Doctrine 2.0 entitymanager->replace() equivalent

looking for a call that will ultimately result in a SQL of the form

INSERT ... ON DUPLICATE KEY UPDAT开发者_运维问答E....

In Doctrine 1.2, $em->replace($obj_to_persist) would achieve that. Any suggestions?

Doctrine 2 does not support INSERT ... ON DUPLICATE KEY UPDATE...., UPSERT, INSERT REPLACE, etc.