gistfile1.rb

  def calculate_response_time
    Message.connection.execute("
      SELECT AVG(q3.response_time) AS average, DATE(created_at AT TIME ZONE '-08:00') AS day FROM
        (SELECT q2.* FROM
          (SELECT q1.*, q1.created_at - LEAD(created_at) OVER (PARTITION BY customer_id ORDER BY created_at) AS response_time FROM
            (SELECT m.*, LEAD(direction) OVER (PARTITION BY customer_id ORDER BY created_at) AS next_direction FROM messages m
              WHERE company_id = 2 AND via_api = false AND mass_message_id IS NULL) AS q1
            WHERE q1.direction <> q1.next_direction AND q1.next_direction IS NOT NULL) AS q2
          WHERE q2.direction = 'received') AS q3
        GROUP BY DATE(created_at AT TIME ZONE '-08:00')
        ")
  end
  
  
  RESULTED IN:
  
   #<PG::Result:0x0000010b3019f0 @connection=#<PG::Connection:0x0000010b50e0e0 @notice_processor=nil, @notice_receiver=nil, @socket_io=nil>>