protected function _buildInsert()
        {
            $query[] = "INSERT INTO";
            $query[] = $this->_quoteIdentifier($this->_table_name);
            $field_list = array_map(array($this, '_quoteIdentifier'), array_keys($this->_dirty_fields));
            $query[] = "(" . join(", ", $field_list) . ")";
            $query[] = "VALUES";

            $placeholders = $this->_createPlaceholders($this->_dirty_fields);
            $query[] = "({$placeholders})";

            if (self::get_db($this->_connection_name)->getAttribute(PDO::ATTR_DRIVER_NAME) == 'pgsql') {
                $query[] = 'RETURNING ' . $this->_quoteIdentifier($this->_getIdColumnName());
            }

            return join(" ", $query);
        }