gistfile1.rb

  def recalculate!
    self.number_of_questions = Match.connection.select_value("SELECT count(*) as c
    FROM
      responses as my_responses
    LEFT JOIN
      responses as their_responses
    ON their_responses.user_id = #{user_b.id}
    AND my_responses.question_id = their_responses.question_id
    WHERE
      my_responses.user_id = #{user_a.id}
    AND
      their_responses.user_id IS NOT NULL").to_i
      
    self.number_of_same_answers = Match.connection.select_value("SELECT count(*) as c
      FROM
        responses as my_responses
      LEFT JOIN
        responses as their_responses
      ON their_responses.user_id = #{user_b.id}
      AND my_responses.answer_id = their_responses.answer_id
      WHERE
        my_responses.user_id = #{user_a.id}
      AND
        their_responses.user_id IS NOT NULL").to_i
        
    self.score = sufficient? ? 100 * (number_of_same_answers.to_f / number_of_questions.to_f) : nil
      
    save!
  end