查找具有零个嵌套has_many关联记录的记录

Question

我碰到了这个post，与我想做的事情类似。

Person.left_outer_joins(:contacts).where( contacts: { id: nil } )

唯一的区别是我需要更深一层。我的设置是Restaurant，其中有许多Dishes，而这些菜肴又与部分具有HMT关联。我只想找到没有相关部分的菜肴。我尝试做类似的事情：

Restaurant.left_outer_joins(:dishes).where(dishes: { section_ids: nil })

但是出现此错误：

ActiveRecord::StatementInvalid (PG::UndefinedColumn: ERROR:  column dishes.section_ids does not exist)
LINE 1: ...ishes"."restaurant_id" = "restaurants"."id" WHERE "dishes"."...
                                                             ^
: SELECT  "restaurants".* FROM "restaurants" LEFT OUTER JOIN "dishes" ON "dishes"."restaurant_id" = "restaurants"."id" WHERE "dishes"."section_ids" IS NULL LIMIT $1

---

class Restaurant < ApplicationRecord
  has_many :dishes, dependent: :destroy
end

class Dish < ApplicationRecord
  has_many :dish_sections, dependent: :destroy
  has_many :sections, through: :dish_sections

  belongs_to :restaurant
end

class Section < ApplicationRecord  
  has_many :dish_sections, dependent: :destroy
  has_many :dishes, through: :dish_sections
end

class DishSection < ApplicationRecord
  belongs_to :dish
  belongs_to :section
end