org.apache.hadoop.mapreduce

Class RecordReader<KEYIN,VALUEIN>

java.lang.Object

org.apache.hadoop.mapreduce.RecordReader<KEYIN,VALUEIN>

Type Parameters:

KEYIN -

VALUEIN -

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

CombineFileRecordReader, DBRecordReader, DelegatingRecordReader, KeyValueLineRecordReader, LineRecordReader, MultiFileWordCount.CombineFileLineRecordReader, SequenceFileAsBinaryInputFormat.SequenceFileAsBinaryRecordReader, SequenceFileAsTextRecordReader, SequenceFileRecordReader

public abstract class RecordReader<KEYIN,VALUEIN>
extends java.lang.Object
implements java.io.Closeable

The record reader breaks the data into key/value pairs for input to the Mapper.

Constructor Summary

Constructors

Constructor and Description
RecordReader()

Method Summary

Methods

Modifier and Type	Method and Description
abstract void	close() Close the record reader.
abstract KEYIN	getCurrentKey() Get the current key
abstract VALUEIN	getCurrentValue() Get the current value.
abstract float	getProgress() The current progress of the record reader through its data.
abstract void	initialize(InputSplit split, TaskAttemptContext context) Called once at initialization.
abstract boolean	nextKeyValue() Read the next key, value pair.

Methods inherited from class java.lang.Object

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

Constructor Detail

RecordReader

public RecordReader()

Method Detail

initialize

public abstract void initialize(InputSplit split,
              TaskAttemptContext context)
                         throws java.io.IOException,
                                java.lang.InterruptedException

Called once at initialization.

Parameters:

split - the split that defines the range of records to read

context - the information about the task

Throws:

java.io.IOException

java.lang.InterruptedException

nextKeyValue

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

Read the next key, value pair.

Returns:

true if a key/value pair was read

Throws:

java.io.IOException

java.lang.InterruptedException

getCurrentKey

public abstract KEYIN getCurrentKey()
                             throws java.io.IOException,
                                    java.lang.InterruptedException

Get the current key

Returns:

the current key or null if there is no current key

Throws:

java.io.IOException

java.lang.InterruptedException

getCurrentValue

public abstract VALUEIN getCurrentValue()
                                 throws java.io.IOException,
                                        java.lang.InterruptedException

Get the current value.

Returns:

the object that was read

Throws:

java.io.IOException

java.lang.InterruptedException

getProgress

public abstract float getProgress()
                           throws java.io.IOException,
                                  java.lang.InterruptedException

The current progress of the record reader through its data.

Returns:

a number between 0.0 and 1.0 that is the fraction of the data read

Throws:

java.io.IOException

java.lang.InterruptedException

close

public abstract void close()
                    throws java.io.IOException

Close the record reader.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Throws:

java.io.IOException