希望让这个 Active Record Query 更高效。 Ruby on Rails

Question

嘿，所以我是活动记录的新手，我在这里有这两个地图功能，我想知道是否有更好/更高效的方法来进行以下查询：

现在，当我执行查询时，我的终端中有数百行，如果很多人同时加载这些对话，恐怕会占用大量内存？

第 1 步获取所有相关对话

第 2 步制作一个对话哈希，其中包含有关发件人、收件人和链接到该对话的消息的所有信息。

第 3 步将所有这些对话按正确的顺序排序，即从对话中对它们进行排序，最新消息位于顶部。

编辑 1：Rails 版本 5.0.1

 def index
      i = 1
      @messages = []
      @user = User.find_by(email: params[:email])
      @message = Conversation.where("sender_id = ? OR recipient_id = ?", @user.id, @user.id)
      @message.map { |conversation|
        @messages << conversation if Message.where(conversation_id: conversation.id).count > 0
      }



      render json: @messages.map { |conversation|
        {
          date: conversation.messages.last.created_at,
          sender: User.find(conversation.sender_id),
          recipient: User.find(conversation.recipient_id),
          conversation: {
            id: conversation.id,
            messages: Message.where(conversation_id: conversation.id).sort_by{|e| e[:created_at]}.reverse.map {|message| {
              sender: {
                email: User.find(message.user_id).email,
                first_name: User.find(message.user_id).first_name,
                last_name: User.find(message.user_id).last_nam },
              body: message.body,
              created_at: message.created_at
              }
            }
          }}
      }.sort_by { |hsh| hsh[:date] }.reverse
 end

Answer 1

class Message < ApplicationRecord
  belongs_to :conversation, touch: true
end

class Conversation < ApplicationRecord
  has_many :messages, -> { order(created_at: :desc) }
  belongs_to :sender, foreign_key: :sender_id, class_name: 'User'
  belongs_to :recipient, foreign_key: :recipient_id, class_name: 'User'
end

class User < ApplicationRecord
  has_many :conversations, -> (user) { unscope(where: :user_id).where('conversations.sender_id = ? OR conversations.recipient_id = ?', user.id, user.id) }
end

class ConversationsController < ApplicationController
  def index
    @user = User.find_by(email: params[:email])

    # "joins(:messages)" allows only retrieving conversations having at least one message, and does not include conversation with 0 message
    # now ordering by `updated_at: :asc` because `Message belongs_to :conversation, touch: true`, in which Conversation's updated_at will be automatically "touched"/updated whenever the associated Messages are updated/created.
    @conversations = @user.conversations.joins(:messages).order(updated_at: :asc).distinct

    json_response = @conversations.as_json(
      only: [:id, :updated_at],
      include: {
        sender: {
          only: [:id, :first_name, :last_name, :email]
        },
        recipient: {
          only: [:id, :first_name, :last_name, :email]
        },
        messages: {
          only: [:body, :created_at]
        }
      }
    )

    render json: json_response
  end
end

示例请求

Started GET "/conversations?email=foobar@example.com"

示例响应

[{
  "id": 2,
  "updated_at": "2018-02-02T11:17:45.376Z",
  "sender": {
    "id": 4,
    "first_name": "Lorem",
    "last_name": "Ipsum",
    "email": "loremipsum@example.com"
  },
  "recipient": {
    "id": 1,
    "first_name": "Foo",
    "last_name": "Bar",
    "email": "foobar@example.com"
  },
  "messages": [{
    "body": "Hello there",
    "created_at": "2018-02-02T11:17:45.367Z"
  }, {
    "body": "Whatcha doin'?",
    "created_at": "2018-02-02T11:17:36.451Z"
  }, {
    "body": "hahaha :)",
    "created_at": "2018-02-02T11:03:29.843Z"
  }]
}, {
  "id": 1,
  "updated_at": "2018-02-02T11:36:14.275Z",
  "sender": {
    "id": 1,
    "first_name": "Foo",
    "last_name": "Bar",
    "email": "foobar@example.com"
  },
  "recipient": {
    "id": 5,
    "first_name": "Ruby",
    "last_name": "Rails",
    "email": "rubyonrails@example.com"
  },
  "messages": [{
    "body": "hello Ruby-on-Rails! :)",
    "created_at": "2018-02-02T11:36:14.267Z"
  }]
}]

您可以查看如何使用.as_jsonhere

您可以查看如何使用touch: truehere

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