Laravel - orderBy 不处理关系集合

Question

I recently moved a Laravel website to a different server with the same setup (slightly different versions of php, mariadb, etc.) and have run into an interesting problem.

I'm using the package Team-Tea-Time/laravel-forum (formerly riari/laravel-forum) to provide message board functionalities. In the forum every thread has a link to get to the newest post, which worked fine before the move. After the move those links lead to the oldest/first post instead.

The functionality is part of the Thread model , specifically the function getLastPostAttribute().

When trying to get to the bottom of this, I realized that the orderBy on the posts relationship is simply not having any effect. No matter what attribute I sort by (eg created_at, sequence) and which sort direction I request, it's always the same post order and the same first post being returned.

Example of a thread with 1811 posts with different timestamps and sequence numbers:

Ordering by sequence ASC works correctly, the first post being the one with the smalles sequence number. This is however also the default order of that relationship (see Model).

$t->posts()->orderBy('sequence', 'asc')->first();
Riari\Forum\Models\Post {#3268
    id: 113544,
    thread_id: 3995,
    author_id: 191,
    sequence: 1,
    created_at: "2018-05-08 08:21:20",
    updated_at: "2018-05-08 10:51:41",
    deleted_at: null,
    vote_count: 0,
}

Now when I change the sort order to desc, it should return the post with the highest sequence number. But instead I get the same result as above.

$t->posts()->orderBy('sequence', 'desc')->first();
Riari\Forum\Models\Post {#3297
    id: 113544,
    thread_id: 3995,
    author_id: 191,
    sequence: 1,
    created_at: "2018-05-08 08:21:20",
    updated_at: "2018-05-08 10:51:41",
    deleted_at: null,
    vote_count: 0,
}

This is the post that should be returned when sorting by sequence desc:

Riari\Forum\Models\Post {#3332
    id: 196449,
    thread_id: 3995,
    author_id: 534,
    sequence: 1814,
    created_at: "2020-12-16 14:55:54",
    updated_at: "2020-12-16 14:55:54",
    deleted_at: null,
    vote_count: 0,
}

Has anybody experienced this before? Everything else works fine after the move, I'm clueless as to what would cause such a specific error.

Answer 1

When you look at the relation definition in the source code of Thread.php , you see that posts are already ordered by created_at by default:

public function posts()
{
        $withTrashed = config('forum.preferences.display_trashed_posts') || Gate::allows('viewTrashedPosts');
        $query = $this->hasMany(Post::class)->orderBy('created_at');
        return $withTrashed ? $query->withTrashed() : $query;
}

I think you would need to override the posts method, remove the orderBy('created_at') statement, and then your own orderBy will work.