[Dbix-class] Filtering out inactive records

[Vladimir Melnik]

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