org.apache.hadoop.mapreduce.lib.join
Interface ResetableIterator<T extends Writable>

All Known Subinterfaces:
ResetableIterator<T>
All Known Implementing Classes:
ArrayListBackedIterator, ArrayListBackedIterator, StreamBackedIterator, StreamBackedIterator

@InterfaceAudience.Public
@InterfaceStability.Stable
public interface ResetableIterator<T extends Writable>

This defines an interface to a stateful Iterator that can replay elements added to it directly. Note that this does not extend Iterator.


Method Summary
 void add(T item)
          Add an element to the collection of elements to iterate over.
 void clear()
          Close datasources, but do not release internal resources.
 void close()
          Close datasources and release resources.
 boolean hasNext()
          True if a call to next may return a value.
 boolean next(T val)
          Assign next value to actual.
 boolean replay(T val)
          Assign last value returned to actual.
 void reset()
          Set iterator to return to the start of its range.
 

Method Detail

hasNext

boolean hasNext()
True if a call to next may return a value. This is permitted false positives, but not false negatives.


next

boolean next(T val)
             throws IOException
Assign next value to actual. It is required that elements added to a ResetableIterator be returned in the same order after a call to reset() (FIFO). Note that a call to this may fail for nested joins (i.e. more elements available, but none satisfying the constraints of the join)

Throws:
IOException

replay

boolean replay(T val)
               throws IOException
Assign last value returned to actual.

Throws:
IOException

reset

void reset()
Set iterator to return to the start of its range. Must be called after calling add(T) to avoid a ConcurrentModificationException.


add

void add(T item)
         throws IOException
Add an element to the collection of elements to iterate over.

Throws:
IOException

close

void close()
           throws IOException
Close datasources and release resources. Calling methods on the iterator after calling close has undefined behavior.

Throws:
IOException

clear

void clear()
Close datasources, but do not release internal resources. Calling this method should permit the object to be reused with a different datasource.



Copyright © 2012 Apache Software Foundation. All Rights Reserved.