通过连接表按关联计数排序

Question

我有一个有许多剧集的节目，剧集中有许多人通过贡献。 （见下图）

我已将has_many :people, through: :contributions添加到Show，因此我可以：game_of_thrones.people.count，甚至：

  has_many :actors, -> { joins(:roles).merge(Role.actors).distinct },
    through: :contributions, source: :person

-

game_of_thrones.actors.count

但我想做的是在game_of_thrones或breaking_bad等上创建一个演员列表，按演出次数排序。

示例：

1. Jon Snow：9集
2. Arya Stark：8集
3. Joffrey Lannister：5集
4. Tyrion Lannister：2集



我的问题是两个人。

1. 如何根据贡献计数返回节目中的顶级演员列表？

2. 我应该通过ActiveRecord还是SQL查询来执行此操作。什么是更好地理解这一点的好参考，所以我可以停止打扰堆栈溢出？

   class Show < ActiveRecord::Base
     has_many :episodes, inverse_of: :show
     has_many :contributions, through: :episodes
     has_many :people, through: :contributions
   
     has_many :actors, -> { joins(:roles).merge(Role.actors) },
       through: :contributions, source: :person
   end
   
   class Episode < ActiveRecord::Base
     belongs_to :show, inverse_of: :episodes
     has_many :contributions, inverse_of: :episode
     has_many :roles, through: :contributions
     has_many :people, through: :contributions
   end
   
   class Contribution < ActiveRecord::Base
     belongs_to :episode, inverse_of: :contributions
     belongs_to :person, inverse_of: :contributions
     belongs_to :role, inverse_of: :contributions
   end
   
   class Person < ActiveRecord::Base
     has_many :contributions, inverse_of: :person
     has_many :episodes, through: :contributions
     has_many :roles, through: :contributions
   
     scope :actors, -> { joins(:roles).merge(Role.actors) }
   end
   
   class Role < ActiveRecord::Base
     has_many :contributions, inverse_of: :role
     has_many :people, through: :contributions
     has_many :episodes, through: :contributions
   
     scope :actors, -> { where(name: 'Actor') }
   end
   

查询失败：game_of_thrones.people.joins(:contributions).distinct.joins(:episodes).where("episodes.show_id = 1").order("count(episodes.show_id) desc")

game_of_thrones.guests.joins(:contributions).order("count(contribuions.id) desc")