Class JoinIterator

java.lang.Object

org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration<BindingSet, QueryEvaluationException>

org.eclipse.rdf4j.common.iteration.LookAheadIteration<BindingSet, QueryEvaluationException>

org.eclipse.rdf4j.query.algebra.evaluation.iterator.JoinIterator

All Implemented Interfaces:

AutoCloseable, CloseableIteration<BindingSet, QueryEvaluationException>, Iteration<BindingSet, QueryEvaluationException>

public class JoinIterator
extends LookAheadIteration<BindingSet, QueryEvaluationException>

Interleaved join iterator.

This join iterator produces results by interleaving results from its left argument into its right argument to speed up bindings and produce fail-fast results. Note that this join strategy is only valid in cases where all bindings from the left argument can be considered in scope for the right argument.

Field Summary

Fields

Modifier and Type	Field	Description
private final CloseableIteration<BindingSet, QueryEvaluationException>	leftIter
private final QueryEvaluationStep	preparedRight
private CloseableIteration<BindingSet, QueryEvaluationException>	rightIter

Constructor Summary

Constructors

Constructor	Description
JoinIterator(EvaluationStrategy strategy, QueryEvaluationStep leftPrepared, QueryEvaluationStep rightPrepared, Join join, BindingSet bindings)
JoinIterator(EvaluationStrategy strategy, Join join, BindingSet bindings, QueryEvaluationContext context)

Method Summary

Modifier and Type	Method	Description
protected BindingSet	getNextElement()	Gets the next element.
protected void	handleClose()	Called by AbstractCloseableIteration.close() when it is called for the first time.

Methods inherited from class LookAheadIteration

hasNext, next, remove

Methods inherited from class AbstractCloseableIteration

close, isClosed

Methods inherited from class Object

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

Methods inherited from interface CloseableIteration

stream

Field Details

leftIter

private final CloseableIteration<BindingSet, QueryEvaluationException> leftIter

rightIter

private CloseableIteration<BindingSet, QueryEvaluationException> rightIter

preparedRight

private final QueryEvaluationStep preparedRight

Constructor Details

JoinIterator

public JoinIterator(EvaluationStrategy strategy,
 QueryEvaluationStep leftPrepared,
 QueryEvaluationStep rightPrepared,
 Join join,
 BindingSet bindings)
             throws QueryEvaluationException

Throws:

QueryEvaluationException

JoinIterator

public JoinIterator(EvaluationStrategy strategy,
 Join join,
 BindingSet bindings,
 QueryEvaluationContext context)
             throws QueryEvaluationException

Throws:

QueryEvaluationException

Method Details

getNextElement

protected BindingSet 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<BindingSet, QueryEvaluationException>

Returns:

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

Throws:

QueryEvaluationException

handleClose

protected void handleClose()
                    throws QueryEvaluationException

Description copied from class: AbstractCloseableIteration

Called by AbstractCloseableIteration.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<BindingSet, QueryEvaluationException>

Throws:

QueryEvaluationException