org.eigenbase.runtime
Class CompoundTupleIter

java.lang.Object
  org.eigenbase.runtime.CompoundTupleIter

All Implemented Interfaces:

TupleIter, ClosableAllocation

public class CompoundTupleIter
extends Object
implements TupleIter

CompoundTupleIter creates an iterator out of several iterators.

CompoundTupleIter is serial: it yields all the elements of its first input Iterator, then all those of its second input, etc. When all inputs are exhausted, it is done. (Cf CompoundParallelTupleIter.)

Version:

$Id: //open/dev/farrago/src/org/eigenbase/runtime/CompoundTupleIter.java#10 $

Author:

Stephan Zuercher

Nested Class Summary

static class

CompoundTupleIter.Test

Nested classes/interfaces inherited from interface org.eigenbase.runtime.TupleIter

TupleIter.NoDataReason, TupleIter.TimeoutException

Field Summary

private int	i
private TupleIter	iterator
private TupleIter[]	iterators
private static Logger	tracer

Fields inherited from interface org.eigenbase.runtime.TupleIter

EMPTY_ITERATOR

Constructor Summary

CompoundTupleIter(TupleIter[] iterators)

Method Summary

void	closeAllocation() Closes this object.
Object	fetchNext() Returns the next element in the iteration.
private void	initIterator()
void	restart() Restarts this iterator, so that a subsequent call to TupleIter.fetchNext() returns the first element in the collection being iterated.
boolean	setTimeout(long timeout, boolean asUnderflow) Sets a timeout for TupleIter.fetchNext(); (optional operation).

Methods inherited from class java.lang.Object

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

Field Detail

tracer

private static final Logger tracer

iterator

private TupleIter iterator

iterators

private TupleIter[] iterators

i

private int i

Constructor Detail

CompoundTupleIter

public CompoundTupleIter(TupleIter[] iterators)

Method Detail

initIterator

private void initIterator()

setTimeout

public boolean setTimeout(long timeout,
                          boolean asUnderflow)

Description copied from interface: TupleIter

Sets a timeout for TupleIter.fetchNext(); (optional operation). Not all implementing classes support a timeout. For those that do, this method provides a common interface, For those that do not, the adapter TimeoutQueueTupleIter puts a timeout queue on top.

Specified by:

setTimeout in interface TupleIter

Parameters:

timeout - in milliseconds. 0 means poll, infinity means block.

asUnderflow - true means indicate timeout by returning TupleIter.NoDataReason.UNDERFLOW; false means throw TupleIter.TimeoutException on a timeout.

Returns:

true if the timeout was set, false if the implementing class does not support a timeout.

fetchNext

public Object fetchNext()

Description copied from interface: TupleIter

Returns the next element in the iteration. If there is no next value, it returns a value from the TupleIter.NoDataReason enumeration indicating why no data was returned.

If this method returns TupleIter.NoDataReason.END_OF_DATA, no further data will be returned by this iterator unless TupleIter.restart() is called.

If this method returns TupleIter.NoDataReason.UNDERFLOW, no data is currently available, but may be come available in the future. It is possible for consecutive calls to return UNDERFLOW and then END_OF_DATA.

The object returned by this method may be re-used for each subsequent call to fetchNext(). In other words, callers must either make certain that the returned value is no longer needed or is copied before any subsequent calls to fetchNext().

Specified by:

fetchNext in interface TupleIter

Returns:

the next element in the iteration, or an instance of TupleIter.NoDataReason.

restart

public void restart()

Description copied from interface: TupleIter

Restarts this iterator, so that a subsequent call to TupleIter.fetchNext() returns the first element in the collection being iterated.

Specified by:

restart in interface TupleIter

closeAllocation

public void closeAllocation()

Description copied from interface: ClosableAllocation

Closes this object.

Specified by:

closeAllocation in interface ClosableAllocation