Unclear how to properly use the get_queryset()

[Jakuje]

All the examples directly set queryset for views. The documentation says that I should override the get_queryset() on them, but call super().get_queryset(), but this really does not work if we do not have the base class that would stop propagation of this call to the rest_framework's get_queryset(), which asserts the queryset is set.

https://github.com/encode/django-rest-framework/blob/e454758fb6edf1dcf5aa5417a388b940c871469c/rest_framework/generics.py#L67

I really liked the concept of this project trying to avoid all the mess with splitting queries and models, but only way how I was able to make this working was something like this:

class BaseVirtualModelListApiView(ListAPIView):
    def get_queryset(self):
        # make sure the ListApiView.get_queryset() is not called
        return self.model.objects

class MyVirtualModelListApiView(v.GenericVirtualModelViewMixin, BaseVirtualModelListApiView):
    pass

class BlogPostsView(MyVirtualModelListApiView):
    model = Blog

Not sure if I am just stupid or there is some better way. In any case, it would be good do document how this should work.

[Jakuje]

This does not sounds ideal as filtering from get_queryset should be done first before the prefetching and annotation. Other not so cool solution that I came up with is to set the self.queryset from within the get_queryset() and then call the super().get_queryset(), which will prevent it failing in rest-framework and which will set the correct optimization.

It does not look like the intended way, but looks like working for now.

[fjsj]

Thanks for the report. Could you please check @hugobessa and compare to how you're doing in recent projects?

[hugobessa]

Well, in GenericVirtualModelViewMixin we include the annotations, prefetches, selects, etc to the original query. If you want to filter on the get_queryset method you can either do it before calling super().get_queryset() or after but if you're filtering on an annotated field it has to be after the super().get_queryset() call.

That requires you to either define the queryset attribute on the view class directly or dynamically set it before calling super().get_queryset() in your implementation of get_queryset.

If you wish to stop calling super().get_queryset() in any point you need to manually include the query optimization like this:

def get_queryset(self):
    queryset = self.model.objects.all()
    return self._get_empty_serializer().get_optimized_queryset(queryset)

What we could do to improve this is to add a non-private get_optimized_queryset method to the GenericVirtualModelViewMixin to make the code look like this instead:

def get_queryset(self):
    queryset = self.model.objects.all()
    return self.get_optimized_queryset(queryset)

What do you think @fjsj ?

[Jakuje]

Thank you for clarifications! I find the use case of setting the queryset property of a view very limited as every more complex view needs some adjustments.

The second suggestion sounds probably closest to what I am looking for. I wanted some simple API call rather than need to go through several hops (that will be mostly verbosely repeated in every view).

If it would be possible to introcuce this API (and provide appropriate documentation and examples), I think it would make getting started easier.

[fjsj]

@hugobessa I think a non-private documented API is the best, thanks for the suggestion. @Jakuje are you available to open a PR addressing this? We can approve it promptly. If not, let us know and we'll address this soon.

[Jakuje]

Probably later this week.