/*
* $Header$
* $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
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*
* 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
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* ====================================================================
*
* 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/>.
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*/
package org.jrdf.query.relation.operation.mem.common;
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.TupleComparator;
import static org.jrdf.query.relation.constants.RelationDEE.RELATION_DEE;
import static org.jrdf.query.relation.constants.RelationDUM.RELATION_DUM;
import org.jrdf.query.relation.operation.mem.join.TupleEngine;
import static org.jrdf.util.param.ParameterUtil.checkNotNull;
import java.util.Iterator;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
/**
* Common tuple processing code - gets headings and then processes tuples using the tuple engine.
*/
public final class RelationProcessorImpl implements RelationProcessor {
private final RelationFactory relationFactory;
private final TupleComparator tupleComparator;
public RelationProcessorImpl(RelationFactory newRelationFactory, TupleComparator newTupleComparator) {
checkNotNull(newRelationFactory, newTupleComparator);
this.relationFactory = newRelationFactory;
this.tupleComparator = newTupleComparator;
}
public EvaluatedRelation processRelations(Set<EvaluatedRelation> relations, TupleEngine tupleEngine) {
Iterator<EvaluatedRelation> iterator = relations.iterator();
EvaluatedRelation relation1 = iterator.next();
EvaluatedRelation relation2 = iterator.next();
EvaluatedRelation resultRelation = processRelationPairs(tupleEngine, relation1, relation2);
while (iterator.hasNext()) {
EvaluatedRelation nextRelation = iterator.next();
resultRelation = processRelationPairs(tupleEngine, resultRelation, nextRelation);
}
return convertToConstants(resultRelation);
}
private EvaluatedRelation processRelationPairs(TupleEngine tupleEngine, EvaluatedRelation relation1,
EvaluatedRelation relation2) {
SortedSet<Attribute> headings = tupleEngine.getHeading(relation1, relation2);
SortedSet<Tuple> result = new TreeSet<Tuple>(tupleComparator);
tupleEngine.processRelations(headings, relation1, relation2, result);
return relationFactory.getRelation(headings, result);
}
public EvaluatedRelation convertToConstants(EvaluatedRelation resultRelation) {
if (resultRelation.getHeading().isEmpty()) {
if (resultRelation.isEmpty()) {
return RELATION_DUM;
} else {
return RELATION_DEE;
}
}
return resultRelation;
}
}