day19（を6日過ぎた）今日はn+1問題を避けるためにまとめてデータを取得する方法を見ていきます。

Doctrine

Entity/Author.php

<?php

declare(strict_types=1);

namespace App\Entity;

use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity]
#[ORM\Table(name: 'authors')]
class Author
{
    #[ORM\Id]
    #[ORM\Column(type: 'integer')]
    #[ORM\GeneratedValue(strategy: 'AUTO')]
    private int $id;

    #[ORM\Column(type: 'string', length: 255)]
    private string $name;

    #[ORM\OneToMany(mappedBy: 'author', targetEntity: Book::class, fetch: 'EAGER')]
    private Collection $books;

    public function __construct()
    {
        $this->books = new ArrayCollection();
    }

    public function getId(): int
    {
        return $this->id;
    }

    public function setId(int $id): void
    {
        $this->id = $id;
    }

    public function getName(): string
    {
        return $this->name;
    }

    public function setName(string $name): void
    {
        $this->name = $name;
    }

    public function getBooks(): Collection
    {
        return $this->books;
    }

    public function addBook(Book $book): void
    {
        if (!$this->books->contains($book)) {
            $book->setAuthor($this);
            $this->books->add($book);
        }
    }
}

<?php

declare(strict_types=1);

use App\Entity\Author;
use Doctrine\ORM\EntityManagerInterface;

require __DIR__.'/../vendor/autoload.php';

/** @var EntityManagerInterface $entityManager */
$entityManager = require __DIR__.'/bootstrap.php';

/** @var Author[] $authors */
$authors = $entityManager->getRepository(Author::class)->findAll();

foreach ($authors as $author) {
    echo $author->getName().PHP_EOL;
    foreach ($author->getBooks() as $book) {
        echo $book->getTitle().PHP_EOL;
    }
}

// 実行されたSQLのログ
// doctrine.DEBUG: Executing query: {sql} {"sql":"SELECT t0.id AS id_1, t0.name AS name_2, t3.id AS id_4, t3.title AS title_5, t3.price AS price_6, t3.description AS description_7, t3.author_id AS author_id_8 FROM authors t0 LEFT JOIN books t3 ON t3.author_id = t0.id"} []

Author::$books に fetch: 'EAGER' を設定すると、SQL的にはjoinした状態で取得したものをAuthorエンティティとBookエンティティとして構築してくれます。

Eloquent

<?php

declare(strict_types=1);

use App\Models\Author;

require __DIR__.'/../vendor/autoload.php';
require __DIR__.'/bootstrap.php';

$authors = Author::with('books')->get();
foreach ($authors as $author) {
    echo $author->name.PHP_EOL;
    foreach ($author->books as $book) {
        echo $book->title.PHP_EOL;
    }
}

modelに指定するのではなく取得時に指定します。