Provide a simple way to retain parent instances after children are deleted

[anonymous]

I have a Location table with two children (using table-inheritance): Restaurant and ChipShop. There should be a simple way to convert a ChipShop to a Restaurant without deleting/recreating the Location which may be referenced by lots of foreign keys, e.g:

location = Location.objects.get(1) # Currently a ChipShop
restaurant = Restaurant(location_ptr=location)
restaurant.save()
location.chipshop.delete() # Deletes the ChipShop row but not the Location

Currently this can be achieved by using raw sql to bypass django's code that deletes the parent when a child is deleted. Doing the following does not work as the parent is still deleted, perhaps this is a bug?

class ChipShop(Location);
   location_ptr = models.OneToOneField(Location, on_delete=DO_NOTHING, parent_link=True)

Modifying the on_delete of the created location_ptr does nothing as well. Perhaps a setting in the parents Meta that could be used to specify that the parent should not be deleted when the child is?

[Anssi Kääriäinen]

I do think having some way to do this would be good. At least I have had need to do obj.delete(delete_parents=False). Not sure if that is the best API...

[Tim Graham]

Duplicate of #15579 which has been fixed.