[Dbix-class] establishing relationship across databases

[Sungsam Gong]

Hi,

I have been creating a manual relationship between tables (mysql
MyISAM) within the same database, which worked very well for my
purpose.
Just wondering whether it's possible to make a relationship between
two tables each of which residues in different database.

For example,
package Nectar::Schema::UNIPROT::Result::SwissVariant;
...
__PACKAGE__->has_many('2UniProts',
'Nectar::Schema::CARDIODB::Result::2UniProt',
{'foreign.uniprot'=>'self.sp_acc',
'foreign.res_num'=>'self.res_num'});

Then, within the controller:
    $c->stash->{humsavars}=[$c->model("UNIPROT::SwissVariant")->search(
        {gene=>$hgnc},
        {
            join=>[qw/2UniProts/],
            '+select'=>[qw/2UniProts.uid/],
            '+as'=>[qw/uid/],
            distinct=>1,
        }
    )];

I tried this, but with no luck.
It complains:
Can't find source for Nectar::Schema::CARDIODB::Result::2UniProt at
/home/sung/perl5/lib/perl5/DBIx/Class/Schema.pm line 1088
	DBIx::Class::Schema::throw_exception('Nectar::Schema::UNIPROT=HASH(0x1fa53990)',
'Can\'t find source for Nectar::Schema::CARDIODB::Result::2Uni...')
called at /home/sung/perl5/lib/perl5/DBIx/Class/Schema.pm line 601
	DBIx::Class::Schema::source('Nectar::Schema::UNIPROT=HASH(0x1fa53990)',
'Nectar::Schema::CARDIODB::Result::2UniProt') called at
/home/sung/perl5/lib/perl5/DBIx/Class/ResultSource.pm line 1853
	DBIx::Class::ResultSource::related_source('DBIx::Class::ResultSource::Table=HASH(0x1f9fc490)',
'2UniProts') called at
/home/sung/perl5/lib/perl5/DBIx/Class/ResultSource.pm line 1511
	DBIx::Class::ResultSource::_resolve_join('DBIx::Class::ResultSource::Table=HASH(0x1f9fc490)',
'2UniProts', 'me', 'HASH(0x21388770)', 'ARRAY(0x22151f30)', 'undef')
called at /home/sung/perl5/lib/perl5/DBIx/Class/ResultSource.pm line
1469
	DBIx::Class::ResultSource::_resolve_join('DBIx::Class::ResultSource::Table=HASH(0x1f9fc490)',
'ARRAY(0x22142e90)', 'me', 'HASH(0x21388770)', 'ARRAY(0x20799980)')
called at /home/sung/perl5/lib/perl5/DBIx/Class/ResultSet.pm line 3251
...

If cross-database joining is not possible, any workaround for this?

Cheers,
Sung