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where.c File Reference
#include "sqliteInt.h"

Go to the source code of this file.

Classes

struct  WhereTerm
struct  WhereClause
struct  ExprMaskSet

Defines

#define BMS   (sizeof(Bitmask)*8)
#define ARRAYSIZE(X)   (sizeof(X)/sizeof(X[0]))
#define TRACE(X)
#define TERM_DYNAMIC   0x01 /* Need to call sqlite3ExprDelete(pExpr) */
#define TERM_VIRTUAL   0x02 /* Added by the optimizer. Do not code */
#define TERM_CODED   0x04 /* This term is already coded */
#define TERM_COPIED   0x08 /* Has a child */
#define TERM_OR_OK   0x10 /* Used during OR-clause processing */
#define WO_IN   1
#define WO_EQ   2
#define WO_LT   (WO_EQ<<(TK_LT-TK_EQ))
#define WO_LE   (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT   (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE   (WO_EQ<<(TK_GE-TK_EQ))
#define WHERE_ROWID_EQ   0x0001 /* rowid=EXPR or rowid IN (...) */
#define WHERE_ROWID_RANGE   0x0002 /* rowid<EXPR and/or rowid>EXPR */
#define WHERE_COLUMN_EQ   0x0010 /* x=EXPR or x IN (...) */
#define WHERE_COLUMN_RANGE   0x0020 /* x<EXPR and/or x>EXPR */
#define WHERE_COLUMN_IN   0x0040 /* x IN (...) */
#define WHERE_TOP_LIMIT   0x0100 /* x<EXPR or x<=EXPR constraint */
#define WHERE_BTM_LIMIT   0x0200 /* x>EXPR or x>=EXPR constraint */
#define WHERE_IDX_ONLY   0x0800 /* Use index only - omit table */
#define WHERE_ORDERBY   0x1000 /* Output will appear in correct order */
#define WHERE_REVERSE   0x2000 /* Scan in reverse order */
#define WHERE_UNIQUE   0x4000 /* Selects no more than one row */
#define initMaskSet(P)   memset(P, 0, sizeof(*P))
#define SWAP(TYPE, A, B)   {TYPE t=A; A=B; B=t;}

Typedefs

typedef struct WhereClause
typedef struct WhereTerm
typedef struct ExprMaskSet

Functions

static void whereClauseInit (WhereClause *pWC, Parse *pParse)
static void whereClauseClear (WhereClause *pWC)
static int whereClauseInsert (WhereClause *pWC, Expr *p, int flags)
static void whereSplit (WhereClause *pWC, Expr *pExpr, int op)
static Bitmask getMask (ExprMaskSet *pMaskSet, int iCursor)
static void createMask (ExprMaskSet *pMaskSet, int iCursor)
static Bitmask exprListTableUsage (ExprMaskSet *, ExprList *)
static Bitmask exprSelectTableUsage (ExprMaskSet *, Select *)
static Bitmask exprTableUsage (ExprMaskSet *pMaskSet, Expr *p)
static int allowedOp (int op)
static void exprCommute (Expr *pExpr)
static int operatorMask (int op)
static WhereTermfindTerm (WhereClause *pWC, int iCur, int iColumn, Bitmask notReady, u16 op, Index *pIdx)
static void exprAnalyze (SrcList *, ExprMaskSet *, WhereClause *, int)
static void exprAnalyzeAll (SrcList *pTabList, ExprMaskSet *pMaskSet, WhereClause *pWC)
static int isLikeOrGlob (sqlite3 *db, Expr *pExpr, int *pnPattern, int *pisComplete)
static void transferJoinMarkings (Expr *pDerived, Expr *pBase)
static int isSortingIndex (Parse *pParse, Index *pIdx, int base, ExprList *pOrderBy, int nEqCol, int *pbRev)
static int sortableByRowid (int base, ExprList *pOrderBy, int *pbRev)
static double estLog (double N)
static double bestIndex (Parse *pParse, WhereClause *pWC, struct SrcList_item *pSrc, Bitmask notReady, ExprList *pOrderBy, Index **ppIndex, int *pFlags, int *pnEq)
static void disableTerm (WhereLevel *pLevel, WhereTerm *pTerm)
static void buildIndexProbe (Vdbe *v, int nColumn, int nExtra, int brk, Index *pIdx)
static void codeEqualityTerm (Parse *pParse, WhereTerm *pTerm, int brk, WhereLevel *pLevel)
static void codeAllEqualityTerms (Parse *pParse, WhereLevel *pLevel, WhereClause *pWC, Bitmask notReady, int brk)
WhereInfosqlite3WhereBegin (Parse *pParse, SrcList *pTabList, Expr *pWhere, ExprList **ppOrderBy)
void sqlite3WhereEnd (WhereInfo *pWInfo)

Class Documentation

struct WhereTerm

Definition at line 81 of file where.c.

Collaboration diagram for WhereTerm:
Class Members
u16 eOperator
u8 flags
i16 iParent
i16 leftColumn
i16 leftCursor
u8 nChild
Expr * pExpr
Bitmask prereqAll
Bitmask prereqRight
WhereClause * pWC
struct WhereClause

Definition at line 107 of file where.c.

Collaboration diagram for WhereClause:
Class Members
WhereTerm * a
WhereTerm aStatic
int nSlot
int nTerm
Parse * pParse
struct ExprMaskSet

Definition at line 142 of file where.c.

Collaboration diagram for ExprMaskSet:
Class Members
int ix
int n

Define Documentation

#define ARRAYSIZE (   X)    (sizeof(X)/sizeof(X[0]))

Definition at line 31 of file where.c.

#define BMS   (sizeof(Bitmask)*8)

Definition at line 26 of file where.c.

#define initMaskSet (   P)    memset(P, 0, sizeof(*P))

Definition at line 263 of file where.c.

#define SWAP (   TYPE,
  A,
  B 
)    {TYPE t=A; A=B; B=t;}

Definition at line 361 of file where.c.

#define TERM_CODED   0x04 /* This term is already coded */

Definition at line 99 of file where.c.

#define TERM_COPIED   0x08 /* Has a child */

Definition at line 100 of file where.c.

#define TERM_DYNAMIC   0x01 /* Need to call sqlite3ExprDelete(pExpr) */

Definition at line 97 of file where.c.

#define TERM_OR_OK   0x10 /* Used during OR-clause processing */

Definition at line 101 of file where.c.

#define TERM_VIRTUAL   0x02 /* Added by the optimizer. Do not code */

Definition at line 98 of file where.c.

#define TRACE (   X)

Definition at line 40 of file where.c.

#define WHERE_BTM_LIMIT   0x0200 /* x>EXPR or x>=EXPR constraint */

Definition at line 169 of file where.c.

#define WHERE_COLUMN_EQ   0x0010 /* x=EXPR or x IN (...) */

Definition at line 165 of file where.c.

#define WHERE_COLUMN_IN   0x0040 /* x IN (...) */

Definition at line 167 of file where.c.

#define WHERE_COLUMN_RANGE   0x0020 /* x<EXPR and/or x>EXPR */

Definition at line 166 of file where.c.

#define WHERE_IDX_ONLY   0x0800 /* Use index only - omit table */

Definition at line 170 of file where.c.

#define WHERE_ORDERBY   0x1000 /* Output will appear in correct order */

Definition at line 171 of file where.c.

#define WHERE_REVERSE   0x2000 /* Scan in reverse order */

Definition at line 172 of file where.c.

#define WHERE_ROWID_EQ   0x0001 /* rowid=EXPR or rowid IN (...) */

Definition at line 163 of file where.c.

#define WHERE_ROWID_RANGE   0x0002 /* rowid<EXPR and/or rowid>EXPR */

Definition at line 164 of file where.c.

#define WHERE_TOP_LIMIT   0x0100 /* x<EXPR or x<=EXPR constraint */

Definition at line 168 of file where.c.

#define WHERE_UNIQUE   0x4000 /* Selects no more than one row */

Definition at line 173 of file where.c.

#define WO_EQ   2

Definition at line 154 of file where.c.

Definition at line 158 of file where.c.

Definition at line 157 of file where.c.

#define WO_IN   1

Definition at line 153 of file where.c.

Definition at line 156 of file where.c.

Definition at line 155 of file where.c.


Typedef Documentation

typedef struct ExprMaskSet

Definition at line 141 of file where.c.

typedef struct WhereClause

Definition at line 45 of file where.c.

typedef struct WhereTerm

Definition at line 80 of file where.c.


Function Documentation

static int allowedOp ( int  op) [static]

Definition at line 350 of file where.c.

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static double bestIndex ( Parse pParse,
WhereClause pWC,
struct SrcList_item *  pSrc,
Bitmask  notReady,
ExprList pOrderBy,
Index **  ppIndex,
int pFlags,
int pnEq 
) [static]

Definition at line 905 of file where.c.

 {
  WhereTerm *pTerm;
  Index *bestIdx = 0;         /* Index that gives the lowest cost */
  double lowestCost;          /* The cost of using bestIdx */
  int bestFlags = 0;          /* Flags associated with bestIdx */
  int bestNEq = 0;            /* Best value for nEq */
  int iCur = pSrc->iCursor;   /* The cursor of the table to be accessed */
  Index *pProbe;              /* An index we are evaluating */
  int rev;                    /* True to scan in reverse order */
  int flags;                  /* Flags associated with pProbe */
  int nEq;                    /* Number of == or IN constraints */
  double cost;                /* Cost of using pProbe */

  TRACE(("bestIndex: tbl=%s notReady=%x\n", pSrc->pTab->zName, notReady));
  lowestCost = SQLITE_BIG_DBL;
  pProbe = pSrc->pTab->pIndex;

  /* If the table has no indices and there are no terms in the where
  ** clause that refer to the ROWID, then we will never be able to do
  ** anything other than a full table scan on this table.  We might as
  ** well put it first in the join order.  That way, perhaps it can be
  ** referenced by other tables in the join.
  */
  if( pProbe==0 &&
     findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 &&
     (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, &rev)) ){
    *pFlags = 0;
    *ppIndex = 0;
    *pnEq = 0;
    return 0.0;
  }

  /* Check for a rowid=EXPR or rowid IN (...) constraints
  */
  pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
  if( pTerm ){
    Expr *pExpr;
    *ppIndex = 0;
    bestFlags = WHERE_ROWID_EQ;
    if( pTerm->eOperator & WO_EQ ){
      /* Rowid== is always the best pick.  Look no further.  Because only
      ** a single row is generated, output is always in sorted order */
      *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE;
      *pnEq = 1;
      TRACE(("... best is rowid\n"));
      return 0.0;
    }else if( (pExpr = pTerm->pExpr)->pList!=0 ){
      /* Rowid IN (LIST): cost is NlogN where N is the number of list
      ** elements.  */
      lowestCost = pExpr->pList->nExpr;
      lowestCost *= estLog(lowestCost);
    }else{
      /* Rowid IN (SELECT): cost is NlogN where N is the number of rows
      ** in the result of the inner select.  We have no way to estimate
      ** that value so make a wild guess. */
      lowestCost = 200;
    }
    TRACE(("... rowid IN cost: %.9g\n", lowestCost));
  }

  /* Estimate the cost of a table scan.  If we do not know how many
  ** entries are in the table, use 1 million as a guess.
  */
  cost = pProbe ? pProbe->aiRowEst[0] : 1000000;
  TRACE(("... table scan base cost: %.9g\n", cost));
  flags = WHERE_ROWID_RANGE;

  /* Check for constraints on a range of rowids in a table scan.
  */
  pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0);
  if( pTerm ){
    if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){
      flags |= WHERE_TOP_LIMIT;
      cost /= 3;  /* Guess that rowid<EXPR eliminates two-thirds or rows */
    }
    if( findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0) ){
      flags |= WHERE_BTM_LIMIT;
      cost /= 3;  /* Guess that rowid>EXPR eliminates two-thirds of rows */
    }
    TRACE(("... rowid range reduces cost to %.9g\n", cost));
  }else{
    flags = 0;
  }

  /* If the table scan does not satisfy the ORDER BY clause, increase
  ** the cost by NlogN to cover the expense of sorting. */
  if( pOrderBy ){
    if( sortableByRowid(iCur, pOrderBy, &rev) ){
      flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE;
      if( rev ){
        flags |= WHERE_REVERSE;
      }
    }else{
      cost += cost*estLog(cost);
      TRACE(("... sorting increases cost to %.9g\n", cost));
    }
  }
  if( cost<lowestCost ){
    lowestCost = cost;
    bestFlags = flags;
  }

  /* Look at each index.
  */
  for(; pProbe; pProbe=pProbe->pNext){
    int i;                       /* Loop counter */
    double inMultiplier = 1;

    TRACE(("... index %s:\n", pProbe->zName));

    /* Count the number of columns in the index that are satisfied
    ** by x=EXPR constraints or x IN (...) constraints.
    */
    flags = 0;
    for(i=0; i<pProbe->nColumn; i++){
      int j = pProbe->aiColumn[i];
      pTerm = findTerm(pWC, iCur, j, notReady, WO_EQ|WO_IN, pProbe);
      if( pTerm==0 ) break;
      flags |= WHERE_COLUMN_EQ;
      if( pTerm->eOperator & WO_IN ){
        Expr *pExpr = pTerm->pExpr;
        flags |= WHERE_COLUMN_IN;
        if( pExpr->pSelect!=0 ){
          inMultiplier *= 25;
        }else if( pExpr->pList!=0 ){
          inMultiplier *= pExpr->pList->nExpr + 1;
        }
      }
    }
    cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier);
    nEq = i;
    if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0
         && nEq==pProbe->nColumn ){
      flags |= WHERE_UNIQUE;
    }
    TRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n", nEq, inMultiplier, cost));

    /* Look for range constraints
    */
    if( nEq<pProbe->nColumn ){
      int j = pProbe->aiColumn[nEq];
      pTerm = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pProbe);
      if( pTerm ){
        flags |= WHERE_COLUMN_RANGE;
        if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pProbe) ){
          flags |= WHERE_TOP_LIMIT;
          cost /= 3;
        }
        if( findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pProbe) ){
          flags |= WHERE_BTM_LIMIT;
          cost /= 3;
        }
        TRACE(("...... range reduces cost to %.9g\n", cost));
      }
    }

    /* Add the additional cost of sorting if that is a factor.
    */
    if( pOrderBy ){
      if( (flags & WHERE_COLUMN_IN)==0 &&
           isSortingIndex(pParse,pProbe,iCur,pOrderBy,nEq,&rev) ){
        if( flags==0 ){
          flags = WHERE_COLUMN_RANGE;
        }
        flags |= WHERE_ORDERBY;
        if( rev ){
          flags |= WHERE_REVERSE;
        }
      }else{
        cost += cost*estLog(cost);
        TRACE(("...... orderby increases cost to %.9g\n", cost));
      }
    }

    /* Check to see if we can get away with using just the index without
    ** ever reading the table.  If that is the case, then halve the
    ** cost of this index.
    */
    if( flags && pSrc->colUsed < (((Bitmask)1)<<(BMS-1)) ){
      Bitmask m = pSrc->colUsed;
      int j;
      for(j=0; j<pProbe->nColumn; j++){
        int x = pProbe->aiColumn[j];
        if( x<BMS-1 ){
          m &= ~(((Bitmask)1)<<x);
        }
      }
      if( m==0 ){
        flags |= WHERE_IDX_ONLY;
        cost /= 2;
        TRACE(("...... idx-only reduces cost to %.9g\n", cost));
      }
    }

    /* If this index has achieved the lowest cost so far, then use it.
    */
    if( cost < lowestCost ){
      bestIdx = pProbe;
      lowestCost = cost;
      assert( flags!=0 );
      bestFlags = flags;
      bestNEq = nEq;
    }
  }

  /* Report the best result
  */
  *ppIndex = bestIdx;
  TRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n",
        bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq));
  *pFlags = bestFlags;
  *pnEq = bestNEq;
  return lowestCost;
}

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static void buildIndexProbe ( Vdbe v,
int  nColumn,
int  nExtra,
int  brk,
Index pIdx 
) [static]

Definition at line 1183 of file where.c.

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static void codeAllEqualityTerms ( Parse pParse,
WhereLevel pLevel,
WhereClause pWC,
Bitmask  notReady,
int  brk 
) [static]

Definition at line 1268 of file where.c.

 {
  int nEq = pLevel->nEq;        /* The number of == or IN constraints to code */
  int termsInMem = 0;           /* If true, store value in mem[] cells */
  Vdbe *v = pParse->pVdbe;      /* The virtual machine under construction */
  Index *pIdx = pLevel->pIdx;   /* The index being used for this loop */
  int iCur = pLevel->iTabCur;   /* The cursor of the table */
  WhereTerm *pTerm;             /* A single constraint term */
  int j;                        /* Loop counter */

  /* Figure out how many memory cells we will need then allocate them.
  ** We always need at least one used to store the loop terminator
  ** value.  If there are IN operators we'll need one for each == or
  ** IN constraint.
  */
  pLevel->iMem = pParse->nMem++;
  if( pLevel->flags & WHERE_COLUMN_IN ){
    pParse->nMem += pLevel->nEq;
    termsInMem = 1;
  }

  /* Evaluate the equality constraints
  */
  for(j=0; j<pIdx->nColumn; j++){
    int k = pIdx->aiColumn[j];
    pTerm = findTerm(pWC, iCur, k, notReady, WO_EQ|WO_IN, pIdx);
    if( pTerm==0 ) break;
    assert( (pTerm->flags & TERM_CODED)==0 );
    codeEqualityTerm(pParse, pTerm, brk, pLevel);
    if( termsInMem ){
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1);
    }
  }
  assert( j==nEq );

  /* Make sure all the constraint values are on the top of the stack
  */
  if( termsInMem ){
    for(j=0; j<nEq; j++){
      sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem+j+1, 0);
    }
  }
}

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static void codeEqualityTerm ( Parse pParse,
WhereTerm pTerm,
int  brk,
WhereLevel pLevel 
) [static]

Definition at line 1209 of file where.c.

 {
  Expr *pX = pTerm->pExpr;
  if( pX->op!=TK_IN ){
    assert( pX->op==TK_EQ );
    sqlite3ExprCode(pParse, pX->pRight);
#ifndef SQLITE_OMIT_SUBQUERY
  }else{
    int iTab;
    int *aIn;
    Vdbe *v = pParse->pVdbe;

    sqlite3CodeSubselect(pParse, pX);
    iTab = pX->iTable;
    sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0);
    VdbeComment((v, "# %.*s", pX->span.n, pX->span.z));
    pLevel->nIn++;
    sqliteReallocOrFree((void**)&pLevel->aInLoop,
                                 sizeof(pLevel->aInLoop[0])*2*pLevel->nIn);
    aIn = pLevel->aInLoop;
    if( aIn ){
      aIn += pLevel->nIn*2 - 2;
      aIn[0] = iTab;
      aIn[1] = sqlite3VdbeAddOp(v, OP_Column, iTab, 0);
    }else{
      pLevel->nIn = 0;
    }
#endif
  }
  disableTerm(pLevel, pTerm);
}

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static void createMask ( ExprMaskSet pMaskSet,
int  iCursor 
) [static]

Definition at line 287 of file where.c.

                                                          {
  assert( pMaskSet->n < ARRAYSIZE(pMaskSet->ix) );
  pMaskSet->ix[pMaskSet->n++] = iCursor;
}

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static void disableTerm ( WhereLevel pLevel,
WhereTerm pTerm 
) [static]

Definition at line 1153 of file where.c.

                                                             {
  if( pTerm
      && (pTerm->flags & TERM_CODED)==0
      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
  ){
    pTerm->flags |= TERM_CODED;
    if( pTerm->iParent>=0 ){
      WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
      if( (--pOther->nChild)==0 ){
        disableTerm(pLevel, pOther);
      }
    }
  }
}

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static double estLog ( double  N) [static]

Definition at line 877 of file where.c.

                              {
  double logN = 1;
  double x = 10;
  while( N>x ){
    logN += 1;
    x *= 10;
  }
  return logN;
}

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static void exprAnalyze ( SrcList pSrc,
ExprMaskSet pMaskSet,
WhereClause pWC,
int  idxTerm 
) [static]

Definition at line 547 of file where.c.

 {
  WhereTerm *pTerm = &pWC->a[idxTerm];
  Expr *pExpr = pTerm->pExpr;
  Bitmask prereqLeft;
  Bitmask prereqAll;
  int nPattern;
  int isComplete;

  if( sqlite3MallocFailed() ) return;
  prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
  if( pExpr->op==TK_IN ){
    assert( pExpr->pRight==0 );
    pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList)
                          | exprSelectTableUsage(pMaskSet, pExpr->pSelect);
  }else{
    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
  }
  prereqAll = exprTableUsage(pMaskSet, pExpr);
  if( ExprHasProperty(pExpr, EP_FromJoin) ){
    prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable);
  }
  pTerm->prereqAll = prereqAll;
  pTerm->leftCursor = -1;
  pTerm->iParent = -1;
  pTerm->eOperator = 0;
  if( allowedOp(pExpr->op) && (pTerm->prereqRight & prereqLeft)==0 ){
    Expr *pLeft = pExpr->pLeft;
    Expr *pRight = pExpr->pRight;
    if( pLeft->op==TK_COLUMN ){
      pTerm->leftCursor = pLeft->iTable;
      pTerm->leftColumn = pLeft->iColumn;
      pTerm->eOperator = operatorMask(pExpr->op);
    }
    if( pRight && pRight->op==TK_COLUMN ){
      WhereTerm *pNew;
      Expr *pDup;
      if( pTerm->leftCursor>=0 ){
        int idxNew;
        pDup = sqlite3ExprDup(pExpr);
        idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
        if( idxNew==0 ) return;
        pNew = &pWC->a[idxNew];
        pNew->iParent = idxTerm;
        pTerm = &pWC->a[idxTerm];
        pTerm->nChild = 1;
        pTerm->flags |= TERM_COPIED;
      }else{
        pDup = pExpr;
        pNew = pTerm;
      }
      exprCommute(pDup);
      pLeft = pDup->pLeft;
      pNew->leftCursor = pLeft->iTable;
      pNew->leftColumn = pLeft->iColumn;
      pNew->prereqRight = prereqLeft;
      pNew->prereqAll = prereqAll;
      pNew->eOperator = operatorMask(pDup->op);
    }
  }

#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
  /* If a term is the BETWEEN operator, create two new virtual terms
  ** that define the range that the BETWEEN implements.
  */
  else if( pExpr->op==TK_BETWEEN ){
    ExprList *pList = pExpr->pList;
    int i;
    static const u8 ops[] = {TK_GE, TK_LE};
    assert( pList!=0 );
    assert( pList->nExpr==2 );
    for(i=0; i<2; i++){
      Expr *pNewExpr;
      int idxNew;
      pNewExpr = sqlite3Expr(ops[i], sqlite3ExprDup(pExpr->pLeft),
                             sqlite3ExprDup(pList->a[i].pExpr), 0);
      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
      exprAnalyze(pSrc, pMaskSet, pWC, idxNew);
      pTerm = &pWC->a[idxTerm];
      pWC->a[idxNew].iParent = idxTerm;
    }
    pTerm->nChild = 2;
  }
#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */

#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
  /* Attempt to convert OR-connected terms into an IN operator so that
  ** they can make use of indices.  Example:
  **
  **      x = expr1  OR  expr2 = x  OR  x = expr3
  **
  ** is converted into
  **
  **      x IN (expr1,expr2,expr3)
  **
  ** This optimization must be omitted if OMIT_SUBQUERY is defined because
  ** the compiler for the the IN operator is part of sub-queries.
  */
  else if( pExpr->op==TK_OR ){
    int ok;
    int i, j;
    int iColumn, iCursor;
    WhereClause sOr;
    WhereTerm *pOrTerm;

    assert( (pTerm->flags & TERM_DYNAMIC)==0 );
    whereClauseInit(&sOr, pWC->pParse);
    whereSplit(&sOr, pExpr, TK_OR);
    exprAnalyzeAll(pSrc, pMaskSet, &sOr);
    assert( sOr.nTerm>0 );
    j = 0;
    do{
      iColumn = sOr.a[j].leftColumn;
      iCursor = sOr.a[j].leftCursor;
      ok = iCursor>=0;
      for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
        if( pOrTerm->eOperator!=WO_EQ ){
          goto or_not_possible;
        }
        if( pOrTerm->leftCursor==iCursor && pOrTerm->leftColumn==iColumn ){
          pOrTerm->flags |= TERM_OR_OK;
        }else if( (pOrTerm->flags & TERM_COPIED)!=0 ||
                    ((pOrTerm->flags & TERM_VIRTUAL)!=0 &&
                     (sOr.a[pOrTerm->iParent].flags & TERM_OR_OK)!=0) ){
          pOrTerm->flags &= ~TERM_OR_OK;
        }else{
          ok = 0;
        }
      }
    }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<sOr.nTerm );
    if( ok ){
      ExprList *pList = 0;
      Expr *pNew, *pDup;
      for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
        if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue;
        pDup = sqlite3ExprDup(pOrTerm->pExpr->pRight);
        pList = sqlite3ExprListAppend(pList, pDup, 0);
      }
      pDup = sqlite3Expr(TK_COLUMN, 0, 0, 0);
      if( pDup ){
        pDup->iTable = iCursor;
        pDup->iColumn = iColumn;
      }
      pNew = sqlite3Expr(TK_IN, pDup, 0, 0);
      if( pNew ){
        int idxNew;
        transferJoinMarkings(pNew, pExpr);
        pNew->pList = pList;
        idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
        exprAnalyze(pSrc, pMaskSet, pWC, idxNew);
        pTerm = &pWC->a[idxTerm];
        pWC->a[idxNew].iParent = idxTerm;
        pTerm->nChild = 1;
      }else{
        sqlite3ExprListDelete(pList);
      }
    }
or_not_possible:
    whereClauseClear(&sOr);
  }
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */

#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
  /* Add constraints to reduce the search space on a LIKE or GLOB
  ** operator.
  */
  if( isLikeOrGlob(pWC->pParse->db, pExpr, &nPattern, &isComplete) ){
    Expr *pLeft, *pRight;
    Expr *pStr1, *pStr2;
    Expr *pNewExpr1, *pNewExpr2;
    int idxNew1, idxNew2;

    pLeft = pExpr->pList->a[1].pExpr;
    pRight = pExpr->pList->a[0].pExpr;
    pStr1 = sqlite3Expr(TK_STRING, 0, 0, 0);
    if( pStr1 ){
      sqlite3TokenCopy(&pStr1->token, &pRight->token);
      pStr1->token.n = nPattern;
    }
    pStr2 = sqlite3ExprDup(pStr1);
    if( pStr2 ){
      assert( pStr2->token.dyn );
      ++*(u8*)&pStr2->token.z[nPattern-1];
    }
    pNewExpr1 = sqlite3Expr(TK_GE, sqlite3ExprDup(pLeft), pStr1, 0);
    idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
    exprAnalyze(pSrc, pMaskSet, pWC, idxNew1);
    pNewExpr2 = sqlite3Expr(TK_LT, sqlite3ExprDup(pLeft), pStr2, 0);
    idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
    exprAnalyze(pSrc, pMaskSet, pWC, idxNew2);
    pTerm = &pWC->a[idxTerm];
    if( isComplete ){
      pWC->a[idxNew1].iParent = idxTerm;
      pWC->a[idxNew2].iParent = idxTerm;
      pTerm->nChild = 2;
    }
  }
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
}

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static void exprAnalyzeAll ( SrcList pTabList,
ExprMaskSet pMaskSet,
WhereClause pWC 
) [static]

Definition at line 459 of file where.c.

 {
  int i;
  for(i=pWC->nTerm-1; i>=0; i--){
    exprAnalyze(pTabList, pMaskSet, pWC, i);
  }
}

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static void exprCommute ( Expr pExpr) [static]

Definition at line 367 of file where.c.

                                    {
  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
  SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
  if( pExpr->op>=TK_GT ){
    assert( TK_LT==TK_GT+2 );
    assert( TK_GE==TK_LE+2 );
    assert( TK_GT>TK_EQ );
    assert( TK_GT<TK_LE );
    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
  }
}

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static Bitmask exprListTableUsage ( ExprMaskSet pMaskSet,
ExprList pList 
) [static]

Definition at line 321 of file where.c.

                                                                         {
  int i;
  Bitmask mask = 0;
  if( pList ){
    for(i=0; i<pList->nExpr; i++){
      mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
    }
  }
  return mask;
}

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static Bitmask exprSelectTableUsage ( ExprMaskSet pMaskSet,
Select pS 
) [static]

Definition at line 331 of file where.c.

                                                                      {
  Bitmask mask;
  if( pS==0 ){
    mask = 0;
  }else{
    mask = exprListTableUsage(pMaskSet, pS->pEList);
    mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
    mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
    mask |= exprTableUsage(pMaskSet, pS->pWhere);
    mask |= exprTableUsage(pMaskSet, pS->pHaving);
  }
  return mask;
}

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static Bitmask exprTableUsage ( ExprMaskSet pMaskSet,
Expr p 
) [static]

Definition at line 308 of file where.c.

                                                             {
  Bitmask mask = 0;
  if( p==0 ) return 0;
  if( p->op==TK_COLUMN ){
    mask = getMask(pMaskSet, p->iTable);
    return mask;
  }
  mask = exprTableUsage(pMaskSet, p->pRight);
  mask |= exprTableUsage(pMaskSet, p->pLeft);
  mask |= exprListTableUsage(pMaskSet, p->pList);
  mask |= exprSelectTableUsage(pMaskSet, p->pSelect);
  return mask;
}

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static WhereTerm* findTerm ( WhereClause pWC,
int  iCur,
int  iColumn,
Bitmask  notReady,
u16  op,
Index pIdx 
) [static]

Definition at line 407 of file where.c.

 {
  WhereTerm *pTerm;
  int k;
  for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
    if( pTerm->leftCursor==iCur
       && (pTerm->prereqRight & notReady)==0
       && pTerm->leftColumn==iColumn
       && (pTerm->eOperator & op)!=0
    ){
      if( iCur>=0 && pIdx ){
        Expr *pX = pTerm->pExpr;
        CollSeq *pColl;
        char idxaff;
        int j;
        Parse *pParse = pWC->pParse;

        idxaff = pIdx->pTable->aCol[iColumn].affinity;
        if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
        pColl = sqlite3ExprCollSeq(pParse, pX->pLeft);
        if( !pColl ){
          if( pX->pRight ){
            pColl = sqlite3ExprCollSeq(pParse, pX->pRight);
          }
          if( !pColl ){
            pColl = pParse->db->pDfltColl;
          }
        }
        for(j=0; j<pIdx->nColumn && pIdx->aiColumn[j]!=iColumn; j++){}
        assert( j<pIdx->nColumn );
        if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
      }
      return pTerm;
    }
  }
  return 0;
}

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static Bitmask getMask ( ExprMaskSet pMaskSet,
int  iCursor 
) [static]

Definition at line 269 of file where.c.

                                                          {
  int i;
  for(i=0; i<pMaskSet->n; i++){
    if( pMaskSet->ix[i]==iCursor ){
      return ((Bitmask)1)<<i;
    }
  }
  return 0;
}

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static int isLikeOrGlob ( sqlite3 db,
Expr pExpr,
int pnPattern,
int pisComplete 
) [static]

Definition at line 479 of file where.c.

 {
  const char *z;
  Expr *pRight, *pLeft;
  ExprList *pList;
  int c, cnt;
  int noCase;
  char wc[3];
  CollSeq *pColl;

  if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){
    return 0;
  }
  pList = pExpr->pList;
  pRight = pList->a[0].pExpr;
  if( pRight->op!=TK_STRING ){
    return 0;
  }
  pLeft = pList->a[1].pExpr;
  if( pLeft->op!=TK_COLUMN ){
    return 0;
  }
  pColl = pLeft->pColl;
  if( pColl==0 ){
    pColl = db->pDfltColl;
  }
  if( (pColl->type!=SQLITE_COLL_BINARY || noCase) &&
      (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){
    return 0;
  }
  sqlite3DequoteExpr(pRight);
  z = (char *)pRight->token.z;
  for(cnt=0; (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2]; cnt++){}
  if( cnt==0 || 255==(u8)z[cnt] ){
    return 0;
  }
  *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0;
  *pnPattern = cnt;
  return 1;
}

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static int isSortingIndex ( Parse pParse,
Index pIdx,
int  base,
ExprList pOrderBy,
int  nEqCol,
int pbRev 
) [static]

Definition at line 771 of file where.c.

 {
  int i, j;                       /* Loop counters */
  int sortOrder = 0;              /* XOR of index and ORDER BY sort direction */
  int nTerm;                      /* Number of ORDER BY terms */
  struct ExprList_item *pTerm;    /* A term of the ORDER BY clause */
  sqlite3 *db = pParse->db;

  assert( pOrderBy!=0 );
  nTerm = pOrderBy->nExpr;
  assert( nTerm>0 );

  /* Match terms of the ORDER BY clause against columns of
  ** the index.
  */
  for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<pIdx->nColumn; i++){
    Expr *pExpr;       /* The expression of the ORDER BY pTerm */
    CollSeq *pColl;    /* The collating sequence of pExpr */
    int termSortOrder; /* Sort order for this term */

    pExpr = pTerm->pExpr;
    if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
      /* Can not use an index sort on anything that is not a column in the
      ** left-most table of the FROM clause */
      return 0;
    }
    pColl = sqlite3ExprCollSeq(pParse, pExpr);
    if( !pColl ) pColl = db->pDfltColl;
    if( pExpr->iColumn!=pIdx->aiColumn[i] || 
        sqlite3StrICmp(pColl->zName, pIdx->azColl[i]) ){
      /* Term j of the ORDER BY clause does not match column i of the index */
      if( i<nEqCol ){
        /* If an index column that is constrained by == fails to match an
        ** ORDER BY term, that is OK.  Just ignore that column of the index
        */
        continue;
      }else{
        /* If an index column fails to match and is not constrained by ==
        ** then the index cannot satisfy the ORDER BY constraint.
        */
        return 0;
      }
    }
    assert( pIdx->aSortOrder!=0 );
    assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
    assert( pIdx->aSortOrder[i]==0 || pIdx->aSortOrder[i]==1 );
    termSortOrder = pIdx->aSortOrder[i] ^ pTerm->sortOrder;
    if( i>nEqCol ){
      if( termSortOrder!=sortOrder ){
        /* Indices can only be used if all ORDER BY terms past the
        ** equality constraints are all either DESC or ASC. */
        return 0;
      }
    }else{
      sortOrder = termSortOrder;
    }
    j++;
    pTerm++;
  }

  /* The index can be used for sorting if all terms of the ORDER BY clause
  ** are covered.
  */
  if( j>=nTerm ){
    *pbRev = sortOrder!=0;
    return 1;
  }
  return 0;
}

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static int operatorMask ( int  op) [static]

Definition at line 384 of file where.c.

                               {
  int c;
  assert( allowedOp(op) );
  if( op==TK_IN ){
    c = WO_IN;
  }else{
    c = WO_EQ<<(op-TK_EQ);
  }
  assert( op!=TK_IN || c==WO_IN );
  assert( op!=TK_EQ || c==WO_EQ );
  assert( op!=TK_LT || c==WO_LT );
  assert( op!=TK_LE || c==WO_LE );
  assert( op!=TK_GT || c==WO_GT );
  assert( op!=TK_GE || c==WO_GE );
  return c;
}

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static int sortableByRowid ( int  base,
ExprList pOrderBy,
int pbRev 
) [static]

Definition at line 852 of file where.c.

 {
  Expr *p;

  assert( pOrderBy!=0 );
  assert( pOrderBy->nExpr>0 );
  p = pOrderBy->a[0].pExpr;
  if( pOrderBy->nExpr==1 && p->op==TK_COLUMN && p->iTable==base
          && p->iColumn==-1 ){
    *pbRev = pOrderBy->a[0].sortOrder;
    return 1;
  }
  return 0;
}

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WhereInfo* sqlite3WhereBegin ( Parse pParse,
SrcList pTabList,
Expr pWhere,
ExprList **  ppOrderBy 
)

Definition at line 1419 of file where.c.

 {
  int i;                     /* Loop counter */
  WhereInfo *pWInfo;         /* Will become the return value of this function */
  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
  int brk, cont = 0;         /* Addresses used during code generation */
  Bitmask notReady;          /* Cursors that are not yet positioned */
  WhereTerm *pTerm;          /* A single term in the WHERE clause */
  ExprMaskSet maskSet;       /* The expression mask set */
  WhereClause wc;            /* The WHERE clause is divided into these terms */
  struct SrcList_item *pTabItem;  /* A single entry from pTabList */
  WhereLevel *pLevel;             /* A single level in the pWInfo list */
  int iFrom;                      /* First unused FROM clause element */
  int andFlags;              /* AND-ed combination of all wc.a[].flags */

  /* The number of tables in the FROM clause is limited by the number of
  ** bits in a Bitmask 
  */
  if( pTabList->nSrc>BMS ){
    sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
    return 0;
  }

  /* Split the WHERE clause into separate subexpressions where each
  ** subexpression is separated by an AND operator.
  */
  initMaskSet(&maskSet);
  whereClauseInit(&wc, pParse);
  whereSplit(&wc, pWhere, TK_AND);
    
  /* Allocate and initialize the WhereInfo structure that will become the
  ** return value.
  */
  pWInfo = sqliteMalloc( sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
  if( sqlite3MallocFailed() ){
    goto whereBeginNoMem;
  }
  pWInfo->pParse = pParse;
  pWInfo->pTabList = pTabList;
  pWInfo->iBreak = sqlite3VdbeMakeLabel(v);

  /* Special case: a WHERE clause that is constant.  Evaluate the
  ** expression and either jump over all of the code or fall thru.
  */
  if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstant(pWhere)) ){
    sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
    pWhere = 0;
  }

  /* Analyze all of the subexpressions.  Note that exprAnalyze() might
  ** add new virtual terms onto the end of the WHERE clause.  We do not
  ** want to analyze these virtual terms, so start analyzing at the end
  ** and work forward so that the added virtual terms are never processed.
  */
  for(i=0; i<pTabList->nSrc; i++){
    createMask(&maskSet, pTabList->a[i].iCursor);
  }
  exprAnalyzeAll(pTabList, &maskSet, &wc);
  if( sqlite3MallocFailed() ){
    goto whereBeginNoMem;
  }

  /* Chose the best index to use for each table in the FROM clause.
  **
  ** This loop fills in the following fields:
  **
  **   pWInfo->a[].pIdx      The index to use for this level of the loop.
  **   pWInfo->a[].flags     WHERE_xxx flags associated with pIdx
  **   pWInfo->a[].nEq       The number of == and IN constraints
  **   pWInfo->a[].iFrom     When term of the FROM clause is being coded
  **   pWInfo->a[].iTabCur   The VDBE cursor for the database table
  **   pWInfo->a[].iIdxCur   The VDBE cursor for the index
  **
  ** This loop also figures out the nesting order of tables in the FROM
  ** clause.
  */
  notReady = ~(Bitmask)0;
  pTabItem = pTabList->a;
  pLevel = pWInfo->a;
  andFlags = ~0;
  TRACE(("*** Optimizer Start ***\n"));
  for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
    Index *pIdx;                /* Index for FROM table at pTabItem */
    int flags;                  /* Flags asssociated with pIdx */
    int nEq;                    /* Number of == or IN constraints */
    double cost;                /* The cost for pIdx */
    int j;                      /* For looping over FROM tables */
    Index *pBest = 0;           /* The best index seen so far */
    int bestFlags = 0;          /* Flags associated with pBest */
    int bestNEq = 0;            /* nEq associated with pBest */
    double lowestCost;          /* Cost of the pBest */
    int bestJ = 0;              /* The value of j */
    Bitmask m;                  /* Bitmask value for j or bestJ */
    int once = 0;               /* True when first table is seen */

    lowestCost = SQLITE_BIG_DBL;
    for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
      if( once && 
          ((pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0
           || (j>0 && (pTabItem[-1].jointype & (JT_LEFT|JT_CROSS))!=0))
      ){
        break;
      }
      m = getMask(&maskSet, pTabItem->iCursor);
      if( (m & notReady)==0 ){
        if( j==iFrom ) iFrom++;
        continue;
      }
      cost = bestIndex(pParse, &wc, pTabItem, notReady,
                       (i==0 && ppOrderBy) ? *ppOrderBy : 0,
                       &pIdx, &flags, &nEq);
      if( cost<lowestCost ){
        once = 1;
        lowestCost = cost;
        pBest = pIdx;
        bestFlags = flags;
        bestNEq = nEq;
        bestJ = j;
      }
    }
    TRACE(("*** Optimizer choose table %d for loop %d\n", bestJ,
           pLevel-pWInfo->a));
    if( (bestFlags & WHERE_ORDERBY)!=0 ){
      *ppOrderBy = 0;
    }
    andFlags &= bestFlags;
    pLevel->flags = bestFlags;
    pLevel->pIdx = pBest;
    pLevel->nEq = bestNEq;
    pLevel->aInLoop = 0;
    pLevel->nIn = 0;
    if( pBest ){
      pLevel->iIdxCur = pParse->nTab++;
    }else{
      pLevel->iIdxCur = -1;
    }
    notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor);
    pLevel->iFrom = bestJ;
  }
  TRACE(("*** Optimizer Finished ***\n"));

  /* If the total query only selects a single row, then the ORDER BY
  ** clause is irrelevant.
  */
  if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
    *ppOrderBy = 0;
  }

  /* Open all tables in the pTabList and any indices selected for
  ** searching those tables.
  */
  sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
  pLevel = pWInfo->a;
  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
    Table *pTab;     /* Table to open */
    Index *pIx;      /* Index used to access pTab (if any) */
    int iDb;         /* Index of database containing table/index */
    int iIdxCur = pLevel->iIdxCur;

#ifndef SQLITE_OMIT_EXPLAIN
    if( pParse->explain==2 ){
      char *zMsg;
      struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
      zMsg = sqlite3MPrintf("TABLE %s", pItem->zName);
      if( pItem->zAlias ){
        zMsg = sqlite3MPrintf("%z AS %s", zMsg, pItem->zAlias);
      }
      if( (pIx = pLevel->pIdx)!=0 ){
        zMsg = sqlite3MPrintf("%z WITH INDEX %s", zMsg, pIx->zName);
      }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
        zMsg = sqlite3MPrintf("%z USING PRIMARY KEY", zMsg);
      }
      if( pLevel->flags & WHERE_ORDERBY ){
        zMsg = sqlite3MPrintf("%z ORDER BY", zMsg);
      }
      sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_DYNAMIC);
    }
#endif /* SQLITE_OMIT_EXPLAIN */
    pTabItem = &pTabList->a[pLevel->iFrom];
    pTab = pTabItem->pTab;
    iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
    if( pTab->isTransient || pTab->pSelect ) continue;
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead);
      if( pTab->nCol<(sizeof(Bitmask)*8) ){
        Bitmask b = pTabItem->colUsed;
        int n = 0;
        for(; b; b=b>>1, n++){}
        sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, n);
        assert( n<=pTab->nCol );
      }
    }else{
      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
    }
    pLevel->iTabCur = pTabItem->iCursor;
    if( (pIx = pLevel->pIdx)!=0 ){
      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
      assert( pIx->pSchema==pTab->pSchema );
      sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
      VdbeComment((v, "# %s", pIx->zName));
      sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
                     (char*)pKey, P3_KEYINFO_HANDOFF);
    }
    if( (pLevel->flags & WHERE_IDX_ONLY)!=0 ){
      sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
    }
    sqlite3CodeVerifySchema(pParse, iDb);
  }
  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);

  /* Generate the code to do the search.  Each iteration of the for
  ** loop below generates code for a single nested loop of the VM
  ** program.
  */
  notReady = ~(Bitmask)0;
  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
    int j;
    int iCur = pTabItem->iCursor;  /* The VDBE cursor for the table */
    Index *pIdx;       /* The index we will be using */
    int iIdxCur;       /* The VDBE cursor for the index */
    int omitTable;     /* True if we use the index only */
    int bRev;          /* True if we need to scan in reverse order */

    pTabItem = &pTabList->a[pLevel->iFrom];
    iCur = pTabItem->iCursor;
    pIdx = pLevel->pIdx;
    iIdxCur = pLevel->iIdxCur;
    bRev = (pLevel->flags & WHERE_REVERSE)!=0;
    omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;

    /* Create labels for the "break" and "continue" instructions
    ** for the current loop.  Jump to brk to break out of a loop.
    ** Jump to cont to go immediately to the next iteration of the
    ** loop.
    */
    brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
    cont = pLevel->cont = sqlite3VdbeMakeLabel(v);

    /* If this is the right table of a LEFT OUTER JOIN, allocate and
    ** initialize a memory cell that records if this table matches any
    ** row of the left table of the join.
    */
    if( pLevel->iFrom>0 && (pTabItem[-1].jointype & JT_LEFT)!=0 ){
      if( !pParse->nMem ) pParse->nMem++;
      pLevel->iLeftJoin = pParse->nMem++;
      sqlite3VdbeAddOp(v, OP_MemInt, 0, pLevel->iLeftJoin);
      VdbeComment((v, "# init LEFT JOIN no-match flag"));
    }

    if( pLevel->flags & WHERE_ROWID_EQ ){
      /* Case 1:  We can directly reference a single row using an
      **          equality comparison against the ROWID field.  Or
      **          we reference multiple rows using a "rowid IN (...)"
      **          construct.
      */
      pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
      assert( pTerm!=0 );
      assert( pTerm->pExpr!=0 );
      assert( pTerm->leftCursor==iCur );
      assert( omitTable==0 );
      codeEqualityTerm(pParse, pTerm, brk, pLevel);
      sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk);
      sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk);
      VdbeComment((v, "pk"));
      pLevel->op = OP_Noop;
    }else if( pLevel->flags & WHERE_ROWID_RANGE ){
      /* Case 2:  We have an inequality comparison against the ROWID field.
      */
      int testOp = OP_Noop;
      int start;
      WhereTerm *pStart, *pEnd;

      assert( omitTable==0 );
      pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
      pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0);
      if( bRev ){
        pTerm = pStart;
        pStart = pEnd;
        pEnd = pTerm;
      }
      if( pStart ){
        Expr *pX;
        pX = pStart->pExpr;
        assert( pX!=0 );
        assert( pStart->leftCursor==iCur );
        sqlite3ExprCode(pParse, pX->pRight);
        sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk);
        sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk);
        VdbeComment((v, "pk"));
        disableTerm(pLevel, pStart);
      }else{
        sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
      }
      if( pEnd ){
        Expr *pX;
        pX = pEnd->pExpr;
        assert( pX!=0 );
        assert( pEnd->leftCursor==iCur );
        sqlite3ExprCode(pParse, pX->pRight);
        pLevel->iMem = pParse->nMem++;
        sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
        if( pX->op==TK_LT || pX->op==TK_GT ){
          testOp = bRev ? OP_Le : OP_Ge;
        }else{
          testOp = bRev ? OP_Lt : OP_Gt;
        }
        disableTerm(pLevel, pEnd);
      }
      start = sqlite3VdbeCurrentAddr(v);
      pLevel->op = bRev ? OP_Prev : OP_Next;
      pLevel->p1 = iCur;
      pLevel->p2 = start;
      if( testOp!=OP_Noop ){
        sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
        sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC, brk);
      }
    }else if( pLevel->flags & WHERE_COLUMN_RANGE ){
      /* Case 3: The WHERE clause term that refers to the right-most
      **         column of the index is an inequality.  For example, if
      **         the index is on (x,y,z) and the WHERE clause is of the
      **         form "x=5 AND y<10" then this case is used.  Only the
      **         right-most column can be an inequality - the rest must
      **         use the "==" and "IN" operators.
      **
      **         This case is also used when there are no WHERE clause
      **         constraints but an index is selected anyway, in order
      **         to force the output order to conform to an ORDER BY.
      */
      int start;
      int nEq = pLevel->nEq;
      int topEq=0;        /* True if top limit uses ==. False is strictly < */
      int btmEq=0;        /* True if btm limit uses ==. False if strictly > */
      int topOp, btmOp;   /* Operators for the top and bottom search bounds */
      int testOp;
      int nNotNull;       /* Number of rows of index that must be non-NULL */
      int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
      int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;

      /* Generate code to evaluate all constraint terms using == or IN
      ** and level the values of those terms on the stack.
      */
      codeAllEqualityTerms(pParse, pLevel, &wc, notReady, brk);

      /* Duplicate the equality term values because they will all be
      ** used twice: once to make the termination key and once to make the
      ** start key.
      */
      for(j=0; j<nEq; j++){
        sqlite3VdbeAddOp(v, OP_Dup, nEq-1, 0);
      }

      /* Figure out what comparison operators to use for top and bottom 
      ** search bounds. For an ascending index, the bottom bound is a > or >=
      ** operator and the top bound is a < or <= operator.  For a descending
      ** index the operators are reversed.
      */
      nNotNull = nEq + topLimit;
      if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){
        topOp = WO_LT|WO_LE;
        btmOp = WO_GT|WO_GE;
      }else{
        topOp = WO_GT|WO_GE;
        btmOp = WO_LT|WO_LE;
        SWAP(int, topLimit, btmLimit);
      }

      /* Generate the termination key.  This is the key value that
      ** will end the search.  There is no termination key if there
      ** are no equality terms and no "X<..." term.
      **
      ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
      ** key computed here really ends up being the start key.
      */
      if( topLimit ){
        Expr *pX;
        int k = pIdx->aiColumn[j];
        pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx);
        assert( pTerm!=0 );
        pX = pTerm->pExpr;
        assert( (pTerm->flags & TERM_CODED)==0 );
        sqlite3ExprCode(pParse, pX->pRight);
        topEq = pTerm->eOperator & (WO_LE|WO_GE);
        disableTerm(pLevel, pTerm);
        testOp = OP_IdxGE;
      }else{
        testOp = nEq>0 ? OP_IdxGE : OP_Noop;
        topEq = 1;
      }
      if( testOp!=OP_Noop ){
        int nCol = nEq + topLimit;
        pLevel->iMem = pParse->nMem++;
        buildIndexProbe(v, nCol, nEq, brk, pIdx);
        if( bRev ){
          int op = topEq ? OP_MoveLe : OP_MoveLt;
          sqlite3VdbeAddOp(v, op, iIdxCur, brk);
        }else{
          sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
        }
      }else if( bRev ){
        sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk);
      }

      /* Generate the start key.  This is the key that defines the lower
      ** bound on the search.  There is no start key if there are no
      ** equality terms and if there is no "X>..." term.  In
      ** that case, generate a "Rewind" instruction in place of the
      ** start key search.
      **
      ** 2002-Dec-04: In the case of a reverse-order search, the so-called
      ** "start" key really ends up being used as the termination key.
      */
      if( btmLimit ){
        Expr *pX;
        int k = pIdx->aiColumn[j];
        pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx);
        assert( pTerm!=0 );
        pX = pTerm->pExpr;
        assert( (pTerm->flags & TERM_CODED)==0 );
        sqlite3ExprCode(pParse, pX->pRight);
        btmEq = pTerm->eOperator & (WO_LE|WO_GE);
        disableTerm(pLevel, pTerm);
      }else{
        btmEq = 1;
      }
      if( nEq>0 || btmLimit ){
        int nCol = nEq + btmLimit;
        buildIndexProbe(v, nCol, 0, brk, pIdx);
        if( bRev ){
          pLevel->iMem = pParse->nMem++;
          sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
          testOp = OP_IdxLT;
        }else{
          int op = btmEq ? OP_MoveGe : OP_MoveGt;
          sqlite3VdbeAddOp(v, op, iIdxCur, brk);
        }
      }else if( bRev ){
        testOp = OP_Noop;
      }else{
        sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk);
      }

      /* Generate the the top of the loop.  If there is a termination
      ** key we have to test for that key and abort at the top of the
      ** loop.
      */
      start = sqlite3VdbeCurrentAddr(v);
      if( testOp!=OP_Noop ){
        sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, testOp, iIdxCur, brk);
        if( (topEq && !bRev) || (!btmEq && bRev) ){
          sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
        }
      }
      sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0);
      sqlite3VdbeAddOp(v, OP_IdxIsNull, nNotNull, cont);
      if( !omitTable ){
        sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
        sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
      }

      /* Record the instruction used to terminate the loop.
      */
      pLevel->op = bRev ? OP_Prev : OP_Next;
      pLevel->p1 = iIdxCur;
      pLevel->p2 = start;
    }else if( pLevel->flags & WHERE_COLUMN_EQ ){
      /* Case 4:  There is an index and all terms of the WHERE clause that
      **          refer to the index using the "==" or "IN" operators.
      */
      int start;
      int nEq = pLevel->nEq;

      /* Generate code to evaluate all constraint terms using == or IN
      ** and leave the values of those terms on the stack.
      */
      codeAllEqualityTerms(pParse, pLevel, &wc, notReady, brk);

      /* Generate a single key that will be used to both start and terminate
      ** the search
      */
      buildIndexProbe(v, nEq, 0, brk, pIdx);
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);

      /* Generate code (1) to move to the first matching element of the table.
      ** Then generate code (2) that jumps to "brk" after the cursor is past
      ** the last matching element of the table.  The code (1) is executed
      ** once to initialize the search, the code (2) is executed before each
      ** iteration of the scan to see if the scan has finished. */
      if( bRev ){
        /* Scan in reverse order */
        sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, brk);
        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, brk);
        pLevel->op = OP_Prev;
      }else{
        /* Scan in the forward order */
        sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, brk);
        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, brk, "+", P3_STATIC);
        pLevel->op = OP_Next;
      }
      sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0);
      sqlite3VdbeAddOp(v, OP_IdxIsNull, nEq, cont);
      if( !omitTable ){
        sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
        sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
      }
      pLevel->p1 = iIdxCur;
      pLevel->p2 = start;
    }else{
      /* Case 5:  There is no usable index.  We must do a complete
      **          scan of the entire table.
      */
      assert( omitTable==0 );
      assert( bRev==0 );
      pLevel->op = OP_Next;
      pLevel->p1 = iCur;
      pLevel->p2 = 1 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk);
    }
    notReady &= ~getMask(&maskSet, iCur);

    /* Insert code to test every subexpression that can be completely
    ** computed using the current set of tables.
    */
    for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
      Expr *pE;
      if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & notReady)!=0 ) continue;
      pE = pTerm->pExpr;
      assert( pE!=0 );
      if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
        continue;
      }
      sqlite3ExprIfFalse(pParse, pE, cont, 1);
      pTerm->flags |= TERM_CODED;
    }

    /* For a LEFT OUTER JOIN, generate code that will record the fact that
    ** at least one row of the right table has matched the left table.  
    */
    if( pLevel->iLeftJoin ){
      pLevel->top = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin);
      VdbeComment((v, "# record LEFT JOIN hit"));
      for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
        if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
        if( (pTerm->prereqAll & notReady)!=0 ) continue;
        assert( pTerm->pExpr );
        sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1);
        pTerm->flags |= TERM_CODED;
      }
    }
  }

#ifdef SQLITE_TEST  /* For testing and debugging use only */
  /* Record in the query plan information about the current table
  ** and the index used to access it (if any).  If the table itself
  ** is not used, its name is just '{}'.  If no index is used
  ** the index is listed as "{}".  If the primary key is used the
  ** index name is '*'.
  */
  for(i=0; i<pTabList->nSrc; i++){
    char *z;
    int n;
    pLevel = &pWInfo->a[i];
    pTabItem = &pTabList->a[pLevel->iFrom];
    z = pTabItem->zAlias;
    if( z==0 ) z = pTabItem->pTab->zName;
    n = strlen(z);
    if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
      if( pLevel->flags & WHERE_IDX_ONLY ){
        strcpy(&sqlite3_query_plan[nQPlan], "{}");
        nQPlan += 2;
      }else{
        strcpy(&sqlite3_query_plan[nQPlan], z);
        nQPlan += n;
      }
      sqlite3_query_plan[nQPlan++] = ' ';
    }
    if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
      strcpy(&sqlite3_query_plan[nQPlan], "* ");
      nQPlan += 2;
    }else if( pLevel->pIdx==0 ){
      strcpy(&sqlite3_query_plan[nQPlan], "{} ");
      nQPlan += 3;
    }else{
      n = strlen(pLevel->pIdx->zName);
      if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
        strcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName);
        nQPlan += n;
        sqlite3_query_plan[nQPlan++] = ' ';
      }
    }
  }
  while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
    sqlite3_query_plan[--nQPlan] = 0;
  }
  sqlite3_query_plan[nQPlan] = 0;
  nQPlan = 0;
#endif /* SQLITE_TEST // Testing and debugging use only */

  /* Record the continuation address in the WhereInfo structure.  Then
  ** clean up and return.
  */
  pWInfo->iContinue = cont;
  whereClauseClear(&wc);
  return pWInfo;

  /* Jump here if malloc fails */
whereBeginNoMem:
  whereClauseClear(&wc);
  sqliteFree(pWInfo);
  return 0;
}

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Definition at line 2043 of file where.c.

                                       {
  Vdbe *v = pWInfo->pParse->pVdbe;
  int i;
  WhereLevel *pLevel;
  SrcList *pTabList = pWInfo->pTabList;

  /* Generate loop termination code.
  */
  for(i=pTabList->nSrc-1; i>=0; i--){
    pLevel = &pWInfo->a[i];
    sqlite3VdbeResolveLabel(v, pLevel->cont);
    if( pLevel->op!=OP_Noop ){
      sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
    }
    sqlite3VdbeResolveLabel(v, pLevel->brk);
    if( pLevel->nIn ){
      int *a;
      int j;
      for(j=pLevel->nIn, a=&pLevel->aInLoop[j*2-2]; j>0; j--, a-=2){
        sqlite3VdbeAddOp(v, OP_Next, a[0], a[1]);
        sqlite3VdbeJumpHere(v, a[1]-1);
      }
      sqliteFree(pLevel->aInLoop);
    }
    if( pLevel->iLeftJoin ){
      int addr;
      addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0);
      sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
      if( pLevel->iIdxCur>=0 ){
        sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0);
      }
      sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top);
      sqlite3VdbeJumpHere(v, addr);
    }
  }

  /* The "break" point is here, just past the end of the outer loop.
  ** Set it.
  */
  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);

  /* Close all of the cursors that were opened by sqlite3WhereBegin.
  */
  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
    struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
    Table *pTab = pTabItem->pTab;
    assert( pTab!=0 );
    if( pTab->isTransient || pTab->pSelect ) continue;
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
    }
    if( pLevel->pIdx!=0 ){
      sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
    }

    /* Make cursor substitutions for cases where we want to use
    ** just the index and never reference the table.
    ** 
    ** Calls to the code generator in between sqlite3WhereBegin and
    ** sqlite3WhereEnd will have created code that references the table
    ** directly.  This loop scans all that code looking for opcodes
    ** that reference the table and converts them into opcodes that
    ** reference the index.
    */
    if( pLevel->flags & WHERE_IDX_ONLY ){
      int k, j, last;
      VdbeOp *pOp;
      Index *pIdx = pLevel->pIdx;

      assert( pIdx!=0 );
      pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
      last = sqlite3VdbeCurrentAddr(v);
      for(k=pWInfo->iTop; k<last; k++, pOp++){
        if( pOp->p1!=pLevel->iTabCur ) continue;
        if( pOp->opcode==OP_Column ){
          pOp->p1 = pLevel->iIdxCur;
          for(j=0; j<pIdx->nColumn; j++){
            if( pOp->p2==pIdx->aiColumn[j] ){
              pOp->p2 = j;
              break;
            }
          }
        }else if( pOp->opcode==OP_Rowid ){
          pOp->p1 = pLevel->iIdxCur;
          pOp->opcode = OP_IdxRowid;
        }else if( pOp->opcode==OP_NullRow ){
          pOp->opcode = OP_Noop;
        }
      }
    }
  }

  /* Final cleanup
  */
  sqliteFree(pWInfo);
  return;
}

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static void transferJoinMarkings ( Expr pDerived,
Expr pBase 
) [static]

Definition at line 529 of file where.c.

                                                             {
  pDerived->flags |= pBase->flags & EP_FromJoin;
  pDerived->iRightJoinTable = pBase->iRightJoinTable;
}

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static void whereClauseClear ( WhereClause pWC) [static]

Definition at line 189 of file where.c.

                                              {
  int i;
  WhereTerm *a;
  for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
    if( a->flags & TERM_DYNAMIC ){
      sqlite3ExprDelete(a->pExpr);
    }
  }
  if( pWC->a!=pWC->aStatic ){
    sqliteFree(pWC->a);
  }
}

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static void whereClauseInit ( WhereClause pWC,
Parse pParse 
) [static]

Definition at line 178 of file where.c.

                                                            {
  pWC->pParse = pParse;
  pWC->nTerm = 0;
  pWC->nSlot = ARRAYSIZE(pWC->aStatic);
  pWC->a = pWC->aStatic;
}

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static int whereClauseInsert ( WhereClause pWC,
Expr p,
int  flags 
) [static]

Definition at line 211 of file where.c.

                                                                  {
  WhereTerm *pTerm;
  int idx;
  if( pWC->nTerm>=pWC->nSlot ){
    WhereTerm *pOld = pWC->a;
    pWC->a = sqliteMalloc( sizeof(pWC->a[0])*pWC->nSlot*2 );
    if( pWC->a==0 ) return 0;
    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
    if( pOld!=pWC->aStatic ){
      sqliteFree(pOld);
    }
    pWC->nSlot *= 2;
  }
  pTerm = &pWC->a[idx = pWC->nTerm];
  pWC->nTerm++;
  pTerm->pExpr = p;
  pTerm->flags = flags;
  pTerm->pWC = pWC;
  pTerm->iParent = -1;
  return idx;
}

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static void whereSplit ( WhereClause pWC,
Expr pExpr,
int  op 
) [static]

Definition at line 250 of file where.c.

                                                             {
  if( pExpr==0 ) return;
  if( pExpr->op!=op ){
    whereClauseInsert(pWC, pExpr, 0);
  }else{
    whereSplit(pWC, pExpr->pLeft, op);
    whereSplit(pWC, pExpr->pRight, op);
  }
}

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