/**
* 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.optimizations.physical.joinorder.staticanalysis.scoring.triplepattern;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedList;
import lupos.datastructures.items.Variable;
import lupos.datastructures.queryresult.QueryResult;
import lupos.engine.operators.index.BasicIndexScan;
import lupos.engine.operators.tripleoperator.TriplePattern;
/**
* This class implements the scoring for least entries by determining the number of results of a triple pattern
*/
public class ScoringTriplePatternLeastEntries implements ScoringTriplePattern<HashSet<Variable>> {
@Override
public int determineScore(final BasicIndexScan indexScan,
final TriplePattern triplePattern, final HashSet<Variable> additonalInformation) {
// just do dirty trick to determine the number of results of a triple pattern...
final LinkedList<TriplePattern> tpc = new LinkedList<TriplePattern>();
tpc.add(triplePattern);
final Collection<TriplePattern> zTP = indexScan.getTriplePattern();
indexScan.setTriplePatterns(tpc);
final QueryResult queryResult = indexScan.join(indexScan.getRoot().dataset);
indexScan.setTriplePatterns(zTP);
final int entries = (queryResult==null)? 0 : queryResult.oneTimeSize();
return entries;
}
@Override
public boolean scoreIsAscending() {
return true;
}
}