Hi Julian， He is my friend and contacted me offline, because I advertise IoTDB in my weChat(like facebook or twitter).
Next time I will try to let him put issue in the mail list himself :) Best, -- 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: "Julian Feinauer" <j.feina...@pragmaticminds.de> > 发送时间: 2019-09-07 13:52:17 (星期六) > 收件人: "dev@iotdb.apache.org" <dev@iotdb.apache.org> > 抄送: > 主题: Re: A new result set format > > Hi Jialin, > > perhaps one question about "wanted by users" means (as I didn’t see anything > on the list). > How do these users get in contact with you? > > Julian > > Am 07.09.19, 04:29 schrieb "Jialin Qiao" <qj...@mails.tsinghua.edu.cn>: > > Hi, > > As described in this issue, a new result set format is wanted by users. > I'd like to open a discussion here. > > For simplicity, I refer this format "time, root.sg1.d1.s1, > root.sg1.d2.s1" to wide table, and "time, deviceId, s1" as narrow table. > > This issue is not only about how to organize the results, but also the > query process. > > There are some advantages about narrow table. > > (1) For wide table, we need to open a SeriesReader for each series at the > same time, each SeriesReader holds some ChunkMetadatas. For narrow table, we > only need to open SeriesReaders for one device at one time, then return > results and open SeriesReaders for the next device, which occupies less > memory compared to the wide table. > (2) Avoid reading all series at once may also improve the query latency. > > There is also a question: > > (1) If we show result in the narrow table format for users, do we need to > highlight the concept of table and device? > (2) If the answer of the first question is yes, do we need to support > sql: "select time, deviceId, s1, s2, s3 from root.sg1 where deviceId=d1"? > This may involve a lot of work... > > From my side, I prefer the answers of the two questions are all NO. Then > we do not need to change the sql grammar and only use a new query process to > organize the result set. > > Best, > -- > 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: "Jialin Qiao (Jira)" <j...@apache.org> > > 发送时间: 2019-09-07 09:40:00 (星期六) > > 收件人: dev@iotdb.apache.org > > 抄送: > > 主题: [jira] [Created] (IOTDB-203) A new result set format > > > > Jialin Qiao created IOTDB-203: > > --------------------------------- > > > > Summary: A new result set format > > Key: IOTDB-203 > > URL: https://issues.apache.org/jira/browse/IOTDB-203 > > Project: Apache IoTDB > > Issue Type: New Feature > > Reporter: Jialin Qiao > > > > > > When executing a SQL like "select d1.s1, d2.s1 from root.sg1", the > default result set format in IoTDB is > > > > "time, root.sg1.d1.s1, root.sg1.d2.s1" > > > > 1 , 1, 1 > > > > 2, 2, 2 > > > > However, some users want to get another format, The results could be > grouped by device, then sorted by time. > > > > "time, deviceId, s1". > > > > 1, root.sg1.d1, 1 > > > > 2, root.sg1.d2, 2 > > > > > > > > This can be done in the client, but it would be better if we support > this format in the server. > > > > > > > > > > > > -- > > This message was sent by Atlassian Jira > > (v8.3.2#803003) > >
