From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 23 Mar 2000 00:58:36 +0000 (+0000)
Subject: If we cannot get a real estimate for the selectivity of a range query,
X-Git-Tag: REL7_0~364
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1afaa2557adb86cef224982093201ad035588eeb;p=postgresql

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.
---

diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
index 09d6d277c9..baa99a7d28 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