[Dbix-class] DBIx::Class::Schema::Loader and on_delete/cascade_delete

[Ben Tilly]

I replied at Perlmonks.  The short version is that this is reasonable behavior.

On Wed, Feb 15, 2012 at 10:18 AM, Andy Lester <andy at petdance.com> wrote:
> (Also posted to http://perlmonks.org/?node_id=954009)
>
> I'm using 0.07017 of DBIx::Class::Schema::Loader, and I'm confused by its output for two tables with a FK relationship.
>
> Here are excerpts of two related tables, List and Notification. Notification is a subtable of List, with a proper FK in the (Postgres) database, and it's defined as ON DELETE CASCADE in the DB. These snippets were from the files generated by ::Loader.
>
>
> # from TT/Schema/List.pm
>
> __PACKAGE__->has_many(
>  "notification",
>  "TT::Schema::Notification",
>  { "foreign.listid" => "self.listid", "foreign.ltype" => "self.ltype"
>  },
>  { cascade_copy => 0, cascade_delete => 0 },
> );
>
> # from TT/Schema/Notification.pm
>
> __PACKAGE__->belongs_to(
>  "list",
>  "TT::Schema::List",
>  { listid => "listid", ltype => "ltype" },
>  { is_deferrable => 1, on_delete => "CASCADE", on_update => "CASCADE"
>  },
> );
>
> The DBIx::Class docs say
>
> "By default, DBIx::Class cascades deletes across has_many, has_one and might_have relationships. You can disable this behaviour on a per-relationship basis by supplying cascade_delete => 0 in the relationship attributes. The cascaded operations are performed after the requested delete, so if your database has a constraint on the relationship, it will have deleted/updated the related records or raised an exception before DBIx::Class gets to perform the cascaded operation."
>
> which I take to mean that cascade_delete should be false if the database is going to take care of the deleting for us. In this case, it will, because there's a foreign key from notification up to list with ON DELETE CASCADE. But then why is on_delete=>'CASCADE'?
>
> It seems to me that the cascade_delete in the List.pm should be set to 1, to match the on_delete => 'CASCADE' in the Notification.pm. Or, that they should be 0 and undef, respectively. But I would think they should match.
>
> Am I misunderstanding something? Or is DBIx::Class::Schema::Loader not building my schema correctly?
>
> Thanks,
> xoxo,
> Andy
>
> --
> Andy Lester => andy at petdance.com => www.petdance.com => AIM:petdance
>
>
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