function fetch_count($params = array(), $sql_params = array())
 {
     $db_table =& $this->_get_db_table();
     $table_name = $db_table->get_table_name();
     $sql_params['tables'][] = ",{$table_name} as tn";
     $sql_params['conditions'][] = 'AND sso.id=tn.object_id AND sso.current_version=tn.version';
     return parent::fetch_count($params, $sql_params);
 }