Fix for UNION selects with constant NULL expressions; e.g.

 SELECT 1 UNION SELECT NULL;

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 732befec240cf438386bce81186bfc233f61505a..a701ffca27922155102458b9ab3106fbc792404b 100644 (file)
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.20 1998/07/09 14:34:05 thomas Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.21 1998/07/14 03:51:42 thomas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -472,7 +472,25 @@ transformUnionClause(List *unionClause, List *targetlist)
                Oid   otype;
                otype = ((TargetEntry *)lfirst(prev_target))->resdom->restype;
                itype = ((TargetEntry *)lfirst(next_target))->resdom->restype;
-               if (itype != otype)
+
+#ifdef PARSEDEBUG
+printf("transformUnionClause: types are %d -> %d\n", itype, otype);
+#endif
+
+               /* one or both is a NULL column? then don't convert... */
+               if (otype == InvalidOid)
+               {
+                   /* propagate a known type forward, if available */
+                   if (itype != InvalidOid)
+                   {
+                       ((TargetEntry *)lfirst(prev_target))->resdom->restype = itype;
+                   }
+               }
+               else if (itype == InvalidOid)
+               {
+               }
+               /* they don't match in type? then convert... */
+               else if (itype != otype)
                {
                    Node *expr;
 
@@ -488,6 +506,7 @@ transformUnionClause(List *unionClause, List *targetlist)
                    ((TargetEntry *)lfirst(next_target))->expr = expr;
                    ((TargetEntry *)lfirst(next_target))->resdom->restype = otype;
                }
+
                /* both are UNKNOWN? then evaluate as text... */
                else if (itype == UNKNOWNOID)
                {