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.Comparator;
27 import java.util.Iterator;
28 import java.util.List;
29
30 /**
31 * An efficient {@link ProcessingComponent} that removes duplicates from an already-sorted set of results.
32 *
33 * @see DistinctComponent
34 */
35 public class DistinctOfSortedComponent extends DelegatingComponent {
36
37 private final Comparator<Object[]> comparator;
38
39 public DistinctOfSortedComponent( SortValuesComponent delegate ) {
40 super(delegate);
41 this.comparator = delegate.getSortingComparator();
42 }
43
44 /**
45 * {@inheritDoc}
46 *
47 * @see org.modeshape.graph.query.process.ProcessingComponent#execute()
48 */
49 @Override
50 public List<Object[]> execute() {
51 List<Object[]> tuples = delegate().execute();
52 Iterator<Object[]> iter = tuples.iterator();
53 Object[] previous = null;
54 while (iter.hasNext()) {
55 Object[] current = iter.next();
56 if (previous != null && this.comparator.compare(previous, current) == 0) {
57 iter.remove();
58 } else {
59 previous = current;
60 }
61 }
62 return tuples;
63 }
64 }