Adding upstream version 3.40.1.upstream/3.40.1upstream

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

1 files changed, 322 insertions, 0 deletions

diff --git a/ext/misc/explain.c b/ext/misc/explain.c
new file mode 100644
index 0000000..0095194
--- /dev/null
+++ b/ext/misc/explain.c
@@ -0,0 +1,322 @@
+/*
+** 2018-09-16
+**
+** 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 demonstrates an eponymous virtual table that returns the
+** EXPLAIN output from an SQL statement.
+**
+** Usage example:
+**
+**     .load ./explain
+**     SELECT p2 FROM explain('SELECT * FROM sqlite_schema')
+**      WHERE opcode='OpenRead';
+**
+** This module was originally written to help simplify SQLite testing,
+** by providing an easier means of verifying certain patterns in the
+** generated bytecode.
+*/
+#if !defined(SQLITEINT_H)
+#include "sqlite3ext.h"
+#endif
+SQLITE_EXTENSION_INIT1
+#include <assert.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/* explain_vtab is a subclass of sqlite3_vtab which will
+** serve as the underlying representation of a explain virtual table
+*/
+typedef struct explain_vtab explain_vtab;
+struct explain_vtab {
+  sqlite3_vtab base;  /* Base class - must be first */
+  sqlite3 *db;        /* Database connection for this explain vtab */
+};
+
+/* explain_cursor is a subclass of sqlite3_vtab_cursor which will
+** serve as the underlying representation of a cursor that scans
+** over rows of the result from an EXPLAIN operation.
+*/
+typedef struct explain_cursor explain_cursor;
+struct explain_cursor {
+  sqlite3_vtab_cursor base;  /* Base class - must be first */
+  sqlite3 *db;               /* Database connection for this cursor */
+  char *zSql;                /* Value for the EXPLN_COLUMN_SQL column */
+  sqlite3_stmt *pExplain;    /* Statement being explained */
+  int rc;                    /* Result of last sqlite3_step() on pExplain */
+};
+
+/*
+** The explainConnect() method is invoked to create a new
+** explain_vtab that describes the explain virtual table.
+**
+** Think of this routine as the constructor for explain_vtab objects.
+**
+** All this routine needs to do is:
+**
+**    (1) Allocate the explain_vtab object and initialize all fields.
+**
+**    (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
+**        result set of queries against explain will look like.
+*/
+static int explainConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  explain_vtab *pNew;
+  int rc;
+
+/* Column numbers */
+#define EXPLN_COLUMN_ADDR     0   /* Instruction address */
+#define EXPLN_COLUMN_OPCODE   1   /* Opcode */
+#define EXPLN_COLUMN_P1       2   /* Operand 1 */
+#define EXPLN_COLUMN_P2       3   /* Operand 2 */
+#define EXPLN_COLUMN_P3       4   /* Operand 3 */
+#define EXPLN_COLUMN_P4       5   /* Operand 4 */
+#define EXPLN_COLUMN_P5       6   /* Operand 5 */
+#define EXPLN_COLUMN_COMMENT  7   /* Comment */
+#define EXPLN_COLUMN_SQL      8   /* SQL that is being explained */
+
+
+  rc = sqlite3_declare_vtab(db,
+     "CREATE TABLE x(addr,opcode,p1,p2,p3,p4,p5,comment,sql HIDDEN)");
+  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;
+  }
+  return rc;
+}
+
+/*
+** This method is the destructor for explain_cursor objects.
+*/
+static int explainDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+
+/*
+** Constructor for a new explain_cursor object.
+*/
+static int explainOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
+  explain_cursor *pCur;
+  pCur = sqlite3_malloc( sizeof(*pCur) );
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(*pCur));
+  pCur->db = ((explain_vtab*)p)->db;
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Destructor for a explain_cursor.
+*/
+static int explainClose(sqlite3_vtab_cursor *cur){
+  explain_cursor *pCur = (explain_cursor*)cur;
+  sqlite3_finalize(pCur->pExplain);
+  sqlite3_free(pCur->zSql);
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+
+/*
+** Advance a explain_cursor to its next row of output.
+*/
+static int explainNext(sqlite3_vtab_cursor *cur){
+  explain_cursor *pCur = (explain_cursor*)cur;
+  pCur->rc = sqlite3_step(pCur->pExplain);
+  if( pCur->rc!=SQLITE_DONE && pCur->rc!=SQLITE_ROW ) return pCur->rc;
+  return SQLITE_OK;
+}
+
+/*
+** Return values of columns for the row at which the explain_cursor
+** is currently pointing.
+*/
+static int explainColumn(
+  sqlite3_vtab_cursor *cur,   /* The cursor */
+  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
+  int i                       /* Which column to return */
+){
+  explain_cursor *pCur = (explain_cursor*)cur;
+  if( i==EXPLN_COLUMN_SQL ){
+    sqlite3_result_text(ctx, pCur->zSql, -1, SQLITE_TRANSIENT);
+  }else{
+    sqlite3_result_value(ctx, sqlite3_column_value(pCur->pExplain, i));
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Return the rowid for the current row.  In this implementation, the
+** rowid is the same as the output value.
+*/
+static int explainRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  explain_cursor *pCur = (explain_cursor*)cur;
+  *pRowid = sqlite3_column_int64(pCur->pExplain, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Return TRUE if the cursor has been moved off of the last
+** row of output.
+*/
+static int explainEof(sqlite3_vtab_cursor *cur){
+  explain_cursor *pCur = (explain_cursor*)cur;
+  return pCur->rc!=SQLITE_ROW;
+}
+
+/*
+** This method is called to "rewind" the explain_cursor object back
+** to the first row of output.  This method is always called at least
+** once prior to any call to explainColumn() or explainRowid() or 
+** explainEof().
+**
+** The argv[0] is the SQL statement that is to be explained.
+*/
+static int explainFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  explain_cursor *pCur = (explain_cursor *)pVtabCursor;
+  char *zSql = 0;
+  int rc;
+  sqlite3_finalize(pCur->pExplain);
+  pCur->pExplain = 0;
+  if( sqlite3_value_type(argv[0])!=SQLITE_TEXT ){
+    pCur->rc = SQLITE_DONE;
+    return SQLITE_OK;
+  }
+  sqlite3_free(pCur->zSql);
+  pCur->zSql = sqlite3_mprintf("%s", sqlite3_value_text(argv[0]));
+  if( pCur->zSql ){
+    zSql = sqlite3_mprintf("EXPLAIN %s", pCur->zSql);
+  }
+  if( zSql==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3_prepare_v2(pCur->db, zSql, -1, &pCur->pExplain, 0);
+    sqlite3_free(zSql);
+  }
+  if( rc ){
+    sqlite3_finalize(pCur->pExplain);
+    pCur->pExplain = 0;
+    sqlite3_free(pCur->zSql);
+    pCur->zSql = 0;
+  }else{
+    pCur->rc = sqlite3_step(pCur->pExplain);
+    rc = (pCur->rc==SQLITE_DONE || pCur->rc==SQLITE_ROW) ? SQLITE_OK : pCur->rc;
+  }
+  return rc;
+}
+
+/*
+** SQLite will invoke this method one or more times while planning a query
+** that uses the explain virtual table.  This routine needs to create
+** a query plan for each invocation and compute an estimated cost for that
+** plan.
+*/
+static int explainBestIndex(
+  sqlite3_vtab *tab,
+  sqlite3_index_info *pIdxInfo
+){
+  int i;                  /* Loop counter */
+  int idx = -1;           /* Index of a usable == constraint against SQL */
+  int unusable = 0;       /* True if there are unusable constraints on SQL */
+
+  pIdxInfo->estimatedRows = 500;
+  for(i=0; i<pIdxInfo->nConstraint; i++){
+    struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i];
+    if( p->iColumn!=EXPLN_COLUMN_SQL ) continue;
+    if( !p->usable ){
+      unusable = 1;
+    }else if( p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      idx = i;
+    }
+  }
+  if( idx>=0 ){
+    /* There exists a usable == constraint against the SQL column */
+    pIdxInfo->estimatedCost = 10.0;
+    pIdxInfo->idxNum = 1;
+    pIdxInfo->aConstraintUsage[idx].argvIndex = 1;
+    pIdxInfo->aConstraintUsage[idx].omit = 1;
+  }else if( unusable ){
+    /* There are unusable constraints against the SQL column.  Do not allow
+    ** this plan to continue forward. */
+    return SQLITE_CONSTRAINT;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This following structure defines all the methods for the 
+** explain virtual table.
+*/
+static sqlite3_module explainModule = {
+  0,                         /* iVersion */
+  0,                         /* xCreate */
+  explainConnect,            /* xConnect */
+  explainBestIndex,          /* xBestIndex */
+  explainDisconnect,         /* xDisconnect */
+  0,                         /* xDestroy */
+  explainOpen,               /* xOpen - open a cursor */
+  explainClose,              /* xClose - close a cursor */
+  explainFilter,             /* xFilter - configure scan constraints */
+  explainNext,               /* xNext - advance a cursor */
+  explainEof,                /* xEof - check for end of scan */
+  explainColumn,             /* xColumn - read data */
+  explainRowid,              /* 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 */
+};
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+int sqlite3ExplainVtabInit(sqlite3 *db){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  rc = sqlite3_create_module(db, "explain", &explainModule, 0);
+#endif
+  return rc;
+}
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_explain_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  int rc = SQLITE_OK;
+  SQLITE_EXTENSION_INIT2(pApi);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  rc = sqlite3ExplainVtabInit(db);
+#endif
+  return rc;
+}