[Dbix-class] Are might_have relationships overly fussy?

[David Cantrell]

Hello classy people!

I have a result class that looks like this ...

   package Database::Chimera::Result::Serviceplan;
   use parent 'DBIx::Class::Core';

   __PACKAGE__->table('serviceplan');
   __PACKAGE__->add_columns(
     id                   => { data_type => 'INT', is_nullable => 0 },
     ...
     renew_serviceplan_id => { data_type => 'INT', is_nullable => 1 },
     ...
   );
   __PACKAGE__->set_primary_key('id');

for this table ...

   CREATE TABLE `serviceplan` (
     `id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
     ...
     `renew_serviceplan_id` mediumint(8) unsigned DEFAULT NULL,
     ...
     PRIMARY KEY (`id`)
);

In brief, a serviceplan is a description of something (a service) that
we sell. They all have a duration, and when a service reaches the end of
its life it can be renewed. Some renew with the same serviceplan, but
some have to renew with different serviceplans. We encode this in the
renew_serviceplan_id. In the case where something should renew with the
same serviceplan, renew_serviceplan_id is null.

I also have ...

   __PACKAGE__->might_have(
     "renew_serviceplan" => "Database::Chimera::Result::Serviceplan",
     { 'foreign.id' => 'self.renew_serviceplan_id' },
   );

That warns like this, although as far as I can tell it returns exactly
the results I need when I prefetch that relationship ...

   DBIx::Class::Relationship::HasOne::_validate_has_one_condition():
   "might_have/has_one" must not be on columns with is_nullable set to
   true (Database::Chimera::Result::Serviceplan/renew_serviceplan_id).
   This might indicate an incorrect use of those relationship helpers
   instead of belongs_to. at /home/dc/Chimera/dancer/../lib/Database
   /Chimera/Result/Serviceplan.pm line 78

I'm a bit surprised that it says that it *must not* be like that but
then works anyway. I'd expect a "must not" to be fatal. Anyway ... if I
change the relationship to a 'belongs_to' with 'join_type' => 'left' it
shuts up, and as far as I can tell I get exactly the same data back. ie,
belongs_to with a left join appears to be *exactly the same* as a
might_have, just with more typing. I wonder therefore whether
'might_have' is being too fussy here and that warning should be got rid of.

--
David Cantrell
David Cantrell
System Architect
The Hut Group<http://www.thehutgroup.com/>

Tel:
Email: david.cantrell at uk2group.com<mailto:david.cantrell at uk2group.com>

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