org.apache.hadoop.mapred.lib.aggregate
Class ValueAggregatorCombiner<K1 extends WritableComparable,V1 extends Writable>

java.lang.Object
  org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorJobBase<K1,V1>
      org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorCombiner<K1,V1>

All Implemented Interfaces:

Closeable, JobConfigurable, Mapper<K1,V1,Text,Text>, Reducer<Text,Text,Text,Text>

@InterfaceAudience.Public
@InterfaceStability.Stable
public class ValueAggregatorCombiner<K1 extends WritableComparable,V1 extends Writable>
extends ValueAggregatorJobBase<K1,V1>

This class implements the generic combiner of Aggregate.

Field Summary

Fields inherited from class org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorJobBase

aggregatorDescriptorList

Constructor Summary

ValueAggregatorCombiner()

Method Summary

void	close() Do nothing.
void	configure(JobConf job) Combiner does not need to configure.
void	map(K1 arg0, V1 arg1, OutputCollector<Text,Text> arg2, Reporter arg3) Do nothing.
void	reduce(Text key, Iterator<Text> values, OutputCollector<Text,Text> output, Reporter reporter) Combines values for a given key.

Methods inherited from class org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorJobBase

logSpec

Methods inherited from class java.lang.Object

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

Constructor Detail

ValueAggregatorCombiner

public ValueAggregatorCombiner()

Method Detail

configure

public void configure(JobConf job)

Combiner does not need to configure.

Specified by:

configure in interface JobConfigurable

Overrides:

configure in class ValueAggregatorJobBase<K1 extends WritableComparable,V1 extends Writable>

Parameters:

job - the configuration

reduce

public void reduce(Text key,
                   Iterator<Text> values,
                   OutputCollector<Text,Text> output,
                   Reporter reporter)
            throws IOException

Combines values for a given key.

Parameters:

key - the key is expected to be a Text object, whose prefix indicates the type of aggregation to aggregate the values.

values - the values to combine

output - to collect combined values

reporter - facility to report progress.

Throws:

IOException

close

public void close()
           throws IOException

Do nothing.

Specified by:

close in interface Closeable

Overrides:

close in class ValueAggregatorJobBase<K1 extends WritableComparable,V1 extends Writable>

Throws:

IOException

map

public void map(K1 arg0,
                V1 arg1,
                OutputCollector<Text,Text> arg2,
                Reporter arg3)
         throws IOException

Do nothing. Should not be called.

Parameters:

arg0 - the input key.

arg1 - the input value.

arg2 - collects mapped keys and values.

arg3 - facility to report progress.

Throws:

IOException