/*
* $Header$
* $Revision: 982 $
* $Date: 2006-12-08 18:42:51 +1000 (Fri, 08 Dec 2006) $
*
* ====================================================================
*
* 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.relation.operation.mem.project;
import org.jrdf.graph.Node;
import org.jrdf.query.relation.Attribute;
import org.jrdf.query.relation.EvaluatedRelation;
import org.jrdf.query.relation.RelationFactory;
import org.jrdf.query.relation.Tuple;
import org.jrdf.query.relation.TupleFactory;
import org.jrdf.query.relation.operation.Project;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
* Implements restrict by going through the relation and removing the columns.
*
* @author Andrew Newman
* @version $Revision:$
*/
public class ProjectImpl implements Project {
private final TupleFactory tupleFactory;
private final RelationFactory relationFactory;
public ProjectImpl(TupleFactory newTupleFactory, RelationFactory newRelationFactory) {
this.tupleFactory = newTupleFactory;
this.relationFactory = newRelationFactory;
}
public EvaluatedRelation include(EvaluatedRelation relation, Set<Attribute> attributes) {
// TODO (AN) Test drive short circuit
if (relation.getHeading().equals(attributes)) {
return relation;
}
Set<Attribute> newHeading = relation.getHeading();
newHeading.retainAll(attributes);
return project(relation, newHeading);
}
public EvaluatedRelation exclude(EvaluatedRelation relation, Set<Attribute> attributes) {
// TODO (AN) Test drive short circuit
if (attributes.isEmpty()) {
return relation;
}
Set<Attribute> newHeading = relation.getHeading();
newHeading.removeAll(attributes);
return project(relation, newHeading);
}
private EvaluatedRelation project(EvaluatedRelation relation, Set<Attribute> newHeading) {
Set<Tuple> newTuples = new HashSet<Tuple>();
Set<Tuple> tuples = relation.getTuples();
for (Tuple tuple : tuples) {
Tuple newTuple = createNewTuples(tuple, newHeading);
// TODO (AN) Only add non empty attributes - this failed.
if (!newTuple.getAttributeValues().isEmpty()) {
newTuples.add(newTuple);
}
}
// TODO (AN) Used to just be getRelation(newHeading) - this failed.
return relationFactory.getRelation(newHeading, newTuples);
}
private Tuple createNewTuples(Tuple tuple, Set<Attribute> newHeading) {
Map<Attribute, Node> avps = tuple.getAttributeValues();
Map<Attribute, Node> newAvps = new HashMap<Attribute, Node>();
for (Map.Entry<Attribute, Node> entry : avps.entrySet()) {
if (newHeading.contains(entry.getKey())) {
newAvps.put(entry.getKey(), entry.getValue());
}
}
return tupleFactory.getTuple(newAvps);
}
}