IntegrityError exception in DeleteView CBV - django

Question

I'm back with more Django Class Based View questions. I have an "extended" user model in the form of a "profile" model. The profile model is using CBVs to implement CRUD functionality but the DeleteView always generates FOREIGN KEY constraint failed IntegrityError exception. I know what that should mean but I am not sure why I am getting that exception.
I have the built-in Django user model plus an "account adaptor" and my custom Profile model. The account adaptor just sets the signup email address as the username:
class AccountAdapter(DefaultAccountAdapter):
def save_user(self, request, user, form, commit=True):
Log.add("")
data = form.cleaned_data
user.username = data['email'] # username not in use
user.email = data['email']
if 'password1' in data:
user.set_password(data['password1'])
else:
user.set_unusable_password()
self.populate_username(request, user)
if commit:
user.save()
return user
The Profile model has a OneToOneField to attach a profile instance to a user.
class Profile(models.Model):
user = models.OneToOneField(
User,
on_delete=models.CASCADE,
blank=False,
null=False,
)
The DeleteView CBV is:
#method_decorator(verified_email_required, name='dispatch')
class Delete(DeleteView):
pk_url_kwarg = "account_number"
model = Profile
form_class = ProfileForm
success_url = "/accounts/logout.html"
def get(self, request, *args, **kwargs):
try:
profile = self.model.objects.get(account_number=self.kwargs[self.pk_url_kwarg])
user = User.objects.get(pk=profile.user.pk)
user.delete()
messages.success(request, "The user is deleted")
my_render = render(request, self.success_url)
except User.DoesNotExist:
messages.error(request, "User does not exist")
my_render = render(request, self.success_url)
except IntegrityError:
messages.error(request, "DB IntegrityError")
my_render = render(request, self.success_url)
return my_render
In the Delete.get method I can put a breakpoint on the user.delete() line and I can see that the profile and user objects are what I think they should be. I try to delete the user object and I get the IntegrityError exception listed above.
The stack-trace looks like:
Environment:
Request Method: GET
Request URL: http://127.0.0.1:8000/Members/Profile/d83622e4-4816-42a4-8419-2fd389c7e3fd/delete?csrfmiddlewaretoken=y3W0ze1SfN50Mx3eymEZQQPd21u5wjf0tHvRZM0PggLX12mdAgdEGUkw3lw2KnKn
Django Version: 2.0.3
Python Version: 3.6.3
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'django_extensions',
'django.contrib.sites',
'allauth',
'allauth.account',
'allauth.socialaccount',
'auditlog',
'widget_tweaks',
'Members.apps.MembersConfig']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware',
'auditlog.middleware.AuditlogMiddleware']
Traceback:
File "C:\Program Files\Python36\lib\site-packages\django\db\backends\base\base.py" in _commit
239. return self.connection.commit()
The above exception (FOREIGN KEY constraint failed) was the direct cause of the following exception:
File "C:\Program Files\Python36\lib\site-packages\django\core\handlers\exception.py" in inner
35. response = get_response(request)
File "C:\Program Files\Python36\lib\site-packages\django\core\handlers\base.py" in _get_response
128. response = self.process_exception_by_middleware(e, request)
File "C:\Program Files\Python36\lib\site-packages\django\core\handlers\base.py" in _get_response
126. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Program Files\Python36\lib\site-packages\django\views\generic\base.py" in view
69. return self.dispatch(request, *args, **kwargs)
File "C:\Program Files\Python36\lib\site-packages\django\utils\decorators.py" in _wrapper
62. return bound_func(*args, **kwargs)
File "C:\Program Files\Python36\lib\site-packages\django\contrib\auth\decorators.py" in _wrapped_view
21. return view_func(request, *args, **kwargs)
File "C:\Program Files\Python36\lib\site-packages\allauth\account\decorators.py" in _wrapped_view
32. return view_func(request, *args, **kwargs)
File "C:\Program Files\Python36\lib\site-packages\django\utils\decorators.py" in bound_func
58. return func.__get__(self, type(self))(*args2, **kwargs2)
File "C:\Program Files\Python36\lib\site-packages\django\views\generic\base.py" in dispatch
89. return handler(request, *args, **kwargs)
File "C:/Users/Me/PycharmProjects/MyProject/MyApp\Members\views\profile.py" in get
103. user.delete()
File "C:\Program Files\Python36\lib\site-packages\django\db\models\base.py" in delete
891. return collector.delete()
File "C:\Program Files\Python36\lib\site-packages\django\db\models\deletion.py" in delete
307. sender=model, instance=obj, using=self.using
File "C:\Program Files\Python36\lib\site-packages\django\db\transaction.py" in __exit__
212. connection.commit()
File "C:\Program Files\Python36\lib\site-packages\django\db\backends\base\base.py" in commit
261. self._commit()
File "C:\Program Files\Python36\lib\site-packages\django\db\backends\base\base.py" in _commit
239. return self.connection.commit()
File "C:\Program Files\Python36\lib\site-packages\django\db\utils.py" in __exit__
89. raise dj_exc_value.with_traceback(traceback) from exc_value
File "C:\Program Files\Python36\lib\site-packages\django\db\backends\base\base.py" in _commit
239. return self.connection.commit()
Exception Type: IntegrityError at /Members/Profile/d83622e4-4819-42d4-8419-2fd389c7e3fd/delete
Exception Value: FOREIGN KEY constraint failed
What am I doing wrong?
EDIT
I think my problem is with sqlite3. My DB backend is sqlite3. I have just discovered that the Django migrations that create the Profile model table DO create a foreign key reference from the profile to the User model but an on delete cascade clause is NOT created. The constraint Django creates looks like:
FOREIGN KEY(`user_id`) REFERENCES `auth_user`(`id`) DEFERRABLE INITIALLY DEFERRED,
I added the on delete cascade option by hand:
FOREIGN KEY(`user_id`) REFERENCES `auth_user`(`id`) on delete cascade DEFERRABLE INITIALLY DEFERRED,
but the delete operation failed as above. I dropped the DEFERRABLE INITIALLY DEFERRED clause and still get the violation.
I have a sqlite gui "management" tool and just tried to delete a user record using that management tool and get a foreign key violation as well so this must be on the sqlite side of things.
Edit 2
After more investigation I see the following: I am new to python and Django. My Django test app is really very small and I am not doing any/many custom actions. Using sqlite as the DB backend and doing the initial project makemigrations and migrate created the standard Django and django-allauth tables. There are a few of these base tables that have FOREIGN KEY relationships with the user table. My last survey of the DB was not extremely rigorous as it was really late last night ... but those that do reference the user table do not have on delete cascade clauses. So, even if I fix "my" table(s) the base Django tables that reference user seem to be "broken" by not having the cascade clause.
I will file a bug report if I can figure out where to send it.

Answer 1

Well, I have learned something. Django does not currently support the on delete cascade DB clause. It looks like you have to implement the behaviour yourself. I have seen posts in the email "Django Users" group about using signals for this.
I decided to try it in the DeleteView.get() method.
class Delete(DeleteView):
pk_url_kwarg = "account_number"
model = Profile
# form_class = ProfileForm
success_url = "account/login.html"
def get(self, request, *args, **kwargs):
try:
profile = get_object_or_404(Profile, account_number=self.kwargs[self.pk_url_kwarg])
user_pk = profile.user.pk
profile.delete()
get_object_or_404(User, pk=user_pk).delete()
messages.success(request, "The user is deleted")
except User.DoesNotExist:
messages.error(request, "User does not exist")
# except IntegrityError:
# messages.error(request, "DB IntegrityError")
return render(request, self.success_url)
It is possible that I don't have to actually delete the profile instance but I am still testing.