Hi，
thanks yuxin and jialin Best ——— Dawei Liu On 07/12/2020 20:48，Jialin Qiao<[email protected]> wrote： Hi, Thanks Justin, I would like to add some details. We first introduced the main idea of hot compaction: When a memtable reaches the threshold but the average number of points in each series does not reach our goal, we flush it to a vm(virtual memory) file. After there is enough (a configuration) vm files, we merged all vm files to the target TsFile and close the TsFile. By this means, we could get a larger chunk that accommodates to the query. The reason we call it hot compaction but not normal compaction is that the vm is not closed, which means it only has data chunks without relating metadata. All metadatas of vm are cached in memory. Therefore, we avoid IO, serializing and deserializing these metadatas when doing hot compaction. It is essentially an exchanging memory for IO and CPU. However, we do not have clear idea about how much percent the reading metadata occupies in compaction. So we decided to do an experiment first. Thanks, -- Jialin Qiao School of Software, Tsinghua University 乔嘉林 清华大学 软件学院 -----原始邮件----- 发件人: "Justin Mclean" <[email protected]> 发送时间: 2020-07-12 17:31:30 (星期日) 收件人: dev <[email protected]> 抄送: 主题: Re: [Weekly Report] IoTDB Weekly News (2020-07-04~2020-07-12) Hi, [Big Event] # We held the first online discussion yesterday, looking forward to more attendances next time. It would be good if the detail and what was discussed was shared with this list. Having meetings like disadvantages those who can not attend sure to time zone or other commitments. Thanks, Justin
