#else
#  define TERM_VNULL    0x00   /* Disabled if not using stat3 */
#endif

/*
** An instance of the following structure holds all information about a
** WHERE clause.  Mostly this is a container for one or more WhereTerms.








*/
struct WhereClause {
  Parse *pParse;           /* The parser context */
  WhereMaskSet *pMaskSet;  /* Mapping of table cursor numbers to bitmasks */
  Bitmask vmask;           /* Bitmask identifying virtual table cursors */

  u8 op;                   /* Split operator.  TK_AND or TK_OR */
  int nTerm;               /* Number of terms */
  int nSlot;               /* Number of entries in a[] */
  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
#if defined(SQLITE_SMALL_STACK)
  WhereTerm aStatic[1];    /* Initial static space for a[] */
#else
................................................................................
static void whereClauseInit(
  WhereClause *pWC,        /* The WhereClause to be initialized */
  Parse *pParse,           /* The parsing context */
  WhereMaskSet *pMaskSet   /* Mapping from table cursor numbers to bitmasks */
){
  pWC->pParse = pParse;
  pWC->pMaskSet = pMaskSet;

  pWC->nTerm = 0;
  pWC->nSlot = ArraySize(pWC->aStatic);
  pWC->a = pWC->aStatic;
  pWC->vmask = 0;
}

/* Forward reference */
................................................................................
  u32 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
){
  WhereTerm *pTerm;
  int k;
  assert( iCur>=0 );
  op &= WO_ALL;

  for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
    if( pTerm->leftCursor==iCur
       && (pTerm->prereqRight & notReady)==0
       && pTerm->u.leftColumn==iColumn
       && (pTerm->eOperator & op)!=0
    ){
      if( pIdx && pTerm->eOperator!=WO_ISNULL ){
        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;

        /* Figure out the collation sequence required from an index for
        ** it to be useful for optimising expression pX. Store this
        ** value in variable pColl.
        */
        assert(pX->pLeft);
        pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
        assert(pColl || pParse->nErr);

        for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
          if( NEVER(j>=pIdx->nColumn) ) return 0;
        }
        if( pColl && sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
      }
      return pTerm;

    }
  }
  return 0;
}

/* Forward reference */
static void exprAnalyze(SrcList*, WhereClause*, int);
................................................................................
        pOrTerm->u.pAndInfo = pAndInfo;
        pOrTerm->wtFlags |= TERM_ANDINFO;
        pOrTerm->eOperator = WO_AND;
        pAndWC = &pAndInfo->wc;
        whereClauseInit(pAndWC, pWC->pParse, pMaskSet);
        whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
        exprAnalyzeAll(pSrc, pAndWC);

        testcase( db->mallocFailed );
        if( !db->mallocFailed ){
          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
            assert( pAndTerm->pExpr );
            if( allowedOp(pAndTerm->pExpr->op) ){
              b |= getMask(pMaskSet, pAndTerm->leftCursor);
            }
................................................................................
        if( pOrTerm->eOperator==WO_AND ){
          WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
          bestIndex(pParse, pAndWC, pSrc, notReady, notValid, 0, &sTermCost);
        }else if( pOrTerm->leftCursor==iCur ){
          WhereClause tempWC;
          tempWC.pParse = pWC->pParse;
          tempWC.pMaskSet = pWC->pMaskSet;

          tempWC.op = TK_AND;
          tempWC.a = pOrTerm;
          tempWC.nTerm = 1;
          bestIndex(pParse, &tempWC, pSrc, notReady, notValid, 0, &sTermCost);
        }else{
          continue;
        }
................................................................................
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
  int iLevel,          /* Which level of pWInfo->a[] should be coded */
  u16 wctrlFlags,      /* One of the WHERE_* flags defined in sqliteInt.h */
  Bitmask notReady     /* Which tables are currently available */

){
  int j, k;            /* Loop counters */
  int iCur;            /* The VDBE cursor for the table */
  int addrNxt;         /* Where to jump to continue with the next IN case */
  int omitTable;       /* True if we use the index only */
  int bRev;            /* True if we need to scan in reverse order */
  WhereLevel *pLevel;  /* The where level to be coded */
................................................................................

    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
    int regRowset = 0;                        /* Register for RowSet object */
    int regRowid = 0;                         /* Register holding rowid */
    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
    int iRetInit;                             /* Address of regReturn init */
    int untestedTerms = 0;             /* Some terms not completely tested */
    int ii;

   
    pTerm = pLevel->plan.u.pTerm;
    assert( pTerm!=0 );
    assert( pTerm->eOperator==WO_OR );
    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
    pOrWc = &pTerm->u.pOrInfo->wc;
    pLevel->op = OP_Return;
................................................................................
    */
    if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
      regRowset = ++pParse->nMem;
      regRowid = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
    }
    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);











    for(ii=0; ii<pOrWc->nTerm; ii++){
      WhereTerm *pOrTerm = &pOrWc->a[ii];
      if( pOrTerm->leftCursor==iCur || pOrTerm->eOperator==WO_AND ){
        WhereInfo *pSubWInfo;          /* Info for single OR-term scan */





        /* Loop through table entries that match term pOrTerm. */
        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrTerm->pExpr, 0, 0,
                        WHERE_OMIT_OPEN | WHERE_OMIT_CLOSE |
                        WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY);
        if( pSubWInfo ){
          explainOneScan(
              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
          );
          if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
................................................................................
          if( pSubWInfo->untestedTerms ) untestedTerms = 1;

          /* Finish the loop through table entries that match term pOrTerm. */
          sqlite3WhereEnd(pSubWInfo);
        }
      }
    }

    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
    sqlite3VdbeResolveLabel(v, iLoopBody);

    if( pWInfo->nLevel>1 ) sqlite3StackFree(pParse->db, pOrTab);
    if( !untestedTerms ) disableTerm(pLevel, pTerm);
  }else
................................................................................
  ** loop below generates code for a single nested loop of the VM
  ** program.
  */
  notReady = ~(Bitmask)0;
  for(i=0; i<nTabList; i++){
    pLevel = &pWInfo->a[i];
    explainOneScan(pParse, pTabList, pLevel, i, pLevel->iFrom, wctrlFlags);
    notReady = codeOneLoopStart(pWInfo, i, wctrlFlags, notReady);
    pWInfo->iContinue = pLevel->addrCont;
  }

#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

#else
#  define TERM_VNULL    0x00   /* Disabled if not using stat3 */
#endif

/*
** An instance of the following structure holds all information about a
** WHERE clause.  Mostly this is a container for one or more WhereTerms.
**
** Explanation of pOuter:  For a WHERE clause of the form
**
**           a AND ((b AND c) OR (d AND e)) AND f
**
** There are separate WhereClause objects for the whole clause and for
** the subclauses "(b AND c)" and "(d AND e)".  The pOuter field of the
** subclauses points to the WhereClause object for the whole clause.
*/
struct WhereClause {
  Parse *pParse;           /* The parser context */
  WhereMaskSet *pMaskSet;  /* Mapping of table cursor numbers to bitmasks */
  Bitmask vmask;           /* Bitmask identifying virtual table cursors */
  WhereClause *pOuter;     /* Outer conjunction */
  u8 op;                   /* Split operator.  TK_AND or TK_OR */
  int nTerm;               /* Number of terms */
  int nSlot;               /* Number of entries in a[] */
  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
#if defined(SQLITE_SMALL_STACK)
  WhereTerm aStatic[1];    /* Initial static space for a[] */
#else
................................................................................
static void whereClauseInit(
  WhereClause *pWC,        /* The WhereClause to be initialized */
  Parse *pParse,           /* The parsing context */
  WhereMaskSet *pMaskSet   /* Mapping from table cursor numbers to bitmasks */
){
  pWC->pParse = pParse;
  pWC->pMaskSet = pMaskSet;
  pWC->pOuter = 0;
  pWC->nTerm = 0;
  pWC->nSlot = ArraySize(pWC->aStatic);
  pWC->a = pWC->aStatic;
  pWC->vmask = 0;
}

/* Forward reference */
................................................................................
  u32 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
){
  WhereTerm *pTerm;
  int k;
  assert( iCur>=0 );
  op &= WO_ALL;
  for(; pWC; pWC=pWC->pOuter){
    for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
      if( pTerm->leftCursor==iCur
         && (pTerm->prereqRight & notReady)==0
         && pTerm->u.leftColumn==iColumn
         && (pTerm->eOperator & op)!=0
      ){
        if( pIdx && pTerm->eOperator!=WO_ISNULL ){
          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;
  
          /* Figure out the collation sequence required from an index for
          ** it to be useful for optimising expression pX. Store this
          ** value in variable pColl.
          */
          assert(pX->pLeft);
          pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
          assert(pColl || pParse->nErr);
  
          for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
            if( NEVER(j>=pIdx->nColumn) ) return 0;
          }
          if( pColl && sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
        }
        return pTerm;
      }
    }
  }
  return 0;
}

/* Forward reference */
static void exprAnalyze(SrcList*, WhereClause*, int);
................................................................................
        pOrTerm->u.pAndInfo = pAndInfo;
        pOrTerm->wtFlags |= TERM_ANDINFO;
        pOrTerm->eOperator = WO_AND;
        pAndWC = &pAndInfo->wc;
        whereClauseInit(pAndWC, pWC->pParse, pMaskSet);
        whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
        exprAnalyzeAll(pSrc, pAndWC);
        pAndWC->pOuter = pWC;
        testcase( db->mallocFailed );
        if( !db->mallocFailed ){
          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
            assert( pAndTerm->pExpr );
            if( allowedOp(pAndTerm->pExpr->op) ){
              b |= getMask(pMaskSet, pAndTerm->leftCursor);
            }
................................................................................
        if( pOrTerm->eOperator==WO_AND ){
          WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
          bestIndex(pParse, pAndWC, pSrc, notReady, notValid, 0, &sTermCost);
        }else if( pOrTerm->leftCursor==iCur ){
          WhereClause tempWC;
          tempWC.pParse = pWC->pParse;
          tempWC.pMaskSet = pWC->pMaskSet;
          tempWC.pOuter = pWC;
          tempWC.op = TK_AND;
          tempWC.a = pOrTerm;
          tempWC.nTerm = 1;
          bestIndex(pParse, &tempWC, pSrc, notReady, notValid, 0, &sTermCost);
        }else{
          continue;
        }
................................................................................
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
  int iLevel,          /* Which level of pWInfo->a[] should be coded */
  u16 wctrlFlags,      /* One of the WHERE_* flags defined in sqliteInt.h */
  Bitmask notReady,    /* Which tables are currently available */
  Expr *pWhere         /* Complete WHERE clause */
){
  int j, k;            /* Loop counters */
  int iCur;            /* The VDBE cursor for the table */
  int addrNxt;         /* Where to jump to continue with the next IN case */
  int omitTable;       /* True if we use the index only */
  int bRev;            /* True if we need to scan in reverse order */
  WhereLevel *pLevel;  /* The where level to be coded */
................................................................................

    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
    int regRowset = 0;                        /* Register for RowSet object */
    int regRowid = 0;                         /* Register holding rowid */
    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
    int iRetInit;                             /* Address of regReturn init */
    int untestedTerms = 0;             /* Some terms not completely tested */
    int ii;                            /* Loop counter */
    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
   
    pTerm = pLevel->plan.u.pTerm;
    assert( pTerm!=0 );
    assert( pTerm->eOperator==WO_OR );
    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
    pOrWc = &pTerm->u.pOrInfo->wc;
    pLevel->op = OP_Return;
................................................................................
    */
    if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
      regRowset = ++pParse->nMem;
      regRowid = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
    }
    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);

    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
    ** Then for every term xN, evaluate as the subexpression: xN AND z
    ** That way, terms in y that are factored into the disjunction will
    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
    */
    if( pWC->nTerm>1 ){
      pAndExpr = sqlite3ExprAlloc(pParse->db, TK_AND, 0, 0);
      pAndExpr->pRight = pWhere;
    }

    for(ii=0; ii<pOrWc->nTerm; ii++){
      WhereTerm *pOrTerm = &pOrWc->a[ii];
      if( pOrTerm->leftCursor==iCur || pOrTerm->eOperator==WO_AND ){
        WhereInfo *pSubWInfo;          /* Info for single OR-term scan */
        Expr *pOrExpr = pOrTerm->pExpr;
        if( pAndExpr ){
          pAndExpr->pLeft = pOrExpr;
          pOrExpr = pAndExpr;
        }
        /* Loop through table entries that match term pOrTerm. */
        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
                        WHERE_OMIT_OPEN | WHERE_OMIT_CLOSE |
                        WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY);
        if( pSubWInfo ){
          explainOneScan(
              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
          );
          if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
................................................................................
          if( pSubWInfo->untestedTerms ) untestedTerms = 1;

          /* Finish the loop through table entries that match term pOrTerm. */
          sqlite3WhereEnd(pSubWInfo);
        }
      }
    }
    sqlite3DbFree(pParse->db, pAndExpr);
    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
    sqlite3VdbeResolveLabel(v, iLoopBody);

    if( pWInfo->nLevel>1 ) sqlite3StackFree(pParse->db, pOrTab);
    if( !untestedTerms ) disableTerm(pLevel, pTerm);
  }else
................................................................................
  ** loop below generates code for a single nested loop of the VM
  ** program.
  */
  notReady = ~(Bitmask)0;
  for(i=0; i<nTabList; i++){
    pLevel = &pWInfo->a[i];
    explainOneScan(pParse, pTabList, pLevel, i, pLevel->iFrom, wctrlFlags);
    notReady = codeOneLoopStart(pWInfo, i, wctrlFlags, notReady, pWhere);
    pWInfo->iContinue = pLevel->addrCont;
  }

#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