protected function getUpdateObjectIdentitySql($pk, array $changes)
    {
        if (0 === count($changes)) {
            throw new \InvalidArgumentException('There are no changes.');
        }

        return sprintf(
            'UPDATE %s SET %s WHERE id = %d',
            $this->options['oid_table_name'],
            implode(', ', $changes),
            $pk
        );
    }