README.md

Creating JBang UDFs

1. Structure: The usrlib contains a sample Java UDF file, but any folder name or subfolder can be used inside the DataSQRL project root.
2. Defining the Function: The main component of this project is the MyScalarFunction class. This is the implementation of a custom flink function. DataSQRL recognizes flink functions that extend any base Flink UDF class.
3. Defining Dependencies: To fetch dependencies JBang will look for lines that start with //DEPS and define a proper artifact. The bare minimum that any Flink UDF will require is flink-table-common, because the custom UDF has to extend a Flink built-in UDF parent class.
4. JAR Compiling: The compile and JAR build is handled by JBang, that DataSQRL will do automatically on the fly.