README.md

Doctrine Entity Preloader

shipmonk/doctrine-entity-preloader is a PHP library designed to tackle the n+1 query problem in Doctrine ORM by efficiently preloading related entities. This library offers a flexible and powerful way to optimize database access patterns, especially in cases with complex entity relationships.

• 🚀 Performance Boost: Minimizes n+1 issues by preloading related entities with constant number of queries.
• 🔄 Flexible: Supports all associations: #[OneToOne], #[OneToMany], #[ManyToOne], and #[ManyToMany].
• 💡 Easy Integration: Simple to integrate with your existing Doctrine setup (supports both v2 and v3).

Comparison

	Default	Manual	Fetch Join	setFetchMode	EntityPreloader
OneToMany	🔴 1 + n	🟢 2	🟠 1, but duplicate rows	🟢 2	🟢 2
OneToManyDeep	🔴 1 + n + n²	🟢 3	🟠 1, but duplicate rows	🔴 2 + n²	🟢 3
OneToManyAbstract	🔴 1 + n + n²	🟠 3, but duplicate rows	🟠 1, but duplicate rows	🔴 2 + n²	🟠 3, but duplicate rows
ManyToOne	🔴 1 + n	🟢 2	🟠 1, but duplicate rows	🟢 2	🟢 2
ManyToOneDeep	🔴 1 + n + n	🟢 3	🟠 1, but duplicate rows	🔴 2 + n	🟢 3
ManyToMany	🔴 1 + n	🟢 2	🟠 1, but duplicate rows	🔴 1 + n	🟢 2

Comparison vs. Manual Preload

Unlike manual preload, the EntityPreloader does not require writing custom queries for each association.

Comparison vs. Fetch Join

Unlike fetch joins, the EntityPreloader does not fetches duplicate data, which slows down both the query and the hydration process, except when necessary to prevent additional queries fired by Doctrine during hydration process.

The fetch join scales poorly with the number of associations. With every preloaded association, the number of duplicate rows grows. The EntityPreloader does not have this problem.

Comparison vs. setFetchMode

Unlike Doctrine\ORM\AbstractQuery::setFetchMode it can

• preload nested associations
• preload #[ManyToMany] association
• avoid additional queries fired by Doctrine during hydration process

Installation

To install the library, use Composer:

composer require shipmonk/doctrine-entity-preloader

Usage

Below is a basic example demonstrating how to use EntityPreloader to preload related entities and avoid the n+1 problem:

use ShipMonk\DoctrineEntityPreloader\EntityPreloader;

$categories = $entityManager->getRepository(Category::class)->findAll();

$preloader = new EntityPreloader($entityManager);
$articles = $preloader->preload($categories, 'articles'); // 1 query to preload articles
$preloader->preload($articles, 'tags'); // 2 queries to preload tags
$preloader->preload($articles, 'comments'); // 1 query to preload comments

// no more queries are needed now
foreach ($categories as $category) {
    foreach ($category->getArticles() as $article) {
        echo $article->getTitle(), "\n";

        foreach ($articles->getTags() as $tag) {
            echo $tag->getLabel(), "\n";
        }

        foreach ($articles->getComments() as $comment) {
            echo $comment->getText(), "\n";
        }
    }
}

Configuration

EntityPreloader allows you to adjust batch sizes and fetch join limits to fit your application's performance needs:

• Batch Size: Set a custom batch size for preloading to optimize memory usage.
• Max Fetch Join Same Field Count: Define the maximum number of join fetches allowed per field.

$preloader->preload(
    $articles,
    'category',
    batchSize: 20,
    maxFetchJoinSameFieldCount: 5
);

Limitations

• no support for indexed collections
• no support for dirty collections
• no support for composite primary keys