在填充中排序不起作用(猫鼬)

问题描述：

我的MongoDB版本3.2，猫鼬版本是4.6.0

My MongoDB version 3.2, mongoose version is 4.6.0

这些是我的模式:

// chat
const chatSchema = new mongoose.Schema({
  users: [{ type: mongoose.Schema.Types.ObjectId, ref: 'User', required: true }],
  lastMessage:  { type: mongoose.Schema.Types.ObjectId, ref: 'Message' }
});
export const ChatModel = mongoose.model('Chat', chatSchema);

// message
const messageSchema = new mongoose.Schema({
  user: { type: mongoose.Schema.Types.ObjectId, ref: 'User', required: true },
  chat: { type: mongoose.Schema.Types.ObjectId, ref: 'Chat', required: true },
  text: { type: String, required: true },
  timestamp: { type: Date, default: Date.now }
});
export const MessageModel = mongoose.model('Message', messageSchema);

我想按desc顺序基于lastMessage的时间戳进行排序.我尝试了这三个

I want to sort based on lastMessage's timestamp in a desc order. I tried these three

ChatModel
  .find({}, 'lastMessage')
  .populate('lastMessage', 'timestamp', null, { sort: { timestamp: -1 }})
  .exec()
  .then(chats => console.log(chats))

ChatModel
  .find({}, 'lastMessage')
  .populate({
    path: 'lastMessage',
    select: 'timestamp',
    options: { sort: { timestamp: -1 }}
  })
  .exec()
  .then(chats => console.log(chats))

ChatModel
  .find({}, 'lastMessage')
  .populate('lastMessage', 'timestamp')
  .sort({ 'lastMessage.timestamp': -1 })
  .exec()
  .then(chats => console.log(chats))

此外，无论我对timestamp使用-1还是1，'desc'或'asc'，它总是给我相同的结果:

Also, no matter I use -1 or 1, 'desc', or 'asc' for timestamp, it always gives me same results:

  [{
    _id: 57c8a682cde8baf5c36eb1fc,
    lastMessage: {
      _id: 57c8baa29a293eace7f9be15,
      timestamp: 2016-09-01T23:32:50.344Z
    }
  }, {
    _id: 57c8a6d0cde8baf5c36eb1fe,
    lastMessage: {
      _id: 57c8fabb4362b3c25d828774,
      timestamp: 2016-09-02T04:06:19.421Z
    }
  }]

这可能是什么原因造成的?谢谢

What may cause this? Thanks

UPDATE1:

好像是猫鼬的虫子.

请在GitHub上跟踪此问题.

Please track this issue on GitHub.

UPDATE2: 它说不支持.但是我不知道为什么...在这种情况下在populate中使用sort是错误的吗?

UPDATE2: It said not supported. But I don't know why... Is using sort in populate wrong for this case?

答

文档( http ://mongoosejs.com/docs/api.html#document_Document-populate )表示类似以下内容:

The documentation (http://mongoosejs.com/docs/api.html#document_Document-populate) states something like:

Chat.find().populate({
    path: 'lastMessage'
  , select: 'timestamp'
  , options: { sort: { timestamp: -1 }}
}).exec(function (err, chats) {
  //do something
})

如果此方法不起作用，请首先使用例如文本进行检查，以查看是否是日期时间排序问题

If this is not working first check it with for example text, to see if it's a datetime sort issue

更新: 当我重新阅读您的问题时，我注意到了这个问题，您想根据上一个消息时间戳对所有消息进行排序.无需对总体进行排序，因为它仅返回1个项目(没有最后一条消息的数组).

UPDATE: When i re-read your question i noticed the issue, you want to sort all messages based on the last message timestamp. There is no need to sort in the population because it only returns 1 item (there is no array of last messages).

因此语法为:

Chat.find().populate({
        path: 'lastMessage'
      , select: 'timestamp'})
.sort('lastMessage.timestamp')
.exec(function (err, chats) {
      //do something
    })

在填充中排序不起作用(猫鼬)

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