Limit number of results in nested query - laravel

Question

I have a table called comments with the following columns:
| id | user_id | post_id | parent_id | text |
I have this setup for a nested comment system, like Disqus:
If the comment has no parent comment, parent_id will be 0. But if a comment has a parent, the parent_id will be the id of the parent comment.
In my Comments.php model, I have this relationship:
public function children()
{
return $this->hasMany('App\Comment', 'parent_id', 'id')->with('children');
}
Now, if I query the comments:
$comments = Comment::where('post_id', 1)
->where('parent_id', 0)
->with('children')
->get();
The output will look something like this:
[
{
"id": 5,
"user_id": "2",
"post_id": "1",
"parent_id": "0",
"text": "Text",
"children": [
{
"id": 7,
"user_id": "1",
"post_id": "1",
"parent_id": "5",
"text": "Text",
"children": [
{
"id": 8,
"user_id": "3",
"post_id": "1",
"parent_id": "7",
"text": "Text",
"children": [
]
},
{
"id": 11,
"user_id": "3",
"post_id": "1",
"parent_id": "7",
"text": "Text",
"children": [
]
},
]
},
{
"id": 9,
"user_id": "1",
"post_id": "1",
"parent_id": "5",
"text": "Text",
"children": [
]
}
,
{
"id": 10,
"user_id": "1",
"post_id": "1",
"parent_id": "5",
"text": "Text",
"children": [
]
}
]
},
{
"id": 6,
"user_id": "3",
"post_id": "1",
"parent_id": "0",
"text": "Text",
"children": [
]
}
]
Or, in simpler terms:
- 5
-- 7
--- 8
--- 11
-- 9
-- 10
- 6
What I want to do is limit the number of results returned per depth.
So, for example, how can I change my query/code such that it returns:
Ten top-level results (parent_id of 0)
Two level-1 results
One level-2 result
So in the end, the query should output the comments like this:
- 5
-- 7
--- 8
-- 9
- 6
As you can see, there are two top-level results (up to 10 allowed), two level-1 results, and one level-2 result.
How can I do this?

Answer 1

Instead of using with in the model that may gets you uncontrolled retrieval of data, why not do it when you need it?
Which means, in your Comment.php, remove the with:
public function children()
{
return $this->hasMany('App\Comment', 'parent_id', 'id');
}
And in your controller/helper/service classes, only retrieve what you need? For example:
$comments = Comment::where('post_id', 1)
->where('parent_id', 0)
->with('children' => function($query) {
$query->with('children' => function($query) {
$query->with('children')
->orderBy('created_at', 'desc')
->take(1); //last 1
})
->orderBy('created_at', 'desc')
->take(2); // intermediate 2
})
->orderBy('created_at', 'desc')
->take(10) //the outermost 10
->get();
Not tested yet, but theoretically should work :)
Note: Added order by created_at because we usually want the latest few comments to comes out at the top :)