Eager loading for belongsToMany pivot table

[projct1]

I have this structure:

class Place extends Model
{
    public function discounts(): BelongsToMany
    {
        return $this->belongsToMany(Discount::class)->using(DiscountPlace::class)->withPivot('id');
    }
}

class Discount extends Model
{
    public function places(): BelongsToMany
    {
        return $this->belongsToMany(Place::class)->using(DiscountPlace::class)->withPivot('id');
    }
}

class DiscountPlace extends Pivot
{
    public $incrementing = true;

    public function activities(): MorphMany
    {
        return $this->morphMany(Activity::class);
    }
}

Now I have to load activities for each discount in a loop:

$place = Place::with('discounts')->first();

$place->discounts->map(fn($discount) => $discount->pivot->load('activities'));

As a result, I receive a lot of queries:

select * from `activity_log` where `activity_log`.`subject_type` = 'App\\Models\\DiscountPlace' and `activity_log`.`subject_id` = 1 and `activity_log`.`subject_id` is not null
select * from `activity_log` where `activity_log`.`subject_type` = 'App\\Models\\DiscountPlace' and `activity_log`.`subject_id` = 2 and `activity_log`.`subject_id` is not null
select * from `activity_log` where `activity_log`.`subject_type` = 'App\\Models\\DiscountPlace' and `activity_log`.`subject_id` = 3 and `activity_log`.`subject_id` is not null
/** etc... */

How can my task be done better without third-party libraries?

[Sandalanka]

Use morphMany with morphToMany-like trick (manual eager load)
$place = Place::with('discounts')->first();

// Get all pivot IDs for this place
$pivotIds = $place->discounts->pluck('pivot.id');

// Preload all activities in one query
$activities = Activity::where('subject_type', DiscountPlace::class)
->whereIn('subject_id', $pivotIds)
->get()
->groupBy('subject_id');

// Attach activities to each pivot
$place->discounts->each(function ($discount) use ($activities) {
$discount->pivot->setRelation('activities', $activities->get($discount->pivot->id, collect()));
});

Now every pivot->activities is already loaded, no extra queries.

Just 2 queries total: one for discounts, one for activities.

[projct1]

Use morphMany with morphToMany-like trick (manual eager load) $place = Place::with('discounts')->first();

// Get all pivot IDs for this place $pivotIds = $place->discounts->pluck('pivot.id');

// Preload all activities in one query $activities = Activity::where('subject_type', DiscountPlace::class) ->whereIn('subject_id', $pivotIds) ->get() ->groupBy('subject_id');

// Attach activities to each pivot $place->discounts->each(function ($discount) use ($activities) { $discount->pivot->setRelation('activities', $activities->get($discount->pivot->id, collect())); });

Now every pivot->activities is already loaded, no extra queries.

Just 2 queries total: one for discounts, one for activities.

Thanks, but its a crutch )

[HusseinAhmed2018]

You’re running into the classic N+1 problem because each pivot model is loading its own activities separately inside the loop.

You can solve this by eager loading the morph relation directly on the pivot models instead of calling load() inside map().

Here’s a cleaner approach:

$place = Place::with([
    'discounts' => function ($query) {
        $query->withPivot('id');
    },
    'discounts.pivot.activities',
])->first();

Now each DiscountPlace pivot will have its activities relationship already loaded, and you’ll avoid the extra queries.

You can access it like:

$place->discounts->each(function ($discount) {
    $activities = $discount->pivot->activities;
    // use $activities here
});

This way Laravel builds everything in as few queries as possible without any third-party packages.

[projct1]

> $place = Place::with([
>     'discounts' => function ($query) {
>         $query->withPivot('id');
>     },
>     'discounts.pivot.activities',
> ])->first();

Its impossible, got error:

Call to undefined relationship [pivot] on model [App\Models\Discount].