models.py

    def get_queryset(self):
        tables = {
            'membership_table': Membership._meta.db_table,
            'question_table': Question._meta.db_table,
            'slide_question_table': SlideQuestion._meta.db_table,
            'test_question_table': TestQuestion._meta.db_table,
            'meta_question_table': MetaQuestion._meta.db_table,
            'answer_table': Answer._meta.db_table,
            'vote_table': Vote._meta.db_table,
            'slide_question_link_table': SlideQuestionLink._meta.db_table,
        }

        def num_question_type(question_type_table):
            return '''
                SELECT COUNT({question_table}.id)
                FROM {question_table}
                INNER JOIN {question_type_table} ON
                {question_table}.id = {question_type_table}.question_ptr_id
                WHERE {question_table}.asked_by_id = {membership_table}.user_id
                AND {question_table}.course_id = {membership_table}.course_id
            '''.format(**tables, question_type_table=question_type_table)

        def num_answer_type(question_type_table):
            return '''
                SELECT COUNT({answer_table}.id)
                FROM {answer_table}
                INNER JOIN {question_table} ON
                {question_table}.id = {answer_table}.question_id
                INNER JOIN {question_type_table} ON
                {question_table}.id = {question_type_table}.question_ptr_id
                WHERE {answer_table}.answered_by_id = {membership_table}.user_id
                AND {answer_table}.hidden_to_others = \'false\'
                AND {question_table}.course_id = {membership_table}.course_id
            '''.format(**tables, question_type_table=question_type_table)

        def question_vote_score():
            return '''
                SELECT SUM(CASE
                    WHEN {vote_table}.type = '+1' THEN 1
                    WHEN {vote_table}.type = '-1' THEN -1
                    ELSE 0
                    END
                )
                FROM {vote_table}
                INNER JOIN {question_table} ON
                {question_table}.id = {vote_table}.question_id
                WHERE {question_table}.asked_by_id = {membership_table}.user_id
                AND {question_table}.course_id = {membership_table}.course_id
            '''.format(**tables)

        def answer_vote_score():
            return '''
                SELECT SUM(CASE
                    WHEN {vote_table}.type = '+1' THEN 1
                    WHEN {vote_table}.type = '-1' THEN -1
                    ELSE 0
                    END
                )
                FROM {vote_table}
                INNER JOIN {answer_table} ON
                {answer_table}.id = {vote_table}.answer_id
                INNER JOIN {question_table} ON
                {question_table}.id = {answer_table}.question_id
                WHERE {answer_table}.answered_by_id = {membership_table}.user_id
                AND {question_table}.course_id = {membership_table}.course_id
            '''.format(**tables)

        def num_helpful_slides():
            return '''
                SELECT COUNT({slide_question_link_table}.id)
                FROM {slide_question_link_table}
                INNER JOIN {question_table} ON
                {question_table}.id = {slide_question_link_table}.question_id
                WHERE {slide_question_link_table}.value=1
                AND {slide_question_link_table}.created_by_id = {membership_table}.user_id
                AND {question_table}.course_id = {membership_table}.course_id
            '''.format(**tables)

        return super().get_queryset().extra({
            'num_slide_questions': num_question_type(tables['slide_question_table']),
            'num_test_questions': num_question_type(tables['test_question_table']),
            'num_meta_questions': num_question_type(tables['meta_question_table']),
            'question_vote_score': question_vote_score(),

            'num_slide_question_answers': num_answer_type(tables['slide_question_table']),
            'num_test_question_answers': num_answer_type(tables['test_question_table']),
            'num_meta_question_answers': num_answer_type(tables['meta_question_table']),
            'answer_vote_score': answer_vote_score(),

            'num_helpful_slides': num_helpful_slides()
        })