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Comment:Completely disable the skip-ahead-distinct optimization for all but the inner-most loop of a DISTINCT join. Fix for ticket [ef9318757b152e3a26e9592]
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SHA3-256:b7595cf2cadcba486e60b3c230ccc412a7cf449c1d56cbe65869e6d5d9f1374d
User & Date: drh 2017-11-23 00:45:21
Context
2017-11-23
04:45
Fix a problem in the omit-table-from-left-join optimization from check-in [0cd82ee9a8413cf] that was discovered by OSSFuzz. check-in: b016c28f user: drh tags: trunk
00:45
Completely disable the skip-ahead-distinct optimization for all but the inner-most loop of a DISTINCT join. Fix for ticket [ef9318757b152e3a26e9592] check-in: b7595cf2 user: drh tags: trunk
2017-11-21
23:38
Fix the skip-ahead-distinct optimization on joins for cases there the table in the inner loop of the join does not contribute any columns to the result set. Proposed fix for ticket [ef9318757b152e3a2] check-in: 2dcef5a9 user: drh tags: trunk
Changes
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Changes to src/where.c.

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    pLoop = pLevel->pWLoop;
    if( pLevel->op!=OP_Noop ){
#ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
      int addrSeek = 0;
      Index *pIdx;
      int n;
      if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED

       && (pLoop->wsFlags & WHERE_INDEXED)!=0
       && (pIdx = pLoop->u.btree.pIndex)->hasStat1
       && (n = pLoop->u.btree.nIdxCol)>0
       && pIdx->aiRowLogEst[n]>=36
      ){
        int r1 = pParse->nMem+1;
        int j, op;
................................................................................
        }
        pParse->nMem += n+1;
        op = pLevel->op==OP_Prev ? OP_SeekLT : OP_SeekGT;
        addrSeek = sqlite3VdbeAddOp4Int(v, op, pLevel->iIdxCur, 0, r1, n);
        VdbeCoverageIf(v, op==OP_SeekLT);
        VdbeCoverageIf(v, op==OP_SeekGT);
        sqlite3VdbeAddOp2(v, OP_Goto, 1, pLevel->p2);
        if( i<pWInfo->nLevel-1 ){
          /* Ticket https://sqlite.org/src/info/ef9318757b152e3 2017-11-21
          ** The break location for the next inner loop is above the code
          ** generated here, but it should be afterwards.  So call re-resolve
          ** the break location to be afterwards. */
          sqlite3VdbeResolveLabel(v, pWInfo->a[i+1].addrBrk);
        }
      }
#endif /* SQLITE_DISABLE_SKIPAHEAD_DISTINCT */
      /* The common case: Advance to the next row */
      sqlite3VdbeResolveLabel(v, pLevel->addrCont);
      sqlite3VdbeAddOp3(v, pLevel->op, pLevel->p1, pLevel->p2, pLevel->p3);
      sqlite3VdbeChangeP5(v, pLevel->p5);
      VdbeCoverage(v);







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    pLoop = pLevel->pWLoop;
    if( pLevel->op!=OP_Noop ){
#ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
      int addrSeek = 0;
      Index *pIdx;
      int n;
      if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED
       && i==pWInfo->nLevel-1  /* Ticket [ef9318757b152e3] 2017-10-21 */
       && (pLoop->wsFlags & WHERE_INDEXED)!=0
       && (pIdx = pLoop->u.btree.pIndex)->hasStat1
       && (n = pLoop->u.btree.nIdxCol)>0
       && pIdx->aiRowLogEst[n]>=36
      ){
        int r1 = pParse->nMem+1;
        int j, op;
................................................................................
        }
        pParse->nMem += n+1;
        op = pLevel->op==OP_Prev ? OP_SeekLT : OP_SeekGT;
        addrSeek = sqlite3VdbeAddOp4Int(v, op, pLevel->iIdxCur, 0, r1, n);
        VdbeCoverageIf(v, op==OP_SeekLT);
        VdbeCoverageIf(v, op==OP_SeekGT);
        sqlite3VdbeAddOp2(v, OP_Goto, 1, pLevel->p2);







      }
#endif /* SQLITE_DISABLE_SKIPAHEAD_DISTINCT */
      /* The common case: Advance to the next row */
      sqlite3VdbeResolveLabel(v, pLevel->addrCont);
      sqlite3VdbeAddOp3(v, pLevel->op, pLevel->p1, pLevel->p2, pLevel->p3);
      sqlite3VdbeChangeP5(v, pLevel->p5);
      VdbeCoverage(v);

Changes to test/distinct2.test.

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    INSERT INTO t1(b) SELECT x/10 - 1 FROM c;
  WITH RECURSIVE c(x) AS (VALUES(-1) UNION ALL SELECT x+1 FROM c WHERE x<19)
    INSERT INTO t2(x,y) SELECT x, 1 FROM c;
  SELECT DISTINCT y FROM t1, t2 WHERE b=x AND b<>-1;
  ANALYZE;
  SELECT DISTINCT y FROM t1, t2 WHERE b=x AND b<>-1;
} {1 1}
































finish_test







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    INSERT INTO t1(b) SELECT x/10 - 1 FROM c;
  WITH RECURSIVE c(x) AS (VALUES(-1) UNION ALL SELECT x+1 FROM c WHERE x<19)
    INSERT INTO t2(x,y) SELECT x, 1 FROM c;
  SELECT DISTINCT y FROM t1, t2 WHERE b=x AND b<>-1;
  ANALYZE;
  SELECT DISTINCT y FROM t1, t2 WHERE b=x AND b<>-1;
} {1 1}
db close
sqlite3 db :memory:
do_execsql_test 1010 {
  CREATE TABLE t1(a INTEGER PRIMARY KEY, b INTEGER);
  CREATE INDEX t1b ON t1(b);
  CREATE TABLE t2(x INTEGER PRIMARY KEY, y INTEGER);
  CREATE INDEX t2y ON t2(y);
  WITH RECURSIVE c(x) AS (VALUES(0) UNION ALL SELECT x+1 FROM c WHERE x<49)
    INSERT INTO t1(b) SELECT -(x/10 - 1) FROM c;
  WITH RECURSIVE c(x) AS (VALUES(-1) UNION ALL SELECT x+1 FROM c WHERE x<19)
    INSERT INTO t2(x,y) SELECT -x, 1 FROM c;
  SELECT DISTINCT y FROM t1, t2 WHERE b=x AND b<>1 ORDER BY y DESC;
  ANALYZE;
  SELECT DISTINCT y FROM t1, t2 WHERE b=x AND b<>1 ORDER BY y DESC;
} {1 1}
db close
sqlite3 db :memory:
do_execsql_test 1020 {
  CREATE TABLE t1(a, b);
  CREATE INDEX t1a ON t1(a, b);
  -- Lots of rows of (1, 'no'), followed by a single (1, 'yes').
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100)
    INSERT INTO t1(a, b) SELECT 1, 'no' FROM c;
  INSERT INTO t1(a, b) VALUES(1, 'yes');
  CREATE TABLE t2(x PRIMARY KEY);
  INSERT INTO t2 VALUES('yes');
  SELECT DISTINCT a FROM t1, t2 WHERE x=b;
  ANALYZE;
  SELECT DISTINCT a FROM t1, t2 WHERE x=b;
} {1 1}


finish_test