join string in hive udf

[Yue Guan]

Hi, hive users

I have the following udf:

package com.name.hadoop.hive.udf;

import java.util.Set;

import org.apache.commons.lang.StringUtils;

import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;


public class MyUDF extends UDF {

    private Map<Long, Set<Long>> aMapping;
    private final Text result = new Text();

    public MyUDF() throws Exception {
        aMapping = someModuleSamePackage.getMapping();
    }

    public Text evaluate(final Text o) throws Exception {
        result.clear();

        if (o != null) {
            Long id = new Long(o.toString());
            Set<Long> ids = aMapping.get(id);
            if (ids != null) {
                    String resultString = StringUtils.join(ids, ",");
                    result.set(resultString);
            }
        }

        return result;
    }
}

However, I always get FAILED: Execution Error, return code 2 from
org.apache.hadoop.hive.ql.exec.MapRedTask. Anyone suggests anything to
work around this? Thank you in advance.