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Posted to dev@iotdb.apache.org by Zhou Yifu <ef...@outlook.com> on 2022/07/19 03:16:00 UTC

回复: [DISCUSSION] The order of last query

Hi Yuan,

Last Query performance is one of the most important benchmarking metrics to comparing other timeseries database. And our IoTDB has a very good performance in Last Query in our pervious POC, so we don’t want any loss of performance in this new version.

So I think the last query should guarantee a best performance by default, if some one want to order it, I remember we have an order by time SQL, so we can just implement order by operator to last query and it will look good.

Thanks,
Yifu Zhou

从 Windows 版邮件<https://go.microsoft.com/fwlink/?LinkId=550986>发送

发件人: Yuan Tian<ma...@gmail.com>
发送时间: 2022年7月19日 10:24
收件人: dev<ma...@iotdb.apache.org>
主题: [DISCUSSION] The order of last query

Hi all,

In previous version, we don't guarantee the result order for last
query which means you may get different order for the same last query
sql. Absolutely, the result set will be same.

The reason for that is to achieve better performance of last query.
Without taking ordering into consideration, last query will have lower
latency.

However, if so, we may fail in current cluster IT, because it will
compare result by line from different datanodes.

So, I made this discussion about whether we should make last query
defaultly order by timeseries which will guarantee the result order.
Definitely, it will be in cost of loss of performance.

Or, we keep unchanged and add order by timeseries clause for each last
query sql in IT.

Best,
---------------
Yuan Tian

Re: 回复: [DISCUSSION] The order of last query

Posted by Guanfei Guo <gu...@qq.com.INVALID>.