如何用另一个many2many过滤many2many字段？

Question

I have following model in my Django:

class Filter(models.Model):
    min_price = models.PositiveIntegerField(null=False, blank=False)
    max_price = models.PositiveIntegerField(null=False, blank=False)
    trait = models.ManyToManyField(Trait, null=True, blank=True)

class Flat(models.Model):
    living_area = models.DecimalField(max_digits=7, decimal_places=2, null=True, blank=True, db_index=True)
    trait = models.ManyToManyField(Trait)

class Trait(models.Model):
    name = models.CharField(max_length=255, blank=False, null=False, db_index=True)

In my case trait can be for example: elevator. If there is connection between Flat and Trait(name="Elevator") then I can assume that Flat has elevator.

What I want to do is to searching flats based on traits - traits from Flat and traits from Filter should be the same.

I did somethink like this:

filte_obj = Filter.objects.get(pk=pk)
flat = Flat.objects.filter(trait__id__in=[x.id for x in filter_obj.trait.all()])

Unfortunately I does not work as I want. I want to see only Flats which Traits QuerySet is the same as Filter's traits QuerySet.

How can I do that?

Answer 1

I have solved my problem using django models annotations:

filter_obj = Filter.objects.get(pk=pk)
traits_list = [x.id for x in filter_obj.trait.all()]
offers = Offer.objects \
    .filter(flat__living_area__range=(filter_obj.min_area, filter_obj.max_area),
            flat__trait__id__in=traits_list) \
    .annotate(num_traits=Count('flat__trait')).filter(num_traits=filter_obj.trait.count())

More information:

Django filter by many to many with exact same query