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

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
View File

@ -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)

11
src/backend/nodes/tidbitmap.c
View File

@ -23,7 +23,7 @@
* Copyright (c) 2003-2005, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.5 2005/07/24 02:25:26 tgl Exp $
* $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.6 2005/08/28 22:47:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -510,6 +510,15 @@ tbm_intersect_page(TIDBitmap *a, PagetableEntry *apage, const TIDBitmap *b)
}
}
/*
* tbm_is_empty - is a TIDBitmap completely empty?
*/
bool
tbm_is_empty(const TIDBitmap *tbm)
{
return (tbm->nentries == 0);
}
/*
* tbm_begin_iterate - prepare to iterate through a TIDBitmap
*

7
src/backend/optimizer/path/indxpath.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.187 2005/07/28 20:26:20 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.188 2005/08/28 22:47:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -538,6 +538,11 @@ choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel, List *paths)
* cases, the partial index will sort before competing non-partial
* indexes and so it makes the right choice, but perhaps we need to
* work harder.
*
* Note: outputting the selected sub-paths in selectivity order is a good
* thing even if we weren't using that as part of the selection method,
* because it makes the short-circuit case in MultiExecBitmapAnd() more
* likely to apply.
*/
/* Convert list to array so we can apply qsort */

4
src/include/nodes/tidbitmap.h
View File

@ -15,7 +15,7 @@
*
* Copyright (c) 2003-2005, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/include/nodes/tidbitmap.h,v 1.1 2005/04/17 22:24:02 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/tidbitmap.h,v 1.2 2005/08/28 22:47:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -49,6 +49,8 @@ extern void tbm_add_tuples(TIDBitmap *tbm, const ItemPointer tids, int ntids);
extern void tbm_union(TIDBitmap *a, const TIDBitmap *b);
extern void tbm_intersect(TIDBitmap *a, const TIDBitmap *b);
extern bool tbm_is_empty(const TIDBitmap *tbm);
extern void tbm_begin_iterate(TIDBitmap *tbm);
extern TBMIterateResult *tbm_iterate(TIDBitmap *tbm);