То что ответил автор книги:
In the Mongo shell try something like this to add an _id to a review
db.locations.update(
{ "name": "INSERT A LOCATION NAME HERE" },
{
$set : {
"reviews.0._id" : ObjectId()
}
}
)
This will add an _id property with an objectId value to the first review subdocument in the location you specify in the command.
