Improve planner estimates for size of tuple hash tables.

tglsfdc · tglsfdc · commit 1c1ecd512406 · 2006-06-28T20:04:38.000Z
diff --git 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
@@ -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;
 

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`*`
`9`	`9`	`*`
`10`	`10`	`* IDENTIFICATION`
`11`		`- * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.199 2006/03/05 15:58:29 momjian Exp $`
	`11`	`+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.200 2006/06/28 20:04:38 tgl Exp $`
`12`	`12`	`*`
`13`	`13`	`*-------------------------------------------------------------------------`
`14`	`14`	`*/`
`@@ -1298,7 +1298,7 @@ choose_hashed_grouping(PlannerInfo *root, double tuple_fraction,`
`1298`	`1298`	`}`
`1299`	`1299`
`1300`	`1300`	`/* Estimate per-hash-entry space at tuple width... */`
`1301`		`- hashentrysize = cheapest_path_width;`
	`1301`	`+ hashentrysize = MAXALIGN(cheapest_path_width) + MAXALIGN(sizeof(MinimalTupleData));`
`1302`	`1302`	`/* plus space for pass-by-ref transition values... */`
`1303`	`1303`	`hashentrysize += agg_counts->transitionSpace;`
`1304`	`1304`	`/* plus the per-hash-entry overhead */`