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Overview
Comment:Fix a bug in the new WHERE-clause processing that tries to use an index to resolve IS NOT NULL constraints when SQLITE_ENABLE_STAT2 is defined. The bug could cause memory overruns and segfaults. The bug was new to the code and has not appeared in an official release. Found during structural testing.
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SHA1: a5c36b9f39ab9629b857ec9c550f3892c0d94fb4
User & Date: drh 2011-02-11 06:59:02.077
Context
2011-02-11
20:52
Skip flattening if subquery has LIMIT and outer query is DISTINCT. Fix for ticket [752e1646fc]. (check-in: 5597399988 user: shaneh tags: trunk)
06:59
Fix a bug in the new WHERE-clause processing that tries to use an index to resolve IS NOT NULL constraints when SQLITE_ENABLE_STAT2 is defined. The bug could cause memory overruns and segfaults. The bug was new to the code and has not appeared in an official release. Found during structural testing. (check-in: a5c36b9f39 user: drh tags: trunk)
03:56
Allow an index paired with an IS NULL constraint to be used for sorting under the condition that the index be treated as a non-unique index. (check-in: d78949fc93 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/where.c.
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    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);
    testcase( idxNew==0 );
    pNewTerm = &pWC->a[idxNew];

    pNewTerm->leftCursor = pLeft->iTable;
    pNewTerm->u.leftColumn = pLeft->iColumn;
    pNewTerm->eOperator = WO_GT;
    pNewTerm->iParent = idxTerm;
    pTerm = &pWC->a[idxTerm];
    pTerm->nChild = 1;
    pTerm->wtFlags |= TERM_COPIED;
    pNewTerm->prereqAll = pTerm->prereqAll;

  }
#endif /* SQLITE_ENABLE_STAT2 */

  /* Prevent ON clause terms of a LEFT JOIN from being used to drive
  ** an index for tables to the left of the join.
  */
  pTerm->prereqRight |= extraRight;








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    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;
      pNewTerm->iParent = idxTerm;
      pTerm = &pWC->a[idxTerm];
      pTerm->nChild = 1;
      pTerm->wtFlags |= TERM_COPIED;
      pNewTerm->prereqAll = pTerm->prereqAll;
    }
  }
#endif /* SQLITE_ENABLE_STAT2 */

  /* Prevent ON clause terms of a LEFT JOIN from being used to drive
  ** an index for tables to the left of the join.
  */
  pTerm->prereqRight |= extraRight;
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