Django querying on model which is involved in generic relation

Question

Here I have 2 models, Company and UserSupervision. Company is related as a foreign key with generic relation model UserSupervision.

I want to have a query as following:

Company.objects.filter(**{'usersupervision__content_type': Company,
                          'usersupervision__user': some_user,
                          'usersupervision__date_cancelled': None})

So, I want to get all companies of some_user appeared in UserSupervision model. I know that Company and UserSupervision are not directly related, so i thought, maybe i have to use raw sql with joins? Or any other more appropriate solution?

class Company(models.Model):
    id = models.UUIDField(blank=True, editable=False, primary_key=True, default=uuid.uuid4)
    name = models.CharField(max_length=150, unique=True)

    users = models.ManyToManyField(User, related_name='companies', through='CompanyMembership')
    date_created = models.DateTimeField('created date', blank=True, editable=False, auto_now_add=True)
    date_updated = models.DateTimeField('updated date', blank=True, editable=False, auto_now=True)


class UserSupervision(models.Model):
    user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    supervision = models.ForeignKey(Supervision, on_delete=models.SET_NULL, null=True)

    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.UUIDField()
    content_object = GenericForeignKey()

    date_assigned = models.DateTimeField('assigned date', blank=True, editable=False, auto_now_add=True)
    date_cancelled = models.DateTimeField('cancelled date', blank=True, null=True, default=None)

Answer 1

So you want to find all the Companies in UserSupervision for a certian UserSupervision.user? Something like:

user_supervisions = UserSupervision.objects.filter(
    content_type=ContentType.objects.get_for_model(Company),
    user=some_user,
    date_cancelled=None
).order_by('content_type_id', 'object_id').distinct('content_type_id', 'object_id')

companies = [us.object_id for us in usersupervisions]  # Loop to create list of company ids.

You can drop the order_by and distinct if you're not using PostgreSQL, but the companies loop would need to be changed to account for duplicate entries.