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How do I get the same parent result regardless of the order of children being queried? (One to Many)

Kyle Corbin Hurst

I’m building a chat with private rooms. What I’m trying to do is find a room that two users belong too. If there isn’t one create one.

Chat Schema

export const ChatSchema = new mongoose.Schema({
    participants: [{
        type: mongoose.Schema.Types.ObjectId,
        ref: "User"
    }],
    created_at: { type: Date, default: Date.now },
});

Query

async findChatBetweenUsers(participantOneId, participantTwoId) {
   return await (await this.chatModel.findOne( { participants: [participantOneId, participantTwoId] } )).populate('participants');
}

Controller

async onJoinRoom(socket: Socket, reciever) {
    const authUser: User = await this.authUser(socket);
    const recievingUser: User = await this.userService.findOne(reciever.username);
    const chat = await this.chatService.findChatBetweenUsers(authUser, recievingUser);

    //Create new chat if doesn't exist
    if(Object.entries(chat).length === 0){
      const newChat = await this.chatService.create(authUser, recievingUser);

      return;
    }

    console.log(chat)
  
}

The problem I’m having

The order of the auth and receiver changes depending who is logged in and produces a different query result for chat. For example:

Example One

const chat = await this.chatService.findChatBetweenUsers('KylesId', 'ChrisId');

Output

"chat" : {
    "_id": 'chatOneId',
    "participants": ['KylesId', 'ChrisId']
}

Example Two

const chat = await this.chatService.findChatBetweenUsers('ChrisId','KylesId');

Output

"chat" : {
    "_id": 'chatTwoId',
    "participants": ['ChrisId', 'KylesId']
}

How do I get the same result despite the order of participants being queried?

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Answer

If, instead, you wish to find an array that contains both the elements “red” and “blank”, without regard to order or other elements in the array, use the $all operator:

this.chatModel.find({
  participants: {$all: [ObjectId('61ce732e33c7e8a9ad80e151'), ObjectId('61ccf3251b9ba5c8a6ecf2a3')]}
});