Refactor user list retrieval

[rr-]

Right now all operations are done client-side (in terms of database connections). Constructing score distribution from 90000 entries means retrieval of 90000 entries from database and grouping them locally in PHP code. Consider doing selects like SELECT COUNT(score) FROM usermedia WHERE ... GROUP BY score inside Distribution classes. In order to achieve this, filters and perhaps sorters too should be moved to their own classes that can convert themselves to SQL expressions. After that getMixedUserMedia should be able to accept sorters and filters as parameters.

[rr-]

Tests proved that multiple JOINs were actually slower than grouping data client-side (1.01s vs 0.97s). Attaching code used for tests.

MediaGenreDistribution.php:

    public static function fromUser($user, $media)
    {
        $dist = new self();
        R::begin();
        $query = 'SELECT mg.mal_id AS mg_mal_id, mg.name AS mg_name, mg.id AS mg_id, m.*, um.*, m.id AS media_id' .
            ' FROM mediagenre mg' .
            ' INNER JOIN media m ON mg.media_id = m.id' .
            ' INNER JOIN usermedia um ON m.mal_id = um.mal_id AND m.media = um.media' .
            ' WHERE um.user_id = ? AND um.media = ?' .
            ' AND status != ?';
        $data = R::getAll($query, [$user->id, $media, UserListStatus::Planned]);
        R::rollback();

        $map = [];
        foreach ($data as $row)
        {
            $key = $row['media_id'];
            if (!isset($map[$key]))
            {
                $entry = new Model_MixedUserMedia($row);
                $map[$key] = $entry;
                $map[$key]->genres = [];
            }
            $g = new StdClass;
            $g->id = $row['mg_id'];
            $g->mal_id = $row['mg_mal_id'];
            $g->name = $row['mg_name'];
            $map[$key]->genres []= $g;
        }

        foreach ($map as $entry)
        {
            $dist->addEntry($entry);
        }
        $dist->finalize();
        return $dist;
    }

UserControllerFavoritesModule.php:

    #$favGenres = MediaGenreDistribution::fromEntries($listNonPlanned);
    $favGenres = MediaGenreDistribution::fromUser($viewContext->user, $viewContext->media);