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

All Known Implementing Classes:

ArrayListBackedIterator, JoinRecordReader.JoinDelegationIterator, MultiFilterRecordReader.MultiFilterDelegationIterator, ResetableIterator.EMPTY, StreamBackedIterator

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.

Nested Class Summary

static class

ResetableIterator.EMPTY<U extends Writable>

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.