/**
* Copyright (c) 2013, Institute of Information Systems (Sven Groppe and contributors of LUPOSDATE), University of Luebeck
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
* following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this list of conditions and the following
* disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other materials provided with the distribution.
* - Neither the name of the University of Luebeck nor the names of its contributors may be used to endorse or promote
* products derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package lupos.engine.operators.index.adaptedRDF3X;
import java.io.Serializable;
import java.util.Comparator;
import lupos.datastructures.dbmergesortedds.heap.Heap;
import lupos.datastructures.dbmergesortedds.heap.SequentialHeap;
import lupos.datastructures.items.Triple;
import lupos.datastructures.items.TripleComparator;
import lupos.misc.util.ImmutableIterator;
public class MergeIndicesTripleIterator extends ImmutableIterator<Triple> {
private final Comparator<Triple> comparator;
private final Heap<HeapEntry> heap;
private int idOfLastElement;
public MergeIndicesTripleIterator(final IndicesTripleIterator[] itia,
final RDF3XIndexScan.CollationOrder collationOrder) {
this.comparator = new TripleComparator(collationOrder);
this.heap = new SequentialHeap<HeapEntry>(itia.length, true);
for (int i = 0; i < itia.length; i++) {
if (itia[i] != null) {
final Triple t = itia[i].next();
if (t != null) {
this.heap.add(new HeapEntry(t, itia[i]));
}
}
}
}
@Override
public boolean hasNext() {
return !(this.heap.isEmpty());
}
@Override
public Triple next() {
if (this.heap.isEmpty()) {
return null;
}
final HeapEntry next = this.heap.pop();
if (next != null) {
final Triple t = next.itt.next();
if (t != null) {
this.heap.add(new HeapEntry(t, next.itt));
}
this.idOfLastElement = next.itt.getId();
return next.t;
}
return null;
}
public int getIdOfLastElement() {
return this.idOfLastElement;
}
private class HeapEntry implements Comparable<HeapEntry>, Serializable {
Triple t;
IndicesTripleIterator itt;
public HeapEntry(final Triple t, final IndicesTripleIterator itt) {
this.t = t;
this.itt = itt;
}
public HeapEntry(final IndicesTripleIterator itt) {
this.itt = itt;
this.t = itt.next();
}
@Override
public int compareTo(final HeapEntry arg0) {
return MergeIndicesTripleIterator.this.comparator.compare(this.t, arg0.t);
}
}
public int getMaxId() {
return this.heap.maxLength();
}
}