Django Admin exception when saving a multi-table model

[relict007]

I am using cacheops in my Django project with multiple apps. Whenever I try to save a multi-table model it gives a FieldError. In my models the hierarchy is like this:
Item -> Issue -> Suggestion

Save operation for Item class works fine but not for Issue or Suggestion. Error comes only when saving through Admin interface and not through API or django shell. I am using Django 1.6.2 with django-cacheops version 2 installed using pip. Please let know if any more information is needed.

class Item(models.Model):
    user=models.ForeignKey(User,verbose_name='Creator',on_delete=models.PROTECT,related_name='items')
...

Here's class Issue:

class Issue(Item):
...

Here's class Suggestion:

class Suggestion(Issue):
  title=models.CharField('Title',max_length=512)
  description=models.TextField('Description',blank=True)

Environment:


Request Method: POST
Request URL: https://127.0.0.1/admin/uiserver/suggestion/314/

Django Version: 1.6.2
Python Version: 2.7.3
Installed Applications:
('django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.sites',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'django.contrib.admin',
 'django.contrib.admindocs',
 'rest_framework',
 'social.apps.django_app.default',
 'apps.secure',
 'rest_framework.authtoken',
 'django_filters',
 'south',
 'django_extensions',
 'djsupervisor',
 'django.contrib.redirects',
 'djcelery',
 'erroneous',
 'debug_toolbar',
 'cacheops',
 'apps.esa',
 'apps.uiserver',
 'apps.device',
 'apps.userprofile',
 'apps.msa',
 'apps.utils')
Installed Middleware:
('django.middleware.common.CommonMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.contrib.redirects.middleware.RedirectFallbackMiddleware',
 'debug_toolbar.middleware.DebugToolbarMiddleware',
 'django_cprofile_middleware.middleware.ProfilerMiddleware')


Traceback:
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
  114.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in wrapper
  432.                 return self.admin_site.admin_view(view)(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
  99.                     response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/views/decorators/cache.py" in _wrapped_view_func
  52.         response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/sites.py" in inner
  198.             return view(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapper
  29.             return bound_func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
  99.                     response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in bound_func
  25.                 return func(self, *args2, **kwargs2)
File "/usr/local/lib/python2.7/dist-packages/django/db/transaction.py" in inner
  339.                 return func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in change_view
  1231.                 self.save_related(request, form, formsets, True)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in save_related
  882.         form.save_m2m()
File "/usr/local/lib/python2.7/dist-packages/django/forms/models.py" in save_m2m
  96.                 f.save_form_data(instance, cleaned_data[f.name])
File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py" in save_form_data
  1527.         setattr(instance, self.attname, data)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py" in __set__
  839.         manager.clear()
File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py" in clear
  597.             self._clear_items(self.source_field_name)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py" in _clear_items
  723.                     model=self.model, pk_set=None, using=db)
File "/usr/local/lib/python2.7/dist-packages/django/dispatch/dispatcher.py" in send
  185.             response = receiver(signal=self, sender=sender, **named)
File "/usr/local/lib/python2.7/dist-packages/cacheops/query.py" in invalidate_m2m
  529.         objects = sender.objects.filter(**{attname: instance.pk})
File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py" in filter
  163.         return self.get_queryset().filter(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py" in filter
  590.         return self._filter_or_exclude(False, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py" in _filter_or_exclude
  608.             clone.query.add_q(Q(*args, **kwargs))
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py" in add_q
  1198.         clause = self._add_q(where_part, used_aliases)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py" in _add_q
  1234.                     current_negated=current_negated)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py" in build_filter
  1100.                     allow_explicit_fk=True)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py" in setup_joins
  1357.             names, opts, allow_many, allow_explicit_fk)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py" in names_to_path
  1277.                                      "Choices are: %s" % (name, ", ".join(available)))

Exception Type: FieldError at /admin/uiserver/suggestion/314/
Exception Value: Cannot resolve keyword 'suggestion' into field. Choices are: id, image, item

[ttyS15]

Hi!

See at this patch. It rejected, but working in my production.

#94

[Suor]

First, sorry for slow response, I'm on vacation right now. Second, multi-table inheritance is not supported right now. README states that it's waiting champion to implement it. I suggest you guys team up on this if you are interested enough.

Regarding #94, I closed it cause it doesn't correspond to stated goal (more robust m2m invalidation) nor does it enables multi-table inheritance support. I will reopen it as solving "Multi-table inheritance exploding" problem. However, it should be complemented with with real support for multi-table models, as silently leaving something hanging up not invalidated would cause grief, see #31.

@4randd, you can try if #94 patch solves your problem. Please come back with a feedback.

[relict007]

Thanks @ttyS15 @Suor . Yes, the patch solves my problem. Saving models from Admin interface doesn't throw an exception any more. As @ttyS15 mentioned that he has been using this in production so I think I am gonna keep it, until I see any problem related to this.

@Suor I understand that multi-table inheritance doesn't work in cacheops but I read your comment somewhere that by 'doesn't work' it just means that cacheops won't invalidate child model when parent model is updated and vice-versa, so I thought that I check with you about my problem.
I would be interested in implementing multi-table inheritance but I am very new to Django and don't yet understand it enough to make changes at that level.

[Suor]

@4randd, you are welcome. You don't really need to understand the whole django to contribute to cacheops. There is also a post explaining how cacheops works - http://hackflow.com/blog/2014/03/09/on-orm-cache-invalidation/.

[relict007]

Thank @Suor for the very informative post. I will try and do some hacking with cacheops/django.

[Suor]

Yes, #94 being merged and released in 2.1 closes this. Thanks everyone.