protected function getPlatformGroupConcat($column, $order, $alias, QueryBuilder $query)
{
$platform = $query->getConnection()->getDatabasePlatform()->getName();
switch ($platform) {
case 'mysql':
return "GROUP_CONCAT({$column} ORDER BY {$order} ASC) as {$alias}";
case 'sqlite':
return "GROUP_CONCAT({$column}) as {$alias}";
case 'postgresql':
return "string_agg({$column}" . "::character varying, ',' ORDER BY {$order}) as {$alias}";
}
}