我需要用pig-udf替换元组的字符。例如，如果我在文件中有一行“hello world，hello world，hello\world”需要转换为“hello\u world，hello\u world，hello\u world”。为此，我尝试了以下自定义项：

package myUDF;
import java.io.IOException;
import org.apache.pig.EvalFunc;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;
public class ReplaceValues extends EvalFunc<Tuple>
{
    public Tuple exec(Tuple input) throws IOException {
        if (input == null || input.size() == 0)
            return null;
     try{
           String str = (String)input.get(0);
           str=str.replace(" ", "_");
           str=str.replace("/","");
           str=str.replace("\\","");
           TupleFactory tf = TupleFactory.getInstance();
           Tuple t = tf.newTuple();
           t.append(str);
           return t;
    }catch(Exception e){
        throw new IOException("Caught exception processing input row ", e);
    }
  }
}

但当通过pig脚本调用此udf时，我面临问题，请帮助我解决此问题：

A = load '/user/cloudera/Stage/ActualDataSet.csv' using PigStorage(',') AS (Rank:chararray,NCTNumber:chararray,Title:chararray,Recruitment:chararray);
B = FILTER A by Rank == 'Rank';
C = FOREACH B GENERATE PigUDF.ReplaceValues(B);

错误：pig脚本未能分析：无效的标量投影：b:需要从关系投影列才能将其用作标量