/*
* $Header$
* $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.
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* "This product includes software developed by the
* the JRDF Project (http://jrdf.sf.net/)."
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package org.jrdf.query.relation.operation.mem.semidifference;
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.SemiDifference;
import org.jrdf.query.relation.operation.mem.common.RelationProcessor;
import java.util.Collections;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
public class SemiDifferenceImpl implements SemiDifference {
private final RelationFactory relationFactory;
private TupleComparator tupleComparator;
private RelationProcessor relationProcessor;
public SemiDifferenceImpl(RelationProcessor newRelationProcessor, RelationFactory newRelationFactory,
TupleComparator newTupleComparator) {
this.relationProcessor = newRelationProcessor;
this.relationFactory = newRelationFactory;
this.tupleComparator = newTupleComparator;
}
public EvaluatedRelation minus(EvaluatedRelation relation1, EvaluatedRelation relation2) {
EvaluatedRelation result = deeOrDumOperations(relation1, relation2);
if (result != null) {
return result;
}
SortedSet<Tuple> resultTuples = new TreeSet<Tuple>(tupleComparator);
performMinus(relation1, relation2, resultTuples);
result = relationFactory.getRelation(resultTuples);
return relationProcessor.convertToConstants(result);
}
private EvaluatedRelation deeOrDumOperations(EvaluatedRelation relation1, EvaluatedRelation relation2) {
EvaluatedRelation result = null;
// DUM - Anything is DUM.
if (relation1 == RELATION_DUM) {
result = RELATION_DUM;
// DEE - DEE is DUM, otherwise it's DEE
} else if (relation1 == RELATION_DEE) {
result = relationDeeShortcuts(relation2);
// Anything - DUM is DUM
} else if (relation2 == RELATION_DUM) {
result = relation1;
// Anything - DEE is just Anything's heading
} else if (relation2 == RELATION_DEE) {
Set<Tuple> noTuples = Collections.emptySet();
result = relationFactory.getRelation(relation1.getSortedHeading(), noTuples);
}
return result;
}
private EvaluatedRelation relationDeeShortcuts(EvaluatedRelation relation2) {
if (relation2 == RELATION_DEE) {
return RELATION_DUM;
} else {
return RELATION_DEE;
}
}
private void performMinus(EvaluatedRelation relation1, EvaluatedRelation relation2, SortedSet<Tuple> resultTuples) {
Set<Tuple> set1 = relation1.getTuples();
Set<Tuple> set2 = relation2.getTuples();
for (Tuple tuple1 : set1) {
if (!set2.contains(tuple1)) {
resultTuples.add(tuple1);
}
}
}
}