We have two modules, one is the order and the other is the sub order. When querying the order list, you don't need to worry about the "n + 1" problem, but if you check the sub order according to the order list, there will be problems. For example, if a order corresponds to multiple sub orders, you need to query the sub order details once every time.
Now using dataloader cannot solve this 1-to-many relationship, because the data will be disordered.