使用mongoid进行反规范化

Question

用mongoid和Rails去规范化的最好方法是什么？

使用“嵌入式”关系似乎不起作用(或者只能用于嵌入整个原始文档)。

我目前的解决方案将非规范化属性作为OrderedHash进行存储和检索：

collection.update({_id: id, ...}, {..., denormalized: {_id: other.id, _type: other._type, a: other.a, b: other.b}}

def denormalized
  Mongoid::Factory.build(attributes[:denormalized]["_type"], attributes[:denormalized])
end

编辑:我应该提一下，我确实尝试过https://github.com/logandk/mongoid_denormalize

它展平了反规范化的属性(在下面的示例中，它将存储author_name而不是author：{name："value"}，并且它不支持多个反规范化关系(例如authors：{name："First Co-Author"，_id: 1}，{name："Second Co-Author"，_id: 2})

编辑:请求了一个示例。

class User # this class uses STI so _type field is important
  include Mongoid::Document

  field :name # this is the field I want to de-normalize to where Users are referenced

   def write_book
     Book.create!({title: "Some Text", author: {_id: self.id, _type: self._type, name: self.name})
   end
end

class Book
  include Mongoid::Document

  field :title

  # embeds_one :author, polymorphic: true
  # tried this but it doesn't seem to be correct usage... it sort of works but
  # I run into problems with cycles and infinite loops when used extensively
  # because (I think) of how mongoid works internally, expecting embeds_one
  # to mean something different

  def author
    Mongoid::Factory.build(attributes[:author]["_type"], attributes[:author])
  end
end

正确的解决方案应该是使用new_record这样的ActiveModel方法。与*_path和*_url路由助手一样工作。

Answer 1

这会将用户存储为书中嵌入的author文档。

class User
  include Mongoid::Document
end

#instead of the write book method, you could just do this:
book = Book.create(title: "Old Man And The Sea", users: [user])

class Book
  include Mongoid::Document

  embeds_many :authors

  field :title

  def users=(users)
    users.each do |user|
      authors.build(user: user, name: user.name)
    end
  end
end

class Author
  include Mongoid::Document

  embedded_in :book
  referenced_in :user

  field :name
end