Restrictions on Field Names Field names cannot contain dots (i.e. .) or null characters, and they must not start with a dollar sign http://docs.mongodb.org/man

Restrictions on Field Names Field names cannot contain dots (i.e. .) or null characters, and they must not start with a dollar sign http://docs.mongodb.org/manual/reference/limits/#Restrictions-on-Field-Names http://docs.mongodb.org/manual/reference/limits/#Restriction...