#28972: `RelatedObjectDoesNotExist` during `loaddata` of models with multi-table
inheritance
------------------------------------------------+------------------------
Reporter: Kal Sze | Owner: nobody
Type: Bug | Status: new
Component: Core (Serialization) | Version: 2.0
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
------------------------------------------------+------------------------
Software versions
* Python 3.6.3
* Django 2.0
* django-model-utils 3.1.1 (from git)
* PostgreSQL 9.4
* psycopg2 2.7.3.2
I have a `licenses` app, with these models:
* `BaseLicense`, a concrete model, with a `ForeignKey` to
`settings.AUTH_USER_MODEL`.
* `CorelDrawLicense`, which inherits from `BaseLicense` through multi-
table inheritance
* `AdobePhotoshopLicense`, which inherits from `BaseLicense` through
multi-table inheritance
I created an instance of `AdobePhotoshopLicense`, then tried to do
`manage.py dumpdata` and `manage.py loaddata`.
`dumpdata` "worked" - there was no error.
However, `loaddata` failed with this traceback:
{{{
Traceback (most recent call last):
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/serializers/json.py", line 69, in Deserializer
yield from PythonDeserializer(objects, **options)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/serializers/python.py", line 170, in Deserializer
obj = base.build_instance(Model, data, using)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/serializers/base.py", line 225, in build_instance
natural_key = obj.natural_key()
File "/home/kal/git/nk_test/licenses/models.py", line 33, in natural_key
return (self.user.natural_key(), self.license_key)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/db/models/fields/related_descriptors.py", line 175, in
__get__
"%s has no %s." % (self.field.model.__name__, self.field.name)
django.db.models.fields.related_descriptors.RelatedObjectDoesNotExist:
BaseLicense has no user.
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "./manage.py", line 15, in <module>
execute_from_command_line(sys.argv)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/management/__init__.py", line 371, in
execute_from_command_line
utility.execute()
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/management/__init__.py", line 365, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **cmd_options)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/management/base.py", line 335, in execute
output = self.handle(*args, **options)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/management/commands/loaddata.py", line 72, in handle
self.loaddata(fixture_labels)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/management/commands/loaddata.py", line 113, in
loaddata
self.load_label(fixture_label)
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/management/commands/loaddata.py", line 168, in
load_label
for obj in objects:
File "/home/kal/.virtualenvs/nk_test-5iWsqJVv/lib/python3.6/site-
packages/django/core/serializers/json.py", line 73, in Deserializer
raise DeserializationError() from exc
django.core.serializers.base.DeserializationError: Problem installing
fixture '/home/kal/git/nk_test/./fixtures/dumpdata.json':
}}}
Here are the exact steps:
1. Create model instances in management shell
{{{
>>> from django.contrib.auth import get_user_model
>>> User = get_user_model()
>>> kal = User.objects.create_user('kal', 'k...@foobar.com', 'qwer1234')
>>> from licenses.models import AdobePhotoshopLicense
>>> l = AdobePhotoshopLicense.objects.create(user=kal,
license_key='12345')
}}}
2. Dump the data into a fixtures json
{{{
$ python manage.py dumpdata -o fixtures.json --format json --natural-
foreign --natural-primary auth licenses
}}}
3. Edit settings.py to switch to an empty database
{{{
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
#'NAME': 'nk_test',
'NAME': 'nk_test_2',
'USER': 'kal',
'HOST': '',
'PORT': 5432,
}
}
}}}
4. Run migrations on the new empty database
{{{
$ python manage.py migrate
}}}
5. Try to load the data from fixtures.json
{{{
$ python manage.py loaddata --format json fixtures.json
}}}
I have attached the models.py and fixtures.json file to the ticket.
--
Ticket URL: <https://code.djangoproject.com/ticket/28972>
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