summaryrefslogtreecommitdiff
blob: 128efe8513f6082d40daa1d6c96139b374cf349e (plain)
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
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
<?php
/**
 * Contains classes for handling the message index.
 *
 * @file
 * @author Niklas Laxstrom
 * @copyright Copyright © 2008-2013, Niklas Laxström
 * @license GPL-2.0-or-later
 */

use MediaWiki\Logger\LoggerFactory;

/**
 * Creates a database of keys in all groups, so that namespace and key can be
 * used to get the groups they belong to. This is used as a fallback when
 * loadgroup parameter is not provided in the request, which happens if someone
 * reaches a messages from somewhere else than Special:Translate. Also used
 * by Special:TranslationStats and alike which need to map lots of titles
 * to message groups.
 */
abstract class MessageIndex {
	private const CACHEKEY = 'Translate-MessageIndex-interim';

	/**
	 * @var self
	 */
	protected static $instance;

	/**
	 * @var MapCacheLRU|null
	 */
	private static $keysCache;

	/** @var BagOStuff */
	protected $interimCache;

	/**
	 * @return self
	 */
	public static function singleton() {
		if ( self::$instance === null ) {
			global $wgTranslateMessageIndex;
			$params = $wgTranslateMessageIndex;
			if ( is_string( $params ) ) {
				$params = (array)$params;
			}
			$class = array_shift( $params );
			// @phan-suppress-next-line PhanTypeExpectedObjectOrClassName
			self::$instance = new $class( $params );
		}

		return self::$instance;
	}

	/**
	 * Override the global instance, for testing.
	 *
	 * @since 2015.04
	 * @param MessageIndex $instance
	 */
	public static function setInstance( self $instance ) {
		self::$instance = $instance;
	}

	/**
	 * Retrieves a list of groups given MessageHandle belongs to.
	 * @since 2012-01-04
	 * @param MessageHandle $handle
	 * @return array
	 */
	public static function getGroupIds( MessageHandle $handle ): array {
		global $wgTranslateMessageNamespaces;

		$title = $handle->getTitle();

		if ( !$title->inNamespaces( $wgTranslateMessageNamespaces ) ) {
			return [];
		}

		$namespace = $title->getNamespace();
		$key = $handle->getKey();
		$normkey = TranslateUtils::normaliseKey( $namespace, $key );

		$cache = self::getCache();
		$value = $cache->get( $normkey );
		if ( $value === null ) {
			$value = (array)self::singleton()->getWithCache( $normkey );
			$cache->set( $normkey, $value );
		}

		return $value;
	}

	/**
	 * @return MapCacheLRU
	 */
	private static function getCache() {
		if ( self::$keysCache === null ) {
			self::$keysCache = new MapCacheLRU( 30 );
		}
		return self::$keysCache;
	}

	/**
	 * @since 2012-01-04
	 * @param MessageHandle $handle
	 * @return MessageGroup|null
	 */
	public static function getPrimaryGroupId( MessageHandle $handle ) {
		$groups = self::getGroupIds( $handle );

		return count( $groups ) ? array_shift( $groups ) : null;
	}

	private function getWithCache( $key ) {
		$interimCacheValue = $this->getInterimCache()->get( self::CACHEKEY );
		if ( $interimCacheValue && isset( $interimCacheValue['newKeys'][$key] ) ) {
			return $interimCacheValue['newKeys'][$key];
		}

		return $this->get( $key );
	}

	/**
	 * Looks up the stored value for single key. Only for testing.
	 * @since 2012-04-10
	 * @param string $key
	 * @return string|array|null
	 */
	protected function get( $key ) {
		// Default implementation
		$mi = $this->retrieve();
		return $mi[$key] ?? null;
	}

	/**
	 * @param bool $forRebuild
	 * @return array
	 */
	abstract public function retrieve( $forRebuild = false );

	/**
	 * @since 2018.01
	 * @return string[]
	 */
	public function getKeys() {
		return array_keys( $this->retrieve() );
	}

	abstract protected function store( array $array, array $diff );

	protected function lock() {
		return true;
	}

	protected function unlock() {
		return true;
	}

	/**
	 * Creates the index from scratch.
	 *
	 * @param float|null $timestamp Purge interim caches older than this timestamp.
	 * @return array
	 * @throws Exception
	 */
	public function rebuild( float $timestamp = null ): array {
		$logger = LoggerFactory::getInstance( 'Translate' );

		static $recursion = 0;

		if ( $recursion > 0 ) {
			$msg = __METHOD__ . ': trying to recurse - building the index first time?';
			wfWarn( $msg );

			$recursion--;
			return [];
		}
		$recursion++;

		$logger->info(
			'[MessageIndex] Started rebuild. Initiated by {callers}',
			[ 'callers' => wfGetAllCallers( 20 ) ]
		);

		$groups = MessageGroups::singleton()->getGroups();

		$tsStart = microtime( true );
		if ( !$this->lock() ) {
			throw new MessageIndexException( __CLASS__ . ': unable to acquire lock' );
		}

		$lockWaitDuration = microtime( true ) - $tsStart;
		$logger->info(
			'[MessageIndex] Got lock in {duration}',
			[ 'duration' => $lockWaitDuration ]
		);

		self::getCache()->clear();

		$new = $old = [];
		$old = $this->retrieve( 'rebuild' );
		$postponed = [];

		/**
		 * @var MessageGroup $g
		 */
		foreach ( $groups as $g ) {
			if ( !$g->exists() ) {
				$id = $g->getId();
				wfWarn( __METHOD__ . ": group '$id' is registered but does not exist" );
				continue;
			}

			# Skip meta thingies
			if ( $g->isMeta() ) {
				$postponed[] = $g;
				continue;
			}

			$this->checkAndAdd( $new, $g );
		}

		foreach ( $postponed as $g ) {
			$this->checkAndAdd( $new, $g, true );
		}

		$diff = self::getArrayDiff( $old, $new );
		$this->store( $new, $diff['keys'] );
		$this->unlock();

		$criticalSectionDuration = microtime( true ) - $tsStart - $lockWaitDuration;
		$logger->info(
			'[MessageIndex] Finished critical section in {duration}',
			[ 'duration' => $criticalSectionDuration ]
		);

		$cache = $this->getInterimCache();
		$interimCacheValue = $cache->get( self::CACHEKEY );
		$timestamp = $timestamp ?? microtime( true );
		if ( $interimCacheValue ) {
			if ( $interimCacheValue['timestamp'] <= $timestamp ) {
				$cache->delete( self::CACHEKEY );
			} else {
				// We got timestamp lower than newest front cache. This may be caused due to
				// job deduplication. Just in case, spin off a new job to clean up the cache.
				$job = MessageIndexRebuildJob::newJob();
				JobQueueGroup::singleton()->push( $job );
			}
		}

		$this->clearMessageGroupStats( $diff );

		$recursion--;

		return $new;
	}

	private function getInterimCache(): BagOStuff {
		return ObjectCache::getInstance( CACHE_ANYTHING );
	}

	public function storeInterim( MessageGroup $group, array $newKeys ): void {
		$namespace = $group->getNamespace();
		$id = $group->getId();

		$normalizedNewKeys = [];
		foreach ( $newKeys as $key ) {
			$normalizedNewKeys[TranslateUtils::normaliseKey( $namespace, $key )] = $id;
		}

		$cache = $this->getInterimCache();
		// Merge existing with existing keys
		$interimCacheValue = $cache->get( self::CACHEKEY, $cache::READ_LATEST );
		if ( $interimCacheValue ) {
			$normalizedNewKeys = array_merge( $interimCacheValue['newKeys'], $normalizedNewKeys );
		}

		$value = [
			'timestamp' => microtime( true ),
			'newKeys' => $normalizedNewKeys,
		];

		$cache->set( self::CACHEKEY, $value, $cache::TTL_DAY );
	}

	/**
	 * Compares two associative arrays.
	 *
	 * Values must be a string or list of strings. Returns an array of added,
	 * deleted and modified keys as well as value changes (you can think values
	 * as categories and keys as pages). Each of the keys ('add', 'del', 'mod'
	 * respectively) maps to an array whose keys are the changed keys of the
	 * original arrays and values are lists where first element contains the
	 * old value and the second element the new value.
	 *
	 * @code
	 * $a = [ 'a' => '1', 'b' => '2', 'c' => '3' ];
	 * $b = [ 'b' => '2', 'c' => [ '3', '2' ], 'd' => '4' ];
	 *
	 * self::getArrayDiff( $a, $b ) ) === [
	 *   'keys' => [
	 *     'add' => [ 'd' => [ [], [ '4' ] ] ],
	 *     'del' => [ 'a' => [ [ '1' ], [] ] ],
	 *     'mod' => [ 'c' => [ [ '3' ], [ '3', '2' ] ] ],
	 *   ],
	 *   'values' => [ 2, 4, 1 ]
	 * ];
	 * @endcode
	 *
	 * @param array $old
	 * @param array $new
	 * @return array
	 */
	public static function getArrayDiff( array $old, array $new ) {
		$values = [];
		$record = function ( $groups ) use ( &$values ) {
			foreach ( $groups as $group ) {
				$values[$group] = true;
			}
		};

		$keys = [
			'add' => [],
			'del' => [],
			'mod' => [],
		];

		foreach ( $new as $key => $groups ) {
			if ( !isset( $old[$key] ) ) {
				$keys['add'][$key] = [ [], (array)$groups ];
				$record( (array)$groups );
			// Using != here on purpose to ignore the order of items
			} elseif ( $groups != $old[$key] ) {
				$keys['mod'][$key] = [ (array)$old[$key], (array)$groups ];
				$record( array_diff( (array)$old[$key], (array)$groups ) );
				$record( array_diff( (array)$groups, (array)$old[$key] ) );
			}
		}

		foreach ( $old as $key => $groups ) {
			if ( !isset( $new[$key] ) ) {
				$keys['del'][$key] = [ (array)$groups, [] ];
				$record( (array)$groups );
			}
			// We already checked for diffs above
		}

		return [
			'keys' => $keys,
			'values' => array_keys( $values ),
		];
	}

	/**
	 * Purge stuff when set of keys have changed.
	 *
	 * @param array $diff
	 */
	protected function clearMessageGroupStats( array $diff ) {
		$job = MessageGroupStatsRebuildJob::newRefreshGroupsJob( $diff['values'] );
		JobQueueGroup::singleton()->push( $job );

		foreach ( $diff['keys'] as $keys ) {
			foreach ( $keys as $key => $data ) {
				[ $ns, $pagename ] = explode( ':', $key, 2 );
				$title = Title::makeTitle( $ns, $pagename );
				$handle = new MessageHandle( $title );
				[ $oldGroups, $newGroups ] = $data;
				Hooks::run( 'TranslateEventMessageMembershipChange',
					[ $handle, $oldGroups, $newGroups ] );
			}
		}
	}

	/**
	 * @param array &$hugearray
	 * @param MessageGroup $g
	 * @param bool $ignore
	 */
	protected function checkAndAdd( &$hugearray, MessageGroup $g, $ignore = false ) {
		$keys = $g->getKeys();
		$id = $g->getId();
		$namespace = $g->getNamespace();

		foreach ( $keys as $key ) {
			# Force all keys to lower case, because the case doesn't matter and it is
			# easier to do comparing when the case of first letter is unknown, because
			# mediawiki forces it to upper case
			$key = TranslateUtils::normaliseKey( $namespace, $key );
			if ( isset( $hugearray[$key] ) ) {
				if ( !$ignore ) {
					$to = implode( ', ', (array)$hugearray[$key] );
					wfWarn( "Key $key already belongs to $to, conflict with $id" );
				}

				if ( is_array( $hugearray[$key] ) ) {
					// Hard work is already done, just add a new reference
					$hugearray[$key][] = & $id;
				} else {
					// Store the actual reference, then remove it from array, to not
					// replace the references value, but to store an array of new
					// references instead. References are hard!
					$value = & $hugearray[$key];
					unset( $hugearray[$key] );
					$hugearray[$key] = [ &$value, &$id ];
				}
			} else {
				$hugearray[$key] = & $id;
			}
		}
		unset( $id ); // Disconnect the previous references to this $id
	}

	/**
	 * These are probably slower than serialize and unserialize,
	 * but they are more space efficient because we only need
	 * strings and arrays.
	 * @param mixed $data
	 * @return mixed
	 */
	protected function serialize( $data ) {
		if ( is_array( $data ) ) {
			return implode( '|', $data );
		} else {
			return $data;
		}
	}

	protected function unserialize( $data ) {
		if ( strpos( $data, '|' ) !== false ) {
			return explode( '|', $data );
		}

		return $data;
	}
}

/**
 * Storage on serialized file.
 *
 * This serializes the whole array. Because this format can preserve
 * the values which are stored as references inside the array, this is
 * the most space efficient storage method and fastest when you want
 * the full index.
 *
 * Unfortunately when the size of index grows to about 50000 items, even
 * though it is only 3,5M on disk, it takes 35M when loaded into memory
 * and the loading can take more than 0,5 seconds. Because usually we
 * need to look up only few keys, it is better to use another backend
 * which provides random access - this backend doesn't support that.
 */
class SerializedMessageIndex extends MessageIndex {
	/**
	 * @var array|null
	 */
	protected $index;

	protected $filename = 'translate_messageindex.ser';

	/**
	 * @param bool $forRebuild
	 * @return array
	 */
	public function retrieve( $forRebuild = false ) {
		if ( $this->index !== null ) {
			return $this->index;
		}

		$file = TranslateUtils::cacheFile( $this->filename );
		if ( file_exists( $file ) ) {
			$this->index = unserialize( file_get_contents( $file ) );
		} else {
			$this->index = $this->rebuild();
		}

		return $this->index;
	}

	protected function store( array $array, array $diff ) {
		$file = TranslateUtils::cacheFile( $this->filename );
		file_put_contents( $file, serialize( $array ) );
		$this->index = $array;
	}
}

/**
 * Storage on the database itself.
 *
 * This is likely to be the slowest backend. However it scales okay
 * and provides random access. It also doesn't need any special setup,
 * the database table is added with update.php together with other tables,
 * which is the reason this is the default backend. It also works well
 * on multi-server setup without needing for shared file storage.
 *
 * @since 2012-04-12
 */
class DatabaseMessageIndex extends MessageIndex {
	/**
	 * @var array|null
	 */
	protected $index;

	protected function lock() {
		$dbw = wfGetDB( DB_MASTER );

		// Any transaction should be flushed after getting the lock to avoid
		// stale pre-lock REPEATABLE-READ snapshot data.
		$ok = $dbw->lock( 'translate-messageindex', __METHOD__, 30 );
		if ( $ok ) {
			$dbw->commit( __METHOD__, 'flush' );
		}

		return $ok;
	}

	protected function unlock() {
		$fname = __METHOD__;
		$dbw = wfGetDB( DB_MASTER );
		// Unlock once the rows are actually unlocked to avoid deadlocks
		if ( !$dbw->trxLevel() ) {
			$dbw->unlock( 'translate-messageindex', $fname );
		} elseif ( is_callable( [ $dbw, 'onTransactionResolution' ] ) ) { // 1.28
			$dbw->onTransactionResolution( function () use ( $dbw, $fname ) {
				$dbw->unlock( 'translate-messageindex', $fname );
			}, $fname );
		} elseif ( is_callable( [ $dbw, 'onTransactionCommitOrIdle' ] ) ) {
			$dbw->onTransactionCommitOrIdle( function () use ( $dbw, $fname ) {
				$dbw->unlock( 'translate-messageindex', $fname );
			}, $fname );
		} else {
			$dbw->onTransactionIdle( function () use ( $dbw, $fname ) {
				$dbw->unlock( 'translate-messageindex', $fname );
			}, $fname );
		}

		return true;
	}

	/**
	 * @param bool $forRebuild
	 * @return array
	 */
	public function retrieve( $forRebuild = false ) {
		if ( $this->index !== null && !$forRebuild ) {
			return $this->index;
		}

		$dbr = wfGetDB( $forRebuild ? DB_MASTER : DB_REPLICA );
		$res = $dbr->select( 'translate_messageindex', '*', [], __METHOD__ );
		$this->index = [];
		foreach ( $res as $row ) {
			$this->index[$row->tmi_key] = $this->unserialize( $row->tmi_value );
		}

		return $this->index;
	}

	protected function get( $key ) {
		$dbr = wfGetDB( DB_REPLICA );
		$value = $dbr->selectField(
			'translate_messageindex',
			'tmi_value',
			[ 'tmi_key' => $key ],
			__METHOD__
		);

		if ( is_string( $value ) ) {
			$value = $this->unserialize( $value );
		} else {
			$value = null;
		}

		return $value;
	}

	protected function store( array $array, array $diff ) {
		$updates = [];

		foreach ( [ $diff['add'], $diff['mod'] ] as $changes ) {
			foreach ( $changes as $key => $data ) {
				[ , $new ] = $data;
				$updates[] = [
					'tmi_key' => $key,
					'tmi_value' => $this->serialize( $new ),
				];
			}
		}

		$index = [ 'tmi_key' ];
		$deletions = array_keys( $diff['del'] );

		$dbw = wfGetDB( DB_MASTER );
		$dbw->startAtomic( __METHOD__ );

		if ( $updates !== [] ) {
			$dbw->replace( 'translate_messageindex', [ $index ], $updates, __METHOD__ );
		}

		if ( $deletions !== [] ) {
			$dbw->delete( 'translate_messageindex', [ 'tmi_key' => $deletions ], __METHOD__ );
		}

		$dbw->endAtomic( __METHOD__ );

		$this->index = $array;
	}
}

/**
 * Storage on the object cache.
 *
 * This can be faster than DatabaseMessageIndex, but it doesn't
 * provide random access, and the data is not guaranteed to be persistent.
 *
 * This is unlikely to be the best backend for you, so don't use it.
 */
class CachedMessageIndex extends MessageIndex {
	protected $key = 'translate-messageindex';
	protected $cache;

	/**
	 * @var array|null
	 */
	protected $index;

	protected function __construct() {
		$this->cache = wfGetCache( CACHE_ANYTHING );
	}

	/**
	 * @param bool $forRebuild
	 * @return array
	 */
	public function retrieve( $forRebuild = false ) {
		if ( $this->index !== null ) {
			return $this->index;
		}

		$key = wfMemcKey( $this->key );
		$data = $this->cache->get( $key );
		if ( is_array( $data ) ) {
			$this->index = $data;
		} else {
			$this->index = $this->rebuild();
		}

		return $this->index;
	}

	protected function store( array $array, array $diff ) {
		$key = wfMemcKey( $this->key );
		$this->cache->set( $key, $array );

		$this->index = $array;
	}
}

/**
 * Storage on CDB files.
 *
 * This is improved version of SerializedMessageIndex. It uses CDB files
 * for storage, which means it provides random access. The CDB files are
 * about double the size of serialized files (~7M for 50000 keys).
 *
 * Loading the whole index is slower than serialized, but about the same
 * as for database. Suitable for single-server setups where
 * SerializedMessageIndex is too slow for sloading the whole index.
 *
 * @since 2012-04-10
 */
class CDBMessageIndex extends MessageIndex {
	/**
	 * @var array|null
	 */
	protected $index;

	/**
	 * @var \Cdb\Reader|null
	 */
	protected $reader;

	/**
	 * @var string
	 */
	protected $filename = 'translate_messageindex.cdb';

	/**
	 * @param bool $forRebuild
	 * @return array
	 */
	public function retrieve( $forRebuild = false ) {
		$reader = $this->getReader();
		// This must be below the line above, which may fill the index
		if ( $this->index !== null ) {
			return $this->index;
		}

		$this->index = [];
		foreach ( $this->getKeys() as $key ) {
			$this->index[$key] = $this->unserialize( $reader->get( $key ) );
		}

		return $this->index;
	}

	public function getKeys() {
		$reader = $this->getReader();
		$keys = [];
		while ( true ) {
			$key = $keys === [] ? $reader->firstkey() : $reader->nextkey();
			if ( $key === false ) {
				break;
			}
			$keys[] = $key;
		}

		return $keys;
	}

	protected function get( $key ) {
		$reader = $this->getReader();
		// We might have the full cache loaded
		if ( $this->index !== null ) {
			return $this->index[$key] ?? null;
		}

		$value = $reader->get( $key );
		if ( !is_string( $value ) ) {
			$value = null;
		} else {
			$value = $this->unserialize( $value );
		}

		return $value;
	}

	protected function store( array $array, array $diff ) {
		$this->reader = null;

		$file = TranslateUtils::cacheFile( $this->filename );
		$cache = \Cdb\Writer::open( $file );

		foreach ( $array as $key => $value ) {
			$value = $this->serialize( $value );
			$cache->set( $key, $value );
		}

		$cache->close();

		$this->index = $array;
	}

	protected function getReader() {
		if ( $this->reader ) {
			return $this->reader;
		}

		$file = TranslateUtils::cacheFile( $this->filename );
		if ( !file_exists( $file ) ) {
			// Create an empty index to allow rebuild
			$this->store( [], [] );
			$this->index = $this->rebuild();
		}

		$this->reader = \Cdb\Reader::open( $file );
		return $this->reader;
	}
}

/**
 * Storage on hash.
 *
 * For testing.
 *
 * @since 2015.04
 */
class HashMessageIndex extends MessageIndex {
	/**
	 * @var array
	 */
	protected $index = [];

	/**
	 * @param bool $forRebuild
	 * @return array
	 */
	public function retrieve( $forRebuild = false ) {
		return $this->index;
	}

	/**
	 * @param string $key
	 *
	 * @return mixed
	 */
	protected function get( $key ) {
		return $this->index[$key] ?? null;
	}

	protected function store( array $array, array $diff ) {
		$this->index = $array;
	}

	protected function clearMessageGroupStats( array $diff ) {
	}
}