Accessing QueryBuilder and add additional where statement f.e.

FooRepository.php

class FooRepository extends Repository {

	/**
	 * @return QueryResultInterface
	 */
	public function findAllWhereSenderEqualsRecipient() {
	
		$query = $this->createQuery();

		/**
		 * @var \Doctrine\ORM\QueryBuilder $queryBuilder
		 */
		$queryBuilder = \TYPO3\Flow\Reflection\ObjectAccess::getProperty($query, 'queryBuilder', TRUE);

		/**
		 * @var \Doctrine\ORM\Query\Expr\From $from
		 */
		$from = $queryBuilder->getDQLPart('from')[0];

		// Only those where sender equals recipient
		$queryBuilder->andWhere($from->getAlias() . '.sender = ' . $from->getAlias() . '.recipient');

		return $query->execute();
	}

}