protected function _getTextualColumns(Garp_Model_Db $model) {
        $columns = $model->info(Zend_Db_Table::METADATA);
        $textTypes = array('varchar', 'text', 'mediumtext', 'longtext', 'tinytext');
        foreach ($columns as $column => $meta) {
            if (!in_array($meta['DATA_TYPE'], $textTypes)) {
                unset($columns[$column]);
            }
        }
        return array_keys($columns);
    }