#22944: Migrate doesn't like ForeignKey being reassigned to a different app's
model
----------------------------+----------------------
Reporter: mozumder@… | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.7-rc-1
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+----------------------
Hi,
Django 1.7 RC1 doesn't like it when I try to migrate an app's models.
I have a couple of models in App "Background". Simplified example:
{{{
class Family(models.Model):
name = models.CharField(
_("name"),
max_length=255,
blank=True,
null=True,
)
order = models.PositiveSmallIntegerField(
_("order"),
default=0,
)
parent = models.ForeignKey(
'self',
blank=True,
null=True,
class ImageLayer(models.Model):
family = models.ForeignKey(
Family,
verbose_name=_("Family Name"),
related_name='background_family_name',
null=True,
blank=True,
)
}}}
I have another separate App, "Styles" with a similar Family model:
{{{
class StyleFamily(models.Model):
name = models.CharField(
_("name"),
max_length=255,
blank=True,
null=True,
)
order = models.PositiveSmallIntegerField(
_("order"),
default=0,
)
parent = models.ForeignKey(
'self',
blank=True,
null=True,
)
}}}
Now, I try to delete my "Family" model from the Background App, and
reassign the family field to 'styles.StyleFamily" as:
{{{
class ImageLayer(models.Model):
family = models.ForeignKey(
'styles.StyleFamily',
verbose_name=_("Family Name"),
related_name='background_family_name',
null=True,
blank=True,
)
}}}
Then I run manage.py makemigration and manage.py migrate
I get the following:
{{{
bobby:engine mozumder$ ./manage.py makemigrations
Migrations for 'background':
0002_auto_20140702_1621.py:
- Remove field parent from family
- Delete model Family
- Alter field family on imagelayer
- Alter field family on stack
bobby:engine mozumder$ ./manage.py migrate
Operations to perform:
Synchronize unmigrated apps: grappelli
Apply all migrations: sessions, styles, background, blocks, borders,
defaults, effects, structure, transform, sites, contenttypes, admin,
typography, content, animation, auth, colors, redirects, layout, text,
articles, categories
Synchronizing apps without migrations:
Creating tables...
Installing custom SQL...
Installing indexes...
Running migrations:
Applying background.0002_auto_20140702_1621...Traceback (most recent
call last):
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/apps/config.py", line 152, in get_model
return self.models[model_name.lower()]
KeyError: 'family'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/db/migrations/state.py", line 79, in render
model = self.apps.get_model(lookup_model[0], lookup_model[1])
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/apps/registry.py", line 190, in get_model
return self.get_app_config(app_label).get_model(model_name.lower())
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/apps/config.py", line 155, in get_model
"App '%s' doesn't have a '%s' model." % (self.label, model_name))
LookupError: App 'background' doesn't have a 'family' model.
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "./manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/core/management/__init__.py", line 385, in
execute_from_command_line
utility.execute()
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/core/management/__init__.py", line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/core/management/base.py", line 337, in execute
output = self.handle(*args, **options)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/core/management/commands/migrate.py", line 160, in
handle
executor.migrate(targets, plan, fake=options.get("fake", False))
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/db/migrations/executor.py", line 62, in migrate
self.apply_migration(migration, fake=fake)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/db/migrations/executor.py", line 96, in
apply_migration
migration.apply(project_state, schema_editor)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/db/migrations/migration.py", line 107, in apply
operation.database_forwards(self.app_label, schema_editor,
project_state, new_state)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/db/migrations/operations/fields.py", line 118, in
database_forwards
from_model = from_state.render().get_model(app_label, self.model_name)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4
/site-packages/django/db/migrations/state.py", line 89, in render
model=lookup_model,
ValueError: Lookup failed for model referenced by field
background.ImageLayer.family: background.Family
}}}
It seems it doesn't like it when I reassign the "family" field to a
ForeignKey outside the App. This happens even with empty "Family" and
"styles.Family" models.
I avoid this situation by rebuilding the database from scratch and calling
in fixtures. I think this is probably a bug?
This is with Django 1.7 RC1, Python 3.4.0, and Postgres 9.3.4
Anyways, let me know if there is a workaround... thank you!
-bobby
--
Ticket URL: <https://code.djangoproject.com/ticket/22944>
Django <https://code.djangoproject.com/>
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