db={"movies":[{"actors":[{"first_name":"Bruce","last_name":"Willis"},{"first_name":"Gary","last_name":"Oldman"},{"first_name":"Robert","last_name":"De Niro"},{"first_name":"Michael","last_name":"Caine"},{"first_name":"Morgan","last_name":"Freeman"}]}]}

db.movies.aggregate([{"$project":{first_name:"$actors.first_name"}}])