Java example: using session parameters

package com.mycompany.example;

import com.vertica.sdk.*;

public class RowCountFactory extends ScalarFunctionFactory {

    @Override
    public void getPrototype(ServerInterface srvInterface, ColumnTypes argTypes, ColumnTypes returnType)
    {
        argTypes.addInt();
        argTypes.addInt();
     returnType.addInt();
    }

public class RowCount extends ScalarFunction {

    private Integer count;
    private Integer rowCount;

    // In the setup method, you look for the rowCount parameter. If it doesn't exist, it is created.
    // Look in the default namespace which is "library," but it could be anything else, most likely "public" if not "library".
    @Override
       public void setup(ServerInterface srvInterface, SizedColumnTypes argTypes) {
    count = new Integer(0);
    ParamReader pSessionParams = srvInterface.getUDSessionParamReader("library");
    String rCount = pSessionParams.containsParameter("rowCount")?
    pSessionParams.getString("rowCount"): "0";
    rowCount = Integer.parseInt(rCount);

    }

    @Override
    public void processBlock(ServerInterface srvInterface, BlockReader arg_reader, BlockWriter res_writer)
        throws UdfException, DestroyInvocation {
        do {
        ++count;
        long a = arg_reader.getLong(0);
        long b = arg_reader.getLong(1);

        res_writer.setLong(a+b);
        res_writer.next();
        } while (arg_reader.next());
    }

    @Override
    public void destroy(ServerInterface srvInterface, SizedColumnTypes argTypes, SessionParamWriterMap udParams){
        rowCount = rowCount+count;
        udParams.getUDSessionParamWriter("library").setString("rowCount", Integer.toString(rowCount));
        srvInterface.log("RowNumber processed %d records", count);
        }
    }

    @Override
    public ScalarFunction createScalarFunction(ServerInterface srvInterface){
        return new RowCount();
    }
}