如何计算雄辩的关系,没有N + 1问题并加载整个模型? [英] How to count eloquent relationship without the N+1 issue and loading the entire model?
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问题描述
我正在显示一个类别列表,以及每个类别中的文章计数。我得到预期的结果,但是我遇到了N + 1个问题。
I am showing a list of categories, and the article count within each category. I get the expected result, but I am having the N+1 problem.
我的 CategoriesController
index function: / p>
My CategoriesController
index function:
public function index()
{
return View::make('categories.index', [
'articleCategories' => Category::where('type', 'articles')->orderBy('name')->get(),
]);
}
类别
与文章有很多关系:
public function articles()
{
return $this->hasMany('Article');
}
我的 categories.index
查看:
@foreach($articleCategories as $articleCategory)
<p>
{{ HTML::link(URL::route('articles.category', array('category' => Str::slug($articleCategory->name))), $articleCategory->name) }}
{{ $articleCategory->articles->count() }}
</p>
@endforeach
编辑:如果我渴望加载所有相关的文章,但由于我只需要文章计数类别这似乎是过度的。会急于加载文章,并执行 - > count()
影响性能?或者这是最好的方式吗?
It works if I eager load all related articles, but since I only need the article count pr category this seems overkill. Will eager loading articles and do ->count()
impact performance? Or is this the best way to do it?
推荐答案
// helper relation
public function articlesCount()
{
return $this->hasOne('Article')->selectRaw('category_id, count(*) as aggregate')->groupBy('category_id');
}
// and accessor for fetching it easier
public function getArticlesCountAttribute()
{
if ( ! array_key_exists('articlesCount', $this->relations)) $this->load('articlesCount');
return $this->getRelation('articlesCount')->aggregate;
}
然后你可以这样做:
// eager load in single query
$categories = Category::with('articlesCount')->get();
// thanks to accessor this will return value and load relation only if needed
$categories->first()->articlesCount;
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