class MySQLClient {

    public synchronized int executeUpdate(final String queryString) {
        responseCallback = new DefaultPromise<>(eventLoopGroup.next());
        MySQLComQueryPacket comQueryPacket = new MySQLComQueryPacket(queryString);
        channel.writeAndFlush(comQueryPacket);
        return (int) waitExpectedResponse(MySQLOKPacket.class).getAffectedRows();
    }

}