mongoose js: should documents be embedded when field is not a list?

Question

Below is my Schema.

var UserModel = new Schema({
    id: ObjectId
  , email: String
  , firstName: String
  , lastName: String
  , password: String
});

var MessageModel = new Schema({
    id: ObjectId
  , createdDate: { type: Date, default: Date.now }
  , user: String // should this be [UserModel]?
  , body: String
});

For my case, every message has a user but only one. Should I Embed UserModel or should I leave the user field as a string. One future use case would be to return a query that has the body of the message, creation date, and user (first name and last name concatenated). Thanks.

Answer 1

Short answer: No, you should not use the UserModel as a subdocument of MessgeModel.

Long answer: First, reconsider your naming. You are actually defining schemas here. Later, you will be associating a model with each of these schemas. So, UserSchema and MessageSchema would be more appropriate here.

But that's not germane. Regarding your question, you're MessageModel schema should not contain embedded documents representing users unless there is a 1-to-1 relationship. However, I expect that each user will be associated with many messages (hopefully). So, you don't want a new copy of the user (each with a new _id ) for every message he creates. You only want one canonical document for each user, and a reference to that user in the MessageModel.

Now, using a string reference may be the right choice for you. But if you anticipate running a query on the MessageModel in which you'd like the user attribute to be populated by the actual UserModel document, then you'll want to use a ref .