Clean up handling of variable-free qual clauses. System now does the

right thing with variable-free clauses that contain noncachable functions,
such as 'WHERE random() < 0.5' --- these are evaluated once per
potential output tuple.  Expressions that contain only Params are
now candidates to be indexscan quals --- for example, 'var = ($1 + 1)'
can now be indexed.  Cope with RelabelType nodes atop potential indexscan
variables --- this oversight prevents 7.0.* from recognizing some
potentially indexscanable situations.

1 files changed, 13 insertions, 6 deletions

diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c
index d2bbff7e600..8ffd35c9bb0 100644
--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/initsplan.c,v 1.48 2000/08/08 15:41:38 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/initsplan.c,v 1.49 2000/08/13 02:50:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -184,7 +184,7 @@ add_restrict_and_join_to_rel(Query *root, Node *clause)
 
 		/*
 		 * There is only one relation participating in 'clause', so
-		 * 'clause' must be a restriction clause for that relation.
+		 * 'clause' is a restriction clause for that relation.
 		 */
 		RelOptInfo *rel = get_base_rel(root, lfirsti(relids));
 
@@ -201,11 +201,11 @@ add_restrict_and_join_to_rel(Query *root, Node *clause)
 		 */
 		check_mergejoinable(restrictinfo);
 	}
-	else
+	else if (relids != NIL)
 	{
 
 		/*
-		 * 'clause' is a join clause, since there is more than one atom in
+		 * 'clause' is a join clause, since there is more than one rel in
 		 * the relid list.	Set additional RestrictInfo fields for
 		 * joining.
 		 *
@@ -219,8 +219,6 @@ add_restrict_and_join_to_rel(Query *root, Node *clause)
 
 		/*
 		 * Add clause to the join lists of all the relevant relations.
-		 * (If, perchance, 'clause' contains NO vars, then nothing will
-		 * happen...)
 		 */
 		add_join_info_to_rels(root, restrictinfo, relids);
 
@@ -232,6 +230,15 @@ add_restrict_and_join_to_rel(Query *root, Node *clause)
 		 */
 		add_vars_to_targetlist(root, vars);
 	}
+	else
+	{
+		/*
+		 * 'clause' references no rels, and therefore we have no place to
+		 * attach it.  This means query_planner() screwed up --- it should
+		 * treat variable-less clauses separately.
+		 */
+		elog(ERROR, "add_restrict_and_join_to_rel: can't cope with variable-free clause");
+	}
 
 	/*
 	 * If the clause has a mergejoinable operator, then the two sides