Fossil

**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.7.16"
#define SQLITE_VERSION_NUMBER 3007016
#define SQLITE_SOURCE_ID      "2013-01-17 17:20:49 38852f158ab20bb4d7b264af987ec1538052bec3"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version, sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros

/*
** A convenience macro that returns the number of elements in
** an array.
*/
#define ArraySize(X)    ((int)(sizeof(X)/sizeof(X[0])))

/*
** Determine if the argument is a power of two
*/
#define IsPowerOfTwo(X) (((X)&((X)-1))==0)

/*
** The following value as a destructor means to use sqlite3DbFree().
** The sqlite3DbFree() routine requires two parameters instead of the 
** one parameter that destructors normally want.  So we have to introduce 
** this magic value that the code knows to handle differently.  Any 
** pointer will work here as long as it is distinct from SQLITE_STATIC
** and SQLITE_TRANSIENT.

#define SQLITE_GroupByOrder   0x0004   /* GROUPBY cover of ORDERBY */
#define SQLITE_FactorOutConst 0x0008   /* Constant factoring */
#define SQLITE_IdxRealAsInt   0x0010   /* Store REAL as INT in indices */
#define SQLITE_DistinctOpt    0x0020   /* DISTINCT using indexes */
#define SQLITE_CoverIdxScan   0x0040   /* Covering index scans */
#define SQLITE_OrderByIdxJoin 0x0080   /* ORDER BY of joins via index */
#define SQLITE_SubqCoroutine  0x0100   /* Evaluate subqueries as coroutines */
#define SQLITE_Transitive     0x0200   /* Transitive constraints */
#define SQLITE_AllOpts        0xffff   /* All optimizations */

/*
** Macros for testing whether or not optimizations are enabled or disabled.
*/
#ifndef SQLITE_OMIT_BUILTIN_TEST
#define OptimizationDisabled(db, mask)  (((db)->dbOptFlags&(mask))!=0)

      sqlite3_key(db, zKey, i/2);
    }else{
      sqlite3_rekey(db, zKey, i/2);
    }
  }else
#endif
#if defined(SQLITE_HAS_CODEC) || defined(SQLITE_ENABLE_CEROD)
  if( sqlite3StrICmp(zLeft, "activate_extensions")==0 && zRight ){
#ifdef SQLITE_HAS_CODEC
    if( sqlite3StrNICmp(zRight, "see-", 4)==0 ){
      sqlite3_activate_see(&zRight[4]);
    }
#endif
#ifdef SQLITE_ENABLE_CEROD
    if( sqlite3StrNICmp(zRight, "cerod-", 6)==0 ){

typedef struct WhereTerm WhereTerm;
struct WhereTerm {
  Expr *pExpr;            /* Pointer to the subexpression that is this term */
  int iParent;            /* Disable pWC->a[iParent] when this term disabled */
  int leftCursor;         /* Cursor number of X in "X <op> <expr>" */
  union {
    int leftColumn;         /* Column number of X in "X <op> <expr>" */
    WhereOrInfo *pOrInfo;   /* Extra information if (eOperator & WO_OR)!=0 */
    WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */
  } u;
  u16 eOperator;          /* A WO_xx value describing <op> */
  u8 wtFlags;             /* TERM_xxx bit flags.  See below */
  u8 nChild;              /* Number of children that must disable us */
  WhereClause *pWC;       /* The clause this term is part of */
  Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
  Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */

#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 WO_MATCH  0x040
#define WO_ISNULL 0x080
#define WO_OR     0x100       /* Two or more OR-connected terms */
#define WO_AND    0x200       /* Two or more AND-connected terms */
#define WO_EQUIV  0x400       /* Of the form A==B, both columns */
#define WO_NOOP   0x800       /* This term does not restrict search space */

#define WO_ALL    0xfff       /* Mask of all possible WO_* values */
#define WO_SINGLE 0x0ff       /* Mask of all non-compound WO_* values */

/*
** Value for wsFlags returned by bestIndex() and stored in

}

/*
** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
** where X is a reference to the iColumn of table iCur and <op> is one of
** the WO_xx operator codes specified by the op parameter.
** Return a pointer to the term.  Return 0 if not found.
**
** The term returned might by Y=<expr> if there is another constraint in
** the WHERE clause that specifies that X=Y.  Any such constraints will be
** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
** aEquiv[] array holds X and all its equivalents, with each SQL variable
** taking up two slots in aEquiv[].  The first slot is for the cursor number
** and the second is for the column number.  There are 22 slots in aEquiv[]
** so that means we can look for X plus up to 10 other equivalent values.
** Hence a search for X will return <expr> if X=A1 and A1=A2 and A2=A3
** and ... and A9=A10 and A10=<expr>.
**
** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
** then try for the one with no dependencies on <expr> - in other words where
** <expr> is a constant expression of some kind.  Only return entries of
** the form "X <op> Y" where Y is a column in another table if no terms of
** the form "X <op> <const-expr>" exist.  Other than this priority, if there
** are two or more terms that match, then the choice of which term to return
** is arbitrary.
*/
static WhereTerm *findTerm(
  WhereClause *pWC,     /* The WHERE clause to be searched */
  int iCur,             /* Cursor number of LHS */
  int iColumn,          /* Column number of LHS */
  Bitmask notReady,     /* RHS must not overlap with this mask */
  u32 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
){
  WhereTerm *pTerm;            /* Term being examined as possible result */
  WhereTerm *pResult = 0;      /* The answer to return */
  WhereClause *pWCOrig = pWC;  /* Original pWC value */
  int j, k;                    /* Loop counters */
  Expr *pX;                /* Pointer to an expression */
  Parse *pParse;           /* Parsing context */
  int iOrigCol = iColumn;  /* Original value of iColumn */
  int nEquiv = 2;          /* Number of entires in aEquiv[] */
  int iEquiv = 2;          /* Number of entries of aEquiv[] processed so far */
  int aEquiv[22];          /* iCur,iColumn and up to 10 other equivalents */

  assert( iCur>=0 );
  aEquiv[0] = iCur;
  aEquiv[1] = iColumn;
  for(;;){
    for(pWC=pWCOrig; pWC; pWC=pWC->pOuter){
      for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
        if( pTerm->leftCursor==iCur

          && pTerm->u.leftColumn==iColumn
        ){
          if( (pTerm->prereqRight & notReady)==0
           && (pTerm->eOperator & op & WO_ALL)!=0
          ){
            if( iOrigCol>=0 && pIdx && (pTerm->eOperator & WO_ISNULL)==0 ){

              CollSeq *pColl;
              char idxaff;
      
              pX = pTerm->pExpr;
              pParse = pWC->pParse;

              idxaff = pIdx->pTable->aCol[iOrigCol].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);
              if( pColl==0 ) pColl = pParse->db->pDfltColl;
      
              for(j=0; pIdx->aiColumn[j]!=iOrigCol; j++){
                if( NEVER(j>=pIdx->nColumn) ) return 0;
              }
              if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ){
                continue;
              }
            }
            pResult = pTerm;
            if( pTerm->prereqRight==0 ) goto findTerm_success;
          }
          if( (pTerm->eOperator & WO_EQUIV)!=0
           && nEquiv<ArraySize(aEquiv)
          ){
            pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight);
            assert( pX->op==TK_COLUMN );
            for(j=0; j<nEquiv; j+=2){
              if( aEquiv[j]==pX->iTable && aEquiv[j+1]==pX->iColumn ) break;
            }
            if( j==nEquiv ){
              aEquiv[j] = pX->iTable;
              aEquiv[j+1] = pX->iColumn;
              nEquiv += 2;
            }
          }
        }
      }
    }
    if( iEquiv>=nEquiv ) break;
    iCur = aEquiv[iEquiv++];
    iColumn = aEquiv[iEquiv++];
  }
findTerm_success:
  return pResult;
}

/* Forward reference */
static void exprAnalyze(SrcList*, WhereClause*, int);

/*
** Call exprAnalyze on all terms in a WHERE clause.  

  ** Compute the set of tables that might satisfy cases 1 or 2.
  */
  indexable = ~(Bitmask)0;
  chngToIN = ~(pWC->vmask);
  for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
    if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
      WhereAndInfo *pAndInfo;

      assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
      chngToIN = 0;
      pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
      if( pAndInfo ){
        WhereClause *pAndWC;
        WhereTerm *pAndTerm;
        int j;

      Bitmask b;
      b = getMask(pMaskSet, pOrTerm->leftCursor);
      if( pOrTerm->wtFlags & TERM_VIRTUAL ){
        WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
        b |= getMask(pMaskSet, pOther->leftCursor);
      }
      indexable &= b;
      if( (pOrTerm->eOperator & WO_EQ)==0 ){
        chngToIN = 0;
      }else{
        chngToIN &= b;
      }
    }
  }

    ** will be recorded in iCursor and iColumn.  There might not be any
    ** such table and column.  Set okToChngToIN if an appropriate table
    ** and column is found but leave okToChngToIN false if not found.
    */
    for(j=0; j<2 && !okToChngToIN; j++){
      pOrTerm = pOrWc->a;
      for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
        assert( pOrTerm->eOperator & WO_EQ );
        pOrTerm->wtFlags &= ~TERM_OR_OK;
        if( pOrTerm->leftCursor==iCursor ){
          /* This is the 2-bit case and we are on the second iteration and
          ** current term is from the first iteration.  So skip this term. */
          assert( j==1 );
          continue;
        }

        iCursor = pOrTerm->leftCursor;
        break;
      }
      if( i<0 ){
        /* No candidate table+column was found.  This can only occur
        ** on the second iteration */
        assert( j==1 );
        assert( IsPowerOfTwo(chngToIN) );
        assert( chngToIN==getMask(pMaskSet, iCursor) );
        break;
      }
      testcase( j==1 );

      /* We have found a candidate table and column.  Check to see if that
      ** table and column is common to every term in the OR clause */
      okToChngToIN = 1;
      for(; i>=0 && okToChngToIN; i--, pOrTerm++){
        assert( pOrTerm->eOperator & WO_EQ );
        if( pOrTerm->leftCursor!=iCursor ){
          pOrTerm->wtFlags &= ~TERM_OR_OK;
        }else if( pOrTerm->u.leftColumn!=iColumn ){
          okToChngToIN = 0;
        }else{
          int affLeft, affRight;
          /* If the right-hand side is also a column, then the affinities

      Expr *pDup;            /* A transient duplicate expression */
      ExprList *pList = 0;   /* The RHS of the IN operator */
      Expr *pLeft = 0;       /* The LHS of the IN operator */
      Expr *pNew;            /* The complete IN operator */

      for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
        if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
        assert( pOrTerm->eOperator & WO_EQ );
        assert( pOrTerm->leftCursor==iCursor );
        assert( pOrTerm->u.leftColumn==iColumn );
        pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
        pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup);
        pLeft = pOrTerm->pExpr->pLeft;
      }
      assert( pLeft!=0 );

        sqlite3ExprListDelete(db, pList);
      }
      pTerm->eOperator = WO_NOOP;  /* case 1 trumps case 2 */
    }
  }
}
#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */


/*
** The input to this routine is an WhereTerm structure with only the
** "pExpr" field filled in.  The job of this routine is to analyze the
** subexpression and populate all the other fields of the WhereTerm
** structure.
**

    extraRight = x-1;  /* ON clause terms may not be used with an index
                       ** on left table of a LEFT JOIN.  Ticket #3015 */
  }
  pTerm->prereqAll = prereqAll;
  pTerm->leftCursor = -1;
  pTerm->iParent = -1;
  pTerm->eOperator = 0;
  if( allowedOp(op) ){
    Expr *pLeft = sqlite3ExprSkipCollate(pExpr->pLeft);
    Expr *pRight = sqlite3ExprSkipCollate(pExpr->pRight);
    u16 opMask = (pTerm->prereqRight & prereqLeft)==0 ? WO_ALL : WO_EQUIV;
    if( pLeft->op==TK_COLUMN ){
      pTerm->leftCursor = pLeft->iTable;
      pTerm->u.leftColumn = pLeft->iColumn;
      pTerm->eOperator = operatorMask(op) & opMask;
    }
    if( pRight && pRight->op==TK_COLUMN ){
      WhereTerm *pNew;
      Expr *pDup;
      u16 eExtraOp = 0;        /* Extra bits for pNew->eOperator */
      if( pTerm->leftCursor>=0 ){
        int idxNew;
        pDup = sqlite3ExprDup(db, pExpr, 0);
        if( db->mallocFailed ){
          sqlite3ExprDelete(db, pDup);
          return;
        }
        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->wtFlags |= TERM_COPIED;
        if( pExpr->op==TK_EQ
         && !ExprHasProperty(pExpr, EP_FromJoin)
         && OptimizationEnabled(db, SQLITE_Transitive)
        ){
          pTerm->eOperator |= WO_EQUIV;
          eExtraOp = WO_EQUIV;
        }
      }else{
        pDup = pExpr;
        pNew = pTerm;
      }
      exprCommute(pParse, pDup);
      pLeft = sqlite3ExprSkipCollate(pDup->pLeft);
      pNew->leftCursor = pLeft->iTable;
      pNew->u.leftColumn = pLeft->iColumn;
      testcase( (prereqLeft | extraRight) != prereqLeft );
      pNew->prereqRight = prereqLeft | extraRight;
      pNew->prereqAll = prereqAll;
      pNew->eOperator = (operatorMask(pDup->op) + eExtraOp) & opMask;
    }
  }

#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.  For example:
  **

  }
  if( pWC->wctrlFlags & WHERE_AND_ONLY ){
    return;
  }

  /* Search the WHERE clause terms for a usable WO_OR term. */
  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
    if( (pTerm->eOperator & WO_OR)!=0
     && ((pTerm->prereqAll & ~maskSrc) & p->notReady)==0
     && (pTerm->u.pOrInfo->indexable & maskSrc)!=0 
    ){
      WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
      WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
      WhereTerm *pOrTerm;
      int flags = WHERE_MULTI_OR;
      double rTotal = 0;
      double nRow = 0;
      Bitmask used = 0;
      WhereBestIdx sBOI;

      sBOI = *p;
      sBOI.pOrderBy = 0;
      sBOI.pDistinct = 0;
      sBOI.ppIdxInfo = 0;
      for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
        WHERETRACE(("... Multi-index OR testing for term %d of %d....\n", 
          (pOrTerm - pOrWC->a), (pTerm - pWC->a)
        ));
        if( (pOrTerm->eOperator& WO_AND)!=0 ){
          sBOI.pWC = &pOrTerm->u.pAndInfo->wc;
          bestIndex(&sBOI);
        }else if( pOrTerm->leftCursor==iCur ){
          WhereClause tempWC;
          tempWC.pParse = pWC->pParse;
          tempWC.pMaskSet = pWC->pMaskSet;
          tempWC.pOuter = pWC;

static int termCanDriveIndex(
  WhereTerm *pTerm,              /* WHERE clause term to check */
  struct SrcList_item *pSrc,     /* Table we are trying to access */
  Bitmask notReady               /* Tables in outer loops of the join */
){
  char aff;
  if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
  if( (pTerm->eOperator & WO_EQ)==0 ) return 0;
  if( (pTerm->prereqRight & notReady)!=0 ) return 0;
  aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
  if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
  return 1;
}
#endif

  WHERETRACE(("Recomputing index info for %s...\n", pSrc->pTab->zName));

  /* Count the number of possible WHERE clause constraints referring
  ** to this virtual table */
  for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    if( pTerm->leftCursor != pSrc->iCursor ) continue;
    assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
    testcase( pTerm->eOperator & WO_IN );
    testcase( pTerm->eOperator & WO_ISNULL );
    if( pTerm->eOperator & (WO_ISNULL) ) continue;
    if( pTerm->wtFlags & TERM_VNULL ) continue;
    nTerm++;
  }

  /* If the ORDER BY clause contains only columns in the current 
  ** virtual table then allocate space for the aOrderBy part of

  *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
  *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
                                                                   pUsage;

  for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    u8 op;
    if( pTerm->leftCursor != pSrc->iCursor ) continue;
    assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
    testcase( pTerm->eOperator & WO_IN );
    testcase( pTerm->eOperator & WO_ISNULL );
    if( pTerm->eOperator & (WO_ISNULL) ) continue;
    if( pTerm->wtFlags & TERM_VNULL ) continue;
    pIdxCons[j].iColumn = pTerm->u.leftColumn;
    pIdxCons[j].iTermOffset = i;
    op = (u8)pTerm->eOperator & WO_ALL;
    if( op==WO_IN ) op = WO_EQ;
    pIdxCons[j].op = op;
    /* The direct assignment in the previous line is possible only because
    ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
    ** following asserts verify this fact. */
    assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
    assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );

    */
    pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
    pUsage = pIdxInfo->aConstraintUsage;
    for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
      j = pIdxCons->iTermOffset;
      pTerm = &pWC->a[j];
      if( (pTerm->prereqRight&p->notReady)==0
       && (bAllowIN || (pTerm->eOperator & WO_IN)==0)
      ){
        pIdxCons->usable = 1;
      }else{
        pIdxCons->usable = 0;
      }
    }
    memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);

  
    pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
    for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
      if( pUsage[i].argvIndex>0 ){
        j = pIdxCons->iTermOffset;
        pTerm = &pWC->a[j];
        p->cost.used |= pTerm->prereqRight;
        if( (pTerm->eOperator & WO_IN)!=0 && pUsage[i].omit==0 ){
          /* Do not attempt to use an IN constraint if the virtual table
          ** says that the equivalent EQ constraint cannot be safely omitted.
          ** If we do attempt to use such a constraint, some rows might be
          ** repeated in the output. */
          break;
        }
      }

    tRowcnt iUpper = p->aiRowEst[0];
    tRowcnt a[2];
    u8 aff = p->pTable->aCol[p->aiColumn[0]].affinity;

    if( pLower ){
      Expr *pExpr = pLower->pExpr->pRight;
      rc = valueFromExpr(pParse, pExpr, aff, &pRangeVal);
      assert( (pLower->eOperator & (WO_GT|WO_GE))!=0 );
      if( rc==SQLITE_OK
       && whereKeyStats(pParse, p, pRangeVal, 0, a)==SQLITE_OK
      ){
        iLower = a[0];
        if( (pLower->eOperator & WO_GT)!=0 ) iLower += a[1];
      }
      sqlite3ValueFree(pRangeVal);
    }
    if( rc==SQLITE_OK && pUpper ){
      Expr *pExpr = pUpper->pExpr->pRight;
      rc = valueFromExpr(pParse, pExpr, aff, &pRangeVal);
      assert( (pUpper->eOperator & (WO_LT|WO_LE))!=0 );
      if( rc==SQLITE_OK
       && whereKeyStats(pParse, p, pRangeVal, 1, a)==SQLITE_OK
      ){
        iUpper = a[0];
        if( (pUpper->eOperator & WO_LE)!=0 ) iUpper += a[1];
      }
      sqlite3ValueFree(pRangeVal);
    }
    if( rc==SQLITE_OK ){
      if( iUpper<=iLower ){
        *pRangeDiv = (double)p->aiRowEst[0];
      }else{

    /* If X is the column in the index and ORDER BY clause, check to see
    ** if there are any X= or X IS NULL constraints in the WHERE clause. */
    pConstraint = findTerm(p->pWC, base, iColumn, p->notReady,
                           WO_EQ|WO_ISNULL|WO_IN, pIdx);
    if( pConstraint==0 ){
      isEq = 0;
    }else if( (pConstraint->eOperator & WO_IN)!=0 ){
      /* Constraints of the form: "X IN ..." cannot be used with an ORDER BY
      ** because we do not know in what order the values on the RHS of the IN
      ** operator will occur. */
      break;
    }else if( (pConstraint->eOperator & WO_ISNULL)!=0 ){
      uniqueNotNull = 0;
      isEq = 1;  /* "X IS NULL" means X has only a single value */
    }else if( pConstraint->prereqRight==0 ){
      isEq = 1;  /* Constraint "X=constant" means X has only a single value */
    }else{
      Expr *pRight = pConstraint->pExpr->pRight;
      if( pRight->op==TK_COLUMN ){

    ** to get a better estimate on the number of rows based on
    ** VALUE and how common that value is according to the histogram.
    */
    if( pc.plan.nRow>(double)1 && pc.plan.nEq==1
     && pFirstTerm!=0 && aiRowEst[1]>1 ){
      assert( (pFirstTerm->eOperator & (WO_EQ|WO_ISNULL|WO_IN))!=0 );
      if( pFirstTerm->eOperator & (WO_EQ|WO_ISNULL) ){
        testcase( pFirstTerm->eOperator & WO_EQ );
        testcase( pFirstTerm->eOperator & WO_EQUIV );
        testcase( pFirstTerm->eOperator & WO_ISNULL );
        whereEqualScanEst(pParse, pProbe, pFirstTerm->pExpr->pRight,
                          &pc.plan.nRow);
      }else if( bInEst==0 ){
        assert( pFirstTerm->eOperator & WO_IN );
        whereInScanEst(pParse, pProbe, pFirstTerm->pExpr->x.pList,
                       &pc.plan.nRow);
      }
    }
#endif /* SQLITE_ENABLE_STAT3 */

    /* Adjust the number of output rows and downward to reflect rows

            ** set size by a factor of 3.  Indexed range constraints reduce
            ** the search space by a larger factor: 4.  We make indexed range
            ** more selective intentionally because of the subjective 
            ** observation that indexed range constraints really are more
            ** selective in practice, on average. */
            pc.plan.nRow /= 3;
          }
        }else if( (pTerm->eOperator & WO_NOOP)==0 ){
          /* Any other expression lowers the output row count by half */
          pc.plan.nRow /= 2;
        }
      }
      if( pc.plan.nRow<2 ) pc.plan.nRow = 2;
    }

  assert( p->pOrderBy || (p->cost.plan.wsFlags&WHERE_ORDERED)==0 );
  assert( p->cost.plan.u.pIdx==0 || (p->cost.plan.wsFlags&WHERE_ROWID_EQ)==0 );
  assert( pSrc->pIndex==0 
       || p->cost.plan.u.pIdx==0 
       || p->cost.plan.u.pIdx==pSrc->pIndex 
  );

  WHERETRACE(("   best index is %s cost=%.1f\n",
         p->cost.plan.u.pIdx ? p->cost.plan.u.pIdx->zName : "ipk",
         p->cost.rCost));
  
  bestOrClauseIndex(p);
  bestAutomaticIndex(p);
  p->cost.plan.wsFlags |= eqTermMask;
}

/*

    **          we reference multiple rows using a "rowid IN (...)"
    **          construct.
    */
    iReleaseReg = sqlite3GetTempReg(pParse);
    pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
    assert( pTerm!=0 );
    assert( pTerm->pExpr!=0 );

    assert( omitTable==0 );
    testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, iReleaseReg);
    addrNxt = pLevel->addrNxt;
    sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt);
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
    sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);

    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;
    pLevel->p1 = regReturn;

    /* Set up a new SrcList in pOrTab containing the table being scanned
    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.

      if( pAndExpr ){
        pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
      }
    }

    for(ii=0; ii<pOrWc->nTerm; ii++){
      WhereTerm *pOrTerm = &pOrWc->a[ii];
      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
        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. */

  for(sWBI.i=iFrom=0, pLevel=pWInfo->a; sWBI.i<nTabList; sWBI.i++, pLevel++){
    WhereCost bestPlan;         /* Most efficient plan seen so far */
    Index *pIdx;                /* Index for FROM table at pTabItem */
    int j;                      /* For looping over FROM tables */
    int bestJ = -1;             /* The value of j */
    Bitmask m;                  /* Bitmask value for j or bestJ */
    int isOptimal;              /* Iterator for optimal/non-optimal search */
    int ckOptimal;              /* Do the optimal scan check */
    int nUnconstrained;         /* Number tables without INDEXED BY */
    Bitmask notIndexed;         /* Mask of tables that cannot use an index */

    memset(&bestPlan, 0, sizeof(bestPlan));
    bestPlan.rCost = SQLITE_BIG_DBL;
    WHERETRACE(("*** Begin search for loop %d ***\n", sWBI.i));

    ** that do not use indices.  But this nRow reduction only happens if the
    ** table really is the innermost join.  
    **
    ** The second loop iteration is only performed if no optimal scan
    ** strategies were found by the first iteration. This second iteration
    ** is used to search for the lowest cost scan overall.
    **
    ** Without the optimal scan step (the first iteration) a suboptimal


    ** plan might be chosen for queries like this:
    **   
    **   CREATE TABLE t1(a, b); 
    **   CREATE TABLE t2(c, d);
    **   SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
    **
    ** The best strategy is to iterate through table t1 first. However it
    ** is not possible to determine this with a simple greedy algorithm.
    ** Since the cost of a linear scan through table t2 is the same 
    ** as the cost of a linear scan through table t1, a simple greedy 
    ** algorithm may choose to use t2 for the outer loop, which is a much
    ** costlier approach.
    */
    nUnconstrained = 0;
    notIndexed = 0;

    /* The optimal scan check only occurs if there are two or more tables
    ** available to be reordered */
    if( iFrom==nTabList-1 ){
      ckOptimal = 0;  /* Common case of just one table in the FROM clause */
    }else{
      ckOptimal = -1;
      for(j=iFrom, sWBI.pSrc=&pTabList->a[j]; j<nTabList; j++, sWBI.pSrc++){




        m = getMask(pMaskSet, sWBI.pSrc->iCursor);
        if( (m & sWBI.notValid)==0 ){
          if( j==iFrom ) iFrom++;
          continue;
        }
        if( j>iFrom && (sWBI.pSrc->jointype & (JT_LEFT|JT_CROSS))!=0 ) break;
        if( ++ckOptimal ) break;
        if( (sWBI.pSrc->jointype & JT_LEFT)!=0 ) break;
      }
    }
    assert( ckOptimal==0 || ckOptimal==1 );

    for(isOptimal=ckOptimal; isOptimal>=0 && bestJ<0; isOptimal--){
      for(j=iFrom, sWBI.pSrc=&pTabList->a[j]; j<nTabList; j++, sWBI.pSrc++){
        if( j>iFrom && (sWBI.pSrc->jointype & (JT_LEFT|JT_CROSS))!=0 ){
          /* This break and one like it in the ckOptimal computation loop
          ** above prevent table reordering across LEFT and CROSS JOINs.
          ** The LEFT JOIN case is necessary for correctness.  The prohibition
          ** against reordering across a CROSS JOIN is an SQLite feature that
          ** allows the developer to control table reordering */
          break;
        }
        m = getMask(pMaskSet, sWBI.pSrc->iCursor);
        if( (m & sWBI.notValid)==0 ){
          assert( j>iFrom );
          continue;
        }
        sWBI.notReady = (isOptimal ? m : sWBI.notValid);
        if( sWBI.pSrc->pIndex==0 ) nUnconstrained++;
  
        WHERETRACE(("   === trying table %d (%s) with isOptimal=%d ===\n",
                    j, sWBI.pSrc->pTab->zName, isOptimal));
        assert( sWBI.pSrc->pTab );

                  || sWBI.cost.plan.u.pIdx==sWBI.pSrc->pIndex );

        if( isOptimal && (sWBI.cost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ){
          notIndexed |= m;
        }
        if( isOptimal ){
          pWInfo->a[j].rOptCost = sWBI.cost.rCost;
        }else if( ckOptimal ){
          /* If two or more tables have nearly the same outer loop cost, but
          ** very different inner loop (optimal) cost, we want to choose
          ** for the outer loop that table which benefits the least from
          ** being in the inner loop.  The following code scales the 
          ** outer loop cost estimate to accomplish that. */
          WHERETRACE(("   scaling cost from %.1f to %.1f\n",
                      sWBI.cost.rCost,
                      sWBI.cost.rCost/pWInfo->a[j].rOptCost));

                      "       cost=%.1f, nRow=%.1f, nOBSat=%d, wsFlags=%08x\n",
                      j, sWBI.pSrc->pTab->zName,
                      sWBI.cost.rCost, sWBI.cost.plan.nRow,
                      sWBI.cost.plan.nOBSat, sWBI.cost.plan.wsFlags));
          bestPlan = sWBI.cost;
          bestJ = j;
        }

        /* In a join like "w JOIN x LEFT JOIN y JOIN z"  make sure that
        ** table y (and not table z) is always the next inner loop inside
        ** of table x. */
        if( (sWBI.pSrc->jointype & JT_LEFT)!=0 ) break;
      }
    }
    assert( bestJ>=0 );
    assert( sWBI.notValid & getMask(pMaskSet, pTabList->a[bestJ].iCursor) );
    assert( bestJ==iFrom || (pTabList->a[iFrom].jointype & JT_LEFT)==0 );
    testcase( bestJ>iFrom && (pTabList->a[iFrom].jointype & JT_CROSS)!=0 );
    testcase( bestJ>iFrom && bestJ<nTabList-1
                          && (pTabList->a[bestJ+1].jointype & JT_LEFT)!=0 );
    WHERETRACE(("*** Optimizer selects table %d (%s) for loop %d with:\n"
                "    cost=%.1f, nRow=%.1f, nOBSat=%d, wsFlags=0x%08x\n",
                bestJ, pTabList->a[bestJ].pTab->zName,
                pLevel-pWInfo->a, bestPlan.rCost, bestPlan.plan.nRow,
                bestPlan.plan.nOBSat, bestPlan.plan.wsFlags));
    if( (bestPlan.plan.wsFlags & WHERE_DISTINCT)!=0 ){
      assert( pWInfo->eDistinct==0 );

** This ensures that each node is stored on a single database page. If the 
** database page-size is so large that more than RTREE_MAXCELLS entries 
** would fit in a single node, use a smaller node-size.
*/
static int getNodeSize(
  sqlite3 *db,                    /* Database handle */
  Rtree *pRtree,                  /* Rtree handle */
  int isCreate,                   /* True for xCreate, false for xConnect */
  char **pzErr                    /* OUT: Error message, if any */
){
  int rc;
  char *zSql;
  if( isCreate ){
    int iPageSize = 0;
    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", pRtree->zDb);
    rc = getIntFromStmt(db, zSql, &iPageSize);
    if( rc==SQLITE_OK ){
      pRtree->iNodeSize = iPageSize-64;
      if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
        pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
      }
    }else{
      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
    }
  }else{
    zSql = sqlite3_mprintf(
        "SELECT length(data) FROM '%q'.'%q_node' WHERE nodeno = 1",
        pRtree->zDb, pRtree->zName
    );
    rc = getIntFromStmt(db, zSql, &pRtree->iNodeSize);
    if( rc!=SQLITE_OK ){
      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
    }
  }

  sqlite3_free(zSql);
  return rc;
}

/* 

  pRtree->nDim = (argc-4)/2;
  pRtree->nBytesPerCell = 8 + pRtree->nDim*4*2;
  pRtree->eCoordType = eCoordType;
  memcpy(pRtree->zDb, argv[1], nDb);
  memcpy(pRtree->zName, argv[2], nName);

  /* Figure out the node size to use. */
  rc = getNodeSize(db, pRtree, isCreate, pzErr);

  /* Create/Connect to the underlying relational database schema. If
  ** that is successful, call sqlite3_declare_vtab() to configure
  ** the r-tree table schema.
  */
  if( rc==SQLITE_OK ){
    if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){