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:

Configurable

Direct Known Subclasses:

InnerJoinRecordReader, OuterJoinRecordReader

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

void	accept(org.apache.hadoop.mapred.join.CompositeRecordReader.JoinCollector jc, K key) While key-value pairs from this RecordReader match the given key, register them with the JoinCollector provided.
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	hasNext() Returns true if the stream is not empty, but provides no guarantee that a call to next(K,V) will succeed.
int	id() Return the position in the collector this class occupies.
K	key() Return the key this RecordReader would supply on a call to next(K,V)
void	key(K key) Clone the key at the head of this RecordReader into the object provided.
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.
void	skip(K key) Skip key-value pairs with keys less than or equal to the key provided.

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.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.

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

See Also:

Writable.readFields(DataInput)

createValue

public TupleWritable createValue()

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

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>

id

public int id()

Return the position in the collector this class occupies.

key

public K key()

Return the key this RecordReader would supply on a call to next(K,V)

key

public void key(K key)
         throws IOException

Clone the key at the head of this RecordReader into the object provided.

Throws:

IOException

hasNext

public boolean hasNext()

Returns true if the stream is not empty, but provides no guarantee that a call to next(K,V) will succeed.

skip

public void skip(K key)
          throws IOException

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

Throws:

IOException

accept

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

While key-value pairs from this RecordReader match the given key, register them with the JoinCollector provided.

Throws:

IOException