summaryrefslogtreecommitdiff
path: root/includes/installer/DatabaseUpdater.php
blob: 25f751c715200a76e53e45dd262c39221f9a6c7a (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
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
<?php
/**
 * DBMS-specific updater helper.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Deployment
 */

require_once( __DIR__ . '/../../maintenance/Maintenance.php' );

/**
 * Class for handling database updates. Roughly based off of updaters.inc, with
 * a few improvements :)
 *
 * @ingroup Deployment
 * @since 1.17
 */
abstract class DatabaseUpdater {

	/**
	 * Array of updates to perform on the database
	 *
	 * @var array
	 */
	protected $updates = array();

	/**
	 * Array of updates that were skipped
	 *
	 * @var array
	 */
	protected $updatesSkipped = array();

	/**
	 * List of extension-provided database updates
	 * @var array
	 */
	protected $extensionUpdates = array();

	/**
	 * Handle to the database subclass
	 *
	 * @var DatabaseBase
	 */
	protected $db;

	protected $shared = false;

	/**
	 * Scripts to run after database update
	 * Should be a subclass of LoggedUpdateMaintenance
	 */
	protected $postDatabaseUpdateMaintenance = array(
		'DeleteDefaultMessages',
		'PopulateRevisionLength',
		'PopulateRevisionSha1',
		'PopulateImageSha1',
		'FixExtLinksProtocolRelative',
		'PopulateFilearchiveSha1',
	);

	/**
	 * File handle for SQL output.
	 *
	 * @var Filehandle
	 */
	protected $fileHandle = null;

	/**
	 * Flag specifying whether or not to skip schema (e.g. SQL-only) updates.
	 *
	 * @var bool
	 */
	protected $skipSchema = false;

	/**
	 * Hold the value of $wgContentHandlerUseDB during the upgrade.
	 */
	protected $wgContentHandlerUseDB = true;

	/**
	 * Constructor
	 *
	 * @param $db DatabaseBase object to perform updates on
	 * @param bool $shared Whether to perform updates on shared tables
	 * @param $maintenance Maintenance Maintenance object which created us
	 */
	protected function __construct( DatabaseBase &$db, $shared, Maintenance $maintenance = null ) {
		$this->db = $db;
		$this->db->setFlag( DBO_DDLMODE ); // For Oracle's handling of schema files
		$this->shared = $shared;
		if ( $maintenance ) {
			$this->maintenance = $maintenance;
			$this->fileHandle = $maintenance->fileHandle;
		} else {
			$this->maintenance = new FakeMaintenance;
		}
		$this->maintenance->setDB( $db );
		$this->initOldGlobals();
		$this->loadExtensions();
		wfRunHooks( 'LoadExtensionSchemaUpdates', array( $this ) );
	}

	/**
	 * Initialize all of the old globals. One day this should all become
	 * something much nicer
	 */
	private function initOldGlobals() {
		global $wgExtNewTables, $wgExtNewFields, $wgExtPGNewFields,
			$wgExtPGAlteredFields, $wgExtNewIndexes, $wgExtModifiedFields;

		# For extensions only, should be populated via hooks
		# $wgDBtype should be checked to specifiy the proper file
		$wgExtNewTables = array(); // table, dir
		$wgExtNewFields = array(); // table, column, dir
		$wgExtPGNewFields = array(); // table, column, column attributes; for PostgreSQL
		$wgExtPGAlteredFields = array(); // table, column, new type, conversion method; for PostgreSQL
		$wgExtNewIndexes = array(); // table, index, dir
		$wgExtModifiedFields = array(); // table, index, dir
	}

	/**
	 * Loads LocalSettings.php, if needed, and initialises everything needed for LoadExtensionSchemaUpdates hook
	 */
	private function loadExtensions() {
		if ( !defined( 'MEDIAWIKI_INSTALL' ) ) {
			return; // already loaded
		}
		$vars = Installer::getExistingLocalSettings();
		if ( !$vars ) {
			return; // no LocalSettings found
		}
		if ( !isset( $vars['wgHooks'] ) || !isset( $vars['wgHooks']['LoadExtensionSchemaUpdates'] ) ) {
			return;
		}
		global $wgHooks, $wgAutoloadClasses;
		$wgHooks['LoadExtensionSchemaUpdates'] = $vars['wgHooks']['LoadExtensionSchemaUpdates'];
		$wgAutoloadClasses = $wgAutoloadClasses + $vars['wgAutoloadClasses'];
	}

	/**
	 * @throws MWException
	 * @param DatabaseBase $db
	 * @param bool $shared
	 * @param null $maintenance
	 * @return DatabaseUpdater
	 */
	public static function newForDB( &$db, $shared = false, $maintenance = null ) {
		$type = $db->getType();
		if( in_array( $type, Installer::getDBTypes() ) ) {
			$class = ucfirst( $type ) . 'Updater';
			return new $class( $db, $shared, $maintenance );
		} else {
			throw new MWException( __METHOD__ . ' called for unsupported $wgDBtype' );
		}
	}

	/**
	 * Get a database connection to run updates
	 *
	 * @return DatabaseBase
	 */
	public function getDB() {
		return $this->db;
	}

	/**
	 * Output some text. If we're running from web, escape the text first.
	 *
	 * @param string $str Text to output
	 */
	public function output( $str ) {
		if ( $this->maintenance->isQuiet() ) {
			return;
		}
		global $wgCommandLineMode;
		if( !$wgCommandLineMode ) {
			$str = htmlspecialchars( $str );
		}
		echo $str;
		flush();
	}

	/**
	 * Add a new update coming from an extension. This should be called by
	 * extensions while executing the LoadExtensionSchemaUpdates hook.
	 *
	 * @since 1.17
	 *
	 * @param array $update the update to run. Format is the following:
	 *                first item is the callback function, it also can be a
	 *                simple string with the name of a function in this class,
	 *                following elements are parameters to the function.
	 *                Note that callback functions will receive this object as
	 *                first parameter.
	 */
	public function addExtensionUpdate( array $update ) {
		$this->extensionUpdates[] = $update;
	}

	/**
	 * Convenience wrapper for addExtensionUpdate() when adding a new table (which
	 * is the most common usage of updaters in an extension)
	 *
	 * @since 1.18
	 *
	 * @param string $tableName Name of table to create
	 * @param string $sqlPath Full path to the schema file
	 */
	public function addExtensionTable( $tableName, $sqlPath ) {
		$this->extensionUpdates[] = array( 'addTable', $tableName, $sqlPath, true );
	}

	/**
	 * @since 1.19
	 *
	 * @param $tableName string
	 * @param $indexName string
	 * @param $sqlPath string
	 */
	public function addExtensionIndex( $tableName, $indexName, $sqlPath ) {
		$this->extensionUpdates[] = array( 'addIndex', $tableName, $indexName, $sqlPath, true );
	}

	/**
	 *
	 * @since 1.19
	 *
	 * @param $tableName string
	 * @param $columnName string
	 * @param $sqlPath string
	 */
	public function addExtensionField( $tableName, $columnName, $sqlPath ) {
		$this->extensionUpdates[] = array( 'addField', $tableName, $columnName, $sqlPath, true );
	}

	/**
	 *
	 * @since 1.20
	 *
	 * @param $tableName string
	 * @param $columnName string
	 * @param $sqlPath string
	 */
	public function dropExtensionField( $tableName, $columnName, $sqlPath ) {
		$this->extensionUpdates[] = array( 'dropField', $tableName, $columnName, $sqlPath, true );
	}

	/**
	 * Drop an index from an extension table
	 *
	 * @since 1.21
	 *
	 * @param string $tableName The table name
	 * @param string $indexName The index name
	 * @param string $sqlPath The path to the SQL change path
	 */
	public function dropExtensionIndex( $tableName, $indexName, $sqlPath ) {
		$this->extensionUpdates[] = array( 'dropIndex', $tableName, $indexName, $sqlPath, true );
	}

	/**
	 *
	 * @since 1.20
	 *
	 * @param $tableName string
	 * @param $sqlPath string
	 */
	public function dropExtensionTable( $tableName, $sqlPath ) {
		$this->extensionUpdates[] = array( 'dropTable', $tableName, $sqlPath, true );
	}

	/**
	 * Rename an index on an extension table
	 *
	 * @since 1.21
	 *
	 * @param string $tableName The table name
	 * @param string $oldIndexName The old index name
	 * @param string $newIndexName The new index name
	 * @param $skipBothIndexExistWarning Boolean: Whether to warn if both the old and the new indexes exist. [facultative; by default, false]
	 * @param string $sqlPath The path to the SQL change path
	 */
	public function renameExtensionIndex( $tableName, $oldIndexName, $newIndexName, $sqlPath, $skipBothIndexExistWarning = false ) {
		$this->extensionUpdates[] = array( 'renameIndex', $tableName, $oldIndexName, $newIndexName, $skipBothIndexExistWarning, $sqlPath, true );
	}

	/**
	 * @since 1.21
	 *
	 * @param string $tableName The table name
	 * @param string $fieldName The field to be modified
	 * @param string $sqlPath The path to the SQL change path
	 */
	public function modifyExtensionField( $tableName, $fieldName, $sqlPath) {
		$this->extensionUpdates[] = array( 'modifyField', $tableName, $fieldName, $sqlPath, true );
	}

	/**
	 *
	 * @since 1.20
	 *
	 * @param $tableName string
	 * @return bool
	 */
	public function tableExists( $tableName ) {
		return ( $this->db->tableExists( $tableName, __METHOD__ ) );
	}

	/**
	 * Add a maintenance script to be run after the database updates are complete.
	 *
	 * Script should subclass LoggedUpdateMaintenance
	 *
	 * @since 1.19
	 *
	 * @param string $class Name of a Maintenance subclass
	 */
	public function addPostDatabaseUpdateMaintenance( $class ) {
		$this->postDatabaseUpdateMaintenance[] = $class;
	}

	/**
	 * Get the list of extension-defined updates
	 *
	 * @return Array
	 */
	protected function getExtensionUpdates() {
		return $this->extensionUpdates;
	}

	/**
	 * @since 1.17
	 *
	 * @return array
	 */
	public function getPostDatabaseUpdateMaintenance() {
		return $this->postDatabaseUpdateMaintenance;
	}

	/**
	 * @since 1.21
	 *
	 * Writes the schema updates desired to a file for the DB Admin to run.
	 */
	private function writeSchemaUpdateFile( $schemaUpdate = array() ) {
		$updates = $this->updatesSkipped;
		$this->updatesSkipped = array();

		foreach( $updates as $funcList ) {
			$func = $funcList[0];
			$arg = $funcList[1];
			$origParams = $funcList[2];
			call_user_func_array( $func, $arg );
			flush();
			$this->updatesSkipped[] = $origParams;
		}
	}

	/**
	 * Do all the updates
	 *
	 * @param array $what what updates to perform
	 */
	public function doUpdates( $what = array( 'core', 'extensions', 'stats' ) ) {
		global $wgVersion, $wgLocalisationCacheConf;

		$this->db->begin( __METHOD__ );
		$what = array_flip( $what );
		$this->skipSchema = isset( $what['noschema'] ) || $this->fileHandle !== null;
		if ( isset( $what['core'] ) ) {
			$this->runUpdates( $this->getCoreUpdateList(), false );
		}
		if ( isset( $what['extensions'] ) ) {
			$this->runUpdates( $this->getOldGlobalUpdates(), false );
			$this->runUpdates( $this->getExtensionUpdates(), true );
		}

		if ( isset( $what['stats'] ) ) {
			$this->checkStats();
		}

		if ( isset( $what['purge'] ) ) {
			$this->purgeCache();

			if ( $wgLocalisationCacheConf['manualRecache'] ) {
				$this->rebuildLocalisationCache();
			}
		}

		$this->setAppliedUpdates( $wgVersion, $this->updates );

		if( $this->fileHandle ) {
			$this->skipSchema = false;
			$this->writeSchemaUpdateFile();
			$this->setAppliedUpdates( "$wgVersion-schema", $this->updatesSkipped );
		}

		$this->db->commit( __METHOD__ );
	}

	/**
	 * Helper function for doUpdates()
	 *
	 * @param array $updates of updates to run
	 * @param $passSelf Boolean: whether to pass this object we calling external
	 *                  functions
	 */
	private function runUpdates( array $updates, $passSelf ) {
		$updatesDone = array();
		$updatesSkipped = array();
		foreach ( $updates as $params ) {
			$origParams = $params;
			$func = array_shift( $params );
			if( !is_array( $func ) && method_exists( $this, $func ) ) {
				$func = array( $this, $func );
			} elseif ( $passSelf ) {
				array_unshift( $params, $this );
			}
			$ret = call_user_func_array( $func, $params );
			flush();
			if( $ret !== false ) {
				$updatesDone[] = $origParams;
			} else {
				$updatesSkipped[] = array( $func, $params, $origParams );
			}
		}
		$this->updatesSkipped = array_merge( $this->updatesSkipped, $updatesSkipped );
		$this->updates = array_merge( $this->updates, $updatesDone );
	}

	/**
	 * @param $version
	 * @param $updates array
	 */
	protected function setAppliedUpdates( $version, $updates = array() ) {
		$this->db->clearFlag( DBO_DDLMODE );
		if( !$this->canUseNewUpdatelog() ) {
			return;
		}
		$key = "updatelist-$version-" . time();
		$this->db->insert( 'updatelog',
			array( 'ul_key' => $key, 'ul_value' => serialize( $updates ) ),
			__METHOD__ );
		$this->db->setFlag( DBO_DDLMODE );
	}

	/**
	 * Helper function: check if the given key is present in the updatelog table.
	 * Obviously, only use this for updates that occur after the updatelog table was
	 * created!
	 * @param string $key Name of the key to check for
	 *
	 * @return bool
	 */
	public function updateRowExists( $key ) {
		$row = $this->db->selectRow(
			'updatelog',
			'1',
			array( 'ul_key' => $key ),
			__METHOD__
		);
		return (bool)$row;
	}

	/**
	 * Helper function: Add a key to the updatelog table
	 * Obviously, only use this for updates that occur after the updatelog table was
	 * created!
	 * @param string $key Name of key to insert
	 * @param string $val [optional] value to insert along with the key
	 */
	public function insertUpdateRow( $key, $val = null ) {
		$this->db->clearFlag( DBO_DDLMODE );
		$values = array( 'ul_key' => $key );
		if( $val && $this->canUseNewUpdatelog() ) {
			$values['ul_value'] = $val;
		}
		$this->db->insert( 'updatelog', $values, __METHOD__, 'IGNORE' );
		$this->db->setFlag( DBO_DDLMODE );
	}

	/**
	 * Updatelog was changed in 1.17 to have a ul_value column so we can record
	 * more information about what kind of updates we've done (that's what this
	 * class does). Pre-1.17 wikis won't have this column, and really old wikis
	 * might not even have updatelog at all
	 *
	 * @return boolean
	 */
	protected function canUseNewUpdatelog() {
		return $this->db->tableExists( 'updatelog', __METHOD__ ) &&
			$this->db->fieldExists( 'updatelog', 'ul_value', __METHOD__ );
	}

	/**
	 * Returns whether updates should be executed on the database table $name.
	 * Updates will be prevented if the table is a shared table and it is not
	 * specified to run updates on shared tables.
	 *
	 * @param string $name table name
	 * @return bool
	 */
	protected function doTable( $name ) {
		global $wgSharedDB, $wgSharedTables;

		// Don't bother to check $wgSharedTables if there isn't a shared database
		// or the user actually also wants to do updates on the shared database.
		if ( $wgSharedDB === null || $this->shared ) {
			return true;
		}

		return !in_array( $name, $wgSharedTables );
	}

	/**
	 * Before 1.17, we used to handle updates via stuff like
	 * $wgExtNewTables/Fields/Indexes. This is nasty :) We refactored a lot
	 * of this in 1.17 but we want to remain back-compatible for a while. So
	 * load up these old global-based things into our update list.
	 *
	 * @return array
	 */
	protected function getOldGlobalUpdates() {
		global $wgExtNewFields, $wgExtNewTables, $wgExtModifiedFields,
			$wgExtNewIndexes;

		$updates = array();

		foreach ( $wgExtNewTables as $tableRecord ) {
			$updates[] = array(
				'addTable', $tableRecord[0], $tableRecord[1], true
			);
		}

		foreach ( $wgExtNewFields as $fieldRecord ) {
			$updates[] = array(
				'addField', $fieldRecord[0], $fieldRecord[1],
					$fieldRecord[2], true
			);
		}

		foreach ( $wgExtNewIndexes as $fieldRecord ) {
			$updates[] = array(
				'addIndex', $fieldRecord[0], $fieldRecord[1],
					$fieldRecord[2], true
			);
		}

		foreach ( $wgExtModifiedFields as $fieldRecord ) {
			$updates[] = array(
				'modifyField', $fieldRecord[0], $fieldRecord[1],
					$fieldRecord[2], true
			);
		}

		return $updates;
	}

	/**
	 * Get an array of updates to perform on the database. Should return a
	 * multi-dimensional array. The main key is the MediaWiki version (1.12,
	 * 1.13...) with the values being arrays of updates, identical to how
	 * updaters.inc did it (for now)
	 *
	 * @return Array
	 */
	abstract protected function getCoreUpdateList();

	/**
	 * Append an SQL fragment to the open file handle.
	 *
	 * @param string $filename File name to open
	 */
	public function copyFile( $filename ) {
		$this->db->sourceFile( $filename, false, false, false,
			array( $this, 'appendLine' )
		);
	}

	/**
	 * Append a line to the open filehandle.  The line is assumed to
	 * be a complete SQL statement.
	 *
	 * This is used as a callback for for sourceLine().
	 *
	 * @param string $line text to append to the file
	 * @return Boolean false to skip actually executing the file
	 * @throws MWException
	 */
	public function appendLine( $line ) {
		$line = rtrim( $line ) . ";\n";
		if( fwrite( $this->fileHandle, $line ) === false ) {
			throw new MWException( "trouble writing file" );
		}
		return false;
	}

	/**
	 * Applies a SQL patch
	 *
	 * @param string $path Path to the patch file
	 * @param $isFullPath Boolean Whether to treat $path as a relative or not
	 * @param string $msg Description of the patch
	 * @return boolean false if patch is skipped.
	 */
	protected function applyPatch( $path, $isFullPath = false, $msg = null ) {
		if ( $msg === null ) {
			$msg = "Applying $path patch";
		}
		if ( $this->skipSchema ) {
			$this->output( "...skipping schema change ($msg).\n" );
			return false;
		}

		$this->output( "$msg ..." );

		if ( !$isFullPath ) {
			$path = $this->db->patchPath( $path );
		}
		if( $this->fileHandle !== null ) {
			$this->copyFile( $path );
		} else {
			$this->db->sourceFile( $path );
		}
		$this->output( "done.\n" );
		return true;
	}

	/**
	 * Add a new table to the database
	 *
	 * @param string $name Name of the new table
	 * @param string $patch Path to the patch file
	 * @param $fullpath Boolean Whether to treat $patch path as a relative or not
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	protected function addTable( $name, $patch, $fullpath = false ) {
		if ( !$this->doTable( $name ) ) {
			return true;
		}

		if ( $this->db->tableExists( $name, __METHOD__ ) ) {
			$this->output( "...$name table already exists.\n" );
		} else {
			return $this->applyPatch( $patch, $fullpath, "Creating $name table" );
		}
		return true;
	}

	/**
	 * Add a new field to an existing table
	 *
	 * @param string $table Name of the table to modify
	 * @param string $field Name of the new field
	 * @param string $patch Path to the patch file
	 * @param $fullpath Boolean Whether to treat $patch path as a relative or not
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	protected function addField( $table, $field, $patch, $fullpath = false ) {
		if ( !$this->doTable( $table ) ) {
			return true;
		}

		if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
			$this->output( "...$table table does not exist, skipping new field patch.\n" );
		} elseif ( $this->db->fieldExists( $table, $field, __METHOD__ ) ) {
			$this->output( "...have $field field in $table table.\n" );
		} else {
			return $this->applyPatch( $patch, $fullpath, "Adding $field field to table $table" );
		}
		return true;
	}

	/**
	 * Add a new index to an existing table
	 *
	 * @param string $table Name of the table to modify
	 * @param string $index Name of the new index
	 * @param string $patch Path to the patch file
	 * @param $fullpath Boolean Whether to treat $patch path as a relative or not
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	protected function addIndex( $table, $index, $patch, $fullpath = false ) {
		if ( !$this->doTable( $table ) ) {
			return true;
		}

		if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
			$this->output( "...skipping: '$table' table doesn't exist yet.\n" );
		} else if ( $this->db->indexExists( $table, $index, __METHOD__ ) ) {
			$this->output( "...index $index already set on $table table.\n" );
		} else {
			return $this->applyPatch( $patch, $fullpath, "Adding index $index to table $table" );
		}
		return true;
	}

	/**
	 * Drop a field from an existing table
	 *
	 * @param string $table Name of the table to modify
	 * @param string $field Name of the old field
	 * @param string $patch Path to the patch file
	 * @param $fullpath Boolean Whether to treat $patch path as a relative or not
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	protected function dropField( $table, $field, $patch, $fullpath = false ) {
		if ( !$this->doTable( $table ) ) {
			return true;
		}

		if ( $this->db->fieldExists( $table, $field, __METHOD__ ) ) {
			return $this->applyPatch( $patch, $fullpath, "Table $table contains $field field. Dropping" );
		} else {
			$this->output( "...$table table does not contain $field field.\n" );
		}
		return true;
	}

	/**
	 * Drop an index from an existing table
	 *
	 * @param string $table Name of the table to modify
	 * @param string $index Name of the index
	 * @param string $patch Path to the patch file
	 * @param $fullpath Boolean: Whether to treat $patch path as a relative or not
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	protected function dropIndex( $table, $index, $patch, $fullpath = false ) {
		if ( !$this->doTable( $table ) ) {
			return true;
		}

		if ( $this->db->indexExists( $table, $index, __METHOD__ ) ) {
			return $this->applyPatch( $patch, $fullpath, "Dropping $index index from table $table" );
		} else {
			$this->output( "...$index key doesn't exist.\n" );
		}
		return true;
	}

	/**
	 * Rename an index from an existing table
	 *
	 * @param string $table Name of the table to modify
	 * @param string $oldIndex Old name of the index
	 * @param string $newIndex New name of the index
	 * @param $skipBothIndexExistWarning Boolean: Whether to warn if both the old and the new indexes exist.
	 * @param string $patch Path to the patch file
	 * @param $fullpath Boolean: Whether to treat $patch path as a relative or not
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	protected function renameIndex( $table, $oldIndex, $newIndex, $skipBothIndexExistWarning, $patch, $fullpath = false ) {
		if ( !$this->doTable( $table ) ) {
			return true;
		}

		// First requirement: the table must exist
		if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
			$this->output( "...skipping: '$table' table doesn't exist yet.\n" );
			return true;
		}

		// Second requirement: the new index must be missing
		if ( $this->db->indexExists( $table, $newIndex, __METHOD__ ) ) {
			$this->output( "...index $newIndex already set on $table table.\n" );
			if ( !$skipBothIndexExistWarning && $this->db->indexExists( $table, $oldIndex, __METHOD__ ) ) {
				$this->output( "...WARNING: $oldIndex still exists, despite it has been renamed into $newIndex (which also exists).\n" .
					"            $oldIndex should be manually removed if not needed anymore.\n" );
			}
			return true;
		}

		// Third requirement: the old index must exist
		if ( !$this->db->indexExists( $table, $oldIndex, __METHOD__ ) ) {
			$this->output( "...skipping: index $oldIndex doesn't exist.\n" );
			return true;
		}

		// Requirements have been satisfied, patch can be applied
		return $this->applyPatch( $patch, $fullpath, "Renaming index $oldIndex into $newIndex to table $table" );
	}

	/**
	 * If the specified table exists, drop it, or execute the
	 * patch if one is provided.
	 *
	 * Public @since 1.20
	 *
	 * @param $table string
	 * @param $patch string|false
	 * @param $fullpath bool
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	public function dropTable( $table, $patch = false, $fullpath = false ) {
		if ( !$this->doTable( $table ) ) {
			return true;
		}

		if ( $this->db->tableExists( $table, __METHOD__ ) ) {
			$msg = "Dropping table $table";

			if ( $patch === false ) {
				$this->output( "$msg ..." );
				$this->db->dropTable( $table, __METHOD__ );
				$this->output( "done.\n" );
			}
			else {
				return $this->applyPatch( $patch, $fullpath, $msg );
			}
		} else {
			$this->output( "...$table doesn't exist.\n" );
		}
		return true;
	}

	/**
	 * Modify an existing field
	 *
	 * @param string $table name of the table to which the field belongs
	 * @param string $field name of the field to modify
	 * @param string $patch path to the patch file
	 * @param $fullpath Boolean: whether to treat $patch path as a relative or not
	 * @return Boolean false if this was skipped because schema changes are skipped
	 */
	public function modifyField( $table, $field, $patch, $fullpath = false ) {
		if ( !$this->doTable( $table ) ) {
			return true;
		}

		$updateKey = "$table-$field-$patch";
		if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
			$this->output( "...$table table does not exist, skipping modify field patch.\n" );
		} elseif ( !$this->db->fieldExists( $table, $field, __METHOD__ ) ) {
			$this->output( "...$field field does not exist in $table table, skipping modify field patch.\n" );
		} elseif( $this->updateRowExists( $updateKey ) ) {
			$this->output( "...$field in table $table already modified by patch $patch.\n" );
		} else {
			$this->insertUpdateRow( $updateKey );
			return $this->applyPatch( $patch, $fullpath, "Modifying $field field of table $table" );
		}
		return true;
	}

	/**
	 * Purge the objectcache table
	 */
	public function purgeCache() {
		global $wgLocalisationCacheConf;
		# We can't guarantee that the user will be able to use TRUNCATE,
		# but we know that DELETE is available to us
		$this->output( "Purging caches..." );
		$this->db->delete( 'objectcache', '*', __METHOD__ );
		if ( $wgLocalisationCacheConf['manualRecache'] ) {
			$this->rebuildLocalisationCache();
		}
		MessageBlobStore::clear();
		$this->output( "done.\n" );
	}

	/**
	 * Check the site_stats table is not properly populated.
	 */
	protected function checkStats() {
		$this->output( "...site_stats is populated..." );
		$row = $this->db->selectRow( 'site_stats', '*', array( 'ss_row_id' => 1 ), __METHOD__ );
		if ( $row === false ) {
			$this->output( "data is missing! rebuilding...\n" );
		} elseif ( isset( $row->site_stats ) && $row->ss_total_pages == -1 ) {
			$this->output( "missing ss_total_pages, rebuilding...\n" );
		} else {
			$this->output( "done.\n" );
			return;
		}
		SiteStatsInit::doAllAndCommit( $this->db );
	}

	# Common updater functions

	/**
	 * Sets the number of active users in the site_stats table
	 */
	protected function doActiveUsersInit() {
		$activeUsers = $this->db->selectField( 'site_stats', 'ss_active_users', false, __METHOD__ );
		if ( $activeUsers == -1 ) {
			$activeUsers = $this->db->selectField( 'recentchanges',
				'COUNT( DISTINCT rc_user_text )',
				array( 'rc_user != 0', 'rc_bot' => 0, "rc_log_type != 'newusers'" ), __METHOD__
			);
			$this->db->update( 'site_stats',
				array( 'ss_active_users' => intval( $activeUsers ) ),
				array( 'ss_row_id' => 1 ), __METHOD__, array( 'LIMIT' => 1 )
			);
		}
		$this->output( "...ss_active_users user count set...\n" );
	}

	/**
	 * Populates the log_user_text field in the logging table
	 */
	protected function doLogUsertextPopulation() {
		if ( !$this->updateRowExists( 'populate log_usertext' ) ) {
			$this->output(
			"Populating log_user_text field, printing progress markers. For large\n" .
			"databases, you may want to hit Ctrl-C and do this manually with\n" .
			"maintenance/populateLogUsertext.php.\n" );

			$task = $this->maintenance->runChild( 'PopulateLogUsertext' );
			$task->execute();
			$this->output( "done.\n" );
		}
	}

	/**
	 * Migrate log params to new table and index for searching
	 */
	protected function doLogSearchPopulation() {
		if ( !$this->updateRowExists( 'populate log_search' ) ) {
			$this->output(
				"Populating log_search table, printing progress markers. For large\n" .
				"databases, you may want to hit Ctrl-C and do this manually with\n" .
				"maintenance/populateLogSearch.php.\n" );

			$task = $this->maintenance->runChild( 'PopulateLogSearch' );
			$task->execute();
			$this->output( "done.\n" );
		}
	}

	/**
	 * Updates the timestamps in the transcache table
	 */
	protected function doUpdateTranscacheField() {
		if ( $this->updateRowExists( 'convert transcache field' ) ) {
			$this->output( "...transcache tc_time already converted.\n" );
			return true;
		}

		return $this->applyPatch( 'patch-tc-timestamp.sql', false,
			"Converting tc_time from UNIX epoch to MediaWiki timestamp" );
	}

	/**
	 * Update CategoryLinks collation
	 */
	protected function doCollationUpdate() {
		global $wgCategoryCollation;
		if ( $this->db->fieldExists( 'categorylinks', 'cl_collation', __METHOD__ ) ) {
			if ( $this->db->selectField(
				'categorylinks',
				'COUNT(*)',
				'cl_collation != ' . $this->db->addQuotes( $wgCategoryCollation ),
				__METHOD__
				) == 0 ) {
					$this->output( "...collations up-to-date.\n" );
					return;
			}

			$this->output( "Updating category collations..." );
			$task = $this->maintenance->runChild( 'UpdateCollation' );
			$task->execute();
			$this->output( "...done.\n" );
		}
	}

	/**
	 * Migrates user options from the user table blob to user_properties
	 */
	protected function doMigrateUserOptions() {
		if( $this->db->tableExists( 'user_properties' ) ) {
			$cl = $this->maintenance->runChild( 'ConvertUserOptions', 'convertUserOptions.php' );
			$cl->execute();
			$this->output( "done.\n" );
		}
	}

	/**
	 * Rebuilds the localisation cache
	 */
	protected function rebuildLocalisationCache() {
		/**
		 * @var $cl RebuildLocalisationCache
		 */
		$cl = $this->maintenance->runChild( 'RebuildLocalisationCache', 'rebuildLocalisationCache.php' );
		$this->output( "Rebuilding localisation cache...\n" );
		$cl->setForce();
		$cl->execute();
		$this->output( "done.\n" );
	}

	/**
	 * Turns off content handler fields during parts of the upgrade
	 * where they aren't available.
	 */
	protected function disableContentHandlerUseDB() {
		global $wgContentHandlerUseDB;

		if( $wgContentHandlerUseDB ) {
			$this->output( "Turning off Content Handler DB fields for this part of upgrade.\n" );
			$this->holdContentHandlerUseDB = $wgContentHandlerUseDB;
			$wgContentHandlerUseDB = false;
		}
	}

	/**
	 * Turns content handler fields back on.
	 */
	protected function enableContentHandlerUseDB() {
		global $wgContentHandlerUseDB;

		if( $this->holdContentHandlerUseDB ) {
			$this->output( "Content Handler DB fields should be usable now.\n" );
			$wgContentHandlerUseDB = $this->holdContentHandlerUseDB;
		}
	}
}