LaravelでAPIリソースを使う場合はN+1問題に注意する

Schema::create('tasks', function (Blueprint $table) {
    $table->id();
    $table->unsignedBigInteger('task_status_id');
    $table->string('name')->comment('タスク名');
    $table->string('description')->comment('説明');
    $table->timestamps();
    $table->foreign('task_status_id')->references('id')->on('task_statuses');
});

Schema::create('task_statuses', function (Blueprint $table) {
    $table->id();
    $table->string('name', 16)->comment('ステータス名');
    $table->string('description')->comment('説明');
    $table->timestamps();
});

class Task extends Model
{
    use HasFactory;

    public function status(): BelongsTo
    {
        return $this->belongsTo(TaskStatus::class, 'task_status_id'); // Taskモデルにリレーションを設定
    }
}

class TaskResource extends JsonResource
{
    public function toArray($request)
    {
        /** @var \App\Models\Task */
        $task = $this->resource;

        return [
            'id' => $task->id,
            'name' => $task->name,
            'description' => $task->description,
            'status' => $task->status->name, // リレーションを使ってステータス名を取得
        ];
    }
}

class TaskController extends Controller
{
    public function __construct(
        private Task $taskModel,
    ) {
    }

    public function index()
    {
        return TaskResource::collection($this->taskModel->all());
    }
}

class TaskController extends Controller
{
    public function index()
    {
        \DB::enableQueryLog(); // 追記

        return TaskResource::collection($this->taskModel->all());
    }
}

$app = require_once __DIR__ . '/../bootstrap/app.php';

$kernel = $app->make(Kernel::class);

$response = $kernel->handle(
    $request = Request::capture()
)->send();

\Log::debug(\DB::getQueryLog()); // 追記

$kernel->terminate($request, $response);

curl localhost:8000/api/tasks | jq .

array (
  0 => 
  array (
    'query' => 'select * from "tasks"',
    'bindings' => 
    array (
    ),
    'time' => 4.44,
  ),
  1 => 
  array (
    'query' => 'select * from "task_statuses" where "task_statuses"."id" = ? limit 1',
    'bindings' => 
    array (
      0 => 2,
    ),
    'time' => 2.0,
  ),
  2 => 
  array (
    'query' => 'select * from "task_statuses" where "task_statuses"."id" = ? limit 1',
    'bindings' => 
    array (
      0 => 4,
    ),
    'time' => 0.35,
  ),
  // (省略)
)

class TaskController extends Controller
{
   　public function index()
    {
        return TaskResource::collection($this->taskModel->with('status')->get());
    }
}

array (
  0 => 
  array (
    'query' => 'select * from "tasks"',
    'bindings' => 
    array (
    ),
    'time' => 5.97,
  ),
  1 => 
  array (
    'query' => 'select * from "task_statuses" where "task_statuses"."id" in (1, 2, 3, 4, 5)',
    'bindings' => 
    array (
    ),
    'time' => 1.91,
  ),
)

class TaskResource extends JsonResource
{
    public function toArray($request)
    {
        /** @var \App\Models\Task */
        $task = $this->resource;
        assert($task->relationLoaded('status')); // ロードされていないとAssertionError

        return [
            'id' => $task->id,
            'name' => $task->name,
            'description' => $task->description,
            'status' => $task->status->name,
        ];
    }
}

class TaskController extends Controller
{
    public function show(Task $task)
    {
        $task->load('status'); // ロードする

        return TaskResource::make($task);
    }
}

protected function whenLoaded($relationship, $value = null, $default = null)
{
    if (func_num_args() < 3) {
        $default = new MissingValue;
    }

    if (! $this->resource->relationLoaded($relationship)) {
        return value($default);
    }

    if (func_num_args() === 1) {
        return $this->resource->{$relationship};
    }

    if ($this->resource->{$relationship} === null) {
        return;
    }

    return value($value);
}

public function toArray($request)
{
    return [
        'id' => $this->id,
        'name' => $this->name,
        'email' => $this->email,
        'posts' => PostResource::collection($this->whenLoaded('posts')), // ロードされている場合のみ返す
    ];
}

public function toArray($request)
{
    /** @var \App\Models\User */
    $user = $user->resource;
    assert($user->relationLoaded('posts'));

    return [
        'id' => $user->id,
        'name' => $user->name,
        'email' => $user->email,
        'posts' => PostResource::collection($user->posts),
        'created_at' => $user->created_at,
        'updated_at' => $user->updated_at,
    ];
}