laravel caching return 0

Question

I am trying to cache request for counting number of users in different categories

my function without caching:

    public function getNumOfUsersInCat()
    {
        $numUsers = count($this -> users);
        $otherCategories = Category::where('id', '<>', $this -> id) -> get();
        foreach($otherCategories as $categ){
            if($this -> isAncestorOf($categ))
                $numUsers += count($categ -> users);
        }
        return $numUsers;
    }

I was trying to cache requests like:

    public function getNumOfUsersInCat()
    {
        $numUsers = count($this -> users);
        $otherCategories = Cache::remember('cache_numuserscat)',60*60*12,function(){
        return
        Category::where('id', '<>', $this -> id) -> get();
        foreach($otherCategories as $categ){
            if($this -> isAncestorOf($categ))
                $numUsers += count($categ -> users);
        }
        });
        return $numUsers;
    }

But I am getting only 0

Laravel 5.7.2

Answer 1

It is because you have put the calculation loop inside your cache and before reaching that part, you return with the category list. So the code you run is actually this:

public function getNumOfUsersInCat()
{
    $numUsers = count($this -> users);
    $otherCategories = Cache::remember('cache_numuserscat)', 60*60*12, function(){
        return Category::where('id', '<>', $this -> id) -> get();
    });
    return $numUsers;
}

Before the correct code, there are a few things you should note:

• Your cache name should only work for this model you are in, so I added $this->id to the name.
• You can use withCount to get the count of all model users in a single query. Your approach have N+1 problem.

The Final code can be like this:

public function getNumOfUsersInCat()
{
    $cacheName = "cache_num_users_cat_" . $this->id;

    return Cache::remember($cacheName, 60 * 60 * 12, function() {
        $numUsers = count($this->users);

        $otherCategories = Category::query()
            ->where('id', '<>', $this->id)
            ->withCount('users')
            ->get();

        foreach ($otherCategories as $categ) {
            if ($this->isAncestorOf($categ)) {
                $numUsers += $categ->users_count;
            }
        }

        return $numUsers;
    });
}