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Overview
Comment:Clearer presentation of the logic. No functional changes.
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Timelines: family | ancestors | descendants | both | skip-scan-improvement
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SHA1: a3dcf6db76cc09bdfedb1bbeba3b359b77762cbe
User & Date: drh 2016-02-22 21:19:54.531
Context
2016-02-22
23:14
Avoid an unnecessary seek operation some corner-case skip-scan operations. (check-in: 2a6003a937 user: drh tags: trunk)
21:19
Clearer presentation of the logic. No functional changes. (Closed-Leaf check-in: a3dcf6db76 user: drh tags: skip-scan-improvement)
20:52
Avoid an unnecessary seek operation on some corner-case skip-scans. (check-in: 38e837e605 user: drh tags: skip-scan-improvement)
Changes
Unified Diff Show Whitespace Changes Patch
Changes to src/wherecode.c.
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    }else if( bSeekPastNull ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      nConstraint++;
      startEq = 0;
      start_constraints = 1;
    }
    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
    if( pLoop->nSkip==0 || nConstraint>pLoop->nSkip ){




      op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
      assert( op!=0 );
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      VdbeCoverage(v);
      VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
      VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
      VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );








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    }else if( bSeekPastNull ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      nConstraint++;
      startEq = 0;
      start_constraints = 1;
    }
    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
    if( pLoop->nSkip>0 && nConstraint==pLoop->nSkip ){
      /* The skip-scan logic inside the call to codeAllEqualityConstraints()
      ** above has already left the cursor sitting on the correct row,
      ** so no further seeking is needed */
    }else{
      op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
      assert( op!=0 );
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      VdbeCoverage(v);
      VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
      VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
      VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
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