mongodb - sort in populate does not work (Mongoose) -

my mongodb version 3.2, mongoose version 4.6.0

these schemas:

// 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); 

i want sort based on lastmessage's timestamp in desc order. 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)) 

also, no matter use -1 or 1, 'desc', or 'asc' timestamp, 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     }   }] 

what may cause this? thanks

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update1:

it seems bug of mongoose.

please track this issue on github.

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update2: said not supported. don't know why... using sort in populate wrong case?

try this..

    chatmodel     .find({})     .populate('lastmessage', 'timestamp', {         options: {             sort: {                 'lastmessage.timestamp': 'desc'             }         }     }) .exec()     .then(chats => console.log('chats', chats))