/**
* Extended find interface used in situations where the implementator may or may not be able to
* answer the complete query. It will attempt to answer the pattern but if its answers are not
* known to be complete then it will also pass the request on to the nested Finder to append more
* results.
*
* @param pattern a TriplePattern to be matched against the data
* @param continuation either a Finder or a normal Graph which will be asked for additional match
* results if the implementor may not have completely satisfied the query.
*/
@Override
public ExtendedIterator<Triple> findWithContinuation(TriplePattern pattern, Finder continuation) {
if (graph == null) return new NullIterator<Triple>();
if (continuation == null) {
return graph.find(pattern.asTripleMatch());
} else {
return graph.find(pattern.asTripleMatch()).andThen(continuation.find(pattern));
}
}
public static ExtendedIterator predicatesFor(Graph g, Node s, Node o) {
Set predicates = CollectionFactory.createHashedSet();
ClosableIterator it = g.find(s, Node.ANY, o);
while (it.hasNext()) predicates.add(((Triple) it.next()).getPredicate());
return WrappedIterator.createNoRemove(predicates.iterator());
}
/**
* Basic pattern lookup interface.
*
* @param pattern a TriplePattern to be matched against the data
* @return a ClosableIterator over all Triples in the data set that match the pattern
*/
@Override
public ExtendedIterator<Triple> find(TriplePattern pattern) {
if (graph == null) return new NullIterator<Triple>();
return graph.find(pattern.asTripleMatch());
}
public static ExtendedIterator subjectsFor(Graph g, Node p, Node o) {
Set objects = CollectionFactory.createHashedSet();
ClosableIterator it = g.find(Node.ANY, p, o);
while (it.hasNext()) objects.add(((Triple) it.next()).getSubject());
return WrappedIterator.createNoRemove(objects.iterator());
}