Refactor planner's pathkeys data structure to create a separate, explicit

representation of equivalence classes of variables.  This is an extensive
rewrite, but it brings a number of benefits:
* planner no longer fails in the presence of "incomplete" operator families
that don't offer operators for every possible combination of datatypes.
* avoid generating and then discarding redundant equality clauses.
* remove bogus assumption that derived equalities always use operators
named "=".
* mergejoins can work with a variety of sort orders (e.g., descending) now,
instead of tying each mergejoinable operator to exactly one sort order.
* better recognition of redundant sort columns.
* can make use of equalities appearing underneath an outer join.

1 files changed, 3 insertions, 5 deletions

diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index cd7952aefde..ec93b0dad07 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.135 2007/01/05 22:19:32 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.136 2007/01/20 20:45:39 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1195,10 +1195,8 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
 		 */
 		newinfo->eval_cost.startup = -1;
 		newinfo->this_selec = -1;
-		newinfo->left_pathkey = NIL;
-		newinfo->right_pathkey = NIL;
-		newinfo->left_mergescansel = -1;
-		newinfo->right_mergescansel = -1;
+		newinfo->left_ec = NULL;
+		newinfo->right_ec = NULL;
 		newinfo->left_bucketsize = -1;
 		newinfo->right_bucketsize = -1;