diff options
Diffstat (limited to 'src/backend/optimizer/path/costsize.c')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 07ddf43c8d6..b07a2599bbe 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -54,7 +54,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.204 2009/02/06 23:43:23 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.205 2009/03/21 00:04:39 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1821,6 +1821,7 @@ cost_hashjoin(HashPath *path, PlannerInfo *root, SpecialJoinInfo *sjinfo) int num_hashclauses = list_length(hashclauses); int numbuckets; int numbatches; + int num_skew_mcvs; double virtualbuckets; Selectivity innerbucketsize; ListCell *hcl; @@ -1862,11 +1863,22 @@ cost_hashjoin(HashPath *path, PlannerInfo *root, SpecialJoinInfo *sjinfo) * inner_path_rows; run_cost += cpu_operator_cost * num_hashclauses * outer_path_rows; - /* Get hash table size that executor would use for inner relation */ + /* + * Get hash table size that executor would use for inner relation. + * + * XXX for the moment, always assume that skew optimization will be + * performed. As long as SKEW_WORK_MEM_PERCENT is small, it's not worth + * trying to determine that for sure. + * + * XXX at some point it might be interesting to try to account for skew + * optimization in the cost estimate, but for now, we don't. + */ ExecChooseHashTableSize(inner_path_rows, inner_path->parent->width, + true, /* useskew */ &numbuckets, - &numbatches); + &numbatches, + &num_skew_mcvs); virtualbuckets = (double) numbuckets *(double) numbatches; /* |