/*
* $Header$
* $Revision: 3027 $
* $Date: 2009-06-15 07:28:38 +1000 (Mon, 15 Jun 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
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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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* ====================================================================
*
* 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.mem;
import org.jrdf.query.relation.Attribute;
import org.jrdf.query.relation.AttributeComparator;
import org.jrdf.query.relation.EvaluatedRelation;
import org.jrdf.query.relation.RelationComparator;
import org.jrdf.query.relation.Tuple;
import org.jrdf.query.relation.TupleComparator;
import java.util.Iterator;
import java.util.Set;
public final class RelationComparatorImpl implements RelationComparator {
private static final long serialVersionUID = 9186461012818411817L;
private AttributeComparator attributeComparator;
private TupleComparator tupleComparator;
private RelationComparatorImpl() {
}
public RelationComparatorImpl(AttributeComparator newAttributeComparator, TupleComparator newTupleComparator) {
this.attributeComparator = newAttributeComparator;
this.tupleComparator = newTupleComparator;
}
public int compare(EvaluatedRelation relation1, EvaluatedRelation relation2) {
ifNullThrowException(relation1, relation2);
int result;
result = compareAttributes(relation1, relation2);
if (result == 0) {
result = compareTuples(relation1, relation2);
}
return result;
}
// TODO Tuple Refactor Duplicate of TupleComparator.
private int compareAttributes(EvaluatedRelation relation1, EvaluatedRelation relation2) {
int result = 0;
Set<Attribute> sortedHeading1 = relation1.getSortedHeading();
Set<Attribute> sortedHeading2 = relation2.getSortedHeading();
Iterator<Attribute> iterator1 = sortedHeading1.iterator();
Iterator<Attribute> iterator2 = sortedHeading2.iterator();
boolean equal = true;
while (iterator1.hasNext() && iterator2.hasNext() && equal) {
Attribute att1 = iterator1.next();
Attribute att2 = iterator2.next();
result = attributeComparator.compare(att1, att2);
equal = result == 0;
}
return result;
}
private int compareTuples(EvaluatedRelation relation1, EvaluatedRelation relation2) {
long tuplesSize1 = relation1.getTupleSize();
long tuplesSize2 = relation2.getTupleSize();
if (tuplesSize1 == tuplesSize2) {
return compareTuplesWithSameCardinality(relation1.iterator(), relation2.iterator());
} else {
if (tuplesSize1 > tuplesSize2) {
return 1;
} else {
return -1;
}
}
}
private int compareTuplesWithSameCardinality(final Iterator<Tuple> iterator1, final Iterator<Tuple> iterator2) {
int result = 0;
boolean equal = true;
while (iterator1.hasNext() && iterator2.hasNext() && equal) {
Tuple tuple1 = iterator1.next();
Tuple tuple2 = iterator2.next();
result = tupleComparator.compare(tuple1, tuple2);
equal = result == 0;
}
return result;
}
private void ifNullThrowException(EvaluatedRelation relation1, EvaluatedRelation relation2) {
if (relation1 == null || relation2 == null) {
throw new NullPointerException();
}
}
}