/**
* 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.logical.rules.rdfs;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import lupos.datastructures.items.Item;
import lupos.engine.operators.BasicOperator;
import lupos.engine.operators.OperatorIDTuple;
import lupos.engine.operators.singleinput.generate.Generate;
import lupos.engine.operators.tripleoperator.TriplePattern;
import lupos.misc.Tuple;
import lupos.optimizations.logical.rules.Rule;
public class RuleEliminateUnnecessaryGenerate extends Rule {
@Override
protected void init() {
final TriplePattern tp = new TriplePattern();
final Generate generate = new Generate();
tp.setSucceedingOperator(new OperatorIDTuple(generate, 0));
generate.setPrecedingOperator(tp);
subGraphMap = new HashMap<BasicOperator, String>();
subGraphMap.put(tp, "triplepattern");
subGraphMap.put(generate, "generate");
startNode = generate;
}
@Override
protected boolean checkPrecondition(final Map<String, BasicOperator> mso) {
final Generate generate = (Generate) mso.get("generate");
final TriplePattern tp = (TriplePattern) mso.get("triplepattern");
final Item[] itemsGenerate = generate.getValueOrVariable();
final Item[] itemsTriplePattern = tp.getItems();
for (int i = 0; i < 3; i++) {
if (!itemsGenerate[i].equals(itemsTriplePattern[i]))
return false;
}
return true;
}
@Override
public Tuple<Collection<BasicOperator>, Collection<BasicOperator>> transformOperatorGraph(
final Map<String, BasicOperator> mso,
final BasicOperator rootOperator) {
final Collection<BasicOperator> deleted = new LinkedList<BasicOperator>();
final Collection<BasicOperator> added = new LinkedList<BasicOperator>();
final Generate generate = (Generate) mso.get("generate");
final TriplePattern tp = (TriplePattern) mso.get("triplepattern");
// remove the generate operator...
for (final OperatorIDTuple oit : generate.getSucceedingOperators()) {
oit.getOperator().removePrecedingOperator(generate);
}
for (final BasicOperator bo : generate.getPrecedingOperators()) {
bo.removeSucceedingOperator(generate);
}
deleted.add(generate);
// generate.setPrecedingOperators(null);
// generate.setSucceedingOperators(null);
// are there no other operators than generate???
if (tp.getSucceedingOperators().size() == 0) {
for (final BasicOperator bo : tp.getPrecedingOperators()) {
bo.removeSucceedingOperator(tp);
}
// tp.setPrecedingOperators(null);
// tp.setSucceedingOperators(null);
deleted.add(tp);
}
if (deleted.size() > 0 || added.size() > 0)
return new Tuple<Collection<BasicOperator>, Collection<BasicOperator>>(
added, deleted);
else
return null;
}
}