如何与Django ManyToMany字段相反的prefetch_related [英] How to prefetch_related in reverse of a Django ManyToMany field

问题描述

在Django中，如果我有ManyToManyField:

In Django, if I have a ManyToManyField:

class Topping(models.Model):
    name = models.CharField(max_length=30)

class Pizza(models.Model):
    name = models.CharField(max_length=50)
    toppings = models.ManyToManyField(Topping)

使用 Pizza.objects.all().prefetch_related('toppings')

如何执行同样的操作，但反过来，是要从 Topping 查询集中预取 pizza_set ?

How can I do the same but in reverse, to prefetch the pizza_set from a Topping queryset?

这不起作用，我在文档中找不到它:

This doesn't work, and I couldn't find it in the docs:

Topping.objects.all().prefetch_related('pizza_set')

推荐答案

如果您以这种方式访问​​预取的披萨，这应该可以工作:

This should work if you access the prefetched pizzas like this:

topping.pizza_set.all()

如果您做类似的事情

topping.pizza_set.filter(...some conditions etc...)

然后它将不起作用，并且这是预期的(因为仅预取特定的查询结果).

then it won't work and this is expected (as only specific query result is prefetched).

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