Bulk, partial updates with Django Rest Framework

Question

I want to partially-update multiple items at once. I've already added a mixin for allowing me to bulk-create (and that works well) but even though I've added a partial argument, it doesn't allow for patching a list.

I'm guessing that this is a routing issue. I need a new view to handle PATCH on / (rather than /id/), but I'm well out of my depth.

Existing answers for this don't work for 3.8, or at least haven't worked for me. What do I need to do to the following?

class ResourceSerializer(serializers.ModelSerializer):
    class Meta:
        model = Resource
        fields = ('id', 'name', ...)
        read_only_fields = ('id',)

 class BulkMixin:
     def get_serializer(self, *args, **kwargs):
        if isinstance(kwargs.get('data', {}), list):
            kwargs['many'] = True
            kwargs['partial'] = True

        return super().get_serializer(*args, **kwargs)

class ResourceViewSet(BulkMixin, viewsets.ModelViewSet):
    serializer_class = ResourceSerializer

Answer 1

After ~10 hours banging my head against this wall, I decided that the right way could take a back seat and I'd make do with the hack way that works. I added the following gnarlfest to my viewset.

from rest_framework.decorators import action

@action(methods=['patch'], detail=False)
def bulk_update(self, request):

    data = {  # we need to separate out the id from the data
        i['id']: {k: v for k, v in i.items() if k != 'id'}
        for i in request.data
    }

    for inst in self.get_queryset().filter(id__in=data.keys()):
        serializer = self.get_serializer(inst, data=data[inst.id], partial=True)
        serializer.is_valid(raise_exception=True)
        serializer.save()

    return Response({})

If I patch in a list of [{id: 123, otherfield: "abc"}, ...] this will now bulk-partial update. I'm fairly sure this is doing n+1 queries and that it'd be a lot more efficient in raw ORM... but for now, it's infinitely better than n requests. Also, if the ID isn't in the queryset, it will pass over rather than erroring. That works for me, but may not for others.

I'll stick a bounty on this question in 48h to tempt in some good answers.

Answer 2

I would suggest not trying to implement this yourself. Consider using django-rest-framework-bulk. It supports bulk, partial updates and provides serializers, views, and a router to make things really simple to setup.