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

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


Copyright © 2012 Apache Software Foundation. All Rights Reserved.