Provide a simple way to retain parent instances after children are deleted
|Reported by:||anonymous||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:||master|
|Cc:||ionel.mc@…, charette.s@…||Triage Stage:||Accepted|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
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?