In pg_upgrade, allow tables using regclass to be upgraded because we

preserve pg_class oids since PG 9.0.

contrib/pg_upgrade/check.c

@@ -611,11 +611,11 @@ check_for_isn_and_int8_passing_mismatch(ClusterInfo *cluster)
 /*
  * check_for_reg_data_type_usage()
  *	pg_upgrade only preserves these system values:
- *		pg_class.relfilenode
+ *		pg_class.oid
  *		pg_type.oid
  *		pg_enum.oid
  *
- *	Most of the reg* data types reference system catalog info that is
+ *	Many of the reg* data types reference system catalog info that is
  *	not preserved, and hence these data types cannot be used in user
  *	tables upgraded by pg_upgrade.
  */
@@ -656,7 +656,7 @@ check_for_reg_data_type_usage(ClusterInfo *cluster)
 		  "			'pg_catalog.regprocedure'::pg_catalog.regtype, "
 		  "			'pg_catalog.regoper'::pg_catalog.regtype, "
 		  "			'pg_catalog.regoperator'::pg_catalog.regtype, "
-		 "			'pg_catalog.regclass'::pg_catalog.regtype, "
+		/* regclass.oid is preserved, so 'regclass' is OK */
 		/* regtype.oid is preserved, so 'regtype' is OK */
 		  "			'pg_catalog.regconfig'::pg_catalog.regtype, "
 		  "			'pg_catalog.regdictionary'::pg_catalog.regtype) AND "

doc/src/sgml/pgupgrade.sgml

@@ -557,7 +557,7 @@ psql --username postgres --file script.sql postgres
    <application>pg_upgrade</> does not support upgrading of databases
    containing these <type>reg*</> OID-referencing system data types:
    <type>regproc</>, <type>regprocedure</>, <type>regoper</>,
-   <type>regoperator</>, <type>regclass</>, <type>regconfig</>, and
+   <type>regoperator</>, <type>regconfig</>, and
    <type>regdictionary</>.  (<type>regtype</> can be upgraded.)
   </para>