E11000 duplicate key error collection when create-CodePudding

I'm developing a chat system with typescript and mongodb (using mongoose) When creating new message I get the following error:

E11000 duplicate key error collection: test.messages index: user.username_1 dup key: { user.username: null }

I'm using reference for the user in the messages collection and I don't understand where this error is coming from.

Schema:

    const user = new Schema({
    username: { type: String, unique: true, required: true },
    email: { type: String, unique: true, required: true },
    password: { type: String, required: true}
});



const message = new Schema({
    userId: { type: Schema.Types.ObjectId, ref: 'user', required: true},
    message: { type: String, required: true},
    timestamp: { type: Date, default: Date.now }
});


export const User = model('User', user);
export const Message = model('Message', message);

user.ts (model file)

export class MUser {
    readonly _id: string;
    readonly username: string;
    readonly email: string;
    readonly password: string;
}

message.ts (model file)

export class MMessage {

    readonly userId: string;
    readonly message: string;
    readonly timestamp: Date;
}

function that I use to create the document and return the error:

async createMessage(user: MUser, msg: string) {
    await Message.create({userId: user._id, message: msg});
}

I'm not considering the userId to be unique. What am I missing here?

Thanks!

CodePudding user response：

Drop the collection and try with new schema it should work.