datafu.pig.bags

Class EmptyBagToNullFields

java.lang.Object

org.apache.pig.EvalFunc<T>

datafu.pig.util.ContextualEvalFunc<org.apache.pig.data.DataBag>

datafu.pig.bags.EmptyBagToNullFields

public class EmptyBagToNullFields
extends ContextualEvalFunc<org.apache.pig.data.DataBag>

For an empty bag, inserts a tuple having null values for all fields; otherwise, the input bag is returned unchanged.

This can be useful when performing FLATTEN on a bag from a COGROUP, as FLATTEN on an empty bag produces no data.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.pig.EvalFunc

org.apache.pig.EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
EmptyBagToNullFields()

Method Summary

Modifier and Type	Method and Description
org.apache.pig.data.DataBag	exec(org.apache.pig.data.Tuple tuple)
org.apache.pig.impl.logicalLayer.schema.Schema	outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema input) Override outputSchema only to add the onSchemaReady hook method.

Methods inherited from class datafu.pig.util.ContextualEvalFunc

getContextProperties, getInstanceName, getInstanceProperties, onReady, setUDFContextSignature

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, progress, setInputSchema, setPigLogger, setReporter, warn

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EmptyBagToNullFields

public EmptyBagToNullFields()

Method Detail

exec

public org.apache.pig.data.DataBag exec(org.apache.pig.data.Tuple tuple)
                                 throws java.io.IOException

Specified by:

exec in class org.apache.pig.EvalFunc<org.apache.pig.data.DataBag>

Throws:

java.io.IOException

outputSchema

public org.apache.pig.impl.logicalLayer.schema.Schema outputSchema(org.apache.pig.impl.logicalLayer.schema.Schema input)

Description copied from class: ContextualEvalFunc

Override outputSchema only to add the onSchemaReady hook method. In all other respects delegates to the superclass outputSchema preparation.

Overrides:

outputSchema in class ContextualEvalFunc<org.apache.pig.data.DataBag>

Parameters:

input - input schema

Returns:

call to super.outputSchema