/**
* 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.multiinput.join.parallel;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import lupos.datastructures.bindings.Bindings;
import lupos.datastructures.queryresult.ParallelIterator;
import lupos.datastructures.queryresult.QueryResult;
import lupos.engine.operators.Operator;
public class ResultCollector extends Operator implements
ParallelIterator<Bindings> {
private static final long serialVersionUID = 1L;
protected final Lock lock = new ReentrantLock();
protected final Condition insertCondition = this.lock.newCondition();
protected int numberOfThreads;
protected int countThreads;
protected List<QueryResult> resultList = new ArrayList<QueryResult>();
private Iterator<Bindings> currentIter;
@Override
public QueryResult process(final QueryResult res, final int arg1) {
this.lock.lock();
try {
this.resultList.add(res);
this.insertCondition.signalAll();
} finally {
this.lock.unlock();
}
return null;
}
public QueryResult getResult() {
return QueryResult.createInstance(this);
}
public void incNumberOfThreads() {
this.lock.lock();
try {
this.countThreads++;
this.insertCondition.signalAll();
} finally {
this.lock.unlock();
}
}
public void setNumberOfThreads(final int numberOfThreads) {
this.numberOfThreads = numberOfThreads;
// does not work for optional: resultList.clear();
this.currentIter = null;
this.countThreads = 0;
}
/**
* If the list is empty and not all threads are ready, wait. If all threads
* are done, move to the last element.
*/
@Override
public boolean hasNext() {
if (this.currentIter != null && this.currentIter.hasNext()) {
// if the iterator from the current QS is not empty
return true;
}
// if the iterator from the current QS is empty and jet QS are
// available renew the currentIter
this.lock.lock();
try {
// list is empty look for new threads
while (this.countThreads < this.numberOfThreads || !this.resultList.isEmpty()) {
// list is empty => wait and let the Threads proceed
while (this.resultList.isEmpty() && this.countThreads < this.numberOfThreads) {
try {
this.insertCondition.await();
} catch (final InterruptedException ignore) { // ignore exception
}
}
// now another result is available
while (!this.resultList.isEmpty()) {
// take the first element
final QueryResult res = this.resultList.remove(0);
if (res != null) {
this.currentIter = res.oneTimeIterator();
if (this.currentIter.hasNext()) {
return true;
}
}
}
}
} finally {
this.lock.unlock();
}
return false;
}
@Override
public Bindings next() {
if (hasNext()) {
return this.currentIter.next();
} else {
return null;
}
}
@Override
public void remove() {
throw new UnsupportedOperationException(
"can not remove from QueryResults");
}
protected void waitForAllThreads() {
this.lock.lock();
try {
while (this.countThreads < this.numberOfThreads) {
try {
this.insertCondition.await();
} catch (final InterruptedException e1) { // ignore exception
}
}
} finally {
this.lock.unlock();
}
}
@Override
public void close() {
waitForAllThreads();
}
@Override
public void finalize() {
close();
}
}