Laravel 11 - N+1 Problem - Lazy vs Eager Loading

We will explore the N+1 problem in Laravel 11 through practical examples. We'll walk through the process of creating a Post model, defining relationships, and observing how lazy loading can lead to excessive queries. Then, we'll see how eager loading can optimize our queries effectively. Let’s dive in!

Step # 1 : Create Post Model, Migration & Factory.

Command : php artisan make:model Post -mf

Step # 2 : Update Post Migration.

public function up()
{
    Schema::create('posts', function (Blueprint $table) {
        $table->id();
        $table->foreignId('user_id')->constrained()->onDelete('cascade'); // Foreign key for user
        $table->string('title');
        $table->text('content');
        $table->timestamps();
    });
}

Step # 3 : Run the Migration.

Command : php artisan migrate

Step # 4 : Define Relationships.

public function posts() // A user can have many posts
{
    return $this->hasMany(Post::class);
}

public function user() // Each post belongs to a user
{
    return $this->belongsTo(User::class);
}

Step # 5 : Update PostFactory.php.

<?php
namespace Database\Factories;
use App\Models\Post;
use Illuminate\Database\Eloquent\Factories\Factory;
class PostFactory extends Factory
{
    protected $model = Post::class;
    public function definition()
    {
        return [
            'title' => $this->faker->sentence,
            'content' => $this->faker->paragraph,
        ];
    }
}

Step # 6 : Update DatabaseSeeder.php.

<?php
namespace Database\Seeders;
use Illuminate\Database\Seeder;
use App\Models\User;
use App\Models\Post;
class DatabaseSeeder extends Seeder
{
    public function run(): void
    {
        // Create 10 users and for each user, create 3 posts
        User::factory(10)->create()->each(function ($user) {
            Post::factory(5)->create(['user_id' => $user->id]); // Associate posts with user
        });
    }
}

Step # 7 : Run the Seeder.

Command : php artisan db:seed

Step # 8 : Let's See N+1 Problem in action.

Command : php artisan serve.

127.0.0.1:8000

Route::get('/', function () {
    $users = User::all(); // 1 query to fetch all users
    foreach ($users as $user) {
        echo $user->posts; // N queries to fetch posts for each user on demand (N = number of users)
    }
    return view('welcome');
});

Route::get('/', function () {
    $users = User::with('posts')->get(); // **1 query to fetch all users and their posts**
    foreach ($users as $user) {
        echo $user->posts; // No additional queries are made for posts
    }
    return view('welcome');
});