public function getSessionColumns() {
        $ini = Zend_Registry::get('config');
        $sessionColumns = Zend_Db_Select::SQL_WILDCARD;
        if (!empty($ini->auth->login->sessionColumns)) {
            $sessionColumns = $ini->auth->login->sessionColumns;
            $sessionColumns = explode(',', $sessionColumns);
        }
        return $sessionColumns;
    }