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When applying the optimization that disables WHERE clause terms that drive

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indexes, make sure not to do so if the term being disabled is a transitive
constraint.  Fix for the problem identified by
[forum:forumpost/eb8613976a|forum post eb8613976a].

FossilOrigin-Name: f1f9b5de3c59489b94963685660b3ddc45eece5535b02fec399b6ece0e38563d
This commit is contained in:
drh
2021-05-04 23:21:35 +00:00
parent 23634898c5
commit 67656ac78a
6 changed files with 55 additions and 11 deletions
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1
src/where.c
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@@ -2646,6 +2646,7 @@ static int whereLoopAddBtreeIndex(
pNew->wsFlags |= WHERE_UNQ_WANTED;
}
}
if( scan.iEquiv>1 ) pNew->wsFlags |= WHERE_TRANSCONS;
}else if( eOp & WO_ISNULL ){
pNew->wsFlags |= WHERE_COLUMN_NULL;
}else if( eOp & (WO_GT|WO_GE) ){

1
src/whereInt.h
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@@ -603,5 +603,6 @@ void sqlite3WhereTabFuncArgs(Parse*, SrcItem*, WhereClause*);
#define WHERE_IN_EARLYOUT 0x00040000 /* Perhaps quit IN loops early */
#define WHERE_BIGNULL_SORT 0x00080000 /* Column nEq of index is BIGNULL */
#define WHERE_IN_SEEKSCAN 0x00100000 /* Seek-scan optimization for IN */
#define WHERE_TRANSCONS 0x00200000 /* Uses a transitive constraint */
#endif /* !defined(SQLITE_WHEREINT_H) */

17
src/wherecode.c
View File

@@ -620,7 +620,22 @@ static int codeEqualityTerm(
sqlite3DbFree(pParse->db, aiMap);
#endif
}
disableTerm(pLevel, pTerm);
/* As an optimization, try to disable the WHERE clause term that is
** driving the index as it will always be true. The correct answer is
** obtained regardless, but we might get the answer with fewer CPU cycles
** by omitting the term.
**
** But do not disable the term unless we are certain that the term is
** not a transitive constraint. For an example of where that does not
** work, see https://sqlite.org/forum/forumpost/eb8613976a (2021-05-04)
*/
if( (pLevel->pWLoop->wsFlags & WHERE_TRANSCONS)==0
|| (pTerm->eOperator & WO_EQUIV)==0
){
disableTerm(pLevel, pTerm);
}
return iReg;
}