Ruby on rails 显示论坛列表中最后一个主题和用户的论坛架构

作为一个更大项目的一部分，我正在构建一个简单的论坛，其中一个要求是在公告板列表中，我们将显示最新的主题以及发布该主题的用户

以下是我拥有的相关模型：

Board
  name
  description
  subjects_count
  has_many Subjects

Subject
  title
  content
  user_id
  replies_count
  belongs_to Board
  belongs_to User
  has_many Replies

Reply
  content
  belongs_to Subject
  belongs_to User

User
  name
  has_many Subjects
  has_many Replies

在boards index视图中，我为每个活动板显示了以下字段（可能有5-10个板）：

要显示此信息，我现在使用以下方法：

 def get_boards_and_latest_subject
    Board.connection.select_all("SELECT boards.id, boards.name, boards.description, subjects.id as most_recent_subject_id, subjects.title as most_recent_subject_title, subjects.user_id, subjects.created_at, users.name as most_recent_subject_user_name, users.id as user_id, (select count(id) FROM subjects where board_id = boards.id) as subject_count
                                 FROM boards
                                 INNER JOIN (SELECT board_id, MAX(created_at) MaxDate FROM subjects s GROUP BY board_id) MAXDATES
                                 ON boards.id = MaxDates.board_id
                                 INNER JOIN subjects ON MaxDates.board_id = subjects.board_id AND MaxDates.MaxDate = subjects.created_at
                                 JOIN users ON subjects.user_id = users.id")
  end

我从我开始这个项目时使用的平台——CodeIgniter——带来了这个SQL，但现在对我来说似乎有点可笑。当时的目标是减少列出董事会时的查询数量

考虑到我拥有的板子数量（5-10个），做一些更像是在一个漂亮的AR调用中返回所有板子，并为每个板子获取最新的主题和用户，不是更好吗

或者，另一种选择是将最新的主题存储在boards表中，就像计数器缓存一样。由于计数器缓存的原因，当我添加主题时，我已经在更新表了，那么更新最后一个主题信息是否明智呢

我们现在正在重建的网站上的boards页面平均每月浏览量约为2万次，所以流量不大

 def get_boards_and_latest_subject
    Board.connection.select_all("SELECT boards.id, boards.name, boards.description, subjects.id as most_recent_subject_id, subjects.title as most_recent_subject_title, subjects.user_id, subjects.created_at, users.name as most_recent_subject_user_name, users.id as user_id, (select count(id) FROM subjects where board_id = boards.id) as subject_count
                                 FROM boards
                                 INNER JOIN (SELECT board_id, MAX(created_at) MaxDate FROM subjects s GROUP BY board_id) MAXDATES
                                 ON boards.id = MaxDates.board_id
                                 INNER JOIN subjects ON MaxDates.board_id = subjects.board_id AND MaxDates.MaxDate = subjects.created_at
                                 JOIN users ON subjects.user_id = users.id")
  end