select_related and prefetch_related should only cache on GET method

[sainttail]

I'm following #1964

by declaring something like queryset = SomeObj.objects.all().prefetch_related('many_object') in Generic Viewset

However this also cache when I patch the object and adding or removing that many_object
so I have to override patch method to called get_object() to refresh in order to get the updated return result

...
instance = self.get_object()
return Response(self.get_serializer(instance).data)

Are there any method to separate this?

[tomchristie]

Duplicate of #2442. Not a lot we can do about this other than suitable documentation.
You could override get_queryset to only perform the prefetch on GET requests, perhaps?