When using a DQL UPDATE with a subselect in the WHERE clause (such as what the size() function generates), the subselect is trying to reference an alias that is not defined in the main UPDATE clause. Using the size() function similarly in a SELECT statement works fine, the problem is only occurring for me when I try an UPDATE. I have not tried it with INSERT or DELETE, but I would suspect a similar inconsistency with anything other than the more common usage with SELECT.
$q = $em->createQuery('UPDATE Event e SET e.no_speakers = 1, e.no_credits = 1 WHERE size(e.Instances) = 0');
UPDATE Event SET no_speakers = 1, no_credits = 1 WHERE (SELECT COUNT(*) FROM Instance c0_ WHERE c0_.Event_id = c1_.id) = 0
And, $q->execute() results in:
PHP Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42S22]: Column not found: 1054 Unknown column 'c1_.id' in 'where clause'' in /var/www/v3-lf/library/Doctrine/DBAL/Connection.php:657
Stack trace: #0 /var/www/v3-lf/library/Doctrine/DBAL/Connection.php(657): PDO->exec('UPDATE Event...')