while (mapping.getJoinablePCSuperclassMapping() != null)
mapping = mapping.getJoinablePCSuperclassMapping();
// select only the PK columns, since we just want to lock
Select select = _store.getSQLFactory().newSelect();
select.select(mapping.getPrimaryKeyColumns());
select.wherePrimaryKey(id, mapping, _store);
SQLBuffer sql = select.toSelect(true, fetch);
ensureStoreManagerTransaction();
Connection conn = _store.getConnection();