Am I doing eager loading correctly? (Eloquent) - php

Question

I have a method that needs to pull in information from three related models. I have a solution that works but I'm afraid that I'm still running into the N+1 query problem (also looking for solutions on how I can check if I'm eager loading correctly).
The three models are Challenge, Entrant, User.
Challenge Model contains:
/**
* Retrieves the Entrants object associated to the Challenge
* #return \Illuminate\Database\Eloquent\Relations\HasMany
*/
public function entrants()
{
return $this->hasMany('App\Entrant');
}
Entrant Model contains:
/**
* Retrieves the Challenge object associated to the Entrant
* #return \Illuminate\Database\Eloquent\Relations\BelongsTo
*/
public function challenge()
{
return $this->belongsTo('App\Challenge', 'challenge_id');
}
/**
* Retrieves the User object associated to the Entrant
* #return \Illuminate\Database\Eloquent\Relations\BelongsTo
*/
public function user()
{
return $this->belongsTo('App\User', 'user_id');
}
and User model contains:
/**
* Retrieves the Entrants object associated to the User
* #return \Illuminate\Database\Eloquent\Relations\HasMany
*/
public function entrants()
{
return $this->hasMany('App\Entrant');
}
The method I am trying to use eager loading looks like this:
/**
* Returns an array of currently running challenges
* with associated entrants and associated users
* #return array
*/
public function liveChallenges()
{
$currentDate = Carbon::now();
$challenges = Challenge::where('end_date', '>', $currentDate)
->with('entrants.user')
->where('start_date', '<', $currentDate)
->where('active', '1')
->get();
$challengesObject = [];
foreach ($challenges as $challenge) {
$entrants = $challenge->entrants->load('user')->sortByDesc('current_total_amount')->all();
$entrantsObject = [];
foreach ($entrants as $entrant) {
$user = $entrant->user;
$entrantsObject[] = [
'entrant' => $entrant,
'user' => $user
];
}
$challengesObject[] = [
'challenge' => $challenge,
'entrants' => $entrantsObject
];
}
return $challengesObject;
}
I feel like I followed what the documentation recommended: https://laravel.com/docs/5.5/eloquent-relationships#eager-loading
but not to sure how to check to make sure I'm not making N+1 queries opposed to just 2. Any tips or suggestions to the code are welcome, along with methods to check that eager loading is working correctly.

Answer 1

Use Laravel Debugbar to check queries your Laravel application is creating for each request.
Your Eloquent query should generate just 3 raw SQL queries and you need to make sure this line doesn't generate N additional queries:
$entrants = $challenge->entrants->load('user')->sortByDesc('current_total_amount')->all()

Answer 2

when you do ->with('entrants.user') it loads both the entrants and the user once you get to ->get(). When you do ->load('user') it runs another query to get the user. but you don't need to do this since you already pulled it when you ran ->with('entrants.user').
If you use ->loadMissing('user') instead of ->load('user') it should prevent the redundant call.
But, if you leverage Collection methods you can get away with just running the 1 query at the beginning where you declared $challenges:
foreach ($challenges as $challenge) {
// at this point, $challenge->entrants is a Collection because you already eager-loaded it
$entrants = $challenge->entrants->sortByDesc('current_total_amount');
// etc...
You don't need to use ->load('user') because $challenge->entrants is already populated with entrants and the related users. so you can just leverage the Collection method ->sortByDesc() to sort the list in php.
also, You don't need to run ->all() because that would convert it into an array of models (you can keep it as a collection of models and still foreach it).