Package org.apache.hadoop.mapred.join

Class CompositeRecordReader<K extends WritableComparable,V extends Writable,X extends Writable>

java.lang.Object

org.apache.hadoop.mapred.join.CompositeRecordReader<K,V,X>

All Implemented Interfaces:

Configurable

Direct Known Subclasses:

JoinRecordReader, MultiFilterRecordReader

@Public
@Stable
public abstract class CompositeRecordReader<K extends WritableComparable,V extends Writable,X extends Writable>
extends Object
implements Configurable

A RecordReader that can effect joins of RecordReaders sharing a common key type and partitioning.

Field Summary

Fields

Modifier and Type	Field	Description
protected final CompositeRecordReader<K,V,X>.org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector	jc
protected final ComposableRecordReader<K,? extends V>[]	kids

Constructor Summary

Constructors

Constructor	Description
CompositeRecordReader(int id, int capacity, Class<? extends WritableComparator> cmpcl)	Create a RecordReader with capacity children to position id in the parent reader.

Method Summary

Modifier and Type	Method	Description
void	accept(org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector jc, K key)	If key provided matches that of this Composite, give JoinCollector iterator over values it may emit.
void	add(ComposableRecordReader<K,? extends V> rr)	Add a RecordReader to this collection.
void	close()	Close all child RRs.
protected abstract boolean	combine(Object[] srcs, TupleWritable value)
int	compareTo(ComposableRecordReader<K,?> other)	Implement Comparable contract (compare key of join or head of heap with that of another).
protected TupleWritable	createInternalValue()	Create a value to be used internally for joins.
K	createKey()	Create a new key value common to all child RRs.
protected void	fillJoinCollector(K iterkey)	For all child RRs offering the key provided, obtain an iterator at that position in the JoinCollector.
protected WritableComparator	getComparator()	Return comparator defining the ordering for RecordReaders in this composite.
Configuration	getConf()	Return the configuration used by this object.
protected abstract ResetableIterator<X>	getDelegate()	Obtain an iterator over the child RRs apropos of the value type ultimately emitted from this join.
long	getPos()	Unsupported (returns zero in all cases).
float	getProgress()	Report progress as the minimum of all child RR progress.
protected PriorityQueue<ComposableRecordReader<K,?>>	getRecordReaderQueue()	Return sorted list of RecordReaders for this composite.
boolean	hasNext()	Return true if it is possible that this could emit more values.
int	id()	Return the position in the collector this class occupies.
K	key()	Return the key for the current join or the value at the top of the RecordReader heap.
void	key(K key)	Clone the key at the top of this RR into the given object.
void	setConf(Configuration conf)	Set the configuration to be used by this object.
void	skip(K key)	Pass skip key to child RRs.

Methods inherited from class java.lang.Object

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

Field Details

jc

protected final CompositeRecordReader<K extends WritableComparable,V extends Writable,X extends Writable>.org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector jc

kids

protected final ComposableRecordReader<K extends WritableComparable,? extends V extends Writable>[] kids

Constructor Details

CompositeRecordReader

public CompositeRecordReader(int id,
 int capacity,
 Class<? extends WritableComparator> cmpcl)
                      throws IOException

Create a RecordReader with capacity children to position id in the parent reader. The id of a root CompositeRecordReader is -1 by convention, but relying on this is not recommended.

Throws:

IOException

Method Details

combine

protected abstract boolean combine(Object[] srcs,
 TupleWritable value)

id

public int id()

Return the position in the collector this class occupies.

setConf

public void setConf(Configuration conf)

Set the configuration to be used by this object.

Specified by:

setConf in interface Configurable

Parameters:

conf - configuration to be used

getConf

public Configuration getConf()

Return the configuration used by this object.

Specified by:

getConf in interface Configurable

Returns:

Configuration

getRecordReaderQueue

protected PriorityQueue<ComposableRecordReader<K,?>> getRecordReaderQueue()

Return sorted list of RecordReaders for this composite.

getComparator

protected WritableComparator getComparator()

Return comparator defining the ordering for RecordReaders in this composite.

add

public void add(ComposableRecordReader<K,? extends V> rr)
         throws IOException

Add a RecordReader to this collection. The id() of a RecordReader determines where in the Tuple its entry will appear. Adding RecordReaders with the same id has undefined behavior.

Throws:

IOException

key

public K key()

Return the key for the current join or the value at the top of the RecordReader heap.

key

public void key(K key)
         throws IOException

Clone the key at the top of this RR into the given object.

Throws:

IOException

hasNext

public boolean hasNext()

Return true if it is possible that this could emit more values.

skip

public void skip(K key)
          throws IOException

Pass skip key to child RRs.

Throws:

IOException

getDelegate

protected abstract ResetableIterator<X> getDelegate()

Obtain an iterator over the child RRs apropos of the value type ultimately emitted from this join.

accept

public void accept(org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector jc,
 K key)
            throws IOException

If key provided matches that of this Composite, give JoinCollector iterator over values it may emit.

Throws:

IOException

fillJoinCollector

protected void fillJoinCollector(K iterkey)
                          throws IOException

For all child RRs offering the key provided, obtain an iterator at that position in the JoinCollector.

Throws:

IOException

compareTo

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

Implement Comparable contract (compare key of join or head of heap with that of another).

createKey

public K createKey()

Create a new key value common to all child RRs.

Throws:

ClassCastException - if key classes differ.

createInternalValue

protected TupleWritable createInternalValue()

Create a value to be used internally for joins.

getPos

public long getPos()
            throws IOException

Unsupported (returns zero in all cases).

Throws:

IOException

close

public void close()
           throws IOException

Close all child RRs.

Throws:

IOException

getProgress

public float getProgress()
                  throws IOException

Report progress as the minimum of all child RR progress.

Throws:

IOException