org.apache.hadoop.mapreduce
Class ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

java.lang.Object
  org.apache.hadoop.mapreduce.JobContext
      org.apache.hadoop.mapreduce.TaskAttemptContext
          org.apache.hadoop.mapreduce.TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>
              org.apache.hadoop.mapreduce.ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

Type Parameters:

KEYIN - the class of the input keys

VALUEIN - the class of the input values

KEYOUT - the class of the output keys

VALUEOUT - the class of the output values

All Implemented Interfaces:

Progressable

Direct Known Subclasses:

Reducer.Context

public class ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>
extends TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

The context passed to the Reducer.

Nested Class Summary

protected class	ReduceContext.ValueIterable
protected class	ReduceContext.ValueIterator

Field Summary

protected Progressable

reporter

Fields inherited from class org.apache.hadoop.mapreduce.JobContext

CACHE_ARCHIVES_VISIBILITIES, CACHE_FILE_VISIBILITIES, COMBINE_CLASS_ATTR, conf, credentials, INPUT_FORMAT_CLASS_ATTR, JOB_ACL_MODIFY_JOB, JOB_ACL_VIEW_JOB, JOB_CANCEL_DELEGATION_TOKEN, JOB_NAMENODES, MAP_CLASS_ATTR, OUTPUT_FORMAT_CLASS_ATTR, PARTITIONER_CLASS_ATTR, REDUCE_CLASS_ATTR, ugi, USER_LOG_RETAIN_HOURS

Constructor Summary

ReduceContext(Configuration conf, TaskAttemptID taskid, RawKeyValueIterator input, Counter inputKeyCounter, Counter inputValueCounter, RecordWriter<KEYOUT,VALUEOUT> output, OutputCommitter committer, StatusReporter reporter, RawComparator<KEYIN> comparator, Class<KEYIN> keyClass, Class<VALUEIN> valueClass)

Method Summary

KEYIN	getCurrentKey() Get the current key.
VALUEIN	getCurrentValue() Get the current value.
Iterable<VALUEIN>	getValues() Iterate through the values for the current key, reusing the same value object, which is stored in the context.
boolean	nextKey() Start processing next unique key.
boolean	nextKeyValue() Advance to the next key/value pair.

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

getCounter, getCounter, getOutputCommitter, getProgress, progress, setStatus, write

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

getStatus, getTaskAttemptID

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

getCombinerClass, getConfiguration, getCredentials, getGroupingComparator, getInputFormatClass, getJar, getJobID, getJobName, getMapOutputKeyClass, getMapOutputValueClass, getMapperClass, getNumReduceTasks, getOutputFormatClass, getOutputKeyClass, getOutputValueClass, getPartitionerClass, getReducerClass, getSortComparator, getWorkingDirectory

Methods inherited from class java.lang.Object

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

Field Detail

reporter

protected Progressable reporter

Constructor Detail

ReduceContext

public ReduceContext(Configuration conf,
                     TaskAttemptID taskid,
                     RawKeyValueIterator input,
                     Counter inputKeyCounter,
                     Counter inputValueCounter,
                     RecordWriter<KEYOUT,VALUEOUT> output,
                     OutputCommitter committer,
                     StatusReporter reporter,
                     RawComparator<KEYIN> comparator,
                     Class<KEYIN> keyClass,
                     Class<VALUEIN> valueClass)
              throws InterruptedException,
                     IOException

Throws:

InterruptedException

IOException

Method Detail

nextKey

public boolean nextKey()
                throws IOException,
                       InterruptedException

Start processing next unique key.

Throws:

IOException

InterruptedException

nextKeyValue

public boolean nextKeyValue()
                     throws IOException,
                            InterruptedException

Advance to the next key/value pair.

Specified by:

nextKeyValue in class TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

Returns:

the key object that was read into, or null if no more

Throws:

IOException

InterruptedException

getCurrentKey

public KEYIN getCurrentKey()

Description copied from class: TaskInputOutputContext

Get the current key.

Specified by:

getCurrentKey in class TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

Returns:

the current key object or null if there isn't one

getCurrentValue

public VALUEIN getCurrentValue()

Description copied from class: TaskInputOutputContext

Get the current value.

Specified by:

getCurrentValue in class TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

Returns:

the value object that was read into

getValues

public Iterable<VALUEIN> getValues()
                            throws IOException,
                                   InterruptedException

Iterate through the values for the current key, reusing the same value object, which is stored in the context.

Returns:

the series of values associated with the current key. All of the objects returned directly and indirectly from this method are reused.

Throws:

IOException

InterruptedException