Very opinionated datafusion user defined functions written in java.

It has been implemented to demonstrate DataFusion FunctionFactory functionality (arrow-datafusion/pull#9333).

Other project utilizing FunctionFactory:

• Torchfusion, Opinionated Torch Inference on DataFusion
• LightGBM Inference on DataFusion

A java user defined function can be defined using CREATE FUNCTION:

CREATE FUNCTION f1(BIGINT, BIGINT)
RETURNS BIGINT
LANGUAGE JAVA
AS '
public class NewClass extends com.github.milenkovicm.adhesive.Adhesive {
    @Override
    public Long compute(org.apache.arrow.vector.table.Row row) {
        return row.getBigInt(0) * row.getBigInt(1); 
    }
}
'

which will be compiled. Or, referencing existing compiled class:

CREATE FUNCTION f2(BIGINT, BIGINT)
RETURNS BIGINT
LANGUAGE CLASS
AS "com.github.milenkovicm.adhesive.example.BasicExample"

Note change of LANGUAGE. In both cases classes should extend com.github.milenkovicm.adhesive.Adhesive abstract class, which will do transition between rust and java.

com.github.milenkovicm.adhesive.example.BasicExample is defined like:

package com.github.milenkovicm.adhesive.example;

import com.github.milenkovicm.adhesive.Adhesive;
import org.apache.arrow.vector.table.Row;

public class BasicExample extends Adhesive {
  @Override
  protected Long compute(Row row) {
    return row.getBigInt(0) + row.getBigInt(1);
  }
}

Defined functions can be invoked in SQL:

SELECT f2(a,b) FROM t

// JAR containing required libraries and additional classes 
const JAR_PATH: &str ="adhesive-1.0-jar-with-dependencies.jar";
let ctx = SessionContext::new()
    .with_function_factory(Arc::new(JvmFunctionFactory::new_with_jar(JAR_PATH)?));