我如何通过评论数量获取所有文章和订单？

Question

  

可能重复：
  How would I grab only articles with comments that were created 20 minutes ago?

使用mongodb和mongoid。如何根据评论数量获取所有文章和订单？

class Article
  include Mongoid::Document

  has_many :comments
end

class Comment
  include Mongoid::Document

  belongs_to :article
end

Answer 1

我不确定你打算排序的方向，所以我包括了两者的索引 - 你应该删除一个，如果你不打算使用它，但这应该为你做的伎俩： / p>

class Article
  include Mongoid::Document

  field :comments_count, :type => Integer, :default => 0
  index [[ :comments_count, Mongo::ASCENDING ]]
  index [[ :comments_count, Mongo::DESCENDING ]]
  has_many :comments

  before_save :update_comments_count

  protected
  def update_comments_count
    self.comments_count = self.comments.count
  end
end