Finding object count where a field is unique in Django

Question

I have a model that is something like this:

class Input(models.Model):
        details = models.CharField(max_length=1000)
        user = models.ForeignKey(User)

class Case(Input):
    title  = models.CharField(max_length=200)
    views = models.IntegerField()

    class Argument(Input):
        case = models.ForeignKey(Case)
        side = models.BooleanField()

A user can submit many arguments, per case. I want to be able to say how many users have submitted side=true arguments.

I mean if 1 user had 10 arguments and another user had 2 arguments (both side=true) I'd want the count to be 2, not 12.

Update:

I am using these methods on the Case object:

 def users_agree(self):
        return self.argument_set.filter(side=True).values('user').distinct()
    def users_disagree(self):
        return self.argument_set.filter(side=False).values('user').distinct()

My template code calls count() on them.

Answer 1

Can you try:

Argument.objects.filter(side=True).values('case__user').distinct().count()

I think it does what you want. It issues one SQL query:

SELECT COUNT(DISTINCT "example_input"."user_id") FROM "example_argument" INNER JOIN "example_case" ON ("example_argument"."case_id" = "example_case"."input_ptr_id") INNER JOIN "example_input" ON ("example_case"."input_ptr_id" = "example_input"."id") WHERE "example_argument"."side" = True

Edit:

For this_case, get all users whose argument.side is True:

Argument.objects.filter(case__id=this_case.id, side=True).values('user').distinct()