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.

3 files changed, 16 insertions, 5 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;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 2f6a93b95ba..645fc56e3f8 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -20,7 +20,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.84 2000/12/12 23:33:33 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.85 2000/12/14 22:30:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -515,8 +515,9 @@ _equalRestrictInfo(RestrictInfo *a, RestrictInfo *b)
 	if (!equal(a->clause, b->clause))
 		return false;
 	/*
-	 * ignore eval_cost, since it may not be set yet, and should be
-	 * derivable from the clause anyway
+	 * ignore eval_cost, left/right_pathkey, and left/right_dispersion,
+	 * since they may not be set yet, and should be derivable from the
+	 * clause anyway
 	 */
 	if (a->ispusheddown != b->ispusheddown)
 		return false;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index d8aa2a5d2dc..4d4ec782e7a 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.101 2000/12/12 23:33:33 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.102 2000/12/14 22:30:42 tgl Exp $
  *
  * NOTES
  *	  Most of the read functions for plan nodes are tested. (In fact, they
@@ -1848,6 +1848,11 @@ _readRestrictInfo(void)
 
 	/* eval_cost is not part of saved representation; compute on first use */
 	local_node->eval_cost = -1;
+	/* ditto for cached pathkeys and dispersion */
+	local_node->left_pathkey = NIL;
+	local_node->right_pathkey = NIL;
+	local_node->left_dispersion = -1;
+	local_node->right_dispersion = -1;
 
 	return local_node;
 }