001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied. See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 *
019 */
020 package org.apache.directory.server.xdbm.search.impl;
021
022
023 import java.util.ArrayList;
024 import java.util.HashSet;
025 import java.util.List;
026 import java.util.Set;
027
028 import org.apache.directory.server.i18n.I18n;
029 import org.apache.directory.server.xdbm.IndexEntry;
030 import org.apache.directory.server.xdbm.AbstractIndexCursor;
031 import org.apache.directory.server.xdbm.IndexCursor;
032 import org.apache.directory.server.xdbm.search.Evaluator;
033 import org.apache.directory.shared.ldap.cursor.Cursor;
034 import org.apache.directory.shared.ldap.cursor.InvalidCursorPositionException;
035 import org.apache.directory.shared.ldap.entry.ServerEntry;
036 import org.apache.directory.shared.ldap.filter.ExprNode;
037
038
039 /**
040 * A Cursor returning candidates satisfying a logical disjunction expression.
041 *
042 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
043 * @version $Rev$
044 */
045 public class OrCursor<V, ID> extends AbstractIndexCursor<V, ServerEntry, ID>
046 {
047 private static final String UNSUPPORTED_MSG = I18n.err( I18n.ERR_722 );
048 private final List<IndexCursor<V, ServerEntry, ID>> cursors;
049 private final List<Evaluator<? extends ExprNode, ServerEntry, ID>> evaluators;
050 private final List<Set<ID>> blacklists;
051 private int cursorIndex = -1;
052 private boolean available = false;
053
054
055 // TODO - do same evaluator fail fast optimization that we do in AndCursor
056 public OrCursor( List<IndexCursor<V, ServerEntry, ID>> cursors,
057 List<Evaluator<? extends ExprNode, ServerEntry, ID>> evaluators )
058 {
059 if ( cursors.size() <= 1 )
060 {
061 throw new IllegalArgumentException( I18n.err( I18n.ERR_723 ) );
062 }
063
064 this.cursors = cursors;
065 this.evaluators = evaluators;
066 this.blacklists = new ArrayList<Set<ID>>();
067
068 for ( int ii = 0; ii < cursors.size(); ii++ )
069 {
070 this.blacklists.add( new HashSet<ID>() );
071 }
072 this.cursorIndex = 0;
073 }
074
075
076 public boolean available()
077 {
078 return available;
079 }
080
081
082 public void before( IndexEntry<V, ServerEntry, ID> element ) throws Exception
083 {
084 throw new UnsupportedOperationException( UNSUPPORTED_MSG );
085 }
086
087
088 public void after( IndexEntry<V, ServerEntry, ID> element ) throws Exception
089 {
090 throw new UnsupportedOperationException( UNSUPPORTED_MSG );
091 }
092
093
094 public void beforeValue( ID id, V value ) throws Exception
095 {
096 throw new UnsupportedOperationException( UNSUPPORTED_MSG );
097 }
098
099
100 public void afterValue( ID id, V value ) throws Exception
101 {
102 throw new UnsupportedOperationException( UNSUPPORTED_MSG );
103 }
104
105
106 public void beforeFirst() throws Exception
107 {
108 checkNotClosed( "beforeFirst()" );
109 cursorIndex = 0;
110 cursors.get( cursorIndex ).beforeFirst();
111 available = false;
112 }
113
114
115 public void afterLast() throws Exception
116 {
117 checkNotClosed( "afterLast()" );
118 cursorIndex = cursors.size() - 1;
119 cursors.get( cursorIndex ).afterLast();
120 available = false;
121 }
122
123
124 public boolean first() throws Exception
125 {
126 beforeFirst();
127 return available = next();
128 }
129
130
131 public boolean last() throws Exception
132 {
133 afterLast();
134 return available = previous();
135 }
136
137
138 private boolean isBlackListed( ID id )
139 {
140 return blacklists.get( cursorIndex ).contains( id );
141 }
142
143
144 /**
145 * The first sub-expression Cursor to advance to an entry adds the entry
146 * to the blacklists of other Cursors that might return that entry.
147 *
148 * @param indexEntry the index entry to blacklist
149 * @throws Exception if there are problems accessing underlying db
150 */
151 private void blackListIfDuplicate( IndexEntry<?, ServerEntry, ID> indexEntry ) throws Exception
152 {
153 for ( int ii = 0; ii < evaluators.size(); ii++ )
154 {
155 if ( ii == cursorIndex )
156 {
157 continue;
158 }
159
160 if ( evaluators.get( ii ).evaluate( indexEntry ) )
161 {
162 blacklists.get( ii ).add( indexEntry.getId() );
163 }
164 }
165 }
166
167
168 public boolean previous() throws Exception
169 {
170 while ( cursors.get( cursorIndex ).previous() )
171 {
172 checkNotClosed( "previous()" );
173 IndexEntry<?, ServerEntry, ID> candidate = cursors.get( cursorIndex ).get();
174 if ( !isBlackListed( candidate.getId() ) )
175 {
176 blackListIfDuplicate( candidate );
177 return available = true;
178 }
179 }
180
181 while ( cursorIndex > 0 )
182 {
183 checkNotClosed( "previous()" );
184 cursorIndex--;
185 cursors.get( cursorIndex ).afterLast();
186
187 while ( cursors.get( cursorIndex ).previous() )
188 {
189 checkNotClosed( "previous()" );
190 IndexEntry<?, ServerEntry, ID> candidate = cursors.get( cursorIndex ).get();
191 if ( !isBlackListed( candidate.getId() ) )
192 {
193 blackListIfDuplicate( candidate );
194 return available = true;
195 }
196 }
197 }
198
199 return available = false;
200 }
201
202
203 public boolean next() throws Exception
204 {
205 while ( cursors.get( cursorIndex ).next() )
206 {
207 checkNotClosed( "next()" );
208 IndexEntry<?, ServerEntry, ID> candidate = cursors.get( cursorIndex ).get();
209 if ( !isBlackListed( candidate.getId() ) )
210 {
211 blackListIfDuplicate( candidate );
212 return available = true;
213 }
214 }
215
216 while ( cursorIndex < cursors.size() - 1 )
217 {
218 checkNotClosed( "previous()" );
219 cursorIndex++;
220 cursors.get( cursorIndex ).beforeFirst();
221
222 while ( cursors.get( cursorIndex ).next() )
223 {
224 checkNotClosed( "previous()" );
225 IndexEntry<?, ServerEntry, ID> candidate = cursors.get( cursorIndex ).get();
226 if ( !isBlackListed( candidate.getId() ) )
227 {
228 blackListIfDuplicate( candidate );
229 return available = true;
230 }
231 }
232 }
233
234 return available = false;
235 }
236
237
238 public IndexEntry<V, ServerEntry, ID> get() throws Exception
239 {
240 checkNotClosed( "get()" );
241 if ( available )
242 {
243 return cursors.get( cursorIndex ).get();
244 }
245
246 throw new InvalidCursorPositionException( I18n.err( I18n.ERR_708 ) );
247 }
248
249
250 public boolean isElementReused()
251 {
252 return cursors.get( cursorIndex ).isElementReused();
253 }
254
255
256 public void close() throws Exception
257 {
258 super.close();
259 for ( Cursor<?> cursor : cursors )
260 {
261 cursor.close();
262 }
263 }
264 }