How To Fix N + 1 Problem in Laravel
What is n + 1 Problem
When accessing Eloquent relationships as properties, the relationship data is "lazy loaded". Laravel provides eloquent relationships . They allow us to access related models from another model.
But if we're not careful, it's easy to introduce a n + 1 problem - which essentially means that we execute an additional query every time we access the relationship that was not eager loaded .
To illustrate the N + 1 query problem, consider a Post model that is related to User. Let's take a look this example that we have multiple $posts and every post has an user, that we can access with $post->user.
If we did not eager load the user, Laravel will still let us access, but it will execute a query to get it. Now imagine we didn't eager load it and we're doing something like this
$posts = Post::all();
foreach ($posts as $post) {
dd($post->user);
}
Do you know what is happening in that query. Every time the $post->user is called, Laravel will execute an extra query to load the author. Something like this for each post:
select * from users where id = ?
This assumes the posts table has an user_id column, by which the user is queried. If we have 100 posts, this will execute 1 query to get all the posts and 100 additional queries to get their related users. This is definitely bad practice.
Laravel Solve this N+1 problem or eager loading problem with (using with('relationship')): Let's think this is our relationship with user and this is our Post model.
app/Post.php
namespace App;use Illuminate\Database\Eloquent\Model; class Post extends Model { /** * Get the user that owns the phone. */ public function user() { return $this->belongsTo('App\User'); } }
Now see our eager loader query to solve N+1 problem in laravel.
$posts = Post::with('user')->all();
foreach ($posts as $post) {
dd($post->user);
}
In this example first query will fetch all the posts, and the 2nd query will fetch all their related users simultaneously. Now our N+1 problem is solved by eager loaded query.
Thankfully, we can use eager loading to reduce this operation to just 2 queries. When querying, you may specify which relationships should be eager loaded using the with method. Something like this
select * from posts
select * from users where id in (1, 2, 3, 4, 5, ...)
Eager Loading Multiple Relationships
Sometimes you may need to eager load several different relationships in a single operation. To do it just see below example.
$posts= App\Post::with(['user', 'publisher'])->get();
Lazy Eager loading
Sometimes you may need to eager load a relationship after the parent model has already been retrieved. For example, this may be useful if you need to dynamically decide whether to load related models:
use App\Models\Book;
$books = Book::all();
if ($someCondition) {
$books->load('author', 'publisher');
}
Hope this Laravel N+1 problem tutorial will help you. In this example tutorial we will try to know what is N+1 problem and how we can solve this problem with Laravel eager loaded.
I hope you found this article useful. let me know if you have any questions and I’ll be happy to answer them.
