Should either include a queryset attribute, or override the get_queryset() method.

[chogarcia]

djangorestframework==3.3.1

[chogarcia]

adding

queryset = ''

works

[MattBroach]

Thanks for catching this problem, @cho-is -- I saw it a couple days ago myself. This problem crept in with DRF 3.3, and I'm gonna release an update today or tomorrow with a very similar patch to the one you proposed

[MattBroach]

Just uploaded released a patch that fixes this error (and created a test to confirm the problem and fix). I did not alter the mixin, because I didn't want to make any assumptions about use. The new version is up on pypi or can be downloaded from the releases here.

[chogarcia]

It seems to be an issue with DjangoRestMultipleModels and cache.

It does not invalidate the cache when you change a model.

I think it might be related with

def get_queryset(self):
        return

I will take a deeper look.

[chogarcia]

The only different thing I found from DRF that your Mixin does not have is:

        if isinstance(queryset, QuerySet):
            # Ensure queryset is re-evaluated on each request.
            queryset = queryset.all()

Do you think this might be why it does not reflect the model changes through the API View when you change a model in the backend?

[chogarcia]

Any help would be much appreciated.

[MattBroach]

I think that line you found in DRF might be the key, @cho-is -- nice sleuthing. The first thing I would try would be replacing these lines in the multiple model mixin:

for pair in queryList:
    # Run the queryset through Django Rest Framework filters
    queryset = self.filter_queryset(pair[0])

with this:

for pair in queryList:
    queryset = pair[0].all()
    # Run the queryset through Django Rest Framework filters
    queryset = self.filter_queryset(queryset)

I won't have time to test this in the next few days, but if you try it out, let me know what happens.

[chogarcia]

It seems to be working fine now.

Many thanks! much appreciated.

[MattBroach]

Glad it's fixed. I'll try to update the repo with the changes in the next week or so.

[tony47]

Hello, I am experiencing caching issues even with this fix.

The only way to receive updated results is by changing line 73 in mixins.py:

queryset = self.filter_queryset(query.queryset)

to this one:

queryset = query.queryset.all()

Please, let me know if you need more details from me.

[MattBroach]

Hmm, the mixin has gone through some refactoring, and I guess the caching problem snuck back in. Rather than replacing line 73 entirely, does the caching work if you insert your suggested line before, like:

queryset = query.queryset.all()
queryset = self.filter_queryset(queryset)

I'd still like to run the queryset through the filter backend, so I don't want to remove that line entirely. Let me know if the above suggestion still fixes the caching issue.

[tony47]

Thanks for your response.

I confirm that doing so still fixes the caching issue.

[MattBroach]

Thanks for confirming, @tony47. Fix is now in PyPI.

[mbox]

We've run into a problem with this - it breaks the ability to cache the querysets and return them from the get_queryList() method.

Code like this used to work:

def get_queryList(self):
    querylist = cache.get(CACHE_KEY)
    if querylist is None:
        # Calculate querylist and cache here...
        ....
    return querylist

And mean that subsequent calls to the API would not result in a new DB query.
But now this doesn't work because each queryset is forced to be re-evalulated by query.all()

Equivalent code works fine in DRF because the re-evaluation is forced in get_queryset, so if get_queryset is overridden it's assumed the user knows what they're doing.

So the right fix is to move this to the get_queryList() function. I'll prepare a PR.

[RobertoKennedy]

adding

queryset = ''

works

holyshit, thanks

[python997]

adding

queryset = ''

works

Genius!

[islombek-cs]

The solution is adding ' ' this in views file. After you have called serializer class like this:
serializer_class = ExampleSerializers
queryset = ' '

that is a solution of our bug!!