I'm trying to better understand many_to_many sugar methods. Specifically,
why I cannot pass a list of ids to a set_$rel
In the familiar "music" database each Cd can have one or more Genres.
Cd->many_to_many( genres => 'cd_genres' => 'genre' );
What I'm wondering is why I cannot use ids directly like $cd->set_genres(
[2, 3] );
Instead I have to supply Genre objects:
my @genres = $schema->resultset('Genre')->search({ id => [2,3]});
$cd->set_genres( \...@genres );
But, that results in these queries where the select is apparently only there
fetch the ids of the Genre objects, which I already have.
SELECT me.id, me.name FROM genre me WHERE ( ( id = ? OR id = ? ) ): '2', '3'
DELETE FROM cd_genre WHERE ( cd = ? ): '1'
INSERT INTO cd_genre ( cd, genre) VALUES ( ?, ? ): '1', '2'
INSERT INTO cd_genre ( cd, genre) VALUES ( ?, ? ): '1', '3'
Is that select necessary for DBIC to work?
(I suppose an additional optimization would be to do the INSERTs in a single
db operation.)
The reason I'm curious is I have only the $cd object, the "genres" name, and
the @ids. So I don't have the "Genre" moniker.
So, it ends up:
my ($key) =
$cd->genres->result_source->primary_columns;$cd->set_genres(
$cd->genres->result_source->resultset->search({ $key => \...@ids}) );
Sorry, if that's the hard way to do that -- all the class relationships in
DBIx::Class are still a bit fuzzy to me.
Anyway, that seems like a bit of work to just fetch the ids (which I already
have).
Also, if all I have is $schema, the "Cd" moniker, and the (non-)relation for
the many_to_many "genres" is this the recommended way to get a list of all
Genre objects?
$schema->resultset( 'Cd'
)->new_result({})->genres->result_source->resultset->all;
Thanks,
--
Bill Moseley
[email protected]
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