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Laravel – Eager Loading with Nested Relationships and Custom Accessors Causing Performance Issues

I’m working on an application using Laravel 10, and I’m facing a performance issue related to eager loading nested relationships and custom accessors.

Scenario:
I have three models: User, Post, and Comment.

A User has many Posts.
A Post has many Comments.
I have set up a custom accessor on the Post model to calculate the number of comments.

Here are the relevant parts of my models:

// User.php
class User extends Model
{
    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

// Post.php
class Post extends Model
{
    protected $appends = ['comment_count'];

    public function comments()
    {
        return $this->hasMany(Comment::class);
    }

    public function getCommentCountAttribute()
    {
        return $this->comments()->count();
    }
}

// Comment.php
class Comment extends Model
{
    public function post()
    {
        return $this->belongsTo(Post::class);
    }
}

Problem:
In my controller, I’m trying to load all users with their posts and the number of comments on each post. Here’s how I’m doing it:

$users = User::with(['posts.comments'])->get();

The issue I’m facing is that this approach is causing a significant performance hit due to the N+1 query problem. The custom accessor getCommentCountAttribute is being called for each post, and it results in a new query being executed for each post’s comment count.

What I’ve Tried:

  1. Adding withCount: I tried to optimize it by using withCount in the controller like this:
$users = User::with(['posts' => function($query) {
    $query->withCount('comments');
}])->get();

This works, but the problem is that it doesn’t use the custom accessor, so the comment_count attribute in the Post model isn’t populated.

  1. Using loadMissing: I attempted to use loadMissing to avoid loading already loaded relations:
$users->loadMissing('posts.comments');

But this doesn’t solve the performance issue as it still leads to excessive queries.

  1. Avoiding Custom Accessors: I considered avoiding the custom accessor altogether, but the accessor is used in multiple places in the application, and refactoring it would be cumbersome.

Is there a way to keep using the custom accessor while avoiding the N+1 query issue? How can I optimize this eager loading to reduce the number of queries while still getting the comment_count for each post efficiently? Any insights or alternative approaches would be greatly appreciated!

Tags:

2

Answers


  1. 0

    Change the accessor to:

    public function getCommentCountAttribute()
{
  return $this->comments->count();
}

    This has the effect of loading the comments relationship on the model if it’s not loaded already. Since you’re using User::with(['posts.comments']);, the posts will have the comments relationship already loaded.

    Alternatively, change the accessor to getCommentsCountAttribute, so that you can call it with comments_count (note the plural). Laravel automatically uses the relationship name to set the count property. The relationship is comments.

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  2. 0

    Since you don’t want to change the attribute, and refactor where you have used it, you can use withCount to resolve your performance issues and update the attribute to depend on withCount instead, ex:

    $users = User::with(['posts' => fn ($query) => $query->withCount('comments')])->get();

public function getCommentCountAttribute()
{
  // use comments_count if already calculated, or calculate manually
  return $this->comments_count ?? $this->comments()->count();
}

    this should not break anything for places where you are not using withCount, and improve the performance in places you apply withCount

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