Currently I have a project using django and rest_framework to get some basic APIs on the run.

The problem is, when i make a view using the generic lib on rest_framework and DjangoModelPermissions, my method get_queryset is being called twice

My Permission Class

class DefaultModelPermissions(DjangoModelPermissions):
    """
    The request is authenticated using `django.contrib.auth` permissions.
    See: https://docs.djangoproject.com/en/dev/topics/auth/#permissions

    It ensures that the user is authenticated, and has the appropriate
    `view`/`add`/`change`/`delete` permissions on the model.

    This permission can only be applied against view classes that
    provide a `.queryset` attribute.
    """
    perms_map = {
        'GET': ['%(app_label)s.view_%(model_name)s'],
        'OPTIONS': ['%(app_label)s.view_%(model_name)s'],
        'HEAD': ['%(app_label)s.view_%(model_name)s'],
        'POST': ['%(app_label)s.add_%(model_name)s'],
        'PUT': ['%(app_label)s.change_%(model_name)s'],
        'PATCH': ['%(app_label)s.change_%(model_name)s'],
        'DELETE': ['%(app_label)s.delete_%(model_name)s'],
    }

class DefaultModelViewPermissions:
    permission_classes = (DefaultModelPermissions,)

My View

class AgentListCreateView(DefaultModelViewPermissions, generics.ListCreateAPIView):
    serializer_class = serializers.AgentSerializer
    
    def get_queryset(self):
         print('get_queryset')
         return models.Agent.objects.all()

Debbuging the app, I found out that the permission also call the get_queryset to retrieve the model to validate the django’s user’s permissions.

permission_calling_get_queryset

From my point of view, this is an unecessary operation. Deppending on the size of the DB table, this could be a major performance problem, and leed many other app issues.

My solution was to override this “has_permission” method. So my class got like

class DefaultModelPermissions(DjangoModelPermissions):
    """
    The request is authenticated using `django.contrib.auth` permissions.
    See: https://docs.djangoproject.com/en/dev/topics/auth/#permissions

    It ensures that the user is authenticated, and has the appropriate
    `view`/`add`/`change`/`delete` permissions on the model.

    This permission can only be applied against view classes that
    provide a `.queryset` attribute.
    """
    perms_map = {
        'GET': ['%(app_label)s.view_%(model_name)s'],
        'OPTIONS': ['%(app_label)s.view_%(model_name)s'],
        'HEAD': ['%(app_label)s.view_%(model_name)s'],
        'POST': ['%(app_label)s.add_%(model_name)s'],
        'PUT': ['%(app_label)s.change_%(model_name)s'],
        'PATCH': ['%(app_label)s.change_%(model_name)s'],
        'DELETE': ['%(app_label)s.delete_%(model_name)s'],
    }
    
    def has_permission(self, request, view):
        if not request.user or (
           not request.user.is_authenticated and self.authenticated_users_only):
            return False

        # Workaround to ensure DjangoModelPermissions are not applied
        # to the root view when using DefaultRouter.
        if getattr(view, '_ignore_model_permissions', False):
            return True

        # Workaround cause base class utilized get_queryset to retrieve the model
        # making unecessary requisitions to the database
        if hasattr(view, 'get_serializer_class'):
            model = view.get_serializer_class().Meta.model
        else:
            model = view.serializer_class.Meta.model
        
        perms = self.get_required_permissions(request.method, model)

        return request.user.has_perms(perms)

My question is:
Is there a better way to get this around? Does anybody else got the same problem?