Extbase Join

$qomFactory = $this->persistenceManager->getBackend()->getQOMFactory();
$source['client'] = $qomFactory->selector ( 'Tx_Hfcrm_Domain_Model_Client', 'tx_hfcrm_domain_model_client' );
$source['project'] = $qomFactory->selector ( 'Tx_Hfcrm_Domain_Model_Project', 'tx_hfcrm_domain_model_project' );
$join = New Tx_Extbase_Persistence_QOM_Join(
  $source['client'],
  $source['project'],
  Tx_Extbase_Persistence_QOM_QueryObjectModelConstantsInterface::JCR_JOIN_TYPE_RIGHT_OUTER,
  $qomFactory->equiJoinCondition (
    'tx_hfcrm_domain_model_client', 'uid',
    'tx_hfcrm_domain_model_project', 'client'
  )
);

$query = $this->createQuery();
foreach( $filter->getFilter() as $attribute => $value ) {
  switch( $attribute ) {

    // ...

    case 'projectManager':
      $query->setSource( $source['project'] );
      $constraint['client'] = $query->equals( 'projectManager', $value );
      break;

    case 'clientName':
      $query->setSource( $source['client'] );
      $constraint['clientName'] = $query->like( 'name', '%'.$value.'%' );
      break;
  }
}

  // set join as actual source
$query->setSource( $join );
if ( $constraint ) { $query->matching( $constraint ); }
return $query->execute();