The pessimistic offline locking manager locks the entire table

Scenario:
$entity = Doctrine::getTable('Steps')->find($pID);
$lockingManager = new Doctrine_Locking_Manager_Pessimistic( Doctrine_Manager::connection() );
$lockingManager->releaseAgedLocks(300);
$gotLock = $lockingManager->getLock($entity, 'user1' );

Running this code locks the entire table "Steps", and not just the record.

in the table "doctrine_lock_tracking", in the fields: "object_type" and "object_key" are saved in this case: "Steps" and "IDStep".
I think that here must be saved "Steps" and "120" (the value of IDStep).