Cache eval cost of qualification expressions in RestrictInfo nodes to

avoid repeated evaluations in cost_qual_eval().  This turns out to save
a useful fraction of planning time.  No change to external representation
of RestrictInfo --- although that node type doesn't appear in stored
rules anyway.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 45d53be5f62..366392df0de 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: relation.h,v 1.50 2000/11/12 00:37:01 tgl Exp $
+ * $Id: relation.h,v 1.51 2000/12/12 23:33:32 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -373,9 +373,9 @@ typedef JoinPath NestPath;
  * A mergejoin path has these fields.
  *
  * path_mergeclauses lists the clauses (in the form of RestrictInfos)
- * that will be used in the merge.	(Before 7.0, this was a list of
- * bare clause expressions, but we can save on list memory by leaving
- * it in the form of a RestrictInfo list.)
+ * that will be used in the merge.	(Before 7.0, this was a list of bare
+ * clause expressions, but we can save on list memory and cost_qual_eval
+ * work by leaving it in the form of a RestrictInfo list.)
  *
  * Note that the mergeclauses are a subset of the parent relation's
  * restriction-clause list.  Any join clauses that are not mergejoinable
@@ -491,6 +491,8 @@ typedef struct RestrictInfo
 
 	Expr	   *clause;			/* the represented clause of WHERE or JOIN */
 
+	Cost		eval_cost;		/* eval cost of clause; -1 if not yet set */
+
 	bool		ispusheddown;	/* TRUE if clause was pushed down in level */
 
 	/* only used if clause is an OR clause: */