1 /*
2 * ModeShape (http://www.modeshape.org)
3 * See the COPYRIGHT.txt file distributed with this work for information
4 * regarding copyright ownership. Some portions may be licensed
5 * to Red Hat, Inc. under one or more contributor license agreements.
6 * See the AUTHORS.txt file in the distribution for a full listing of
7 * individual contributors.
8 *
9 * ModeShape is free software. Unless otherwise indicated, all code in ModeShape
10 * is licensed to you under the terms of the GNU Lesser General Public License as
11 * published by the Free Software Foundation; either version 2.1 of
12 * the License, or (at your option) any later version.
13 *
14 * ModeShape is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this software; if not, write to the Free
21 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
22 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
23 */
24 package org.modeshape.graph.query.optimize;
25
26 import java.util.LinkedList;
27 import net.jcip.annotations.Immutable;
28 import org.modeshape.graph.query.QueryContext;
29 import org.modeshape.graph.query.model.JoinType;
30 import org.modeshape.graph.query.plan.PlanNode;
31 import org.modeshape.graph.query.plan.PlanNode.Property;
32 import org.modeshape.graph.query.plan.PlanNode.Type;
33
34 /**
35 * An {@link OptimizerRule optimizer rule} that converts {@link JoinType#RIGHT_OUTER right outer joins} into
36 * {@link JoinType#LEFT_OUTER left outer joins}.
37 */
38 @Immutable
39 public class RightOuterToLeftOuterJoins implements OptimizerRule {
40
41 public static final RightOuterToLeftOuterJoins INSTANCE = new RightOuterToLeftOuterJoins();
42
43 /**
44 * {@inheritDoc}
45 *
46 * @see org.modeshape.graph.query.optimize.OptimizerRule#execute(org.modeshape.graph.query.QueryContext,
47 * org.modeshape.graph.query.plan.PlanNode, java.util.LinkedList)
48 */
49 public PlanNode execute( QueryContext context,
50 PlanNode plan,
51 LinkedList<OptimizerRule> ruleStack ) {
52 // For each of the JOIN nodes ...
53 for (PlanNode joinNode : plan.findAllAtOrBelow(Type.JOIN)) {
54 if (JoinType.RIGHT_OUTER == joinNode.getProperty(Property.JOIN_TYPE, JoinType.class)) {
55 // Swap the information ...
56 PlanNode left = joinNode.getFirstChild();
57 left.removeFromParent(); // right is now the first child ...
58 left.setParent(joinNode);
59 joinNode.setProperty(Property.JOIN_TYPE, JoinType.LEFT_OUTER);
60 // The JoinCondition and Constraints don't need to be changed
61 }
62 }
63 return plan;
64 }
65
66 /**
67 * {@inheritDoc}
68 *
69 * @see java.lang.Object#toString()
70 */
71 @Override
72 public String toString() {
73 return getClass().getSimpleName();
74 }
75
76 }