[Dbix-class] DBIC hits DB thoguh using prefetch (repost)

[Hartmaier Alexander]

Hi Moritz!

You have to use the rels the same way to prefetch them, without using the many_to_many helper (which I can't see in your code).
Imho the ->all is the problem.
But why have the MapCategories table at all?
Just store the parent or child in your Categories table!
Or is it really possible to have multiple parents and childs?

-Alex


-----Original Message-----
From: Moritz Onken [mailto:onken at houseofdesign.de]
Sent: Tuesday, July 08, 2008 9:48 AM
To: DBIx::Class user and developer list
Subject: [Dbix-class] DBIC hits DB thoguh using prefetch (repost)

Hi,

sorry for the repost, but there was no answer to my previous post.

I have a table 'categories' which has a many_to_many relationship to
itself using a table 'map_categories'.

I found out that prefetching a many_to_many rel does not work. So I
prefetched the has_many rel to 'map_categories' (parents) and prefetch
the belongs_to rel (parent) from 'map_categories' to 'categories' ($rs-
 >search({},{prefetch => {'parents' => 'parent'}})->all). This does
the sql statement I expect but when I call $row->parents->all (or $rs-
first->parents->first->parent) on a row of this rs it hits the
database again. Although the resultset already contains all rows it
needs.

Any ideas what I did wrong?

cheers,

moritz

package Schema::Categories;

use strict;
use warnings;

use base 'DBIx::Class';

__PACKAGE__->load_components("PK::Auto", "Core");
__PACKAGE__->table("categories");
__PACKAGE__->add_columns(
  "title",
  {
    data_type => "character varying",
    default_value => undef,
    is_nullable => 1,
    size => 100,
  },
  "id",
  {
    data_type => "integer",
    is_nullable => 0
  });

__PACKAGE__->set_primary_key("id");

__PACKAGE__->has_many("parents" => 'Schema::MapCategories' => "child");


1;

package Schema::MapCategories;

use strict;
use warnings;

use base 'DBIx::Class';

__PACKAGE__->load_components("PK::Auto", "Core");
__PACKAGE__->table("map_categories");
__PACKAGE__->add_columns(
  "child",
  {
    data_type => "integer",
    is_nullable => 0,
  },
  "parent",
  {
    data_type => "integer",
    is_nullable => 0
  });

__PACKAGE__->belongs_to("child" => "Schema::Categories", "child");
__PACKAGE__->belongs_to("parent" => "Schema::Categories", "parent");
__PACKAGE__->add_unique_constraint([ qw/child parent/ ]);


1;

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