Adding upstream version 3.40.1.upstream/3.40.1upstream

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

1 files changed, 7908 insertions, 0 deletions

diff --git a/src/select.c b/src/select.c
new file mode 100644
index 0000000..b0f79f8
--- /dev/null
+++ b/src/select.c
@@ -0,0 +1,7908 @@
+/*
+** 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 */
+};
+#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);
+}
+
+/*
+** 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 non-sensical 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) );
+      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 approprate 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_REFERENCE optimization, or due to the
+  **       SQLITE_ECEL_OMITREF optimization, or due to the 
+  **       SortCtx.pDeferredRowLoad optimiation.  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 );
+
+  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 sqltie3VdbeAddOp3() */
+    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));
+  }
+}
+
+/*
+** 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 ephermal
+**     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( pDest->zAffSdst ){
+        sqlite3VdbeChangeP4(v, -1, pDest->zAffSdst, nResultCol);
+      }
+#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;
+
+  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));
+    }
+  }
+  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);
+  }
+  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 */
+
+#ifndef SQLITE_OMIT_EXPLAIN
+  /* If this is an EXPLAIN, skip this step */
+  if( pParse->explain ){
+    return;
+  }
+#endif
+
+  if( pParse->colNamesSet ) return;
+  /* Column names are determined by the left-most term of a compound select */
+  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
+  SELECTTRACE(1,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 && !db->mallocFailed; 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);
+      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( db->mallocFailed ){
+    for(j=0; j<i; j++){
+      sqlite3DbFree(db, aCol[j].zCnName);
+    }
+    sqlite3DbFree(db, aCol);
+    *paCol = 0;
+    *pnCol = 0;
+    return SQLITE_NOMEM_BKPT;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Add type and collation information to a column list based on
+** a SELECT statement.
+** 
+** The column list presumably came from selectColumnNamesFromExprList().
+** The column list has only names, not types or collations.  This
+** routine goes through and adds the types and collations.
+**
+** This routine requires that all identifiers in the SELECT
+** statement be resolved.
+*/
+void sqlite3SelectAddColumnTypeAndCollation(
+  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 for columns */
+){
+  sqlite3 *db = pParse->db;
+  NameContext sNC;
+  Column *pCol;
+  CollSeq *pColl;
+  int i;
+  Expr *p;
+  struct ExprList_item *a;
+
+  assert( pSelect!=0 );
+  assert( (pSelect->selFlags & SF_Resolved)!=0 );
+  assert( pTab->nCol==pSelect->pEList->nExpr || db->mallocFailed );
+  if( db->mallocFailed ) return;
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pSrcList = pSelect->pSrc;
+  a = pSelect->pEList->a;
+  for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
+    const char *zType;
+    i64 n, m;
+    pTab->tabFlags |= (pCol->colFlags & COLFLAG_NOINSERT);
+    p = a[i].pExpr;
+    zType = columnType(&sNC, p, 0, 0, 0);
+    /* pCol->szEst = ... // Column size est for SELECT tables never used */
+    pCol->affinity = sqlite3ExprAffinity(p);
+    if( zType ){
+      m = sqlite3Strlen30(zType);
+      n = sqlite3Strlen30(pCol->zCnName);
+      pCol->zCnName = sqlite3DbReallocOrFree(db, pCol->zCnName, n+m+2);
+      if( pCol->zCnName ){
+        memcpy(&pCol->zCnName[n+1], zType, m+1);
+        pCol->colFlags |= COLFLAG_HASTYPE;
+      }else{
+        testcase( pCol->colFlags & COLFLAG_HASTYPE );
+        pCol->colFlags &= ~(COLFLAG_HASTYPE|COLFLAG_HASCOLL);
+      }
+    }
+    if( pCol->affinity<=SQLITE_AFF_NONE ) pCol->affinity = aff;
+    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);
+  sqlite3SelectAddColumnTypeAndCollation(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 targetting 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;
+        SELECTTRACE(1, 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"));
+        SELECTTRACE(1, 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);
+        SELECTTRACE(1, 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)));
+        SELECTTRACE(1, 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);
+        SELECTTRACE(1, 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)));
+        SELECTTRACE(1, 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,
+        (void(*)(sqlite3*,void*))sqlite3SelectDelete,
+        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 statment.
+**
+** 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" labe.  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 retargetted */
+  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, 
+       (void(*)(sqlite3*,void*))sqlite3SelectDelete, 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 = pExpr->iColumn;
+      Expr *pCopy = pSubst->pEList->a[iColumn].pExpr;
+      Expr ifNullRow;
+      assert( pSubst->pEList!=0 && iColumn<pSubst->pEList->nExpr );
+      assert( pExpr->pRight==0 );
+      if( sqlite3ExprIsVector(pCopy) ){
+        sqlite3VectorErrorMsg(pSubst->pParse, pCopy);
+      }else{
+        sqlite3 *db = pSubst->pParse->db;
+        if( pSubst->isOuterJoin && pCopy->op!=TK_COLUMN ){
+          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;
+}
+
+#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
+**        accidently 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.
+**
+**
+** 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) */
+  }
+  if( pSubitem->fg.isCte && pSubitem->u2.pCteUse->eM10d==M10d_Yes ){
+    return 0;       /* (28) */
+  }
+
+  /* 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) */
+    for(ii=0; ii<pSub->pEList->nExpr; ii++){
+      char aff;
+      assert( pSub->pEList->a[ii].pExpr!=0 );
+      aff = sqlite3ExprAffinity(pSub->pEList->a[ii].pExpr);
+      for(pSub1=pSub->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 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. *****/
+  SELECTTRACE(1,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 thesubquery */
+  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;
+      SELECTTRACE(2,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, 
+         (void(*)(sqlite3*,void*))sqlite3DeleteTable,
+         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 transfering 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]);
+    }
+  }
+
+  /* Finially, delete what is left of the subquery and return
+  ** success.
+  */
+  sqlite3AggInfoPersistWalkerInit(&w, pParse);
+  sqlite3WalkSelect(&w,pSub1);
+  sqlite3SelectDelete(db, pSub1);
+
+#if TREETRACE_ENABLED
+  if( sqlite3TreeTrace & 0x100 ){
+    SELECTTRACE(0x100,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 entires.  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 alway 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 clase.
+*/
+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) The subquery may not be a compound that uses UNION, INTERSECT,
+**       or EXCEPT.  (We could, perhaps, relax this restriction to allow
+**       this case if none of the comparisons operators between left and
+**       right arms of the compound use a collation other than BINARY.
+**       But it is a lot of work to check that case for an obscure and
+**       minor optimization, so we omit it for now.)
+**
+** 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 */
+  SrcItem *pSrc         /* The subquery term of the outer FROM clause */
+){
+  Expr *pNew;
+  int nChng = 0;
+  if( pWhere==0 ) return 0;
+  if( pSubq->selFlags & (SF_Recursive|SF_MultiPart) ) return 0;
+  if( pSrc->fg.jointype & (JT_LTORJ|JT_RIGHT) ) return 0;
+
+#ifndef SQLITE_OMIT_WINDOWFUNC
+  if( pSubq->pPrior ){
+    Select *pSel;
+    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 ) return 0;  /* restriction (8) */
+      if( pSel->pWin ) return 0;    /* restriction (6b) */
+    }
+  }else{
+    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, pSrc);
+    pWhere = pWhere->pLeft;
+  }
+
+#if 0  /* Legacy code. Checks now done by sqlite3ExprIsTableConstraint() */
+  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( sqlite3ExprIsTableConstraint(pWhere, pSrc) ){
+    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) */
+
+/*
+** 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, 
+                      (void(*)(sqlite3*,void*))sqlite3WithDelete,
+                      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++;
+    if( pCteUse->nUse>=2 && pCteUse->eM10d==M10d_Any ){
+      pCteUse->eM10d = M10d_Yes;
+    }
+
+    /* 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 */
+        if( pE->op==TK_DOT ){
+          assert( pE->pLeft!=0 );
+          assert( !ExprHasProperty(pE->pLeft, EP_IntValue) );
+          zTName = pE->pLeft->u.zToken;
+        }
+        for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+          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 );
+          }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);
+              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;
+          }
+          for(j=0; j<pTab->nCol; j++){
+            char *zName = pTab->aCol[j].zCnName;
+            struct ExprList_item *pX; /* Newly added ExprList term */
+
+            assert( zName );
+            if( zTName
+             && pNestedFrom
+             && sqlite3MatchEName(&pNestedFrom->a[j], 0, zTName, 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;
+            }
+            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;
+            }
+            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 = ENAME_TAB;
+              if( (pFrom->fg.isUsing
+                   && sqlite3IdListIndex(pFrom->u3.pUsing, zName)>=0)
+               || (pUsing && sqlite3IdListIndex(pUsing, zName)>=0)
+               || (pTab->aCol[j].colFlags & COLFLAG_NOEXPAND)!=0
+              ){
+                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 & 0x100 ){
+    SELECTTRACE(0x100,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 and Column.zColl
+** 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 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;
+
+  assert( p->selFlags & SF_Resolved );
+  if( p->selFlags & SF_HasTypeInfo ) return;
+  p->selFlags |= SF_HasTypeInfo;
+  pParse = pWalker->pParse;
+  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 ){
+        while( pSel->pPrior ) pSel = pSel->pPrior;
+        sqlite3SelectAddColumnTypeAndCollation(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);
+}
+
+/*
+** 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( pParse->db->pParse==pParse );
+  assert( pParse->db->mallocFailed==0 || pParse->nErr!=0 );
+  if( nReg==0 ) return;
+  if( pParse->nErr ) return;
+#ifdef SQLITE_DEBUG
+  /* Verify that all AggInfo registers are within the range specified by
+  ** AggInfo.mnReg..AggInfo.mxReg */
+  assert( nReg==pAggInfo->mxReg-pAggInfo->mnReg+1 );
+  for(i=0; i<pAggInfo->nColumn; i++){
+    assert( pAggInfo->aCol[i].iMem>=pAggInfo->mnReg
+         && pAggInfo->aCol[i].iMem<=pAggInfo->mxReg );
+  }
+  for(i=0; i<pAggInfo->nFunc; i++){
+    assert( pAggInfo->aFunc[i].iMem>=pAggInfo->mnReg
+         && pAggInfo->aFunc[i].iMem<=pAggInfo->mxReg );
+  }
+#endif
+  sqlite3VdbeAddOp3(v, OP_Null, 0, pAggInfo->mnReg, pAggInfo->mxReg);
+  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));
+      }
+    }
+  }
+}
+
+/*
+** 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;
+    sqlite3VdbeAddOp2(v, OP_AggFinal, pF->iMem, pList ? pList->nExpr : 0);
+    sqlite3VdbeAppendP4(v, pF->pFunc, P4_FUNCDEF);
+  }
+}
+
+
+/*
+** 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.
+*/
+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;
+
+  pAggInfo->directMode = 1;
+  for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
+    int nArg;
+    int addrNext = 0;
+    int regAgg;
+    ExprList *pList;
+    assert( ExprUseXList(pF->pFExpr) );
+    assert( !IsWindowFunc(pF->pFExpr) );
+    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( pList ){
+      nArg = pList->nExpr;
+      regAgg = sqlite3GetTempRange(pParse, nArg);
+      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, regAgg);
+    }
+    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, pF->iMem);
+    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, pC->iMem);
+  }
+
+  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 ){
+    SELECTTRACE(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 a prior view.
+** If it is, then return the SrcItem for the prior view.  If it is not,
+** 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 */
+){
+  SrcItem *pItem;
+  assert( pThis->pSelect!=0 );
+  if( pThis->pSelect->selFlags & SF_PushDown ) return 0;
+  for(pItem = pTabList->a; pItem<pThis; pItem++){
+    Select *pS1;
+    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, AggInfo *p){
+  sqlite3DbFree(db, p->aCol);
+  sqlite3DbFree(db, p->aFunc);
+  sqlite3DbFreeNN(db, p);
+}
+
+#ifdef SQLITE_COUNTOFVIEW_OPTIMIZATION
+/*
+** 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->pGroupBy ) 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  */
+  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 ry */
+  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 */
+    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;
+    sqlite3ExprListDelete(db, 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 & 0x400 ){
+    SELECTTRACE(0x400,pParse,p,("After count-of-view optimization:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+  return 1;
+}
+#endif /* SQLITE_COUNTOFVIEW_OPTIMIZATION */
+
+/*
+** 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;
+}
+
+/*
+** 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
+  SELECTTRACE(1,pParse,p, ("begin processing:\n", pParse->addrExplain));
+  if( sqlite3TreeTrace & 0x10100 ){
+    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
+      SELECTTRACE(1,pParse,p, ("dropping superfluous ORDER BY:\n"));
+      if( sqlite3TreeTrace & 0x100 ){
+        sqlite3TreeViewExprList(0, p->pOrderBy, 0, "ORDERBY");
+      }
+#endif    
+      sqlite3ParserAddCleanup(pParse,
+        (void(*)(sqlite3*,void*))sqlite3ExprListDelete,
+        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 & 0x104 ){
+    SELECTTRACE(0x104,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 & 0x108)!=0 ){
+    SELECTTRACE(0x104,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 );
+
+    /* Convert LEFT JOIN into JOIN if there are terms of the right table
+    ** of the LEFT JOIN used in the WHERE clause.
+    */
+    if( (pItem->fg.jointype & (JT_LEFT|JT_RIGHT))==JT_LEFT
+     && sqlite3ExprImpliesNonNullRow(p->pWhere, pItem->iCursor)
+     && OptimizationEnabled(db, SQLITE_SimplifyJoin)
+    ){
+      SELECTTRACE(0x100,pParse,p,
+                ("LEFT-JOIN simplifies to JOIN on term %d\n",i));
+      pItem->fg.jointype &= ~(JT_LEFT|JT_OUTER);
+      assert( pItem->iCursor>=0 );
+      unsetJoinExpr(p->pWhere, pItem->iCursor,
+                    pTabList->a[0].fg.jointype & JT_LTORJ);
+    }
+
+    /* No futher action if this term of the FROM clause is no 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 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
+    */
+    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)
+    ){
+      SELECTTRACE(0x100,pParse,p,
+                ("omit superfluous ORDER BY on %r FROM-clause subquery\n",i+1));
+      sqlite3ParserAddCleanup(pParse, 
+         (void(*)(sqlite3*,void*))sqlite3ExprListDelete,
+         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
+    SELECTTRACE(0x1,pParse,p,("end compound-select processing\n"));
+    if( (sqlite3TreeTrace & 0x2000)!=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 & 0x100 ){
+      SELECTTRACE(0x100,pParse,p,("After constant propagation:\n"));
+      sqlite3TreeViewSelect(0, p, 0);
+    }
+#endif
+  }else{
+    SELECTTRACE(0x100,pParse,p,("Constant propagation not helpful\n"));
+  }
+
+#ifdef SQLITE_COUNTOFVIEW_OPTIMIZATION
+  if( OptimizationEnabled(db, SQLITE_QueryFlattener|SQLITE_CountOfView)
+   && countOfViewOptimization(pParse, p)
+  ){
+    if( db->mallocFailed ) goto select_end;
+    pEList = p->pEList;
+    pTabList = p->pSrc;
+  }
+#endif
+
+  /* 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, pItem)
+    ){
+#if TREETRACE_ENABLED
+      if( sqlite3TreeTrace & 0x100 ){
+        SELECTTRACE(0x100,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{
+      SELECTTRACE(0x100,pParse,p,("Push-down not possible\n"));
+    }
+
+    zSavedAuthContext = pParse->zAuthContext;
+    pParse->zAuthContext = pItem->zName;
+
+    /* Generate code to implement the subquery
+    **
+    ** The subquery is implemented as a co-routine if all of the following are
+    ** true:
+    **
+    **    (1)  the subquery is guaranteed to be the outer loop (so that
+    **         it does not need to be computed more than once), and
+    **    (2)  the subquery is not a CTE that should be materialized
+    **    (3)  the subquery is not part of a left operand for a RIGHT JOIN
+    */
+    if( i==0
+     && (pTabList->nSrc==1
+            || (pTabList->a[1].fg.jointype&(JT_OUTER|JT_CROSS))!=0)  /* (1) */
+     && (pItem->fg.isCte==0 || pItem->u2.pCteUse->eM10d!=M10d_Yes)   /* (2) */
+     && (pTabList->a[0].fg.jointype & JT_LTORJ)==0                   /* (3) */
+    ){
+      /* 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 ephemerial 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 ){
+      /* 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;
+
+      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);
+      ExplainQueryPlan((pParse, 1, "MATERIALIZE %!S", pItem));
+      dest.zAffSdst = sqlite3TableAffinityStr(db, pItem->pTab);
+      sqlite3Select(pParse, pSub, &dest);
+      sqlite3DbFree(db, dest.zAffSdst);
+      dest.zAffSdst = 0;
+      pItem->pTab->nRowLogEst = pSub->nSelectRow;
+      if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
+      sqlite3VdbeAddOp2(v, OP_Return, pItem->regReturn, topAddr+1);
+      VdbeComment((v, "end %!S", pItem));
+      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 & 0x400 ){
+    SELECTTRACE(0x400,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 & 0x400 ){
+      SELECTTRACE(0x400,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. */
+    SELECTTRACE(1,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;
+      }
+    }
+    SELECTTRACE(1,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.
+      */
+      SELECTTRACE(1,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,
+          (void(*)(sqlite3*,void*))agginfoFree, pAggInfo);
+      testcase( pParse->earlyCleanup );
+    }
+    if( db->mallocFailed ){
+      goto select_end;
+    }
+    pAggInfo->selId = p->selId;
+    memset(&sNC, 0, sizeof(sNC));
+    sNC.pParse = pParse;
+    sNC.pSrcList = pTabList;
+    sNC.uNC.pAggInfo = pAggInfo;
+    VVA_ONLY( sNC.ncFlags = NC_UAggInfo; )
+    pAggInfo->mnReg = pParse->nMem+1;
+    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;
+    }
+    for(i=0; i<pAggInfo->nFunc; i++){
+      Expr *pExpr = pAggInfo->aFunc[i].pFExpr;
+      assert( ExprUseXList(pExpr) );
+      sNC.ncFlags |= NC_InAggFunc;
+      sqlite3ExprAnalyzeAggList(&sNC, pExpr->x.pList);
+#ifndef SQLITE_OMIT_WINDOWFUNC
+      assert( !IsWindowFunc(pExpr) );
+      if( ExprHasProperty(pExpr, EP_WinFunc) ){
+        sqlite3ExprAnalyzeAggregates(&sNC, pExpr->y.pWin->pFilter);
+      }
+#endif
+      sNC.ncFlags &= ~NC_InAggFunc;
+    }
+    pAggInfo->mxReg = pParse->nMem;
+    if( db->mallocFailed ) goto select_end;
+#if TREETRACE_ENABLED
+    if( sqlite3TreeTrace & 0x400 ){
+      int ii;
+      SELECTTRACE(0x400,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");
+      }
+      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\n",
+           ii, pCol->pTab ? pCol->pTab->zName : "NULL", 
+           pCol->iTable, pCol->iColumn, pCol->iMem,
+           pCol->iSorterColumn);
+        sqlite3TreeViewExpr(0, pAggInfo->aCol[ii].pCExpr, 0);
+      }
+      for(ii=0; ii<pAggInfo->nFunc; ii++){
+        sqlite3DebugPrintf("agg-func[%d]: iMem=%d\n",
+            ii, pAggInfo->aFunc[ii].iMem);
+        sqlite3TreeViewExpr(0, pAggInfo->aFunc[ii].pFExpr, 0);
+      }
+    }
+#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 comparision 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);
+      SELECTTRACE(1,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;
+      }
+      eDist = sqlite3WhereIsDistinct(pWInfo);
+      SELECTTRACE(1,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;
+
+        explainTempTable(pParse, 
+            (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);
+        sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
+        sqlite3VdbeAddOp2(v, OP_SorterInsert, pAggInfo->sortingIdx, regRecord);
+        sqlite3ReleaseTempReg(pParse, regRecord);
+        sqlite3ReleaseTempRange(pParse, regBase, nCol);
+        SELECTTRACE(1,pParse,p,("WhereEnd\n"));
+        sqlite3WhereEnd(pWInfo);
+        pAggInfo->sortingIdxPTab = sortPTab = pParse->nTab++;
+        sortOut = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp3(v, OP_OpenPseudo, sortPTab, sortOut, nCol);
+        sqlite3VdbeAddOp2(v, OP_SorterSort, pAggInfo->sortingIdx, addrEnd);
+        VdbeComment((v, "GROUP BY sort")); VdbeCoverage(v);
+        pAggInfo->useSortingIdx = 1;
+      }
+
+      /* 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{
+        SELECTTRACE(1,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);
+        }
+        sqlite3VdbeAddOp2(v, OP_Count, iCsr, pAggInfo->aFunc[0].iMem);
+        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;
+        }
+
+        /* 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 );
+
+        SELECTTRACE(1,pParse,p,("WhereBegin\n"));
+        pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pMinMaxOrderBy,
+                                   pDistinct, p, minMaxFlag|distFlag, 0);
+        if( pWInfo==0 ){
+          goto select_end;
+        }
+        SELECTTRACE(1,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);
+        }
+        SELECTTRACE(1,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 ){
+    explainTempTable(pParse,
+                     sSort.nOBSat>0 ? "RIGHT PART OF ORDER BY":"ORDER BY");
+    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;
+      assert( pExpr!=0 );
+      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
+  SELECTTRACE(0x1,pParse,p,("end processing\n"));
+  if( (sqlite3TreeTrace & 0x2000)!=0 && ExplainQueryPlanParent(pParse)==0 ){
+    sqlite3TreeViewSelect(0, p, 0);
+  }
+#endif
+  ExplainQueryPlanPop(pParse);
+  return rc;
+}