[Dbix-class] Help me with subclassing

[dreel]

I wana enhance SQL::Abstract::Limit

It's working wrong with MS SQL Server
if i make sql like this 


->search(
    {
        	'rt.net_id'	 => $c->stash->{net_id},

    },
	{
		alias => 'rt', # alias columns in accordance with "from"
        from => [
        	{ rt => 'vi_route' },
            [
				{ n_1 => 'vi_nodes', -join_type => 'inner'  },
			    {
			    	'rt.route_beg' => 'n_1.node_id',
			    	'rt.net_id' => 'n_1.net_id'
			    }
			],
			[
				{ n_2 => 'vi_nodes', -join_type => 'inner'  },
				{
					'rt.route_end' => 'n_2.node_id',
					'rt.net_id' => 'n_2.net_id'
				}
			],
		],
		'select' => [
			{ distinct => ['rt.route_beg']},
			'rt.route_end',
			\'n_1.node_name AS node_name_beg',
			\'n_2.node_name AS node_name_end',
			'(SELECT COUNT(v.route_beg) FROM vi_route v WHERE v.net_id = \''.$c->stash->{net_id}.'\' and v.route_beg = rt.route_beg  and v.route_end = rt.route_end) as grp_count',
		],
      	'as'     => [ qw/ route_beg route_end node_name_beg node_name_end route_grp_count / ],
      	'order_by' => $order_by,
      	page => $page,  # page to return (defaults to 1)use Data::Dumper; die "SEARCH" . Dumper($new_attrs);
      	rows => $rows, # number of results per page
	},
  	)

it becomes WRONG syntax in sql:
SELECT * FROM
(
    SELECT TOP 10 * FROM
    (
        SELECT TOP 10  DISTINCT ...sql ORDER BY node_name_beg ASC
    ) AS foo
    ORDER BY node_name_beg DESC
) AS bar
ORDER BY node_name_beg ASC


SQL Server has another syntax:  SELECT DISTINCT TOP 10  (DISTINCT BEFORE TOP)

I wana do right sql - it work fine when looks like:

sub _Top {
    my ( $self, $sql, $order, $rows, $offset ) = @_;

    my $last = $rows + $offset;

    my ( $order_by_up, $order_by_down ) = $self->_order_directions( $order );

    $sql = <<"";
SELECT * FROM
(
    SELECT TOP $rows * FROM
    (
        SELECT TOP $last * FROM
        (
            $sql
        ) AS doo
        $order_by_up
    ) AS foo
    $order_by_down
) AS bar
$order_by_up

    return $sql;
}

But I don't have enough experience to subclass it - i never do it (