Laravel – How to use Eager Loading approach

Laravel application performance is very crucial and plays an important role, one way to optimize it is through the Eager Loading approach.

Laravel Eloquent Relationships such as has one, has many, and many to many provide an efficient way to manage related data without writing complex SQL queries.

This tutorial will discuss the importance of Eager Loading and show examples of its various techniques.

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Importance of Eager Loading

Eager Loading is essential in Laravel applications to optimize Eloquent queries and prevent server crashes due to excessive MySQL queries.

By using Eager Loading, we can reduce the number of queries fired on the backend, which ensures smooth application performance.

Laravel Eloquent Relationships

Laravel offers various Eloquent Relationships, such as has one, has many, and many to many.

These relationships simplify the process of fetching related data and removes the need for writing lengthy SQL queries having joines.

Problem with Lazy Loading

Lazy Loading can lead to performance issues as it fires one query for each related record, which loads the server with too many queries.

Let’s have a look at an example using a “posts” and “comments” table, with each post having multiple comments.

Consider the following Eloquent models for Post and Comment:

// Post.php
namespace App;
use Illuminate\Database\Eloquent\Model;

class Post extends Model {
    public function comments() {
        return $this->hasMany(Comment::class);
    }
}

// Comment.php
namespace App;
use Illuminate\Database\Eloquent\Model;

class Comment extends Model {
    public function post() {
        return $this->belongsTo(Post::class);
    }
}

Using Lazy Loading, you would fetch all posts and their comments like this:

$posts = Post::all();

foreach ($posts as $post) {
    echo $post->name;

    $comments = $post->comments;
    // ... Loop again for comments
}

This approach fires multiple queries on the backend one for each post’s comments.

Solution: Eager Loading

Eager Loading is an efficient solution to this problem, as it fetches all related data in a single query. Here’s an example using Eager Loading:

$posts = Post::with('comments')->get();

foreach ($posts as $post) {
    echo $post->name;

    $comments = $post->comments;
    // ... Loop again for comments
}

Now, only two queries are fired: one for all posts and another for all comments related to the fetched posts.

Eager Loading Techniques

Multiple Relationships

$posts = Post::with(['comments', 'author'])->get();

Count

$posts = Post::withCount('comments')->get();
// Accessible with comments_count

Nested Relationships

$posts = Post::with(['comments', 'comments.user'])->get();

$posts = Post::with(['comments:id,body'])->get();

$posts = Post::with(['comments' => function ($query) {
    $query->where('type', 1);
}])->get();

Order By

$posts = Post::with(['comments' => function ($query) {
    $query->orderBy('created_at', 'desc');
}])->get();

FAQs

What is Eager Loading in Laravel?

Eager Loading is a technique used to optimize Eloquent queries in Laravel applications by fetching all related data in a single query, thus reducing the number of queries fired on the backend.

How does Eager Loading improve application performance?

Eager Loading improves application performance by minimizing the number of queries fired on the backend, thus reducing server load and preventing potential server crashes due to excessive MySQL queries.

What is the difference between Lazy Loading and Eager Loading in Laravel?

Lazy Loading fires one query for each related record, while Eager Loading fetches all related data in a single query, reducing the number of queries on the backend.

How do I use Eager Loading with multiple relationships in Laravel?

To use Eager Loading with multiple relationships, pass an array of relationship names to the with() method, like this: $posts = Post::with(['comments', 'author'])->get();

Can I use Eager Loading with conditions, such as where and order by?

Yes, you can use Eager Loading with conditions by passing a closure to the with() method, like this: $posts = Post::with(['comments' => function ($query) { $query->where('type', 1); }])->get();

Conclusion

Eager Loading is an essential technique to optimize Laravel applications and reduce the number of queries fired on the backend.

By understanding and utilizing Eager Loading, you can enhance your application’s performance and prevent server crashes due to excessive MySQL queries.