org.apache.pig.builtin

Class IsEmpty

java.lang.Object

org.apache.pig.EvalFunc<Boolean>

org.apache.pig.FilterFunc

org.apache.pig.builtin.IsEmpty

public class IsEmpty
extends FilterFunc

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

Modifier and Type	Method and Description
boolean	allowCompileTimeCalculation() Whether the UDF should be evaluated at compile time if all inputs are constant.
Boolean	exec(Tuple input) This callback method must be implemented by all subclasses.

Methods inherited from class org.apache.pig.FilterFunc

finish

Methods inherited from class org.apache.pig.EvalFunc

getArgToFuncMapping, getCacheFiles, getInputSchema, getLoadCaster, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, needEndOfAllInputProcessing, outputSchema, progress, setEndOfAllInput, 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

allowCompileTimeCalculation

public boolean allowCompileTimeCalculation()

Description copied from class: EvalFunc

Whether the UDF should be evaluated at compile time if all inputs are constant. This is applicable for most UDF, however, if a UDF will access hdfs file which is not available at compile time, it has to be false

Overrides:

allowCompileTimeCalculation in class EvalFunc<Boolean>

Returns:

Whether or not compile time calculation is allowed, default to false to ensure legacy UDF will get the right behavior