Laravel Lazy Loading Demo

A practical demonstration of the N+1 query problem in Laravel and how to solve it using eager loading. This project includes automatic lazy loading detection that logs violations without breaking your application.

🎯 Purpose

This project demonstrates:

• N+1 Query Problem: How lazy loading can cause performance issues
• Eager Loading Solution: Using with() to optimize database queries
• Lazy Loading Detection: Automatic logging of lazy loading violations
• Performance Comparison: Visual comparison using Laravel Debugbar

⚠️ Important Notice

This project is for educational purposes and has not been fully tested for production use. The lazy loading detection code provided is a code example that could be adapted for production environments to find lazy loading issues, but it should be thoroughly tested and reviewed before being deployed to production systems.

🏗️ Project Structure

Models

• Product (app/Models/Product.php) - Products with name and description
• Price (app/Models/Price.php) - Price history for products (50 prices per product)

Controllers

• ProductsLazyController (app/Http/Controllers/ProductsLazyController.php) - Demonstrates N+1 problem
• ProductsEagerController (app/Http/Controllers/ProductsEagerController.php) - Shows optimized eager loading

Database

• 5 Products with 50 prices each (250 total price records)
• SQLite database for easy setup and portability

Lazy Loading Detection

• AppServiceProvider (app/Providers/AppServiceProvider.php) - Logs lazy loading violations with detailed context

🚀 Setup Instructions

1. Clone the Repository

git clone <repository-url>
cd example-stop-lazy-loading

2. Install Dependencies

composer install -o

3. Environment Setup

# Copy environment file (already configured for SQLite)
cp .env.example .env

# Generate application key
php artisan key:generate

4. Database Setup

# Create the database directory if it doesn't exist
mkdir -p database

# Create the SQLite database file
touch database/database.sqlite

# Run migrations and seed the database
php artisan migrate:fresh --seed

This creates:

• 5 products (Laptop, Smartphone, Tablet, Desktop Computer, Headphones)
• 50 price records for each product (250 total)

5. Start the Application

# Option 1: Full development environment (recommended)
composer dev

# Option 2: Just the Laravel server
php artisan serve

🧪 Testing the Demo

1. Visit the Homepage

Open http://localhost:8000 to see two comparison buttons:

• Red Button: Products with Lazy Loading (N+1 Problem)
• Green Button: Products with Eager Loading (Optimized)

2. Compare Performance

Lazy Loading (/products-lazy)

• Queries: 6 total (1 for products + 5 for each product's prices)
• Problem: Each product triggers a separate query for its prices

Eager Loading (/products-eager)

• Queries: 2 total (1 for products + 1 for all prices)
• Solution: All prices loaded in a single optimized query

3. View Performance Data

The Laravel Debugbar appears at the bottom of each page showing:

• Total execution time
• Memory usage
• Database queries (click to see all queries)
• Query timing details

📊 Code Comparison

Lazy Loading (N+1 Problem)

// ProductsLazyController.php
$products = Product::all(); // 1 query

foreach ($products as $product) {
    $product->prices->count(); // 5 additional queries (1 per product)
}
// Total: 6 queries

Eager Loading (Optimized)

// ProductsEagerController.php
$products = Product::with('prices')->get(); // 2 queries total

foreach ($products as $product) {
    $product->prices->count(); // No additional queries - data already loaded
}
// Total: 2 queries

🕵️ Lazy Loading Detection

Automatic Monitoring

The project includes automatic lazy loading detection that:

• Monitors all Eloquent model relationships
• Logs violations without breaking the application
• Provides context for easy debugging

Log File Location

View lazy loading violations in:

storage/logs/laravel.log

Sample Log Entry

[2025-08-29 15:12:05] local.ERROR: Lazy loading detected {"model":"App\\Models\\Product","model_id":1,"relation":"prices","file":"/home/marcovie/projects/example-stop-lazy-loading/app/Http/Controllers/ProductsLazyController.php","line":22,"url":"http://127.0.0.1:8000/products-lazy","method":"GET"}

Log Information Includes:

• Model: Which model triggered the lazy loading
• Model ID: Specific model instance
• Relation: Which relationship was lazy loaded
• File & Line: Exact location in your code
• URL & Method: Request context

🐛 Troubleshooting

Database File Not Found Error

If you encounter the error:

Database file at path [database/database.sqlite] does not exist. Ensure this is an absolute path to the database.

Solution:

1. Create the database directory: mkdir -p database
2. Create the SQLite database file: touch database/database.sqlite
3. Run migrations: php artisan migrate:fresh --seed

Vendor Directory Missing Error

If you encounter:

Failed to open stream: No such file or directory in .../vendor/autoload.php

Solution: Install dependencies first:

composer install -o

Other Common Issues

• Permission denied: Ensure the database directory has write permissions
• Path issues: The .env file should have DB_DATABASE=database/database.sqlite (relative path from project root)
• SQLite not installed: Install SQLite3 on your system if missing

🛠️ Key Files Modified

Database Configuration

• .env - SQLite database configuration
• .env.example - Template with SQLite setup

Models & Relationships

• app/Models/Product.php - Product model with hasMany prices relationship
• app/Models/Price.php - Price model with belongsTo product relationship

Migrations & Seeders

• database/migrations/*_create_products_table.php - Products table schema
• database/migrations/*_create_prices_table.php - Prices table schema with foreign key
• database/seeders/ProductSeeder.php - Seeds 5 products with 50 prices each
• database/seeders/DatabaseSeeder.php - Calls ProductSeeder

Controllers

• app/Http/Controllers/ProductsLazyController.php - Demonstrates N+1 problem
• app/Http/Controllers/ProductsEagerController.php - Shows eager loading solution

Routes & Views

• routes/web.php - Routes for both controllers
• resources/views/welcome.blade.php - Homepage with comparison buttons

Lazy Loading Detection

• app/Providers/AppServiceProvider.php - Configures lazy loading detection and logging

Dependencies

• composer.json - Added Laravel Debugbar for query visualization
• package.json - Frontend dependencies

📚 Learning Outcomes

After exploring this project, you'll understand:

1. N+1 Query Problem: How innocent-looking code can cause performance issues
2. Eager Loading: Using with() to optimize database queries
3. Performance Monitoring: Using Laravel Debugbar to identify bottlenecks
4. Lazy Loading Detection: Implementing automatic monitoring in production
5. Best Practices: Writing efficient Eloquent queries

🎯 Production Tips

Enable Lazy Loading Detection

The lazy loading detection is already configured in AppServiceProvider.php. Important: This code is provided as an educational example and should be thoroughly tested before production use.

For production consideration:

1. Test thoroughly in staging environments first
2. Monitor logs regularly for lazy loading violations
3. Fix violations by adding appropriate with() clauses
4. Consider alerting for critical performance issues
5. Review performance impact of the detection mechanism itself

Performance Monitoring

• Use Laravel Debugbar in development
• Consider tools like Laravel Telescope for production debugging
• Monitor database query counts and execution times
• Always test detection code in non-production environments first

🤝 Contributing

Feel free to submit issues and pull requests to improve this educational example!

📄 License

This project is open source and available under the MIT License.