From 1afaa2557adb86cef224982093201ad035588eeb Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 23 Mar 2000 00:58:36 +0000
Subject: [PATCH] If we cannot get a real estimate for the selectivity of a
range query, use a default value that's fairly small. We were generating a
result of about 0.1, but I think 0.01 is probably better --- want to
encourage use of an indexscan in this situation.
---
src/backend/optimizer/path/clausesel.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
index 09d6d277c9a..baa99a7d28b 100644
--- a/src/backend/optimizer/path/clausesel.c
+++ b/src/backend/optimizer/path/clausesel.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.31 2000/03/17 02:36:14 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.32 2000/03/23 00:58:36 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -194,9 +194,11 @@ clauselist_selectivity(Query *root,
else
{
/* One or both is probably a default estimate,
- * so punt and just merge them in generically.
+ * so supply a default estimate for the selectivity
+ * of the range query. We rather optimistically assume
+ * that the range is tight...
*/
- s1 *= rqlist->hibound * rqlist->lobound;
+ s1 *= 0.01;
}
}
else
--
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