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

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

All Implemented Interfaces:

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

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

This class implements the generic mapper of Aggregate.

Field Summary

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

aggregatorDescriptorList

Constructor Summary

ValueAggregatorMapper()

Method Summary

void	map(K1 key, V1 value, OutputCollector<Text,Text> output, Reporter reporter) the map function.
void	reduce(Text arg0, Iterator<Text> arg1, OutputCollector<Text,Text> arg2, Reporter arg3) Do nothing.

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

close, configure, logSpec

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

map

public void map(K1 key,
                V1 value,
                OutputCollector<Text,Text> output,
                Reporter reporter)
         throws IOException

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

Parameters:

key - the input key.

value - the input value.

output - collects mapped keys and values.

reporter - facility to report progress.

Throws:

IOException

reduce

public void reduce(Text arg0,
                   Iterator<Text> arg1,
                   OutputCollector<Text,Text> arg2,
                   Reporter arg3)
            throws IOException

Do nothing. Should not be called.

Parameters:

arg0 - the key.

arg1 - the list of values to reduce.

arg2 - to collect keys and combined values.

arg3 - facility to report progress.

Throws:

IOException