public function id($name = null)
    {
        if (!$name) {
            $name = 'id';
        }

        $val = $this->connection->expr($this->primary_key_expr);

        $this->args['field'] =
            [$name => $val] + (isset($this->args['field']) ? $this->args['field'] : []);

        return $this;
    }