Código PHP:
Ver original/**
* Computes all the changes that have been done to entities and collections
* since the last commit and stores these changes in the _entityChangeSet map
* temporarily for access by the persisters, until the UoW commit is finished.
*
* @return void
*/
public function computeChangeSets()
{
// Compute changes for INSERTed entities first. This must always happen.
$this->computeScheduleInsertsChangeSets();
Así que si no estas agregando una nuvea entidad, no es necesario que hagas persist() en ese punto.
Mas detalles:
https://github.com/doctrine/doctrine...UnitOfWork.php