Inheritance overhaul by Chris Bitmead <chris@bitmead.com>

src/backend/optimizer/util/plancat.c

@@ -9,7 +9,11 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.53 2000/05/30 04:24:48 tgl Exp $
+<<<<<<< plancat.c
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.54 2000/06/09 01:44:16 momjian Exp $
+=======
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.54 2000/06/09 01:44:16 momjian Exp $
+>>>>>>> 1.53
  *
  *-------------------------------------------------------------------------
  */
@@ -278,6 +282,25 @@ find_inheritance_children(Oid inhparent)
 	return list;
 }
 
+/*
+ * has_subclass -
+ * In the current implementation, has_subclass returns whether a 
+ * particular class *might* have a subclass. It will not return the
+ * correct result if a class had a subclass which was later dropped.
+ * This is because relhassubclass in pg_class is not updated,
+ * possibly because of efficiency and/or concurrency concerns.
+ * Currently has_subclass is only used as an efficiency hack, so this
+ * is ok.
+ */
+bool has_subclass(Oid relationId)
+{
+        HeapTuple       tuple = 
+          SearchSysCacheTuple(RELOID,
+                              ObjectIdGetDatum(relationId),
+                              0, 0, 0);
+        return ((Form_pg_class) GETSTRUCT(tuple))->relhassubclass;
+}
+
 #ifdef NOT_USED
 /*
  * VersionGetParents