Mongoose schema inheritance and model populate

You are looking for a Boss, not a Person:

Boss.findOne({  name: 'Billy'}).populate('bossStatus').exec(callback);

Looks like a bug. With debugging active, this is what's being shown for the population query:

Mongoose: people.findOne({ name: 'Billy' }) { fields: undefined }Mongoose: people.find({ _id: { '$in': [ ObjectId("52a221ee639cc03d71000001") ] } }) { fields: undefined }

So Mongoose is querying the wrong collection (people instead of bossstatuses).

As @regretoverflow pointed out, if you're looking for a boss, use the Boss model and not the Person model.

If you do want to populate bossStatus through the Person model, you can explicitly state a model that needs to be searched for population:

.populate({  path  : 'bossStatus',  model : 'BossStatus'})// or shorter but less clear:// .populate('bossStatus', {}, 'BossStatus')

EDIT: (with your Device examples)

driver is part of LocalDeviceSchema, but you're querying the Device model, which has no notion of what driver is and populating driver within the context of a Device instance doesn't make sense to Mongoose.

Another possibility for populating each instance is to do it after you retrieved the document. You already have the deviceCallback function, and this will probably work:

var deviceCallback = function(err, device) {  if(err) {    console.log(err);  }  switch(device.__t) { // or `device.constructor.modelName`    case 'LocalDevice':      device.populate('driver', ...);      break;    case 'RemoteDevice':      device.populate('networkAddress', ...);      break;  }};

The reason is that the document is already cast into the correct model there, something that apparently doesn't happen when you chain populate with the find.