立即加载多态关联的关联

Question

class Flat < ActiveRecord::Base
  belongs_to :owner, polymorphic: true
end

class Agency < ActiveRecord::Base
  has_many :flats, as: :owner
end

class User < ActiveRecord::Base
  has_many :flats, as: :owner
  has_one :profile
end

class Profile < ActiveRecord::Base
  belongs_to :user
end

Flat.includes(:owner)工作得很好，但对于代理来说，Flat.includes(owner: :profile)将失败。如何在flats.owner_type == "User"时包含仅配置文件，以防止N+1查询？

Answer 1

使用squeel，您可以轻松地做到这一点：

Flat.joins{owner(User).profile}.includes(owner: :profile).first.owner.profile
Flat.joins{owner(Agency)}.includes(owner).first.owner

此查询将使用1+n查询。