#29000: RenameModel does not rename M2M column when run after
AlterField/RenameField
-------------------------------------+-------------------------------------
Reporter: David Nelson Adamec | Owner:
| shangdahao
Type: Bug | Status: assigned
Component: Migrations | Version: 2.0
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
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Comment (by David Nelson Adamec):
After doing a little more digging, it appears that the `reload_model` with
`delay=True` in the RenameField migration is the culprit. Because of the
`delay` flag, only the original model and its directly related models
(ModelA and ModelB in the example) are reloaded, so ModelC is untouched
and its `b_set` field continues to point at the old version of ModelB
that's no longer registered. Since ModelC isn't pointing at the new
ModelB, it's not included in ModelB's `related_objects`.
I'm not sure what the performance implication would be if delayed loading
were removed from RenameField/AlterField, but I'm sure it's not good.
Perhaps there's another clever solution out there, but I feel a bit out of
my depth. Here's the workaround I'm using for the time being.
{{{#!python
class RenameModelWorkaround(migrations.RenameModel):
def database_forwards(self, app_label, schema_editor, from_state,
to_state):
from_state.reload_model(app_label, self.old_name_lower)
super(RenameModelWorkaround, self).database_forwards(
app_label, schema_editor, from_state, to_state)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/29000#comment:6>
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