Django：来自ManyToManyField的* all *值的queryset过滤器

Question

Hi (sorry for my bad english :p)

Imagine these models :

class Fruit(models.Model):
    # ...

class Basket(models.Model):
    fruits = models.ManyToManyField(Fruit)

Now I would like to retrieve Basket instances related to all fruits. The problem is that the code bellow returns Basket instances related to any fruits :

baskets = Basket.objects.filter(fruits__in=Fruit.objects.all())

# This doesn't work:
baskets = Basket.objects.filter(fruits=Fruit.objects.all())

Any solution do resolve this problem ?

Thank you very much. :)

Answer 1

I don't have a dataset handy to test this, but I think it should work:

Basket.objects.annotate(num_fruits=Count('fruits')).filter(num_fruits=len(Fruit.objects.all()))

It annotates every basket object with the count of related fruits and filters out those baskets that have a fruit count that equals the total amount of fruits.

Note: you need Django 1.1 for this to work.