org.apache.hadoop.mapred.join
Class JoinRecordReader<K extends WritableComparable>

java.lang.Object
  org.apache.hadoop.mapred.join.CompositeRecordReader<K,Writable,TupleWritable>
      org.apache.hadoop.mapred.join.JoinRecordReader<K>

All Implemented Interfaces:

Comparable<ComposableRecordReader<K,?>>, Configurable, ComposableRecordReader<K,TupleWritable>, RecordReader<K,TupleWritable>

Direct Known Subclasses:

InnerJoinRecordReader, OuterJoinRecordReader

public abstract class JoinRecordReader<K extends WritableComparable>
extends CompositeRecordReader<K,Writable,TupleWritable>
implements ComposableRecordReader<K,TupleWritable>

Base class for Composite joins returning Tuples of arbitrary Writables.

Nested Class Summary

protected class

JoinRecordReader.JoinDelegationIterator Since the JoinCollector is effecting our operation, we need only provide an iterator proxy wrapping its operation.

Field Summary

Fields inherited from class org.apache.hadoop.mapred.join.CompositeRecordReader

jc, kids

Constructor Summary

JoinRecordReader(int id, JobConf conf, int capacity, Class<? extends WritableComparator> cmpcl)

Method Summary

TupleWritable	createValue() Create an object of the appropriate type to be used as a value.
protected ResetableIterator<TupleWritable>	getDelegate() Return an iterator wrapping the JoinCollector.
boolean	next(K key, TupleWritable value) Emit the next set of key, value pairs as defined by the child RecordReaders and operation associated with this composite RR.

Methods inherited from class org.apache.hadoop.mapred.join.CompositeRecordReader

accept, add, close, combine, compareTo, createInternalValue, createKey, fillJoinCollector, getComparator, getConf, getPos, getProgress, getRecordReaderQueue, hasNext, id, key, key, setConf, skip

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.mapred.join.ComposableRecordReader

accept, hasNext, id, key, key, skip

Methods inherited from interface org.apache.hadoop.mapred.RecordReader

close, createKey, getPos, getProgress

Methods inherited from interface java.lang.Comparable

compareTo

Constructor Detail

JoinRecordReader

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

Throws:

IOException

Method Detail

next

public boolean next(K key,
                    TupleWritable value)
             throws IOException

Emit the next set of key, value pairs as defined by the child RecordReaders and operation associated with this composite RR.

Specified by:

next in interface RecordReader<K extends WritableComparable,TupleWritable>

Parameters:

key - the key to read data into

value - the value to read data into

Returns:

true iff a key/value was read, false if at EOF

Throws:

IOException

createValue

public TupleWritable createValue()

Create an object of the appropriate type to be used as a value.

Specified by:

createValue in interface RecordReader<K extends WritableComparable,TupleWritable>

Returns:

a new value object.

getDelegate

protected ResetableIterator<TupleWritable> getDelegate()

Return an iterator wrapping the JoinCollector.

Specified by:

getDelegate in class CompositeRecordReader<K extends WritableComparable,Writable,TupleWritable>