Use an alias on Pig UDF paramter - hadoop

Question

I need your help to know how to use an alias (stored tuple) on my Pig udf function, i exmplain:
my_file.csv
101,message here
102,message here
103,message here
...
My script PIG:
X = load'mydata.csv' using PigStorage(',') as (myVar:chararray);
A = load'my_file.csv' using PigStorage(',') as (key:chararray,value:chararray);
B = GROUP par ALL;
C = foreach B {
D = ORDER par BY key;
GENERATE BagToTuple(D);
};
the result of the C is something like (101,message here, 102, message here, 103, message here...)
Now what i need is to pass this result in my udf function like :
Z = foreach X generate MYUDF(myVar, C);
the alias "C" is the tuple key,value,key,value...
MYUDF :
import java.io.IOException;
import java.util.regex.Pattern;
import org.apache.pig.EvalFunc;
import org.apache.pig.data.Tuple;
import org.apache.pig.PigWarning;
import org.apache.pig.data.DataType;
import org.apache.pig.impl.util.WrappedIOException;
import org.apache.pig.impl.logicalLayer.schema.Schema;
public class ReDecode extends EvalFunc<String> {
int numParams = -1;
Pattern mPattern = null;
#Override
public Schema outputSchema(Schema input) {
try {
return new Schema(new Schema.FieldSchema(getSchemaName(this
.getClass().getName().toLowerCase(), input),
DataType.CHARARRAY));
} catch (Exception e) {
return null;
}
}
#Override
public String exec(Tuple tuple) throws IOException {
if (numParams==-1) // Not initialized
{
numParams = tuple.size();
if (numParams <= 2) {
String msg = "Decode: Atleast an expression and default string is required.";
throw new IOException(msg);
}
if (tuple.size()%2!=0) {
String msg = "ItssPigUDFs.ReDecode : Some parameters are unmatched.";
throw new IOException(msg);
}
}
if (tuple.get(0)==null)
return null;
try {
for (int count = 1; count < numParams - 1; count += 2)
{
mPattern=Pattern.compile((String)tuple.get(count));
if (mPattern.matcher((String)tuple.get(0)).matches())
{
return (String)tuple.get(count+1);
}
}
} catch (ClassCastException e) {
warn("ItssPigUDFs.ReDecode : Data type error", PigWarning.UDF_WARNING_1);
return null;
} catch (NullPointerException e) {
String msg = "ItssPigUDFs.ReDecode : Encounter null in the input";
throw new IOException(msg);
}
return (String)tuple.get(tuple.size()-1);
}
Thank you for your help

Answer 1

I don't think numParams is needed; the number of params that you get to the UDF will be input.size().
Therefore, if you call MYUDF(myVar, C), then you should be able to get those values in Java like String myVar = (String) input.get(0) and Tuple param2 = input.get(1).