org.openrdf.query.algebra.evaluation.federation

Class JoinExecutorBase<T>

java.lang.Object

info.aduna.iteration.CloseableIterationBase<E,X>

info.aduna.iteration.LookAheadIteration<T,QueryEvaluationException>

org.openrdf.query.algebra.evaluation.federation.JoinExecutorBase<T>

All Implemented Interfaces:

CloseableIteration<T,QueryEvaluationException>, Iteration<T,QueryEvaluationException>

Direct Known Subclasses:

ServiceFallbackIteration, ServiceJoinIterator

public abstract class JoinExecutorBase<T>
extends LookAheadIteration<T,QueryEvaluationException>

Base class for any join parallel join executor. Note that this class extends LookAheadIteration and thus any implementation of this class is applicable for pipelining when used in a different thread (access to shared variables is synchronized).

Author:

Andreas Schwarte

Field Summary

Fields

Modifier and Type	Field and Description
protected BindingSet	bindings
protected boolean	closed
protected boolean	finished
protected CloseableIteration<T,QueryEvaluationException>	leftIter
protected static int	NEXT_JOIN_ID
protected TupleExpr	rightArg
protected CloseableIteration<T,QueryEvaluationException>	rightIter
protected QueueCursor<CloseableIteration<T,QueryEvaluationException>>	rightQueue

Constructor Summary

Constructors

Constructor and Description
JoinExecutorBase(CloseableIteration<T,QueryEvaluationException> leftIter, TupleExpr rightArg, BindingSet bindings)

Method Summary

Modifier and Type	Method and Description
void	addResult(CloseableIteration<T,QueryEvaluationException> res)
void	done()
T	getNextElement() Gets the next element.
protected abstract void	handleBindings() Implementations must implement this method to handle bindings.
void	handleClose() Called by CloseableIterationBase.close() when it is called for the first time.
boolean	isFinished() Gets whether this executor is finished or aborted.
void	run()
void	toss(Exception e)

Methods inherited from class info.aduna.iteration.LookAheadIteration

hasNext, next, remove

Methods inherited from class info.aduna.iteration.CloseableIterationBase

close, isClosed

Methods inherited from class java.lang.Object

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

Field Detail

NEXT_JOIN_ID

protected static int NEXT_JOIN_ID

rightArg

protected final TupleExpr rightArg

bindings

protected final BindingSet bindings

leftIter

protected CloseableIteration<T,QueryEvaluationException> leftIter

rightIter

protected CloseableIteration<T,QueryEvaluationException> rightIter

closed

protected volatile boolean closed

finished

protected boolean finished

rightQueue

protected final QueueCursor<CloseableIteration<T,QueryEvaluationException>> rightQueue

Constructor Detail

JoinExecutorBase

public JoinExecutorBase(CloseableIteration<T,QueryEvaluationException> leftIter,
                        TupleExpr rightArg,
                        BindingSet bindings)
                 throws QueryEvaluationException

Throws:

QueryEvaluationException

Method Detail

run

public final void run()

handleBindings

protected abstract void handleBindings()
                                throws Exception

Implementations must implement this method to handle bindings. Use the following as a template while (!closed && leftIter.hasNext()) { // your code } and add results to rightQueue. Note that addResult() is implemented synchronized and thus thread safe. In case you can guarantee sequential access, it is also possible to directly access rightQueue

Throws:

Exception

addResult

public void addResult(CloseableIteration<T,QueryEvaluationException> res)

done

public void done()

toss

public void toss(Exception e)

getNextElement

public T getNextElement()
                 throws QueryEvaluationException

Description copied from class: LookAheadIteration

Gets the next element. Subclasses should implement this method so that it returns the next element.

Specified by:

getNextElement in class LookAheadIteration<T,QueryEvaluationException>

Returns:

The next element, or null if no more elements are available.

Throws:

QueryEvaluationException

handleClose

public void handleClose()
                 throws QueryEvaluationException

Description copied from class: CloseableIterationBase

Called by CloseableIterationBase.close() when it is called for the first time. This method is only called once on each iteration. By default, this method does nothing.

Overrides:

handleClose in class LookAheadIteration<T,QueryEvaluationException>

Throws:

QueryEvaluationException

isFinished

public boolean isFinished()

Gets whether this executor is finished or aborted.

Returns:

true if this executor is finished or aborted