Translatable default locale query hint

gistfile1.php

<?php

$qb = $em->createQueryBuilder();
$qb->select('a')
    ->from('Entity\\Article', 'a')
    ->add('where', $qb->expr()->not($qb->expr()->eq('a.title', ':title')))
    ->setParameter('title', 'NA')
;

$translationListener->setTranslatableLocale('es');
$translationListener->setDefaultLocale('en');
$translationListener->setTranslationFallback(true);
$q = $qb->getQuery();
$q->setHint(
    \Doctrine\ORM\Query::HINT_CUSTOM_OUTPUT_WALKER, 
    'Gedmo\\Translatable\\Query\\TreeWalker\\TranslationWalker'
);

$result = $q->getArrayResult();

// would produce sql like:

/*
SELECT a0_.id AS id0, 

   COALESCE(t1_.content, t2_.content) AS title1, 

   COALESCE(t3_.content, t4_.content) AS content2, 

   a0_.title AS title_fallback3, 

   a0_.content AS content_fallback4 

FROM Article a0_ 

LEFT JOIN ext_translations t1_ ON t1_.locale = 'es' AND t1_.object_class = 'Entity\\Article' 

   AND t1_.field = 'title' AND t1_.foreign_key = a0_.id 

LEFT JOIN ext_translations t2_ ON t2_.locale = 'en' AND t2_.object_class = 'Entity\\Article' 

   AND t2_.field = 'title' AND t2_.foreign_key = a0_.id 

LEFT JOIN ext_translations t3_ ON t3_.locale = 'es' AND t3_.object_class = 'Entity\\Article' 

   AND t3_.field = 'content' AND t3_.foreign_key = a0_.id 

LEFT JOIN ext_translations t4_ ON t4_.locale = 'en' AND t4_.object_class = 'Entity\\Article' 

   AND t4_.field = 'content' AND t4_.foreign_key = a0_.id 

WHERE NOT (COALESCE(t1_.content, t2_.content) = 'NA');
*/

// Which would join translations of current locale "en" and default locale "es"
// in case if there is no translation in "en" for a specific field, it will use "es" translation
// and in case if their both translations are empty it will use original record value as a fallback on hydration