"Raw query must include the primary key" when inheriting models

[Tobias Wolff]

Hi,

I have created two models as this:

class Campaign(models.Model):
    name = models.CharField(max_length=255)

class CampaignExt(Campaign):
    status = models.IntegerField()

In my APIView I do this:

    def get(self, request, campaign_id, response_format=None):
        campaigns = CampaignExt.objects.raw("""\
          SELECT
            c.id,
            c.name,
            c.status
          FROM campaign c
          WHERE c.id = %(id)s
        """ % { "id": campaign_id });

The traceback looks like this:

Traceback:
File ".../env/lib/python3.4/site-packages/django/core/handlers/base.py" in get_response
  111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File ".../env/lib/python3.4/site-packages/django/views/decorators/csrf.py" in wrapped_view
  57.         return view_func(*args, **kwargs)
File ".../env/lib/python3.4/site-packages/django/views/generic/base.py" in view
  69.             return self.dispatch(request, *args, **kwargs)
File ".../env/lib/python3.4/site-packages/rest_framework/views.py" in dispatch
  403.             response = self.handle_exception(exc)
File ".../env/lib/python3.4/site-packages/rest_framework/views.py" in dispatch
  400.             response = handler(request, *args, **kwargs)
File ".../campaigns/views.py" in get
  35.         return Response({'result': serializer.data[0]})
File ".../env/lib/python3.4/site-packages/rest_framework/serializers.py" in data
  570.                 self._data = [self.to_native(item) for item in obj]
File ".../env/lib/python3.4/site-packages/rest_framework/serializers.py" in <listcomp>
  570.                 self._data = [self.to_native(item) for item in obj]
File ".../env/lib/python3.4/site-packages/django/db/models/query.py" in __iter__
  1553.                     raise InvalidQuery('Raw query must include the primary key')

Exception Type: InvalidQuery at /campaigns/4858
Exception Value: Raw query must include the primary key

As I have the primary key in the query I reckon that this should work. But it seems that the CampaignExt model does not know about the primary key as if it has not inherited this from the Campaign model.

When I just create two models with a separated list of fields like this:

class Campaign(models.Model):
    name = models.CharField(max_length=255)

class CampaignExt(models.Model):
    name = models.CharField(max_length=255)
    status = models.IntegerField()


It works as expected. Can you help me what I am missing? Here is my environment:

Django 1.7.1
Python 3.4.2
Rest_Framework 2.4.3

Thanks,
   Tobias.

--
Gruß/Regards,
Tobias Wolff

Senior Architect Workflow Solutions
IPONWEB GmbH

Conrad-Niemann-Straße 28
33442 Herzebrock-Clarholz

Mobil: +49 172 1940702
eMail: two...@iponweb.net

Geschäftsführer: Thomas Servatius
Amtsgericht: Düsseldorf, HRB 72195

[Collin Anderson]

Hi Tobias,

Based on your database query, it looks like you are not doing multiple table inheritance, but your models are set up for multiple table inheritance.

https://docs.djangoproject.com/en/dev/topics/db/models/#model-inheritance

Why not just have a status field on your Campaign model? Django expects each (non abstract, non proxy) model to map to a database table.

If you are doing multiple table inheritance, I'm guessing the primary key that django is expecting would be the auto generated campaign_ptr_id, which would live on the campaignext table.

In you are doing multiple table inheritance, why not just do CampaignExt.objects.get(id=campaign_id) ?

Collin