Support for this isn't implemented yet. (May be related to virtual collections.)

1. 1. preparation

use hej;
var a = {_id:1, question:"what is my name?", answers:[{_id:11, text:"its earl", comments:[{_id:111, text:"I agree"}]}]};
db.hej.save(a);

1. 1. query

db.hej.update({_id:1, "answers._id":11}, {"$push":{"answers.comments": {_id:112, text:"I dont agree"} }});

1. 1. error

> db.getLastError()
Modifier spec implies existence of an encapsulating object with a name that already represents a non-object, or is referenced in another $set clause

1. 1. notes