org.apache.pig.builtin

Class IsEmpty

java.lang.Object

org.apache.pig.EvalFunc<Boolean>

org.apache.pig.FilterFunc

org.apache.pig.builtin.IsEmpty

All Implemented Interfaces:

Accumulator<Boolean>, TerminatingAccumulator<Boolean>

public class IsEmpty
extends FilterFunc
implements TerminatingAccumulator<Boolean>

Determine whether a bag or map is empty.

Nested Class Summary

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

EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
IsEmpty()

Method Summary

Methods

Modifier and Type	Method and Description
void	accumulate(Tuple b) Pass tuples to the UDF.
void	cleanup() Called after getValue() to prepare processing for next key.
Boolean	exec(Tuple input) This callback method must be implemented by all subclasses.
Boolean	getValue() Called when all tuples from current key have been passed to accumulate.
boolean	isFinished()

Methods inherited from class org.apache.pig.FilterFunc

finish

Methods inherited from class org.apache.pig.EvalFunc

getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, isAsynchronous, outputSchema, progress, setInputSchema, setPigLogger, setReporter, setUDFContextSignature, warn

Methods inherited from class java.lang.Object

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

Constructor Detail

IsEmpty

public IsEmpty()

Method Detail

exec

public Boolean exec(Tuple input)
             throws IOException

Description copied from class: EvalFunc

This callback method must be implemented by all subclasses. This is the method that will be invoked on every Tuple of a given dataset. Since the dataset may be divided up in a variety of ways the programmer should not make assumptions about state that is maintained between invocations of this method.

Specified by:

exec in class EvalFunc<Boolean>

Parameters:

input - the Tuple to be processed.

Returns:

result, of type T.

Throws:

IOException

isFinished

public boolean isFinished()

Specified by:

isFinished in interface TerminatingAccumulator<Boolean>

accumulate

public void accumulate(Tuple b)
                throws IOException

Description copied from interface: Accumulator

Pass tuples to the UDF.

Specified by:

accumulate in interface Accumulator<Boolean>

Parameters:

b - A tuple containing a single field, which is a bag. The bag will contain the set of tuples being passed to the UDF in this iteration.

Throws:

IOException

cleanup

public void cleanup()

Description copied from interface: Accumulator

Called after getValue() to prepare processing for next key.

Specified by:

cleanup in interface Accumulator<Boolean>

getValue

public Boolean getValue()

Description copied from interface: Accumulator

Called when all tuples from current key have been passed to accumulate.

Specified by:

getValue in interface Accumulator<Boolean>

Returns:

the value for the UDF for this key.