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.HashSet; 27 import java.util.Iterator; 28 import java.util.List; 29 import java.util.Set; 30 import org.modeshape.graph.Location; 31 32 /** 33 * A {@link ProcessingComponent} implementation that removes duplicates. The results from the delegate component do not need to be 34 * sorted; in fact, if the delegate component is a {@link SortValuesComponent}, then use {@link DistinctOfSortedComponent} instead of 35 * this class. 36 */ 37 public class DistinctComponent extends DelegatingComponent { 38 39 public DistinctComponent( ProcessingComponent delegate ) { 40 super(delegate); 41 } 42 43 /** 44 * {@inheritDoc} 45 * 46 * @see org.modeshape.graph.query.process.ProcessingComponent#execute() 47 */ 48 @Override 49 public List<Object[]> execute() { 50 List<Object[]> tuples = delegate().execute(); 51 if (tuples.size() > 1) { 52 // Go through this list and remove any tuples that appear more than once ... 53 Iterator<Object[]> iter = tuples.iterator(); 54 55 int locationCount = getColumns().getLocationCount(); 56 int firstLocationIndex = getColumns().getColumnCount(); 57 if (locationCount == 1) { 58 // We can determine duplicates faster/cheaper using a single Set<Location> ... 59 Set<Location> found = new HashSet<Location>(); 60 while (iter.hasNext()) { 61 Location location = (Location)iter.next()[firstLocationIndex]; 62 if (!found.add(location)) { 63 // Was already found, so remove this tuple from the results ... 64 iter.remove(); 65 } 66 } 67 } else { 68 assert locationCount > 1; 69 // Duplicate tuples are removed using a Set<Location[]> ... 70 Set<Location[]> found = new HashSet<Location[]>(); 71 while (iter.hasNext()) { 72 Object[] tuple = iter.next(); 73 Location[] locations = new Location[locationCount]; 74 System.arraycopy(tuple, firstLocationIndex, locations, 0, locationCount); 75 if (!found.add(locations)) { 76 // Was already found, so remove this tuple from the results ... 77 iter.remove(); 78 } 79 } 80 } 81 } 82 return tuples; 83 } 84 }