Segmentation faults during doctrine hydration - how to debug? - doctrine-orm

Question

I am running a console command that fetches all entities of one type (and reads some data from them).
$q = $this->em->createQuery(/** #lang DQL */'select u from App\Entity\DataSample u order by u.creationDate ASC');
Both iteration strategies:
foreach ($q->getResult() as $d) {
}
and
$iterableResult = $q->iterate();
foreach ($iterableResult as $onerow) {
/* #var $d DataSample */
$d = $onerow[0];
}
lead to a segmentation fault!
Note, I am actually doing nothing inside the loop!
The second loop does run for some few tenthousand iterations and segfaults then, the first one segfaults during getResult().
There is also enough memory available, the program breaks at roughly 200 MB memory usage.
My xdebug trace is not really helpful to me, it ends as follows:
240.2365 489614864 -> str_pad() /var/www/rrr/vendor/ramsey/uuid/src/Codec/StringCodec.php:167
240.2365 489614904 -> Ramsey\Uuid\Builder\DefaultUuidBuilder->build() /var/www/rrr/vendor/ramsey/uuid/src/Codec/StringCodec.php:84
240.2365 489615000 -> Ramsey\Uuid\Uuid->__construct() /var/www/rrr/vendor/ramsey/uuid/src/Builder/DefaultUuidBuilder.php:52
240.2365 489614448 -> Doctrine\ORM\Internal\Hydration\ObjectHydrator->hydrateColumnInfo() /var/www/rrr/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php:270
240.2365 489614448 -> Ramsey\Uuid\Doctrine\UuidType->convertToPHPValue() /var/www/rrr/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php:315
I checked all (ramsey/uuid) ids in the corresponding table, and all return true on Uuid::isValid()
Fun fact: When outputting all ids, I found out that it always happens at the same DataSample!?

Answer 1

Ok, I found a "solution":
I inserted a call to $em->clear() as well as a gc_collect_cycles every 100 iterations, now it terminates (and is in fact way faster!).
$i = 0;
$iterableResult = $q->iterate();
foreach ($iterableResult as $onerow) {
/* #var $d DataSample */
$d = $onerow[0];
if($i % 100 === 0){
$this->em->clear();
gc_collect_cycles();
}
$i++;
}
But obviously, this only works for the iterableResult, using getResult should theoretically work as well??