gistfile1.scala

//load all relevant meetings with their attendees
      meetings
        .leftJoin(attendeeLinks).on { case (meeting, attendeeLink) =>
          meeting.id  === attendeeLink.meetingId
        }
        .leftJoin(users).on { case ((meeting, attendeeLink), user) =>
          attendeeLink.userId === user.id
        }
        .where { case ((meeting, attendeeLink), user) =>
          meeting.id in meetingIds
        }
        .sortBy { case ((meeting, attendeeLink), user) =>
          meeting.startTime.desc
        }
        .map { case ((meeting, attendeeLink), attendee) =>
          (meeting, attendee.?)
        }
        //for every result row, put the attendee on the meeting
        .mapResult { case (meeting: Meeting, attendeeOption: Option[User]) =>
          meeting.attendees = attendeeOption.map(Set(_)).orElse(Some(Set.empty[User]))
          meeting
        }
        //merge meetings with the same id
        .list.groupBy(_.id).mapValues { meetingsWithSameId =>
          meetingsWithSameId.reduce { (previousMeeting, meeting) =>
            previousMeeting.attendees = Some(previousMeeting.attendees.get ++ meeting.attendees.get)
            previousMeeting
          }
        }.values.toList
    }