if (sup == null)
throw new MetaDataException(_loc.get("not-sub", cls));
ClassMappingInfo info = cls.getMappingInfo();
info.assertNoIndex(cls, false);
info.assertNoUnique(cls, false);
// foreign key from this class to our superclass
Table table = info.getTable(cls, adapt);
ForeignKey fk = info.getSuperclassJoin(cls, table, adapt);
Column[] pkCols = fk.getColumns();