diff options
| author | Tom Lane <tgl@sss.pgh.pa.us> | 2006-06-28 20:04:38 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2006-06-28 20:04:38 +0000 |
| commit | 1c1ecd5124068a45fdecc0dcc4ba2581c15acf9f (patch) | |
| tree | c7ecc0e07e153f32c35c4450e018b73c8570c72a /src/backend/optimizer/plan/subselect.c | |
| parent | 485375a1c9270fb3eefe4b9391dd976e563c2c1c (diff) | |
Improve planner estimates for size of tuple hash tables.
Diffstat (limited to 'src/backend/optimizer/plan/subselect.c')
| -rw-r--r-- | src/backend/optimizer/plan/subselect.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c index 1b5533cded4..c1304042a1d 100644 --- a/src/backend/optimizer/plan/subselect.c +++ b/src/backend/optimizer/plan/subselect.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.107 2006/05/03 00:24:56 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.108 2006/06/28 20:04:38 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -585,11 +585,13 @@ subplan_is_hashable(SubLink *slink, SubPlan *node) return false; /* - * The estimated size of the subquery result must fit in work_mem. (XXX - * what about hashtable overhead?) + * The estimated size of the subquery result must fit in work_mem. + * (Note: we use sizeof(HeapTupleHeaderData) here even though the tuples + * will actually be stored as MinimalTuples; this provides some fudge + * factor for hashtable overhead.) */ subquery_size = node->plan->plan_rows * - (MAXALIGN(node->plan->plan_width) + MAXALIGN(sizeof(HeapTupleData))); + (MAXALIGN(node->plan->plan_width) + MAXALIGN(sizeof(HeapTupleHeaderData))); if (subquery_size > work_mem * 1024L) return false; |