org.apache.hadoop.mapreduce.lib.aggregate

Class ValueAggregatorMapper<K1 extends WritableComparable<?>,V1 extends Writable>

java.lang.Object

org.apache.hadoop.mapreduce.Mapper<K1,V1,Text,Text>

org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorMapper<K1,V1>

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class ValueAggregatorMapper<K1 extends WritableComparable<?>,V1 extends Writable>
extends Mapper<K1,V1,Text,Text>

This class implements the generic mapper of Aggregate.

Constructor Summary

Constructors

Constructor and Description
ValueAggregatorMapper()

Method Summary

Modifier and Type	Method and Description
void	map(K1 key, V1 value, org.apache.hadoop.mapreduce.Mapper.Context context) the map function.
void	setup(org.apache.hadoop.mapreduce.Mapper.Context context) Called once at the beginning of the task.

Methods inherited from class org.apache.hadoop.mapreduce.Mapper

cleanup, run

Methods inherited from class java.lang.Object

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

Constructor Detail

ValueAggregatorMapper

public ValueAggregatorMapper()

Method Detail

setup

public void setup(org.apache.hadoop.mapreduce.Mapper.Context context)
           throws IOException,
                  InterruptedException

Description copied from class: Mapper

Called once at the beginning of the task.

Overrides:

setup in class Mapper<K1 extends WritableComparable<?>,V1 extends Writable,Text,Text>

Throws:

IOException

InterruptedException

map

public void map(K1 key,
                V1 value,
                org.apache.hadoop.mapreduce.Mapper.Context context)
         throws IOException,
                InterruptedException

the map function. It iterates through the value aggregator descriptor list to generate aggregation id/value pairs and emit them.

Overrides:

map in class Mapper<K1 extends WritableComparable<?>,V1 extends Writable,Text,Text>

Throws:

IOException

InterruptedException