[Dbix-class] Confused by search_related

[John Napiorkowski]

--- Paul Makepeace <paulm at paulm.com> wrote:

> On 10/6/07, John Napiorkowski <jjn1056 at yahoo.com>
> wrote:
> >
> > --- Paul Makepeace <paulm at paulm.com> wrote:
> >
> > > In the docs
> > >
> >
>
http://search.cpan.org/~ash/DBIx-Class-0.08007/lib/DBIx/Class/Relationship.pm
> > > there's an example of search_related doing a
> "select
> > > *" which I think
> > > is misleading as it's actually only selecting
> from
> > > the related
> > > resultset not the base(?) resultset, at least in
> my
> > > experiments.
> > >
> > > I have SavedView with,
> > >
> > > __PACKAGE__->belongs_to('web_chart_spec' =>
> > > 'IDL::Schema::WebChartSpec' =>
> > > 'web_chart_spec_uid');
> > >
> > > My controller does,
> > >
> > >   my @saved_views :Stashed =
> > >
> >
>
$c->model('DBIC_Readonly')->resultset('SavedView')->search_related(
> > >               'web_chart_spec' =>
> {service_profile_uid =>
> > > $chart->{service_profile_uid}});
> > >
> > > I get results but nothing from SavedView, just
> > > WebChartSpec! Debugging
> > > the SQL reveals it's only selecting on
> > > web_chart_spec.*. I dunno, if I
> > > called "resultset('SavedView')" I'm expecting
> stuff
> > > with SavedView in
> > > it.
> >
> > When you do a search_related you get a new
> resultset
> > from the related result_source (in this case it's
> > WebChartSpec, which is the resultset you specify
> in
> > the relationship).
> 
> (Yep. I find this counter-intuitive, but whatever.)
> Do you agree then
> the SQL in the docs is misleading? It's saying "*"
> is being returned
> whereas in fact only related_result_class.* is.
> 

Doc patches to clarify stuff definitely welcomed. 
It's a great way to remember the learning curve by :).

> >  It should also 'limit' the related
> > resultset by any conditions you've already done.
> so
> > for example:
> >
> >
> $schema->resultset('rs1')->related_resultset('rs2');
> >
> > should return a resultset of rs2 where all rs
> > 'belong_to' rs1 (assuming a definition similar to
> the
> > one you described).
> >
> > On the other hand:
> >
> > $schema
> >   ->resultset('rs1')
> >   ->search({value=>$search})
> >   ->related_resultset('rs2');
> >
> > returns a resultset of rs2 that belong to rs1 and
> > where 'value=$search' in rs1.
> 
> Is this just the same as
>
resultset('rs1')->search_related('me.value'=>$search})
> ?

The first arg in search_related has to be the
relationship name as you've named it in the
relationship definition. 'me.value' sounds like a
column name to me.  Although it's common for
relationships to be named by their columns they are
definitely different things.

> 
> >
> > Remember the SQL doesn't actually get run until
> you
> > want some values, so you can continue to add
> > conditions until you get the exact query you need.
> 
> Yeah, but I can't get back rs1 :-)

Yes you can, you did with the join conditions you have
below!

> 
> >
> > >
> > > How can I achieve what I'm intending here? In
> > > essence,
> > >
> > > select sv.* from saved_view sv
> > > join web_chart_spec ws on ws.uid =
> > > sv.web_chart_spec_uid
> > > where ws.service_profile_uid = ?;
> > >
> > >   my @saved_views :Stashed =
> > >
> >
>
$c->model('DBIC_Readonly')->resultset('SavedView')->search(
> > >              
> {'web_chart_spec.service_profile_uid' =>
> > > $chart->{service_profile_uid}},
> > >               {join => ['web_chart_spec']});
> > >
> > > Works but maybe there's a nicer way.
> > >
> > > P
> >
> > This is correct, if you want to limit a resultset
> via
> > it's relations, you need to join those relations.
> >
> > The only cleaning thing I can think of is to make
> this
> > into a custom resultset class method so that you
> can
> > just do:
> >
> > my $rs = $c->model('DBIC::SavedView')->custom_rs;
> >
> > In your controller.
> >
> > There's examples of making a custom resultset in
> the
> > cookbook and also there is a new feature that
> makes it
> > simple to add custom resultsets.  See:
> >
> >
>
http://search.cpan.org/~ash/DBIx-Class-0.08007/lib/DBIx/Class/Schema.pm#load_namespaces
> >
> > for some of this.  With this plus the ability to
> set a
> > custom result_class in your resultset methods, it
> > makes it much easier to link your physical model
> (AKA
> > the result_sources) to true domain logic.
> 
> Is this the sort of thing you mean?
> 
> My::Schema::SavedView,
>
__PACKAGE__->resultset_class('My::ResultSet::SavedView');
> 
> #...
> 
> package My::ResultSet::SavedView;
> use base 'DBIx::Class::ResultSet';
> 
> sub search_by_profile_uid {
>   my ($self, $profile_uid) = @_;
>   $self->search(
>     {'web_chart_spec.service_profile_uid' =>
> $profile_uid},
>     {join => ['web_chart_spec']});
> }
> 
> 1;

You got it.  Although if you use the
$schema->load_namespaces method you can skip setting
__PACKAGE__->resultset_class in the result_source
classes since it will do it for you.

> 
> Thanks for the tips, P
> 
No problem.  Hope you enjoy DBIC. --john

> >
> > Just stay away from the 'ResultSetManager'
> component,
> > which has been superceded by the above methods.
> >
> > --John
> >
> > >
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> > >
> >
> >
> >
> >      
>
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