private function emptyTables(EntityManager $em)
    {
        $meta = $em->getClassMetadata('Alchemy\Phrasea\Model\Entities\User');
        $connection = $em->getConnection();
        $dbPlatform = $connection->getDatabasePlatform();

        if ($connection->getSchemaManager()->tablesExist([ $meta->getTableName() ])) {
            $connection->beginTransaction();

            try {
                $connection->query('SET FOREIGN_KEY_CHECKS=0');
                $connection->executeUpdate($dbPlatform->getTruncateTableSql($meta->getTableName()));
                $connection->query('SET FOREIGN_KEY_CHECKS=1');
                $connection->commit();
            } catch (\Exception $e) {
                $connection->rollback();
                throw $e;
            }
        }
    }