[Dbix-class] Filtering out inactive records

[Colin Newell]

The general ambiguity problem is easily solvable, what you need is the
'current_source_alias'.  That allows you to disambiguate your field
references and it works perfectly in the chained searches.

http://search.cpan.org/~ribasushi/DBIx-Class-0.082840/lib/DBIx/Class/ResultSet.pm#current_source_alias


Colin.

On 9 February 2017 at 11:55, Vladimir Melnik <v.melnik at uplink.ua> wrote:
> Hello,
>
> Lots of thanks to the founders and maintainers for such a useful and handy framework! :)
>
> The database schema of the project I'm currently working on implies presence of 3 additional fields in each table:
>   `valid_since` datetime NOT NULL,
>   `valid_till` datetime DEFAULT NULL,
>   `removed` datetime DEFAULT NULL
>
> Their names are pretty self-descriptive: most of queries (not all, but most of them) should select only the rows that are "valid" (valid_since <= NOW() AND valid_till > NOW()) and aren't "removed" (removed IS NULL).
>
> I decided to create a package that is called ***::Schema::DefaultResultSet with the following method:
>
>     method filter_valid (
>         DateTime $now? = DateTime->now
>     ) {
>         $self->search(
>             {
>                 -and => [
>                     { removed       => { '='    => undef } },
>                     { valid_since   => { '<='   => $now } },
>                     {
>                         -or => [
>                             { valid_till    => { '=' => undef } },
>                             { valid_till    => { '>' => $now } }
>                         ]
>                     }
>                 ]
>             }
>         );
>     }
>
> It lets me to do call the filter_valid method for filtering out the "disabled" records for each result. For example:
>     $db_schema->resultset("Actor")->search({ name => 'Vasya' })->filter_valid;
>
> It works fine until I'm not trying to implement it for many-to-many relations. There are 2 problems I'm facing.
>
> (1) "Column 'valid_till' in where clause is ambiguous"
>
> There's the "actor_x_movie" table which is being used for building the many-to-many relation between the "actor" and "movie" tables. In the ***::Schema::Result::Actor I've added the following:
>
>     __PACKAGE__->many_to_many("movies" => "actor_x_movie", "movie");
>
> It works fine, so I can do the following:
>     my $actor = $db_schema->resultset("Actor")->search({ name => 'Vasya' })->filter_valid->first;
>     my $movie = $actor->movie->first;
> ...and it gives me the first result from the "movie" table that the first result of the "actor" table is related to. That's fine.
>
> The problem appears when I add the filter_valid:
>     my $movie = $actor->movie->filter_valid->first;
>
> I'm getting the following exception:
> DBIx::Class::Storage::DBI::_dbh_execute(): DBI Exception: DBD::mysql::st execute failed: Column 'valid_till' in where clause is ambiguous [for Statement "SELECT movie.id, movie.valid_since, movie.valid_till, movie.removed, movie.name, movie.movie_type_id, movie.provider FROM actor_x_movie me  JOIN movie movie ON movie.id = me.movie_id WHERE ( ( ( valid_till IS NULL OR valid_till > ? ) AND me.actor_id = ? AND removed IS NULL AND valid_since <= ? ) )" with ParamValues: 0='2017-02-08 12:38:02', 1=2, 2='2017-02-08 12:38:02']
>
> Is there a way to make DBIx::Class performing the "filter_valid" part _after_ performing the "movie" query? Without something like that:
>     $my $movie = $actor->movie; $movie = $movie->filter_valid->first?
>
> (2) Filtering out the "disabled" records from the "actor_x_movie" table
>
> Can I make DBIx::Class calling the "filter_valid" method for the records of "actor_x_movie" too? Of corse, I can do something like that:
>     __PACKAGE__->many_to_many("movies" => "actor_x_movie", "movie", {
>         -and => [
>             { removed       => { '='    => undef } },
>             { valid_since   => { '<='   => \'NOW()' } },
>             {
>                 -or => [
>                     { valid_till    => { '=' => undef } },
>                     { valid_till    => { '>' => \'NOW()' } }
>                 ]
>             }
>         ]
>     } );
> ...but adding it for EACH many-to-many relation doesn't seem to be a good idea. :( Is there a way to call "filter_valid" for the "actor_x_movie" resultset when performing the many-to-many query?
>
> I'm considering using MySQL Views. Maybe I need to make a separate view for each table: valid_actor, valid_movie, valid_actor_x_movie and so on, but it won't be tidy. :( What would you suggest? Did you have to deal with similar problems? What practices are the best? I'll be very grateful for any hints and tips regarding this topic.
>
> Thanks!
>
> --
> V.Melnik
>
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