Django：如何使用模型实例预取相关对象？

Question

ClassA:
 ...

ClassB:
    ForeignKey(A)

ClassC：
    ForeignKey(B)

now I have a instance of C. 现在我有一个C的实例。

c = C()
b = c.b
a = b.a

This way, the db will be visited for three times. 这样，数据库将被访问三次。

How can I let them be fetched at once like prefetch_related. 我该如何像prefetch_related一样立即获取它们。

Answer 1

I think you're looking for select_related . 我认为您正在寻找select_related 。

c = C.objects.select_related('b__a').get()

This will fetch both the b and a instances that were related to it. 这将同时获取b和与其相关的实例。