void sqlite3ExprCodeGetColumnOfTable(
  Vdbe *v,        /* The VDBE under construction */
  Table *pTab,    /* The table containing the value */
  int iTabCur,    /* The table cursor.  Or the PK cursor for WITHOUT ROWID */
  int iCol,       /* Index of the column to extract */
  int regOut      /* Extract the value into this register */
){
  if( pTab==0 ){
    sqlite3VdbeAddOp3(v, OP_Column, iTabCur, iCol, regOut);
    return;
  }
  if( iCol<0 || iCol==pTab->iPKey ){
    sqlite3VdbeAddOp2(v, OP_Rowid, iTabCur, regOut);
  }else{
    int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;
    int x = iCol;
    if( !HasRowid(pTab) && !IsVirtual(pTab) ){
      x = sqlite3ColumnOfIndex(sqlite3PrimaryKeyIndex(pTab), iCol);

){
#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;

#else
    zType = columnType(&sNC, p, 0, 0, 0, 0);
#endif
    sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, SQLITE_TRANSIENT);
  }
#endif /* !defined(SQLITE_OMIT_DECLTYPE) */
}

/*
** Return the Table objecct in the SrcList that has cursor iCursor.
** Or return NULL if no such Table object exists in the SrcList.
*/
static Table *tableWithCursor(SrcList *pList, int iCursor){
  int j;
  for(j=0; j<pList->nSrc; j++){
    if( pList->a[j].iCursor==iCursor ) return pList->a[j].pTab;
  }
  return 0;
}


/*
** Generate code that will tell the VDBE the names of columns
** in the result set.  This information is used to provide the
** azCol[] values in the callback.
*/
static void generateColumnNames(
  Parse *pParse,      /* Parser context */
  SrcList *pTabList,  /* List of tables */
  ExprList *pEList    /* Expressions defining the result set */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  Table *pTab;
  sqlite3 *db = pParse->db;
  int fullNames, shortNames;

#ifndef SQLITE_OMIT_EXPLAIN
  /* If this is an EXPLAIN, skip this step */
  if( pParse->explain ){
    return;

  for(i=0; i<pEList->nExpr; i++){
    Expr *p;
    p = pEList->a[i].pExpr;
    if( NEVER(p==0) ) continue;
    if( pEList->a[i].zName ){
      char *zName = pEList->a[i].zName;
      sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT);
    }else if( (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN)
           && (pTab = tableWithCursor(pTabList, p->iTable))!=0
    ){
      char *zCol;
      int iCol = p->iColumn;





      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;
      }

** a column in table number iTable with a copy of the iColumn-th
** entry in pEList.  (But leave references to the ROWID column 
** unchanged.)
**
** This routine is part of the flattening procedure.  A subquery
** whose result set is defined by pEList appears as entry in the
** FROM clause of a SELECT such that the VDBE cursor assigned to that
** FORM clause entry is iTable.  This routine makes the necessary 
** changes to pExpr so that it refers directly to the source table
** of the subquery rather the result set of the subquery.
*/
static Expr *substExpr(
  Parse *pParse,      /* Report errors here */
  Expr *pExpr,        /* Expr in which substitution occurs */
  int iTable,         /* Table to be substituted */

    int n;                                     /* A counter */
    int iCur;                                  /* A cursor number */
    SrcList *pSrcList;                         /* FROM clause */
    struct SrcCount *pSrcCount;                /* Counting column references */
    struct CCurHint *pCCurHint;                /* Used by codeCursorHint() */
    int *aiCol;                                /* array of column indexes */
    struct IdxCover *pIdxCover;                /* Check for index coverage */
    struct IdxExprTrans *pIdxTrans;            /* Convert indexed expr to column */
  } u;
};

/* Forward declarations */
int sqlite3WalkExpr(Walker*, Expr*);
int sqlite3WalkExprList(Walker*, ExprList*);
int sqlite3WalkSelect(Walker*, Select*);

    sqlite3DbFree(db, pWInfo);
    pWInfo = 0;
    goto whereBeginError;
  }
  pWInfo->pParse = pParse;
  pWInfo->pTabList = pTabList;
  pWInfo->pOrderBy = pOrderBy;
  pWInfo->pWhere = pWhere;
  pWInfo->pResultSet = pResultSet;
  pWInfo->aiCurOnePass[0] = pWInfo->aiCurOnePass[1] = -1;
  pWInfo->nLevel = nTabList;
  pWInfo->iBreak = pWInfo->iContinue = sqlite3VdbeMakeLabel(v);
  pWInfo->wctrlFlags = wctrlFlags;
  pWInfo->iLimit = iAuxArg;
  pWInfo->savedNQueryLoop = pParse->nQueryLoop;

** planner.
*/
struct WhereInfo {
  Parse *pParse;            /* Parsing and code generating context */
  SrcList *pTabList;        /* List of tables in the join */
  ExprList *pOrderBy;       /* The ORDER BY clause or NULL */
  ExprList *pResultSet;     /* Result set of the query */
  Expr *pWhere;             /* The complete WHERE clause */
  LogEst iLimit;            /* LIMIT if wctrlFlags has WHERE_USE_LIMIT */
  int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
  int iContinue;            /* Jump here to continue with next record */
  int iBreak;               /* Jump here to break out of the loop */
  int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
  u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
  u8 nLevel;                /* Number of nested loop */

      }
    }
  }else{
    assert( nReg==1 );
    sqlite3ExprCode(pParse, p, iReg);
  }
}

/* An instance of the IdxExprTrans object carries information about a
** mapping from an expression on table columns into a column in an index
** down through the Walker.
*/
typedef struct IdxExprTrans {
  Expr *pIdxExpr;    /* The index expression */
  int iTabCur;       /* The cursor of the corresponding table */
  int iIdxCur;       /* The cursor for the index */
  int iIdxCol;       /* The column for the index */
} IdxExprTrans;

/* The walker node callback used to transform matching expressions into
** a reference to an index column for an index on an expression.
**
** If pExpr matches, then transform it into a reference to the index column
** that contains the value of pExpr.
*/
static int whereIndexExprTransNode(Walker *p, Expr *pExpr){
  IdxExprTrans *pX = p->u.pIdxTrans;
  if( sqlite3ExprCompare(pExpr, pX->pIdxExpr, pX->iTabCur)==0 ){
    pExpr->op = TK_COLUMN;
    pExpr->iTable = pX->iIdxCur;
    pExpr->iColumn = pX->iIdxCol;
    pExpr->pTab = 0;
    return WRC_Prune;
  }else{
    return WRC_Continue;
  }
}

/*
** For an indexes on expression X, locate every instance of expression X in pExpr
** and change that subexpression into a reference to the appropriate column of
** the index.
*/
static void whereIndexExprTrans(
  Index *pIdx,      /* The Index */
  int iTabCur,      /* Cursor of the table that is being indexed */
  int iIdxCur,      /* Cursor of the index itself */
  WhereInfo *pWInfo /* Transform expressions in this WHERE clause */
){
  int iIdxCol;               /* Column number of the index */
  ExprList *aColExpr;        /* Expressions that are indexed */
  Walker w;
  IdxExprTrans x;
  aColExpr = pIdx->aColExpr;
  if( aColExpr==0 ) return;  /* Not an index on expressions */
  memset(&w, 0, sizeof(w));
  w.xExprCallback = whereIndexExprTransNode;
  w.u.pIdxTrans = &x;
  x.iTabCur = iTabCur;
  x.iIdxCur = iIdxCur;
  for(iIdxCol=0; iIdxCol<aColExpr->nExpr; iIdxCol++){
    if( pIdx->aiColumn[iIdxCol]!=XN_EXPR ) continue;
    assert( aColExpr->a[iIdxCol].pExpr!=0 );
    x.iIdxCol = iIdxCol;
    x.pIdxExpr = aColExpr->a[iIdxCol].pExpr;
    sqlite3WalkExpr(&w, pWInfo->pWhere);
    sqlite3WalkExprList(&w, pWInfo->pOrderBy);
    sqlite3WalkExprList(&w, pWInfo->pResultSet);
  }
}

/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
Bitmask sqlite3WhereCodeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */

      for(j=0; j<pPk->nKeyCol; j++){
        k = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[j]);
        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
      }
      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
    }

    /* If pIdx is an index on one or more expressions, then look through
    ** all the expressions in pWInfo and try to transform matching expressions
    ** into reference to index columns.
    */
    whereIndexExprTrans(pIdx, iCur, iIdxCur, pWInfo);


    /* Record the instruction used to terminate the loop. */
    if( pLoop->wsFlags & WHERE_ONEROW ){
      pLevel->op = OP_Noop;
    }else if( bRev ){
      pLevel->op = OP_Prev;
    }else{