/
DirectoryReader.cs
465 lines (434 loc) · 24 KB
/
DirectoryReader.cs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
using Lucene.Net.Diagnostics;
using System;
using System.Collections.Generic;
using System.IO;
using JCG = J2N.Collections.Generic;
namespace Lucene.Net.Index
{
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// javadocs
using Directory = Lucene.Net.Store.Directory;
/// <summary>
/// <see cref="DirectoryReader"/> is an implementation of <see cref="CompositeReader"/>
/// that can read indexes in a <see cref="Store.Directory"/>.
///
/// <para/><see cref="DirectoryReader"/> instances are usually constructed with a call to
/// one of the static <c>Open()</c> methods, e.g. <see cref="Open(Directory)"/>.
///
/// <para/> For efficiency, in this API documents are often referred to via
/// <i>document numbers</i>, non-negative integers which each name a unique
/// document in the index. These document numbers are ephemeral -- they may change
/// as documents are added to and deleted from an index. Clients should thus not
/// rely on a given document having the same number between sessions.
///
/// <para/><b>NOTE</b>:
/// <see cref="IndexReader"/> instances are completely thread
/// safe, meaning multiple threads can call any of its methods,
/// concurrently. If your application requires external
/// synchronization, you should <b>not</b> synchronize on the
/// <see cref="IndexReader"/> instance; use your own
/// (non-Lucene) objects instead.
/// </summary>
public abstract class DirectoryReader : BaseCompositeReader<AtomicReader>
{
/// <summary>
/// Default termInfosIndexDivisor. </summary>
public static readonly int DEFAULT_TERMS_INDEX_DIVISOR = 1;
/// <summary>
/// The index directory. </summary>
protected readonly Directory m_directory;
/// <summary>
/// Returns a <see cref="IndexReader"/> reading the index in the given
/// <see cref="Store.Directory"/> </summary>
/// <param name="directory"> the index directory </param>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
new public static DirectoryReader Open(Directory directory)
{
return StandardDirectoryReader.Open(directory, null, DEFAULT_TERMS_INDEX_DIVISOR);
}
/// <summary>
/// Expert: Returns a <see cref="IndexReader"/> reading the index in the given
/// <see cref="Store.Directory"/> with the given termInfosIndexDivisor. </summary>
/// <param name="directory"> the index directory </param>
/// <param name="termInfosIndexDivisor"> Subsamples which indexed
/// terms are loaded into RAM. this has the same effect as setting
/// <see cref="LiveIndexWriterConfig.TermIndexInterval"/> (on <see cref="IndexWriterConfig"/>) except that setting
/// must be done at indexing time while this setting can be
/// set per reader. When set to N, then one in every
/// N*termIndexInterval terms in the index is loaded into
/// memory. By setting this to a value > 1 you can reduce
/// memory usage, at the expense of higher latency when
/// loading a TermInfo. The default value is 1. Set this
/// to -1 to skip loading the terms index entirely.
/// <b>NOTE:</b> divisor settings > 1 do not apply to all <see cref="Codecs.PostingsFormat"/>
/// implementations, including the default one in this release. It only makes
/// sense for terms indexes that can efficiently re-sample terms at load time. </param>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
new public static DirectoryReader Open(Directory directory, int termInfosIndexDivisor)
{
return StandardDirectoryReader.Open(directory, null, termInfosIndexDivisor);
}
/// <summary>
/// Open a near real time <see cref="IndexReader"/> from the <see cref="IndexWriter"/>.
/// <para/>
/// @lucene.experimental
/// </summary>
/// <param name="writer"> The <see cref="IndexWriter"/> to open from </param>
/// <param name="applyAllDeletes"> If <c>true</c>, all buffered deletes will
/// be applied (made visible) in the returned reader. If
/// <c>false</c>, the deletes are not applied but remain buffered
/// (in IndexWriter) so that they will be applied in the
/// future. Applying deletes can be costly, so if your app
/// can tolerate deleted documents being returned you might
/// gain some performance by passing <c>false</c>. </param>
/// <returns> The new <see cref="IndexReader"/> </returns>
/// <exception cref="CorruptIndexException"> if the index is corrupt </exception>
/// <exception cref="IOException"> if there is a low-level IO error
/// </exception>
/// <seealso cref="OpenIfChanged(DirectoryReader, IndexWriter, bool)"/>
new public static DirectoryReader Open(IndexWriter writer, bool applyAllDeletes)
{
return writer.GetReader(applyAllDeletes);
}
/// <summary>
/// Expert: returns an <see cref="IndexReader"/> reading the index in the given
/// <see cref="Index.IndexCommit"/>. </summary>
/// <param name="commit"> the commit point to open </param>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
new public static DirectoryReader Open(IndexCommit commit)
{
return StandardDirectoryReader.Open(commit.Directory, commit, DEFAULT_TERMS_INDEX_DIVISOR);
}
/// <summary>
/// Expert: returns an <see cref="IndexReader"/> reading the index in the given
/// <seealso cref="Index.IndexCommit"/> and <paramref name="termInfosIndexDivisor"/>. </summary>
/// <param name="commit"> the commit point to open </param>
/// <param name="termInfosIndexDivisor"> Subsamples which indexed
/// terms are loaded into RAM. this has the same effect as setting
/// <see cref="LiveIndexWriterConfig.TermIndexInterval"/> (on <see cref="IndexWriterConfig"/>) except that setting
/// must be done at indexing time while this setting can be
/// set per reader. When set to N, then one in every
/// N*termIndexInterval terms in the index is loaded into
/// memory. By setting this to a value > 1 you can reduce
/// memory usage, at the expense of higher latency when
/// loading a TermInfo. The default value is 1. Set this
/// to -1 to skip loading the terms index entirely.
/// <b>NOTE:</b> divisor settings > 1 do not apply to all <see cref="Codecs.PostingsFormat"/>
/// implementations, including the default one in this release. It only makes
/// sense for terms indexes that can efficiently re-sample terms at load time. </param>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
new public static DirectoryReader Open(IndexCommit commit, int termInfosIndexDivisor)
{
return StandardDirectoryReader.Open(commit.Directory, commit, termInfosIndexDivisor);
}
/// <summary>
/// If the index has changed since the provided reader was
/// opened, open and return a new reader; else, return
/// <c>null</c>. The new reader, if not <c>null</c>, will be the same
/// type of reader as the previous one, ie a near-real-time (NRT) reader
/// will open a new NRT reader, a <see cref="MultiReader"/> will open a
/// new <see cref="MultiReader"/>, etc.
///
/// <para/>This method is typically far less costly than opening a
/// fully new <see cref="DirectoryReader"/> as it shares
/// resources (for example sub-readers) with the provided
/// <see cref="DirectoryReader"/>, when possible.
///
/// <para/>The provided reader is not disposed (you are responsible
/// for doing so); if a new reader is returned you also
/// must eventually dispose it. Be sure to never dispose a
/// reader while other threads are still using it; see
/// <see cref="Search.SearcherManager"/> to simplify managing this.
/// </summary>
/// <exception cref="CorruptIndexException"> if the index is corrupt </exception>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
/// <returns> <c>null</c> if there are no changes; else, a new
/// <see cref="DirectoryReader"/> instance which you must eventually dispose </returns>
public static DirectoryReader OpenIfChanged(DirectoryReader oldReader)
{
DirectoryReader newReader = oldReader.DoOpenIfChanged();
if (Debugging.AssertsEnabled) Debugging.Assert(newReader != oldReader);
return newReader;
}
/// <summary>
/// If the <see cref="Index.IndexCommit"/> differs from what the
/// provided reader is searching, open and return a new
/// reader; else, return <c>null</c>.
/// </summary>
/// <seealso cref="OpenIfChanged(DirectoryReader)"/>
public static DirectoryReader OpenIfChanged(DirectoryReader oldReader, IndexCommit commit)
{
DirectoryReader newReader = oldReader.DoOpenIfChanged(commit);
if (Debugging.AssertsEnabled) Debugging.Assert(newReader != oldReader);
return newReader;
}
/// <summary>
/// Expert: If there changes (committed or not) in the
/// <see cref="IndexWriter"/> versus what the provided reader is
/// searching, then open and return a new
/// <see cref="IndexReader"/> searching both committed and uncommitted
/// changes from the writer; else, return <c>null</c> (though, the
/// current implementation never returns <c>null</c>).
///
/// <para/>This provides "near real-time" searching, in that
/// changes made during an <see cref="IndexWriter"/> session can be
/// quickly made available for searching without closing
/// the writer nor calling <see cref="IndexWriter.Commit()"/>.
///
/// <para>It's <i>near</i> real-time because there is no hard
/// guarantee on how quickly you can get a new reader after
/// making changes with <see cref="IndexWriter"/>. You'll have to
/// experiment in your situation to determine if it's
/// fast enough. As this is a new and experimental
/// feature, please report back on your findings so we can
/// learn, improve and iterate.</para>
///
/// <para>The very first time this method is called, this
/// writer instance will make every effort to pool the
/// readers that it opens for doing merges, applying
/// deletes, etc. This means additional resources (RAM,
/// file descriptors, CPU time) will be consumed.</para>
///
/// <para>For lower latency on reopening a reader, you should
/// call <see cref="LiveIndexWriterConfig.MergedSegmentWarmer"/> (on <see cref="IndexWriterConfig"/>) to
/// pre-warm a newly merged segment before it's committed
/// to the index. This is important for minimizing
/// index-to-search delay after a large merge. </para>
///
/// <para>If an AddIndexes* call is running in another thread,
/// then this reader will only search those segments from
/// the foreign index that have been successfully copied
/// over, so far.</para>
///
/// <para><b>NOTE</b>: Once the writer is disposed, any
/// outstanding readers may continue to be used. However,
/// if you attempt to reopen any of those readers, you'll
/// hit an <see cref="ObjectDisposedException"/>.</para>
///
/// @lucene.experimental
/// </summary>
/// <returns> <see cref="DirectoryReader"/> that covers entire index plus all
/// changes made so far by this <see cref="IndexWriter"/> instance, or
/// <c>null</c> if there are no new changes
/// </returns>
/// <param name="writer"> The <see cref="IndexWriter"/> to open from
/// </param>
/// <param name="applyAllDeletes"> If <c>true</c>, all buffered deletes will
/// be applied (made visible) in the returned reader. If
/// <c>false</c>, the deletes are not applied but remain buffered
/// (in <see cref="IndexWriter"/>) so that they will be applied in the
/// future. Applying deletes can be costly, so if your app
/// can tolerate deleted documents being returned you might
/// gain some performance by passing <c>false</c>.
/// </param>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
public static DirectoryReader OpenIfChanged(DirectoryReader oldReader, IndexWriter writer, bool applyAllDeletes)
{
DirectoryReader newReader = oldReader.DoOpenIfChanged(writer, applyAllDeletes);
if (Debugging.AssertsEnabled) Debugging.Assert(newReader != oldReader);
return newReader;
}
/// <summary>
/// Returns all commit points that exist in the <see cref="Store.Directory"/>.
/// Normally, because the default is
/// <see cref="KeepOnlyLastCommitDeletionPolicy"/>, there would be only
/// one commit point. But if you're using a custom
/// <see cref="IndexDeletionPolicy"/> then there could be many commits.
/// Once you have a given commit, you can open a reader on
/// it by calling <see cref="DirectoryReader.Open(IndexCommit)"/>
/// There must be at least one commit in
/// the <see cref="Store.Directory"/>, else this method throws
/// <see cref="IndexNotFoundException"/>. Note that if a commit is in
/// progress while this method is running, that commit
/// may or may not be returned.
/// </summary>
/// <returns> a sorted list of <see cref="Index.IndexCommit"/>s, from oldest
/// to latest. </returns>
public static IList<IndexCommit> ListCommits(Directory dir)
{
string[] files = dir.ListAll();
JCG.List<IndexCommit> commits = new JCG.List<IndexCommit>();
SegmentInfos latest = new SegmentInfos();
latest.Read(dir);
long currentGen = latest.Generation;
commits.Add(new StandardDirectoryReader.ReaderCommit(latest, dir));
for (int i = 0; i < files.Length; i++)
{
string fileName = files[i];
if (fileName.StartsWith(IndexFileNames.SEGMENTS, StringComparison.Ordinal) && !fileName.Equals(IndexFileNames.SEGMENTS_GEN, StringComparison.Ordinal) && SegmentInfos.GenerationFromSegmentsFileName(fileName) < currentGen)
{
SegmentInfos sis = new SegmentInfos();
try
{
// IOException allowed to throw there, in case
// segments_N is corrupt
sis.Read(dir, fileName);
}
catch (Exception fnfe) when (fnfe.IsNoSuchFileExceptionOrFileNotFoundException())
{
// LUCENE-948: on NFS (and maybe others), if
// you have writers switching back and forth
// between machines, it's very likely that the
// dir listing will be stale and will claim a
// file segments_X exists when in fact it
// doesn't. So, we catch this and handle it
// as if the file does not exist
sis = null;
}
if (sis != null)
{
commits.Add(new StandardDirectoryReader.ReaderCommit(sis, dir));
}
}
}
// Ensure that the commit points are sorted in ascending order.
commits.Sort();
return commits;
}
/// <summary>
/// Returns <c>true</c> if an index likely exists at
/// the specified directory. Note that if a corrupt index
/// exists, or if an index in the process of committing </summary>
/// <param name="directory"> the directory to check for an index </param>
/// <returns> <c>true</c> if an index exists; <c>false</c> otherwise </returns>
public static bool IndexExists(Directory directory)
{
// LUCENE-2812, LUCENE-2727, LUCENE-4738: this logic will
// return true in cases that should arguably be false,
// such as only IW.prepareCommit has been called, or a
// corrupt first commit, but it's too deadly to make
// this logic "smarter" and risk accidentally returning
// false due to various cases like file description
// exhaustion, access denied, etc., because in that
// case IndexWriter may delete the entire index. It's
// safer to err towards "index exists" than try to be
// smart about detecting not-yet-fully-committed or
// corrupt indices. this means that IndexWriter will
// throw an exception on such indices and the app must
// resolve the situation manually:
string[] files;
try
{
files = directory.ListAll();
}
catch (Exception nsde) when (nsde.IsNoSuchDirectoryException())
{
// Directory does not exist --> no index exists
return false;
}
// Defensive: maybe a Directory impl returns null
// instead of throwing NoSuchDirectoryException:
if (files != null)
{
string prefix = IndexFileNames.SEGMENTS + "_";
foreach (string file in files)
{
if (file.StartsWith(prefix, StringComparison.Ordinal) || file.Equals(IndexFileNames.SEGMENTS_GEN, StringComparison.Ordinal))
{
return true;
}
}
}
return false;
}
/// <summary>
/// Expert: Constructs a <see cref="DirectoryReader"/> on the given <paramref name="segmentReaders"/>. </summary>
/// <param name="segmentReaders"> the wrapped atomic index segment readers. This array is
/// returned by <see cref="CompositeReader.GetSequentialSubReaders"/> and used to resolve the correct
/// subreader for docID-based methods. <b>Please note:</b> this array is <b>not</b>
/// cloned and not protected for modification outside of this reader.
/// Subclasses of <see cref="DirectoryReader"/> should take care to not allow
/// modification of this internal array, e.g. <see cref="DoOpenIfChanged()"/>. </param>
protected DirectoryReader(Directory directory, AtomicReader[] segmentReaders)
: base(segmentReaders)
{
this.m_directory = directory;
}
/// <summary>
/// Returns the directory this index resides in. </summary>
public Directory Directory =>
// Don't ensureOpen here -- in certain cases, when a
// cloned/reopened reader needs to commit, it may call
// this method on the closed original reader
m_directory;
/// <summary>
/// Implement this method to support <see cref="OpenIfChanged(DirectoryReader)"/>.
/// If this reader does not support reopen, return <c>null</c>, so
/// client code is happy. This should be consistent with <see cref="IsCurrent()"/>
/// (should always return <c>true</c>) if reopen is not supported. </summary>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
/// <returns> <c>null</c> if there are no changes; else, a new
/// <see cref="DirectoryReader"/> instance. </returns>
protected internal abstract DirectoryReader DoOpenIfChanged();
/// <summary>
/// Implement this method to support <see cref="OpenIfChanged(DirectoryReader, IndexCommit)"/>.
/// If this reader does not support reopen from a specific <see cref="Index.IndexCommit"/>,
/// throw <see cref="NotSupportedException"/>. </summary>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
/// <returns> <c>null</c> if there are no changes; else, a new
/// <see cref="DirectoryReader"/> instance. </returns>
protected internal abstract DirectoryReader DoOpenIfChanged(IndexCommit commit);
/// <summary>
/// Implement this method to support <see cref="OpenIfChanged(DirectoryReader, IndexWriter, bool)"/>.
/// If this reader does not support reopen from <see cref="IndexWriter"/>,
/// throw <see cref="NotSupportedException"/>. </summary>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
/// <returns> <c>null</c> if there are no changes; else, a new
/// <see cref="DirectoryReader"/> instance. </returns>
protected internal abstract DirectoryReader DoOpenIfChanged(IndexWriter writer, bool applyAllDeletes);
/// <summary>
/// Version number when this <see cref="IndexReader"/> was opened.
///
/// <para>This method
/// returns the version recorded in the commit that the
/// reader opened. This version is advanced every time
/// a change is made with <see cref="IndexWriter"/>.</para>
/// </summary>
public abstract long Version { get; }
/// <summary>
/// Check whether any new changes have occurred to the
/// index since this reader was opened.
///
/// <para>If this reader was created by calling an overload of <see cref="Open(Directory)"/>,
/// then this method checks if any further commits
/// (see <see cref="IndexWriter.Commit()"/>) have occurred in the
/// directory.</para>
///
/// <para>If instead this reader is a near real-time reader
/// (ie, obtained by a call to
/// <see cref="DirectoryReader.Open(IndexWriter, bool)"/>, or by calling an overload of <see cref="OpenIfChanged(DirectoryReader)"/>
/// on a near real-time reader), then this method checks if
/// either a new commit has occurred, or any new
/// uncommitted changes have taken place via the writer.
/// Note that even if the writer has only performed
/// merging, this method will still return <c>false</c>.</para>
///
/// <para>In any event, if this returns <c>false</c>, you should call
/// an overload of <see cref="OpenIfChanged(DirectoryReader)"/> to get a new reader that sees the
/// changes.</para>
/// </summary>
/// <exception cref="IOException"> if there is a low-level IO error </exception>
public abstract bool IsCurrent();
/// <summary>
/// Expert: return the <see cref="Index.IndexCommit"/> that this reader has opened.
/// <para/>
/// @lucene.experimental
/// </summary>
public abstract IndexCommit IndexCommit { get; }
}
}