Improve the check for pg_catalog.unknown data type in pg_upgrade

The pg_upgrade check for pg_catalog.unknown type when upgrading from 9.6
had a couple of issues with domains and composite types - it detected
even composite types unused in objects with storage. So for example this
was enough to trigger an unnecessary pg_upgrade failure:

  CREATE TYPE unknown_composite AS (u pg_catalog.unknown)

On the other hand, this only happened with composite types directly on
the pg_catalog.unknown data type, but not with a domain. So this was not
detected

  CREATE DOMAIN unknown_domain AS pg_catalog.unknown;
  CREATE TYPE unknown_composite_2 AS (u unknown_domain);

unlike the first example. These false positives and inconsistencies are
unfortunate, but what's worse we've failed to detected objects using the
pg_catalog.unknown type through a domain. So we missed cases like this

  CREATE TABLE t (u unknown_composite_2);

The consequence is clusters broken after a pg_upgrade.

This fixes these false positives and false negatives by using the same
recursive CTE introduced by eaf900e842 for sql_identifier. Backpatch all
the way to 10, where the of pg_catalog.unknown data type was restricted.

Author: Tomas Vondra
Backpatch-to: 10-
Discussion: https://postgr.es/m/16045-673e8fa6b5ace196%40postgresql.org

src/bin/pg_upgrade/version.c

@@ -229,7 +229,8 @@ old_9_3_check_for_line_data_type_usage(ClusterInfo *cluster)
  *	mid-upgrade.  Worse, if there's a matview with such a column, the
  *	DDL reload will silently change it to "text" which won't match the
  *	on-disk storage (which is like "cstring").  So we *must* reject that.
- *	Also check composite types, in case they are used for table columns.
+ *	Also check composite types and domains on the "unknwown" type (even
+ *	combinations of both), in case they are used for table columns.
  *	We needn't check indexes, because "unknown" has no opclasses.
  */
 void
@@ -256,17 +257,40 @@ old_9_6_check_for_unknown_data_type_usage(ClusterInfo *cluster)
 		DbInfo	   *active_db = &cluster->dbarr.dbs[dbnum];
 		PGconn	   *conn = connectToServer(cluster, active_db->db_name);
 
+		/*
+		 * The pg_catalog.unknown type may be wrapped in a domain or composite
+		 * type, or both (9.3 did not allow domains on composite types, but
+		 * there may be multi-level composite type). To detect these cases
+		 * we need a recursive CTE.
+		 */
 		res = executeQueryOrDie(conn,
+								"WITH RECURSIVE oids AS ( "
+		/* the pg_catalog.unknown type itself */
+								"	SELECT 'pg_catalog.unknown'::pg_catalog.regtype AS oid "
+								"	UNION ALL "
+								"	SELECT * FROM ( "
+		/* domains on the type */
+								"		WITH x AS (SELECT oid FROM oids) "
+								"			SELECT t.oid FROM pg_catalog.pg_type t, x WHERE typbasetype = x.oid AND typtype = 'd' "
+								"			UNION "
+		/* composite types containing the type */
+								"			SELECT t.oid FROM pg_catalog.pg_type t, pg_catalog.pg_class c, pg_catalog.pg_attribute a, x "
+								"			WHERE t.typtype = 'c' AND "
+								"				  t.oid = c.reltype AND "
+								"				  c.oid = a.attrelid AND "
+								"				  NOT a.attisdropped AND "
+								"				  a.atttypid = x.oid "
+								"	) foo "
+								") "
 								"SELECT n.nspname, c.relname, a.attname "
 								"FROM	pg_catalog.pg_class c, "
 								"		pg_catalog.pg_namespace n, "
 								"		pg_catalog.pg_attribute a "
 								"WHERE	c.oid = a.attrelid AND "
 								"		NOT a.attisdropped AND "
-								"		a.atttypid = 'pg_catalog.unknown'::pg_catalog.regtype AND "
+								"		a.atttypid IN (SELECT oid FROM oids) AND "
 								"		c.relkind IN ("
 								CppAsString2(RELKIND_RELATION) ", "
-								CppAsString2(RELKIND_COMPOSITE_TYPE) ", "
 								CppAsString2(RELKIND_MATVIEW) ") AND "
 								"		c.relnamespace = n.oid AND "
 		/* exclude possible orphaned temp tables */