From 443175822942ef1f15cd047cda58990a089ef180 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 9 Jan 2007 02:14:16 +0000
Subject: Support ORDER BY ... NULLS FIRST/LAST, and add ASC/DESC/NULLS
 FIRST/NULLS LAST per-column options for btree indexes.  The planner's support
 for this is still pretty rudimentary; it does not yet know how to plan
 mergejoins with nondefault ordering options.  The documentation is pretty
 rudimentary, too. I'll work on improving that stuff later.

Note incompatible change from prior behavior: ORDER BY ... USING will now be
rejected if the operator is not a less-than or greater-than member of some
btree opclass.  This prevents less-than-sane behavior if an operator that
doesn't actually define a proper sort ordering is selected.
---
 src/backend/utils/adt/selfuncs.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

(limited to 'src/backend/utils/adt/selfuncs.c')

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 31cc62d68bb..875c7c524af 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.218 2007/01/05 22:19:42 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.219 2007/01/09 02:14:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -5101,7 +5101,7 @@ btcostestimate(PG_FUNCTION_ARGS)
 
 		if (get_attstatsslot(tuple, InvalidOid, 0,
 							 STATISTIC_KIND_CORRELATION,
-							 index->ordering[0],
+							 index->fwdsortop[0],
 							 NULL, NULL, &numbers, &nnumbers))
 		{
 			double		varCorrelation;
@@ -5116,6 +5116,23 @@ btcostestimate(PG_FUNCTION_ARGS)
 
 			free_attstatsslot(InvalidOid, NULL, 0, numbers, nnumbers);
 		}
+		else if (get_attstatsslot(tuple, InvalidOid, 0,
+								  STATISTIC_KIND_CORRELATION,
+								  index->revsortop[0],
+								  NULL, NULL, &numbers, &nnumbers))
+		{
+			double		varCorrelation;
+
+			Assert(nnumbers == 1);
+			varCorrelation = numbers[0];
+
+			if (index->ncolumns > 1)
+				*indexCorrelation = - varCorrelation * 0.75;
+			else
+				*indexCorrelation = - varCorrelation;
+
+			free_attstatsslot(InvalidOid, NULL, 0, numbers, nnumbers);
+		}
 		ReleaseSysCache(tuple);
 	}
 
-- 
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