mass rename of an attribute in Mongo

MongoRename.js

// Mass rename of an attribute in Mongo

var cursor = db.my_collection.find({old_attribute: {$exists: true}});
while(cursor.hasNext()) { 
  db.my_collection.update({_id:elem._id}, {$unset: {old_attribute:1}, $set: {new_attribute: elem.old_attribute}});
}