/**
* 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
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*/
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.datastructures.items.Variable;
import lupos.engine.operators.BasicOperator;
import lupos.engine.operators.OperatorIDTuple;
import lupos.engine.operators.messages.BoundVariablesMessage;
import lupos.engine.operators.singleinput.Projection;
import lupos.engine.operators.singleinput.ReplaceLit;
import lupos.engine.operators.singleinput.ReplaceVar;
import lupos.engine.operators.tripleoperator.TriplePattern;
import lupos.misc.Tuple;
import lupos.optimizations.logical.rules.Rule;
public class RuleOptimizeReplaceByPat extends Rule {
@Override
protected void init() {
final TriplePattern pat = new TriplePattern();
final ReplaceVar replaceVar = new ReplaceVar();
pat.setSucceedingOperator(new OperatorIDTuple(replaceVar, 0));
replaceVar.setPrecedingOperator(pat);
subGraphMap = new HashMap<BasicOperator, String>();
subGraphMap.put(pat, "pat");
subGraphMap.put(replaceVar, "replaceVar");
startNode = replaceVar;
}
@Override
protected boolean checkPrecondition(final Map<String, BasicOperator> mso) {
final TriplePattern pat = (TriplePattern) mso.get("pat");
// Because of time aspects triplepattern should not have more than one
// successor
if (pat.getSucceedingOperators().size() != 1) {
return false;
}
final ReplaceVar replaceVar = (ReplaceVar) mso.get("replaceVar");
BasicOperator op = replaceVar.getSucceedingOperators().get(0)
.getOperator();
// Ignore ReplaceLit and get the Projection
if (op instanceof ReplaceLit) {
op = op.getSucceedingOperators().get(0).getOperator();
}
if (!(op instanceof Projection)) {
System.err
.println("Replace has not Projection as direct successor or after its ReplaceLit => Correct RuleOptimizeReplaceByPat!!!");
return false;
} else {
final Projection proj = (Projection) op;
final Object[] projVars = proj.getProjectedVariables().toArray();
final Item[] patItems = pat.getItems();
for (int i = 0; i < patItems.length; i++) {
// Only if a variable in TriplePattern is not projected later
// (TP creates temporary tuples)
if (patItems[i].isVariable()) {
if (!arrayContains(projVars, (Variable) patItems[i])) {
return true;
}
}
}
}
return false;
}
@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 TriplePattern pat = (TriplePattern) mso.get("pat");
final ReplaceVar replaceVar = (ReplaceVar) mso.get("replaceVar");
BasicOperator op = replaceVar.getSucceedingOperators().get(0)
.getOperator();
if (op instanceof ReplaceLit) {
op = op.getSucceedingOperators().get(0).getOperator();
}
final Projection proj = (Projection) op;
final LinkedList<Variable> replaceVarLeft = replaceVar
.getSubstitutionsVariableLeft();
final LinkedList<Variable> replaceVarRight = replaceVar
.getSubstitutionsVariableRight();
final Object[] projVars = proj.getProjectedVariables().toArray();
final Item[] patItems = pat.getItems();
Variable var;
Variable newTripleVar;
// Before transformation: TriplePattern generates (p,lit) ,
// ReplaceVar makes (y,lit) [because it has the tupel (y,p)] and
// the Projection deletes (p,lit)
// => Transformation replaces p by y in TriplePattern directly
for (int i = 0; i < patItems.length; i++) {
if (patItems[i].isVariable()) {
var = (Variable) patItems[i];
if (!arrayContains(projVars, var)) {
final LinkedList<Integer> indices = getPositions(
replaceVarRight, var);
// Variable can be substituted by a ReplaceVar-variable
if (indices.size() > 0) {
newTripleVar = replaceVarLeft.get(indices.getFirst());
// Replacement in TriplePattern
pat.replace(var, newTripleVar);
// Replacement same Replacement in ReplaceVar
for (int a = 1; a < indices.size(); a++) {
replaceVarRight.set(indices.get(a), newTripleVar);
}
// Delete the Tupel for Replacement
replaceVar.removeSubstitutionVars(indices.getFirst());
}
}
}
}
// Delete empty ReplaceVar
if (replaceVar.getSubstitutionsVariableLeft().size() == 0) {
final OperatorIDTuple succ = replaceVar.getSucceedingOperators()
.get(0);
pat.addSucceedingOperator(succ);
pat.removeSucceedingOperator(replaceVar);
succ.getOperator().removePrecedingOperator(replaceVar);
succ.getOperator().addPrecedingOperator(pat);
rootOperator.deleteParents();
rootOperator.setParents();
rootOperator.detectCycles();
rootOperator.sendMessage(new BoundVariablesMessage());
deleted.add(replaceVar);
}
if (deleted.size() > 0 || added.size() > 0)
return new Tuple<Collection<BasicOperator>, Collection<BasicOperator>>(
added, deleted);
else
return null;
}
private LinkedList<Integer> getPositions(
final LinkedList<Variable> replaceVarRight, final Variable var) {
final LinkedList<Integer> pos = new LinkedList<Integer>();
for (int i = 0; i < replaceVarRight.size(); i++) {
if (replaceVarRight.get(i).equals(var)) {
pos.add(i);
}
}
return pos;
}
private boolean arrayContains(final Object[] vars, final Variable var) {
for (int i = 0; i < vars.length; i++) {
if (vars[i].equals(var))
return true;
}
return false;
}
}