Allow to clear object before deleting to avoid data loss because delete cascade behaviour
|Reported by:||Manuel Saelices||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:||1.0|
|Cc:||Carl Meyer||Triage Stage:||Design decision needed|
|Has patch:||yes||Needs documentation:||yes|
|Needs tests:||no||Patch needs improvement:||no|
Imaging a model like this:
class Master(models.Model): name = models.CharField(max_length=100) class Slave(models.Model): name = models.CharField(max_length=100) master = models.ForeignKey(Master, null=True)
And this object creation:
>>> m1 = Master.objects.create(name="master1") >>> s1 = Slave.objects.create(name="slave1", master=m1) >>> m1.delete() # this will also delete s1
Django by default, delete in cascade all related objects... even with
If you want to avoid this, you can do this:
>>> m1.slave_set.clear() >>> m1.delete()
This is ok, but it was wonderful if I can change behaviour to not delete cascade. You can think in admin site for example. If you want to delete a Category object you have previously to enter in maybe a hundred objects to set null by hand.
I propose a definition like this:
class Slave(models.Model): name = models.CharField(max_length=100) master = models.ForeignKey(Master, null=True, delete_cascade=False)
delete_cascade=False (by default would be
delete() method will clear this relation previously deletion.
I've attached a patch that implements this idea.