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Comment:Simplified implementation of indexing with the IS operator.
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Timelines: family | ancestors | descendants | both | index-is-operator
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SHA1: 95b1f9bf14e490c6c6bba9ea78aeab712a44aab5
User & Date: drh 2015-05-13 19:33:41
Context
2015-05-14
01:05
A new implementation of indexing with the IS operator that works correctly when the IS operator is in the WHERE clause and the operands are from opposite sides of a LEFT JOIN. check-in: 4541688b user: drh tags: index-is-operator
2015-05-13
19:33
Simplified implementation of indexing with the IS operator. check-in: 95b1f9bf user: drh tags: index-is-operator
17:54
Add testcase() macros and comments and a few test-cases. check-in: 24263d08 user: drh tags: index-is-operator
Changes
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Changes to src/where.c. 

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    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( op==TK_IS ) pTerm->wtFlags |= TERM_NULLOK;
    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( pExpr->op==TK_EQ
         && !ExprHasProperty(pExpr, EP_FromJoin)
         && OptimizationEnabled(db, SQLITE_Transitive)
        ){
          pTerm->eOperator |= WO_EQUIV;
          eExtraOp = WO_EQUIV;
        }
        if( op==TK_IS ) pNew->wtFlags |= TERM_NULLOK;
      }else{
        pDup = pExpr;
        pNew = pTerm;
      }
      exprCommute(pParse, pDup);
      pLeft = sqlite3ExprSkipCollate(pDup->pLeft);
      pNew->leftCursor = pLeft->iTable;
................................................................................

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  /* When sqlite_stat3 histogram data is available an operator of the
  ** form "x IS NOT NULL" can sometimes be evaluated more efficiently
  ** as "x>NULL" if x is not an INTEGER PRIMARY KEY.  So construct a
  ** virtual term of that form.
  **
  ** Note that the virtual term must be tagged with both TERM_VNULL
  ** and TERM_NULLOK.
  */
  if( pExpr->op==TK_NOTNULL
   && pExpr->pLeft->op==TK_COLUMN
   && pExpr->pLeft->iColumn>=0
   && OptimizationEnabled(db, SQLITE_Stat34)
  ){
    Expr *pNewExpr;
................................................................................
    WhereTerm *pNewTerm;

    pNewExpr = sqlite3PExpr(pParse, TK_GT,
                            sqlite3ExprDup(db, pLeft, 0),
                            sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);

    idxNew = whereClauseInsert(pWC, pNewExpr,
                              TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL|TERM_NULLOK);
    if( idxNew ){
      pNewTerm = &pWC->a[idxNew];
      pNewTerm->prereqRight = 0;
      pNewTerm->leftCursor = pLeft->iTable;
      pNewTerm->u.leftColumn = pLeft->iColumn;
      pNewTerm->eOperator = WO_GT;
      markTermAsChild(pWC, idxNew, idxTerm);
................................................................................
        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
      }
    }
    testcase( pTerm->eOperator & WO_ISNULL );
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      Expr *pRight = pTerm->pExpr->pRight;
      testcase( pTerm->pExpr->op==TK_IS );
      if( (pTerm->wtFlags & TERM_NULLOK)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
        VdbeCoverage(v);
      }
      if( zAff ){
        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
          zAff[j] = SQLITE_AFF_NONE;
        }
................................................................................

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight = pRangeStart->pExpr->pRight;
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
      testcase( pRangeStart->pExpr->op==TK_IS );
      if( (pRangeStart->wtFlags & TERM_NULLOK)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( zStartAff ){
        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
................................................................................
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
      testcase( pRangeEnd->pExpr->op==TK_IS );
      if( (pRangeEnd->wtFlags & TERM_NULLOK)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_NONE
       && !sqlite3ExprNeedsNoAffinityChange(pRight, cEndAff)








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    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( op==TK_IS ) pTerm->wtFlags |= TERM_IS;
    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( pExpr->op==TK_EQ
         && !ExprHasProperty(pExpr, EP_FromJoin)
         && OptimizationEnabled(db, SQLITE_Transitive)
        ){
          pTerm->eOperator |= WO_EQUIV;
          eExtraOp = WO_EQUIV;
        }
        if( op==TK_IS ) pNew->wtFlags |= TERM_IS;
      }else{
        pDup = pExpr;
        pNew = pTerm;
      }
      exprCommute(pParse, pDup);
      pLeft = sqlite3ExprSkipCollate(pDup->pLeft);
      pNew->leftCursor = pLeft->iTable;
................................................................................

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  /* When sqlite_stat3 histogram data is available an operator of the
  ** form "x IS NOT NULL" can sometimes be evaluated more efficiently
  ** as "x>NULL" if x is not an INTEGER PRIMARY KEY.  So construct a
  ** virtual term of that form.
  **
  ** Note that the virtual term must be tagged with TERM_VNULL.

  */
  if( pExpr->op==TK_NOTNULL
   && pExpr->pLeft->op==TK_COLUMN
   && pExpr->pLeft->iColumn>=0
   && OptimizationEnabled(db, SQLITE_Stat34)
  ){
    Expr *pNewExpr;
................................................................................
    WhereTerm *pNewTerm;

    pNewExpr = sqlite3PExpr(pParse, TK_GT,
                            sqlite3ExprDup(db, pLeft, 0),
                            sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);

    idxNew = whereClauseInsert(pWC, pNewExpr,
                              TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
    if( idxNew ){
      pNewTerm = &pWC->a[idxNew];
      pNewTerm->prereqRight = 0;
      pNewTerm->leftCursor = pLeft->iTable;
      pNewTerm->u.leftColumn = pLeft->iColumn;
      pNewTerm->eOperator = WO_GT;
      markTermAsChild(pWC, idxNew, idxTerm);
................................................................................
        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
      }
    }
    testcase( pTerm->eOperator & WO_ISNULL );
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      Expr *pRight = pTerm->pExpr->pRight;


      if( (pTerm->wtFlags & TERM_IS)==0 && sqlite3ExprCanBeNull(pRight) ){

        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
        VdbeCoverage(v);
      }
      if( zAff ){
        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
          zAff[j] = SQLITE_AFF_NONE;
        }
................................................................................

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight = pRangeStart->pExpr->pRight;
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);

      if( (pRangeStart->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( zStartAff ){
        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
................................................................................
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);

      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_NONE
       && !sqlite3ExprNeedsNoAffinityChange(pRight, cEndAff)

Changes to src/whereInt.h. 

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#  define TERM_VNULL    0x80   /* Manufactured x>NULL or x<=NULL term */
#else
#  define TERM_VNULL    0x00   /* Disabled if not using stat3 */
#endif
#define TERM_LIKEOPT    0x100  /* Virtual terms from the LIKE optimization */
#define TERM_LIKECOND   0x200  /* Conditionally this LIKE operator term */
#define TERM_LIKE       0x400  /* The original LIKE operator */
#define TERM_NULLOK     0x800  /* Comparison operators against NULL work */

/*
** An instance of the WhereScan object is used as an iterator for locating
** terms in the WHERE clause that are useful to the query planner.
*/
struct WhereScan {
  WhereClause *pOrigWC;      /* Original, innermost WhereClause */
................................................................................
/*
** Bitmasks for the operators on WhereTerm objects.  These are all
** operators that are of interest to the query planner.  An
** OR-ed combination of these values can be used when searching for
** particular WhereTerms within a WhereClause.
*/
#define WO_IN     0x001
#define WO_EQ     0x002
#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 WO_MATCH  0x040
#define WO_ISNULL 0x080
#define WO_OR     0x100       /* Two or more OR-connected terms */








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#  define TERM_VNULL    0x80   /* Manufactured x>NULL or x<=NULL term */
#else
#  define TERM_VNULL    0x00   /* Disabled if not using stat3 */
#endif
#define TERM_LIKEOPT    0x100  /* Virtual terms from the LIKE optimization */
#define TERM_LIKECOND   0x200  /* Conditionally this LIKE operator term */
#define TERM_LIKE       0x400  /* The original LIKE operator */
#define TERM_IS         0x800  /* Term.pExpr is an IS operator */

/*
** An instance of the WhereScan object is used as an iterator for locating
** terms in the WHERE clause that are useful to the query planner.
*/
struct WhereScan {
  WhereClause *pOrigWC;      /* Original, innermost WhereClause */
................................................................................
/*
** Bitmasks for the operators on WhereTerm objects.  These are all
** operators that are of interest to the query planner.  An
** OR-ed combination of these values can be used when searching for
** particular WhereTerms within a WhereClause.
*/
#define WO_IN     0x001
#define WO_EQ     0x002                      /* Used for both == and IS */
#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 WO_MATCH  0x040
#define WO_ISNULL 0x080
#define WO_OR     0x100       /* Two or more OR-connected terms */

Changes to test/whereC.test. 

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  8   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 10 AND 12" {10 11 12}
  9   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 11 AND 12" {11 12}
 10   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 10 AND 11" {10 11}
 11   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 12 AND 10" {}
 12   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i<NULL"      {}
 13   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i>=NULL"     {}
 14   "SELECT i FROM t1 WHERE a=1 AND b='2' AND i<4.5"     {3 4}

} {
  do_execsql_test 1.$tn.1 $sql $res
  do_execsql_test 1.$tn.2 "$sql ORDER BY i ASC"  [lsort -integer -inc  $res]
  do_execsql_test 1.$tn.3 "$sql ORDER BY i DESC" [lsort -integer -dec  $res]
}


finish_test








>









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  8   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 10 AND 12" {10 11 12}
  9   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 11 AND 12" {11 12}
 10   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 10 AND 11" {10 11}
 11   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i BETWEEN 12 AND 10" {}
 12   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i<NULL"      {}
 13   "SELECT i FROM t1 WHERE a=2 AND b=2 AND i>=NULL"     {}
 14   "SELECT i FROM t1 WHERE a=1 AND b='2' AND i<4.5"     {3 4}
 15   "SELECT i FROM t1 WHERE rowid IS '12'"               {12}
} {
  do_execsql_test 1.$tn.1 $sql $res
  do_execsql_test 1.$tn.2 "$sql ORDER BY i ASC"  [lsort -integer -inc  $res]
  do_execsql_test 1.$tn.3 "$sql ORDER BY i DESC" [lsort -integer -dec  $res]
}


finish_test

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