Pig UDF Outputformat

If your UDF returns a scalar or a map, no work is required. However, if your UDF returns a tuple or a bag (of tuples), it needs to help Pig figure out the structure of the tuple.

If a UDF returns a tuple or a bag and schema information is not provided, Pig assumes that the tuple contains a single field of type bytearray. If this is not the case, then not specifying the schema can cause failures

Below is an example to output a bag of tuples.

@Override

public Schema outputSchema(Schema input) {

try {

return new Schema(

new FieldSchema(null,

new Schema(

new FieldSchema(null,

new Schema(

new FieldSchema("passivedataxml", DataType.CHARARRAY)), DataType.TUPLE)),

DataType.BAG));

} catch (Exception e) {

return null;

}

}

Reference:

1. http://pig.apache.org/docs/r0.9.1/udf.html#udf-java