如果我有这个问题：

select 
    id,
    @product_rank := IF(@current_category = category_id, @product_rank + 1, 1) AS product_rank,
    @current_category := category_id
from products

并使用eloquent builder创建查询：

Products::from(DB::raw('
    (select 
        id,
        @product_rank := IF(@current_category = category_id, @product_rank + 1, 1) AS product_rank,
        @current_category := category_id
    from products) as q 
'))->where('product_rank', '<=', 10)->paginate(5);

因为laravel分页希望获得所有记录的总数，所以它会执行一个额外的查询，如下所示：

select count(*) as aggregate from (
    select 
        id,
        @product_rank := IF(@current_category = category_id, @product_rank + 1, 1) AS product_rank,
        @current_category := category_id
    from products 
) q where product_rank <= 10

所以呢 @current_category 以及 @product_rank 不会重新初始化，主查询返回错误的结果。
我想知道是否有办法重新初始化这两个变量。