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

Class DescribeIteration

java.lang.Object

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

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

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

All Implemented Interfaces:

AutoCloseable, Iterator<BindingSet>, CloseableIteration<BindingSet>

Direct Known Subclasses:

FederatedDescribeIteration

public class DescribeIteration
extends LookAheadIteration<BindingSet>

Iteration that implements a simplified version of Symmetric Concise Bounded Description (omitting reified statements).

Author:

Jeen Broekstra

See Also:

• Concise Bounded Description - alternatives

Field Summary

Fields

Modifier and Type	Field	Description
protected BindingSet	parentBindings
protected static final String	VARNAME_OBJECT
protected static final String	VARNAME_PREDICATE
protected static final String	VARNAME_SUBJECT

Constructor Summary

Constructors

Constructor	Description
DescribeIteration(CloseableIteration<BindingSet> sourceIter, EvaluationStrategy strategy, Set<String> describeExprNames, BindingSet parentBindings)

Method Summary

Modifier and Type	Method	Description
protected CloseableIteration<BindingSet>	createNextIteration(Value subject, Value object)
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 org.eclipse.rdf4j.common.iteration.LookAheadIteration

hasNext, next, remove

Methods inherited from class org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration

close, isClosed

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eclipse.rdf4j.common.iteration.CloseableIteration

stream

Methods inherited from interface java.util.Iterator

forEachRemaining

Field Details

VARNAME_SUBJECT

protected static final String VARNAME_SUBJECT

See Also:

• Constant Field Values

VARNAME_PREDICATE

protected static final String VARNAME_PREDICATE

See Also:

• Constant Field Values

VARNAME_OBJECT

protected static final String VARNAME_OBJECT

See Also:

• Constant Field Values

parentBindings

protected BindingSet parentBindings

Constructor Details

DescribeIteration

public DescribeIteration(CloseableIteration<BindingSet> sourceIter,
 EvaluationStrategy strategy,
 Set<String> describeExprNames,
 BindingSet parentBindings)

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>

Returns:

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

Throws:

QueryEvaluationException

createNextIteration

protected CloseableIteration<BindingSet> createNextIteration(Value subject,
 Value object)
                                                      throws QueryEvaluationException

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.

Specified by:

handleClose in class AbstractCloseableIteration<BindingSet>

Throws:

QueryEvaluationException