基于post-count和frequency的趋势分析算法

假设我有一个板模型。董事会有许多职位。我只想找到在(x)天内拥有最高职位数的董事会。下面是我非常天真的做法。如果我得到了错误代码:

ActiveRecord::StatementInvalid (PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "posts")
LINE 1: SELECT  "boards".* FROM "boards" WHERE (board.posts.created_...
                                                ^
: SELECT  "boards".* FROM "boards" WHERE (board.posts.created_at >= '2019-06-05 12:14:30.661233') LIMIT $1

请让我知道,除了我收到的错误之外,还有没有更好的方法可以做到这一点。

class Board < ApplicationRecord
  has_many :posts

  scope :trending, -> { includes(:posts).where('board.posts.created_at >= ?', Time.now-7.days).order(posts_count: :desc) }
end

class Post < ApplicationRecord
  belongs_to :board, counter_cache: true
end

更新: 所以我设法想出了一个工作范围,但不能百分之百确定它是否是最理想的。您的想法将不胜感激:

scope :trending, -> { includes(:posts).where(posts: { created_at: Time.now - 7.days }).order(posts_count: :desc) }