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Overview
Comment:Fix the LIKE optimization so that it works even if there are additional range contraints on the column that is subject to the LIKE or GLOB.
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SHA1: 984c3fd5261619fb542a5a95dab37707b5d79dbf
User & Date: drh 2015-03-09 13:01:02
Context
2015-03-10
13:50
Revise test cases in malloc5.test to accommodate varying allocation sizes returned by some system malloc() implementations. check-in: fbae6baf user: drh tags: trunk
2015-03-09
13:24
Merge recent trunk enhancements into the ota-update branch. check-in: 5489cb68 user: drh tags: ota-update
13:18
Merge recent trunk enhancements into the apple-osx branch. check-in: 5e04eec8 user: drh tags: apple-osx
13:07
Merge recent trunk enhancements into the sessions branch. check-in: 68c8937e user: drh tags: sessions
13:01
Fix the LIKE optimization so that it works even if there are additional range contraints on the column that is subject to the LIKE or GLOB. check-in: 984c3fd5 user: drh tags: trunk
12:11
Always use LIKE optimization range constraints in pairs. Closed-Leaf check-in: 0e02dc94 user: drh tags: like-opt-fix
10:40
Increase the version number to 3.8.9 check-in: e5da5e7d user: drh tags: trunk
Changes
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Changes to src/where.c.

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  );
}
#else
# define addScanStatus(a, b, c, d) ((void)d)
#endif

/*
** Look at the last instruction coded.  If that instruction is OP_String8
** and if pLoop->iLikeRepCntr is non-zero, then change the P3 to be
** pLoop->iLikeRepCntr and set P5.
**
** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
** scan loop run twice, once for strings and a second time for BLOBs.
** The OP_String opcodes on the second pass convert the upper and lower
** bound string contants to blobs.  This routine makes the necessary changes
** to the OP_String opcodes for that to happen.
*/
static void whereLikeOptimizationStringFixup(Vdbe *v, WhereLevel *pLevel){





  VdbeOp *pOp;

  pOp = sqlite3VdbeGetOp(v, -1);

  if( pLevel->iLikeRepCntr && pOp->opcode==OP_String8 ){

    pOp->p3 = pLevel->iLikeRepCntr;
    pOp->p5 = 1;
  }
}

/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
................................................................................
    /* Find any inequality constraint terms for the start and end 
    ** of the range. 
    */
    j = nEq;
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
      pRangeStart = pLoop->aLTerm[j++];
      nExtraReg = 1;



    }
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
      pRangeEnd = pLoop->aLTerm[j++];
      nExtraReg = 1;
      if( pRangeStart
       && (pRangeStart->wtFlags & TERM_LIKEOPT)!=0

       && (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0
      ){
        pLevel->iLikeRepCntr = ++pParse->nMem;
        testcase( bRev );
        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
        sqlite3VdbeAddOp2(v, OP_Integer,
                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
                          pLevel->iLikeRepCntr);
        VdbeComment((v, "LIKE loop counter"));
................................................................................
    start_constraints = pRangeStart || nEq>0;

    /* 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);
      if( (pRangeStart->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( zStartAff ){
................................................................................
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel);
      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_NONE
................................................................................
    if( (eOp==WO_ISNULL || (pTerm->wtFlags&TERM_VNULL)!=0)
     && (iCol<0 || pSrc->pTab->aCol[iCol].notNull)
    ){
      continue; /* ignore IS [NOT] NULL constraints on NOT NULL columns */
    }
    if( pTerm->prereqRight & pNew->maskSelf ) continue;





    pNew->wsFlags = saved_wsFlags;
    pNew->u.btree.nEq = saved_nEq;
    pNew->nLTerm = saved_nLTerm;
    if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
    pNew->aLTerm[pNew->nLTerm++] = pTerm;
    pNew->prereq = (saved_prereq | pTerm->prereqRight) & ~pNew->maskSelf;

................................................................................
      pNew->wsFlags |= WHERE_COLUMN_NULL;
    }else if( eOp & (WO_GT|WO_GE) ){
      testcase( eOp & WO_GT );
      testcase( eOp & WO_GE );
      pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_BTM_LIMIT;
      pBtm = pTerm;
      pTop = 0;











    }else{
      assert( eOp & (WO_LT|WO_LE) );
      testcase( eOp & WO_LT );
      testcase( eOp & WO_LE );
      pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_TOP_LIMIT;
      pTop = pTerm;
      pBtm = (pNew->wsFlags & WHERE_BTM_LIMIT)!=0 ?







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  );
}
#else
# define addScanStatus(a, b, c, d) ((void)d)
#endif

/*
** If the most recently coded instruction is a constant range contraint
** that originated from the LIKE optimization, then change the P3 to be
** pLoop->iLikeRepCntr and set P5.
**
** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
** scan loop run twice, once for strings and a second time for BLOBs.
** The OP_String opcodes on the second pass convert the upper and lower
** bound string contants to blobs.  This routine makes the necessary changes
** to the OP_String opcodes for that to happen.
*/
static void whereLikeOptimizationStringFixup(
  Vdbe *v,                /* prepared statement under construction */
  WhereLevel *pLevel,     /* The loop that contains the LIKE operator */
  WhereTerm *pTerm        /* The upper or lower bound just coded */
){
  if( pTerm->wtFlags & TERM_LIKEOPT ){
    VdbeOp *pOp;
    assert( pLevel->iLikeRepCntr>0 );
    pOp = sqlite3VdbeGetOp(v, -1);
    assert( pOp!=0 );
    assert( pOp->opcode==OP_String8 
            || pTerm->pWC->pWInfo->pParse->db->mallocFailed );
    pOp->p3 = pLevel->iLikeRepCntr;
    pOp->p5 = 1;
  }
}

/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
................................................................................
    /* Find any inequality constraint terms for the start and end 
    ** of the range. 
    */
    j = nEq;
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
      pRangeStart = pLoop->aLTerm[j++];
      nExtraReg = 1;
      /* Like optimization range constraints always occur in pairs */
      assert( (pRangeStart->wtFlags & TERM_LIKEOPT)==0 || 
              (pLoop->wsFlags & WHERE_TOP_LIMIT)!=0 );
    }
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
      pRangeEnd = pLoop->aLTerm[j++];
      nExtraReg = 1;

      if( (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0 ){
        assert( pRangeStart!=0 );                     /* LIKE opt constraints */
        assert( pRangeStart->wtFlags & TERM_LIKEOPT );   /* occur in pairs */

        pLevel->iLikeRepCntr = ++pParse->nMem;
        testcase( bRev );
        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
        sqlite3VdbeAddOp2(v, OP_Integer,
                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
                          pLevel->iLikeRepCntr);
        VdbeComment((v, "LIKE loop counter"));
................................................................................
    start_constraints = pRangeStart || nEq>0;

    /* 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 ){
................................................................................
    ** range (if any).
    */
    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
................................................................................
    if( (eOp==WO_ISNULL || (pTerm->wtFlags&TERM_VNULL)!=0)
     && (iCol<0 || pSrc->pTab->aCol[iCol].notNull)
    ){
      continue; /* ignore IS [NOT] NULL constraints on NOT NULL columns */
    }
    if( pTerm->prereqRight & pNew->maskSelf ) continue;

    /* Do not allow the upper bound of a LIKE optimization range constraint
    ** to mix with a lower range bound from some other source */
    if( pTerm->wtFlags & TERM_LIKEOPT && pTerm->eOperator==WO_LT ) continue;

    pNew->wsFlags = saved_wsFlags;
    pNew->u.btree.nEq = saved_nEq;
    pNew->nLTerm = saved_nLTerm;
    if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
    pNew->aLTerm[pNew->nLTerm++] = pTerm;
    pNew->prereq = (saved_prereq | pTerm->prereqRight) & ~pNew->maskSelf;

................................................................................
      pNew->wsFlags |= WHERE_COLUMN_NULL;
    }else if( eOp & (WO_GT|WO_GE) ){
      testcase( eOp & WO_GT );
      testcase( eOp & WO_GE );
      pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_BTM_LIMIT;
      pBtm = pTerm;
      pTop = 0;
      if( pTerm->wtFlags & TERM_LIKEOPT ){
        /* Range contraints that come from the LIKE optimization are
        ** always used in pairs. */
        pTop = &pTerm[1];
        assert( (pTop-(pTerm->pWC->a))<pTerm->pWC->nTerm );
        assert( pTop->wtFlags & TERM_LIKEOPT );
        assert( pTop->eOperator==WO_LT );
        if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
        pNew->aLTerm[pNew->nLTerm++] = pTop;
        pNew->wsFlags |= WHERE_TOP_LIMIT;
      }
    }else{
      assert( eOp & (WO_LT|WO_LE) );
      testcase( eOp & WO_LT );
      testcase( eOp & WO_LE );
      pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_TOP_LIMIT;
      pTop = pTerm;
      pBtm = (pNew->wsFlags & WHERE_BTM_LIMIT)!=0 ?