Teach the system how to use hashing for UNION. (INTERSECT/EXCEPT will follow,

[postgresql] / src / backend / optimizer / util / clauses.c

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 04ef2224c915f8367d1b8057b3d839bbeb5101d0..858d4abcbd87c1680e14c6cda67075cb94767c40 100644 (file)
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.260 2008/08/02 21:32:00 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.261 2008/08/07 01:11:50 tgl Exp $
  *
  * HISTORY
  *       AUTHOR                        DATE                    MAJOR EVENT
@@ -3933,6 +3933,8 @@ expression_tree_walker(Node *node,
                                        return true;
                                if (walker(setop->rarg, context))
                                        return true;
+
+                               /* groupClauses are deemed uninteresting */
                        }
                        break;
                case T_InClauseInfo:
@@ -4535,6 +4537,7 @@ expression_tree_mutator(Node *node,
                                FLATCOPY(newnode, setop, SetOperationStmt);
                                MUTATE(newnode->larg, setop->larg, Node *);
                                MUTATE(newnode->rarg, setop->rarg, Node *);
+                               /* We do not mutate groupClauses by default */
                                return (Node *) newnode;
                        }
                        break;