Enable fallback to string type when argument(s) are of UNKNOWN type.

 Same code exactly as for function resolution.
 An obvious example is for
  select '1' = '01';
 which used to throw an error and which now resolves to two text strings.

diff --git a/src/backend/parser/parse_oper.c b/src/backend/parser/parse_oper.c
index 5e898a22a6ab4614de2343a91ea35d775a0cf0f7..c858437c3cde45c55dfbf28b9bdcc621d4aeb813 100644 (file)
--- a/src/backend/parser/parse_oper.c
+++ b/src/backend/parser/parse_oper.c
@@ -443,8 +443,21 @@ oper_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)
                                {