/**
* 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.modifiers;
import java.util.Iterator;
import lupos.datastructures.bindings.Bindings;
import lupos.datastructures.queryresult.ParallelIterator;
import lupos.datastructures.queryresult.QueryResult;
import lupos.engine.operators.singleinput.SingleInputOperator;
import lupos.engine.operators.singleinput.sort.comparator.ComparatorBindings;
import lupos.misc.util.ImmutableIterator;
public class SortLimit extends SingleInputOperator {
private ComparatorBindings comparator;
private Bindings[] smallestBindings;
private Bindings max = null;
private int posMax = -1;
private int pos = 0;
public SortLimit(final ComparatorBindings comparator, final int limit) {
this.setComparator(comparator);
this.setLimit(limit);
}
public SortLimit() {
this.comparator=null;
this.smallestBindings=null;
}
public void setComparator(final ComparatorBindings comp){
this.comparator=comp;
}
public void setLimit(final int limit){
this.smallestBindings = new Bindings[limit];
}
@Override
public QueryResult process(final QueryResult bindings, final int operandID) {
final Iterator<Bindings> itb = bindings.oneTimeIterator();
while (this.pos < this.smallestBindings.length && itb.hasNext()) {
final Bindings b = itb.next();
if (this.max == null || this.comparator.compare(b, this.max) > 0) {
this.posMax = this.pos;
this.max = b;
}
this.smallestBindings[this.pos++] = b;
}
if (itb.hasNext()) {
while (itb.hasNext()) {
final Bindings b = itb.next();
if (this.comparator.compare(b, this.max) < 0) {
this.smallestBindings[this.posMax] = b;
this.max = b;
// find new maximum
for (int i = 0; i < this.smallestBindings.length; i++) {
if (this.comparator.compare(this.smallestBindings[i], this.max) > 0) {
this.max = this.smallestBindings[i];
this.posMax = i;
}
}
}
}
}
if (itb instanceof ParallelIterator) {
((ParallelIterator<Bindings>) itb).close();
}
return QueryResult.createInstance(new ImmutableIterator<Bindings>() {
int i = 0;
@Override
public boolean hasNext() {
return this.i < SortLimit.this.pos;
}
@Override
public Bindings next() {
if (this.hasNext()) {
return SortLimit.this.smallestBindings[this.i++];
} else {
return null;
}
}
});
}
@Override
public String toString() {
return super.toString()+" " + this.smallestBindings.length;
}
}