[Dbix-class] Relationship to the same table

[Oleg Kostyuk]

Also read DBIx::Class::Manual::Joining, I think it might be helpful,
especially "Joining to the same table twice" part.

2010/1/2 Charlie Garrison <garrison at zeta.org.au>:
> Good morning,
>
> On 2/01/10 at 12:36 AM -0600, Pavel O. Karoukin <hippich at gmail.com> wrote:
>
>> Yeah, this work for one record as my example above, but I want to get more
>> "generic" aproach. For example how to code schema join for the following
>> query:
>>
>> SELECT * FROM
>> things as t1
>> JOIN
>> things as t2
>> ON
>> t1.type <> t2.type
>> AND
>> t1.uid  <> t2.uid
>
> Create a self-join relationship (other_things in my previous example)
>
> __PACKAGE__->has_many(other_things => 'MyApp::Schema::Result::Things',
> 'thing_id');
>
>
>> If I will be able to make it joined this way then I will be able to apply
>> any conditions later and not write custom accessor each time.
>
> Since the custom method returns a resultset, you can continue to chain other
> criteria from it:
>
> my $things =
> $schema->resultset("Thing")->first->different_things->search({other_cond=>'type2'});
>
> I think you might be stuck on what relationships are in DBIC; they are
> really just very fancy glue for returning resultsets; you can also compose
> and return your own resultsets. Write methods that take different arguments
> which allow you to compose the desired results. Eg. the example method I
> gave allows the 'type' to be passed as an argument or taken from the current
> record as a default.
>
> Anything you are wanting to define in the %attr for relationships can also
> be defined in your custom method. There is some fancy glue you don't get
> (eg. add_to_* methods), but for doing different queries the technique works
> a treat.
>
> Charlie
>
> --
>   Ꮚ Charlie Garrison ♊ <garrison at zeta.org.au>
>   〠 PO Box 141, Windsor, NSW 2756, Australia
>
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-- 
Sincerely yours,
Oleg Kostyuk (CUB-UANIC)