Yep, thanks! I would like to. Just need to find the time. :P Regards, dgargcs
On Mon, 8 Mar 2021 at 17:40, Xiangdong Huang <[email protected]> wrote: > By the way, welcome to contribute left, right, inner join to IoTDB if you > like ~ :D > > ----------------------------------- > Xiangdong Huang > School of Software, Tsinghua University > > 黄向东 > 清华大学 软件学院 > > > Xiangdong Huang <[email protected]> 于2021年3月8日周一 下午8:09写道： > > > Hi, yes, root is like "/" in Unix-like OS. > > > > ----------------------------------- > > Xiangdong Huang > > School of Software, Tsinghua University > > > > 黄向东 > > 清华大学 软件学院 > > > > > > Dhruv Garg <[email protected]> 于2021年3月8日周一 下午6:14写道： > > > >> Hello Xiangdong, > >> > >> Thanks for confirming! One last question for now, all storage groups > must > >> start with "root" right? I cannot have storage groups like root1.demo, > >> correct? > >> > >> Regards, > >> dgargcs > >> > >> On Mon, 8 Mar 2021 at 15:37, Xiangdong Huang <[email protected]> > wrote: > >> > >> > Hi Dhruv, > >> > > >> > Yes you are right. and IoTDB also supports join on timestamp across > >> > storage groups. > >> > > >> > Q2: IoTDB does not support that now. > >> > Current join looks like outer-join in RDBMS. > >> > Supporting left join, right join and inner-join is not hard to > >> implement, > >> > just omit the rows that contain NULL. > >> > (Better implementation will need CBO cost-based optimization, but > IoTDB > >> > lacks the statistics info for that.) > >> > > >> > Best, > >> > ----------------------------------- > >> > Xiangdong Huang > >> > School of Software, Tsinghua University > >> > > >> > 黄向东 > >> > 清华大学 软件学院 > >> > > >> > > >> > Dhruv Garg <[email protected]> 于2021年3月8日周一 下午5:56写道： > >> > > >> > > Hello Xiangdong, > >> > > > >> > > Yes. Let me elaborate a bit about the join requirement. Suppose I > >> want to > >> > > do a join to print out values in root.demo.d1.m1 and root.demo.d2.m2 > >> for > >> > a > >> > > common time range say 2019-12-11 00:00:00 to 2020-12-18 23:59:59. It > >> > should > >> > > print out the last two rows from your table. > >> > > > >> > > In SQL, when we do a join, there are two different tables and then > we > >> do > >> > a > >> > > join based on some common column => root.demo.d1 is one table (has > an > >> > "m1" > >> > > column) and another table root.demo.d2 (has an "m2" column). If I > do a > >> > join > >> > > on d1 and d2 based on timestamp, it will return some rows containing > >> m1 > >> > and > >> > > m2 where timestamps are the same. > >> > > > >> > > I think the way to look at join queries in IoTDB is slightly > >> different. > >> > > Here, we have a storage group (root.demo) with different time-series > >> > (d1.m1 > >> > > and d2.m2). For each insert in a storage group, I think IoTDB > >> > automatically > >> > > joins these time-series on timestamp since it assumes null values > for > >> > other > >> > > time-series that were not given a value during insert. For example, > >> if I > >> > > do an "insert root.demo.d2(timestamp,m2) values > (2021-08-03T00:00:00, > >> > > 2021)", it will also append NULL value for root.demo.d1.m1 for this > >> > > timestamp. > >> > > > >> > > Thus, to do a join within a storage group for *any number* of > >> time-series > >> > > is straightforward. I think this is trivially done by just giving > the > >> > time > >> > > range and time-series names => "select d1.m1, d2.m2 from root.demo > >> where > >> > > timestamp >= 2019-19-11T00:00:00". > >> > > > >> > > Next, I thought about a similar query across storage groups, say > >> > root.demo1 > >> > > and root.demo2. Here as well, I can run a similar query, but only > >> start > >> > > from a higher level in the storage hierarchy, i.e. "root" alone. > >> "select > >> > > demo1.m1, demo2.m2 from root where timestamp >= > 2019-19-11T00:00:00". > >> > > > >> > > Q1. Is my interpretation of join on timestamp correct for IoTDB? > >> > > > >> > > Q2. Is there a way to omit rows that return one or more null column > >> > values > >> > > in the result? > >> > > > >> > > PS: Sorry for the long email. I am exploring IoTDB for a research > >> project > >> > > and just want to be clear in my understanding. > >> > > > >> > > Thanks in advance! > >> > > > >> > > Regards, > >> > > dgargcs > >> > > > >> > > On Mon, 8 Mar 2021 at 14:12, Xiangdong Huang <[email protected]> > >> wrote: > >> > > > >> > > > Hi Dhruv, > >> > > > > >> > > > 1. Could you give me an example to describe what you want to > query? > >> > > > e.g., there are two time series: > >> > > > > >> > > > +-----------------------------+---------------+---------------+ > >> > > > | Time|root.demo.d1.m1|root.demo.d2.m2| > >> > > > +-----------------------------+---------------+---------------+ > >> > > > |1970-01-01T08:00:00.001+08:00| 1.0| 2.0| > >> > > > |2019-12-11T10:00:00.000+08:00| 1.0| NULL| > >> > > > |2020-12-18T11:45:14.519+08:00| 2.0| 2.0| > >> > > > +-----------------------------+---------------+---------------+ > >> > > > > >> > > > or, > >> > > > > >> > > > What you want to query? (you can consider it as a table in MySQL, > >> and > >> > > just > >> > > > write the sqls you need in mysql.) > >> > > > > >> > > > 2. Ah, we are testing the performance of v0.12. maybe 2-3 weeks, I > >> > think. > >> > > > > >> > > > Best, > >> > > > ----------------------------------- > >> > > > Xiangdong Huang > >> > > > School of Software, Tsinghua University > >> > > > > >> > > > 黄向东 > >> > > > 清华大学 软件学院 > >> > > > > >> > > > > >> > > > Dhruv Garg <[email protected]> 于2021年3月8日周一 下午4:11写道： > >> > > > > >> > > > > Hello Xiangdong, > >> > > > > > >> > > > > Thanks for your response. > >> > > > > > >> > > > > 1. I have the same use-case: I want to run a join query on two > >> time > >> > > > > series but I think I am getting the syntax wrong. > >> > > > > I tried a few SQL-like join queries on IoTDB v0.11.2 and got the > >> > > > following > >> > > > > error: "mismatched input 'JOIN' expecting {<EOF>, WHERE, ORDER, > >> > > SLIMIT, > >> > > > > LIMIT, OFFSET, SOFFSET, FILL, GROUP, DISABLE, ALIGN, ',', '.'}" > >> > > > > Could you please refer me to some documentation or provide a > >> simple > >> > > > example > >> > > > > join query for IoTDB? > >> > > > > > >> > > > > 2. I am also excited to try out the cluster version. Is there an > >> > > > > approximate timeline for v0.12 rollout? > >> > > > > > >> > > > > Thanks in advance. > >> > > > > > >> > > > > Regards, > >> > > > > dgargcs > >> > > > > > >> > > > > On Tue, 2 Mar 2021 at 17:24, Xiangdong Huang < > [email protected]> > >> > > wrote: > >> > > > > > >> > > > > > Hi Dhruv, > >> > > > > > > >> > > > > > Welcome! > >> > > > > > > >> > > > > > 1. "join" for what requirements? > >> > > > > > > >> > > > > > IoTDB supports JOIN two time series ON their timestamp, i.e., > >> time > >> > > > series > >> > > > > > alignment. > >> > > > > > > >> > > > > > 2. I think the cluster version is coming... In the coming > >> v0.12, I > >> > > > think > >> > > > > a > >> > > > > > cluster version (that does > >> > > > > > not support dynamically scale-out) will be released, and the > >> > > scale-out > >> > > > > > feature may be released in v0.13 or 0.14. > >> > > > > > > >> > > > > > Best, > >> > > > > > ----------------------------------- > >> > > > > > Xiangdong Huang > >> > > > > > School of Software, Tsinghua University > >> > > > > > > >> > > > > > Dhruv Garg <[email protected]> 于2021年3月2日周二 下午3:54写道： > >> > > > > > > >> > > > > > > Hello, > >> > > > > > > > >> > > > > > > I am a researcher and a new user of IoTDB. I was excited > when > >> I > >> > saw > >> > > > the > >> > > > > > > performance numbers of IoTDB compared to InfluxDB, and I > have > >> set > >> > > it > >> > > > up > >> > > > > > on > >> > > > > > > a few workstations and a Raspberry Pi device. > >> > > > > > > > >> > > > > > > I am becoming familiar with it and have a few queries: > >> > > > > > > > >> > > > > > > 1. Does IoTDB support Join queries? - I tried looking up > >> some > >> > > > > > > documentation on it, but could not find any. If the > >> feature is > >> > > > > > > available, > >> > > > > > > could you please provide a sample query or the predicates > >> for > >> > > join > >> > > > > > > queries? > >> > > > > > > 2. I also browsed through the IoTDB Jira issues page. I > saw > >> > that > >> > > > the > >> > > > > > > distributed / cluster version is being developed. > >> > Approximately > >> > > > how > >> > > > > > much > >> > > > > > > time would it take to get a stable / working version of > the > >> > > > cluster > >> > > > > > > IoTDB? > >> > > > > > > > >> > > > > > > It would be great if someone can respond to my queries. I > >> would > >> > be > >> > > > > > > waiting for a reply. Thanks in advance. > >> > > > > > > > >> > > > > > > Regards, > >> > > > > > > dgargcs > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > >> > > >
