Lazy loading and N+1 prevention in Laravel - Mini Project: Build & Apply

Lazy Loading and N+1 Prevention in Laravel

📖 Scenario: You are building a simple blog application using Laravel. Each blog post has many comments. You want to display a list of posts with their comments efficiently.

🎯 Goal: Learn how to set up Eloquent relationships and use lazy loading with eager loading to prevent the N+1 query problem.

📋 What You'll Learn

Create a Post model with a relationship to Comment model

Create a Comment model with a relationship to Post model

Write a query to get all posts with their comments using eager loading

Display posts with their comments without causing N+1 queries

💡 Why This Matters

🌍 Real World

Efficiently loading related data in Laravel applications is crucial for performance, especially when displaying lists with related items like posts and comments.

💼 Career

Understanding and preventing N+1 query problems is a key skill for Laravel developers to write optimized database queries and improve app speed.

1

Define the Post and Comment models with relationships

Create a Post model class with a comments() method that returns a hasMany relationship to the Comment model. Also create a Comment model class with a post() method that returns a belongsTo relationship to the Post model.

Laravel

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    // Define comments relationship here
    // Your code here
}

class Comment extends Model
{
    // Define post relationship here
    // Your code here
}

Need a hint?

Use hasMany in Post for comments and belongsTo in Comment for post.

2

Create a variable to hold all posts

In a controller or route closure, create a variable called $posts and assign it the result of Post::all() to get all posts without comments loaded yet.

Laravel

hasMany(Comment::class);
    }
}

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

// Create $posts variable to get all posts
// Your code here

Need a hint?

Use Post::all() to get all posts.

3

Use eager loading to load comments with posts

Modify the $posts variable assignment to use Post::with('comments')->get() so that comments are loaded eagerly with posts, preventing N+1 queries.

Laravel

hasMany(Comment::class);
    }
}

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

// Modify $posts to eager load comments
// Your code here

Need a hint?

Use with('comments') before get() to eager load.

4

Display posts with their comments in a Blade view

In a Blade template, use a @foreach loop to iterate over $posts. Inside it, display the post title and use another @foreach loop to display each comment's content from $post->comments. This shows how eager loading prevents N+1 queries.

Laravel

hasMany(Comment::class);
    }
}

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

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

/*
@foreach ($posts as $post)
    
    comments to display comment content -->
@endforeach
*/
// Your code here

Need a hint?

Use nested @foreach loops in Blade to display posts and their comments.