Improve planner estimates for size of tuple hash tables.

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index ea6a052918ec3aebedda2a85b84dc5f83b1b4064..da1cadcd0db83998ad9acf7bf9d4be285598deec 100644 (file)
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.199 2006/03/05 15:58:29 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.200 2006/06/28 20:04:38 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1298,7 +1298,7 @@ choose_hashed_grouping(PlannerInfo *root, double tuple_fraction,
    }
 
    /* Estimate per-hash-entry space at tuple width... */
-   hashentrysize = cheapest_path_width;
+   hashentrysize = MAXALIGN(cheapest_path_width) + MAXALIGN(sizeof(MinimalTupleData));
    /* plus space for pass-by-ref transition values... */
    hashentrysize += agg_counts->transitionSpace;
    /* plus the per-hash-entry overhead */

diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 1b5533cded4a06d6a628552383efd5ae767c64dd..c1304042a1d3c407b6859066720a27d02b118429 100644 (file)
--- 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;