Django ManyToMany filter()

Question

I have a model:

class Zone(models.Model):
    name = models.CharField(max_length=128)
    users = models.ManyToManyField(User, related_name=\'zones\', null=T         


        

Answer 1

another way to do this is by going through the intermediate table. I'd express this within the Django ORM like this:

UserZone = User.zones.through

# for a single zone
users_in_zone = User.objects.filter(
  id__in=UserZone.objects.filter(zone=zone1).values('user'))

# for multiple zones
users_in_zones = User.objects.filter(
  id__in=UserZone.objects.filter(zone__in=[zone1, zone2, zone3]).values('user'))

it would be nice if it didn't need the .values('user') specified, but Django (version 3.0.7) seems to need it.

the above code will end up generating SQL that looks something like:

SELECT * FROM users WHERE id IN (SELECT user_id FROM userzones WHERE zone_id IN (1,2,3))

which is nice because it doesn't have any intermediate joins that could cause duplicate users to be returned