id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
14043	Incorrect and/or confusing behaviour with nullable OneToOneField	theevilgeek	Anssi Kääriäinen <akaariai@…>	"Attempting to ""null"" out a nullable OneToOneField before deleting the related object fails to prevent a cascading delete (i.e., both objects are still deleted whereas it seems only the related object ought to be deleted).

Example code:

{{{

# Note: using Django trunk

###### MODELS ######

class Person(models.Model):
  age = models.PositiveIntegerField()

  def die(self):
    self.soul.become_ghost()
    self.delete()


class Soul(models.Model):
  person = models.OneToOneField(Person, null=True)
  is_alive = models.BooleanField(default=True)

  def become_ghost(self):
    self.person = None
    self.is_alive = False                                                                                                                                                    
    self.save()


###### TESTCASE (INTERACTIVE) ######

# Type a few commands in ""python manage.py shell""

>>> from app.models import Person, Soul
>>>
>>> bob = Person.objects.create(age=34)
>>> bobs_soul = Soul.objects.create(person=bob)

# Let's see what's happening in MySQL (switching programs...)

mysql> select * from app_person;
+----+-----+
| id | age |
+----+-----+
|  2 |  34 |
+----+-----+
1 row in set (0.00 sec)

mysql> select * from app_soul;
+----+-----------+----------+
| id | person_id | is_alive |
+----+-----------+----------+
|  2 |         2 |        1 |
+----+-----------+----------+
1 row in set (0.00 sec)

# Okay, that looks good; let's kill him (switching programs again...)

>>> bob.die()

# Back to MySQL

mysql> select * from app_person;
Empty set (0.00 sec)

mysql> select * from app_soul;
Empty set (0.00 sec)

### Huh!??! Why is app_soul being deleted?

}}}"	Bug	closed	Database layer (models, ORM)	dev	Normal	fixed	OneToOneField, cascading delete, nullable	George Sakkis	Accepted	1	0	1	1	0	0