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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.process;
25  
26  import java.util.ArrayList;
27  import java.util.List;
28  import org.modeshape.graph.query.QueryContext;
29  import org.modeshape.graph.query.model.JoinCondition;
30  import org.modeshape.graph.query.model.JoinType;
31  
32  /**
33   * 
34   */
35  public class NestedLoopJoinComponent extends JoinComponent {
36  
37      public NestedLoopJoinComponent( QueryContext context,
38                                      ProcessingComponent left,
39                                      ProcessingComponent right,
40                                      JoinCondition condition,
41                                      JoinType joinType ) {
42          super(context, left, right, condition, joinType);
43      }
44  
45      /**
46       * {@inheritDoc}
47       * 
48       * @see org.modeshape.graph.query.process.ProcessingComponent#execute()
49       */
50      @Override
51      public List<Object[]> execute() {
52          // Construct the necessary components ...
53          final ValueSelector leftSelector = valueSelectorFor(left(), getJoinCondition());
54          final ValueSelector rightSelector = valueSelectorFor(right(), getJoinCondition());
55          final Joinable joinable = joinableFor(left(), right(), getJoinCondition());
56          final TupleMerger merger = createMerger(getColumns(), left().getColumns(), right().getColumns());
57  
58          // Walk through the left and right results ...
59          List<Object[]> leftTuples = left().execute();
60          List<Object[]> rightTuples = right().execute();
61          List<Object[]> tuples = new ArrayList<Object[]>(leftTuples.size() * rightTuples.size());
62          for (Object[] leftTuple : leftTuples) {
63              for (Object[] rightTuple : rightTuples) {
64                  // Get the value from the left and right side ...
65                  Object leftValue = leftSelector.evaluate(leftTuple);
66                  Object rightValue = rightSelector.evaluate(rightTuple);
67                  // Determine if the tuples should be joined ...
68                  if (joinable.evaluate(leftValue, rightValue)) {
69                      Object[] result = merger.merge(leftTuple, rightTuple);
70                      tuples.add(result);
71                  }
72              }
73          }
74          return tuples;
75      }
76  }