Question

When dealing whith model inheritance in django is it possible to remove a instance of model subclass, without removing the superclass itself?

Using the Django example, can you remove just the Resturaunt object and retain the Place object?

Answer 1

Yesterday I was looking for an answer to this question and I came up with this solution, which was enough for my problem but could be scaled up as needed.

Assuming you have a Restaurant and a Place django models, the way to delete a restaurant only without touching the row inside the Place’s table is creating a “fake” Restaurant model like this:

class FakeRestaurant(models.Model):
    place_ptr = models.PositiveIntegerField(db_column="place_ptr_id", primary_key=True)
    serves_hot_dogs = models.BooleanField()
    serves_pizza = models.BooleanField()

    class Meta:
        app_label = Restaurant._meta.app_label
        db_table = Restaurant._meta.db_table
        managed = False

Now, you can retrieve objects from that table as if it had no bound external relationship:

place = Place.objects.get(pk=1)
restaurant = Restaurant.objects.get(pk=1)
fake_restaurant = FakeRestaurant.objects.get(pk=1)
fake_restaurant.delete()

fake_restaurant and restaurant won’t exist anymore, place will remain untouched.

Cheers,
Davide