/**
* 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;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import lupos.datastructures.items.Variable;
import lupos.engine.operators.BasicOperator;
import lupos.engine.operators.Operator;
import lupos.engine.operators.OperatorIDTuple;
import lupos.engine.operators.messages.BoundVariablesMessage;
import lupos.engine.operators.multiinput.join.Join;
import lupos.misc.Tuple;
/**
* super class for all those rules, the left side of which is
*
* operator | filter
**/
public class RuleMakeBinaryJoin extends Rule {
public RuleMakeBinaryJoin() {
super();
}
@Override
protected void init() {
// Define left side of rule
final Operator a = new Join();
subGraphMap = new HashMap<BasicOperator, String>();
subGraphMap.put(a, "join");
startNode = a;
}
@Override
protected boolean checkPrecondition(final Map<String, BasicOperator> mso) {
final Join join = (Join) mso.get("join");
if (join.getNumberOfOperands() > 2)
return true;
else
return false;
}
@Override
protected 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 Join join = (Join) mso.get("join");
final List<BasicOperator> ctp = join.getPrecedingOperators();
final BasicOperator finalJoin = getBinaryJoin(ctp, added);
finalJoin.setSucceedingOperators(join.getSucceedingOperators());
rootOperator.deleteParents();
rootOperator.setParents();
rootOperator.detectCycles();
rootOperator.sendMessage(new BoundVariablesMessage());
deleted.add(join);
if (deleted.size() > 0 || added.size() > 0)
return new Tuple<Collection<BasicOperator>, Collection<BasicOperator>>(
added, deleted);
else
return null;
}
public BasicOperator getBinaryJoin(final List<BasicOperator> ctp,
final Collection<BasicOperator> added) {
final Collection<BasicOperator> newOrder = optimizeJoinOrderAccordingToMostRestrictionsForMergeJoin(ctp);
final Collection<BasicOperator> remainingJoins = new LinkedList<BasicOperator>();
final Iterator<BasicOperator> itp = newOrder.iterator();
while (itp.hasNext()) {
final BasicOperator first = itp.next();
if (itp.hasNext()) {
final Join newJoin = new Join();
added.add(newJoin);
first.setSucceedingOperator(new OperatorIDTuple(newJoin, 0));
final BasicOperator second = itp.next();
second.setSucceedingOperator(new OperatorIDTuple(newJoin, 1));
final HashSet<Variable> hv = new HashSet<Variable>();
hv.addAll(first.getUnionVariables());
hv.addAll(second.getUnionVariables());
newJoin.setUnionVariables(hv);
remainingJoins.add(newJoin);
} else {
remainingJoins.add(first);
}
}
while (remainingJoins.size() > 1) {
// choose best combination
final Collection<BasicOperator> co = getNextJoin(remainingJoins);
final Iterator<BasicOperator> io = co.iterator();
final BasicOperator first = io.next();
final BasicOperator second = io.next();
final Join join = new Join();
added.add(join);
join.setIntersectionVariables(new HashSet<Variable>());
join.setUnionVariables(new HashSet<Variable>());
join.getUnionVariables().addAll(first.getUnionVariables());
join.getUnionVariables().addAll(second.getUnionVariables());
first.setSucceedingOperator(new OperatorIDTuple(join, 0));
second.setSucceedingOperator(new OperatorIDTuple(join, 1));
remainingJoins.remove(first);
remainingJoins.remove(second);
remainingJoins.add(join);
}
return remainingJoins.iterator().next();
}
private Collection<BasicOperator> optimizeJoinOrderAccordingToMostRestrictionsForMergeJoin(
final List<BasicOperator> remaining) {
final Collection<BasicOperator> newOrder = new LinkedList<BasicOperator>();
while (remaining.size() > 1) {
BasicOperator best1 = null;
BasicOperator best2 = null;
int minOpenPositions = 4;
for (final BasicOperator bo1 : remaining) {
for (final BasicOperator bo2 : remaining) {
if (!bo1.equals(bo2)) {
final Collection<Variable> v = bo1.getUnionVariables();
v.retainAll(bo2.getUnionVariables());
final int openPositions = bo1.getUnionVariables()
.size()
- v.size();
if (openPositions < minOpenPositions) {
minOpenPositions = openPositions;
best1 = bo1;
best2 = bo2;
}
}
}
}
newOrder.add(best1);
newOrder.add(best2);
remaining.remove(best1);
remaining.remove(best2);
}
if (remaining.size() == 1) {
for (final BasicOperator bo1 : remaining) {
newOrder.add(bo1);
}
}
return newOrder;
}
private Collection<BasicOperator> getNextJoin(
final Collection<BasicOperator> remainingJoins) {
final Collection<BasicOperator> co = new LinkedList<BasicOperator>();
BasicOperator best1 = null;
BasicOperator best2 = null;
int minCommonVariables = -1;
for (final BasicOperator o1 : remainingJoins) {
for (final BasicOperator o2 : remainingJoins) {
if (!o1.equals(o2)) {
final Collection<Variable> v = o1.getUnionVariables();
v.retainAll(o2.getUnionVariables());
final int commonVariables = v.size();
if (commonVariables > minCommonVariables) {
minCommonVariables = commonVariables;
best1 = o1;
best2 = o2;
}
}
}
}
co.add(best1);
co.add(best2);
return co;
}
@Override
public String getName() {
return "Binary Join";
}
}