在laravel4

Question

我有这样的选择：

StoreProduct::where('user_id', Auth::user()->main_id)
            ->whereNotExists(function($query)
            {
                 $query->select(DB::raw(1))
                       ->from('store_products')
                       ->whereRaw('store_products.store_product_id = store_product.id');
            })
            ->orderBy('id', 'desc')->paginate($perPage) 

在我的数据库中有20K行，此选择执行大约65秒。

我正在使用laravel debugbar。查询转储2选择：

select count(*) as aggregate from `store_product` where `store_product`.`deleted_at` is null and `user_id` = '20' and not exists (select 1 from `store_products` where store_products.store_product_id = store_product.id)65.88s
select * from `store_product` where `store_product`.`deleted_at` is null and `user_id` = '20' and not exists (select 1 from `store_products` where store_products.store_product_id = store_product.id) order by `id` desc limit 24 offset 0

为什么laravel会select count(*) as aggregate？如何优化此查询？