/**
* 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.mergeunion;
import java.util.Collection;
import java.util.Comparator;
import lupos.datastructures.bindings.Bindings;
import lupos.datastructures.items.Variable;
import lupos.datastructures.items.literal.Literal;
/**
* This operator computes the union of its operands.
* The input of this operator must be sorted according to a given sort criterium.
* The sorted order remains also in the output.
*/
public class MergeUnion extends ComparatorMergeUnion {
protected final Collection<Variable> sortCriterium;
/**
* @param sortCriterium the sort criterium after which the input of this operator must be sorted. Furthermore, the result of this operator follows this sort criterium.
*/
public MergeUnion(final Collection<Variable> sortCriterium) {
super(new Comparator<Bindings>() {
@Override
public int compare(final Bindings o1, final Bindings o2) {
for (final Variable var : sortCriterium) {
final Literal l1 = o1.get(var);
final Literal l2 = o2.get(var);
if (l1 != null && l2 != null) {
final int compare = l1
.compareToNotNecessarilySPARQLSpecificationConform(l2);
if (compare != 0) {
return compare;
}
} else if (l1 != null) {
return -1;
} else if (l2 != null) {
return 1;
}
}
return 0;
}
@Override
public String toString() {
return "Comparator on " + sortCriterium;
}
});
this.sortCriterium = sortCriterium;
}
/**
* @return the sort criterium after which the input of this operator must be sorted. Furthermore, the result of this operator follows this sort criterium.
*/
public Collection<Variable> getSortCriterium(){
return this.sortCriterium;
}
}