laravel-shopping-cart/.claude/skills/laravel-best-practices/rules/db-performance.md

Database Performance Best Practices

Always Eager Load Relationships

Lazy loading causes N+1 query problems — one query per loop iteration. Always use with() to load relationships upfront.

Incorrect (N+1 — executes 1 + N queries):

$posts = Post::all();
foreach ($posts as $post) {
    echo $post->author->name;
}

Correct (2 queries total):

$posts = Post::with('author')->get();
foreach ($posts as $post) {
    echo $post->author->name;
}

Constrain eager loads to select only needed columns (always include the foreign key):

$users = User::with(['posts' => function ($query) {
    $query->select('id', 'user_id', 'title')
          ->where('published', true)
          ->latest()
          ->limit(10);
}])->get();

Prevent Lazy Loading in Development

Enable this in AppServiceProvider::boot() to catch N+1 issues during development.

public function boot(): void
{
    Model::preventLazyLoading(! app()->isProduction());
}

Throws LazyLoadingViolationException when a relationship is accessed without being eager-loaded.

Select Only Needed Columns

Avoid SELECT * — especially when tables have large text or JSON columns.

Incorrect:

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

Correct:

$posts = Post::select('id', 'title', 'user_id', 'created_at')
    ->with(['author:id,name,avatar'])
    ->get();

When selecting columns on eager-loaded relationships, always include the foreign key column or the relationship won't match.

Chunk Large Datasets

Never load thousands of records at once. Use chunking for batch processing.

Incorrect:

$users = User::all();
foreach ($users as $user) {
    $user->notify(new WeeklyDigest);
}

Correct:

User::where('subscribed', true)->chunk(200, function ($users) {
    foreach ($users as $user) {
        $user->notify(new WeeklyDigest);
    }
});

Use chunkById() when modifying records during iteration — standard chunk() uses OFFSET which shifts when rows change:

User::where('active', false)->chunkById(200, function ($users) {
    $users->each->delete();
});

Add Database Indexes

Index columns that appear in WHERE, ORDER BY, JOIN, and GROUP BY clauses.

Incorrect:

Schema::create('orders', function (Blueprint $table) {
    $table->id();
    $table->foreignId('user_id')->constrained();
    $table->string('status');
    $table->timestamps();
});

Correct:

Schema::create('orders', function (Blueprint $table) {
    $table->id();
    $table->foreignId('user_id')->index()->constrained();
    $table->string('status')->index();
    $table->timestamps();
    $table->index(['status', 'created_at']);
});

Add composite indexes for common query patterns (e.g., WHERE status = ? ORDER BY created_at).

Use withCount() for Counting Relations

Never load entire collections just to count them.

Incorrect:

$posts = Post::all();
foreach ($posts as $post) {
    echo $post->comments->count();
}

Correct:

$posts = Post::withCount('comments')->get();
foreach ($posts as $post) {
    echo $post->comments_count;
}

Conditional counting:

$posts = Post::withCount([
    'comments',
    'comments as approved_comments_count' => function ($query) {
        $query->where('approved', true);
    },
])->get();

Use cursor() for Memory-Efficient Iteration

For read-only iteration over large result sets, cursor() loads one record at a time via a PHP generator.

Incorrect:

$users = User::where('active', true)->get();

Correct:

foreach (User::where('active', true)->cursor() as $user) {
    ProcessUser::dispatch($user->id);
}

Use cursor() for read-only iteration. Use chunk() / chunkById() when modifying records.

No Queries in Blade Templates

Never execute queries in Blade templates. Pass data from controllers.

Incorrect:

@foreach (User::all() as $user)
    {{ $user->profile->name }}
@endforeach

Correct:

// Controller
$users = User::with('profile')->get();
return view('users.index', compact('users'));

@foreach ($users as $user)
    {{ $user->profile->name }}
@endforeach