models.py

    def get_queryset(self):
        def filter_question(question_type=None, prefix='user__questions'):
            kwargs = {
                '{}__course'.format(prefix): models.F('course'),
            }
            if question_type:
                kwargs['{}__{}__isnull'.format(prefix, question_type)] = False
            return models.Q(**kwargs)

        def filter_answer(question_type=None):
            return models.Q()
            return (filter_question(question_type, prefix='user__answers__question') &
                    models.Q(user__answers__hidden_to_others=False))

        def votes(vote_type, field, filter):
            return models.Count('user__{}__votes'.format(field), filter=(
                filter & models.Q(user__questions__votes__type=vote_type)
            ), distinct=True)

        return super().get_queryset().annotate(
            num_slide_questions=models.Count('user__questions', filter=filter_question('slidequestion'), distinct=True),
            num_meta_questions=models.Count('user__questions', filter=filter_question('metaquestion'), distinct=True),

            num_slide_question_answers=models.Count('user__answers', filter=filter_answer('slidequestion'), distinct=True),
            num_test_question_answers=models.Count('user__answers', filter=filter_answer('testquestion'), distinct=True),
            num_meta_question_answers=models.Count('user__answers', filter=filter_answer('metaquestion'), distinct=True),

            question_upvotes=votes('+1', 'questions', filter_question()),
            question_downvotes=votes('-1', 'questions', filter_question()),

            answer_upvotes=votes('+1', 'answers', filter_answer()),
            answer_downvotes=votes('-1', 'answers', filter_answer()),

            num_helpful_slides=models.Count('user__slide_question_links', filter=models.Q(
                user__slide_question_links__value=1,
                user__slide_question_links__question__course=models.F('course'),
            ), distinct=True),
        )