From ca3d14f2a98b49d989090c800835b80087286cb4 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 21 Apr 2007 02:41:13 +0000
Subject: [PATCH] Tweak set_rel_width() to avoid redundant executions of
getrelid(). In very large queries this accounts for a noticeable fraction of
planning time. Per an example from Greg Stark.
---
src/backend/optimizer/path/costsize.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index ff5bb783372..42a5520b974 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 1.179 2007/03/27 23:21:09 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.180 2007/04/21 02:41:13 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -2357,12 +2357,22 @@ set_rel_width(PlannerInfo *root, RelOptInfo *rel)
{
int32 tuple_width = 0;
ListCell *tllist;
+ Oid rel_reloid;
+
+ /*
+ * Usually (perhaps always), all the Vars have the same reloid, so we can
+ * save some redundant list-searching by doing getrelid just once.
+ */
+ if (rel->relid > 0)
+ rel_reloid = getrelid(rel->relid, root->parse->rtable);
+ else
+ rel_reloid = InvalidOid; /* probably can't happen */
foreach(tllist, rel->reltargetlist)
{
Var *var = (Var *) lfirst(tllist);
int ndx;
- Oid relid;
+ Oid var_reloid;
int32 item_width;
/* For now, punt on whole-row child Vars */
@@ -2383,10 +2393,14 @@ set_rel_width(PlannerInfo *root, RelOptInfo *rel)
continue;
}
- relid = getrelid(var->varno, root->parse->rtable);
- if (relid != InvalidOid)
+ if (var->varno == rel->relid)
+ var_reloid = rel_reloid;
+ else
+ var_reloid = getrelid(var->varno, root->parse->rtable);
+
+ if (var_reloid != InvalidOid)
{
- item_width = get_attavgwidth(relid, var->varattno);
+ item_width = get_attavgwidth(var_reloid, var->varattno);
if (item_width > 0)
{
rel->attr_widths[ndx] = item_width;
--
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