep(
+  Parse *pParse,          /* Parser */
+  Token *pTableName,      /* The table from which rows are deleted */
+  Expr *pWhere,           /* The WHERE clause */
+  const char *zStart,     /* Start of SQL text */
+  const char *zEnd        /* End of SQL text */
+){
+  sqlite3 *db = pParse->db;
+  TriggerStep *pTriggerStep;
+
+  pTriggerStep = triggerStepAllocate(pParse, TK_DELETE, pTableName,zStart,zEnd);
+  if( pTriggerStep ){
+    if( IN_RENAME_OBJECT ){
+      pTriggerStep->pWhere = pWhere;
+      pWhere = 0;
+    }else{
+      pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
+    }
+    pTriggerStep->orconf = OE_Default;
+  }
+  sqlite3ExprDelete(db, pWhere);
+  return pTriggerStep;
+}
+
+/* 
+** Recursively delete a Trigger structure
+*/
+void sqlite3DeleteTrigger(sqlite3 *db, Trigger *pTrigger){
+  if( pTrigger==0 || pTrigger->bReturning ) return;
+  sqlite3DeleteTriggerStep(db, pTrigger->step_list);
+  sqlite3DbFree(db, pTrigger->zName);
+  sqlite3DbFree(db, pTrigger->table);
+  sqlite3ExprDelete(db, pTrigger->pWhen);
+  sqlite3IdListDelete(db, pTrigger->pColumns);
+  sqlite3DbFree(db, pTrigger);
+}
+
+/*
+** This function is called to drop a trigger from the database schema. 
+**
+** This may be called directly from the parser and therefore identifies
+** the trigger by name.  The sqlite3DropTriggerPtr() routine does the
+** same job as this routine except it takes a pointer to the trigger
+** instead of the trigger name.
+**/
+void sqlite3DropTrigger(Parse *pParse, SrcList *pName, int noErr){
+  Trigger *pTrigger = 0;
+  int i;
+  const char *zDb;
+  const char *zName;
+  sqlite3 *db = pParse->db;
+
+  if( db->mallocFailed ) goto drop_trigger_cleanup;
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    goto drop_trigger_cleanup;
+  }
+
+  assert( pName->nSrc==1 );
+  zDb = pName->a[0].zDatabase;
+  zName = pName->a[0].zName;
+  assert( zDb!=0 || sqlite3BtreeHoldsAllMutexes(db) );
+  for(i=OMIT_TEMPDB; i<db->nDb; i++){
+    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
+    if( zDb && sqlite3DbIsNamed(db, j, zDb)==0 ) continue;
+    assert( sqlite3SchemaMutexHeld(db, j, 0) );
+    pTrigger = sqlite3HashFind(&(db->aDb[j].pSchema->trigHash), zName);
+    if( pTrigger ) break;
+  }
+  if( !pTrigger ){
+    if( !noErr ){
+      sqlite3ErrorMsg(pParse, "no such trigger: %S", pName->a);
+    }else{
+      sqlite3CodeVerifyNamedSchema(pParse, zDb);
+    }
+    pParse->checkSchema = 1;
+    goto drop_trigger_cleanup;
+  }
+  sqlite3DropTriggerPtr(pParse, pTrigger);
+
+drop_trigger_cleanup:
+  sqlite3SrcListDelete(db, pName);
+}
+
+/*
+** Return a pointer to the Table structure for the table that a trigger
+** is set on.
+*/
+static Table *tableOfTrigger(Trigger *pTrigger){
+  return sqlite3HashFind(&pTrigger->pTabSchema->tblHash, pTrigger->table);
+}
+
+
+/*
+** Drop a trigger given a pointer to that trigger. 
+*/
+void sqlite3DropTriggerPtr(Parse *pParse, Trigger *pTrigger){
+  Table   *pTable;
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  iDb = sqlite3SchemaToIndex(pParse->db, pTrigger->pSchema);
+  assert( iDb>=0 && iDb<db->nDb );
+  pTable = tableOfTrigger(pTrigger);
+  assert( (pTable && pTable->pSchema==pTrigger->pSchema) || iDb==1 );
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( pTable ){
+    int code = SQLITE_DROP_TRIGGER;
+    const char *zDb = db->aDb[iDb].zDbSName;
+    const char *zTab = SCHEMA_TABLE(iDb);
+    if( iDb==1 ) code = SQLITE_DROP_TEMP_TRIGGER;
+    if( sqlite3AuthCheck(pParse, code, pTrigger->zName, pTable->zName, zDb) ||
+      sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
+      return;
+    }
+  }
+#endif
+
+  /* Generate code to destroy the database record of the trigger.
+  */
+  if( (v = sqlite3GetVdbe(pParse))!=0 ){
+    sqlite3NestedParse(pParse,
+       "DELETE FROM %Q." LEGACY_SCHEMA_TABLE " WHERE name=%Q AND type='trigger'",
+       db->aDb[iDb].zDbSName, pTrigger->zName
+    );
+    sqlite3ChangeCookie(pParse, iDb);
+    sqlite3VdbeAddOp4(v, OP_DropTrigger, iDb, 0, 0, pTrigger->zName, 0);
+  }
+}
+
+/*
+** Remove a trigger from the hash tables of the sqlite* pointer.
+*/
+void sqlite3UnlinkAndDeleteTrigger(sqlite3 *db, int iDb, const char *zName){
+  Trigger *pTrigger;
+  Hash *pHash;
+
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  pHash = &(db->aDb[iDb].pSchema->trigHash);
+  pTrigger = sqlite3HashInsert(pHash, zName, 0);
+  if( ALWAYS(pTrigger) ){
+    if( pTrigger->pSchema==pTrigger->pTabSchema ){
+      Table *pTab = tableOfTrigger(pTrigger);
+      if( pTab ){
+        Trigger **pp;
+        for(pp=&pTab->pTrigger; *pp; pp=&((*pp)->pNext)){
+          if( *pp==pTrigger ){
+            *pp = (*pp)->pNext;
+            break;
+          }
+        }
+      }
+    }
+    sqlite3DeleteTrigger(db, pTrigger);
+    db->mDbFlags |= DBFLAG_SchemaChange;
+  }
+}
+
+/*
+** pEList is the SET clause of an UPDATE statement.  Each entry
+** in pEList is of the format <id>=<expr>.  If any of the entries
+** in pEList have an <id> which matches an identifier in pIdList,
+** then return TRUE.  If pIdList==NULL, then it is considered a
+** wildcard that matches anything.  Likewise if pEList==NULL then
+** it matches anything so always return true.  Return false only
+** if there is no match.
+*/
+static int checkColumnOverlap(IdList *pIdList, ExprList *pEList){
+  int e;
+  if( pIdList==0 || NEVER(pEList==0) ) return 1;
+  for(e=0; e<pEList->nExpr; e++){
+    if( sqlite3IdListIndex(pIdList, pEList->a[e].zEName)>=0 ) return 1;
+  }
+  return 0; 
+}
+
+/*
+** Return true if any TEMP triggers exist
+*/
+static int tempTriggersExist(sqlite3 *db){
+  if( NEVER(db->aDb[1].pSchema==0) ) return 0;
+  if( sqliteHashFirst(&db->aDb[1].pSchema->trigHash)==0 ) return 0;
+  return 1;
+}
+
+/*
+** Return a list of all triggers on table pTab if there exists at least
+** one trigger that must be fired when an operation of type 'op' is 
+** performed on the table, and, if that operation is an UPDATE, if at
+** least one of the columns in pChanges is being modified.
+*/
+static SQLITE_NOINLINE Trigger *triggersReallyExist(
+  Parse *pParse,          /* Parse context */
+  Table *pTab,            /* The table the contains the triggers */
+  int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */
+  ExprList *pChanges,     /* Columns that change in an UPDATE statement */
+  int *pMask              /* OUT: Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
+){
+  int mask = 0;
+  Trigger *pList = 0;
+  Trigger *p;
+
+  pList = sqlite3TriggerList(pParse, pTab);
+  assert( pList==0 || IsVirtual(pTab)==0 
+           || (pList->bReturning && pList->pNext==0) );
+  if( pList!=0 ){
+    p = pList;
+    if( (pParse->db->flags & SQLITE_EnableTrigger)==0
+     && pTab->pTrigger!=0
+    ){
+      /* The SQLITE_DBCONFIG_ENABLE_TRIGGER setting is off.  That means that
+      ** only TEMP triggers are allowed.  Truncate the pList so that it
+      ** includes only TEMP triggers */
+      if( pList==pTab->pTrigger ){
+        pList = 0;
+        goto exit_triggers_exist;
+      }
+      while( ALWAYS(p->pNext) && p->pNext!=pTab->pTrigger ) p = p->pNext;
+      p->pNext = 0;
+      p = pList;
+    }
+    do{
+      if( p->op==op && checkColumnOverlap(p->pColumns, pChanges) ){
+        mask |= p->tr_tm;
+      }else if( p->op==TK_RETURNING ){
+        /* The first time a RETURNING trigger is seen, the "op" value tells
+        ** us what time of trigger it should be. */
+        assert( sqlite3IsToplevel(pParse) );
+        p->op = op;
+        if( IsVirtual(pTab) ){
+          if( op!=TK_INSERT ){
+            sqlite3ErrorMsg(pParse,
+              "%s RETURNING is not available on virtual tables",
+              op==TK_DELETE ? "DELETE" : "UPDATE");
+          }
+          p->tr_tm = TRIGGER_BEFORE;
+        }else{
+          p->tr_tm = TRIGGER_AFTER;
+        }
+        mask |= p->tr_tm;
+      }else if( p->bReturning && p->op==TK_INSERT && op==TK_UPDATE
+                && sqlite3IsToplevel(pParse) ){
+        /* Also fire a RETURNING trigger for an UPSERT */
+        mask |= p->tr_tm;
+      }
+      p = p->pNext;
+    }while( p );
+  }
+exit_triggers_exist:
+  if( pMask ){
+    *pMask = mask;
+  }
+  return (mask ? pList : 0);
+}
+Trigger *sqlite3TriggersExist(
+  Parse *pParse,          /* Parse context */
+  Table *pTab,            /* The table the contains the triggers */
+  int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */
+  ExprList *pChanges,     /* Columns that change in an UPDATE statement */
+  int *pMask              /* OUT: Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
+){
+  assert( pTab!=0 );
+  if( (pTab->pTrigger==0 && !tempTriggersExist(pParse->db))
+   || pParse->disableTriggers
+  ){
+    if( pMask ) *pMask = 0;
+    return 0;
+  }
+  return triggersReallyExist(pParse,pTab,op,pChanges,pMask);
+}
+
+/*
+** Convert the pStep->zTarget string into a SrcList and return a pointer
+** to that SrcList.
+**
+** This routine adds a specific database name, if needed, to the target when
+** forming the SrcList.  This prevents a trigger in one database from
+** referring to a target in another database.  An exception is when the
+** trigger is in TEMP in which case it can refer to any other database it
+** wants.
+*/
+SrcList *sqlite3TriggerStepSrc(
+  Parse *pParse,       /* The parsing context */
+  TriggerStep *pStep   /* The trigger containing the target token */
+){
+  sqlite3 *db = pParse->db;
+  SrcList *pSrc;                  /* SrcList to be returned */
+  char *zName = sqlite3DbStrDup(db, pStep->zTarget);
+  pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
+  assert( pSrc==0 || pSrc->nSrc==1 );
+  assert( zName || pSrc==0 );
+  if( pSrc ){
+    Schema *pSchema = pStep->pTrig->pSchema;
+    pSrc->a[0].zName = zName;
+    if( pSchema!=db->aDb[1].pSchema ){
+      pSrc->a[0].pSchema = pSchema;
+    }
+    if( pStep->pFrom ){
+      SrcList *pDup = sqlite3SrcListDup(db, pStep->pFrom, 0);
+      if( pDup && pDup->nSrc>1 && !IN_RENAME_OBJECT ){
+        Select *pSubquery;
+        Token as;
+        pSubquery = sqlite3SelectNew(pParse,0,pDup,0,0,0,0,SF_NestedFrom,0);
+        as.n = 0;
+        as.z = 0;
+        pDup = sqlite3SrcListAppendFromTerm(pParse,0,0,0,&as,pSubquery,0);
+      }
+      pSrc = sqlite3SrcListAppendList(pParse, pSrc, pDup);
+    }
+  }else{
+    sqlite3DbFree(db, zName);
+  }
+  return pSrc;
+}
+
+/*
+** Return true if the pExpr term from the RETURNING clause argument
+** list is of the form "*".  Raise an error if the terms if of the
+** form "table.*".
+*/
+static int isAsteriskTerm(
+  Parse *pParse,      /* Parsing context */
+  Expr *pTerm         /* A term in the RETURNING clause */
+){
+  assert( pTerm!=0 );
+  if( pTerm->op==TK_ASTERISK ) return 1;
+  if( pTerm->op!=TK_DOT ) return 0;
+  assert( pTerm->pRight!=0 );
+  assert( pTerm->pLeft!=0 );
+  if( pTerm->pRight->op!=TK_ASTERISK ) return 0;
+  sqlite3ErrorMsg(pParse, "RETURNING may not use \"TABLE.*\" wildcards");
+  return 1;
+}
+
+/* The input list pList is the list of result set terms from a RETURNING
+** clause.  The table that we are returning from is pTab.
+**
+** This routine makes a copy of the pList, and at the same time expands
+** any "*" wildcards to be the complete set of columns from pTab.
+*/
+static ExprList *sqlite3ExpandReturning(
+  Parse *pParse,        /* Parsing context */
+  ExprList *pList,      /* The arguments to RETURNING */
+  Table *pTab           /* The table being updated */
+){
+  ExprList *pNew = 0;
+  sqlite3 *db = pParse->db;
+  int i;
+
+  for(i=0; i<pList->nExpr; i++){
+    Expr *pOldExpr = pList->a[i].pExpr;
+    if( NEVER(pOldExpr==0) ) continue;
+    if( isAsteriskTerm(pParse, pOldExpr) ){
+      int jj;
+      for(jj=0; jj<pTab->nCol; jj++){
+        Expr *pNewExpr;
+        if( IsHiddenColumn(pTab->aCol+jj) ) continue;
+        pNewExpr = sqlite3Expr(db, TK_ID, pTab->aCol[jj].zCnName);
+        pNew = sqlite3ExprListAppend(pParse, pNew, pNewExpr);
+        if( !db->mallocFailed ){
+          struct ExprList_item *pItem = &pNew->a[pNew->nExpr-1];
+          pItem->zEName = sqlite3DbStrDup(db, pTab->aCol[jj].zCnName);
+          pItem->fg.eEName = ENAME_NAME;
+        }
+      }
+    }else{
+      Expr *pNewExpr = sqlite3ExprDup(db, pOldExpr, 0);
+      pNew = sqlite3ExprListAppend(pParse, pNew, pNewExpr);
+      if( !db->mallocFailed && ALWAYS(pList->a[i].zEName!=0) ){
+        struct ExprList_item *pItem = &pNew->a[pNew->nExpr-1];
+        pItem->zEName = sqlite3DbStrDup(db, pList->a[i].zEName);
+        pItem->fg.eEName = pList->a[i].fg.eEName;
+      }
+    }
+  }
+  return pNew;
+}
+
+/*
+** Generate code for the RETURNING trigger.  Unlike other triggers
+** that invoke a subprogram in the bytecode, the code for RETURNING
+** is generated in-line.
+*/
+static void codeReturningTrigger(
+  Parse *pParse,       /* Parse context */
+  Trigger *pTrigger,   /* The trigger step that defines the RETURNING */
+  Table *pTab,         /* The table to code triggers from */
+  int regIn            /* The first in an array of registers */
+){
+  Vdbe *v = pParse->pVdbe;
+  sqlite3 *db = pParse->db;
+  ExprList *pNew;
+  Returning *pReturning;
+  Select sSelect;
+  SrcList sFrom;
+
+  assert( v!=0 );
+  if( !pParse->bReturning ){
+    /* This RETURNING trigger must be for a different statement as
+    ** this statement lacks a RETURNING clause. */
+    return;
+  }
+  assert( db->pParse==pParse );
+  pReturning = pParse->u1.pReturning;
+  if( pTrigger != &(pReturning->retTrig) ){
+    /* This RETURNING trigger is for a different statement */
+    return;
+  }
+  memset(&sSelect, 0, sizeof(sSelect));
+  memset(&sFrom, 0, sizeof(sFrom));
+  sSelect.pEList = sqlite3ExprListDup(db, pReturning->pReturnEL, 0);
+  sSelect.pSrc = &sFrom;
+  sFrom.nSrc = 1;
+  sFrom.a[0].pTab = pTab;
+  sFrom.a[0].iCursor = -1;
+  sqlite3SelectPrep(pParse, &sSelect, 0);
+  if( pParse->nErr==0 ){
+    assert( db->mallocFailed==0 );
+    sqlite3GenerateColumnNames(pParse, &sSelect);
+  }
+  sqlite3ExprListDelete(db, sSelect.pEList);
+  pNew = sqlite3ExpandReturning(pParse, pReturning->pReturnEL, pTab);
+  if( pParse->nErr==0 ){
+    NameContext sNC;
+    memset(&sNC, 0, sizeof(sNC));
+    if( pReturning->nRetCol==0 ){
+      pReturning->nRetCol = pNew->nExpr;
+      pReturning->iRetCur = pParse->nTab++;
+    }
+    sNC.pParse = pParse;
+    sNC.uNC.iBaseReg = regIn;
+    sNC.ncFlags = NC_UBaseReg;
+    pParse->eTriggerOp = pTrigger->op;
+    pParse->pTriggerTab = pTab;
+    if( sqlite3ResolveExprListNames(&sNC, pNew)==SQLITE_OK
+     && ALWAYS(!db->mallocFailed)
+    ){
+      int i;
+      int nCol = pNew->nExpr;
+      int reg = pParse->nMem+1;
+      pParse->nMem += nCol+2;
+      pReturning->iRetReg = reg;
+      for(i=0; i<nCol; i++){
+        Expr *pCol = pNew->a[i].pExpr;
+        assert( pCol!=0 ); /* Due to !db->mallocFailed ~9 lines above */
+        sqlite3ExprCodeFactorable(pParse, pCol, reg+i);
+        if( sqlite3ExprAffinity(pCol)==SQLITE_AFF_REAL ){
+          sqlite3VdbeAddOp1(v, OP_RealAffinity, reg+i);
+        }
+      }
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, reg, i, reg+i);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, pReturning->iRetCur, reg+i+1);
+      sqlite3VdbeAddOp3(v, OP_Insert, pReturning->iRetCur, reg+i, reg+i+1);
+    }
+  }
+  sqlite3ExprListDelete(db, pNew);
+  pParse->eTriggerOp = 0;
+  pParse->pTriggerTab = 0;
+}
+
+
+
+/*
+** Generate VDBE code for the statements inside the body of a single 
+** trigger.
+*/
+static int codeTriggerProgram(
+  Parse *pParse,            /* The parser context */
+  TriggerStep *pStepList,   /* List of statements inside the trigger body */
+  int orconf                /* Conflict algorithm. (OE_Abort, etc) */  
+){
+  TriggerStep *pStep;
+  Vdbe *v = pParse->pVdbe;
+  sqlite3 *db = pParse->db;
+
+  assert( pParse->pTriggerTab && pParse->pToplevel );
+  assert( pStepList );
+  assert( v!=0 );
+  for(pStep=pStepList; pStep; pStep=pStep->pNext){
+    /* Figure out the ON CONFLICT policy that will be used for this step
+    ** of the trigger program. If the statement that caused this trigger
+    ** to fire had an explicit ON CONFLICT, then use it. Otherwise, use
+    ** the ON CONFLICT policy that was specified as part of the trigger
+    ** step statement. Example:
+    **
+    **   CREATE TRIGGER AFTER INSERT ON t1 BEGIN;
+    **     INSERT OR REPLACE INTO t2 VALUES(new.a, new.b);
+    **   END;
+    **
+    **   INSERT INTO t1 ... ;            -- insert into t2 uses REPLACE policy
+    **   INSERT OR IGNORE INTO t1 ... ;  -- insert into t2 uses IGNORE policy
+    */
+    pParse->eOrconf = (orconf==OE_Default)?pStep->orconf:(u8)orconf;
+    assert( pParse->okConstFactor==0 );
+
+#ifndef SQLITE_OMIT_TRACE
+    if( pStep->zSpan ){
+      sqlite3VdbeAddOp4(v, OP_Trace, 0x7fffffff, 1, 0,
+                        sqlite3MPrintf(db, "-- %s", pStep->zSpan),
+                        P4_DYNAMIC);
+    }
+#endif
+
+    switch( pStep->op ){
+      case TK_UPDATE: {
+        sqlite3Update(pParse, 
+          sqlite3TriggerStepSrc(pParse, pStep),
+          sqlite3ExprListDup(db, pStep->pExprList, 0), 
+          sqlite3ExprDup(db, pStep->pWhere, 0), 
+          pParse->eOrconf, 0, 0, 0
+        );
+        sqlite3VdbeAddOp0(v, OP_ResetCount);
+        break;
+      }
+      case TK_INSERT: {
+        sqlite3Insert(pParse, 
+          sqlite3TriggerStepSrc(pParse, pStep),
+          sqlite3SelectDup(db, pStep->pSelect, 0), 
+          sqlite3IdListDup(db, pStep->pIdList), 
+          pParse->eOrconf,
+          sqlite3UpsertDup(db, pStep->pUpsert)
+        );
+        sqlite3VdbeAddOp0(v, OP_ResetCount);
+        break;
+      }
+      case TK_DELETE: {
+        sqlite3DeleteFrom(pParse, 
+          sqlite3TriggerStepSrc(pParse, pStep),
+          sqlite3ExprDup(db, pStep->pWhere, 0), 0, 0
+        );
+        sqlite3VdbeAddOp0(v, OP_ResetCount);
+        break;
+      }
+      default: assert( pStep->op==TK_SELECT ); {
+        SelectDest sDest;
+        Select *pSelect = sqlite3SelectDup(db, pStep->pSelect, 0);
+        sqlite3SelectDestInit(&sDest, SRT_Discard, 0);
+        sqlite3Select(pParse, pSelect, &sDest);
+        sqlite3SelectDelete(db, pSelect);
+        break;
+      }
+    } 
+  }
+
+  return 0;
+}
+
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+/*
+** This function is used to add VdbeComment() annotations to a VDBE
+** program. It is not used in production code, only for debugging.
+*/
+static const char *onErrorText(int onError){
+  switch( onError ){
+    case OE_Abort:    return "abort";
+    case OE_Rollback: return "rollback";
+    case OE_Fail:     return "fail";
+    case OE_Replace:  return "replace";
+    case OE_Ignore:   return "ignore";
+    case OE_Default:  return "default";
+  }
+  return "n/a";
+}
+#endif
+
+/*
+** Parse context structure pFrom has just been used to create a sub-vdbe
+** (trigger program). If an error has occurred, transfer error information
+** from pFrom to pTo.
+*/
+static void transferParseError(Parse *pTo, Parse *pFrom){
+  assert( pFrom->zErrMsg==0 || pFrom->nErr );
+  assert( pTo->zErrMsg==0 || pTo->nErr );
+  if( pTo->nErr==0 ){
+    pTo->zErrMsg = pFrom->zErrMsg;
+    pTo->nErr = pFrom->nErr;
+    pTo->rc = pFrom->rc;
+  }else{
+    sqlite3DbFree(pFrom->db, pFrom->zErrMsg);
+  }
+}
+
+/*
+** Create and populate a new TriggerPrg object with a sub-program 
+** implementing trigger pTrigger with ON CONFLICT policy orconf.
+*/
+static TriggerPrg *codeRowTrigger(
+  Parse *pParse,       /* Current parse context */
+  Trigger *pTrigger,   /* Trigger to code */
+  Table *pTab,         /* The table pTrigger is attached to */
+  int orconf           /* ON CONFLICT policy to code trigger program with */
+){
+  Parse *pTop = sqlite3ParseToplevel(pParse);
+  sqlite3 *db = pParse->db;   /* Database handle */
+  TriggerPrg *pPrg;           /* Value to return */
+  Expr *pWhen = 0;            /* Duplicate of trigger WHEN expression */
+  Vdbe *v;                    /* Temporary VM */
+  NameContext sNC;            /* Name context for sub-vdbe */
+  SubProgram *pProgram = 0;   /* Sub-vdbe for trigger program */
+  int iEndTrigger = 0;        /* Label to jump to if WHEN is false */
+  Parse sSubParse;            /* Parse context for sub-vdbe */
+
+  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
+  assert( pTop->pVdbe );
+
+  /* Allocate the TriggerPrg and SubProgram objects. To ensure that they
+  ** are freed if an error occurs, link them into the Parse.pTriggerPrg 
+  ** list of the top-level Parse object sooner rather than later.  */
+  pPrg = sqlite3DbMallocZero(db, sizeof(TriggerPrg));
+  if( !pPrg ) return 0;
+  pPrg->pNext = pTop->pTriggerPrg;
+  pTop->pTriggerPrg = pPrg;
+  pPrg->pProgram = pProgram = sqlite3DbMallocZero(db, sizeof(SubProgram));
+  if( !pProgram ) return 0;
+  sqlite3VdbeLinkSubProgram(pTop->pVdbe, pProgram);
+  pPrg->pTrigger = pTrigger;
+  pPrg->orconf = orconf;
+  pPrg->aColmask[0] = 0xffffffff;
+  pPrg->aColmask[1] = 0xffffffff;
+
+  /* Allocate and populate a new Parse context to use for coding the 
+  ** trigger sub-program.  */
+  sqlite3ParseObjectInit(&sSubParse, db);
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = &sSubParse;
+  sSubParse.pTriggerTab = pTab;
+  sSubParse.pToplevel = pTop;
+  sSubParse.zAuthContext = pTrigger->zName;
+  sSubParse.eTriggerOp = pTrigger->op;
+  sSubParse.nQueryLoop = pParse->nQueryLoop;
+  sSubParse.prepFlags = pParse->prepFlags;
+
+  v = sqlite3GetVdbe(&sSubParse);
+  if( v ){
+    VdbeComment((v, "Start: %s.%s (%s %s%s%s ON %s)", 
+      pTrigger->zName, onErrorText(orconf),
+      (pTrigger->tr_tm==TRIGGER_BEFORE ? "BEFORE" : "AFTER"),
+        (pTrigger->op==TK_UPDATE ? "UPDATE" : ""),
+        (pTrigger->op==TK_INSERT ? "INSERT" : ""),
+        (pTrigger->op==TK_DELETE ? "DELETE" : ""),
+      pTab->zName
+    ));
+#ifndef SQLITE_OMIT_TRACE
+    if( pTrigger->zName ){
+      sqlite3VdbeChangeP4(v, -1, 
+        sqlite3MPrintf(db, "-- TRIGGER %s", pTrigger->zName), P4_DYNAMIC
+      );
+    }
+#endif
+
+    /* If one was specified, code the WHEN clause. If it evaluates to false
+    ** (or NULL) the sub-vdbe is immediately halted by jumping to the 
+    ** OP_Halt inserted at the end of the program.  */
+    if( pTrigger->pWhen ){
+      pWhen = sqlite3ExprDup(db, pTrigger->pWhen, 0);
+      if( db->mallocFailed==0
+       && SQLITE_OK==sqlite3ResolveExprNames(&sNC, pWhen) 
+      ){
+        iEndTrigger = sqlite3VdbeMakeLabel(&sSubParse);
+        sqlite3ExprIfFalse(&sSubParse, pWhen, iEndTrigger, SQLITE_JUMPIFNULL);
+      }
+      sqlite3ExprDelete(db, pWhen);
+    }
+
+    /* Code the trigger program into the sub-vdbe. */
+    codeTriggerProgram(&sSubParse, pTrigger->step_list, orconf);
+
+    /* Insert an OP_Halt at the end of the sub-program. */
+    if( iEndTrigger ){
+      sqlite3VdbeResolveLabel(v, iEndTrigger);
+    }
+    sqlite3VdbeAddOp0(v, OP_Halt);
+    VdbeComment((v, "End: %s.%s", pTrigger->zName, onErrorText(orconf)));
+    transferParseError(pParse, &sSubParse);
+
+    if( pParse->nErr==0 ){
+      assert( db->mallocFailed==0 );
+      pProgram->aOp = sqlite3VdbeTakeOpArray(v, &pProgram->nOp, &pTop->nMaxArg);
+    }
+    pProgram->nMem = sSubParse.nMem;
+    pProgram->nCsr = sSubParse.nTab;
+    pProgram->token = (void *)pTrigger;
+    pPrg->aColmask[0] = sSubParse.oldmask;
+    pPrg->aColmask[1] = sSubParse.newmask;
+    sqlite3VdbeDelete(v);
+  }else{
+    transferParseError(pParse, &sSubParse);
+  }
+
+  assert( !sSubParse.pTriggerPrg && !sSubParse.nMaxArg );
+  sqlite3ParseObjectReset(&sSubParse);
+  return pPrg;
+}
+    
+/*
+** Return a pointer to a TriggerPrg object containing the sub-program for
+** trigger pTrigger with default ON CONFLICT algorithm orconf. If no such
+** TriggerPrg object exists, a new object is allocated and populated before
+** being returned.
+*/
+static TriggerPrg *getRowTrigger(
+  Parse *pParse,       /* Current parse context */
+  Trigger *pTrigger,   /* Trigger to code */
+  Table *pTab,         /* The table trigger pTrigger is attached to */
+  int orconf           /* ON CONFLICT algorithm. */
+){
+  Parse *pRoot = sqlite3ParseToplevel(pParse);
+  TriggerPrg *pPrg;
+
+  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
+
+  /* It may be that this trigger has already been coded (or is in the
+  ** process of being coded). If this is the case, then an entry with
+  ** a matching TriggerPrg.pTrigger field will be present somewhere
+  ** in the Parse.pTriggerPrg list. Search for such an entry.  */
+  for(pPrg=pRoot->pTriggerPrg; 
+      pPrg && (pPrg->pTrigger!=pTrigger || pPrg->orconf!=orconf); 
+      pPrg=pPrg->pNext
+  );
+
+  /* If an existing TriggerPrg could not be located, create a new one. */
+  if( !pPrg ){
+    pPrg = codeRowTrigger(pParse, pTrigger, pTab, orconf);
+    pParse->db->errByteOffset = -1;
+  }
+
+  return pPrg;
+}
+
+/*
+** Generate code for the trigger program associated with trigger p on 
+** table pTab. The reg, orconf and ignoreJump parameters passed to this
+** function are the same as those described in the header function for
+** sqlite3CodeRowTrigger()
+*/
+void sqlite3CodeRowTriggerDirect(
+  Parse *pParse,       /* Parse context */
+  Trigger *p,          /* Trigger to code */
+  Table *pTab,         /* The table to code triggers from */
+  int reg,             /* Reg array containing OLD.* and NEW.* values */
+  int orconf,          /* ON CONFLICT policy */
+  int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
+){
+  Vdbe *v = sqlite3GetVdbe(pParse); /* Main VM */
+  TriggerPrg *pPrg;
+  pPrg = getRowTrigger(pParse, p, pTab, orconf);
+  assert( pPrg || pParse->nErr );
+
+  /* Code the OP_Program opcode in the parent VDBE. P4 of the OP_Program 
+  ** is a pointer to the sub-vdbe containing the trigger program.  */
+  if( pPrg ){
+    int bRecursive = (p->zName && 0==(pParse->db->flags&SQLITE_RecTriggers));
+
+    sqlite3VdbeAddOp4(v, OP_Program, reg, ignoreJump, ++pParse->nMem,
+                      (const char *)pPrg->pProgram, P4_SUBPROGRAM);
+    VdbeComment(
+        (v, "Call: %s.%s", (p->zName?p->zName:"fkey"), onErrorText(orconf)));
+
+    /* Set the P5 operand of the OP_Program instruction to non-zero if
+    ** recursive invocation of this trigger program is disallowed. Recursive
+    ** invocation is disallowed if (a) the sub-program is really a trigger,
+    ** not a foreign key action, and (b) the flag to enable recursive triggers
+    ** is clear.  */
+    sqlite3VdbeChangeP5(v, (u8)bRecursive);
+  }
+}
+
+/*
+** This is called to code the required FOR EACH ROW triggers for an operation
+** on table pTab. The operation to code triggers for (INSERT, UPDATE or DELETE)
+** is given by the op parameter. The tr_tm parameter determines whether the
+** BEFORE or AFTER triggers are coded. If the operation is an UPDATE, then
+** parameter pChanges is passed the list of columns being modified.
+**
+** If there are no triggers that fire at the specified time for the specified
+** operation on pTab, this function is a no-op.
+**
+** The reg argument is the address of the first in an array of registers 
+** that contain the values substituted for the new.* and old.* references
+** in the trigger program. If N is the number of columns in table pTab
+** (a copy of pTab->nCol), then registers are populated as follows:
+**
+**   Register       Contains
+**   ------------------------------------------------------
+**   reg+0          OLD.rowid
+**   reg+1          OLD.* value of left-most column of pTab
+**   ...            ...
+**   reg+N          OLD.* value of right-most column of pTab
+**   reg+N+1        NEW.rowid
+**   reg+N+2        NEW.* value of left-most column of pTab
+**   ...            ...
+**   reg+N+N+1      NEW.* value of right-most column of pTab
+**
+** For ON DELETE triggers, the registers containing the NEW.* values will
+** never be accessed by the trigger program, so they are not allocated or 
+** populated by the caller (there is no data to populate them with anyway). 
+** Similarly, for ON INSERT triggers the values stored in the OLD.* registers
+** are never accessed, and so are not allocated by the caller. So, for an
+** ON INSERT trigger, the value passed to this function as parameter reg
+** is not a readable register, although registers (reg+N) through 
+** (reg+N+N+1) are.
+**
+** Parameter orconf is the default conflict resolution algorithm for the
+** trigger program to use (REPLACE, IGNORE etc.). Parameter ignoreJump
+** is the instruction that control should jump to if a trigger program
+** raises an IGNORE exception.
+*/
+void sqlite3CodeRowTrigger(
+  Parse *pParse,       /* Parse context */
+  Trigger *pTrigger,   /* List of triggers on table pTab */
+  int op,              /* One of TK_UPDATE, TK_INSERT, TK_DELETE */
+  ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
+  int tr_tm,           /* One of TRIGGER_BEFORE, TRIGGER_AFTER */
+  Table *pTab,         /* The table to code triggers from */
+  int reg,             /* The first in an array of registers (see above) */
+  int orconf,          /* ON CONFLICT policy */
+  int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
+){
+  Trigger *p;          /* Used to iterate through pTrigger list */
+
+  assert( op==TK_UPDATE || op==TK_INSERT || op==TK_DELETE );
+  assert( tr_tm==TRIGGER_BEFORE || tr_tm==TRIGGER_AFTER );
+  assert( (op==TK_UPDATE)==(pChanges!=0) );
+
+  for(p=pTrigger; p; p=p->pNext){
+
+    /* Sanity checking:  The schema for the trigger and for the table are
+    ** always defined.  The trigger must be in the same schema as the table
+    ** or else it must be a TEMP trigger. */
+    assert( p->pSchema!=0 );
+    assert( p->pTabSchema!=0 );
+    assert( p->pSchema==p->pTabSchema 
+         || p->pSchema==pParse->db->aDb[1].pSchema );
+
+    /* Determine whether we should code this trigger.  One of two choices:
+    **   1. The trigger is an exact match to the current DML statement
+    **   2. This is a RETURNING trigger for INSERT but we are currently
+    **      doing the UPDATE part of an UPSERT.
+    */
+    if( (p->op==op || (p->bReturning && p->op==TK_INSERT && op==TK_UPDATE))
+     && p->tr_tm==tr_tm 
+     && checkColumnOverlap(p->pColumns, pChanges)
+    ){
+      if( !p->bReturning ){
+        sqlite3CodeRowTriggerDirect(pParse, p, pTab, reg, orconf, ignoreJump);
+      }else if( sqlite3IsToplevel(pParse) ){
+        codeReturningTrigger(pParse, p, pTab, reg);
+      }
+    }
+  }
+}
+
+/*
+** Triggers may access values stored in the old.* or new.* pseudo-table. 
+** This function returns a 32-bit bitmask indicating which columns of the 
+** old.* or new.* tables actually are used by triggers. This information 
+** may be used by the caller, for example, to avoid having to load the entire
+** old.* record into memory when executing an UPDATE or DELETE command.
+**
+** Bit 0 of the returned mask is set if the left-most column of the
+** table may be accessed using an [old|new].<col> reference. Bit 1 is set if
+** the second leftmost column value is required, and so on. If there
+** are more than 32 columns in the table, and at least one of the columns
+** with an index greater than 32 may be accessed, 0xffffffff is returned.
+**
+** It is not possible to determine if the old.rowid or new.rowid column is 
+** accessed by triggers. The caller must always assume that it is.
+**
+** Parameter isNew must be either 1 or 0. If it is 0, then the mask returned
+** applies to the old.* table. If 1, the new.* table.
+**
+** Parameter tr_tm must be a mask with one or both of the TRIGGER_BEFORE
+** and TRIGGER_AFTER bits set. Values accessed by BEFORE triggers are only
+** included in the returned mask if the TRIGGER_BEFORE bit is set in the
+** tr_tm parameter. Similarly, values accessed by AFTER triggers are only
+** included in the returned mask if the TRIGGER_AFTER bit is set in tr_tm.
+*/
+u32 sqlite3TriggerColmask(
+  Parse *pParse,       /* Parse context */
+  Trigger *pTrigger,   /* List of triggers on table pTab */
+  ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
+  int isNew,           /* 1 for new.* ref mask, 0 for old.* ref mask */
+  int tr_tm,           /* Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
+  Table *pTab,         /* The table to code triggers from */
+  int orconf           /* Default ON CONFLICT policy for trigger steps */
+){
+  const int op = pChanges ? TK_UPDATE : TK_DELETE;
+  u32 mask = 0;
+  Trigger *p;
+
+  assert( isNew==1 || isNew==0 );
+  if( IsView(pTab) ){
+    return 0xffffffff;
+  }
+  for(p=pTrigger; p; p=p->pNext){
+    if( p->op==op
+     && (tr_tm&p->tr_tm)
+     && checkColumnOverlap(p->pColumns,pChanges)
+    ){
+      if( p->bReturning ){
+        mask = 0xffffffff;
+      }else{
+        TriggerPrg *pPrg;
+        pPrg = getRowTrigger(pParse, p, pTab, orconf);
+        if( pPrg ){
+          mask |= pPrg->aColmask[isNew];
+        }
+      }
+    }
+  }
+
+  return mask;
+}
+
+#endif /* !defined(SQLITE_OMIT_TRIGGER) */
diff --git a/src/update.c b/src/update.c
new file mode 100644
index 0000000..cd7d73f
--- /dev/null
+++ b/src/update.c
@@ -0,0 +1,1365 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle UPDATE statements.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Forward declaration */
+static void updateVirtualTable(
+  Parse *pParse,       /* The parsing context */
+  SrcList *pSrc,       /* The virtual table to be modified */
+  Table *pTab,         /* The virtual table */
+  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
+  Expr *pRowidExpr,    /* Expression used to recompute the rowid */
+  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
+  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
+  int onError          /* ON CONFLICT strategy */
+);
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** The most recently coded instruction was an OP_Column to retrieve the
+** i-th column of table pTab. This routine sets the P4 parameter of the
+** OP_Column to the default value, if any.
+**
+** The default value of a column is specified by a DEFAULT clause in the
+** column definition. This was either supplied by the user when the table
+** was created, or added later to the table definition by an ALTER TABLE
+** command. If the latter, then the row-records in the table btree on disk
+** may not contain a value for the column and the default value, taken
+** from the P4 parameter of the OP_Column instruction, is returned instead.
+** If the former, then all row-records are guaranteed to include a value
+** for the column and the P4 value is not required.
+**
+** Column definitions created by an ALTER TABLE command may only have
+** literal default values specified: a number, null or a string. (If a more
+** complicated default expression value was provided, it is evaluated
+** when the ALTER TABLE is executed and one of the literal values written
+** into the sqlite_schema table.)
+**
+** Therefore, the P4 parameter is only required if the default value for
+** the column is a literal number, string or null. The sqlite3ValueFromExpr()
+** function is capable of transforming these types of expressions into
+** sqlite3_value objects.
+**
+** If column as REAL affinity and the table is an ordinary b-tree table
+** (not a virtual table) then the value might have been stored as an
+** integer.  In that case, add an OP_RealAffinity opcode to make sure
+** it has been converted into REAL.
+*/
+void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i, int iReg){
+  Column *pCol;
+  assert( pTab!=0 );
+  assert( pTab->nCol>i );
+  pCol = &pTab->aCol[i];
+  if( pCol->iDflt ){
+    sqlite3_value *pValue = 0;
+    u8 enc = ENC(sqlite3VdbeDb(v));
+    assert( !IsView(pTab) );
+    VdbeComment((v, "%s.%s", pTab->zName, pCol->zCnName));
+    assert( i<pTab->nCol );
+    sqlite3ValueFromExpr(sqlite3VdbeDb(v),
+                         sqlite3ColumnExpr(pTab,pCol), enc,
+                         pCol->affinity, &pValue);
+    if( pValue ){
+      sqlite3VdbeAppendP4(v, pValue, P4_MEM);
+    }
+  }
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  if( pCol->affinity==SQLITE_AFF_REAL && !IsVirtual(pTab) ){
+    sqlite3VdbeAddOp1(v, OP_RealAffinity, iReg);
+  }
+#endif
+}
+
+/*
+** Check to see if column iCol of index pIdx references any of the
+** columns defined by aXRef and chngRowid.  Return true if it does
+** and false if not.  This is an optimization.  False-positives are a
+** performance degradation, but false-negatives can result in a corrupt
+** index and incorrect answers.
+**
+** aXRef[j] will be non-negative if column j of the original table is
+** being updated.  chngRowid will be true if the rowid of the table is
+** being updated.
+*/
+static int indexColumnIsBeingUpdated(
+  Index *pIdx,      /* The index to check */
+  int iCol,         /* Which column of the index to check */
+  int *aXRef,       /* aXRef[j]>=0 if column j is being updated */
+  int chngRowid     /* true if the rowid is being updated */
+){
+  i16 iIdxCol = pIdx->aiColumn[iCol];
+  assert( iIdxCol!=XN_ROWID ); /* Cannot index rowid */
+  if( iIdxCol>=0 ){
+    return aXRef[iIdxCol]>=0;
+  }
+  assert( iIdxCol==XN_EXPR );
+  assert( pIdx->aColExpr!=0 );
+  assert( pIdx->aColExpr->a[iCol].pExpr!=0 );
+  return sqlite3ExprReferencesUpdatedColumn(pIdx->aColExpr->a[iCol].pExpr,
+                                            aXRef,chngRowid);
+}
+
+/*
+** Check to see if index pIdx is a partial index whose conditional
+** expression might change values due to an UPDATE.  Return true if
+** the index is subject to change and false if the index is guaranteed
+** to be unchanged.  This is an optimization.  False-positives are a
+** performance degradation, but false-negatives can result in a corrupt
+** index and incorrect answers.
+**
+** aXRef[j] will be non-negative if column j of the original table is
+** being updated.  chngRowid will be true if the rowid of the table is
+** being updated.
+*/
+static int indexWhereClauseMightChange(
+  Index *pIdx,      /* The index to check */
+  int *aXRef,       /* aXRef[j]>=0 if column j is being updated */
+  int chngRowid     /* true if the rowid is being updated */
+){
+  if( pIdx->pPartIdxWhere==0 ) return 0;
+  return sqlite3ExprReferencesUpdatedColumn(pIdx->pPartIdxWhere,
+                                            aXRef, chngRowid);
+}
+
+/*
+** Allocate and return a pointer to an expression of type TK_ROW with
+** Expr.iColumn set to value (iCol+1). The resolver will modify the
+** expression to be a TK_COLUMN reading column iCol of the first
+** table in the source-list (pSrc->a[0]).
+*/
+static Expr *exprRowColumn(Parse *pParse, int iCol){
+  Expr *pRet = sqlite3PExpr(pParse, TK_ROW, 0, 0);
+  if( pRet ) pRet->iColumn = iCol+1;
+  return pRet;
+}
+
+/*
+** Assuming both the pLimit and pOrderBy parameters are NULL, this function
+** generates VM code to run the query:
+**
+**   SELECT <other-columns>, pChanges FROM pTabList WHERE pWhere
+**
+** and write the results to the ephemeral table already opened as cursor
+** iEph. None of pChanges, pTabList or pWhere are modified or consumed by
+** this function, they must be deleted by the caller.
+**
+** Or, if pLimit and pOrderBy are not NULL, and pTab is not a view:
+**
+**   SELECT <other-columns>, pChanges FROM pTabList
+**   WHERE pWhere
+**   GROUP BY <other-columns>
+**   ORDER BY pOrderBy LIMIT pLimit
+**
+** If pTab is a view, the GROUP BY clause is omitted.
+**
+** Exactly how results are written to table iEph, and exactly what
+** the <other-columns> in the query above are is determined by the type
+** of table pTabList->a[0].pTab.
+**
+** If the table is a WITHOUT ROWID table, then argument pPk must be its
+** PRIMARY KEY. In this case <other-columns> are the primary key columns
+** of the table, in order. The results of the query are written to ephemeral
+** table iEph as index keys, using OP_IdxInsert.
+**
+** If the table is actually a view, then <other-columns> are all columns of
+** the view. The results are written to the ephemeral table iEph as records
+** with automatically assigned integer keys.
+**
+** If the table is a virtual or ordinary intkey table, then <other-columns>
+** is its rowid. For a virtual table, the results are written to iEph as
+** records with automatically assigned integer keys For intkey tables, the
+** rowid value in <other-columns> is used as the integer key, and the
+** remaining fields make up the table record.
+*/
+static void updateFromSelect(
+  Parse *pParse,                  /* Parse context */
+  int iEph,                       /* Cursor for open eph. table */
+  Index *pPk,                     /* PK if table 0 is WITHOUT ROWID */
+  ExprList *pChanges,             /* List of expressions to return */
+  SrcList *pTabList,              /* List of tables to select from */
+  Expr *pWhere,                   /* WHERE clause for query */
+  ExprList *pOrderBy,             /* ORDER BY clause */
+  Expr *pLimit                    /* LIMIT clause */
+){
+  int i;
+  SelectDest dest;
+  Select *pSelect = 0;
+  ExprList *pList = 0;
+  ExprList *pGrp = 0;
+  Expr *pLimit2 = 0;
+  ExprList *pOrderBy2 = 0;
+  sqlite3 *db = pParse->db;
+  Table *pTab = pTabList->a[0].pTab;
+  SrcList *pSrc;
+  Expr *pWhere2;
+  int eDest;
+
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  if( pOrderBy && pLimit==0 ) {
+    sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on UPDATE");
+    return;
+  }
+  pOrderBy2 = sqlite3ExprListDup(db, pOrderBy, 0);
+  pLimit2 = sqlite3ExprDup(db, pLimit, 0);
+#else
+  UNUSED_PARAMETER(pOrderBy);
+  UNUSED_PARAMETER(pLimit);
+#endif
+
+  pSrc = sqlite3SrcListDup(db, pTabList, 0);
+  pWhere2 = sqlite3ExprDup(db, pWhere, 0);
+
+  assert( pTabList->nSrc>1 );
+  if( pSrc ){
+    assert( pSrc->a[0].fg.notCte );
+    pSrc->a[0].iCursor = -1;
+    pSrc->a[0].pTab->nTabRef--;
+    pSrc->a[0].pTab = 0;
+  }
+  if( pPk ){
+    for(i=0; i<pPk->nKeyCol; i++){
+      Expr *pNew = exprRowColumn(pParse, pPk->aiColumn[i]);
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+      if( pLimit ){
+        pGrp = sqlite3ExprListAppend(pParse, pGrp, sqlite3ExprDup(db, pNew, 0));
+      }
+#endif
+      pList = sqlite3ExprListAppend(pParse, pList, pNew);
+    }
+    eDest = IsVirtual(pTab) ? SRT_Table : SRT_Upfrom;
+  }else if( IsView(pTab) ){
+    for(i=0; i<pTab->nCol; i++){
+      pList = sqlite3ExprListAppend(pParse, pList, exprRowColumn(pParse, i));
+    }
+    eDest = SRT_Table;
+  }else{
+    eDest = IsVirtual(pTab) ? SRT_Table : SRT_Upfrom;
+    pList = sqlite3ExprListAppend(pParse, 0, sqlite3PExpr(pParse,TK_ROW,0,0));
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+    if( pLimit ){
+      pGrp = sqlite3ExprListAppend(pParse, 0, sqlite3PExpr(pParse,TK_ROW,0,0));
+    }
+#endif
+  }
+  assert( pChanges!=0 || pParse->db->mallocFailed );
+  if( pChanges ){
+    for(i=0; i<pChanges->nExpr; i++){
+      pList = sqlite3ExprListAppend(pParse, pList,
+          sqlite3ExprDup(db, pChanges->a[i].pExpr, 0)
+      );
+    }
+  }
+  pSelect = sqlite3SelectNew(pParse, pList,
+      pSrc, pWhere2, pGrp, 0, pOrderBy2,
+      SF_UFSrcCheck|SF_IncludeHidden|SF_UpdateFrom, pLimit2
+  );
+  if( pSelect ) pSelect->selFlags |= SF_OrderByReqd;
+  sqlite3SelectDestInit(&dest, eDest, iEph);
+  dest.iSDParm2 = (pPk ? pPk->nKeyCol : -1);
+  sqlite3Select(pParse, pSelect, &dest);
+  sqlite3SelectDelete(db, pSelect);
+}
+
+/*
+** Process an UPDATE statement.
+**
+**   UPDATE OR IGNORE tbl SET a=b, c=d FROM tbl2... WHERE e<5 AND f NOT NULL;
+**          \_______/ \_/     \______/      \_____/       \________________/
+**           onError   |      pChanges         |                pWhere
+**                     \_______________________/
+**                               pTabList
+*/
+void sqlite3Update(
+  Parse *pParse,         /* The parser context */
+  SrcList *pTabList,     /* The table in which we should change things */
+  ExprList *pChanges,    /* Things to be changed */
+  Expr *pWhere,          /* The WHERE clause.  May be null */
+  int onError,           /* How to handle constraint errors */
+  ExprList *pOrderBy,    /* ORDER BY clause. May be null */
+  Expr *pLimit,          /* LIMIT clause. May be null */
+  Upsert *pUpsert        /* ON CONFLICT clause, or null */
+){
+  int i, j, k;           /* Loop counters */
+  Table *pTab;           /* The table to be updated */
+  int addrTop = 0;       /* VDBE instruction address of the start of the loop */
+  WhereInfo *pWInfo = 0; /* Information about the WHERE clause */
+  Vdbe *v;               /* The virtual database engine */
+  Index *pIdx;           /* For looping over indices */
+  Index *pPk;            /* The PRIMARY KEY index for WITHOUT ROWID tables */
+  int nIdx;              /* Number of indices that need updating */
+  int nAllIdx;           /* Total number of indexes */
+  int iBaseCur;          /* Base cursor number */
+  int iDataCur;          /* Cursor for the canonical data btree */
+  int iIdxCur;           /* Cursor for the first index */
+  sqlite3 *db;           /* The database structure */
+  int *aRegIdx = 0;      /* Registers for to each index and the main table */
+  int *aXRef = 0;        /* aXRef[i] is the index in pChanges->a[] of the
+                         ** an expression for the i-th column of the table.
+                         ** aXRef[i]==-1 if the i-th column is not changed. */
+  u8 *aToOpen;           /* 1 for tables and indices to be opened */
+  u8 chngPk;             /* PRIMARY KEY changed in a WITHOUT ROWID table */
+  u8 chngRowid;          /* Rowid changed in a normal table */
+  u8 chngKey;            /* Either chngPk or chngRowid */
+  Expr *pRowidExpr = 0;  /* Expression defining the new record number */
+  int iRowidExpr = -1;   /* Index of "rowid=" (or IPK) assignment in pChanges */
+  AuthContext sContext;  /* The authorization context */
+  NameContext sNC;       /* The name-context to resolve expressions in */
+  int iDb;               /* Database containing the table being updated */
+  int eOnePass;          /* ONEPASS_XXX value from where.c */
+  int hasFK;             /* True if foreign key processing is required */
+  int labelBreak;        /* Jump here to break out of UPDATE loop */
+  int labelContinue;     /* Jump here to continue next step of UPDATE loop */
+  int flags;             /* Flags for sqlite3WhereBegin() */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  int isView;            /* True when updating a view (INSTEAD OF trigger) */
+  Trigger *pTrigger;     /* List of triggers on pTab, if required */
+  int tmask;             /* Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
+#endif
+  int newmask;           /* Mask of NEW.* columns accessed by BEFORE triggers */
+  int iEph = 0;          /* Ephemeral table holding all primary key values */
+  int nKey = 0;          /* Number of elements in regKey for WITHOUT ROWID */
+  int aiCurOnePass[2];   /* The write cursors opened by WHERE_ONEPASS */
+  int addrOpen = 0;      /* Address of OP_OpenEphemeral */
+  int iPk = 0;           /* First of nPk cells holding PRIMARY KEY value */
+  i16 nPk = 0;           /* Number of components of the PRIMARY KEY */
+  int bReplace = 0;      /* True if REPLACE conflict resolution might happen */
+  int bFinishSeek = 1;   /* The OP_FinishSeek opcode is needed */
+  int nChangeFrom = 0;   /* If there is a FROM, pChanges->nExpr, else 0 */
+
+  /* Register Allocations */
+  int regRowCount = 0;   /* A count of rows changed */
+  int regOldRowid = 0;   /* The old rowid */
+  int regNewRowid = 0;   /* The new rowid */
+  int regNew = 0;        /* Content of the NEW.* table in triggers */
+  int regOld = 0;        /* Content of OLD.* table in triggers */
+  int regRowSet = 0;     /* Rowset of rows to be updated */
+  int regKey = 0;        /* composite PRIMARY KEY value */
+
+  memset(&sContext, 0, sizeof(sContext));
+  db = pParse->db;
+  assert( db->pParse==pParse );
+  if( pParse->nErr ){
+    goto update_cleanup;
+  }
+  assert( db->mallocFailed==0 );
+
+  /* Locate the table which we want to update.
+  */
+  pTab = sqlite3SrcListLookup(pParse, pTabList);
+  if( pTab==0 ) goto update_cleanup;
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+
+  /* Figure out if we have any triggers and if the table being
+  ** updated is a view.
+  */
+#ifndef SQLITE_OMIT_TRIGGER
+  pTrigger = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges, &tmask);
+  isView = IsView(pTab);
+  assert( pTrigger || tmask==0 );
+#else
+# define pTrigger 0
+# define isView 0
+# define tmask 0
+#endif
+#ifdef SQLITE_OMIT_VIEW
+# undef isView
+# define isView 0
+#endif
+
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x10000 ){
+    sqlite3TreeViewLine(0, "In sqlite3Update() at %s:%d", __FILE__, __LINE__);
+    sqlite3TreeViewUpdate(pParse->pWith, pTabList, pChanges, pWhere,
+                          onError, pOrderBy, pLimit, pUpsert, pTrigger);
+  }
+#endif
+
+  /* If there was a FROM clause, set nChangeFrom to the number of expressions
+  ** in the change-list. Otherwise, set it to 0. There cannot be a FROM
+  ** clause if this function is being called to generate code for part of
+  ** an UPSERT statement.  */
+  nChangeFrom = (pTabList->nSrc>1) ? pChanges->nExpr : 0;
+  assert( nChangeFrom==0 || pUpsert==0 );
+
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  if( !isView && nChangeFrom==0 ){
+    pWhere = sqlite3LimitWhere(
+        pParse, pTabList, pWhere, pOrderBy, pLimit, "UPDATE"
+    );
+    pOrderBy = 0;
+    pLimit = 0;
+  }
+#endif
+
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto update_cleanup;
+  }
+  if( sqlite3IsReadOnly(pParse, pTab, pTrigger) ){
+    goto update_cleanup;
+  }
+
+  /* Allocate a cursors for the main database table and for all indices.
+  ** The index cursors might not be used, but if they are used they
+  ** need to occur right after the database cursor.  So go ahead and
+  ** allocate enough space, just in case.
+  */
+  iBaseCur = iDataCur = pParse->nTab++;
+  iIdxCur = iDataCur+1;
+  pPk = HasRowid(pTab) ? 0 : sqlite3PrimaryKeyIndex(pTab);
+  testcase( pPk!=0 && pPk!=pTab->pIndex );
+  for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){
+    if( pPk==pIdx ){
+      iDataCur = pParse->nTab;
+    }
+    pParse->nTab++;
+  }
+  if( pUpsert ){
+    /* On an UPSERT, reuse the same cursors already opened by INSERT */
+    iDataCur = pUpsert->iDataCur;
+    iIdxCur = pUpsert->iIdxCur;
+    pParse->nTab = iBaseCur;
+  }
+  pTabList->a[0].iCursor = iDataCur;
+
+  /* Allocate space for aXRef[], aRegIdx[], and aToOpen[].
+  ** Initialize aXRef[] and aToOpen[] to their default values.
+  */
+  aXRef = sqlite3DbMallocRawNN(db, sizeof(int) * (pTab->nCol+nIdx+1) + nIdx+2 );
+  if( aXRef==0 ) goto update_cleanup;
+  aRegIdx = aXRef+pTab->nCol;
+  aToOpen = (u8*)(aRegIdx+nIdx+1);
+  memset(aToOpen, 1, nIdx+1);
+  aToOpen[nIdx+1] = 0;
+  for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
+
+  /* Initialize the name-context */
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = pParse;
+  sNC.pSrcList = pTabList;
+  sNC.uNC.pUpsert = pUpsert;
+  sNC.ncFlags = NC_UUpsert;
+
+  /* Begin generating code. */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) goto update_cleanup;
+
+  /* Resolve the column names in all the expressions of the
+  ** of the UPDATE statement.  Also find the column index
+  ** for each column to be updated in the pChanges array.  For each
+  ** column to be updated, make sure we have authorization to change
+  ** that column.
+  */
+  chngRowid = chngPk = 0;
+  for(i=0; i<pChanges->nExpr; i++){
+    u8 hCol = sqlite3StrIHash(pChanges->a[i].zEName);
+    /* If this is an UPDATE with a FROM clause, do not resolve expressions
+    ** here. The call to sqlite3Select() below will do that. */
+    if( nChangeFrom==0 && sqlite3ResolveExprNames(&sNC, pChanges->a[i].pExpr) ){
+      goto update_cleanup;
+    }
+    for(j=0; j<pTab->nCol; j++){
+      if( pTab->aCol[j].hName==hCol
+       && sqlite3StrICmp(pTab->aCol[j].zCnName, pChanges->a[i].zEName)==0
+      ){
+        if( j==pTab->iPKey ){
+          chngRowid = 1;
+          pRowidExpr = pChanges->a[i].pExpr;
+          iRowidExpr = i;
+        }else if( pPk && (pTab->aCol[j].colFlags & COLFLAG_PRIMKEY)!=0 ){
+          chngPk = 1;
+        }
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+        else if( pTab->aCol[j].colFlags & COLFLAG_GENERATED ){
+          testcase( pTab->aCol[j].colFlags & COLFLAG_VIRTUAL );
+          testcase( pTab->aCol[j].colFlags & COLFLAG_STORED );
+          sqlite3ErrorMsg(pParse,
+             "cannot UPDATE generated column \"%s\"",
+             pTab->aCol[j].zCnName);
+          goto update_cleanup;
+        }
+#endif
+        aXRef[j] = i;
+        break;
+      }
+    }
+    if( j>=pTab->nCol ){
+      if( pPk==0 && sqlite3IsRowid(pChanges->a[i].zEName) ){
+        j = -1;
+        chngRowid = 1;
+        pRowidExpr = pChanges->a[i].pExpr;
+        iRowidExpr = i;
+      }else{
+        sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zEName);
+        pParse->checkSchema = 1;
+        goto update_cleanup;
+      }
+    }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    {
+      int rc;
+      rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
+                            j<0 ? "ROWID" : pTab->aCol[j].zCnName,
+                            db->aDb[iDb].zDbSName);
+      if( rc==SQLITE_DENY ){
+        goto update_cleanup;
+      }else if( rc==SQLITE_IGNORE ){
+        aXRef[j] = -1;
+      }
+    }
+#endif
+  }
+  assert( (chngRowid & chngPk)==0 );
+  assert( chngRowid==0 || chngRowid==1 );
+  assert( chngPk==0 || chngPk==1 );
+  chngKey = chngRowid + chngPk;
+
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  /* Mark generated columns as changing if their generator expressions
+  ** reference any changing column.  The actual aXRef[] value for
+  ** generated expressions is not used, other than to check to see that it
+  ** is non-negative, so the value of aXRef[] for generated columns can be
+  ** set to any non-negative number.  We use 99999 so that the value is
+  ** obvious when looking at aXRef[] in a symbolic debugger.
+  */
+  if( pTab->tabFlags & TF_HasGenerated ){
+    int bProgress;
+    testcase( pTab->tabFlags & TF_HasVirtual );
+    testcase( pTab->tabFlags & TF_HasStored );
+    do{
+      bProgress = 0;
+      for(i=0; i<pTab->nCol; i++){
+        if( aXRef[i]>=0 ) continue;
+        if( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 ) continue;
+        if( sqlite3ExprReferencesUpdatedColumn(
+                sqlite3ColumnExpr(pTab, &pTab->aCol[i]),
+                 aXRef, chngRowid)
+        ){
+          aXRef[i] = 99999;
+          bProgress = 1;
+        }
+      }
+    }while( bProgress );
+  }
+#endif
+
+  /* The SET expressions are not actually used inside the WHERE loop.
+  ** So reset the colUsed mask. Unless this is a virtual table. In that
+  ** case, set all bits of the colUsed mask (to ensure that the virtual
+  ** table implementation makes all columns available).
+  */
+  pTabList->a[0].colUsed = IsVirtual(pTab) ? ALLBITS : 0;
+
+  hasFK = sqlite3FkRequired(pParse, pTab, aXRef, chngKey);
+
+  /* There is one entry in the aRegIdx[] array for each index on the table
+  ** being updated.  Fill in aRegIdx[] with a register number that will hold
+  ** the key for accessing each index.
+  */
+  if( onError==OE_Replace ) bReplace = 1;
+  for(nAllIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nAllIdx++){
+    int reg;
+    if( chngKey || hasFK>1 || pIdx==pPk
+     || indexWhereClauseMightChange(pIdx,aXRef,chngRowid)
+    ){
+      reg = ++pParse->nMem;
+      pParse->nMem += pIdx->nColumn;
+    }else{
+      reg = 0;
+      for(i=0; i<pIdx->nKeyCol; i++){
+        if( indexColumnIsBeingUpdated(pIdx, i, aXRef, chngRowid) ){
+          reg = ++pParse->nMem;
+          pParse->nMem += pIdx->nColumn;
+          if( onError==OE_Default && pIdx->onError==OE_Replace ){
+            bReplace = 1;
+          }
+          break;
+        }
+      }
+    }
+    if( reg==0 ) aToOpen[nAllIdx+1] = 0;
+    aRegIdx[nAllIdx] = reg;
+  }
+  aRegIdx[nAllIdx] = ++pParse->nMem;  /* Register storing the table record */
+  if( bReplace ){
+    /* If REPLACE conflict resolution might be invoked, open cursors on all
+    ** indexes in case they are needed to delete records.  */
+    memset(aToOpen, 1, nIdx+1);
+  }
+
+  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
+  sqlite3BeginWriteOperation(pParse, pTrigger || hasFK, iDb);
+
+  /* Allocate required registers. */
+  if( !IsVirtual(pTab) ){
+    /* For now, regRowSet and aRegIdx[nAllIdx] share the same register.
+    ** If regRowSet turns out to be needed, then aRegIdx[nAllIdx] will be
+    ** reallocated.  aRegIdx[nAllIdx] is the register in which the main
+    ** table record is written.  regRowSet holds the RowSet for the
+    ** two-pass update algorithm. */
+    assert( aRegIdx[nAllIdx]==pParse->nMem );
+    regRowSet = aRegIdx[nAllIdx];
+    regOldRowid = regNewRowid = ++pParse->nMem;
+    if( chngPk || pTrigger || hasFK ){
+      regOld = pParse->nMem + 1;
+      pParse->nMem += pTab->nCol;
+    }
+    if( chngKey || pTrigger || hasFK ){
+      regNewRowid = ++pParse->nMem;
+    }
+    regNew = pParse->nMem + 1;
+    pParse->nMem += pTab->nCol;
+  }
+
+  /* Start the view context. */
+  if( isView ){
+    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
+  }
+
+  /* If we are trying to update a view, realize that view into
+  ** an ephemeral table.
+  */
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+  if( nChangeFrom==0 && isView ){
+    sqlite3MaterializeView(pParse, pTab,
+        pWhere, pOrderBy, pLimit, iDataCur
+    );
+    pOrderBy = 0;
+    pLimit = 0;
+  }
+#endif
+
+  /* Resolve the column names in all the expressions in the
+  ** WHERE clause.
+  */
+  if( nChangeFrom==0 && sqlite3ResolveExprNames(&sNC, pWhere) ){
+    goto update_cleanup;
+  }
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  /* Virtual tables must be handled separately */
+  if( IsVirtual(pTab) ){
+    updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
+                       pWhere, onError);
+    goto update_cleanup;
+  }
+#endif
+
+  /* Jump to labelBreak to abandon further processing of this UPDATE */
+  labelContinue = labelBreak = sqlite3VdbeMakeLabel(pParse);
+
+  /* Not an UPSERT.  Normal processing.  Begin by
+  ** initialize the count of updated rows */
+  if( (db->flags&SQLITE_CountRows)!=0
+   && !pParse->pTriggerTab
+   && !pParse->nested
+   && !pParse->bReturning
+   && pUpsert==0
+  ){
+    regRowCount = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
+  }
+
+  if( nChangeFrom==0 && HasRowid(pTab) ){
+    sqlite3VdbeAddOp3(v, OP_Null, 0, regRowSet, regOldRowid);
+    iEph = pParse->nTab++;
+    addrOpen = sqlite3VdbeAddOp3(v, OP_OpenEphemeral, iEph, 0, regRowSet);
+  }else{
+    assert( pPk!=0 || HasRowid(pTab) );
+    nPk = pPk ? pPk->nKeyCol : 0;
+    iPk = pParse->nMem+1;
+    pParse->nMem += nPk;
+    pParse->nMem += nChangeFrom;
+    regKey = ++pParse->nMem;
+    if( pUpsert==0 ){
+      int nEphCol = nPk + nChangeFrom + (isView ? pTab->nCol : 0);
+      iEph = pParse->nTab++;
+      if( pPk ) sqlite3VdbeAddOp3(v, OP_Null, 0, iPk, iPk+nPk-1);
+      addrOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEph, nEphCol);
+      if( pPk ){
+        KeyInfo *pKeyInfo = sqlite3KeyInfoOfIndex(pParse, pPk);
+        if( pKeyInfo ){
+          pKeyInfo->nAllField = nEphCol;
+          sqlite3VdbeAppendP4(v, pKeyInfo, P4_KEYINFO);
+        }
+      }
+      if( nChangeFrom ){
+        updateFromSelect(
+            pParse, iEph, pPk, pChanges, pTabList, pWhere, pOrderBy, pLimit
+        );
+#ifndef SQLITE_OMIT_SUBQUERY
+        if( isView ) iDataCur = iEph;
+#endif
+      }
+    }
+  }
+
+  if( nChangeFrom ){
+    sqlite3MultiWrite(pParse);
+    eOnePass = ONEPASS_OFF;
+    nKey = nPk;
+    regKey = iPk;
+  }else{
+    if( pUpsert ){
+      /* If this is an UPSERT, then all cursors have already been opened by
+      ** the outer INSERT and the data cursor should be pointing at the row
+      ** that is to be updated.  So bypass the code that searches for the
+      ** row(s) to be updated.
+      */
+      pWInfo = 0;
+      eOnePass = ONEPASS_SINGLE;
+      sqlite3ExprIfFalse(pParse, pWhere, labelBreak, SQLITE_JUMPIFNULL);
+      bFinishSeek = 0;
+    }else{
+      /* Begin the database scan.
+      **
+      ** Do not consider a single-pass strategy for a multi-row update if
+      ** there is anything that might disrupt the cursor being used to do
+      ** the UPDATE:
+      **   (1) This is a nested UPDATE
+      **   (2) There are triggers
+      **   (3) There are FOREIGN KEY constraints
+      **   (4) There are REPLACE conflict handlers
+      **   (5) There are subqueries in the WHERE clause
+      */
+      flags = WHERE_ONEPASS_DESIRED;
+      if( !pParse->nested
+       && !pTrigger
+       && !hasFK
+       && !chngKey
+       && !bReplace
+       && (pWhere==0 || !ExprHasProperty(pWhere, EP_Subquery))
+      ){
+        flags |= WHERE_ONEPASS_MULTIROW;
+      }
+      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere,0,0,0,flags,iIdxCur);
+      if( pWInfo==0 ) goto update_cleanup;
+
+      /* A one-pass strategy that might update more than one row may not
+      ** be used if any column of the index used for the scan is being
+      ** updated. Otherwise, if there is an index on "b", statements like
+      ** the following could create an infinite loop:
+      **
+      **   UPDATE t1 SET b=b+1 WHERE b>?
+      **
+      ** Fall back to ONEPASS_OFF if where.c has selected a ONEPASS_MULTI
+      ** strategy that uses an index for which one or more columns are being
+      ** updated.  */
+      eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
+      bFinishSeek = sqlite3WhereUsesDeferredSeek(pWInfo);
+      if( eOnePass!=ONEPASS_SINGLE ){
+        sqlite3MultiWrite(pParse);
+        if( eOnePass==ONEPASS_MULTI ){
+          int iCur = aiCurOnePass[1];
+          if( iCur>=0 && iCur!=iDataCur && aToOpen[iCur-iBaseCur] ){
+            eOnePass = ONEPASS_OFF;
+          }
+          assert( iCur!=iDataCur || !HasRowid(pTab) );
+        }
+      }
+    }
+
+    if( HasRowid(pTab) ){
+      /* Read the rowid of the current row of the WHERE scan. In ONEPASS_OFF
+      ** mode, write the rowid into the FIFO. In either of the one-pass modes,
+      ** leave it in register regOldRowid.  */
+      sqlite3VdbeAddOp2(v, OP_Rowid, iDataCur, regOldRowid);
+      if( eOnePass==ONEPASS_OFF ){
+        aRegIdx[nAllIdx] = ++pParse->nMem;
+        sqlite3VdbeAddOp3(v, OP_Insert, iEph, regRowSet, regOldRowid);
+      }else{
+        if( ALWAYS(addrOpen) ) sqlite3VdbeChangeToNoop(v, addrOpen);
+      }
+    }else{
+      /* Read the PK of the current row into an array of registers. In
+      ** ONEPASS_OFF mode, serialize the array into a record and store it in
+      ** the ephemeral table. Or, in ONEPASS_SINGLE or MULTI mode, change
+      ** the OP_OpenEphemeral instruction to a Noop (the ephemeral table
+      ** is not required) and leave the PK fields in the array of registers.  */
+      for(i=0; i<nPk; i++){
+        assert( pPk->aiColumn[i]>=0 );
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur,
+                                        pPk->aiColumn[i], iPk+i);
+      }
+      if( eOnePass ){
+        if( addrOpen ) sqlite3VdbeChangeToNoop(v, addrOpen);
+        nKey = nPk;
+        regKey = iPk;
+      }else{
+        sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, regKey,
+                          sqlite3IndexAffinityStr(db, pPk), nPk);
+        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iEph, regKey, iPk, nPk);
+      }
+    }
+  }
+
+  if( pUpsert==0 ){
+    if( nChangeFrom==0 && eOnePass!=ONEPASS_MULTI ){
+      sqlite3WhereEnd(pWInfo);
+    }
+
+    if( !isView ){
+      int addrOnce = 0;
+      int iNotUsed1 = 0;
+      int iNotUsed2 = 0;
+
+      /* Open every index that needs updating. */
+      if( eOnePass!=ONEPASS_OFF ){
+        if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iBaseCur] = 0;
+        if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iBaseCur] = 0;
+      }
+
+      if( eOnePass==ONEPASS_MULTI && (nIdx-(aiCurOnePass[1]>=0))>0 ){
+        addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+      }
+      sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, 0, iBaseCur,
+                                 aToOpen, &iNotUsed1, &iNotUsed2);
+      if( addrOnce ){
+        sqlite3VdbeJumpHereOrPopInst(v, addrOnce);
+      }
+    }
+
+    /* Top of the update loop */
+    if( eOnePass!=ONEPASS_OFF ){
+      if( aiCurOnePass[0]!=iDataCur
+       && aiCurOnePass[1]!=iDataCur
+#ifdef SQLITE_ALLOW_ROWID_IN_VIEW
+       && !isView
+#endif
+      ){
+        assert( pPk );
+        sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, labelBreak, regKey,nKey);
+        VdbeCoverage(v);
+      }
+      if( eOnePass!=ONEPASS_SINGLE ){
+        labelContinue = sqlite3VdbeMakeLabel(pParse);
+      }
+      sqlite3VdbeAddOp2(v, OP_IsNull, pPk ? regKey : regOldRowid, labelBreak);
+      VdbeCoverageIf(v, pPk==0);
+      VdbeCoverageIf(v, pPk!=0);
+    }else if( pPk || nChangeFrom ){
+      labelContinue = sqlite3VdbeMakeLabel(pParse);
+      sqlite3VdbeAddOp2(v, OP_Rewind, iEph, labelBreak); VdbeCoverage(v);
+      addrTop = sqlite3VdbeCurrentAddr(v);
+      if( nChangeFrom ){
+        if( !isView ){
+          if( pPk ){
+            for(i=0; i<nPk; i++){
+              sqlite3VdbeAddOp3(v, OP_Column, iEph, i, iPk+i);
+            }
+            sqlite3VdbeAddOp4Int(
+                v, OP_NotFound, iDataCur, labelContinue, iPk, nPk
+            ); VdbeCoverage(v);
+          }else{
+            sqlite3VdbeAddOp2(v, OP_Rowid, iEph, regOldRowid);
+            sqlite3VdbeAddOp3(
+                v, OP_NotExists, iDataCur, labelContinue, regOldRowid
+            ); VdbeCoverage(v);
+          }
+        }
+      }else{
+        sqlite3VdbeAddOp2(v, OP_RowData, iEph, regKey);
+        sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, labelContinue, regKey,0);
+        VdbeCoverage(v);
+      }
+    }else{
+      sqlite3VdbeAddOp2(v, OP_Rewind, iEph, labelBreak); VdbeCoverage(v);
+      labelContinue = sqlite3VdbeMakeLabel(pParse);
+      addrTop = sqlite3VdbeAddOp2(v, OP_Rowid, iEph, regOldRowid);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, labelContinue, regOldRowid);
+      VdbeCoverage(v);
+    }
+  }
+
+  /* If the rowid value will change, set register regNewRowid to
+  ** contain the new value. If the rowid is not being modified,
+  ** then regNewRowid is the same register as regOldRowid, which is
+  ** already populated.  */
+  assert( chngKey || pTrigger || hasFK || regOldRowid==regNewRowid );
+  if( chngRowid ){
+    assert( iRowidExpr>=0 );
+    if( nChangeFrom==0 ){
+      sqlite3ExprCode(pParse, pRowidExpr, regNewRowid);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_Column, iEph, iRowidExpr, regNewRowid);
+    }
+    sqlite3VdbeAddOp1(v, OP_MustBeInt, regNewRowid); VdbeCoverage(v);
+  }
+
+  /* Compute the old pre-UPDATE content of the row being changed, if that
+  ** information is needed */
+  if( chngPk || hasFK || pTrigger ){
+    u32 oldmask = (hasFK ? sqlite3FkOldmask(pParse, pTab) : 0);
+    oldmask |= sqlite3TriggerColmask(pParse,
+        pTrigger, pChanges, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onError
+    );
+    for(i=0; i<pTab->nCol; i++){
+      u32 colFlags = pTab->aCol[i].colFlags;
+      k = sqlite3TableColumnToStorage(pTab, i) + regOld;
+      if( oldmask==0xffffffff
+       || (i<32 && (oldmask & MASKBIT32(i))!=0)
+       || (colFlags & COLFLAG_PRIMKEY)!=0
+      ){
+        testcase(  oldmask!=0xffffffff && i==31 );
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, k);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Null, 0, k);
+      }
+    }
+    if( chngRowid==0 && pPk==0 ){
+      sqlite3VdbeAddOp2(v, OP_Copy, regOldRowid, regNewRowid);
+    }
+  }
+
+  /* Populate the array of registers beginning at regNew with the new
+  ** row data. This array is used to check constants, create the new
+  ** table and index records, and as the values for any new.* references
+  ** made by triggers.
+  **
+  ** If there are one or more BEFORE triggers, then do not populate the
+  ** registers associated with columns that are (a) not modified by
+  ** this UPDATE statement and (b) not accessed by new.* references. The
+  ** values for registers not modified by the UPDATE must be reloaded from
+  ** the database after the BEFORE triggers are fired anyway (as the trigger
+  ** may have modified them). So not loading those that are not going to
+  ** be used eliminates some redundant opcodes.
+  */
+  newmask = sqlite3TriggerColmask(
+      pParse, pTrigger, pChanges, 1, TRIGGER_BEFORE, pTab, onError
+  );
+  for(i=0, k=regNew; i<pTab->nCol; i++, k++){
+    if( i==pTab->iPKey ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, k);
+    }else if( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)!=0 ){
+      if( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL ) k--;
+    }else{
+      j = aXRef[i];
+      if( j>=0 ){
+        if( nChangeFrom ){
+          int nOff = (isView ? pTab->nCol : nPk);
+          assert( eOnePass==ONEPASS_OFF );
+          sqlite3VdbeAddOp3(v, OP_Column, iEph, nOff+j, k);
+        }else{
+          sqlite3ExprCode(pParse, pChanges->a[j].pExpr, k);
+        }
+      }else if( 0==(tmask&TRIGGER_BEFORE) || i>31 || (newmask & MASKBIT32(i)) ){
+        /* This branch loads the value of a column that will not be changed
+        ** into a register. This is done if there are no BEFORE triggers, or
+        ** if there are one or more BEFORE triggers that use this value via
+        ** a new.* reference in a trigger program.
+        */
+        testcase( i==31 );
+        testcase( i==32 );
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, k);
+        bFinishSeek = 0;
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Null, 0, k);
+      }
+    }
+  }
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  if( pTab->tabFlags & TF_HasGenerated ){
+    testcase( pTab->tabFlags & TF_HasVirtual );
+    testcase( pTab->tabFlags & TF_HasStored );
+    sqlite3ComputeGeneratedColumns(pParse, regNew, pTab);
+  }
+#endif
+
+  /* Fire any BEFORE UPDATE triggers. This happens before constraints are
+  ** verified. One could argue that this is wrong.
+  */
+  if( tmask&TRIGGER_BEFORE ){
+    sqlite3TableAffinity(v, pTab, regNew);
+    sqlite3CodeRowTrigger(pParse, pTrigger, TK_UPDATE, pChanges,
+        TRIGGER_BEFORE, pTab, regOldRowid, onError, labelContinue);
+
+    if( !isView ){
+      /* The row-trigger may have deleted the row being updated. In this
+      ** case, jump to the next row. No updates or AFTER triggers are
+      ** required. This behavior - what happens when the row being updated
+      ** is deleted or renamed by a BEFORE trigger - is left undefined in the
+      ** documentation.
+      */
+      if( pPk ){
+        sqlite3VdbeAddOp4Int(v, OP_NotFound,iDataCur,labelContinue,regKey,nKey);
+        VdbeCoverage(v);
+      }else{
+        sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, labelContinue,regOldRowid);
+        VdbeCoverage(v);
+      }
+
+      /* After-BEFORE-trigger-reload-loop:
+      ** If it did not delete it, the BEFORE trigger may still have modified
+      ** some of the columns of the row being updated. Load the values for
+      ** all columns not modified by the update statement into their registers
+      ** in case this has happened. Only unmodified columns are reloaded.
+      ** The values computed for modified columns use the values before the
+      ** BEFORE trigger runs.  See test case trigger1-18.0 (added 2018-04-26)
+      ** for an example.
+      */
+      for(i=0, k=regNew; i<pTab->nCol; i++, k++){
+        if( pTab->aCol[i].colFlags & COLFLAG_GENERATED ){
+          if( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL ) k--;
+        }else if( aXRef[i]<0 && i!=pTab->iPKey ){
+          sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, k);
+        }
+      }
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+      if( pTab->tabFlags & TF_HasGenerated ){
+        testcase( pTab->tabFlags & TF_HasVirtual );
+        testcase( pTab->tabFlags & TF_HasStored );
+        sqlite3ComputeGeneratedColumns(pParse, regNew, pTab);
+      }
+#endif
+    }
+  }
+
+  if( !isView ){
+    /* Do constraint checks. */
+    assert( regOldRowid>0 );
+    sqlite3GenerateConstraintChecks(pParse, pTab, aRegIdx, iDataCur, iIdxCur,
+        regNewRowid, regOldRowid, chngKey, onError, labelContinue, &bReplace,
+        aXRef, 0);
+
+    /* If REPLACE conflict handling may have been used, or if the PK of the
+    ** row is changing, then the GenerateConstraintChecks() above may have
+    ** moved cursor iDataCur. Reseek it. */
+    if( bReplace || chngKey ){
+      if( pPk ){
+        sqlite3VdbeAddOp4Int(v, OP_NotFound,iDataCur,labelContinue,regKey,nKey);
+      }else{
+        sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, labelContinue,regOldRowid);
+      }
+      VdbeCoverage(v);
+    }
+
+    /* Do FK constraint checks. */
+    if( hasFK ){
+      sqlite3FkCheck(pParse, pTab, regOldRowid, 0, aXRef, chngKey);
+    }
+
+    /* Delete the index entries associated with the current record.  */
+    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur, aRegIdx, -1);
+
+    /* We must run the OP_FinishSeek opcode to resolve a prior
+    ** OP_DeferredSeek if there is any possibility that there have been
+    ** no OP_Column opcodes since the OP_DeferredSeek was issued.  But
+    ** we want to avoid the OP_FinishSeek if possible, as running it
+    ** costs CPU cycles. */
+    if( bFinishSeek ){
+      sqlite3VdbeAddOp1(v, OP_FinishSeek, iDataCur);
+    }
+
+    /* If changing the rowid value, or if there are foreign key constraints
+    ** to process, delete the old record. Otherwise, add a noop OP_Delete
+    ** to invoke the pre-update hook.
+    **
+    ** That (regNew==regnewRowid+1) is true is also important for the
+    ** pre-update hook. If the caller invokes preupdate_new(), the returned
+    ** value is copied from memory cell (regNewRowid+1+iCol), where iCol
+    ** is the column index supplied by the user.
+    */
+    assert( regNew==regNewRowid+1 );
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+    sqlite3VdbeAddOp3(v, OP_Delete, iDataCur,
+        OPFLAG_ISUPDATE | ((hasFK>1 || chngKey) ? 0 : OPFLAG_ISNOOP),
+        regNewRowid
+    );
+    if( eOnePass==ONEPASS_MULTI ){
+      assert( hasFK==0 && chngKey==0 );
+      sqlite3VdbeChangeP5(v, OPFLAG_SAVEPOSITION);
+    }
+    if( !pParse->nested ){
+      sqlite3VdbeAppendP4(v, pTab, P4_TABLE);
+    }
+#else
+    if( hasFK>1 || chngKey ){
+      sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, 0);
+    }
+#endif
+
+    if( hasFK ){
+      sqlite3FkCheck(pParse, pTab, 0, regNewRowid, aXRef, chngKey);
+    }
+
+    /* Insert the new index entries and the new record. */
+    sqlite3CompleteInsertion(
+        pParse, pTab, iDataCur, iIdxCur, regNewRowid, aRegIdx,
+        OPFLAG_ISUPDATE | (eOnePass==ONEPASS_MULTI ? OPFLAG_SAVEPOSITION : 0),
+        0, 0
+    );
+
+    /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
+    ** handle rows (possibly in other tables) that refer via a foreign key
+    ** to the row just updated. */
+    if( hasFK ){
+      sqlite3FkActions(pParse, pTab, pChanges, regOldRowid, aXRef, chngKey);
+    }
+  }
+
+  /* Increment the row counter
+  */
+  if( regRowCount ){
+    sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
+  }
+
+  if( pTrigger ){
+    sqlite3CodeRowTrigger(pParse, pTrigger, TK_UPDATE, pChanges,
+        TRIGGER_AFTER, pTab, regOldRowid, onError, labelContinue);
+  }
+
+  /* Repeat the above with the next record to be updated, until
+  ** all record selected by the WHERE clause have been updated.
+  */
+  if( eOnePass==ONEPASS_SINGLE ){
+    /* Nothing to do at end-of-loop for a single-pass */
+  }else if( eOnePass==ONEPASS_MULTI ){
+    sqlite3VdbeResolveLabel(v, labelContinue);
+    sqlite3WhereEnd(pWInfo);
+  }else{
+    sqlite3VdbeResolveLabel(v, labelContinue);
+    sqlite3VdbeAddOp2(v, OP_Next, iEph, addrTop); VdbeCoverage(v);
+  }
+  sqlite3VdbeResolveLabel(v, labelBreak);
+
+  /* Update the sqlite_sequence table by storing the content of the
+  ** maximum rowid counter values recorded while inserting into
+  ** autoincrement tables.
+  */
+  if( pParse->nested==0 && pParse->pTriggerTab==0 && pUpsert==0 ){
+    sqlite3AutoincrementEnd(pParse);
+  }
+
+  /*
+  ** Return the number of rows that were changed, if we are tracking
+  ** that information.
+  */
+  if( regRowCount ){
+    sqlite3CodeChangeCount(v, regRowCount, "rows updated");
+  }
+
+update_cleanup:
+  sqlite3AuthContextPop(&sContext);
+  sqlite3DbFree(db, aXRef); /* Also frees aRegIdx[] and aToOpen[] */
+  sqlite3SrcListDelete(db, pTabList);
+  sqlite3ExprListDelete(db, pChanges);
+  sqlite3ExprDelete(db, pWhere);
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT)
+  sqlite3ExprListDelete(db, pOrderBy);
+  sqlite3ExprDelete(db, pLimit);
+#endif
+  return;
+}
+/* Make sure "isView" and other macros defined above are undefined. Otherwise
+** they may interfere with compilation of other functions in this file
+** (or in another file, if this file becomes part of the amalgamation).  */
+#ifdef isView
+ #undef isView
+#endif
+#ifdef pTrigger
+ #undef pTrigger
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Generate code for an UPDATE of a virtual table.
+**
+** There are two possible strategies - the default and the special
+** "onepass" strategy. Onepass is only used if the virtual table
+** implementation indicates that pWhere may match at most one row.
+**
+** The default strategy is to create an ephemeral table that contains
+** for each row to be changed:
+**
+**   (A)  The original rowid of that row.
+**   (B)  The revised rowid for the row.
+**   (C)  The content of every column in the row.
+**
+** Then loop through the contents of this ephemeral table executing a
+** VUpdate for each row. When finished, drop the ephemeral table.
+**
+** The "onepass" strategy does not use an ephemeral table. Instead, it
+** stores the same values (A, B and C above) in a register array and
+** makes a single invocation of VUpdate.
+*/
+static void updateVirtualTable(
+  Parse *pParse,       /* The parsing context */
+  SrcList *pSrc,       /* The virtual table to be modified */
+  Table *pTab,         /* The virtual table */
+  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
+  Expr *pRowid,        /* Expression used to recompute the rowid */
+  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
+  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
+  int onError          /* ON CONFLICT strategy */
+){
+  Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
+  int ephemTab;             /* Table holding the result of the SELECT */
+  int i;                    /* Loop counter */
+  sqlite3 *db = pParse->db; /* Database connection */
+  const char *pVTab = (const char*)sqlite3GetVTable(db, pTab);
+  WhereInfo *pWInfo = 0;
+  int nArg = 2 + pTab->nCol;      /* Number of arguments to VUpdate */
+  int regArg;                     /* First register in VUpdate arg array */
+  int regRec;                     /* Register in which to assemble record */
+  int regRowid;                   /* Register for ephemeral table rowid */
+  int iCsr = pSrc->a[0].iCursor;  /* Cursor used for virtual table scan */
+  int aDummy[2];                  /* Unused arg for sqlite3WhereOkOnePass() */
+  int eOnePass;                   /* True to use onepass strategy */
+  int addr;                       /* Address of OP_OpenEphemeral */
+
+  /* Allocate nArg registers in which to gather the arguments for VUpdate. Then
+  ** create and open the ephemeral table in which the records created from
+  ** these arguments will be temporarily stored. */
+  assert( v );
+  ephemTab = pParse->nTab++;
+  addr= sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, nArg);
+  regArg = pParse->nMem + 1;
+  pParse->nMem += nArg;
+  if( pSrc->nSrc>1 ){
+    Index *pPk = 0;
+    Expr *pRow;
+    ExprList *pList;
+    if( HasRowid(pTab) ){
+      if( pRowid ){
+        pRow = sqlite3ExprDup(db, pRowid, 0);
+      }else{
+        pRow = sqlite3PExpr(pParse, TK_ROW, 0, 0);
+      }
+    }else{
+      i16 iPk;      /* PRIMARY KEY column */
+      pPk = sqlite3PrimaryKeyIndex(pTab);
+      assert( pPk!=0 );
+      assert( pPk->nKeyCol==1 );
+      iPk = pPk->aiColumn[0];
+      if( aXRef[iPk]>=0 ){
+        pRow = sqlite3ExprDup(db, pChanges->a[aXRef[iPk]].pExpr, 0);
+      }else{
+        pRow = exprRowColumn(pParse, iPk);
+      }
+    }
+    pList = sqlite3ExprListAppend(pParse, 0, pRow);
+
+    for(i=0; i<pTab->nCol; i++){
+      if( aXRef[i]>=0 ){
+        pList = sqlite3ExprListAppend(pParse, pList,
+          sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr, 0)
+        );
+      }else{
+        Expr *pRowExpr = exprRowColumn(pParse, i);
+        if( pRowExpr ) pRowExpr->op2 = OPFLAG_NOCHNG;
+        pList = sqlite3ExprListAppend(pParse, pList, pRowExpr);
+      }
+    }
+
+    updateFromSelect(pParse, ephemTab, pPk, pList, pSrc, pWhere, 0, 0);
+    sqlite3ExprListDelete(db, pList);
+    eOnePass = ONEPASS_OFF;
+  }else{
+    regRec = ++pParse->nMem;
+    regRowid = ++pParse->nMem;
+
+    /* Start scanning the virtual table */
+    pWInfo = sqlite3WhereBegin(
+        pParse, pSrc, pWhere, 0, 0, 0, WHERE_ONEPASS_DESIRED, 0
+    );
+    if( pWInfo==0 ) return;
+
+    /* Populate the argument registers. */
+    for(i=0; i<pTab->nCol; i++){
+      assert( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 );
+      if( aXRef[i]>=0 ){
+        sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
+      }else{
+        sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
+        sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG);/* For sqlite3_vtab_nochange() */
+      }
+    }
+    if( HasRowid(pTab) ){
+      sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg);
+      if( pRowid ){
+        sqlite3ExprCode(pParse, pRowid, regArg+1);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg+1);
+      }
+    }else{
+      Index *pPk;   /* PRIMARY KEY index */
+      i16 iPk;      /* PRIMARY KEY column */
+      pPk = sqlite3PrimaryKeyIndex(pTab);
+      assert( pPk!=0 );
+      assert( pPk->nKeyCol==1 );
+      iPk = pPk->aiColumn[0];
+      sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, iPk, regArg);
+      sqlite3VdbeAddOp2(v, OP_SCopy, regArg+2+iPk, regArg+1);
+    }
+
+    eOnePass = sqlite3WhereOkOnePass(pWInfo, aDummy);
+
+    /* There is no ONEPASS_MULTI on virtual tables */
+    assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
+
+    if( eOnePass ){
+      /* If using the onepass strategy, no-op out the OP_OpenEphemeral coded
+      ** above. */
+      sqlite3VdbeChangeToNoop(v, addr);
+      sqlite3VdbeAddOp1(v, OP_Close, iCsr);
+    }else{
+      /* Create a record from the argument register contents and insert it into
+      ** the ephemeral table. */
+      sqlite3MultiWrite(pParse);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regArg, nArg, regRec);
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_ENABLE_NULL_TRIM)
+      /* Signal an assert() within OP_MakeRecord that it is allowed to
+      ** accept no-change records with serial_type 10 */
+      sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG_MAGIC);
+#endif
+      sqlite3VdbeAddOp2(v, OP_NewRowid, ephemTab, regRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, ephemTab, regRec, regRowid);
+    }
+  }
+
+
+  if( eOnePass==ONEPASS_OFF ){
+    /* End the virtual table scan */
+    if( pSrc->nSrc==1 ){
+      sqlite3WhereEnd(pWInfo);
+    }
+
+    /* Begin scanning through the ephemeral table. */
+    addr = sqlite3VdbeAddOp1(v, OP_Rewind, ephemTab); VdbeCoverage(v);
+
+    /* Extract arguments from the current row of the ephemeral table and
+    ** invoke the VUpdate method.  */
+    for(i=0; i<nArg; i++){
+      sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i, regArg+i);
+    }
+  }
+  sqlite3VtabMakeWritable(pParse, pTab);
+  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, nArg, regArg, pVTab, P4_VTAB);
+  sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
+  sqlite3MayAbort(pParse);
+
+  /* End of the ephemeral table scan. Or, if using the onepass strategy,
+  ** jump to here if the scan visited zero rows. */
+  if( eOnePass==ONEPASS_OFF ){
+    sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr+1); VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addr);
+    sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);
+  }else{
+    sqlite3WhereEnd(pWInfo);
+  }
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
diff --git a/src/upsert.c b/src/upsert.c
new file mode 100644
index 0000000..be0d055
--- /dev/null
+++ b/src/upsert.c
@@ -0,0 +1,316 @@
+/*
+** 2018-04-12
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code to implement various aspects of UPSERT
+** processing and handling of the Upsert object.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_UPSERT
+/*
+** Free a list of Upsert objects
+*/
+static void SQLITE_NOINLINE upsertDelete(sqlite3 *db, Upsert *p){
+  do{
+    Upsert *pNext = p->pNextUpsert;
+    sqlite3ExprListDelete(db, p->pUpsertTarget);
+    sqlite3ExprDelete(db, p->pUpsertTargetWhere);
+    sqlite3ExprListDelete(db, p->pUpsertSet);
+    sqlite3ExprDelete(db, p->pUpsertWhere);
+    sqlite3DbFree(db, p->pToFree);
+    sqlite3DbFree(db, p);
+    p = pNext;
+  }while( p );
+}
+void sqlite3UpsertDelete(sqlite3 *db, Upsert *p){
+  if( p ) upsertDelete(db, p);
+}
+
+
+/*
+** Duplicate an Upsert object.
+*/
+Upsert *sqlite3UpsertDup(sqlite3 *db, Upsert *p){
+  if( p==0 ) return 0;
+  return sqlite3UpsertNew(db,
+           sqlite3ExprListDup(db, p->pUpsertTarget, 0),
+           sqlite3ExprDup(db, p->pUpsertTargetWhere, 0),
+           sqlite3ExprListDup(db, p->pUpsertSet, 0),
+           sqlite3ExprDup(db, p->pUpsertWhere, 0),
+           sqlite3UpsertDup(db, p->pNextUpsert)
+         );
+}
+
+/*
+** Create a new Upsert object.
+*/
+Upsert *sqlite3UpsertNew(
+  sqlite3 *db,           /* Determines which memory allocator to use */
+  ExprList *pTarget,     /* Target argument to ON CONFLICT, or NULL */
+  Expr *pTargetWhere,    /* Optional WHERE clause on the target */
+  ExprList *pSet,        /* UPDATE columns, or NULL for a DO NOTHING */
+  Expr *pWhere,          /* WHERE clause for the ON CONFLICT UPDATE */
+  Upsert *pNext          /* Next ON CONFLICT clause in the list */
+){
+  Upsert *pNew;
+  pNew = sqlite3DbMallocZero(db, sizeof(Upsert));
+  if( pNew==0 ){
+    sqlite3ExprListDelete(db, pTarget);
+    sqlite3ExprDelete(db, pTargetWhere);
+    sqlite3ExprListDelete(db, pSet);
+    sqlite3ExprDelete(db, pWhere);
+    sqlite3UpsertDelete(db, pNext);
+    return 0;
+  }else{
+    pNew->pUpsertTarget = pTarget;
+    pNew->pUpsertTargetWhere = pTargetWhere;
+    pNew->pUpsertSet = pSet;
+    pNew->pUpsertWhere = pWhere;
+    pNew->isDoUpdate = pSet!=0;
+    pNew->pNextUpsert = pNext;
+  }
+  return pNew;
+}
+
+/*
+** Analyze the ON CONFLICT clause described by pUpsert.  Resolve all
+** symbols in the conflict-target.
+**
+** Return SQLITE_OK if everything works, or an error code is something
+** is wrong.
+*/
+int sqlite3UpsertAnalyzeTarget(
+  Parse *pParse,     /* The parsing context */
+  SrcList *pTabList, /* Table into which we are inserting */
+  Upsert *pUpsert    /* The ON CONFLICT clauses */
+){
+  Table *pTab;            /* That table into which we are inserting */
+  int rc;                 /* Result code */
+  int iCursor;            /* Cursor used by pTab */
+  Index *pIdx;            /* One of the indexes of pTab */
+  ExprList *pTarget;      /* The conflict-target clause */
+  Expr *pTerm;            /* One term of the conflict-target clause */
+  NameContext sNC;        /* Context for resolving symbolic names */
+  Expr sCol[2];           /* Index column converted into an Expr */
+  int nClause = 0;        /* Counter of ON CONFLICT clauses */
+
+  assert( pTabList->nSrc==1 );
+  assert( pTabList->a[0].pTab!=0 );
+  assert( pUpsert!=0 );
+  assert( pUpsert->pUpsertTarget!=0 );
+
+  /* Resolve all symbolic names in the conflict-target clause, which
+  ** includes both the list of columns and the optional partial-index
+  ** WHERE clause.
+  */
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = pParse;
+  sNC.pSrcList = pTabList;
+  for(; pUpsert && pUpsert->pUpsertTarget;
+        pUpsert=pUpsert->pNextUpsert, nClause++){
+    rc = sqlite3ResolveExprListNames(&sNC, pUpsert->pUpsertTarget);
+    if( rc ) return rc;
+    rc = sqlite3ResolveExprNames(&sNC, pUpsert->pUpsertTargetWhere);
+    if( rc ) return rc;
+  
+    /* Check to see if the conflict target matches the rowid. */  
+    pTab = pTabList->a[0].pTab;
+    pTarget = pUpsert->pUpsertTarget;
+    iCursor = pTabList->a[0].iCursor;
+    if( HasRowid(pTab) 
+     && pTarget->nExpr==1
+     && (pTerm = pTarget->a[0].pExpr)->op==TK_COLUMN
+     && pTerm->iColumn==XN_ROWID
+    ){
+      /* The conflict-target is the rowid of the primary table */
+      assert( pUpsert->pUpsertIdx==0 );
+      continue;
+    }
+  
+    /* Initialize sCol[0..1] to be an expression parse tree for a
+    ** single column of an index.  The sCol[0] node will be the TK_COLLATE
+    ** operator and sCol[1] will be the TK_COLUMN operator.  Code below
+    ** will populate the specific collation and column number values
+    ** prior to comparing against the conflict-target expression.
+    */
+    memset(sCol, 0, sizeof(sCol));
+    sCol[0].op = TK_COLLATE;
+    sCol[0].pLeft = &sCol[1];
+    sCol[1].op = TK_COLUMN;
+    sCol[1].iTable = pTabList->a[0].iCursor;
+  
+    /* Check for matches against other indexes */
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      int ii, jj, nn;
+      if( !IsUniqueIndex(pIdx) ) continue;
+      if( pTarget->nExpr!=pIdx->nKeyCol ) continue;
+      if( pIdx->pPartIdxWhere ){
+        if( pUpsert->pUpsertTargetWhere==0 ) continue;
+        if( sqlite3ExprCompare(pParse, pUpsert->pUpsertTargetWhere,
+                               pIdx->pPartIdxWhere, iCursor)!=0 ){
+          continue;
+        }
+      }
+      nn = pIdx->nKeyCol;
+      for(ii=0; ii<nn; ii++){
+        Expr *pExpr;
+        sCol[0].u.zToken = (char*)pIdx->azColl[ii];
+        if( pIdx->aiColumn[ii]==XN_EXPR ){
+          assert( pIdx->aColExpr!=0 );
+          assert( pIdx->aColExpr->nExpr>ii );
+          assert( pIdx->bHasExpr );
+          pExpr = pIdx->aColExpr->a[ii].pExpr;
+          if( pExpr->op!=TK_COLLATE ){
+            sCol[0].pLeft = pExpr;
+            pExpr = &sCol[0];
+          }
+        }else{
+          sCol[0].pLeft = &sCol[1];
+          sCol[1].iColumn = pIdx->aiColumn[ii];
+          pExpr = &sCol[0];
+        }
+        for(jj=0; jj<nn; jj++){
+          if( sqlite3ExprCompare(0,pTarget->a[jj].pExpr,pExpr,iCursor)<2 ){
+            break;  /* Column ii of the index matches column jj of target */
+          }
+        }
+        if( jj>=nn ){
+          /* The target contains no match for column jj of the index */
+          break;
+        }
+      }
+      if( ii<nn ){
+        /* Column ii of the index did not match any term of the conflict target.
+        ** Continue the search with the next index. */
+        continue;
+      }
+      pUpsert->pUpsertIdx = pIdx;
+      break;
+    }
+    if( pUpsert->pUpsertIdx==0 ){
+      char zWhich[16];
+      if( nClause==0 && pUpsert->pNextUpsert==0 ){
+        zWhich[0] = 0;
+      }else{
+        sqlite3_snprintf(sizeof(zWhich),zWhich,"%r ", nClause+1);
+      }
+      sqlite3ErrorMsg(pParse, "%sON CONFLICT clause does not match any "
+                              "PRIMARY KEY or UNIQUE constraint", zWhich);
+      return SQLITE_ERROR;
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Return true if pUpsert is the last ON CONFLICT clause with a
+** conflict target, or if pUpsert is followed by another ON CONFLICT
+** clause that targets the INTEGER PRIMARY KEY.
+*/
+int sqlite3UpsertNextIsIPK(Upsert *pUpsert){
+  Upsert *pNext;
+  if( NEVER(pUpsert==0) ) return 0;
+  pNext = pUpsert->pNextUpsert;
+  if( pNext==0 ) return 1;
+  if( pNext->pUpsertTarget==0 ) return 1;
+  if( pNext->pUpsertIdx==0 ) return 1;
+  return 0;
+}
+
+/*
+** Given the list of ON CONFLICT clauses described by pUpsert, and
+** a particular index pIdx, return a pointer to the particular ON CONFLICT
+** clause that applies to the index.  Or, if the index is not subject to
+** any ON CONFLICT clause, return NULL.
+*/
+Upsert *sqlite3UpsertOfIndex(Upsert *pUpsert, Index *pIdx){
+  while(
+      pUpsert
+   && pUpsert->pUpsertTarget!=0
+   && pUpsert->pUpsertIdx!=pIdx
+  ){
+     pUpsert = pUpsert->pNextUpsert;
+  }
+  return pUpsert;
+}
+
+/*
+** Generate bytecode that does an UPDATE as part of an upsert.
+**
+** If pIdx is NULL, then the UNIQUE constraint that failed was the IPK.
+** In this case parameter iCur is a cursor open on the table b-tree that
+** currently points to the conflicting table row. Otherwise, if pIdx
+** is not NULL, then pIdx is the constraint that failed and iCur is a
+** cursor points to the conflicting row.
+*/
+void sqlite3UpsertDoUpdate(
+  Parse *pParse,        /* The parsing and code-generating context */
+  Upsert *pUpsert,      /* The ON CONFLICT clause for the upsert */
+  Table *pTab,          /* The table being updated */
+  Index *pIdx,          /* The UNIQUE constraint that failed */
+  int iCur              /* Cursor for pIdx (or pTab if pIdx==NULL) */
+){
+  Vdbe *v = pParse->pVdbe;
+  sqlite3 *db = pParse->db;
+  SrcList *pSrc;            /* FROM clause for the UPDATE */
+  int iDataCur;
+  int i;
+  Upsert *pTop = pUpsert;
+
+  assert( v!=0 );
+  assert( pUpsert!=0 );
+  iDataCur = pUpsert->iDataCur;
+  pUpsert = sqlite3UpsertOfIndex(pTop, pIdx);
+  VdbeNoopComment((v, "Begin DO UPDATE of UPSERT"));
+  if( pIdx && iCur!=iDataCur ){
+    if( HasRowid(pTab) ){
+      int regRowid = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp2(v, OP_IdxRowid, iCur, regRowid);
+      sqlite3VdbeAddOp3(v, OP_SeekRowid, iDataCur, 0, regRowid);
+      VdbeCoverage(v);
+      sqlite3ReleaseTempReg(pParse, regRowid);
+    }else{
+      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+      int nPk = pPk->nKeyCol;
+      int iPk = pParse->nMem+1;
+      pParse->nMem += nPk;
+      for(i=0; i<nPk; i++){
+        int k;
+        assert( pPk->aiColumn[i]>=0 );
+        k = sqlite3TableColumnToIndex(pIdx, pPk->aiColumn[i]);
+        sqlite3VdbeAddOp3(v, OP_Column, iCur, k, iPk+i);
+        VdbeComment((v, "%s.%s", pIdx->zName,
+                    pTab->aCol[pPk->aiColumn[i]].zCnName));
+      }
+      sqlite3VdbeVerifyAbortable(v, OE_Abort);
+      i = sqlite3VdbeAddOp4Int(v, OP_Found, iDataCur, 0, iPk, nPk);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp4(v, OP_Halt, SQLITE_CORRUPT, OE_Abort, 0, 
+            "corrupt database", P4_STATIC);
+      sqlite3MayAbort(pParse);
+      sqlite3VdbeJumpHere(v, i);
+    }
+  }
+  /* pUpsert does not own pTop->pUpsertSrc - the outer INSERT statement does.
+  ** So we have to make a copy before passing it down into sqlite3Update() */
+  pSrc = sqlite3SrcListDup(db, pTop->pUpsertSrc, 0);
+  /* excluded.* columns of type REAL need to be converted to a hard real */
+  for(i=0; i<pTab->nCol; i++){
+    if( pTab->aCol[i].affinity==SQLITE_AFF_REAL ){
+      sqlite3VdbeAddOp1(v, OP_RealAffinity, pTop->regData+i);
+    }
+  }
+  sqlite3Update(pParse, pSrc, sqlite3ExprListDup(db,pUpsert->pUpsertSet,0),
+      sqlite3ExprDup(db,pUpsert->pUpsertWhere,0), OE_Abort, 0, 0, pUpsert);
+  VdbeNoopComment((v, "End DO UPDATE of UPSERT"));
+}
+
+#endif /* SQLITE_OMIT_UPSERT */
diff --git a/src/utf.c b/src/utf.c
new file mode 100644
index 0000000..216864f
--- /dev/null
+++ b/src/utf.c
@@ -0,0 +1,566 @@
+/*
+** 2004 April 13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains routines used to translate between UTF-8, 
+** UTF-16, UTF-16BE, and UTF-16LE.
+**
+** Notes on UTF-8:
+**
+**   Byte-0    Byte-1    Byte-2    Byte-3    Value
+**  0xxxxxxx                                 00000000 00000000 0xxxxxxx
+**  110yyyyy  10xxxxxx                       00000000 00000yyy yyxxxxxx
+**  1110zzzz  10yyyyyy  10xxxxxx             00000000 zzzzyyyy yyxxxxxx
+**  11110uuu  10uuzzzz  10yyyyyy  10xxxxxx   000uuuuu zzzzyyyy yyxxxxxx
+**
+**
+** Notes on UTF-16:  (with wwww+1==uuuuu)
+**
+**      Word-0               Word-1          Value
+**  110110ww wwzzzzyy   110111yy yyxxxxxx    000uuuuu zzzzyyyy yyxxxxxx
+**  zzzzyyyy yyxxxxxx                        00000000 zzzzyyyy yyxxxxxx
+**
+**
+** BOM or Byte Order Mark:
+**     0xff 0xfe   little-endian utf-16 follows
+**     0xfe 0xff   big-endian utf-16 follows
+**
+*/
+#include "sqliteInt.h"
+#include <assert.h>
+#include "vdbeInt.h"
+
+#if !defined(SQLITE_AMALGAMATION) && SQLITE_BYTEORDER==0
+/*
+** The following constant value is used by the SQLITE_BIGENDIAN and
+** SQLITE_LITTLEENDIAN macros.
+*/
+const int sqlite3one = 1;
+#endif /* SQLITE_AMALGAMATION && SQLITE_BYTEORDER==0 */
+
+/*
+** This lookup table is used to help decode the first byte of
+** a multi-byte UTF8 character.
+*/
+static const unsigned char sqlite3Utf8Trans1[] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00,
+};
+
+
+#define WRITE_UTF8(zOut, c) {                          \
+  if( c<0x00080 ){                                     \
+    *zOut++ = (u8)(c&0xFF);                            \
+  }                                                    \
+  else if( c<0x00800 ){                                \
+    *zOut++ = 0xC0 + (u8)((c>>6)&0x1F);                \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+  else if( c<0x10000 ){                                \
+    *zOut++ = 0xE0 + (u8)((c>>12)&0x0F);               \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }else{                                               \
+    *zOut++ = 0xF0 + (u8)((c>>18) & 0x07);             \
+    *zOut++ = 0x80 + (u8)((c>>12) & 0x3F);             \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+}
+
+#define WRITE_UTF16LE(zOut, c) {                                    \
+  if( c<=0xFFFF ){                                                  \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+    *zOut++ = (u8)((c>>8)&0x00FF);                                  \
+  }else{                                                            \
+    *zOut++ = (u8)(((c>>10)&0x003F) + (((c-0x10000)>>10)&0x00C0));  \
+    *zOut++ = (u8)(0x00D8 + (((c-0x10000)>>18)&0x03));              \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+    *zOut++ = (u8)(0x00DC + ((c>>8)&0x03));                         \
+  }                                                                 \
+}
+
+#define WRITE_UTF16BE(zOut, c) {                                    \
+  if( c<=0xFFFF ){                                                  \
+    *zOut++ = (u8)((c>>8)&0x00FF);                                  \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+  }else{                                                            \
+    *zOut++ = (u8)(0x00D8 + (((c-0x10000)>>18)&0x03));              \
+    *zOut++ = (u8)(((c>>10)&0x003F) + (((c-0x10000)>>10)&0x00C0));  \
+    *zOut++ = (u8)(0x00DC + ((c>>8)&0x03));                         \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+  }                                                                 \
+}
+
+/*
+** Translate a single UTF-8 character.  Return the unicode value.
+**
+** During translation, assume that the byte that zTerm points
+** is a 0x00.
+**
+** Write a pointer to the next unread byte back into *pzNext.
+**
+** Notes On Invalid UTF-8:
+**
+**  *  This routine never allows a 7-bit character (0x00 through 0x7f) to
+**     be encoded as a multi-byte character.  Any multi-byte character that
+**     attempts to encode a value between 0x00 and 0x7f is rendered as 0xfffd.
+**
+**  *  This routine never allows a UTF16 surrogate value to be encoded.
+**     If a multi-byte character attempts to encode a value between
+**     0xd800 and 0xe000 then it is rendered as 0xfffd.
+**
+**  *  Bytes in the range of 0x80 through 0xbf which occur as the first
+**     byte of a character are interpreted as single-byte characters
+**     and rendered as themselves even though they are technically
+**     invalid characters.
+**
+**  *  This routine accepts over-length UTF8 encodings
+**     for unicode values 0x80 and greater.  It does not change over-length
+**     encodings to 0xfffd as some systems recommend.
+*/
+#define READ_UTF8(zIn, zTerm, c)                           \
+  c = *(zIn++);                                            \
+  if( c>=0xc0 ){                                           \
+    c = sqlite3Utf8Trans1[c-0xc0];                         \
+    while( zIn!=zTerm && (*zIn & 0xc0)==0x80 ){            \
+      c = (c<<6) + (0x3f & *(zIn++));                      \
+    }                                                      \
+    if( c<0x80                                             \
+        || (c&0xFFFFF800)==0xD800                          \
+        || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }        \
+  }
+u32 sqlite3Utf8Read(
+  const unsigned char **pz    /* Pointer to string from which to read char */
+){
+  unsigned int c;
+
+  /* Same as READ_UTF8() above but without the zTerm parameter.
+  ** For this routine, we assume the UTF8 string is always zero-terminated.
+  */
+  c = *((*pz)++);
+  if( c>=0xc0 ){
+    c = sqlite3Utf8Trans1[c-0xc0];
+    while( (*(*pz) & 0xc0)==0x80 ){
+      c = (c<<6) + (0x3f & *((*pz)++));
+    }
+    if( c<0x80
+        || (c&0xFFFFF800)==0xD800
+        || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }
+  }
+  return c;
+}
+
+/*
+** Read a single UTF8 character out of buffer z[], but reading no
+** more than n characters from the buffer.  z[] is not zero-terminated.
+**
+** Return the number of bytes used to construct the character.
+**
+** Invalid UTF8 might generate a strange result.  No effort is made
+** to detect invalid UTF8.
+**
+** At most 4 bytes will be read out of z[].  The return value will always
+** be between 1 and 4.
+*/
+int sqlite3Utf8ReadLimited(
+  const u8 *z,
+  int n,
+  u32 *piOut
+){
+  u32 c;
+  int i = 1;
+  assert( n>0 );
+  c = z[0];
+  if( c>=0xc0 ){
+    c = sqlite3Utf8Trans1[c-0xc0];
+    if( n>4 ) n = 4;
+    while( i<n && (z[i] & 0xc0)==0x80 ){
+      c = (c<<6) + (0x3f & z[i]);
+      i++;
+    }
+  }
+  *piOut = c;
+  return i;
+}
+
+
+/*
+** If the TRANSLATE_TRACE macro is defined, the value of each Mem is
+** printed on stderr on the way into and out of sqlite3VdbeMemTranslate().
+*/ 
+/* #define TRANSLATE_TRACE 1 */
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** This routine transforms the internal text encoding used by pMem to
+** desiredEnc. It is an error if the string is already of the desired
+** encoding, or if *pMem does not contain a string value.
+*/
+SQLITE_NOINLINE int sqlite3VdbeMemTranslate(Mem *pMem, u8 desiredEnc){
+  sqlite3_int64 len;          /* Maximum length of output string in bytes */
+  unsigned char *zOut;        /* Output buffer */
+  unsigned char *zIn;         /* Input iterator */
+  unsigned char *zTerm;       /* End of input */
+  unsigned char *z;           /* Output iterator */
+  unsigned int c;
+
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( pMem->flags&MEM_Str );
+  assert( pMem->enc!=desiredEnc );
+  assert( pMem->enc!=0 );
+  assert( pMem->n>=0 );
+
+#if defined(TRANSLATE_TRACE) && defined(SQLITE_DEBUG)
+  {
+    StrAccum acc;
+    char zBuf[1000];
+    sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);  
+    sqlite3VdbeMemPrettyPrint(pMem, &acc);
+    fprintf(stderr, "INPUT:  %s\n", sqlite3StrAccumFinish(&acc));
+  }
+#endif
+
+  /* If the translation is between UTF-16 little and big endian, then 
+  ** all that is required is to swap the byte order. This case is handled
+  ** differently from the others.
+  */
+  if( pMem->enc!=SQLITE_UTF8 && desiredEnc!=SQLITE_UTF8 ){
+    u8 temp;
+    int rc;
+    rc = sqlite3VdbeMemMakeWriteable(pMem);
+    if( rc!=SQLITE_OK ){
+      assert( rc==SQLITE_NOMEM );
+      return SQLITE_NOMEM_BKPT;
+    }
+    zIn = (u8*)pMem->z;
+    zTerm = &zIn[pMem->n&~1];
+    while( zIn<zTerm ){
+      temp = *zIn;
+      *zIn = *(zIn+1);
+      zIn++;
+      *zIn++ = temp;
+    }
+    pMem->enc = desiredEnc;
+    goto translate_out;
+  }
+
+  /* Set len to the maximum number of bytes required in the output buffer. */
+  if( desiredEnc==SQLITE_UTF8 ){
+    /* When converting from UTF-16, the maximum growth results from
+    ** translating a 2-byte character to a 4-byte UTF-8 character.
+    ** A single byte is required for the output string
+    ** nul-terminator.
+    */
+    pMem->n &= ~1;
+    len = 2 * (sqlite3_int64)pMem->n + 1;
+  }else{
+    /* When converting from UTF-8 to UTF-16 the maximum growth is caused
+    ** when a 1-byte UTF-8 character is translated into a 2-byte UTF-16
+    ** character. Two bytes are required in the output buffer for the
+    ** nul-terminator.
+    */
+    len = 2 * (sqlite3_int64)pMem->n + 2;
+  }
+
+  /* Set zIn to point at the start of the input buffer and zTerm to point 1
+  ** byte past the end.
+  **
+  ** Variable zOut is set to point at the output buffer, space obtained
+  ** from sqlite3_malloc().
+  */
+  zIn = (u8*)pMem->z;
+  zTerm = &zIn[pMem->n];
+  zOut = sqlite3DbMallocRaw(pMem->db, len);
+  if( !zOut ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  z = zOut;
+
+  if( pMem->enc==SQLITE_UTF8 ){
+    if( desiredEnc==SQLITE_UTF16LE ){
+      /* UTF-8 -> UTF-16 Little-endian */
+      while( zIn<zTerm ){
+        READ_UTF8(zIn, zTerm, c);
+        WRITE_UTF16LE(z, c);
+      }
+    }else{
+      assert( desiredEnc==SQLITE_UTF16BE );
+      /* UTF-8 -> UTF-16 Big-endian */
+      while( zIn<zTerm ){
+        READ_UTF8(zIn, zTerm, c);
+        WRITE_UTF16BE(z, c);
+      }
+    }
+    pMem->n = (int)(z - zOut);
+    *z++ = 0;
+  }else{
+    assert( desiredEnc==SQLITE_UTF8 );
+    if( pMem->enc==SQLITE_UTF16LE ){
+      /* UTF-16 Little-endian -> UTF-8 */
+      while( zIn<zTerm ){
+        c = *(zIn++);
+        c += (*(zIn++))<<8;
+        if( c>=0xd800 && c<0xe000 ){
+#ifdef SQLITE_REPLACE_INVALID_UTF
+          if( c>=0xdc00 || zIn>=zTerm ){
+            c = 0xfffd;
+          }else{
+            int c2 = *(zIn++);
+            c2 += (*(zIn++))<<8;
+            if( c2<0xdc00 || c2>=0xe000 ){
+              zIn -= 2;
+              c = 0xfffd;
+            }else{
+              c = ((c&0x3ff)<<10) + (c2&0x3ff) + 0x10000;
+            }
+          }
+#else
+          if( zIn<zTerm ){
+            int c2 = (*zIn++);
+            c2 += ((*zIn++)<<8);
+            c = (c2&0x03FF) + ((c&0x003F)<<10) + (((c&0x03C0)+0x0040)<<10);
+          }
+#endif
+        }
+        WRITE_UTF8(z, c);
+      }
+    }else{
+      /* UTF-16 Big-endian -> UTF-8 */
+      while( zIn<zTerm ){
+        c = (*(zIn++))<<8;
+        c += *(zIn++);
+        if( c>=0xd800 && c<0xe000 ){
+#ifdef SQLITE_REPLACE_INVALID_UTF
+          if( c>=0xdc00 || zIn>=zTerm ){
+            c = 0xfffd;
+          }else{
+            int c2 = (*(zIn++))<<8;
+            c2 += *(zIn++);
+            if( c2<0xdc00 || c2>=0xe000 ){
+              zIn -= 2;
+              c = 0xfffd;
+            }else{
+              c = ((c&0x3ff)<<10) + (c2&0x3ff) + 0x10000;
+            }
+          }
+#else
+          if( zIn<zTerm ){
+            int c2 = ((*zIn++)<<8);
+            c2 += (*zIn++);
+            c = (c2&0x03FF) + ((c&0x003F)<<10) + (((c&0x03C0)+0x0040)<<10);
+          }
+#endif
+        }
+        WRITE_UTF8(z, c);
+      }
+    }
+    pMem->n = (int)(z - zOut);
+  }
+  *z = 0;
+  assert( (pMem->n+(desiredEnc==SQLITE_UTF8?1:2))<=len );
+
+  c = MEM_Str|MEM_Term|(pMem->flags&(MEM_AffMask|MEM_Subtype));
+  sqlite3VdbeMemRelease(pMem);
+  pMem->flags = c;
+  pMem->enc = desiredEnc;
+  pMem->z = (char*)zOut;
+  pMem->zMalloc = pMem->z;
+  pMem->szMalloc = sqlite3DbMallocSize(pMem->db, pMem->z);
+
+translate_out:
+#if defined(TRANSLATE_TRACE) && defined(SQLITE_DEBUG)
+  {
+    StrAccum acc;
+    char zBuf[1000];
+    sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);  
+    sqlite3VdbeMemPrettyPrint(pMem, &acc);
+    fprintf(stderr, "OUTPUT: %s\n", sqlite3StrAccumFinish(&acc));
+  }
+#endif
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** This routine checks for a byte-order mark at the beginning of the 
+** UTF-16 string stored in *pMem. If one is present, it is removed and
+** the encoding of the Mem adjusted. This routine does not do any
+** byte-swapping, it just sets Mem.enc appropriately.
+**
+** The allocation (static, dynamic etc.) and encoding of the Mem may be
+** changed by this function.
+*/
+int sqlite3VdbeMemHandleBom(Mem *pMem){
+  int rc = SQLITE_OK;
+  u8 bom = 0;
+
+  assert( pMem->n>=0 );
+  if( pMem->n>1 ){
+    u8 b1 = *(u8 *)pMem->z;
+    u8 b2 = *(((u8 *)pMem->z) + 1);
+    if( b1==0xFE && b2==0xFF ){
+      bom = SQLITE_UTF16BE;
+    }
+    if( b1==0xFF && b2==0xFE ){
+      bom = SQLITE_UTF16LE;
+    }
+  }
+  
+  if( bom ){
+    rc = sqlite3VdbeMemMakeWriteable(pMem);
+    if( rc==SQLITE_OK ){
+      pMem->n -= 2;
+      memmove(pMem->z, &pMem->z[2], pMem->n);
+      pMem->z[pMem->n] = '\0';
+      pMem->z[pMem->n+1] = '\0';
+      pMem->flags |= MEM_Term;
+      pMem->enc = bom;
+    }
+  }
+  return rc;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** pZ is a UTF-8 encoded unicode string. If nByte is less than zero,
+** return the number of unicode characters in pZ up to (but not including)
+** the first 0x00 byte. If nByte is not less than zero, return the
+** number of unicode characters in the first nByte of pZ (or up to 
+** the first 0x00, whichever comes first).
+*/
+int sqlite3Utf8CharLen(const char *zIn, int nByte){
+  int r = 0;
+  const u8 *z = (const u8*)zIn;
+  const u8 *zTerm;
+  if( nByte>=0 ){
+    zTerm = &z[nByte];
+  }else{
+    zTerm = (const u8*)(-1);
+  }
+  assert( z<=zTerm );
+  while( *z!=0 && z<zTerm ){
+    SQLITE_SKIP_UTF8(z);
+    r++;
+  }
+  return r;
+}
+
+/* This test function is not currently used by the automated test-suite. 
+** Hence it is only available in debug builds.
+*/
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+/*
+** Translate UTF-8 to UTF-8.
+**
+** This has the effect of making sure that the string is well-formed
+** UTF-8.  Miscoded characters are removed.
+**
+** The translation is done in-place and aborted if the output
+** overruns the input.
+*/
+int sqlite3Utf8To8(unsigned char *zIn){
+  unsigned char *zOut = zIn;
+  unsigned char *zStart = zIn;
+  u32 c;
+
+  while( zIn[0] && zOut<=zIn ){
+    c = sqlite3Utf8Read((const u8**)&zIn);
+    if( c!=0xfffd ){
+      WRITE_UTF8(zOut, c);
+    }
+  }
+  *zOut = 0;
+  return (int)(zOut - zStart);
+}
+#endif
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Convert a UTF-16 string in the native encoding into a UTF-8 string.
+** Memory to hold the UTF-8 string is obtained from sqlite3_malloc and must
+** be freed by the calling function.
+**
+** NULL is returned if there is an allocation error.
+*/
+char *sqlite3Utf16to8(sqlite3 *db, const void *z, int nByte, u8 enc){
+  Mem m;
+  memset(&m, 0, sizeof(m));
+  m.db = db;
+  sqlite3VdbeMemSetStr(&m, z, nByte, enc, SQLITE_STATIC);
+  sqlite3VdbeChangeEncoding(&m, SQLITE_UTF8);
+  if( db->mallocFailed ){
+    sqlite3VdbeMemRelease(&m);
+    m.z = 0;
+  }
+  assert( (m.flags & MEM_Term)!=0 || db->mallocFailed );
+  assert( (m.flags & MEM_Str)!=0 || db->mallocFailed );
+  assert( m.z || db->mallocFailed );
+  return m.z;
+}
+
+/*
+** zIn is a UTF-16 encoded unicode string at least nChar characters long.
+** Return the number of bytes in the first nChar unicode characters
+** in pZ.  nChar must be non-negative.
+*/
+int sqlite3Utf16ByteLen(const void *zIn, int nChar){
+  int c;
+  unsigned char const *z = zIn;
+  int n = 0;
+  
+  if( SQLITE_UTF16NATIVE==SQLITE_UTF16LE ) z++;
+  while( n<nChar ){
+    c = z[0];
+    z += 2;
+    if( c>=0xd8 && c<0xdc && z[0]>=0xdc && z[0]<0xe0 ) z += 2;
+    n++;
+  }
+  return (int)(z-(unsigned char const *)zIn) 
+              - (SQLITE_UTF16NATIVE==SQLITE_UTF16LE);
+}
+
+#if defined(SQLITE_TEST)
+/*
+** This routine is called from the TCL test function "translate_selftest".
+** It checks that the primitives for serializing and deserializing
+** characters in each encoding are inverses of each other.
+*/
+void sqlite3UtfSelfTest(void){
+  unsigned int i, t;
+  unsigned char zBuf[20];
+  unsigned char *z;
+  int n;
+  unsigned int c;
+
+  for(i=0; i<0x00110000; i++){
+    z = zBuf;
+    WRITE_UTF8(z, i);
+    n = (int)(z-zBuf);
+    assert( n>0 && n<=4 );
+    z[0] = 0;
+    z = zBuf;
+    c = sqlite3Utf8Read((const u8**)&z);
+    t = i;
+    if( i>=0xD800 && i<=0xDFFF ) t = 0xFFFD;
+    if( (i&0xFFFFFFFE)==0xFFFE ) t = 0xFFFD;
+    assert( c==t );
+    assert( (z-zBuf)==n );
+  }
+}
+#endif /* SQLITE_TEST */
+#endif /* SQLITE_OMIT_UTF16 */
diff --git a/src/util.c b/src/util.c
new file mode 100644
index 0000000..207b901
--- /dev/null
+++ b/src/util.c
@@ -0,0 +1,1839 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Utility functions used throughout sqlite.
+**
+** This file contains functions for allocating memory, comparing
+** strings, and stuff like that.
+**
+*/
+#include "sqliteInt.h"
+#include <stdarg.h>
+#ifndef SQLITE_OMIT_FLOATING_POINT
+#include <math.h>
+#endif
+
+/*
+** Calls to sqlite3FaultSim() are used to simulate a failure during testing,
+** or to bypass normal error detection during testing in order to let
+** execute proceed further downstream.
+**
+** In deployment, sqlite3FaultSim() *always* return SQLITE_OK (0).  The
+** sqlite3FaultSim() function only returns non-zero during testing.
+**
+** During testing, if the test harness has set a fault-sim callback using
+** a call to sqlite3_test_control(SQLITE_TESTCTRL_FAULT_INSTALL), then
+** each call to sqlite3FaultSim() is relayed to that application-supplied
+** callback and the integer return value form the application-supplied
+** callback is returned by sqlite3FaultSim().
+**
+** The integer argument to sqlite3FaultSim() is a code to identify which
+** sqlite3FaultSim() instance is being invoked. Each call to sqlite3FaultSim()
+** should have a unique code.  To prevent legacy testing applications from
+** breaking, the codes should not be changed or reused.
+*/
+#ifndef SQLITE_UNTESTABLE
+int sqlite3FaultSim(int iTest){
+  int (*xCallback)(int) = sqlite3GlobalConfig.xTestCallback;
+  return xCallback ? xCallback(iTest) : SQLITE_OK;
+}
+#endif
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/*
+** Return true if the floating point value is Not a Number (NaN).
+**
+** Use the math library isnan() function if compiled with SQLITE_HAVE_ISNAN.
+** Otherwise, we have our own implementation that works on most systems.
+*/
+int sqlite3IsNaN(double x){
+  int rc;   /* The value return */
+#if !SQLITE_HAVE_ISNAN && !HAVE_ISNAN
+  u64 y;
+  memcpy(&y,&x,sizeof(y));
+  rc = IsNaN(y);
+#else
+  rc = isnan(x);
+#endif /* HAVE_ISNAN */
+  testcase( rc );
+  return rc;
+}
+#endif /* SQLITE_OMIT_FLOATING_POINT */
+
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+**
+** The value returned will never be negative.  Nor will it ever be greater
+** than the actual length of the string.  For very long strings (greater
+** than 1GiB) the value returned might be less than the true string length.
+*/
+int sqlite3Strlen30(const char *z){
+  if( z==0 ) return 0;
+  return 0x3fffffff & (int)strlen(z);
+}
+
+/*
+** Return the declared type of a column.  Or return zDflt if the column
+** has no declared type.
+**
+** The column type is an extra string stored after the zero-terminator on
+** the column name if and only if the COLFLAG_HASTYPE flag is set.
+*/
+char *sqlite3ColumnType(Column *pCol, char *zDflt){
+  if( pCol->colFlags & COLFLAG_HASTYPE ){
+    return pCol->zCnName + strlen(pCol->zCnName) + 1;
+  }else if( pCol->eCType ){
+    assert( pCol->eCType<=SQLITE_N_STDTYPE );
+    return (char*)sqlite3StdType[pCol->eCType-1];
+  }else{
+    return zDflt;
+  }
+}
+
+/*
+** Helper function for sqlite3Error() - called rarely.  Broken out into
+** a separate routine to avoid unnecessary register saves on entry to
+** sqlite3Error().
+*/
+static SQLITE_NOINLINE void  sqlite3ErrorFinish(sqlite3 *db, int err_code){
+  if( db->pErr ) sqlite3ValueSetNull(db->pErr);
+  sqlite3SystemError(db, err_code);
+}
+
+/*
+** Set the current error code to err_code and clear any prior error message.
+** Also set iSysErrno (by calling sqlite3System) if the err_code indicates
+** that would be appropriate.
+*/
+void sqlite3Error(sqlite3 *db, int err_code){
+  assert( db!=0 );
+  db->errCode = err_code;
+  if( err_code || db->pErr ){
+    sqlite3ErrorFinish(db, err_code);
+  }else{
+    db->errByteOffset = -1;
+  }
+}
+
+/*
+** The equivalent of sqlite3Error(db, SQLITE_OK).  Clear the error state
+** and error message.
+*/
+void sqlite3ErrorClear(sqlite3 *db){
+  assert( db!=0 );
+  db->errCode = SQLITE_OK;
+  db->errByteOffset = -1;
+  if( db->pErr ) sqlite3ValueSetNull(db->pErr);
+}
+
+/*
+** Load the sqlite3.iSysErrno field if that is an appropriate thing
+** to do based on the SQLite error code in rc.
+*/
+void sqlite3SystemError(sqlite3 *db, int rc){
+  if( rc==SQLITE_IOERR_NOMEM ) return;
+#if defined(SQLITE_USE_SEH) && !defined(SQLITE_OMIT_WAL)
+  if( rc==SQLITE_IOERR_IN_PAGE ){
+    int ii;
+    int iErr;
+    sqlite3BtreeEnterAll(db);
+    for(ii=0; ii<db->nDb; ii++){
+      if( db->aDb[ii].pBt ){
+        iErr = sqlite3PagerWalSystemErrno(sqlite3BtreePager(db->aDb[ii].pBt));
+        if( iErr ){
+          db->iSysErrno = iErr;
+        }
+      }
+    }
+    sqlite3BtreeLeaveAll(db);
+    return;
+  }
+#endif
+  rc &= 0xff;
+  if( rc==SQLITE_CANTOPEN || rc==SQLITE_IOERR ){
+    db->iSysErrno = sqlite3OsGetLastError(db->pVfs);
+  }
+}
+
+/*
+** Set the most recent error code and error string for the sqlite
+** handle "db". The error code is set to "err_code".
+**
+** If it is not NULL, string zFormat specifies the format of the
+** error string.  zFormat and any string tokens that follow it are
+** assumed to be encoded in UTF-8.
+**
+** To clear the most recent error for sqlite handle "db", sqlite3Error
+** should be called with err_code set to SQLITE_OK and zFormat set
+** to NULL.
+*/
+void sqlite3ErrorWithMsg(sqlite3 *db, int err_code, const char *zFormat, ...){
+  assert( db!=0 );
+  db->errCode = err_code;
+  sqlite3SystemError(db, err_code);
+  if( zFormat==0 ){
+    sqlite3Error(db, err_code);
+  }else if( db->pErr || (db->pErr = sqlite3ValueNew(db))!=0 ){
+    char *z;
+    va_list ap;
+    va_start(ap, zFormat);
+    z = sqlite3VMPrintf(db, zFormat, ap);
+    va_end(ap);
+    sqlite3ValueSetStr(db->pErr, -1, z, SQLITE_UTF8, SQLITE_DYNAMIC);
+  }
+}
+
+/*
+** Check for interrupts and invoke progress callback.
+*/
+void sqlite3ProgressCheck(Parse *p){
+  sqlite3 *db = p->db;
+  if( AtomicLoad(&db->u1.isInterrupted) ){
+    p->nErr++;
+    p->rc = SQLITE_INTERRUPT;
+  }
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  if( db->xProgress ){
+    if( p->rc==SQLITE_INTERRUPT ){
+      p->nProgressSteps = 0;
+    }else if( (++p->nProgressSteps)>=db->nProgressOps ){
+      if( db->xProgress(db->pProgressArg) ){
+        p->nErr++;
+        p->rc = SQLITE_INTERRUPT;
+      }
+      p->nProgressSteps = 0;
+    }
+  }
+#endif
+}
+
+/*
+** Add an error message to pParse->zErrMsg and increment pParse->nErr.
+**
+** This function should be used to report any error that occurs while
+** compiling an SQL statement (i.e. within sqlite3_prepare()). The
+** last thing the sqlite3_prepare() function does is copy the error
+** stored by this function into the database handle using sqlite3Error().
+** Functions sqlite3Error() or sqlite3ErrorWithMsg() should be used
+** during statement execution (sqlite3_step() etc.).
+*/
+void sqlite3ErrorMsg(Parse *pParse, const char *zFormat, ...){
+  char *zMsg;
+  va_list ap;
+  sqlite3 *db = pParse->db;
+  assert( db!=0 );
+  assert( db->pParse==pParse || db->pParse->pToplevel==pParse );
+  db->errByteOffset = -2;
+  va_start(ap, zFormat);
+  zMsg = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  if( db->errByteOffset<-1 ) db->errByteOffset = -1;
+  if( db->suppressErr ){
+    sqlite3DbFree(db, zMsg);
+    if( db->mallocFailed ){
+      pParse->nErr++;
+      pParse->rc = SQLITE_NOMEM;
+    }
+  }else{
+    pParse->nErr++;
+    sqlite3DbFree(db, pParse->zErrMsg);
+    pParse->zErrMsg = zMsg;
+    pParse->rc = SQLITE_ERROR;
+    pParse->pWith = 0;
+  }
+}
+
+/*
+** If database connection db is currently parsing SQL, then transfer
+** error code errCode to that parser if the parser has not already
+** encountered some other kind of error.
+*/
+int sqlite3ErrorToParser(sqlite3 *db, int errCode){
+  Parse *pParse;
+  if( db==0 || (pParse = db->pParse)==0 ) return errCode;
+  pParse->rc = errCode;
+  pParse->nErr++;
+  return errCode;
+}
+
+/*
+** Convert an SQL-style quoted string into a normal string by removing
+** the quote characters.  The conversion is done in-place.  If the
+** input does not begin with a quote character, then this routine
+** is a no-op.
+**
+** The input string must be zero-terminated.  A new zero-terminator
+** is added to the dequoted string.
+**
+** The return value is -1 if no dequoting occurs or the length of the
+** dequoted string, exclusive of the zero terminator, if dequoting does
+** occur.
+**
+** 2002-02-14: This routine is extended to remove MS-Access style
+** brackets from around identifiers.  For example:  "[a-b-c]" becomes
+** "a-b-c".
+*/
+void sqlite3Dequote(char *z){
+  char quote;
+  int i, j;
+  if( z==0 ) return;
+  quote = z[0];
+  if( !sqlite3Isquote(quote) ) return;
+  if( quote=='[' ) quote = ']';
+  for(i=1, j=0;; i++){
+    assert( z[i] );
+    if( z[i]==quote ){
+      if( z[i+1]==quote ){
+        z[j++] = quote;
+        i++;
+      }else{
+        break;
+      }
+    }else{
+      z[j++] = z[i];
+    }
+  }
+  z[j] = 0;
+}
+void sqlite3DequoteExpr(Expr *p){
+  assert( !ExprHasProperty(p, EP_IntValue) );
+  assert( sqlite3Isquote(p->u.zToken[0]) );
+  p->flags |= p->u.zToken[0]=='"' ? EP_Quoted|EP_DblQuoted : EP_Quoted;
+  sqlite3Dequote(p->u.zToken);
+}
+
+/*
+** If the input token p is quoted, try to adjust the token to remove
+** the quotes.  This is not always possible:
+**
+**     "abc"     ->   abc
+**     "ab""cd"  ->   (not possible because of the interior "")
+**
+** Remove the quotes if possible.  This is a optimization.  The overall
+** system should still return the correct answer even if this routine
+** is always a no-op.
+*/
+void sqlite3DequoteToken(Token *p){
+  unsigned int i;
+  if( p->n<2 ) return;
+  if( !sqlite3Isquote(p->z[0]) ) return;
+  for(i=1; i<p->n-1; i++){
+    if( sqlite3Isquote(p->z[i]) ) return;
+  }
+  p->n -= 2;
+  p->z++;
+}
+
+/*
+** Generate a Token object from a string
+*/
+void sqlite3TokenInit(Token *p, char *z){
+  p->z = z;
+  p->n = sqlite3Strlen30(z);
+}
+
+/* Convenient short-hand */
+#define UpperToLower sqlite3UpperToLower
+
+/*
+** Some systems have stricmp().  Others have strcasecmp().  Because
+** there is no consistency, we will define our own.
+**
+** IMPLEMENTATION-OF: R-30243-02494 The sqlite3_stricmp() and
+** sqlite3_strnicmp() APIs allow applications and extensions to compare
+** the contents of two buffers containing UTF-8 strings in a
+** case-independent fashion, using the same definition of "case
+** independence" that SQLite uses internally when comparing identifiers.
+*/
+int sqlite3_stricmp(const char *zLeft, const char *zRight){
+  if( zLeft==0 ){
+    return zRight ? -1 : 0;
+  }else if( zRight==0 ){
+    return 1;
+  }
+  return sqlite3StrICmp(zLeft, zRight);
+}
+int sqlite3StrICmp(const char *zLeft, const char *zRight){
+  unsigned char *a, *b;
+  int c, x;
+  a = (unsigned char *)zLeft;
+  b = (unsigned char *)zRight;
+  for(;;){
+    c = *a;
+    x = *b;
+    if( c==x ){
+      if( c==0 ) break;
+    }else{
+      c = (int)UpperToLower[c] - (int)UpperToLower[x];
+      if( c ) break;
+    }
+    a++;
+    b++;
+  }
+  return c;
+}
+int sqlite3_strnicmp(const char *zLeft, const char *zRight, int N){
+  register unsigned char *a, *b;
+  if( zLeft==0 ){
+    return zRight ? -1 : 0;
+  }else if( zRight==0 ){
+    return 1;
+  }
+  a = (unsigned char *)zLeft;
+  b = (unsigned char *)zRight;
+  while( N-- > 0 && *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
+  return N<0 ? 0 : UpperToLower[*a] - UpperToLower[*b];
+}
+
+/*
+** Compute an 8-bit hash on a string that is insensitive to case differences
+*/
+u8 sqlite3StrIHash(const char *z){
+  u8 h = 0;
+  if( z==0 ) return 0;
+  while( z[0] ){
+    h += UpperToLower[(unsigned char)z[0]];
+    z++;
+  }
+  return h;
+}
+
+/* Double-Double multiplication.  (x[0],x[1]) *= (y,yy)
+**
+** Reference:
+**   T. J. Dekker, "A Floating-Point Technique for Extending the
+**   Available Precision".  1971-07-26.
+*/
+static void dekkerMul2(volatile double *x, double y, double yy){
+  /*
+  ** The "volatile" keywords on parameter x[] and on local variables
+  ** below are needed force intermediate results to be truncated to
+  ** binary64 rather than be carried around in an extended-precision
+  ** format.  The truncation is necessary for the Dekker algorithm to
+  ** work.  Intel x86 floating point might omit the truncation without
+  ** the use of volatile. 
+  */
+  volatile double tx, ty, p, q, c, cc;
+  double hx, hy;
+  u64 m;
+  memcpy(&m, (void*)&x[0], 8);
+  m &= 0xfffffffffc000000LL;
+  memcpy(&hx, &m, 8);
+  tx = x[0] - hx;
+  memcpy(&m, &y, 8);
+  m &= 0xfffffffffc000000LL;
+  memcpy(&hy, &m, 8);
+  ty = y - hy;
+  p = hx*hy;
+  q = hx*ty + tx*hy;
+  c = p+q;
+  cc = p - c + q + tx*ty;
+  cc = x[0]*yy + x[1]*y + cc;
+  x[0] = c + cc;
+  x[1] = c - x[0];
+  x[1] += cc;
+}
+
+/*
+** The string z[] is an text representation of a real number.
+** Convert this string to a double and write it into *pResult.
+**
+** The string z[] is length bytes in length (bytes, not characters) and
+** uses the encoding enc.  The string is not necessarily zero-terminated.
+**
+** Return TRUE if the result is a valid real number (or integer) and FALSE
+** if the string is empty or contains extraneous text.  More specifically
+** return
+**      1          =>  The input string is a pure integer
+**      2 or more  =>  The input has a decimal point or eNNN clause
+**      0 or less  =>  The input string is not a valid number
+**     -1          =>  Not a valid number, but has a valid prefix which
+**                     includes a decimal point and/or an eNNN clause
+**
+** Valid numbers are in one of these formats:
+**
+**    [+-]digits[E[+-]digits]
+**    [+-]digits.[digits][E[+-]digits]
+**    [+-].digits[E[+-]digits]
+**
+** Leading and trailing whitespace is ignored for the purpose of determining
+** validity.
+**
+** If some prefix of the input string is a valid number, this routine
+** returns FALSE but it still converts the prefix and writes the result
+** into *pResult.
+*/
+#if defined(_MSC_VER)
+#pragma warning(disable : 4756)
+#endif
+int sqlite3AtoF(const char *z, double *pResult, int length, u8 enc){
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  int incr;
+  const char *zEnd;
+  /* sign * significand * (10 ^ (esign * exponent)) */
+  int sign = 1;    /* sign of significand */
+  u64 s = 0;       /* significand */
+  int d = 0;       /* adjust exponent for shifting decimal point */
+  int esign = 1;   /* sign of exponent */
+  int e = 0;       /* exponent */
+  int eValid = 1;  /* True exponent is either not used or is well-formed */
+  int nDigit = 0;  /* Number of digits processed */
+  int eType = 1;   /* 1: pure integer,  2+: fractional  -1 or less: bad UTF16 */
+
+  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
+  *pResult = 0.0;   /* Default return value, in case of an error */
+  if( length==0 ) return 0;
+
+  if( enc==SQLITE_UTF8 ){
+    incr = 1;
+    zEnd = z + length;
+  }else{
+    int i;
+    incr = 2;
+    length &= ~1;
+    assert( SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
+    testcase( enc==SQLITE_UTF16LE );
+    testcase( enc==SQLITE_UTF16BE );
+    for(i=3-enc; i<length && z[i]==0; i+=2){}
+    if( i<length ) eType = -100;
+    zEnd = &z[i^1];
+    z += (enc&1);
+  }
+
+  /* skip leading spaces */
+  while( z<zEnd && sqlite3Isspace(*z) ) z+=incr;
+  if( z>=zEnd ) return 0;
+
+  /* get sign of significand */
+  if( *z=='-' ){
+    sign = -1;
+    z+=incr;
+  }else if( *z=='+' ){
+    z+=incr;
+  }
+
+  /* copy max significant digits to significand */
+  while( z<zEnd && sqlite3Isdigit(*z) ){
+    s = s*10 + (*z - '0');
+    z+=incr; nDigit++;
+    if( s>=((LARGEST_UINT64-9)/10) ){
+      /* skip non-significant significand digits
+      ** (increase exponent by d to shift decimal left) */
+      while( z<zEnd && sqlite3Isdigit(*z) ){ z+=incr; d++; }
+    }
+  }
+  if( z>=zEnd ) goto do_atof_calc;
+
+  /* if decimal point is present */
+  if( *z=='.' ){
+    z+=incr;
+    eType++;
+    /* copy digits from after decimal to significand
+    ** (decrease exponent by d to shift decimal right) */
+    while( z<zEnd && sqlite3Isdigit(*z) ){
+      if( s<((LARGEST_UINT64-9)/10) ){
+        s = s*10 + (*z - '0');
+        d--;
+        nDigit++;
+      }
+      z+=incr;
+    }
+  }
+  if( z>=zEnd ) goto do_atof_calc;
+
+  /* if exponent is present */
+  if( *z=='e' || *z=='E' ){
+    z+=incr;
+    eValid = 0;
+    eType++;
+
+    /* This branch is needed to avoid a (harmless) buffer overread.  The
+    ** special comment alerts the mutation tester that the correct answer
+    ** is obtained even if the branch is omitted */
+    if( z>=zEnd ) goto do_atof_calc;              /*PREVENTS-HARMLESS-OVERREAD*/
+
+    /* get sign of exponent */
+    if( *z=='-' ){
+      esign = -1;
+      z+=incr;
+    }else if( *z=='+' ){
+      z+=incr;
+    }
+    /* copy digits to exponent */
+    while( z<zEnd && sqlite3Isdigit(*z) ){
+      e = e<10000 ? (e*10 + (*z - '0')) : 10000;
+      z+=incr;
+      eValid = 1;
+    }
+  }
+
+  /* skip trailing spaces */
+  while( z<zEnd && sqlite3Isspace(*z) ) z+=incr;
+
+do_atof_calc:
+  /* Zero is a special case */
+  if( s==0 ){
+    *pResult = sign<0 ? -0.0 : +0.0;
+    goto atof_return;
+  }
+
+  /* adjust exponent by d, and update sign */
+  e = (e*esign) + d;
+
+  /* Try to adjust the exponent to make it smaller */
+  while( e>0 && s<(LARGEST_UINT64/10) ){
+    s *= 10;
+    e--;
+  }
+  while( e<0 && (s%10)==0 ){
+    s /= 10;
+    e++;
+  }
+
+  if( e==0 ){
+    *pResult = s;
+  }else if( sqlite3Config.bUseLongDouble ){
+    LONGDOUBLE_TYPE r = (LONGDOUBLE_TYPE)s;
+    if( e>0 ){
+      while( e>=100  ){ e-=100; r *= 1.0e+100L; }
+      while( e>=10   ){ e-=10;  r *= 1.0e+10L;  }
+      while( e>=1    ){ e-=1;   r *= 1.0e+01L;  }
+    }else{
+      while( e<=-100 ){ e+=100; r *= 1.0e-100L; }
+      while( e<=-10  ){ e+=10;  r *= 1.0e-10L;  }
+      while( e<=-1   ){ e+=1;   r *= 1.0e-01L;  }
+    }
+    assert( r>=0.0 );
+    if( r>+1.7976931348623157081452742373e+308L ){
+#ifdef INFINITY
+      *pResult = +INFINITY;
+#else
+      *pResult = 1.0e308*10.0;
+#endif
+    }else{
+      *pResult = (double)r;
+    }
+  }else{
+    double rr[2];
+    u64 s2;
+    rr[0] = (double)s;
+    s2 = (u64)rr[0];
+    rr[1] = s>=s2 ? (double)(s - s2) : -(double)(s2 - s);
+    if( e>0 ){
+      while( e>=100  ){
+        e -= 100;
+        dekkerMul2(rr, 1.0e+100, -1.5902891109759918046e+83);
+      }
+      while( e>=10   ){
+        e -= 10;
+        dekkerMul2(rr, 1.0e+10, 0.0);
+      }
+      while( e>=1    ){
+        e -= 1;
+        dekkerMul2(rr, 1.0e+01, 0.0);
+      }
+    }else{
+      while( e<=-100 ){
+        e += 100;
+        dekkerMul2(rr, 1.0e-100, -1.99918998026028836196e-117);
+      }
+      while( e<=-10  ){
+        e += 10;
+        dekkerMul2(rr, 1.0e-10, -3.6432197315497741579e-27);
+      }
+      while( e<=-1   ){
+        e += 1;
+        dekkerMul2(rr, 1.0e-01, -5.5511151231257827021e-18);
+      }
+    }
+    *pResult = rr[0]+rr[1];
+    if( sqlite3IsNaN(*pResult) ) *pResult = 1e300*1e300;
+  }
+  if( sign<0 ) *pResult = -*pResult;
+  assert( !sqlite3IsNaN(*pResult) );
+
+atof_return:
+  /* return true if number and no extra non-whitespace characters after */
+  if( z==zEnd && nDigit>0 && eValid && eType>0 ){
+    return eType;
+  }else if( eType>=2 && (eType==3 || eValid) && nDigit>0 ){
+    return -1;
+  }else{
+    return 0;
+  }
+#else
+  return !sqlite3Atoi64(z, pResult, length, enc);
+#endif /* SQLITE_OMIT_FLOATING_POINT */
+}
+#if defined(_MSC_VER)
+#pragma warning(default : 4756)
+#endif
+
+/*
+** Render an signed 64-bit integer as text.  Store the result in zOut[] and
+** return the length of the string that was stored, in bytes.  The value
+** returned does not include the zero terminator at the end of the output
+** string.
+**
+** The caller must ensure that zOut[] is at least 21 bytes in size.
+*/
+int sqlite3Int64ToText(i64 v, char *zOut){
+  int i;
+  u64 x;
+  char zTemp[22];
+  if( v<0 ){
+    x = (v==SMALLEST_INT64) ? ((u64)1)<<63 : (u64)-v;
+  }else{
+    x = v;
+  }
+  i = sizeof(zTemp)-2;
+  zTemp[sizeof(zTemp)-1] = 0;
+  while( 1 /*exit-by-break*/ ){
+    zTemp[i] = (x%10) + '0';
+    x = x/10;
+    if( x==0 ) break;
+    i--;
+  };
+  if( v<0 ) zTemp[--i] = '-';
+  memcpy(zOut, &zTemp[i], sizeof(zTemp)-i);
+  return sizeof(zTemp)-1-i;
+}
+
+/*
+** Compare the 19-character string zNum against the text representation
+** value 2^63:  9223372036854775808.  Return negative, zero, or positive
+** if zNum is less than, equal to, or greater than the string.
+** Note that zNum must contain exactly 19 characters.
+**
+** Unlike memcmp() this routine is guaranteed to return the difference
+** in the values of the last digit if the only difference is in the
+** last digit.  So, for example,
+**
+**      compare2pow63("9223372036854775800", 1)
+**
+** will return -8.
+*/
+static int compare2pow63(const char *zNum, int incr){
+  int c = 0;
+  int i;
+                    /* 012345678901234567 */
+  const char *pow63 = "922337203685477580";
+  for(i=0; c==0 && i<18; i++){
+    c = (zNum[i*incr]-pow63[i])*10;
+  }
+  if( c==0 ){
+    c = zNum[18*incr] - '8';
+    testcase( c==(-1) );
+    testcase( c==0 );
+    testcase( c==(+1) );
+  }
+  return c;
+}
+
+/*
+** Convert zNum to a 64-bit signed integer.  zNum must be decimal. This
+** routine does *not* accept hexadecimal notation.
+**
+** Returns:
+**
+**    -1    Not even a prefix of the input text looks like an integer
+**     0    Successful transformation.  Fits in a 64-bit signed integer.
+**     1    Excess non-space text after the integer value
+**     2    Integer too large for a 64-bit signed integer or is malformed
+**     3    Special case of 9223372036854775808
+**
+** length is the number of bytes in the string (bytes, not characters).
+** The string is not necessarily zero-terminated.  The encoding is
+** given by enc.
+*/
+int sqlite3Atoi64(const char *zNum, i64 *pNum, int length, u8 enc){
+  int incr;
+  u64 u = 0;
+  int neg = 0; /* assume positive */
+  int i;
+  int c = 0;
+  int nonNum = 0;  /* True if input contains UTF16 with high byte non-zero */
+  int rc;          /* Baseline return code */
+  const char *zStart;
+  const char *zEnd = zNum + length;
+  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
+  if( enc==SQLITE_UTF8 ){
+    incr = 1;
+  }else{
+    incr = 2;
+    length &= ~1;
+    assert( SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
+    for(i=3-enc; i<length && zNum[i]==0; i+=2){}
+    nonNum = i<length;
+    zEnd = &zNum[i^1];
+    zNum += (enc&1);
+  }
+  while( zNum<zEnd && sqlite3Isspace(*zNum) ) zNum+=incr;
+  if( zNum<zEnd ){
+    if( *zNum=='-' ){
+      neg = 1;
+      zNum+=incr;
+    }else if( *zNum=='+' ){
+      zNum+=incr;
+    }
+  }
+  zStart = zNum;
+  while( zNum<zEnd && zNum[0]=='0' ){ zNum+=incr; } /* Skip leading zeros. */
+  for(i=0; &zNum[i]<zEnd && (c=zNum[i])>='0' && c<='9'; i+=incr){
+    u = u*10 + c - '0';
+  }
+  testcase( i==18*incr );
+  testcase( i==19*incr );
+  testcase( i==20*incr );
+  if( u>LARGEST_INT64 ){
+    /* This test and assignment is needed only to suppress UB warnings
+    ** from clang and -fsanitize=undefined.  This test and assignment make
+    ** the code a little larger and slower, and no harm comes from omitting
+    ** them, but we must appease the undefined-behavior pharisees. */
+    *pNum = neg ? SMALLEST_INT64 : LARGEST_INT64;
+  }else if( neg ){
+    *pNum = -(i64)u;
+  }else{
+    *pNum = (i64)u;
+  }
+  rc = 0;
+  if( i==0 && zStart==zNum ){    /* No digits */
+    rc = -1;
+  }else if( nonNum ){            /* UTF16 with high-order bytes non-zero */
+    rc = 1;
+  }else if( &zNum[i]<zEnd ){     /* Extra bytes at the end */
+    int jj = i;
+    do{
+      if( !sqlite3Isspace(zNum[jj]) ){
+        rc = 1;          /* Extra non-space text after the integer */
+        break;
+      }
+      jj += incr;
+    }while( &zNum[jj]<zEnd );
+  }
+  if( i<19*incr ){
+    /* Less than 19 digits, so we know that it fits in 64 bits */
+    assert( u<=LARGEST_INT64 );
+    return rc;
+  }else{
+    /* zNum is a 19-digit numbers.  Compare it against 9223372036854775808. */
+    c = i>19*incr ? 1 : compare2pow63(zNum, incr);
+    if( c<0 ){
+      /* zNum is less than 9223372036854775808 so it fits */
+      assert( u<=LARGEST_INT64 );
+      return rc;
+    }else{
+      *pNum = neg ? SMALLEST_INT64 : LARGEST_INT64;
+      if( c>0 ){
+        /* zNum is greater than 9223372036854775808 so it overflows */
+        return 2;
+      }else{
+        /* zNum is exactly 9223372036854775808.  Fits if negative.  The
+        ** special case 2 overflow if positive */
+        assert( u-1==LARGEST_INT64 );
+        return neg ? rc : 3;
+      }
+    }
+  }
+}
+
+/*
+** Transform a UTF-8 integer literal, in either decimal or hexadecimal,
+** into a 64-bit signed integer.  This routine accepts hexadecimal literals,
+** whereas sqlite3Atoi64() does not.
+**
+** Returns:
+**
+**     0    Successful transformation.  Fits in a 64-bit signed integer.
+**     1    Excess text after the integer value
+**     2    Integer too large for a 64-bit signed integer or is malformed
+**     3    Special case of 9223372036854775808
+*/
+int sqlite3DecOrHexToI64(const char *z, i64 *pOut){
+#ifndef SQLITE_OMIT_HEX_INTEGER
+  if( z[0]=='0'
+   && (z[1]=='x' || z[1]=='X')
+  ){
+    u64 u = 0;
+    int i, k;
+    for(i=2; z[i]=='0'; i++){}
+    for(k=i; sqlite3Isxdigit(z[k]); k++){
+      u = u*16 + sqlite3HexToInt(z[k]);
+    }
+    memcpy(pOut, &u, 8);
+    if( k-i>16 ) return 2;
+    if( z[k]!=0 ) return 1;
+    return 0;
+  }else
+#endif /* SQLITE_OMIT_HEX_INTEGER */
+  {
+    int n = (int)(0x3fffffff&strspn(z,"+- \n\t0123456789"));
+    if( z[n] ) n++;
+    return sqlite3Atoi64(z, pOut, n, SQLITE_UTF8);
+  }
+}
+
+/*
+** If zNum represents an integer that will fit in 32-bits, then set
+** *pValue to that integer and return true.  Otherwise return false.
+**
+** This routine accepts both decimal and hexadecimal notation for integers.
+**
+** Any non-numeric characters that following zNum are ignored.
+** This is different from sqlite3Atoi64() which requires the
+** input number to be zero-terminated.
+*/
+int sqlite3GetInt32(const char *zNum, int *pValue){
+  sqlite_int64 v = 0;
+  int i, c;
+  int neg = 0;
+  if( zNum[0]=='-' ){
+    neg = 1;
+    zNum++;
+  }else if( zNum[0]=='+' ){
+    zNum++;
+  }
+#ifndef SQLITE_OMIT_HEX_INTEGER
+  else if( zNum[0]=='0'
+        && (zNum[1]=='x' || zNum[1]=='X')
+        && sqlite3Isxdigit(zNum[2])
+  ){
+    u32 u = 0;
+    zNum += 2;
+    while( zNum[0]=='0' ) zNum++;
+    for(i=0; i<8 && sqlite3Isxdigit(zNum[i]); i++){
+      u = u*16 + sqlite3HexToInt(zNum[i]);
+    }
+    if( (u&0x80000000)==0 && sqlite3Isxdigit(zNum[i])==0 ){
+      memcpy(pValue, &u, 4);
+      return 1;
+    }else{
+      return 0;
+    }
+  }
+#endif
+  if( !sqlite3Isdigit(zNum[0]) ) return 0;
+  while( zNum[0]=='0' ) zNum++;
+  for(i=0; i<11 && (c = zNum[i] - '0')>=0 && c<=9; i++){
+    v = v*10 + c;
+  }
+
+  /* The longest decimal representation of a 32 bit integer is 10 digits:
+  **
+  **             1234567890
+  **     2^31 -> 2147483648
+  */
+  testcase( i==10 );
+  if( i>10 ){
+    return 0;
+  }
+  testcase( v-neg==2147483647 );
+  if( v-neg>2147483647 ){
+    return 0;
+  }
+  if( neg ){
+    v = -v;
+  }
+  *pValue = (int)v;
+  return 1;
+}
+
+/*
+** Return a 32-bit integer value extracted from a string.  If the
+** string is not an integer, just return 0.
+*/
+int sqlite3Atoi(const char *z){
+  int x = 0;
+  sqlite3GetInt32(z, &x);
+  return x;
+}
+
+/*
+** Decode a floating-point value into an approximate decimal
+** representation.
+**
+** Round the decimal representation to n significant digits if
+** n is positive.  Or round to -n signficant digits after the
+** decimal point if n is negative.  No rounding is performed if
+** n is zero.
+**
+** The significant digits of the decimal representation are
+** stored in p->z[] which is a often (but not always) a pointer
+** into the middle of p->zBuf[].  There are p->n significant digits.
+** The p->z[] array is *not* zero-terminated.
+*/
+void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
+  int i;
+  u64 v;
+  int e, exp = 0;
+  p->isSpecial = 0;
+  p->z = p->zBuf;
+
+  /* Convert negative numbers to positive.  Deal with Infinity, 0.0, and
+  ** NaN. */
+  if( r<0.0 ){
+    p->sign = '-';
+    r = -r;
+  }else if( r==0.0 ){
+    p->sign = '+';
+    p->n = 1;
+    p->iDP = 1;
+    p->z = "0";
+    return;
+  }else{
+    p->sign = '+';
+  }
+  memcpy(&v,&r,8);
+  e = v>>52;
+  if( (e&0x7ff)==0x7ff ){
+    p->isSpecial = 1 + (v!=0x7ff0000000000000LL);
+    p->n = 0;
+    p->iDP = 0;
+    return;
+  }
+
+  /* Multiply r by powers of ten until it lands somewhere in between
+  ** 1.0e+19 and 1.0e+17.
+  */
+  if( sqlite3Config.bUseLongDouble ){
+    LONGDOUBLE_TYPE rr = r;
+    if( rr>=1.0e+19 ){
+      while( rr>=1.0e+119L ){ exp+=100; rr *= 1.0e-100L; }
+      while( rr>=1.0e+29L  ){ exp+=10;  rr *= 1.0e-10L;  }
+      while( rr>=1.0e+19L  ){ exp++;    rr *= 1.0e-1L;   }
+    }else{
+      while( rr<1.0e-97L   ){ exp-=100; rr *= 1.0e+100L; }
+      while( rr<1.0e+07L   ){ exp-=10;  rr *= 1.0e+10L;  }
+      while( rr<1.0e+17L   ){ exp--;    rr *= 1.0e+1L;   }
+    }
+    v = (u64)rr;
+  }else{
+    /* If high-precision floating point is not available using "long double",
+    ** then use Dekker-style double-double computation to increase the
+    ** precision.
+    **
+    ** The error terms on constants like 1.0e+100 computed using the
+    ** decimal extension, for example as follows:
+    **
+    **   SELECT decimal_exp(decimal_sub('1.0e+100',decimal(1.0e+100)));
+    */
+    double rr[2];
+    rr[0] = r;
+    rr[1] = 0.0;
+    if( rr[0]>9.223372036854774784e+18 ){
+      while( rr[0]>9.223372036854774784e+118 ){
+        exp += 100;
+        dekkerMul2(rr, 1.0e-100, -1.99918998026028836196e-117);
+      }
+      while( rr[0]>9.223372036854774784e+28 ){
+        exp += 10;
+        dekkerMul2(rr, 1.0e-10, -3.6432197315497741579e-27);
+      }
+      while( rr[0]>9.223372036854774784e+18 ){
+        exp += 1;
+        dekkerMul2(rr, 1.0e-01, -5.5511151231257827021e-18);
+      }
+    }else{
+      while( rr[0]<9.223372036854774784e-83  ){
+        exp -= 100;
+        dekkerMul2(rr, 1.0e+100, -1.5902891109759918046e+83);
+      }
+      while( rr[0]<9.223372036854774784e+07  ){
+        exp -= 10;
+        dekkerMul2(rr, 1.0e+10, 0.0);
+      }
+      while( rr[0]<9.22337203685477478e+17  ){
+        exp -= 1;
+        dekkerMul2(rr, 1.0e+01, 0.0);
+      }
+    }
+    v = rr[1]<0.0 ? (u64)rr[0]-(u64)(-rr[1]) : (u64)rr[0]+(u64)rr[1];
+  }
+
+
+  /* Extract significant digits. */
+  i = sizeof(p->zBuf)-1;
+  assert( v>0 );
+  while( v ){  p->zBuf[i--] = (v%10) + '0'; v /= 10; }
+  assert( i>=0 && i<sizeof(p->zBuf)-1 );
+  p->n = sizeof(p->zBuf) - 1 - i;
+  assert( p->n>0 );
+  assert( p->n<sizeof(p->zBuf) );
+  p->iDP = p->n + exp;
+  if( iRound<0 ){
+    iRound = p->iDP - iRound;
+    if( iRound==0 && p->zBuf[i+1]>='5' ){
+      iRound = 1;
+      p->zBuf[i--] = '0';
+      p->n++;
+      p->iDP++;
+    }
+  }
+  if( iRound>0 && (iRound<p->n || p->n>mxRound) ){
+    char *z = &p->zBuf[i+1];
+    if( iRound>mxRound ) iRound = mxRound;
+    p->n = iRound;
+    if( z[iRound]>='5' ){
+      int j = iRound-1;
+      while( 1 /*exit-by-break*/ ){
+        z[j]++;
+        if( z[j]<='9' ) break;
+        z[j] = '0';
+        if( j==0 ){
+          p->z[i--] = '1';
+          p->n++;
+          p->iDP++;
+          break;
+        }else{
+          j--;
+        }
+      }
+    }
+  }
+  p->z = &p->zBuf[i+1];
+  assert( i+p->n < sizeof(p->zBuf) );
+  while( ALWAYS(p->n>0) && p->z[p->n-1]=='0' ){ p->n--; }
+}
+
+/*
+** Try to convert z into an unsigned 32-bit integer.  Return true on
+** success and false if there is an error.
+**
+** Only decimal notation is accepted.
+*/
+int sqlite3GetUInt32(const char *z, u32 *pI){
+  u64 v = 0;
+  int i;
+  for(i=0; sqlite3Isdigit(z[i]); i++){
+    v = v*10 + z[i] - '0';
+    if( v>4294967296LL ){ *pI = 0; return 0; }
+  }
+  if( i==0 || z[i]!=0 ){ *pI = 0; return 0; }
+  *pI = (u32)v;
+  return 1;
+}
+
+/*
+** The variable-length integer encoding is as follows:
+**
+** KEY:
+**         A = 0xxxxxxx    7 bits of data and one flag bit
+**         B = 1xxxxxxx    7 bits of data and one flag bit
+**         C = xxxxxxxx    8 bits of data
+**
+**  7 bits - A
+** 14 bits - BA
+** 21 bits - BBA
+** 28 bits - BBBA
+** 35 bits - BBBBA
+** 42 bits - BBBBBA
+** 49 bits - BBBBBBA
+** 56 bits - BBBBBBBA
+** 64 bits - BBBBBBBBC
+*/
+
+/*
+** Write a 64-bit variable-length integer to memory starting at p[0].
+** The length of data write will be between 1 and 9 bytes.  The number
+** of bytes written is returned.
+**
+** A variable-length integer consists of the lower 7 bits of each byte
+** for all bytes that have the 8th bit set and one byte with the 8th
+** bit clear.  Except, if we get to the 9th byte, it stores the full
+** 8 bits and is the last byte.
+*/
+static int SQLITE_NOINLINE putVarint64(unsigned char *p, u64 v){
+  int i, j, n;
+  u8 buf[10];
+  if( v & (((u64)0xff000000)<<32) ){
+    p[8] = (u8)v;
+    v >>= 8;
+    for(i=7; i>=0; i--){
+      p[i] = (u8)((v & 0x7f) | 0x80);
+      v >>= 7;
+    }
+    return 9;
+  }   
+  n = 0;
+  do{
+    buf[n++] = (u8)((v & 0x7f) | 0x80);
+    v >>= 7;
+  }while( v!=0 );
+  buf[0] &= 0x7f;
+  assert( n<=9 );
+  for(i=0, j=n-1; j>=0; j--, i++){
+    p[i] = buf[j];
+  }
+  return n;
+}
+int sqlite3PutVarint(unsigned char *p, u64 v){
+  if( v<=0x7f ){
+    p[0] = v&0x7f;
+    return 1;
+  }
+  if( v<=0x3fff ){
+    p[0] = ((v>>7)&0x7f)|0x80;
+    p[1] = v&0x7f;
+    return 2;
+  }
+  return putVarint64(p,v);
+}
+
+/*
+** Bitmasks used by sqlite3GetVarint().  These precomputed constants
+** are defined here rather than simply putting the constant expressions
+** inline in order to work around bugs in the RVT compiler.
+**
+** SLOT_2_0     A mask for  (0x7f<<14) | 0x7f
+**
+** SLOT_4_2_0   A mask for  (0x7f<<28) | SLOT_2_0
+*/
+#define SLOT_2_0     0x001fc07f
+#define SLOT_4_2_0   0xf01fc07f
+
+
+/*
+** Read a 64-bit variable-length integer from memory starting at p[0].
+** Return the number of bytes read.  The value is stored in *v.
+*/
+u8 sqlite3GetVarint(const unsigned char *p, u64 *v){
+  u32 a,b,s;
+
+  if( ((signed char*)p)[0]>=0 ){
+    *v = *p;
+    return 1;
+  }
+  if( ((signed char*)p)[1]>=0 ){
+    *v = ((u32)(p[0]&0x7f)<<7) | p[1];
+    return 2;
+  }
+
+  /* Verify that constants are precomputed correctly */
+  assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
+  assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
+
+  a = ((u32)p[0])<<14;
+  b = p[1];
+  p += 2;
+  a |= *p;
+  /* a: p0<<14 | p2 (unmasked) */
+  if (!(a&0x80))
+  {
+    a &= SLOT_2_0;
+    b &= 0x7f;
+    b = b<<7;
+    a |= b;
+    *v = a;
+    return 3;
+  }
+
+  /* CSE1 from below */
+  a &= SLOT_2_0;
+  p++;
+  b = b<<14;
+  b |= *p;
+  /* b: p1<<14 | p3 (unmasked) */
+  if (!(b&0x80))
+  {
+    b &= SLOT_2_0;
+    /* moved CSE1 up */
+    /* a &= (0x7f<<14)|(0x7f); */
+    a = a<<7;
+    a |= b;
+    *v = a;
+    return 4;
+  }
+
+  /* a: p0<<14 | p2 (masked) */
+  /* b: p1<<14 | p3 (unmasked) */
+  /* 1:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
+  /* moved CSE1 up */
+  /* a &= (0x7f<<14)|(0x7f); */
+  b &= SLOT_2_0;
+  s = a;
+  /* s: p0<<14 | p2 (masked) */
+
+  p++;
+  a = a<<14;
+  a |= *p;
+  /* a: p0<<28 | p2<<14 | p4 (unmasked) */
+  if (!(a&0x80))
+  {
+    /* we can skip these cause they were (effectively) done above
+    ** while calculating s */
+    /* a &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
+    /* b &= (0x7f<<14)|(0x7f); */
+    b = b<<7;
+    a |= b;
+    s = s>>18;
+    *v = ((u64)s)<<32 | a;
+    return 5;
+  }
+
+  /* 2:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
+  s = s<<7;
+  s |= b;
+  /* s: p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
+
+  p++;
+  b = b<<14;
+  b |= *p;
+  /* b: p1<<28 | p3<<14 | p5 (unmasked) */
+  if (!(b&0x80))
+  {
+    /* we can skip this cause it was (effectively) done above in calc'ing s */
+    /* b &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
+    a &= SLOT_2_0;
+    a = a<<7;
+    a |= b;
+    s = s>>18;
+    *v = ((u64)s)<<32 | a;
+    return 6;
+  }
+
+  p++;
+  a = a<<14;
+  a |= *p;
+  /* a: p2<<28 | p4<<14 | p6 (unmasked) */
+  if (!(a&0x80))
+  {
+    a &= SLOT_4_2_0;
+    b &= SLOT_2_0;
+    b = b<<7;
+    a |= b;
+    s = s>>11;
+    *v = ((u64)s)<<32 | a;
+    return 7;
+  }
+
+  /* CSE2 from below */
+  a &= SLOT_2_0;
+  p++;
+  b = b<<14;
+  b |= *p;
+  /* b: p3<<28 | p5<<14 | p7 (unmasked) */
+  if (!(b&0x80))
+  {
+    b &= SLOT_4_2_0;
+    /* moved CSE2 up */
+    /* a &= (0x7f<<14)|(0x7f); */
+    a = a<<7;
+    a |= b;
+    s = s>>4;
+    *v = ((u64)s)<<32 | a;
+    return 8;
+  }
+
+  p++;
+  a = a<<15;
+  a |= *p;
+  /* a: p4<<29 | p6<<15 | p8 (unmasked) */
+
+  /* moved CSE2 up */
+  /* a &= (0x7f<<29)|(0x7f<<15)|(0xff); */
+  b &= SLOT_2_0;
+  b = b<<8;
+  a |= b;
+
+  s = s<<4;
+  b = p[-4];
+  b &= 0x7f;
+  b = b>>3;
+  s |= b;
+
+  *v = ((u64)s)<<32 | a;
+
+  return 9;
+}
+
+/*
+** Read a 32-bit variable-length integer from memory starting at p[0].
+** Return the number of bytes read.  The value is stored in *v.
+**
+** If the varint stored in p[0] is larger than can fit in a 32-bit unsigned
+** integer, then set *v to 0xffffffff.
+**
+** A MACRO version, getVarint32, is provided which inlines the
+** single-byte case.  All code should use the MACRO version as
+** this function assumes the single-byte case has already been handled.
+*/
+u8 sqlite3GetVarint32(const unsigned char *p, u32 *v){
+  u64 v64;
+  u8 n;
+
+  /* Assume that the single-byte case has already been handled by
+  ** the getVarint32() macro */
+  assert( (p[0] & 0x80)!=0 );
+
+  if( (p[1] & 0x80)==0 ){
+    /* This is the two-byte case */
+    *v = ((p[0]&0x7f)<<7) | p[1];
+    return 2;
+  }
+  if( (p[2] & 0x80)==0 ){
+    /* This is the three-byte case */
+    *v = ((p[0]&0x7f)<<14) | ((p[1]&0x7f)<<7) | p[2];
+    return 3;
+  }
+  /* four or more bytes */
+  n = sqlite3GetVarint(p, &v64);
+  assert( n>3 && n<=9 );
+  if( (v64 & SQLITE_MAX_U32)!=v64 ){
+    *v = 0xffffffff;
+  }else{
+    *v = (u32)v64;
+  }
+  return n;
+}
+
+/*
+** Return the number of bytes that will be needed to store the given
+** 64-bit integer.
+*/
+int sqlite3VarintLen(u64 v){
+  int i;
+  for(i=1; (v >>= 7)!=0; i++){ assert( i<10 ); }
+  return i;
+}
+
+
+/*
+** Read or write a four-byte big-endian integer value.
+*/
+u32 sqlite3Get4byte(const u8 *p){
+#if SQLITE_BYTEORDER==4321
+  u32 x;
+  memcpy(&x,p,4);
+  return x;
+#elif SQLITE_BYTEORDER==1234 && GCC_VERSION>=4003000
+  u32 x;
+  memcpy(&x,p,4);
+  return __builtin_bswap32(x);
+#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+  u32 x;
+  memcpy(&x,p,4);
+  return _byteswap_ulong(x);
+#else
+  testcase( p[0]&0x80 );
+  return ((unsigned)p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
+#endif
+}
+void sqlite3Put4byte(unsigned char *p, u32 v){
+#if SQLITE_BYTEORDER==4321
+  memcpy(p,&v,4);
+#elif SQLITE_BYTEORDER==1234 && GCC_VERSION>=4003000
+  u32 x = __builtin_bswap32(v);
+  memcpy(p,&x,4);
+#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
+  u32 x = _byteswap_ulong(v);
+  memcpy(p,&x,4);
+#else
+  p[0] = (u8)(v>>24);
+  p[1] = (u8)(v>>16);
+  p[2] = (u8)(v>>8);
+  p[3] = (u8)v;
+#endif
+}
+
+
+
+/*
+** Translate a single byte of Hex into an integer.
+** This routine only works if h really is a valid hexadecimal
+** character:  0..9a..fA..F
+*/
+u8 sqlite3HexToInt(int h){
+  assert( (h>='0' && h<='9') ||  (h>='a' && h<='f') ||  (h>='A' && h<='F') );
+#ifdef SQLITE_ASCII
+  h += 9*(1&(h>>6));
+#endif
+#ifdef SQLITE_EBCDIC
+  h += 9*(1&~(h>>4));
+#endif
+  return (u8)(h & 0xf);
+}
+
+#if !defined(SQLITE_OMIT_BLOB_LITERAL)
+/*
+** Convert a BLOB literal of the form "x'hhhhhh'" into its binary
+** value.  Return a pointer to its binary value.  Space to hold the
+** binary value has been obtained from malloc and must be freed by
+** the calling routine.
+*/
+void *sqlite3HexToBlob(sqlite3 *db, const char *z, int n){
+  char *zBlob;
+  int i;
+
+  zBlob = (char *)sqlite3DbMallocRawNN(db, n/2 + 1);
+  n--;
+  if( zBlob ){
+    for(i=0; i<n; i+=2){
+      zBlob[i/2] = (sqlite3HexToInt(z[i])<<4) | sqlite3HexToInt(z[i+1]);
+    }
+    zBlob[i/2] = 0;
+  }
+  return zBlob;
+}
+#endif /* !SQLITE_OMIT_BLOB_LITERAL */
+
+/*
+** Log an error that is an API call on a connection pointer that should
+** not have been used.  The "type" of connection pointer is given as the
+** argument.  The zType is a word like "NULL" or "closed" or "invalid".
+*/
+static void logBadConnection(const char *zType){
+  sqlite3_log(SQLITE_MISUSE,
+     "API call with %s database connection pointer",
+     zType
+  );
+}
+
+/*
+** Check to make sure we have a valid db pointer.  This test is not
+** foolproof but it does provide some measure of protection against
+** misuse of the interface such as passing in db pointers that are
+** NULL or which have been previously closed.  If this routine returns
+** 1 it means that the db pointer is valid and 0 if it should not be
+** dereferenced for any reason.  The calling function should invoke
+** SQLITE_MISUSE immediately.
+**
+** sqlite3SafetyCheckOk() requires that the db pointer be valid for
+** use.  sqlite3SafetyCheckSickOrOk() allows a db pointer that failed to
+** open properly and is not fit for general use but which can be
+** used as an argument to sqlite3_errmsg() or sqlite3_close().
+*/
+int sqlite3SafetyCheckOk(sqlite3 *db){
+  u8 eOpenState;
+  if( db==0 ){
+    logBadConnection("NULL");
+    return 0;
+  }
+  eOpenState = db->eOpenState;
+  if( eOpenState!=SQLITE_STATE_OPEN ){
+    if( sqlite3SafetyCheckSickOrOk(db) ){
+      testcase( sqlite3GlobalConfig.xLog!=0 );
+      logBadConnection("unopened");
+    }
+    return 0;
+  }else{
+    return 1;
+  }
+}
+int sqlite3SafetyCheckSickOrOk(sqlite3 *db){
+  u8 eOpenState;
+  eOpenState = db->eOpenState;
+  if( eOpenState!=SQLITE_STATE_SICK &&
+      eOpenState!=SQLITE_STATE_OPEN &&
+      eOpenState!=SQLITE_STATE_BUSY ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    logBadConnection("invalid");
+    return 0;
+  }else{
+    return 1;
+  }
+}
+
+/*
+** Attempt to add, subtract, or multiply the 64-bit signed value iB against
+** the other 64-bit signed integer at *pA and store the result in *pA.
+** Return 0 on success.  Or if the operation would have resulted in an
+** overflow, leave *pA unchanged and return 1.
+*/
+int sqlite3AddInt64(i64 *pA, i64 iB){
+#if GCC_VERSION>=5004000 && !defined(__INTEL_COMPILER)
+  return __builtin_add_overflow(*pA, iB, pA);
+#else
+  i64 iA = *pA;
+  testcase( iA==0 ); testcase( iA==1 );
+  testcase( iB==-1 ); testcase( iB==0 );
+  if( iB>=0 ){
+    testcase( iA>0 && LARGEST_INT64 - iA == iB );
+    testcase( iA>0 && LARGEST_INT64 - iA == iB - 1 );
+    if( iA>0 && LARGEST_INT64 - iA < iB ) return 1;
+  }else{
+    testcase( iA<0 && -(iA + LARGEST_INT64) == iB + 1 );
+    testcase( iA<0 && -(iA + LARGEST_INT64) == iB + 2 );
+    if( iA<0 && -(iA + LARGEST_INT64) > iB + 1 ) return 1;
+  }
+  *pA += iB;
+  return 0;
+#endif
+}
+int sqlite3SubInt64(i64 *pA, i64 iB){
+#if GCC_VERSION>=5004000 && !defined(__INTEL_COMPILER)
+  return __builtin_sub_overflow(*pA, iB, pA);
+#else
+  testcase( iB==SMALLEST_INT64+1 );
+  if( iB==SMALLEST_INT64 ){
+    testcase( (*pA)==(-1) ); testcase( (*pA)==0 );
+    if( (*pA)>=0 ) return 1;
+    *pA -= iB;
+    return 0;
+  }else{
+    return sqlite3AddInt64(pA, -iB);
+  }
+#endif
+}
+int sqlite3MulInt64(i64 *pA, i64 iB){
+#if GCC_VERSION>=5004000 && !defined(__INTEL_COMPILER)
+  return __builtin_mul_overflow(*pA, iB, pA);
+#else
+  i64 iA = *pA;
+  if( iB>0 ){
+    if( iA>LARGEST_INT64/iB ) return 1;
+    if( iA<SMALLEST_INT64/iB ) return 1;
+  }else if( iB<0 ){
+    if( iA>0 ){
+      if( iB<SMALLEST_INT64/iA ) return 1;
+    }else if( iA<0 ){
+      if( iB==SMALLEST_INT64 ) return 1;
+      if( iA==SMALLEST_INT64 ) return 1;
+      if( -iA>LARGEST_INT64/-iB ) return 1;
+    }
+  }
+  *pA = iA*iB;
+  return 0;
+#endif
+}
+
+/*
+** Compute the absolute value of a 32-bit signed integer, of possible.  Or
+** if the integer has a value of -2147483648, return +2147483647
+*/
+int sqlite3AbsInt32(int x){
+  if( x>=0 ) return x;
+  if( x==(int)0x80000000 ) return 0x7fffffff;
+  return -x;
+}
+
+#ifdef SQLITE_ENABLE_8_3_NAMES
+/*
+** If SQLITE_ENABLE_8_3_NAMES is set at compile-time and if the database
+** filename in zBaseFilename is a URI with the "8_3_names=1" parameter and
+** if filename in z[] has a suffix (a.k.a. "extension") that is longer than
+** three characters, then shorten the suffix on z[] to be the last three
+** characters of the original suffix.
+**
+** If SQLITE_ENABLE_8_3_NAMES is set to 2 at compile-time, then always
+** do the suffix shortening regardless of URI parameter.
+**
+** Examples:
+**
+**     test.db-journal    =>   test.nal
+**     test.db-wal        =>   test.wal
+**     test.db-shm        =>   test.shm
+**     test.db-mj7f3319fa =>   test.9fa
+*/
+void sqlite3FileSuffix3(const char *zBaseFilename, char *z){
+#if SQLITE_ENABLE_8_3_NAMES<2
+  if( sqlite3_uri_boolean(zBaseFilename, "8_3_names", 0) )
+#endif
+  {
+    int i, sz;
+    sz = sqlite3Strlen30(z);
+    for(i=sz-1; i>0 && z[i]!='/' && z[i]!='.'; i--){}
+    if( z[i]=='.' && ALWAYS(sz>i+4) ) memmove(&z[i+1], &z[sz-3], 4);
+  }
+}
+#endif
+
+/*
+** Find (an approximate) sum of two LogEst values.  This computation is
+** not a simple "+" operator because LogEst is stored as a logarithmic
+** value.
+**
+*/
+LogEst sqlite3LogEstAdd(LogEst a, LogEst b){
+  static const unsigned char x[] = {
+     10, 10,                         /* 0,1 */
+      9, 9,                          /* 2,3 */
+      8, 8,                          /* 4,5 */
+      7, 7, 7,                       /* 6,7,8 */
+      6, 6, 6,                       /* 9,10,11 */
+      5, 5, 5,                       /* 12-14 */
+      4, 4, 4, 4,                    /* 15-18 */
+      3, 3, 3, 3, 3, 3,              /* 19-24 */
+      2, 2, 2, 2, 2, 2, 2,           /* 25-31 */
+  };
+  if( a>=b ){
+    if( a>b+49 ) return a;
+    if( a>b+31 ) return a+1;
+    return a+x[a-b];
+  }else{
+    if( b>a+49 ) return b;
+    if( b>a+31 ) return b+1;
+    return b+x[b-a];
+  }
+}
+
+/*
+** Convert an integer into a LogEst.  In other words, compute an
+** approximation for 10*log2(x).
+*/
+LogEst sqlite3LogEst(u64 x){
+  static LogEst a[] = { 0, 2, 3, 5, 6, 7, 8, 9 };
+  LogEst y = 40;
+  if( x<8 ){
+    if( x<2 ) return 0;
+    while( x<8 ){  y -= 10; x <<= 1; }
+  }else{
+#if GCC_VERSION>=5004000
+    int i = 60 - __builtin_clzll(x);
+    y += i*10;
+    x >>= i;
+#else
+    while( x>255 ){ y += 40; x >>= 4; }  /*OPTIMIZATION-IF-TRUE*/
+    while( x>15 ){  y += 10; x >>= 1; }
+#endif
+  }
+  return a[x&7] + y - 10;
+}
+
+/*
+** Convert a double into a LogEst
+** In other words, compute an approximation for 10*log2(x).
+*/
+LogEst sqlite3LogEstFromDouble(double x){
+  u64 a;
+  LogEst e;
+  assert( sizeof(x)==8 && sizeof(a)==8 );
+  if( x<=1 ) return 0;
+  if( x<=2000000000 ) return sqlite3LogEst((u64)x);
+  memcpy(&a, &x, 8);
+  e = (a>>52) - 1022;
+  return e*10;
+}
+
+/*
+** Convert a LogEst into an integer.
+*/
+u64 sqlite3LogEstToInt(LogEst x){
+  u64 n;
+  n = x%10;
+  x /= 10;
+  if( n>=5 ) n -= 2;
+  else if( n>=1 ) n -= 1;
+  if( x>60 ) return (u64)LARGEST_INT64;
+  return x>=3 ? (n+8)<<(x-3) : (n+8)>>(3-x);
+}
+
+/*
+** Add a new name/number pair to a VList.  This might require that the
+** VList object be reallocated, so return the new VList.  If an OOM
+** error occurs, the original VList returned and the
+** db->mallocFailed flag is set.
+**
+** A VList is really just an array of integers.  To destroy a VList,
+** simply pass it to sqlite3DbFree().
+**
+** The first integer is the number of integers allocated for the whole
+** VList.  The second integer is the number of integers actually used.
+** Each name/number pair is encoded by subsequent groups of 3 or more
+** integers.
+**
+** Each name/number pair starts with two integers which are the numeric
+** value for the pair and the size of the name/number pair, respectively.
+** The text name overlays one or more following integers.  The text name
+** is always zero-terminated.
+**
+** Conceptually:
+**
+**    struct VList {
+**      int nAlloc;   // Number of allocated slots
+**      int nUsed;    // Number of used slots
+**      struct VListEntry {
+**        int iValue;    // Value for this entry
+**        int nSlot;     // Slots used by this entry
+**        // ... variable name goes here
+**      } a[0];
+**    }
+**
+** During code generation, pointers to the variable names within the
+** VList are taken.  When that happens, nAlloc is set to zero as an
+** indication that the VList may never again be enlarged, since the
+** accompanying realloc() would invalidate the pointers.
+*/
+VList *sqlite3VListAdd(
+  sqlite3 *db,           /* The database connection used for malloc() */
+  VList *pIn,            /* The input VList.  Might be NULL */
+  const char *zName,     /* Name of symbol to add */
+  int nName,             /* Bytes of text in zName */
+  int iVal               /* Value to associate with zName */
+){
+  int nInt;              /* number of sizeof(int) objects needed for zName */
+  char *z;               /* Pointer to where zName will be stored */
+  int i;                 /* Index in pIn[] where zName is stored */
+
+  nInt = nName/4 + 3;
+  assert( pIn==0 || pIn[0]>=3 );  /* Verify ok to add new elements */
+  if( pIn==0 || pIn[1]+nInt > pIn[0] ){
+    /* Enlarge the allocation */
+    sqlite3_int64 nAlloc = (pIn ? 2*(sqlite3_int64)pIn[0] : 10) + nInt;
+    VList *pOut = sqlite3DbRealloc(db, pIn, nAlloc*sizeof(int));
+    if( pOut==0 ) return pIn;
+    if( pIn==0 ) pOut[1] = 2;
+    pIn = pOut;
+    pIn[0] = nAlloc;
+  }
+  i = pIn[1];
+  pIn[i] = iVal;
+  pIn[i+1] = nInt;
+  z = (char*)&pIn[i+2];
+  pIn[1] = i+nInt;
+  assert( pIn[1]<=pIn[0] );
+  memcpy(z, zName, nName);
+  z[nName] = 0;
+  return pIn;
+}
+
+/*
+** Return a pointer to the name of a variable in the given VList that
+** has the value iVal.  Or return a NULL if there is no such variable in
+** the list
+*/
+const char *sqlite3VListNumToName(VList *pIn, int iVal){
+  int i, mx;
+  if( pIn==0 ) return 0;
+  mx = pIn[1];
+  i = 2;
+  do{
+    if( pIn[i]==iVal ) return (char*)&pIn[i+2];
+    i += pIn[i+1];
+  }while( i<mx );
+  return 0;
+}
+
+/*
+** Return the number of the variable named zName, if it is in VList.
+** or return 0 if there is no such variable.
+*/
+int sqlite3VListNameToNum(VList *pIn, const char *zName, int nName){
+  int i, mx;
+  if( pIn==0 ) return 0;
+  mx = pIn[1];
+  i = 2;
+  do{
+    const char *z = (const char*)&pIn[i+2];
+    if( strncmp(z,zName,nName)==0 && z[nName]==0 ) return pIn[i];
+    i += pIn[i+1];
+  }while( i<mx );
+  return 0;
+}
+
+/*
+** High-resolution hardware timer used for debugging and testing only.
+*/
+#if defined(VDBE_PROFILE)  \
+ || defined(SQLITE_PERFORMANCE_TRACE) \
+ || defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+# include "hwtime.h"
+#endif
diff --git a/src/vacuum.c b/src/vacuum.c
new file mode 100644
index 0000000..c0ae4bc
--- /dev/null
+++ b/src/vacuum.c
@@ -0,0 +1,413 @@
+/*
+** 2003 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the VACUUM command.
+**
+** Most of the code in this file may be omitted by defining the
+** SQLITE_OMIT_VACUUM macro.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
+
+/*
+** Execute zSql on database db.
+**
+** If zSql returns rows, then each row will have exactly one
+** column.  (This will only happen if zSql begins with "SELECT".)
+** Take each row of result and call execSql() again recursively.
+**
+** The execSqlF() routine does the same thing, except it accepts
+** a format string as its third argument
+*/
+static int execSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  /* printf("SQL: [%s]\n", zSql); fflush(stdout); */
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+  while( SQLITE_ROW==(rc = sqlite3_step(pStmt)) ){
+    const char *zSubSql = (const char*)sqlite3_column_text(pStmt,0);
+    assert( sqlite3_strnicmp(zSql,"SELECT",6)==0 );
+    /* The secondary SQL must be one of CREATE TABLE, CREATE INDEX,
+    ** or INSERT.  Historically there have been attacks that first
+    ** corrupt the sqlite_schema.sql field with other kinds of statements
+    ** then run VACUUM to get those statements to execute at inappropriate
+    ** times. */
+    if( zSubSql
+     && (strncmp(zSubSql,"CRE",3)==0 || strncmp(zSubSql,"INS",3)==0)
+    ){
+      rc = execSql(db, pzErrMsg, zSubSql);
+      if( rc!=SQLITE_OK ) break;
+    }
+  }
+  assert( rc!=SQLITE_ROW );
+  if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+  if( rc ){
+    sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+  }
+  (void)sqlite3_finalize(pStmt);
+  return rc;
+}
+static int execSqlF(sqlite3 *db, char **pzErrMsg, const char *zSql, ...){
+  char *z;
+  va_list ap;
+  int rc;
+  va_start(ap, zSql);
+  z = sqlite3VMPrintf(db, zSql, ap);
+  va_end(ap);
+  if( z==0 ) return SQLITE_NOMEM;
+  rc = execSql(db, pzErrMsg, z);
+  sqlite3DbFree(db, z);
+  return rc;
+}
+
+/*
+** The VACUUM command is used to clean up the database,
+** collapse free space, etc.  It is modelled after the VACUUM command
+** in PostgreSQL.  The VACUUM command works as follows:
+**
+**   (1)  Create a new transient database file
+**   (2)  Copy all content from the database being vacuumed into
+**        the new transient database file
+**   (3)  Copy content from the transient database back into the
+**        original database.
+**
+** The transient database requires temporary disk space approximately
+** equal to the size of the original database.  The copy operation of
+** step (3) requires additional temporary disk space approximately equal
+** to the size of the original database for the rollback journal.
+** Hence, temporary disk space that is approximately 2x the size of the
+** original database is required.  Every page of the database is written
+** approximately 3 times:  Once for step (2) and twice for step (3).
+** Two writes per page are required in step (3) because the original
+** database content must be written into the rollback journal prior to
+** overwriting the database with the vacuumed content.
+**
+** Only 1x temporary space and only 1x writes would be required if
+** the copy of step (3) were replaced by deleting the original database
+** and renaming the transient database as the original.  But that will
+** not work if other processes are attached to the original database.
+** And a power loss in between deleting the original and renaming the
+** transient would cause the database file to appear to be deleted
+** following reboot.
+*/
+void sqlite3Vacuum(Parse *pParse, Token *pNm, Expr *pInto){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int iDb = 0;
+  if( v==0 ) goto build_vacuum_end;
+  if( pParse->nErr ) goto build_vacuum_end;
+  if( pNm ){
+#ifndef SQLITE_BUG_COMPATIBLE_20160819
+    /* Default behavior:  Report an error if the argument to VACUUM is
+    ** not recognized */
+    iDb = sqlite3TwoPartName(pParse, pNm, pNm, &pNm);
+    if( iDb<0 ) goto build_vacuum_end;
+#else
+    /* When SQLITE_BUG_COMPATIBLE_20160819 is defined, unrecognized arguments
+    ** to VACUUM are silently ignored.  This is a back-out of a bug fix that
+    ** occurred on 2016-08-19 (https://www.sqlite.org/src/info/083f9e6270).
+    ** The buggy behavior is required for binary compatibility with some
+    ** legacy applications. */
+    iDb = sqlite3FindDb(pParse->db, pNm);
+    if( iDb<0 ) iDb = 0;
+#endif
+  }
+  if( iDb!=1 ){
+    int iIntoReg = 0;
+    if( pInto && sqlite3ResolveSelfReference(pParse,0,0,pInto,0)==0 ){
+      iIntoReg = ++pParse->nMem;
+      sqlite3ExprCode(pParse, pInto, iIntoReg);
+    }
+    sqlite3VdbeAddOp2(v, OP_Vacuum, iDb, iIntoReg);
+    sqlite3VdbeUsesBtree(v, iDb);
+  }
+build_vacuum_end:
+  sqlite3ExprDelete(pParse->db, pInto);
+  return;
+}
+
+/*
+** This routine implements the OP_Vacuum opcode of the VDBE.
+*/
+SQLITE_NOINLINE int sqlite3RunVacuum(
+  char **pzErrMsg,        /* Write error message here */
+  sqlite3 *db,            /* Database connection */
+  int iDb,                /* Which attached DB to vacuum */
+  sqlite3_value *pOut     /* Write results here, if not NULL. VACUUM INTO */
+){
+  int rc = SQLITE_OK;     /* Return code from service routines */
+  Btree *pMain;           /* The database being vacuumed */
+  Btree *pTemp;           /* The temporary database we vacuum into */
+  u32 saved_mDbFlags;     /* Saved value of db->mDbFlags */
+  u64 saved_flags;        /* Saved value of db->flags */
+  i64 saved_nChange;      /* Saved value of db->nChange */
+  i64 saved_nTotalChange; /* Saved value of db->nTotalChange */
+  u32 saved_openFlags;    /* Saved value of db->openFlags */
+  u8 saved_mTrace;        /* Saved trace settings */
+  Db *pDb = 0;            /* Database to detach at end of vacuum */
+  int isMemDb;            /* True if vacuuming a :memory: database */
+  int nRes;               /* Bytes of reserved space at the end of each page */
+  int nDb;                /* Number of attached databases */
+  const char *zDbMain;    /* Schema name of database to vacuum */
+  const char *zOut;       /* Name of output file */
+  u32 pgflags = PAGER_SYNCHRONOUS_OFF; /* sync flags for output db */
+
+  if( !db->autoCommit ){
+    sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
+    return SQLITE_ERROR; /* IMP: R-12218-18073 */
+  }
+  if( db->nVdbeActive>1 ){
+    sqlite3SetString(pzErrMsg, db,"cannot VACUUM - SQL statements in progress");
+    return SQLITE_ERROR; /* IMP: R-15610-35227 */
+  }
+  saved_openFlags = db->openFlags;
+  if( pOut ){
+    if( sqlite3_value_type(pOut)!=SQLITE_TEXT ){
+      sqlite3SetString(pzErrMsg, db, "non-text filename");
+      return SQLITE_ERROR;
+    }
+    zOut = (const char*)sqlite3_value_text(pOut);
+    db->openFlags &= ~SQLITE_OPEN_READONLY;
+    db->openFlags |= SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE;
+  }else{
+    zOut = "";
+  }
+
+  /* Save the current value of the database flags so that it can be 
+  ** restored before returning. Then set the writable-schema flag, and
+  ** disable CHECK and foreign key constraints.  */
+  saved_flags = db->flags;
+  saved_mDbFlags = db->mDbFlags;
+  saved_nChange = db->nChange;
+  saved_nTotalChange = db->nTotalChange;
+  saved_mTrace = db->mTrace;
+  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks;
+  db->mDbFlags |= DBFLAG_PreferBuiltin | DBFLAG_Vacuum;
+  db->flags &= ~(u64)(SQLITE_ForeignKeys | SQLITE_ReverseOrder
+                   | SQLITE_Defensive | SQLITE_CountRows);
+  db->mTrace = 0;
+
+  zDbMain = db->aDb[iDb].zDbSName;
+  pMain = db->aDb[iDb].pBt;
+  isMemDb = sqlite3PagerIsMemdb(sqlite3BtreePager(pMain));
+
+  /* Attach the temporary database as 'vacuum_db'. The synchronous pragma
+  ** can be set to 'off' for this file, as it is not recovered if a crash
+  ** occurs anyway. The integrity of the database is maintained by a
+  ** (possibly synchronous) transaction opened on the main database before
+  ** sqlite3BtreeCopyFile() is called.
+  **
+  ** An optimization would be to use a non-journaled pager.
+  ** (Later:) I tried setting "PRAGMA vacuum_db.journal_mode=OFF" but
+  ** that actually made the VACUUM run slower.  Very little journalling
+  ** actually occurs when doing a vacuum since the vacuum_db is initially
+  ** empty.  Only the journal header is written.  Apparently it takes more
+  ** time to parse and run the PRAGMA to turn journalling off than it does
+  ** to write the journal header file.
+  */
+  nDb = db->nDb;
+  rc = execSqlF(db, pzErrMsg, "ATTACH %Q AS vacuum_db", zOut);
+  db->openFlags = saved_openFlags;
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  assert( (db->nDb-1)==nDb );
+  pDb = &db->aDb[nDb];
+  assert( strcmp(pDb->zDbSName,"vacuum_db")==0 );
+  pTemp = pDb->pBt;
+  if( pOut ){
+    sqlite3_file *id = sqlite3PagerFile(sqlite3BtreePager(pTemp));
+    i64 sz = 0;
+    if( id->pMethods!=0 && (sqlite3OsFileSize(id, &sz)!=SQLITE_OK || sz>0) ){
+      rc = SQLITE_ERROR;
+      sqlite3SetString(pzErrMsg, db, "output file already exists");
+      goto end_of_vacuum;
+    }
+    db->mDbFlags |= DBFLAG_VacuumInto;
+
+    /* For a VACUUM INTO, the pager-flags are set to the same values as
+    ** they are for the database being vacuumed, except that PAGER_CACHESPILL
+    ** is always set. */
+    pgflags = db->aDb[iDb].safety_level | (db->flags & PAGER_FLAGS_MASK);
+  }
+  nRes = sqlite3BtreeGetRequestedReserve(pMain);
+
+  sqlite3BtreeSetCacheSize(pTemp, db->aDb[iDb].pSchema->cache_size);
+  sqlite3BtreeSetSpillSize(pTemp, sqlite3BtreeSetSpillSize(pMain,0));
+  sqlite3BtreeSetPagerFlags(pTemp, pgflags|PAGER_CACHESPILL);
+
+  /* Begin a transaction and take an exclusive lock on the main database
+  ** file. This is done before the sqlite3BtreeGetPageSize(pMain) call below,
+  ** to ensure that we do not try to change the page-size on a WAL database.
+  */
+  rc = execSql(db, pzErrMsg, "BEGIN");
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  rc = sqlite3BtreeBeginTrans(pMain, pOut==0 ? 2 : 0, 0);
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+  /* Do not attempt to change the page size for a WAL database */
+  if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain))
+                                               ==PAGER_JOURNALMODE_WAL
+   && pOut==0
+  ){
+    db->nextPagesize = 0;
+  }
+
+  if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
+   || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
+   || NEVER(db->mallocFailed)
+  ){
+    rc = SQLITE_NOMEM_BKPT;
+    goto end_of_vacuum;
+  }
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac :
+                                           sqlite3BtreeGetAutoVacuum(pMain));
+#endif
+
+  /* Query the schema of the main database. Create a mirror schema
+  ** in the temporary database.
+  */
+  db->init.iDb = nDb; /* force new CREATE statements into vacuum_db */
+  rc = execSqlF(db, pzErrMsg,
+      "SELECT sql FROM \"%w\".sqlite_schema"
+      " WHERE type='table'AND name<>'sqlite_sequence'"
+      " AND coalesce(rootpage,1)>0",
+      zDbMain
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  rc = execSqlF(db, pzErrMsg,
+      "SELECT sql FROM \"%w\".sqlite_schema"
+      " WHERE type='index'",
+      zDbMain
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  db->init.iDb = 0;
+
+  /* Loop through the tables in the main database. For each, do
+  ** an "INSERT INTO vacuum_db.xxx SELECT * FROM main.xxx;" to copy
+  ** the contents to the temporary database.
+  */
+  rc = execSqlF(db, pzErrMsg,
+      "SELECT'INSERT INTO vacuum_db.'||quote(name)"
+      "||' SELECT*FROM\"%w\".'||quote(name)"
+      "FROM vacuum_db.sqlite_schema "
+      "WHERE type='table'AND coalesce(rootpage,1)>0",
+      zDbMain
+  );
+  assert( (db->mDbFlags & DBFLAG_Vacuum)!=0 );
+  db->mDbFlags &= ~DBFLAG_Vacuum;
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+  /* Copy the triggers, views, and virtual tables from the main database
+  ** over to the temporary database.  None of these objects has any
+  ** associated storage, so all we have to do is copy their entries
+  ** from the schema table.
+  */
+  rc = execSqlF(db, pzErrMsg,
+      "INSERT INTO vacuum_db.sqlite_schema"
+      " SELECT*FROM \"%w\".sqlite_schema"
+      " WHERE type IN('view','trigger')"
+      " OR(type='table'AND rootpage=0)",
+      zDbMain
+  );
+  if( rc ) goto end_of_vacuum;
+
+  /* At this point, there is a write transaction open on both the 
+  ** vacuum database and the main database. Assuming no error occurs,
+  ** both transactions are closed by this block - the main database
+  ** transaction by sqlite3BtreeCopyFile() and the other by an explicit
+  ** call to sqlite3BtreeCommit().
+  */
+  {
+    u32 meta;
+    int i;
+
+    /* This array determines which meta meta values are preserved in the
+    ** vacuum.  Even entries are the meta value number and odd entries
+    ** are an increment to apply to the meta value after the vacuum.
+    ** The increment is used to increase the schema cookie so that other
+    ** connections to the same database will know to reread the schema.
+    */
+    static const unsigned char aCopy[] = {
+       BTREE_SCHEMA_VERSION,     1,  /* Add one to the old schema cookie */
+       BTREE_DEFAULT_CACHE_SIZE, 0,  /* Preserve the default page cache size */
+       BTREE_TEXT_ENCODING,      0,  /* Preserve the text encoding */
+       BTREE_USER_VERSION,       0,  /* Preserve the user version */
+       BTREE_APPLICATION_ID,     0,  /* Preserve the application id */
+    };
+
+    assert( SQLITE_TXN_WRITE==sqlite3BtreeTxnState(pTemp) );
+    assert( pOut!=0 || SQLITE_TXN_WRITE==sqlite3BtreeTxnState(pMain) );
+
+    /* Copy Btree meta values */
+    for(i=0; i<ArraySize(aCopy); i+=2){
+      /* GetMeta() and UpdateMeta() cannot fail in this context because
+      ** we already have page 1 loaded into cache and marked dirty. */
+      sqlite3BtreeGetMeta(pMain, aCopy[i], &meta);
+      rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]);
+      if( NEVER(rc!=SQLITE_OK) ) goto end_of_vacuum;
+    }
+
+    if( pOut==0 ){
+      rc = sqlite3BtreeCopyFile(pMain, pTemp);
+    }
+    if( rc!=SQLITE_OK ) goto end_of_vacuum;
+    rc = sqlite3BtreeCommit(pTemp);
+    if( rc!=SQLITE_OK ) goto end_of_vacuum;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pOut==0 ){
+      sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp));
+    }
+#endif
+  }
+
+  assert( rc==SQLITE_OK );
+  if( pOut==0 ){
+    nRes = sqlite3BtreeGetRequestedReserve(pTemp);
+    rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1);
+  }
+
+end_of_vacuum:
+  /* Restore the original value of db->flags */
+  db->init.iDb = 0;
+  db->mDbFlags = saved_mDbFlags;
+  db->flags = saved_flags;
+  db->nChange = saved_nChange;
+  db->nTotalChange = saved_nTotalChange;
+  db->mTrace = saved_mTrace;
+  sqlite3BtreeSetPageSize(pMain, -1, 0, 1);
+
+  /* Currently there is an SQL level transaction open on the vacuum
+  ** database. No locks are held on any other files (since the main file
+  ** was committed at the btree level). So it safe to end the transaction
+  ** by manually setting the autoCommit flag to true and detaching the
+  ** vacuum database. The vacuum_db journal file is deleted when the pager
+  ** is closed by the DETACH.
+  */
+  db->autoCommit = 1;
+
+  if( pDb ){
+    sqlite3BtreeClose(pDb->pBt);
+    pDb->pBt = 0;
+    pDb->pSchema = 0;
+  }
+
+  /* This both clears the schemas and reduces the size of the db->aDb[]
+  ** array. */ 
+  sqlite3ResetAllSchemasOfConnection(db);
+
+  return rc;
+}
+
+#endif  /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */
diff --git a/src/vdbe.c b/src/vdbe.c
new file mode 100644
index 0000000..6d45bbb
--- /dev/null
+++ b/src/vdbe.c
@@ -0,0 +1,9131 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** The code in this file implements the function that runs the
+** bytecode of a prepared statement.
+**
+** Various scripts scan this source file in order to generate HTML
+** documentation, headers files, or other derived files.  The formatting
+** of the code in this file is, therefore, important.  See other comments
+** in this file for details.  If in doubt, do not deviate from existing
+** commenting and indentation practices when changing or adding code.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/*
+** Invoke this macro on memory cells just prior to changing the
+** value of the cell.  This macro verifies that shallow copies are
+** not misused.  A shallow copy of a string or blob just copies a
+** pointer to the string or blob, not the content.  If the original
+** is changed while the copy is still in use, the string or blob might
+** be changed out from under the copy.  This macro verifies that nothing
+** like that ever happens.
+*/
+#ifdef SQLITE_DEBUG
+# define memAboutToChange(P,M) sqlite3VdbeMemAboutToChange(P,M)
+#else
+# define memAboutToChange(P,M)
+#endif
+
+/*
+** The following global variable is incremented every time a cursor
+** moves, either by the OP_SeekXX, OP_Next, or OP_Prev opcodes.  The test
+** procedures use this information to make sure that indices are
+** working correctly.  This variable has no function other than to
+** help verify the correct operation of the library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_search_count = 0;
+#endif
+
+/*
+** When this global variable is positive, it gets decremented once before
+** each instruction in the VDBE.  When it reaches zero, the u1.isInterrupted
+** field of the sqlite3 structure is set in order to simulate an interrupt.
+**
+** This facility is used for testing purposes only.  It does not function
+** in an ordinary build.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_interrupt_count = 0;
+#endif
+
+/*
+** The next global variable is incremented each type the OP_Sort opcode
+** is executed.  The test procedures use this information to make sure that
+** sorting is occurring or not occurring at appropriate times.   This variable
+** has no function other than to help verify the correct operation of the
+** library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_sort_count = 0;
+#endif
+
+/*
+** The next global variable records the size of the largest MEM_Blob
+** or MEM_Str that has been used by a VDBE opcode.  The test procedures
+** use this information to make sure that the zero-blob functionality
+** is working correctly.   This variable has no function other than to
+** help verify the correct operation of the library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_max_blobsize = 0;
+static void updateMaxBlobsize(Mem *p){
+  if( (p->flags & (MEM_Str|MEM_Blob))!=0 && p->n>sqlite3_max_blobsize ){
+    sqlite3_max_blobsize = p->n;
+  }
+}
+#endif
+
+/*
+** This macro evaluates to true if either the update hook or the preupdate
+** hook are enabled for database connect DB.
+*/
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+# define HAS_UPDATE_HOOK(DB) ((DB)->xPreUpdateCallback||(DB)->xUpdateCallback)
+#else
+# define HAS_UPDATE_HOOK(DB) ((DB)->xUpdateCallback)
+#endif
+
+/*
+** The next global variable is incremented each time the OP_Found opcode
+** is executed. This is used to test whether or not the foreign key
+** operation implemented using OP_FkIsZero is working. This variable
+** has no function other than to help verify the correct operation of the
+** library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_found_count = 0;
+#endif
+
+/*
+** Test a register to see if it exceeds the current maximum blob size.
+** If it does, record the new maximum blob size.
+*/
+#if defined(SQLITE_TEST) && !defined(SQLITE_UNTESTABLE)
+# define UPDATE_MAX_BLOBSIZE(P)  updateMaxBlobsize(P)
+#else
+# define UPDATE_MAX_BLOBSIZE(P)
+#endif
+
+#ifdef SQLITE_DEBUG
+/* This routine provides a convenient place to set a breakpoint during
+** tracing with PRAGMA vdbe_trace=on.  The breakpoint fires right after
+** each opcode is printed.  Variables "pc" (program counter) and pOp are
+** available to add conditionals to the breakpoint.  GDB example:
+**
+**         break test_trace_breakpoint if pc=22
+**
+** Other useful labels for breakpoints include:
+**   test_addop_breakpoint(pc,pOp)
+**   sqlite3CorruptError(lineno)
+**   sqlite3MisuseError(lineno)
+**   sqlite3CantopenError(lineno)
+*/
+static void test_trace_breakpoint(int pc, Op *pOp, Vdbe *v){
+  static u64 n = 0;
+  (void)pc;
+  (void)pOp;
+  (void)v;
+  n++;
+  if( n==LARGEST_UINT64 ) abort(); /* So that n is used, preventing a warning */
+}
+#endif
+
+/*
+** Invoke the VDBE coverage callback, if that callback is defined.  This
+** feature is used for test suite validation only and does not appear an
+** production builds.
+**
+** M is the type of branch.  I is the direction taken for this instance of
+** the branch.
+**
+**   M: 2 - two-way branch (I=0: fall-thru   1: jump                )
+**      3 - two-way + NULL (I=0: fall-thru   1: jump      2: NULL   )
+**      4 - OP_Jump        (I=0: jump p1     1: jump p2   2: jump p3)
+**
+** In other words, if M is 2, then I is either 0 (for fall-through) or
+** 1 (for when the branch is taken).  If M is 3, the I is 0 for an
+** ordinary fall-through, I is 1 if the branch was taken, and I is 2
+** if the result of comparison is NULL.  For M=3, I=2 the jump may or
+** may not be taken, depending on the SQLITE_JUMPIFNULL flags in p5.
+** When M is 4, that means that an OP_Jump is being run.  I is 0, 1, or 2
+** depending on if the operands are less than, equal, or greater than.
+**
+** iSrcLine is the source code line (from the __LINE__ macro) that
+** generated the VDBE instruction combined with flag bits.  The source
+** code line number is in the lower 24 bits of iSrcLine and the upper
+** 8 bytes are flags.  The lower three bits of the flags indicate
+** values for I that should never occur.  For example, if the branch is
+** always taken, the flags should be 0x05 since the fall-through and
+** alternate branch are never taken.  If a branch is never taken then
+** flags should be 0x06 since only the fall-through approach is allowed.
+**
+** Bit 0x08 of the flags indicates an OP_Jump opcode that is only
+** interested in equal or not-equal.  In other words, I==0 and I==2
+** should be treated as equivalent
+**
+** Since only a line number is retained, not the filename, this macro
+** only works for amalgamation builds.  But that is ok, since these macros
+** should be no-ops except for special builds used to measure test coverage.
+*/
+#if !defined(SQLITE_VDBE_COVERAGE)
+# define VdbeBranchTaken(I,M)
+#else
+# define VdbeBranchTaken(I,M) vdbeTakeBranch(pOp->iSrcLine,I,M)
+  static void vdbeTakeBranch(u32 iSrcLine, u8 I, u8 M){
+    u8 mNever;
+    assert( I<=2 );  /* 0: fall through,  1: taken,  2: alternate taken */
+    assert( M<=4 );  /* 2: two-way branch, 3: three-way branch, 4: OP_Jump */
+    assert( I<M );   /* I can only be 2 if M is 3 or 4 */
+    /* Transform I from a integer [0,1,2] into a bitmask of [1,2,4] */
+    I = 1<<I;
+    /* The upper 8 bits of iSrcLine are flags.  The lower three bits of
+    ** the flags indicate directions that the branch can never go.  If
+    ** a branch really does go in one of those directions, assert right
+    ** away. */
+    mNever = iSrcLine >> 24;
+    assert( (I & mNever)==0 );
+    if( sqlite3GlobalConfig.xVdbeBranch==0 ) return;  /*NO_TEST*/
+    /* Invoke the branch coverage callback with three arguments:
+    **    iSrcLine - the line number of the VdbeCoverage() macro, with
+    **               flags removed.
+    **    I        - Mask of bits 0x07 indicating which cases are are
+    **               fulfilled by this instance of the jump.  0x01 means
+    **               fall-thru, 0x02 means taken, 0x04 means NULL.  Any
+    **               impossible cases (ex: if the comparison is never NULL)
+    **               are filled in automatically so that the coverage
+    **               measurement logic does not flag those impossible cases
+    **               as missed coverage.
+    **    M        - Type of jump.  Same as M argument above
+    */
+    I |= mNever;
+    if( M==2 ) I |= 0x04;
+    if( M==4 ){
+      I |= 0x08;
+      if( (mNever&0x08)!=0 && (I&0x05)!=0) I |= 0x05; /*NO_TEST*/
+    }
+    sqlite3GlobalConfig.xVdbeBranch(sqlite3GlobalConfig.pVdbeBranchArg,
+                                    iSrcLine&0xffffff, I, M);
+  }
+#endif
+
+/*
+** An ephemeral string value (signified by the MEM_Ephem flag) contains
+** a pointer to a dynamically allocated string where some other entity
+** is responsible for deallocating that string.  Because the register
+** does not control the string, it might be deleted without the register
+** knowing it.
+**
+** This routine converts an ephemeral string into a dynamically allocated
+** string that the register itself controls.  In other words, it
+** converts an MEM_Ephem string into a string with P.z==P.zMalloc.
+*/
+#define Deephemeralize(P) \
+   if( ((P)->flags&MEM_Ephem)!=0 \
+       && sqlite3VdbeMemMakeWriteable(P) ){ goto no_mem;}
+
+/* Return true if the cursor was opened using the OP_OpenSorter opcode. */
+#define isSorter(x) ((x)->eCurType==CURTYPE_SORTER)
+
+/*
+** Allocate VdbeCursor number iCur.  Return a pointer to it.  Return NULL
+** if we run out of memory.
+*/
+static VdbeCursor *allocateCursor(
+  Vdbe *p,              /* The virtual machine */
+  int iCur,             /* Index of the new VdbeCursor */
+  int nField,           /* Number of fields in the table or index */
+  u8 eCurType           /* Type of the new cursor */
+){
+  /* Find the memory cell that will be used to store the blob of memory
+  ** required for this VdbeCursor structure. It is convenient to use a
+  ** vdbe memory cell to manage the memory allocation required for a
+  ** VdbeCursor structure for the following reasons:
+  **
+  **   * Sometimes cursor numbers are used for a couple of different
+  **     purposes in a vdbe program. The different uses might require
+  **     different sized allocations. Memory cells provide growable
+  **     allocations.
+  **
+  **   * When using ENABLE_MEMORY_MANAGEMENT, memory cell buffers can
+  **     be freed lazily via the sqlite3_release_memory() API. This
+  **     minimizes the number of malloc calls made by the system.
+  **
+  ** The memory cell for cursor 0 is aMem[0]. The rest are allocated from
+  ** the top of the register space.  Cursor 1 is at Mem[p->nMem-1].
+  ** Cursor 2 is at Mem[p->nMem-2]. And so forth.
+  */
+  Mem *pMem = iCur>0 ? &p->aMem[p->nMem-iCur] : p->aMem;
+
+  int nByte;
+  VdbeCursor *pCx = 0;
+  nByte =
+      ROUND8P(sizeof(VdbeCursor)) + 2*sizeof(u32)*nField +
+      (eCurType==CURTYPE_BTREE?sqlite3BtreeCursorSize():0);
+
+  assert( iCur>=0 && iCur<p->nCursor );
+  if( p->apCsr[iCur] ){ /*OPTIMIZATION-IF-FALSE*/
+    sqlite3VdbeFreeCursorNN(p, p->apCsr[iCur]);
+    p->apCsr[iCur] = 0;
+  }
+
+  /* There used to be a call to sqlite3VdbeMemClearAndResize() to make sure
+  ** the pMem used to hold space for the cursor has enough storage available
+  ** in pMem->zMalloc.  But for the special case of the aMem[] entries used
+  ** to hold cursors, it is faster to in-line the logic. */
+  assert( pMem->flags==MEM_Undefined );
+  assert( (pMem->flags & MEM_Dyn)==0 );
+  assert( pMem->szMalloc==0 || pMem->z==pMem->zMalloc );
+  if( pMem->szMalloc<nByte ){
+    if( pMem->szMalloc>0 ){
+      sqlite3DbFreeNN(pMem->db, pMem->zMalloc);
+    }
+    pMem->z = pMem->zMalloc = sqlite3DbMallocRaw(pMem->db, nByte);
+    if( pMem->zMalloc==0 ){
+      pMem->szMalloc = 0;
+      return 0;
+    }
+    pMem->szMalloc = nByte;
+  }
+
+  p->apCsr[iCur] = pCx = (VdbeCursor*)pMem->zMalloc;
+  memset(pCx, 0, offsetof(VdbeCursor,pAltCursor));
+  pCx->eCurType = eCurType;
+  pCx->nField = nField;
+  pCx->aOffset = &pCx->aType[nField];
+  if( eCurType==CURTYPE_BTREE ){
+    pCx->uc.pCursor = (BtCursor*)
+        &pMem->z[ROUND8P(sizeof(VdbeCursor))+2*sizeof(u32)*nField];
+    sqlite3BtreeCursorZero(pCx->uc.pCursor);
+  }
+  return pCx;
+}
+
+/*
+** The string in pRec is known to look like an integer and to have a
+** floating point value of rValue.  Return true and set *piValue to the
+** integer value if the string is in range to be an integer.  Otherwise,
+** return false.
+*/
+static int alsoAnInt(Mem *pRec, double rValue, i64 *piValue){
+  i64 iValue;
+  iValue = sqlite3RealToI64(rValue);
+  if( sqlite3RealSameAsInt(rValue,iValue) ){
+    *piValue = iValue;
+    return 1;
+  }
+  return 0==sqlite3Atoi64(pRec->z, piValue, pRec->n, pRec->enc);
+}
+
+/*
+** Try to convert a value into a numeric representation if we can
+** do so without loss of information.  In other words, if the string
+** looks like a number, convert it into a number.  If it does not
+** look like a number, leave it alone.
+**
+** If the bTryForInt flag is true, then extra effort is made to give
+** an integer representation.  Strings that look like floating point
+** values but which have no fractional component (example: '48.00')
+** will have a MEM_Int representation when bTryForInt is true.
+**
+** If bTryForInt is false, then if the input string contains a decimal
+** point or exponential notation, the result is only MEM_Real, even
+** if there is an exact integer representation of the quantity.
+*/
+static void applyNumericAffinity(Mem *pRec, int bTryForInt){
+  double rValue;
+  u8 enc = pRec->enc;
+  int rc;
+  assert( (pRec->flags & (MEM_Str|MEM_Int|MEM_Real|MEM_IntReal))==MEM_Str );
+  rc = sqlite3AtoF(pRec->z, &rValue, pRec->n, enc);
+  if( rc<=0 ) return;
+  if( rc==1 && alsoAnInt(pRec, rValue, &pRec->u.i) ){
+    pRec->flags |= MEM_Int;
+  }else{
+    pRec->u.r = rValue;
+    pRec->flags |= MEM_Real;
+    if( bTryForInt ) sqlite3VdbeIntegerAffinity(pRec);
+  }
+  /* TEXT->NUMERIC is many->one.  Hence, it is important to invalidate the
+  ** string representation after computing a numeric equivalent, because the
+  ** string representation might not be the canonical representation for the
+  ** numeric value.  Ticket [343634942dd54ab57b7024] 2018-01-31. */
+  pRec->flags &= ~MEM_Str;
+}
+
+/*
+** Processing is determine by the affinity parameter:
+**
+** SQLITE_AFF_INTEGER:
+** SQLITE_AFF_REAL:
+** SQLITE_AFF_NUMERIC:
+**    Try to convert pRec to an integer representation or a
+**    floating-point representation if an integer representation
+**    is not possible.  Note that the integer representation is
+**    always preferred, even if the affinity is REAL, because
+**    an integer representation is more space efficient on disk.
+**
+** SQLITE_AFF_FLEXNUM:
+**    If the value is text, then try to convert it into a number of
+**    some kind (integer or real) but do not make any other changes.
+**
+** SQLITE_AFF_TEXT:
+**    Convert pRec to a text representation.
+**
+** SQLITE_AFF_BLOB:
+** SQLITE_AFF_NONE:
+**    No-op.  pRec is unchanged.
+*/
+static void applyAffinity(
+  Mem *pRec,          /* The value to apply affinity to */
+  char affinity,      /* The affinity to be applied */
+  u8 enc              /* Use this text encoding */
+){
+  if( affinity>=SQLITE_AFF_NUMERIC ){
+    assert( affinity==SQLITE_AFF_INTEGER || affinity==SQLITE_AFF_REAL
+             || affinity==SQLITE_AFF_NUMERIC || affinity==SQLITE_AFF_FLEXNUM );
+    if( (pRec->flags & MEM_Int)==0 ){ /*OPTIMIZATION-IF-FALSE*/
+      if( (pRec->flags & (MEM_Real|MEM_IntReal))==0 ){
+        if( pRec->flags & MEM_Str ) applyNumericAffinity(pRec,1);
+      }else if( affinity<=SQLITE_AFF_REAL ){
+        sqlite3VdbeIntegerAffinity(pRec);
+      }
+    }
+  }else if( affinity==SQLITE_AFF_TEXT ){
+    /* Only attempt the conversion to TEXT if there is an integer or real
+    ** representation (blob and NULL do not get converted) but no string
+    ** representation.  It would be harmless to repeat the conversion if
+    ** there is already a string rep, but it is pointless to waste those
+    ** CPU cycles. */
+    if( 0==(pRec->flags&MEM_Str) ){ /*OPTIMIZATION-IF-FALSE*/
+      if( (pRec->flags&(MEM_Real|MEM_Int|MEM_IntReal)) ){
+        testcase( pRec->flags & MEM_Int );
+        testcase( pRec->flags & MEM_Real );
+        testcase( pRec->flags & MEM_IntReal );
+        sqlite3VdbeMemStringify(pRec, enc, 1);
+      }
+    }
+    pRec->flags &= ~(MEM_Real|MEM_Int|MEM_IntReal);
+  }
+}
+
+/*
+** Try to convert the type of a function argument or a result column
+** into a numeric representation.  Use either INTEGER or REAL whichever
+** is appropriate.  But only do the conversion if it is possible without
+** loss of information and return the revised type of the argument.
+*/
+int sqlite3_value_numeric_type(sqlite3_value *pVal){
+  int eType = sqlite3_value_type(pVal);
+  if( eType==SQLITE_TEXT ){
+    Mem *pMem = (Mem*)pVal;
+    applyNumericAffinity(pMem, 0);
+    eType = sqlite3_value_type(pVal);
+  }
+  return eType;
+}
+
+/*
+** Exported version of applyAffinity(). This one works on sqlite3_value*,
+** not the internal Mem* type.
+*/
+void sqlite3ValueApplyAffinity(
+  sqlite3_value *pVal,
+  u8 affinity,
+  u8 enc
+){
+  applyAffinity((Mem *)pVal, affinity, enc);
+}
+
+/*
+** pMem currently only holds a string type (or maybe a BLOB that we can
+** interpret as a string if we want to).  Compute its corresponding
+** numeric type, if has one.  Set the pMem->u.r and pMem->u.i fields
+** accordingly.
+*/
+static u16 SQLITE_NOINLINE computeNumericType(Mem *pMem){
+  int rc;
+  sqlite3_int64 ix;
+  assert( (pMem->flags & (MEM_Int|MEM_Real|MEM_IntReal))==0 );
+  assert( (pMem->flags & (MEM_Str|MEM_Blob))!=0 );
+  if( ExpandBlob(pMem) ){
+    pMem->u.i = 0;
+    return MEM_Int;
+  }
+  rc = sqlite3AtoF(pMem->z, &pMem->u.r, pMem->n, pMem->enc);
+  if( rc<=0 ){
+    if( rc==0 && sqlite3Atoi64(pMem->z, &ix, pMem->n, pMem->enc)<=1 ){
+      pMem->u.i = ix;
+      return MEM_Int;
+    }else{
+      return MEM_Real;
+    }
+  }else if( rc==1 && sqlite3Atoi64(pMem->z, &ix, pMem->n, pMem->enc)==0 ){
+    pMem->u.i = ix;
+    return MEM_Int;
+  }
+  return MEM_Real;
+}
+
+/*
+** Return the numeric type for pMem, either MEM_Int or MEM_Real or both or
+** none. 
+**
+** Unlike applyNumericAffinity(), this routine does not modify pMem->flags.
+** But it does set pMem->u.r and pMem->u.i appropriately.
+*/
+static u16 numericType(Mem *pMem){
+  assert( (pMem->flags & MEM_Null)==0
+       || pMem->db==0 || pMem->db->mallocFailed );
+  if( pMem->flags & (MEM_Int|MEM_Real|MEM_IntReal|MEM_Null) ){
+    testcase( pMem->flags & MEM_Int );
+    testcase( pMem->flags & MEM_Real );
+    testcase( pMem->flags & MEM_IntReal );
+    return pMem->flags & (MEM_Int|MEM_Real|MEM_IntReal|MEM_Null);
+  }
+  assert( pMem->flags & (MEM_Str|MEM_Blob) );
+  testcase( pMem->flags & MEM_Str );
+  testcase( pMem->flags & MEM_Blob );
+  return computeNumericType(pMem);
+  return 0;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Write a nice string representation of the contents of cell pMem
+** into buffer zBuf, length nBuf.
+*/
+void sqlite3VdbeMemPrettyPrint(Mem *pMem, StrAccum *pStr){
+  int f = pMem->flags;
+  static const char *const encnames[] = {"(X)", "(8)", "(16LE)", "(16BE)"};
+  if( f&MEM_Blob ){
+    int i;
+    char c;
+    if( f & MEM_Dyn ){
+      c = 'z';
+      assert( (f & (MEM_Static|MEM_Ephem))==0 );
+    }else if( f & MEM_Static ){
+      c = 't';
+      assert( (f & (MEM_Dyn|MEM_Ephem))==0 );
+    }else if( f & MEM_Ephem ){
+      c = 'e';
+      assert( (f & (MEM_Static|MEM_Dyn))==0 );
+    }else{
+      c = 's';
+    }
+    sqlite3_str_appendf(pStr, "%cx[", c);
+    for(i=0; i<25 && i<pMem->n; i++){
+      sqlite3_str_appendf(pStr, "%02X", ((int)pMem->z[i] & 0xFF));
+    }
+    sqlite3_str_appendf(pStr, "|");
+    for(i=0; i<25 && i<pMem->n; i++){
+      char z = pMem->z[i];
+      sqlite3_str_appendchar(pStr, 1, (z<32||z>126)?'.':z);
+    }
+    sqlite3_str_appendf(pStr,"]");
+    if( f & MEM_Zero ){
+      sqlite3_str_appendf(pStr, "+%dz",pMem->u.nZero);
+    }
+  }else if( f & MEM_Str ){
+    int j;
+    u8 c;
+    if( f & MEM_Dyn ){
+      c = 'z';
+      assert( (f & (MEM_Static|MEM_Ephem))==0 );
+    }else if( f & MEM_Static ){
+      c = 't';
+      assert( (f & (MEM_Dyn|MEM_Ephem))==0 );
+    }else if( f & MEM_Ephem ){
+      c = 'e';
+      assert( (f & (MEM_Static|MEM_Dyn))==0 );
+    }else{
+      c = 's';
+    }
+    sqlite3_str_appendf(pStr, " %c%d[", c, pMem->n);
+    for(j=0; j<25 && j<pMem->n; j++){
+      c = pMem->z[j];
+      sqlite3_str_appendchar(pStr, 1, (c>=0x20&&c<=0x7f) ? c : '.');
+    }
+    sqlite3_str_appendf(pStr, "]%s", encnames[pMem->enc]);
+    if( f & MEM_Term ){
+      sqlite3_str_appendf(pStr, "(0-term)");
+    }
+  }
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Print the value of a register for tracing purposes:
+*/
+static void memTracePrint(Mem *p){
+  if( p->flags & MEM_Undefined ){
+    printf(" undefined");
+  }else if( p->flags & MEM_Null ){
+    printf(p->flags & MEM_Zero ? " NULL-nochng" : " NULL");
+  }else if( (p->flags & (MEM_Int|MEM_Str))==(MEM_Int|MEM_Str) ){
+    printf(" si:%lld", p->u.i);
+  }else if( (p->flags & (MEM_IntReal))!=0 ){
+    printf(" ir:%lld", p->u.i);
+  }else if( p->flags & MEM_Int ){
+    printf(" i:%lld", p->u.i);
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  }else if( p->flags & MEM_Real ){
+    printf(" r:%.17g", p->u.r);
+#endif
+  }else if( sqlite3VdbeMemIsRowSet(p) ){
+    printf(" (rowset)");
+  }else{
+    StrAccum acc;
+    char zBuf[1000];
+    sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
+    sqlite3VdbeMemPrettyPrint(p, &acc);
+    printf(" %s", sqlite3StrAccumFinish(&acc));
+  }
+  if( p->flags & MEM_Subtype ) printf(" subtype=0x%02x", p->eSubtype);
+}
+static void registerTrace(int iReg, Mem *p){
+  printf("R[%d] = ", iReg);
+  memTracePrint(p);
+  if( p->pScopyFrom ){
+    printf(" <== R[%d]", (int)(p->pScopyFrom - &p[-iReg]));
+  }
+  printf("\n");
+  sqlite3VdbeCheckMemInvariants(p);
+}
+/**/ void sqlite3PrintMem(Mem *pMem){
+  memTracePrint(pMem);
+  printf("\n");
+  fflush(stdout);
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Show the values of all registers in the virtual machine.  Used for
+** interactive debugging.
+*/
+void sqlite3VdbeRegisterDump(Vdbe *v){
+  int i;
+  for(i=1; i<v->nMem; i++) registerTrace(i, v->aMem+i);
+}
+#endif /* SQLITE_DEBUG */
+
+
+#ifdef SQLITE_DEBUG
+#  define REGISTER_TRACE(R,M) if(db->flags&SQLITE_VdbeTrace)registerTrace(R,M)
+#else
+#  define REGISTER_TRACE(R,M)
+#endif
+
+#ifndef NDEBUG
+/*
+** This function is only called from within an assert() expression. It
+** checks that the sqlite3.nTransaction variable is correctly set to
+** the number of non-transaction savepoints currently in the
+** linked list starting at sqlite3.pSavepoint.
+**
+** Usage:
+**
+**     assert( checkSavepointCount(db) );
+*/
+static int checkSavepointCount(sqlite3 *db){
+  int n = 0;
+  Savepoint *p;
+  for(p=db->pSavepoint; p; p=p->pNext) n++;
+  assert( n==(db->nSavepoint + db->isTransactionSavepoint) );
+  return 1;
+}
+#endif
+
+/*
+** Return the register of pOp->p2 after first preparing it to be
+** overwritten with an integer value.
+*/
+static SQLITE_NOINLINE Mem *out2PrereleaseWithClear(Mem *pOut){
+  sqlite3VdbeMemSetNull(pOut);
+  pOut->flags = MEM_Int;
+  return pOut;
+}
+static Mem *out2Prerelease(Vdbe *p, VdbeOp *pOp){
+  Mem *pOut;
+  assert( pOp->p2>0 );
+  assert( pOp->p2<=(p->nMem+1 - p->nCursor) );
+  pOut = &p->aMem[pOp->p2];
+  memAboutToChange(p, pOut);
+  if( VdbeMemDynamic(pOut) ){ /*OPTIMIZATION-IF-FALSE*/
+    return out2PrereleaseWithClear(pOut);
+  }else{
+    pOut->flags = MEM_Int;
+    return pOut;
+  }
+}
+
+/*
+** Compute a bloom filter hash using pOp->p4.i registers from aMem[] beginning
+** with pOp->p3.  Return the hash.
+*/
+static u64 filterHash(const Mem *aMem, const Op *pOp){
+  int i, mx;
+  u64 h = 0;
+
+  assert( pOp->p4type==P4_INT32 );
+  for(i=pOp->p3, mx=i+pOp->p4.i; i<mx; i++){
+    const Mem *p = &aMem[i];
+    if( p->flags & (MEM_Int|MEM_IntReal) ){
+      h += p->u.i;
+    }else if( p->flags & MEM_Real ){
+      h += sqlite3VdbeIntValue(p);
+    }else if( p->flags & (MEM_Str|MEM_Blob) ){
+      /* All strings have the same hash and all blobs have the same hash,
+      ** though, at least, those hashes are different from each other and
+      ** from NULL. */
+      h += 4093 + (p->flags & (MEM_Str|MEM_Blob));
+    }
+  }
+  return h;
+}
+
+
+/*
+** For OP_Column, factor out the case where content is loaded from
+** overflow pages, so that the code to implement this case is separate
+** the common case where all content fits on the page.  Factoring out
+** the code reduces register pressure and helps the common case
+** to run faster.
+*/
+static SQLITE_NOINLINE int vdbeColumnFromOverflow(
+  VdbeCursor *pC,       /* The BTree cursor from which we are reading */
+  int iCol,             /* The column to read */
+  int t,                /* The serial-type code for the column value */
+  i64 iOffset,          /* Offset to the start of the content value */
+  u32 cacheStatus,      /* Current Vdbe.cacheCtr value */
+  u32 colCacheCtr,      /* Current value of the column cache counter */
+  Mem *pDest            /* Store the value into this register. */
+){
+  int rc;
+  sqlite3 *db = pDest->db;
+  int encoding = pDest->enc;
+  int len = sqlite3VdbeSerialTypeLen(t);
+  assert( pC->eCurType==CURTYPE_BTREE );
+  if( len>db->aLimit[SQLITE_LIMIT_LENGTH] ) return SQLITE_TOOBIG;
+  if( len > 4000 && pC->pKeyInfo==0 ){
+    /* Cache large column values that are on overflow pages using
+    ** an RCStr (reference counted string) so that if they are reloaded,
+    ** that do not have to be copied a second time.  The overhead of
+    ** creating and managing the cache is such that this is only
+    ** profitable for larger TEXT and BLOB values.
+    **
+    ** Only do this on table-btrees so that writes to index-btrees do not
+    ** need to clear the cache.  This buys performance in the common case
+    ** in exchange for generality.
+    */
+    VdbeTxtBlbCache *pCache;
+    char *pBuf;
+    if( pC->colCache==0 ){
+      pC->pCache = sqlite3DbMallocZero(db, sizeof(VdbeTxtBlbCache) );
+      if( pC->pCache==0 ) return SQLITE_NOMEM;
+      pC->colCache = 1;
+    }
+    pCache = pC->pCache;
+    if( pCache->pCValue==0
+     || pCache->iCol!=iCol
+     || pCache->cacheStatus!=cacheStatus
+     || pCache->colCacheCtr!=colCacheCtr
+     || pCache->iOffset!=sqlite3BtreeOffset(pC->uc.pCursor)
+    ){
+      if( pCache->pCValue ) sqlite3RCStrUnref(pCache->pCValue);
+      pBuf = pCache->pCValue = sqlite3RCStrNew( len+3 );
+      if( pBuf==0 ) return SQLITE_NOMEM;
+      rc = sqlite3BtreePayload(pC->uc.pCursor, iOffset, len, pBuf);
+      if( rc ) return rc;
+      pBuf[len] = 0;
+      pBuf[len+1] = 0;
+      pBuf[len+2] = 0;
+      pCache->iCol = iCol;
+      pCache->cacheStatus = cacheStatus;
+      pCache->colCacheCtr = colCacheCtr;
+      pCache->iOffset = sqlite3BtreeOffset(pC->uc.pCursor);
+    }else{
+      pBuf = pCache->pCValue;
+    }
+    assert( t>=12 );
+    sqlite3RCStrRef(pBuf);
+    if( t&1 ){
+      rc = sqlite3VdbeMemSetStr(pDest, pBuf, len, encoding,
+                                sqlite3RCStrUnref);
+      pDest->flags |= MEM_Term;
+    }else{
+      rc = sqlite3VdbeMemSetStr(pDest, pBuf, len, 0,
+                                sqlite3RCStrUnref);
+    }
+  }else{
+    rc = sqlite3VdbeMemFromBtree(pC->uc.pCursor, iOffset, len, pDest);
+    if( rc ) return rc;
+    sqlite3VdbeSerialGet((const u8*)pDest->z, t, pDest);
+    if( (t&1)!=0 && encoding==SQLITE_UTF8 ){
+      pDest->z[len] = 0;
+      pDest->flags |= MEM_Term;
+    }
+  }
+  pDest->flags &= ~MEM_Ephem;
+  return rc;
+}
+
+
+/*
+** Return the symbolic name for the data type of a pMem
+*/
+static const char *vdbeMemTypeName(Mem *pMem){
+  static const char *azTypes[] = {
+      /* SQLITE_INTEGER */ "INT",
+      /* SQLITE_FLOAT   */ "REAL",
+      /* SQLITE_TEXT    */ "TEXT",
+      /* SQLITE_BLOB    */ "BLOB",
+      /* SQLITE_NULL    */ "NULL"
+  };
+  return azTypes[sqlite3_value_type(pMem)-1];
+}
+
+/*
+** Execute as much of a VDBE program as we can.
+** This is the core of sqlite3_step(). 
+*/
+int sqlite3VdbeExec(
+  Vdbe *p                    /* The VDBE */
+){
+  Op *aOp = p->aOp;          /* Copy of p->aOp */
+  Op *pOp = aOp;             /* Current operation */
+#ifdef SQLITE_DEBUG
+  Op *pOrigOp;               /* Value of pOp at the top of the loop */
+  int nExtraDelete = 0;      /* Verifies FORDELETE and AUXDELETE flags */
+  u8 iCompareIsInit = 0;     /* iCompare is initialized */
+#endif
+  int rc = SQLITE_OK;        /* Value to return */
+  sqlite3 *db = p->db;       /* The database */
+  u8 resetSchemaOnFault = 0; /* Reset schema after an error if positive */
+  u8 encoding = ENC(db);     /* The database encoding */
+  int iCompare = 0;          /* Result of last comparison */
+  u64 nVmStep = 0;           /* Number of virtual machine steps */
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  u64 nProgressLimit;        /* Invoke xProgress() when nVmStep reaches this */
+#endif
+  Mem *aMem = p->aMem;       /* Copy of p->aMem */
+  Mem *pIn1 = 0;             /* 1st input operand */
+  Mem *pIn2 = 0;             /* 2nd input operand */
+  Mem *pIn3 = 0;             /* 3rd input operand */
+  Mem *pOut = 0;             /* Output operand */
+  u32 colCacheCtr = 0;       /* Column cache counter */
+#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || defined(VDBE_PROFILE)
+  u64 *pnCycle = 0;
+  int bStmtScanStatus = IS_STMT_SCANSTATUS(db)!=0;
+#endif
+  /*** INSERT STACK UNION HERE ***/
+
+  assert( p->eVdbeState==VDBE_RUN_STATE );  /* sqlite3_step() verifies this */
+  if( DbMaskNonZero(p->lockMask) ){
+    sqlite3VdbeEnter(p);
+  }
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  if( db->xProgress ){
+    u32 iPrior = p->aCounter[SQLITE_STMTSTATUS_VM_STEP];
+    assert( 0 < db->nProgressOps );
+    nProgressLimit = db->nProgressOps - (iPrior % db->nProgressOps);
+  }else{
+    nProgressLimit = LARGEST_UINT64;
+  }
+#endif
+  if( p->rc==SQLITE_NOMEM ){
+    /* This happens if a malloc() inside a call to sqlite3_column_text() or
+    ** sqlite3_column_text16() failed.  */
+    goto no_mem;
+  }
+  assert( p->rc==SQLITE_OK || (p->rc&0xff)==SQLITE_BUSY );
+  testcase( p->rc!=SQLITE_OK );
+  p->rc = SQLITE_OK;
+  assert( p->bIsReader || p->readOnly!=0 );
+  p->iCurrentTime = 0;
+  assert( p->explain==0 );
+  db->busyHandler.nBusy = 0;
+  if( AtomicLoad(&db->u1.isInterrupted) ) goto abort_due_to_interrupt;
+  sqlite3VdbeIOTraceSql(p);
+#ifdef SQLITE_DEBUG
+  sqlite3BeginBenignMalloc();
+  if( p->pc==0
+   && (p->db->flags & (SQLITE_VdbeListing|SQLITE_VdbeEQP|SQLITE_VdbeTrace))!=0
+  ){
+    int i;
+    int once = 1;
+    sqlite3VdbePrintSql(p);
+    if( p->db->flags & SQLITE_VdbeListing ){
+      printf("VDBE Program Listing:\n");
+      for(i=0; i<p->nOp; i++){
+        sqlite3VdbePrintOp(stdout, i, &aOp[i]);
+      }
+    }
+    if( p->db->flags & SQLITE_VdbeEQP ){
+      for(i=0; i<p->nOp; i++){
+        if( aOp[i].opcode==OP_Explain ){
+          if( once ) printf("VDBE Query Plan:\n");
+          printf("%s\n", aOp[i].p4.z);
+          once = 0;
+        }
+      }
+    }
+    if( p->db->flags & SQLITE_VdbeTrace )  printf("VDBE Trace:\n");
+  }
+  sqlite3EndBenignMalloc();
+#endif
+  for(pOp=&aOp[p->pc]; 1; pOp++){
+    /* Errors are detected by individual opcodes, with an immediate
+    ** jumps to abort_due_to_error. */
+    assert( rc==SQLITE_OK );
+
+    assert( pOp>=aOp && pOp<&aOp[p->nOp]);
+    nVmStep++;
+
+#if defined(VDBE_PROFILE)
+    pOp->nExec++;
+    pnCycle = &pOp->nCycle;
+    if( sqlite3NProfileCnt==0 ) *pnCycle -= sqlite3Hwtime();
+#elif defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+    if( bStmtScanStatus ){
+      pOp->nExec++;
+      pnCycle = &pOp->nCycle;
+      *pnCycle -= sqlite3Hwtime();
+    }
+#endif
+
+    /* Only allow tracing if SQLITE_DEBUG is defined.
+    */
+#ifdef SQLITE_DEBUG
+    if( db->flags & SQLITE_VdbeTrace ){
+      sqlite3VdbePrintOp(stdout, (int)(pOp - aOp), pOp);
+      test_trace_breakpoint((int)(pOp - aOp),pOp,p);
+    }
+#endif
+     
+
+    /* Check to see if we need to simulate an interrupt.  This only happens
+    ** if we have a special test build.
+    */
+#ifdef SQLITE_TEST
+    if( sqlite3_interrupt_count>0 ){
+      sqlite3_interrupt_count--;
+      if( sqlite3_interrupt_count==0 ){
+        sqlite3_interrupt(db);
+      }
+    }
+#endif
+
+    /* Sanity checking on other operands */
+#ifdef SQLITE_DEBUG
+    {
+      u8 opProperty = sqlite3OpcodeProperty[pOp->opcode];
+      if( (opProperty & OPFLG_IN1)!=0 ){
+        assert( pOp->p1>0 );
+        assert( pOp->p1<=(p->nMem+1 - p->nCursor) );
+        assert( memIsValid(&aMem[pOp->p1]) );
+        assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p1]) );
+        REGISTER_TRACE(pOp->p1, &aMem[pOp->p1]);
+      }
+      if( (opProperty & OPFLG_IN2)!=0 ){
+        assert( pOp->p2>0 );
+        assert( pOp->p2<=(p->nMem+1 - p->nCursor) );
+        assert( memIsValid(&aMem[pOp->p2]) );
+        assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p2]) );
+        REGISTER_TRACE(pOp->p2, &aMem[pOp->p2]);
+      }
+      if( (opProperty & OPFLG_IN3)!=0 ){
+        assert( pOp->p3>0 );
+        assert( pOp->p3<=(p->nMem+1 - p->nCursor) );
+        assert( memIsValid(&aMem[pOp->p3]) );
+        assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p3]) );
+        REGISTER_TRACE(pOp->p3, &aMem[pOp->p3]);
+      }
+      if( (opProperty & OPFLG_OUT2)!=0 ){
+        assert( pOp->p2>0 );
+        assert( pOp->p2<=(p->nMem+1 - p->nCursor) );
+        memAboutToChange(p, &aMem[pOp->p2]);
+      }
+      if( (opProperty & OPFLG_OUT3)!=0 ){
+        assert( pOp->p3>0 );
+        assert( pOp->p3<=(p->nMem+1 - p->nCursor) );
+        memAboutToChange(p, &aMem[pOp->p3]);
+      }
+    }
+#endif
+#ifdef SQLITE_DEBUG
+    pOrigOp = pOp;
+#endif
+ 
+    switch( pOp->opcode ){
+
+/*****************************************************************************
+** What follows is a massive switch statement where each case implements a
+** separate instruction in the virtual machine.  If we follow the usual
+** indentation conventions, each case should be indented by 6 spaces.  But
+** that is a lot of wasted space on the left margin.  So the code within
+** the switch statement will break with convention and be flush-left. Another
+** big comment (similar to this one) will mark the point in the code where
+** we transition back to normal indentation.
+**
+** The formatting of each case is important.  The makefile for SQLite
+** generates two C files "opcodes.h" and "opcodes.c" by scanning this
+** file looking for lines that begin with "case OP_".  The opcodes.h files
+** will be filled with #defines that give unique integer values to each
+** opcode and the opcodes.c file is filled with an array of strings where
+** each string is the symbolic name for the corresponding opcode.  If the
+** case statement is followed by a comment of the form "/# same as ... #/"
+** that comment is used to determine the particular value of the opcode.
+**
+** Other keywords in the comment that follows each case are used to
+** construct the OPFLG_INITIALIZER value that initializes opcodeProperty[].
+** Keywords include: in1, in2, in3, out2, out3.  See
+** the mkopcodeh.awk script for additional information.
+**
+** Documentation about VDBE opcodes is generated by scanning this file
+** for lines of that contain "Opcode:".  That line and all subsequent
+** comment lines are used in the generation of the opcode.html documentation
+** file.
+**
+** SUMMARY:
+**
+**     Formatting is important to scripts that scan this file.
+**     Do not deviate from the formatting style currently in use.
+**
+*****************************************************************************/
+
+/* Opcode:  Goto * P2 * * *
+**
+** An unconditional jump to address P2.
+** The next instruction executed will be
+** the one at index P2 from the beginning of
+** the program.
+**
+** The P1 parameter is not actually used by this opcode.  However, it
+** is sometimes set to 1 instead of 0 as a hint to the command-line shell
+** that this Goto is the bottom of a loop and that the lines from P2 down
+** to the current line should be indented for EXPLAIN output.
+*/
+case OP_Goto: {             /* jump */
+
+#ifdef SQLITE_DEBUG
+  /* In debugging mode, when the p5 flags is set on an OP_Goto, that
+  ** means we should really jump back to the preceding OP_ReleaseReg
+  ** instruction. */
+  if( pOp->p5 ){
+    assert( pOp->p2 < (int)(pOp - aOp) );
+    assert( pOp->p2 > 1 );
+    pOp = &aOp[pOp->p2 - 2];
+    assert( pOp[1].opcode==OP_ReleaseReg );
+    goto check_for_interrupt;
+  }
+#endif
+
+jump_to_p2_and_check_for_interrupt:
+  pOp = &aOp[pOp->p2 - 1];
+
+  /* Opcodes that are used as the bottom of a loop (OP_Next, OP_Prev,
+  ** OP_VNext, or OP_SorterNext) all jump here upon
+  ** completion.  Check to see if sqlite3_interrupt() has been called
+  ** or if the progress callback needs to be invoked.
+  **
+  ** This code uses unstructured "goto" statements and does not look clean.
+  ** But that is not due to sloppy coding habits. The code is written this
+  ** way for performance, to avoid having to run the interrupt and progress
+  ** checks on every opcode.  This helps sqlite3_step() to run about 1.5%
+  ** faster according to "valgrind --tool=cachegrind" */
+check_for_interrupt:
+  if( AtomicLoad(&db->u1.isInterrupted) ) goto abort_due_to_interrupt;
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  /* Call the progress callback if it is configured and the required number
+  ** of VDBE ops have been executed (either since this invocation of
+  ** sqlite3VdbeExec() or since last time the progress callback was called).
+  ** If the progress callback returns non-zero, exit the virtual machine with
+  ** a return code SQLITE_ABORT.
+  */
+  while( nVmStep>=nProgressLimit && db->xProgress!=0 ){
+    assert( db->nProgressOps!=0 );
+    nProgressLimit += db->nProgressOps;
+    if( db->xProgress(db->pProgressArg) ){
+      nProgressLimit = LARGEST_UINT64;
+      rc = SQLITE_INTERRUPT;
+      goto abort_due_to_error;
+    }
+  }
+#endif
+ 
+  break;
+}
+
+/* Opcode:  Gosub P1 P2 * * *
+**
+** Write the current address onto register P1
+** and then jump to address P2.
+*/
+case OP_Gosub: {            /* jump */
+  assert( pOp->p1>0 && pOp->p1<=(p->nMem+1 - p->nCursor) );
+  pIn1 = &aMem[pOp->p1];
+  assert( VdbeMemDynamic(pIn1)==0 );
+  memAboutToChange(p, pIn1);
+  pIn1->flags = MEM_Int;
+  pIn1->u.i = (int)(pOp-aOp);
+  REGISTER_TRACE(pOp->p1, pIn1);
+  goto jump_to_p2_and_check_for_interrupt;
+}
+
+/* Opcode:  Return P1 P2 P3 * *
+**
+** Jump to the address stored in register P1.  If P1 is a return address
+** register, then this accomplishes a return from a subroutine.
+**
+** If P3 is 1, then the jump is only taken if register P1 holds an integer
+** values, otherwise execution falls through to the next opcode, and the
+** OP_Return becomes a no-op. If P3 is 0, then register P1 must hold an
+** integer or else an assert() is raised.  P3 should be set to 1 when
+** this opcode is used in combination with OP_BeginSubrtn, and set to 0
+** otherwise.
+**
+** The value in register P1 is unchanged by this opcode.
+**
+** P2 is not used by the byte-code engine.  However, if P2 is positive
+** and also less than the current address, then the "EXPLAIN" output
+** formatter in the CLI will indent all opcodes from the P2 opcode up
+** to be not including the current Return.   P2 should be the first opcode
+** in the subroutine from which this opcode is returning.  Thus the P2
+** value is a byte-code indentation hint.  See tag-20220407a in
+** wherecode.c and shell.c.
+*/
+case OP_Return: {           /* in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( pIn1->flags & MEM_Int ){
+    if( pOp->p3 ){ VdbeBranchTaken(1, 2); }
+    pOp = &aOp[pIn1->u.i];
+  }else if( ALWAYS(pOp->p3) ){
+    VdbeBranchTaken(0, 2);
+  }
+  break;
+}
+
+/* Opcode: InitCoroutine P1 P2 P3 * *
+**
+** Set up register P1 so that it will Yield to the coroutine
+** located at address P3.
+**
+** If P2!=0 then the coroutine implementation immediately follows
+** this opcode.  So jump over the coroutine implementation to
+** address P2.
+**
+** See also: EndCoroutine
+*/
+case OP_InitCoroutine: {     /* jump */
+  assert( pOp->p1>0 &&  pOp->p1<=(p->nMem+1 - p->nCursor) );
+  assert( pOp->p2>=0 && pOp->p2<p->nOp );
+  assert( pOp->p3>=0 && pOp->p3<p->nOp );
+  pOut = &aMem[pOp->p1];
+  assert( !VdbeMemDynamic(pOut) );
+  pOut->u.i = pOp->p3 - 1;
+  pOut->flags = MEM_Int;
+  if( pOp->p2==0 ) break;
+
+  /* Most jump operations do a goto to this spot in order to update
+  ** the pOp pointer. */
+jump_to_p2:
+  assert( pOp->p2>0 );       /* There are never any jumps to instruction 0 */
+  assert( pOp->p2<p->nOp );  /* Jumps must be in range */
+  pOp = &aOp[pOp->p2 - 1];
+  break;
+}
+
+/* Opcode:  EndCoroutine P1 * * * *
+**
+** The instruction at the address in register P1 is a Yield.
+** Jump to the P2 parameter of that Yield.
+** After the jump, register P1 becomes undefined.
+**
+** See also: InitCoroutine
+*/
+case OP_EndCoroutine: {           /* in1 */
+  VdbeOp *pCaller;
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags==MEM_Int );
+  assert( pIn1->u.i>=0 && pIn1->u.i<p->nOp );
+  pCaller = &aOp[pIn1->u.i];
+  assert( pCaller->opcode==OP_Yield );
+  assert( pCaller->p2>=0 && pCaller->p2<p->nOp );
+  pOp = &aOp[pCaller->p2 - 1];
+  pIn1->flags = MEM_Undefined;
+  break;
+}
+
+/* Opcode:  Yield P1 P2 * * *
+**
+** Swap the program counter with the value in register P1.  This
+** has the effect of yielding to a coroutine.
+**
+** If the coroutine that is launched by this instruction ends with
+** Yield or Return then continue to the next instruction.  But if
+** the coroutine launched by this instruction ends with
+** EndCoroutine, then jump to P2 rather than continuing with the
+** next instruction.
+**
+** See also: InitCoroutine
+*/
+case OP_Yield: {            /* in1, jump */
+  int pcDest;
+  pIn1 = &aMem[pOp->p1];
+  assert( VdbeMemDynamic(pIn1)==0 );
+  pIn1->flags = MEM_Int;
+  pcDest = (int)pIn1->u.i;
+  pIn1->u.i = (int)(pOp - aOp);
+  REGISTER_TRACE(pOp->p1, pIn1);
+  pOp = &aOp[pcDest];
+  break;
+}
+
+/* Opcode:  HaltIfNull  P1 P2 P3 P4 P5
+** Synopsis: if r[P3]=null halt
+**
+** Check the value in register P3.  If it is NULL then Halt using
+** parameter P1, P2, and P4 as if this were a Halt instruction.  If the
+** value in register P3 is not NULL, then this routine is a no-op.
+** The P5 parameter should be 1.
+*/
+case OP_HaltIfNull: {      /* in3 */
+  pIn3 = &aMem[pOp->p3];
+#ifdef SQLITE_DEBUG
+  if( pOp->p2==OE_Abort ){ sqlite3VdbeAssertAbortable(p); }
+#endif
+  if( (pIn3->flags & MEM_Null)==0 ) break;
+  /* Fall through into OP_Halt */
+  /* no break */ deliberate_fall_through
+}
+
+/* Opcode:  Halt P1 P2 * P4 P5
+**
+** Exit immediately.  All open cursors, etc are closed
+** automatically.
+**
+** P1 is the result code returned by sqlite3_exec(), sqlite3_reset(),
+** or sqlite3_finalize().  For a normal halt, this should be SQLITE_OK (0).
+** For errors, it can be some other value.  If P1!=0 then P2 will determine
+** whether or not to rollback the current transaction.  Do not rollback
+** if P2==OE_Fail. Do the rollback if P2==OE_Rollback.  If P2==OE_Abort,
+** then back out all changes that have occurred during this execution of the
+** VDBE, but do not rollback the transaction.
+**
+** If P4 is not null then it is an error message string.
+**
+** P5 is a value between 0 and 4, inclusive, that modifies the P4 string.
+**
+**    0:  (no change)
+**    1:  NOT NULL constraint failed: P4
+**    2:  UNIQUE constraint failed: P4
+**    3:  CHECK constraint failed: P4
+**    4:  FOREIGN KEY constraint failed: P4
+**
+** If P5 is not zero and P4 is NULL, then everything after the ":" is
+** omitted.
+**
+** There is an implied "Halt 0 0 0" instruction inserted at the very end of
+** every program.  So a jump past the last instruction of the program
+** is the same as executing Halt.
+*/
+case OP_Halt: {
+  VdbeFrame *pFrame;
+  int pcx;
+
+#ifdef SQLITE_DEBUG
+  if( pOp->p2==OE_Abort ){ sqlite3VdbeAssertAbortable(p); }
+#endif
+
+  /* A deliberately coded "OP_Halt SQLITE_INTERNAL * * * *" opcode indicates
+  ** something is wrong with the code generator.  Raise an assertion in order
+  ** to bring this to the attention of fuzzers and other testing tools. */
+  assert( pOp->p1!=SQLITE_INTERNAL );
+
+  if( p->pFrame && pOp->p1==SQLITE_OK ){
+    /* Halt the sub-program. Return control to the parent frame. */
+    pFrame = p->pFrame;
+    p->pFrame = pFrame->pParent;
+    p->nFrame--;
+    sqlite3VdbeSetChanges(db, p->nChange);
+    pcx = sqlite3VdbeFrameRestore(pFrame);
+    if( pOp->p2==OE_Ignore ){
+      /* Instruction pcx is the OP_Program that invoked the sub-program
+      ** currently being halted. If the p2 instruction of this OP_Halt
+      ** instruction is set to OE_Ignore, then the sub-program is throwing
+      ** an IGNORE exception. In this case jump to the address specified
+      ** as the p2 of the calling OP_Program.  */
+      pcx = p->aOp[pcx].p2-1;
+    }
+    aOp = p->aOp;
+    aMem = p->aMem;
+    pOp = &aOp[pcx];
+    break;
+  }
+  p->rc = pOp->p1;
+  p->errorAction = (u8)pOp->p2;
+  assert( pOp->p5<=4 );
+  if( p->rc ){
+    if( pOp->p5 ){
+      static const char * const azType[] = { "NOT NULL", "UNIQUE", "CHECK",
+                                             "FOREIGN KEY" };
+      testcase( pOp->p5==1 );
+      testcase( pOp->p5==2 );
+      testcase( pOp->p5==3 );
+      testcase( pOp->p5==4 );
+      sqlite3VdbeError(p, "%s constraint failed", azType[pOp->p5-1]);
+      if( pOp->p4.z ){
+        p->zErrMsg = sqlite3MPrintf(db, "%z: %s", p->zErrMsg, pOp->p4.z);
+      }
+    }else{
+      sqlite3VdbeError(p, "%s", pOp->p4.z);
+    }
+    pcx = (int)(pOp - aOp);
+    sqlite3_log(pOp->p1, "abort at %d in [%s]: %s", pcx, p->zSql, p->zErrMsg);
+  }
+  rc = sqlite3VdbeHalt(p);
+  assert( rc==SQLITE_BUSY || rc==SQLITE_OK || rc==SQLITE_ERROR );
+  if( rc==SQLITE_BUSY ){
+    p->rc = SQLITE_BUSY;
+  }else{
+    assert( rc==SQLITE_OK || (p->rc&0xff)==SQLITE_CONSTRAINT );
+    assert( rc==SQLITE_OK || db->nDeferredCons>0 || db->nDeferredImmCons>0 );
+    rc = p->rc ? SQLITE_ERROR : SQLITE_DONE;
+  }
+  goto vdbe_return;
+}
+
+/* Opcode: Integer P1 P2 * * *
+** Synopsis: r[P2]=P1
+**
+** The 32-bit integer value P1 is written into register P2.
+*/
+case OP_Integer: {         /* out2 */
+  pOut = out2Prerelease(p, pOp);
+  pOut->u.i = pOp->p1;
+  break;
+}
+
+/* Opcode: Int64 * P2 * P4 *
+** Synopsis: r[P2]=P4
+**
+** P4 is a pointer to a 64-bit integer value.
+** Write that value into register P2.
+*/
+case OP_Int64: {           /* out2 */
+  pOut = out2Prerelease(p, pOp);
+  assert( pOp->p4.pI64!=0 );
+  pOut->u.i = *pOp->p4.pI64;
+  break;
+}
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/* Opcode: Real * P2 * P4 *
+** Synopsis: r[P2]=P4
+**
+** P4 is a pointer to a 64-bit floating point value.
+** Write that value into register P2.
+*/
+case OP_Real: {            /* same as TK_FLOAT, out2 */
+  pOut = out2Prerelease(p, pOp);
+  pOut->flags = MEM_Real;
+  assert( !sqlite3IsNaN(*pOp->p4.pReal) );
+  pOut->u.r = *pOp->p4.pReal;
+  break;
+}
+#endif
+
+/* Opcode: String8 * P2 * P4 *
+** Synopsis: r[P2]='P4'
+**
+** P4 points to a nul terminated UTF-8 string. This opcode is transformed
+** into a String opcode before it is executed for the first time.  During
+** this transformation, the length of string P4 is computed and stored
+** as the P1 parameter.
+*/
+case OP_String8: {         /* same as TK_STRING, out2 */
+  assert( pOp->p4.z!=0 );
+  pOut = out2Prerelease(p, pOp);
+  pOp->p1 = sqlite3Strlen30(pOp->p4.z);
+
+#ifndef SQLITE_OMIT_UTF16
+  if( encoding!=SQLITE_UTF8 ){
+    rc = sqlite3VdbeMemSetStr(pOut, pOp->p4.z, -1, SQLITE_UTF8, SQLITE_STATIC);
+    assert( rc==SQLITE_OK || rc==SQLITE_TOOBIG );
+    if( rc ) goto too_big;
+    if( SQLITE_OK!=sqlite3VdbeChangeEncoding(pOut, encoding) ) goto no_mem;
+    assert( pOut->szMalloc>0 && pOut->zMalloc==pOut->z );
+    assert( VdbeMemDynamic(pOut)==0 );
+    pOut->szMalloc = 0;
+    pOut->flags |= MEM_Static;
+    if( pOp->p4type==P4_DYNAMIC ){
+      sqlite3DbFree(db, pOp->p4.z);
+    }
+    pOp->p4type = P4_DYNAMIC;
+    pOp->p4.z = pOut->z;
+    pOp->p1 = pOut->n;
+  }
+#endif
+  if( pOp->p1>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    goto too_big;
+  }
+  pOp->opcode = OP_String;
+  assert( rc==SQLITE_OK );
+  /* Fall through to the next case, OP_String */
+  /* no break */ deliberate_fall_through
+}
+ 
+/* Opcode: String P1 P2 P3 P4 P5
+** Synopsis: r[P2]='P4' (len=P1)
+**
+** The string value P4 of length P1 (bytes) is stored in register P2.
+**
+** If P3 is not zero and the content of register P3 is equal to P5, then
+** the datatype of the register P2 is converted to BLOB.  The content is
+** the same sequence of bytes, it is merely interpreted as a BLOB instead
+** of a string, as if it had been CAST.  In other words:
+**
+** if( P3!=0 and reg[P3]==P5 ) reg[P2] := CAST(reg[P2] as BLOB)
+*/
+case OP_String: {          /* out2 */
+  assert( pOp->p4.z!=0 );
+  pOut = out2Prerelease(p, pOp);
+  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
+  pOut->z = pOp->p4.z;
+  pOut->n = pOp->p1;
+  pOut->enc = encoding;
+  UPDATE_MAX_BLOBSIZE(pOut);
+#ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+  if( pOp->p3>0 ){
+    assert( pOp->p3<=(p->nMem+1 - p->nCursor) );
+    pIn3 = &aMem[pOp->p3];
+    assert( pIn3->flags & MEM_Int );
+    if( pIn3->u.i==pOp->p5 ) pOut->flags = MEM_Blob|MEM_Static|MEM_Term;
+  }
+#endif
+  break;
+}
+
+/* Opcode: BeginSubrtn * P2 * * *
+** Synopsis: r[P2]=NULL
+**
+** Mark the beginning of a subroutine that can be entered in-line
+** or that can be called using OP_Gosub.  The subroutine should
+** be terminated by an OP_Return instruction that has a P1 operand that
+** is the same as the P2 operand to this opcode and that has P3 set to 1.
+** If the subroutine is entered in-line, then the OP_Return will simply
+** fall through.  But if the subroutine is entered using OP_Gosub, then
+** the OP_Return will jump back to the first instruction after the OP_Gosub.
+**
+** This routine works by loading a NULL into the P2 register.  When the
+** return address register contains a NULL, the OP_Return instruction is
+** a no-op that simply falls through to the next instruction (assuming that
+** the OP_Return opcode has a P3 value of 1).  Thus if the subroutine is
+** entered in-line, then the OP_Return will cause in-line execution to
+** continue.  But if the subroutine is entered via OP_Gosub, then the
+** OP_Return will cause a return to the address following the OP_Gosub.
+**
+** This opcode is identical to OP_Null.  It has a different name
+** only to make the byte code easier to read and verify.
+*/
+/* Opcode: Null P1 P2 P3 * *
+** Synopsis: r[P2..P3]=NULL
+**
+** Write a NULL into registers P2.  If P3 greater than P2, then also write
+** NULL into register P3 and every register in between P2 and P3.  If P3
+** is less than P2 (typically P3 is zero) then only register P2 is
+** set to NULL.
+**
+** If the P1 value is non-zero, then also set the MEM_Cleared flag so that
+** NULL values will not compare equal even if SQLITE_NULLEQ is set on
+** OP_Ne or OP_Eq.
+*/
+case OP_BeginSubrtn:
+case OP_Null: {           /* out2 */
+  int cnt;
+  u16 nullFlag;
+  pOut = out2Prerelease(p, pOp);
+  cnt = pOp->p3-pOp->p2;
+  assert( pOp->p3<=(p->nMem+1 - p->nCursor) );
+  pOut->flags = nullFlag = pOp->p1 ? (MEM_Null|MEM_Cleared) : MEM_Null;
+  pOut->n = 0;
+#ifdef SQLITE_DEBUG
+  pOut->uTemp = 0;
+#endif
+  while( cnt>0 ){
+    pOut++;
+    memAboutToChange(p, pOut);
+    sqlite3VdbeMemSetNull(pOut);
+    pOut->flags = nullFlag;
+    pOut->n = 0;
+    cnt--;
+  }
+  break;
+}
+
+/* Opcode: SoftNull P1 * * * *
+** Synopsis: r[P1]=NULL
+**
+** Set register P1 to have the value NULL as seen by the OP_MakeRecord
+** instruction, but do not free any string or blob memory associated with
+** the register, so that if the value was a string or blob that was
+** previously copied using OP_SCopy, the copies will continue to be valid.
+*/
+case OP_SoftNull: {
+  assert( pOp->p1>0 && pOp->p1<=(p->nMem+1 - p->nCursor) );
+  pOut = &aMem[pOp->p1];
+  pOut->flags = (pOut->flags&~(MEM_Undefined|MEM_AffMask))|MEM_Null;
+  break;
+}
+
+/* Opcode: Blob P1 P2 * P4 *
+** Synopsis: r[P2]=P4 (len=P1)
+**
+** P4 points to a blob of data P1 bytes long.  Store this
+** blob in register P2.  If P4 is a NULL pointer, then construct
+** a zero-filled blob that is P1 bytes long in P2.
+*/
+case OP_Blob: {                /* out2 */
+  assert( pOp->p1 <= SQLITE_MAX_LENGTH );
+  pOut = out2Prerelease(p, pOp);
+  if( pOp->p4.z==0 ){
+    sqlite3VdbeMemSetZeroBlob(pOut, pOp->p1);
+    if( sqlite3VdbeMemExpandBlob(pOut) ) goto no_mem;
+  }else{
+    sqlite3VdbeMemSetStr(pOut, pOp->p4.z, pOp->p1, 0, 0);
+  }
+  pOut->enc = encoding;
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Variable P1 P2 * P4 *
+** Synopsis: r[P2]=parameter(P1,P4)
+**
+** Transfer the values of bound parameter P1 into register P2
+**
+** If the parameter is named, then its name appears in P4.
+** The P4 value is used by sqlite3_bind_parameter_name().
+*/
+case OP_Variable: {            /* out2 */
+  Mem *pVar;       /* Value being transferred */
+
+  assert( pOp->p1>0 && pOp->p1<=p->nVar );
+  assert( pOp->p4.z==0 || pOp->p4.z==sqlite3VListNumToName(p->pVList,pOp->p1) );
+  pVar = &p->aVar[pOp->p1 - 1];
+  if( sqlite3VdbeMemTooBig(pVar) ){
+    goto too_big;
+  }
+  pOut = &aMem[pOp->p2];
+  if( VdbeMemDynamic(pOut) ) sqlite3VdbeMemSetNull(pOut);
+  memcpy(pOut, pVar, MEMCELLSIZE);
+  pOut->flags &= ~(MEM_Dyn|MEM_Ephem);
+  pOut->flags |= MEM_Static|MEM_FromBind;
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Move P1 P2 P3 * *
+** Synopsis: r[P2@P3]=r[P1@P3]
+**
+** Move the P3 values in register P1..P1+P3-1 over into
+** registers P2..P2+P3-1.  Registers P1..P1+P3-1 are
+** left holding a NULL.  It is an error for register ranges
+** P1..P1+P3-1 and P2..P2+P3-1 to overlap.  It is an error
+** for P3 to be less than 1.
+*/
+case OP_Move: {
+  int n;           /* Number of registers left to copy */
+  int p1;          /* Register to copy from */
+  int p2;          /* Register to copy to */
+
+  n = pOp->p3;
+  p1 = pOp->p1;
+  p2 = pOp->p2;
+  assert( n>0 && p1>0 && p2>0 );
+  assert( p1+n<=p2 || p2+n<=p1 );
+
+  pIn1 = &aMem[p1];
+  pOut = &aMem[p2];
+  do{
+    assert( pOut<=&aMem[(p->nMem+1 - p->nCursor)] );
+    assert( pIn1<=&aMem[(p->nMem+1 - p->nCursor)] );
+    assert( memIsValid(pIn1) );
+    memAboutToChange(p, pOut);
+    sqlite3VdbeMemMove(pOut, pIn1);
+#ifdef SQLITE_DEBUG
+    pIn1->pScopyFrom = 0;
+    { int i;
+      for(i=1; i<p->nMem; i++){
+        if( aMem[i].pScopyFrom==pIn1 ){
+          aMem[i].pScopyFrom = pOut;
+        }
+      }
+    }
+#endif
+    Deephemeralize(pOut);
+    REGISTER_TRACE(p2++, pOut);
+    pIn1++;
+    pOut++;
+  }while( --n );
+  break;
+}
+
+/* Opcode: Copy P1 P2 P3 * P5
+** Synopsis: r[P2@P3+1]=r[P1@P3+1]
+**
+** Make a copy of registers P1..P1+P3 into registers P2..P2+P3.
+**
+** If the 0x0002 bit of P5 is set then also clear the MEM_Subtype flag in the
+** destination.  The 0x0001 bit of P5 indicates that this Copy opcode cannot
+** be merged.  The 0x0001 bit is used by the query planner and does not
+** come into play during query execution.
+**
+** This instruction makes a deep copy of the value.  A duplicate
+** is made of any string or blob constant.  See also OP_SCopy.
+*/
+case OP_Copy: {
+  int n;
+
+  n = pOp->p3;
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  assert( pOut!=pIn1 );
+  while( 1 ){
+    memAboutToChange(p, pOut);
+    sqlite3VdbeMemShallowCopy(pOut, pIn1, MEM_Ephem);
+    Deephemeralize(pOut);
+    if( (pOut->flags & MEM_Subtype)!=0 &&  (pOp->p5 & 0x0002)!=0 ){
+      pOut->flags &= ~MEM_Subtype;
+    }
+#ifdef SQLITE_DEBUG
+    pOut->pScopyFrom = 0;
+#endif
+    REGISTER_TRACE(pOp->p2+pOp->p3-n, pOut);
+    if( (n--)==0 ) break;
+    pOut++;
+    pIn1++;
+  }
+  break;
+}
+
+/* Opcode: SCopy P1 P2 * * *
+** Synopsis: r[P2]=r[P1]
+**
+** Make a shallow copy of register P1 into register P2.
+**
+** This instruction makes a shallow copy of the value.  If the value
+** is a string or blob, then the copy is only a pointer to the
+** original and hence if the original changes so will the copy.
+** Worse, if the original is deallocated, the copy becomes invalid.
+** Thus the program must guarantee that the original will not change
+** during the lifetime of the copy.  Use OP_Copy to make a complete
+** copy.
+*/
+case OP_SCopy: {            /* out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  assert( pOut!=pIn1 );
+  sqlite3VdbeMemShallowCopy(pOut, pIn1, MEM_Ephem);
+#ifdef SQLITE_DEBUG
+  pOut->pScopyFrom = pIn1;
+  pOut->mScopyFlags = pIn1->flags;
+#endif
+  break;
+}
+
+/* Opcode: IntCopy P1 P2 * * *
+** Synopsis: r[P2]=r[P1]
+**
+** Transfer the integer value held in register P1 into register P2.
+**
+** This is an optimized version of SCopy that works only for integer
+** values.
+*/
+case OP_IntCopy: {            /* out2 */
+  pIn1 = &aMem[pOp->p1];
+  assert( (pIn1->flags & MEM_Int)!=0 );
+  pOut = &aMem[pOp->p2];
+  sqlite3VdbeMemSetInt64(pOut, pIn1->u.i);
+  break;
+}
+
+/* Opcode: FkCheck * * * * *
+**
+** Halt with an SQLITE_CONSTRAINT error if there are any unresolved
+** foreign key constraint violations.  If there are no foreign key
+** constraint violations, this is a no-op.
+**
+** FK constraint violations are also checked when the prepared statement
+** exits.  This opcode is used to raise foreign key constraint errors prior
+** to returning results such as a row change count or the result of a
+** RETURNING clause.
+*/
+case OP_FkCheck: {
+  if( (rc = sqlite3VdbeCheckFk(p,0))!=SQLITE_OK ){
+    goto abort_due_to_error;
+  }
+  break;
+}
+
+/* Opcode: ResultRow P1 P2 * * *
+** Synopsis: output=r[P1@P2]
+**
+** The registers P1 through P1+P2-1 contain a single row of
+** results. This opcode causes the sqlite3_step() call to terminate
+** with an SQLITE_ROW return code and it sets up the sqlite3_stmt
+** structure to provide access to the r(P1)..r(P1+P2-1) values as
+** the result row.
+*/
+case OP_ResultRow: {
+  assert( p->nResColumn==pOp->p2 );
+  assert( pOp->p1>0 || CORRUPT_DB );
+  assert( pOp->p1+pOp->p2<=(p->nMem+1 - p->nCursor)+1 );
+
+  p->cacheCtr = (p->cacheCtr + 2)|1;
+  p->pResultRow = &aMem[pOp->p1];
+#ifdef SQLITE_DEBUG
+  {
+    Mem *pMem = p->pResultRow;
+    int i;
+    for(i=0; i<pOp->p2; i++){
+      assert( memIsValid(&pMem[i]) );
+      REGISTER_TRACE(pOp->p1+i, &pMem[i]);
+      /* The registers in the result will not be used again when the
+      ** prepared statement restarts.  This is because sqlite3_column()
+      ** APIs might have caused type conversions of made other changes to
+      ** the register values.  Therefore, we can go ahead and break any
+      ** OP_SCopy dependencies. */
+      pMem[i].pScopyFrom = 0;
+    }
+  }
+#endif
+  if( db->mallocFailed ) goto no_mem;
+  if( db->mTrace & SQLITE_TRACE_ROW ){
+    db->trace.xV2(SQLITE_TRACE_ROW, db->pTraceArg, p, 0);
+  }
+  p->pc = (int)(pOp - aOp) + 1;
+  rc = SQLITE_ROW;
+  goto vdbe_return;
+}
+
+/* Opcode: Concat P1 P2 P3 * *
+** Synopsis: r[P3]=r[P2]+r[P1]
+**
+** Add the text in register P1 onto the end of the text in
+** register P2 and store the result in register P3.
+** If either the P1 or P2 text are NULL then store NULL in P3.
+**
+**   P3 = P2 || P1
+**
+** It is illegal for P1 and P3 to be the same register. Sometimes,
+** if P3 is the same register as P2, the implementation is able
+** to avoid a memcpy().
+*/
+case OP_Concat: {           /* same as TK_CONCAT, in1, in2, out3 */
+  i64 nByte;          /* Total size of the output string or blob */
+  u16 flags1;         /* Initial flags for P1 */
+  u16 flags2;         /* Initial flags for P2 */
+
+  pIn1 = &aMem[pOp->p1];
+  pIn2 = &aMem[pOp->p2];
+  pOut = &aMem[pOp->p3];
+  testcase( pOut==pIn2 );
+  assert( pIn1!=pOut );
+  flags1 = pIn1->flags;
+  testcase( flags1 & MEM_Null );
+  testcase( pIn2->flags & MEM_Null );
+  if( (flags1 | pIn2->flags) & MEM_Null ){
+    sqlite3VdbeMemSetNull(pOut);
+    break;
+  }
+  if( (flags1 & (MEM_Str|MEM_Blob))==0 ){
+    if( sqlite3VdbeMemStringify(pIn1,encoding,0) ) goto no_mem;
+    flags1 = pIn1->flags & ~MEM_Str;
+  }else if( (flags1 & MEM_Zero)!=0 ){
+    if( sqlite3VdbeMemExpandBlob(pIn1) ) goto no_mem;
+    flags1 = pIn1->flags & ~MEM_Str;
+  }
+  flags2 = pIn2->flags;
+  if( (flags2 & (MEM_Str|MEM_Blob))==0 ){
+    if( sqlite3VdbeMemStringify(pIn2,encoding,0) ) goto no_mem;
+    flags2 = pIn2->flags & ~MEM_Str;
+  }else if( (flags2 & MEM_Zero)!=0 ){
+    if( sqlite3VdbeMemExpandBlob(pIn2) ) goto no_mem;
+    flags2 = pIn2->flags & ~MEM_Str;
+  }
+  nByte = pIn1->n + pIn2->n;
+  if( nByte>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    goto too_big;
+  }
+  if( sqlite3VdbeMemGrow(pOut, (int)nByte+2, pOut==pIn2) ){
+    goto no_mem;
+  }
+  MemSetTypeFlag(pOut, MEM_Str);
+  if( pOut!=pIn2 ){
+    memcpy(pOut->z, pIn2->z, pIn2->n);
+    assert( (pIn2->flags & MEM_Dyn) == (flags2 & MEM_Dyn) );
+    pIn2->flags = flags2;
+  }
+  memcpy(&pOut->z[pIn2->n], pIn1->z, pIn1->n);
+  assert( (pIn1->flags & MEM_Dyn) == (flags1 & MEM_Dyn) );
+  pIn1->flags = flags1;
+  if( encoding>SQLITE_UTF8 ) nByte &= ~1;
+  pOut->z[nByte]=0;
+  pOut->z[nByte+1] = 0;
+  pOut->flags |= MEM_Term;
+  pOut->n = (int)nByte;
+  pOut->enc = encoding;
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Add P1 P2 P3 * *
+** Synopsis: r[P3]=r[P1]+r[P2]
+**
+** Add the value in register P1 to the value in register P2
+** and store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: Multiply P1 P2 P3 * *
+** Synopsis: r[P3]=r[P1]*r[P2]
+**
+**
+** Multiply the value in register P1 by the value in register P2
+** and store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: Subtract P1 P2 P3 * *
+** Synopsis: r[P3]=r[P2]-r[P1]
+**
+** Subtract the value in register P1 from the value in register P2
+** and store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: Divide P1 P2 P3 * *
+** Synopsis: r[P3]=r[P2]/r[P1]
+**
+** Divide the value in register P1 by the value in register P2
+** and store the result in register P3 (P3=P2/P1). If the value in
+** register P1 is zero, then the result is NULL. If either input is
+** NULL, the result is NULL.
+*/
+/* Opcode: Remainder P1 P2 P3 * *
+** Synopsis: r[P3]=r[P2]%r[P1]
+**
+** Compute the remainder after integer register P2 is divided by
+** register P1 and store the result in register P3.
+** If the value in register P1 is zero the result is NULL.
+** If either operand is NULL, the result is NULL.
+*/
+case OP_Add:                   /* same as TK_PLUS, in1, in2, out3 */
+case OP_Subtract:              /* same as TK_MINUS, in1, in2, out3 */
+case OP_Multiply:              /* same as TK_STAR, in1, in2, out3 */
+case OP_Divide:                /* same as TK_SLASH, in1, in2, out3 */
+case OP_Remainder: {           /* same as TK_REM, in1, in2, out3 */
+  u16 type1;      /* Numeric type of left operand */
+  u16 type2;      /* Numeric type of right operand */
+  i64 iA;         /* Integer value of left operand */
+  i64 iB;         /* Integer value of right operand */
+  double rA;      /* Real value of left operand */
+  double rB;      /* Real value of right operand */
+
+  pIn1 = &aMem[pOp->p1];
+  type1 = pIn1->flags;
+  pIn2 = &aMem[pOp->p2];
+  type2 = pIn2->flags;
+  pOut = &aMem[pOp->p3];
+  if( (type1 & type2 & MEM_Int)!=0 ){
+int_math:
+    iA = pIn1->u.i;
+    iB = pIn2->u.i;
+    switch( pOp->opcode ){
+      case OP_Add:       if( sqlite3AddInt64(&iB,iA) ) goto fp_math;  break;
+      case OP_Subtract:  if( sqlite3SubInt64(&iB,iA) ) goto fp_math;  break;
+      case OP_Multiply:  if( sqlite3MulInt64(&iB,iA) ) goto fp_math;  break;
+      case OP_Divide: {
+        if( iA==0 ) goto arithmetic_result_is_null;
+        if( iA==-1 && iB==SMALLEST_INT64 ) goto fp_math;
+        iB /= iA;
+        break;
+      }
+      default: {
+        if( iA==0 ) goto arithmetic_result_is_null;
+        if( iA==-1 ) iA = 1;
+        iB %= iA;
+        break;
+      }
+    }
+    pOut->u.i = iB;
+    MemSetTypeFlag(pOut, MEM_Int);
+  }else if( ((type1 | type2) & MEM_Null)!=0 ){
+    goto arithmetic_result_is_null;
+  }else{
+    type1 = numericType(pIn1);
+    type2 = numericType(pIn2);
+    if( (type1 & type2 & MEM_Int)!=0 ) goto int_math;
+fp_math:
+    rA = sqlite3VdbeRealValue(pIn1);
+    rB = sqlite3VdbeRealValue(pIn2);
+    switch( pOp->opcode ){
+      case OP_Add:         rB += rA;       break;
+      case OP_Subtract:    rB -= rA;       break;
+      case OP_Multiply:    rB *= rA;       break;
+      case OP_Divide: {
+        /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+        if( rA==(double)0 ) goto arithmetic_result_is_null;
+        rB /= rA;
+        break;
+      }
+      default: {
+        iA = sqlite3VdbeIntValue(pIn1);
+        iB = sqlite3VdbeIntValue(pIn2);
+        if( iA==0 ) goto arithmetic_result_is_null;
+        if( iA==-1 ) iA = 1;
+        rB = (double)(iB % iA);
+        break;
+      }
+    }
+#ifdef SQLITE_OMIT_FLOATING_POINT
+    pOut->u.i = rB;
+    MemSetTypeFlag(pOut, MEM_Int);
+#else
+    if( sqlite3IsNaN(rB) ){
+      goto arithmetic_result_is_null;
+    }
+    pOut->u.r = rB;
+    MemSetTypeFlag(pOut, MEM_Real);
+#endif
+  }
+  break;
+
+arithmetic_result_is_null:
+  sqlite3VdbeMemSetNull(pOut);
+  break;
+}
+
+/* Opcode: CollSeq P1 * * P4
+**
+** P4 is a pointer to a CollSeq object. If the next call to a user function
+** or aggregate calls sqlite3GetFuncCollSeq(), this collation sequence will
+** be returned. This is used by the built-in min(), max() and nullif()
+** functions.
+**
+** If P1 is not zero, then it is a register that a subsequent min() or
+** max() aggregate will set to 1 if the current row is not the minimum or
+** maximum.  The P1 register is initialized to 0 by this instruction.
+**
+** The interface used by the implementation of the aforementioned functions
+** to retrieve the collation sequence set by this opcode is not available
+** publicly.  Only built-in functions have access to this feature.
+*/
+case OP_CollSeq: {
+  assert( pOp->p4type==P4_COLLSEQ );
+  if( pOp->p1 ){
+    sqlite3VdbeMemSetInt64(&aMem[pOp->p1], 0);
+  }
+  break;
+}
+
+/* Opcode: BitAnd P1 P2 P3 * *
+** Synopsis: r[P3]=r[P1]&r[P2]
+**
+** Take the bit-wise AND of the values in register P1 and P2 and
+** store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: BitOr P1 P2 P3 * *
+** Synopsis: r[P3]=r[P1]|r[P2]
+**
+** Take the bit-wise OR of the values in register P1 and P2 and
+** store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: ShiftLeft P1 P2 P3 * *
+** Synopsis: r[P3]=r[P2]<<r[P1]
+**
+** Shift the integer value in register P2 to the left by the
+** number of bits specified by the integer in register P1.
+** Store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: ShiftRight P1 P2 P3 * *
+** Synopsis: r[P3]=r[P2]>>r[P1]
+**
+** Shift the integer value in register P2 to the right by the
+** number of bits specified by the integer in register P1.
+** Store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+case OP_BitAnd:                 /* same as TK_BITAND, in1, in2, out3 */
+case OP_BitOr:                  /* same as TK_BITOR, in1, in2, out3 */
+case OP_ShiftLeft:              /* same as TK_LSHIFT, in1, in2, out3 */
+case OP_ShiftRight: {           /* same as TK_RSHIFT, in1, in2, out3 */
+  i64 iA;
+  u64 uA;
+  i64 iB;
+  u8 op;
+
+  pIn1 = &aMem[pOp->p1];
+  pIn2 = &aMem[pOp->p2];
+  pOut = &aMem[pOp->p3];
+  if( (pIn1->flags | pIn2->flags) & MEM_Null ){
+    sqlite3VdbeMemSetNull(pOut);
+    break;
+  }
+  iA = sqlite3VdbeIntValue(pIn2);
+  iB = sqlite3VdbeIntValue(pIn1);
+  op = pOp->opcode;
+  if( op==OP_BitAnd ){
+    iA &= iB;
+  }else if( op==OP_BitOr ){
+    iA |= iB;
+  }else if( iB!=0 ){
+    assert( op==OP_ShiftRight || op==OP_ShiftLeft );
+
+    /* If shifting by a negative amount, shift in the other direction */
+    if( iB<0 ){
+      assert( OP_ShiftRight==OP_ShiftLeft+1 );
+      op = 2*OP_ShiftLeft + 1 - op;
+      iB = iB>(-64) ? -iB : 64;
+    }
+
+    if( iB>=64 ){
+      iA = (iA>=0 || op==OP_ShiftLeft) ? 0 : -1;
+    }else{
+      memcpy(&uA, &iA, sizeof(uA));
+      if( op==OP_ShiftLeft ){
+        uA <<= iB;
+      }else{
+        uA >>= iB;
+        /* Sign-extend on a right shift of a negative number */
+        if( iA<0 ) uA |= ((((u64)0xffffffff)<<32)|0xffffffff) << (64-iB);
+      }
+      memcpy(&iA, &uA, sizeof(iA));
+    }
+  }
+  pOut->u.i = iA;
+  MemSetTypeFlag(pOut, MEM_Int);
+  break;
+}
+
+/* Opcode: AddImm  P1 P2 * * *
+** Synopsis: r[P1]=r[P1]+P2
+**
+** Add the constant P2 to the value in register P1.
+** The result is always an integer.
+**
+** To force any register to be an integer, just add 0.
+*/
+case OP_AddImm: {            /* in1 */
+  pIn1 = &aMem[pOp->p1];
+  memAboutToChange(p, pIn1);
+  sqlite3VdbeMemIntegerify(pIn1);
+  *(u64*)&pIn1->u.i += (u64)pOp->p2;
+  break;
+}
+
+/* Opcode: MustBeInt P1 P2 * * *
+**
+** Force the value in register P1 to be an integer.  If the value
+** in P1 is not an integer and cannot be converted into an integer
+** without data loss, then jump immediately to P2, or if P2==0
+** raise an SQLITE_MISMATCH exception.
+*/
+case OP_MustBeInt: {            /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( (pIn1->flags & MEM_Int)==0 ){
+    applyAffinity(pIn1, SQLITE_AFF_NUMERIC, encoding);
+    if( (pIn1->flags & MEM_Int)==0 ){
+      VdbeBranchTaken(1, 2);
+      if( pOp->p2==0 ){
+        rc = SQLITE_MISMATCH;
+        goto abort_due_to_error;
+      }else{
+        goto jump_to_p2;
+      }
+    }
+  }
+  VdbeBranchTaken(0, 2);
+  MemSetTypeFlag(pIn1, MEM_Int);
+  break;
+}
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/* Opcode: RealAffinity P1 * * * *
+**
+** If register P1 holds an integer convert it to a real value.
+**
+** This opcode is used when extracting information from a column that
+** has REAL affinity.  Such column values may still be stored as
+** integers, for space efficiency, but after extraction we want them
+** to have only a real value.
+*/
+case OP_RealAffinity: {                  /* in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( pIn1->flags & (MEM_Int|MEM_IntReal) ){
+    testcase( pIn1->flags & MEM_Int );
+    testcase( pIn1->flags & MEM_IntReal );
+    sqlite3VdbeMemRealify(pIn1);
+    REGISTER_TRACE(pOp->p1, pIn1);
+  }
+  break;
+}
+#endif
+
+#ifndef SQLITE_OMIT_CAST
+/* Opcode: Cast P1 P2 * * *
+** Synopsis: affinity(r[P1])
+**
+** Force the value in register P1 to be the type defined by P2.
+**
+** <ul>
+** <li> P2=='A' &rarr; BLOB
+** <li> P2=='B' &rarr; TEXT
+** <li> P2=='C' &rarr; NUMERIC
+** <li> P2=='D' &rarr; INTEGER
+** <li> P2=='E' &rarr; REAL
+** </ul>
+**
+** A NULL value is not changed by this routine.  It remains NULL.
+*/
+case OP_Cast: {                  /* in1 */
+  assert( pOp->p2>=SQLITE_AFF_BLOB && pOp->p2<=SQLITE_AFF_REAL );
+  testcase( pOp->p2==SQLITE_AFF_TEXT );
+  testcase( pOp->p2==SQLITE_AFF_BLOB );
+  testcase( pOp->p2==SQLITE_AFF_NUMERIC );
+  testcase( pOp->p2==SQLITE_AFF_INTEGER );
+  testcase( pOp->p2==SQLITE_AFF_REAL );
+  pIn1 = &aMem[pOp->p1];
+  memAboutToChange(p, pIn1);
+  rc = ExpandBlob(pIn1);
+  if( rc ) goto abort_due_to_error;
+  rc = sqlite3VdbeMemCast(pIn1, pOp->p2, encoding);
+  if( rc ) goto abort_due_to_error;
+  UPDATE_MAX_BLOBSIZE(pIn1);
+  REGISTER_TRACE(pOp->p1, pIn1);
+  break;
+}
+#endif /* SQLITE_OMIT_CAST */
+
+/* Opcode: Eq P1 P2 P3 P4 P5
+** Synopsis: IF r[P3]==r[P1]
+**
+** Compare the values in register P1 and P3.  If reg(P3)==reg(P1) then
+** jump to address P2.
+**
+** The SQLITE_AFF_MASK portion of P5 must be an affinity character -
+** SQLITE_AFF_TEXT, SQLITE_AFF_INTEGER, and so forth. An attempt is made
+** to coerce both inputs according to this affinity before the
+** comparison is made. If the SQLITE_AFF_MASK is 0x00, then numeric
+** affinity is used. Note that the affinity conversions are stored
+** back into the input registers P1 and P3.  So this opcode can cause
+** persistent changes to registers P1 and P3.
+**
+** Once any conversions have taken place, and neither value is NULL,
+** the values are compared. If both values are blobs then memcmp() is
+** used to determine the results of the comparison.  If both values
+** are text, then the appropriate collating function specified in
+** P4 is used to do the comparison.  If P4 is not specified then
+** memcmp() is used to compare text string.  If both values are
+** numeric, then a numeric comparison is used. If the two values
+** are of different types, then numbers are considered less than
+** strings and strings are considered less than blobs.
+**
+** If SQLITE_NULLEQ is set in P5 then the result of comparison is always either
+** true or false and is never NULL.  If both operands are NULL then the result
+** of comparison is true.  If either operand is NULL then the result is false.
+** If neither operand is NULL the result is the same as it would be if
+** the SQLITE_NULLEQ flag were omitted from P5.
+**
+** This opcode saves the result of comparison for use by the new
+** OP_Jump opcode.
+*/
+/* Opcode: Ne P1 P2 P3 P4 P5
+** Synopsis: IF r[P3]!=r[P1]
+**
+** This works just like the Eq opcode except that the jump is taken if
+** the operands in registers P1 and P3 are not equal.  See the Eq opcode for
+** additional information.
+*/
+/* Opcode: Lt P1 P2 P3 P4 P5
+** Synopsis: IF r[P3]<r[P1]
+**
+** Compare the values in register P1 and P3.  If reg(P3)<reg(P1) then
+** jump to address P2.
+**
+** If the SQLITE_JUMPIFNULL bit of P5 is set and either reg(P1) or
+** reg(P3) is NULL then the take the jump.  If the SQLITE_JUMPIFNULL
+** bit is clear then fall through if either operand is NULL.
+**
+** The SQLITE_AFF_MASK portion of P5 must be an affinity character -
+** SQLITE_AFF_TEXT, SQLITE_AFF_INTEGER, and so forth. An attempt is made
+** to coerce both inputs according to this affinity before the
+** comparison is made. If the SQLITE_AFF_MASK is 0x00, then numeric
+** affinity is used. Note that the affinity conversions are stored
+** back into the input registers P1 and P3.  So this opcode can cause
+** persistent changes to registers P1 and P3.
+**
+** Once any conversions have taken place, and neither value is NULL,
+** the values are compared. If both values are blobs then memcmp() is
+** used to determine the results of the comparison.  If both values
+** are text, then the appropriate collating function specified in
+** P4 is  used to do the comparison.  If P4 is not specified then
+** memcmp() is used to compare text string.  If both values are
+** numeric, then a numeric comparison is used. If the two values
+** are of different types, then numbers are considered less than
+** strings and strings are considered less than blobs.
+**
+** This opcode saves the result of comparison for use by the new
+** OP_Jump opcode.
+*/
+/* Opcode: Le P1 P2 P3 P4 P5
+** Synopsis: IF r[P3]<=r[P1]
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the content of register P3 is less than or equal to the content of
+** register P1.  See the Lt opcode for additional information.
+*/
+/* Opcode: Gt P1 P2 P3 P4 P5
+** Synopsis: IF r[P3]>r[P1]
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the content of register P3 is greater than the content of
+** register P1.  See the Lt opcode for additional information.
+*/
+/* Opcode: Ge P1 P2 P3 P4 P5
+** Synopsis: IF r[P3]>=r[P1]
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the content of register P3 is greater than or equal to the content of
+** register P1.  See the Lt opcode for additional information.
+*/
+case OP_Eq:               /* same as TK_EQ, jump, in1, in3 */
+case OP_Ne:               /* same as TK_NE, jump, in1, in3 */
+case OP_Lt:               /* same as TK_LT, jump, in1, in3 */
+case OP_Le:               /* same as TK_LE, jump, in1, in3 */
+case OP_Gt:               /* same as TK_GT, jump, in1, in3 */
+case OP_Ge: {             /* same as TK_GE, jump, in1, in3 */
+  int res, res2;      /* Result of the comparison of pIn1 against pIn3 */
+  char affinity;      /* Affinity to use for comparison */
+  u16 flags1;         /* Copy of initial value of pIn1->flags */
+  u16 flags3;         /* Copy of initial value of pIn3->flags */
+
+  pIn1 = &aMem[pOp->p1];
+  pIn3 = &aMem[pOp->p3];
+  flags1 = pIn1->flags;
+  flags3 = pIn3->flags;
+  if( (flags1 & flags3 & MEM_Int)!=0 ){
+    /* Common case of comparison of two integers */
+    if( pIn3->u.i > pIn1->u.i ){
+      if( sqlite3aGTb[pOp->opcode] ){
+        VdbeBranchTaken(1, (pOp->p5 & SQLITE_NULLEQ)?2:3);
+        goto jump_to_p2;
+      }
+      iCompare = +1;
+      VVA_ONLY( iCompareIsInit = 1; )
+    }else if( pIn3->u.i < pIn1->u.i ){
+      if( sqlite3aLTb[pOp->opcode] ){
+        VdbeBranchTaken(1, (pOp->p5 & SQLITE_NULLEQ)?2:3);
+        goto jump_to_p2;
+      }
+      iCompare = -1;
+      VVA_ONLY( iCompareIsInit = 1; )
+    }else{
+      if( sqlite3aEQb[pOp->opcode] ){
+        VdbeBranchTaken(1, (pOp->p5 & SQLITE_NULLEQ)?2:3);
+        goto jump_to_p2;
+      }
+      iCompare = 0;
+      VVA_ONLY( iCompareIsInit = 1; )
+    }
+    VdbeBranchTaken(0, (pOp->p5 & SQLITE_NULLEQ)?2:3);
+    break;
+  }
+  if( (flags1 | flags3)&MEM_Null ){
+    /* One or both operands are NULL */
+    if( pOp->p5 & SQLITE_NULLEQ ){
+      /* If SQLITE_NULLEQ is set (which will only happen if the operator is
+      ** OP_Eq or OP_Ne) then take the jump or not depending on whether
+      ** or not both operands are null.
+      */
+      assert( (flags1 & MEM_Cleared)==0 );
+      assert( (pOp->p5 & SQLITE_JUMPIFNULL)==0 || CORRUPT_DB );
+      testcase( (pOp->p5 & SQLITE_JUMPIFNULL)!=0 );
+      if( (flags1&flags3&MEM_Null)!=0
+       && (flags3&MEM_Cleared)==0
+      ){
+        res = 0;  /* Operands are equal */
+      }else{
+        res = ((flags3 & MEM_Null) ? -1 : +1);  /* Operands are not equal */
+      }
+    }else{
+      /* SQLITE_NULLEQ is clear and at least one operand is NULL,
+      ** then the result is always NULL.
+      ** The jump is taken if the SQLITE_JUMPIFNULL bit is set.
+      */
+      VdbeBranchTaken(2,3);
+      if( pOp->p5 & SQLITE_JUMPIFNULL ){
+        goto jump_to_p2;
+      }
+      iCompare = 1;    /* Operands are not equal */
+      VVA_ONLY( iCompareIsInit = 1; )
+      break;
+    }
+  }else{
+    /* Neither operand is NULL and we couldn't do the special high-speed
+    ** integer comparison case.  So do a general-case comparison. */
+    affinity = pOp->p5 & SQLITE_AFF_MASK;
+    if( affinity>=SQLITE_AFF_NUMERIC ){
+      if( (flags1 | flags3)&MEM_Str ){
+        if( (flags1 & (MEM_Int|MEM_IntReal|MEM_Real|MEM_Str))==MEM_Str ){
+          applyNumericAffinity(pIn1,0);
+          assert( flags3==pIn3->flags || CORRUPT_DB );
+          flags3 = pIn3->flags;
+        }
+        if( (flags3 & (MEM_Int|MEM_IntReal|MEM_Real|MEM_Str))==MEM_Str ){
+          applyNumericAffinity(pIn3,0);
+        }
+      }
+    }else if( affinity==SQLITE_AFF_TEXT && ((flags1 | flags3) & MEM_Str)!=0 ){
+      if( (flags1 & MEM_Str)==0 && (flags1&(MEM_Int|MEM_Real|MEM_IntReal))!=0 ){
+        testcase( pIn1->flags & MEM_Int );
+        testcase( pIn1->flags & MEM_Real );
+        testcase( pIn1->flags & MEM_IntReal );
+        sqlite3VdbeMemStringify(pIn1, encoding, 1);
+        testcase( (flags1&MEM_Dyn) != (pIn1->flags&MEM_Dyn) );
+        flags1 = (pIn1->flags & ~MEM_TypeMask) | (flags1 & MEM_TypeMask);
+        if( NEVER(pIn1==pIn3) ) flags3 = flags1 | MEM_Str;
+      }
+      if( (flags3 & MEM_Str)==0 && (flags3&(MEM_Int|MEM_Real|MEM_IntReal))!=0 ){
+        testcase( pIn3->flags & MEM_Int );
+        testcase( pIn3->flags & MEM_Real );
+        testcase( pIn3->flags & MEM_IntReal );
+        sqlite3VdbeMemStringify(pIn3, encoding, 1);
+        testcase( (flags3&MEM_Dyn) != (pIn3->flags&MEM_Dyn) );
+        flags3 = (pIn3->flags & ~MEM_TypeMask) | (flags3 & MEM_TypeMask);
+      }
+    }
+    assert( pOp->p4type==P4_COLLSEQ || pOp->p4.pColl==0 );
+    res = sqlite3MemCompare(pIn3, pIn1, pOp->p4.pColl);
+  }
+
+  /* At this point, res is negative, zero, or positive if reg[P1] is
+  ** less than, equal to, or greater than reg[P3], respectively.  Compute
+  ** the answer to this operator in res2, depending on what the comparison
+  ** operator actually is.  The next block of code depends on the fact
+  ** that the 6 comparison operators are consecutive integers in this
+  ** order:  NE, EQ, GT, LE, LT, GE */
+  assert( OP_Eq==OP_Ne+1 ); assert( OP_Gt==OP_Ne+2 ); assert( OP_Le==OP_Ne+3 );
+  assert( OP_Lt==OP_Ne+4 ); assert( OP_Ge==OP_Ne+5 );
+  if( res<0 ){
+    res2 = sqlite3aLTb[pOp->opcode];
+  }else if( res==0 ){
+    res2 = sqlite3aEQb[pOp->opcode];
+  }else{
+    res2 = sqlite3aGTb[pOp->opcode];
+  }
+  iCompare = res;
+  VVA_ONLY( iCompareIsInit = 1; )
+
+  /* Undo any changes made by applyAffinity() to the input registers. */
+  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
+  pIn3->flags = flags3;
+  assert( (pIn1->flags & MEM_Dyn) == (flags1 & MEM_Dyn) );
+  pIn1->flags = flags1;
+
+  VdbeBranchTaken(res2!=0, (pOp->p5 & SQLITE_NULLEQ)?2:3);
+  if( res2 ){
+    goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: ElseEq * P2 * * *
+**
+** This opcode must follow an OP_Lt or OP_Gt comparison operator.  There
+** can be zero or more OP_ReleaseReg opcodes intervening, but no other
+** opcodes are allowed to occur between this instruction and the previous
+** OP_Lt or OP_Gt.
+**
+** If the result of an OP_Eq comparison on the same two operands as
+** the prior OP_Lt or OP_Gt would have been true, then jump to P2.  If
+** the result of an OP_Eq comparison on the two previous operands
+** would have been false or NULL, then fall through.
+*/
+case OP_ElseEq: {       /* same as TK_ESCAPE, jump */
+
+#ifdef SQLITE_DEBUG
+  /* Verify the preconditions of this opcode - that it follows an OP_Lt or
+  ** OP_Gt with zero or more intervening OP_ReleaseReg opcodes */
+  int iAddr;
+  for(iAddr = (int)(pOp - aOp) - 1; ALWAYS(iAddr>=0); iAddr--){
+    if( aOp[iAddr].opcode==OP_ReleaseReg ) continue;
+    assert( aOp[iAddr].opcode==OP_Lt || aOp[iAddr].opcode==OP_Gt );
+    break;
+  }
+#endif /* SQLITE_DEBUG */
+  assert( iCompareIsInit );
+  VdbeBranchTaken(iCompare==0, 2);
+  if( iCompare==0 ) goto jump_to_p2;
+  break;
+}
+
+
+/* Opcode: Permutation * * * P4 *
+**
+** Set the permutation used by the OP_Compare operator in the next
+** instruction.  The permutation is stored in the P4 operand.
+**
+** The permutation is only valid for the next opcode which must be
+** an OP_Compare that has the OPFLAG_PERMUTE bit set in P5.
+**
+** The first integer in the P4 integer array is the length of the array
+** and does not become part of the permutation.
+*/
+case OP_Permutation: {
+  assert( pOp->p4type==P4_INTARRAY );
+  assert( pOp->p4.ai );
+  assert( pOp[1].opcode==OP_Compare );
+  assert( pOp[1].p5 & OPFLAG_PERMUTE );
+  break;
+}
+
+/* Opcode: Compare P1 P2 P3 P4 P5
+** Synopsis: r[P1@P3] <-> r[P2@P3]
+**
+** Compare two vectors of registers in reg(P1)..reg(P1+P3-1) (call this
+** vector "A") and in reg(P2)..reg(P2+P3-1) ("B").  Save the result of
+** the comparison for use by the next OP_Jump instruct.
+**
+** If P5 has the OPFLAG_PERMUTE bit set, then the order of comparison is
+** determined by the most recent OP_Permutation operator.  If the
+** OPFLAG_PERMUTE bit is clear, then register are compared in sequential
+** order.
+**
+** P4 is a KeyInfo structure that defines collating sequences and sort
+** orders for the comparison.  The permutation applies to registers
+** only.  The KeyInfo elements are used sequentially.
+**
+** The comparison is a sort comparison, so NULLs compare equal,
+** NULLs are less than numbers, numbers are less than strings,
+** and strings are less than blobs.
+**
+** This opcode must be immediately followed by an OP_Jump opcode.
+*/
+case OP_Compare: {
+  int n;
+  int i;
+  int p1;
+  int p2;
+  const KeyInfo *pKeyInfo;
+  u32 idx;
+  CollSeq *pColl;    /* Collating sequence to use on this term */
+  int bRev;          /* True for DESCENDING sort order */
+  u32 *aPermute;     /* The permutation */
+
+  if( (pOp->p5 & OPFLAG_PERMUTE)==0 ){
+    aPermute = 0;
+  }else{
+    assert( pOp>aOp );
+    assert( pOp[-1].opcode==OP_Permutation );
+    assert( pOp[-1].p4type==P4_INTARRAY );
+    aPermute = pOp[-1].p4.ai + 1;
+    assert( aPermute!=0 );
+  }
+  n = pOp->p3;
+  pKeyInfo = pOp->p4.pKeyInfo;
+  assert( n>0 );
+  assert( pKeyInfo!=0 );
+  p1 = pOp->p1;
+  p2 = pOp->p2;
+#ifdef SQLITE_DEBUG
+  if( aPermute ){
+    int k, mx = 0;
+    for(k=0; k<n; k++) if( aPermute[k]>(u32)mx ) mx = aPermute[k];
+    assert( p1>0 && p1+mx<=(p->nMem+1 - p->nCursor)+1 );
+    assert( p2>0 && p2+mx<=(p->nMem+1 - p->nCursor)+1 );
+  }else{
+    assert( p1>0 && p1+n<=(p->nMem+1 - p->nCursor)+1 );
+    assert( p2>0 && p2+n<=(p->nMem+1 - p->nCursor)+1 );
+  }
+#endif /* SQLITE_DEBUG */
+  for(i=0; i<n; i++){
+    idx = aPermute ? aPermute[i] : (u32)i;
+    assert( memIsValid(&aMem[p1+idx]) );
+    assert( memIsValid(&aMem[p2+idx]) );
+    REGISTER_TRACE(p1+idx, &aMem[p1+idx]);
+    REGISTER_TRACE(p2+idx, &aMem[p2+idx]);
+    assert( i<pKeyInfo->nKeyField );
+    pColl = pKeyInfo->aColl[i];
+    bRev = (pKeyInfo->aSortFlags[i] & KEYINFO_ORDER_DESC);
+    iCompare = sqlite3MemCompare(&aMem[p1+idx], &aMem[p2+idx], pColl);
+    VVA_ONLY( iCompareIsInit = 1; )
+    if( iCompare ){
+      if( (pKeyInfo->aSortFlags[i] & KEYINFO_ORDER_BIGNULL)
+       && ((aMem[p1+idx].flags & MEM_Null) || (aMem[p2+idx].flags & MEM_Null))
+      ){
+        iCompare = -iCompare;
+      }
+      if( bRev ) iCompare = -iCompare;
+      break;
+    }
+  }
+  assert( pOp[1].opcode==OP_Jump );
+  break;
+}
+
+/* Opcode: Jump P1 P2 P3 * *
+**
+** Jump to the instruction at address P1, P2, or P3 depending on whether
+** in the most recent OP_Compare instruction the P1 vector was less than,
+** equal to, or greater than the P2 vector, respectively.
+**
+** This opcode must immediately follow an OP_Compare opcode.
+*/
+case OP_Jump: {             /* jump */
+  assert( pOp>aOp && pOp[-1].opcode==OP_Compare );
+  assert( iCompareIsInit );
+  if( iCompare<0 ){
+    VdbeBranchTaken(0,4); pOp = &aOp[pOp->p1 - 1];
+  }else if( iCompare==0 ){
+    VdbeBranchTaken(1,4); pOp = &aOp[pOp->p2 - 1];
+  }else{
+    VdbeBranchTaken(2,4); pOp = &aOp[pOp->p3 - 1];
+  }
+  break;
+}
+
+/* Opcode: And P1 P2 P3 * *
+** Synopsis: r[P3]=(r[P1] && r[P2])
+**
+** Take the logical AND of the values in registers P1 and P2 and
+** write the result into register P3.
+**
+** If either P1 or P2 is 0 (false) then the result is 0 even if
+** the other input is NULL.  A NULL and true or two NULLs give
+** a NULL output.
+*/
+/* Opcode: Or P1 P2 P3 * *
+** Synopsis: r[P3]=(r[P1] || r[P2])
+**
+** Take the logical OR of the values in register P1 and P2 and
+** store the answer in register P3.
+**
+** If either P1 or P2 is nonzero (true) then the result is 1 (true)
+** even if the other input is NULL.  A NULL and false or two NULLs
+** give a NULL output.
+*/
+case OP_And:              /* same as TK_AND, in1, in2, out3 */
+case OP_Or: {             /* same as TK_OR, in1, in2, out3 */
+  int v1;    /* Left operand:  0==FALSE, 1==TRUE, 2==UNKNOWN or NULL */
+  int v2;    /* Right operand: 0==FALSE, 1==TRUE, 2==UNKNOWN or NULL */
+
+  v1 = sqlite3VdbeBooleanValue(&aMem[pOp->p1], 2);
+  v2 = sqlite3VdbeBooleanValue(&aMem[pOp->p2], 2);
+  if( pOp->opcode==OP_And ){
+    static const unsigned char and_logic[] = { 0, 0, 0, 0, 1, 2, 0, 2, 2 };
+    v1 = and_logic[v1*3+v2];
+  }else{
+    static const unsigned char or_logic[] = { 0, 1, 2, 1, 1, 1, 2, 1, 2 };
+    v1 = or_logic[v1*3+v2];
+  }
+  pOut = &aMem[pOp->p3];
+  if( v1==2 ){
+    MemSetTypeFlag(pOut, MEM_Null);
+  }else{
+    pOut->u.i = v1;
+    MemSetTypeFlag(pOut, MEM_Int);
+  }
+  break;
+}
+
+/* Opcode: IsTrue P1 P2 P3 P4 *
+** Synopsis: r[P2] = coalesce(r[P1]==TRUE,P3) ^ P4
+**
+** This opcode implements the IS TRUE, IS FALSE, IS NOT TRUE, and
+** IS NOT FALSE operators.
+**
+** Interpret the value in register P1 as a boolean value.  Store that
+** boolean (a 0 or 1) in register P2.  Or if the value in register P1 is
+** NULL, then the P3 is stored in register P2.  Invert the answer if P4
+** is 1.
+**
+** The logic is summarized like this:
+**
+** <ul>
+** <li> If P3==0 and P4==0  then  r[P2] := r[P1] IS TRUE
+** <li> If P3==1 and P4==1  then  r[P2] := r[P1] IS FALSE
+** <li> If P3==0 and P4==1  then  r[P2] := r[P1] IS NOT TRUE
+** <li> If P3==1 and P4==0  then  r[P2] := r[P1] IS NOT FALSE
+** </ul>
+*/
+case OP_IsTrue: {               /* in1, out2 */
+  assert( pOp->p4type==P4_INT32 );
+  assert( pOp->p4.i==0 || pOp->p4.i==1 );
+  assert( pOp->p3==0 || pOp->p3==1 );
+  sqlite3VdbeMemSetInt64(&aMem[pOp->p2],
+      sqlite3VdbeBooleanValue(&aMem[pOp->p1], pOp->p3) ^ pOp->p4.i);
+  break;
+}
+
+/* Opcode: Not P1 P2 * * *
+** Synopsis: r[P2]= !r[P1]
+**
+** Interpret the value in register P1 as a boolean value.  Store the
+** boolean complement in register P2.  If the value in register P1 is
+** NULL, then a NULL is stored in P2.
+*/
+case OP_Not: {                /* same as TK_NOT, in1, out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  if( (pIn1->flags & MEM_Null)==0 ){
+    sqlite3VdbeMemSetInt64(pOut, !sqlite3VdbeBooleanValue(pIn1,0));
+  }else{
+    sqlite3VdbeMemSetNull(pOut);
+  }
+  break;
+}
+
+/* Opcode: BitNot P1 P2 * * *
+** Synopsis: r[P2]= ~r[P1]
+**
+** Interpret the content of register P1 as an integer.  Store the
+** ones-complement of the P1 value into register P2.  If P1 holds
+** a NULL then store a NULL in P2.
+*/
+case OP_BitNot: {             /* same as TK_BITNOT, in1, out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  sqlite3VdbeMemSetNull(pOut);
+  if( (pIn1->flags & MEM_Null)==0 ){
+    pOut->flags = MEM_Int;
+    pOut->u.i = ~sqlite3VdbeIntValue(pIn1);
+  }
+  break;
+}
+
+/* Opcode: Once P1 P2 * * *
+**
+** Fall through to the next instruction the first time this opcode is
+** encountered on each invocation of the byte-code program.  Jump to P2
+** on the second and all subsequent encounters during the same invocation.
+**
+** Top-level programs determine first invocation by comparing the P1
+** operand against the P1 operand on the OP_Init opcode at the beginning
+** of the program.  If the P1 values differ, then fall through and make
+** the P1 of this opcode equal to the P1 of OP_Init.  If P1 values are
+** the same then take the jump.
+**
+** For subprograms, there is a bitmask in the VdbeFrame that determines
+** whether or not the jump should be taken.  The bitmask is necessary
+** because the self-altering code trick does not work for recursive
+** triggers.
+*/
+case OP_Once: {             /* jump */
+  u32 iAddr;                /* Address of this instruction */
+  assert( p->aOp[0].opcode==OP_Init );
+  if( p->pFrame ){
+    iAddr = (int)(pOp - p->aOp);
+    if( (p->pFrame->aOnce[iAddr/8] & (1<<(iAddr & 7)))!=0 ){
+      VdbeBranchTaken(1, 2);
+      goto jump_to_p2;
+    }
+    p->pFrame->aOnce[iAddr/8] |= 1<<(iAddr & 7);
+  }else{
+    if( p->aOp[0].p1==pOp->p1 ){
+      VdbeBranchTaken(1, 2);
+      goto jump_to_p2;
+    }
+  }
+  VdbeBranchTaken(0, 2);
+  pOp->p1 = p->aOp[0].p1;
+  break;
+}
+
+/* Opcode: If P1 P2 P3 * *
+**
+** Jump to P2 if the value in register P1 is true.  The value
+** is considered true if it is numeric and non-zero.  If the value
+** in P1 is NULL then take the jump if and only if P3 is non-zero.
+*/
+case OP_If:  {               /* jump, in1 */
+  int c;
+  c = sqlite3VdbeBooleanValue(&aMem[pOp->p1], pOp->p3);
+  VdbeBranchTaken(c!=0, 2);
+  if( c ) goto jump_to_p2;
+  break;
+}
+
+/* Opcode: IfNot P1 P2 P3 * *
+**
+** Jump to P2 if the value in register P1 is False.  The value
+** is considered false if it has a numeric value of zero.  If the value
+** in P1 is NULL then take the jump if and only if P3 is non-zero.
+*/
+case OP_IfNot: {            /* jump, in1 */
+  int c;
+  c = !sqlite3VdbeBooleanValue(&aMem[pOp->p1], !pOp->p3);
+  VdbeBranchTaken(c!=0, 2);
+  if( c ) goto jump_to_p2;
+  break;
+}
+
+/* Opcode: IsNull P1 P2 * * *
+** Synopsis: if r[P1]==NULL goto P2
+**
+** Jump to P2 if the value in register P1 is NULL.
+*/
+case OP_IsNull: {            /* same as TK_ISNULL, jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  VdbeBranchTaken( (pIn1->flags & MEM_Null)!=0, 2);
+  if( (pIn1->flags & MEM_Null)!=0 ){
+    goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: IsType P1 P2 P3 P4 P5
+** Synopsis: if typeof(P1.P3) in P5 goto P2
+**
+** Jump to P2 if the type of a column in a btree is one of the types specified
+** by the P5 bitmask.
+**
+** P1 is normally a cursor on a btree for which the row decode cache is
+** valid through at least column P3.  In other words, there should have been
+** a prior OP_Column for column P3 or greater.  If the cursor is not valid,
+** then this opcode might give spurious results.
+** The the btree row has fewer than P3 columns, then use P4 as the
+** datatype.
+**
+** If P1 is -1, then P3 is a register number and the datatype is taken
+** from the value in that register.
+**
+** P5 is a bitmask of data types.  SQLITE_INTEGER is the least significant
+** (0x01) bit. SQLITE_FLOAT is the 0x02 bit. SQLITE_TEXT is 0x04.
+** SQLITE_BLOB is 0x08.  SQLITE_NULL is 0x10.
+**
+** WARNING: This opcode does not reliably distinguish between NULL and REAL
+** when P1>=0.  If the database contains a NaN value, this opcode will think
+** that the datatype is REAL when it should be NULL.  When P1<0 and the value
+** is already stored in register P3, then this opcode does reliably
+** distinguish between NULL and REAL.  The problem only arises then P1>=0.
+**
+** Take the jump to address P2 if and only if the datatype of the
+** value determined by P1 and P3 corresponds to one of the bits in the
+** P5 bitmask.
+**
+*/
+case OP_IsType: {        /* jump */
+  VdbeCursor *pC;
+  u16 typeMask;
+  u32 serialType;
+
+  assert( pOp->p1>=(-1) && pOp->p1<p->nCursor );
+  assert( pOp->p1>=0 || (pOp->p3>=0 && pOp->p3<=(p->nMem+1 - p->nCursor)) );
+  if( pOp->p1>=0 ){
+    pC = p->apCsr[pOp->p1];
+    assert( pC!=0 );
+    assert( pOp->p3>=0 );
+    if( pOp->p3<pC->nHdrParsed ){
+      serialType = pC->aType[pOp->p3];
+      if( serialType>=12 ){
+        if( serialType&1 ){
+          typeMask = 0x04;   /* SQLITE_TEXT */
+        }else{
+          typeMask = 0x08;   /* SQLITE_BLOB */
+        }
+      }else{
+        static const unsigned char aMask[] = {
+           0x10, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x2,
+           0x01, 0x01, 0x10, 0x10
+        };
+        testcase( serialType==0 );
+        testcase( serialType==1 );
+        testcase( serialType==2 );
+        testcase( serialType==3 );
+        testcase( serialType==4 );
+        testcase( serialType==5 );
+        testcase( serialType==6 );
+        testcase( serialType==7 );
+        testcase( serialType==8 );
+        testcase( serialType==9 );
+        testcase( serialType==10 );
+        testcase( serialType==11 );
+        typeMask = aMask[serialType];
+      }
+    }else{
+      typeMask = 1 << (pOp->p4.i - 1);
+      testcase( typeMask==0x01 );
+      testcase( typeMask==0x02 );
+      testcase( typeMask==0x04 );
+      testcase( typeMask==0x08 );
+      testcase( typeMask==0x10 );
+    }
+  }else{
+    assert( memIsValid(&aMem[pOp->p3]) );
+    typeMask = 1 << (sqlite3_value_type((sqlite3_value*)&aMem[pOp->p3])-1);
+    testcase( typeMask==0x01 );
+    testcase( typeMask==0x02 );
+    testcase( typeMask==0x04 );
+    testcase( typeMask==0x08 );
+    testcase( typeMask==0x10 );
+  }
+  VdbeBranchTaken( (typeMask & pOp->p5)!=0, 2);
+  if( typeMask & pOp->p5 ){
+    goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: ZeroOrNull P1 P2 P3 * *
+** Synopsis: r[P2] = 0 OR NULL
+**
+** If both registers P1 and P3 are NOT NULL, then store a zero in
+** register P2.  If either registers P1 or P3 are NULL then put
+** a NULL in register P2.
+*/
+case OP_ZeroOrNull: {            /* in1, in2, out2, in3 */
+  if( (aMem[pOp->p1].flags & MEM_Null)!=0
+   || (aMem[pOp->p3].flags & MEM_Null)!=0
+  ){
+    sqlite3VdbeMemSetNull(aMem + pOp->p2);
+  }else{
+    sqlite3VdbeMemSetInt64(aMem + pOp->p2, 0);
+  }
+  break;
+}
+
+/* Opcode: NotNull P1 P2 * * *
+** Synopsis: if r[P1]!=NULL goto P2
+**
+** Jump to P2 if the value in register P1 is not NULL. 
+*/
+case OP_NotNull: {            /* same as TK_NOTNULL, jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  VdbeBranchTaken( (pIn1->flags & MEM_Null)==0, 2);
+  if( (pIn1->flags & MEM_Null)==0 ){
+    goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: IfNullRow P1 P2 P3 * *
+** Synopsis: if P1.nullRow then r[P3]=NULL, goto P2
+**
+** Check the cursor P1 to see if it is currently pointing at a NULL row.
+** If it is, then set register P3 to NULL and jump immediately to P2.
+** If P1 is not on a NULL row, then fall through without making any
+** changes.
+**
+** If P1 is not an open cursor, then this opcode is a no-op.
+*/
+case OP_IfNullRow: {         /* jump */
+  VdbeCursor *pC;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  if( pC && pC->nullRow ){
+    sqlite3VdbeMemSetNull(aMem + pOp->p3);
+    goto jump_to_p2;
+  }
+  break;
+}
+
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+/* Opcode: Offset P1 P2 P3 * *
+** Synopsis: r[P3] = sqlite_offset(P1)
+**
+** Store in register r[P3] the byte offset into the database file that is the
+** start of the payload for the record at which that cursor P1 is currently
+** pointing.
+**
+** P2 is the column number for the argument to the sqlite_offset() function.
+** This opcode does not use P2 itself, but the P2 value is used by the
+** code generator.  The P1, P2, and P3 operands to this opcode are the
+** same as for OP_Column.
+**
+** This opcode is only available if SQLite is compiled with the
+** -DSQLITE_ENABLE_OFFSET_SQL_FUNC option.
+*/
+case OP_Offset: {          /* out3 */
+  VdbeCursor *pC;    /* The VDBE cursor */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  pOut = &p->aMem[pOp->p3];
+  if( pC==0 || pC->eCurType!=CURTYPE_BTREE ){
+    sqlite3VdbeMemSetNull(pOut);
+  }else{
+    if( pC->deferredMoveto ){
+      rc = sqlite3VdbeFinishMoveto(pC);
+      if( rc ) goto abort_due_to_error;
+    }
+    if( sqlite3BtreeEof(pC->uc.pCursor) ){
+      sqlite3VdbeMemSetNull(pOut);
+    }else{
+      sqlite3VdbeMemSetInt64(pOut, sqlite3BtreeOffset(pC->uc.pCursor));
+    }
+  }
+  break;
+}
+#endif /* SQLITE_ENABLE_OFFSET_SQL_FUNC */
+
+/* Opcode: Column P1 P2 P3 P4 P5
+** Synopsis: r[P3]=PX cursor P1 column P2
+**
+** Interpret the data that cursor P1 points to as a structure built using
+** the MakeRecord instruction.  (See the MakeRecord opcode for additional
+** information about the format of the data.)  Extract the P2-th column
+** from this record.  If there are less than (P2+1)
+** values in the record, extract a NULL.
+**
+** The value extracted is stored in register P3.
+**
+** If the record contains fewer than P2 fields, then extract a NULL.  Or,
+** if the P4 argument is a P4_MEM use the value of the P4 argument as
+** the result.
+**
+** If the OPFLAG_LENGTHARG bit is set in P5 then the result is guaranteed
+** to only be used by the length() function or the equivalent.  The content
+** of large blobs is not loaded, thus saving CPU cycles.  If the
+** OPFLAG_TYPEOFARG bit is set then the result will only be used by the
+** typeof() function or the IS NULL or IS NOT NULL operators or the
+** equivalent.  In this case, all content loading can be omitted.
+*/
+case OP_Column: {            /* ncycle */
+  u32 p2;            /* column number to retrieve */
+  VdbeCursor *pC;    /* The VDBE cursor */
+  BtCursor *pCrsr;   /* The B-Tree cursor corresponding to pC */
+  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
+  int len;           /* The length of the serialized data for the column */
+  int i;             /* Loop counter */
+  Mem *pDest;        /* Where to write the extracted value */
+  Mem sMem;          /* For storing the record being decoded */
+  const u8 *zData;   /* Part of the record being decoded */
+  const u8 *zHdr;    /* Next unparsed byte of the header */
+  const u8 *zEndHdr; /* Pointer to first byte after the header */
+  u64 offset64;      /* 64-bit offset */
+  u32 t;             /* A type code from the record header */
+  Mem *pReg;         /* PseudoTable input register */
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p3>0 && pOp->p3<=(p->nMem+1 - p->nCursor) );
+  pC = p->apCsr[pOp->p1];
+  p2 = (u32)pOp->p2;
+
+op_column_restart:
+  assert( pC!=0 );
+  assert( p2<(u32)pC->nField
+       || (pC->eCurType==CURTYPE_PSEUDO && pC->seekResult==0) );
+  aOffset = pC->aOffset;
+  assert( aOffset==pC->aType+pC->nField );
+  assert( pC->eCurType!=CURTYPE_VTAB );
+  assert( pC->eCurType!=CURTYPE_PSEUDO || pC->nullRow );
+  assert( pC->eCurType!=CURTYPE_SORTER );
+
+  if( pC->cacheStatus!=p->cacheCtr ){                /*OPTIMIZATION-IF-FALSE*/
+    if( pC->nullRow ){
+      if( pC->eCurType==CURTYPE_PSEUDO && pC->seekResult>0 ){
+        /* For the special case of as pseudo-cursor, the seekResult field
+        ** identifies the register that holds the record */
+        pReg = &aMem[pC->seekResult];
+        assert( pReg->flags & MEM_Blob );
+        assert( memIsValid(pReg) );
+        pC->payloadSize = pC->szRow = pReg->n;
+        pC->aRow = (u8*)pReg->z;
+      }else{
+        pDest = &aMem[pOp->p3];
+        memAboutToChange(p, pDest);
+        sqlite3VdbeMemSetNull(pDest);
+        goto op_column_out;
+      }
+    }else{
+      pCrsr = pC->uc.pCursor;
+      if( pC->deferredMoveto ){
+        u32 iMap;
+        assert( !pC->isEphemeral );
+        if( pC->ub.aAltMap && (iMap = pC->ub.aAltMap[1+p2])>0  ){
+          pC = pC->pAltCursor;
+          p2 = iMap - 1;
+          goto op_column_restart;
+        }
+        rc = sqlite3VdbeFinishMoveto(pC);
+        if( rc ) goto abort_due_to_error;
+      }else if( sqlite3BtreeCursorHasMoved(pCrsr) ){
+        rc = sqlite3VdbeHandleMovedCursor(pC);
+        if( rc ) goto abort_due_to_error;
+        goto op_column_restart;
+      }
+      assert( pC->eCurType==CURTYPE_BTREE );
+      assert( pCrsr );
+      assert( sqlite3BtreeCursorIsValid(pCrsr) );
+      pC->payloadSize = sqlite3BtreePayloadSize(pCrsr);
+      pC->aRow = sqlite3BtreePayloadFetch(pCrsr, &pC->szRow);
+      assert( pC->szRow<=pC->payloadSize );
+      assert( pC->szRow<=65536 );  /* Maximum page size is 64KiB */
+    }
+    pC->cacheStatus = p->cacheCtr;
+    if( (aOffset[0] = pC->aRow[0])<0x80 ){
+      pC->iHdrOffset = 1;
+    }else{
+      pC->iHdrOffset = sqlite3GetVarint32(pC->aRow, aOffset);
+    }
+    pC->nHdrParsed = 0;
+
+    if( pC->szRow<aOffset[0] ){      /*OPTIMIZATION-IF-FALSE*/
+      /* pC->aRow does not have to hold the entire row, but it does at least
+      ** need to cover the header of the record.  If pC->aRow does not contain
+      ** the complete header, then set it to zero, forcing the header to be
+      ** dynamically allocated. */
+      pC->aRow = 0;
+      pC->szRow = 0;
+
+      /* Make sure a corrupt database has not given us an oversize header.
+      ** Do this now to avoid an oversize memory allocation.
+      **
+      ** Type entries can be between 1 and 5 bytes each.  But 4 and 5 byte
+      ** types use so much data space that there can only be 4096 and 32 of
+      ** them, respectively.  So the maximum header length results from a
+      ** 3-byte type for each of the maximum of 32768 columns plus three
+      ** extra bytes for the header length itself.  32768*3 + 3 = 98307.
+      */
+      if( aOffset[0] > 98307 || aOffset[0] > pC->payloadSize ){
+        goto op_column_corrupt;
+      }
+    }else{
+      /* This is an optimization.  By skipping over the first few tests
+      ** (ex: pC->nHdrParsed<=p2) in the next section, we achieve a
+      ** measurable performance gain.
+      **
+      ** This branch is taken even if aOffset[0]==0.  Such a record is never
+      ** generated by SQLite, and could be considered corruption, but we
+      ** accept it for historical reasons.  When aOffset[0]==0, the code this
+      ** branch jumps to reads past the end of the record, but never more
+      ** than a few bytes.  Even if the record occurs at the end of the page
+      ** content area, the "page header" comes after the page content and so
+      ** this overread is harmless.  Similar overreads can occur for a corrupt
+      ** database file.
+      */
+      zData = pC->aRow;
+      assert( pC->nHdrParsed<=p2 );         /* Conditional skipped */
+      testcase( aOffset[0]==0 );
+      goto op_column_read_header;
+    }
+  }else if( sqlite3BtreeCursorHasMoved(pC->uc.pCursor) ){
+    rc = sqlite3VdbeHandleMovedCursor(pC);
+    if( rc ) goto abort_due_to_error;
+    goto op_column_restart;
+  }
+
+  /* Make sure at least the first p2+1 entries of the header have been
+  ** parsed and valid information is in aOffset[] and pC->aType[].
+  */
+  if( pC->nHdrParsed<=p2 ){
+    /* If there is more header available for parsing in the record, try
+    ** to extract additional fields up through the p2+1-th field
+    */
+    if( pC->iHdrOffset<aOffset[0] ){
+      /* Make sure zData points to enough of the record to cover the header. */
+      if( pC->aRow==0 ){
+        memset(&sMem, 0, sizeof(sMem));
+        rc = sqlite3VdbeMemFromBtreeZeroOffset(pC->uc.pCursor,aOffset[0],&sMem);
+        if( rc!=SQLITE_OK ) goto abort_due_to_error;
+        zData = (u8*)sMem.z;
+      }else{
+        zData = pC->aRow;
+      }
+ 
+      /* Fill in pC->aType[i] and aOffset[i] values through the p2-th field. */
+    op_column_read_header:
+      i = pC->nHdrParsed;
+      offset64 = aOffset[i];
+      zHdr = zData + pC->iHdrOffset;
+      zEndHdr = zData + aOffset[0];
+      testcase( zHdr>=zEndHdr );
+      do{
+        if( (pC->aType[i] = t = zHdr[0])<0x80 ){
+          zHdr++;
+          offset64 += sqlite3VdbeOneByteSerialTypeLen(t);
+        }else{
+          zHdr += sqlite3GetVarint32(zHdr, &t);
+          pC->aType[i] = t;
+          offset64 += sqlite3VdbeSerialTypeLen(t);
+        }
+        aOffset[++i] = (u32)(offset64 & 0xffffffff);
+      }while( (u32)i<=p2 && zHdr<zEndHdr );
+
+      /* The record is corrupt if any of the following are true:
+      ** (1) the bytes of the header extend past the declared header size
+      ** (2) the entire header was used but not all data was used
+      ** (3) the end of the data extends beyond the end of the record.
+      */
+      if( (zHdr>=zEndHdr && (zHdr>zEndHdr || offset64!=pC->payloadSize))
+       || (offset64 > pC->payloadSize)
+      ){
+        if( aOffset[0]==0 ){
+          i = 0;
+          zHdr = zEndHdr;
+        }else{
+          if( pC->aRow==0 ) sqlite3VdbeMemRelease(&sMem);
+          goto op_column_corrupt;
+        }
+      }
+
+      pC->nHdrParsed = i;
+      pC->iHdrOffset = (u32)(zHdr - zData);
+      if( pC->aRow==0 ) sqlite3VdbeMemRelease(&sMem);
+    }else{
+      t = 0;
+    }
+
+    /* If after trying to extract new entries from the header, nHdrParsed is
+    ** still not up to p2, that means that the record has fewer than p2
+    ** columns.  So the result will be either the default value or a NULL.
+    */
+    if( pC->nHdrParsed<=p2 ){
+      pDest = &aMem[pOp->p3];
+      memAboutToChange(p, pDest);
+      if( pOp->p4type==P4_MEM ){
+        sqlite3VdbeMemShallowCopy(pDest, pOp->p4.pMem, MEM_Static);
+      }else{
+        sqlite3VdbeMemSetNull(pDest);
+      }
+      goto op_column_out;
+    }
+  }else{
+    t = pC->aType[p2];
+  }
+
+  /* Extract the content for the p2+1-th column.  Control can only
+  ** reach this point if aOffset[p2], aOffset[p2+1], and pC->aType[p2] are
+  ** all valid.
+  */
+  assert( p2<pC->nHdrParsed );
+  assert( rc==SQLITE_OK );
+  pDest = &aMem[pOp->p3];
+  memAboutToChange(p, pDest);
+  assert( sqlite3VdbeCheckMemInvariants(pDest) );
+  if( VdbeMemDynamic(pDest) ){
+    sqlite3VdbeMemSetNull(pDest);
+  }
+  assert( t==pC->aType[p2] );
+  if( pC->szRow>=aOffset[p2+1] ){
+    /* This is the common case where the desired content fits on the original
+    ** page - where the content is not on an overflow page */
+    zData = pC->aRow + aOffset[p2];
+    if( t<12 ){
+      sqlite3VdbeSerialGet(zData, t, pDest);
+    }else{
+      /* If the column value is a string, we need a persistent value, not
+      ** a MEM_Ephem value.  This branch is a fast short-cut that is equivalent
+      ** to calling sqlite3VdbeSerialGet() and sqlite3VdbeDeephemeralize().
+      */
+      static const u16 aFlag[] = { MEM_Blob, MEM_Str|MEM_Term };
+      pDest->n = len = (t-12)/2;
+      pDest->enc = encoding;
+      if( pDest->szMalloc < len+2 ){
+        if( len>db->aLimit[SQLITE_LIMIT_LENGTH] ) goto too_big;
+        pDest->flags = MEM_Null;
+        if( sqlite3VdbeMemGrow(pDest, len+2, 0) ) goto no_mem;
+      }else{
+        pDest->z = pDest->zMalloc;
+      }
+      memcpy(pDest->z, zData, len);
+      pDest->z[len] = 0;
+      pDest->z[len+1] = 0;
+      pDest->flags = aFlag[t&1];
+    }
+  }else{
+    u8 p5;
+    pDest->enc = encoding;
+    assert( pDest->db==db );
+    /* This branch happens only when content is on overflow pages */
+    if( ((p5 = (pOp->p5 & OPFLAG_BYTELENARG))!=0
+          && (p5==OPFLAG_TYPEOFARG
+              || (t>=12 && ((t&1)==0 || p5==OPFLAG_BYTELENARG))
+             )
+        )
+     || sqlite3VdbeSerialTypeLen(t)==0
+    ){
+      /* Content is irrelevant for
+      **    1. the typeof() function,
+      **    2. the length(X) function if X is a blob, and
+      **    3. if the content length is zero.
+      ** So we might as well use bogus content rather than reading
+      ** content from disk.
+      **
+      ** Although sqlite3VdbeSerialGet() may read at most 8 bytes from the
+      ** buffer passed to it, debugging function VdbeMemPrettyPrint() may
+      ** read more.  Use the global constant sqlite3CtypeMap[] as the array,
+      ** as that array is 256 bytes long (plenty for VdbeMemPrettyPrint())
+      ** and it begins with a bunch of zeros.
+      */
+      sqlite3VdbeSerialGet((u8*)sqlite3CtypeMap, t, pDest);
+    }else{
+      rc = vdbeColumnFromOverflow(pC, p2, t, aOffset[p2],
+                p->cacheCtr, colCacheCtr, pDest);
+      if( rc ){
+        if( rc==SQLITE_NOMEM ) goto no_mem;
+        if( rc==SQLITE_TOOBIG ) goto too_big;
+        goto abort_due_to_error;
+      }
+    }
+  }
+
+op_column_out:
+  UPDATE_MAX_BLOBSIZE(pDest);
+  REGISTER_TRACE(pOp->p3, pDest);
+  break;
+
+op_column_corrupt:
+  if( aOp[0].p3>0 ){
+    pOp = &aOp[aOp[0].p3-1];
+    break;
+  }else{
+    rc = SQLITE_CORRUPT_BKPT;
+    goto abort_due_to_error;
+  }
+}
+
+/* Opcode: TypeCheck P1 P2 P3 P4 *
+** Synopsis: typecheck(r[P1@P2])
+**
+** Apply affinities to the range of P2 registers beginning with P1.
+** Take the affinities from the Table object in P4.  If any value
+** cannot be coerced into the correct type, then raise an error.
+**
+** This opcode is similar to OP_Affinity except that this opcode
+** forces the register type to the Table column type.  This is used
+** to implement "strict affinity".
+**
+** GENERATED ALWAYS AS ... STATIC columns are only checked if P3
+** is zero.  When P3 is non-zero, no type checking occurs for
+** static generated columns.  Virtual columns are computed at query time
+** and so they are never checked.
+**
+** Preconditions:
+**
+** <ul>
+** <li> P2 should be the number of non-virtual columns in the
+**      table of P4.
+** <li> Table P4 should be a STRICT table.
+** </ul>
+**
+** If any precondition is false, an assertion fault occurs.
+*/
+case OP_TypeCheck: {
+  Table *pTab;
+  Column *aCol;
+  int i;
+
+  assert( pOp->p4type==P4_TABLE );
+  pTab = pOp->p4.pTab;
+  assert( pTab->tabFlags & TF_Strict );
+  assert( pTab->nNVCol==pOp->p2 );
+  aCol = pTab->aCol;
+  pIn1 = &aMem[pOp->p1];
+  for(i=0; i<pTab->nCol; i++){
+    if( aCol[i].colFlags & COLFLAG_GENERATED ){
+      if( aCol[i].colFlags & COLFLAG_VIRTUAL ) continue;
+      if( pOp->p3 ){ pIn1++; continue; }
+    }
+    assert( pIn1 < &aMem[pOp->p1+pOp->p2] );
+    applyAffinity(pIn1, aCol[i].affinity, encoding);
+    if( (pIn1->flags & MEM_Null)==0 ){
+      switch( aCol[i].eCType ){
+        case COLTYPE_BLOB: {
+          if( (pIn1->flags & MEM_Blob)==0 ) goto vdbe_type_error;
+          break;
+        }
+        case COLTYPE_INTEGER:
+        case COLTYPE_INT: {
+          if( (pIn1->flags & MEM_Int)==0 ) goto vdbe_type_error;
+          break;
+        }
+        case COLTYPE_TEXT: {
+          if( (pIn1->flags & MEM_Str)==0 ) goto vdbe_type_error;
+          break;
+        }
+        case COLTYPE_REAL: {
+          testcase( (pIn1->flags & (MEM_Real|MEM_IntReal))==MEM_Real );
+          assert( (pIn1->flags & MEM_IntReal)==0 );
+          if( pIn1->flags & MEM_Int ){
+            /* When applying REAL affinity, if the result is still an MEM_Int
+            ** that will fit in 6 bytes, then change the type to MEM_IntReal
+            ** so that we keep the high-resolution integer value but know that
+            ** the type really wants to be REAL. */
+            testcase( pIn1->u.i==140737488355328LL );
+            testcase( pIn1->u.i==140737488355327LL );
+            testcase( pIn1->u.i==-140737488355328LL );
+            testcase( pIn1->u.i==-140737488355329LL );
+            if( pIn1->u.i<=140737488355327LL && pIn1->u.i>=-140737488355328LL){
+              pIn1->flags |= MEM_IntReal;
+              pIn1->flags &= ~MEM_Int;
+            }else{
+              pIn1->u.r = (double)pIn1->u.i;
+              pIn1->flags |= MEM_Real;
+              pIn1->flags &= ~MEM_Int;
+            }
+          }else if( (pIn1->flags & (MEM_Real|MEM_IntReal))==0 ){
+            goto vdbe_type_error;
+          }
+          break;
+        }
+        default: {
+          /* COLTYPE_ANY.  Accept anything. */
+          break;
+        }
+      }
+    }
+    REGISTER_TRACE((int)(pIn1-aMem), pIn1);
+    pIn1++;
+  }
+  assert( pIn1 == &aMem[pOp->p1+pOp->p2] );
+  break;
+
+vdbe_type_error:
+  sqlite3VdbeError(p, "cannot store %s value in %s column %s.%s",
+     vdbeMemTypeName(pIn1), sqlite3StdType[aCol[i].eCType-1],
+     pTab->zName, aCol[i].zCnName);
+  rc = SQLITE_CONSTRAINT_DATATYPE;
+  goto abort_due_to_error;
+}
+
+/* Opcode: Affinity P1 P2 * P4 *
+** Synopsis: affinity(r[P1@P2])
+**
+** Apply affinities to a range of P2 registers starting with P1.
+**
+** P4 is a string that is P2 characters long. The N-th character of the
+** string indicates the column affinity that should be used for the N-th
+** memory cell in the range.
+*/
+case OP_Affinity: {
+  const char *zAffinity;   /* The affinity to be applied */
+
+  zAffinity = pOp->p4.z;
+  assert( zAffinity!=0 );
+  assert( pOp->p2>0 );
+  assert( zAffinity[pOp->p2]==0 );
+  pIn1 = &aMem[pOp->p1];
+  while( 1 /*exit-by-break*/ ){
+    assert( pIn1 <= &p->aMem[(p->nMem+1 - p->nCursor)] );
+    assert( zAffinity[0]==SQLITE_AFF_NONE || memIsValid(pIn1) );
+    applyAffinity(pIn1, zAffinity[0], encoding);
+    if( zAffinity[0]==SQLITE_AFF_REAL && (pIn1->flags & MEM_Int)!=0 ){
+      /* When applying REAL affinity, if the result is still an MEM_Int
+      ** that will fit in 6 bytes, then change the type to MEM_IntReal
+      ** so that we keep the high-resolution integer value but know that
+      ** the type really wants to be REAL. */
+      testcase( pIn1->u.i==140737488355328LL );
+      testcase( pIn1->u.i==140737488355327LL );
+      testcase( pIn1->u.i==-140737488355328LL );
+      testcase( pIn1->u.i==-140737488355329LL );
+      if( pIn1->u.i<=140737488355327LL && pIn1->u.i>=-140737488355328LL ){
+        pIn1->flags |= MEM_IntReal;
+        pIn1->flags &= ~MEM_Int;
+      }else{
+        pIn1->u.r = (double)pIn1->u.i;
+        pIn1->flags |= MEM_Real;
+        pIn1->flags &= ~(MEM_Int|MEM_Str);
+      }
+    }
+    REGISTER_TRACE((int)(pIn1-aMem), pIn1);
+    zAffinity++;
+    if( zAffinity[0]==0 ) break;
+    pIn1++;
+  }
+  break;
+}
+
+/* Opcode: MakeRecord P1 P2 P3 P4 *
+** Synopsis: r[P3]=mkrec(r[P1@P2])
+**
+** Convert P2 registers beginning with P1 into the [record format]
+** use as a data record in a database table or as a key
+** in an index.  The OP_Column opcode can decode the record later.
+**
+** P4 may be a string that is P2 characters long.  The N-th character of the
+** string indicates the column affinity that should be used for the N-th
+** field of the index key.
+**
+** The mapping from character to affinity is given by the SQLITE_AFF_
+** macros defined in sqliteInt.h.
+**
+** If P4 is NULL then all index fields have the affinity BLOB.
+**
+** The meaning of P5 depends on whether or not the SQLITE_ENABLE_NULL_TRIM
+** compile-time option is enabled:
+**
+**   * If SQLITE_ENABLE_NULL_TRIM is enabled, then the P5 is the index
+**     of the right-most table that can be null-trimmed.
+**
+**   * If SQLITE_ENABLE_NULL_TRIM is omitted, then P5 has the value
+**     OPFLAG_NOCHNG_MAGIC if the OP_MakeRecord opcode is allowed to
+**     accept no-change records with serial_type 10.  This value is
+**     only used inside an assert() and does not affect the end result.
+*/
+case OP_MakeRecord: {
+  Mem *pRec;             /* The new record */
+  u64 nData;             /* Number of bytes of data space */
+  int nHdr;              /* Number of bytes of header space */
+  i64 nByte;             /* Data space required for this record */
+  i64 nZero;             /* Number of zero bytes at the end of the record */
+  int nVarint;           /* Number of bytes in a varint */
+  u32 serial_type;       /* Type field */
+  Mem *pData0;           /* First field to be combined into the record */
+  Mem *pLast;            /* Last field of the record */
+  int nField;            /* Number of fields in the record */
+  char *zAffinity;       /* The affinity string for the record */
+  u32 len;               /* Length of a field */
+  u8 *zHdr;              /* Where to write next byte of the header */
+  u8 *zPayload;          /* Where to write next byte of the payload */
+
+  /* Assuming the record contains N fields, the record format looks
+  ** like this:
+  **
+  ** ------------------------------------------------------------------------
+  ** | hdr-size | type 0 | type 1 | ... | type N-1 | data0 | ... | data N-1 |
+  ** ------------------------------------------------------------------------
+  **
+  ** Data(0) is taken from register P1.  Data(1) comes from register P1+1
+  ** and so forth.
+  **
+  ** Each type field is a varint representing the serial type of the
+  ** corresponding data element (see sqlite3VdbeSerialType()). The
+  ** hdr-size field is also a varint which is the offset from the beginning
+  ** of the record to data0.
+  */
+  nData = 0;         /* Number of bytes of data space */
+  nHdr = 0;          /* Number of bytes of header space */
+  nZero = 0;         /* Number of zero bytes at the end of the record */
+  nField = pOp->p1;
+  zAffinity = pOp->p4.z;
+  assert( nField>0 && pOp->p2>0 && pOp->p2+nField<=(p->nMem+1 - p->nCursor)+1 );
+  pData0 = &aMem[nField];
+  nField = pOp->p2;
+  pLast = &pData0[nField-1];
+
+  /* Identify the output register */
+  assert( pOp->p3<pOp->p1 || pOp->p3>=pOp->p1+pOp->p2 );
+  pOut = &aMem[pOp->p3];
+  memAboutToChange(p, pOut);
+
+  /* Apply the requested affinity to all inputs
+  */
+  assert( pData0<=pLast );
+  if( zAffinity ){
+    pRec = pData0;
+    do{
+      applyAffinity(pRec, zAffinity[0], encoding);
+      if( zAffinity[0]==SQLITE_AFF_REAL && (pRec->flags & MEM_Int) ){
+        pRec->flags |= MEM_IntReal;
+        pRec->flags &= ~(MEM_Int);
+      }
+      REGISTER_TRACE((int)(pRec-aMem), pRec);
+      zAffinity++;
+      pRec++;
+      assert( zAffinity[0]==0 || pRec<=pLast );
+    }while( zAffinity[0] );
+  }
+
+#ifdef SQLITE_ENABLE_NULL_TRIM
+  /* NULLs can be safely trimmed from the end of the record, as long as
+  ** as the schema format is 2 or more and none of the omitted columns
+  ** have a non-NULL default value.  Also, the record must be left with
+  ** at least one field.  If P5>0 then it will be one more than the
+  ** index of the right-most column with a non-NULL default value */
+  if( pOp->p5 ){
+    while( (pLast->flags & MEM_Null)!=0 && nField>pOp->p5 ){
+      pLast--;
+      nField--;
+    }
+  }
+#endif
+
+  /* Loop through the elements that will make up the record to figure
+  ** out how much space is required for the new record.  After this loop,
+  ** the Mem.uTemp field of each term should hold the serial-type that will
+  ** be used for that term in the generated record:
+  **
+  **   Mem.uTemp value    type
+  **   ---------------    ---------------
+  **      0               NULL
+  **      1               1-byte signed integer
+  **      2               2-byte signed integer
+  **      3               3-byte signed integer
+  **      4               4-byte signed integer
+  **      5               6-byte signed integer
+  **      6               8-byte signed integer
+  **      7               IEEE float
+  **      8               Integer constant 0
+  **      9               Integer constant 1
+  **     10,11            reserved for expansion
+  **    N>=12 and even    BLOB
+  **    N>=13 and odd     text
+  **
+  ** The following additional values are computed:
+  **     nHdr        Number of bytes needed for the record header
+  **     nData       Number of bytes of data space needed for the record
+  **     nZero       Zero bytes at the end of the record
+  */
+  pRec = pLast;
+  do{
+    assert( memIsValid(pRec) );
+    if( pRec->flags & MEM_Null ){
+      if( pRec->flags & MEM_Zero ){
+        /* Values with MEM_Null and MEM_Zero are created by xColumn virtual
+        ** table methods that never invoke sqlite3_result_xxxxx() while
+        ** computing an unchanging column value in an UPDATE statement.
+        ** Give such values a special internal-use-only serial-type of 10
+        ** so that they can be passed through to xUpdate and have
+        ** a true sqlite3_value_nochange(). */
+#ifndef SQLITE_ENABLE_NULL_TRIM
+        assert( pOp->p5==OPFLAG_NOCHNG_MAGIC || CORRUPT_DB );
+#endif
+        pRec->uTemp = 10;
+      }else{
+        pRec->uTemp = 0;
+      }
+      nHdr++;
+    }else if( pRec->flags & (MEM_Int|MEM_IntReal) ){
+      /* Figure out whether to use 1, 2, 4, 6 or 8 bytes. */
+      i64 i = pRec->u.i;
+      u64 uu;
+      testcase( pRec->flags & MEM_Int );
+      testcase( pRec->flags & MEM_IntReal );
+      if( i<0 ){
+        uu = ~i;
+      }else{
+        uu = i;
+      }
+      nHdr++;
+      testcase( uu==127 );               testcase( uu==128 );
+      testcase( uu==32767 );             testcase( uu==32768 );
+      testcase( uu==8388607 );           testcase( uu==8388608 );
+      testcase( uu==2147483647 );        testcase( uu==2147483648LL );
+      testcase( uu==140737488355327LL ); testcase( uu==140737488355328LL );
+      if( uu<=127 ){
+        if( (i&1)==i && p->minWriteFileFormat>=4 ){
+          pRec->uTemp = 8+(u32)uu;
+        }else{
+          nData++;
+          pRec->uTemp = 1;
+        }
+      }else if( uu<=32767 ){
+        nData += 2;
+        pRec->uTemp = 2;
+      }else if( uu<=8388607 ){
+        nData += 3;
+        pRec->uTemp = 3;
+      }else if( uu<=2147483647 ){
+        nData += 4;
+        pRec->uTemp = 4;
+      }else if( uu<=140737488355327LL ){
+        nData += 6;
+        pRec->uTemp = 5;
+      }else{
+        nData += 8;
+        if( pRec->flags & MEM_IntReal ){
+          /* If the value is IntReal and is going to take up 8 bytes to store
+          ** as an integer, then we might as well make it an 8-byte floating
+          ** point value */
+          pRec->u.r = (double)pRec->u.i;
+          pRec->flags &= ~MEM_IntReal;
+          pRec->flags |= MEM_Real;
+          pRec->uTemp = 7;
+        }else{
+          pRec->uTemp = 6;
+        }
+      }
+    }else if( pRec->flags & MEM_Real ){
+      nHdr++;
+      nData += 8;
+      pRec->uTemp = 7;
+    }else{
+      assert( db->mallocFailed || pRec->flags&(MEM_Str|MEM_Blob) );
+      assert( pRec->n>=0 );
+      len = (u32)pRec->n;
+      serial_type = (len*2) + 12 + ((pRec->flags & MEM_Str)!=0);
+      if( pRec->flags & MEM_Zero ){
+        serial_type += pRec->u.nZero*2;
+        if( nData ){
+          if( sqlite3VdbeMemExpandBlob(pRec) ) goto no_mem;
+          len += pRec->u.nZero;
+        }else{
+          nZero += pRec->u.nZero;
+        }
+      }
+      nData += len;
+      nHdr += sqlite3VarintLen(serial_type);
+      pRec->uTemp = serial_type;
+    }
+    if( pRec==pData0 ) break;
+    pRec--;
+  }while(1);
+
+  /* EVIDENCE-OF: R-22564-11647 The header begins with a single varint
+  ** which determines the total number of bytes in the header. The varint
+  ** value is the size of the header in bytes including the size varint
+  ** itself. */
+  testcase( nHdr==126 );
+  testcase( nHdr==127 );
+  if( nHdr<=126 ){
+    /* The common case */
+    nHdr += 1;
+  }else{
+    /* Rare case of a really large header */
+    nVarint = sqlite3VarintLen(nHdr);
+    nHdr += nVarint;
+    if( nVarint<sqlite3VarintLen(nHdr) ) nHdr++;
+  }
+  nByte = nHdr+nData;
+
+  /* Make sure the output register has a buffer large enough to store
+  ** the new record. The output register (pOp->p3) is not allowed to
+  ** be one of the input registers (because the following call to
+  ** sqlite3VdbeMemClearAndResize() could clobber the value before it is used).
+  */
+  if( nByte+nZero<=pOut->szMalloc ){
+    /* The output register is already large enough to hold the record.
+    ** No error checks or buffer enlargement is required */
+    pOut->z = pOut->zMalloc;
+  }else{
+    /* Need to make sure that the output is not too big and then enlarge
+    ** the output register to hold the full result */
+    if( nByte+nZero>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+      goto too_big;
+    }
+    if( sqlite3VdbeMemClearAndResize(pOut, (int)nByte) ){
+      goto no_mem;
+    }
+  }
+  pOut->n = (int)nByte;
+  pOut->flags = MEM_Blob;
+  if( nZero ){
+    pOut->u.nZero = nZero;
+    pOut->flags |= MEM_Zero;
+  }
+  UPDATE_MAX_BLOBSIZE(pOut);
+  zHdr = (u8 *)pOut->z;
+  zPayload = zHdr + nHdr;
+
+  /* Write the record */
+  if( nHdr<0x80 ){
+    *(zHdr++) = nHdr;
+  }else{
+    zHdr += sqlite3PutVarint(zHdr,nHdr);
+  }
+  assert( pData0<=pLast );
+  pRec = pData0;
+  while( 1 /*exit-by-break*/ ){
+    serial_type = pRec->uTemp;
+    /* EVIDENCE-OF: R-06529-47362 Following the size varint are one or more
+    ** additional varints, one per column.
+    ** EVIDENCE-OF: R-64536-51728 The values for each column in the record
+    ** immediately follow the header. */
+    if( serial_type<=7 ){
+      *(zHdr++) = serial_type;
+      if( serial_type==0 ){
+        /* NULL value.  No change in zPayload */
+      }else{
+        u64 v;
+        if( serial_type==7 ){
+          assert( sizeof(v)==sizeof(pRec->u.r) );
+          memcpy(&v, &pRec->u.r, sizeof(v));
+          swapMixedEndianFloat(v);
+        }else{
+          v = pRec->u.i;
+        }
+        len = sqlite3SmallTypeSizes[serial_type];
+        assert( len>=1 && len<=8 && len!=5 && len!=7 );
+        switch( len ){
+          default: zPayload[7] = (u8)(v&0xff); v >>= 8;
+                   zPayload[6] = (u8)(v&0xff); v >>= 8;
+          case 6:  zPayload[5] = (u8)(v&0xff); v >>= 8;
+                   zPayload[4] = (u8)(v&0xff); v >>= 8;
+          case 4:  zPayload[3] = (u8)(v&0xff); v >>= 8;
+          case 3:  zPayload[2] = (u8)(v&0xff); v >>= 8;
+          case 2:  zPayload[1] = (u8)(v&0xff); v >>= 8;
+          case 1:  zPayload[0] = (u8)(v&0xff);
+        }
+        zPayload += len;
+      }
+    }else if( serial_type<0x80 ){
+      *(zHdr++) = serial_type;
+      if( serial_type>=14 && pRec->n>0 ){
+        assert( pRec->z!=0 );
+        memcpy(zPayload, pRec->z, pRec->n);
+        zPayload += pRec->n;
+      }
+    }else{
+      zHdr += sqlite3PutVarint(zHdr, serial_type);
+      if( pRec->n ){
+        assert( pRec->z!=0 );
+        memcpy(zPayload, pRec->z, pRec->n);
+        zPayload += pRec->n;
+      }
+    }
+    if( pRec==pLast ) break;
+    pRec++;
+  }
+  assert( nHdr==(int)(zHdr - (u8*)pOut->z) );
+  assert( nByte==(int)(zPayload - (u8*)pOut->z) );
+
+  assert( pOp->p3>0 && pOp->p3<=(p->nMem+1 - p->nCursor) );
+  REGISTER_TRACE(pOp->p3, pOut);
+  break;
+}
+
+/* Opcode: Count P1 P2 P3 * *
+** Synopsis: r[P2]=count()
+**
+** Store the number of entries (an integer value) in the table or index
+** opened by cursor P1 in register P2.
+**
+** If P3==0, then an exact count is obtained, which involves visiting
+** every btree page of the table.  But if P3 is non-zero, an estimate
+** is returned based on the current cursor position. 
+*/
+case OP_Count: {         /* out2 */
+  i64 nEntry;
+  BtCursor *pCrsr;
+
+  assert( p->apCsr[pOp->p1]->eCurType==CURTYPE_BTREE );
+  pCrsr = p->apCsr[pOp->p1]->uc.pCursor;
+  assert( pCrsr );
+  if( pOp->p3 ){
+    nEntry = sqlite3BtreeRowCountEst(pCrsr);
+  }else{
+    nEntry = 0;  /* Not needed.  Only used to silence a warning. */
+    rc = sqlite3BtreeCount(db, pCrsr, &nEntry);
+    if( rc ) goto abort_due_to_error;
+  }
+  pOut = out2Prerelease(p, pOp);
+  pOut->u.i = nEntry;
+  goto check_for_interrupt;
+}
+
+/* Opcode: Savepoint P1 * * P4 *
+**
+** Open, release or rollback the savepoint named by parameter P4, depending
+** on the value of P1. To open a new savepoint set P1==0 (SAVEPOINT_BEGIN).
+** To release (commit) an existing savepoint set P1==1 (SAVEPOINT_RELEASE).
+** To rollback an existing savepoint set P1==2 (SAVEPOINT_ROLLBACK).
+*/
+case OP_Savepoint: {
+  int p1;                         /* Value of P1 operand */
+  char *zName;                    /* Name of savepoint */
+  int nName;
+  Savepoint *pNew;
+  Savepoint *pSavepoint;
+  Savepoint *pTmp;
+  int iSavepoint;
+  int ii;
+
+  p1 = pOp->p1;
+  zName = pOp->p4.z;
+
+  /* Assert that the p1 parameter is valid. Also that if there is no open
+  ** transaction, then there cannot be any savepoints.
+  */
+  assert( db->pSavepoint==0 || db->autoCommit==0 );
+  assert( p1==SAVEPOINT_BEGIN||p1==SAVEPOINT_RELEASE||p1==SAVEPOINT_ROLLBACK );
+  assert( db->pSavepoint || db->isTransactionSavepoint==0 );
+  assert( checkSavepointCount(db) );
+  assert( p->bIsReader );
+
+  if( p1==SAVEPOINT_BEGIN ){
+    if( db->nVdbeWrite>0 ){
+      /* A new savepoint cannot be created if there are active write
+      ** statements (i.e. open read/write incremental blob handles).
+      */
+      sqlite3VdbeError(p, "cannot open savepoint - SQL statements in progress");
+      rc = SQLITE_BUSY;
+    }else{
+      nName = sqlite3Strlen30(zName);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+      /* This call is Ok even if this savepoint is actually a transaction
+      ** savepoint (and therefore should not prompt xSavepoint()) callbacks.
+      ** If this is a transaction savepoint being opened, it is guaranteed
+      ** that the db->aVTrans[] array is empty.  */
+      assert( db->autoCommit==0 || db->nVTrans==0 );
+      rc = sqlite3VtabSavepoint(db, SAVEPOINT_BEGIN,
+                                db->nStatement+db->nSavepoint);
+      if( rc!=SQLITE_OK ) goto abort_due_to_error;
+#endif
+
+      /* Create a new savepoint structure. */
+      pNew = sqlite3DbMallocRawNN(db, sizeof(Savepoint)+nName+1);
+      if( pNew ){
+        pNew->zName = (char *)&pNew[1];
+        memcpy(pNew->zName, zName, nName+1);
+   
+        /* If there is no open transaction, then mark this as a special
+        ** "transaction savepoint". */
+        if( db->autoCommit ){
+          db->autoCommit = 0;
+          db->isTransactionSavepoint = 1;
+        }else{
+          db->nSavepoint++;
+        }
+
+        /* Link the new savepoint into the database handle's list. */
+        pNew->pNext = db->pSavepoint;
+        db->pSavepoint = pNew;
+        pNew->nDeferredCons = db->nDeferredCons;
+        pNew->nDeferredImmCons = db->nDeferredImmCons;
+      }
+    }
+  }else{
+    assert( p1==SAVEPOINT_RELEASE || p1==SAVEPOINT_ROLLBACK );
+    iSavepoint = 0;
+
+    /* Find the named savepoint. If there is no such savepoint, then an
+    ** an error is returned to the user.  */
+    for(
+      pSavepoint = db->pSavepoint;
+      pSavepoint && sqlite3StrICmp(pSavepoint->zName, zName);
+      pSavepoint = pSavepoint->pNext
+    ){
+      iSavepoint++;
+    }
+    if( !pSavepoint ){
+      sqlite3VdbeError(p, "no such savepoint: %s", zName);
+      rc = SQLITE_ERROR;
+    }else if( db->nVdbeWrite>0 && p1==SAVEPOINT_RELEASE ){
+      /* It is not possible to release (commit) a savepoint if there are
+      ** active write statements.
+      */
+      sqlite3VdbeError(p, "cannot release savepoint - "
+                          "SQL statements in progress");
+      rc = SQLITE_BUSY;
+    }else{
+
+      /* Determine whether or not this is a transaction savepoint. If so,
+      ** and this is a RELEASE command, then the current transaction
+      ** is committed.
+      */
+      int isTransaction = pSavepoint->pNext==0 && db->isTransactionSavepoint;
+      if( isTransaction && p1==SAVEPOINT_RELEASE ){
+        if( (rc = sqlite3VdbeCheckFk(p, 1))!=SQLITE_OK ){
+          goto vdbe_return;
+        }
+        db->autoCommit = 1;
+        if( sqlite3VdbeHalt(p)==SQLITE_BUSY ){
+          p->pc = (int)(pOp - aOp);
+          db->autoCommit = 0;
+          p->rc = rc = SQLITE_BUSY;
+          goto vdbe_return;
+        }
+        rc = p->rc;
+        if( rc ){
+          db->autoCommit = 0;
+        }else{
+          db->isTransactionSavepoint = 0;
+        }
+      }else{
+        int isSchemaChange;
+        iSavepoint = db->nSavepoint - iSavepoint - 1;
+        if( p1==SAVEPOINT_ROLLBACK ){
+          isSchemaChange = (db->mDbFlags & DBFLAG_SchemaChange)!=0;
+          for(ii=0; ii<db->nDb; ii++){
+            rc = sqlite3BtreeTripAllCursors(db->aDb[ii].pBt,
+                                       SQLITE_ABORT_ROLLBACK,
+                                       isSchemaChange==0);
+            if( rc!=SQLITE_OK ) goto abort_due_to_error;
+          }
+        }else{
+          assert( p1==SAVEPOINT_RELEASE );
+          isSchemaChange = 0;
+        }
+        for(ii=0; ii<db->nDb; ii++){
+          rc = sqlite3BtreeSavepoint(db->aDb[ii].pBt, p1, iSavepoint);
+          if( rc!=SQLITE_OK ){
+            goto abort_due_to_error;
+          }
+        }
+        if( isSchemaChange ){
+          sqlite3ExpirePreparedStatements(db, 0);
+          sqlite3ResetAllSchemasOfConnection(db);
+          db->mDbFlags |= DBFLAG_SchemaChange;
+        }
+      }
+      if( rc ) goto abort_due_to_error;
+ 
+      /* Regardless of whether this is a RELEASE or ROLLBACK, destroy all
+      ** savepoints nested inside of the savepoint being operated on. */
+      while( db->pSavepoint!=pSavepoint ){
+        pTmp = db->pSavepoint;
+        db->pSavepoint = pTmp->pNext;
+        sqlite3DbFree(db, pTmp);
+        db->nSavepoint--;
+      }
+
+      /* If it is a RELEASE, then destroy the savepoint being operated on
+      ** too. If it is a ROLLBACK TO, then set the number of deferred
+      ** constraint violations present in the database to the value stored
+      ** when the savepoint was created.  */
+      if( p1==SAVEPOINT_RELEASE ){
+        assert( pSavepoint==db->pSavepoint );
+        db->pSavepoint = pSavepoint->pNext;
+        sqlite3DbFree(db, pSavepoint);
+        if( !isTransaction ){
+          db->nSavepoint--;
+        }
+      }else{
+        assert( p1==SAVEPOINT_ROLLBACK );
+        db->nDeferredCons = pSavepoint->nDeferredCons;
+        db->nDeferredImmCons = pSavepoint->nDeferredImmCons;
+      }
+
+      if( !isTransaction || p1==SAVEPOINT_ROLLBACK ){
+        rc = sqlite3VtabSavepoint(db, p1, iSavepoint);
+        if( rc!=SQLITE_OK ) goto abort_due_to_error;
+      }
+    }
+  }
+  if( rc ) goto abort_due_to_error;
+  if( p->eVdbeState==VDBE_HALT_STATE ){
+    rc = SQLITE_DONE;
+    goto vdbe_return;
+  }
+  break;
+}
+
+/* Opcode: AutoCommit P1 P2 * * *
+**
+** Set the database auto-commit flag to P1 (1 or 0). If P2 is true, roll
+** back any currently active btree transactions. If there are any active
+** VMs (apart from this one), then a ROLLBACK fails.  A COMMIT fails if
+** there are active writing VMs or active VMs that use shared cache.
+**
+** This instruction causes the VM to halt.
+*/
+case OP_AutoCommit: {
+  int desiredAutoCommit;
+  int iRollback;
+
+  desiredAutoCommit = pOp->p1;
+  iRollback = pOp->p2;
+  assert( desiredAutoCommit==1 || desiredAutoCommit==0 );
+  assert( desiredAutoCommit==1 || iRollback==0 );
+  assert( db->nVdbeActive>0 );  /* At least this one VM is active */
+  assert( p->bIsReader );
+
+  if( desiredAutoCommit!=db->autoCommit ){
+    if( iRollback ){
+      assert( desiredAutoCommit==1 );
+      sqlite3RollbackAll(db, SQLITE_ABORT_ROLLBACK);
+      db->autoCommit = 1;
+    }else if( desiredAutoCommit && db->nVdbeWrite>0 ){
+      /* If this instruction implements a COMMIT and other VMs are writing
+      ** return an error indicating that the other VMs must complete first.
+      */
+      sqlite3VdbeError(p, "cannot commit transaction - "
+                          "SQL statements in progress");
+      rc = SQLITE_BUSY;
+      goto abort_due_to_error;
+    }else if( (rc = sqlite3VdbeCheckFk(p, 1))!=SQLITE_OK ){
+      goto vdbe_return;
+    }else{
+      db->autoCommit = (u8)desiredAutoCommit;
+    }
+    if( sqlite3VdbeHalt(p)==SQLITE_BUSY ){
+      p->pc = (int)(pOp - aOp);
+      db->autoCommit = (u8)(1-desiredAutoCommit);
+      p->rc = rc = SQLITE_BUSY;
+      goto vdbe_return;
+    }
+    sqlite3CloseSavepoints(db);
+    if( p->rc==SQLITE_OK ){
+      rc = SQLITE_DONE;
+    }else{
+      rc = SQLITE_ERROR;
+    }
+    goto vdbe_return;
+  }else{
+    sqlite3VdbeError(p,
+        (!desiredAutoCommit)?"cannot start a transaction within a transaction":(
+        (iRollback)?"cannot rollback - no transaction is active":
+                   "cannot commit - no transaction is active"));
+        
+    rc = SQLITE_ERROR;
+    goto abort_due_to_error;
+  }
+  /*NOTREACHED*/ assert(0);
+}
+
+/* Opcode: Transaction P1 P2 P3 P4 P5
+**
+** Begin a transaction on database P1 if a transaction is not already
+** active.
+** If P2 is non-zero, then a write-transaction is started, or if a
+** read-transaction is already active, it is upgraded to a write-transaction.
+** If P2 is zero, then a read-transaction is started.  If P2 is 2 or more
+** then an exclusive transaction is started.
+**
+** P1 is the index of the database file on which the transaction is
+** started.  Index 0 is the main database file and index 1 is the
+** file used for temporary tables.  Indices of 2 or more are used for
+** attached databases.
+**
+** If a write-transaction is started and the Vdbe.usesStmtJournal flag is
+** true (this flag is set if the Vdbe may modify more than one row and may
+** throw an ABORT exception), a statement transaction may also be opened.
+** More specifically, a statement transaction is opened iff the database
+** connection is currently not in autocommit mode, or if there are other
+** active statements. A statement transaction allows the changes made by this
+** VDBE to be rolled back after an error without having to roll back the
+** entire transaction. If no error is encountered, the statement transaction
+** will automatically commit when the VDBE halts.
+**
+** If P5!=0 then this opcode also checks the schema cookie against P3
+** and the schema generation counter against P4.
+** The cookie changes its value whenever the database schema changes.
+** This operation is used to detect when that the cookie has changed
+** and that the current process needs to reread the schema.  If the schema
+** cookie in P3 differs from the schema cookie in the database header or
+** if the schema generation counter in P4 differs from the current
+** generation counter, then an SQLITE_SCHEMA error is raised and execution
+** halts.  The sqlite3_step() wrapper function might then reprepare the
+** statement and rerun it from the beginning.
+*/
+case OP_Transaction: {
+  Btree *pBt;
+  Db *pDb;
+  int iMeta = 0;
+
+  assert( p->bIsReader );
+  assert( p->readOnly==0 || pOp->p2==0 );
+  assert( pOp->p2>=0 && pOp->p2<=2 );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( DbMaskTest(p->btreeMask, pOp->p1) );
+  assert( rc==SQLITE_OK );
+  if( pOp->p2 && (db->flags & (SQLITE_QueryOnly|SQLITE_CorruptRdOnly))!=0 ){
+    if( db->flags & SQLITE_QueryOnly ){
+      /* Writes prohibited by the "PRAGMA query_only=TRUE" statement */
+      rc = SQLITE_READONLY;
+    }else{
+      /* Writes prohibited due to a prior SQLITE_CORRUPT in the current
+      ** transaction */
+      rc = SQLITE_CORRUPT;
+    }
+    goto abort_due_to_error;
+  }
+  pDb = &db->aDb[pOp->p1];
+  pBt = pDb->pBt;
+
+  if( pBt ){
+    rc = sqlite3BtreeBeginTrans(pBt, pOp->p2, &iMeta);
+    testcase( rc==SQLITE_BUSY_SNAPSHOT );
+    testcase( rc==SQLITE_BUSY_RECOVERY );
+    if( rc!=SQLITE_OK ){
+      if( (rc&0xff)==SQLITE_BUSY ){
+        p->pc = (int)(pOp - aOp);
+        p->rc = rc;
+        goto vdbe_return;
+      }
+      goto abort_due_to_error;
+    }
+
+    if( p->usesStmtJournal
+     && pOp->p2
+     && (db->autoCommit==0 || db->nVdbeRead>1)
+    ){
+      assert( sqlite3BtreeTxnState(pBt)==SQLITE_TXN_WRITE );
+      if( p->iStatement==0 ){
+        assert( db->nStatement>=0 && db->nSavepoint>=0 );
+        db->nStatement++;
+        p->iStatement = db->nSavepoint + db->nStatement;
+      }
+
+      rc = sqlite3VtabSavepoint(db, SAVEPOINT_BEGIN, p->iStatement-1);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3BtreeBeginStmt(pBt, p->iStatement);
+      }
+
+      /* Store the current value of the database handles deferred constraint
+      ** counter. If the statement transaction needs to be rolled back,
+      ** the value of this counter needs to be restored too.  */
+      p->nStmtDefCons = db->nDeferredCons;
+      p->nStmtDefImmCons = db->nDeferredImmCons;
+    }
+  }
+  assert( pOp->p5==0 || pOp->p4type==P4_INT32 );
+  if( rc==SQLITE_OK
+   && pOp->p5
+   && (iMeta!=pOp->p3 || pDb->pSchema->iGeneration!=pOp->p4.i)
+  ){
+    /*
+    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
+    ** version is checked to ensure that the schema has not changed since the
+    ** SQL statement was prepared.
+    */
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
+    /* If the schema-cookie from the database file matches the cookie
+    ** stored with the in-memory representation of the schema, do
+    ** not reload the schema from the database file.
+    **
+    ** If virtual-tables are in use, this is not just an optimization.
+    ** Often, v-tables store their data in other SQLite tables, which
+    ** are queried from within xNext() and other v-table methods using
+    ** prepared queries. If such a query is out-of-date, we do not want to
+    ** discard the database schema, as the user code implementing the
+    ** v-table would have to be ready for the sqlite3_vtab structure itself
+    ** to be invalidated whenever sqlite3_step() is called from within
+    ** a v-table method.
+    */
+    if( db->aDb[pOp->p1].pSchema->schema_cookie!=iMeta ){
+      sqlite3ResetOneSchema(db, pOp->p1);
+    }
+    p->expired = 1;
+    rc = SQLITE_SCHEMA;
+
+    /* Set changeCntOn to 0 to prevent the value returned by sqlite3_changes()
+    ** from being modified in sqlite3VdbeHalt(). If this statement is
+    ** reprepared, changeCntOn will be set again. */
+    p->changeCntOn = 0;
+  }
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: ReadCookie P1 P2 P3 * *
+**
+** Read cookie number P3 from database P1 and write it into register P2.
+** P3==1 is the schema version.  P3==2 is the database format.
+** P3==3 is the recommended pager cache size, and so forth.  P1==0 is
+** the main database file and P1==1 is the database file used to store
+** temporary tables.
+**
+** There must be a read-lock on the database (either a transaction
+** must be started or there must be an open cursor) before
+** executing this instruction.
+*/
+case OP_ReadCookie: {               /* out2 */
+  int iMeta;
+  int iDb;
+  int iCookie;
+
+  assert( p->bIsReader );
+  iDb = pOp->p1;
+  iCookie = pOp->p3;
+  assert( pOp->p3<SQLITE_N_BTREE_META );
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( db->aDb[iDb].pBt!=0 );
+  assert( DbMaskTest(p->btreeMask, iDb) );
+
+  sqlite3BtreeGetMeta(db->aDb[iDb].pBt, iCookie, (u32 *)&iMeta);
+  pOut = out2Prerelease(p, pOp);
+  pOut->u.i = iMeta;
+  break;
+}
+
+/* Opcode: SetCookie P1 P2 P3 * P5
+**
+** Write the integer value P3 into cookie number P2 of database P1.
+** P2==1 is the schema version.  P2==2 is the database format.
+** P2==3 is the recommended pager cache
+** size, and so forth.  P1==0 is the main database file and P1==1 is the
+** database file used to store temporary tables.
+**
+** A transaction must be started before executing this opcode.
+**
+** If P2 is the SCHEMA_VERSION cookie (cookie number 1) then the internal
+** schema version is set to P3-P5.  The "PRAGMA schema_version=N" statement
+** has P5 set to 1, so that the internal schema version will be different
+** from the database schema version, resulting in a schema reset.
+*/
+case OP_SetCookie: {
+  Db *pDb;
+
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  assert( pOp->p2<SQLITE_N_BTREE_META );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( DbMaskTest(p->btreeMask, pOp->p1) );
+  assert( p->readOnly==0 );
+  pDb = &db->aDb[pOp->p1];
+  assert( pDb->pBt!=0 );
+  assert( sqlite3SchemaMutexHeld(db, pOp->p1, 0) );
+  /* See note about index shifting on OP_ReadCookie */
+  rc = sqlite3BtreeUpdateMeta(pDb->pBt, pOp->p2, pOp->p3);
+  if( pOp->p2==BTREE_SCHEMA_VERSION ){
+    /* When the schema cookie changes, record the new cookie internally */
+    *(u32*)&pDb->pSchema->schema_cookie = *(u32*)&pOp->p3 - pOp->p5;
+    db->mDbFlags |= DBFLAG_SchemaChange;
+    sqlite3FkClearTriggerCache(db, pOp->p1);
+  }else if( pOp->p2==BTREE_FILE_FORMAT ){
+    /* Record changes in the file format */
+    pDb->pSchema->file_format = pOp->p3;
+  }
+  if( pOp->p1==1 ){
+    /* Invalidate all prepared statements whenever the TEMP database
+    ** schema is changed.  Ticket #1644 */
+    sqlite3ExpirePreparedStatements(db, 0);
+    p->expired = 0;
+  }
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: OpenRead P1 P2 P3 P4 P5
+** Synopsis: root=P2 iDb=P3
+**
+** Open a read-only cursor for the database table whose root page is
+** P2 in a database file.  The database file is determined by P3.
+** P3==0 means the main database, P3==1 means the database used for
+** temporary tables, and P3>1 means used the corresponding attached
+** database.  Give the new cursor an identifier of P1.  The P1
+** values need not be contiguous but all P1 values should be small integers.
+** It is an error for P1 to be negative.
+**
+** Allowed P5 bits:
+** <ul>
+** <li>  <b>0x02 OPFLAG_SEEKEQ</b>: This cursor will only be used for
+**       equality lookups (implemented as a pair of opcodes OP_SeekGE/OP_IdxGT
+**       of OP_SeekLE/OP_IdxLT)
+** </ul>
+**
+** The P4 value may be either an integer (P4_INT32) or a pointer to
+** a KeyInfo structure (P4_KEYINFO). If it is a pointer to a KeyInfo
+** object, then table being opened must be an [index b-tree] where the
+** KeyInfo object defines the content and collating
+** sequence of that index b-tree. Otherwise, if P4 is an integer
+** value, then the table being opened must be a [table b-tree] with a
+** number of columns no less than the value of P4.
+**
+** See also: OpenWrite, ReopenIdx
+*/
+/* Opcode: ReopenIdx P1 P2 P3 P4 P5
+** Synopsis: root=P2 iDb=P3
+**
+** The ReopenIdx opcode works like OP_OpenRead except that it first
+** checks to see if the cursor on P1 is already open on the same
+** b-tree and if it is this opcode becomes a no-op.  In other words,
+** if the cursor is already open, do not reopen it.
+**
+** The ReopenIdx opcode may only be used with P5==0 or P5==OPFLAG_SEEKEQ
+** and with P4 being a P4_KEYINFO object.  Furthermore, the P3 value must
+** be the same as every other ReopenIdx or OpenRead for the same cursor
+** number.
+**
+** Allowed P5 bits:
+** <ul>
+** <li>  <b>0x02 OPFLAG_SEEKEQ</b>: This cursor will only be used for
+**       equality lookups (implemented as a pair of opcodes OP_SeekGE/OP_IdxGT
+**       of OP_SeekLE/OP_IdxLT)
+** </ul>
+**
+** See also: OP_OpenRead, OP_OpenWrite
+*/
+/* Opcode: OpenWrite P1 P2 P3 P4 P5
+** Synopsis: root=P2 iDb=P3
+**
+** Open a read/write cursor named P1 on the table or index whose root
+** page is P2 (or whose root page is held in register P2 if the
+** OPFLAG_P2ISREG bit is set in P5 - see below).
+**
+** The P4 value may be either an integer (P4_INT32) or a pointer to
+** a KeyInfo structure (P4_KEYINFO). If it is a pointer to a KeyInfo
+** object, then table being opened must be an [index b-tree] where the
+** KeyInfo object defines the content and collating
+** sequence of that index b-tree. Otherwise, if P4 is an integer
+** value, then the table being opened must be a [table b-tree] with a
+** number of columns no less than the value of P4.
+**
+** Allowed P5 bits:
+** <ul>
+** <li>  <b>0x02 OPFLAG_SEEKEQ</b>: This cursor will only be used for
+**       equality lookups (implemented as a pair of opcodes OP_SeekGE/OP_IdxGT
+**       of OP_SeekLE/OP_IdxLT)
+** <li>  <b>0x08 OPFLAG_FORDELETE</b>: This cursor is used only to seek
+**       and subsequently delete entries in an index btree.  This is a
+**       hint to the storage engine that the storage engine is allowed to
+**       ignore.  The hint is not used by the official SQLite b*tree storage
+**       engine, but is used by COMDB2.
+** <li>  <b>0x10 OPFLAG_P2ISREG</b>: Use the content of register P2
+**       as the root page, not the value of P2 itself.
+** </ul>
+**
+** This instruction works like OpenRead except that it opens the cursor
+** in read/write mode.
+**
+** See also: OP_OpenRead, OP_ReopenIdx
+*/
+case OP_ReopenIdx: {         /* ncycle */
+  int nField;
+  KeyInfo *pKeyInfo;
+  u32 p2;
+  int iDb;
+  int wrFlag;
+  Btree *pX;
+  VdbeCursor *pCur;
+  Db *pDb;
+
+  assert( pOp->p5==0 || pOp->p5==OPFLAG_SEEKEQ );
+  assert( pOp->p4type==P4_KEYINFO );
+  pCur = p->apCsr[pOp->p1];
+  if( pCur && pCur->pgnoRoot==(u32)pOp->p2 ){
+    assert( pCur->iDb==pOp->p3 );      /* Guaranteed by the code generator */
+    assert( pCur->eCurType==CURTYPE_BTREE );
+    sqlite3BtreeClearCursor(pCur->uc.pCursor);
+    goto open_cursor_set_hints;
+  }
+  /* If the cursor is not currently open or is open on a different
+  ** index, then fall through into OP_OpenRead to force a reopen */
+case OP_OpenRead:            /* ncycle */
+case OP_OpenWrite:
+
+  assert( pOp->opcode==OP_OpenWrite || pOp->p5==0 || pOp->p5==OPFLAG_SEEKEQ );
+  assert( p->bIsReader );
+  assert( pOp->opcode==OP_OpenRead || pOp->opcode==OP_ReopenIdx
+          || p->readOnly==0 );
+
+  if( p->expired==1 ){
+    rc = SQLITE_ABORT_ROLLBACK;
+    goto abort_due_to_error;
+  }
+
+  nField = 0;
+  pKeyInfo = 0;
+  p2 = (u32)pOp->p2;
+  iDb = pOp->p3;
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( DbMaskTest(p->btreeMask, iDb) );
+  pDb = &db->aDb[iDb];
+  pX = pDb->pBt;
+  assert( pX!=0 );
+  if( pOp->opcode==OP_OpenWrite ){
+    assert( OPFLAG_FORDELETE==BTREE_FORDELETE );
+    wrFlag = BTREE_WRCSR | (pOp->p5 & OPFLAG_FORDELETE);
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( pDb->pSchema->file_format < p->minWriteFileFormat ){
+      p->minWriteFileFormat = pDb->pSchema->file_format;
+    }
+  }else{
+    wrFlag = 0;
+  }
+  if( pOp->p5 & OPFLAG_P2ISREG ){
+    assert( p2>0 );
+    assert( p2<=(u32)(p->nMem+1 - p->nCursor) );
+    assert( pOp->opcode==OP_OpenWrite );
+    pIn2 = &aMem[p2];
+    assert( memIsValid(pIn2) );
+    assert( (pIn2->flags & MEM_Int)!=0 );
+    sqlite3VdbeMemIntegerify(pIn2);
+    p2 = (int)pIn2->u.i;
+    /* The p2 value always comes from a prior OP_CreateBtree opcode and
+    ** that opcode will always set the p2 value to 2 or more or else fail.
+    ** If there were a failure, the prepared statement would have halted
+    ** before reaching this instruction. */
+    assert( p2>=2 );
+  }
+  if( pOp->p4type==P4_KEYINFO ){
+    pKeyInfo = pOp->p4.pKeyInfo;
+    assert( pKeyInfo->enc==ENC(db) );
+    assert( pKeyInfo->db==db );
+    nField = pKeyInfo->nAllField;
+  }else if( pOp->p4type==P4_INT32 ){
+    nField = pOp->p4.i;
+  }
+  assert( pOp->p1>=0 );
+  assert( nField>=0 );
+  testcase( nField==0 );  /* Table with INTEGER PRIMARY KEY and nothing else */
+  pCur = allocateCursor(p, pOp->p1, nField, CURTYPE_BTREE);
+  if( pCur==0 ) goto no_mem;
+  pCur->iDb = iDb;
+  pCur->nullRow = 1;
+  pCur->isOrdered = 1;
+  pCur->pgnoRoot = p2;
+#ifdef SQLITE_DEBUG
+  pCur->wrFlag = wrFlag;
+#endif
+  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->uc.pCursor);
+  pCur->pKeyInfo = pKeyInfo;
+  /* Set the VdbeCursor.isTable variable. Previous versions of
+  ** SQLite used to check if the root-page flags were sane at this point
+  ** and report database corruption if they were not, but this check has
+  ** since moved into the btree layer.  */ 
+  pCur->isTable = pOp->p4type!=P4_KEYINFO;
+
+open_cursor_set_hints:
+  assert( OPFLAG_BULKCSR==BTREE_BULKLOAD );
+  assert( OPFLAG_SEEKEQ==BTREE_SEEK_EQ );
+  testcase( pOp->p5 & OPFLAG_BULKCSR );
+  testcase( pOp->p2 & OPFLAG_SEEKEQ );
+  sqlite3BtreeCursorHintFlags(pCur->uc.pCursor,
+                               (pOp->p5 & (OPFLAG_BULKCSR|OPFLAG_SEEKEQ)));
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: OpenDup P1 P2 * * *
+**
+** Open a new cursor P1 that points to the same ephemeral table as
+** cursor P2.  The P2 cursor must have been opened by a prior OP_OpenEphemeral
+** opcode.  Only ephemeral cursors may be duplicated.
+**
+** Duplicate ephemeral cursors are used for self-joins of materialized views.
+*/
+case OP_OpenDup: {           /* ncycle */
+  VdbeCursor *pOrig;    /* The original cursor to be duplicated */
+  VdbeCursor *pCx;      /* The new cursor */
+
+  pOrig = p->apCsr[pOp->p2];
+  assert( pOrig );
+  assert( pOrig->isEphemeral );  /* Only ephemeral cursors can be duplicated */
+
+  pCx = allocateCursor(p, pOp->p1, pOrig->nField, CURTYPE_BTREE);
+  if( pCx==0 ) goto no_mem;
+  pCx->nullRow = 1;
+  pCx->isEphemeral = 1;
+  pCx->pKeyInfo = pOrig->pKeyInfo;
+  pCx->isTable = pOrig->isTable;
+  pCx->pgnoRoot = pOrig->pgnoRoot;
+  pCx->isOrdered = pOrig->isOrdered;
+  pCx->ub.pBtx = pOrig->ub.pBtx;
+  pCx->noReuse = 1;
+  pOrig->noReuse = 1;
+  rc = sqlite3BtreeCursor(pCx->ub.pBtx, pCx->pgnoRoot, BTREE_WRCSR,
+                          pCx->pKeyInfo, pCx->uc.pCursor);
+  /* The sqlite3BtreeCursor() routine can only fail for the first cursor
+  ** opened for a database.  Since there is already an open cursor when this
+  ** opcode is run, the sqlite3BtreeCursor() cannot fail */
+  assert( rc==SQLITE_OK );
+  break;
+}
+
+
+/* Opcode: OpenEphemeral P1 P2 P3 P4 P5
+** Synopsis: nColumn=P2
+**
+** Open a new cursor P1 to a transient table.
+** The cursor is always opened read/write even if
+** the main database is read-only.  The ephemeral
+** table is deleted automatically when the cursor is closed.
+**
+** If the cursor P1 is already opened on an ephemeral table, the table
+** is cleared (all content is erased).
+**
+** P2 is the number of columns in the ephemeral table.
+** The cursor points to a BTree table if P4==0 and to a BTree index
+** if P4 is not 0.  If P4 is not NULL, it points to a KeyInfo structure
+** that defines the format of keys in the index.
+**
+** The P5 parameter can be a mask of the BTREE_* flags defined
+** in btree.h.  These flags control aspects of the operation of
+** the btree.  The BTREE_OMIT_JOURNAL and BTREE_SINGLE flags are
+** added automatically.
+**
+** If P3 is positive, then reg[P3] is modified slightly so that it
+** can be used as zero-length data for OP_Insert.  This is an optimization
+** that avoids an extra OP_Blob opcode to initialize that register.
+*/
+/* Opcode: OpenAutoindex P1 P2 * P4 *
+** Synopsis: nColumn=P2
+**
+** This opcode works the same as OP_OpenEphemeral.  It has a
+** different name to distinguish its use.  Tables created using
+** by this opcode will be used for automatically created transient
+** indices in joins.
+*/
+case OP_OpenAutoindex:       /* ncycle */
+case OP_OpenEphemeral: {     /* ncycle */
+  VdbeCursor *pCx;
+  KeyInfo *pKeyInfo;
+
+  static const int vfsFlags =
+      SQLITE_OPEN_READWRITE |
+      SQLITE_OPEN_CREATE |
+      SQLITE_OPEN_EXCLUSIVE |
+      SQLITE_OPEN_DELETEONCLOSE |
+      SQLITE_OPEN_TRANSIENT_DB;
+  assert( pOp->p1>=0 );
+  assert( pOp->p2>=0 );
+  if( pOp->p3>0 ){
+    /* Make register reg[P3] into a value that can be used as the data
+    ** form sqlite3BtreeInsert() where the length of the data is zero. */
+    assert( pOp->p2==0 ); /* Only used when number of columns is zero */
+    assert( pOp->opcode==OP_OpenEphemeral );
+    assert( aMem[pOp->p3].flags & MEM_Null );
+    aMem[pOp->p3].n = 0;
+    aMem[pOp->p3].z = "";
+  }
+  pCx = p->apCsr[pOp->p1];
+  if( pCx && !pCx->noReuse &&  ALWAYS(pOp->p2<=pCx->nField) ){
+    /* If the ephemeral table is already open and has no duplicates from
+    ** OP_OpenDup, then erase all existing content so that the table is
+    ** empty again, rather than creating a new table. */
+    assert( pCx->isEphemeral );
+    pCx->seqCount = 0;
+    pCx->cacheStatus = CACHE_STALE;
+    rc = sqlite3BtreeClearTable(pCx->ub.pBtx, pCx->pgnoRoot, 0);
+  }else{
+    pCx = allocateCursor(p, pOp->p1, pOp->p2, CURTYPE_BTREE);
+    if( pCx==0 ) goto no_mem;
+    pCx->isEphemeral = 1;
+    rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->ub.pBtx,
+                          BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5,
+                          vfsFlags);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3BtreeBeginTrans(pCx->ub.pBtx, 1, 0);
+      if( rc==SQLITE_OK ){
+        /* If a transient index is required, create it by calling
+        ** sqlite3BtreeCreateTable() with the BTREE_BLOBKEY flag before
+        ** opening it. If a transient table is required, just use the
+        ** automatically created table with root-page 1 (an BLOB_INTKEY table).
+        */
+        if( (pCx->pKeyInfo = pKeyInfo = pOp->p4.pKeyInfo)!=0 ){
+          assert( pOp->p4type==P4_KEYINFO );
+          rc = sqlite3BtreeCreateTable(pCx->ub.pBtx, &pCx->pgnoRoot,
+              BTREE_BLOBKEY | pOp->p5);
+          if( rc==SQLITE_OK ){
+            assert( pCx->pgnoRoot==SCHEMA_ROOT+1 );
+            assert( pKeyInfo->db==db );
+            assert( pKeyInfo->enc==ENC(db) );
+            rc = sqlite3BtreeCursor(pCx->ub.pBtx, pCx->pgnoRoot, BTREE_WRCSR,
+                pKeyInfo, pCx->uc.pCursor);
+          }
+          pCx->isTable = 0;
+        }else{
+          pCx->pgnoRoot = SCHEMA_ROOT;
+          rc = sqlite3BtreeCursor(pCx->ub.pBtx, SCHEMA_ROOT, BTREE_WRCSR,
+              0, pCx->uc.pCursor);
+          pCx->isTable = 1;
+        }
+      }
+      pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
+      if( rc ){
+        sqlite3BtreeClose(pCx->ub.pBtx);
+      }
+    }
+  }
+  if( rc ) goto abort_due_to_error;
+  pCx->nullRow = 1;
+  break;
+}
+
+/* Opcode: SorterOpen P1 P2 P3 P4 *
+**
+** This opcode works like OP_OpenEphemeral except that it opens
+** a transient index that is specifically designed to sort large
+** tables using an external merge-sort algorithm.
+**
+** If argument P3 is non-zero, then it indicates that the sorter may
+** assume that a stable sort considering the first P3 fields of each
+** key is sufficient to produce the required results.
+*/
+case OP_SorterOpen: {
+  VdbeCursor *pCx;
+
+  assert( pOp->p1>=0 );
+  assert( pOp->p2>=0 );
+  pCx = allocateCursor(p, pOp->p1, pOp->p2, CURTYPE_SORTER);
+  if( pCx==0 ) goto no_mem;
+  pCx->pKeyInfo = pOp->p4.pKeyInfo;
+  assert( pCx->pKeyInfo->db==db );
+  assert( pCx->pKeyInfo->enc==ENC(db) );
+  rc = sqlite3VdbeSorterInit(db, pOp->p3, pCx);
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: SequenceTest P1 P2 * * *
+** Synopsis: if( cursor[P1].ctr++ ) pc = P2
+**
+** P1 is a sorter cursor. If the sequence counter is currently zero, jump
+** to P2. Regardless of whether or not the jump is taken, increment the
+** the sequence value.
+*/
+case OP_SequenceTest: {
+  VdbeCursor *pC;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( isSorter(pC) );
+  if( (pC->seqCount++)==0 ){
+    goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: OpenPseudo P1 P2 P3 * *
+** Synopsis: P3 columns in r[P2]
+**
+** Open a new cursor that points to a fake table that contains a single
+** row of data.  The content of that one row is the content of memory
+** register P2.  In other words, cursor P1 becomes an alias for the
+** MEM_Blob content contained in register P2.
+**
+** A pseudo-table created by this opcode is used to hold a single
+** row output from the sorter so that the row can be decomposed into
+** individual columns using the OP_Column opcode.  The OP_Column opcode
+** is the only cursor opcode that works with a pseudo-table.
+**
+** P3 is the number of fields in the records that will be stored by
+** the pseudo-table.
+*/
+case OP_OpenPseudo: {
+  VdbeCursor *pCx;
+
+  assert( pOp->p1>=0 );
+  assert( pOp->p3>=0 );
+  pCx = allocateCursor(p, pOp->p1, pOp->p3, CURTYPE_PSEUDO);
+  if( pCx==0 ) goto no_mem;
+  pCx->nullRow = 1;
+  pCx->seekResult = pOp->p2;
+  pCx->isTable = 1;
+  /* Give this pseudo-cursor a fake BtCursor pointer so that pCx
+  ** can be safely passed to sqlite3VdbeCursorMoveto().  This avoids a test
+  ** for pCx->eCurType==CURTYPE_BTREE inside of sqlite3VdbeCursorMoveto()
+  ** which is a performance optimization */
+  pCx->uc.pCursor = sqlite3BtreeFakeValidCursor();
+  assert( pOp->p5==0 );
+  break;
+}
+
+/* Opcode: Close P1 * * * *
+**
+** Close a cursor previously opened as P1.  If P1 is not
+** currently open, this instruction is a no-op.
+*/
+case OP_Close: {             /* ncycle */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  sqlite3VdbeFreeCursor(p, p->apCsr[pOp->p1]);
+  p->apCsr[pOp->p1] = 0;
+  break;
+}
+
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+/* Opcode: ColumnsUsed P1 * * P4 *
+**
+** This opcode (which only exists if SQLite was compiled with
+** SQLITE_ENABLE_COLUMN_USED_MASK) identifies which columns of the
+** table or index for cursor P1 are used.  P4 is a 64-bit integer
+** (P4_INT64) in which the first 63 bits are one for each of the
+** first 63 columns of the table or index that are actually used
+** by the cursor.  The high-order bit is set if any column after
+** the 64th is used.
+*/
+case OP_ColumnsUsed: {
+  VdbeCursor *pC;
+  pC = p->apCsr[pOp->p1];
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pC->maskUsed = *(u64*)pOp->p4.pI64;
+  break;
+}
+#endif
+
+/* Opcode: SeekGE P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys),
+** use the value in register P3 as the key.  If cursor P1 refers
+** to an SQL index, then P3 is the first in an array of P4 registers
+** that are used as an unpacked index key.
+**
+** Reposition cursor P1 so that  it points to the smallest entry that
+** is greater than or equal to the key value. If there are no records
+** greater than or equal to the key and P2 is not zero, then jump to P2.
+**
+** If the cursor P1 was opened using the OPFLAG_SEEKEQ flag, then this
+** opcode will either land on a record that exactly matches the key, or
+** else it will cause a jump to P2.  When the cursor is OPFLAG_SEEKEQ,
+** this opcode must be followed by an IdxLE opcode with the same arguments.
+** The IdxGT opcode will be skipped if this opcode succeeds, but the
+** IdxGT opcode will be used on subsequent loop iterations.  The
+** OPFLAG_SEEKEQ flags is a hint to the btree layer to say that this
+** is an equality search.
+**
+** This opcode leaves the cursor configured to move in forward order,
+** from the beginning toward the end.  In other words, the cursor is
+** configured to use Next, not Prev.
+**
+** See also: Found, NotFound, SeekLt, SeekGt, SeekLe
+*/
+/* Opcode: SeekGT P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys),
+** use the value in register P3 as a key. If cursor P1 refers
+** to an SQL index, then P3 is the first in an array of P4 registers
+** that are used as an unpacked index key.
+**
+** Reposition cursor P1 so that it points to the smallest entry that
+** is greater than the key value. If there are no records greater than
+** the key and P2 is not zero, then jump to P2.
+**
+** This opcode leaves the cursor configured to move in forward order,
+** from the beginning toward the end.  In other words, the cursor is
+** configured to use Next, not Prev.
+**
+** See also: Found, NotFound, SeekLt, SeekGe, SeekLe
+*/
+/* Opcode: SeekLT P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys),
+** use the value in register P3 as a key. If cursor P1 refers
+** to an SQL index, then P3 is the first in an array of P4 registers
+** that are used as an unpacked index key.
+**
+** Reposition cursor P1 so that  it points to the largest entry that
+** is less than the key value. If there are no records less than
+** the key and P2 is not zero, then jump to P2.
+**
+** This opcode leaves the cursor configured to move in reverse order,
+** from the end toward the beginning.  In other words, the cursor is
+** configured to use Prev, not Next.
+**
+** See also: Found, NotFound, SeekGt, SeekGe, SeekLe
+*/
+/* Opcode: SeekLE P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys),
+** use the value in register P3 as a key. If cursor P1 refers
+** to an SQL index, then P3 is the first in an array of P4 registers
+** that are used as an unpacked index key.
+**
+** Reposition cursor P1 so that it points to the largest entry that
+** is less than or equal to the key value. If there are no records
+** less than or equal to the key and P2 is not zero, then jump to P2.
+**
+** This opcode leaves the cursor configured to move in reverse order,
+** from the end toward the beginning.  In other words, the cursor is
+** configured to use Prev, not Next.
+**
+** If the cursor P1 was opened using the OPFLAG_SEEKEQ flag, then this
+** opcode will either land on a record that exactly matches the key, or
+** else it will cause a jump to P2.  When the cursor is OPFLAG_SEEKEQ,
+** this opcode must be followed by an IdxLE opcode with the same arguments.
+** The IdxGE opcode will be skipped if this opcode succeeds, but the
+** IdxGE opcode will be used on subsequent loop iterations.  The
+** OPFLAG_SEEKEQ flags is a hint to the btree layer to say that this
+** is an equality search.
+**
+** See also: Found, NotFound, SeekGt, SeekGe, SeekLt
+*/
+case OP_SeekLT:         /* jump, in3, group, ncycle */
+case OP_SeekLE:         /* jump, in3, group, ncycle */
+case OP_SeekGE:         /* jump, in3, group, ncycle */
+case OP_SeekGT: {       /* jump, in3, group, ncycle */
+  int res;           /* Comparison result */
+  int oc;            /* Opcode */
+  VdbeCursor *pC;    /* The cursor to seek */
+  UnpackedRecord r;  /* The key to seek for */
+  int nField;        /* Number of columns or fields in the key */
+  i64 iKey;          /* The rowid we are to seek to */
+  int eqOnly;        /* Only interested in == results */
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p2!=0 );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( OP_SeekLE == OP_SeekLT+1 );
+  assert( OP_SeekGE == OP_SeekLT+2 );
+  assert( OP_SeekGT == OP_SeekLT+3 );
+  assert( pC->isOrdered );
+  assert( pC->uc.pCursor!=0 );
+  oc = pOp->opcode;
+  eqOnly = 0;
+  pC->nullRow = 0;
+#ifdef SQLITE_DEBUG
+  pC->seekOp = pOp->opcode;
+#endif
+
+  pC->deferredMoveto = 0;
+  pC->cacheStatus = CACHE_STALE;
+  if( pC->isTable ){
+    u16 flags3, newType;
+    /* The OPFLAG_SEEKEQ/BTREE_SEEK_EQ flag is only set on index cursors */
+    assert( sqlite3BtreeCursorHasHint(pC->uc.pCursor, BTREE_SEEK_EQ)==0
+              || CORRUPT_DB );
+
+    /* The input value in P3 might be of any type: integer, real, string,
+    ** blob, or NULL.  But it needs to be an integer before we can do
+    ** the seek, so convert it. */
+    pIn3 = &aMem[pOp->p3];
+    flags3 = pIn3->flags;
+    if( (flags3 & (MEM_Int|MEM_Real|MEM_IntReal|MEM_Str))==MEM_Str ){
+      applyNumericAffinity(pIn3, 0);
+    }
+    iKey = sqlite3VdbeIntValue(pIn3); /* Get the integer key value */
+    newType = pIn3->flags; /* Record the type after applying numeric affinity */
+    pIn3->flags = flags3;  /* But convert the type back to its original */
+
+    /* If the P3 value could not be converted into an integer without
+    ** loss of information, then special processing is required... */
+    if( (newType & (MEM_Int|MEM_IntReal))==0 ){
+      int c;
+      if( (newType & MEM_Real)==0 ){
+        if( (newType & MEM_Null) || oc>=OP_SeekGE ){
+          VdbeBranchTaken(1,2);
+          goto jump_to_p2;
+        }else{
+          rc = sqlite3BtreeLast(pC->uc.pCursor, &res);
+          if( rc!=SQLITE_OK ) goto abort_due_to_error;
+          goto seek_not_found;
+        }
+      }
+      c = sqlite3IntFloatCompare(iKey, pIn3->u.r);
+
+      /* If the approximation iKey is larger than the actual real search
+      ** term, substitute >= for > and < for <=. e.g. if the search term
+      ** is 4.9 and the integer approximation 5:
+      **
+      **        (x >  4.9)    ->     (x >= 5)
+      **        (x <= 4.9)    ->     (x <  5)
+      */
+      if( c>0 ){
+        assert( OP_SeekGE==(OP_SeekGT-1) );
+        assert( OP_SeekLT==(OP_SeekLE-1) );
+        assert( (OP_SeekLE & 0x0001)==(OP_SeekGT & 0x0001) );
+        if( (oc & 0x0001)==(OP_SeekGT & 0x0001) ) oc--;
+      }
+
+      /* If the approximation iKey is smaller than the actual real search
+      ** term, substitute <= for < and > for >=.  */
+      else if( c<0 ){
+        assert( OP_SeekLE==(OP_SeekLT+1) );
+        assert( OP_SeekGT==(OP_SeekGE+1) );
+        assert( (OP_SeekLT & 0x0001)==(OP_SeekGE & 0x0001) );
+        if( (oc & 0x0001)==(OP_SeekLT & 0x0001) ) oc++;
+      }
+    }
+    rc = sqlite3BtreeTableMoveto(pC->uc.pCursor, (u64)iKey, 0, &res);
+    pC->movetoTarget = iKey;  /* Used by OP_Delete */
+    if( rc!=SQLITE_OK ){
+      goto abort_due_to_error;
+    }
+  }else{
+    /* For a cursor with the OPFLAG_SEEKEQ/BTREE_SEEK_EQ hint, only the
+    ** OP_SeekGE and OP_SeekLE opcodes are allowed, and these must be
+    ** immediately followed by an OP_IdxGT or OP_IdxLT opcode, respectively,
+    ** with the same key.
+    */
+    if( sqlite3BtreeCursorHasHint(pC->uc.pCursor, BTREE_SEEK_EQ) ){
+      eqOnly = 1;
+      assert( pOp->opcode==OP_SeekGE || pOp->opcode==OP_SeekLE );
+      assert( pOp[1].opcode==OP_IdxLT || pOp[1].opcode==OP_IdxGT );
+      assert( pOp->opcode==OP_SeekGE || pOp[1].opcode==OP_IdxLT );
+      assert( pOp->opcode==OP_SeekLE || pOp[1].opcode==OP_IdxGT );
+      assert( pOp[1].p1==pOp[0].p1 );
+      assert( pOp[1].p2==pOp[0].p2 );
+      assert( pOp[1].p3==pOp[0].p3 );
+      assert( pOp[1].p4.i==pOp[0].p4.i );
+    }
+
+    nField = pOp->p4.i;
+    assert( pOp->p4type==P4_INT32 );
+    assert( nField>0 );
+    r.pKeyInfo = pC->pKeyInfo;
+    r.nField = (u16)nField;
+
+    /* The next line of code computes as follows, only faster:
+    **   if( oc==OP_SeekGT || oc==OP_SeekLE ){
+    **     r.default_rc = -1;
+    **   }else{
+    **     r.default_rc = +1;
+    **   }
+    */
+    r.default_rc = ((1 & (oc - OP_SeekLT)) ? -1 : +1);
+    assert( oc!=OP_SeekGT || r.default_rc==-1 );
+    assert( oc!=OP_SeekLE || r.default_rc==-1 );
+    assert( oc!=OP_SeekGE || r.default_rc==+1 );
+    assert( oc!=OP_SeekLT || r.default_rc==+1 );
+
+    r.aMem = &aMem[pOp->p3];
+#ifdef SQLITE_DEBUG
+    {
+      int i;
+      for(i=0; i<r.nField; i++){
+        assert( memIsValid(&r.aMem[i]) );
+        if( i>0 ) REGISTER_TRACE(pOp->p3+i, &r.aMem[i]);
+      }
+    }
+#endif
+    r.eqSeen = 0;
+    rc = sqlite3BtreeIndexMoveto(pC->uc.pCursor, &r, &res);
+    if( rc!=SQLITE_OK ){
+      goto abort_due_to_error;
+    }
+    if( eqOnly && r.eqSeen==0 ){
+      assert( res!=0 );
+      goto seek_not_found;
+    }
+  }
+#ifdef SQLITE_TEST
+  sqlite3_search_count++;
+#endif
+  if( oc>=OP_SeekGE ){  assert( oc==OP_SeekGE || oc==OP_SeekGT );
+    if( res<0 || (res==0 && oc==OP_SeekGT) ){
+      res = 0;
+      rc = sqlite3BtreeNext(pC->uc.pCursor, 0);
+      if( rc!=SQLITE_OK ){
+        if( rc==SQLITE_DONE ){
+          rc = SQLITE_OK;
+          res = 1;
+        }else{
+          goto abort_due_to_error;
+        }
+      }
+    }else{
+      res = 0;
+    }
+  }else{
+    assert( oc==OP_SeekLT || oc==OP_SeekLE );
+    if( res>0 || (res==0 && oc==OP_SeekLT) ){
+      res = 0;
+      rc = sqlite3BtreePrevious(pC->uc.pCursor, 0);
+      if( rc!=SQLITE_OK ){
+        if( rc==SQLITE_DONE ){
+          rc = SQLITE_OK;
+          res = 1;
+        }else{
+          goto abort_due_to_error;
+        }
+      }
+    }else{
+      /* res might be negative because the table is empty.  Check to
+      ** see if this is the case.
+      */
+      res = sqlite3BtreeEof(pC->uc.pCursor);
+    }
+  }
+seek_not_found:
+  assert( pOp->p2>0 );
+  VdbeBranchTaken(res!=0,2);
+  if( res ){
+    goto jump_to_p2;
+  }else if( eqOnly ){
+    assert( pOp[1].opcode==OP_IdxLT || pOp[1].opcode==OP_IdxGT );
+    pOp++; /* Skip the OP_IdxLt or OP_IdxGT that follows */
+  }
+  break;
+}
+
+
+/* Opcode: SeekScan  P1 P2 * * P5
+** Synopsis: Scan-ahead up to P1 rows
+**
+** This opcode is a prefix opcode to OP_SeekGE.  In other words, this
+** opcode must be immediately followed by OP_SeekGE. This constraint is
+** checked by assert() statements.
+**
+** This opcode uses the P1 through P4 operands of the subsequent
+** OP_SeekGE.  In the text that follows, the operands of the subsequent
+** OP_SeekGE opcode are denoted as SeekOP.P1 through SeekOP.P4.   Only
+** the P1, P2 and P5 operands of this opcode are also used, and  are called
+** This.P1, This.P2 and This.P5.
+**
+** This opcode helps to optimize IN operators on a multi-column index
+** where the IN operator is on the later terms of the index by avoiding
+** unnecessary seeks on the btree, substituting steps to the next row
+** of the b-tree instead.  A correct answer is obtained if this opcode
+** is omitted or is a no-op.
+**
+** The SeekGE.P3 and SeekGE.P4 operands identify an unpacked key which
+** is the desired entry that we want the cursor SeekGE.P1 to be pointing
+** to.  Call this SeekGE.P3/P4 row the "target".
+**
+** If the SeekGE.P1 cursor is not currently pointing to a valid row,
+** then this opcode is a no-op and control passes through into the OP_SeekGE.
+**
+** If the SeekGE.P1 cursor is pointing to a valid row, then that row
+** might be the target row, or it might be near and slightly before the
+** target row, or it might be after the target row.  If the cursor is
+** currently before the target row, then this opcode attempts to position
+** the cursor on or after the target row by invoking sqlite3BtreeStep()
+** on the cursor between 1 and This.P1 times.
+**
+** The This.P5 parameter is a flag that indicates what to do if the
+** cursor ends up pointing at a valid row that is past the target
+** row.  If This.P5 is false (0) then a jump is made to SeekGE.P2.  If
+** This.P5 is true (non-zero) then a jump is made to This.P2.  The P5==0
+** case occurs when there are no inequality constraints to the right of
+** the IN constraint.  The jump to SeekGE.P2 ends the loop.  The P5!=0 case
+** occurs when there are inequality constraints to the right of the IN
+** operator.  In that case, the This.P2 will point either directly to or
+** to setup code prior to the OP_IdxGT or OP_IdxGE opcode that checks for
+** loop terminate.
+**
+** Possible outcomes from this opcode:<ol>
+**
+** <li> If the cursor is initially not pointed to any valid row, then
+**      fall through into the subsequent OP_SeekGE opcode.
+**
+** <li> If the cursor is left pointing to a row that is before the target
+**      row, even after making as many as This.P1 calls to
+**      sqlite3BtreeNext(), then also fall through into OP_SeekGE.
+**
+** <li> If the cursor is left pointing at the target row, either because it
+**      was at the target row to begin with or because one or more
+**      sqlite3BtreeNext() calls moved the cursor to the target row,
+**      then jump to This.P2..,
+**
+** <li> If the cursor started out before the target row and a call to
+**      to sqlite3BtreeNext() moved the cursor off the end of the index
+**      (indicating that the target row definitely does not exist in the
+**      btree) then jump to SeekGE.P2, ending the loop.
+**
+** <li> If the cursor ends up on a valid row that is past the target row
+**      (indicating that the target row does not exist in the btree) then
+**      jump to SeekOP.P2 if This.P5==0 or to This.P2 if This.P5>0.
+** </ol>
+*/
+case OP_SeekScan: {          /* ncycle */
+  VdbeCursor *pC;
+  int res;
+  int nStep;
+  UnpackedRecord r;
+
+  assert( pOp[1].opcode==OP_SeekGE );
+
+  /* If pOp->p5 is clear, then pOp->p2 points to the first instruction past the
+  ** OP_IdxGT that follows the OP_SeekGE. Otherwise, it points to the first
+  ** opcode past the OP_SeekGE itself.  */
+  assert( pOp->p2>=(int)(pOp-aOp)+2 );
+#ifdef SQLITE_DEBUG
+  if( pOp->p5==0 ){
+    /* There are no inequality constraints following the IN constraint. */
+    assert( pOp[1].p1==aOp[pOp->p2-1].p1 );
+    assert( pOp[1].p2==aOp[pOp->p2-1].p2 );
+    assert( pOp[1].p3==aOp[pOp->p2-1].p3 );
+    assert( aOp[pOp->p2-1].opcode==OP_IdxGT
+         || aOp[pOp->p2-1].opcode==OP_IdxGE );
+    testcase( aOp[pOp->p2-1].opcode==OP_IdxGE );
+  }else{
+    /* There are inequality constraints.  */
+    assert( pOp->p2==(int)(pOp-aOp)+2 );
+    assert( aOp[pOp->p2-1].opcode==OP_SeekGE );
+  }
+#endif
+
+  assert( pOp->p1>0 );
+  pC = p->apCsr[pOp[1].p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( !pC->isTable );
+  if( !sqlite3BtreeCursorIsValidNN(pC->uc.pCursor) ){
+#ifdef SQLITE_DEBUG
+     if( db->flags&SQLITE_VdbeTrace ){
+       printf("... cursor not valid - fall through\n");
+     }       
+#endif
+    break;
+  }
+  nStep = pOp->p1;
+  assert( nStep>=1 );
+  r.pKeyInfo = pC->pKeyInfo;
+  r.nField = (u16)pOp[1].p4.i;
+  r.default_rc = 0;
+  r.aMem = &aMem[pOp[1].p3];
+#ifdef SQLITE_DEBUG
+  {
+    int i;
+    for(i=0; i<r.nField; i++){
+      assert( memIsValid(&r.aMem[i]) );
+      REGISTER_TRACE(pOp[1].p3+i, &aMem[pOp[1].p3+i]);
+    }
+  }
+#endif
+  res = 0;  /* Not needed.  Only used to silence a warning. */
+  while(1){
+    rc = sqlite3VdbeIdxKeyCompare(db, pC, &r, &res);
+    if( rc ) goto abort_due_to_error;
+    if( res>0 && pOp->p5==0 ){
+      seekscan_search_fail:
+      /* Jump to SeekGE.P2, ending the loop */
+#ifdef SQLITE_DEBUG
+      if( db->flags&SQLITE_VdbeTrace ){
+        printf("... %d steps and then skip\n", pOp->p1 - nStep);
+      }       
+#endif
+      VdbeBranchTaken(1,3);
+      pOp++;
+      goto jump_to_p2;
+    }
+    if( res>=0 ){
+      /* Jump to This.P2, bypassing the OP_SeekGE opcode */
+#ifdef SQLITE_DEBUG
+      if( db->flags&SQLITE_VdbeTrace ){
+        printf("... %d steps and then success\n", pOp->p1 - nStep);
+      }       
+#endif
+      VdbeBranchTaken(2,3);
+      goto jump_to_p2;
+      break;
+    }
+    if( nStep<=0 ){
+#ifdef SQLITE_DEBUG
+      if( db->flags&SQLITE_VdbeTrace ){
+        printf("... fall through after %d steps\n", pOp->p1);
+      }       
+#endif
+      VdbeBranchTaken(0,3);
+      break;
+    }
+    nStep--;
+    pC->cacheStatus = CACHE_STALE;
+    rc = sqlite3BtreeNext(pC->uc.pCursor, 0);
+    if( rc ){
+      if( rc==SQLITE_DONE ){
+        rc = SQLITE_OK;
+        goto seekscan_search_fail;
+      }else{
+        goto abort_due_to_error;
+      }
+    }
+  }
+ 
+  break;
+}
+
+
+/* Opcode: SeekHit P1 P2 P3 * *
+** Synopsis: set P2<=seekHit<=P3
+**
+** Increase or decrease the seekHit value for cursor P1, if necessary,
+** so that it is no less than P2 and no greater than P3.
+**
+** The seekHit integer represents the maximum of terms in an index for which
+** there is known to be at least one match.  If the seekHit value is smaller
+** than the total number of equality terms in an index lookup, then the
+** OP_IfNoHope opcode might run to see if the IN loop can be abandoned
+** early, thus saving work.  This is part of the IN-early-out optimization.
+**
+** P1 must be a valid b-tree cursor.
+*/
+case OP_SeekHit: {           /* ncycle */
+  VdbeCursor *pC;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pOp->p3>=pOp->p2 );
+  if( pC->seekHit<pOp->p2 ){
+#ifdef SQLITE_DEBUG
+    if( db->flags&SQLITE_VdbeTrace ){
+      printf("seekHit changes from %d to %d\n", pC->seekHit, pOp->p2);
+    }       
+#endif
+    pC->seekHit = pOp->p2;
+  }else if( pC->seekHit>pOp->p3 ){
+#ifdef SQLITE_DEBUG
+    if( db->flags&SQLITE_VdbeTrace ){
+      printf("seekHit changes from %d to %d\n", pC->seekHit, pOp->p3);
+    }       
+#endif
+    pC->seekHit = pOp->p3;
+  }
+  break;
+}
+
+/* Opcode: IfNotOpen P1 P2 * * *
+** Synopsis: if( !csr[P1] ) goto P2
+**
+** If cursor P1 is not open or if P1 is set to a NULL row using the
+** OP_NullRow opcode, then jump to instruction P2. Otherwise, fall through.
+*/
+case OP_IfNotOpen: {        /* jump */
+  VdbeCursor *pCur;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pCur = p->apCsr[pOp->p1];
+  VdbeBranchTaken(pCur==0 || pCur->nullRow, 2);
+  if( pCur==0 || pCur->nullRow ){
+    goto jump_to_p2_and_check_for_interrupt;
+  }
+  break;
+}
+
+/* Opcode: Found P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
+** P4>0 then register P3 is the first of P4 registers that form an unpacked
+** record.
+**
+** Cursor P1 is on an index btree.  If the record identified by P3 and P4
+** is a prefix of any entry in P1 then a jump is made to P2 and
+** P1 is left pointing at the matching entry.
+**
+** This operation leaves the cursor in a state where it can be
+** advanced in the forward direction.  The Next instruction will work,
+** but not the Prev instruction.
+**
+** See also: NotFound, NoConflict, NotExists. SeekGe
+*/
+/* Opcode: NotFound P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
+** P4>0 then register P3 is the first of P4 registers that form an unpacked
+** record.
+**
+** Cursor P1 is on an index btree.  If the record identified by P3 and P4
+** is not the prefix of any entry in P1 then a jump is made to P2.  If P1
+** does contain an entry whose prefix matches the P3/P4 record then control
+** falls through to the next instruction and P1 is left pointing at the
+** matching entry.
+**
+** This operation leaves the cursor in a state where it cannot be
+** advanced in either direction.  In other words, the Next and Prev
+** opcodes do not work after this operation.
+**
+** See also: Found, NotExists, NoConflict, IfNoHope
+*/
+/* Opcode: IfNoHope P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** Register P3 is the first of P4 registers that form an unpacked
+** record.  Cursor P1 is an index btree.  P2 is a jump destination.
+** In other words, the operands to this opcode are the same as the
+** operands to OP_NotFound and OP_IdxGT.
+**
+** This opcode is an optimization attempt only.  If this opcode always
+** falls through, the correct answer is still obtained, but extra work
+** is performed.
+**
+** A value of N in the seekHit flag of cursor P1 means that there exists
+** a key P3:N that will match some record in the index.  We want to know
+** if it is possible for a record P3:P4 to match some record in the
+** index.  If it is not possible, we can skip some work.  So if seekHit
+** is less than P4, attempt to find out if a match is possible by running
+** OP_NotFound.
+**
+** This opcode is used in IN clause processing for a multi-column key.
+** If an IN clause is attached to an element of the key other than the
+** left-most element, and if there are no matches on the most recent
+** seek over the whole key, then it might be that one of the key element
+** to the left is prohibiting a match, and hence there is "no hope" of
+** any match regardless of how many IN clause elements are checked.
+** In such a case, we abandon the IN clause search early, using this
+** opcode.  The opcode name comes from the fact that the
+** jump is taken if there is "no hope" of achieving a match.
+**
+** See also: NotFound, SeekHit
+*/
+/* Opcode: NoConflict P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
+** P4>0 then register P3 is the first of P4 registers that form an unpacked
+** record.
+**
+** Cursor P1 is on an index btree.  If the record identified by P3 and P4
+** contains any NULL value, jump immediately to P2.  If all terms of the
+** record are not-NULL then a check is done to determine if any row in the
+** P1 index btree has a matching key prefix.  If there are no matches, jump
+** immediately to P2.  If there is a match, fall through and leave the P1
+** cursor pointing to the matching row.
+**
+** This opcode is similar to OP_NotFound with the exceptions that the
+** branch is always taken if any part of the search key input is NULL.
+**
+** This operation leaves the cursor in a state where it cannot be
+** advanced in either direction.  In other words, the Next and Prev
+** opcodes do not work after this operation.
+**
+** See also: NotFound, Found, NotExists
+*/
+case OP_IfNoHope: {     /* jump, in3, ncycle */
+  VdbeCursor *pC;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+#ifdef SQLITE_DEBUG
+  if( db->flags&SQLITE_VdbeTrace ){
+    printf("seekHit is %d\n", pC->seekHit);
+  }       
+#endif
+  if( pC->seekHit>=pOp->p4.i ) break;
+  /* Fall through into OP_NotFound */
+  /* no break */ deliberate_fall_through
+}
+case OP_NoConflict:     /* jump, in3, ncycle */
+case OP_NotFound:       /* jump, in3, ncycle */
+case OP_Found: {        /* jump, in3, ncycle */
+  int alreadyExists;
+  int ii;
+  VdbeCursor *pC;
+  UnpackedRecord *pIdxKey;
+  UnpackedRecord r;
+
+#ifdef SQLITE_TEST
+  if( pOp->opcode!=OP_NoConflict ) sqlite3_found_count++;
+#endif
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p4type==P4_INT32 );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+#ifdef SQLITE_DEBUG
+  pC->seekOp = pOp->opcode;
+#endif
+  r.aMem = &aMem[pOp->p3];
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
+  assert( pC->isTable==0 );
+  r.nField = (u16)pOp->p4.i;
+  if( r.nField>0 ){
+    /* Key values in an array of registers */
+    r.pKeyInfo = pC->pKeyInfo;
+    r.default_rc = 0;
+#ifdef SQLITE_DEBUG
+    for(ii=0; ii<r.nField; ii++){
+      assert( memIsValid(&r.aMem[ii]) );
+      assert( (r.aMem[ii].flags & MEM_Zero)==0 || r.aMem[ii].n==0 );
+      if( ii ) REGISTER_TRACE(pOp->p3+ii, &r.aMem[ii]);
+    }
+#endif
+    rc = sqlite3BtreeIndexMoveto(pC->uc.pCursor, &r, &pC->seekResult);
+  }else{
+    /* Composite key generated by OP_MakeRecord */
+    assert( r.aMem->flags & MEM_Blob );
+    assert( pOp->opcode!=OP_NoConflict );
+    rc = ExpandBlob(r.aMem);
+    assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+    if( rc ) goto no_mem;
+    pIdxKey = sqlite3VdbeAllocUnpackedRecord(pC->pKeyInfo);
+    if( pIdxKey==0 ) goto no_mem;
+    sqlite3VdbeRecordUnpack(pC->pKeyInfo, r.aMem->n, r.aMem->z, pIdxKey);
+    pIdxKey->default_rc = 0;
+    rc = sqlite3BtreeIndexMoveto(pC->uc.pCursor, pIdxKey, &pC->seekResult);
+    sqlite3DbFreeNN(db, pIdxKey);
+  }
+  if( rc!=SQLITE_OK ){
+    goto abort_due_to_error;
+  }
+  alreadyExists = (pC->seekResult==0);
+  pC->nullRow = 1-alreadyExists;
+  pC->deferredMoveto = 0;
+  pC->cacheStatus = CACHE_STALE;
+  if( pOp->opcode==OP_Found ){
+    VdbeBranchTaken(alreadyExists!=0,2);
+    if( alreadyExists ) goto jump_to_p2;
+  }else{
+    if( !alreadyExists ){
+      VdbeBranchTaken(1,2);
+      goto jump_to_p2;
+    }
+    if( pOp->opcode==OP_NoConflict ){
+      /* For the OP_NoConflict opcode, take the jump if any of the
+      ** input fields are NULL, since any key with a NULL will not
+      ** conflict */
+      for(ii=0; ii<r.nField; ii++){
+        if( r.aMem[ii].flags & MEM_Null ){
+          VdbeBranchTaken(1,2);
+          goto jump_to_p2;
+        }
+      }
+    }
+    VdbeBranchTaken(0,2);
+    if( pOp->opcode==OP_IfNoHope ){
+      pC->seekHit = pOp->p4.i;
+    }
+  }
+  break;
+}
+
+/* Opcode: SeekRowid P1 P2 P3 * *
+** Synopsis: intkey=r[P3]
+**
+** P1 is the index of a cursor open on an SQL table btree (with integer
+** keys).  If register P3 does not contain an integer or if P1 does not
+** contain a record with rowid P3 then jump immediately to P2. 
+** Or, if P2 is 0, raise an SQLITE_CORRUPT error. If P1 does contain
+** a record with rowid P3 then
+** leave the cursor pointing at that record and fall through to the next
+** instruction.
+**
+** The OP_NotExists opcode performs the same operation, but with OP_NotExists
+** the P3 register must be guaranteed to contain an integer value.  With this
+** opcode, register P3 might not contain an integer.
+**
+** The OP_NotFound opcode performs the same operation on index btrees
+** (with arbitrary multi-value keys).
+**
+** This opcode leaves the cursor in a state where it cannot be advanced
+** in either direction.  In other words, the Next and Prev opcodes will
+** not work following this opcode.
+**
+** See also: Found, NotFound, NoConflict, SeekRowid
+*/
+/* Opcode: NotExists P1 P2 P3 * *
+** Synopsis: intkey=r[P3]
+**
+** P1 is the index of a cursor open on an SQL table btree (with integer
+** keys).  P3 is an integer rowid.  If P1 does not contain a record with
+** rowid P3 then jump immediately to P2.  Or, if P2 is 0, raise an
+** SQLITE_CORRUPT error. If P1 does contain a record with rowid P3 then
+** leave the cursor pointing at that record and fall through to the next
+** instruction.
+**
+** The OP_SeekRowid opcode performs the same operation but also allows the
+** P3 register to contain a non-integer value, in which case the jump is
+** always taken.  This opcode requires that P3 always contain an integer.
+**
+** The OP_NotFound opcode performs the same operation on index btrees
+** (with arbitrary multi-value keys).
+**
+** This opcode leaves the cursor in a state where it cannot be advanced
+** in either direction.  In other words, the Next and Prev opcodes will
+** not work following this opcode.
+**
+** See also: Found, NotFound, NoConflict, SeekRowid
+*/
+case OP_SeekRowid: {        /* jump, in3, ncycle */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+  u64 iKey;
+
+  pIn3 = &aMem[pOp->p3];
+  testcase( pIn3->flags & MEM_Int );
+  testcase( pIn3->flags & MEM_IntReal );
+  testcase( pIn3->flags & MEM_Real );
+  testcase( (pIn3->flags & (MEM_Str|MEM_Int))==MEM_Str );
+  if( (pIn3->flags & (MEM_Int|MEM_IntReal))==0 ){
+    /* If pIn3->u.i does not contain an integer, compute iKey as the
+    ** integer value of pIn3.  Jump to P2 if pIn3 cannot be converted
+    ** into an integer without loss of information.  Take care to avoid
+    ** changing the datatype of pIn3, however, as it is used by other
+    ** parts of the prepared statement. */
+    Mem x = pIn3[0];
+    applyAffinity(&x, SQLITE_AFF_NUMERIC, encoding);
+    if( (x.flags & MEM_Int)==0 ) goto jump_to_p2;
+    iKey = x.u.i;
+    goto notExistsWithKey;
+  }
+  /* Fall through into OP_NotExists */
+  /* no break */ deliberate_fall_through
+case OP_NotExists:          /* jump, in3, ncycle */
+  pIn3 = &aMem[pOp->p3];
+  assert( (pIn3->flags & MEM_Int)!=0 || pOp->opcode==OP_SeekRowid );
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  iKey = pIn3->u.i;
+notExistsWithKey:
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+#ifdef SQLITE_DEBUG
+  if( pOp->opcode==OP_SeekRowid ) pC->seekOp = OP_SeekRowid;
+#endif
+  assert( pC->isTable );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCrsr = pC->uc.pCursor;
+  assert( pCrsr!=0 );
+  res = 0;
+  rc = sqlite3BtreeTableMoveto(pCrsr, iKey, 0, &res);
+  assert( rc==SQLITE_OK || res==0 );
+  pC->movetoTarget = iKey;  /* Used by OP_Delete */
+  pC->nullRow = 0;
+  pC->cacheStatus = CACHE_STALE;
+  pC->deferredMoveto = 0;
+  VdbeBranchTaken(res!=0,2);
+  pC->seekResult = res;
+  if( res!=0 ){
+    assert( rc==SQLITE_OK );
+    if( pOp->p2==0 ){
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      goto jump_to_p2;
+    }
+  }
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: Sequence P1 P2 * * *
+** Synopsis: r[P2]=cursor[P1].ctr++
+**
+** Find the next available sequence number for cursor P1.
+** Write the sequence number into register P2.
+** The sequence number on the cursor is incremented after this
+** instruction. 
+*/
+case OP_Sequence: {           /* out2 */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( p->apCsr[pOp->p1]!=0 );
+  assert( p->apCsr[pOp->p1]->eCurType!=CURTYPE_VTAB );
+  pOut = out2Prerelease(p, pOp);
+  pOut->u.i = p->apCsr[pOp->p1]->seqCount++;
+  break;
+}
+
+
+/* Opcode: NewRowid P1 P2 P3 * *
+** Synopsis: r[P2]=rowid
+**
+** Get a new integer record number (a.k.a "rowid") used as the key to a table.
+** The record number is not previously used as a key in the database
+** table that cursor P1 points to.  The new record number is written
+** written to register P2.
+**
+** If P3>0 then P3 is a register in the root frame of this VDBE that holds
+** the largest previously generated record number. No new record numbers are
+** allowed to be less than this value. When this value reaches its maximum,
+** an SQLITE_FULL error is generated. The P3 register is updated with the '
+** generated record number. This P3 mechanism is used to help implement the
+** AUTOINCREMENT feature.
+*/
+case OP_NewRowid: {           /* out2 */
+  i64 v;                 /* The new rowid */
+  VdbeCursor *pC;        /* Cursor of table to get the new rowid */
+  int res;               /* Result of an sqlite3BtreeLast() */
+  int cnt;               /* Counter to limit the number of searches */
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  Mem *pMem;             /* Register holding largest rowid for AUTOINCREMENT */
+  VdbeFrame *pFrame;     /* Root frame of VDBE */
+#endif
+
+  v = 0;
+  res = 0;
+  pOut = out2Prerelease(p, pOp);
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->isTable );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
+  {
+    /* The next rowid or record number (different terms for the same
+    ** thing) is obtained in a two-step algorithm.
+    **
+    ** First we attempt to find the largest existing rowid and add one
+    ** to that.  But if the largest existing rowid is already the maximum
+    ** positive integer, we have to fall through to the second
+    ** probabilistic algorithm
+    **
+    ** The second algorithm is to select a rowid at random and see if
+    ** it already exists in the table.  If it does not exist, we have
+    ** succeeded.  If the random rowid does exist, we select a new one
+    ** and try again, up to 100 times.
+    */
+    assert( pC->isTable );
+
+#ifdef SQLITE_32BIT_ROWID
+#   define MAX_ROWID 0x7fffffff
+#else
+    /* Some compilers complain about constants of the form 0x7fffffffffffffff.
+    ** Others complain about 0x7ffffffffffffffffLL.  The following macro seems
+    ** to provide the constant while making all compilers happy.
+    */
+#   define MAX_ROWID  (i64)( (((u64)0x7fffffff)<<32) | (u64)0xffffffff )
+#endif
+
+    if( !pC->useRandomRowid ){
+      rc = sqlite3BtreeLast(pC->uc.pCursor, &res);
+      if( rc!=SQLITE_OK ){
+        goto abort_due_to_error;
+      }
+      if( res ){
+        v = 1;   /* IMP: R-61914-48074 */
+      }else{
+        assert( sqlite3BtreeCursorIsValid(pC->uc.pCursor) );
+        v = sqlite3BtreeIntegerKey(pC->uc.pCursor);
+        if( v>=MAX_ROWID ){
+          pC->useRandomRowid = 1;
+        }else{
+          v++;   /* IMP: R-29538-34987 */
+        }
+      }
+    }
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+    if( pOp->p3 ){
+      /* Assert that P3 is a valid memory cell. */
+      assert( pOp->p3>0 );
+      if( p->pFrame ){
+        for(pFrame=p->pFrame; pFrame->pParent; pFrame=pFrame->pParent);
+        /* Assert that P3 is a valid memory cell. */
+        assert( pOp->p3<=pFrame->nMem );
+        pMem = &pFrame->aMem[pOp->p3];
+      }else{
+        /* Assert that P3 is a valid memory cell. */
+        assert( pOp->p3<=(p->nMem+1 - p->nCursor) );
+        pMem = &aMem[pOp->p3];
+        memAboutToChange(p, pMem);
+      }
+      assert( memIsValid(pMem) );
+
+      REGISTER_TRACE(pOp->p3, pMem);
+      sqlite3VdbeMemIntegerify(pMem);
+      assert( (pMem->flags & MEM_Int)!=0 );  /* mem(P3) holds an integer */
+      if( pMem->u.i==MAX_ROWID || pC->useRandomRowid ){
+        rc = SQLITE_FULL;   /* IMP: R-17817-00630 */
+        goto abort_due_to_error;
+      }
+      if( v<pMem->u.i+1 ){
+        v = pMem->u.i + 1;
+      }
+      pMem->u.i = v;
+    }
+#endif
+    if( pC->useRandomRowid ){
+      /* IMPLEMENTATION-OF: R-07677-41881 If the largest ROWID is equal to the
+      ** largest possible integer (9223372036854775807) then the database
+      ** engine starts picking positive candidate ROWIDs at random until
+      ** it finds one that is not previously used. */
+      assert( pOp->p3==0 );  /* We cannot be in random rowid mode if this is
+                             ** an AUTOINCREMENT table. */
+      cnt = 0;
+      do{
+        sqlite3_randomness(sizeof(v), &v);
+        v &= (MAX_ROWID>>1); v++;  /* Ensure that v is greater than zero */
+      }while(  ((rc = sqlite3BtreeTableMoveto(pC->uc.pCursor, (u64)v,
+                                                 0, &res))==SQLITE_OK)
+            && (res==0)
+            && (++cnt<100));
+      if( rc ) goto abort_due_to_error;
+      if( res==0 ){
+        rc = SQLITE_FULL;   /* IMP: R-38219-53002 */
+        goto abort_due_to_error;
+      }
+      assert( v>0 );  /* EV: R-40812-03570 */
+    }
+    pC->deferredMoveto = 0;
+    pC->cacheStatus = CACHE_STALE;
+  }
+  pOut->u.i = v;
+  break;
+}
+
+/* Opcode: Insert P1 P2 P3 P4 P5
+** Synopsis: intkey=r[P3] data=r[P2]
+**
+** Write an entry into the table of cursor P1.  A new entry is
+** created if it doesn't already exist or the data for an existing
+** entry is overwritten.  The data is the value MEM_Blob stored in register
+** number P2. The key is stored in register P3. The key must
+** be a MEM_Int.
+**
+** If the OPFLAG_NCHANGE flag of P5 is set, then the row change count is
+** incremented (otherwise not).  If the OPFLAG_LASTROWID flag of P5 is set,
+** then rowid is stored for subsequent return by the
+** sqlite3_last_insert_rowid() function (otherwise it is unmodified).
+**
+** If the OPFLAG_USESEEKRESULT flag of P5 is set, the implementation might
+** run faster by avoiding an unnecessary seek on cursor P1.  However,
+** the OPFLAG_USESEEKRESULT flag must only be set if there have been no prior
+** seeks on the cursor or if the most recent seek used a key equal to P3.
+**
+** If the OPFLAG_ISUPDATE flag is set, then this opcode is part of an
+** UPDATE operation.  Otherwise (if the flag is clear) then this opcode
+** is part of an INSERT operation.  The difference is only important to
+** the update hook.
+**
+** Parameter P4 may point to a Table structure, or may be NULL. If it is
+** not NULL, then the update-hook (sqlite3.xUpdateCallback) is invoked
+** following a successful insert.
+**
+** (WARNING/TODO: If P1 is a pseudo-cursor and P2 is dynamically
+** allocated, then ownership of P2 is transferred to the pseudo-cursor
+** and register P2 becomes ephemeral.  If the cursor is changed, the
+** value of register P2 will then change.  Make sure this does not
+** cause any problems.)
+**
+** This instruction only works on tables.  The equivalent instruction
+** for indices is OP_IdxInsert.
+*/
+case OP_Insert: {
+  Mem *pData;       /* MEM cell holding data for the record to be inserted */
+  Mem *pKey;        /* MEM cell holding key  for the record */
+  VdbeCursor *pC;   /* Cursor to table into which insert is written */
+  int seekResult;   /* Result of prior seek or 0 if no USESEEKRESULT flag */
+  const char *zDb;  /* database name - used by the update hook */
+  Table *pTab;      /* Table structure - used by update and pre-update hooks */
+  BtreePayload x;   /* Payload to be inserted */
+
+  pData = &aMem[pOp->p2];
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( memIsValid(pData) );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->deferredMoveto==0 );
+  assert( pC->uc.pCursor!=0 );
+  assert( (pOp->p5 & OPFLAG_ISNOOP) || pC->isTable );
+  assert( pOp->p4type==P4_TABLE || pOp->p4type>=P4_STATIC );
+  REGISTER_TRACE(pOp->p2, pData);
+  sqlite3VdbeIncrWriteCounter(p, pC);
+
+  pKey = &aMem[pOp->p3];
+  assert( pKey->flags & MEM_Int );
+  assert( memIsValid(pKey) );
+  REGISTER_TRACE(pOp->p3, pKey);
+  x.nKey = pKey->u.i;
+
+  if( pOp->p4type==P4_TABLE && HAS_UPDATE_HOOK(db) ){
+    assert( pC->iDb>=0 );
+    zDb = db->aDb[pC->iDb].zDbSName;
+    pTab = pOp->p4.pTab;
+    assert( (pOp->p5 & OPFLAG_ISNOOP) || HasRowid(pTab) );
+  }else{
+    pTab = 0;
+    zDb = 0;
+  }
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  /* Invoke the pre-update hook, if any */
+  if( pTab ){
+    if( db->xPreUpdateCallback && !(pOp->p5 & OPFLAG_ISUPDATE) ){
+      sqlite3VdbePreUpdateHook(p,pC,SQLITE_INSERT,zDb,pTab,x.nKey,pOp->p2,-1);
+    }
+    if( db->xUpdateCallback==0 || pTab->aCol==0 ){
+      /* Prevent post-update hook from running in cases when it should not */
+      pTab = 0;
+    }
+  }
+  if( pOp->p5 & OPFLAG_ISNOOP ) break;
+#endif
+
+  assert( (pOp->p5 & OPFLAG_LASTROWID)==0 || (pOp->p5 & OPFLAG_NCHANGE)!=0 );
+  if( pOp->p5 & OPFLAG_NCHANGE ){
+    p->nChange++;
+    if( pOp->p5 & OPFLAG_LASTROWID ) db->lastRowid = x.nKey;
+  }
+  assert( (pData->flags & (MEM_Blob|MEM_Str))!=0 || pData->n==0 );
+  x.pData = pData->z;
+  x.nData = pData->n;
+  seekResult = ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0);
+  if( pData->flags & MEM_Zero ){
+    x.nZero = pData->u.nZero;
+  }else{
+    x.nZero = 0;
+  }
+  x.pKey = 0;
+  assert( BTREE_PREFORMAT==OPFLAG_PREFORMAT );
+  rc = sqlite3BtreeInsert(pC->uc.pCursor, &x,
+      (pOp->p5 & (OPFLAG_APPEND|OPFLAG_SAVEPOSITION|OPFLAG_PREFORMAT)),
+      seekResult
+  );
+  pC->deferredMoveto = 0;
+  pC->cacheStatus = CACHE_STALE;
+  colCacheCtr++;
+
+  /* Invoke the update-hook if required. */
+  if( rc ) goto abort_due_to_error;
+  if( pTab ){
+    assert( db->xUpdateCallback!=0 );
+    assert( pTab->aCol!=0 );
+    db->xUpdateCallback(db->pUpdateArg,
+           (pOp->p5 & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_INSERT,
+           zDb, pTab->zName, x.nKey);
+  }
+  break;
+}
+
+/* Opcode: RowCell P1 P2 P3 * *
+**
+** P1 and P2 are both open cursors. Both must be opened on the same type
+** of table - intkey or index. This opcode is used as part of copying
+** the current row from P2 into P1. If the cursors are opened on intkey
+** tables, register P3 contains the rowid to use with the new record in
+** P1. If they are opened on index tables, P3 is not used.
+**
+** This opcode must be followed by either an Insert or InsertIdx opcode
+** with the OPFLAG_PREFORMAT flag set to complete the insert operation.
+*/
+case OP_RowCell: {
+  VdbeCursor *pDest;              /* Cursor to write to */
+  VdbeCursor *pSrc;               /* Cursor to read from */
+  i64 iKey;                       /* Rowid value to insert with */
+  assert( pOp[1].opcode==OP_Insert || pOp[1].opcode==OP_IdxInsert );
+  assert( pOp[1].opcode==OP_Insert    || pOp->p3==0 );
+  assert( pOp[1].opcode==OP_IdxInsert || pOp->p3>0 );
+  assert( pOp[1].p5 & OPFLAG_PREFORMAT );
+  pDest = p->apCsr[pOp->p1];
+  pSrc = p->apCsr[pOp->p2];
+  iKey = pOp->p3 ? aMem[pOp->p3].u.i : 0;
+  rc = sqlite3BtreeTransferRow(pDest->uc.pCursor, pSrc->uc.pCursor, iKey);
+  if( rc!=SQLITE_OK ) goto abort_due_to_error;
+  break;
+};
+
+/* Opcode: Delete P1 P2 P3 P4 P5
+**
+** Delete the record at which the P1 cursor is currently pointing.
+**
+** If the OPFLAG_SAVEPOSITION bit of the P5 parameter is set, then
+** the cursor will be left pointing at  either the next or the previous
+** record in the table. If it is left pointing at the next record, then
+** the next Next instruction will be a no-op. As a result, in this case
+** it is ok to delete a record from within a Next loop. If
+** OPFLAG_SAVEPOSITION bit of P5 is clear, then the cursor will be
+** left in an undefined state.
+**
+** If the OPFLAG_AUXDELETE bit is set on P5, that indicates that this
+** delete is one of several associated with deleting a table row and
+** all its associated index entries.  Exactly one of those deletes is
+** the "primary" delete.  The others are all on OPFLAG_FORDELETE
+** cursors or else are marked with the AUXDELETE flag.
+**
+** If the OPFLAG_NCHANGE (0x01) flag of P2 (NB: P2 not P5) is set, then
+** the row change count is incremented (otherwise not).
+**
+** If the OPFLAG_ISNOOP (0x40) flag of P2 (not P5!) is set, then the
+** pre-update-hook for deletes is run, but the btree is otherwise unchanged.
+** This happens when the OP_Delete is to be shortly followed by an OP_Insert
+** with the same key, causing the btree entry to be overwritten.
+**
+** P1 must not be pseudo-table.  It has to be a real table with
+** multiple rows.
+**
+** If P4 is not NULL then it points to a Table object. In this case either
+** the update or pre-update hook, or both, may be invoked. The P1 cursor must
+** have been positioned using OP_NotFound prior to invoking this opcode in
+** this case. Specifically, if one is configured, the pre-update hook is
+** invoked if P4 is not NULL. The update-hook is invoked if one is configured,
+** P4 is not NULL, and the OPFLAG_NCHANGE flag is set in P2.
+**
+** If the OPFLAG_ISUPDATE flag is set in P2, then P3 contains the address
+** of the memory cell that contains the value that the rowid of the row will
+** be set to by the update.
+*/
+case OP_Delete: {
+  VdbeCursor *pC;
+  const char *zDb;
+  Table *pTab;
+  int opflags;
+
+  opflags = pOp->p2;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
+  assert( pC->deferredMoveto==0 );
+  sqlite3VdbeIncrWriteCounter(p, pC);
+
+#ifdef SQLITE_DEBUG
+  if( pOp->p4type==P4_TABLE
+   && HasRowid(pOp->p4.pTab)
+   && pOp->p5==0
+   && sqlite3BtreeCursorIsValidNN(pC->uc.pCursor)
+  ){
+    /* If p5 is zero, the seek operation that positioned the cursor prior to
+    ** OP_Delete will have also set the pC->movetoTarget field to the rowid of
+    ** the row that is being deleted */
+    i64 iKey = sqlite3BtreeIntegerKey(pC->uc.pCursor);
+    assert( CORRUPT_DB || pC->movetoTarget==iKey );
+  }
+#endif
+
+  /* If the update-hook or pre-update-hook will be invoked, set zDb to
+  ** the name of the db to pass as to it. Also set local pTab to a copy
+  ** of p4.pTab. Finally, if p5 is true, indicating that this cursor was
+  ** last moved with OP_Next or OP_Prev, not Seek or NotFound, set
+  ** VdbeCursor.movetoTarget to the current rowid.  */
+  if( pOp->p4type==P4_TABLE && HAS_UPDATE_HOOK(db) ){
+    assert( pC->iDb>=0 );
+    assert( pOp->p4.pTab!=0 );
+    zDb = db->aDb[pC->iDb].zDbSName;
+    pTab = pOp->p4.pTab;
+    if( (pOp->p5 & OPFLAG_SAVEPOSITION)!=0 && pC->isTable ){
+      pC->movetoTarget = sqlite3BtreeIntegerKey(pC->uc.pCursor);
+    }
+  }else{
+    zDb = 0;
+    pTab = 0;
+  }
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+  /* Invoke the pre-update-hook if required. */
+  assert( db->xPreUpdateCallback==0 || pTab==pOp->p4.pTab );
+  if( db->xPreUpdateCallback && pTab ){
+    assert( !(opflags & OPFLAG_ISUPDATE)
+         || HasRowid(pTab)==0
+         || (aMem[pOp->p3].flags & MEM_Int)
+    );
+    sqlite3VdbePreUpdateHook(p, pC,
+        (opflags & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_DELETE,
+        zDb, pTab, pC->movetoTarget,
+        pOp->p3, -1
+    );
+  }
+  if( opflags & OPFLAG_ISNOOP ) break;
+#endif
+
+  /* Only flags that can be set are SAVEPOISTION and AUXDELETE */
+  assert( (pOp->p5 & ~(OPFLAG_SAVEPOSITION|OPFLAG_AUXDELETE))==0 );
+  assert( OPFLAG_SAVEPOSITION==BTREE_SAVEPOSITION );
+  assert( OPFLAG_AUXDELETE==BTREE_AUXDELETE );
+
+#ifdef SQLITE_DEBUG
+  if( p->pFrame==0 ){
+    if( pC->isEphemeral==0
+        && (pOp->p5 & OPFLAG_AUXDELETE)==0
+        && (pC->wrFlag & OPFLAG_FORDELETE)==0
+      ){
+      nExtraDelete++;
+    }
+    if( pOp->p2 & OPFLAG_NCHANGE ){
+      nExtraDelete--;
+    }
+  }
+#endif
+
+  rc = sqlite3BtreeDelete(pC->uc.pCursor, pOp->p5);
+  pC->cacheStatus = CACHE_STALE;
+  colCacheCtr++;
+  pC->seekResult = 0;
+  if( rc ) goto abort_due_to_error;
+
+  /* Invoke the update-hook if required. */
+  if( opflags & OPFLAG_NCHANGE ){
+    p->nChange++;
+    if( db->xUpdateCallback && ALWAYS(pTab!=0) && HasRowid(pTab) ){
+      db->xUpdateCallback(db->pUpdateArg, SQLITE_DELETE, zDb, pTab->zName,
+          pC->movetoTarget);
+      assert( pC->iDb>=0 );
+    }
+  }
+
+  break;
+}
+/* Opcode: ResetCount * * * * *
+**
+** The value of the change counter is copied to the database handle
+** change counter (returned by subsequent calls to sqlite3_changes()).
+** Then the VMs internal change counter resets to 0.
+** This is used by trigger programs.
+*/
+case OP_ResetCount: {
+  sqlite3VdbeSetChanges(db, p->nChange);
+  p->nChange = 0;
+  break;
+}
+
+/* Opcode: SorterCompare P1 P2 P3 P4
+** Synopsis: if key(P1)!=trim(r[P3],P4) goto P2
+**
+** P1 is a sorter cursor. This instruction compares a prefix of the
+** record blob in register P3 against a prefix of the entry that
+** the sorter cursor currently points to.  Only the first P4 fields
+** of r[P3] and the sorter record are compared.
+**
+** If either P3 or the sorter contains a NULL in one of their significant
+** fields (not counting the P4 fields at the end which are ignored) then
+** the comparison is assumed to be equal.
+**
+** Fall through to next instruction if the two records compare equal to
+** each other.  Jump to P2 if they are different.
+*/
+case OP_SorterCompare: {
+  VdbeCursor *pC;
+  int res;
+  int nKeyCol;
+
+  pC = p->apCsr[pOp->p1];
+  assert( isSorter(pC) );
+  assert( pOp->p4type==P4_INT32 );
+  pIn3 = &aMem[pOp->p3];
+  nKeyCol = pOp->p4.i;
+  res = 0;
+  rc = sqlite3VdbeSorterCompare(pC, pIn3, nKeyCol, &res);
+  VdbeBranchTaken(res!=0,2);
+  if( rc ) goto abort_due_to_error;
+  if( res ) goto jump_to_p2;
+  break;
+};
+
+/* Opcode: SorterData P1 P2 P3 * *
+** Synopsis: r[P2]=data
+**
+** Write into register P2 the current sorter data for sorter cursor P1.
+** Then clear the column header cache on cursor P3.
+**
+** This opcode is normally used to move a record out of the sorter and into
+** a register that is the source for a pseudo-table cursor created using
+** OpenPseudo.  That pseudo-table cursor is the one that is identified by
+** parameter P3.  Clearing the P3 column cache as part of this opcode saves
+** us from having to issue a separate NullRow instruction to clear that cache.
+*/
+case OP_SorterData: {       /* ncycle */
+  VdbeCursor *pC;
+
+  pOut = &aMem[pOp->p2];
+  pC = p->apCsr[pOp->p1];
+  assert( isSorter(pC) );
+  rc = sqlite3VdbeSorterRowkey(pC, pOut);
+  assert( rc!=SQLITE_OK || (pOut->flags & MEM_Blob) );
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  if( rc ) goto abort_due_to_error;
+  p->apCsr[pOp->p3]->cacheStatus = CACHE_STALE;
+  break;
+}
+
+/* Opcode: RowData P1 P2 P3 * *
+** Synopsis: r[P2]=data
+**
+** Write into register P2 the complete row content for the row at
+** which cursor P1 is currently pointing.
+** There is no interpretation of the data. 
+** It is just copied onto the P2 register exactly as
+** it is found in the database file.
+**
+** If cursor P1 is an index, then the content is the key of the row.
+** If cursor P2 is a table, then the content extracted is the data.
+**
+** If the P1 cursor must be pointing to a valid row (not a NULL row)
+** of a real table, not a pseudo-table.
+**
+** If P3!=0 then this opcode is allowed to make an ephemeral pointer
+** into the database page.  That means that the content of the output
+** register will be invalidated as soon as the cursor moves - including
+** moves caused by other cursors that "save" the current cursors
+** position in order that they can write to the same table.  If P3==0
+** then a copy of the data is made into memory.  P3!=0 is faster, but
+** P3==0 is safer.
+**
+** If P3!=0 then the content of the P2 register is unsuitable for use
+** in OP_Result and any OP_Result will invalidate the P2 register content.
+** The P2 register content is invalidated by opcodes like OP_Function or
+** by any use of another cursor pointing to the same table.
+*/
+case OP_RowData: {
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  u32 n;
+
+  pOut = out2Prerelease(p, pOp);
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( isSorter(pC)==0 );
+  assert( pC->nullRow==0 );
+  assert( pC->uc.pCursor!=0 );
+  pCrsr = pC->uc.pCursor;
+
+  /* The OP_RowData opcodes always follow OP_NotExists or
+  ** OP_SeekRowid or OP_Rewind/Op_Next with no intervening instructions
+  ** that might invalidate the cursor.
+  ** If this where not the case, on of the following assert()s
+  ** would fail.  Should this ever change (because of changes in the code
+  ** generator) then the fix would be to insert a call to
+  ** sqlite3VdbeCursorMoveto().
+  */
+  assert( pC->deferredMoveto==0 );
+  assert( sqlite3BtreeCursorIsValid(pCrsr) );
+
+  n = sqlite3BtreePayloadSize(pCrsr);
+  if( n>(u32)db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    goto too_big;
+  }
+  testcase( n==0 );
+  rc = sqlite3VdbeMemFromBtreeZeroOffset(pCrsr, n, pOut);
+  if( rc ) goto abort_due_to_error;
+  if( !pOp->p3 ) Deephemeralize(pOut);
+  UPDATE_MAX_BLOBSIZE(pOut);
+  REGISTER_TRACE(pOp->p2, pOut);
+  break;
+}
+
+/* Opcode: Rowid P1 P2 * * *
+** Synopsis: r[P2]=PX rowid of P1
+**
+** Store in register P2 an integer which is the key of the table entry that
+** P1 is currently point to.
+**
+** P1 can be either an ordinary table or a virtual table.  There used to
+** be a separate OP_VRowid opcode for use with virtual tables, but this
+** one opcode now works for both table types.
+*/
+case OP_Rowid: {                 /* out2, ncycle */
+  VdbeCursor *pC;
+  i64 v;
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+
+  pOut = out2Prerelease(p, pOp);
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType!=CURTYPE_PSEUDO || pC->nullRow );
+  if( pC->nullRow ){
+    pOut->flags = MEM_Null;
+    break;
+  }else if( pC->deferredMoveto ){
+    v = pC->movetoTarget;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  }else if( pC->eCurType==CURTYPE_VTAB ){
+    assert( pC->uc.pVCur!=0 );
+    pVtab = pC->uc.pVCur->pVtab;
+    pModule = pVtab->pModule;
+    assert( pModule->xRowid );
+    rc = pModule->xRowid(pC->uc.pVCur, &v);
+    sqlite3VtabImportErrmsg(p, pVtab);
+    if( rc ) goto abort_due_to_error;
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+  }else{
+    assert( pC->eCurType==CURTYPE_BTREE );
+    assert( pC->uc.pCursor!=0 );
+    rc = sqlite3VdbeCursorRestore(pC);
+    if( rc ) goto abort_due_to_error;
+    if( pC->nullRow ){
+      pOut->flags = MEM_Null;
+      break;
+    }
+    v = sqlite3BtreeIntegerKey(pC->uc.pCursor);
+  }
+  pOut->u.i = v;
+  break;
+}
+
+/* Opcode: NullRow P1 * * * *
+**
+** Move the cursor P1 to a null row.  Any OP_Column operations
+** that occur while the cursor is on the null row will always
+** write a NULL.
+**
+** If cursor P1 is not previously opened, open it now to a special
+** pseudo-cursor that always returns NULL for every column.
+*/
+case OP_NullRow: {
+  VdbeCursor *pC;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  if( pC==0 ){
+    /* If the cursor is not already open, create a special kind of
+    ** pseudo-cursor that always gives null rows. */
+    pC = allocateCursor(p, pOp->p1, 1, CURTYPE_PSEUDO);
+    if( pC==0 ) goto no_mem;
+    pC->seekResult = 0;
+    pC->isTable = 1;
+    pC->noReuse = 1;
+    pC->uc.pCursor = sqlite3BtreeFakeValidCursor();
+  }
+  pC->nullRow = 1;
+  pC->cacheStatus = CACHE_STALE;
+  if( pC->eCurType==CURTYPE_BTREE ){
+    assert( pC->uc.pCursor!=0 );
+    sqlite3BtreeClearCursor(pC->uc.pCursor);
+  }
+#ifdef SQLITE_DEBUG
+  if( pC->seekOp==0 ) pC->seekOp = OP_NullRow;
+#endif
+  break;
+}
+
+/* Opcode: SeekEnd P1 * * * *
+**
+** Position cursor P1 at the end of the btree for the purpose of
+** appending a new entry onto the btree.
+**
+** It is assumed that the cursor is used only for appending and so
+** if the cursor is valid, then the cursor must already be pointing
+** at the end of the btree and so no changes are made to
+** the cursor.
+*/
+/* Opcode: Last P1 P2 * * *
+**
+** The next use of the Rowid or Column or Prev instruction for P1
+** will refer to the last entry in the database table or index.
+** If the table or index is empty and P2>0, then jump immediately to P2.
+** If P2 is 0 or if the table or index is not empty, fall through
+** to the following instruction.
+**
+** This opcode leaves the cursor configured to move in reverse order,
+** from the end toward the beginning.  In other words, the cursor is
+** configured to use Prev, not Next.
+*/
+case OP_SeekEnd:             /* ncycle */
+case OP_Last: {              /* jump, ncycle */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCrsr = pC->uc.pCursor;
+  res = 0;
+  assert( pCrsr!=0 );
+#ifdef SQLITE_DEBUG
+  pC->seekOp = pOp->opcode;
+#endif
+  if( pOp->opcode==OP_SeekEnd ){
+    assert( pOp->p2==0 );
+    pC->seekResult = -1;
+    if( sqlite3BtreeCursorIsValidNN(pCrsr) ){
+      break;
+    }
+  }
+  rc = sqlite3BtreeLast(pCrsr, &res);
+  pC->nullRow = (u8)res;
+  pC->deferredMoveto = 0;
+  pC->cacheStatus = CACHE_STALE;
+  if( rc ) goto abort_due_to_error;
+  if( pOp->p2>0 ){
+    VdbeBranchTaken(res!=0,2);
+    if( res ) goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: IfSmaller P1 P2 P3 * *
+**
+** Estimate the number of rows in the table P1.  Jump to P2 if that
+** estimate is less than approximately 2**(0.1*P3).
+*/
+case OP_IfSmaller: {        /* jump */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+  i64 sz;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  pCrsr = pC->uc.pCursor;
+  assert( pCrsr );
+  rc = sqlite3BtreeFirst(pCrsr, &res);
+  if( rc ) goto abort_due_to_error;
+  if( res==0 ){
+    sz = sqlite3BtreeRowCountEst(pCrsr);
+    if( ALWAYS(sz>=0) && sqlite3LogEst((u64)sz)<pOp->p3 ) res = 1;
+  }
+  VdbeBranchTaken(res!=0,2);
+  if( res ) goto jump_to_p2;
+  break;
+}
+
+
+/* Opcode: SorterSort P1 P2 * * *
+**
+** After all records have been inserted into the Sorter object
+** identified by P1, invoke this opcode to actually do the sorting.
+** Jump to P2 if there are no records to be sorted.
+**
+** This opcode is an alias for OP_Sort and OP_Rewind that is used
+** for Sorter objects.
+*/
+/* Opcode: Sort P1 P2 * * *
+**
+** This opcode does exactly the same thing as OP_Rewind except that
+** it increments an undocumented global variable used for testing.
+**
+** Sorting is accomplished by writing records into a sorting index,
+** then rewinding that index and playing it back from beginning to
+** end.  We use the OP_Sort opcode instead of OP_Rewind to do the
+** rewinding so that the global variable will be incremented and
+** regression tests can determine whether or not the optimizer is
+** correctly optimizing out sorts.
+*/
+case OP_SorterSort:    /* jump ncycle */
+case OP_Sort: {        /* jump ncycle */
+#ifdef SQLITE_TEST
+  sqlite3_sort_count++;
+  sqlite3_search_count--;
+#endif
+  p->aCounter[SQLITE_STMTSTATUS_SORT]++;
+  /* Fall through into OP_Rewind */
+  /* no break */ deliberate_fall_through
+}
+/* Opcode: Rewind P1 P2 * * *
+**
+** The next use of the Rowid or Column or Next instruction for P1
+** will refer to the first entry in the database table or index.
+** If the table or index is empty, jump immediately to P2.
+** If the table or index is not empty, fall through to the following
+** instruction.
+**
+** If P2 is zero, that is an assertion that the P1 table is never
+** empty and hence the jump will never be taken.
+**
+** This opcode leaves the cursor configured to move in forward order,
+** from the beginning toward the end.  In other words, the cursor is
+** configured to use Next, not Prev.
+*/
+case OP_Rewind: {        /* jump, ncycle */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p5==0 );
+  assert( pOp->p2>=0 && pOp->p2<p->nOp );
+
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( isSorter(pC)==(pOp->opcode==OP_SorterSort) );
+  res = 1;
+#ifdef SQLITE_DEBUG
+  pC->seekOp = OP_Rewind;
+#endif
+  if( isSorter(pC) ){
+    rc = sqlite3VdbeSorterRewind(pC, &res);
+  }else{
+    assert( pC->eCurType==CURTYPE_BTREE );
+    pCrsr = pC->uc.pCursor;
+    assert( pCrsr );
+    rc = sqlite3BtreeFirst(pCrsr, &res);
+    pC->deferredMoveto = 0;
+    pC->cacheStatus = CACHE_STALE;
+  }
+  if( rc ) goto abort_due_to_error;
+  pC->nullRow = (u8)res;
+  if( pOp->p2>0 ){
+    VdbeBranchTaken(res!=0,2);
+    if( res ) goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: Next P1 P2 P3 * P5
+**
+** Advance cursor P1 so that it points to the next key/data pair in its
+** table or index.  If there are no more key/value pairs then fall through
+** to the following instruction.  But if the cursor advance was successful,
+** jump immediately to P2.
+**
+** The Next opcode is only valid following an SeekGT, SeekGE, or
+** OP_Rewind opcode used to position the cursor.  Next is not allowed
+** to follow SeekLT, SeekLE, or OP_Last.
+**
+** The P1 cursor must be for a real table, not a pseudo-table.  P1 must have
+** been opened prior to this opcode or the program will segfault.
+**
+** The P3 value is a hint to the btree implementation. If P3==1, that
+** means P1 is an SQL index and that this instruction could have been
+** omitted if that index had been unique.  P3 is usually 0.  P3 is
+** always either 0 or 1.
+**
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
+**
+** See also: Prev
+*/
+/* Opcode: Prev P1 P2 P3 * P5
+**
+** Back up cursor P1 so that it points to the previous key/data pair in its
+** table or index.  If there is no previous key/value pairs then fall through
+** to the following instruction.  But if the cursor backup was successful,
+** jump immediately to P2.
+**
+**
+** The Prev opcode is only valid following an SeekLT, SeekLE, or
+** OP_Last opcode used to position the cursor.  Prev is not allowed
+** to follow SeekGT, SeekGE, or OP_Rewind.
+**
+** The P1 cursor must be for a real table, not a pseudo-table.  If P1 is
+** not open then the behavior is undefined.
+**
+** The P3 value is a hint to the btree implementation. If P3==1, that
+** means P1 is an SQL index and that this instruction could have been
+** omitted if that index had been unique.  P3 is usually 0.  P3 is
+** always either 0 or 1.
+**
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
+*/
+/* Opcode: SorterNext P1 P2 * * P5
+**
+** This opcode works just like OP_Next except that P1 must be a
+** sorter object for which the OP_SorterSort opcode has been
+** invoked.  This opcode advances the cursor to the next sorted
+** record, or jumps to P2 if there are no more sorted records.
+*/
+case OP_SorterNext: {  /* jump */
+  VdbeCursor *pC;
+
+  pC = p->apCsr[pOp->p1];
+  assert( isSorter(pC) );
+  rc = sqlite3VdbeSorterNext(db, pC);
+  goto next_tail;
+
+case OP_Prev:          /* jump, ncycle */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p5==0
+       || pOp->p5==SQLITE_STMTSTATUS_FULLSCAN_STEP
+       || pOp->p5==SQLITE_STMTSTATUS_AUTOINDEX);
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->deferredMoveto==0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->seekOp==OP_SeekLT || pC->seekOp==OP_SeekLE
+       || pC->seekOp==OP_Last   || pC->seekOp==OP_IfNoHope
+       || pC->seekOp==OP_NullRow);
+  rc = sqlite3BtreePrevious(pC->uc.pCursor, pOp->p3);
+  goto next_tail;
+
+case OP_Next:          /* jump, ncycle */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p5==0
+       || pOp->p5==SQLITE_STMTSTATUS_FULLSCAN_STEP
+       || pOp->p5==SQLITE_STMTSTATUS_AUTOINDEX);
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->deferredMoveto==0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->seekOp==OP_SeekGT || pC->seekOp==OP_SeekGE
+       || pC->seekOp==OP_Rewind || pC->seekOp==OP_Found
+       || pC->seekOp==OP_NullRow|| pC->seekOp==OP_SeekRowid
+       || pC->seekOp==OP_IfNoHope);
+  rc = sqlite3BtreeNext(pC->uc.pCursor, pOp->p3);
+
+next_tail:
+  pC->cacheStatus = CACHE_STALE;
+  VdbeBranchTaken(rc==SQLITE_OK,2);
+  if( rc==SQLITE_OK ){
+    pC->nullRow = 0;
+    p->aCounter[pOp->p5]++;
+#ifdef SQLITE_TEST
+    sqlite3_search_count++;
+#endif
+    goto jump_to_p2_and_check_for_interrupt;
+  }
+  if( rc!=SQLITE_DONE ) goto abort_due_to_error;
+  rc = SQLITE_OK;
+  pC->nullRow = 1;
+  goto check_for_interrupt;
+}
+
+/* Opcode: IdxInsert P1 P2 P3 P4 P5
+** Synopsis: key=r[P2]
+**
+** Register P2 holds an SQL index key made using the
+** MakeRecord instructions.  This opcode writes that key
+** into the index P1.  Data for the entry is nil.
+**
+** If P4 is not zero, then it is the number of values in the unpacked
+** key of reg(P2).  In that case, P3 is the index of the first register
+** for the unpacked key.  The availability of the unpacked key can sometimes
+** be an optimization.
+**
+** If P5 has the OPFLAG_APPEND bit set, that is a hint to the b-tree layer
+** that this insert is likely to be an append.
+**
+** If P5 has the OPFLAG_NCHANGE bit set, then the change counter is
+** incremented by this instruction.  If the OPFLAG_NCHANGE bit is clear,
+** then the change counter is unchanged.
+**
+** If the OPFLAG_USESEEKRESULT flag of P5 is set, the implementation might
+** run faster by avoiding an unnecessary seek on cursor P1.  However,
+** the OPFLAG_USESEEKRESULT flag must only be set if there have been no prior
+** seeks on the cursor or if the most recent seek used a key equivalent
+** to P2.
+**
+** This instruction only works for indices.  The equivalent instruction
+** for tables is OP_Insert.
+*/
+case OP_IdxInsert: {        /* in2 */
+  VdbeCursor *pC;
+  BtreePayload x;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  sqlite3VdbeIncrWriteCounter(p, pC);
+  assert( pC!=0 );
+  assert( !isSorter(pC) );
+  pIn2 = &aMem[pOp->p2];
+  assert( (pIn2->flags & MEM_Blob) || (pOp->p5 & OPFLAG_PREFORMAT) );
+  if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->isTable==0 );
+  rc = ExpandBlob(pIn2);
+  if( rc ) goto abort_due_to_error;
+  x.nKey = pIn2->n;
+  x.pKey = pIn2->z;
+  x.aMem = aMem + pOp->p3;
+  x.nMem = (u16)pOp->p4.i;
+  rc = sqlite3BtreeInsert(pC->uc.pCursor, &x,
+       (pOp->p5 & (OPFLAG_APPEND|OPFLAG_SAVEPOSITION|OPFLAG_PREFORMAT)),
+      ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0)
+      );
+  assert( pC->deferredMoveto==0 );
+  pC->cacheStatus = CACHE_STALE;
+  if( rc) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: SorterInsert P1 P2 * * *
+** Synopsis: key=r[P2]
+**
+** Register P2 holds an SQL index key made using the
+** MakeRecord instructions.  This opcode writes that key
+** into the sorter P1.  Data for the entry is nil.
+*/
+case OP_SorterInsert: {     /* in2 */
+  VdbeCursor *pC;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  sqlite3VdbeIncrWriteCounter(p, pC);
+  assert( pC!=0 );
+  assert( isSorter(pC) );
+  pIn2 = &aMem[pOp->p2];
+  assert( pIn2->flags & MEM_Blob );
+  assert( pC->isTable==0 );
+  rc = ExpandBlob(pIn2);
+  if( rc ) goto abort_due_to_error;
+  rc = sqlite3VdbeSorterWrite(pC, pIn2);
+  if( rc) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: IdxDelete P1 P2 P3 * P5
+** Synopsis: key=r[P2@P3]
+**
+** The content of P3 registers starting at register P2 form
+** an unpacked index key. This opcode removes that entry from the
+** index opened by cursor P1.
+**
+** If P5 is not zero, then raise an SQLITE_CORRUPT_INDEX error
+** if no matching index entry is found.  This happens when running
+** an UPDATE or DELETE statement and the index entry to be updated
+** or deleted is not found.  For some uses of IdxDelete
+** (example:  the EXCEPT operator) it does not matter that no matching
+** entry is found.  For those cases, P5 is zero.  Also, do not raise
+** this (self-correcting and non-critical) error if in writable_schema mode.
+*/
+case OP_IdxDelete: {
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+  UnpackedRecord r;
+
+  assert( pOp->p3>0 );
+  assert( pOp->p2>0 && pOp->p2+pOp->p3<=(p->nMem+1 - p->nCursor)+1 );
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  sqlite3VdbeIncrWriteCounter(p, pC);
+  pCrsr = pC->uc.pCursor;
+  assert( pCrsr!=0 );
+  r.pKeyInfo = pC->pKeyInfo;
+  r.nField = (u16)pOp->p3;
+  r.default_rc = 0;
+  r.aMem = &aMem[pOp->p2];
+  rc = sqlite3BtreeIndexMoveto(pCrsr, &r, &res);
+  if( rc ) goto abort_due_to_error;
+  if( res==0 ){
+    rc = sqlite3BtreeDelete(pCrsr, BTREE_AUXDELETE);
+    if( rc ) goto abort_due_to_error;
+  }else if( pOp->p5 && !sqlite3WritableSchema(db) ){
+    rc = sqlite3ReportError(SQLITE_CORRUPT_INDEX, __LINE__, "index corruption");
+    goto abort_due_to_error;
+  }
+  assert( pC->deferredMoveto==0 );
+  pC->cacheStatus = CACHE_STALE;
+  pC->seekResult = 0;
+  break;
+}
+
+/* Opcode: DeferredSeek P1 * P3 P4 *
+** Synopsis: Move P3 to P1.rowid if needed
+**
+** P1 is an open index cursor and P3 is a cursor on the corresponding
+** table.  This opcode does a deferred seek of the P3 table cursor
+** to the row that corresponds to the current row of P1.
+**
+** This is a deferred seek.  Nothing actually happens until
+** the cursor is used to read a record.  That way, if no reads
+** occur, no unnecessary I/O happens.
+**
+** P4 may be an array of integers (type P4_INTARRAY) containing
+** one entry for each column in the P3 table.  If array entry a(i)
+** is non-zero, then reading column a(i)-1 from cursor P3 is
+** equivalent to performing the deferred seek and then reading column i
+** from P1.  This information is stored in P3 and used to redirect
+** reads against P3 over to P1, thus possibly avoiding the need to
+** seek and read cursor P3.
+*/
+/* Opcode: IdxRowid P1 P2 * * *
+** Synopsis: r[P2]=rowid
+**
+** Write into register P2 an integer which is the last entry in the record at
+** the end of the index key pointed to by cursor P1.  This integer should be
+** the rowid of the table entry to which this index entry points.
+**
+** See also: Rowid, MakeRecord.
+*/
+case OP_DeferredSeek:         /* ncycle */
+case OP_IdxRowid: {           /* out2, ncycle */
+  VdbeCursor *pC;             /* The P1 index cursor */
+  VdbeCursor *pTabCur;        /* The P2 table cursor (OP_DeferredSeek only) */
+  i64 rowid;                  /* Rowid that P1 current points to */
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE || IsNullCursor(pC) );
+  assert( pC->uc.pCursor!=0 );
+  assert( pC->isTable==0 || IsNullCursor(pC) );
+  assert( pC->deferredMoveto==0 );
+  assert( !pC->nullRow || pOp->opcode==OP_IdxRowid );
+
+  /* The IdxRowid and Seek opcodes are combined because of the commonality
+  ** of sqlite3VdbeCursorRestore() and sqlite3VdbeIdxRowid(). */
+  rc = sqlite3VdbeCursorRestore(pC);
+
+  /* sqlite3VdbeCursorRestore() may fail if the cursor has been disturbed
+  ** since it was last positioned and an error (e.g. OOM or an IO error)
+  ** occurs while trying to reposition it. */
+  if( rc!=SQLITE_OK ) goto abort_due_to_error;
+
+  if( !pC->nullRow ){
+    rowid = 0;  /* Not needed.  Only used to silence a warning. */
+    rc = sqlite3VdbeIdxRowid(db, pC->uc.pCursor, &rowid);
+    if( rc!=SQLITE_OK ){
+      goto abort_due_to_error;
+    }
+    if( pOp->opcode==OP_DeferredSeek ){
+      assert( pOp->p3>=0 && pOp->p3<p->nCursor );
+      pTabCur = p->apCsr[pOp->p3];
+      assert( pTabCur!=0 );
+      assert( pTabCur->eCurType==CURTYPE_BTREE );
+      assert( pTabCur->uc.pCursor!=0 );
+      assert( pTabCur->isTable );
+      pTabCur->nullRow = 0;
+      pTabCur->movetoTarget = rowid;
+      pTabCur->deferredMoveto = 1;
+      pTabCur->cacheStatus = CACHE_STALE;
+      assert( pOp->p4type==P4_INTARRAY || pOp->p4.ai==0 );
+      assert( !pTabCur->isEphemeral );
+      pTabCur->ub.aAltMap = pOp->p4.ai;
+      assert( !pC->isEphemeral );
+      pTabCur->pAltCursor = pC;
+    }else{
+      pOut = out2Prerelease(p, pOp);
+      pOut->u.i = rowid;
+    }
+  }else{
+    assert( pOp->opcode==OP_IdxRowid );
+    sqlite3VdbeMemSetNull(&aMem[pOp->p2]);
+  }
+  break;
+}
+
+/* Opcode: FinishSeek P1 * * * *
+**
+** If cursor P1 was previously moved via OP_DeferredSeek, complete that
+** seek operation now, without further delay.  If the cursor seek has
+** already occurred, this instruction is a no-op.
+*/
+case OP_FinishSeek: {        /* ncycle */
+  VdbeCursor *pC;            /* The P1 index cursor */
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  if( pC->deferredMoveto ){
+    rc = sqlite3VdbeFinishMoveto(pC);
+    if( rc ) goto abort_due_to_error;
+  }
+  break;
+}
+
+/* Opcode: IdxGE P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** The P4 register values beginning with P3 form an unpacked index
+** key that omits the PRIMARY KEY.  Compare this key value against the index
+** that P1 is currently pointing to, ignoring the PRIMARY KEY or ROWID
+** fields at the end.
+**
+** If the P1 index entry is greater than or equal to the key value
+** then jump to P2.  Otherwise fall through to the next instruction.
+*/
+/* Opcode: IdxGT P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** The P4 register values beginning with P3 form an unpacked index
+** key that omits the PRIMARY KEY.  Compare this key value against the index
+** that P1 is currently pointing to, ignoring the PRIMARY KEY or ROWID
+** fields at the end.
+**
+** If the P1 index entry is greater than the key value
+** then jump to P2.  Otherwise fall through to the next instruction.
+*/
+/* Opcode: IdxLT P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** The P4 register values beginning with P3 form an unpacked index
+** key that omits the PRIMARY KEY or ROWID.  Compare this key value against
+** the index that P1 is currently pointing to, ignoring the PRIMARY KEY or
+** ROWID on the P1 index.
+**
+** If the P1 index entry is less than the key value then jump to P2.
+** Otherwise fall through to the next instruction.
+*/
+/* Opcode: IdxLE P1 P2 P3 P4 *
+** Synopsis: key=r[P3@P4]
+**
+** The P4 register values beginning with P3 form an unpacked index
+** key that omits the PRIMARY KEY or ROWID.  Compare this key value against
+** the index that P1 is currently pointing to, ignoring the PRIMARY KEY or
+** ROWID on the P1 index.
+**
+** If the P1 index entry is less than or equal to the key value then jump
+** to P2. Otherwise fall through to the next instruction.
+*/
+case OP_IdxLE:          /* jump, ncycle */
+case OP_IdxGT:          /* jump, ncycle */
+case OP_IdxLT:          /* jump, ncycle */
+case OP_IdxGE:  {       /* jump, ncycle */
+  VdbeCursor *pC;
+  int res;
+  UnpackedRecord r;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->isOrdered );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0);
+  assert( pC->deferredMoveto==0 );
+  assert( pOp->p4type==P4_INT32 );
+  r.pKeyInfo = pC->pKeyInfo;
+  r.nField = (u16)pOp->p4.i;
+  if( pOp->opcode<OP_IdxLT ){
+    assert( pOp->opcode==OP_IdxLE || pOp->opcode==OP_IdxGT );
+    r.default_rc = -1;
+  }else{
+    assert( pOp->opcode==OP_IdxGE || pOp->opcode==OP_IdxLT );
+    r.default_rc = 0;
+  }
+  r.aMem = &aMem[pOp->p3];
+#ifdef SQLITE_DEBUG
+  {
+    int i;
+    for(i=0; i<r.nField; i++){
+      assert( memIsValid(&r.aMem[i]) );
+      REGISTER_TRACE(pOp->p3+i, &aMem[pOp->p3+i]);
+    }
+  }
+#endif
+
+  /* Inlined version of sqlite3VdbeIdxKeyCompare() */
+  {
+    i64 nCellKey = 0;
+    BtCursor *pCur;
+    Mem m;
+
+    assert( pC->eCurType==CURTYPE_BTREE );
+    pCur = pC->uc.pCursor;
+    assert( sqlite3BtreeCursorIsValid(pCur) );
+    nCellKey = sqlite3BtreePayloadSize(pCur);
+    /* nCellKey will always be between 0 and 0xffffffff because of the way
+    ** that btreeParseCellPtr() and sqlite3GetVarint32() are implemented */
+    if( nCellKey<=0 || nCellKey>0x7fffffff ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto abort_due_to_error;
+    }
+    sqlite3VdbeMemInit(&m, db, 0);
+    rc = sqlite3VdbeMemFromBtreeZeroOffset(pCur, (u32)nCellKey, &m);
+    if( rc ) goto abort_due_to_error;
+    res = sqlite3VdbeRecordCompareWithSkip(m.n, m.z, &r, 0);
+    sqlite3VdbeMemReleaseMalloc(&m);
+  }
+  /* End of inlined sqlite3VdbeIdxKeyCompare() */
+
+  assert( (OP_IdxLE&1)==(OP_IdxLT&1) && (OP_IdxGE&1)==(OP_IdxGT&1) );
+  if( (pOp->opcode&1)==(OP_IdxLT&1) ){
+    assert( pOp->opcode==OP_IdxLE || pOp->opcode==OP_IdxLT );
+    res = -res;
+  }else{
+    assert( pOp->opcode==OP_IdxGE || pOp->opcode==OP_IdxGT );
+    res++;
+  }
+  VdbeBranchTaken(res>0,2);
+  assert( rc==SQLITE_OK );
+  if( res>0 ) goto jump_to_p2;
+  break;
+}
+
+/* Opcode: Destroy P1 P2 P3 * *
+**
+** Delete an entire database table or index whose root page in the database
+** file is given by P1.
+**
+** The table being destroyed is in the main database file if P3==0.  If
+** P3==1 then the table to be destroyed is in the auxiliary database file
+** that is used to store tables create using CREATE TEMPORARY TABLE.
+**
+** If AUTOVACUUM is enabled then it is possible that another root page
+** might be moved into the newly deleted root page in order to keep all
+** root pages contiguous at the beginning of the database.  The former
+** value of the root page that moved - its value before the move occurred -
+** is stored in register P2. If no page movement was required (because the
+** table being dropped was already the last one in the database) then a
+** zero is stored in register P2.  If AUTOVACUUM is disabled then a zero
+** is stored in register P2.
+**
+** This opcode throws an error if there are any active reader VMs when
+** it is invoked. This is done to avoid the difficulty associated with
+** updating existing cursors when a root page is moved in an AUTOVACUUM
+** database. This error is thrown even if the database is not an AUTOVACUUM
+** db in order to avoid introducing an incompatibility between autovacuum
+** and non-autovacuum modes.
+**
+** See also: Clear
+*/
+case OP_Destroy: {     /* out2 */
+  int iMoved;
+  int iDb;
+
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  assert( p->readOnly==0 );
+  assert( pOp->p1>1 );
+  pOut = out2Prerelease(p, pOp);
+  pOut->flags = MEM_Null;
+  if( db->nVdbeRead > db->nVDestroy+1 ){
+    rc = SQLITE_LOCKED;
+    p->errorAction = OE_Abort;
+    goto abort_due_to_error;
+  }else{
+    iDb = pOp->p3;
+    assert( DbMaskTest(p->btreeMask, iDb) );
+    iMoved = 0;  /* Not needed.  Only to silence a warning. */
+    rc = sqlite3BtreeDropTable(db->aDb[iDb].pBt, pOp->p1, &iMoved);
+    pOut->flags = MEM_Int;
+    pOut->u.i = iMoved;
+    if( rc ) goto abort_due_to_error;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( iMoved!=0 ){
+      sqlite3RootPageMoved(db, iDb, iMoved, pOp->p1);
+      /* All OP_Destroy operations occur on the same btree */
+      assert( resetSchemaOnFault==0 || resetSchemaOnFault==iDb+1 );
+      resetSchemaOnFault = iDb+1;
+    }
+#endif
+  }
+  break;
+}
+
+/* Opcode: Clear P1 P2 P3
+**
+** Delete all contents of the database table or index whose root page
+** in the database file is given by P1.  But, unlike Destroy, do not
+** remove the table or index from the database file.
+**
+** The table being cleared is in the main database file if P2==0.  If
+** P2==1 then the table to be cleared is in the auxiliary database file
+** that is used to store tables create using CREATE TEMPORARY TABLE.
+**
+** If the P3 value is non-zero, then the row change count is incremented
+** by the number of rows in the table being cleared. If P3 is greater
+** than zero, then the value stored in register P3 is also incremented
+** by the number of rows in the table being cleared.
+**
+** See also: Destroy
+*/
+case OP_Clear: {
+  i64 nChange;
+
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  nChange = 0;
+  assert( p->readOnly==0 );
+  assert( DbMaskTest(p->btreeMask, pOp->p2) );
+  rc = sqlite3BtreeClearTable(db->aDb[pOp->p2].pBt, (u32)pOp->p1, &nChange);
+  if( pOp->p3 ){
+    p->nChange += nChange;
+    if( pOp->p3>0 ){
+      assert( memIsValid(&aMem[pOp->p3]) );
+      memAboutToChange(p, &aMem[pOp->p3]);
+      aMem[pOp->p3].u.i += nChange;
+    }
+  }
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
+/* Opcode: ResetSorter P1 * * * *
+**
+** Delete all contents from the ephemeral table or sorter
+** that is open on cursor P1.
+**
+** This opcode only works for cursors used for sorting and
+** opened with OP_OpenEphemeral or OP_SorterOpen.
+*/
+case OP_ResetSorter: {
+  VdbeCursor *pC;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  if( isSorter(pC) ){
+    sqlite3VdbeSorterReset(db, pC->uc.pSorter);
+  }else{
+    assert( pC->eCurType==CURTYPE_BTREE );
+    assert( pC->isEphemeral );
+    rc = sqlite3BtreeClearTableOfCursor(pC->uc.pCursor);
+    if( rc ) goto abort_due_to_error;
+  }
+  break;
+}
+
+/* Opcode: CreateBtree P1 P2 P3 * *
+** Synopsis: r[P2]=root iDb=P1 flags=P3
+**
+** Allocate a new b-tree in the main database file if P1==0 or in the
+** TEMP database file if P1==1 or in an attached database if
+** P1>1.  The P3 argument must be 1 (BTREE_INTKEY) for a rowid table
+** it must be 2 (BTREE_BLOBKEY) for an index or WITHOUT ROWID table.
+** The root page number of the new b-tree is stored in register P2.
+*/
+case OP_CreateBtree: {          /* out2 */
+  Pgno pgno;
+  Db *pDb;
+
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  pOut = out2Prerelease(p, pOp);
+  pgno = 0;
+  assert( pOp->p3==BTREE_INTKEY || pOp->p3==BTREE_BLOBKEY );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( DbMaskTest(p->btreeMask, pOp->p1) );
+  assert( p->readOnly==0 );
+  pDb = &db->aDb[pOp->p1];
+  assert( pDb->pBt!=0 );
+  rc = sqlite3BtreeCreateTable(pDb->pBt, &pgno, pOp->p3);
+  if( rc ) goto abort_due_to_error;
+  pOut->u.i = pgno;
+  break;
+}
+
+/* Opcode: SqlExec * * * P4 *
+**
+** Run the SQL statement or statements specified in the P4 string.
+** Disable Auth and Trace callbacks while those statements are running if
+** P1 is true.
+*/
+case OP_SqlExec: {
+  char *zErr;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  sqlite3_xauth xAuth;
+#endif
+  u8 mTrace;
+
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  db->nSqlExec++;
+  zErr = 0;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  xAuth = db->xAuth;
+#endif
+  mTrace = db->mTrace;
+  if( pOp->p1 ){
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    db->xAuth = 0;
+#endif
+    db->mTrace = 0;
+  }
+  rc = sqlite3_exec(db, pOp->p4.z, 0, 0, &zErr);
+  db->nSqlExec--;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  db->xAuth = xAuth;
+#endif
+  db->mTrace = mTrace;
+  if( zErr || rc ){
+    sqlite3VdbeError(p, "%s", zErr);
+    sqlite3_free(zErr);
+    if( rc==SQLITE_NOMEM ) goto no_mem;
+    goto abort_due_to_error;
+  }
+  break;
+}
+
+/* Opcode: ParseSchema P1 * * P4 *
+**
+** Read and parse all entries from the schema table of database P1
+** that match the WHERE clause P4.  If P4 is a NULL pointer, then the
+** entire schema for P1 is reparsed.
+**
+** This opcode invokes the parser to create a new virtual machine,
+** then runs the new virtual machine.  It is thus a re-entrant opcode.
+*/
+case OP_ParseSchema: {
+  int iDb;
+  const char *zSchema;
+  char *zSql;
+  InitData initData;
+
+  /* Any prepared statement that invokes this opcode will hold mutexes
+  ** on every btree.  This is a prerequisite for invoking
+  ** sqlite3InitCallback().
+  */
+#ifdef SQLITE_DEBUG
+  for(iDb=0; iDb<db->nDb; iDb++){
+    assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
+  }
+#endif
+
+  iDb = pOp->p1;
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( DbHasProperty(db, iDb, DB_SchemaLoaded)
+           || db->mallocFailed
+           || (CORRUPT_DB && (db->flags & SQLITE_NoSchemaError)!=0) );
+
+#ifndef SQLITE_OMIT_ALTERTABLE
+  if( pOp->p4.z==0 ){
+    sqlite3SchemaClear(db->aDb[iDb].pSchema);
+    db->mDbFlags &= ~DBFLAG_SchemaKnownOk;
+    rc = sqlite3InitOne(db, iDb, &p->zErrMsg, pOp->p5);
+    db->mDbFlags |= DBFLAG_SchemaChange;
+    p->expired = 0;
+  }else
+#endif
+  {
+    zSchema = LEGACY_SCHEMA_TABLE;
+    initData.db = db;
+    initData.iDb = iDb;
+    initData.pzErrMsg = &p->zErrMsg;
+    initData.mInitFlags = 0;
+    initData.mxPage = sqlite3BtreeLastPage(db->aDb[iDb].pBt);
+    zSql = sqlite3MPrintf(db,
+       "SELECT*FROM\"%w\".%s WHERE %s ORDER BY rowid",
+       db->aDb[iDb].zDbSName, zSchema, pOp->p4.z);
+    if( zSql==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+    }else{
+      assert( db->init.busy==0 );
+      db->init.busy = 1;
+      initData.rc = SQLITE_OK;
+      initData.nInitRow = 0;
+      assert( !db->mallocFailed );
+      rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
+      if( rc==SQLITE_OK ) rc = initData.rc;
+      if( rc==SQLITE_OK && initData.nInitRow==0 ){
+        /* The OP_ParseSchema opcode with a non-NULL P4 argument should parse
+        ** at least one SQL statement. Any less than that indicates that
+        ** the sqlite_schema table is corrupt. */
+        rc = SQLITE_CORRUPT_BKPT;
+      }
+      sqlite3DbFreeNN(db, zSql);
+      db->init.busy = 0;
+    }
+  }
+  if( rc ){
+    sqlite3ResetAllSchemasOfConnection(db);
+    if( rc==SQLITE_NOMEM ){
+      goto no_mem;
+    }
+    goto abort_due_to_error;
+  }
+  break; 
+}
+
+#if !defined(SQLITE_OMIT_ANALYZE)
+/* Opcode: LoadAnalysis P1 * * * *
+**
+** Read the sqlite_stat1 table for database P1 and load the content
+** of that table into the internal index hash table.  This will cause
+** the analysis to be used when preparing all subsequent queries.
+*/
+case OP_LoadAnalysis: {
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  rc = sqlite3AnalysisLoad(db, pOp->p1);
+  if( rc ) goto abort_due_to_error;
+  break; 
+}
+#endif /* !defined(SQLITE_OMIT_ANALYZE) */
+
+/* Opcode: DropTable P1 * * P4 *
+**
+** Remove the internal (in-memory) data structures that describe
+** the table named P4 in database P1.  This is called after a table
+** is dropped from disk (using the Destroy opcode) in order to keep
+** the internal representation of the
+** schema consistent with what is on disk.
+*/
+case OP_DropTable: {
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  sqlite3UnlinkAndDeleteTable(db, pOp->p1, pOp->p4.z);
+  break;
+}
+
+/* Opcode: DropIndex P1 * * P4 *
+**
+** Remove the internal (in-memory) data structures that describe
+** the index named P4 in database P1.  This is called after an index
+** is dropped from disk (using the Destroy opcode)
+** in order to keep the internal representation of the
+** schema consistent with what is on disk.
+*/
+case OP_DropIndex: {
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  sqlite3UnlinkAndDeleteIndex(db, pOp->p1, pOp->p4.z);
+  break;
+}
+
+/* Opcode: DropTrigger P1 * * P4 *
+**
+** Remove the internal (in-memory) data structures that describe
+** the trigger named P4 in database P1.  This is called after a trigger
+** is dropped from disk (using the Destroy opcode) in order to keep
+** the internal representation of the
+** schema consistent with what is on disk.
+*/
+case OP_DropTrigger: {
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  sqlite3UnlinkAndDeleteTrigger(db, pOp->p1, pOp->p4.z);
+  break;
+}
+
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/* Opcode: IntegrityCk P1 P2 P3 P4 P5
+**
+** Do an analysis of the currently open database.  Store in
+** register P1 the text of an error message describing any problems.
+** If no problems are found, store a NULL in register P1.
+**
+** The register P3 contains one less than the maximum number of allowed errors.
+** At most reg(P3) errors will be reported.
+** In other words, the analysis stops as soon as reg(P1) errors are
+** seen.  Reg(P1) is updated with the number of errors remaining.
+**
+** The root page numbers of all tables in the database are integers
+** stored in P4_INTARRAY argument.
+**
+** If P5 is not zero, the check is done on the auxiliary database
+** file, not the main database file.
+**
+** This opcode is used to implement the integrity_check pragma.
+*/
+case OP_IntegrityCk: {
+  int nRoot;      /* Number of tables to check.  (Number of root pages.) */
+  Pgno *aRoot;    /* Array of rootpage numbers for tables to be checked */
+  int nErr;       /* Number of errors reported */
+  char *z;        /* Text of the error report */
+  Mem *pnErr;     /* Register keeping track of errors remaining */
+
+  assert( p->bIsReader );
+  nRoot = pOp->p2;
+  aRoot = pOp->p4.ai;
+  assert( nRoot>0 );
+  assert( aRoot[0]==(Pgno)nRoot );
+  assert( pOp->p3>0 && pOp->p3<=(p->nMem+1 - p->nCursor) );
+  pnErr = &aMem[pOp->p3];
+  assert( (pnErr->flags & MEM_Int)!=0 );
+  assert( (pnErr->flags & (MEM_Str|MEM_Blob))==0 );
+  pIn1 = &aMem[pOp->p1];
+  assert( pOp->p5<db->nDb );
+  assert( DbMaskTest(p->btreeMask, pOp->p5) );
+  rc = sqlite3BtreeIntegrityCheck(db, db->aDb[pOp->p5].pBt, &aRoot[1], nRoot,
+                                 (int)pnErr->u.i+1, &nErr, &z);
+  sqlite3VdbeMemSetNull(pIn1);
+  if( nErr==0 ){
+    assert( z==0 );
+  }else if( rc ){
+    sqlite3_free(z);
+    goto abort_due_to_error;
+  }else{
+    pnErr->u.i -= nErr-1;
+    sqlite3VdbeMemSetStr(pIn1, z, -1, SQLITE_UTF8, sqlite3_free);
+  }
+  UPDATE_MAX_BLOBSIZE(pIn1);
+  sqlite3VdbeChangeEncoding(pIn1, encoding);
+  goto check_for_interrupt;
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+/* Opcode: RowSetAdd P1 P2 * * *
+** Synopsis: rowset(P1)=r[P2]
+**
+** Insert the integer value held by register P2 into a RowSet object
+** held in register P1.
+**
+** An assertion fails if P2 is not an integer.
+*/
+case OP_RowSetAdd: {       /* in1, in2 */
+  pIn1 = &aMem[pOp->p1];
+  pIn2 = &aMem[pOp->p2];
+  assert( (pIn2->flags & MEM_Int)!=0 );
+  if( (pIn1->flags & MEM_Blob)==0 ){
+    if( sqlite3VdbeMemSetRowSet(pIn1) ) goto no_mem;
+  }
+  assert( sqlite3VdbeMemIsRowSet(pIn1) );
+  sqlite3RowSetInsert((RowSet*)pIn1->z, pIn2->u.i);
+  break;
+}
+
+/* Opcode: RowSetRead P1 P2 P3 * *
+** Synopsis: r[P3]=rowset(P1)
+**
+** Extract the smallest value from the RowSet object in P1
+** and put that value into register P3.
+** Or, if RowSet object P1 is initially empty, leave P3
+** unchanged and jump to instruction P2.
+*/
+case OP_RowSetRead: {       /* jump, in1, out3 */
+  i64 val;
+
+  pIn1 = &aMem[pOp->p1];
+  assert( (pIn1->flags & MEM_Blob)==0 || sqlite3VdbeMemIsRowSet(pIn1) );
+  if( (pIn1->flags & MEM_Blob)==0
+   || sqlite3RowSetNext((RowSet*)pIn1->z, &val)==0
+  ){
+    /* The boolean index is empty */
+    sqlite3VdbeMemSetNull(pIn1);
+    VdbeBranchTaken(1,2);
+    goto jump_to_p2_and_check_for_interrupt;
+  }else{
+    /* A value was pulled from the index */
+    VdbeBranchTaken(0,2);
+    sqlite3VdbeMemSetInt64(&aMem[pOp->p3], val);
+  }
+  goto check_for_interrupt;
+}
+
+/* Opcode: RowSetTest P1 P2 P3 P4
+** Synopsis: if r[P3] in rowset(P1) goto P2
+**
+** Register P3 is assumed to hold a 64-bit integer value. If register P1
+** contains a RowSet object and that RowSet object contains
+** the value held in P3, jump to register P2. Otherwise, insert the
+** integer in P3 into the RowSet and continue on to the
+** next opcode.
+**
+** The RowSet object is optimized for the case where sets of integers
+** are inserted in distinct phases, which each set contains no duplicates.
+** Each set is identified by a unique P4 value. The first set
+** must have P4==0, the final set must have P4==-1, and for all other sets
+** must have P4>0.
+**
+** This allows optimizations: (a) when P4==0 there is no need to test
+** the RowSet object for P3, as it is guaranteed not to contain it,
+** (b) when P4==-1 there is no need to insert the value, as it will
+** never be tested for, and (c) when a value that is part of set X is
+** inserted, there is no need to search to see if the same value was
+** previously inserted as part of set X (only if it was previously
+** inserted as part of some other set).
+*/
+case OP_RowSetTest: {                     /* jump, in1, in3 */
+  int iSet;
+  int exists;
+
+  pIn1 = &aMem[pOp->p1];
+  pIn3 = &aMem[pOp->p3];
+  iSet = pOp->p4.i;
+  assert( pIn3->flags&MEM_Int );
+
+  /* If there is anything other than a rowset object in memory cell P1,
+  ** delete it now and initialize P1 with an empty rowset
+  */
+  if( (pIn1->flags & MEM_Blob)==0 ){
+    if( sqlite3VdbeMemSetRowSet(pIn1) ) goto no_mem;
+  }
+  assert( sqlite3VdbeMemIsRowSet(pIn1) );
+  assert( pOp->p4type==P4_INT32 );
+  assert( iSet==-1 || iSet>=0 );
+  if( iSet ){
+    exists = sqlite3RowSetTest((RowSet*)pIn1->z, iSet, pIn3->u.i);
+    VdbeBranchTaken(exists!=0,2);
+    if( exists ) goto jump_to_p2;
+  }
+  if( iSet>=0 ){
+    sqlite3RowSetInsert((RowSet*)pIn1->z, pIn3->u.i);
+  }
+  break;
+}
+
+
+#ifndef SQLITE_OMIT_TRIGGER
+
+/* Opcode: Program P1 P2 P3 P4 P5
+**
+** Execute the trigger program passed as P4 (type P4_SUBPROGRAM).
+**
+** P1 contains the address of the memory cell that contains the first memory
+** cell in an array of values used as arguments to the sub-program. P2
+** contains the address to jump to if the sub-program throws an IGNORE
+** exception using the RAISE() function. Register P3 contains the address
+** of a memory cell in this (the parent) VM that is used to allocate the
+** memory required by the sub-vdbe at runtime.
+**
+** P4 is a pointer to the VM containing the trigger program.
+**
+** If P5 is non-zero, then recursive program invocation is enabled.
+*/
+case OP_Program: {        /* jump */
+  int nMem;               /* Number of memory registers for sub-program */
+  int nByte;              /* Bytes of runtime space required for sub-program */
+  Mem *pRt;               /* Register to allocate runtime space */
+  Mem *pMem;              /* Used to iterate through memory cells */
+  Mem *pEnd;              /* Last memory cell in new array */
+  VdbeFrame *pFrame;      /* New vdbe frame to execute in */
+  SubProgram *pProgram;   /* Sub-program to execute */
+  void *t;                /* Token identifying trigger */
+
+  pProgram = pOp->p4.pProgram;
+  pRt = &aMem[pOp->p3];
+  assert( pProgram->nOp>0 );
+ 
+  /* If the p5 flag is clear, then recursive invocation of triggers is
+  ** disabled for backwards compatibility (p5 is set if this sub-program
+  ** is really a trigger, not a foreign key action, and the flag set
+  ** and cleared by the "PRAGMA recursive_triggers" command is clear).
+  **
+  ** It is recursive invocation of triggers, at the SQL level, that is
+  ** disabled. In some cases a single trigger may generate more than one
+  ** SubProgram (if the trigger may be executed with more than one different
+  ** ON CONFLICT algorithm). SubProgram structures associated with a
+  ** single trigger all have the same value for the SubProgram.token
+  ** variable.  */
+  if( pOp->p5 ){
+    t = pProgram->token;
+    for(pFrame=p->pFrame; pFrame && pFrame->token!=t; pFrame=pFrame->pParent);
+    if( pFrame ) break;
+  }
+
+  if( p->nFrame>=db->aLimit[SQLITE_LIMIT_TRIGGER_DEPTH] ){
+    rc = SQLITE_ERROR;
+    sqlite3VdbeError(p, "too many levels of trigger recursion");
+    goto abort_due_to_error;
+  }
+
+  /* Register pRt is used to store the memory required to save the state
+  ** of the current program, and the memory required at runtime to execute
+  ** the trigger program. If this trigger has been fired before, then pRt
+  ** is already allocated. Otherwise, it must be initialized.  */
+  if( (pRt->flags&MEM_Blob)==0 ){
+    /* SubProgram.nMem is set to the number of memory cells used by the
+    ** program stored in SubProgram.aOp. As well as these, one memory
+    ** cell is required for each cursor used by the program. Set local
+    ** variable nMem (and later, VdbeFrame.nChildMem) to this value.
+    */
+    nMem = pProgram->nMem + pProgram->nCsr;
+    assert( nMem>0 );
+    if( pProgram->nCsr==0 ) nMem++;
+    nByte = ROUND8(sizeof(VdbeFrame))
+              + nMem * sizeof(Mem)
+              + pProgram->nCsr * sizeof(VdbeCursor*)
+              + (pProgram->nOp + 7)/8;
+    pFrame = sqlite3DbMallocZero(db, nByte);
+    if( !pFrame ){
+      goto no_mem;
+    }
+    sqlite3VdbeMemRelease(pRt);
+    pRt->flags = MEM_Blob|MEM_Dyn;
+    pRt->z = (char*)pFrame;
+    pRt->n = nByte;
+    pRt->xDel = sqlite3VdbeFrameMemDel;
+
+    pFrame->v = p;
+    pFrame->nChildMem = nMem;
+    pFrame->nChildCsr = pProgram->nCsr;
+    pFrame->pc = (int)(pOp - aOp);
+    pFrame->aMem = p->aMem;
+    pFrame->nMem = p->nMem;
+    pFrame->apCsr = p->apCsr;
+    pFrame->nCursor = p->nCursor;
+    pFrame->aOp = p->aOp;
+    pFrame->nOp = p->nOp;
+    pFrame->token = pProgram->token;
+#ifdef SQLITE_DEBUG
+    pFrame->iFrameMagic = SQLITE_FRAME_MAGIC;
+#endif
+
+    pEnd = &VdbeFrameMem(pFrame)[pFrame->nChildMem];
+    for(pMem=VdbeFrameMem(pFrame); pMem!=pEnd; pMem++){
+      pMem->flags = MEM_Undefined;
+      pMem->db = db;
+    }
+  }else{
+    pFrame = (VdbeFrame*)pRt->z;
+    assert( pRt->xDel==sqlite3VdbeFrameMemDel );
+    assert( pProgram->nMem+pProgram->nCsr==pFrame->nChildMem
+        || (pProgram->nCsr==0 && pProgram->nMem+1==pFrame->nChildMem) );
+    assert( pProgram->nCsr==pFrame->nChildCsr );
+    assert( (int)(pOp - aOp)==pFrame->pc );
+  }
+
+  p->nFrame++;
+  pFrame->pParent = p->pFrame;
+  pFrame->lastRowid = db->lastRowid;
+  pFrame->nChange = p->nChange;
+  pFrame->nDbChange = p->db->nChange;
+  assert( pFrame->pAuxData==0 );
+  pFrame->pAuxData = p->pAuxData;
+  p->pAuxData = 0;
+  p->nChange = 0;
+  p->pFrame = pFrame;
+  p->aMem = aMem = VdbeFrameMem(pFrame);
+  p->nMem = pFrame->nChildMem;
+  p->nCursor = (u16)pFrame->nChildCsr;
+  p->apCsr = (VdbeCursor **)&aMem[p->nMem];
+  pFrame->aOnce = (u8*)&p->apCsr[pProgram->nCsr];
+  memset(pFrame->aOnce, 0, (pProgram->nOp + 7)/8);
+  p->aOp = aOp = pProgram->aOp;
+  p->nOp = pProgram->nOp;
+#ifdef SQLITE_DEBUG
+  /* Verify that second and subsequent executions of the same trigger do not
+  ** try to reuse register values from the first use. */
+  {
+    int i;
+    for(i=0; i<p->nMem; i++){
+      aMem[i].pScopyFrom = 0;  /* Prevent false-positive AboutToChange() errs */
+      MemSetTypeFlag(&aMem[i], MEM_Undefined); /* Fault if this reg is reused */
+    }
+  }
+#endif
+  pOp = &aOp[-1];
+  goto check_for_interrupt;
+}
+
+/* Opcode: Param P1 P2 * * *
+**
+** This opcode is only ever present in sub-programs called via the
+** OP_Program instruction. Copy a value currently stored in a memory
+** cell of the calling (parent) frame to cell P2 in the current frames
+** address space. This is used by trigger programs to access the new.*
+** and old.* values.
+**
+** The address of the cell in the parent frame is determined by adding
+** the value of the P1 argument to the value of the P1 argument to the
+** calling OP_Program instruction.
+*/
+case OP_Param: {           /* out2 */
+  VdbeFrame *pFrame;
+  Mem *pIn;
+  pOut = out2Prerelease(p, pOp);
+  pFrame = p->pFrame;
+  pIn = &pFrame->aMem[pOp->p1 + pFrame->aOp[pFrame->pc].p1];  
+  sqlite3VdbeMemShallowCopy(pOut, pIn, MEM_Ephem);
+  break;
+}
+
+#endif /* #ifndef SQLITE_OMIT_TRIGGER */
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+/* Opcode: FkCounter P1 P2 * * *
+** Synopsis: fkctr[P1]+=P2
+**
+** Increment a "constraint counter" by P2 (P2 may be negative or positive).
+** If P1 is non-zero, the database constraint counter is incremented
+** (deferred foreign key constraints). Otherwise, if P1 is zero, the
+** statement counter is incremented (immediate foreign key constraints).
+*/
+case OP_FkCounter: {
+  if( db->flags & SQLITE_DeferFKs ){
+    db->nDeferredImmCons += pOp->p2;
+  }else if( pOp->p1 ){
+    db->nDeferredCons += pOp->p2;
+  }else{
+    p->nFkConstraint += pOp->p2;
+  }
+  break;
+}
+
+/* Opcode: FkIfZero P1 P2 * * *
+** Synopsis: if fkctr[P1]==0 goto P2
+**
+** This opcode tests if a foreign key constraint-counter is currently zero.
+** If so, jump to instruction P2. Otherwise, fall through to the next
+** instruction.
+**
+** If P1 is non-zero, then the jump is taken if the database constraint-counter
+** is zero (the one that counts deferred constraint violations). If P1 is
+** zero, the jump is taken if the statement constraint-counter is zero
+** (immediate foreign key constraint violations).
+*/
+case OP_FkIfZero: {         /* jump */
+  if( pOp->p1 ){
+    VdbeBranchTaken(db->nDeferredCons==0 && db->nDeferredImmCons==0, 2);
+    if( db->nDeferredCons==0 && db->nDeferredImmCons==0 ) goto jump_to_p2;
+  }else{
+    VdbeBranchTaken(p->nFkConstraint==0 && db->nDeferredImmCons==0, 2);
+    if( p->nFkConstraint==0 && db->nDeferredImmCons==0 ) goto jump_to_p2;
+  }
+  break;
+}
+#endif /* #ifndef SQLITE_OMIT_FOREIGN_KEY */
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+/* Opcode: MemMax P1 P2 * * *
+** Synopsis: r[P1]=max(r[P1],r[P2])
+**
+** P1 is a register in the root frame of this VM (the root frame is
+** different from the current frame if this instruction is being executed
+** within a sub-program). Set the value of register P1 to the maximum of
+** its current value and the value in register P2.
+**
+** This instruction throws an error if the memory cell is not initially
+** an integer.
+*/
+case OP_MemMax: {        /* in2 */
+  VdbeFrame *pFrame;
+  if( p->pFrame ){
+    for(pFrame=p->pFrame; pFrame->pParent; pFrame=pFrame->pParent);
+    pIn1 = &pFrame->aMem[pOp->p1];
+  }else{
+    pIn1 = &aMem[pOp->p1];
+  }
+  assert( memIsValid(pIn1) );
+  sqlite3VdbeMemIntegerify(pIn1);
+  pIn2 = &aMem[pOp->p2];
+  sqlite3VdbeMemIntegerify(pIn2);
+  if( pIn1->u.i<pIn2->u.i){
+    pIn1->u.i = pIn2->u.i;
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_AUTOINCREMENT */
+
+/* Opcode: IfPos P1 P2 P3 * *
+** Synopsis: if r[P1]>0 then r[P1]-=P3, goto P2
+**
+** Register P1 must contain an integer.
+** If the value of register P1 is 1 or greater, subtract P3 from the
+** value in P1 and jump to P2.
+**
+** If the initial value of register P1 is less than 1, then the
+** value is unchanged and control passes through to the next instruction.
+*/
+case OP_IfPos: {        /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags&MEM_Int );
+  VdbeBranchTaken( pIn1->u.i>0, 2);
+  if( pIn1->u.i>0 ){
+    pIn1->u.i -= pOp->p3;
+    goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: OffsetLimit P1 P2 P3 * *
+** Synopsis: if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1)
+**
+** This opcode performs a commonly used computation associated with
+** LIMIT and OFFSET processing.  r[P1] holds the limit counter.  r[P3]
+** holds the offset counter.  The opcode computes the combined value
+** of the LIMIT and OFFSET and stores that value in r[P2].  The r[P2]
+** value computed is the total number of rows that will need to be
+** visited in order to complete the query.
+**
+** If r[P3] is zero or negative, that means there is no OFFSET
+** and r[P2] is set to be the value of the LIMIT, r[P1].
+**
+** if r[P1] is zero or negative, that means there is no LIMIT
+** and r[P2] is set to -1.
+**
+** Otherwise, r[P2] is set to the sum of r[P1] and r[P3].
+*/
+case OP_OffsetLimit: {    /* in1, out2, in3 */
+  i64 x;
+  pIn1 = &aMem[pOp->p1];
+  pIn3 = &aMem[pOp->p3];
+  pOut = out2Prerelease(p, pOp);
+  assert( pIn1->flags & MEM_Int );
+  assert( pIn3->flags & MEM_Int );
+  x = pIn1->u.i;
+  if( x<=0 || sqlite3AddInt64(&x, pIn3->u.i>0?pIn3->u.i:0) ){
+    /* If the LIMIT is less than or equal to zero, loop forever.  This
+    ** is documented.  But also, if the LIMIT+OFFSET exceeds 2^63 then
+    ** also loop forever.  This is undocumented.  In fact, one could argue
+    ** that the loop should terminate.  But assuming 1 billion iterations
+    ** per second (far exceeding the capabilities of any current hardware)
+    ** it would take nearly 300 years to actually reach the limit.  So
+    ** looping forever is a reasonable approximation. */
+    pOut->u.i = -1;
+  }else{
+    pOut->u.i = x;
+  }
+  break;
+}
+
+/* Opcode: IfNotZero P1 P2 * * *
+** Synopsis: if r[P1]!=0 then r[P1]--, goto P2
+**
+** Register P1 must contain an integer.  If the content of register P1 is
+** initially greater than zero, then decrement the value in register P1.
+** If it is non-zero (negative or positive) and then also jump to P2. 
+** If register P1 is initially zero, leave it unchanged and fall through.
+*/
+case OP_IfNotZero: {        /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags&MEM_Int );
+  VdbeBranchTaken(pIn1->u.i<0, 2);
+  if( pIn1->u.i ){
+     if( pIn1->u.i>0 ) pIn1->u.i--;
+     goto jump_to_p2;
+  }
+  break;
+}
+
+/* Opcode: DecrJumpZero P1 P2 * * *
+** Synopsis: if (--r[P1])==0 goto P2
+**
+** Register P1 must hold an integer.  Decrement the value in P1
+** and jump to P2 if the new value is exactly zero.
+*/
+case OP_DecrJumpZero: {      /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags&MEM_Int );
+  if( pIn1->u.i>SMALLEST_INT64 ) pIn1->u.i--;
+  VdbeBranchTaken(pIn1->u.i==0, 2);
+  if( pIn1->u.i==0 ) goto jump_to_p2;
+  break;
+}
+
+
+/* Opcode: AggStep * P2 P3 P4 P5
+** Synopsis: accum=r[P3] step(r[P2@P5])
+**
+** Execute the xStep function for an aggregate.
+** The function has P5 arguments.  P4 is a pointer to the
+** FuncDef structure that specifies the function.  Register P3 is the
+** accumulator.
+**
+** The P5 arguments are taken from register P2 and its
+** successors.
+*/
+/* Opcode: AggInverse * P2 P3 P4 P5
+** Synopsis: accum=r[P3] inverse(r[P2@P5])
+**
+** Execute the xInverse function for an aggregate.
+** The function has P5 arguments.  P4 is a pointer to the
+** FuncDef structure that specifies the function.  Register P3 is the
+** accumulator.
+**
+** The P5 arguments are taken from register P2 and its
+** successors.
+*/
+/* Opcode: AggStep1 P1 P2 P3 P4 P5
+** Synopsis: accum=r[P3] step(r[P2@P5])
+**
+** Execute the xStep (if P1==0) or xInverse (if P1!=0) function for an
+** aggregate.  The function has P5 arguments.  P4 is a pointer to the
+** FuncDef structure that specifies the function.  Register P3 is the
+** accumulator.
+**
+** The P5 arguments are taken from register P2 and its
+** successors.
+**
+** This opcode is initially coded as OP_AggStep0.  On first evaluation,
+** the FuncDef stored in P4 is converted into an sqlite3_context and
+** the opcode is changed.  In this way, the initialization of the
+** sqlite3_context only happens once, instead of on each call to the
+** step function.
+*/
+case OP_AggInverse:
+case OP_AggStep: {
+  int n;
+  sqlite3_context *pCtx;
+
+  assert( pOp->p4type==P4_FUNCDEF );
+  n = pOp->p5;
+  assert( pOp->p3>0 && pOp->p3<=(p->nMem+1 - p->nCursor) );
+  assert( n==0 || (pOp->p2>0 && pOp->p2+n<=(p->nMem+1 - p->nCursor)+1) );
+  assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
+  pCtx = sqlite3DbMallocRawNN(db, n*sizeof(sqlite3_value*) +
+               (sizeof(pCtx[0]) + sizeof(Mem) - sizeof(sqlite3_value*)));
+  if( pCtx==0 ) goto no_mem;
+  pCtx->pMem = 0;
+  pCtx->pOut = (Mem*)&(pCtx->argv[n]);
+  sqlite3VdbeMemInit(pCtx->pOut, db, MEM_Null);
+  pCtx->pFunc = pOp->p4.pFunc;
+  pCtx->iOp = (int)(pOp - aOp);
+  pCtx->pVdbe = p;
+  pCtx->skipFlag = 0;
+  pCtx->isError = 0;
+  pCtx->enc = encoding;
+  pCtx->argc = n;
+  pOp->p4type = P4_FUNCCTX;
+  pOp->p4.pCtx = pCtx;
+
+  /* OP_AggInverse must have P1==1 and OP_AggStep must have P1==0 */
+  assert( pOp->p1==(pOp->opcode==OP_AggInverse) );
+
+  pOp->opcode = OP_AggStep1;
+  /* Fall through into OP_AggStep */
+  /* no break */ deliberate_fall_through
+}
+case OP_AggStep1: {
+  int i;
+  sqlite3_context *pCtx;
+  Mem *pMem;
+
+  assert( pOp->p4type==P4_FUNCCTX );
+  pCtx = pOp->p4.pCtx;
+  pMem = &aMem[pOp->p3];
+
+#ifdef SQLITE_DEBUG
+  if( pOp->p1 ){
+    /* This is an OP_AggInverse call.  Verify that xStep has always
+    ** been called at least once prior to any xInverse call. */
+    assert( pMem->uTemp==0x1122e0e3 );
+  }else{
+    /* This is an OP_AggStep call.  Mark it as such. */
+    pMem->uTemp = 0x1122e0e3;
+  }
+#endif
+
+  /* If this function is inside of a trigger, the register array in aMem[]
+  ** might change from one evaluation to the next.  The next block of code
+  ** checks to see if the register array has changed, and if so it
+  ** reinitializes the relevant parts of the sqlite3_context object */
+  if( pCtx->pMem != pMem ){
+    pCtx->pMem = pMem;
+    for(i=pCtx->argc-1; i>=0; i--) pCtx->argv[i] = &aMem[pOp->p2+i];
+  }
+
+#ifdef SQLITE_DEBUG
+  for(i=0; i<pCtx->argc; i++){
+    assert( memIsValid(pCtx->argv[i]) );
+    REGISTER_TRACE(pOp->p2+i, pCtx->argv[i]);
+  }
+#endif
+
+  pMem->n++;
+  assert( pCtx->pOut->flags==MEM_Null );
+  assert( pCtx->isError==0 );
+  assert( pCtx->skipFlag==0 );
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( pOp->p1 ){
+    (pCtx->pFunc->xInverse)(pCtx,pCtx->argc,pCtx->argv);
+  }else
+#endif
+  (pCtx->pFunc->xSFunc)(pCtx,pCtx->argc,pCtx->argv); /* IMP: R-24505-23230 */
+
+  if( pCtx->isError ){
+    if( pCtx->isError>0 ){
+      sqlite3VdbeError(p, "%s", sqlite3_value_text(pCtx->pOut));
+      rc = pCtx->isError;
+    }
+    if( pCtx->skipFlag ){
+      assert( pOp[-1].opcode==OP_CollSeq );
+      i = pOp[-1].p1;
+      if( i ) sqlite3VdbeMemSetInt64(&aMem[i], 1);
+      pCtx->skipFlag = 0;
+    }
+    sqlite3VdbeMemRelease(pCtx->pOut);
+    pCtx->pOut->flags = MEM_Null;
+    pCtx->isError = 0;
+    if( rc ) goto abort_due_to_error;
+  }
+  assert( pCtx->pOut->flags==MEM_Null );
+  assert( pCtx->skipFlag==0 );
+  break;
+}
+
+/* Opcode: AggFinal P1 P2 * P4 *
+** Synopsis: accum=r[P1] N=P2
+**
+** P1 is the memory location that is the accumulator for an aggregate
+** or window function.  Execute the finalizer function
+** for an aggregate and store the result in P1.
+**
+** P2 is the number of arguments that the step function takes and
+** P4 is a pointer to the FuncDef for this function.  The P2
+** argument is not used by this opcode.  It is only there to disambiguate
+** functions that can take varying numbers of arguments.  The
+** P4 argument is only needed for the case where
+** the step function was not previously called.
+*/
+/* Opcode: AggValue * P2 P3 P4 *
+** Synopsis: r[P3]=value N=P2
+**
+** Invoke the xValue() function and store the result in register P3.
+**
+** P2 is the number of arguments that the step function takes and
+** P4 is a pointer to the FuncDef for this function.  The P2
+** argument is not used by this opcode.  It is only there to disambiguate
+** functions that can take varying numbers of arguments.  The
+** P4 argument is only needed for the case where
+** the step function was not previously called.
+*/
+case OP_AggValue:
+case OP_AggFinal: {
+  Mem *pMem;
+  assert( pOp->p1>0 && pOp->p1<=(p->nMem+1 - p->nCursor) );
+  assert( pOp->p3==0 || pOp->opcode==OP_AggValue );
+  pMem = &aMem[pOp->p1];
+  assert( (pMem->flags & ~(MEM_Null|MEM_Agg))==0 );
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( pOp->p3 ){
+    memAboutToChange(p, &aMem[pOp->p3]);
+    rc = sqlite3VdbeMemAggValue(pMem, &aMem[pOp->p3], pOp->p4.pFunc);
+    pMem = &aMem[pOp->p3];
+  }else
+#endif
+  {
+    rc = sqlite3VdbeMemFinalize(pMem, pOp->p4.pFunc);
+  }
+ 
+  if( rc ){
+    sqlite3VdbeError(p, "%s", sqlite3_value_text(pMem));
+    goto abort_due_to_error;
+  }
+  sqlite3VdbeChangeEncoding(pMem, encoding);
+  UPDATE_MAX_BLOBSIZE(pMem);
+  REGISTER_TRACE((int)(pMem-aMem), pMem);
+  break;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/* Opcode: Checkpoint P1 P2 P3 * *
+**
+** Checkpoint database P1. This is a no-op if P1 is not currently in
+** WAL mode. Parameter P2 is one of SQLITE_CHECKPOINT_PASSIVE, FULL,
+** RESTART, or TRUNCATE.  Write 1 or 0 into mem[P3] if the checkpoint returns
+** SQLITE_BUSY or not, respectively.  Write the number of pages in the
+** WAL after the checkpoint into mem[P3+1] and the number of pages
+** in the WAL that have been checkpointed after the checkpoint
+** completes into mem[P3+2].  However on an error, mem[P3+1] and
+** mem[P3+2] are initialized to -1.
+*/
+case OP_Checkpoint: {
+  int i;                          /* Loop counter */
+  int aRes[3];                    /* Results */
+  Mem *pMem;                      /* Write results here */
+
+  assert( p->readOnly==0 );
+  aRes[0] = 0;
+  aRes[1] = aRes[2] = -1;
+  assert( pOp->p2==SQLITE_CHECKPOINT_PASSIVE
+       || pOp->p2==SQLITE_CHECKPOINT_FULL
+       || pOp->p2==SQLITE_CHECKPOINT_RESTART
+       || pOp->p2==SQLITE_CHECKPOINT_TRUNCATE
+  );
+  rc = sqlite3Checkpoint(db, pOp->p1, pOp->p2, &aRes[1], &aRes[2]);
+  if( rc ){
+    if( rc!=SQLITE_BUSY ) goto abort_due_to_error;
+    rc = SQLITE_OK;
+    aRes[0] = 1;
+  }
+  for(i=0, pMem = &aMem[pOp->p3]; i<3; i++, pMem++){
+    sqlite3VdbeMemSetInt64(pMem, (i64)aRes[i]);
+  }   
+  break;
+}; 
+#endif
+
+#ifndef SQLITE_OMIT_PRAGMA
+/* Opcode: JournalMode P1 P2 P3 * *
+**
+** Change the journal mode of database P1 to P3. P3 must be one of the
+** PAGER_JOURNALMODE_XXX values. If changing between the various rollback
+** modes (delete, truncate, persist, off and memory), this is a simple
+** operation. No IO is required.
+**
+** If changing into or out of WAL mode the procedure is more complicated.
+**
+** Write a string containing the final journal-mode to register P2.
+*/
+case OP_JournalMode: {    /* out2 */
+  Btree *pBt;                     /* Btree to change journal mode of */
+  Pager *pPager;                  /* Pager associated with pBt */
+  int eNew;                       /* New journal mode */
+  int eOld;                       /* The old journal mode */
+#ifndef SQLITE_OMIT_WAL
+  const char *zFilename;          /* Name of database file for pPager */
+#endif
+
+  pOut = out2Prerelease(p, pOp);
+  eNew = pOp->p3;
+  assert( eNew==PAGER_JOURNALMODE_DELETE
+       || eNew==PAGER_JOURNALMODE_TRUNCATE
+       || eNew==PAGER_JOURNALMODE_PERSIST
+       || eNew==PAGER_JOURNALMODE_OFF
+       || eNew==PAGER_JOURNALMODE_MEMORY
+       || eNew==PAGER_JOURNALMODE_WAL
+       || eNew==PAGER_JOURNALMODE_QUERY
+  );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( p->readOnly==0 );
+
+  pBt = db->aDb[pOp->p1].pBt;
+  pPager = sqlite3BtreePager(pBt);
+  eOld = sqlite3PagerGetJournalMode(pPager);
+  if( eNew==PAGER_JOURNALMODE_QUERY ) eNew = eOld;
+  assert( sqlite3BtreeHoldsMutex(pBt) );
+  if( !sqlite3PagerOkToChangeJournalMode(pPager) ) eNew = eOld;
+
+#ifndef SQLITE_OMIT_WAL
+  zFilename = sqlite3PagerFilename(pPager, 1);
+
+  /* Do not allow a transition to journal_mode=WAL for a database
+  ** in temporary storage or if the VFS does not support shared memory
+  */
+  if( eNew==PAGER_JOURNALMODE_WAL
+   && (sqlite3Strlen30(zFilename)==0           /* Temp file */
+       || !sqlite3PagerWalSupported(pPager))   /* No shared-memory support */
+  ){
+    eNew = eOld;
+  }
+
+  if( (eNew!=eOld)
+   && (eOld==PAGER_JOURNALMODE_WAL || eNew==PAGER_JOURNALMODE_WAL)
+  ){
+    if( !db->autoCommit || db->nVdbeRead>1 ){
+      rc = SQLITE_ERROR;
+      sqlite3VdbeError(p,
+          "cannot change %s wal mode from within a transaction",
+          (eNew==PAGER_JOURNALMODE_WAL ? "into" : "out of")
+      );
+      goto abort_due_to_error;
+    }else{
+
+      if( eOld==PAGER_JOURNALMODE_WAL ){
+        /* If leaving WAL mode, close the log file. If successful, the call
+        ** to PagerCloseWal() checkpoints and deletes the write-ahead-log
+        ** file. An EXCLUSIVE lock may still be held on the database file
+        ** after a successful return.
+        */
+        rc = sqlite3PagerCloseWal(pPager, db);
+        if( rc==SQLITE_OK ){
+          sqlite3PagerSetJournalMode(pPager, eNew);
+        }
+      }else if( eOld==PAGER_JOURNALMODE_MEMORY ){
+        /* Cannot transition directly from MEMORY to WAL.  Use mode OFF
+        ** as an intermediate */
+        sqlite3PagerSetJournalMode(pPager, PAGER_JOURNALMODE_OFF);
+      }
+ 
+      /* Open a transaction on the database file. Regardless of the journal
+      ** mode, this transaction always uses a rollback journal.
+      */
+      assert( sqlite3BtreeTxnState(pBt)!=SQLITE_TXN_WRITE );
+      if( rc==SQLITE_OK ){
+        rc = sqlite3BtreeSetVersion(pBt, (eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
+      }
+    }
+  }
+#endif /* ifndef SQLITE_OMIT_WAL */
+
+  if( rc ) eNew = eOld;
+  eNew = sqlite3PagerSetJournalMode(pPager, eNew);
+
+  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
+  pOut->z = (char *)sqlite3JournalModename(eNew);
+  pOut->n = sqlite3Strlen30(pOut->z);
+  pOut->enc = SQLITE_UTF8;
+  sqlite3VdbeChangeEncoding(pOut, encoding);
+  if( rc ) goto abort_due_to_error;
+  break;
+};
+#endif /* SQLITE_OMIT_PRAGMA */
+
+#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
+/* Opcode: Vacuum P1 P2 * * *
+**
+** Vacuum the entire database P1.  P1 is 0 for "main", and 2 or more
+** for an attached database.  The "temp" database may not be vacuumed.
+**
+** If P2 is not zero, then it is a register holding a string which is
+** the file into which the result of vacuum should be written.  When
+** P2 is zero, the vacuum overwrites the original database.
+*/
+case OP_Vacuum: {
+  assert( p->readOnly==0 );
+  rc = sqlite3RunVacuum(&p->zErrMsg, db, pOp->p1,
+                        pOp->p2 ? &aMem[pOp->p2] : 0);
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+#endif
+
+#if !defined(SQLITE_OMIT_AUTOVACUUM)
+/* Opcode: IncrVacuum P1 P2 * * *
+**
+** Perform a single step of the incremental vacuum procedure on
+** the P1 database. If the vacuum has finished, jump to instruction
+** P2. Otherwise, fall through to the next instruction.
+*/
+case OP_IncrVacuum: {        /* jump */
+  Btree *pBt;
+
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( DbMaskTest(p->btreeMask, pOp->p1) );
+  assert( p->readOnly==0 );
+  pBt = db->aDb[pOp->p1].pBt;
+  rc = sqlite3BtreeIncrVacuum(pBt);
+  VdbeBranchTaken(rc==SQLITE_DONE,2);
+  if( rc ){
+    if( rc!=SQLITE_DONE ) goto abort_due_to_error;
+    rc = SQLITE_OK;
+    goto jump_to_p2;
+  }
+  break;
+}
+#endif
+
+/* Opcode: Expire P1 P2 * * *
+**
+** Cause precompiled statements to expire.  When an expired statement
+** is executed using sqlite3_step() it will either automatically
+** reprepare itself (if it was originally created using sqlite3_prepare_v2())
+** or it will fail with SQLITE_SCHEMA.
+**
+** If P1 is 0, then all SQL statements become expired. If P1 is non-zero,
+** then only the currently executing statement is expired.
+**
+** If P2 is 0, then SQL statements are expired immediately.  If P2 is 1,
+** then running SQL statements are allowed to continue to run to completion.
+** The P2==1 case occurs when a CREATE INDEX or similar schema change happens
+** that might help the statement run faster but which does not affect the
+** correctness of operation.
+*/
+case OP_Expire: {
+  assert( pOp->p2==0 || pOp->p2==1 );
+  if( !pOp->p1 ){
+    sqlite3ExpirePreparedStatements(db, pOp->p2);
+  }else{
+    p->expired = pOp->p2+1;
+  }
+  break;
+}
+
+/* Opcode: CursorLock P1 * * * *
+**
+** Lock the btree to which cursor P1 is pointing so that the btree cannot be
+** written by an other cursor.
+*/
+case OP_CursorLock: {
+  VdbeCursor *pC;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  sqlite3BtreeCursorPin(pC->uc.pCursor);
+  break;
+}
+
+/* Opcode: CursorUnlock P1 * * * *
+**
+** Unlock the btree to which cursor P1 is pointing so that it can be
+** written by other cursors.
+*/
+case OP_CursorUnlock: {
+  VdbeCursor *pC;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  sqlite3BtreeCursorUnpin(pC->uc.pCursor);
+  break;
+}
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/* Opcode: TableLock P1 P2 P3 P4 *
+** Synopsis: iDb=P1 root=P2 write=P3
+**
+** Obtain a lock on a particular table. This instruction is only used when
+** the shared-cache feature is enabled.
+**
+** P1 is the index of the database in sqlite3.aDb[] of the database
+** on which the lock is acquired.  A readlock is obtained if P3==0 or
+** a write lock if P3==1.
+**
+** P2 contains the root-page of the table to lock.
+**
+** P4 contains a pointer to the name of the table being locked. This is only
+** used to generate an error message if the lock cannot be obtained.
+*/
+case OP_TableLock: {
+  u8 isWriteLock = (u8)pOp->p3;
+  if( isWriteLock || 0==(db->flags&SQLITE_ReadUncommit) ){
+    int p1 = pOp->p1;
+    assert( p1>=0 && p1<db->nDb );
+    assert( DbMaskTest(p->btreeMask, p1) );
+    assert( isWriteLock==0 || isWriteLock==1 );
+    rc = sqlite3BtreeLockTable(db->aDb[p1].pBt, pOp->p2, isWriteLock);
+    if( rc ){
+      if( (rc&0xFF)==SQLITE_LOCKED ){
+        const char *z = pOp->p4.z;
+        sqlite3VdbeError(p, "database table is locked: %s", z);
+      }
+      goto abort_due_to_error;
+    }
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VBegin * * * P4 *
+**
+** P4 may be a pointer to an sqlite3_vtab structure. If so, call the
+** xBegin method for that table.
+**
+** Also, whether or not P4 is set, check that this is not being called from
+** within a callback to a virtual table xSync() method. If it is, the error
+** code will be set to SQLITE_LOCKED.
+*/
+case OP_VBegin: {
+  VTable *pVTab;
+  pVTab = pOp->p4.pVtab;
+  rc = sqlite3VtabBegin(db, pVTab);
+  if( pVTab ) sqlite3VtabImportErrmsg(p, pVTab->pVtab);
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VCreate P1 P2 * * *
+**
+** P2 is a register that holds the name of a virtual table in database
+** P1. Call the xCreate method for that table.
+*/
+case OP_VCreate: {
+  Mem sMem;          /* For storing the record being decoded */
+  const char *zTab;  /* Name of the virtual table */
+
+  memset(&sMem, 0, sizeof(sMem));
+  sMem.db = db;
+  /* Because P2 is always a static string, it is impossible for the
+  ** sqlite3VdbeMemCopy() to fail */
+  assert( (aMem[pOp->p2].flags & MEM_Str)!=0 );
+  assert( (aMem[pOp->p2].flags & MEM_Static)!=0 );
+  rc = sqlite3VdbeMemCopy(&sMem, &aMem[pOp->p2]);
+  assert( rc==SQLITE_OK );
+  zTab = (const char*)sqlite3_value_text(&sMem);
+  assert( zTab || db->mallocFailed );
+  if( zTab ){
+    rc = sqlite3VtabCallCreate(db, pOp->p1, zTab, &p->zErrMsg);
+  }
+  sqlite3VdbeMemRelease(&sMem);
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VDestroy P1 * * P4 *
+**
+** P4 is the name of a virtual table in database P1.  Call the xDestroy method
+** of that table.
+*/
+case OP_VDestroy: {
+  db->nVDestroy++;
+  rc = sqlite3VtabCallDestroy(db, pOp->p1, pOp->p4.z);
+  db->nVDestroy--;
+  assert( p->errorAction==OE_Abort && p->usesStmtJournal );
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VOpen P1 * * P4 *
+**
+** P4 is a pointer to a virtual table object, an sqlite3_vtab structure.
+** P1 is a cursor number.  This opcode opens a cursor to the virtual
+** table and stores that cursor in P1.
+*/
+case OP_VOpen: {             /* ncycle */
+  VdbeCursor *pCur;
+  sqlite3_vtab_cursor *pVCur;
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+
+  assert( p->bIsReader );
+  pCur = 0;
+  pVCur = 0;
+  pVtab = pOp->p4.pVtab->pVtab;
+  if( pVtab==0 || NEVER(pVtab->pModule==0) ){
+    rc = SQLITE_LOCKED;
+    goto abort_due_to_error;
+  }
+  pModule = pVtab->pModule;
+  rc = pModule->xOpen(pVtab, &pVCur);
+  sqlite3VtabImportErrmsg(p, pVtab);
+  if( rc ) goto abort_due_to_error;
+
+  /* Initialize sqlite3_vtab_cursor base class */
+  pVCur->pVtab = pVtab;
+
+  /* Initialize vdbe cursor object */
+  pCur = allocateCursor(p, pOp->p1, 0, CURTYPE_VTAB);
+  if( pCur ){
+    pCur->uc.pVCur = pVCur;
+    pVtab->nRef++;
+  }else{
+    assert( db->mallocFailed );
+    pModule->xClose(pVCur);
+    goto no_mem;
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VCheck P1 P2 P3 P4 *
+**
+** P4 is a pointer to a Table object that is a virtual table in schema P1
+** that supports the xIntegrity() method.  This opcode runs the xIntegrity()
+** method for that virtual table, using P3 as the integer argument.  If
+** an error is reported back, the table name is prepended to the error
+** message and that message is stored in P2.  If no errors are seen,
+** register P2 is set to NULL.
+*/
+case OP_VCheck: {             /* out2 */
+  Table *pTab;
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+  char *zErr = 0;
+
+  pOut = &aMem[pOp->p2];
+  sqlite3VdbeMemSetNull(pOut);  /* Innocent until proven guilty */
+  assert( pOp->p4type==P4_TABLEREF );
+  pTab = pOp->p4.pTab;
+  assert( pTab!=0 );
+  assert( pTab->nTabRef>0 );
+  assert( IsVirtual(pTab) );
+  if( pTab->u.vtab.p==0 ) break;
+  pVtab = pTab->u.vtab.p->pVtab;
+  assert( pVtab!=0 );
+  pModule = pVtab->pModule;
+  assert( pModule!=0 );
+  assert( pModule->iVersion>=4 );
+  assert( pModule->xIntegrity!=0 );
+  sqlite3VtabLock(pTab->u.vtab.p);
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  rc = pModule->xIntegrity(pVtab, db->aDb[pOp->p1].zDbSName, pTab->zName,
+                           pOp->p3, &zErr);
+  sqlite3VtabUnlock(pTab->u.vtab.p);
+  if( rc ){
+    sqlite3_free(zErr);
+    goto abort_due_to_error;
+  }
+  if( zErr ){
+    sqlite3VdbeMemSetStr(pOut, zErr, -1, SQLITE_UTF8, sqlite3_free);
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VInitIn P1 P2 P3 * *
+** Synopsis: r[P2]=ValueList(P1,P3)
+**
+** Set register P2 to be a pointer to a ValueList object for cursor P1
+** with cache register P3 and output register P3+1.  This ValueList object
+** can be used as the first argument to sqlite3_vtab_in_first() and
+** sqlite3_vtab_in_next() to extract all of the values stored in the P1
+** cursor.  Register P3 is used to hold the values returned by
+** sqlite3_vtab_in_first() and sqlite3_vtab_in_next().
+*/
+case OP_VInitIn: {        /* out2, ncycle */
+  VdbeCursor *pC;         /* The cursor containing the RHS values */
+  ValueList *pRhs;        /* New ValueList object to put in reg[P2] */
+
+  pC = p->apCsr[pOp->p1];
+  pRhs = sqlite3_malloc64( sizeof(*pRhs) );
+  if( pRhs==0 ) goto no_mem;
+  pRhs->pCsr = pC->uc.pCursor;
+  pRhs->pOut = &aMem[pOp->p3];
+  pOut = out2Prerelease(p, pOp);
+  pOut->flags = MEM_Null;
+  sqlite3VdbeMemSetPointer(pOut, pRhs, "ValueList", sqlite3VdbeValueListFree);
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VFilter P1 P2 P3 P4 *
+** Synopsis: iplan=r[P3] zplan='P4'
+**
+** P1 is a cursor opened using VOpen.  P2 is an address to jump to if
+** the filtered result set is empty.
+**
+** P4 is either NULL or a string that was generated by the xBestIndex
+** method of the module.  The interpretation of the P4 string is left
+** to the module implementation.
+**
+** This opcode invokes the xFilter method on the virtual table specified
+** by P1.  The integer query plan parameter to xFilter is stored in register
+** P3. Register P3+1 stores the argc parameter to be passed to the
+** xFilter method. Registers P3+2..P3+1+argc are the argc
+** additional parameters which are passed to
+** xFilter as argv. Register P3+2 becomes argv[0] when passed to xFilter.
+**
+** A jump is made to P2 if the result set after filtering would be empty.
+*/
+case OP_VFilter: {   /* jump, ncycle */
+  int nArg;
+  int iQuery;
+  const sqlite3_module *pModule;
+  Mem *pQuery;
+  Mem *pArgc;
+  sqlite3_vtab_cursor *pVCur;
+  sqlite3_vtab *pVtab;
+  VdbeCursor *pCur;
+  int res;
+  int i;
+  Mem **apArg;
+
+  pQuery = &aMem[pOp->p3];
+  pArgc = &pQuery[1];
+  pCur = p->apCsr[pOp->p1];
+  assert( memIsValid(pQuery) );
+  REGISTER_TRACE(pOp->p3, pQuery);
+  assert( pCur!=0 );
+  assert( pCur->eCurType==CURTYPE_VTAB );
+  pVCur = pCur->uc.pVCur;
+  pVtab = pVCur->pVtab;
+  pModule = pVtab->pModule;
+
+  /* Grab the index number and argc parameters */
+  assert( (pQuery->flags&MEM_Int)!=0 && pArgc->flags==MEM_Int );
+  nArg = (int)pArgc->u.i;
+  iQuery = (int)pQuery->u.i;
+
+  /* Invoke the xFilter method */
+  apArg = p->apArg;
+  for(i = 0; i<nArg; i++){
+    apArg[i] = &pArgc[i+1];
+  }
+  rc = pModule->xFilter(pVCur, iQuery, pOp->p4.z, nArg, apArg);
+  sqlite3VtabImportErrmsg(p, pVtab);
+  if( rc ) goto abort_due_to_error;
+  res = pModule->xEof(pVCur);
+  pCur->nullRow = 0;
+  VdbeBranchTaken(res!=0,2);
+  if( res ) goto jump_to_p2;
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VColumn P1 P2 P3 * P5
+** Synopsis: r[P3]=vcolumn(P2)
+**
+** Store in register P3 the value of the P2-th column of
+** the current row of the virtual-table of cursor P1.
+**
+** If the VColumn opcode is being used to fetch the value of
+** an unchanging column during an UPDATE operation, then the P5
+** value is OPFLAG_NOCHNG.  This will cause the sqlite3_vtab_nochange()
+** function to return true inside the xColumn method of the virtual
+** table implementation.  The P5 column might also contain other
+** bits (OPFLAG_LENGTHARG or OPFLAG_TYPEOFARG) but those bits are
+** unused by OP_VColumn.
+*/
+case OP_VColumn: {           /* ncycle */
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+  Mem *pDest;
+  sqlite3_context sContext;
+  FuncDef nullFunc;
+
+  VdbeCursor *pCur = p->apCsr[pOp->p1];
+  assert( pCur!=0 );
+  assert( pOp->p3>0 && pOp->p3<=(p->nMem+1 - p->nCursor) );
+  pDest = &aMem[pOp->p3];
+  memAboutToChange(p, pDest);
+  if( pCur->nullRow ){
+    sqlite3VdbeMemSetNull(pDest);
+    break;
+  }
+  assert( pCur->eCurType==CURTYPE_VTAB );
+  pVtab = pCur->uc.pVCur->pVtab;
+  pModule = pVtab->pModule;
+  assert( pModule->xColumn );
+  memset(&sContext, 0, sizeof(sContext));
+  sContext.pOut = pDest;
+  sContext.enc = encoding;
+  nullFunc.pUserData = 0;
+  nullFunc.funcFlags = SQLITE_RESULT_SUBTYPE;
+  sContext.pFunc = &nullFunc;
+  assert( pOp->p5==OPFLAG_NOCHNG || pOp->p5==0 );
+  if( pOp->p5 & OPFLAG_NOCHNG ){
+    sqlite3VdbeMemSetNull(pDest);
+    pDest->flags = MEM_Null|MEM_Zero;
+    pDest->u.nZero = 0;
+  }else{
+    MemSetTypeFlag(pDest, MEM_Null);
+  }
+  rc = pModule->xColumn(pCur->uc.pVCur, &sContext, pOp->p2);
+  sqlite3VtabImportErrmsg(p, pVtab);
+  if( sContext.isError>0 ){
+    sqlite3VdbeError(p, "%s", sqlite3_value_text(pDest));
+    rc = sContext.isError;
+  }
+  sqlite3VdbeChangeEncoding(pDest, encoding);
+  REGISTER_TRACE(pOp->p3, pDest);
+  UPDATE_MAX_BLOBSIZE(pDest);
+
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VNext P1 P2 * * *
+**
+** Advance virtual table P1 to the next row in its result set and
+** jump to instruction P2.  Or, if the virtual table has reached
+** the end of its result set, then fall through to the next instruction.
+*/
+case OP_VNext: {   /* jump, ncycle */
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+  int res;
+  VdbeCursor *pCur;
+
+  pCur = p->apCsr[pOp->p1];
+  assert( pCur!=0 );
+  assert( pCur->eCurType==CURTYPE_VTAB );
+  if( pCur->nullRow ){
+    break;
+  }
+  pVtab = pCur->uc.pVCur->pVtab;
+  pModule = pVtab->pModule;
+  assert( pModule->xNext );
+
+  /* Invoke the xNext() method of the module. There is no way for the
+  ** underlying implementation to return an error if one occurs during
+  ** xNext(). Instead, if an error occurs, true is returned (indicating that
+  ** data is available) and the error code returned when xColumn or
+  ** some other method is next invoked on the save virtual table cursor.
+  */
+  rc = pModule->xNext(pCur->uc.pVCur);
+  sqlite3VtabImportErrmsg(p, pVtab);
+  if( rc ) goto abort_due_to_error;
+  res = pModule->xEof(pCur->uc.pVCur);
+  VdbeBranchTaken(!res,2);
+  if( !res ){
+    /* If there is data, jump to P2 */
+    goto jump_to_p2_and_check_for_interrupt;
+  }
+  goto check_for_interrupt;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VRename P1 * * P4 *
+**
+** P4 is a pointer to a virtual table object, an sqlite3_vtab structure.
+** This opcode invokes the corresponding xRename method. The value
+** in register P1 is passed as the zName argument to the xRename method.
+*/
+case OP_VRename: {
+  sqlite3_vtab *pVtab;
+  Mem *pName;
+  int isLegacy;
+ 
+  isLegacy = (db->flags & SQLITE_LegacyAlter);
+  db->flags |= SQLITE_LegacyAlter;
+  pVtab = pOp->p4.pVtab->pVtab;
+  pName = &aMem[pOp->p1];
+  assert( pVtab->pModule->xRename );
+  assert( memIsValid(pName) );
+  assert( p->readOnly==0 );
+  REGISTER_TRACE(pOp->p1, pName);
+  assert( pName->flags & MEM_Str );
+  testcase( pName->enc==SQLITE_UTF8 );
+  testcase( pName->enc==SQLITE_UTF16BE );
+  testcase( pName->enc==SQLITE_UTF16LE );
+  rc = sqlite3VdbeChangeEncoding(pName, SQLITE_UTF8);
+  if( rc ) goto abort_due_to_error;
+  rc = pVtab->pModule->xRename(pVtab, pName->z);
+  if( isLegacy==0 ) db->flags &= ~(u64)SQLITE_LegacyAlter;
+  sqlite3VtabImportErrmsg(p, pVtab);
+  p->expired = 0;
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VUpdate P1 P2 P3 P4 P5
+** Synopsis: data=r[P3@P2]
+**
+** P4 is a pointer to a virtual table object, an sqlite3_vtab structure.
+** This opcode invokes the corresponding xUpdate method. P2 values
+** are contiguous memory cells starting at P3 to pass to the xUpdate
+** invocation. The value in register (P3+P2-1) corresponds to the
+** p2th element of the argv array passed to xUpdate.
+**
+** The xUpdate method will do a DELETE or an INSERT or both.
+** The argv[0] element (which corresponds to memory cell P3)
+** is the rowid of a row to delete.  If argv[0] is NULL then no
+** deletion occurs.  The argv[1] element is the rowid of the new
+** row.  This can be NULL to have the virtual table select the new
+** rowid for itself.  The subsequent elements in the array are
+** the values of columns in the new row.
+**
+** If P2==1 then no insert is performed.  argv[0] is the rowid of
+** a row to delete.
+**
+** P1 is a boolean flag. If it is set to true and the xUpdate call
+** is successful, then the value returned by sqlite3_last_insert_rowid()
+** is set to the value of the rowid for the row just inserted.
+**
+** P5 is the error actions (OE_Replace, OE_Fail, OE_Ignore, etc) to
+** apply in the case of a constraint failure on an insert or update.
+*/
+case OP_VUpdate: {
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+  int nArg;
+  int i;
+  sqlite_int64 rowid = 0;
+  Mem **apArg;
+  Mem *pX;
+
+  assert( pOp->p2==1        || pOp->p5==OE_Fail   || pOp->p5==OE_Rollback
+       || pOp->p5==OE_Abort || pOp->p5==OE_Ignore || pOp->p5==OE_Replace
+  );
+  assert( p->readOnly==0 );
+  if( db->mallocFailed ) goto no_mem;
+  sqlite3VdbeIncrWriteCounter(p, 0);
+  pVtab = pOp->p4.pVtab->pVtab;
+  if( pVtab==0 || NEVER(pVtab->pModule==0) ){
+    rc = SQLITE_LOCKED;
+    goto abort_due_to_error;
+  }
+  pModule = pVtab->pModule;
+  nArg = pOp->p2;
+  assert( pOp->p4type==P4_VTAB );
+  if( ALWAYS(pModule->xUpdate) ){
+    u8 vtabOnConflict = db->vtabOnConflict;
+    apArg = p->apArg;
+    pX = &aMem[pOp->p3];
+    for(i=0; i<nArg; i++){
+      assert( memIsValid(pX) );
+      memAboutToChange(p, pX);
+      apArg[i] = pX;
+      pX++;
+    }
+    db->vtabOnConflict = pOp->p5;
+    rc = pModule->xUpdate(pVtab, nArg, apArg, &rowid);
+    db->vtabOnConflict = vtabOnConflict;
+    sqlite3VtabImportErrmsg(p, pVtab);
+    if( rc==SQLITE_OK && pOp->p1 ){
+      assert( nArg>1 && apArg[0] && (apArg[0]->flags&MEM_Null) );
+      db->lastRowid = rowid;
+    }
+    if( (rc&0xff)==SQLITE_CONSTRAINT && pOp->p4.pVtab->bConstraint ){
+      if( pOp->p5==OE_Ignore ){
+        rc = SQLITE_OK;
+      }else{
+        p->errorAction = ((pOp->p5==OE_Replace) ? OE_Abort : pOp->p5);
+      }
+    }else{
+      p->nChange++;
+    }
+    if( rc ) goto abort_due_to_error;
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
+/* Opcode: Pagecount P1 P2 * * *
+**
+** Write the current number of pages in database P1 to memory cell P2.
+*/
+case OP_Pagecount: {            /* out2 */
+  pOut = out2Prerelease(p, pOp);
+  pOut->u.i = sqlite3BtreeLastPage(db->aDb[pOp->p1].pBt);
+  break;
+}
+#endif
+
+
+#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
+/* Opcode: MaxPgcnt P1 P2 P3 * *
+**
+** Try to set the maximum page count for database P1 to the value in P3.
+** Do not let the maximum page count fall below the current page count and
+** do not change the maximum page count value if P3==0.
+**
+** Store the maximum page count after the change in register P2.
+*/
+case OP_MaxPgcnt: {            /* out2 */
+  unsigned int newMax;
+  Btree *pBt;
+
+  pOut = out2Prerelease(p, pOp);
+  pBt = db->aDb[pOp->p1].pBt;
+  newMax = 0;
+  if( pOp->p3 ){
+    newMax = sqlite3BtreeLastPage(pBt);
+    if( newMax < (unsigned)pOp->p3 ) newMax = (unsigned)pOp->p3;
+  }
+  pOut->u.i = sqlite3BtreeMaxPageCount(pBt, newMax);
+  break;
+}
+#endif
+
+/* Opcode: Function P1 P2 P3 P4 *
+** Synopsis: r[P3]=func(r[P2@NP])
+**
+** Invoke a user function (P4 is a pointer to an sqlite3_context object that
+** contains a pointer to the function to be run) with arguments taken
+** from register P2 and successors.  The number of arguments is in
+** the sqlite3_context object that P4 points to.
+** The result of the function is stored
+** in register P3.  Register P3 must not be one of the function inputs.
+**
+** P1 is a 32-bit bitmask indicating whether or not each argument to the
+** function was determined to be constant at compile time. If the first
+** argument was constant then bit 0 of P1 is set. This is used to determine
+** whether meta data associated with a user function argument using the
+** sqlite3_set_auxdata() API may be safely retained until the next
+** invocation of this opcode.
+**
+** See also: AggStep, AggFinal, PureFunc
+*/
+/* Opcode: PureFunc P1 P2 P3 P4 *
+** Synopsis: r[P3]=func(r[P2@NP])
+**
+** Invoke a user function (P4 is a pointer to an sqlite3_context object that
+** contains a pointer to the function to be run) with arguments taken
+** from register P2 and successors.  The number of arguments is in
+** the sqlite3_context object that P4 points to.
+** The result of the function is stored
+** in register P3.  Register P3 must not be one of the function inputs.
+**
+** P1 is a 32-bit bitmask indicating whether or not each argument to the
+** function was determined to be constant at compile time. If the first
+** argument was constant then bit 0 of P1 is set. This is used to determine
+** whether meta data associated with a user function argument using the
+** sqlite3_set_auxdata() API may be safely retained until the next
+** invocation of this opcode.
+**
+** This opcode works exactly like OP_Function.  The only difference is in
+** its name.  This opcode is used in places where the function must be
+** purely non-deterministic.  Some built-in date/time functions can be
+** either deterministic of non-deterministic, depending on their arguments.
+** When those function are used in a non-deterministic way, they will check
+** to see if they were called using OP_PureFunc instead of OP_Function, and
+** if they were, they throw an error.
+**
+** See also: AggStep, AggFinal, Function
+*/
+case OP_PureFunc:              /* group */
+case OP_Function: {            /* group */
+  int i;
+  sqlite3_context *pCtx;
+
+  assert( pOp->p4type==P4_FUNCCTX );
+  pCtx = pOp->p4.pCtx;
+
+  /* If this function is inside of a trigger, the register array in aMem[]
+  ** might change from one evaluation to the next.  The next block of code
+  ** checks to see if the register array has changed, and if so it
+  ** reinitializes the relevant parts of the sqlite3_context object */
+  pOut = &aMem[pOp->p3];
+  if( pCtx->pOut != pOut ){
+    pCtx->pVdbe = p;
+    pCtx->pOut = pOut;
+    pCtx->enc = encoding;
+    for(i=pCtx->argc-1; i>=0; i--) pCtx->argv[i] = &aMem[pOp->p2+i];
+  }
+  assert( pCtx->pVdbe==p );
+
+  memAboutToChange(p, pOut);
+#ifdef SQLITE_DEBUG
+  for(i=0; i<pCtx->argc; i++){
+    assert( memIsValid(pCtx->argv[i]) );
+    REGISTER_TRACE(pOp->p2+i, pCtx->argv[i]);
+  }
+#endif
+  MemSetTypeFlag(pOut, MEM_Null);
+  assert( pCtx->isError==0 );
+  (*pCtx->pFunc->xSFunc)(pCtx, pCtx->argc, pCtx->argv);/* IMP: R-24505-23230 */
+
+  /* If the function returned an error, throw an exception */
+  if( pCtx->isError ){
+    if( pCtx->isError>0 ){
+      sqlite3VdbeError(p, "%s", sqlite3_value_text(pOut));
+      rc = pCtx->isError;
+    }
+    sqlite3VdbeDeleteAuxData(db, &p->pAuxData, pCtx->iOp, pOp->p1);
+    pCtx->isError = 0;
+    if( rc ) goto abort_due_to_error;
+  }
+
+  assert( (pOut->flags&MEM_Str)==0
+       || pOut->enc==encoding
+       || db->mallocFailed );
+  assert( !sqlite3VdbeMemTooBig(pOut) );
+
+  REGISTER_TRACE(pOp->p3, pOut);
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: ClrSubtype P1 * * * *
+** Synopsis:  r[P1].subtype = 0
+**
+** Clear the subtype from register P1.
+*/
+case OP_ClrSubtype: {   /* in1 */
+  pIn1 = &aMem[pOp->p1];
+  pIn1->flags &= ~MEM_Subtype;
+  break;
+}
+
+/* Opcode: GetSubtype P1 P2 * * *
+** Synopsis:  r[P2] = r[P1].subtype
+**
+** Extract the subtype value from register P1 and write that subtype
+** into register P2.  If P1 has no subtype, then P1 gets a NULL.
+*/
+case OP_GetSubtype: {   /* in1 out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  if( pIn1->flags & MEM_Subtype ){
+    sqlite3VdbeMemSetInt64(pOut, pIn1->eSubtype);
+  }else{
+    sqlite3VdbeMemSetNull(pOut);
+  }
+  break;
+}
+
+/* Opcode: SetSubtype P1 P2 * * *
+** Synopsis:  r[P2].subtype = r[P1]
+**
+** Set the subtype value of register P2 to the integer from register P1.
+** If P1 is NULL, clear the subtype from p2.
+*/
+case OP_SetSubtype: {   /* in1 out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  if( pIn1->flags & MEM_Null ){
+    pOut->flags &= ~MEM_Subtype;
+  }else{
+    assert( pIn1->flags & MEM_Int );
+    pOut->flags |= MEM_Subtype;
+    pOut->eSubtype = (u8)(pIn1->u.i & 0xff);
+  }
+  break;
+}
+
+/* Opcode: FilterAdd P1 * P3 P4 *
+** Synopsis: filter(P1) += key(P3@P4)
+**
+** Compute a hash on the P4 registers starting with r[P3] and
+** add that hash to the bloom filter contained in r[P1].
+*/
+case OP_FilterAdd: {
+  u64 h;
+
+  assert( pOp->p1>0 && pOp->p1<=(p->nMem+1 - p->nCursor) );
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags & MEM_Blob );
+  assert( pIn1->n>0 );
+  h = filterHash(aMem, pOp);
+#ifdef SQLITE_DEBUG
+  if( db->flags&SQLITE_VdbeTrace ){
+    int ii;
+    for(ii=pOp->p3; ii<pOp->p3+pOp->p4.i; ii++){
+      registerTrace(ii, &aMem[ii]);
+    }
+    printf("hash: %llu modulo %d -> %u\n", h, pIn1->n, (int)(h%pIn1->n));
+  }
+#endif
+  h %= (pIn1->n*8);
+  pIn1->z[h/8] |= 1<<(h&7);
+  break;
+}
+
+/* Opcode: Filter P1 P2 P3 P4 *
+** Synopsis: if key(P3@P4) not in filter(P1) goto P2
+**
+** Compute a hash on the key contained in the P4 registers starting
+** with r[P3].  Check to see if that hash is found in the
+** bloom filter hosted by register P1.  If it is not present then
+** maybe jump to P2.  Otherwise fall through.
+**
+** False negatives are harmless.  It is always safe to fall through,
+** even if the value is in the bloom filter.  A false negative causes
+** more CPU cycles to be used, but it should still yield the correct
+** answer.  However, an incorrect answer may well arise from a
+** false positive - if the jump is taken when it should fall through.
+*/
+case OP_Filter: {          /* jump */
+  u64 h;
+
+  assert( pOp->p1>0 && pOp->p1<=(p->nMem+1 - p->nCursor) );
+  pIn1 = &aMem[pOp->p1];
+  assert( (pIn1->flags & MEM_Blob)!=0 );
+  assert( pIn1->n >= 1 );
+  h = filterHash(aMem, pOp);
+#ifdef SQLITE_DEBUG
+  if( db->flags&SQLITE_VdbeTrace ){
+    int ii;
+    for(ii=pOp->p3; ii<pOp->p3+pOp->p4.i; ii++){
+      registerTrace(ii, &aMem[ii]);
+    }
+    printf("hash: %llu modulo %d -> %u\n", h, pIn1->n, (int)(h%pIn1->n));
+  }
+#endif
+  h %= (pIn1->n*8);
+  if( (pIn1->z[h/8] & (1<<(h&7)))==0 ){
+    VdbeBranchTaken(1, 2);
+    p->aCounter[SQLITE_STMTSTATUS_FILTER_HIT]++;
+    goto jump_to_p2;
+  }else{
+    p->aCounter[SQLITE_STMTSTATUS_FILTER_MISS]++;
+    VdbeBranchTaken(0, 2);
+  }
+  break;
+}
+
+/* Opcode: Trace P1 P2 * P4 *
+**
+** Write P4 on the statement trace output if statement tracing is
+** enabled.
+**
+** Operand P1 must be 0x7fffffff and P2 must positive.
+*/
+/* Opcode: Init P1 P2 P3 P4 *
+** Synopsis: Start at P2
+**
+** Programs contain a single instance of this opcode as the very first
+** opcode.
+**
+** If tracing is enabled (by the sqlite3_trace()) interface, then
+** the UTF-8 string contained in P4 is emitted on the trace callback.
+** Or if P4 is blank, use the string returned by sqlite3_sql().
+**
+** If P2 is not zero, jump to instruction P2.
+**
+** Increment the value of P1 so that OP_Once opcodes will jump the
+** first time they are evaluated for this run.
+**
+** If P3 is not zero, then it is an address to jump to if an SQLITE_CORRUPT
+** error is encountered.
+*/
+case OP_Trace:
+case OP_Init: {          /* jump */
+  int i;
+#ifndef SQLITE_OMIT_TRACE
+  char *zTrace;
+#endif
+
+  /* If the P4 argument is not NULL, then it must be an SQL comment string.
+  ** The "--" string is broken up to prevent false-positives with srcck1.c.
+  **
+  ** This assert() provides evidence for:
+  ** EVIDENCE-OF: R-50676-09860 The callback can compute the same text that
+  ** would have been returned by the legacy sqlite3_trace() interface by
+  ** using the X argument when X begins with "--" and invoking
+  ** sqlite3_expanded_sql(P) otherwise.
+  */
+  assert( pOp->p4.z==0 || strncmp(pOp->p4.z, "-" "- ", 3)==0 );
+
+  /* OP_Init is always instruction 0 */
+  assert( pOp==p->aOp || pOp->opcode==OP_Trace );
+
+#ifndef SQLITE_OMIT_TRACE
+  if( (db->mTrace & (SQLITE_TRACE_STMT|SQLITE_TRACE_LEGACY))!=0
+   && p->minWriteFileFormat!=254  /* tag-20220401a */
+   && (zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql))!=0
+  ){
+#ifndef SQLITE_OMIT_DEPRECATED
+    if( db->mTrace & SQLITE_TRACE_LEGACY ){
+      char *z = sqlite3VdbeExpandSql(p, zTrace);
+      db->trace.xLegacy(db->pTraceArg, z);
+      sqlite3_free(z);
+    }else
+#endif
+    if( db->nVdbeExec>1 ){
+      char *z = sqlite3MPrintf(db, "-- %s", zTrace);
+      (void)db->trace.xV2(SQLITE_TRACE_STMT, db->pTraceArg, p, z);
+      sqlite3DbFree(db, z);
+    }else{
+      (void)db->trace.xV2(SQLITE_TRACE_STMT, db->pTraceArg, p, zTrace);
+    }
+  }
+#ifdef SQLITE_USE_FCNTL_TRACE
+  zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql);
+  if( zTrace ){
+    int j;
+    for(j=0; j<db->nDb; j++){
+      if( DbMaskTest(p->btreeMask, j)==0 ) continue;
+      sqlite3_file_control(db, db->aDb[j].zDbSName, SQLITE_FCNTL_TRACE, zTrace);
+    }
+  }
+#endif /* SQLITE_USE_FCNTL_TRACE */
+#ifdef SQLITE_DEBUG
+  if( (db->flags & SQLITE_SqlTrace)!=0
+   && (zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql))!=0
+  ){
+    sqlite3DebugPrintf("SQL-trace: %s\n", zTrace);
+  }
+#endif /* SQLITE_DEBUG */
+#endif /* SQLITE_OMIT_TRACE */
+  assert( pOp->p2>0 );
+  if( pOp->p1>=sqlite3GlobalConfig.iOnceResetThreshold ){
+    if( pOp->opcode==OP_Trace ) break;
+    for(i=1; i<p->nOp; i++){
+      if( p->aOp[i].opcode==OP_Once ) p->aOp[i].p1 = 0;
+    }
+    pOp->p1 = 0;
+  }
+  pOp->p1++;
+  p->aCounter[SQLITE_STMTSTATUS_RUN]++;
+  goto jump_to_p2;
+}
+
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+/* Opcode: CursorHint P1 * * P4 *
+**
+** Provide a hint to cursor P1 that it only needs to return rows that
+** satisfy the Expr in P4.  TK_REGISTER terms in the P4 expression refer
+** to values currently held in registers.  TK_COLUMN terms in the P4
+** expression refer to columns in the b-tree to which cursor P1 is pointing.
+*/
+case OP_CursorHint: {
+  VdbeCursor *pC;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p4type==P4_EXPR );
+  pC = p->apCsr[pOp->p1];
+  if( pC ){
+    assert( pC->eCurType==CURTYPE_BTREE );
+    sqlite3BtreeCursorHint(pC->uc.pCursor, BTREE_HINT_RANGE,
+                           pOp->p4.pExpr, aMem);
+  }
+  break;
+}
+#endif /* SQLITE_ENABLE_CURSOR_HINTS */
+
+#ifdef SQLITE_DEBUG
+/* Opcode:  Abortable   * * * * *
+**
+** Verify that an Abort can happen.  Assert if an Abort at this point
+** might cause database corruption.  This opcode only appears in debugging
+** builds.
+**
+** An Abort is safe if either there have been no writes, or if there is
+** an active statement journal.
+*/
+case OP_Abortable: {
+  sqlite3VdbeAssertAbortable(p);
+  break;
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+/* Opcode:  ReleaseReg   P1 P2 P3 * P5
+** Synopsis: release r[P1@P2] mask P3
+**
+** Release registers from service.  Any content that was in the
+** the registers is unreliable after this opcode completes.
+**
+** The registers released will be the P2 registers starting at P1,
+** except if bit ii of P3 set, then do not release register P1+ii.
+** In other words, P3 is a mask of registers to preserve.
+**
+** Releasing a register clears the Mem.pScopyFrom pointer.  That means
+** that if the content of the released register was set using OP_SCopy,
+** a change to the value of the source register for the OP_SCopy will no longer
+** generate an assertion fault in sqlite3VdbeMemAboutToChange().
+**
+** If P5 is set, then all released registers have their type set
+** to MEM_Undefined so that any subsequent attempt to read the released
+** register (before it is reinitialized) will generate an assertion fault.
+**
+** P5 ought to be set on every call to this opcode.
+** However, there are places in the code generator will release registers
+** before their are used, under the (valid) assumption that the registers
+** will not be reallocated for some other purpose before they are used and
+** hence are safe to release.
+**
+** This opcode is only available in testing and debugging builds.  It is
+** not generated for release builds.  The purpose of this opcode is to help
+** validate the generated bytecode.  This opcode does not actually contribute
+** to computing an answer.
+*/
+case OP_ReleaseReg: {
+  Mem *pMem;
+  int i;
+  u32 constMask;
+  assert( pOp->p1>0 );
+  assert( pOp->p1+pOp->p2<=(p->nMem+1 - p->nCursor)+1 );
+  pMem = &aMem[pOp->p1];
+  constMask = pOp->p3;
+  for(i=0; i<pOp->p2; i++, pMem++){
+    if( i>=32 || (constMask & MASKBIT32(i))==0 ){
+      pMem->pScopyFrom = 0;
+      if( i<32 && pOp->p5 ) MemSetTypeFlag(pMem, MEM_Undefined);
+    }
+  }
+  break;
+}
+#endif
+
+/* Opcode: Noop * * * * *
+**
+** Do nothing.  This instruction is often useful as a jump
+** destination.
+*/
+/*
+** The magic Explain opcode are only inserted when explain==2 (which
+** is to say when the EXPLAIN QUERY PLAN syntax is used.)
+** This opcode records information from the optimizer.  It is the
+** the same as a no-op.  This opcodesnever appears in a real VM program.
+*/
+default: {          /* This is really OP_Noop, OP_Explain */
+  assert( pOp->opcode==OP_Noop || pOp->opcode==OP_Explain );
+
+  break;
+}
+
+/*****************************************************************************
+** The cases of the switch statement above this line should all be indented
+** by 6 spaces.  But the left-most 6 spaces have been removed to improve the
+** readability.  From this point on down, the normal indentation rules are
+** restored.
+*****************************************************************************/
+    }
+
+#if defined(VDBE_PROFILE)
+    *pnCycle += sqlite3NProfileCnt ? sqlite3NProfileCnt : sqlite3Hwtime();
+    pnCycle = 0;
+#elif defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+    if( pnCycle ){
+      *pnCycle += sqlite3Hwtime();
+      pnCycle = 0;
+    }
+#endif
+
+    /* The following code adds nothing to the actual functionality
+    ** of the program.  It is only here for testing and debugging.
+    ** On the other hand, it does burn CPU cycles every time through
+    ** the evaluator loop.  So we can leave it out when NDEBUG is defined.
+    */
+#ifndef NDEBUG
+    assert( pOp>=&aOp[-1] && pOp<&aOp[p->nOp-1] );
+
+#ifdef SQLITE_DEBUG
+    if( db->flags & SQLITE_VdbeTrace ){
+      u8 opProperty = sqlite3OpcodeProperty[pOrigOp->opcode];
+      if( rc!=0 ) printf("rc=%d\n",rc);
+      if( opProperty & (OPFLG_OUT2) ){
+        registerTrace(pOrigOp->p2, &aMem[pOrigOp->p2]);
+      }
+      if( opProperty & OPFLG_OUT3 ){
+        registerTrace(pOrigOp->p3, &aMem[pOrigOp->p3]);
+      }
+      if( opProperty==0xff ){
+        /* Never happens.  This code exists to avoid a harmless linkage
+        ** warning about sqlite3VdbeRegisterDump() being defined but not
+        ** used. */
+        sqlite3VdbeRegisterDump(p);
+      }
+    }
+#endif  /* SQLITE_DEBUG */
+#endif  /* NDEBUG */
+  }  /* The end of the for(;;) loop the loops through opcodes */
+
+  /* If we reach this point, it means that execution is finished with
+  ** an error of some kind.
+  */
+abort_due_to_error:
+  if( db->mallocFailed ){
+    rc = SQLITE_NOMEM_BKPT;
+  }else if( rc==SQLITE_IOERR_CORRUPTFS ){
+    rc = SQLITE_CORRUPT_BKPT;
+  }
+  assert( rc );
+#ifdef SQLITE_DEBUG
+  if( db->flags & SQLITE_VdbeTrace ){
+    const char *zTrace = p->zSql;
+    if( zTrace==0 ){
+      if( aOp[0].opcode==OP_Trace ){
+        zTrace = aOp[0].p4.z;
+      }
+      if( zTrace==0 ) zTrace = "???";
+    }
+    printf("ABORT-due-to-error (rc=%d): %s\n", rc, zTrace);
+  }
+#endif
+  if( p->zErrMsg==0 && rc!=SQLITE_IOERR_NOMEM ){
+    sqlite3VdbeError(p, "%s", sqlite3ErrStr(rc));
+  }
+  p->rc = rc;
+  sqlite3SystemError(db, rc);
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  sqlite3_log(rc, "statement aborts at %d: [%s] %s",
+                   (int)(pOp - aOp), p->zSql, p->zErrMsg);
+  if( p->eVdbeState==VDBE_RUN_STATE ) sqlite3VdbeHalt(p);
+  if( rc==SQLITE_IOERR_NOMEM ) sqlite3OomFault(db);
+  if( rc==SQLITE_CORRUPT && db->autoCommit==0 ){
+    db->flags |= SQLITE_CorruptRdOnly;
+  }
+  rc = SQLITE_ERROR;
+  if( resetSchemaOnFault>0 ){
+    sqlite3ResetOneSchema(db, resetSchemaOnFault-1);
+  }
+
+  /* This is the only way out of this procedure.  We have to
+  ** release the mutexes on btrees that were acquired at the
+  ** top. */
+vdbe_return:
+#if defined(VDBE_PROFILE)
+  if( pnCycle ){
+    *pnCycle += sqlite3NProfileCnt ? sqlite3NProfileCnt : sqlite3Hwtime();
+    pnCycle = 0;
+  }
+#elif defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+  if( pnCycle ){
+    *pnCycle += sqlite3Hwtime();
+    pnCycle = 0;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  while( nVmStep>=nProgressLimit && db->xProgress!=0 ){
+    nProgressLimit += db->nProgressOps;
+    if( db->xProgress(db->pProgressArg) ){
+      nProgressLimit = LARGEST_UINT64;
+      rc = SQLITE_INTERRUPT;
+      goto abort_due_to_error;
+    }
+  }
+#endif
+  p->aCounter[SQLITE_STMTSTATUS_VM_STEP] += (int)nVmStep;
+  if( DbMaskNonZero(p->lockMask) ){
+    sqlite3VdbeLeave(p);
+  }
+  assert( rc!=SQLITE_OK || nExtraDelete==0
+       || sqlite3_strlike("DELETE%",p->zSql,0)!=0
+  );
+  return rc;
+
+  /* Jump to here if a string or blob larger than SQLITE_MAX_LENGTH
+  ** is encountered.
+  */
+too_big:
+  sqlite3VdbeError(p, "string or blob too big");
+  rc = SQLITE_TOOBIG;
+  goto abort_due_to_error;
+
+  /* Jump to here if a malloc() fails.
+  */
+no_mem:
+  sqlite3OomFault(db);
+  sqlite3VdbeError(p, "out of memory");
+  rc = SQLITE_NOMEM_BKPT;
+  goto abort_due_to_error;
+
+  /* Jump to here if the sqlite3_interrupt() API sets the interrupt
+  ** flag.
+  */
+abort_due_to_interrupt:
+  assert( AtomicLoad(&db->u1.isInterrupted) );
+  rc = SQLITE_INTERRUPT;
+  goto abort_due_to_error;
+}
diff --git a/src/vdbe.h b/src/vdbe.h
new file mode 100644
index 0000000..25bda6b
--- /dev/null
+++ b/src/vdbe.h
@@ -0,0 +1,411 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Header file for the Virtual DataBase Engine (VDBE)
+**
+** This header defines the interface to the virtual database engine
+** or VDBE.  The VDBE implements an abstract machine that runs a
+** simple program to access and modify the underlying database.
+*/
+#ifndef SQLITE_VDBE_H
+#define SQLITE_VDBE_H
+#include <stdio.h>
+
+/*
+** A single VDBE is an opaque structure named "Vdbe".  Only routines
+** in the source file sqliteVdbe.c are allowed to see the insides
+** of this structure.
+*/
+typedef struct Vdbe Vdbe;
+
+/*
+** The names of the following types declared in vdbeInt.h are required
+** for the VdbeOp definition.
+*/
+typedef struct sqlite3_value Mem;
+typedef struct SubProgram SubProgram;
+
+/*
+** A single instruction of the virtual machine has an opcode
+** and as many as three operands.  The instruction is recorded
+** as an instance of the following structure:
+*/
+struct VdbeOp {
+  u8 opcode;          /* What operation to perform */
+  signed char p4type; /* One of the P4_xxx constants for p4 */
+  u16 p5;             /* Fifth parameter is an unsigned 16-bit integer */
+  int p1;             /* First operand */
+  int p2;             /* Second parameter (often the jump destination) */
+  int p3;             /* The third parameter */
+  union p4union {     /* fourth parameter */
+    int i;                 /* Integer value if p4type==P4_INT32 */
+    void *p;               /* Generic pointer */
+    char *z;               /* Pointer to data for string (char array) types */
+    i64 *pI64;             /* Used when p4type is P4_INT64 */
+    double *pReal;         /* Used when p4type is P4_REAL */
+    FuncDef *pFunc;        /* Used when p4type is P4_FUNCDEF */
+    sqlite3_context *pCtx; /* Used when p4type is P4_FUNCCTX */
+    CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
+    Mem *pMem;             /* Used when p4type is P4_MEM */
+    VTable *pVtab;         /* Used when p4type is P4_VTAB */
+    KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */
+    u32 *ai;               /* Used when p4type is P4_INTARRAY */
+    SubProgram *pProgram;  /* Used when p4type is P4_SUBPROGRAM */
+    Table *pTab;           /* Used when p4type is P4_TABLE */
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+    Expr *pExpr;           /* Used when p4type is P4_EXPR */
+#endif
+  } p4;
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  char *zComment;          /* Comment to improve readability */
+#endif
+#ifdef SQLITE_VDBE_COVERAGE
+  u32 iSrcLine;            /* Source-code line that generated this opcode
+                           ** with flags in the upper 8 bits */
+#endif
+#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || defined(VDBE_PROFILE)
+  u64 nExec;
+  u64 nCycle;
+#endif
+};
+typedef struct VdbeOp VdbeOp;
+
+
+/*
+** A sub-routine used to implement a trigger program.
+*/
+struct SubProgram {
+  VdbeOp *aOp;                  /* Array of opcodes for sub-program */
+  int nOp;                      /* Elements in aOp[] */
+  int nMem;                     /* Number of memory cells required */
+  int nCsr;                     /* Number of cursors required */
+  u8 *aOnce;                    /* Array of OP_Once flags */
+  void *token;                  /* id that may be used to recursive triggers */
+  SubProgram *pNext;            /* Next sub-program already visited */
+};
+
+/*
+** A smaller version of VdbeOp used for the VdbeAddOpList() function because
+** it takes up less space.
+*/
+struct VdbeOpList {
+  u8 opcode;          /* What operation to perform */
+  signed char p1;     /* First operand */
+  signed char p2;     /* Second parameter (often the jump destination) */
+  signed char p3;     /* Third parameter */
+};
+typedef struct VdbeOpList VdbeOpList;
+
+/*
+** Allowed values of VdbeOp.p4type
+*/
+#define P4_NOTUSED      0   /* The P4 parameter is not used */
+#define P4_TRANSIENT    0   /* P4 is a pointer to a transient string */
+#define P4_STATIC     (-1)  /* Pointer to a static string */
+#define P4_COLLSEQ    (-2)  /* P4 is a pointer to a CollSeq structure */
+#define P4_INT32      (-3)  /* P4 is a 32-bit signed integer */
+#define P4_SUBPROGRAM (-4)  /* P4 is a pointer to a SubProgram structure */
+#define P4_TABLE      (-5)  /* P4 is a pointer to a Table structure */
+/* Above do not own any resources.  Must free those below */
+#define P4_FREE_IF_LE (-6)
+#define P4_DYNAMIC    (-6)  /* Pointer to memory from sqliteMalloc() */
+#define P4_FUNCDEF    (-7)  /* P4 is a pointer to a FuncDef structure */
+#define P4_KEYINFO    (-8)  /* P4 is a pointer to a KeyInfo structure */
+#define P4_EXPR       (-9) /* P4 is a pointer to an Expr tree */
+#define P4_MEM        (-10) /* P4 is a pointer to a Mem*    structure */
+#define P4_VTAB       (-11) /* P4 is a pointer to an sqlite3_vtab structure */
+#define P4_REAL       (-12) /* P4 is a 64-bit floating point value */
+#define P4_INT64      (-13) /* P4 is a 64-bit signed integer */
+#define P4_INTARRAY   (-14) /* P4 is a vector of 32-bit integers */
+#define P4_FUNCCTX    (-15) /* P4 is a pointer to an sqlite3_context object */
+#define P4_TABLEREF   (-16) /* Like P4_TABLE, but reference counted */
+
+/* Error message codes for OP_Halt */
+#define P5_ConstraintNotNull 1
+#define P5_ConstraintUnique  2
+#define P5_ConstraintCheck   3
+#define P5_ConstraintFK      4
+
+/*
+** The Vdbe.aColName array contains 5n Mem structures, where n is the 
+** number of columns of data returned by the statement.
+*/
+#define COLNAME_NAME     0
+#define COLNAME_DECLTYPE 1
+#define COLNAME_DATABASE 2
+#define COLNAME_TABLE    3
+#define COLNAME_COLUMN   4
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+# define COLNAME_N        5      /* Number of COLNAME_xxx symbols */
+#else
+# ifdef SQLITE_OMIT_DECLTYPE
+#   define COLNAME_N      1      /* Store only the name */
+# else
+#   define COLNAME_N      2      /* Store the name and decltype */
+# endif
+#endif
+
+/*
+** The following macro converts a label returned by sqlite3VdbeMakeLabel()
+** into an index into the Parse.aLabel[] array that contains the resolved
+** address of that label.
+*/
+#define ADDR(X)  (~(X))
+
+/*
+** The makefile scans the vdbe.c source file and creates the "opcodes.h"
+** header file that defines a number for each opcode used by the VDBE.
+*/
+#include "opcodes.h"
+
+/*
+** Additional non-public SQLITE_PREPARE_* flags
+*/
+#define SQLITE_PREPARE_SAVESQL  0x80  /* Preserve SQL text */
+#define SQLITE_PREPARE_MASK     0x0f  /* Mask of public flags */
+
+/*
+** Prototypes for the VDBE interface.  See comments on the implementation
+** for a description of what each of these routines does.
+*/
+Vdbe *sqlite3VdbeCreate(Parse*);
+Parse *sqlite3VdbeParser(Vdbe*);
+int sqlite3VdbeAddOp0(Vdbe*,int);
+int sqlite3VdbeAddOp1(Vdbe*,int,int);
+int sqlite3VdbeAddOp2(Vdbe*,int,int,int);
+int sqlite3VdbeGoto(Vdbe*,int);
+int sqlite3VdbeLoadString(Vdbe*,int,const char*);
+void sqlite3VdbeMultiLoad(Vdbe*,int,const char*,...);
+int sqlite3VdbeAddOp3(Vdbe*,int,int,int,int);
+int sqlite3VdbeAddOp4(Vdbe*,int,int,int,int,const char *zP4,int);
+int sqlite3VdbeAddOp4Dup8(Vdbe*,int,int,int,int,const u8*,int);
+int sqlite3VdbeAddOp4Int(Vdbe*,int,int,int,int,int);
+int sqlite3VdbeAddFunctionCall(Parse*,int,int,int,int,const FuncDef*,int);
+void sqlite3VdbeEndCoroutine(Vdbe*,int);
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_TEST_REALLOC_STRESS)
+  void sqlite3VdbeVerifyNoMallocRequired(Vdbe *p, int N);
+  void sqlite3VdbeVerifyNoResultRow(Vdbe *p);
+#else
+# define sqlite3VdbeVerifyNoMallocRequired(A,B)
+# define sqlite3VdbeVerifyNoResultRow(A)
+#endif
+#if defined(SQLITE_DEBUG)
+  void sqlite3VdbeVerifyAbortable(Vdbe *p, int);
+  void sqlite3VdbeNoJumpsOutsideSubrtn(Vdbe*,int,int,int);
+#else
+# define sqlite3VdbeVerifyAbortable(A,B)
+# define sqlite3VdbeNoJumpsOutsideSubrtn(A,B,C,D)
+#endif
+VdbeOp *sqlite3VdbeAddOpList(Vdbe*, int nOp, VdbeOpList const *aOp,int iLineno);
+#ifndef SQLITE_OMIT_EXPLAIN
+  int sqlite3VdbeExplain(Parse*,u8,const char*,...);
+  void sqlite3VdbeExplainPop(Parse*);
+  int sqlite3VdbeExplainParent(Parse*);
+# define ExplainQueryPlan(P)        sqlite3VdbeExplain P
+# ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+#  define ExplainQueryPlan2(V,P)     (V = sqlite3VdbeExplain P)
+# else
+#  define ExplainQueryPlan2(V,P)     ExplainQueryPlan(P)
+# endif
+# define ExplainQueryPlanPop(P)     sqlite3VdbeExplainPop(P)
+# define ExplainQueryPlanParent(P)  sqlite3VdbeExplainParent(P)
+#else
+# define ExplainQueryPlan(P)
+# define ExplainQueryPlan2(V,P)
+# define ExplainQueryPlanPop(P)
+# define ExplainQueryPlanParent(P) 0
+# define sqlite3ExplainBreakpoint(A,B) /*no-op*/
+#endif
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_OMIT_EXPLAIN)
+  void sqlite3ExplainBreakpoint(const char*,const char*);
+#else
+# define sqlite3ExplainBreakpoint(A,B) /*no-op*/
+#endif
+void sqlite3VdbeAddParseSchemaOp(Vdbe*, int, char*, u16);
+void sqlite3VdbeChangeOpcode(Vdbe*, int addr, u8);
+void sqlite3VdbeChangeP1(Vdbe*, int addr, int P1);
+void sqlite3VdbeChangeP2(Vdbe*, int addr, int P2);
+void sqlite3VdbeChangeP3(Vdbe*, int addr, int P3);
+void sqlite3VdbeChangeP5(Vdbe*, u16 P5);
+void sqlite3VdbeTypeofColumn(Vdbe*, int);
+void sqlite3VdbeJumpHere(Vdbe*, int addr);
+void sqlite3VdbeJumpHereOrPopInst(Vdbe*, int addr);
+int sqlite3VdbeChangeToNoop(Vdbe*, int addr);
+int sqlite3VdbeDeletePriorOpcode(Vdbe*, u8 op);
+#ifdef SQLITE_DEBUG
+  void sqlite3VdbeReleaseRegisters(Parse*,int addr, int n, u32 mask, int);
+#else
+# define sqlite3VdbeReleaseRegisters(P,A,N,M,F)
+#endif
+void sqlite3VdbeChangeP4(Vdbe*, int addr, const char *zP4, int N);
+void sqlite3VdbeAppendP4(Vdbe*, void *pP4, int p4type);
+void sqlite3VdbeSetP4KeyInfo(Parse*, Index*);
+void sqlite3VdbeUsesBtree(Vdbe*, int);
+VdbeOp *sqlite3VdbeGetOp(Vdbe*, int);
+VdbeOp *sqlite3VdbeGetLastOp(Vdbe*);
+int sqlite3VdbeMakeLabel(Parse*);
+void sqlite3VdbeRunOnlyOnce(Vdbe*);
+void sqlite3VdbeReusable(Vdbe*);
+void sqlite3VdbeDelete(Vdbe*);
+void sqlite3VdbeMakeReady(Vdbe*,Parse*);
+int sqlite3VdbeFinalize(Vdbe*);
+void sqlite3VdbeResolveLabel(Vdbe*, int);
+int sqlite3VdbeCurrentAddr(Vdbe*);
+#ifdef SQLITE_DEBUG
+  int sqlite3VdbeAssertMayAbort(Vdbe *, int);
+#endif
+void sqlite3VdbeResetStepResult(Vdbe*);
+void sqlite3VdbeRewind(Vdbe*);
+int sqlite3VdbeReset(Vdbe*);
+void sqlite3VdbeSetNumCols(Vdbe*,int);
+int sqlite3VdbeSetColName(Vdbe*, int, int, const char *, void(*)(void*));
+void sqlite3VdbeCountChanges(Vdbe*);
+sqlite3 *sqlite3VdbeDb(Vdbe*);
+u8 sqlite3VdbePrepareFlags(Vdbe*);
+void sqlite3VdbeSetSql(Vdbe*, const char *z, int n, u8);
+#ifdef SQLITE_ENABLE_NORMALIZE
+void sqlite3VdbeAddDblquoteStr(sqlite3*,Vdbe*,const char*);
+int sqlite3VdbeUsesDoubleQuotedString(Vdbe*,const char*);
+#endif
+void sqlite3VdbeSwap(Vdbe*,Vdbe*);
+VdbeOp *sqlite3VdbeTakeOpArray(Vdbe*, int*, int*);
+sqlite3_value *sqlite3VdbeGetBoundValue(Vdbe*, int, u8);
+void sqlite3VdbeSetVarmask(Vdbe*, int);
+#ifndef SQLITE_OMIT_TRACE
+  char *sqlite3VdbeExpandSql(Vdbe*, const char*);
+#endif
+int sqlite3MemCompare(const Mem*, const Mem*, const CollSeq*);
+int sqlite3BlobCompare(const Mem*, const Mem*);
+
+void sqlite3VdbeRecordUnpack(KeyInfo*,int,const void*,UnpackedRecord*);
+int sqlite3VdbeRecordCompare(int,const void*,UnpackedRecord*);
+int sqlite3VdbeRecordCompareWithSkip(int, const void *, UnpackedRecord *, int);
+UnpackedRecord *sqlite3VdbeAllocUnpackedRecord(KeyInfo*);
+
+typedef int (*RecordCompare)(int,const void*,UnpackedRecord*);
+RecordCompare sqlite3VdbeFindCompare(UnpackedRecord*);
+
+void sqlite3VdbeLinkSubProgram(Vdbe *, SubProgram *);
+int sqlite3VdbeHasSubProgram(Vdbe*);
+
+int sqlite3NotPureFunc(sqlite3_context*);
+#ifdef SQLITE_ENABLE_BYTECODE_VTAB
+int sqlite3VdbeBytecodeVtabInit(sqlite3*);
+#endif
+
+/* Use SQLITE_ENABLE_COMMENTS to enable generation of extra comments on
+** each VDBE opcode.
+**
+** Use the SQLITE_ENABLE_MODULE_COMMENTS macro to see some extra no-op
+** comments in VDBE programs that show key decision points in the code
+** generator.
+*/
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  void sqlite3VdbeComment(Vdbe*, const char*, ...);
+# define VdbeComment(X)  sqlite3VdbeComment X
+  void sqlite3VdbeNoopComment(Vdbe*, const char*, ...);
+# define VdbeNoopComment(X)  sqlite3VdbeNoopComment X
+# ifdef SQLITE_ENABLE_MODULE_COMMENTS
+#   define VdbeModuleComment(X)  sqlite3VdbeNoopComment X
+# else
+#   define VdbeModuleComment(X)
+# endif
+#else
+# define VdbeComment(X)
+# define VdbeNoopComment(X)
+# define VdbeModuleComment(X)
+#endif
+
+/*
+** The VdbeCoverage macros are used to set a coverage testing point
+** for VDBE branch instructions.  The coverage testing points are line
+** numbers in the sqlite3.c source file.  VDBE branch coverage testing
+** only works with an amalgamation build.  That's ok since a VDBE branch
+** coverage build designed for testing the test suite only.  No application
+** should ever ship with VDBE branch coverage measuring turned on.
+**
+**    VdbeCoverage(v)                  // Mark the previously coded instruction
+**                                     // as a branch
+**
+**    VdbeCoverageIf(v, conditional)   // Mark previous if conditional true
+**
+**    VdbeCoverageAlwaysTaken(v)       // Previous branch is always taken
+**
+**    VdbeCoverageNeverTaken(v)        // Previous branch is never taken
+**
+**    VdbeCoverageNeverNull(v)         // Previous three-way branch is only
+**                                     // taken on the first two ways.  The
+**                                     // NULL option is not possible
+**
+**    VdbeCoverageEqNe(v)              // Previous OP_Jump is only interested
+**                                     // in distinguishing equal and not-equal.
+**
+** Every VDBE branch operation must be tagged with one of the macros above.
+** If not, then when "make test" is run with -DSQLITE_VDBE_COVERAGE and
+** -DSQLITE_DEBUG then an ALWAYS() will fail in the vdbeTakeBranch()
+** routine in vdbe.c, alerting the developer to the missed tag.
+**
+** During testing, the test application will invoke
+** sqlite3_test_control(SQLITE_TESTCTRL_VDBE_COVERAGE,...) to set a callback
+** routine that is invoked as each bytecode branch is taken.  The callback
+** contains the sqlite3.c source line number of the VdbeCoverage macro and
+** flags to indicate whether or not the branch was taken.  The test application
+** is responsible for keeping track of this and reporting byte-code branches
+** that are never taken.
+**
+** See the VdbeBranchTaken() macro and vdbeTakeBranch() function in the
+** vdbe.c source file for additional information.
+*/
+#ifdef SQLITE_VDBE_COVERAGE
+  void sqlite3VdbeSetLineNumber(Vdbe*,int);
+# define VdbeCoverage(v) sqlite3VdbeSetLineNumber(v,__LINE__)
+# define VdbeCoverageIf(v,x) if(x)sqlite3VdbeSetLineNumber(v,__LINE__)
+# define VdbeCoverageAlwaysTaken(v) \
+         sqlite3VdbeSetLineNumber(v,__LINE__|0x5000000);
+# define VdbeCoverageNeverTaken(v) \
+         sqlite3VdbeSetLineNumber(v,__LINE__|0x6000000);
+# define VdbeCoverageNeverNull(v) \
+         sqlite3VdbeSetLineNumber(v,__LINE__|0x4000000);
+# define VdbeCoverageNeverNullIf(v,x) \
+         if(x)sqlite3VdbeSetLineNumber(v,__LINE__|0x4000000);
+# define VdbeCoverageEqNe(v) \
+         sqlite3VdbeSetLineNumber(v,__LINE__|0x8000000);
+# define VDBE_OFFSET_LINENO(x) (__LINE__+x)
+#else
+# define VdbeCoverage(v)
+# define VdbeCoverageIf(v,x)
+# define VdbeCoverageAlwaysTaken(v)
+# define VdbeCoverageNeverTaken(v)
+# define VdbeCoverageNeverNull(v)
+# define VdbeCoverageNeverNullIf(v,x)
+# define VdbeCoverageEqNe(v)
+# define VDBE_OFFSET_LINENO(x) 0
+#endif
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+void sqlite3VdbeScanStatus(Vdbe*, int, int, int, LogEst, const char*);
+void sqlite3VdbeScanStatusRange(Vdbe*, int, int, int);
+void sqlite3VdbeScanStatusCounters(Vdbe*, int, int, int);
+#else
+# define sqlite3VdbeScanStatus(a,b,c,d,e,f)
+# define sqlite3VdbeScanStatusRange(a,b,c,d)
+# define sqlite3VdbeScanStatusCounters(a,b,c,d)
+#endif
+
+#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
+void sqlite3VdbePrintOp(FILE*, int, VdbeOp*);
+#endif
+
+#if defined(SQLITE_ENABLE_CURSOR_HINTS) && defined(SQLITE_DEBUG)
+int sqlite3CursorRangeHintExprCheck(Walker *pWalker, Expr *pExpr);
+#endif
+
+#endif /* SQLITE_VDBE_H */
diff --git a/src/vdbeInt.h b/src/vdbeInt.h
new file mode 100644
index 0000000..2a23c3f
--- /dev/null
+++ b/src/vdbeInt.h
@@ -0,0 +1,731 @@
+/*
+** 2003 September 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the header file for information that is private to the
+** VDBE.  This information used to all be at the top of the single
+** source code file "vdbe.c".  When that file became too big (over
+** 6000 lines long) it was split up into several smaller files and
+** this header information was factored out.
+*/
+#ifndef SQLITE_VDBEINT_H
+#define SQLITE_VDBEINT_H
+
+/*
+** The maximum number of times that a statement will try to reparse
+** itself before giving up and returning SQLITE_SCHEMA.
+*/
+#ifndef SQLITE_MAX_SCHEMA_RETRY
+# define SQLITE_MAX_SCHEMA_RETRY 50
+#endif
+
+/*
+** VDBE_DISPLAY_P4 is true or false depending on whether or not the
+** "explain" P4 display logic is enabled.
+*/
+#if !defined(SQLITE_OMIT_EXPLAIN) || !defined(NDEBUG) \
+     || defined(VDBE_PROFILE) || defined(SQLITE_DEBUG) \
+     || defined(SQLITE_ENABLE_BYTECODE_VTAB)
+# define VDBE_DISPLAY_P4 1
+#else
+# define VDBE_DISPLAY_P4 0
+#endif
+
+/*
+** SQL is translated into a sequence of instructions to be
+** executed by a virtual machine.  Each instruction is an instance
+** of the following structure.
+*/
+typedef struct VdbeOp Op;
+
+/*
+** Boolean values
+*/
+typedef unsigned Bool;
+
+/* Opaque type used by code in vdbesort.c */
+typedef struct VdbeSorter VdbeSorter;
+
+/* Elements of the linked list at Vdbe.pAuxData */
+typedef struct AuxData AuxData;
+
+/* A cache of large TEXT or BLOB values in a VdbeCursor */
+typedef struct VdbeTxtBlbCache VdbeTxtBlbCache;
+
+/* Types of VDBE cursors */
+#define CURTYPE_BTREE       0
+#define CURTYPE_SORTER      1
+#define CURTYPE_VTAB        2
+#define CURTYPE_PSEUDO      3
+
+/*
+** A VdbeCursor is an superclass (a wrapper) for various cursor objects:
+**
+**      * A b-tree cursor
+**          -  In the main database or in an ephemeral database
+**          -  On either an index or a table
+**      * A sorter
+**      * A virtual table
+**      * A one-row "pseudotable" stored in a single register
+*/
+typedef struct VdbeCursor VdbeCursor;
+struct VdbeCursor {
+  u8 eCurType;            /* One of the CURTYPE_* values above */
+  i8 iDb;                 /* Index of cursor database in db->aDb[] */
+  u8 nullRow;             /* True if pointing to a row with no data */
+  u8 deferredMoveto;      /* A call to sqlite3BtreeMoveto() is needed */
+  u8 isTable;             /* True for rowid tables.  False for indexes */
+#ifdef SQLITE_DEBUG
+  u8 seekOp;              /* Most recent seek operation on this cursor */
+  u8 wrFlag;              /* The wrFlag argument to sqlite3BtreeCursor() */
+#endif
+  Bool isEphemeral:1;     /* True for an ephemeral table */
+  Bool useRandomRowid:1;  /* Generate new record numbers semi-randomly */
+  Bool isOrdered:1;       /* True if the table is not BTREE_UNORDERED */
+  Bool noReuse:1;         /* OpenEphemeral may not reuse this cursor */
+  Bool colCache:1;        /* pCache pointer is initialized and non-NULL */
+  u16 seekHit;            /* See the OP_SeekHit and OP_IfNoHope opcodes */
+  union {                 /* pBtx for isEphermeral.  pAltMap otherwise */
+    Btree *pBtx;            /* Separate file holding temporary table */
+    u32 *aAltMap;           /* Mapping from table to index column numbers */
+  } ub;
+  i64 seqCount;           /* Sequence counter */
+
+  /* Cached OP_Column parse information is only valid if cacheStatus matches
+  ** Vdbe.cacheCtr.  Vdbe.cacheCtr will never take on the value of
+  ** CACHE_STALE (0) and so setting cacheStatus=CACHE_STALE guarantees that
+  ** the cache is out of date. */
+  u32 cacheStatus;        /* Cache is valid if this matches Vdbe.cacheCtr */
+  int seekResult;         /* Result of previous sqlite3BtreeMoveto() or 0
+                          ** if there have been no prior seeks on the cursor. */
+  /* seekResult does not distinguish between "no seeks have ever occurred
+  ** on this cursor" and "the most recent seek was an exact match".
+  ** For CURTYPE_PSEUDO, seekResult is the register holding the record */
+
+  /* When a new VdbeCursor is allocated, only the fields above are zeroed.
+  ** The fields that follow are uninitialized, and must be individually
+  ** initialized prior to first use. */
+  VdbeCursor *pAltCursor; /* Associated index cursor from which to read */
+  union {
+    BtCursor *pCursor;          /* CURTYPE_BTREE or _PSEUDO.  Btree cursor */
+    sqlite3_vtab_cursor *pVCur; /* CURTYPE_VTAB.              Vtab cursor */
+    VdbeSorter *pSorter;        /* CURTYPE_SORTER.            Sorter object */
+  } uc;
+  KeyInfo *pKeyInfo;      /* Info about index keys needed by index cursors */
+  u32 iHdrOffset;         /* Offset to next unparsed byte of the header */
+  Pgno pgnoRoot;          /* Root page of the open btree cursor */
+  i16 nField;             /* Number of fields in the header */
+  u16 nHdrParsed;         /* Number of header fields parsed so far */
+  i64 movetoTarget;       /* Argument to the deferred sqlite3BtreeMoveto() */
+  u32 *aOffset;           /* Pointer to aType[nField] */
+  const u8 *aRow;         /* Data for the current row, if all on one page */
+  u32 payloadSize;        /* Total number of bytes in the record */
+  u32 szRow;              /* Byte available in aRow */
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+  u64 maskUsed;           /* Mask of columns used by this cursor */
+#endif
+  VdbeTxtBlbCache *pCache; /* Cache of large TEXT or BLOB values */
+
+  /* 2*nField extra array elements allocated for aType[], beyond the one
+  ** static element declared in the structure.  nField total array slots for
+  ** aType[] and nField+1 array slots for aOffset[] */
+  u32 aType[1];           /* Type values record decode.  MUST BE LAST */
+};
+
+/* Return true if P is a null-only cursor
+*/
+#define IsNullCursor(P) \
+  ((P)->eCurType==CURTYPE_PSEUDO && (P)->nullRow && (P)->seekResult==0)
+
+/*
+** A value for VdbeCursor.cacheStatus that means the cache is always invalid.
+*/
+#define CACHE_STALE 0
+
+/*
+** Large TEXT or BLOB values can be slow to load, so we want to avoid
+** loading them more than once.  For that reason, large TEXT and BLOB values
+** can be stored in a cache defined by this object, and attached to the
+** VdbeCursor using the pCache field.
+*/
+struct VdbeTxtBlbCache {
+  char *pCValue;        /* A RCStr buffer to hold the value */
+  i64 iOffset;          /* File offset of the row being cached */
+  int iCol;             /* Column for which the cache is valid */
+  u32 cacheStatus;      /* Vdbe.cacheCtr value */
+  u32 colCacheCtr;      /* Column cache counter */
+};
+
+/*
+** When a sub-program is executed (OP_Program), a structure of this type
+** is allocated to store the current value of the program counter, as
+** well as the current memory cell array and various other frame specific
+** values stored in the Vdbe struct. When the sub-program is finished,
+** these values are copied back to the Vdbe from the VdbeFrame structure,
+** restoring the state of the VM to as it was before the sub-program
+** began executing.
+**
+** The memory for a VdbeFrame object is allocated and managed by a memory
+** cell in the parent (calling) frame. When the memory cell is deleted or
+** overwritten, the VdbeFrame object is not freed immediately. Instead, it
+** is linked into the Vdbe.pDelFrame list. The contents of the Vdbe.pDelFrame
+** list is deleted when the VM is reset in VdbeHalt(). The reason for doing
+** this instead of deleting the VdbeFrame immediately is to avoid recursive
+** calls to sqlite3VdbeMemRelease() when the memory cells belonging to the
+** child frame are released.
+**
+** The currently executing frame is stored in Vdbe.pFrame. Vdbe.pFrame is
+** set to NULL if the currently executing frame is the main program.
+*/
+typedef struct VdbeFrame VdbeFrame;
+struct VdbeFrame {
+  Vdbe *v;                /* VM this frame belongs to */
+  VdbeFrame *pParent;     /* Parent of this frame, or NULL if parent is main */
+  Op *aOp;                /* Program instructions for parent frame */
+  Mem *aMem;              /* Array of memory cells for parent frame */
+  VdbeCursor **apCsr;     /* Array of Vdbe cursors for parent frame */
+  u8 *aOnce;              /* Bitmask used by OP_Once */
+  void *token;            /* Copy of SubProgram.token */
+  i64 lastRowid;          /* Last insert rowid (sqlite3.lastRowid) */
+  AuxData *pAuxData;      /* Linked list of auxdata allocations */
+#if SQLITE_DEBUG
+  u32 iFrameMagic;        /* magic number for sanity checking */
+#endif
+  int nCursor;            /* Number of entries in apCsr */
+  int pc;                 /* Program Counter in parent (calling) frame */
+  int nOp;                /* Size of aOp array */
+  int nMem;               /* Number of entries in aMem */
+  int nChildMem;          /* Number of memory cells for child frame */
+  int nChildCsr;          /* Number of cursors for child frame */
+  i64 nChange;            /* Statement changes (Vdbe.nChange)     */
+  i64 nDbChange;          /* Value of db->nChange */
+};
+
+/* Magic number for sanity checking on VdbeFrame objects */
+#define SQLITE_FRAME_MAGIC 0x879fb71e
+
+/*
+** Return a pointer to the array of registers allocated for use
+** by a VdbeFrame.
+*/
+#define VdbeFrameMem(p) ((Mem *)&((u8 *)p)[ROUND8(sizeof(VdbeFrame))])
+
+/*
+** Internally, the vdbe manipulates nearly all SQL values as Mem
+** structures. Each Mem struct may cache multiple representations (string,
+** integer etc.) of the same value.
+*/
+struct sqlite3_value {
+  union MemValue {
+    double r;           /* Real value used when MEM_Real is set in flags */
+    i64 i;              /* Integer value used when MEM_Int is set in flags */
+    int nZero;          /* Extra zero bytes when MEM_Zero and MEM_Blob set */
+    const char *zPType; /* Pointer type when MEM_Term|MEM_Subtype|MEM_Null */
+    FuncDef *pDef;      /* Used only when flags==MEM_Agg */
+  } u;
+  char *z;            /* String or BLOB value */
+  int n;              /* Number of characters in string value, excluding '\0' */
+  u16 flags;          /* Some combination of MEM_Null, MEM_Str, MEM_Dyn, etc. */
+  u8  enc;            /* SQLITE_UTF8, SQLITE_UTF16BE, SQLITE_UTF16LE */
+  u8  eSubtype;       /* Subtype for this value */
+  /* ShallowCopy only needs to copy the information above */
+  sqlite3 *db;        /* The associated database connection */
+  int szMalloc;       /* Size of the zMalloc allocation */
+  u32 uTemp;          /* Transient storage for serial_type in OP_MakeRecord */
+  char *zMalloc;      /* Space to hold MEM_Str or MEM_Blob if szMalloc>0 */
+  void (*xDel)(void*);/* Destructor for Mem.z - only valid if MEM_Dyn */
+#ifdef SQLITE_DEBUG
+  Mem *pScopyFrom;    /* This Mem is a shallow copy of pScopyFrom */
+  u16 mScopyFlags;    /* flags value immediately after the shallow copy */
+#endif
+};
+
+/*
+** Size of struct Mem not including the Mem.zMalloc member or anything that
+** follows.
+*/
+#define MEMCELLSIZE offsetof(Mem,db)
+
+/* One or more of the following flags are set to indicate the
+** representations of the value stored in the Mem struct.
+**
+**  *  MEM_Null                An SQL NULL value
+**
+**  *  MEM_Null|MEM_Zero       An SQL NULL with the virtual table
+**                             UPDATE no-change flag set
+**
+**  *  MEM_Null|MEM_Term|      An SQL NULL, but also contains a
+**        MEM_Subtype          pointer accessible using
+**                             sqlite3_value_pointer().
+**
+**  *  MEM_Null|MEM_Cleared    Special SQL NULL that compares non-equal
+**                             to other NULLs even using the IS operator.
+**
+**  *  MEM_Str                 A string, stored in Mem.z with
+**                             length Mem.n.  Zero-terminated if
+**                             MEM_Term is set.  This flag is
+**                             incompatible with MEM_Blob and
+**                             MEM_Null, but can appear with MEM_Int,
+**                             MEM_Real, and MEM_IntReal.
+**
+**  *  MEM_Blob                A blob, stored in Mem.z length Mem.n.
+**                             Incompatible with MEM_Str, MEM_Null,
+**                             MEM_Int, MEM_Real, and MEM_IntReal.
+**
+**  *  MEM_Blob|MEM_Zero       A blob in Mem.z of length Mem.n plus
+**                             MEM.u.i extra 0x00 bytes at the end.
+**
+**  *  MEM_Int                 Integer stored in Mem.u.i.
+**
+**  *  MEM_Real                Real stored in Mem.u.r.
+**
+**  *  MEM_IntReal             Real stored as an integer in Mem.u.i.
+**
+** If the MEM_Null flag is set, then the value is an SQL NULL value.
+** For a pointer type created using sqlite3_bind_pointer() or
+** sqlite3_result_pointer() the MEM_Term and MEM_Subtype flags are also set.
+**
+** If the MEM_Str flag is set then Mem.z points at a string representation.
+** Usually this is encoded in the same unicode encoding as the main
+** database (see below for exceptions). If the MEM_Term flag is also
+** set, then the string is nul terminated. The MEM_Int and MEM_Real
+** flags may coexist with the MEM_Str flag.
+*/
+#define MEM_Undefined 0x0000   /* Value is undefined */
+#define MEM_Null      0x0001   /* Value is NULL (or a pointer) */
+#define MEM_Str       0x0002   /* Value is a string */
+#define MEM_Int       0x0004   /* Value is an integer */
+#define MEM_Real      0x0008   /* Value is a real number */
+#define MEM_Blob      0x0010   /* Value is a BLOB */
+#define MEM_IntReal   0x0020   /* MEM_Int that stringifies like MEM_Real */
+#define MEM_AffMask   0x003f   /* Mask of affinity bits */
+
+/* Extra bits that modify the meanings of the core datatypes above
+*/
+#define MEM_FromBind  0x0040   /* Value originates from sqlite3_bind() */
+ /*                   0x0080   // Available */
+#define MEM_Cleared   0x0100   /* NULL set by OP_Null, not from data */
+#define MEM_Term      0x0200   /* String in Mem.z is zero terminated */
+#define MEM_Zero      0x0400   /* Mem.i contains count of 0s appended to blob */
+#define MEM_Subtype   0x0800   /* Mem.eSubtype is valid */
+#define MEM_TypeMask  0x0dbf   /* Mask of type bits */
+
+/* Bits that determine the storage for Mem.z for a string or blob or
+** aggregate accumulator.
+*/
+#define MEM_Dyn       0x1000   /* Need to call Mem.xDel() on Mem.z */
+#define MEM_Static    0x2000   /* Mem.z points to a static string */
+#define MEM_Ephem     0x4000   /* Mem.z points to an ephemeral string */
+#define MEM_Agg       0x8000   /* Mem.z points to an agg function context */
+
+/* Return TRUE if Mem X contains dynamically allocated content - anything
+** that needs to be deallocated to avoid a leak.
+*/
+#define VdbeMemDynamic(X)  \
+  (((X)->flags&(MEM_Agg|MEM_Dyn))!=0)
+
+/*
+** Clear any existing type flags from a Mem and replace them with f
+*/
+#define MemSetTypeFlag(p, f) \
+   ((p)->flags = ((p)->flags&~(MEM_TypeMask|MEM_Zero))|f)
+
+/*
+** True if Mem X is a NULL-nochng type.
+*/
+#define MemNullNochng(X) \
+  (((X)->flags&MEM_TypeMask)==(MEM_Null|MEM_Zero) \
+    && (X)->n==0 && (X)->u.nZero==0)
+
+/*
+** Return true if a memory cell has been initialized and is valid.
+** is for use inside assert() statements only.
+**
+** A Memory cell is initialized if at least one of the
+** MEM_Null, MEM_Str, MEM_Int, MEM_Real, MEM_Blob, or MEM_IntReal bits
+** is set.  It is "undefined" if all those bits are zero.
+*/
+#ifdef SQLITE_DEBUG
+#define memIsValid(M)  ((M)->flags & MEM_AffMask)!=0
+#endif
+
+/*
+** Each auxiliary data pointer stored by a user defined function
+** implementation calling sqlite3_set_auxdata() is stored in an instance
+** of this structure. All such structures associated with a single VM
+** are stored in a linked list headed at Vdbe.pAuxData. All are destroyed
+** when the VM is halted (if not before).
+*/
+struct AuxData {
+  int iAuxOp;                     /* Instruction number of OP_Function opcode */
+  int iAuxArg;                    /* Index of function argument. */
+  void *pAux;                     /* Aux data pointer */
+  void (*xDeleteAux)(void*);      /* Destructor for the aux data */
+  AuxData *pNextAux;              /* Next element in list */
+};
+
+/*
+** The "context" argument for an installable function.  A pointer to an
+** instance of this structure is the first argument to the routines used
+** implement the SQL functions.
+**
+** There is a typedef for this structure in sqlite.h.  So all routines,
+** even the public interface to SQLite, can use a pointer to this structure.
+** But this file is the only place where the internal details of this
+** structure are known.
+**
+** This structure is defined inside of vdbeInt.h because it uses substructures
+** (Mem) which are only defined there.
+*/
+struct sqlite3_context {
+  Mem *pOut;              /* The return value is stored here */
+  FuncDef *pFunc;         /* Pointer to function information */
+  Mem *pMem;              /* Memory cell used to store aggregate context */
+  Vdbe *pVdbe;            /* The VM that owns this context */
+  int iOp;                /* Instruction number of OP_Function */
+  int isError;            /* Error code returned by the function. */
+  u8 enc;                 /* Encoding to use for results */
+  u8 skipFlag;            /* Skip accumulator loading if true */
+  u8 argc;                /* Number of arguments */
+  sqlite3_value *argv[1]; /* Argument set */
+};
+
+/* A bitfield type for use inside of structures.  Always follow with :N where
+** N is the number of bits.
+*/
+typedef unsigned bft;  /* Bit Field Type */
+
+/* The ScanStatus object holds a single value for the
+** sqlite3_stmt_scanstatus() interface.
+**
+** aAddrRange[]:
+**   This array is used by ScanStatus elements associated with EQP
+**   notes that make an SQLITE_SCANSTAT_NCYCLE value available. It is
+**   an array of up to 3 ranges of VM addresses for which the Vdbe.anCycle[]
+**   values should be summed to calculate the NCYCLE value. Each pair of
+**   integer addresses is a start and end address (both inclusive) for a range
+**   instructions. A start value of 0 indicates an empty range.
+*/
+typedef struct ScanStatus ScanStatus;
+struct ScanStatus {
+  int addrExplain;                /* OP_Explain for loop */
+  int aAddrRange[6];
+  int addrLoop;                   /* Address of "loops" counter */
+  int addrVisit;                  /* Address of "rows visited" counter */
+  int iSelectID;                  /* The "Select-ID" for this loop */
+  LogEst nEst;                    /* Estimated output rows per loop */
+  char *zName;                    /* Name of table or index */
+};
+
+/* The DblquoteStr object holds the text of a double-quoted
+** string for a prepared statement.  A linked list of these objects
+** is constructed during statement parsing and is held on Vdbe.pDblStr.
+** When computing a normalized SQL statement for an SQL statement, that
+** list is consulted for each double-quoted identifier to see if the
+** identifier should really be a string literal.
+*/
+typedef struct DblquoteStr DblquoteStr;
+struct DblquoteStr {
+  DblquoteStr *pNextStr;   /* Next string literal in the list */
+  char z[8];               /* Dequoted value for the string */
+};
+
+/*
+** An instance of the virtual machine.  This structure contains the complete
+** state of the virtual machine.
+**
+** The "sqlite3_stmt" structure pointer that is returned by sqlite3_prepare()
+** is really a pointer to an instance of this structure.
+*/
+struct Vdbe {
+  sqlite3 *db;            /* The database connection that owns this statement */
+  Vdbe **ppVPrev,*pVNext; /* Linked list of VDBEs with the same Vdbe.db */
+  Parse *pParse;          /* Parsing context used to create this Vdbe */
+  ynVar nVar;             /* Number of entries in aVar[] */
+  int nMem;               /* Number of memory locations currently allocated */
+  int nCursor;            /* Number of slots in apCsr[] */
+  u32 cacheCtr;           /* VdbeCursor row cache generation counter */
+  int pc;                 /* The program counter */
+  int rc;                 /* Value to return */
+  i64 nChange;            /* Number of db changes made since last reset */
+  int iStatement;         /* Statement number (or 0 if has no opened stmt) */
+  i64 iCurrentTime;       /* Value of julianday('now') for this statement */
+  i64 nFkConstraint;      /* Number of imm. FK constraints this VM */
+  i64 nStmtDefCons;       /* Number of def. constraints when stmt started */
+  i64 nStmtDefImmCons;    /* Number of def. imm constraints when stmt started */
+  Mem *aMem;              /* The memory locations */
+  Mem **apArg;            /* Arguments to currently executing user function */
+  VdbeCursor **apCsr;     /* One element of this array for each open cursor */
+  Mem *aVar;              /* Values for the OP_Variable opcode. */
+
+  /* When allocating a new Vdbe object, all of the fields below should be
+  ** initialized to zero or NULL */
+
+  Op *aOp;                /* Space to hold the virtual machine's program */
+  int nOp;                /* Number of instructions in the program */
+  int nOpAlloc;           /* Slots allocated for aOp[] */
+  Mem *aColName;          /* Column names to return */
+  Mem *pResultRow;        /* Current output row */
+  char *zErrMsg;          /* Error message written here */
+  VList *pVList;          /* Name of variables */
+#ifndef SQLITE_OMIT_TRACE
+  i64 startTime;          /* Time when query started - used for profiling */
+#endif
+#ifdef SQLITE_DEBUG
+  int rcApp;              /* errcode set by sqlite3_result_error_code() */
+  u32 nWrite;             /* Number of write operations that have occurred */
+#endif
+  u16 nResColumn;         /* Number of columns in one row of the result set */
+  u16 nResAlloc;          /* Column slots allocated to aColName[] */
+  u8 errorAction;         /* Recovery action to do in case of an error */
+  u8 minWriteFileFormat;  /* Minimum file format for writable database files */
+  u8 prepFlags;           /* SQLITE_PREPARE_* flags */
+  u8 eVdbeState;          /* On of the VDBE_*_STATE values */
+  bft expired:2;          /* 1: recompile VM immediately  2: when convenient */
+  bft explain:2;          /* 0: normal, 1: EXPLAIN, 2: EXPLAIN QUERY PLAN */
+  bft changeCntOn:1;      /* True to update the change-counter */
+  bft usesStmtJournal:1;  /* True if uses a statement journal */
+  bft readOnly:1;         /* True for statements that do not write */
+  bft bIsReader:1;        /* True for statements that read */
+  bft haveEqpOps:1;       /* Bytecode supports EXPLAIN QUERY PLAN */
+  yDbMask btreeMask;      /* Bitmask of db->aDb[] entries referenced */
+  yDbMask lockMask;       /* Subset of btreeMask that requires a lock */
+  u32 aCounter[9];        /* Counters used by sqlite3_stmt_status() */
+  char *zSql;             /* Text of the SQL statement that generated this */
+#ifdef SQLITE_ENABLE_NORMALIZE
+  char *zNormSql;         /* Normalization of the associated SQL statement */
+  DblquoteStr *pDblStr;   /* List of double-quoted string literals */
+#endif
+  void *pFree;            /* Free this when deleting the vdbe */
+  VdbeFrame *pFrame;      /* Parent frame */
+  VdbeFrame *pDelFrame;   /* List of frame objects to free on VM reset */
+  int nFrame;             /* Number of frames in pFrame list */
+  u32 expmask;            /* Binding to these vars invalidates VM */
+  SubProgram *pProgram;   /* Linked list of all sub-programs used by VM */
+  AuxData *pAuxData;      /* Linked list of auxdata allocations */
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  int nScan;              /* Entries in aScan[] */
+  ScanStatus *aScan;      /* Scan definitions for sqlite3_stmt_scanstatus() */
+#endif
+};
+
+/*
+** The following are allowed values for Vdbe.eVdbeState
+*/
+#define VDBE_INIT_STATE     0   /* Prepared statement under construction */
+#define VDBE_READY_STATE    1   /* Ready to run but not yet started */
+#define VDBE_RUN_STATE      2   /* Run in progress */
+#define VDBE_HALT_STATE     3   /* Finished.  Need reset() or finalize() */
+
+/*
+** Structure used to store the context required by the
+** sqlite3_preupdate_*() API functions.
+*/
+struct PreUpdate {
+  Vdbe *v;
+  VdbeCursor *pCsr;               /* Cursor to read old values from */
+  int op;                         /* One of SQLITE_INSERT, UPDATE, DELETE */
+  u8 *aRecord;                    /* old.* database record */
+  KeyInfo keyinfo;
+  UnpackedRecord *pUnpacked;      /* Unpacked version of aRecord[] */
+  UnpackedRecord *pNewUnpacked;   /* Unpacked version of new.* record */
+  int iNewReg;                    /* Register for new.* values */
+  int iBlobWrite;                 /* Value returned by preupdate_blobwrite() */
+  i64 iKey1;                      /* First key value passed to hook */
+  i64 iKey2;                      /* Second key value passed to hook */
+  Mem *aNew;                      /* Array of new.* values */
+  Table *pTab;                    /* Schema object being updated */
+  Index *pPk;                     /* PK index if pTab is WITHOUT ROWID */
+};
+
+/*
+** An instance of this object is used to pass an vector of values into
+** OP_VFilter, the xFilter method of a virtual table.  The vector is the
+** set of values on the right-hand side of an IN constraint.
+**
+** The value as passed into xFilter is an sqlite3_value with a "pointer"
+** type, such as is generated by sqlite3_result_pointer() and read by
+** sqlite3_value_pointer.  Such values have MEM_Term|MEM_Subtype|MEM_Null
+** and a subtype of 'p'.  The sqlite3_vtab_in_first() and _next() interfaces
+** know how to use this object to step through all the values in the
+** right operand of the IN constraint.
+*/
+typedef struct ValueList ValueList;
+struct ValueList {
+  BtCursor *pCsr;          /* An ephemeral table holding all values */
+  sqlite3_value *pOut;     /* Register to hold each decoded output value */
+};
+
+/* Size of content associated with serial types that fit into a
+** single-byte varint.
+*/
+#ifndef SQLITE_AMALGAMATION
+extern const u8 sqlite3SmallTypeSizes[];
+#endif
+
+/*
+** Function prototypes
+*/
+void sqlite3VdbeError(Vdbe*, const char *, ...);
+void sqlite3VdbeFreeCursor(Vdbe *, VdbeCursor*);
+void sqlite3VdbeFreeCursorNN(Vdbe*,VdbeCursor*);
+void sqliteVdbePopStack(Vdbe*,int);
+int SQLITE_NOINLINE sqlite3VdbeHandleMovedCursor(VdbeCursor *p);
+int SQLITE_NOINLINE sqlite3VdbeFinishMoveto(VdbeCursor*);
+int sqlite3VdbeCursorRestore(VdbeCursor*);
+u32 sqlite3VdbeSerialTypeLen(u32);
+u8 sqlite3VdbeOneByteSerialTypeLen(u8);
+#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+  u64 sqlite3FloatSwap(u64 in);
+# define swapMixedEndianFloat(X)  X = sqlite3FloatSwap(X)
+#else
+# define swapMixedEndianFloat(X)
+#endif
+void sqlite3VdbeSerialGet(const unsigned char*, u32, Mem*);
+void sqlite3VdbeDeleteAuxData(sqlite3*, AuxData**, int, int);
+
+int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
+int sqlite3VdbeIdxKeyCompare(sqlite3*,VdbeCursor*,UnpackedRecord*,int*);
+int sqlite3VdbeIdxRowid(sqlite3*, BtCursor*, i64*);
+int sqlite3VdbeExec(Vdbe*);
+#if !defined(SQLITE_OMIT_EXPLAIN) || defined(SQLITE_ENABLE_BYTECODE_VTAB)
+int sqlite3VdbeNextOpcode(Vdbe*,Mem*,int,int*,int*,Op**);
+char *sqlite3VdbeDisplayP4(sqlite3*,Op*);
+#endif
+#if defined(SQLITE_ENABLE_EXPLAIN_COMMENTS)
+char *sqlite3VdbeDisplayComment(sqlite3*,const Op*,const char*);
+#endif
+#if !defined(SQLITE_OMIT_EXPLAIN)
+int sqlite3VdbeList(Vdbe*);
+#endif
+int sqlite3VdbeHalt(Vdbe*);
+int sqlite3VdbeChangeEncoding(Mem *, int);
+int sqlite3VdbeMemTooBig(Mem*);
+int sqlite3VdbeMemCopy(Mem*, const Mem*);
+void sqlite3VdbeMemShallowCopy(Mem*, const Mem*, int);
+void sqlite3VdbeMemMove(Mem*, Mem*);
+int sqlite3VdbeMemNulTerminate(Mem*);
+int sqlite3VdbeMemSetStr(Mem*, const char*, i64, u8, void(*)(void*));
+void sqlite3VdbeMemSetInt64(Mem*, i64);
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define sqlite3VdbeMemSetDouble sqlite3VdbeMemSetInt64
+#else
+  void sqlite3VdbeMemSetDouble(Mem*, double);
+#endif
+void sqlite3VdbeMemSetPointer(Mem*, void*, const char*, void(*)(void*));
+void sqlite3VdbeMemInit(Mem*,sqlite3*,u16);
+void sqlite3VdbeMemSetNull(Mem*);
+#ifndef SQLITE_OMIT_INCRBLOB
+void sqlite3VdbeMemSetZeroBlob(Mem*,int);
+#else
+int sqlite3VdbeMemSetZeroBlob(Mem*,int);
+#endif
+#ifdef SQLITE_DEBUG
+int sqlite3VdbeMemIsRowSet(const Mem*);
+#endif
+int sqlite3VdbeMemSetRowSet(Mem*);
+void sqlite3VdbeMemZeroTerminateIfAble(Mem*);
+int sqlite3VdbeMemMakeWriteable(Mem*);
+int sqlite3VdbeMemStringify(Mem*, u8, u8);
+int sqlite3IntFloatCompare(i64,double);
+i64 sqlite3VdbeIntValue(const Mem*);
+int sqlite3VdbeMemIntegerify(Mem*);
+double sqlite3VdbeRealValue(Mem*);
+int sqlite3VdbeBooleanValue(Mem*, int ifNull);
+void sqlite3VdbeIntegerAffinity(Mem*);
+int sqlite3VdbeMemRealify(Mem*);
+int sqlite3VdbeMemNumerify(Mem*);
+int sqlite3VdbeMemCast(Mem*,u8,u8);
+int sqlite3VdbeMemFromBtree(BtCursor*,u32,u32,Mem*);
+int sqlite3VdbeMemFromBtreeZeroOffset(BtCursor*,u32,Mem*);
+void sqlite3VdbeMemRelease(Mem *p);
+void sqlite3VdbeMemReleaseMalloc(Mem*p);
+int sqlite3VdbeMemFinalize(Mem*, FuncDef*);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+int sqlite3VdbeMemAggValue(Mem*, Mem*, FuncDef*);
+#endif
+#if !defined(SQLITE_OMIT_EXPLAIN) || defined(SQLITE_ENABLE_BYTECODE_VTAB)
+const char *sqlite3OpcodeName(int);
+#endif
+int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve);
+int sqlite3VdbeMemClearAndResize(Mem *pMem, int n);
+int sqlite3VdbeCloseStatement(Vdbe *, int);
+#ifdef SQLITE_DEBUG
+int sqlite3VdbeFrameIsValid(VdbeFrame*);
+#endif
+void sqlite3VdbeFrameMemDel(void*);      /* Destructor on Mem */
+void sqlite3VdbeFrameDelete(VdbeFrame*); /* Actually deletes the Frame */
+int sqlite3VdbeFrameRestore(VdbeFrame *);
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+void sqlite3VdbePreUpdateHook(
+    Vdbe*,VdbeCursor*,int,const char*,Table*,i64,int,int);
+#endif
+int sqlite3VdbeTransferError(Vdbe *p);
+
+int sqlite3VdbeSorterInit(sqlite3 *, int, VdbeCursor *);
+void sqlite3VdbeSorterReset(sqlite3 *, VdbeSorter *);
+void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
+int sqlite3VdbeSorterRowkey(const VdbeCursor *, Mem *);
+int sqlite3VdbeSorterNext(sqlite3 *, const VdbeCursor *);
+int sqlite3VdbeSorterRewind(const VdbeCursor *, int *);
+int sqlite3VdbeSorterWrite(const VdbeCursor *, Mem *);
+int sqlite3VdbeSorterCompare(const VdbeCursor *, Mem *, int, int *);
+
+void sqlite3VdbeValueListFree(void*);
+
+#ifdef SQLITE_DEBUG
+  void sqlite3VdbeIncrWriteCounter(Vdbe*, VdbeCursor*);
+  void sqlite3VdbeAssertAbortable(Vdbe*);
+#else
+# define sqlite3VdbeIncrWriteCounter(V,C)
+# define sqlite3VdbeAssertAbortable(V)
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE)
+  void sqlite3VdbeEnter(Vdbe*);
+#else
+# define sqlite3VdbeEnter(X)
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
+  void sqlite3VdbeLeave(Vdbe*);
+#else
+# define sqlite3VdbeLeave(X)
+#endif
+
+#ifdef SQLITE_DEBUG
+void sqlite3VdbeMemAboutToChange(Vdbe*,Mem*);
+int sqlite3VdbeCheckMemInvariants(Mem*);
+#endif
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+int sqlite3VdbeCheckFk(Vdbe *, int);
+#else
+# define sqlite3VdbeCheckFk(p,i) 0
+#endif
+
+#ifdef SQLITE_DEBUG
+  void sqlite3VdbePrintSql(Vdbe*);
+  void sqlite3VdbeMemPrettyPrint(Mem *pMem, StrAccum *pStr);
+#endif
+#ifndef SQLITE_OMIT_UTF16
+  int sqlite3VdbeMemTranslate(Mem*, u8);
+  int sqlite3VdbeMemHandleBom(Mem *pMem);
+#endif
+
+#ifndef SQLITE_OMIT_INCRBLOB
+  int sqlite3VdbeMemExpandBlob(Mem *);
+  #define ExpandBlob(P) (((P)->flags&MEM_Zero)?sqlite3VdbeMemExpandBlob(P):0)
+#else
+  #define sqlite3VdbeMemExpandBlob(x) SQLITE_OK
+  #define ExpandBlob(P) SQLITE_OK
+#endif
+
+#endif /* !defined(SQLITE_VDBEINT_H) */
diff --git a/src/vdbeapi.c b/src/vdbeapi.c
new file mode 100644
index 0000000..14c6091
--- /dev/null
+++ b/src/vdbeapi.c
@@ -0,0 +1,2538 @@
+/*
+** 2004 May 26
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code use to implement APIs that are part of the
+** VDBE.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+#include "opcodes.h"
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Return TRUE (non-zero) of the statement supplied as an argument needs
+** to be recompiled.  A statement needs to be recompiled whenever the
+** execution environment changes in a way that would alter the program
+** that sqlite3_prepare() generates.  For example, if new functions or
+** collating sequences are registered or if an authorizer function is
+** added or changed.
+*/
+int sqlite3_expired(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe*)pStmt;
+  return p==0 || p->expired;
+}
+#endif
+
+/*
+** Check on a Vdbe to make sure it has not been finalized.  Log
+** an error and return true if it has been finalized (or is otherwise
+** invalid).  Return false if it is ok.
+*/
+static int vdbeSafety(Vdbe *p){
+  if( p->db==0 ){
+    sqlite3_log(SQLITE_MISUSE, "API called with finalized prepared statement");
+    return 1;
+  }else{
+    return 0;
+  }
+}
+static int vdbeSafetyNotNull(Vdbe *p){
+  if( p==0 ){
+    sqlite3_log(SQLITE_MISUSE, "API called with NULL prepared statement");
+    return 1;
+  }else{
+    return vdbeSafety(p);
+  }
+}
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** Invoke the profile callback.  This routine is only called if we already
+** know that the profile callback is defined and needs to be invoked.
+*/
+static SQLITE_NOINLINE void invokeProfileCallback(sqlite3 *db, Vdbe *p){
+  sqlite3_int64 iNow;
+  sqlite3_int64 iElapse;
+  assert( p->startTime>0 );
+  assert( (db->mTrace & (SQLITE_TRACE_PROFILE|SQLITE_TRACE_XPROFILE))!=0 );
+  assert( db->init.busy==0 );
+  assert( p->zSql!=0 );
+  sqlite3OsCurrentTimeInt64(db->pVfs, &iNow);
+  iElapse = (iNow - p->startTime)*1000000;
+#ifndef SQLITE_OMIT_DEPRECATED
+  if( db->xProfile ){
+    db->xProfile(db->pProfileArg, p->zSql, iElapse);
+  }
+#endif
+  if( db->mTrace & SQLITE_TRACE_PROFILE ){
+    db->trace.xV2(SQLITE_TRACE_PROFILE, db->pTraceArg, p, (void*)&iElapse);
+  }
+  p->startTime = 0;
+}
+/*
+** The checkProfileCallback(DB,P) macro checks to see if a profile callback
+** is needed, and it invokes the callback if it is needed.
+*/
+# define checkProfileCallback(DB,P) \
+   if( ((P)->startTime)>0 ){ invokeProfileCallback(DB,P); }
+#else
+# define checkProfileCallback(DB,P)  /*no-op*/
+#endif
+
+/*
+** The following routine destroys a virtual machine that is created by
+** the sqlite3_compile() routine. The integer returned is an SQLITE_
+** success/failure code that describes the result of executing the virtual
+** machine.
+**
+** This routine sets the error code and string returned by
+** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16().
+*/
+int sqlite3_finalize(sqlite3_stmt *pStmt){
+  int rc;
+  if( pStmt==0 ){
+    /* IMPLEMENTATION-OF: R-57228-12904 Invoking sqlite3_finalize() on a NULL
+    ** pointer is a harmless no-op. */
+    rc = SQLITE_OK;
+  }else{
+    Vdbe *v = (Vdbe*)pStmt;
+    sqlite3 *db = v->db;
+    if( vdbeSafety(v) ) return SQLITE_MISUSE_BKPT;
+    sqlite3_mutex_enter(db->mutex);
+    checkProfileCallback(db, v);
+    assert( v->eVdbeState>=VDBE_READY_STATE );
+    rc = sqlite3VdbeReset(v);
+    sqlite3VdbeDelete(v);
+    rc = sqlite3ApiExit(db, rc);
+    sqlite3LeaveMutexAndCloseZombie(db);
+  }
+  return rc;
+}
+
+/*
+** Terminate the current execution of an SQL statement and reset it
+** back to its starting state so that it can be reused. A success code from
+** the prior execution is returned.
+**
+** This routine sets the error code and string returned by
+** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16().
+*/
+int sqlite3_reset(sqlite3_stmt *pStmt){
+  int rc;
+  if( pStmt==0 ){
+    rc = SQLITE_OK;
+  }else{
+    Vdbe *v = (Vdbe*)pStmt;
+    sqlite3 *db = v->db;
+    sqlite3_mutex_enter(db->mutex);
+    checkProfileCallback(db, v);
+    rc = sqlite3VdbeReset(v);
+    sqlite3VdbeRewind(v);
+    assert( (rc & (db->errMask))==rc );
+    rc = sqlite3ApiExit(db, rc);
+    sqlite3_mutex_leave(db->mutex);
+  }
+  return rc;
+}
+
+/*
+** Set all the parameters in the compiled SQL statement to NULL.
+*/
+int sqlite3_clear_bindings(sqlite3_stmt *pStmt){
+  int i;
+  int rc = SQLITE_OK;
+  Vdbe *p = (Vdbe*)pStmt;
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex;
+#endif
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pStmt==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+#if SQLITE_THREADSAFE
+  mutex = p->db->mutex;
+#endif
+  sqlite3_mutex_enter(mutex);
+  for(i=0; i<p->nVar; i++){
+    sqlite3VdbeMemRelease(&p->aVar[i]);
+    p->aVar[i].flags = MEM_Null;
+  }
+  assert( (p->prepFlags & SQLITE_PREPARE_SAVESQL)!=0 || p->expmask==0 );
+  if( p->expmask ){
+    p->expired = 1;
+  }
+  sqlite3_mutex_leave(mutex);
+  return rc;
+}
+
+
+/**************************** sqlite3_value_  *******************************
+** The following routines extract information from a Mem or sqlite3_value
+** structure.
+*/
+const void *sqlite3_value_blob(sqlite3_value *pVal){
+  Mem *p = (Mem*)pVal;
+  if( p->flags & (MEM_Blob|MEM_Str) ){
+    if( ExpandBlob(p)!=SQLITE_OK ){
+      assert( p->flags==MEM_Null && p->z==0 );
+      return 0;
+    }
+    p->flags |= MEM_Blob;
+    return p->n ? p->z : 0;
+  }else{
+    return sqlite3_value_text(pVal);
+  }
+}
+int sqlite3_value_bytes(sqlite3_value *pVal){
+  return sqlite3ValueBytes(pVal, SQLITE_UTF8);
+}
+int sqlite3_value_bytes16(sqlite3_value *pVal){
+  return sqlite3ValueBytes(pVal, SQLITE_UTF16NATIVE);
+}
+double sqlite3_value_double(sqlite3_value *pVal){
+  return sqlite3VdbeRealValue((Mem*)pVal);
+}
+int sqlite3_value_int(sqlite3_value *pVal){
+  return (int)sqlite3VdbeIntValue((Mem*)pVal);
+}
+sqlite_int64 sqlite3_value_int64(sqlite3_value *pVal){
+  return sqlite3VdbeIntValue((Mem*)pVal);
+}
+unsigned int sqlite3_value_subtype(sqlite3_value *pVal){
+  Mem *pMem = (Mem*)pVal;
+  return ((pMem->flags & MEM_Subtype) ? pMem->eSubtype : 0);
+}
+void *sqlite3_value_pointer(sqlite3_value *pVal, const char *zPType){
+  Mem *p = (Mem*)pVal;
+  if( (p->flags&(MEM_TypeMask|MEM_Term|MEM_Subtype)) ==
+                 (MEM_Null|MEM_Term|MEM_Subtype)
+   && zPType!=0
+   && p->eSubtype=='p'
+   && strcmp(p->u.zPType, zPType)==0
+  ){
+    return (void*)p->z;
+  }else{
+    return 0;
+  }
+}
+const unsigned char *sqlite3_value_text(sqlite3_value *pVal){
+  return (const unsigned char *)sqlite3ValueText(pVal, SQLITE_UTF8);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_value_text16(sqlite3_value* pVal){
+  return sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);
+}
+const void *sqlite3_value_text16be(sqlite3_value *pVal){
+  return sqlite3ValueText(pVal, SQLITE_UTF16BE);
+}
+const void *sqlite3_value_text16le(sqlite3_value *pVal){
+  return sqlite3ValueText(pVal, SQLITE_UTF16LE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+/* EVIDENCE-OF: R-12793-43283 Every value in SQLite has one of five
+** fundamental datatypes: 64-bit signed integer 64-bit IEEE floating
+** point number string BLOB NULL
+*/
+int sqlite3_value_type(sqlite3_value* pVal){
+  static const u8 aType[] = {
+     SQLITE_BLOB,     /* 0x00 (not possible) */
+     SQLITE_NULL,     /* 0x01 NULL */
+     SQLITE_TEXT,     /* 0x02 TEXT */
+     SQLITE_NULL,     /* 0x03 (not possible) */
+     SQLITE_INTEGER,  /* 0x04 INTEGER */
+     SQLITE_NULL,     /* 0x05 (not possible) */
+     SQLITE_INTEGER,  /* 0x06 INTEGER + TEXT */
+     SQLITE_NULL,     /* 0x07 (not possible) */
+     SQLITE_FLOAT,    /* 0x08 FLOAT */
+     SQLITE_NULL,     /* 0x09 (not possible) */
+     SQLITE_FLOAT,    /* 0x0a FLOAT + TEXT */
+     SQLITE_NULL,     /* 0x0b (not possible) */
+     SQLITE_INTEGER,  /* 0x0c (not possible) */
+     SQLITE_NULL,     /* 0x0d (not possible) */
+     SQLITE_INTEGER,  /* 0x0e (not possible) */
+     SQLITE_NULL,     /* 0x0f (not possible) */
+     SQLITE_BLOB,     /* 0x10 BLOB */
+     SQLITE_NULL,     /* 0x11 (not possible) */
+     SQLITE_TEXT,     /* 0x12 (not possible) */
+     SQLITE_NULL,     /* 0x13 (not possible) */
+     SQLITE_INTEGER,  /* 0x14 INTEGER + BLOB */
+     SQLITE_NULL,     /* 0x15 (not possible) */
+     SQLITE_INTEGER,  /* 0x16 (not possible) */
+     SQLITE_NULL,     /* 0x17 (not possible) */
+     SQLITE_FLOAT,    /* 0x18 FLOAT + BLOB */
+     SQLITE_NULL,     /* 0x19 (not possible) */
+     SQLITE_FLOAT,    /* 0x1a (not possible) */
+     SQLITE_NULL,     /* 0x1b (not possible) */
+     SQLITE_INTEGER,  /* 0x1c (not possible) */
+     SQLITE_NULL,     /* 0x1d (not possible) */
+     SQLITE_INTEGER,  /* 0x1e (not possible) */
+     SQLITE_NULL,     /* 0x1f (not possible) */
+     SQLITE_FLOAT,    /* 0x20 INTREAL */
+     SQLITE_NULL,     /* 0x21 (not possible) */
+     SQLITE_FLOAT,    /* 0x22 INTREAL + TEXT */
+     SQLITE_NULL,     /* 0x23 (not possible) */
+     SQLITE_FLOAT,    /* 0x24 (not possible) */
+     SQLITE_NULL,     /* 0x25 (not possible) */
+     SQLITE_FLOAT,    /* 0x26 (not possible) */
+     SQLITE_NULL,     /* 0x27 (not possible) */
+     SQLITE_FLOAT,    /* 0x28 (not possible) */
+     SQLITE_NULL,     /* 0x29 (not possible) */
+     SQLITE_FLOAT,    /* 0x2a (not possible) */
+     SQLITE_NULL,     /* 0x2b (not possible) */
+     SQLITE_FLOAT,    /* 0x2c (not possible) */
+     SQLITE_NULL,     /* 0x2d (not possible) */
+     SQLITE_FLOAT,    /* 0x2e (not possible) */
+     SQLITE_NULL,     /* 0x2f (not possible) */
+     SQLITE_BLOB,     /* 0x30 (not possible) */
+     SQLITE_NULL,     /* 0x31 (not possible) */
+     SQLITE_TEXT,     /* 0x32 (not possible) */
+     SQLITE_NULL,     /* 0x33 (not possible) */
+     SQLITE_FLOAT,    /* 0x34 (not possible) */
+     SQLITE_NULL,     /* 0x35 (not possible) */
+     SQLITE_FLOAT,    /* 0x36 (not possible) */
+     SQLITE_NULL,     /* 0x37 (not possible) */
+     SQLITE_FLOAT,    /* 0x38 (not possible) */
+     SQLITE_NULL,     /* 0x39 (not possible) */
+     SQLITE_FLOAT,    /* 0x3a (not possible) */
+     SQLITE_NULL,     /* 0x3b (not possible) */
+     SQLITE_FLOAT,    /* 0x3c (not possible) */
+     SQLITE_NULL,     /* 0x3d (not possible) */
+     SQLITE_FLOAT,    /* 0x3e (not possible) */
+     SQLITE_NULL,     /* 0x3f (not possible) */
+  };
+#ifdef SQLITE_DEBUG
+  {
+    int eType = SQLITE_BLOB;
+    if( pVal->flags & MEM_Null ){
+      eType = SQLITE_NULL;
+    }else if( pVal->flags & (MEM_Real|MEM_IntReal) ){
+      eType = SQLITE_FLOAT;
+    }else if( pVal->flags & MEM_Int ){
+      eType = SQLITE_INTEGER;
+    }else if( pVal->flags & MEM_Str ){
+      eType = SQLITE_TEXT;
+    }
+    assert( eType == aType[pVal->flags&MEM_AffMask] );
+  }
+#endif
+  return aType[pVal->flags&MEM_AffMask];
+}
+int sqlite3_value_encoding(sqlite3_value *pVal){
+  return pVal->enc;
+}
+
+/* Return true if a parameter to xUpdate represents an unchanged column */
+int sqlite3_value_nochange(sqlite3_value *pVal){
+  return (pVal->flags&(MEM_Null|MEM_Zero))==(MEM_Null|MEM_Zero);
+}
+
+/* Return true if a parameter value originated from an sqlite3_bind() */
+int sqlite3_value_frombind(sqlite3_value *pVal){
+  return (pVal->flags&MEM_FromBind)!=0;
+}
+
+/* Make a copy of an sqlite3_value object
+*/
+sqlite3_value *sqlite3_value_dup(const sqlite3_value *pOrig){
+  sqlite3_value *pNew;
+  if( pOrig==0 ) return 0;
+  pNew = sqlite3_malloc( sizeof(*pNew) );
+  if( pNew==0 ) return 0;
+  memset(pNew, 0, sizeof(*pNew));
+  memcpy(pNew, pOrig, MEMCELLSIZE);
+  pNew->flags &= ~MEM_Dyn;
+  pNew->db = 0;
+  if( pNew->flags&(MEM_Str|MEM_Blob) ){
+    pNew->flags &= ~(MEM_Static|MEM_Dyn);
+    pNew->flags |= MEM_Ephem;
+    if( sqlite3VdbeMemMakeWriteable(pNew)!=SQLITE_OK ){
+      sqlite3ValueFree(pNew);
+      pNew = 0;
+    }
+  }else if( pNew->flags & MEM_Null ){
+    /* Do not duplicate pointer values */
+    pNew->flags &= ~(MEM_Term|MEM_Subtype);
+  }
+  return pNew;
+}
+
+/* Destroy an sqlite3_value object previously obtained from
+** sqlite3_value_dup().
+*/
+void sqlite3_value_free(sqlite3_value *pOld){
+  sqlite3ValueFree(pOld);
+}
+ 
+
+/**************************** sqlite3_result_  *******************************
+** The following routines are used by user-defined functions to specify
+** the function result.
+**
+** The setStrOrError() function calls sqlite3VdbeMemSetStr() to store the
+** result as a string or blob.  Appropriate errors are set if the string/blob
+** is too big or if an OOM occurs.
+**
+** The invokeValueDestructor(P,X) routine invokes destructor function X()
+** on value P if P is not going to be used and need to be destroyed.
+*/
+static void setResultStrOrError(
+  sqlite3_context *pCtx,  /* Function context */
+  const char *z,          /* String pointer */
+  int n,                  /* Bytes in string, or negative */
+  u8 enc,                 /* Encoding of z.  0 for BLOBs */
+  void (*xDel)(void*)     /* Destructor function */
+){
+  Mem *pOut = pCtx->pOut;
+  int rc = sqlite3VdbeMemSetStr(pOut, z, n, enc, xDel);
+  if( rc ){
+    if( rc==SQLITE_TOOBIG ){
+      sqlite3_result_error_toobig(pCtx);
+    }else{
+      /* The only errors possible from sqlite3VdbeMemSetStr are
+      ** SQLITE_TOOBIG and SQLITE_NOMEM */
+      assert( rc==SQLITE_NOMEM );
+      sqlite3_result_error_nomem(pCtx);
+    }
+    return;
+  }
+  sqlite3VdbeChangeEncoding(pOut, pCtx->enc);
+  if( sqlite3VdbeMemTooBig(pOut) ){
+    sqlite3_result_error_toobig(pCtx);
+  }
+}
+static int invokeValueDestructor(
+  const void *p,             /* Value to destroy */
+  void (*xDel)(void*),       /* The destructor */
+  sqlite3_context *pCtx      /* Set a SQLITE_TOOBIG error if not NULL */
+){
+  assert( xDel!=SQLITE_DYNAMIC );
+  if( xDel==0 ){
+    /* noop */
+  }else if( xDel==SQLITE_TRANSIENT ){
+    /* noop */
+  }else{
+    xDel((void*)p);
+  }
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx!=0 ){
+    sqlite3_result_error_toobig(pCtx);
+  }
+#else
+  assert( pCtx!=0 );
+  sqlite3_result_error_toobig(pCtx);
+#endif
+  return SQLITE_TOOBIG;
+}
+void sqlite3_result_blob(
+  sqlite3_context *pCtx,
+  const void *z,
+  int n,
+  void (*xDel)(void *)
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 || n<0 ){
+    invokeValueDestructor(z, xDel, pCtx);
+    return;
+  }
+#endif
+  assert( n>=0 );
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  setResultStrOrError(pCtx, z, n, 0, xDel);
+}
+void sqlite3_result_blob64(
+  sqlite3_context *pCtx,
+  const void *z,
+  sqlite3_uint64 n,
+  void (*xDel)(void *)
+){
+  assert( xDel!=SQLITE_DYNAMIC );
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ){
+    invokeValueDestructor(z, xDel, 0);
+    return;
+  }
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  if( n>0x7fffffff ){
+    (void)invokeValueDestructor(z, xDel, pCtx);
+  }else{
+    setResultStrOrError(pCtx, z, (int)n, 0, xDel);
+  }
+}
+void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  sqlite3VdbeMemSetDouble(pCtx->pOut, rVal);
+}
+void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  pCtx->isError = SQLITE_ERROR;
+  sqlite3VdbeMemSetStr(pCtx->pOut, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
+}
+#ifndef SQLITE_OMIT_UTF16
+void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  pCtx->isError = SQLITE_ERROR;
+  sqlite3VdbeMemSetStr(pCtx->pOut, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
+}
+#endif
+void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  sqlite3VdbeMemSetInt64(pCtx->pOut, (i64)iVal);
+}
+void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  sqlite3VdbeMemSetInt64(pCtx->pOut, iVal);
+}
+void sqlite3_result_null(sqlite3_context *pCtx){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  sqlite3VdbeMemSetNull(pCtx->pOut);
+}
+void sqlite3_result_pointer(
+  sqlite3_context *pCtx,
+  void *pPtr,
+  const char *zPType,
+  void (*xDestructor)(void*)
+){
+  Mem *pOut;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ){
+    invokeValueDestructor(pPtr, xDestructor, 0);
+    return;
+  }
+#endif
+  pOut = pCtx->pOut;
+  assert( sqlite3_mutex_held(pOut->db->mutex) );
+  sqlite3VdbeMemRelease(pOut);
+  pOut->flags = MEM_Null;
+  sqlite3VdbeMemSetPointer(pOut, pPtr, zPType, xDestructor);
+}
+void sqlite3_result_subtype(sqlite3_context *pCtx, unsigned int eSubtype){
+  Mem *pOut;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+#if defined(SQLITE_STRICT_SUBTYPE) && SQLITE_STRICT_SUBTYPE+0!=0
+  if( pCtx->pFunc!=0
+   && (pCtx->pFunc->funcFlags & SQLITE_RESULT_SUBTYPE)==0
+  ){
+    char zErr[200];
+    sqlite3_snprintf(sizeof(zErr), zErr,
+                     "misuse of sqlite3_result_subtype() by %s()", 
+                     pCtx->pFunc->zName);
+    sqlite3_result_error(pCtx, zErr, -1);
+    return;
+  }
+#endif /* SQLITE_STRICT_SUBTYPE */
+  pOut = pCtx->pOut;
+  assert( sqlite3_mutex_held(pOut->db->mutex) );
+  pOut->eSubtype = eSubtype & 0xff;
+  pOut->flags |= MEM_Subtype;
+}
+void sqlite3_result_text(
+  sqlite3_context *pCtx,
+  const char *z,
+  int n,
+  void (*xDel)(void *)
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ){
+    invokeValueDestructor(z, xDel, 0);
+    return;
+  }
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  setResultStrOrError(pCtx, z, n, SQLITE_UTF8, xDel);
+}
+void sqlite3_result_text64(
+  sqlite3_context *pCtx,
+  const char *z,
+  sqlite3_uint64 n,
+  void (*xDel)(void *),
+  unsigned char enc
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ){
+    invokeValueDestructor(z, xDel, 0);
+    return;
+  }
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  assert( xDel!=SQLITE_DYNAMIC );
+  if( enc!=SQLITE_UTF8 ){
+    if( enc==SQLITE_UTF16 ) enc = SQLITE_UTF16NATIVE;
+    n &= ~(u64)1;
+  }
+  if( n>0x7fffffff ){
+    (void)invokeValueDestructor(z, xDel, pCtx);
+  }else{
+    setResultStrOrError(pCtx, z, (int)n, enc, xDel);
+    sqlite3VdbeMemZeroTerminateIfAble(pCtx->pOut);
+  }
+}
+#ifndef SQLITE_OMIT_UTF16
+void sqlite3_result_text16(
+  sqlite3_context *pCtx,
+  const void *z,
+  int n,
+  void (*xDel)(void *)
+){
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  setResultStrOrError(pCtx, z, n & ~(u64)1, SQLITE_UTF16NATIVE, xDel);
+}
+void sqlite3_result_text16be(
+  sqlite3_context *pCtx,
+  const void *z,
+  int n,
+  void (*xDel)(void *)
+){
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  setResultStrOrError(pCtx, z, n & ~(u64)1, SQLITE_UTF16BE, xDel);
+}
+void sqlite3_result_text16le(
+  sqlite3_context *pCtx,
+  const void *z,
+  int n,
+  void (*xDel)(void *)
+){
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  setResultStrOrError(pCtx, z, n & ~(u64)1, SQLITE_UTF16LE, xDel);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+void sqlite3_result_value(sqlite3_context *pCtx, sqlite3_value *pValue){
+  Mem *pOut;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+  if( pValue==0 ){
+    sqlite3_result_null(pCtx);
+    return;
+  }
+#endif
+  pOut = pCtx->pOut;
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  sqlite3VdbeMemCopy(pOut, pValue);
+  sqlite3VdbeChangeEncoding(pOut, pCtx->enc);
+  if( sqlite3VdbeMemTooBig(pOut) ){
+    sqlite3_result_error_toobig(pCtx);
+  }
+}
+void sqlite3_result_zeroblob(sqlite3_context *pCtx, int n){
+  sqlite3_result_zeroblob64(pCtx, n>0 ? n : 0);
+}
+int sqlite3_result_zeroblob64(sqlite3_context *pCtx, u64 n){
+  Mem *pOut;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  pOut = pCtx->pOut;
+  assert( sqlite3_mutex_held(pOut->db->mutex) );
+  if( n>(u64)pOut->db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    sqlite3_result_error_toobig(pCtx);
+    return SQLITE_TOOBIG;
+  }
+#ifndef SQLITE_OMIT_INCRBLOB
+  sqlite3VdbeMemSetZeroBlob(pCtx->pOut, (int)n);
+  return SQLITE_OK;
+#else
+  return sqlite3VdbeMemSetZeroBlob(pCtx->pOut, (int)n);
+#endif
+}
+void sqlite3_result_error_code(sqlite3_context *pCtx, int errCode){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  pCtx->isError = errCode ? errCode : -1;
+#ifdef SQLITE_DEBUG
+  if( pCtx->pVdbe ) pCtx->pVdbe->rcApp = errCode;
+#endif
+  if( pCtx->pOut->flags & MEM_Null ){
+    setResultStrOrError(pCtx, sqlite3ErrStr(errCode), -1, SQLITE_UTF8,
+                        SQLITE_STATIC);
+  }
+}
+
+/* Force an SQLITE_TOOBIG error. */
+void sqlite3_result_error_toobig(sqlite3_context *pCtx){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  pCtx->isError = SQLITE_TOOBIG;
+  sqlite3VdbeMemSetStr(pCtx->pOut, "string or blob too big", -1,
+                       SQLITE_UTF8, SQLITE_STATIC);
+}
+
+/* An SQLITE_NOMEM error. */
+void sqlite3_result_error_nomem(sqlite3_context *pCtx){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  sqlite3VdbeMemSetNull(pCtx->pOut);
+  pCtx->isError = SQLITE_NOMEM_BKPT;
+  sqlite3OomFault(pCtx->pOut->db);
+}
+
+#ifndef SQLITE_UNTESTABLE
+/* Force the INT64 value currently stored as the result to be
+** a MEM_IntReal value.  See the SQLITE_TESTCTRL_RESULT_INTREAL
+** test-control.
+*/
+void sqlite3ResultIntReal(sqlite3_context *pCtx){
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+  if( pCtx->pOut->flags & MEM_Int ){
+    pCtx->pOut->flags &= ~MEM_Int;
+    pCtx->pOut->flags |= MEM_IntReal;
+  }
+}
+#endif
+
+
+/*
+** This function is called after a transaction has been committed. It
+** invokes callbacks registered with sqlite3_wal_hook() as required.
+*/
+static int doWalCallbacks(sqlite3 *db){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_WAL
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ){
+      int nEntry;
+      sqlite3BtreeEnter(pBt);
+      nEntry = sqlite3PagerWalCallback(sqlite3BtreePager(pBt));
+      sqlite3BtreeLeave(pBt);
+      if( nEntry>0 && db->xWalCallback && rc==SQLITE_OK ){
+        rc = db->xWalCallback(db->pWalArg, db, db->aDb[i].zDbSName, nEntry);
+      }
+    }
+  }
+#endif
+  return rc;
+}
+
+
+/*
+** Execute the statement pStmt, either until a row of data is ready, the
+** statement is completely executed or an error occurs.
+**
+** This routine implements the bulk of the logic behind the sqlite_step()
+** API.  The only thing omitted is the automatic recompile if a
+** schema change has occurred.  That detail is handled by the
+** outer sqlite3_step() wrapper procedure.
+*/
+static int sqlite3Step(Vdbe *p){
+  sqlite3 *db;
+  int rc;
+
+  assert(p);
+  db = p->db;
+  if( p->eVdbeState!=VDBE_RUN_STATE ){
+    restart_step:
+    if( p->eVdbeState==VDBE_READY_STATE ){
+      if( p->expired ){
+        p->rc = SQLITE_SCHEMA;
+        rc = SQLITE_ERROR;
+        if( (p->prepFlags & SQLITE_PREPARE_SAVESQL)!=0 ){
+          /* If this statement was prepared using saved SQL and an
+          ** error has occurred, then return the error code in p->rc to the
+          ** caller. Set the error code in the database handle to the same
+          ** value.
+          */
+          rc = sqlite3VdbeTransferError(p);
+        }
+        goto end_of_step;
+      }
+
+      /* If there are no other statements currently running, then
+      ** reset the interrupt flag.  This prevents a call to sqlite3_interrupt
+      ** from interrupting a statement that has not yet started.
+      */
+      if( db->nVdbeActive==0 ){
+        AtomicStore(&db->u1.isInterrupted, 0);
+      }
+
+      assert( db->nVdbeWrite>0 || db->autoCommit==0
+          || (db->nDeferredCons==0 && db->nDeferredImmCons==0)
+      );
+
+#ifndef SQLITE_OMIT_TRACE
+      if( (db->mTrace & (SQLITE_TRACE_PROFILE|SQLITE_TRACE_XPROFILE))!=0
+          && !db->init.busy && p->zSql ){
+        sqlite3OsCurrentTimeInt64(db->pVfs, &p->startTime);
+      }else{
+        assert( p->startTime==0 );
+      }
+#endif
+
+      db->nVdbeActive++;
+      if( p->readOnly==0 ) db->nVdbeWrite++;
+      if( p->bIsReader ) db->nVdbeRead++;
+      p->pc = 0;
+      p->eVdbeState = VDBE_RUN_STATE;
+    }else
+
+    if( ALWAYS(p->eVdbeState==VDBE_HALT_STATE) ){
+      /* We used to require that sqlite3_reset() be called before retrying
+      ** sqlite3_step() after any error or after SQLITE_DONE.  But beginning
+      ** with version 3.7.0, we changed this so that sqlite3_reset() would
+      ** be called automatically instead of throwing the SQLITE_MISUSE error.
+      ** This "automatic-reset" change is not technically an incompatibility,
+      ** since any application that receives an SQLITE_MISUSE is broken by
+      ** definition.
+      **
+      ** Nevertheless, some published applications that were originally written
+      ** for version 3.6.23 or earlier do in fact depend on SQLITE_MISUSE
+      ** returns, and those were broken by the automatic-reset change.  As a
+      ** a work-around, the SQLITE_OMIT_AUTORESET compile-time restores the
+      ** legacy behavior of returning SQLITE_MISUSE for cases where the
+      ** previous sqlite3_step() returned something other than a SQLITE_LOCKED
+      ** or SQLITE_BUSY error.
+      */
+#ifdef SQLITE_OMIT_AUTORESET
+      if( (rc = p->rc&0xff)==SQLITE_BUSY || rc==SQLITE_LOCKED ){
+        sqlite3_reset((sqlite3_stmt*)p);
+      }else{
+        return SQLITE_MISUSE_BKPT;
+      }
+#else
+      sqlite3_reset((sqlite3_stmt*)p);
+#endif
+      assert( p->eVdbeState==VDBE_READY_STATE );
+      goto restart_step;
+    }
+  }
+
+#ifdef SQLITE_DEBUG
+  p->rcApp = SQLITE_OK;
+#endif
+#ifndef SQLITE_OMIT_EXPLAIN
+  if( p->explain ){
+    rc = sqlite3VdbeList(p);
+  }else
+#endif /* SQLITE_OMIT_EXPLAIN */
+  {
+    db->nVdbeExec++;
+    rc = sqlite3VdbeExec(p);
+    db->nVdbeExec--;
+  }
+
+  if( rc==SQLITE_ROW ){
+    assert( p->rc==SQLITE_OK );
+    assert( db->mallocFailed==0 );
+    db->errCode = SQLITE_ROW;
+    return SQLITE_ROW;
+  }else{
+#ifndef SQLITE_OMIT_TRACE
+    /* If the statement completed successfully, invoke the profile callback */
+    checkProfileCallback(db, p);
+#endif
+    p->pResultRow = 0;
+    if( rc==SQLITE_DONE && db->autoCommit ){
+      assert( p->rc==SQLITE_OK );
+      p->rc = doWalCallbacks(db);
+      if( p->rc!=SQLITE_OK ){
+        rc = SQLITE_ERROR;
+      }
+    }else if( rc!=SQLITE_DONE && (p->prepFlags & SQLITE_PREPARE_SAVESQL)!=0 ){
+      /* If this statement was prepared using saved SQL and an
+      ** error has occurred, then return the error code in p->rc to the
+      ** caller. Set the error code in the database handle to the same value.
+      */
+      rc = sqlite3VdbeTransferError(p);
+    }
+  }
+
+  db->errCode = rc;
+  if( SQLITE_NOMEM==sqlite3ApiExit(p->db, p->rc) ){
+    p->rc = SQLITE_NOMEM_BKPT;
+    if( (p->prepFlags & SQLITE_PREPARE_SAVESQL)!=0 ) rc = p->rc;
+  }
+end_of_step:
+  /* There are only a limited number of result codes allowed from the
+  ** statements prepared using the legacy sqlite3_prepare() interface */
+  assert( (p->prepFlags & SQLITE_PREPARE_SAVESQL)!=0
+       || rc==SQLITE_ROW  || rc==SQLITE_DONE   || rc==SQLITE_ERROR
+       || (rc&0xff)==SQLITE_BUSY || rc==SQLITE_MISUSE
+  );
+  return (rc&db->errMask);
+}
+
+/*
+** This is the top-level implementation of sqlite3_step().  Call
+** sqlite3Step() to do most of the work.  If a schema error occurs,
+** call sqlite3Reprepare() and try again.
+*/
+int sqlite3_step(sqlite3_stmt *pStmt){
+  int rc = SQLITE_OK;      /* Result from sqlite3Step() */
+  Vdbe *v = (Vdbe*)pStmt;  /* the prepared statement */
+  int cnt = 0;             /* Counter to prevent infinite loop of reprepares */
+  sqlite3 *db;             /* The database connection */
+
+  if( vdbeSafetyNotNull(v) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  db = v->db;
+  sqlite3_mutex_enter(db->mutex);
+  while( (rc = sqlite3Step(v))==SQLITE_SCHEMA
+         && cnt++ < SQLITE_MAX_SCHEMA_RETRY ){
+    int savedPc = v->pc;
+    rc = sqlite3Reprepare(v);
+    if( rc!=SQLITE_OK ){
+      /* This case occurs after failing to recompile an sql statement.
+      ** The error message from the SQL compiler has already been loaded
+      ** into the database handle. This block copies the error message
+      ** from the database handle into the statement and sets the statement
+      ** program counter to 0 to ensure that when the statement is
+      ** finalized or reset the parser error message is available via
+      ** sqlite3_errmsg() and sqlite3_errcode().
+      */
+      const char *zErr = (const char *)sqlite3_value_text(db->pErr);
+      sqlite3DbFree(db, v->zErrMsg);
+      if( !db->mallocFailed ){
+        v->zErrMsg = sqlite3DbStrDup(db, zErr);
+        v->rc = rc = sqlite3ApiExit(db, rc);
+      } else {
+        v->zErrMsg = 0;
+        v->rc = rc = SQLITE_NOMEM_BKPT;
+      }
+      break;
+    }
+    sqlite3_reset(pStmt);
+    if( savedPc>=0 ){
+      /* Setting minWriteFileFormat to 254 is a signal to the OP_Init and
+      ** OP_Trace opcodes to *not* perform SQLITE_TRACE_STMT because it has
+      ** already been done once on a prior invocation that failed due to
+      ** SQLITE_SCHEMA.   tag-20220401a  */
+      v->minWriteFileFormat = 254;
+    }
+    assert( v->expired==0 );
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+
+/*
+** Extract the user data from a sqlite3_context structure and return a
+** pointer to it.
+*/
+void *sqlite3_user_data(sqlite3_context *p){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 ) return 0;
+#endif
+  assert( p && p->pFunc );
+  return p->pFunc->pUserData;
+}
+
+/*
+** Extract the user data from a sqlite3_context structure and return a
+** pointer to it.
+**
+** IMPLEMENTATION-OF: R-46798-50301 The sqlite3_context_db_handle() interface
+** returns a copy of the pointer to the database connection (the 1st
+** parameter) of the sqlite3_create_function() and
+** sqlite3_create_function16() routines that originally registered the
+** application defined function.
+*/
+sqlite3 *sqlite3_context_db_handle(sqlite3_context *p){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 ) return 0;
+#else
+  assert( p && p->pOut );
+#endif
+  return p->pOut->db;
+}
+
+/*
+** If this routine is invoked from within an xColumn method of a virtual
+** table, then it returns true if and only if the the call is during an
+** UPDATE operation and the value of the column will not be modified
+** by the UPDATE.
+**
+** If this routine is called from any context other than within the
+** xColumn method of a virtual table, then the return value is meaningless
+** and arbitrary.
+**
+** Virtual table implements might use this routine to optimize their
+** performance by substituting a NULL result, or some other light-weight
+** value, as a signal to the xUpdate routine that the column is unchanged.
+*/
+int sqlite3_vtab_nochange(sqlite3_context *p){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 ) return 0;
+#else
+  assert( p );
+#endif
+  return sqlite3_value_nochange(p->pOut);
+}
+
+/*
+** The destructor function for a ValueList object.  This needs to be
+** a separate function, unknowable to the application, to ensure that
+** calls to sqlite3_vtab_in_first()/sqlite3_vtab_in_next() that are not
+** preceded by activation of IN processing via sqlite3_vtab_int() do not
+** try to access a fake ValueList object inserted by a hostile extension.
+*/
+void sqlite3VdbeValueListFree(void *pToDelete){
+  sqlite3_free(pToDelete);
+}
+
+/*
+** Implementation of sqlite3_vtab_in_first() (if bNext==0) and
+** sqlite3_vtab_in_next() (if bNext!=0).
+*/
+static int valueFromValueList(
+  sqlite3_value *pVal,        /* Pointer to the ValueList object */
+  sqlite3_value **ppOut,      /* Store the next value from the list here */
+  int bNext                   /* 1 for _next(). 0 for _first() */
+){
+  int rc;
+  ValueList *pRhs;
+
+  *ppOut = 0;
+  if( pVal==0 ) return SQLITE_MISUSE_BKPT;
+  if( (pVal->flags & MEM_Dyn)==0 || pVal->xDel!=sqlite3VdbeValueListFree ){
+    return SQLITE_ERROR;
+  }else{
+    assert( (pVal->flags&(MEM_TypeMask|MEM_Term|MEM_Subtype)) ==
+                 (MEM_Null|MEM_Term|MEM_Subtype) );
+    assert( pVal->eSubtype=='p' );
+    assert( pVal->u.zPType!=0 && strcmp(pVal->u.zPType,"ValueList")==0 );
+    pRhs = (ValueList*)pVal->z;
+  }
+  if( bNext ){
+    rc = sqlite3BtreeNext(pRhs->pCsr, 0);
+  }else{
+    int dummy = 0;
+    rc = sqlite3BtreeFirst(pRhs->pCsr, &dummy);
+    assert( rc==SQLITE_OK || sqlite3BtreeEof(pRhs->pCsr) );
+    if( sqlite3BtreeEof(pRhs->pCsr) ) rc = SQLITE_DONE;
+  }
+  if( rc==SQLITE_OK ){
+    u32 sz;       /* Size of current row in bytes */
+    Mem sMem;     /* Raw content of current row */
+    memset(&sMem, 0, sizeof(sMem));
+    sz = sqlite3BtreePayloadSize(pRhs->pCsr);
+    rc = sqlite3VdbeMemFromBtreeZeroOffset(pRhs->pCsr,(int)sz,&sMem);
+    if( rc==SQLITE_OK ){
+      u8 *zBuf = (u8*)sMem.z;
+      u32 iSerial;
+      sqlite3_value *pOut = pRhs->pOut;
+      int iOff = 1 + getVarint32(&zBuf[1], iSerial);
+      sqlite3VdbeSerialGet(&zBuf[iOff], iSerial, pOut);
+      pOut->enc = ENC(pOut->db);
+      if( (pOut->flags & MEM_Ephem)!=0 && sqlite3VdbeMemMakeWriteable(pOut) ){
+        rc = SQLITE_NOMEM;
+      }else{
+        *ppOut = pOut;
+      }
+    }
+    sqlite3VdbeMemRelease(&sMem);
+  }
+  return rc;
+}
+
+/*
+** Set the iterator value pVal to point to the first value in the set.
+** Set (*ppOut) to point to this value before returning.
+*/
+int sqlite3_vtab_in_first(sqlite3_value *pVal, sqlite3_value **ppOut){
+  return valueFromValueList(pVal, ppOut, 0);
+}
+
+/*
+** Set the iterator value pVal to point to the next value in the set.
+** Set (*ppOut) to point to this value before returning.
+*/
+int sqlite3_vtab_in_next(sqlite3_value *pVal, sqlite3_value **ppOut){
+  return valueFromValueList(pVal, ppOut, 1);
+}
+
+/*
+** Return the current time for a statement.  If the current time
+** is requested more than once within the same run of a single prepared
+** statement, the exact same time is returned for each invocation regardless
+** of the amount of time that elapses between invocations.  In other words,
+** the time returned is always the time of the first call.
+*/
+sqlite3_int64 sqlite3StmtCurrentTime(sqlite3_context *p){
+  int rc;
+#ifndef SQLITE_ENABLE_STAT4
+  sqlite3_int64 *piTime = &p->pVdbe->iCurrentTime;
+  assert( p->pVdbe!=0 );
+#else
+  sqlite3_int64 iTime = 0;
+  sqlite3_int64 *piTime = p->pVdbe!=0 ? &p->pVdbe->iCurrentTime : &iTime;
+#endif
+  if( *piTime==0 ){
+    rc = sqlite3OsCurrentTimeInt64(p->pOut->db->pVfs, piTime);
+    if( rc ) *piTime = 0;
+  }
+  return *piTime;
+}
+
+/*
+** Create a new aggregate context for p and return a pointer to
+** its pMem->z element.
+*/
+static SQLITE_NOINLINE void *createAggContext(sqlite3_context *p, int nByte){
+  Mem *pMem = p->pMem;
+  assert( (pMem->flags & MEM_Agg)==0 );
+  if( nByte<=0 ){
+    sqlite3VdbeMemSetNull(pMem);
+    pMem->z = 0;
+  }else{
+    sqlite3VdbeMemClearAndResize(pMem, nByte);
+    pMem->flags = MEM_Agg;
+    pMem->u.pDef = p->pFunc;
+    if( pMem->z ){
+      memset(pMem->z, 0, nByte);
+    }
+  }
+  return (void*)pMem->z;
+}
+
+/*
+** Allocate or return the aggregate context for a user function.  A new
+** context is allocated on the first call.  Subsequent calls return the
+** same context that was returned on prior calls.
+*/
+void *sqlite3_aggregate_context(sqlite3_context *p, int nByte){
+  assert( p && p->pFunc && p->pFunc->xFinalize );
+  assert( sqlite3_mutex_held(p->pOut->db->mutex) );
+  testcase( nByte<0 );
+  if( (p->pMem->flags & MEM_Agg)==0 ){
+    return createAggContext(p, nByte);
+  }else{
+    return (void*)p->pMem->z;
+  }
+}
+
+/*
+** Return the auxiliary data pointer, if any, for the iArg'th argument to
+** the user-function defined by pCtx.
+**
+** The left-most argument is 0.
+**
+** Undocumented behavior:  If iArg is negative then access a cache of
+** auxiliary data pointers that is available to all functions within a
+** single prepared statement.  The iArg values must match.
+*/
+void *sqlite3_get_auxdata(sqlite3_context *pCtx, int iArg){
+  AuxData *pAuxData;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return 0;
+#endif
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+#if SQLITE_ENABLE_STAT4
+  if( pCtx->pVdbe==0 ) return 0;
+#else
+  assert( pCtx->pVdbe!=0 );
+#endif
+  for(pAuxData=pCtx->pVdbe->pAuxData; pAuxData; pAuxData=pAuxData->pNextAux){
+    if(  pAuxData->iAuxArg==iArg && (pAuxData->iAuxOp==pCtx->iOp || iArg<0) ){
+      return pAuxData->pAux;
+    }
+  }
+  return 0;
+}
+
+/*
+** Set the auxiliary data pointer and delete function, for the iArg'th
+** argument to the user-function defined by pCtx. Any previous value is
+** deleted by calling the delete function specified when it was set.
+**
+** The left-most argument is 0.
+**
+** Undocumented behavior:  If iArg is negative then make the data available
+** to all functions within the current prepared statement using iArg as an
+** access code.
+*/
+void sqlite3_set_auxdata(
+  sqlite3_context *pCtx,
+  int iArg,
+  void *pAux,
+  void (*xDelete)(void*)
+){
+  AuxData *pAuxData;
+  Vdbe *pVdbe;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pCtx==0 ) return;
+#endif
+  pVdbe= pCtx->pVdbe;
+  assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
+#ifdef SQLITE_ENABLE_STAT4
+  if( pVdbe==0 ) goto failed;
+#else
+  assert( pVdbe!=0 );
+#endif
+
+  for(pAuxData=pVdbe->pAuxData; pAuxData; pAuxData=pAuxData->pNextAux){
+    if( pAuxData->iAuxArg==iArg && (pAuxData->iAuxOp==pCtx->iOp || iArg<0) ){
+      break;
+    }
+  }
+  if( pAuxData==0 ){
+    pAuxData = sqlite3DbMallocZero(pVdbe->db, sizeof(AuxData));
+    if( !pAuxData ) goto failed;
+    pAuxData->iAuxOp = pCtx->iOp;
+    pAuxData->iAuxArg = iArg;
+    pAuxData->pNextAux = pVdbe->pAuxData;
+    pVdbe->pAuxData = pAuxData;
+    if( pCtx->isError==0 ) pCtx->isError = -1;
+  }else if( pAuxData->xDeleteAux ){
+    pAuxData->xDeleteAux(pAuxData->pAux);
+  }
+
+  pAuxData->pAux = pAux;
+  pAuxData->xDeleteAux = xDelete;
+  return;
+
+failed:
+  if( xDelete ){
+    xDelete(pAux);
+  }
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Return the number of times the Step function of an aggregate has been
+** called.
+**
+** This function is deprecated.  Do not use it for new code.  It is
+** provide only to avoid breaking legacy code.  New aggregate function
+** implementations should keep their own counts within their aggregate
+** context.
+*/
+int sqlite3_aggregate_count(sqlite3_context *p){
+  assert( p && p->pMem && p->pFunc && p->pFunc->xFinalize );
+  return p->pMem->n;
+}
+#endif
+
+/*
+** Return the number of columns in the result set for the statement pStmt.
+*/
+int sqlite3_column_count(sqlite3_stmt *pStmt){
+  Vdbe *pVm = (Vdbe *)pStmt;
+  if( pVm==0 ) return 0;
+  return pVm->nResColumn;
+}
+
+/*
+** Return the number of values available from the current row of the
+** currently executing statement pStmt.
+*/
+int sqlite3_data_count(sqlite3_stmt *pStmt){
+  Vdbe *pVm = (Vdbe *)pStmt;
+  if( pVm==0 || pVm->pResultRow==0 ) return 0;
+  return pVm->nResColumn;
+}
+
+/*
+** Return a pointer to static memory containing an SQL NULL value.
+*/
+static const Mem *columnNullValue(void){
+  /* Even though the Mem structure contains an element
+  ** of type i64, on certain architectures (x86) with certain compiler
+  ** switches (-Os), gcc may align this Mem object on a 4-byte boundary
+  ** instead of an 8-byte one. This all works fine, except that when
+  ** running with SQLITE_DEBUG defined the SQLite code sometimes assert()s
+  ** that a Mem structure is located on an 8-byte boundary. To prevent
+  ** these assert()s from failing, when building with SQLITE_DEBUG defined
+  ** using gcc, we force nullMem to be 8-byte aligned using the magical
+  ** __attribute__((aligned(8))) macro.  */
+  static const Mem nullMem
+#if defined(SQLITE_DEBUG) && defined(__GNUC__)
+    __attribute__((aligned(8)))
+#endif
+    = {
+        /* .u          = */ {0},
+        /* .z          = */ (char*)0,
+        /* .n          = */ (int)0,
+        /* .flags      = */ (u16)MEM_Null,
+        /* .enc        = */ (u8)0,
+        /* .eSubtype   = */ (u8)0,
+        /* .db         = */ (sqlite3*)0,
+        /* .szMalloc   = */ (int)0,
+        /* .uTemp      = */ (u32)0,
+        /* .zMalloc    = */ (char*)0,
+        /* .xDel       = */ (void(*)(void*))0,
+#ifdef SQLITE_DEBUG
+        /* .pScopyFrom = */ (Mem*)0,
+        /* .mScopyFlags= */ 0,
+#endif
+      };
+  return &nullMem;
+}
+
+/*
+** Check to see if column iCol of the given statement is valid.  If
+** it is, return a pointer to the Mem for the value of that column.
+** If iCol is not valid, return a pointer to a Mem which has a value
+** of NULL.
+*/
+static Mem *columnMem(sqlite3_stmt *pStmt, int i){
+  Vdbe *pVm;
+  Mem *pOut;
+
+  pVm = (Vdbe *)pStmt;
+  if( pVm==0 ) return (Mem*)columnNullValue();
+  assert( pVm->db );
+  sqlite3_mutex_enter(pVm->db->mutex);
+  if( pVm->pResultRow!=0 && i<pVm->nResColumn && i>=0 ){
+    pOut = &pVm->pResultRow[i];
+  }else{
+    sqlite3Error(pVm->db, SQLITE_RANGE);
+    pOut = (Mem*)columnNullValue();
+  }
+  return pOut;
+}
+
+/*
+** This function is called after invoking an sqlite3_value_XXX function on a
+** column value (i.e. a value returned by evaluating an SQL expression in the
+** select list of a SELECT statement) that may cause a malloc() failure. If
+** malloc() has failed, the threads mallocFailed flag is cleared and the result
+** code of statement pStmt set to SQLITE_NOMEM.
+**
+** Specifically, this is called from within:
+**
+**     sqlite3_column_int()
+**     sqlite3_column_int64()
+**     sqlite3_column_text()
+**     sqlite3_column_text16()
+**     sqlite3_column_real()
+**     sqlite3_column_bytes()
+**     sqlite3_column_bytes16()
+**     sqlite3_column_blob()
+*/
+static void columnMallocFailure(sqlite3_stmt *pStmt)
+{
+  /* If malloc() failed during an encoding conversion within an
+  ** sqlite3_column_XXX API, then set the return code of the statement to
+  ** SQLITE_NOMEM. The next call to _step() (if any) will return SQLITE_ERROR
+  ** and _finalize() will return NOMEM.
+  */
+  Vdbe *p = (Vdbe *)pStmt;
+  if( p ){
+    assert( p->db!=0 );
+    assert( sqlite3_mutex_held(p->db->mutex) );
+    p->rc = sqlite3ApiExit(p->db, p->rc);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+}
+
+/**************************** sqlite3_column_  *******************************
+** The following routines are used to access elements of the current row
+** in the result set.
+*/
+const void *sqlite3_column_blob(sqlite3_stmt *pStmt, int i){
+  const void *val;
+  val = sqlite3_value_blob( columnMem(pStmt,i) );
+  /* Even though there is no encoding conversion, value_blob() might
+  ** need to call malloc() to expand the result of a zeroblob()
+  ** expression.
+  */
+  columnMallocFailure(pStmt);
+  return val;
+}
+int sqlite3_column_bytes(sqlite3_stmt *pStmt, int i){
+  int val = sqlite3_value_bytes( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+int sqlite3_column_bytes16(sqlite3_stmt *pStmt, int i){
+  int val = sqlite3_value_bytes16( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+double sqlite3_column_double(sqlite3_stmt *pStmt, int i){
+  double val = sqlite3_value_double( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+int sqlite3_column_int(sqlite3_stmt *pStmt, int i){
+  int val = sqlite3_value_int( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+sqlite_int64 sqlite3_column_int64(sqlite3_stmt *pStmt, int i){
+  sqlite_int64 val = sqlite3_value_int64( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+const unsigned char *sqlite3_column_text(sqlite3_stmt *pStmt, int i){
+  const unsigned char *val = sqlite3_value_text( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+sqlite3_value *sqlite3_column_value(sqlite3_stmt *pStmt, int i){
+  Mem *pOut = columnMem(pStmt, i);
+  if( pOut->flags&MEM_Static ){
+    pOut->flags &= ~MEM_Static;
+    pOut->flags |= MEM_Ephem;
+  }
+  columnMallocFailure(pStmt);
+  return (sqlite3_value *)pOut;
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_text16(sqlite3_stmt *pStmt, int i){
+  const void *val = sqlite3_value_text16( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+int sqlite3_column_type(sqlite3_stmt *pStmt, int i){
+  int iType = sqlite3_value_type( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return iType;
+}
+
+/*
+** Column names appropriate for EXPLAIN or EXPLAIN QUERY PLAN.
+*/
+static const char * const azExplainColNames8[] = {
+   "addr", "opcode", "p1", "p2", "p3", "p4", "p5", "comment",  /* EXPLAIN */
+   "id", "parent", "notused", "detail"                         /* EQP */
+};
+static const u16 azExplainColNames16data[] = {
+  /*   0 */  'a', 'd', 'd', 'r',                0,
+  /*   5 */  'o', 'p', 'c', 'o', 'd', 'e',      0,
+  /*  12 */  'p', '1',                          0, 
+  /*  15 */  'p', '2',                          0,
+  /*  18 */  'p', '3',                          0,
+  /*  21 */  'p', '4',                          0,
+  /*  24 */  'p', '5',                          0,
+  /*  27 */  'c', 'o', 'm', 'm', 'e', 'n', 't', 0,
+  /*  35 */  'i', 'd',                          0,
+  /*  38 */  'p', 'a', 'r', 'e', 'n', 't',      0,
+  /*  45 */  'n', 'o', 't', 'u', 's', 'e', 'd', 0,
+  /*  53 */  'd', 'e', 't', 'a', 'i', 'l',      0
+};
+static const u8 iExplainColNames16[] = {
+  0, 5, 12, 15, 18, 21, 24, 27,
+  35, 38, 45, 53
+};
+
+/*
+** Convert the N-th element of pStmt->pColName[] into a string using
+** xFunc() then return that string.  If N is out of range, return 0.
+**
+** There are up to 5 names for each column.  useType determines which
+** name is returned.  Here are the names:
+**
+**    0      The column name as it should be displayed for output
+**    1      The datatype name for the column
+**    2      The name of the database that the column derives from
+**    3      The name of the table that the column derives from
+**    4      The name of the table column that the result column derives from
+**
+** If the result is not a simple column reference (if it is an expression
+** or a constant) then useTypes 2, 3, and 4 return NULL.
+*/
+static const void *columnName(
+  sqlite3_stmt *pStmt,     /* The statement */
+  int N,                   /* Which column to get the name for */
+  int useUtf16,            /* True to return the name as UTF16 */
+  int useType              /* What type of name */
+){
+  const void *ret;
+  Vdbe *p;
+  int n;
+  sqlite3 *db;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pStmt==0 ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  if( N<0 ) return 0;
+  ret = 0;
+  p = (Vdbe *)pStmt;
+  db = p->db;
+  assert( db!=0 );
+  sqlite3_mutex_enter(db->mutex);
+
+  if( p->explain ){
+    if( useType>0 ) goto columnName_end;
+    n = p->explain==1 ? 8 : 4;
+    if( N>=n ) goto columnName_end;
+    if( useUtf16 ){
+      int i = iExplainColNames16[N + 8*p->explain - 8];
+      ret = (void*)&azExplainColNames16data[i];
+    }else{
+      ret = (void*)azExplainColNames8[N + 8*p->explain - 8];
+    }
+    goto columnName_end;
+  }
+  n = p->nResColumn;
+  if( N<n ){
+    u8 prior_mallocFailed = db->mallocFailed;
+    N += useType*n;
+#ifndef SQLITE_OMIT_UTF16
+    if( useUtf16 ){
+      ret = sqlite3_value_text16((sqlite3_value*)&p->aColName[N]);
+    }else
+#endif
+    {
+      ret = sqlite3_value_text((sqlite3_value*)&p->aColName[N]);
+    }
+    /* A malloc may have failed inside of the _text() call. If this
+    ** is the case, clear the mallocFailed flag and return NULL.
+    */
+    assert( db->mallocFailed==0 || db->mallocFailed==1 );
+    if( db->mallocFailed > prior_mallocFailed ){
+      sqlite3OomClear(db);
+      ret = 0;
+    }
+  }
+columnName_end:
+  sqlite3_mutex_leave(db->mutex);
+  return ret;
+}
+
+/*
+** Return the name of the Nth column of the result set returned by SQL
+** statement pStmt.
+*/
+const char *sqlite3_column_name(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 0, COLNAME_NAME);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 1, COLNAME_NAME);
+}
+#endif
+
+/*
+** Constraint:  If you have ENABLE_COLUMN_METADATA then you must
+** not define OMIT_DECLTYPE.
+*/
+#if defined(SQLITE_OMIT_DECLTYPE) && defined(SQLITE_ENABLE_COLUMN_METADATA)
+# error "Must not define both SQLITE_OMIT_DECLTYPE \
+         and SQLITE_ENABLE_COLUMN_METADATA"
+#endif
+
+#ifndef SQLITE_OMIT_DECLTYPE
+/*
+** Return the column declaration type (if applicable) of the 'i'th column
+** of the result set of SQL statement pStmt.
+*/
+const char *sqlite3_column_decltype(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 0, COLNAME_DECLTYPE);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_decltype16(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 1, COLNAME_DECLTYPE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+#endif /* SQLITE_OMIT_DECLTYPE */
+
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+/*
+** Return the name of the database from which a result column derives.
+** NULL is returned if the result column is an expression or constant or
+** anything else which is not an unambiguous reference to a database column.
+*/
+const char *sqlite3_column_database_name(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 0, COLNAME_DATABASE);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_database_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 1, COLNAME_DATABASE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Return the name of the table from which a result column derives.
+** NULL is returned if the result column is an expression or constant or
+** anything else which is not an unambiguous reference to a database column.
+*/
+const char *sqlite3_column_table_name(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 0, COLNAME_TABLE);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_table_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 1, COLNAME_TABLE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Return the name of the table column from which a result column derives.
+** NULL is returned if the result column is an expression or constant or
+** anything else which is not an unambiguous reference to a database column.
+*/
+const char *sqlite3_column_origin_name(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 0, COLNAME_COLUMN);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_origin_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(pStmt, N, 1, COLNAME_COLUMN);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+#endif /* SQLITE_ENABLE_COLUMN_METADATA */
+
+
+/******************************* sqlite3_bind_  ***************************
+**
+** Routines used to attach values to wildcards in a compiled SQL statement.
+*/
+/*
+** Unbind the value bound to variable i in virtual machine p. This is the
+** the same as binding a NULL value to the column. If the "i" parameter is
+** out of range, then SQLITE_RANGE is returned. Otherwise SQLITE_OK.
+**
+** A successful evaluation of this routine acquires the mutex on p.
+** the mutex is released if any kind of error occurs.
+**
+** The error code stored in database p->db is overwritten with the return
+** value in any case.
+*/
+static int vdbeUnbind(Vdbe *p, unsigned int i){
+  Mem *pVar;
+  if( vdbeSafetyNotNull(p) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  sqlite3_mutex_enter(p->db->mutex);
+  if( p->eVdbeState!=VDBE_READY_STATE ){
+    sqlite3Error(p->db, SQLITE_MISUSE_BKPT);
+    sqlite3_mutex_leave(p->db->mutex);
+    sqlite3_log(SQLITE_MISUSE,
+        "bind on a busy prepared statement: [%s]", p->zSql);
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( i>=(unsigned int)p->nVar ){
+    sqlite3Error(p->db, SQLITE_RANGE);
+    sqlite3_mutex_leave(p->db->mutex);
+    return SQLITE_RANGE;
+  }
+  pVar = &p->aVar[i];
+  sqlite3VdbeMemRelease(pVar);
+  pVar->flags = MEM_Null;
+  p->db->errCode = SQLITE_OK;
+
+  /* If the bit corresponding to this variable in Vdbe.expmask is set, then
+  ** binding a new value to this variable invalidates the current query plan.
+  **
+  ** IMPLEMENTATION-OF: R-57496-20354 If the specific value bound to a host
+  ** parameter in the WHERE clause might influence the choice of query plan
+  ** for a statement, then the statement will be automatically recompiled,
+  ** as if there had been a schema change, on the first sqlite3_step() call
+  ** following any change to the bindings of that parameter.
+  */
+  assert( (p->prepFlags & SQLITE_PREPARE_SAVESQL)!=0 || p->expmask==0 );
+  if( p->expmask!=0 && (p->expmask & (i>=31 ? 0x80000000 : (u32)1<<i))!=0 ){
+    p->expired = 1;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Bind a text or BLOB value.
+*/
+static int bindText(
+  sqlite3_stmt *pStmt,   /* The statement to bind against */
+  int i,                 /* Index of the parameter to bind */
+  const void *zData,     /* Pointer to the data to be bound */
+  i64 nData,             /* Number of bytes of data to be bound */
+  void (*xDel)(void*),   /* Destructor for the data */
+  u8 encoding            /* Encoding for the data */
+){
+  Vdbe *p = (Vdbe *)pStmt;
+  Mem *pVar;
+  int rc;
+
+  rc = vdbeUnbind(p, (u32)(i-1));
+  if( rc==SQLITE_OK ){
+    if( zData!=0 ){
+      pVar = &p->aVar[i-1];
+      rc = sqlite3VdbeMemSetStr(pVar, zData, nData, encoding, xDel);
+      if( rc==SQLITE_OK && encoding!=0 ){
+        rc = sqlite3VdbeChangeEncoding(pVar, ENC(p->db));
+      }
+      if( rc ){
+        sqlite3Error(p->db, rc);
+        rc = sqlite3ApiExit(p->db, rc);
+      }
+    }
+    sqlite3_mutex_leave(p->db->mutex);
+  }else if( xDel!=SQLITE_STATIC && xDel!=SQLITE_TRANSIENT ){
+    xDel((void*)zData);
+  }
+  return rc;
+}
+
+
+/*
+** Bind a blob value to an SQL statement variable.
+*/
+int sqlite3_bind_blob(
+  sqlite3_stmt *pStmt,
+  int i,
+  const void *zData,
+  int nData,
+  void (*xDel)(void*)
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( nData<0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  return bindText(pStmt, i, zData, nData, xDel, 0);
+}
+int sqlite3_bind_blob64(
+  sqlite3_stmt *pStmt,
+  int i,
+  const void *zData,
+  sqlite3_uint64 nData,
+  void (*xDel)(void*)
+){
+  assert( xDel!=SQLITE_DYNAMIC );
+  return bindText(pStmt, i, zData, nData, xDel, 0);
+}
+int sqlite3_bind_double(sqlite3_stmt *pStmt, int i, double rValue){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+  rc = vdbeUnbind(p, (u32)(i-1));
+  if( rc==SQLITE_OK ){
+    sqlite3VdbeMemSetDouble(&p->aVar[i-1], rValue);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+int sqlite3_bind_int(sqlite3_stmt *p, int i, int iValue){
+  return sqlite3_bind_int64(p, i, (i64)iValue);
+}
+int sqlite3_bind_int64(sqlite3_stmt *pStmt, int i, sqlite_int64 iValue){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+  rc = vdbeUnbind(p, (u32)(i-1));
+  if( rc==SQLITE_OK ){
+    sqlite3VdbeMemSetInt64(&p->aVar[i-1], iValue);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+int sqlite3_bind_null(sqlite3_stmt *pStmt, int i){
+  int rc;
+  Vdbe *p = (Vdbe*)pStmt;
+  rc = vdbeUnbind(p, (u32)(i-1));
+  if( rc==SQLITE_OK ){
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+int sqlite3_bind_pointer(
+  sqlite3_stmt *pStmt,
+  int i,
+  void *pPtr,
+  const char *zPTtype,
+  void (*xDestructor)(void*)
+){
+  int rc;
+  Vdbe *p = (Vdbe*)pStmt;
+  rc = vdbeUnbind(p, (u32)(i-1));
+  if( rc==SQLITE_OK ){
+    sqlite3VdbeMemSetPointer(&p->aVar[i-1], pPtr, zPTtype, xDestructor);
+    sqlite3_mutex_leave(p->db->mutex);
+  }else if( xDestructor ){
+    xDestructor(pPtr);
+  }
+  return rc;
+}
+int sqlite3_bind_text(
+  sqlite3_stmt *pStmt,
+  int i,
+  const char *zData,
+  int nData,
+  void (*xDel)(void*)
+){
+  return bindText(pStmt, i, zData, nData, xDel, SQLITE_UTF8);
+}
+int sqlite3_bind_text64(
+  sqlite3_stmt *pStmt,
+  int i,
+  const char *zData,
+  sqlite3_uint64 nData,
+  void (*xDel)(void*),
+  unsigned char enc
+){
+  assert( xDel!=SQLITE_DYNAMIC );
+  if( enc!=SQLITE_UTF8 ){
+    if( enc==SQLITE_UTF16 ) enc = SQLITE_UTF16NATIVE;
+    nData &= ~(u16)1;
+  }
+  return bindText(pStmt, i, zData, nData, xDel, enc);
+}
+#ifndef SQLITE_OMIT_UTF16
+int sqlite3_bind_text16(
+  sqlite3_stmt *pStmt,
+  int i,
+  const void *zData,
+  int n,
+  void (*xDel)(void*)
+){
+  return bindText(pStmt, i, zData, n & ~(u64)1, xDel, SQLITE_UTF16NATIVE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+int sqlite3_bind_value(sqlite3_stmt *pStmt, int i, const sqlite3_value *pValue){
+  int rc;
+  switch( sqlite3_value_type((sqlite3_value*)pValue) ){
+    case SQLITE_INTEGER: {
+      rc = sqlite3_bind_int64(pStmt, i, pValue->u.i);
+      break;
+    }
+    case SQLITE_FLOAT: {
+      assert( pValue->flags & (MEM_Real|MEM_IntReal) );
+      rc = sqlite3_bind_double(pStmt, i,
+          (pValue->flags & MEM_Real) ? pValue->u.r : (double)pValue->u.i
+      );
+      break;
+    }
+    case SQLITE_BLOB: {
+      if( pValue->flags & MEM_Zero ){
+        rc = sqlite3_bind_zeroblob(pStmt, i, pValue->u.nZero);
+      }else{
+        rc = sqlite3_bind_blob(pStmt, i, pValue->z, pValue->n,SQLITE_TRANSIENT);
+      }
+      break;
+    }
+    case SQLITE_TEXT: {
+      rc = bindText(pStmt,i,  pValue->z, pValue->n, SQLITE_TRANSIENT,
+                              pValue->enc);
+      break;
+    }
+    default: {
+      rc = sqlite3_bind_null(pStmt, i);
+      break;
+    }
+  }
+  return rc;
+}
+int sqlite3_bind_zeroblob(sqlite3_stmt *pStmt, int i, int n){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+  rc = vdbeUnbind(p, (u32)(i-1));
+  if( rc==SQLITE_OK ){
+#ifndef SQLITE_OMIT_INCRBLOB
+    sqlite3VdbeMemSetZeroBlob(&p->aVar[i-1], n);
+#else
+    rc = sqlite3VdbeMemSetZeroBlob(&p->aVar[i-1], n);
+#endif
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+int sqlite3_bind_zeroblob64(sqlite3_stmt *pStmt, int i, sqlite3_uint64 n){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(p->db->mutex);
+  if( n>(u64)p->db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    rc = SQLITE_TOOBIG;
+  }else{
+    assert( (n & 0x7FFFFFFF)==n );
+    rc = sqlite3_bind_zeroblob(pStmt, i, n);
+  }
+  rc = sqlite3ApiExit(p->db, rc);
+  sqlite3_mutex_leave(p->db->mutex);
+  return rc;
+}
+
+/*
+** Return the number of wildcards that can be potentially bound to.
+** This routine is added to support DBD::SQLite. 
+*/
+int sqlite3_bind_parameter_count(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe*)pStmt;
+  return p ? p->nVar : 0;
+}
+
+/*
+** Return the name of a wildcard parameter.  Return NULL if the index
+** is out of range or if the wildcard is unnamed.
+**
+** The result is always UTF-8.
+*/
+const char *sqlite3_bind_parameter_name(sqlite3_stmt *pStmt, int i){
+  Vdbe *p = (Vdbe*)pStmt;
+  if( p==0 ) return 0;
+  return sqlite3VListNumToName(p->pVList, i);
+}
+
+/*
+** Given a wildcard parameter name, return the index of the variable
+** with that name.  If there is no variable with the given name,
+** return 0.
+*/
+int sqlite3VdbeParameterIndex(Vdbe *p, const char *zName, int nName){
+  if( p==0 || zName==0 ) return 0;
+  return sqlite3VListNameToNum(p->pVList, zName, nName);
+}
+int sqlite3_bind_parameter_index(sqlite3_stmt *pStmt, const char *zName){
+  return sqlite3VdbeParameterIndex((Vdbe*)pStmt, zName, sqlite3Strlen30(zName));
+}
+
+/*
+** Transfer all bindings from the first statement over to the second.
+*/
+int sqlite3TransferBindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
+  Vdbe *pFrom = (Vdbe*)pFromStmt;
+  Vdbe *pTo = (Vdbe*)pToStmt;
+  int i;
+  assert( pTo->db==pFrom->db );
+  assert( pTo->nVar==pFrom->nVar );
+  sqlite3_mutex_enter(pTo->db->mutex);
+  for(i=0; i<pFrom->nVar; i++){
+    sqlite3VdbeMemMove(&pTo->aVar[i], &pFrom->aVar[i]);
+  }
+  sqlite3_mutex_leave(pTo->db->mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Deprecated external interface.  Internal/core SQLite code
+** should call sqlite3TransferBindings.
+**
+** It is misuse to call this routine with statements from different
+** database connections.  But as this is a deprecated interface, we
+** will not bother to check for that condition.
+**
+** If the two statements contain a different number of bindings, then
+** an SQLITE_ERROR is returned.  Nothing else can go wrong, so otherwise
+** SQLITE_OK is returned.
+*/
+int sqlite3_transfer_bindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
+  Vdbe *pFrom = (Vdbe*)pFromStmt;
+  Vdbe *pTo = (Vdbe*)pToStmt;
+  if( pFrom->nVar!=pTo->nVar ){
+    return SQLITE_ERROR;
+  }
+  assert( (pTo->prepFlags & SQLITE_PREPARE_SAVESQL)!=0 || pTo->expmask==0 );
+  if( pTo->expmask ){
+    pTo->expired = 1;
+  }
+  assert( (pFrom->prepFlags & SQLITE_PREPARE_SAVESQL)!=0 || pFrom->expmask==0 );
+  if( pFrom->expmask ){
+    pFrom->expired = 1;
+  }
+  return sqlite3TransferBindings(pFromStmt, pToStmt);
+}
+#endif
+
+/*
+** Return the sqlite3* database handle to which the prepared statement given
+** in the argument belongs.  This is the same database handle that was
+** the first argument to the sqlite3_prepare() that was used to create
+** the statement in the first place.
+*/
+sqlite3 *sqlite3_db_handle(sqlite3_stmt *pStmt){
+  return pStmt ? ((Vdbe*)pStmt)->db : 0;
+}
+
+/*
+** Return true if the prepared statement is guaranteed to not modify the
+** database.
+*/
+int sqlite3_stmt_readonly(sqlite3_stmt *pStmt){
+  return pStmt ? ((Vdbe*)pStmt)->readOnly : 1;
+}
+
+/*
+** Return 1 if the statement is an EXPLAIN and return 2 if the
+** statement is an EXPLAIN QUERY PLAN
+*/
+int sqlite3_stmt_isexplain(sqlite3_stmt *pStmt){
+  return pStmt ? ((Vdbe*)pStmt)->explain : 0;
+}
+
+/*
+** Set the explain mode for a statement.
+*/
+int sqlite3_stmt_explain(sqlite3_stmt *pStmt, int eMode){
+  Vdbe *v = (Vdbe*)pStmt;
+  int rc;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( pStmt==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(v->db->mutex);
+  if( ((int)v->explain)==eMode ){
+    rc = SQLITE_OK;
+  }else if( eMode<0 || eMode>2 ){
+    rc = SQLITE_ERROR;
+  }else if( (v->prepFlags & SQLITE_PREPARE_SAVESQL)==0 ){
+    rc = SQLITE_ERROR;
+  }else if( v->eVdbeState!=VDBE_READY_STATE ){
+    rc = SQLITE_BUSY;
+  }else if( v->nMem>=10 && (eMode!=2 || v->haveEqpOps) ){
+    /* No reprepare necessary */
+    v->explain = eMode;
+    rc = SQLITE_OK;
+  }else{
+    v->explain = eMode;
+    rc = sqlite3Reprepare(v);
+    v->haveEqpOps = eMode==2;
+  }
+  if( v->explain ){
+    v->nResColumn = 12 - 4*v->explain;
+  }else{
+    v->nResColumn = v->nResAlloc;
+  }
+  sqlite3_mutex_leave(v->db->mutex);
+  return rc;
+}
+
+/*
+** Return true if the prepared statement is in need of being reset.
+*/
+int sqlite3_stmt_busy(sqlite3_stmt *pStmt){
+  Vdbe *v = (Vdbe*)pStmt;
+  return v!=0 && v->eVdbeState==VDBE_RUN_STATE;
+}
+
+/*
+** Return a pointer to the next prepared statement after pStmt associated
+** with database connection pDb.  If pStmt is NULL, return the first
+** prepared statement for the database connection.  Return NULL if there
+** are no more.
+*/
+sqlite3_stmt *sqlite3_next_stmt(sqlite3 *pDb, sqlite3_stmt *pStmt){
+  sqlite3_stmt *pNext;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(pDb) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  sqlite3_mutex_enter(pDb->mutex);
+  if( pStmt==0 ){
+    pNext = (sqlite3_stmt*)pDb->pVdbe;
+  }else{
+    pNext = (sqlite3_stmt*)((Vdbe*)pStmt)->pVNext;
+  }
+  sqlite3_mutex_leave(pDb->mutex);
+  return pNext;
+}
+
+/*
+** Return the value of a status counter for a prepared statement
+*/
+int sqlite3_stmt_status(sqlite3_stmt *pStmt, int op, int resetFlag){
+  Vdbe *pVdbe = (Vdbe*)pStmt;
+  u32 v;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !pStmt
+   || (op!=SQLITE_STMTSTATUS_MEMUSED && (op<0||op>=ArraySize(pVdbe->aCounter)))
+  ){
+    (void)SQLITE_MISUSE_BKPT;
+    return 0;
+  }
+#endif
+  if( op==SQLITE_STMTSTATUS_MEMUSED ){
+    sqlite3 *db = pVdbe->db;
+    sqlite3_mutex_enter(db->mutex);
+    v = 0;
+    db->pnBytesFreed = (int*)&v;
+    assert( db->lookaside.pEnd==db->lookaside.pTrueEnd );
+    db->lookaside.pEnd = db->lookaside.pStart;
+    sqlite3VdbeDelete(pVdbe);
+    db->pnBytesFreed = 0;
+    db->lookaside.pEnd = db->lookaside.pTrueEnd;
+    sqlite3_mutex_leave(db->mutex);
+  }else{
+    v = pVdbe->aCounter[op];
+    if( resetFlag ) pVdbe->aCounter[op] = 0;
+  }
+  return (int)v;
+}
+
+/*
+** Return the SQL associated with a prepared statement
+*/
+const char *sqlite3_sql(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe *)pStmt;
+  return p ? p->zSql : 0;
+}
+
+/*
+** Return the SQL associated with a prepared statement with
+** bound parameters expanded.  Space to hold the returned string is
+** obtained from sqlite3_malloc().  The caller is responsible for
+** freeing the returned string by passing it to sqlite3_free().
+**
+** The SQLITE_TRACE_SIZE_LIMIT puts an upper bound on the size of
+** expanded bound parameters.
+*/
+char *sqlite3_expanded_sql(sqlite3_stmt *pStmt){
+#ifdef SQLITE_OMIT_TRACE
+  return 0;
+#else
+  char *z = 0;
+  const char *zSql = sqlite3_sql(pStmt);
+  if( zSql ){
+    Vdbe *p = (Vdbe *)pStmt;
+    sqlite3_mutex_enter(p->db->mutex);
+    z = sqlite3VdbeExpandSql(p, zSql);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return z;
+#endif
+}
+
+#ifdef SQLITE_ENABLE_NORMALIZE
+/*
+** Return the normalized SQL associated with a prepared statement.
+*/
+const char *sqlite3_normalized_sql(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe *)pStmt;
+  if( p==0 ) return 0;
+  if( p->zNormSql==0 && ALWAYS(p->zSql!=0) ){
+    sqlite3_mutex_enter(p->db->mutex);
+    p->zNormSql = sqlite3Normalize(p, p->zSql);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return p->zNormSql;
+}
+#endif /* SQLITE_ENABLE_NORMALIZE */
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** Allocate and populate an UnpackedRecord structure based on the serialized
+** record in nKey/pKey. Return a pointer to the new UnpackedRecord structure
+** if successful, or a NULL pointer if an OOM error is encountered.
+*/
+static UnpackedRecord *vdbeUnpackRecord(
+  KeyInfo *pKeyInfo,
+  int nKey,
+  const void *pKey
+){
+  UnpackedRecord *pRet;           /* Return value */
+
+  pRet = sqlite3VdbeAllocUnpackedRecord(pKeyInfo);
+  if( pRet ){
+    memset(pRet->aMem, 0, sizeof(Mem)*(pKeyInfo->nKeyField+1));
+    sqlite3VdbeRecordUnpack(pKeyInfo, nKey, pKey, pRet);
+  }
+  return pRet;
+}
+
+/*
+** This function is called from within a pre-update callback to retrieve
+** a field of the row currently being updated or deleted.
+*/
+int sqlite3_preupdate_old(sqlite3 *db, int iIdx, sqlite3_value **ppValue){
+  PreUpdate *p;
+  Mem *pMem;
+  int rc = SQLITE_OK;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( db==0 || ppValue==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  p = db->pPreUpdate;
+  /* Test that this call is being made from within an SQLITE_DELETE or
+  ** SQLITE_UPDATE pre-update callback, and that iIdx is within range. */
+  if( !p || p->op==SQLITE_INSERT ){
+    rc = SQLITE_MISUSE_BKPT;
+    goto preupdate_old_out;
+  }
+  if( p->pPk ){
+    iIdx = sqlite3TableColumnToIndex(p->pPk, iIdx);
+  }
+  if( iIdx>=p->pCsr->nField || iIdx<0 ){
+    rc = SQLITE_RANGE;
+    goto preupdate_old_out;
+  }
+
+  /* If the old.* record has not yet been loaded into memory, do so now. */
+  if( p->pUnpacked==0 ){
+    u32 nRec;
+    u8 *aRec;
+
+    assert( p->pCsr->eCurType==CURTYPE_BTREE );
+    nRec = sqlite3BtreePayloadSize(p->pCsr->uc.pCursor);
+    aRec = sqlite3DbMallocRaw(db, nRec);
+    if( !aRec ) goto preupdate_old_out;
+    rc = sqlite3BtreePayload(p->pCsr->uc.pCursor, 0, nRec, aRec);
+    if( rc==SQLITE_OK ){
+      p->pUnpacked = vdbeUnpackRecord(&p->keyinfo, nRec, aRec);
+      if( !p->pUnpacked ) rc = SQLITE_NOMEM;
+    }
+    if( rc!=SQLITE_OK ){
+      sqlite3DbFree(db, aRec);
+      goto preupdate_old_out;
+    }
+    p->aRecord = aRec;
+  }
+
+  pMem = *ppValue = &p->pUnpacked->aMem[iIdx];
+  if( iIdx==p->pTab->iPKey ){
+    sqlite3VdbeMemSetInt64(pMem, p->iKey1);
+  }else if( iIdx>=p->pUnpacked->nField ){
+    *ppValue = (sqlite3_value *)columnNullValue();
+  }else if( p->pTab->aCol[iIdx].affinity==SQLITE_AFF_REAL ){
+    if( pMem->flags & (MEM_Int|MEM_IntReal) ){
+      testcase( pMem->flags & MEM_Int );
+      testcase( pMem->flags & MEM_IntReal );
+      sqlite3VdbeMemRealify(pMem);
+    }
+  }
+
+ preupdate_old_out:
+  sqlite3Error(db, rc);
+  return sqlite3ApiExit(db, rc);
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** This function is called from within a pre-update callback to retrieve
+** the number of columns in the row being updated, deleted or inserted.
+*/
+int sqlite3_preupdate_count(sqlite3 *db){
+  PreUpdate *p;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  p = db!=0 ? db->pPreUpdate : 0;
+#else
+  p = db->pPreUpdate;
+#endif
+  return (p ? p->keyinfo.nKeyField : 0);
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** This function is designed to be called from within a pre-update callback
+** only. It returns zero if the change that caused the callback was made
+** immediately by a user SQL statement. Or, if the change was made by a
+** trigger program, it returns the number of trigger programs currently
+** on the stack (1 for a top-level trigger, 2 for a trigger fired by a
+** top-level trigger etc.).
+**
+** For the purposes of the previous paragraph, a foreign key CASCADE, SET NULL
+** or SET DEFAULT action is considered a trigger.
+*/
+int sqlite3_preupdate_depth(sqlite3 *db){
+  PreUpdate *p;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  p = db!=0 ? db->pPreUpdate : 0;
+#else
+  p = db->pPreUpdate;
+#endif
+  return (p ? p->v->nFrame : 0);
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** This function is designed to be called from within a pre-update callback
+** only.
+*/
+int sqlite3_preupdate_blobwrite(sqlite3 *db){
+  PreUpdate *p;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  p = db!=0 ? db->pPreUpdate : 0;
+#else
+  p = db->pPreUpdate;
+#endif
+  return (p ? p->iBlobWrite : -1);
+}
+#endif
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** This function is called from within a pre-update callback to retrieve
+** a field of the row currently being updated or inserted.
+*/
+int sqlite3_preupdate_new(sqlite3 *db, int iIdx, sqlite3_value **ppValue){
+  PreUpdate *p;
+  int rc = SQLITE_OK;
+  Mem *pMem;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( db==0 || ppValue==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  p = db->pPreUpdate;
+  if( !p || p->op==SQLITE_DELETE ){
+    rc = SQLITE_MISUSE_BKPT;
+    goto preupdate_new_out;
+  }
+  if( p->pPk && p->op!=SQLITE_UPDATE ){
+    iIdx = sqlite3TableColumnToIndex(p->pPk, iIdx);
+  }
+  if( iIdx>=p->pCsr->nField || iIdx<0 ){
+    rc = SQLITE_RANGE;
+    goto preupdate_new_out;
+  }
+
+  if( p->op==SQLITE_INSERT ){
+    /* For an INSERT, memory cell p->iNewReg contains the serialized record
+    ** that is being inserted. Deserialize it. */
+    UnpackedRecord *pUnpack = p->pNewUnpacked;
+    if( !pUnpack ){
+      Mem *pData = &p->v->aMem[p->iNewReg];
+      rc = ExpandBlob(pData);
+      if( rc!=SQLITE_OK ) goto preupdate_new_out;
+      pUnpack = vdbeUnpackRecord(&p->keyinfo, pData->n, pData->z);
+      if( !pUnpack ){
+        rc = SQLITE_NOMEM;
+        goto preupdate_new_out;
+      }
+      p->pNewUnpacked = pUnpack;
+    }
+    pMem = &pUnpack->aMem[iIdx];
+    if( iIdx==p->pTab->iPKey ){
+      sqlite3VdbeMemSetInt64(pMem, p->iKey2);
+    }else if( iIdx>=pUnpack->nField ){
+      pMem = (sqlite3_value *)columnNullValue();
+    }
+  }else{
+    /* For an UPDATE, memory cell (p->iNewReg+1+iIdx) contains the required
+    ** value. Make a copy of the cell contents and return a pointer to it.
+    ** It is not safe to return a pointer to the memory cell itself as the
+    ** caller may modify the value text encoding.
+    */
+    assert( p->op==SQLITE_UPDATE );
+    if( !p->aNew ){
+      p->aNew = (Mem *)sqlite3DbMallocZero(db, sizeof(Mem) * p->pCsr->nField);
+      if( !p->aNew ){
+        rc = SQLITE_NOMEM;
+        goto preupdate_new_out;
+      }
+    }
+    assert( iIdx>=0 && iIdx<p->pCsr->nField );
+    pMem = &p->aNew[iIdx];
+    if( pMem->flags==0 ){
+      if( iIdx==p->pTab->iPKey ){
+        sqlite3VdbeMemSetInt64(pMem, p->iKey2);
+      }else{
+        rc = sqlite3VdbeMemCopy(pMem, &p->v->aMem[p->iNewReg+1+iIdx]);
+        if( rc!=SQLITE_OK ) goto preupdate_new_out;
+      }
+    }
+  }
+  *ppValue = pMem;
+
+ preupdate_new_out:
+  sqlite3Error(db, rc);
+  return sqlite3ApiExit(db, rc);
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+/*
+** Return status data for a single loop within query pStmt.
+*/
+int sqlite3_stmt_scanstatus_v2(
+  sqlite3_stmt *pStmt,            /* Prepared statement being queried */
+  int iScan,                      /* Index of loop to report on */
+  int iScanStatusOp,              /* Which metric to return */
+  int flags,
+  void *pOut                      /* OUT: Write the answer here */
+){
+  Vdbe *p = (Vdbe*)pStmt;
+  VdbeOp *aOp;
+  int nOp;
+  ScanStatus *pScan = 0;
+  int idx;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( p==0 || pOut==0
+      || iScanStatusOp<SQLITE_SCANSTAT_NLOOP
+      || iScanStatusOp>SQLITE_SCANSTAT_NCYCLE ){
+    return 1;
+  }
+#endif
+  aOp = p->aOp;
+  nOp = p->nOp;
+  if( p->pFrame ){
+    VdbeFrame *pFrame;
+    for(pFrame=p->pFrame; pFrame->pParent; pFrame=pFrame->pParent);
+    aOp = pFrame->aOp;
+    nOp = pFrame->nOp;
+  }
+
+  if( iScan<0 ){
+    int ii;
+    if( iScanStatusOp==SQLITE_SCANSTAT_NCYCLE ){
+      i64 res = 0;
+      for(ii=0; ii<nOp; ii++){
+        res += aOp[ii].nCycle;
+      }
+      *(i64*)pOut = res;
+      return 0;
+    }
+    return 1;
+  }
+  if( flags & SQLITE_SCANSTAT_COMPLEX ){
+    idx = iScan;
+    pScan = &p->aScan[idx];
+  }else{
+    /* If the COMPLEX flag is clear, then this function must ignore any
+    ** ScanStatus structures with ScanStatus.addrLoop set to 0. */
+    for(idx=0; idx<p->nScan; idx++){
+      pScan = &p->aScan[idx];
+      if( pScan->zName ){
+        iScan--;
+        if( iScan<0 ) break;
+      }
+    }
+  }
+  if( idx>=p->nScan ) return 1;
+
+  switch( iScanStatusOp ){
+    case SQLITE_SCANSTAT_NLOOP: {
+      if( pScan->addrLoop>0 ){
+        *(sqlite3_int64*)pOut = aOp[pScan->addrLoop].nExec;
+      }else{
+        *(sqlite3_int64*)pOut = -1;
+      }
+      break;
+    }
+    case SQLITE_SCANSTAT_NVISIT: {
+      if( pScan->addrVisit>0 ){
+        *(sqlite3_int64*)pOut = aOp[pScan->addrVisit].nExec;
+      }else{
+        *(sqlite3_int64*)pOut = -1;
+      }
+      break;
+    }
+    case SQLITE_SCANSTAT_EST: {
+      double r = 1.0;
+      LogEst x = pScan->nEst;
+      while( x<100 ){
+        x += 10;
+        r *= 0.5;
+      }
+      *(double*)pOut = r*sqlite3LogEstToInt(x);
+      break;
+    }
+    case SQLITE_SCANSTAT_NAME: {
+      *(const char**)pOut = pScan->zName;
+      break;
+    }
+    case SQLITE_SCANSTAT_EXPLAIN: {
+      if( pScan->addrExplain ){
+        *(const char**)pOut = aOp[ pScan->addrExplain ].p4.z;
+      }else{
+        *(const char**)pOut = 0;
+      }
+      break;
+    }
+    case SQLITE_SCANSTAT_SELECTID: {
+      if( pScan->addrExplain ){
+        *(int*)pOut = aOp[ pScan->addrExplain ].p1;
+      }else{
+        *(int*)pOut = -1;
+      }
+      break;
+    }
+    case SQLITE_SCANSTAT_PARENTID: {
+      if( pScan->addrExplain ){
+        *(int*)pOut = aOp[ pScan->addrExplain ].p2;
+      }else{
+        *(int*)pOut = -1;
+      }
+      break;
+    }
+    case SQLITE_SCANSTAT_NCYCLE: {
+      i64 res = 0;
+      if( pScan->aAddrRange[0]==0 ){
+        res = -1;
+      }else{
+        int ii;
+        for(ii=0; ii<ArraySize(pScan->aAddrRange); ii+=2){
+          int iIns = pScan->aAddrRange[ii];
+          int iEnd = pScan->aAddrRange[ii+1];
+          if( iIns==0 ) break;
+          if( iIns>0 ){
+            while( iIns<=iEnd ){
+              res += aOp[iIns].nCycle;
+              iIns++;
+            }
+          }else{
+            int iOp;
+            for(iOp=0; iOp<nOp; iOp++){
+              Op *pOp = &aOp[iOp];
+              if( pOp->p1!=iEnd ) continue;
+              if( (sqlite3OpcodeProperty[pOp->opcode] & OPFLG_NCYCLE)==0 ){
+                continue;
+              }
+              res += aOp[iOp].nCycle;
+            }
+          }
+        }
+      }
+      *(i64*)pOut = res;
+      break;
+    }
+    default: {
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Return status data for a single loop within query pStmt.
+*/
+int sqlite3_stmt_scanstatus(
+  sqlite3_stmt *pStmt,            /* Prepared statement being queried */
+  int iScan,                      /* Index of loop to report on */
+  int iScanStatusOp,              /* Which metric to return */
+  void *pOut                      /* OUT: Write the answer here */
+){
+  return sqlite3_stmt_scanstatus_v2(pStmt, iScan, iScanStatusOp, 0, pOut);
+}
+
+/*
+** Zero all counters associated with the sqlite3_stmt_scanstatus() data.
+*/
+void sqlite3_stmt_scanstatus_reset(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe*)pStmt;
+  int ii;
+  for(ii=0; p!=0 && ii<p->nOp; ii++){
+    Op *pOp = &p->aOp[ii];
+    pOp->nExec = 0;
+    pOp->nCycle = 0;
+  }
+}
+#endif /* SQLITE_ENABLE_STMT_SCANSTATUS */
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
new file mode 100644
index 0000000..420365e
--- /dev/null
+++ b/src/vdbeaux.c
@@ -0,0 +1,5499 @@
+/*
+** 2003 September 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used for creating, destroying, and populating
+** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.)
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/* Forward references */
+static void freeEphemeralFunction(sqlite3 *db, FuncDef *pDef);
+static void vdbeFreeOpArray(sqlite3 *, Op *, int);
+
+/*
+** Create a new virtual database engine.
+*/
+Vdbe *sqlite3VdbeCreate(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  Vdbe *p;
+  p = sqlite3DbMallocRawNN(db, sizeof(Vdbe) );
+  if( p==0 ) return 0;
+  memset(&p->aOp, 0, sizeof(Vdbe)-offsetof(Vdbe,aOp));
+  p->db = db;
+  if( db->pVdbe ){
+    db->pVdbe->ppVPrev = &p->pVNext;
+  }
+  p->pVNext = db->pVdbe;
+  p->ppVPrev = &db->pVdbe;
+  db->pVdbe = p;
+  assert( p->eVdbeState==VDBE_INIT_STATE );
+  p->pParse = pParse;
+  pParse->pVdbe = p;
+  assert( pParse->aLabel==0 );
+  assert( pParse->nLabel==0 );
+  assert( p->nOpAlloc==0 );
+  assert( pParse->szOpAlloc==0 );
+  sqlite3VdbeAddOp2(p, OP_Init, 0, 1);
+  return p;
+}
+
+/*
+** Return the Parse object that owns a Vdbe object.
+*/
+Parse *sqlite3VdbeParser(Vdbe *p){
+  return p->pParse;
+}
+
+/*
+** Change the error string stored in Vdbe.zErrMsg
+*/
+void sqlite3VdbeError(Vdbe *p, const char *zFormat, ...){
+  va_list ap;
+  sqlite3DbFree(p->db, p->zErrMsg);
+  va_start(ap, zFormat);
+  p->zErrMsg = sqlite3VMPrintf(p->db, zFormat, ap);
+  va_end(ap);
+}
+
+/*
+** Remember the SQL string for a prepared statement.
+*/
+void sqlite3VdbeSetSql(Vdbe *p, const char *z, int n, u8 prepFlags){
+  if( p==0 ) return;
+  p->prepFlags = prepFlags;
+  if( (prepFlags & SQLITE_PREPARE_SAVESQL)==0 ){
+    p->expmask = 0;
+  }
+  assert( p->zSql==0 );
+  p->zSql = sqlite3DbStrNDup(p->db, z, n);
+}
+
+#ifdef SQLITE_ENABLE_NORMALIZE
+/*
+** Add a new element to the Vdbe->pDblStr list.
+*/
+void sqlite3VdbeAddDblquoteStr(sqlite3 *db, Vdbe *p, const char *z){
+  if( p ){
+    int n = sqlite3Strlen30(z);
+    DblquoteStr *pStr = sqlite3DbMallocRawNN(db,
+                            sizeof(*pStr)+n+1-sizeof(pStr->z));
+    if( pStr ){
+      pStr->pNextStr = p->pDblStr;
+      p->pDblStr = pStr;
+      memcpy(pStr->z, z, n+1);
+    }
+  }
+}
+#endif
+
+#ifdef SQLITE_ENABLE_NORMALIZE
+/*
+** zId of length nId is a double-quoted identifier.  Check to see if
+** that identifier is really used as a string literal.
+*/
+int sqlite3VdbeUsesDoubleQuotedString(
+  Vdbe *pVdbe,            /* The prepared statement */
+  const char *zId         /* The double-quoted identifier, already dequoted */
+){
+  DblquoteStr *pStr;
+  assert( zId!=0 );
+  if( pVdbe->pDblStr==0 ) return 0;
+  for(pStr=pVdbe->pDblStr; pStr; pStr=pStr->pNextStr){
+    if( strcmp(zId, pStr->z)==0 ) return 1;
+  }
+  return 0;
+}
+#endif
+
+/*
+** Swap byte-code between two VDBE structures.
+**
+** This happens after pB was previously run and returned
+** SQLITE_SCHEMA.  The statement was then reprepared in pA.
+** This routine transfers the new bytecode in pA over to pB
+** so that pB can be run again.  The old pB byte code is
+** moved back to pA so that it will be cleaned up when pA is
+** finalized.
+*/
+void sqlite3VdbeSwap(Vdbe *pA, Vdbe *pB){
+  Vdbe tmp, *pTmp, **ppTmp;
+  char *zTmp;
+  assert( pA->db==pB->db );
+  tmp = *pA;
+  *pA = *pB;
+  *pB = tmp;
+  pTmp = pA->pVNext;
+  pA->pVNext = pB->pVNext;
+  pB->pVNext = pTmp;
+  ppTmp = pA->ppVPrev;
+  pA->ppVPrev = pB->ppVPrev;
+  pB->ppVPrev = ppTmp;
+  zTmp = pA->zSql;
+  pA->zSql = pB->zSql;
+  pB->zSql = zTmp;
+#ifdef SQLITE_ENABLE_NORMALIZE
+  zTmp = pA->zNormSql;
+  pA->zNormSql = pB->zNormSql;
+  pB->zNormSql = zTmp;
+#endif
+  pB->expmask = pA->expmask;
+  pB->prepFlags = pA->prepFlags;
+  memcpy(pB->aCounter, pA->aCounter, sizeof(pB->aCounter));
+  pB->aCounter[SQLITE_STMTSTATUS_REPREPARE]++;
+}
+
+/*
+** Resize the Vdbe.aOp array so that it is at least nOp elements larger
+** than its current size. nOp is guaranteed to be less than or equal
+** to 1024/sizeof(Op).
+**
+** If an out-of-memory error occurs while resizing the array, return
+** SQLITE_NOMEM. In this case Vdbe.aOp and Vdbe.nOpAlloc remain
+** unchanged (this is so that any opcodes already allocated can be
+** correctly deallocated along with the rest of the Vdbe).
+*/
+static int growOpArray(Vdbe *v, int nOp){
+  VdbeOp *pNew;
+  Parse *p = v->pParse;
+
+  /* The SQLITE_TEST_REALLOC_STRESS compile-time option is designed to force
+  ** more frequent reallocs and hence provide more opportunities for
+  ** simulated OOM faults.  SQLITE_TEST_REALLOC_STRESS is generally used
+  ** during testing only.  With SQLITE_TEST_REALLOC_STRESS grow the op array
+  ** by the minimum* amount required until the size reaches 512.  Normal
+  ** operation (without SQLITE_TEST_REALLOC_STRESS) is to double the current
+  ** size of the op array or add 1KB of space, whichever is smaller. */
+#ifdef SQLITE_TEST_REALLOC_STRESS
+  sqlite3_int64 nNew = (v->nOpAlloc>=512 ? 2*(sqlite3_int64)v->nOpAlloc
+                        : (sqlite3_int64)v->nOpAlloc+nOp);
+#else
+  sqlite3_int64 nNew = (v->nOpAlloc ? 2*(sqlite3_int64)v->nOpAlloc
+                        : (sqlite3_int64)(1024/sizeof(Op)));
+  UNUSED_PARAMETER(nOp);
+#endif
+
+  /* Ensure that the size of a VDBE does not grow too large */
+  if( nNew > p->db->aLimit[SQLITE_LIMIT_VDBE_OP] ){
+    sqlite3OomFault(p->db);
+    return SQLITE_NOMEM;
+  }
+
+  assert( nOp<=(int)(1024/sizeof(Op)) );
+  assert( nNew>=(v->nOpAlloc+nOp) );
+  pNew = sqlite3DbRealloc(p->db, v->aOp, nNew*sizeof(Op));
+  if( pNew ){
+    p->szOpAlloc = sqlite3DbMallocSize(p->db, pNew);
+    v->nOpAlloc = p->szOpAlloc/sizeof(Op);
+    v->aOp = pNew;
+  }
+  return (pNew ? SQLITE_OK : SQLITE_NOMEM_BKPT);
+}
+
+#ifdef SQLITE_DEBUG
+/* This routine is just a convenient place to set a breakpoint that will
+** fire after each opcode is inserted and displayed using
+** "PRAGMA vdbe_addoptrace=on".  Parameters "pc" (program counter) and
+** pOp are available to make the breakpoint conditional.
+**
+** Other useful labels for breakpoints include:
+**   test_trace_breakpoint(pc,pOp)
+**   sqlite3CorruptError(lineno)
+**   sqlite3MisuseError(lineno)
+**   sqlite3CantopenError(lineno)
+*/
+static void test_addop_breakpoint(int pc, Op *pOp){
+  static u64 n = 0;
+  (void)pc;
+  (void)pOp;
+  n++;
+  if( n==LARGEST_UINT64 ) abort(); /* so that n is used, preventing a warning */
+}
+#endif
+
+/*
+** Slow paths for sqlite3VdbeAddOp3() and sqlite3VdbeAddOp4Int() for the
+** unusual case when we need to increase the size of the Vdbe.aOp[] array
+** before adding the new opcode.
+*/
+static SQLITE_NOINLINE int growOp3(Vdbe *p, int op, int p1, int p2, int p3){
+  assert( p->nOpAlloc<=p->nOp );
+  if( growOpArray(p, 1) ) return 1;
+  assert( p->nOpAlloc>p->nOp );
+  return sqlite3VdbeAddOp3(p, op, p1, p2, p3);
+}
+static SQLITE_NOINLINE int addOp4IntSlow(
+  Vdbe *p,            /* Add the opcode to this VM */
+  int op,             /* The new opcode */
+  int p1,             /* The P1 operand */
+  int p2,             /* The P2 operand */
+  int p3,             /* The P3 operand */
+  int p4              /* The P4 operand as an integer */
+){
+  int addr = sqlite3VdbeAddOp3(p, op, p1, p2, p3);
+  if( p->db->mallocFailed==0 ){
+    VdbeOp *pOp = &p->aOp[addr];
+    pOp->p4type = P4_INT32;
+    pOp->p4.i = p4;
+  }
+  return addr;
+}
+
+
+/*
+** Add a new instruction to the list of instructions current in the
+** VDBE.  Return the address of the new instruction.
+**
+** Parameters:
+**
+**    p               Pointer to the VDBE
+**
+**    op              The opcode for this instruction
+**
+**    p1, p2, p3, p4  Operands
+*/
+int sqlite3VdbeAddOp0(Vdbe *p, int op){
+  return sqlite3VdbeAddOp3(p, op, 0, 0, 0);
+}
+int sqlite3VdbeAddOp1(Vdbe *p, int op, int p1){
+  return sqlite3VdbeAddOp3(p, op, p1, 0, 0);
+}
+int sqlite3VdbeAddOp2(Vdbe *p, int op, int p1, int p2){
+  return sqlite3VdbeAddOp3(p, op, p1, p2, 0);
+}
+int sqlite3VdbeAddOp3(Vdbe *p, int op, int p1, int p2, int p3){
+  int i;
+  VdbeOp *pOp;
+
+  i = p->nOp;
+  assert( p->eVdbeState==VDBE_INIT_STATE );
+  assert( op>=0 && op<0xff );
+  if( p->nOpAlloc<=i ){
+    return growOp3(p, op, p1, p2, p3);
+  }
+  assert( p->aOp!=0 );
+  p->nOp++;
+  pOp = &p->aOp[i];
+  assert( pOp!=0 );
+  pOp->opcode = (u8)op;
+  pOp->p5 = 0;
+  pOp->p1 = p1;
+  pOp->p2 = p2;
+  pOp->p3 = p3;
+  pOp->p4.p = 0;
+  pOp->p4type = P4_NOTUSED;
+
+  /* Replicate this logic in sqlite3VdbeAddOp4Int()
+  ** vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv   */
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  pOp->zComment = 0;
+#endif
+#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || defined(VDBE_PROFILE)
+  pOp->nExec = 0;
+  pOp->nCycle = 0;
+#endif
+#ifdef SQLITE_DEBUG
+  if( p->db->flags & SQLITE_VdbeAddopTrace ){
+    sqlite3VdbePrintOp(0, i, &p->aOp[i]);
+    test_addop_breakpoint(i, &p->aOp[i]);
+  }
+#endif
+#ifdef SQLITE_VDBE_COVERAGE
+  pOp->iSrcLine = 0;
+#endif
+  /* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  ** Replicate in sqlite3VdbeAddOp4Int() */
+
+  return i;
+}
+int sqlite3VdbeAddOp4Int(
+  Vdbe *p,            /* Add the opcode to this VM */
+  int op,             /* The new opcode */
+  int p1,             /* The P1 operand */
+  int p2,             /* The P2 operand */
+  int p3,             /* The P3 operand */
+  int p4              /* The P4 operand as an integer */
+){
+  int i;
+  VdbeOp *pOp;
+
+  i = p->nOp;
+  if( p->nOpAlloc<=i ){
+    return addOp4IntSlow(p, op, p1, p2, p3, p4);
+  }
+  p->nOp++;
+  pOp = &p->aOp[i];
+  assert( pOp!=0 );
+  pOp->opcode = (u8)op;
+  pOp->p5 = 0;
+  pOp->p1 = p1;
+  pOp->p2 = p2;
+  pOp->p3 = p3;
+  pOp->p4.i = p4;
+  pOp->p4type = P4_INT32;
+
+  /* Replicate this logic in sqlite3VdbeAddOp3()
+  ** vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv   */
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  pOp->zComment = 0;
+#endif
+#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || defined(VDBE_PROFILE)
+  pOp->nExec = 0;
+  pOp->nCycle = 0;
+#endif
+#ifdef SQLITE_DEBUG
+  if( p->db->flags & SQLITE_VdbeAddopTrace ){
+    sqlite3VdbePrintOp(0, i, &p->aOp[i]);
+    test_addop_breakpoint(i, &p->aOp[i]);
+  }
+#endif
+#ifdef SQLITE_VDBE_COVERAGE
+  pOp->iSrcLine = 0;
+#endif
+  /* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  ** Replicate in sqlite3VdbeAddOp3() */
+
+  return i;
+}
+
+/* Generate code for an unconditional jump to instruction iDest
+*/
+int sqlite3VdbeGoto(Vdbe *p, int iDest){
+  return sqlite3VdbeAddOp3(p, OP_Goto, 0, iDest, 0);
+}
+
+/* Generate code to cause the string zStr to be loaded into
+** register iDest
+*/
+int sqlite3VdbeLoadString(Vdbe *p, int iDest, const char *zStr){
+  return sqlite3VdbeAddOp4(p, OP_String8, 0, iDest, 0, zStr, 0);
+}
+
+/*
+** Generate code that initializes multiple registers to string or integer
+** constants.  The registers begin with iDest and increase consecutively.
+** One register is initialized for each characgter in zTypes[].  For each
+** "s" character in zTypes[], the register is a string if the argument is
+** not NULL, or OP_Null if the value is a null pointer.  For each "i" character
+** in zTypes[], the register is initialized to an integer.
+**
+** If the input string does not end with "X" then an OP_ResultRow instruction
+** is generated for the values inserted.
+*/
+void sqlite3VdbeMultiLoad(Vdbe *p, int iDest, const char *zTypes, ...){
+  va_list ap;
+  int i;
+  char c;
+  va_start(ap, zTypes);
+  for(i=0; (c = zTypes[i])!=0; i++){
+    if( c=='s' ){
+      const char *z = va_arg(ap, const char*);
+      sqlite3VdbeAddOp4(p, z==0 ? OP_Null : OP_String8, 0, iDest+i, 0, z, 0);
+    }else if( c=='i' ){
+      sqlite3VdbeAddOp2(p, OP_Integer, va_arg(ap, int), iDest+i);
+    }else{
+      goto skip_op_resultrow;
+    }
+  }
+  sqlite3VdbeAddOp2(p, OP_ResultRow, iDest, i);
+skip_op_resultrow:
+  va_end(ap);
+}
+
+/*
+** Add an opcode that includes the p4 value as a pointer.
+*/
+int sqlite3VdbeAddOp4(
+  Vdbe *p,            /* Add the opcode to this VM */
+  int op,             /* The new opcode */
+  int p1,             /* The P1 operand */
+  int p2,             /* The P2 operand */
+  int p3,             /* The P3 operand */
+  const char *zP4,    /* The P4 operand */
+  int p4type          /* P4 operand type */
+){
+  int addr = sqlite3VdbeAddOp3(p, op, p1, p2, p3);
+  sqlite3VdbeChangeP4(p, addr, zP4, p4type);
+  return addr;
+}
+
+/*
+** Add an OP_Function or OP_PureFunc opcode.
+**
+** The eCallCtx argument is information (typically taken from Expr.op2)
+** that describes the calling context of the function.  0 means a general
+** function call.  NC_IsCheck means called by a check constraint,
+** NC_IdxExpr means called as part of an index expression.  NC_PartIdx
+** means in the WHERE clause of a partial index.  NC_GenCol means called
+** while computing a generated column value.  0 is the usual case.
+*/
+int sqlite3VdbeAddFunctionCall(
+  Parse *pParse,        /* Parsing context */
+  int p1,               /* Constant argument mask */
+  int p2,               /* First argument register */
+  int p3,               /* Register into which results are written */
+  int nArg,             /* Number of argument */
+  const FuncDef *pFunc, /* The function to be invoked */
+  int eCallCtx          /* Calling context */
+){
+  Vdbe *v = pParse->pVdbe;
+  int nByte;
+  int addr;
+  sqlite3_context *pCtx;
+  assert( v );
+  nByte = sizeof(*pCtx) + (nArg-1)*sizeof(sqlite3_value*);
+  pCtx = sqlite3DbMallocRawNN(pParse->db, nByte);
+  if( pCtx==0 ){
+    assert( pParse->db->mallocFailed );
+    freeEphemeralFunction(pParse->db, (FuncDef*)pFunc);
+    return 0;
+  }
+  pCtx->pOut = 0;
+  pCtx->pFunc = (FuncDef*)pFunc;
+  pCtx->pVdbe = 0;
+  pCtx->isError = 0;
+  pCtx->argc = nArg;
+  pCtx->iOp = sqlite3VdbeCurrentAddr(v);
+  addr = sqlite3VdbeAddOp4(v, eCallCtx ? OP_PureFunc : OP_Function,
+                           p1, p2, p3, (char*)pCtx, P4_FUNCCTX);
+  sqlite3VdbeChangeP5(v, eCallCtx & NC_SelfRef);
+  sqlite3MayAbort(pParse);
+  return addr;
+}
+
+/*
+** Add an opcode that includes the p4 value with a P4_INT64 or
+** P4_REAL type.
+*/
+int sqlite3VdbeAddOp4Dup8(
+  Vdbe *p,            /* Add the opcode to this VM */
+  int op,             /* The new opcode */
+  int p1,             /* The P1 operand */
+  int p2,             /* The P2 operand */
+  int p3,             /* The P3 operand */
+  const u8 *zP4,      /* The P4 operand */
+  int p4type          /* P4 operand type */
+){
+  char *p4copy = sqlite3DbMallocRawNN(sqlite3VdbeDb(p), 8);
+  if( p4copy ) memcpy(p4copy, zP4, 8);
+  return sqlite3VdbeAddOp4(p, op, p1, p2, p3, p4copy, p4type);
+}
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** Return the address of the current EXPLAIN QUERY PLAN baseline.
+** 0 means "none".
+*/
+int sqlite3VdbeExplainParent(Parse *pParse){
+  VdbeOp *pOp;
+  if( pParse->addrExplain==0 ) return 0;
+  pOp = sqlite3VdbeGetOp(pParse->pVdbe, pParse->addrExplain);
+  return pOp->p2;
+}
+
+/*
+** Set a debugger breakpoint on the following routine in order to
+** monitor the EXPLAIN QUERY PLAN code generation.
+*/
+#if defined(SQLITE_DEBUG)
+void sqlite3ExplainBreakpoint(const char *z1, const char *z2){
+  (void)z1;
+  (void)z2;
+}
+#endif
+
+/*
+** Add a new OP_Explain opcode.
+**
+** If the bPush flag is true, then make this opcode the parent for
+** subsequent Explains until sqlite3VdbeExplainPop() is called.
+*/
+int sqlite3VdbeExplain(Parse *pParse, u8 bPush, const char *zFmt, ...){
+  int addr = 0;
+#if !defined(SQLITE_DEBUG)
+  /* Always include the OP_Explain opcodes if SQLITE_DEBUG is defined.
+  ** But omit them (for performance) during production builds */
+  if( pParse->explain==2 || IS_STMT_SCANSTATUS(pParse->db) )
+#endif
+  {
+    char *zMsg;
+    Vdbe *v;
+    va_list ap;
+    int iThis;
+    va_start(ap, zFmt);
+    zMsg = sqlite3VMPrintf(pParse->db, zFmt, ap);
+    va_end(ap);
+    v = pParse->pVdbe;
+    iThis = v->nOp;
+    addr = sqlite3VdbeAddOp4(v, OP_Explain, iThis, pParse->addrExplain, 0,
+                      zMsg, P4_DYNAMIC);
+    sqlite3ExplainBreakpoint(bPush?"PUSH":"", sqlite3VdbeGetLastOp(v)->p4.z);
+    if( bPush){
+      pParse->addrExplain = iThis;
+    }
+    sqlite3VdbeScanStatus(v, iThis, -1, -1, 0, 0);
+  }
+  return addr;
+}
+
+/*
+** Pop the EXPLAIN QUERY PLAN stack one level.
+*/
+void sqlite3VdbeExplainPop(Parse *pParse){
+  sqlite3ExplainBreakpoint("POP", 0);
+  pParse->addrExplain = sqlite3VdbeExplainParent(pParse);
+}
+#endif /* SQLITE_OMIT_EXPLAIN */
+
+/*
+** Add an OP_ParseSchema opcode.  This routine is broken out from
+** sqlite3VdbeAddOp4() since it needs to also needs to mark all btrees
+** as having been used.
+**
+** The zWhere string must have been obtained from sqlite3_malloc().
+** This routine will take ownership of the allocated memory.
+*/
+void sqlite3VdbeAddParseSchemaOp(Vdbe *p, int iDb, char *zWhere, u16 p5){
+  int j;
+  sqlite3VdbeAddOp4(p, OP_ParseSchema, iDb, 0, 0, zWhere, P4_DYNAMIC);
+  sqlite3VdbeChangeP5(p, p5);
+  for(j=0; j<p->db->nDb; j++) sqlite3VdbeUsesBtree(p, j);
+  sqlite3MayAbort(p->pParse);
+}
+
+/* Insert the end of a co-routine
+*/
+void sqlite3VdbeEndCoroutine(Vdbe *v, int regYield){
+  sqlite3VdbeAddOp1(v, OP_EndCoroutine, regYield);
+
+  /* Clear the temporary register cache, thereby ensuring that each
+  ** co-routine has its own independent set of registers, because co-routines
+  ** might expect their registers to be preserved across an OP_Yield, and
+  ** that could cause problems if two or more co-routines are using the same
+  ** temporary register.
+  */
+  v->pParse->nTempReg = 0;
+  v->pParse->nRangeReg = 0;
+}
+
+/*
+** Create a new symbolic label for an instruction that has yet to be
+** coded.  The symbolic label is really just a negative number.  The
+** label can be used as the P2 value of an operation.  Later, when
+** the label is resolved to a specific address, the VDBE will scan
+** through its operation list and change all values of P2 which match
+** the label into the resolved address.
+**
+** The VDBE knows that a P2 value is a label because labels are
+** always negative and P2 values are suppose to be non-negative.
+** Hence, a negative P2 value is a label that has yet to be resolved.
+** (Later:) This is only true for opcodes that have the OPFLG_JUMP
+** property.
+**
+** Variable usage notes:
+**
+**     Parse.aLabel[x]     Stores the address that the x-th label resolves
+**                         into.  For testing (SQLITE_DEBUG), unresolved
+**                         labels stores -1, but that is not required.
+**     Parse.nLabelAlloc   Number of slots allocated to Parse.aLabel[]
+**     Parse.nLabel        The *negative* of the number of labels that have
+**                         been issued.  The negative is stored because
+**                         that gives a performance improvement over storing
+**                         the equivalent positive value.
+*/
+int sqlite3VdbeMakeLabel(Parse *pParse){
+  return --pParse->nLabel;
+}
+
+/*
+** Resolve label "x" to be the address of the next instruction to
+** be inserted.  The parameter "x" must have been obtained from
+** a prior call to sqlite3VdbeMakeLabel().
+*/
+static SQLITE_NOINLINE void resizeResolveLabel(Parse *p, Vdbe *v, int j){
+  int nNewSize = 10 - p->nLabel;
+  p->aLabel = sqlite3DbReallocOrFree(p->db, p->aLabel,
+                     nNewSize*sizeof(p->aLabel[0]));
+  if( p->aLabel==0 ){
+    p->nLabelAlloc = 0;
+  }else{
+#ifdef SQLITE_DEBUG
+    int i;
+    for(i=p->nLabelAlloc; i<nNewSize; i++) p->aLabel[i] = -1;
+#endif
+    if( nNewSize>=100 && (nNewSize/100)>(p->nLabelAlloc/100) ){
+      sqlite3ProgressCheck(p);
+    }
+    p->nLabelAlloc = nNewSize;
+    p->aLabel[j] = v->nOp;
+  }
+}
+void sqlite3VdbeResolveLabel(Vdbe *v, int x){
+  Parse *p = v->pParse;
+  int j = ADDR(x);
+  assert( v->eVdbeState==VDBE_INIT_STATE );
+  assert( j<-p->nLabel );
+  assert( j>=0 );
+#ifdef SQLITE_DEBUG
+  if( p->db->flags & SQLITE_VdbeAddopTrace ){
+    printf("RESOLVE LABEL %d to %d\n", x, v->nOp);
+  }
+#endif
+  if( p->nLabelAlloc + p->nLabel < 0 ){
+    resizeResolveLabel(p,v,j);
+  }else{
+    assert( p->aLabel[j]==(-1) ); /* Labels may only be resolved once */
+    p->aLabel[j] = v->nOp;
+  }
+}
+
+/*
+** Mark the VDBE as one that can only be run one time.
+*/
+void sqlite3VdbeRunOnlyOnce(Vdbe *p){
+  sqlite3VdbeAddOp2(p, OP_Expire, 1, 1);
+}
+
+/*
+** Mark the VDBE as one that can be run multiple times.
+*/
+void sqlite3VdbeReusable(Vdbe *p){
+  int i;
+  for(i=1; ALWAYS(i<p->nOp); i++){
+    if( ALWAYS(p->aOp[i].opcode==OP_Expire) ){
+      p->aOp[1].opcode = OP_Noop;
+      break;
+    }
+  }
+}
+
+#ifdef SQLITE_DEBUG /* sqlite3AssertMayAbort() logic */
+
+/*
+** The following type and function are used to iterate through all opcodes
+** in a Vdbe main program and each of the sub-programs (triggers) it may
+** invoke directly or indirectly. It should be used as follows:
+**
+**   Op *pOp;
+**   VdbeOpIter sIter;
+**
+**   memset(&sIter, 0, sizeof(sIter));
+**   sIter.v = v;                            // v is of type Vdbe*
+**   while( (pOp = opIterNext(&sIter)) ){
+**     // Do something with pOp
+**   }
+**   sqlite3DbFree(v->db, sIter.apSub);
+**
+*/
+typedef struct VdbeOpIter VdbeOpIter;
+struct VdbeOpIter {
+  Vdbe *v;                   /* Vdbe to iterate through the opcodes of */
+  SubProgram **apSub;        /* Array of subprograms */
+  int nSub;                  /* Number of entries in apSub */
+  int iAddr;                 /* Address of next instruction to return */
+  int iSub;                  /* 0 = main program, 1 = first sub-program etc. */
+};
+static Op *opIterNext(VdbeOpIter *p){
+  Vdbe *v = p->v;
+  Op *pRet = 0;
+  Op *aOp;
+  int nOp;
+
+  if( p->iSub<=p->nSub ){
+
+    if( p->iSub==0 ){
+      aOp = v->aOp;
+      nOp = v->nOp;
+    }else{
+      aOp = p->apSub[p->iSub-1]->aOp;
+      nOp = p->apSub[p->iSub-1]->nOp;
+    }
+    assert( p->iAddr<nOp );
+
+    pRet = &aOp[p->iAddr];
+    p->iAddr++;
+    if( p->iAddr==nOp ){
+      p->iSub++;
+      p->iAddr = 0;
+    }
+ 
+    if( pRet->p4type==P4_SUBPROGRAM ){
+      int nByte = (p->nSub+1)*sizeof(SubProgram*);
+      int j;
+      for(j=0; j<p->nSub; j++){
+        if( p->apSub[j]==pRet->p4.pProgram ) break;
+      }
+      if( j==p->nSub ){
+        p->apSub = sqlite3DbReallocOrFree(v->db, p->apSub, nByte);
+        if( !p->apSub ){
+          pRet = 0;
+        }else{
+          p->apSub[p->nSub++] = pRet->p4.pProgram;
+        }
+      }
+    }
+  }
+
+  return pRet;
+}
+
+/*
+** Check if the program stored in the VM associated with pParse may
+** throw an ABORT exception (causing the statement, but not entire transaction
+** to be rolled back). This condition is true if the main program or any
+** sub-programs contains any of the following:
+**
+**   *  OP_Halt with P1=SQLITE_CONSTRAINT and P2=OE_Abort.
+**   *  OP_HaltIfNull with P1=SQLITE_CONSTRAINT and P2=OE_Abort.
+**   *  OP_Destroy
+**   *  OP_VUpdate
+**   *  OP_VCreate
+**   *  OP_VRename
+**   *  OP_FkCounter with P2==0 (immediate foreign key constraint)
+**   *  OP_CreateBtree/BTREE_INTKEY and OP_InitCoroutine
+**      (for CREATE TABLE AS SELECT ...)
+**
+** Then check that the value of Parse.mayAbort is true if an
+** ABORT may be thrown, or false otherwise. Return true if it does
+** match, or false otherwise. This function is intended to be used as
+** part of an assert statement in the compiler. Similar to:
+**
+**   assert( sqlite3VdbeAssertMayAbort(pParse->pVdbe, pParse->mayAbort) );
+*/
+int sqlite3VdbeAssertMayAbort(Vdbe *v, int mayAbort){
+  int hasAbort = 0;
+  int hasFkCounter = 0;
+  int hasCreateTable = 0;
+  int hasCreateIndex = 0;
+  int hasInitCoroutine = 0;
+  Op *pOp;
+  VdbeOpIter sIter;
+
+  if( v==0 ) return 0;
+  memset(&sIter, 0, sizeof(sIter));
+  sIter.v = v;
+
+  while( (pOp = opIterNext(&sIter))!=0 ){
+    int opcode = pOp->opcode;
+    if( opcode==OP_Destroy || opcode==OP_VUpdate || opcode==OP_VRename
+     || opcode==OP_VDestroy
+     || opcode==OP_VCreate
+     || opcode==OP_ParseSchema
+     || opcode==OP_Function || opcode==OP_PureFunc
+     || ((opcode==OP_Halt || opcode==OP_HaltIfNull)
+      && ((pOp->p1)!=SQLITE_OK && pOp->p2==OE_Abort))
+    ){
+      hasAbort = 1;
+      break;
+    }
+    if( opcode==OP_CreateBtree && pOp->p3==BTREE_INTKEY ) hasCreateTable = 1;
+    if( mayAbort ){
+      /* hasCreateIndex may also be set for some DELETE statements that use
+      ** OP_Clear. So this routine may end up returning true in the case
+      ** where a "DELETE FROM tbl" has a statement-journal but does not
+      ** require one. This is not so bad - it is an inefficiency, not a bug. */
+      if( opcode==OP_CreateBtree && pOp->p3==BTREE_BLOBKEY ) hasCreateIndex = 1;
+      if( opcode==OP_Clear ) hasCreateIndex = 1;
+    }
+    if( opcode==OP_InitCoroutine ) hasInitCoroutine = 1;
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+    if( opcode==OP_FkCounter && pOp->p1==0 && pOp->p2==1 ){
+      hasFkCounter = 1;
+    }
+#endif
+  }
+  sqlite3DbFree(v->db, sIter.apSub);
+
+  /* Return true if hasAbort==mayAbort. Or if a malloc failure occurred.
+  ** If malloc failed, then the while() loop above may not have iterated
+  ** through all opcodes and hasAbort may be set incorrectly. Return
+  ** true for this case to prevent the assert() in the callers frame
+  ** from failing.  */
+  return ( v->db->mallocFailed || hasAbort==mayAbort || hasFkCounter
+        || (hasCreateTable && hasInitCoroutine) || hasCreateIndex
+  );
+}
+#endif /* SQLITE_DEBUG - the sqlite3AssertMayAbort() function */
+
+#ifdef SQLITE_DEBUG
+/*
+** Increment the nWrite counter in the VDBE if the cursor is not an
+** ephemeral cursor, or if the cursor argument is NULL.
+*/
+void sqlite3VdbeIncrWriteCounter(Vdbe *p, VdbeCursor *pC){
+  if( pC==0
+   || (pC->eCurType!=CURTYPE_SORTER
+       && pC->eCurType!=CURTYPE_PSEUDO
+       && !pC->isEphemeral)
+  ){
+    p->nWrite++;
+  }
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Assert if an Abort at this point in time might result in a corrupt
+** database.
+*/
+void sqlite3VdbeAssertAbortable(Vdbe *p){
+  assert( p->nWrite==0 || p->usesStmtJournal );
+}
+#endif
+
+/*
+** This routine is called after all opcodes have been inserted.  It loops
+** through all the opcodes and fixes up some details.
+**
+** (1) For each jump instruction with a negative P2 value (a label)
+**     resolve the P2 value to an actual address.
+**
+** (2) Compute the maximum number of arguments used by any SQL function
+**     and store that value in *pMaxFuncArgs.
+**
+** (3) Update the Vdbe.readOnly and Vdbe.bIsReader flags to accurately
+**     indicate what the prepared statement actually does.
+**
+** (4) (discontinued)
+**
+** (5) Reclaim the memory allocated for storing labels.
+**
+** This routine will only function correctly if the mkopcodeh.tcl generator
+** script numbers the opcodes correctly.  Changes to this routine must be
+** coordinated with changes to mkopcodeh.tcl.
+*/
+static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs){
+  int nMaxArgs = *pMaxFuncArgs;
+  Op *pOp;
+  Parse *pParse = p->pParse;
+  int *aLabel = pParse->aLabel;
+
+  assert( pParse->db->mallocFailed==0 ); /* tag-20230419-1 */
+  p->readOnly = 1;
+  p->bIsReader = 0;
+  pOp = &p->aOp[p->nOp-1];
+  assert( p->aOp[0].opcode==OP_Init );
+  while( 1 /* Loop terminates when it reaches the OP_Init opcode */ ){
+    /* Only JUMP opcodes and the short list of special opcodes in the switch
+    ** below need to be considered.  The mkopcodeh.tcl generator script groups
+    ** all these opcodes together near the front of the opcode list.  Skip
+    ** any opcode that does not need processing by virtual of the fact that
+    ** it is larger than SQLITE_MX_JUMP_OPCODE, as a performance optimization.
+    */
+    if( pOp->opcode<=SQLITE_MX_JUMP_OPCODE ){
+      /* NOTE: Be sure to update mkopcodeh.tcl when adding or removing
+      ** cases from this switch! */
+      switch( pOp->opcode ){
+        case OP_Transaction: {
+          if( pOp->p2!=0 ) p->readOnly = 0;
+          /* no break */ deliberate_fall_through
+        }
+        case OP_AutoCommit:
+        case OP_Savepoint: {
+          p->bIsReader = 1;
+          break;
+        }
+#ifndef SQLITE_OMIT_WAL
+        case OP_Checkpoint:
+#endif
+        case OP_Vacuum:
+        case OP_JournalMode: {
+          p->readOnly = 0;
+          p->bIsReader = 1;
+          break;
+        }
+        case OP_Init: {
+          assert( pOp->p2>=0 );
+          goto resolve_p2_values_loop_exit;
+        }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+        case OP_VUpdate: {
+          if( pOp->p2>nMaxArgs ) nMaxArgs = pOp->p2;
+          break;
+        }
+        case OP_VFilter: {
+          int n;
+          assert( (pOp - p->aOp) >= 3 );
+          assert( pOp[-1].opcode==OP_Integer );
+          n = pOp[-1].p1;
+          if( n>nMaxArgs ) nMaxArgs = n;
+          /* Fall through into the default case */
+          /* no break */ deliberate_fall_through
+        }
+#endif
+        default: {
+          if( pOp->p2<0 ){
+            /* The mkopcodeh.tcl script has so arranged things that the only
+            ** non-jump opcodes less than SQLITE_MX_JUMP_CODE are guaranteed to
+            ** have non-negative values for P2. */
+            assert( (sqlite3OpcodeProperty[pOp->opcode] & OPFLG_JUMP)!=0 );
+            assert( ADDR(pOp->p2)<-pParse->nLabel );
+            assert( aLabel!=0 );  /* True because of tag-20230419-1 */
+            pOp->p2 = aLabel[ADDR(pOp->p2)];
+          }
+          break;
+        }
+      }
+      /* The mkopcodeh.tcl script has so arranged things that the only
+      ** non-jump opcodes less than SQLITE_MX_JUMP_CODE are guaranteed to
+      ** have non-negative values for P2. */
+      assert( (sqlite3OpcodeProperty[pOp->opcode]&OPFLG_JUMP)==0 || pOp->p2>=0);
+    }
+    assert( pOp>p->aOp );   
+    pOp--;
+  }
+resolve_p2_values_loop_exit:
+  if( aLabel ){
+    sqlite3DbNNFreeNN(p->db, pParse->aLabel);
+    pParse->aLabel = 0;
+  }
+  pParse->nLabel = 0;
+  *pMaxFuncArgs = nMaxArgs;
+  assert( p->bIsReader!=0 || DbMaskAllZero(p->btreeMask) );
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Check to see if a subroutine contains a jump to a location outside of
+** the subroutine.  If a jump outside the subroutine is detected, add code
+** that will cause the program to halt with an error message.
+**
+** The subroutine consists of opcodes between iFirst and iLast.  Jumps to
+** locations within the subroutine are acceptable.  iRetReg is a register
+** that contains the return address.  Jumps to outside the range of iFirst
+** through iLast are also acceptable as long as the jump destination is
+** an OP_Return to iReturnAddr.
+**
+** A jump to an unresolved label means that the jump destination will be
+** beyond the current address.  That is normally a jump to an early
+** termination and is consider acceptable.
+**
+** This routine only runs during debug builds.  The purpose is (of course)
+** to detect invalid escapes out of a subroutine.  The OP_Halt opcode
+** is generated rather than an assert() or other error, so that ".eqp full"
+** will still work to show the original bytecode, to aid in debugging.
+*/
+void sqlite3VdbeNoJumpsOutsideSubrtn(
+  Vdbe *v,          /* The byte-code program under construction */
+  int iFirst,       /* First opcode of the subroutine */
+  int iLast,        /* Last opcode of the subroutine */
+  int iRetReg       /* Subroutine return address register */
+){
+  VdbeOp *pOp;
+  Parse *pParse;
+  int i;
+  sqlite3_str *pErr = 0;
+  assert( v!=0 );
+  pParse = v->pParse;
+  assert( pParse!=0 );
+  if( pParse->nErr ) return;
+  assert( iLast>=iFirst );
+  assert( iLast<v->nOp );
+  pOp = &v->aOp[iFirst];
+  for(i=iFirst; i<=iLast; i++, pOp++){
+    if( (sqlite3OpcodeProperty[pOp->opcode] & OPFLG_JUMP)!=0 ){
+      int iDest = pOp->p2;   /* Jump destination */
+      if( iDest==0 ) continue;
+      if( pOp->opcode==OP_Gosub ) continue;
+      if( pOp->p3==20230325 && pOp->opcode==OP_NotNull ){
+        /* This is a deliberately taken illegal branch.  tag-20230325-2 */
+        continue;
+      }
+      if( iDest<0 ){
+        int j = ADDR(iDest);
+        assert( j>=0 );
+        if( j>=-pParse->nLabel || pParse->aLabel[j]<0 ){
+          continue;
+        }
+        iDest = pParse->aLabel[j];
+      }
+      if( iDest<iFirst || iDest>iLast ){
+        int j = iDest;
+        for(; j<v->nOp; j++){
+          VdbeOp *pX = &v->aOp[j];
+          if( pX->opcode==OP_Return ){
+            if( pX->p1==iRetReg ) break;
+            continue;
+          }
+          if( pX->opcode==OP_Noop ) continue;
+          if( pX->opcode==OP_Explain ) continue;
+          if( pErr==0 ){
+            pErr = sqlite3_str_new(0);
+          }else{
+            sqlite3_str_appendchar(pErr, 1, '\n');
+          }
+          sqlite3_str_appendf(pErr,
+              "Opcode at %d jumps to %d which is outside the "
+              "subroutine at %d..%d",
+              i, iDest, iFirst, iLast);
+          break;
+        }
+      }
+    }
+  }
+  if( pErr ){
+    char *zErr = sqlite3_str_finish(pErr);
+    sqlite3VdbeAddOp4(v, OP_Halt, SQLITE_INTERNAL, OE_Abort, 0, zErr, 0);
+    sqlite3_free(zErr);
+    sqlite3MayAbort(pParse);
+  }
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** Return the address of the next instruction to be inserted.
+*/
+int sqlite3VdbeCurrentAddr(Vdbe *p){
+  assert( p->eVdbeState==VDBE_INIT_STATE );
+  return p->nOp;
+}
+
+/*
+** Verify that at least N opcode slots are available in p without
+** having to malloc for more space (except when compiled using
+** SQLITE_TEST_REALLOC_STRESS).  This interface is used during testing
+** to verify that certain calls to sqlite3VdbeAddOpList() can never
+** fail due to a OOM fault and hence that the return value from
+** sqlite3VdbeAddOpList() will always be non-NULL.
+*/
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_TEST_REALLOC_STRESS)
+void sqlite3VdbeVerifyNoMallocRequired(Vdbe *p, int N){
+  assert( p->nOp + N <= p->nOpAlloc );
+}
+#endif
+
+/*
+** Verify that the VM passed as the only argument does not contain
+** an OP_ResultRow opcode. Fail an assert() if it does. This is used
+** by code in pragma.c to ensure that the implementation of certain
+** pragmas comports with the flags specified in the mkpragmatab.tcl
+** script.
+*/
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_TEST_REALLOC_STRESS)
+void sqlite3VdbeVerifyNoResultRow(Vdbe *p){
+  int i;
+  for(i=0; i<p->nOp; i++){
+    assert( p->aOp[i].opcode!=OP_ResultRow );
+  }
+}
+#endif
+
+/*
+** Generate code (a single OP_Abortable opcode) that will
+** verify that the VDBE program can safely call Abort in the current
+** context.
+*/
+#if defined(SQLITE_DEBUG)
+void sqlite3VdbeVerifyAbortable(Vdbe *p, int onError){
+  if( onError==OE_Abort ) sqlite3VdbeAddOp0(p, OP_Abortable);
+}
+#endif
+
+/*
+** This function returns a pointer to the array of opcodes associated with
+** the Vdbe passed as the first argument. It is the callers responsibility
+** to arrange for the returned array to be eventually freed using the
+** vdbeFreeOpArray() function.
+**
+** Before returning, *pnOp is set to the number of entries in the returned
+** array. Also, *pnMaxArg is set to the larger of its current value and
+** the number of entries in the Vdbe.apArg[] array required to execute the
+** returned program.
+*/
+VdbeOp *sqlite3VdbeTakeOpArray(Vdbe *p, int *pnOp, int *pnMaxArg){
+  VdbeOp *aOp = p->aOp;
+  assert( aOp && !p->db->mallocFailed );
+
+  /* Check that sqlite3VdbeUsesBtree() was not called on this VM */
+  assert( DbMaskAllZero(p->btreeMask) );
+
+  resolveP2Values(p, pnMaxArg);
+  *pnOp = p->nOp;
+  p->aOp = 0;
+  return aOp;
+}
+
+/*
+** Add a whole list of operations to the operation stack.  Return a
+** pointer to the first operation inserted.
+**
+** Non-zero P2 arguments to jump instructions are automatically adjusted
+** so that the jump target is relative to the first operation inserted.
+*/
+VdbeOp *sqlite3VdbeAddOpList(
+  Vdbe *p,                     /* Add opcodes to the prepared statement */
+  int nOp,                     /* Number of opcodes to add */
+  VdbeOpList const *aOp,       /* The opcodes to be added */
+  int iLineno                  /* Source-file line number of first opcode */
+){
+  int i;
+  VdbeOp *pOut, *pFirst;
+  assert( nOp>0 );
+  assert( p->eVdbeState==VDBE_INIT_STATE );
+  if( p->nOp + nOp > p->nOpAlloc && growOpArray(p, nOp) ){
+    return 0;
+  }
+  pFirst = pOut = &p->aOp[p->nOp];
+  for(i=0; i<nOp; i++, aOp++, pOut++){
+    pOut->opcode = aOp->opcode;
+    pOut->p1 = aOp->p1;
+    pOut->p2 = aOp->p2;
+    assert( aOp->p2>=0 );
+    if( (sqlite3OpcodeProperty[aOp->opcode] & OPFLG_JUMP)!=0 && aOp->p2>0 ){
+      pOut->p2 += p->nOp;
+    }
+    pOut->p3 = aOp->p3;
+    pOut->p4type = P4_NOTUSED;
+    pOut->p4.p = 0;
+    pOut->p5 = 0;
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+    pOut->zComment = 0;
+#endif
+#ifdef SQLITE_VDBE_COVERAGE
+    pOut->iSrcLine = iLineno+i;
+#else
+    (void)iLineno;
+#endif
+#ifdef SQLITE_DEBUG
+    if( p->db->flags & SQLITE_VdbeAddopTrace ){
+      sqlite3VdbePrintOp(0, i+p->nOp, &p->aOp[i+p->nOp]);
+    }
+#endif
+  }
+  p->nOp += nOp;
+  return pFirst;
+}
+
+#if defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+/*
+** Add an entry to the array of counters managed by sqlite3_stmt_scanstatus().
+*/
+void sqlite3VdbeScanStatus(
+  Vdbe *p,                        /* VM to add scanstatus() to */
+  int addrExplain,                /* Address of OP_Explain (or 0) */
+  int addrLoop,                   /* Address of loop counter */
+  int addrVisit,                  /* Address of rows visited counter */
+  LogEst nEst,                    /* Estimated number of output rows */
+  const char *zName               /* Name of table or index being scanned */
+){
+  if( IS_STMT_SCANSTATUS(p->db) ){
+    sqlite3_int64 nByte = (p->nScan+1) * sizeof(ScanStatus);
+    ScanStatus *aNew;
+    aNew = (ScanStatus*)sqlite3DbRealloc(p->db, p->aScan, nByte);
+    if( aNew ){
+      ScanStatus *pNew = &aNew[p->nScan++];
+      memset(pNew, 0, sizeof(ScanStatus));
+      pNew->addrExplain = addrExplain;
+      pNew->addrLoop = addrLoop;
+      pNew->addrVisit = addrVisit;
+      pNew->nEst = nEst;
+      pNew->zName = sqlite3DbStrDup(p->db, zName);
+      p->aScan = aNew;
+    }
+  }
+}
+
+/*
+** Add the range of instructions from addrStart to addrEnd (inclusive) to
+** the set of those corresponding to the sqlite3_stmt_scanstatus() counters
+** associated with the OP_Explain instruction at addrExplain. The
+** sum of the sqlite3Hwtime() values for each of these instructions
+** will be returned for SQLITE_SCANSTAT_NCYCLE requests.
+*/
+void sqlite3VdbeScanStatusRange(
+  Vdbe *p,
+  int addrExplain,
+  int addrStart,
+  int addrEnd
+){
+  if( IS_STMT_SCANSTATUS(p->db) ){
+    ScanStatus *pScan = 0;
+    int ii;
+    for(ii=p->nScan-1; ii>=0; ii--){
+      pScan = &p->aScan[ii];
+      if( pScan->addrExplain==addrExplain ) break;
+      pScan = 0;
+    }
+    if( pScan ){
+      if( addrEnd<0 ) addrEnd = sqlite3VdbeCurrentAddr(p)-1;
+      for(ii=0; ii<ArraySize(pScan->aAddrRange); ii+=2){
+        if( pScan->aAddrRange[ii]==0 ){
+          pScan->aAddrRange[ii] = addrStart;
+          pScan->aAddrRange[ii+1] = addrEnd;
+          break;
+        }
+      }
+    }
+  }
+}
+
+/*
+** Set the addresses for the SQLITE_SCANSTAT_NLOOP and SQLITE_SCANSTAT_NROW
+** counters for the query element associated with the OP_Explain at
+** addrExplain.
+*/
+void sqlite3VdbeScanStatusCounters(
+  Vdbe *p,
+  int addrExplain,
+  int addrLoop,
+  int addrVisit
+){
+  if( IS_STMT_SCANSTATUS(p->db) ){
+    ScanStatus *pScan = 0;
+    int ii;
+    for(ii=p->nScan-1; ii>=0; ii--){
+      pScan = &p->aScan[ii];
+      if( pScan->addrExplain==addrExplain ) break;
+      pScan = 0;
+    }
+    if( pScan ){
+      if( addrLoop>0 ) pScan->addrLoop = addrLoop;
+      if( addrVisit>0 ) pScan->addrVisit = addrVisit;
+    }
+  }
+}
+#endif /* defined(SQLITE_ENABLE_STMT_SCANSTATUS) */
+
+
+/*
+** Change the value of the opcode, or P1, P2, P3, or P5 operands
+** for a specific instruction.
+*/
+void sqlite3VdbeChangeOpcode(Vdbe *p, int addr, u8 iNewOpcode){
+  assert( addr>=0 );
+  sqlite3VdbeGetOp(p,addr)->opcode = iNewOpcode;
+}
+void sqlite3VdbeChangeP1(Vdbe *p, int addr, int val){
+  assert( addr>=0 );
+  sqlite3VdbeGetOp(p,addr)->p1 = val;
+}
+void sqlite3VdbeChangeP2(Vdbe *p, int addr, int val){
+  assert( addr>=0 || p->db->mallocFailed );
+  sqlite3VdbeGetOp(p,addr)->p2 = val;
+}
+void sqlite3VdbeChangeP3(Vdbe *p, int addr, int val){
+  assert( addr>=0 );
+  sqlite3VdbeGetOp(p,addr)->p3 = val;
+}
+void sqlite3VdbeChangeP5(Vdbe *p, u16 p5){
+  assert( p->nOp>0 || p->db->mallocFailed );
+  if( p->nOp>0 ) p->aOp[p->nOp-1].p5 = p5;
+}
+
+/*
+** If the previous opcode is an OP_Column that delivers results
+** into register iDest, then add the OPFLAG_TYPEOFARG flag to that
+** opcode.
+*/
+void sqlite3VdbeTypeofColumn(Vdbe *p, int iDest){
+  VdbeOp *pOp = sqlite3VdbeGetLastOp(p);
+  if( pOp->p3==iDest && pOp->opcode==OP_Column ){
+    pOp->p5 |= OPFLAG_TYPEOFARG;
+  }
+}
+
+/*
+** Change the P2 operand of instruction addr so that it points to
+** the address of the next instruction to be coded.
+*/
+void sqlite3VdbeJumpHere(Vdbe *p, int addr){
+  sqlite3VdbeChangeP2(p, addr, p->nOp);
+}
+
+/*
+** Change the P2 operand of the jump instruction at addr so that
+** the jump lands on the next opcode.  Or if the jump instruction was
+** the previous opcode (and is thus a no-op) then simply back up
+** the next instruction counter by one slot so that the jump is
+** overwritten by the next inserted opcode.
+**
+** This routine is an optimization of sqlite3VdbeJumpHere() that
+** strives to omit useless byte-code like this:
+**
+**        7   Once 0 8 0
+**        8   ...
+*/
+void sqlite3VdbeJumpHereOrPopInst(Vdbe *p, int addr){
+  if( addr==p->nOp-1 ){
+    assert( p->aOp[addr].opcode==OP_Once
+         || p->aOp[addr].opcode==OP_If
+         || p->aOp[addr].opcode==OP_FkIfZero );
+    assert( p->aOp[addr].p4type==0 );
+#ifdef SQLITE_VDBE_COVERAGE
+    sqlite3VdbeGetLastOp(p)->iSrcLine = 0;  /* Erase VdbeCoverage() macros */
+#endif
+    p->nOp--;
+  }else{
+    sqlite3VdbeChangeP2(p, addr, p->nOp);
+  }
+}
+
+
+/*
+** If the input FuncDef structure is ephemeral, then free it.  If
+** the FuncDef is not ephemeral, then do nothing.
+*/
+static void freeEphemeralFunction(sqlite3 *db, FuncDef *pDef){
+  assert( db!=0 );
+  if( (pDef->funcFlags & SQLITE_FUNC_EPHEM)!=0 ){
+    sqlite3DbNNFreeNN(db, pDef);
+  }
+}
+
+/*
+** Delete a P4 value if necessary.
+*/
+static SQLITE_NOINLINE void freeP4Mem(sqlite3 *db, Mem *p){
+  if( p->szMalloc ) sqlite3DbFree(db, p->zMalloc);
+  sqlite3DbNNFreeNN(db, p);
+}
+static SQLITE_NOINLINE void freeP4FuncCtx(sqlite3 *db, sqlite3_context *p){
+  assert( db!=0 );
+  freeEphemeralFunction(db, p->pFunc);
+  sqlite3DbNNFreeNN(db, p);
+}
+static void freeP4(sqlite3 *db, int p4type, void *p4){
+  assert( db );
+  switch( p4type ){
+    case P4_FUNCCTX: {
+      freeP4FuncCtx(db, (sqlite3_context*)p4);
+      break;
+    }
+    case P4_REAL:
+    case P4_INT64:
+    case P4_DYNAMIC:
+    case P4_INTARRAY: {
+      if( p4 ) sqlite3DbNNFreeNN(db, p4);
+      break;
+    }
+    case P4_KEYINFO: {
+      if( db->pnBytesFreed==0 ) sqlite3KeyInfoUnref((KeyInfo*)p4);
+      break;
+    }
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+    case P4_EXPR: {
+      sqlite3ExprDelete(db, (Expr*)p4);
+      break;
+    }
+#endif
+    case P4_FUNCDEF: {
+      freeEphemeralFunction(db, (FuncDef*)p4);
+      break;
+    }
+    case P4_MEM: {
+      if( db->pnBytesFreed==0 ){
+        sqlite3ValueFree((sqlite3_value*)p4);
+      }else{
+        freeP4Mem(db, (Mem*)p4);
+      }
+      break;
+    }
+    case P4_VTAB : {
+      if( db->pnBytesFreed==0 ) sqlite3VtabUnlock((VTable *)p4);
+      break;
+    }
+    case P4_TABLEREF: {
+      if( db->pnBytesFreed==0 ) sqlite3DeleteTable(db, (Table*)p4);
+      break;
+    }
+  }
+}
+
+/*
+** Free the space allocated for aOp and any p4 values allocated for the
+** opcodes contained within. If aOp is not NULL it is assumed to contain
+** nOp entries.
+*/
+static void vdbeFreeOpArray(sqlite3 *db, Op *aOp, int nOp){
+  assert( nOp>=0 );
+  assert( db!=0 );
+  if( aOp ){
+    Op *pOp = &aOp[nOp-1];
+    while(1){  /* Exit via break */
+      if( pOp->p4type <= P4_FREE_IF_LE ) freeP4(db, pOp->p4type, pOp->p4.p);
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+      sqlite3DbFree(db, pOp->zComment);
+#endif    
+      if( pOp==aOp ) break;
+      pOp--;
+    }
+    sqlite3DbNNFreeNN(db, aOp);
+  }
+}
+
+/*
+** Link the SubProgram object passed as the second argument into the linked
+** list at Vdbe.pSubProgram. This list is used to delete all sub-program
+** objects when the VM is no longer required.
+*/
+void sqlite3VdbeLinkSubProgram(Vdbe *pVdbe, SubProgram *p){
+  p->pNext = pVdbe->pProgram;
+  pVdbe->pProgram = p;
+}
+
+/*
+** Return true if the given Vdbe has any SubPrograms.
+*/
+int sqlite3VdbeHasSubProgram(Vdbe *pVdbe){
+  return pVdbe->pProgram!=0;
+}
+
+/*
+** Change the opcode at addr into OP_Noop
+*/
+int sqlite3VdbeChangeToNoop(Vdbe *p, int addr){
+  VdbeOp *pOp;
+  if( p->db->mallocFailed ) return 0;
+  assert( addr>=0 && addr<p->nOp );
+  pOp = &p->aOp[addr];
+  freeP4(p->db, pOp->p4type, pOp->p4.p);
+  pOp->p4type = P4_NOTUSED;
+  pOp->p4.z = 0;
+  pOp->opcode = OP_Noop;
+  return 1;
+}
+
+/*
+** If the last opcode is "op" and it is not a jump destination,
+** then remove it.  Return true if and only if an opcode was removed.
+*/
+int sqlite3VdbeDeletePriorOpcode(Vdbe *p, u8 op){
+  if( p->nOp>0 && p->aOp[p->nOp-1].opcode==op ){
+    return sqlite3VdbeChangeToNoop(p, p->nOp-1);
+  }else{
+    return 0;
+  }
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Generate an OP_ReleaseReg opcode to indicate that a range of
+** registers, except any identified by mask, are no longer in use.
+*/
+void sqlite3VdbeReleaseRegisters(
+  Parse *pParse,       /* Parsing context */
+  int iFirst,          /* Index of first register to be released */
+  int N,               /* Number of registers to release */
+  u32 mask,            /* Mask of registers to NOT release */
+  int bUndefine        /* If true, mark registers as undefined */
+){
+  if( N==0 || OptimizationDisabled(pParse->db, SQLITE_ReleaseReg) ) return;
+  assert( pParse->pVdbe );
+  assert( iFirst>=1 );
+  assert( iFirst+N-1<=pParse->nMem );
+  if( N<=31 && mask!=0 ){
+    while( N>0 && (mask&1)!=0 ){
+      mask >>= 1;
+      iFirst++;
+      N--;
+    }
+    while( N>0 && N<=32 && (mask & MASKBIT32(N-1))!=0 ){
+      mask &= ~MASKBIT32(N-1);
+      N--;
+    }
+  }
+  if( N>0 ){
+    sqlite3VdbeAddOp3(pParse->pVdbe, OP_ReleaseReg, iFirst, N, *(int*)&mask);
+    if( bUndefine ) sqlite3VdbeChangeP5(pParse->pVdbe, 1);
+  }
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** Change the value of the P4 operand for a specific instruction.
+** This routine is useful when a large program is loaded from a
+** static array using sqlite3VdbeAddOpList but we want to make a
+** few minor changes to the program.
+**
+** If n>=0 then the P4 operand is dynamic, meaning that a copy of
+** the string is made into memory obtained from sqlite3_malloc().
+** A value of n==0 means copy bytes of zP4 up to and including the
+** first null byte.  If n>0 then copy n+1 bytes of zP4.
+**
+** Other values of n (P4_STATIC, P4_COLLSEQ etc.) indicate that zP4 points
+** to a string or structure that is guaranteed to exist for the lifetime of
+** the Vdbe. In these cases we can just copy the pointer.
+**
+** If addr<0 then change P4 on the most recently inserted instruction.
+*/
+static void SQLITE_NOINLINE vdbeChangeP4Full(
+  Vdbe *p,
+  Op *pOp,
+  const char *zP4,
+  int n
+){
+  if( pOp->p4type ){
+    assert( pOp->p4type > P4_FREE_IF_LE );
+    pOp->p4type = 0;
+    pOp->p4.p = 0;
+  }
+  if( n<0 ){
+    sqlite3VdbeChangeP4(p, (int)(pOp - p->aOp), zP4, n);
+  }else{
+    if( n==0 ) n = sqlite3Strlen30(zP4);
+    pOp->p4.z = sqlite3DbStrNDup(p->db, zP4, n);
+    pOp->p4type = P4_DYNAMIC;
+  }
+}
+void sqlite3VdbeChangeP4(Vdbe *p, int addr, const char *zP4, int n){
+  Op *pOp;
+  sqlite3 *db;
+  assert( p!=0 );
+  db = p->db;
+  assert( p->eVdbeState==VDBE_INIT_STATE );
+  assert( p->aOp!=0 || db->mallocFailed );
+  if( db->mallocFailed ){
+    if( n!=P4_VTAB ) freeP4(db, n, (void*)*(char**)&zP4);
+    return;
+  }
+  assert( p->nOp>0 );
+  assert( addr<p->nOp );
+  if( addr<0 ){
+    addr = p->nOp - 1;
+  }
+  pOp = &p->aOp[addr];
+  if( n>=0 || pOp->p4type ){
+    vdbeChangeP4Full(p, pOp, zP4, n);
+    return;
+  }
+  if( n==P4_INT32 ){
+    /* Note: this cast is safe, because the origin data point was an int
+    ** that was cast to a (const char *). */
+    pOp->p4.i = SQLITE_PTR_TO_INT(zP4);
+    pOp->p4type = P4_INT32;
+  }else if( zP4!=0 ){
+    assert( n<0 );
+    pOp->p4.p = (void*)zP4;
+    pOp->p4type = (signed char)n;
+    if( n==P4_VTAB ) sqlite3VtabLock((VTable*)zP4);
+  }
+}
+
+/*
+** Change the P4 operand of the most recently coded instruction
+** to the value defined by the arguments.  This is a high-speed
+** version of sqlite3VdbeChangeP4().
+**
+** The P4 operand must not have been previously defined.  And the new
+** P4 must not be P4_INT32.  Use sqlite3VdbeChangeP4() in either of
+** those cases.
+*/
+void sqlite3VdbeAppendP4(Vdbe *p, void *pP4, int n){
+  VdbeOp *pOp;
+  assert( n!=P4_INT32 && n!=P4_VTAB );
+  assert( n<=0 );
+  if( p->db->mallocFailed ){
+    freeP4(p->db, n, pP4);
+  }else{
+    assert( pP4!=0 || n==P4_DYNAMIC );
+    assert( p->nOp>0 );
+    pOp = &p->aOp[p->nOp-1];
+    assert( pOp->p4type==P4_NOTUSED );
+    pOp->p4type = n;
+    pOp->p4.p = pP4;
+  }
+}
+
+/*
+** Set the P4 on the most recently added opcode to the KeyInfo for the
+** index given.
+*/
+void sqlite3VdbeSetP4KeyInfo(Parse *pParse, Index *pIdx){
+  Vdbe *v = pParse->pVdbe;
+  KeyInfo *pKeyInfo;
+  assert( v!=0 );
+  assert( pIdx!=0 );
+  pKeyInfo = sqlite3KeyInfoOfIndex(pParse, pIdx);
+  if( pKeyInfo ) sqlite3VdbeAppendP4(v, pKeyInfo, P4_KEYINFO);
+}
+
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+/*
+** Change the comment on the most recently coded instruction.  Or
+** insert a No-op and add the comment to that new instruction.  This
+** makes the code easier to read during debugging.  None of this happens
+** in a production build.
+*/
+static void vdbeVComment(Vdbe *p, const char *zFormat, va_list ap){
+  assert( p->nOp>0 || p->aOp==0 );
+  assert( p->aOp==0 || p->aOp[p->nOp-1].zComment==0 || p->pParse->nErr>0 );
+  if( p->nOp ){
+    assert( p->aOp );
+    sqlite3DbFree(p->db, p->aOp[p->nOp-1].zComment);
+    p->aOp[p->nOp-1].zComment = sqlite3VMPrintf(p->db, zFormat, ap);
+  }
+}
+void sqlite3VdbeComment(Vdbe *p, const char *zFormat, ...){
+  va_list ap;
+  if( p ){
+    va_start(ap, zFormat);
+    vdbeVComment(p, zFormat, ap);
+    va_end(ap);
+  }
+}
+void sqlite3VdbeNoopComment(Vdbe *p, const char *zFormat, ...){
+  va_list ap;
+  if( p ){
+    sqlite3VdbeAddOp0(p, OP_Noop);
+    va_start(ap, zFormat);
+    vdbeVComment(p, zFormat, ap);
+    va_end(ap);
+  }
+}
+#endif  /* NDEBUG */
+
+#ifdef SQLITE_VDBE_COVERAGE
+/*
+** Set the value if the iSrcLine field for the previously coded instruction.
+*/
+void sqlite3VdbeSetLineNumber(Vdbe *v, int iLine){
+  sqlite3VdbeGetLastOp(v)->iSrcLine = iLine;
+}
+#endif /* SQLITE_VDBE_COVERAGE */
+
+/*
+** Return the opcode for a given address.  The address must be non-negative.
+** See sqlite3VdbeGetLastOp() to get the most recently added opcode.
+**
+** If a memory allocation error has occurred prior to the calling of this
+** routine, then a pointer to a dummy VdbeOp will be returned.  That opcode
+** is readable but not writable, though it is cast to a writable value.
+** The return of a dummy opcode allows the call to continue functioning
+** after an OOM fault without having to check to see if the return from
+** this routine is a valid pointer.  But because the dummy.opcode is 0,
+** dummy will never be written to.  This is verified by code inspection and
+** by running with Valgrind.
+*/
+VdbeOp *sqlite3VdbeGetOp(Vdbe *p, int addr){
+  /* C89 specifies that the constant "dummy" will be initialized to all
+  ** zeros, which is correct.  MSVC generates a warning, nevertheless. */
+  static VdbeOp dummy;  /* Ignore the MSVC warning about no initializer */
+  assert( p->eVdbeState==VDBE_INIT_STATE );
+  assert( (addr>=0 && addr<p->nOp) || p->db->mallocFailed );
+  if( p->db->mallocFailed ){
+    return (VdbeOp*)&dummy;
+  }else{
+    return &p->aOp[addr];
+  }
+}
+
+/* Return the most recently added opcode
+*/
+VdbeOp *sqlite3VdbeGetLastOp(Vdbe *p){
+  return sqlite3VdbeGetOp(p, p->nOp - 1);
+}
+
+#if defined(SQLITE_ENABLE_EXPLAIN_COMMENTS)
+/*
+** Return an integer value for one of the parameters to the opcode pOp
+** determined by character c.
+*/
+static int translateP(char c, const Op *pOp){
+  if( c=='1' ) return pOp->p1;
+  if( c=='2' ) return pOp->p2;
+  if( c=='3' ) return pOp->p3;
+  if( c=='4' ) return pOp->p4.i;
+  return pOp->p5;
+}
+
+/*
+** Compute a string for the "comment" field of a VDBE opcode listing.
+**
+** The Synopsis: field in comments in the vdbe.c source file gets converted
+** to an extra string that is appended to the sqlite3OpcodeName().  In the
+** absence of other comments, this synopsis becomes the comment on the opcode.
+** Some translation occurs:
+**
+**       "PX"      ->  "r[X]"
+**       "PX@PY"   ->  "r[X..X+Y-1]"  or "r[x]" if y is 0 or 1
+**       "PX@PY+1" ->  "r[X..X+Y]"    or "r[x]" if y is 0
+**       "PY..PY"  ->  "r[X..Y]"      or "r[x]" if y<=x
+*/
+char *sqlite3VdbeDisplayComment(
+  sqlite3 *db,       /* Optional - Oom error reporting only */
+  const Op *pOp,     /* The opcode to be commented */
+  const char *zP4    /* Previously obtained value for P4 */
+){
+  const char *zOpName;
+  const char *zSynopsis;
+  int nOpName;
+  int ii;
+  char zAlt[50];
+  StrAccum x;
+
+  sqlite3StrAccumInit(&x, 0, 0, 0, SQLITE_MAX_LENGTH);
+  zOpName = sqlite3OpcodeName(pOp->opcode);
+  nOpName = sqlite3Strlen30(zOpName);
+  if( zOpName[nOpName+1] ){
+    int seenCom = 0;
+    char c;
+    zSynopsis = zOpName + nOpName + 1;
+    if( strncmp(zSynopsis,"IF ",3)==0 ){
+      sqlite3_snprintf(sizeof(zAlt), zAlt, "if %s goto P2", zSynopsis+3);
+      zSynopsis = zAlt;
+    }
+    for(ii=0; (c = zSynopsis[ii])!=0; ii++){
+      if( c=='P' ){
+        c = zSynopsis[++ii];
+        if( c=='4' ){
+          sqlite3_str_appendall(&x, zP4);
+        }else if( c=='X' ){
+          if( pOp->zComment && pOp->zComment[0] ){
+            sqlite3_str_appendall(&x, pOp->zComment);
+            seenCom = 1;
+            break;
+          }
+        }else{
+          int v1 = translateP(c, pOp);
+          int v2;
+          if( strncmp(zSynopsis+ii+1, "@P", 2)==0 ){
+            ii += 3;
+            v2 = translateP(zSynopsis[ii], pOp);
+            if( strncmp(zSynopsis+ii+1,"+1",2)==0 ){
+              ii += 2;
+              v2++;
+            }
+            if( v2<2 ){
+              sqlite3_str_appendf(&x, "%d", v1);
+            }else{
+              sqlite3_str_appendf(&x, "%d..%d", v1, v1+v2-1);
+            }
+          }else if( strncmp(zSynopsis+ii+1, "@NP", 3)==0 ){
+            sqlite3_context *pCtx = pOp->p4.pCtx;
+            if( pOp->p4type!=P4_FUNCCTX || pCtx->argc==1 ){
+              sqlite3_str_appendf(&x, "%d", v1);
+            }else if( pCtx->argc>1 ){
+              sqlite3_str_appendf(&x, "%d..%d", v1, v1+pCtx->argc-1);
+            }else if( x.accError==0 ){
+              assert( x.nChar>2 );
+              x.nChar -= 2;
+              ii++;
+            }
+            ii += 3;
+          }else{
+            sqlite3_str_appendf(&x, "%d", v1);
+            if( strncmp(zSynopsis+ii+1, "..P3", 4)==0 && pOp->p3==0 ){
+              ii += 4;
+            }
+          }
+        }
+      }else{
+        sqlite3_str_appendchar(&x, 1, c);
+      }
+    }
+    if( !seenCom && pOp->zComment ){
+      sqlite3_str_appendf(&x, "; %s", pOp->zComment);
+    }
+  }else if( pOp->zComment ){
+    sqlite3_str_appendall(&x, pOp->zComment);
+  }
+  if( (x.accError & SQLITE_NOMEM)!=0 && db!=0 ){
+    sqlite3OomFault(db);
+  }
+  return sqlite3StrAccumFinish(&x);
+}
+#endif /* SQLITE_ENABLE_EXPLAIN_COMMENTS */
+
+#if VDBE_DISPLAY_P4 && defined(SQLITE_ENABLE_CURSOR_HINTS)
+/*
+** Translate the P4.pExpr value for an OP_CursorHint opcode into text
+** that can be displayed in the P4 column of EXPLAIN output.
+*/
+static void displayP4Expr(StrAccum *p, Expr *pExpr){
+  const char *zOp = 0;
+  switch( pExpr->op ){
+    case TK_STRING:
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3_str_appendf(p, "%Q", pExpr->u.zToken);
+      break;
+    case TK_INTEGER:
+      sqlite3_str_appendf(p, "%d", pExpr->u.iValue);
+      break;
+    case TK_NULL:
+      sqlite3_str_appendf(p, "NULL");
+      break;
+    case TK_REGISTER: {
+      sqlite3_str_appendf(p, "r[%d]", pExpr->iTable);
+      break;
+    }
+    case TK_COLUMN: {
+      if( pExpr->iColumn<0 ){
+        sqlite3_str_appendf(p, "rowid");
+      }else{
+        sqlite3_str_appendf(p, "c%d", (int)pExpr->iColumn);
+      }
+      break;
+    }
+    case TK_LT:      zOp = "LT";      break;
+    case TK_LE:      zOp = "LE";      break;
+    case TK_GT:      zOp = "GT";      break;
+    case TK_GE:      zOp = "GE";      break;
+    case TK_NE:      zOp = "NE";      break;
+    case TK_EQ:      zOp = "EQ";      break;
+    case TK_IS:      zOp = "IS";      break;
+    case TK_ISNOT:   zOp = "ISNOT";   break;
+    case TK_AND:     zOp = "AND";     break;
+    case TK_OR:      zOp = "OR";      break;
+    case TK_PLUS:    zOp = "ADD";     break;
+    case TK_STAR:    zOp = "MUL";     break;
+    case TK_MINUS:   zOp = "SUB";     break;
+    case TK_REM:     zOp = "REM";     break;
+    case TK_BITAND:  zOp = "BITAND";  break;
+    case TK_BITOR:   zOp = "BITOR";   break;
+    case TK_SLASH:   zOp = "DIV";     break;
+    case TK_LSHIFT:  zOp = "LSHIFT";  break;
+    case TK_RSHIFT:  zOp = "RSHIFT";  break;
+    case TK_CONCAT:  zOp = "CONCAT";  break;
+    case TK_UMINUS:  zOp = "MINUS";   break;
+    case TK_UPLUS:   zOp = "PLUS";    break;
+    case TK_BITNOT:  zOp = "BITNOT";  break;
+    case TK_NOT:     zOp = "NOT";     break;
+    case TK_ISNULL:  zOp = "ISNULL";  break;
+    case TK_NOTNULL: zOp = "NOTNULL"; break;
+
+    default:
+      sqlite3_str_appendf(p, "%s", "expr");
+      break;
+  }
+
+  if( zOp ){
+    sqlite3_str_appendf(p, "%s(", zOp);
+    displayP4Expr(p, pExpr->pLeft);
+    if( pExpr->pRight ){
+      sqlite3_str_append(p, ",", 1);
+      displayP4Expr(p, pExpr->pRight);
+    }
+    sqlite3_str_append(p, ")", 1);
+  }
+}
+#endif /* VDBE_DISPLAY_P4 && defined(SQLITE_ENABLE_CURSOR_HINTS) */
+
+
+#if VDBE_DISPLAY_P4
+/*
+** Compute a string that describes the P4 parameter for an opcode.
+** Use zTemp for any required temporary buffer space.
+*/
+char *sqlite3VdbeDisplayP4(sqlite3 *db, Op *pOp){
+  char *zP4 = 0;
+  StrAccum x;
+
+  sqlite3StrAccumInit(&x, 0, 0, 0, SQLITE_MAX_LENGTH);
+  switch( pOp->p4type ){
+    case P4_KEYINFO: {
+      int j;
+      KeyInfo *pKeyInfo = pOp->p4.pKeyInfo;
+      assert( pKeyInfo->aSortFlags!=0 );
+      sqlite3_str_appendf(&x, "k(%d", pKeyInfo->nKeyField);
+      for(j=0; j<pKeyInfo->nKeyField; j++){
+        CollSeq *pColl = pKeyInfo->aColl[j];
+        const char *zColl = pColl ? pColl->zName : "";
+        if( strcmp(zColl, "BINARY")==0 ) zColl = "B";
+        sqlite3_str_appendf(&x, ",%s%s%s",
+               (pKeyInfo->aSortFlags[j] & KEYINFO_ORDER_DESC) ? "-" : "",
+               (pKeyInfo->aSortFlags[j] & KEYINFO_ORDER_BIGNULL)? "N." : "",
+               zColl);
+      }
+      sqlite3_str_append(&x, ")", 1);
+      break;
+    }
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+    case P4_EXPR: {
+      displayP4Expr(&x, pOp->p4.pExpr);
+      break;
+    }
+#endif
+    case P4_COLLSEQ: {
+      static const char *const encnames[] = {"?", "8", "16LE", "16BE"};
+      CollSeq *pColl = pOp->p4.pColl;
+      assert( pColl->enc<4 );
+      sqlite3_str_appendf(&x, "%.18s-%s", pColl->zName,
+                          encnames[pColl->enc]);
+      break;
+    }
+    case P4_FUNCDEF: {
+      FuncDef *pDef = pOp->p4.pFunc;
+      sqlite3_str_appendf(&x, "%s(%d)", pDef->zName, pDef->nArg);
+      break;
+    }
+    case P4_FUNCCTX: {
+      FuncDef *pDef = pOp->p4.pCtx->pFunc;
+      sqlite3_str_appendf(&x, "%s(%d)", pDef->zName, pDef->nArg);
+      break;
+    }
+    case P4_INT64: {
+      sqlite3_str_appendf(&x, "%lld", *pOp->p4.pI64);
+      break;
+    }
+    case P4_INT32: {
+      sqlite3_str_appendf(&x, "%d", pOp->p4.i);
+      break;
+    }
+    case P4_REAL: {
+      sqlite3_str_appendf(&x, "%.16g", *pOp->p4.pReal);
+      break;
+    }
+    case P4_MEM: {
+      Mem *pMem = pOp->p4.pMem;
+      if( pMem->flags & MEM_Str ){
+        zP4 = pMem->z;
+      }else if( pMem->flags & (MEM_Int|MEM_IntReal) ){
+        sqlite3_str_appendf(&x, "%lld", pMem->u.i);
+      }else if( pMem->flags & MEM_Real ){
+        sqlite3_str_appendf(&x, "%.16g", pMem->u.r);
+      }else if( pMem->flags & MEM_Null ){
+        zP4 = "NULL";
+      }else{
+        assert( pMem->flags & MEM_Blob );
+        zP4 = "(blob)";
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    case P4_VTAB: {
+      sqlite3_vtab *pVtab = pOp->p4.pVtab->pVtab;
+      sqlite3_str_appendf(&x, "vtab:%p", pVtab);
+      break;
+    }
+#endif
+    case P4_INTARRAY: {
+      u32 i;
+      u32 *ai = pOp->p4.ai;
+      u32 n = ai[0];   /* The first element of an INTARRAY is always the
+                       ** count of the number of elements to follow */
+      for(i=1; i<=n; i++){
+        sqlite3_str_appendf(&x, "%c%u", (i==1 ? '[' : ','), ai[i]);
+      }
+      sqlite3_str_append(&x, "]", 1);
+      break;
+    }
+    case P4_SUBPROGRAM: {
+      zP4 = "program";
+      break;
+    }
+    case P4_TABLE: {
+      zP4 = pOp->p4.pTab->zName;
+      break;
+    }
+    default: {
+      zP4 = pOp->p4.z;
+    }
+  }
+  if( zP4 ) sqlite3_str_appendall(&x, zP4);
+  if( (x.accError & SQLITE_NOMEM)!=0 ){
+    sqlite3OomFault(db);
+  }
+  return sqlite3StrAccumFinish(&x);
+}
+#endif /* VDBE_DISPLAY_P4 */
+
+/*
+** Declare to the Vdbe that the BTree object at db->aDb[i] is used.
+**
+** The prepared statements need to know in advance the complete set of
+** attached databases that will be use.  A mask of these databases
+** is maintained in p->btreeMask.  The p->lockMask value is the subset of
+** p->btreeMask of databases that will require a lock.
+*/
+void sqlite3VdbeUsesBtree(Vdbe *p, int i){
+  assert( i>=0 && i<p->db->nDb && i<(int)sizeof(yDbMask)*8 );
+  assert( i<(int)sizeof(p->btreeMask)*8 );
+  DbMaskSet(p->btreeMask, i);
+  if( i!=1 && sqlite3BtreeSharable(p->db->aDb[i].pBt) ){
+    DbMaskSet(p->lockMask, i);
+  }
+}
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE)
+/*
+** If SQLite is compiled to support shared-cache mode and to be threadsafe,
+** this routine obtains the mutex associated with each BtShared structure
+** that may be accessed by the VM passed as an argument. In doing so it also
+** sets the BtShared.db member of each of the BtShared structures, ensuring
+** that the correct busy-handler callback is invoked if required.
+**
+** If SQLite is not threadsafe but does support shared-cache mode, then
+** sqlite3BtreeEnter() is invoked to set the BtShared.db variables
+** of all of BtShared structures accessible via the database handle
+** associated with the VM.
+**
+** If SQLite is not threadsafe and does not support shared-cache mode, this
+** function is a no-op.
+**
+** The p->btreeMask field is a bitmask of all btrees that the prepared
+** statement p will ever use.  Let N be the number of bits in p->btreeMask
+** corresponding to btrees that use shared cache.  Then the runtime of
+** this routine is N*N.  But as N is rarely more than 1, this should not
+** be a problem.
+*/
+void sqlite3VdbeEnter(Vdbe *p){
+  int i;
+  sqlite3 *db;
+  Db *aDb;
+  int nDb;
+  if( DbMaskAllZero(p->lockMask) ) return;  /* The common case */
+  db = p->db;
+  aDb = db->aDb;
+  nDb = db->nDb;
+  for(i=0; i<nDb; i++){
+    if( i!=1 && DbMaskTest(p->lockMask,i) && ALWAYS(aDb[i].pBt!=0) ){
+      sqlite3BtreeEnter(aDb[i].pBt);
+    }
+  }
+}
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
+/*
+** Unlock all of the btrees previously locked by a call to sqlite3VdbeEnter().
+*/
+static SQLITE_NOINLINE void vdbeLeave(Vdbe *p){
+  int i;
+  sqlite3 *db;
+  Db *aDb;
+  int nDb;
+  db = p->db;
+  aDb = db->aDb;
+  nDb = db->nDb;
+  for(i=0; i<nDb; i++){
+    if( i!=1 && DbMaskTest(p->lockMask,i) && ALWAYS(aDb[i].pBt!=0) ){
+      sqlite3BtreeLeave(aDb[i].pBt);
+    }
+  }
+}
+void sqlite3VdbeLeave(Vdbe *p){
+  if( DbMaskAllZero(p->lockMask) ) return;  /* The common case */
+  vdbeLeave(p);
+}
+#endif
+
+#if defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
+/*
+** Print a single opcode.  This routine is used for debugging only.
+*/
+void sqlite3VdbePrintOp(FILE *pOut, int pc, VdbeOp *pOp){
+  char *zP4;
+  char *zCom;
+  sqlite3 dummyDb;
+  static const char *zFormat1 = "%4d %-13s %4d %4d %4d %-13s %.2X %s\n";
+  if( pOut==0 ) pOut = stdout;
+  sqlite3BeginBenignMalloc();
+  dummyDb.mallocFailed = 1;
+  zP4 = sqlite3VdbeDisplayP4(&dummyDb, pOp);
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+  zCom = sqlite3VdbeDisplayComment(0, pOp, zP4);
+#else
+  zCom = 0;
+#endif
+  /* NB:  The sqlite3OpcodeName() function is implemented by code created
+  ** by the mkopcodeh.awk and mkopcodec.awk scripts which extract the
+  ** information from the vdbe.c source text */
+  fprintf(pOut, zFormat1, pc,
+      sqlite3OpcodeName(pOp->opcode), pOp->p1, pOp->p2, pOp->p3,
+      zP4 ? zP4 : "", pOp->p5,
+      zCom ? zCom : ""
+  );
+  fflush(pOut);
+  sqlite3_free(zP4);
+  sqlite3_free(zCom);
+  sqlite3EndBenignMalloc();
+}
+#endif
+
+/*
+** Initialize an array of N Mem element.
+**
+** This is a high-runner, so only those fields that really do need to
+** be initialized are set.  The Mem structure is organized so that
+** the fields that get initialized are nearby and hopefully on the same
+** cache line.
+**
+**    Mem.flags = flags
+**    Mem.db = db
+**    Mem.szMalloc = 0
+**
+** All other fields of Mem can safely remain uninitialized for now.  They
+** will be initialized before use.
+*/
+static void initMemArray(Mem *p, int N, sqlite3 *db, u16 flags){
+  if( N>0 ){
+    do{
+      p->flags = flags;
+      p->db = db;
+      p->szMalloc = 0;
+#ifdef SQLITE_DEBUG
+      p->pScopyFrom = 0;
+#endif
+      p++;
+    }while( (--N)>0 );
+  }
+}
+
+/*
+** Release auxiliary memory held in an array of N Mem elements.
+**
+** After this routine returns, all Mem elements in the array will still
+** be valid.  Those Mem elements that were not holding auxiliary resources
+** will be unchanged.  Mem elements which had something freed will be
+** set to MEM_Undefined.
+*/
+static void releaseMemArray(Mem *p, int N){
+  if( p && N ){
+    Mem *pEnd = &p[N];
+    sqlite3 *db = p->db;
+    if( db->pnBytesFreed ){
+      do{
+        if( p->szMalloc ) sqlite3DbFree(db, p->zMalloc);
+      }while( (++p)<pEnd );
+      return;
+    }
+    do{
+      assert( (&p[1])==pEnd || p[0].db==p[1].db );
+      assert( sqlite3VdbeCheckMemInvariants(p) );
+
+      /* This block is really an inlined version of sqlite3VdbeMemRelease()
+      ** that takes advantage of the fact that the memory cell value is
+      ** being set to NULL after releasing any dynamic resources.
+      **
+      ** The justification for duplicating code is that according to
+      ** callgrind, this causes a certain test case to hit the CPU 4.7
+      ** percent less (x86 linux, gcc version 4.1.2, -O6) than if
+      ** sqlite3MemRelease() were called from here. With -O2, this jumps
+      ** to 6.6 percent. The test case is inserting 1000 rows into a table
+      ** with no indexes using a single prepared INSERT statement, bind()
+      ** and reset(). Inserts are grouped into a transaction.
+      */
+      testcase( p->flags & MEM_Agg );
+      testcase( p->flags & MEM_Dyn );
+      if( p->flags&(MEM_Agg|MEM_Dyn) ){
+        testcase( (p->flags & MEM_Dyn)!=0 && p->xDel==sqlite3VdbeFrameMemDel );
+        sqlite3VdbeMemRelease(p);
+        p->flags = MEM_Undefined;
+      }else if( p->szMalloc ){
+        sqlite3DbNNFreeNN(db, p->zMalloc);
+        p->szMalloc = 0;
+        p->flags = MEM_Undefined;
+      }
+#ifdef SQLITE_DEBUG
+      else{
+        p->flags = MEM_Undefined;
+      }
+#endif
+    }while( (++p)<pEnd );
+  }
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Verify that pFrame is a valid VdbeFrame pointer.  Return true if it is
+** and false if something is wrong.
+**
+** This routine is intended for use inside of assert() statements only.
+*/
+int sqlite3VdbeFrameIsValid(VdbeFrame *pFrame){
+  if( pFrame->iFrameMagic!=SQLITE_FRAME_MAGIC ) return 0;
+  return 1;
+}
+#endif
+
+
+/*
+** This is a destructor on a Mem object (which is really an sqlite3_value)
+** that deletes the Frame object that is attached to it as a blob.
+**
+** This routine does not delete the Frame right away.  It merely adds the
+** frame to a list of frames to be deleted when the Vdbe halts.
+*/
+void sqlite3VdbeFrameMemDel(void *pArg){
+  VdbeFrame *pFrame = (VdbeFrame*)pArg;
+  assert( sqlite3VdbeFrameIsValid(pFrame) );
+  pFrame->pParent = pFrame->v->pDelFrame;
+  pFrame->v->pDelFrame = pFrame;
+}
+
+#if defined(SQLITE_ENABLE_BYTECODE_VTAB) || !defined(SQLITE_OMIT_EXPLAIN)
+/*
+** Locate the next opcode to be displayed in EXPLAIN or EXPLAIN
+** QUERY PLAN output.
+**
+** Return SQLITE_ROW on success.  Return SQLITE_DONE if there are no
+** more opcodes to be displayed.
+*/
+int sqlite3VdbeNextOpcode(
+  Vdbe *p,         /* The statement being explained */
+  Mem *pSub,       /* Storage for keeping track of subprogram nesting */
+  int eMode,       /* 0: normal.  1: EQP.  2:  TablesUsed */
+  int *piPc,       /* IN/OUT: Current rowid.  Overwritten with next rowid */
+  int *piAddr,     /* OUT: Write index into (*paOp)[] here */
+  Op **paOp        /* OUT: Write the opcode array here */
+){
+  int nRow;                            /* Stop when row count reaches this */
+  int nSub = 0;                        /* Number of sub-vdbes seen so far */
+  SubProgram **apSub = 0;              /* Array of sub-vdbes */
+  int i;                               /* Next instruction address */
+  int rc = SQLITE_OK;                  /* Result code */
+  Op *aOp = 0;                         /* Opcode array */
+  int iPc;                             /* Rowid.  Copy of value in *piPc */
+
+  /* When the number of output rows reaches nRow, that means the
+  ** listing has finished and sqlite3_step() should return SQLITE_DONE.
+  ** nRow is the sum of the number of rows in the main program, plus
+  ** the sum of the number of rows in all trigger subprograms encountered
+  ** so far.  The nRow value will increase as new trigger subprograms are
+  ** encountered, but p->pc will eventually catch up to nRow.
+  */
+  nRow = p->nOp;
+  if( pSub!=0 ){
+    if( pSub->flags&MEM_Blob ){
+      /* pSub is initiallly NULL.  It is initialized to a BLOB by
+      ** the P4_SUBPROGRAM processing logic below */
+      nSub = pSub->n/sizeof(Vdbe*);
+      apSub = (SubProgram **)pSub->z;
+    }
+    for(i=0; i<nSub; i++){
+      nRow += apSub[i]->nOp;
+    }
+  }
+  iPc = *piPc;
+  while(1){  /* Loop exits via break */
+    i = iPc++;
+    if( i>=nRow ){
+      p->rc = SQLITE_OK;
+      rc = SQLITE_DONE;
+      break;
+    }
+    if( i<p->nOp ){
+      /* The rowid is small enough that we are still in the
+      ** main program. */
+      aOp = p->aOp;
+    }else{
+      /* We are currently listing subprograms.  Figure out which one and
+      ** pick up the appropriate opcode. */
+      int j;
+      i -= p->nOp;
+      assert( apSub!=0 );
+      assert( nSub>0 );
+      for(j=0; i>=apSub[j]->nOp; j++){
+        i -= apSub[j]->nOp;
+        assert( i<apSub[j]->nOp || j+1<nSub );
+      }
+      aOp = apSub[j]->aOp;
+    }
+
+    /* When an OP_Program opcode is encounter (the only opcode that has
+    ** a P4_SUBPROGRAM argument), expand the size of the array of subprograms
+    ** kept in p->aMem[9].z to hold the new program - assuming this subprogram
+    ** has not already been seen.
+    */
+    if( pSub!=0 && aOp[i].p4type==P4_SUBPROGRAM ){
+      int nByte = (nSub+1)*sizeof(SubProgram*);
+      int j;
+      for(j=0; j<nSub; j++){
+        if( apSub[j]==aOp[i].p4.pProgram ) break;
+      }
+      if( j==nSub ){
+        p->rc = sqlite3VdbeMemGrow(pSub, nByte, nSub!=0);
+        if( p->rc!=SQLITE_OK ){
+          rc = SQLITE_ERROR;
+          break;
+        }
+        apSub = (SubProgram **)pSub->z;
+        apSub[nSub++] = aOp[i].p4.pProgram;
+        MemSetTypeFlag(pSub, MEM_Blob);
+        pSub->n = nSub*sizeof(SubProgram*);
+        nRow += aOp[i].p4.pProgram->nOp;
+      }
+    }
+    if( eMode==0 ) break;
+#ifdef SQLITE_ENABLE_BYTECODE_VTAB
+    if( eMode==2 ){
+      Op *pOp = aOp + i;
+      if( pOp->opcode==OP_OpenRead ) break;
+      if( pOp->opcode==OP_OpenWrite && (pOp->p5 & OPFLAG_P2ISREG)==0 ) break;
+      if( pOp->opcode==OP_ReopenIdx ) break;     
+    }else
+#endif
+    {
+      assert( eMode==1 );
+      if( aOp[i].opcode==OP_Explain ) break;
+      if( aOp[i].opcode==OP_Init && iPc>1 ) break;
+    }
+  }
+  *piPc = iPc;
+  *piAddr = i;
+  *paOp = aOp;
+  return rc;
+}
+#endif /* SQLITE_ENABLE_BYTECODE_VTAB || !SQLITE_OMIT_EXPLAIN */
+
+
+/*
+** Delete a VdbeFrame object and its contents. VdbeFrame objects are
+** allocated by the OP_Program opcode in sqlite3VdbeExec().
+*/
+void sqlite3VdbeFrameDelete(VdbeFrame *p){
+  int i;
+  Mem *aMem = VdbeFrameMem(p);
+  VdbeCursor **apCsr = (VdbeCursor **)&aMem[p->nChildMem];
+  assert( sqlite3VdbeFrameIsValid(p) );
+  for(i=0; i<p->nChildCsr; i++){
+    if( apCsr[i] ) sqlite3VdbeFreeCursorNN(p->v, apCsr[i]);
+  }
+  releaseMemArray(aMem, p->nChildMem);
+  sqlite3VdbeDeleteAuxData(p->v->db, &p->pAuxData, -1, 0);
+  sqlite3DbFree(p->v->db, p);
+}
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** Give a listing of the program in the virtual machine.
+**
+** The interface is the same as sqlite3VdbeExec().  But instead of
+** running the code, it invokes the callback once for each instruction.
+** This feature is used to implement "EXPLAIN".
+**
+** When p->explain==1, each instruction is listed.  When
+** p->explain==2, only OP_Explain instructions are listed and these
+** are shown in a different format.  p->explain==2 is used to implement
+** EXPLAIN QUERY PLAN.
+** 2018-04-24:  In p->explain==2 mode, the OP_Init opcodes of triggers
+** are also shown, so that the boundaries between the main program and
+** each trigger are clear.
+**
+** When p->explain==1, first the main program is listed, then each of
+** the trigger subprograms are listed one by one.
+*/
+int sqlite3VdbeList(
+  Vdbe *p                   /* The VDBE */
+){
+  Mem *pSub = 0;                       /* Memory cell hold array of subprogs */
+  sqlite3 *db = p->db;                 /* The database connection */
+  int i;                               /* Loop counter */
+  int rc = SQLITE_OK;                  /* Return code */
+  Mem *pMem = &p->aMem[1];             /* First Mem of result set */
+  int bListSubprogs = (p->explain==1 || (db->flags & SQLITE_TriggerEQP)!=0);
+  Op *aOp;                             /* Array of opcodes */
+  Op *pOp;                             /* Current opcode */
+
+  assert( p->explain );
+  assert( p->eVdbeState==VDBE_RUN_STATE );
+  assert( p->rc==SQLITE_OK || p->rc==SQLITE_BUSY || p->rc==SQLITE_NOMEM );
+
+  /* Even though this opcode does not use dynamic strings for
+  ** the result, result columns may become dynamic if the user calls
+  ** sqlite3_column_text16(), causing a translation to UTF-16 encoding.
+  */
+  releaseMemArray(pMem, 8);
+
+  if( p->rc==SQLITE_NOMEM ){
+    /* This happens if a malloc() inside a call to sqlite3_column_text() or
+    ** sqlite3_column_text16() failed.  */
+    sqlite3OomFault(db);
+    return SQLITE_ERROR;
+  }
+
+  if( bListSubprogs ){
+    /* The first 8 memory cells are used for the result set.  So we will
+    ** commandeer the 9th cell to use as storage for an array of pointers
+    ** to trigger subprograms.  The VDBE is guaranteed to have at least 9
+    ** cells.  */
+    assert( p->nMem>9 );
+    pSub = &p->aMem[9];
+  }else{
+    pSub = 0;
+  }
+
+  /* Figure out which opcode is next to display */
+  rc = sqlite3VdbeNextOpcode(p, pSub, p->explain==2, &p->pc, &i, &aOp);
+
+  if( rc==SQLITE_OK ){
+    pOp = aOp + i;
+    if( AtomicLoad(&db->u1.isInterrupted) ){
+      p->rc = SQLITE_INTERRUPT;
+      rc = SQLITE_ERROR;
+      sqlite3VdbeError(p, sqlite3ErrStr(p->rc));
+    }else{
+      char *zP4 = sqlite3VdbeDisplayP4(db, pOp);
+      if( p->explain==2 ){
+        sqlite3VdbeMemSetInt64(pMem, pOp->p1);
+        sqlite3VdbeMemSetInt64(pMem+1, pOp->p2);
+        sqlite3VdbeMemSetInt64(pMem+2, pOp->p3);
+        sqlite3VdbeMemSetStr(pMem+3, zP4, -1, SQLITE_UTF8, sqlite3_free);
+        assert( p->nResColumn==4 );
+      }else{
+        sqlite3VdbeMemSetInt64(pMem+0, i);
+        sqlite3VdbeMemSetStr(pMem+1, (char*)sqlite3OpcodeName(pOp->opcode),
+                             -1, SQLITE_UTF8, SQLITE_STATIC);
+        sqlite3VdbeMemSetInt64(pMem+2, pOp->p1);
+        sqlite3VdbeMemSetInt64(pMem+3, pOp->p2);
+        sqlite3VdbeMemSetInt64(pMem+4, pOp->p3);
+        /* pMem+5 for p4 is done last */
+        sqlite3VdbeMemSetInt64(pMem+6, pOp->p5);
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+        {
+          char *zCom = sqlite3VdbeDisplayComment(db, pOp, zP4);
+          sqlite3VdbeMemSetStr(pMem+7, zCom, -1, SQLITE_UTF8, sqlite3_free);
+        }
+#else
+        sqlite3VdbeMemSetNull(pMem+7);
+#endif
+        sqlite3VdbeMemSetStr(pMem+5, zP4, -1, SQLITE_UTF8, sqlite3_free);
+        assert( p->nResColumn==8 );
+      }
+      p->pResultRow = pMem;
+      if( db->mallocFailed ){
+        p->rc = SQLITE_NOMEM;
+        rc = SQLITE_ERROR;
+      }else{
+        p->rc = SQLITE_OK;
+        rc = SQLITE_ROW;
+      }
+    }
+  }
+  return rc;
+}
+#endif /* SQLITE_OMIT_EXPLAIN */
+
+#ifdef SQLITE_DEBUG
+/*
+** Print the SQL that was used to generate a VDBE program.
+*/
+void sqlite3VdbePrintSql(Vdbe *p){
+  const char *z = 0;
+  if( p->zSql ){
+    z = p->zSql;
+  }else if( p->nOp>=1 ){
+    const VdbeOp *pOp = &p->aOp[0];
+    if( pOp->opcode==OP_Init && pOp->p4.z!=0 ){
+      z = pOp->p4.z;
+      while( sqlite3Isspace(*z) ) z++;
+    }
+  }
+  if( z ) printf("SQL: [%s]\n", z);
+}
+#endif
+
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+/*
+** Print an IOTRACE message showing SQL content.
+*/
+void sqlite3VdbeIOTraceSql(Vdbe *p){
+  int nOp = p->nOp;
+  VdbeOp *pOp;
+  if( sqlite3IoTrace==0 ) return;
+  if( nOp<1 ) return;
+  pOp = &p->aOp[0];
+  if( pOp->opcode==OP_Init && pOp->p4.z!=0 ){
+    int i, j;
+    char z[1000];
+    sqlite3_snprintf(sizeof(z), z, "%s", pOp->p4.z);
+    for(i=0; sqlite3Isspace(z[i]); i++){}
+    for(j=0; z[i]; i++){
+      if( sqlite3Isspace(z[i]) ){
+        if( z[i-1]!=' ' ){
+          z[j++] = ' ';
+        }
+      }else{
+        z[j++] = z[i];
+      }
+    }
+    z[j] = 0;
+    sqlite3IoTrace("SQL %s\n", z);
+  }
+}
+#endif /* !SQLITE_OMIT_TRACE && SQLITE_ENABLE_IOTRACE */
+
+/* An instance of this object describes bulk memory available for use
+** by subcomponents of a prepared statement.  Space is allocated out
+** of a ReusableSpace object by the allocSpace() routine below.
+*/
+struct ReusableSpace {
+  u8 *pSpace;            /* Available memory */
+  sqlite3_int64 nFree;   /* Bytes of available memory */
+  sqlite3_int64 nNeeded; /* Total bytes that could not be allocated */
+};
+
+/* Try to allocate nByte bytes of 8-byte aligned bulk memory for pBuf
+** from the ReusableSpace object.  Return a pointer to the allocated
+** memory on success.  If insufficient memory is available in the
+** ReusableSpace object, increase the ReusableSpace.nNeeded
+** value by the amount needed and return NULL.
+**
+** If pBuf is not initially NULL, that means that the memory has already
+** been allocated by a prior call to this routine, so just return a copy
+** of pBuf and leave ReusableSpace unchanged.
+**
+** This allocator is employed to repurpose unused slots at the end of the
+** opcode array of prepared state for other memory needs of the prepared
+** statement.
+*/
+static void *allocSpace(
+  struct ReusableSpace *p,  /* Bulk memory available for allocation */
+  void *pBuf,               /* Pointer to a prior allocation */
+  sqlite3_int64 nByte       /* Bytes of memory needed. */
+){
+  assert( EIGHT_BYTE_ALIGNMENT(p->pSpace) );
+  if( pBuf==0 ){
+    nByte = ROUND8P(nByte);
+    if( nByte <= p->nFree ){
+      p->nFree -= nByte;
+      pBuf = &p->pSpace[p->nFree];
+    }else{
+      p->nNeeded += nByte;
+    }
+  }
+  assert( EIGHT_BYTE_ALIGNMENT(pBuf) );
+  return pBuf;
+}
+
+/*
+** Rewind the VDBE back to the beginning in preparation for
+** running it.
+*/
+void sqlite3VdbeRewind(Vdbe *p){
+#if defined(SQLITE_DEBUG)
+  int i;
+#endif
+  assert( p!=0 );
+  assert( p->eVdbeState==VDBE_INIT_STATE
+       || p->eVdbeState==VDBE_READY_STATE
+       || p->eVdbeState==VDBE_HALT_STATE );
+
+  /* There should be at least one opcode.
+  */
+  assert( p->nOp>0 );
+
+  p->eVdbeState = VDBE_READY_STATE;
+
+#ifdef SQLITE_DEBUG
+  for(i=0; i<p->nMem; i++){
+    assert( p->aMem[i].db==p->db );
+  }
+#endif
+  p->pc = -1;
+  p->rc = SQLITE_OK;
+  p->errorAction = OE_Abort;
+  p->nChange = 0;
+  p->cacheCtr = 1;
+  p->minWriteFileFormat = 255;
+  p->iStatement = 0;
+  p->nFkConstraint = 0;
+#ifdef VDBE_PROFILE
+  for(i=0; i<p->nOp; i++){
+    p->aOp[i].nExec = 0;
+    p->aOp[i].nCycle = 0;
+  }
+#endif
+}
+
+/*
+** Prepare a virtual machine for execution for the first time after
+** creating the virtual machine.  This involves things such
+** as allocating registers and initializing the program counter.
+** After the VDBE has be prepped, it can be executed by one or more
+** calls to sqlite3VdbeExec(). 
+**
+** This function may be called exactly once on each virtual machine.
+** After this routine is called the VM has been "packaged" and is ready
+** to run.  After this routine is called, further calls to
+** sqlite3VdbeAddOp() functions are prohibited.  This routine disconnects
+** the Vdbe from the Parse object that helped generate it so that the
+** the Vdbe becomes an independent entity and the Parse object can be
+** destroyed.
+**
+** Use the sqlite3VdbeRewind() procedure to restore a virtual machine back
+** to its initial state after it has been run.
+*/
+void sqlite3VdbeMakeReady(
+  Vdbe *p,                       /* The VDBE */
+  Parse *pParse                  /* Parsing context */
+){
+  sqlite3 *db;                   /* The database connection */
+  int nVar;                      /* Number of parameters */
+  int nMem;                      /* Number of VM memory registers */
+  int nCursor;                   /* Number of cursors required */
+  int nArg;                      /* Number of arguments in subprograms */
+  int n;                         /* Loop counter */
+  struct ReusableSpace x;        /* Reusable bulk memory */
+
+  assert( p!=0 );
+  assert( p->nOp>0 );
+  assert( pParse!=0 );
+  assert( p->eVdbeState==VDBE_INIT_STATE );
+  assert( pParse==p->pParse );
+  p->pVList = pParse->pVList;
+  pParse->pVList =  0;
+  db = p->db;
+  assert( db->mallocFailed==0 );
+  nVar = pParse->nVar;
+  nMem = pParse->nMem;
+  nCursor = pParse->nTab;
+  nArg = pParse->nMaxArg;
+ 
+  /* Each cursor uses a memory cell.  The first cursor (cursor 0) can
+  ** use aMem[0] which is not otherwise used by the VDBE program.  Allocate
+  ** space at the end of aMem[] for cursors 1 and greater.
+  ** See also: allocateCursor().
+  */
+  nMem += nCursor;
+  if( nCursor==0 && nMem>0 ) nMem++;  /* Space for aMem[0] even if not used */
+
+  /* Figure out how much reusable memory is available at the end of the
+  ** opcode array.  This extra memory will be reallocated for other elements
+  ** of the prepared statement.
+  */
+  n = ROUND8P(sizeof(Op)*p->nOp);             /* Bytes of opcode memory used */
+  x.pSpace = &((u8*)p->aOp)[n];               /* Unused opcode memory */
+  assert( EIGHT_BYTE_ALIGNMENT(x.pSpace) );
+  x.nFree = ROUNDDOWN8(pParse->szOpAlloc - n);  /* Bytes of unused memory */
+  assert( x.nFree>=0 );
+  assert( EIGHT_BYTE_ALIGNMENT(&x.pSpace[x.nFree]) );
+
+  resolveP2Values(p, &nArg);
+  p->usesStmtJournal = (u8)(pParse->isMultiWrite && pParse->mayAbort);
+  if( pParse->explain ){
+    if( nMem<10 ) nMem = 10;
+    p->explain = pParse->explain;
+    p->nResColumn = 12 - 4*p->explain;
+  }
+  p->expired = 0;
+
+  /* Memory for registers, parameters, cursor, etc, is allocated in one or two
+  ** passes.  On the first pass, we try to reuse unused memory at the
+  ** end of the opcode array.  If we are unable to satisfy all memory
+  ** requirements by reusing the opcode array tail, then the second
+  ** pass will fill in the remainder using a fresh memory allocation. 
+  **
+  ** This two-pass approach that reuses as much memory as possible from
+  ** the leftover memory at the end of the opcode array.  This can significantly
+  ** reduce the amount of memory held by a prepared statement.
+  */
+  x.nNeeded = 0;
+  p->aMem = allocSpace(&x, 0, nMem*sizeof(Mem));
+  p->aVar = allocSpace(&x, 0, nVar*sizeof(Mem));
+  p->apArg = allocSpace(&x, 0, nArg*sizeof(Mem*));
+  p->apCsr = allocSpace(&x, 0, nCursor*sizeof(VdbeCursor*));
+  if( x.nNeeded ){
+    x.pSpace = p->pFree = sqlite3DbMallocRawNN(db, x.nNeeded);
+    x.nFree = x.nNeeded;
+    if( !db->mallocFailed ){
+      p->aMem = allocSpace(&x, p->aMem, nMem*sizeof(Mem));
+      p->aVar = allocSpace(&x, p->aVar, nVar*sizeof(Mem));
+      p->apArg = allocSpace(&x, p->apArg, nArg*sizeof(Mem*));
+      p->apCsr = allocSpace(&x, p->apCsr, nCursor*sizeof(VdbeCursor*));
+    }
+  }
+
+  if( db->mallocFailed ){
+    p->nVar = 0;
+    p->nCursor = 0;
+    p->nMem = 0;
+  }else{
+    p->nCursor = nCursor;
+    p->nVar = (ynVar)nVar;
+    initMemArray(p->aVar, nVar, db, MEM_Null);
+    p->nMem = nMem;
+    initMemArray(p->aMem, nMem, db, MEM_Undefined);
+    memset(p->apCsr, 0, nCursor*sizeof(VdbeCursor*));
+  }
+  sqlite3VdbeRewind(p);
+}
+
+/*
+** Close a VDBE cursor and release all the resources that cursor
+** happens to hold.
+*/
+void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
+  if( pCx ) sqlite3VdbeFreeCursorNN(p,pCx);
+}
+static SQLITE_NOINLINE void freeCursorWithCache(Vdbe *p, VdbeCursor *pCx){
+  VdbeTxtBlbCache *pCache = pCx->pCache;
+  assert( pCx->colCache );
+  pCx->colCache = 0;
+  pCx->pCache = 0;
+  if( pCache->pCValue ){
+    sqlite3RCStrUnref(pCache->pCValue);
+    pCache->pCValue = 0;
+  }
+  sqlite3DbFree(p->db, pCache);
+  sqlite3VdbeFreeCursorNN(p, pCx);
+}
+void sqlite3VdbeFreeCursorNN(Vdbe *p, VdbeCursor *pCx){
+  if( pCx->colCache ){
+    freeCursorWithCache(p, pCx);
+    return;
+  }
+  switch( pCx->eCurType ){
+    case CURTYPE_SORTER: {
+      sqlite3VdbeSorterClose(p->db, pCx);
+      break;
+    }
+    case CURTYPE_BTREE: {
+      assert( pCx->uc.pCursor!=0 );
+      sqlite3BtreeCloseCursor(pCx->uc.pCursor);
+      break;
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    case CURTYPE_VTAB: {
+      sqlite3_vtab_cursor *pVCur = pCx->uc.pVCur;
+      const sqlite3_module *pModule = pVCur->pVtab->pModule;
+      assert( pVCur->pVtab->nRef>0 );
+      pVCur->pVtab->nRef--;
+      pModule->xClose(pVCur);
+      break;
+    }
+#endif
+  }
+}
+
+/*
+** Close all cursors in the current frame.
+*/
+static void closeCursorsInFrame(Vdbe *p){
+  int i;
+  for(i=0; i<p->nCursor; i++){
+    VdbeCursor *pC = p->apCsr[i];
+    if( pC ){
+      sqlite3VdbeFreeCursorNN(p, pC);
+      p->apCsr[i] = 0;
+    }
+  }
+}
+
+/*
+** Copy the values stored in the VdbeFrame structure to its Vdbe. This
+** is used, for example, when a trigger sub-program is halted to restore
+** control to the main program.
+*/
+int sqlite3VdbeFrameRestore(VdbeFrame *pFrame){
+  Vdbe *v = pFrame->v;
+  closeCursorsInFrame(v);
+  v->aOp = pFrame->aOp;
+  v->nOp = pFrame->nOp;
+  v->aMem = pFrame->aMem;
+  v->nMem = pFrame->nMem;
+  v->apCsr = pFrame->apCsr;
+  v->nCursor = pFrame->nCursor;
+  v->db->lastRowid = pFrame->lastRowid;
+  v->nChange = pFrame->nChange;
+  v->db->nChange = pFrame->nDbChange;
+  sqlite3VdbeDeleteAuxData(v->db, &v->pAuxData, -1, 0);
+  v->pAuxData = pFrame->pAuxData;
+  pFrame->pAuxData = 0;
+  return pFrame->pc;
+}
+
+/*
+** Close all cursors.
+**
+** Also release any dynamic memory held by the VM in the Vdbe.aMem memory
+** cell array. This is necessary as the memory cell array may contain
+** pointers to VdbeFrame objects, which may in turn contain pointers to
+** open cursors.
+*/
+static void closeAllCursors(Vdbe *p){
+  if( p->pFrame ){
+    VdbeFrame *pFrame;
+    for(pFrame=p->pFrame; pFrame->pParent; pFrame=pFrame->pParent);
+    sqlite3VdbeFrameRestore(pFrame);
+    p->pFrame = 0;
+    p->nFrame = 0;
+  }
+  assert( p->nFrame==0 );
+  closeCursorsInFrame(p);
+  releaseMemArray(p->aMem, p->nMem);
+  while( p->pDelFrame ){
+    VdbeFrame *pDel = p->pDelFrame;
+    p->pDelFrame = pDel->pParent;
+    sqlite3VdbeFrameDelete(pDel);
+  }
+
+  /* Delete any auxdata allocations made by the VM */
+  if( p->pAuxData ) sqlite3VdbeDeleteAuxData(p->db, &p->pAuxData, -1, 0);
+  assert( p->pAuxData==0 );
+}
+
+/*
+** Set the number of result columns that will be returned by this SQL
+** statement. This is now set at compile time, rather than during
+** execution of the vdbe program so that sqlite3_column_count() can
+** be called on an SQL statement before sqlite3_step().
+*/
+void sqlite3VdbeSetNumCols(Vdbe *p, int nResColumn){
+  int n;
+  sqlite3 *db = p->db;
+
+  if( p->nResAlloc ){
+    releaseMemArray(p->aColName, p->nResAlloc*COLNAME_N);
+    sqlite3DbFree(db, p->aColName);
+  }
+  n = nResColumn*COLNAME_N;
+  p->nResColumn = p->nResAlloc = (u16)nResColumn;
+  p->aColName = (Mem*)sqlite3DbMallocRawNN(db, sizeof(Mem)*n );
+  if( p->aColName==0 ) return;
+  initMemArray(p->aColName, n, db, MEM_Null);
+}
+
+/*
+** Set the name of the idx'th column to be returned by the SQL statement.
+** zName must be a pointer to a nul terminated string.
+**
+** This call must be made after a call to sqlite3VdbeSetNumCols().
+**
+** The final parameter, xDel, must be one of SQLITE_DYNAMIC, SQLITE_STATIC
+** or SQLITE_TRANSIENT. If it is SQLITE_DYNAMIC, then the buffer pointed
+** to by zName will be freed by sqlite3DbFree() when the vdbe is destroyed.
+*/
+int sqlite3VdbeSetColName(
+  Vdbe *p,                         /* Vdbe being configured */
+  int idx,                         /* Index of column zName applies to */
+  int var,                         /* One of the COLNAME_* constants */
+  const char *zName,               /* Pointer to buffer containing name */
+  void (*xDel)(void*)              /* Memory management strategy for zName */
+){
+  int rc;
+  Mem *pColName;
+  assert( idx<p->nResAlloc );
+  assert( var<COLNAME_N );
+  if( p->db->mallocFailed ){
+    assert( !zName || xDel!=SQLITE_DYNAMIC );
+    return SQLITE_NOMEM_BKPT;
+  }
+  assert( p->aColName!=0 );
+  pColName = &(p->aColName[idx+var*p->nResAlloc]);
+  rc = sqlite3VdbeMemSetStr(pColName, zName, -1, SQLITE_UTF8, xDel);
+  assert( rc!=0 || !zName || (pColName->flags&MEM_Term)!=0 );
+  return rc;
+}
+
+/*
+** A read or write transaction may or may not be active on database handle
+** db. If a transaction is active, commit it. If there is a
+** write-transaction spanning more than one database file, this routine
+** takes care of the super-journal trickery.
+*/
+static int vdbeCommit(sqlite3 *db, Vdbe *p){
+  int i;
+  int nTrans = 0;  /* Number of databases with an active write-transaction
+                   ** that are candidates for a two-phase commit using a
+                   ** super-journal */
+  int rc = SQLITE_OK;
+  int needXcommit = 0;
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  /* With this option, sqlite3VtabSync() is defined to be simply
+  ** SQLITE_OK so p is not used.
+  */
+  UNUSED_PARAMETER(p);
+#endif
+
+  /* Before doing anything else, call the xSync() callback for any
+  ** virtual module tables written in this transaction. This has to
+  ** be done before determining whether a super-journal file is
+  ** required, as an xSync() callback may add an attached database
+  ** to the transaction.
+  */
+  rc = sqlite3VtabSync(db, p);
+
+  /* This loop determines (a) if the commit hook should be invoked and
+  ** (b) how many database files have open write transactions, not
+  ** including the temp database. (b) is important because if more than
+  ** one database file has an open write transaction, a super-journal
+  ** file is required for an atomic commit.
+  */
+  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( sqlite3BtreeTxnState(pBt)==SQLITE_TXN_WRITE ){
+      /* Whether or not a database might need a super-journal depends upon
+      ** its journal mode (among other things).  This matrix determines which
+      ** journal modes use a super-journal and which do not */
+      static const u8 aMJNeeded[] = {
+        /* DELETE   */  1,
+        /* PERSIST   */ 1,
+        /* OFF       */ 0,
+        /* TRUNCATE  */ 1,
+        /* MEMORY    */ 0,
+        /* WAL       */ 0
+      };
+      Pager *pPager;   /* Pager associated with pBt */
+      needXcommit = 1;
+      sqlite3BtreeEnter(pBt);
+      pPager = sqlite3BtreePager(pBt);
+      if( db->aDb[i].safety_level!=PAGER_SYNCHRONOUS_OFF
+       && aMJNeeded[sqlite3PagerGetJournalMode(pPager)]
+       && sqlite3PagerIsMemdb(pPager)==0
+      ){
+        assert( i!=1 );
+        nTrans++;
+      }
+      rc = sqlite3PagerExclusiveLock(pPager);
+      sqlite3BtreeLeave(pBt);
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* If there are any write-transactions at all, invoke the commit hook */
+  if( needXcommit && db->xCommitCallback ){
+    rc = db->xCommitCallback(db->pCommitArg);
+    if( rc ){
+      return SQLITE_CONSTRAINT_COMMITHOOK;
+    }
+  }
+
+  /* The simple case - no more than one database file (not counting the
+  ** TEMP database) has a transaction active.   There is no need for the
+  ** super-journal.
+  **
+  ** If the return value of sqlite3BtreeGetFilename() is a zero length
+  ** string, it means the main database is :memory: or a temp file.  In
+  ** that case we do not support atomic multi-file commits, so use the
+  ** simple case then too.
+  */
+  if( 0==sqlite3Strlen30(sqlite3BtreeGetFilename(db->aDb[0].pBt))
+   || nTrans<=1
+  ){
+    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        rc = sqlite3BtreeCommitPhaseOne(pBt, 0);
+      }
+    }
+
+    /* Do the commit only if all databases successfully complete phase 1.
+    ** If one of the BtreeCommitPhaseOne() calls fails, this indicates an
+    ** IO error while deleting or truncating a journal file. It is unlikely,
+    ** but could happen. In this case abandon processing and return the error.
+    */
+    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        rc = sqlite3BtreeCommitPhaseTwo(pBt, 0);
+      }
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3VtabCommit(db);
+    }
+  }
+
+  /* The complex case - There is a multi-file write-transaction active.
+  ** This requires a super-journal file to ensure the transaction is
+  ** committed atomically.
+  */
+#ifndef SQLITE_OMIT_DISKIO
+  else{
+    sqlite3_vfs *pVfs = db->pVfs;
+    char *zSuper = 0;   /* File-name for the super-journal */
+    char const *zMainFile = sqlite3BtreeGetFilename(db->aDb[0].pBt);
+    sqlite3_file *pSuperJrnl = 0;
+    i64 offset = 0;
+    int res;
+    int retryCount = 0;
+    int nMainFile;
+
+    /* Select a super-journal file name */
+    nMainFile = sqlite3Strlen30(zMainFile);
+    zSuper = sqlite3MPrintf(db, "%.4c%s%.16c", 0,zMainFile,0);
+    if( zSuper==0 ) return SQLITE_NOMEM_BKPT;
+    zSuper += 4;
+    do {
+      u32 iRandom;
+      if( retryCount ){
+        if( retryCount>100 ){
+          sqlite3_log(SQLITE_FULL, "MJ delete: %s", zSuper);
+          sqlite3OsDelete(pVfs, zSuper, 0);
+          break;
+        }else if( retryCount==1 ){
+          sqlite3_log(SQLITE_FULL, "MJ collide: %s", zSuper);
+        }
+      }
+      retryCount++;
+      sqlite3_randomness(sizeof(iRandom), &iRandom);
+      sqlite3_snprintf(13, &zSuper[nMainFile], "-mj%06X9%02X",
+                               (iRandom>>8)&0xffffff, iRandom&0xff);
+      /* The antipenultimate character of the super-journal name must
+      ** be "9" to avoid name collisions when using 8+3 filenames. */
+      assert( zSuper[sqlite3Strlen30(zSuper)-3]=='9' );
+      sqlite3FileSuffix3(zMainFile, zSuper);
+      rc = sqlite3OsAccess(pVfs, zSuper, SQLITE_ACCESS_EXISTS, &res);
+    }while( rc==SQLITE_OK && res );
+    if( rc==SQLITE_OK ){
+      /* Open the super-journal. */
+      rc = sqlite3OsOpenMalloc(pVfs, zSuper, &pSuperJrnl,
+          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
+          SQLITE_OPEN_EXCLUSIVE|SQLITE_OPEN_SUPER_JOURNAL, 0
+      );
+    }
+    if( rc!=SQLITE_OK ){
+      sqlite3DbFree(db, zSuper-4);
+      return rc;
+    }
+
+    /* Write the name of each database file in the transaction into the new
+    ** super-journal file. If an error occurs at this point close
+    ** and delete the super-journal file. All the individual journal files
+    ** still have 'null' as the super-journal pointer, so they will roll
+    ** back independently if a failure occurs.
+    */
+    for(i=0; i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( sqlite3BtreeTxnState(pBt)==SQLITE_TXN_WRITE ){
+        char const *zFile = sqlite3BtreeGetJournalname(pBt);
+        if( zFile==0 ){
+          continue;  /* Ignore TEMP and :memory: databases */
+        }
+        assert( zFile[0]!=0 );
+        rc = sqlite3OsWrite(pSuperJrnl, zFile, sqlite3Strlen30(zFile)+1,offset);
+        offset += sqlite3Strlen30(zFile)+1;
+        if( rc!=SQLITE_OK ){
+          sqlite3OsCloseFree(pSuperJrnl);
+          sqlite3OsDelete(pVfs, zSuper, 0);
+          sqlite3DbFree(db, zSuper-4);
+          return rc;
+        }
+      }
+    }
+
+    /* Sync the super-journal file. If the IOCAP_SEQUENTIAL device
+    ** flag is set this is not required.
+    */
+    if( 0==(sqlite3OsDeviceCharacteristics(pSuperJrnl)&SQLITE_IOCAP_SEQUENTIAL)
+     && SQLITE_OK!=(rc = sqlite3OsSync(pSuperJrnl, SQLITE_SYNC_NORMAL))
+    ){
+      sqlite3OsCloseFree(pSuperJrnl);
+      sqlite3OsDelete(pVfs, zSuper, 0);
+      sqlite3DbFree(db, zSuper-4);
+      return rc;
+    }
+
+    /* Sync all the db files involved in the transaction. The same call
+    ** sets the super-journal pointer in each individual journal. If
+    ** an error occurs here, do not delete the super-journal file.
+    **
+    ** If the error occurs during the first call to
+    ** sqlite3BtreeCommitPhaseOne(), then there is a chance that the
+    ** super-journal file will be orphaned. But we cannot delete it,
+    ** in case the super-journal file name was written into the journal
+    ** file before the failure occurred.
+    */
+    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        rc = sqlite3BtreeCommitPhaseOne(pBt, zSuper);
+      }
+    }
+    sqlite3OsCloseFree(pSuperJrnl);
+    assert( rc!=SQLITE_BUSY );
+    if( rc!=SQLITE_OK ){
+      sqlite3DbFree(db, zSuper-4);
+      return rc;
+    }
+
+    /* Delete the super-journal file. This commits the transaction. After
+    ** doing this the directory is synced again before any individual
+    ** transaction files are deleted.
+    */
+    rc = sqlite3OsDelete(pVfs, zSuper, 1);
+    sqlite3DbFree(db, zSuper-4);
+    zSuper = 0;
+    if( rc ){
+      return rc;
+    }
+
+    /* All files and directories have already been synced, so the following
+    ** calls to sqlite3BtreeCommitPhaseTwo() are only closing files and
+    ** deleting or truncating journals. If something goes wrong while
+    ** this is happening we don't really care. The integrity of the
+    ** transaction is already guaranteed, but some stray 'cold' journals
+    ** may be lying around. Returning an error code won't help matters.
+    */
+    disable_simulated_io_errors();
+    sqlite3BeginBenignMalloc();
+    for(i=0; i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        sqlite3BtreeCommitPhaseTwo(pBt, 1);
+      }
+    }
+    sqlite3EndBenignMalloc();
+    enable_simulated_io_errors();
+
+    sqlite3VtabCommit(db);
+  }
+#endif
+
+  return rc;
+}
+
+/*
+** This routine checks that the sqlite3.nVdbeActive count variable
+** matches the number of vdbe's in the list sqlite3.pVdbe that are
+** currently active. An assertion fails if the two counts do not match.
+** This is an internal self-check only - it is not an essential processing
+** step.
+**
+** This is a no-op if NDEBUG is defined.
+*/
+#ifndef NDEBUG
+static void checkActiveVdbeCnt(sqlite3 *db){
+  Vdbe *p;
+  int cnt = 0;
+  int nWrite = 0;
+  int nRead = 0;
+  p = db->pVdbe;
+  while( p ){
+    if( sqlite3_stmt_busy((sqlite3_stmt*)p) ){
+      cnt++;
+      if( p->readOnly==0 ) nWrite++;
+      if( p->bIsReader ) nRead++;
+    }
+    p = p->pVNext;
+  }
+  assert( cnt==db->nVdbeActive );
+  assert( nWrite==db->nVdbeWrite );
+  assert( nRead==db->nVdbeRead );
+}
+#else
+#define checkActiveVdbeCnt(x)
+#endif
+
+/*
+** If the Vdbe passed as the first argument opened a statement-transaction,
+** close it now. Argument eOp must be either SAVEPOINT_ROLLBACK or
+** SAVEPOINT_RELEASE. If it is SAVEPOINT_ROLLBACK, then the statement
+** transaction is rolled back. If eOp is SAVEPOINT_RELEASE, then the
+** statement transaction is committed.
+**
+** If an IO error occurs, an SQLITE_IOERR_XXX error code is returned.
+** Otherwise SQLITE_OK.
+*/
+static SQLITE_NOINLINE int vdbeCloseStatement(Vdbe *p, int eOp){
+  sqlite3 *const db = p->db;
+  int rc = SQLITE_OK;
+  int i;
+  const int iSavepoint = p->iStatement-1;
+
+  assert( eOp==SAVEPOINT_ROLLBACK || eOp==SAVEPOINT_RELEASE);
+  assert( db->nStatement>0 );
+  assert( p->iStatement==(db->nStatement+db->nSavepoint) );
+
+  for(i=0; i<db->nDb; i++){
+    int rc2 = SQLITE_OK;
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ){
+      if( eOp==SAVEPOINT_ROLLBACK ){
+        rc2 = sqlite3BtreeSavepoint(pBt, SAVEPOINT_ROLLBACK, iSavepoint);
+      }
+      if( rc2==SQLITE_OK ){
+        rc2 = sqlite3BtreeSavepoint(pBt, SAVEPOINT_RELEASE, iSavepoint);
+      }
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
+  }
+  db->nStatement--;
+  p->iStatement = 0;
+
+  if( rc==SQLITE_OK ){
+    if( eOp==SAVEPOINT_ROLLBACK ){
+      rc = sqlite3VtabSavepoint(db, SAVEPOINT_ROLLBACK, iSavepoint);
+    }
+    if( rc==SQLITE_OK ){
+      rc = sqlite3VtabSavepoint(db, SAVEPOINT_RELEASE, iSavepoint);
+    }
+  }
+
+  /* If the statement transaction is being rolled back, also restore the
+  ** database handles deferred constraint counter to the value it had when
+  ** the statement transaction was opened.  */
+  if( eOp==SAVEPOINT_ROLLBACK ){
+    db->nDeferredCons = p->nStmtDefCons;
+    db->nDeferredImmCons = p->nStmtDefImmCons;
+  }
+  return rc;
+}
+int sqlite3VdbeCloseStatement(Vdbe *p, int eOp){
+  if( p->db->nStatement && p->iStatement ){
+    return vdbeCloseStatement(p, eOp);
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** This function is called when a transaction opened by the database
+** handle associated with the VM passed as an argument is about to be
+** committed. If there are outstanding deferred foreign key constraint
+** violations, return SQLITE_ERROR. Otherwise, SQLITE_OK.
+**
+** If there are outstanding FK violations and this function returns
+** SQLITE_ERROR, set the result of the VM to SQLITE_CONSTRAINT_FOREIGNKEY
+** and write an error message to it. Then return SQLITE_ERROR.
+*/
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+int sqlite3VdbeCheckFk(Vdbe *p, int deferred){
+  sqlite3 *db = p->db;
+  if( (deferred && (db->nDeferredCons+db->nDeferredImmCons)>0)
+   || (!deferred && p->nFkConstraint>0)
+  ){
+    p->rc = SQLITE_CONSTRAINT_FOREIGNKEY;
+    p->errorAction = OE_Abort;
+    sqlite3VdbeError(p, "FOREIGN KEY constraint failed");
+    if( (p->prepFlags & SQLITE_PREPARE_SAVESQL)==0 ) return SQLITE_ERROR;
+    return SQLITE_CONSTRAINT_FOREIGNKEY;
+  }
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** This routine is called the when a VDBE tries to halt.  If the VDBE
+** has made changes and is in autocommit mode, then commit those
+** changes.  If a rollback is needed, then do the rollback.
+**
+** This routine is the only way to move the sqlite3eOpenState of a VM from
+** SQLITE_STATE_RUN to SQLITE_STATE_HALT.  It is harmless to
+** call this on a VM that is in the SQLITE_STATE_HALT state.
+**
+** Return an error code.  If the commit could not complete because of
+** lock contention, return SQLITE_BUSY.  If SQLITE_BUSY is returned, it
+** means the close did not happen and needs to be repeated.
+*/
+int sqlite3VdbeHalt(Vdbe *p){
+  int rc;                         /* Used to store transient return codes */
+  sqlite3 *db = p->db;
+
+  /* This function contains the logic that determines if a statement or
+  ** transaction will be committed or rolled back as a result of the
+  ** execution of this virtual machine.
+  **
+  ** If any of the following errors occur:
+  **
+  **     SQLITE_NOMEM
+  **     SQLITE_IOERR
+  **     SQLITE_FULL
+  **     SQLITE_INTERRUPT
+  **
+  ** Then the internal cache might have been left in an inconsistent
+  ** state.  We need to rollback the statement transaction, if there is
+  ** one, or the complete transaction if there is no statement transaction.
+  */
+
+  assert( p->eVdbeState==VDBE_RUN_STATE );
+  if( db->mallocFailed ){
+    p->rc = SQLITE_NOMEM_BKPT;
+  }
+  closeAllCursors(p);
+  checkActiveVdbeCnt(db);
+
+  /* No commit or rollback needed if the program never started or if the
+  ** SQL statement does not read or write a database file.  */
+  if( p->bIsReader ){
+    int mrc;   /* Primary error code from p->rc */
+    int eStatementOp = 0;
+    int isSpecialError;            /* Set to true if a 'special' error */
+
+    /* Lock all btrees used by the statement */
+    sqlite3VdbeEnter(p);
+
+    /* Check for one of the special errors */
+    if( p->rc ){
+      mrc = p->rc & 0xff;
+      isSpecialError = mrc==SQLITE_NOMEM
+                    || mrc==SQLITE_IOERR
+                    || mrc==SQLITE_INTERRUPT
+                    || mrc==SQLITE_FULL;
+    }else{
+      mrc = isSpecialError = 0;
+    }
+    if( isSpecialError ){
+      /* If the query was read-only and the error code is SQLITE_INTERRUPT,
+      ** no rollback is necessary. Otherwise, at least a savepoint
+      ** transaction must be rolled back to restore the database to a
+      ** consistent state.
+      **
+      ** Even if the statement is read-only, it is important to perform
+      ** a statement or transaction rollback operation. If the error
+      ** occurred while writing to the journal, sub-journal or database
+      ** file as part of an effort to free up cache space (see function
+      ** pagerStress() in pager.c), the rollback is required to restore
+      ** the pager to a consistent state.
+      */
+      if( !p->readOnly || mrc!=SQLITE_INTERRUPT ){
+        if( (mrc==SQLITE_NOMEM || mrc==SQLITE_FULL) && p->usesStmtJournal ){
+          eStatementOp = SAVEPOINT_ROLLBACK;
+        }else{
+          /* We are forced to roll back the active transaction. Before doing
+          ** so, abort any other statements this handle currently has active.
+          */
+          sqlite3RollbackAll(db, SQLITE_ABORT_ROLLBACK);
+          sqlite3CloseSavepoints(db);
+          db->autoCommit = 1;
+          p->nChange = 0;
+        }
+      }
+    }
+
+    /* Check for immediate foreign key violations. */
+    if( p->rc==SQLITE_OK || (p->errorAction==OE_Fail && !isSpecialError) ){
+      sqlite3VdbeCheckFk(p, 0);
+    }
+ 
+    /* If the auto-commit flag is set and this is the only active writer
+    ** VM, then we do either a commit or rollback of the current transaction.
+    **
+    ** Note: This block also runs if one of the special errors handled
+    ** above has occurred.
+    */
+    if( !sqlite3VtabInSync(db)
+     && db->autoCommit
+     && db->nVdbeWrite==(p->readOnly==0)
+    ){
+      if( p->rc==SQLITE_OK || (p->errorAction==OE_Fail && !isSpecialError) ){
+        rc = sqlite3VdbeCheckFk(p, 1);
+        if( rc!=SQLITE_OK ){
+          if( NEVER(p->readOnly) ){
+            sqlite3VdbeLeave(p);
+            return SQLITE_ERROR;
+          }
+          rc = SQLITE_CONSTRAINT_FOREIGNKEY;
+        }else if( db->flags & SQLITE_CorruptRdOnly ){
+          rc = SQLITE_CORRUPT;
+          db->flags &= ~SQLITE_CorruptRdOnly;
+        }else{
+          /* The auto-commit flag is true, the vdbe program was successful
+          ** or hit an 'OR FAIL' constraint and there are no deferred foreign
+          ** key constraints to hold up the transaction. This means a commit
+          ** is required. */
+          rc = vdbeCommit(db, p);
+        }
+        if( rc==SQLITE_BUSY && p->readOnly ){
+          sqlite3VdbeLeave(p);
+          return SQLITE_BUSY;
+        }else if( rc!=SQLITE_OK ){
+          sqlite3SystemError(db, rc);
+          p->rc = rc;
+          sqlite3RollbackAll(db, SQLITE_OK);
+          p->nChange = 0;
+        }else{
+          db->nDeferredCons = 0;
+          db->nDeferredImmCons = 0;
+          db->flags &= ~(u64)SQLITE_DeferFKs;
+          sqlite3CommitInternalChanges(db);
+        }
+      }else if( p->rc==SQLITE_SCHEMA && db->nVdbeActive>1 ){
+        p->nChange = 0;
+      }else{
+        sqlite3RollbackAll(db, SQLITE_OK);
+        p->nChange = 0;
+      }
+      db->nStatement = 0;
+    }else if( eStatementOp==0 ){
+      if( p->rc==SQLITE_OK || p->errorAction==OE_Fail ){
+        eStatementOp = SAVEPOINT_RELEASE;
+      }else if( p->errorAction==OE_Abort ){
+        eStatementOp = SAVEPOINT_ROLLBACK;
+      }else{
+        sqlite3RollbackAll(db, SQLITE_ABORT_ROLLBACK);
+        sqlite3CloseSavepoints(db);
+        db->autoCommit = 1;
+        p->nChange = 0;
+      }
+    }
+ 
+    /* If eStatementOp is non-zero, then a statement transaction needs to
+    ** be committed or rolled back. Call sqlite3VdbeCloseStatement() to
+    ** do so. If this operation returns an error, and the current statement
+    ** error code is SQLITE_OK or SQLITE_CONSTRAINT, then promote the
+    ** current statement error code.
+    */
+    if( eStatementOp ){
+      rc = sqlite3VdbeCloseStatement(p, eStatementOp);
+      if( rc ){
+        if( p->rc==SQLITE_OK || (p->rc&0xff)==SQLITE_CONSTRAINT ){
+          p->rc = rc;
+          sqlite3DbFree(db, p->zErrMsg);
+          p->zErrMsg = 0;
+        }
+        sqlite3RollbackAll(db, SQLITE_ABORT_ROLLBACK);
+        sqlite3CloseSavepoints(db);
+        db->autoCommit = 1;
+        p->nChange = 0;
+      }
+    }
+ 
+    /* If this was an INSERT, UPDATE or DELETE and no statement transaction
+    ** has been rolled back, update the database connection change-counter.
+    */
+    if( p->changeCntOn ){
+      if( eStatementOp!=SAVEPOINT_ROLLBACK ){
+        sqlite3VdbeSetChanges(db, p->nChange);
+      }else{
+        sqlite3VdbeSetChanges(db, 0);
+      }
+      p->nChange = 0;
+    }
+
+    /* Release the locks */
+    sqlite3VdbeLeave(p);
+  }
+
+  /* We have successfully halted and closed the VM.  Record this fact. */
+  db->nVdbeActive--;
+  if( !p->readOnly ) db->nVdbeWrite--;
+  if( p->bIsReader ) db->nVdbeRead--;
+  assert( db->nVdbeActive>=db->nVdbeRead );
+  assert( db->nVdbeRead>=db->nVdbeWrite );
+  assert( db->nVdbeWrite>=0 );
+  p->eVdbeState = VDBE_HALT_STATE;
+  checkActiveVdbeCnt(db);
+  if( db->mallocFailed ){
+    p->rc = SQLITE_NOMEM_BKPT;
+  }
+
+  /* If the auto-commit flag is set to true, then any locks that were held
+  ** by connection db have now been released. Call sqlite3ConnectionUnlocked()
+  ** to invoke any required unlock-notify callbacks.
+  */
+  if( db->autoCommit ){
+    sqlite3ConnectionUnlocked(db);
+  }
+
+  assert( db->nVdbeActive>0 || db->autoCommit==0 || db->nStatement==0 );
+  return (p->rc==SQLITE_BUSY ? SQLITE_BUSY : SQLITE_OK);
+}
+
+
+/*
+** Each VDBE holds the result of the most recent sqlite3_step() call
+** in p->rc.  This routine sets that result back to SQLITE_OK.
+*/
+void sqlite3VdbeResetStepResult(Vdbe *p){
+  p->rc = SQLITE_OK;
+}
+
+/*
+** Copy the error code and error message belonging to the VDBE passed
+** as the first argument to its database handle (so that they will be
+** returned by calls to sqlite3_errcode() and sqlite3_errmsg()).
+**
+** This function does not clear the VDBE error code or message, just
+** copies them to the database handle.
+*/
+int sqlite3VdbeTransferError(Vdbe *p){
+  sqlite3 *db = p->db;
+  int rc = p->rc;
+  if( p->zErrMsg ){
+    db->bBenignMalloc++;
+    sqlite3BeginBenignMalloc();
+    if( db->pErr==0 ) db->pErr = sqlite3ValueNew(db);
+    sqlite3ValueSetStr(db->pErr, -1, p->zErrMsg, SQLITE_UTF8, SQLITE_TRANSIENT);
+    sqlite3EndBenignMalloc();
+    db->bBenignMalloc--;
+  }else if( db->pErr ){
+    sqlite3ValueSetNull(db->pErr);
+  }
+  db->errCode = rc;
+  db->errByteOffset = -1;
+  return rc;
+}
+
+#ifdef SQLITE_ENABLE_SQLLOG
+/*
+** If an SQLITE_CONFIG_SQLLOG hook is registered and the VM has been run,
+** invoke it.
+*/
+static void vdbeInvokeSqllog(Vdbe *v){
+  if( sqlite3GlobalConfig.xSqllog && v->rc==SQLITE_OK && v->zSql && v->pc>=0 ){
+    char *zExpanded = sqlite3VdbeExpandSql(v, v->zSql);
+    assert( v->db->init.busy==0 );
+    if( zExpanded ){
+      sqlite3GlobalConfig.xSqllog(
+          sqlite3GlobalConfig.pSqllogArg, v->db, zExpanded, 1
+      );
+      sqlite3DbFree(v->db, zExpanded);
+    }
+  }
+}
+#else
+# define vdbeInvokeSqllog(x)
+#endif
+
+/*
+** Clean up a VDBE after execution but do not delete the VDBE just yet.
+** Write any error messages into *pzErrMsg.  Return the result code.
+**
+** After this routine is run, the VDBE should be ready to be executed
+** again.
+**
+** To look at it another way, this routine resets the state of the
+** virtual machine from VDBE_RUN_STATE or VDBE_HALT_STATE back to
+** VDBE_READY_STATE.
+*/
+int sqlite3VdbeReset(Vdbe *p){
+#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
+  int i;
+#endif
+
+  sqlite3 *db;
+  db = p->db;
+
+  /* If the VM did not run to completion or if it encountered an
+  ** error, then it might not have been halted properly.  So halt
+  ** it now.
+  */
+  if( p->eVdbeState==VDBE_RUN_STATE ) sqlite3VdbeHalt(p);
+
+  /* If the VDBE has been run even partially, then transfer the error code
+  ** and error message from the VDBE into the main database structure.  But
+  ** if the VDBE has just been set to run but has not actually executed any
+  ** instructions yet, leave the main database error information unchanged.
+  */
+  if( p->pc>=0 ){
+    vdbeInvokeSqllog(p);
+    if( db->pErr || p->zErrMsg ){
+      sqlite3VdbeTransferError(p);
+    }else{
+      db->errCode = p->rc;
+    }
+  }
+
+  /* Reset register contents and reclaim error message memory.
+  */
+#ifdef SQLITE_DEBUG
+  /* Execute assert() statements to ensure that the Vdbe.apCsr[] and
+  ** Vdbe.aMem[] arrays have already been cleaned up.  */
+  if( p->apCsr ) for(i=0; i<p->nCursor; i++) assert( p->apCsr[i]==0 );
+  if( p->aMem ){
+    for(i=0; i<p->nMem; i++) assert( p->aMem[i].flags==MEM_Undefined );
+  }
+#endif
+  if( p->zErrMsg ){
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = 0;
+  }
+  p->pResultRow = 0;
+#ifdef SQLITE_DEBUG
+  p->nWrite = 0;
+#endif
+
+  /* Save profiling information from this VDBE run.
+  */
+#ifdef VDBE_PROFILE
+  {
+    FILE *out = fopen("vdbe_profile.out", "a");
+    if( out ){
+      fprintf(out, "---- ");
+      for(i=0; i<p->nOp; i++){
+        fprintf(out, "%02x", p->aOp[i].opcode);
+      }
+      fprintf(out, "\n");
+      if( p->zSql ){
+        char c, pc = 0;
+        fprintf(out, "-- ");
+        for(i=0; (c = p->zSql[i])!=0; i++){
+          if( pc=='\n' ) fprintf(out, "-- ");
+          putc(c, out);
+          pc = c;
+        }
+        if( pc!='\n' ) fprintf(out, "\n");
+      }
+      for(i=0; i<p->nOp; i++){
+        char zHdr[100];
+        i64 cnt = p->aOp[i].nExec;
+        i64 cycles = p->aOp[i].nCycle;
+        sqlite3_snprintf(sizeof(zHdr), zHdr, "%6u %12llu %8llu ",
+           cnt,
+           cycles,
+           cnt>0 ? cycles/cnt : 0
+        );
+        fprintf(out, "%s", zHdr);
+        sqlite3VdbePrintOp(out, i, &p->aOp[i]);
+      }
+      fclose(out);
+    }
+  }
+#endif
+  return p->rc & db->errMask;
+}
+
+/*
+** Clean up and delete a VDBE after execution.  Return an integer which is
+** the result code.  Write any error message text into *pzErrMsg.
+*/
+int sqlite3VdbeFinalize(Vdbe *p){
+  int rc = SQLITE_OK;
+  assert( VDBE_RUN_STATE>VDBE_READY_STATE );
+  assert( VDBE_HALT_STATE>VDBE_READY_STATE );
+  assert( VDBE_INIT_STATE<VDBE_READY_STATE );
+  if( p->eVdbeState>=VDBE_READY_STATE ){
+    rc = sqlite3VdbeReset(p);
+    assert( (rc & p->db->errMask)==rc );
+  }
+  sqlite3VdbeDelete(p);
+  return rc;
+}
+
+/*
+** If parameter iOp is less than zero, then invoke the destructor for
+** all auxiliary data pointers currently cached by the VM passed as
+** the first argument.
+**
+** Or, if iOp is greater than or equal to zero, then the destructor is
+** only invoked for those auxiliary data pointers created by the user
+** function invoked by the OP_Function opcode at instruction iOp of
+** VM pVdbe, and only then if:
+**
+**    * the associated function parameter is the 32nd or later (counting
+**      from left to right), or
+**
+**    * the corresponding bit in argument mask is clear (where the first
+**      function parameter corresponds to bit 0 etc.).
+*/
+void sqlite3VdbeDeleteAuxData(sqlite3 *db, AuxData **pp, int iOp, int mask){
+  while( *pp ){
+    AuxData *pAux = *pp;
+    if( (iOp<0)
+     || (pAux->iAuxOp==iOp
+          && pAux->iAuxArg>=0
+          && (pAux->iAuxArg>31 || !(mask & MASKBIT32(pAux->iAuxArg))))
+    ){
+      testcase( pAux->iAuxArg==31 );
+      if( pAux->xDeleteAux ){
+        pAux->xDeleteAux(pAux->pAux);
+      }
+      *pp = pAux->pNextAux;
+      sqlite3DbFree(db, pAux);
+    }else{
+      pp= &pAux->pNextAux;
+    }
+  }
+}
+
+/*
+** Free all memory associated with the Vdbe passed as the second argument,
+** except for object itself, which is preserved.
+**
+** The difference between this function and sqlite3VdbeDelete() is that
+** VdbeDelete() also unlinks the Vdbe from the list of VMs associated with
+** the database connection and frees the object itself.
+*/
+static void sqlite3VdbeClearObject(sqlite3 *db, Vdbe *p){
+  SubProgram *pSub, *pNext;
+  assert( db!=0 );
+  assert( p->db==0 || p->db==db );
+  if( p->aColName ){
+    releaseMemArray(p->aColName, p->nResAlloc*COLNAME_N);
+    sqlite3DbNNFreeNN(db, p->aColName);
+  }
+  for(pSub=p->pProgram; pSub; pSub=pNext){
+    pNext = pSub->pNext;
+    vdbeFreeOpArray(db, pSub->aOp, pSub->nOp);
+    sqlite3DbFree(db, pSub);
+  }
+  if( p->eVdbeState!=VDBE_INIT_STATE ){
+    releaseMemArray(p->aVar, p->nVar);
+    if( p->pVList ) sqlite3DbNNFreeNN(db, p->pVList);
+    if( p->pFree ) sqlite3DbNNFreeNN(db, p->pFree);
+  }
+  vdbeFreeOpArray(db, p->aOp, p->nOp);
+  if( p->zSql ) sqlite3DbNNFreeNN(db, p->zSql);
+#ifdef SQLITE_ENABLE_NORMALIZE
+  sqlite3DbFree(db, p->zNormSql);
+  {
+    DblquoteStr *pThis, *pNxt;
+    for(pThis=p->pDblStr; pThis; pThis=pNxt){
+      pNxt = pThis->pNextStr;
+      sqlite3DbFree(db, pThis);
+    }
+  }
+#endif
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  {
+    int i;
+    for(i=0; i<p->nScan; i++){
+      sqlite3DbFree(db, p->aScan[i].zName);
+    }
+    sqlite3DbFree(db, p->aScan);
+  }
+#endif
+}
+
+/*
+** Delete an entire VDBE.
+*/
+void sqlite3VdbeDelete(Vdbe *p){
+  sqlite3 *db;
+
+  assert( p!=0 );
+  db = p->db;
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  sqlite3VdbeClearObject(db, p);
+  if( db->pnBytesFreed==0 ){
+    assert( p->ppVPrev!=0 );
+    *p->ppVPrev = p->pVNext;
+    if( p->pVNext ){
+      p->pVNext->ppVPrev = p->ppVPrev;
+    }
+  }
+  sqlite3DbNNFreeNN(db, p);
+}
+
+/*
+** The cursor "p" has a pending seek operation that has not yet been
+** carried out.  Seek the cursor now.  If an error occurs, return
+** the appropriate error code.
+*/
+int SQLITE_NOINLINE sqlite3VdbeFinishMoveto(VdbeCursor *p){
+  int res, rc;
+#ifdef SQLITE_TEST
+  extern int sqlite3_search_count;
+#endif
+  assert( p->deferredMoveto );
+  assert( p->isTable );
+  assert( p->eCurType==CURTYPE_BTREE );
+  rc = sqlite3BtreeTableMoveto(p->uc.pCursor, p->movetoTarget, 0, &res);
+  if( rc ) return rc;
+  if( res!=0 ) return SQLITE_CORRUPT_BKPT;
+#ifdef SQLITE_TEST
+  sqlite3_search_count++;
+#endif
+  p->deferredMoveto = 0;
+  p->cacheStatus = CACHE_STALE;
+  return SQLITE_OK;
+}
+
+/*
+** Something has moved cursor "p" out of place.  Maybe the row it was
+** pointed to was deleted out from under it.  Or maybe the btree was
+** rebalanced.  Whatever the cause, try to restore "p" to the place it
+** is supposed to be pointing.  If the row was deleted out from under the
+** cursor, set the cursor to point to a NULL row.
+*/
+int SQLITE_NOINLINE sqlite3VdbeHandleMovedCursor(VdbeCursor *p){
+  int isDifferentRow, rc;
+  assert( p->eCurType==CURTYPE_BTREE );
+  assert( p->uc.pCursor!=0 );
+  assert( sqlite3BtreeCursorHasMoved(p->uc.pCursor) );
+  rc = sqlite3BtreeCursorRestore(p->uc.pCursor, &isDifferentRow);
+  p->cacheStatus = CACHE_STALE;
+  if( isDifferentRow ) p->nullRow = 1;
+  return rc;
+}
+
+/*
+** Check to ensure that the cursor is valid.  Restore the cursor
+** if need be.  Return any I/O error from the restore operation.
+*/
+int sqlite3VdbeCursorRestore(VdbeCursor *p){
+  assert( p->eCurType==CURTYPE_BTREE || IsNullCursor(p) );
+  if( sqlite3BtreeCursorHasMoved(p->uc.pCursor) ){
+    return sqlite3VdbeHandleMovedCursor(p);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The following functions:
+**
+** sqlite3VdbeSerialType()
+** sqlite3VdbeSerialTypeLen()
+** sqlite3VdbeSerialLen()
+** sqlite3VdbeSerialPut()  <--- in-lined into OP_MakeRecord as of 2022-04-02
+** sqlite3VdbeSerialGet()
+**
+** encapsulate the code that serializes values for storage in SQLite
+** data and index records. Each serialized value consists of a
+** 'serial-type' and a blob of data. The serial type is an 8-byte unsigned
+** integer, stored as a varint.
+**
+** In an SQLite index record, the serial type is stored directly before
+** the blob of data that it corresponds to. In a table record, all serial
+** types are stored at the start of the record, and the blobs of data at
+** the end. Hence these functions allow the caller to handle the
+** serial-type and data blob separately.
+**
+** The following table describes the various storage classes for data:
+**
+**   serial type        bytes of data      type
+**   --------------     ---------------    ---------------
+**      0                     0            NULL
+**      1                     1            signed integer
+**      2                     2            signed integer
+**      3                     3            signed integer
+**      4                     4            signed integer
+**      5                     6            signed integer
+**      6                     8            signed integer
+**      7                     8            IEEE float
+**      8                     0            Integer constant 0
+**      9                     0            Integer constant 1
+**     10,11                               reserved for expansion
+**    N>=12 and even       (N-12)/2        BLOB
+**    N>=13 and odd        (N-13)/2        text
+**
+** The 8 and 9 types were added in 3.3.0, file format 4.  Prior versions
+** of SQLite will not understand those serial types.
+*/
+
+#if 0 /* Inlined into the OP_MakeRecord opcode */
+/*
+** Return the serial-type for the value stored in pMem.
+**
+** This routine might convert a large MEM_IntReal value into MEM_Real.
+**
+** 2019-07-11:  The primary user of this subroutine was the OP_MakeRecord
+** opcode in the byte-code engine.  But by moving this routine in-line, we
+** can omit some redundant tests and make that opcode a lot faster.  So
+** this routine is now only used by the STAT3 logic and STAT3 support has
+** ended.  The code is kept here for historical reference only.
+*/
+u32 sqlite3VdbeSerialType(Mem *pMem, int file_format, u32 *pLen){
+  int flags = pMem->flags;
+  u32 n;
+
+  assert( pLen!=0 );
+  if( flags&MEM_Null ){
+    *pLen = 0;
+    return 0;
+  }
+  if( flags&(MEM_Int|MEM_IntReal) ){
+    /* Figure out whether to use 1, 2, 4, 6 or 8 bytes. */
+#   define MAX_6BYTE ((((i64)0x00008000)<<32)-1)
+    i64 i = pMem->u.i;
+    u64 u;
+    testcase( flags & MEM_Int );
+    testcase( flags & MEM_IntReal );
+    if( i<0 ){
+      u = ~i;
+    }else{
+      u = i;
+    }
+    if( u<=127 ){
+      if( (i&1)==i && file_format>=4 ){
+        *pLen = 0;
+        return 8+(u32)u;
+      }else{
+        *pLen = 1;
+        return 1;
+      }
+    }
+    if( u<=32767 ){ *pLen = 2; return 2; }
+    if( u<=8388607 ){ *pLen = 3; return 3; }
+    if( u<=2147483647 ){ *pLen = 4; return 4; }
+    if( u<=MAX_6BYTE ){ *pLen = 6; return 5; }
+    *pLen = 8;
+    if( flags&MEM_IntReal ){
+      /* If the value is IntReal and is going to take up 8 bytes to store
+      ** as an integer, then we might as well make it an 8-byte floating
+      ** point value */
+      pMem->u.r = (double)pMem->u.i;
+      pMem->flags &= ~MEM_IntReal;
+      pMem->flags |= MEM_Real;
+      return 7;
+    }
+    return 6;
+  }
+  if( flags&MEM_Real ){
+    *pLen = 8;
+    return 7;
+  }
+  assert( pMem->db->mallocFailed || flags&(MEM_Str|MEM_Blob) );
+  assert( pMem->n>=0 );
+  n = (u32)pMem->n;
+  if( flags & MEM_Zero ){
+    n += pMem->u.nZero;
+  }
+  *pLen = n;
+  return ((n*2) + 12 + ((flags&MEM_Str)!=0));
+}
+#endif /* inlined into OP_MakeRecord */
+
+/*
+** The sizes for serial types less than 128
+*/
+const u8 sqlite3SmallTypeSizes[128] = {
+        /*  0   1   2   3   4   5   6   7   8   9 */  
+/*   0 */   0,  1,  2,  3,  4,  6,  8,  8,  0,  0,
+/*  10 */   0,  0,  0,  0,  1,  1,  2,  2,  3,  3,
+/*  20 */   4,  4,  5,  5,  6,  6,  7,  7,  8,  8,
+/*  30 */   9,  9, 10, 10, 11, 11, 12, 12, 13, 13,
+/*  40 */  14, 14, 15, 15, 16, 16, 17, 17, 18, 18,
+/*  50 */  19, 19, 20, 20, 21, 21, 22, 22, 23, 23,
+/*  60 */  24, 24, 25, 25, 26, 26, 27, 27, 28, 28,
+/*  70 */  29, 29, 30, 30, 31, 31, 32, 32, 33, 33,
+/*  80 */  34, 34, 35, 35, 36, 36, 37, 37, 38, 38,
+/*  90 */  39, 39, 40, 40, 41, 41, 42, 42, 43, 43,
+/* 100 */  44, 44, 45, 45, 46, 46, 47, 47, 48, 48,
+/* 110 */  49, 49, 50, 50, 51, 51, 52, 52, 53, 53,
+/* 120 */  54, 54, 55, 55, 56, 56, 57, 57
+};
+
+/*
+** Return the length of the data corresponding to the supplied serial-type.
+*/
+u32 sqlite3VdbeSerialTypeLen(u32 serial_type){
+  if( serial_type>=128 ){
+    return (serial_type-12)/2;
+  }else{
+    assert( serial_type<12
+            || sqlite3SmallTypeSizes[serial_type]==(serial_type - 12)/2 );
+    return sqlite3SmallTypeSizes[serial_type];
+  }
+}
+u8 sqlite3VdbeOneByteSerialTypeLen(u8 serial_type){
+  assert( serial_type<128 );
+  return sqlite3SmallTypeSizes[serial_type]; 
+}
+
+/*
+** If we are on an architecture with mixed-endian floating
+** points (ex: ARM7) then swap the lower 4 bytes with the
+** upper 4 bytes.  Return the result.
+**
+** For most architectures, this is a no-op.
+**
+** (later):  It is reported to me that the mixed-endian problem
+** on ARM7 is an issue with GCC, not with the ARM7 chip.  It seems
+** that early versions of GCC stored the two words of a 64-bit
+** float in the wrong order.  And that error has been propagated
+** ever since.  The blame is not necessarily with GCC, though.
+** GCC might have just copying the problem from a prior compiler.
+** I am also told that newer versions of GCC that follow a different
+** ABI get the byte order right.
+**
+** Developers using SQLite on an ARM7 should compile and run their
+** application using -DSQLITE_DEBUG=1 at least once.  With DEBUG
+** enabled, some asserts below will ensure that the byte order of
+** floating point values is correct.
+**
+** (2007-08-30)  Frank van Vugt has studied this problem closely
+** and has send his findings to the SQLite developers.  Frank
+** writes that some Linux kernels offer floating point hardware
+** emulation that uses only 32-bit mantissas instead of a full
+** 48-bits as required by the IEEE standard.  (This is the
+** CONFIG_FPE_FASTFPE option.)  On such systems, floating point
+** byte swapping becomes very complicated.  To avoid problems,
+** the necessary byte swapping is carried out using a 64-bit integer
+** rather than a 64-bit float.  Frank assures us that the code here
+** works for him.  We, the developers, have no way to independently
+** verify this, but Frank seems to know what he is talking about
+** so we trust him.
+*/
+#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+u64 sqlite3FloatSwap(u64 in){
+  union {
+    u64 r;
+    u32 i[2];
+  } u;
+  u32 t;
+
+  u.r = in;
+  t = u.i[0];
+  u.i[0] = u.i[1];
+  u.i[1] = t;
+  return u.r;
+}
+#endif /* SQLITE_MIXED_ENDIAN_64BIT_FLOAT */
+
+
+/* Input "x" is a sequence of unsigned characters that represent a
+** big-endian integer.  Return the equivalent native integer
+*/
+#define ONE_BYTE_INT(x)    ((i8)(x)[0])
+#define TWO_BYTE_INT(x)    (256*(i8)((x)[0])|(x)[1])
+#define THREE_BYTE_INT(x)  (65536*(i8)((x)[0])|((x)[1]<<8)|(x)[2])
+#define FOUR_BYTE_UINT(x)  (((u32)(x)[0]<<24)|((x)[1]<<16)|((x)[2]<<8)|(x)[3])
+#define FOUR_BYTE_INT(x) (16777216*(i8)((x)[0])|((x)[1]<<16)|((x)[2]<<8)|(x)[3])
+
+/*
+** Deserialize the data blob pointed to by buf as serial type serial_type
+** and store the result in pMem.
+**
+** This function is implemented as two separate routines for performance.
+** The few cases that require local variables are broken out into a separate
+** routine so that in most cases the overhead of moving the stack pointer
+** is avoided.
+*/
+static void serialGet(
+  const unsigned char *buf,     /* Buffer to deserialize from */
+  u32 serial_type,              /* Serial type to deserialize */
+  Mem *pMem                     /* Memory cell to write value into */
+){
+  u64 x = FOUR_BYTE_UINT(buf);
+  u32 y = FOUR_BYTE_UINT(buf+4);
+  x = (x<<32) + y;
+  if( serial_type==6 ){
+    /* EVIDENCE-OF: R-29851-52272 Value is a big-endian 64-bit
+    ** twos-complement integer. */
+    pMem->u.i = *(i64*)&x;
+    pMem->flags = MEM_Int;
+    testcase( pMem->u.i<0 );
+  }else{
+    /* EVIDENCE-OF: R-57343-49114 Value is a big-endian IEEE 754-2008 64-bit
+    ** floating point number. */
+#if !defined(NDEBUG) && !defined(SQLITE_OMIT_FLOATING_POINT)
+    /* Verify that integers and floating point values use the same
+    ** byte order.  Or, that if SQLITE_MIXED_ENDIAN_64BIT_FLOAT is
+    ** defined that 64-bit floating point values really are mixed
+    ** endian.
+    */
+    static const u64 t1 = ((u64)0x3ff00000)<<32;
+    static const double r1 = 1.0;
+    u64 t2 = t1;
+    swapMixedEndianFloat(t2);
+    assert( sizeof(r1)==sizeof(t2) && memcmp(&r1, &t2, sizeof(r1))==0 );
+#endif
+    assert( sizeof(x)==8 && sizeof(pMem->u.r)==8 );
+    swapMixedEndianFloat(x);
+    memcpy(&pMem->u.r, &x, sizeof(x));
+    pMem->flags = IsNaN(x) ? MEM_Null : MEM_Real;
+  }
+}
+void sqlite3VdbeSerialGet(
+  const unsigned char *buf,     /* Buffer to deserialize from */
+  u32 serial_type,              /* Serial type to deserialize */
+  Mem *pMem                     /* Memory cell to write value into */
+){
+  switch( serial_type ){
+    case 10: { /* Internal use only: NULL with virtual table
+               ** UPDATE no-change flag set */
+      pMem->flags = MEM_Null|MEM_Zero;
+      pMem->n = 0;
+      pMem->u.nZero = 0;
+      return;
+    }
+    case 11:   /* Reserved for future use */
+    case 0: {  /* Null */
+      /* EVIDENCE-OF: R-24078-09375 Value is a NULL. */
+      pMem->flags = MEM_Null;
+      return;
+    }
+    case 1: {
+      /* EVIDENCE-OF: R-44885-25196 Value is an 8-bit twos-complement
+      ** integer. */
+      pMem->u.i = ONE_BYTE_INT(buf);
+      pMem->flags = MEM_Int;
+      testcase( pMem->u.i<0 );
+      return;
+    }
+    case 2: { /* 2-byte signed integer */
+      /* EVIDENCE-OF: R-49794-35026 Value is a big-endian 16-bit
+      ** twos-complement integer. */
+      pMem->u.i = TWO_BYTE_INT(buf);
+      pMem->flags = MEM_Int;
+      testcase( pMem->u.i<0 );
+      return;
+    }
+    case 3: { /* 3-byte signed integer */
+      /* EVIDENCE-OF: R-37839-54301 Value is a big-endian 24-bit
+      ** twos-complement integer. */
+      pMem->u.i = THREE_BYTE_INT(buf);
+      pMem->flags = MEM_Int;
+      testcase( pMem->u.i<0 );
+      return;
+    }
+    case 4: { /* 4-byte signed integer */
+      /* EVIDENCE-OF: R-01849-26079 Value is a big-endian 32-bit
+      ** twos-complement integer. */
+      pMem->u.i = FOUR_BYTE_INT(buf);
+#ifdef __HP_cc
+      /* Work around a sign-extension bug in the HP compiler for HP/UX */
+      if( buf[0]&0x80 ) pMem->u.i |= 0xffffffff80000000LL;
+#endif
+      pMem->flags = MEM_Int;
+      testcase( pMem->u.i<0 );
+      return;
+    }
+    case 5: { /* 6-byte signed integer */
+      /* EVIDENCE-OF: R-50385-09674 Value is a big-endian 48-bit
+      ** twos-complement integer. */
+      pMem->u.i = FOUR_BYTE_UINT(buf+2) + (((i64)1)<<32)*TWO_BYTE_INT(buf);
+      pMem->flags = MEM_Int;
+      testcase( pMem->u.i<0 );
+      return;
+    }
+    case 6:   /* 8-byte signed integer */
+    case 7: { /* IEEE floating point */
+      /* These use local variables, so do them in a separate routine
+      ** to avoid having to move the frame pointer in the common case */
+      serialGet(buf,serial_type,pMem);
+      return;
+    }
+    case 8:    /* Integer 0 */
+    case 9: {  /* Integer 1 */
+      /* EVIDENCE-OF: R-12976-22893 Value is the integer 0. */
+      /* EVIDENCE-OF: R-18143-12121 Value is the integer 1. */
+      pMem->u.i = serial_type-8;
+      pMem->flags = MEM_Int;
+      return;
+    }
+    default: {
+      /* EVIDENCE-OF: R-14606-31564 Value is a BLOB that is (N-12)/2 bytes in
+      ** length.
+      ** EVIDENCE-OF: R-28401-00140 Value is a string in the text encoding and
+      ** (N-13)/2 bytes in length. */
+      static const u16 aFlag[] = { MEM_Blob|MEM_Ephem, MEM_Str|MEM_Ephem };
+      pMem->z = (char *)buf;
+      pMem->n = (serial_type-12)/2;
+      pMem->flags = aFlag[serial_type&1];
+      return;
+    }
+  }
+  return;
+}
+/*
+** This routine is used to allocate sufficient space for an UnpackedRecord
+** structure large enough to be used with sqlite3VdbeRecordUnpack() if
+** the first argument is a pointer to KeyInfo structure pKeyInfo.
+**
+** The space is either allocated using sqlite3DbMallocRaw() or from within
+** the unaligned buffer passed via the second and third arguments (presumably
+** stack space). If the former, then *ppFree is set to a pointer that should
+** be eventually freed by the caller using sqlite3DbFree(). Or, if the
+** allocation comes from the pSpace/szSpace buffer, *ppFree is set to NULL
+** before returning.
+**
+** If an OOM error occurs, NULL is returned.
+*/
+UnpackedRecord *sqlite3VdbeAllocUnpackedRecord(
+  KeyInfo *pKeyInfo               /* Description of the record */
+){
+  UnpackedRecord *p;              /* Unpacked record to return */
+  int nByte;                      /* Number of bytes required for *p */
+  nByte = ROUND8P(sizeof(UnpackedRecord)) + sizeof(Mem)*(pKeyInfo->nKeyField+1);
+  p = (UnpackedRecord *)sqlite3DbMallocRaw(pKeyInfo->db, nByte);
+  if( !p ) return 0;
+  p->aMem = (Mem*)&((char*)p)[ROUND8P(sizeof(UnpackedRecord))];
+  assert( pKeyInfo->aSortFlags!=0 );
+  p->pKeyInfo = pKeyInfo;
+  p->nField = pKeyInfo->nKeyField + 1;
+  return p;
+}
+
+/*
+** Given the nKey-byte encoding of a record in pKey[], populate the
+** UnpackedRecord structure indicated by the fourth argument with the
+** contents of the decoded record.
+*/
+void sqlite3VdbeRecordUnpack(
+  KeyInfo *pKeyInfo,     /* Information about the record format */
+  int nKey,              /* Size of the binary record */
+  const void *pKey,      /* The binary record */
+  UnpackedRecord *p      /* Populate this structure before returning. */
+){
+  const unsigned char *aKey = (const unsigned char *)pKey;
+  u32 d;
+  u32 idx;                        /* Offset in aKey[] to read from */
+  u16 u;                          /* Unsigned loop counter */
+  u32 szHdr;
+  Mem *pMem = p->aMem;
+
+  p->default_rc = 0;
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+  idx = getVarint32(aKey, szHdr);
+  d = szHdr;
+  u = 0;
+  while( idx<szHdr && d<=(u32)nKey ){
+    u32 serial_type;
+
+    idx += getVarint32(&aKey[idx], serial_type);
+    pMem->enc = pKeyInfo->enc;
+    pMem->db = pKeyInfo->db;
+    /* pMem->flags = 0; // sqlite3VdbeSerialGet() will set this for us */
+    pMem->szMalloc = 0;
+    pMem->z = 0;
+    sqlite3VdbeSerialGet(&aKey[d], serial_type, pMem);
+    d += sqlite3VdbeSerialTypeLen(serial_type);
+    pMem++;
+    if( (++u)>=p->nField ) break;
+  }
+  if( d>(u32)nKey && u ){
+    assert( CORRUPT_DB );
+    /* In a corrupt record entry, the last pMem might have been set up using
+    ** uninitialized memory. Overwrite its value with NULL, to prevent
+    ** warnings from MSAN. */
+    sqlite3VdbeMemSetNull(pMem-1);
+  }
+  assert( u<=pKeyInfo->nKeyField + 1 );
+  p->nField = u;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** This function compares two index or table record keys in the same way
+** as the sqlite3VdbeRecordCompare() routine. Unlike VdbeRecordCompare(),
+** this function deserializes and compares values using the
+** sqlite3VdbeSerialGet() and sqlite3MemCompare() functions. It is used
+** in assert() statements to ensure that the optimized code in
+** sqlite3VdbeRecordCompare() returns results with these two primitives.
+**
+** Return true if the result of comparison is equivalent to desiredResult.
+** Return false if there is a disagreement.
+*/
+static int vdbeRecordCompareDebug(
+  int nKey1, const void *pKey1, /* Left key */
+  const UnpackedRecord *pPKey2, /* Right key */
+  int desiredResult             /* Correct answer */
+){
+  u32 d1;            /* Offset into aKey[] of next data element */
+  u32 idx1;          /* Offset into aKey[] of next header element */
+  u32 szHdr1;        /* Number of bytes in header */
+  int i = 0;
+  int rc = 0;
+  const unsigned char *aKey1 = (const unsigned char *)pKey1;
+  KeyInfo *pKeyInfo;
+  Mem mem1;
+
+  pKeyInfo = pPKey2->pKeyInfo;
+  if( pKeyInfo->db==0 ) return 1;
+  mem1.enc = pKeyInfo->enc;
+  mem1.db = pKeyInfo->db;
+  /* mem1.flags = 0;  // Will be initialized by sqlite3VdbeSerialGet() */
+  VVA_ONLY( mem1.szMalloc = 0; ) /* Only needed by assert() statements */
+
+  /* Compilers may complain that mem1.u.i is potentially uninitialized.
+  ** We could initialize it, as shown here, to silence those complaints.
+  ** But in fact, mem1.u.i will never actually be used uninitialized, and doing
+  ** the unnecessary initialization has a measurable negative performance
+  ** impact, since this routine is a very high runner.  And so, we choose
+  ** to ignore the compiler warnings and leave this variable uninitialized.
+  */
+  /*  mem1.u.i = 0;  // not needed, here to silence compiler warning */
+ 
+  idx1 = getVarint32(aKey1, szHdr1);
+  if( szHdr1>98307 ) return SQLITE_CORRUPT;
+  d1 = szHdr1;
+  assert( pKeyInfo->nAllField>=pPKey2->nField || CORRUPT_DB );
+  assert( pKeyInfo->aSortFlags!=0 );
+  assert( pKeyInfo->nKeyField>0 );
+  assert( idx1<=szHdr1 || CORRUPT_DB );
+  do{
+    u32 serial_type1;
+
+    /* Read the serial types for the next element in each key. */
+    idx1 += getVarint32( aKey1+idx1, serial_type1 );
+
+    /* Verify that there is enough key space remaining to avoid
+    ** a buffer overread.  The "d1+serial_type1+2" subexpression will
+    ** always be greater than or equal to the amount of required key space.
+    ** Use that approximation to avoid the more expensive call to
+    ** sqlite3VdbeSerialTypeLen() in the common case.
+    */
+    if( d1+(u64)serial_type1+2>(u64)nKey1
+     && d1+(u64)sqlite3VdbeSerialTypeLen(serial_type1)>(u64)nKey1
+    ){
+      if( serial_type1>=1
+       && serial_type1<=7
+       && d1+(u64)sqlite3VdbeSerialTypeLen(serial_type1)<=(u64)nKey1+8
+       && CORRUPT_DB
+      ){
+        return 1;  /* corrupt record not detected by
+                   ** sqlite3VdbeRecordCompareWithSkip().  Return true
+                   ** to avoid firing the assert() */
+      }
+      break;
+    }
+
+    /* Extract the values to be compared.
+    */
+    sqlite3VdbeSerialGet(&aKey1[d1], serial_type1, &mem1);
+    d1 += sqlite3VdbeSerialTypeLen(serial_type1);
+
+    /* Do the comparison
+    */
+    rc = sqlite3MemCompare(&mem1, &pPKey2->aMem[i],
+                           pKeyInfo->nAllField>i ? pKeyInfo->aColl[i] : 0);
+    if( rc!=0 ){
+      assert( mem1.szMalloc==0 );  /* See comment below */
+      if( (pKeyInfo->aSortFlags[i] & KEYINFO_ORDER_BIGNULL)
+       && ((mem1.flags & MEM_Null) || (pPKey2->aMem[i].flags & MEM_Null))
+      ){
+        rc = -rc;
+      }
+      if( pKeyInfo->aSortFlags[i] & KEYINFO_ORDER_DESC ){
+        rc = -rc;  /* Invert the result for DESC sort order. */
+      }
+      goto debugCompareEnd;
+    }
+    i++;
+  }while( idx1<szHdr1 && i<pPKey2->nField );
+
+  /* No memory allocation is ever used on mem1.  Prove this using
+  ** the following assert().  If the assert() fails, it indicates a
+  ** memory leak and a need to call sqlite3VdbeMemRelease(&mem1).
+  */
+  assert( mem1.szMalloc==0 );
+
+  /* rc==0 here means that one of the keys ran out of fields and
+  ** all the fields up to that point were equal. Return the default_rc
+  ** value.  */
+  rc = pPKey2->default_rc;
+
+debugCompareEnd:
+  if( desiredResult==0 && rc==0 ) return 1;
+  if( desiredResult<0 && rc<0 ) return 1;
+  if( desiredResult>0 && rc>0 ) return 1;
+  if( CORRUPT_DB ) return 1;
+  if( pKeyInfo->db->mallocFailed ) return 1;
+  return 0;
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Count the number of fields (a.k.a. columns) in the record given by
+** pKey,nKey.  The verify that this count is less than or equal to the
+** limit given by pKeyInfo->nAllField.
+**
+** If this constraint is not satisfied, it means that the high-speed
+** vdbeRecordCompareInt() and vdbeRecordCompareString() routines will
+** not work correctly.  If this assert() ever fires, it probably means
+** that the KeyInfo.nKeyField or KeyInfo.nAllField values were computed
+** incorrectly.
+*/
+static void vdbeAssertFieldCountWithinLimits(
+  int nKey, const void *pKey,   /* The record to verify */
+  const KeyInfo *pKeyInfo       /* Compare size with this KeyInfo */
+){
+  int nField = 0;
+  u32 szHdr;
+  u32 idx;
+  u32 notUsed;
+  const unsigned char *aKey = (const unsigned char*)pKey;
+
+  if( CORRUPT_DB ) return;
+  idx = getVarint32(aKey, szHdr);
+  assert( nKey>=0 );
+  assert( szHdr<=(u32)nKey );
+  while( idx<szHdr ){
+    idx += getVarint32(aKey+idx, notUsed);
+    nField++;
+  }
+  assert( nField <= pKeyInfo->nAllField );
+}
+#else
+# define vdbeAssertFieldCountWithinLimits(A,B,C)
+#endif
+
+/*
+** Both *pMem1 and *pMem2 contain string values. Compare the two values
+** using the collation sequence pColl. As usual, return a negative , zero
+** or positive value if *pMem1 is less than, equal to or greater than
+** *pMem2, respectively. Similar in spirit to "rc = (*pMem1) - (*pMem2);".
+*/
+static int vdbeCompareMemString(
+  const Mem *pMem1,
+  const Mem *pMem2,
+  const CollSeq *pColl,
+  u8 *prcErr                      /* If an OOM occurs, set to SQLITE_NOMEM */
+){
+  if( pMem1->enc==pColl->enc ){
+    /* The strings are already in the correct encoding.  Call the
+     ** comparison function directly */
+    return pColl->xCmp(pColl->pUser,pMem1->n,pMem1->z,pMem2->n,pMem2->z);
+  }else{
+    int rc;
+    const void *v1, *v2;
+    Mem c1;
+    Mem c2;
+    sqlite3VdbeMemInit(&c1, pMem1->db, MEM_Null);
+    sqlite3VdbeMemInit(&c2, pMem1->db, MEM_Null);
+    sqlite3VdbeMemShallowCopy(&c1, pMem1, MEM_Ephem);
+    sqlite3VdbeMemShallowCopy(&c2, pMem2, MEM_Ephem);
+    v1 = sqlite3ValueText((sqlite3_value*)&c1, pColl->enc);
+    v2 = sqlite3ValueText((sqlite3_value*)&c2, pColl->enc);
+    if( (v1==0 || v2==0) ){
+      if( prcErr ) *prcErr = SQLITE_NOMEM_BKPT;
+      rc = 0;
+    }else{
+      rc = pColl->xCmp(pColl->pUser, c1.n, v1, c2.n, v2);
+    }
+    sqlite3VdbeMemReleaseMalloc(&c1);
+    sqlite3VdbeMemReleaseMalloc(&c2);
+    return rc;
+  }
+}
+
+/*
+** The input pBlob is guaranteed to be a Blob that is not marked
+** with MEM_Zero.  Return true if it could be a zero-blob.
+*/
+static int isAllZero(const char *z, int n){
+  int i;
+  for(i=0; i<n; i++){
+    if( z[i] ) return 0;
+  }
+  return 1;
+}
+
+/*
+** Compare two blobs.  Return negative, zero, or positive if the first
+** is less than, equal to, or greater than the second, respectively.
+** If one blob is a prefix of the other, then the shorter is the lessor.
+*/
+SQLITE_NOINLINE int sqlite3BlobCompare(const Mem *pB1, const Mem *pB2){
+  int c;
+  int n1 = pB1->n;
+  int n2 = pB2->n;
+
+  /* It is possible to have a Blob value that has some non-zero content
+  ** followed by zero content.  But that only comes up for Blobs formed
+  ** by the OP_MakeRecord opcode, and such Blobs never get passed into
+  ** sqlite3MemCompare(). */
+  assert( (pB1->flags & MEM_Zero)==0 || n1==0 );
+  assert( (pB2->flags & MEM_Zero)==0 || n2==0 );
+
+  if( (pB1->flags|pB2->flags) & MEM_Zero ){
+    if( pB1->flags & pB2->flags & MEM_Zero ){
+      return pB1->u.nZero - pB2->u.nZero;
+    }else if( pB1->flags & MEM_Zero ){
+      if( !isAllZero(pB2->z, pB2->n) ) return -1;
+      return pB1->u.nZero - n2;
+    }else{
+      if( !isAllZero(pB1->z, pB1->n) ) return +1;
+      return n1 - pB2->u.nZero;
+    }
+  }
+  c = memcmp(pB1->z, pB2->z, n1>n2 ? n2 : n1);
+  if( c ) return c;
+  return n1 - n2;
+}
+
+/* The following two functions are used only within testcase() to prove
+** test coverage.  These functions do no exist for production builds.
+** We must use separate SQLITE_NOINLINE functions here, since otherwise
+** optimizer code movement causes gcov to become very confused.
+*/
+#if  defined(SQLITE_COVERAGE_TEST) || defined(SQLITE_DEBUG)
+static int SQLITE_NOINLINE doubleLt(double a, double b){ return a<b; }
+static int SQLITE_NOINLINE doubleEq(double a, double b){ return a==b; }
+#endif
+
+/*
+** Do a comparison between a 64-bit signed integer and a 64-bit floating-point
+** number.  Return negative, zero, or positive if the first (i64) is less than,
+** equal to, or greater than the second (double).
+*/
+int sqlite3IntFloatCompare(i64 i, double r){
+  if( sqlite3IsNaN(r) ){
+    /* SQLite considers NaN to be a NULL. And all integer values are greater
+    ** than NULL */
+    return 1;
+  }
+  if( sqlite3Config.bUseLongDouble ){
+    LONGDOUBLE_TYPE x = (LONGDOUBLE_TYPE)i;
+    testcase( x<r );
+    testcase( x>r );
+    testcase( x==r );
+    return (x<r) ? -1 : (x>r);
+  }else{
+    i64 y;
+    double s;
+    if( r<-9223372036854775808.0 ) return +1;
+    if( r>=9223372036854775808.0 ) return -1;
+    y = (i64)r;
+    if( i<y ) return -1;
+    if( i>y ) return +1;
+    s = (double)i;
+    testcase( doubleLt(s,r) );
+    testcase( doubleLt(r,s) );
+    testcase( doubleEq(r,s) );
+    return (s<r) ? -1 : (s>r);
+  }
+}
+
+/*
+** Compare the values contained by the two memory cells, returning
+** negative, zero or positive if pMem1 is less than, equal to, or greater
+** than pMem2. Sorting order is NULL's first, followed by numbers (integers
+** and reals) sorted numerically, followed by text ordered by the collating
+** sequence pColl and finally blob's ordered by memcmp().
+**
+** Two NULL values are considered equal by this function.
+*/
+int sqlite3MemCompare(const Mem *pMem1, const Mem *pMem2, const CollSeq *pColl){
+  int f1, f2;
+  int combined_flags;
+
+  f1 = pMem1->flags;
+  f2 = pMem2->flags;
+  combined_flags = f1|f2;
+  assert( !sqlite3VdbeMemIsRowSet(pMem1) && !sqlite3VdbeMemIsRowSet(pMem2) );
+
+  /* If one value is NULL, it is less than the other. If both values
+  ** are NULL, return 0.
+  */
+  if( combined_flags&MEM_Null ){
+    return (f2&MEM_Null) - (f1&MEM_Null);
+  }
+
+  /* At least one of the two values is a number
+  */
+  if( combined_flags&(MEM_Int|MEM_Real|MEM_IntReal) ){
+    testcase( combined_flags & MEM_Int );
+    testcase( combined_flags & MEM_Real );
+    testcase( combined_flags & MEM_IntReal );
+    if( (f1 & f2 & (MEM_Int|MEM_IntReal))!=0 ){
+      testcase( f1 & f2 & MEM_Int );
+      testcase( f1 & f2 & MEM_IntReal );
+      if( pMem1->u.i < pMem2->u.i ) return -1;
+      if( pMem1->u.i > pMem2->u.i ) return +1;
+      return 0;
+    }
+    if( (f1 & f2 & MEM_Real)!=0 ){
+      if( pMem1->u.r < pMem2->u.r ) return -1;
+      if( pMem1->u.r > pMem2->u.r ) return +1;
+      return 0;
+    }
+    if( (f1&(MEM_Int|MEM_IntReal))!=0 ){
+      testcase( f1 & MEM_Int );
+      testcase( f1 & MEM_IntReal );
+      if( (f2&MEM_Real)!=0 ){
+        return sqlite3IntFloatCompare(pMem1->u.i, pMem2->u.r);
+      }else if( (f2&(MEM_Int|MEM_IntReal))!=0 ){
+        if( pMem1->u.i < pMem2->u.i ) return -1;
+        if( pMem1->u.i > pMem2->u.i ) return +1;
+        return 0;
+      }else{
+        return -1;
+      }
+    }
+    if( (f1&MEM_Real)!=0 ){
+      if( (f2&(MEM_Int|MEM_IntReal))!=0 ){
+        testcase( f2 & MEM_Int );
+        testcase( f2 & MEM_IntReal );
+        return -sqlite3IntFloatCompare(pMem2->u.i, pMem1->u.r);
+      }else{
+        return -1;
+      }
+    }
+    return +1;
+  }
+
+  /* If one value is a string and the other is a blob, the string is less.
+  ** If both are strings, compare using the collating functions.
+  */
+  if( combined_flags&MEM_Str ){
+    if( (f1 & MEM_Str)==0 ){
+      return 1;
+    }
+    if( (f2 & MEM_Str)==0 ){
+      return -1;
+    }
+
+    assert( pMem1->enc==pMem2->enc || pMem1->db->mallocFailed );
+    assert( pMem1->enc==SQLITE_UTF8 ||
+            pMem1->enc==SQLITE_UTF16LE || pMem1->enc==SQLITE_UTF16BE );
+
+    /* The collation sequence must be defined at this point, even if
+    ** the user deletes the collation sequence after the vdbe program is
+    ** compiled (this was not always the case).
+    */
+    assert( !pColl || pColl->xCmp );
+
+    if( pColl ){
+      return vdbeCompareMemString(pMem1, pMem2, pColl, 0);
+    }
+    /* If a NULL pointer was passed as the collate function, fall through
+    ** to the blob case and use memcmp().  */
+  }
+
+  /* Both values must be blobs.  Compare using memcmp().  */
+  return sqlite3BlobCompare(pMem1, pMem2);
+}
+
+
+/*
+** The first argument passed to this function is a serial-type that
+** corresponds to an integer - all values between 1 and 9 inclusive
+** except 7. The second points to a buffer containing an integer value
+** serialized according to serial_type. This function deserializes
+** and returns the value.
+*/
+static i64 vdbeRecordDecodeInt(u32 serial_type, const u8 *aKey){
+  u32 y;
+  assert( CORRUPT_DB || (serial_type>=1 && serial_type<=9 && serial_type!=7) );
+  switch( serial_type ){
+    case 0:
+    case 1:
+      testcase( aKey[0]&0x80 );
+      return ONE_BYTE_INT(aKey);
+    case 2:
+      testcase( aKey[0]&0x80 );
+      return TWO_BYTE_INT(aKey);
+    case 3:
+      testcase( aKey[0]&0x80 );
+      return THREE_BYTE_INT(aKey);
+    case 4: {
+      testcase( aKey[0]&0x80 );
+      y = FOUR_BYTE_UINT(aKey);
+      return (i64)*(int*)&y;
+    }
+    case 5: {
+      testcase( aKey[0]&0x80 );
+      return FOUR_BYTE_UINT(aKey+2) + (((i64)1)<<32)*TWO_BYTE_INT(aKey);
+    }
+    case 6: {
+      u64 x = FOUR_BYTE_UINT(aKey);
+      testcase( aKey[0]&0x80 );
+      x = (x<<32) | FOUR_BYTE_UINT(aKey+4);
+      return (i64)*(i64*)&x;
+    }
+  }
+
+  return (serial_type - 8);
+}
+
+/*
+** This function compares the two table rows or index records
+** specified by {nKey1, pKey1} and pPKey2.  It returns a negative, zero
+** or positive integer if key1 is less than, equal to or
+** greater than key2.  The {nKey1, pKey1} key must be a blob
+** created by the OP_MakeRecord opcode of the VDBE.  The pPKey2
+** key must be a parsed key such as obtained from
+** sqlite3VdbeParseRecord.
+**
+** If argument bSkip is non-zero, it is assumed that the caller has already
+** determined that the first fields of the keys are equal.
+**
+** Key1 and Key2 do not have to contain the same number of fields. If all
+** fields that appear in both keys are equal, then pPKey2->default_rc is
+** returned.
+**
+** If database corruption is discovered, set pPKey2->errCode to
+** SQLITE_CORRUPT and return 0. If an OOM error is encountered,
+** pPKey2->errCode is set to SQLITE_NOMEM and, if it is not NULL, the
+** malloc-failed flag set on database handle (pPKey2->pKeyInfo->db).
+*/
+int sqlite3VdbeRecordCompareWithSkip(
+  int nKey1, const void *pKey1,   /* Left key */
+  UnpackedRecord *pPKey2,         /* Right key */
+  int bSkip                       /* If true, skip the first field */
+){
+  u32 d1;                         /* Offset into aKey[] of next data element */
+  int i;                          /* Index of next field to compare */
+  u32 szHdr1;                     /* Size of record header in bytes */
+  u32 idx1;                       /* Offset of first type in header */
+  int rc = 0;                     /* Return value */
+  Mem *pRhs = pPKey2->aMem;       /* Next field of pPKey2 to compare */
+  KeyInfo *pKeyInfo;
+  const unsigned char *aKey1 = (const unsigned char *)pKey1;
+  Mem mem1;
+
+  /* If bSkip is true, then the caller has already determined that the first
+  ** two elements in the keys are equal. Fix the various stack variables so
+  ** that this routine begins comparing at the second field. */
+  if( bSkip ){
+    u32 s1 = aKey1[1];
+    if( s1<0x80 ){
+      idx1 = 2;
+    }else{
+      idx1 = 1 + sqlite3GetVarint32(&aKey1[1], &s1);
+    }
+    szHdr1 = aKey1[0];
+    d1 = szHdr1 + sqlite3VdbeSerialTypeLen(s1);
+    i = 1;
+    pRhs++;
+  }else{
+    if( (szHdr1 = aKey1[0])<0x80 ){
+      idx1 = 1;
+    }else{
+      idx1 = sqlite3GetVarint32(aKey1, &szHdr1);
+    }
+    d1 = szHdr1;
+    i = 0;
+  }
+  if( d1>(unsigned)nKey1 ){
+    pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
+    return 0;  /* Corruption */
+  }
+
+  VVA_ONLY( mem1.szMalloc = 0; ) /* Only needed by assert() statements */
+  assert( pPKey2->pKeyInfo->nAllField>=pPKey2->nField
+       || CORRUPT_DB );
+  assert( pPKey2->pKeyInfo->aSortFlags!=0 );
+  assert( pPKey2->pKeyInfo->nKeyField>0 );
+  assert( idx1<=szHdr1 || CORRUPT_DB );
+  while( 1 /*exit-by-break*/ ){
+    u32 serial_type;
+
+    /* RHS is an integer */
+    if( pRhs->flags & (MEM_Int|MEM_IntReal) ){
+      testcase( pRhs->flags & MEM_Int );
+      testcase( pRhs->flags & MEM_IntReal );
+      serial_type = aKey1[idx1];
+      testcase( serial_type==12 );
+      if( serial_type>=10 ){
+        rc = serial_type==10 ? -1 : +1;
+      }else if( serial_type==0 ){
+        rc = -1;
+      }else if( serial_type==7 ){
+        sqlite3VdbeSerialGet(&aKey1[d1], serial_type, &mem1);
+        rc = -sqlite3IntFloatCompare(pRhs->u.i, mem1.u.r);
+      }else{
+        i64 lhs = vdbeRecordDecodeInt(serial_type, &aKey1[d1]);
+        i64 rhs = pRhs->u.i;
+        if( lhs<rhs ){
+          rc = -1;
+        }else if( lhs>rhs ){
+          rc = +1;
+        }
+      }
+    }
+
+    /* RHS is real */
+    else if( pRhs->flags & MEM_Real ){
+      serial_type = aKey1[idx1];
+      if( serial_type>=10 ){
+        /* Serial types 12 or greater are strings and blobs (greater than
+        ** numbers). Types 10 and 11 are currently "reserved for future
+        ** use", so it doesn't really matter what the results of comparing
+        ** them to numeric values are.  */
+        rc = serial_type==10 ? -1 : +1;
+      }else if( serial_type==0 ){
+        rc = -1;
+      }else{
+        sqlite3VdbeSerialGet(&aKey1[d1], serial_type, &mem1);
+        if( serial_type==7 ){
+          if( mem1.u.r<pRhs->u.r ){
+            rc = -1;
+          }else if( mem1.u.r>pRhs->u.r ){
+            rc = +1;
+          }
+        }else{
+          rc = sqlite3IntFloatCompare(mem1.u.i, pRhs->u.r);
+        }
+      }
+    }
+
+    /* RHS is a string */
+    else if( pRhs->flags & MEM_Str ){
+      getVarint32NR(&aKey1[idx1], serial_type);
+      testcase( serial_type==12 );
+      if( serial_type<12 ){
+        rc = -1;
+      }else if( !(serial_type & 0x01) ){
+        rc = +1;
+      }else{
+        mem1.n = (serial_type - 12) / 2;
+        testcase( (d1+mem1.n)==(unsigned)nKey1 );
+        testcase( (d1+mem1.n+1)==(unsigned)nKey1 );
+        if( (d1+mem1.n) > (unsigned)nKey1
+         || (pKeyInfo = pPKey2->pKeyInfo)->nAllField<=i
+        ){
+          pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
+          return 0;                /* Corruption */
+        }else if( pKeyInfo->aColl[i] ){
+          mem1.enc = pKeyInfo->enc;
+          mem1.db = pKeyInfo->db;
+          mem1.flags = MEM_Str;
+          mem1.z = (char*)&aKey1[d1];
+          rc = vdbeCompareMemString(
+              &mem1, pRhs, pKeyInfo->aColl[i], &pPKey2->errCode
+          );
+        }else{
+          int nCmp = MIN(mem1.n, pRhs->n);
+          rc = memcmp(&aKey1[d1], pRhs->z, nCmp);
+          if( rc==0 ) rc = mem1.n - pRhs->n;
+        }
+      }
+    }
+
+    /* RHS is a blob */
+    else if( pRhs->flags & MEM_Blob ){
+      assert( (pRhs->flags & MEM_Zero)==0 || pRhs->n==0 );
+      getVarint32NR(&aKey1[idx1], serial_type);
+      testcase( serial_type==12 );
+      if( serial_type<12 || (serial_type & 0x01) ){
+        rc = -1;
+      }else{
+        int nStr = (serial_type - 12) / 2;
+        testcase( (d1+nStr)==(unsigned)nKey1 );
+        testcase( (d1+nStr+1)==(unsigned)nKey1 );
+        if( (d1+nStr) > (unsigned)nKey1 ){
+          pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
+          return 0;                /* Corruption */
+        }else if( pRhs->flags & MEM_Zero ){
+          if( !isAllZero((const char*)&aKey1[d1],nStr) ){
+            rc = 1;
+          }else{
+            rc = nStr - pRhs->u.nZero;
+          }
+        }else{
+          int nCmp = MIN(nStr, pRhs->n);
+          rc = memcmp(&aKey1[d1], pRhs->z, nCmp);
+          if( rc==0 ) rc = nStr - pRhs->n;
+        }
+      }
+    }
+
+    /* RHS is null */
+    else{
+      serial_type = aKey1[idx1];
+      rc = (serial_type!=0 && serial_type!=10);
+    }
+
+    if( rc!=0 ){
+      int sortFlags = pPKey2->pKeyInfo->aSortFlags[i];
+      if( sortFlags ){
+        if( (sortFlags & KEYINFO_ORDER_BIGNULL)==0
+         || ((sortFlags & KEYINFO_ORDER_DESC)
+           !=(serial_type==0 || (pRhs->flags&MEM_Null)))
+        ){
+          rc = -rc;
+        }
+      }
+      assert( vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, rc) );
+      assert( mem1.szMalloc==0 );  /* See comment below */
+      return rc;
+    }
+
+    i++;
+    if( i==pPKey2->nField ) break;
+    pRhs++;
+    d1 += sqlite3VdbeSerialTypeLen(serial_type);
+    if( d1>(unsigned)nKey1 ) break;
+    idx1 += sqlite3VarintLen(serial_type);
+    if( idx1>=(unsigned)szHdr1 ){
+      pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
+      return 0;  /* Corrupt index */
+    }
+  }
+
+  /* No memory allocation is ever used on mem1.  Prove this using
+  ** the following assert().  If the assert() fails, it indicates a
+  ** memory leak and a need to call sqlite3VdbeMemRelease(&mem1).  */
+  assert( mem1.szMalloc==0 );
+
+  /* rc==0 here means that one or both of the keys ran out of fields and
+  ** all the fields up to that point were equal. Return the default_rc
+  ** value.  */
+  assert( CORRUPT_DB
+       || vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, pPKey2->default_rc)
+       || pPKey2->pKeyInfo->db->mallocFailed
+  );
+  pPKey2->eqSeen = 1;
+  return pPKey2->default_rc;
+}
+int sqlite3VdbeRecordCompare(
+  int nKey1, const void *pKey1,   /* Left key */
+  UnpackedRecord *pPKey2          /* Right key */
+){
+  return sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, pPKey2, 0);
+}
+
+
+/*
+** This function is an optimized version of sqlite3VdbeRecordCompare()
+** that (a) the first field of pPKey2 is an integer, and (b) the
+** size-of-header varint at the start of (pKey1/nKey1) fits in a single
+** byte (i.e. is less than 128).
+**
+** To avoid concerns about buffer overreads, this routine is only used
+** on schemas where the maximum valid header size is 63 bytes or less.
+*/
+static int vdbeRecordCompareInt(
+  int nKey1, const void *pKey1, /* Left key */
+  UnpackedRecord *pPKey2        /* Right key */
+){
+  const u8 *aKey = &((const u8*)pKey1)[*(const u8*)pKey1 & 0x3F];
+  int serial_type = ((const u8*)pKey1)[1];
+  int res;
+  u32 y;
+  u64 x;
+  i64 v;
+  i64 lhs;
+
+  vdbeAssertFieldCountWithinLimits(nKey1, pKey1, pPKey2->pKeyInfo);
+  assert( (*(u8*)pKey1)<=0x3F || CORRUPT_DB );
+  switch( serial_type ){
+    case 1: { /* 1-byte signed integer */
+      lhs = ONE_BYTE_INT(aKey);
+      testcase( lhs<0 );
+      break;
+    }
+    case 2: { /* 2-byte signed integer */
+      lhs = TWO_BYTE_INT(aKey);
+      testcase( lhs<0 );
+      break;
+    }
+    case 3: { /* 3-byte signed integer */
+      lhs = THREE_BYTE_INT(aKey);
+      testcase( lhs<0 );
+      break;
+    }
+    case 4: { /* 4-byte signed integer */
+      y = FOUR_BYTE_UINT(aKey);
+      lhs = (i64)*(int*)&y;
+      testcase( lhs<0 );
+      break;
+    }
+    case 5: { /* 6-byte signed integer */
+      lhs = FOUR_BYTE_UINT(aKey+2) + (((i64)1)<<32)*TWO_BYTE_INT(aKey);
+      testcase( lhs<0 );
+      break;
+    }
+    case 6: { /* 8-byte signed integer */
+      x = FOUR_BYTE_UINT(aKey);
+      x = (x<<32) | FOUR_BYTE_UINT(aKey+4);
+      lhs = *(i64*)&x;
+      testcase( lhs<0 );
+      break;
+    }
+    case 8:
+      lhs = 0;
+      break;
+    case 9:
+      lhs = 1;
+      break;
+
+    /* This case could be removed without changing the results of running
+    ** this code. Including it causes gcc to generate a faster switch
+    ** statement (since the range of switch targets now starts at zero and
+    ** is contiguous) but does not cause any duplicate code to be generated
+    ** (as gcc is clever enough to combine the two like cases). Other
+    ** compilers might be similar.  */
+    case 0: case 7:
+      return sqlite3VdbeRecordCompare(nKey1, pKey1, pPKey2);
+
+    default:
+      return sqlite3VdbeRecordCompare(nKey1, pKey1, pPKey2);
+  }
+
+  assert( pPKey2->u.i == pPKey2->aMem[0].u.i );
+  v = pPKey2->u.i;
+  if( v>lhs ){
+    res = pPKey2->r1;
+  }else if( v<lhs ){
+    res = pPKey2->r2;
+  }else if( pPKey2->nField>1 ){
+    /* The first fields of the two keys are equal. Compare the trailing
+    ** fields.  */
+    res = sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, pPKey2, 1);
+  }else{
+    /* The first fields of the two keys are equal and there are no trailing
+    ** fields. Return pPKey2->default_rc in this case. */
+    res = pPKey2->default_rc;
+    pPKey2->eqSeen = 1;
+  }
+
+  assert( vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, res) );
+  return res;
+}
+
+/*
+** This function is an optimized version of sqlite3VdbeRecordCompare()
+** that (a) the first field of pPKey2 is a string, that (b) the first field
+** uses the collation sequence BINARY and (c) that the size-of-header varint
+** at the start of (pKey1/nKey1) fits in a single byte.
+*/
+static int vdbeRecordCompareString(
+  int nKey1, const void *pKey1, /* Left key */
+  UnpackedRecord *pPKey2        /* Right key */
+){
+  const u8 *aKey1 = (const u8*)pKey1;
+  int serial_type;
+  int res;
+
+  assert( pPKey2->aMem[0].flags & MEM_Str );
+  assert( pPKey2->aMem[0].n == pPKey2->n );
+  assert( pPKey2->aMem[0].z == pPKey2->u.z );
+  vdbeAssertFieldCountWithinLimits(nKey1, pKey1, pPKey2->pKeyInfo);
+  serial_type = (signed char)(aKey1[1]);
+
+vrcs_restart:
+  if( serial_type<12 ){
+    if( serial_type<0 ){
+      sqlite3GetVarint32(&aKey1[1], (u32*)&serial_type);
+      if( serial_type>=12 ) goto vrcs_restart;
+      assert( CORRUPT_DB );
+    }
+    res = pPKey2->r1;      /* (pKey1/nKey1) is a number or a null */
+  }else if( !(serial_type & 0x01) ){
+    res = pPKey2->r2;      /* (pKey1/nKey1) is a blob */
+  }else{
+    int nCmp;
+    int nStr;
+    int szHdr = aKey1[0];
+
+    nStr = (serial_type-12) / 2;
+    if( (szHdr + nStr) > nKey1 ){
+      pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
+      return 0;    /* Corruption */
+    }
+    nCmp = MIN( pPKey2->n, nStr );
+    res = memcmp(&aKey1[szHdr], pPKey2->u.z, nCmp);
+
+    if( res>0 ){
+      res = pPKey2->r2;
+    }else if( res<0 ){
+      res = pPKey2->r1;
+    }else{
+      res = nStr - pPKey2->n;
+      if( res==0 ){
+        if( pPKey2->nField>1 ){
+          res = sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, pPKey2, 1);
+        }else{
+          res = pPKey2->default_rc;
+          pPKey2->eqSeen = 1;
+        }
+      }else if( res>0 ){
+        res = pPKey2->r2;
+      }else{
+        res = pPKey2->r1;
+      }
+    }
+  }
+
+  assert( vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, res)
+       || CORRUPT_DB
+       || pPKey2->pKeyInfo->db->mallocFailed
+  );
+  return res;
+}
+
+/*
+** Return a pointer to an sqlite3VdbeRecordCompare() compatible function
+** suitable for comparing serialized records to the unpacked record passed
+** as the only argument.
+*/
+RecordCompare sqlite3VdbeFindCompare(UnpackedRecord *p){
+  /* varintRecordCompareInt() and varintRecordCompareString() both assume
+  ** that the size-of-header varint that occurs at the start of each record
+  ** fits in a single byte (i.e. is 127 or less). varintRecordCompareInt()
+  ** also assumes that it is safe to overread a buffer by at least the
+  ** maximum possible legal header size plus 8 bytes. Because there is
+  ** guaranteed to be at least 74 (but not 136) bytes of padding following each
+  ** buffer passed to varintRecordCompareInt() this makes it convenient to
+  ** limit the size of the header to 64 bytes in cases where the first field
+  ** is an integer.
+  **
+  ** The easiest way to enforce this limit is to consider only records with
+  ** 13 fields or less. If the first field is an integer, the maximum legal
+  ** header size is (12*5 + 1 + 1) bytes.  */
+  if( p->pKeyInfo->nAllField<=13 ){
+    int flags = p->aMem[0].flags;
+    if( p->pKeyInfo->aSortFlags[0] ){
+      if( p->pKeyInfo->aSortFlags[0] & KEYINFO_ORDER_BIGNULL ){
+        return sqlite3VdbeRecordCompare;
+      }
+      p->r1 = 1;
+      p->r2 = -1;
+    }else{
+      p->r1 = -1;
+      p->r2 = 1;
+    }
+    if( (flags & MEM_Int) ){
+      p->u.i = p->aMem[0].u.i;
+      return vdbeRecordCompareInt;
+    }
+    testcase( flags & MEM_Real );
+    testcase( flags & MEM_Null );
+    testcase( flags & MEM_Blob );
+    if( (flags & (MEM_Real|MEM_IntReal|MEM_Null|MEM_Blob))==0
+     && p->pKeyInfo->aColl[0]==0
+    ){
+      assert( flags & MEM_Str );
+      p->u.z = p->aMem[0].z;
+      p->n = p->aMem[0].n;
+      return vdbeRecordCompareString;
+    }
+  }
+
+  return sqlite3VdbeRecordCompare;
+}
+
+/*
+** pCur points at an index entry created using the OP_MakeRecord opcode.
+** Read the rowid (the last field in the record) and store it in *rowid.
+** Return SQLITE_OK if everything works, or an error code otherwise.
+**
+** pCur might be pointing to text obtained from a corrupt database file.
+** So the content cannot be trusted.  Do appropriate checks on the content.
+*/
+int sqlite3VdbeIdxRowid(sqlite3 *db, BtCursor *pCur, i64 *rowid){
+  i64 nCellKey = 0;
+  int rc;
+  u32 szHdr;        /* Size of the header */
+  u32 typeRowid;    /* Serial type of the rowid */
+  u32 lenRowid;     /* Size of the rowid */
+  Mem m, v;
+
+  /* Get the size of the index entry.  Only indices entries of less
+  ** than 2GiB are support - anything large must be database corruption.
+  ** Any corruption is detected in sqlite3BtreeParseCellPtr(), though, so
+  ** this code can safely assume that nCellKey is 32-bits 
+  */
+  assert( sqlite3BtreeCursorIsValid(pCur) );
+  nCellKey = sqlite3BtreePayloadSize(pCur);
+  assert( (nCellKey & SQLITE_MAX_U32)==(u64)nCellKey );
+
+  /* Read in the complete content of the index entry */
+  sqlite3VdbeMemInit(&m, db, 0);
+  rc = sqlite3VdbeMemFromBtreeZeroOffset(pCur, (u32)nCellKey, &m);
+  if( rc ){
+    return rc;
+  }
+
+  /* The index entry must begin with a header size */
+  getVarint32NR((u8*)m.z, szHdr);
+  testcase( szHdr==3 );
+  testcase( szHdr==(u32)m.n );
+  testcase( szHdr>0x7fffffff );
+  assert( m.n>=0 );
+  if( unlikely(szHdr<3 || szHdr>(unsigned)m.n) ){
+    goto idx_rowid_corruption;
+  }
+
+  /* The last field of the index should be an integer - the ROWID.
+  ** Verify that the last entry really is an integer. */
+  getVarint32NR((u8*)&m.z[szHdr-1], typeRowid);
+  testcase( typeRowid==1 );
+  testcase( typeRowid==2 );
+  testcase( typeRowid==3 );
+  testcase( typeRowid==4 );
+  testcase( typeRowid==5 );
+  testcase( typeRowid==6 );
+  testcase( typeRowid==8 );
+  testcase( typeRowid==9 );
+  if( unlikely(typeRowid<1 || typeRowid>9 || typeRowid==7) ){
+    goto idx_rowid_corruption;
+  }
+  lenRowid = sqlite3SmallTypeSizes[typeRowid];
+  testcase( (u32)m.n==szHdr+lenRowid );
+  if( unlikely((u32)m.n<szHdr+lenRowid) ){
+    goto idx_rowid_corruption;
+  }
+
+  /* Fetch the integer off the end of the index record */
+  sqlite3VdbeSerialGet((u8*)&m.z[m.n-lenRowid], typeRowid, &v);
+  *rowid = v.u.i;
+  sqlite3VdbeMemReleaseMalloc(&m);
+  return SQLITE_OK;
+
+  /* Jump here if database corruption is detected after m has been
+  ** allocated.  Free the m object and return SQLITE_CORRUPT. */
+idx_rowid_corruption:
+  testcase( m.szMalloc!=0 );
+  sqlite3VdbeMemReleaseMalloc(&m);
+  return SQLITE_CORRUPT_BKPT;
+}
+
+/*
+** Compare the key of the index entry that cursor pC is pointing to against
+** the key string in pUnpacked.  Write into *pRes a number
+** that is negative, zero, or positive if pC is less than, equal to,
+** or greater than pUnpacked.  Return SQLITE_OK on success.
+**
+** pUnpacked is either created without a rowid or is truncated so that it
+** omits the rowid at the end.  The rowid at the end of the index entry
+** is ignored as well.  Hence, this routine only compares the prefixes
+** of the keys prior to the final rowid, not the entire key.
+*/
+int sqlite3VdbeIdxKeyCompare(
+  sqlite3 *db,                     /* Database connection */
+  VdbeCursor *pC,                  /* The cursor to compare against */
+  UnpackedRecord *pUnpacked,       /* Unpacked version of key */
+  int *res                         /* Write the comparison result here */
+){
+  i64 nCellKey = 0;
+  int rc;
+  BtCursor *pCur;
+  Mem m;
+
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCur = pC->uc.pCursor;
+  assert( sqlite3BtreeCursorIsValid(pCur) );
+  nCellKey = sqlite3BtreePayloadSize(pCur);
+  /* nCellKey will always be between 0 and 0xffffffff because of the way
+  ** that btreeParseCellPtr() and sqlite3GetVarint32() are implemented */
+  if( nCellKey<=0 || nCellKey>0x7fffffff ){
+    *res = 0;
+    return SQLITE_CORRUPT_BKPT;
+  }
+  sqlite3VdbeMemInit(&m, db, 0);
+  rc = sqlite3VdbeMemFromBtreeZeroOffset(pCur, (u32)nCellKey, &m);
+  if( rc ){
+    return rc;
+  }
+  *res = sqlite3VdbeRecordCompareWithSkip(m.n, m.z, pUnpacked, 0);
+  sqlite3VdbeMemReleaseMalloc(&m);
+  return SQLITE_OK;
+}
+
+/*
+** This routine sets the value to be returned by subsequent calls to
+** sqlite3_changes() on the database handle 'db'.
+*/
+void sqlite3VdbeSetChanges(sqlite3 *db, i64 nChange){
+  assert( sqlite3_mutex_held(db->mutex) );
+  db->nChange = nChange;
+  db->nTotalChange += nChange;
+}
+
+/*
+** Set a flag in the vdbe to update the change counter when it is finalised
+** or reset.
+*/
+void sqlite3VdbeCountChanges(Vdbe *v){
+  v->changeCntOn = 1;
+}
+
+/*
+** Mark every prepared statement associated with a database connection
+** as expired.
+**
+** An expired statement means that recompilation of the statement is
+** recommend.  Statements expire when things happen that make their
+** programs obsolete.  Removing user-defined functions or collating
+** sequences, or changing an authorization function are the types of
+** things that make prepared statements obsolete.
+**
+** If iCode is 1, then expiration is advisory.  The statement should
+** be reprepared before being restarted, but if it is already running
+** it is allowed to run to completion.
+**
+** Internally, this function just sets the Vdbe.expired flag on all
+** prepared statements.  The flag is set to 1 for an immediate expiration
+** and set to 2 for an advisory expiration.
+*/
+void sqlite3ExpirePreparedStatements(sqlite3 *db, int iCode){
+  Vdbe *p;
+  for(p = db->pVdbe; p; p=p->pVNext){
+    p->expired = iCode+1;
+  }
+}
+
+/*
+** Return the database associated with the Vdbe.
+*/
+sqlite3 *sqlite3VdbeDb(Vdbe *v){
+  return v->db;
+}
+
+/*
+** Return the SQLITE_PREPARE flags for a Vdbe.
+*/
+u8 sqlite3VdbePrepareFlags(Vdbe *v){
+  return v->prepFlags;
+}
+
+/*
+** Return a pointer to an sqlite3_value structure containing the value bound
+** parameter iVar of VM v. Except, if the value is an SQL NULL, return
+** 0 instead. Unless it is NULL, apply affinity aff (one of the SQLITE_AFF_*
+** constants) to the value before returning it.
+**
+** The returned value must be freed by the caller using sqlite3ValueFree().
+*/
+sqlite3_value *sqlite3VdbeGetBoundValue(Vdbe *v, int iVar, u8 aff){
+  assert( iVar>0 );
+  if( v ){
+    Mem *pMem = &v->aVar[iVar-1];
+    assert( (v->db->flags & SQLITE_EnableQPSG)==0 );
+    if( 0==(pMem->flags & MEM_Null) ){
+      sqlite3_value *pRet = sqlite3ValueNew(v->db);
+      if( pRet ){
+        sqlite3VdbeMemCopy((Mem *)pRet, pMem);
+        sqlite3ValueApplyAffinity(pRet, aff, SQLITE_UTF8);
+      }
+      return pRet;
+    }
+  }
+  return 0;
+}
+
+/*
+** Configure SQL variable iVar so that binding a new value to it signals
+** to sqlite3_reoptimize() that re-preparing the statement may result
+** in a better query plan.
+*/
+void sqlite3VdbeSetVarmask(Vdbe *v, int iVar){
+  assert( iVar>0 );
+  assert( (v->db->flags & SQLITE_EnableQPSG)==0 );
+  if( iVar>=32 ){
+    v->expmask |= 0x80000000;
+  }else{
+    v->expmask |= ((u32)1 << (iVar-1));
+  }
+}
+
+/*
+** Cause a function to throw an error if it was call from OP_PureFunc
+** rather than OP_Function.
+**
+** OP_PureFunc means that the function must be deterministic, and should
+** throw an error if it is given inputs that would make it non-deterministic.
+** This routine is invoked by date/time functions that use non-deterministic
+** features such as 'now'.
+*/
+int sqlite3NotPureFunc(sqlite3_context *pCtx){
+  const VdbeOp *pOp;
+#ifdef SQLITE_ENABLE_STAT4
+  if( pCtx->pVdbe==0 ) return 1;
+#endif
+  pOp = pCtx->pVdbe->aOp + pCtx->iOp;
+  if( pOp->opcode==OP_PureFunc ){
+    const char *zContext;
+    char *zMsg;
+    if( pOp->p5 & NC_IsCheck ){
+      zContext = "a CHECK constraint";
+    }else if( pOp->p5 & NC_GenCol ){
+      zContext = "a generated column";
+    }else{
+      zContext = "an index";
+    }
+    zMsg = sqlite3_mprintf("non-deterministic use of %s() in %s",
+                           pCtx->pFunc->zName, zContext);
+    sqlite3_result_error(pCtx, zMsg, -1);
+    sqlite3_free(zMsg);
+    return 0;
+  }
+  return 1;
+}
+
+#if defined(SQLITE_ENABLE_CURSOR_HINTS) && defined(SQLITE_DEBUG)
+/*
+** This Walker callback is used to help verify that calls to
+** sqlite3BtreeCursorHint() with opcode BTREE_HINT_RANGE have
+** byte-code register values correctly initialized.
+*/
+int sqlite3CursorRangeHintExprCheck(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_REGISTER ){
+    assert( (pWalker->u.aMem[pExpr->iTable].flags & MEM_Undefined)==0 );
+  }
+  return WRC_Continue;
+}
+#endif /* SQLITE_ENABLE_CURSOR_HINTS && SQLITE_DEBUG */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Transfer error message text from an sqlite3_vtab.zErrMsg (text stored
+** in memory obtained from sqlite3_malloc) into a Vdbe.zErrMsg (text stored
+** in memory obtained from sqlite3DbMalloc).
+*/
+void sqlite3VtabImportErrmsg(Vdbe *p, sqlite3_vtab *pVtab){
+  if( pVtab->zErrMsg ){
+    sqlite3 *db = p->db;
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = sqlite3DbStrDup(db, pVtab->zErrMsg);
+    sqlite3_free(pVtab->zErrMsg);
+    pVtab->zErrMsg = 0;
+  }
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+
+/*
+** If the second argument is not NULL, release any allocations associated
+** with the memory cells in the p->aMem[] array. Also free the UnpackedRecord
+** structure itself, using sqlite3DbFree().
+**
+** This function is used to free UnpackedRecord structures allocated by
+** the vdbeUnpackRecord() function found in vdbeapi.c.
+*/
+static void vdbeFreeUnpacked(sqlite3 *db, int nField, UnpackedRecord *p){
+  assert( db!=0 );
+  if( p ){
+    int i;
+    for(i=0; i<nField; i++){
+      Mem *pMem = &p->aMem[i];
+      if( pMem->zMalloc ) sqlite3VdbeMemReleaseMalloc(pMem);
+    }
+    sqlite3DbNNFreeNN(db, p);
+  }
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** Invoke the pre-update hook. If this is an UPDATE or DELETE pre-update call,
+** then cursor passed as the second argument should point to the row about
+** to be update or deleted. If the application calls sqlite3_preupdate_old(),
+** the required value will be read from the row the cursor points to.
+*/
+void sqlite3VdbePreUpdateHook(
+  Vdbe *v,                        /* Vdbe pre-update hook is invoked by */
+  VdbeCursor *pCsr,               /* Cursor to grab old.* values from */
+  int op,                         /* SQLITE_INSERT, UPDATE or DELETE */
+  const char *zDb,                /* Database name */
+  Table *pTab,                    /* Modified table */
+  i64 iKey1,                      /* Initial key value */
+  int iReg,                       /* Register for new.* record */
+  int iBlobWrite
+){
+  sqlite3 *db = v->db;
+  i64 iKey2;
+  PreUpdate preupdate;
+  const char *zTbl = pTab->zName;
+  static const u8 fakeSortOrder = 0;
+#ifdef SQLITE_DEBUG
+  int nRealCol;
+  if( pTab->tabFlags & TF_WithoutRowid ){
+    nRealCol = sqlite3PrimaryKeyIndex(pTab)->nColumn;
+  }else if( pTab->tabFlags & TF_HasVirtual ){
+    nRealCol = pTab->nNVCol;
+  }else{
+    nRealCol = pTab->nCol;
+  }
+#endif
+
+  assert( db->pPreUpdate==0 );
+  memset(&preupdate, 0, sizeof(PreUpdate));
+  if( HasRowid(pTab)==0 ){
+    iKey1 = iKey2 = 0;
+    preupdate.pPk = sqlite3PrimaryKeyIndex(pTab);
+  }else{
+    if( op==SQLITE_UPDATE ){
+      iKey2 = v->aMem[iReg].u.i;
+    }else{
+      iKey2 = iKey1;
+    }
+  }
+
+  assert( pCsr!=0 );
+  assert( pCsr->eCurType==CURTYPE_BTREE );
+  assert( pCsr->nField==nRealCol
+       || (pCsr->nField==nRealCol+1 && op==SQLITE_DELETE && iReg==-1)
+  );
+
+  preupdate.v = v;
+  preupdate.pCsr = pCsr;
+  preupdate.op = op;
+  preupdate.iNewReg = iReg;
+  preupdate.keyinfo.db = db;
+  preupdate.keyinfo.enc = ENC(db);
+  preupdate.keyinfo.nKeyField = pTab->nCol;
+  preupdate.keyinfo.aSortFlags = (u8*)&fakeSortOrder;
+  preupdate.iKey1 = iKey1;
+  preupdate.iKey2 = iKey2;
+  preupdate.pTab = pTab;
+  preupdate.iBlobWrite = iBlobWrite;
+
+  db->pPreUpdate = &preupdate;
+  db->xPreUpdateCallback(db->pPreUpdateArg, db, op, zDb, zTbl, iKey1, iKey2);
+  db->pPreUpdate = 0;
+  sqlite3DbFree(db, preupdate.aRecord);
+  vdbeFreeUnpacked(db, preupdate.keyinfo.nKeyField+1, preupdate.pUnpacked);
+  vdbeFreeUnpacked(db, preupdate.keyinfo.nKeyField+1, preupdate.pNewUnpacked);
+  if( preupdate.aNew ){
+    int i;
+    for(i=0; i<pCsr->nField; i++){
+      sqlite3VdbeMemRelease(&preupdate.aNew[i]);
+    }
+    sqlite3DbNNFreeNN(db, preupdate.aNew);
+  }
+}
+#endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
diff --git a/src/vdbeblob.c b/src/vdbeblob.c
new file mode 100644
index 0000000..522447d
--- /dev/null
+++ b/src/vdbeblob.c
@@ -0,0 +1,515 @@
+/*
+** 2007 May 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to implement incremental BLOB I/O.
+*/
+
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#ifndef SQLITE_OMIT_INCRBLOB
+
+/*
+** Valid sqlite3_blob* handles point to Incrblob structures.
+*/
+typedef struct Incrblob Incrblob;
+struct Incrblob {
+  int nByte;              /* Size of open blob, in bytes */
+  int iOffset;            /* Byte offset of blob in cursor data */
+  u16 iCol;               /* Table column this handle is open on */
+  BtCursor *pCsr;         /* Cursor pointing at blob row */
+  sqlite3_stmt *pStmt;    /* Statement holding cursor open */
+  sqlite3 *db;            /* The associated database */
+  char *zDb;              /* Database name */
+  Table *pTab;            /* Table object */
+};
+
+
+/*
+** This function is used by both blob_open() and blob_reopen(). It seeks
+** the b-tree cursor associated with blob handle p to point to row iRow.
+** If successful, SQLITE_OK is returned and subsequent calls to
+** sqlite3_blob_read() or sqlite3_blob_write() access the specified row.
+**
+** If an error occurs, or if the specified row does not exist or does not
+** contain a value of type TEXT or BLOB in the column nominated when the
+** blob handle was opened, then an error code is returned and *pzErr may
+** be set to point to a buffer containing an error message. It is the
+** responsibility of the caller to free the error message buffer using
+** sqlite3DbFree().
+**
+** If an error does occur, then the b-tree cursor is closed. All subsequent
+** calls to sqlite3_blob_read(), blob_write() or blob_reopen() will 
+** immediately return SQLITE_ABORT.
+*/
+static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
+  int rc;                         /* Error code */
+  char *zErr = 0;                 /* Error message */
+  Vdbe *v = (Vdbe *)p->pStmt;
+
+  /* Set the value of register r[1] in the SQL statement to integer iRow. 
+  ** This is done directly as a performance optimization
+  */
+  sqlite3VdbeMemSetInt64(&v->aMem[1], iRow);
+
+  /* If the statement has been run before (and is paused at the OP_ResultRow)
+  ** then back it up to the point where it does the OP_NotExists.  This could
+  ** have been down with an extra OP_Goto, but simply setting the program
+  ** counter is faster. */
+  if( v->pc>4 ){
+    v->pc = 4;
+    assert( v->aOp[v->pc].opcode==OP_NotExists );
+    rc = sqlite3VdbeExec(v);
+  }else{
+    rc = sqlite3_step(p->pStmt);
+  }
+  if( rc==SQLITE_ROW ){
+    VdbeCursor *pC = v->apCsr[0];
+    u32 type;
+    assert( pC!=0 );
+    assert( pC->eCurType==CURTYPE_BTREE );
+    type = pC->nHdrParsed>p->iCol ? pC->aType[p->iCol] : 0;
+    testcase( pC->nHdrParsed==p->iCol );
+    testcase( pC->nHdrParsed==p->iCol+1 );
+    if( type<12 ){
+      zErr = sqlite3MPrintf(p->db, "cannot open value of type %s",
+          type==0?"null": type==7?"real": "integer"
+      );
+      rc = SQLITE_ERROR;
+      sqlite3_finalize(p->pStmt);
+      p->pStmt = 0;
+    }else{
+      p->iOffset = pC->aType[p->iCol + pC->nField];
+      p->nByte = sqlite3VdbeSerialTypeLen(type);
+      p->pCsr =  pC->uc.pCursor;
+      sqlite3BtreeIncrblobCursor(p->pCsr);
+    }
+  }
+
+  if( rc==SQLITE_ROW ){
+    rc = SQLITE_OK;
+  }else if( p->pStmt ){
+    rc = sqlite3_finalize(p->pStmt);
+    p->pStmt = 0;
+    if( rc==SQLITE_OK ){
+      zErr = sqlite3MPrintf(p->db, "no such rowid: %lld", iRow);
+      rc = SQLITE_ERROR;
+    }else{
+      zErr = sqlite3MPrintf(p->db, "%s", sqlite3_errmsg(p->db));
+    }
+  }
+
+  assert( rc!=SQLITE_OK || zErr==0 );
+  assert( rc!=SQLITE_ROW && rc!=SQLITE_DONE );
+
+  *pzErr = zErr;
+  return rc;
+}
+
+/*
+** Open a blob handle.
+*/
+int sqlite3_blob_open(
+  sqlite3* db,            /* The database connection */
+  const char *zDb,        /* The attached database containing the blob */
+  const char *zTable,     /* The table containing the blob */
+  const char *zColumn,    /* The column containing the blob */
+  sqlite_int64 iRow,      /* The row containing the glob */
+  int wrFlag,             /* True -> read/write access, false -> read-only */
+  sqlite3_blob **ppBlob   /* Handle for accessing the blob returned here */
+){
+  int nAttempt = 0;
+  int iCol;               /* Index of zColumn in row-record */
+  int rc = SQLITE_OK;
+  char *zErr = 0;
+  Table *pTab;
+  Incrblob *pBlob = 0;
+  Parse sParse;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( ppBlob==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  *ppBlob = 0;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zTable==0 || zColumn==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  wrFlag = !!wrFlag;                /* wrFlag = (wrFlag ? 1 : 0); */
+
+  sqlite3_mutex_enter(db->mutex);
+
+  pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
+  while(1){
+    sqlite3ParseObjectInit(&sParse,db);
+    if( !pBlob ) goto blob_open_out;
+    sqlite3DbFree(db, zErr);
+    zErr = 0;
+
+    sqlite3BtreeEnterAll(db);
+    pTab = sqlite3LocateTable(&sParse, 0, zTable, zDb);
+    if( pTab && IsVirtual(pTab) ){
+      pTab = 0;
+      sqlite3ErrorMsg(&sParse, "cannot open virtual table: %s", zTable);
+    }
+    if( pTab && !HasRowid(pTab) ){
+      pTab = 0;
+      sqlite3ErrorMsg(&sParse, "cannot open table without rowid: %s", zTable);
+    }
+#ifndef SQLITE_OMIT_VIEW
+    if( pTab && IsView(pTab) ){
+      pTab = 0;
+      sqlite3ErrorMsg(&sParse, "cannot open view: %s", zTable);
+    }
+#endif
+    if( !pTab ){
+      if( sParse.zErrMsg ){
+        sqlite3DbFree(db, zErr);
+        zErr = sParse.zErrMsg;
+        sParse.zErrMsg = 0;
+      }
+      rc = SQLITE_ERROR;
+      sqlite3BtreeLeaveAll(db);
+      goto blob_open_out;
+    }
+    pBlob->pTab = pTab;
+    pBlob->zDb = db->aDb[sqlite3SchemaToIndex(db, pTab->pSchema)].zDbSName;
+
+    /* Now search pTab for the exact column. */
+    for(iCol=0; iCol<pTab->nCol; iCol++) {
+      if( sqlite3StrICmp(pTab->aCol[iCol].zCnName, zColumn)==0 ){
+        break;
+      }
+    }
+    if( iCol==pTab->nCol ){
+      sqlite3DbFree(db, zErr);
+      zErr = sqlite3MPrintf(db, "no such column: \"%s\"", zColumn);
+      rc = SQLITE_ERROR;
+      sqlite3BtreeLeaveAll(db);
+      goto blob_open_out;
+    }
+
+    /* If the value is being opened for writing, check that the
+    ** column is not indexed, and that it is not part of a foreign key. 
+    */
+    if( wrFlag ){
+      const char *zFault = 0;
+      Index *pIdx;
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+      if( db->flags&SQLITE_ForeignKeys ){
+        /* Check that the column is not part of an FK child key definition. It
+        ** is not necessary to check if it is part of a parent key, as parent
+        ** key columns must be indexed. The check below will pick up this 
+        ** case.  */
+        FKey *pFKey;
+        assert( IsOrdinaryTable(pTab) );
+        for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
+          int j;
+          for(j=0; j<pFKey->nCol; j++){
+            if( pFKey->aCol[j].iFrom==iCol ){
+              zFault = "foreign key";
+            }
+          }
+        }
+      }
+#endif
+      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+        int j;
+        for(j=0; j<pIdx->nKeyCol; j++){
+          /* FIXME: Be smarter about indexes that use expressions */
+          if( pIdx->aiColumn[j]==iCol || pIdx->aiColumn[j]==XN_EXPR ){
+            zFault = "indexed";
+          }
+        }
+      }
+      if( zFault ){
+        sqlite3DbFree(db, zErr);
+        zErr = sqlite3MPrintf(db, "cannot open %s column for writing", zFault);
+        rc = SQLITE_ERROR;
+        sqlite3BtreeLeaveAll(db);
+        goto blob_open_out;
+      }
+    }
+
+    pBlob->pStmt = (sqlite3_stmt *)sqlite3VdbeCreate(&sParse);
+    assert( pBlob->pStmt || db->mallocFailed );
+    if( pBlob->pStmt ){
+      
+      /* This VDBE program seeks a btree cursor to the identified 
+      ** db/table/row entry. The reason for using a vdbe program instead
+      ** of writing code to use the b-tree layer directly is that the
+      ** vdbe program will take advantage of the various transaction,
+      ** locking and error handling infrastructure built into the vdbe.
+      **
+      ** After seeking the cursor, the vdbe executes an OP_ResultRow.
+      ** Code external to the Vdbe then "borrows" the b-tree cursor and
+      ** uses it to implement the blob_read(), blob_write() and 
+      ** blob_bytes() functions.
+      **
+      ** The sqlite3_blob_close() function finalizes the vdbe program,
+      ** which closes the b-tree cursor and (possibly) commits the 
+      ** transaction.
+      */
+      static const int iLn = VDBE_OFFSET_LINENO(2);
+      static const VdbeOpList openBlob[] = {
+        {OP_TableLock,      0, 0, 0},  /* 0: Acquire a read or write lock */
+        {OP_OpenRead,       0, 0, 0},  /* 1: Open a cursor */
+        /* blobSeekToRow() will initialize r[1] to the desired rowid */
+        {OP_NotExists,      0, 5, 1},  /* 2: Seek the cursor to rowid=r[1] */
+        {OP_Column,         0, 0, 1},  /* 3  */
+        {OP_ResultRow,      1, 0, 0},  /* 4  */
+        {OP_Halt,           0, 0, 0},  /* 5  */
+      };
+      Vdbe *v = (Vdbe *)pBlob->pStmt;
+      int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+      VdbeOp *aOp;
+
+      sqlite3VdbeAddOp4Int(v, OP_Transaction, iDb, wrFlag, 
+                           pTab->pSchema->schema_cookie,
+                           pTab->pSchema->iGeneration);
+      sqlite3VdbeChangeP5(v, 1);
+      assert( sqlite3VdbeCurrentAddr(v)==2 || db->mallocFailed );
+      aOp = sqlite3VdbeAddOpList(v, ArraySize(openBlob), openBlob, iLn);
+
+      /* Make sure a mutex is held on the table to be accessed */
+      sqlite3VdbeUsesBtree(v, iDb); 
+
+      if( db->mallocFailed==0 ){
+        assert( aOp!=0 );
+        /* Configure the OP_TableLock instruction */
+#ifdef SQLITE_OMIT_SHARED_CACHE
+        aOp[0].opcode = OP_Noop;
+#else
+        aOp[0].p1 = iDb;
+        aOp[0].p2 = pTab->tnum;
+        aOp[0].p3 = wrFlag;
+        sqlite3VdbeChangeP4(v, 2, pTab->zName, P4_TRANSIENT);
+      }
+      if( db->mallocFailed==0 ){
+#endif
+
+        /* Remove either the OP_OpenWrite or OpenRead. Set the P2 
+        ** parameter of the other to pTab->tnum.  */
+        if( wrFlag ) aOp[1].opcode = OP_OpenWrite;
+        aOp[1].p2 = pTab->tnum;
+        aOp[1].p3 = iDb;   
+
+        /* Configure the number of columns. Configure the cursor to
+        ** think that the table has one more column than it really
+        ** does. An OP_Column to retrieve this imaginary column will
+        ** always return an SQL NULL. This is useful because it means
+        ** we can invoke OP_Column to fill in the vdbe cursors type 
+        ** and offset cache without causing any IO.
+        */
+        aOp[1].p4type = P4_INT32;
+        aOp[1].p4.i = pTab->nCol+1;
+        aOp[3].p2 = pTab->nCol;
+
+        sParse.nVar = 0;
+        sParse.nMem = 1;
+        sParse.nTab = 1;
+        sqlite3VdbeMakeReady(v, &sParse);
+      }
+    }
+   
+    pBlob->iCol = iCol;
+    pBlob->db = db;
+    sqlite3BtreeLeaveAll(db);
+    if( db->mallocFailed ){
+      goto blob_open_out;
+    }
+    rc = blobSeekToRow(pBlob, iRow, &zErr);
+    if( (++nAttempt)>=SQLITE_MAX_SCHEMA_RETRY || rc!=SQLITE_SCHEMA ) break;
+    sqlite3ParseObjectReset(&sParse);
+  }
+
+blob_open_out:
+  if( rc==SQLITE_OK && db->mallocFailed==0 ){
+    *ppBlob = (sqlite3_blob *)pBlob;
+  }else{
+    if( pBlob && pBlob->pStmt ) sqlite3VdbeFinalize((Vdbe *)pBlob->pStmt);
+    sqlite3DbFree(db, pBlob);
+  }
+  sqlite3ErrorWithMsg(db, rc, (zErr ? "%s" : (char*)0), zErr);
+  sqlite3DbFree(db, zErr);
+  sqlite3ParseObjectReset(&sParse);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Close a blob handle that was previously created using
+** sqlite3_blob_open().
+*/
+int sqlite3_blob_close(sqlite3_blob *pBlob){
+  Incrblob *p = (Incrblob *)pBlob;
+  int rc;
+  sqlite3 *db;
+
+  if( p ){
+    sqlite3_stmt *pStmt = p->pStmt;
+    db = p->db;
+    sqlite3_mutex_enter(db->mutex);
+    sqlite3DbFree(db, p);
+    sqlite3_mutex_leave(db->mutex);
+    rc = sqlite3_finalize(pStmt);
+  }else{
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Perform a read or write operation on a blob
+*/
+static int blobReadWrite(
+  sqlite3_blob *pBlob, 
+  void *z, 
+  int n, 
+  int iOffset, 
+  int (*xCall)(BtCursor*, u32, u32, void*)
+){
+  int rc;
+  Incrblob *p = (Incrblob *)pBlob;
+  Vdbe *v;
+  sqlite3 *db;
+
+  if( p==0 ) return SQLITE_MISUSE_BKPT;
+  db = p->db;
+  sqlite3_mutex_enter(db->mutex);
+  v = (Vdbe*)p->pStmt;
+
+  if( n<0 || iOffset<0 || ((sqlite3_int64)iOffset+n)>p->nByte ){
+    /* Request is out of range. Return a transient error. */
+    rc = SQLITE_ERROR;
+  }else if( v==0 ){
+    /* If there is no statement handle, then the blob-handle has
+    ** already been invalidated. Return SQLITE_ABORT in this case.
+    */
+    rc = SQLITE_ABORT;
+  }else{
+    /* Call either BtreeData() or BtreePutData(). If SQLITE_ABORT is
+    ** returned, clean-up the statement handle.
+    */
+    assert( db == v->db );
+    sqlite3BtreeEnterCursor(p->pCsr);
+
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+    if( xCall==sqlite3BtreePutData && db->xPreUpdateCallback ){
+      /* If a pre-update hook is registered and this is a write cursor, 
+      ** invoke it here. 
+      ** 
+      ** TODO: The preupdate-hook is passed SQLITE_DELETE, even though this
+      ** operation should really be an SQLITE_UPDATE. This is probably
+      ** incorrect, but is convenient because at this point the new.* values 
+      ** are not easily obtainable. And for the sessions module, an 
+      ** SQLITE_UPDATE where the PK columns do not change is handled in the 
+      ** same way as an SQLITE_DELETE (the SQLITE_DELETE code is actually
+      ** slightly more efficient). Since you cannot write to a PK column
+      ** using the incremental-blob API, this works. For the sessions module
+      ** anyhow.
+      */
+      sqlite3_int64 iKey;
+      iKey = sqlite3BtreeIntegerKey(p->pCsr);
+      assert( v->apCsr[0]!=0 );
+      assert( v->apCsr[0]->eCurType==CURTYPE_BTREE );
+      sqlite3VdbePreUpdateHook(
+          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1, p->iCol
+      );
+    }
+#endif
+
+    rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
+    sqlite3BtreeLeaveCursor(p->pCsr);
+    if( rc==SQLITE_ABORT ){
+      sqlite3VdbeFinalize(v);
+      p->pStmt = 0;
+    }else{
+      v->rc = rc;
+    }
+  }
+  sqlite3Error(db, rc);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Read data from a blob handle.
+*/
+int sqlite3_blob_read(sqlite3_blob *pBlob, void *z, int n, int iOffset){
+  return blobReadWrite(pBlob, z, n, iOffset, sqlite3BtreePayloadChecked);
+}
+
+/*
+** Write data to a blob handle.
+*/
+int sqlite3_blob_write(sqlite3_blob *pBlob, const void *z, int n, int iOffset){
+  return blobReadWrite(pBlob, (void *)z, n, iOffset, sqlite3BtreePutData);
+}
+
+/*
+** Query a blob handle for the size of the data.
+**
+** The Incrblob.nByte field is fixed for the lifetime of the Incrblob
+** so no mutex is required for access.
+*/
+int sqlite3_blob_bytes(sqlite3_blob *pBlob){
+  Incrblob *p = (Incrblob *)pBlob;
+  return (p && p->pStmt) ? p->nByte : 0;
+}
+
+/*
+** Move an existing blob handle to point to a different row of the same
+** database table.
+**
+** If an error occurs, or if the specified row does not exist or does not
+** contain a blob or text value, then an error code is returned and the
+** database handle error code and message set. If this happens, then all 
+** subsequent calls to sqlite3_blob_xxx() functions (except blob_close()) 
+** immediately return SQLITE_ABORT.
+*/
+int sqlite3_blob_reopen(sqlite3_blob *pBlob, sqlite3_int64 iRow){
+  int rc;
+  Incrblob *p = (Incrblob *)pBlob;
+  sqlite3 *db;
+
+  if( p==0 ) return SQLITE_MISUSE_BKPT;
+  db = p->db;
+  sqlite3_mutex_enter(db->mutex);
+
+  if( p->pStmt==0 ){
+    /* If there is no statement handle, then the blob-handle has
+    ** already been invalidated. Return SQLITE_ABORT in this case.
+    */
+    rc = SQLITE_ABORT;
+  }else{
+    char *zErr;
+    ((Vdbe*)p->pStmt)->rc = SQLITE_OK;
+    rc = blobSeekToRow(p, iRow, &zErr);
+    if( rc!=SQLITE_OK ){
+      sqlite3ErrorWithMsg(db, rc, (zErr ? "%s" : (char*)0), zErr);
+      sqlite3DbFree(db, zErr);
+    }
+    assert( rc!=SQLITE_SCHEMA );
+  }
+
+  rc = sqlite3ApiExit(db, rc);
+  assert( rc==SQLITE_OK || p->pStmt==0 );
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#endif /* #ifndef SQLITE_OMIT_INCRBLOB */
diff --git a/src/vdbemem.c b/src/vdbemem.c
new file mode 100644
index 0000000..d527164
--- /dev/null
+++ b/src/vdbemem.c
@@ -0,0 +1,2025 @@
+/*
+** 2004 May 26
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code use to manipulate "Mem" structure.  A "Mem"
+** stores a single value in the VDBE.  Mem is an opaque structure visible
+** only within the VDBE.  Interface routines refer to a Mem using the
+** name sqlite_value
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/* True if X is a power of two.  0 is considered a power of two here.
+** In other words, return true if X has at most one bit set.
+*/
+#define ISPOWEROF2(X)  (((X)&((X)-1))==0)
+
+#ifdef SQLITE_DEBUG
+/*
+** Check invariants on a Mem object.
+**
+** This routine is intended for use inside of assert() statements, like
+** this:    assert( sqlite3VdbeCheckMemInvariants(pMem) );
+*/
+int sqlite3VdbeCheckMemInvariants(Mem *p){
+  /* If MEM_Dyn is set then Mem.xDel!=0.  
+  ** Mem.xDel might not be initialized if MEM_Dyn is clear.
+  */
+  assert( (p->flags & MEM_Dyn)==0 || p->xDel!=0 );
+
+  /* MEM_Dyn may only be set if Mem.szMalloc==0.  In this way we
+  ** ensure that if Mem.szMalloc>0 then it is safe to do
+  ** Mem.z = Mem.zMalloc without having to check Mem.flags&MEM_Dyn.
+  ** That saves a few cycles in inner loops. */
+  assert( (p->flags & MEM_Dyn)==0 || p->szMalloc==0 );
+
+  /* Cannot have more than one of MEM_Int, MEM_Real, or MEM_IntReal */
+  assert( ISPOWEROF2(p->flags & (MEM_Int|MEM_Real|MEM_IntReal)) );
+
+  if( p->flags & MEM_Null ){
+    /* Cannot be both MEM_Null and some other type */
+    assert( (p->flags & (MEM_Int|MEM_Real|MEM_Str|MEM_Blob|MEM_Agg))==0 );
+
+    /* If MEM_Null is set, then either the value is a pure NULL (the usual
+    ** case) or it is a pointer set using sqlite3_bind_pointer() or
+    ** sqlite3_result_pointer().  If a pointer, then MEM_Term must also be
+    ** set.
+    */
+    if( (p->flags & (MEM_Term|MEM_Subtype))==(MEM_Term|MEM_Subtype) ){
+      /* This is a pointer type.  There may be a flag to indicate what to
+      ** do with the pointer. */
+      assert( ((p->flags&MEM_Dyn)!=0 ? 1 : 0) +
+              ((p->flags&MEM_Ephem)!=0 ? 1 : 0) +
+              ((p->flags&MEM_Static)!=0 ? 1 : 0) <= 1 );
+
+      /* No other bits set */
+      assert( (p->flags & ~(MEM_Null|MEM_Term|MEM_Subtype|MEM_FromBind
+                           |MEM_Dyn|MEM_Ephem|MEM_Static))==0 );
+    }else{
+      /* A pure NULL might have other flags, such as MEM_Static, MEM_Dyn,
+      ** MEM_Ephem, MEM_Cleared, or MEM_Subtype */
+    }
+  }else{
+    /* The MEM_Cleared bit is only allowed on NULLs */
+    assert( (p->flags & MEM_Cleared)==0 );
+  }
+
+  /* The szMalloc field holds the correct memory allocation size */
+  assert( p->szMalloc==0
+       || (p->flags==MEM_Undefined 
+           && p->szMalloc<=sqlite3DbMallocSize(p->db,p->zMalloc))
+       || p->szMalloc==sqlite3DbMallocSize(p->db,p->zMalloc));
+
+  /* If p holds a string or blob, the Mem.z must point to exactly
+  ** one of the following:
+  **
+  **   (1) Memory in Mem.zMalloc and managed by the Mem object
+  **   (2) Memory to be freed using Mem.xDel
+  **   (3) An ephemeral string or blob
+  **   (4) A static string or blob
+  */
+  if( (p->flags & (MEM_Str|MEM_Blob)) && p->n>0 ){
+    assert( 
+      ((p->szMalloc>0 && p->z==p->zMalloc)? 1 : 0) +
+      ((p->flags&MEM_Dyn)!=0 ? 1 : 0) +
+      ((p->flags&MEM_Ephem)!=0 ? 1 : 0) +
+      ((p->flags&MEM_Static)!=0 ? 1 : 0) == 1
+    );
+  }
+  return 1;
+}
+#endif
+
+/*
+** Render a Mem object which is one of MEM_Int, MEM_Real, or MEM_IntReal
+** into a buffer.
+*/
+static void vdbeMemRenderNum(int sz, char *zBuf, Mem *p){
+  StrAccum acc;
+  assert( p->flags & (MEM_Int|MEM_Real|MEM_IntReal) );
+  assert( sz>22 );
+  if( p->flags & MEM_Int ){
+#if GCC_VERSION>=7000000
+    /* Work-around for GCC bug
+    ** https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96270 */
+    i64 x;
+    assert( (p->flags&MEM_Int)*2==sizeof(x) );
+    memcpy(&x, (char*)&p->u, (p->flags&MEM_Int)*2);
+    p->n = sqlite3Int64ToText(x, zBuf);
+#else
+    p->n = sqlite3Int64ToText(p->u.i, zBuf);
+#endif
+  }else{
+    sqlite3StrAccumInit(&acc, 0, zBuf, sz, 0);
+    sqlite3_str_appendf(&acc, "%!.15g", 
+         (p->flags & MEM_IntReal)!=0 ? (double)p->u.i : p->u.r);
+    assert( acc.zText==zBuf && acc.mxAlloc<=0 );
+    zBuf[acc.nChar] = 0; /* Fast version of sqlite3StrAccumFinish(&acc) */
+    p->n = acc.nChar;
+  }
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Validity checks on pMem.  pMem holds a string.
+**
+** (1) Check that string value of pMem agrees with its integer or real value.
+** (2) Check that the string is correctly zero terminated
+**
+** A single int or real value always converts to the same strings.  But
+** many different strings can be converted into the same int or real.
+** If a table contains a numeric value and an index is based on the
+** corresponding string value, then it is important that the string be
+** derived from the numeric value, not the other way around, to ensure
+** that the index and table are consistent.  See ticket
+** https://www.sqlite.org/src/info/343634942dd54ab (2018-01-31) for
+** an example.
+**
+** This routine looks at pMem to verify that if it has both a numeric
+** representation and a string representation then the string rep has
+** been derived from the numeric and not the other way around.  It returns
+** true if everything is ok and false if there is a problem.
+**
+** This routine is for use inside of assert() statements only.
+*/
+int sqlite3VdbeMemValidStrRep(Mem *p){
+  Mem tmp;
+  char zBuf[100];
+  char *z;
+  int i, j, incr;
+  if( (p->flags & MEM_Str)==0 ) return 1;
+  if( p->db && p->db->mallocFailed ) return 1;
+  if( p->flags & MEM_Term ){
+    /* Insure that the string is properly zero-terminated.  Pay particular
+    ** attention to the case where p->n is odd */
+    if( p->szMalloc>0 && p->z==p->zMalloc ){
+      assert( p->enc==SQLITE_UTF8 || p->szMalloc >= ((p->n+1)&~1)+2 );
+      assert( p->enc!=SQLITE_UTF8 || p->szMalloc >= p->n+1 );
+    }
+    assert( p->z[p->n]==0 );
+    assert( p->enc==SQLITE_UTF8 || p->z[(p->n+1)&~1]==0 );
+    assert( p->enc==SQLITE_UTF8 || p->z[((p->n+1)&~1)+1]==0 );
+  }
+  if( (p->flags & (MEM_Int|MEM_Real|MEM_IntReal))==0 ) return 1;
+  memcpy(&tmp, p, sizeof(tmp));
+  vdbeMemRenderNum(sizeof(zBuf), zBuf, &tmp);
+  z = p->z;
+  i = j = 0;
+  incr = 1;
+  if( p->enc!=SQLITE_UTF8 ){
+    incr = 2;
+    if( p->enc==SQLITE_UTF16BE ) z++;
+  }
+  while( zBuf[j] ){
+    if( zBuf[j++]!=z[i] ) return 0;
+    i += incr;
+  }
+  return 1;
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** If pMem is an object with a valid string representation, this routine
+** ensures the internal encoding for the string representation is
+** 'desiredEnc', one of SQLITE_UTF8, SQLITE_UTF16LE or SQLITE_UTF16BE.
+**
+** If pMem is not a string object, or the encoding of the string
+** representation is already stored using the requested encoding, then this
+** routine is a no-op.
+**
+** SQLITE_OK is returned if the conversion is successful (or not required).
+** SQLITE_NOMEM may be returned if a malloc() fails during conversion
+** between formats.
+*/
+int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
+#ifndef SQLITE_OMIT_UTF16
+  int rc;
+#endif
+  assert( pMem!=0 );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  assert( desiredEnc==SQLITE_UTF8 || desiredEnc==SQLITE_UTF16LE
+           || desiredEnc==SQLITE_UTF16BE );
+  if( !(pMem->flags&MEM_Str) ){
+    pMem->enc = desiredEnc;
+    return SQLITE_OK;
+  }
+  if( pMem->enc==desiredEnc ){
+    return SQLITE_OK;
+  }
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+#ifdef SQLITE_OMIT_UTF16
+  return SQLITE_ERROR;
+#else
+
+  /* MemTranslate() may return SQLITE_OK or SQLITE_NOMEM. If NOMEM is returned,
+  ** then the encoding of the value may not have changed.
+  */
+  rc = sqlite3VdbeMemTranslate(pMem, (u8)desiredEnc);
+  assert(rc==SQLITE_OK    || rc==SQLITE_NOMEM);
+  assert(rc==SQLITE_OK    || pMem->enc!=desiredEnc);
+  assert(rc==SQLITE_NOMEM || pMem->enc==desiredEnc);
+  return rc;
+#endif
+}
+
+/*
+** Make sure pMem->z points to a writable allocation of at least n bytes.
+**
+** If the bPreserve argument is true, then copy of the content of
+** pMem->z into the new allocation.  pMem must be either a string or
+** blob if bPreserve is true.  If bPreserve is false, any prior content
+** in pMem->z is discarded.
+*/
+SQLITE_NOINLINE int sqlite3VdbeMemGrow(Mem *pMem, int n, int bPreserve){
+  assert( sqlite3VdbeCheckMemInvariants(pMem) );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  testcase( pMem->db==0 );
+
+  /* If the bPreserve flag is set to true, then the memory cell must already
+  ** contain a valid string or blob value.  */
+  assert( bPreserve==0 || pMem->flags&(MEM_Blob|MEM_Str) );
+  testcase( bPreserve && pMem->z==0 );
+
+  assert( pMem->szMalloc==0
+       || (pMem->flags==MEM_Undefined 
+           && pMem->szMalloc<=sqlite3DbMallocSize(pMem->db,pMem->zMalloc))
+       || pMem->szMalloc==sqlite3DbMallocSize(pMem->db,pMem->zMalloc));
+  if( pMem->szMalloc>0 && bPreserve && pMem->z==pMem->zMalloc ){
+    if( pMem->db ){
+      pMem->z = pMem->zMalloc = sqlite3DbReallocOrFree(pMem->db, pMem->z, n);
+    }else{
+      pMem->zMalloc = sqlite3Realloc(pMem->z, n);
+      if( pMem->zMalloc==0 ) sqlite3_free(pMem->z);
+      pMem->z = pMem->zMalloc;
+    }
+    bPreserve = 0;
+  }else{
+    if( pMem->szMalloc>0 ) sqlite3DbFreeNN(pMem->db, pMem->zMalloc);
+    pMem->zMalloc = sqlite3DbMallocRaw(pMem->db, n);
+  }
+  if( pMem->zMalloc==0 ){
+    sqlite3VdbeMemSetNull(pMem);
+    pMem->z = 0;
+    pMem->szMalloc = 0;
+    return SQLITE_NOMEM_BKPT;
+  }else{
+    pMem->szMalloc = sqlite3DbMallocSize(pMem->db, pMem->zMalloc);
+  }
+
+  if( bPreserve && pMem->z ){
+    assert( pMem->z!=pMem->zMalloc );
+    memcpy(pMem->zMalloc, pMem->z, pMem->n);
+  }
+  if( (pMem->flags&MEM_Dyn)!=0 ){
+    assert( pMem->xDel!=0 && pMem->xDel!=SQLITE_DYNAMIC );
+    pMem->xDel((void *)(pMem->z));
+  }
+
+  pMem->z = pMem->zMalloc;
+  pMem->flags &= ~(MEM_Dyn|MEM_Ephem|MEM_Static);
+  return SQLITE_OK;
+}
+
+/*
+** Change the pMem->zMalloc allocation to be at least szNew bytes.
+** If pMem->zMalloc already meets or exceeds the requested size, this
+** routine is a no-op.
+**
+** Any prior string or blob content in the pMem object may be discarded.
+** The pMem->xDel destructor is called, if it exists.  Though MEM_Str
+** and MEM_Blob values may be discarded, MEM_Int, MEM_Real, MEM_IntReal,
+** and MEM_Null values are preserved.
+**
+** Return SQLITE_OK on success or an error code (probably SQLITE_NOMEM)
+** if unable to complete the resizing.
+*/
+int sqlite3VdbeMemClearAndResize(Mem *pMem, int szNew){
+  assert( CORRUPT_DB || szNew>0 );
+  assert( (pMem->flags & MEM_Dyn)==0 || pMem->szMalloc==0 );
+  if( pMem->szMalloc<szNew ){
+    return sqlite3VdbeMemGrow(pMem, szNew, 0);
+  }
+  assert( (pMem->flags & MEM_Dyn)==0 );
+  pMem->z = pMem->zMalloc;
+  pMem->flags &= (MEM_Null|MEM_Int|MEM_Real|MEM_IntReal);
+  return SQLITE_OK;
+}
+
+/*
+** If pMem is already a string, detect if it is a zero-terminated
+** string, or make it into one if possible, and mark it as such.
+**
+** This is an optimization.  Correct operation continues even if
+** this routine is a no-op.
+*/
+void sqlite3VdbeMemZeroTerminateIfAble(Mem *pMem){
+  if( (pMem->flags & (MEM_Str|MEM_Term|MEM_Ephem|MEM_Static))!=MEM_Str ){
+    /* pMem must be a string, and it cannot be an ephemeral or static string */
+    return;
+  }
+  if( pMem->enc!=SQLITE_UTF8 ) return;
+  if( NEVER(pMem->z==0) ) return;
+  if( pMem->flags & MEM_Dyn ){
+    if( pMem->xDel==sqlite3_free
+     && sqlite3_msize(pMem->z) >= (u64)(pMem->n+1)
+    ){
+      pMem->z[pMem->n] = 0;
+      pMem->flags |= MEM_Term;
+      return;
+    }
+    if( pMem->xDel==sqlite3RCStrUnref ){
+      /* Blindly assume that all RCStr objects are zero-terminated */
+      pMem->flags |= MEM_Term;
+      return;
+    }
+  }else if( pMem->szMalloc >= pMem->n+1 ){
+    pMem->z[pMem->n] = 0;
+    pMem->flags |= MEM_Term;
+    return;
+  }
+}
+
+/*
+** It is already known that pMem contains an unterminated string.
+** Add the zero terminator.
+**
+** Three bytes of zero are added.  In this way, there is guaranteed
+** to be a double-zero byte at an even byte boundary in order to
+** terminate a UTF16 string, even if the initial size of the buffer
+** is an odd number of bytes.
+*/
+static SQLITE_NOINLINE int vdbeMemAddTerminator(Mem *pMem){
+  if( sqlite3VdbeMemGrow(pMem, pMem->n+3, 1) ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  pMem->z[pMem->n] = 0;
+  pMem->z[pMem->n+1] = 0;
+  pMem->z[pMem->n+2] = 0;
+  pMem->flags |= MEM_Term;
+  return SQLITE_OK;
+}
+
+/*
+** Change pMem so that its MEM_Str or MEM_Blob value is stored in
+** MEM.zMalloc, where it can be safely written.
+**
+** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
+*/
+int sqlite3VdbeMemMakeWriteable(Mem *pMem){
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  if( (pMem->flags & (MEM_Str|MEM_Blob))!=0 ){
+    if( ExpandBlob(pMem) ) return SQLITE_NOMEM;
+    if( pMem->szMalloc==0 || pMem->z!=pMem->zMalloc ){
+      int rc = vdbeMemAddTerminator(pMem);
+      if( rc ) return rc;
+    }
+  }
+  pMem->flags &= ~MEM_Ephem;
+#ifdef SQLITE_DEBUG
+  pMem->pScopyFrom = 0;
+#endif
+
+  return SQLITE_OK;
+}
+
+/*
+** If the given Mem* has a zero-filled tail, turn it into an ordinary
+** blob stored in dynamically allocated space.
+*/
+#ifndef SQLITE_OMIT_INCRBLOB
+int sqlite3VdbeMemExpandBlob(Mem *pMem){
+  int nByte;
+  assert( pMem!=0 );
+  assert( pMem->flags & MEM_Zero );
+  assert( (pMem->flags&MEM_Blob)!=0 || MemNullNochng(pMem) );
+  testcase( sqlite3_value_nochange(pMem) );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+
+  /* Set nByte to the number of bytes required to store the expanded blob. */
+  nByte = pMem->n + pMem->u.nZero;
+  if( nByte<=0 ){
+    if( (pMem->flags & MEM_Blob)==0 ) return SQLITE_OK;
+    nByte = 1;
+  }
+  if( sqlite3VdbeMemGrow(pMem, nByte, 1) ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  assert( pMem->z!=0 );
+  assert( sqlite3DbMallocSize(pMem->db,pMem->z) >= nByte );
+
+  memset(&pMem->z[pMem->n], 0, pMem->u.nZero);
+  pMem->n += pMem->u.nZero;
+  pMem->flags &= ~(MEM_Zero|MEM_Term);
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Make sure the given Mem is \u0000 terminated.
+*/
+int sqlite3VdbeMemNulTerminate(Mem *pMem){
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  testcase( (pMem->flags & (MEM_Term|MEM_Str))==(MEM_Term|MEM_Str) );
+  testcase( (pMem->flags & (MEM_Term|MEM_Str))==0 );
+  if( (pMem->flags & (MEM_Term|MEM_Str))!=MEM_Str ){
+    return SQLITE_OK;   /* Nothing to do */
+  }else{
+    return vdbeMemAddTerminator(pMem);
+  }
+}
+
+/*
+** Add MEM_Str to the set of representations for the given Mem.  This
+** routine is only called if pMem is a number of some kind, not a NULL
+** or a BLOB.
+**
+** Existing representations MEM_Int, MEM_Real, or MEM_IntReal are invalidated
+** if bForce is true but are retained if bForce is false.
+**
+** A MEM_Null value will never be passed to this function. This function is
+** used for converting values to text for returning to the user (i.e. via
+** sqlite3_value_text()), or for ensuring that values to be used as btree
+** keys are strings. In the former case a NULL pointer is returned the
+** user and the latter is an internal programming error.
+*/
+int sqlite3VdbeMemStringify(Mem *pMem, u8 enc, u8 bForce){
+  const int nByte = 32;
+
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( !(pMem->flags&MEM_Zero) );
+  assert( !(pMem->flags&(MEM_Str|MEM_Blob)) );
+  assert( pMem->flags&(MEM_Int|MEM_Real|MEM_IntReal) );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+
+  if( sqlite3VdbeMemClearAndResize(pMem, nByte) ){
+    pMem->enc = 0;
+    return SQLITE_NOMEM_BKPT;
+  }
+
+  vdbeMemRenderNum(nByte, pMem->z, pMem);
+  assert( pMem->z!=0 );
+  assert( pMem->n==(int)sqlite3Strlen30NN(pMem->z) );
+  pMem->enc = SQLITE_UTF8;
+  pMem->flags |= MEM_Str|MEM_Term;
+  if( bForce ) pMem->flags &= ~(MEM_Int|MEM_Real|MEM_IntReal);
+  sqlite3VdbeChangeEncoding(pMem, enc);
+  return SQLITE_OK;
+}
+
+/*
+** Memory cell pMem contains the context of an aggregate function.
+** This routine calls the finalize method for that function.  The
+** result of the aggregate is stored back into pMem.
+**
+** Return SQLITE_ERROR if the finalizer reports an error.  SQLITE_OK
+** otherwise.
+*/
+int sqlite3VdbeMemFinalize(Mem *pMem, FuncDef *pFunc){
+  sqlite3_context ctx;
+  Mem t;
+  assert( pFunc!=0 );
+  assert( pMem!=0 );
+  assert( pMem->db!=0 );
+  assert( pFunc->xFinalize!=0 );
+  assert( (pMem->flags & MEM_Null)!=0 || pFunc==pMem->u.pDef );
+  assert( sqlite3_mutex_held(pMem->db->mutex) );
+  memset(&ctx, 0, sizeof(ctx));
+  memset(&t, 0, sizeof(t));
+  t.flags = MEM_Null;
+  t.db = pMem->db;
+  ctx.pOut = &t;
+  ctx.pMem = pMem;
+  ctx.pFunc = pFunc;
+  ctx.enc = ENC(t.db);
+  pFunc->xFinalize(&ctx); /* IMP: R-24505-23230 */
+  assert( (pMem->flags & MEM_Dyn)==0 );
+  if( pMem->szMalloc>0 ) sqlite3DbFreeNN(pMem->db, pMem->zMalloc);
+  memcpy(pMem, &t, sizeof(t));
+  return ctx.isError;
+}
+
+/*
+** Memory cell pAccum contains the context of an aggregate function.
+** This routine calls the xValue method for that function and stores
+** the results in memory cell pMem.
+**
+** SQLITE_ERROR is returned if xValue() reports an error. SQLITE_OK 
+** otherwise.
+*/
+#ifndef SQLITE_OMIT_WINDOWFUNC
+int sqlite3VdbeMemAggValue(Mem *pAccum, Mem *pOut, FuncDef *pFunc){
+  sqlite3_context ctx;
+  assert( pFunc!=0 );
+  assert( pFunc->xValue!=0 );
+  assert( (pAccum->flags & MEM_Null)!=0 || pFunc==pAccum->u.pDef );
+  assert( pAccum->db!=0 );
+  assert( sqlite3_mutex_held(pAccum->db->mutex) );
+  memset(&ctx, 0, sizeof(ctx));
+  sqlite3VdbeMemSetNull(pOut);
+  ctx.pOut = pOut;
+  ctx.pMem = pAccum;
+  ctx.pFunc = pFunc;
+  ctx.enc = ENC(pAccum->db);
+  pFunc->xValue(&ctx);
+  return ctx.isError;
+}
+#endif /* SQLITE_OMIT_WINDOWFUNC */
+
+/*
+** If the memory cell contains a value that must be freed by
+** invoking the external callback in Mem.xDel, then this routine
+** will free that value.  It also sets Mem.flags to MEM_Null.
+**
+** This is a helper routine for sqlite3VdbeMemSetNull() and
+** for sqlite3VdbeMemRelease().  Use those other routines as the
+** entry point for releasing Mem resources.
+*/
+static SQLITE_NOINLINE void vdbeMemClearExternAndSetNull(Mem *p){
+  assert( p->db==0 || sqlite3_mutex_held(p->db->mutex) );
+  assert( VdbeMemDynamic(p) );
+  if( p->flags&MEM_Agg ){
+    sqlite3VdbeMemFinalize(p, p->u.pDef);
+    assert( (p->flags & MEM_Agg)==0 );
+    testcase( p->flags & MEM_Dyn );
+  }
+  if( p->flags&MEM_Dyn ){
+    assert( p->xDel!=SQLITE_DYNAMIC && p->xDel!=0 );
+    p->xDel((void *)p->z);
+  }
+  p->flags = MEM_Null;
+}
+
+/*
+** Release memory held by the Mem p, both external memory cleared
+** by p->xDel and memory in p->zMalloc.
+**
+** This is a helper routine invoked by sqlite3VdbeMemRelease() in
+** the unusual case where there really is memory in p that needs
+** to be freed.
+*/
+static SQLITE_NOINLINE void vdbeMemClear(Mem *p){
+  if( VdbeMemDynamic(p) ){
+    vdbeMemClearExternAndSetNull(p);
+  }
+  if( p->szMalloc ){
+    sqlite3DbFreeNN(p->db, p->zMalloc);
+    p->szMalloc = 0;
+  }
+  p->z = 0;
+}
+
+/*
+** Release any memory resources held by the Mem.  Both the memory that is
+** free by Mem.xDel and the Mem.zMalloc allocation are freed.
+**
+** Use this routine prior to clean up prior to abandoning a Mem, or to
+** reset a Mem back to its minimum memory utilization.
+**
+** Use sqlite3VdbeMemSetNull() to release just the Mem.xDel space
+** prior to inserting new content into the Mem.
+*/
+void sqlite3VdbeMemRelease(Mem *p){
+  assert( sqlite3VdbeCheckMemInvariants(p) );
+  if( VdbeMemDynamic(p) || p->szMalloc ){
+    vdbeMemClear(p);
+  }
+}
+
+/* Like sqlite3VdbeMemRelease() but faster for cases where we
+** know in advance that the Mem is not MEM_Dyn or MEM_Agg.
+*/
+void sqlite3VdbeMemReleaseMalloc(Mem *p){
+  assert( !VdbeMemDynamic(p) );
+  if( p->szMalloc ) vdbeMemClear(p);
+}
+
+/*
+** Return some kind of integer value which is the best we can do
+** at representing the value that *pMem describes as an integer.
+** If pMem is an integer, then the value is exact.  If pMem is
+** a floating-point then the value returned is the integer part.
+** If pMem is a string or blob, then we make an attempt to convert
+** it into an integer and return that.  If pMem represents an
+** an SQL-NULL value, return 0.
+**
+** If pMem represents a string value, its encoding might be changed.
+*/
+static SQLITE_NOINLINE i64 memIntValue(const Mem *pMem){
+  i64 value = 0;
+  sqlite3Atoi64(pMem->z, &value, pMem->n, pMem->enc);
+  return value;
+}
+i64 sqlite3VdbeIntValue(const Mem *pMem){
+  int flags;
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+  flags = pMem->flags;
+  if( flags & (MEM_Int|MEM_IntReal) ){
+    testcase( flags & MEM_IntReal );
+    return pMem->u.i;
+  }else if( flags & MEM_Real ){
+    return sqlite3RealToI64(pMem->u.r);
+  }else if( (flags & (MEM_Str|MEM_Blob))!=0 && pMem->z!=0 ){
+    return memIntValue(pMem);
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Return the best representation of pMem that we can get into a
+** double.  If pMem is already a double or an integer, return its
+** value.  If it is a string or blob, try to convert it to a double.
+** If it is a NULL, return 0.0.
+*/
+static SQLITE_NOINLINE double memRealValue(Mem *pMem){
+  /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+  double val = (double)0;
+  sqlite3AtoF(pMem->z, &val, pMem->n, pMem->enc);
+  return val;
+}
+double sqlite3VdbeRealValue(Mem *pMem){
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+  if( pMem->flags & MEM_Real ){
+    return pMem->u.r;
+  }else if( pMem->flags & (MEM_Int|MEM_IntReal) ){
+    testcase( pMem->flags & MEM_IntReal );
+    return (double)pMem->u.i;
+  }else if( pMem->flags & (MEM_Str|MEM_Blob) ){
+    return memRealValue(pMem);
+  }else{
+    /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+    return (double)0;
+  }
+}
+
+/*
+** Return 1 if pMem represents true, and return 0 if pMem represents false.
+** Return the value ifNull if pMem is NULL.  
+*/
+int sqlite3VdbeBooleanValue(Mem *pMem, int ifNull){
+  testcase( pMem->flags & MEM_IntReal );
+  if( pMem->flags & (MEM_Int|MEM_IntReal) ) return pMem->u.i!=0;
+  if( pMem->flags & MEM_Null ) return ifNull;
+  return sqlite3VdbeRealValue(pMem)!=0.0;
+}
+
+/*
+** The MEM structure is already a MEM_Real or MEM_IntReal. Try to 
+** make it a MEM_Int if we can.
+*/
+void sqlite3VdbeIntegerAffinity(Mem *pMem){
+  assert( pMem!=0 );
+  assert( pMem->flags & (MEM_Real|MEM_IntReal) );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+  if( pMem->flags & MEM_IntReal ){
+    MemSetTypeFlag(pMem, MEM_Int);
+  }else{
+    i64 ix = sqlite3RealToI64(pMem->u.r);
+
+    /* Only mark the value as an integer if
+    **
+    **    (1) the round-trip conversion real->int->real is a no-op, and
+    **    (2) The integer is neither the largest nor the smallest
+    **        possible integer (ticket #3922)
+    **
+    ** The second and third terms in the following conditional enforces
+    ** the second condition under the assumption that addition overflow causes
+    ** values to wrap around.
+    */
+    if( pMem->u.r==ix && ix>SMALLEST_INT64 && ix<LARGEST_INT64 ){
+      pMem->u.i = ix;
+      MemSetTypeFlag(pMem, MEM_Int);
+    }
+  }
+}
+
+/*
+** Convert pMem to type integer.  Invalidate any prior representations.
+*/
+int sqlite3VdbeMemIntegerify(Mem *pMem){
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+  pMem->u.i = sqlite3VdbeIntValue(pMem);
+  MemSetTypeFlag(pMem, MEM_Int);
+  return SQLITE_OK;
+}
+
+/*
+** Convert pMem so that it is of type MEM_Real.
+** Invalidate any prior representations.
+*/
+int sqlite3VdbeMemRealify(Mem *pMem){
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+  pMem->u.r = sqlite3VdbeRealValue(pMem);
+  MemSetTypeFlag(pMem, MEM_Real);
+  return SQLITE_OK;
+}
+
+/* Compare a floating point value to an integer.  Return true if the two
+** values are the same within the precision of the floating point value.
+**
+** This function assumes that i was obtained by assignment from r1.
+**
+** For some versions of GCC on 32-bit machines, if you do the more obvious
+** comparison of "r1==(double)i" you sometimes get an answer of false even
+** though the r1 and (double)i values are bit-for-bit the same.
+*/
+int sqlite3RealSameAsInt(double r1, sqlite3_int64 i){
+  double r2 = (double)i;
+  return r1==0.0
+      || (memcmp(&r1, &r2, sizeof(r1))==0
+          && i >= -2251799813685248LL && i < 2251799813685248LL);
+}
+
+/* Convert a floating point value to its closest integer.  Do so in
+** a way that avoids 'outside the range of representable values' warnings
+** from UBSAN.
+*/
+i64 sqlite3RealToI64(double r){
+  if( r<-9223372036854774784.0 ) return SMALLEST_INT64;
+  if( r>+9223372036854774784.0 ) return LARGEST_INT64;
+  return (i64)r;
+}
+
+/*
+** Convert pMem so that it has type MEM_Real or MEM_Int.
+** Invalidate any prior representations.
+**
+** Every effort is made to force the conversion, even if the input
+** is a string that does not look completely like a number.  Convert
+** as much of the string as we can and ignore the rest.
+*/
+int sqlite3VdbeMemNumerify(Mem *pMem){
+  assert( pMem!=0 );
+  testcase( pMem->flags & MEM_Int );
+  testcase( pMem->flags & MEM_Real );
+  testcase( pMem->flags & MEM_IntReal );
+  testcase( pMem->flags & MEM_Null );
+  if( (pMem->flags & (MEM_Int|MEM_Real|MEM_IntReal|MEM_Null))==0 ){
+    int rc;
+    sqlite3_int64 ix;
+    assert( (pMem->flags & (MEM_Blob|MEM_Str))!=0 );
+    assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+    rc = sqlite3AtoF(pMem->z, &pMem->u.r, pMem->n, pMem->enc);
+    if( ((rc==0 || rc==1) && sqlite3Atoi64(pMem->z, &ix, pMem->n, pMem->enc)<=1)
+     || sqlite3RealSameAsInt(pMem->u.r, (ix = sqlite3RealToI64(pMem->u.r)))
+    ){
+      pMem->u.i = ix;
+      MemSetTypeFlag(pMem, MEM_Int);
+    }else{
+      MemSetTypeFlag(pMem, MEM_Real);
+    }
+  }
+  assert( (pMem->flags & (MEM_Int|MEM_Real|MEM_IntReal|MEM_Null))!=0 );
+  pMem->flags &= ~(MEM_Str|MEM_Blob|MEM_Zero);
+  return SQLITE_OK;
+}
+
+/*
+** Cast the datatype of the value in pMem according to the affinity
+** "aff".  Casting is different from applying affinity in that a cast
+** is forced.  In other words, the value is converted into the desired
+** affinity even if that results in loss of data.  This routine is
+** used (for example) to implement the SQL "cast()" operator.
+*/
+int sqlite3VdbeMemCast(Mem *pMem, u8 aff, u8 encoding){
+  if( pMem->flags & MEM_Null ) return SQLITE_OK;
+  switch( aff ){
+    case SQLITE_AFF_BLOB: {   /* Really a cast to BLOB */
+      if( (pMem->flags & MEM_Blob)==0 ){
+        sqlite3ValueApplyAffinity(pMem, SQLITE_AFF_TEXT, encoding);
+        assert( pMem->flags & MEM_Str || pMem->db->mallocFailed );
+        if( pMem->flags & MEM_Str ) MemSetTypeFlag(pMem, MEM_Blob);
+      }else{
+        pMem->flags &= ~(MEM_TypeMask&~MEM_Blob);
+      }
+      break;
+    }
+    case SQLITE_AFF_NUMERIC: {
+      sqlite3VdbeMemNumerify(pMem);
+      break;
+    }
+    case SQLITE_AFF_INTEGER: {
+      sqlite3VdbeMemIntegerify(pMem);
+      break;
+    }
+    case SQLITE_AFF_REAL: {
+      sqlite3VdbeMemRealify(pMem);
+      break;
+    }
+    default: {
+      int rc;
+      assert( aff==SQLITE_AFF_TEXT );
+      assert( MEM_Str==(MEM_Blob>>3) );
+      pMem->flags |= (pMem->flags&MEM_Blob)>>3;
+      sqlite3ValueApplyAffinity(pMem, SQLITE_AFF_TEXT, encoding);
+      assert( pMem->flags & MEM_Str || pMem->db->mallocFailed );
+      pMem->flags &= ~(MEM_Int|MEM_Real|MEM_IntReal|MEM_Blob|MEM_Zero);
+      if( encoding!=SQLITE_UTF8 ) pMem->n &= ~1;
+      rc = sqlite3VdbeChangeEncoding(pMem, encoding);
+      if( rc ) return rc;
+      sqlite3VdbeMemZeroTerminateIfAble(pMem);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Initialize bulk memory to be a consistent Mem object.
+**
+** The minimum amount of initialization feasible is performed.
+*/
+void sqlite3VdbeMemInit(Mem *pMem, sqlite3 *db, u16 flags){
+  assert( (flags & ~MEM_TypeMask)==0 );
+  pMem->flags = flags;
+  pMem->db = db;
+  pMem->szMalloc = 0;
+}
+
+
+/*
+** Delete any previous value and set the value stored in *pMem to NULL.
+**
+** This routine calls the Mem.xDel destructor to dispose of values that
+** require the destructor.  But it preserves the Mem.zMalloc memory allocation.
+** To free all resources, use sqlite3VdbeMemRelease(), which both calls this
+** routine to invoke the destructor and deallocates Mem.zMalloc.
+**
+** Use this routine to reset the Mem prior to insert a new value.
+**
+** Use sqlite3VdbeMemRelease() to complete erase the Mem prior to abandoning it.
+*/
+void sqlite3VdbeMemSetNull(Mem *pMem){
+  if( VdbeMemDynamic(pMem) ){
+    vdbeMemClearExternAndSetNull(pMem);
+  }else{
+    pMem->flags = MEM_Null;
+  }
+}
+void sqlite3ValueSetNull(sqlite3_value *p){
+  sqlite3VdbeMemSetNull((Mem*)p); 
+}
+
+/*
+** Delete any previous value and set the value to be a BLOB of length
+** n containing all zeros.
+*/
+#ifndef SQLITE_OMIT_INCRBLOB
+void sqlite3VdbeMemSetZeroBlob(Mem *pMem, int n){
+  sqlite3VdbeMemRelease(pMem);
+  pMem->flags = MEM_Blob|MEM_Zero;
+  pMem->n = 0;
+  if( n<0 ) n = 0;
+  pMem->u.nZero = n;
+  pMem->enc = SQLITE_UTF8;
+  pMem->z = 0;
+}
+#else
+int sqlite3VdbeMemSetZeroBlob(Mem *pMem, int n){
+  int nByte = n>0?n:1;
+  if( sqlite3VdbeMemGrow(pMem, nByte, 0) ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  assert( pMem->z!=0 );
+  assert( sqlite3DbMallocSize(pMem->db, pMem->z)>=nByte );
+  memset(pMem->z, 0, nByte);
+  pMem->n = n>0?n:0;
+  pMem->flags = MEM_Blob;
+  pMem->enc = SQLITE_UTF8;
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** The pMem is known to contain content that needs to be destroyed prior
+** to a value change.  So invoke the destructor, then set the value to
+** a 64-bit integer.
+*/
+static SQLITE_NOINLINE void vdbeReleaseAndSetInt64(Mem *pMem, i64 val){
+  sqlite3VdbeMemSetNull(pMem);
+  pMem->u.i = val;
+  pMem->flags = MEM_Int;
+}
+
+/*
+** Delete any previous value and set the value stored in *pMem to val,
+** manifest type INTEGER.
+*/
+void sqlite3VdbeMemSetInt64(Mem *pMem, i64 val){
+  if( VdbeMemDynamic(pMem) ){
+    vdbeReleaseAndSetInt64(pMem, val);
+  }else{
+    pMem->u.i = val;
+    pMem->flags = MEM_Int;
+  }
+}
+
+/* A no-op destructor */
+void sqlite3NoopDestructor(void *p){ UNUSED_PARAMETER(p); }
+
+/*
+** Set the value stored in *pMem should already be a NULL.
+** Also store a pointer to go with it.
+*/
+void sqlite3VdbeMemSetPointer(
+  Mem *pMem,
+  void *pPtr,
+  const char *zPType,
+  void (*xDestructor)(void*)
+){
+  assert( pMem->flags==MEM_Null );
+  vdbeMemClear(pMem);
+  pMem->u.zPType = zPType ? zPType : "";
+  pMem->z = pPtr;
+  pMem->flags = MEM_Null|MEM_Dyn|MEM_Subtype|MEM_Term;
+  pMem->eSubtype = 'p';
+  pMem->xDel = xDestructor ? xDestructor : sqlite3NoopDestructor;
+}
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/*
+** Delete any previous value and set the value stored in *pMem to val,
+** manifest type REAL.
+*/
+void sqlite3VdbeMemSetDouble(Mem *pMem, double val){
+  sqlite3VdbeMemSetNull(pMem);
+  if( !sqlite3IsNaN(val) ){
+    pMem->u.r = val;
+    pMem->flags = MEM_Real;
+  }
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Return true if the Mem holds a RowSet object.  This routine is intended
+** for use inside of assert() statements.
+*/
+int sqlite3VdbeMemIsRowSet(const Mem *pMem){
+  return (pMem->flags&(MEM_Blob|MEM_Dyn))==(MEM_Blob|MEM_Dyn)
+         && pMem->xDel==sqlite3RowSetDelete;
+}
+#endif
+
+/*
+** Delete any previous value and set the value of pMem to be an
+** empty boolean index.
+**
+** Return SQLITE_OK on success and SQLITE_NOMEM if a memory allocation
+** error occurs.
+*/
+int sqlite3VdbeMemSetRowSet(Mem *pMem){
+  sqlite3 *db = pMem->db;
+  RowSet *p;
+  assert( db!=0 );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  sqlite3VdbeMemRelease(pMem);
+  p = sqlite3RowSetInit(db);
+  if( p==0 ) return SQLITE_NOMEM;
+  pMem->z = (char*)p;
+  pMem->flags = MEM_Blob|MEM_Dyn;
+  pMem->xDel = sqlite3RowSetDelete;
+  return SQLITE_OK;
+}
+
+/*
+** Return true if the Mem object contains a TEXT or BLOB that is
+** too large - whose size exceeds SQLITE_MAX_LENGTH.
+*/
+int sqlite3VdbeMemTooBig(Mem *p){
+  assert( p->db!=0 );
+  if( p->flags & (MEM_Str|MEM_Blob) ){
+    int n = p->n;
+    if( p->flags & MEM_Zero ){
+      n += p->u.nZero;
+    }
+    return n>p->db->aLimit[SQLITE_LIMIT_LENGTH];
+  }
+  return 0; 
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** This routine prepares a memory cell for modification by breaking
+** its link to a shallow copy and by marking any current shallow
+** copies of this cell as invalid.
+**
+** This is used for testing and debugging only - to help ensure that shallow
+** copies (created by OP_SCopy) are not misused.
+*/
+void sqlite3VdbeMemAboutToChange(Vdbe *pVdbe, Mem *pMem){
+  int i;
+  Mem *pX;
+  for(i=1, pX=pVdbe->aMem+1; i<pVdbe->nMem; i++, pX++){
+    if( pX->pScopyFrom==pMem ){
+      u16 mFlags;
+      if( pVdbe->db->flags & SQLITE_VdbeTrace ){
+        sqlite3DebugPrintf("Invalidate R[%d] due to change in R[%d]\n",
+          (int)(pX - pVdbe->aMem), (int)(pMem - pVdbe->aMem));
+      }
+      /* If pX is marked as a shallow copy of pMem, then try to verify that
+      ** no significant changes have been made to pX since the OP_SCopy.
+      ** A significant change would indicated a missed call to this
+      ** function for pX.  Minor changes, such as adding or removing a
+      ** dual type, are allowed, as long as the underlying value is the
+      ** same. */
+      mFlags = pMem->flags & pX->flags & pX->mScopyFlags;
+      assert( (mFlags&(MEM_Int|MEM_IntReal))==0 || pMem->u.i==pX->u.i );
+      
+      /* pMem is the register that is changing.  But also mark pX as
+      ** undefined so that we can quickly detect the shallow-copy error */
+      pX->flags = MEM_Undefined;
+      pX->pScopyFrom = 0;
+    }
+  }
+  pMem->pScopyFrom = 0;
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** Make an shallow copy of pFrom into pTo.  Prior contents of
+** pTo are freed.  The pFrom->z field is not duplicated.  If
+** pFrom->z is used, then pTo->z points to the same thing as pFrom->z
+** and flags gets srcType (either MEM_Ephem or MEM_Static).
+*/
+static SQLITE_NOINLINE void vdbeClrCopy(Mem *pTo, const Mem *pFrom, int eType){
+  vdbeMemClearExternAndSetNull(pTo);
+  assert( !VdbeMemDynamic(pTo) );
+  sqlite3VdbeMemShallowCopy(pTo, pFrom, eType);
+}
+void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int srcType){
+  assert( !sqlite3VdbeMemIsRowSet(pFrom) );
+  assert( pTo->db==pFrom->db );
+  if( VdbeMemDynamic(pTo) ){ vdbeClrCopy(pTo,pFrom,srcType); return; }
+  memcpy(pTo, pFrom, MEMCELLSIZE);
+  if( (pFrom->flags&MEM_Static)==0 ){
+    pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Ephem);
+    assert( srcType==MEM_Ephem || srcType==MEM_Static );
+    pTo->flags |= srcType;
+  }
+}
+
+/*
+** Make a full copy of pFrom into pTo.  Prior contents of pTo are
+** freed before the copy is made.
+*/
+int sqlite3VdbeMemCopy(Mem *pTo, const Mem *pFrom){
+  int rc = SQLITE_OK;
+
+  assert( !sqlite3VdbeMemIsRowSet(pFrom) );
+  if( VdbeMemDynamic(pTo) ) vdbeMemClearExternAndSetNull(pTo);
+  memcpy(pTo, pFrom, MEMCELLSIZE);
+  pTo->flags &= ~MEM_Dyn;
+  if( pTo->flags&(MEM_Str|MEM_Blob) ){
+    if( 0==(pFrom->flags&MEM_Static) ){
+      pTo->flags |= MEM_Ephem;
+      rc = sqlite3VdbeMemMakeWriteable(pTo);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Transfer the contents of pFrom to pTo. Any existing value in pTo is
+** freed. If pFrom contains ephemeral data, a copy is made.
+**
+** pFrom contains an SQL NULL when this routine returns.
+*/
+void sqlite3VdbeMemMove(Mem *pTo, Mem *pFrom){
+  assert( pFrom->db==0 || sqlite3_mutex_held(pFrom->db->mutex) );
+  assert( pTo->db==0 || sqlite3_mutex_held(pTo->db->mutex) );
+  assert( pFrom->db==0 || pTo->db==0 || pFrom->db==pTo->db );
+
+  sqlite3VdbeMemRelease(pTo);
+  memcpy(pTo, pFrom, sizeof(Mem));
+  pFrom->flags = MEM_Null;
+  pFrom->szMalloc = 0;
+}
+
+/*
+** Change the value of a Mem to be a string or a BLOB.
+**
+** The memory management strategy depends on the value of the xDel
+** parameter. If the value passed is SQLITE_TRANSIENT, then the 
+** string is copied into a (possibly existing) buffer managed by the 
+** Mem structure. Otherwise, any existing buffer is freed and the
+** pointer copied.
+**
+** If the string is too large (if it exceeds the SQLITE_LIMIT_LENGTH
+** size limit) then no memory allocation occurs.  If the string can be
+** stored without allocating memory, then it is.  If a memory allocation
+** is required to store the string, then value of pMem is unchanged.  In
+** either case, SQLITE_TOOBIG is returned.
+**
+** The "enc" parameter is the text encoding for the string, or zero
+** to store a blob.
+**
+** If n is negative, then the string consists of all bytes up to but
+** excluding the first zero character.  The n parameter must be
+** non-negative for blobs.
+*/
+int sqlite3VdbeMemSetStr(
+  Mem *pMem,          /* Memory cell to set to string value */
+  const char *z,      /* String pointer */
+  i64 n,              /* Bytes in string, or negative */
+  u8 enc,             /* Encoding of z.  0 for BLOBs */
+  void (*xDel)(void*) /* Destructor function */
+){
+  i64 nByte = n;      /* New value for pMem->n */
+  int iLimit;         /* Maximum allowed string or blob size */
+  u16 flags;          /* New value for pMem->flags */
+
+  assert( pMem!=0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  assert( enc!=0 || n>=0 );
+
+  /* If z is a NULL pointer, set pMem to contain an SQL NULL. */
+  if( !z ){
+    sqlite3VdbeMemSetNull(pMem);
+    return SQLITE_OK;
+  }
+
+  if( pMem->db ){
+    iLimit = pMem->db->aLimit[SQLITE_LIMIT_LENGTH];
+  }else{
+    iLimit = SQLITE_MAX_LENGTH;
+  }
+  if( nByte<0 ){
+    assert( enc!=0 );
+    if( enc==SQLITE_UTF8 ){
+      nByte = strlen(z);
+    }else{
+      for(nByte=0; nByte<=iLimit && (z[nByte] | z[nByte+1]); nByte+=2){}
+    }
+    flags= MEM_Str|MEM_Term;
+  }else if( enc==0 ){
+    flags = MEM_Blob;
+    enc = SQLITE_UTF8;
+  }else{
+    flags = MEM_Str;
+  }
+  if( nByte>iLimit ){
+    if( xDel && xDel!=SQLITE_TRANSIENT ){
+      if( xDel==SQLITE_DYNAMIC ){
+        sqlite3DbFree(pMem->db, (void*)z);
+      }else{
+        xDel((void*)z);
+      }
+    }
+    sqlite3VdbeMemSetNull(pMem);
+    return sqlite3ErrorToParser(pMem->db, SQLITE_TOOBIG);
+  }
+
+  /* The following block sets the new values of Mem.z and Mem.xDel. It
+  ** also sets a flag in local variable "flags" to indicate the memory
+  ** management (one of MEM_Dyn or MEM_Static).
+  */
+  if( xDel==SQLITE_TRANSIENT ){
+    i64 nAlloc = nByte;
+    if( flags&MEM_Term ){
+      nAlloc += (enc==SQLITE_UTF8?1:2);
+    }
+    testcase( nAlloc==0 );
+    testcase( nAlloc==31 );
+    testcase( nAlloc==32 );
+    if( sqlite3VdbeMemClearAndResize(pMem, (int)MAX(nAlloc,32)) ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    memcpy(pMem->z, z, nAlloc);
+  }else{
+    sqlite3VdbeMemRelease(pMem);
+    pMem->z = (char *)z;
+    if( xDel==SQLITE_DYNAMIC ){
+      pMem->zMalloc = pMem->z;
+      pMem->szMalloc = sqlite3DbMallocSize(pMem->db, pMem->zMalloc);
+    }else{
+      pMem->xDel = xDel;
+      flags |= ((xDel==SQLITE_STATIC)?MEM_Static:MEM_Dyn);
+    }
+  }
+
+  pMem->n = (int)(nByte & 0x7fffffff);
+  pMem->flags = flags;
+  pMem->enc = enc;
+
+#ifndef SQLITE_OMIT_UTF16
+  if( enc>SQLITE_UTF8 && sqlite3VdbeMemHandleBom(pMem) ){
+    return SQLITE_NOMEM_BKPT;
+  }
+#endif
+
+
+  return SQLITE_OK;
+}
+
+/*
+** Move data out of a btree key or data field and into a Mem structure.
+** The data is payload from the entry that pCur is currently pointing
+** to.  offset and amt determine what portion of the data or key to retrieve.
+** The result is written into the pMem element.
+**
+** The pMem object must have been initialized.  This routine will use
+** pMem->zMalloc to hold the content from the btree, if possible.  New
+** pMem->zMalloc space will be allocated if necessary.  The calling routine
+** is responsible for making sure that the pMem object is eventually
+** destroyed.
+**
+** If this routine fails for any reason (malloc returns NULL or unable
+** to read from the disk) then the pMem is left in an inconsistent state.
+*/
+int sqlite3VdbeMemFromBtree(
+  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
+  u32 offset,       /* Offset from the start of data to return bytes from. */
+  u32 amt,          /* Number of bytes to return. */
+  Mem *pMem         /* OUT: Return data in this Mem structure. */
+){
+  int rc;
+  pMem->flags = MEM_Null;
+  if( sqlite3BtreeMaxRecordSize(pCur)<offset+amt ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  if( SQLITE_OK==(rc = sqlite3VdbeMemClearAndResize(pMem, amt+1)) ){
+    rc = sqlite3BtreePayload(pCur, offset, amt, pMem->z);
+    if( rc==SQLITE_OK ){
+      pMem->z[amt] = 0;   /* Overrun area used when reading malformed records */
+      pMem->flags = MEM_Blob;
+      pMem->n = (int)amt;
+    }else{
+      sqlite3VdbeMemRelease(pMem);
+    }
+  }
+  return rc;
+}
+int sqlite3VdbeMemFromBtreeZeroOffset(
+  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
+  u32 amt,          /* Number of bytes to return. */
+  Mem *pMem         /* OUT: Return data in this Mem structure. */
+){
+  u32 available = 0;  /* Number of bytes available on the local btree page */
+  int rc = SQLITE_OK; /* Return code */
+
+  assert( sqlite3BtreeCursorIsValid(pCur) );
+  assert( !VdbeMemDynamic(pMem) );
+
+  /* Note: the calls to BtreeKeyFetch() and DataFetch() below assert() 
+  ** that both the BtShared and database handle mutexes are held. */
+  assert( !sqlite3VdbeMemIsRowSet(pMem) );
+  pMem->z = (char *)sqlite3BtreePayloadFetch(pCur, &available);
+  assert( pMem->z!=0 );
+
+  if( amt<=available ){
+    pMem->flags = MEM_Blob|MEM_Ephem;
+    pMem->n = (int)amt;
+  }else{
+    rc = sqlite3VdbeMemFromBtree(pCur, 0, amt, pMem);
+  }
+
+  return rc;
+}
+
+/*
+** The pVal argument is known to be a value other than NULL.
+** Convert it into a string with encoding enc and return a pointer
+** to a zero-terminated version of that string.
+*/
+static SQLITE_NOINLINE const void *valueToText(sqlite3_value* pVal, u8 enc){
+  assert( pVal!=0 );
+  assert( pVal->db==0 || sqlite3_mutex_held(pVal->db->mutex) );
+  assert( (enc&3)==(enc&~SQLITE_UTF16_ALIGNED) );
+  assert( !sqlite3VdbeMemIsRowSet(pVal) );
+  assert( (pVal->flags & (MEM_Null))==0 );
+  if( pVal->flags & (MEM_Blob|MEM_Str) ){
+    if( ExpandBlob(pVal) ) return 0;
+    pVal->flags |= MEM_Str;
+    if( pVal->enc != (enc & ~SQLITE_UTF16_ALIGNED) ){
+      sqlite3VdbeChangeEncoding(pVal, enc & ~SQLITE_UTF16_ALIGNED);
+    }
+    if( (enc & SQLITE_UTF16_ALIGNED)!=0 && 1==(1&SQLITE_PTR_TO_INT(pVal->z)) ){
+      assert( (pVal->flags & (MEM_Ephem|MEM_Static))!=0 );
+      if( sqlite3VdbeMemMakeWriteable(pVal)!=SQLITE_OK ){
+        return 0;
+      }
+    }
+    sqlite3VdbeMemNulTerminate(pVal); /* IMP: R-31275-44060 */
+  }else{
+    sqlite3VdbeMemStringify(pVal, enc, 0);
+    assert( 0==(1&SQLITE_PTR_TO_INT(pVal->z)) );
+  }
+  assert(pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) || pVal->db==0
+              || pVal->db->mallocFailed );
+  if( pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) ){
+    assert( sqlite3VdbeMemValidStrRep(pVal) );
+    return pVal->z;
+  }else{
+    return 0;
+  }
+}
+
+/* This function is only available internally, it is not part of the
+** external API. It works in a similar way to sqlite3_value_text(),
+** except the data returned is in the encoding specified by the second
+** parameter, which must be one of SQLITE_UTF16BE, SQLITE_UTF16LE or
+** SQLITE_UTF8.
+**
+** (2006-02-16:)  The enc value can be or-ed with SQLITE_UTF16_ALIGNED.
+** If that is the case, then the result must be aligned on an even byte
+** boundary.
+*/
+const void *sqlite3ValueText(sqlite3_value* pVal, u8 enc){
+  if( !pVal ) return 0;
+  assert( pVal->db==0 || sqlite3_mutex_held(pVal->db->mutex) );
+  assert( (enc&3)==(enc&~SQLITE_UTF16_ALIGNED) );
+  assert( !sqlite3VdbeMemIsRowSet(pVal) );
+  if( (pVal->flags&(MEM_Str|MEM_Term))==(MEM_Str|MEM_Term) && pVal->enc==enc ){
+    assert( sqlite3VdbeMemValidStrRep(pVal) );
+    return pVal->z;
+  }
+  if( pVal->flags&MEM_Null ){
+    return 0;
+  }
+  return valueToText(pVal, enc);
+}
+
+/* Return true if sqlit3_value object pVal is a string or blob value
+** that uses the destructor specified in the second argument.
+**
+** TODO:  Maybe someday promote this interface into a published API so
+** that third-party extensions can get access to it?
+*/
+int sqlite3ValueIsOfClass(const sqlite3_value *pVal, void(*xFree)(void*)){
+  if( ALWAYS(pVal!=0)
+   && ALWAYS((pVal->flags & (MEM_Str|MEM_Blob))!=0)
+   && (pVal->flags & MEM_Dyn)!=0
+   && pVal->xDel==xFree
+  ){
+    return 1;
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Create a new sqlite3_value object.
+*/
+sqlite3_value *sqlite3ValueNew(sqlite3 *db){
+  Mem *p = sqlite3DbMallocZero(db, sizeof(*p));
+  if( p ){
+    p->flags = MEM_Null;
+    p->db = db;
+  }
+  return p;
+}
+
+/*
+** Context object passed by sqlite3Stat4ProbeSetValue() through to 
+** valueNew(). See comments above valueNew() for details.
+*/
+struct ValueNewStat4Ctx {
+  Parse *pParse;
+  Index *pIdx;
+  UnpackedRecord **ppRec;
+  int iVal;
+};
+
+/*
+** Allocate and return a pointer to a new sqlite3_value object. If
+** the second argument to this function is NULL, the object is allocated
+** by calling sqlite3ValueNew().
+**
+** Otherwise, if the second argument is non-zero, then this function is 
+** being called indirectly by sqlite3Stat4ProbeSetValue(). If it has not
+** already been allocated, allocate the UnpackedRecord structure that 
+** that function will return to its caller here. Then return a pointer to
+** an sqlite3_value within the UnpackedRecord.a[] array.
+*/
+static sqlite3_value *valueNew(sqlite3 *db, struct ValueNewStat4Ctx *p){
+#ifdef SQLITE_ENABLE_STAT4
+  if( p ){
+    UnpackedRecord *pRec = p->ppRec[0];
+
+    if( pRec==0 ){
+      Index *pIdx = p->pIdx;      /* Index being probed */
+      int nByte;                  /* Bytes of space to allocate */
+      int i;                      /* Counter variable */
+      int nCol = pIdx->nColumn;   /* Number of index columns including rowid */
+  
+      nByte = sizeof(Mem) * nCol + ROUND8(sizeof(UnpackedRecord));
+      pRec = (UnpackedRecord*)sqlite3DbMallocZero(db, nByte);
+      if( pRec ){
+        pRec->pKeyInfo = sqlite3KeyInfoOfIndex(p->pParse, pIdx);
+        if( pRec->pKeyInfo ){
+          assert( pRec->pKeyInfo->nAllField==nCol );
+          assert( pRec->pKeyInfo->enc==ENC(db) );
+          pRec->aMem = (Mem *)((u8*)pRec + ROUND8(sizeof(UnpackedRecord)));
+          for(i=0; i<nCol; i++){
+            pRec->aMem[i].flags = MEM_Null;
+            pRec->aMem[i].db = db;
+          }
+        }else{
+          sqlite3DbFreeNN(db, pRec);
+          pRec = 0;
+        }
+      }
+      if( pRec==0 ) return 0;
+      p->ppRec[0] = pRec;
+    }
+  
+    pRec->nField = p->iVal+1;
+    sqlite3VdbeMemSetNull(&pRec->aMem[p->iVal]);
+    return &pRec->aMem[p->iVal];
+  }
+#else
+  UNUSED_PARAMETER(p);
+#endif /* defined(SQLITE_ENABLE_STAT4) */
+  return sqlite3ValueNew(db);
+}
+
+/*
+** The expression object indicated by the second argument is guaranteed
+** to be a scalar SQL function. If
+**
+**   * all function arguments are SQL literals,
+**   * one of the SQLITE_FUNC_CONSTANT or _SLOCHNG function flags is set, and
+**   * the SQLITE_FUNC_NEEDCOLL function flag is not set,
+**
+** then this routine attempts to invoke the SQL function. Assuming no
+** error occurs, output parameter (*ppVal) is set to point to a value 
+** object containing the result before returning SQLITE_OK.
+**
+** Affinity aff is applied to the result of the function before returning.
+** If the result is a text value, the sqlite3_value object uses encoding 
+** enc.
+**
+** If the conditions above are not met, this function returns SQLITE_OK
+** and sets (*ppVal) to NULL. Or, if an error occurs, (*ppVal) is set to
+** NULL and an SQLite error code returned.
+*/
+#ifdef SQLITE_ENABLE_STAT4
+static int valueFromFunction(
+  sqlite3 *db,                    /* The database connection */
+  const Expr *p,                  /* The expression to evaluate */
+  u8 enc,                         /* Encoding to use */
+  u8 aff,                         /* Affinity to use */
+  sqlite3_value **ppVal,          /* Write the new value here */
+  struct ValueNewStat4Ctx *pCtx   /* Second argument for valueNew() */
+){
+  sqlite3_context ctx;            /* Context object for function invocation */
+  sqlite3_value **apVal = 0;      /* Function arguments */
+  int nVal = 0;                   /* Size of apVal[] array */
+  FuncDef *pFunc = 0;             /* Function definition */
+  sqlite3_value *pVal = 0;        /* New value */
+  int rc = SQLITE_OK;             /* Return code */
+  ExprList *pList = 0;            /* Function arguments */
+  int i;                          /* Iterator variable */
+
+  assert( pCtx!=0 );
+  assert( (p->flags & EP_TokenOnly)==0 );
+  assert( ExprUseXList(p) );
+  pList = p->x.pList;
+  if( pList ) nVal = pList->nExpr;
+  assert( !ExprHasProperty(p, EP_IntValue) );
+  pFunc = sqlite3FindFunction(db, p->u.zToken, nVal, enc, 0);
+#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
+  if( pFunc==0 ) return SQLITE_OK;
+#endif
+  assert( pFunc );
+  if( (pFunc->funcFlags & (SQLITE_FUNC_CONSTANT|SQLITE_FUNC_SLOCHNG))==0
+   || (pFunc->funcFlags & (SQLITE_FUNC_NEEDCOLL|SQLITE_FUNC_RUNONLY))!=0
+  ){
+    return SQLITE_OK;
+  }
+
+  if( pList ){
+    apVal = (sqlite3_value**)sqlite3DbMallocZero(db, sizeof(apVal[0]) * nVal);
+    if( apVal==0 ){
+      rc = SQLITE_NOMEM_BKPT;
+      goto value_from_function_out;
+    }
+    for(i=0; i<nVal; i++){
+      rc = sqlite3ValueFromExpr(db, pList->a[i].pExpr, enc, aff, &apVal[i]);
+      if( apVal[i]==0 || rc!=SQLITE_OK ) goto value_from_function_out;
+    }
+  }
+
+  pVal = valueNew(db, pCtx);
+  if( pVal==0 ){
+    rc = SQLITE_NOMEM_BKPT;
+    goto value_from_function_out;
+  }
+
+  memset(&ctx, 0, sizeof(ctx));
+  ctx.pOut = pVal;
+  ctx.pFunc = pFunc;
+  ctx.enc = ENC(db);
+  pFunc->xSFunc(&ctx, nVal, apVal);
+  if( ctx.isError ){
+    rc = ctx.isError;
+    sqlite3ErrorMsg(pCtx->pParse, "%s", sqlite3_value_text(pVal));
+  }else{
+    sqlite3ValueApplyAffinity(pVal, aff, SQLITE_UTF8);
+    assert( rc==SQLITE_OK );
+    rc = sqlite3VdbeChangeEncoding(pVal, enc);
+    if( NEVER(rc==SQLITE_OK && sqlite3VdbeMemTooBig(pVal)) ){
+      rc = SQLITE_TOOBIG;
+      pCtx->pParse->nErr++;
+    }
+  }
+
+ value_from_function_out:
+  if( rc!=SQLITE_OK ){
+    pVal = 0;
+    pCtx->pParse->rc = rc;
+  }
+  if( apVal ){
+    for(i=0; i<nVal; i++){
+      sqlite3ValueFree(apVal[i]);
+    }
+    sqlite3DbFreeNN(db, apVal);
+  }
+
+  *ppVal = pVal;
+  return rc;
+}
+#else
+# define valueFromFunction(a,b,c,d,e,f) SQLITE_OK
+#endif /* defined(SQLITE_ENABLE_STAT4) */
+
+/*
+** Extract a value from the supplied expression in the manner described
+** above sqlite3ValueFromExpr(). Allocate the sqlite3_value object
+** using valueNew().
+**
+** If pCtx is NULL and an error occurs after the sqlite3_value object
+** has been allocated, it is freed before returning. Or, if pCtx is not
+** NULL, it is assumed that the caller will free any allocated object
+** in all cases.
+*/
+static int valueFromExpr(
+  sqlite3 *db,                    /* The database connection */
+  const Expr *pExpr,              /* The expression to evaluate */
+  u8 enc,                         /* Encoding to use */
+  u8 affinity,                    /* Affinity to use */
+  sqlite3_value **ppVal,          /* Write the new value here */
+  struct ValueNewStat4Ctx *pCtx   /* Second argument for valueNew() */
+){
+  int op;
+  char *zVal = 0;
+  sqlite3_value *pVal = 0;
+  int negInt = 1;
+  const char *zNeg = "";
+  int rc = SQLITE_OK;
+
+  assert( pExpr!=0 );
+  while( (op = pExpr->op)==TK_UPLUS || op==TK_SPAN ) pExpr = pExpr->pLeft;
+  if( op==TK_REGISTER ) op = pExpr->op2;
+
+  /* Compressed expressions only appear when parsing the DEFAULT clause
+  ** on a table column definition, and hence only when pCtx==0.  This
+  ** check ensures that an EP_TokenOnly expression is never passed down
+  ** into valueFromFunction(). */
+  assert( (pExpr->flags & EP_TokenOnly)==0 || pCtx==0 );
+
+  if( op==TK_CAST ){
+    u8 aff;
+    assert( !ExprHasProperty(pExpr, EP_IntValue) );
+    aff = sqlite3AffinityType(pExpr->u.zToken,0);
+    rc = valueFromExpr(db, pExpr->pLeft, enc, aff, ppVal, pCtx);
+    testcase( rc!=SQLITE_OK );
+    if( *ppVal ){
+#ifdef SQLITE_ENABLE_STAT4
+      rc = ExpandBlob(*ppVal);
+#else
+      /* zero-blobs only come from functions, not literal values.  And
+      ** functions are only processed under STAT4 */
+      assert( (ppVal[0][0].flags & MEM_Zero)==0 );
+#endif
+      sqlite3VdbeMemCast(*ppVal, aff, enc);
+      sqlite3ValueApplyAffinity(*ppVal, affinity, enc);
+    }
+    return rc;
+  }
+
+  /* Handle negative integers in a single step.  This is needed in the
+  ** case when the value is -9223372036854775808.
+  */
+  if( op==TK_UMINUS
+   && (pExpr->pLeft->op==TK_INTEGER || pExpr->pLeft->op==TK_FLOAT) ){
+    pExpr = pExpr->pLeft;
+    op = pExpr->op;
+    negInt = -1;
+    zNeg = "-";
+  }
+
+  if( op==TK_STRING || op==TK_FLOAT || op==TK_INTEGER ){
+    pVal = valueNew(db, pCtx);
+    if( pVal==0 ) goto no_mem;
+    if( ExprHasProperty(pExpr, EP_IntValue) ){
+      sqlite3VdbeMemSetInt64(pVal, (i64)pExpr->u.iValue*negInt);
+    }else{
+      zVal = sqlite3MPrintf(db, "%s%s", zNeg, pExpr->u.zToken);
+      if( zVal==0 ) goto no_mem;
+      sqlite3ValueSetStr(pVal, -1, zVal, SQLITE_UTF8, SQLITE_DYNAMIC);
+    }
+    if( (op==TK_INTEGER || op==TK_FLOAT ) && affinity==SQLITE_AFF_BLOB ){
+      sqlite3ValueApplyAffinity(pVal, SQLITE_AFF_NUMERIC, SQLITE_UTF8);
+    }else{
+      sqlite3ValueApplyAffinity(pVal, affinity, SQLITE_UTF8);
+    }
+    assert( (pVal->flags & MEM_IntReal)==0 );
+    if( pVal->flags & (MEM_Int|MEM_IntReal|MEM_Real) ){
+      testcase( pVal->flags & MEM_Int );
+      testcase( pVal->flags & MEM_Real );
+      pVal->flags &= ~MEM_Str;
+    }
+    if( enc!=SQLITE_UTF8 ){
+      rc = sqlite3VdbeChangeEncoding(pVal, enc);
+    }
+  }else if( op==TK_UMINUS ) {
+    /* This branch happens for multiple negative signs.  Ex: -(-5) */
+    if( SQLITE_OK==valueFromExpr(db,pExpr->pLeft,enc,affinity,&pVal,pCtx) 
+     && pVal!=0
+    ){
+      sqlite3VdbeMemNumerify(pVal);
+      if( pVal->flags & MEM_Real ){
+        pVal->u.r = -pVal->u.r;
+      }else if( pVal->u.i==SMALLEST_INT64 ){
+#ifndef SQLITE_OMIT_FLOATING_POINT
+        pVal->u.r = -(double)SMALLEST_INT64;
+#else
+        pVal->u.r = LARGEST_INT64;
+#endif
+        MemSetTypeFlag(pVal, MEM_Real);
+      }else{
+        pVal->u.i = -pVal->u.i;
+      }
+      sqlite3ValueApplyAffinity(pVal, affinity, enc);
+    }
+  }else if( op==TK_NULL ){
+    pVal = valueNew(db, pCtx);
+    if( pVal==0 ) goto no_mem;
+    sqlite3VdbeMemSetNull(pVal);
+  }
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+  else if( op==TK_BLOB ){
+    int nVal;
+    assert( !ExprHasProperty(pExpr, EP_IntValue) );
+    assert( pExpr->u.zToken[0]=='x' || pExpr->u.zToken[0]=='X' );
+    assert( pExpr->u.zToken[1]=='\'' );
+    pVal = valueNew(db, pCtx);
+    if( !pVal ) goto no_mem;
+    zVal = &pExpr->u.zToken[2];
+    nVal = sqlite3Strlen30(zVal)-1;
+    assert( zVal[nVal]=='\'' );
+    sqlite3VdbeMemSetStr(pVal, sqlite3HexToBlob(db, zVal, nVal), nVal/2,
+                         0, SQLITE_DYNAMIC);
+  }
+#endif
+#ifdef SQLITE_ENABLE_STAT4
+  else if( op==TK_FUNCTION && pCtx!=0 ){
+    rc = valueFromFunction(db, pExpr, enc, affinity, &pVal, pCtx);
+  }
+#endif
+  else if( op==TK_TRUEFALSE ){
+    assert( !ExprHasProperty(pExpr, EP_IntValue) );
+    pVal = valueNew(db, pCtx);
+    if( pVal ){
+      pVal->flags = MEM_Int;
+      pVal->u.i = pExpr->u.zToken[4]==0;
+      sqlite3ValueApplyAffinity(pVal, affinity, enc);
+    }
+  }
+
+  *ppVal = pVal;
+  return rc;
+
+no_mem:
+#ifdef SQLITE_ENABLE_STAT4
+  if( pCtx==0 || NEVER(pCtx->pParse->nErr==0) )
+#endif
+    sqlite3OomFault(db);
+  sqlite3DbFree(db, zVal);
+  assert( *ppVal==0 );
+#ifdef SQLITE_ENABLE_STAT4
+  if( pCtx==0 ) sqlite3ValueFree(pVal);
+#else
+  assert( pCtx==0 ); sqlite3ValueFree(pVal);
+#endif
+  return SQLITE_NOMEM_BKPT;
+}
+
+/*
+** Create a new sqlite3_value object, containing the value of pExpr.
+**
+** This only works for very simple expressions that consist of one constant
+** token (i.e. "5", "5.1", "'a string'"). If the expression can
+** be converted directly into a value, then the value is allocated and
+** a pointer written to *ppVal. The caller is responsible for deallocating
+** the value by passing it to sqlite3ValueFree() later on. If the expression
+** cannot be converted to a value, then *ppVal is set to NULL.
+*/
+int sqlite3ValueFromExpr(
+  sqlite3 *db,              /* The database connection */
+  const Expr *pExpr,        /* The expression to evaluate */
+  u8 enc,                   /* Encoding to use */
+  u8 affinity,              /* Affinity to use */
+  sqlite3_value **ppVal     /* Write the new value here */
+){
+  return pExpr ? valueFromExpr(db, pExpr, enc, affinity, ppVal, 0) : 0;
+}
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Attempt to extract a value from pExpr and use it to construct *ppVal.
+**
+** If pAlloc is not NULL, then an UnpackedRecord object is created for
+** pAlloc if one does not exist and the new value is added to the
+** UnpackedRecord object.
+**
+** A value is extracted in the following cases:
+**
+**  * (pExpr==0). In this case the value is assumed to be an SQL NULL,
+**
+**  * The expression is a bound variable, and this is a reprepare, or
+**
+**  * The expression is a literal value.
+**
+** On success, *ppVal is made to point to the extracted value.  The caller
+** is responsible for ensuring that the value is eventually freed.
+*/
+static int stat4ValueFromExpr(
+  Parse *pParse,                  /* Parse context */
+  Expr *pExpr,                    /* The expression to extract a value from */
+  u8 affinity,                    /* Affinity to use */
+  struct ValueNewStat4Ctx *pAlloc,/* How to allocate space.  Or NULL */
+  sqlite3_value **ppVal           /* OUT: New value object (or NULL) */
+){
+  int rc = SQLITE_OK;
+  sqlite3_value *pVal = 0;
+  sqlite3 *db = pParse->db;
+
+  /* Skip over any TK_COLLATE nodes */
+  pExpr = sqlite3ExprSkipCollate(pExpr);
+
+  assert( pExpr==0 || pExpr->op!=TK_REGISTER || pExpr->op2!=TK_VARIABLE );
+  if( !pExpr ){
+    pVal = valueNew(db, pAlloc);
+    if( pVal ){
+      sqlite3VdbeMemSetNull((Mem*)pVal);
+    }
+  }else if( pExpr->op==TK_VARIABLE && (db->flags & SQLITE_EnableQPSG)==0 ){
+    Vdbe *v;
+    int iBindVar = pExpr->iColumn;
+    sqlite3VdbeSetVarmask(pParse->pVdbe, iBindVar);
+    if( (v = pParse->pReprepare)!=0 ){
+      pVal = valueNew(db, pAlloc);
+      if( pVal ){
+        rc = sqlite3VdbeMemCopy((Mem*)pVal, &v->aVar[iBindVar-1]);
+        sqlite3ValueApplyAffinity(pVal, affinity, ENC(db));
+        pVal->db = pParse->db;
+      }
+    }
+  }else{
+    rc = valueFromExpr(db, pExpr, ENC(db), affinity, &pVal, pAlloc);
+  }
+
+  assert( pVal==0 || pVal->db==db );
+  *ppVal = pVal;
+  return rc;
+}
+
+/*
+** This function is used to allocate and populate UnpackedRecord 
+** structures intended to be compared against sample index keys stored 
+** in the sqlite_stat4 table.
+**
+** A single call to this function populates zero or more fields of the
+** record starting with field iVal (fields are numbered from left to
+** right starting with 0). A single field is populated if:
+**
+**  * (pExpr==0). In this case the value is assumed to be an SQL NULL,
+**
+**  * The expression is a bound variable, and this is a reprepare, or
+**
+**  * The sqlite3ValueFromExpr() function is able to extract a value 
+**    from the expression (i.e. the expression is a literal value).
+**
+** Or, if pExpr is a TK_VECTOR, one field is populated for each of the
+** vector components that match either of the two latter criteria listed
+** above.
+**
+** Before any value is appended to the record, the affinity of the 
+** corresponding column within index pIdx is applied to it. Before
+** this function returns, output parameter *pnExtract is set to the
+** number of values appended to the record.
+**
+** When this function is called, *ppRec must either point to an object
+** allocated by an earlier call to this function, or must be NULL. If it
+** is NULL and a value can be successfully extracted, a new UnpackedRecord
+** is allocated (and *ppRec set to point to it) before returning.
+**
+** Unless an error is encountered, SQLITE_OK is returned. It is not an
+** error if a value cannot be extracted from pExpr. If an error does
+** occur, an SQLite error code is returned.
+*/
+int sqlite3Stat4ProbeSetValue(
+  Parse *pParse,                  /* Parse context */
+  Index *pIdx,                    /* Index being probed */
+  UnpackedRecord **ppRec,         /* IN/OUT: Probe record */
+  Expr *pExpr,                    /* The expression to extract a value from */
+  int nElem,                      /* Maximum number of values to append */
+  int iVal,                       /* Array element to populate */
+  int *pnExtract                  /* OUT: Values appended to the record */
+){
+  int rc = SQLITE_OK;
+  int nExtract = 0;
+
+  if( pExpr==0 || pExpr->op!=TK_SELECT ){
+    int i;
+    struct ValueNewStat4Ctx alloc;
+
+    alloc.pParse = pParse;
+    alloc.pIdx = pIdx;
+    alloc.ppRec = ppRec;
+
+    for(i=0; i<nElem; i++){
+      sqlite3_value *pVal = 0;
+      Expr *pElem = (pExpr ? sqlite3VectorFieldSubexpr(pExpr, i) : 0);
+      u8 aff = sqlite3IndexColumnAffinity(pParse->db, pIdx, iVal+i);
+      alloc.iVal = iVal+i;
+      rc = stat4ValueFromExpr(pParse, pElem, aff, &alloc, &pVal);
+      if( !pVal ) break;
+      nExtract++;
+    }
+  }
+
+  *pnExtract = nExtract;
+  return rc;
+}
+
+/*
+** Attempt to extract a value from expression pExpr using the methods
+** as described for sqlite3Stat4ProbeSetValue() above. 
+**
+** If successful, set *ppVal to point to a new value object and return 
+** SQLITE_OK. If no value can be extracted, but no other error occurs
+** (e.g. OOM), return SQLITE_OK and set *ppVal to NULL. Or, if an error
+** does occur, return an SQLite error code. The final value of *ppVal
+** is undefined in this case.
+*/
+int sqlite3Stat4ValueFromExpr(
+  Parse *pParse,                  /* Parse context */
+  Expr *pExpr,                    /* The expression to extract a value from */
+  u8 affinity,                    /* Affinity to use */
+  sqlite3_value **ppVal           /* OUT: New value object (or NULL) */
+){
+  return stat4ValueFromExpr(pParse, pExpr, affinity, 0, ppVal);
+}
+
+/*
+** Extract the iCol-th column from the nRec-byte record in pRec.  Write
+** the column value into *ppVal.  If *ppVal is initially NULL then a new
+** sqlite3_value object is allocated.
+**
+** If *ppVal is initially NULL then the caller is responsible for 
+** ensuring that the value written into *ppVal is eventually freed.
+*/
+int sqlite3Stat4Column(
+  sqlite3 *db,                    /* Database handle */
+  const void *pRec,               /* Pointer to buffer containing record */
+  int nRec,                       /* Size of buffer pRec in bytes */
+  int iCol,                       /* Column to extract */
+  sqlite3_value **ppVal           /* OUT: Extracted value */
+){
+  u32 t = 0;                      /* a column type code */
+  int nHdr;                       /* Size of the header in the record */
+  int iHdr;                       /* Next unread header byte */
+  int iField;                     /* Next unread data byte */
+  int szField = 0;                /* Size of the current data field */
+  int i;                          /* Column index */
+  u8 *a = (u8*)pRec;              /* Typecast byte array */
+  Mem *pMem = *ppVal;             /* Write result into this Mem object */
+
+  assert( iCol>0 );
+  iHdr = getVarint32(a, nHdr);
+  if( nHdr>nRec || iHdr>=nHdr ) return SQLITE_CORRUPT_BKPT;
+  iField = nHdr;
+  for(i=0; i<=iCol; i++){
+    iHdr += getVarint32(&a[iHdr], t);
+    testcase( iHdr==nHdr );
+    testcase( iHdr==nHdr+1 );
+    if( iHdr>nHdr ) return SQLITE_CORRUPT_BKPT;
+    szField = sqlite3VdbeSerialTypeLen(t);
+    iField += szField;
+  }
+  testcase( iField==nRec );
+  testcase( iField==nRec+1 );
+  if( iField>nRec ) return SQLITE_CORRUPT_BKPT;
+  if( pMem==0 ){
+    pMem = *ppVal = sqlite3ValueNew(db);
+    if( pMem==0 ) return SQLITE_NOMEM_BKPT;
+  }
+  sqlite3VdbeSerialGet(&a[iField-szField], t, pMem);
+  pMem->enc = ENC(db);
+  return SQLITE_OK;
+}
+
+/*
+** Unless it is NULL, the argument must be an UnpackedRecord object returned
+** by an earlier call to sqlite3Stat4ProbeSetValue(). This call deletes
+** the object.
+*/
+void sqlite3Stat4ProbeFree(UnpackedRecord *pRec){
+  if( pRec ){
+    int i;
+    int nCol = pRec->pKeyInfo->nAllField;
+    Mem *aMem = pRec->aMem;
+    sqlite3 *db = aMem[0].db;
+    for(i=0; i<nCol; i++){
+      sqlite3VdbeMemRelease(&aMem[i]);
+    }
+    sqlite3KeyInfoUnref(pRec->pKeyInfo);
+    sqlite3DbFreeNN(db, pRec);
+  }
+}
+#endif /* ifdef SQLITE_ENABLE_STAT4 */
+
+/*
+** Change the string value of an sqlite3_value object
+*/
+void sqlite3ValueSetStr(
+  sqlite3_value *v,     /* Value to be set */
+  int n,                /* Length of string z */
+  const void *z,        /* Text of the new string */
+  u8 enc,               /* Encoding to use */
+  void (*xDel)(void*)   /* Destructor for the string */
+){
+  if( v ) sqlite3VdbeMemSetStr((Mem *)v, z, n, enc, xDel);
+}
+
+/*
+** Free an sqlite3_value object
+*/
+void sqlite3ValueFree(sqlite3_value *v){
+  if( !v ) return;
+  sqlite3VdbeMemRelease((Mem *)v);
+  sqlite3DbFreeNN(((Mem*)v)->db, v);
+}
+
+/*
+** The sqlite3ValueBytes() routine returns the number of bytes in the
+** sqlite3_value object assuming that it uses the encoding "enc".
+** The valueBytes() routine is a helper function.
+*/
+static SQLITE_NOINLINE int valueBytes(sqlite3_value *pVal, u8 enc){
+  return valueToText(pVal, enc)!=0 ? pVal->n : 0;
+}
+int sqlite3ValueBytes(sqlite3_value *pVal, u8 enc){
+  Mem *p = (Mem*)pVal;
+  assert( (p->flags & MEM_Null)==0 || (p->flags & (MEM_Str|MEM_Blob))==0 );
+  if( (p->flags & MEM_Str)!=0 && pVal->enc==enc ){
+    return p->n;
+  }
+  if( (p->flags & MEM_Str)!=0 && enc!=SQLITE_UTF8 && pVal->enc!=SQLITE_UTF8 ){
+    return p->n;
+  }
+  if( (p->flags & MEM_Blob)!=0 ){
+    if( p->flags & MEM_Zero ){
+      return p->n + p->u.nZero;
+    }else{
+      return p->n;
+    }
+  }
+  if( p->flags & MEM_Null ) return 0;
+  return valueBytes(pVal, enc);
+}
diff --git a/src/vdbesort.c b/src/vdbesort.c
new file mode 100644
index 0000000..0083690
--- /dev/null
+++ b/src/vdbesort.c
@@ -0,0 +1,2766 @@
+/*
+** 2011-07-09
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code for the VdbeSorter object, used in concert with
+** a VdbeCursor to sort large numbers of keys for CREATE INDEX statements
+** or by SELECT statements with ORDER BY clauses that cannot be satisfied
+** using indexes and without LIMIT clauses.
+**
+** The VdbeSorter object implements a multi-threaded external merge sort
+** algorithm that is efficient even if the number of elements being sorted
+** exceeds the available memory.
+**
+** Here is the (internal, non-API) interface between this module and the
+** rest of the SQLite system:
+**
+**    sqlite3VdbeSorterInit()       Create a new VdbeSorter object.
+**
+**    sqlite3VdbeSorterWrite()      Add a single new row to the VdbeSorter
+**                                  object.  The row is a binary blob in the
+**                                  OP_MakeRecord format that contains both
+**                                  the ORDER BY key columns and result columns
+**                                  in the case of a SELECT w/ ORDER BY, or
+**                                  the complete record for an index entry
+**                                  in the case of a CREATE INDEX.
+**
+**    sqlite3VdbeSorterRewind()     Sort all content previously added.
+**                                  Position the read cursor on the
+**                                  first sorted element.
+**
+**    sqlite3VdbeSorterNext()       Advance the read cursor to the next sorted
+**                                  element.
+**
+**    sqlite3VdbeSorterRowkey()     Return the complete binary blob for the
+**                                  row currently under the read cursor.
+**
+**    sqlite3VdbeSorterCompare()    Compare the binary blob for the row
+**                                  currently under the read cursor against
+**                                  another binary blob X and report if
+**                                  X is strictly less than the read cursor.
+**                                  Used to enforce uniqueness in a
+**                                  CREATE UNIQUE INDEX statement.
+**
+**    sqlite3VdbeSorterClose()      Close the VdbeSorter object and reclaim
+**                                  all resources.
+**
+**    sqlite3VdbeSorterReset()      Refurbish the VdbeSorter for reuse.  This
+**                                  is like Close() followed by Init() only
+**                                  much faster.
+**
+** The interfaces above must be called in a particular order.  Write() can
+** only occur in between Init()/Reset() and Rewind().  Next(), Rowkey(), and
+** Compare() can only occur in between Rewind() and Close()/Reset(). i.e.
+**
+**   Init()
+**   for each record: Write()
+**   Rewind()
+**     Rowkey()/Compare()
+**   Next()
+**   Close()
+**
+** Algorithm:
+**
+** Records passed to the sorter via calls to Write() are initially held
+** unsorted in main memory. Assuming the amount of memory used never exceeds
+** a threshold, when Rewind() is called the set of records is sorted using
+** an in-memory merge sort. In this case, no temporary files are required
+** and subsequent calls to Rowkey(), Next() and Compare() read records
+** directly from main memory.
+**
+** If the amount of space used to store records in main memory exceeds the
+** threshold, then the set of records currently in memory are sorted and
+** written to a temporary file in "Packed Memory Array" (PMA) format.
+** A PMA created at this point is known as a "level-0 PMA". Higher levels
+** of PMAs may be created by merging existing PMAs together - for example
+** merging two or more level-0 PMAs together creates a level-1 PMA.
+**
+** The threshold for the amount of main memory to use before flushing
+** records to a PMA is roughly the same as the limit configured for the
+** page-cache of the main database. Specifically, the threshold is set to
+** the value returned by "PRAGMA main.page_size" multiplied by
+** that returned by "PRAGMA main.cache_size", in bytes.
+**
+** If the sorter is running in single-threaded mode, then all PMAs generated
+** are appended to a single temporary file. Or, if the sorter is running in
+** multi-threaded mode then up to (N+1) temporary files may be opened, where
+** N is the configured number of worker threads. In this case, instead of
+** sorting the records and writing the PMA to a temporary file itself, the
+** calling thread usually launches a worker thread to do so. Except, if
+** there are already N worker threads running, the main thread does the work
+** itself.
+**
+** The sorter is running in multi-threaded mode if (a) the library was built
+** with pre-processor symbol SQLITE_MAX_WORKER_THREADS set to a value greater
+** than zero, and (b) worker threads have been enabled at runtime by calling
+** "PRAGMA threads=N" with some value of N greater than 0.
+**
+** When Rewind() is called, any data remaining in memory is flushed to a
+** final PMA. So at this point the data is stored in some number of sorted
+** PMAs within temporary files on disk.
+**
+** If there are fewer than SORTER_MAX_MERGE_COUNT PMAs in total and the
+** sorter is running in single-threaded mode, then these PMAs are merged
+** incrementally as keys are retrieved from the sorter by the VDBE.  The
+** MergeEngine object, described in further detail below, performs this
+** merge.
+**
+** Or, if running in multi-threaded mode, then a background thread is
+** launched to merge the existing PMAs. Once the background thread has
+** merged T bytes of data into a single sorted PMA, the main thread
+** begins reading keys from that PMA while the background thread proceeds
+** with merging the next T bytes of data. And so on.
+**
+** Parameter T is set to half the value of the memory threshold used
+** by Write() above to determine when to create a new PMA.
+**
+** If there are more than SORTER_MAX_MERGE_COUNT PMAs in total when
+** Rewind() is called, then a hierarchy of incremental-merges is used.
+** First, T bytes of data from the first SORTER_MAX_MERGE_COUNT PMAs on
+** disk are merged together. Then T bytes of data from the second set, and
+** so on, such that no operation ever merges more than SORTER_MAX_MERGE_COUNT
+** PMAs at a time. This done is to improve locality.
+**
+** If running in multi-threaded mode and there are more than
+** SORTER_MAX_MERGE_COUNT PMAs on disk when Rewind() is called, then more
+** than one background thread may be created. Specifically, there may be
+** one background thread for each temporary file on disk, and one background
+** thread to merge the output of each of the others to a single PMA for
+** the main thread to read from.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/*
+** If SQLITE_DEBUG_SORTER_THREADS is defined, this module outputs various
+** messages to stderr that may be helpful in understanding the performance
+** characteristics of the sorter in multi-threaded mode.
+*/
+#if 0
+# define SQLITE_DEBUG_SORTER_THREADS 1
+#endif
+
+/*
+** Hard-coded maximum amount of data to accumulate in memory before flushing
+** to a level 0 PMA. The purpose of this limit is to prevent various integer
+** overflows. 512MiB.
+*/
+#define SQLITE_MAX_PMASZ    (1<<29)
+
+/*
+** Private objects used by the sorter
+*/
+typedef struct MergeEngine MergeEngine;     /* Merge PMAs together */
+typedef struct PmaReader PmaReader;         /* Incrementally read one PMA */
+typedef struct PmaWriter PmaWriter;         /* Incrementally write one PMA */
+typedef struct SorterRecord SorterRecord;   /* A record being sorted */
+typedef struct SortSubtask SortSubtask;     /* A sub-task in the sort process */
+typedef struct SorterFile SorterFile;       /* Temporary file object wrapper */
+typedef struct SorterList SorterList;       /* In-memory list of records */
+typedef struct IncrMerger IncrMerger;       /* Read & merge multiple PMAs */
+
+/*
+** A container for a temp file handle and the current amount of data
+** stored in the file.
+*/
+struct SorterFile {
+  sqlite3_file *pFd;              /* File handle */
+  i64 iEof;                       /* Bytes of data stored in pFd */
+};
+
+/*
+** An in-memory list of objects to be sorted.
+**
+** If aMemory==0 then each object is allocated separately and the objects
+** are connected using SorterRecord.u.pNext.  If aMemory!=0 then all objects
+** are stored in the aMemory[] bulk memory, one right after the other, and
+** are connected using SorterRecord.u.iNext.
+*/
+struct SorterList {
+  SorterRecord *pList;            /* Linked list of records */
+  u8 *aMemory;                    /* If non-NULL, bulk memory to hold pList */
+  i64 szPMA;                      /* Size of pList as PMA in bytes */
+};
+
+/*
+** The MergeEngine object is used to combine two or more smaller PMAs into
+** one big PMA using a merge operation.  Separate PMAs all need to be
+** combined into one big PMA in order to be able to step through the sorted
+** records in order.
+**
+** The aReadr[] array contains a PmaReader object for each of the PMAs being
+** merged.  An aReadr[] object either points to a valid key or else is at EOF.
+** ("EOF" means "End Of File".  When aReadr[] is at EOF there is no more data.)
+** For the purposes of the paragraphs below, we assume that the array is
+** actually N elements in size, where N is the smallest power of 2 greater
+** to or equal to the number of PMAs being merged. The extra aReadr[] elements
+** are treated as if they are empty (always at EOF).
+**
+** The aTree[] array is also N elements in size. The value of N is stored in
+** the MergeEngine.nTree variable.
+**
+** The final (N/2) elements of aTree[] contain the results of comparing
+** pairs of PMA keys together. Element i contains the result of
+** comparing aReadr[2*i-N] and aReadr[2*i-N+1]. Whichever key is smaller, the
+** aTree element is set to the index of it.
+**
+** For the purposes of this comparison, EOF is considered greater than any
+** other key value. If the keys are equal (only possible with two EOF
+** values), it doesn't matter which index is stored.
+**
+** The (N/4) elements of aTree[] that precede the final (N/2) described
+** above contains the index of the smallest of each block of 4 PmaReaders
+** And so on. So that aTree[1] contains the index of the PmaReader that
+** currently points to the smallest key value. aTree[0] is unused.
+**
+** Example:
+**
+**     aReadr[0] -> Banana
+**     aReadr[1] -> Feijoa
+**     aReadr[2] -> Elderberry
+**     aReadr[3] -> Currant
+**     aReadr[4] -> Grapefruit
+**     aReadr[5] -> Apple
+**     aReadr[6] -> Durian
+**     aReadr[7] -> EOF
+**
+**     aTree[] = { X, 5   0, 5    0, 3, 5, 6 }
+**
+** The current element is "Apple" (the value of the key indicated by
+** PmaReader 5). When the Next() operation is invoked, PmaReader 5 will
+** be advanced to the next key in its segment. Say the next key is
+** "Eggplant":
+**
+**     aReadr[5] -> Eggplant
+**
+** The contents of aTree[] are updated first by comparing the new PmaReader
+** 5 key to the current key of PmaReader 4 (still "Grapefruit"). The PmaReader
+** 5 value is still smaller, so aTree[6] is set to 5. And so on up the tree.
+** The value of PmaReader 6 - "Durian" - is now smaller than that of PmaReader
+** 5, so aTree[3] is set to 6. Key 0 is smaller than key 6 (Banana<Durian),
+** so the value written into element 1 of the array is 0. As follows:
+**
+**     aTree[] = { X, 0   0, 6    0, 3, 5, 6 }
+**
+** In other words, each time we advance to the next sorter element, log2(N)
+** key comparison operations are required, where N is the number of segments
+** being merged (rounded up to the next power of 2).
+*/
+struct MergeEngine {
+  int nTree;                 /* Used size of aTree/aReadr (power of 2) */
+  SortSubtask *pTask;        /* Used by this thread only */
+  int *aTree;                /* Current state of incremental merge */
+  PmaReader *aReadr;         /* Array of PmaReaders to merge data from */
+};
+
+/*
+** This object represents a single thread of control in a sort operation.
+** Exactly VdbeSorter.nTask instances of this object are allocated
+** as part of each VdbeSorter object. Instances are never allocated any
+** other way. VdbeSorter.nTask is set to the number of worker threads allowed
+** (see SQLITE_CONFIG_WORKER_THREADS) plus one (the main thread).  Thus for
+** single-threaded operation, there is exactly one instance of this object
+** and for multi-threaded operation there are two or more instances.
+**
+** Essentially, this structure contains all those fields of the VdbeSorter
+** structure for which each thread requires a separate instance. For example,
+** each thread requeries its own UnpackedRecord object to unpack records in
+** as part of comparison operations.
+**
+** Before a background thread is launched, variable bDone is set to 0. Then,
+** right before it exits, the thread itself sets bDone to 1. This is used for
+** two purposes:
+**
+**   1. When flushing the contents of memory to a level-0 PMA on disk, to
+**      attempt to select a SortSubtask for which there is not already an
+**      active background thread (since doing so causes the main thread
+**      to block until it finishes).
+**
+**   2. If SQLITE_DEBUG_SORTER_THREADS is defined, to determine if a call
+**      to sqlite3ThreadJoin() is likely to block. Cases that are likely to
+**      block provoke debugging output.
+**
+** In both cases, the effects of the main thread seeing (bDone==0) even
+** after the thread has finished are not dire. So we don't worry about
+** memory barriers and such here.
+*/
+typedef int (*SorterCompare)(SortSubtask*,int*,const void*,int,const void*,int);
+struct SortSubtask {
+  SQLiteThread *pThread;          /* Background thread, if any */
+  int bDone;                      /* Set if thread is finished but not joined */
+  int nPMA;                       /* Number of PMAs currently in file */
+  VdbeSorter *pSorter;            /* Sorter that owns this sub-task */
+  UnpackedRecord *pUnpacked;      /* Space to unpack a record */
+  SorterList list;                /* List for thread to write to a PMA */
+  SorterCompare xCompare;         /* Compare function to use */
+  SorterFile file;                /* Temp file for level-0 PMAs */
+  SorterFile file2;               /* Space for other PMAs */
+};
+
+
+/*
+** Main sorter structure. A single instance of this is allocated for each
+** sorter cursor created by the VDBE.
+**
+** mxKeysize:
+**   As records are added to the sorter by calls to sqlite3VdbeSorterWrite(),
+**   this variable is updated so as to be set to the size on disk of the
+**   largest record in the sorter.
+*/
+struct VdbeSorter {
+  int mnPmaSize;                  /* Minimum PMA size, in bytes */
+  int mxPmaSize;                  /* Maximum PMA size, in bytes.  0==no limit */
+  int mxKeysize;                  /* Largest serialized key seen so far */
+  int pgsz;                       /* Main database page size */
+  PmaReader *pReader;             /* Readr data from here after Rewind() */
+  MergeEngine *pMerger;           /* Or here, if bUseThreads==0 */
+  sqlite3 *db;                    /* Database connection */
+  KeyInfo *pKeyInfo;              /* How to compare records */
+  UnpackedRecord *pUnpacked;      /* Used by VdbeSorterCompare() */
+  SorterList list;                /* List of in-memory records */
+  int iMemory;                    /* Offset of free space in list.aMemory */
+  int nMemory;                    /* Size of list.aMemory allocation in bytes */
+  u8 bUsePMA;                     /* True if one or more PMAs created */
+  u8 bUseThreads;                 /* True to use background threads */
+  u8 iPrev;                       /* Previous thread used to flush PMA */
+  u8 nTask;                       /* Size of aTask[] array */
+  u8 typeMask;
+  SortSubtask aTask[1];           /* One or more subtasks */
+};
+
+#define SORTER_TYPE_INTEGER 0x01
+#define SORTER_TYPE_TEXT    0x02
+
+/*
+** An instance of the following object is used to read records out of a
+** PMA, in sorted order.  The next key to be read is cached in nKey/aKey.
+** aKey might point into aMap or into aBuffer.  If neither of those locations
+** contain a contiguous representation of the key, then aAlloc is allocated
+** and the key is copied into aAlloc and aKey is made to point to aAlloc.
+**
+** pFd==0 at EOF.
+*/
+struct PmaReader {
+  i64 iReadOff;               /* Current read offset */
+  i64 iEof;                   /* 1 byte past EOF for this PmaReader */
+  int nAlloc;                 /* Bytes of space at aAlloc */
+  int nKey;                   /* Number of bytes in key */
+  sqlite3_file *pFd;          /* File handle we are reading from */
+  u8 *aAlloc;                 /* Space for aKey if aBuffer and pMap wont work */
+  u8 *aKey;                   /* Pointer to current key */
+  u8 *aBuffer;                /* Current read buffer */
+  int nBuffer;                /* Size of read buffer in bytes */
+  u8 *aMap;                   /* Pointer to mapping of entire file */
+  IncrMerger *pIncr;          /* Incremental merger */
+};
+
+/*
+** Normally, a PmaReader object iterates through an existing PMA stored
+** within a temp file. However, if the PmaReader.pIncr variable points to
+** an object of the following type, it may be used to iterate/merge through
+** multiple PMAs simultaneously.
+**
+** There are two types of IncrMerger object - single (bUseThread==0) and
+** multi-threaded (bUseThread==1).
+**
+** A multi-threaded IncrMerger object uses two temporary files - aFile[0]
+** and aFile[1]. Neither file is allowed to grow to more than mxSz bytes in
+** size. When the IncrMerger is initialized, it reads enough data from
+** pMerger to populate aFile[0]. It then sets variables within the
+** corresponding PmaReader object to read from that file and kicks off
+** a background thread to populate aFile[1] with the next mxSz bytes of
+** sorted record data from pMerger.
+**
+** When the PmaReader reaches the end of aFile[0], it blocks until the
+** background thread has finished populating aFile[1]. It then exchanges
+** the contents of the aFile[0] and aFile[1] variables within this structure,
+** sets the PmaReader fields to read from the new aFile[0] and kicks off
+** another background thread to populate the new aFile[1]. And so on, until
+** the contents of pMerger are exhausted.
+**
+** A single-threaded IncrMerger does not open any temporary files of its
+** own. Instead, it has exclusive access to mxSz bytes of space beginning
+** at offset iStartOff of file pTask->file2. And instead of using a
+** background thread to prepare data for the PmaReader, with a single
+** threaded IncrMerger the allocate part of pTask->file2 is "refilled" with
+** keys from pMerger by the calling thread whenever the PmaReader runs out
+** of data.
+*/
+struct IncrMerger {
+  SortSubtask *pTask;             /* Task that owns this merger */
+  MergeEngine *pMerger;           /* Merge engine thread reads data from */
+  i64 iStartOff;                  /* Offset to start writing file at */
+  int mxSz;                       /* Maximum bytes of data to store */
+  int bEof;                       /* Set to true when merge is finished */
+  int bUseThread;                 /* True to use a bg thread for this object */
+  SorterFile aFile[2];            /* aFile[0] for reading, [1] for writing */
+};
+
+/*
+** An instance of this object is used for writing a PMA.
+**
+** The PMA is written one record at a time.  Each record is of an arbitrary
+** size.  But I/O is more efficient if it occurs in page-sized blocks where
+** each block is aligned on a page boundary.  This object caches writes to
+** the PMA so that aligned, page-size blocks are written.
+*/
+struct PmaWriter {
+  int eFWErr;                     /* Non-zero if in an error state */
+  u8 *aBuffer;                    /* Pointer to write buffer */
+  int nBuffer;                    /* Size of write buffer in bytes */
+  int iBufStart;                  /* First byte of buffer to write */
+  int iBufEnd;                    /* Last byte of buffer to write */
+  i64 iWriteOff;                  /* Offset of start of buffer in file */
+  sqlite3_file *pFd;              /* File handle to write to */
+};
+
+/*
+** This object is the header on a single record while that record is being
+** held in memory and prior to being written out as part of a PMA.
+**
+** How the linked list is connected depends on how memory is being managed
+** by this module. If using a separate allocation for each in-memory record
+** (VdbeSorter.list.aMemory==0), then the list is always connected using the
+** SorterRecord.u.pNext pointers.
+**
+** Or, if using the single large allocation method (VdbeSorter.list.aMemory!=0),
+** then while records are being accumulated the list is linked using the
+** SorterRecord.u.iNext offset. This is because the aMemory[] array may
+** be sqlite3Realloc()ed while records are being accumulated. Once the VM
+** has finished passing records to the sorter, or when the in-memory buffer
+** is full, the list is sorted. As part of the sorting process, it is
+** converted to use the SorterRecord.u.pNext pointers. See function
+** vdbeSorterSort() for details.
+*/
+struct SorterRecord {
+  int nVal;                       /* Size of the record in bytes */
+  union {
+    SorterRecord *pNext;          /* Pointer to next record in list */
+    int iNext;                    /* Offset within aMemory of next record */
+  } u;
+  /* The data for the record immediately follows this header */
+};
+
+/* Return a pointer to the buffer containing the record data for SorterRecord
+** object p. Should be used as if:
+**
+**   void *SRVAL(SorterRecord *p) { return (void*)&p[1]; }
+*/
+#define SRVAL(p) ((void*)((SorterRecord*)(p) + 1))
+
+
+/* Maximum number of PMAs that a single MergeEngine can merge */
+#define SORTER_MAX_MERGE_COUNT 16
+
+static int vdbeIncrSwap(IncrMerger*);
+static void vdbeIncrFree(IncrMerger *);
+
+/*
+** Free all memory belonging to the PmaReader object passed as the
+** argument. All structure fields are set to zero before returning.
+*/
+static void vdbePmaReaderClear(PmaReader *pReadr){
+  sqlite3_free(pReadr->aAlloc);
+  sqlite3_free(pReadr->aBuffer);
+  if( pReadr->aMap ) sqlite3OsUnfetch(pReadr->pFd, 0, pReadr->aMap);
+  vdbeIncrFree(pReadr->pIncr);
+  memset(pReadr, 0, sizeof(PmaReader));
+}
+
+/*
+** Read the next nByte bytes of data from the PMA p.
+** If successful, set *ppOut to point to a buffer containing the data
+** and return SQLITE_OK. Otherwise, if an error occurs, return an SQLite
+** error code.
+**
+** The buffer returned in *ppOut is only valid until the
+** next call to this function.
+*/
+static int vdbePmaReadBlob(
+  PmaReader *p,                   /* PmaReader from which to take the blob */
+  int nByte,                      /* Bytes of data to read */
+  u8 **ppOut                      /* OUT: Pointer to buffer containing data */
+){
+  int iBuf;                       /* Offset within buffer to read from */
+  int nAvail;                     /* Bytes of data available in buffer */
+
+  if( p->aMap ){
+    *ppOut = &p->aMap[p->iReadOff];
+    p->iReadOff += nByte;
+    return SQLITE_OK;
+  }
+
+  assert( p->aBuffer );
+
+  /* If there is no more data to be read from the buffer, read the next
+  ** p->nBuffer bytes of data from the file into it. Or, if there are less
+  ** than p->nBuffer bytes remaining in the PMA, read all remaining data.  */
+  iBuf = p->iReadOff % p->nBuffer;
+  if( iBuf==0 ){
+    int nRead;                    /* Bytes to read from disk */
+    int rc;                       /* sqlite3OsRead() return code */
+
+    /* Determine how many bytes of data to read. */
+    if( (p->iEof - p->iReadOff) > (i64)p->nBuffer ){
+      nRead = p->nBuffer;
+    }else{
+      nRead = (int)(p->iEof - p->iReadOff);
+    }
+    assert( nRead>0 );
+
+    /* Readr data from the file. Return early if an error occurs. */
+    rc = sqlite3OsRead(p->pFd, p->aBuffer, nRead, p->iReadOff);
+    assert( rc!=SQLITE_IOERR_SHORT_READ );
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  nAvail = p->nBuffer - iBuf;
+
+  if( nByte<=nAvail ){
+    /* The requested data is available in the in-memory buffer. In this
+    ** case there is no need to make a copy of the data, just return a
+    ** pointer into the buffer to the caller.  */
+    *ppOut = &p->aBuffer[iBuf];
+    p->iReadOff += nByte;
+  }else{
+    /* The requested data is not all available in the in-memory buffer.
+    ** In this case, allocate space at p->aAlloc[] to copy the requested
+    ** range into. Then return a copy of pointer p->aAlloc to the caller.  */
+    int nRem;                     /* Bytes remaining to copy */
+
+    /* Extend the p->aAlloc[] allocation if required. */
+    if( p->nAlloc<nByte ){
+      u8 *aNew;
+      sqlite3_int64 nNew = MAX(128, 2*(sqlite3_int64)p->nAlloc);
+      while( nByte>nNew ) nNew = nNew*2;
+      aNew = sqlite3Realloc(p->aAlloc, nNew);
+      if( !aNew ) return SQLITE_NOMEM_BKPT;
+      p->nAlloc = nNew;
+      p->aAlloc = aNew;
+    }
+
+    /* Copy as much data as is available in the buffer into the start of
+    ** p->aAlloc[].  */
+    memcpy(p->aAlloc, &p->aBuffer[iBuf], nAvail);
+    p->iReadOff += nAvail;
+    nRem = nByte - nAvail;
+
+    /* The following loop copies up to p->nBuffer bytes per iteration into
+    ** the p->aAlloc[] buffer.  */
+    while( nRem>0 ){
+      int rc;                     /* vdbePmaReadBlob() return code */
+      int nCopy;                  /* Number of bytes to copy */
+      u8 *aNext;                  /* Pointer to buffer to copy data from */
+
+      nCopy = nRem;
+      if( nRem>p->nBuffer ) nCopy = p->nBuffer;
+      rc = vdbePmaReadBlob(p, nCopy, &aNext);
+      if( rc!=SQLITE_OK ) return rc;
+      assert( aNext!=p->aAlloc );
+      memcpy(&p->aAlloc[nByte - nRem], aNext, nCopy);
+      nRem -= nCopy;
+    }
+
+    *ppOut = p->aAlloc;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Read a varint from the stream of data accessed by p. Set *pnOut to
+** the value read.
+*/
+static int vdbePmaReadVarint(PmaReader *p, u64 *pnOut){
+  int iBuf;
+
+  if( p->aMap ){
+    p->iReadOff += sqlite3GetVarint(&p->aMap[p->iReadOff], pnOut);
+  }else{
+    iBuf = p->iReadOff % p->nBuffer;
+    if( iBuf && (p->nBuffer-iBuf)>=9 ){
+      p->iReadOff += sqlite3GetVarint(&p->aBuffer[iBuf], pnOut);
+    }else{
+      u8 aVarint[16], *a;
+      int i = 0, rc;
+      do{
+        rc = vdbePmaReadBlob(p, 1, &a);
+        if( rc ) return rc;
+        aVarint[(i++)&0xf] = a[0];
+      }while( (a[0]&0x80)!=0 );
+      sqlite3GetVarint(aVarint, pnOut);
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Attempt to memory map file pFile. If successful, set *pp to point to the
+** new mapping and return SQLITE_OK. If the mapping is not attempted
+** (because the file is too large or the VFS layer is configured not to use
+** mmap), return SQLITE_OK and set *pp to NULL.
+**
+** Or, if an error occurs, return an SQLite error code. The final value of
+** *pp is undefined in this case.
+*/
+static int vdbeSorterMapFile(SortSubtask *pTask, SorterFile *pFile, u8 **pp){
+  int rc = SQLITE_OK;
+  if( pFile->iEof<=(i64)(pTask->pSorter->db->nMaxSorterMmap) ){
+    sqlite3_file *pFd = pFile->pFd;
+    if( pFd->pMethods->iVersion>=3 ){
+      rc = sqlite3OsFetch(pFd, 0, (int)pFile->iEof, (void**)pp);
+      testcase( rc!=SQLITE_OK );
+    }
+  }
+  return rc;
+}
+
+/*
+** Attach PmaReader pReadr to file pFile (if it is not already attached to
+** that file) and seek it to offset iOff within the file.  Return SQLITE_OK
+** if successful, or an SQLite error code if an error occurs.
+*/
+static int vdbePmaReaderSeek(
+  SortSubtask *pTask,             /* Task context */
+  PmaReader *pReadr,              /* Reader whose cursor is to be moved */
+  SorterFile *pFile,              /* Sorter file to read from */
+  i64 iOff                        /* Offset in pFile */
+){
+  int rc = SQLITE_OK;
+
+  assert( pReadr->pIncr==0 || pReadr->pIncr->bEof==0 );
+
+  if( sqlite3FaultSim(201) ) return SQLITE_IOERR_READ;
+  if( pReadr->aMap ){
+    sqlite3OsUnfetch(pReadr->pFd, 0, pReadr->aMap);
+    pReadr->aMap = 0;
+  }
+  pReadr->iReadOff = iOff;
+  pReadr->iEof = pFile->iEof;
+  pReadr->pFd = pFile->pFd;
+
+  rc = vdbeSorterMapFile(pTask, pFile, &pReadr->aMap);
+  if( rc==SQLITE_OK && pReadr->aMap==0 ){
+    int pgsz = pTask->pSorter->pgsz;
+    int iBuf = pReadr->iReadOff % pgsz;
+    if( pReadr->aBuffer==0 ){
+      pReadr->aBuffer = (u8*)sqlite3Malloc(pgsz);
+      if( pReadr->aBuffer==0 ) rc = SQLITE_NOMEM_BKPT;
+      pReadr->nBuffer = pgsz;
+    }
+    if( rc==SQLITE_OK && iBuf ){
+      int nRead = pgsz - iBuf;
+      if( (pReadr->iReadOff + nRead) > pReadr->iEof ){
+        nRead = (int)(pReadr->iEof - pReadr->iReadOff);
+      }
+      rc = sqlite3OsRead(
+          pReadr->pFd, &pReadr->aBuffer[iBuf], nRead, pReadr->iReadOff
+      );
+      testcase( rc!=SQLITE_OK );
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Advance PmaReader pReadr to the next key in its PMA. Return SQLITE_OK if
+** no error occurs, or an SQLite error code if one does.
+*/
+static int vdbePmaReaderNext(PmaReader *pReadr){
+  int rc = SQLITE_OK;             /* Return Code */
+  u64 nRec = 0;                   /* Size of record in bytes */
+
+
+  if( pReadr->iReadOff>=pReadr->iEof ){
+    IncrMerger *pIncr = pReadr->pIncr;
+    int bEof = 1;
+    if( pIncr ){
+      rc = vdbeIncrSwap(pIncr);
+      if( rc==SQLITE_OK && pIncr->bEof==0 ){
+        rc = vdbePmaReaderSeek(
+            pIncr->pTask, pReadr, &pIncr->aFile[0], pIncr->iStartOff
+        );
+        bEof = 0;
+      }
+    }
+
+    if( bEof ){
+      /* This is an EOF condition */
+      vdbePmaReaderClear(pReadr);
+      testcase( rc!=SQLITE_OK );
+      return rc;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = vdbePmaReadVarint(pReadr, &nRec);
+  }
+  if( rc==SQLITE_OK ){
+    pReadr->nKey = (int)nRec;
+    rc = vdbePmaReadBlob(pReadr, (int)nRec, &pReadr->aKey);
+    testcase( rc!=SQLITE_OK );
+  }
+
+  return rc;
+}
+
+/*
+** Initialize PmaReader pReadr to scan through the PMA stored in file pFile
+** starting at offset iStart and ending at offset iEof-1. This function
+** leaves the PmaReader pointing to the first key in the PMA (or EOF if the
+** PMA is empty).
+**
+** If the pnByte parameter is NULL, then it is assumed that the file
+** contains a single PMA, and that that PMA omits the initial length varint.
+*/
+static int vdbePmaReaderInit(
+  SortSubtask *pTask,             /* Task context */
+  SorterFile *pFile,              /* Sorter file to read from */
+  i64 iStart,                     /* Start offset in pFile */
+  PmaReader *pReadr,              /* PmaReader to populate */
+  i64 *pnByte                     /* IN/OUT: Increment this value by PMA size */
+){
+  int rc;
+
+  assert( pFile->iEof>iStart );
+  assert( pReadr->aAlloc==0 && pReadr->nAlloc==0 );
+  assert( pReadr->aBuffer==0 );
+  assert( pReadr->aMap==0 );
+
+  rc = vdbePmaReaderSeek(pTask, pReadr, pFile, iStart);
+  if( rc==SQLITE_OK ){
+    u64 nByte = 0;                 /* Size of PMA in bytes */
+    rc = vdbePmaReadVarint(pReadr, &nByte);
+    pReadr->iEof = pReadr->iReadOff + nByte;
+    *pnByte += nByte;
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = vdbePmaReaderNext(pReadr);
+  }
+  return rc;
+}
+
+/*
+** A version of vdbeSorterCompare() that assumes that it has already been
+** determined that the first field of key1 is equal to the first field of
+** key2.
+*/
+static int vdbeSorterCompareTail(
+  SortSubtask *pTask,             /* Subtask context (for pKeyInfo) */
+  int *pbKey2Cached,              /* True if pTask->pUnpacked is pKey2 */
+  const void *pKey1, int nKey1,   /* Left side of comparison */
+  const void *pKey2, int nKey2    /* Right side of comparison */
+){
+  UnpackedRecord *r2 = pTask->pUnpacked;
+  if( *pbKey2Cached==0 ){
+    sqlite3VdbeRecordUnpack(pTask->pSorter->pKeyInfo, nKey2, pKey2, r2);
+    *pbKey2Cached = 1;
+  }
+  return sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, r2, 1);
+}
+
+/*
+** Compare key1 (buffer pKey1, size nKey1 bytes) with key2 (buffer pKey2,
+** size nKey2 bytes). Use (pTask->pKeyInfo) for the collation sequences
+** used by the comparison. Return the result of the comparison.
+**
+** If IN/OUT parameter *pbKey2Cached is true when this function is called,
+** it is assumed that (pTask->pUnpacked) contains the unpacked version
+** of key2. If it is false, (pTask->pUnpacked) is populated with the unpacked
+** version of key2 and *pbKey2Cached set to true before returning.
+**
+** If an OOM error is encountered, (pTask->pUnpacked->error_rc) is set
+** to SQLITE_NOMEM.
+*/
+static int vdbeSorterCompare(
+  SortSubtask *pTask,             /* Subtask context (for pKeyInfo) */
+  int *pbKey2Cached,              /* True if pTask->pUnpacked is pKey2 */
+  const void *pKey1, int nKey1,   /* Left side of comparison */
+  const void *pKey2, int nKey2    /* Right side of comparison */
+){
+  UnpackedRecord *r2 = pTask->pUnpacked;
+  if( !*pbKey2Cached ){
+    sqlite3VdbeRecordUnpack(pTask->pSorter->pKeyInfo, nKey2, pKey2, r2);
+    *pbKey2Cached = 1;
+  }
+  return sqlite3VdbeRecordCompare(nKey1, pKey1, r2);
+}
+
+/*
+** A specially optimized version of vdbeSorterCompare() that assumes that
+** the first field of each key is a TEXT value and that the collation
+** sequence to compare them with is BINARY.
+*/
+static int vdbeSorterCompareText(
+  SortSubtask *pTask,             /* Subtask context (for pKeyInfo) */
+  int *pbKey2Cached,              /* True if pTask->pUnpacked is pKey2 */
+  const void *pKey1, int nKey1,   /* Left side of comparison */
+  const void *pKey2, int nKey2    /* Right side of comparison */
+){
+  const u8 * const p1 = (const u8 * const)pKey1;
+  const u8 * const p2 = (const u8 * const)pKey2;
+  const u8 * const v1 = &p1[ p1[0] ];   /* Pointer to value 1 */
+  const u8 * const v2 = &p2[ p2[0] ];   /* Pointer to value 2 */
+
+  int n1;
+  int n2;
+  int res;
+
+  getVarint32NR(&p1[1], n1);
+  getVarint32NR(&p2[1], n2);
+  res = memcmp(v1, v2, (MIN(n1, n2) - 13)/2);
+  if( res==0 ){
+    res = n1 - n2;
+  }
+
+  if( res==0 ){
+    if( pTask->pSorter->pKeyInfo->nKeyField>1 ){
+      res = vdbeSorterCompareTail(
+          pTask, pbKey2Cached, pKey1, nKey1, pKey2, nKey2
+      );
+    }
+  }else{
+    assert( !(pTask->pSorter->pKeyInfo->aSortFlags[0]&KEYINFO_ORDER_BIGNULL) );
+    if( pTask->pSorter->pKeyInfo->aSortFlags[0] ){
+      res = res * -1;
+    }
+  }
+
+  return res;
+}
+
+/*
+** A specially optimized version of vdbeSorterCompare() that assumes that
+** the first field of each key is an INTEGER value.
+*/
+static int vdbeSorterCompareInt(
+  SortSubtask *pTask,             /* Subtask context (for pKeyInfo) */
+  int *pbKey2Cached,              /* True if pTask->pUnpacked is pKey2 */
+  const void *pKey1, int nKey1,   /* Left side of comparison */
+  const void *pKey2, int nKey2    /* Right side of comparison */
+){
+  const u8 * const p1 = (const u8 * const)pKey1;
+  const u8 * const p2 = (const u8 * const)pKey2;
+  const int s1 = p1[1];                 /* Left hand serial type */
+  const int s2 = p2[1];                 /* Right hand serial type */
+  const u8 * const v1 = &p1[ p1[0] ];   /* Pointer to value 1 */
+  const u8 * const v2 = &p2[ p2[0] ];   /* Pointer to value 2 */
+  int res;                              /* Return value */
+
+  assert( (s1>0 && s1<7) || s1==8 || s1==9 );
+  assert( (s2>0 && s2<7) || s2==8 || s2==9 );
+
+  if( s1==s2 ){
+    /* The two values have the same sign. Compare using memcmp(). */
+    static const u8 aLen[] = {0, 1, 2, 3, 4, 6, 8, 0, 0, 0 };
+    const u8 n = aLen[s1];
+    int i;
+    res = 0;
+    for(i=0; i<n; i++){
+      if( (res = v1[i] - v2[i])!=0 ){
+        if( ((v1[0] ^ v2[0]) & 0x80)!=0 ){
+          res = v1[0] & 0x80 ? -1 : +1;
+        }
+        break;
+      }
+    }
+  }else if( s1>7 && s2>7 ){
+    res = s1 - s2;
+  }else{
+    if( s2>7 ){
+      res = +1;
+    }else if( s1>7 ){
+      res = -1;
+    }else{
+      res = s1 - s2;
+    }
+    assert( res!=0 );
+
+    if( res>0 ){
+      if( *v1 & 0x80 ) res = -1;
+    }else{
+      if( *v2 & 0x80 ) res = +1;
+    }
+  }
+
+  if( res==0 ){
+    if( pTask->pSorter->pKeyInfo->nKeyField>1 ){
+      res = vdbeSorterCompareTail(
+          pTask, pbKey2Cached, pKey1, nKey1, pKey2, nKey2
+      );
+    }
+  }else if( pTask->pSorter->pKeyInfo->aSortFlags[0] ){
+    assert( !(pTask->pSorter->pKeyInfo->aSortFlags[0]&KEYINFO_ORDER_BIGNULL) );
+    res = res * -1;
+  }
+
+  return res;
+}
+
+/*
+** Initialize the temporary index cursor just opened as a sorter cursor.
+**
+** Usually, the sorter module uses the value of (pCsr->pKeyInfo->nKeyField)
+** to determine the number of fields that should be compared from the
+** records being sorted. However, if the value passed as argument nField
+** is non-zero and the sorter is able to guarantee a stable sort, nField
+** is used instead. This is used when sorting records for a CREATE INDEX
+** statement. In this case, keys are always delivered to the sorter in
+** order of the primary key, which happens to be make up the final part
+** of the records being sorted. So if the sort is stable, there is never
+** any reason to compare PK fields and they can be ignored for a small
+** performance boost.
+**
+** The sorter can guarantee a stable sort when running in single-threaded
+** mode, but not in multi-threaded mode.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+int sqlite3VdbeSorterInit(
+  sqlite3 *db,                    /* Database connection (for malloc()) */
+  int nField,                     /* Number of key fields in each record */
+  VdbeCursor *pCsr                /* Cursor that holds the new sorter */
+){
+  int pgsz;                       /* Page size of main database */
+  int i;                          /* Used to iterate through aTask[] */
+  VdbeSorter *pSorter;            /* The new sorter */
+  KeyInfo *pKeyInfo;              /* Copy of pCsr->pKeyInfo with db==0 */
+  int szKeyInfo;                  /* Size of pCsr->pKeyInfo in bytes */
+  int sz;                         /* Size of pSorter in bytes */
+  int rc = SQLITE_OK;
+#if SQLITE_MAX_WORKER_THREADS==0
+# define nWorker 0
+#else
+  int nWorker;
+#endif
+
+  /* Initialize the upper limit on the number of worker threads */
+#if SQLITE_MAX_WORKER_THREADS>0
+  if( sqlite3TempInMemory(db) || sqlite3GlobalConfig.bCoreMutex==0 ){
+    nWorker = 0;
+  }else{
+    nWorker = db->aLimit[SQLITE_LIMIT_WORKER_THREADS];
+  }
+#endif
+
+  /* Do not allow the total number of threads (main thread + all workers)
+  ** to exceed the maximum merge count */
+#if SQLITE_MAX_WORKER_THREADS>=SORTER_MAX_MERGE_COUNT
+  if( nWorker>=SORTER_MAX_MERGE_COUNT ){
+    nWorker = SORTER_MAX_MERGE_COUNT-1;
+  }
+#endif
+
+  assert( pCsr->pKeyInfo );
+  assert( !pCsr->isEphemeral );
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  szKeyInfo = sizeof(KeyInfo) + (pCsr->pKeyInfo->nKeyField-1)*sizeof(CollSeq*);
+  sz = sizeof(VdbeSorter) + nWorker * sizeof(SortSubtask);
+
+  pSorter = (VdbeSorter*)sqlite3DbMallocZero(db, sz + szKeyInfo);
+  pCsr->uc.pSorter = pSorter;
+  if( pSorter==0 ){
+    rc = SQLITE_NOMEM_BKPT;
+  }else{
+    Btree *pBt = db->aDb[0].pBt;
+    pSorter->pKeyInfo = pKeyInfo = (KeyInfo*)((u8*)pSorter + sz);
+    memcpy(pKeyInfo, pCsr->pKeyInfo, szKeyInfo);
+    pKeyInfo->db = 0;
+    if( nField && nWorker==0 ){
+      pKeyInfo->nKeyField = nField;
+    }
+    sqlite3BtreeEnter(pBt);
+    pSorter->pgsz = pgsz = sqlite3BtreeGetPageSize(pBt);
+    sqlite3BtreeLeave(pBt);
+    pSorter->nTask = nWorker + 1;
+    pSorter->iPrev = (u8)(nWorker - 1);
+    pSorter->bUseThreads = (pSorter->nTask>1);
+    pSorter->db = db;
+    for(i=0; i<pSorter->nTask; i++){
+      SortSubtask *pTask = &pSorter->aTask[i];
+      pTask->pSorter = pSorter;
+    }
+
+    if( !sqlite3TempInMemory(db) ){
+      i64 mxCache;                /* Cache size in bytes*/
+      u32 szPma = sqlite3GlobalConfig.szPma;
+      pSorter->mnPmaSize = szPma * pgsz;
+
+      mxCache = db->aDb[0].pSchema->cache_size;
+      if( mxCache<0 ){
+        /* A negative cache-size value C indicates that the cache is abs(C)
+        ** KiB in size.  */
+        mxCache = mxCache * -1024;
+      }else{
+        mxCache = mxCache * pgsz;
+      }
+      mxCache = MIN(mxCache, SQLITE_MAX_PMASZ);
+      pSorter->mxPmaSize = MAX(pSorter->mnPmaSize, (int)mxCache);
+
+      /* Avoid large memory allocations if the application has requested
+      ** SQLITE_CONFIG_SMALL_MALLOC. */
+      if( sqlite3GlobalConfig.bSmallMalloc==0 ){
+        assert( pSorter->iMemory==0 );
+        pSorter->nMemory = pgsz;
+        pSorter->list.aMemory = (u8*)sqlite3Malloc(pgsz);
+        if( !pSorter->list.aMemory ) rc = SQLITE_NOMEM_BKPT;
+      }
+    }
+
+    if( pKeyInfo->nAllField<13
+     && (pKeyInfo->aColl[0]==0 || pKeyInfo->aColl[0]==db->pDfltColl)
+     && (pKeyInfo->aSortFlags[0] & KEYINFO_ORDER_BIGNULL)==0
+    ){
+      pSorter->typeMask = SORTER_TYPE_INTEGER | SORTER_TYPE_TEXT;
+    }
+  }
+
+  return rc;
+}
+#undef nWorker   /* Defined at the top of this function */
+
+/*
+** Free the list of sorted records starting at pRecord.
+*/
+static void vdbeSorterRecordFree(sqlite3 *db, SorterRecord *pRecord){
+  SorterRecord *p;
+  SorterRecord *pNext;
+  for(p=pRecord; p; p=pNext){
+    pNext = p->u.pNext;
+    sqlite3DbFree(db, p);
+  }
+}
+
+/*
+** Free all resources owned by the object indicated by argument pTask. All
+** fields of *pTask are zeroed before returning.
+*/
+static void vdbeSortSubtaskCleanup(sqlite3 *db, SortSubtask *pTask){
+  sqlite3DbFree(db, pTask->pUnpacked);
+#if SQLITE_MAX_WORKER_THREADS>0
+  /* pTask->list.aMemory can only be non-zero if it was handed memory
+  ** from the main thread.  That only occurs SQLITE_MAX_WORKER_THREADS>0 */
+  if( pTask->list.aMemory ){
+    sqlite3_free(pTask->list.aMemory);
+  }else
+#endif
+  {
+    assert( pTask->list.aMemory==0 );
+    vdbeSorterRecordFree(0, pTask->list.pList);
+  }
+  if( pTask->file.pFd ){
+    sqlite3OsCloseFree(pTask->file.pFd);
+  }
+  if( pTask->file2.pFd ){
+    sqlite3OsCloseFree(pTask->file2.pFd);
+  }
+  memset(pTask, 0, sizeof(SortSubtask));
+}
+
+#ifdef SQLITE_DEBUG_SORTER_THREADS
+static void vdbeSorterWorkDebug(SortSubtask *pTask, const char *zEvent){
+  i64 t;
+  int iTask = (pTask - pTask->pSorter->aTask);
+  sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
+  fprintf(stderr, "%lld:%d %s\n", t, iTask, zEvent);
+}
+static void vdbeSorterRewindDebug(const char *zEvent){
+  i64 t = 0;
+  sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+  if( ALWAYS(pVfs) ) sqlite3OsCurrentTimeInt64(pVfs, &t);
+  fprintf(stderr, "%lld:X %s\n", t, zEvent);
+}
+static void vdbeSorterPopulateDebug(
+  SortSubtask *pTask,
+  const char *zEvent
+){
+  i64 t;
+  int iTask = (pTask - pTask->pSorter->aTask);
+  sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
+  fprintf(stderr, "%lld:bg%d %s\n", t, iTask, zEvent);
+}
+static void vdbeSorterBlockDebug(
+  SortSubtask *pTask,
+  int bBlocked,
+  const char *zEvent
+){
+  if( bBlocked ){
+    i64 t;
+    sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
+    fprintf(stderr, "%lld:main %s\n", t, zEvent);
+  }
+}
+#else
+# define vdbeSorterWorkDebug(x,y)
+# define vdbeSorterRewindDebug(y)
+# define vdbeSorterPopulateDebug(x,y)
+# define vdbeSorterBlockDebug(x,y,z)
+#endif
+
+#if SQLITE_MAX_WORKER_THREADS>0
+/*
+** Join thread pTask->thread.
+*/
+static int vdbeSorterJoinThread(SortSubtask *pTask){
+  int rc = SQLITE_OK;
+  if( pTask->pThread ){
+#ifdef SQLITE_DEBUG_SORTER_THREADS
+    int bDone = pTask->bDone;
+#endif
+    void *pRet = SQLITE_INT_TO_PTR(SQLITE_ERROR);
+    vdbeSorterBlockDebug(pTask, !bDone, "enter");
+    (void)sqlite3ThreadJoin(pTask->pThread, &pRet);
+    vdbeSorterBlockDebug(pTask, !bDone, "exit");
+    rc = SQLITE_PTR_TO_INT(pRet);
+    assert( pTask->bDone==1 );
+    pTask->bDone = 0;
+    pTask->pThread = 0;
+  }
+  return rc;
+}
+
+/*
+** Launch a background thread to run xTask(pIn).
+*/
+static int vdbeSorterCreateThread(
+  SortSubtask *pTask,             /* Thread will use this task object */
+  void *(*xTask)(void*),          /* Routine to run in a separate thread */
+  void *pIn                       /* Argument passed into xTask() */
+){
+  assert( pTask->pThread==0 && pTask->bDone==0 );
+  return sqlite3ThreadCreate(&pTask->pThread, xTask, pIn);
+}
+
+/*
+** Join all outstanding threads launched by SorterWrite() to create
+** level-0 PMAs.
+*/
+static int vdbeSorterJoinAll(VdbeSorter *pSorter, int rcin){
+  int rc = rcin;
+  int i;
+
+  /* This function is always called by the main user thread.
+  **
+  ** If this function is being called after SorterRewind() has been called,
+  ** it is possible that thread pSorter->aTask[pSorter->nTask-1].pThread
+  ** is currently attempt to join one of the other threads. To avoid a race
+  ** condition where this thread also attempts to join the same object, join
+  ** thread pSorter->aTask[pSorter->nTask-1].pThread first. */
+  for(i=pSorter->nTask-1; i>=0; i--){
+    SortSubtask *pTask = &pSorter->aTask[i];
+    int rc2 = vdbeSorterJoinThread(pTask);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+  return rc;
+}
+#else
+# define vdbeSorterJoinAll(x,rcin) (rcin)
+# define vdbeSorterJoinThread(pTask) SQLITE_OK
+#endif
+
+/*
+** Allocate a new MergeEngine object capable of handling up to
+** nReader PmaReader inputs.
+**
+** nReader is automatically rounded up to the next power of two.
+** nReader may not exceed SORTER_MAX_MERGE_COUNT even after rounding up.
+*/
+static MergeEngine *vdbeMergeEngineNew(int nReader){
+  int N = 2;                      /* Smallest power of two >= nReader */
+  int nByte;                      /* Total bytes of space to allocate */
+  MergeEngine *pNew;              /* Pointer to allocated object to return */
+
+  assert( nReader<=SORTER_MAX_MERGE_COUNT );
+
+  while( N<nReader ) N += N;
+  nByte = sizeof(MergeEngine) + N * (sizeof(int) + sizeof(PmaReader));
+
+  pNew = sqlite3FaultSim(100) ? 0 : (MergeEngine*)sqlite3MallocZero(nByte);
+  if( pNew ){
+    pNew->nTree = N;
+    pNew->pTask = 0;
+    pNew->aReadr = (PmaReader*)&pNew[1];
+    pNew->aTree = (int*)&pNew->aReadr[N];
+  }
+  return pNew;
+}
+
+/*
+** Free the MergeEngine object passed as the only argument.
+*/
+static void vdbeMergeEngineFree(MergeEngine *pMerger){
+  int i;
+  if( pMerger ){
+    for(i=0; i<pMerger->nTree; i++){
+      vdbePmaReaderClear(&pMerger->aReadr[i]);
+    }
+  }
+  sqlite3_free(pMerger);
+}
+
+/*
+** Free all resources associated with the IncrMerger object indicated by
+** the first argument.
+*/
+static void vdbeIncrFree(IncrMerger *pIncr){
+  if( pIncr ){
+#if SQLITE_MAX_WORKER_THREADS>0
+    if( pIncr->bUseThread ){
+      vdbeSorterJoinThread(pIncr->pTask);
+      if( pIncr->aFile[0].pFd ) sqlite3OsCloseFree(pIncr->aFile[0].pFd);
+      if( pIncr->aFile[1].pFd ) sqlite3OsCloseFree(pIncr->aFile[1].pFd);
+    }
+#endif
+    vdbeMergeEngineFree(pIncr->pMerger);
+    sqlite3_free(pIncr);
+  }
+}
+
+/*
+** Reset a sorting cursor back to its original empty state.
+*/
+void sqlite3VdbeSorterReset(sqlite3 *db, VdbeSorter *pSorter){
+  int i;
+  (void)vdbeSorterJoinAll(pSorter, SQLITE_OK);
+  assert( pSorter->bUseThreads || pSorter->pReader==0 );
+#if SQLITE_MAX_WORKER_THREADS>0
+  if( pSorter->pReader ){
+    vdbePmaReaderClear(pSorter->pReader);
+    sqlite3DbFree(db, pSorter->pReader);
+    pSorter->pReader = 0;
+  }
+#endif
+  vdbeMergeEngineFree(pSorter->pMerger);
+  pSorter->pMerger = 0;
+  for(i=0; i<pSorter->nTask; i++){
+    SortSubtask *pTask = &pSorter->aTask[i];
+    vdbeSortSubtaskCleanup(db, pTask);
+    pTask->pSorter = pSorter;
+  }
+  if( pSorter->list.aMemory==0 ){
+    vdbeSorterRecordFree(0, pSorter->list.pList);
+  }
+  pSorter->list.pList = 0;
+  pSorter->list.szPMA = 0;
+  pSorter->bUsePMA = 0;
+  pSorter->iMemory = 0;
+  pSorter->mxKeysize = 0;
+  sqlite3DbFree(db, pSorter->pUnpacked);
+  pSorter->pUnpacked = 0;
+}
+
+/*
+** Free any cursor components allocated by sqlite3VdbeSorterXXX routines.
+*/
+void sqlite3VdbeSorterClose(sqlite3 *db, VdbeCursor *pCsr){
+  VdbeSorter *pSorter;
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
+  if( pSorter ){
+    sqlite3VdbeSorterReset(db, pSorter);
+    sqlite3_free(pSorter->list.aMemory);
+    sqlite3DbFree(db, pSorter);
+    pCsr->uc.pSorter = 0;
+  }
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/*
+** The first argument is a file-handle open on a temporary file. The file
+** is guaranteed to be nByte bytes or smaller in size. This function
+** attempts to extend the file to nByte bytes in size and to ensure that
+** the VFS has memory mapped it.
+**
+** Whether or not the file does end up memory mapped of course depends on
+** the specific VFS implementation.
+*/
+static void vdbeSorterExtendFile(sqlite3 *db, sqlite3_file *pFd, i64 nByte){
+  if( nByte<=(i64)(db->nMaxSorterMmap) && pFd->pMethods->iVersion>=3 ){
+    void *p = 0;
+    int chunksize = 4*1024;
+    sqlite3OsFileControlHint(pFd, SQLITE_FCNTL_CHUNK_SIZE, &chunksize);
+    sqlite3OsFileControlHint(pFd, SQLITE_FCNTL_SIZE_HINT, &nByte);
+    sqlite3OsFetch(pFd, 0, (int)nByte, &p);
+    if( p ) sqlite3OsUnfetch(pFd, 0, p);
+  }
+}
+#else
+# define vdbeSorterExtendFile(x,y,z)
+#endif
+
+/*
+** Allocate space for a file-handle and open a temporary file. If successful,
+** set *ppFd to point to the malloc'd file-handle and return SQLITE_OK.
+** Otherwise, set *ppFd to 0 and return an SQLite error code.
+*/
+static int vdbeSorterOpenTempFile(
+  sqlite3 *db,                    /* Database handle doing sort */
+  i64 nExtend,                    /* Attempt to extend file to this size */
+  sqlite3_file **ppFd
+){
+  int rc;
+  if( sqlite3FaultSim(202) ) return SQLITE_IOERR_ACCESS;
+  rc = sqlite3OsOpenMalloc(db->pVfs, 0, ppFd,
+      SQLITE_OPEN_TEMP_JOURNAL |
+      SQLITE_OPEN_READWRITE    | SQLITE_OPEN_CREATE |
+      SQLITE_OPEN_EXCLUSIVE    | SQLITE_OPEN_DELETEONCLOSE, &rc
+  );
+  if( rc==SQLITE_OK ){
+    i64 max = SQLITE_MAX_MMAP_SIZE;
+    sqlite3OsFileControlHint(*ppFd, SQLITE_FCNTL_MMAP_SIZE, (void*)&max);
+    if( nExtend>0 ){
+      vdbeSorterExtendFile(db, *ppFd, nExtend);
+    }
+  }
+  return rc;
+}
+
+/*
+** If it has not already been allocated, allocate the UnpackedRecord
+** structure at pTask->pUnpacked. Return SQLITE_OK if successful (or
+** if no allocation was required), or SQLITE_NOMEM otherwise.
+*/
+static int vdbeSortAllocUnpacked(SortSubtask *pTask){
+  if( pTask->pUnpacked==0 ){
+    pTask->pUnpacked = sqlite3VdbeAllocUnpackedRecord(pTask->pSorter->pKeyInfo);
+    if( pTask->pUnpacked==0 ) return SQLITE_NOMEM_BKPT;
+    pTask->pUnpacked->nField = pTask->pSorter->pKeyInfo->nKeyField;
+    pTask->pUnpacked->errCode = 0;
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** Merge the two sorted lists p1 and p2 into a single list.
+*/
+static SorterRecord *vdbeSorterMerge(
+  SortSubtask *pTask,             /* Calling thread context */
+  SorterRecord *p1,               /* First list to merge */
+  SorterRecord *p2                /* Second list to merge */
+){
+  SorterRecord *pFinal = 0;
+  SorterRecord **pp = &pFinal;
+  int bCached = 0;
+
+  assert( p1!=0 && p2!=0 );
+  for(;;){
+    int res;
+    res = pTask->xCompare(
+        pTask, &bCached, SRVAL(p1), p1->nVal, SRVAL(p2), p2->nVal
+    );
+
+    if( res<=0 ){
+      *pp = p1;
+      pp = &p1->u.pNext;
+      p1 = p1->u.pNext;
+      if( p1==0 ){
+        *pp = p2;
+        break;
+      }
+    }else{
+      *pp = p2;
+      pp = &p2->u.pNext;
+      p2 = p2->u.pNext;
+      bCached = 0;
+      if( p2==0 ){
+        *pp = p1;
+        break;
+      }
+    }
+  }
+  return pFinal;
+}
+
+/*
+** Return the SorterCompare function to compare values collected by the
+** sorter object passed as the only argument.
+*/
+static SorterCompare vdbeSorterGetCompare(VdbeSorter *p){
+  if( p->typeMask==SORTER_TYPE_INTEGER ){
+    return vdbeSorterCompareInt;
+  }else if( p->typeMask==SORTER_TYPE_TEXT ){
+    return vdbeSorterCompareText;
+  }
+  return vdbeSorterCompare;
+}
+
+/*
+** Sort the linked list of records headed at pTask->pList. Return
+** SQLITE_OK if successful, or an SQLite error code (i.e. SQLITE_NOMEM) if
+** an error occurs.
+*/
+static int vdbeSorterSort(SortSubtask *pTask, SorterList *pList){
+  int i;
+  SorterRecord *p;
+  int rc;
+  SorterRecord *aSlot[64];
+
+  rc = vdbeSortAllocUnpacked(pTask);
+  if( rc!=SQLITE_OK ) return rc;
+
+  p = pList->pList;
+  pTask->xCompare = vdbeSorterGetCompare(pTask->pSorter);
+  memset(aSlot, 0, sizeof(aSlot));
+
+  while( p ){
+    SorterRecord *pNext;
+    if( pList->aMemory ){
+      if( (u8*)p==pList->aMemory ){
+        pNext = 0;
+      }else{
+        assert( p->u.iNext<sqlite3MallocSize(pList->aMemory) );
+        pNext = (SorterRecord*)&pList->aMemory[p->u.iNext];
+      }
+    }else{
+      pNext = p->u.pNext;
+    }
+
+    p->u.pNext = 0;
+    for(i=0; aSlot[i]; i++){
+      p = vdbeSorterMerge(pTask, p, aSlot[i]);
+      aSlot[i] = 0;
+    }
+    aSlot[i] = p;
+    p = pNext;
+  }
+
+  p = 0;
+  for(i=0; i<ArraySize(aSlot); i++){
+    if( aSlot[i]==0 ) continue;
+    p = p ? vdbeSorterMerge(pTask, p, aSlot[i]) : aSlot[i];
+  }
+  pList->pList = p;
+
+  assert( pTask->pUnpacked->errCode==SQLITE_OK
+       || pTask->pUnpacked->errCode==SQLITE_NOMEM
+  );
+  return pTask->pUnpacked->errCode;
+}
+
+/*
+** Initialize a PMA-writer object.
+*/
+static void vdbePmaWriterInit(
+  sqlite3_file *pFd,              /* File handle to write to */
+  PmaWriter *p,                   /* Object to populate */
+  int nBuf,                       /* Buffer size */
+  i64 iStart                      /* Offset of pFd to begin writing at */
+){
+  memset(p, 0, sizeof(PmaWriter));
+  p->aBuffer = (u8*)sqlite3Malloc(nBuf);
+  if( !p->aBuffer ){
+    p->eFWErr = SQLITE_NOMEM_BKPT;
+  }else{
+    p->iBufEnd = p->iBufStart = (iStart % nBuf);
+    p->iWriteOff = iStart - p->iBufStart;
+    p->nBuffer = nBuf;
+    p->pFd = pFd;
+  }
+}
+
+/*
+** Write nData bytes of data to the PMA. Return SQLITE_OK
+** if successful, or an SQLite error code if an error occurs.
+*/
+static void vdbePmaWriteBlob(PmaWriter *p, u8 *pData, int nData){
+  int nRem = nData;
+  while( nRem>0 && p->eFWErr==0 ){
+    int nCopy = nRem;
+    if( nCopy>(p->nBuffer - p->iBufEnd) ){
+      nCopy = p->nBuffer - p->iBufEnd;
+    }
+
+    memcpy(&p->aBuffer[p->iBufEnd], &pData[nData-nRem], nCopy);
+    p->iBufEnd += nCopy;
+    if( p->iBufEnd==p->nBuffer ){
+      p->eFWErr = sqlite3OsWrite(p->pFd,
+          &p->aBuffer[p->iBufStart], p->iBufEnd - p->iBufStart,
+          p->iWriteOff + p->iBufStart
+      );
+      p->iBufStart = p->iBufEnd = 0;
+      p->iWriteOff += p->nBuffer;
+    }
+    assert( p->iBufEnd<p->nBuffer );
+
+    nRem -= nCopy;
+  }
+}
+
+/*
+** Flush any buffered data to disk and clean up the PMA-writer object.
+** The results of using the PMA-writer after this call are undefined.
+** Return SQLITE_OK if flushing the buffered data succeeds or is not
+** required. Otherwise, return an SQLite error code.
+**
+** Before returning, set *piEof to the offset immediately following the
+** last byte written to the file.
+*/
+static int vdbePmaWriterFinish(PmaWriter *p, i64 *piEof){
+  int rc;
+  if( p->eFWErr==0 && ALWAYS(p->aBuffer) && p->iBufEnd>p->iBufStart ){
+    p->eFWErr = sqlite3OsWrite(p->pFd,
+        &p->aBuffer[p->iBufStart], p->iBufEnd - p->iBufStart,
+        p->iWriteOff + p->iBufStart
+    );
+  }
+  *piEof = (p->iWriteOff + p->iBufEnd);
+  sqlite3_free(p->aBuffer);
+  rc = p->eFWErr;
+  memset(p, 0, sizeof(PmaWriter));
+  return rc;
+}
+
+/*
+** Write value iVal encoded as a varint to the PMA. Return
+** SQLITE_OK if successful, or an SQLite error code if an error occurs.
+*/
+static void vdbePmaWriteVarint(PmaWriter *p, u64 iVal){
+  int nByte;
+  u8 aByte[10];
+  nByte = sqlite3PutVarint(aByte, iVal);
+  vdbePmaWriteBlob(p, aByte, nByte);
+}
+
+/*
+** Write the current contents of in-memory linked-list pList to a level-0
+** PMA in the temp file belonging to sub-task pTask. Return SQLITE_OK if
+** successful, or an SQLite error code otherwise.
+**
+** The format of a PMA is:
+**
+**     * A varint. This varint contains the total number of bytes of content
+**       in the PMA (not including the varint itself).
+**
+**     * One or more records packed end-to-end in order of ascending keys.
+**       Each record consists of a varint followed by a blob of data (the
+**       key). The varint is the number of bytes in the blob of data.
+*/
+static int vdbeSorterListToPMA(SortSubtask *pTask, SorterList *pList){
+  sqlite3 *db = pTask->pSorter->db;
+  int rc = SQLITE_OK;             /* Return code */
+  PmaWriter writer;               /* Object used to write to the file */
+
+#ifdef SQLITE_DEBUG
+  /* Set iSz to the expected size of file pTask->file after writing the PMA.
+  ** This is used by an assert() statement at the end of this function.  */
+  i64 iSz = pList->szPMA + sqlite3VarintLen(pList->szPMA) + pTask->file.iEof;
+#endif
+
+  vdbeSorterWorkDebug(pTask, "enter");
+  memset(&writer, 0, sizeof(PmaWriter));
+  assert( pList->szPMA>0 );
+
+  /* If the first temporary PMA file has not been opened, open it now. */
+  if( pTask->file.pFd==0 ){
+    rc = vdbeSorterOpenTempFile(db, 0, &pTask->file.pFd);
+    assert( rc!=SQLITE_OK || pTask->file.pFd );
+    assert( pTask->file.iEof==0 );
+    assert( pTask->nPMA==0 );
+  }
+
+  /* Try to get the file to memory map */
+  if( rc==SQLITE_OK ){
+    vdbeSorterExtendFile(db, pTask->file.pFd, pTask->file.iEof+pList->szPMA+9);
+  }
+
+  /* Sort the list */
+  if( rc==SQLITE_OK ){
+    rc = vdbeSorterSort(pTask, pList);
+  }
+
+  if( rc==SQLITE_OK ){
+    SorterRecord *p;
+    SorterRecord *pNext = 0;
+
+    vdbePmaWriterInit(pTask->file.pFd, &writer, pTask->pSorter->pgsz,
+                      pTask->file.iEof);
+    pTask->nPMA++;
+    vdbePmaWriteVarint(&writer, pList->szPMA);
+    for(p=pList->pList; p; p=pNext){
+      pNext = p->u.pNext;
+      vdbePmaWriteVarint(&writer, p->nVal);
+      vdbePmaWriteBlob(&writer, SRVAL(p), p->nVal);
+      if( pList->aMemory==0 ) sqlite3_free(p);
+    }
+    pList->pList = p;
+    rc = vdbePmaWriterFinish(&writer, &pTask->file.iEof);
+  }
+
+  vdbeSorterWorkDebug(pTask, "exit");
+  assert( rc!=SQLITE_OK || pList->pList==0 );
+  assert( rc!=SQLITE_OK || pTask->file.iEof==iSz );
+  return rc;
+}
+
+/*
+** Advance the MergeEngine to its next entry.
+** Set *pbEof to true there is no next entry because
+** the MergeEngine has reached the end of all its inputs.
+**
+** Return SQLITE_OK if successful or an error code if an error occurs.
+*/
+static int vdbeMergeEngineStep(
+  MergeEngine *pMerger,      /* The merge engine to advance to the next row */
+  int *pbEof                 /* Set TRUE at EOF.  Set false for more content */
+){
+  int rc;
+  int iPrev = pMerger->aTree[1];/* Index of PmaReader to advance */
+  SortSubtask *pTask = pMerger->pTask;
+
+  /* Advance the current PmaReader */
+  rc = vdbePmaReaderNext(&pMerger->aReadr[iPrev]);
+
+  /* Update contents of aTree[] */
+  if( rc==SQLITE_OK ){
+    int i;                      /* Index of aTree[] to recalculate */
+    PmaReader *pReadr1;         /* First PmaReader to compare */
+    PmaReader *pReadr2;         /* Second PmaReader to compare */
+    int bCached = 0;
+
+    /* Find the first two PmaReaders to compare. The one that was just
+    ** advanced (iPrev) and the one next to it in the array.  */
+    pReadr1 = &pMerger->aReadr[(iPrev & 0xFFFE)];
+    pReadr2 = &pMerger->aReadr[(iPrev | 0x0001)];
+
+    for(i=(pMerger->nTree+iPrev)/2; i>0; i=i/2){
+      /* Compare pReadr1 and pReadr2. Store the result in variable iRes. */
+      int iRes;
+      if( pReadr1->pFd==0 ){
+        iRes = +1;
+      }else if( pReadr2->pFd==0 ){
+        iRes = -1;
+      }else{
+        iRes = pTask->xCompare(pTask, &bCached,
+            pReadr1->aKey, pReadr1->nKey, pReadr2->aKey, pReadr2->nKey
+        );
+      }
+
+      /* If pReadr1 contained the smaller value, set aTree[i] to its index.
+      ** Then set pReadr2 to the next PmaReader to compare to pReadr1. In this
+      ** case there is no cache of pReadr2 in pTask->pUnpacked, so set
+      ** pKey2 to point to the record belonging to pReadr2.
+      **
+      ** Alternatively, if pReadr2 contains the smaller of the two values,
+      ** set aTree[i] to its index and update pReadr1. If vdbeSorterCompare()
+      ** was actually called above, then pTask->pUnpacked now contains
+      ** a value equivalent to pReadr2. So set pKey2 to NULL to prevent
+      ** vdbeSorterCompare() from decoding pReadr2 again.
+      **
+      ** If the two values were equal, then the value from the oldest
+      ** PMA should be considered smaller. The VdbeSorter.aReadr[] array
+      ** is sorted from oldest to newest, so pReadr1 contains older values
+      ** than pReadr2 iff (pReadr1<pReadr2).  */
+      if( iRes<0 || (iRes==0 && pReadr1<pReadr2) ){
+        pMerger->aTree[i] = (int)(pReadr1 - pMerger->aReadr);
+        pReadr2 = &pMerger->aReadr[ pMerger->aTree[i ^ 0x0001] ];
+        bCached = 0;
+      }else{
+        if( pReadr1->pFd ) bCached = 0;
+        pMerger->aTree[i] = (int)(pReadr2 - pMerger->aReadr);
+        pReadr1 = &pMerger->aReadr[ pMerger->aTree[i ^ 0x0001] ];
+      }
+    }
+    *pbEof = (pMerger->aReadr[pMerger->aTree[1]].pFd==0);
+  }
+
+  return (rc==SQLITE_OK ? pTask->pUnpacked->errCode : rc);
+}
+
+#if SQLITE_MAX_WORKER_THREADS>0
+/*
+** The main routine for background threads that write level-0 PMAs.
+*/
+static void *vdbeSorterFlushThread(void *pCtx){
+  SortSubtask *pTask = (SortSubtask*)pCtx;
+  int rc;                         /* Return code */
+  assert( pTask->bDone==0 );
+  rc = vdbeSorterListToPMA(pTask, &pTask->list);
+  pTask->bDone = 1;
+  return SQLITE_INT_TO_PTR(rc);
+}
+#endif /* SQLITE_MAX_WORKER_THREADS>0 */
+
+/*
+** Flush the current contents of VdbeSorter.list to a new PMA, possibly
+** using a background thread.
+*/
+static int vdbeSorterFlushPMA(VdbeSorter *pSorter){
+#if SQLITE_MAX_WORKER_THREADS==0
+  pSorter->bUsePMA = 1;
+  return vdbeSorterListToPMA(&pSorter->aTask[0], &pSorter->list);
+#else
+  int rc = SQLITE_OK;
+  int i;
+  SortSubtask *pTask = 0;    /* Thread context used to create new PMA */
+  int nWorker = (pSorter->nTask-1);
+
+  /* Set the flag to indicate that at least one PMA has been written.
+  ** Or will be, anyhow.  */
+  pSorter->bUsePMA = 1;
+
+  /* Select a sub-task to sort and flush the current list of in-memory
+  ** records to disk. If the sorter is running in multi-threaded mode,
+  ** round-robin between the first (pSorter->nTask-1) tasks. Except, if
+  ** the background thread from a sub-tasks previous turn is still running,
+  ** skip it. If the first (pSorter->nTask-1) sub-tasks are all still busy,
+  ** fall back to using the final sub-task. The first (pSorter->nTask-1)
+  ** sub-tasks are preferred as they use background threads - the final
+  ** sub-task uses the main thread. */
+  for(i=0; i<nWorker; i++){
+    int iTest = (pSorter->iPrev + i + 1) % nWorker;
+    pTask = &pSorter->aTask[iTest];
+    if( pTask->bDone ){
+      rc = vdbeSorterJoinThread(pTask);
+    }
+    if( rc!=SQLITE_OK || pTask->pThread==0 ) break;
+  }
+
+  if( rc==SQLITE_OK ){
+    if( i==nWorker ){
+      /* Use the foreground thread for this operation */
+      rc = vdbeSorterListToPMA(&pSorter->aTask[nWorker], &pSorter->list);
+    }else{
+      /* Launch a background thread for this operation */
+      u8 *aMem;
+      void *pCtx;
+
+      assert( pTask!=0 );
+      assert( pTask->pThread==0 && pTask->bDone==0 );
+      assert( pTask->list.pList==0 );
+      assert( pTask->list.aMemory==0 || pSorter->list.aMemory!=0 );
+
+      aMem = pTask->list.aMemory;
+      pCtx = (void*)pTask;
+      pSorter->iPrev = (u8)(pTask - pSorter->aTask);
+      pTask->list = pSorter->list;
+      pSorter->list.pList = 0;
+      pSorter->list.szPMA = 0;
+      if( aMem ){
+        pSorter->list.aMemory = aMem;
+        pSorter->nMemory = sqlite3MallocSize(aMem);
+      }else if( pSorter->list.aMemory ){
+        pSorter->list.aMemory = sqlite3Malloc(pSorter->nMemory);
+        if( !pSorter->list.aMemory ) return SQLITE_NOMEM_BKPT;
+      }
+
+      rc = vdbeSorterCreateThread(pTask, vdbeSorterFlushThread, pCtx);
+    }
+  }
+
+  return rc;
+#endif /* SQLITE_MAX_WORKER_THREADS!=0 */
+}
+
+/*
+** Add a record to the sorter.
+*/
+int sqlite3VdbeSorterWrite(
+  const VdbeCursor *pCsr,         /* Sorter cursor */
+  Mem *pVal                       /* Memory cell containing record */
+){
+  VdbeSorter *pSorter;
+  int rc = SQLITE_OK;             /* Return Code */
+  SorterRecord *pNew;             /* New list element */
+  int bFlush;                     /* True to flush contents of memory to PMA */
+  i64 nReq;                       /* Bytes of memory required */
+  i64 nPMA;                       /* Bytes of PMA space required */
+  int t;                          /* serial type of first record field */
+
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
+  getVarint32NR((const u8*)&pVal->z[1], t);
+  if( t>0 && t<10 && t!=7 ){
+    pSorter->typeMask &= SORTER_TYPE_INTEGER;
+  }else if( t>10 && (t & 0x01) ){
+    pSorter->typeMask &= SORTER_TYPE_TEXT;
+  }else{
+    pSorter->typeMask = 0;
+  }
+
+  assert( pSorter );
+
+  /* Figure out whether or not the current contents of memory should be
+  ** flushed to a PMA before continuing. If so, do so.
+  **
+  ** If using the single large allocation mode (pSorter->aMemory!=0), then
+  ** flush the contents of memory to a new PMA if (a) at least one value is
+  ** already in memory and (b) the new value will not fit in memory.
+  **
+  ** Or, if using separate allocations for each record, flush the contents
+  ** of memory to a PMA if either of the following are true:
+  **
+  **   * The total memory allocated for the in-memory list is greater
+  **     than (page-size * cache-size), or
+  **
+  **   * The total memory allocated for the in-memory list is greater
+  **     than (page-size * 10) and sqlite3HeapNearlyFull() returns true.
+  */
+  nReq = pVal->n + sizeof(SorterRecord);
+  nPMA = pVal->n + sqlite3VarintLen(pVal->n);
+  if( pSorter->mxPmaSize ){
+    if( pSorter->list.aMemory ){
+      bFlush = pSorter->iMemory && (pSorter->iMemory+nReq) > pSorter->mxPmaSize;
+    }else{
+      bFlush = (
+          (pSorter->list.szPMA > pSorter->mxPmaSize)
+       || (pSorter->list.szPMA > pSorter->mnPmaSize && sqlite3HeapNearlyFull())
+      );
+    }
+    if( bFlush ){
+      rc = vdbeSorterFlushPMA(pSorter);
+      pSorter->list.szPMA = 0;
+      pSorter->iMemory = 0;
+      assert( rc!=SQLITE_OK || pSorter->list.pList==0 );
+    }
+  }
+
+  pSorter->list.szPMA += nPMA;
+  if( nPMA>pSorter->mxKeysize ){
+    pSorter->mxKeysize = nPMA;
+  }
+
+  if( pSorter->list.aMemory ){
+    int nMin = pSorter->iMemory + nReq;
+
+    if( nMin>pSorter->nMemory ){
+      u8 *aNew;
+      sqlite3_int64 nNew = 2 * (sqlite3_int64)pSorter->nMemory;
+      int iListOff = -1;
+      if( pSorter->list.pList ){
+        iListOff = (u8*)pSorter->list.pList - pSorter->list.aMemory;
+      }
+      while( nNew < nMin ) nNew = nNew*2;
+      if( nNew > pSorter->mxPmaSize ) nNew = pSorter->mxPmaSize;
+      if( nNew < nMin ) nNew = nMin;
+      aNew = sqlite3Realloc(pSorter->list.aMemory, nNew);
+      if( !aNew ) return SQLITE_NOMEM_BKPT;
+      if( iListOff>=0 ){
+        pSorter->list.pList = (SorterRecord*)&aNew[iListOff];
+      }
+      pSorter->list.aMemory = aNew;
+      pSorter->nMemory = nNew;
+    }
+
+    pNew = (SorterRecord*)&pSorter->list.aMemory[pSorter->iMemory];
+    pSorter->iMemory += ROUND8(nReq);
+    if( pSorter->list.pList ){
+      pNew->u.iNext = (int)((u8*)(pSorter->list.pList) - pSorter->list.aMemory);
+    }
+  }else{
+    pNew = (SorterRecord *)sqlite3Malloc(nReq);
+    if( pNew==0 ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    pNew->u.pNext = pSorter->list.pList;
+  }
+
+  memcpy(SRVAL(pNew), pVal->z, pVal->n);
+  pNew->nVal = pVal->n;
+  pSorter->list.pList = pNew;
+
+  return rc;
+}
+
+/*
+** Read keys from pIncr->pMerger and populate pIncr->aFile[1]. The format
+** of the data stored in aFile[1] is the same as that used by regular PMAs,
+** except that the number-of-bytes varint is omitted from the start.
+*/
+static int vdbeIncrPopulate(IncrMerger *pIncr){
+  int rc = SQLITE_OK;
+  int rc2;
+  i64 iStart = pIncr->iStartOff;
+  SorterFile *pOut = &pIncr->aFile[1];
+  SortSubtask *pTask = pIncr->pTask;
+  MergeEngine *pMerger = pIncr->pMerger;
+  PmaWriter writer;
+  assert( pIncr->bEof==0 );
+
+  vdbeSorterPopulateDebug(pTask, "enter");
+
+  vdbePmaWriterInit(pOut->pFd, &writer, pTask->pSorter->pgsz, iStart);
+  while( rc==SQLITE_OK ){
+    int dummy;
+    PmaReader *pReader = &pMerger->aReadr[ pMerger->aTree[1] ];
+    int nKey = pReader->nKey;
+    i64 iEof = writer.iWriteOff + writer.iBufEnd;
+
+    /* Check if the output file is full or if the input has been exhausted.
+    ** In either case exit the loop. */
+    if( pReader->pFd==0 ) break;
+    if( (iEof + nKey + sqlite3VarintLen(nKey))>(iStart + pIncr->mxSz) ) break;
+
+    /* Write the next key to the output. */
+    vdbePmaWriteVarint(&writer, nKey);
+    vdbePmaWriteBlob(&writer, pReader->aKey, nKey);
+    assert( pIncr->pMerger->pTask==pTask );
+    rc = vdbeMergeEngineStep(pIncr->pMerger, &dummy);
+  }
+
+  rc2 = vdbePmaWriterFinish(&writer, &pOut->iEof);
+  if( rc==SQLITE_OK ) rc = rc2;
+  vdbeSorterPopulateDebug(pTask, "exit");
+  return rc;
+}
+
+#if SQLITE_MAX_WORKER_THREADS>0
+/*
+** The main routine for background threads that populate aFile[1] of
+** multi-threaded IncrMerger objects.
+*/
+static void *vdbeIncrPopulateThread(void *pCtx){
+  IncrMerger *pIncr = (IncrMerger*)pCtx;
+  void *pRet = SQLITE_INT_TO_PTR( vdbeIncrPopulate(pIncr) );
+  pIncr->pTask->bDone = 1;
+  return pRet;
+}
+
+/*
+** Launch a background thread to populate aFile[1] of pIncr.
+*/
+static int vdbeIncrBgPopulate(IncrMerger *pIncr){
+  void *p = (void*)pIncr;
+  assert( pIncr->bUseThread );
+  return vdbeSorterCreateThread(pIncr->pTask, vdbeIncrPopulateThread, p);
+}
+#endif
+
+/*
+** This function is called when the PmaReader corresponding to pIncr has
+** finished reading the contents of aFile[0]. Its purpose is to "refill"
+** aFile[0] such that the PmaReader should start rereading it from the
+** beginning.
+**
+** For single-threaded objects, this is accomplished by literally reading
+** keys from pIncr->pMerger and repopulating aFile[0].
+**
+** For multi-threaded objects, all that is required is to wait until the
+** background thread is finished (if it is not already) and then swap
+** aFile[0] and aFile[1] in place. If the contents of pMerger have not
+** been exhausted, this function also launches a new background thread
+** to populate the new aFile[1].
+**
+** SQLITE_OK is returned on success, or an SQLite error code otherwise.
+*/
+static int vdbeIncrSwap(IncrMerger *pIncr){
+  int rc = SQLITE_OK;
+
+#if SQLITE_MAX_WORKER_THREADS>0
+  if( pIncr->bUseThread ){
+    rc = vdbeSorterJoinThread(pIncr->pTask);
+
+    if( rc==SQLITE_OK ){
+      SorterFile f0 = pIncr->aFile[0];
+      pIncr->aFile[0] = pIncr->aFile[1];
+      pIncr->aFile[1] = f0;
+    }
+
+    if( rc==SQLITE_OK ){
+      if( pIncr->aFile[0].iEof==pIncr->iStartOff ){
+        pIncr->bEof = 1;
+      }else{
+        rc = vdbeIncrBgPopulate(pIncr);
+      }
+    }
+  }else
+#endif
+  {
+    rc = vdbeIncrPopulate(pIncr);
+    pIncr->aFile[0] = pIncr->aFile[1];
+    if( pIncr->aFile[0].iEof==pIncr->iStartOff ){
+      pIncr->bEof = 1;
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Allocate and return a new IncrMerger object to read data from pMerger.
+**
+** If an OOM condition is encountered, return NULL. In this case free the
+** pMerger argument before returning.
+*/
+static int vdbeIncrMergerNew(
+  SortSubtask *pTask,     /* The thread that will be using the new IncrMerger */
+  MergeEngine *pMerger,   /* The MergeEngine that the IncrMerger will control */
+  IncrMerger **ppOut      /* Write the new IncrMerger here */
+){
+  int rc = SQLITE_OK;
+  IncrMerger *pIncr = *ppOut = (IncrMerger*)
+       (sqlite3FaultSim(100) ? 0 : sqlite3MallocZero(sizeof(*pIncr)));
+  if( pIncr ){
+    pIncr->pMerger = pMerger;
+    pIncr->pTask = pTask;
+    pIncr->mxSz = MAX(pTask->pSorter->mxKeysize+9,pTask->pSorter->mxPmaSize/2);
+    pTask->file2.iEof += pIncr->mxSz;
+  }else{
+    vdbeMergeEngineFree(pMerger);
+    rc = SQLITE_NOMEM_BKPT;
+  }
+  assert( *ppOut!=0 || rc!=SQLITE_OK );
+  return rc;
+}
+
+#if SQLITE_MAX_WORKER_THREADS>0
+/*
+** Set the "use-threads" flag on object pIncr.
+*/
+static void vdbeIncrMergerSetThreads(IncrMerger *pIncr){
+  pIncr->bUseThread = 1;
+  pIncr->pTask->file2.iEof -= pIncr->mxSz;
+}
+#endif /* SQLITE_MAX_WORKER_THREADS>0 */
+
+
+
+/*
+** Recompute pMerger->aTree[iOut] by comparing the next keys on the
+** two PmaReaders that feed that entry.  Neither of the PmaReaders
+** are advanced.  This routine merely does the comparison.
+*/
+static void vdbeMergeEngineCompare(
+  MergeEngine *pMerger,  /* Merge engine containing PmaReaders to compare */
+  int iOut               /* Store the result in pMerger->aTree[iOut] */
+){
+  int i1;
+  int i2;
+  int iRes;
+  PmaReader *p1;
+  PmaReader *p2;
+
+  assert( iOut<pMerger->nTree && iOut>0 );
+
+  if( iOut>=(pMerger->nTree/2) ){
+    i1 = (iOut - pMerger->nTree/2) * 2;
+    i2 = i1 + 1;
+  }else{
+    i1 = pMerger->aTree[iOut*2];
+    i2 = pMerger->aTree[iOut*2+1];
+  }
+
+  p1 = &pMerger->aReadr[i1];
+  p2 = &pMerger->aReadr[i2];
+
+  if( p1->pFd==0 ){
+    iRes = i2;
+  }else if( p2->pFd==0 ){
+    iRes = i1;
+  }else{
+    SortSubtask *pTask = pMerger->pTask;
+    int bCached = 0;
+    int res;
+    assert( pTask->pUnpacked!=0 );  /* from vdbeSortSubtaskMain() */
+    res = pTask->xCompare(
+        pTask, &bCached, p1->aKey, p1->nKey, p2->aKey, p2->nKey
+    );
+    if( res<=0 ){
+      iRes = i1;
+    }else{
+      iRes = i2;
+    }
+  }
+
+  pMerger->aTree[iOut] = iRes;
+}
+
+/*
+** Allowed values for the eMode parameter to vdbeMergeEngineInit()
+** and vdbePmaReaderIncrMergeInit().
+**
+** Only INCRINIT_NORMAL is valid in single-threaded builds (when
+** SQLITE_MAX_WORKER_THREADS==0).  The other values are only used
+** when there exists one or more separate worker threads.
+*/
+#define INCRINIT_NORMAL 0
+#define INCRINIT_TASK   1
+#define INCRINIT_ROOT   2
+
+/*
+** Forward reference required as the vdbeIncrMergeInit() and
+** vdbePmaReaderIncrInit() routines are called mutually recursively when
+** building a merge tree.
+*/
+static int vdbePmaReaderIncrInit(PmaReader *pReadr, int eMode);
+
+/*
+** Initialize the MergeEngine object passed as the second argument. Once this
+** function returns, the first key of merged data may be read from the
+** MergeEngine object in the usual fashion.
+**
+** If argument eMode is INCRINIT_ROOT, then it is assumed that any IncrMerge
+** objects attached to the PmaReader objects that the merger reads from have
+** already been populated, but that they have not yet populated aFile[0] and
+** set the PmaReader objects up to read from it. In this case all that is
+** required is to call vdbePmaReaderNext() on each PmaReader to point it at
+** its first key.
+**
+** Otherwise, if eMode is any value other than INCRINIT_ROOT, then use
+** vdbePmaReaderIncrMergeInit() to initialize each PmaReader that feeds data
+** to pMerger.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+static int vdbeMergeEngineInit(
+  SortSubtask *pTask,             /* Thread that will run pMerger */
+  MergeEngine *pMerger,           /* MergeEngine to initialize */
+  int eMode                       /* One of the INCRINIT_XXX constants */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* For looping over PmaReader objects */
+  int nTree;                      /* Number of subtrees to merge */
+
+  /* Failure to allocate the merge would have been detected prior to
+  ** invoking this routine */
+  assert( pMerger!=0 );
+
+  /* eMode is always INCRINIT_NORMAL in single-threaded mode */
+  assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );
+
+  /* Verify that the MergeEngine is assigned to a single thread */
+  assert( pMerger->pTask==0 );
+  pMerger->pTask = pTask;
+
+  nTree = pMerger->nTree;
+  for(i=0; i<nTree; i++){
+    if( SQLITE_MAX_WORKER_THREADS>0 && eMode==INCRINIT_ROOT ){
+      /* PmaReaders should be normally initialized in order, as if they are
+      ** reading from the same temp file this makes for more linear file IO.
+      ** However, in the INCRINIT_ROOT case, if PmaReader aReadr[nTask-1] is
+      ** in use it will block the vdbePmaReaderNext() call while it uses
+      ** the main thread to fill its buffer. So calling PmaReaderNext()
+      ** on this PmaReader before any of the multi-threaded PmaReaders takes
+      ** better advantage of multi-processor hardware. */
+      rc = vdbePmaReaderNext(&pMerger->aReadr[nTree-i-1]);
+    }else{
+      rc = vdbePmaReaderIncrInit(&pMerger->aReadr[i], INCRINIT_NORMAL);
+    }
+    if( rc!=SQLITE_OK ) return rc;
+  }
+
+  for(i=pMerger->nTree-1; i>0; i--){
+    vdbeMergeEngineCompare(pMerger, i);
+  }
+  return pTask->pUnpacked->errCode;
+}
+
+/*
+** The PmaReader passed as the first argument is guaranteed to be an
+** incremental-reader (pReadr->pIncr!=0). This function serves to open
+** and/or initialize the temp file related fields of the IncrMerge
+** object at (pReadr->pIncr).
+**
+** If argument eMode is set to INCRINIT_NORMAL, then all PmaReaders
+** in the sub-tree headed by pReadr are also initialized. Data is then
+** loaded into the buffers belonging to pReadr and it is set to point to
+** the first key in its range.
+**
+** If argument eMode is set to INCRINIT_TASK, then pReadr is guaranteed
+** to be a multi-threaded PmaReader and this function is being called in a
+** background thread. In this case all PmaReaders in the sub-tree are
+** initialized as for INCRINIT_NORMAL and the aFile[1] buffer belonging to
+** pReadr is populated. However, pReadr itself is not set up to point
+** to its first key. A call to vdbePmaReaderNext() is still required to do
+** that.
+**
+** The reason this function does not call vdbePmaReaderNext() immediately
+** in the INCRINIT_TASK case is that vdbePmaReaderNext() assumes that it has
+** to block on thread (pTask->thread) before accessing aFile[1]. But, since
+** this entire function is being run by thread (pTask->thread), that will
+** lead to the current background thread attempting to join itself.
+**
+** Finally, if argument eMode is set to INCRINIT_ROOT, it may be assumed
+** that pReadr->pIncr is a multi-threaded IncrMerge objects, and that all
+** child-trees have already been initialized using IncrInit(INCRINIT_TASK).
+** In this case vdbePmaReaderNext() is called on all child PmaReaders and
+** the current PmaReader set to point to the first key in its range.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+static int vdbePmaReaderIncrMergeInit(PmaReader *pReadr, int eMode){
+  int rc = SQLITE_OK;
+  IncrMerger *pIncr = pReadr->pIncr;
+  SortSubtask *pTask = pIncr->pTask;
+  sqlite3 *db = pTask->pSorter->db;
+
+  /* eMode is always INCRINIT_NORMAL in single-threaded mode */
+  assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );
+
+  rc = vdbeMergeEngineInit(pTask, pIncr->pMerger, eMode);
+
+  /* Set up the required files for pIncr. A multi-threaded IncrMerge object
+  ** requires two temp files to itself, whereas a single-threaded object
+  ** only requires a region of pTask->file2. */
+  if( rc==SQLITE_OK ){
+    int mxSz = pIncr->mxSz;
+#if SQLITE_MAX_WORKER_THREADS>0
+    if( pIncr->bUseThread ){
+      rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[0].pFd);
+      if( rc==SQLITE_OK ){
+        rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[1].pFd);
+      }
+    }else
+#endif
+    /*if( !pIncr->bUseThread )*/{
+      if( pTask->file2.pFd==0 ){
+        assert( pTask->file2.iEof>0 );
+        rc = vdbeSorterOpenTempFile(db, pTask->file2.iEof, &pTask->file2.pFd);
+        pTask->file2.iEof = 0;
+      }
+      if( rc==SQLITE_OK ){
+        pIncr->aFile[1].pFd = pTask->file2.pFd;
+        pIncr->iStartOff = pTask->file2.iEof;
+        pTask->file2.iEof += mxSz;
+      }
+    }
+  }
+
+#if SQLITE_MAX_WORKER_THREADS>0
+  if( rc==SQLITE_OK && pIncr->bUseThread ){
+    /* Use the current thread to populate aFile[1], even though this
+    ** PmaReader is multi-threaded. If this is an INCRINIT_TASK object,
+    ** then this function is already running in background thread
+    ** pIncr->pTask->thread.
+    **
+    ** If this is the INCRINIT_ROOT object, then it is running in the
+    ** main VDBE thread. But that is Ok, as that thread cannot return
+    ** control to the VDBE or proceed with anything useful until the
+    ** first results are ready from this merger object anyway.
+    */
+    assert( eMode==INCRINIT_ROOT || eMode==INCRINIT_TASK );
+    rc = vdbeIncrPopulate(pIncr);
+  }
+#endif
+
+  if( rc==SQLITE_OK && (SQLITE_MAX_WORKER_THREADS==0 || eMode!=INCRINIT_TASK) ){
+    rc = vdbePmaReaderNext(pReadr);
+  }
+
+  return rc;
+}
+
+#if SQLITE_MAX_WORKER_THREADS>0
+/*
+** The main routine for vdbePmaReaderIncrMergeInit() operations run in
+** background threads.
+*/
+static void *vdbePmaReaderBgIncrInit(void *pCtx){
+  PmaReader *pReader = (PmaReader*)pCtx;
+  void *pRet = SQLITE_INT_TO_PTR(
+                  vdbePmaReaderIncrMergeInit(pReader,INCRINIT_TASK)
+               );
+  pReader->pIncr->pTask->bDone = 1;
+  return pRet;
+}
+#endif
+
+/*
+** If the PmaReader passed as the first argument is not an incremental-reader
+** (if pReadr->pIncr==0), then this function is a no-op. Otherwise, it invokes
+** the vdbePmaReaderIncrMergeInit() function with the parameters passed to
+** this routine to initialize the incremental merge.
+**
+** If the IncrMerger object is multi-threaded (IncrMerger.bUseThread==1),
+** then a background thread is launched to call vdbePmaReaderIncrMergeInit().
+** Or, if the IncrMerger is single threaded, the same function is called
+** using the current thread.
+*/
+static int vdbePmaReaderIncrInit(PmaReader *pReadr, int eMode){
+  IncrMerger *pIncr = pReadr->pIncr;   /* Incremental merger */
+  int rc = SQLITE_OK;                  /* Return code */
+  if( pIncr ){
+#if SQLITE_MAX_WORKER_THREADS>0
+    assert( pIncr->bUseThread==0 || eMode==INCRINIT_TASK );
+    if( pIncr->bUseThread ){
+      void *pCtx = (void*)pReadr;
+      rc = vdbeSorterCreateThread(pIncr->pTask, vdbePmaReaderBgIncrInit, pCtx);
+    }else
+#endif
+    {
+      rc = vdbePmaReaderIncrMergeInit(pReadr, eMode);
+    }
+  }
+  return rc;
+}
+
+/*
+** Allocate a new MergeEngine object to merge the contents of nPMA level-0
+** PMAs from pTask->file. If no error occurs, set *ppOut to point to
+** the new object and return SQLITE_OK. Or, if an error does occur, set *ppOut
+** to NULL and return an SQLite error code.
+**
+** When this function is called, *piOffset is set to the offset of the
+** first PMA to read from pTask->file. Assuming no error occurs, it is
+** set to the offset immediately following the last byte of the last
+** PMA before returning. If an error does occur, then the final value of
+** *piOffset is undefined.
+*/
+static int vdbeMergeEngineLevel0(
+  SortSubtask *pTask,             /* Sorter task to read from */
+  int nPMA,                       /* Number of PMAs to read */
+  i64 *piOffset,                  /* IN/OUT: Readr offset in pTask->file */
+  MergeEngine **ppOut             /* OUT: New merge-engine */
+){
+  MergeEngine *pNew;              /* Merge engine to return */
+  i64 iOff = *piOffset;
+  int i;
+  int rc = SQLITE_OK;
+
+  *ppOut = pNew = vdbeMergeEngineNew(nPMA);
+  if( pNew==0 ) rc = SQLITE_NOMEM_BKPT;
+
+  for(i=0; i<nPMA && rc==SQLITE_OK; i++){
+    i64 nDummy = 0;
+    PmaReader *pReadr = &pNew->aReadr[i];
+    rc = vdbePmaReaderInit(pTask, &pTask->file, iOff, pReadr, &nDummy);
+    iOff = pReadr->iEof;
+  }
+
+  if( rc!=SQLITE_OK ){
+    vdbeMergeEngineFree(pNew);
+    *ppOut = 0;
+  }
+  *piOffset = iOff;
+  return rc;
+}
+
+/*
+** Return the depth of a tree comprising nPMA PMAs, assuming a fanout of
+** SORTER_MAX_MERGE_COUNT. The returned value does not include leaf nodes.
+**
+** i.e.
+**
+**   nPMA<=16    -> TreeDepth() == 0
+**   nPMA<=256   -> TreeDepth() == 1
+**   nPMA<=65536 -> TreeDepth() == 2
+*/
+static int vdbeSorterTreeDepth(int nPMA){
+  int nDepth = 0;
+  i64 nDiv = SORTER_MAX_MERGE_COUNT;
+  while( nDiv < (i64)nPMA ){
+    nDiv = nDiv * SORTER_MAX_MERGE_COUNT;
+    nDepth++;
+  }
+  return nDepth;
+}
+
+/*
+** pRoot is the root of an incremental merge-tree with depth nDepth (according
+** to vdbeSorterTreeDepth()). pLeaf is the iSeq'th leaf to be added to the
+** tree, counting from zero. This function adds pLeaf to the tree.
+**
+** If successful, SQLITE_OK is returned. If an error occurs, an SQLite error
+** code is returned and pLeaf is freed.
+*/
+static int vdbeSorterAddToTree(
+  SortSubtask *pTask,             /* Task context */
+  int nDepth,                     /* Depth of tree according to TreeDepth() */
+  int iSeq,                       /* Sequence number of leaf within tree */
+  MergeEngine *pRoot,             /* Root of tree */
+  MergeEngine *pLeaf              /* Leaf to add to tree */
+){
+  int rc = SQLITE_OK;
+  int nDiv = 1;
+  int i;
+  MergeEngine *p = pRoot;
+  IncrMerger *pIncr;
+
+  rc = vdbeIncrMergerNew(pTask, pLeaf, &pIncr);
+
+  for(i=1; i<nDepth; i++){
+    nDiv = nDiv * SORTER_MAX_MERGE_COUNT;
+  }
+
+  for(i=1; i<nDepth && rc==SQLITE_OK; i++){
+    int iIter = (iSeq / nDiv) % SORTER_MAX_MERGE_COUNT;
+    PmaReader *pReadr = &p->aReadr[iIter];
+
+    if( pReadr->pIncr==0 ){
+      MergeEngine *pNew = vdbeMergeEngineNew(SORTER_MAX_MERGE_COUNT);
+      if( pNew==0 ){
+        rc = SQLITE_NOMEM_BKPT;
+      }else{
+        rc = vdbeIncrMergerNew(pTask, pNew, &pReadr->pIncr);
+      }
+    }
+    if( rc==SQLITE_OK ){
+      p = pReadr->pIncr->pMerger;
+      nDiv = nDiv / SORTER_MAX_MERGE_COUNT;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    p->aReadr[iSeq % SORTER_MAX_MERGE_COUNT].pIncr = pIncr;
+  }else{
+    vdbeIncrFree(pIncr);
+  }
+  return rc;
+}
+
+/*
+** This function is called as part of a SorterRewind() operation on a sorter
+** that has already written two or more level-0 PMAs to one or more temp
+** files. It builds a tree of MergeEngine/IncrMerger/PmaReader objects that
+** can be used to incrementally merge all PMAs on disk.
+**
+** If successful, SQLITE_OK is returned and *ppOut set to point to the
+** MergeEngine object at the root of the tree before returning. Or, if an
+** error occurs, an SQLite error code is returned and the final value
+** of *ppOut is undefined.
+*/
+static int vdbeSorterMergeTreeBuild(
+  VdbeSorter *pSorter,       /* The VDBE cursor that implements the sort */
+  MergeEngine **ppOut        /* Write the MergeEngine here */
+){
+  MergeEngine *pMain = 0;
+  int rc = SQLITE_OK;
+  int iTask;
+
+#if SQLITE_MAX_WORKER_THREADS>0
+  /* If the sorter uses more than one task, then create the top-level
+  ** MergeEngine here. This MergeEngine will read data from exactly
+  ** one PmaReader per sub-task.  */
+  assert( pSorter->bUseThreads || pSorter->nTask==1 );
+  if( pSorter->nTask>1 ){
+    pMain = vdbeMergeEngineNew(pSorter->nTask);
+    if( pMain==0 ) rc = SQLITE_NOMEM_BKPT;
+  }
+#endif
+
+  for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
+    SortSubtask *pTask = &pSorter->aTask[iTask];
+    assert( pTask->nPMA>0 || SQLITE_MAX_WORKER_THREADS>0 );
+    if( SQLITE_MAX_WORKER_THREADS==0 || pTask->nPMA ){
+      MergeEngine *pRoot = 0;     /* Root node of tree for this task */
+      int nDepth = vdbeSorterTreeDepth(pTask->nPMA);
+      i64 iReadOff = 0;
+
+      if( pTask->nPMA<=SORTER_MAX_MERGE_COUNT ){
+        rc = vdbeMergeEngineLevel0(pTask, pTask->nPMA, &iReadOff, &pRoot);
+      }else{
+        int i;
+        int iSeq = 0;
+        pRoot = vdbeMergeEngineNew(SORTER_MAX_MERGE_COUNT);
+        if( pRoot==0 ) rc = SQLITE_NOMEM_BKPT;
+        for(i=0; i<pTask->nPMA && rc==SQLITE_OK; i += SORTER_MAX_MERGE_COUNT){
+          MergeEngine *pMerger = 0; /* New level-0 PMA merger */
+          int nReader;              /* Number of level-0 PMAs to merge */
+
+          nReader = MIN(pTask->nPMA - i, SORTER_MAX_MERGE_COUNT);
+          rc = vdbeMergeEngineLevel0(pTask, nReader, &iReadOff, &pMerger);
+          if( rc==SQLITE_OK ){
+            rc = vdbeSorterAddToTree(pTask, nDepth, iSeq++, pRoot, pMerger);
+          }
+        }
+      }
+
+      if( rc==SQLITE_OK ){
+#if SQLITE_MAX_WORKER_THREADS>0
+        if( pMain!=0 ){
+          rc = vdbeIncrMergerNew(pTask, pRoot, &pMain->aReadr[iTask].pIncr);
+        }else
+#endif
+        {
+          assert( pMain==0 );
+          pMain = pRoot;
+        }
+      }else{
+        vdbeMergeEngineFree(pRoot);
+      }
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    vdbeMergeEngineFree(pMain);
+    pMain = 0;
+  }
+  *ppOut = pMain;
+  return rc;
+}
+
+/*
+** This function is called as part of an sqlite3VdbeSorterRewind() operation
+** on a sorter that has written two or more PMAs to temporary files. It sets
+** up either VdbeSorter.pMerger (for single threaded sorters) or pReader
+** (for multi-threaded sorters) so that it can be used to iterate through
+** all records stored in the sorter.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+static int vdbeSorterSetupMerge(VdbeSorter *pSorter){
+  int rc;                         /* Return code */
+  SortSubtask *pTask0 = &pSorter->aTask[0];
+  MergeEngine *pMain = 0;
+#if SQLITE_MAX_WORKER_THREADS
+  sqlite3 *db = pTask0->pSorter->db;
+  int i;
+  SorterCompare xCompare = vdbeSorterGetCompare(pSorter);
+  for(i=0; i<pSorter->nTask; i++){
+    pSorter->aTask[i].xCompare = xCompare;
+  }
+#endif
+
+  rc = vdbeSorterMergeTreeBuild(pSorter, &pMain);
+  if( rc==SQLITE_OK ){
+#if SQLITE_MAX_WORKER_THREADS
+    assert( pSorter->bUseThreads==0 || pSorter->nTask>1 );
+    if( pSorter->bUseThreads ){
+      int iTask;
+      PmaReader *pReadr = 0;
+      SortSubtask *pLast = &pSorter->aTask[pSorter->nTask-1];
+      rc = vdbeSortAllocUnpacked(pLast);
+      if( rc==SQLITE_OK ){
+        pReadr = (PmaReader*)sqlite3DbMallocZero(db, sizeof(PmaReader));
+        pSorter->pReader = pReadr;
+        if( pReadr==0 ) rc = SQLITE_NOMEM_BKPT;
+      }
+      if( rc==SQLITE_OK ){
+        rc = vdbeIncrMergerNew(pLast, pMain, &pReadr->pIncr);
+        if( rc==SQLITE_OK ){
+          vdbeIncrMergerSetThreads(pReadr->pIncr);
+          for(iTask=0; iTask<(pSorter->nTask-1); iTask++){
+            IncrMerger *pIncr;
+            if( (pIncr = pMain->aReadr[iTask].pIncr) ){
+              vdbeIncrMergerSetThreads(pIncr);
+              assert( pIncr->pTask!=pLast );
+            }
+          }
+          for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
+            /* Check that:
+            **  
+            **   a) The incremental merge object is configured to use the
+            **      right task, and
+            **   b) If it is using task (nTask-1), it is configured to run
+            **      in single-threaded mode. This is important, as the
+            **      root merge (INCRINIT_ROOT) will be using the same task
+            **      object.
+            */
+            PmaReader *p = &pMain->aReadr[iTask];
+            assert( p->pIncr==0 || (
+                (p->pIncr->pTask==&pSorter->aTask[iTask])             /* a */
+             && (iTask!=pSorter->nTask-1 || p->pIncr->bUseThread==0)  /* b */
+            ));
+            rc = vdbePmaReaderIncrInit(p, INCRINIT_TASK);
+          }
+        }
+        pMain = 0;
+      }
+      if( rc==SQLITE_OK ){
+        rc = vdbePmaReaderIncrMergeInit(pReadr, INCRINIT_ROOT);
+      }
+    }else
+#endif
+    {
+      rc = vdbeMergeEngineInit(pTask0, pMain, INCRINIT_NORMAL);
+      pSorter->pMerger = pMain;
+      pMain = 0;
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    vdbeMergeEngineFree(pMain);
+  }
+  return rc;
+}
+
+
+/*
+** Once the sorter has been populated by calls to sqlite3VdbeSorterWrite,
+** this function is called to prepare for iterating through the records
+** in sorted order.
+*/
+int sqlite3VdbeSorterRewind(const VdbeCursor *pCsr, int *pbEof){
+  VdbeSorter *pSorter;
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
+  assert( pSorter );
+
+  /* If no data has been written to disk, then do not do so now. Instead,
+  ** sort the VdbeSorter.pRecord list. The vdbe layer will read data directly
+  ** from the in-memory list.  */
+  if( pSorter->bUsePMA==0 ){
+    if( pSorter->list.pList ){
+      *pbEof = 0;
+      rc = vdbeSorterSort(&pSorter->aTask[0], &pSorter->list);
+    }else{
+      *pbEof = 1;
+    }
+    return rc;
+  }
+
+  /* Write the current in-memory list to a PMA. When the VdbeSorterWrite()
+  ** function flushes the contents of memory to disk, it immediately always
+  ** creates a new list consisting of a single key immediately afterwards.
+  ** So the list is never empty at this point.  */
+  assert( pSorter->list.pList );
+  rc = vdbeSorterFlushPMA(pSorter);
+
+  /* Join all threads */
+  rc = vdbeSorterJoinAll(pSorter, rc);
+
+  vdbeSorterRewindDebug("rewind");
+
+  /* Assuming no errors have occurred, set up a merger structure to
+  ** incrementally read and merge all remaining PMAs.  */
+  assert( pSorter->pReader==0 );
+  if( rc==SQLITE_OK ){
+    rc = vdbeSorterSetupMerge(pSorter);
+    *pbEof = 0;
+  }
+
+  vdbeSorterRewindDebug("rewinddone");
+  return rc;
+}
+
+/*
+** Advance to the next element in the sorter.  Return value:
+**
+**    SQLITE_OK     success
+**    SQLITE_DONE   end of data
+**    otherwise     some kind of error.
+*/
+int sqlite3VdbeSorterNext(sqlite3 *db, const VdbeCursor *pCsr){
+  VdbeSorter *pSorter;
+  int rc;                         /* Return code */
+
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
+  assert( pSorter->bUsePMA || (pSorter->pReader==0 && pSorter->pMerger==0) );
+  if( pSorter->bUsePMA ){
+    assert( pSorter->pReader==0 || pSorter->pMerger==0 );
+    assert( pSorter->bUseThreads==0 || pSorter->pReader );
+    assert( pSorter->bUseThreads==1 || pSorter->pMerger );
+#if SQLITE_MAX_WORKER_THREADS>0
+    if( pSorter->bUseThreads ){
+      rc = vdbePmaReaderNext(pSorter->pReader);
+      if( rc==SQLITE_OK && pSorter->pReader->pFd==0 ) rc = SQLITE_DONE;
+    }else
+#endif
+    /*if( !pSorter->bUseThreads )*/ {
+      int res = 0;
+      assert( pSorter->pMerger!=0 );
+      assert( pSorter->pMerger->pTask==(&pSorter->aTask[0]) );
+      rc = vdbeMergeEngineStep(pSorter->pMerger, &res);
+      if( rc==SQLITE_OK && res ) rc = SQLITE_DONE;
+    }
+  }else{
+    SorterRecord *pFree = pSorter->list.pList;
+    pSorter->list.pList = pFree->u.pNext;
+    pFree->u.pNext = 0;
+    if( pSorter->list.aMemory==0 ) vdbeSorterRecordFree(db, pFree);
+    rc = pSorter->list.pList ? SQLITE_OK : SQLITE_DONE;
+  }
+  return rc;
+}
+
+/*
+** Return a pointer to a buffer owned by the sorter that contains the
+** current key.
+*/
+static void *vdbeSorterRowkey(
+  const VdbeSorter *pSorter,      /* Sorter object */
+  int *pnKey                      /* OUT: Size of current key in bytes */
+){
+  void *pKey;
+  if( pSorter->bUsePMA ){
+    PmaReader *pReader;
+#if SQLITE_MAX_WORKER_THREADS>0
+    if( pSorter->bUseThreads ){
+      pReader = pSorter->pReader;
+    }else
+#endif
+    /*if( !pSorter->bUseThreads )*/{
+      pReader = &pSorter->pMerger->aReadr[pSorter->pMerger->aTree[1]];
+    }
+    *pnKey = pReader->nKey;
+    pKey = pReader->aKey;
+  }else{
+    *pnKey = pSorter->list.pList->nVal;
+    pKey = SRVAL(pSorter->list.pList);
+  }
+  return pKey;
+}
+
+/*
+** Copy the current sorter key into the memory cell pOut.
+*/
+int sqlite3VdbeSorterRowkey(const VdbeCursor *pCsr, Mem *pOut){
+  VdbeSorter *pSorter;
+  void *pKey; int nKey;           /* Sorter key to copy into pOut */
+
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
+  pKey = vdbeSorterRowkey(pSorter, &nKey);
+  if( sqlite3VdbeMemClearAndResize(pOut, nKey) ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  pOut->n = nKey;
+  MemSetTypeFlag(pOut, MEM_Blob);
+  memcpy(pOut->z, pKey, nKey);
+
+  return SQLITE_OK;
+}
+
+/*
+** Compare the key in memory cell pVal with the key that the sorter cursor
+** passed as the first argument currently points to. For the purposes of
+** the comparison, ignore the rowid field at the end of each record.
+**
+** If the sorter cursor key contains any NULL values, consider it to be
+** less than pVal. Even if pVal also contains NULL values.
+**
+** If an error occurs, return an SQLite error code (i.e. SQLITE_NOMEM).
+** Otherwise, set *pRes to a negative, zero or positive value if the
+** key in pVal is smaller than, equal to or larger than the current sorter
+** key.
+**
+** This routine forms the core of the OP_SorterCompare opcode, which in
+** turn is used to verify uniqueness when constructing a UNIQUE INDEX.
+*/
+int sqlite3VdbeSorterCompare(
+  const VdbeCursor *pCsr,         /* Sorter cursor */
+  Mem *pVal,                      /* Value to compare to current sorter key */
+  int nKeyCol,                    /* Compare this many columns */
+  int *pRes                       /* OUT: Result of comparison */
+){
+  VdbeSorter *pSorter;
+  UnpackedRecord *r2;
+  KeyInfo *pKeyInfo;
+  int i;
+  void *pKey; int nKey;           /* Sorter key to compare pVal with */
+
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
+  r2 = pSorter->pUnpacked;
+  pKeyInfo = pCsr->pKeyInfo;
+  if( r2==0 ){
+    r2 = pSorter->pUnpacked = sqlite3VdbeAllocUnpackedRecord(pKeyInfo);
+    if( r2==0 ) return SQLITE_NOMEM_BKPT;
+    r2->nField = nKeyCol;
+  }
+  assert( r2->nField==nKeyCol );
+
+  pKey = vdbeSorterRowkey(pSorter, &nKey);
+  sqlite3VdbeRecordUnpack(pKeyInfo, nKey, pKey, r2);
+  for(i=0; i<nKeyCol; i++){
+    if( r2->aMem[i].flags & MEM_Null ){
+      *pRes = -1;
+      return SQLITE_OK;
+    }
+  }
+
+  *pRes = sqlite3VdbeRecordCompare(pVal->n, pVal->z, r2);
+  return SQLITE_OK;
+}
diff --git a/src/vdbetrace.c b/src/vdbetrace.c
new file mode 100644
index 0000000..ae8ad31
--- /dev/null
+++ b/src/vdbetrace.c
@@ -0,0 +1,192 @@
+/*
+** 2009 November 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to insert the values of host parameters
+** (aka "wildcards") into the SQL text output by sqlite3_trace().
+**
+** The Vdbe parse-tree explainer is also found here.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#ifndef SQLITE_OMIT_TRACE
+
+/*
+** zSql is a zero-terminated string of UTF-8 SQL text.  Return the number of
+** bytes in this text up to but excluding the first character in
+** a host parameter.  If the text contains no host parameters, return
+** the total number of bytes in the text.
+*/
+static int findNextHostParameter(const char *zSql, int *pnToken){
+  int tokenType;
+  int nTotal = 0;
+  int n;
+
+  *pnToken = 0;
+  while( zSql[0] ){
+    n = sqlite3GetToken((u8*)zSql, &tokenType);
+    assert( n>0 && tokenType!=TK_ILLEGAL );
+    if( tokenType==TK_VARIABLE ){
+      *pnToken = n;
+      break;
+    }
+    nTotal += n;
+    zSql += n;
+  }
+  return nTotal;
+}
+
+/*
+** This function returns a pointer to a nul-terminated string in memory
+** obtained from sqlite3DbMalloc(). If sqlite3.nVdbeExec is 1, then the
+** string contains a copy of zRawSql but with host parameters expanded to 
+** their current bindings. Or, if sqlite3.nVdbeExec is greater than 1, 
+** then the returned string holds a copy of zRawSql with "-- " prepended
+** to each line of text.
+**
+** If the SQLITE_TRACE_SIZE_LIMIT macro is defined to an integer, then
+** then long strings and blobs are truncated to that many bytes.  This
+** can be used to prevent unreasonably large trace strings when dealing
+** with large (multi-megabyte) strings and blobs.
+**
+** The calling function is responsible for making sure the memory returned
+** is eventually freed.
+**
+** ALGORITHM:  Scan the input string looking for host parameters in any of
+** these forms:  ?, ?N, $A, @A, :A.  Take care to avoid text within
+** string literals, quoted identifier names, and comments.  For text forms,
+** the host parameter index is found by scanning the prepared
+** statement for the corresponding OP_Variable opcode.  Once the host
+** parameter index is known, locate the value in p->aVar[].  Then render
+** the value as a literal in place of the host parameter name.
+*/
+char *sqlite3VdbeExpandSql(
+  Vdbe *p,                 /* The prepared statement being evaluated */
+  const char *zRawSql      /* Raw text of the SQL statement */
+){
+  sqlite3 *db;             /* The database connection */
+  int idx = 0;             /* Index of a host parameter */
+  int nextIndex = 1;       /* Index of next ? host parameter */
+  int n;                   /* Length of a token prefix */
+  int nToken;              /* Length of the parameter token */
+  int i;                   /* Loop counter */
+  Mem *pVar;               /* Value of a host parameter */
+  StrAccum out;            /* Accumulate the output here */
+#ifndef SQLITE_OMIT_UTF16
+  Mem utf8;                /* Used to convert UTF16 into UTF8 for display */
+#endif
+
+  db = p->db;
+  sqlite3StrAccumInit(&out, 0, 0, 0, db->aLimit[SQLITE_LIMIT_LENGTH]);
+  if( db->nVdbeExec>1 ){
+    while( *zRawSql ){
+      const char *zStart = zRawSql;
+      while( *(zRawSql++)!='\n' && *zRawSql );
+      sqlite3_str_append(&out, "-- ", 3);
+      assert( (zRawSql - zStart) > 0 );
+      sqlite3_str_append(&out, zStart, (int)(zRawSql-zStart));
+    }
+  }else if( p->nVar==0 ){
+    sqlite3_str_append(&out, zRawSql, sqlite3Strlen30(zRawSql));
+  }else{
+    while( zRawSql[0] ){
+      n = findNextHostParameter(zRawSql, &nToken);
+      assert( n>0 );
+      sqlite3_str_append(&out, zRawSql, n);
+      zRawSql += n;
+      assert( zRawSql[0] || nToken==0 );
+      if( nToken==0 ) break;
+      if( zRawSql[0]=='?' ){
+        if( nToken>1 ){
+          assert( sqlite3Isdigit(zRawSql[1]) );
+          sqlite3GetInt32(&zRawSql[1], &idx);
+        }else{
+          idx = nextIndex;
+        }
+      }else{
+        assert( zRawSql[0]==':' || zRawSql[0]=='$' ||
+                zRawSql[0]=='@' || zRawSql[0]=='#' );
+        testcase( zRawSql[0]==':' );
+        testcase( zRawSql[0]=='$' );
+        testcase( zRawSql[0]=='@' );
+        testcase( zRawSql[0]=='#' );
+        idx = sqlite3VdbeParameterIndex(p, zRawSql, nToken);
+        assert( idx>0 );
+      }
+      zRawSql += nToken;
+      nextIndex = MAX(idx + 1, nextIndex);
+      assert( idx>0 && idx<=p->nVar );
+      pVar = &p->aVar[idx-1];
+      if( pVar->flags & MEM_Null ){
+        sqlite3_str_append(&out, "NULL", 4);
+      }else if( pVar->flags & (MEM_Int|MEM_IntReal) ){
+        sqlite3_str_appendf(&out, "%lld", pVar->u.i);
+      }else if( pVar->flags & MEM_Real ){
+        sqlite3_str_appendf(&out, "%!.15g", pVar->u.r);
+      }else if( pVar->flags & MEM_Str ){
+        int nOut;  /* Number of bytes of the string text to include in output */
+#ifndef SQLITE_OMIT_UTF16
+        u8 enc = ENC(db);
+        if( enc!=SQLITE_UTF8 ){
+          memset(&utf8, 0, sizeof(utf8));
+          utf8.db = db;
+          sqlite3VdbeMemSetStr(&utf8, pVar->z, pVar->n, enc, SQLITE_STATIC);
+          if( SQLITE_NOMEM==sqlite3VdbeChangeEncoding(&utf8, SQLITE_UTF8) ){
+            out.accError = SQLITE_NOMEM;
+            out.nAlloc = 0;
+          }
+          pVar = &utf8;
+        }
+#endif
+        nOut = pVar->n;
+#ifdef SQLITE_TRACE_SIZE_LIMIT
+        if( nOut>SQLITE_TRACE_SIZE_LIMIT ){
+          nOut = SQLITE_TRACE_SIZE_LIMIT;
+          while( nOut<pVar->n && (pVar->z[nOut]&0xc0)==0x80 ){ nOut++; }
+        }
+#endif    
+        sqlite3_str_appendf(&out, "'%.*q'", nOut, pVar->z);
+#ifdef SQLITE_TRACE_SIZE_LIMIT
+        if( nOut<pVar->n ){
+          sqlite3_str_appendf(&out, "/*+%d bytes*/", pVar->n-nOut);
+        }
+#endif
+#ifndef SQLITE_OMIT_UTF16
+        if( enc!=SQLITE_UTF8 ) sqlite3VdbeMemRelease(&utf8);
+#endif
+      }else if( pVar->flags & MEM_Zero ){
+        sqlite3_str_appendf(&out, "zeroblob(%d)", pVar->u.nZero);
+      }else{
+        int nOut;  /* Number of bytes of the blob to include in output */
+        assert( pVar->flags & MEM_Blob );
+        sqlite3_str_append(&out, "x'", 2);
+        nOut = pVar->n;
+#ifdef SQLITE_TRACE_SIZE_LIMIT
+        if( nOut>SQLITE_TRACE_SIZE_LIMIT ) nOut = SQLITE_TRACE_SIZE_LIMIT;
+#endif
+        for(i=0; i<nOut; i++){
+          sqlite3_str_appendf(&out, "%02x", pVar->z[i]&0xff);
+        }
+        sqlite3_str_append(&out, "'", 1);
+#ifdef SQLITE_TRACE_SIZE_LIMIT
+        if( nOut<pVar->n ){
+          sqlite3_str_appendf(&out, "/*+%d bytes*/", pVar->n-nOut);
+        }
+#endif
+      }
+    }
+  }
+  if( out.accError ) sqlite3_str_reset(&out);
+  return sqlite3StrAccumFinish(&out);
+}
+
+#endif /* #ifndef SQLITE_OMIT_TRACE */
diff --git a/src/vdbevtab.c b/src/vdbevtab.c
new file mode 100644
index 0000000..b295dff
--- /dev/null
+++ b/src/vdbevtab.c
@@ -0,0 +1,446 @@
+/*
+** 2020-03-23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements virtual-tables for examining the bytecode content
+** of a prepared statement.
+*/
+#include "sqliteInt.h"
+#if defined(SQLITE_ENABLE_BYTECODE_VTAB) && !defined(SQLITE_OMIT_VIRTUALTABLE)
+#include "vdbeInt.h"
+
+/* An instance of the bytecode() table-valued function.
+*/
+typedef struct bytecodevtab bytecodevtab;
+struct bytecodevtab {
+  sqlite3_vtab base;     /* Base class - must be first */
+  sqlite3 *db;           /* Database connection */
+  int bTablesUsed;       /* 2 for tables_used().  0 for bytecode(). */
+};
+
+/* A cursor for scanning through the bytecode
+*/
+typedef struct bytecodevtab_cursor bytecodevtab_cursor;
+struct bytecodevtab_cursor {
+  sqlite3_vtab_cursor base;  /* Base class - must be first */
+  sqlite3_stmt *pStmt;       /* The statement whose bytecode is displayed */
+  int iRowid;                /* The rowid of the output table */
+  int iAddr;                 /* Address */
+  int needFinalize;          /* Cursors owns pStmt and must finalize it */
+  int showSubprograms;       /* Provide a listing of subprograms */
+  Op *aOp;                   /* Operand array */
+  char *zP4;                 /* Rendered P4 value */
+  const char *zType;         /* tables_used.type */
+  const char *zSchema;       /* tables_used.schema */
+  const char *zName;         /* tables_used.name */
+  Mem sub;                   /* Subprograms */
+};
+
+/*
+** Create a new bytecode() table-valued function.
+*/
+static int bytecodevtabConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  bytecodevtab *pNew;
+  int rc;
+  int isTabUsed = pAux!=0;
+  const char *azSchema[2] = {
+    /* bytecode() schema */
+    "CREATE TABLE x("
+      "addr INT,"
+      "opcode TEXT,"
+      "p1 INT,"
+      "p2 INT,"
+      "p3 INT,"
+      "p4 TEXT,"
+      "p5 INT,"
+      "comment TEXT,"
+      "subprog TEXT," 
+      "nexec INT,"
+      "ncycle INT,"
+      "stmt HIDDEN"
+    ");",
+
+    /* Tables_used() schema */
+    "CREATE TABLE x("
+      "type TEXT,"
+      "schema TEXT,"
+      "name TEXT,"
+      "wr INT,"
+      "subprog TEXT," 
+      "stmt HIDDEN"
+   ");"
+  };
+
+  (void)argc;
+  (void)argv;
+  (void)pzErr;
+  rc = sqlite3_declare_vtab(db, azSchema[isTabUsed]);
+  if( rc==SQLITE_OK ){
+    pNew = sqlite3_malloc( sizeof(*pNew) );
+    *ppVtab = (sqlite3_vtab*)pNew;
+    if( pNew==0 ) return SQLITE_NOMEM;
+    memset(pNew, 0, sizeof(*pNew));
+    pNew->db = db;
+    pNew->bTablesUsed = isTabUsed*2;
+  }
+  return rc;
+}
+
+/*
+** This method is the destructor for bytecodevtab objects.
+*/
+static int bytecodevtabDisconnect(sqlite3_vtab *pVtab){
+  bytecodevtab *p = (bytecodevtab*)pVtab;
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Constructor for a new bytecodevtab_cursor object.
+*/
+static int bytecodevtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
+  bytecodevtab *pVTab = (bytecodevtab*)p;
+  bytecodevtab_cursor *pCur;
+  pCur = sqlite3_malloc( sizeof(*pCur) );
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(*pCur));
+  sqlite3VdbeMemInit(&pCur->sub, pVTab->db, 1);
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Clear all internal content from a bytecodevtab cursor.
+*/
+static void bytecodevtabCursorClear(bytecodevtab_cursor *pCur){
+  sqlite3_free(pCur->zP4);
+  pCur->zP4 = 0;
+  sqlite3VdbeMemRelease(&pCur->sub);
+  sqlite3VdbeMemSetNull(&pCur->sub);
+  if( pCur->needFinalize ){
+    sqlite3_finalize(pCur->pStmt);
+  }
+  pCur->pStmt = 0;
+  pCur->needFinalize = 0;
+  pCur->zType = 0;
+  pCur->zSchema = 0;
+  pCur->zName = 0;
+}
+
+/*
+** Destructor for a bytecodevtab_cursor.
+*/
+static int bytecodevtabClose(sqlite3_vtab_cursor *cur){
+  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
+  bytecodevtabCursorClear(pCur);
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+
+/*
+** Advance a bytecodevtab_cursor to its next row of output.
+*/
+static int bytecodevtabNext(sqlite3_vtab_cursor *cur){
+  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
+  bytecodevtab *pTab = (bytecodevtab*)cur->pVtab;
+  int rc;
+  if( pCur->zP4 ){
+    sqlite3_free(pCur->zP4);
+    pCur->zP4 = 0;
+  }
+  if( pCur->zName ){
+    pCur->zName = 0;
+    pCur->zType = 0;
+    pCur->zSchema = 0;
+  }
+  rc = sqlite3VdbeNextOpcode(
+           (Vdbe*)pCur->pStmt, 
+           pCur->showSubprograms ? &pCur->sub : 0,
+           pTab->bTablesUsed,
+           &pCur->iRowid,
+           &pCur->iAddr,
+           &pCur->aOp);
+  if( rc!=SQLITE_OK ){
+    sqlite3VdbeMemSetNull(&pCur->sub);
+    pCur->aOp = 0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Return TRUE if the cursor has been moved off of the last
+** row of output.
+*/
+static int bytecodevtabEof(sqlite3_vtab_cursor *cur){
+  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
+  return pCur->aOp==0;
+}
+
+/*
+** Return values of columns for the row at which the bytecodevtab_cursor
+** is currently pointing.
+*/
+static int bytecodevtabColumn(
+  sqlite3_vtab_cursor *cur,   /* The cursor */
+  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
+  int i                       /* Which column to return */
+){
+  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
+  bytecodevtab *pVTab = (bytecodevtab*)cur->pVtab;
+  Op *pOp = pCur->aOp + pCur->iAddr;
+  if( pVTab->bTablesUsed ){
+    if( i==4 ){
+      i = 8;
+    }else{
+      if( i<=2 && pCur->zType==0 ){
+        Schema *pSchema;
+        HashElem *k;
+        int iDb = pOp->p3;
+        Pgno iRoot = (Pgno)pOp->p2;
+        sqlite3 *db = pVTab->db;
+        pSchema = db->aDb[iDb].pSchema;
+        pCur->zSchema = db->aDb[iDb].zDbSName;
+        for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
+          Table *pTab = (Table*)sqliteHashData(k);
+          if( !IsVirtual(pTab) && pTab->tnum==iRoot ){
+            pCur->zName = pTab->zName;
+            pCur->zType = "table";
+            break;
+          }
+        }
+        if( pCur->zName==0 ){
+          for(k=sqliteHashFirst(&pSchema->idxHash); k; k=sqliteHashNext(k)){
+            Index *pIdx = (Index*)sqliteHashData(k);
+            if( pIdx->tnum==iRoot ){
+              pCur->zName = pIdx->zName;
+              pCur->zType = "index";
+            }
+          }
+        }
+      }
+      i += 20;
+    }
+  }
+  switch( i ){
+    case 0:   /* addr */
+      sqlite3_result_int(ctx, pCur->iAddr);
+      break;
+    case 1:   /* opcode */
+      sqlite3_result_text(ctx, (char*)sqlite3OpcodeName(pOp->opcode),
+                          -1, SQLITE_STATIC);
+      break;
+    case 2:   /* p1 */
+      sqlite3_result_int(ctx, pOp->p1);
+      break;
+    case 3:   /* p2 */
+      sqlite3_result_int(ctx, pOp->p2);
+      break;
+    case 4:   /* p3 */
+      sqlite3_result_int(ctx, pOp->p3);
+      break;
+    case 5:   /* p4 */
+    case 7:   /* comment */
+      if( pCur->zP4==0 ){
+        pCur->zP4 = sqlite3VdbeDisplayP4(pVTab->db, pOp);
+      }
+      if( i==5 ){
+        sqlite3_result_text(ctx, pCur->zP4, -1, SQLITE_STATIC);
+      }else{
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+        char *zCom = sqlite3VdbeDisplayComment(pVTab->db, pOp, pCur->zP4);
+        sqlite3_result_text(ctx, zCom, -1, sqlite3_free);
+#endif
+      }
+      break;
+    case 6:     /* p5 */
+      sqlite3_result_int(ctx, pOp->p5);
+      break;
+    case 8: {   /* subprog */
+      Op *aOp = pCur->aOp;
+      assert( aOp[0].opcode==OP_Init );
+      assert( aOp[0].p4.z==0 || strncmp(aOp[0].p4.z,"-" "- ",3)==0 );
+      if( pCur->iRowid==pCur->iAddr+1 ){
+        break;  /* Result is NULL for the main program */
+      }else if( aOp[0].p4.z!=0 ){
+         sqlite3_result_text(ctx, aOp[0].p4.z+3, -1, SQLITE_STATIC);
+      }else{
+         sqlite3_result_text(ctx, "(FK)", 4, SQLITE_STATIC);
+      }
+      break;
+    }
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+    case 9:     /* nexec */
+      sqlite3_result_int(ctx, pOp->nExec);
+      break;
+    case 10:    /* ncycle */
+      sqlite3_result_int(ctx, pOp->nCycle);
+      break;
+#else
+    case 9:     /* nexec */
+    case 10:    /* ncycle */
+      sqlite3_result_int(ctx, 0);
+      break;
+#endif
+
+    case 20:  /* tables_used.type */
+      sqlite3_result_text(ctx, pCur->zType, -1, SQLITE_STATIC);
+      break;
+    case 21:  /* tables_used.schema */
+      sqlite3_result_text(ctx, pCur->zSchema, -1, SQLITE_STATIC);
+      break;
+    case 22:  /* tables_used.name */
+      sqlite3_result_text(ctx, pCur->zName, -1, SQLITE_STATIC);
+      break;
+    case 23:  /* tables_used.wr */
+      sqlite3_result_int(ctx, pOp->opcode==OP_OpenWrite);
+      break;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Return the rowid for the current row.  In this implementation, the
+** rowid is the same as the output value.
+*/
+static int bytecodevtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
+  *pRowid = pCur->iRowid;
+  return SQLITE_OK;
+}
+
+/*
+** Initialize a cursor.
+**
+**    idxNum==0     means show all subprograms
+**    idxNum==1     means show only the main bytecode and omit subprograms.
+*/
+static int bytecodevtabFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  bytecodevtab_cursor *pCur = (bytecodevtab_cursor *)pVtabCursor;
+  bytecodevtab *pVTab = (bytecodevtab *)pVtabCursor->pVtab;
+  int rc = SQLITE_OK;
+  (void)idxStr;
+
+  bytecodevtabCursorClear(pCur);
+  pCur->iRowid = 0;
+  pCur->iAddr = 0;
+  pCur->showSubprograms = idxNum==0;
+  assert( argc==1 );
+  if( sqlite3_value_type(argv[0])==SQLITE_TEXT ){
+    const char *zSql = (const char*)sqlite3_value_text(argv[0]);
+    if( zSql==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare_v2(pVTab->db, zSql, -1, &pCur->pStmt, 0);
+      pCur->needFinalize = 1;
+    }
+  }else{
+    pCur->pStmt = (sqlite3_stmt*)sqlite3_value_pointer(argv[0],"stmt-pointer");
+  }
+  if( pCur->pStmt==0 ){
+    pVTab->base.zErrMsg = sqlite3_mprintf(
+       "argument to %s() is not a valid SQL statement",
+       pVTab->bTablesUsed ? "tables_used" : "bytecode"
+    );
+    rc = SQLITE_ERROR;
+  }else{
+    bytecodevtabNext(pVtabCursor);
+  }
+  return rc;
+}
+
+/*
+** We must have a single stmt=? constraint that will be passed through
+** into the xFilter method.  If there is no valid stmt=? constraint,
+** then return an SQLITE_CONSTRAINT error.
+*/
+static int bytecodevtabBestIndex(
+  sqlite3_vtab *tab,
+  sqlite3_index_info *pIdxInfo
+){
+  int i;
+  int rc = SQLITE_CONSTRAINT;
+  struct sqlite3_index_constraint *p;
+  bytecodevtab *pVTab = (bytecodevtab*)tab;
+  int iBaseCol = pVTab->bTablesUsed ? 4 : 10;
+  pIdxInfo->estimatedCost = (double)100;
+  pIdxInfo->estimatedRows = 100;
+  pIdxInfo->idxNum = 0;
+  for(i=0, p=pIdxInfo->aConstraint; i<pIdxInfo->nConstraint; i++, p++){
+    if( p->usable==0 ) continue;
+    if( p->op==SQLITE_INDEX_CONSTRAINT_EQ && p->iColumn==iBaseCol+1 ){
+      rc = SQLITE_OK;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+      pIdxInfo->aConstraintUsage[i].argvIndex = 1;
+    }
+    if( p->op==SQLITE_INDEX_CONSTRAINT_ISNULL && p->iColumn==iBaseCol ){
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+      pIdxInfo->idxNum = 1;
+    }
+  }
+  return rc;
+}
+
+/*
+** This following structure defines all the methods for the 
+** virtual table.
+*/
+static sqlite3_module bytecodevtabModule = {
+  /* iVersion    */ 0,
+  /* xCreate     */ 0,
+  /* xConnect    */ bytecodevtabConnect,
+  /* xBestIndex  */ bytecodevtabBestIndex,
+  /* xDisconnect */ bytecodevtabDisconnect,
+  /* xDestroy    */ 0,
+  /* xOpen       */ bytecodevtabOpen,
+  /* xClose      */ bytecodevtabClose,
+  /* xFilter     */ bytecodevtabFilter,
+  /* xNext       */ bytecodevtabNext,
+  /* xEof        */ bytecodevtabEof,
+  /* xColumn     */ bytecodevtabColumn,
+  /* xRowid      */ bytecodevtabRowid,
+  /* xUpdate     */ 0,
+  /* xBegin      */ 0,
+  /* xSync       */ 0,
+  /* xCommit     */ 0,
+  /* xRollback   */ 0,
+  /* xFindMethod */ 0,
+  /* xRename     */ 0,
+  /* xSavepoint  */ 0,
+  /* xRelease    */ 0,
+  /* xRollbackTo */ 0,
+  /* xShadowName */ 0,
+  /* xIntegrity  */ 0
+};
+
+
+int sqlite3VdbeBytecodeVtabInit(sqlite3 *db){
+  int rc;
+  rc = sqlite3_create_module(db, "bytecode", &bytecodevtabModule, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_module(db, "tables_used", &bytecodevtabModule, &db);
+  }
+  return rc;
+}
+#elif defined(SQLITE_ENABLE_BYTECODE_VTAB)
+int sqlite3VdbeBytecodeVtabInit(sqlite3 *db){ return SQLITE_OK; }
+#endif /* SQLITE_ENABLE_BYTECODE_VTAB */
diff --git a/src/vtab.c b/src/vtab.c
new file mode 100644
index 0000000..f839216
--- /dev/null
+++ b/src/vtab.c
@@ -0,0 +1,1353 @@
+/*
+** 2006 June 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to help implement virtual tables.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+#include "sqliteInt.h"
+
+/*
+** Before a virtual table xCreate() or xConnect() method is invoked, the
+** sqlite3.pVtabCtx member variable is set to point to an instance of
+** this struct allocated on the stack. It is used by the implementation of
+** the sqlite3_declare_vtab() and sqlite3_vtab_config() APIs, both of which
+** are invoked only from within xCreate and xConnect methods.
+*/
+struct VtabCtx {
+  VTable *pVTable;    /* The virtual table being constructed */
+  Table *pTab;        /* The Table object to which the virtual table belongs */
+  VtabCtx *pPrior;    /* Parent context (if any) */
+  int bDeclared;      /* True after sqlite3_declare_vtab() is called */
+};
+
+/*
+** Construct and install a Module object for a virtual table.  When this
+** routine is called, it is guaranteed that all appropriate locks are held
+** and the module is not already part of the connection.
+**
+** If there already exists a module with zName, replace it with the new one.
+** If pModule==0, then delete the module zName if it exists.
+*/
+Module *sqlite3VtabCreateModule(
+  sqlite3 *db,                    /* Database in which module is registered */
+  const char *zName,              /* Name assigned to this module */
+  const sqlite3_module *pModule,  /* The definition of the module */
+  void *pAux,                     /* Context pointer for xCreate/xConnect */
+  void (*xDestroy)(void *)        /* Module destructor function */
+){
+  Module *pMod;
+  Module *pDel;
+  char *zCopy;
+  if( pModule==0 ){
+    zCopy = (char*)zName;
+    pMod = 0;
+  }else{
+    int nName = sqlite3Strlen30(zName);
+    pMod = (Module *)sqlite3Malloc(sizeof(Module) + nName + 1);
+    if( pMod==0 ){
+      sqlite3OomFault(db);
+      return 0;
+    }
+    zCopy = (char *)(&pMod[1]);
+    memcpy(zCopy, zName, nName+1);
+    pMod->zName = zCopy;
+    pMod->pModule = pModule;
+    pMod->pAux = pAux;
+    pMod->xDestroy = xDestroy;
+    pMod->pEpoTab = 0;
+    pMod->nRefModule = 1;
+  }
+  pDel = (Module *)sqlite3HashInsert(&db->aModule,zCopy,(void*)pMod);
+  if( pDel ){
+    if( pDel==pMod ){
+      sqlite3OomFault(db);
+      sqlite3DbFree(db, pDel);
+      pMod = 0;
+    }else{
+      sqlite3VtabEponymousTableClear(db, pDel);
+      sqlite3VtabModuleUnref(db, pDel);
+    }
+  }
+  return pMod;
+}
+
+/*
+** The actual function that does the work of creating a new module.
+** This function implements the sqlite3_create_module() and
+** sqlite3_create_module_v2() interfaces.
+*/
+static int createModule(
+  sqlite3 *db,                    /* Database in which module is registered */
+  const char *zName,              /* Name assigned to this module */
+  const sqlite3_module *pModule,  /* The definition of the module */
+  void *pAux,                     /* Context pointer for xCreate/xConnect */
+  void (*xDestroy)(void *)        /* Module destructor function */
+){
+  int rc = SQLITE_OK;
+
+  sqlite3_mutex_enter(db->mutex);
+  (void)sqlite3VtabCreateModule(db, zName, pModule, pAux, xDestroy);
+  rc = sqlite3ApiExit(db, rc);
+  if( rc!=SQLITE_OK && xDestroy ) xDestroy(pAux);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+
+/*
+** External API function used to create a new virtual-table module.
+*/
+int sqlite3_create_module(
+  sqlite3 *db,                    /* Database in which module is registered */
+  const char *zName,              /* Name assigned to this module */
+  const sqlite3_module *pModule,  /* The definition of the module */
+  void *pAux                      /* Context pointer for xCreate/xConnect */
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zName==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  return createModule(db, zName, pModule, pAux, 0);
+}
+
+/*
+** External API function used to create a new virtual-table module.
+*/
+int sqlite3_create_module_v2(
+  sqlite3 *db,                    /* Database in which module is registered */
+  const char *zName,              /* Name assigned to this module */
+  const sqlite3_module *pModule,  /* The definition of the module */
+  void *pAux,                     /* Context pointer for xCreate/xConnect */
+  void (*xDestroy)(void *)        /* Module destructor function */
+){
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zName==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+  return createModule(db, zName, pModule, pAux, xDestroy);
+}
+
+/*
+** External API to drop all virtual-table modules, except those named
+** on the azNames list.
+*/
+int sqlite3_drop_modules(sqlite3 *db, const char** azNames){
+  HashElem *pThis, *pNext;
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  for(pThis=sqliteHashFirst(&db->aModule); pThis; pThis=pNext){
+    Module *pMod = (Module*)sqliteHashData(pThis);
+    pNext = sqliteHashNext(pThis);
+    if( azNames ){
+      int ii;
+      for(ii=0; azNames[ii]!=0 && strcmp(azNames[ii],pMod->zName)!=0; ii++){}
+      if( azNames[ii]!=0 ) continue;
+    }
+    createModule(db, pMod->zName, 0, 0, 0);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Decrement the reference count on a Module object.  Destroy the
+** module when the reference count reaches zero.
+*/
+void sqlite3VtabModuleUnref(sqlite3 *db, Module *pMod){
+  assert( pMod->nRefModule>0 );
+  pMod->nRefModule--;
+  if( pMod->nRefModule==0 ){
+    if( pMod->xDestroy ){
+      pMod->xDestroy(pMod->pAux);
+    }
+    assert( pMod->pEpoTab==0 );
+    sqlite3DbFree(db, pMod);
+  }
+}
+
+/*
+** Lock the virtual table so that it cannot be disconnected.
+** Locks nest.  Every lock should have a corresponding unlock.
+** If an unlock is omitted, resources leaks will occur.
+**
+** If a disconnect is attempted while a virtual table is locked,
+** the disconnect is deferred until all locks have been removed.
+*/
+void sqlite3VtabLock(VTable *pVTab){
+  pVTab->nRef++;
+}
+
+
+/*
+** pTab is a pointer to a Table structure representing a virtual-table.
+** Return a pointer to the VTable object used by connection db to access
+** this virtual-table, if one has been created, or NULL otherwise.
+*/
+VTable *sqlite3GetVTable(sqlite3 *db, Table *pTab){
+  VTable *pVtab;
+  assert( IsVirtual(pTab) );
+  for(pVtab=pTab->u.vtab.p; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);
+  return pVtab;
+}
+
+/*
+** Decrement the ref-count on a virtual table object. When the ref-count
+** reaches zero, call the xDisconnect() method to delete the object.
+*/
+void sqlite3VtabUnlock(VTable *pVTab){
+  sqlite3 *db = pVTab->db;
+
+  assert( db );
+  assert( pVTab->nRef>0 );
+  assert( db->eOpenState==SQLITE_STATE_OPEN
+       || db->eOpenState==SQLITE_STATE_ZOMBIE );
+
+  pVTab->nRef--;
+  if( pVTab->nRef==0 ){
+    sqlite3_vtab *p = pVTab->pVtab;
+    if( p ){
+      p->pModule->xDisconnect(p);
+    }
+    sqlite3VtabModuleUnref(pVTab->db, pVTab->pMod);
+    sqlite3DbFree(db, pVTab);
+  }
+}
+
+/*
+** Table p is a virtual table. This function moves all elements in the
+** p->u.vtab.p list to the sqlite3.pDisconnect lists of their associated
+** database connections to be disconnected at the next opportunity.
+** Except, if argument db is not NULL, then the entry associated with
+** connection db is left in the p->u.vtab.p list.
+*/
+static VTable *vtabDisconnectAll(sqlite3 *db, Table *p){
+  VTable *pRet = 0;
+  VTable *pVTable;
+
+  assert( IsVirtual(p) );
+  pVTable = p->u.vtab.p;
+  p->u.vtab.p = 0;
+
+  /* Assert that the mutex (if any) associated with the BtShared database
+  ** that contains table p is held by the caller. See header comments
+  ** above function sqlite3VtabUnlockList() for an explanation of why
+  ** this makes it safe to access the sqlite3.pDisconnect list of any
+  ** database connection that may have an entry in the p->u.vtab.p list.
+  */
+  assert( db==0 || sqlite3SchemaMutexHeld(db, 0, p->pSchema) );
+
+  while( pVTable ){
+    sqlite3 *db2 = pVTable->db;
+    VTable *pNext = pVTable->pNext;
+    assert( db2 );
+    if( db2==db ){
+      pRet = pVTable;
+      p->u.vtab.p = pRet;
+      pRet->pNext = 0;
+    }else{
+      pVTable->pNext = db2->pDisconnect;
+      db2->pDisconnect = pVTable;
+    }
+    pVTable = pNext;
+  }
+
+  assert( !db || pRet );
+  return pRet;
+}
+
+/*
+** Table *p is a virtual table. This function removes the VTable object
+** for table *p associated with database connection db from the linked
+** list in p->pVTab. It also decrements the VTable ref count. This is
+** used when closing database connection db to free all of its VTable
+** objects without disturbing the rest of the Schema object (which may
+** be being used by other shared-cache connections).
+*/
+void sqlite3VtabDisconnect(sqlite3 *db, Table *p){
+  VTable **ppVTab;
+
+  assert( IsVirtual(p) );
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  for(ppVTab=&p->u.vtab.p; *ppVTab; ppVTab=&(*ppVTab)->pNext){
+    if( (*ppVTab)->db==db  ){
+      VTable *pVTab = *ppVTab;
+      *ppVTab = pVTab->pNext;
+      sqlite3VtabUnlock(pVTab);
+      break;
+    }
+  }
+}
+
+
+/*
+** Disconnect all the virtual table objects in the sqlite3.pDisconnect list.
+**
+** This function may only be called when the mutexes associated with all
+** shared b-tree databases opened using connection db are held by the
+** caller. This is done to protect the sqlite3.pDisconnect list. The
+** sqlite3.pDisconnect list is accessed only as follows:
+**
+**   1) By this function. In this case, all BtShared mutexes and the mutex
+**      associated with the database handle itself must be held.
+**
+**   2) By function vtabDisconnectAll(), when it adds a VTable entry to
+**      the sqlite3.pDisconnect list. In this case either the BtShared mutex
+**      associated with the database the virtual table is stored in is held
+**      or, if the virtual table is stored in a non-sharable database, then
+**      the database handle mutex is held.
+**
+** As a result, a sqlite3.pDisconnect cannot be accessed simultaneously
+** by multiple threads. It is thread-safe.
+*/
+void sqlite3VtabUnlockList(sqlite3 *db){
+  VTable *p = db->pDisconnect;
+
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  if( p ){
+    db->pDisconnect = 0;
+    do {
+      VTable *pNext = p->pNext;
+      sqlite3VtabUnlock(p);
+      p = pNext;
+    }while( p );
+  }
+}
+
+/*
+** Clear any and all virtual-table information from the Table record.
+** This routine is called, for example, just before deleting the Table
+** record.
+**
+** Since it is a virtual-table, the Table structure contains a pointer
+** to the head of a linked list of VTable structures. Each VTable
+** structure is associated with a single sqlite3* user of the schema.
+** The reference count of the VTable structure associated with database
+** connection db is decremented immediately (which may lead to the
+** structure being xDisconnected and free). Any other VTable structures
+** in the list are moved to the sqlite3.pDisconnect list of the associated
+** database connection.
+*/
+void sqlite3VtabClear(sqlite3 *db, Table *p){
+  assert( IsVirtual(p) );
+  assert( db!=0 );
+  if( db->pnBytesFreed==0 ) vtabDisconnectAll(0, p);
+  if( p->u.vtab.azArg ){
+    int i;
+    for(i=0; i<p->u.vtab.nArg; i++){
+      if( i!=1 ) sqlite3DbFree(db, p->u.vtab.azArg[i]);
+    }
+    sqlite3DbFree(db, p->u.vtab.azArg);
+  }
+}
+
+/*
+** Add a new module argument to pTable->u.vtab.azArg[].
+** The string is not copied - the pointer is stored.  The
+** string will be freed automatically when the table is
+** deleted.
+*/
+static void addModuleArgument(Parse *pParse, Table *pTable, char *zArg){
+  sqlite3_int64 nBytes;
+  char **azModuleArg;
+  sqlite3 *db = pParse->db;
+
+  assert( IsVirtual(pTable) );
+  nBytes = sizeof(char *)*(2+pTable->u.vtab.nArg);
+  if( pTable->u.vtab.nArg+3>=db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many columns on %s", pTable->zName);
+  }
+  azModuleArg = sqlite3DbRealloc(db, pTable->u.vtab.azArg, nBytes);
+  if( azModuleArg==0 ){
+    sqlite3DbFree(db, zArg);
+  }else{
+    int i = pTable->u.vtab.nArg++;
+    azModuleArg[i] = zArg;
+    azModuleArg[i+1] = 0;
+    pTable->u.vtab.azArg = azModuleArg;
+  }
+}
+
+/*
+** The parser calls this routine when it first sees a CREATE VIRTUAL TABLE
+** statement.  The module name has been parsed, but the optional list
+** of parameters that follow the module name are still pending.
+*/
+void sqlite3VtabBeginParse(
+  Parse *pParse,        /* Parsing context */
+  Token *pName1,        /* Name of new table, or database name */
+  Token *pName2,        /* Name of new table or NULL */
+  Token *pModuleName,   /* Name of the module for the virtual table */
+  int ifNotExists       /* No error if the table already exists */
+){
+  Table *pTable;        /* The new virtual table */
+  sqlite3 *db;          /* Database connection */
+
+  sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, ifNotExists);
+  pTable = pParse->pNewTable;
+  if( pTable==0 ) return;
+  assert( 0==pTable->pIndex );
+  pTable->eTabType = TABTYP_VTAB;
+
+  db = pParse->db;
+
+  assert( pTable->u.vtab.nArg==0 );
+  addModuleArgument(pParse, pTable, sqlite3NameFromToken(db, pModuleName));
+  addModuleArgument(pParse, pTable, 0);
+  addModuleArgument(pParse, pTable, sqlite3DbStrDup(db, pTable->zName));
+  assert( (pParse->sNameToken.z==pName2->z && pName2->z!=0)
+       || (pParse->sNameToken.z==pName1->z && pName2->z==0)
+  );
+  pParse->sNameToken.n = (int)(
+      &pModuleName->z[pModuleName->n] - pParse->sNameToken.z
+  );
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Creating a virtual table invokes the authorization callback twice.
+  ** The first invocation, to obtain permission to INSERT a row into the
+  ** sqlite_schema table, has already been made by sqlite3StartTable().
+  ** The second call, to obtain permission to create the table, is made now.
+  */
+  if( pTable->u.vtab.azArg ){
+    int iDb = sqlite3SchemaToIndex(db, pTable->pSchema);
+    assert( iDb>=0 ); /* The database the table is being created in */
+    sqlite3AuthCheck(pParse, SQLITE_CREATE_VTABLE, pTable->zName,
+            pTable->u.vtab.azArg[0], pParse->db->aDb[iDb].zDbSName);
+  }
+#endif
+}
+
+/*
+** This routine takes the module argument that has been accumulating
+** in pParse->zArg[] and appends it to the list of arguments on the
+** virtual table currently under construction in pParse->pTable.
+*/
+static void addArgumentToVtab(Parse *pParse){
+  if( pParse->sArg.z && pParse->pNewTable ){
+    const char *z = (const char*)pParse->sArg.z;
+    int n = pParse->sArg.n;
+    sqlite3 *db = pParse->db;
+    addModuleArgument(pParse, pParse->pNewTable, sqlite3DbStrNDup(db, z, n));
+  }
+}
+
+/*
+** The parser calls this routine after the CREATE VIRTUAL TABLE statement
+** has been completely parsed.
+*/
+void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){
+  Table *pTab = pParse->pNewTable;  /* The table being constructed */
+  sqlite3 *db = pParse->db;         /* The database connection */
+
+  if( pTab==0 ) return;
+  assert( IsVirtual(pTab) );
+  addArgumentToVtab(pParse);
+  pParse->sArg.z = 0;
+  if( pTab->u.vtab.nArg<1 ) return;
+
+  /* If the CREATE VIRTUAL TABLE statement is being entered for the
+  ** first time (in other words if the virtual table is actually being
+  ** created now instead of just being read out of sqlite_schema) then
+  ** do additional initialization work and store the statement text
+  ** in the sqlite_schema table.
+  */
+  if( !db->init.busy ){
+    char *zStmt;
+    char *zWhere;
+    int iDb;
+    int iReg;
+    Vdbe *v;
+
+    sqlite3MayAbort(pParse);
+
+    /* Compute the complete text of the CREATE VIRTUAL TABLE statement */
+    if( pEnd ){
+      pParse->sNameToken.n = (int)(pEnd->z - pParse->sNameToken.z) + pEnd->n;
+    }
+    zStmt = sqlite3MPrintf(db, "CREATE VIRTUAL TABLE %T", &pParse->sNameToken);
+
+    /* A slot for the record has already been allocated in the
+    ** schema table.  We just need to update that slot with all
+    ** the information we've collected.
+    **
+    ** The VM register number pParse->regRowid holds the rowid of an
+    ** entry in the sqlite_schema table that was created for this vtab
+    ** by sqlite3StartTable().
+    */
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    sqlite3NestedParse(pParse,
+      "UPDATE %Q." LEGACY_SCHEMA_TABLE " "
+         "SET type='table', name=%Q, tbl_name=%Q, rootpage=0, sql=%Q "
+       "WHERE rowid=#%d",
+      db->aDb[iDb].zDbSName,
+      pTab->zName,
+      pTab->zName,
+      zStmt,
+      pParse->regRowid
+    );
+    v = sqlite3GetVdbe(pParse);
+    sqlite3ChangeCookie(pParse, iDb);
+
+    sqlite3VdbeAddOp0(v, OP_Expire);
+    zWhere = sqlite3MPrintf(db, "name=%Q AND sql=%Q", pTab->zName, zStmt);
+    sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere, 0);
+    sqlite3DbFree(db, zStmt);
+
+    iReg = ++pParse->nMem;
+    sqlite3VdbeLoadString(v, iReg, pTab->zName);
+    sqlite3VdbeAddOp2(v, OP_VCreate, iDb, iReg);
+  }else{
+    /* If we are rereading the sqlite_schema table create the in-memory
+    ** record of the table. */
+    Table *pOld;
+    Schema *pSchema = pTab->pSchema;
+    const char *zName = pTab->zName;
+    assert( zName!=0 );
+    sqlite3MarkAllShadowTablesOf(db, pTab);
+    pOld = sqlite3HashInsert(&pSchema->tblHash, zName, pTab);
+    if( pOld ){
+      sqlite3OomFault(db);
+      assert( pTab==pOld );  /* Malloc must have failed inside HashInsert() */
+      return;
+    }
+    pParse->pNewTable = 0;
+  }
+}
+
+/*
+** The parser calls this routine when it sees the first token
+** of an argument to the module name in a CREATE VIRTUAL TABLE statement.
+*/
+void sqlite3VtabArgInit(Parse *pParse){
+  addArgumentToVtab(pParse);
+  pParse->sArg.z = 0;
+  pParse->sArg.n = 0;
+}
+
+/*
+** The parser calls this routine for each token after the first token
+** in an argument to the module name in a CREATE VIRTUAL TABLE statement.
+*/
+void sqlite3VtabArgExtend(Parse *pParse, Token *p){
+  Token *pArg = &pParse->sArg;
+  if( pArg->z==0 ){
+    pArg->z = p->z;
+    pArg->n = p->n;
+  }else{
+    assert(pArg->z <= p->z);
+    pArg->n = (int)(&p->z[p->n] - pArg->z);
+  }
+}
+
+/*
+** Invoke a virtual table constructor (either xCreate or xConnect). The
+** pointer to the function to invoke is passed as the fourth parameter
+** to this procedure.
+*/
+static int vtabCallConstructor(
+  sqlite3 *db,
+  Table *pTab,
+  Module *pMod,
+  int (*xConstruct)(sqlite3*,void*,int,const char*const*,sqlite3_vtab**,char**),
+  char **pzErr
+){
+  VtabCtx sCtx;
+  VTable *pVTable;
+  int rc;
+  const char *const*azArg;
+  int nArg = pTab->u.vtab.nArg;
+  char *zErr = 0;
+  char *zModuleName;
+  int iDb;
+  VtabCtx *pCtx;
+
+  assert( IsVirtual(pTab) );
+  azArg = (const char *const*)pTab->u.vtab.azArg;
+
+  /* Check that the virtual-table is not already being initialized */
+  for(pCtx=db->pVtabCtx; pCtx; pCtx=pCtx->pPrior){
+    if( pCtx->pTab==pTab ){
+      *pzErr = sqlite3MPrintf(db,
+          "vtable constructor called recursively: %s", pTab->zName
+      );
+      return SQLITE_LOCKED;
+    }
+  }
+
+  zModuleName = sqlite3DbStrDup(db, pTab->zName);
+  if( !zModuleName ){
+    return SQLITE_NOMEM_BKPT;
+  }
+
+  pVTable = sqlite3MallocZero(sizeof(VTable));
+  if( !pVTable ){
+    sqlite3OomFault(db);
+    sqlite3DbFree(db, zModuleName);
+    return SQLITE_NOMEM_BKPT;
+  }
+  pVTable->db = db;
+  pVTable->pMod = pMod;
+  pVTable->eVtabRisk = SQLITE_VTABRISK_Normal;
+
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  pTab->u.vtab.azArg[1] = db->aDb[iDb].zDbSName;
+
+  /* Invoke the virtual table constructor */
+  assert( &db->pVtabCtx );
+  assert( xConstruct );
+  sCtx.pTab = pTab;
+  sCtx.pVTable = pVTable;
+  sCtx.pPrior = db->pVtabCtx;
+  sCtx.bDeclared = 0;
+  db->pVtabCtx = &sCtx;
+  pTab->nTabRef++;
+  rc = xConstruct(db, pMod->pAux, nArg, azArg, &pVTable->pVtab, &zErr);
+  sqlite3DeleteTable(db, pTab);
+  db->pVtabCtx = sCtx.pPrior;
+  if( rc==SQLITE_NOMEM ) sqlite3OomFault(db);
+  assert( sCtx.pTab==pTab );
+
+  if( SQLITE_OK!=rc ){
+    if( zErr==0 ){
+      *pzErr = sqlite3MPrintf(db, "vtable constructor failed: %s", zModuleName);
+    }else {
+      *pzErr = sqlite3MPrintf(db, "%s", zErr);
+      sqlite3_free(zErr);
+    }
+    sqlite3DbFree(db, pVTable);
+  }else if( ALWAYS(pVTable->pVtab) ){
+    /* Justification of ALWAYS():  A correct vtab constructor must allocate
+    ** the sqlite3_vtab object if successful.  */
+    memset(pVTable->pVtab, 0, sizeof(pVTable->pVtab[0]));
+    pVTable->pVtab->pModule = pMod->pModule;
+    pMod->nRefModule++;
+    pVTable->nRef = 1;
+    if( sCtx.bDeclared==0 ){
+      const char *zFormat = "vtable constructor did not declare schema: %s";
+      *pzErr = sqlite3MPrintf(db, zFormat, pTab->zName);
+      sqlite3VtabUnlock(pVTable);
+      rc = SQLITE_ERROR;
+    }else{
+      int iCol;
+      u16 oooHidden = 0;
+      /* If everything went according to plan, link the new VTable structure
+      ** into the linked list headed by pTab->u.vtab.p. Then loop through the
+      ** columns of the table to see if any of them contain the token "hidden".
+      ** If so, set the Column COLFLAG_HIDDEN flag and remove the token from
+      ** the type string.  */
+      pVTable->pNext = pTab->u.vtab.p;
+      pTab->u.vtab.p = pVTable;
+
+      for(iCol=0; iCol<pTab->nCol; iCol++){
+        char *zType = sqlite3ColumnType(&pTab->aCol[iCol], "");
+        int nType;
+        int i = 0;
+        nType = sqlite3Strlen30(zType);
+        for(i=0; i<nType; i++){
+          if( 0==sqlite3StrNICmp("hidden", &zType[i], 6)
+           && (i==0 || zType[i-1]==' ')
+           && (zType[i+6]=='\0' || zType[i+6]==' ')
+          ){
+            break;
+          }
+        }
+        if( i<nType ){
+          int j;
+          int nDel = 6 + (zType[i+6] ? 1 : 0);
+          for(j=i; (j+nDel)<=nType; j++){
+            zType[j] = zType[j+nDel];
+          }
+          if( zType[i]=='\0' && i>0 ){
+            assert(zType[i-1]==' ');
+            zType[i-1] = '\0';
+          }
+          pTab->aCol[iCol].colFlags |= COLFLAG_HIDDEN;
+          pTab->tabFlags |= TF_HasHidden;
+          oooHidden = TF_OOOHidden;
+        }else{
+          pTab->tabFlags |= oooHidden;
+        }
+      }
+    }
+  }
+
+  sqlite3DbFree(db, zModuleName);
+  return rc;
+}
+
+/*
+** This function is invoked by the parser to call the xConnect() method
+** of the virtual table pTab. If an error occurs, an error code is returned
+** and an error left in pParse.
+**
+** This call is a no-op if table pTab is not a virtual table.
+*/
+int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
+  sqlite3 *db = pParse->db;
+  const char *zMod;
+  Module *pMod;
+  int rc;
+
+  assert( pTab );
+  assert( IsVirtual(pTab) );
+  if( sqlite3GetVTable(db, pTab) ){
+    return SQLITE_OK;
+  }
+
+  /* Locate the required virtual table module */
+  zMod = pTab->u.vtab.azArg[0];
+  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod);
+
+  if( !pMod ){
+    const char *zModule = pTab->u.vtab.azArg[0];
+    sqlite3ErrorMsg(pParse, "no such module: %s", zModule);
+    rc = SQLITE_ERROR;
+  }else{
+    char *zErr = 0;
+    rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xConnect, &zErr);
+    if( rc!=SQLITE_OK ){
+      sqlite3ErrorMsg(pParse, "%s", zErr);
+      pParse->rc = rc;
+    }
+    sqlite3DbFree(db, zErr);
+  }
+
+  return rc;
+}
+/*
+** Grow the db->aVTrans[] array so that there is room for at least one
+** more v-table. Return SQLITE_NOMEM if a malloc fails, or SQLITE_OK otherwise.
+*/
+static int growVTrans(sqlite3 *db){
+  const int ARRAY_INCR = 5;
+
+  /* Grow the sqlite3.aVTrans array if required */
+  if( (db->nVTrans%ARRAY_INCR)==0 ){
+    VTable **aVTrans;
+    sqlite3_int64 nBytes = sizeof(sqlite3_vtab*)*
+                                 ((sqlite3_int64)db->nVTrans + ARRAY_INCR);
+    aVTrans = sqlite3DbRealloc(db, (void *)db->aVTrans, nBytes);
+    if( !aVTrans ){
+      return SQLITE_NOMEM_BKPT;
+    }
+    memset(&aVTrans[db->nVTrans], 0, sizeof(sqlite3_vtab *)*ARRAY_INCR);
+    db->aVTrans = aVTrans;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Add the virtual table pVTab to the array sqlite3.aVTrans[]. Space should
+** have already been reserved using growVTrans().
+*/
+static void addToVTrans(sqlite3 *db, VTable *pVTab){
+  /* Add pVtab to the end of sqlite3.aVTrans */
+  db->aVTrans[db->nVTrans++] = pVTab;
+  sqlite3VtabLock(pVTab);
+}
+
+/*
+** This function is invoked by the vdbe to call the xCreate method
+** of the virtual table named zTab in database iDb.
+**
+** If an error occurs, *pzErr is set to point to an English language
+** description of the error and an SQLITE_XXX error code is returned.
+** In this case the caller must call sqlite3DbFree(db, ) on *pzErr.
+*/
+int sqlite3VtabCallCreate(sqlite3 *db, int iDb, const char *zTab, char **pzErr){
+  int rc = SQLITE_OK;
+  Table *pTab;
+  Module *pMod;
+  const char *zMod;
+
+  pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zDbSName);
+  assert( pTab && IsVirtual(pTab) && !pTab->u.vtab.p );
+
+  /* Locate the required virtual table module */
+  zMod = pTab->u.vtab.azArg[0];
+  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod);
+
+  /* If the module has been registered and includes a Create method,
+  ** invoke it now. If the module has not been registered, return an
+  ** error. Otherwise, do nothing.
+  */
+  if( pMod==0 || pMod->pModule->xCreate==0 || pMod->pModule->xDestroy==0 ){
+    *pzErr = sqlite3MPrintf(db, "no such module: %s", zMod);
+    rc = SQLITE_ERROR;
+  }else{
+    rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xCreate, pzErr);
+  }
+
+  /* Justification of ALWAYS():  The xConstructor method is required to
+  ** create a valid sqlite3_vtab if it returns SQLITE_OK. */
+  if( rc==SQLITE_OK && ALWAYS(sqlite3GetVTable(db, pTab)) ){
+    rc = growVTrans(db);
+    if( rc==SQLITE_OK ){
+      addToVTrans(db, sqlite3GetVTable(db, pTab));
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function is used to set the schema of a virtual table.  It is only
+** valid to call this function from within the xCreate() or xConnect() of a
+** virtual table module.
+*/
+int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
+  VtabCtx *pCtx;
+  int rc = SQLITE_OK;
+  Table *pTab;
+  Parse sParse;
+  int initBusy;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) || zCreateTable==0 ){
+    return SQLITE_MISUSE_BKPT;
+  }
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  pCtx = db->pVtabCtx;
+  if( !pCtx || pCtx->bDeclared ){
+    sqlite3Error(db, SQLITE_MISUSE_BKPT);
+    sqlite3_mutex_leave(db->mutex);
+    return SQLITE_MISUSE_BKPT;
+  }
+  pTab = pCtx->pTab;
+  assert( IsVirtual(pTab) );
+
+  sqlite3ParseObjectInit(&sParse, db);
+  sParse.eParseMode = PARSE_MODE_DECLARE_VTAB;
+  sParse.disableTriggers = 1;
+  /* We should never be able to reach this point while loading the
+  ** schema.  Nevertheless, defend against that (turn off db->init.busy)
+  ** in case a bug arises. */
+  assert( db->init.busy==0 );
+  initBusy = db->init.busy;
+  db->init.busy = 0;
+  sParse.nQueryLoop = 1;
+  if( SQLITE_OK==sqlite3RunParser(&sParse, zCreateTable)
+   && ALWAYS(sParse.pNewTable!=0)
+   && ALWAYS(!db->mallocFailed)
+   && IsOrdinaryTable(sParse.pNewTable)
+  ){
+    assert( sParse.zErrMsg==0 );
+    if( !pTab->aCol ){
+      Table *pNew = sParse.pNewTable;
+      Index *pIdx;
+      pTab->aCol = pNew->aCol;
+      sqlite3ExprListDelete(db, pNew->u.tab.pDfltList);
+      pTab->nNVCol = pTab->nCol = pNew->nCol;
+      pTab->tabFlags |= pNew->tabFlags & (TF_WithoutRowid|TF_NoVisibleRowid);
+      pNew->nCol = 0;
+      pNew->aCol = 0;
+      assert( pTab->pIndex==0 );
+      assert( HasRowid(pNew) || sqlite3PrimaryKeyIndex(pNew)!=0 );
+      if( !HasRowid(pNew)
+       && pCtx->pVTable->pMod->pModule->xUpdate!=0
+       && sqlite3PrimaryKeyIndex(pNew)->nKeyCol!=1
+      ){
+        /* WITHOUT ROWID virtual tables must either be read-only (xUpdate==0)
+        ** or else must have a single-column PRIMARY KEY */
+        rc = SQLITE_ERROR;
+      }
+      pIdx = pNew->pIndex;
+      if( pIdx ){
+        assert( pIdx->pNext==0 );
+        pTab->pIndex = pIdx;
+        pNew->pIndex = 0;
+        pIdx->pTable = pTab;
+      }
+    }
+    pCtx->bDeclared = 1;
+  }else{
+    sqlite3ErrorWithMsg(db, SQLITE_ERROR,
+          (sParse.zErrMsg ? "%s" : 0), sParse.zErrMsg);
+    sqlite3DbFree(db, sParse.zErrMsg);
+    rc = SQLITE_ERROR;
+  }
+  sParse.eParseMode = PARSE_MODE_NORMAL;
+
+  if( sParse.pVdbe ){
+    sqlite3VdbeFinalize(sParse.pVdbe);
+  }
+  sqlite3DeleteTable(db, sParse.pNewTable);
+  sqlite3ParseObjectReset(&sParse);
+  db->init.busy = initBusy;
+
+  assert( (rc&0xff)==rc );
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** This function is invoked by the vdbe to call the xDestroy method
+** of the virtual table named zTab in database iDb. This occurs
+** when a DROP TABLE is mentioned.
+**
+** This call is a no-op if zTab is not a virtual table.
+*/
+int sqlite3VtabCallDestroy(sqlite3 *db, int iDb, const char *zTab){
+  int rc = SQLITE_OK;
+  Table *pTab;
+
+  pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zDbSName);
+  if( ALWAYS(pTab!=0)
+   && ALWAYS(IsVirtual(pTab))
+   && ALWAYS(pTab->u.vtab.p!=0)
+  ){
+    VTable *p;
+    int (*xDestroy)(sqlite3_vtab *);
+    for(p=pTab->u.vtab.p; p; p=p->pNext){
+      assert( p->pVtab );
+      if( p->pVtab->nRef>0 ){
+        return SQLITE_LOCKED;
+      }
+    }
+    p = vtabDisconnectAll(db, pTab);
+    xDestroy = p->pMod->pModule->xDestroy;
+    if( xDestroy==0 ) xDestroy = p->pMod->pModule->xDisconnect;
+    assert( xDestroy!=0 );
+    pTab->nTabRef++;
+    rc = xDestroy(p->pVtab);
+    /* Remove the sqlite3_vtab* from the aVTrans[] array, if applicable */
+    if( rc==SQLITE_OK ){
+      assert( pTab->u.vtab.p==p && p->pNext==0 );
+      p->pVtab = 0;
+      pTab->u.vtab.p = 0;
+      sqlite3VtabUnlock(p);
+    }
+    sqlite3DeleteTable(db, pTab);
+  }
+
+  return rc;
+}
+
+/*
+** This function invokes either the xRollback or xCommit method
+** of each of the virtual tables in the sqlite3.aVTrans array. The method
+** called is identified by the second argument, "offset", which is
+** the offset of the method to call in the sqlite3_module structure.
+**
+** The array is cleared after invoking the callbacks.
+*/
+static void callFinaliser(sqlite3 *db, int offset){
+  int i;
+  if( db->aVTrans ){
+    VTable **aVTrans = db->aVTrans;
+    db->aVTrans = 0;
+    for(i=0; i<db->nVTrans; i++){
+      VTable *pVTab = aVTrans[i];
+      sqlite3_vtab *p = pVTab->pVtab;
+      if( p ){
+        int (*x)(sqlite3_vtab *);
+        x = *(int (**)(sqlite3_vtab *))((char *)p->pModule + offset);
+        if( x ) x(p);
+      }
+      pVTab->iSavepoint = 0;
+      sqlite3VtabUnlock(pVTab);
+    }
+    sqlite3DbFree(db, aVTrans);
+    db->nVTrans = 0;
+  }
+}
+
+/*
+** Invoke the xSync method of all virtual tables in the sqlite3.aVTrans
+** array. Return the error code for the first error that occurs, or
+** SQLITE_OK if all xSync operations are successful.
+**
+** If an error message is available, leave it in p->zErrMsg.
+*/
+int sqlite3VtabSync(sqlite3 *db, Vdbe *p){
+  int i;
+  int rc = SQLITE_OK;
+  VTable **aVTrans = db->aVTrans;
+
+  db->aVTrans = 0;
+  for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
+    int (*x)(sqlite3_vtab *);
+    sqlite3_vtab *pVtab = aVTrans[i]->pVtab;
+    if( pVtab && (x = pVtab->pModule->xSync)!=0 ){
+      rc = x(pVtab);
+      sqlite3VtabImportErrmsg(p, pVtab);
+    }
+  }
+  db->aVTrans = aVTrans;
+  return rc;
+}
+
+/*
+** Invoke the xRollback method of all virtual tables in the
+** sqlite3.aVTrans array. Then clear the array itself.
+*/
+int sqlite3VtabRollback(sqlite3 *db){
+  callFinaliser(db, offsetof(sqlite3_module,xRollback));
+  return SQLITE_OK;
+}
+
+/*
+** Invoke the xCommit method of all virtual tables in the
+** sqlite3.aVTrans array. Then clear the array itself.
+*/
+int sqlite3VtabCommit(sqlite3 *db){
+  callFinaliser(db, offsetof(sqlite3_module,xCommit));
+  return SQLITE_OK;
+}
+
+/*
+** If the virtual table pVtab supports the transaction interface
+** (xBegin/xRollback/xCommit and optionally xSync) and a transaction is
+** not currently open, invoke the xBegin method now.
+**
+** If the xBegin call is successful, place the sqlite3_vtab pointer
+** in the sqlite3.aVTrans array.
+*/
+int sqlite3VtabBegin(sqlite3 *db, VTable *pVTab){
+  int rc = SQLITE_OK;
+  const sqlite3_module *pModule;
+
+  /* Special case: If db->aVTrans is NULL and db->nVTrans is greater
+  ** than zero, then this function is being called from within a
+  ** virtual module xSync() callback. It is illegal to write to
+  ** virtual module tables in this case, so return SQLITE_LOCKED.
+  */
+  if( sqlite3VtabInSync(db) ){
+    return SQLITE_LOCKED;
+  }
+  if( !pVTab ){
+    return SQLITE_OK;
+  }
+  pModule = pVTab->pVtab->pModule;
+
+  if( pModule->xBegin ){
+    int i;
+
+    /* If pVtab is already in the aVTrans array, return early */
+    for(i=0; i<db->nVTrans; i++){
+      if( db->aVTrans[i]==pVTab ){
+        return SQLITE_OK;
+      }
+    }
+
+    /* Invoke the xBegin method. If successful, add the vtab to the
+    ** sqlite3.aVTrans[] array. */
+    rc = growVTrans(db);
+    if( rc==SQLITE_OK ){
+      rc = pModule->xBegin(pVTab->pVtab);
+      if( rc==SQLITE_OK ){
+        int iSvpt = db->nStatement + db->nSavepoint;
+        addToVTrans(db, pVTab);
+        if( iSvpt && pModule->xSavepoint ){
+          pVTab->iSavepoint = iSvpt;
+          rc = pModule->xSavepoint(pVTab->pVtab, iSvpt-1);
+        }
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Invoke either the xSavepoint, xRollbackTo or xRelease method of all
+** virtual tables that currently have an open transaction. Pass iSavepoint
+** as the second argument to the virtual table method invoked.
+**
+** If op is SAVEPOINT_BEGIN, the xSavepoint method is invoked. If it is
+** SAVEPOINT_ROLLBACK, the xRollbackTo method. Otherwise, if op is
+** SAVEPOINT_RELEASE, then the xRelease method of each virtual table with
+** an open transaction is invoked.
+**
+** If any virtual table method returns an error code other than SQLITE_OK,
+** processing is abandoned and the error returned to the caller of this
+** function immediately. If all calls to virtual table methods are successful,
+** SQLITE_OK is returned.
+*/
+int sqlite3VtabSavepoint(sqlite3 *db, int op, int iSavepoint){
+  int rc = SQLITE_OK;
+
+  assert( op==SAVEPOINT_RELEASE||op==SAVEPOINT_ROLLBACK||op==SAVEPOINT_BEGIN );
+  assert( iSavepoint>=-1 );
+  if( db->aVTrans ){
+    int i;
+    for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
+      VTable *pVTab = db->aVTrans[i];
+      const sqlite3_module *pMod = pVTab->pMod->pModule;
+      if( pVTab->pVtab && pMod->iVersion>=2 ){
+        int (*xMethod)(sqlite3_vtab *, int);
+        sqlite3VtabLock(pVTab);
+        switch( op ){
+          case SAVEPOINT_BEGIN:
+            xMethod = pMod->xSavepoint;
+            pVTab->iSavepoint = iSavepoint+1;
+            break;
+          case SAVEPOINT_ROLLBACK:
+            xMethod = pMod->xRollbackTo;
+            break;
+          default:
+            xMethod = pMod->xRelease;
+            break;
+        }
+        if( xMethod && pVTab->iSavepoint>iSavepoint ){
+          u64 savedFlags = (db->flags & SQLITE_Defensive);
+          db->flags &= ~(u64)SQLITE_Defensive;
+          rc = xMethod(pVTab->pVtab, iSavepoint);
+          db->flags |= savedFlags;
+        }
+        sqlite3VtabUnlock(pVTab);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** The first parameter (pDef) is a function implementation.  The
+** second parameter (pExpr) is the first argument to this function.
+** If pExpr is a column in a virtual table, then let the virtual
+** table implementation have an opportunity to overload the function.
+**
+** This routine is used to allow virtual table implementations to
+** overload MATCH, LIKE, GLOB, and REGEXP operators.
+**
+** Return either the pDef argument (indicating no change) or a
+** new FuncDef structure that is marked as ephemeral using the
+** SQLITE_FUNC_EPHEM flag.
+*/
+FuncDef *sqlite3VtabOverloadFunction(
+  sqlite3 *db,    /* Database connection for reporting malloc problems */
+  FuncDef *pDef,  /* Function to possibly overload */
+  int nArg,       /* Number of arguments to the function */
+  Expr *pExpr     /* First argument to the function */
+){
+  Table *pTab;
+  sqlite3_vtab *pVtab;
+  sqlite3_module *pMod;
+  void (*xSFunc)(sqlite3_context*,int,sqlite3_value**) = 0;
+  void *pArg = 0;
+  FuncDef *pNew;
+  int rc = 0;
+
+  /* Check to see the left operand is a column in a virtual table */
+  if( NEVER(pExpr==0) ) return pDef;
+  if( pExpr->op!=TK_COLUMN ) return pDef;
+  assert( ExprUseYTab(pExpr) );
+  pTab = pExpr->y.pTab;
+  if( NEVER(pTab==0) ) return pDef;
+  if( !IsVirtual(pTab) ) return pDef;
+  pVtab = sqlite3GetVTable(db, pTab)->pVtab;
+  assert( pVtab!=0 );
+  assert( pVtab->pModule!=0 );
+  pMod = (sqlite3_module *)pVtab->pModule;
+  if( pMod->xFindFunction==0 ) return pDef;
+
+  /* Call the xFindFunction method on the virtual table implementation
+  ** to see if the implementation wants to overload this function.
+  **
+  ** Though undocumented, we have historically always invoked xFindFunction
+  ** with an all lower-case function name.  Continue in this tradition to
+  ** avoid any chance of an incompatibility.
+  */
+#ifdef SQLITE_DEBUG
+  {
+    int i;
+    for(i=0; pDef->zName[i]; i++){
+      unsigned char x = (unsigned char)pDef->zName[i];
+      assert( x==sqlite3UpperToLower[x] );
+    }
+  }
+#endif
+  rc = pMod->xFindFunction(pVtab, nArg, pDef->zName, &xSFunc, &pArg);
+  if( rc==0 ){
+    return pDef;
+  }
+
+  /* Create a new ephemeral function definition for the overloaded
+  ** function */
+  pNew = sqlite3DbMallocZero(db, sizeof(*pNew)
+                             + sqlite3Strlen30(pDef->zName) + 1);
+  if( pNew==0 ){
+    return pDef;
+  }
+  *pNew = *pDef;
+  pNew->zName = (const char*)&pNew[1];
+  memcpy((char*)&pNew[1], pDef->zName, sqlite3Strlen30(pDef->zName)+1);
+  pNew->xSFunc = xSFunc;
+  pNew->pUserData = pArg;
+  pNew->funcFlags |= SQLITE_FUNC_EPHEM;
+  return pNew;
+}
+
+/*
+** Make sure virtual table pTab is contained in the pParse->apVirtualLock[]
+** array so that an OP_VBegin will get generated for it.  Add pTab to the
+** array if it is missing.  If pTab is already in the array, this routine
+** is a no-op.
+*/
+void sqlite3VtabMakeWritable(Parse *pParse, Table *pTab){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  int i, n;
+  Table **apVtabLock;
+
+  assert( IsVirtual(pTab) );
+  for(i=0; i<pToplevel->nVtabLock; i++){
+    if( pTab==pToplevel->apVtabLock[i] ) return;
+  }
+  n = (pToplevel->nVtabLock+1)*sizeof(pToplevel->apVtabLock[0]);
+  apVtabLock = sqlite3Realloc(pToplevel->apVtabLock, n);
+  if( apVtabLock ){
+    pToplevel->apVtabLock = apVtabLock;
+    pToplevel->apVtabLock[pToplevel->nVtabLock++] = pTab;
+  }else{
+    sqlite3OomFault(pToplevel->db);
+  }
+}
+
+/*
+** Check to see if virtual table module pMod can be have an eponymous
+** virtual table instance.  If it can, create one if one does not already
+** exist. Return non-zero if either the eponymous virtual table instance
+** exists when this routine returns or if an attempt to create it failed
+** and an error message was left in pParse.
+**
+** An eponymous virtual table instance is one that is named after its
+** module, and more importantly, does not require a CREATE VIRTUAL TABLE
+** statement in order to come into existence.  Eponymous virtual table
+** instances always exist.  They cannot be DROP-ed.
+**
+** Any virtual table module for which xConnect and xCreate are the same
+** method can have an eponymous virtual table instance.
+*/
+int sqlite3VtabEponymousTableInit(Parse *pParse, Module *pMod){
+  const sqlite3_module *pModule = pMod->pModule;
+  Table *pTab;
+  char *zErr = 0;
+  int rc;
+  sqlite3 *db = pParse->db;
+  if( pMod->pEpoTab ) return 1;
+  if( pModule->xCreate!=0 && pModule->xCreate!=pModule->xConnect ) return 0;
+  pTab = sqlite3DbMallocZero(db, sizeof(Table));
+  if( pTab==0 ) return 0;
+  pTab->zName = sqlite3DbStrDup(db, pMod->zName);
+  if( pTab->zName==0 ){
+    sqlite3DbFree(db, pTab);
+    return 0;
+  }
+  pMod->pEpoTab = pTab;
+  pTab->nTabRef = 1;
+  pTab->eTabType = TABTYP_VTAB;
+  pTab->pSchema = db->aDb[0].pSchema;
+  assert( pTab->u.vtab.nArg==0 );
+  pTab->iPKey = -1;
+  pTab->tabFlags |= TF_Eponymous;
+  addModuleArgument(pParse, pTab, sqlite3DbStrDup(db, pTab->zName));
+  addModuleArgument(pParse, pTab, 0);
+  addModuleArgument(pParse, pTab, sqlite3DbStrDup(db, pTab->zName));
+  rc = vtabCallConstructor(db, pTab, pMod, pModule->xConnect, &zErr);
+  if( rc ){
+    sqlite3ErrorMsg(pParse, "%s", zErr);
+    sqlite3DbFree(db, zErr);
+    sqlite3VtabEponymousTableClear(db, pMod);
+  }
+  return 1;
+}
+
+/*
+** Erase the eponymous virtual table instance associated with
+** virtual table module pMod, if it exists.
+*/
+void sqlite3VtabEponymousTableClear(sqlite3 *db, Module *pMod){
+  Table *pTab = pMod->pEpoTab;
+  if( pTab!=0 ){
+    /* Mark the table as Ephemeral prior to deleting it, so that the
+    ** sqlite3DeleteTable() routine will know that it is not stored in
+    ** the schema. */
+    pTab->tabFlags |= TF_Ephemeral;
+    sqlite3DeleteTable(db, pTab);
+    pMod->pEpoTab = 0;
+  }
+}
+
+/*
+** Return the ON CONFLICT resolution mode in effect for the virtual
+** table update operation currently in progress.
+**
+** The results of this routine are undefined unless it is called from
+** within an xUpdate method.
+*/
+int sqlite3_vtab_on_conflict(sqlite3 *db){
+  static const unsigned char aMap[] = {
+    SQLITE_ROLLBACK, SQLITE_ABORT, SQLITE_FAIL, SQLITE_IGNORE, SQLITE_REPLACE
+  };
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  assert( OE_Rollback==1 && OE_Abort==2 && OE_Fail==3 );
+  assert( OE_Ignore==4 && OE_Replace==5 );
+  assert( db->vtabOnConflict>=1 && db->vtabOnConflict<=5 );
+  return (int)aMap[db->vtabOnConflict-1];
+}
+
+/*
+** Call from within the xCreate() or xConnect() methods to provide
+** the SQLite core with additional information about the behavior
+** of the virtual table being implemented.
+*/
+int sqlite3_vtab_config(sqlite3 *db, int op, ...){
+  va_list ap;
+  int rc = SQLITE_OK;
+  VtabCtx *p;
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+#endif
+  sqlite3_mutex_enter(db->mutex);
+  p = db->pVtabCtx;
+  if( !p ){
+    rc = SQLITE_MISUSE_BKPT;
+  }else{
+    assert( p->pTab==0 || IsVirtual(p->pTab) );
+    va_start(ap, op);
+    switch( op ){
+      case SQLITE_VTAB_CONSTRAINT_SUPPORT: {
+        p->pVTable->bConstraint = (u8)va_arg(ap, int);
+        break;
+      }
+      case SQLITE_VTAB_INNOCUOUS: {
+        p->pVTable->eVtabRisk = SQLITE_VTABRISK_Low;
+        break;
+      }
+      case SQLITE_VTAB_DIRECTONLY: {
+        p->pVTable->eVtabRisk = SQLITE_VTABRISK_High;
+        break;
+      }
+      case SQLITE_VTAB_USES_ALL_SCHEMAS: {
+        p->pVTable->bAllSchemas = 1;
+        break;
+      }
+      default: {
+        rc = SQLITE_MISUSE_BKPT;
+        break;
+      }
+    }
+    va_end(ap);
+  }
+
+  if( rc!=SQLITE_OK ) sqlite3Error(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
diff --git a/src/vxworks.h b/src/vxworks.h
new file mode 100644
index 0000000..e7013c3
--- /dev/null
+++ b/src/vxworks.h
@@ -0,0 +1,32 @@
+/*
+** 2015-03-02
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that is specific to Wind River's VxWorks
+*/
+#if defined(__RTP__) || defined(_WRS_KERNEL)
+/* This is VxWorks.  Set up things specially for that OS
+*/
+#include <vxWorks.h>
+#include <pthread.h>  /* amalgamator: dontcache */
+#define OS_VXWORKS 1
+#define SQLITE_OS_OTHER 0
+#define SQLITE_HOMEGROWN_RECURSIVE_MUTEX 1
+#define SQLITE_OMIT_LOAD_EXTENSION 1
+#define SQLITE_ENABLE_LOCKING_STYLE 0
+#define HAVE_UTIME 1
+#else
+/* This is not VxWorks. */
+#define OS_VXWORKS 0
+#define HAVE_FCHOWN 1
+#define HAVE_READLINK 1
+#define HAVE_LSTAT 1
+#endif /* defined(_WRS_KERNEL) */
diff --git a/src/wal.c b/src/wal.c
new file mode 100644
index 0000000..fd2eabf
--- /dev/null
+++ b/src/wal.c
@@ -0,0 +1,4579 @@
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of a write-ahead log (WAL) used in
+** "journal_mode=WAL" mode.
+**
+** WRITE-AHEAD LOG (WAL) FILE FORMAT
+**
+** A WAL file consists of a header followed by zero or more "frames".
+** Each frame records the revised content of a single page from the
+** database file.  All changes to the database are recorded by writing
+** frames into the WAL.  Transactions commit when a frame is written that
+** contains a commit marker.  A single WAL can and usually does record
+** multiple transactions.  Periodically, the content of the WAL is
+** transferred back into the database file in an operation called a
+** "checkpoint".
+**
+** A single WAL file can be used multiple times.  In other words, the
+** WAL can fill up with frames and then be checkpointed and then new
+** frames can overwrite the old ones.  A WAL always grows from beginning
+** toward the end.  Checksums and counters attached to each frame are
+** used to determine which frames within the WAL are valid and which
+** are leftovers from prior checkpoints.
+**
+** The WAL header is 32 bytes in size and consists of the following eight
+** big-endian 32-bit unsigned integer values:
+**
+**     0: Magic number.  0x377f0682 or 0x377f0683
+**     4: File format version.  Currently 3007000
+**     8: Database page size.  Example: 1024
+**    12: Checkpoint sequence number
+**    16: Salt-1, random integer incremented with each checkpoint
+**    20: Salt-2, a different random integer changing with each ckpt
+**    24: Checksum-1 (first part of checksum for first 24 bytes of header).
+**    28: Checksum-2 (second part of checksum for first 24 bytes of header).
+**
+** Immediately following the wal-header are zero or more frames. Each
+** frame consists of a 24-byte frame-header followed by a <page-size> bytes
+** of page data. The frame-header is six big-endian 32-bit unsigned
+** integer values, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the header)
+**    12: Salt-2 (copied from the header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+**
+** A frame is considered valid if and only if the following conditions are
+** true:
+**
+**    (1) The salt-1 and salt-2 values in the frame-header match
+**        salt values in the wal-header
+**
+**    (2) The checksum values in the final 8 bytes of the frame-header
+**        exactly match the checksum computed consecutively on the
+**        WAL header and the first 8 bytes and the content of all frames
+**        up to and including the current frame.
+**
+** The checksum is computed using 32-bit big-endian integers if the
+** magic number in the first 4 bytes of the WAL is 0x377f0683 and it
+** is computed using little-endian if the magic number is 0x377f0682.
+** The checksum values are always stored in the frame header in a
+** big-endian format regardless of which byte order is used to compute
+** the checksum.  The checksum is computed by interpreting the input as
+** an even number of unsigned 32-bit integers: x[0] through x[N].  The
+** algorithm used for the checksum is as follows:
+**
+**   for i from 0 to n-1 step 2:
+**     s0 += x[i] + s1;
+**     s1 += x[i+1] + s0;
+**   endfor
+**
+** Note that s0 and s1 are both weighted checksums using fibonacci weights
+** in reverse order (the largest fibonacci weight occurs on the first element
+** of the sequence being summed.)  The s1 value spans all 32-bit
+** terms of the sequence whereas s0 omits the final term.
+**
+** On a checkpoint, the WAL is first VFS.xSync-ed, then valid content of the
+** WAL is transferred into the database, then the database is VFS.xSync-ed.
+** The VFS.xSync operations serve as write barriers - all writes launched
+** before the xSync must complete before any write that launches after the
+** xSync begins.
+**
+** After each checkpoint, the salt-1 value is incremented and the salt-2
+** value is randomized.  This prevents old and new frames in the WAL from
+** being considered valid at the same time and being checkpointing together
+** following a crash.
+**
+** READER ALGORITHM
+**
+** To read a page from the database (call it page number P), a reader
+** first checks the WAL to see if it contains page P.  If so, then the
+** last valid instance of page P that is a followed by a commit frame
+** or is a commit frame itself becomes the value read.  If the WAL
+** contains no copies of page P that are valid and which are a commit
+** frame or are followed by a commit frame, then page P is read from
+** the database file.
+**
+** To start a read transaction, the reader records the index of the last
+** valid frame in the WAL.  The reader uses this recorded "mxFrame" value
+** for all subsequent read operations.  New transactions can be appended
+** to the WAL, but as long as the reader uses its original mxFrame value
+** and ignores the newly appended content, it will see a consistent snapshot
+** of the database from a single point in time.  This technique allows
+** multiple concurrent readers to view different versions of the database
+** content simultaneously.
+**
+** The reader algorithm in the previous paragraphs works correctly, but
+** because frames for page P can appear anywhere within the WAL, the
+** reader has to scan the entire WAL looking for page P frames.  If the
+** WAL is large (multiple megabytes is typical) that scan can be slow,
+** and read performance suffers.  To overcome this problem, a separate
+** data structure called the wal-index is maintained to expedite the
+** search for frames of a particular page.
+**
+** WAL-INDEX FORMAT
+**
+** Conceptually, the wal-index is shared memory, though VFS implementations
+** might choose to implement the wal-index using a mmapped file.  Because
+** the wal-index is shared memory, SQLite does not support journal_mode=WAL
+** on a network filesystem.  All users of the database must be able to
+** share memory.
+**
+** In the default unix and windows implementation, the wal-index is a mmapped
+** file whose name is the database name with a "-shm" suffix added.  For that
+** reason, the wal-index is sometimes called the "shm" file.
+**
+** The wal-index is transient.  After a crash, the wal-index can (and should
+** be) reconstructed from the original WAL file.  In fact, the VFS is required
+** to either truncate or zero the header of the wal-index when the last
+** connection to it closes.  Because the wal-index is transient, it can
+** use an architecture-specific format; it does not have to be cross-platform.
+** Hence, unlike the database and WAL file formats which store all values
+** as big endian, the wal-index can store multi-byte values in the native
+** byte order of the host computer.
+**
+** The purpose of the wal-index is to answer this question quickly:  Given
+** a page number P and a maximum frame index M, return the index of the
+** last frame in the wal before frame M for page P in the WAL, or return
+** NULL if there are no frames for page P in the WAL prior to M.
+**
+** The wal-index consists of a header region, followed by an one or
+** more index blocks.
+**
+** The wal-index header contains the total number of frames within the WAL
+** in the mxFrame field.
+**
+** Each index block except for the first contains information on
+** HASHTABLE_NPAGE frames. The first index block contains information on
+** HASHTABLE_NPAGE_ONE frames. The values of HASHTABLE_NPAGE_ONE and
+** HASHTABLE_NPAGE are selected so that together the wal-index header and
+** first index block are the same size as all other index blocks in the
+** wal-index.  The values are:
+**
+**   HASHTABLE_NPAGE      4096
+**   HASHTABLE_NPAGE_ONE  4062
+**
+** Each index block contains two sections, a page-mapping that contains the
+** database page number associated with each wal frame, and a hash-table
+** that allows readers to query an index block for a specific page number.
+** The page-mapping is an array of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE
+** for the first index block) 32-bit page numbers. The first entry in the
+** first index-block contains the database page number corresponding to the
+** first frame in the WAL file. The first entry in the second index block
+** in the WAL file corresponds to the (HASHTABLE_NPAGE_ONE+1)th frame in
+** the log, and so on.
+**
+** The last index block in a wal-index usually contains less than the full
+** complement of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE) page-numbers,
+** depending on the contents of the WAL file. This does not change the
+** allocated size of the page-mapping array - the page-mapping array merely
+** contains unused entries.
+**
+** Even without using the hash table, the last frame for page P
+** can be found by scanning the page-mapping sections of each index block
+** starting with the last index block and moving toward the first, and
+** within each index block, starting at the end and moving toward the
+** beginning.  The first entry that equals P corresponds to the frame
+** holding the content for that page.
+**
+** The hash table consists of HASHTABLE_NSLOT 16-bit unsigned integers.
+** HASHTABLE_NSLOT = 2*HASHTABLE_NPAGE, and there is one entry in the
+** hash table for each page number in the mapping section, so the hash
+** table is never more than half full.  The expected number of collisions
+** prior to finding a match is 1.  Each entry of the hash table is an
+** 1-based index of an entry in the mapping section of the same
+** index block.   Let K be the 1-based index of the largest entry in
+** the mapping section.  (For index blocks other than the last, K will
+** always be exactly HASHTABLE_NPAGE (4096) and for the last index block
+** K will be (mxFrame%HASHTABLE_NPAGE).)  Unused slots of the hash table
+** contain a value of 0.
+**
+** To look for page P in the hash table, first compute a hash iKey on
+** P as follows:
+**
+**      iKey = (P * 383) % HASHTABLE_NSLOT
+**
+** Then start scanning entries of the hash table, starting with iKey
+** (wrapping around to the beginning when the end of the hash table is
+** reached) until an unused hash slot is found. Let the first unused slot
+** be at index iUnused.  (iUnused might be less than iKey if there was
+** wrap-around.) Because the hash table is never more than half full,
+** the search is guaranteed to eventually hit an unused entry.  Let
+** iMax be the value between iKey and iUnused, closest to iUnused,
+** where aHash[iMax]==P.  If there is no iMax entry (if there exists
+** no hash slot such that aHash[i]==p) then page P is not in the
+** current index block.  Otherwise the iMax-th mapping entry of the
+** current index block corresponds to the last entry that references
+** page P.
+**
+** A hash search begins with the last index block and moves toward the
+** first index block, looking for entries corresponding to page P.  On
+** average, only two or three slots in each index block need to be
+** examined in order to either find the last entry for page P, or to
+** establish that no such entry exists in the block.  Each index block
+** holds over 4000 entries.  So two or three index blocks are sufficient
+** to cover a typical 10 megabyte WAL file, assuming 1K pages.  8 or 10
+** comparisons (on average) suffice to either locate a frame in the
+** WAL or to establish that the frame does not exist in the WAL.  This
+** is much faster than scanning the entire 10MB WAL.
+**
+** Note that entries are added in order of increasing K.  Hence, one
+** reader might be using some value K0 and a second reader that started
+** at a later time (after additional transactions were added to the WAL
+** and to the wal-index) might be using a different value K1, where K1>K0.
+** Both readers can use the same hash table and mapping section to get
+** the correct result.  There may be entries in the hash table with
+** K>K0 but to the first reader, those entries will appear to be unused
+** slots in the hash table and so the first reader will get an answer as
+** if no values greater than K0 had ever been inserted into the hash table
+** in the first place - which is what reader one wants.  Meanwhile, the
+** second reader using K1 will see additional values that were inserted
+** later, which is exactly what reader two wants.
+**
+** When a rollback occurs, the value of K is decreased. Hash table entries
+** that correspond to frames greater than the new K value are removed
+** from the hash table at this point.
+*/
+#ifndef SQLITE_OMIT_WAL
+
+#include "wal.h"
+
+/*
+** Trace output macros
+*/
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+int sqlite3WalTrace = 0;
+# define WALTRACE(X)  if(sqlite3WalTrace) sqlite3DebugPrintf X
+#else
+# define WALTRACE(X)
+#endif
+
+/*
+** The maximum (and only) versions of the wal and wal-index formats
+** that may be interpreted by this version of SQLite.
+**
+** If a client begins recovering a WAL file and finds that (a) the checksum
+** values in the wal-header are correct and (b) the version field is not
+** WAL_MAX_VERSION, recovery fails and SQLite returns SQLITE_CANTOPEN.
+**
+** Similarly, if a client successfully reads a wal-index header (i.e. the
+** checksum test is successful) and finds that the version field is not
+** WALINDEX_MAX_VERSION, then no read-transaction is opened and SQLite
+** returns SQLITE_CANTOPEN.
+*/
+#define WAL_MAX_VERSION      3007000
+#define WALINDEX_MAX_VERSION 3007000
+
+/*
+** Index numbers for various locking bytes.   WAL_NREADER is the number
+** of available reader locks and should be at least 3.  The default
+** is SQLITE_SHM_NLOCK==8 and  WAL_NREADER==5.
+**
+** Technically, the various VFSes are free to implement these locks however
+** they see fit.  However, compatibility is encouraged so that VFSes can
+** interoperate.  The standard implementation used on both unix and windows
+** is for the index number to indicate a byte offset into the
+** WalCkptInfo.aLock[] array in the wal-index header.  In other words, all
+** locks are on the shm file.  The WALINDEX_LOCK_OFFSET constant (which
+** should be 120) is the location in the shm file for the first locking
+** byte.
+*/
+#define WAL_WRITE_LOCK         0
+#define WAL_ALL_BUT_WRITE      1
+#define WAL_CKPT_LOCK          1
+#define WAL_RECOVER_LOCK       2
+#define WAL_READ_LOCK(I)       (3+(I))
+#define WAL_NREADER            (SQLITE_SHM_NLOCK-3)
+
+
+/* Object declarations */
+typedef struct WalIndexHdr WalIndexHdr;
+typedef struct WalIterator WalIterator;
+typedef struct WalCkptInfo WalCkptInfo;
+
+
+/*
+** The following object holds a copy of the wal-index header content.
+**
+** The actual header in the wal-index consists of two copies of this
+** object followed by one instance of the WalCkptInfo object.
+** For all versions of SQLite through 3.10.0 and probably beyond,
+** the locking bytes (WalCkptInfo.aLock) start at offset 120 and
+** the total header size is 136 bytes.
+**
+** The szPage value can be any power of 2 between 512 and 32768, inclusive.
+** Or it can be 1 to represent a 65536-byte page.  The latter case was
+** added in 3.7.1 when support for 64K pages was added.
+*/
+struct WalIndexHdr {
+  u32 iVersion;                   /* Wal-index version */
+  u32 unused;                     /* Unused (padding) field */
+  u32 iChange;                    /* Counter incremented each transaction */
+  u8 isInit;                      /* 1 when initialized */
+  u8 bigEndCksum;                 /* True if checksums in WAL are big-endian */
+  u16 szPage;                     /* Database page size in bytes. 1==64K */
+  u32 mxFrame;                    /* Index of last valid frame in the WAL */
+  u32 nPage;                      /* Size of database in pages */
+  u32 aFrameCksum[2];             /* Checksum of last frame in log */
+  u32 aSalt[2];                   /* Two salt values copied from WAL header */
+  u32 aCksum[2];                  /* Checksum over all prior fields */
+};
+
+/*
+** A copy of the following object occurs in the wal-index immediately
+** following the second copy of the WalIndexHdr.  This object stores
+** information used by checkpoint.
+**
+** nBackfill is the number of frames in the WAL that have been written
+** back into the database. (We call the act of moving content from WAL to
+** database "backfilling".)  The nBackfill number is never greater than
+** WalIndexHdr.mxFrame.  nBackfill can only be increased by threads
+** holding the WAL_CKPT_LOCK lock (which includes a recovery thread).
+** However, a WAL_WRITE_LOCK thread can move the value of nBackfill from
+** mxFrame back to zero when the WAL is reset.
+**
+** nBackfillAttempted is the largest value of nBackfill that a checkpoint
+** has attempted to achieve.  Normally nBackfill==nBackfillAtempted, however
+** the nBackfillAttempted is set before any backfilling is done and the
+** nBackfill is only set after all backfilling completes.  So if a checkpoint
+** crashes, nBackfillAttempted might be larger than nBackfill.  The
+** WalIndexHdr.mxFrame must never be less than nBackfillAttempted.
+**
+** The aLock[] field is a set of bytes used for locking.  These bytes should
+** never be read or written.
+**
+** There is one entry in aReadMark[] for each reader lock.  If a reader
+** holds read-lock K, then the value in aReadMark[K] is no greater than
+** the mxFrame for that reader.  The value READMARK_NOT_USED (0xffffffff)
+** for any aReadMark[] means that entry is unused.  aReadMark[0] is
+** a special case; its value is never used and it exists as a place-holder
+** to avoid having to offset aReadMark[] indexes by one.  Readers holding
+** WAL_READ_LOCK(0) always ignore the entire WAL and read all content
+** directly from the database.
+**
+** The value of aReadMark[K] may only be changed by a thread that
+** is holding an exclusive lock on WAL_READ_LOCK(K).  Thus, the value of
+** aReadMark[K] cannot changed while there is a reader is using that mark
+** since the reader will be holding a shared lock on WAL_READ_LOCK(K).
+**
+** The checkpointer may only transfer frames from WAL to database where
+** the frame numbers are less than or equal to every aReadMark[] that is
+** in use (that is, every aReadMark[j] for which there is a corresponding
+** WAL_READ_LOCK(j)).  New readers (usually) pick the aReadMark[] with the
+** largest value and will increase an unused aReadMark[] to mxFrame if there
+** is not already an aReadMark[] equal to mxFrame.  The exception to the
+** previous sentence is when nBackfill equals mxFrame (meaning that everything
+** in the WAL has been backfilled into the database) then new readers
+** will choose aReadMark[0] which has value 0 and hence such reader will
+** get all their all content directly from the database file and ignore
+** the WAL.
+**
+** Writers normally append new frames to the end of the WAL.  However,
+** if nBackfill equals mxFrame (meaning that all WAL content has been
+** written back into the database) and if no readers are using the WAL
+** (in other words, if there are no WAL_READ_LOCK(i) where i>0) then
+** the writer will first "reset" the WAL back to the beginning and start
+** writing new content beginning at frame 1.
+**
+** We assume that 32-bit loads are atomic and so no locks are needed in
+** order to read from any aReadMark[] entries.
+*/
+struct WalCkptInfo {
+  u32 nBackfill;                  /* Number of WAL frames backfilled into DB */
+  u32 aReadMark[WAL_NREADER];     /* Reader marks */
+  u8 aLock[SQLITE_SHM_NLOCK];     /* Reserved space for locks */
+  u32 nBackfillAttempted;         /* WAL frames perhaps written, or maybe not */
+  u32 notUsed0;                   /* Available for future enhancements */
+};
+#define READMARK_NOT_USED  0xffffffff
+
+/*
+** This is a schematic view of the complete 136-byte header of the
+** wal-index file (also known as the -shm file):
+**
+**      +-----------------------------+
+**   0: | iVersion                    | \
+**      +-----------------------------+  |
+**   4: | (unused padding)            |  |
+**      +-----------------------------+  |
+**   8: | iChange                     |  |
+**      +-------+-------+-------------+  |
+**  12: | bInit |  bBig |   szPage    |  |
+**      +-------+-------+-------------+  |
+**  16: | mxFrame                     |  |  First copy of the
+**      +-----------------------------+  |  WalIndexHdr object
+**  20: | nPage                       |  |
+**      +-----------------------------+  |
+**  24: | aFrameCksum                 |  |
+**      |                             |  |
+**      +-----------------------------+  |
+**  32: | aSalt                       |  |
+**      |                             |  |
+**      +-----------------------------+  |
+**  40: | aCksum                      |  |
+**      |                             | /
+**      +-----------------------------+
+**  48: | iVersion                    | \
+**      +-----------------------------+  |
+**  52: | (unused padding)            |  |
+**      +-----------------------------+  |
+**  56: | iChange                     |  |
+**      +-------+-------+-------------+  |
+**  60: | bInit |  bBig |   szPage    |  |
+**      +-------+-------+-------------+  |  Second copy of the
+**  64: | mxFrame                     |  |  WalIndexHdr
+**      +-----------------------------+  |
+**  68: | nPage                       |  |
+**      +-----------------------------+  |
+**  72: | aFrameCksum                 |  |
+**      |                             |  |
+**      +-----------------------------+  |
+**  80: | aSalt                       |  |
+**      |                             |  |
+**      +-----------------------------+  |
+**  88: | aCksum                      |  |
+**      |                             | /
+**      +-----------------------------+
+**  96: | nBackfill                   |
+**      +-----------------------------+
+** 100: | 5 read marks                |
+**      |                             |
+**      |                             |
+**      |                             |
+**      |                             |
+**      +-------+-------+------+------+
+** 120: | Write | Ckpt  | Rcvr | Rd0  | \
+**      +-------+-------+------+------+  ) 8 lock bytes
+**      | Read1 | Read2 | Rd3  | Rd4  | /
+**      +-------+-------+------+------+
+** 128: | nBackfillAttempted          |
+**      +-----------------------------+
+** 132: | (unused padding)            |
+**      +-----------------------------+
+*/
+
+/* A block of WALINDEX_LOCK_RESERVED bytes beginning at
+** WALINDEX_LOCK_OFFSET is reserved for locks. Since some systems
+** only support mandatory file-locks, we do not read or write data
+** from the region of the file on which locks are applied.
+*/
+#define WALINDEX_LOCK_OFFSET (sizeof(WalIndexHdr)*2+offsetof(WalCkptInfo,aLock))
+#define WALINDEX_HDR_SIZE    (sizeof(WalIndexHdr)*2+sizeof(WalCkptInfo))
+
+/* Size of header before each frame in wal */
+#define WAL_FRAME_HDRSIZE 24
+
+/* Size of write ahead log header, including checksum. */
+#define WAL_HDRSIZE 32
+
+/* WAL magic value. Either this value, or the same value with the least
+** significant bit also set (WAL_MAGIC | 0x00000001) is stored in 32-bit
+** big-endian format in the first 4 bytes of a WAL file.
+**
+** If the LSB is set, then the checksums for each frame within the WAL
+** file are calculated by treating all data as an array of 32-bit
+** big-endian words. Otherwise, they are calculated by interpreting
+** all data as 32-bit little-endian words.
+*/
+#define WAL_MAGIC 0x377f0682
+
+/*
+** Return the offset of frame iFrame in the write-ahead log file,
+** assuming a database page size of szPage bytes. The offset returned
+** is to the start of the write-ahead log frame-header.
+*/
+#define walFrameOffset(iFrame, szPage) (                               \
+  WAL_HDRSIZE + ((iFrame)-1)*(i64)((szPage)+WAL_FRAME_HDRSIZE)         \
+)
+
+/*
+** An open write-ahead log file is represented by an instance of the
+** following object.
+*/
+struct Wal {
+  sqlite3_vfs *pVfs;         /* The VFS used to create pDbFd */
+  sqlite3_file *pDbFd;       /* File handle for the database file */
+  sqlite3_file *pWalFd;      /* File handle for WAL file */
+  u32 iCallback;             /* Value to pass to log callback (or 0) */
+  i64 mxWalSize;             /* Truncate WAL to this size upon reset */
+  int nWiData;               /* Size of array apWiData */
+  int szFirstBlock;          /* Size of first block written to WAL file */
+  volatile u32 **apWiData;   /* Pointer to wal-index content in memory */
+  u32 szPage;                /* Database page size */
+  i16 readLock;              /* Which read lock is being held.  -1 for none */
+  u8 syncFlags;              /* Flags to use to sync header writes */
+  u8 exclusiveMode;          /* Non-zero if connection is in exclusive mode */
+  u8 writeLock;              /* True if in a write transaction */
+  u8 ckptLock;               /* True if holding a checkpoint lock */
+  u8 readOnly;               /* WAL_RDWR, WAL_RDONLY, or WAL_SHM_RDONLY */
+  u8 truncateOnCommit;       /* True to truncate WAL file on commit */
+  u8 syncHeader;             /* Fsync the WAL header if true */
+  u8 padToSectorBoundary;    /* Pad transactions out to the next sector */
+  u8 bShmUnreliable;         /* SHM content is read-only and unreliable */
+  WalIndexHdr hdr;           /* Wal-index header for current transaction */
+  u32 minFrame;              /* Ignore wal frames before this one */
+  u32 iReCksum;              /* On commit, recalculate checksums from here */
+  const char *zWalName;      /* Name of WAL file */
+  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
+#ifdef SQLITE_USE_SEH
+  u32 lockMask;              /* Mask of locks held */
+  void *pFree;               /* Pointer to sqlite3_free() if exception thrown */
+  u32 *pWiValue;             /* Value to write into apWiData[iWiPg] */
+  int iWiPg;                 /* Write pWiValue into apWiData[iWiPg] */
+  int iSysErrno;             /* System error code following exception */
+#endif
+#ifdef SQLITE_DEBUG
+  int nSehTry;               /* Number of nested SEH_TRY{} blocks */
+  u8 lockError;              /* True if a locking error has occurred */
+#endif
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  WalIndexHdr *pSnapshot;    /* Start transaction here if not NULL */
+#endif
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  sqlite3 *db;
+#endif
+};
+
+/*
+** Candidate values for Wal.exclusiveMode.
+*/
+#define WAL_NORMAL_MODE     0
+#define WAL_EXCLUSIVE_MODE  1
+#define WAL_HEAPMEMORY_MODE 2
+
+/*
+** Possible values for WAL.readOnly
+*/
+#define WAL_RDWR        0    /* Normal read/write connection */
+#define WAL_RDONLY      1    /* The WAL file is readonly */
+#define WAL_SHM_RDONLY  2    /* The SHM file is readonly */
+
+/*
+** Each page of the wal-index mapping contains a hash-table made up of
+** an array of HASHTABLE_NSLOT elements of the following type.
+*/
+typedef u16 ht_slot;
+
+/*
+** This structure is used to implement an iterator that loops through
+** all frames in the WAL in database page order. Where two or more frames
+** correspond to the same database page, the iterator visits only the
+** frame most recently written to the WAL (in other words, the frame with
+** the largest index).
+**
+** The internals of this structure are only accessed by:
+**
+**   walIteratorInit() - Create a new iterator,
+**   walIteratorNext() - Step an iterator,
+**   walIteratorFree() - Free an iterator.
+**
+** This functionality is used by the checkpoint code (see walCheckpoint()).
+*/
+struct WalIterator {
+  u32 iPrior;                     /* Last result returned from the iterator */
+  int nSegment;                   /* Number of entries in aSegment[] */
+  struct WalSegment {
+    int iNext;                    /* Next slot in aIndex[] not yet returned */
+    ht_slot *aIndex;              /* i0, i1, i2... such that aPgno[iN] ascend */
+    u32 *aPgno;                   /* Array of page numbers. */
+    int nEntry;                   /* Nr. of entries in aPgno[] and aIndex[] */
+    int iZero;                    /* Frame number associated with aPgno[0] */
+  } aSegment[1];                  /* One for every 32KB page in the wal-index */
+};
+
+/*
+** Define the parameters of the hash tables in the wal-index file. There
+** is a hash-table following every HASHTABLE_NPAGE page numbers in the
+** wal-index.
+**
+** Changing any of these constants will alter the wal-index format and
+** create incompatibilities.
+*/
+#define HASHTABLE_NPAGE      4096                 /* Must be power of 2 */
+#define HASHTABLE_HASH_1     383                  /* Should be prime */
+#define HASHTABLE_NSLOT      (HASHTABLE_NPAGE*2)  /* Must be a power of 2 */
+
+/*
+** The block of page numbers associated with the first hash-table in a
+** wal-index is smaller than usual. This is so that there is a complete
+** hash-table on each aligned 32KB page of the wal-index.
+*/
+#define HASHTABLE_NPAGE_ONE  (HASHTABLE_NPAGE - (WALINDEX_HDR_SIZE/sizeof(u32)))
+
+/* The wal-index is divided into pages of WALINDEX_PGSZ bytes each. */
+#define WALINDEX_PGSZ   (                                         \
+    sizeof(ht_slot)*HASHTABLE_NSLOT + HASHTABLE_NPAGE*sizeof(u32) \
+)
+
+/*
+** Structured Exception Handling (SEH) is a Windows-specific technique
+** for catching exceptions raised while accessing memory-mapped files.
+**
+** The -DSQLITE_USE_SEH compile-time option means to use SEH to catch and
+** deal with system-level errors that arise during WAL -shm file processing.
+** Without this compile-time option, any system-level faults that appear
+** while accessing the memory-mapped -shm file will cause a process-wide
+** signal to be deliver, which will more than likely cause the entire
+** process to exit.
+*/
+#ifdef SQLITE_USE_SEH
+#include <Windows.h>
+
+/* Beginning of a block of code in which an exception might occur */
+# define SEH_TRY    __try { \
+   assert( walAssertLockmask(pWal) && pWal->nSehTry==0 ); \
+   VVA_ONLY(pWal->nSehTry++);
+
+/* The end of a block of code in which an exception might occur */
+# define SEH_EXCEPT(X) \
+   VVA_ONLY(pWal->nSehTry--); \
+   assert( pWal->nSehTry==0 ); \
+   } __except( sehExceptionFilter(pWal, GetExceptionCode(), GetExceptionInformation() ) ){ X }
+
+/* Simulate a memory-mapping fault in the -shm file for testing purposes */
+# define SEH_INJECT_FAULT sehInjectFault(pWal) 
+
+/*
+** The second argument is the return value of GetExceptionCode() for the 
+** current exception. Return EXCEPTION_EXECUTE_HANDLER if the exception code
+** indicates that the exception may have been caused by accessing the *-shm 
+** file mapping. Or EXCEPTION_CONTINUE_SEARCH otherwise.
+*/
+static int sehExceptionFilter(Wal *pWal, int eCode, EXCEPTION_POINTERS *p){
+  VVA_ONLY(pWal->nSehTry--);
+  if( eCode==EXCEPTION_IN_PAGE_ERROR ){
+    if( p && p->ExceptionRecord && p->ExceptionRecord->NumberParameters>=3 ){
+      /* From MSDN: For this type of exception, the first element of the
+      ** ExceptionInformation[] array is a read-write flag - 0 if the exception
+      ** was thrown while reading, 1 if while writing. The second element is
+      ** the virtual address being accessed. The "third array element specifies
+      ** the underlying NTSTATUS code that resulted in the exception". */
+      pWal->iSysErrno = (int)p->ExceptionRecord->ExceptionInformation[2];
+    }
+    return EXCEPTION_EXECUTE_HANDLER;
+  }
+  return EXCEPTION_CONTINUE_SEARCH;
+}
+
+/*
+** If one is configured, invoke the xTestCallback callback with 650 as
+** the argument. If it returns true, throw the same exception that is
+** thrown by the system if the *-shm file mapping is accessed after it
+** has been invalidated.
+*/
+static void sehInjectFault(Wal *pWal){
+  int res;
+  assert( pWal->nSehTry>0 );
+
+  res = sqlite3FaultSim(650);
+  if( res!=0 ){
+    ULONG_PTR aArg[3];
+    aArg[0] = 0;
+    aArg[1] = 0;
+    aArg[2] = (ULONG_PTR)res;
+    RaiseException(EXCEPTION_IN_PAGE_ERROR, 0, 3, (const ULONG_PTR*)aArg);
+  }
+}
+
+/*
+** There are two ways to use this macro. To set a pointer to be freed
+** if an exception is thrown:
+**
+**   SEH_FREE_ON_ERROR(0, pPtr);
+**
+** and to cancel the same:
+**
+**   SEH_FREE_ON_ERROR(pPtr, 0);
+**
+** In the first case, there must not already be a pointer registered to
+** be freed. In the second case, pPtr must be the registered pointer.
+*/
+#define SEH_FREE_ON_ERROR(X,Y) \
+  assert( (X==0 || Y==0) && pWal->pFree==X ); pWal->pFree = Y
+
+/*
+** There are two ways to use this macro. To arrange for pWal->apWiData[iPg]
+** to be set to pValue if an exception is thrown:
+**
+**   SEH_SET_ON_ERROR(iPg, pValue);
+**
+** and to cancel the same:
+**
+**   SEH_SET_ON_ERROR(0, 0);
+*/
+#define SEH_SET_ON_ERROR(X,Y)  pWal->iWiPg = X; pWal->pWiValue = Y
+
+#else
+# define SEH_TRY          VVA_ONLY(pWal->nSehTry++);
+# define SEH_EXCEPT(X)    VVA_ONLY(pWal->nSehTry--); assert( pWal->nSehTry==0 );
+# define SEH_INJECT_FAULT assert( pWal->nSehTry>0 );
+# define SEH_FREE_ON_ERROR(X,Y)
+# define SEH_SET_ON_ERROR(X,Y)
+#endif /* ifdef SQLITE_USE_SEH */
+
+
+/*
+** Obtain a pointer to the iPage'th page of the wal-index. The wal-index
+** is broken into pages of WALINDEX_PGSZ bytes. Wal-index pages are
+** numbered from zero.
+**
+** If the wal-index is currently smaller the iPage pages then the size
+** of the wal-index might be increased, but only if it is safe to do
+** so.  It is safe to enlarge the wal-index if pWal->writeLock is true
+** or pWal->exclusiveMode==WAL_HEAPMEMORY_MODE.
+**
+** Three possible result scenarios:
+**
+**   (1)  rc==SQLITE_OK    and *ppPage==Requested-Wal-Index-Page
+**   (2)  rc>=SQLITE_ERROR and *ppPage==NULL
+**   (3)  rc==SQLITE_OK    and *ppPage==NULL  // only if iPage==0
+**
+** Scenario (3) can only occur when pWal->writeLock is false and iPage==0
+*/
+static SQLITE_NOINLINE int walIndexPageRealloc(
+  Wal *pWal,               /* The WAL context */
+  int iPage,               /* The page we seek */
+  volatile u32 **ppPage    /* Write the page pointer here */
+){
+  int rc = SQLITE_OK;
+
+  /* Enlarge the pWal->apWiData[] array if required */
+  if( pWal->nWiData<=iPage ){
+    sqlite3_int64 nByte = sizeof(u32*)*(iPage+1);
+    volatile u32 **apNew;
+    apNew = (volatile u32 **)sqlite3Realloc((void *)pWal->apWiData, nByte);
+    if( !apNew ){
+      *ppPage = 0;
+      return SQLITE_NOMEM_BKPT;
+    }
+    memset((void*)&apNew[pWal->nWiData], 0,
+           sizeof(u32*)*(iPage+1-pWal->nWiData));
+    pWal->apWiData = apNew;
+    pWal->nWiData = iPage+1;
+  }
+
+  /* Request a pointer to the required page from the VFS */
+  assert( pWal->apWiData[iPage]==0 );
+  if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
+    pWal->apWiData[iPage] = (u32 volatile *)sqlite3MallocZero(WALINDEX_PGSZ);
+    if( !pWal->apWiData[iPage] ) rc = SQLITE_NOMEM_BKPT;
+  }else{
+    rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ,
+        pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
+    );
+    assert( pWal->apWiData[iPage]!=0
+         || rc!=SQLITE_OK
+         || (pWal->writeLock==0 && iPage==0) );
+    testcase( pWal->apWiData[iPage]==0 && rc==SQLITE_OK );
+    if( rc==SQLITE_OK ){
+      if( iPage>0 && sqlite3FaultSim(600) ) rc = SQLITE_NOMEM;
+    }else if( (rc&0xff)==SQLITE_READONLY ){
+      pWal->readOnly |= WAL_SHM_RDONLY;
+      if( rc==SQLITE_READONLY ){
+        rc = SQLITE_OK;
+      }
+    }
+  }
+
+  *ppPage = pWal->apWiData[iPage];
+  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
+  return rc;
+}
+static int walIndexPage(
+  Wal *pWal,               /* The WAL context */
+  int iPage,               /* The page we seek */
+  volatile u32 **ppPage    /* Write the page pointer here */
+){
+  SEH_INJECT_FAULT;
+  if( pWal->nWiData<=iPage || (*ppPage = pWal->apWiData[iPage])==0 ){
+    return walIndexPageRealloc(pWal, iPage, ppPage);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Return a pointer to the WalCkptInfo structure in the wal-index.
+*/
+static volatile WalCkptInfo *walCkptInfo(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  SEH_INJECT_FAULT;
+  return (volatile WalCkptInfo*)&(pWal->apWiData[0][sizeof(WalIndexHdr)/2]);
+}
+
+/*
+** Return a pointer to the WalIndexHdr structure in the wal-index.
+*/
+static volatile WalIndexHdr *walIndexHdr(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  SEH_INJECT_FAULT;
+  return (volatile WalIndexHdr*)pWal->apWiData[0];
+}
+
+/*
+** The argument to this macro must be of type u32. On a little-endian
+** architecture, it returns the u32 value that results from interpreting
+** the 4 bytes as a big-endian value. On a big-endian architecture, it
+** returns the value that would be produced by interpreting the 4 bytes
+** of the input value as a little-endian integer.
+*/
+#define BYTESWAP32(x) ( \
+    (((x)&0x000000FF)<<24) + (((x)&0x0000FF00)<<8)  \
+  + (((x)&0x00FF0000)>>8)  + (((x)&0xFF000000)>>24) \
+)
+
+/*
+** Generate or extend an 8 byte checksum based on the data in
+** array aByte[] and the initial values of aIn[0] and aIn[1] (or
+** initial values of 0 and 0 if aIn==NULL).
+**
+** The checksum is written back into aOut[] before returning.
+**
+** nByte must be a positive multiple of 8.
+*/
+static void walChecksumBytes(
+  int nativeCksum, /* True for native byte-order, false for non-native */
+  u8 *a,           /* Content to be checksummed */
+  int nByte,       /* Bytes of content in a[].  Must be a multiple of 8. */
+  const u32 *aIn,  /* Initial checksum value input */
+  u32 *aOut        /* OUT: Final checksum value output */
+){
+  u32 s1, s2;
+  u32 *aData = (u32 *)a;
+  u32 *aEnd = (u32 *)&a[nByte];
+
+  if( aIn ){
+    s1 = aIn[0];
+    s2 = aIn[1];
+  }else{
+    s1 = s2 = 0;
+  }
+
+  assert( nByte>=8 );
+  assert( (nByte&0x00000007)==0 );
+  assert( nByte<=65536 );
+  assert( nByte%4==0 );
+
+  if( !nativeCksum ){
+    do {
+      s1 += BYTESWAP32(aData[0]) + s2;
+      s2 += BYTESWAP32(aData[1]) + s1;
+      aData += 2;
+    }while( aData<aEnd );
+  }else if( nByte%64==0 ){
+    do {
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+    }while( aData<aEnd );
+  }else{
+    do {
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+    }while( aData<aEnd );
+  }
+  assert( aData==aEnd );
+
+  aOut[0] = s1;
+  aOut[1] = s2;
+}
+
+/*
+** If there is the possibility of concurrent access to the SHM file
+** from multiple threads and/or processes, then do a memory barrier.
+*/
+static void walShmBarrier(Wal *pWal){
+  if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
+    sqlite3OsShmBarrier(pWal->pDbFd);
+  }
+}
+
+/*
+** Add the SQLITE_NO_TSAN as part of the return-type of a function
+** definition as a hint that the function contains constructs that
+** might give false-positive TSAN warnings.
+**
+** See tag-20200519-1.
+*/
+#if defined(__clang__) && !defined(SQLITE_NO_TSAN)
+# define SQLITE_NO_TSAN __attribute__((no_sanitize_thread))
+#else
+# define SQLITE_NO_TSAN
+#endif
+
+/*
+** Write the header information in pWal->hdr into the wal-index.
+**
+** The checksum on pWal->hdr is updated before it is written.
+*/
+static SQLITE_NO_TSAN void walIndexWriteHdr(Wal *pWal){
+  volatile WalIndexHdr *aHdr = walIndexHdr(pWal);
+  const int nCksum = offsetof(WalIndexHdr, aCksum);
+
+  assert( pWal->writeLock );
+  pWal->hdr.isInit = 1;
+  pWal->hdr.iVersion = WALINDEX_MAX_VERSION;
+  walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
+  /* Possible TSAN false-positive.  See tag-20200519-1 */
+  memcpy((void*)&aHdr[1], (const void*)&pWal->hdr, sizeof(WalIndexHdr));
+  walShmBarrier(pWal);
+  memcpy((void*)&aHdr[0], (const void*)&pWal->hdr, sizeof(WalIndexHdr));
+}
+
+/*
+** This function encodes a single frame header and writes it to a buffer
+** supplied by the caller. A frame-header is made up of a series of
+** 4-byte big-endian integers, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the wal-header)
+**    12: Salt-2 (copied from the wal-header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+*/
+static void walEncodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 iPage,                      /* Database page number for frame */
+  u32 nTruncate,                  /* New db size (or 0 for non-commit frames) */
+  u8 *aData,                      /* Pointer to page data */
+  u8 *aFrame                      /* OUT: Write encoded frame here */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  assert( WAL_FRAME_HDRSIZE==24 );
+  sqlite3Put4byte(&aFrame[0], iPage);
+  sqlite3Put4byte(&aFrame[4], nTruncate);
+  if( pWal->iReCksum==0 ){
+    memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
+
+    nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+    walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+    walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+
+    sqlite3Put4byte(&aFrame[16], aCksum[0]);
+    sqlite3Put4byte(&aFrame[20], aCksum[1]);
+  }else{
+    memset(&aFrame[8], 0, 16);
+  }
+}
+
+/*
+** Check to see if the frame with header in aFrame[] and content
+** in aData[] is valid.  If it is a valid frame, fill *piPage and
+** *pnTruncate and return true.  Return if the frame is not valid.
+*/
+static int walDecodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 *piPage,                    /* OUT: Database page number for frame */
+  u32 *pnTruncate,                /* OUT: New db size (or 0 if not commit) */
+  u8 *aData,                      /* Pointer to page data (for checksum) */
+  u8 *aFrame                      /* Frame data */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  u32 pgno;                       /* Page number of the frame */
+  assert( WAL_FRAME_HDRSIZE==24 );
+
+  /* A frame is only valid if the salt values in the frame-header
+  ** match the salt values in the wal-header.
+  */
+  if( memcmp(&pWal->hdr.aSalt, &aFrame[8], 8)!=0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if the page number is greater than zero.
+  */
+  pgno = sqlite3Get4byte(&aFrame[0]);
+  if( pgno==0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if a checksum of the WAL header,
+  ** all prior frames, the first 16 bytes of this frame-header,
+  ** and the frame-data matches the checksum in the last 8
+  ** bytes of this frame-header.
+  */
+  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+  if( aCksum[0]!=sqlite3Get4byte(&aFrame[16])
+   || aCksum[1]!=sqlite3Get4byte(&aFrame[20])
+  ){
+    /* Checksum failed. */
+    return 0;
+  }
+
+  /* If we reach this point, the frame is valid.  Return the page number
+  ** and the new database size.
+  */
+  *piPage = pgno;
+  *pnTruncate = sqlite3Get4byte(&aFrame[4]);
+  return 1;
+}
+
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+/*
+** Names of locks.  This routine is used to provide debugging output and is not
+** a part of an ordinary build.
+*/
+static const char *walLockName(int lockIdx){
+  if( lockIdx==WAL_WRITE_LOCK ){
+    return "WRITE-LOCK";
+  }else if( lockIdx==WAL_CKPT_LOCK ){
+    return "CKPT-LOCK";
+  }else if( lockIdx==WAL_RECOVER_LOCK ){
+    return "RECOVER-LOCK";
+  }else{
+    static char zName[15];
+    sqlite3_snprintf(sizeof(zName), zName, "READ-LOCK[%d]",
+                     lockIdx-WAL_READ_LOCK(0));
+    return zName;
+  }
+}
+#endif /*defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
+
+
+/*
+** Set or release locks on the WAL.  Locks are either shared or exclusive.
+** A lock cannot be moved directly between shared and exclusive - it must go
+** through the unlocked state first.
+**
+** In locking_mode=EXCLUSIVE, all of these routines become no-ops.
+*/
+static int walLockShared(Wal *pWal, int lockIdx){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_SHARED);
+  WALTRACE(("WAL%p: acquire SHARED-%s %s\n", pWal,
+            walLockName(lockIdx), rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (u8)(rc!=SQLITE_OK && (rc&0xFF)!=SQLITE_BUSY); )
+#ifdef SQLITE_USE_SEH
+  if( rc==SQLITE_OK ) pWal->lockMask |= (1 << lockIdx);
+#endif
+  return rc;
+}
+static void walUnlockShared(Wal *pWal, int lockIdx){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED);
+#ifdef SQLITE_USE_SEH
+  pWal->lockMask &= ~(1 << lockIdx);
+#endif
+  WALTRACE(("WAL%p: release SHARED-%s\n", pWal, walLockName(lockIdx)));
+}
+static int walLockExclusive(Wal *pWal, int lockIdx, int n){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE);
+  WALTRACE(("WAL%p: acquire EXCLUSIVE-%s cnt=%d %s\n", pWal,
+            walLockName(lockIdx), n, rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (u8)(rc!=SQLITE_OK && (rc&0xFF)!=SQLITE_BUSY); )
+#ifdef SQLITE_USE_SEH
+  if( rc==SQLITE_OK ){
+    pWal->lockMask |= (((1<<n)-1) << (SQLITE_SHM_NLOCK+lockIdx));
+  }
+#endif
+  return rc;
+}
+static void walUnlockExclusive(Wal *pWal, int lockIdx, int n){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE);
+#ifdef SQLITE_USE_SEH
+  pWal->lockMask &= ~(((1<<n)-1) << (SQLITE_SHM_NLOCK+lockIdx));
+#endif
+  WALTRACE(("WAL%p: release EXCLUSIVE-%s cnt=%d\n", pWal,
+             walLockName(lockIdx), n));
+}
+
+/*
+** Compute a hash on a page number.  The resulting hash value must land
+** between 0 and (HASHTABLE_NSLOT-1).  The walHashNext() function advances
+** the hash to the next value in the event of a collision.
+*/
+static int walHash(u32 iPage){
+  assert( iPage>0 );
+  assert( (HASHTABLE_NSLOT & (HASHTABLE_NSLOT-1))==0 );
+  return (iPage*HASHTABLE_HASH_1) & (HASHTABLE_NSLOT-1);
+}
+static int walNextHash(int iPriorHash){
+  return (iPriorHash+1)&(HASHTABLE_NSLOT-1);
+}
+
+/*
+** An instance of the WalHashLoc object is used to describe the location
+** of a page hash table in the wal-index.  This becomes the return value
+** from walHashGet().
+*/
+typedef struct WalHashLoc WalHashLoc;
+struct WalHashLoc {
+  volatile ht_slot *aHash;  /* Start of the wal-index hash table */
+  volatile u32 *aPgno;      /* aPgno[1] is the page of first frame indexed */
+  u32 iZero;                /* One less than the frame number of first indexed*/
+};
+
+/*
+** Return pointers to the hash table and page number array stored on
+** page iHash of the wal-index. The wal-index is broken into 32KB pages
+** numbered starting from 0.
+**
+** Set output variable pLoc->aHash to point to the start of the hash table
+** in the wal-index file. Set pLoc->iZero to one less than the frame
+** number of the first frame indexed by this hash table. If a
+** slot in the hash table is set to N, it refers to frame number
+** (pLoc->iZero+N) in the log.
+**
+** Finally, set pLoc->aPgno so that pLoc->aPgno[0] is the page number of the
+** first frame indexed by the hash table, frame (pLoc->iZero).
+*/
+static int walHashGet(
+  Wal *pWal,                      /* WAL handle */
+  int iHash,                      /* Find the iHash'th table */
+  WalHashLoc *pLoc                /* OUT: Hash table location */
+){
+  int rc;                         /* Return code */
+
+  rc = walIndexPage(pWal, iHash, &pLoc->aPgno);
+  assert( rc==SQLITE_OK || iHash>0 );
+
+  if( pLoc->aPgno ){
+    pLoc->aHash = (volatile ht_slot *)&pLoc->aPgno[HASHTABLE_NPAGE];
+    if( iHash==0 ){
+      pLoc->aPgno = &pLoc->aPgno[WALINDEX_HDR_SIZE/sizeof(u32)];
+      pLoc->iZero = 0;
+    }else{
+      pLoc->iZero = HASHTABLE_NPAGE_ONE + (iHash-1)*HASHTABLE_NPAGE;
+    }
+  }else if( NEVER(rc==SQLITE_OK) ){
+    rc = SQLITE_ERROR;
+  }
+  return rc;
+}
+
+/*
+** Return the number of the wal-index page that contains the hash-table
+** and page-number array that contain entries corresponding to WAL frame
+** iFrame. The wal-index is broken up into 32KB pages. Wal-index pages
+** are numbered starting from 0.
+*/
+static int walFramePage(u32 iFrame){
+  int iHash = (iFrame+HASHTABLE_NPAGE-HASHTABLE_NPAGE_ONE-1) / HASHTABLE_NPAGE;
+  assert( (iHash==0 || iFrame>HASHTABLE_NPAGE_ONE)
+       && (iHash>=1 || iFrame<=HASHTABLE_NPAGE_ONE)
+       && (iHash<=1 || iFrame>(HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE))
+       && (iHash>=2 || iFrame<=HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE)
+       && (iHash<=2 || iFrame>(HASHTABLE_NPAGE_ONE+2*HASHTABLE_NPAGE))
+  );
+  assert( iHash>=0 );
+  return iHash;
+}
+
+/*
+** Return the page number associated with frame iFrame in this WAL.
+*/
+static u32 walFramePgno(Wal *pWal, u32 iFrame){
+  int iHash = walFramePage(iFrame);
+  SEH_INJECT_FAULT;
+  if( iHash==0 ){
+    return pWal->apWiData[0][WALINDEX_HDR_SIZE/sizeof(u32) + iFrame - 1];
+  }
+  return pWal->apWiData[iHash][(iFrame-1-HASHTABLE_NPAGE_ONE)%HASHTABLE_NPAGE];
+}
+
+/*
+** Remove entries from the hash table that point to WAL slots greater
+** than pWal->hdr.mxFrame.
+**
+** This function is called whenever pWal->hdr.mxFrame is decreased due
+** to a rollback or savepoint.
+**
+** At most only the hash table containing pWal->hdr.mxFrame needs to be
+** updated.  Any later hash tables will be automatically cleared when
+** pWal->hdr.mxFrame advances to the point where those hash tables are
+** actually needed.
+*/
+static void walCleanupHash(Wal *pWal){
+  WalHashLoc sLoc;                /* Hash table location */
+  int iLimit = 0;                 /* Zero values greater than this */
+  int nByte;                      /* Number of bytes to zero in aPgno[] */
+  int i;                          /* Used to iterate through aHash[] */
+
+  assert( pWal->writeLock );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE-1 );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE+1 );
+
+  if( pWal->hdr.mxFrame==0 ) return;
+
+  /* Obtain pointers to the hash-table and page-number array containing
+  ** the entry that corresponds to frame pWal->hdr.mxFrame. It is guaranteed
+  ** that the page said hash-table and array reside on is already mapped.(1)
+  */
+  assert( pWal->nWiData>walFramePage(pWal->hdr.mxFrame) );
+  assert( pWal->apWiData[walFramePage(pWal->hdr.mxFrame)] );
+  i = walHashGet(pWal, walFramePage(pWal->hdr.mxFrame), &sLoc);
+  if( NEVER(i) ) return; /* Defense-in-depth, in case (1) above is wrong */
+
+  /* Zero all hash-table entries that correspond to frame numbers greater
+  ** than pWal->hdr.mxFrame.
+  */
+  iLimit = pWal->hdr.mxFrame - sLoc.iZero;
+  assert( iLimit>0 );
+  for(i=0; i<HASHTABLE_NSLOT; i++){
+    if( sLoc.aHash[i]>iLimit ){
+      sLoc.aHash[i] = 0;
+    }
+  }
+
+  /* Zero the entries in the aPgno array that correspond to frames with
+  ** frame numbers greater than pWal->hdr.mxFrame.
+  */
+  nByte = (int)((char *)sLoc.aHash - (char *)&sLoc.aPgno[iLimit]);
+  assert( nByte>=0 );
+  memset((void *)&sLoc.aPgno[iLimit], 0, nByte);
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* Verify that the every entry in the mapping region is still reachable
+  ** via the hash table even after the cleanup.
+  */
+  if( iLimit ){
+    int j;           /* Loop counter */
+    int iKey;        /* Hash key */
+    for(j=0; j<iLimit; j++){
+      for(iKey=walHash(sLoc.aPgno[j]);sLoc.aHash[iKey];iKey=walNextHash(iKey)){
+        if( sLoc.aHash[iKey]==j+1 ) break;
+      }
+      assert( sLoc.aHash[iKey]==j+1 );
+    }
+  }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+}
+
+
+/*
+** Set an entry in the wal-index that will map database page number
+** pPage into WAL frame iFrame.
+*/
+static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
+  int rc;                         /* Return code */
+  WalHashLoc sLoc;                /* Wal-index hash table location */
+
+  rc = walHashGet(pWal, walFramePage(iFrame), &sLoc);
+
+  /* Assuming the wal-index file was successfully mapped, populate the
+  ** page number array and hash table entry.
+  */
+  if( rc==SQLITE_OK ){
+    int iKey;                     /* Hash table key */
+    int idx;                      /* Value to write to hash-table slot */
+    int nCollide;                 /* Number of hash collisions */
+
+    idx = iFrame - sLoc.iZero;
+    assert( idx <= HASHTABLE_NSLOT/2 + 1 );
+
+    /* If this is the first entry to be added to this hash-table, zero the
+    ** entire hash table and aPgno[] array before proceeding.
+    */
+    if( idx==1 ){
+      int nByte = (int)((u8*)&sLoc.aHash[HASHTABLE_NSLOT] - (u8*)sLoc.aPgno);
+      assert( nByte>=0 );
+      memset((void*)sLoc.aPgno, 0, nByte);
+    }
+
+    /* If the entry in aPgno[] is already set, then the previous writer
+    ** must have exited unexpectedly in the middle of a transaction (after
+    ** writing one or more dirty pages to the WAL to free up memory).
+    ** Remove the remnants of that writers uncommitted transaction from
+    ** the hash-table before writing any new entries.
+    */
+    if( sLoc.aPgno[idx-1] ){
+      walCleanupHash(pWal);
+      assert( !sLoc.aPgno[idx-1] );
+    }
+
+    /* Write the aPgno[] array entry and the hash-table slot. */
+    nCollide = idx;
+    for(iKey=walHash(iPage); sLoc.aHash[iKey]; iKey=walNextHash(iKey)){
+      if( (nCollide--)==0 ) return SQLITE_CORRUPT_BKPT;
+    }
+    sLoc.aPgno[idx-1] = iPage;
+    AtomicStore(&sLoc.aHash[iKey], (ht_slot)idx);
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+    /* Verify that the number of entries in the hash table exactly equals
+    ** the number of entries in the mapping region.
+    */
+    {
+      int i;           /* Loop counter */
+      int nEntry = 0;  /* Number of entries in the hash table */
+      for(i=0; i<HASHTABLE_NSLOT; i++){ if( sLoc.aHash[i] ) nEntry++; }
+      assert( nEntry==idx );
+    }
+
+    /* Verify that the every entry in the mapping region is reachable
+    ** via the hash table.  This turns out to be a really, really expensive
+    ** thing to check, so only do this occasionally - not on every
+    ** iteration.
+    */
+    if( (idx&0x3ff)==0 ){
+      int i;           /* Loop counter */
+      for(i=0; i<idx; i++){
+        for(iKey=walHash(sLoc.aPgno[i]);
+            sLoc.aHash[iKey];
+            iKey=walNextHash(iKey)){
+          if( sLoc.aHash[iKey]==i+1 ) break;
+        }
+        assert( sLoc.aHash[iKey]==i+1 );
+      }
+    }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+  }
+
+  return rc;
+}
+
+
+/*
+** Recover the wal-index by reading the write-ahead log file.
+**
+** This routine first tries to establish an exclusive lock on the
+** wal-index to prevent other threads/processes from doing anything
+** with the WAL or wal-index while recovery is running.  The
+** WAL_RECOVER_LOCK is also held so that other threads will know
+** that this thread is running recovery.  If unable to establish
+** the necessary locks, this routine returns SQLITE_BUSY.
+*/
+static int walIndexRecover(Wal *pWal){
+  int rc;                         /* Return Code */
+  i64 nSize;                      /* Size of log file */
+  u32 aFrameCksum[2] = {0, 0};
+  int iLock;                      /* Lock offset to lock for checkpoint */
+
+  /* Obtain an exclusive lock on all byte in the locking range not already
+  ** locked by the caller. The caller is guaranteed to have locked the
+  ** WAL_WRITE_LOCK byte, and may have also locked the WAL_CKPT_LOCK byte.
+  ** If successful, the same bytes that are locked here are unlocked before
+  ** this function returns.
+  */
+  assert( pWal->ckptLock==1 || pWal->ckptLock==0 );
+  assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 );
+  assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
+  assert( pWal->writeLock );
+  iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
+  rc = walLockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
+  if( rc ){
+    return rc;
+  }
+
+  WALTRACE(("WAL%p: recovery begin...\n", pWal));
+
+  memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+
+  rc = sqlite3OsFileSize(pWal->pWalFd, &nSize);
+  if( rc!=SQLITE_OK ){
+    goto recovery_error;
+  }
+
+  if( nSize>WAL_HDRSIZE ){
+    u8 aBuf[WAL_HDRSIZE];         /* Buffer to load WAL header into */
+    u32 *aPrivate = 0;            /* Heap copy of *-shm hash being populated */
+    u8 *aFrame = 0;               /* Malloc'd buffer to load entire frame */
+    int szFrame;                  /* Number of bytes in buffer aFrame[] */
+    u8 *aData;                    /* Pointer to data part of aFrame buffer */
+    int szPage;                   /* Page size according to the log */
+    u32 magic;                    /* Magic value read from WAL header */
+    u32 version;                  /* Magic value read from WAL header */
+    int isValid;                  /* True if this frame is valid */
+    u32 iPg;                      /* Current 32KB wal-index page */
+    u32 iLastFrame;               /* Last frame in wal, based on nSize alone */
+
+    /* Read in the WAL header. */
+    rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
+    if( rc!=SQLITE_OK ){
+      goto recovery_error;
+    }
+
+    /* If the database page size is not a power of two, or is greater than
+    ** SQLITE_MAX_PAGE_SIZE, conclude that the WAL file contains no valid
+    ** data. Similarly, if the 'magic' value is invalid, ignore the whole
+    ** WAL file.
+    */
+    magic = sqlite3Get4byte(&aBuf[0]);
+    szPage = sqlite3Get4byte(&aBuf[8]);
+    if( (magic&0xFFFFFFFE)!=WAL_MAGIC
+     || szPage&(szPage-1)
+     || szPage>SQLITE_MAX_PAGE_SIZE
+     || szPage<512
+    ){
+      goto finished;
+    }
+    pWal->hdr.bigEndCksum = (u8)(magic&0x00000001);
+    pWal->szPage = szPage;
+    pWal->nCkpt = sqlite3Get4byte(&aBuf[12]);
+    memcpy(&pWal->hdr.aSalt, &aBuf[16], 8);
+
+    /* Verify that the WAL header checksum is correct */
+    walChecksumBytes(pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN,
+        aBuf, WAL_HDRSIZE-2*4, 0, pWal->hdr.aFrameCksum
+    );
+    if( pWal->hdr.aFrameCksum[0]!=sqlite3Get4byte(&aBuf[24])
+     || pWal->hdr.aFrameCksum[1]!=sqlite3Get4byte(&aBuf[28])
+    ){
+      goto finished;
+    }
+
+    /* Verify that the version number on the WAL format is one that
+    ** are able to understand */
+    version = sqlite3Get4byte(&aBuf[4]);
+    if( version!=WAL_MAX_VERSION ){
+      rc = SQLITE_CANTOPEN_BKPT;
+      goto finished;
+    }
+
+    /* Malloc a buffer to read frames into. */
+    szFrame = szPage + WAL_FRAME_HDRSIZE;
+    aFrame = (u8 *)sqlite3_malloc64(szFrame + WALINDEX_PGSZ);
+    SEH_FREE_ON_ERROR(0, aFrame);
+    if( !aFrame ){
+      rc = SQLITE_NOMEM_BKPT;
+      goto recovery_error;
+    }
+    aData = &aFrame[WAL_FRAME_HDRSIZE];
+    aPrivate = (u32*)&aData[szPage];
+
+    /* Read all frames from the log file. */
+    iLastFrame = (nSize - WAL_HDRSIZE) / szFrame;
+    for(iPg=0; iPg<=(u32)walFramePage(iLastFrame); iPg++){
+      u32 *aShare;
+      u32 iFrame;                 /* Index of last frame read */
+      u32 iLast = MIN(iLastFrame, HASHTABLE_NPAGE_ONE+iPg*HASHTABLE_NPAGE);
+      u32 iFirst = 1 + (iPg==0?0:HASHTABLE_NPAGE_ONE+(iPg-1)*HASHTABLE_NPAGE);
+      u32 nHdr, nHdr32;
+      rc = walIndexPage(pWal, iPg, (volatile u32**)&aShare);
+      assert( aShare!=0 || rc!=SQLITE_OK );
+      if( aShare==0 ) break;
+      SEH_SET_ON_ERROR(iPg, aShare);
+      pWal->apWiData[iPg] = aPrivate;
+
+      for(iFrame=iFirst; iFrame<=iLast; iFrame++){
+        i64 iOffset = walFrameOffset(iFrame, szPage);
+        u32 pgno;                 /* Database page number for frame */
+        u32 nTruncate;            /* dbsize field from frame header */
+
+        /* Read and decode the next log frame. */
+        rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
+        if( rc!=SQLITE_OK ) break;
+        isValid = walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame);
+        if( !isValid ) break;
+        rc = walIndexAppend(pWal, iFrame, pgno);
+        if( NEVER(rc!=SQLITE_OK) ) break;
+
+        /* If nTruncate is non-zero, this is a commit record. */
+        if( nTruncate ){
+          pWal->hdr.mxFrame = iFrame;
+          pWal->hdr.nPage = nTruncate;
+          pWal->hdr.szPage = (u16)((szPage&0xff00) | (szPage>>16));
+          testcase( szPage<=32768 );
+          testcase( szPage>=65536 );
+          aFrameCksum[0] = pWal->hdr.aFrameCksum[0];
+          aFrameCksum[1] = pWal->hdr.aFrameCksum[1];
+        }
+      }
+      pWal->apWiData[iPg] = aShare;
+      SEH_SET_ON_ERROR(0,0);
+      nHdr = (iPg==0 ? WALINDEX_HDR_SIZE : 0);
+      nHdr32 = nHdr / sizeof(u32);
+#ifndef SQLITE_SAFER_WALINDEX_RECOVERY
+      /* Memcpy() should work fine here, on all reasonable implementations.
+      ** Technically, memcpy() might change the destination to some
+      ** intermediate value before setting to the final value, and that might
+      ** cause a concurrent reader to malfunction.  Memcpy() is allowed to
+      ** do that, according to the spec, but no memcpy() implementation that
+      ** we know of actually does that, which is why we say that memcpy()
+      ** is safe for this.  Memcpy() is certainly a lot faster.
+      */
+      memcpy(&aShare[nHdr32], &aPrivate[nHdr32], WALINDEX_PGSZ-nHdr);
+#else
+      /* In the event that some platform is found for which memcpy()
+      ** changes the destination to some intermediate value before
+      ** setting the final value, this alternative copy routine is
+      ** provided.
+      */
+      {
+        int i;
+        for(i=nHdr32; i<WALINDEX_PGSZ/sizeof(u32); i++){
+          if( aShare[i]!=aPrivate[i] ){
+            /* Atomic memory operations are not required here because if
+            ** the value needs to be changed, that means it is not being
+            ** accessed concurrently. */
+            aShare[i] = aPrivate[i];
+          }
+        }
+      }
+#endif
+      SEH_INJECT_FAULT;
+      if( iFrame<=iLast ) break;
+    }
+
+    SEH_FREE_ON_ERROR(aFrame, 0);
+    sqlite3_free(aFrame);
+  }
+
+finished:
+  if( rc==SQLITE_OK ){
+    volatile WalCkptInfo *pInfo;
+    int i;
+    pWal->hdr.aFrameCksum[0] = aFrameCksum[0];
+    pWal->hdr.aFrameCksum[1] = aFrameCksum[1];
+    walIndexWriteHdr(pWal);
+
+    /* Reset the checkpoint-header. This is safe because this thread is
+    ** currently holding locks that exclude all other writers and
+    ** checkpointers. Then set the values of read-mark slots 1 through N.
+    */
+    pInfo = walCkptInfo(pWal);
+    pInfo->nBackfill = 0;
+    pInfo->nBackfillAttempted = pWal->hdr.mxFrame;
+    pInfo->aReadMark[0] = 0;
+    for(i=1; i<WAL_NREADER; i++){
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      if( rc==SQLITE_OK ){
+        if( i==1 && pWal->hdr.mxFrame ){
+          pInfo->aReadMark[i] = pWal->hdr.mxFrame;
+        }else{
+          pInfo->aReadMark[i] = READMARK_NOT_USED;
+        }
+        SEH_INJECT_FAULT;
+        walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      }else if( rc!=SQLITE_BUSY ){
+        goto recovery_error;
+      }
+    }
+
+    /* If more than one frame was recovered from the log file, report an
+    ** event via sqlite3_log(). This is to help with identifying performance
+    ** problems caused by applications routinely shutting down without
+    ** checkpointing the log file.
+    */
+    if( pWal->hdr.nPage ){
+      sqlite3_log(SQLITE_NOTICE_RECOVER_WAL,
+          "recovered %d frames from WAL file %s",
+          pWal->hdr.mxFrame, pWal->zWalName
+      );
+    }
+  }
+
+recovery_error:
+  WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
+  walUnlockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
+  return rc;
+}
+
+/*
+** Close an open wal-index.
+*/
+static void walIndexClose(Wal *pWal, int isDelete){
+  if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE || pWal->bShmUnreliable ){
+    int i;
+    for(i=0; i<pWal->nWiData; i++){
+      sqlite3_free((void *)pWal->apWiData[i]);
+      pWal->apWiData[i] = 0;
+    }
+  }
+  if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
+    sqlite3OsShmUnmap(pWal->pDbFd, isDelete);
+  }
+}
+
+/*
+** Open a connection to the WAL file zWalName. The database file must
+** already be opened on connection pDbFd. The buffer that zWalName points
+** to must remain valid for the lifetime of the returned Wal* handle.
+**
+** A SHARED lock should be held on the database file when this function
+** is called. The purpose of this SHARED lock is to prevent any other
+** client from unlinking the WAL or wal-index file. If another process
+** were to do this just after this client opened one of these files, the
+** system would be badly broken.
+**
+** If the log file is successfully opened, SQLITE_OK is returned and
+** *ppWal is set to point to a new WAL handle. If an error occurs,
+** an SQLite error code is returned and *ppWal is left unmodified.
+*/
+int sqlite3WalOpen(
+  sqlite3_vfs *pVfs,              /* vfs module to open wal and wal-index */
+  sqlite3_file *pDbFd,            /* The open database file */
+  const char *zWalName,           /* Name of the WAL file */
+  int bNoShm,                     /* True to run in heap-memory mode */
+  i64 mxWalSize,                  /* Truncate WAL to this size on reset */
+  Wal **ppWal                     /* OUT: Allocated Wal handle */
+){
+  int rc;                         /* Return Code */
+  Wal *pRet;                      /* Object to allocate and return */
+  int flags;                      /* Flags passed to OsOpen() */
+
+  assert( zWalName && zWalName[0] );
+  assert( pDbFd );
+
+  /* Verify the values of various constants.  Any changes to the values
+  ** of these constants would result in an incompatible on-disk format
+  ** for the -shm file.  Any change that causes one of these asserts to
+  ** fail is a backward compatibility problem, even if the change otherwise
+  ** works.
+  **
+  ** This table also serves as a helpful cross-reference when trying to
+  ** interpret hex dumps of the -shm file.
+  */
+  assert(    48 ==  sizeof(WalIndexHdr)  );
+  assert(    40 ==  sizeof(WalCkptInfo)  );
+  assert(   120 ==  WALINDEX_LOCK_OFFSET );
+  assert(   136 ==  WALINDEX_HDR_SIZE    );
+  assert(  4096 ==  HASHTABLE_NPAGE      );
+  assert(  4062 ==  HASHTABLE_NPAGE_ONE  );
+  assert(  8192 ==  HASHTABLE_NSLOT      );
+  assert(   383 ==  HASHTABLE_HASH_1     );
+  assert( 32768 ==  WALINDEX_PGSZ        );
+  assert(     8 ==  SQLITE_SHM_NLOCK     );
+  assert(     5 ==  WAL_NREADER          );
+  assert(    24 ==  WAL_FRAME_HDRSIZE    );
+  assert(    32 ==  WAL_HDRSIZE          );
+  assert(   120 ==  WALINDEX_LOCK_OFFSET + WAL_WRITE_LOCK   );
+  assert(   121 ==  WALINDEX_LOCK_OFFSET + WAL_CKPT_LOCK    );
+  assert(   122 ==  WALINDEX_LOCK_OFFSET + WAL_RECOVER_LOCK );
+  assert(   123 ==  WALINDEX_LOCK_OFFSET + WAL_READ_LOCK(0) );
+  assert(   124 ==  WALINDEX_LOCK_OFFSET + WAL_READ_LOCK(1) );
+  assert(   125 ==  WALINDEX_LOCK_OFFSET + WAL_READ_LOCK(2) );
+  assert(   126 ==  WALINDEX_LOCK_OFFSET + WAL_READ_LOCK(3) );
+  assert(   127 ==  WALINDEX_LOCK_OFFSET + WAL_READ_LOCK(4) );
+
+  /* In the amalgamation, the os_unix.c and os_win.c source files come before
+  ** this source file.  Verify that the #defines of the locking byte offsets
+  ** in os_unix.c and os_win.c agree with the WALINDEX_LOCK_OFFSET value.
+  ** For that matter, if the lock offset ever changes from its initial design
+  ** value of 120, we need to know that so there is an assert() to check it.
+  */
+#ifdef WIN_SHM_BASE
+  assert( WIN_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+#ifdef UNIX_SHM_BASE
+  assert( UNIX_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+
+
+  /* Allocate an instance of struct Wal to return. */
+  *ppWal = 0;
+  pRet = (Wal*)sqlite3MallocZero(sizeof(Wal) + pVfs->szOsFile);
+  if( !pRet ){
+    return SQLITE_NOMEM_BKPT;
+  }
+
+  pRet->pVfs = pVfs;
+  pRet->pWalFd = (sqlite3_file *)&pRet[1];
+  pRet->pDbFd = pDbFd;
+  pRet->readLock = -1;
+  pRet->mxWalSize = mxWalSize;
+  pRet->zWalName = zWalName;
+  pRet->syncHeader = 1;
+  pRet->padToSectorBoundary = 1;
+  pRet->exclusiveMode = (bNoShm ? WAL_HEAPMEMORY_MODE: WAL_NORMAL_MODE);
+
+  /* Open file handle on the write-ahead log file. */
+  flags = (SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_WAL);
+  rc = sqlite3OsOpen(pVfs, zWalName, pRet->pWalFd, flags, &flags);
+  if( rc==SQLITE_OK && flags&SQLITE_OPEN_READONLY ){
+    pRet->readOnly = WAL_RDONLY;
+  }
+
+  if( rc!=SQLITE_OK ){
+    walIndexClose(pRet, 0);
+    sqlite3OsClose(pRet->pWalFd);
+    sqlite3_free(pRet);
+  }else{
+    int iDC = sqlite3OsDeviceCharacteristics(pDbFd);
+    if( iDC & SQLITE_IOCAP_SEQUENTIAL ){ pRet->syncHeader = 0; }
+    if( iDC & SQLITE_IOCAP_POWERSAFE_OVERWRITE ){
+      pRet->padToSectorBoundary = 0;
+    }
+    *ppWal = pRet;
+    WALTRACE(("WAL%d: opened\n", pRet));
+  }
+  return rc;
+}
+
+/*
+** Change the size to which the WAL file is truncated on each reset.
+*/
+void sqlite3WalLimit(Wal *pWal, i64 iLimit){
+  if( pWal ) pWal->mxWalSize = iLimit;
+}
+
+/*
+** Find the smallest page number out of all pages held in the WAL that
+** has not been returned by any prior invocation of this method on the
+** same WalIterator object.   Write into *piFrame the frame index where
+** that page was last written into the WAL.  Write into *piPage the page
+** number.
+**
+** Return 0 on success.  If there are no pages in the WAL with a page
+** number larger than *piPage, then return 1.
+*/
+static int walIteratorNext(
+  WalIterator *p,               /* Iterator */
+  u32 *piPage,                  /* OUT: The page number of the next page */
+  u32 *piFrame                  /* OUT: Wal frame index of next page */
+){
+  u32 iMin;                     /* Result pgno must be greater than iMin */
+  u32 iRet = 0xFFFFFFFF;        /* 0xffffffff is never a valid page number */
+  int i;                        /* For looping through segments */
+
+  iMin = p->iPrior;
+  assert( iMin<0xffffffff );
+  for(i=p->nSegment-1; i>=0; i--){
+    struct WalSegment *pSegment = &p->aSegment[i];
+    while( pSegment->iNext<pSegment->nEntry ){
+      u32 iPg = pSegment->aPgno[pSegment->aIndex[pSegment->iNext]];
+      if( iPg>iMin ){
+        if( iPg<iRet ){
+          iRet = iPg;
+          *piFrame = pSegment->iZero + pSegment->aIndex[pSegment->iNext];
+        }
+        break;
+      }
+      pSegment->iNext++;
+    }
+  }
+
+  *piPage = p->iPrior = iRet;
+  return (iRet==0xFFFFFFFF);
+}
+
+/*
+** This function merges two sorted lists into a single sorted list.
+**
+** aLeft[] and aRight[] are arrays of indices.  The sort key is
+** aContent[aLeft[]] and aContent[aRight[]].  Upon entry, the following
+** is guaranteed for all J<K:
+**
+**        aContent[aLeft[J]] < aContent[aLeft[K]]
+**        aContent[aRight[J]] < aContent[aRight[K]]
+**
+** This routine overwrites aRight[] with a new (probably longer) sequence
+** of indices such that the aRight[] contains every index that appears in
+** either aLeft[] or the old aRight[] and such that the second condition
+** above is still met.
+**
+** The aContent[aLeft[X]] values will be unique for all X.  And the
+** aContent[aRight[X]] values will be unique too.  But there might be
+** one or more combinations of X and Y such that
+**
+**      aLeft[X]!=aRight[Y]  &&  aContent[aLeft[X]] == aContent[aRight[Y]]
+**
+** When that happens, omit the aLeft[X] and use the aRight[Y] index.
+*/
+static void walMerge(
+  const u32 *aContent,            /* Pages in wal - keys for the sort */
+  ht_slot *aLeft,                 /* IN: Left hand input list */
+  int nLeft,                      /* IN: Elements in array *paLeft */
+  ht_slot **paRight,              /* IN/OUT: Right hand input list */
+  int *pnRight,                   /* IN/OUT: Elements in *paRight */
+  ht_slot *aTmp                   /* Temporary buffer */
+){
+  int iLeft = 0;                  /* Current index in aLeft */
+  int iRight = 0;                 /* Current index in aRight */
+  int iOut = 0;                   /* Current index in output buffer */
+  int nRight = *pnRight;
+  ht_slot *aRight = *paRight;
+
+  assert( nLeft>0 && nRight>0 );
+  while( iRight<nRight || iLeft<nLeft ){
+    ht_slot logpage;
+    Pgno dbpage;
+
+    if( (iLeft<nLeft)
+     && (iRight>=nRight || aContent[aLeft[iLeft]]<aContent[aRight[iRight]])
+    ){
+      logpage = aLeft[iLeft++];
+    }else{
+      logpage = aRight[iRight++];
+    }
+    dbpage = aContent[logpage];
+
+    aTmp[iOut++] = logpage;
+    if( iLeft<nLeft && aContent[aLeft[iLeft]]==dbpage ) iLeft++;
+
+    assert( iLeft>=nLeft || aContent[aLeft[iLeft]]>dbpage );
+    assert( iRight>=nRight || aContent[aRight[iRight]]>dbpage );
+  }
+
+  *paRight = aLeft;
+  *pnRight = iOut;
+  memcpy(aLeft, aTmp, sizeof(aTmp[0])*iOut);
+}
+
+/*
+** Sort the elements in list aList using aContent[] as the sort key.
+** Remove elements with duplicate keys, preferring to keep the
+** larger aList[] values.
+**
+** The aList[] entries are indices into aContent[].  The values in
+** aList[] are to be sorted so that for all J<K:
+**
+**      aContent[aList[J]] < aContent[aList[K]]
+**
+** For any X and Y such that
+**
+**      aContent[aList[X]] == aContent[aList[Y]]
+**
+** Keep the larger of the two values aList[X] and aList[Y] and discard
+** the smaller.
+*/
+static void walMergesort(
+  const u32 *aContent,            /* Pages in wal */
+  ht_slot *aBuffer,               /* Buffer of at least *pnList items to use */
+  ht_slot *aList,                 /* IN/OUT: List to sort */
+  int *pnList                     /* IN/OUT: Number of elements in aList[] */
+){
+  struct Sublist {
+    int nList;                    /* Number of elements in aList */
+    ht_slot *aList;               /* Pointer to sub-list content */
+  };
+
+  const int nList = *pnList;      /* Size of input list */
+  int nMerge = 0;                 /* Number of elements in list aMerge */
+  ht_slot *aMerge = 0;            /* List to be merged */
+  int iList;                      /* Index into input list */
+  u32 iSub = 0;                   /* Index into aSub array */
+  struct Sublist aSub[13];        /* Array of sub-lists */
+
+  memset(aSub, 0, sizeof(aSub));
+  assert( nList<=HASHTABLE_NPAGE && nList>0 );
+  assert( HASHTABLE_NPAGE==(1<<(ArraySize(aSub)-1)) );
+
+  for(iList=0; iList<nList; iList++){
+    nMerge = 1;
+    aMerge = &aList[iList];
+    for(iSub=0; iList & (1<<iSub); iSub++){
+      struct Sublist *p;
+      assert( iSub<ArraySize(aSub) );
+      p = &aSub[iSub];
+      assert( p->aList && p->nList<=(1<<iSub) );
+      assert( p->aList==&aList[iList&~((2<<iSub)-1)] );
+      walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
+    }
+    aSub[iSub].aList = aMerge;
+    aSub[iSub].nList = nMerge;
+  }
+
+  for(iSub++; iSub<ArraySize(aSub); iSub++){
+    if( nList & (1<<iSub) ){
+      struct Sublist *p;
+      assert( iSub<ArraySize(aSub) );
+      p = &aSub[iSub];
+      assert( p->nList<=(1<<iSub) );
+      assert( p->aList==&aList[nList&~((2<<iSub)-1)] );
+      walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
+    }
+  }
+  assert( aMerge==aList );
+  *pnList = nMerge;
+
+#ifdef SQLITE_DEBUG
+  {
+    int i;
+    for(i=1; i<*pnList; i++){
+      assert( aContent[aList[i]] > aContent[aList[i-1]] );
+    }
+  }
+#endif
+}
+
+/*
+** Free an iterator allocated by walIteratorInit().
+*/
+static void walIteratorFree(WalIterator *p){
+  sqlite3_free(p);
+}
+
+/*
+** Construct a WalInterator object that can be used to loop over all
+** pages in the WAL following frame nBackfill in ascending order. Frames
+** nBackfill or earlier may be included - excluding them is an optimization
+** only. The caller must hold the checkpoint lock.
+**
+** On success, make *pp point to the newly allocated WalInterator object
+** return SQLITE_OK. Otherwise, return an error code. If this routine
+** returns an error, the value of *pp is undefined.
+**
+** The calling routine should invoke walIteratorFree() to destroy the
+** WalIterator object when it has finished with it.
+*/
+static int walIteratorInit(Wal *pWal, u32 nBackfill, WalIterator **pp){
+  WalIterator *p;                 /* Return value */
+  int nSegment;                   /* Number of segments to merge */
+  u32 iLast;                      /* Last frame in log */
+  sqlite3_int64 nByte;            /* Number of bytes to allocate */
+  int i;                          /* Iterator variable */
+  ht_slot *aTmp;                  /* Temp space used by merge-sort */
+  int rc = SQLITE_OK;             /* Return Code */
+
+  /* This routine only runs while holding the checkpoint lock. And
+  ** it only runs if there is actually content in the log (mxFrame>0).
+  */
+  assert( pWal->ckptLock && pWal->hdr.mxFrame>0 );
+  iLast = pWal->hdr.mxFrame;
+
+  /* Allocate space for the WalIterator object. */
+  nSegment = walFramePage(iLast) + 1;
+  nByte = sizeof(WalIterator)
+        + (nSegment-1)*sizeof(struct WalSegment)
+        + iLast*sizeof(ht_slot);
+  p = (WalIterator *)sqlite3_malloc64(nByte
+      + sizeof(ht_slot) * (iLast>HASHTABLE_NPAGE?HASHTABLE_NPAGE:iLast)
+  );
+  if( !p ){
+    return SQLITE_NOMEM_BKPT;
+  }
+  memset(p, 0, nByte);
+  p->nSegment = nSegment;
+  aTmp = (ht_slot*)&(((u8*)p)[nByte]);
+  SEH_FREE_ON_ERROR(0, p);
+  for(i=walFramePage(nBackfill+1); rc==SQLITE_OK && i<nSegment; i++){
+    WalHashLoc sLoc;
+
+    rc = walHashGet(pWal, i, &sLoc);
+    if( rc==SQLITE_OK ){
+      int j;                      /* Counter variable */
+      int nEntry;                 /* Number of entries in this segment */
+      ht_slot *aIndex;            /* Sorted index for this segment */
+
+      if( (i+1)==nSegment ){
+        nEntry = (int)(iLast - sLoc.iZero);
+      }else{
+        nEntry = (int)((u32*)sLoc.aHash - (u32*)sLoc.aPgno);
+      }
+      aIndex = &((ht_slot *)&p->aSegment[p->nSegment])[sLoc.iZero];
+      sLoc.iZero++;
+
+      for(j=0; j<nEntry; j++){
+        aIndex[j] = (ht_slot)j;
+      }
+      walMergesort((u32 *)sLoc.aPgno, aTmp, aIndex, &nEntry);
+      p->aSegment[i].iZero = sLoc.iZero;
+      p->aSegment[i].nEntry = nEntry;
+      p->aSegment[i].aIndex = aIndex;
+      p->aSegment[i].aPgno = (u32 *)sLoc.aPgno;
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    SEH_FREE_ON_ERROR(p, 0);
+    walIteratorFree(p);
+    p = 0;
+  }
+  *pp = p;
+  return rc;
+}
+
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+
+
+/*
+** Attempt to enable blocking locks that block for nMs ms. Return 1 if 
+** blocking locks are successfully enabled, or 0 otherwise.
+*/
+static int walEnableBlockingMs(Wal *pWal, int nMs){
+  int rc = sqlite3OsFileControl(
+      pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&nMs
+  );
+  return (rc==SQLITE_OK);
+}
+
+/*
+** Attempt to enable blocking locks. Blocking locks are enabled only if (a)
+** they are supported by the VFS, and (b) the database handle is configured
+** with a busy-timeout. Return 1 if blocking locks are successfully enabled,
+** or 0 otherwise.
+*/
+static int walEnableBlocking(Wal *pWal){
+  int res = 0;
+  if( pWal->db ){
+    int tmout = pWal->db->busyTimeout;
+    if( tmout ){
+      res = walEnableBlockingMs(pWal, tmout);
+    }
+  }
+  return res;
+}
+
+/*
+** Disable blocking locks.
+*/
+static void walDisableBlocking(Wal *pWal){
+  int tmout = 0;
+  sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&tmout);
+}
+
+/*
+** If parameter bLock is true, attempt to enable blocking locks, take
+** the WRITER lock, and then disable blocking locks. If blocking locks
+** cannot be enabled, no attempt to obtain the WRITER lock is made. Return
+** an SQLite error code if an error occurs, or SQLITE_OK otherwise. It is not
+** an error if blocking locks can not be enabled.
+**
+** If the bLock parameter is false and the WRITER lock is held, release it.
+*/
+int sqlite3WalWriteLock(Wal *pWal, int bLock){
+  int rc = SQLITE_OK;
+  assert( pWal->readLock<0 || bLock==0 );
+  if( bLock ){
+    assert( pWal->db );
+    if( walEnableBlocking(pWal) ){
+      rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
+      if( rc==SQLITE_OK ){
+        pWal->writeLock = 1;
+      }
+      walDisableBlocking(pWal);
+    }
+  }else if( pWal->writeLock ){
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    pWal->writeLock = 0;
+  }
+  return rc;
+}
+
+/*
+** Set the database handle used to determine if blocking locks are required.
+*/
+void sqlite3WalDb(Wal *pWal, sqlite3 *db){
+  pWal->db = db;
+}
+
+#else
+# define walEnableBlocking(x) 0
+# define walDisableBlocking(x)
+# define walEnableBlockingMs(pWal, ms) 0
+# define sqlite3WalDb(pWal, db)
+#endif   /* ifdef SQLITE_ENABLE_SETLK_TIMEOUT */
+
+
+/*
+** Attempt to obtain the exclusive WAL lock defined by parameters lockIdx and
+** n. If the attempt fails and parameter xBusy is not NULL, then it is a
+** busy-handler function. Invoke it and retry the lock until either the
+** lock is successfully obtained or the busy-handler returns 0.
+*/
+static int walBusyLock(
+  Wal *pWal,                      /* WAL connection */
+  int (*xBusy)(void*),            /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int lockIdx,                    /* Offset of first byte to lock */
+  int n                           /* Number of bytes to lock */
+){
+  int rc;
+  do {
+    rc = walLockExclusive(pWal, lockIdx, n);
+  }while( xBusy && rc==SQLITE_BUSY && xBusy(pBusyArg) );
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  if( rc==SQLITE_BUSY_TIMEOUT ){
+    walDisableBlocking(pWal);
+    rc = SQLITE_BUSY;
+  }
+#endif
+  return rc;
+}
+
+/*
+** The cache of the wal-index header must be valid to call this function.
+** Return the page-size in bytes used by the database.
+*/
+static int walPagesize(Wal *pWal){
+  return (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
+}
+
+/*
+** The following is guaranteed when this function is called:
+**
+**   a) the WRITER lock is held,
+**   b) the entire log file has been checkpointed, and
+**   c) any existing readers are reading exclusively from the database
+**      file - there are no readers that may attempt to read a frame from
+**      the log file.
+**
+** This function updates the shared-memory structures so that the next
+** client to write to the database (which may be this one) does so by
+** writing frames into the start of the log file.
+**
+** The value of parameter salt1 is used as the aSalt[1] value in the
+** new wal-index header. It should be passed a pseudo-random value (i.e.
+** one obtained from sqlite3_randomness()).
+*/
+static void walRestartHdr(Wal *pWal, u32 salt1){
+  volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+  int i;                          /* Loop counter */
+  u32 *aSalt = pWal->hdr.aSalt;   /* Big-endian salt values */
+  pWal->nCkpt++;
+  pWal->hdr.mxFrame = 0;
+  sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0]));
+  memcpy(&pWal->hdr.aSalt[1], &salt1, 4);
+  walIndexWriteHdr(pWal);
+  AtomicStore(&pInfo->nBackfill, 0);
+  pInfo->nBackfillAttempted = 0;
+  pInfo->aReadMark[1] = 0;
+  for(i=2; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
+  assert( pInfo->aReadMark[0]==0 );
+}
+
+/*
+** Copy as much content as we can from the WAL back into the database file
+** in response to an sqlite3_wal_checkpoint() request or the equivalent.
+**
+** The amount of information copies from WAL to database might be limited
+** by active readers.  This routine will never overwrite a database page
+** that a concurrent reader might be using.
+**
+** All I/O barrier operations (a.k.a fsyncs) occur in this routine when
+** SQLite is in WAL-mode in synchronous=NORMAL.  That means that if
+** checkpoints are always run by a background thread or background
+** process, foreground threads will never block on a lengthy fsync call.
+**
+** Fsync is called on the WAL before writing content out of the WAL and
+** into the database.  This ensures that if the new content is persistent
+** in the WAL and can be recovered following a power-loss or hard reset.
+**
+** Fsync is also called on the database file if (and only if) the entire
+** WAL content is copied into the database file.  This second fsync makes
+** it safe to delete the WAL since the new content will persist in the
+** database file.
+**
+** This routine uses and updates the nBackfill field of the wal-index header.
+** This is the only routine that will increase the value of nBackfill.
+** (A WAL reset or recovery will revert nBackfill to zero, but not increase
+** its value.)
+**
+** The caller must be holding sufficient locks to ensure that no other
+** checkpoint is running (in any other thread or process) at the same
+** time.
+*/
+static int walCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  sqlite3 *db,                    /* Check for interrupts on this handle */
+  int eMode,                      /* One of PASSIVE, FULL or RESTART */
+  int (*xBusy)(void*),            /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int sync_flags,                 /* Flags for OsSync() (or 0) */
+  u8 *zBuf                        /* Temporary buffer to use */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  int szPage;                     /* Database page-size */
+  WalIterator *pIter = 0;         /* Wal iterator context */
+  u32 iDbpage = 0;                /* Next database page to write */
+  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */
+  u32 mxSafeFrame;                /* Max frame that can be backfilled */
+  u32 mxPage;                     /* Max database page to write */
+  int i;                          /* Loop counter */
+  volatile WalCkptInfo *pInfo;    /* The checkpoint status information */
+
+  szPage = walPagesize(pWal);
+  testcase( szPage<=32768 );
+  testcase( szPage>=65536 );
+  pInfo = walCkptInfo(pWal);
+  if( pInfo->nBackfill<pWal->hdr.mxFrame ){
+
+    /* EVIDENCE-OF: R-62920-47450 The busy-handler callback is never invoked
+    ** in the SQLITE_CHECKPOINT_PASSIVE mode. */
+    assert( eMode!=SQLITE_CHECKPOINT_PASSIVE || xBusy==0 );
+
+    /* Compute in mxSafeFrame the index of the last frame of the WAL that is
+    ** safe to write into the database.  Frames beyond mxSafeFrame might
+    ** overwrite database pages that are in use by active readers and thus
+    ** cannot be backfilled from the WAL.
+    */
+    mxSafeFrame = pWal->hdr.mxFrame;
+    mxPage = pWal->hdr.nPage;
+    for(i=1; i<WAL_NREADER; i++){
+      u32 y = AtomicLoad(pInfo->aReadMark+i); SEH_INJECT_FAULT;
+      if( mxSafeFrame>y ){
+        assert( y<=pWal->hdr.mxFrame );
+        rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(i), 1);
+        if( rc==SQLITE_OK ){
+          u32 iMark = (i==1 ? mxSafeFrame : READMARK_NOT_USED);
+          AtomicStore(pInfo->aReadMark+i, iMark); SEH_INJECT_FAULT;
+          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+        }else if( rc==SQLITE_BUSY ){
+          mxSafeFrame = y;
+          xBusy = 0;
+        }else{
+          goto walcheckpoint_out;
+        }
+      }
+    }
+
+    /* Allocate the iterator */
+    if( pInfo->nBackfill<mxSafeFrame ){
+      rc = walIteratorInit(pWal, pInfo->nBackfill, &pIter);
+      assert( rc==SQLITE_OK || pIter==0 );
+    }
+
+    if( pIter
+     && (rc = walBusyLock(pWal,xBusy,pBusyArg,WAL_READ_LOCK(0),1))==SQLITE_OK
+    ){
+      u32 nBackfill = pInfo->nBackfill;
+      pInfo->nBackfillAttempted = mxSafeFrame; SEH_INJECT_FAULT;
+
+      /* Sync the WAL to disk */
+      rc = sqlite3OsSync(pWal->pWalFd, CKPT_SYNC_FLAGS(sync_flags));
+
+      /* If the database may grow as a result of this checkpoint, hint
+      ** about the eventual size of the db file to the VFS layer.
+      */
+      if( rc==SQLITE_OK ){
+        i64 nReq = ((i64)mxPage * szPage);
+        i64 nSize;                    /* Current size of database file */
+        sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_CKPT_START, 0);
+        rc = sqlite3OsFileSize(pWal->pDbFd, &nSize);
+        if( rc==SQLITE_OK && nSize<nReq ){
+          if( (nSize+65536+(i64)pWal->hdr.mxFrame*szPage)<nReq ){
+            /* If the size of the final database is larger than the current
+            ** database plus the amount of data in the wal file, plus the
+            ** maximum size of the pending-byte page (65536 bytes), then
+            ** must be corruption somewhere.  */
+            rc = SQLITE_CORRUPT_BKPT;
+          }else{
+            sqlite3OsFileControlHint(pWal->pDbFd, SQLITE_FCNTL_SIZE_HINT,&nReq);
+          }
+        }
+
+      }
+
+      /* Iterate through the contents of the WAL, copying data to the db file */
+      while( rc==SQLITE_OK && 0==walIteratorNext(pIter, &iDbpage, &iFrame) ){
+        i64 iOffset;
+        assert( walFramePgno(pWal, iFrame)==iDbpage );
+        SEH_INJECT_FAULT;
+        if( AtomicLoad(&db->u1.isInterrupted) ){
+          rc = db->mallocFailed ? SQLITE_NOMEM_BKPT : SQLITE_INTERRUPT;
+          break;
+        }
+        if( iFrame<=nBackfill || iFrame>mxSafeFrame || iDbpage>mxPage ){
+          continue;
+        }
+        iOffset = walFrameOffset(iFrame, szPage) + WAL_FRAME_HDRSIZE;
+        /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL file */
+        rc = sqlite3OsRead(pWal->pWalFd, zBuf, szPage, iOffset);
+        if( rc!=SQLITE_OK ) break;
+        iOffset = (iDbpage-1)*(i64)szPage;
+        testcase( IS_BIG_INT(iOffset) );
+        rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, iOffset);
+        if( rc!=SQLITE_OK ) break;
+      }
+      sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_CKPT_DONE, 0);
+
+      /* If work was actually accomplished... */
+      if( rc==SQLITE_OK ){
+        if( mxSafeFrame==walIndexHdr(pWal)->mxFrame ){
+          i64 szDb = pWal->hdr.nPage*(i64)szPage;
+          testcase( IS_BIG_INT(szDb) );
+          rc = sqlite3OsTruncate(pWal->pDbFd, szDb);
+          if( rc==SQLITE_OK ){
+            rc = sqlite3OsSync(pWal->pDbFd, CKPT_SYNC_FLAGS(sync_flags));
+          }
+        }
+        if( rc==SQLITE_OK ){
+          AtomicStore(&pInfo->nBackfill, mxSafeFrame); SEH_INJECT_FAULT;
+        }
+      }
+
+      /* Release the reader lock held while backfilling */
+      walUnlockExclusive(pWal, WAL_READ_LOCK(0), 1);
+    }
+
+    if( rc==SQLITE_BUSY ){
+      /* Reset the return code so as not to report a checkpoint failure
+      ** just because there are active readers.  */
+      rc = SQLITE_OK;
+    }
+  }
+
+  /* If this is an SQLITE_CHECKPOINT_RESTART or TRUNCATE operation, and the
+  ** entire wal file has been copied into the database file, then block
+  ** until all readers have finished using the wal file. This ensures that
+  ** the next process to write to the database restarts the wal file.
+  */
+  if( rc==SQLITE_OK && eMode!=SQLITE_CHECKPOINT_PASSIVE ){
+    assert( pWal->writeLock );
+    SEH_INJECT_FAULT;
+    if( pInfo->nBackfill<pWal->hdr.mxFrame ){
+      rc = SQLITE_BUSY;
+    }else if( eMode>=SQLITE_CHECKPOINT_RESTART ){
+      u32 salt1;
+      sqlite3_randomness(4, &salt1);
+      assert( pInfo->nBackfill==pWal->hdr.mxFrame );
+      rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(1), WAL_NREADER-1);
+      if( rc==SQLITE_OK ){
+        if( eMode==SQLITE_CHECKPOINT_TRUNCATE ){
+          /* IMPLEMENTATION-OF: R-44699-57140 This mode works the same way as
+          ** SQLITE_CHECKPOINT_RESTART with the addition that it also
+          ** truncates the log file to zero bytes just prior to a
+          ** successful return.
+          **
+          ** In theory, it might be safe to do this without updating the
+          ** wal-index header in shared memory, as all subsequent reader or
+          ** writer clients should see that the entire log file has been
+          ** checkpointed and behave accordingly. This seems unsafe though,
+          ** as it would leave the system in a state where the contents of
+          ** the wal-index header do not match the contents of the
+          ** file-system. To avoid this, update the wal-index header to
+          ** indicate that the log file contains zero valid frames.  */
+          walRestartHdr(pWal, salt1);
+          rc = sqlite3OsTruncate(pWal->pWalFd, 0);
+        }
+        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      }
+    }
+  }
+
+ walcheckpoint_out:
+  SEH_FREE_ON_ERROR(pIter, 0);
+  walIteratorFree(pIter);
+  return rc;
+}
+
+/*
+** If the WAL file is currently larger than nMax bytes in size, truncate
+** it to exactly nMax bytes. If an error occurs while doing so, ignore it.
+*/
+static void walLimitSize(Wal *pWal, i64 nMax){
+  i64 sz;
+  int rx;
+  sqlite3BeginBenignMalloc();
+  rx = sqlite3OsFileSize(pWal->pWalFd, &sz);
+  if( rx==SQLITE_OK && (sz > nMax ) ){
+    rx = sqlite3OsTruncate(pWal->pWalFd, nMax);
+  }
+  sqlite3EndBenignMalloc();
+  if( rx ){
+    sqlite3_log(rx, "cannot limit WAL size: %s", pWal->zWalName);
+  }
+}
+
+#ifdef SQLITE_USE_SEH
+/*
+** This is the "standard" exception handler used in a few places to handle 
+** an exception thrown by reading from the *-shm mapping after it has become
+** invalid in SQLITE_USE_SEH builds. It is used as follows:
+**
+**   SEH_TRY { ... }
+**   SEH_EXCEPT( rc = walHandleException(pWal); )
+**
+** This function does three things:
+**
+**   1) Determines the locks that should be held, based on the contents of
+**      the Wal.readLock, Wal.writeLock and Wal.ckptLock variables. All other
+**      held locks are assumed to be transient locks that would have been
+**      released had the exception not been thrown and are dropped.
+**
+**   2) Frees the pointer at Wal.pFree, if any, using sqlite3_free().
+**
+**   3) Set pWal->apWiData[pWal->iWiPg] to pWal->pWiValue if not NULL
+**
+**   4) Returns SQLITE_IOERR.
+*/
+static int walHandleException(Wal *pWal){
+  if( pWal->exclusiveMode==0 ){
+    static const int S = 1;
+    static const int E = (1<<SQLITE_SHM_NLOCK);
+    int ii;
+    u32 mUnlock = pWal->lockMask & ~(
+        (pWal->readLock<0 ? 0 : (S << WAL_READ_LOCK(pWal->readLock)))
+        | (pWal->writeLock ? (E << WAL_WRITE_LOCK) : 0)
+        | (pWal->ckptLock ? (E << WAL_CKPT_LOCK) : 0)
+        );
+    for(ii=0; ii<SQLITE_SHM_NLOCK; ii++){
+      if( (S<<ii) & mUnlock ) walUnlockShared(pWal, ii);
+      if( (E<<ii) & mUnlock ) walUnlockExclusive(pWal, ii, 1);
+    }
+  }
+  sqlite3_free(pWal->pFree);
+  pWal->pFree = 0;
+  if( pWal->pWiValue ){
+    pWal->apWiData[pWal->iWiPg] = pWal->pWiValue;
+    pWal->pWiValue = 0;
+  }
+  return SQLITE_IOERR_IN_PAGE;
+}
+
+/*
+** Assert that the Wal.lockMask mask, which indicates the locks held
+** by the connenction, is consistent with the Wal.readLock, Wal.writeLock
+** and Wal.ckptLock variables. To be used as:
+**
+**   assert( walAssertLockmask(pWal) );
+*/
+static int walAssertLockmask(Wal *pWal){
+  if( pWal->exclusiveMode==0 ){
+    static const int S = 1;
+    static const int E = (1<<SQLITE_SHM_NLOCK);
+    u32 mExpect = (
+        (pWal->readLock<0 ? 0 : (S << WAL_READ_LOCK(pWal->readLock)))
+      | (pWal->writeLock ? (E << WAL_WRITE_LOCK) : 0)
+      | (pWal->ckptLock ? (E << WAL_CKPT_LOCK) : 0)
+#ifdef SQLITE_ENABLE_SNAPSHOT
+      | (pWal->pSnapshot ? (pWal->lockMask & (1 << WAL_CKPT_LOCK)) : 0)
+#endif
+    );
+    assert( mExpect==pWal->lockMask );
+  }
+  return 1;
+}
+
+/*
+** Return and zero the "system error" field set when an 
+** EXCEPTION_IN_PAGE_ERROR exception is caught.
+*/
+int sqlite3WalSystemErrno(Wal *pWal){
+  int iRet = 0;
+  if( pWal ){
+    iRet = pWal->iSysErrno;
+    pWal->iSysErrno = 0;
+  }
+  return iRet;
+}
+
+#else
+# define walAssertLockmask(x) 1
+#endif /* ifdef SQLITE_USE_SEH */
+
+/*
+** Close a connection to a log file.
+*/
+int sqlite3WalClose(
+  Wal *pWal,                      /* Wal to close */
+  sqlite3 *db,                    /* For interrupt flag */
+  int sync_flags,                 /* Flags to pass to OsSync() (or 0) */
+  int nBuf,
+  u8 *zBuf                        /* Buffer of at least nBuf bytes */
+){
+  int rc = SQLITE_OK;
+  if( pWal ){
+    int isDelete = 0;             /* True to unlink wal and wal-index files */
+
+    assert( walAssertLockmask(pWal) );
+
+    /* If an EXCLUSIVE lock can be obtained on the database file (using the
+    ** ordinary, rollback-mode locking methods, this guarantees that the
+    ** connection associated with this log file is the only connection to
+    ** the database. In this case checkpoint the database and unlink both
+    ** the wal and wal-index files.
+    **
+    ** The EXCLUSIVE lock is not released before returning.
+    */
+    if( zBuf!=0
+     && SQLITE_OK==(rc = sqlite3OsLock(pWal->pDbFd, SQLITE_LOCK_EXCLUSIVE))
+    ){
+      if( pWal->exclusiveMode==WAL_NORMAL_MODE ){
+        pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
+      }
+      rc = sqlite3WalCheckpoint(pWal, db,
+          SQLITE_CHECKPOINT_PASSIVE, 0, 0, sync_flags, nBuf, zBuf, 0, 0
+      );
+      if( rc==SQLITE_OK ){
+        int bPersist = -1;
+        sqlite3OsFileControlHint(
+            pWal->pDbFd, SQLITE_FCNTL_PERSIST_WAL, &bPersist
+        );
+        if( bPersist!=1 ){
+          /* Try to delete the WAL file if the checkpoint completed and
+          ** fsynced (rc==SQLITE_OK) and if we are not in persistent-wal
+          ** mode (!bPersist) */
+          isDelete = 1;
+        }else if( pWal->mxWalSize>=0 ){
+          /* Try to truncate the WAL file to zero bytes if the checkpoint
+          ** completed and fsynced (rc==SQLITE_OK) and we are in persistent
+          ** WAL mode (bPersist) and if the PRAGMA journal_size_limit is a
+          ** non-negative value (pWal->mxWalSize>=0).  Note that we truncate
+          ** to zero bytes as truncating to the journal_size_limit might
+          ** leave a corrupt WAL file on disk. */
+          walLimitSize(pWal, 0);
+        }
+      }
+    }
+
+    walIndexClose(pWal, isDelete);
+    sqlite3OsClose(pWal->pWalFd);
+    if( isDelete ){
+      sqlite3BeginBenignMalloc();
+      sqlite3OsDelete(pWal->pVfs, pWal->zWalName, 0);
+      sqlite3EndBenignMalloc();
+    }
+    WALTRACE(("WAL%p: closed\n", pWal));
+    sqlite3_free((void *)pWal->apWiData);
+    sqlite3_free(pWal);
+  }
+  return rc;
+}
+
+/*
+** Try to read the wal-index header.  Return 0 on success and 1 if
+** there is a problem.
+**
+** The wal-index is in shared memory.  Another thread or process might
+** be writing the header at the same time this procedure is trying to
+** read it, which might result in inconsistency.  A dirty read is detected
+** by verifying that both copies of the header are the same and also by
+** a checksum on the header.
+**
+** If and only if the read is consistent and the header is different from
+** pWal->hdr, then pWal->hdr is updated to the content of the new header
+** and *pChanged is set to 1.
+**
+** If the checksum cannot be verified return non-zero. If the header
+** is read successfully and the checksum verified, return zero.
+*/
+static SQLITE_NO_TSAN int walIndexTryHdr(Wal *pWal, int *pChanged){
+  u32 aCksum[2];                  /* Checksum on the header content */
+  WalIndexHdr h1, h2;             /* Two copies of the header content */
+  WalIndexHdr volatile *aHdr;     /* Header in shared memory */
+
+  /* The first page of the wal-index must be mapped at this point. */
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+
+  /* Read the header. This might happen concurrently with a write to the
+  ** same area of shared memory on a different CPU in a SMP,
+  ** meaning it is possible that an inconsistent snapshot is read
+  ** from the file. If this happens, return non-zero.
+  **
+  ** tag-20200519-1:
+  ** There are two copies of the header at the beginning of the wal-index.
+  ** When reading, read [0] first then [1].  Writes are in the reverse order.
+  ** Memory barriers are used to prevent the compiler or the hardware from
+  ** reordering the reads and writes.  TSAN and similar tools can sometimes
+  ** give false-positive warnings about these accesses because the tools do not
+  ** account for the double-read and the memory barrier. The use of mutexes
+  ** here would be problematic as the memory being accessed is potentially
+  ** shared among multiple processes and not all mutex implementations work
+  ** reliably in that environment.
+  */
+  aHdr = walIndexHdr(pWal);
+  memcpy(&h1, (void *)&aHdr[0], sizeof(h1)); /* Possible TSAN false-positive */
+  walShmBarrier(pWal);
+  memcpy(&h2, (void *)&aHdr[1], sizeof(h2));
+
+  if( memcmp(&h1, &h2, sizeof(h1))!=0 ){
+    return 1;   /* Dirty read */
+  }
+  if( h1.isInit==0 ){
+    return 1;   /* Malformed header - probably all zeros */
+  }
+  walChecksumBytes(1, (u8*)&h1, sizeof(h1)-sizeof(h1.aCksum), 0, aCksum);
+  if( aCksum[0]!=h1.aCksum[0] || aCksum[1]!=h1.aCksum[1] ){
+    return 1;   /* Checksum does not match */
+  }
+
+  if( memcmp(&pWal->hdr, &h1, sizeof(WalIndexHdr)) ){
+    *pChanged = 1;
+    memcpy(&pWal->hdr, &h1, sizeof(WalIndexHdr));
+    pWal->szPage = (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
+    testcase( pWal->szPage<=32768 );
+    testcase( pWal->szPage>=65536 );
+  }
+
+  /* The header was successfully read. Return zero. */
+  return 0;
+}
+
+/*
+** This is the value that walTryBeginRead returns when it needs to
+** be retried.
+*/
+#define WAL_RETRY  (-1)
+
+/*
+** Read the wal-index header from the wal-index and into pWal->hdr.
+** If the wal-header appears to be corrupt, try to reconstruct the
+** wal-index from the WAL before returning.
+**
+** Set *pChanged to 1 if the wal-index header value in pWal->hdr is
+** changed by this operation.  If pWal->hdr is unchanged, set *pChanged
+** to 0.
+**
+** If the wal-index header is successfully read, return SQLITE_OK.
+** Otherwise an SQLite error code.
+*/
+static int walIndexReadHdr(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int badHdr;                     /* True if a header read failed */
+  volatile u32 *page0;            /* Chunk of wal-index containing header */
+
+  /* Ensure that page 0 of the wal-index (the page that contains the
+  ** wal-index header) is mapped. Return early if an error occurs here.
+  */
+  assert( pChanged );
+  rc = walIndexPage(pWal, 0, &page0);
+  if( rc!=SQLITE_OK ){
+    assert( rc!=SQLITE_READONLY ); /* READONLY changed to OK in walIndexPage */
+    if( rc==SQLITE_READONLY_CANTINIT ){
+      /* The SQLITE_READONLY_CANTINIT return means that the shared-memory
+      ** was openable but is not writable, and this thread is unable to
+      ** confirm that another write-capable connection has the shared-memory
+      ** open, and hence the content of the shared-memory is unreliable,
+      ** since the shared-memory might be inconsistent with the WAL file
+      ** and there is no writer on hand to fix it. */
+      assert( page0==0 );
+      assert( pWal->writeLock==0 );
+      assert( pWal->readOnly & WAL_SHM_RDONLY );
+      pWal->bShmUnreliable = 1;
+      pWal->exclusiveMode = WAL_HEAPMEMORY_MODE;
+      *pChanged = 1;
+    }else{
+      return rc; /* Any other non-OK return is just an error */
+    }
+  }else{
+    /* page0 can be NULL if the SHM is zero bytes in size and pWal->writeLock
+    ** is zero, which prevents the SHM from growing */
+    testcase( page0!=0 );
+  }
+  assert( page0!=0 || pWal->writeLock==0 );
+
+  /* If the first page of the wal-index has been mapped, try to read the
+  ** wal-index header immediately, without holding any lock. This usually
+  ** works, but may fail if the wal-index header is corrupt or currently
+  ** being modified by another thread or process.
+  */
+  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);
+
+  /* If the first attempt failed, it might have been due to a race
+  ** with a writer.  So get a WRITE lock and try again.
+  */
+  if( badHdr ){
+    if( pWal->bShmUnreliable==0 && (pWal->readOnly & WAL_SHM_RDONLY) ){
+      if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){
+        walUnlockShared(pWal, WAL_WRITE_LOCK);
+        rc = SQLITE_READONLY_RECOVERY;
+      }
+    }else{
+      int bWriteLock = pWal->writeLock;
+      if( bWriteLock 
+       || SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) 
+      ){
+        pWal->writeLock = 1;
+        if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
+          badHdr = walIndexTryHdr(pWal, pChanged);
+          if( badHdr ){
+            /* If the wal-index header is still malformed even while holding
+            ** a WRITE lock, it can only mean that the header is corrupted and
+            ** needs to be reconstructed.  So run recovery to do exactly that.
+            ** Disable blocking locks first.  */
+            walDisableBlocking(pWal);
+            rc = walIndexRecover(pWal);
+            *pChanged = 1;
+          }
+        }
+        if( bWriteLock==0 ){
+          pWal->writeLock = 0;
+          walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+        }
+      }
+    }
+  }
+
+  /* If the header is read successfully, check the version number to make
+  ** sure the wal-index was not constructed with some future format that
+  ** this version of SQLite cannot understand.
+  */
+  if( badHdr==0 && pWal->hdr.iVersion!=WALINDEX_MAX_VERSION ){
+    rc = SQLITE_CANTOPEN_BKPT;
+  }
+  if( pWal->bShmUnreliable ){
+    if( rc!=SQLITE_OK ){
+      walIndexClose(pWal, 0);
+      pWal->bShmUnreliable = 0;
+      assert( pWal->nWiData>0 && pWal->apWiData[0]==0 );
+      /* walIndexRecover() might have returned SHORT_READ if a concurrent
+      ** writer truncated the WAL out from under it.  If that happens, it
+      ** indicates that a writer has fixed the SHM file for us, so retry */
+      if( rc==SQLITE_IOERR_SHORT_READ ) rc = WAL_RETRY;
+    }
+    pWal->exclusiveMode = WAL_NORMAL_MODE;
+  }
+
+  return rc;
+}
+
+/*
+** Open a transaction in a connection where the shared-memory is read-only
+** and where we cannot verify that there is a separate write-capable connection
+** on hand to keep the shared-memory up-to-date with the WAL file.
+**
+** This can happen, for example, when the shared-memory is implemented by
+** memory-mapping a *-shm file, where a prior writer has shut down and
+** left the *-shm file on disk, and now the present connection is trying
+** to use that database but lacks write permission on the *-shm file.
+** Other scenarios are also possible, depending on the VFS implementation.
+**
+** Precondition:
+**
+**    The *-wal file has been read and an appropriate wal-index has been
+**    constructed in pWal->apWiData[] using heap memory instead of shared
+**    memory.
+**
+** If this function returns SQLITE_OK, then the read transaction has
+** been successfully opened. In this case output variable (*pChanged)
+** is set to true before returning if the caller should discard the
+** contents of the page cache before proceeding. Or, if it returns
+** WAL_RETRY, then the heap memory wal-index has been discarded and
+** the caller should retry opening the read transaction from the
+** beginning (including attempting to map the *-shm file).
+**
+** If an error occurs, an SQLite error code is returned.
+*/
+static int walBeginShmUnreliable(Wal *pWal, int *pChanged){
+  i64 szWal;                      /* Size of wal file on disk in bytes */
+  i64 iOffset;                    /* Current offset when reading wal file */
+  u8 aBuf[WAL_HDRSIZE];           /* Buffer to load WAL header into */
+  u8 *aFrame = 0;                 /* Malloc'd buffer to load entire frame */
+  int szFrame;                    /* Number of bytes in buffer aFrame[] */
+  u8 *aData;                      /* Pointer to data part of aFrame buffer */
+  volatile void *pDummy;          /* Dummy argument for xShmMap */
+  int rc;                         /* Return code */
+  u32 aSaveCksum[2];              /* Saved copy of pWal->hdr.aFrameCksum */
+
+  assert( pWal->bShmUnreliable );
+  assert( pWal->readOnly & WAL_SHM_RDONLY );
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+
+  /* Take WAL_READ_LOCK(0). This has the effect of preventing any
+  ** writers from running a checkpoint, but does not stop them
+  ** from running recovery.  */
+  rc = walLockShared(pWal, WAL_READ_LOCK(0));
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_BUSY ) rc = WAL_RETRY;
+    goto begin_unreliable_shm_out;
+  }
+  pWal->readLock = 0;
+
+  /* Check to see if a separate writer has attached to the shared-memory area,
+  ** thus making the shared-memory "reliable" again.  Do this by invoking
+  ** the xShmMap() routine of the VFS and looking to see if the return
+  ** is SQLITE_READONLY instead of SQLITE_READONLY_CANTINIT.
+  **
+  ** If the shared-memory is now "reliable" return WAL_RETRY, which will
+  ** cause the heap-memory WAL-index to be discarded and the actual
+  ** shared memory to be used in its place.
+  **
+  ** This step is important because, even though this connection is holding
+  ** the WAL_READ_LOCK(0) which prevents a checkpoint, a writer might
+  ** have already checkpointed the WAL file and, while the current
+  ** is active, wrap the WAL and start overwriting frames that this
+  ** process wants to use.
+  **
+  ** Once sqlite3OsShmMap() has been called for an sqlite3_file and has
+  ** returned any SQLITE_READONLY value, it must return only SQLITE_READONLY
+  ** or SQLITE_READONLY_CANTINIT or some error for all subsequent invocations,
+  ** even if some external agent does a "chmod" to make the shared-memory
+  ** writable by us, until sqlite3OsShmUnmap() has been called.
+  ** This is a requirement on the VFS implementation.
+   */
+  rc = sqlite3OsShmMap(pWal->pDbFd, 0, WALINDEX_PGSZ, 0, &pDummy);
+  assert( rc!=SQLITE_OK ); /* SQLITE_OK not possible for read-only connection */
+  if( rc!=SQLITE_READONLY_CANTINIT ){
+    rc = (rc==SQLITE_READONLY ? WAL_RETRY : rc);
+    goto begin_unreliable_shm_out;
+  }
+
+  /* We reach this point only if the real shared-memory is still unreliable.
+  ** Assume the in-memory WAL-index substitute is correct and load it
+  ** into pWal->hdr.
+  */
+  memcpy(&pWal->hdr, (void*)walIndexHdr(pWal), sizeof(WalIndexHdr));
+
+  /* Make sure some writer hasn't come in and changed the WAL file out
+  ** from under us, then disconnected, while we were not looking.
+  */
+  rc = sqlite3OsFileSize(pWal->pWalFd, &szWal);
+  if( rc!=SQLITE_OK ){
+    goto begin_unreliable_shm_out;
+  }
+  if( szWal<WAL_HDRSIZE ){
+    /* If the wal file is too small to contain a wal-header and the
+    ** wal-index header has mxFrame==0, then it must be safe to proceed
+    ** reading the database file only. However, the page cache cannot
+    ** be trusted, as a read/write connection may have connected, written
+    ** the db, run a checkpoint, truncated the wal file and disconnected
+    ** since this client's last read transaction.  */
+    *pChanged = 1;
+    rc = (pWal->hdr.mxFrame==0 ? SQLITE_OK : WAL_RETRY);
+    goto begin_unreliable_shm_out;
+  }
+
+  /* Check the salt keys at the start of the wal file still match. */
+  rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
+  if( rc!=SQLITE_OK ){
+    goto begin_unreliable_shm_out;
+  }
+  if( memcmp(&pWal->hdr.aSalt, &aBuf[16], 8) ){
+    /* Some writer has wrapped the WAL file while we were not looking.
+    ** Return WAL_RETRY which will cause the in-memory WAL-index to be
+    ** rebuilt. */
+    rc = WAL_RETRY;
+    goto begin_unreliable_shm_out;
+  }
+
+  /* Allocate a buffer to read frames into */
+  assert( (pWal->szPage & (pWal->szPage-1))==0 );
+  assert( pWal->szPage>=512 && pWal->szPage<=65536 );
+  szFrame = pWal->szPage + WAL_FRAME_HDRSIZE;
+  aFrame = (u8 *)sqlite3_malloc64(szFrame);
+  if( aFrame==0 ){
+    rc = SQLITE_NOMEM_BKPT;
+    goto begin_unreliable_shm_out;
+  }
+  aData = &aFrame[WAL_FRAME_HDRSIZE];
+
+  /* Check to see if a complete transaction has been appended to the
+  ** wal file since the heap-memory wal-index was created. If so, the
+  ** heap-memory wal-index is discarded and WAL_RETRY returned to
+  ** the caller.  */
+  aSaveCksum[0] = pWal->hdr.aFrameCksum[0];
+  aSaveCksum[1] = pWal->hdr.aFrameCksum[1];
+  for(iOffset=walFrameOffset(pWal->hdr.mxFrame+1, pWal->szPage);
+      iOffset+szFrame<=szWal;
+      iOffset+=szFrame
+  ){
+    u32 pgno;                   /* Database page number for frame */
+    u32 nTruncate;              /* dbsize field from frame header */
+
+    /* Read and decode the next log frame. */
+    rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
+    if( rc!=SQLITE_OK ) break;
+    if( !walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame) ) break;
+
+    /* If nTruncate is non-zero, then a complete transaction has been
+    ** appended to this wal file. Set rc to WAL_RETRY and break out of
+    ** the loop.  */
+    if( nTruncate ){
+      rc = WAL_RETRY;
+      break;
+    }
+  }
+  pWal->hdr.aFrameCksum[0] = aSaveCksum[0];
+  pWal->hdr.aFrameCksum[1] = aSaveCksum[1];
+
+ begin_unreliable_shm_out:
+  sqlite3_free(aFrame);
+  if( rc!=SQLITE_OK ){
+    int i;
+    for(i=0; i<pWal->nWiData; i++){
+      sqlite3_free((void*)pWal->apWiData[i]);
+      pWal->apWiData[i] = 0;
+    }
+    pWal->bShmUnreliable = 0;
+    sqlite3WalEndReadTransaction(pWal);
+    *pChanged = 1;
+  }
+  return rc;
+}
+
+/*
+** The final argument passed to walTryBeginRead() is of type (int*). The
+** caller should invoke walTryBeginRead as follows:
+**
+**   int cnt = 0;
+**   do {
+**     rc = walTryBeginRead(..., &cnt);
+**   }while( rc==WAL_RETRY );
+**
+** The final value of "cnt" is of no use to the caller. It is used by
+** the implementation of walTryBeginRead() as follows:
+**
+**   + Each time walTryBeginRead() is called, it is incremented. Once
+**     it reaches WAL_RETRY_PROTOCOL_LIMIT - indicating that walTryBeginRead()
+**     has many times been invoked and failed with WAL_RETRY - walTryBeginRead()
+**     returns SQLITE_PROTOCOL.
+**
+**   + If SQLITE_ENABLE_SETLK_TIMEOUT is defined and walTryBeginRead() failed
+**     because a blocking lock timed out (SQLITE_BUSY_TIMEOUT from the OS
+**     layer), the WAL_RETRY_BLOCKED_MASK bit is set in "cnt". In this case
+**     the next invocation of walTryBeginRead() may omit an expected call to 
+**     sqlite3OsSleep(). There has already been a delay when the previous call
+**     waited on a lock.
+*/
+#define WAL_RETRY_PROTOCOL_LIMIT 100
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+# define WAL_RETRY_BLOCKED_MASK    0x10000000
+#else
+# define WAL_RETRY_BLOCKED_MASK    0
+#endif
+
+/*
+** Attempt to start a read transaction.  This might fail due to a race or
+** other transient condition.  When that happens, it returns WAL_RETRY to
+** indicate to the caller that it is safe to retry immediately.
+**
+** On success return SQLITE_OK.  On a permanent failure (such an
+** I/O error or an SQLITE_BUSY because another process is running
+** recovery) return a positive error code.
+**
+** The useWal parameter is true to force the use of the WAL and disable
+** the case where the WAL is bypassed because it has been completely
+** checkpointed.  If useWal==0 then this routine calls walIndexReadHdr()
+** to make a copy of the wal-index header into pWal->hdr.  If the
+** wal-index header has changed, *pChanged is set to 1 (as an indication
+** to the caller that the local page cache is obsolete and needs to be
+** flushed.)  When useWal==1, the wal-index header is assumed to already
+** be loaded and the pChanged parameter is unused.
+**
+** The caller must set the cnt parameter to the number of prior calls to
+** this routine during the current read attempt that returned WAL_RETRY.
+** This routine will start taking more aggressive measures to clear the
+** race conditions after multiple WAL_RETRY returns, and after an excessive
+** number of errors will ultimately return SQLITE_PROTOCOL.  The
+** SQLITE_PROTOCOL return indicates that some other process has gone rogue
+** and is not honoring the locking protocol.  There is a vanishingly small
+** chance that SQLITE_PROTOCOL could be returned because of a run of really
+** bad luck when there is lots of contention for the wal-index, but that
+** possibility is so small that it can be safely neglected, we believe.
+**
+** On success, this routine obtains a read lock on
+** WAL_READ_LOCK(pWal->readLock).  The pWal->readLock integer is
+** in the range 0 <= pWal->readLock < WAL_NREADER.  If pWal->readLock==(-1)
+** that means the Wal does not hold any read lock.  The reader must not
+** access any database page that is modified by a WAL frame up to and
+** including frame number aReadMark[pWal->readLock].  The reader will
+** use WAL frames up to and including pWal->hdr.mxFrame if pWal->readLock>0
+** Or if pWal->readLock==0, then the reader will ignore the WAL
+** completely and get all content directly from the database file.
+** If the useWal parameter is 1 then the WAL will never be ignored and
+** this routine will always set pWal->readLock>0 on success.
+** When the read transaction is completed, the caller must release the
+** lock on WAL_READ_LOCK(pWal->readLock) and set pWal->readLock to -1.
+**
+** This routine uses the nBackfill and aReadMark[] fields of the header
+** to select a particular WAL_READ_LOCK() that strives to let the
+** checkpoint process do as much work as possible.  This routine might
+** update values of the aReadMark[] array in the header, but if it does
+** so it takes care to hold an exclusive lock on the corresponding
+** WAL_READ_LOCK() while changing values.
+*/
+static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int *pCnt){
+  volatile WalCkptInfo *pInfo;    /* Checkpoint information in wal-index */
+  u32 mxReadMark;                 /* Largest aReadMark[] value */
+  int mxI;                        /* Index of largest aReadMark[] value */
+  int i;                          /* Loop counter */
+  int rc = SQLITE_OK;             /* Return code  */
+  u32 mxFrame;                    /* Wal frame to lock to */
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  int nBlockTmout = 0;
+#endif
+
+  assert( pWal->readLock<0 );     /* Not currently locked */
+
+  /* useWal may only be set for read/write connections */
+  assert( (pWal->readOnly & WAL_SHM_RDONLY)==0 || useWal==0 );
+
+  /* Take steps to avoid spinning forever if there is a protocol error.
+  **
+  ** Circumstances that cause a RETRY should only last for the briefest
+  ** instances of time.  No I/O or other system calls are done while the
+  ** locks are held, so the locks should not be held for very long. But
+  ** if we are unlucky, another process that is holding a lock might get
+  ** paged out or take a page-fault that is time-consuming to resolve,
+  ** during the few nanoseconds that it is holding the lock.  In that case,
+  ** it might take longer than normal for the lock to free.
+  **
+  ** After 5 RETRYs, we begin calling sqlite3OsSleep().  The first few
+  ** calls to sqlite3OsSleep() have a delay of 1 microsecond.  Really this
+  ** is more of a scheduler yield than an actual delay.  But on the 10th
+  ** an subsequent retries, the delays start becoming longer and longer,
+  ** so that on the 100th (and last) RETRY we delay for 323 milliseconds.
+  ** The total delay time before giving up is less than 10 seconds.
+  */
+  (*pCnt)++;
+  if( *pCnt>5 ){
+    int nDelay = 1;                      /* Pause time in microseconds */
+    int cnt = (*pCnt & ~WAL_RETRY_BLOCKED_MASK);
+    if( cnt>WAL_RETRY_PROTOCOL_LIMIT ){
+      VVA_ONLY( pWal->lockError = 1; )
+      return SQLITE_PROTOCOL;
+    }
+    if( *pCnt>=10 ) nDelay = (cnt-9)*(cnt-9)*39;
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    /* In SQLITE_ENABLE_SETLK_TIMEOUT builds, configure the file-descriptor
+    ** to block for locks for approximately nDelay us. This affects three
+    ** locks: (a) the shared lock taken on the DMS slot in os_unix.c (if
+    ** using os_unix.c), (b) the WRITER lock taken in walIndexReadHdr() if the
+    ** first attempted read fails, and (c) the shared lock taken on the 
+    ** read-mark.  
+    **
+    ** If the previous call failed due to an SQLITE_BUSY_TIMEOUT error,
+    ** then sleep for the minimum of 1us. The previous call already provided 
+    ** an extra delay while it was blocking on the lock.
+    */
+    nBlockTmout = (nDelay+998) / 1000;
+    if( !useWal && walEnableBlockingMs(pWal, nBlockTmout) ){
+      if( *pCnt & WAL_RETRY_BLOCKED_MASK ) nDelay = 1;
+    }
+#endif
+    sqlite3OsSleep(pWal->pVfs, nDelay);
+    *pCnt &= ~WAL_RETRY_BLOCKED_MASK;
+  }
+
+  if( !useWal ){
+    assert( rc==SQLITE_OK );
+    if( pWal->bShmUnreliable==0 ){
+      rc = walIndexReadHdr(pWal, pChanged);
+    }
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    walDisableBlocking(pWal);
+    if( rc==SQLITE_BUSY_TIMEOUT ){
+      rc = SQLITE_BUSY;
+      *pCnt |= WAL_RETRY_BLOCKED_MASK;
+    }
+#endif
+    if( rc==SQLITE_BUSY ){
+      /* If there is not a recovery running in another thread or process
+      ** then convert BUSY errors to WAL_RETRY.  If recovery is known to
+      ** be running, convert BUSY to BUSY_RECOVERY.  There is a race here
+      ** which might cause WAL_RETRY to be returned even if BUSY_RECOVERY
+      ** would be technically correct.  But the race is benign since with
+      ** WAL_RETRY this routine will be called again and will probably be
+      ** right on the second iteration.
+      */
+      if( pWal->apWiData[0]==0 ){
+        /* This branch is taken when the xShmMap() method returns SQLITE_BUSY.
+        ** We assume this is a transient condition, so return WAL_RETRY. The
+        ** xShmMap() implementation used by the default unix and win32 VFS
+        ** modules may return SQLITE_BUSY due to a race condition in the
+        ** code that determines whether or not the shared-memory region
+        ** must be zeroed before the requested page is returned.
+        */
+        rc = WAL_RETRY;
+      }else if( SQLITE_OK==(rc = walLockShared(pWal, WAL_RECOVER_LOCK)) ){
+        walUnlockShared(pWal, WAL_RECOVER_LOCK);
+        rc = WAL_RETRY;
+      }else if( rc==SQLITE_BUSY ){
+        rc = SQLITE_BUSY_RECOVERY;
+      }
+    }
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    else if( pWal->bShmUnreliable ){
+      return walBeginShmUnreliable(pWal, pChanged);
+    }
+  }
+
+  assert( pWal->nWiData>0 );
+  assert( pWal->apWiData[0]!=0 );
+  pInfo = walCkptInfo(pWal);
+  SEH_INJECT_FAULT;
+  if( !useWal && AtomicLoad(&pInfo->nBackfill)==pWal->hdr.mxFrame
+#ifdef SQLITE_ENABLE_SNAPSHOT
+   && (pWal->pSnapshot==0 || pWal->hdr.mxFrame==0)
+#endif
+  ){
+    /* The WAL has been completely backfilled (or it is empty).
+    ** and can be safely ignored.
+    */
+    rc = walLockShared(pWal, WAL_READ_LOCK(0));
+    walShmBarrier(pWal);
+    if( rc==SQLITE_OK ){
+      if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){
+        /* It is not safe to allow the reader to continue here if frames
+        ** may have been appended to the log before READ_LOCK(0) was obtained.
+        ** When holding READ_LOCK(0), the reader ignores the entire log file,
+        ** which implies that the database file contains a trustworthy
+        ** snapshot. Since holding READ_LOCK(0) prevents a checkpoint from
+        ** happening, this is usually correct.
+        **
+        ** However, if frames have been appended to the log (or if the log
+        ** is wrapped and written for that matter) before the READ_LOCK(0)
+        ** is obtained, that is not necessarily true. A checkpointer may
+        ** have started to backfill the appended frames but crashed before
+        ** it finished. Leaving a corrupt image in the database file.
+        */
+        walUnlockShared(pWal, WAL_READ_LOCK(0));
+        return WAL_RETRY;
+      }
+      pWal->readLock = 0;
+      return SQLITE_OK;
+    }else if( rc!=SQLITE_BUSY ){
+      return rc;
+    }
+  }
+
+  /* If we get this far, it means that the reader will want to use
+  ** the WAL to get at content from recent commits.  The job now is
+  ** to select one of the aReadMark[] entries that is closest to
+  ** but not exceeding pWal->hdr.mxFrame and lock that entry.
+  */
+  mxReadMark = 0;
+  mxI = 0;
+  mxFrame = pWal->hdr.mxFrame;
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  if( pWal->pSnapshot && pWal->pSnapshot->mxFrame<mxFrame ){
+    mxFrame = pWal->pSnapshot->mxFrame;
+  }
+#endif
+  for(i=1; i<WAL_NREADER; i++){
+    u32 thisMark = AtomicLoad(pInfo->aReadMark+i); SEH_INJECT_FAULT;
+    if( mxReadMark<=thisMark && thisMark<=mxFrame ){
+      assert( thisMark!=READMARK_NOT_USED );
+      mxReadMark = thisMark;
+      mxI = i;
+    }
+  }
+  if( (pWal->readOnly & WAL_SHM_RDONLY)==0
+   && (mxReadMark<mxFrame || mxI==0)
+  ){
+    for(i=1; i<WAL_NREADER; i++){
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      if( rc==SQLITE_OK ){
+        AtomicStore(pInfo->aReadMark+i,mxFrame);
+        mxReadMark = mxFrame;
+        mxI = i;
+        walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+        break;
+      }else if( rc!=SQLITE_BUSY ){
+        return rc;
+      }
+    }
+  }
+  if( mxI==0 ){
+    assert( rc==SQLITE_BUSY || (pWal->readOnly & WAL_SHM_RDONLY)!=0 );
+    return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTINIT;
+  }
+
+  (void)walEnableBlockingMs(pWal, nBlockTmout);
+  rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
+  walDisableBlocking(pWal);
+  if( rc ){
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+    if( rc==SQLITE_BUSY_TIMEOUT ){
+      *pCnt |= WAL_RETRY_BLOCKED_MASK;
+    }
+#else
+    assert( rc!=SQLITE_BUSY_TIMEOUT );
+#endif
+    assert( (rc&0xFF)!=SQLITE_BUSY||rc==SQLITE_BUSY||rc==SQLITE_BUSY_TIMEOUT );
+    return (rc&0xFF)==SQLITE_BUSY ? WAL_RETRY : rc;
+  }
+  /* Now that the read-lock has been obtained, check that neither the
+  ** value in the aReadMark[] array or the contents of the wal-index
+  ** header have changed.
+  **
+  ** It is necessary to check that the wal-index header did not change
+  ** between the time it was read and when the shared-lock was obtained
+  ** on WAL_READ_LOCK(mxI) was obtained to account for the possibility
+  ** that the log file may have been wrapped by a writer, or that frames
+  ** that occur later in the log than pWal->hdr.mxFrame may have been
+  ** copied into the database by a checkpointer. If either of these things
+  ** happened, then reading the database with the current value of
+  ** pWal->hdr.mxFrame risks reading a corrupted snapshot. So, retry
+  ** instead.
+  **
+  ** Before checking that the live wal-index header has not changed
+  ** since it was read, set Wal.minFrame to the first frame in the wal
+  ** file that has not yet been checkpointed. This client will not need
+  ** to read any frames earlier than minFrame from the wal file - they
+  ** can be safely read directly from the database file.
+  **
+  ** Because a ShmBarrier() call is made between taking the copy of
+  ** nBackfill and checking that the wal-header in shared-memory still
+  ** matches the one cached in pWal->hdr, it is guaranteed that the
+  ** checkpointer that set nBackfill was not working with a wal-index
+  ** header newer than that cached in pWal->hdr. If it were, that could
+  ** cause a problem. The checkpointer could omit to checkpoint
+  ** a version of page X that lies before pWal->minFrame (call that version
+  ** A) on the basis that there is a newer version (version B) of the same
+  ** page later in the wal file. But if version B happens to like past
+  ** frame pWal->hdr.mxFrame - then the client would incorrectly assume
+  ** that it can read version A from the database file. However, since
+  ** we can guarantee that the checkpointer that set nBackfill could not
+  ** see any pages past pWal->hdr.mxFrame, this problem does not come up.
+  */
+  pWal->minFrame = AtomicLoad(&pInfo->nBackfill)+1; SEH_INJECT_FAULT;
+  walShmBarrier(pWal);
+  if( AtomicLoad(pInfo->aReadMark+mxI)!=mxReadMark
+   || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
+  ){
+    walUnlockShared(pWal, WAL_READ_LOCK(mxI));
+    return WAL_RETRY;
+  }else{
+    assert( mxReadMark<=pWal->hdr.mxFrame );
+    pWal->readLock = (i16)mxI;
+  }
+  return rc;
+}
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** This function does the work of sqlite3WalSnapshotRecover().
+*/
+static int walSnapshotRecover(
+  Wal *pWal,                      /* WAL handle */
+  void *pBuf1,                    /* Temp buffer pWal->szPage bytes in size */
+  void *pBuf2                     /* Temp buffer pWal->szPage bytes in size */
+){
+  int szPage = (int)pWal->szPage;
+  int rc;
+  i64 szDb;                       /* Size of db file in bytes */
+
+  rc = sqlite3OsFileSize(pWal->pDbFd, &szDb);
+  if( rc==SQLITE_OK ){
+    volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+    u32 i = pInfo->nBackfillAttempted;
+    for(i=pInfo->nBackfillAttempted; i>AtomicLoad(&pInfo->nBackfill); i--){
+      WalHashLoc sLoc;          /* Hash table location */
+      u32 pgno;                 /* Page number in db file */
+      i64 iDbOff;               /* Offset of db file entry */
+      i64 iWalOff;              /* Offset of wal file entry */
+
+      rc = walHashGet(pWal, walFramePage(i), &sLoc);
+      if( rc!=SQLITE_OK ) break;
+      assert( i - sLoc.iZero - 1 >=0 );
+      pgno = sLoc.aPgno[i-sLoc.iZero-1];
+      iDbOff = (i64)(pgno-1) * szPage;
+
+      if( iDbOff+szPage<=szDb ){
+        iWalOff = walFrameOffset(i, szPage) + WAL_FRAME_HDRSIZE;
+        rc = sqlite3OsRead(pWal->pWalFd, pBuf1, szPage, iWalOff);
+
+        if( rc==SQLITE_OK ){
+          rc = sqlite3OsRead(pWal->pDbFd, pBuf2, szPage, iDbOff);
+        }
+
+        if( rc!=SQLITE_OK || 0==memcmp(pBuf1, pBuf2, szPage) ){
+          break;
+        }
+      }
+
+      pInfo->nBackfillAttempted = i-1;
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Attempt to reduce the value of the WalCkptInfo.nBackfillAttempted
+** variable so that older snapshots can be accessed. To do this, loop
+** through all wal frames from nBackfillAttempted to (nBackfill+1),
+** comparing their content to the corresponding page with the database
+** file, if any. Set nBackfillAttempted to the frame number of the
+** first frame for which the wal file content matches the db file.
+**
+** This is only really safe if the file-system is such that any page
+** writes made by earlier checkpointers were atomic operations, which
+** is not always true. It is also possible that nBackfillAttempted
+** may be left set to a value larger than expected, if a wal frame
+** contains content that duplicate of an earlier version of the same
+** page.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code if an
+** error occurs. It is not an error if nBackfillAttempted cannot be
+** decreased at all.
+*/
+int sqlite3WalSnapshotRecover(Wal *pWal){
+  int rc;
+
+  assert( pWal->readLock>=0 );
+  rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  if( rc==SQLITE_OK ){
+    void *pBuf1 = sqlite3_malloc(pWal->szPage);
+    void *pBuf2 = sqlite3_malloc(pWal->szPage);
+    if( pBuf1==0 || pBuf2==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      pWal->ckptLock = 1;
+      SEH_TRY {
+        rc = walSnapshotRecover(pWal, pBuf1, pBuf2);
+      }
+      SEH_EXCEPT( rc = SQLITE_IOERR_IN_PAGE; )
+      pWal->ckptLock = 0;
+    }
+
+    sqlite3_free(pBuf1);
+    sqlite3_free(pBuf2);
+    walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  }
+
+  return rc;
+}
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+/*
+** This function does the work of sqlite3WalBeginReadTransaction() (see 
+** below). That function simply calls this one inside an SEH_TRY{...} block.
+*/
+static int walBeginReadTransaction(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int cnt = 0;                    /* Number of TryBeginRead attempts */
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  int ckptLock = 0;
+  int bChanged = 0;
+  WalIndexHdr *pSnapshot = pWal->pSnapshot;
+#endif
+
+  assert( pWal->ckptLock==0 );
+  assert( pWal->nSehTry>0 );
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  if( pSnapshot ){
+    if( memcmp(pSnapshot, &pWal->hdr, sizeof(WalIndexHdr))!=0 ){
+      bChanged = 1;
+    }
+
+    /* It is possible that there is a checkpointer thread running
+    ** concurrent with this code. If this is the case, it may be that the
+    ** checkpointer has already determined that it will checkpoint
+    ** snapshot X, where X is later in the wal file than pSnapshot, but
+    ** has not yet set the pInfo->nBackfillAttempted variable to indicate
+    ** its intent. To avoid the race condition this leads to, ensure that
+    ** there is no checkpointer process by taking a shared CKPT lock
+    ** before checking pInfo->nBackfillAttempted.  */
+    (void)walEnableBlocking(pWal);
+    rc = walLockShared(pWal, WAL_CKPT_LOCK);
+    walDisableBlocking(pWal);
+
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    ckptLock = 1;
+  }
+#endif
+
+  do{
+    rc = walTryBeginRead(pWal, pChanged, 0, &cnt);
+  }while( rc==WAL_RETRY );
+  testcase( (rc&0xff)==SQLITE_BUSY );
+  testcase( (rc&0xff)==SQLITE_IOERR );
+  testcase( rc==SQLITE_PROTOCOL );
+  testcase( rc==SQLITE_OK );
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+  if( rc==SQLITE_OK ){
+    if( pSnapshot && memcmp(pSnapshot, &pWal->hdr, sizeof(WalIndexHdr))!=0 ){
+      /* At this point the client has a lock on an aReadMark[] slot holding
+      ** a value equal to or smaller than pSnapshot->mxFrame, but pWal->hdr
+      ** is populated with the wal-index header corresponding to the head
+      ** of the wal file. Verify that pSnapshot is still valid before
+      ** continuing.  Reasons why pSnapshot might no longer be valid:
+      **
+      **    (1)  The WAL file has been reset since the snapshot was taken.
+      **         In this case, the salt will have changed.
+      **
+      **    (2)  A checkpoint as been attempted that wrote frames past
+      **         pSnapshot->mxFrame into the database file.  Note that the
+      **         checkpoint need not have completed for this to cause problems.
+      */
+      volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+
+      assert( pWal->readLock>0 || pWal->hdr.mxFrame==0 );
+      assert( pInfo->aReadMark[pWal->readLock]<=pSnapshot->mxFrame );
+
+      /* Check that the wal file has not been wrapped. Assuming that it has
+      ** not, also check that no checkpointer has attempted to checkpoint any
+      ** frames beyond pSnapshot->mxFrame. If either of these conditions are
+      ** true, return SQLITE_ERROR_SNAPSHOT. Otherwise, overwrite pWal->hdr
+      ** with *pSnapshot and set *pChanged as appropriate for opening the
+      ** snapshot.  */
+      if( !memcmp(pSnapshot->aSalt, pWal->hdr.aSalt, sizeof(pWal->hdr.aSalt))
+       && pSnapshot->mxFrame>=pInfo->nBackfillAttempted
+      ){
+        assert( pWal->readLock>0 );
+        memcpy(&pWal->hdr, pSnapshot, sizeof(WalIndexHdr));
+        *pChanged = bChanged;
+      }else{
+        rc = SQLITE_ERROR_SNAPSHOT;
+      }
+
+      /* A client using a non-current snapshot may not ignore any frames
+      ** from the start of the wal file. This is because, for a system
+      ** where (minFrame < iSnapshot < maxFrame), a checkpointer may
+      ** have omitted to checkpoint a frame earlier than minFrame in
+      ** the file because there exists a frame after iSnapshot that
+      ** is the same database page.  */
+      pWal->minFrame = 1;
+
+      if( rc!=SQLITE_OK ){
+        sqlite3WalEndReadTransaction(pWal);
+      }
+    }
+  }
+
+  /* Release the shared CKPT lock obtained above. */
+  if( ckptLock ){
+    assert( pSnapshot );
+    walUnlockShared(pWal, WAL_CKPT_LOCK);
+  }
+#endif
+  return rc;
+}
+
+/*
+** Begin a read transaction on the database.
+**
+** This routine used to be called sqlite3OpenSnapshot() and with good reason:
+** it takes a snapshot of the state of the WAL and wal-index for the current
+** instant in time.  The current thread will continue to use this snapshot.
+** Other threads might append new content to the WAL and wal-index but
+** that extra content is ignored by the current thread.
+**
+** If the database contents have changes since the previous read
+** transaction, then *pChanged is set to 1 before returning.  The
+** Pager layer will use this to know that its cache is stale and
+** needs to be flushed.
+*/
+int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
+  int rc;
+  SEH_TRY {
+    rc = walBeginReadTransaction(pWal, pChanged);
+  }
+  SEH_EXCEPT( rc = walHandleException(pWal); )
+  return rc;
+}
+
+/*
+** Finish with a read transaction.  All this does is release the
+** read-lock.
+*/
+void sqlite3WalEndReadTransaction(Wal *pWal){
+  sqlite3WalEndWriteTransaction(pWal);
+  if( pWal->readLock>=0 ){
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->readLock = -1;
+  }
+}
+
+/*
+** Search the wal file for page pgno. If found, set *piRead to the frame that
+** contains the page. Otherwise, if pgno is not in the wal file, set *piRead
+** to zero.
+**
+** Return SQLITE_OK if successful, or an error code if an error occurs. If an
+** error does occur, the final value of *piRead is undefined.
+*/
+static int walFindFrame(
+  Wal *pWal,                      /* WAL handle */
+  Pgno pgno,                      /* Database page number to read data for */
+  u32 *piRead                     /* OUT: Frame number (or zero) */
+){
+  u32 iRead = 0;                  /* If !=0, WAL frame to return data from */
+  u32 iLast = pWal->hdr.mxFrame;  /* Last page in WAL for this reader */
+  int iHash;                      /* Used to loop through N hash tables */
+  int iMinHash;
+
+  /* This routine is only be called from within a read transaction. */
+  assert( pWal->readLock>=0 || pWal->lockError );
+
+  /* If the "last page" field of the wal-index header snapshot is 0, then
+  ** no data will be read from the wal under any circumstances. Return early
+  ** in this case as an optimization.  Likewise, if pWal->readLock==0,
+  ** then the WAL is ignored by the reader so return early, as if the
+  ** WAL were empty.
+  */
+  if( iLast==0 || (pWal->readLock==0 && pWal->bShmUnreliable==0) ){
+    *piRead = 0;
+    return SQLITE_OK;
+  }
+
+  /* Search the hash table or tables for an entry matching page number
+  ** pgno. Each iteration of the following for() loop searches one
+  ** hash table (each hash table indexes up to HASHTABLE_NPAGE frames).
+  **
+  ** This code might run concurrently to the code in walIndexAppend()
+  ** that adds entries to the wal-index (and possibly to this hash
+  ** table). This means the value just read from the hash
+  ** slot (aHash[iKey]) may have been added before or after the
+  ** current read transaction was opened. Values added after the
+  ** read transaction was opened may have been written incorrectly -
+  ** i.e. these slots may contain garbage data. However, we assume
+  ** that any slots written before the current read transaction was
+  ** opened remain unmodified.
+  **
+  ** For the reasons above, the if(...) condition featured in the inner
+  ** loop of the following block is more stringent that would be required
+  ** if we had exclusive access to the hash-table:
+  **
+  **   (aPgno[iFrame]==pgno):
+  **     This condition filters out normal hash-table collisions.
+  **
+  **   (iFrame<=iLast):
+  **     This condition filters out entries that were added to the hash
+  **     table after the current read-transaction had started.
+  */
+  iMinHash = walFramePage(pWal->minFrame);
+  for(iHash=walFramePage(iLast); iHash>=iMinHash; iHash--){
+    WalHashLoc sLoc;              /* Hash table location */
+    int iKey;                     /* Hash slot index */
+    int nCollide;                 /* Number of hash collisions remaining */
+    int rc;                       /* Error code */
+    u32 iH;
+
+    rc = walHashGet(pWal, iHash, &sLoc);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    nCollide = HASHTABLE_NSLOT;
+    iKey = walHash(pgno);
+    SEH_INJECT_FAULT;
+    while( (iH = AtomicLoad(&sLoc.aHash[iKey]))!=0 ){
+      u32 iFrame = iH + sLoc.iZero;
+      if( iFrame<=iLast && iFrame>=pWal->minFrame && sLoc.aPgno[iH-1]==pgno ){
+        assert( iFrame>iRead || CORRUPT_DB );
+        iRead = iFrame;
+      }
+      if( (nCollide--)==0 ){
+        *piRead = 0;
+        return SQLITE_CORRUPT_BKPT;
+      }
+      iKey = walNextHash(iKey);
+    }
+    if( iRead ) break;
+  }
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* If expensive assert() statements are available, do a linear search
+  ** of the wal-index file content. Make sure the results agree with the
+  ** result obtained using the hash indexes above.  */
+  {
+    u32 iRead2 = 0;
+    u32 iTest;
+    assert( pWal->bShmUnreliable || pWal->minFrame>0 );
+    for(iTest=iLast; iTest>=pWal->minFrame && iTest>0; iTest--){
+      if( walFramePgno(pWal, iTest)==pgno ){
+        iRead2 = iTest;
+        break;
+      }
+    }
+    assert( iRead==iRead2 );
+  }
+#endif
+
+  *piRead = iRead;
+  return SQLITE_OK;
+}
+
+/*
+** Search the wal file for page pgno. If found, set *piRead to the frame that
+** contains the page. Otherwise, if pgno is not in the wal file, set *piRead
+** to zero.
+**
+** Return SQLITE_OK if successful, or an error code if an error occurs. If an
+** error does occur, the final value of *piRead is undefined.
+**
+** The difference between this function and walFindFrame() is that this
+** function wraps walFindFrame() in an SEH_TRY{...} block.
+*/
+int sqlite3WalFindFrame(
+  Wal *pWal,                      /* WAL handle */
+  Pgno pgno,                      /* Database page number to read data for */
+  u32 *piRead                     /* OUT: Frame number (or zero) */
+){
+  int rc;
+  SEH_TRY {
+    rc = walFindFrame(pWal, pgno, piRead);
+  }
+  SEH_EXCEPT( rc = SQLITE_IOERR_IN_PAGE; )
+  return rc;
+}
+
+/*
+** Read the contents of frame iRead from the wal file into buffer pOut
+** (which is nOut bytes in size). Return SQLITE_OK if successful, or an
+** error code otherwise.
+*/
+int sqlite3WalReadFrame(
+  Wal *pWal,                      /* WAL handle */
+  u32 iRead,                      /* Frame to read */
+  int nOut,                       /* Size of buffer pOut in bytes */
+  u8 *pOut                        /* Buffer to write page data to */
+){
+  int sz;
+  i64 iOffset;
+  sz = pWal->hdr.szPage;
+  sz = (sz&0xfe00) + ((sz&0x0001)<<16);
+  testcase( sz<=32768 );
+  testcase( sz>=65536 );
+  iOffset = walFrameOffset(iRead, sz) + WAL_FRAME_HDRSIZE;
+  /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL */
+  return sqlite3OsRead(pWal->pWalFd, pOut, (nOut>sz ? sz : nOut), iOffset);
+}
+
+/*
+** Return the size of the database in pages (or zero, if unknown).
+*/
+Pgno sqlite3WalDbsize(Wal *pWal){
+  if( pWal && ALWAYS(pWal->readLock>=0) ){
+    return pWal->hdr.nPage;
+  }
+  return 0;
+}
+
+
+/*
+** This function starts a write transaction on the WAL.
+**
+** A read transaction must have already been started by a prior call
+** to sqlite3WalBeginReadTransaction().
+**
+** If another thread or process has written into the database since
+** the read transaction was started, then it is not possible for this
+** thread to write as doing so would cause a fork.  So this routine
+** returns SQLITE_BUSY in that case and no write transaction is started.
+**
+** There can only be a single writer active at a time.
+*/
+int sqlite3WalBeginWriteTransaction(Wal *pWal){
+  int rc;
+
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  /* If the write-lock is already held, then it was obtained before the
+  ** read-transaction was even opened, making this call a no-op.
+  ** Return early. */
+  if( pWal->writeLock ){
+    assert( !memcmp(&pWal->hdr,(void *)walIndexHdr(pWal),sizeof(WalIndexHdr)) );
+    return SQLITE_OK;
+  }
+#endif
+
+  /* Cannot start a write transaction without first holding a read
+  ** transaction. */
+  assert( pWal->readLock>=0 );
+  assert( pWal->writeLock==0 && pWal->iReCksum==0 );
+
+  if( pWal->readOnly ){
+    return SQLITE_READONLY;
+  }
+
+  /* Only one writer allowed at a time.  Get the write lock.  Return
+  ** SQLITE_BUSY if unable.
+  */
+  rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  if( rc ){
+    return rc;
+  }
+  pWal->writeLock = 1;
+
+  /* If another connection has written to the database file since the
+  ** time the read transaction on this connection was started, then
+  ** the write is disallowed.
+  */
+  SEH_TRY {
+    if( memcmp(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr))!=0 ){
+      rc = SQLITE_BUSY_SNAPSHOT;
+    }
+  }
+  SEH_EXCEPT( rc = SQLITE_IOERR_IN_PAGE; )
+
+  if( rc!=SQLITE_OK ){
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    pWal->writeLock = 0;
+  }
+  return rc;
+}
+
+/*
+** End a write transaction.  The commit has already been done.  This
+** routine merely releases the lock.
+*/
+int sqlite3WalEndWriteTransaction(Wal *pWal){
+  if( pWal->writeLock ){
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    pWal->writeLock = 0;
+    pWal->iReCksum = 0;
+    pWal->truncateOnCommit = 0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** If any data has been written (but not committed) to the log file, this
+** function moves the write-pointer back to the start of the transaction.
+**
+** Additionally, the callback function is invoked for each frame written
+** to the WAL since the start of the transaction. If the callback returns
+** other than SQLITE_OK, it is not invoked again and the error code is
+** returned to the caller.
+**
+** Otherwise, if the callback function does not return an error, this
+** function returns SQLITE_OK.
+*/
+int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
+  int rc = SQLITE_OK;
+  if( ALWAYS(pWal->writeLock) ){
+    Pgno iMax = pWal->hdr.mxFrame;
+    Pgno iFrame;
+
+    SEH_TRY {
+      /* Restore the clients cache of the wal-index header to the state it
+      ** was in before the client began writing to the database. 
+      */
+      memcpy(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr));
+  
+      for(iFrame=pWal->hdr.mxFrame+1; 
+          ALWAYS(rc==SQLITE_OK) && iFrame<=iMax; 
+          iFrame++
+      ){
+        /* This call cannot fail. Unless the page for which the page number
+        ** is passed as the second argument is (a) in the cache and
+        ** (b) has an outstanding reference, then xUndo is either a no-op
+        ** (if (a) is false) or simply expels the page from the cache (if (b)
+        ** is false).
+        **
+        ** If the upper layer is doing a rollback, it is guaranteed that there
+        ** are no outstanding references to any page other than page 1. And
+        ** page 1 is never written to the log until the transaction is
+        ** committed. As a result, the call to xUndo may not fail.
+        */
+        assert( walFramePgno(pWal, iFrame)!=1 );
+        rc = xUndo(pUndoCtx, walFramePgno(pWal, iFrame));
+      }
+      if( iMax!=pWal->hdr.mxFrame ) walCleanupHash(pWal);
+    }
+    SEH_EXCEPT( rc = SQLITE_IOERR_IN_PAGE; )
+  }
+  return rc;
+}
+
+/*
+** Argument aWalData must point to an array of WAL_SAVEPOINT_NDATA u32
+** values. This function populates the array with values required to
+** "rollback" the write position of the WAL handle back to the current
+** point in the event of a savepoint rollback (via WalSavepointUndo()).
+*/
+void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData){
+  assert( pWal->writeLock );
+  aWalData[0] = pWal->hdr.mxFrame;
+  aWalData[1] = pWal->hdr.aFrameCksum[0];
+  aWalData[2] = pWal->hdr.aFrameCksum[1];
+  aWalData[3] = pWal->nCkpt;
+}
+
+/*
+** Move the write position of the WAL back to the point identified by
+** the values in the aWalData[] array. aWalData must point to an array
+** of WAL_SAVEPOINT_NDATA u32 values that has been previously populated
+** by a call to WalSavepoint().
+*/
+int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData){
+  int rc = SQLITE_OK;
+
+  assert( pWal->writeLock );
+  assert( aWalData[3]!=pWal->nCkpt || aWalData[0]<=pWal->hdr.mxFrame );
+
+  if( aWalData[3]!=pWal->nCkpt ){
+    /* This savepoint was opened immediately after the write-transaction
+    ** was started. Right after that, the writer decided to wrap around
+    ** to the start of the log. Update the savepoint values to match.
+    */
+    aWalData[0] = 0;
+    aWalData[3] = pWal->nCkpt;
+  }
+
+  if( aWalData[0]<pWal->hdr.mxFrame ){
+    pWal->hdr.mxFrame = aWalData[0];
+    pWal->hdr.aFrameCksum[0] = aWalData[1];
+    pWal->hdr.aFrameCksum[1] = aWalData[2];
+    SEH_TRY {
+      walCleanupHash(pWal);
+    }
+    SEH_EXCEPT( rc = SQLITE_IOERR_IN_PAGE; )
+  }
+
+  return rc;
+}
+
+/*
+** This function is called just before writing a set of frames to the log
+** file (see sqlite3WalFrames()). It checks to see if, instead of appending
+** to the current log file, it is possible to overwrite the start of the
+** existing log file with the new frames (i.e. "reset" the log). If so,
+** it sets pWal->hdr.mxFrame to 0. Otherwise, pWal->hdr.mxFrame is left
+** unchanged.
+**
+** SQLITE_OK is returned if no error is encountered (regardless of whether
+** or not pWal->hdr.mxFrame is modified). An SQLite error code is returned
+** if an error occurs.
+*/
+static int walRestartLog(Wal *pWal){
+  int rc = SQLITE_OK;
+  int cnt;
+
+  if( pWal->readLock==0 ){
+    volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+    assert( pInfo->nBackfill==pWal->hdr.mxFrame );
+    if( pInfo->nBackfill>0 ){
+      u32 salt1;
+      sqlite3_randomness(4, &salt1);
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      if( rc==SQLITE_OK ){
+        /* If all readers are using WAL_READ_LOCK(0) (in other words if no
+        ** readers are currently using the WAL), then the transactions
+        ** frames will overwrite the start of the existing log. Update the
+        ** wal-index header to reflect this.
+        **
+        ** In theory it would be Ok to update the cache of the header only
+        ** at this point. But updating the actual wal-index header is also
+        ** safe and means there is no special case for sqlite3WalUndo()
+        ** to handle if this transaction is rolled back.  */
+        walRestartHdr(pWal, salt1);
+        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      }else if( rc!=SQLITE_BUSY ){
+        return rc;
+      }
+    }
+    walUnlockShared(pWal, WAL_READ_LOCK(0));
+    pWal->readLock = -1;
+    cnt = 0;
+    do{
+      int notUsed;
+      rc = walTryBeginRead(pWal, &notUsed, 1, &cnt);
+    }while( rc==WAL_RETRY );
+    assert( (rc&0xff)!=SQLITE_BUSY ); /* BUSY not possible when useWal==1 */
+    testcase( (rc&0xff)==SQLITE_IOERR );
+    testcase( rc==SQLITE_PROTOCOL );
+    testcase( rc==SQLITE_OK );
+  }
+  return rc;
+}
+
+/*
+** Information about the current state of the WAL file and where
+** the next fsync should occur - passed from sqlite3WalFrames() into
+** walWriteToLog().
+*/
+typedef struct WalWriter {
+  Wal *pWal;                   /* The complete WAL information */
+  sqlite3_file *pFd;           /* The WAL file to which we write */
+  sqlite3_int64 iSyncPoint;    /* Fsync at this offset */
+  int syncFlags;               /* Flags for the fsync */
+  int szPage;                  /* Size of one page */
+} WalWriter;
+
+/*
+** Write iAmt bytes of content into the WAL file beginning at iOffset.
+** Do a sync when crossing the p->iSyncPoint boundary.
+**
+** In other words, if iSyncPoint is in between iOffset and iOffset+iAmt,
+** first write the part before iSyncPoint, then sync, then write the
+** rest.
+*/
+static int walWriteToLog(
+  WalWriter *p,              /* WAL to write to */
+  void *pContent,            /* Content to be written */
+  int iAmt,                  /* Number of bytes to write */
+  sqlite3_int64 iOffset      /* Start writing at this offset */
+){
+  int rc;
+  if( iOffset<p->iSyncPoint && iOffset+iAmt>=p->iSyncPoint ){
+    int iFirstAmt = (int)(p->iSyncPoint - iOffset);
+    rc = sqlite3OsWrite(p->pFd, pContent, iFirstAmt, iOffset);
+    if( rc ) return rc;
+    iOffset += iFirstAmt;
+    iAmt -= iFirstAmt;
+    pContent = (void*)(iFirstAmt + (char*)pContent);
+    assert( WAL_SYNC_FLAGS(p->syncFlags)!=0 );
+    rc = sqlite3OsSync(p->pFd, WAL_SYNC_FLAGS(p->syncFlags));
+    if( iAmt==0 || rc ) return rc;
+  }
+  rc = sqlite3OsWrite(p->pFd, pContent, iAmt, iOffset);
+  return rc;
+}
+
+/*
+** Write out a single frame of the WAL
+*/
+static int walWriteOneFrame(
+  WalWriter *p,               /* Where to write the frame */
+  PgHdr *pPage,               /* The page of the frame to be written */
+  int nTruncate,              /* The commit flag.  Usually 0.  >0 for commit */
+  sqlite3_int64 iOffset       /* Byte offset at which to write */
+){
+  int rc;                         /* Result code from subfunctions */
+  void *pData;                    /* Data actually written */
+  u8 aFrame[WAL_FRAME_HDRSIZE];   /* Buffer to assemble frame-header in */
+  pData = pPage->pData;
+  walEncodeFrame(p->pWal, pPage->pgno, nTruncate, pData, aFrame);
+  rc = walWriteToLog(p, aFrame, sizeof(aFrame), iOffset);
+  if( rc ) return rc;
+  /* Write the page data */
+  rc = walWriteToLog(p, pData, p->szPage, iOffset+sizeof(aFrame));
+  return rc;
+}
+
+/*
+** This function is called as part of committing a transaction within which
+** one or more frames have been overwritten. It updates the checksums for
+** all frames written to the wal file by the current transaction starting
+** with the earliest to have been overwritten.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+static int walRewriteChecksums(Wal *pWal, u32 iLast){
+  const int szPage = pWal->szPage;/* Database page size */
+  int rc = SQLITE_OK;             /* Return code */
+  u8 *aBuf;                       /* Buffer to load data from wal file into */
+  u8 aFrame[WAL_FRAME_HDRSIZE];   /* Buffer to assemble frame-headers in */
+  u32 iRead;                      /* Next frame to read from wal file */
+  i64 iCksumOff;
+
+  aBuf = sqlite3_malloc(szPage + WAL_FRAME_HDRSIZE);
+  if( aBuf==0 ) return SQLITE_NOMEM_BKPT;
+
+  /* Find the checksum values to use as input for the recalculating the
+  ** first checksum. If the first frame is frame 1 (implying that the current
+  ** transaction restarted the wal file), these values must be read from the
+  ** wal-file header. Otherwise, read them from the frame header of the
+  ** previous frame.  */
+  assert( pWal->iReCksum>0 );
+  if( pWal->iReCksum==1 ){
+    iCksumOff = 24;
+  }else{
+    iCksumOff = walFrameOffset(pWal->iReCksum-1, szPage) + 16;
+  }
+  rc = sqlite3OsRead(pWal->pWalFd, aBuf, sizeof(u32)*2, iCksumOff);
+  pWal->hdr.aFrameCksum[0] = sqlite3Get4byte(aBuf);
+  pWal->hdr.aFrameCksum[1] = sqlite3Get4byte(&aBuf[sizeof(u32)]);
+
+  iRead = pWal->iReCksum;
+  pWal->iReCksum = 0;
+  for(; rc==SQLITE_OK && iRead<=iLast; iRead++){
+    i64 iOff = walFrameOffset(iRead, szPage);
+    rc = sqlite3OsRead(pWal->pWalFd, aBuf, szPage+WAL_FRAME_HDRSIZE, iOff);
+    if( rc==SQLITE_OK ){
+      u32 iPgno, nDbSize;
+      iPgno = sqlite3Get4byte(aBuf);
+      nDbSize = sqlite3Get4byte(&aBuf[4]);
+
+      walEncodeFrame(pWal, iPgno, nDbSize, &aBuf[WAL_FRAME_HDRSIZE], aFrame);
+      rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOff);
+    }
+  }
+
+  sqlite3_free(aBuf);
+  return rc;
+}
+
+/*
+** Write a set of frames to the log. The caller must hold the write-lock
+** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
+*/
+static int walFrames(
+  Wal *pWal,                      /* Wal handle to write to */
+  int szPage,                     /* Database page-size in bytes */
+  PgHdr *pList,                   /* List of dirty pages to write */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;                         /* Used to catch return codes */
+  u32 iFrame;                     /* Next frame address */
+  PgHdr *p;                       /* Iterator to run through pList with. */
+  PgHdr *pLast = 0;               /* Last frame in list */
+  int nExtra = 0;                 /* Number of extra copies of last page */
+  int szFrame;                    /* The size of a single frame */
+  i64 iOffset;                    /* Next byte to write in WAL file */
+  WalWriter w;                    /* The writer */
+  u32 iFirst = 0;                 /* First frame that may be overwritten */
+  WalIndexHdr *pLive;             /* Pointer to shared header */
+
+  assert( pList );
+  assert( pWal->writeLock );
+
+  /* If this frame set completes a transaction, then nTruncate>0.  If
+  ** nTruncate==0 then this frame set does not complete the transaction. */
+  assert( (isCommit!=0)==(nTruncate!=0) );
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}
+    WALTRACE(("WAL%p: frame write begin. %d frames. mxFrame=%d. %s\n",
+              pWal, cnt, pWal->hdr.mxFrame, isCommit ? "Commit" : "Spill"));
+  }
+#endif
+
+  pLive = (WalIndexHdr*)walIndexHdr(pWal);
+  if( memcmp(&pWal->hdr, (void *)pLive, sizeof(WalIndexHdr))!=0 ){
+    iFirst = pLive->mxFrame+1;
+  }
+
+  /* See if it is possible to write these frames into the start of the
+  ** log file, instead of appending to it at pWal->hdr.mxFrame.
+  */
+  if( SQLITE_OK!=(rc = walRestartLog(pWal)) ){
+    return rc;
+  }
+
+  /* If this is the first frame written into the log, write the WAL
+  ** header to the start of the WAL file. See comments at the top of
+  ** this source file for a description of the WAL header format.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  if( iFrame==0 ){
+    u8 aWalHdr[WAL_HDRSIZE];      /* Buffer to assemble wal-header in */
+    u32 aCksum[2];                /* Checksum for wal-header */
+
+    sqlite3Put4byte(&aWalHdr[0], (WAL_MAGIC | SQLITE_BIGENDIAN));
+    sqlite3Put4byte(&aWalHdr[4], WAL_MAX_VERSION);
+    sqlite3Put4byte(&aWalHdr[8], szPage);
+    sqlite3Put4byte(&aWalHdr[12], pWal->nCkpt);
+    if( pWal->nCkpt==0 ) sqlite3_randomness(8, pWal->hdr.aSalt);
+    memcpy(&aWalHdr[16], pWal->hdr.aSalt, 8);
+    walChecksumBytes(1, aWalHdr, WAL_HDRSIZE-2*4, 0, aCksum);
+    sqlite3Put4byte(&aWalHdr[24], aCksum[0]);
+    sqlite3Put4byte(&aWalHdr[28], aCksum[1]);
+
+    pWal->szPage = szPage;
+    pWal->hdr.bigEndCksum = SQLITE_BIGENDIAN;
+    pWal->hdr.aFrameCksum[0] = aCksum[0];
+    pWal->hdr.aFrameCksum[1] = aCksum[1];
+    pWal->truncateOnCommit = 1;
+
+    rc = sqlite3OsWrite(pWal->pWalFd, aWalHdr, sizeof(aWalHdr), 0);
+    WALTRACE(("WAL%p: wal-header write %s\n", pWal, rc ? "failed" : "ok"));
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+
+    /* Sync the header (unless SQLITE_IOCAP_SEQUENTIAL is true or unless
+    ** all syncing is turned off by PRAGMA synchronous=OFF).  Otherwise
+    ** an out-of-order write following a WAL restart could result in
+    ** database corruption.  See the ticket:
+    **
+    **     https://sqlite.org/src/info/ff5be73dee
+    */
+    if( pWal->syncHeader ){
+      rc = sqlite3OsSync(pWal->pWalFd, CKPT_SYNC_FLAGS(sync_flags));
+      if( rc ) return rc;
+    }
+  }
+  if( (int)pWal->szPage!=szPage ){
+    return SQLITE_CORRUPT_BKPT;  /* TH3 test case: cov1/corrupt155.test */
+  }
+
+  /* Setup information needed to write frames into the WAL */
+  w.pWal = pWal;
+  w.pFd = pWal->pWalFd;
+  w.iSyncPoint = 0;
+  w.syncFlags = sync_flags;
+  w.szPage = szPage;
+  iOffset = walFrameOffset(iFrame+1, szPage);
+  szFrame = szPage + WAL_FRAME_HDRSIZE;
+
+  /* Write all frames into the log file exactly once */
+  for(p=pList; p; p=p->pDirty){
+    int nDbSize;   /* 0 normally.  Positive == commit flag */
+
+    /* Check if this page has already been written into the wal file by
+    ** the current transaction. If so, overwrite the existing frame and
+    ** set Wal.writeLock to WAL_WRITELOCK_RECKSUM - indicating that
+    ** checksums must be recomputed when the transaction is committed.  */
+    if( iFirst && (p->pDirty || isCommit==0) ){
+      u32 iWrite = 0;
+      VVA_ONLY(rc =) walFindFrame(pWal, p->pgno, &iWrite);
+      assert( rc==SQLITE_OK || iWrite==0 );
+      if( iWrite>=iFirst ){
+        i64 iOff = walFrameOffset(iWrite, szPage) + WAL_FRAME_HDRSIZE;
+        void *pData;
+        if( pWal->iReCksum==0 || iWrite<pWal->iReCksum ){
+          pWal->iReCksum = iWrite;
+        }
+        pData = p->pData;
+        rc = sqlite3OsWrite(pWal->pWalFd, pData, szPage, iOff);
+        if( rc ) return rc;
+        p->flags &= ~PGHDR_WAL_APPEND;
+        continue;
+      }
+    }
+
+    iFrame++;
+    assert( iOffset==walFrameOffset(iFrame, szPage) );
+    nDbSize = (isCommit && p->pDirty==0) ? nTruncate : 0;
+    rc = walWriteOneFrame(&w, p, nDbSize, iOffset);
+    if( rc ) return rc;
+    pLast = p;
+    iOffset += szFrame;
+    p->flags |= PGHDR_WAL_APPEND;
+  }
+
+  /* Recalculate checksums within the wal file if required. */
+  if( isCommit && pWal->iReCksum ){
+    rc = walRewriteChecksums(pWal, iFrame);
+    if( rc ) return rc;
+  }
+
+  /* If this is the end of a transaction, then we might need to pad
+  ** the transaction and/or sync the WAL file.
+  **
+  ** Padding and syncing only occur if this set of frames complete a
+  ** transaction and if PRAGMA synchronous=FULL.  If synchronous==NORMAL
+  ** or synchronous==OFF, then no padding or syncing are needed.
+  **
+  ** If SQLITE_IOCAP_POWERSAFE_OVERWRITE is defined, then padding is not
+  ** needed and only the sync is done.  If padding is needed, then the
+  ** final frame is repeated (with its commit mark) until the next sector
+  ** boundary is crossed.  Only the part of the WAL prior to the last
+  ** sector boundary is synced; the part of the last frame that extends
+  ** past the sector boundary is written after the sync.
+  */
+  if( isCommit && WAL_SYNC_FLAGS(sync_flags)!=0 ){
+    int bSync = 1;
+    if( pWal->padToSectorBoundary ){
+      int sectorSize = sqlite3SectorSize(pWal->pWalFd);
+      w.iSyncPoint = ((iOffset+sectorSize-1)/sectorSize)*sectorSize;
+      bSync = (w.iSyncPoint==iOffset);
+      testcase( bSync );
+      while( iOffset<w.iSyncPoint ){
+        rc = walWriteOneFrame(&w, pLast, nTruncate, iOffset);
+        if( rc ) return rc;
+        iOffset += szFrame;
+        nExtra++;
+        assert( pLast!=0 );
+      }
+    }
+    if( bSync ){
+      assert( rc==SQLITE_OK );
+      rc = sqlite3OsSync(w.pFd, WAL_SYNC_FLAGS(sync_flags));
+    }
+  }
+
+  /* If this frame set completes the first transaction in the WAL and
+  ** if PRAGMA journal_size_limit is set, then truncate the WAL to the
+  ** journal size limit, if possible.
+  */
+  if( isCommit && pWal->truncateOnCommit && pWal->mxWalSize>=0 ){
+    i64 sz = pWal->mxWalSize;
+    if( walFrameOffset(iFrame+nExtra+1, szPage)>pWal->mxWalSize ){
+      sz = walFrameOffset(iFrame+nExtra+1, szPage);
+    }
+    walLimitSize(pWal, sz);
+    pWal->truncateOnCommit = 0;
+  }
+
+  /* Append data to the wal-index. It is not necessary to lock the
+  ** wal-index to do this as the SQLITE_SHM_WRITE lock held on the wal-index
+  ** guarantees that there are no other writers, and no data that may
+  ** be in use by existing readers is being overwritten.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  for(p=pList; p && rc==SQLITE_OK; p=p->pDirty){
+    if( (p->flags & PGHDR_WAL_APPEND)==0 ) continue;
+    iFrame++;
+    rc = walIndexAppend(pWal, iFrame, p->pgno);
+  }
+  assert( pLast!=0 || nExtra==0 );
+  while( rc==SQLITE_OK && nExtra>0 ){
+    iFrame++;
+    nExtra--;
+    rc = walIndexAppend(pWal, iFrame, pLast->pgno);
+  }
+
+  if( rc==SQLITE_OK ){
+    /* Update the private copy of the header. */
+    pWal->hdr.szPage = (u16)((szPage&0xff00) | (szPage>>16));
+    testcase( szPage<=32768 );
+    testcase( szPage>=65536 );
+    pWal->hdr.mxFrame = iFrame;
+    if( isCommit ){
+      pWal->hdr.iChange++;
+      pWal->hdr.nPage = nTruncate;
+    }
+    /* If this is a commit, update the wal-index header too. */
+    if( isCommit ){
+      walIndexWriteHdr(pWal);
+      pWal->iCallback = iFrame;
+    }
+  }
+
+  WALTRACE(("WAL%p: frame write %s\n", pWal, rc ? "failed" : "ok"));
+  return rc;
+}
+
+/* 
+** Write a set of frames to the log. The caller must hold the write-lock
+** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
+**
+** The difference between this function and walFrames() is that this
+** function wraps walFrames() in an SEH_TRY{...} block.
+*/
+int sqlite3WalFrames(
+  Wal *pWal,                      /* Wal handle to write to */
+  int szPage,                     /* Database page-size in bytes */
+  PgHdr *pList,                   /* List of dirty pages to write */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;
+  SEH_TRY {
+    rc = walFrames(pWal, szPage, pList, nTruncate, isCommit, sync_flags);
+  }
+  SEH_EXCEPT( rc = walHandleException(pWal); )
+  return rc;
+}
+
+/*
+** This routine is called to implement sqlite3_wal_checkpoint() and
+** related interfaces.
+**
+** Obtain a CHECKPOINT lock and then backfill as much information as
+** we can from WAL into the database.
+**
+** If parameter xBusy is not NULL, it is a pointer to a busy-handler
+** callback. In this case this function runs a blocking checkpoint.
+*/
+int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  sqlite3 *db,                    /* Check this handle's interrupt flag */
+  int eMode,                      /* PASSIVE, FULL, RESTART, or TRUNCATE */
+  int (*xBusy)(void*),            /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of temporary buffer */
+  u8 *zBuf,                       /* Temporary buffer to use */
+  int *pnLog,                     /* OUT: Number of frames in WAL */
+  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
+){
+  int rc;                         /* Return code */
+  int isChanged = 0;              /* True if a new wal-index header is loaded */
+  int eMode2 = eMode;             /* Mode to pass to walCheckpoint() */
+  int (*xBusy2)(void*) = xBusy;   /* Busy handler for eMode2 */
+
+  assert( pWal->ckptLock==0 );
+  assert( pWal->writeLock==0 );
+
+  /* EVIDENCE-OF: R-62920-47450 The busy-handler callback is never invoked
+  ** in the SQLITE_CHECKPOINT_PASSIVE mode. */
+  assert( eMode!=SQLITE_CHECKPOINT_PASSIVE || xBusy==0 );
+
+  if( pWal->readOnly ) return SQLITE_READONLY;
+  WALTRACE(("WAL%p: checkpoint begins\n", pWal));
+
+  /* Enable blocking locks, if possible. */
+  sqlite3WalDb(pWal, db);
+  if( xBusy2 ) (void)walEnableBlocking(pWal);
+
+  /* IMPLEMENTATION-OF: R-62028-47212 All calls obtain an exclusive
+  ** "checkpoint" lock on the database file.
+  ** EVIDENCE-OF: R-10421-19736 If any other process is running a
+  ** checkpoint operation at the same time, the lock cannot be obtained and
+  ** SQLITE_BUSY is returned.
+  ** EVIDENCE-OF: R-53820-33897 Even if there is a busy-handler configured,
+  ** it will not be invoked in this case.
+  */
+  rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  testcase( rc==SQLITE_BUSY );
+  testcase( rc!=SQLITE_OK && xBusy2!=0 );
+  if( rc==SQLITE_OK ){
+    pWal->ckptLock = 1;
+
+    /* IMPLEMENTATION-OF: R-59782-36818 The SQLITE_CHECKPOINT_FULL, RESTART and
+    ** TRUNCATE modes also obtain the exclusive "writer" lock on the database
+    ** file.
+    **
+    ** EVIDENCE-OF: R-60642-04082 If the writer lock cannot be obtained
+    ** immediately, and a busy-handler is configured, it is invoked and the
+    ** writer lock retried until either the busy-handler returns 0 or the
+    ** lock is successfully obtained.
+    */
+    if( eMode!=SQLITE_CHECKPOINT_PASSIVE ){
+      rc = walBusyLock(pWal, xBusy2, pBusyArg, WAL_WRITE_LOCK, 1);
+      if( rc==SQLITE_OK ){
+        pWal->writeLock = 1;
+      }else if( rc==SQLITE_BUSY ){
+        eMode2 = SQLITE_CHECKPOINT_PASSIVE;
+        xBusy2 = 0;
+        rc = SQLITE_OK;
+      }
+    }
+  }
+
+
+  /* Read the wal-index header. */
+  SEH_TRY {
+    if( rc==SQLITE_OK ){
+      /* For a passive checkpoint, do not re-enable blocking locks after
+      ** reading the wal-index header. A passive checkpoint should not block 
+      ** or invoke the busy handler. The only lock such a checkpoint may 
+      ** attempt to obtain is a lock on a read-slot, and it should give up
+      ** immediately and do a partial checkpoint if it cannot obtain it. */
+      walDisableBlocking(pWal);
+      rc = walIndexReadHdr(pWal, &isChanged);
+      if( eMode2!=SQLITE_CHECKPOINT_PASSIVE ) (void)walEnableBlocking(pWal);
+      if( isChanged && pWal->pDbFd->pMethods->iVersion>=3 ){
+        sqlite3OsUnfetch(pWal->pDbFd, 0, 0);
+      }
+    }
+  
+    /* Copy data from the log to the database file. */
+    if( rc==SQLITE_OK ){
+      if( pWal->hdr.mxFrame && walPagesize(pWal)!=nBuf ){
+        rc = SQLITE_CORRUPT_BKPT;
+      }else{
+        rc = walCheckpoint(pWal, db, eMode2, xBusy2, pBusyArg, sync_flags,zBuf);
+      }
+
+      /* If no error occurred, set the output variables. */
+      if( rc==SQLITE_OK || rc==SQLITE_BUSY ){
+        if( pnLog ) *pnLog = (int)pWal->hdr.mxFrame;
+        SEH_INJECT_FAULT;
+        if( pnCkpt ) *pnCkpt = (int)(walCkptInfo(pWal)->nBackfill);
+      }
+    }
+  }
+  SEH_EXCEPT( rc = walHandleException(pWal); )
+
+  if( isChanged ){
+    /* If a new wal-index header was loaded before the checkpoint was
+    ** performed, then the pager-cache associated with pWal is now
+    ** out of date. So zero the cached wal-index header to ensure that
+    ** next time the pager opens a snapshot on this database it knows that
+    ** the cache needs to be reset.
+    */
+    memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+  }
+
+  walDisableBlocking(pWal);
+  sqlite3WalDb(pWal, 0);
+
+  /* Release the locks. */
+  sqlite3WalEndWriteTransaction(pWal);
+  if( pWal->ckptLock ){
+    walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
+    pWal->ckptLock = 0;
+  }
+  WALTRACE(("WAL%p: checkpoint %s\n", pWal, rc ? "failed" : "ok"));
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+  if( rc==SQLITE_BUSY_TIMEOUT ) rc = SQLITE_BUSY;
+#endif
+  return (rc==SQLITE_OK && eMode!=eMode2 ? SQLITE_BUSY : rc);
+}
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+int sqlite3WalCallback(Wal *pWal){
+  u32 ret = 0;
+  if( pWal ){
+    ret = pWal->iCallback;
+    pWal->iCallback = 0;
+  }
+  return (int)ret;
+}
+
+/*
+** This function is called to change the WAL subsystem into or out
+** of locking_mode=EXCLUSIVE.
+**
+** If op is zero, then attempt to change from locking_mode=EXCLUSIVE
+** into locking_mode=NORMAL.  This means that we must acquire a lock
+** on the pWal->readLock byte.  If the WAL is already in locking_mode=NORMAL
+** or if the acquisition of the lock fails, then return 0.  If the
+** transition out of exclusive-mode is successful, return 1.  This
+** operation must occur while the pager is still holding the exclusive
+** lock on the main database file.
+**
+** If op is one, then change from locking_mode=NORMAL into
+** locking_mode=EXCLUSIVE.  This means that the pWal->readLock must
+** be released.  Return 1 if the transition is made and 0 if the
+** WAL is already in exclusive-locking mode - meaning that this
+** routine is a no-op.  The pager must already hold the exclusive lock
+** on the main database file before invoking this operation.
+**
+** If op is negative, then do a dry-run of the op==1 case but do
+** not actually change anything. The pager uses this to see if it
+** should acquire the database exclusive lock prior to invoking
+** the op==1 case.
+*/
+int sqlite3WalExclusiveMode(Wal *pWal, int op){
+  int rc;
+  assert( pWal->writeLock==0 );
+  assert( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE || op==-1 );
+
+  /* pWal->readLock is usually set, but might be -1 if there was a
+  ** prior error while attempting to acquire are read-lock. This cannot
+  ** happen if the connection is actually in exclusive mode (as no xShmLock
+  ** locks are taken in this case). Nor should the pager attempt to
+  ** upgrade to exclusive-mode following such an error.
+  */
+#ifndef SQLITE_USE_SEH
+  assert( pWal->readLock>=0 || pWal->lockError );
+#endif
+  assert( pWal->readLock>=0 || (op<=0 && pWal->exclusiveMode==0) );
+
+  if( op==0 ){
+    if( pWal->exclusiveMode!=WAL_NORMAL_MODE ){
+      pWal->exclusiveMode = WAL_NORMAL_MODE;
+      if( walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK ){
+        pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
+      }
+      rc = pWal->exclusiveMode==WAL_NORMAL_MODE;
+    }else{
+      /* Already in locking_mode=NORMAL */
+      rc = 0;
+    }
+  }else if( op>0 ){
+    assert( pWal->exclusiveMode==WAL_NORMAL_MODE );
+    assert( pWal->readLock>=0 );
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
+    rc = 1;
+  }else{
+    rc = pWal->exclusiveMode==WAL_NORMAL_MODE;
+  }
+  return rc;
+}
+
+/*
+** Return true if the argument is non-NULL and the WAL module is using
+** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
+** WAL module is using shared-memory, return false.
+*/
+int sqlite3WalHeapMemory(Wal *pWal){
+  return (pWal && pWal->exclusiveMode==WAL_HEAPMEMORY_MODE );
+}
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/* Create a snapshot object.  The content of a snapshot is opaque to
+** every other subsystem, so the WAL module can put whatever it needs
+** in the object.
+*/
+int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot){
+  int rc = SQLITE_OK;
+  WalIndexHdr *pRet;
+  static const u32 aZero[4] = { 0, 0, 0, 0 };
+
+  assert( pWal->readLock>=0 && pWal->writeLock==0 );
+
+  if( memcmp(&pWal->hdr.aFrameCksum[0],aZero,16)==0 ){
+    *ppSnapshot = 0;
+    return SQLITE_ERROR;
+  }
+  pRet = (WalIndexHdr*)sqlite3_malloc(sizeof(WalIndexHdr));
+  if( pRet==0 ){
+    rc = SQLITE_NOMEM_BKPT;
+  }else{
+    memcpy(pRet, &pWal->hdr, sizeof(WalIndexHdr));
+    *ppSnapshot = (sqlite3_snapshot*)pRet;
+  }
+
+  return rc;
+}
+
+/* Try to open on pSnapshot when the next read-transaction starts
+*/
+void sqlite3WalSnapshotOpen(
+  Wal *pWal,
+  sqlite3_snapshot *pSnapshot
+){
+  pWal->pSnapshot = (WalIndexHdr*)pSnapshot;
+}
+
+/*
+** Return a +ve value if snapshot p1 is newer than p2. A -ve value if
+** p1 is older than p2 and zero if p1 and p2 are the same snapshot.
+*/
+int sqlite3_snapshot_cmp(sqlite3_snapshot *p1, sqlite3_snapshot *p2){
+  WalIndexHdr *pHdr1 = (WalIndexHdr*)p1;
+  WalIndexHdr *pHdr2 = (WalIndexHdr*)p2;
+
+  /* aSalt[0] is a copy of the value stored in the wal file header. It
+  ** is incremented each time the wal file is restarted.  */
+  if( pHdr1->aSalt[0]<pHdr2->aSalt[0] ) return -1;
+  if( pHdr1->aSalt[0]>pHdr2->aSalt[0] ) return +1;
+  if( pHdr1->mxFrame<pHdr2->mxFrame ) return -1;
+  if( pHdr1->mxFrame>pHdr2->mxFrame ) return +1;
+  return 0;
+}
+
+/*
+** The caller currently has a read transaction open on the database.
+** This function takes a SHARED lock on the CHECKPOINTER slot and then
+** checks if the snapshot passed as the second argument is still
+** available. If so, SQLITE_OK is returned.
+**
+** If the snapshot is not available, SQLITE_ERROR is returned. Or, if
+** the CHECKPOINTER lock cannot be obtained, SQLITE_BUSY. If any error
+** occurs (any value other than SQLITE_OK is returned), the CHECKPOINTER
+** lock is released before returning.
+*/
+int sqlite3WalSnapshotCheck(Wal *pWal, sqlite3_snapshot *pSnapshot){
+  int rc;
+  SEH_TRY {
+    rc = walLockShared(pWal, WAL_CKPT_LOCK);
+    if( rc==SQLITE_OK ){
+      WalIndexHdr *pNew = (WalIndexHdr*)pSnapshot;
+      if( memcmp(pNew->aSalt, pWal->hdr.aSalt, sizeof(pWal->hdr.aSalt))
+       || pNew->mxFrame<walCkptInfo(pWal)->nBackfillAttempted
+      ){
+        rc = SQLITE_ERROR_SNAPSHOT;
+        walUnlockShared(pWal, WAL_CKPT_LOCK);
+      }
+    }
+  }
+  SEH_EXCEPT( rc = walHandleException(pWal); )
+  return rc;
+}
+
+/*
+** Release a lock obtained by an earlier successful call to
+** sqlite3WalSnapshotCheck().
+*/
+void sqlite3WalSnapshotUnlock(Wal *pWal){
+  assert( pWal );
+  walUnlockShared(pWal, WAL_CKPT_LOCK);
+}
+
+
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+/*
+** If the argument is not NULL, it points to a Wal object that holds a
+** read-lock. This function returns the database page-size if it is known,
+** or zero if it is not (or if pWal is NULL).
+*/
+int sqlite3WalFramesize(Wal *pWal){
+  assert( pWal==0 || pWal->readLock>=0 );
+  return (pWal ? pWal->szPage : 0);
+}
+#endif
+
+/* Return the sqlite3_file object for the WAL file
+*/
+sqlite3_file *sqlite3WalFile(Wal *pWal){
+  return pWal->pWalFd;
+}
+
+#endif /* #ifndef SQLITE_OMIT_WAL */
diff --git a/src/wal.h b/src/wal.h
new file mode 100644
index 0000000..1b17d2d
--- /dev/null
+++ b/src/wal.h
@@ -0,0 +1,160 @@
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface to the write-ahead logging 
+** system. Refer to the comments below and the header comment attached to 
+** the implementation of each function in log.c for further details.
+*/
+
+#ifndef SQLITE_WAL_H
+#define SQLITE_WAL_H
+
+#include "sqliteInt.h"
+
+/* Macros for extracting appropriate sync flags for either transaction
+** commits (WAL_SYNC_FLAGS(X)) or for checkpoint ops (CKPT_SYNC_FLAGS(X)):
+*/
+#define WAL_SYNC_FLAGS(X)   ((X)&0x03)
+#define CKPT_SYNC_FLAGS(X)  (((X)>>2)&0x03)
+
+#ifdef SQLITE_OMIT_WAL
+# define sqlite3WalOpen(x,y,z)                   0
+# define sqlite3WalLimit(x,y)
+# define sqlite3WalClose(v,w,x,y,z)              0
+# define sqlite3WalBeginReadTransaction(y,z)     0
+# define sqlite3WalEndReadTransaction(z)
+# define sqlite3WalDbsize(y)                     0
+# define sqlite3WalBeginWriteTransaction(y)      0
+# define sqlite3WalEndWriteTransaction(x)        0
+# define sqlite3WalUndo(x,y,z)                   0
+# define sqlite3WalSavepoint(y,z)
+# define sqlite3WalSavepointUndo(y,z)            0
+# define sqlite3WalFrames(u,v,w,x,y,z)           0
+# define sqlite3WalCheckpoint(q,r,s,t,u,v,w,x,y,z) 0
+# define sqlite3WalCallback(z)                   0
+# define sqlite3WalExclusiveMode(y,z)            0
+# define sqlite3WalHeapMemory(z)                 0
+# define sqlite3WalFramesize(z)                  0
+# define sqlite3WalFindFrame(x,y,z)              0
+# define sqlite3WalFile(x)                       0
+# undef SQLITE_USE_SEH
+#else
+
+#define WAL_SAVEPOINT_NDATA 4
+
+/* Connection to a write-ahead log (WAL) file. 
+** There is one object of this type for each pager. 
+*/
+typedef struct Wal Wal;
+
+/* Open and close a connection to a write-ahead log. */
+int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *, int, i64, Wal**);
+int sqlite3WalClose(Wal *pWal, sqlite3*, int sync_flags, int, u8 *);
+
+/* Set the limiting size of a WAL file. */
+void sqlite3WalLimit(Wal*, i64);
+
+/* Used by readers to open (lock) and close (unlock) a snapshot.  A 
+** snapshot is like a read-transaction.  It is the state of the database
+** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
+** preserves the current state even if the other threads or processes
+** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
+** transaction and releases the lock.
+*/
+int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
+void sqlite3WalEndReadTransaction(Wal *pWal);
+
+/* Read a page from the write-ahead log, if it is present. */
+int sqlite3WalFindFrame(Wal *, Pgno, u32 *);
+int sqlite3WalReadFrame(Wal *, u32, int, u8 *);
+
+/* If the WAL is not empty, return the size of the database. */
+Pgno sqlite3WalDbsize(Wal *pWal);
+
+/* Obtain or release the WRITER lock. */
+int sqlite3WalBeginWriteTransaction(Wal *pWal);
+int sqlite3WalEndWriteTransaction(Wal *pWal);
+
+/* Undo any frames written (but not committed) to the log */
+int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
+
+/* Return an integer that records the current (uncommitted) write
+** position in the WAL */
+void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);
+
+/* Move the write position of the WAL back to iFrame.  Called in
+** response to a ROLLBACK TO command. */
+int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);
+
+/* Write a frame or frames to the log. */
+int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
+
+/* Copy pages from the log to the database file */ 
+int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Write-ahead log connection */
+  sqlite3 *db,                    /* Check this handle's interrupt flag */
+  int eMode,                      /* One of PASSIVE, FULL and RESTART */
+  int (*xBusy)(void*),            /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of buffer nBuf */
+  u8 *zBuf,                       /* Temporary buffer to use */
+  int *pnLog,                     /* OUT: Number of frames in WAL */
+  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
+);
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+int sqlite3WalCallback(Wal *pWal);
+
+/* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
+** by the pager layer on the database file.
+*/
+int sqlite3WalExclusiveMode(Wal *pWal, int op);
+
+/* Return true if the argument is non-NULL and the WAL module is using
+** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
+** WAL module is using shared-memory, return false. 
+*/
+int sqlite3WalHeapMemory(Wal *pWal);
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot);
+void sqlite3WalSnapshotOpen(Wal *pWal, sqlite3_snapshot *pSnapshot);
+int sqlite3WalSnapshotRecover(Wal *pWal);
+int sqlite3WalSnapshotCheck(Wal *pWal, sqlite3_snapshot *pSnapshot);
+void sqlite3WalSnapshotUnlock(Wal *pWal);
+#endif
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+/* If the WAL file is not empty, return the number of bytes of content
+** stored in each frame (i.e. the db page-size when the WAL was created).
+*/
+int sqlite3WalFramesize(Wal *pWal);
+#endif
+
+/* Return the sqlite3_file object for the WAL file */
+sqlite3_file *sqlite3WalFile(Wal *pWal);
+
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+int sqlite3WalWriteLock(Wal *pWal, int bLock);
+void sqlite3WalDb(Wal *pWal, sqlite3 *db);
+#endif
+
+#ifdef SQLITE_USE_SEH
+int sqlite3WalSystemErrno(Wal*);
+#endif
+
+#endif /* ifndef SQLITE_OMIT_WAL */
+#endif /* SQLITE_WAL_H */
diff --git a/src/walker.c b/src/walker.c
new file mode 100644
index 0000000..0fe4a1d
--- /dev/null
+++ b/src/walker.c
@@ -0,0 +1,259 @@
+/*
+** 2008 August 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains routines used for walking the parser tree for
+** an SQL statement.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <string.h>
+
+
+#if !defined(SQLITE_OMIT_WINDOWFUNC)
+/*
+** Walk all expressions linked into the list of Window objects passed
+** as the second argument.
+*/
+static int walkWindowList(Walker *pWalker, Window *pList, int bOneOnly){
+  Window *pWin;
+  for(pWin=pList; pWin; pWin=pWin->pNextWin){
+    int rc;
+    rc = sqlite3WalkExprList(pWalker, pWin->pOrderBy);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExprList(pWalker, pWin->pPartition);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExpr(pWalker, pWin->pFilter);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExpr(pWalker, pWin->pStart);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExpr(pWalker, pWin->pEnd);
+    if( rc ) return WRC_Abort;
+    if( bOneOnly ) break;
+  }
+  return WRC_Continue;
+}
+#endif
+
+/*
+** Walk an expression tree.  Invoke the callback once for each node
+** of the expression, while descending.  (In other words, the callback
+** is invoked before visiting children.)
+**
+** The return value from the callback should be one of the WRC_*
+** constants to specify how to proceed with the walk.
+**
+**    WRC_Continue      Continue descending down the tree.
+**
+**    WRC_Prune         Do not descend into child nodes, but allow
+**                      the walk to continue with sibling nodes.
+**
+**    WRC_Abort         Do no more callbacks.  Unwind the stack and
+**                      return from the top-level walk call.
+**
+** The return value from this routine is WRC_Abort to abandon the tree walk
+** and WRC_Continue to continue.
+*/
+SQLITE_NOINLINE int sqlite3WalkExprNN(Walker *pWalker, Expr *pExpr){
+  int rc;
+  testcase( ExprHasProperty(pExpr, EP_TokenOnly) );
+  testcase( ExprHasProperty(pExpr, EP_Reduced) );
+  while(1){
+    rc = pWalker->xExprCallback(pWalker, pExpr);
+    if( rc ) return rc & WRC_Abort;
+    if( !ExprHasProperty(pExpr,(EP_TokenOnly|EP_Leaf)) ){
+      assert( pExpr->x.pList==0 || pExpr->pRight==0 );
+      if( pExpr->pLeft && sqlite3WalkExprNN(pWalker, pExpr->pLeft) ){
+        return WRC_Abort;
+      }
+      if( pExpr->pRight ){
+        assert( !ExprHasProperty(pExpr, EP_WinFunc) );
+        pExpr = pExpr->pRight;
+        continue;
+      }else if( ExprUseXSelect(pExpr) ){
+        assert( !ExprHasProperty(pExpr, EP_WinFunc) );
+        if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort;
+      }else{
+        if( pExpr->x.pList ){
+          if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
+        }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+        if( ExprHasProperty(pExpr, EP_WinFunc) ){
+          if( walkWindowList(pWalker, pExpr->y.pWin, 1) ) return WRC_Abort;
+        }
+#endif
+      }
+    }
+    break;
+  }
+  return WRC_Continue;
+}
+int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
+  return pExpr ? sqlite3WalkExprNN(pWalker,pExpr) : WRC_Continue;
+}
+
+/*
+** Call sqlite3WalkExpr() for every expression in list p or until
+** an abort request is seen.
+*/
+int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
+  int i;
+  struct ExprList_item *pItem;
+  if( p ){
+    for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
+      if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** This is a no-op callback for Walker->xSelectCallback2.  If this
+** callback is set, then the Select->pWinDefn list is traversed.
+*/
+void sqlite3WalkWinDefnDummyCallback(Walker *pWalker, Select *p){
+  UNUSED_PARAMETER(pWalker);
+  UNUSED_PARAMETER(p);
+  /* No-op */
+}
+
+/*
+** Walk all expressions associated with SELECT statement p.  Do
+** not invoke the SELECT callback on p, but do (of course) invoke
+** any expr callbacks and SELECT callbacks that come from subqueries.
+** Return WRC_Abort or WRC_Continue.
+*/
+int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
+  if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
+  if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
+  if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
+#if !defined(SQLITE_OMIT_WINDOWFUNC)
+  if( p->pWinDefn ){
+    Parse *pParse;
+    if( pWalker->xSelectCallback2==sqlite3WalkWinDefnDummyCallback
+     || ((pParse = pWalker->pParse)!=0 && IN_RENAME_OBJECT)
+#ifndef SQLITE_OMIT_CTE
+     || pWalker->xSelectCallback2==sqlite3SelectPopWith
+#endif
+    ){
+      /* The following may return WRC_Abort if there are unresolvable
+      ** symbols (e.g. a table that does not exist) in a window definition. */
+      int rc = walkWindowList(pWalker, p->pWinDefn, 0);
+      return rc;
+    }
+  }
+#endif
+  return WRC_Continue;
+}
+
+/*
+** Walk the parse trees associated with all subqueries in the
+** FROM clause of SELECT statement p.  Do not invoke the select
+** callback on p, but do invoke it on each FROM clause subquery
+** and on any subqueries further down in the tree.  Return 
+** WRC_Abort or WRC_Continue;
+*/
+int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
+  SrcList *pSrc;
+  int i;
+  SrcItem *pItem;
+
+  pSrc = p->pSrc;
+  if( ALWAYS(pSrc) ){
+    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
+      if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){
+        return WRC_Abort;
+      }
+      if( pItem->fg.isTabFunc
+       && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg)
+      ){
+        return WRC_Abort;
+      }
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Call sqlite3WalkExpr() for every expression in Select statement p.
+** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
+** on the compound select chain, p->pPrior. 
+**
+** If it is not NULL, the xSelectCallback() callback is invoked before
+** the walk of the expressions and FROM clause. The xSelectCallback2()
+** method is invoked following the walk of the expressions and FROM clause,
+** but only if both xSelectCallback and xSelectCallback2 are both non-NULL
+** and if the expressions and FROM clause both return WRC_Continue;
+**
+** Return WRC_Continue under normal conditions.  Return WRC_Abort if
+** there is an abort request.
+**
+** If the Walker does not have an xSelectCallback() then this routine
+** is a no-op returning WRC_Continue.
+*/
+int sqlite3WalkSelect(Walker *pWalker, Select *p){
+  int rc;
+  if( p==0 ) return WRC_Continue;
+  if( pWalker->xSelectCallback==0 ) return WRC_Continue;
+  do{
+    rc = pWalker->xSelectCallback(pWalker, p);
+    if( rc ) return rc & WRC_Abort;
+    if( sqlite3WalkSelectExpr(pWalker, p)
+     || sqlite3WalkSelectFrom(pWalker, p)
+    ){
+      return WRC_Abort;
+    }
+    if( pWalker->xSelectCallback2 ){
+      pWalker->xSelectCallback2(pWalker, p);
+    }
+    p = p->pPrior;
+  }while( p!=0 );
+  return WRC_Continue;
+}
+
+/* Increase the walkerDepth when entering a subquery, and
+** decrease when leaving the subquery.
+*/
+int sqlite3WalkerDepthIncrease(Walker *pWalker, Select *pSelect){
+  UNUSED_PARAMETER(pSelect);
+  pWalker->walkerDepth++;
+  return WRC_Continue;
+}
+void sqlite3WalkerDepthDecrease(Walker *pWalker, Select *pSelect){
+  UNUSED_PARAMETER(pSelect);
+  pWalker->walkerDepth--;
+}
+
+
+/*
+** No-op routine for the parse-tree walker.
+**
+** When this routine is the Walker.xExprCallback then expression trees
+** are walked without any actions being taken at each node.  Presumably,
+** when this routine is used for Walker.xExprCallback then 
+** Walker.xSelectCallback is set to do something useful for every 
+** subquery in the parser tree.
+*/
+int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return WRC_Continue;
+}
+
+/*
+** No-op routine for the parse-tree walker for SELECT statements.
+** subquery in the parser tree.
+*/
+int sqlite3SelectWalkNoop(Walker *NotUsed, Select *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return WRC_Continue;
+}
diff --git a/src/where.c b/src/where.c
new file mode 100644
index 0000000..7781366
--- /dev/null
+++ b/src/where.c
@@ -0,0 +1,7030 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This module contains C code that generates VDBE code used to process
+** the WHERE clause of SQL statements.  This module is responsible for
+** generating the code that loops through a table looking for applicable
+** rows.  Indices are selected and used to speed the search when doing
+** so is applicable.  Because this module is responsible for selecting
+** indices, you might also think of this module as the "query optimizer".
+*/
+#include "sqliteInt.h"
+#include "whereInt.h"
+
+/*
+** Extra information appended to the end of sqlite3_index_info but not
+** visible to the xBestIndex function, at least not directly.  The
+** sqlite3_vtab_collation() interface knows how to reach it, however.
+**
+** This object is not an API and can be changed from one release to the
+** next.  As long as allocateIndexInfo() and sqlite3_vtab_collation()
+** agree on the structure, all will be well.
+*/
+typedef struct HiddenIndexInfo HiddenIndexInfo;
+struct HiddenIndexInfo {
+  WhereClause *pWC;        /* The Where clause being analyzed */
+  Parse *pParse;           /* The parsing context */
+  int eDistinct;           /* Value to return from sqlite3_vtab_distinct() */
+  u32 mIn;                 /* Mask of terms that are <col> IN (...) */
+  u32 mHandleIn;           /* Terms that vtab will handle as <col> IN (...) */
+  sqlite3_value *aRhs[1];  /* RHS values for constraints. MUST BE LAST
+                           ** because extra space is allocated to hold up
+                           ** to nTerm such values */
+};
+
+/* Forward declaration of methods */
+static int whereLoopResize(sqlite3*, WhereLoop*, int);
+
+/*
+** Return the estimated number of output rows from a WHERE clause
+*/
+LogEst sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
+  return pWInfo->nRowOut;
+}
+
+/*
+** Return one of the WHERE_DISTINCT_xxxxx values to indicate how this
+** WHERE clause returns outputs for DISTINCT processing.
+*/
+int sqlite3WhereIsDistinct(WhereInfo *pWInfo){
+  return pWInfo->eDistinct;
+}
+
+/*
+** Return the number of ORDER BY terms that are satisfied by the
+** WHERE clause.  A return of 0 means that the output must be
+** completely sorted.  A return equal to the number of ORDER BY
+** terms means that no sorting is needed at all.  A return that
+** is positive but less than the number of ORDER BY terms means that
+** block sorting is required.
+*/
+int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
+  return pWInfo->nOBSat<0 ? 0 : pWInfo->nOBSat;
+}
+
+/*
+** In the ORDER BY LIMIT optimization, if the inner-most loop is known
+** to emit rows in increasing order, and if the last row emitted by the
+** inner-most loop did not fit within the sorter, then we can skip all
+** subsequent rows for the current iteration of the inner loop (because they
+** will not fit in the sorter either) and continue with the second inner
+** loop - the loop immediately outside the inner-most.
+**
+** When a row does not fit in the sorter (because the sorter already
+** holds LIMIT+OFFSET rows that are smaller), then a jump is made to the
+** label returned by this function.
+**
+** If the ORDER BY LIMIT optimization applies, the jump destination should
+** be the continuation for the second-inner-most loop.  If the ORDER BY
+** LIMIT optimization does not apply, then the jump destination should
+** be the continuation for the inner-most loop.
+**
+** It is always safe for this routine to return the continuation of the
+** inner-most loop, in the sense that a correct answer will result. 
+** Returning the continuation the second inner loop is an optimization
+** that might make the code run a little faster, but should not change
+** the final answer.
+*/
+int sqlite3WhereOrderByLimitOptLabel(WhereInfo *pWInfo){
+  WhereLevel *pInner;
+  if( !pWInfo->bOrderedInnerLoop ){
+    /* The ORDER BY LIMIT optimization does not apply.  Jump to the
+    ** continuation of the inner-most loop. */
+    return pWInfo->iContinue;
+  }
+  pInner = &pWInfo->a[pWInfo->nLevel-1];
+  assert( pInner->addrNxt!=0 );
+  return pInner->pRJ ? pWInfo->iContinue : pInner->addrNxt;
+}
+
+/*
+** While generating code for the min/max optimization, after handling
+** the aggregate-step call to min() or max(), check to see if any
+** additional looping is required.  If the output order is such that
+** we are certain that the correct answer has already been found, then
+** code an OP_Goto to by pass subsequent processing.
+**
+** Any extra OP_Goto that is coded here is an optimization.  The
+** correct answer should be obtained regardless.  This OP_Goto just
+** makes the answer appear faster.
+*/
+void sqlite3WhereMinMaxOptEarlyOut(Vdbe *v, WhereInfo *pWInfo){
+  WhereLevel *pInner;
+  int i;
+  if( !pWInfo->bOrderedInnerLoop ) return;
+  if( pWInfo->nOBSat==0 ) return;
+  for(i=pWInfo->nLevel-1; i>=0; i--){
+    pInner = &pWInfo->a[i];
+    if( (pInner->pWLoop->wsFlags & WHERE_COLUMN_IN)!=0 ){
+      sqlite3VdbeGoto(v, pInner->addrNxt);
+      return;
+    }
+  }
+  sqlite3VdbeGoto(v, pWInfo->iBreak);
+}
+
+/*
+** Return the VDBE address or label to jump to in order to continue
+** immediately with the next row of a WHERE clause.
+*/
+int sqlite3WhereContinueLabel(WhereInfo *pWInfo){
+  assert( pWInfo->iContinue!=0 );
+  return pWInfo->iContinue;
+}
+
+/*
+** Return the VDBE address or label to jump to in order to break
+** out of a WHERE loop.
+*/
+int sqlite3WhereBreakLabel(WhereInfo *pWInfo){
+  return pWInfo->iBreak;
+}
+
+/*
+** Return ONEPASS_OFF (0) if an UPDATE or DELETE statement is unable to
+** operate directly on the rowids returned by a WHERE clause.  Return
+** ONEPASS_SINGLE (1) if the statement can operation directly because only
+** a single row is to be changed.  Return ONEPASS_MULTI (2) if the one-pass
+** optimization can be used on multiple
+**
+** If the ONEPASS optimization is used (if this routine returns true)
+** then also write the indices of open cursors used by ONEPASS
+** into aiCur[0] and aiCur[1].  iaCur[0] gets the cursor of the data
+** table and iaCur[1] gets the cursor used by an auxiliary index.
+** Either value may be -1, indicating that cursor is not used.
+** Any cursors returned will have been opened for writing.
+**
+** aiCur[0] and aiCur[1] both get -1 if the where-clause logic is
+** unable to use the ONEPASS optimization.
+*/
+int sqlite3WhereOkOnePass(WhereInfo *pWInfo, int *aiCur){
+  memcpy(aiCur, pWInfo->aiCurOnePass, sizeof(int)*2);
+#ifdef WHERETRACE_ENABLED
+  if( sqlite3WhereTrace && pWInfo->eOnePass!=ONEPASS_OFF ){
+    sqlite3DebugPrintf("%s cursors: %d %d\n",
+         pWInfo->eOnePass==ONEPASS_SINGLE ? "ONEPASS_SINGLE" : "ONEPASS_MULTI",
+         aiCur[0], aiCur[1]);
+  }
+#endif
+  return pWInfo->eOnePass;
+}
+
+/*
+** Return TRUE if the WHERE loop uses the OP_DeferredSeek opcode to move
+** the data cursor to the row selected by the index cursor.
+*/
+int sqlite3WhereUsesDeferredSeek(WhereInfo *pWInfo){
+  return pWInfo->bDeferredSeek;
+}
+
+/*
+** Move the content of pSrc into pDest
+*/
+static void whereOrMove(WhereOrSet *pDest, WhereOrSet *pSrc){
+  pDest->n = pSrc->n;
+  memcpy(pDest->a, pSrc->a, pDest->n*sizeof(pDest->a[0]));
+}
+
+/*
+** Try to insert a new prerequisite/cost entry into the WhereOrSet pSet.
+**
+** The new entry might overwrite an existing entry, or it might be
+** appended, or it might be discarded.  Do whatever is the right thing
+** so that pSet keeps the N_OR_COST best entries seen so far.
+*/
+static int whereOrInsert(
+  WhereOrSet *pSet,      /* The WhereOrSet to be updated */
+  Bitmask prereq,        /* Prerequisites of the new entry */
+  LogEst rRun,           /* Run-cost of the new entry */
+  LogEst nOut            /* Number of outputs for the new entry */
+){
+  u16 i;
+  WhereOrCost *p;
+  for(i=pSet->n, p=pSet->a; i>0; i--, p++){
+    if( rRun<=p->rRun && (prereq & p->prereq)==prereq ){
+      goto whereOrInsert_done;
+    }
+    if( p->rRun<=rRun && (p->prereq & prereq)==p->prereq ){
+      return 0;
+    }
+  }
+  if( pSet->n<N_OR_COST ){
+    p = &pSet->a[pSet->n++];
+    p->nOut = nOut;
+  }else{
+    p = pSet->a;
+    for(i=1; i<pSet->n; i++){
+      if( p->rRun>pSet->a[i].rRun ) p = pSet->a + i;
+    }
+    if( p->rRun<=rRun ) return 0;
+  }
+whereOrInsert_done:
+  p->prereq = prereq;
+  p->rRun = rRun;
+  if( p->nOut>nOut ) p->nOut = nOut;
+  return 1;
+}
+
+/*
+** Return the bitmask for the given cursor number.  Return 0 if
+** iCursor is not in the set.
+*/
+Bitmask sqlite3WhereGetMask(WhereMaskSet *pMaskSet, int iCursor){
+  int i;
+  assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
+  assert( pMaskSet->n>0 || pMaskSet->ix[0]<0 );
+  assert( iCursor>=-1 );
+  if( pMaskSet->ix[0]==iCursor ){
+    return 1;
+  }
+  for(i=1; i<pMaskSet->n; i++){
+    if( pMaskSet->ix[i]==iCursor ){
+      return MASKBIT(i);
+    }
+  }
+  return 0;
+}
+
+/* Allocate memory that is automatically freed when pWInfo is freed.
+*/
+void *sqlite3WhereMalloc(WhereInfo *pWInfo, u64 nByte){
+  WhereMemBlock *pBlock;
+  pBlock = sqlite3DbMallocRawNN(pWInfo->pParse->db, nByte+sizeof(*pBlock));
+  if( pBlock ){
+    pBlock->pNext = pWInfo->pMemToFree;
+    pBlock->sz = nByte;
+    pWInfo->pMemToFree = pBlock;
+    pBlock++;
+  }
+  return (void*)pBlock;
+}
+void *sqlite3WhereRealloc(WhereInfo *pWInfo, void *pOld, u64 nByte){
+  void *pNew = sqlite3WhereMalloc(pWInfo, nByte);
+  if( pNew && pOld ){
+    WhereMemBlock *pOldBlk = (WhereMemBlock*)pOld;
+    pOldBlk--;
+    assert( pOldBlk->sz<nByte );
+    memcpy(pNew, pOld, pOldBlk->sz);
+  }
+  return pNew;
+}
+
+/*
+** Create a new mask for cursor iCursor.
+**
+** There is one cursor per table in the FROM clause.  The number of
+** tables in the FROM clause is limited by a test early in the
+** sqlite3WhereBegin() routine.  So we know that the pMaskSet->ix[]
+** array will never overflow.
+*/
+static void createMask(WhereMaskSet *pMaskSet, int iCursor){
+  assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
+  pMaskSet->ix[pMaskSet->n++] = iCursor;
+}
+
+/*
+** If the right-hand branch of the expression is a TK_COLUMN, then return
+** a pointer to the right-hand branch.  Otherwise, return NULL.
+*/
+static Expr *whereRightSubexprIsColumn(Expr *p){
+  p = sqlite3ExprSkipCollateAndLikely(p->pRight);
+  if( ALWAYS(p!=0) && p->op==TK_COLUMN && !ExprHasProperty(p, EP_FixedCol) ){
+    return p;
+  }
+  return 0;
+}
+
+/*
+** Advance to the next WhereTerm that matches according to the criteria
+** established when the pScan object was initialized by whereScanInit().
+** Return NULL if there are no more matching WhereTerms.
+*/
+static WhereTerm *whereScanNext(WhereScan *pScan){
+  int iCur;            /* The cursor on the LHS of the term */
+  i16 iColumn;         /* The column on the LHS of the term.  -1 for IPK */
+  Expr *pX;            /* An expression being tested */
+  WhereClause *pWC;    /* Shorthand for pScan->pWC */
+  WhereTerm *pTerm;    /* The term being tested */
+  int k = pScan->k;    /* Where to start scanning */
+
+  assert( pScan->iEquiv<=pScan->nEquiv );
+  pWC = pScan->pWC;
+  while(1){
+    iColumn = pScan->aiColumn[pScan->iEquiv-1];
+    iCur = pScan->aiCur[pScan->iEquiv-1];
+    assert( pWC!=0 );
+    assert( iCur>=0 );
+    do{
+      for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
+        assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 || pTerm->leftCursor<0 );
+        if( pTerm->leftCursor==iCur
+         && pTerm->u.x.leftColumn==iColumn
+         && (iColumn!=XN_EXPR
+             || sqlite3ExprCompareSkip(pTerm->pExpr->pLeft,
+                                       pScan->pIdxExpr,iCur)==0)
+         && (pScan->iEquiv<=1 || !ExprHasProperty(pTerm->pExpr, EP_OuterON))
+        ){
+          if( (pTerm->eOperator & WO_EQUIV)!=0
+           && pScan->nEquiv<ArraySize(pScan->aiCur)
+           && (pX = whereRightSubexprIsColumn(pTerm->pExpr))!=0
+          ){
+            int j;
+            for(j=0; j<pScan->nEquiv; j++){
+              if( pScan->aiCur[j]==pX->iTable
+               && pScan->aiColumn[j]==pX->iColumn ){
+                  break;
+              }
+            }
+            if( j==pScan->nEquiv ){
+              pScan->aiCur[j] = pX->iTable;
+              pScan->aiColumn[j] = pX->iColumn;
+              pScan->nEquiv++;
+            }
+          }
+          if( (pTerm->eOperator & pScan->opMask)!=0 ){
+            /* Verify the affinity and collating sequence match */
+            if( pScan->zCollName && (pTerm->eOperator & WO_ISNULL)==0 ){
+              CollSeq *pColl;
+              Parse *pParse = pWC->pWInfo->pParse;
+              pX = pTerm->pExpr;
+              if( !sqlite3IndexAffinityOk(pX, pScan->idxaff) ){
+                continue;
+              }
+              assert(pX->pLeft);
+              pColl = sqlite3ExprCompareCollSeq(pParse, pX);
+              if( pColl==0 ) pColl = pParse->db->pDfltColl;
+              if( sqlite3StrICmp(pColl->zName, pScan->zCollName) ){
+                continue;
+              }
+            }
+            if( (pTerm->eOperator & (WO_EQ|WO_IS))!=0
+             && (pX = pTerm->pExpr->pRight, ALWAYS(pX!=0))
+             && pX->op==TK_COLUMN
+             && pX->iTable==pScan->aiCur[0]
+             && pX->iColumn==pScan->aiColumn[0]
+            ){
+              testcase( pTerm->eOperator & WO_IS );
+              continue;
+            }
+            pScan->pWC = pWC;
+            pScan->k = k+1;
+#ifdef WHERETRACE_ENABLED
+            if( sqlite3WhereTrace & 0x20000 ){
+              int ii;
+              sqlite3DebugPrintf("SCAN-TERM %p: nEquiv=%d",
+                 pTerm, pScan->nEquiv);
+              for(ii=0; ii<pScan->nEquiv; ii++){
+                sqlite3DebugPrintf(" {%d:%d}",
+                   pScan->aiCur[ii], pScan->aiColumn[ii]);
+              }
+              sqlite3DebugPrintf("\n");
+            }
+#endif
+            return pTerm;
+          }
+        }
+      }
+      pWC = pWC->pOuter;
+      k = 0;
+    }while( pWC!=0 );
+    if( pScan->iEquiv>=pScan->nEquiv ) break;
+    pWC = pScan->pOrigWC;
+    k = 0;
+    pScan->iEquiv++;
+  }
+  return 0;
+}
+
+/*
+** This is whereScanInit() for the case of an index on an expression.
+** It is factored out into a separate tail-recursion subroutine so that
+** the normal whereScanInit() routine, which is a high-runner, does not
+** need to push registers onto the stack as part of its prologue.
+*/
+static SQLITE_NOINLINE WhereTerm *whereScanInitIndexExpr(WhereScan *pScan){
+  pScan->idxaff = sqlite3ExprAffinity(pScan->pIdxExpr);
+  return whereScanNext(pScan);
+}
+
+/*
+** Initialize a WHERE clause scanner object.  Return a pointer to the
+** first match.  Return NULL if there are no matches.
+**
+** The scanner will be searching the WHERE clause pWC.  It will look
+** for terms of the form "X <op> <expr>" where X is column iColumn of table
+** iCur.   Or if pIdx!=0 then X is column iColumn of index pIdx.  pIdx
+** must be one of the indexes of table iCur.
+**
+** The <op> must be one of the operators described by opMask.
+**
+** If the search is for X and the WHERE clause contains terms of the
+** form X=Y then this routine might also return terms of the form
+** "Y <op> <expr>".  The number of levels of transitivity is limited,
+** but is enough to handle most commonly occurring SQL statements.
+**
+** If X is not the INTEGER PRIMARY KEY then X must be compatible with
+** index pIdx.
+*/
+static WhereTerm *whereScanInit(
+  WhereScan *pScan,       /* The WhereScan object being initialized */
+  WhereClause *pWC,       /* The WHERE clause to be scanned */
+  int iCur,               /* Cursor to scan for */
+  int iColumn,            /* Column to scan for */
+  u32 opMask,             /* Operator(s) to scan for */
+  Index *pIdx             /* Must be compatible with this index */
+){
+  pScan->pOrigWC = pWC;
+  pScan->pWC = pWC;
+  pScan->pIdxExpr = 0;
+  pScan->idxaff = 0;
+  pScan->zCollName = 0;
+  pScan->opMask = opMask;
+  pScan->k = 0;
+  pScan->aiCur[0] = iCur;
+  pScan->nEquiv = 1;
+  pScan->iEquiv = 1;
+  if( pIdx ){
+    int j = iColumn;
+    iColumn = pIdx->aiColumn[j];
+    if( iColumn==pIdx->pTable->iPKey ){
+      iColumn = XN_ROWID;
+    }else if( iColumn>=0 ){
+      pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
+      pScan->zCollName = pIdx->azColl[j];
+    }else if( iColumn==XN_EXPR ){
+      pScan->pIdxExpr = pIdx->aColExpr->a[j].pExpr;
+      pScan->zCollName = pIdx->azColl[j];
+      pScan->aiColumn[0] = XN_EXPR;
+      return whereScanInitIndexExpr(pScan);
+    }
+  }else if( iColumn==XN_EXPR ){
+    return 0;
+  }
+  pScan->aiColumn[0] = iColumn;
+  return whereScanNext(pScan);
+}
+
+/*
+** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
+** where X is a reference to the iColumn of table iCur or of index pIdx
+** if pIdx!=0 and <op> is one of the WO_xx operator codes specified by
+** the op parameter.  Return a pointer to the term.  Return 0 if not found.
+**
+** If pIdx!=0 then it must be one of the indexes of table iCur. 
+** Search for terms matching the iColumn-th column of pIdx
+** rather than the iColumn-th column of table iCur.
+**
+** The term returned might by Y=<expr> if there is another constraint in
+** the WHERE clause that specifies that X=Y.  Any such constraints will be
+** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
+** aiCur[]/iaColumn[] arrays hold X and all its equivalents. There are 11
+** slots in aiCur[]/aiColumn[] so that means we can look for X plus up to 10
+** other equivalent values.  Hence a search for X will return <expr> if X=A1
+** and A1=A2 and A2=A3 and ... and A9=A10 and A10=<expr>.
+**
+** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
+** then try for the one with no dependencies on <expr> - in other words where
+** <expr> is a constant expression of some kind.  Only return entries of
+** the form "X <op> Y" where Y is a column in another table if no terms of
+** the form "X <op> <const-expr>" exist.   If no terms with a constant RHS
+** exist, try to return a term that does not use WO_EQUIV.
+*/
+WhereTerm *sqlite3WhereFindTerm(
+  WhereClause *pWC,     /* The WHERE clause to be searched */
+  int iCur,             /* Cursor number of LHS */
+  int iColumn,          /* Column number of LHS */
+  Bitmask notReady,     /* RHS must not overlap with this mask */
+  u32 op,               /* Mask of WO_xx values describing operator */
+  Index *pIdx           /* Must be compatible with this index, if not NULL */
+){
+  WhereTerm *pResult = 0;
+  WhereTerm *p;
+  WhereScan scan;
+
+  p = whereScanInit(&scan, pWC, iCur, iColumn, op, pIdx);
+  op &= WO_EQ|WO_IS;
+  while( p ){
+    if( (p->prereqRight & notReady)==0 ){
+      if( p->prereqRight==0 && (p->eOperator&op)!=0 ){
+        testcase( p->eOperator & WO_IS );
+        return p;
+      }
+      if( pResult==0 ) pResult = p;
+    }
+    p = whereScanNext(&scan);
+  }
+  return pResult;
+}
+
+/*
+** This function searches pList for an entry that matches the iCol-th column
+** of index pIdx.
+**
+** If such an expression is found, its index in pList->a[] is returned. If
+** no expression is found, -1 is returned.
+*/
+static int findIndexCol(
+  Parse *pParse,                  /* Parse context */
+  ExprList *pList,                /* Expression list to search */
+  int iBase,                      /* Cursor for table associated with pIdx */
+  Index *pIdx,                    /* Index to match column of */
+  int iCol                        /* Column of index to match */
+){
+  int i;
+  const char *zColl = pIdx->azColl[iCol];
+
+  for(i=0; i<pList->nExpr; i++){
+    Expr *p = sqlite3ExprSkipCollateAndLikely(pList->a[i].pExpr);
+    if( ALWAYS(p!=0)
+     && (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN)
+     && p->iColumn==pIdx->aiColumn[iCol]
+     && p->iTable==iBase
+    ){
+      CollSeq *pColl = sqlite3ExprNNCollSeq(pParse, pList->a[i].pExpr);
+      if( 0==sqlite3StrICmp(pColl->zName, zColl) ){
+        return i;
+      }
+    }
+  }
+
+  return -1;
+}
+
+/*
+** Return TRUE if the iCol-th column of index pIdx is NOT NULL
+*/
+static int indexColumnNotNull(Index *pIdx, int iCol){
+  int j;
+  assert( pIdx!=0 );
+  assert( iCol>=0 && iCol<pIdx->nColumn );
+  j = pIdx->aiColumn[iCol];
+  if( j>=0 ){
+    return pIdx->pTable->aCol[j].notNull;
+  }else if( j==(-1) ){
+    return 1;
+  }else{
+    assert( j==(-2) );
+    return 0;  /* Assume an indexed expression can always yield a NULL */
+
+  }
+}
+
+/*
+** Return true if the DISTINCT expression-list passed as the third argument
+** is redundant.
+**
+** A DISTINCT list is redundant if any subset of the columns in the
+** DISTINCT list are collectively unique and individually non-null.
+*/
+static int isDistinctRedundant(
+  Parse *pParse,            /* Parsing context */
+  SrcList *pTabList,        /* The FROM clause */
+  WhereClause *pWC,         /* The WHERE clause */
+  ExprList *pDistinct       /* The result set that needs to be DISTINCT */
+){
+  Table *pTab;
+  Index *pIdx;
+  int i;                         
+  int iBase;
+
+  /* If there is more than one table or sub-select in the FROM clause of
+  ** this query, then it will not be possible to show that the DISTINCT
+  ** clause is redundant. */
+  if( pTabList->nSrc!=1 ) return 0;
+  iBase = pTabList->a[0].iCursor;
+  pTab = pTabList->a[0].pTab;
+
+  /* If any of the expressions is an IPK column on table iBase, then return
+  ** true. Note: The (p->iTable==iBase) part of this test may be false if the
+  ** current SELECT is a correlated sub-query.
+  */
+  for(i=0; i<pDistinct->nExpr; i++){
+    Expr *p = sqlite3ExprSkipCollateAndLikely(pDistinct->a[i].pExpr);
+    if( NEVER(p==0) ) continue;
+    if( p->op!=TK_COLUMN && p->op!=TK_AGG_COLUMN ) continue;
+    if( p->iTable==iBase && p->iColumn<0 ) return 1;
+  }
+
+  /* Loop through all indices on the table, checking each to see if it makes
+  ** the DISTINCT qualifier redundant. It does so if:
+  **
+  **   1. The index is itself UNIQUE, and
+  **
+  **   2. All of the columns in the index are either part of the pDistinct
+  **      list, or else the WHERE clause contains a term of the form "col=X",
+  **      where X is a constant value. The collation sequences of the
+  **      comparison and select-list expressions must match those of the index.
+  **
+  **   3. All of those index columns for which the WHERE clause does not
+  **      contain a "col=X" term are subject to a NOT NULL constraint.
+  */
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    if( !IsUniqueIndex(pIdx) ) continue;
+    if( pIdx->pPartIdxWhere ) continue;
+    for(i=0; i<pIdx->nKeyCol; i++){
+      if( 0==sqlite3WhereFindTerm(pWC, iBase, i, ~(Bitmask)0, WO_EQ, pIdx) ){
+        if( findIndexCol(pParse, pDistinct, iBase, pIdx, i)<0 ) break;
+        if( indexColumnNotNull(pIdx, i)==0 ) break;
+      }
+    }
+    if( i==pIdx->nKeyCol ){
+      /* This index implies that the DISTINCT qualifier is redundant. */
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+
+/*
+** Estimate the logarithm of the input value to base 2.
+*/
+static LogEst estLog(LogEst N){
+  return N<=10 ? 0 : sqlite3LogEst(N) - 33;
+}
+
+/*
+** Convert OP_Column opcodes to OP_Copy in previously generated code.
+**
+** This routine runs over generated VDBE code and translates OP_Column
+** opcodes into OP_Copy when the table is being accessed via co-routine
+** instead of via table lookup.
+**
+** If the iAutoidxCur is not zero, then any OP_Rowid instructions on
+** cursor iTabCur are transformed into OP_Sequence opcode for the
+** iAutoidxCur cursor, in order to generate unique rowids for the
+** automatic index being generated.
+*/
+static void translateColumnToCopy(
+  Parse *pParse,      /* Parsing context */
+  int iStart,         /* Translate from this opcode to the end */
+  int iTabCur,        /* OP_Column/OP_Rowid references to this table */
+  int iRegister,      /* The first column is in this register */
+  int iAutoidxCur     /* If non-zero, cursor of autoindex being generated */
+){
+  Vdbe *v = pParse->pVdbe;
+  VdbeOp *pOp = sqlite3VdbeGetOp(v, iStart);
+  int iEnd = sqlite3VdbeCurrentAddr(v);
+  if( pParse->db->mallocFailed ) return;
+  for(; iStart<iEnd; iStart++, pOp++){
+    if( pOp->p1!=iTabCur ) continue;
+    if( pOp->opcode==OP_Column ){
+#ifdef SQLITE_DEBUG
+      if( pParse->db->flags & SQLITE_VdbeAddopTrace ){
+        printf("TRANSLATE OP_Column to OP_Copy at %d\n", iStart);
+      }
+#endif
+      pOp->opcode = OP_Copy;
+      pOp->p1 = pOp->p2 + iRegister;
+      pOp->p2 = pOp->p3;
+      pOp->p3 = 0;
+      pOp->p5 = 2;  /* Cause the MEM_Subtype flag to be cleared */
+    }else if( pOp->opcode==OP_Rowid ){
+#ifdef SQLITE_DEBUG
+      if( pParse->db->flags & SQLITE_VdbeAddopTrace ){
+        printf("TRANSLATE OP_Rowid to OP_Sequence at %d\n", iStart);
+      }
+#endif
+      pOp->opcode = OP_Sequence;
+      pOp->p1 = iAutoidxCur;
+#ifdef SQLITE_ALLOW_ROWID_IN_VIEW
+      if( iAutoidxCur==0 ){
+        pOp->opcode = OP_Null;
+        pOp->p3 = 0;
+      }
+#endif
+    }
+  }
+}
+
+/*
+** Two routines for printing the content of an sqlite3_index_info
+** structure.  Used for testing and debugging only.  If neither
+** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
+** are no-ops.
+*/
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(WHERETRACE_ENABLED)
+static void whereTraceIndexInfoInputs(sqlite3_index_info *p){
+  int i;
+  if( (sqlite3WhereTrace & 0x10)==0 ) return;
+  for(i=0; i<p->nConstraint; i++){
+    sqlite3DebugPrintf(
+       "  constraint[%d]: col=%d termid=%d op=%d usabled=%d collseq=%s\n",
+       i,
+       p->aConstraint[i].iColumn,
+       p->aConstraint[i].iTermOffset,
+       p->aConstraint[i].op,
+       p->aConstraint[i].usable,
+       sqlite3_vtab_collation(p,i));
+  }
+  for(i=0; i<p->nOrderBy; i++){
+    sqlite3DebugPrintf("  orderby[%d]: col=%d desc=%d\n",
+       i,
+       p->aOrderBy[i].iColumn,
+       p->aOrderBy[i].desc);
+  }
+}
+static void whereTraceIndexInfoOutputs(sqlite3_index_info *p){
+  int i;
+  if( (sqlite3WhereTrace & 0x10)==0 ) return;
+  for(i=0; i<p->nConstraint; i++){
+    sqlite3DebugPrintf("  usage[%d]: argvIdx=%d omit=%d\n",
+       i,
+       p->aConstraintUsage[i].argvIndex,
+       p->aConstraintUsage[i].omit);
+  }
+  sqlite3DebugPrintf("  idxNum=%d\n", p->idxNum);
+  sqlite3DebugPrintf("  idxStr=%s\n", p->idxStr);
+  sqlite3DebugPrintf("  orderByConsumed=%d\n", p->orderByConsumed);
+  sqlite3DebugPrintf("  estimatedCost=%g\n", p->estimatedCost);
+  sqlite3DebugPrintf("  estimatedRows=%lld\n", p->estimatedRows);
+}
+#else
+#define whereTraceIndexInfoInputs(A)
+#define whereTraceIndexInfoOutputs(A)
+#endif
+
+/*
+** We know that pSrc is an operand of an outer join.  Return true if
+** pTerm is a constraint that is compatible with that join.
+**
+** pTerm must be EP_OuterON if pSrc is the right operand of an
+** outer join.  pTerm can be either EP_OuterON or EP_InnerON if pSrc
+** is the left operand of a RIGHT join.
+**
+** See https://sqlite.org/forum/forumpost/206d99a16dd9212f
+** for an example of a WHERE clause constraints that may not be used on
+** the right table of a RIGHT JOIN because the constraint implies a
+** not-NULL condition on the left table of the RIGHT JOIN.
+*/
+static int constraintCompatibleWithOuterJoin(
+  const WhereTerm *pTerm,       /* WHERE clause term to check */
+  const SrcItem *pSrc           /* Table we are trying to access */
+){
+  assert( (pSrc->fg.jointype&(JT_LEFT|JT_LTORJ|JT_RIGHT))!=0 ); /* By caller */
+  testcase( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))==JT_LEFT );
+  testcase( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))==JT_LTORJ );
+  testcase( ExprHasProperty(pTerm->pExpr, EP_OuterON) )
+  testcase( ExprHasProperty(pTerm->pExpr, EP_InnerON) );
+  if( !ExprHasProperty(pTerm->pExpr, EP_OuterON|EP_InnerON)
+   || pTerm->pExpr->w.iJoin != pSrc->iCursor
+  ){
+    return 0;
+  }
+  if( (pSrc->fg.jointype & (JT_LEFT|JT_RIGHT))!=0
+   && ExprHasProperty(pTerm->pExpr, EP_InnerON)
+  ){
+    return 0;
+  }
+  return 1;
+}
+
+
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** Return TRUE if the WHERE clause term pTerm is of a form where it
+** could be used with an index to access pSrc, assuming an appropriate
+** index existed.
+*/
+static int termCanDriveIndex(
+  const WhereTerm *pTerm,        /* WHERE clause term to check */
+  const SrcItem *pSrc,           /* Table we are trying to access */
+  const Bitmask notReady         /* Tables in outer loops of the join */
+){
+  char aff;
+  if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
+  if( (pTerm->eOperator & (WO_EQ|WO_IS))==0 ) return 0;
+  assert( (pSrc->fg.jointype & JT_RIGHT)==0 );
+  if( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))!=0
+   && !constraintCompatibleWithOuterJoin(pTerm,pSrc)
+  ){
+    return 0;  /* See https://sqlite.org/forum/forumpost/51e6959f61 */
+  }
+  if( (pTerm->prereqRight & notReady)!=0 ) return 0;
+  assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+  if( pTerm->u.x.leftColumn<0 ) return 0;
+  aff = pSrc->pTab->aCol[pTerm->u.x.leftColumn].affinity;
+  if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
+  testcase( pTerm->pExpr->op==TK_IS );
+  return 1;
+}
+#endif
+
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+/*
+** Argument pIdx represents an automatic index that the current statement
+** will create and populate. Add an OP_Explain with text of the form:
+**
+**     CREATE AUTOMATIC INDEX ON <table>(<cols>) [WHERE <expr>]
+**
+** This is only required if sqlite3_stmt_scanstatus() is enabled, to
+** associate an SQLITE_SCANSTAT_NCYCLE and SQLITE_SCANSTAT_NLOOP
+** values with. In order to avoid breaking legacy code and test cases,
+** the OP_Explain is not added if this is an EXPLAIN QUERY PLAN command.
+*/
+static void explainAutomaticIndex(
+  Parse *pParse,
+  Index *pIdx,                    /* Automatic index to explain */
+  int bPartial,                   /* True if pIdx is a partial index */
+  int *pAddrExplain               /* OUT: Address of OP_Explain */
+){
+  if( IS_STMT_SCANSTATUS(pParse->db) && pParse->explain!=2 ){
+    Table *pTab = pIdx->pTable;
+    const char *zSep = "";
+    char *zText = 0;
+    int ii = 0;
+    sqlite3_str *pStr = sqlite3_str_new(pParse->db);
+    sqlite3_str_appendf(pStr,"CREATE AUTOMATIC INDEX ON %s(", pTab->zName);
+    assert( pIdx->nColumn>1 );
+    assert( pIdx->aiColumn[pIdx->nColumn-1]==XN_ROWID );
+    for(ii=0; ii<(pIdx->nColumn-1); ii++){
+      const char *zName = 0;
+      int iCol = pIdx->aiColumn[ii];
+
+      zName = pTab->aCol[iCol].zCnName;
+      sqlite3_str_appendf(pStr, "%s%s", zSep, zName);
+      zSep = ", ";
+    }
+    zText = sqlite3_str_finish(pStr);
+    if( zText==0 ){
+      sqlite3OomFault(pParse->db);
+    }else{
+      *pAddrExplain = sqlite3VdbeExplain(
+          pParse, 0, "%s)%s", zText, (bPartial ? " WHERE <expr>" : "")
+      );
+      sqlite3_free(zText);
+    }
+  }
+}
+#else
+# define explainAutomaticIndex(a,b,c,d)
+#endif
+
+/*
+** Generate code to construct the Index object for an automatic index
+** and to set up the WhereLevel object pLevel so that the code generator
+** makes use of the automatic index.
+*/
+static SQLITE_NOINLINE void constructAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  const Bitmask notReady,     /* Mask of cursors that are not available */
+  WhereLevel *pLevel          /* Write new index here */
+){
+  int nKeyCol;                /* Number of columns in the constructed index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  Index *pIdx;                /* Object describing the transient index */
+  Vdbe *v;                    /* Prepared statement under construction */
+  int addrInit;               /* Address of the initialization bypass jump */
+  Table *pTable;              /* The table being indexed */
+  int addrTop;                /* Top of the index fill loop */
+  int regRecord;              /* Register holding an index record */
+  int n;                      /* Column counter */
+  int i;                      /* Loop counter */
+  int mxBitCol;               /* Maximum column in pSrc->colUsed */
+  CollSeq *pColl;             /* Collating sequence to on a column */
+  WhereLoop *pLoop;           /* The Loop object */
+  char *zNotUsed;             /* Extra space on the end of pIdx */
+  Bitmask idxCols;            /* Bitmap of columns used for indexing */
+  Bitmask extraCols;          /* Bitmap of additional columns */
+  u8 sentWarning = 0;         /* True if a warning has been issued */
+  u8 useBloomFilter = 0;      /* True to also add a Bloom filter */
+  Expr *pPartial = 0;         /* Partial Index Expression */
+  int iContinue = 0;          /* Jump here to skip excluded rows */
+  SrcList *pTabList;          /* The complete FROM clause */
+  SrcItem *pSrc;              /* The FROM clause term to get the next index */
+  int addrCounter = 0;        /* Address where integer counter is initialized */
+  int regBase;                /* Array of registers where record is assembled */
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  int addrExp = 0;            /* Address of OP_Explain */
+#endif
+
+  /* Generate code to skip over the creation and initialization of the
+  ** transient index on 2nd and subsequent iterations of the loop. */
+  v = pParse->pVdbe;
+  assert( v!=0 );
+  addrInit = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+
+  /* Count the number of columns that will be added to the index
+  ** and used to match WHERE clause constraints */
+  nKeyCol = 0;
+  pTabList = pWC->pWInfo->pTabList;
+  pSrc = &pTabList->a[pLevel->iFrom];
+  pTable = pSrc->pTab;
+  pWCEnd = &pWC->a[pWC->nTerm];
+  pLoop = pLevel->pWLoop;
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    Expr *pExpr = pTerm->pExpr;
+    /* Make the automatic index a partial index if there are terms in the
+    ** WHERE clause (or the ON clause of a LEFT join) that constrain which
+    ** rows of the target table (pSrc) that can be used. */
+    if( (pTerm->wtFlags & TERM_VIRTUAL)==0
+     && sqlite3ExprIsSingleTableConstraint(pExpr, pTabList, pLevel->iFrom)
+    ){
+      pPartial = sqlite3ExprAnd(pParse, pPartial,
+                                sqlite3ExprDup(pParse->db, pExpr, 0));
+    }
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol;
+      Bitmask cMask;
+      assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+      iCol = pTerm->u.x.leftColumn;
+      cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
+      if( !sentWarning ){
+        sqlite3_log(SQLITE_WARNING_AUTOINDEX,
+            "automatic index on %s(%s)", pTable->zName,
+            pTable->aCol[iCol].zCnName);
+        sentWarning = 1;
+      }
+      if( (idxCols & cMask)==0 ){
+        if( whereLoopResize(pParse->db, pLoop, nKeyCol+1) ){
+          goto end_auto_index_create;
+        }
+        pLoop->aLTerm[nKeyCol++] = pTerm;
+        idxCols |= cMask;
+      }
+    }
+  }
+  assert( nKeyCol>0 || pParse->db->mallocFailed );
+  pLoop->u.btree.nEq = pLoop->nLTerm = nKeyCol;
+  pLoop->wsFlags = WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WHERE_INDEXED
+                     | WHERE_AUTO_INDEX;
+
+  /* Count the number of additional columns needed to create a
+  ** covering index.  A "covering index" is an index that contains all
+  ** columns that are needed by the query.  With a covering index, the
+  ** original table never needs to be accessed.  Automatic indices must
+  ** be a covering index because the index will not be updated if the
+  ** original table changes and the index and table cannot both be used
+  ** if they go out of sync.
+  */
+  if( IsView(pTable) ){
+    extraCols = ALLBITS;
+  }else{
+    extraCols = pSrc->colUsed & (~idxCols | MASKBIT(BMS-1));
+  }
+  mxBitCol = MIN(BMS-1,pTable->nCol);
+  testcase( pTable->nCol==BMS-1 );
+  testcase( pTable->nCol==BMS-2 );
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & MASKBIT(i) ) nKeyCol++;
+  }
+  if( pSrc->colUsed & MASKBIT(BMS-1) ){
+    nKeyCol += pTable->nCol - BMS + 1;
+  }
+
+  /* Construct the Index object to describe this index */
+  pIdx = sqlite3AllocateIndexObject(pParse->db, nKeyCol+1, 0, &zNotUsed);
+  if( pIdx==0 ) goto end_auto_index_create;
+  pLoop->u.btree.pIndex = pIdx;
+  pIdx->zName = "auto-index";
+  pIdx->pTable = pTable;
+  n = 0;
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol;
+      Bitmask cMask;
+      assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+      iCol = pTerm->u.x.leftColumn;
+      cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
+      testcase( iCol==BMS-1 );
+      testcase( iCol==BMS );
+      if( (idxCols & cMask)==0 ){
+        Expr *pX = pTerm->pExpr;
+        idxCols |= cMask;
+        pIdx->aiColumn[n] = pTerm->u.x.leftColumn;
+        pColl = sqlite3ExprCompareCollSeq(pParse, pX);
+        assert( pColl!=0 || pParse->nErr>0 ); /* TH3 collate01.800 */
+        pIdx->azColl[n] = pColl ? pColl->zName : sqlite3StrBINARY;
+        n++;
+        if( ALWAYS(pX->pLeft!=0)
+         && sqlite3ExprAffinity(pX->pLeft)!=SQLITE_AFF_TEXT
+        ){
+          /* TUNING: only use a Bloom filter on an automatic index
+          ** if one or more key columns has the ability to hold numeric
+          ** values, since strings all have the same hash in the Bloom
+          ** filter implementation and hence a Bloom filter on a text column
+          ** is not usually helpful. */
+          useBloomFilter = 1;
+        }
+      }
+    }
+  }
+  assert( (u32)n==pLoop->u.btree.nEq );
+
+  /* Add additional columns needed to make the automatic index into
+  ** a covering index */
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & MASKBIT(i) ){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = sqlite3StrBINARY;
+      n++;
+    }
+  }
+  if( pSrc->colUsed & MASKBIT(BMS-1) ){
+    for(i=BMS-1; i<pTable->nCol; i++){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = sqlite3StrBINARY;
+      n++;
+    }
+  }
+  assert( n==nKeyCol );
+  pIdx->aiColumn[n] = XN_ROWID;
+  pIdx->azColl[n] = sqlite3StrBINARY;
+
+  /* Create the automatic index */
+  explainAutomaticIndex(pParse, pIdx, pPartial!=0, &addrExp);
+  assert( pLevel->iIdxCur>=0 );
+  pLevel->iIdxCur = pParse->nTab++;
+  sqlite3VdbeAddOp2(v, OP_OpenAutoindex, pLevel->iIdxCur, nKeyCol+1);
+  sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
+  VdbeComment((v, "for %s", pTable->zName));
+  if( OptimizationEnabled(pParse->db, SQLITE_BloomFilter) && useBloomFilter ){
+    sqlite3WhereExplainBloomFilter(pParse, pWC->pWInfo, pLevel);
+    pLevel->regFilter = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Blob, 10000, pLevel->regFilter);
+  }
+
+  /* Fill the automatic index with content */
+  assert( pSrc == &pWC->pWInfo->pTabList->a[pLevel->iFrom] );
+  if( pSrc->fg.viaCoroutine ){
+    int regYield = pSrc->regReturn;
+    addrCounter = sqlite3VdbeAddOp2(v, OP_Integer, 0, 0);
+    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pSrc->addrFillSub);
+    addrTop =  sqlite3VdbeAddOp1(v, OP_Yield, regYield);
+    VdbeCoverage(v);
+    VdbeComment((v, "next row of %s", pSrc->pTab->zName));
+  }else{
+    addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur); VdbeCoverage(v);
+  }
+  if( pPartial ){
+    iContinue = sqlite3VdbeMakeLabel(pParse);
+    sqlite3ExprIfFalse(pParse, pPartial, iContinue, SQLITE_JUMPIFNULL);
+    pLoop->wsFlags |= WHERE_PARTIALIDX;
+  }
+  regRecord = sqlite3GetTempReg(pParse);
+  regBase = sqlite3GenerateIndexKey(
+      pParse, pIdx, pLevel->iTabCur, regRecord, 0, 0, 0, 0
+  );
+  if( pLevel->regFilter ){
+    sqlite3VdbeAddOp4Int(v, OP_FilterAdd, pLevel->regFilter, 0,
+                         regBase, pLoop->u.btree.nEq);
+  }
+  sqlite3VdbeScanStatusCounters(v, addrExp, addrExp, sqlite3VdbeCurrentAddr(v));
+  sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+  if( pPartial ) sqlite3VdbeResolveLabel(v, iContinue);
+  if( pSrc->fg.viaCoroutine ){
+    sqlite3VdbeChangeP2(v, addrCounter, regBase+n);
+    testcase( pParse->db->mallocFailed );
+    assert( pLevel->iIdxCur>0 );
+    translateColumnToCopy(pParse, addrTop, pLevel->iTabCur,
+                          pSrc->regResult, pLevel->iIdxCur);
+    sqlite3VdbeGoto(v, addrTop);
+    pSrc->fg.viaCoroutine = 0;
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1); VdbeCoverage(v);
+    sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
+  }
+  sqlite3VdbeJumpHere(v, addrTop);
+  sqlite3ReleaseTempReg(pParse, regRecord);
+ 
+  /* Jump here when skipping the initialization */
+  sqlite3VdbeJumpHere(v, addrInit);
+  sqlite3VdbeScanStatusRange(v, addrExp, addrExp, -1);
+
+end_auto_index_create:
+  sqlite3ExprDelete(pParse->db, pPartial);
+}
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
+/*
+** Generate bytecode that will initialize a Bloom filter that is appropriate
+** for pLevel.
+**
+** If there are inner loops within pLevel that have the WHERE_BLOOMFILTER
+** flag set, initialize a Bloomfilter for them as well.  Except don't do
+** this recursive initialization if the SQLITE_BloomPulldown optimization has
+** been turned off.
+**
+** When the Bloom filter is initialized, the WHERE_BLOOMFILTER flag is cleared
+** from the loop, but the regFilter value is set to a register that implements
+** the Bloom filter.  When regFilter is positive, the
+** sqlite3WhereCodeOneLoopStart() will generate code to test the Bloom filter
+** and skip the subsequence B-Tree seek if the Bloom filter indicates that
+** no matching rows exist.
+**
+** This routine may only be called if it has previously been determined that
+** the loop would benefit from a Bloom filter, and the WHERE_BLOOMFILTER bit
+** is set.
+*/
+static SQLITE_NOINLINE void sqlite3ConstructBloomFilter(
+  WhereInfo *pWInfo,    /* The WHERE clause */
+  int iLevel,           /* Index in pWInfo->a[] that is pLevel */
+  WhereLevel *pLevel,   /* Make a Bloom filter for this FROM term */
+  Bitmask notReady      /* Loops that are not ready */
+){
+  int addrOnce;                        /* Address of opening OP_Once */
+  int addrTop;                         /* Address of OP_Rewind */
+  int addrCont;                        /* Jump here to skip a row */
+  const WhereTerm *pTerm;              /* For looping over WHERE clause terms */
+  const WhereTerm *pWCEnd;             /* Last WHERE clause term */
+  Parse *pParse = pWInfo->pParse;      /* Parsing context */
+  Vdbe *v = pParse->pVdbe;             /* VDBE under construction */
+  WhereLoop *pLoop = pLevel->pWLoop;   /* The loop being coded */
+  int iCur;                            /* Cursor for table getting the filter */
+  IndexedExpr *saved_pIdxEpr;          /* saved copy of Parse.pIdxEpr */
+  IndexedExpr *saved_pIdxPartExpr;     /* saved copy of Parse.pIdxPartExpr */
+
+  saved_pIdxEpr = pParse->pIdxEpr;
+  saved_pIdxPartExpr = pParse->pIdxPartExpr;
+  pParse->pIdxEpr = 0;
+  pParse->pIdxPartExpr = 0;
+
+  assert( pLoop!=0 );
+  assert( v!=0 );
+  assert( pLoop->wsFlags & WHERE_BLOOMFILTER );
+  assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0 );
+
+  addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
+  do{
+    const SrcList *pTabList;
+    const SrcItem *pItem;
+    const Table *pTab;
+    u64 sz;
+    int iSrc;
+    sqlite3WhereExplainBloomFilter(pParse, pWInfo, pLevel);
+    addrCont = sqlite3VdbeMakeLabel(pParse);
+    iCur = pLevel->iTabCur;
+    pLevel->regFilter = ++pParse->nMem;
+
+    /* The Bloom filter is a Blob held in a register.  Initialize it
+    ** to zero-filled blob of at least 80K bits, but maybe more if the
+    ** estimated size of the table is larger.  We could actually
+    ** measure the size of the table at run-time using OP_Count with
+    ** P3==1 and use that value to initialize the blob.  But that makes
+    ** testing complicated.  By basing the blob size on the value in the
+    ** sqlite_stat1 table, testing is much easier.
+    */
+    pTabList = pWInfo->pTabList;
+    iSrc = pLevel->iFrom;
+    pItem = &pTabList->a[iSrc];
+    assert( pItem!=0 );
+    pTab = pItem->pTab;
+    assert( pTab!=0 );
+    sz = sqlite3LogEstToInt(pTab->nRowLogEst);
+    if( sz<10000 ){
+      sz = 10000;
+    }else if( sz>10000000 ){
+      sz = 10000000;
+    }
+    sqlite3VdbeAddOp2(v, OP_Blob, (int)sz, pLevel->regFilter);
+
+    addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
+    pWCEnd = &pWInfo->sWC.a[pWInfo->sWC.nTerm];
+    for(pTerm=pWInfo->sWC.a; pTerm<pWCEnd; pTerm++){
+      Expr *pExpr = pTerm->pExpr;
+      if( (pTerm->wtFlags & TERM_VIRTUAL)==0
+       && sqlite3ExprIsSingleTableConstraint(pExpr, pTabList, iSrc)
+      ){
+        sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
+      }
+    }
+    if( pLoop->wsFlags & WHERE_IPK ){
+      int r1 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);
+      sqlite3VdbeAddOp4Int(v, OP_FilterAdd, pLevel->regFilter, 0, r1, 1);
+      sqlite3ReleaseTempReg(pParse, r1);
+    }else{
+      Index *pIdx = pLoop->u.btree.pIndex;
+      int n = pLoop->u.btree.nEq;
+      int r1 = sqlite3GetTempRange(pParse, n);
+      int jj;
+      for(jj=0; jj<n; jj++){
+        assert( pIdx->pTable==pItem->pTab );
+        sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iCur, jj, r1+jj);
+      }
+      sqlite3VdbeAddOp4Int(v, OP_FilterAdd, pLevel->regFilter, 0, r1, n);
+      sqlite3ReleaseTempRange(pParse, r1, n);
+    }
+    sqlite3VdbeResolveLabel(v, addrCont);
+    sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1);
+    VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addrTop);
+    pLoop->wsFlags &= ~WHERE_BLOOMFILTER;
+    if( OptimizationDisabled(pParse->db, SQLITE_BloomPulldown) ) break;
+    while( ++iLevel < pWInfo->nLevel ){
+      const SrcItem *pTabItem;
+      pLevel = &pWInfo->a[iLevel];
+      pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
+      if( pTabItem->fg.jointype & (JT_LEFT|JT_LTORJ) ) continue;
+      pLoop = pLevel->pWLoop;
+      if( NEVER(pLoop==0) ) continue;
+      if( pLoop->prereq & notReady ) continue;
+      if( (pLoop->wsFlags & (WHERE_BLOOMFILTER|WHERE_COLUMN_IN))
+                 ==WHERE_BLOOMFILTER
+      ){
+        /* This is a candidate for bloom-filter pull-down (early evaluation).
+        ** The test that WHERE_COLUMN_IN is omitted is important, as we are
+        ** not able to do early evaluation of bloom filters that make use of
+        ** the IN operator */
+        break;
+      }
+    }
+  }while( iLevel < pWInfo->nLevel );
+  sqlite3VdbeJumpHere(v, addrOnce);
+  pParse->pIdxEpr = saved_pIdxEpr;
+  pParse->pIdxPartExpr = saved_pIdxPartExpr;
+}
+
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Allocate and populate an sqlite3_index_info structure. It is the
+** responsibility of the caller to eventually release the structure
+** by passing the pointer returned by this function to freeIndexInfo().
+*/
+static sqlite3_index_info *allocateIndexInfo(
+  WhereInfo *pWInfo,              /* The WHERE clause */
+  WhereClause *pWC,               /* The WHERE clause being analyzed */
+  Bitmask mUnusable,              /* Ignore terms with these prereqs */
+  SrcItem *pSrc,                  /* The FROM clause term that is the vtab */
+  u16 *pmNoOmit                   /* Mask of terms not to omit */
+){
+  int i, j;
+  int nTerm;
+  Parse *pParse = pWInfo->pParse;
+  struct sqlite3_index_constraint *pIdxCons;
+  struct sqlite3_index_orderby *pIdxOrderBy;
+  struct sqlite3_index_constraint_usage *pUsage;
+  struct HiddenIndexInfo *pHidden;
+  WhereTerm *pTerm;
+  int nOrderBy;
+  sqlite3_index_info *pIdxInfo;
+  u16 mNoOmit = 0;
+  const Table *pTab;
+  int eDistinct = 0;
+  ExprList *pOrderBy = pWInfo->pOrderBy;
+
+  assert( pSrc!=0 );
+  pTab = pSrc->pTab;
+  assert( pTab!=0 );
+  assert( IsVirtual(pTab) );
+
+  /* Find all WHERE clause constraints referring to this virtual table.
+  ** Mark each term with the TERM_OK flag.  Set nTerm to the number of
+  ** terms found.
+  */
+  for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    pTerm->wtFlags &= ~TERM_OK;
+    if( pTerm->leftCursor != pSrc->iCursor ) continue;
+    if( pTerm->prereqRight & mUnusable ) continue;
+    assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
+    testcase( pTerm->eOperator & WO_IN );
+    testcase( pTerm->eOperator & WO_ISNULL );
+    testcase( pTerm->eOperator & WO_IS );
+    testcase( pTerm->eOperator & WO_ALL );
+    if( (pTerm->eOperator & ~(WO_EQUIV))==0 ) continue;
+    if( pTerm->wtFlags & TERM_VNULL ) continue;
+
+    assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+    assert( pTerm->u.x.leftColumn>=XN_ROWID );
+    assert( pTerm->u.x.leftColumn<pTab->nCol );
+    if( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))!=0
+     && !constraintCompatibleWithOuterJoin(pTerm,pSrc)
+    ){
+      continue;
+    }
+    nTerm++;
+    pTerm->wtFlags |= TERM_OK;
+  }
+
+  /* If the ORDER BY clause contains only columns in the current
+  ** virtual table then allocate space for the aOrderBy part of
+  ** the sqlite3_index_info structure.
+  */
+  nOrderBy = 0;
+  if( pOrderBy ){
+    int n = pOrderBy->nExpr;
+    for(i=0; i<n; i++){
+      Expr *pExpr = pOrderBy->a[i].pExpr;
+      Expr *pE2;
+
+      /* Skip over constant terms in the ORDER BY clause */
+      if( sqlite3ExprIsConstant(pExpr) ){
+        continue;
+      }
+
+      /* Virtual tables are unable to deal with NULLS FIRST */
+      if( pOrderBy->a[i].fg.sortFlags & KEYINFO_ORDER_BIGNULL ) break;
+
+      /* First case - a direct column references without a COLLATE operator */
+      if( pExpr->op==TK_COLUMN && pExpr->iTable==pSrc->iCursor ){
+        assert( pExpr->iColumn>=XN_ROWID && pExpr->iColumn<pTab->nCol );
+        continue;
+      }
+
+      /* 2nd case - a column reference with a COLLATE operator.  Only match
+      ** of the COLLATE operator matches the collation of the column. */
+      if( pExpr->op==TK_COLLATE
+       && (pE2 = pExpr->pLeft)->op==TK_COLUMN
+       && pE2->iTable==pSrc->iCursor
+      ){
+        const char *zColl;  /* The collating sequence name */
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        assert( pExpr->u.zToken!=0 );
+        assert( pE2->iColumn>=XN_ROWID && pE2->iColumn<pTab->nCol );
+        pExpr->iColumn = pE2->iColumn;
+        if( pE2->iColumn<0 ) continue;  /* Collseq does not matter for rowid */
+        zColl = sqlite3ColumnColl(&pTab->aCol[pE2->iColumn]);
+        if( zColl==0 ) zColl = sqlite3StrBINARY;
+        if( sqlite3_stricmp(pExpr->u.zToken, zColl)==0 ) continue;
+      }
+
+      /* No matches cause a break out of the loop */
+      break;
+    }
+    if( i==n ){
+      nOrderBy = n;
+      if( (pWInfo->wctrlFlags & WHERE_DISTINCTBY) ){
+        eDistinct = 2 + ((pWInfo->wctrlFlags & WHERE_SORTBYGROUP)!=0);
+      }else if( pWInfo->wctrlFlags & WHERE_GROUPBY ){
+        eDistinct = 1;
+      }
+    }
+  }
+
+  /* Allocate the sqlite3_index_info structure
+  */
+  pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
+                           + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
+                           + sizeof(*pIdxOrderBy)*nOrderBy + sizeof(*pHidden)
+                           + sizeof(sqlite3_value*)*nTerm );
+  if( pIdxInfo==0 ){
+    sqlite3ErrorMsg(pParse, "out of memory");
+    return 0;
+  }
+  pHidden = (struct HiddenIndexInfo*)&pIdxInfo[1];
+  pIdxCons = (struct sqlite3_index_constraint*)&pHidden->aRhs[nTerm];
+  pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
+  pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
+  pIdxInfo->aConstraint = pIdxCons;
+  pIdxInfo->aOrderBy = pIdxOrderBy;
+  pIdxInfo->aConstraintUsage = pUsage;
+  pHidden->pWC = pWC;
+  pHidden->pParse = pParse;
+  pHidden->eDistinct = eDistinct;
+  pHidden->mIn = 0;
+  for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    u16 op;
+    if( (pTerm->wtFlags & TERM_OK)==0 ) continue;
+    pIdxCons[j].iColumn = pTerm->u.x.leftColumn;
+    pIdxCons[j].iTermOffset = i;
+    op = pTerm->eOperator & WO_ALL;
+    if( op==WO_IN ){
+      if( (pTerm->wtFlags & TERM_SLICE)==0 ){
+        pHidden->mIn |= SMASKBIT32(j);
+      }
+      op = WO_EQ;
+    }
+    if( op==WO_AUX ){
+      pIdxCons[j].op = pTerm->eMatchOp;
+    }else if( op & (WO_ISNULL|WO_IS) ){
+      if( op==WO_ISNULL ){
+        pIdxCons[j].op = SQLITE_INDEX_CONSTRAINT_ISNULL;
+      }else{
+        pIdxCons[j].op = SQLITE_INDEX_CONSTRAINT_IS;
+      }
+    }else{
+      pIdxCons[j].op = (u8)op;
+      /* The direct assignment in the previous line is possible only because
+      ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
+      ** following asserts verify this fact. */
+      assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
+      assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
+      assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
+      assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
+      assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
+      assert( pTerm->eOperator&(WO_IN|WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_AUX) );
+
+      if( op & (WO_LT|WO_LE|WO_GT|WO_GE)
+       && sqlite3ExprIsVector(pTerm->pExpr->pRight)
+      ){
+        testcase( j!=i );
+        if( j<16 ) mNoOmit |= (1 << j);
+        if( op==WO_LT ) pIdxCons[j].op = WO_LE;
+        if( op==WO_GT ) pIdxCons[j].op = WO_GE;
+      }
+    }
+
+    j++;
+  }
+  assert( j==nTerm );
+  pIdxInfo->nConstraint = j;
+  for(i=j=0; i<nOrderBy; i++){
+    Expr *pExpr = pOrderBy->a[i].pExpr;
+    if( sqlite3ExprIsConstant(pExpr) ) continue;
+    assert( pExpr->op==TK_COLUMN
+         || (pExpr->op==TK_COLLATE && pExpr->pLeft->op==TK_COLUMN
+              && pExpr->iColumn==pExpr->pLeft->iColumn) );
+    pIdxOrderBy[j].iColumn = pExpr->iColumn;
+    pIdxOrderBy[j].desc = pOrderBy->a[i].fg.sortFlags & KEYINFO_ORDER_DESC;
+    j++;
+  }
+  pIdxInfo->nOrderBy = j;
+
+  *pmNoOmit = mNoOmit;
+  return pIdxInfo;
+}
+
+/*
+** Free an sqlite3_index_info structure allocated by allocateIndexInfo()
+** and possibly modified by xBestIndex methods.
+*/
+static void freeIndexInfo(sqlite3 *db, sqlite3_index_info *pIdxInfo){
+  HiddenIndexInfo *pHidden;
+  int i;
+  assert( pIdxInfo!=0 );
+  pHidden = (HiddenIndexInfo*)&pIdxInfo[1];
+  assert( pHidden->pParse!=0 );
+  assert( pHidden->pParse->db==db );
+  for(i=0; i<pIdxInfo->nConstraint; i++){
+    sqlite3ValueFree(pHidden->aRhs[i]); /* IMP: R-14553-25174 */
+    pHidden->aRhs[i] = 0;
+  }
+  sqlite3DbFree(db, pIdxInfo);
+}
+
+/*
+** The table object reference passed as the second argument to this function
+** must represent a virtual table. This function invokes the xBestIndex()
+** method of the virtual table with the sqlite3_index_info object that
+** comes in as the 3rd argument to this function.
+**
+** If an error occurs, pParse is populated with an error message and an
+** appropriate error code is returned.  A return of SQLITE_CONSTRAINT from
+** xBestIndex is not considered an error.  SQLITE_CONSTRAINT indicates that
+** the current configuration of "unusable" flags in sqlite3_index_info can
+** not result in a valid plan.
+**
+** Whether or not an error is returned, it is the responsibility of the
+** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
+** that this is required.
+*/
+static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
+  sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
+  int rc;
+
+  whereTraceIndexInfoInputs(p);
+  pParse->db->nSchemaLock++;
+  rc = pVtab->pModule->xBestIndex(pVtab, p);
+  pParse->db->nSchemaLock--;
+  whereTraceIndexInfoOutputs(p);
+
+  if( rc!=SQLITE_OK && rc!=SQLITE_CONSTRAINT ){
+    if( rc==SQLITE_NOMEM ){
+      sqlite3OomFault(pParse->db);
+    }else if( !pVtab->zErrMsg ){
+      sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
+    }else{
+      sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
+    }
+  }
+  if( pTab->u.vtab.p->bAllSchemas ){
+    sqlite3VtabUsesAllSchemas(pParse);
+  }
+  sqlite3_free(pVtab->zErrMsg);
+  pVtab->zErrMsg = 0;
+  return rc;
+}
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Estimate the location of a particular key among all keys in an
+** index.  Store the results in aStat as follows:
+**
+**    aStat[0]      Est. number of rows less than pRec
+**    aStat[1]      Est. number of rows equal to pRec
+**
+** Return the index of the sample that is the smallest sample that
+** is greater than or equal to pRec. Note that this index is not an index
+** into the aSample[] array - it is an index into a virtual set of samples
+** based on the contents of aSample[] and the number of fields in record
+** pRec.
+*/
+static int whereKeyStats(
+  Parse *pParse,              /* Database connection */
+  Index *pIdx,                /* Index to consider domain of */
+  UnpackedRecord *pRec,       /* Vector of values to consider */
+  int roundUp,                /* Round up if true.  Round down if false */
+  tRowcnt *aStat              /* OUT: stats written here */
+){
+  IndexSample *aSample = pIdx->aSample;
+  int iCol;                   /* Index of required stats in anEq[] etc. */
+  int i;                      /* Index of first sample >= pRec */
+  int iSample;                /* Smallest sample larger than or equal to pRec */
+  int iMin = 0;               /* Smallest sample not yet tested */
+  int iTest;                  /* Next sample to test */
+  int res;                    /* Result of comparison operation */
+  int nField;                 /* Number of fields in pRec */
+  tRowcnt iLower = 0;         /* anLt[] + anEq[] of largest sample pRec is > */
+
+#ifndef SQLITE_DEBUG
+  UNUSED_PARAMETER( pParse );
+#endif
+  assert( pRec!=0 );
+  assert( pIdx->nSample>0 );
+  assert( pRec->nField>0 );
+
+
+  /* Do a binary search to find the first sample greater than or equal
+  ** to pRec. If pRec contains a single field, the set of samples to search
+  ** is simply the aSample[] array. If the samples in aSample[] contain more
+  ** than one fields, all fields following the first are ignored.
+  **
+  ** If pRec contains N fields, where N is more than one, then as well as the
+  ** samples in aSample[] (truncated to N fields), the search also has to
+  ** consider prefixes of those samples. For example, if the set of samples
+  ** in aSample is:
+  **
+  **     aSample[0] = (a, 5)
+  **     aSample[1] = (a, 10)
+  **     aSample[2] = (b, 5)
+  **     aSample[3] = (c, 100)
+  **     aSample[4] = (c, 105)
+  **
+  ** Then the search space should ideally be the samples above and the
+  ** unique prefixes [a], [b] and [c]. But since that is hard to organize,
+  ** the code actually searches this set:
+  **
+  **     0: (a)
+  **     1: (a, 5)
+  **     2: (a, 10)
+  **     3: (a, 10)
+  **     4: (b)
+  **     5: (b, 5)
+  **     6: (c)
+  **     7: (c, 100)
+  **     8: (c, 105)
+  **     9: (c, 105)
+  **
+  ** For each sample in the aSample[] array, N samples are present in the
+  ** effective sample array. In the above, samples 0 and 1 are based on
+  ** sample aSample[0]. Samples 2 and 3 on aSample[1] etc.
+  **
+  ** Often, sample i of each block of N effective samples has (i+1) fields.
+  ** Except, each sample may be extended to ensure that it is greater than or
+  ** equal to the previous sample in the array. For example, in the above,
+  ** sample 2 is the first sample of a block of N samples, so at first it
+  ** appears that it should be 1 field in size. However, that would make it
+  ** smaller than sample 1, so the binary search would not work. As a result,
+  ** it is extended to two fields. The duplicates that this creates do not
+  ** cause any problems.
+  */
+  if( !HasRowid(pIdx->pTable) && IsPrimaryKeyIndex(pIdx) ){
+    nField = pIdx->nKeyCol;
+  }else{
+    nField = pIdx->nColumn;
+  }
+  nField = MIN(pRec->nField, nField);
+  iCol = 0;
+  iSample = pIdx->nSample * nField;
+  do{
+    int iSamp;                    /* Index in aSample[] of test sample */
+    int n;                        /* Number of fields in test sample */
+
+    iTest = (iMin+iSample)/2;
+    iSamp = iTest / nField;
+    if( iSamp>0 ){
+      /* The proposed effective sample is a prefix of sample aSample[iSamp].
+      ** Specifically, the shortest prefix of at least (1 + iTest%nField)
+      ** fields that is greater than the previous effective sample.  */
+      for(n=(iTest % nField) + 1; n<nField; n++){
+        if( aSample[iSamp-1].anLt[n-1]!=aSample[iSamp].anLt[n-1] ) break;
+      }
+    }else{
+      n = iTest + 1;
+    }
+
+    pRec->nField = n;
+    res = sqlite3VdbeRecordCompare(aSample[iSamp].n, aSample[iSamp].p, pRec);
+    if( res<0 ){
+      iLower = aSample[iSamp].anLt[n-1] + aSample[iSamp].anEq[n-1];
+      iMin = iTest+1;
+    }else if( res==0 && n<nField ){
+      iLower = aSample[iSamp].anLt[n-1];
+      iMin = iTest+1;
+      res = -1;
+    }else{
+      iSample = iTest;
+      iCol = n-1;
+    }
+  }while( res && iMin<iSample );
+  i = iSample / nField;
+
+#ifdef SQLITE_DEBUG
+  /* The following assert statements check that the binary search code
+  ** above found the right answer. This block serves no purpose other
+  ** than to invoke the asserts.  */
+  if( pParse->db->mallocFailed==0 ){
+    if( res==0 ){
+      /* If (res==0) is true, then pRec must be equal to sample i. */
+      assert( i<pIdx->nSample );
+      assert( iCol==nField-1 );
+      pRec->nField = nField;
+      assert( 0==sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)
+           || pParse->db->mallocFailed
+      );
+    }else{
+      /* Unless i==pIdx->nSample, indicating that pRec is larger than
+      ** all samples in the aSample[] array, pRec must be smaller than the
+      ** (iCol+1) field prefix of sample i.  */
+      assert( i<=pIdx->nSample && i>=0 );
+      pRec->nField = iCol+1;
+      assert( i==pIdx->nSample
+           || sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)>0
+           || pParse->db->mallocFailed );
+
+      /* if i==0 and iCol==0, then record pRec is smaller than all samples
+      ** in the aSample[] array. Otherwise, if (iCol>0) then pRec must
+      ** be greater than or equal to the (iCol) field prefix of sample i.
+      ** If (i>0), then pRec must also be greater than sample (i-1).  */
+      if( iCol>0 ){
+        pRec->nField = iCol;
+        assert( sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)<=0
+             || pParse->db->mallocFailed || CORRUPT_DB );
+      }
+      if( i>0 ){
+        pRec->nField = nField;
+        assert( sqlite3VdbeRecordCompare(aSample[i-1].n, aSample[i-1].p, pRec)<0
+             || pParse->db->mallocFailed || CORRUPT_DB );
+      }
+    }
+  }
+#endif /* ifdef SQLITE_DEBUG */
+
+  if( res==0 ){
+    /* Record pRec is equal to sample i */
+    assert( iCol==nField-1 );
+    aStat[0] = aSample[i].anLt[iCol];
+    aStat[1] = aSample[i].anEq[iCol];
+  }else{
+    /* At this point, the (iCol+1) field prefix of aSample[i] is the first
+    ** sample that is greater than pRec. Or, if i==pIdx->nSample then pRec
+    ** is larger than all samples in the array. */
+    tRowcnt iUpper, iGap;
+    if( i>=pIdx->nSample ){
+      iUpper = pIdx->nRowEst0;
+    }else{
+      iUpper = aSample[i].anLt[iCol];
+    }
+
+    if( iLower>=iUpper ){
+      iGap = 0;
+    }else{
+      iGap = iUpper - iLower;
+    }
+    if( roundUp ){
+      iGap = (iGap*2)/3;
+    }else{
+      iGap = iGap/3;
+    }
+    aStat[0] = iLower + iGap;
+    aStat[1] = pIdx->aAvgEq[nField-1];
+  }
+
+  /* Restore the pRec->nField value before returning.  */
+  pRec->nField = nField;
+  return i;
+}
+#endif /* SQLITE_ENABLE_STAT4 */
+
+/*
+** If it is not NULL, pTerm is a term that provides an upper or lower
+** bound on a range scan. Without considering pTerm, it is estimated
+** that the scan will visit nNew rows. This function returns the number
+** estimated to be visited after taking pTerm into account.
+**
+** If the user explicitly specified a likelihood() value for this term,
+** then the return value is the likelihood multiplied by the number of
+** input rows. Otherwise, this function assumes that an "IS NOT NULL" term
+** has a likelihood of 0.50, and any other term a likelihood of 0.25.
+*/
+static LogEst whereRangeAdjust(WhereTerm *pTerm, LogEst nNew){
+  LogEst nRet = nNew;
+  if( pTerm ){
+    if( pTerm->truthProb<=0 ){
+      nRet += pTerm->truthProb;
+    }else if( (pTerm->wtFlags & TERM_VNULL)==0 ){
+      nRet -= 20;        assert( 20==sqlite3LogEst(4) );
+    }
+  }
+  return nRet;
+}
+
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Return the affinity for a single column of an index.
+*/
+char sqlite3IndexColumnAffinity(sqlite3 *db, Index *pIdx, int iCol){
+  assert( iCol>=0 && iCol<pIdx->nColumn );
+  if( !pIdx->zColAff ){
+    if( sqlite3IndexAffinityStr(db, pIdx)==0 ) return SQLITE_AFF_BLOB;
+  }
+  assert( pIdx->zColAff[iCol]!=0 );
+  return pIdx->zColAff[iCol];
+}
+#endif
+
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** This function is called to estimate the number of rows visited by a
+** range-scan on a skip-scan index. For example:
+**
+**   CREATE INDEX i1 ON t1(a, b, c);
+**   SELECT * FROM t1 WHERE a=? AND c BETWEEN ? AND ?;
+**
+** Value pLoop->nOut is currently set to the estimated number of rows
+** visited for scanning (a=? AND b=?). This function reduces that estimate
+** by some factor to account for the (c BETWEEN ? AND ?) expression based
+** on the stat4 data for the index. this scan will be performed multiple
+** times (once for each (a,b) combination that matches a=?) is dealt with
+** by the caller.
+**
+** It does this by scanning through all stat4 samples, comparing values
+** extracted from pLower and pUpper with the corresponding column in each
+** sample. If L and U are the number of samples found to be less than or
+** equal to the values extracted from pLower and pUpper respectively, and
+** N is the total number of samples, the pLoop->nOut value is adjusted
+** as follows:
+**
+**   nOut = nOut * ( min(U - L, 1) / N )
+**
+** If pLower is NULL, or a value cannot be extracted from the term, L is
+** set to zero. If pUpper is NULL, or a value cannot be extracted from it,
+** U is set to N.
+**
+** Normally, this function sets *pbDone to 1 before returning. However,
+** if no value can be extracted from either pLower or pUpper (and so the
+** estimate of the number of rows delivered remains unchanged), *pbDone
+** is left as is.
+**
+** If an error occurs, an SQLite error code is returned. Otherwise,
+** SQLITE_OK.
+*/
+static int whereRangeSkipScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
+  WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
+  WhereLoop *pLoop,    /* Update the .nOut value of this loop */
+  int *pbDone          /* Set to true if at least one expr. value extracted */
+){
+  Index *p = pLoop->u.btree.pIndex;
+  int nEq = pLoop->u.btree.nEq;
+  sqlite3 *db = pParse->db;
+  int nLower = -1;
+  int nUpper = p->nSample+1;
+  int rc = SQLITE_OK;
+  u8 aff = sqlite3IndexColumnAffinity(db, p, nEq);
+  CollSeq *pColl;
+ 
+  sqlite3_value *p1 = 0;          /* Value extracted from pLower */
+  sqlite3_value *p2 = 0;          /* Value extracted from pUpper */
+  sqlite3_value *pVal = 0;        /* Value extracted from record */
+
+  pColl = sqlite3LocateCollSeq(pParse, p->azColl[nEq]);
+  if( pLower ){
+    rc = sqlite3Stat4ValueFromExpr(pParse, pLower->pExpr->pRight, aff, &p1);
+    nLower = 0;
+  }
+  if( pUpper && rc==SQLITE_OK ){
+    rc = sqlite3Stat4ValueFromExpr(pParse, pUpper->pExpr->pRight, aff, &p2);
+    nUpper = p2 ? 0 : p->nSample;
+  }
+
+  if( p1 || p2 ){
+    int i;
+    int nDiff;
+    for(i=0; rc==SQLITE_OK && i<p->nSample; i++){
+      rc = sqlite3Stat4Column(db, p->aSample[i].p, p->aSample[i].n, nEq, &pVal);
+      if( rc==SQLITE_OK && p1 ){
+        int res = sqlite3MemCompare(p1, pVal, pColl);
+        if( res>=0 ) nLower++;
+      }
+      if( rc==SQLITE_OK && p2 ){
+        int res = sqlite3MemCompare(p2, pVal, pColl);
+        if( res>=0 ) nUpper++;
+      }
+    }
+    nDiff = (nUpper - nLower);
+    if( nDiff<=0 ) nDiff = 1;
+
+    /* If there is both an upper and lower bound specified, and the
+    ** comparisons indicate that they are close together, use the fallback
+    ** method (assume that the scan visits 1/64 of the rows) for estimating
+    ** the number of rows visited. Otherwise, estimate the number of rows
+    ** using the method described in the header comment for this function. */
+    if( nDiff!=1 || pUpper==0 || pLower==0 ){
+      int nAdjust = (sqlite3LogEst(p->nSample) - sqlite3LogEst(nDiff));
+      pLoop->nOut -= nAdjust;
+      *pbDone = 1;
+      WHERETRACE(0x20, ("range skip-scan regions: %u..%u  adjust=%d est=%d\n",
+                           nLower, nUpper, nAdjust*-1, pLoop->nOut));
+    }
+
+  }else{
+    assert( *pbDone==0 );
+  }
+
+  sqlite3ValueFree(p1);
+  sqlite3ValueFree(p2);
+  sqlite3ValueFree(pVal);
+
+  return rc;
+}
+#endif /* SQLITE_ENABLE_STAT4 */
+
+/*
+** This function is used to estimate the number of rows that will be visited
+** by scanning an index for a range of values. The range may have an upper
+** bound, a lower bound, or both. The WHERE clause terms that set the upper
+** and lower bounds are represented by pLower and pUpper respectively. For
+** example, assuming that index p is on t1(a):
+**
+**   ... FROM t1 WHERE a > ? AND a < ? ...
+**                    |_____|   |_____|
+**                       |         |
+**                     pLower    pUpper
+**
+** If either of the upper or lower bound is not present, then NULL is passed in
+** place of the corresponding WhereTerm.
+**
+** The value in (pBuilder->pNew->u.btree.nEq) is the number of the index
+** column subject to the range constraint. Or, equivalently, the number of
+** equality constraints optimized by the proposed index scan. For example,
+** assuming index p is on t1(a, b), and the SQL query is:
+**
+**   ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
+**
+** then nEq is set to 1 (as the range restricted column, b, is the second
+** left-most column of the index). Or, if the query is:
+**
+**   ... FROM t1 WHERE a > ? AND a < ? ...
+**
+** then nEq is set to 0.
+**
+** When this function is called, *pnOut is set to the sqlite3LogEst() of the
+** number of rows that the index scan is expected to visit without
+** considering the range constraints. If nEq is 0, then *pnOut is the number of
+** rows in the index. Assuming no error occurs, *pnOut is adjusted (reduced)
+** to account for the range constraints pLower and pUpper.
+**
+** In the absence of sqlite_stat4 ANALYZE data, or if such data cannot be
+** used, a single range inequality reduces the search space by a factor of 4.
+** and a pair of constraints (x>? AND x<?) reduces the expected number of
+** rows visited by a factor of 64.
+*/
+static int whereRangeScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereLoopBuilder *pBuilder,
+  WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
+  WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
+  WhereLoop *pLoop     /* Modify the .nOut and maybe .rRun fields */
+){
+  int rc = SQLITE_OK;
+  int nOut = pLoop->nOut;
+  LogEst nNew;
+
+#ifdef SQLITE_ENABLE_STAT4
+  Index *p = pLoop->u.btree.pIndex;
+  int nEq = pLoop->u.btree.nEq;
+
+  if( p->nSample>0 && ALWAYS(nEq<p->nSampleCol)
+   && OptimizationEnabled(pParse->db, SQLITE_Stat4)
+  ){
+    if( nEq==pBuilder->nRecValid ){
+      UnpackedRecord *pRec = pBuilder->pRec;
+      tRowcnt a[2];
+      int nBtm = pLoop->u.btree.nBtm;
+      int nTop = pLoop->u.btree.nTop;
+
+      /* Variable iLower will be set to the estimate of the number of rows in
+      ** the index that are less than the lower bound of the range query. The
+      ** lower bound being the concatenation of $P and $L, where $P is the
+      ** key-prefix formed by the nEq values matched against the nEq left-most
+      ** columns of the index, and $L is the value in pLower.
+      **
+      ** Or, if pLower is NULL or $L cannot be extracted from it (because it
+      ** is not a simple variable or literal value), the lower bound of the
+      ** range is $P. Due to a quirk in the way whereKeyStats() works, even
+      ** if $L is available, whereKeyStats() is called for both ($P) and
+      ** ($P:$L) and the larger of the two returned values is used.
+      **
+      ** Similarly, iUpper is to be set to the estimate of the number of rows
+      ** less than the upper bound of the range query. Where the upper bound
+      ** is either ($P) or ($P:$U). Again, even if $U is available, both values
+      ** of iUpper are requested of whereKeyStats() and the smaller used.
+      **
+      ** The number of rows between the two bounds is then just iUpper-iLower.
+      */
+      tRowcnt iLower;     /* Rows less than the lower bound */
+      tRowcnt iUpper;     /* Rows less than the upper bound */
+      int iLwrIdx = -2;   /* aSample[] for the lower bound */
+      int iUprIdx = -1;   /* aSample[] for the upper bound */
+
+      if( pRec ){
+        testcase( pRec->nField!=pBuilder->nRecValid );
+        pRec->nField = pBuilder->nRecValid;
+      }
+      /* Determine iLower and iUpper using ($P) only. */
+      if( nEq==0 ){
+        iLower = 0;
+        iUpper = p->nRowEst0;
+      }else{
+        /* Note: this call could be optimized away - since the same values must
+        ** have been requested when testing key $P in whereEqualScanEst().  */
+        whereKeyStats(pParse, p, pRec, 0, a);
+        iLower = a[0];
+        iUpper = a[0] + a[1];
+      }
+
+      assert( pLower==0 || (pLower->eOperator & (WO_GT|WO_GE))!=0 );
+      assert( pUpper==0 || (pUpper->eOperator & (WO_LT|WO_LE))!=0 );
+      assert( p->aSortOrder!=0 );
+      if( p->aSortOrder[nEq] ){
+        /* The roles of pLower and pUpper are swapped for a DESC index */
+        SWAP(WhereTerm*, pLower, pUpper);
+        SWAP(int, nBtm, nTop);
+      }
+
+      /* If possible, improve on the iLower estimate using ($P:$L). */
+      if( pLower ){
+        int n;                    /* Values extracted from pExpr */
+        Expr *pExpr = pLower->pExpr->pRight;
+        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, nBtm, nEq, &n);
+        if( rc==SQLITE_OK && n ){
+          tRowcnt iNew;
+          u16 mask = WO_GT|WO_LE;
+          if( sqlite3ExprVectorSize(pExpr)>n ) mask = (WO_LE|WO_LT);
+          iLwrIdx = whereKeyStats(pParse, p, pRec, 0, a);
+          iNew = a[0] + ((pLower->eOperator & mask) ? a[1] : 0);
+          if( iNew>iLower ) iLower = iNew;
+          nOut--;
+          pLower = 0;
+        }
+      }
+
+      /* If possible, improve on the iUpper estimate using ($P:$U). */
+      if( pUpper ){
+        int n;                    /* Values extracted from pExpr */
+        Expr *pExpr = pUpper->pExpr->pRight;
+        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, nTop, nEq, &n);
+        if( rc==SQLITE_OK && n ){
+          tRowcnt iNew;
+          u16 mask = WO_GT|WO_LE;
+          if( sqlite3ExprVectorSize(pExpr)>n ) mask = (WO_LE|WO_LT);
+          iUprIdx = whereKeyStats(pParse, p, pRec, 1, a);
+          iNew = a[0] + ((pUpper->eOperator & mask) ? a[1] : 0);
+          if( iNew<iUpper ) iUpper = iNew;
+          nOut--;
+          pUpper = 0;
+        }
+      }
+
+      pBuilder->pRec = pRec;
+      if( rc==SQLITE_OK ){
+        if( iUpper>iLower ){
+          nNew = sqlite3LogEst(iUpper - iLower);
+          /* TUNING:  If both iUpper and iLower are derived from the same
+          ** sample, then assume they are 4x more selective.  This brings
+          ** the estimated selectivity more in line with what it would be
+          ** if estimated without the use of STAT4 tables. */
+          if( iLwrIdx==iUprIdx ){ nNew -= 20; }
+          assert( 20==sqlite3LogEst(4) );
+        }else{
+          nNew = 10;        assert( 10==sqlite3LogEst(2) );
+        }
+        if( nNew<nOut ){
+          nOut = nNew;
+        }
+        WHERETRACE(0x20, ("STAT4 range scan: %u..%u  est=%d\n",
+                           (u32)iLower, (u32)iUpper, nOut));
+      }
+    }else{
+      int bDone = 0;
+      rc = whereRangeSkipScanEst(pParse, pLower, pUpper, pLoop, &bDone);
+      if( bDone ) return rc;
+    }
+  }
+#else
+  UNUSED_PARAMETER(pParse);
+  UNUSED_PARAMETER(pBuilder);
+  assert( pLower || pUpper );
+#endif
+  assert( pUpper==0 || (pUpper->wtFlags & TERM_VNULL)==0 || pParse->nErr>0 );
+  nNew = whereRangeAdjust(pLower, nOut);
+  nNew = whereRangeAdjust(pUpper, nNew);
+
+  /* TUNING: If there is both an upper and lower limit and neither limit
+  ** has an application-defined likelihood(), assume the range is
+  ** reduced by an additional 75%. This means that, by default, an open-ended
+  ** range query (e.g. col > ?) is assumed to match 1/4 of the rows in the
+  ** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
+  ** match 1/64 of the index. */
+  if( pLower && pLower->truthProb>0 && pUpper && pUpper->truthProb>0 ){
+    nNew -= 20;
+  }
+
+  nOut -= (pLower!=0) + (pUpper!=0);
+  if( nNew<10 ) nNew = 10;
+  if( nNew<nOut ) nOut = nNew;
+#if defined(WHERETRACE_ENABLED)
+  if( pLoop->nOut>nOut ){
+    WHERETRACE(0x20,("Range scan lowers nOut from %d to %d\n",
+                    pLoop->nOut, nOut));
+  }
+#endif
+  pLoop->nOut = (LogEst)nOut;
+  return rc;
+}
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Estimate the number of rows that will be returned based on
+** an equality constraint x=VALUE and where that VALUE occurs in
+** the histogram data.  This only works when x is the left-most
+** column of an index and sqlite_stat4 histogram data is available
+** for that index.  When pExpr==NULL that means the constraint is
+** "x IS NULL" instead of "x=VALUE".
+**
+** Write the estimated row count into *pnRow and return SQLITE_OK.
+** If unable to make an estimate, leave *pnRow unchanged and return
+** non-zero.
+**
+** This routine can fail if it is unable to load a collating sequence
+** required for string comparison, or if unable to allocate memory
+** for a UTF conversion required for comparison.  The error is stored
+** in the pParse structure.
+*/
+static int whereEqualScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereLoopBuilder *pBuilder,
+  Expr *pExpr,         /* Expression for VALUE in the x=VALUE constraint */
+  tRowcnt *pnRow       /* Write the revised row estimate here */
+){
+  Index *p = pBuilder->pNew->u.btree.pIndex;
+  int nEq = pBuilder->pNew->u.btree.nEq;
+  UnpackedRecord *pRec = pBuilder->pRec;
+  int rc;                   /* Subfunction return code */
+  tRowcnt a[2];             /* Statistics */
+  int bOk;
+
+  assert( nEq>=1 );
+  assert( nEq<=p->nColumn );
+  assert( p->aSample!=0 );
+  assert( p->nSample>0 );
+  assert( pBuilder->nRecValid<nEq );
+
+  /* If values are not available for all fields of the index to the left
+  ** of this one, no estimate can be made. Return SQLITE_NOTFOUND. */
+  if( pBuilder->nRecValid<(nEq-1) ){
+    return SQLITE_NOTFOUND;
+  }
+
+  /* This is an optimization only. The call to sqlite3Stat4ProbeSetValue()
+  ** below would return the same value.  */
+  if( nEq>=p->nColumn ){
+    *pnRow = 1;
+    return SQLITE_OK;
+  }
+
+  rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, 1, nEq-1, &bOk);
+  pBuilder->pRec = pRec;
+  if( rc!=SQLITE_OK ) return rc;
+  if( bOk==0 ) return SQLITE_NOTFOUND;
+  pBuilder->nRecValid = nEq;
+
+  whereKeyStats(pParse, p, pRec, 0, a);
+  WHERETRACE(0x20,("equality scan regions %s(%d): %d\n",
+                   p->zName, nEq-1, (int)a[1]));
+  *pnRow = a[1];
+ 
+  return rc;
+}
+#endif /* SQLITE_ENABLE_STAT4 */
+
+#ifdef SQLITE_ENABLE_STAT4
+/*
+** Estimate the number of rows that will be returned based on
+** an IN constraint where the right-hand side of the IN operator
+** is a list of values.  Example:
+**
+**        WHERE x IN (1,2,3,4)
+**
+** Write the estimated row count into *pnRow and return SQLITE_OK.
+** If unable to make an estimate, leave *pnRow unchanged and return
+** non-zero.
+**
+** This routine can fail if it is unable to load a collating sequence
+** required for string comparison, or if unable to allocate memory
+** for a UTF conversion required for comparison.  The error is stored
+** in the pParse structure.
+*/
+static int whereInScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereLoopBuilder *pBuilder,
+  ExprList *pList,     /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
+  tRowcnt *pnRow       /* Write the revised row estimate here */
+){
+  Index *p = pBuilder->pNew->u.btree.pIndex;
+  i64 nRow0 = sqlite3LogEstToInt(p->aiRowLogEst[0]);
+  int nRecValid = pBuilder->nRecValid;
+  int rc = SQLITE_OK;     /* Subfunction return code */
+  tRowcnt nEst;           /* Number of rows for a single term */
+  tRowcnt nRowEst = 0;    /* New estimate of the number of rows */
+  int i;                  /* Loop counter */
+
+  assert( p->aSample!=0 );
+  for(i=0; rc==SQLITE_OK && i<pList->nExpr; i++){
+    nEst = nRow0;
+    rc = whereEqualScanEst(pParse, pBuilder, pList->a[i].pExpr, &nEst);
+    nRowEst += nEst;
+    pBuilder->nRecValid = nRecValid;
+  }
+
+  if( rc==SQLITE_OK ){
+    if( nRowEst > (tRowcnt)nRow0 ) nRowEst = nRow0;
+    *pnRow = nRowEst;
+    WHERETRACE(0x20,("IN row estimate: est=%d\n", nRowEst));
+  }
+  assert( pBuilder->nRecValid==nRecValid );
+  return rc;
+}
+#endif /* SQLITE_ENABLE_STAT4 */
+
+
+#ifdef WHERETRACE_ENABLED
+/*
+** Print the content of a WhereTerm object
+*/
+void sqlite3WhereTermPrint(WhereTerm *pTerm, int iTerm){
+  if( pTerm==0 ){
+    sqlite3DebugPrintf("TERM-%-3d NULL\n", iTerm);
+  }else{
+    char zType[8];
+    char zLeft[50];
+    memcpy(zType, "....", 5);
+    if( pTerm->wtFlags & TERM_VIRTUAL ) zType[0] = 'V';
+    if( pTerm->eOperator & WO_EQUIV  ) zType[1] = 'E';
+    if( ExprHasProperty(pTerm->pExpr, EP_OuterON) ) zType[2] = 'L';
+    if( pTerm->wtFlags & TERM_CODED  ) zType[3] = 'C';
+    if( pTerm->eOperator & WO_SINGLE ){
+      assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+      sqlite3_snprintf(sizeof(zLeft),zLeft,"left={%d:%d}",
+                       pTerm->leftCursor, pTerm->u.x.leftColumn);
+    }else if( (pTerm->eOperator & WO_OR)!=0 && pTerm->u.pOrInfo!=0 ){
+      sqlite3_snprintf(sizeof(zLeft),zLeft,"indexable=0x%llx",
+                       pTerm->u.pOrInfo->indexable);
+    }else{
+      sqlite3_snprintf(sizeof(zLeft),zLeft,"left=%d", pTerm->leftCursor);
+    }
+    sqlite3DebugPrintf(
+       "TERM-%-3d %p %s %-12s op=%03x wtFlags=%04x",
+       iTerm, pTerm, zType, zLeft, pTerm->eOperator, pTerm->wtFlags);
+    /* The 0x10000 .wheretrace flag causes extra information to be
+    ** shown about each Term */
+    if( sqlite3WhereTrace & 0x10000 ){
+      sqlite3DebugPrintf(" prob=%-3d prereq=%llx,%llx",
+        pTerm->truthProb, (u64)pTerm->prereqAll, (u64)pTerm->prereqRight);
+    }
+    if( (pTerm->eOperator & (WO_OR|WO_AND))==0 && pTerm->u.x.iField ){
+      sqlite3DebugPrintf(" iField=%d", pTerm->u.x.iField);
+    }
+    if( pTerm->iParent>=0 ){
+      sqlite3DebugPrintf(" iParent=%d", pTerm->iParent);
+    }
+    sqlite3DebugPrintf("\n");
+    sqlite3TreeViewExpr(0, pTerm->pExpr, 0);
+  }
+}
+#endif
+
+#ifdef WHERETRACE_ENABLED
+/*
+** Show the complete content of a WhereClause
+*/
+void sqlite3WhereClausePrint(WhereClause *pWC){
+  int i;
+  for(i=0; i<pWC->nTerm; i++){
+    sqlite3WhereTermPrint(&pWC->a[i], i);
+  }
+}
+#endif
+
+#ifdef WHERETRACE_ENABLED
+/*
+** Print a WhereLoop object for debugging purposes
+**
+** Format example:
+**
+**     .--- Position in WHERE clause           rSetup, rRun, nOut ---.
+**     |                                                             |
+**     |  .--- selfMask                       nTerm ------.          |
+**     |  |                                               |          |
+**     |  |   .-- prereq    Idx          wsFlags----.     |          |
+**     |  |   |             Name                    |     |          |
+**     |  |   |           __|__        nEq ---.  ___|__   |        __|__
+**     | / \ / \         /     \              | /      \ / \      /     \
+**     1.002.001         t2.t2xy              2 f 010241 N 2 cost 0,56,31
+*/
+void sqlite3WhereLoopPrint(const WhereLoop *p, const WhereClause *pWC){
+  if( pWC ){
+    WhereInfo *pWInfo = pWC->pWInfo;
+    int nb = 1+(pWInfo->pTabList->nSrc+3)/4;
+    SrcItem *pItem = pWInfo->pTabList->a + p->iTab;
+    Table *pTab = pItem->pTab;
+    Bitmask mAll = (((Bitmask)1)<<(nb*4)) - 1;
+    sqlite3DebugPrintf("%c%2d.%0*llx.%0*llx", p->cId,
+                       p->iTab, nb, p->maskSelf, nb, p->prereq & mAll);
+    sqlite3DebugPrintf(" %12s",
+                       pItem->zAlias ? pItem->zAlias : pTab->zName);
+  }else{
+    sqlite3DebugPrintf("%c%2d.%03llx.%03llx %c%d",
+         p->cId, p->iTab, p->maskSelf, p->prereq & 0xfff, p->cId, p->iTab);
+  }
+  if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
+    const char *zName;
+    if( p->u.btree.pIndex && (zName = p->u.btree.pIndex->zName)!=0 ){
+      if( strncmp(zName, "sqlite_autoindex_", 17)==0 ){
+        int i = sqlite3Strlen30(zName) - 1;
+        while( zName[i]!='_' ) i--;
+        zName += i;
+      }
+      sqlite3DebugPrintf(".%-16s %2d", zName, p->u.btree.nEq);
+    }else{
+      sqlite3DebugPrintf("%20s","");
+    }
+  }else{
+    char *z;
+    if( p->u.vtab.idxStr ){
+      z = sqlite3_mprintf("(%d,\"%s\",%#x)",
+                p->u.vtab.idxNum, p->u.vtab.idxStr, p->u.vtab.omitMask);
+    }else{
+      z = sqlite3_mprintf("(%d,%x)", p->u.vtab.idxNum, p->u.vtab.omitMask);
+    }
+    sqlite3DebugPrintf(" %-19s", z);
+    sqlite3_free(z);
+  }
+  if( p->wsFlags & WHERE_SKIPSCAN ){
+    sqlite3DebugPrintf(" f %06x %d-%d", p->wsFlags, p->nLTerm,p->nSkip);
+  }else{
+    sqlite3DebugPrintf(" f %06x N %d", p->wsFlags, p->nLTerm);
+  }
+  sqlite3DebugPrintf(" cost %d,%d,%d\n", p->rSetup, p->rRun, p->nOut);
+  if( p->nLTerm && (sqlite3WhereTrace & 0x4000)!=0 ){
+    int i;
+    for(i=0; i<p->nLTerm; i++){
+      sqlite3WhereTermPrint(p->aLTerm[i], i);
+    }
+  }
+}
+void sqlite3ShowWhereLoop(const WhereLoop *p){
+  if( p ) sqlite3WhereLoopPrint(p, 0);
+}
+void sqlite3ShowWhereLoopList(const WhereLoop *p){
+  while( p ){
+    sqlite3ShowWhereLoop(p);
+    p = p->pNextLoop;
+  }
+}
+#endif
+
+/*
+** Convert bulk memory into a valid WhereLoop that can be passed
+** to whereLoopClear harmlessly.
+*/
+static void whereLoopInit(WhereLoop *p){
+  p->aLTerm = p->aLTermSpace;
+  p->nLTerm = 0;
+  p->nLSlot = ArraySize(p->aLTermSpace);
+  p->wsFlags = 0;
+}
+
+/*
+** Clear the WhereLoop.u union.  Leave WhereLoop.pLTerm intact.
+*/
+static void whereLoopClearUnion(sqlite3 *db, WhereLoop *p){
+  if( p->wsFlags & (WHERE_VIRTUALTABLE|WHERE_AUTO_INDEX) ){
+    if( (p->wsFlags & WHERE_VIRTUALTABLE)!=0 && p->u.vtab.needFree ){
+      sqlite3_free(p->u.vtab.idxStr);
+      p->u.vtab.needFree = 0;
+      p->u.vtab.idxStr = 0;
+    }else if( (p->wsFlags & WHERE_AUTO_INDEX)!=0 && p->u.btree.pIndex!=0 ){
+      sqlite3DbFree(db, p->u.btree.pIndex->zColAff);
+      sqlite3DbFreeNN(db, p->u.btree.pIndex);
+      p->u.btree.pIndex = 0;
+    }
+  }
+}
+
+/*
+** Deallocate internal memory used by a WhereLoop object.  Leave the
+** object in an initialized state, as if it had been newly allocated.
+*/
+static void whereLoopClear(sqlite3 *db, WhereLoop *p){
+  if( p->aLTerm!=p->aLTermSpace ){
+    sqlite3DbFreeNN(db, p->aLTerm);
+    p->aLTerm = p->aLTermSpace;
+    p->nLSlot = ArraySize(p->aLTermSpace);
+  }
+  whereLoopClearUnion(db, p);
+  p->nLTerm = 0;
+  p->wsFlags = 0;
+}
+
+/*
+** Increase the memory allocation for pLoop->aLTerm[] to be at least n.
+*/
+static int whereLoopResize(sqlite3 *db, WhereLoop *p, int n){
+  WhereTerm **paNew;
+  if( p->nLSlot>=n ) return SQLITE_OK;
+  n = (n+7)&~7;
+  paNew = sqlite3DbMallocRawNN(db, sizeof(p->aLTerm[0])*n);
+  if( paNew==0 ) return SQLITE_NOMEM_BKPT;
+  memcpy(paNew, p->aLTerm, sizeof(p->aLTerm[0])*p->nLSlot);
+  if( p->aLTerm!=p->aLTermSpace ) sqlite3DbFreeNN(db, p->aLTerm);
+  p->aLTerm = paNew;
+  p->nLSlot = n;
+  return SQLITE_OK;
+}
+
+/*
+** Transfer content from the second pLoop into the first.
+*/
+static int whereLoopXfer(sqlite3 *db, WhereLoop *pTo, WhereLoop *pFrom){
+  whereLoopClearUnion(db, pTo);
+  if( pFrom->nLTerm > pTo->nLSlot
+   && whereLoopResize(db, pTo, pFrom->nLTerm)
+  ){
+    memset(pTo, 0, WHERE_LOOP_XFER_SZ);
+    return SQLITE_NOMEM_BKPT;
+  }
+  memcpy(pTo, pFrom, WHERE_LOOP_XFER_SZ);
+  memcpy(pTo->aLTerm, pFrom->aLTerm, pTo->nLTerm*sizeof(pTo->aLTerm[0]));
+  if( pFrom->wsFlags & WHERE_VIRTUALTABLE ){
+    pFrom->u.vtab.needFree = 0;
+  }else if( (pFrom->wsFlags & WHERE_AUTO_INDEX)!=0 ){
+    pFrom->u.btree.pIndex = 0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Delete a WhereLoop object
+*/
+static void whereLoopDelete(sqlite3 *db, WhereLoop *p){
+  assert( db!=0 );
+  whereLoopClear(db, p);
+  sqlite3DbNNFreeNN(db, p);
+}
+
+/*
+** Free a WhereInfo structure
+*/
+static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
+  assert( pWInfo!=0 );
+  assert( db!=0 );
+  sqlite3WhereClauseClear(&pWInfo->sWC);
+  while( pWInfo->pLoops ){
+    WhereLoop *p = pWInfo->pLoops;
+    pWInfo->pLoops = p->pNextLoop;
+    whereLoopDelete(db, p);
+  }
+  while( pWInfo->pMemToFree ){
+    WhereMemBlock *pNext = pWInfo->pMemToFree->pNext;
+    sqlite3DbNNFreeNN(db, pWInfo->pMemToFree);
+    pWInfo->pMemToFree = pNext;
+  }
+  sqlite3DbNNFreeNN(db, pWInfo);
+}
+
+/*
+** Return TRUE if X is a proper subset of Y but is of equal or less cost.
+** In other words, return true if all constraints of X are also part of Y
+** and Y has additional constraints that might speed the search that X lacks
+** but the cost of running X is not more than the cost of running Y.
+**
+** In other words, return true if the cost relationwship between X and Y
+** is inverted and needs to be adjusted.
+**
+** Case 1:
+**
+**   (1a)  X and Y use the same index.
+**   (1b)  X has fewer == terms than Y
+**   (1c)  Neither X nor Y use skip-scan
+**   (1d)  X does not have a a greater cost than Y
+**
+** Case 2:
+**
+**   (2a)  X has the same or lower cost, or returns the same or fewer rows,
+**         than Y.
+**   (2b)  X uses fewer WHERE clause terms than Y
+**   (2c)  Every WHERE clause term used by X is also used by Y
+**   (2d)  X skips at least as many columns as Y
+**   (2e)  If X is a covering index, than Y is too
+*/
+static int whereLoopCheaperProperSubset(
+  const WhereLoop *pX,       /* First WhereLoop to compare */
+  const WhereLoop *pY        /* Compare against this WhereLoop */
+){
+  int i, j;
+  if( pX->rRun>pY->rRun && pX->nOut>pY->nOut ) return 0; /* (1d) and (2a) */
+  assert( (pX->wsFlags & WHERE_VIRTUALTABLE)==0 );
+  assert( (pY->wsFlags & WHERE_VIRTUALTABLE)==0 );
+  if( pX->u.btree.nEq < pY->u.btree.nEq                  /* (1b) */
+   && pX->u.btree.pIndex==pY->u.btree.pIndex             /* (1a) */
+   && pX->nSkip==0 && pY->nSkip==0                       /* (1c) */
+  ){
+    return 1;  /* Case 1 is true */
+  }
+  if( pX->nLTerm-pX->nSkip >= pY->nLTerm-pY->nSkip ){
+    return 0;                                            /* (2b) */
+  }
+  if( pY->nSkip > pX->nSkip ) return 0;                  /* (2d) */
+  for(i=pX->nLTerm-1; i>=0; i--){
+    if( pX->aLTerm[i]==0 ) continue;
+    for(j=pY->nLTerm-1; j>=0; j--){
+      if( pY->aLTerm[j]==pX->aLTerm[i] ) break;
+    }
+    if( j<0 ) return 0;                                  /* (2c) */
+  }
+  if( (pX->wsFlags&WHERE_IDX_ONLY)!=0
+   && (pY->wsFlags&WHERE_IDX_ONLY)==0 ){
+    return 0;                                            /* (2e) */
+  }
+  return 1;  /* Case 2 is true */
+}
+
+/*
+** Try to adjust the cost and number of output rows of WhereLoop pTemplate
+** upwards or downwards so that:
+**
+**   (1) pTemplate costs less than any other WhereLoops that are a proper
+**       subset of pTemplate
+**
+**   (2) pTemplate costs more than any other WhereLoops for which pTemplate
+**       is a proper subset.
+**
+** To say "WhereLoop X is a proper subset of Y" means that X uses fewer
+** WHERE clause terms than Y and that every WHERE clause term used by X is
+** also used by Y.
+*/
+static void whereLoopAdjustCost(const WhereLoop *p, WhereLoop *pTemplate){
+  if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
+  for(; p; p=p->pNextLoop){
+    if( p->iTab!=pTemplate->iTab ) continue;
+    if( (p->wsFlags & WHERE_INDEXED)==0 ) continue;
+    if( whereLoopCheaperProperSubset(p, pTemplate) ){
+      /* Adjust pTemplate cost downward so that it is cheaper than its
+      ** subset p. */
+      WHERETRACE(0x80,("subset cost adjustment %d,%d to %d,%d\n",
+                       pTemplate->rRun, pTemplate->nOut,
+                       MIN(p->rRun, pTemplate->rRun),
+                       MIN(p->nOut - 1, pTemplate->nOut)));
+      pTemplate->rRun = MIN(p->rRun, pTemplate->rRun);
+      pTemplate->nOut = MIN(p->nOut - 1, pTemplate->nOut);
+    }else if( whereLoopCheaperProperSubset(pTemplate, p) ){
+      /* Adjust pTemplate cost upward so that it is costlier than p since
+      ** pTemplate is a proper subset of p */
+      WHERETRACE(0x80,("subset cost adjustment %d,%d to %d,%d\n",
+                       pTemplate->rRun, pTemplate->nOut,
+                       MAX(p->rRun, pTemplate->rRun),
+                       MAX(p->nOut + 1, pTemplate->nOut)));
+      pTemplate->rRun = MAX(p->rRun, pTemplate->rRun);
+      pTemplate->nOut = MAX(p->nOut + 1, pTemplate->nOut);
+    }
+  }
+}
+
+/*
+** Search the list of WhereLoops in *ppPrev looking for one that can be
+** replaced by pTemplate.
+**
+** Return NULL if pTemplate does not belong on the WhereLoop list.
+** In other words if pTemplate ought to be dropped from further consideration.
+**
+** If pX is a WhereLoop that pTemplate can replace, then return the
+** link that points to pX.
+**
+** If pTemplate cannot replace any existing element of the list but needs
+** to be added to the list as a new entry, then return a pointer to the
+** tail of the list.
+*/
+static WhereLoop **whereLoopFindLesser(
+  WhereLoop **ppPrev,
+  const WhereLoop *pTemplate
+){
+  WhereLoop *p;
+  for(p=(*ppPrev); p; ppPrev=&p->pNextLoop, p=*ppPrev){
+    if( p->iTab!=pTemplate->iTab || p->iSortIdx!=pTemplate->iSortIdx ){
+      /* If either the iTab or iSortIdx values for two WhereLoop are different
+      ** then those WhereLoops need to be considered separately.  Neither is
+      ** a candidate to replace the other. */
+      continue;
+    }
+    /* In the current implementation, the rSetup value is either zero
+    ** or the cost of building an automatic index (NlogN) and the NlogN
+    ** is the same for compatible WhereLoops. */
+    assert( p->rSetup==0 || pTemplate->rSetup==0
+                 || p->rSetup==pTemplate->rSetup );
+
+    /* whereLoopAddBtree() always generates and inserts the automatic index
+    ** case first.  Hence compatible candidate WhereLoops never have a larger
+    ** rSetup. Call this SETUP-INVARIANT */
+    assert( p->rSetup>=pTemplate->rSetup );
+
+    /* Any loop using an application-defined index (or PRIMARY KEY or
+    ** UNIQUE constraint) with one or more == constraints is better
+    ** than an automatic index. Unless it is a skip-scan. */
+    if( (p->wsFlags & WHERE_AUTO_INDEX)!=0
+     && (pTemplate->nSkip)==0
+     && (pTemplate->wsFlags & WHERE_INDEXED)!=0
+     && (pTemplate->wsFlags & WHERE_COLUMN_EQ)!=0
+     && (p->prereq & pTemplate->prereq)==pTemplate->prereq
+    ){
+      break;
+    }
+
+    /* If existing WhereLoop p is better than pTemplate, pTemplate can be
+    ** discarded.  WhereLoop p is better if:
+    **   (1)  p has no more dependencies than pTemplate, and
+    **   (2)  p has an equal or lower cost than pTemplate
+    */
+    if( (p->prereq & pTemplate->prereq)==p->prereq    /* (1)  */
+     && p->rSetup<=pTemplate->rSetup                  /* (2a) */
+     && p->rRun<=pTemplate->rRun                      /* (2b) */
+     && p->nOut<=pTemplate->nOut                      /* (2c) */
+    ){
+      return 0;  /* Discard pTemplate */
+    }
+
+    /* If pTemplate is always better than p, then cause p to be overwritten
+    ** with pTemplate.  pTemplate is better than p if:
+    **   (1)  pTemplate has no more dependencies than p, and
+    **   (2)  pTemplate has an equal or lower cost than p.
+    */
+    if( (p->prereq & pTemplate->prereq)==pTemplate->prereq   /* (1)  */
+     && p->rRun>=pTemplate->rRun                             /* (2a) */
+     && p->nOut>=pTemplate->nOut                             /* (2b) */
+    ){
+      assert( p->rSetup>=pTemplate->rSetup ); /* SETUP-INVARIANT above */
+      break;   /* Cause p to be overwritten by pTemplate */
+    }
+  }
+  return ppPrev;
+}
+
+/*
+** Insert or replace a WhereLoop entry using the template supplied.
+**
+** An existing WhereLoop entry might be overwritten if the new template
+** is better and has fewer dependencies.  Or the template will be ignored
+** and no insert will occur if an existing WhereLoop is faster and has
+** fewer dependencies than the template.  Otherwise a new WhereLoop is
+** added based on the template.
+**
+** If pBuilder->pOrSet is not NULL then we care about only the
+** prerequisites and rRun and nOut costs of the N best loops.  That
+** information is gathered in the pBuilder->pOrSet object.  This special
+** processing mode is used only for OR clause processing.
+**
+** When accumulating multiple loops (when pBuilder->pOrSet is NULL) we
+** still might overwrite similar loops with the new template if the
+** new template is better.  Loops may be overwritten if the following
+** conditions are met:
+**
+**    (1)  They have the same iTab.
+**    (2)  They have the same iSortIdx.
+**    (3)  The template has same or fewer dependencies than the current loop
+**    (4)  The template has the same or lower cost than the current loop
+*/
+static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
+  WhereLoop **ppPrev, *p;
+  WhereInfo *pWInfo = pBuilder->pWInfo;
+  sqlite3 *db = pWInfo->pParse->db;
+  int rc;
+
+  /* Stop the search once we hit the query planner search limit */
+  if( pBuilder->iPlanLimit==0 ){
+    WHERETRACE(0xffffffff,("=== query planner search limit reached ===\n"));
+    if( pBuilder->pOrSet ) pBuilder->pOrSet->n = 0;
+    return SQLITE_DONE;
+  }
+  pBuilder->iPlanLimit--;
+
+  whereLoopAdjustCost(pWInfo->pLoops, pTemplate);
+
+  /* If pBuilder->pOrSet is defined, then only keep track of the costs
+  ** and prereqs.
+  */
+  if( pBuilder->pOrSet!=0 ){
+    if( pTemplate->nLTerm ){
+#if WHERETRACE_ENABLED
+      u16 n = pBuilder->pOrSet->n;
+      int x =
+#endif
+      whereOrInsert(pBuilder->pOrSet, pTemplate->prereq, pTemplate->rRun,
+                                    pTemplate->nOut);
+#if WHERETRACE_ENABLED /* 0x8 */
+      if( sqlite3WhereTrace & 0x8 ){
+        sqlite3DebugPrintf(x?"   or-%d:  ":"   or-X:  ", n);
+        sqlite3WhereLoopPrint(pTemplate, pBuilder->pWC);
+      }
+#endif
+    }
+    return SQLITE_OK;
+  }
+
+  /* Look for an existing WhereLoop to replace with pTemplate
+  */
+  ppPrev = whereLoopFindLesser(&pWInfo->pLoops, pTemplate);
+
+  if( ppPrev==0 ){
+    /* There already exists a WhereLoop on the list that is better
+    ** than pTemplate, so just ignore pTemplate */
+#if WHERETRACE_ENABLED /* 0x8 */
+    if( sqlite3WhereTrace & 0x8 ){
+      sqlite3DebugPrintf("   skip: ");
+      sqlite3WhereLoopPrint(pTemplate, pBuilder->pWC);
+    }
+#endif
+    return SQLITE_OK; 
+  }else{
+    p = *ppPrev;
+  }
+
+  /* If we reach this point it means that either p[] should be overwritten
+  ** with pTemplate[] if p[] exists, or if p==NULL then allocate a new
+  ** WhereLoop and insert it.
+  */
+#if WHERETRACE_ENABLED /* 0x8 */
+  if( sqlite3WhereTrace & 0x8 ){
+    if( p!=0 ){
+      sqlite3DebugPrintf("replace: ");
+      sqlite3WhereLoopPrint(p, pBuilder->pWC);
+      sqlite3DebugPrintf("   with: ");
+    }else{
+      sqlite3DebugPrintf("    add: ");
+    }
+    sqlite3WhereLoopPrint(pTemplate, pBuilder->pWC);
+  }
+#endif
+  if( p==0 ){
+    /* Allocate a new WhereLoop to add to the end of the list */
+    *ppPrev = p = sqlite3DbMallocRawNN(db, sizeof(WhereLoop));
+    if( p==0 ) return SQLITE_NOMEM_BKPT;
+    whereLoopInit(p);
+    p->pNextLoop = 0;
+  }else{
+    /* We will be overwriting WhereLoop p[].  But before we do, first
+    ** go through the rest of the list and delete any other entries besides
+    ** p[] that are also supplanted by pTemplate */
+    WhereLoop **ppTail = &p->pNextLoop;
+    WhereLoop *pToDel;
+    while( *ppTail ){
+      ppTail = whereLoopFindLesser(ppTail, pTemplate);
+      if( ppTail==0 ) break;
+      pToDel = *ppTail;
+      if( pToDel==0 ) break;
+      *ppTail = pToDel->pNextLoop;
+#if WHERETRACE_ENABLED /* 0x8 */
+      if( sqlite3WhereTrace & 0x8 ){
+        sqlite3DebugPrintf(" delete: ");
+        sqlite3WhereLoopPrint(pToDel, pBuilder->pWC);
+      }
+#endif
+      whereLoopDelete(db, pToDel);
+    }
+  }
+  rc = whereLoopXfer(db, p, pTemplate);
+  if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
+    Index *pIndex = p->u.btree.pIndex;
+    if( pIndex && pIndex->idxType==SQLITE_IDXTYPE_IPK ){
+      p->u.btree.pIndex = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Adjust the WhereLoop.nOut value downward to account for terms of the
+** WHERE clause that reference the loop but which are not used by an
+** index.
+*
+** For every WHERE clause term that is not used by the index
+** and which has a truth probability assigned by one of the likelihood(),
+** likely(), or unlikely() SQL functions, reduce the estimated number
+** of output rows by the probability specified.
+**
+** TUNING:  For every WHERE clause term that is not used by the index
+** and which does not have an assigned truth probability, heuristics
+** described below are used to try to estimate the truth probability.
+** TODO --> Perhaps this is something that could be improved by better
+** table statistics.
+**
+** Heuristic 1:  Estimate the truth probability as 93.75%.  The 93.75%
+** value corresponds to -1 in LogEst notation, so this means decrement
+** the WhereLoop.nOut field for every such WHERE clause term.
+**
+** Heuristic 2:  If there exists one or more WHERE clause terms of the
+** form "x==EXPR" and EXPR is not a constant 0 or 1, then make sure the
+** final output row estimate is no greater than 1/4 of the total number
+** of rows in the table.  In other words, assume that x==EXPR will filter
+** out at least 3 out of 4 rows.  If EXPR is -1 or 0 or 1, then maybe the
+** "x" column is boolean or else -1 or 0 or 1 is a common default value
+** on the "x" column and so in that case only cap the output row estimate
+** at 1/2 instead of 1/4.
+*/
+static void whereLoopOutputAdjust(
+  WhereClause *pWC,      /* The WHERE clause */
+  WhereLoop *pLoop,      /* The loop to adjust downward */
+  LogEst nRow            /* Number of rows in the entire table */
+){
+  WhereTerm *pTerm, *pX;
+  Bitmask notAllowed = ~(pLoop->prereq|pLoop->maskSelf);
+  int i, j;
+  LogEst iReduce = 0;    /* pLoop->nOut should not exceed nRow-iReduce */
+
+  assert( (pLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
+  for(i=pWC->nBase, pTerm=pWC->a; i>0; i--, pTerm++){
+    assert( pTerm!=0 );
+    if( (pTerm->prereqAll & notAllowed)!=0 ) continue;
+    if( (pTerm->prereqAll & pLoop->maskSelf)==0 ) continue;
+    if( (pTerm->wtFlags & TERM_VIRTUAL)!=0 ) continue;
+    for(j=pLoop->nLTerm-1; j>=0; j--){
+      pX = pLoop->aLTerm[j];
+      if( pX==0 ) continue;
+      if( pX==pTerm ) break;
+      if( pX->iParent>=0 && (&pWC->a[pX->iParent])==pTerm ) break;
+    }
+    if( j<0 ){
+      sqlite3ProgressCheck(pWC->pWInfo->pParse);
+      if( pLoop->maskSelf==pTerm->prereqAll ){
+        /* If there are extra terms in the WHERE clause not used by an index
+        ** that depend only on the table being scanned, and that will tend to
+        ** cause many rows to be omitted, then mark that table as
+        ** "self-culling".
+        **
+        ** 2022-03-24:  Self-culling only applies if either the extra terms
+        ** are straight comparison operators that are non-true with NULL
+        ** operand, or if the loop is not an OUTER JOIN.
+        */
+        if( (pTerm->eOperator & 0x3f)!=0
+         || (pWC->pWInfo->pTabList->a[pLoop->iTab].fg.jointype
+                  & (JT_LEFT|JT_LTORJ))==0
+        ){
+          pLoop->wsFlags |= WHERE_SELFCULL;
+        }
+      }
+      if( pTerm->truthProb<=0 ){
+        /* If a truth probability is specified using the likelihood() hints,
+        ** then use the probability provided by the application. */
+        pLoop->nOut += pTerm->truthProb;
+      }else{
+        /* In the absence of explicit truth probabilities, use heuristics to
+        ** guess a reasonable truth probability. */
+        pLoop->nOut--;
+        if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0
+         && (pTerm->wtFlags & TERM_HIGHTRUTH)==0  /* tag-20200224-1 */
+        ){
+          Expr *pRight = pTerm->pExpr->pRight;
+          int k = 0;
+          testcase( pTerm->pExpr->op==TK_IS );
+          if( sqlite3ExprIsInteger(pRight, &k) && k>=(-1) && k<=1 ){
+            k = 10;
+          }else{
+            k = 20;
+          }
+          if( iReduce<k ){
+            pTerm->wtFlags |= TERM_HEURTRUTH;
+            iReduce = k;
+          }
+        }
+      }
+    }
+  }
+  if( pLoop->nOut > nRow-iReduce ){
+    pLoop->nOut = nRow - iReduce;
+  }
+}
+
+/*
+** Term pTerm is a vector range comparison operation. The first comparison
+** in the vector can be optimized using column nEq of the index. This
+** function returns the total number of vector elements that can be used
+** as part of the range comparison.
+**
+** For example, if the query is:
+**
+**   WHERE a = ? AND (b, c, d) > (?, ?, ?)
+**
+** and the index:
+**
+**   CREATE INDEX ... ON (a, b, c, d, e)
+**
+** then this function would be invoked with nEq=1. The value returned in
+** this case is 3.
+*/
+static int whereRangeVectorLen(
+  Parse *pParse,       /* Parsing context */
+  int iCur,            /* Cursor open on pIdx */
+  Index *pIdx,         /* The index to be used for a inequality constraint */
+  int nEq,             /* Number of prior equality constraints on same index */
+  WhereTerm *pTerm     /* The vector inequality constraint */
+){
+  int nCmp = sqlite3ExprVectorSize(pTerm->pExpr->pLeft);
+  int i;
+
+  nCmp = MIN(nCmp, (pIdx->nColumn - nEq));
+  for(i=1; i<nCmp; i++){
+    /* Test if comparison i of pTerm is compatible with column (i+nEq)
+    ** of the index. If not, exit the loop.  */
+    char aff;                     /* Comparison affinity */
+    char idxaff = 0;              /* Indexed columns affinity */
+    CollSeq *pColl;               /* Comparison collation sequence */
+    Expr *pLhs, *pRhs;
+
+    assert( ExprUseXList(pTerm->pExpr->pLeft) );
+    pLhs = pTerm->pExpr->pLeft->x.pList->a[i].pExpr;
+    pRhs = pTerm->pExpr->pRight;
+    if( ExprUseXSelect(pRhs) ){
+      pRhs = pRhs->x.pSelect->pEList->a[i].pExpr;
+    }else{
+      pRhs = pRhs->x.pList->a[i].pExpr;
+    }
+
+    /* Check that the LHS of the comparison is a column reference to
+    ** the right column of the right source table. And that the sort
+    ** order of the index column is the same as the sort order of the
+    ** leftmost index column.  */
+    if( pLhs->op!=TK_COLUMN
+     || pLhs->iTable!=iCur
+     || pLhs->iColumn!=pIdx->aiColumn[i+nEq]
+     || pIdx->aSortOrder[i+nEq]!=pIdx->aSortOrder[nEq]
+    ){
+      break;
+    }
+
+    testcase( pLhs->iColumn==XN_ROWID );
+    aff = sqlite3CompareAffinity(pRhs, sqlite3ExprAffinity(pLhs));
+    idxaff = sqlite3TableColumnAffinity(pIdx->pTable, pLhs->iColumn);
+    if( aff!=idxaff ) break;
+
+    pColl = sqlite3BinaryCompareCollSeq(pParse, pLhs, pRhs);
+    if( pColl==0 ) break;
+    if( sqlite3StrICmp(pColl->zName, pIdx->azColl[i+nEq]) ) break;
+  }
+  return i;
+}
+
+/*
+** Adjust the cost C by the costMult factor T.  This only occurs if
+** compiled with -DSQLITE_ENABLE_COSTMULT
+*/
+#ifdef SQLITE_ENABLE_COSTMULT
+# define ApplyCostMultiplier(C,T)  C += T
+#else
+# define ApplyCostMultiplier(C,T)
+#endif
+
+/*
+** We have so far matched pBuilder->pNew->u.btree.nEq terms of the
+** index pIndex. Try to match one more.
+**
+** When this function is called, pBuilder->pNew->nOut contains the
+** number of rows expected to be visited by filtering using the nEq
+** terms only. If it is modified, this value is restored before this
+** function returns.
+**
+** If pProbe->idxType==SQLITE_IDXTYPE_IPK, that means pIndex is
+** a fake index used for the INTEGER PRIMARY KEY.
+*/
+static int whereLoopAddBtreeIndex(
+  WhereLoopBuilder *pBuilder,     /* The WhereLoop factory */
+  SrcItem *pSrc,                  /* FROM clause term being analyzed */
+  Index *pProbe,                  /* An index on pSrc */
+  LogEst nInMul                   /* log(Number of iterations due to IN) */
+){
+  WhereInfo *pWInfo = pBuilder->pWInfo;  /* WHERE analyze context */
+  Parse *pParse = pWInfo->pParse;        /* Parsing context */
+  sqlite3 *db = pParse->db;       /* Database connection malloc context */
+  WhereLoop *pNew;                /* Template WhereLoop under construction */
+  WhereTerm *pTerm;               /* A WhereTerm under consideration */
+  int opMask;                     /* Valid operators for constraints */
+  WhereScan scan;                 /* Iterator for WHERE terms */
+  Bitmask saved_prereq;           /* Original value of pNew->prereq */
+  u16 saved_nLTerm;               /* Original value of pNew->nLTerm */
+  u16 saved_nEq;                  /* Original value of pNew->u.btree.nEq */
+  u16 saved_nBtm;                 /* Original value of pNew->u.btree.nBtm */
+  u16 saved_nTop;                 /* Original value of pNew->u.btree.nTop */
+  u16 saved_nSkip;                /* Original value of pNew->nSkip */
+  u32 saved_wsFlags;              /* Original value of pNew->wsFlags */
+  LogEst saved_nOut;              /* Original value of pNew->nOut */
+  int rc = SQLITE_OK;             /* Return code */
+  LogEst rSize;                   /* Number of rows in the table */
+  LogEst rLogSize;                /* Logarithm of table size */
+  WhereTerm *pTop = 0, *pBtm = 0; /* Top and bottom range constraints */
+
+  pNew = pBuilder->pNew;
+  assert( db->mallocFailed==0 || pParse->nErr>0 );
+  if( pParse->nErr ){
+    return pParse->rc;
+  }
+  WHERETRACE(0x800, ("BEGIN %s.addBtreeIdx(%s), nEq=%d, nSkip=%d, rRun=%d\n",
+                     pProbe->pTable->zName,pProbe->zName,
+                     pNew->u.btree.nEq, pNew->nSkip, pNew->rRun));
+
+  assert( (pNew->wsFlags & WHERE_VIRTUALTABLE)==0 );
+  assert( (pNew->wsFlags & WHERE_TOP_LIMIT)==0 );
+  if( pNew->wsFlags & WHERE_BTM_LIMIT ){
+    opMask = WO_LT|WO_LE;
+  }else{
+    assert( pNew->u.btree.nBtm==0 );
+    opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE|WO_ISNULL|WO_IS;
+  }
+  if( pProbe->bUnordered || pProbe->bLowQual ){
+    if( pProbe->bUnordered ) opMask &= ~(WO_GT|WO_GE|WO_LT|WO_LE);
+    if( pProbe->bLowQual )   opMask &= ~(WO_EQ|WO_IN|WO_IS);
+  }
+
+  assert( pNew->u.btree.nEq<pProbe->nColumn );
+  assert( pNew->u.btree.nEq<pProbe->nKeyCol
+       || pProbe->idxType!=SQLITE_IDXTYPE_PRIMARYKEY );
+
+  saved_nEq = pNew->u.btree.nEq;
+  saved_nBtm = pNew->u.btree.nBtm;
+  saved_nTop = pNew->u.btree.nTop;
+  saved_nSkip = pNew->nSkip;
+  saved_nLTerm = pNew->nLTerm;
+  saved_wsFlags = pNew->wsFlags;
+  saved_prereq = pNew->prereq;
+  saved_nOut = pNew->nOut;
+  pTerm = whereScanInit(&scan, pBuilder->pWC, pSrc->iCursor, saved_nEq,
+                        opMask, pProbe);
+  pNew->rSetup = 0;
+  rSize = pProbe->aiRowLogEst[0];
+  rLogSize = estLog(rSize);
+  for(; rc==SQLITE_OK && pTerm!=0; pTerm = whereScanNext(&scan)){
+    u16 eOp = pTerm->eOperator;   /* Shorthand for pTerm->eOperator */
+    LogEst rCostIdx;
+    LogEst nOutUnadjusted;        /* nOut before IN() and WHERE adjustments */
+    int nIn = 0;
+#ifdef SQLITE_ENABLE_STAT4
+    int nRecValid = pBuilder->nRecValid;
+#endif
+    if( (eOp==WO_ISNULL || (pTerm->wtFlags&TERM_VNULL)!=0)
+     && indexColumnNotNull(pProbe, saved_nEq)
+    ){
+      continue; /* ignore IS [NOT] NULL constraints on NOT NULL columns */
+    }
+    if( pTerm->prereqRight & pNew->maskSelf ) continue;
+
+    /* Do not allow the upper bound of a LIKE optimization range constraint
+    ** to mix with a lower range bound from some other source */
+    if( pTerm->wtFlags & TERM_LIKEOPT && pTerm->eOperator==WO_LT ) continue;
+
+    if( (pSrc->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))!=0
+     && !constraintCompatibleWithOuterJoin(pTerm,pSrc)
+    ){
+      continue;
+    }
+    if( IsUniqueIndex(pProbe) && saved_nEq==pProbe->nKeyCol-1 ){
+      pBuilder->bldFlags1 |= SQLITE_BLDF1_UNIQUE;
+    }else{
+      pBuilder->bldFlags1 |= SQLITE_BLDF1_INDEXED;
+    }
+    pNew->wsFlags = saved_wsFlags;
+    pNew->u.btree.nEq = saved_nEq;
+    pNew->u.btree.nBtm = saved_nBtm;
+    pNew->u.btree.nTop = saved_nTop;
+    pNew->nLTerm = saved_nLTerm;
+    if( pNew->nLTerm>=pNew->nLSlot
+     && whereLoopResize(db, pNew, pNew->nLTerm+1)
+    ){
+       break; /* OOM while trying to enlarge the pNew->aLTerm array */
+    }
+    pNew->aLTerm[pNew->nLTerm++] = pTerm;
+    pNew->prereq = (saved_prereq | pTerm->prereqRight) & ~pNew->maskSelf;
+
+    assert( nInMul==0
+        || (pNew->wsFlags & WHERE_COLUMN_NULL)!=0
+        || (pNew->wsFlags & WHERE_COLUMN_IN)!=0
+        || (pNew->wsFlags & WHERE_SKIPSCAN)!=0
+    );
+
+    if( eOp & WO_IN ){
+      Expr *pExpr = pTerm->pExpr;
+      if( ExprUseXSelect(pExpr) ){
+        /* "x IN (SELECT ...)":  TUNING: the SELECT returns 25 rows */
+        int i;
+        nIn = 46;  assert( 46==sqlite3LogEst(25) );
+
+        /* The expression may actually be of the form (x, y) IN (SELECT...).
+        ** In this case there is a separate term for each of (x) and (y).
+        ** However, the nIn multiplier should only be applied once, not once
+        ** for each such term. The following loop checks that pTerm is the
+        ** first such term in use, and sets nIn back to 0 if it is not. */
+        for(i=0; i<pNew->nLTerm-1; i++){
+          if( pNew->aLTerm[i] && pNew->aLTerm[i]->pExpr==pExpr ) nIn = 0;
+        }
+      }else if( ALWAYS(pExpr->x.pList && pExpr->x.pList->nExpr) ){
+        /* "x IN (value, value, ...)" */
+        nIn = sqlite3LogEst(pExpr->x.pList->nExpr);
+      }
+      if( pProbe->hasStat1 && rLogSize>=10 ){
+        LogEst M, logK, x;
+        /* Let:
+        **   N = the total number of rows in the table
+        **   K = the number of entries on the RHS of the IN operator
+        **   M = the number of rows in the table that match terms to the
+        **       to the left in the same index.  If the IN operator is on
+        **       the left-most index column, M==N.
+        **
+        ** Given the definitions above, it is better to omit the IN operator
+        ** from the index lookup and instead do a scan of the M elements,
+        ** testing each scanned row against the IN operator separately, if:
+        **
+        **        M*log(K) < K*log(N)
+        **
+        ** Our estimates for M, K, and N might be inaccurate, so we build in
+        ** a safety margin of 2 (LogEst: 10) that favors using the IN operator
+        ** with the index, as using an index has better worst-case behavior.
+        ** If we do not have real sqlite_stat1 data, always prefer to use
+        ** the index.  Do not bother with this optimization on very small
+        ** tables (less than 2 rows) as it is pointless in that case.
+        */
+        M = pProbe->aiRowLogEst[saved_nEq];
+        logK = estLog(nIn);
+        /* TUNING      v-----  10 to bias toward indexed IN */
+        x = M + logK + 10 - (nIn + rLogSize);
+        if( x>=0 ){
+          WHERETRACE(0x40,
+            ("IN operator (N=%d M=%d logK=%d nIn=%d rLogSize=%d x=%d) "
+             "prefers indexed lookup\n",
+             saved_nEq, M, logK, nIn, rLogSize, x));
+        }else if( nInMul<2 && OptimizationEnabled(db, SQLITE_SeekScan) ){
+          WHERETRACE(0x40,
+            ("IN operator (N=%d M=%d logK=%d nIn=%d rLogSize=%d x=%d"
+             " nInMul=%d) prefers skip-scan\n",
+             saved_nEq, M, logK, nIn, rLogSize, x, nInMul));
+          pNew->wsFlags |= WHERE_IN_SEEKSCAN;
+        }else{
+          WHERETRACE(0x40,
+            ("IN operator (N=%d M=%d logK=%d nIn=%d rLogSize=%d x=%d"
+             " nInMul=%d) prefers normal scan\n",
+             saved_nEq, M, logK, nIn, rLogSize, x, nInMul));
+          continue;
+        }
+      }
+      pNew->wsFlags |= WHERE_COLUMN_IN;
+    }else if( eOp & (WO_EQ|WO_IS) ){
+      int iCol = pProbe->aiColumn[saved_nEq];
+      pNew->wsFlags |= WHERE_COLUMN_EQ;
+      assert( saved_nEq==pNew->u.btree.nEq );
+      if( iCol==XN_ROWID
+       || (iCol>=0 && nInMul==0 && saved_nEq==pProbe->nKeyCol-1)
+      ){
+        if( iCol==XN_ROWID || pProbe->uniqNotNull
+         || (pProbe->nKeyCol==1 && pProbe->onError && eOp==WO_EQ)
+        ){
+          pNew->wsFlags |= WHERE_ONEROW;
+        }else{
+          pNew->wsFlags |= WHERE_UNQ_WANTED;
+        }
+      }
+      if( scan.iEquiv>1 ) pNew->wsFlags |= WHERE_TRANSCONS;
+    }else if( eOp & WO_ISNULL ){
+      pNew->wsFlags |= WHERE_COLUMN_NULL;
+    }else{
+      int nVecLen = whereRangeVectorLen(
+          pParse, pSrc->iCursor, pProbe, saved_nEq, pTerm
+      );
+      if( eOp & (WO_GT|WO_GE) ){
+        testcase( eOp & WO_GT );
+        testcase( eOp & WO_GE );
+        pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_BTM_LIMIT;
+        pNew->u.btree.nBtm = nVecLen;
+        pBtm = pTerm;
+        pTop = 0;
+        if( pTerm->wtFlags & TERM_LIKEOPT ){
+          /* Range constraints that come from the LIKE optimization are
+          ** always used in pairs. */
+          pTop = &pTerm[1];
+          assert( (pTop-(pTerm->pWC->a))<pTerm->pWC->nTerm );
+          assert( pTop->wtFlags & TERM_LIKEOPT );
+          assert( pTop->eOperator==WO_LT );
+          if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
+          pNew->aLTerm[pNew->nLTerm++] = pTop;
+          pNew->wsFlags |= WHERE_TOP_LIMIT;
+          pNew->u.btree.nTop = 1;
+        }
+      }else{
+        assert( eOp & (WO_LT|WO_LE) );
+        testcase( eOp & WO_LT );
+        testcase( eOp & WO_LE );
+        pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_TOP_LIMIT;
+        pNew->u.btree.nTop = nVecLen;
+        pTop = pTerm;
+        pBtm = (pNew->wsFlags & WHERE_BTM_LIMIT)!=0 ?
+                       pNew->aLTerm[pNew->nLTerm-2] : 0;
+      }
+    }
+
+    /* At this point pNew->nOut is set to the number of rows expected to
+    ** be visited by the index scan before considering term pTerm, or the
+    ** values of nIn and nInMul. In other words, assuming that all
+    ** "x IN(...)" terms are replaced with "x = ?". This block updates
+    ** the value of pNew->nOut to account for pTerm (but not nIn/nInMul).  */
+    assert( pNew->nOut==saved_nOut );
+    if( pNew->wsFlags & WHERE_COLUMN_RANGE ){
+      /* Adjust nOut using stat4 data. Or, if there is no stat4
+      ** data, using some other estimate.  */
+      whereRangeScanEst(pParse, pBuilder, pBtm, pTop, pNew);
+    }else{
+      int nEq = ++pNew->u.btree.nEq;
+      assert( eOp & (WO_ISNULL|WO_EQ|WO_IN|WO_IS) );
+
+      assert( pNew->nOut==saved_nOut );
+      if( pTerm->truthProb<=0 && pProbe->aiColumn[saved_nEq]>=0 ){
+        assert( (eOp & WO_IN) || nIn==0 );
+        testcase( eOp & WO_IN );
+        pNew->nOut += pTerm->truthProb;
+        pNew->nOut -= nIn;
+      }else{
+#ifdef SQLITE_ENABLE_STAT4
+        tRowcnt nOut = 0;
+        if( nInMul==0
+         && pProbe->nSample
+         && ALWAYS(pNew->u.btree.nEq<=pProbe->nSampleCol)
+         && ((eOp & WO_IN)==0 || ExprUseXList(pTerm->pExpr))
+         && OptimizationEnabled(db, SQLITE_Stat4)
+        ){
+          Expr *pExpr = pTerm->pExpr;
+          if( (eOp & (WO_EQ|WO_ISNULL|WO_IS))!=0 ){
+            testcase( eOp & WO_EQ );
+            testcase( eOp & WO_IS );
+            testcase( eOp & WO_ISNULL );
+            rc = whereEqualScanEst(pParse, pBuilder, pExpr->pRight, &nOut);
+          }else{
+            rc = whereInScanEst(pParse, pBuilder, pExpr->x.pList, &nOut);
+          }
+          if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+          if( rc!=SQLITE_OK ) break;          /* Jump out of the pTerm loop */
+          if( nOut ){
+            pNew->nOut = sqlite3LogEst(nOut);
+            if( nEq==1
+             /* TUNING: Mark terms as "low selectivity" if they seem likely
+             ** to be true for half or more of the rows in the table.
+             ** See tag-202002240-1 */
+             && pNew->nOut+10 > pProbe->aiRowLogEst[0]
+            ){
+#if WHERETRACE_ENABLED /* 0x01 */
+              if( sqlite3WhereTrace & 0x20 ){
+                sqlite3DebugPrintf(
+                   "STAT4 determines term has low selectivity:\n");
+                sqlite3WhereTermPrint(pTerm, 999);
+              }
+#endif
+              pTerm->wtFlags |= TERM_HIGHTRUTH;
+              if( pTerm->wtFlags & TERM_HEURTRUTH ){
+                /* If the term has previously been used with an assumption of
+                ** higher selectivity, then set the flag to rerun the
+                ** loop computations. */
+                pBuilder->bldFlags2 |= SQLITE_BLDF2_2NDPASS;
+              }
+            }
+            if( pNew->nOut>saved_nOut ) pNew->nOut = saved_nOut;
+            pNew->nOut -= nIn;
+          }
+        }
+        if( nOut==0 )
+#endif
+        {
+          pNew->nOut += (pProbe->aiRowLogEst[nEq] - pProbe->aiRowLogEst[nEq-1]);
+          if( eOp & WO_ISNULL ){
+            /* TUNING: If there is no likelihood() value, assume that a
+            ** "col IS NULL" expression matches twice as many rows
+            ** as (col=?). */
+            pNew->nOut += 10;
+          }
+        }
+      }
+    }
+
+    /* Set rCostIdx to the cost of visiting selected rows in index. Add
+    ** it to pNew->rRun, which is currently set to the cost of the index
+    ** seek only. Then, if this is a non-covering index, add the cost of
+    ** visiting the rows in the main table.  */
+    assert( pSrc->pTab->szTabRow>0 );
+    if( pProbe->idxType==SQLITE_IDXTYPE_IPK ){
+      /* The pProbe->szIdxRow is low for an IPK table since the interior
+      ** pages are small.  Thus szIdxRow gives a good estimate of seek cost.
+      ** But the leaf pages are full-size, so pProbe->szIdxRow would badly
+      ** under-estimate the scanning cost. */
+      rCostIdx = pNew->nOut + 16;
+    }else{
+      rCostIdx = pNew->nOut + 1 + (15*pProbe->szIdxRow)/pSrc->pTab->szTabRow;
+    }
+    pNew->rRun = sqlite3LogEstAdd(rLogSize, rCostIdx);
+    if( (pNew->wsFlags & (WHERE_IDX_ONLY|WHERE_IPK|WHERE_EXPRIDX))==0 ){
+      pNew->rRun = sqlite3LogEstAdd(pNew->rRun, pNew->nOut + 16);
+    }
+    ApplyCostMultiplier(pNew->rRun, pProbe->pTable->costMult);
+
+    nOutUnadjusted = pNew->nOut;
+    pNew->rRun += nInMul + nIn;
+    pNew->nOut += nInMul + nIn;
+    whereLoopOutputAdjust(pBuilder->pWC, pNew, rSize);
+    rc = whereLoopInsert(pBuilder, pNew);
+
+    if( pNew->wsFlags & WHERE_COLUMN_RANGE ){
+      pNew->nOut = saved_nOut;
+    }else{
+      pNew->nOut = nOutUnadjusted;
+    }
+
+    if( (pNew->wsFlags & WHERE_TOP_LIMIT)==0
+     && pNew->u.btree.nEq<pProbe->nColumn
+     && (pNew->u.btree.nEq<pProbe->nKeyCol ||
+           pProbe->idxType!=SQLITE_IDXTYPE_PRIMARYKEY)
+    ){
+      if( pNew->u.btree.nEq>3 ){
+        sqlite3ProgressCheck(pParse);
+      }
+      whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nInMul+nIn);
+    }
+    pNew->nOut = saved_nOut;
+#ifdef SQLITE_ENABLE_STAT4
+    pBuilder->nRecValid = nRecValid;
+#endif
+  }
+  pNew->prereq = saved_prereq;
+  pNew->u.btree.nEq = saved_nEq;
+  pNew->u.btree.nBtm = saved_nBtm;
+  pNew->u.btree.nTop = saved_nTop;
+  pNew->nSkip = saved_nSkip;
+  pNew->wsFlags = saved_wsFlags;
+  pNew->nOut = saved_nOut;
+  pNew->nLTerm = saved_nLTerm;
+
+  /* Consider using a skip-scan if there are no WHERE clause constraints
+  ** available for the left-most terms of the index, and if the average
+  ** number of repeats in the left-most terms is at least 18.
+  **
+  ** The magic number 18 is selected on the basis that scanning 17 rows
+  ** is almost always quicker than an index seek (even though if the index
+  ** contains fewer than 2^17 rows we assume otherwise in other parts of
+  ** the code). And, even if it is not, it should not be too much slower.
+  ** On the other hand, the extra seeks could end up being significantly
+  ** more expensive.  */
+  assert( 42==sqlite3LogEst(18) );
+  if( saved_nEq==saved_nSkip
+   && saved_nEq+1<pProbe->nKeyCol
+   && saved_nEq==pNew->nLTerm
+   && pProbe->noSkipScan==0
+   && pProbe->hasStat1!=0
+   && OptimizationEnabled(db, SQLITE_SkipScan)
+   && pProbe->aiRowLogEst[saved_nEq+1]>=42  /* TUNING: Minimum for skip-scan */
+   && (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
+  ){
+    LogEst nIter;
+    pNew->u.btree.nEq++;
+    pNew->nSkip++;
+    pNew->aLTerm[pNew->nLTerm++] = 0;
+    pNew->wsFlags |= WHERE_SKIPSCAN;
+    nIter = pProbe->aiRowLogEst[saved_nEq] - pProbe->aiRowLogEst[saved_nEq+1];
+    pNew->nOut -= nIter;
+    /* TUNING:  Because uncertainties in the estimates for skip-scan queries,
+    ** add a 1.375 fudge factor to make skip-scan slightly less likely. */
+    nIter += 5;
+    whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nIter + nInMul);
+    pNew->nOut = saved_nOut;
+    pNew->u.btree.nEq = saved_nEq;
+    pNew->nSkip = saved_nSkip;
+    pNew->wsFlags = saved_wsFlags;
+  }
+
+  WHERETRACE(0x800, ("END %s.addBtreeIdx(%s), nEq=%d, rc=%d\n",
+                      pProbe->pTable->zName, pProbe->zName, saved_nEq, rc));
+  return rc;
+}
+
+/*
+** Return True if it is possible that pIndex might be useful in
+** implementing the ORDER BY clause in pBuilder.
+**
+** Return False if pBuilder does not contain an ORDER BY clause or
+** if there is no way for pIndex to be useful in implementing that
+** ORDER BY clause.
+*/
+static int indexMightHelpWithOrderBy(
+  WhereLoopBuilder *pBuilder,
+  Index *pIndex,
+  int iCursor
+){
+  ExprList *pOB;
+  ExprList *aColExpr;
+  int ii, jj;
+
+  if( pIndex->bUnordered ) return 0;
+  if( (pOB = pBuilder->pWInfo->pOrderBy)==0 ) return 0;
+  for(ii=0; ii<pOB->nExpr; ii++){
+    Expr *pExpr = sqlite3ExprSkipCollateAndLikely(pOB->a[ii].pExpr);
+    if( NEVER(pExpr==0) ) continue;
+    if( pExpr->op==TK_COLUMN && pExpr->iTable==iCursor ){
+      if( pExpr->iColumn<0 ) return 1;
+      for(jj=0; jj<pIndex->nKeyCol; jj++){
+        if( pExpr->iColumn==pIndex->aiColumn[jj] ) return 1;
+      }
+    }else if( (aColExpr = pIndex->aColExpr)!=0 ){
+      for(jj=0; jj<pIndex->nKeyCol; jj++){
+        if( pIndex->aiColumn[jj]!=XN_EXPR ) continue;
+        if( sqlite3ExprCompareSkip(pExpr,aColExpr->a[jj].pExpr,iCursor)==0 ){
+          return 1;
+        }
+      }
+    }
+  }
+  return 0;
+}
+
+/* Check to see if a partial index with pPartIndexWhere can be used
+** in the current query.  Return true if it can be and false if not.
+*/
+static int whereUsablePartialIndex(
+  int iTab,             /* The table for which we want an index */
+  u8 jointype,          /* The JT_* flags on the join */
+  WhereClause *pWC,     /* The WHERE clause of the query */
+  Expr *pWhere          /* The WHERE clause from the partial index */
+){
+  int i;
+  WhereTerm *pTerm;
+  Parse *pParse;
+
+  if( jointype & JT_LTORJ ) return 0;
+  pParse = pWC->pWInfo->pParse;
+  while( pWhere->op==TK_AND ){
+    if( !whereUsablePartialIndex(iTab,jointype,pWC,pWhere->pLeft) ) return 0;
+    pWhere = pWhere->pRight;
+  }
+  if( pParse->db->flags & SQLITE_EnableQPSG ) pParse = 0;
+  for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    Expr *pExpr;
+    pExpr = pTerm->pExpr;
+    if( (!ExprHasProperty(pExpr, EP_OuterON) || pExpr->w.iJoin==iTab)
+     && ((jointype & JT_OUTER)==0 || ExprHasProperty(pExpr, EP_OuterON))
+     && sqlite3ExprImpliesExpr(pParse, pExpr, pWhere, iTab)
+     && (pTerm->wtFlags & TERM_VNULL)==0
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** pIdx is an index containing expressions.  Check it see if any of the
+** expressions in the index match the pExpr expression.
+*/
+static int exprIsCoveredByIndex(
+  const Expr *pExpr,
+  const Index *pIdx,
+  int iTabCur
+){
+  int i;
+  for(i=0; i<pIdx->nColumn; i++){
+    if( pIdx->aiColumn[i]==XN_EXPR
+     && sqlite3ExprCompare(0, pExpr, pIdx->aColExpr->a[i].pExpr, iTabCur)==0
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Structure passed to the whereIsCoveringIndex Walker callback.
+*/
+typedef struct CoveringIndexCheck CoveringIndexCheck;
+struct CoveringIndexCheck {
+  Index *pIdx;       /* The index */
+  int iTabCur;       /* Cursor number for the corresponding table */
+  u8 bExpr;          /* Uses an indexed expression */
+  u8 bUnidx;         /* Uses an unindexed column not within an indexed expr */
+};
+
+/*
+** Information passed in is pWalk->u.pCovIdxCk.  Call it pCk.
+**
+** If the Expr node references the table with cursor pCk->iTabCur, then
+** make sure that column is covered by the index pCk->pIdx.  We know that
+** all columns less than 63 (really BMS-1) are covered, so we don't need
+** to check them.  But we do need to check any column at 63 or greater.
+**
+** If the index does not cover the column, then set pWalk->eCode to
+** non-zero and return WRC_Abort to stop the search.
+**
+** If this node does not disprove that the index can be a covering index,
+** then just return WRC_Continue, to continue the search.
+**
+** If pCk->pIdx contains indexed expressions and one of those expressions
+** matches pExpr, then prune the search.
+*/
+static int whereIsCoveringIndexWalkCallback(Walker *pWalk, Expr *pExpr){
+  int i;                    /* Loop counter */
+  const Index *pIdx;        /* The index of interest */
+  const i16 *aiColumn;      /* Columns contained in the index */
+  u16 nColumn;              /* Number of columns in the index */
+  CoveringIndexCheck *pCk;  /* Info about this search */
+
+  pCk = pWalk->u.pCovIdxCk;
+  pIdx = pCk->pIdx;
+  if( (pExpr->op==TK_COLUMN || pExpr->op==TK_AGG_COLUMN) ){
+    /* if( pExpr->iColumn<(BMS-1) && pIdx->bHasExpr==0 ) return WRC_Continue;*/
+    if( pExpr->iTable!=pCk->iTabCur ) return WRC_Continue;
+    pIdx = pWalk->u.pCovIdxCk->pIdx;
+    aiColumn = pIdx->aiColumn;
+    nColumn = pIdx->nColumn;
+    for(i=0; i<nColumn; i++){
+      if( aiColumn[i]==pExpr->iColumn ) return WRC_Continue;
+    }
+    pCk->bUnidx = 1;
+    return WRC_Abort;
+  }else if( pIdx->bHasExpr
+         && exprIsCoveredByIndex(pExpr, pIdx, pWalk->u.pCovIdxCk->iTabCur) ){
+    pCk->bExpr = 1;
+    return WRC_Prune;
+  }
+  return WRC_Continue;
+}
+
+
+/*
+** pIdx is an index that covers all of the low-number columns used by
+** pWInfo->pSelect (columns from 0 through 62) or an index that has
+** expressions terms.  Hence, we cannot determine whether or not it is
+** a covering index by using the colUsed bitmasks.  We have to do a search
+** to see if the index is covering.  This routine does that search.
+**
+** The return value is one of these:
+**
+**      0                The index is definitely not a covering index
+**
+**      WHERE_IDX_ONLY   The index is definitely a covering index
+**
+**      WHERE_EXPRIDX    The index is likely a covering index, but it is
+**                       difficult to determine precisely because of the
+**                       expressions that are indexed.  Score it as a
+**                       covering index, but still keep the main table open
+**                       just in case we need it.
+**
+** This routine is an optimization.  It is always safe to return zero.
+** But returning one of the other two values when zero should have been
+** returned can lead to incorrect bytecode and assertion faults.
+*/
+static SQLITE_NOINLINE u32 whereIsCoveringIndex(
+  WhereInfo *pWInfo,     /* The WHERE clause context */
+  Index *pIdx,           /* Index that is being tested */
+  int iTabCur            /* Cursor for the table being indexed */
+){
+  int i, rc;
+  struct CoveringIndexCheck ck;
+  Walker w;
+  if( pWInfo->pSelect==0 ){
+    /* We don't have access to the full query, so we cannot check to see
+    ** if pIdx is covering.  Assume it is not. */
+    return 0;
+  }
+  if( pIdx->bHasExpr==0 ){
+    for(i=0; i<pIdx->nColumn; i++){
+      if( pIdx->aiColumn[i]>=BMS-1 ) break;
+    }
+    if( i>=pIdx->nColumn ){
+      /* pIdx does not index any columns greater than 62, but we know from
+      ** colMask that columns greater than 62 are used, so this is not a
+      ** covering index */
+      return 0;
+    }
+  }
+  ck.pIdx = pIdx;
+  ck.iTabCur = iTabCur;
+  ck.bExpr = 0;
+  ck.bUnidx = 0;
+  memset(&w, 0, sizeof(w));
+  w.xExprCallback = whereIsCoveringIndexWalkCallback;
+  w.xSelectCallback = sqlite3SelectWalkNoop;
+  w.u.pCovIdxCk = &ck;
+  sqlite3WalkSelect(&w, pWInfo->pSelect);
+  if( ck.bUnidx ){
+    rc = 0;
+  }else if( ck.bExpr ){
+    rc = WHERE_EXPRIDX;
+  }else{
+    rc = WHERE_IDX_ONLY;
+  }
+  return rc;
+}
+
+/*
+** This is an sqlite3ParserAddCleanup() callback that is invoked to
+** free the Parse->pIdxEpr list when the Parse object is destroyed.
+*/
+static void whereIndexedExprCleanup(sqlite3 *db, void *pObject){
+  IndexedExpr **pp = (IndexedExpr**)pObject;
+  while( *pp!=0 ){
+    IndexedExpr *p = *pp;
+    *pp = p->pIENext;
+    sqlite3ExprDelete(db, p->pExpr);
+    sqlite3DbFreeNN(db, p);
+  }
+}
+
+/*
+** This function is called for a partial index - one with a WHERE clause - in 
+** two scenarios. In both cases, it determines whether or not the WHERE 
+** clause on the index implies that a column of the table may be safely
+** replaced by a constant expression. For example, in the following 
+** SELECT:
+**
+**   CREATE INDEX i1 ON t1(b, c) WHERE a=<expr>;
+**   SELECT a, b, c FROM t1 WHERE a=<expr> AND b=?;
+**
+** The "a" in the select-list may be replaced by <expr>, iff:
+**
+**    (a) <expr> is a constant expression, and
+**    (b) The (a=<expr>) comparison uses the BINARY collation sequence, and
+**    (c) Column "a" has an affinity other than NONE or BLOB.
+**
+** If argument pItem is NULL, then pMask must not be NULL. In this case this 
+** function is being called as part of determining whether or not pIdx
+** is a covering index. This function clears any bits in (*pMask) 
+** corresponding to columns that may be replaced by constants as described
+** above.
+**
+** Otherwise, if pItem is not NULL, then this function is being called
+** as part of coding a loop that uses index pIdx. In this case, add entries
+** to the Parse.pIdxPartExpr list for each column that can be replaced
+** by a constant.
+*/
+static void wherePartIdxExpr(
+  Parse *pParse,                  /* Parse context */
+  Index *pIdx,                    /* Partial index being processed */
+  Expr *pPart,                    /* WHERE clause being processed */
+  Bitmask *pMask,                 /* Mask to clear bits in */
+  int iIdxCur,                    /* Cursor number for index */
+  SrcItem *pItem                  /* The FROM clause entry for the table */
+){
+  assert( pItem==0 || (pItem->fg.jointype & JT_RIGHT)==0 );
+  assert( (pItem==0 || pMask==0) && (pMask!=0 || pItem!=0) );
+
+  if( pPart->op==TK_AND ){
+    wherePartIdxExpr(pParse, pIdx, pPart->pRight, pMask, iIdxCur, pItem);
+    pPart = pPart->pLeft;
+  }
+
+  if( (pPart->op==TK_EQ || pPart->op==TK_IS) ){
+    Expr *pLeft = pPart->pLeft;
+    Expr *pRight = pPart->pRight;
+    u8 aff;
+
+    if( pLeft->op!=TK_COLUMN ) return;
+    if( !sqlite3ExprIsConstant(pRight) ) return;
+    if( !sqlite3IsBinary(sqlite3ExprCompareCollSeq(pParse, pPart)) ) return;
+    if( pLeft->iColumn<0 ) return;
+    aff = pIdx->pTable->aCol[pLeft->iColumn].affinity;
+    if( aff>=SQLITE_AFF_TEXT ){
+      if( pItem ){
+        sqlite3 *db = pParse->db;
+        IndexedExpr *p = (IndexedExpr*)sqlite3DbMallocRaw(db, sizeof(*p));
+        if( p ){
+          int bNullRow = (pItem->fg.jointype&(JT_LEFT|JT_LTORJ))!=0;
+          p->pExpr = sqlite3ExprDup(db, pRight, 0);
+          p->iDataCur = pItem->iCursor;
+          p->iIdxCur = iIdxCur;
+          p->iIdxCol = pLeft->iColumn;
+          p->bMaybeNullRow = bNullRow;
+          p->pIENext = pParse->pIdxPartExpr;
+          p->aff = aff;
+          pParse->pIdxPartExpr = p;
+          if( p->pIENext==0 ){
+            void *pArg = (void*)&pParse->pIdxPartExpr;
+            sqlite3ParserAddCleanup(pParse, whereIndexedExprCleanup, pArg);
+          }
+        }
+      }else if( pLeft->iColumn<(BMS-1) ){
+        *pMask &= ~((Bitmask)1 << pLeft->iColumn);
+      }
+    }
+  }
+}
+
+
+/*
+** Add all WhereLoop objects for a single table of the join where the table
+** is identified by pBuilder->pNew->iTab.  That table is guaranteed to be
+** a b-tree table, not a virtual table.
+**
+** The costs (WhereLoop.rRun) of the b-tree loops added by this function
+** are calculated as follows:
+**
+** For a full scan, assuming the table (or index) contains nRow rows:
+**
+**     cost = nRow * 3.0                    // full-table scan
+**     cost = nRow * K                      // scan of covering index
+**     cost = nRow * (K+3.0)                // scan of non-covering index
+**
+** where K is a value between 1.1 and 3.0 set based on the relative
+** estimated average size of the index and table records.
+**
+** For an index scan, where nVisit is the number of index rows visited
+** by the scan, and nSeek is the number of seek operations required on
+** the index b-tree:
+**
+**     cost = nSeek * (log(nRow) + K * nVisit)          // covering index
+**     cost = nSeek * (log(nRow) + (K+3.0) * nVisit)    // non-covering index
+**
+** Normally, nSeek is 1. nSeek values greater than 1 come about if the
+** WHERE clause includes "x IN (....)" terms used in place of "x=?". Or when
+** implicit "x IN (SELECT x FROM tbl)" terms are added for skip-scans.
+**
+** The estimated values (nRow, nVisit, nSeek) often contain a large amount
+** of uncertainty.  For this reason, scoring is designed to pick plans that
+** "do the least harm" if the estimates are inaccurate.  For example, a
+** log(nRow) factor is omitted from a non-covering index scan in order to
+** bias the scoring in favor of using an index, since the worst-case
+** performance of using an index is far better than the worst-case performance
+** of a full table scan.
+*/
+static int whereLoopAddBtree(
+  WhereLoopBuilder *pBuilder, /* WHERE clause information */
+  Bitmask mPrereq             /* Extra prerequisites for using this table */
+){
+  WhereInfo *pWInfo;          /* WHERE analysis context */
+  Index *pProbe;              /* An index we are evaluating */
+  Index sPk;                  /* A fake index object for the primary key */
+  LogEst aiRowEstPk[2];       /* The aiRowLogEst[] value for the sPk index */
+  i16 aiColumnPk = -1;        /* The aColumn[] value for the sPk index */
+  SrcList *pTabList;          /* The FROM clause */
+  SrcItem *pSrc;              /* The FROM clause btree term to add */
+  WhereLoop *pNew;            /* Template WhereLoop object */
+  int rc = SQLITE_OK;         /* Return code */
+  int iSortIdx = 1;           /* Index number */
+  int b;                      /* A boolean value */
+  LogEst rSize;               /* number of rows in the table */
+  WhereClause *pWC;           /* The parsed WHERE clause */
+  Table *pTab;                /* Table being queried */
+ 
+  pNew = pBuilder->pNew;
+  pWInfo = pBuilder->pWInfo;
+  pTabList = pWInfo->pTabList;
+  pSrc = pTabList->a + pNew->iTab;
+  pTab = pSrc->pTab;
+  pWC = pBuilder->pWC;
+  assert( !IsVirtual(pSrc->pTab) );
+
+  if( pSrc->fg.isIndexedBy ){
+    assert( pSrc->fg.isCte==0 );
+    /* An INDEXED BY clause specifies a particular index to use */
+    pProbe = pSrc->u2.pIBIndex;
+  }else if( !HasRowid(pTab) ){
+    pProbe = pTab->pIndex;
+  }else{
+    /* There is no INDEXED BY clause.  Create a fake Index object in local
+    ** variable sPk to represent the rowid primary key index.  Make this
+    ** fake index the first in a chain of Index objects with all of the real
+    ** indices to follow */
+    Index *pFirst;                  /* First of real indices on the table */
+    memset(&sPk, 0, sizeof(Index));
+    sPk.nKeyCol = 1;
+    sPk.nColumn = 1;
+    sPk.aiColumn = &aiColumnPk;
+    sPk.aiRowLogEst = aiRowEstPk;
+    sPk.onError = OE_Replace;
+    sPk.pTable = pTab;
+    sPk.szIdxRow = 3;  /* TUNING: Interior rows of IPK table are very small */
+    sPk.idxType = SQLITE_IDXTYPE_IPK;
+    aiRowEstPk[0] = pTab->nRowLogEst;
+    aiRowEstPk[1] = 0;
+    pFirst = pSrc->pTab->pIndex;
+    if( pSrc->fg.notIndexed==0 ){
+      /* The real indices of the table are only considered if the
+      ** NOT INDEXED qualifier is omitted from the FROM clause */
+      sPk.pNext = pFirst;
+    }
+    pProbe = &sPk;
+  }
+  rSize = pTab->nRowLogEst;
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+  /* Automatic indexes */
+  if( !pBuilder->pOrSet      /* Not part of an OR optimization */
+   && (pWInfo->wctrlFlags & (WHERE_RIGHT_JOIN|WHERE_OR_SUBCLAUSE))==0
+   && (pWInfo->pParse->db->flags & SQLITE_AutoIndex)!=0
+   && !pSrc->fg.isIndexedBy  /* Has no INDEXED BY clause */
+   && !pSrc->fg.notIndexed   /* Has no NOT INDEXED clause */
+   && HasRowid(pTab)         /* Not WITHOUT ROWID table. (FIXME: Why not?) */
+   && !pSrc->fg.isCorrelated /* Not a correlated subquery */
+   && !pSrc->fg.isRecursive  /* Not a recursive common table expression. */
+   && (pSrc->fg.jointype & JT_RIGHT)==0 /* Not the right tab of a RIGHT JOIN */
+  ){
+    /* Generate auto-index WhereLoops */
+    LogEst rLogSize;         /* Logarithm of the number of rows in the table */
+    WhereTerm *pTerm;
+    WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
+    rLogSize = estLog(rSize);
+    for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
+      if( pTerm->prereqRight & pNew->maskSelf ) continue;
+      if( termCanDriveIndex(pTerm, pSrc, 0) ){
+        pNew->u.btree.nEq = 1;
+        pNew->nSkip = 0;
+        pNew->u.btree.pIndex = 0;
+        pNew->nLTerm = 1;
+        pNew->aLTerm[0] = pTerm;
+        /* TUNING: One-time cost for computing the automatic index is
+        ** estimated to be X*N*log2(N) where N is the number of rows in
+        ** the table being indexed and where X is 7 (LogEst=28) for normal
+        ** tables or 0.5 (LogEst=-10) for views and subqueries.  The value
+        ** of X is smaller for views and subqueries so that the query planner
+        ** will be more aggressive about generating automatic indexes for
+        ** those objects, since there is no opportunity to add schema
+        ** indexes on subqueries and views. */
+        pNew->rSetup = rLogSize + rSize;
+        if( !IsView(pTab) && (pTab->tabFlags & TF_Ephemeral)==0 ){
+          pNew->rSetup += 28;
+        }else{
+          pNew->rSetup -= 25;  /* Greatly reduced setup cost for auto indexes
+                               ** on ephemeral materializations of views */
+        }
+        ApplyCostMultiplier(pNew->rSetup, pTab->costMult);
+        if( pNew->rSetup<0 ) pNew->rSetup = 0;
+        /* TUNING: Each index lookup yields 20 rows in the table.  This
+        ** is more than the usual guess of 10 rows, since we have no way
+        ** of knowing how selective the index will ultimately be.  It would
+        ** not be unreasonable to make this value much larger. */
+        pNew->nOut = 43;  assert( 43==sqlite3LogEst(20) );
+        pNew->rRun = sqlite3LogEstAdd(rLogSize,pNew->nOut);
+        pNew->wsFlags = WHERE_AUTO_INDEX;
+        pNew->prereq = mPrereq | pTerm->prereqRight;
+        rc = whereLoopInsert(pBuilder, pNew);
+      }
+    }
+  }
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
+  /* Loop over all indices. If there was an INDEXED BY clause, then only
+  ** consider index pProbe.  */
+  for(; rc==SQLITE_OK && pProbe;
+      pProbe=(pSrc->fg.isIndexedBy ? 0 : pProbe->pNext), iSortIdx++
+  ){
+    if( pProbe->pPartIdxWhere!=0
+     && !whereUsablePartialIndex(pSrc->iCursor, pSrc->fg.jointype, pWC,
+                                 pProbe->pPartIdxWhere)
+    ){
+      testcase( pNew->iTab!=pSrc->iCursor );  /* See ticket [98d973b8f5] */
+      continue;  /* Partial index inappropriate for this query */
+    }
+    if( pProbe->bNoQuery ) continue;
+    rSize = pProbe->aiRowLogEst[0];
+    pNew->u.btree.nEq = 0;
+    pNew->u.btree.nBtm = 0;
+    pNew->u.btree.nTop = 0;
+    pNew->nSkip = 0;
+    pNew->nLTerm = 0;
+    pNew->iSortIdx = 0;
+    pNew->rSetup = 0;
+    pNew->prereq = mPrereq;
+    pNew->nOut = rSize;
+    pNew->u.btree.pIndex = pProbe;
+    b = indexMightHelpWithOrderBy(pBuilder, pProbe, pSrc->iCursor);
+
+    /* The ONEPASS_DESIRED flags never occurs together with ORDER BY */
+    assert( (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || b==0 );
+    if( pProbe->idxType==SQLITE_IDXTYPE_IPK ){
+      /* Integer primary key index */
+      pNew->wsFlags = WHERE_IPK;
+
+      /* Full table scan */
+      pNew->iSortIdx = b ? iSortIdx : 0;
+      /* TUNING: Cost of full table scan is 3.0*N.  The 3.0 factor is an
+      ** extra cost designed to discourage the use of full table scans,
+      ** since index lookups have better worst-case performance if our
+      ** stat guesses are wrong.  Reduce the 3.0 penalty slightly
+      ** (to 2.75) if we have valid STAT4 information for the table.
+      ** At 2.75, a full table scan is preferred over using an index on
+      ** a column with just two distinct values where each value has about
+      ** an equal number of appearances.  Without STAT4 data, we still want
+      ** to use an index in that case, since the constraint might be for
+      ** the scarcer of the two values, and in that case an index lookup is
+      ** better.
+      */
+#ifdef SQLITE_ENABLE_STAT4
+      pNew->rRun = rSize + 16 - 2*((pTab->tabFlags & TF_HasStat4)!=0);
+#else
+      pNew->rRun = rSize + 16;
+#endif
+      ApplyCostMultiplier(pNew->rRun, pTab->costMult);
+      whereLoopOutputAdjust(pWC, pNew, rSize);
+      rc = whereLoopInsert(pBuilder, pNew);
+      pNew->nOut = rSize;
+      if( rc ) break;
+    }else{
+      Bitmask m;
+      if( pProbe->isCovering ){
+        m = 0;
+        pNew->wsFlags = WHERE_IDX_ONLY | WHERE_INDEXED;
+      }else{
+        m = pSrc->colUsed & pProbe->colNotIdxed;
+        if( pProbe->pPartIdxWhere ){
+          wherePartIdxExpr(
+              pWInfo->pParse, pProbe, pProbe->pPartIdxWhere, &m, 0, 0
+          );
+        }
+        pNew->wsFlags = WHERE_INDEXED;
+        if( m==TOPBIT || (pProbe->bHasExpr && !pProbe->bHasVCol && m!=0) ){
+          u32 isCov = whereIsCoveringIndex(pWInfo, pProbe, pSrc->iCursor);
+          if( isCov==0 ){
+            WHERETRACE(0x200,
+               ("-> %s is not a covering index"
+                " according to whereIsCoveringIndex()\n", pProbe->zName));
+            assert( m!=0 );
+          }else{
+            m = 0;
+            pNew->wsFlags |= isCov;
+            if( isCov & WHERE_IDX_ONLY ){
+              WHERETRACE(0x200,
+                 ("-> %s is a covering expression index"
+                  " according to whereIsCoveringIndex()\n", pProbe->zName));
+            }else{
+              assert( isCov==WHERE_EXPRIDX );
+              WHERETRACE(0x200,
+                 ("-> %s might be a covering expression index"
+                  " according to whereIsCoveringIndex()\n", pProbe->zName));
+            }
+          }
+        }else if( m==0 ){
+          WHERETRACE(0x200,
+             ("-> %s a covering index according to bitmasks\n",
+             pProbe->zName, m==0 ? "is" : "is not"));
+          pNew->wsFlags = WHERE_IDX_ONLY | WHERE_INDEXED;
+        }
+      }
+
+      /* Full scan via index */
+      if( b
+       || !HasRowid(pTab)
+       || pProbe->pPartIdxWhere!=0
+       || pSrc->fg.isIndexedBy
+       || ( m==0
+         && pProbe->bUnordered==0
+         && (pProbe->szIdxRow<pTab->szTabRow)
+         && (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
+         && sqlite3GlobalConfig.bUseCis
+         && OptimizationEnabled(pWInfo->pParse->db, SQLITE_CoverIdxScan)
+          )
+      ){
+        pNew->iSortIdx = b ? iSortIdx : 0;
+
+        /* The cost of visiting the index rows is N*K, where K is
+        ** between 1.1 and 3.0, depending on the relative sizes of the
+        ** index and table rows. */
+        pNew->rRun = rSize + 1 + (15*pProbe->szIdxRow)/pTab->szTabRow;
+        if( m!=0 ){
+          /* If this is a non-covering index scan, add in the cost of
+          ** doing table lookups.  The cost will be 3x the number of
+          ** lookups.  Take into account WHERE clause terms that can be
+          ** satisfied using just the index, and that do not require a
+          ** table lookup. */
+          LogEst nLookup = rSize + 16;  /* Base cost:  N*3 */
+          int ii;
+          int iCur = pSrc->iCursor;
+          WhereClause *pWC2 = &pWInfo->sWC;
+          for(ii=0; ii<pWC2->nTerm; ii++){
+            WhereTerm *pTerm = &pWC2->a[ii];
+            if( !sqlite3ExprCoveredByIndex(pTerm->pExpr, iCur, pProbe) ){
+              break;
+            }
+            /* pTerm can be evaluated using just the index.  So reduce
+            ** the expected number of table lookups accordingly */
+            if( pTerm->truthProb<=0 ){
+              nLookup += pTerm->truthProb;
+            }else{
+              nLookup--;
+              if( pTerm->eOperator & (WO_EQ|WO_IS) ) nLookup -= 19;
+            }
+          }
+         
+          pNew->rRun = sqlite3LogEstAdd(pNew->rRun, nLookup);
+        }
+        ApplyCostMultiplier(pNew->rRun, pTab->costMult);
+        whereLoopOutputAdjust(pWC, pNew, rSize);
+        if( (pSrc->fg.jointype & JT_RIGHT)!=0 && pProbe->aColExpr ){
+          /* Do not do an SCAN of a index-on-expression in a RIGHT JOIN
+          ** because the cursor used to access the index might not be
+          ** positioned to the correct row during the right-join no-match
+          ** loop. */
+        }else{
+          rc = whereLoopInsert(pBuilder, pNew);
+        }
+        pNew->nOut = rSize;
+        if( rc ) break;
+      }
+    }
+
+    pBuilder->bldFlags1 = 0;
+    rc = whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, 0);
+    if( pBuilder->bldFlags1==SQLITE_BLDF1_INDEXED ){
+      /* If a non-unique index is used, or if a prefix of the key for
+      ** unique index is used (making the index functionally non-unique)
+      ** then the sqlite_stat1 data becomes important for scoring the
+      ** plan */
+      pTab->tabFlags |= TF_StatsUsed;
+    }
+#ifdef SQLITE_ENABLE_STAT4
+    sqlite3Stat4ProbeFree(pBuilder->pRec);
+    pBuilder->nRecValid = 0;
+    pBuilder->pRec = 0;
+#endif
+  }
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Return true if pTerm is a virtual table LIMIT or OFFSET term.
+*/
+static int isLimitTerm(WhereTerm *pTerm){
+  assert( pTerm->eOperator==WO_AUX || pTerm->eMatchOp==0 );
+  return pTerm->eMatchOp>=SQLITE_INDEX_CONSTRAINT_LIMIT
+      && pTerm->eMatchOp<=SQLITE_INDEX_CONSTRAINT_OFFSET;
+}
+
+/*
+** Argument pIdxInfo is already populated with all constraints that may
+** be used by the virtual table identified by pBuilder->pNew->iTab. This
+** function marks a subset of those constraints usable, invokes the
+** xBestIndex method and adds the returned plan to pBuilder.
+**
+** A constraint is marked usable if:
+**
+**   * Argument mUsable indicates that its prerequisites are available, and
+**
+**   * It is not one of the operators specified in the mExclude mask passed
+**     as the fourth argument (which in practice is either WO_IN or 0).
+**
+** Argument mPrereq is a mask of tables that must be scanned before the
+** virtual table in question. These are added to the plans prerequisites
+** before it is added to pBuilder.
+**
+** Output parameter *pbIn is set to true if the plan added to pBuilder
+** uses one or more WO_IN terms, or false otherwise.
+*/
+static int whereLoopAddVirtualOne(
+  WhereLoopBuilder *pBuilder,
+  Bitmask mPrereq,                /* Mask of tables that must be used. */
+  Bitmask mUsable,                /* Mask of usable tables */
+  u16 mExclude,                   /* Exclude terms using these operators */
+  sqlite3_index_info *pIdxInfo,   /* Populated object for xBestIndex */
+  u16 mNoOmit,                    /* Do not omit these constraints */
+  int *pbIn,                      /* OUT: True if plan uses an IN(...) op */
+  int *pbRetryLimit               /* OUT: Retry without LIMIT/OFFSET */
+){
+  WhereClause *pWC = pBuilder->pWC;
+  HiddenIndexInfo *pHidden = (HiddenIndexInfo*)&pIdxInfo[1];
+  struct sqlite3_index_constraint *pIdxCons;
+  struct sqlite3_index_constraint_usage *pUsage = pIdxInfo->aConstraintUsage;
+  int i;
+  int mxTerm;
+  int rc = SQLITE_OK;
+  WhereLoop *pNew = pBuilder->pNew;
+  Parse *pParse = pBuilder->pWInfo->pParse;
+  SrcItem *pSrc = &pBuilder->pWInfo->pTabList->a[pNew->iTab];
+  int nConstraint = pIdxInfo->nConstraint;
+
+  assert( (mUsable & mPrereq)==mPrereq );
+  *pbIn = 0;
+  pNew->prereq = mPrereq;
+
+  /* Set the usable flag on the subset of constraints identified by
+  ** arguments mUsable and mExclude. */
+  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
+  for(i=0; i<nConstraint; i++, pIdxCons++){
+    WhereTerm *pTerm = &pWC->a[pIdxCons->iTermOffset];
+    pIdxCons->usable = 0;
+    if( (pTerm->prereqRight & mUsable)==pTerm->prereqRight
+     && (pTerm->eOperator & mExclude)==0
+     && (pbRetryLimit || !isLimitTerm(pTerm))
+    ){
+      pIdxCons->usable = 1;
+    }
+  }
+
+  /* Initialize the output fields of the sqlite3_index_info structure */
+  memset(pUsage, 0, sizeof(pUsage[0])*nConstraint);
+  assert( pIdxInfo->needToFreeIdxStr==0 );
+  pIdxInfo->idxStr = 0;
+  pIdxInfo->idxNum = 0;
+  pIdxInfo->orderByConsumed = 0;
+  pIdxInfo->estimatedCost = SQLITE_BIG_DBL / (double)2;
+  pIdxInfo->estimatedRows = 25;
+  pIdxInfo->idxFlags = 0;
+  pIdxInfo->colUsed = (sqlite3_int64)pSrc->colUsed;
+  pHidden->mHandleIn = 0;
+
+  /* Invoke the virtual table xBestIndex() method */
+  rc = vtabBestIndex(pParse, pSrc->pTab, pIdxInfo);
+  if( rc ){
+    if( rc==SQLITE_CONSTRAINT ){
+      /* If the xBestIndex method returns SQLITE_CONSTRAINT, that means
+      ** that the particular combination of parameters provided is unusable.
+      ** Make no entries in the loop table.
+      */
+      WHERETRACE(0xffffffff, ("  ^^^^--- non-viable plan rejected!\n"));
+      return SQLITE_OK;
+    }
+    return rc;
+  }
+
+  mxTerm = -1;
+  assert( pNew->nLSlot>=nConstraint );
+  memset(pNew->aLTerm, 0, sizeof(pNew->aLTerm[0])*nConstraint );
+  memset(&pNew->u.vtab, 0, sizeof(pNew->u.vtab));
+  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
+  for(i=0; i<nConstraint; i++, pIdxCons++){
+    int iTerm;
+    if( (iTerm = pUsage[i].argvIndex - 1)>=0 ){
+      WhereTerm *pTerm;
+      int j = pIdxCons->iTermOffset;
+      if( iTerm>=nConstraint
+       || j<0
+       || j>=pWC->nTerm
+       || pNew->aLTerm[iTerm]!=0
+       || pIdxCons->usable==0
+      ){
+        sqlite3ErrorMsg(pParse,"%s.xBestIndex malfunction",pSrc->pTab->zName);
+        testcase( pIdxInfo->needToFreeIdxStr );
+        return SQLITE_ERROR;
+      }
+      testcase( iTerm==nConstraint-1 );
+      testcase( j==0 );
+      testcase( j==pWC->nTerm-1 );
+      pTerm = &pWC->a[j];
+      pNew->prereq |= pTerm->prereqRight;
+      assert( iTerm<pNew->nLSlot );
+      pNew->aLTerm[iTerm] = pTerm;
+      if( iTerm>mxTerm ) mxTerm = iTerm;
+      testcase( iTerm==15 );
+      testcase( iTerm==16 );
+      if( pUsage[i].omit ){
+        if( i<16 && ((1<<i)&mNoOmit)==0 ){
+          testcase( i!=iTerm );
+          pNew->u.vtab.omitMask |= 1<<iTerm;
+        }else{
+          testcase( i!=iTerm );
+        }
+        if( pTerm->eMatchOp==SQLITE_INDEX_CONSTRAINT_OFFSET ){
+          pNew->u.vtab.bOmitOffset = 1;
+        }
+      }
+      if( SMASKBIT32(i) & pHidden->mHandleIn ){
+        pNew->u.vtab.mHandleIn |= MASKBIT32(iTerm);
+      }else if( (pTerm->eOperator & WO_IN)!=0 ){
+        /* A virtual table that is constrained by an IN clause may not
+        ** consume the ORDER BY clause because (1) the order of IN terms
+        ** is not necessarily related to the order of output terms and
+        ** (2) Multiple outputs from a single IN value will not merge
+        ** together.  */
+        pIdxInfo->orderByConsumed = 0;
+        pIdxInfo->idxFlags &= ~SQLITE_INDEX_SCAN_UNIQUE;
+        *pbIn = 1; assert( (mExclude & WO_IN)==0 );
+      }
+
+      assert( pbRetryLimit || !isLimitTerm(pTerm) );
+      if( isLimitTerm(pTerm) && *pbIn ){
+        /* If there is an IN(...) term handled as an == (separate call to
+        ** xFilter for each value on the RHS of the IN) and a LIMIT or
+        ** OFFSET term handled as well, the plan is unusable. Set output
+        ** variable *pbRetryLimit to true to tell the caller to retry with
+        ** LIMIT and OFFSET disabled. */
+        if( pIdxInfo->needToFreeIdxStr ){
+          sqlite3_free(pIdxInfo->idxStr);
+          pIdxInfo->idxStr = 0;
+          pIdxInfo->needToFreeIdxStr = 0;
+        }
+        *pbRetryLimit = 1;
+        return SQLITE_OK;
+      }
+    }
+  }
+
+  pNew->nLTerm = mxTerm+1;
+  for(i=0; i<=mxTerm; i++){
+    if( pNew->aLTerm[i]==0 ){
+      /* The non-zero argvIdx values must be contiguous.  Raise an
+      ** error if they are not */
+      sqlite3ErrorMsg(pParse,"%s.xBestIndex malfunction",pSrc->pTab->zName);
+      testcase( pIdxInfo->needToFreeIdxStr );
+      return SQLITE_ERROR;
+    }
+  }
+  assert( pNew->nLTerm<=pNew->nLSlot );
+  pNew->u.vtab.idxNum = pIdxInfo->idxNum;
+  pNew->u.vtab.needFree = pIdxInfo->needToFreeIdxStr;
+  pIdxInfo->needToFreeIdxStr = 0;
+  pNew->u.vtab.idxStr = pIdxInfo->idxStr;
+  pNew->u.vtab.isOrdered = (i8)(pIdxInfo->orderByConsumed ?
+      pIdxInfo->nOrderBy : 0);
+  pNew->rSetup = 0;
+  pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
+  pNew->nOut = sqlite3LogEst(pIdxInfo->estimatedRows);
+
+  /* Set the WHERE_ONEROW flag if the xBestIndex() method indicated
+  ** that the scan will visit at most one row. Clear it otherwise. */
+  if( pIdxInfo->idxFlags & SQLITE_INDEX_SCAN_UNIQUE ){
+    pNew->wsFlags |= WHERE_ONEROW;
+  }else{
+    pNew->wsFlags &= ~WHERE_ONEROW;
+  }
+  rc = whereLoopInsert(pBuilder, pNew);
+  if( pNew->u.vtab.needFree ){
+    sqlite3_free(pNew->u.vtab.idxStr);
+    pNew->u.vtab.needFree = 0;
+  }
+  WHERETRACE(0xffffffff, ("  bIn=%d prereqIn=%04llx prereqOut=%04llx\n",
+                      *pbIn, (sqlite3_uint64)mPrereq,
+                      (sqlite3_uint64)(pNew->prereq & ~mPrereq)));
+
+  return rc;
+}
+
+/*
+** Return the collating sequence for a constraint passed into xBestIndex.
+**
+** pIdxInfo must be an sqlite3_index_info structure passed into xBestIndex.
+** This routine depends on there being a HiddenIndexInfo structure immediately
+** following the sqlite3_index_info structure.
+**
+** Return a pointer to the collation name:
+**
+**    1. If there is an explicit COLLATE operator on the constraint, return it.
+**
+**    2. Else, if the column has an alternative collation, return that.
+**
+**    3. Otherwise, return "BINARY".
+*/
+const char *sqlite3_vtab_collation(sqlite3_index_info *pIdxInfo, int iCons){
+  HiddenIndexInfo *pHidden = (HiddenIndexInfo*)&pIdxInfo[1];
+  const char *zRet = 0;
+  if( iCons>=0 && iCons<pIdxInfo->nConstraint ){
+    CollSeq *pC = 0;
+    int iTerm = pIdxInfo->aConstraint[iCons].iTermOffset;
+    Expr *pX = pHidden->pWC->a[iTerm].pExpr;
+    if( pX->pLeft ){
+      pC = sqlite3ExprCompareCollSeq(pHidden->pParse, pX);
+    }
+    zRet = (pC ? pC->zName : sqlite3StrBINARY);
+  }
+  return zRet;
+}
+
+/*
+** Return true if constraint iCons is really an IN(...) constraint, or
+** false otherwise. If iCons is an IN(...) constraint, set (if bHandle!=0)
+** or clear (if bHandle==0) the flag to handle it using an iterator.
+*/
+int sqlite3_vtab_in(sqlite3_index_info *pIdxInfo, int iCons, int bHandle){
+  HiddenIndexInfo *pHidden = (HiddenIndexInfo*)&pIdxInfo[1];
+  u32 m = SMASKBIT32(iCons);
+  if( m & pHidden->mIn ){
+    if( bHandle==0 ){
+      pHidden->mHandleIn &= ~m;
+    }else if( bHandle>0 ){
+      pHidden->mHandleIn |= m;
+    }
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** This interface is callable from within the xBestIndex callback only.
+**
+** If possible, set (*ppVal) to point to an object containing the value
+** on the right-hand-side of constraint iCons.
+*/
+int sqlite3_vtab_rhs_value(
+  sqlite3_index_info *pIdxInfo,   /* Copy of first argument to xBestIndex */
+  int iCons,                      /* Constraint for which RHS is wanted */
+  sqlite3_value **ppVal           /* Write value extracted here */
+){
+  HiddenIndexInfo *pH = (HiddenIndexInfo*)&pIdxInfo[1];
+  sqlite3_value *pVal = 0;
+  int rc = SQLITE_OK;
+  if( iCons<0 || iCons>=pIdxInfo->nConstraint ){
+    rc = SQLITE_MISUSE_BKPT; /* EV: R-30545-25046 */
+  }else{
+    if( pH->aRhs[iCons]==0 ){
+      WhereTerm *pTerm = &pH->pWC->a[pIdxInfo->aConstraint[iCons].iTermOffset];
+      rc = sqlite3ValueFromExpr(
+          pH->pParse->db, pTerm->pExpr->pRight, ENC(pH->pParse->db),
+          SQLITE_AFF_BLOB, &pH->aRhs[iCons]
+      );
+      testcase( rc!=SQLITE_OK );
+    }
+    pVal = pH->aRhs[iCons];
+  }
+  *ppVal = pVal;
+
+  if( rc==SQLITE_OK && pVal==0 ){  /* IMP: R-19933-32160 */
+    rc = SQLITE_NOTFOUND;          /* IMP: R-36424-56542 */
+  }
+
+  return rc;
+}
+
+/*
+** Return true if ORDER BY clause may be handled as DISTINCT.
+*/
+int sqlite3_vtab_distinct(sqlite3_index_info *pIdxInfo){
+  HiddenIndexInfo *pHidden = (HiddenIndexInfo*)&pIdxInfo[1];
+  assert( pHidden->eDistinct>=0 && pHidden->eDistinct<=3 );
+  return pHidden->eDistinct;
+}
+
+/*
+** Cause the prepared statement that is associated with a call to
+** xBestIndex to potentially use all schemas.  If the statement being
+** prepared is read-only, then just start read transactions on all
+** schemas.  But if this is a write operation, start writes on all
+** schemas.
+**
+** This is used by the (built-in) sqlite_dbpage virtual table.
+*/
+void sqlite3VtabUsesAllSchemas(Parse *pParse){
+  int nDb = pParse->db->nDb;
+  int i;
+  for(i=0; i<nDb; i++){
+    sqlite3CodeVerifySchema(pParse, i);
+  }
+  if( DbMaskNonZero(pParse->writeMask) ){
+    for(i=0; i<nDb; i++){
+      sqlite3BeginWriteOperation(pParse, 0, i);
+    }
+  }
+}
+
+/*
+** Add all WhereLoop objects for a table of the join identified by
+** pBuilder->pNew->iTab.  That table is guaranteed to be a virtual table.
+**
+** If there are no LEFT or CROSS JOIN joins in the query, both mPrereq and
+** mUnusable are set to 0. Otherwise, mPrereq is a mask of all FROM clause
+** entries that occur before the virtual table in the FROM clause and are
+** separated from it by at least one LEFT or CROSS JOIN. Similarly, the
+** mUnusable mask contains all FROM clause entries that occur after the
+** virtual table and are separated from it by at least one LEFT or
+** CROSS JOIN.
+**
+** For example, if the query were:
+**
+**   ... FROM t1, t2 LEFT JOIN t3, t4, vt CROSS JOIN t5, t6;
+**
+** then mPrereq corresponds to (t1, t2) and mUnusable to (t5, t6).
+**
+** All the tables in mPrereq must be scanned before the current virtual
+** table. So any terms for which all prerequisites are satisfied by
+** mPrereq may be specified as "usable" in all calls to xBestIndex.
+** Conversely, all tables in mUnusable must be scanned after the current
+** virtual table, so any terms for which the prerequisites overlap with
+** mUnusable should always be configured as "not-usable" for xBestIndex.
+*/
+static int whereLoopAddVirtual(
+  WhereLoopBuilder *pBuilder,  /* WHERE clause information */
+  Bitmask mPrereq,             /* Tables that must be scanned before this one */
+  Bitmask mUnusable            /* Tables that must be scanned after this one */
+){
+  int rc = SQLITE_OK;          /* Return code */
+  WhereInfo *pWInfo;           /* WHERE analysis context */
+  Parse *pParse;               /* The parsing context */
+  WhereClause *pWC;            /* The WHERE clause */
+  SrcItem *pSrc;               /* The FROM clause term to search */
+  sqlite3_index_info *p;       /* Object to pass to xBestIndex() */
+  int nConstraint;             /* Number of constraints in p */
+  int bIn;                     /* True if plan uses IN(...) operator */
+  WhereLoop *pNew;
+  Bitmask mBest;               /* Tables used by best possible plan */
+  u16 mNoOmit;
+  int bRetry = 0;              /* True to retry with LIMIT/OFFSET disabled */
+
+  assert( (mPrereq & mUnusable)==0 );
+  pWInfo = pBuilder->pWInfo;
+  pParse = pWInfo->pParse;
+  pWC = pBuilder->pWC;
+  pNew = pBuilder->pNew;
+  pSrc = &pWInfo->pTabList->a[pNew->iTab];
+  assert( IsVirtual(pSrc->pTab) );
+  p = allocateIndexInfo(pWInfo, pWC, mUnusable, pSrc, &mNoOmit);
+  if( p==0 ) return SQLITE_NOMEM_BKPT;
+  pNew->rSetup = 0;
+  pNew->wsFlags = WHERE_VIRTUALTABLE;
+  pNew->nLTerm = 0;
+  pNew->u.vtab.needFree = 0;
+  nConstraint = p->nConstraint;
+  if( whereLoopResize(pParse->db, pNew, nConstraint) ){
+    freeIndexInfo(pParse->db, p);
+    return SQLITE_NOMEM_BKPT;
+  }
+
+  /* First call xBestIndex() with all constraints usable. */
+  WHERETRACE(0x800, ("BEGIN %s.addVirtual()\n", pSrc->pTab->zName));
+  WHERETRACE(0x800, ("  VirtualOne: all usable\n"));
+  rc = whereLoopAddVirtualOne(
+      pBuilder, mPrereq, ALLBITS, 0, p, mNoOmit, &bIn, &bRetry
+  );
+  if( bRetry ){
+    assert( rc==SQLITE_OK );
+    rc = whereLoopAddVirtualOne(
+        pBuilder, mPrereq, ALLBITS, 0, p, mNoOmit, &bIn, 0
+    );
+  }
+
+  /* If the call to xBestIndex() with all terms enabled produced a plan
+  ** that does not require any source tables (IOW: a plan with mBest==0)
+  ** and does not use an IN(...) operator, then there is no point in making
+  ** any further calls to xBestIndex() since they will all return the same
+  ** result (if the xBestIndex() implementation is sane). */
+  if( rc==SQLITE_OK && ((mBest = (pNew->prereq & ~mPrereq))!=0 || bIn) ){
+    int seenZero = 0;             /* True if a plan with no prereqs seen */
+    int seenZeroNoIN = 0;         /* Plan with no prereqs and no IN(...) seen */
+    Bitmask mPrev = 0;
+    Bitmask mBestNoIn = 0;
+
+    /* If the plan produced by the earlier call uses an IN(...) term, call
+    ** xBestIndex again, this time with IN(...) terms disabled. */
+    if( bIn ){
+      WHERETRACE(0x800, ("  VirtualOne: all usable w/o IN\n"));
+      rc = whereLoopAddVirtualOne(
+          pBuilder, mPrereq, ALLBITS, WO_IN, p, mNoOmit, &bIn, 0);
+      assert( bIn==0 );
+      mBestNoIn = pNew->prereq & ~mPrereq;
+      if( mBestNoIn==0 ){
+        seenZero = 1;
+        seenZeroNoIN = 1;
+      }
+    }
+
+    /* Call xBestIndex once for each distinct value of (prereqRight & ~mPrereq)
+    ** in the set of terms that apply to the current virtual table.  */
+    while( rc==SQLITE_OK ){
+      int i;
+      Bitmask mNext = ALLBITS;
+      assert( mNext>0 );
+      for(i=0; i<nConstraint; i++){
+        Bitmask mThis = (
+            pWC->a[p->aConstraint[i].iTermOffset].prereqRight & ~mPrereq
+        );
+        if( mThis>mPrev && mThis<mNext ) mNext = mThis;
+      }
+      mPrev = mNext;
+      if( mNext==ALLBITS ) break;
+      if( mNext==mBest || mNext==mBestNoIn ) continue;
+      WHERETRACE(0x800, ("  VirtualOne: mPrev=%04llx mNext=%04llx\n",
+                       (sqlite3_uint64)mPrev, (sqlite3_uint64)mNext));
+      rc = whereLoopAddVirtualOne(
+          pBuilder, mPrereq, mNext|mPrereq, 0, p, mNoOmit, &bIn, 0);
+      if( pNew->prereq==mPrereq ){
+        seenZero = 1;
+        if( bIn==0 ) seenZeroNoIN = 1;
+      }
+    }
+
+    /* If the calls to xBestIndex() in the above loop did not find a plan
+    ** that requires no source tables at all (i.e. one guaranteed to be
+    ** usable), make a call here with all source tables disabled */
+    if( rc==SQLITE_OK && seenZero==0 ){
+      WHERETRACE(0x800, ("  VirtualOne: all disabled\n"));
+      rc = whereLoopAddVirtualOne(
+          pBuilder, mPrereq, mPrereq, 0, p, mNoOmit, &bIn, 0);
+      if( bIn==0 ) seenZeroNoIN = 1;
+    }
+
+    /* If the calls to xBestIndex() have so far failed to find a plan
+    ** that requires no source tables at all and does not use an IN(...)
+    ** operator, make a final call to obtain one here.  */
+    if( rc==SQLITE_OK && seenZeroNoIN==0 ){
+      WHERETRACE(0x800, ("  VirtualOne: all disabled and w/o IN\n"));
+      rc = whereLoopAddVirtualOne(
+          pBuilder, mPrereq, mPrereq, WO_IN, p, mNoOmit, &bIn, 0);
+    }
+  }
+
+  if( p->needToFreeIdxStr ) sqlite3_free(p->idxStr);
+  freeIndexInfo(pParse->db, p);
+  WHERETRACE(0x800, ("END %s.addVirtual(), rc=%d\n", pSrc->pTab->zName, rc));
+  return rc;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** Add WhereLoop entries to handle OR terms.  This works for either
+** btrees or virtual tables.
+*/
+static int whereLoopAddOr(
+  WhereLoopBuilder *pBuilder,
+  Bitmask mPrereq,
+  Bitmask mUnusable
+){
+  WhereInfo *pWInfo = pBuilder->pWInfo;
+  WhereClause *pWC;
+  WhereLoop *pNew;
+  WhereTerm *pTerm, *pWCEnd;
+  int rc = SQLITE_OK;
+  int iCur;
+  WhereClause tempWC;
+  WhereLoopBuilder sSubBuild;
+  WhereOrSet sSum, sCur;
+  SrcItem *pItem;
+ 
+  pWC = pBuilder->pWC;
+  pWCEnd = pWC->a + pWC->nTerm;
+  pNew = pBuilder->pNew;
+  memset(&sSum, 0, sizeof(sSum));
+  pItem = pWInfo->pTabList->a + pNew->iTab;
+  iCur = pItem->iCursor;
+
+  /* The multi-index OR optimization does not work for RIGHT and FULL JOIN */
+  if( pItem->fg.jointype & JT_RIGHT ) return SQLITE_OK;
+
+  for(pTerm=pWC->a; pTerm<pWCEnd && rc==SQLITE_OK; pTerm++){
+    if( (pTerm->eOperator & WO_OR)!=0
+     && (pTerm->u.pOrInfo->indexable & pNew->maskSelf)!=0
+    ){
+      WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
+      WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
+      WhereTerm *pOrTerm;
+      int once = 1;
+      int i, j;
+   
+      sSubBuild = *pBuilder;
+      sSubBuild.pOrSet = &sCur;
+
+      WHERETRACE(0x400, ("Begin processing OR-clause %p\n", pTerm));
+      for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
+        if( (pOrTerm->eOperator & WO_AND)!=0 ){
+          sSubBuild.pWC = &pOrTerm->u.pAndInfo->wc;
+        }else if( pOrTerm->leftCursor==iCur ){
+          tempWC.pWInfo = pWC->pWInfo;
+          tempWC.pOuter = pWC;
+          tempWC.op = TK_AND;
+          tempWC.nTerm = 1;
+          tempWC.nBase = 1;
+          tempWC.a = pOrTerm;
+          sSubBuild.pWC = &tempWC;
+        }else{
+          continue;
+        }
+        sCur.n = 0;
+#ifdef WHERETRACE_ENABLED
+        WHERETRACE(0x400, ("OR-term %d of %p has %d subterms:\n",
+                   (int)(pOrTerm-pOrWC->a), pTerm, sSubBuild.pWC->nTerm));
+        if( sqlite3WhereTrace & 0x20000 ){
+          sqlite3WhereClausePrint(sSubBuild.pWC);
+        }
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+        if( IsVirtual(pItem->pTab) ){
+          rc = whereLoopAddVirtual(&sSubBuild, mPrereq, mUnusable);
+        }else
+#endif
+        {
+          rc = whereLoopAddBtree(&sSubBuild, mPrereq);
+        }
+        if( rc==SQLITE_OK ){
+          rc = whereLoopAddOr(&sSubBuild, mPrereq, mUnusable);
+        }
+        testcase( rc==SQLITE_NOMEM && sCur.n>0 );
+        testcase( rc==SQLITE_DONE );
+        if( sCur.n==0 ){
+          sSum.n = 0;
+          break;
+        }else if( once ){
+          whereOrMove(&sSum, &sCur);
+          once = 0;
+        }else{
+          WhereOrSet sPrev;
+          whereOrMove(&sPrev, &sSum);
+          sSum.n = 0;
+          for(i=0; i<sPrev.n; i++){
+            for(j=0; j<sCur.n; j++){
+              whereOrInsert(&sSum, sPrev.a[i].prereq | sCur.a[j].prereq,
+                            sqlite3LogEstAdd(sPrev.a[i].rRun, sCur.a[j].rRun),
+                            sqlite3LogEstAdd(sPrev.a[i].nOut, sCur.a[j].nOut));
+            }
+          }
+        }
+      }
+      pNew->nLTerm = 1;
+      pNew->aLTerm[0] = pTerm;
+      pNew->wsFlags = WHERE_MULTI_OR;
+      pNew->rSetup = 0;
+      pNew->iSortIdx = 0;
+      memset(&pNew->u, 0, sizeof(pNew->u));
+      for(i=0; rc==SQLITE_OK && i<sSum.n; i++){
+        /* TUNING: Currently sSum.a[i].rRun is set to the sum of the costs
+        ** of all sub-scans required by the OR-scan. However, due to rounding
+        ** errors, it may be that the cost of the OR-scan is equal to its
+        ** most expensive sub-scan. Add the smallest possible penalty
+        ** (equivalent to multiplying the cost by 1.07) to ensure that
+        ** this does not happen. Otherwise, for WHERE clauses such as the
+        ** following where there is an index on "y":
+        **
+        **     WHERE likelihood(x=?, 0.99) OR y=?
+        **
+        ** the planner may elect to "OR" together a full-table scan and an
+        ** index lookup. And other similarly odd results.  */
+        pNew->rRun = sSum.a[i].rRun + 1;
+        pNew->nOut = sSum.a[i].nOut;
+        pNew->prereq = sSum.a[i].prereq;
+        rc = whereLoopInsert(pBuilder, pNew);
+      }
+      WHERETRACE(0x400, ("End processing OR-clause %p\n", pTerm));
+    }
+  }
+  return rc;
+}
+
+/*
+** Add all WhereLoop objects for all tables
+*/
+static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
+  WhereInfo *pWInfo = pBuilder->pWInfo;
+  Bitmask mPrereq = 0;
+  Bitmask mPrior = 0;
+  int iTab;
+  SrcList *pTabList = pWInfo->pTabList;
+  SrcItem *pItem;
+  SrcItem *pEnd = &pTabList->a[pWInfo->nLevel];
+  sqlite3 *db = pWInfo->pParse->db;
+  int rc = SQLITE_OK;
+  int bFirstPastRJ = 0;
+  int hasRightJoin = 0;
+  WhereLoop *pNew;
+
+
+  /* Loop over the tables in the join, from left to right */
+  pNew = pBuilder->pNew;
+
+  /* Verify that pNew has already been initialized */
+  assert( pNew->nLTerm==0 );
+  assert( pNew->wsFlags==0 );
+  assert( pNew->nLSlot>=ArraySize(pNew->aLTermSpace) );
+  assert( pNew->aLTerm!=0 );
+
+  pBuilder->iPlanLimit = SQLITE_QUERY_PLANNER_LIMIT;
+  for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
+    Bitmask mUnusable = 0;
+    pNew->iTab = iTab;
+    pBuilder->iPlanLimit += SQLITE_QUERY_PLANNER_LIMIT_INCR;
+    pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
+    if( bFirstPastRJ
+     || (pItem->fg.jointype & (JT_OUTER|JT_CROSS|JT_LTORJ))!=0
+    ){
+      /* Add prerequisites to prevent reordering of FROM clause terms
+      ** across CROSS joins and outer joins.  The bFirstPastRJ boolean
+      ** prevents the right operand of a RIGHT JOIN from being swapped with
+      ** other elements even further to the right.
+      **
+      ** The JT_LTORJ case and the hasRightJoin flag work together to
+      ** prevent FROM-clause terms from moving from the right side of
+      ** a LEFT JOIN over to the left side of that join if the LEFT JOIN
+      ** is itself on the left side of a RIGHT JOIN.
+      */
+      if( pItem->fg.jointype & JT_LTORJ ) hasRightJoin = 1;
+      mPrereq |= mPrior;
+      bFirstPastRJ = (pItem->fg.jointype & JT_RIGHT)!=0;
+    }else if( !hasRightJoin ){
+      mPrereq = 0;
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( IsVirtual(pItem->pTab) ){
+      SrcItem *p;
+      for(p=&pItem[1]; p<pEnd; p++){
+        if( mUnusable || (p->fg.jointype & (JT_OUTER|JT_CROSS)) ){
+          mUnusable |= sqlite3WhereGetMask(&pWInfo->sMaskSet, p->iCursor);
+        }
+      }
+      rc = whereLoopAddVirtual(pBuilder, mPrereq, mUnusable);
+    }else
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+    {
+      rc = whereLoopAddBtree(pBuilder, mPrereq);
+    }
+    if( rc==SQLITE_OK && pBuilder->pWC->hasOr ){
+      rc = whereLoopAddOr(pBuilder, mPrereq, mUnusable);
+    }
+    mPrior |= pNew->maskSelf;
+    if( rc || db->mallocFailed ){
+      if( rc==SQLITE_DONE ){
+        /* We hit the query planner search limit set by iPlanLimit */
+        sqlite3_log(SQLITE_WARNING, "abbreviated query algorithm search");
+        rc = SQLITE_OK;
+      }else{
+        break;
+      }
+    }
+  }
+
+  whereLoopClear(db, pNew);
+  return rc;
+}
+
+/*
+** Examine a WherePath (with the addition of the extra WhereLoop of the 6th
+** parameters) to see if it outputs rows in the requested ORDER BY
+** (or GROUP BY) without requiring a separate sort operation.  Return N:
+**
+**   N>0:   N terms of the ORDER BY clause are satisfied
+**   N==0:  No terms of the ORDER BY clause are satisfied
+**   N<0:   Unknown yet how many terms of ORDER BY might be satisfied.  
+**
+** Note that processing for WHERE_GROUPBY and WHERE_DISTINCTBY is not as
+** strict.  With GROUP BY and DISTINCT the only requirement is that
+** equivalent rows appear immediately adjacent to one another.  GROUP BY
+** and DISTINCT do not require rows to appear in any particular order as long
+** as equivalent rows are grouped together.  Thus for GROUP BY and DISTINCT
+** the pOrderBy terms can be matched in any order.  With ORDER BY, the
+** pOrderBy terms must be matched in strict left-to-right order.
+*/
+static i8 wherePathSatisfiesOrderBy(
+  WhereInfo *pWInfo,    /* The WHERE clause */
+  ExprList *pOrderBy,   /* ORDER BY or GROUP BY or DISTINCT clause to check */
+  WherePath *pPath,     /* The WherePath to check */
+  u16 wctrlFlags,       /* WHERE_GROUPBY or _DISTINCTBY or _ORDERBY_LIMIT */
+  u16 nLoop,            /* Number of entries in pPath->aLoop[] */
+  WhereLoop *pLast,     /* Add this WhereLoop to the end of pPath->aLoop[] */
+  Bitmask *pRevMask     /* OUT: Mask of WhereLoops to run in reverse order */
+){
+  u8 revSet;            /* True if rev is known */
+  u8 rev;               /* Composite sort order */
+  u8 revIdx;            /* Index sort order */
+  u8 isOrderDistinct;   /* All prior WhereLoops are order-distinct */
+  u8 distinctColumns;   /* True if the loop has UNIQUE NOT NULL columns */
+  u8 isMatch;           /* iColumn matches a term of the ORDER BY clause */
+  u16 eqOpMask;         /* Allowed equality operators */
+  u16 nKeyCol;          /* Number of key columns in pIndex */
+  u16 nColumn;          /* Total number of ordered columns in the index */
+  u16 nOrderBy;         /* Number terms in the ORDER BY clause */
+  int iLoop;            /* Index of WhereLoop in pPath being processed */
+  int i, j;             /* Loop counters */
+  int iCur;             /* Cursor number for current WhereLoop */
+  int iColumn;          /* A column number within table iCur */
+  WhereLoop *pLoop = 0; /* Current WhereLoop being processed. */
+  WhereTerm *pTerm;     /* A single term of the WHERE clause */
+  Expr *pOBExpr;        /* An expression from the ORDER BY clause */
+  CollSeq *pColl;       /* COLLATE function from an ORDER BY clause term */
+  Index *pIndex;        /* The index associated with pLoop */
+  sqlite3 *db = pWInfo->pParse->db;  /* Database connection */
+  Bitmask obSat = 0;    /* Mask of ORDER BY terms satisfied so far */
+  Bitmask obDone;       /* Mask of all ORDER BY terms */
+  Bitmask orderDistinctMask;  /* Mask of all well-ordered loops */
+  Bitmask ready;              /* Mask of inner loops */
+
+  /*
+  ** We say the WhereLoop is "one-row" if it generates no more than one
+  ** row of output.  A WhereLoop is one-row if all of the following are true:
+  **  (a) All index columns match with WHERE_COLUMN_EQ.
+  **  (b) The index is unique
+  ** Any WhereLoop with an WHERE_COLUMN_EQ constraint on the rowid is one-row.
+  ** Every one-row WhereLoop will have the WHERE_ONEROW bit set in wsFlags.
+  **
+  ** We say the WhereLoop is "order-distinct" if the set of columns from
+  ** that WhereLoop that are in the ORDER BY clause are different for every
+  ** row of the WhereLoop.  Every one-row WhereLoop is automatically
+  ** order-distinct.   A WhereLoop that has no columns in the ORDER BY clause
+  ** is not order-distinct. To be order-distinct is not quite the same as being
+  ** UNIQUE since a UNIQUE column or index can have multiple rows that
+  ** are NULL and NULL values are equivalent for the purpose of order-distinct.
+  ** To be order-distinct, the columns must be UNIQUE and NOT NULL.
+  **
+  ** The rowid for a table is always UNIQUE and NOT NULL so whenever the
+  ** rowid appears in the ORDER BY clause, the corresponding WhereLoop is
+  ** automatically order-distinct.
+  */
+
+  assert( pOrderBy!=0 );
+  if( nLoop && OptimizationDisabled(db, SQLITE_OrderByIdxJoin) ) return 0;
+
+  nOrderBy = pOrderBy->nExpr;
+  testcase( nOrderBy==BMS-1 );
+  if( nOrderBy>BMS-1 ) return 0;  /* Cannot optimize overly large ORDER BYs */
+  isOrderDistinct = 1;
+  obDone = MASKBIT(nOrderBy)-1;
+  orderDistinctMask = 0;
+  ready = 0;
+  eqOpMask = WO_EQ | WO_IS | WO_ISNULL;
+  if( wctrlFlags & (WHERE_ORDERBY_LIMIT|WHERE_ORDERBY_MAX|WHERE_ORDERBY_MIN) ){
+    eqOpMask |= WO_IN;
+  }
+  for(iLoop=0; isOrderDistinct && obSat<obDone && iLoop<=nLoop; iLoop++){
+    if( iLoop>0 ) ready |= pLoop->maskSelf;
+    if( iLoop<nLoop ){
+      pLoop = pPath->aLoop[iLoop];
+      if( wctrlFlags & WHERE_ORDERBY_LIMIT ) continue;
+    }else{
+      pLoop = pLast;
+    }
+    if( pLoop->wsFlags & WHERE_VIRTUALTABLE ){
+      if( pLoop->u.vtab.isOrdered
+       && ((wctrlFlags&(WHERE_DISTINCTBY|WHERE_SORTBYGROUP))!=WHERE_DISTINCTBY)
+      ){
+        obSat = obDone;
+      }
+      break;
+    }else if( wctrlFlags & WHERE_DISTINCTBY ){
+      pLoop->u.btree.nDistinctCol = 0;
+    }
+    iCur = pWInfo->pTabList->a[pLoop->iTab].iCursor;
+
+    /* Mark off any ORDER BY term X that is a column in the table of
+    ** the current loop for which there is term in the WHERE
+    ** clause of the form X IS NULL or X=? that reference only outer
+    ** loops.
+    */
+    for(i=0; i<nOrderBy; i++){
+      if( MASKBIT(i) & obSat ) continue;
+      pOBExpr = sqlite3ExprSkipCollateAndLikely(pOrderBy->a[i].pExpr);
+      if( NEVER(pOBExpr==0) ) continue;
+      if( pOBExpr->op!=TK_COLUMN && pOBExpr->op!=TK_AGG_COLUMN ) continue;
+      if( pOBExpr->iTable!=iCur ) continue;
+      pTerm = sqlite3WhereFindTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
+                       ~ready, eqOpMask, 0);
+      if( pTerm==0 ) continue;
+      if( pTerm->eOperator==WO_IN ){
+        /* IN terms are only valid for sorting in the ORDER BY LIMIT
+        ** optimization, and then only if they are actually used
+        ** by the query plan */
+        assert( wctrlFlags &
+               (WHERE_ORDERBY_LIMIT|WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX) );
+        for(j=0; j<pLoop->nLTerm && pTerm!=pLoop->aLTerm[j]; j++){}
+        if( j>=pLoop->nLTerm ) continue;
+      }
+      if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0 && pOBExpr->iColumn>=0 ){
+        Parse *pParse = pWInfo->pParse;
+        CollSeq *pColl1 = sqlite3ExprNNCollSeq(pParse, pOrderBy->a[i].pExpr);
+        CollSeq *pColl2 = sqlite3ExprCompareCollSeq(pParse, pTerm->pExpr);
+        assert( pColl1 );
+        if( pColl2==0 || sqlite3StrICmp(pColl1->zName, pColl2->zName) ){
+          continue;
+        }
+        testcase( pTerm->pExpr->op==TK_IS );
+      }
+      obSat |= MASKBIT(i);
+    }
+
+    if( (pLoop->wsFlags & WHERE_ONEROW)==0 ){
+      if( pLoop->wsFlags & WHERE_IPK ){
+        pIndex = 0;
+        nKeyCol = 0;
+        nColumn = 1;
+      }else if( (pIndex = pLoop->u.btree.pIndex)==0 || pIndex->bUnordered ){
+        return 0;
+      }else{
+        nKeyCol = pIndex->nKeyCol;
+        nColumn = pIndex->nColumn;
+        assert( nColumn==nKeyCol+1 || !HasRowid(pIndex->pTable) );
+        assert( pIndex->aiColumn[nColumn-1]==XN_ROWID
+                          || !HasRowid(pIndex->pTable));
+        /* All relevant terms of the index must also be non-NULL in order
+        ** for isOrderDistinct to be true.  So the isOrderDistint value
+        ** computed here might be a false positive.  Corrections will be
+        ** made at tag-20210426-1 below */
+        isOrderDistinct = IsUniqueIndex(pIndex)
+                          && (pLoop->wsFlags & WHERE_SKIPSCAN)==0;
+      }
+
+      /* Loop through all columns of the index and deal with the ones
+      ** that are not constrained by == or IN.
+      */
+      rev = revSet = 0;
+      distinctColumns = 0;
+      for(j=0; j<nColumn; j++){
+        u8 bOnce = 1; /* True to run the ORDER BY search loop */
+
+        assert( j>=pLoop->u.btree.nEq
+            || (pLoop->aLTerm[j]==0)==(j<pLoop->nSkip)
+        );
+        if( j<pLoop->u.btree.nEq && j>=pLoop->nSkip ){
+          u16 eOp = pLoop->aLTerm[j]->eOperator;
+
+          /* Skip over == and IS and ISNULL terms.  (Also skip IN terms when
+          ** doing WHERE_ORDERBY_LIMIT processing).  Except, IS and ISNULL
+          ** terms imply that the index is not UNIQUE NOT NULL in which case
+          ** the loop need to be marked as not order-distinct because it can
+          ** have repeated NULL rows.
+          **
+          ** If the current term is a column of an ((?,?) IN (SELECT...))
+          ** expression for which the SELECT returns more than one column,
+          ** check that it is the only column used by this loop. Otherwise,
+          ** if it is one of two or more, none of the columns can be
+          ** considered to match an ORDER BY term.
+          */
+          if( (eOp & eqOpMask)!=0 ){
+            if( eOp & (WO_ISNULL|WO_IS) ){
+              testcase( eOp & WO_ISNULL );
+              testcase( eOp & WO_IS );
+              testcase( isOrderDistinct );
+              isOrderDistinct = 0;
+            }
+            continue; 
+          }else if( ALWAYS(eOp & WO_IN) ){
+            /* ALWAYS() justification: eOp is an equality operator due to the
+            ** j<pLoop->u.btree.nEq constraint above.  Any equality other
+            ** than WO_IN is captured by the previous "if".  So this one
+            ** always has to be WO_IN. */
+            Expr *pX = pLoop->aLTerm[j]->pExpr;
+            for(i=j+1; i<pLoop->u.btree.nEq; i++){
+              if( pLoop->aLTerm[i]->pExpr==pX ){
+                assert( (pLoop->aLTerm[i]->eOperator & WO_IN) );
+                bOnce = 0;
+                break;
+              }
+            }
+          }
+        }
+
+        /* Get the column number in the table (iColumn) and sort order
+        ** (revIdx) for the j-th column of the index.
+        */
+        if( pIndex ){
+          iColumn = pIndex->aiColumn[j];
+          revIdx = pIndex->aSortOrder[j] & KEYINFO_ORDER_DESC;
+          if( iColumn==pIndex->pTable->iPKey ) iColumn = XN_ROWID;
+        }else{
+          iColumn = XN_ROWID;
+          revIdx = 0;
+        }
+
+        /* An unconstrained column that might be NULL means that this
+        ** WhereLoop is not well-ordered.  tag-20210426-1
+        */
+        if( isOrderDistinct ){
+          if( iColumn>=0
+           && j>=pLoop->u.btree.nEq
+           && pIndex->pTable->aCol[iColumn].notNull==0
+          ){
+            isOrderDistinct = 0;
+          }
+          if( iColumn==XN_EXPR ){
+            isOrderDistinct = 0;
+          }
+        }
+
+        /* Find the ORDER BY term that corresponds to the j-th column
+        ** of the index and mark that ORDER BY term off
+        */
+        isMatch = 0;
+        for(i=0; bOnce && i<nOrderBy; i++){
+          if( MASKBIT(i) & obSat ) continue;
+          pOBExpr = sqlite3ExprSkipCollateAndLikely(pOrderBy->a[i].pExpr);
+          testcase( wctrlFlags & WHERE_GROUPBY );
+          testcase( wctrlFlags & WHERE_DISTINCTBY );
+          if( NEVER(pOBExpr==0) ) continue;
+          if( (wctrlFlags & (WHERE_GROUPBY|WHERE_DISTINCTBY))==0 ) bOnce = 0;
+          if( iColumn>=XN_ROWID ){
+            if( pOBExpr->op!=TK_COLUMN && pOBExpr->op!=TK_AGG_COLUMN ) continue;
+            if( pOBExpr->iTable!=iCur ) continue;
+            if( pOBExpr->iColumn!=iColumn ) continue;
+          }else{
+            Expr *pIxExpr = pIndex->aColExpr->a[j].pExpr;
+            if( sqlite3ExprCompareSkip(pOBExpr, pIxExpr, iCur) ){
+              continue;
+            }
+          }
+          if( iColumn!=XN_ROWID ){
+            pColl = sqlite3ExprNNCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
+            if( sqlite3StrICmp(pColl->zName, pIndex->azColl[j])!=0 ) continue;
+          }
+          if( wctrlFlags & WHERE_DISTINCTBY ){
+            pLoop->u.btree.nDistinctCol = j+1;
+          }
+          isMatch = 1;
+          break;
+        }
+        if( isMatch && (wctrlFlags & WHERE_GROUPBY)==0 ){
+          /* Make sure the sort order is compatible in an ORDER BY clause.
+          ** Sort order is irrelevant for a GROUP BY clause. */
+          if( revSet ){
+            if( (rev ^ revIdx)
+                           != (pOrderBy->a[i].fg.sortFlags&KEYINFO_ORDER_DESC)
+            ){
+              isMatch = 0;
+            }
+          }else{
+            rev = revIdx ^ (pOrderBy->a[i].fg.sortFlags & KEYINFO_ORDER_DESC);
+            if( rev ) *pRevMask |= MASKBIT(iLoop);
+            revSet = 1;
+          }
+        }
+        if( isMatch && (pOrderBy->a[i].fg.sortFlags & KEYINFO_ORDER_BIGNULL) ){
+          if( j==pLoop->u.btree.nEq ){
+            pLoop->wsFlags |= WHERE_BIGNULL_SORT;
+          }else{
+            isMatch = 0;
+          }
+        }
+        if( isMatch ){
+          if( iColumn==XN_ROWID ){
+            testcase( distinctColumns==0 );
+            distinctColumns = 1;
+          }
+          obSat |= MASKBIT(i);
+        }else{
+          /* No match found */
+          if( j==0 || j<nKeyCol ){
+            testcase( isOrderDistinct!=0 );
+            isOrderDistinct = 0;
+          }
+          break;
+        }
+      } /* end Loop over all index columns */
+      if( distinctColumns ){
+        testcase( isOrderDistinct==0 );
+        isOrderDistinct = 1;
+      }
+    } /* end-if not one-row */
+
+    /* Mark off any other ORDER BY terms that reference pLoop */
+    if( isOrderDistinct ){
+      orderDistinctMask |= pLoop->maskSelf;
+      for(i=0; i<nOrderBy; i++){
+        Expr *p;
+        Bitmask mTerm;
+        if( MASKBIT(i) & obSat ) continue;
+        p = pOrderBy->a[i].pExpr;
+        mTerm = sqlite3WhereExprUsage(&pWInfo->sMaskSet,p);
+        if( mTerm==0 && !sqlite3ExprIsConstant(p) ) continue;
+        if( (mTerm&~orderDistinctMask)==0 ){
+          obSat |= MASKBIT(i);
+        }
+      }
+    }
+  } /* End the loop over all WhereLoops from outer-most down to inner-most */
+  if( obSat==obDone ) return (i8)nOrderBy;
+  if( !isOrderDistinct ){
+    for(i=nOrderBy-1; i>0; i--){
+      Bitmask m = ALWAYS(i<BMS) ? MASKBIT(i) - 1 : 0;
+      if( (obSat&m)==m ) return i;
+    }
+    return 0;
+  }
+  return -1;
+}
+
+
+/*
+** If the WHERE_GROUPBY flag is set in the mask passed to sqlite3WhereBegin(),
+** the planner assumes that the specified pOrderBy list is actually a GROUP
+** BY clause - and so any order that groups rows as required satisfies the
+** request.
+**
+** Normally, in this case it is not possible for the caller to determine
+** whether or not the rows are really being delivered in sorted order, or
+** just in some other order that provides the required grouping. However,
+** if the WHERE_SORTBYGROUP flag is also passed to sqlite3WhereBegin(), then
+** this function may be called on the returned WhereInfo object. It returns
+** true if the rows really will be sorted in the specified order, or false
+** otherwise.
+**
+** For example, assuming:
+**
+**   CREATE INDEX i1 ON t1(x, Y);
+**
+** then
+**
+**   SELECT * FROM t1 GROUP BY x,y ORDER BY x,y;   -- IsSorted()==1
+**   SELECT * FROM t1 GROUP BY y,x ORDER BY y,x;   -- IsSorted()==0
+*/
+int sqlite3WhereIsSorted(WhereInfo *pWInfo){
+  assert( pWInfo->wctrlFlags & (WHERE_GROUPBY|WHERE_DISTINCTBY) );
+  assert( pWInfo->wctrlFlags & WHERE_SORTBYGROUP );
+  return pWInfo->sorted;
+}
+
+#ifdef WHERETRACE_ENABLED
+/* For debugging use only: */
+static const char *wherePathName(WherePath *pPath, int nLoop, WhereLoop *pLast){
+  static char zName[65];
+  int i;
+  for(i=0; i<nLoop; i++){ zName[i] = pPath->aLoop[i]->cId; }
+  if( pLast ) zName[i++] = pLast->cId;
+  zName[i] = 0;
+  return zName;
+}
+#endif
+
+/*
+** Return the cost of sorting nRow rows, assuming that the keys have
+** nOrderby columns and that the first nSorted columns are already in
+** order.
+*/
+static LogEst whereSortingCost(
+  WhereInfo *pWInfo, /* Query planning context */
+  LogEst nRow,       /* Estimated number of rows to sort */
+  int nOrderBy,      /* Number of ORDER BY clause terms */
+  int nSorted        /* Number of initial ORDER BY terms naturally in order */
+){
+  /* Estimated cost of a full external sort, where N is
+  ** the number of rows to sort is:
+  **
+  **   cost = (K * N * log(N)).
+  **
+  ** Or, if the order-by clause has X terms but only the last Y
+  ** terms are out of order, then block-sorting will reduce the
+  ** sorting cost to:
+  **
+  **   cost = (K * N * log(N)) * (Y/X)
+  **
+  ** The constant K is at least 2.0 but will be larger if there are a
+  ** large number of columns to be sorted, as the sorting time is
+  ** proportional to the amount of content to be sorted.  The algorithm
+  ** does not currently distinguish between fat columns (BLOBs and TEXTs)
+  ** and skinny columns (INTs).  It just uses the number of columns as
+  ** an approximation for the row width.
+  **
+  ** And extra factor of 2.0 or 3.0 is added to the sorting cost if the sort
+  ** is built using OP_IdxInsert and OP_Sort rather than with OP_SorterInsert.
+  */
+  LogEst rSortCost, nCol;
+  assert( pWInfo->pSelect!=0 );
+  assert( pWInfo->pSelect->pEList!=0 );
+  /* TUNING: sorting cost proportional to the number of output columns: */
+  nCol = sqlite3LogEst((pWInfo->pSelect->pEList->nExpr+59)/30);
+  rSortCost = nRow + nCol;
+  if( nSorted>0 ){
+    /* Scale the result by (Y/X) */
+    rSortCost += sqlite3LogEst((nOrderBy-nSorted)*100/nOrderBy) - 66;
+  }
+
+  /* Multiple by log(M) where M is the number of output rows.
+  ** Use the LIMIT for M if it is smaller.  Or if this sort is for
+  ** a DISTINCT operator, M will be the number of distinct output
+  ** rows, so fudge it downwards a bit.
+  */
+  if( (pWInfo->wctrlFlags & WHERE_USE_LIMIT)!=0 ){
+    rSortCost += 10;       /* TUNING: Extra 2.0x if using LIMIT */
+    if( nSorted!=0 ){
+      rSortCost += 6;      /* TUNING: Extra 1.5x if also using partial sort */
+    }
+    if( pWInfo->iLimit<nRow ){
+      nRow = pWInfo->iLimit;
+    }
+  }else if( (pWInfo->wctrlFlags & WHERE_WANT_DISTINCT) ){
+    /* TUNING: In the sort for a DISTINCT operator, assume that the DISTINCT
+    ** reduces the number of output rows by a factor of 2 */
+    if( nRow>10 ){ nRow -= 10;  assert( 10==sqlite3LogEst(2) ); }
+  }
+  rSortCost += estLog(nRow);
+  return rSortCost;
+}
+
+/*
+** Given the list of WhereLoop objects at pWInfo->pLoops, this routine
+** attempts to find the lowest cost path that visits each WhereLoop
+** once.  This path is then loaded into the pWInfo->a[].pWLoop fields.
+**
+** Assume that the total number of output rows that will need to be sorted
+** will be nRowEst (in the 10*log2 representation).  Or, ignore sorting
+** costs if nRowEst==0.
+**
+** Return SQLITE_OK on success or SQLITE_NOMEM of a memory allocation
+** error occurs.
+*/
+static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
+  int mxChoice;             /* Maximum number of simultaneous paths tracked */
+  int nLoop;                /* Number of terms in the join */
+  Parse *pParse;            /* Parsing context */
+  int iLoop;                /* Loop counter over the terms of the join */
+  int ii, jj;               /* Loop counters */
+  int mxI = 0;              /* Index of next entry to replace */
+  int nOrderBy;             /* Number of ORDER BY clause terms */
+  LogEst mxCost = 0;        /* Maximum cost of a set of paths */
+  LogEst mxUnsorted = 0;    /* Maximum unsorted cost of a set of path */
+  int nTo, nFrom;           /* Number of valid entries in aTo[] and aFrom[] */
+  WherePath *aFrom;         /* All nFrom paths at the previous level */
+  WherePath *aTo;           /* The nTo best paths at the current level */
+  WherePath *pFrom;         /* An element of aFrom[] that we are working on */
+  WherePath *pTo;           /* An element of aTo[] that we are working on */
+  WhereLoop *pWLoop;        /* One of the WhereLoop objects */
+  WhereLoop **pX;           /* Used to divy up the pSpace memory */
+  LogEst *aSortCost = 0;    /* Sorting and partial sorting costs */
+  char *pSpace;             /* Temporary memory used by this routine */
+  int nSpace;               /* Bytes of space allocated at pSpace */
+
+  pParse = pWInfo->pParse;
+  nLoop = pWInfo->nLevel;
+  /* TUNING: For simple queries, only the best path is tracked.
+  ** For 2-way joins, the 5 best paths are followed.
+  ** For joins of 3 or more tables, track the 10 best paths */
+  mxChoice = (nLoop<=1) ? 1 : (nLoop==2 ? 5 : 10);
+  assert( nLoop<=pWInfo->pTabList->nSrc );
+  WHERETRACE(0x002, ("---- begin solver.  (nRowEst=%d, nQueryLoop=%d)\n",
+                     nRowEst, pParse->nQueryLoop));
+
+  /* If nRowEst is zero and there is an ORDER BY clause, ignore it. In this
+  ** case the purpose of this call is to estimate the number of rows returned
+  ** by the overall query. Once this estimate has been obtained, the caller
+  ** will invoke this function a second time, passing the estimate as the
+  ** nRowEst parameter.  */
+  if( pWInfo->pOrderBy==0 || nRowEst==0 ){
+    nOrderBy = 0;
+  }else{
+    nOrderBy = pWInfo->pOrderBy->nExpr;
+  }
+
+  /* Allocate and initialize space for aTo, aFrom and aSortCost[] */
+  nSpace = (sizeof(WherePath)+sizeof(WhereLoop*)*nLoop)*mxChoice*2;
+  nSpace += sizeof(LogEst) * nOrderBy;
+  pSpace = sqlite3StackAllocRawNN(pParse->db, nSpace);
+  if( pSpace==0 ) return SQLITE_NOMEM_BKPT;
+  aTo = (WherePath*)pSpace;
+  aFrom = aTo+mxChoice;
+  memset(aFrom, 0, sizeof(aFrom[0]));
+  pX = (WhereLoop**)(aFrom+mxChoice);
+  for(ii=mxChoice*2, pFrom=aTo; ii>0; ii--, pFrom++, pX += nLoop){
+    pFrom->aLoop = pX;
+  }
+  if( nOrderBy ){
+    /* If there is an ORDER BY clause and it is not being ignored, set up
+    ** space for the aSortCost[] array. Each element of the aSortCost array
+    ** is either zero - meaning it has not yet been initialized - or the
+    ** cost of sorting nRowEst rows of data where the first X terms of
+    ** the ORDER BY clause are already in order, where X is the array
+    ** index.  */
+    aSortCost = (LogEst*)pX;
+    memset(aSortCost, 0, sizeof(LogEst) * nOrderBy);
+  }
+  assert( aSortCost==0 || &pSpace[nSpace]==(char*)&aSortCost[nOrderBy] );
+  assert( aSortCost!=0 || &pSpace[nSpace]==(char*)pX );
+
+  /* Seed the search with a single WherePath containing zero WhereLoops.
+  **
+  ** TUNING: Do not let the number of iterations go above 28.  If the cost
+  ** of computing an automatic index is not paid back within the first 28
+  ** rows, then do not use the automatic index. */
+  aFrom[0].nRow = MIN(pParse->nQueryLoop, 48);  assert( 48==sqlite3LogEst(28) );
+  nFrom = 1;
+  assert( aFrom[0].isOrdered==0 );
+  if( nOrderBy ){
+    /* If nLoop is zero, then there are no FROM terms in the query. Since
+    ** in this case the query may return a maximum of one row, the results
+    ** are already in the requested order. Set isOrdered to nOrderBy to
+    ** indicate this. Or, if nLoop is greater than zero, set isOrdered to
+    ** -1, indicating that the result set may or may not be ordered,
+    ** depending on the loops added to the current plan.  */
+    aFrom[0].isOrdered = nLoop>0 ? -1 : nOrderBy;
+  }
+
+  /* Compute successively longer WherePaths using the previous generation
+  ** of WherePaths as the basis for the next.  Keep track of the mxChoice
+  ** best paths at each generation */
+  for(iLoop=0; iLoop<nLoop; iLoop++){
+    nTo = 0;
+    for(ii=0, pFrom=aFrom; ii<nFrom; ii++, pFrom++){
+      for(pWLoop=pWInfo->pLoops; pWLoop; pWLoop=pWLoop->pNextLoop){
+        LogEst nOut;                      /* Rows visited by (pFrom+pWLoop) */
+        LogEst rCost;                     /* Cost of path (pFrom+pWLoop) */
+        LogEst rUnsorted;                 /* Unsorted cost of (pFrom+pWLoop) */
+        i8 isOrdered;                     /* isOrdered for (pFrom+pWLoop) */
+        Bitmask maskNew;                  /* Mask of src visited by (..) */
+        Bitmask revMask;                  /* Mask of rev-order loops for (..) */
+
+        if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
+        if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
+        if( (pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 && pFrom->nRow<3 ){
+          /* Do not use an automatic index if the this loop is expected
+          ** to run less than 1.25 times.  It is tempting to also exclude
+          ** automatic index usage on an outer loop, but sometimes an automatic
+          ** index is useful in the outer loop of a correlated subquery. */
+          assert( 10==sqlite3LogEst(2) );
+          continue;
+        }
+
+        /* At this point, pWLoop is a candidate to be the next loop.
+        ** Compute its cost */
+        rUnsorted = sqlite3LogEstAdd(pWLoop->rSetup,pWLoop->rRun + pFrom->nRow);
+        rUnsorted = sqlite3LogEstAdd(rUnsorted, pFrom->rUnsorted);
+        nOut = pFrom->nRow + pWLoop->nOut;
+        maskNew = pFrom->maskLoop | pWLoop->maskSelf;
+        isOrdered = pFrom->isOrdered;
+        if( isOrdered<0 ){
+          revMask = 0;
+          isOrdered = wherePathSatisfiesOrderBy(pWInfo,
+                       pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
+                       iLoop, pWLoop, &revMask);
+        }else{
+          revMask = pFrom->revLoop;
+        }
+        if( isOrdered>=0 && isOrdered<nOrderBy ){
+          if( aSortCost[isOrdered]==0 ){
+            aSortCost[isOrdered] = whereSortingCost(
+                pWInfo, nRowEst, nOrderBy, isOrdered
+            );
+          }
+          /* TUNING:  Add a small extra penalty (3) to sorting as an
+          ** extra encouragement to the query planner to select a plan
+          ** where the rows emerge in the correct order without any sorting
+          ** required. */
+          rCost = sqlite3LogEstAdd(rUnsorted, aSortCost[isOrdered]) + 3;
+
+          WHERETRACE(0x002,
+              ("---- sort cost=%-3d (%d/%d) increases cost %3d to %-3d\n",
+               aSortCost[isOrdered], (nOrderBy-isOrdered), nOrderBy,
+               rUnsorted, rCost));
+        }else{
+          rCost = rUnsorted;
+          rUnsorted -= 2;  /* TUNING:  Slight bias in favor of no-sort plans */
+        }
+
+        /* Check to see if pWLoop should be added to the set of
+        ** mxChoice best-so-far paths.
+        **
+        ** First look for an existing path among best-so-far paths
+        ** that covers the same set of loops and has the same isOrdered
+        ** setting as the current path candidate.
+        **
+        ** The term "((pTo->isOrdered^isOrdered)&0x80)==0" is equivalent
+        ** to (pTo->isOrdered==(-1))==(isOrdered==(-1))" for the range
+        ** of legal values for isOrdered, -1..64.
+        */
+        for(jj=0, pTo=aTo; jj<nTo; jj++, pTo++){
+          if( pTo->maskLoop==maskNew
+           && ((pTo->isOrdered^isOrdered)&0x80)==0
+          ){
+            testcase( jj==nTo-1 );
+            break;
+          }
+        }
+        if( jj>=nTo ){
+          /* None of the existing best-so-far paths match the candidate. */
+          if( nTo>=mxChoice
+           && (rCost>mxCost || (rCost==mxCost && rUnsorted>=mxUnsorted))
+          ){
+            /* The current candidate is no better than any of the mxChoice
+            ** paths currently in the best-so-far buffer.  So discard
+            ** this candidate as not viable. */
+#ifdef WHERETRACE_ENABLED /* 0x4 */
+            if( sqlite3WhereTrace&0x4 ){
+              sqlite3DebugPrintf("Skip   %s cost=%-3d,%3d,%3d order=%c\n",
+                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
+                  isOrdered>=0 ? isOrdered+'0' : '?');
+            }
+#endif
+            continue;
+          }
+          /* If we reach this points it means that the new candidate path
+          ** needs to be added to the set of best-so-far paths. */
+          if( nTo<mxChoice ){
+            /* Increase the size of the aTo set by one */
+            jj = nTo++;
+          }else{
+            /* New path replaces the prior worst to keep count below mxChoice */
+            jj = mxI;
+          }
+          pTo = &aTo[jj];
+#ifdef WHERETRACE_ENABLED /* 0x4 */
+          if( sqlite3WhereTrace&0x4 ){
+            sqlite3DebugPrintf("New    %s cost=%-3d,%3d,%3d order=%c\n",
+                wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
+                isOrdered>=0 ? isOrdered+'0' : '?');
+          }
+#endif
+        }else{
+          /* Control reaches here if best-so-far path pTo=aTo[jj] covers the
+          ** same set of loops and has the same isOrdered setting as the
+          ** candidate path.  Check to see if the candidate should replace
+          ** pTo or if the candidate should be skipped.
+          **
+          ** The conditional is an expanded vector comparison equivalent to:
+          **   (pTo->rCost,pTo->nRow,pTo->rUnsorted) <= (rCost,nOut,rUnsorted)
+          */
+          if( pTo->rCost<rCost
+           || (pTo->rCost==rCost
+               && (pTo->nRow<nOut
+                   || (pTo->nRow==nOut && pTo->rUnsorted<=rUnsorted)
+                  )
+              )
+          ){
+#ifdef WHERETRACE_ENABLED /* 0x4 */
+            if( sqlite3WhereTrace&0x4 ){
+              sqlite3DebugPrintf(
+                  "Skip   %s cost=%-3d,%3d,%3d order=%c",
+                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
+                  isOrdered>=0 ? isOrdered+'0' : '?');
+              sqlite3DebugPrintf("   vs %s cost=%-3d,%3d,%3d order=%c\n",
+                  wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
+                  pTo->rUnsorted, pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
+            }
+#endif
+            /* Discard the candidate path from further consideration */
+            testcase( pTo->rCost==rCost );
+            continue;
+          }
+          testcase( pTo->rCost==rCost+1 );
+          /* Control reaches here if the candidate path is better than the
+          ** pTo path.  Replace pTo with the candidate. */
+#ifdef WHERETRACE_ENABLED /* 0x4 */
+          if( sqlite3WhereTrace&0x4 ){
+            sqlite3DebugPrintf(
+                "Update %s cost=%-3d,%3d,%3d order=%c",
+                wherePathName(pFrom, iLoop, pWLoop), rCost, nOut, rUnsorted,
+                isOrdered>=0 ? isOrdered+'0' : '?');
+            sqlite3DebugPrintf("  was %s cost=%-3d,%3d,%3d order=%c\n",
+                wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
+                pTo->rUnsorted, pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
+          }
+#endif
+        }
+        /* pWLoop is a winner.  Add it to the set of best so far */
+        pTo->maskLoop = pFrom->maskLoop | pWLoop->maskSelf;
+        pTo->revLoop = revMask;
+        pTo->nRow = nOut;
+        pTo->rCost = rCost;
+        pTo->rUnsorted = rUnsorted;
+        pTo->isOrdered = isOrdered;
+        memcpy(pTo->aLoop, pFrom->aLoop, sizeof(WhereLoop*)*iLoop);
+        pTo->aLoop[iLoop] = pWLoop;
+        if( nTo>=mxChoice ){
+          mxI = 0;
+          mxCost = aTo[0].rCost;
+          mxUnsorted = aTo[0].nRow;
+          for(jj=1, pTo=&aTo[1]; jj<mxChoice; jj++, pTo++){
+            if( pTo->rCost>mxCost
+             || (pTo->rCost==mxCost && pTo->rUnsorted>mxUnsorted)
+            ){
+              mxCost = pTo->rCost;
+              mxUnsorted = pTo->rUnsorted;
+              mxI = jj;
+            }
+          }
+        }
+      }
+    }
+
+#ifdef WHERETRACE_ENABLED  /* >=2 */
+    if( sqlite3WhereTrace & 0x02 ){
+      sqlite3DebugPrintf("---- after round %d ----\n", iLoop);
+      for(ii=0, pTo=aTo; ii<nTo; ii++, pTo++){
+        sqlite3DebugPrintf(" %s cost=%-3d nrow=%-3d order=%c",
+           wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
+           pTo->isOrdered>=0 ? (pTo->isOrdered+'0') : '?');
+        if( pTo->isOrdered>0 ){
+          sqlite3DebugPrintf(" rev=0x%llx\n", pTo->revLoop);
+        }else{
+          sqlite3DebugPrintf("\n");
+        }
+      }
+    }
+#endif
+
+    /* Swap the roles of aFrom and aTo for the next generation */
+    pFrom = aTo;
+    aTo = aFrom;
+    aFrom = pFrom;
+    nFrom = nTo;
+  }
+
+  if( nFrom==0 ){
+    sqlite3ErrorMsg(pParse, "no query solution");
+    sqlite3StackFreeNN(pParse->db, pSpace);
+    return SQLITE_ERROR;
+  }
+ 
+  /* Find the lowest cost path.  pFrom will be left pointing to that path */
+  pFrom = aFrom;
+  for(ii=1; ii<nFrom; ii++){
+    if( pFrom->rCost>aFrom[ii].rCost ) pFrom = &aFrom[ii];
+  }
+  assert( pWInfo->nLevel==nLoop );
+  /* Load the lowest cost path into pWInfo */
+  for(iLoop=0; iLoop<nLoop; iLoop++){
+    WhereLevel *pLevel = pWInfo->a + iLoop;
+    pLevel->pWLoop = pWLoop = pFrom->aLoop[iLoop];
+    pLevel->iFrom = pWLoop->iTab;
+    pLevel->iTabCur = pWInfo->pTabList->a[pLevel->iFrom].iCursor;
+  }
+  if( (pWInfo->wctrlFlags & WHERE_WANT_DISTINCT)!=0
+   && (pWInfo->wctrlFlags & WHERE_DISTINCTBY)==0
+   && pWInfo->eDistinct==WHERE_DISTINCT_NOOP
+   && nRowEst
+  ){
+    Bitmask notUsed;
+    int rc = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pResultSet, pFrom,
+                 WHERE_DISTINCTBY, nLoop-1, pFrom->aLoop[nLoop-1], &notUsed);
+    if( rc==pWInfo->pResultSet->nExpr ){
+      pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
+    }
+  }
+  pWInfo->bOrderedInnerLoop = 0;
+  if( pWInfo->pOrderBy ){
+    pWInfo->nOBSat = pFrom->isOrdered;
+    if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
+      if( pFrom->isOrdered==pWInfo->pOrderBy->nExpr ){
+        pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
+      }
+      if( pWInfo->pSelect->pOrderBy
+       && pWInfo->nOBSat > pWInfo->pSelect->pOrderBy->nExpr ){
+        pWInfo->nOBSat = pWInfo->pSelect->pOrderBy->nExpr;
+      }
+    }else{
+      pWInfo->revMask = pFrom->revLoop;
+      if( pWInfo->nOBSat<=0 ){
+        pWInfo->nOBSat = 0;
+        if( nLoop>0 ){
+          u32 wsFlags = pFrom->aLoop[nLoop-1]->wsFlags;
+          if( (wsFlags & WHERE_ONEROW)==0
+           && (wsFlags&(WHERE_IPK|WHERE_COLUMN_IN))!=(WHERE_IPK|WHERE_COLUMN_IN)
+          ){
+            Bitmask m = 0;
+            int rc = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pOrderBy, pFrom,
+                      WHERE_ORDERBY_LIMIT, nLoop-1, pFrom->aLoop[nLoop-1], &m);
+            testcase( wsFlags & WHERE_IPK );
+            testcase( wsFlags & WHERE_COLUMN_IN );
+            if( rc==pWInfo->pOrderBy->nExpr ){
+              pWInfo->bOrderedInnerLoop = 1;
+              pWInfo->revMask = m;
+            }
+          }
+        }
+      }else if( nLoop
+            && pWInfo->nOBSat==1
+            && (pWInfo->wctrlFlags & (WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX))!=0
+            ){
+        pWInfo->bOrderedInnerLoop = 1;
+      }
+    }
+    if( (pWInfo->wctrlFlags & WHERE_SORTBYGROUP)
+        && pWInfo->nOBSat==pWInfo->pOrderBy->nExpr && nLoop>0
+    ){
+      Bitmask revMask = 0;
+      int nOrder = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pOrderBy,
+          pFrom, 0, nLoop-1, pFrom->aLoop[nLoop-1], &revMask
+      );
+      assert( pWInfo->sorted==0 );
+      if( nOrder==pWInfo->pOrderBy->nExpr ){
+        pWInfo->sorted = 1;
+        pWInfo->revMask = revMask;
+      }
+    }
+  }
+
+
+  pWInfo->nRowOut = pFrom->nRow;
+
+  /* Free temporary memory and return success */
+  sqlite3StackFreeNN(pParse->db, pSpace);
+  return SQLITE_OK;
+}
+
+/*
+** Most queries use only a single table (they are not joins) and have
+** simple == constraints against indexed fields.  This routine attempts
+** to plan those simple cases using much less ceremony than the
+** general-purpose query planner, and thereby yield faster sqlite3_prepare()
+** times for the common case.
+**
+** Return non-zero on success, if this query can be handled by this
+** no-frills query planner.  Return zero if this query needs the
+** general-purpose query planner.
+*/
+static int whereShortCut(WhereLoopBuilder *pBuilder){
+  WhereInfo *pWInfo;
+  SrcItem *pItem;
+  WhereClause *pWC;
+  WhereTerm *pTerm;
+  WhereLoop *pLoop;
+  int iCur;
+  int j;
+  Table *pTab;
+  Index *pIdx;
+  WhereScan scan;
+
+  pWInfo = pBuilder->pWInfo;
+  if( pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE ) return 0;
+  assert( pWInfo->pTabList->nSrc>=1 );
+  pItem = pWInfo->pTabList->a;
+  pTab = pItem->pTab;
+  if( IsVirtual(pTab) ) return 0;
+  if( pItem->fg.isIndexedBy || pItem->fg.notIndexed ){
+    testcase( pItem->fg.isIndexedBy );
+    testcase( pItem->fg.notIndexed );
+    return 0;
+  }
+  iCur = pItem->iCursor;
+  pWC = &pWInfo->sWC;
+  pLoop = pBuilder->pNew;
+  pLoop->wsFlags = 0;
+  pLoop->nSkip = 0;
+  pTerm = whereScanInit(&scan, pWC, iCur, -1, WO_EQ|WO_IS, 0);
+  while( pTerm && pTerm->prereqRight ) pTerm = whereScanNext(&scan);
+  if( pTerm ){
+    testcase( pTerm->eOperator & WO_IS );
+    pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_IPK|WHERE_ONEROW;
+    pLoop->aLTerm[0] = pTerm;
+    pLoop->nLTerm = 1;
+    pLoop->u.btree.nEq = 1;
+    /* TUNING: Cost of a rowid lookup is 10 */
+    pLoop->rRun = 33;  /* 33==sqlite3LogEst(10) */
+  }else{
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      int opMask;
+      assert( pLoop->aLTermSpace==pLoop->aLTerm );
+      if( !IsUniqueIndex(pIdx)
+       || pIdx->pPartIdxWhere!=0
+       || pIdx->nKeyCol>ArraySize(pLoop->aLTermSpace)
+      ) continue;
+      opMask = pIdx->uniqNotNull ? (WO_EQ|WO_IS) : WO_EQ;
+      for(j=0; j<pIdx->nKeyCol; j++){
+        pTerm = whereScanInit(&scan, pWC, iCur, j, opMask, pIdx);
+        while( pTerm && pTerm->prereqRight ) pTerm = whereScanNext(&scan);
+        if( pTerm==0 ) break;
+        testcase( pTerm->eOperator & WO_IS );
+        pLoop->aLTerm[j] = pTerm;
+      }
+      if( j!=pIdx->nKeyCol ) continue;
+      pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_ONEROW|WHERE_INDEXED;
+      if( pIdx->isCovering || (pItem->colUsed & pIdx->colNotIdxed)==0 ){
+        pLoop->wsFlags |= WHERE_IDX_ONLY;
+      }
+      pLoop->nLTerm = j;
+      pLoop->u.btree.nEq = j;
+      pLoop->u.btree.pIndex = pIdx;
+      /* TUNING: Cost of a unique index lookup is 15 */
+      pLoop->rRun = 39;  /* 39==sqlite3LogEst(15) */
+      break;
+    }
+  }
+  if( pLoop->wsFlags ){
+    pLoop->nOut = (LogEst)1;
+    pWInfo->a[0].pWLoop = pLoop;
+    assert( pWInfo->sMaskSet.n==1 && iCur==pWInfo->sMaskSet.ix[0] );
+    pLoop->maskSelf = 1; /* sqlite3WhereGetMask(&pWInfo->sMaskSet, iCur); */
+    pWInfo->a[0].iTabCur = iCur;
+    pWInfo->nRowOut = 1;
+    if( pWInfo->pOrderBy ) pWInfo->nOBSat =  pWInfo->pOrderBy->nExpr;
+    if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
+      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
+    }
+    if( scan.iEquiv>1 ) pLoop->wsFlags |= WHERE_TRANSCONS;
+#ifdef SQLITE_DEBUG
+    pLoop->cId = '0';
+#endif
+#ifdef WHERETRACE_ENABLED
+    if( sqlite3WhereTrace & 0x02 ){
+      sqlite3DebugPrintf("whereShortCut() used to compute solution\n");
+    }
+#endif
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Helper function for exprIsDeterministic().
+*/
+static int exprNodeIsDeterministic(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_FUNCTION && ExprHasProperty(pExpr, EP_ConstFunc)==0 ){
+    pWalker->eCode = 0;
+    return WRC_Abort;
+  }
+  return WRC_Continue;
+}
+
+/*
+** Return true if the expression contains no non-deterministic SQL
+** functions. Do not consider non-deterministic SQL functions that are
+** part of sub-select statements.
+*/
+static int exprIsDeterministic(Expr *p){
+  Walker w;
+  memset(&w, 0, sizeof(w));
+  w.eCode = 1;
+  w.xExprCallback = exprNodeIsDeterministic;
+  w.xSelectCallback = sqlite3SelectWalkFail;
+  sqlite3WalkExpr(&w, p);
+  return w.eCode;
+}
+
+ 
+#ifdef WHERETRACE_ENABLED
+/*
+** Display all WhereLoops in pWInfo
+*/
+static void showAllWhereLoops(WhereInfo *pWInfo, WhereClause *pWC){
+  if( sqlite3WhereTrace ){    /* Display all of the WhereLoop objects */
+    WhereLoop *p;
+    int i;
+    static const char zLabel[] = "0123456789abcdefghijklmnopqrstuvwyxz"
+                                           "ABCDEFGHIJKLMNOPQRSTUVWYXZ";
+    for(p=pWInfo->pLoops, i=0; p; p=p->pNextLoop, i++){
+      p->cId = zLabel[i%(sizeof(zLabel)-1)];
+      sqlite3WhereLoopPrint(p, pWC);
+    }
+  }
+}
+# define WHERETRACE_ALL_LOOPS(W,C) showAllWhereLoops(W,C)
+#else
+# define WHERETRACE_ALL_LOOPS(W,C)
+#endif
+
+/* Attempt to omit tables from a join that do not affect the result.
+** For a table to not affect the result, the following must be true:
+**
+**   1) The query must not be an aggregate.
+**   2) The table must be the RHS of a LEFT JOIN.
+**   3) Either the query must be DISTINCT, or else the ON or USING clause
+**      must contain a constraint that limits the scan of the table to
+**      at most a single row.
+**   4) The table must not be referenced by any part of the query apart
+**      from its own USING or ON clause.
+**   5) The table must not have an inner-join ON or USING clause if there is
+**      a RIGHT JOIN anywhere in the query.  Otherwise the ON/USING clause
+**      might move from the right side to the left side of the RIGHT JOIN.
+**      Note: Due to (2), this condition can only arise if the table is
+**      the right-most table of a subquery that was flattened into the
+**      main query and that subquery was the right-hand operand of an
+**      inner join that held an ON or USING clause.
+**
+** For example, given:
+**
+**     CREATE TABLE t1(ipk INTEGER PRIMARY KEY, v1);
+**     CREATE TABLE t2(ipk INTEGER PRIMARY KEY, v2);
+**     CREATE TABLE t3(ipk INTEGER PRIMARY KEY, v3);
+**
+** then table t2 can be omitted from the following:
+**
+**     SELECT v1, v3 FROM t1
+**       LEFT JOIN t2 ON (t1.ipk=t2.ipk)
+**       LEFT JOIN t3 ON (t1.ipk=t3.ipk)
+**
+** or from:
+**
+**     SELECT DISTINCT v1, v3 FROM t1
+**       LEFT JOIN t2
+**       LEFT JOIN t3 ON (t1.ipk=t3.ipk)
+*/
+static SQLITE_NOINLINE Bitmask whereOmitNoopJoin(
+  WhereInfo *pWInfo,
+  Bitmask notReady
+){
+  int i;
+  Bitmask tabUsed;
+  int hasRightJoin;
+
+  /* Preconditions checked by the caller */
+  assert( pWInfo->nLevel>=2 );
+  assert( OptimizationEnabled(pWInfo->pParse->db, SQLITE_OmitNoopJoin) );
+
+  /* These two preconditions checked by the caller combine to guarantee
+  ** condition (1) of the header comment */
+  assert( pWInfo->pResultSet!=0 );
+  assert( 0==(pWInfo->wctrlFlags & WHERE_AGG_DISTINCT) );
+
+  tabUsed = sqlite3WhereExprListUsage(&pWInfo->sMaskSet, pWInfo->pResultSet);
+  if( pWInfo->pOrderBy ){
+    tabUsed |= sqlite3WhereExprListUsage(&pWInfo->sMaskSet, pWInfo->pOrderBy);
+  }
+  hasRightJoin = (pWInfo->pTabList->a[0].fg.jointype & JT_LTORJ)!=0;
+  for(i=pWInfo->nLevel-1; i>=1; i--){
+    WhereTerm *pTerm, *pEnd;
+    SrcItem *pItem;
+    WhereLoop *pLoop;
+    pLoop = pWInfo->a[i].pWLoop;
+    pItem = &pWInfo->pTabList->a[pLoop->iTab];
+    if( (pItem->fg.jointype & (JT_LEFT|JT_RIGHT))!=JT_LEFT ) continue;
+    if( (pWInfo->wctrlFlags & WHERE_WANT_DISTINCT)==0
+     && (pLoop->wsFlags & WHERE_ONEROW)==0
+    ){
+      continue;
+    }
+    if( (tabUsed & pLoop->maskSelf)!=0 ) continue;
+    pEnd = pWInfo->sWC.a + pWInfo->sWC.nTerm;
+    for(pTerm=pWInfo->sWC.a; pTerm<pEnd; pTerm++){
+      if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
+        if( !ExprHasProperty(pTerm->pExpr, EP_OuterON)
+         || pTerm->pExpr->w.iJoin!=pItem->iCursor
+        ){
+          break;
+        }
+      }
+      if( hasRightJoin
+       && ExprHasProperty(pTerm->pExpr, EP_InnerON)
+       && pTerm->pExpr->w.iJoin==pItem->iCursor
+      ){
+        break;  /* restriction (5) */
+      }
+    }
+    if( pTerm<pEnd ) continue;
+    WHERETRACE(0xffffffff, ("-> drop loop %c not used\n", pLoop->cId));
+    notReady &= ~pLoop->maskSelf;
+    for(pTerm=pWInfo->sWC.a; pTerm<pEnd; pTerm++){
+      if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
+        pTerm->wtFlags |= TERM_CODED;
+      }
+    }
+    if( i!=pWInfo->nLevel-1 ){
+      int nByte = (pWInfo->nLevel-1-i) * sizeof(WhereLevel);
+      memmove(&pWInfo->a[i], &pWInfo->a[i+1], nByte);
+    }
+    pWInfo->nLevel--;
+    assert( pWInfo->nLevel>0 );
+  }
+  return notReady;
+}
+
+/*
+** Check to see if there are any SEARCH loops that might benefit from
+** using a Bloom filter.  Consider a Bloom filter if:
+**
+**   (1)  The SEARCH happens more than N times where N is the number
+**        of rows in the table that is being considered for the Bloom
+**        filter.
+**   (2)  Some searches are expected to find zero rows.  (This is determined
+**        by the WHERE_SELFCULL flag on the term.)
+**   (3)  Bloom-filter processing is not disabled.  (Checked by the
+**        caller.)
+**   (4)  The size of the table being searched is known by ANALYZE.
+**
+** This block of code merely checks to see if a Bloom filter would be
+** appropriate, and if so sets the WHERE_BLOOMFILTER flag on the
+** WhereLoop.  The implementation of the Bloom filter comes further
+** down where the code for each WhereLoop is generated.
+*/
+static SQLITE_NOINLINE void whereCheckIfBloomFilterIsUseful(
+  const WhereInfo *pWInfo
+){
+  int i;
+  LogEst nSearch = 0;
+
+  assert( pWInfo->nLevel>=2 );
+  assert( OptimizationEnabled(pWInfo->pParse->db, SQLITE_BloomFilter) );
+  for(i=0; i<pWInfo->nLevel; i++){
+    WhereLoop *pLoop = pWInfo->a[i].pWLoop;
+    const unsigned int reqFlags = (WHERE_SELFCULL|WHERE_COLUMN_EQ);
+    SrcItem *pItem = &pWInfo->pTabList->a[pLoop->iTab];
+    Table *pTab = pItem->pTab;
+    if( (pTab->tabFlags & TF_HasStat1)==0 ) break;
+    pTab->tabFlags |= TF_StatsUsed;
+    if( i>=1
+     && (pLoop->wsFlags & reqFlags)==reqFlags
+     /* vvvvvv--- Always the case if WHERE_COLUMN_EQ is defined */
+     && ALWAYS((pLoop->wsFlags & (WHERE_IPK|WHERE_INDEXED))!=0)
+    ){
+      if( nSearch > pTab->nRowLogEst ){
+        testcase( pItem->fg.jointype & JT_LEFT );
+        pLoop->wsFlags |= WHERE_BLOOMFILTER;
+        pLoop->wsFlags &= ~WHERE_IDX_ONLY;
+        WHERETRACE(0xffffffff, (
+           "-> use Bloom-filter on loop %c because there are ~%.1e "
+           "lookups into %s which has only ~%.1e rows\n",
+           pLoop->cId, (double)sqlite3LogEstToInt(nSearch), pTab->zName,
+           (double)sqlite3LogEstToInt(pTab->nRowLogEst)));
+      }
+    }
+    nSearch += pLoop->nOut;
+  }
+}
+
+/*
+** The index pIdx is used by a query and contains one or more expressions.
+** In other words pIdx is an index on an expression.  iIdxCur is the cursor
+** number for the index and iDataCur is the cursor number for the corresponding
+** table.
+**
+** This routine adds IndexedExpr entries to the Parse->pIdxEpr field for
+** each of the expressions in the index so that the expression code generator
+** will know to replace occurrences of the indexed expression with
+** references to the corresponding column of the index.
+*/
+static SQLITE_NOINLINE void whereAddIndexedExpr(
+  Parse *pParse,     /* Add IndexedExpr entries to pParse->pIdxEpr */
+  Index *pIdx,       /* The index-on-expression that contains the expressions */
+  int iIdxCur,       /* Cursor number for pIdx */
+  SrcItem *pTabItem  /* The FROM clause entry for the table */
+){
+  int i;
+  IndexedExpr *p;
+  Table *pTab;
+  assert( pIdx->bHasExpr );
+  pTab = pIdx->pTable;
+  for(i=0; i<pIdx->nColumn; i++){
+    Expr *pExpr;
+    int j = pIdx->aiColumn[i];
+    int bMaybeNullRow;
+    if( j==XN_EXPR ){
+      pExpr = pIdx->aColExpr->a[i].pExpr;
+      testcase( pTabItem->fg.jointype & JT_LEFT );
+      testcase( pTabItem->fg.jointype & JT_RIGHT );
+      testcase( pTabItem->fg.jointype & JT_LTORJ );
+      bMaybeNullRow = (pTabItem->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT))!=0;
+    }else if( j>=0 && (pTab->aCol[j].colFlags & COLFLAG_VIRTUAL)!=0 ){
+      pExpr = sqlite3ColumnExpr(pTab, &pTab->aCol[j]);
+      bMaybeNullRow = 0;
+    }else{
+      continue;
+    }
+    if( sqlite3ExprIsConstant(pExpr) ) continue;
+    if( pExpr->op==TK_FUNCTION ){
+      /* Functions that might set a subtype should not be replaced by the
+      ** value taken from an expression index since the index omits the
+      ** subtype.  https://sqlite.org/forum/forumpost/68d284c86b082c3e */
+      int n;
+      FuncDef *pDef;
+      sqlite3 *db = pParse->db;
+      assert( ExprUseXList(pExpr) );
+      n = pExpr->x.pList ? pExpr->x.pList->nExpr : 0;
+      pDef = sqlite3FindFunction(db, pExpr->u.zToken, n, ENC(db), 0);
+      if( pDef==0 || (pDef->funcFlags & SQLITE_RESULT_SUBTYPE)!=0 ){
+        continue;
+      }
+    }
+    p = sqlite3DbMallocRaw(pParse->db,  sizeof(IndexedExpr));
+    if( p==0 ) break;
+    p->pIENext = pParse->pIdxEpr;
+#ifdef WHERETRACE_ENABLED
+    if( sqlite3WhereTrace & 0x200 ){
+      sqlite3DebugPrintf("New pParse->pIdxEpr term {%d,%d}\n", iIdxCur, i);
+      if( sqlite3WhereTrace & 0x5000 ) sqlite3ShowExpr(pExpr);
+    }
+#endif
+    p->pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
+    p->iDataCur = pTabItem->iCursor;
+    p->iIdxCur = iIdxCur;
+    p->iIdxCol = i;
+    p->bMaybeNullRow = bMaybeNullRow;
+    if( sqlite3IndexAffinityStr(pParse->db, pIdx) ){
+      p->aff = pIdx->zColAff[i];
+    }
+#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
+    p->zIdxName = pIdx->zName;
+#endif
+    pParse->pIdxEpr = p;
+    if( p->pIENext==0 ){
+      void *pArg = (void*)&pParse->pIdxEpr;
+      sqlite3ParserAddCleanup(pParse, whereIndexedExprCleanup, pArg);
+    }
+  }
+}
+
+/*
+** Set the reverse-scan order mask to one for all tables in the query
+** with the exception of MATERIALIZED common table expressions that have
+** their own internal ORDER BY clauses.
+**
+** This implements the PRAGMA reverse_unordered_selects=ON setting.
+** (Also SQLITE_DBCONFIG_REVERSE_SCANORDER).
+*/
+static SQLITE_NOINLINE void whereReverseScanOrder(WhereInfo *pWInfo){
+  int ii;
+  for(ii=0; ii<pWInfo->pTabList->nSrc; ii++){
+    SrcItem *pItem = &pWInfo->pTabList->a[ii];
+    if( !pItem->fg.isCte
+     || pItem->u2.pCteUse->eM10d!=M10d_Yes
+     || NEVER(pItem->pSelect==0)
+     || pItem->pSelect->pOrderBy==0
+    ){
+      pWInfo->revMask |= MASKBIT(ii);
+    }
+  }
+}
+
+/*
+** Generate the beginning of the loop used for WHERE clause processing.
+** The return value is a pointer to an opaque structure that contains
+** information needed to terminate the loop.  Later, the calling routine
+** should invoke sqlite3WhereEnd() with the return value of this function
+** in order to complete the WHERE clause processing.
+**
+** If an error occurs, this routine returns NULL.
+**
+** The basic idea is to do a nested loop, one loop for each table in
+** the FROM clause of a select.  (INSERT and UPDATE statements are the
+** same as a SELECT with only a single table in the FROM clause.)  For
+** example, if the SQL is this:
+**
+**       SELECT * FROM t1, t2, t3 WHERE ...;
+**
+** Then the code generated is conceptually like the following:
+**
+**      foreach row1 in t1 do       \    Code generated
+**        foreach row2 in t2 do      |-- by sqlite3WhereBegin()
+**          foreach row3 in t3 do   /
+**            ...
+**          end                     \    Code generated
+**        end                        |-- by sqlite3WhereEnd()
+**      end                         /
+**
+** Note that the loops might not be nested in the order in which they
+** appear in the FROM clause if a different order is better able to make
+** use of indices.  Note also that when the IN operator appears in
+** the WHERE clause, it might result in additional nested loops for
+** scanning through all values on the right-hand side of the IN.
+**
+** There are Btree cursors associated with each table.  t1 uses cursor
+** number pTabList->a[0].iCursor.  t2 uses the cursor pTabList->a[1].iCursor.
+** And so forth.  This routine generates code to open those VDBE cursors
+** and sqlite3WhereEnd() generates the code to close them.
+**
+** The code that sqlite3WhereBegin() generates leaves the cursors named
+** in pTabList pointing at their appropriate entries.  The [...] code
+** can use OP_Column and OP_Rowid opcodes on these cursors to extract
+** data from the various tables of the loop.
+**
+** If the WHERE clause is empty, the foreach loops must each scan their
+** entire tables.  Thus a three-way join is an O(N^3) operation.  But if
+** the tables have indices and there are terms in the WHERE clause that
+** refer to those indices, a complete table scan can be avoided and the
+** code will run much faster.  Most of the work of this routine is checking
+** to see if there are indices that can be used to speed up the loop.
+**
+** Terms of the WHERE clause are also used to limit which rows actually
+** make it to the "..." in the middle of the loop.  After each "foreach",
+** terms of the WHERE clause that use only terms in that loop and outer
+** loops are evaluated and if false a jump is made around all subsequent
+** inner loops (or around the "..." if the test occurs within the inner-
+** most loop)
+**
+** OUTER JOINS
+**
+** An outer join of tables t1 and t2 is conceptually coded as follows:
+**
+**    foreach row1 in t1 do
+**      flag = 0
+**      foreach row2 in t2 do
+**        start:
+**          ...
+**          flag = 1
+**      end
+**      if flag==0 then
+**        move the row2 cursor to a null row
+**        goto start
+**      fi
+**    end
+**
+** ORDER BY CLAUSE PROCESSING
+**
+** pOrderBy is a pointer to the ORDER BY clause (or the GROUP BY clause
+** if the WHERE_GROUPBY flag is set in wctrlFlags) of a SELECT statement
+** if there is one.  If there is no ORDER BY clause or if this routine
+** is called from an UPDATE or DELETE statement, then pOrderBy is NULL.
+**
+** The iIdxCur parameter is the cursor number of an index.  If
+** WHERE_OR_SUBCLAUSE is set, iIdxCur is the cursor number of an index
+** to use for OR clause processing.  The WHERE clause should use this
+** specific cursor.  If WHERE_ONEPASS_DESIRED is set, then iIdxCur is
+** the first cursor in an array of cursors for all indices.  iIdxCur should
+** be used to compute the appropriate cursor depending on which index is
+** used.
+*/
+WhereInfo *sqlite3WhereBegin(
+  Parse *pParse,          /* The parser context */
+  SrcList *pTabList,      /* FROM clause: A list of all tables to be scanned */
+  Expr *pWhere,           /* The WHERE clause */
+  ExprList *pOrderBy,     /* An ORDER BY (or GROUP BY) clause, or NULL */
+  ExprList *pResultSet,   /* Query result set.  Req'd for DISTINCT */
+  Select *pSelect,        /* The entire SELECT statement */
+  u16 wctrlFlags,         /* The WHERE_* flags defined in sqliteInt.h */
+  int iAuxArg             /* If WHERE_OR_SUBCLAUSE is set, index cursor number
+                          ** If WHERE_USE_LIMIT, then the limit amount */
+){
+  int nByteWInfo;            /* Num. bytes allocated for WhereInfo struct */
+  int nTabList;              /* Number of elements in pTabList */
+  WhereInfo *pWInfo;         /* Will become the return value of this function */
+  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
+  Bitmask notReady;          /* Cursors that are not yet positioned */
+  WhereLoopBuilder sWLB;     /* The WhereLoop builder */
+  WhereMaskSet *pMaskSet;    /* The expression mask set */
+  WhereLevel *pLevel;        /* A single level in pWInfo->a[] */
+  WhereLoop *pLoop;          /* Pointer to a single WhereLoop object */
+  int ii;                    /* Loop counter */
+  sqlite3 *db;               /* Database connection */
+  int rc;                    /* Return code */
+  u8 bFordelete = 0;         /* OPFLAG_FORDELETE or zero, as appropriate */
+
+  assert( (wctrlFlags & WHERE_ONEPASS_MULTIROW)==0 || (
+        (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0
+     && (wctrlFlags & WHERE_OR_SUBCLAUSE)==0
+  ));
+
+  /* Only one of WHERE_OR_SUBCLAUSE or WHERE_USE_LIMIT */
+  assert( (wctrlFlags & WHERE_OR_SUBCLAUSE)==0
+            || (wctrlFlags & WHERE_USE_LIMIT)==0 );
+
+  /* Variable initialization */
+  db = pParse->db;
+  memset(&sWLB, 0, sizeof(sWLB));
+
+  /* An ORDER/GROUP BY clause of more than 63 terms cannot be optimized */
+  testcase( pOrderBy && pOrderBy->nExpr==BMS-1 );
+  if( pOrderBy && pOrderBy->nExpr>=BMS ){
+    pOrderBy = 0;
+    wctrlFlags &= ~WHERE_WANT_DISTINCT;
+  }
+
+  /* The number of tables in the FROM clause is limited by the number of
+  ** bits in a Bitmask
+  */
+  testcase( pTabList->nSrc==BMS );
+  if( pTabList->nSrc>BMS ){
+    sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
+    return 0;
+  }
+
+  /* This function normally generates a nested loop for all tables in
+  ** pTabList.  But if the WHERE_OR_SUBCLAUSE flag is set, then we should
+  ** only generate code for the first table in pTabList and assume that
+  ** any cursors associated with subsequent tables are uninitialized.
+  */
+  nTabList = (wctrlFlags & WHERE_OR_SUBCLAUSE) ? 1 : pTabList->nSrc;
+
+  /* Allocate and initialize the WhereInfo structure that will become the
+  ** return value. A single allocation is used to store the WhereInfo
+  ** struct, the contents of WhereInfo.a[], the WhereClause structure
+  ** and the WhereMaskSet structure. Since WhereClause contains an 8-byte
+  ** field (type Bitmask) it must be aligned on an 8-byte boundary on
+  ** some architectures. Hence the ROUND8() below.
+  */
+  nByteWInfo = ROUND8P(sizeof(WhereInfo));
+  if( nTabList>1 ){
+    nByteWInfo = ROUND8P(nByteWInfo + (nTabList-1)*sizeof(WhereLevel));
+  }
+  pWInfo = sqlite3DbMallocRawNN(db, nByteWInfo + sizeof(WhereLoop));
+  if( db->mallocFailed ){
+    sqlite3DbFree(db, pWInfo);
+    pWInfo = 0;
+    goto whereBeginError;
+  }
+  pWInfo->pParse = pParse;
+  pWInfo->pTabList = pTabList;
+  pWInfo->pOrderBy = pOrderBy;
+#if WHERETRACE_ENABLED
+  pWInfo->pWhere = pWhere;
+#endif
+  pWInfo->pResultSet = pResultSet;
+  pWInfo->aiCurOnePass[0] = pWInfo->aiCurOnePass[1] = -1;
+  pWInfo->nLevel = nTabList;
+  pWInfo->iBreak = pWInfo->iContinue = sqlite3VdbeMakeLabel(pParse);
+  pWInfo->wctrlFlags = wctrlFlags;
+  pWInfo->iLimit = iAuxArg;
+  pWInfo->savedNQueryLoop = pParse->nQueryLoop;
+  pWInfo->pSelect = pSelect;
+  memset(&pWInfo->nOBSat, 0,
+         offsetof(WhereInfo,sWC) - offsetof(WhereInfo,nOBSat));
+  memset(&pWInfo->a[0], 0, sizeof(WhereLoop)+nTabList*sizeof(WhereLevel));
+  assert( pWInfo->eOnePass==ONEPASS_OFF );  /* ONEPASS defaults to OFF */
+  pMaskSet = &pWInfo->sMaskSet;
+  pMaskSet->n = 0;
+  pMaskSet->ix[0] = -99; /* Initialize ix[0] to a value that can never be
+                         ** a valid cursor number, to avoid an initial
+                         ** test for pMaskSet->n==0 in sqlite3WhereGetMask() */
+  sWLB.pWInfo = pWInfo;
+  sWLB.pWC = &pWInfo->sWC;
+  sWLB.pNew = (WhereLoop*)(((char*)pWInfo)+nByteWInfo);
+  assert( EIGHT_BYTE_ALIGNMENT(sWLB.pNew) );
+  whereLoopInit(sWLB.pNew);
+#ifdef SQLITE_DEBUG
+  sWLB.pNew->cId = '*';
+#endif
+
+  /* Split the WHERE clause into separate subexpressions where each
+  ** subexpression is separated by an AND operator.
+  */
+  sqlite3WhereClauseInit(&pWInfo->sWC, pWInfo);
+  sqlite3WhereSplit(&pWInfo->sWC, pWhere, TK_AND);
+   
+  /* Special case: No FROM clause
+  */
+  if( nTabList==0 ){
+    if( pOrderBy ) pWInfo->nOBSat = pOrderBy->nExpr;
+    if( (wctrlFlags & WHERE_WANT_DISTINCT)!=0
+     && OptimizationEnabled(db, SQLITE_DistinctOpt)
+    ){
+      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
+    }
+    ExplainQueryPlan((pParse, 0, "SCAN CONSTANT ROW"));
+  }else{
+    /* Assign a bit from the bitmask to every term in the FROM clause.
+    **
+    ** The N-th term of the FROM clause is assigned a bitmask of 1<<N.
+    **
+    ** The rule of the previous sentence ensures that if X is the bitmask for
+    ** a table T, then X-1 is the bitmask for all other tables to the left of T.
+    ** Knowing the bitmask for all tables to the left of a left join is
+    ** important.  Ticket #3015.
+    **
+    ** Note that bitmasks are created for all pTabList->nSrc tables in
+    ** pTabList, not just the first nTabList tables.  nTabList is normally
+    ** equal to pTabList->nSrc but might be shortened to 1 if the
+    ** WHERE_OR_SUBCLAUSE flag is set.
+    */
+    ii = 0;
+    do{
+      createMask(pMaskSet, pTabList->a[ii].iCursor);
+      sqlite3WhereTabFuncArgs(pParse, &pTabList->a[ii], &pWInfo->sWC);
+    }while( (++ii)<pTabList->nSrc );
+  #ifdef SQLITE_DEBUG
+    {
+      Bitmask mx = 0;
+      for(ii=0; ii<pTabList->nSrc; ii++){
+        Bitmask m = sqlite3WhereGetMask(pMaskSet, pTabList->a[ii].iCursor);
+        assert( m>=mx );
+        mx = m;
+      }
+    }
+  #endif
+  }
+ 
+  /* Analyze all of the subexpressions. */
+  sqlite3WhereExprAnalyze(pTabList, &pWInfo->sWC);
+  if( pSelect && pSelect->pLimit ){
+    sqlite3WhereAddLimit(&pWInfo->sWC, pSelect);
+  }
+  if( pParse->nErr ) goto whereBeginError;
+
+  /* The False-WHERE-Term-Bypass optimization:
+  **
+  ** If there are WHERE terms that are false, then no rows will be output,
+  ** so skip over all of the code generated here.
+  **
+  ** Conditions:
+  **
+  **   (1)  The WHERE term must not refer to any tables in the join.
+  **   (2)  The term must not come from an ON clause on the
+  **        right-hand side of a LEFT or FULL JOIN.
+  **   (3)  The term must not come from an ON clause, or there must be
+  **        no RIGHT or FULL OUTER joins in pTabList.
+  **   (4)  If the expression contains non-deterministic functions
+  **        that are not within a sub-select. This is not required
+  **        for correctness but rather to preserves SQLite's legacy
+  **        behaviour in the following two cases:
+  **
+  **          WHERE random()>0;           -- eval random() once per row
+  **          WHERE (SELECT random())>0;  -- eval random() just once overall
+  **
+  ** Note that the Where term need not be a constant in order for this
+  ** optimization to apply, though it does need to be constant relative to
+  ** the current subquery (condition 1).  The term might include variables
+  ** from outer queries so that the value of the term changes from one
+  ** invocation of the current subquery to the next.
+  */
+  for(ii=0; ii<sWLB.pWC->nBase; ii++){
+    WhereTerm *pT = &sWLB.pWC->a[ii];  /* A term of the WHERE clause */
+    Expr *pX;                          /* The expression of pT */
+    if( pT->wtFlags & TERM_VIRTUAL ) continue;
+    pX = pT->pExpr;
+    assert( pX!=0 );
+    assert( pT->prereqAll!=0 || !ExprHasProperty(pX, EP_OuterON) );
+    if( pT->prereqAll==0                           /* Conditions (1) and (2) */
+     && (nTabList==0 || exprIsDeterministic(pX))   /* Condition (4) */
+     && !(ExprHasProperty(pX, EP_InnerON)          /* Condition (3) */
+          && (pTabList->a[0].fg.jointype & JT_LTORJ)!=0 )
+    ){
+      sqlite3ExprIfFalse(pParse, pX, pWInfo->iBreak, SQLITE_JUMPIFNULL);
+      pT->wtFlags |= TERM_CODED;
+    }
+  }
+
+  if( wctrlFlags & WHERE_WANT_DISTINCT ){
+    if( OptimizationDisabled(db, SQLITE_DistinctOpt) ){
+      /* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via
+      ** sqlite3_test_ctrl(SQLITE_TESTCTRL_OPTIMIZATIONS,...) */
+      wctrlFlags &= ~WHERE_WANT_DISTINCT;
+      pWInfo->wctrlFlags &= ~WHERE_WANT_DISTINCT;
+    }else if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
+      /* The DISTINCT marking is pointless.  Ignore it. */
+      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
+    }else if( pOrderBy==0 ){
+      /* Try to ORDER BY the result set to make distinct processing easier */
+      pWInfo->wctrlFlags |= WHERE_DISTINCTBY;
+      pWInfo->pOrderBy = pResultSet;
+    }
+  }
+
+  /* Construct the WhereLoop objects */
+#if defined(WHERETRACE_ENABLED)
+  if( sqlite3WhereTrace & 0xffffffff ){
+    sqlite3DebugPrintf("*** Optimizer Start *** (wctrlFlags: 0x%x",wctrlFlags);
+    if( wctrlFlags & WHERE_USE_LIMIT ){
+      sqlite3DebugPrintf(", limit: %d", iAuxArg);
+    }
+    sqlite3DebugPrintf(")\n");
+    if( sqlite3WhereTrace & 0x8000 ){
+      Select sSelect;
+      memset(&sSelect, 0, sizeof(sSelect));
+      sSelect.selFlags = SF_WhereBegin;
+      sSelect.pSrc = pTabList;
+      sSelect.pWhere = pWhere;
+      sSelect.pOrderBy = pOrderBy;
+      sSelect.pEList = pResultSet;
+      sqlite3TreeViewSelect(0, &sSelect, 0);
+    }
+    if( sqlite3WhereTrace & 0x4000 ){ /* Display all WHERE clause terms */
+      sqlite3DebugPrintf("---- WHERE clause at start of analysis:\n");
+      sqlite3WhereClausePrint(sWLB.pWC);
+    }
+  }
+#endif
+
+  if( nTabList!=1 || whereShortCut(&sWLB)==0 ){
+    rc = whereLoopAddAll(&sWLB);
+    if( rc ) goto whereBeginError;
+
+#ifdef SQLITE_ENABLE_STAT4
+    /* If one or more WhereTerm.truthProb values were used in estimating
+    ** loop parameters, but then those truthProb values were subsequently
+    ** changed based on STAT4 information while computing subsequent loops,
+    ** then we need to rerun the whole loop building process so that all
+    ** loops will be built using the revised truthProb values. */
+    if( sWLB.bldFlags2 & SQLITE_BLDF2_2NDPASS ){
+      WHERETRACE_ALL_LOOPS(pWInfo, sWLB.pWC);
+      WHERETRACE(0xffffffff,
+           ("**** Redo all loop computations due to"
+            " TERM_HIGHTRUTH changes ****\n"));
+      while( pWInfo->pLoops ){
+        WhereLoop *p = pWInfo->pLoops;
+        pWInfo->pLoops = p->pNextLoop;
+        whereLoopDelete(db, p);
+      }
+      rc = whereLoopAddAll(&sWLB);
+      if( rc ) goto whereBeginError;
+    }
+#endif
+    WHERETRACE_ALL_LOOPS(pWInfo, sWLB.pWC);
+ 
+    wherePathSolver(pWInfo, 0);
+    if( db->mallocFailed ) goto whereBeginError;
+    if( pWInfo->pOrderBy ){
+       wherePathSolver(pWInfo, pWInfo->nRowOut+1);
+       if( db->mallocFailed ) goto whereBeginError;
+    }
+
+    /* TUNING:  Assume that a DISTINCT clause on a subquery reduces
+    ** the output size by a factor of 8 (LogEst -30).
+    */
+    if( (pWInfo->wctrlFlags & WHERE_WANT_DISTINCT)!=0 ){
+      WHERETRACE(0x0080,("nRowOut reduced from %d to %d due to DISTINCT\n",
+                         pWInfo->nRowOut, pWInfo->nRowOut-30));
+      pWInfo->nRowOut -= 30;
+    }
+
+  }
+  assert( pWInfo->pTabList!=0 );
+  if( pWInfo->pOrderBy==0 && (db->flags & SQLITE_ReverseOrder)!=0 ){
+    whereReverseScanOrder(pWInfo);
+  }
+  if( pParse->nErr ){
+    goto whereBeginError;
+  }
+  assert( db->mallocFailed==0 );
+#ifdef WHERETRACE_ENABLED
+  if( sqlite3WhereTrace ){
+    sqlite3DebugPrintf("---- Solution nRow=%d", pWInfo->nRowOut);
+    if( pWInfo->nOBSat>0 ){
+      sqlite3DebugPrintf(" ORDERBY=%d,0x%llx", pWInfo->nOBSat, pWInfo->revMask);
+    }
+    switch( pWInfo->eDistinct ){
+      case WHERE_DISTINCT_UNIQUE: {
+        sqlite3DebugPrintf("  DISTINCT=unique");
+        break;
+      }
+      case WHERE_DISTINCT_ORDERED: {
+        sqlite3DebugPrintf("  DISTINCT=ordered");
+        break;
+      }
+      case WHERE_DISTINCT_UNORDERED: {
+        sqlite3DebugPrintf("  DISTINCT=unordered");
+        break;
+      }
+    }
+    sqlite3DebugPrintf("\n");
+    for(ii=0; ii<pWInfo->nLevel; ii++){
+      sqlite3WhereLoopPrint(pWInfo->a[ii].pWLoop, sWLB.pWC);
+    }
+  }
+#endif
+
+  /* Attempt to omit tables from a join that do not affect the result.
+  ** See the comment on whereOmitNoopJoin() for further information.
+  **
+  ** This query optimization is factored out into a separate "no-inline"
+  ** procedure to keep the sqlite3WhereBegin() procedure from becoming
+  ** too large.  If sqlite3WhereBegin() becomes too large, that prevents
+  ** some C-compiler optimizers from in-lining the
+  ** sqlite3WhereCodeOneLoopStart() procedure, and it is important to
+  ** in-line sqlite3WhereCodeOneLoopStart() for performance reasons.
+  */
+  notReady = ~(Bitmask)0;
+  if( pWInfo->nLevel>=2
+   && pResultSet!=0                         /* these two combine to guarantee */
+   && 0==(wctrlFlags & WHERE_AGG_DISTINCT)  /* condition (1) above */
+   && OptimizationEnabled(db, SQLITE_OmitNoopJoin)
+  ){
+    notReady = whereOmitNoopJoin(pWInfo, notReady);
+    nTabList = pWInfo->nLevel;
+    assert( nTabList>0 );
+  }
+
+  /* Check to see if there are any SEARCH loops that might benefit from
+  ** using a Bloom filter.
+  */
+  if( pWInfo->nLevel>=2
+   && OptimizationEnabled(db, SQLITE_BloomFilter)
+  ){
+    whereCheckIfBloomFilterIsUseful(pWInfo);
+  }
+
+#if defined(WHERETRACE_ENABLED)
+  if( sqlite3WhereTrace & 0x4000 ){ /* Display all terms of the WHERE clause */
+    sqlite3DebugPrintf("---- WHERE clause at end of analysis:\n");
+    sqlite3WhereClausePrint(sWLB.pWC);
+  }
+  WHERETRACE(0xffffffff,("*** Optimizer Finished ***\n"));
+#endif
+  pWInfo->pParse->nQueryLoop += pWInfo->nRowOut;
+
+  /* If the caller is an UPDATE or DELETE statement that is requesting
+  ** to use a one-pass algorithm, determine if this is appropriate.
+  **
+  ** A one-pass approach can be used if the caller has requested one
+  ** and either (a) the scan visits at most one row or (b) each
+  ** of the following are true:
+  **
+  **   * the caller has indicated that a one-pass approach can be used
+  **     with multiple rows (by setting WHERE_ONEPASS_MULTIROW), and
+  **   * the table is not a virtual table, and
+  **   * either the scan does not use the OR optimization or the caller
+  **     is a DELETE operation (WHERE_DUPLICATES_OK is only specified
+  **     for DELETE).
+  **
+  ** The last qualification is because an UPDATE statement uses
+  ** WhereInfo.aiCurOnePass[1] to determine whether or not it really can
+  ** use a one-pass approach, and this is not set accurately for scans
+  ** that use the OR optimization.
+  */
+  assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
+  if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 ){
+    int wsFlags = pWInfo->a[0].pWLoop->wsFlags;
+    int bOnerow = (wsFlags & WHERE_ONEROW)!=0;
+    assert( !(wsFlags & WHERE_VIRTUALTABLE) || IsVirtual(pTabList->a[0].pTab) );
+    if( bOnerow || (
+        0!=(wctrlFlags & WHERE_ONEPASS_MULTIROW)
+     && !IsVirtual(pTabList->a[0].pTab)
+     && (0==(wsFlags & WHERE_MULTI_OR) || (wctrlFlags & WHERE_DUPLICATES_OK))
+     && OptimizationEnabled(db, SQLITE_OnePass)
+    )){
+      pWInfo->eOnePass = bOnerow ? ONEPASS_SINGLE : ONEPASS_MULTI;
+      if( HasRowid(pTabList->a[0].pTab) && (wsFlags & WHERE_IDX_ONLY) ){
+        if( wctrlFlags & WHERE_ONEPASS_MULTIROW ){
+          bFordelete = OPFLAG_FORDELETE;
+        }
+        pWInfo->a[0].pWLoop->wsFlags = (wsFlags & ~WHERE_IDX_ONLY);
+      }
+    }
+  }
+
+  /* Open all tables in the pTabList and any indices selected for
+  ** searching those tables.
+  */
+  for(ii=0, pLevel=pWInfo->a; ii<nTabList; ii++, pLevel++){
+    Table *pTab;     /* Table to open */
+    int iDb;         /* Index of database containing table/index */
+    SrcItem *pTabItem;
+
+    pTabItem = &pTabList->a[pLevel->iFrom];
+    pTab = pTabItem->pTab;
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    pLoop = pLevel->pWLoop;
+    if( (pTab->tabFlags & TF_Ephemeral)!=0 || IsView(pTab) ){
+      /* Do nothing */
+    }else
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
+      int iCur = pTabItem->iCursor;
+      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
+    }else if( IsVirtual(pTab) ){
+      /* noop */
+    }else
+#endif
+    if( ((pLoop->wsFlags & WHERE_IDX_ONLY)==0
+         && (wctrlFlags & WHERE_OR_SUBCLAUSE)==0)
+     || (pTabItem->fg.jointype & (JT_LTORJ|JT_RIGHT))!=0
+    ){
+      int op = OP_OpenRead;
+      if( pWInfo->eOnePass!=ONEPASS_OFF ){
+        op = OP_OpenWrite;
+        pWInfo->aiCurOnePass[0] = pTabItem->iCursor;
+      };
+      sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
+      assert( pTabItem->iCursor==pLevel->iTabCur );
+      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS-1 );
+      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS );
+      if( pWInfo->eOnePass==ONEPASS_OFF
+       && pTab->nCol<BMS
+       && (pTab->tabFlags & (TF_HasGenerated|TF_WithoutRowid))==0
+       && (pLoop->wsFlags & (WHERE_AUTO_INDEX|WHERE_BLOOMFILTER))==0
+      ){
+        /* If we know that only a prefix of the record will be used,
+        ** it is advantageous to reduce the "column count" field in
+        ** the P4 operand of the OP_OpenRead/Write opcode. */
+        Bitmask b = pTabItem->colUsed;
+        int n = 0;
+        for(; b; b=b>>1, n++){}
+        sqlite3VdbeChangeP4(v, -1, SQLITE_INT_TO_PTR(n), P4_INT32);
+        assert( n<=pTab->nCol );
+      }
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+      if( pLoop->u.btree.pIndex!=0 && (pTab->tabFlags & TF_WithoutRowid)==0 ){
+        sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ|bFordelete);
+      }else
+#endif
+      {
+        sqlite3VdbeChangeP5(v, bFordelete);
+      }
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+      sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, pTabItem->iCursor, 0, 0,
+                            (const u8*)&pTabItem->colUsed, P4_INT64);
+#endif
+    }else{
+      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+    }
+    if( pLoop->wsFlags & WHERE_INDEXED ){
+      Index *pIx = pLoop->u.btree.pIndex;
+      int iIndexCur;
+      int op = OP_OpenRead;
+      /* iAuxArg is always set to a positive value if ONEPASS is possible */
+      assert( iAuxArg!=0 || (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 );
+      if( !HasRowid(pTab) && IsPrimaryKeyIndex(pIx)
+       && (wctrlFlags & WHERE_OR_SUBCLAUSE)!=0
+      ){
+        /* This is one term of an OR-optimization using the PRIMARY KEY of a
+        ** WITHOUT ROWID table.  No need for a separate index */
+        iIndexCur = pLevel->iTabCur;
+        op = 0;
+      }else if( pWInfo->eOnePass!=ONEPASS_OFF ){
+        Index *pJ = pTabItem->pTab->pIndex;
+        iIndexCur = iAuxArg;
+        assert( wctrlFlags & WHERE_ONEPASS_DESIRED );
+        while( ALWAYS(pJ) && pJ!=pIx ){
+          iIndexCur++;
+          pJ = pJ->pNext;
+        }
+        op = OP_OpenWrite;
+        pWInfo->aiCurOnePass[1] = iIndexCur;
+      }else if( iAuxArg && (wctrlFlags & WHERE_OR_SUBCLAUSE)!=0 ){
+        iIndexCur = iAuxArg;
+        op = OP_ReopenIdx;
+      }else{
+        iIndexCur = pParse->nTab++;
+        if( pIx->bHasExpr && OptimizationEnabled(db, SQLITE_IndexedExpr) ){
+          whereAddIndexedExpr(pParse, pIx, iIndexCur, pTabItem);
+        }
+        if( pIx->pPartIdxWhere && (pTabItem->fg.jointype & JT_RIGHT)==0 ){
+          wherePartIdxExpr(
+              pParse, pIx, pIx->pPartIdxWhere, 0, iIndexCur, pTabItem
+          );
+        }
+      }
+      pLevel->iIdxCur = iIndexCur;
+      assert( pIx!=0 );
+      assert( pIx->pSchema==pTab->pSchema );
+      assert( iIndexCur>=0 );
+      if( op ){
+        sqlite3VdbeAddOp3(v, op, iIndexCur, pIx->tnum, iDb);
+        sqlite3VdbeSetP4KeyInfo(pParse, pIx);
+        if( (pLoop->wsFlags & WHERE_CONSTRAINT)!=0
+         && (pLoop->wsFlags & (WHERE_COLUMN_RANGE|WHERE_SKIPSCAN))==0
+         && (pLoop->wsFlags & WHERE_BIGNULL_SORT)==0
+         && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)==0
+         && (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0
+         && pWInfo->eDistinct!=WHERE_DISTINCT_ORDERED
+        ){
+          sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ);
+        }
+        VdbeComment((v, "%s", pIx->zName));
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+        {
+          u64 colUsed = 0;
+          int ii, jj;
+          for(ii=0; ii<pIx->nColumn; ii++){
+            jj = pIx->aiColumn[ii];
+            if( jj<0 ) continue;
+            if( jj>63 ) jj = 63;
+            if( (pTabItem->colUsed & MASKBIT(jj))==0 ) continue;
+            colUsed |= ((u64)1)<<(ii<63 ? ii : 63);
+          }
+          sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, iIndexCur, 0, 0,
+                                (u8*)&colUsed, P4_INT64);
+        }
+#endif /* SQLITE_ENABLE_COLUMN_USED_MASK */
+      }
+    }
+    if( iDb>=0 ) sqlite3CodeVerifySchema(pParse, iDb);
+    if( (pTabItem->fg.jointype & JT_RIGHT)!=0
+     && (pLevel->pRJ = sqlite3WhereMalloc(pWInfo, sizeof(WhereRightJoin)))!=0
+    ){
+      WhereRightJoin *pRJ = pLevel->pRJ;
+      pRJ->iMatch = pParse->nTab++;
+      pRJ->regBloom = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Blob, 65536, pRJ->regBloom);
+      pRJ->regReturn = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Null, 0, pRJ->regReturn);
+      assert( pTab==pTabItem->pTab );
+      if( HasRowid(pTab) ){
+        KeyInfo *pInfo;
+        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pRJ->iMatch, 1);
+        pInfo = sqlite3KeyInfoAlloc(pParse->db, 1, 0);
+        if( pInfo ){
+          pInfo->aColl[0] = 0;
+          pInfo->aSortFlags[0] = 0;
+          sqlite3VdbeAppendP4(v, pInfo, P4_KEYINFO);
+        }
+      }else{
+        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pRJ->iMatch, pPk->nKeyCol);
+        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
+      }
+      pLoop->wsFlags &= ~WHERE_IDX_ONLY;
+      /* The nature of RIGHT JOIN processing is such that it messes up
+      ** the output order.  So omit any ORDER BY/GROUP BY elimination
+      ** optimizations.  We need to do an actual sort for RIGHT JOIN. */
+      pWInfo->nOBSat = 0;
+      pWInfo->eDistinct = WHERE_DISTINCT_UNORDERED;
+    }
+  }
+  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
+  if( db->mallocFailed ) goto whereBeginError;
+
+  /* Generate the code to do the search.  Each iteration of the for
+  ** loop below generates code for a single nested loop of the VM
+  ** program.
+  */
+  for(ii=0; ii<nTabList; ii++){
+    int addrExplain;
+    int wsFlags;
+    SrcItem *pSrc;
+    if( pParse->nErr ) goto whereBeginError;
+    pLevel = &pWInfo->a[ii];
+    wsFlags = pLevel->pWLoop->wsFlags;
+    pSrc = &pTabList->a[pLevel->iFrom];
+    if( pSrc->fg.isMaterialized ){
+      if( pSrc->fg.isCorrelated ){
+        sqlite3VdbeAddOp2(v, OP_Gosub, pSrc->regReturn, pSrc->addrFillSub);
+      }else{
+        int iOnce = sqlite3VdbeAddOp0(v, OP_Once);  VdbeCoverage(v);
+        sqlite3VdbeAddOp2(v, OP_Gosub, pSrc->regReturn, pSrc->addrFillSub);
+        sqlite3VdbeJumpHere(v, iOnce);
+      }
+    }
+    assert( pTabList == pWInfo->pTabList );
+    if( (wsFlags & (WHERE_AUTO_INDEX|WHERE_BLOOMFILTER))!=0 ){
+      if( (wsFlags & WHERE_AUTO_INDEX)!=0 ){
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+        constructAutomaticIndex(pParse, &pWInfo->sWC, notReady, pLevel);
+#endif
+      }else{
+        sqlite3ConstructBloomFilter(pWInfo, ii, pLevel, notReady);
+      }
+      if( db->mallocFailed ) goto whereBeginError;
+    }
+    addrExplain = sqlite3WhereExplainOneScan(
+        pParse, pTabList, pLevel, wctrlFlags
+    );
+    pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
+    notReady = sqlite3WhereCodeOneLoopStart(pParse,v,pWInfo,ii,pLevel,notReady);
+    pWInfo->iContinue = pLevel->addrCont;
+    if( (wsFlags&WHERE_MULTI_OR)==0 && (wctrlFlags&WHERE_OR_SUBCLAUSE)==0 ){
+      sqlite3WhereAddScanStatus(v, pTabList, pLevel, addrExplain);
+    }
+  }
+
+  /* Done. */
+  VdbeModuleComment((v, "Begin WHERE-core"));
+  pWInfo->iEndWhere = sqlite3VdbeCurrentAddr(v);
+  return pWInfo;
+
+  /* Jump here if malloc fails */
+whereBeginError:
+  if( pWInfo ){
+    pParse->nQueryLoop = pWInfo->savedNQueryLoop;
+    whereInfoFree(db, pWInfo);
+  }
+#ifdef WHERETRACE_ENABLED
+  /* Prevent harmless compiler warnings about debugging routines
+  ** being declared but never used */
+  sqlite3ShowWhereLoopList(0);
+#endif /* WHERETRACE_ENABLED */
+  return 0;
+}
+
+/*
+** Part of sqlite3WhereEnd() will rewrite opcodes to reference the
+** index rather than the main table.  In SQLITE_DEBUG mode, we want
+** to trace those changes if PRAGMA vdbe_addoptrace=on.  This routine
+** does that.
+*/
+#ifndef SQLITE_DEBUG
+# define OpcodeRewriteTrace(D,K,P) /* no-op */
+#else
+# define OpcodeRewriteTrace(D,K,P) sqlite3WhereOpcodeRewriteTrace(D,K,P)
+  static void sqlite3WhereOpcodeRewriteTrace(
+    sqlite3 *db,
+    int pc,
+    VdbeOp *pOp
+  ){
+    if( (db->flags & SQLITE_VdbeAddopTrace)==0 ) return;
+    sqlite3VdbePrintOp(0, pc, pOp);
+  }
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Return true if cursor iCur is opened by instruction k of the
+** bytecode.  Used inside of assert() only.
+*/
+static int cursorIsOpen(Vdbe *v, int iCur, int k){
+  while( k>=0 ){
+    VdbeOp *pOp = sqlite3VdbeGetOp(v,k--);
+    if( pOp->p1!=iCur ) continue;
+    if( pOp->opcode==OP_Close ) return 0;
+    if( pOp->opcode==OP_OpenRead ) return 1;
+    if( pOp->opcode==OP_OpenWrite ) return 1;
+    if( pOp->opcode==OP_OpenDup ) return 1;
+    if( pOp->opcode==OP_OpenAutoindex ) return 1;
+    if( pOp->opcode==OP_OpenEphemeral ) return 1;
+  }
+  return 0;
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** Generate the end of the WHERE loop.  See comments on
+** sqlite3WhereBegin() for additional information.
+*/
+void sqlite3WhereEnd(WhereInfo *pWInfo){
+  Parse *pParse = pWInfo->pParse;
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  WhereLevel *pLevel;
+  WhereLoop *pLoop;
+  SrcList *pTabList = pWInfo->pTabList;
+  sqlite3 *db = pParse->db;
+  int iEnd = sqlite3VdbeCurrentAddr(v);
+  int nRJ = 0;
+
+  /* Generate loop termination code.
+  */
+  VdbeModuleComment((v, "End WHERE-core"));
+  for(i=pWInfo->nLevel-1; i>=0; i--){
+    int addr;
+    pLevel = &pWInfo->a[i];
+    if( pLevel->pRJ ){
+      /* Terminate the subroutine that forms the interior of the loop of
+      ** the RIGHT JOIN table */
+      WhereRightJoin *pRJ = pLevel->pRJ;
+      sqlite3VdbeResolveLabel(v, pLevel->addrCont);
+      pLevel->addrCont = 0;
+      pRJ->endSubrtn = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp3(v, OP_Return, pRJ->regReturn, pRJ->addrSubrtn, 1);
+      VdbeCoverage(v);
+      nRJ++;
+    }
+    pLoop = pLevel->pWLoop;
+    if( pLevel->op!=OP_Noop ){
+#ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
+      int addrSeek = 0;
+      Index *pIdx;
+      int n;
+      if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED
+       && i==pWInfo->nLevel-1  /* Ticket [ef9318757b152e3] 2017-10-21 */
+       && (pLoop->wsFlags & WHERE_INDEXED)!=0
+       && (pIdx = pLoop->u.btree.pIndex)->hasStat1
+       && (n = pLoop->u.btree.nDistinctCol)>0
+       && pIdx->aiRowLogEst[n]>=36
+      ){
+        int r1 = pParse->nMem+1;
+        int j, op;
+        for(j=0; j<n; j++){
+          sqlite3VdbeAddOp3(v, OP_Column, pLevel->iIdxCur, j, r1+j);
+        }
+        pParse->nMem += n+1;
+        op = pLevel->op==OP_Prev ? OP_SeekLT : OP_SeekGT;
+        addrSeek = sqlite3VdbeAddOp4Int(v, op, pLevel->iIdxCur, 0, r1, n);
+        VdbeCoverageIf(v, op==OP_SeekLT);
+        VdbeCoverageIf(v, op==OP_SeekGT);
+        sqlite3VdbeAddOp2(v, OP_Goto, 1, pLevel->p2);
+      }
+#endif /* SQLITE_DISABLE_SKIPAHEAD_DISTINCT */
+      /* The common case: Advance to the next row */
+      if( pLevel->addrCont ) sqlite3VdbeResolveLabel(v, pLevel->addrCont);
+      sqlite3VdbeAddOp3(v, pLevel->op, pLevel->p1, pLevel->p2, pLevel->p3);
+      sqlite3VdbeChangeP5(v, pLevel->p5);
+      VdbeCoverage(v);
+      VdbeCoverageIf(v, pLevel->op==OP_Next);
+      VdbeCoverageIf(v, pLevel->op==OP_Prev);
+      VdbeCoverageIf(v, pLevel->op==OP_VNext);
+      if( pLevel->regBignull ){
+        sqlite3VdbeResolveLabel(v, pLevel->addrBignull);
+        sqlite3VdbeAddOp2(v, OP_DecrJumpZero, pLevel->regBignull, pLevel->p2-1);
+        VdbeCoverage(v);
+      }
+#ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
+      if( addrSeek ) sqlite3VdbeJumpHere(v, addrSeek);
+#endif
+    }else if( pLevel->addrCont ){
+      sqlite3VdbeResolveLabel(v, pLevel->addrCont);
+    }
+    if( (pLoop->wsFlags & WHERE_IN_ABLE)!=0 && pLevel->u.in.nIn>0 ){
+      struct InLoop *pIn;
+      int j;
+      sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
+      for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
+        assert( sqlite3VdbeGetOp(v, pIn->addrInTop+1)->opcode==OP_IsNull
+                 || pParse->db->mallocFailed );
+        sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
+        if( pIn->eEndLoopOp!=OP_Noop ){
+          if( pIn->nPrefix ){
+            int bEarlyOut =
+                (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
+                 && (pLoop->wsFlags & WHERE_IN_EARLYOUT)!=0;
+            if( pLevel->iLeftJoin ){
+              /* For LEFT JOIN queries, cursor pIn->iCur may not have been
+              ** opened yet. This occurs for WHERE clauses such as
+              ** "a = ? AND b IN (...)", where the index is on (a, b). If
+              ** the RHS of the (a=?) is NULL, then the "b IN (...)" may
+              ** never have been coded, but the body of the loop run to
+              ** return the null-row. So, if the cursor is not open yet,
+              ** jump over the OP_Next or OP_Prev instruction about to
+              ** be coded.  */
+              sqlite3VdbeAddOp2(v, OP_IfNotOpen, pIn->iCur,
+                  sqlite3VdbeCurrentAddr(v) + 2 + bEarlyOut);
+              VdbeCoverage(v);
+            }
+            if( bEarlyOut ){
+              sqlite3VdbeAddOp4Int(v, OP_IfNoHope, pLevel->iIdxCur,
+                  sqlite3VdbeCurrentAddr(v)+2,
+                  pIn->iBase, pIn->nPrefix);
+              VdbeCoverage(v);
+              /* Retarget the OP_IsNull against the left operand of IN so
+              ** it jumps past the OP_IfNoHope.  This is because the
+              ** OP_IsNull also bypasses the OP_Affinity opcode that is
+              ** required by OP_IfNoHope. */
+              sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
+            }
+          }
+          sqlite3VdbeAddOp2(v, pIn->eEndLoopOp, pIn->iCur, pIn->addrInTop);
+          VdbeCoverage(v);
+          VdbeCoverageIf(v, pIn->eEndLoopOp==OP_Prev);
+          VdbeCoverageIf(v, pIn->eEndLoopOp==OP_Next);
+        }
+        sqlite3VdbeJumpHere(v, pIn->addrInTop-1);
+      }
+    }
+    sqlite3VdbeResolveLabel(v, pLevel->addrBrk);
+    if( pLevel->pRJ ){
+      sqlite3VdbeAddOp3(v, OP_Return, pLevel->pRJ->regReturn, 0, 1);
+      VdbeCoverage(v);
+    }
+    if( pLevel->addrSkip ){
+      sqlite3VdbeGoto(v, pLevel->addrSkip);
+      VdbeComment((v, "next skip-scan on %s", pLoop->u.btree.pIndex->zName));
+      sqlite3VdbeJumpHere(v, pLevel->addrSkip);
+      sqlite3VdbeJumpHere(v, pLevel->addrSkip-2);
+    }
+#ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+    if( pLevel->addrLikeRep ){
+      sqlite3VdbeAddOp2(v, OP_DecrJumpZero, (int)(pLevel->iLikeRepCntr>>1),
+                        pLevel->addrLikeRep);
+      VdbeCoverage(v);
+    }
+#endif
+    if( pLevel->iLeftJoin ){
+      int ws = pLoop->wsFlags;
+      addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin); VdbeCoverage(v);
+      assert( (ws & WHERE_IDX_ONLY)==0 || (ws & WHERE_INDEXED)!=0 );
+      if( (ws & WHERE_IDX_ONLY)==0 ){
+        assert( pLevel->iTabCur==pTabList->a[pLevel->iFrom].iCursor );
+        sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iTabCur);
+      }
+      if( (ws & WHERE_INDEXED)
+       || ((ws & WHERE_MULTI_OR) && pLevel->u.pCoveringIdx)
+      ){
+        if( ws & WHERE_MULTI_OR ){
+          Index *pIx = pLevel->u.pCoveringIdx;
+          int iDb = sqlite3SchemaToIndex(db, pIx->pSchema);
+          sqlite3VdbeAddOp3(v, OP_ReopenIdx, pLevel->iIdxCur, pIx->tnum, iDb);
+          sqlite3VdbeSetP4KeyInfo(pParse, pIx);
+        }
+        sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
+      }
+      if( pLevel->op==OP_Return ){
+        sqlite3VdbeAddOp2(v, OP_Gosub, pLevel->p1, pLevel->addrFirst);
+      }else{
+        sqlite3VdbeGoto(v, pLevel->addrFirst);
+      }
+      sqlite3VdbeJumpHere(v, addr);
+    }
+    VdbeModuleComment((v, "End WHERE-loop%d: %s", i,
+                     pWInfo->pTabList->a[pLevel->iFrom].pTab->zName));
+  }
+
+  assert( pWInfo->nLevel<=pTabList->nSrc );
+  for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
+    int k, last;
+    VdbeOp *pOp, *pLastOp;
+    Index *pIdx = 0;
+    SrcItem *pTabItem = &pTabList->a[pLevel->iFrom];
+    Table *pTab = pTabItem->pTab;
+    assert( pTab!=0 );
+    pLoop = pLevel->pWLoop;
+
+    /* Do RIGHT JOIN processing.  Generate code that will output the
+    ** unmatched rows of the right operand of the RIGHT JOIN with
+    ** all of the columns of the left operand set to NULL.
+    */
+    if( pLevel->pRJ ){
+      sqlite3WhereRightJoinLoop(pWInfo, i, pLevel);
+      continue;
+    }
+
+    /* For a co-routine, change all OP_Column references to the table of
+    ** the co-routine into OP_Copy of result contained in a register.
+    ** OP_Rowid becomes OP_Null.
+    */
+    if( pTabItem->fg.viaCoroutine ){
+      testcase( pParse->db->mallocFailed );
+      translateColumnToCopy(pParse, pLevel->addrBody, pLevel->iTabCur,
+                            pTabItem->regResult, 0);
+      continue;
+    }
+
+    /* If this scan uses an index, make VDBE code substitutions to read data
+    ** from the index instead of from the table where possible.  In some cases
+    ** this optimization prevents the table from ever being read, which can
+    ** yield a significant performance boost.
+    **
+    ** Calls to the code generator in between sqlite3WhereBegin and
+    ** sqlite3WhereEnd will have created code that references the table
+    ** directly.  This loop scans all that code looking for opcodes
+    ** that reference the table and converts them into opcodes that
+    ** reference the index.
+    */
+    if( pLoop->wsFlags & (WHERE_INDEXED|WHERE_IDX_ONLY) ){
+      pIdx = pLoop->u.btree.pIndex;
+    }else if( pLoop->wsFlags & WHERE_MULTI_OR ){
+      pIdx = pLevel->u.pCoveringIdx;
+    }
+    if( pIdx
+     && !db->mallocFailed
+    ){
+      if( pWInfo->eOnePass==ONEPASS_OFF || !HasRowid(pIdx->pTable) ){
+        last = iEnd;
+      }else{
+        last = pWInfo->iEndWhere;
+      }
+      if( pIdx->bHasExpr ){
+        IndexedExpr *p = pParse->pIdxEpr;
+        while( p ){
+          if( p->iIdxCur==pLevel->iIdxCur ){
+#ifdef WHERETRACE_ENABLED
+            if( sqlite3WhereTrace & 0x200 ){
+              sqlite3DebugPrintf("Disable pParse->pIdxEpr term {%d,%d}\n",
+                                  p->iIdxCur, p->iIdxCol);
+              if( sqlite3WhereTrace & 0x5000 ) sqlite3ShowExpr(p->pExpr);
+            }
+#endif
+            p->iDataCur = -1;
+            p->iIdxCur = -1;
+          }
+          p = p->pIENext;
+        }
+      }
+      k = pLevel->addrBody + 1;
+#ifdef SQLITE_DEBUG
+      if( db->flags & SQLITE_VdbeAddopTrace ){
+        printf("TRANSLATE cursor %d->%d in opcode range %d..%d\n",
+                pLevel->iTabCur, pLevel->iIdxCur, k, last-1);
+      }
+      /* Proof that the "+1" on the k value above is safe */
+      pOp = sqlite3VdbeGetOp(v, k - 1);
+      assert( pOp->opcode!=OP_Column || pOp->p1!=pLevel->iTabCur );
+      assert( pOp->opcode!=OP_Rowid  || pOp->p1!=pLevel->iTabCur );
+      assert( pOp->opcode!=OP_IfNullRow || pOp->p1!=pLevel->iTabCur );
+#endif
+      pOp = sqlite3VdbeGetOp(v, k);
+      pLastOp = pOp + (last - k);
+      assert( pOp<=pLastOp );
+      do{
+        if( pOp->p1!=pLevel->iTabCur ){
+          /* no-op */
+        }else if( pOp->opcode==OP_Column
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+         || pOp->opcode==OP_Offset
+#endif
+        ){
+          int x = pOp->p2;
+          assert( pIdx->pTable==pTab );
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+          if( pOp->opcode==OP_Offset ){
+            /* Do not need to translate the column number */
+          }else
+#endif
+          if( !HasRowid(pTab) ){
+            Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+            x = pPk->aiColumn[x];
+            assert( x>=0 );
+          }else{
+            testcase( x!=sqlite3StorageColumnToTable(pTab,x) );
+            x = sqlite3StorageColumnToTable(pTab,x);
+          }
+          x = sqlite3TableColumnToIndex(pIdx, x);
+          if( x>=0 ){
+            pOp->p2 = x;
+            pOp->p1 = pLevel->iIdxCur;
+            OpcodeRewriteTrace(db, k, pOp);
+          }else{
+            /* Unable to translate the table reference into an index
+            ** reference.  Verify that this is harmless - that the
+            ** table being referenced really is open.
+            */
+#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
+            assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
+                 || cursorIsOpen(v,pOp->p1,k)
+                 || pOp->opcode==OP_Offset
+            );
+#else
+            assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
+                 || cursorIsOpen(v,pOp->p1,k)
+            );
+#endif
+          }
+        }else if( pOp->opcode==OP_Rowid ){
+          pOp->p1 = pLevel->iIdxCur;
+          pOp->opcode = OP_IdxRowid;
+          OpcodeRewriteTrace(db, k, pOp);
+        }else if( pOp->opcode==OP_IfNullRow ){
+          pOp->p1 = pLevel->iIdxCur;
+          OpcodeRewriteTrace(db, k, pOp);
+        }
+#ifdef SQLITE_DEBUG
+        k++;
+#endif
+      }while( (++pOp)<pLastOp );
+#ifdef SQLITE_DEBUG
+      if( db->flags & SQLITE_VdbeAddopTrace ) printf("TRANSLATE complete\n");
+#endif
+    }
+  }
+
+  /* The "break" point is here, just past the end of the outer loop.
+  ** Set it.
+  */
+  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
+
+  /* Final cleanup
+  */
+  pParse->nQueryLoop = pWInfo->savedNQueryLoop;
+  whereInfoFree(db, pWInfo);
+  pParse->withinRJSubrtn -= nRJ;
+  return;
+}
diff --git a/src/whereInt.h b/src/whereInt.h
new file mode 100644
index 0000000..f3cc577
--- /dev/null
+++ b/src/whereInt.h
@@ -0,0 +1,639 @@
+/*
+** 2013-11-12
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains structure and macro definitions for the query
+** planner logic in "where.c".  These definitions are broken out into
+** a separate source file for easier editing.
+*/
+#ifndef SQLITE_WHEREINT_H
+#define SQLITE_WHEREINT_H
+
+
+/* Forward references
+*/
+typedef struct WhereClause WhereClause;
+typedef struct WhereMaskSet WhereMaskSet;
+typedef struct WhereOrInfo WhereOrInfo;
+typedef struct WhereAndInfo WhereAndInfo;
+typedef struct WhereLevel WhereLevel;
+typedef struct WhereLoop WhereLoop;
+typedef struct WherePath WherePath;
+typedef struct WhereTerm WhereTerm;
+typedef struct WhereLoopBuilder WhereLoopBuilder;
+typedef struct WhereScan WhereScan;
+typedef struct WhereOrCost WhereOrCost;
+typedef struct WhereOrSet WhereOrSet;
+typedef struct WhereMemBlock WhereMemBlock;
+typedef struct WhereRightJoin WhereRightJoin;
+
+/*
+** This object is a header on a block of allocated memory that will be
+** automatically freed when its WInfo object is destructed.
+*/
+struct WhereMemBlock {
+  WhereMemBlock *pNext;      /* Next block in the chain */
+  u64 sz;                    /* Bytes of space */
+};
+
+/*
+** Extra information attached to a WhereLevel that is a RIGHT JOIN.
+*/
+struct WhereRightJoin {
+  int iMatch;          /* Cursor used to determine prior matched rows */
+  int regBloom;        /* Bloom filter for iRJMatch */
+  int regReturn;       /* Return register for the interior subroutine */
+  int addrSubrtn;      /* Starting address for the interior subroutine */
+  int endSubrtn;       /* The last opcode in the interior subroutine */
+};
+
+/*
+** This object contains information needed to implement a single nested
+** loop in WHERE clause.
+**
+** Contrast this object with WhereLoop.  This object describes the
+** implementation of the loop.  WhereLoop describes the algorithm.
+** This object contains a pointer to the WhereLoop algorithm as one of
+** its elements.
+**
+** The WhereInfo object contains a single instance of this object for
+** each term in the FROM clause (which is to say, for each of the
+** nested loops as implemented).  The order of WhereLevel objects determines
+** the loop nested order, with WhereInfo.a[0] being the outer loop and
+** WhereInfo.a[WhereInfo.nLevel-1] being the inner loop.
+*/
+struct WhereLevel {
+  int iLeftJoin;        /* Memory cell used to implement LEFT OUTER JOIN */
+  int iTabCur;          /* The VDBE cursor used to access the table */
+  int iIdxCur;          /* The VDBE cursor used to access pIdx */
+  int addrBrk;          /* Jump here to break out of the loop */
+  int addrNxt;          /* Jump here to start the next IN combination */
+  int addrSkip;         /* Jump here for next iteration of skip-scan */
+  int addrCont;         /* Jump here to continue with the next loop cycle */
+  int addrFirst;        /* First instruction of interior of the loop */
+  int addrBody;         /* Beginning of the body of this loop */
+  int regBignull;       /* big-null flag reg. True if a NULL-scan is needed */
+  int addrBignull;      /* Jump here for next part of big-null scan */
+#ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+  u32 iLikeRepCntr;     /* LIKE range processing counter register (times 2) */
+  int addrLikeRep;      /* LIKE range processing address */
+#endif
+  int regFilter;        /* Bloom filter */
+  WhereRightJoin *pRJ;  /* Extra information for RIGHT JOIN */
+  u8 iFrom;             /* Which entry in the FROM clause */
+  u8 op, p3, p5;        /* Opcode, P3 & P5 of the opcode that ends the loop */
+  int p1, p2;           /* Operands of the opcode used to end the loop */
+  union {               /* Information that depends on pWLoop->wsFlags */
+    struct {
+      int nIn;              /* Number of entries in aInLoop[] */
+      struct InLoop {
+        int iCur;              /* The VDBE cursor used by this IN operator */
+        int addrInTop;         /* Top of the IN loop */
+        int iBase;             /* Base register of multi-key index record */
+        int nPrefix;           /* Number of prior entries in the key */
+        u8 eEndLoopOp;         /* IN Loop terminator. OP_Next or OP_Prev */
+      } *aInLoop;           /* Information about each nested IN operator */
+    } in;                 /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
+    Index *pCoveringIdx;  /* Possible covering index for WHERE_MULTI_OR */
+  } u;
+  struct WhereLoop *pWLoop;  /* The selected WhereLoop object */
+  Bitmask notReady;          /* FROM entries not usable at this level */
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  int addrVisit;        /* Address at which row is visited */
+#endif
+};
+
+/*
+** Each instance of this object represents an algorithm for evaluating one
+** term of a join.  Every term of the FROM clause will have at least
+** one corresponding WhereLoop object (unless INDEXED BY constraints
+** prevent a query solution - which is an error) and many terms of the
+** FROM clause will have multiple WhereLoop objects, each describing a
+** potential way of implementing that FROM-clause term, together with
+** dependencies and cost estimates for using the chosen algorithm.
+**
+** Query planning consists of building up a collection of these WhereLoop
+** objects, then computing a particular sequence of WhereLoop objects, with
+** one WhereLoop object per FROM clause term, that satisfy all dependencies
+** and that minimize the overall cost.
+*/
+struct WhereLoop {
+  Bitmask prereq;       /* Bitmask of other loops that must run first */
+  Bitmask maskSelf;     /* Bitmask identifying table iTab */
+#ifdef SQLITE_DEBUG
+  char cId;             /* Symbolic ID of this loop for debugging use */
+#endif
+  u8 iTab;              /* Position in FROM clause of table for this loop */
+  u8 iSortIdx;          /* Sorting index number.  0==None */
+  LogEst rSetup;        /* One-time setup cost (ex: create transient index) */
+  LogEst rRun;          /* Cost of running each loop */
+  LogEst nOut;          /* Estimated number of output rows */
+  union {
+    struct {               /* Information for internal btree tables */
+      u16 nEq;               /* Number of equality constraints */
+      u16 nBtm;              /* Size of BTM vector */
+      u16 nTop;              /* Size of TOP vector */
+      u16 nDistinctCol;      /* Index columns used to sort for DISTINCT */
+      Index *pIndex;         /* Index used, or NULL */
+    } btree;
+    struct {               /* Information for virtual tables */
+      int idxNum;            /* Index number */
+      u32 needFree : 1;      /* True if sqlite3_free(idxStr) is needed */
+      u32 bOmitOffset : 1;   /* True to let virtual table handle offset */
+      i8 isOrdered;          /* True if satisfies ORDER BY */
+      u16 omitMask;          /* Terms that may be omitted */
+      char *idxStr;          /* Index identifier string */
+      u32 mHandleIn;         /* Terms to handle as IN(...) instead of == */
+    } vtab;
+  } u;
+  u32 wsFlags;          /* WHERE_* flags describing the plan */
+  u16 nLTerm;           /* Number of entries in aLTerm[] */
+  u16 nSkip;            /* Number of NULL aLTerm[] entries */
+  /**** whereLoopXfer() copies fields above ***********************/
+# define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot)
+  u16 nLSlot;           /* Number of slots allocated for aLTerm[] */
+  WhereTerm **aLTerm;   /* WhereTerms used */
+  WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */
+  WhereTerm *aLTermSpace[3];  /* Initial aLTerm[] space */
+};
+
+/* This object holds the prerequisites and the cost of running a
+** subquery on one operand of an OR operator in the WHERE clause.
+** See WhereOrSet for additional information
+*/
+struct WhereOrCost {
+  Bitmask prereq;     /* Prerequisites */
+  LogEst rRun;        /* Cost of running this subquery */
+  LogEst nOut;        /* Number of outputs for this subquery */
+};
+
+/* The WhereOrSet object holds a set of possible WhereOrCosts that
+** correspond to the subquery(s) of OR-clause processing.  Only the
+** best N_OR_COST elements are retained.
+*/
+#define N_OR_COST 3
+struct WhereOrSet {
+  u16 n;                      /* Number of valid a[] entries */
+  WhereOrCost a[N_OR_COST];   /* Set of best costs */
+};
+
+/*
+** Each instance of this object holds a sequence of WhereLoop objects
+** that implement some or all of a query plan.
+**
+** Think of each WhereLoop object as a node in a graph with arcs
+** showing dependencies and costs for travelling between nodes.  (That is
+** not a completely accurate description because WhereLoop costs are a
+** vector, not a scalar, and because dependencies are many-to-one, not
+** one-to-one as are graph nodes.  But it is a useful visualization aid.)
+** Then a WherePath object is a path through the graph that visits some
+** or all of the WhereLoop objects once.
+**
+** The "solver" works by creating the N best WherePath objects of length
+** 1.  Then using those as a basis to compute the N best WherePath objects
+** of length 2.  And so forth until the length of WherePaths equals the
+** number of nodes in the FROM clause.  The best (lowest cost) WherePath
+** at the end is the chosen query plan.
+*/
+struct WherePath {
+  Bitmask maskLoop;     /* Bitmask of all WhereLoop objects in this path */
+  Bitmask revLoop;      /* aLoop[]s that should be reversed for ORDER BY */
+  LogEst nRow;          /* Estimated number of rows generated by this path */
+  LogEst rCost;         /* Total cost of this path */
+  LogEst rUnsorted;     /* Total cost of this path ignoring sorting costs */
+  i8 isOrdered;         /* No. of ORDER BY terms satisfied. -1 for unknown */
+  WhereLoop **aLoop;    /* Array of WhereLoop objects implementing this path */
+};
+
+/*
+** The query generator uses an array of instances of this structure to
+** help it analyze the subexpressions of the WHERE clause.  Each WHERE
+** clause subexpression is separated from the others by AND operators,
+** usually, or sometimes subexpressions separated by OR.
+**
+** All WhereTerms are collected into a single WhereClause structure. 
+** The following identity holds:
+**
+**        WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
+**
+** When a term is of the form:
+**
+**              X <op> <expr>
+**
+** where X is a column name and <op> is one of certain operators,
+** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
+** cursor number and column number for X.  WhereTerm.eOperator records
+** the <op> using a bitmask encoding defined by WO_xxx below.  The
+** use of a bitmask encoding for the operator allows us to search
+** quickly for terms that match any of several different operators.
+**
+** A WhereTerm might also be two or more subterms connected by OR:
+**
+**         (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
+**
+** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR
+** and the WhereTerm.u.pOrInfo field points to auxiliary information that
+** is collected about the OR clause.
+**
+** If a term in the WHERE clause does not match either of the two previous
+** categories, then eOperator==0.  The WhereTerm.pExpr field is still set
+** to the original subexpression content and wtFlags is set up appropriately
+** but no other fields in the WhereTerm object are meaningful.
+**
+** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
+** but they do so indirectly.  A single WhereMaskSet structure translates
+** cursor number into bits and the translated bit is stored in the prereq
+** fields.  The translation is used in order to maximize the number of
+** bits that will fit in a Bitmask.  The VDBE cursor numbers might be
+** spread out over the non-negative integers.  For example, the cursor
+** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45.  The WhereMaskSet
+** translates these sparse cursor numbers into consecutive integers
+** beginning with 0 in order to make the best possible use of the available
+** bits in the Bitmask.  So, in the example above, the cursor numbers
+** would be mapped into integers 0 through 7.
+**
+** The number of terms in a join is limited by the number of bits
+** in prereqRight and prereqAll.  The default is 64 bits, hence SQLite
+** is only able to process joins with 64 or fewer tables.
+*/
+struct WhereTerm {
+  Expr *pExpr;            /* Pointer to the subexpression that is this term */
+  WhereClause *pWC;       /* The clause this term is part of */
+  LogEst truthProb;       /* Probability of truth for this expression */
+  u16 wtFlags;            /* TERM_xxx bit flags.  See below */
+  u16 eOperator;          /* A WO_xx value describing <op> */
+  u8 nChild;              /* Number of children that must disable us */
+  u8 eMatchOp;            /* Op for vtab MATCH/LIKE/GLOB/REGEXP terms */
+  int iParent;            /* Disable pWC->a[iParent] when this term disabled */
+  int leftCursor;         /* Cursor number of X in "X <op> <expr>" */
+  union {
+    struct {
+      int leftColumn;         /* Column number of X in "X <op> <expr>" */
+      int iField;             /* Field in (?,?,?) IN (SELECT...) vector */
+    } x;                    /* Opcode other than OP_OR or OP_AND */
+    WhereOrInfo *pOrInfo;   /* Extra information if (eOperator & WO_OR)!=0 */
+    WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */
+  } u;
+  Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
+  Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */
+};
+
+/*
+** Allowed values of WhereTerm.wtFlags
+*/
+#define TERM_DYNAMIC    0x0001 /* Need to call sqlite3ExprDelete(db, pExpr) */
+#define TERM_VIRTUAL    0x0002 /* Added by the optimizer.  Do not code */
+#define TERM_CODED      0x0004 /* This term is already coded */
+#define TERM_COPIED     0x0008 /* Has a child */
+#define TERM_ORINFO     0x0010 /* Need to free the WhereTerm.u.pOrInfo object */
+#define TERM_ANDINFO    0x0020 /* Need to free the WhereTerm.u.pAndInfo obj */
+#define TERM_OK         0x0040 /* Used during OR-clause processing */
+#define TERM_VNULL      0x0080 /* Manufactured x>NULL or x<=NULL term */
+#define TERM_LIKEOPT    0x0100 /* Virtual terms from the LIKE optimization */
+#define TERM_LIKECOND   0x0200 /* Conditionally this LIKE operator term */
+#define TERM_LIKE       0x0400 /* The original LIKE operator */
+#define TERM_IS         0x0800 /* Term.pExpr is an IS operator */
+#define TERM_VARSELECT  0x1000 /* Term.pExpr contains a correlated sub-query */
+#define TERM_HEURTRUTH  0x2000 /* Heuristic truthProb used */
+#ifdef SQLITE_ENABLE_STAT4
+#  define TERM_HIGHTRUTH  0x4000 /* Term excludes few rows */
+#else
+#  define TERM_HIGHTRUTH  0      /* Only used with STAT4 */
+#endif
+#define TERM_SLICE      0x8000 /* One slice of a row-value/vector comparison */
+
+/*
+** An instance of the WhereScan object is used as an iterator for locating
+** terms in the WHERE clause that are useful to the query planner.
+*/
+struct WhereScan {
+  WhereClause *pOrigWC;      /* Original, innermost WhereClause */
+  WhereClause *pWC;          /* WhereClause currently being scanned */
+  const char *zCollName;     /* Required collating sequence, if not NULL */
+  Expr *pIdxExpr;            /* Search for this index expression */
+  int k;                     /* Resume scanning at this->pWC->a[this->k] */
+  u32 opMask;                /* Acceptable operators */
+  char idxaff;               /* Must match this affinity, if zCollName!=NULL */
+  unsigned char iEquiv;      /* Current slot in aiCur[] and aiColumn[] */
+  unsigned char nEquiv;      /* Number of entries in aiCur[] and aiColumn[] */
+  int aiCur[11];             /* Cursors in the equivalence class */
+  i16 aiColumn[11];          /* Corresponding column number in the eq-class */
+};
+
+/*
+** An instance of the following structure holds all information about a
+** WHERE clause.  Mostly this is a container for one or more WhereTerms.
+**
+** Explanation of pOuter:  For a WHERE clause of the form
+**
+**           a AND ((b AND c) OR (d AND e)) AND f
+**
+** There are separate WhereClause objects for the whole clause and for
+** the subclauses "(b AND c)" and "(d AND e)".  The pOuter field of the
+** subclauses points to the WhereClause object for the whole clause.
+*/
+struct WhereClause {
+  WhereInfo *pWInfo;       /* WHERE clause processing context */
+  WhereClause *pOuter;     /* Outer conjunction */
+  u8 op;                   /* Split operator.  TK_AND or TK_OR */
+  u8 hasOr;                /* True if any a[].eOperator is WO_OR */
+  int nTerm;               /* Number of terms */
+  int nSlot;               /* Number of entries in a[] */
+  int nBase;               /* Number of terms through the last non-Virtual */
+  WhereTerm *a;            /* Each a[] describes a term of the WHERE clause */
+#if defined(SQLITE_SMALL_STACK)
+  WhereTerm aStatic[1];    /* Initial static space for a[] */
+#else
+  WhereTerm aStatic[8];    /* Initial static space for a[] */
+#endif
+};
+
+/*
+** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
+** a dynamically allocated instance of the following structure.
+*/
+struct WhereOrInfo {
+  WhereClause wc;          /* Decomposition into subterms */
+  Bitmask indexable;       /* Bitmask of all indexable tables in the clause */
+};
+
+/*
+** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
+** a dynamically allocated instance of the following structure.
+*/
+struct WhereAndInfo {
+  WhereClause wc;          /* The subexpression broken out */
+};
+
+/*
+** An instance of the following structure keeps track of a mapping
+** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
+**
+** The VDBE cursor numbers are small integers contained in
+** SrcItem.iCursor and Expr.iTable fields.  For any given WHERE
+** clause, the cursor numbers might not begin with 0 and they might
+** contain gaps in the numbering sequence.  But we want to make maximum
+** use of the bits in our bitmasks.  This structure provides a mapping
+** from the sparse cursor numbers into consecutive integers beginning
+** with 0.
+**
+** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
+** corresponds VDBE cursor number B.  The A-th bit of a bitmask is 1<<A.
+**
+** For example, if the WHERE clause expression used these VDBE
+** cursors:  4, 5, 8, 29, 57, 73.  Then the  WhereMaskSet structure
+** would map those cursor numbers into bits 0 through 5.
+**
+** Note that the mapping is not necessarily ordered.  In the example
+** above, the mapping might go like this:  4->3, 5->1, 8->2, 29->0,
+** 57->5, 73->4.  Or one of 719 other combinations might be used. It
+** does not really matter.  What is important is that sparse cursor
+** numbers all get mapped into bit numbers that begin with 0 and contain
+** no gaps.
+*/
+struct WhereMaskSet {
+  int bVarSelect;               /* Used by sqlite3WhereExprUsage() */
+  int n;                        /* Number of assigned cursor values */
+  int ix[BMS];                  /* Cursor assigned to each bit */
+};
+
+/*
+** This object is a convenience wrapper holding all information needed
+** to construct WhereLoop objects for a particular query.
+*/
+struct WhereLoopBuilder {
+  WhereInfo *pWInfo;        /* Information about this WHERE */
+  WhereClause *pWC;         /* WHERE clause terms */
+  WhereLoop *pNew;          /* Template WhereLoop */
+  WhereOrSet *pOrSet;       /* Record best loops here, if not NULL */
+#ifdef SQLITE_ENABLE_STAT4
+  UnpackedRecord *pRec;     /* Probe for stat4 (if required) */
+  int nRecValid;            /* Number of valid fields currently in pRec */
+#endif
+  unsigned char bldFlags1;  /* First set of SQLITE_BLDF_* flags */
+  unsigned char bldFlags2;  /* Second set of SQLITE_BLDF_* flags */
+  unsigned int iPlanLimit;  /* Search limiter */
+};
+
+/* Allowed values for WhereLoopBuider.bldFlags */
+#define SQLITE_BLDF1_INDEXED  0x0001   /* An index is used */
+#define SQLITE_BLDF1_UNIQUE   0x0002   /* All keys of a UNIQUE index used */
+
+#define SQLITE_BLDF2_2NDPASS  0x0004   /* Second builder pass needed */
+
+/* The WhereLoopBuilder.iPlanLimit is used to limit the number of
+** index+constraint combinations the query planner will consider for a
+** particular query.  If this parameter is unlimited, then certain
+** pathological queries can spend excess time in the sqlite3WhereBegin()
+** routine.  The limit is high enough that is should not impact real-world
+** queries.
+**
+** SQLITE_QUERY_PLANNER_LIMIT is the baseline limit.  The limit is
+** increased by SQLITE_QUERY_PLANNER_LIMIT_INCR before each term of the FROM
+** clause is processed, so that every table in a join is guaranteed to be
+** able to propose a some index+constraint combinations even if the initial
+** baseline limit was exhausted by prior tables of the join.
+*/
+#ifndef SQLITE_QUERY_PLANNER_LIMIT
+# define SQLITE_QUERY_PLANNER_LIMIT 20000
+#endif
+#ifndef SQLITE_QUERY_PLANNER_LIMIT_INCR
+# define SQLITE_QUERY_PLANNER_LIMIT_INCR 1000
+#endif
+
+/*
+** The WHERE clause processing routine has two halves.  The
+** first part does the start of the WHERE loop and the second
+** half does the tail of the WHERE loop.  An instance of
+** this structure is returned by the first half and passed
+** into the second half to give some continuity.
+**
+** An instance of this object holds the complete state of the query
+** planner.
+*/
+struct WhereInfo {
+  Parse *pParse;            /* Parsing and code generating context */
+  SrcList *pTabList;        /* List of tables in the join */
+  ExprList *pOrderBy;       /* The ORDER BY clause or NULL */
+  ExprList *pResultSet;     /* Result set of the query */
+#if WHERETRACE_ENABLED
+  Expr *pWhere;             /* The complete WHERE clause */
+#endif
+  Select *pSelect;          /* The entire SELECT statement containing WHERE */
+  int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
+  int iContinue;            /* Jump here to continue with next record */
+  int iBreak;               /* Jump here to break out of the loop */
+  int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
+  u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
+  LogEst iLimit;            /* LIMIT if wctrlFlags has WHERE_USE_LIMIT */
+  u8 nLevel;                /* Number of nested loop */
+  i8 nOBSat;                /* Number of ORDER BY terms satisfied by indices */
+  u8 eOnePass;              /* ONEPASS_OFF, or _SINGLE, or _MULTI */
+  u8 eDistinct;             /* One of the WHERE_DISTINCT_* values */
+  unsigned bDeferredSeek :1;   /* Uses OP_DeferredSeek */
+  unsigned untestedTerms :1;   /* Not all WHERE terms resolved by outer loop */
+  unsigned bOrderedInnerLoop:1;/* True if only the inner-most loop is ordered */
+  unsigned sorted :1;          /* True if really sorted (not just grouped) */
+  LogEst nRowOut;           /* Estimated number of output rows */
+  int iTop;                 /* The very beginning of the WHERE loop */
+  int iEndWhere;            /* End of the WHERE clause itself */
+  WhereLoop *pLoops;        /* List of all WhereLoop objects */
+  WhereMemBlock *pMemToFree;/* Memory to free when this object destroyed */
+  Bitmask revMask;          /* Mask of ORDER BY terms that need reversing */
+  WhereClause sWC;          /* Decomposition of the WHERE clause */
+  WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
+  WhereLevel a[1];          /* Information about each nest loop in WHERE */
+};
+
+/*
+** Private interfaces - callable only by other where.c routines.
+**
+** where.c:
+*/
+Bitmask sqlite3WhereGetMask(WhereMaskSet*,int);
+#ifdef WHERETRACE_ENABLED
+void sqlite3WhereClausePrint(WhereClause *pWC);
+void sqlite3WhereTermPrint(WhereTerm *pTerm, int iTerm);
+void sqlite3WhereLoopPrint(const WhereLoop *p, const WhereClause *pWC);
+#endif
+WhereTerm *sqlite3WhereFindTerm(
+  WhereClause *pWC,     /* The WHERE clause to be searched */
+  int iCur,             /* Cursor number of LHS */
+  int iColumn,          /* Column number of LHS */
+  Bitmask notReady,     /* RHS must not overlap with this mask */
+  u32 op,               /* Mask of WO_xx values describing operator */
+  Index *pIdx           /* Must be compatible with this index, if not NULL */
+);
+void *sqlite3WhereMalloc(WhereInfo *pWInfo, u64 nByte);
+void *sqlite3WhereRealloc(WhereInfo *pWInfo, void *pOld, u64 nByte);
+
+/* wherecode.c: */
+#ifndef SQLITE_OMIT_EXPLAIN
+int sqlite3WhereExplainOneScan(
+  Parse *pParse,                  /* Parse context */
+  SrcList *pTabList,              /* Table list this loop refers to */
+  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
+  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
+);
+int sqlite3WhereExplainBloomFilter(
+  const Parse *pParse,            /* Parse context */
+  const WhereInfo *pWInfo,        /* WHERE clause */
+  const WhereLevel *pLevel        /* Bloom filter on this level */
+);
+#else
+# define sqlite3WhereExplainOneScan(u,v,w,x) 0
+# define sqlite3WhereExplainBloomFilter(u,v,w) 0
+#endif /* SQLITE_OMIT_EXPLAIN */
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+void sqlite3WhereAddScanStatus(
+  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
+  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
+  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
+  int addrExplain                 /* Address of OP_Explain (or 0) */
+);
+#else
+# define sqlite3WhereAddScanStatus(a, b, c, d) ((void)d)
+#endif
+Bitmask sqlite3WhereCodeOneLoopStart(
+  Parse *pParse,       /* Parsing context */
+  Vdbe *v,             /* Prepared statement under construction */
+  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
+  int iLevel,          /* Which level of pWInfo->a[] should be coded */
+  WhereLevel *pLevel,  /* The current level pointer */
+  Bitmask notReady     /* Which tables are currently available */
+);
+SQLITE_NOINLINE void sqlite3WhereRightJoinLoop(
+  WhereInfo *pWInfo,
+  int iLevel,
+  WhereLevel *pLevel
+);
+
+/* whereexpr.c: */
+void sqlite3WhereClauseInit(WhereClause*,WhereInfo*);
+void sqlite3WhereClauseClear(WhereClause*);
+void sqlite3WhereSplit(WhereClause*,Expr*,u8);
+void sqlite3WhereAddLimit(WhereClause*, Select*);
+Bitmask sqlite3WhereExprUsage(WhereMaskSet*, Expr*);
+Bitmask sqlite3WhereExprUsageNN(WhereMaskSet*, Expr*);
+Bitmask sqlite3WhereExprListUsage(WhereMaskSet*, ExprList*);
+void sqlite3WhereExprAnalyze(SrcList*, WhereClause*);
+void sqlite3WhereTabFuncArgs(Parse*, SrcItem*, WhereClause*);
+
+
+
+
+
+/*
+** Bitmasks for the operators on WhereTerm objects.  These are all
+** operators that are of interest to the query planner.  An
+** OR-ed combination of these values can be used when searching for
+** particular WhereTerms within a WhereClause.
+**
+** Value constraints:
+**     WO_EQ    == SQLITE_INDEX_CONSTRAINT_EQ
+**     WO_LT    == SQLITE_INDEX_CONSTRAINT_LT
+**     WO_LE    == SQLITE_INDEX_CONSTRAINT_LE
+**     WO_GT    == SQLITE_INDEX_CONSTRAINT_GT
+**     WO_GE    == SQLITE_INDEX_CONSTRAINT_GE
+*/
+#define WO_IN     0x0001
+#define WO_EQ     0x0002
+#define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
+#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
+#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
+#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
+#define WO_AUX    0x0040       /* Op useful to virtual tables only */
+#define WO_IS     0x0080
+#define WO_ISNULL 0x0100
+#define WO_OR     0x0200       /* Two or more OR-connected terms */
+#define WO_AND    0x0400       /* Two or more AND-connected terms */
+#define WO_EQUIV  0x0800       /* Of the form A==B, both columns */
+#define WO_NOOP   0x1000       /* This term does not restrict search space */
+#define WO_ROWVAL 0x2000       /* A row-value term */
+
+#define WO_ALL    0x3fff       /* Mask of all possible WO_* values */
+#define WO_SINGLE 0x01ff       /* Mask of all non-compound WO_* values */
+
+/*
+** These are definitions of bits in the WhereLoop.wsFlags field.
+** The particular combination of bits in each WhereLoop help to
+** determine the algorithm that WhereLoop represents.
+*/
+#define WHERE_COLUMN_EQ    0x00000001  /* x=EXPR */
+#define WHERE_COLUMN_RANGE 0x00000002  /* x<EXPR and/or x>EXPR */
+#define WHERE_COLUMN_IN    0x00000004  /* x IN (...) */
+#define WHERE_COLUMN_NULL  0x00000008  /* x IS NULL */
+#define WHERE_CONSTRAINT   0x0000000f  /* Any of the WHERE_COLUMN_xxx values */
+#define WHERE_TOP_LIMIT    0x00000010  /* x<EXPR or x<=EXPR constraint */
+#define WHERE_BTM_LIMIT    0x00000020  /* x>EXPR or x>=EXPR constraint */
+#define WHERE_BOTH_LIMIT   0x00000030  /* Both x>EXPR and x<EXPR */
+#define WHERE_IDX_ONLY     0x00000040  /* Use index only - omit table */
+#define WHERE_IPK          0x00000100  /* x is the INTEGER PRIMARY KEY */
+#define WHERE_INDEXED      0x00000200  /* WhereLoop.u.btree.pIndex is valid */
+#define WHERE_VIRTUALTABLE 0x00000400  /* WhereLoop.u.vtab is valid */
+#define WHERE_IN_ABLE      0x00000800  /* Able to support an IN operator */
+#define WHERE_ONEROW       0x00001000  /* Selects no more than one row */
+#define WHERE_MULTI_OR     0x00002000  /* OR using multiple indices */
+#define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
+#define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
+#define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
+#define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
+#define WHERE_IN_EARLYOUT  0x00040000  /* Perhaps quit IN loops early */
+#define WHERE_BIGNULL_SORT 0x00080000  /* Column nEq of index is BIGNULL */
+#define WHERE_IN_SEEKSCAN  0x00100000  /* Seek-scan optimization for IN */
+#define WHERE_TRANSCONS    0x00200000  /* Uses a transitive constraint */
+#define WHERE_BLOOMFILTER  0x00400000  /* Consider using a Bloom-filter */
+#define WHERE_SELFCULL     0x00800000  /* nOut reduced by extra WHERE terms */
+#define WHERE_OMIT_OFFSET  0x01000000  /* Set offset counter to zero */
+                      /*   0x02000000  -- available for reuse */
+#define WHERE_EXPRIDX      0x04000000  /* Uses an index-on-expressions */
+
+#endif /* !defined(SQLITE_WHEREINT_H) */
diff --git a/src/wherecode.c b/src/wherecode.c
new file mode 100644
index 0000000..47ce36c
--- /dev/null
+++ b/src/wherecode.c
@@ -0,0 +1,2789 @@
+/*
+** 2015-06-06
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This module contains C code that generates VDBE code used to process
+** the WHERE clause of SQL statements.
+**
+** This file was split off from where.c on 2015-06-06 in order to reduce the
+** size of where.c and make it easier to edit.  This file contains the routines
+** that actually generate the bulk of the WHERE loop code.  The original where.c
+** file retains the code that does query planning and analysis.
+*/
+#include "sqliteInt.h"
+#include "whereInt.h"
+
+#ifndef SQLITE_OMIT_EXPLAIN
+
+/*
+** Return the name of the i-th column of the pIdx index.
+*/
+static const char *explainIndexColumnName(Index *pIdx, int i){
+  i = pIdx->aiColumn[i];
+  if( i==XN_EXPR ) return "<expr>";
+  if( i==XN_ROWID ) return "rowid";
+  return pIdx->pTable->aCol[i].zCnName;
+}
+
+/*
+** This routine is a helper for explainIndexRange() below
+**
+** pStr holds the text of an expression that we are building up one term
+** at a time.  This routine adds a new term to the end of the expression.
+** Terms are separated by AND so add the "AND" text for second and subsequent
+** terms only.
+*/
+static void explainAppendTerm(
+  StrAccum *pStr,             /* The text expression being built */
+  Index *pIdx,                /* Index to read column names from */
+  int nTerm,                  /* Number of terms */
+  int iTerm,                  /* Zero-based index of first term. */
+  int bAnd,                   /* Non-zero to append " AND " */
+  const char *zOp             /* Name of the operator */
+){
+  int i;
+
+  assert( nTerm>=1 );
+  if( bAnd ) sqlite3_str_append(pStr, " AND ", 5);
+
+  if( nTerm>1 ) sqlite3_str_append(pStr, "(", 1);
+  for(i=0; i<nTerm; i++){
+    if( i ) sqlite3_str_append(pStr, ",", 1);
+    sqlite3_str_appendall(pStr, explainIndexColumnName(pIdx, iTerm+i));
+  }
+  if( nTerm>1 ) sqlite3_str_append(pStr, ")", 1);
+
+  sqlite3_str_append(pStr, zOp, 1);
+
+  if( nTerm>1 ) sqlite3_str_append(pStr, "(", 1);
+  for(i=0; i<nTerm; i++){
+    if( i ) sqlite3_str_append(pStr, ",", 1);
+    sqlite3_str_append(pStr, "?", 1);
+  }
+  if( nTerm>1 ) sqlite3_str_append(pStr, ")", 1);
+}
+
+/*
+** Argument pLevel describes a strategy for scanning table pTab. This
+** function appends text to pStr that describes the subset of table
+** rows scanned by the strategy in the form of an SQL expression.
+**
+** For example, if the query:
+**
+**   SELECT * FROM t1 WHERE a=1 AND b>2;
+**
+** is run and there is an index on (a, b), then this function returns a
+** string similar to:
+**
+**   "a=? AND b>?"
+*/
+static void explainIndexRange(StrAccum *pStr, WhereLoop *pLoop){
+  Index *pIndex = pLoop->u.btree.pIndex;
+  u16 nEq = pLoop->u.btree.nEq;
+  u16 nSkip = pLoop->nSkip;
+  int i, j;
+
+  if( nEq==0 && (pLoop->wsFlags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ) return;
+  sqlite3_str_append(pStr, " (", 2);
+  for(i=0; i<nEq; i++){
+    const char *z = explainIndexColumnName(pIndex, i);
+    if( i ) sqlite3_str_append(pStr, " AND ", 5);
+    sqlite3_str_appendf(pStr, i>=nSkip ? "%s=?" : "ANY(%s)", z);
+  }
+
+  j = i;
+  if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
+    explainAppendTerm(pStr, pIndex, pLoop->u.btree.nBtm, j, i, ">");
+    i = 1;
+  }
+  if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
+    explainAppendTerm(pStr, pIndex, pLoop->u.btree.nTop, j, i, "<");
+  }
+  sqlite3_str_append(pStr, ")", 1);
+}
+
+/*
+** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
+** command, or if stmt_scanstatus_v2() stats are enabled, or if SQLITE_DEBUG
+** was defined at compile-time. If it is not a no-op, a single OP_Explain
+** opcode is added to the output to describe the table scan strategy in pLevel.
+**
+** If an OP_Explain opcode is added to the VM, its address is returned.
+** Otherwise, if no OP_Explain is coded, zero is returned.
+*/
+int sqlite3WhereExplainOneScan(
+  Parse *pParse,                  /* Parse context */
+  SrcList *pTabList,              /* Table list this loop refers to */
+  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
+  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
+){
+  int ret = 0;
+#if !defined(SQLITE_DEBUG)
+  if( sqlite3ParseToplevel(pParse)->explain==2 || IS_STMT_SCANSTATUS(pParse->db) )
+#endif
+  {
+    SrcItem *pItem = &pTabList->a[pLevel->iFrom];
+    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
+    sqlite3 *db = pParse->db;     /* Database handle */
+    int isSearch;                 /* True for a SEARCH. False for SCAN. */
+    WhereLoop *pLoop;             /* The controlling WhereLoop object */
+    u32 flags;                    /* Flags that describe this loop */
+    char *zMsg;                   /* Text to add to EQP output */
+    StrAccum str;                 /* EQP output string */
+    char zBuf[100];               /* Initial space for EQP output string */
+
+    pLoop = pLevel->pWLoop;
+    flags = pLoop->wsFlags;
+    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_OR_SUBCLAUSE) ) return 0;
+
+    isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
+            || ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
+            || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
+
+    sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
+    str.printfFlags = SQLITE_PRINTF_INTERNAL;
+    sqlite3_str_appendf(&str, "%s %S", isSearch ? "SEARCH" : "SCAN", pItem);
+    if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
+      const char *zFmt = 0;
+      Index *pIdx;
+
+      assert( pLoop->u.btree.pIndex!=0 );
+      pIdx = pLoop->u.btree.pIndex;
+      assert( !(flags&WHERE_AUTO_INDEX) || (flags&WHERE_IDX_ONLY) );
+      if( !HasRowid(pItem->pTab) && IsPrimaryKeyIndex(pIdx) ){
+        if( isSearch ){
+          zFmt = "PRIMARY KEY";
+        }
+      }else if( flags & WHERE_PARTIALIDX ){
+        zFmt = "AUTOMATIC PARTIAL COVERING INDEX";
+      }else if( flags & WHERE_AUTO_INDEX ){
+        zFmt = "AUTOMATIC COVERING INDEX";
+      }else if( flags & WHERE_IDX_ONLY ){
+        zFmt = "COVERING INDEX %s";
+      }else{
+        zFmt = "INDEX %s";
+      }
+      if( zFmt ){
+        sqlite3_str_append(&str, " USING ", 7);
+        sqlite3_str_appendf(&str, zFmt, pIdx->zName);
+        explainIndexRange(&str, pLoop);
+      }
+    }else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
+      char cRangeOp;
+#if 0  /* Better output, but breaks many tests */
+      const Table *pTab = pItem->pTab;
+      const char *zRowid = pTab->iPKey>=0 ? pTab->aCol[pTab->iPKey].zCnName:
+                              "rowid";
+#else
+      const char *zRowid = "rowid";
+#endif
+      sqlite3_str_appendf(&str, " USING INTEGER PRIMARY KEY (%s", zRowid);
+      if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
+        cRangeOp = '=';
+      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
+        sqlite3_str_appendf(&str, ">? AND %s", zRowid);
+        cRangeOp = '<';
+      }else if( flags&WHERE_BTM_LIMIT ){
+        cRangeOp = '>';
+      }else{
+        assert( flags&WHERE_TOP_LIMIT);
+        cRangeOp = '<';
+      }
+      sqlite3_str_appendf(&str, "%c?)", cRangeOp);
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
+      sqlite3_str_appendf(&str, " VIRTUAL TABLE INDEX %d:%s",
+                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
+    }
+#endif
+    if( pItem->fg.jointype & JT_LEFT ){
+      sqlite3_str_appendf(&str, " LEFT-JOIN");
+    }
+#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
+    if( pLoop->nOut>=10 ){
+      sqlite3_str_appendf(&str, " (~%llu rows)",
+             sqlite3LogEstToInt(pLoop->nOut));
+    }else{
+      sqlite3_str_append(&str, " (~1 row)", 9);
+    }
+#endif
+    zMsg = sqlite3StrAccumFinish(&str);
+    sqlite3ExplainBreakpoint("",zMsg);
+    ret = sqlite3VdbeAddOp4(v, OP_Explain, sqlite3VdbeCurrentAddr(v),
+                            pParse->addrExplain, 0, zMsg,P4_DYNAMIC);
+  }
+  return ret;
+}
+
+/*
+** Add a single OP_Explain opcode that describes a Bloom filter.
+**
+** Or if not processing EXPLAIN QUERY PLAN and not in a SQLITE_DEBUG and/or
+** SQLITE_ENABLE_STMT_SCANSTATUS build, then OP_Explain opcodes are not
+** required and this routine is a no-op.
+**
+** If an OP_Explain opcode is added to the VM, its address is returned.
+** Otherwise, if no OP_Explain is coded, zero is returned.
+*/
+int sqlite3WhereExplainBloomFilter(
+  const Parse *pParse,               /* Parse context */
+  const WhereInfo *pWInfo,           /* WHERE clause */
+  const WhereLevel *pLevel           /* Bloom filter on this level */
+){
+  int ret = 0;
+  SrcItem *pItem = &pWInfo->pTabList->a[pLevel->iFrom];
+  Vdbe *v = pParse->pVdbe;      /* VM being constructed */
+  sqlite3 *db = pParse->db;     /* Database handle */
+  char *zMsg;                   /* Text to add to EQP output */
+  int i;                        /* Loop counter */
+  WhereLoop *pLoop;             /* The where loop */
+  StrAccum str;                 /* EQP output string */
+  char zBuf[100];               /* Initial space for EQP output string */
+
+  sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
+  str.printfFlags = SQLITE_PRINTF_INTERNAL;
+  sqlite3_str_appendf(&str, "BLOOM FILTER ON %S (", pItem);
+  pLoop = pLevel->pWLoop;
+  if( pLoop->wsFlags & WHERE_IPK ){
+    const Table *pTab = pItem->pTab;
+    if( pTab->iPKey>=0 ){
+      sqlite3_str_appendf(&str, "%s=?", pTab->aCol[pTab->iPKey].zCnName);
+    }else{
+      sqlite3_str_appendf(&str, "rowid=?");
+    }
+  }else{
+    for(i=pLoop->nSkip; i<pLoop->u.btree.nEq; i++){
+      const char *z = explainIndexColumnName(pLoop->u.btree.pIndex, i);
+      if( i>pLoop->nSkip ) sqlite3_str_append(&str, " AND ", 5);
+      sqlite3_str_appendf(&str, "%s=?", z);
+    }
+  }
+  sqlite3_str_append(&str, ")", 1);
+  zMsg = sqlite3StrAccumFinish(&str);
+  ret = sqlite3VdbeAddOp4(v, OP_Explain, sqlite3VdbeCurrentAddr(v),
+                          pParse->addrExplain, 0, zMsg,P4_DYNAMIC);
+
+  sqlite3VdbeScanStatus(v, sqlite3VdbeCurrentAddr(v)-1, 0, 0, 0, 0);
+  return ret;
+}
+#endif /* SQLITE_OMIT_EXPLAIN */
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+/*
+** Configure the VM passed as the first argument with an
+** sqlite3_stmt_scanstatus() entry corresponding to the scan used to
+** implement level pLvl. Argument pSrclist is a pointer to the FROM
+** clause that the scan reads data from.
+**
+** If argument addrExplain is not 0, it must be the address of an
+** OP_Explain instruction that describes the same loop.
+*/
+void sqlite3WhereAddScanStatus(
+  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
+  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
+  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
+  int addrExplain                 /* Address of OP_Explain (or 0) */
+){
+  if( IS_STMT_SCANSTATUS( sqlite3VdbeDb(v) ) ){
+    const char *zObj = 0;
+    WhereLoop *pLoop = pLvl->pWLoop;
+    int wsFlags = pLoop->wsFlags;
+    int viaCoroutine = 0;
+
+    if( (wsFlags & WHERE_VIRTUALTABLE)==0  &&  pLoop->u.btree.pIndex!=0 ){
+      zObj = pLoop->u.btree.pIndex->zName;
+    }else{
+      zObj = pSrclist->a[pLvl->iFrom].zName;
+      viaCoroutine = pSrclist->a[pLvl->iFrom].fg.viaCoroutine;
+    }
+    sqlite3VdbeScanStatus(
+        v, addrExplain, pLvl->addrBody, pLvl->addrVisit, pLoop->nOut, zObj
+    );
+
+    if( viaCoroutine==0 ){
+      if( (wsFlags & (WHERE_MULTI_OR|WHERE_AUTO_INDEX))==0 ){
+        sqlite3VdbeScanStatusRange(v, addrExplain, -1, pLvl->iTabCur);
+      }
+      if( wsFlags & WHERE_INDEXED ){
+        sqlite3VdbeScanStatusRange(v, addrExplain, -1, pLvl->iIdxCur);
+      }
+    }else{
+      int addr = pSrclist->a[pLvl->iFrom].addrFillSub;
+      VdbeOp *pOp = sqlite3VdbeGetOp(v, addr-1);
+      assert( sqlite3VdbeDb(v)->mallocFailed || pOp->opcode==OP_InitCoroutine );
+      assert( sqlite3VdbeDb(v)->mallocFailed || pOp->p2>addr );
+      sqlite3VdbeScanStatusRange(v, addrExplain, addr, pOp->p2-1);
+    }
+  }
+}
+#endif
+
+
+/*
+** Disable a term in the WHERE clause.  Except, do not disable the term
+** if it controls a LEFT OUTER JOIN and it did not originate in the ON
+** or USING clause of that join.
+**
+** Consider the term t2.z='ok' in the following queries:
+**
+**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
+**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
+**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
+**
+** The t2.z='ok' is disabled in the in (2) because it originates
+** in the ON clause.  The term is disabled in (3) because it is not part
+** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
+**
+** Disabling a term causes that term to not be tested in the inner loop
+** of the join.  Disabling is an optimization.  When terms are satisfied
+** by indices, we disable them to prevent redundant tests in the inner
+** loop.  We would get the correct results if nothing were ever disabled,
+** but joins might run a little slower.  The trick is to disable as much
+** as we can without disabling too much.  If we disabled in (1), we'd get
+** the wrong answer.  See ticket #813.
+**
+** If all the children of a term are disabled, then that term is also
+** automatically disabled.  In this way, terms get disabled if derived
+** virtual terms are tested first.  For example:
+**
+**      x GLOB 'abc*' AND x>='abc' AND x<'acd'
+**      \___________/     \______/     \_____/
+**         parent          child1       child2
+**
+** Only the parent term was in the original WHERE clause.  The child1
+** and child2 terms were added by the LIKE optimization.  If both of
+** the virtual child terms are valid, then testing of the parent can be
+** skipped.
+**
+** Usually the parent term is marked as TERM_CODED.  But if the parent
+** term was originally TERM_LIKE, then the parent gets TERM_LIKECOND instead.
+** The TERM_LIKECOND marking indicates that the term should be coded inside
+** a conditional such that is only evaluated on the second pass of a
+** LIKE-optimization loop, when scanning BLOBs instead of strings.
+*/
+static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
+  int nLoop = 0;
+  assert( pTerm!=0 );
+  while( (pTerm->wtFlags & TERM_CODED)==0
+      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_OuterON))
+      && (pLevel->notReady & pTerm->prereqAll)==0
+  ){
+    if( nLoop && (pTerm->wtFlags & TERM_LIKE)!=0 ){
+      pTerm->wtFlags |= TERM_LIKECOND;
+    }else{
+      pTerm->wtFlags |= TERM_CODED;
+    }
+#ifdef WHERETRACE_ENABLED
+    if( (sqlite3WhereTrace & 0x4001)==0x4001 ){
+      sqlite3DebugPrintf("DISABLE-");
+      sqlite3WhereTermPrint(pTerm, (int)(pTerm - (pTerm->pWC->a)));
+    }
+#endif
+    if( pTerm->iParent<0 ) break;
+    pTerm = &pTerm->pWC->a[pTerm->iParent];
+    assert( pTerm!=0 );
+    pTerm->nChild--;
+    if( pTerm->nChild!=0 ) break;
+    nLoop++;
+  }
+}
+
+/*
+** Code an OP_Affinity opcode to apply the column affinity string zAff
+** to the n registers starting at base.
+**
+** As an optimization, SQLITE_AFF_BLOB and SQLITE_AFF_NONE entries (which
+** are no-ops) at the beginning and end of zAff are ignored.  If all entries
+** in zAff are SQLITE_AFF_BLOB or SQLITE_AFF_NONE, then no code gets generated.
+**
+** This routine makes its own copy of zAff so that the caller is free
+** to modify zAff after this routine returns.
+*/
+static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
+  Vdbe *v = pParse->pVdbe;
+  if( zAff==0 ){
+    assert( pParse->db->mallocFailed );
+    return;
+  }
+  assert( v!=0 );
+
+  /* Adjust base and n to skip over SQLITE_AFF_BLOB and SQLITE_AFF_NONE
+  ** entries at the beginning and end of the affinity string.
+  */
+  assert( SQLITE_AFF_NONE<SQLITE_AFF_BLOB );
+  while( n>0 && zAff[0]<=SQLITE_AFF_BLOB ){
+    n--;
+    base++;
+    zAff++;
+  }
+  while( n>1 && zAff[n-1]<=SQLITE_AFF_BLOB ){
+    n--;
+  }
+
+  /* Code the OP_Affinity opcode if there is anything left to do. */
+  if( n>0 ){
+    sqlite3VdbeAddOp4(v, OP_Affinity, base, n, 0, zAff, n);
+  }
+}
+
+/*
+** Expression pRight, which is the RHS of a comparison operation, is
+** either a vector of n elements or, if n==1, a scalar expression.
+** Before the comparison operation, affinity zAff is to be applied
+** to the pRight values. This function modifies characters within the
+** affinity string to SQLITE_AFF_BLOB if either:
+**
+**   * the comparison will be performed with no affinity, or
+**   * the affinity change in zAff is guaranteed not to change the value.
+*/
+static void updateRangeAffinityStr(
+  Expr *pRight,                   /* RHS of comparison */
+  int n,                          /* Number of vector elements in comparison */
+  char *zAff                      /* Affinity string to modify */
+){
+  int i;
+  for(i=0; i<n; i++){
+    Expr *p = sqlite3VectorFieldSubexpr(pRight, i);
+    if( sqlite3CompareAffinity(p, zAff[i])==SQLITE_AFF_BLOB
+     || sqlite3ExprNeedsNoAffinityChange(p, zAff[i])
+    ){
+      zAff[i] = SQLITE_AFF_BLOB;
+    }
+  }
+}
+
+
+/*
+** pX is an expression of the form:  (vector) IN (SELECT ...)
+** In other words, it is a vector IN operator with a SELECT clause on the
+** LHS.  But not all terms in the vector are indexable and the terms might
+** not be in the correct order for indexing.
+**
+** This routine makes a copy of the input pX expression and then adjusts
+** the vector on the LHS with corresponding changes to the SELECT so that
+** the vector contains only index terms and those terms are in the correct
+** order.  The modified IN expression is returned.  The caller is responsible
+** for deleting the returned expression.
+**
+** Example:
+**
+**    CREATE TABLE t1(a,b,c,d,e,f);
+**    CREATE INDEX t1x1 ON t1(e,c);
+**    SELECT * FROM t1 WHERE (a,b,c,d,e) IN (SELECT v,w,x,y,z FROM t2)
+**                           \_______________________________________/
+**                                     The pX expression
+**
+** Since only columns e and c can be used with the index, in that order,
+** the modified IN expression that is returned will be:
+**
+**        (e,c) IN (SELECT z,x FROM t2)
+**
+** The reduced pX is different from the original (obviously) and thus is
+** only used for indexing, to improve performance.  The original unaltered
+** IN expression must also be run on each output row for correctness.
+*/
+static Expr *removeUnindexableInClauseTerms(
+  Parse *pParse,        /* The parsing context */
+  int iEq,              /* Look at loop terms starting here */
+  WhereLoop *pLoop,     /* The current loop */
+  Expr *pX              /* The IN expression to be reduced */
+){
+  sqlite3 *db = pParse->db;
+  Select *pSelect;            /* Pointer to the SELECT on the RHS */
+  Expr *pNew;
+  pNew = sqlite3ExprDup(db, pX, 0);
+  if( db->mallocFailed==0 ){
+    for(pSelect=pNew->x.pSelect; pSelect; pSelect=pSelect->pPrior){
+      ExprList *pOrigRhs;         /* Original unmodified RHS */
+      ExprList *pOrigLhs = 0;     /* Original unmodified LHS */
+      ExprList *pRhs = 0;         /* New RHS after modifications */
+      ExprList *pLhs = 0;         /* New LHS after mods */
+      int i;                      /* Loop counter */
+
+      assert( ExprUseXSelect(pNew) );
+      pOrigRhs = pSelect->pEList;
+      assert( pNew->pLeft!=0 );
+      assert( ExprUseXList(pNew->pLeft) );
+      if( pSelect==pNew->x.pSelect ){
+        pOrigLhs = pNew->pLeft->x.pList;
+      }
+      for(i=iEq; i<pLoop->nLTerm; i++){
+        if( pLoop->aLTerm[i]->pExpr==pX ){
+          int iField;
+          assert( (pLoop->aLTerm[i]->eOperator & (WO_OR|WO_AND))==0 );
+          iField = pLoop->aLTerm[i]->u.x.iField - 1;
+          if( pOrigRhs->a[iField].pExpr==0 ) continue; /* Duplicate PK column */
+          pRhs = sqlite3ExprListAppend(pParse, pRhs, pOrigRhs->a[iField].pExpr);
+          pOrigRhs->a[iField].pExpr = 0;
+          if( pOrigLhs ){
+            assert( pOrigLhs->a[iField].pExpr!=0 );
+            pLhs = sqlite3ExprListAppend(pParse,pLhs,pOrigLhs->a[iField].pExpr);
+            pOrigLhs->a[iField].pExpr = 0;
+          }
+        }
+      }
+      sqlite3ExprListDelete(db, pOrigRhs);
+      if( pOrigLhs ){
+        sqlite3ExprListDelete(db, pOrigLhs);
+        pNew->pLeft->x.pList = pLhs;
+      }
+      pSelect->pEList = pRhs;
+      if( pLhs && pLhs->nExpr==1 ){
+        /* Take care here not to generate a TK_VECTOR containing only a
+        ** single value. Since the parser never creates such a vector, some
+        ** of the subroutines do not handle this case.  */
+        Expr *p = pLhs->a[0].pExpr;
+        pLhs->a[0].pExpr = 0;
+        sqlite3ExprDelete(db, pNew->pLeft);
+        pNew->pLeft = p;
+      }
+      if( pSelect->pOrderBy ){
+        /* If the SELECT statement has an ORDER BY clause, zero the
+        ** iOrderByCol variables. These are set to non-zero when an
+        ** ORDER BY term exactly matches one of the terms of the
+        ** result-set. Since the result-set of the SELECT statement may
+        ** have been modified or reordered, these variables are no longer
+        ** set correctly.  Since setting them is just an optimization,
+        ** it's easiest just to zero them here.  */
+        ExprList *pOrderBy = pSelect->pOrderBy;
+        for(i=0; i<pOrderBy->nExpr; i++){
+          pOrderBy->a[i].u.x.iOrderByCol = 0;
+        }
+      }
+
+#if 0
+      printf("For indexing, change the IN expr:\n");
+      sqlite3TreeViewExpr(0, pX, 0);
+      printf("Into:\n");
+      sqlite3TreeViewExpr(0, pNew, 0);
+#endif
+    }
+  }
+  return pNew;
+}
+
+
+/*
+** Generate code for a single equality term of the WHERE clause.  An equality
+** term can be either X=expr or X IN (...).   pTerm is the term to be
+** coded.
+**
+** The current value for the constraint is left in a register, the index
+** of which is returned.  An attempt is made store the result in iTarget but
+** this is only guaranteed for TK_ISNULL and TK_IN constraints.  If the
+** constraint is a TK_EQ or TK_IS, then the current value might be left in
+** some other register and it is the caller's responsibility to compensate.
+**
+** For a constraint of the form X=expr, the expression is evaluated in
+** straight-line code.  For constraints of the form X IN (...)
+** this routine sets up a loop that will iterate over all values of X.
+*/
+static int codeEqualityTerm(
+  Parse *pParse,      /* The parsing context */
+  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
+  WhereLevel *pLevel, /* The level of the FROM clause we are working on */
+  int iEq,            /* Index of the equality term within this level */
+  int bRev,           /* True for reverse-order IN operations */
+  int iTarget         /* Attempt to leave results in this register */
+){
+  Expr *pX = pTerm->pExpr;
+  Vdbe *v = pParse->pVdbe;
+  int iReg;                  /* Register holding results */
+
+  assert( pLevel->pWLoop->aLTerm[iEq]==pTerm );
+  assert( iTarget>0 );
+  if( pX->op==TK_EQ || pX->op==TK_IS ){
+    iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
+  }else if( pX->op==TK_ISNULL ){
+    iReg = iTarget;
+    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
+#ifndef SQLITE_OMIT_SUBQUERY
+  }else{
+    int eType = IN_INDEX_NOOP;
+    int iTab;
+    struct InLoop *pIn;
+    WhereLoop *pLoop = pLevel->pWLoop;
+    int i;
+    int nEq = 0;
+    int *aiMap = 0;
+
+    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
+      && pLoop->u.btree.pIndex!=0
+      && pLoop->u.btree.pIndex->aSortOrder[iEq]
+    ){
+      testcase( iEq==0 );
+      testcase( bRev );
+      bRev = !bRev;
+    }
+    assert( pX->op==TK_IN );
+    iReg = iTarget;
+
+    for(i=0; i<iEq; i++){
+      if( pLoop->aLTerm[i] && pLoop->aLTerm[i]->pExpr==pX ){
+        disableTerm(pLevel, pTerm);
+        return iTarget;
+      }
+    }
+    for(i=iEq;i<pLoop->nLTerm; i++){
+      assert( pLoop->aLTerm[i]!=0 );
+      if( pLoop->aLTerm[i]->pExpr==pX ) nEq++;
+    }
+
+    iTab = 0;
+    if( !ExprUseXSelect(pX) || pX->x.pSelect->pEList->nExpr==1 ){
+      eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, 0, &iTab);
+    }else{
+      Expr *pExpr = pTerm->pExpr;
+      if( pExpr->iTable==0 || !ExprHasProperty(pExpr, EP_Subrtn) ){
+        sqlite3 *db = pParse->db;
+        pX = removeUnindexableInClauseTerms(pParse, iEq, pLoop, pX);
+        if( !db->mallocFailed ){
+          aiMap = (int*)sqlite3DbMallocZero(pParse->db, sizeof(int)*nEq);
+          eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, aiMap,&iTab);
+          pExpr->iTable = iTab;
+        }
+        sqlite3ExprDelete(db, pX);
+      }else{
+        int n = sqlite3ExprVectorSize(pX->pLeft);
+        aiMap = (int*)sqlite3DbMallocZero(pParse->db, sizeof(int)*MAX(nEq,n));
+        eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, aiMap, &iTab);
+      }
+      pX = pExpr;
+    }
+
+    if( eType==IN_INDEX_INDEX_DESC ){
+      testcase( bRev );
+      bRev = !bRev;
+    }
+    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
+    VdbeCoverageIf(v, bRev);
+    VdbeCoverageIf(v, !bRev);
+
+    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
+    pLoop->wsFlags |= WHERE_IN_ABLE;
+    if( pLevel->u.in.nIn==0 ){
+      pLevel->addrNxt = sqlite3VdbeMakeLabel(pParse);
+    }
+    if( iEq>0 && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)==0 ){
+      pLoop->wsFlags |= WHERE_IN_EARLYOUT;
+    }
+
+    i = pLevel->u.in.nIn;
+    pLevel->u.in.nIn += nEq;
+    pLevel->u.in.aInLoop =
+       sqlite3WhereRealloc(pTerm->pWC->pWInfo,
+                           pLevel->u.in.aInLoop,
+                           sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
+    pIn = pLevel->u.in.aInLoop;
+    if( pIn ){
+      int iMap = 0;               /* Index in aiMap[] */
+      pIn += i;
+      for(i=iEq;i<pLoop->nLTerm; i++){
+        if( pLoop->aLTerm[i]->pExpr==pX ){
+          int iOut = iReg + i - iEq;
+          if( eType==IN_INDEX_ROWID ){
+            pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iOut);
+          }else{
+            int iCol = aiMap ? aiMap[iMap++] : 0;
+            pIn->addrInTop = sqlite3VdbeAddOp3(v,OP_Column,iTab, iCol, iOut);
+          }
+          sqlite3VdbeAddOp1(v, OP_IsNull, iOut); VdbeCoverage(v);
+          if( i==iEq ){
+            pIn->iCur = iTab;
+            pIn->eEndLoopOp = bRev ? OP_Prev : OP_Next;
+            if( iEq>0 ){
+              pIn->iBase = iReg - i;
+              pIn->nPrefix = i;
+            }else{
+              pIn->nPrefix = 0;
+            }
+          }else{
+            pIn->eEndLoopOp = OP_Noop;
+          }
+          pIn++;
+        }
+      }
+      testcase( iEq>0
+                && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)==0
+                && (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 );
+      if( iEq>0
+       && (pLoop->wsFlags & (WHERE_IN_SEEKSCAN|WHERE_VIRTUALTABLE))==0
+      ){
+        sqlite3VdbeAddOp3(v, OP_SeekHit, pLevel->iIdxCur, 0, iEq);
+      }
+    }else{
+      pLevel->u.in.nIn = 0;
+    }
+    sqlite3DbFree(pParse->db, aiMap);
+#endif
+  }
+
+  /* As an optimization, try to disable the WHERE clause term that is
+  ** driving the index as it will always be true.  The correct answer is
+  ** obtained regardless, but we might get the answer with fewer CPU cycles
+  ** by omitting the term.
+  **
+  ** But do not disable the term unless we are certain that the term is
+  ** not a transitive constraint.  For an example of where that does not
+  ** work, see https://sqlite.org/forum/forumpost/eb8613976a (2021-05-04)
+  */
+  if( (pLevel->pWLoop->wsFlags & WHERE_TRANSCONS)==0
+   || (pTerm->eOperator & WO_EQUIV)==0
+  ){
+    disableTerm(pLevel, pTerm);
+  }
+
+  return iReg;
+}
+
+/*
+** Generate code that will evaluate all == and IN constraints for an
+** index scan.
+**
+** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
+** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
+** The index has as many as three equality constraints, but in this
+** example, the third "c" value is an inequality.  So only two
+** constraints are coded.  This routine will generate code to evaluate
+** a==5 and b IN (1,2,3).  The current values for a and b will be stored
+** in consecutive registers and the index of the first register is returned.
+**
+** In the example above nEq==2.  But this subroutine works for any value
+** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
+** The only thing it does is allocate the pLevel->iMem memory cell and
+** compute the affinity string.
+**
+** The nExtraReg parameter is 0 or 1.  It is 0 if all WHERE clause constraints
+** are == or IN and are covered by the nEq.  nExtraReg is 1 if there is
+** an inequality constraint (such as the "c>=5 AND c<10" in the example) that
+** occurs after the nEq quality constraints.
+**
+** This routine allocates a range of nEq+nExtraReg memory cells and returns
+** the index of the first memory cell in that range. The code that
+** calls this routine will use that memory range to store keys for
+** start and termination conditions of the loop.
+** key value of the loop.  If one or more IN operators appear, then
+** this routine allocates an additional nEq memory cells for internal
+** use.
+**
+** Before returning, *pzAff is set to point to a buffer containing a
+** copy of the column affinity string of the index allocated using
+** sqlite3DbMalloc(). Except, entries in the copy of the string associated
+** with equality constraints that use BLOB or NONE affinity are set to
+** SQLITE_AFF_BLOB. This is to deal with SQL such as the following:
+**
+**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
+**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
+**
+** In the example above, the index on t1(a) has TEXT affinity. But since
+** the right hand side of the equality constraint (t2.b) has BLOB/NONE affinity,
+** no conversion should be attempted before using a t2.b value as part of
+** a key to search the index. Hence the first byte in the returned affinity
+** string in this example would be set to SQLITE_AFF_BLOB.
+*/
+static int codeAllEqualityTerms(
+  Parse *pParse,        /* Parsing context */
+  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
+  int bRev,             /* Reverse the order of IN operators */
+  int nExtraReg,        /* Number of extra registers to allocate */
+  char **pzAff          /* OUT: Set to point to affinity string */
+){
+  u16 nEq;                      /* The number of == or IN constraints to code */
+  u16 nSkip;                    /* Number of left-most columns to skip */
+  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
+  Index *pIdx;                  /* The index being used for this loop */
+  WhereTerm *pTerm;             /* A single constraint term */
+  WhereLoop *pLoop;             /* The WhereLoop object */
+  int j;                        /* Loop counter */
+  int regBase;                  /* Base register */
+  int nReg;                     /* Number of registers to allocate */
+  char *zAff;                   /* Affinity string to return */
+
+  /* This module is only called on query plans that use an index. */
+  pLoop = pLevel->pWLoop;
+  assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
+  nEq = pLoop->u.btree.nEq;
+  nSkip = pLoop->nSkip;
+  pIdx = pLoop->u.btree.pIndex;
+  assert( pIdx!=0 );
+
+  /* Figure out how many memory cells we will need then allocate them.
+  */
+  regBase = pParse->nMem + 1;
+  nReg = nEq + nExtraReg;
+  pParse->nMem += nReg;
+
+  zAff = sqlite3DbStrDup(pParse->db,sqlite3IndexAffinityStr(pParse->db,pIdx));
+  assert( zAff!=0 || pParse->db->mallocFailed );
+
+  if( nSkip ){
+    int iIdxCur = pLevel->iIdxCur;
+    sqlite3VdbeAddOp3(v, OP_Null, 0, regBase, regBase+nSkip-1);
+    sqlite3VdbeAddOp1(v, (bRev?OP_Last:OP_Rewind), iIdxCur);
+    VdbeCoverageIf(v, bRev==0);
+    VdbeCoverageIf(v, bRev!=0);
+    VdbeComment((v, "begin skip-scan on %s", pIdx->zName));
+    j = sqlite3VdbeAddOp0(v, OP_Goto);
+    assert( pLevel->addrSkip==0 );
+    pLevel->addrSkip = sqlite3VdbeAddOp4Int(v, (bRev?OP_SeekLT:OP_SeekGT),
+                            iIdxCur, 0, regBase, nSkip);
+    VdbeCoverageIf(v, bRev==0);
+    VdbeCoverageIf(v, bRev!=0);
+    sqlite3VdbeJumpHere(v, j);
+    for(j=0; j<nSkip; j++){
+      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
+      testcase( pIdx->aiColumn[j]==XN_EXPR );
+      VdbeComment((v, "%s", explainIndexColumnName(pIdx, j)));
+    }
+  }   
+
+  /* Evaluate the equality constraints
+  */
+  assert( zAff==0 || (int)strlen(zAff)>=nEq );
+  for(j=nSkip; j<nEq; j++){
+    int r1;
+    pTerm = pLoop->aLTerm[j];
+    assert( pTerm!=0 );
+    /* The following testcase is true for indices with redundant columns.
+    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
+    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
+    testcase( pTerm->wtFlags & TERM_VIRTUAL );
+    r1 = codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, regBase+j);
+    if( r1!=regBase+j ){
+      if( nReg==1 ){
+        sqlite3ReleaseTempReg(pParse, regBase);
+        regBase = r1;
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Copy, r1, regBase+j);
+      }
+    }
+    if( pTerm->eOperator & WO_IN ){
+      if( pTerm->pExpr->flags & EP_xIsSelect ){
+        /* No affinity ever needs to be (or should be) applied to a value
+        ** from the RHS of an "? IN (SELECT ...)" expression. The
+        ** sqlite3FindInIndex() routine has already ensured that the
+        ** affinity of the comparison has been applied to the value.  */
+        if( zAff ) zAff[j] = SQLITE_AFF_BLOB;
+      }
+    }else if( (pTerm->eOperator & WO_ISNULL)==0 ){
+      Expr *pRight = pTerm->pExpr->pRight;
+      if( (pTerm->wtFlags & TERM_IS)==0 && sqlite3ExprCanBeNull(pRight) ){
+        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
+        VdbeCoverage(v);
+      }
+      if( pParse->nErr==0 ){
+        assert( pParse->db->mallocFailed==0 );
+        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_BLOB ){
+          zAff[j] = SQLITE_AFF_BLOB;
+        }
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
+          zAff[j] = SQLITE_AFF_BLOB;
+        }
+      }
+    }
+  }
+  *pzAff = zAff;
+  return regBase;
+}
+
+#ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+/*
+** If the most recently coded instruction is a constant range constraint
+** (a string literal) that originated from the LIKE optimization, then
+** set P3 and P5 on the OP_String opcode so that the string will be cast
+** to a BLOB at appropriate times.
+**
+** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
+** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
+** scan loop run twice, once for strings and a second time for BLOBs.
+** The OP_String opcodes on the second pass convert the upper and lower
+** bound string constants to blobs.  This routine makes the necessary changes
+** to the OP_String opcodes for that to happen.
+**
+** Except, of course, if SQLITE_LIKE_DOESNT_MATCH_BLOBS is defined, then
+** only the one pass through the string space is required, so this routine
+** becomes a no-op.
+*/
+static void whereLikeOptimizationStringFixup(
+  Vdbe *v,                /* prepared statement under construction */
+  WhereLevel *pLevel,     /* The loop that contains the LIKE operator */
+  WhereTerm *pTerm        /* The upper or lower bound just coded */
+){
+  if( pTerm->wtFlags & TERM_LIKEOPT ){
+    VdbeOp *pOp;
+    assert( pLevel->iLikeRepCntr>0 );
+    pOp = sqlite3VdbeGetLastOp(v);
+    assert( pOp!=0 );
+    assert( pOp->opcode==OP_String8
+            || pTerm->pWC->pWInfo->pParse->db->mallocFailed );
+    pOp->p3 = (int)(pLevel->iLikeRepCntr>>1);  /* Register holding counter */
+    pOp->p5 = (u8)(pLevel->iLikeRepCntr&1);    /* ASC or DESC */
+  }
+}
+#else
+# define whereLikeOptimizationStringFixup(A,B,C)
+#endif
+
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+/*
+** Information is passed from codeCursorHint() down to individual nodes of
+** the expression tree (by sqlite3WalkExpr()) using an instance of this
+** structure.
+*/
+struct CCurHint {
+  int iTabCur;    /* Cursor for the main table */
+  int iIdxCur;    /* Cursor for the index, if pIdx!=0.  Unused otherwise */
+  Index *pIdx;    /* The index used to access the table */
+};
+
+/*
+** This function is called for every node of an expression that is a candidate
+** for a cursor hint on an index cursor.  For TK_COLUMN nodes that reference
+** the table CCurHint.iTabCur, verify that the same column can be
+** accessed through the index.  If it cannot, then set pWalker->eCode to 1.
+*/
+static int codeCursorHintCheckExpr(Walker *pWalker, Expr *pExpr){
+  struct CCurHint *pHint = pWalker->u.pCCurHint;
+  assert( pHint->pIdx!=0 );
+  if( pExpr->op==TK_COLUMN
+   && pExpr->iTable==pHint->iTabCur
+   && sqlite3TableColumnToIndex(pHint->pIdx, pExpr->iColumn)<0
+  ){
+    pWalker->eCode = 1;
+  }
+  return WRC_Continue;
+}
+
+/*
+** Test whether or not expression pExpr, which was part of a WHERE clause,
+** should be included in the cursor-hint for a table that is on the rhs
+** of a LEFT JOIN. Set Walker.eCode to non-zero before returning if the
+** expression is not suitable.
+**
+** An expression is unsuitable if it might evaluate to non NULL even if
+** a TK_COLUMN node that does affect the value of the expression is set
+** to NULL. For example:
+**
+**   col IS NULL
+**   col IS NOT NULL
+**   coalesce(col, 1)
+**   CASE WHEN col THEN 0 ELSE 1 END
+*/
+static int codeCursorHintIsOrFunction(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_IS
+   || pExpr->op==TK_ISNULL || pExpr->op==TK_ISNOT
+   || pExpr->op==TK_NOTNULL || pExpr->op==TK_CASE
+  ){
+    pWalker->eCode = 1;
+  }else if( pExpr->op==TK_FUNCTION ){
+    int d1;
+    char d2[4];
+    if( 0==sqlite3IsLikeFunction(pWalker->pParse->db, pExpr, &d1, d2) ){
+      pWalker->eCode = 1;
+    }
+  }
+
+  return WRC_Continue;
+}
+
+
+/*
+** This function is called on every node of an expression tree used as an
+** argument to the OP_CursorHint instruction. If the node is a TK_COLUMN
+** that accesses any table other than the one identified by
+** CCurHint.iTabCur, then do the following:
+**
+**   1) allocate a register and code an OP_Column instruction to read
+**      the specified column into the new register, and
+**
+**   2) transform the expression node to a TK_REGISTER node that reads
+**      from the newly populated register.
+**
+** Also, if the node is a TK_COLUMN that does access the table identified
+** by pCCurHint.iTabCur, and an index is being used (which we will
+** know because CCurHint.pIdx!=0) then transform the TK_COLUMN into
+** an access of the index rather than the original table.
+*/
+static int codeCursorHintFixExpr(Walker *pWalker, Expr *pExpr){
+  int rc = WRC_Continue;
+  int reg;
+  struct CCurHint *pHint = pWalker->u.pCCurHint;
+  if( pExpr->op==TK_COLUMN ){
+    if( pExpr->iTable!=pHint->iTabCur ){
+      reg = ++pWalker->pParse->nMem;   /* Register for column value */
+      reg = sqlite3ExprCodeTarget(pWalker->pParse, pExpr, reg);
+      pExpr->op = TK_REGISTER;
+      pExpr->iTable = reg;
+    }else if( pHint->pIdx!=0 ){
+      pExpr->iTable = pHint->iIdxCur;
+      pExpr->iColumn = sqlite3TableColumnToIndex(pHint->pIdx, pExpr->iColumn);
+      assert( pExpr->iColumn>=0 );
+    }
+  }else if( pExpr->pAggInfo ){
+    rc = WRC_Prune;
+    reg = ++pWalker->pParse->nMem;   /* Register for column value */
+    reg = sqlite3ExprCodeTarget(pWalker->pParse, pExpr, reg);
+    pExpr->op = TK_REGISTER;
+    pExpr->iTable = reg;
+  }else if( pExpr->op==TK_TRUEFALSE ){
+    /* Do not walk disabled expressions.  tag-20230504-1 */
+    return WRC_Prune;
+  }
+  return rc;
+}
+
+/*
+** Insert an OP_CursorHint instruction if it is appropriate to do so.
+*/
+static void codeCursorHint(
+  SrcItem *pTabItem,  /* FROM clause item */
+  WhereInfo *pWInfo,    /* The where clause */
+  WhereLevel *pLevel,   /* Which loop to provide hints for */
+  WhereTerm *pEndRange  /* Hint this end-of-scan boundary term if not NULL */
+){
+  Parse *pParse = pWInfo->pParse;
+  sqlite3 *db = pParse->db;
+  Vdbe *v = pParse->pVdbe;
+  Expr *pExpr = 0;
+  WhereLoop *pLoop = pLevel->pWLoop;
+  int iCur;
+  WhereClause *pWC;
+  WhereTerm *pTerm;
+  int i, j;
+  struct CCurHint sHint;
+  Walker sWalker;
+
+  if( OptimizationDisabled(db, SQLITE_CursorHints) ) return;
+  iCur = pLevel->iTabCur;
+  assert( iCur==pWInfo->pTabList->a[pLevel->iFrom].iCursor );
+  sHint.iTabCur = iCur;
+  sHint.iIdxCur = pLevel->iIdxCur;
+  sHint.pIdx = pLoop->u.btree.pIndex;
+  memset(&sWalker, 0, sizeof(sWalker));
+  sWalker.pParse = pParse;
+  sWalker.u.pCCurHint = &sHint;
+  pWC = &pWInfo->sWC;
+  for(i=0; i<pWC->nBase; i++){
+    pTerm = &pWC->a[i];
+    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+    if( pTerm->prereqAll & pLevel->notReady ) continue;
+
+    /* Any terms specified as part of the ON(...) clause for any LEFT
+    ** JOIN for which the current table is not the rhs are omitted
+    ** from the cursor-hint.
+    **
+    ** If this table is the rhs of a LEFT JOIN, "IS" or "IS NULL" terms
+    ** that were specified as part of the WHERE clause must be excluded.
+    ** This is to address the following:
+    **
+    **   SELECT ... t1 LEFT JOIN t2 ON (t1.a=t2.b) WHERE t2.c IS NULL;
+    **
+    ** Say there is a single row in t2 that matches (t1.a=t2.b), but its
+    ** t2.c values is not NULL. If the (t2.c IS NULL) constraint is
+    ** pushed down to the cursor, this row is filtered out, causing
+    ** SQLite to synthesize a row of NULL values. Which does match the
+    ** WHERE clause, and so the query returns a row. Which is incorrect.
+    **
+    ** For the same reason, WHERE terms such as:
+    **
+    **   WHERE 1 = (t2.c IS NULL)
+    **
+    ** are also excluded. See codeCursorHintIsOrFunction() for details.
+    */
+    if( pTabItem->fg.jointype & JT_LEFT ){
+      Expr *pExpr = pTerm->pExpr;
+      if( !ExprHasProperty(pExpr, EP_OuterON)
+       || pExpr->w.iJoin!=pTabItem->iCursor
+      ){
+        sWalker.eCode = 0;
+        sWalker.xExprCallback = codeCursorHintIsOrFunction;
+        sqlite3WalkExpr(&sWalker, pTerm->pExpr);
+        if( sWalker.eCode ) continue;
+      }
+    }else{
+      if( ExprHasProperty(pTerm->pExpr, EP_OuterON) ) continue;
+    }
+
+    /* All terms in pWLoop->aLTerm[] except pEndRange are used to initialize
+    ** the cursor.  These terms are not needed as hints for a pure range
+    ** scan (that has no == terms) so omit them. */
+    if( pLoop->u.btree.nEq==0 && pTerm!=pEndRange ){
+      for(j=0; j<pLoop->nLTerm && pLoop->aLTerm[j]!=pTerm; j++){}
+      if( j<pLoop->nLTerm ) continue;
+    }
+
+    /* No subqueries or non-deterministic functions allowed */
+    if( sqlite3ExprContainsSubquery(pTerm->pExpr) ) continue;
+
+    /* For an index scan, make sure referenced columns are actually in
+    ** the index. */
+    if( sHint.pIdx!=0 ){
+      sWalker.eCode = 0;
+      sWalker.xExprCallback = codeCursorHintCheckExpr;
+      sqlite3WalkExpr(&sWalker, pTerm->pExpr);
+      if( sWalker.eCode ) continue;
+    }
+
+    /* If we survive all prior tests, that means this term is worth hinting */
+    pExpr = sqlite3ExprAnd(pParse, pExpr, sqlite3ExprDup(db, pTerm->pExpr, 0));
+  }
+  if( pExpr!=0 ){
+    sWalker.xExprCallback = codeCursorHintFixExpr;
+    if( pParse->nErr==0 ) sqlite3WalkExpr(&sWalker, pExpr);
+    sqlite3VdbeAddOp4(v, OP_CursorHint,
+                      (sHint.pIdx ? sHint.iIdxCur : sHint.iTabCur), 0, 0,
+                      (const char*)pExpr, P4_EXPR);
+  }
+}
+#else
+# define codeCursorHint(A,B,C,D)  /* No-op */
+#endif /* SQLITE_ENABLE_CURSOR_HINTS */
+
+/*
+** Cursor iCur is open on an intkey b-tree (a table). Register iRowid contains
+** a rowid value just read from cursor iIdxCur, open on index pIdx. This
+** function generates code to do a deferred seek of cursor iCur to the
+** rowid stored in register iRowid.
+**
+** Normally, this is just:
+**
+**   OP_DeferredSeek $iCur $iRowid
+**
+** Which causes a seek on $iCur to the row with rowid $iRowid.
+**
+** However, if the scan currently being coded is a branch of an OR-loop and
+** the statement currently being coded is a SELECT, then additional information
+** is added that might allow OP_Column to omit the seek and instead do its
+** lookup on the index, thus avoiding an expensive seek operation.  To
+** enable this optimization, the P3 of OP_DeferredSeek is set to iIdxCur
+** and P4 is set to an array of integers containing one entry for each column
+** in the table.  For each table column, if the column is the i'th
+** column of the index, then the corresponding array entry is set to (i+1).
+** If the column does not appear in the index at all, the array entry is set
+** to 0.  The OP_Column opcode can check this array to see if the column it
+** wants is in the index and if it is, it will substitute the index cursor
+** and column number and continue with those new values, rather than seeking
+** the table cursor.
+*/
+static void codeDeferredSeek(
+  WhereInfo *pWInfo,              /* Where clause context */
+  Index *pIdx,                    /* Index scan is using */
+  int iCur,                       /* Cursor for IPK b-tree */
+  int iIdxCur                     /* Index cursor */
+){
+  Parse *pParse = pWInfo->pParse; /* Parse context */
+  Vdbe *v = pParse->pVdbe;        /* Vdbe to generate code within */
+
+  assert( iIdxCur>0 );
+  assert( pIdx->aiColumn[pIdx->nColumn-1]==-1 );
+ 
+  pWInfo->bDeferredSeek = 1;
+  sqlite3VdbeAddOp3(v, OP_DeferredSeek, iIdxCur, 0, iCur);
+  if( (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))
+   && DbMaskAllZero(sqlite3ParseToplevel(pParse)->writeMask)
+  ){
+    int i;
+    Table *pTab = pIdx->pTable;
+    u32 *ai = (u32*)sqlite3DbMallocZero(pParse->db, sizeof(u32)*(pTab->nCol+1));
+    if( ai ){
+      ai[0] = pTab->nCol;
+      for(i=0; i<pIdx->nColumn-1; i++){
+        int x1, x2;
+        assert( pIdx->aiColumn[i]<pTab->nCol );
+        x1 = pIdx->aiColumn[i];
+        x2 = sqlite3TableColumnToStorage(pTab, x1);
+        testcase( x1!=x2 );
+        if( x1>=0 ) ai[x2+1] = i+1;
+      }
+      sqlite3VdbeChangeP4(v, -1, (char*)ai, P4_INTARRAY);
+    }
+  }
+}
+
+/*
+** If the expression passed as the second argument is a vector, generate
+** code to write the first nReg elements of the vector into an array
+** of registers starting with iReg.
+**
+** If the expression is not a vector, then nReg must be passed 1. In
+** this case, generate code to evaluate the expression and leave the
+** result in register iReg.
+*/
+static void codeExprOrVector(Parse *pParse, Expr *p, int iReg, int nReg){
+  assert( nReg>0 );
+  if( p && sqlite3ExprIsVector(p) ){
+#ifndef SQLITE_OMIT_SUBQUERY
+    if( ExprUseXSelect(p) ){
+      Vdbe *v = pParse->pVdbe;
+      int iSelect;
+      assert( p->op==TK_SELECT );
+      iSelect = sqlite3CodeSubselect(pParse, p);
+      sqlite3VdbeAddOp3(v, OP_Copy, iSelect, iReg, nReg-1);
+    }else
+#endif
+    {
+      int i;
+      const ExprList *pList;
+      assert( ExprUseXList(p) );
+      pList = p->x.pList;
+      assert( nReg<=pList->nExpr );
+      for(i=0; i<nReg; i++){
+        sqlite3ExprCode(pParse, pList->a[i].pExpr, iReg+i);
+      }
+    }
+  }else{
+    assert( nReg==1 || pParse->nErr );
+    sqlite3ExprCode(pParse, p, iReg);
+  }
+}
+
+/*
+** The pTruth expression is always true because it is the WHERE clause
+** a partial index that is driving a query loop.  Look through all of the
+** WHERE clause terms on the query, and if any of those terms must be
+** true because pTruth is true, then mark those WHERE clause terms as
+** coded.
+*/
+static void whereApplyPartialIndexConstraints(
+  Expr *pTruth,
+  int iTabCur,
+  WhereClause *pWC
+){
+  int i;
+  WhereTerm *pTerm;
+  while( pTruth->op==TK_AND ){
+    whereApplyPartialIndexConstraints(pTruth->pLeft, iTabCur, pWC);
+    pTruth = pTruth->pRight;
+  }
+  for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    Expr *pExpr;
+    if( pTerm->wtFlags & TERM_CODED ) continue;
+    pExpr = pTerm->pExpr;
+    if( sqlite3ExprCompare(0, pExpr, pTruth, iTabCur)==0 ){
+      pTerm->wtFlags |= TERM_CODED;
+    }
+  }
+}
+
+/*
+** This routine is called right after An OP_Filter has been generated and
+** before the corresponding index search has been performed.  This routine
+** checks to see if there are additional Bloom filters in inner loops that
+** can be checked prior to doing the index lookup.  If there are available
+** inner-loop Bloom filters, then evaluate those filters now, before the
+** index lookup.  The idea is that a Bloom filter check is way faster than
+** an index lookup, and the Bloom filter might return false, meaning that
+** the index lookup can be skipped.
+**
+** We know that an inner loop uses a Bloom filter because it has the
+** WhereLevel.regFilter set.  If an inner-loop Bloom filter is checked,
+** then clear the WhereLevel.regFilter value to prevent the Bloom filter
+** from being checked a second time when the inner loop is evaluated.
+*/
+static SQLITE_NOINLINE void filterPullDown(
+  Parse *pParse,       /* Parsing context */
+  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
+  int iLevel,          /* Which level of pWInfo->a[] should be coded */
+  int addrNxt,         /* Jump here to bypass inner loops */
+  Bitmask notReady     /* Loops that are not ready */
+){
+  while( ++iLevel < pWInfo->nLevel ){
+    WhereLevel *pLevel = &pWInfo->a[iLevel];
+    WhereLoop *pLoop = pLevel->pWLoop;
+    if( pLevel->regFilter==0 ) continue;
+    if( pLevel->pWLoop->nSkip ) continue;
+    /*         ,--- Because sqlite3ConstructBloomFilter() has will not have set
+    **  vvvvv--'    pLevel->regFilter if this were true. */
+    if( NEVER(pLoop->prereq & notReady) ) continue;
+    assert( pLevel->addrBrk==0 );
+    pLevel->addrBrk = addrNxt;
+    if( pLoop->wsFlags & WHERE_IPK ){
+      WhereTerm *pTerm = pLoop->aLTerm[0];
+      int regRowid;
+      assert( pTerm!=0 );
+      assert( pTerm->pExpr!=0 );
+      testcase( pTerm->wtFlags & TERM_VIRTUAL );
+      regRowid = sqlite3GetTempReg(pParse);
+      regRowid = codeEqualityTerm(pParse, pTerm, pLevel, 0, 0, regRowid);
+      sqlite3VdbeAddOp2(pParse->pVdbe, OP_MustBeInt, regRowid, addrNxt);
+      VdbeCoverage(pParse->pVdbe);
+      sqlite3VdbeAddOp4Int(pParse->pVdbe, OP_Filter, pLevel->regFilter,
+                           addrNxt, regRowid, 1);
+      VdbeCoverage(pParse->pVdbe);
+    }else{
+      u16 nEq = pLoop->u.btree.nEq;
+      int r1;
+      char *zStartAff;
+
+      assert( pLoop->wsFlags & WHERE_INDEXED );
+      assert( (pLoop->wsFlags & WHERE_COLUMN_IN)==0 );
+      r1 = codeAllEqualityTerms(pParse,pLevel,0,0,&zStartAff);
+      codeApplyAffinity(pParse, r1, nEq, zStartAff);
+      sqlite3DbFree(pParse->db, zStartAff);
+      sqlite3VdbeAddOp4Int(pParse->pVdbe, OP_Filter, pLevel->regFilter,
+                           addrNxt, r1, nEq);
+      VdbeCoverage(pParse->pVdbe);
+    }
+    pLevel->regFilter = 0;
+    pLevel->addrBrk = 0;
+  }
+}
+
+/*
+** Generate code for the start of the iLevel-th loop in the WHERE clause
+** implementation described by pWInfo.
+*/
+Bitmask sqlite3WhereCodeOneLoopStart(
+  Parse *pParse,       /* Parsing context */
+  Vdbe *v,             /* Prepared statement under construction */
+  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
+  int iLevel,          /* Which level of pWInfo->a[] should be coded */
+  WhereLevel *pLevel,  /* The current level pointer */
+  Bitmask notReady     /* Which tables are currently available */
+){
+  int j, k;            /* Loop counters */
+  int iCur;            /* The VDBE cursor for the table */
+  int addrNxt;         /* Where to jump to continue with the next IN case */
+  int bRev;            /* True if we need to scan in reverse order */
+  WhereLoop *pLoop;    /* The WhereLoop object being coded */
+  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
+  WhereTerm *pTerm;               /* A WHERE clause term */
+  sqlite3 *db;                    /* Database connection */
+  SrcItem *pTabItem;              /* FROM clause term being coded */
+  int addrBrk;                    /* Jump here to break out of the loop */
+  int addrHalt;                   /* addrBrk for the outermost loop */
+  int addrCont;                   /* Jump here to continue with next cycle */
+  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
+  int iReleaseReg = 0;      /* Temp register to free before returning */
+  Index *pIdx = 0;          /* Index used by loop (if any) */
+  int iLoop;                /* Iteration of constraint generator loop */
+
+  pWC = &pWInfo->sWC;
+  db = pParse->db;
+  pLoop = pLevel->pWLoop;
+  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
+  iCur = pTabItem->iCursor;
+  pLevel->notReady = notReady & ~sqlite3WhereGetMask(&pWInfo->sMaskSet, iCur);
+  bRev = (pWInfo->revMask>>iLevel)&1;
+  VdbeModuleComment((v, "Begin WHERE-loop%d: %s",iLevel,pTabItem->pTab->zName));
+#if WHERETRACE_ENABLED /* 0x4001 */
+  if( sqlite3WhereTrace & 0x1 ){
+    sqlite3DebugPrintf("Coding level %d of %d:  notReady=%llx  iFrom=%d\n",
+       iLevel, pWInfo->nLevel, (u64)notReady, pLevel->iFrom);
+    if( sqlite3WhereTrace & 0x1000 ){
+      sqlite3WhereLoopPrint(pLoop, pWC);
+    }
+  }
+  if( (sqlite3WhereTrace & 0x4001)==0x4001 ){
+    if( iLevel==0 ){
+      sqlite3DebugPrintf("WHERE clause being coded:\n");
+      sqlite3TreeViewExpr(0, pWInfo->pWhere, 0);
+    }
+    sqlite3DebugPrintf("All WHERE-clause terms before coding:\n");
+    sqlite3WhereClausePrint(pWC);
+  }
+#endif
+
+  /* Create labels for the "break" and "continue" instructions
+  ** for the current loop.  Jump to addrBrk to break out of a loop.
+  ** Jump to cont to go immediately to the next iteration of the
+  ** loop.
+  **
+  ** When there is an IN operator, we also have a "addrNxt" label that
+  ** means to continue with the next IN value combination.  When
+  ** there are no IN operators in the constraints, the "addrNxt" label
+  ** is the same as "addrBrk".
+  */
+  addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(pParse);
+  addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(pParse);
+
+  /* If this is the right table of a LEFT OUTER JOIN, allocate and
+  ** initialize a memory cell that records if this table matches any
+  ** row of the left table of the join.
+  */
+  assert( (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))
+       || pLevel->iFrom>0 || (pTabItem[0].fg.jointype & JT_LEFT)==0
+  );
+  if( pLevel->iFrom>0 && (pTabItem[0].fg.jointype & JT_LEFT)!=0 ){
+    pLevel->iLeftJoin = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
+    VdbeComment((v, "init LEFT JOIN no-match flag"));
+  }
+
+  /* Compute a safe address to jump to if we discover that the table for
+  ** this loop is empty and can never contribute content. */
+  for(j=iLevel; j>0; j--){
+    if( pWInfo->a[j].iLeftJoin ) break;
+    if( pWInfo->a[j].pRJ ) break;
+  }
+  addrHalt = pWInfo->a[j].addrBrk;
+
+  /* Special case of a FROM clause subquery implemented as a co-routine */
+  if( pTabItem->fg.viaCoroutine ){
+    int regYield = pTabItem->regReturn;
+    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pTabItem->addrFillSub);
+    pLevel->p2 =  sqlite3VdbeAddOp2(v, OP_Yield, regYield, addrBrk);
+    VdbeCoverage(v);
+    VdbeComment((v, "next row of %s", pTabItem->pTab->zName));
+    pLevel->op = OP_Goto;
+  }else
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if(  (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
+    /* Case 1:  The table is a virtual-table.  Use the VFilter and VNext
+    **          to access the data.
+    */
+    int iReg;   /* P3 Value for OP_VFilter */
+    int addrNotFound;
+    int nConstraint = pLoop->nLTerm;
+
+    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
+    addrNotFound = pLevel->addrBrk;
+    for(j=0; j<nConstraint; j++){
+      int iTarget = iReg+j+2;
+      pTerm = pLoop->aLTerm[j];
+      if( NEVER(pTerm==0) ) continue;
+      if( pTerm->eOperator & WO_IN ){
+        if( SMASKBIT32(j) & pLoop->u.vtab.mHandleIn ){
+          int iTab = pParse->nTab++;
+          int iCache = ++pParse->nMem;
+          sqlite3CodeRhsOfIN(pParse, pTerm->pExpr, iTab);
+          sqlite3VdbeAddOp3(v, OP_VInitIn, iTab, iTarget, iCache);
+        }else{
+          codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
+          addrNotFound = pLevel->addrNxt;
+        }
+      }else{
+        Expr *pRight = pTerm->pExpr->pRight;
+        codeExprOrVector(pParse, pRight, iTarget, 1);
+        if( pTerm->eMatchOp==SQLITE_INDEX_CONSTRAINT_OFFSET
+         && pLoop->u.vtab.bOmitOffset
+        ){
+          assert( pTerm->eOperator==WO_AUX );
+          assert( pWInfo->pSelect!=0 );
+          assert( pWInfo->pSelect->iOffset>0 );
+          sqlite3VdbeAddOp2(v, OP_Integer, 0, pWInfo->pSelect->iOffset);
+          VdbeComment((v,"Zero OFFSET counter"));
+        }
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
+    sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
+    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
+                      pLoop->u.vtab.idxStr,
+                      pLoop->u.vtab.needFree ? P4_DYNAMIC : P4_STATIC);
+    VdbeCoverage(v);
+    pLoop->u.vtab.needFree = 0;
+    /* An OOM inside of AddOp4(OP_VFilter) instruction above might have freed
+    ** the u.vtab.idxStr.  NULL it out to prevent a use-after-free */
+    if( db->mallocFailed ) pLoop->u.vtab.idxStr = 0;
+    pLevel->p1 = iCur;
+    pLevel->op = pWInfo->eOnePass ? OP_Noop : OP_VNext;
+    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
+
+    for(j=0; j<nConstraint; j++){
+      pTerm = pLoop->aLTerm[j];
+      if( j<16 && (pLoop->u.vtab.omitMask>>j)&1 ){
+        disableTerm(pLevel, pTerm);
+        continue;
+      }
+      if( (pTerm->eOperator & WO_IN)!=0
+       && (SMASKBIT32(j) & pLoop->u.vtab.mHandleIn)==0
+       && !db->mallocFailed
+      ){
+        Expr *pCompare;  /* The comparison operator */
+        Expr *pRight;    /* RHS of the comparison */
+        VdbeOp *pOp;     /* Opcode to access the value of the IN constraint */
+        int iIn;         /* IN loop corresponding to the j-th constraint */
+
+        /* Reload the constraint value into reg[iReg+j+2].  The same value
+        ** was loaded into the same register prior to the OP_VFilter, but
+        ** the xFilter implementation might have changed the datatype or
+        ** encoding of the value in the register, so it *must* be reloaded.
+        */
+        for(iIn=0; ALWAYS(iIn<pLevel->u.in.nIn); iIn++){
+          pOp = sqlite3VdbeGetOp(v, pLevel->u.in.aInLoop[iIn].addrInTop);
+          if( (pOp->opcode==OP_Column && pOp->p3==iReg+j+2)
+           || (pOp->opcode==OP_Rowid && pOp->p2==iReg+j+2)
+          ){
+            testcase( pOp->opcode==OP_Rowid );
+            sqlite3VdbeAddOp3(v, pOp->opcode, pOp->p1, pOp->p2, pOp->p3);
+            break;
+          }
+        }
+
+        /* Generate code that will continue to the next row if
+        ** the IN constraint is not satisfied
+        */
+        pCompare = sqlite3PExpr(pParse, TK_EQ, 0, 0);
+        if( !db->mallocFailed ){
+          int iFld = pTerm->u.x.iField;
+          Expr *pLeft = pTerm->pExpr->pLeft;
+          assert( pLeft!=0 );
+          if( iFld>0 ){
+            assert( pLeft->op==TK_VECTOR );
+            assert( ExprUseXList(pLeft) );
+            assert( iFld<=pLeft->x.pList->nExpr );
+            pCompare->pLeft = pLeft->x.pList->a[iFld-1].pExpr;
+          }else{
+            pCompare->pLeft = pLeft;
+          }
+          pCompare->pRight = pRight = sqlite3Expr(db, TK_REGISTER, 0);
+          if( pRight ){
+            pRight->iTable = iReg+j+2;
+            sqlite3ExprIfFalse(
+                pParse, pCompare, pLevel->addrCont, SQLITE_JUMPIFNULL
+            );
+          }
+          pCompare->pLeft = 0;
+        }
+        sqlite3ExprDelete(db, pCompare);
+      }
+    }
+
+    /* These registers need to be preserved in case there is an IN operator
+    ** loop.  So we could deallocate the registers here (and potentially
+    ** reuse them later) if (pLoop->wsFlags & WHERE_IN_ABLE)==0.  But it seems
+    ** simpler and safer to simply not reuse the registers.
+    **
+    **    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
+    */
+  }else
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+  if( (pLoop->wsFlags & WHERE_IPK)!=0
+   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
+  ){
+    /* Case 2:  We can directly reference a single row using an
+    **          equality comparison against the ROWID field.  Or
+    **          we reference multiple rows using a "rowid IN (...)"
+    **          construct.
+    */
+    assert( pLoop->u.btree.nEq==1 );
+    pTerm = pLoop->aLTerm[0];
+    assert( pTerm!=0 );
+    assert( pTerm->pExpr!=0 );
+    testcase( pTerm->wtFlags & TERM_VIRTUAL );
+    iReleaseReg = ++pParse->nMem;
+    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, 0, bRev, iReleaseReg);
+    if( iRowidReg!=iReleaseReg ) sqlite3ReleaseTempReg(pParse, iReleaseReg);
+    addrNxt = pLevel->addrNxt;
+    if( pLevel->regFilter ){
+      sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp4Int(v, OP_Filter, pLevel->regFilter, addrNxt,
+                           iRowidReg, 1);
+      VdbeCoverage(v);
+      filterPullDown(pParse, pWInfo, iLevel, addrNxt, notReady);
+    }
+    sqlite3VdbeAddOp3(v, OP_SeekRowid, iCur, addrNxt, iRowidReg);
+    VdbeCoverage(v);
+    pLevel->op = OP_Noop;
+  }else if( (pLoop->wsFlags & WHERE_IPK)!=0
+         && (pLoop->wsFlags & WHERE_COLUMN_RANGE)!=0
+  ){
+    /* Case 3:  We have an inequality comparison against the ROWID field.
+    */
+    int testOp = OP_Noop;
+    int start;
+    int memEndValue = 0;
+    WhereTerm *pStart, *pEnd;
+
+    j = 0;
+    pStart = pEnd = 0;
+    if( pLoop->wsFlags & WHERE_BTM_LIMIT ) pStart = pLoop->aLTerm[j++];
+    if( pLoop->wsFlags & WHERE_TOP_LIMIT ) pEnd = pLoop->aLTerm[j++];
+    assert( pStart!=0 || pEnd!=0 );
+    if( bRev ){
+      pTerm = pStart;
+      pStart = pEnd;
+      pEnd = pTerm;
+    }
+    codeCursorHint(pTabItem, pWInfo, pLevel, pEnd);
+    if( pStart ){
+      Expr *pX;             /* The expression that defines the start bound */
+      int r1, rTemp;        /* Registers for holding the start boundary */
+      int op;               /* Cursor seek operation */
+
+      /* The following constant maps TK_xx codes into corresponding
+      ** seek opcodes.  It depends on a particular ordering of TK_xx
+      */
+      const u8 aMoveOp[] = {
+           /* TK_GT */  OP_SeekGT,
+           /* TK_LE */  OP_SeekLE,
+           /* TK_LT */  OP_SeekLT,
+           /* TK_GE */  OP_SeekGE
+      };
+      assert( TK_LE==TK_GT+1 );      /* Make sure the ordering.. */
+      assert( TK_LT==TK_GT+2 );      /*  ... of the TK_xx values... */
+      assert( TK_GE==TK_GT+3 );      /*  ... is correct. */
+
+      assert( (pStart->wtFlags & TERM_VNULL)==0 );
+      testcase( pStart->wtFlags & TERM_VIRTUAL );
+      pX = pStart->pExpr;
+      assert( pX!=0 );
+      testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
+      if( sqlite3ExprIsVector(pX->pRight) ){
+        r1 = rTemp = sqlite3GetTempReg(pParse);
+        codeExprOrVector(pParse, pX->pRight, r1, 1);
+        testcase( pX->op==TK_GT );
+        testcase( pX->op==TK_GE );
+        testcase( pX->op==TK_LT );
+        testcase( pX->op==TK_LE );
+        op = aMoveOp[((pX->op - TK_GT - 1) & 0x3) | 0x1];
+        assert( pX->op!=TK_GT || op==OP_SeekGE );
+        assert( pX->op!=TK_GE || op==OP_SeekGE );
+        assert( pX->op!=TK_LT || op==OP_SeekLE );
+        assert( pX->op!=TK_LE || op==OP_SeekLE );
+      }else{
+        r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
+        disableTerm(pLevel, pStart);
+        op = aMoveOp[(pX->op - TK_GT)];
+      }
+      sqlite3VdbeAddOp3(v, op, iCur, addrBrk, r1);
+      VdbeComment((v, "pk"));
+      VdbeCoverageIf(v, pX->op==TK_GT);
+      VdbeCoverageIf(v, pX->op==TK_LE);
+      VdbeCoverageIf(v, pX->op==TK_LT);
+      VdbeCoverageIf(v, pX->op==TK_GE);
+      sqlite3ReleaseTempReg(pParse, rTemp);
+    }else{
+      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrHalt);
+      VdbeCoverageIf(v, bRev==0);
+      VdbeCoverageIf(v, bRev!=0);
+    }
+    if( pEnd ){
+      Expr *pX;
+      pX = pEnd->pExpr;
+      assert( pX!=0 );
+      assert( (pEnd->wtFlags & TERM_VNULL)==0 );
+      testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
+      testcase( pEnd->wtFlags & TERM_VIRTUAL );
+      memEndValue = ++pParse->nMem;
+      codeExprOrVector(pParse, pX->pRight, memEndValue, 1);
+      if( 0==sqlite3ExprIsVector(pX->pRight)
+       && (pX->op==TK_LT || pX->op==TK_GT)
+      ){
+        testOp = bRev ? OP_Le : OP_Ge;
+      }else{
+        testOp = bRev ? OP_Lt : OP_Gt;
+      }
+      if( 0==sqlite3ExprIsVector(pX->pRight) ){
+        disableTerm(pLevel, pEnd);
+      }
+    }
+    start = sqlite3VdbeCurrentAddr(v);
+    pLevel->op = bRev ? OP_Prev : OP_Next;
+    pLevel->p1 = iCur;
+    pLevel->p2 = start;
+    assert( pLevel->p5==0 );
+    if( testOp!=OP_Noop ){
+      iRowidReg = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
+      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
+      VdbeCoverageIf(v, testOp==OP_Le);
+      VdbeCoverageIf(v, testOp==OP_Lt);
+      VdbeCoverageIf(v, testOp==OP_Ge);
+      VdbeCoverageIf(v, testOp==OP_Gt);
+      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
+    }
+  }else if( pLoop->wsFlags & WHERE_INDEXED ){
+    /* Case 4: A scan using an index.
+    **
+    **         The WHERE clause may contain zero or more equality
+    **         terms ("==" or "IN" operators) that refer to the N
+    **         left-most columns of the index. It may also contain
+    **         inequality constraints (>, <, >= or <=) on the indexed
+    **         column that immediately follows the N equalities. Only
+    **         the right-most column can be an inequality - the rest must
+    **         use the "==" and "IN" operators. For example, if the
+    **         index is on (x,y,z), then the following clauses are all
+    **         optimized:
+    **
+    **            x=5
+    **            x=5 AND y=10
+    **            x=5 AND y<10
+    **            x=5 AND y>5 AND y<10
+    **            x=5 AND y=5 AND z<=10
+    **
+    **         The z<10 term of the following cannot be used, only
+    **         the x=5 term:
+    **
+    **            x=5 AND z<10
+    **
+    **         N may be zero if there are inequality constraints.
+    **         If there are no inequality constraints, then N is at
+    **         least one.
+    **
+    **         This case is also used when there are no WHERE clause
+    **         constraints but an index is selected anyway, in order
+    **         to force the output order to conform to an ORDER BY.
+    */ 
+    static const u8 aStartOp[] = {
+      0,
+      0,
+      OP_Rewind,           /* 2: (!start_constraints && startEq &&  !bRev) */
+      OP_Last,             /* 3: (!start_constraints && startEq &&   bRev) */
+      OP_SeekGT,           /* 4: (start_constraints  && !startEq && !bRev) */
+      OP_SeekLT,           /* 5: (start_constraints  && !startEq &&  bRev) */
+      OP_SeekGE,           /* 6: (start_constraints  &&  startEq && !bRev) */
+      OP_SeekLE            /* 7: (start_constraints  &&  startEq &&  bRev) */
+    };
+    static const u8 aEndOp[] = {
+      OP_IdxGE,            /* 0: (end_constraints && !bRev && !endEq) */
+      OP_IdxGT,            /* 1: (end_constraints && !bRev &&  endEq) */
+      OP_IdxLE,            /* 2: (end_constraints &&  bRev && !endEq) */
+      OP_IdxLT,            /* 3: (end_constraints &&  bRev &&  endEq) */
+    };
+    u16 nEq = pLoop->u.btree.nEq;     /* Number of == or IN terms */
+    u16 nBtm = pLoop->u.btree.nBtm;   /* Length of BTM vector */
+    u16 nTop = pLoop->u.btree.nTop;   /* Length of TOP vector */
+    int regBase;                 /* Base register holding constraint values */
+    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
+    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
+    int startEq;                 /* True if range start uses ==, >= or <= */
+    int endEq;                   /* True if range end uses ==, >= or <= */
+    int start_constraints;       /* Start of range is constrained */
+    int nConstraint;             /* Number of constraint terms */
+    int iIdxCur;                 /* The VDBE cursor for the index */
+    int nExtraReg = 0;           /* Number of extra registers needed */
+    int op;                      /* Instruction opcode */
+    char *zStartAff;             /* Affinity for start of range constraint */
+    char *zEndAff = 0;           /* Affinity for end of range constraint */
+    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
+    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */
+    int omitTable;               /* True if we use the index only */
+    int regBignull = 0;          /* big-null flag register */
+    int addrSeekScan = 0;        /* Opcode of the OP_SeekScan, if any */
+
+    pIdx = pLoop->u.btree.pIndex;
+    iIdxCur = pLevel->iIdxCur;
+    assert( nEq>=pLoop->nSkip );
+
+    /* Find any inequality constraint terms for the start and end
+    ** of the range.
+    */
+    j = nEq;
+    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
+      pRangeStart = pLoop->aLTerm[j++];
+      nExtraReg = MAX(nExtraReg, pLoop->u.btree.nBtm);
+      /* Like optimization range constraints always occur in pairs */
+      assert( (pRangeStart->wtFlags & TERM_LIKEOPT)==0 ||
+              (pLoop->wsFlags & WHERE_TOP_LIMIT)!=0 );
+    }
+    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
+      pRangeEnd = pLoop->aLTerm[j++];
+      nExtraReg = MAX(nExtraReg, pLoop->u.btree.nTop);
+#ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+      if( (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0 ){
+        assert( pRangeStart!=0 );                     /* LIKE opt constraints */
+        assert( pRangeStart->wtFlags & TERM_LIKEOPT );   /* occur in pairs */
+        pLevel->iLikeRepCntr = (u32)++pParse->nMem;
+        sqlite3VdbeAddOp2(v, OP_Integer, 1, (int)pLevel->iLikeRepCntr);
+        VdbeComment((v, "LIKE loop counter"));
+        pLevel->addrLikeRep = sqlite3VdbeCurrentAddr(v);
+        /* iLikeRepCntr actually stores 2x the counter register number.  The
+        ** bottom bit indicates whether the search order is ASC or DESC. */
+        testcase( bRev );
+        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
+        assert( (bRev & ~1)==0 );
+        pLevel->iLikeRepCntr <<=1;
+        pLevel->iLikeRepCntr |= bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC);
+      }
+#endif
+      if( pRangeStart==0 ){
+        j = pIdx->aiColumn[nEq];
+        if( (j>=0 && pIdx->pTable->aCol[j].notNull==0) || j==XN_EXPR ){
+          bSeekPastNull = 1;
+        }
+      }
+    }
+    assert( pRangeEnd==0 || (pRangeEnd->wtFlags & TERM_VNULL)==0 );
+
+    /* If the WHERE_BIGNULL_SORT flag is set, then index column nEq uses
+    ** a non-default "big-null" sort (either ASC NULLS LAST or DESC NULLS
+    ** FIRST). In both cases separate ordered scans are made of those
+    ** index entries for which the column is null and for those for which
+    ** it is not. For an ASC sort, the non-NULL entries are scanned first.
+    ** For DESC, NULL entries are scanned first.
+    */
+    if( (pLoop->wsFlags & (WHERE_TOP_LIMIT|WHERE_BTM_LIMIT))==0
+     && (pLoop->wsFlags & WHERE_BIGNULL_SORT)!=0
+    ){
+      assert( bSeekPastNull==0 && nExtraReg==0 && nBtm==0 && nTop==0 );
+      assert( pRangeEnd==0 && pRangeStart==0 );
+      testcase( pLoop->nSkip>0 );
+      nExtraReg = 1;
+      bSeekPastNull = 1;
+      pLevel->regBignull = regBignull = ++pParse->nMem;
+      if( pLevel->iLeftJoin ){
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, regBignull);
+      }
+      pLevel->addrBignull = sqlite3VdbeMakeLabel(pParse);
+    }
+
+    /* If we are doing a reverse order scan on an ascending index, or
+    ** a forward order scan on a descending index, interchange the
+    ** start and end terms (pRangeStart and pRangeEnd).
+    */
+    if( (nEq<pIdx->nColumn && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC)) ){
+      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
+      SWAP(u8, bSeekPastNull, bStopAtNull);
+      SWAP(u8, nBtm, nTop);
+    }
+
+    if( iLevel>0 && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)!=0 ){
+      /* In case OP_SeekScan is used, ensure that the index cursor does not
+      ** point to a valid row for the first iteration of this loop. */
+      sqlite3VdbeAddOp1(v, OP_NullRow, iIdxCur);
+    }
+
+    /* Generate code to evaluate all constraint terms using == or IN
+    ** and store the values of those terms in an array of registers
+    ** starting at regBase.
+    */
+    codeCursorHint(pTabItem, pWInfo, pLevel, pRangeEnd);
+    regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
+    assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
+    if( zStartAff && nTop ){
+      zEndAff = sqlite3DbStrDup(db, &zStartAff[nEq]);
+    }
+    addrNxt = (regBignull ? pLevel->addrBignull : pLevel->addrNxt);
+
+    testcase( pRangeStart && (pRangeStart->eOperator & WO_LE)!=0 );
+    testcase( pRangeStart && (pRangeStart->eOperator & WO_GE)!=0 );
+    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_LE)!=0 );
+    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_GE)!=0 );
+    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
+    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
+    start_constraints = pRangeStart || nEq>0;
+
+    /* Seek the index cursor to the start of the range. */
+    nConstraint = nEq;
+    if( pRangeStart ){
+      Expr *pRight = pRangeStart->pExpr->pRight;
+      codeExprOrVector(pParse, pRight, regBase+nEq, nBtm);
+      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
+      if( (pRangeStart->wtFlags & TERM_VNULL)==0
+       && sqlite3ExprCanBeNull(pRight)
+      ){
+        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
+        VdbeCoverage(v);
+      }
+      if( zStartAff ){
+        updateRangeAffinityStr(pRight, nBtm, &zStartAff[nEq]);
+      } 
+      nConstraint += nBtm;
+      testcase( pRangeStart->wtFlags & TERM_VIRTUAL );
+      if( sqlite3ExprIsVector(pRight)==0 ){
+        disableTerm(pLevel, pRangeStart);
+      }else{
+        startEq = 1;
+      }
+      bSeekPastNull = 0;
+    }else if( bSeekPastNull ){
+      startEq = 0;
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
+      start_constraints = 1;
+      nConstraint++;
+    }else if( regBignull ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
+      start_constraints = 1;
+      nConstraint++;
+    }
+    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
+    if( pLoop->nSkip>0 && nConstraint==pLoop->nSkip ){
+      /* The skip-scan logic inside the call to codeAllEqualityConstraints()
+      ** above has already left the cursor sitting on the correct row,
+      ** so no further seeking is needed */
+    }else{
+      if( regBignull ){
+        sqlite3VdbeAddOp2(v, OP_Integer, 1, regBignull);
+        VdbeComment((v, "NULL-scan pass ctr"));
+      }
+      if( pLevel->regFilter ){
+        sqlite3VdbeAddOp4Int(v, OP_Filter, pLevel->regFilter, addrNxt,
+                             regBase, nEq);
+        VdbeCoverage(v);
+        filterPullDown(pParse, pWInfo, iLevel, addrNxt, notReady);
+      }
+
+      op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
+      assert( op!=0 );
+      if( (pLoop->wsFlags & WHERE_IN_SEEKSCAN)!=0 && op==OP_SeekGE ){
+        assert( regBignull==0 );
+        /* TUNING:  The OP_SeekScan opcode seeks to reduce the number
+        ** of expensive seek operations by replacing a single seek with
+        ** 1 or more step operations.  The question is, how many steps
+        ** should we try before giving up and going with a seek.  The cost
+        ** of a seek is proportional to the logarithm of the of the number
+        ** of entries in the tree, so basing the number of steps to try
+        ** on the estimated number of rows in the btree seems like a good
+        ** guess. */
+        addrSeekScan = sqlite3VdbeAddOp1(v, OP_SeekScan,
+                                         (pIdx->aiRowLogEst[0]+9)/10);
+        if( pRangeStart || pRangeEnd ){
+          sqlite3VdbeChangeP5(v, 1);
+          sqlite3VdbeChangeP2(v, addrSeekScan, sqlite3VdbeCurrentAddr(v)+1);
+          addrSeekScan = 0;
+        }
+        VdbeCoverage(v);
+      }
+      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
+      VdbeCoverage(v);
+      VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
+      VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
+      VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
+      VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
+      VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
+      VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );
+
+      assert( bSeekPastNull==0 || bStopAtNull==0 );
+      if( regBignull ){
+        assert( bSeekPastNull==1 || bStopAtNull==1 );
+        assert( bSeekPastNull==!bStopAtNull );
+        assert( bStopAtNull==startEq );
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
+        op = aStartOp[(nConstraint>1)*4 + 2 + bRev];
+        sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase,
+                             nConstraint-startEq);
+        VdbeCoverage(v);
+        VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
+        VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
+        VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
+        VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
+        assert( op==OP_Rewind || op==OP_Last || op==OP_SeekGE || op==OP_SeekLE);
+      }
+    }
+
+    /* Load the value for the inequality constraint at the end of the
+    ** range (if any).
+    */
+    nConstraint = nEq;
+    assert( pLevel->p2==0 );
+    if( pRangeEnd ){
+      Expr *pRight = pRangeEnd->pExpr->pRight;
+      assert( addrSeekScan==0 );
+      codeExprOrVector(pParse, pRight, regBase+nEq, nTop);
+      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
+      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
+       && sqlite3ExprCanBeNull(pRight)
+      ){
+        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
+        VdbeCoverage(v);
+      }
+      if( zEndAff ){
+        updateRangeAffinityStr(pRight, nTop, zEndAff);
+        codeApplyAffinity(pParse, regBase+nEq, nTop, zEndAff);
+      }else{
+        assert( pParse->db->mallocFailed );
+      }
+      nConstraint += nTop;
+      testcase( pRangeEnd->wtFlags & TERM_VIRTUAL );
+
+      if( sqlite3ExprIsVector(pRight)==0 ){
+        disableTerm(pLevel, pRangeEnd);
+      }else{
+        endEq = 1;
+      }
+    }else if( bStopAtNull ){
+      if( regBignull==0 ){
+        sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
+        endEq = 0;
+      }
+      nConstraint++;
+    }
+    if( zStartAff ) sqlite3DbNNFreeNN(db, zStartAff);
+    if( zEndAff ) sqlite3DbNNFreeNN(db, zEndAff);
+
+    /* Top of the loop body */
+    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+
+    /* Check if the index cursor is past the end of the range. */
+    if( nConstraint ){
+      if( regBignull ){
+        /* Except, skip the end-of-range check while doing the NULL-scan */
+        sqlite3VdbeAddOp2(v, OP_IfNot, regBignull, sqlite3VdbeCurrentAddr(v)+3);
+        VdbeComment((v, "If NULL-scan 2nd pass"));
+        VdbeCoverage(v);
+      }
+      op = aEndOp[bRev*2 + endEq];
+      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
+      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
+      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
+      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
+      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
+      if( addrSeekScan ) sqlite3VdbeJumpHere(v, addrSeekScan);
+    }
+    if( regBignull ){
+      /* During a NULL-scan, check to see if we have reached the end of
+      ** the NULLs */
+      assert( bSeekPastNull==!bStopAtNull );
+      assert( bSeekPastNull+bStopAtNull==1 );
+      assert( nConstraint+bSeekPastNull>0 );
+      sqlite3VdbeAddOp2(v, OP_If, regBignull, sqlite3VdbeCurrentAddr(v)+2);
+      VdbeComment((v, "If NULL-scan 1st pass"));
+      VdbeCoverage(v);
+      op = aEndOp[bRev*2 + bSeekPastNull];
+      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase,
+                           nConstraint+bSeekPastNull);
+      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
+      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
+      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
+      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
+    }
+
+    if( (pLoop->wsFlags & WHERE_IN_EARLYOUT)!=0 ){
+      sqlite3VdbeAddOp3(v, OP_SeekHit, iIdxCur, nEq, nEq);
+    }
+
+    /* Seek the table cursor, if required */
+    omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0
+           && (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))==0;
+    if( omitTable ){
+      /* pIdx is a covering index.  No need to access the main table. */
+    }else if( HasRowid(pIdx->pTable) ){
+      codeDeferredSeek(pWInfo, pIdx, iCur, iIdxCur);
+    }else if( iCur!=iIdxCur ){
+      Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
+      iRowidReg = sqlite3GetTempRange(pParse, pPk->nKeyCol);
+      for(j=0; j<pPk->nKeyCol; j++){
+        k = sqlite3TableColumnToIndex(pIdx, pPk->aiColumn[j]);
+        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
+      }
+      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
+                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
+    }
+
+    if( pLevel->iLeftJoin==0 ){
+      /* If a partial index is driving the loop, try to eliminate WHERE clause
+      ** terms from the query that must be true due to the WHERE clause of
+      ** the partial index.
+      **
+      ** 2019-11-02 ticket 623eff57e76d45f6: This optimization does not work
+      ** for a LEFT JOIN.
+      */
+      if( pIdx->pPartIdxWhere ){
+        whereApplyPartialIndexConstraints(pIdx->pPartIdxWhere, iCur, pWC);
+      }
+    }else{
+      testcase( pIdx->pPartIdxWhere );
+      /* The following assert() is not a requirement, merely an observation:
+      ** The OR-optimization doesn't work for the right hand table of
+      ** a LEFT JOIN: */
+      assert( (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))==0 );
+    }
+ 
+    /* Record the instruction used to terminate the loop. */
+    if( pLoop->wsFlags & WHERE_ONEROW ){
+      pLevel->op = OP_Noop;
+    }else if( bRev ){
+      pLevel->op = OP_Prev;
+    }else{
+      pLevel->op = OP_Next;
+    }
+    pLevel->p1 = iIdxCur;
+    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
+    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
+      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    }else{
+      assert( pLevel->p5==0 );
+    }
+    if( omitTable ) pIdx = 0;
+  }else
+
+#ifndef SQLITE_OMIT_OR_OPTIMIZATION
+  if( pLoop->wsFlags & WHERE_MULTI_OR ){
+    /* Case 5:  Two or more separately indexed terms connected by OR
+    **
+    ** Example:
+    **
+    **   CREATE TABLE t1(a,b,c,d);
+    **   CREATE INDEX i1 ON t1(a);
+    **   CREATE INDEX i2 ON t1(b);
+    **   CREATE INDEX i3 ON t1(c);
+    **
+    **   SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
+    **
+    ** In the example, there are three indexed terms connected by OR.
+    ** The top of the loop looks like this:
+    **
+    **          Null       1                # Zero the rowset in reg 1
+    **
+    ** Then, for each indexed term, the following. The arguments to
+    ** RowSetTest are such that the rowid of the current row is inserted
+    ** into the RowSet. If it is already present, control skips the
+    ** Gosub opcode and jumps straight to the code generated by WhereEnd().
+    **
+    **        sqlite3WhereBegin(<term>)
+    **          RowSetTest                  # Insert rowid into rowset
+    **          Gosub      2 A
+    **        sqlite3WhereEnd()
+    **
+    ** Following the above, code to terminate the loop. Label A, the target
+    ** of the Gosub above, jumps to the instruction right after the Goto.
+    **
+    **          Null       1                # Zero the rowset in reg 1
+    **          Goto       B                # The loop is finished.
+    **
+    **       A: <loop body>                 # Return data, whatever.
+    **
+    **          Return     2                # Jump back to the Gosub
+    **
+    **       B: <after the loop>
+    **
+    ** Added 2014-05-26: If the table is a WITHOUT ROWID table, then
+    ** use an ephemeral index instead of a RowSet to record the primary
+    ** keys of the rows we have already seen.
+    **
+    */
+    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
+    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
+    Index *pCov = 0;             /* Potential covering index (or NULL) */
+    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */
+
+    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
+    int regRowset = 0;                        /* Register for RowSet object */
+    int regRowid = 0;                         /* Register holding rowid */
+    int iLoopBody = sqlite3VdbeMakeLabel(pParse);/* Start of loop body */
+    int iRetInit;                             /* Address of regReturn init */
+    int untestedTerms = 0;             /* Some terms not completely tested */
+    int ii;                            /* Loop counter */
+    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
+    Table *pTab = pTabItem->pTab;
+
+    pTerm = pLoop->aLTerm[0];
+    assert( pTerm!=0 );
+    assert( pTerm->eOperator & WO_OR );
+    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
+    pOrWc = &pTerm->u.pOrInfo->wc;
+    pLevel->op = OP_Return;
+    pLevel->p1 = regReturn;
+
+    /* Set up a new SrcList in pOrTab containing the table being scanned
+    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
+    ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
+    */
+    if( pWInfo->nLevel>1 ){
+      int nNotReady;                 /* The number of notReady tables */
+      SrcItem *origSrc;              /* Original list of tables */
+      nNotReady = pWInfo->nLevel - iLevel - 1;
+      pOrTab = sqlite3DbMallocRawNN(db,
+                            sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
+      if( pOrTab==0 ) return notReady;
+      pOrTab->nAlloc = (u8)(nNotReady + 1);
+      pOrTab->nSrc = pOrTab->nAlloc;
+      memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
+      origSrc = pWInfo->pTabList->a;
+      for(k=1; k<=nNotReady; k++){
+        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
+      }
+    }else{
+      pOrTab = pWInfo->pTabList;
+    }
+
+    /* Initialize the rowset register to contain NULL. An SQL NULL is
+    ** equivalent to an empty rowset.  Or, create an ephemeral index
+    ** capable of holding primary keys in the case of a WITHOUT ROWID.
+    **
+    ** Also initialize regReturn to contain the address of the instruction
+    ** immediately following the OP_Return at the bottom of the loop. This
+    ** is required in a few obscure LEFT JOIN cases where control jumps
+    ** over the top of the loop into the body of it. In this case the
+    ** correct response for the end-of-loop code (the OP_Return) is to
+    ** fall through to the next instruction, just as an OP_Next does if
+    ** called on an uninitialized cursor.
+    */
+    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
+      if( HasRowid(pTab) ){
+        regRowset = ++pParse->nMem;
+        sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
+      }else{
+        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+        regRowset = pParse->nTab++;
+        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, regRowset, pPk->nKeyCol);
+        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
+      }
+      regRowid = ++pParse->nMem;
+    }
+    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
+
+    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
+    ** Then for every term xN, evaluate as the subexpression: xN AND y
+    ** That way, terms in y that are factored into the disjunction will
+    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
+    **
+    ** Actually, each subexpression is converted to "xN AND w" where w is
+    ** the "interesting" terms of z - terms that did not originate in the
+    ** ON or USING clause of a LEFT JOIN, and terms that are usable as
+    ** indices.
+    **
+    ** This optimization also only applies if the (x1 OR x2 OR ...) term
+    ** is not contained in the ON clause of a LEFT JOIN.
+    ** See ticket http://www.sqlite.org/src/info/f2369304e4
+    **
+    ** 2022-02-04:  Do not push down slices of a row-value comparison.
+    ** In other words, "w" or "y" may not be a slice of a vector.  Otherwise,
+    ** the initialization of the right-hand operand of the vector comparison
+    ** might not occur, or might occur only in an OR branch that is not
+    ** taken.  dbsqlfuzz 80a9fade844b4fb43564efc972bcb2c68270f5d1.
+    **
+    ** 2022-03-03:  Do not push down expressions that involve subqueries.
+    ** The subquery might get coded as a subroutine.  Any table-references
+    ** in the subquery might be resolved to index-references for the index on
+    ** the OR branch in which the subroutine is coded.  But if the subroutine
+    ** is invoked from a different OR branch that uses a different index, such
+    ** index-references will not work.  tag-20220303a
+    ** https://sqlite.org/forum/forumpost/36937b197273d403
+    */
+    if( pWC->nTerm>1 ){
+      int iTerm;
+      for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
+        Expr *pExpr = pWC->a[iTerm].pExpr;
+        if( &pWC->a[iTerm] == pTerm ) continue;
+        testcase( pWC->a[iTerm].wtFlags & TERM_VIRTUAL );
+        testcase( pWC->a[iTerm].wtFlags & TERM_CODED );
+        testcase( pWC->a[iTerm].wtFlags & TERM_SLICE );
+        if( (pWC->a[iTerm].wtFlags & (TERM_VIRTUAL|TERM_CODED|TERM_SLICE))!=0 ){
+          continue;
+        }
+        if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
+        if( ExprHasProperty(pExpr, EP_Subquery) ) continue;  /* tag-20220303a */
+        pExpr = sqlite3ExprDup(db, pExpr, 0);
+        pAndExpr = sqlite3ExprAnd(pParse, pAndExpr, pExpr);
+      }
+      if( pAndExpr ){
+        /* The extra 0x10000 bit on the opcode is masked off and does not
+        ** become part of the new Expr.op.  However, it does make the
+        ** op==TK_AND comparison inside of sqlite3PExpr() false, and this
+        ** prevents sqlite3PExpr() from applying the AND short-circuit
+        ** optimization, which we do not want here. */
+        pAndExpr = sqlite3PExpr(pParse, TK_AND|0x10000, 0, pAndExpr);
+      }
+    }
+
+    /* Run a separate WHERE clause for each term of the OR clause.  After
+    ** eliminating duplicates from other WHERE clauses, the action for each
+    ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
+    */
+    ExplainQueryPlan((pParse, 1, "MULTI-INDEX OR"));
+    for(ii=0; ii<pOrWc->nTerm; ii++){
+      WhereTerm *pOrTerm = &pOrWc->a[ii];
+      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
+        WhereInfo *pSubWInfo;           /* Info for single OR-term scan */
+        Expr *pOrExpr = pOrTerm->pExpr; /* Current OR clause term */
+        Expr *pDelete;                  /* Local copy of OR clause term */
+        int jmp1 = 0;                   /* Address of jump operation */
+        testcase( (pTabItem[0].fg.jointype & JT_LEFT)!=0
+               && !ExprHasProperty(pOrExpr, EP_OuterON)
+        ); /* See TH3 vtab25.400 and ticket 614b25314c766238 */
+        pDelete = pOrExpr = sqlite3ExprDup(db, pOrExpr, 0);
+        if( db->mallocFailed ){
+          sqlite3ExprDelete(db, pDelete);
+          continue;
+        }
+        if( pAndExpr ){
+          pAndExpr->pLeft = pOrExpr;
+          pOrExpr = pAndExpr;
+        }
+        /* Loop through table entries that match term pOrTerm. */
+        ExplainQueryPlan((pParse, 1, "INDEX %d", ii+1));
+        WHERETRACE(0xffffffff, ("Subplan for OR-clause:\n"));
+        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0, 0,
+                                      WHERE_OR_SUBCLAUSE, iCovCur);
+        assert( pSubWInfo || pParse->nErr );
+        if( pSubWInfo ){
+          WhereLoop *pSubLoop;
+          int addrExplain = sqlite3WhereExplainOneScan(
+              pParse, pOrTab, &pSubWInfo->a[0], 0
+          );
+          sqlite3WhereAddScanStatus(v, pOrTab, &pSubWInfo->a[0], addrExplain);
+
+          /* This is the sub-WHERE clause body.  First skip over
+          ** duplicate rows from prior sub-WHERE clauses, and record the
+          ** rowid (or PRIMARY KEY) for the current row so that the same
+          ** row will be skipped in subsequent sub-WHERE clauses.
+          */
+          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
+            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
+            if( HasRowid(pTab) ){
+              sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, -1, regRowid);
+              jmp1 = sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset, 0,
+                                          regRowid, iSet);
+              VdbeCoverage(v);
+            }else{
+              Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+              int nPk = pPk->nKeyCol;
+              int iPk;
+              int r;
+
+              /* Read the PK into an array of temp registers. */
+              r = sqlite3GetTempRange(pParse, nPk);
+              for(iPk=0; iPk<nPk; iPk++){
+                int iCol = pPk->aiColumn[iPk];
+                sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol,r+iPk);
+              }
+
+              /* Check if the temp table already contains this key. If so,
+              ** the row has already been included in the result set and
+              ** can be ignored (by jumping past the Gosub below). Otherwise,
+              ** insert the key into the temp table and proceed with processing
+              ** the row.
+              **
+              ** Use some of the same optimizations as OP_RowSetTest: If iSet
+              ** is zero, assume that the key cannot already be present in
+              ** the temp table. And if iSet is -1, assume that there is no
+              ** need to insert the key into the temp table, as it will never
+              ** be tested for.  */
+              if( iSet ){
+                jmp1 = sqlite3VdbeAddOp4Int(v, OP_Found, regRowset, 0, r, nPk);
+                VdbeCoverage(v);
+              }
+              if( iSet>=0 ){
+                sqlite3VdbeAddOp3(v, OP_MakeRecord, r, nPk, regRowid);
+                sqlite3VdbeAddOp4Int(v, OP_IdxInsert, regRowset, regRowid,
+                                     r, nPk);
+                if( iSet ) sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+              }
+
+              /* Release the array of temp registers */
+              sqlite3ReleaseTempRange(pParse, r, nPk);
+            }
+          }
+
+          /* Invoke the main loop body as a subroutine */
+          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
+
+          /* Jump here (skipping the main loop body subroutine) if the
+          ** current sub-WHERE row is a duplicate from prior sub-WHEREs. */
+          if( jmp1 ) sqlite3VdbeJumpHere(v, jmp1);
+
+          /* The pSubWInfo->untestedTerms flag means that this OR term
+          ** contained one or more AND term from a notReady table.  The
+          ** terms from the notReady table could not be tested and will
+          ** need to be tested later.
+          */
+          if( pSubWInfo->untestedTerms ) untestedTerms = 1;
+
+          /* If all of the OR-connected terms are optimized using the same
+          ** index, and the index is opened using the same cursor number
+          ** by each call to sqlite3WhereBegin() made by this loop, it may
+          ** be possible to use that index as a covering index.
+          **
+          ** If the call to sqlite3WhereBegin() above resulted in a scan that
+          ** uses an index, and this is either the first OR-connected term
+          ** processed or the index is the same as that used by all previous
+          ** terms, set pCov to the candidate covering index. Otherwise, set
+          ** pCov to NULL to indicate that no candidate covering index will
+          ** be available.
+          */
+          pSubLoop = pSubWInfo->a[0].pWLoop;
+          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
+          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
+           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
+           && (HasRowid(pTab) || !IsPrimaryKeyIndex(pSubLoop->u.btree.pIndex))
+          ){
+            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
+            pCov = pSubLoop->u.btree.pIndex;
+          }else{
+            pCov = 0;
+          }
+          if( sqlite3WhereUsesDeferredSeek(pSubWInfo) ){
+            pWInfo->bDeferredSeek = 1;
+          }
+
+          /* Finish the loop through table entries that match term pOrTerm. */
+          sqlite3WhereEnd(pSubWInfo);
+          ExplainQueryPlanPop(pParse);
+        }
+        sqlite3ExprDelete(db, pDelete);
+      }
+    }
+    ExplainQueryPlanPop(pParse);
+    assert( pLevel->pWLoop==pLoop );
+    assert( (pLoop->wsFlags & WHERE_MULTI_OR)!=0 );
+    assert( (pLoop->wsFlags & WHERE_IN_ABLE)==0 );
+    pLevel->u.pCoveringIdx = pCov;
+    if( pCov ) pLevel->iIdxCur = iCovCur;
+    if( pAndExpr ){
+      pAndExpr->pLeft = 0;
+      sqlite3ExprDelete(db, pAndExpr);
+    }
+    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
+    sqlite3VdbeGoto(v, pLevel->addrBrk);
+    sqlite3VdbeResolveLabel(v, iLoopBody);
+
+    /* Set the P2 operand of the OP_Return opcode that will end the current
+    ** loop to point to this spot, which is the top of the next containing
+    ** loop.  The byte-code formatter will use that P2 value as a hint to
+    ** indent everything in between the this point and the final OP_Return.
+    ** See tag-20220407a in vdbe.c and shell.c */
+    assert( pLevel->op==OP_Return );
+    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+
+    if( pWInfo->nLevel>1 ){ sqlite3DbFreeNN(db, pOrTab); }
+    if( !untestedTerms ) disableTerm(pLevel, pTerm);
+  }else
+#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+
+  {
+    /* Case 6:  There is no usable index.  We must do a complete
+    **          scan of the entire table.
+    */
+    static const u8 aStep[] = { OP_Next, OP_Prev };
+    static const u8 aStart[] = { OP_Rewind, OP_Last };
+    assert( bRev==0 || bRev==1 );
+    if( pTabItem->fg.isRecursive ){
+      /* Tables marked isRecursive have only a single row that is stored in
+      ** a pseudo-cursor.  No need to Rewind or Next such cursors. */
+      pLevel->op = OP_Noop;
+    }else{
+      codeCursorHint(pTabItem, pWInfo, pLevel, 0);
+      pLevel->op = aStep[bRev];
+      pLevel->p1 = iCur;
+      pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrHalt);
+      VdbeCoverageIf(v, bRev==0);
+      VdbeCoverageIf(v, bRev!=0);
+      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    }
+  }
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
+#endif
+
+  /* Insert code to test every subexpression that can be completely
+  ** computed using the current set of tables.
+  **
+  ** This loop may run between one and three times, depending on the
+  ** constraints to be generated. The value of stack variable iLoop
+  ** determines the constraints coded by each iteration, as follows:
+  **
+  ** iLoop==1: Code only expressions that are entirely covered by pIdx.
+  ** iLoop==2: Code remaining expressions that do not contain correlated
+  **           sub-queries. 
+  ** iLoop==3: Code all remaining expressions.
+  **
+  ** An effort is made to skip unnecessary iterations of the loop.
+  */
+  iLoop = (pIdx ? 1 : 2);
+  do{
+    int iNext = 0;                /* Next value for iLoop */
+    for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
+      Expr *pE;
+      int skipLikeAddr = 0;
+      testcase( pTerm->wtFlags & TERM_VIRTUAL );
+      testcase( pTerm->wtFlags & TERM_CODED );
+      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
+        testcase( pWInfo->untestedTerms==0
+            && (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)!=0 );
+        pWInfo->untestedTerms = 1;
+        continue;
+      }
+      pE = pTerm->pExpr;
+      assert( pE!=0 );
+      if( pTabItem->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT) ){
+        if( !ExprHasProperty(pE,EP_OuterON|EP_InnerON) ){
+          /* Defer processing WHERE clause constraints until after outer
+          ** join processing.  tag-20220513a */
+          continue;
+        }else if( (pTabItem->fg.jointype & JT_LEFT)==JT_LEFT
+               && !ExprHasProperty(pE,EP_OuterON) ){
+          continue;
+        }else{
+          Bitmask m = sqlite3WhereGetMask(&pWInfo->sMaskSet, pE->w.iJoin);
+          if( m & pLevel->notReady ){
+            /* An ON clause that is not ripe */
+            continue;
+          }
+        }
+      }
+      if( iLoop==1 && !sqlite3ExprCoveredByIndex(pE, pLevel->iTabCur, pIdx) ){
+        iNext = 2;
+        continue;
+      }
+      if( iLoop<3 && (pTerm->wtFlags & TERM_VARSELECT) ){
+        if( iNext==0 ) iNext = 3;
+        continue;
+      }
+
+      if( (pTerm->wtFlags & TERM_LIKECOND)!=0 ){
+        /* If the TERM_LIKECOND flag is set, that means that the range search
+        ** is sufficient to guarantee that the LIKE operator is true, so we
+        ** can skip the call to the like(A,B) function.  But this only works
+        ** for strings.  So do not skip the call to the function on the pass
+        ** that compares BLOBs. */
+#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+        continue;
+#else
+        u32 x = pLevel->iLikeRepCntr;
+        if( x>0 ){
+          skipLikeAddr = sqlite3VdbeAddOp1(v, (x&1)?OP_IfNot:OP_If,(int)(x>>1));
+          VdbeCoverageIf(v, (x&1)==1);
+          VdbeCoverageIf(v, (x&1)==0);
+        }
+#endif
+      }
+#ifdef WHERETRACE_ENABLED /* 0xffffffff */
+      if( sqlite3WhereTrace ){
+        VdbeNoopComment((v, "WhereTerm[%d] (%p) priority=%d",
+                         pWC->nTerm-j, pTerm, iLoop));
+      }
+      if( sqlite3WhereTrace & 0x4000 ){
+        sqlite3DebugPrintf("Coding auxiliary constraint:\n");
+        sqlite3WhereTermPrint(pTerm, pWC->nTerm-j);
+      }
+#endif
+      sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
+      if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr);
+      pTerm->wtFlags |= TERM_CODED;
+    }
+    iLoop = iNext;
+  }while( iLoop>0 );
+
+  /* Insert code to test for implied constraints based on transitivity
+  ** of the "==" operator.
+  **
+  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
+  ** and we are coding the t1 loop and the t2 loop has not yet coded,
+  ** then we cannot use the "t1.a=t2.b" constraint, but we can code
+  ** the implied "t1.a=123" constraint.
+  */
+  for(pTerm=pWC->a, j=pWC->nBase; j>0; j--, pTerm++){
+    Expr *pE, sEAlt;
+    WhereTerm *pAlt;
+    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+    if( (pTerm->eOperator & (WO_EQ|WO_IS))==0 ) continue;
+    if( (pTerm->eOperator & WO_EQUIV)==0 ) continue;
+    if( pTerm->leftCursor!=iCur ) continue;
+    if( pTabItem->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT) ) continue;
+    pE = pTerm->pExpr;
+#ifdef WHERETRACE_ENABLED /* 0x4001 */
+    if( (sqlite3WhereTrace & 0x4001)==0x4001 ){
+      sqlite3DebugPrintf("Coding transitive constraint:\n");
+      sqlite3WhereTermPrint(pTerm, pWC->nTerm-j);
+    }
+#endif
+    assert( !ExprHasProperty(pE, EP_OuterON) );
+    assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
+    assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+    pAlt = sqlite3WhereFindTerm(pWC, iCur, pTerm->u.x.leftColumn, notReady,
+                    WO_EQ|WO_IN|WO_IS, 0);
+    if( pAlt==0 ) continue;
+    if( pAlt->wtFlags & (TERM_CODED) ) continue;
+    if( (pAlt->eOperator & WO_IN)
+     && ExprUseXSelect(pAlt->pExpr)
+     && (pAlt->pExpr->x.pSelect->pEList->nExpr>1)
+    ){
+      continue;
+    }
+    testcase( pAlt->eOperator & WO_EQ );
+    testcase( pAlt->eOperator & WO_IS );
+    testcase( pAlt->eOperator & WO_IN );
+    VdbeModuleComment((v, "begin transitive constraint"));
+    sEAlt = *pAlt->pExpr;
+    sEAlt.pLeft = pE->pLeft;
+    sqlite3ExprIfFalse(pParse, &sEAlt, addrCont, SQLITE_JUMPIFNULL);
+    pAlt->wtFlags |= TERM_CODED;
+  }
+
+  /* For a RIGHT OUTER JOIN, record the fact that the current row has
+  ** been matched at least once.
+  */
+  if( pLevel->pRJ ){
+    Table *pTab;
+    int nPk;
+    int r;
+    int jmp1 = 0;
+    WhereRightJoin *pRJ = pLevel->pRJ;
+
+    /* pTab is the right-hand table of the RIGHT JOIN.  Generate code that
+    ** will record that the current row of that table has been matched at
+    ** least once.  This is accomplished by storing the PK for the row in
+    ** both the iMatch index and the regBloom Bloom filter.
+    */
+    pTab = pWInfo->pTabList->a[pLevel->iFrom].pTab;
+    if( HasRowid(pTab) ){
+      r = sqlite3GetTempRange(pParse, 2);
+      sqlite3ExprCodeGetColumnOfTable(v, pTab, pLevel->iTabCur, -1, r+1);
+      nPk = 1;
+    }else{
+      int iPk;
+      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+      nPk = pPk->nKeyCol;
+      r = sqlite3GetTempRange(pParse, nPk+1);
+      for(iPk=0; iPk<nPk; iPk++){
+        int iCol = pPk->aiColumn[iPk];
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol,r+1+iPk);
+      }
+    }
+    jmp1 = sqlite3VdbeAddOp4Int(v, OP_Found, pRJ->iMatch, 0, r+1, nPk);
+    VdbeCoverage(v);
+    VdbeComment((v, "match against %s", pTab->zName));
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, r+1, nPk, r);
+    sqlite3VdbeAddOp4Int(v, OP_IdxInsert, pRJ->iMatch, r, r+1, nPk);
+    sqlite3VdbeAddOp4Int(v, OP_FilterAdd, pRJ->regBloom, 0, r+1, nPk);
+    sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+    sqlite3VdbeJumpHere(v, jmp1);
+    sqlite3ReleaseTempRange(pParse, r, nPk+1);
+  }
+
+  /* For a LEFT OUTER JOIN, generate code that will record the fact that
+  ** at least one row of the right table has matched the left table.
+  */
+  if( pLevel->iLeftJoin ){
+    pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
+    VdbeComment((v, "record LEFT JOIN hit"));
+    if( pLevel->pRJ==0 ){
+      goto code_outer_join_constraints; /* WHERE clause constraints */
+    }
+  }
+
+  if( pLevel->pRJ ){
+    /* Create a subroutine used to process all interior loops and code
+    ** of the RIGHT JOIN.  During normal operation, the subroutine will
+    ** be in-line with the rest of the code.  But at the end, a separate
+    ** loop will run that invokes this subroutine for unmatched rows
+    ** of pTab, with all tables to left begin set to NULL.
+    */
+    WhereRightJoin *pRJ = pLevel->pRJ;
+    sqlite3VdbeAddOp2(v, OP_BeginSubrtn, 0, pRJ->regReturn);
+    pRJ->addrSubrtn = sqlite3VdbeCurrentAddr(v);
+    assert( pParse->withinRJSubrtn < 255 );
+    pParse->withinRJSubrtn++;
+
+    /* WHERE clause constraints must be deferred until after outer join
+    ** row elimination has completed, since WHERE clause constraints apply
+    ** to the results of the OUTER JOIN.  The following loop generates the
+    ** appropriate WHERE clause constraint checks.  tag-20220513a.
+    */
+  code_outer_join_constraints:
+    for(pTerm=pWC->a, j=0; j<pWC->nBase; j++, pTerm++){
+      testcase( pTerm->wtFlags & TERM_VIRTUAL );
+      testcase( pTerm->wtFlags & TERM_CODED );
+      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
+        assert( pWInfo->untestedTerms );
+        continue;
+      }
+      if( pTabItem->fg.jointype & JT_LTORJ ) continue;
+      assert( pTerm->pExpr );
+      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
+      pTerm->wtFlags |= TERM_CODED;
+    }
+  }
+
+#if WHERETRACE_ENABLED /* 0x4001 */
+  if( sqlite3WhereTrace & 0x4000 ){
+    sqlite3DebugPrintf("All WHERE-clause terms after coding level %d:\n",
+                       iLevel);
+    sqlite3WhereClausePrint(pWC);
+  }
+  if( sqlite3WhereTrace & 0x1 ){
+    sqlite3DebugPrintf("End Coding level %d:  notReady=%llx\n",
+       iLevel, (u64)pLevel->notReady);
+  }
+#endif
+  return pLevel->notReady;
+}
+
+/*
+** Generate the code for the loop that finds all non-matched terms
+** for a RIGHT JOIN.
+*/
+SQLITE_NOINLINE void sqlite3WhereRightJoinLoop(
+  WhereInfo *pWInfo,
+  int iLevel,
+  WhereLevel *pLevel
+){
+  Parse *pParse = pWInfo->pParse;
+  Vdbe *v = pParse->pVdbe;
+  WhereRightJoin *pRJ = pLevel->pRJ;
+  Expr *pSubWhere = 0;
+  WhereClause *pWC = &pWInfo->sWC;
+  WhereInfo *pSubWInfo;
+  WhereLoop *pLoop = pLevel->pWLoop;
+  SrcItem *pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
+  SrcList sFrom;
+  Bitmask mAll = 0;
+  int k;
+
+  ExplainQueryPlan((pParse, 1, "RIGHT-JOIN %s", pTabItem->pTab->zName));
+  sqlite3VdbeNoJumpsOutsideSubrtn(v, pRJ->addrSubrtn, pRJ->endSubrtn,
+                                  pRJ->regReturn);
+  for(k=0; k<iLevel; k++){
+    int iIdxCur;
+    mAll |= pWInfo->a[k].pWLoop->maskSelf;
+    sqlite3VdbeAddOp1(v, OP_NullRow, pWInfo->a[k].iTabCur);
+    iIdxCur = pWInfo->a[k].iIdxCur;
+    if( iIdxCur ){
+      sqlite3VdbeAddOp1(v, OP_NullRow, iIdxCur);
+    }
+  }
+  if( (pTabItem->fg.jointype & JT_LTORJ)==0 ){
+    mAll |= pLoop->maskSelf;
+    for(k=0; k<pWC->nTerm; k++){
+      WhereTerm *pTerm = &pWC->a[k];
+      if( (pTerm->wtFlags & (TERM_VIRTUAL|TERM_SLICE))!=0
+       && pTerm->eOperator!=WO_ROWVAL
+      ){
+        break;
+      }
+      if( pTerm->prereqAll & ~mAll ) continue;
+      if( ExprHasProperty(pTerm->pExpr, EP_OuterON|EP_InnerON) ) continue;
+      pSubWhere = sqlite3ExprAnd(pParse, pSubWhere,
+                                 sqlite3ExprDup(pParse->db, pTerm->pExpr, 0));
+    }
+  }
+  sFrom.nSrc = 1;
+  sFrom.nAlloc = 1;
+  memcpy(&sFrom.a[0], pTabItem, sizeof(SrcItem));
+  sFrom.a[0].fg.jointype = 0;
+  assert( pParse->withinRJSubrtn < 100 );
+  pParse->withinRJSubrtn++;
+  pSubWInfo = sqlite3WhereBegin(pParse, &sFrom, pSubWhere, 0, 0, 0,
+                                WHERE_RIGHT_JOIN, 0);
+  if( pSubWInfo ){
+    int iCur = pLevel->iTabCur;
+    int r = ++pParse->nMem;
+    int nPk;
+    int jmp;
+    int addrCont = sqlite3WhereContinueLabel(pSubWInfo);
+    Table *pTab = pTabItem->pTab;
+    if( HasRowid(pTab) ){
+      sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, -1, r);
+      nPk = 1;
+    }else{
+      int iPk;
+      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+      nPk = pPk->nKeyCol;
+      pParse->nMem += nPk - 1;
+      for(iPk=0; iPk<nPk; iPk++){
+        int iCol = pPk->aiColumn[iPk];
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol,r+iPk);
+      }
+    }
+    jmp = sqlite3VdbeAddOp4Int(v, OP_Filter, pRJ->regBloom, 0, r, nPk);
+    VdbeCoverage(v);
+    sqlite3VdbeAddOp4Int(v, OP_Found, pRJ->iMatch, addrCont, r, nPk);
+    VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, jmp);
+    sqlite3VdbeAddOp2(v, OP_Gosub, pRJ->regReturn, pRJ->addrSubrtn);
+    sqlite3WhereEnd(pSubWInfo);
+  }
+  sqlite3ExprDelete(pParse->db, pSubWhere);
+  ExplainQueryPlanPop(pParse);
+  assert( pParse->withinRJSubrtn>0 );
+  pParse->withinRJSubrtn--;
+}
diff --git a/src/whereexpr.c b/src/whereexpr.c
new file mode 100644
index 0000000..daf3d5d
--- /dev/null
+++ b/src/whereexpr.c
@@ -0,0 +1,1870 @@
+/*
+** 2015-06-08
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This module contains C code that generates VDBE code used to process
+** the WHERE clause of SQL statements.
+**
+** This file was originally part of where.c but was split out to improve
+** readability and editability.  This file contains utility routines for
+** analyzing Expr objects in the WHERE clause.
+*/
+#include "sqliteInt.h"
+#include "whereInt.h"
+
+/* Forward declarations */
+static void exprAnalyze(SrcList*, WhereClause*, int);
+
+/*
+** Deallocate all memory associated with a WhereOrInfo object.
+*/
+static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
+  sqlite3WhereClauseClear(&p->wc);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** Deallocate all memory associated with a WhereAndInfo object.
+*/
+static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
+  sqlite3WhereClauseClear(&p->wc);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** Add a single new WhereTerm entry to the WhereClause object pWC.
+** The new WhereTerm object is constructed from Expr p and with wtFlags.
+** The index in pWC->a[] of the new WhereTerm is returned on success.
+** 0 is returned if the new WhereTerm could not be added due to a memory
+** allocation error.  The memory allocation failure will be recorded in
+** the db->mallocFailed flag so that higher-level functions can detect it.
+**
+** This routine will increase the size of the pWC->a[] array as necessary.
+**
+** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
+** for freeing the expression p is assumed by the WhereClause object pWC.
+** This is true even if this routine fails to allocate a new WhereTerm.
+**
+** WARNING:  This routine might reallocate the space used to store
+** WhereTerms.  All pointers to WhereTerms should be invalidated after
+** calling this routine.  Such pointers may be reinitialized by referencing
+** the pWC->a[] array.
+*/
+static int whereClauseInsert(WhereClause *pWC, Expr *p, u16 wtFlags){
+  WhereTerm *pTerm;
+  int idx;
+  testcase( wtFlags & TERM_VIRTUAL );
+  if( pWC->nTerm>=pWC->nSlot ){
+    WhereTerm *pOld = pWC->a;
+    sqlite3 *db = pWC->pWInfo->pParse->db;
+    pWC->a = sqlite3WhereMalloc(pWC->pWInfo, sizeof(pWC->a[0])*pWC->nSlot*2 );
+    if( pWC->a==0 ){
+      if( wtFlags & TERM_DYNAMIC ){
+        sqlite3ExprDelete(db, p);
+      }
+      pWC->a = pOld;
+      return 0;
+    }
+    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
+    pWC->nSlot = pWC->nSlot*2;
+  }
+  pTerm = &pWC->a[idx = pWC->nTerm++];
+  if( (wtFlags & TERM_VIRTUAL)==0 ) pWC->nBase = pWC->nTerm;
+  if( p && ExprHasProperty(p, EP_Unlikely) ){
+    pTerm->truthProb = sqlite3LogEst(p->iTable) - 270;
+  }else{
+    pTerm->truthProb = 1;
+  }
+  pTerm->pExpr = sqlite3ExprSkipCollateAndLikely(p);
+  pTerm->wtFlags = wtFlags;
+  pTerm->pWC = pWC;
+  pTerm->iParent = -1;
+  memset(&pTerm->eOperator, 0,
+         sizeof(WhereTerm) - offsetof(WhereTerm,eOperator));
+  return idx;
+}
+
+/*
+** Return TRUE if the given operator is one of the operators that is
+** allowed for an indexable WHERE clause term.  The allowed operators are
+** "=", "<", ">", "<=", ">=", "IN", "IS", and "IS NULL"
+*/
+static int allowedOp(int op){
+  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
+  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
+  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
+  assert( TK_GE==TK_EQ+4 );
+  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL || op==TK_IS;
+}
+
+/*
+** Commute a comparison operator.  Expressions of the form "X op Y"
+** are converted into "Y op X".
+*/
+static u16 exprCommute(Parse *pParse, Expr *pExpr){
+  if( pExpr->pLeft->op==TK_VECTOR
+   || pExpr->pRight->op==TK_VECTOR
+   || sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft, pExpr->pRight) !=
+      sqlite3BinaryCompareCollSeq(pParse, pExpr->pRight, pExpr->pLeft)
+  ){
+    pExpr->flags ^= EP_Commuted;
+  }
+  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
+  if( pExpr->op>=TK_GT ){
+    assert( TK_LT==TK_GT+2 );
+    assert( TK_GE==TK_LE+2 );
+    assert( TK_GT>TK_EQ );
+    assert( TK_GT<TK_LE );
+    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
+    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
+  }
+  return 0;
+}
+
+/*
+** Translate from TK_xx operator to WO_xx bitmask.
+*/
+static u16 operatorMask(int op){
+  u16 c;
+  assert( allowedOp(op) );
+  if( op==TK_IN ){
+    c = WO_IN;
+  }else if( op==TK_ISNULL ){
+    c = WO_ISNULL;
+  }else if( op==TK_IS ){
+    c = WO_IS;
+  }else{
+    assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
+    c = (u16)(WO_EQ<<(op-TK_EQ));
+  }
+  assert( op!=TK_ISNULL || c==WO_ISNULL );
+  assert( op!=TK_IN || c==WO_IN );
+  assert( op!=TK_EQ || c==WO_EQ );
+  assert( op!=TK_LT || c==WO_LT );
+  assert( op!=TK_LE || c==WO_LE );
+  assert( op!=TK_GT || c==WO_GT );
+  assert( op!=TK_GE || c==WO_GE );
+  assert( op!=TK_IS || c==WO_IS );
+  return c;
+}
+
+
+#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+/*
+** Check to see if the given expression is a LIKE or GLOB operator that
+** can be optimized using inequality constraints.  Return TRUE if it is
+** so and false if not.
+**
+** In order for the operator to be optimizible, the RHS must be a string
+** literal that does not begin with a wildcard.  The LHS must be a column
+** that may only be NULL, a string, or a BLOB, never a number. (This means
+** that virtual tables cannot participate in the LIKE optimization.)  The
+** collating sequence for the column on the LHS must be appropriate for
+** the operator.
+*/
+static int isLikeOrGlob(
+  Parse *pParse,    /* Parsing and code generating context */
+  Expr *pExpr,      /* Test this expression */
+  Expr **ppPrefix,  /* Pointer to TK_STRING expression with pattern prefix */
+  int *pisComplete, /* True if the only wildcard is % in the last character */
+  int *pnoCase      /* True if uppercase is equivalent to lowercase */
+){
+  const u8 *z = 0;           /* String on RHS of LIKE operator */
+  Expr *pRight, *pLeft;      /* Right and left size of LIKE operator */
+  ExprList *pList;           /* List of operands to the LIKE operator */
+  u8 c;                      /* One character in z[] */
+  int cnt;                   /* Number of non-wildcard prefix characters */
+  u8 wc[4];                  /* Wildcard characters */
+  sqlite3 *db = pParse->db;  /* Database connection */
+  sqlite3_value *pVal = 0;
+  int op;                    /* Opcode of pRight */
+  int rc;                    /* Result code to return */
+
+  if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, (char*)wc) ){
+    return 0;
+  }
+#ifdef SQLITE_EBCDIC
+  if( *pnoCase ) return 0;
+#endif
+  assert( ExprUseXList(pExpr) );
+  pList = pExpr->x.pList;
+  pLeft = pList->a[1].pExpr;
+
+  pRight = sqlite3ExprSkipCollate(pList->a[0].pExpr);
+  op = pRight->op;
+  if( op==TK_VARIABLE && (db->flags & SQLITE_EnableQPSG)==0 ){
+    Vdbe *pReprepare = pParse->pReprepare;
+    int iCol = pRight->iColumn;
+    pVal = sqlite3VdbeGetBoundValue(pReprepare, iCol, SQLITE_AFF_BLOB);
+    if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
+      z = sqlite3_value_text(pVal);
+    }
+    sqlite3VdbeSetVarmask(pParse->pVdbe, iCol);
+    assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER );
+  }else if( op==TK_STRING ){
+    assert( !ExprHasProperty(pRight, EP_IntValue) );
+     z = (u8*)pRight->u.zToken;
+  }
+  if( z ){
+
+    /* Count the number of prefix characters prior to the first wildcard */
+    cnt = 0;
+    while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
+      cnt++;
+      if( c==wc[3] && z[cnt]!=0 ) cnt++;
+    }
+
+    /* The optimization is possible only if (1) the pattern does not begin
+    ** with a wildcard and if (2) the non-wildcard prefix does not end with
+    ** an (illegal 0xff) character, or (3) the pattern does not consist of
+    ** a single escape character. The second condition is necessary so
+    ** that we can increment the prefix key to find an upper bound for the
+    ** range search. The third is because the caller assumes that the pattern
+    ** consists of at least one character after all escapes have been
+    ** removed.  */
+    if( (cnt>1 || (cnt>0 && z[0]!=wc[3])) && 255!=(u8)z[cnt-1] ){
+      Expr *pPrefix;
+
+      /* A "complete" match if the pattern ends with "*" or "%" */
+      *pisComplete = c==wc[0] && z[cnt+1]==0;
+
+      /* Get the pattern prefix.  Remove all escapes from the prefix. */
+      pPrefix = sqlite3Expr(db, TK_STRING, (char*)z);
+      if( pPrefix ){
+        int iFrom, iTo;
+        char *zNew;
+        assert( !ExprHasProperty(pPrefix, EP_IntValue) );
+        zNew = pPrefix->u.zToken;
+        zNew[cnt] = 0;
+        for(iFrom=iTo=0; iFrom<cnt; iFrom++){
+          if( zNew[iFrom]==wc[3] ) iFrom++;
+          zNew[iTo++] = zNew[iFrom];
+        }
+        zNew[iTo] = 0;
+        assert( iTo>0 );
+
+        /* If the LHS is not an ordinary column with TEXT affinity, then the
+        ** pattern prefix boundaries (both the start and end boundaries) must
+        ** not look like a number.  Otherwise the pattern might be treated as
+        ** a number, which will invalidate the LIKE optimization.
+        **
+        ** Getting this right has been a persistent source of bugs in the
+        ** LIKE optimization.  See, for example:
+        **    2018-09-10 https://sqlite.org/src/info/c94369cae9b561b1
+        **    2019-05-02 https://sqlite.org/src/info/b043a54c3de54b28
+        **    2019-06-10 https://sqlite.org/src/info/fd76310a5e843e07
+        **    2019-06-14 https://sqlite.org/src/info/ce8717f0885af975
+        **    2019-09-03 https://sqlite.org/src/info/0f0428096f17252a
+        */
+        if( pLeft->op!=TK_COLUMN
+         || sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT
+         || (ALWAYS( ExprUseYTab(pLeft) )
+             && ALWAYS(pLeft->y.pTab)
+             && IsVirtual(pLeft->y.pTab))  /* Might be numeric */
+        ){
+          int isNum;
+          double rDummy;
+          isNum = sqlite3AtoF(zNew, &rDummy, iTo, SQLITE_UTF8);
+          if( isNum<=0 ){
+            if( iTo==1 && zNew[0]=='-' ){
+              isNum = +1;
+            }else{
+              zNew[iTo-1]++;
+              isNum = sqlite3AtoF(zNew, &rDummy, iTo, SQLITE_UTF8);
+              zNew[iTo-1]--;
+            }
+          }
+          if( isNum>0 ){
+            sqlite3ExprDelete(db, pPrefix);
+            sqlite3ValueFree(pVal);
+            return 0;
+          }
+        }
+      }
+      *ppPrefix = pPrefix;
+
+      /* If the RHS pattern is a bound parameter, make arrangements to
+      ** reprepare the statement when that parameter is rebound */
+      if( op==TK_VARIABLE ){
+        Vdbe *v = pParse->pVdbe;
+        sqlite3VdbeSetVarmask(v, pRight->iColumn);
+        assert( !ExprHasProperty(pRight, EP_IntValue) );
+        if( *pisComplete && pRight->u.zToken[1] ){
+          /* If the rhs of the LIKE expression is a variable, and the current
+          ** value of the variable means there is no need to invoke the LIKE
+          ** function, then no OP_Variable will be added to the program.
+          ** This causes problems for the sqlite3_bind_parameter_name()
+          ** API. To work around them, add a dummy OP_Variable here.
+          */
+          int r1 = sqlite3GetTempReg(pParse);
+          sqlite3ExprCodeTarget(pParse, pRight, r1);
+          sqlite3VdbeChangeP3(v, sqlite3VdbeCurrentAddr(v)-1, 0);
+          sqlite3ReleaseTempReg(pParse, r1);
+        }
+      }
+    }else{
+      z = 0;
+    }
+  }
+
+  rc = (z!=0);
+  sqlite3ValueFree(pVal);
+  return rc;
+}
+#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
+
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Check to see if the pExpr expression is a form that needs to be passed
+** to the xBestIndex method of virtual tables.  Forms of interest include:
+**
+**          Expression                   Virtual Table Operator
+**          -----------------------      ---------------------------------
+**      1.  column MATCH expr            SQLITE_INDEX_CONSTRAINT_MATCH
+**      2.  column GLOB expr             SQLITE_INDEX_CONSTRAINT_GLOB
+**      3.  column LIKE expr             SQLITE_INDEX_CONSTRAINT_LIKE
+**      4.  column REGEXP expr           SQLITE_INDEX_CONSTRAINT_REGEXP
+**      5.  column != expr               SQLITE_INDEX_CONSTRAINT_NE
+**      6.  expr != column               SQLITE_INDEX_CONSTRAINT_NE
+**      7.  column IS NOT expr           SQLITE_INDEX_CONSTRAINT_ISNOT
+**      8.  expr IS NOT column           SQLITE_INDEX_CONSTRAINT_ISNOT
+**      9.  column IS NOT NULL           SQLITE_INDEX_CONSTRAINT_ISNOTNULL
+**
+** In every case, "column" must be a column of a virtual table.  If there
+** is a match, set *ppLeft to the "column" expression, set *ppRight to the
+** "expr" expression (even though in forms (6) and (8) the column is on the
+** right and the expression is on the left).  Also set *peOp2 to the
+** appropriate virtual table operator.  The return value is 1 or 2 if there
+** is a match.  The usual return is 1, but if the RHS is also a column
+** of virtual table in forms (5) or (7) then return 2.
+**
+** If the expression matches none of the patterns above, return 0.
+*/
+static int isAuxiliaryVtabOperator(
+  sqlite3 *db,                    /* Parsing context */
+  Expr *pExpr,                    /* Test this expression */
+  unsigned char *peOp2,           /* OUT: 0 for MATCH, or else an op2 value */
+  Expr **ppLeft,                  /* Column expression to left of MATCH/op2 */
+  Expr **ppRight                  /* Expression to left of MATCH/op2 */
+){
+  if( pExpr->op==TK_FUNCTION ){
+    static const struct Op2 {
+      const char *zOp;
+      unsigned char eOp2;
+    } aOp[] = {
+      { "match",  SQLITE_INDEX_CONSTRAINT_MATCH },
+      { "glob",   SQLITE_INDEX_CONSTRAINT_GLOB },
+      { "like",   SQLITE_INDEX_CONSTRAINT_LIKE },
+      { "regexp", SQLITE_INDEX_CONSTRAINT_REGEXP }
+    };
+    ExprList *pList;
+    Expr *pCol;                     /* Column reference */
+    int i;
+
+    assert( ExprUseXList(pExpr) );
+    pList = pExpr->x.pList;
+    if( pList==0 || pList->nExpr!=2 ){
+      return 0;
+    }
+
+    /* Built-in operators MATCH, GLOB, LIKE, and REGEXP attach to a
+    ** virtual table on their second argument, which is the same as
+    ** the left-hand side operand in their in-fix form.
+    **
+    **       vtab_column MATCH expression
+    **       MATCH(expression,vtab_column)
+    */
+    pCol = pList->a[1].pExpr;
+    assert( pCol->op!=TK_COLUMN || (ExprUseYTab(pCol) && pCol->y.pTab!=0) );
+    if( ExprIsVtab(pCol) ){
+      for(i=0; i<ArraySize(aOp); i++){
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        if( sqlite3StrICmp(pExpr->u.zToken, aOp[i].zOp)==0 ){
+          *peOp2 = aOp[i].eOp2;
+          *ppRight = pList->a[0].pExpr;
+          *ppLeft = pCol;
+          return 1;
+        }
+      }
+    }
+
+    /* We can also match against the first column of overloaded
+    ** functions where xFindFunction returns a value of at least
+    ** SQLITE_INDEX_CONSTRAINT_FUNCTION.
+    **
+    **      OVERLOADED(vtab_column,expression)
+    **
+    ** Historically, xFindFunction expected to see lower-case function
+    ** names.  But for this use case, xFindFunction is expected to deal
+    ** with function names in an arbitrary case.
+    */
+    pCol = pList->a[0].pExpr;
+    assert( pCol->op!=TK_COLUMN || ExprUseYTab(pCol) );
+    assert( pCol->op!=TK_COLUMN || (ExprUseYTab(pCol) && pCol->y.pTab!=0) );
+    if( ExprIsVtab(pCol) ){
+      sqlite3_vtab *pVtab;
+      sqlite3_module *pMod;
+      void (*xNotUsed)(sqlite3_context*,int,sqlite3_value**);
+      void *pNotUsed;
+      pVtab = sqlite3GetVTable(db, pCol->y.pTab)->pVtab;
+      assert( pVtab!=0 );
+      assert( pVtab->pModule!=0 );
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      pMod = (sqlite3_module *)pVtab->pModule;
+      if( pMod->xFindFunction!=0 ){
+        i = pMod->xFindFunction(pVtab,2, pExpr->u.zToken, &xNotUsed, &pNotUsed);
+        if( i>=SQLITE_INDEX_CONSTRAINT_FUNCTION ){
+          *peOp2 = i;
+          *ppRight = pList->a[1].pExpr;
+          *ppLeft = pCol;
+          return 1;
+        }
+      }
+    }
+  }else if( pExpr->op==TK_NE || pExpr->op==TK_ISNOT || pExpr->op==TK_NOTNULL ){
+    int res = 0;
+    Expr *pLeft = pExpr->pLeft;
+    Expr *pRight = pExpr->pRight;
+    assert( pLeft->op!=TK_COLUMN || (ExprUseYTab(pLeft) && pLeft->y.pTab!=0) );
+    if( ExprIsVtab(pLeft) ){
+      res++;
+    }
+    assert( pRight==0 || pRight->op!=TK_COLUMN
+            || (ExprUseYTab(pRight) && pRight->y.pTab!=0) );
+    if( pRight && ExprIsVtab(pRight) ){
+      res++;
+      SWAP(Expr*, pLeft, pRight);
+    }
+    *ppLeft = pLeft;
+    *ppRight = pRight;
+    if( pExpr->op==TK_NE ) *peOp2 = SQLITE_INDEX_CONSTRAINT_NE;
+    if( pExpr->op==TK_ISNOT ) *peOp2 = SQLITE_INDEX_CONSTRAINT_ISNOT;
+    if( pExpr->op==TK_NOTNULL ) *peOp2 = SQLITE_INDEX_CONSTRAINT_ISNOTNULL;
+    return res;
+  }
+  return 0;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** If the pBase expression originated in the ON or USING clause of
+** a join, then transfer the appropriate markings over to derived.
+*/
+static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
+  if( pDerived && ExprHasProperty(pBase, EP_OuterON|EP_InnerON) ){
+    pDerived->flags |= pBase->flags & (EP_OuterON|EP_InnerON);
+    pDerived->w.iJoin = pBase->w.iJoin;
+  }
+}
+
+/*
+** Mark term iChild as being a child of term iParent
+*/
+static void markTermAsChild(WhereClause *pWC, int iChild, int iParent){
+  pWC->a[iChild].iParent = iParent;
+  pWC->a[iChild].truthProb = pWC->a[iParent].truthProb;
+  pWC->a[iParent].nChild++;
+}
+
+/*
+** Return the N-th AND-connected subterm of pTerm.  Or if pTerm is not
+** a conjunction, then return just pTerm when N==0.  If N is exceeds
+** the number of available subterms, return NULL.
+*/
+static WhereTerm *whereNthSubterm(WhereTerm *pTerm, int N){
+  if( pTerm->eOperator!=WO_AND ){
+    return N==0 ? pTerm : 0;
+  }
+  if( N<pTerm->u.pAndInfo->wc.nTerm ){
+    return &pTerm->u.pAndInfo->wc.a[N];
+  }
+  return 0;
+}
+
+/*
+** Subterms pOne and pTwo are contained within WHERE clause pWC.  The
+** two subterms are in disjunction - they are OR-ed together.
+**
+** If these two terms are both of the form:  "A op B" with the same
+** A and B values but different operators and if the operators are
+** compatible (if one is = and the other is <, for example) then
+** add a new virtual AND term to pWC that is the combination of the
+** two.
+**
+** Some examples:
+**
+**    x<y OR x=y    -->     x<=y
+**    x=y OR x=y    -->     x=y
+**    x<=y OR x<y   -->     x<=y
+**
+** The following is NOT generated:
+**
+**    x<y OR x>y    -->     x!=y    
+*/
+static void whereCombineDisjuncts(
+  SrcList *pSrc,         /* the FROM clause */
+  WhereClause *pWC,      /* The complete WHERE clause */
+  WhereTerm *pOne,       /* First disjunct */
+  WhereTerm *pTwo        /* Second disjunct */
+){
+  u16 eOp = pOne->eOperator | pTwo->eOperator;
+  sqlite3 *db;           /* Database connection (for malloc) */
+  Expr *pNew;            /* New virtual expression */
+  int op;                /* Operator for the combined expression */
+  int idxNew;            /* Index in pWC of the next virtual term */
+
+  if( (pOne->wtFlags | pTwo->wtFlags) & TERM_VNULL ) return;
+  if( (pOne->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
+  if( (pTwo->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
+  if( (eOp & (WO_EQ|WO_LT|WO_LE))!=eOp
+   && (eOp & (WO_EQ|WO_GT|WO_GE))!=eOp ) return;
+  assert( pOne->pExpr->pLeft!=0 && pOne->pExpr->pRight!=0 );
+  assert( pTwo->pExpr->pLeft!=0 && pTwo->pExpr->pRight!=0 );
+  if( sqlite3ExprCompare(0,pOne->pExpr->pLeft, pTwo->pExpr->pLeft, -1) ) return;
+  if( sqlite3ExprCompare(0,pOne->pExpr->pRight, pTwo->pExpr->pRight,-1) )return;
+  /* If we reach this point, it means the two subterms can be combined */
+  if( (eOp & (eOp-1))!=0 ){
+    if( eOp & (WO_LT|WO_LE) ){
+      eOp = WO_LE;
+    }else{
+      assert( eOp & (WO_GT|WO_GE) );
+      eOp = WO_GE;
+    }
+  }
+  db = pWC->pWInfo->pParse->db;
+  pNew = sqlite3ExprDup(db, pOne->pExpr, 0);
+  if( pNew==0 ) return;
+  for(op=TK_EQ; eOp!=(WO_EQ<<(op-TK_EQ)); op++){ assert( op<TK_GE ); }
+  pNew->op = op;
+  idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
+  exprAnalyze(pSrc, pWC, idxNew);
+}
+
+#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
+/*
+** Analyze a term that consists of two or more OR-connected
+** subterms.  So in:
+**
+**     ... WHERE  (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
+**                          ^^^^^^^^^^^^^^^^^^^^
+**
+** This routine analyzes terms such as the middle term in the above example.
+** A WhereOrTerm object is computed and attached to the term under
+** analysis, regardless of the outcome of the analysis.  Hence:
+**
+**     WhereTerm.wtFlags   |=  TERM_ORINFO
+**     WhereTerm.u.pOrInfo  =  a dynamically allocated WhereOrTerm object
+**
+** The term being analyzed must have two or more of OR-connected subterms.
+** A single subterm might be a set of AND-connected sub-subterms.
+** Examples of terms under analysis:
+**
+**     (A)     t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
+**     (B)     x=expr1 OR expr2=x OR x=expr3
+**     (C)     t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
+**     (D)     x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
+**     (E)     (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
+**     (F)     x>A OR (x=A AND y>=B)
+**
+** CASE 1:
+**
+** If all subterms are of the form T.C=expr for some single column of C and
+** a single table T (as shown in example B above) then create a new virtual
+** term that is an equivalent IN expression.  In other words, if the term
+** being analyzed is:
+**
+**      x = expr1  OR  expr2 = x  OR  x = expr3
+**
+** then create a new virtual term like this:
+**
+**      x IN (expr1,expr2,expr3)
+**
+** CASE 2:
+**
+** If there are exactly two disjuncts and one side has x>A and the other side
+** has x=A (for the same x and A) then add a new virtual conjunct term to the
+** WHERE clause of the form "x>=A".  Example:
+**
+**      x>A OR (x=A AND y>B)    adds:    x>=A
+**
+** The added conjunct can sometimes be helpful in query planning.
+**
+** CASE 3:
+**
+** If all subterms are indexable by a single table T, then set
+**
+**     WhereTerm.eOperator              =  WO_OR
+**     WhereTerm.u.pOrInfo->indexable  |=  the cursor number for table T
+**
+** A subterm is "indexable" if it is of the form
+** "T.C <op> <expr>" where C is any column of table T and
+** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
+** A subterm is also indexable if it is an AND of two or more
+** subsubterms at least one of which is indexable.  Indexable AND
+** subterms have their eOperator set to WO_AND and they have
+** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
+**
+** From another point of view, "indexable" means that the subterm could
+** potentially be used with an index if an appropriate index exists.
+** This analysis does not consider whether or not the index exists; that
+** is decided elsewhere.  This analysis only looks at whether subterms
+** appropriate for indexing exist.
+**
+** All examples A through E above satisfy case 3.  But if a term
+** also satisfies case 1 (such as B) we know that the optimizer will
+** always prefer case 1, so in that case we pretend that case 3 is not
+** satisfied.
+**
+** It might be the case that multiple tables are indexable.  For example,
+** (E) above is indexable on tables P, Q, and R.
+**
+** Terms that satisfy case 3 are candidates for lookup by using
+** separate indices to find rowids for each subterm and composing
+** the union of all rowids using a RowSet object.  This is similar
+** to "bitmap indices" in other database engines.
+**
+** OTHERWISE:
+**
+** If none of cases 1, 2, or 3 apply, then leave the eOperator set to
+** zero.  This term is not useful for search.
+*/
+static void exprAnalyzeOrTerm(
+  SrcList *pSrc,            /* the FROM clause */
+  WhereClause *pWC,         /* the complete WHERE clause */
+  int idxTerm               /* Index of the OR-term to be analyzed */
+){
+  WhereInfo *pWInfo = pWC->pWInfo;        /* WHERE clause processing context */
+  Parse *pParse = pWInfo->pParse;         /* Parser context */
+  sqlite3 *db = pParse->db;               /* Database connection */
+  WhereTerm *pTerm = &pWC->a[idxTerm];    /* The term to be analyzed */
+  Expr *pExpr = pTerm->pExpr;             /* The expression of the term */
+  int i;                                  /* Loop counters */
+  WhereClause *pOrWc;       /* Breakup of pTerm into subterms */
+  WhereTerm *pOrTerm;       /* A Sub-term within the pOrWc */
+  WhereOrInfo *pOrInfo;     /* Additional information associated with pTerm */
+  Bitmask chngToIN;         /* Tables that might satisfy case 1 */
+  Bitmask indexable;        /* Tables that are indexable, satisfying case 2 */
+
+  /*
+  ** Break the OR clause into its separate subterms.  The subterms are
+  ** stored in a WhereClause structure containing within the WhereOrInfo
+  ** object that is attached to the original OR clause term.
+  */
+  assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
+  assert( pExpr->op==TK_OR );
+  pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
+  if( pOrInfo==0 ) return;
+  pTerm->wtFlags |= TERM_ORINFO;
+  pOrWc = &pOrInfo->wc;
+  memset(pOrWc->aStatic, 0, sizeof(pOrWc->aStatic));
+  sqlite3WhereClauseInit(pOrWc, pWInfo);
+  sqlite3WhereSplit(pOrWc, pExpr, TK_OR);
+  sqlite3WhereExprAnalyze(pSrc, pOrWc);
+  if( db->mallocFailed ) return;
+  assert( pOrWc->nTerm>=2 );
+
+  /*
+  ** Compute the set of tables that might satisfy cases 1 or 3.
+  */
+  indexable = ~(Bitmask)0;
+  chngToIN = ~(Bitmask)0;
+  for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
+    if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
+      WhereAndInfo *pAndInfo;
+      assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
+      chngToIN = 0;
+      pAndInfo = sqlite3DbMallocRawNN(db, sizeof(*pAndInfo));
+      if( pAndInfo ){
+        WhereClause *pAndWC;
+        WhereTerm *pAndTerm;
+        int j;
+        Bitmask b = 0;
+        pOrTerm->u.pAndInfo = pAndInfo;
+        pOrTerm->wtFlags |= TERM_ANDINFO;
+        pOrTerm->eOperator = WO_AND;
+        pOrTerm->leftCursor = -1;
+        pAndWC = &pAndInfo->wc;
+        memset(pAndWC->aStatic, 0, sizeof(pAndWC->aStatic));
+        sqlite3WhereClauseInit(pAndWC, pWC->pWInfo);
+        sqlite3WhereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
+        sqlite3WhereExprAnalyze(pSrc, pAndWC);
+        pAndWC->pOuter = pWC;
+        if( !db->mallocFailed ){
+          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
+            assert( pAndTerm->pExpr );
+            if( allowedOp(pAndTerm->pExpr->op)
+             || pAndTerm->eOperator==WO_AUX
+            ){
+              b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
+            }
+          }
+        }
+        indexable &= b;
+      }
+    }else if( pOrTerm->wtFlags & TERM_COPIED ){
+      /* Skip this term for now.  We revisit it when we process the
+      ** corresponding TERM_VIRTUAL term */
+    }else{
+      Bitmask b;
+      b = sqlite3WhereGetMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
+      if( pOrTerm->wtFlags & TERM_VIRTUAL ){
+        WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
+        b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pOther->leftCursor);
+      }
+      indexable &= b;
+      if( (pOrTerm->eOperator & WO_EQ)==0 ){
+        chngToIN = 0;
+      }else{
+        chngToIN &= b;
+      }
+    }
+  }
+
+  /*
+  ** Record the set of tables that satisfy case 3.  The set might be
+  ** empty.
+  */
+  pOrInfo->indexable = indexable;
+  pTerm->eOperator = WO_OR;
+  pTerm->leftCursor = -1;
+  if( indexable ){
+    pWC->hasOr = 1;
+  }
+
+  /* For a two-way OR, attempt to implementation case 2.
+  */
+  if( indexable && pOrWc->nTerm==2 ){
+    int iOne = 0;
+    WhereTerm *pOne;
+    while( (pOne = whereNthSubterm(&pOrWc->a[0],iOne++))!=0 ){
+      int iTwo = 0;
+      WhereTerm *pTwo;
+      while( (pTwo = whereNthSubterm(&pOrWc->a[1],iTwo++))!=0 ){
+        whereCombineDisjuncts(pSrc, pWC, pOne, pTwo);
+      }
+    }
+  }
+
+  /*
+  ** chngToIN holds a set of tables that *might* satisfy case 1.  But
+  ** we have to do some additional checking to see if case 1 really
+  ** is satisfied.
+  **
+  ** chngToIN will hold either 0, 1, or 2 bits.  The 0-bit case means
+  ** that there is no possibility of transforming the OR clause into an
+  ** IN operator because one or more terms in the OR clause contain
+  ** something other than == on a column in the single table.  The 1-bit
+  ** case means that every term of the OR clause is of the form
+  ** "table.column=expr" for some single table.  The one bit that is set
+  ** will correspond to the common table.  We still need to check to make
+  ** sure the same column is used on all terms.  The 2-bit case is when
+  ** the all terms are of the form "table1.column=table2.column".  It
+  ** might be possible to form an IN operator with either table1.column
+  ** or table2.column as the LHS if either is common to every term of
+  ** the OR clause.
+  **
+  ** Note that terms of the form "table.column1=table.column2" (the
+  ** same table on both sizes of the ==) cannot be optimized.
+  */
+  if( chngToIN ){
+    int okToChngToIN = 0;     /* True if the conversion to IN is valid */
+    int iColumn = -1;         /* Column index on lhs of IN operator */
+    int iCursor = -1;         /* Table cursor common to all terms */
+    int j = 0;                /* Loop counter */
+
+    /* Search for a table and column that appears on one side or the
+    ** other of the == operator in every subterm.  That table and column
+    ** will be recorded in iCursor and iColumn.  There might not be any
+    ** such table and column.  Set okToChngToIN if an appropriate table
+    ** and column is found but leave okToChngToIN false if not found.
+    */
+    for(j=0; j<2 && !okToChngToIN; j++){
+      Expr *pLeft = 0;
+      pOrTerm = pOrWc->a;
+      for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
+        assert( pOrTerm->eOperator & WO_EQ );
+        pOrTerm->wtFlags &= ~TERM_OK;
+        if( pOrTerm->leftCursor==iCursor ){
+          /* This is the 2-bit case and we are on the second iteration and
+          ** current term is from the first iteration.  So skip this term. */
+          assert( j==1 );
+          continue;
+        }
+        if( (chngToIN & sqlite3WhereGetMask(&pWInfo->sMaskSet,
+                                            pOrTerm->leftCursor))==0 ){
+          /* This term must be of the form t1.a==t2.b where t2 is in the
+          ** chngToIN set but t1 is not.  This term will be either preceded
+          ** or followed by an inverted copy (t2.b==t1.a).  Skip this term
+          ** and use its inversion. */
+          testcase( pOrTerm->wtFlags & TERM_COPIED );
+          testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
+          assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
+          continue;
+        }
+        assert( (pOrTerm->eOperator & (WO_OR|WO_AND))==0 );
+        iColumn = pOrTerm->u.x.leftColumn;
+        iCursor = pOrTerm->leftCursor;
+        pLeft = pOrTerm->pExpr->pLeft;
+        break;
+      }
+      if( i<0 ){
+        /* No candidate table+column was found.  This can only occur
+        ** on the second iteration */
+        assert( j==1 );
+        assert( IsPowerOfTwo(chngToIN) );
+        assert( chngToIN==sqlite3WhereGetMask(&pWInfo->sMaskSet, iCursor) );
+        break;
+      }
+      testcase( j==1 );
+
+      /* We have found a candidate table and column.  Check to see if that
+      ** table and column is common to every term in the OR clause */
+      okToChngToIN = 1;
+      for(; i>=0 && okToChngToIN; i--, pOrTerm++){
+        assert( pOrTerm->eOperator & WO_EQ );
+        assert( (pOrTerm->eOperator & (WO_OR|WO_AND))==0 );
+        if( pOrTerm->leftCursor!=iCursor ){
+          pOrTerm->wtFlags &= ~TERM_OK;
+        }else if( pOrTerm->u.x.leftColumn!=iColumn || (iColumn==XN_EXPR
+               && sqlite3ExprCompare(pParse, pOrTerm->pExpr->pLeft, pLeft, -1)
+        )){
+          okToChngToIN = 0;
+        }else{
+          int affLeft, affRight;
+          /* If the right-hand side is also a column, then the affinities
+          ** of both right and left sides must be such that no type
+          ** conversions are required on the right.  (Ticket #2249)
+          */
+          affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
+          affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
+          if( affRight!=0 && affRight!=affLeft ){
+            okToChngToIN = 0;
+          }else{
+            pOrTerm->wtFlags |= TERM_OK;
+          }
+        }
+      }
+    }
+
+    /* At this point, okToChngToIN is true if original pTerm satisfies
+    ** case 1.  In that case, construct a new virtual term that is
+    ** pTerm converted into an IN operator.
+    */
+    if( okToChngToIN ){
+      Expr *pDup;            /* A transient duplicate expression */
+      ExprList *pList = 0;   /* The RHS of the IN operator */
+      Expr *pLeft = 0;       /* The LHS of the IN operator */
+      Expr *pNew;            /* The complete IN operator */
+
+      for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
+        if( (pOrTerm->wtFlags & TERM_OK)==0 ) continue;
+        assert( pOrTerm->eOperator & WO_EQ );
+        assert( (pOrTerm->eOperator & (WO_OR|WO_AND))==0 );
+        assert( pOrTerm->leftCursor==iCursor );
+        assert( pOrTerm->u.x.leftColumn==iColumn );
+        pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
+        pList = sqlite3ExprListAppend(pWInfo->pParse, pList, pDup);
+        pLeft = pOrTerm->pExpr->pLeft;
+      }
+      assert( pLeft!=0 );
+      pDup = sqlite3ExprDup(db, pLeft, 0);
+      pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0);
+      if( pNew ){
+        int idxNew;
+        transferJoinMarkings(pNew, pExpr);
+        assert( ExprUseXList(pNew) );
+        pNew->x.pList = pList;
+        idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
+        testcase( idxNew==0 );
+        exprAnalyze(pSrc, pWC, idxNew);
+        /* pTerm = &pWC->a[idxTerm]; // would be needed if pTerm where reused */
+        markTermAsChild(pWC, idxNew, idxTerm);
+      }else{
+        sqlite3ExprListDelete(db, pList);
+      }
+    }
+  }
+}
+#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
+
+/*
+** We already know that pExpr is a binary operator where both operands are
+** column references.  This routine checks to see if pExpr is an equivalence
+** relation:
+**   1.  The SQLITE_Transitive optimization must be enabled
+**   2.  Must be either an == or an IS operator
+**   3.  Not originating in the ON clause of an OUTER JOIN
+**   4.  The affinities of A and B must be compatible
+**   5a. Both operands use the same collating sequence OR
+**   5b. The overall collating sequence is BINARY
+** If this routine returns TRUE, that means that the RHS can be substituted
+** for the LHS anyplace else in the WHERE clause where the LHS column occurs.
+** This is an optimization.  No harm comes from returning 0.  But if 1 is
+** returned when it should not be, then incorrect answers might result.
+*/
+static int termIsEquivalence(Parse *pParse, Expr *pExpr){
+  char aff1, aff2;
+  CollSeq *pColl;
+  if( !OptimizationEnabled(pParse->db, SQLITE_Transitive) ) return 0;
+  if( pExpr->op!=TK_EQ && pExpr->op!=TK_IS ) return 0;
+  if( ExprHasProperty(pExpr, EP_OuterON) ) return 0;
+  aff1 = sqlite3ExprAffinity(pExpr->pLeft);
+  aff2 = sqlite3ExprAffinity(pExpr->pRight);
+  if( aff1!=aff2
+   && (!sqlite3IsNumericAffinity(aff1) || !sqlite3IsNumericAffinity(aff2))
+  ){
+    return 0;
+  }
+  pColl = sqlite3ExprCompareCollSeq(pParse, pExpr);
+  if( sqlite3IsBinary(pColl) ) return 1;
+  return sqlite3ExprCollSeqMatch(pParse, pExpr->pLeft, pExpr->pRight);
+}
+
+/*
+** Recursively walk the expressions of a SELECT statement and generate
+** a bitmask indicating which tables are used in that expression
+** tree.
+*/
+static Bitmask exprSelectUsage(WhereMaskSet *pMaskSet, Select *pS){
+  Bitmask mask = 0;
+  while( pS ){
+    SrcList *pSrc = pS->pSrc;
+    mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pEList);
+    mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pGroupBy);
+    mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pOrderBy);
+    mask |= sqlite3WhereExprUsage(pMaskSet, pS->pWhere);
+    mask |= sqlite3WhereExprUsage(pMaskSet, pS->pHaving);
+    if( ALWAYS(pSrc!=0) ){
+      int i;
+      for(i=0; i<pSrc->nSrc; i++){
+        mask |= exprSelectUsage(pMaskSet, pSrc->a[i].pSelect);
+        if( pSrc->a[i].fg.isUsing==0 ){
+          mask |= sqlite3WhereExprUsage(pMaskSet, pSrc->a[i].u3.pOn);
+        }
+        if( pSrc->a[i].fg.isTabFunc ){
+          mask |= sqlite3WhereExprListUsage(pMaskSet, pSrc->a[i].u1.pFuncArg);
+        }
+      }
+    }
+    pS = pS->pPrior;
+  }
+  return mask;
+}
+
+/*
+** Expression pExpr is one operand of a comparison operator that might
+** be useful for indexing.  This routine checks to see if pExpr appears
+** in any index.  Return TRUE (1) if pExpr is an indexed term and return
+** FALSE (0) if not.  If TRUE is returned, also set aiCurCol[0] to the cursor
+** number of the table that is indexed and aiCurCol[1] to the column number
+** of the column that is indexed, or XN_EXPR (-2) if an expression is being
+** indexed.
+**
+** If pExpr is a TK_COLUMN column reference, then this routine always returns
+** true even if that particular column is not indexed, because the column
+** might be added to an automatic index later.
+*/
+static SQLITE_NOINLINE int exprMightBeIndexed2(
+  SrcList *pFrom,        /* The FROM clause */
+  int *aiCurCol,         /* Write the referenced table cursor and column here */
+  Expr *pExpr,           /* An operand of a comparison operator */
+  int j                  /* Start looking with the j-th pFrom entry */
+){
+  Index *pIdx;
+  int i;
+  int iCur;
+  do{
+    iCur = pFrom->a[j].iCursor;
+    for(pIdx=pFrom->a[j].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      if( pIdx->aColExpr==0 ) continue;
+      for(i=0; i<pIdx->nKeyCol; i++){
+        if( pIdx->aiColumn[i]!=XN_EXPR ) continue;
+        assert( pIdx->bHasExpr );
+        if( sqlite3ExprCompareSkip(pExpr,pIdx->aColExpr->a[i].pExpr,iCur)==0
+          && pExpr->op!=TK_STRING
+        ){
+          aiCurCol[0] = iCur;
+          aiCurCol[1] = XN_EXPR;
+          return 1;
+        }
+      }
+    }
+  }while( ++j < pFrom->nSrc );
+  return 0;
+}
+static int exprMightBeIndexed(
+  SrcList *pFrom,        /* The FROM clause */
+  int *aiCurCol,         /* Write the referenced table cursor & column here */
+  Expr *pExpr,           /* An operand of a comparison operator */
+  int op                 /* The specific comparison operator */
+){
+  int i;
+
+  /* If this expression is a vector to the left or right of a
+  ** inequality constraint (>, <, >= or <=), perform the processing
+  ** on the first element of the vector.  */
+  assert( TK_GT+1==TK_LE && TK_GT+2==TK_LT && TK_GT+3==TK_GE );
+  assert( TK_IS<TK_GE && TK_ISNULL<TK_GE && TK_IN<TK_GE );
+  assert( op<=TK_GE );
+  if( pExpr->op==TK_VECTOR && (op>=TK_GT && ALWAYS(op<=TK_GE)) ){
+    assert( ExprUseXList(pExpr) );
+    pExpr = pExpr->x.pList->a[0].pExpr;
+  }
+
+  if( pExpr->op==TK_COLUMN ){
+    aiCurCol[0] = pExpr->iTable;
+    aiCurCol[1] = pExpr->iColumn;
+    return 1;
+  }
+
+  for(i=0; i<pFrom->nSrc; i++){
+    Index *pIdx;
+    for(pIdx=pFrom->a[i].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      if( pIdx->aColExpr ){
+        return exprMightBeIndexed2(pFrom,aiCurCol,pExpr,i);
+      }
+    }
+  }
+  return 0;
+}
+
+
+/*
+** The input to this routine is an WhereTerm structure with only the
+** "pExpr" field filled in.  The job of this routine is to analyze the
+** subexpression and populate all the other fields of the WhereTerm
+** structure.
+**
+** If the expression is of the form "<expr> <op> X" it gets commuted
+** to the standard form of "X <op> <expr>".
+**
+** If the expression is of the form "X <op> Y" where both X and Y are
+** columns, then the original expression is unchanged and a new virtual
+** term of the form "Y <op> X" is added to the WHERE clause and
+** analyzed separately.  The original term is marked with TERM_COPIED
+** and the new term is marked with TERM_DYNAMIC (because it's pExpr
+** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
+** is a commuted copy of a prior term.)  The original term has nChild=1
+** and the copy has idxParent set to the index of the original term.
+*/
+static void exprAnalyze(
+  SrcList *pSrc,            /* the FROM clause */
+  WhereClause *pWC,         /* the WHERE clause */
+  int idxTerm               /* Index of the term to be analyzed */
+){
+  WhereInfo *pWInfo = pWC->pWInfo; /* WHERE clause processing context */
+  WhereTerm *pTerm;                /* The term to be analyzed */
+  WhereMaskSet *pMaskSet;          /* Set of table index masks */
+  Expr *pExpr;                     /* The expression to be analyzed */
+  Bitmask prereqLeft;              /* Prerequisites of the pExpr->pLeft */
+  Bitmask prereqAll;               /* Prerequisites of pExpr */
+  Bitmask extraRight = 0;          /* Extra dependencies on LEFT JOIN */
+  Expr *pStr1 = 0;                 /* RHS of LIKE/GLOB operator */
+  int isComplete = 0;              /* RHS of LIKE/GLOB ends with wildcard */
+  int noCase = 0;                  /* uppercase equivalent to lowercase */
+  int op;                          /* Top-level operator.  pExpr->op */
+  Parse *pParse = pWInfo->pParse;  /* Parsing context */
+  sqlite3 *db = pParse->db;        /* Database connection */
+  unsigned char eOp2 = 0;          /* op2 value for LIKE/REGEXP/GLOB */
+  int nLeft;                       /* Number of elements on left side vector */
+
+  if( db->mallocFailed ){
+    return;
+  }
+  assert( pWC->nTerm > idxTerm );
+  pTerm = &pWC->a[idxTerm];
+  pMaskSet = &pWInfo->sMaskSet;
+  pExpr = pTerm->pExpr;
+  assert( pExpr!=0 ); /* Because malloc() has not failed */
+  assert( pExpr->op!=TK_AS && pExpr->op!=TK_COLLATE );
+  pMaskSet->bVarSelect = 0;
+  prereqLeft = sqlite3WhereExprUsage(pMaskSet, pExpr->pLeft);
+  op = pExpr->op;
+  if( op==TK_IN ){
+    assert( pExpr->pRight==0 );
+    if( sqlite3ExprCheckIN(pParse, pExpr) ) return;
+    if( ExprUseXSelect(pExpr) ){
+      pTerm->prereqRight = exprSelectUsage(pMaskSet, pExpr->x.pSelect);
+    }else{
+      pTerm->prereqRight = sqlite3WhereExprListUsage(pMaskSet, pExpr->x.pList);
+    }
+    prereqAll = prereqLeft | pTerm->prereqRight;
+  }else{
+    pTerm->prereqRight = sqlite3WhereExprUsage(pMaskSet, pExpr->pRight);
+    if( pExpr->pLeft==0
+     || ExprHasProperty(pExpr, EP_xIsSelect|EP_IfNullRow)
+     || pExpr->x.pList!=0
+    ){
+      prereqAll = sqlite3WhereExprUsageNN(pMaskSet, pExpr);
+    }else{
+      prereqAll = prereqLeft | pTerm->prereqRight;
+    }
+  }
+  if( pMaskSet->bVarSelect ) pTerm->wtFlags |= TERM_VARSELECT;
+
+#ifdef SQLITE_DEBUG
+  if( prereqAll!=sqlite3WhereExprUsageNN(pMaskSet, pExpr) ){
+    printf("\n*** Incorrect prereqAll computed for:\n");
+    sqlite3TreeViewExpr(0,pExpr,0);
+    assert( 0 );
+  }
+#endif
+
+  if( ExprHasProperty(pExpr, EP_OuterON|EP_InnerON) ){
+    Bitmask x = sqlite3WhereGetMask(pMaskSet, pExpr->w.iJoin);
+    if( ExprHasProperty(pExpr, EP_OuterON) ){
+      prereqAll |= x;
+      extraRight = x-1;  /* ON clause terms may not be used with an index
+                         ** on left table of a LEFT JOIN.  Ticket #3015 */
+      if( (prereqAll>>1)>=x ){
+        sqlite3ErrorMsg(pParse, "ON clause references tables to its right");
+        return;
+      }
+    }else if( (prereqAll>>1)>=x ){
+      /* The ON clause of an INNER JOIN references a table to its right.
+      ** Most other SQL database engines raise an error.  But SQLite versions
+      ** 3.0 through 3.38 just put the ON clause constraint into the WHERE
+      ** clause and carried on.   Beginning with 3.39, raise an error only
+      ** if there is a RIGHT or FULL JOIN in the query.  This makes SQLite
+      ** more like other systems, and also preserves legacy. */
+      if( ALWAYS(pSrc->nSrc>0) && (pSrc->a[0].fg.jointype & JT_LTORJ)!=0 ){
+        sqlite3ErrorMsg(pParse, "ON clause references tables to its right");
+        return;
+      }
+      ExprClearProperty(pExpr, EP_InnerON);
+    }
+  }
+  pTerm->prereqAll = prereqAll;
+  pTerm->leftCursor = -1;
+  pTerm->iParent = -1;
+  pTerm->eOperator = 0;
+  if( allowedOp(op) ){
+    int aiCurCol[2];
+    Expr *pLeft = sqlite3ExprSkipCollate(pExpr->pLeft);
+    Expr *pRight = sqlite3ExprSkipCollate(pExpr->pRight);
+    u16 opMask = (pTerm->prereqRight & prereqLeft)==0 ? WO_ALL : WO_EQUIV;
+
+    if( pTerm->u.x.iField>0 ){
+      assert( op==TK_IN );
+      assert( pLeft->op==TK_VECTOR );
+      assert( ExprUseXList(pLeft) );
+      pLeft = pLeft->x.pList->a[pTerm->u.x.iField-1].pExpr;
+    }
+
+    if( exprMightBeIndexed(pSrc, aiCurCol, pLeft, op) ){
+      pTerm->leftCursor = aiCurCol[0];
+      assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+      pTerm->u.x.leftColumn = aiCurCol[1];
+      pTerm->eOperator = operatorMask(op) & opMask;
+    }
+    if( op==TK_IS ) pTerm->wtFlags |= TERM_IS;
+    if( pRight
+     && exprMightBeIndexed(pSrc, aiCurCol, pRight, op)
+     && !ExprHasProperty(pRight, EP_FixedCol)
+    ){
+      WhereTerm *pNew;
+      Expr *pDup;
+      u16 eExtraOp = 0;        /* Extra bits for pNew->eOperator */
+      assert( pTerm->u.x.iField==0 );
+      if( pTerm->leftCursor>=0 ){
+        int idxNew;
+        pDup = sqlite3ExprDup(db, pExpr, 0);
+        if( db->mallocFailed ){
+          sqlite3ExprDelete(db, pDup);
+          return;
+        }
+        idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
+        if( idxNew==0 ) return;
+        pNew = &pWC->a[idxNew];
+        markTermAsChild(pWC, idxNew, idxTerm);
+        if( op==TK_IS ) pNew->wtFlags |= TERM_IS;
+        pTerm = &pWC->a[idxTerm];
+        pTerm->wtFlags |= TERM_COPIED;
+
+        if( termIsEquivalence(pParse, pDup) ){
+          pTerm->eOperator |= WO_EQUIV;
+          eExtraOp = WO_EQUIV;
+        }
+      }else{
+        pDup = pExpr;
+        pNew = pTerm;
+      }
+      pNew->wtFlags |= exprCommute(pParse, pDup);
+      pNew->leftCursor = aiCurCol[0];
+      assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
+      pNew->u.x.leftColumn = aiCurCol[1];
+      testcase( (prereqLeft | extraRight) != prereqLeft );
+      pNew->prereqRight = prereqLeft | extraRight;
+      pNew->prereqAll = prereqAll;
+      pNew->eOperator = (operatorMask(pDup->op) + eExtraOp) & opMask;
+    }else
+    if( op==TK_ISNULL
+     && !ExprHasProperty(pExpr,EP_OuterON)
+     && 0==sqlite3ExprCanBeNull(pLeft)
+    ){
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      pExpr->op = TK_TRUEFALSE;  /* See tag-20230504-1 */
+      pExpr->u.zToken = "false";
+      ExprSetProperty(pExpr, EP_IsFalse);
+      pTerm->prereqAll = 0;
+      pTerm->eOperator = 0;
+    }
+  }
+
+#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  /* If a term is the BETWEEN operator, create two new virtual terms
+  ** that define the range that the BETWEEN implements.  For example:
+  **
+  **      a BETWEEN b AND c
+  **
+  ** is converted into:
+  **
+  **      (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
+  **
+  ** The two new terms are added onto the end of the WhereClause object.
+  ** The new terms are "dynamic" and are children of the original BETWEEN
+  ** term.  That means that if the BETWEEN term is coded, the children are
+  ** skipped.  Or, if the children are satisfied by an index, the original
+  ** BETWEEN term is skipped.
+  */
+  else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
+    ExprList *pList;
+    int i;
+    static const u8 ops[] = {TK_GE, TK_LE};
+    assert( ExprUseXList(pExpr) );
+    pList = pExpr->x.pList;
+    assert( pList!=0 );
+    assert( pList->nExpr==2 );
+    for(i=0; i<2; i++){
+      Expr *pNewExpr;
+      int idxNew;
+      pNewExpr = sqlite3PExpr(pParse, ops[i],
+                             sqlite3ExprDup(db, pExpr->pLeft, 0),
+                             sqlite3ExprDup(db, pList->a[i].pExpr, 0));
+      transferJoinMarkings(pNewExpr, pExpr);
+      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
+      testcase( idxNew==0 );
+      exprAnalyze(pSrc, pWC, idxNew);
+      pTerm = &pWC->a[idxTerm];
+      markTermAsChild(pWC, idxNew, idxTerm);
+    }
+  }
+#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
+
+#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
+  /* Analyze a term that is composed of two or more subterms connected by
+  ** an OR operator.
+  */
+  else if( pExpr->op==TK_OR ){
+    assert( pWC->op==TK_AND );
+    exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
+    pTerm = &pWC->a[idxTerm];
+  }
+#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+  /* The form "x IS NOT NULL" can sometimes be evaluated more efficiently
+  ** as "x>NULL" if x is not an INTEGER PRIMARY KEY.  So construct a
+  ** virtual term of that form.
+  **
+  ** The virtual term must be tagged with TERM_VNULL.
+  */
+  else if( pExpr->op==TK_NOTNULL ){
+    if( pExpr->pLeft->op==TK_COLUMN
+     && pExpr->pLeft->iColumn>=0
+     && !ExprHasProperty(pExpr, EP_OuterON)
+    ){
+      Expr *pNewExpr;
+      Expr *pLeft = pExpr->pLeft;
+      int idxNew;
+      WhereTerm *pNewTerm;
+ 
+      pNewExpr = sqlite3PExpr(pParse, TK_GT,
+                              sqlite3ExprDup(db, pLeft, 0),
+                              sqlite3ExprAlloc(db, TK_NULL, 0, 0));
+ 
+      idxNew = whereClauseInsert(pWC, pNewExpr,
+                                TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
+      if( idxNew ){
+        pNewTerm = &pWC->a[idxNew];
+        pNewTerm->prereqRight = 0;
+        pNewTerm->leftCursor = pLeft->iTable;
+        pNewTerm->u.x.leftColumn = pLeft->iColumn;
+        pNewTerm->eOperator = WO_GT;
+        markTermAsChild(pWC, idxNew, idxTerm);
+        pTerm = &pWC->a[idxTerm];
+        pTerm->wtFlags |= TERM_COPIED;
+        pNewTerm->prereqAll = pTerm->prereqAll;
+      }
+    }
+  }
+
+
+#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+  /* Add constraints to reduce the search space on a LIKE or GLOB
+  ** operator.
+  **
+  ** A like pattern of the form "x LIKE 'aBc%'" is changed into constraints
+  **
+  **          x>='ABC' AND x<'abd' AND x LIKE 'aBc%'
+  **
+  ** The last character of the prefix "abc" is incremented to form the
+  ** termination condition "abd".  If case is not significant (the default
+  ** for LIKE) then the lower-bound is made all uppercase and the upper-
+  ** bound is made all lowercase so that the bounds also work when comparing
+  ** BLOBs.
+  */
+  else if( pExpr->op==TK_FUNCTION
+   && pWC->op==TK_AND
+   && isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
+  ){
+    Expr *pLeft;       /* LHS of LIKE/GLOB operator */
+    Expr *pStr2;       /* Copy of pStr1 - RHS of LIKE/GLOB operator */
+    Expr *pNewExpr1;
+    Expr *pNewExpr2;
+    int idxNew1;
+    int idxNew2;
+    const char *zCollSeqName;     /* Name of collating sequence */
+    const u16 wtFlags = TERM_LIKEOPT | TERM_VIRTUAL | TERM_DYNAMIC;
+
+    assert( ExprUseXList(pExpr) );
+    pLeft = pExpr->x.pList->a[1].pExpr;
+    pStr2 = sqlite3ExprDup(db, pStr1, 0);
+    assert( pStr1==0 || !ExprHasProperty(pStr1, EP_IntValue) );
+    assert( pStr2==0 || !ExprHasProperty(pStr2, EP_IntValue) );
+
+
+    /* Convert the lower bound to upper-case and the upper bound to
+    ** lower-case (upper-case is less than lower-case in ASCII) so that
+    ** the range constraints also work for BLOBs
+    */
+    if( noCase && !pParse->db->mallocFailed ){
+      int i;
+      char c;
+      pTerm->wtFlags |= TERM_LIKE;
+      for(i=0; (c = pStr1->u.zToken[i])!=0; i++){
+        pStr1->u.zToken[i] = sqlite3Toupper(c);
+        pStr2->u.zToken[i] = sqlite3Tolower(c);
+      }
+    }
+
+    if( !db->mallocFailed ){
+      u8 c, *pC;       /* Last character before the first wildcard */
+      pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
+      c = *pC;
+      if( noCase ){
+        /* The point is to increment the last character before the first
+        ** wildcard.  But if we increment '@', that will push it into the
+        ** alphabetic range where case conversions will mess up the
+        ** inequality.  To avoid this, make sure to also run the full
+        ** LIKE on all candidate expressions by clearing the isComplete flag
+        */
+        if( c=='A'-1 ) isComplete = 0;
+        c = sqlite3UpperToLower[c];
+      }
+      *pC = c + 1;
+    }
+    zCollSeqName = noCase ? "NOCASE" : sqlite3StrBINARY;
+    pNewExpr1 = sqlite3ExprDup(db, pLeft, 0);
+    pNewExpr1 = sqlite3PExpr(pParse, TK_GE,
+           sqlite3ExprAddCollateString(pParse,pNewExpr1,zCollSeqName),
+           pStr1);
+    transferJoinMarkings(pNewExpr1, pExpr);
+    idxNew1 = whereClauseInsert(pWC, pNewExpr1, wtFlags);
+    testcase( idxNew1==0 );
+    pNewExpr2 = sqlite3ExprDup(db, pLeft, 0);
+    pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
+           sqlite3ExprAddCollateString(pParse,pNewExpr2,zCollSeqName),
+           pStr2);
+    transferJoinMarkings(pNewExpr2, pExpr);
+    idxNew2 = whereClauseInsert(pWC, pNewExpr2, wtFlags);
+    testcase( idxNew2==0 );
+    exprAnalyze(pSrc, pWC, idxNew1);
+    exprAnalyze(pSrc, pWC, idxNew2);
+    pTerm = &pWC->a[idxTerm];
+    if( isComplete ){
+      markTermAsChild(pWC, idxNew1, idxTerm);
+      markTermAsChild(pWC, idxNew2, idxTerm);
+    }
+  }
+#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
+
+  /* If there is a vector == or IS term - e.g. "(a, b) == (?, ?)" - create
+  ** new terms for each component comparison - "a = ?" and "b = ?".  The
+  ** new terms completely replace the original vector comparison, which is
+  ** no longer used.
+  **
+  ** This is only required if at least one side of the comparison operation
+  ** is not a sub-select.
+  **
+  ** tag-20220128a
+  */
+  if( (pExpr->op==TK_EQ || pExpr->op==TK_IS)
+   && (nLeft = sqlite3ExprVectorSize(pExpr->pLeft))>1
+   && sqlite3ExprVectorSize(pExpr->pRight)==nLeft
+   && ( (pExpr->pLeft->flags & EP_xIsSelect)==0
+     || (pExpr->pRight->flags & EP_xIsSelect)==0)
+   && pWC->op==TK_AND
+  ){
+    int i;
+    for(i=0; i<nLeft; i++){
+      int idxNew;
+      Expr *pNew;
+      Expr *pLeft = sqlite3ExprForVectorField(pParse, pExpr->pLeft, i, nLeft);
+      Expr *pRight = sqlite3ExprForVectorField(pParse, pExpr->pRight, i, nLeft);
+
+      pNew = sqlite3PExpr(pParse, pExpr->op, pLeft, pRight);
+      transferJoinMarkings(pNew, pExpr);
+      idxNew = whereClauseInsert(pWC, pNew, TERM_DYNAMIC|TERM_SLICE);
+      exprAnalyze(pSrc, pWC, idxNew);
+    }
+    pTerm = &pWC->a[idxTerm];
+    pTerm->wtFlags |= TERM_CODED|TERM_VIRTUAL;  /* Disable the original */
+    pTerm->eOperator = WO_ROWVAL;
+  }
+
+  /* If there is a vector IN term - e.g. "(a, b) IN (SELECT ...)" - create
+  ** a virtual term for each vector component. The expression object
+  ** used by each such virtual term is pExpr (the full vector IN(...)
+  ** expression). The WhereTerm.u.x.iField variable identifies the index within
+  ** the vector on the LHS that the virtual term represents.
+  **
+  ** This only works if the RHS is a simple SELECT (not a compound) that does
+  ** not use window functions.
+  */
+  else if( pExpr->op==TK_IN
+   && pTerm->u.x.iField==0
+   && pExpr->pLeft->op==TK_VECTOR
+   && ALWAYS( ExprUseXSelect(pExpr) )
+   && (pExpr->x.pSelect->pPrior==0 || (pExpr->x.pSelect->selFlags & SF_Values))
+#ifndef SQLITE_OMIT_WINDOWFUNC
+   && pExpr->x.pSelect->pWin==0
+#endif
+   && pWC->op==TK_AND
+  ){
+    int i;
+    for(i=0; i<sqlite3ExprVectorSize(pExpr->pLeft); i++){
+      int idxNew;
+      idxNew = whereClauseInsert(pWC, pExpr, TERM_VIRTUAL|TERM_SLICE);
+      pWC->a[idxNew].u.x.iField = i+1;
+      exprAnalyze(pSrc, pWC, idxNew);
+      markTermAsChild(pWC, idxNew, idxTerm);
+    }
+  }
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  /* Add a WO_AUX auxiliary term to the constraint set if the
+  ** current expression is of the form "column OP expr" where OP
+  ** is an operator that gets passed into virtual tables but which is
+  ** not normally optimized for ordinary tables.  In other words, OP
+  ** is one of MATCH, LIKE, GLOB, REGEXP, !=, IS, IS NOT, or NOT NULL.
+  ** This information is used by the xBestIndex methods of
+  ** virtual tables.  The native query optimizer does not attempt
+  ** to do anything with MATCH functions.
+  */
+  else if( pWC->op==TK_AND ){
+    Expr *pRight = 0, *pLeft = 0;
+    int res = isAuxiliaryVtabOperator(db, pExpr, &eOp2, &pLeft, &pRight);
+    while( res-- > 0 ){
+      int idxNew;
+      WhereTerm *pNewTerm;
+      Bitmask prereqColumn, prereqExpr;
+
+      prereqExpr = sqlite3WhereExprUsage(pMaskSet, pRight);
+      prereqColumn = sqlite3WhereExprUsage(pMaskSet, pLeft);
+      if( (prereqExpr & prereqColumn)==0 ){
+        Expr *pNewExpr;
+        pNewExpr = sqlite3PExpr(pParse, TK_MATCH,
+            0, sqlite3ExprDup(db, pRight, 0));
+        if( ExprHasProperty(pExpr, EP_OuterON) && pNewExpr ){
+          ExprSetProperty(pNewExpr, EP_OuterON);
+          pNewExpr->w.iJoin = pExpr->w.iJoin;
+        }
+        idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
+        testcase( idxNew==0 );
+        pNewTerm = &pWC->a[idxNew];
+        pNewTerm->prereqRight = prereqExpr;
+        pNewTerm->leftCursor = pLeft->iTable;
+        pNewTerm->u.x.leftColumn = pLeft->iColumn;
+        pNewTerm->eOperator = WO_AUX;
+        pNewTerm->eMatchOp = eOp2;
+        markTermAsChild(pWC, idxNew, idxTerm);
+        pTerm = &pWC->a[idxTerm];
+        pTerm->wtFlags |= TERM_COPIED;
+        pNewTerm->prereqAll = pTerm->prereqAll;
+      }
+      SWAP(Expr*, pLeft, pRight);
+    }
+  }
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+  /* Prevent ON clause terms of a LEFT JOIN from being used to drive
+  ** an index for tables to the left of the join.
+  */
+  testcase( pTerm!=&pWC->a[idxTerm] );
+  pTerm = &pWC->a[idxTerm];
+  pTerm->prereqRight |= extraRight;
+}
+
+/***************************************************************************
+** Routines with file scope above.  Interface to the rest of the where.c
+** subsystem follows.
+***************************************************************************/
+
+/*
+** This routine identifies subexpressions in the WHERE clause where
+** each subexpression is separated by the AND operator or some other
+** operator specified in the op parameter.  The WhereClause structure
+** is filled with pointers to subexpressions.  For example:
+**
+**    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
+**           \________/     \_______________/     \________________/
+**            slot[0]            slot[1]               slot[2]
+**
+** The original WHERE clause in pExpr is unaltered.  All this routine
+** does is make slot[] entries point to substructure within pExpr.
+**
+** In the previous sentence and in the diagram, "slot[]" refers to
+** the WhereClause.a[] array.  The slot[] array grows as needed to contain
+** all terms of the WHERE clause.
+*/
+void sqlite3WhereSplit(WhereClause *pWC, Expr *pExpr, u8 op){
+  Expr *pE2 = sqlite3ExprSkipCollateAndLikely(pExpr);
+  pWC->op = op;
+  assert( pE2!=0 || pExpr==0 );
+  if( pE2==0 ) return;
+  if( pE2->op!=op ){
+    whereClauseInsert(pWC, pExpr, 0);
+  }else{
+    sqlite3WhereSplit(pWC, pE2->pLeft, op);
+    sqlite3WhereSplit(pWC, pE2->pRight, op);
+  }
+}
+
+/*
+** Add either a LIMIT (if eMatchOp==SQLITE_INDEX_CONSTRAINT_LIMIT) or
+** OFFSET (if eMatchOp==SQLITE_INDEX_CONSTRAINT_OFFSET) term to the
+** where-clause passed as the first argument. The value for the term
+** is found in register iReg.
+**
+** In the common case where the value is a simple integer
+** (example: "LIMIT 5 OFFSET 10") then the expression codes as a
+** TK_INTEGER so that it will be available to sqlite3_vtab_rhs_value().
+** If not, then it codes as a TK_REGISTER expression.
+*/
+static void whereAddLimitExpr(
+  WhereClause *pWC,   /* Add the constraint to this WHERE clause */
+  int iReg,           /* Register that will hold value of the limit/offset */
+  Expr *pExpr,        /* Expression that defines the limit/offset */
+  int iCsr,           /* Cursor to which the constraint applies */
+  int eMatchOp        /* SQLITE_INDEX_CONSTRAINT_LIMIT or _OFFSET */
+){
+  Parse *pParse = pWC->pWInfo->pParse;
+  sqlite3 *db = pParse->db;
+  Expr *pNew;
+  int iVal = 0;
+
+  if( sqlite3ExprIsInteger(pExpr, &iVal) && iVal>=0 ){
+    Expr *pVal = sqlite3Expr(db, TK_INTEGER, 0);
+    if( pVal==0 ) return;
+    ExprSetProperty(pVal, EP_IntValue);
+    pVal->u.iValue = iVal;
+    pNew = sqlite3PExpr(pParse, TK_MATCH, 0, pVal);
+  }else{
+    Expr *pVal = sqlite3Expr(db, TK_REGISTER, 0);
+    if( pVal==0 ) return;
+    pVal->iTable = iReg;
+    pNew = sqlite3PExpr(pParse, TK_MATCH, 0, pVal);
+  }
+  if( pNew ){
+    WhereTerm *pTerm;
+    int idx;
+    idx = whereClauseInsert(pWC, pNew, TERM_DYNAMIC|TERM_VIRTUAL);
+    pTerm = &pWC->a[idx];
+    pTerm->leftCursor = iCsr;
+    pTerm->eOperator = WO_AUX;
+    pTerm->eMatchOp = eMatchOp;
+  }
+}
+
+/*
+** Possibly add terms corresponding to the LIMIT and OFFSET clauses of the
+** SELECT statement passed as the second argument. These terms are only
+** added if:
+**
+**   1. The SELECT statement has a LIMIT clause, and
+**   2. The SELECT statement is not an aggregate or DISTINCT query, and
+**   3. The SELECT statement has exactly one object in its from clause, and
+**      that object is a virtual table, and
+**   4. There are no terms in the WHERE clause that will not be passed
+**      to the virtual table xBestIndex method.
+**   5. The ORDER BY clause, if any, will be made available to the xBestIndex
+**      method.
+**
+** LIMIT and OFFSET terms are ignored by most of the planner code. They
+** exist only so that they may be passed to the xBestIndex method of the
+** single virtual table in the FROM clause of the SELECT.
+*/
+void SQLITE_NOINLINE sqlite3WhereAddLimit(WhereClause *pWC, Select *p){
+  assert( p!=0 && p->pLimit!=0 );                 /* 1 -- checked by caller */
+  if( p->pGroupBy==0
+   && (p->selFlags & (SF_Distinct|SF_Aggregate))==0             /* 2 */
+   && (p->pSrc->nSrc==1 && IsVirtual(p->pSrc->a[0].pTab))       /* 3 */
+  ){
+    ExprList *pOrderBy = p->pOrderBy;
+    int iCsr = p->pSrc->a[0].iCursor;
+    int ii;
+
+    /* Check condition (4). Return early if it is not met. */
+    for(ii=0; ii<pWC->nTerm; ii++){
+      if( pWC->a[ii].wtFlags & TERM_CODED ){
+        /* This term is a vector operation that has been decomposed into
+        ** other, subsequent terms.  It can be ignored. See tag-20220128a */
+        assert( pWC->a[ii].wtFlags & TERM_VIRTUAL );
+        assert( pWC->a[ii].eOperator==WO_ROWVAL );
+        continue;
+      }
+      if( pWC->a[ii].nChild ){
+        /* If this term has child terms, then they are also part of the
+        ** pWC->a[] array. So this term can be ignored, as a LIMIT clause
+        ** will only be added if each of the child terms passes the
+        ** (leftCursor==iCsr) test below.  */
+        continue;
+      }
+      if( pWC->a[ii].leftCursor!=iCsr ) return;
+    }
+
+    /* Check condition (5). Return early if it is not met. */
+    if( pOrderBy ){
+      for(ii=0; ii<pOrderBy->nExpr; ii++){
+        Expr *pExpr = pOrderBy->a[ii].pExpr;
+        if( pExpr->op!=TK_COLUMN ) return;
+        if( pExpr->iTable!=iCsr ) return;
+        if( pOrderBy->a[ii].fg.sortFlags & KEYINFO_ORDER_BIGNULL ) return;
+      }
+    }
+
+    /* All conditions are met. Add the terms to the where-clause object. */
+    assert( p->pLimit->op==TK_LIMIT );
+    whereAddLimitExpr(pWC, p->iLimit, p->pLimit->pLeft,
+                      iCsr, SQLITE_INDEX_CONSTRAINT_LIMIT);
+    if( p->iOffset>0 ){
+      whereAddLimitExpr(pWC, p->iOffset, p->pLimit->pRight,
+                        iCsr, SQLITE_INDEX_CONSTRAINT_OFFSET);
+    }
+  }
+}
+
+/*
+** Initialize a preallocated WhereClause structure.
+*/
+void sqlite3WhereClauseInit(
+  WhereClause *pWC,        /* The WhereClause to be initialized */
+  WhereInfo *pWInfo        /* The WHERE processing context */
+){
+  pWC->pWInfo = pWInfo;
+  pWC->hasOr = 0;
+  pWC->pOuter = 0;
+  pWC->nTerm = 0;
+  pWC->nBase = 0;
+  pWC->nSlot = ArraySize(pWC->aStatic);
+  pWC->a = pWC->aStatic;
+}
+
+/*
+** Deallocate a WhereClause structure.  The WhereClause structure
+** itself is not freed.  This routine is the inverse of
+** sqlite3WhereClauseInit().
+*/
+void sqlite3WhereClauseClear(WhereClause *pWC){
+  sqlite3 *db = pWC->pWInfo->pParse->db;
+  assert( pWC->nTerm>=pWC->nBase );
+  if( pWC->nTerm>0 ){
+    WhereTerm *a = pWC->a;
+    WhereTerm *aLast = &pWC->a[pWC->nTerm-1];
+#ifdef SQLITE_DEBUG
+    int i;
+    /* Verify that every term past pWC->nBase is virtual */
+    for(i=pWC->nBase; i<pWC->nTerm; i++){
+      assert( (pWC->a[i].wtFlags & TERM_VIRTUAL)!=0 );
+    }
+#endif
+    while(1){
+      assert( a->eMatchOp==0 || a->eOperator==WO_AUX );
+      if( a->wtFlags & TERM_DYNAMIC ){
+        sqlite3ExprDelete(db, a->pExpr);
+      }
+      if( a->wtFlags & (TERM_ORINFO|TERM_ANDINFO) ){
+        if( a->wtFlags & TERM_ORINFO ){
+          assert( (a->wtFlags & TERM_ANDINFO)==0 );
+          whereOrInfoDelete(db, a->u.pOrInfo);
+        }else{
+          assert( (a->wtFlags & TERM_ANDINFO)!=0 );
+          whereAndInfoDelete(db, a->u.pAndInfo);
+        }
+      }
+      if( a==aLast ) break;
+      a++;
+    }
+  }
+}
+
+
+/*
+** These routines walk (recursively) an expression tree and generate
+** a bitmask indicating which tables are used in that expression
+** tree.
+**
+** sqlite3WhereExprUsage(MaskSet, Expr) ->
+**
+**       Return a Bitmask of all tables referenced by Expr.  Expr can be
+**       be NULL, in which case 0 is returned.
+**
+** sqlite3WhereExprUsageNN(MaskSet, Expr) ->
+**
+**       Same as sqlite3WhereExprUsage() except that Expr must not be
+**       NULL.  The "NN" suffix on the name stands for "Not Null".
+**
+** sqlite3WhereExprListUsage(MaskSet, ExprList) ->
+**
+**       Return a Bitmask of all tables referenced by every expression
+**       in the expression list ExprList.  ExprList can be NULL, in which
+**       case 0 is returned.
+**
+** sqlite3WhereExprUsageFull(MaskSet, ExprList) ->
+**
+**       Internal use only.  Called only by sqlite3WhereExprUsageNN() for
+**       complex expressions that require pushing register values onto
+**       the stack.  Many calls to sqlite3WhereExprUsageNN() do not need
+**       the more complex analysis done by this routine.  Hence, the
+**       computations done by this routine are broken out into a separate
+**       "no-inline" function to avoid the stack push overhead in the
+**       common case where it is not needed.
+*/
+static SQLITE_NOINLINE Bitmask sqlite3WhereExprUsageFull(
+  WhereMaskSet *pMaskSet,
+  Expr *p
+){
+  Bitmask mask;
+  mask = (p->op==TK_IF_NULL_ROW) ? sqlite3WhereGetMask(pMaskSet, p->iTable) : 0;
+  if( p->pLeft ) mask |= sqlite3WhereExprUsageNN(pMaskSet, p->pLeft);
+  if( p->pRight ){
+    mask |= sqlite3WhereExprUsageNN(pMaskSet, p->pRight);
+    assert( p->x.pList==0 );
+  }else if( ExprUseXSelect(p) ){
+    if( ExprHasProperty(p, EP_VarSelect) ) pMaskSet->bVarSelect = 1;
+    mask |= exprSelectUsage(pMaskSet, p->x.pSelect);
+  }else if( p->x.pList ){
+    mask |= sqlite3WhereExprListUsage(pMaskSet, p->x.pList);
+  }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( (p->op==TK_FUNCTION || p->op==TK_AGG_FUNCTION) && ExprUseYWin(p) ){
+    assert( p->y.pWin!=0 );
+    mask |= sqlite3WhereExprListUsage(pMaskSet, p->y.pWin->pPartition);
+    mask |= sqlite3WhereExprListUsage(pMaskSet, p->y.pWin->pOrderBy);
+    mask |= sqlite3WhereExprUsage(pMaskSet, p->y.pWin->pFilter);
+  }
+#endif
+  return mask;
+}
+Bitmask sqlite3WhereExprUsageNN(WhereMaskSet *pMaskSet, Expr *p){
+  if( p->op==TK_COLUMN && !ExprHasProperty(p, EP_FixedCol) ){
+    return sqlite3WhereGetMask(pMaskSet, p->iTable);
+  }else if( ExprHasProperty(p, EP_TokenOnly|EP_Leaf) ){
+    assert( p->op!=TK_IF_NULL_ROW );
+    return 0;
+  }
+  return sqlite3WhereExprUsageFull(pMaskSet, p);
+}
+Bitmask sqlite3WhereExprUsage(WhereMaskSet *pMaskSet, Expr *p){
+  return p ? sqlite3WhereExprUsageNN(pMaskSet,p) : 0;
+}
+Bitmask sqlite3WhereExprListUsage(WhereMaskSet *pMaskSet, ExprList *pList){
+  int i;
+  Bitmask mask = 0;
+  if( pList ){
+    for(i=0; i<pList->nExpr; i++){
+      mask |= sqlite3WhereExprUsage(pMaskSet, pList->a[i].pExpr);
+    }
+  }
+  return mask;
+}
+
+
+/*
+** Call exprAnalyze on all terms in a WHERE clause. 
+**
+** Note that exprAnalyze() might add new virtual terms onto the
+** end of the WHERE clause.  We do not want to analyze these new
+** virtual terms, so start analyzing at the end and work forward
+** so that the added virtual terms are never processed.
+*/
+void sqlite3WhereExprAnalyze(
+  SrcList *pTabList,       /* the FROM clause */
+  WhereClause *pWC         /* the WHERE clause to be analyzed */
+){
+  int i;
+  for(i=pWC->nTerm-1; i>=0; i--){
+    exprAnalyze(pTabList, pWC, i);
+  }
+}
+
+/*
+** For table-valued-functions, transform the function arguments into
+** new WHERE clause terms. 
+**
+** Each function argument translates into an equality constraint against
+** a HIDDEN column in the table.
+*/
+void sqlite3WhereTabFuncArgs(
+  Parse *pParse,                    /* Parsing context */
+  SrcItem *pItem,                   /* The FROM clause term to process */
+  WhereClause *pWC                  /* Xfer function arguments to here */
+){
+  Table *pTab;
+  int j, k;
+  ExprList *pArgs;
+  Expr *pColRef;
+  Expr *pTerm;
+  if( pItem->fg.isTabFunc==0 ) return;
+  pTab = pItem->pTab;
+  assert( pTab!=0 );
+  pArgs = pItem->u1.pFuncArg;
+  if( pArgs==0 ) return;
+  for(j=k=0; j<pArgs->nExpr; j++){
+    Expr *pRhs;
+    u32 joinType;
+    while( k<pTab->nCol && (pTab->aCol[k].colFlags & COLFLAG_HIDDEN)==0 ){k++;}
+    if( k>=pTab->nCol ){
+      sqlite3ErrorMsg(pParse, "too many arguments on %s() - max %d",
+                      pTab->zName, j);
+      return;
+    }
+    pColRef = sqlite3ExprAlloc(pParse->db, TK_COLUMN, 0, 0);
+    if( pColRef==0 ) return;
+    pColRef->iTable = pItem->iCursor;
+    pColRef->iColumn = k++;
+    assert( ExprUseYTab(pColRef) );
+    pColRef->y.pTab = pTab;
+    pItem->colUsed |= sqlite3ExprColUsed(pColRef);
+    pRhs = sqlite3PExpr(pParse, TK_UPLUS,
+        sqlite3ExprDup(pParse->db, pArgs->a[j].pExpr, 0), 0);
+    pTerm = sqlite3PExpr(pParse, TK_EQ, pColRef, pRhs);
+    if( pItem->fg.jointype & (JT_LEFT|JT_RIGHT) ){
+      testcase( pItem->fg.jointype & JT_LEFT );  /* testtag-20230227a */
+      testcase( pItem->fg.jointype & JT_RIGHT ); /* testtag-20230227b */
+      joinType = EP_OuterON;
+    }else{
+      testcase( pItem->fg.jointype & JT_LTORJ ); /* testtag-20230227c */
+      joinType = EP_InnerON;
+    }
+    sqlite3SetJoinExpr(pTerm, pItem->iCursor, joinType);
+    whereClauseInsert(pWC, pTerm, TERM_DYNAMIC);
+  }
+}
diff --git a/src/window.c b/src/window.c
new file mode 100644
index 0000000..62df349
--- /dev/null
+++ b/src/window.c
@@ -0,0 +1,3102 @@
+/*
+** 2018 May 08
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+
+/*
+** SELECT REWRITING
+**
+**   Any SELECT statement that contains one or more window functions in
+**   either the select list or ORDER BY clause (the only two places window
+**   functions may be used) is transformed by function sqlite3WindowRewrite()
+**   in order to support window function processing. For example, with the
+**   schema:
+**
+**     CREATE TABLE t1(a, b, c, d, e, f, g);
+**
+**   the statement:
+**
+**     SELECT a+1, max(b) OVER (PARTITION BY c ORDER BY d) FROM t1 ORDER BY e;
+**
+**   is transformed to:
+**
+**     SELECT a+1, max(b) OVER (PARTITION BY c ORDER BY d) FROM (
+**         SELECT a, e, c, d, b FROM t1 ORDER BY c, d
+**     ) ORDER BY e;
+**
+**   The flattening optimization is disabled when processing this transformed
+**   SELECT statement. This allows the implementation of the window function
+**   (in this case max()) to process rows sorted in order of (c, d), which
+**   makes things easier for obvious reasons. More generally:
+**
+**     * FROM, WHERE, GROUP BY and HAVING clauses are all moved to
+**       the sub-query.
+**
+**     * ORDER BY, LIMIT and OFFSET remain part of the parent query.
+**
+**     * Terminals from each of the expression trees that make up the
+**       select-list and ORDER BY expressions in the parent query are
+**       selected by the sub-query. For the purposes of the transformation,
+**       terminals are column references and aggregate functions.
+**
+**   If there is more than one window function in the SELECT that uses
+**   the same window declaration (the OVER bit), then a single scan may
+**   be used to process more than one window function. For example:
+**
+**     SELECT max(b) OVER (PARTITION BY c ORDER BY d),
+**            min(e) OVER (PARTITION BY c ORDER BY d)
+**     FROM t1;
+**
+**   is transformed in the same way as the example above. However:
+**
+**     SELECT max(b) OVER (PARTITION BY c ORDER BY d),
+**            min(e) OVER (PARTITION BY a ORDER BY b)
+**     FROM t1;
+**
+**   Must be transformed to:
+**
+**     SELECT max(b) OVER (PARTITION BY c ORDER BY d) FROM (
+**         SELECT e, min(e) OVER (PARTITION BY a ORDER BY b), c, d, b FROM
+**           SELECT a, e, c, d, b FROM t1 ORDER BY a, b
+**         ) ORDER BY c, d
+**     ) ORDER BY e;
+**
+**   so that both min() and max() may process rows in the order defined by
+**   their respective window declarations.
+**
+** INTERFACE WITH SELECT.C
+**
+**   When processing the rewritten SELECT statement, code in select.c calls
+**   sqlite3WhereBegin() to begin iterating through the results of the
+**   sub-query, which is always implemented as a co-routine. It then calls
+**   sqlite3WindowCodeStep() to process rows and finish the scan by calling
+**   sqlite3WhereEnd().
+**
+**   sqlite3WindowCodeStep() generates VM code so that, for each row returned
+**   by the sub-query a sub-routine (OP_Gosub) coded by select.c is invoked.
+**   When the sub-routine is invoked:
+**
+**     * The results of all window-functions for the row are stored
+**       in the associated Window.regResult registers.
+**
+**     * The required terminal values are stored in the current row of
+**       temp table Window.iEphCsr.
+**
+**   In some cases, depending on the window frame and the specific window
+**   functions invoked, sqlite3WindowCodeStep() caches each entire partition
+**   in a temp table before returning any rows. In other cases it does not.
+**   This detail is encapsulated within this file, the code generated by
+**   select.c is the same in either case.
+**
+** BUILT-IN WINDOW FUNCTIONS
+**
+**   This implementation features the following built-in window functions:
+**
+**     row_number()
+**     rank()
+**     dense_rank()
+**     percent_rank()
+**     cume_dist()
+**     ntile(N)
+**     lead(expr [, offset [, default]])
+**     lag(expr [, offset [, default]])
+**     first_value(expr)
+**     last_value(expr)
+**     nth_value(expr, N)
+**  
+**   These are the same built-in window functions supported by Postgres.
+**   Although the behaviour of aggregate window functions (functions that
+**   can be used as either aggregates or window functions) allows them to
+**   be implemented using an API, built-in window functions are much more
+**   esoteric. Additionally, some window functions (e.g. nth_value())
+**   may only be implemented by caching the entire partition in memory.
+**   As such, some built-in window functions use the same API as aggregate
+**   window functions and some are implemented directly using VDBE
+**   instructions. Additionally, for those functions that use the API, the
+**   window frame is sometimes modified before the SELECT statement is
+**   rewritten. For example, regardless of the specified window frame, the
+**   row_number() function always uses:
+**
+**     ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
+**
+**   See sqlite3WindowUpdate() for details.
+**
+**   As well as some of the built-in window functions, aggregate window
+**   functions min() and max() are implemented using VDBE instructions if
+**   the start of the window frame is declared as anything other than
+**   UNBOUNDED PRECEDING.
+*/
+
+/*
+** Implementation of built-in window function row_number(). Assumes that the
+** window frame has been coerced to:
+**
+**   ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
+*/
+static void row_numberStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  i64 *p = (i64*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ) (*p)++;
+  UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(apArg);
+}
+static void row_numberValueFunc(sqlite3_context *pCtx){
+  i64 *p = (i64*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  sqlite3_result_int64(pCtx, (p ? *p : 0));
+}
+
+/*
+** Context object type used by rank(), dense_rank(), percent_rank() and
+** cume_dist().
+*/
+struct CallCount {
+  i64 nValue;
+  i64 nStep;
+  i64 nTotal;
+};
+
+/*
+** Implementation of built-in window function dense_rank(). Assumes that
+** the window frame has been set to:
+**
+**   RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
+*/
+static void dense_rankStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct CallCount *p;
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ) p->nStep = 1;
+  UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(apArg);
+}
+static void dense_rankValueFunc(sqlite3_context *pCtx){
+  struct CallCount *p;
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    if( p->nStep ){
+      p->nValue++;
+      p->nStep = 0;
+    }
+    sqlite3_result_int64(pCtx, p->nValue);
+  }
+}
+
+/*
+** Implementation of built-in window function nth_value(). This
+** implementation is used in "slow mode" only - when the EXCLUDE clause
+** is not set to the default value "NO OTHERS".
+*/
+struct NthValueCtx {
+  i64 nStep;
+  sqlite3_value *pValue;
+};
+static void nth_valueStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct NthValueCtx *p;
+  p = (struct NthValueCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    i64 iVal;
+    switch( sqlite3_value_numeric_type(apArg[1]) ){
+      case SQLITE_INTEGER:
+        iVal = sqlite3_value_int64(apArg[1]);
+        break;
+      case SQLITE_FLOAT: {
+        double fVal = sqlite3_value_double(apArg[1]);
+        if( ((i64)fVal)!=fVal ) goto error_out;
+        iVal = (i64)fVal;
+        break;
+      }
+      default:
+        goto error_out;
+    }
+    if( iVal<=0 ) goto error_out;
+
+    p->nStep++;
+    if( iVal==p->nStep ){
+      p->pValue = sqlite3_value_dup(apArg[0]);
+      if( !p->pValue ){
+        sqlite3_result_error_nomem(pCtx);
+      }
+    }
+  }
+  UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(apArg);
+  return;
+
+ error_out:
+  sqlite3_result_error(
+      pCtx, "second argument to nth_value must be a positive integer", -1
+  );
+}
+static void nth_valueFinalizeFunc(sqlite3_context *pCtx){
+  struct NthValueCtx *p;
+  p = (struct NthValueCtx*)sqlite3_aggregate_context(pCtx, 0);
+  if( p && p->pValue ){
+    sqlite3_result_value(pCtx, p->pValue);
+    sqlite3_value_free(p->pValue);
+    p->pValue = 0;
+  }
+}
+#define nth_valueInvFunc noopStepFunc
+#define nth_valueValueFunc noopValueFunc
+
+static void first_valueStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct NthValueCtx *p;
+  p = (struct NthValueCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p && p->pValue==0 ){
+    p->pValue = sqlite3_value_dup(apArg[0]);
+    if( !p->pValue ){
+      sqlite3_result_error_nomem(pCtx);
+    }
+  }
+  UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(apArg);
+}
+static void first_valueFinalizeFunc(sqlite3_context *pCtx){
+  struct NthValueCtx *p;
+  p = (struct NthValueCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p && p->pValue ){
+    sqlite3_result_value(pCtx, p->pValue);
+    sqlite3_value_free(p->pValue);
+    p->pValue = 0;
+  }
+}
+#define first_valueInvFunc noopStepFunc
+#define first_valueValueFunc noopValueFunc
+
+/*
+** Implementation of built-in window function rank(). Assumes that
+** the window frame has been set to:
+**
+**   RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
+*/
+static void rankStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct CallCount *p;
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    p->nStep++;
+    if( p->nValue==0 ){
+      p->nValue = p->nStep;
+    }
+  }
+  UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(apArg);
+}
+static void rankValueFunc(sqlite3_context *pCtx){
+  struct CallCount *p;
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    sqlite3_result_int64(pCtx, p->nValue);
+    p->nValue = 0;
+  }
+}
+
+/*
+** Implementation of built-in window function percent_rank(). Assumes that
+** the window frame has been set to:
+**
+**   GROUPS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
+*/
+static void percent_rankStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct CallCount *p;
+  UNUSED_PARAMETER(nArg); assert( nArg==0 );
+  UNUSED_PARAMETER(apArg);
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    p->nTotal++;
+  }
+}
+static void percent_rankInvFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct CallCount *p;
+  UNUSED_PARAMETER(nArg); assert( nArg==0 );
+  UNUSED_PARAMETER(apArg);
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  p->nStep++;
+}
+static void percent_rankValueFunc(sqlite3_context *pCtx){
+  struct CallCount *p;
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    p->nValue = p->nStep;
+    if( p->nTotal>1 ){
+      double r = (double)p->nValue / (double)(p->nTotal-1);
+      sqlite3_result_double(pCtx, r);
+    }else{
+      sqlite3_result_double(pCtx, 0.0);
+    }
+  }
+}
+#define percent_rankFinalizeFunc percent_rankValueFunc
+
+/*
+** Implementation of built-in window function cume_dist(). Assumes that
+** the window frame has been set to:
+**
+**   GROUPS BETWEEN 1 FOLLOWING AND UNBOUNDED FOLLOWING
+*/
+static void cume_distStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct CallCount *p;
+  UNUSED_PARAMETER(nArg); assert( nArg==0 );
+  UNUSED_PARAMETER(apArg);
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    p->nTotal++;
+  }
+}
+static void cume_distInvFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct CallCount *p;
+  UNUSED_PARAMETER(nArg); assert( nArg==0 );
+  UNUSED_PARAMETER(apArg);
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  p->nStep++;
+}
+static void cume_distValueFunc(sqlite3_context *pCtx){
+  struct CallCount *p;
+  p = (struct CallCount*)sqlite3_aggregate_context(pCtx, 0);
+  if( p ){
+    double r = (double)(p->nStep) / (double)(p->nTotal);
+    sqlite3_result_double(pCtx, r);
+  }
+}
+#define cume_distFinalizeFunc cume_distValueFunc
+
+/*
+** Context object for ntile() window function.
+*/
+struct NtileCtx {
+  i64 nTotal;                     /* Total rows in partition */
+  i64 nParam;                     /* Parameter passed to ntile(N) */
+  i64 iRow;                       /* Current row */
+};
+
+/*
+** Implementation of ntile(). This assumes that the window frame has
+** been coerced to:
+**
+**   ROWS CURRENT ROW AND UNBOUNDED FOLLOWING
+*/
+static void ntileStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct NtileCtx *p;
+  assert( nArg==1 ); UNUSED_PARAMETER(nArg);
+  p = (struct NtileCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    if( p->nTotal==0 ){
+      p->nParam = sqlite3_value_int64(apArg[0]);
+      if( p->nParam<=0 ){
+        sqlite3_result_error(
+            pCtx, "argument of ntile must be a positive integer", -1
+        );
+      }
+    }
+    p->nTotal++;
+  }
+}
+static void ntileInvFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct NtileCtx *p;
+  assert( nArg==1 ); UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(apArg);
+  p = (struct NtileCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  p->iRow++;
+}
+static void ntileValueFunc(sqlite3_context *pCtx){
+  struct NtileCtx *p;
+  p = (struct NtileCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p && p->nParam>0 ){
+    int nSize = (p->nTotal / p->nParam);
+    if( nSize==0 ){
+      sqlite3_result_int64(pCtx, p->iRow+1);
+    }else{
+      i64 nLarge = p->nTotal - p->nParam*nSize;
+      i64 iSmall = nLarge*(nSize+1);
+      i64 iRow = p->iRow;
+
+      assert( (nLarge*(nSize+1) + (p->nParam-nLarge)*nSize)==p->nTotal );
+
+      if( iRow<iSmall ){
+        sqlite3_result_int64(pCtx, 1 + iRow/(nSize+1));
+      }else{
+        sqlite3_result_int64(pCtx, 1 + nLarge + (iRow-iSmall)/nSize);
+      }
+    }
+  }
+}
+#define ntileFinalizeFunc ntileValueFunc
+
+/*
+** Context object for last_value() window function.
+*/
+struct LastValueCtx {
+  sqlite3_value *pVal;
+  int nVal;
+};
+
+/*
+** Implementation of last_value().
+*/
+static void last_valueStepFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct LastValueCtx *p;
+  UNUSED_PARAMETER(nArg);
+  p = (struct LastValueCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p ){
+    sqlite3_value_free(p->pVal);
+    p->pVal = sqlite3_value_dup(apArg[0]);
+    if( p->pVal==0 ){
+      sqlite3_result_error_nomem(pCtx);
+    }else{
+      p->nVal++;
+    }
+  }
+}
+static void last_valueInvFunc(
+  sqlite3_context *pCtx,
+  int nArg,
+  sqlite3_value **apArg
+){
+  struct LastValueCtx *p;
+  UNUSED_PARAMETER(nArg);
+  UNUSED_PARAMETER(apArg);
+  p = (struct LastValueCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( ALWAYS(p) ){
+    p->nVal--;
+    if( p->nVal==0 ){
+      sqlite3_value_free(p->pVal);
+      p->pVal = 0;
+    }
+  }
+}
+static void last_valueValueFunc(sqlite3_context *pCtx){
+  struct LastValueCtx *p;
+  p = (struct LastValueCtx*)sqlite3_aggregate_context(pCtx, 0);
+  if( p && p->pVal ){
+    sqlite3_result_value(pCtx, p->pVal);
+  }
+}
+static void last_valueFinalizeFunc(sqlite3_context *pCtx){
+  struct LastValueCtx *p;
+  p = (struct LastValueCtx*)sqlite3_aggregate_context(pCtx, sizeof(*p));
+  if( p && p->pVal ){
+    sqlite3_result_value(pCtx, p->pVal);
+    sqlite3_value_free(p->pVal);
+    p->pVal = 0;
+  }
+}
+
+/*
+** Static names for the built-in window function names.  These static
+** names are used, rather than string literals, so that FuncDef objects
+** can be associated with a particular window function by direct
+** comparison of the zName pointer.  Example:
+**
+**       if( pFuncDef->zName==row_valueName ){ ... }
+*/
+static const char row_numberName[] =   "row_number";
+static const char dense_rankName[] =   "dense_rank";
+static const char rankName[] =         "rank";
+static const char percent_rankName[] = "percent_rank";
+static const char cume_distName[] =    "cume_dist";
+static const char ntileName[] =        "ntile";
+static const char last_valueName[] =   "last_value";
+static const char nth_valueName[] =    "nth_value";
+static const char first_valueName[] =  "first_value";
+static const char leadName[] =         "lead";
+static const char lagName[] =          "lag";
+
+/*
+** No-op implementations of xStep() and xFinalize().  Used as place-holders
+** for built-in window functions that never call those interfaces.
+**
+** The noopValueFunc() is called but is expected to do nothing.  The
+** noopStepFunc() is never called, and so it is marked with NO_TEST to
+** let the test coverage routine know not to expect this function to be
+** invoked.
+*/
+static void noopStepFunc(    /*NO_TEST*/
+  sqlite3_context *p,        /*NO_TEST*/
+  int n,                     /*NO_TEST*/
+  sqlite3_value **a          /*NO_TEST*/
+){                           /*NO_TEST*/
+  UNUSED_PARAMETER(p);       /*NO_TEST*/
+  UNUSED_PARAMETER(n);       /*NO_TEST*/
+  UNUSED_PARAMETER(a);       /*NO_TEST*/
+  assert(0);                 /*NO_TEST*/
+}                            /*NO_TEST*/
+static void noopValueFunc(sqlite3_context *p){ UNUSED_PARAMETER(p); /*no-op*/ }
+
+/* Window functions that use all window interfaces: xStep, xFinal,
+** xValue, and xInverse */
+#define WINDOWFUNCALL(name,nArg,extra) {                                   \
+  nArg, (SQLITE_FUNC_BUILTIN|SQLITE_UTF8|SQLITE_FUNC_WINDOW|extra), 0, 0,  \
+  name ## StepFunc, name ## FinalizeFunc, name ## ValueFunc,               \
+  name ## InvFunc, name ## Name, {0}                                       \
+}
+
+/* Window functions that are implemented using bytecode and thus have
+** no-op routines for their methods */
+#define WINDOWFUNCNOOP(name,nArg,extra) {                                  \
+  nArg, (SQLITE_FUNC_BUILTIN|SQLITE_UTF8|SQLITE_FUNC_WINDOW|extra), 0, 0,  \
+  noopStepFunc, noopValueFunc, noopValueFunc,                              \
+  noopStepFunc, name ## Name, {0}                                          \
+}
+
+/* Window functions that use all window interfaces: xStep, the
+** same routine for xFinalize and xValue and which never call
+** xInverse. */
+#define WINDOWFUNCX(name,nArg,extra) {                                     \
+  nArg, (SQLITE_FUNC_BUILTIN|SQLITE_UTF8|SQLITE_FUNC_WINDOW|extra), 0, 0,  \
+  name ## StepFunc, name ## ValueFunc, name ## ValueFunc,                  \
+  noopStepFunc, name ## Name, {0}                                          \
+}
+
+
+/*
+** Register those built-in window functions that are not also aggregates.
+*/
+void sqlite3WindowFunctions(void){
+  static FuncDef aWindowFuncs[] = {
+    WINDOWFUNCX(row_number, 0, 0),
+    WINDOWFUNCX(dense_rank, 0, 0),
+    WINDOWFUNCX(rank, 0, 0),
+    WINDOWFUNCALL(percent_rank, 0, 0),
+    WINDOWFUNCALL(cume_dist, 0, 0),
+    WINDOWFUNCALL(ntile, 1, 0),
+    WINDOWFUNCALL(last_value, 1, 0),
+    WINDOWFUNCALL(nth_value, 2, 0),
+    WINDOWFUNCALL(first_value, 1, 0),
+    WINDOWFUNCNOOP(lead, 1, 0),
+    WINDOWFUNCNOOP(lead, 2, 0),
+    WINDOWFUNCNOOP(lead, 3, 0),
+    WINDOWFUNCNOOP(lag, 1, 0),
+    WINDOWFUNCNOOP(lag, 2, 0),
+    WINDOWFUNCNOOP(lag, 3, 0),
+  };
+  sqlite3InsertBuiltinFuncs(aWindowFuncs, ArraySize(aWindowFuncs));
+}
+
+static Window *windowFind(Parse *pParse, Window *pList, const char *zName){
+  Window *p;
+  for(p=pList; p; p=p->pNextWin){
+    if( sqlite3StrICmp(p->zName, zName)==0 ) break;
+  }
+  if( p==0 ){
+    sqlite3ErrorMsg(pParse, "no such window: %s", zName);
+  }
+  return p;
+}
+
+/*
+** This function is called immediately after resolving the function name
+** for a window function within a SELECT statement. Argument pList is a
+** linked list of WINDOW definitions for the current SELECT statement.
+** Argument pFunc is the function definition just resolved and pWin
+** is the Window object representing the associated OVER clause. This
+** function updates the contents of pWin as follows:
+**
+**   * If the OVER clause referred to a named window (as in "max(x) OVER win"),
+**     search list pList for a matching WINDOW definition, and update pWin
+**     accordingly. If no such WINDOW clause can be found, leave an error
+**     in pParse.
+**
+**   * If the function is a built-in window function that requires the
+**     window to be coerced (see "BUILT-IN WINDOW FUNCTIONS" at the top
+**     of this file), pWin is updated here.
+*/
+void sqlite3WindowUpdate(
+  Parse *pParse,
+  Window *pList,                  /* List of named windows for this SELECT */
+  Window *pWin,                   /* Window frame to update */
+  FuncDef *pFunc                  /* Window function definition */
+){
+  if( pWin->zName && pWin->eFrmType==0 ){
+    Window *p = windowFind(pParse, pList, pWin->zName);
+    if( p==0 ) return;
+    pWin->pPartition = sqlite3ExprListDup(pParse->db, p->pPartition, 0);
+    pWin->pOrderBy = sqlite3ExprListDup(pParse->db, p->pOrderBy, 0);
+    pWin->pStart = sqlite3ExprDup(pParse->db, p->pStart, 0);
+    pWin->pEnd = sqlite3ExprDup(pParse->db, p->pEnd, 0);
+    pWin->eStart = p->eStart;
+    pWin->eEnd = p->eEnd;
+    pWin->eFrmType = p->eFrmType;
+    pWin->eExclude = p->eExclude;
+  }else{
+    sqlite3WindowChain(pParse, pWin, pList);
+  }
+  if( (pWin->eFrmType==TK_RANGE)
+   && (pWin->pStart || pWin->pEnd)
+   && (pWin->pOrderBy==0 || pWin->pOrderBy->nExpr!=1)
+  ){
+    sqlite3ErrorMsg(pParse,
+      "RANGE with offset PRECEDING/FOLLOWING requires one ORDER BY expression"
+    );
+  }else
+  if( pFunc->funcFlags & SQLITE_FUNC_WINDOW ){
+    sqlite3 *db = pParse->db;
+    if( pWin->pFilter ){
+      sqlite3ErrorMsg(pParse,
+          "FILTER clause may only be used with aggregate window functions"
+      );
+    }else{
+      struct WindowUpdate {
+        const char *zFunc;
+        int eFrmType;
+        int eStart;
+        int eEnd;
+      } aUp[] = {
+        { row_numberName,   TK_ROWS,   TK_UNBOUNDED, TK_CURRENT },
+        { dense_rankName,   TK_RANGE,  TK_UNBOUNDED, TK_CURRENT },
+        { rankName,         TK_RANGE,  TK_UNBOUNDED, TK_CURRENT },
+        { percent_rankName, TK_GROUPS, TK_CURRENT,   TK_UNBOUNDED },
+        { cume_distName,    TK_GROUPS, TK_FOLLOWING, TK_UNBOUNDED },
+        { ntileName,        TK_ROWS,   TK_CURRENT,   TK_UNBOUNDED },
+        { leadName,         TK_ROWS,   TK_UNBOUNDED, TK_UNBOUNDED },
+        { lagName,          TK_ROWS,   TK_UNBOUNDED, TK_CURRENT },
+      };
+      int i;
+      for(i=0; i<ArraySize(aUp); i++){
+        if( pFunc->zName==aUp[i].zFunc ){
+          sqlite3ExprDelete(db, pWin->pStart);
+          sqlite3ExprDelete(db, pWin->pEnd);
+          pWin->pEnd = pWin->pStart = 0;
+          pWin->eFrmType = aUp[i].eFrmType;
+          pWin->eStart = aUp[i].eStart;
+          pWin->eEnd = aUp[i].eEnd;
+          pWin->eExclude = 0;
+          if( pWin->eStart==TK_FOLLOWING ){
+            pWin->pStart = sqlite3Expr(db, TK_INTEGER, "1");
+          }
+          break;
+        }
+      }
+    }
+  }
+  pWin->pWFunc = pFunc;
+}
+
+/*
+** Context object passed through sqlite3WalkExprList() to
+** selectWindowRewriteExprCb() by selectWindowRewriteEList().
+*/
+typedef struct WindowRewrite WindowRewrite;
+struct WindowRewrite {
+  Window *pWin;
+  SrcList *pSrc;
+  ExprList *pSub;
+  Table *pTab;
+  Select *pSubSelect;             /* Current sub-select, if any */
+};
+
+/*
+** Callback function used by selectWindowRewriteEList(). If necessary,
+** this function appends to the output expression-list and updates
+** expression (*ppExpr) in place.
+*/
+static int selectWindowRewriteExprCb(Walker *pWalker, Expr *pExpr){
+  struct WindowRewrite *p = pWalker->u.pRewrite;
+  Parse *pParse = pWalker->pParse;
+  assert( p!=0 );
+  assert( p->pWin!=0 );
+
+  /* If this function is being called from within a scalar sub-select
+  ** that used by the SELECT statement being processed, only process
+  ** TK_COLUMN expressions that refer to it (the outer SELECT). Do
+  ** not process aggregates or window functions at all, as they belong
+  ** to the scalar sub-select.  */
+  if( p->pSubSelect ){
+    if( pExpr->op!=TK_COLUMN ){
+      return WRC_Continue;
+    }else{
+      int nSrc = p->pSrc->nSrc;
+      int i;
+      for(i=0; i<nSrc; i++){
+        if( pExpr->iTable==p->pSrc->a[i].iCursor ) break;
+      }
+      if( i==nSrc ) return WRC_Continue;
+    }
+  }
+
+  switch( pExpr->op ){
+
+    case TK_FUNCTION:
+      if( !ExprHasProperty(pExpr, EP_WinFunc) ){
+        break;
+      }else{
+        Window *pWin;
+        for(pWin=p->pWin; pWin; pWin=pWin->pNextWin){
+          if( pExpr->y.pWin==pWin ){
+            assert( pWin->pOwner==pExpr );
+            return WRC_Prune;
+          }
+        }
+      }
+      /* no break */ deliberate_fall_through
+
+    case TK_IF_NULL_ROW:
+    case TK_AGG_FUNCTION:
+    case TK_COLUMN: {
+      int iCol = -1;
+      if( pParse->db->mallocFailed ) return WRC_Abort;
+      if( p->pSub ){
+        int i;
+        for(i=0; i<p->pSub->nExpr; i++){
+          if( 0==sqlite3ExprCompare(0, p->pSub->a[i].pExpr, pExpr, -1) ){
+            iCol = i;
+            break;
+          }
+        }
+      }
+      if( iCol<0 ){
+        Expr *pDup = sqlite3ExprDup(pParse->db, pExpr, 0);
+        if( pDup && pDup->op==TK_AGG_FUNCTION ) pDup->op = TK_FUNCTION;
+        p->pSub = sqlite3ExprListAppend(pParse, p->pSub, pDup);
+      }
+      if( p->pSub ){
+        int f = pExpr->flags & EP_Collate;
+        assert( ExprHasProperty(pExpr, EP_Static)==0 );
+        ExprSetProperty(pExpr, EP_Static);
+        sqlite3ExprDelete(pParse->db, pExpr);
+        ExprClearProperty(pExpr, EP_Static);
+        memset(pExpr, 0, sizeof(Expr));
+
+        pExpr->op = TK_COLUMN;
+        pExpr->iColumn = (iCol<0 ? p->pSub->nExpr-1: iCol);
+        pExpr->iTable = p->pWin->iEphCsr;
+        pExpr->y.pTab = p->pTab;
+        pExpr->flags = f;
+      }
+      if( pParse->db->mallocFailed ) return WRC_Abort;
+      break;
+    }
+
+    default: /* no-op */
+      break;
+  }
+
+  return WRC_Continue;
+}
+static int selectWindowRewriteSelectCb(Walker *pWalker, Select *pSelect){
+  struct WindowRewrite *p = pWalker->u.pRewrite;
+  Select *pSave = p->pSubSelect;
+  if( pSave==pSelect ){
+    return WRC_Continue;
+  }else{
+    p->pSubSelect = pSelect;
+    sqlite3WalkSelect(pWalker, pSelect);
+    p->pSubSelect = pSave;
+  }
+  return WRC_Prune;
+}
+
+
+/*
+** Iterate through each expression in expression-list pEList. For each:
+**
+**   * TK_COLUMN,
+**   * aggregate function, or
+**   * window function with a Window object that is not a member of the
+**     Window list passed as the second argument (pWin).
+**
+** Append the node to output expression-list (*ppSub). And replace it
+** with a TK_COLUMN that reads the (N-1)th element of table
+** pWin->iEphCsr, where N is the number of elements in (*ppSub) after
+** appending the new one.
+*/
+static void selectWindowRewriteEList(
+  Parse *pParse,
+  Window *pWin,
+  SrcList *pSrc,
+  ExprList *pEList,               /* Rewrite expressions in this list */
+  Table *pTab,
+  ExprList **ppSub                /* IN/OUT: Sub-select expression-list */
+){
+  Walker sWalker;
+  WindowRewrite sRewrite;
+
+  assert( pWin!=0 );
+  memset(&sWalker, 0, sizeof(Walker));
+  memset(&sRewrite, 0, sizeof(WindowRewrite));
+
+  sRewrite.pSub = *ppSub;
+  sRewrite.pWin = pWin;
+  sRewrite.pSrc = pSrc;
+  sRewrite.pTab = pTab;
+
+  sWalker.pParse = pParse;
+  sWalker.xExprCallback = selectWindowRewriteExprCb;
+  sWalker.xSelectCallback = selectWindowRewriteSelectCb;
+  sWalker.u.pRewrite = &sRewrite;
+
+  (void)sqlite3WalkExprList(&sWalker, pEList);
+
+  *ppSub = sRewrite.pSub;
+}
+
+/*
+** Append a copy of each expression in expression-list pAppend to
+** expression list pList. Return a pointer to the result list.
+*/
+static ExprList *exprListAppendList(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pList,        /* List to which to append. Might be NULL */
+  ExprList *pAppend,      /* List of values to append. Might be NULL */
+  int bIntToNull
+){
+  if( pAppend ){
+    int i;
+    int nInit = pList ? pList->nExpr : 0;
+    for(i=0; i<pAppend->nExpr; i++){
+      sqlite3 *db = pParse->db;
+      Expr *pDup = sqlite3ExprDup(db, pAppend->a[i].pExpr, 0);
+      if( db->mallocFailed ){
+        sqlite3ExprDelete(db, pDup);
+        break;
+      }
+      if( bIntToNull ){
+        int iDummy;
+        Expr *pSub;
+        pSub = sqlite3ExprSkipCollateAndLikely(pDup);
+        if( sqlite3ExprIsInteger(pSub, &iDummy) ){
+          pSub->op = TK_NULL;
+          pSub->flags &= ~(EP_IntValue|EP_IsTrue|EP_IsFalse);
+          pSub->u.zToken = 0;
+        }
+      }
+      pList = sqlite3ExprListAppend(pParse, pList, pDup);
+      if( pList ) pList->a[nInit+i].fg.sortFlags = pAppend->a[i].fg.sortFlags;
+    }
+  }
+  return pList;
+}
+
+/*
+** When rewriting a query, if the new subquery in the FROM clause
+** contains TK_AGG_FUNCTION nodes that refer to an outer query,
+** then we have to increase the Expr->op2 values of those nodes
+** due to the extra subquery layer that was added.
+**
+** See also the incrAggDepth() routine in resolve.c
+*/
+static int sqlite3WindowExtraAggFuncDepth(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_AGG_FUNCTION
+   && pExpr->op2>=pWalker->walkerDepth
+  ){
+    pExpr->op2++;
+  }
+  return WRC_Continue;
+}
+
+static int disallowAggregatesInOrderByCb(Walker *pWalker, Expr *pExpr){
+  if( pExpr->op==TK_AGG_FUNCTION && pExpr->pAggInfo==0 ){
+    assert( !ExprHasProperty(pExpr, EP_IntValue) );
+     sqlite3ErrorMsg(pWalker->pParse,
+         "misuse of aggregate: %s()", pExpr->u.zToken);
+  }
+  return WRC_Continue;
+}
+
+/*
+** If the SELECT statement passed as the second argument does not invoke
+** any SQL window functions, this function is a no-op. Otherwise, it
+** rewrites the SELECT statement so that window function xStep functions
+** are invoked in the correct order as described under "SELECT REWRITING"
+** at the top of this file.
+*/
+int sqlite3WindowRewrite(Parse *pParse, Select *p){
+  int rc = SQLITE_OK;
+  if( p->pWin
+   && p->pPrior==0
+   && ALWAYS((p->selFlags & SF_WinRewrite)==0)
+   && ALWAYS(!IN_RENAME_OBJECT)
+  ){
+    Vdbe *v = sqlite3GetVdbe(pParse);
+    sqlite3 *db = pParse->db;
+    Select *pSub = 0;             /* The subquery */
+    SrcList *pSrc = p->pSrc;
+    Expr *pWhere = p->pWhere;
+    ExprList *pGroupBy = p->pGroupBy;
+    Expr *pHaving = p->pHaving;
+    ExprList *pSort = 0;
+
+    ExprList *pSublist = 0;       /* Expression list for sub-query */
+    Window *pMWin = p->pWin;      /* Main window object */
+    Window *pWin;                 /* Window object iterator */
+    Table *pTab;
+    Walker w;
+
+    u32 selFlags = p->selFlags;
+
+    pTab = sqlite3DbMallocZero(db, sizeof(Table));
+    if( pTab==0 ){
+      return sqlite3ErrorToParser(db, SQLITE_NOMEM);
+    }
+    sqlite3AggInfoPersistWalkerInit(&w, pParse);
+    sqlite3WalkSelect(&w, p);
+    if( (p->selFlags & SF_Aggregate)==0 ){
+      w.xExprCallback = disallowAggregatesInOrderByCb;
+      w.xSelectCallback = 0;
+      sqlite3WalkExprList(&w, p->pOrderBy);
+    }
+
+    p->pSrc = 0;
+    p->pWhere = 0;
+    p->pGroupBy = 0;
+    p->pHaving = 0;
+    p->selFlags &= ~SF_Aggregate;
+    p->selFlags |= SF_WinRewrite;
+
+    /* Create the ORDER BY clause for the sub-select. This is the concatenation
+    ** of the window PARTITION and ORDER BY clauses. Then, if this makes it
+    ** redundant, remove the ORDER BY from the parent SELECT.  */
+    pSort = exprListAppendList(pParse, 0, pMWin->pPartition, 1);
+    pSort = exprListAppendList(pParse, pSort, pMWin->pOrderBy, 1);
+    if( pSort && p->pOrderBy && p->pOrderBy->nExpr<=pSort->nExpr ){
+      int nSave = pSort->nExpr;
+      pSort->nExpr = p->pOrderBy->nExpr;
+      if( sqlite3ExprListCompare(pSort, p->pOrderBy, -1)==0 ){
+        sqlite3ExprListDelete(db, p->pOrderBy);
+        p->pOrderBy = 0;
+      }
+      pSort->nExpr = nSave;
+    }
+
+    /* Assign a cursor number for the ephemeral table used to buffer rows.
+    ** The OpenEphemeral instruction is coded later, after it is known how
+    ** many columns the table will have.  */
+    pMWin->iEphCsr = pParse->nTab++;
+    pParse->nTab += 3;
+
+    selectWindowRewriteEList(pParse, pMWin, pSrc, p->pEList, pTab, &pSublist);
+    selectWindowRewriteEList(pParse, pMWin, pSrc, p->pOrderBy, pTab, &pSublist);
+    pMWin->nBufferCol = (pSublist ? pSublist->nExpr : 0);
+
+    /* Append the PARTITION BY and ORDER BY expressions to the to the
+    ** sub-select expression list. They are required to figure out where
+    ** boundaries for partitions and sets of peer rows lie.  */
+    pSublist = exprListAppendList(pParse, pSublist, pMWin->pPartition, 0);
+    pSublist = exprListAppendList(pParse, pSublist, pMWin->pOrderBy, 0);
+
+    /* Append the arguments passed to each window function to the
+    ** sub-select expression list. Also allocate two registers for each
+    ** window function - one for the accumulator, another for interim
+    ** results.  */
+    for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+      ExprList *pArgs;
+      assert( ExprUseXList(pWin->pOwner) );
+      assert( pWin->pWFunc!=0 );
+      pArgs = pWin->pOwner->x.pList;
+      if( pWin->pWFunc->funcFlags & SQLITE_SUBTYPE ){
+        selectWindowRewriteEList(pParse, pMWin, pSrc, pArgs, pTab, &pSublist);
+        pWin->iArgCol = (pSublist ? pSublist->nExpr : 0);
+        pWin->bExprArgs = 1;
+      }else{
+        pWin->iArgCol = (pSublist ? pSublist->nExpr : 0);
+        pSublist = exprListAppendList(pParse, pSublist, pArgs, 0);
+      }
+      if( pWin->pFilter ){
+        Expr *pFilter = sqlite3ExprDup(db, pWin->pFilter, 0);
+        pSublist = sqlite3ExprListAppend(pParse, pSublist, pFilter);
+      }
+      pWin->regAccum = ++pParse->nMem;
+      pWin->regResult = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);
+    }
+
+    /* If there is no ORDER BY or PARTITION BY clause, and the window
+    ** function accepts zero arguments, and there are no other columns
+    ** selected (e.g. "SELECT row_number() OVER () FROM t1"), it is possible
+    ** that pSublist is still NULL here. Add a constant expression here to
+    ** keep everything legal in this case.
+    */
+    if( pSublist==0 ){
+      pSublist = sqlite3ExprListAppend(pParse, 0,
+        sqlite3Expr(db, TK_INTEGER, "0")
+      );
+    }
+
+    pSub = sqlite3SelectNew(
+        pParse, pSublist, pSrc, pWhere, pGroupBy, pHaving, pSort, 0, 0
+    );
+    TREETRACE(0x40,pParse,pSub,
+       ("New window-function subquery in FROM clause of (%u/%p)\n",
+       p->selId, p));
+    p->pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
+    assert( pSub!=0 || p->pSrc==0 ); /* Due to db->mallocFailed test inside
+                                     ** of sqlite3DbMallocRawNN() called from
+                                     ** sqlite3SrcListAppend() */
+    if( p->pSrc ){
+      Table *pTab2;
+      p->pSrc->a[0].pSelect = pSub;
+      p->pSrc->a[0].fg.isCorrelated = 1;
+      sqlite3SrcListAssignCursors(pParse, p->pSrc);
+      pSub->selFlags |= SF_Expanded|SF_OrderByReqd;
+      pTab2 = sqlite3ResultSetOfSelect(pParse, pSub, SQLITE_AFF_NONE);
+      pSub->selFlags |= (selFlags & SF_Aggregate);
+      if( pTab2==0 ){
+        /* Might actually be some other kind of error, but in that case
+        ** pParse->nErr will be set, so if SQLITE_NOMEM is set, we will get
+        ** the correct error message regardless. */
+        rc = SQLITE_NOMEM;
+      }else{
+        memcpy(pTab, pTab2, sizeof(Table));
+        pTab->tabFlags |= TF_Ephemeral;
+        p->pSrc->a[0].pTab = pTab;
+        pTab = pTab2;
+        memset(&w, 0, sizeof(w));
+        w.xExprCallback = sqlite3WindowExtraAggFuncDepth;
+        w.xSelectCallback = sqlite3WalkerDepthIncrease;
+        w.xSelectCallback2 = sqlite3WalkerDepthDecrease;
+        sqlite3WalkSelect(&w, pSub);
+      }
+    }else{
+      sqlite3SelectDelete(db, pSub);
+    }
+    if( db->mallocFailed ) rc = SQLITE_NOMEM;
+
+    /* Defer deleting the temporary table pTab because if an error occurred,
+    ** there could still be references to that table embedded in the
+    ** result-set or ORDER BY clause of the SELECT statement p.  */
+    sqlite3ParserAddCleanup(pParse, sqlite3DbFree, pTab);
+  }
+
+  assert( rc==SQLITE_OK || pParse->nErr!=0 );
+  return rc;
+}
+
+/*
+** Unlink the Window object from the Select to which it is attached,
+** if it is attached.
+*/
+void sqlite3WindowUnlinkFromSelect(Window *p){
+  if( p->ppThis ){
+    *p->ppThis = p->pNextWin;
+    if( p->pNextWin ) p->pNextWin->ppThis = p->ppThis;
+    p->ppThis = 0;
+  }
+}
+
+/*
+** Free the Window object passed as the second argument.
+*/
+void sqlite3WindowDelete(sqlite3 *db, Window *p){
+  if( p ){
+    sqlite3WindowUnlinkFromSelect(p);
+    sqlite3ExprDelete(db, p->pFilter);
+    sqlite3ExprListDelete(db, p->pPartition);
+    sqlite3ExprListDelete(db, p->pOrderBy);
+    sqlite3ExprDelete(db, p->pEnd);
+    sqlite3ExprDelete(db, p->pStart);
+    sqlite3DbFree(db, p->zName);
+    sqlite3DbFree(db, p->zBase);
+    sqlite3DbFree(db, p);
+  }
+}
+
+/*
+** Free the linked list of Window objects starting at the second argument.
+*/
+void sqlite3WindowListDelete(sqlite3 *db, Window *p){
+  while( p ){
+    Window *pNext = p->pNextWin;
+    sqlite3WindowDelete(db, p);
+    p = pNext;
+  }
+}
+
+/*
+** The argument expression is an PRECEDING or FOLLOWING offset.  The
+** value should be a non-negative integer.  If the value is not a
+** constant, change it to NULL.  The fact that it is then a non-negative
+** integer will be caught later.  But it is important not to leave
+** variable values in the expression tree.
+*/
+static Expr *sqlite3WindowOffsetExpr(Parse *pParse, Expr *pExpr){
+  if( 0==sqlite3ExprIsConstant(pExpr) ){
+    if( IN_RENAME_OBJECT ) sqlite3RenameExprUnmap(pParse, pExpr);
+    sqlite3ExprDelete(pParse->db, pExpr);
+    pExpr = sqlite3ExprAlloc(pParse->db, TK_NULL, 0, 0);
+  }
+  return pExpr;
+}
+
+/*
+** Allocate and return a new Window object describing a Window Definition.
+*/
+Window *sqlite3WindowAlloc(
+  Parse *pParse,    /* Parsing context */
+  int eType,        /* Frame type. TK_RANGE, TK_ROWS, TK_GROUPS, or 0 */
+  int eStart,       /* Start type: CURRENT, PRECEDING, FOLLOWING, UNBOUNDED */
+  Expr *pStart,     /* Start window size if TK_PRECEDING or FOLLOWING */
+  int eEnd,         /* End type: CURRENT, FOLLOWING, TK_UNBOUNDED, PRECEDING */
+  Expr *pEnd,       /* End window size if TK_FOLLOWING or PRECEDING */
+  u8 eExclude       /* EXCLUDE clause */
+){
+  Window *pWin = 0;
+  int bImplicitFrame = 0;
+
+  /* Parser assures the following: */
+  assert( eType==0 || eType==TK_RANGE || eType==TK_ROWS || eType==TK_GROUPS );
+  assert( eStart==TK_CURRENT || eStart==TK_PRECEDING
+           || eStart==TK_UNBOUNDED || eStart==TK_FOLLOWING );
+  assert( eEnd==TK_CURRENT || eEnd==TK_FOLLOWING
+           || eEnd==TK_UNBOUNDED || eEnd==TK_PRECEDING );
+  assert( (eStart==TK_PRECEDING || eStart==TK_FOLLOWING)==(pStart!=0) );
+  assert( (eEnd==TK_FOLLOWING || eEnd==TK_PRECEDING)==(pEnd!=0) );
+
+  if( eType==0 ){
+    bImplicitFrame = 1;
+    eType = TK_RANGE;
+  }
+
+  /* Additionally, the
+  ** starting boundary type may not occur earlier in the following list than
+  ** the ending boundary type:
+  **
+  **   UNBOUNDED PRECEDING
+  **   <expr> PRECEDING
+  **   CURRENT ROW
+  **   <expr> FOLLOWING
+  **   UNBOUNDED FOLLOWING
+  **
+  ** The parser ensures that "UNBOUNDED PRECEDING" cannot be used as an ending
+  ** boundary, and than "UNBOUNDED FOLLOWING" cannot be used as a starting
+  ** frame boundary.
+  */
+  if( (eStart==TK_CURRENT && eEnd==TK_PRECEDING)
+   || (eStart==TK_FOLLOWING && (eEnd==TK_PRECEDING || eEnd==TK_CURRENT))
+  ){
+    sqlite3ErrorMsg(pParse, "unsupported frame specification");
+    goto windowAllocErr;
+  }
+
+  pWin = (Window*)sqlite3DbMallocZero(pParse->db, sizeof(Window));
+  if( pWin==0 ) goto windowAllocErr;
+  pWin->eFrmType = eType;
+  pWin->eStart = eStart;
+  pWin->eEnd = eEnd;
+  if( eExclude==0 && OptimizationDisabled(pParse->db, SQLITE_WindowFunc) ){
+    eExclude = TK_NO;
+  }
+  pWin->eExclude = eExclude;
+  pWin->bImplicitFrame = bImplicitFrame;
+  pWin->pEnd = sqlite3WindowOffsetExpr(pParse, pEnd);
+  pWin->pStart = sqlite3WindowOffsetExpr(pParse, pStart);
+  return pWin;
+
+windowAllocErr:
+  sqlite3ExprDelete(pParse->db, pEnd);
+  sqlite3ExprDelete(pParse->db, pStart);
+  return 0;
+}
+
+/*
+** Attach PARTITION and ORDER BY clauses pPartition and pOrderBy to window
+** pWin. Also, if parameter pBase is not NULL, set pWin->zBase to the
+** equivalent nul-terminated string.
+*/
+Window *sqlite3WindowAssemble(
+  Parse *pParse,
+  Window *pWin,
+  ExprList *pPartition,
+  ExprList *pOrderBy,
+  Token *pBase
+){
+  if( pWin ){
+    pWin->pPartition = pPartition;
+    pWin->pOrderBy = pOrderBy;
+    if( pBase ){
+      pWin->zBase = sqlite3DbStrNDup(pParse->db, pBase->z, pBase->n);
+    }
+  }else{
+    sqlite3ExprListDelete(pParse->db, pPartition);
+    sqlite3ExprListDelete(pParse->db, pOrderBy);
+  }
+  return pWin;
+}
+
+/*
+** Window *pWin has just been created from a WINDOW clause. Token pBase
+** is the base window. Earlier windows from the same WINDOW clause are
+** stored in the linked list starting at pWin->pNextWin. This function
+** either updates *pWin according to the base specification, or else
+** leaves an error in pParse.
+*/
+void sqlite3WindowChain(Parse *pParse, Window *pWin, Window *pList){
+  if( pWin->zBase ){
+    sqlite3 *db = pParse->db;
+    Window *pExist = windowFind(pParse, pList, pWin->zBase);
+    if( pExist ){
+      const char *zErr = 0;
+      /* Check for errors */
+      if( pWin->pPartition ){
+        zErr = "PARTITION clause";
+      }else if( pExist->pOrderBy && pWin->pOrderBy ){
+        zErr = "ORDER BY clause";
+      }else if( pExist->bImplicitFrame==0 ){
+        zErr = "frame specification";
+      }
+      if( zErr ){
+        sqlite3ErrorMsg(pParse,
+            "cannot override %s of window: %s", zErr, pWin->zBase
+        );
+      }else{
+        pWin->pPartition = sqlite3ExprListDup(db, pExist->pPartition, 0);
+        if( pExist->pOrderBy ){
+          assert( pWin->pOrderBy==0 );
+          pWin->pOrderBy = sqlite3ExprListDup(db, pExist->pOrderBy, 0);
+        }
+        sqlite3DbFree(db, pWin->zBase);
+        pWin->zBase = 0;
+      }
+    }
+  }
+}
+
+/*
+** Attach window object pWin to expression p.
+*/
+void sqlite3WindowAttach(Parse *pParse, Expr *p, Window *pWin){
+  if( p ){
+    assert( p->op==TK_FUNCTION );
+    assert( pWin );
+    assert( ExprIsFullSize(p) );
+    p->y.pWin = pWin;
+    ExprSetProperty(p, EP_WinFunc|EP_FullSize);
+    pWin->pOwner = p;
+    if( (p->flags & EP_Distinct) && pWin->eFrmType!=TK_FILTER ){
+      sqlite3ErrorMsg(pParse,
+          "DISTINCT is not supported for window functions"
+      );
+    }
+  }else{
+    sqlite3WindowDelete(pParse->db, pWin);
+  }
+}
+
+/*
+** Possibly link window pWin into the list at pSel->pWin (window functions
+** to be processed as part of SELECT statement pSel). The window is linked
+** in if either (a) there are no other windows already linked to this
+** SELECT, or (b) the windows already linked use a compatible window frame.
+*/
+void sqlite3WindowLink(Select *pSel, Window *pWin){
+  if( pSel ){
+    if( 0==pSel->pWin || 0==sqlite3WindowCompare(0, pSel->pWin, pWin, 0) ){
+      pWin->pNextWin = pSel->pWin;
+      if( pSel->pWin ){
+        pSel->pWin->ppThis = &pWin->pNextWin;
+      }
+      pSel->pWin = pWin;
+      pWin->ppThis = &pSel->pWin;
+    }else{
+      if( sqlite3ExprListCompare(pWin->pPartition, pSel->pWin->pPartition,-1) ){
+        pSel->selFlags |= SF_MultiPart;
+      }
+    }
+  }
+}
+
+/*
+** Return 0 if the two window objects are identical, 1 if they are
+** different, or 2 if it cannot be determined if the objects are identical
+** or not. Identical window objects can be processed in a single scan.
+*/
+int sqlite3WindowCompare(
+  const Parse *pParse,
+  const Window *p1,
+  const Window *p2,
+  int bFilter
+){
+  int res;
+  if( NEVER(p1==0) || NEVER(p2==0) ) return 1;
+  if( p1->eFrmType!=p2->eFrmType ) return 1;
+  if( p1->eStart!=p2->eStart ) return 1;
+  if( p1->eEnd!=p2->eEnd ) return 1;
+  if( p1->eExclude!=p2->eExclude ) return 1;
+  if( sqlite3ExprCompare(pParse, p1->pStart, p2->pStart, -1) ) return 1;
+  if( sqlite3ExprCompare(pParse, p1->pEnd, p2->pEnd, -1) ) return 1;
+  if( (res = sqlite3ExprListCompare(p1->pPartition, p2->pPartition, -1)) ){
+    return res;
+  }
+  if( (res = sqlite3ExprListCompare(p1->pOrderBy, p2->pOrderBy, -1)) ){
+    return res;
+  }
+  if( bFilter ){
+    if( (res = sqlite3ExprCompare(pParse, p1->pFilter, p2->pFilter, -1)) ){
+      return res;
+    }
+  }
+  return 0;
+}
+
+
+/*
+** This is called by code in select.c before it calls sqlite3WhereBegin()
+** to begin iterating through the sub-query results. It is used to allocate
+** and initialize registers and cursors used by sqlite3WindowCodeStep().
+*/
+void sqlite3WindowCodeInit(Parse *pParse, Select *pSelect){
+  int nEphExpr = pSelect->pSrc->a[0].pSelect->pEList->nExpr;
+  Window *pMWin = pSelect->pWin;
+  Window *pWin;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+
+  sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pMWin->iEphCsr, nEphExpr);
+  sqlite3VdbeAddOp2(v, OP_OpenDup, pMWin->iEphCsr+1, pMWin->iEphCsr);
+  sqlite3VdbeAddOp2(v, OP_OpenDup, pMWin->iEphCsr+2, pMWin->iEphCsr);
+  sqlite3VdbeAddOp2(v, OP_OpenDup, pMWin->iEphCsr+3, pMWin->iEphCsr);
+
+  /* Allocate registers to use for PARTITION BY values, if any. Initialize
+  ** said registers to NULL.  */
+  if( pMWin->pPartition ){
+    int nExpr = pMWin->pPartition->nExpr;
+    pMWin->regPart = pParse->nMem+1;
+    pParse->nMem += nExpr;
+    sqlite3VdbeAddOp3(v, OP_Null, 0, pMWin->regPart, pMWin->regPart+nExpr-1);
+  }
+
+  pMWin->regOne = ++pParse->nMem;
+  sqlite3VdbeAddOp2(v, OP_Integer, 1, pMWin->regOne);
+
+  if( pMWin->eExclude ){
+    pMWin->regStartRowid = ++pParse->nMem;
+    pMWin->regEndRowid = ++pParse->nMem;
+    pMWin->csrApp = pParse->nTab++;
+    sqlite3VdbeAddOp2(v, OP_Integer, 1, pMWin->regStartRowid);
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, pMWin->regEndRowid);
+    sqlite3VdbeAddOp2(v, OP_OpenDup, pMWin->csrApp, pMWin->iEphCsr);
+    return;
+  }
+
+  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+    FuncDef *p = pWin->pWFunc;
+    if( (p->funcFlags & SQLITE_FUNC_MINMAX) && pWin->eStart!=TK_UNBOUNDED ){
+      /* The inline versions of min() and max() require a single ephemeral
+      ** table and 3 registers. The registers are used as follows:
+      **
+      **   regApp+0: slot to copy min()/max() argument to for MakeRecord
+      **   regApp+1: integer value used to ensure keys are unique
+      **   regApp+2: output of MakeRecord
+      */
+      ExprList *pList;
+      KeyInfo *pKeyInfo;
+      assert( ExprUseXList(pWin->pOwner) );
+      pList = pWin->pOwner->x.pList;
+      pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pList, 0, 0);
+      pWin->csrApp = pParse->nTab++;
+      pWin->regApp = pParse->nMem+1;
+      pParse->nMem += 3;
+      if( pKeyInfo && pWin->pWFunc->zName[1]=='i' ){
+        assert( pKeyInfo->aSortFlags[0]==0 );
+        pKeyInfo->aSortFlags[0] = KEYINFO_ORDER_DESC;
+      }
+      sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pWin->csrApp, 2);
+      sqlite3VdbeAppendP4(v, pKeyInfo, P4_KEYINFO);
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, pWin->regApp+1);
+    }
+    else if( p->zName==nth_valueName || p->zName==first_valueName ){
+      /* Allocate two registers at pWin->regApp. These will be used to
+      ** store the start and end index of the current frame.  */
+      pWin->regApp = pParse->nMem+1;
+      pWin->csrApp = pParse->nTab++;
+      pParse->nMem += 2;
+      sqlite3VdbeAddOp2(v, OP_OpenDup, pWin->csrApp, pMWin->iEphCsr);
+    }
+    else if( p->zName==leadName || p->zName==lagName ){
+      pWin->csrApp = pParse->nTab++;
+      sqlite3VdbeAddOp2(v, OP_OpenDup, pWin->csrApp, pMWin->iEphCsr);
+    }
+  }
+}
+
+#define WINDOW_STARTING_INT  0
+#define WINDOW_ENDING_INT    1
+#define WINDOW_NTH_VALUE_INT 2
+#define WINDOW_STARTING_NUM  3
+#define WINDOW_ENDING_NUM    4
+
+/*
+** A "PRECEDING <expr>" (eCond==0) or "FOLLOWING <expr>" (eCond==1) or the
+** value of the second argument to nth_value() (eCond==2) has just been
+** evaluated and the result left in register reg. This function generates VM
+** code to check that the value is a non-negative integer and throws an
+** exception if it is not.
+*/
+static void windowCheckValue(Parse *pParse, int reg, int eCond){
+  static const char *azErr[] = {
+    "frame starting offset must be a non-negative integer",
+    "frame ending offset must be a non-negative integer",
+    "second argument to nth_value must be a positive integer",
+    "frame starting offset must be a non-negative number",
+    "frame ending offset must be a non-negative number",
+  };
+  static int aOp[] = { OP_Ge, OP_Ge, OP_Gt, OP_Ge, OP_Ge };
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int regZero = sqlite3GetTempReg(pParse);
+  assert( eCond>=0 && eCond<ArraySize(azErr) );
+  sqlite3VdbeAddOp2(v, OP_Integer, 0, regZero);
+  if( eCond>=WINDOW_STARTING_NUM ){
+    int regString = sqlite3GetTempReg(pParse);
+    sqlite3VdbeAddOp4(v, OP_String8, 0, regString, 0, "", P4_STATIC);
+    sqlite3VdbeAddOp3(v, OP_Ge, regString, sqlite3VdbeCurrentAddr(v)+2, reg);
+    sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC|SQLITE_JUMPIFNULL);
+    VdbeCoverage(v);
+    assert( eCond==3 || eCond==4 );
+    VdbeCoverageIf(v, eCond==3);
+    VdbeCoverageIf(v, eCond==4);
+  }else{
+    sqlite3VdbeAddOp2(v, OP_MustBeInt, reg, sqlite3VdbeCurrentAddr(v)+2);
+    VdbeCoverage(v);
+    assert( eCond==0 || eCond==1 || eCond==2 );
+    VdbeCoverageIf(v, eCond==0);
+    VdbeCoverageIf(v, eCond==1);
+    VdbeCoverageIf(v, eCond==2);
+  }
+  sqlite3VdbeAddOp3(v, aOp[eCond], regZero, sqlite3VdbeCurrentAddr(v)+2, reg);
+  sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC);
+  VdbeCoverageNeverNullIf(v, eCond==0); /* NULL case captured by */
+  VdbeCoverageNeverNullIf(v, eCond==1); /*   the OP_MustBeInt */
+  VdbeCoverageNeverNullIf(v, eCond==2);
+  VdbeCoverageNeverNullIf(v, eCond==3); /* NULL case caught by */
+  VdbeCoverageNeverNullIf(v, eCond==4); /*   the OP_Ge */
+  sqlite3MayAbort(pParse);
+  sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_ERROR, OE_Abort);
+  sqlite3VdbeAppendP4(v, (void*)azErr[eCond], P4_STATIC);
+  sqlite3ReleaseTempReg(pParse, regZero);
+}
+
+/*
+** Return the number of arguments passed to the window-function associated
+** with the object passed as the only argument to this function.
+*/
+static int windowArgCount(Window *pWin){
+  const ExprList *pList;
+  assert( ExprUseXList(pWin->pOwner) );
+  pList = pWin->pOwner->x.pList;
+  return (pList ? pList->nExpr : 0);
+}
+
+typedef struct WindowCodeArg WindowCodeArg;
+typedef struct WindowCsrAndReg WindowCsrAndReg;
+
+/*
+** See comments above struct WindowCodeArg.
+*/
+struct WindowCsrAndReg {
+  int csr;                        /* Cursor number */
+  int reg;                        /* First in array of peer values */
+};
+
+/*
+** A single instance of this structure is allocated on the stack by
+** sqlite3WindowCodeStep() and a pointer to it passed to the various helper
+** routines. This is to reduce the number of arguments required by each
+** helper function.
+**
+** regArg:
+**   Each window function requires an accumulator register (just as an
+**   ordinary aggregate function does). This variable is set to the first
+**   in an array of accumulator registers - one for each window function
+**   in the WindowCodeArg.pMWin list.
+**
+** eDelete:
+**   The window functions implementation sometimes caches the input rows
+**   that it processes in a temporary table. If it is not zero, this
+**   variable indicates when rows may be removed from the temp table (in
+**   order to reduce memory requirements - it would always be safe just
+**   to leave them there). Possible values for eDelete are:
+**
+**      WINDOW_RETURN_ROW:
+**        An input row can be discarded after it is returned to the caller.
+**
+**      WINDOW_AGGINVERSE:
+**        An input row can be discarded after the window functions xInverse()
+**        callbacks have been invoked in it.
+**
+**      WINDOW_AGGSTEP:
+**        An input row can be discarded after the window functions xStep()
+**        callbacks have been invoked in it.
+**
+** start,current,end
+**   Consider a window-frame similar to the following:
+**
+**     (ORDER BY a, b GROUPS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+**
+**   The windows functions implementation caches the input rows in a temp
+**   table, sorted by "a, b" (it actually populates the cache lazily, and
+**   aggressively removes rows once they are no longer required, but that's
+**   a mere detail). It keeps three cursors open on the temp table. One
+**   (current) that points to the next row to return to the query engine
+**   once its window function values have been calculated. Another (end)
+**   points to the next row to call the xStep() method of each window function
+**   on (so that it is 2 groups ahead of current). And a third (start) that
+**   points to the next row to call the xInverse() method of each window
+**   function on.
+**
+**   Each cursor (start, current and end) consists of a VDBE cursor
+**   (WindowCsrAndReg.csr) and an array of registers (starting at
+**   WindowCodeArg.reg) that always contains a copy of the peer values
+**   read from the corresponding cursor.
+**
+**   Depending on the window-frame in question, all three cursors may not
+**   be required. In this case both WindowCodeArg.csr and reg are set to
+**   0.
+*/
+struct WindowCodeArg {
+  Parse *pParse;             /* Parse context */
+  Window *pMWin;             /* First in list of functions being processed */
+  Vdbe *pVdbe;               /* VDBE object */
+  int addrGosub;             /* OP_Gosub to this address to return one row */
+  int regGosub;              /* Register used with OP_Gosub(addrGosub) */
+  int regArg;                /* First in array of accumulator registers */
+  int eDelete;               /* See above */
+  int regRowid;
+
+  WindowCsrAndReg start;
+  WindowCsrAndReg current;
+  WindowCsrAndReg end;
+};
+
+/*
+** Generate VM code to read the window frames peer values from cursor csr into
+** an array of registers starting at reg.
+*/
+static void windowReadPeerValues(
+  WindowCodeArg *p,
+  int csr,
+  int reg
+){
+  Window *pMWin = p->pMWin;
+  ExprList *pOrderBy = pMWin->pOrderBy;
+  if( pOrderBy ){
+    Vdbe *v = sqlite3GetVdbe(p->pParse);
+    ExprList *pPart = pMWin->pPartition;
+    int iColOff = pMWin->nBufferCol + (pPart ? pPart->nExpr : 0);
+    int i;
+    for(i=0; i<pOrderBy->nExpr; i++){
+      sqlite3VdbeAddOp3(v, OP_Column, csr, iColOff+i, reg+i);
+    }
+  }
+}
+
+/*
+** Generate VM code to invoke either xStep() (if bInverse is 0) or
+** xInverse (if bInverse is non-zero) for each window function in the
+** linked list starting at pMWin. Or, for built-in window functions
+** that do not use the standard function API, generate the required
+** inline VM code.
+**
+** If argument csr is greater than or equal to 0, then argument reg is
+** the first register in an array of registers guaranteed to be large
+** enough to hold the array of arguments for each function. In this case
+** the arguments are extracted from the current row of csr into the
+** array of registers before invoking OP_AggStep or OP_AggInverse
+**
+** Or, if csr is less than zero, then the array of registers at reg is
+** already populated with all columns from the current row of the sub-query.
+**
+** If argument regPartSize is non-zero, then it is a register containing the
+** number of rows in the current partition.
+*/
+static void windowAggStep(
+  WindowCodeArg *p,
+  Window *pMWin,                  /* Linked list of window functions */
+  int csr,                        /* Read arguments from this cursor */
+  int bInverse,                   /* True to invoke xInverse instead of xStep */
+  int reg                         /* Array of registers */
+){
+  Parse *pParse = p->pParse;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  Window *pWin;
+  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+    FuncDef *pFunc = pWin->pWFunc;
+    int regArg;
+    int nArg = pWin->bExprArgs ? 0 : windowArgCount(pWin);
+    int i;
+
+    assert( bInverse==0 || pWin->eStart!=TK_UNBOUNDED );
+
+    /* All OVER clauses in the same window function aggregate step must
+    ** be the same. */
+    assert( pWin==pMWin || sqlite3WindowCompare(pParse,pWin,pMWin,0)!=1 );
+
+    for(i=0; i<nArg; i++){
+      if( i!=1 || pFunc->zName!=nth_valueName ){
+        sqlite3VdbeAddOp3(v, OP_Column, csr, pWin->iArgCol+i, reg+i);
+      }else{
+        sqlite3VdbeAddOp3(v, OP_Column, pMWin->iEphCsr, pWin->iArgCol+i, reg+i);
+      }
+    }
+    regArg = reg;
+
+    if( pMWin->regStartRowid==0
+     && (pFunc->funcFlags & SQLITE_FUNC_MINMAX)
+     && (pWin->eStart!=TK_UNBOUNDED)
+    ){
+      int addrIsNull = sqlite3VdbeAddOp1(v, OP_IsNull, regArg);
+      VdbeCoverage(v);
+      if( bInverse==0 ){
+        sqlite3VdbeAddOp2(v, OP_AddImm, pWin->regApp+1, 1);
+        sqlite3VdbeAddOp2(v, OP_SCopy, regArg, pWin->regApp);
+        sqlite3VdbeAddOp3(v, OP_MakeRecord, pWin->regApp, 2, pWin->regApp+2);
+        sqlite3VdbeAddOp2(v, OP_IdxInsert, pWin->csrApp, pWin->regApp+2);
+      }else{
+        sqlite3VdbeAddOp4Int(v, OP_SeekGE, pWin->csrApp, 0, regArg, 1);
+        VdbeCoverageNeverTaken(v);
+        sqlite3VdbeAddOp1(v, OP_Delete, pWin->csrApp);
+        sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
+      }
+      sqlite3VdbeJumpHere(v, addrIsNull);
+    }else if( pWin->regApp ){
+      assert( pFunc->zName==nth_valueName
+           || pFunc->zName==first_valueName
+      );
+      assert( bInverse==0 || bInverse==1 );
+      sqlite3VdbeAddOp2(v, OP_AddImm, pWin->regApp+1-bInverse, 1);
+    }else if( pFunc->xSFunc!=noopStepFunc ){
+      int addrIf = 0;
+      if( pWin->pFilter ){
+        int regTmp;
+        assert( ExprUseXList(pWin->pOwner) );
+        assert( pWin->bExprArgs || !nArg ||nArg==pWin->pOwner->x.pList->nExpr );
+        assert( pWin->bExprArgs || nArg  ||pWin->pOwner->x.pList==0 );
+        regTmp = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp3(v, OP_Column, csr, pWin->iArgCol+nArg,regTmp);
+        addrIf = sqlite3VdbeAddOp3(v, OP_IfNot, regTmp, 0, 1);
+        VdbeCoverage(v);
+        sqlite3ReleaseTempReg(pParse, regTmp);
+      }
+     
+      if( pWin->bExprArgs ){
+        int iOp = sqlite3VdbeCurrentAddr(v);
+        int iEnd;
+
+        assert( ExprUseXList(pWin->pOwner) );
+        nArg = pWin->pOwner->x.pList->nExpr;
+        regArg = sqlite3GetTempRange(pParse, nArg);
+        sqlite3ExprCodeExprList(pParse, pWin->pOwner->x.pList, regArg, 0, 0);
+
+        for(iEnd=sqlite3VdbeCurrentAddr(v); iOp<iEnd; iOp++){
+          VdbeOp *pOp = sqlite3VdbeGetOp(v, iOp);
+          if( pOp->opcode==OP_Column && pOp->p1==pMWin->iEphCsr ){
+            pOp->p1 = csr;
+          }
+        }
+      }
+      if( pFunc->funcFlags & SQLITE_FUNC_NEEDCOLL ){
+        CollSeq *pColl;
+        assert( nArg>0 );
+        assert( ExprUseXList(pWin->pOwner) );
+        pColl = sqlite3ExprNNCollSeq(pParse, pWin->pOwner->x.pList->a[0].pExpr);
+        sqlite3VdbeAddOp4(v, OP_CollSeq, 0,0,0, (const char*)pColl, P4_COLLSEQ);
+      }
+      sqlite3VdbeAddOp3(v, bInverse? OP_AggInverse : OP_AggStep,
+                        bInverse, regArg, pWin->regAccum);
+      sqlite3VdbeAppendP4(v, pFunc, P4_FUNCDEF);
+      sqlite3VdbeChangeP5(v, (u8)nArg);
+      if( pWin->bExprArgs ){
+        sqlite3ReleaseTempRange(pParse, regArg, nArg);
+      }
+      if( addrIf ) sqlite3VdbeJumpHere(v, addrIf);
+    }
+  }
+}
+
+/*
+** Values that may be passed as the second argument to windowCodeOp().
+*/
+#define WINDOW_RETURN_ROW 1
+#define WINDOW_AGGINVERSE 2
+#define WINDOW_AGGSTEP    3
+
+/*
+** Generate VM code to invoke either xValue() (bFin==0) or xFinalize()
+** (bFin==1) for each window function in the linked list starting at
+** pMWin. Or, for built-in window-functions that do not use the standard
+** API, generate the equivalent VM code.
+*/
+static void windowAggFinal(WindowCodeArg *p, int bFin){
+  Parse *pParse = p->pParse;
+  Window *pMWin = p->pMWin;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  Window *pWin;
+
+  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+    if( pMWin->regStartRowid==0
+     && (pWin->pWFunc->funcFlags & SQLITE_FUNC_MINMAX)
+     && (pWin->eStart!=TK_UNBOUNDED)
+    ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regResult);
+      sqlite3VdbeAddOp1(v, OP_Last, pWin->csrApp);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_Column, pWin->csrApp, 0, pWin->regResult);
+      sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
+    }else if( pWin->regApp ){
+      assert( pMWin->regStartRowid==0 );
+    }else{
+      int nArg = windowArgCount(pWin);
+      if( bFin ){
+        sqlite3VdbeAddOp2(v, OP_AggFinal, pWin->regAccum, nArg);
+        sqlite3VdbeAppendP4(v, pWin->pWFunc, P4_FUNCDEF);
+        sqlite3VdbeAddOp2(v, OP_Copy, pWin->regAccum, pWin->regResult);
+        sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);
+      }else{
+        sqlite3VdbeAddOp3(v, OP_AggValue,pWin->regAccum,nArg,pWin->regResult);
+        sqlite3VdbeAppendP4(v, pWin->pWFunc, P4_FUNCDEF);
+      }
+    }
+  }
+}
+
+/*
+** Generate code to calculate the current values of all window functions in the
+** p->pMWin list by doing a full scan of the current window frame. Store the
+** results in the Window.regResult registers, ready to return the upper
+** layer.
+*/
+static void windowFullScan(WindowCodeArg *p){
+  Window *pWin;
+  Parse *pParse = p->pParse;
+  Window *pMWin = p->pMWin;
+  Vdbe *v = p->pVdbe;
+
+  int regCRowid = 0;              /* Current rowid value */
+  int regCPeer = 0;               /* Current peer values */
+  int regRowid = 0;               /* AggStep rowid value */
+  int regPeer = 0;                /* AggStep peer values */
+
+  int nPeer;
+  int lblNext;
+  int lblBrk;
+  int addrNext;
+  int csr;
+
+  VdbeModuleComment((v, "windowFullScan begin"));
+
+  assert( pMWin!=0 );
+  csr = pMWin->csrApp;
+  nPeer = (pMWin->pOrderBy ? pMWin->pOrderBy->nExpr : 0);
+
+  lblNext = sqlite3VdbeMakeLabel(pParse);
+  lblBrk = sqlite3VdbeMakeLabel(pParse);
+
+  regCRowid = sqlite3GetTempReg(pParse);
+  regRowid = sqlite3GetTempReg(pParse);
+  if( nPeer ){
+    regCPeer = sqlite3GetTempRange(pParse, nPeer);
+    regPeer = sqlite3GetTempRange(pParse, nPeer);
+  }
+
+  sqlite3VdbeAddOp2(v, OP_Rowid, pMWin->iEphCsr, regCRowid);
+  windowReadPeerValues(p, pMWin->iEphCsr, regCPeer);
+
+  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+    sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);
+  }
+
+  sqlite3VdbeAddOp3(v, OP_SeekGE, csr, lblBrk, pMWin->regStartRowid);
+  VdbeCoverage(v);
+  addrNext = sqlite3VdbeCurrentAddr(v);
+  sqlite3VdbeAddOp2(v, OP_Rowid, csr, regRowid);
+  sqlite3VdbeAddOp3(v, OP_Gt, pMWin->regEndRowid, lblBrk, regRowid);
+  VdbeCoverageNeverNull(v);
+
+  if( pMWin->eExclude==TK_CURRENT ){
+    sqlite3VdbeAddOp3(v, OP_Eq, regCRowid, lblNext, regRowid);
+    VdbeCoverageNeverNull(v);
+  }else if( pMWin->eExclude!=TK_NO ){
+    int addr;
+    int addrEq = 0;
+    KeyInfo *pKeyInfo = 0;
+
+    if( pMWin->pOrderBy ){
+      pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pMWin->pOrderBy, 0, 0);
+    }
+    if( pMWin->eExclude==TK_TIES ){
+      addrEq = sqlite3VdbeAddOp3(v, OP_Eq, regCRowid, 0, regRowid);
+      VdbeCoverageNeverNull(v);
+    }
+    if( pKeyInfo ){
+      windowReadPeerValues(p, csr, regPeer);
+      sqlite3VdbeAddOp3(v, OP_Compare, regPeer, regCPeer, nPeer);
+      sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
+      addr = sqlite3VdbeCurrentAddr(v)+1;
+      sqlite3VdbeAddOp3(v, OP_Jump, addr, lblNext, addr);
+      VdbeCoverageEqNe(v);
+    }else{
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, lblNext);
+    }
+    if( addrEq ) sqlite3VdbeJumpHere(v, addrEq);
+  }
+
+  windowAggStep(p, pMWin, csr, 0, p->regArg);
+
+  sqlite3VdbeResolveLabel(v, lblNext);
+  sqlite3VdbeAddOp2(v, OP_Next, csr, addrNext);
+  VdbeCoverage(v);
+  sqlite3VdbeJumpHere(v, addrNext-1);
+  sqlite3VdbeJumpHere(v, addrNext+1);
+  sqlite3ReleaseTempReg(pParse, regRowid);
+  sqlite3ReleaseTempReg(pParse, regCRowid);
+  if( nPeer ){
+    sqlite3ReleaseTempRange(pParse, regPeer, nPeer);
+    sqlite3ReleaseTempRange(pParse, regCPeer, nPeer);
+  }
+
+  windowAggFinal(p, 1);
+  VdbeModuleComment((v, "windowFullScan end"));
+}
+
+/*
+** Invoke the sub-routine at regGosub (generated by code in select.c) to
+** return the current row of Window.iEphCsr. If all window functions are
+** aggregate window functions that use the standard API, a single
+** OP_Gosub instruction is all that this routine generates. Extra VM code
+** for per-row processing is only generated for the following built-in window
+** functions:
+**
+**   nth_value()
+**   first_value()
+**   lag()
+**   lead()
+*/
+static void windowReturnOneRow(WindowCodeArg *p){
+  Window *pMWin = p->pMWin;
+  Vdbe *v = p->pVdbe;
+
+  if( pMWin->regStartRowid ){
+    windowFullScan(p);
+  }else{
+    Parse *pParse = p->pParse;
+    Window *pWin;
+
+    for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+      FuncDef *pFunc = pWin->pWFunc;
+      assert( ExprUseXList(pWin->pOwner) );
+      if( pFunc->zName==nth_valueName
+       || pFunc->zName==first_valueName
+      ){
+        int csr = pWin->csrApp;
+        int lbl = sqlite3VdbeMakeLabel(pParse);
+        int tmpReg = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regResult);
+ 
+        if( pFunc->zName==nth_valueName ){
+          sqlite3VdbeAddOp3(v, OP_Column,pMWin->iEphCsr,pWin->iArgCol+1,tmpReg);
+          windowCheckValue(pParse, tmpReg, 2);
+        }else{
+          sqlite3VdbeAddOp2(v, OP_Integer, 1, tmpReg);
+        }
+        sqlite3VdbeAddOp3(v, OP_Add, tmpReg, pWin->regApp, tmpReg);
+        sqlite3VdbeAddOp3(v, OP_Gt, pWin->regApp+1, lbl, tmpReg);
+        VdbeCoverageNeverNull(v);
+        sqlite3VdbeAddOp3(v, OP_SeekRowid, csr, 0, tmpReg);
+        VdbeCoverageNeverTaken(v);
+        sqlite3VdbeAddOp3(v, OP_Column, csr, pWin->iArgCol, pWin->regResult);
+        sqlite3VdbeResolveLabel(v, lbl);
+        sqlite3ReleaseTempReg(pParse, tmpReg);
+      }
+      else if( pFunc->zName==leadName || pFunc->zName==lagName ){
+        int nArg = pWin->pOwner->x.pList->nExpr;
+        int csr = pWin->csrApp;
+        int lbl = sqlite3VdbeMakeLabel(pParse);
+        int tmpReg = sqlite3GetTempReg(pParse);
+        int iEph = pMWin->iEphCsr;
+ 
+        if( nArg<3 ){
+          sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regResult);
+        }else{
+          sqlite3VdbeAddOp3(v, OP_Column, iEph,pWin->iArgCol+2,pWin->regResult);
+        }
+        sqlite3VdbeAddOp2(v, OP_Rowid, iEph, tmpReg);
+        if( nArg<2 ){
+          int val = (pFunc->zName==leadName ? 1 : -1);
+          sqlite3VdbeAddOp2(v, OP_AddImm, tmpReg, val);
+        }else{
+          int op = (pFunc->zName==leadName ? OP_Add : OP_Subtract);
+          int tmpReg2 = sqlite3GetTempReg(pParse);
+          sqlite3VdbeAddOp3(v, OP_Column, iEph, pWin->iArgCol+1, tmpReg2);
+          sqlite3VdbeAddOp3(v, op, tmpReg2, tmpReg, tmpReg);
+          sqlite3ReleaseTempReg(pParse, tmpReg2);
+        }
+ 
+        sqlite3VdbeAddOp3(v, OP_SeekRowid, csr, lbl, tmpReg);
+        VdbeCoverage(v);
+        sqlite3VdbeAddOp3(v, OP_Column, csr, pWin->iArgCol, pWin->regResult);
+        sqlite3VdbeResolveLabel(v, lbl);
+        sqlite3ReleaseTempReg(pParse, tmpReg);
+      }
+    }
+  }
+  sqlite3VdbeAddOp2(v, OP_Gosub, p->regGosub, p->addrGosub);
+}
+
+/*
+** Generate code to set the accumulator register for each window function
+** in the linked list passed as the second argument to NULL. And perform
+** any equivalent initialization required by any built-in window functions
+** in the list.
+*/
+static int windowInitAccum(Parse *pParse, Window *pMWin){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int regArg;
+  int nArg = 0;
+  Window *pWin;
+  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+    FuncDef *pFunc = pWin->pWFunc;
+    assert( pWin->regAccum );
+    sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);
+    nArg = MAX(nArg, windowArgCount(pWin));
+    if( pMWin->regStartRowid==0 ){
+      if( pFunc->zName==nth_valueName || pFunc->zName==first_valueName ){
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, pWin->regApp);
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, pWin->regApp+1);
+      }
+
+      if( (pFunc->funcFlags & SQLITE_FUNC_MINMAX) && pWin->csrApp ){
+        assert( pWin->eStart!=TK_UNBOUNDED );
+        sqlite3VdbeAddOp1(v, OP_ResetSorter, pWin->csrApp);
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, pWin->regApp+1);
+      }
+    }
+  }
+  regArg = pParse->nMem+1;
+  pParse->nMem += nArg;
+  return regArg;
+}
+
+/*
+** Return true if the current frame should be cached in the ephemeral table,
+** even if there are no xInverse() calls required.
+*/
+static int windowCacheFrame(Window *pMWin){
+  Window *pWin;
+  if( pMWin->regStartRowid ) return 1;
+  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
+    FuncDef *pFunc = pWin->pWFunc;
+    if( (pFunc->zName==nth_valueName)
+     || (pFunc->zName==first_valueName)
+     || (pFunc->zName==leadName)
+     || (pFunc->zName==lagName)
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** regOld and regNew are each the first register in an array of size
+** pOrderBy->nExpr. This function generates code to compare the two
+** arrays of registers using the collation sequences and other comparison
+** parameters specified by pOrderBy.
+**
+** If the two arrays are not equal, the contents of regNew is copied to
+** regOld and control falls through. Otherwise, if the contents of the arrays
+** are equal, an OP_Goto is executed. The address of the OP_Goto is returned.
+*/
+static void windowIfNewPeer(
+  Parse *pParse,
+  ExprList *pOrderBy,
+  int regNew,                     /* First in array of new values */
+  int regOld,                     /* First in array of old values */
+  int addr                        /* Jump here */
+){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( pOrderBy ){
+    int nVal = pOrderBy->nExpr;
+    KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pOrderBy, 0, 0);
+    sqlite3VdbeAddOp3(v, OP_Compare, regOld, regNew, nVal);
+    sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
+    sqlite3VdbeAddOp3(v, OP_Jump,
+      sqlite3VdbeCurrentAddr(v)+1, addr, sqlite3VdbeCurrentAddr(v)+1
+    );
+    VdbeCoverageEqNe(v);
+    sqlite3VdbeAddOp3(v, OP_Copy, regNew, regOld, nVal-1);
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
+  }
+}
+
+/*
+** This function is called as part of generating VM programs for RANGE
+** offset PRECEDING/FOLLOWING frame boundaries. Assuming "ASC" order for
+** the ORDER BY term in the window, and that argument op is OP_Ge, it generates
+** code equivalent to:
+**
+**   if( csr1.peerVal + regVal >= csr2.peerVal ) goto lbl;
+**
+** The value of parameter op may also be OP_Gt or OP_Le. In these cases the
+** operator in the above pseudo-code is replaced with ">" or "<=", respectively.
+**
+** If the sort-order for the ORDER BY term in the window is DESC, then the
+** comparison is reversed. Instead of adding regVal to csr1.peerVal, it is
+** subtracted. And the comparison operator is inverted to - ">=" becomes "<=",
+** ">" becomes "<", and so on. So, with DESC sort order, if the argument op
+** is OP_Ge, the generated code is equivalent to:
+**
+**   if( csr1.peerVal - regVal <= csr2.peerVal ) goto lbl;
+**
+** A special type of arithmetic is used such that if csr1.peerVal is not
+** a numeric type (real or integer), then the result of the addition
+** or subtraction is a a copy of csr1.peerVal.
+*/
+static void windowCodeRangeTest(
+  WindowCodeArg *p,
+  int op,                         /* OP_Ge, OP_Gt, or OP_Le */
+  int csr1,                       /* Cursor number for cursor 1 */
+  int regVal,                     /* Register containing non-negative number */
+  int csr2,                       /* Cursor number for cursor 2 */
+  int lbl                         /* Jump destination if condition is true */
+){
+  Parse *pParse = p->pParse;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  ExprList *pOrderBy = p->pMWin->pOrderBy;  /* ORDER BY clause for window */
+  int reg1 = sqlite3GetTempReg(pParse);     /* Reg. for csr1.peerVal+regVal */
+  int reg2 = sqlite3GetTempReg(pParse);     /* Reg. for csr2.peerVal */
+  int regString = ++pParse->nMem;           /* Reg. for constant value '' */
+  int arith = OP_Add;                       /* OP_Add or OP_Subtract */
+  int addrGe;                               /* Jump destination */
+  int addrDone = sqlite3VdbeMakeLabel(pParse);   /* Address past OP_Ge */
+  CollSeq *pColl;
+
+  /* Read the peer-value from each cursor into a register */
+  windowReadPeerValues(p, csr1, reg1);
+  windowReadPeerValues(p, csr2, reg2);
+
+  assert( op==OP_Ge || op==OP_Gt || op==OP_Le );
+  assert( pOrderBy && pOrderBy->nExpr==1 );
+  if( pOrderBy->a[0].fg.sortFlags & KEYINFO_ORDER_DESC ){
+    switch( op ){
+      case OP_Ge: op = OP_Le; break;
+      case OP_Gt: op = OP_Lt; break;
+      default: assert( op==OP_Le ); op = OP_Ge; break;
+    }
+    arith = OP_Subtract;
+  }
+
+  VdbeModuleComment((v, "CodeRangeTest: if( R%d %s R%d %s R%d ) goto lbl",
+      reg1, (arith==OP_Add ? "+" : "-"), regVal,
+      ((op==OP_Ge) ? ">=" : (op==OP_Le) ? "<=" : (op==OP_Gt) ? ">" : "<"), reg2
+  ));
+
+  /* If the BIGNULL flag is set for the ORDER BY, then it is required to
+  ** consider NULL values to be larger than all other values, instead of
+  ** the usual smaller. The VDBE opcodes OP_Ge and so on do not handle this
+  ** (and adding that capability causes a performance regression), so
+  ** instead if the BIGNULL flag is set then cases where either reg1 or
+  ** reg2 are NULL are handled separately in the following block. The code
+  ** generated is equivalent to:
+  **
+  **   if( reg1 IS NULL ){
+  **     if( op==OP_Ge ) goto lbl;
+  **     if( op==OP_Gt && reg2 IS NOT NULL ) goto lbl;
+  **     if( op==OP_Le && reg2 IS NULL ) goto lbl;
+  **   }else if( reg2 IS NULL ){
+  **     if( op==OP_Le ) goto lbl;
+  **   }
+  **
+  ** Additionally, if either reg1 or reg2 are NULL but the jump to lbl is
+  ** not taken, control jumps over the comparison operator coded below this
+  ** block.  */
+  if( pOrderBy->a[0].fg.sortFlags & KEYINFO_ORDER_BIGNULL ){
+    /* This block runs if reg1 contains a NULL. */
+    int addr = sqlite3VdbeAddOp1(v, OP_NotNull, reg1); VdbeCoverage(v);
+    switch( op ){
+      case OP_Ge:
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, lbl);
+        break;
+      case OP_Gt:
+        sqlite3VdbeAddOp2(v, OP_NotNull, reg2, lbl);
+        VdbeCoverage(v);
+        break;
+      case OP_Le:
+        sqlite3VdbeAddOp2(v, OP_IsNull, reg2, lbl);
+        VdbeCoverage(v);
+        break;
+      default: assert( op==OP_Lt ); /* no-op */ break;
+    }
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrDone);
+
+    /* This block runs if reg1 is not NULL, but reg2 is. */
+    sqlite3VdbeJumpHere(v, addr);
+    sqlite3VdbeAddOp2(v, OP_IsNull, reg2,
+                      (op==OP_Gt || op==OP_Ge) ? addrDone : lbl);
+    VdbeCoverage(v);
+  }
+
+  /* Register reg1 currently contains csr1.peerVal (the peer-value from csr1).
+  ** This block adds (or subtracts for DESC) the numeric value in regVal
+  ** from it. Or, if reg1 is not numeric (it is a NULL, a text value or a blob),
+  ** then leave reg1 as it is. In pseudo-code, this is implemented as:
+  **
+  **   if( reg1>='' ) goto addrGe;
+  **   reg1 = reg1 +/- regVal
+  **   addrGe:
+  **
+  ** Since all strings and blobs are greater-than-or-equal-to an empty string,
+  ** the add/subtract is skipped for these, as required. If reg1 is a NULL,
+  ** then the arithmetic is performed, but since adding or subtracting from
+  ** NULL is always NULL anyway, this case is handled as required too.  */
+  sqlite3VdbeAddOp4(v, OP_String8, 0, regString, 0, "", P4_STATIC);
+  addrGe = sqlite3VdbeAddOp3(v, OP_Ge, regString, 0, reg1);
+  VdbeCoverage(v);
+  if( (op==OP_Ge && arith==OP_Add) || (op==OP_Le && arith==OP_Subtract) ){
+    sqlite3VdbeAddOp3(v, op, reg2, lbl, reg1); VdbeCoverage(v);
+  }
+  sqlite3VdbeAddOp3(v, arith, regVal, reg1, reg1);
+  sqlite3VdbeJumpHere(v, addrGe);
+
+  /* Compare registers reg2 and reg1, taking the jump if required. Note that
+  ** control skips over this test if the BIGNULL flag is set and either
+  ** reg1 or reg2 contain a NULL value.  */
+  sqlite3VdbeAddOp3(v, op, reg2, lbl, reg1); VdbeCoverage(v);
+  pColl = sqlite3ExprNNCollSeq(pParse, pOrderBy->a[0].pExpr);
+  sqlite3VdbeAppendP4(v, (void*)pColl, P4_COLLSEQ);
+  sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
+  sqlite3VdbeResolveLabel(v, addrDone);
+
+  assert( op==OP_Ge || op==OP_Gt || op==OP_Lt || op==OP_Le );
+  testcase(op==OP_Ge); VdbeCoverageIf(v, op==OP_Ge);
+  testcase(op==OP_Lt); VdbeCoverageIf(v, op==OP_Lt);
+  testcase(op==OP_Le); VdbeCoverageIf(v, op==OP_Le);
+  testcase(op==OP_Gt); VdbeCoverageIf(v, op==OP_Gt);
+  sqlite3ReleaseTempReg(pParse, reg1);
+  sqlite3ReleaseTempReg(pParse, reg2);
+
+  VdbeModuleComment((v, "CodeRangeTest: end"));
+}
+
+/*
+** Helper function for sqlite3WindowCodeStep(). Each call to this function
+** generates VM code for a single RETURN_ROW, AGGSTEP or AGGINVERSE
+** operation. Refer to the header comment for sqlite3WindowCodeStep() for
+** details.
+*/
+static int windowCodeOp(
+ WindowCodeArg *p,                /* Context object */
+ int op,                          /* WINDOW_RETURN_ROW, AGGSTEP or AGGINVERSE */
+ int regCountdown,                /* Register for OP_IfPos countdown */
+ int jumpOnEof                    /* Jump here if stepped cursor reaches EOF */
+){
+  int csr, reg;
+  Parse *pParse = p->pParse;
+  Window *pMWin = p->pMWin;
+  int ret = 0;
+  Vdbe *v = p->pVdbe;
+  int addrContinue = 0;
+  int bPeer = (pMWin->eFrmType!=TK_ROWS);
+
+  int lblDone = sqlite3VdbeMakeLabel(pParse);
+  int addrNextRange = 0;
+
+  /* Special case - WINDOW_AGGINVERSE is always a no-op if the frame
+  ** starts with UNBOUNDED PRECEDING. */
+  if( op==WINDOW_AGGINVERSE && pMWin->eStart==TK_UNBOUNDED ){
+    assert( regCountdown==0 && jumpOnEof==0 );
+    return 0;
+  }
+
+  if( regCountdown>0 ){
+    if( pMWin->eFrmType==TK_RANGE ){
+      addrNextRange = sqlite3VdbeCurrentAddr(v);
+      assert( op==WINDOW_AGGINVERSE || op==WINDOW_AGGSTEP );
+      if( op==WINDOW_AGGINVERSE ){
+        if( pMWin->eStart==TK_FOLLOWING ){
+          windowCodeRangeTest(
+              p, OP_Le, p->current.csr, regCountdown, p->start.csr, lblDone
+          );
+        }else{
+          windowCodeRangeTest(
+              p, OP_Ge, p->start.csr, regCountdown, p->current.csr, lblDone
+          );
+        }
+      }else{
+        windowCodeRangeTest(
+            p, OP_Gt, p->end.csr, regCountdown, p->current.csr, lblDone
+        );
+      }
+    }else{
+      sqlite3VdbeAddOp3(v, OP_IfPos, regCountdown, lblDone, 1);
+      VdbeCoverage(v);
+    }
+  }
+
+  if( op==WINDOW_RETURN_ROW && pMWin->regStartRowid==0 ){
+    windowAggFinal(p, 0);
+  }
+  addrContinue = sqlite3VdbeCurrentAddr(v);
+
+  /* If this is a (RANGE BETWEEN a FOLLOWING AND b FOLLOWING) or
+  ** (RANGE BETWEEN b PRECEDING AND a PRECEDING) frame, ensure the
+  ** start cursor does not advance past the end cursor within the
+  ** temporary table. It otherwise might, if (a>b). Also ensure that,
+  ** if the input cursor is still finding new rows, that the end
+  ** cursor does not go past it to EOF. */
+  if( pMWin->eStart==pMWin->eEnd && regCountdown
+   && pMWin->eFrmType==TK_RANGE
+  ){
+    int regRowid1 = sqlite3GetTempReg(pParse);
+    int regRowid2 = sqlite3GetTempReg(pParse);
+    if( op==WINDOW_AGGINVERSE ){
+      sqlite3VdbeAddOp2(v, OP_Rowid, p->start.csr, regRowid1);
+      sqlite3VdbeAddOp2(v, OP_Rowid, p->end.csr, regRowid2);
+      sqlite3VdbeAddOp3(v, OP_Ge, regRowid2, lblDone, regRowid1);
+      VdbeCoverage(v);
+    }else if( p->regRowid ){
+      sqlite3VdbeAddOp2(v, OP_Rowid, p->end.csr, regRowid1);
+      sqlite3VdbeAddOp3(v, OP_Ge, p->regRowid, lblDone, regRowid1);
+      VdbeCoverageNeverNull(v);
+    }
+    sqlite3ReleaseTempReg(pParse, regRowid1);
+    sqlite3ReleaseTempReg(pParse, regRowid2);
+    assert( pMWin->eStart==TK_PRECEDING || pMWin->eStart==TK_FOLLOWING );
+  }
+
+  switch( op ){
+    case WINDOW_RETURN_ROW:
+      csr = p->current.csr;
+      reg = p->current.reg;
+      windowReturnOneRow(p);
+      break;
+
+    case WINDOW_AGGINVERSE:
+      csr = p->start.csr;
+      reg = p->start.reg;
+      if( pMWin->regStartRowid ){
+        assert( pMWin->regEndRowid );
+        sqlite3VdbeAddOp2(v, OP_AddImm, pMWin->regStartRowid, 1);
+      }else{
+        windowAggStep(p, pMWin, csr, 1, p->regArg);
+      }
+      break;
+
+    default:
+      assert( op==WINDOW_AGGSTEP );
+      csr = p->end.csr;
+      reg = p->end.reg;
+      if( pMWin->regStartRowid ){
+        assert( pMWin->regEndRowid );
+        sqlite3VdbeAddOp2(v, OP_AddImm, pMWin->regEndRowid, 1);
+      }else{
+        windowAggStep(p, pMWin, csr, 0, p->regArg);
+      }
+      break;
+  }
+
+  if( op==p->eDelete ){
+    sqlite3VdbeAddOp1(v, OP_Delete, csr);
+    sqlite3VdbeChangeP5(v, OPFLAG_SAVEPOSITION);
+  }
+
+  if( jumpOnEof ){
+    sqlite3VdbeAddOp2(v, OP_Next, csr, sqlite3VdbeCurrentAddr(v)+2);
+    VdbeCoverage(v);
+    ret = sqlite3VdbeAddOp0(v, OP_Goto);
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Next, csr, sqlite3VdbeCurrentAddr(v)+1+bPeer);
+    VdbeCoverage(v);
+    if( bPeer ){
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, lblDone);
+    }
+  }
+
+  if( bPeer ){
+    int nReg = (pMWin->pOrderBy ? pMWin->pOrderBy->nExpr : 0);
+    int regTmp = (nReg ? sqlite3GetTempRange(pParse, nReg) : 0);
+    windowReadPeerValues(p, csr, regTmp);
+    windowIfNewPeer(pParse, pMWin->pOrderBy, regTmp, reg, addrContinue);
+    sqlite3ReleaseTempRange(pParse, regTmp, nReg);
+  }
+
+  if( addrNextRange ){
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrNextRange);
+  }
+  sqlite3VdbeResolveLabel(v, lblDone);
+  return ret;
+}
+
+
+/*
+** Allocate and return a duplicate of the Window object indicated by the
+** third argument. Set the Window.pOwner field of the new object to
+** pOwner.
+*/
+Window *sqlite3WindowDup(sqlite3 *db, Expr *pOwner, Window *p){
+  Window *pNew = 0;
+  if( ALWAYS(p) ){
+    pNew = sqlite3DbMallocZero(db, sizeof(Window));
+    if( pNew ){
+      pNew->zName = sqlite3DbStrDup(db, p->zName);
+      pNew->zBase = sqlite3DbStrDup(db, p->zBase);
+      pNew->pFilter = sqlite3ExprDup(db, p->pFilter, 0);
+      pNew->pWFunc = p->pWFunc;
+      pNew->pPartition = sqlite3ExprListDup(db, p->pPartition, 0);
+      pNew->pOrderBy = sqlite3ExprListDup(db, p->pOrderBy, 0);
+      pNew->eFrmType = p->eFrmType;
+      pNew->eEnd = p->eEnd;
+      pNew->eStart = p->eStart;
+      pNew->eExclude = p->eExclude;
+      pNew->regResult = p->regResult;
+      pNew->regAccum = p->regAccum;
+      pNew->iArgCol = p->iArgCol;
+      pNew->iEphCsr = p->iEphCsr;
+      pNew->bExprArgs = p->bExprArgs;
+      pNew->pStart = sqlite3ExprDup(db, p->pStart, 0);
+      pNew->pEnd = sqlite3ExprDup(db, p->pEnd, 0);
+      pNew->pOwner = pOwner;
+      pNew->bImplicitFrame = p->bImplicitFrame;
+    }
+  }
+  return pNew;
+}
+
+/*
+** Return a copy of the linked list of Window objects passed as the
+** second argument.
+*/
+Window *sqlite3WindowListDup(sqlite3 *db, Window *p){
+  Window *pWin;
+  Window *pRet = 0;
+  Window **pp = &pRet;
+
+  for(pWin=p; pWin; pWin=pWin->pNextWin){
+    *pp = sqlite3WindowDup(db, 0, pWin);
+    if( *pp==0 ) break;
+    pp = &((*pp)->pNextWin);
+  }
+
+  return pRet;
+}
+
+/*
+** Return true if it can be determined at compile time that expression
+** pExpr evaluates to a value that, when cast to an integer, is greater
+** than zero. False otherwise.
+**
+** If an OOM error occurs, this function sets the Parse.db.mallocFailed
+** flag and returns zero.
+*/
+static int windowExprGtZero(Parse *pParse, Expr *pExpr){
+  int ret = 0;
+  sqlite3 *db = pParse->db;
+  sqlite3_value *pVal = 0;
+  sqlite3ValueFromExpr(db, pExpr, db->enc, SQLITE_AFF_NUMERIC, &pVal);
+  if( pVal && sqlite3_value_int(pVal)>0 ){
+    ret = 1;
+  }
+  sqlite3ValueFree(pVal);
+  return ret;
+}
+
+/*
+** sqlite3WhereBegin() has already been called for the SELECT statement
+** passed as the second argument when this function is invoked. It generates
+** code to populate the Window.regResult register for each window function
+** and invoke the sub-routine at instruction addrGosub once for each row.
+** sqlite3WhereEnd() is always called before returning.
+**
+** This function handles several different types of window frames, which
+** require slightly different processing. The following pseudo code is
+** used to implement window frames of the form:
+**
+**   ROWS BETWEEN <expr1> PRECEDING AND <expr2> FOLLOWING
+**
+** Other window frame types use variants of the following:
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**       if( new partition ){
+**         Gosub flush
+**       }
+**       Insert new row into eph table.
+**      
+**       if( first row of partition ){
+**         // Rewind three cursors, all open on the eph table.
+**         Rewind(csrEnd);
+**         Rewind(csrStart);
+**         Rewind(csrCurrent);
+**      
+**         regEnd = <expr2>          // FOLLOWING expression
+**         regStart = <expr1>        // PRECEDING expression
+**       }else{
+**         // First time this branch is taken, the eph table contains two
+**         // rows. The first row in the partition, which all three cursors
+**         // currently point to, and the following row.
+**         AGGSTEP
+**         if( (regEnd--)<=0 ){
+**           RETURN_ROW
+**           if( (regStart--)<=0 ){
+**             AGGINVERSE
+**           }
+**         }
+**       }
+**     }
+**     flush:
+**       AGGSTEP
+**       while( 1 ){
+**         RETURN ROW
+**         if( csrCurrent is EOF ) break;
+**         if( (regStart--)<=0 ){
+**           AggInverse(csrStart)
+**           Next(csrStart)
+**         }
+**       }
+**
+** The pseudo-code above uses the following shorthand:
+**
+**   AGGSTEP:    invoke the aggregate xStep() function for each window function
+**               with arguments read from the current row of cursor csrEnd, then
+**               step cursor csrEnd forward one row (i.e. sqlite3BtreeNext()).
+**
+**   RETURN_ROW: return a row to the caller based on the contents of the
+**               current row of csrCurrent and the current state of all
+**               aggregates. Then step cursor csrCurrent forward one row.
+**
+**   AGGINVERSE: invoke the aggregate xInverse() function for each window
+**               functions with arguments read from the current row of cursor
+**               csrStart. Then step csrStart forward one row.
+**
+** There are two other ROWS window frames that are handled significantly
+** differently from the above - "BETWEEN <expr> PRECEDING AND <expr> PRECEDING"
+** and "BETWEEN <expr> FOLLOWING AND <expr> FOLLOWING". These are special
+** cases because they change the order in which the three cursors (csrStart,
+** csrCurrent and csrEnd) iterate through the ephemeral table. Cases that
+** use UNBOUNDED or CURRENT ROW are much simpler variations on one of these
+** three.
+**
+**   ROWS BETWEEN <expr1> PRECEDING AND <expr2> PRECEDING
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**       if( new partition ){
+**         Gosub flush
+**       }
+**       Insert new row into eph table.
+**       if( first row of partition ){
+**         Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**         regEnd = <expr2>
+**         regStart = <expr1>
+**       }else{
+**         if( (regEnd--)<=0 ){
+**           AGGSTEP
+**         }
+**         RETURN_ROW
+**         if( (regStart--)<=0 ){
+**           AGGINVERSE
+**         }
+**       }
+**     }
+**     flush:
+**       if( (regEnd--)<=0 ){
+**         AGGSTEP
+**       }
+**       RETURN_ROW
+**
+**
+**   ROWS BETWEEN <expr1> FOLLOWING AND <expr2> FOLLOWING
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**     if( new partition ){
+**       Gosub flush
+**     }
+**     Insert new row into eph table.
+**     if( first row of partition ){
+**       Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**       regEnd = <expr2>
+**       regStart = regEnd - <expr1>
+**     }else{
+**       AGGSTEP
+**       if( (regEnd--)<=0 ){
+**         RETURN_ROW
+**       }
+**       if( (regStart--)<=0 ){
+**         AGGINVERSE
+**       }
+**     }
+**   }
+**   flush:
+**     AGGSTEP
+**     while( 1 ){
+**       if( (regEnd--)<=0 ){
+**         RETURN_ROW
+**         if( eof ) break;
+**       }
+**       if( (regStart--)<=0 ){
+**         AGGINVERSE
+**         if( eof ) break
+**       }
+**     }
+**     while( !eof csrCurrent ){
+**       RETURN_ROW
+**     }
+**
+** For the most part, the patterns above are adapted to support UNBOUNDED by
+** assuming that it is equivalent to "infinity PRECEDING/FOLLOWING" and
+** CURRENT ROW by assuming that it is equivalent to "0 PRECEDING/FOLLOWING".
+** This is optimized of course - branches that will never be taken and
+** conditions that are always true are omitted from the VM code. The only
+** exceptional case is:
+**
+**   ROWS BETWEEN <expr1> FOLLOWING AND UNBOUNDED FOLLOWING
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**     if( new partition ){
+**       Gosub flush
+**     }
+**     Insert new row into eph table.
+**     if( first row of partition ){
+**       Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**       regStart = <expr1>
+**     }else{
+**       AGGSTEP
+**     }
+**   }
+**   flush:
+**     AGGSTEP
+**     while( 1 ){
+**       if( (regStart--)<=0 ){
+**         AGGINVERSE
+**         if( eof ) break
+**       }
+**       RETURN_ROW
+**     }
+**     while( !eof csrCurrent ){
+**       RETURN_ROW
+**     }
+**
+** Also requiring special handling are the cases:
+**
+**   ROWS BETWEEN <expr1> PRECEDING AND <expr2> PRECEDING
+**   ROWS BETWEEN <expr1> FOLLOWING AND <expr2> FOLLOWING
+**
+** when (expr1 < expr2). This is detected at runtime, not by this function.
+** To handle this case, the pseudo-code programs depicted above are modified
+** slightly to be:
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**     if( new partition ){
+**       Gosub flush
+**     }
+**     Insert new row into eph table.
+**     if( first row of partition ){
+**       Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**       regEnd = <expr2>
+**       regStart = <expr1>
+**       if( regEnd < regStart ){
+**         RETURN_ROW
+**         delete eph table contents
+**         continue
+**       }
+**     ...
+**
+** The new "continue" statement in the above jumps to the next iteration
+** of the outer loop - the one started by sqlite3WhereBegin().
+**
+** The various GROUPS cases are implemented using the same patterns as
+** ROWS. The VM code is modified slightly so that:
+**
+**   1. The else branch in the main loop is only taken if the row just
+**      added to the ephemeral table is the start of a new group. In
+**      other words, it becomes:
+**
+**         ... loop started by sqlite3WhereBegin() ...
+**         if( new partition ){
+**           Gosub flush
+**         }
+**         Insert new row into eph table.
+**         if( first row of partition ){
+**           Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**           regEnd = <expr2>
+**           regStart = <expr1>
+**         }else if( new group ){
+**           ...
+**         }
+**       }
+**
+**   2. Instead of processing a single row, each RETURN_ROW, AGGSTEP or
+**      AGGINVERSE step processes the current row of the relevant cursor and
+**      all subsequent rows belonging to the same group.
+**
+** RANGE window frames are a little different again. As for GROUPS, the
+** main loop runs once per group only. And RETURN_ROW, AGGSTEP and AGGINVERSE
+** deal in groups instead of rows. As for ROWS and GROUPS, there are three
+** basic cases:
+**
+**   RANGE BETWEEN <expr1> PRECEDING AND <expr2> FOLLOWING
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**       if( new partition ){
+**         Gosub flush
+**       }
+**       Insert new row into eph table.
+**       if( first row of partition ){
+**         Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**         regEnd = <expr2>
+**         regStart = <expr1>
+**       }else{
+**         AGGSTEP
+**         while( (csrCurrent.key + regEnd) < csrEnd.key ){
+**           RETURN_ROW
+**           while( csrStart.key + regStart) < csrCurrent.key ){
+**             AGGINVERSE
+**           }
+**         }
+**       }
+**     }
+**     flush:
+**       AGGSTEP
+**       while( 1 ){
+**         RETURN ROW
+**         if( csrCurrent is EOF ) break;
+**           while( csrStart.key + regStart) < csrCurrent.key ){
+**             AGGINVERSE
+**           }
+**         }
+**       }
+**
+** In the above notation, "csr.key" means the current value of the ORDER BY
+** expression (there is only ever 1 for a RANGE that uses an <expr> FOLLOWING
+** or <expr PRECEDING) read from cursor csr.
+**
+**   RANGE BETWEEN <expr1> PRECEDING AND <expr2> PRECEDING
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**       if( new partition ){
+**         Gosub flush
+**       }
+**       Insert new row into eph table.
+**       if( first row of partition ){
+**         Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**         regEnd = <expr2>
+**         regStart = <expr1>
+**       }else{
+**         while( (csrEnd.key + regEnd) <= csrCurrent.key ){
+**           AGGSTEP
+**         }
+**         while( (csrStart.key + regStart) < csrCurrent.key ){
+**           AGGINVERSE
+**         }
+**         RETURN_ROW
+**       }
+**     }
+**     flush:
+**       while( (csrEnd.key + regEnd) <= csrCurrent.key ){
+**         AGGSTEP
+**       }
+**       while( (csrStart.key + regStart) < csrCurrent.key ){
+**         AGGINVERSE
+**       }
+**       RETURN_ROW
+**
+**   RANGE BETWEEN <expr1> FOLLOWING AND <expr2> FOLLOWING
+**
+**     ... loop started by sqlite3WhereBegin() ...
+**       if( new partition ){
+**         Gosub flush
+**       }
+**       Insert new row into eph table.
+**       if( first row of partition ){
+**         Rewind(csrEnd) ; Rewind(csrStart) ; Rewind(csrCurrent)
+**         regEnd = <expr2>
+**         regStart = <expr1>
+**       }else{
+**         AGGSTEP
+**         while( (csrCurrent.key + regEnd) < csrEnd.key ){
+**           while( (csrCurrent.key + regStart) > csrStart.key ){
+**             AGGINVERSE
+**           }
+**           RETURN_ROW
+**         }
+**       }
+**     }
+**     flush:
+**       AGGSTEP
+**       while( 1 ){
+**         while( (csrCurrent.key + regStart) > csrStart.key ){
+**           AGGINVERSE
+**           if( eof ) break "while( 1 )" loop.
+**         }
+**         RETURN_ROW
+**       }
+**       while( !eof csrCurrent ){
+**         RETURN_ROW
+**       }
+**
+** The text above leaves out many details. Refer to the code and comments
+** below for a more complete picture.
+*/
+void sqlite3WindowCodeStep(
+  Parse *pParse,                  /* Parse context */
+  Select *p,                      /* Rewritten SELECT statement */
+  WhereInfo *pWInfo,              /* Context returned by sqlite3WhereBegin() */
+  int regGosub,                   /* Register for OP_Gosub */
+  int addrGosub                   /* OP_Gosub here to return each row */
+){
+  Window *pMWin = p->pWin;
+  ExprList *pOrderBy = pMWin->pOrderBy;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int csrWrite;                   /* Cursor used to write to eph. table */
+  int csrInput = p->pSrc->a[0].iCursor;     /* Cursor of sub-select */
+  int nInput = p->pSrc->a[0].pTab->nCol;    /* Number of cols returned by sub */
+  int iInput;                               /* To iterate through sub cols */
+  int addrNe;                     /* Address of OP_Ne */
+  int addrGosubFlush = 0;         /* Address of OP_Gosub to flush: */
+  int addrInteger = 0;            /* Address of OP_Integer */
+  int addrEmpty;                  /* Address of OP_Rewind in flush: */
+  int regNew;                     /* Array of registers holding new input row */
+  int regRecord;                  /* regNew array in record form */
+  int regNewPeer = 0;             /* Peer values for new row (part of regNew) */
+  int regPeer = 0;                /* Peer values for current row */
+  int regFlushPart = 0;           /* Register for "Gosub flush_partition" */
+  WindowCodeArg s;                /* Context object for sub-routines */
+  int lblWhereEnd;                /* Label just before sqlite3WhereEnd() code */
+  int regStart = 0;               /* Value of <expr> PRECEDING */
+  int regEnd = 0;                 /* Value of <expr> FOLLOWING */
+
+  assert( pMWin->eStart==TK_PRECEDING || pMWin->eStart==TK_CURRENT
+       || pMWin->eStart==TK_FOLLOWING || pMWin->eStart==TK_UNBOUNDED
+  );
+  assert( pMWin->eEnd==TK_FOLLOWING || pMWin->eEnd==TK_CURRENT
+       || pMWin->eEnd==TK_UNBOUNDED || pMWin->eEnd==TK_PRECEDING
+  );
+  assert( pMWin->eExclude==0 || pMWin->eExclude==TK_CURRENT
+       || pMWin->eExclude==TK_GROUP || pMWin->eExclude==TK_TIES
+       || pMWin->eExclude==TK_NO
+  );
+
+  lblWhereEnd = sqlite3VdbeMakeLabel(pParse);
+
+  /* Fill in the context object */
+  memset(&s, 0, sizeof(WindowCodeArg));
+  s.pParse = pParse;
+  s.pMWin = pMWin;
+  s.pVdbe = v;
+  s.regGosub = regGosub;
+  s.addrGosub = addrGosub;
+  s.current.csr = pMWin->iEphCsr;
+  csrWrite = s.current.csr+1;
+  s.start.csr = s.current.csr+2;
+  s.end.csr = s.current.csr+3;
+
+  /* Figure out when rows may be deleted from the ephemeral table. There
+  ** are four options - they may never be deleted (eDelete==0), they may
+  ** be deleted as soon as they are no longer part of the window frame
+  ** (eDelete==WINDOW_AGGINVERSE), they may be deleted as after the row
+  ** has been returned to the caller (WINDOW_RETURN_ROW), or they may
+  ** be deleted after they enter the frame (WINDOW_AGGSTEP). */
+  switch( pMWin->eStart ){
+    case TK_FOLLOWING:
+      if( pMWin->eFrmType!=TK_RANGE
+       && windowExprGtZero(pParse, pMWin->pStart)
+      ){
+        s.eDelete = WINDOW_RETURN_ROW;
+      }
+      break;
+    case TK_UNBOUNDED:
+      if( windowCacheFrame(pMWin)==0 ){
+        if( pMWin->eEnd==TK_PRECEDING ){
+          if( pMWin->eFrmType!=TK_RANGE
+           && windowExprGtZero(pParse, pMWin->pEnd)
+          ){
+            s.eDelete = WINDOW_AGGSTEP;
+          }
+        }else{
+          s.eDelete = WINDOW_RETURN_ROW;
+        }
+      }
+      break;
+    default:
+      s.eDelete = WINDOW_AGGINVERSE;
+      break;
+  }
+
+  /* Allocate registers for the array of values from the sub-query, the
+  ** same values in record form, and the rowid used to insert said record
+  ** into the ephemeral table.  */
+  regNew = pParse->nMem+1;
+  pParse->nMem += nInput;
+  regRecord = ++pParse->nMem;
+  s.regRowid = ++pParse->nMem;
+
+  /* If the window frame contains an "<expr> PRECEDING" or "<expr> FOLLOWING"
+  ** clause, allocate registers to store the results of evaluating each
+  ** <expr>.  */
+  if( pMWin->eStart==TK_PRECEDING || pMWin->eStart==TK_FOLLOWING ){
+    regStart = ++pParse->nMem;
+  }
+  if( pMWin->eEnd==TK_PRECEDING || pMWin->eEnd==TK_FOLLOWING ){
+    regEnd = ++pParse->nMem;
+  }
+
+  /* If this is not a "ROWS BETWEEN ..." frame, then allocate arrays of
+  ** registers to store copies of the ORDER BY expressions (peer values)
+  ** for the main loop, and for each cursor (start, current and end). */
+  if( pMWin->eFrmType!=TK_ROWS ){
+    int nPeer = (pOrderBy ? pOrderBy->nExpr : 0);
+    regNewPeer = regNew + pMWin->nBufferCol;
+    if( pMWin->pPartition ) regNewPeer += pMWin->pPartition->nExpr;
+    regPeer = pParse->nMem+1;       pParse->nMem += nPeer;
+    s.start.reg = pParse->nMem+1;   pParse->nMem += nPeer;
+    s.current.reg = pParse->nMem+1; pParse->nMem += nPeer;
+    s.end.reg = pParse->nMem+1;     pParse->nMem += nPeer;
+  }
+
+  /* Load the column values for the row returned by the sub-select
+  ** into an array of registers starting at regNew. Assemble them into
+  ** a record in register regRecord. */
+  for(iInput=0; iInput<nInput; iInput++){
+    sqlite3VdbeAddOp3(v, OP_Column, csrInput, iInput, regNew+iInput);
+  }
+  sqlite3VdbeAddOp3(v, OP_MakeRecord, regNew, nInput, regRecord);
+
+  /* An input row has just been read into an array of registers starting
+  ** at regNew. If the window has a PARTITION clause, this block generates
+  ** VM code to check if the input row is the start of a new partition.
+  ** If so, it does an OP_Gosub to an address to be filled in later. The
+  ** address of the OP_Gosub is stored in local variable addrGosubFlush. */
+  if( pMWin->pPartition ){
+    int addr;
+    ExprList *pPart = pMWin->pPartition;
+    int nPart = pPart->nExpr;
+    int regNewPart = regNew + pMWin->nBufferCol;
+    KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pPart, 0, 0);
+
+    regFlushPart = ++pParse->nMem;
+    addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPart, pMWin->regPart, nPart);
+    sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
+    sqlite3VdbeAddOp3(v, OP_Jump, addr+2, addr+4, addr+2);
+    VdbeCoverageEqNe(v);
+    addrGosubFlush = sqlite3VdbeAddOp1(v, OP_Gosub, regFlushPart);
+    VdbeComment((v, "call flush_partition"));
+    sqlite3VdbeAddOp3(v, OP_Copy, regNewPart, pMWin->regPart, nPart-1);
+  }
+
+  /* Insert the new row into the ephemeral table */
+  sqlite3VdbeAddOp2(v, OP_NewRowid, csrWrite, s.regRowid);
+  sqlite3VdbeAddOp3(v, OP_Insert, csrWrite, regRecord, s.regRowid);
+  addrNe = sqlite3VdbeAddOp3(v, OP_Ne, pMWin->regOne, 0, s.regRowid);
+  VdbeCoverageNeverNull(v);
+
+  /* This block is run for the first row of each partition */
+  s.regArg = windowInitAccum(pParse, pMWin);
+
+  if( regStart ){
+    sqlite3ExprCode(pParse, pMWin->pStart, regStart);
+    windowCheckValue(pParse, regStart, 0 + (pMWin->eFrmType==TK_RANGE?3:0));
+  }
+  if( regEnd ){
+    sqlite3ExprCode(pParse, pMWin->pEnd, regEnd);
+    windowCheckValue(pParse, regEnd, 1 + (pMWin->eFrmType==TK_RANGE?3:0));
+  }
+
+  if( pMWin->eFrmType!=TK_RANGE && pMWin->eStart==pMWin->eEnd && regStart ){
+    int op = ((pMWin->eStart==TK_FOLLOWING) ? OP_Ge : OP_Le);
+    int addrGe = sqlite3VdbeAddOp3(v, op, regStart, 0, regEnd);
+    VdbeCoverageNeverNullIf(v, op==OP_Ge); /* NeverNull because bound <expr> */
+    VdbeCoverageNeverNullIf(v, op==OP_Le); /*   values previously checked */
+    windowAggFinal(&s, 0);
+    sqlite3VdbeAddOp1(v, OP_Rewind, s.current.csr);
+    windowReturnOneRow(&s);
+    sqlite3VdbeAddOp1(v, OP_ResetSorter, s.current.csr);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, lblWhereEnd);
+    sqlite3VdbeJumpHere(v, addrGe);
+  }
+  if( pMWin->eStart==TK_FOLLOWING && pMWin->eFrmType!=TK_RANGE && regEnd ){
+    assert( pMWin->eEnd==TK_FOLLOWING );
+    sqlite3VdbeAddOp3(v, OP_Subtract, regStart, regEnd, regStart);
+  }
+
+  if( pMWin->eStart!=TK_UNBOUNDED ){
+    sqlite3VdbeAddOp1(v, OP_Rewind, s.start.csr);
+  }
+  sqlite3VdbeAddOp1(v, OP_Rewind, s.current.csr);
+  sqlite3VdbeAddOp1(v, OP_Rewind, s.end.csr);
+  if( regPeer && pOrderBy ){
+    sqlite3VdbeAddOp3(v, OP_Copy, regNewPeer, regPeer, pOrderBy->nExpr-1);
+    sqlite3VdbeAddOp3(v, OP_Copy, regPeer, s.start.reg, pOrderBy->nExpr-1);
+    sqlite3VdbeAddOp3(v, OP_Copy, regPeer, s.current.reg, pOrderBy->nExpr-1);
+    sqlite3VdbeAddOp3(v, OP_Copy, regPeer, s.end.reg, pOrderBy->nExpr-1);
+  }
+
+  sqlite3VdbeAddOp2(v, OP_Goto, 0, lblWhereEnd);
+
+  sqlite3VdbeJumpHere(v, addrNe);
+
+  /* Beginning of the block executed for the second and subsequent rows. */
+  if( regPeer ){
+    windowIfNewPeer(pParse, pOrderBy, regNewPeer, regPeer, lblWhereEnd);
+  }
+  if( pMWin->eStart==TK_FOLLOWING ){
+    windowCodeOp(&s, WINDOW_AGGSTEP, 0, 0);
+    if( pMWin->eEnd!=TK_UNBOUNDED ){
+      if( pMWin->eFrmType==TK_RANGE ){
+        int lbl = sqlite3VdbeMakeLabel(pParse);
+        int addrNext = sqlite3VdbeCurrentAddr(v);
+        windowCodeRangeTest(&s, OP_Ge, s.current.csr, regEnd, s.end.csr, lbl);
+        windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+        windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 0);
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, addrNext);
+        sqlite3VdbeResolveLabel(v, lbl);
+      }else{
+        windowCodeOp(&s, WINDOW_RETURN_ROW, regEnd, 0);
+        windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+      }
+    }
+  }else
+  if( pMWin->eEnd==TK_PRECEDING ){
+    int bRPS = (pMWin->eStart==TK_PRECEDING && pMWin->eFrmType==TK_RANGE);
+    windowCodeOp(&s, WINDOW_AGGSTEP, regEnd, 0);
+    if( bRPS ) windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+    windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 0);
+    if( !bRPS ) windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+  }else{
+    int addr = 0;
+    windowCodeOp(&s, WINDOW_AGGSTEP, 0, 0);
+    if( pMWin->eEnd!=TK_UNBOUNDED ){
+      if( pMWin->eFrmType==TK_RANGE ){
+        int lbl = 0;
+        addr = sqlite3VdbeCurrentAddr(v);
+        if( regEnd ){
+          lbl = sqlite3VdbeMakeLabel(pParse);
+          windowCodeRangeTest(&s, OP_Ge, s.current.csr, regEnd, s.end.csr, lbl);
+        }
+        windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 0);
+        windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+        if( regEnd ){
+          sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
+          sqlite3VdbeResolveLabel(v, lbl);
+        }
+      }else{
+        if( regEnd ){
+          addr = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0, 1);
+          VdbeCoverage(v);
+        }
+        windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 0);
+        windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+        if( regEnd ) sqlite3VdbeJumpHere(v, addr);
+      }
+    }
+  }
+
+  /* End of the main input loop */
+  sqlite3VdbeResolveLabel(v, lblWhereEnd);
+  sqlite3WhereEnd(pWInfo);
+
+  /* Fall through */
+  if( pMWin->pPartition ){
+    addrInteger = sqlite3VdbeAddOp2(v, OP_Integer, 0, regFlushPart);
+    sqlite3VdbeJumpHere(v, addrGosubFlush);
+  }
+
+  s.regRowid = 0;
+  addrEmpty = sqlite3VdbeAddOp1(v, OP_Rewind, csrWrite);
+  VdbeCoverage(v);
+  if( pMWin->eEnd==TK_PRECEDING ){
+    int bRPS = (pMWin->eStart==TK_PRECEDING && pMWin->eFrmType==TK_RANGE);
+    windowCodeOp(&s, WINDOW_AGGSTEP, regEnd, 0);
+    if( bRPS ) windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+    windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 0);
+  }else if( pMWin->eStart==TK_FOLLOWING ){
+    int addrStart;
+    int addrBreak1;
+    int addrBreak2;
+    int addrBreak3;
+    windowCodeOp(&s, WINDOW_AGGSTEP, 0, 0);
+    if( pMWin->eFrmType==TK_RANGE ){
+      addrStart = sqlite3VdbeCurrentAddr(v);
+      addrBreak2 = windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 1);
+      addrBreak1 = windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 1);
+    }else
+    if( pMWin->eEnd==TK_UNBOUNDED ){
+      addrStart = sqlite3VdbeCurrentAddr(v);
+      addrBreak1 = windowCodeOp(&s, WINDOW_RETURN_ROW, regStart, 1);
+      addrBreak2 = windowCodeOp(&s, WINDOW_AGGINVERSE, 0, 1);
+    }else{
+      assert( pMWin->eEnd==TK_FOLLOWING );
+      addrStart = sqlite3VdbeCurrentAddr(v);
+      addrBreak1 = windowCodeOp(&s, WINDOW_RETURN_ROW, regEnd, 1);
+      addrBreak2 = windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 1);
+    }
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrStart);
+    sqlite3VdbeJumpHere(v, addrBreak2);
+    addrStart = sqlite3VdbeCurrentAddr(v);
+    addrBreak3 = windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 1);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrStart);
+    sqlite3VdbeJumpHere(v, addrBreak1);
+    sqlite3VdbeJumpHere(v, addrBreak3);
+  }else{
+    int addrBreak;
+    int addrStart;
+    windowCodeOp(&s, WINDOW_AGGSTEP, 0, 0);
+    addrStart = sqlite3VdbeCurrentAddr(v);
+    addrBreak = windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 1);
+    windowCodeOp(&s, WINDOW_AGGINVERSE, regStart, 0);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrStart);
+    sqlite3VdbeJumpHere(v, addrBreak);
+  }
+  sqlite3VdbeJumpHere(v, addrEmpty);
+
+  sqlite3VdbeAddOp1(v, OP_ResetSorter, s.current.csr);
+  if( pMWin->pPartition ){
+    if( pMWin->regStartRowid ){
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, pMWin->regStartRowid);
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, pMWin->regEndRowid);
+    }
+    sqlite3VdbeChangeP1(v, addrInteger, sqlite3VdbeCurrentAddr(v));
+    sqlite3VdbeAddOp1(v, OP_Return, regFlushPart);
+  }
+}
+
+#endif /* SQLITE_OMIT_WINDOWFUNC */