Planner speedup hacking. Avoid saving useless pathkeys, so that path

comparison does not consider paths different when they differ only in
uninteresting aspects of sort order.  (We had a special case of this
consideration for indexscans already, but generalize it to apply to
ordered join paths too.)  Be stricter about what is a canonical pathkey
to allow faster pathkey comparison.  Cache canonical pathkeys and
dispersion stats for left and right sides of a RestrictInfo's clause,
to avoid repeated computation.  Total speedup will depend on number of
tables in a query, but I see about 4x speedup of planning phase for
a sample seven-table query.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 3e4a6d91dd1..62ce708f0bb 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.134 2000/12/12 23:33:32 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.135 2000/12/14 22:30:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1424,7 +1424,12 @@ _copyRestrictInfo(RestrictInfo *from)
 	newnode->mergejoinoperator = from->mergejoinoperator;
 	newnode->left_sortop = from->left_sortop;
 	newnode->right_sortop = from->right_sortop;
+	/* Do not copy pathkeys, since they'd not be canonical in a copied query */
+	newnode->left_pathkey = NIL;
+	newnode->right_pathkey = NIL;
 	newnode->hashjoinoperator = from->hashjoinoperator;
+	newnode->left_dispersion = from->left_dispersion;
+	newnode->right_dispersion = from->right_dispersion;
 
 	return newnode;
 }