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.List;
27 import org.modeshape.graph.query.model.Limit;
28
29 /**
30 */
31 public class LimitComponent extends DelegatingComponent {
32
33 private final Limit limit;
34
35 public LimitComponent( ProcessingComponent delegate,
36 Limit limit ) {
37 super(delegate);
38 this.limit = limit;
39 assert this.limit != null;
40 }
41
42 /**
43 * {@inheritDoc}
44 *
45 * @see org.modeshape.graph.query.process.ProcessingComponent#execute()
46 */
47 @Override
48 public List<Object[]> execute() {
49 if (limit.rowLimit() == 0) {
50 return emptyTuples();
51 }
52 List<Object[]> tuples = delegate().execute();
53 if (limit.isOffset()) {
54 if (limit.offset() >= tuples.size()) {
55 // There aren't enough results, so return an empty list ...
56 return emptyTuples();
57 }
58 if (limit.hasRowLimited()) {
59 // Both an offset AND a row limit (which may be more than the number of rows available)...
60 int toIndex = Math.min(tuples.size(), Math.max(0, limit.offset() + limit.rowLimit()));
61 tuples = tuples.subList(limit.offset(), toIndex);
62 } else {
63 // An offset, but no row limit ...
64 tuples = tuples.subList(limit.offset(), tuples.size());
65 }
66 } else {
67 // No offset, but perhaps there's a row limit ...
68 if (limit.hasRowLimited()) {
69 int toIndex = Math.min(limit.rowLimit(), tuples.size());
70 tuples = tuples.subList(0, toIndex);
71 }
72 }
73 return tuples;
74 }
75 }