PIG Algebraic UDF with arguments : Combiner optimizer error - optimization

Question

I'm trying to build a Pig UDF that performs some aggregation on a variable of type double. To do so, I built an algebraic UDF called Aggreg. It is called in the following script:
REGISTER 'Test.jar';
DEFINE Aggreg com.pig.test.Agreg();
records = LOAD '/tmp/Test.csv' USING PigStorage(',') AS (v1:chararray, v2:double);
grouped_rec = GROUP records ALL;
test = FOREACH grouped_rec GENERATE Aggreg(records.v2) AS val;
DUMP test;
This works fine as it is. Then, I wanted to use the arguments for this UDF so I added a public constructor with one String argument.
I just changed the DEFINE statement in the previous script but haven't yet used the argument in the UDF Java code:
DEFINE Aggreg com.pig.test.Agreg('Test');
And now I get the following error:
ERROR org.apache.pig.tools.grunt.Grunt - ERROR 2018: Internal error. Unable to introduce the combiner for optimization.
Any ideas where this could come from?

Answer 1

Using Algebraic interface, you must implement two constructors in classes Initial, Intermed and Final, the default constructor and constructor with the parameter you use.
static public class Initial extends EvalFunc<Tuple> {
public Initial(){}
public Initial(String str){Aggreg.string=trs;}
#Override
public Tuple exec(Tuple input) throws IOException {
...
}
}
static public class Intermed extends EvalFunc<Tuple> {
public Intermed(){}
public Intermed(String str){Aggreg.string=trs;}
#Override
public Tuple exec(Tuple input) throws IOException {
...
}
}
static public class Final extends EvalFunc<Tuple> {
public Final(){}
public Final(String str){Aggreg.string=trs;}
#Override
public Tuple exec(Tuple input) throws IOException {
...
}
}
public String getInitial() {
return Initial.class.getName();
}
public String getIntermed() {
return Intermed.class.getName();
}
public String getFinal() {
return Final.class.getName();
}