Hi Trevor, Thanks for sharing the usage of UDTF. I have starred your GitHub repo :D
> Besides, could we rename the column from time to count in UDF? Sadly, no. This can be a new feature. > Unless I am mistaken a time column must be returned via UDTF - if you look at > IoTDB-Quality UDTFDistinct it returns a incrementing Long value as the time > column. In our design, we do expect a UDTF to return an increasing long value column as a time column. But as you see, a non-increasing long value column is also okay. To be honest, I was very surprised to see this can work. > Initially I wanted to return Col1 (Distinct Values) and Col2 (Count as Int) > but at this release it looks like you have to return Col1 (Time) and Col2 (A > computed value) - so at this version it does not look possible to return more > than 1 computed value so using the time column is just a work around to get > the count in the results. Not ideal but gets the job done. In fact, many users wanted us to support UDTFs that can output multiple columns, but we haven't figured out how to define this feature: what the Java interface should look like, what the SQL should look like, and so on. I want to hear your suggestions :D Steve Su ------------------ Original ------------------ From: "[email protected][email protected]" <[email protected]>; Date: Tue, Nov 2, 2021 09:15 AM To: "dev"<[email protected]>; Cc: "qiaojialin"<[email protected]>;"steveyurongsu"<[email protected]>; Subject: Re: New UDTF iotDBExtras Hello Jialin Yes digital time does look better - this is how I will access it through JDBC anyway. I treat all times as Long. Unless I am mistaken a time column must be returned via UDTF - if you look at IoTDB-Quality UDTFDistinct it returns a incrementing Long value as the time column. The UTDF method to put the values together only accepts two parameters ie time and a value. Initially I wanted to return Col1 (Distinct Values) and Col2 (Count as Int) but at this release it looks like you have to return Col1 (Time) and Col2 (A computed value) - so at this version it does not look possible to return more than 1 computed value so using the time column is just a work around to get the count in the results. Not ideal but gets the job done. Thanks Trevor ---- On Tue, 02 Nov 2021 14:07:03 +1300 Jialin Qiao <[email protected]> wrote ---- Hi, Digital time looks more intuitive. Besides, could we rename the column from time to count in UDF? @mailto:[email protected] <mailto:[email protected]> Thanks, ?????????????????????????????????? Jialin Qiao Trevor Hart <mailto:[email protected]> ??2021??11??2?????? ????6:09?????? > I have put my first UDTF on GitHub - https://github.com/ope-nz/iotDBExtras > > > > The first function I have developed is called UDTFDistinctCount. It > returns the distinct values (similar to IoTDB-Quality UDTFDistinct) but it > includes the count of each distinct values (as the time column). > > > > Example query; > > > > IoTDB> select distinct_count(temperature) from root.ln.wf01.wt01 > > > +-----------------------------+---------------------------------------------+ > > | > Time|distinct_count(root.ln.wf01.wt01.temperature)| > > > +-----------------------------+---------------------------------------------+ > > |1970-01-01T12:00:00.020+12:00| > 24.37| > > |1970-01-01T12:00:00.009+12:00| > 24.12| > > |1970-01-01T12:00:00.016+12:00| > 24.87| > > > +-----------------------------+---------------------------------------------+ > > > > Or as digital time; > > > > +----+---------------------------------------------+ > > > |Time|distinct_count(root.ln.wf01.wt01.temperature)| > > +----+---------------------------------------------+ > > | 20| 24.37| > > | 9| 24.12| > > | 16| 24.87| > > +----+---------------------------------------------+ > > > > > > Thanks > > Trevor Hart > > Ope Limited > > w: http://www.ope.nz/ > > m: +64212728039
