Get ObjectId of To-One Relationship Without Faulting

[David Feshbach]

Is there any way to get the ObjectId or raw foreign key of a related object 
without faulting? I'd like to implement getArtistObjectId() or getArtistPK() 
without calling getArtist().getObjectId() or 
Cayenne.longPKForObject(getArtist()).

Thanks,

David