Source Code Cross Referenced for DbSearchIndexer.java in  » Forum » yazd » com » Yasna » forum » database » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Forum » yazd » com.Yasna.forum.database 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /**
002:         * Copyright (C) 2001 Yasna.com. All rights reserved.
003:         *
004:         * ===================================================================
005:         * The Apache Software License, Version 1.1
006:         *
007:         * Redistribution and use in source and binary forms, with or without
008:         * modification, are permitted provided that the following conditions
009:         * are met:
010:         *
011:         * 1. Redistributions of source code must retain the above copyright
012:         *    notice, this list of conditions and the following disclaimer.
013:         *
014:         * 2. Redistributions in binary form must reproduce the above copyright
015:         *    notice, this list of conditions and the following disclaimer in
016:         *    the documentation and/or other materials provided with the
017:         *    distribution.
018:         *
019:         * 3. The end-user documentation included with the redistribution,
020:         *    if any, must include the following acknowledgment:
021:         *       "This product includes software developed by
022:         *        Yasna.com (http://www.yasna.com)."
023:         *    Alternately, this acknowledgment may appear in the software itself,
024:         *    if and wherever such third-party acknowledgments normally appear.
025:         *
026:         * 4. The names "Yazd" and "Yasna.com" must not be used to
027:         *    endorse or promote products derived from this software without
028:         *    prior written permission. For written permission, please
029:         *    contact yazd@yasna.com.
030:         *
031:         * 5. Products derived from this software may not be called "Yazd",
032:         *    nor may "Yazd" appear in their name, without prior written
033:         *    permission of Yasna.com.
034:         *
035:         * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
036:         * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
037:         * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
038:         * DISCLAIMED.  IN NO EVENT SHALL YASNA.COM OR
039:         * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
040:         * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
041:         * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
042:         * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
043:         * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
044:         * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
045:         * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
046:         * SUCH DAMAGE.
047:         * ====================================================================
048:         *
049:         * This software consists of voluntary contributions made by many
050:         * individuals on behalf of Yasna.com. For more information
051:         * on Yasna.com, please see <http://www.yasna.com>.
052:         */
053:
054:        /**
055:         * Copyright (C) 2000 CoolServlets.com. All rights reserved.
056:         *
057:         * ===================================================================
058:         * The Apache Software License, Version 1.1
059:         *
060:         * Redistribution and use in source and binary forms, with or without
061:         * modification, are permitted provided that the following conditions
062:         * are met:
063:         *
064:         * 1. Redistributions of source code must retain the above copyright
065:         *    notice, this list of conditions and the following disclaimer.
066:         *
067:         * 2. Redistributions in binary form must reproduce the above copyright
068:         *    notice, this list of conditions and the following disclaimer in
069:         *    the documentation and/or other materials provided with the
070:         *    distribution.
071:         *
072:         * 3. The end-user documentation included with the redistribution,
073:         *    if any, must include the following acknowledgment:
074:         *       "This product includes software developed by
075:         *        CoolServlets.com (http://www.coolservlets.com)."
076:         *    Alternately, this acknowledgment may appear in the software itself,
077:         *    if and wherever such third-party acknowledgments normally appear.
078:         *
079:         * 4. The names "Jive" and "CoolServlets.com" must not be used to
080:         *    endorse or promote products derived from this software without
081:         *    prior written permission. For written permission, please
082:         *    contact webmaster@coolservlets.com.
083:         *
084:         * 5. Products derived from this software may not be called "Jive",
085:         *    nor may "Jive" appear in their name, without prior written
086:         *    permission of CoolServlets.com.
087:         *
088:         * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
089:         * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
090:         * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
091:         * DISCLAIMED.  IN NO EVENT SHALL COOLSERVLETS.COM OR
092:         * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
093:         * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
094:         * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
095:         * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
096:         * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
097:         * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
098:         * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
099:         * SUCH DAMAGE.
100:         * ====================================================================
101:         *
102:         * This software consists of voluntary contributions made by many
103:         * individuals on behalf of CoolServlets.com. For more information
104:         * on CoolServlets.com, please see <http://www.coolservlets.com>.
105:         */package com.Yasna.forum.database;
106:
107:        import java.sql.*;
108:        import java.util.*;
109:        import java.io.*;
110:
111:        import org.apache.lucene.document.*;
112:        import org.apache.lucene.analysis.*;
113:        import org.apache.lucene.analysis.standard.*;
114:        import org.apache.lucene.index.*;
115:        import org.apache.lucene.store.*;
116:
117:        import com.Yasna.forum.*;
118:        import com.Yasna.util.*;
119:
120:        /**
121:         * Database implementation of SearchIndexer using the Lucene search package.
122:         *
123:         * Search indexes are stored in the "search" subdirectory of directory pointed to
124:         * by the Yazd property "yazdHome".
125:         */
126:        public class DbSearchIndexer extends Thread implements  SearchIndexer {
127:
128:            /** DATABASE QUERIES **/
129:            //private static final String MESSAGES_BEFORE_DATE =
130:            //  "SELECT messageID FROM yazdMessage WHERE modifiedDate < ?";
131:            private static final String MESSAGES_BEFORE_DATE = "SELECT messageID, userID, yazdMessage.threadID, forumID, "
132:                    + "subject, body, yazdMessage.creationDate "
133:                    + "FROM yazdMessage, yazdThread WHERE yazdMessage.threadID=yazdThread.threadID "
134:                    + "AND yazdMessage.modifiedDate < ?";
135:            private static final String MESSAGES_BEFORE_DATE_COUNT = "SELECT count(messageID) FROM yazdMessage WHERE modifiedDate < ?";
136:            private static final String MESSAGES_SINCE_DATE = "SELECT messageID FROM yazdMessage WHERE modifiedDate > ? "
137:                    + "AND modifiedDate < ?";
138:            private static final String MESSAGES_SINCE_DATE_COUNT = "SELECT count(messageID) FROM yazdMessage WHERE modifiedDate > ? "
139:                    + "AND modifiedDate < ?";
140:            private static final String LOAD_MESSAGE = "SELECT subject, body, userID, yazdMessage.threadID, forumID, "
141:                    + "yazdMessage.creationDate FROM yazdMessage, yazdThread WHERE "
142:                    + "yazdMessage.threadID=yazdThread.threadID AND yazdMessage.messageID=?";
143:
144:            /**
145:             * Path to where index is stored.
146:             */
147:            private static String indexPath = null;
148:
149:            /**
150:             * Time constants (in milleseconds)
151:             */
152:            private static final long MINUTE = 1000 * 60;
153:            private static final long HOUR = MINUTE * 60;
154:
155:            /**
156:             * Maintains the amount of time that should elapse until the next index.
157:             */
158:            private long updateInterval;
159:
160:            /**
161:             * Maintains the time that the last index took place.
162:             */
163:            private long lastIndexed;
164:
165:            /**
166:             * Indicates whether auto-indexing should be on or off. When on, an update
167:             * will be run at the "updateInterval".
168:             */
169:            private boolean autoIndex = true;
170:
171:            /**
172:             * ForumFactory so that we can load message objects based on their ID.
173:             */
174:            private DbForumFactory factory;
175:
176:            /**
177:             * Lock so that only one indexing function can be executed at once. Not
178:             * locking could impact the database integrity. Therefore, in a cluster of
179:             * Yazd servers all pointed at the same db, only one indexer should be
180:             * running once.
181:             */
182:            private Object indexLock = new Object();
183:
184:            private static Analyzer analyzer = new StopAnalyzer();
185:
186:            /**
187:             * Creates a new DbSearchIndexer. It attempts to load properties for
188:             * the update interval and when the last index occured from the Yazd
189:             * properties then starts the indexing thread.
190:             */
191:            public DbSearchIndexer(DbForumFactory factory) {
192:                this .factory = factory;
193:
194:                //Default to performing updates ever 10 minutes.
195:                updateInterval = 80 * MINUTE;
196:                //If the update interval property exists, use that
197:                String updInterval = PropertyManager
198:                        .getProperty("DbSearchIndexer.updateInterval");
199:                try {
200:                    updateInterval = Long.parseLong(updInterval);
201:                } catch (Exception e) { /* ignore */
202:                }
203:
204:                //Attempt to get the last updated time from the Yazd properties
205:                String lastInd = PropertyManager
206:                        .getProperty("DbSearchIndexer.lastIndexed");
207:                try {
208:                    lastIndexed = Long.parseLong(lastInd);
209:                } catch (Exception e) {
210:                    //Something went wrong. Therefore, set lastIndexed far into the past
211:                    //so that we'll do a full index.
212:                    lastIndexed = 0;
213:                }
214:                //Make this a daemon thread.
215:                this .setDaemon(true);
216:                //Start the indexing thread.
217:                start();
218:            }
219:
220:            public int getHoursUpdateInterval() {
221:                return (int) (updateInterval / HOUR);
222:            }
223:
224:            public int getMinutesUpdateInterval() {
225:                return (int) ((updateInterval - getHoursUpdateInterval() * HOUR) / MINUTE);
226:            }
227:
228:            public void setUpdateInterval(int minutes, int hours) {
229:                updateInterval = (minutes * MINUTE) + (hours * HOUR);
230:                //Save it to the properties
231:                PropertyManager.setProperty("DbSearchIndexer.updateInterval",
232:                        "" + updateInterval);
233:            }
234:
235:            public java.util.Date getLastIndexedDate() {
236:                return new java.util.Date(lastIndexed);
237:            }
238:
239:            public boolean isAutoIndexEnabled() {
240:                return autoIndex;
241:            }
242:
243:            public void setAutoIndexEnabled(boolean value) {
244:                autoIndex = value;
245:            }
246:
247:            public void addToIndex(ForumMessage message) {
248:                //acquire the index lock so that no other indexing operations
249:                //are performed.
250:                synchronized (indexLock) {
251:                    IndexWriter writer = null;
252:                    try {
253:                        writer = getWriter(false);
254:                        addMessageToIndex(writer, message.getID(), message
255:                                .getUnfilteredSubject(), message
256:                                .getUnfilteredBody(),
257:                                message.getUser().getID(), message
258:                                        .getForumThread().getID(), message
259:                                        .getForumThread().getForum().getID(),
260:                                message.getCreationDate());
261:                    } catch (IOException ioe) {
262:                        ioe.printStackTrace();
263:                    } finally {
264:                        try {
265:                            writer.close();
266:                        } catch (Exception e) {
267:                        }
268:                    }
269:                }
270:            }
271:
272:            public void removeFromIndex(ForumMessage message) {
273:                //acquire the index lock so that no other indexing operations
274:                //are performed.
275:                synchronized (indexLock) {
276:                    try {
277:                        int[] toDelete = new int[] { message.getID() };
278:                        deleteMessagesFromIndex(toDelete);
279:                    } catch (IOException ioe) {
280:                        ioe.printStackTrace();
281:                    }
282:                }
283:            }
284:
285:            public void updateIndex() {
286:                //acquire the index lock so that no other indexing operations
287:                //are performed.
288:                synchronized (indexLock) {
289:                    long now = System.currentTimeMillis();
290:                    updateIndex(lastIndexed, now);
291:                    lastIndexed = now;
292:                    //Save the time as a Yazd property.
293:                    PropertyManager.setProperty("DbSearchIndexer.lastIndexed",
294:                            "" + lastIndexed);
295:                }
296:            }
297:
298:            public void rebuildIndex() {
299:                //acquire the index lock so that no other indexing operations
300:                //are performed.
301:                synchronized (indexLock) {
302:                    long now = System.currentTimeMillis();
303:                    rebuildIndex(now);
304:                    lastIndexed = now;
305:                    //Save the time as a Yazd property.
306:                    PropertyManager.setProperty("DbSearchIndexer.lastIndexed",
307:                            "" + lastIndexed);
308:                }
309:            }
310:
311:            /**
312:             * Indexing thread logic. It wakes up once a minute to see if any threaded
313:             * action should take place.
314:             */
315:            public void run() {
316:                while (true) {
317:                    //If auto indexing is on
318:                    if (autoIndex) {
319:                        long now = System.currentTimeMillis();
320:                        //If we want to re-index everything.
321:                        if (lastIndexed == 0) {
322:                            synchronized (indexLock) {
323:                                rebuildIndex(now);
324:                                lastIndexed = now;
325:                                //Save the time as a Yazd property.
326:                                PropertyManager.setProperty(
327:                                        "DbSearchIndexer.lastIndexed", ""
328:                                                + lastIndexed);
329:                            }
330:                        }
331:                        //We only want to do an update.
332:                        else {
333:                            long nextIndex = lastIndexed + updateInterval;
334:                            if (now > nextIndex) {
335:                                synchronized (indexLock) {
336:                                    updateIndex(lastIndexed, now);
337:                                    lastIndexed = now;
338:                                    //Save the time as a Yazd property.
339:                                    PropertyManager.setProperty(
340:                                            "DbSearchIndexer.lastIndexed", ""
341:                                                    + lastIndexed);
342:                                }
343:                            }
344:                        }
345:                    }
346:                    //sleep for 1 minute and then check again.
347:                    try {
348:                        this .sleep(60000);
349:                    } catch (Exception e) {
350:                        e.printStackTrace();
351:                    }
352:                }
353:            }
354:
355:            /**
356:             * Indexes an indivual message. The connection is assumed to be open when
357:             * passed in and will remain open after the method is done executing.
358:             */
359:            protected final void addMessageToIndex(IndexWriter writer,
360:                    int messageID, String subject, String body, int userID,
361:                    int threadID, int forumID, java.util.Date creationDate)
362:                    throws IOException {
363:                if (writer == null) {
364:                    return;
365:                }
366:                //Ignore messages with a null subject or body.
367:                if (subject == null || body == null) {
368:                    return;
369:                }
370:
371:                Document doc = new Document();
372:                doc
373:                        .add(Field.Keyword("messageID", Integer
374:                                .toString(messageID)));
375:                doc.add(new Field("userID", Integer.toString(userID), false,
376:                        true, false));
377:                doc.add(new Field("threadID", Integer.toString(threadID),
378:                        false, true, false));
379:                doc.add(new Field("forumID", Integer.toString(forumID), false,
380:                        true, false));
381:                doc.add(new Field("Indexer", "FORUMS", false, true, false));
382:                doc.add(Field.UnStored("subject", subject));
383:                doc.add(Field.UnStored("body", body));
384:                doc.add(new Field("creationDate", DateField
385:                        .dateToString(creationDate), false, true, false));
386:
387:                writer.addDocument(doc);
388:            }
389:
390:            /**
391:             * Deletes a message from the index.
392:             */
393:            protected final void deleteMessagesFromIndex(int[] messages)
394:                    throws IOException {
395:                if (messages == null) {
396:                    return;
397:                }
398:                IndexReader reader = getReader();
399:                if (reader == null) {
400:                    //Reader will be null if the search index doesn't exist.
401:                    return;
402:                }
403:                Term messageIDTerm;
404:                for (int i = 0; i < messages.length; i++) {
405:                    messageIDTerm = new Term("messageID", Integer
406:                            .toString(messages[i]));
407:                    try {
408:                        reader.delete(messageIDTerm);
409:                    } catch (Exception e) {
410:                    }
411:                }
412:                try {
413:                    reader.close();
414:                } catch (Exception e) {
415:                }
416:            }
417:
418:            /**
419:             * Rebuilds the search index from scratch. It deletes the entire index
420:             * and word tables and then indexes every message up to the end time.
421:             */
422:            protected final void rebuildIndex(long end) {
423:                System.err.println("Rebuilding index...");
424:
425:                IndexWriter writer = null;
426:                Connection con = null;
427:                try {
428:                    writer = getWriter(true);
429:                    con = DbConnectionManager.getConnection();
430:                    PreparedStatement pstmt = con
431:                            .prepareStatement(MESSAGES_BEFORE_DATE);
432:                    pstmt.setString(1, Long.toString(end));
433:                    ResultSet rs = pstmt.executeQuery();
434:                    while (rs.next()) {
435:                        int messageID = rs.getInt(1);
436:                        int userID = rs.getInt(2);
437:                        int threadID = rs.getInt(3);
438:                        int forumID = rs.getInt(4);
439:                        String subject = rs.getString(5);
440:                        String body = rs.getString(6);
441:                        java.util.Date creationDate = new java.util.Date(Long
442:                                .parseLong(rs.getString(7).trim()));
443:                        //ForumMessage message = new DbForumMessage(messageID, factory);// factory.getMessage(messageID);
444:                        addMessageToIndex(writer, messageID, subject, body,
445:                                userID, threadID, forumID, creationDate);
446:                    }
447:                    pstmt.close();
448:                } catch (Exception sqle) {
449:                    sqle.printStackTrace();
450:                } finally {
451:                    try {
452:                        con.close();
453:                    } catch (Exception e) {
454:                        e.printStackTrace();
455:                    }
456:                    try {
457:                        //A rebuild of the index warrants calling optimize.
458:                        writer.optimize();
459:                    } catch (Exception e) {
460:                    }
461:                    try {
462:                        writer.close();
463:                    } catch (Exception e) {
464:                        e.printStackTrace();
465:                    }
466:                }
467:                System.err.println("Done rebuilding index.");
468:            }
469:
470:            /**
471:             * Updates the index. It first deletes any messages in the index between
472:             * the start and end times, and then adds all messages to the index that
473:             * are between the start and end times.
474:             */
475:            protected final void updateIndex(long start, long end) {
476:                Connection con = null;
477:                PreparedStatement pstmt = null;
478:                IndexWriter writer = null;
479:                int[] messages = null;
480:
481:                try {
482:                    con = DbConnectionManager.getConnection();
483:                    //For a clean update, we need to make sure that we first delete
484:                    //any index entries that were made since we last updated. This
485:                    //might happen if a process was calling indexMessage() between runs
486:                    //of this method. For this reason, the two types of indexing (manual
487:                    //and automatic) should not be intermixed. However, we still perform
488:                    //this deletion to be safe.
489:                    pstmt = con.prepareStatement(MESSAGES_SINCE_DATE_COUNT);
490:                    pstmt.setString(1, Long.toString(start));
491:                    pstmt.setString(2, Long.toString(end));
492:                    ResultSet rs = pstmt.executeQuery();
493:                    rs.next();
494:                    int messageCount = rs.getInt(1);
495:                    messages = new int[messageCount];
496:                    pstmt.close();
497:                    pstmt = con.prepareStatement(MESSAGES_SINCE_DATE);
498:                    pstmt.setString(1, Long.toString(start));
499:                    pstmt.setString(2, Long.toString(end));
500:                    rs = pstmt.executeQuery();
501:                    for (int i = 0; i < messages.length; i++) {
502:                        rs.next();
503:                        messages[i] = rs.getInt("messageID");
504:                    }
505:                } catch (Exception e) {
506:                    e.printStackTrace();
507:                } finally {
508:                    try {
509:                        pstmt.close();
510:                    } catch (Exception e) {
511:                        e.printStackTrace();
512:                    }
513:                    try {
514:                        con.close();
515:                    } catch (Exception e) {
516:                        e.printStackTrace();
517:                    }
518:                }
519:
520:                try {
521:                    deleteMessagesFromIndex(messages);
522:
523:                    //Finally, index all new messages;
524:                    writer = getWriter(false);
525:                    for (int i = 0; i < messages.length; i++) {
526:                        ForumMessage message = factory.getMessage(messages[i]);
527:                        addMessageToIndex(writer, message.getID(), message
528:                                .getUnfilteredSubject(), message
529:                                .getUnfilteredBody(),
530:                                message.getUser().getID(), message
531:                                        .getForumThread().getID(), message
532:                                        .getForumThread().getForum().getID(),
533:                                message.getCreationDate());
534:                    }
535:                } catch (Exception e) {
536:                    e.printStackTrace();
537:                } finally {
538:                    try {
539:                        writer.close();
540:                    } catch (Exception e) {
541:                        e.printStackTrace();
542:                    }
543:                }
544:            }
545:
546:            /**
547:             * Returns a Lucene IndexWriter.
548:             */
549:            private static IndexWriter getWriter(boolean create)
550:                    throws IOException {
551:                if (indexPath == null) {
552:                    //Get path of where search index should be. It should be
553:                    //the search subdirectory of [yazdHome].
554:                    String yazdHome = PropertyManager.getProperty("yazdHome");
555:                    if (yazdHome == null) {
556:                        System.err
557:                                .println("ERROR: the yazdHome property is not set.");
558:                        throw new IOException(
559:                                "Unable to open index for searching "
560:                                        + "because yazdHome was not set.");
561:                    }
562:                    indexPath = yazdHome + File.separator + "search";
563:                }
564:
565:                IndexWriter writer = null;
566:
567:                //If create is true, we always want to create a new index writer.
568:                if (create) {
569:                    try {
570:                        writer = new IndexWriter(indexPath, analyzer, true);
571:                    } catch (Exception e) {
572:                        System.err
573:                                .println("ERROR: Failed to create a new index writer.");
574:                        e.printStackTrace();
575:                    }
576:                }
577:                //Otherwise, use an existing index if it exists.
578:                else {
579:                    if (indexExists(indexPath)) {
580:                        try {
581:                            writer = new IndexWriter(indexPath, analyzer, false);
582:                        } catch (Exception e) {
583:                            System.err
584:                                    .println("ERROR: Failed to open an index writer.");
585:                            e.printStackTrace();
586:                        }
587:                    } else {
588:                        try {
589:                            writer = new IndexWriter(indexPath, analyzer, true);
590:                        } catch (Exception e) {
591:                            System.err
592:                                    .println("ERROR: Failed to create a new index writer.");
593:                            e.printStackTrace();
594:                        }
595:                    }
596:                }
597:
598:                return writer;
599:            }
600:
601:            /**
602:             * Returns a Lucene IndexReader.
603:             */
604:            private static IndexReader getReader() throws IOException {
605:                if (indexPath == null) {
606:                    //Get path of where search index should be. It should be
607:                    //the search subdirectory of [yazdHome].
608:                    String yazdHome = PropertyManager.getProperty("yazdHome");
609:                    if (yazdHome == null) {
610:                        System.err
611:                                .println("ERROR: the yazdHome property is not set.");
612:                        throw new IOException(
613:                                "Unable to open index for searching "
614:                                        + "because yazdHome was not set.");
615:                    }
616:                    indexPath = yazdHome + File.separator + "search";
617:                }
618:
619:                if (indexExists(indexPath)) {
620:                    IndexReader reader = IndexReader.open(indexPath);
621:                    return reader;
622:                } else {
623:                    return null;
624:                }
625:            }
626:
627:            /**
628:             * Returns true if the search index exists at the specified path.
629:             *
630:             * @param indexPath the path to check for the search index at.
631:             */
632:            private static boolean indexExists(String indexPath) {
633:                //Lucene always creates a file called "segments" -- if it exists, we
634:                //assume that the search index exists.
635:                File segments = new File(indexPath + File.separator
636:                        + "segments");
637:                return segments.exists();
638:            }
639:        }
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