Allow type resolution for UNKNOWN arguments to functions to fall back to

 any available string type. Previously, all candidate choices must have
 fallen within the same "type category" for PostgreSQL to be willing to
 choose any of them.
Need to apply the same fixup to operator type resolution.

Author: Thomas G. Lockhart

src/backend/parser/parse_func.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_func.c,v 1.91 2000/09/29 18:21:36 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_func.c,v 1.92 2000/11/06 15:42:30 thomas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -921,6 +921,10 @@ func_select_candidate(int nargs,
 	 * eliminate some candidates because they are non-preferred at the
 	 * first slot, we won't notice that they didn't have the same type
 	 * category for a later slot.
+	 * XXX Hmm. How else would you do this? These candidates are here because
+	 * they all have the same number of matches on arguments with explicit
+	 * types, so from here on left-to-right resolution is as good as any.
+	 * Need a counterexample to see otherwise...
 	 */
 	for (i = 0; i < nargs; i++)
 	{
@@ -944,8 +948,21 @@ func_select_candidate(int nargs,
 				}
 				else if (current_category != slot_category)
 				{
-					/* punt if more than one category for this slot */
-					return NULL;
+					/* started out as unknown type, so give preference to string type, if available */
+					if (current_category == STRING_TYPE)
+					{
+						/* forget all previous candidates */
+						candidates = current_candidate;
+						last_candidate = current_candidate;
+					}
+					else if (slot_category == STRING_TYPE)
+					{
+						/* forget this candidate */
+						if (last_candidate)
+							last_candidate->next = current_candidate->next;
+						else
+							candidates = current_candidate->next;
+					}
 				}
 				else if (current_type != slot_type)
 				{
@@ -982,6 +999,7 @@ func_select_candidate(int nargs,
 		return NULL;			/* no remaining candidates */
 	if (candidates->next != NULL)
 		return NULL;			/* more than one remaining candidate */
+
 	return candidates->args;
 }	/* func_select_candidate() */