static int tableAndColumnIndex(
  SrcList *pSrc,       /* Array of tables to search */
  int N,               /* Number of tables in pSrc->a[] to search */
  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    /* True to ignore hidden columns */
){
  int i;               /* For looping over tables in pSrc */
  int iCol;            /* Index of column matching zCol */

  assert( (piTab==0)==(piCol==0) );  /* Both or neither are NULL */
  for(i=0; i<N; i++){
    iCol = columnIndex(pSrc->a[i].pTab, zCol);
    if( iCol>=0
     && (bIgnoreHidden==0 || IsHiddenColumn(&pSrc->a[i].pTab->aCol[iCol])==0)
    ){
      if( piTab ){
        *piTab = i;
        *piCol = iCol;
      }
      return 1;
    }
  }
  return 0;
}

int sqlite3SelectTrace = 0;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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 */
  if( sqlite3_stricmp(pExpr->u.zToken,"count") ) return 0;  /* Is count() */
  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 SELECTTRACE_ENABLED
  if( sqlite3SelectTrace & 0x400 ){
    SELECTTRACE(0x400,pParse,p,("After count-of-view optimization:\n"));
    sqlite3TreeViewSelect(0, p, 0);
  }
#endif
  return 1;
}

Early-out on the INTERSECT query processing following an error.

FossilOrigin-Name: a67cf5b7d37d5b1484be32092635faafd8f76e5881898cd9435517c4b287d663

int sqlite3SelectTrace = 0;

# define SELECTTRACE(K,P,S,X)  \
  if(sqlite3SelectTrace&(K))   \
    sqlite3DebugPrintf("%u/%d/%p: ",(S)->selId,(P)->addrExplain,(S)),\
    sqlite3DebugPrintf X

# define SELECTTRACE(K,P,S,X)

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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[] = {
    /* natural */ { 0,  7, JT_NATURAL                },
    /* left    */ { 6,  4, JT_LEFT|JT_OUTER          },
    /* outer   */ { 10, 5, JT_OUTER                  },
    /* right   */ { 14, 5, JT_RIGHT|JT_OUTER         },
    /* full    */ { 19, 4, JT_LEFT|JT_RIGHT|JT_OUTER },
    /* inner   */ { 23, 5, JT_INNER                  },
    /* 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
  ){
    const char *zSp = " ";
    assert( pB!=0 );
    if( pC==0 ){ zSp++; }
    sqlite3ErrorMsg(pParse, "unknown or unsupported join type: "
       "%T %T%s%T", pA, pB, zSp, pC);
    jointype = JT_INNER;
  }else if( (jointype & JT_OUTER)!=0
         && (jointype & (JT_LEFT|JT_RIGHT))!=JT_LEFT ){
    sqlite3ErrorMsg(pParse,
      "RIGHT and FULL OUTER JOINs are not currently supported");
    jointype = JT_INNER;
  }
  return jointype;
}

int sqlite3SelectTrace = 0;

typedef struct DistinctCtx DistinctCtx;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

typedef struct WhereConst WhereConst;

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
  Vdbe *v = pParse->pVdbe;
  int i;
  struct AggInfo_func *pFunc;
  int nReg = pAggInfo->nFunc + pAggInfo->nColumn;
  if( nReg==0 ) 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->pExpr;
      assert( !ExprHasProperty(pE, EP_xIsSelect) );
      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);
        sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pFunc->iDistinct, 0, 0,
                          (char*)pKeyInfo, P4_KEYINFO);
      }
    }
  }
}


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 && 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>=0 && iCol<pS->pEList->nExpr ){
          /* 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].zName;
          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 = pExpr->x.pSelect;
      Expr *p = pS->pEList->a[0].pExpr;
      assert( ExprHasProperty(pExpr, EP_xIsSelect) );
      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;
}

int sqlite3SelectTrace = 0;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

# define columnType(A,B,C,D,E) columnTypeImpl(A,B,C,D,E)

# define columnType(A,B,C,D,E) columnTypeImpl(A,B)

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


void sqlite3SelectWalkAssert2(Walker *NotUsed, Select *NotUsed2){
  UNUSED_PARAMETER2(NotUsed, NotUsed2);
  assert( 0 );
}

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 */
);

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);


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;
}


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 = pF->pExpr->x.pList;
    assert( !ExprHasProperty(pF->pExpr, EP_xIsSelect) );
    sqlite3VdbeAddOp2(v, OP_AggFinal, pF->iMem, pList ? pList->nExpr : 0);
    sqlite3VdbeAppendP4(v, pF->pFunc, P4_FUNCDEF);
  }
}


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;
  if( pPrior->pOrderBy || pPrior->pLimit ){
    sqlite3ErrorMsg(pParse,"%s clause should come after %s not before",
      pPrior->pOrderBy!=0 ? "ORDER BY" : "LIMIT", selectOpName(p->op));
    rc = 1;
    goto multi_select_end;
  }

  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 ){
    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;
        assert( !pPrior->pLimit );
        pPrior->iLimit = p->iLimit;
        pPrior->iOffset = p->iOffset;
        pPrior->pLimit = p->pLimit;
        rc = sqlite3Select(pParse, pPrior, &dest);
        p->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"));
        rc = sqlite3Select(pParse, p, &dest);
        testcase( rc!=SQLITE_OK );
        pDelete = p->pPrior;
        p->pPrior = pPrior;
        p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
        if( pPrior->pLimit
         && sqlite3ExprIsInteger(pPrior->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);
        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",
                          selectOpName(p->op)));
        rc = sqlite3Select(pParse, p, &uniondest);
        testcase( rc!=SQLITE_OK );
        /* Query flattening in sqlite3Select() might refill p->pOrderBy.
        ** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */
        sqlite3ExprListDelete(db, p->pOrderBy);
        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);
        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",
                          selectOpName(p->op)));
        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 );
    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;
  sqlite3SelectDelete(db, pDelete);
  return rc;
}


static void codeDistinct(
  Parse *pParse,     /* Parsing and code generating context */
  int iTab,          /* A sorting index used to test for distinctness */
  int addrRepeat,    /* Jump to here if not distinct */
  int N,             /* Number of elements */
  int iMem           /* First element */
){
  Vdbe *v;
  int r1;

  v = pParse->pVdbe;
  r1 = sqlite3GetTempReg(pParse);
  sqlite3VdbeAddOp4Int(v, OP_Found, iTab, addrRepeat, iMem, N); VdbeCoverage(v);
  sqlite3VdbeAddOp3(v, OP_MakeRecord, iMem, N, r1);
  sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iTab, r1, iMem, N);
  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
  sqlite3ReleaseTempReg(pParse, r1);
}


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) */
}


static const char *selectOpName(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;
}


void sqlite3SelectReset(Parse *pParse, Select *p){
  if( ALWAYS(p) ){
    clearSelect(pParse->db, p, 0);
    memset(&p->iLimit, 0, sizeof(Select) - offsetof(Select,iLimit));
    p->pEList = sqlite3ExprListAppend(pParse, 0,
                     sqlite3ExprAlloc(pParse->db,TK_NULL,0,0));
    p->pSrc = sqlite3DbMallocZero(pParse->db, sizeof(SrcList));
  }
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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 = p->pPrior;   /* The setup query */
  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;

  /* Store the results of the setup-query in Queue. */
  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.
  */
  if( p->selFlags & SF_Aggregate ){
    sqlite3ErrorMsg(pParse, "recursive aggregate queries not supported");
  }else{
    p->pPrior = 0;
    ExplainQueryPlan((pParse, 1, "RECURSIVE STEP"));
    sqlite3Select(pParse, p, &destQueue);
    assert( p->pPrior==0 );
    p->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;
}


void sqlite3SelectDestInit(SelectDest *pDest, int eDest, int iParm){
  pDest->eDest = (u8)eDest;
  pDest->iSDParm = iParm;
  pDest->zAffSdst = 0;
  pDest->iSdst = 0;
  pDest->nSdst = 0;
}


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 */
  int iCursor,          /* Cursor number of the subquery */
  int isLeftJoin        /* True if pSubq is the right term of a LEFT JOIN */
){
  Expr *pNew;
  int nChng = 0;
  if( pWhere==0 ) return 0;
  if( pSubq->selFlags & SF_Recursive ) return 0;  /* restriction (2) */

#ifndef SQLITE_OMIT_WINDOWFUNC
  if( pSubq->pWin ) return 0;    /* restriction (6) */
#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,
                                iCursor, isLeftJoin);
    pWhere = pWhere->pLeft;
  }
  if( isLeftJoin
   && (ExprHasProperty(pWhere,EP_FromJoin)==0
         || pWhere->iRightJoinTable!=iCursor)
  ){
    return 0; /* restriction (4) */
  }
  if( ExprHasProperty(pWhere,EP_FromJoin) && pWhere->iRightJoinTable!=iCursor ){
    return 0; /* restriction (5) */
  }
  if( sqlite3ExprIsTableConstant(pWhere, iCursor) ){
    nChng++;
    while( pSubq ){
      SubstContext x;
      pNew = sqlite3ExprDup(pParse->db, pWhere, 0);
      unsetJoinExpr(pNew, -1);
      x.pParse = pParse;
      x.iTable = iCursor;
      x.iNewTable = iCursor;
      x.isLeftJoin = 0;
      x.pEList = pSubq->pEList;
      pNew = substExpr(&x, pNew);
      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;
}


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: {
      if( pParse->nErr==0 ){
        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;
}


int sqlite3IndexedByLookup(Parse *pParse, struct SrcList_item *pFrom){
  if( pFrom->pTab && pFrom->fg.isIndexedBy ){
    Table *pTab = pFrom->pTab;
    char *zIndexedBy = pFrom->u1.zIndexedBy;
    Index *pIdx;
    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;
    }
    pFrom->pIBIndex = pIdx;
  }
  return SQLITE_OK;
}

int sqlite3SelectTrace = 0;

typedef struct DistinctCtx DistinctCtx;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substSelect(SubstContext*, Select*, int);

typedef struct WhereConst WhereConst;

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
  UNUSED_PARAMETER2(NotUsed, NotUsed2);
  return WRC_Continue;
}

int sqlite3SelectTrace = 0;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


int sqlite3ExpandSubquery(Parse *pParse, struct SrcList_item *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, "subquery_%u", pSel->selId);
  }
  while( pSel->pPrior ){ pSel = pSel->pPrior; }
  sqlite3ColumnsFromExprList(pParse, pSel->pEList,&pTab->nCol,&pTab->aCol);
  pTab->iPKey = -1;
  pTab->nRowLogEst = 200; assert( 200==sqlite3LogEst(1048576) );
  pTab->tabFlags |= TF_Ephemeral;

  return pParse->nErr ? SQLITE_ERROR : SQLITE_OK;
}

int sqlite3SelectTrace = 0;

# define SELECTTRACE(K,P,S,X)  \
  if(sqlite3SelectTrace&(K))   \
    sqlite3DebugPrintf("%u/%d/%p: ",(S)->selId,(P)->addrExplain,(S)),\
    sqlite3DebugPrintf X

typedef struct DistinctCtx DistinctCtx;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substSelect(SubstContext*, Select*, int);

typedef struct WhereConst WhereConst;

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


void sqlite3WithPush(Parse *pParse, With *pWith, u8 bFree){
  assert( bFree==0 || (pParse->pWith==0 && pParse->pWithToFree==0) );
  if( pWith ){
    assert( pParse->pWith!=pWith );
    pWith->pOuter = pParse->pWith;
    pParse->pWith = pWith;
    if( bFree ) pParse->pWithToFree = pWith;
  }
}


static void unsetJoinExpr(Expr *p, int iTable){
  while( p ){
    if( ExprHasProperty(p, EP_FromJoin)
     && (iTable<0 || p->iRightJoinTable==iTable) ){
      ExprClearProperty(p, EP_FromJoin);
    }
    if( p->op==TK_FUNCTION && p->x.pList ){
      int i;
      for(i=0; i<p->x.pList->nExpr; i++){
        unsetJoinExpr(p->x.pList->a[i].pExpr, iTable);
      }
    }
    unsetJoinExpr(p->pLeft, iTable);
    p = p->pRight;
  }
}


static struct Cte *searchWith(
  With *pWith,                    /* Current innermost WITH clause */
  struct SrcList_item *pItem,     /* FROM clause element to resolve */
  With **ppContext                /* OUT: WITH clause return value belongs to */
){
  const char *zName;
  if( pItem->zDatabase==0 && (zName = pItem->zName)!=0 ){
    With *p;
    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];
        }
      }
    }
  }
  return 0;
}


static void selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
  Parse *pParse;
  int i;
  SrcList *pTabList;
  struct SrcList_item *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);
      }
    }
  }
}


void sqlite3KeyInfoUnref(KeyInfo *p){
  if( p ){
    assert( p->nRef>0 );
    p->nRef--;
    if( p->nRef==0 ) sqlite3DbFreeNN(p->db, p);
  }
}

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);


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;
}


static int columnIndex(Table *pTab, const char *zCol){
  int i;
  for(i=0; i<pTab->nCol; i++){
    if( sqlite3StrICmp(pTab->aCol[i].zName, zCol)==0 ) return i;
  }
  return -1;
}


static void generateColumnNames(
  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 || p->y.pTab!=0 ); /* Covering idx not yet coded */
    if( pEList->a[i].zEName && pEList->a[i].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].zName;
      }
      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);
}


static void findConstInWhere(WhereConst *pConst, Expr *pExpr){
  Expr *pRight, *pLeft;
  if( pExpr==0 ) return;
  if( ExprHasProperty(pExpr, EP_FromJoin) ) 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);
  }
}

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 */
}

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 */
);

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

typedef struct WhereConst WhereConst;

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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);
}

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 */
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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"));
  }
}


int sqlite3KeyInfoIsWriteable(KeyInfo *p){ return p->nRef==1; }


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 isLeftJoin = 0; /* True if pSub is the right side of a LEFT JOIN */
  int i;              /* Loop counter */
  Expr *pWhere;                    /* The WHERE clause */
  struct SrcList_item *pSubitem;   /* The subquery */
  sqlite3 *db = pParse->db;

  /* 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.
  **
  ** If the subquery is the right operand of a LEFT JOIN, then the outer
  ** query cannot be an aggregate. (3c)  This is an artifact of the way
  ** aggregates are processed - there is no mechanism to determine if
  ** the LEFT JOIN table should be all-NULL.
  **
  ** See also tickets #306, #350, and #3300.
  */
  if( (pSubitem->fg.jointype & JT_OUTER)!=0 ){
    isLeftJoin = 1;
    if( pSubSrc->nSrc>1                   /* (3a) */
     || isAgg                             /* (3b) */
     || IsVirtual(pSubSrc->a[0].pTab)     /* (3c) */
     || (p->selFlags & SF_Distinct)!=0    /* (3d) */
    ){
      return 0;
    }
  }
#ifdef SQLITE_EXTRA_IFNULLROW
  else if( iFrom>0 && !isAgg ){
    /* Setting isLeftJoin to -1 causes OP_IfNullRow opcodes to be generated for
    ** every reference to any result column from subquery in a join, even
    ** though they are not necessary.  This will stress-test the OP_IfNullRow
    ** opcode. */
    isLeftJoin = -1;
  }
#endif

  /* 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 ){
    if( pSub->pOrderBy ){
      return 0;  /* Restriction (20) */
    }
    if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
      return 0; /* (17d1), (17d2), or (17d3) */
    }
    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->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;
      }
      testcase( pSub1->pSrc->nSrc>1 );
    }

    /* Restriction (18). */
    if( p->pOrderBy ){
      int ii;
      for(ii=0; ii<p->pOrderBy->nExpr; ii++){
        if( p->pOrderBy->a[ii].u.x.iOrderByCol==0 ) return 0;
      }
    }
  }

  /* Ex-restriction (23):
  ** The only way that the recursive part of a CTE can contain a compound
  ** subquery is for the subquery to be one term of a join.  But if the
  ** subquery is a join, then the flattening has already been stopped by
  ** restriction (17d3)
  */
  assert( (p->selFlags & SF_Recursive)==0 || pSub->pPrior==0 );

  /***** 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;

  /* 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;
    p->pOrderBy = 0;
    p->pSrc = 0;
    p->pPrior = 0;
    p->pLimit = 0;
    pNew = sqlite3SelectDup(db, p, 0);
    p->pLimit = pLimit;
    p->pOrderBy = pOrderBy;
    p->pSrc = pSrc;
    p->op = TK_ALL;
    if( pNew==0 ){
      p->pPrior = pPrior;
    }else{
      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));
    }
    if( db->mallocFailed ) return 1;
  }

  /* Begin flattening the iFrom-th entry of the FROM clause
  ** in the outer query.
  */
  pSub = pSub1 = pSubitem->pSelect;

  /* Delete the transient table structure associated with the
  ** subquery
  */
  sqlite3DbFree(db, pSubitem->zDatabase);
  sqlite3DbFree(db, pSubitem->zName);
  sqlite3DbFree(db, pSubitem->zAlias);
  pSubitem->zDatabase = 0;
  pSubitem->zName = 0;
  pSubitem->zAlias = 0;
  pSubitem->pSelect = 0;

  /* 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);
      pTabToDel->pNextZombie = pToplevel->pZombieTab;
      pToplevel->pZombieTab = pTabToDel;
    }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.
  */
  for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
    int nSubSrc;
    u8 jointype = 0;
    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( pSrc ){
      assert( pParent==p );  /* First time through the loop */
      jointype = pSubitem->fg.jointype;
    }else{
      assert( pParent!=p );  /* 2nd and subsequent times through the loop */
      pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
      if( pSrc==0 ) break;
      pParent->pSrc = pSrc;
    }

    /* 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++){
      sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
      assert( pSrc->a[i+iFrom].fg.isTabFunc==0 );
      pSrc->a[i+iFrom] = pSubSrc->a[i];
      iNewParent = pSubSrc->a[i].iCursor;
      memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
    }
    pSrc->a[iFrom].fg.jointype = jointype;

    /* 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 ){
      /* 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( isLeftJoin>0 ){
      sqlite3SetJoinExpr(pWhere, iNewParent);
    }
    pParent->pWhere = sqlite3ExprAnd(pParse, pWhere, pParent->pWhere);
    if( db->mallocFailed==0 ){
      SubstContext x;
      x.pParse = pParse;
      x.iTable = iParent;
      x.iNewTable = iNewParent;
      x.isLeftJoin = isLeftJoin;
      x.pEList = pSub->pEList;
      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;
    }
  }

  /* Finially, delete what is left of the subquery and return
  ** success.
  */
  sqlite3SelectDelete(db, pSub1);

#if SELECTTRACE_ENABLED
  if( sqlite3SelectTrace & 0x100 ){
    SELECTTRACE(0x100,pParse,p,("After flattening:\n"));
    sqlite3TreeViewSelect(0, p, 0);
  }
#endif

  return 1;
}

int sqlite3SelectTrace = 0;

# define SELECTTRACE(K,P,S,X)  \
  if(sqlite3SelectTrace&(K))   \
    sqlite3DebugPrintf("%u/%d/%p: ",(S)->selId,(P)->addrExplain,(S)),\
    sqlite3DebugPrintf X

# define SELECTTRACE(K,P,S,X)

typedef struct DistinctCtx DistinctCtx;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

typedef struct WhereConst WhereConst;

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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 SELECTTRACE_ENABLED
  if( sWalker.eCode && (sqlite3SelectTrace & 0x100)!=0 ){
    SELECTTRACE(0x100,pParse,p,("Move HAVING terms into WHERE:\n"));
    sqlite3TreeViewSelect(0, p, 0);
  }
#endif
}

int sqlite3SelectTrace = 0;

# define SELECTTRACE(K,P,S,X)  \
  if(sqlite3SelectTrace&(K))   \
    sqlite3DebugPrintf("%u/%d/%p: ",(S)->selId,(P)->addrExplain,(S)),\
    sqlite3DebugPrintf X

# define SELECTTRACE(K,P,S,X)

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}


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->sortFlags;
    }
  }
  return pInfo;
}


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 TABLE %s%s%s",
        pTab->zName,
        bCover ? " USING COVERING INDEX " : "",
        bCover ? pIdx->zName : ""
    );
  }
}

int sqlite3SelectTrace = 0;

struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  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 */
}

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 */
}

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
}

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 */
);

typedef struct SubstContext {
  Parse *pParse;            /* The parsing context */
  int iTable;               /* Replace references to this table */
  int iNewTable;            /* New table number */
  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
  ExprList *pEList;         /* Replacement expressions */
} SubstContext;

static void substExprList(SubstContext*, ExprList*);

static void substSelect(SubstContext*, Select*, int);

struct WhereConst {
  Parse *pParse;   /* Parsing context */
  int nConst;      /* Number for COLUMN=CONSTANT terms */
  int nChng;       /* Number of times a constant is propagated */
  Expr **apExpr;   /* [i*2] is COLUMN and [i*2+1] is VALUE */
}

# define explainSimpleCount(a,b,c)