```
@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable ="false")
public class Foo implements IsSerializable {

 @PrimaryKey
 @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
 private Long id;

    @Persistent
    private Long revision;

    @Persistent
    private String information;
}

```

The problem is this object keeps overwriting itself when persisted, not creating a new 'record' with the next revision.
In a traditional [RDBMS](http://en.wikipedia.org/wiki/Relational_database_management_system) it'd be a two-column primary key.

How do I accomplish this with [Google App Engine Datastore](http://en.wikipedia.org/wiki/Google_App_Engine#Differences_between_SQL_and_GQL)?