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authorTom Lane <tgl@sss.pgh.pa.us>2006-05-18 19:56:46 +0000
committerTom Lane <tgl@sss.pgh.pa.us>2006-05-18 19:56:46 +0000
commiteed57b1b9259ee7cf95c022b39cddde3ee4604a9 (patch)
tree8168977e07b352ea2f57ac2dda6cd9d4a360d8cb /src
parentf32325264273e5d101064a7133aa5a3d90b0ad34 (diff)
downloadpostgresql-eed57b1b9259ee7cf95c022b39cddde3ee4604a9.tar.gz
postgresql-eed57b1b9259ee7cf95c022b39cddde3ee4604a9.zip
Fix choose_bitmap_and() so that partial index predicates are considered when
deciding whether a potential additional indexscan is redundant or not. As now coded, any use of a partial index that was already used in a previous AND arm will be rejected as redundant. This might be overly restrictive, but not considering the point at all is definitely bad, as per example in bug #2441 from Arjen van der Meijden. In particular, a clauseless scan of a partial index was *never* considered redundant by the previous coding, and that's surely wrong. Being more flexible would also require some consideration of how not to double-count the index predicate's selectivity.
Diffstat (limited to 'src')
-rw-r--r--src/backend/optimizer/path/indxpath.c19
1 files changed, 10 insertions, 9 deletions
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 935494e0778..ac6de3d82a5 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.205 2006/05/18 17:12:10 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.206 2006/05/18 19:56:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -616,10 +616,10 @@ choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel, List *paths)
* non-selective. In any case, we'd surely be drastically misestimating
* the selectivity if we count the same condition twice.
*
- * XXX is there any risk of throwing away a useful partial index here
- * because we don't explicitly look at indpred? At least in simple 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.
+ * We include index predicate conditions in the redundancy test. Because
+ * the test is just for pointer equality and not equal(), the effect is
+ * that use of the same partial index in two different AND elements is
+ * considered redundant. (XXX is this too strong?)
*
* 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,
@@ -732,14 +732,14 @@ bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel, List *paths)
/*
* pull_indexpath_quals
*
- * Given the Path structure for a plain or bitmap indexscan, extract a
- * list of RestrictInfo nodes for all the indexquals used in the Path.
+ * Given the Path structure for a plain or bitmap indexscan, extract a list
+ * of all the indexquals and index predicate conditions used in the Path.
*
* This is sort of a simplified version of make_restrictinfo_from_bitmapqual;
* here, we are not trying to produce an accurate representation of the AND/OR
* semantics of the Path, but just find out all the base conditions used.
*
- * The result list contains pointers to the RestrictInfos used in the Path,
+ * The result list contains pointers to the expressions used in the Path,
* but all the list cells are freshly built, so it's safe to destructively
* modify the list (eg, by concat'ing it with other lists).
*/
@@ -777,7 +777,8 @@ pull_indexpath_quals(Path *bitmapqual)
{
IndexPath *ipath = (IndexPath *) bitmapqual;
- result = list_copy(ipath->indexclauses);
+ result = get_actual_clauses(ipath->indexclauses);
+ result = list_concat(result, list_copy(ipath->indexinfo->indpred));
}
else
elog(ERROR, "unrecognized node type: %d", nodeTag(bitmapqual));