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Tweak nodeBitmapAnd to stop evaluating sub-plan scans if it finds it's

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got an empty bitmap after any step; the remaining subplans can no longer
affect the result.  Per a suggestion from Ilia Kantor.
This commit is contained in:
Tom Lane
2005-08-28 22:47:20 +00:00
parent 75e90bbf69
commit 46a0eee300
4 changed files with 30 additions and 4 deletions
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12
src/backend/executor/nodeBitmapAnd.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeBitmapAnd.c,v 1.2 2005/04/20 15:48:36 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeBitmapAnd.c,v 1.3 2005/08/28 22:47:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -143,6 +143,16 @@ MultiExecBitmapAnd(BitmapAndState *node)
tbm_intersect(result, subresult);
tbm_free(subresult);
}
/*
* If at any stage we have a completely empty bitmap, we can fall
* out without evaluating the remaining subplans, since ANDing them
* can no longer change the result. (Note: the fact that indxpath.c
* orders the subplans by selectivity should make this case more
* likely to occur.)
*/
if (tbm_is_empty(result))
break;
}
if (result == NULL)