/*
* $Header$
* $Revision: 3191 $
* $Date: 2009-11-11 05:54:46 +1000 (Wed, 11 Nov 2009) $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2003-2009 The JRDF Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. 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.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* the JRDF Project (http://jrdf.sf.net/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The JRDF Project" and "JRDF" must not be used to endorse
* or promote products derived from this software without prior written
* permission. For written permission, please contact
* newmana@users.sourceforge.net.
*
* 5. Products derived from this software may not be called "JRDF"
* nor may "JRDF" appear in their names without prior written
* permission of the JRDF Project.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
* ITS 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the JRDF Project. For more
* information on JRDF, please see <http://jrdf.sourceforge.net/>.
*
*/
package org.jrdf.query;
import org.jrdf.graph.Graph;
import org.jrdf.query.answer.Answer;
import org.jrdf.query.answer.AskAnswerImpl;
import org.jrdf.query.execute.ExpressionSimplifier;
import org.jrdf.query.execute.ExpressionSimplifierImpl;
import org.jrdf.query.execute.QueryEngine;
import org.jrdf.query.expression.Expression;
import org.jrdf.query.relation.EvaluatedRelation;
import org.jrdf.query.relation.mem.GraphRelationFactory;
import static org.jrdf.util.param.ParameterUtil.checkNotNull;
/**
* @author Yuan-Fang Li
* @version $Id: AskQueryImpl.java 3191 2009-11-10 19:54:46Z newmana $
*/
public class AskQueryImpl implements Query {
private Expression expression;
private final GraphRelationFactory graphRelationFactory;
public AskQueryImpl(Expression newExpression, GraphRelationFactory newGraphRelationFactory) {
checkNotNull(newExpression, newGraphRelationFactory);
this.expression = newExpression;
this.graphRelationFactory = newGraphRelationFactory;
}
public Expression getNext() {
return expression;
}
public Answer executeQuery(Graph graph, QueryEngine queryEngine) {
checkNotNull(graph, queryEngine);
long timeStarted = System.currentTimeMillis();
boolean result = getResult(graph, queryEngine);
return new AskAnswerImpl(System.currentTimeMillis() - timeStarted, result);
}
private boolean getResult(Graph graph, QueryEngine queryEngine) {
EvaluatedRelation entireGraph = graphRelationFactory.createRelation(graph);
queryEngine.initialiseBaseRelation(entireGraph);
ExpressionSimplifier<Void> simplifier = new ExpressionSimplifierImpl();
expression.accept(simplifier);
expression = simplifier.getExpression();
if (simplifier.parseAgain()) {
expression.accept(simplifier);
expression = simplifier.getExpression();
}
EvaluatedRelation relation = expression.accept(queryEngine);
return !relation.isEmpty();
}
}