ksql-math-udf

UDF which implements basic math functions for ksql

Inspiration for this library was this github issue

Usage

Getting the jar

1. Either download from releases

wget https://github.com/tokenanalyst/ksql-math-udf/releases/download/basic-math/ta-math-udfs.jar

2. Bulding from source

$ # get source code
$ git clone https://github.com/tokenanalyst/ksql-math-udf.git
$ # install sbt (https://www.scala-sbt.org/1.0/docs/Setup.html)
$ sudo apt-get install agt
$ # build the binary
$ sbt assembly

Using the JAR in ksql

1. Create a directory for UDF jar's and put the jar file there

$ mkdir \var\lib\ksql-ext\
$ mv ta-math-udfs.jar \var\lib\ksql-ext\

2. Update the location in ksqlserver.properties

$ echo ksql.extension.dir=/var/lib/ksql-ext >> /etc/ksql/ksql-server.properties

3. Restart KSQL server

$ systemctl restart confluent-ksql

4. Start ksql and show functions to see if the new functions have been added

$ ksql
ksql> show functions;

 Function Name           | Type      
-------------------------------------
 SQUARE                  | SCALAR    
 POW                     | SCALAR    
 SQRT                    | SCALAR  

5. The functions are now ready to use

ksql> SELECT key, sqrt(value) as sqrt_value from STREAM_NAME;
ksql> CREATE table MEAN_TABLE as SELECT sum(value)/count() as mean, key from STREAM_NAME group by key; 
ksql> SELECT STREAM_NAME.key, sqrt(sum(square(value - mean))/count()) as stdev_value \
      from STREAM_NAME left join MEAN_TABLE \
      STREAM_NAME.key = MEAN_TABLE.key \
      group by key;