Uses of Interface
org.apache.hadoop.mapred.Reducer

Packages that use Reducer

org.apache.hadoop.contrib.index.mapred
org.apache.hadoop.contrib.utils.join
org.apache.hadoop.examples	Hadoop example code.
org.apache.hadoop.mapred	A software framework for easily writing applications which process vast amounts of data (multi-terabyte data-sets) parallelly on large clusters (thousands of nodes) built of commodity hardware in a reliable, fault-tolerant manner.
org.apache.hadoop.mapred.lib	Library of generally useful mappers, reducers, and partitioners.
org.apache.hadoop.mapred.lib.aggregate	Classes for performing various counting and aggregations.
org.apache.hadoop.streaming	Hadoop Streaming is a utility which allows users to create and run Map-Reduce jobs with any executables (e.g.

Uses of Reducer in org.apache.hadoop.contrib.index.mapred

Classes in org.apache.hadoop.contrib.index.mapred that implement Reducer

class	IndexUpdateCombiner This combiner combines multiple intermediate forms into one intermediate form.
class	IndexUpdateReducer This reducer applies to a shard the changes for it.

Uses of Reducer in org.apache.hadoop.contrib.utils.join

Classes in org.apache.hadoop.contrib.utils.join that implement Reducer

class	DataJoinMapperBase This abstract class serves as the base class for the mapper class of a data join job.
class	DataJoinReducerBase This abstract class serves as the base class for the reducer class of a data join job.
class	JobBase A common base implementing some statics collecting mechanisms that are commonly used in a typical map/reduce job.

Uses of Reducer in org.apache.hadoop.examples

Classes in org.apache.hadoop.examples that implement Reducer

static class	PiEstimator.PiReducer Reducer class for Pi estimation.
class	SleepJob Dummy class for testing MR framefork.

Uses of Reducer in org.apache.hadoop.mapred

Methods in org.apache.hadoop.mapred that return types with arguments of type Reducer

Class<? extends Reducer>	JobConf.getCombinerClass() Get the user-defined combiner class used to combine map-outputs before being sent to the reducers.
Class<? extends Reducer>	JobConf.getReducerClass() Get the Reducer class for the job.

Method parameters in org.apache.hadoop.mapred with type arguments of type Reducer

void	JobConf.setCombinerClass(Class<? extends Reducer> theClass) Set the user-defined combiner class used to combine map-outputs before being sent to the reducers.
void	JobConf.setReducerClass(Class<? extends Reducer> theClass) Set the Reducer class for the job.

Constructor parameters in org.apache.hadoop.mapred with type arguments of type Reducer

Task.OldCombinerRunner(Class<? extends Reducer<K,V,K,V>> cls, JobConf conf, Counters.Counter inputCounter, Task.TaskReporter reporter)

Uses of Reducer in org.apache.hadoop.mapred.lib

Classes in org.apache.hadoop.mapred.lib that implement Reducer

class	ChainReducer The ChainReducer class allows to chain multiple Mapper classes after a Reducer within the Reducer task.
class	FieldSelectionMapReduce<K,V> This class implements a mapper/reducer class that can be used to perform field selections in a manner similar to unix cut.
class	IdentityReducer<K,V> Performs no reduction, writing all input values directly to the output.
class	LongSumReducer<K> A Reducer that sums long values.

Method parameters in org.apache.hadoop.mapred.lib with type arguments of type Reducer

static <K1,V1,K2,V2> void

ChainReducer.setReducer(JobConf job, Class<? extends Reducer<K1,V1,K2,V2>> klass, Class<? extends K1> inputKeyClass, Class<? extends V1> inputValueClass, Class<? extends K2> outputKeyClass, Class<? extends V2> outputValueClass, boolean byValue, JobConf reducerConf) Sets the Reducer class to the chain job's JobConf.

Uses of Reducer in org.apache.hadoop.mapred.lib.aggregate

Classes in org.apache.hadoop.mapred.lib.aggregate that implement Reducer

class	ValueAggregatorCombiner<K1 extends WritableComparable,V1 extends Writable> This class implements the generic combiner of Aggregate.
class	ValueAggregatorJobBase<K1 extends WritableComparable,V1 extends Writable> This abstract class implements some common functionalities of the the generic mapper, reducer and combiner classes of Aggregate.
class	ValueAggregatorMapper<K1 extends WritableComparable,V1 extends Writable> This class implements the generic mapper of Aggregate.
class	ValueAggregatorReducer<K1 extends WritableComparable,V1 extends Writable> This class implements the generic reducer of Aggregate.

Uses of Reducer in org.apache.hadoop.streaming

Classes in org.apache.hadoop.streaming that implement Reducer

class	PipeCombiner
class	PipeReducer A generic Reducer bridge.