Simplify the planner's join clause management by storing join clauses

of a relation in a flat 'joininfo' list.  The former arrangement grouped
the join clauses according to the set of unjoined relids used in each;
however, profiling on test cases involving lots of joins proves that
that data structure is a net loss.  It takes more time to group the
join clauses together than is saved by avoiding duplicate tests later.
It doesn't help any that there are usually not more than one or two
clauses per group ...

1 files changed, 16 insertions, 25 deletions

diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c
index 2994421e5b7..52075fbf465 100644
--- a/src/backend/optimizer/path/pathkeys.c
+++ b/src/backend/optimizer/path/pathkeys.c
@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.67 2005/06/05 22:32:55 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.68 2005/06/09 04:18:59 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1157,11 +1157,11 @@ make_pathkeys_for_mergeclauses(PlannerInfo *root,
 /*
  * pathkeys_useful_for_merging
  *		Count the number of pathkeys that may be useful for mergejoins
- *		above the given relation (by looking at its joininfo lists).
+ *		above the given relation (by looking at its joininfo list).
  *
  * We consider a pathkey potentially useful if it corresponds to the merge
  * ordering of either side of any joinclause for the rel.  This might be
- * overoptimistic, since joinclauses that appear in different join lists
+ * overoptimistic, since joinclauses that require different other relations
  * might never be usable at the same time, but trying to be exact is likely
  * to be more trouble than it's worth.
  */
@@ -1179,31 +1179,22 @@ pathkeys_useful_for_merging(PlannerInfo *root, RelOptInfo *rel, List *pathkeys)
 
 		foreach(j, rel->joininfo)
 		{
-			JoinInfo   *joininfo = (JoinInfo *) lfirst(j);
-			ListCell   *k;
-
-			foreach(k, joininfo->jinfo_restrictinfo)
-			{
-				RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(k);
-
-				if (restrictinfo->mergejoinoperator == InvalidOid)
-					continue;
-				cache_mergeclause_pathkeys(root, restrictinfo);
+			RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(j);
 
-				/*
-				 * We can compare canonical pathkey sublists by simple
-				 * pointer equality; see compare_pathkeys.
-				 */
-				if (pathkey == restrictinfo->left_pathkey ||
-					pathkey == restrictinfo->right_pathkey)
-				{
-					matched = true;
-					break;
-				}
-			}
+			if (restrictinfo->mergejoinoperator == InvalidOid)
+				continue;
+			cache_mergeclause_pathkeys(root, restrictinfo);
 
-			if (matched)
+			/*
+			 * We can compare canonical pathkey sublists by simple
+			 * pointer equality; see compare_pathkeys.
+			 */
+			if (pathkey == restrictinfo->left_pathkey ||
+				pathkey == restrictinfo->right_pathkey)
+			{
+				matched = true;
 				break;
+			}
 		}
 
 		/*