#33586: Cannot delete object (A) referenced by another object (B) if said object
(A) has a foreign key to a custom user.
-------------------------------+------------------------------------
Reporter: Jeremy Poulin | Owner: Bhuvnesh
Type: Bug | Status: assigned
Component: Migrations | Version: 4.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------+------------------------------------
Comment (by Bhuvnesh):
you were right, the problem was inside {{{RunPython.state_forwards}}} as
it is not mutating any state . but it looks like like we need to reload
apps cache before running backwards migration after forward migration.
{{{
def state_forwards(self, app_label, state):
# RunPython objects have no state effect. To add some, combine
this
# with SeparateDatabaseAndState.
pass
}}}
one thing we can do is re-creating the apps inside
{{{database_backwards}}} for RunPython Operation. This should also not
affect the performance much.
{{{ #!patch
diff --git a/django/db/migrations/operations/special.py
b/django/db/migrations/operations/special.py
index 94a6ec72de..835f2c7017 100644
--- a/django/db/migrations/operations/special.py
+++ b/django/db/migrations/operations/special.py
@@ -193,6 +193,7 @@ class RunPython(Operation):
self.code(from_state.apps, schema_editor)
def database_backwards(self, app_label, schema_editor, from_state,
to_state):
+ from_state.__dict__.pop('apps', None)
if self.reverse_code is None:
raise NotImplementedError("You cannot reverse this
operation")
if router.allow_migrate(
}}}
we could've done the same thing inside {{{RunPython.state_forwards}}} but
since reloading apps is not required for forward migrations, we can save
some time there.
Ps: Passing all tests.
--
Ticket URL: <https://code.djangoproject.com/ticket/33586#comment:16>
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