org.apache.hadoop.mapreduce.lib.join

Class WrappedRecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>

java.lang.Object

org.apache.hadoop.mapreduce.RecordReader<K,V>

org.apache.hadoop.mapreduce.lib.join.ComposableRecordReader<K,U>

org.apache.hadoop.mapreduce.lib.join.WrappedRecordReader<K,U>

All Implemented Interfaces:

Closeable, AutoCloseable, Comparable<ComposableRecordReader<K,?>>

@InterfaceAudience.Public
@InterfaceStability.Stable
public class WrappedRecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>
extends ComposableRecordReader<K,U>

Proxy class for a RecordReader participating in the join framework. This class keeps track of the "head" key-value pair for the provided RecordReader and keeps a store of values matching a key when this source is participating in a join.

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.hadoop.io.WritableComparator	cmp
protected boolean	empty

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	WrappedRecordReader(int id)

Method Summary

Methods

Modifier and Type	Method and Description
void	accept(CompositeRecordReader.JoinCollector i, K key) Add an iterator to the collector at the position occupied by this RecordReader over the values in this stream paired with the key provided (ie register a stream of values from this source matching K with a collector).
void	close() Forward close request to proxied RR.
int	compareTo(ComposableRecordReader<K,?> other) Implement Comparable contract (compare key at head of proxied RR with that of another).
K	createKey() Request new key from proxied RR.
U	createValue() Create instance of value.
boolean	equals(Object other) Return true iff compareTo(other) retn true.
K	getCurrentKey() Get current key
U	getCurrentValue() Get current value
float	getProgress() Request progress from proxied RR.
int	hashCode()
boolean	hasNext() Return true if the RR- including the k,v pair stored in this object- is exhausted.
int	id() Return the position in the collector this class occupies.
void	initialize(InputSplit split, TaskAttemptContext context) Called once at initialization.
K	key() Return the key at the head of this RR.
void	key(K qkey) Clone the key at the head of this RR into the object supplied.
boolean	nextKeyValue() Read the next k,v pair into the head of this object; return true iff the RR and this are exhausted.
void	skip(K key) Skip key-value pairs with keys less than or equal to the key provided.

Methods inherited from class java.lang.Object

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

Field Detail

empty

protected boolean empty

cmp

protected org.apache.hadoop.io.WritableComparator cmp

Constructor Detail

WrappedRecordReader

protected WrappedRecordReader(int id)

Method Detail

initialize

public void initialize(InputSplit split,
              TaskAttemptContext context)
                throws IOException,
                       InterruptedException

Description copied from class: RecordReader

Called once at initialization.

Specified by:

initialize in class RecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>

Parameters:

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

context - the information about the task

Throws:

IOException

InterruptedException

createKey

public K createKey()

Request new key from proxied RR.

createValue

public U createValue()

Description copied from class: ComposableRecordReader

Create instance of value.

id

public int id()

Return the position in the collector this class occupies.

key

public K key()

Return the key at the head of this RR.

key

public void key(K qkey)
         throws IOException

Clone the key at the head of this RR into the object supplied.

Throws:

IOException

hasNext

public boolean hasNext()

Return true if the RR- including the k,v pair stored in this object- is exhausted.

skip

public void skip(K key)
          throws IOException,
                 InterruptedException

Skip key-value pairs with keys less than or equal to the key provided.

Throws:

IOException

InterruptedException

accept

public void accept(CompositeRecordReader.JoinCollector i,
          K key)
            throws IOException,
                   InterruptedException

Add an iterator to the collector at the position occupied by this RecordReader over the values in this stream paired with the key provided (ie register a stream of values from this source matching K with a collector).

Throws:

IOException

InterruptedException

nextKeyValue

public boolean nextKeyValue()
                     throws IOException,
                            InterruptedException

Read the next k,v pair into the head of this object; return true iff the RR and this are exhausted.

Specified by:

nextKeyValue in class RecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>

Returns:

true if a key/value pair was read

Throws:

IOException

InterruptedException

getCurrentKey

public K getCurrentKey()
                                                                   throws IOException,
                                                                          InterruptedException

Get current key

Specified by:

getCurrentKey in class RecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>

Returns:

the current key or null if there is no current key

Throws:

IOException

InterruptedException

getCurrentValue

public U getCurrentValue()
                                                        throws IOException,
                                                               InterruptedException

Get current value

Specified by:

getCurrentValue in class RecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>

Returns:

the object that was read

Throws:

IOException

InterruptedException

getProgress

public float getProgress()
                  throws IOException,
                         InterruptedException

Request progress from proxied RR.

Specified by:

getProgress in class RecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>

Returns:

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

Throws:

IOException

InterruptedException

close

public void close()
           throws IOException

Forward close request to proxied RR.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in class RecordReader<K extends org.apache.hadoop.io.WritableComparable<?>,U extends org.apache.hadoop.io.Writable>

Throws:

IOException

compareTo

public int compareTo(ComposableRecordReader<K,?> other)

Implement Comparable contract (compare key at head of proxied RR with that of another).

equals

public boolean equals(Object other)

Return true iff compareTo(other) retn true.

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object