[5.6] eloquent withDefault() and N queries problem

[shadoWalker89]

• Laravel Version: 5.6.33
• PHP Version: 7.1
• Database Driver & Version: mysql 5.6.31

Short version of the description

When we have a model A with a relation b() that uses the withDefault() and the B model has a relation c()
when we try and do

$rows = A::with('b.c');
foreach($rows as $row)
{
    $row->b->c;
}

For every b instance that is a default model and not a row in the database, when we do ->c it will trigger a database query.

So if we have 50 $rows, where only 2 acutally have a b related row
the eager loading will work only on the 2 existing b rows and we will have 48 other queries trying to fetch the c relation of the b default models

Long version of the description and details:

The withDefault() eloquent method was added to make reduce the conditionals and make the code better.

But when i have a model like this

class Complaint extends Model
{
    public function status()
    {
        return $this->belongsTo(Status::class)->withDefault();
    }
}

And then when i want to display a grid of my complaints by doing something like this

class ComplaintsController extends Controller
{

    public function index(Request $request)
    {
        $complaints = Complaint::with(['status.translations'])->get();
        
        
        return view('modules.complaints.index', compact('complaints'));
    }
}

<table>
...
<tr>
...
<!-- the ->name will get the name from the translation that matches the application locale -->
<td>{{ $complaint->status->name }}</td>
...
</tr>
...
</table>

The problem being is that for every Status that is a default model and does not really exist when i try to fetch the name from the translation a new query will be exectued.

So to avoid having N queries problem now i'm doing this in my blade template

<table>
...
<tr>
...
<!-- the ->name will get the name from the translation that matches the application locale -->
<td>{{ $complaint->status->exists ? $complaint->status->name : null }}</td>
...
</tr>
...
</table>

Which is basically the thing that the default models were addedd for (writing this conditions)

This has been brought up before and closed without a real solution from the laravel framework core team #24241

@jonnsl added a suggestion for solving this issue

[driesvints]

I see the problem and agree that this might need some tweaking. I don't have time to deep dive into this atm but I'll mark it as an enhancement so someone might be able to pick this up. This isn't really a bug but something that could be improved.