Add copy/equal support for XID lists

alvherre · alvherre · commit 5ca0fe5c8ad7 · 2022-07-12T16:11:04.000+02:00
Commit f10a025 added support for List to store Xids, but didn't handle the new type in all cases. Add some obviously necessary pieces. As far as I am aware, this is all dead code as far as core code is concerned, but it seems unacceptable not to have it in case third-party code wants to rely on this type of list. (Some parts of the List API remain unimplemented, but that can be fixed as and when needed -- see lack of list_intersection_oid, list_deduplicate_int as precedents.) Discussion: https://postgr.es/m/20220708164534.nbejhgt4ajz35p65@alvherre.pgsql
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
@@ -187,11 +187,12 @@ copyObjectImpl(const void *from)
 			break;
 
 			/*
-			 * Lists of integers and OIDs don't need to be deep-copied, so we
-			 * perform a shallow copy via list_copy()
+			 * Lists of integers, OIDs and XIDs don't need to be deep-copied,
+			 * so we perform a shallow copy via list_copy()
 			 */
 		case T_IntList:
 		case T_OidList:
+		case T_XidList:
 			retval = list_copy(from);
 			break;
 
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
@@ -188,6 +188,13 @@ _equalList(const List *a, const List *b)
 					return false;
 			}
 			break;
+		case T_XidList:
+			forboth(item_a, a, item_b, b)
+			{
+				if (lfirst_xid(item_a) != lfirst_xid(item_b))
+					return false;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized list node type: %d",
 				 (int) a->type);
@@ -238,6 +245,7 @@ equal(const void *a, const void *b)
 		case T_List:
 		case T_IntList:
 		case T_OidList:
+		case T_XidList:
 			retval = _equalList(a, b);
 			break;
 
diff --git a/src/test/modules/test_oat_hooks/test_oat_hooks.c b/src/test/modules/test_oat_hooks/test_oat_hooks.c
@@ -1122,6 +1122,9 @@ nodetag_to_string(NodeTag tag)
 		case T_OidList:
 			return "OidList";
 			break;
+		case T_XidList:
+			return "XidList";
+			break;
 		case T_ExtensibleNode:
 			return "ExtensibleNode";
 			break;
