How to batch change a key on a mongodb collection

gistfile1.sh

Run with
> mongo <server>/<db> mongodb_change_document_key.js

mongodb_change_document_key.js

print('marking documents as "old"');
db.Commands.update({}, {
  $set : { old : true}
}, false, true);

print('iterate on old documents');
var cursor = db.Commands.find({old:true}).sort({'Command.IssuedAt' : 1});

var doc = null;
do
{
  var  doc = cursor.hasNext() ? cursor.next() : null;

	if (doc) {
		var oldId = doc._id; 
		doc._id = ObjectId();
		
		db.Commands.insert(doc);
		db.Commands.remove({_id : oldId});
		
		print('changed key from ' + oldId + ' to ' + doc._id);
	}
}while(doc != null)

print('removing the "old" mark')
db.Commands.update({}, {
	$unset : { old : 1}
}, false, true);

print('conversion done');