org.apache.hadoop.mapreduce.task

Class ReduceContextImpl<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

java.lang.Object

org.apache.hadoop.mapreduce.task.JobContextImpl

org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl

org.apache.hadoop.mapreduce.task.TaskInputOutputContextImpl<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

org.apache.hadoop.mapreduce.task.ReduceContextImpl<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:

JobContext, ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>, TaskAttemptContext, TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>, org.apache.hadoop.util.Progressable

public class ReduceContextImpl<KEYIN,VALUEIN,KEYOUT,VALUEOUT>
extends TaskInputOutputContextImpl<KEYIN,VALUEIN,KEYOUT,VALUEOUT>
implements ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

The context passed to the Reducer.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	ReduceContextImpl.ValueIterable
protected class	ReduceContextImpl.ValueIterator

Nested classes/interfaces inherited from class org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl

TaskAttemptContextImpl.DummyReporter

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.hadoop.util.Progressable	reporter

Fields inherited from class org.apache.hadoop.mapreduce.task.JobContextImpl

credentials, ugi

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

CACHE_ARCHIVES_VISIBILITIES, CACHE_FILE_VISIBILITIES, COMBINE_CLASS_ATTR, INPUT_FORMAT_CLASS_ATTR, JAR_UNPACK_PATTERN, JOB_ACL_MODIFY_JOB, JOB_ACL_VIEW_JOB, JOB_CANCEL_DELEGATION_TOKEN, JOB_NAMENODES, MAP_CLASS_ATTR, MAP_MEMORY_PHYSICAL_MB, MAP_OUTPUT_COLLECTOR_CLASS_ATTR, MAPREDUCE_TASK_CLASSPATH_PRECEDENCE, OUTPUT_FORMAT_CLASS_ATTR, PARTITIONER_CLASS_ATTR, REDUCE_CLASS_ATTR, REDUCE_MEMORY_PHYSICAL_MB, SHUFFLE_CONSUMER_PLUGIN_ATTR, USER_LOG_RETAIN_HOURS

Constructor Summary

Constructors

Constructor and Description
ReduceContextImpl(org.apache.hadoop.conf.Configuration conf, TaskAttemptID taskid, RawKeyValueIterator input, Counter inputKeyCounter, Counter inputValueCounter, RecordWriter<KEYOUT,VALUEOUT> output, OutputCommitter committer, StatusReporter reporter, org.apache.hadoop.io.RawComparator<KEYIN> comparator, java.lang.Class<KEYIN> keyClass, java.lang.Class<VALUEIN> valueClass)

Method Summary

Methods

Modifier and Type	Method and Description
KEYIN	getCurrentKey() Get the current key.
VALUEIN	getCurrentValue() Get the current value.
java.lang.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.task.TaskInputOutputContextImpl

getOutputCommitter, write

Methods inherited from class org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl

getCounter, getCounter, getStatus, getTaskAttemptID, progress, setStatus, setStatusString

Methods inherited from class org.apache.hadoop.mapreduce.task.JobContextImpl

getArchiveClassPaths, getArchiveTimestamps, getCacheArchives, getCacheFiles, getCombinerClass, getCombinerKeyGroupingComparator, getConfiguration, getCredentials, getFileClassPaths, getFileTimestamps, getGroupingComparator, getInputFormatClass, getJar, getJobID, getJobName, getJobSetupCleanupNeeded, getLocalCacheArchives, getLocalCacheFiles, getMapOutputKeyClass, getMapOutputValueClass, getMapperClass, getMaxMapAttempts, getMaxReduceAttempts, getNumReduceTasks, getOutputFormatClass, getOutputKeyClass, getOutputValueClass, getPartitionerClass, getProfileEnabled, getProfileParams, getProfileTaskRange, getReducerClass, getSortComparator, getSymlink, getUser, getWorkingDirectory, setJobID, userClassesTakesPrecedence

Methods inherited from class java.lang.Object

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

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

getOutputCommitter, write

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

getCounter, getCounter, getStatus, getTaskAttemptID, setStatus

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

getArchiveClassPaths, getArchiveTimestamps, getCacheArchives, getCacheFiles, getCombinerClass, getCombinerKeyGroupingComparator, getConfiguration, getCredentials, getFileClassPaths, getFileTimestamps, getGroupingComparator, getInputFormatClass, getJar, getJobID, getJobName, getJobSetupCleanupNeeded, getLocalCacheArchives, getLocalCacheFiles, getMapOutputKeyClass, getMapOutputValueClass, getMapperClass, getMaxMapAttempts, getMaxReduceAttempts, getNumReduceTasks, getOutputFormatClass, getOutputKeyClass, getOutputValueClass, getPartitionerClass, getProfileEnabled, getProfileParams, getReducerClass, getSortComparator, getSymlink, getUser, getWorkingDirectory, userClassesTakesPrecedence

Methods inherited from interface org.apache.hadoop.util.Progressable

progress

Field Detail

reporter

protected org.apache.hadoop.util.Progressable reporter

Constructor Detail

ReduceContextImpl

public ReduceContextImpl(org.apache.hadoop.conf.Configuration conf,
                 TaskAttemptID taskid,
                 RawKeyValueIterator input,
                 Counter inputKeyCounter,
                 Counter inputValueCounter,
                 RecordWriter<KEYOUT,VALUEOUT> output,
                 OutputCommitter committer,
                 StatusReporter reporter,
                 org.apache.hadoop.io.RawComparator<KEYIN> comparator,
                 java.lang.Class<KEYIN> keyClass,
                 java.lang.Class<VALUEIN> valueClass)
                  throws java.lang.InterruptedException,
                         java.io.IOException

Throws:

java.lang.InterruptedException

java.io.IOException

Method Detail

nextKey

public boolean nextKey()
                throws java.io.IOException,
                       java.lang.InterruptedException

Start processing next unique key.

Specified by:

nextKey in interface ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

Throws:

java.io.IOException

java.lang.InterruptedException

nextKeyValue

public boolean nextKeyValue()
                     throws java.io.IOException,
                            java.lang.InterruptedException

Advance to the next key/value pair.

Specified by:

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

Specified by:

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

Returns:

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

Throws:

java.io.IOException

java.lang.InterruptedException

getCurrentKey

public KEYIN getCurrentKey()

Description copied from class: TaskInputOutputContextImpl

Get the current key.

Specified by:

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

Specified by:

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

Returns:

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

getCurrentValue

public VALUEIN getCurrentValue()

Description copied from class: TaskInputOutputContextImpl

Get the current value.

Specified by:

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

Specified by:

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

Returns:

the value object that was read into

getValues

public java.lang.Iterable<VALUEIN> getValues()
                                      throws java.io.IOException,
                                             java.lang.InterruptedException

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

Specified by:

getValues in interface ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

Returns:

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

Throws:

java.io.IOException

java.lang.InterruptedException