org.apache.pig.builtin

Class Distinct

java.lang.Object

org.apache.pig.EvalFunc<DataBag>

org.apache.pig.builtin.Distinct

All Implemented Interfaces:

Algebraic

public class Distinct
extends EvalFunc<DataBag>
implements Algebraic

Find the distinct set of tuples in a bag. This is a blocking operator. All the input is put in the hashset implemented in DistinctDataBag which also provides the other DataBag interfaces.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Distinct.Final
static class	Distinct.Initial
static class	Distinct.Intermediate

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
Distinct()

Method Summary

Modifier and Type	Method and Description
DataBag	exec(Tuple input) This callback method must be implemented by all subclasses.
protected DataBag	getDistinct(Tuple input)
java.lang.String	getFinal() Get the final function.
java.lang.String	getInitial() Get the initial function.
java.lang.String	getIntermed() Get the intermediate function.

Methods inherited from class org.apache.pig.EvalFunc

addCredentials, allowCompileTimeCalculation, finish, 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

Distinct

public Distinct()

Method Detail

exec

public DataBag exec(Tuple input)
             throws java.io.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<DataBag>

Parameters:

input - the Tuple to be processed.

Returns:

result, of type T.

Throws:

java.io.IOException

getFinal

public java.lang.String getFinal()

Description copied from interface: Algebraic

Get the final function.

Specified by:

getFinal in interface Algebraic

Returns:

A function name of f_final. f_final should be an eval func parametrized by the same datum as the eval func implementing this interface.

getInitial

public java.lang.String getInitial()

Description copied from interface: Algebraic

Get the initial function.

Specified by:

getInitial in interface Algebraic

Returns:

A function name of f_init. f_init should be an eval func. The return type of f_init.exec() has to be Tuple

getIntermed

public java.lang.String getIntermed()

Description copied from interface: Algebraic

Get the intermediate function.

Specified by:

getIntermed in interface Algebraic

Returns:

A function name of f_intermed. f_intermed should be an eval func. The return type of f_intermed.exec() has to be Tuple

getDistinct

protected DataBag getDistinct(Tuple input)
                       throws java.io.IOException

Throws:

java.io.IOException