def _get_queryset(self):
        user_slugs = self.request.GET.getlist(EMWF.slug)
        user_ids = self._get_user_ids(user_slugs)
        # return empty queryset if no matching users were found
        if user_slugs and not user_ids:
            return UserHistory.objects.none()

        changed_by_user_slugs = self.request.GET.getlist(ChangedByUserFilter.slug)
        changed_by_user_ids = self._get_user_ids(changed_by_user_slugs)
        # return empty queryset if no matching users were found
        if changed_by_user_slugs and not changed_by_user_ids:
            return UserHistory.objects.none()

        user_property = self.request.GET.get('user_property')
        actions = self.request.GET.getlist('action')
        user_upload_record_id = self.request.GET.get('user_upload_record')
        query = self._build_query(user_ids, changed_by_user_ids, user_property, actions, user_upload_record_id)
        return query