/**
* 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.singleinput;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import lupos.datastructures.bindings.Bindings;
import lupos.datastructures.bindings.BindingsFactory;
import lupos.datastructures.items.Variable;
import lupos.datastructures.queryresult.ParallelIterator;
import lupos.datastructures.queryresult.QueryResult;
import lupos.engine.operators.messages.BindingsFactoryMessage;
import lupos.engine.operators.messages.BoundVariablesMessage;
import lupos.engine.operators.messages.Message;
public class Projection extends SingleInputOperator {
private final HashSet<Variable> s = new HashSet<Variable>();
protected BindingsFactory bindingsFactory;
public Projection() {
}
public void addProjectionElement(final Variable var) {
if (!this.s.contains(var)) {
this.s.add(var);
}
}
public HashSet<Variable> getProjectedVariables() {
return this.s;
}
/**
* Handles the BoundVariablesMessage by removing all variables from it that
* are not projected to.
*
* @param msg
* The BoundVariablesMessage
* @return The modified message
*/
@Override
public Message preProcessMessage(final BoundVariablesMessage msg) {
final BoundVariablesMessage result = new BoundVariablesMessage(msg);
for (final Variable v : msg.getVariables()) {
if (this.s.contains(v)) {
result.getVariables().add(v);
}
}
this.unionVariables = result.getVariables();
this.intersectionVariables = result.getVariables();
return result;
}
@Override
public Message preProcessMessage(final BindingsFactoryMessage msg){
this.bindingsFactory = msg.getBindingsFactory();
return msg;
}
@Override
public QueryResult process(final QueryResult bindings, final int operandID) {
final Iterator<Bindings> itb = new ParallelIterator<Bindings>() {
final Iterator<Bindings> itbold = bindings.oneTimeIterator();
@Override
public boolean hasNext() {
return this.itbold.hasNext();
}
@Override
public Bindings next() {
if (!this.itbold.hasNext()) {
return null;
}
final Bindings bind1 = this.itbold.next();
if (!this.itbold.hasNext()) {
if (this.itbold instanceof ParallelIterator) {
((ParallelIterator) this.itbold).close();
}
}
final Bindings bnew = Projection.this.bindingsFactory.createInstance();
final Iterator<Variable> it = Projection.this.s.iterator();
while (it.hasNext()) {
final Variable elem = it.next();
bnew.add(elem, bind1.get(elem));
}
bnew.addAllTriples(bind1);
bnew.addAllPresortingNumbers(bind1);
return bnew;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void finalize() {
this.close();
}
@Override
public void close() {
if (this.itbold instanceof ParallelIterator) {
((ParallelIterator) this.itbold).close();
}
}
};
return QueryResult.createInstance(itb);
}
@Override
public String toString() {
return super.toString()+" to " + this.s;
}
@Override
public boolean remainsSortedData(final Collection<Variable> sortCriterium){
return true;
}
}