Eager Loadingとクエリスコープ

N+1 問題

<?php
$posts = Post::all(); // 1 query
foreach ($posts as $post) {
    echo $post->author->name; // 1 query per post = N+1 total!
}

with() による Eager Loading

<?php
$posts = Post::with("author")->get(); // 2 queries total
foreach ($posts as $post) {
    echo $post->author->name; // no extra query
}

複数のリレーションシップの Eager Loading

<?php
$posts = Post::with(["author", "tags", "comments"])->get();

ネストした Eager Loading

<?php
$posts = Post::with("comments.author")->get();
// Loads posts, their comments, and each comment's author

条件付き Eager Loading

<?php
$posts = Post::with(["comments" => function ($q) {
    $q->where("approved", true)->latest();
}])->get();

withCount()

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

遅延 Eager Loading（load()）

<?php
$posts = Post::all();
// Later, when you know you need the authors:
$posts->load("author");

グローバルクエリスコープ

<?php
class PublishedScope implements \Illuminate\Database\Eloquent\Scope {
    public function apply(Builder $builder, Model $model): void {
        $builder->where("is_published", true);
    }
}

ローカルクエリスコープ

<?php
class Post extends Model {
    public function scopePublished(Builder $query): void {
        $query->where("is_published", true);
    }
    public function scopeByUser(Builder $query, int $userId): void {
        $query->where("user_id", $userId);
    }
}
// Usage:
Post::published()->byUser(1)->latest()->get();

スコープの組み合わせ

<?php
$posts = Post::published()
             ->byUser(auth()->id())
             ->orderBy("created_at", "desc")
             ->paginate(15);

開発中の N+1 の検出

まとめ

確認問題