我在MongoDB3.6上运行。以下是我的文档结构，它存储产品列表的每月费率信息：{"_id":12345,"_class":"com.example.ProductRates","rates":[{"productId":NumberInt(1234),"rate":100.0,"rateCardId":NumberInt(1),"month":NumberInt(201801)},{"productId":NumberInt(1234),"rate":200.0,"rateCardId":NumberInt(1),"month":NumberInt(201802)},{"produ