includes/db/Database.php

   1 <?php
   2
   3 /**
   4  * @defgroup Database Database
   5  *
   6  * This file deals with database interface functions
   7  * and query specifics/optimisations.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  * @ingroup Database
  26  */
  27
  28 /**
  29  * Database abstraction object
  30  * @ingroup Database
  31  */
  32 abstract class DatabaseBase implements IDatabase {
  33         /** Number of times to re-try an operation in case of deadlock */
  34         const DEADLOCK_TRIES = 4;
  35         /** Minimum time to wait before retry, in microseconds */
  36         const DEADLOCK_DELAY_MIN = 500000;
  37         /** Maximum time to wait before retry */
  38         const DEADLOCK_DELAY_MAX = 1500000;
  39
  40         /** How long before it is worth doing a dummy query to test the connection */
  41         const PING_TTL = 1.0;
  42
  43         /** @var string SQL query */
  44         protected $mLastQuery = '';
  45         /** @var bool */
  46         protected $mDoneWrites = false;
  47         /** @var string|bool */
  48         protected $mPHPError = false;
  49         /** @var string */
  50         protected $mServer;
  51         /** @var string */
  52         protected $mUser;
  53         /** @var string */
  54         protected $mPassword;
  55         /** @var string */
  56         protected $mDBname;
  57
  58         /** @var BagOStuff APC cache */
  59         protected $srvCache;
  60
  61         /** @var resource Database connection */
  62         protected $mConn = null;
  63         /** @var bool */
  64         protected $mOpened = false;
  65
  66         /** @var array[] List of (callable, method name) */
  67         protected $mTrxIdleCallbacks = [];
  68         /** @var array[] List of (callable, method name) */
  69         protected $mTrxPreCommitCallbacks = [];
  70         /** @var array[] List of (callable, method name) */
  71         protected $mTrxEndCallbacks = [];
  72         /** @var bool Whether to suppress triggering of post-commit callbacks */
  73         protected $suppressPostCommitCallbacks = false;
  74
  75         /** @var string */
  76         protected $mTablePrefix;
  77         /** @var string */
  78         protected $mSchema;
  79         /** @var integer */
  80         protected $mFlags;
  81         /** @var bool */
  82         protected $mForeign;
  83         /** @var array */
  84         protected $mLBInfo = [];
  85         /** @var bool|null */
  86         protected $mDefaultBigSelects = null;
  87         /** @var array|bool */
  88         protected $mSchemaVars = false;
  89         /** @var array */
  90         protected $mSessionVars = [];
  91         /** @var array|null */
  92         protected $preparedArgs;
  93         /** @var string|bool|null Stashed value of html_errors INI setting */
  94         protected $htmlErrors;
  95         /** @var string */
  96         protected $delimiter = ';';
  97
  98         /**
  99          * Either 1 if a transaction is active or 0 otherwise.
 100          * The other Trx fields may not be meaningfull if this is 0.
 101          *
 102          * @var int
 103          */
 104         protected $mTrxLevel = 0;
 105
 106         /**
 107          * Either a short hexidecimal string if a transaction is active or ""
 108          *
 109          * @var string
 110          * @see DatabaseBase::mTrxLevel
 111          */
 112         protected $mTrxShortId = '';
 113
 114         /**
 115          * The UNIX time that the transaction started. Callers can assume that if
 116          * snapshot isolation is used, then the data is *at least* up to date to that
 117          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 118          *
 119          * @var float|null
 120          * @see DatabaseBase::mTrxLevel
 121          */
 122         private $mTrxTimestamp = null;
 123
 124         /** @var float Lag estimate at the time of BEGIN */
 125         private $mTrxSlaveLag = null;
 126
 127         /**
 128          * Remembers the function name given for starting the most recent transaction via begin().
 129          * Used to provide additional context for error reporting.
 130          *
 131          * @var string
 132          * @see DatabaseBase::mTrxLevel
 133          */
 134         private $mTrxFname = null;
 135
 136         /**
 137          * Record if possible write queries were done in the last transaction started
 138          *
 139          * @var bool
 140          * @see DatabaseBase::mTrxLevel
 141          */
 142         private $mTrxDoneWrites = false;
 143
 144         /**
 145          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 146          *
 147          * @var bool
 148          * @see DatabaseBase::mTrxLevel
 149          */
 150         private $mTrxAutomatic = false;
 151
 152         /**
 153          * Array of levels of atomicity within transactions
 154          *
 155          * @var array
 156          */
 157         private $mTrxAtomicLevels = [];
 158
 159         /**
 160          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 161          *
 162          * @var bool
 163          */
 164         private $mTrxAutomaticAtomic = false;
 165
 166         /**
 167          * Track the write query callers of the current transaction
 168          *
 169          * @var string[]
 170          */
 171         private $mTrxWriteCallers = [];
 172
 173         /**
 174          * Track the seconds spent in write queries for the current transaction
 175          *
 176          * @var float
 177          */
 178         private $mTrxWriteDuration = 0.0;
 179
 180         /** @var array Map of (name => 1) for locks obtained via lock() */
 181         private $mNamedLocksHeld = [];
 182
 183         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 184         private $lazyMasterHandle;
 185
 186         /**
 187          * @since 1.21
 188          * @var resource File handle for upgrade
 189          */
 190         protected $fileHandle = null;
 191
 192         /**
 193          * @since 1.22
 194          * @var string[] Process cache of VIEWs names in the database
 195          */
 196         protected $allViews = null;
 197
 198         /** @var float UNIX timestamp */
 199         protected $lastPing = 0.0;
 200
 201         /** @var int[] Prior mFlags values */
 202         private $priorFlags = [];
 203
 204         /** @var TransactionProfiler */
 205         protected $trxProfiler;
 206
 207         public function getServerInfo() {
 208                 return $this->getServerVersion();
 209         }
 210
 211         /**
 212          * @return string Command delimiter used by this database engine
 213          */
 214         public function getDelimiter() {
 215                 return $this->delimiter;
 216         }
 217
 218         /**
 219          * Boolean, controls output of large amounts of debug information.
 220          * @param bool|null $debug
 221          *   - true to enable debugging
 222          *   - false to disable debugging
 223          *   - omitted or null to do nothing
 224          *
 225          * @return bool|null Previous value of the flag
 226          */
 227         public function debug( $debug = null ) {
 228                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 229         }
 230
 231         public function bufferResults( $buffer = null ) {
 232                 if ( is_null( $buffer ) ) {
 233                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 234                 } else {
 235                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 236                 }
 237         }
 238
 239         /**
 240          * Turns on (false) or off (true) the automatic generation and sending
 241          * of a "we're sorry, but there has been a database error" page on
 242          * database errors. Default is on (false). When turned off, the
 243          * code should use lastErrno() and lastError() to handle the
 244          * situation as appropriate.
 245          *
 246          * Do not use this function outside of the Database classes.
 247          *
 248          * @param null|bool $ignoreErrors
 249          * @return bool The previous value of the flag.
 250          */
 251         protected function ignoreErrors( $ignoreErrors = null ) {
 252                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 253         }
 254
 255         public function trxLevel() {
 256                 return $this->mTrxLevel;
 257         }
 258
 259         public function trxTimestamp() {
 260                 return $this->mTrxLevel ? $this->mTrxTimestamp : null;
 261         }
 262
 263         public function tablePrefix( $prefix = null ) {
 264                 return wfSetVar( $this->mTablePrefix, $prefix );
 265         }
 266
 267         public function dbSchema( $schema = null ) {
 268                 return wfSetVar( $this->mSchema, $schema );
 269         }
 270
 271         /**
 272          * Set the filehandle to copy write statements to.
 273          *
 274          * @param resource $fh File handle
 275          */
 276         public function setFileHandle( $fh ) {
 277                 $this->fileHandle = $fh;
 278         }
 279
 280         public function getLBInfo( $name = null ) {
 281                 if ( is_null( $name ) ) {
 282                         return $this->mLBInfo;
 283                 } else {
 284                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 285                                 return $this->mLBInfo[$name];
 286                         } else {
 287                                 return null;
 288                         }
 289                 }
 290         }
 291
 292         public function setLBInfo( $name, $value = null ) {
 293                 if ( is_null( $value ) ) {
 294                         $this->mLBInfo = $name;
 295                 } else {
 296                         $this->mLBInfo[$name] = $value;
 297                 }
 298         }
 299
 300         /**
 301          * Set a lazy-connecting DB handle to the master DB (for replication status purposes)
 302          *
 303          * @param IDatabase $conn
 304          * @since 1.27
 305          */
 306         public function setLazyMasterHandle( IDatabase $conn ) {
 307                 $this->lazyMasterHandle = $conn;
 308         }
 309
 310         /**
 311          * @return IDatabase|null
 312          * @see setLazyMasterHandle()
 313          * @since 1.27
 314          */
 315         public function getLazyMasterHandle() {
 316                 return $this->lazyMasterHandle;
 317         }
 318
 319         /**
 320          * @return TransactionProfiler
 321          */
 322         protected function getTransactionProfiler() {
 323                 if ( !$this->trxProfiler ) {
 324                         $this->trxProfiler = new TransactionProfiler();
 325                 }
 326
 327                 return $this->trxProfiler;
 328         }
 329
 330         /**
 331          * @param TransactionProfiler $profiler
 332          * @since 1.27
 333          */
 334         public function setTransactionProfiler( TransactionProfiler $profiler ) {
 335                 $this->trxProfiler = $profiler;
 336         }
 337
 338         /**
 339          * Returns true if this database supports (and uses) cascading deletes
 340          *
 341          * @return bool
 342          */
 343         public function cascadingDeletes() {
 344                 return false;
 345         }
 346
 347         /**
 348          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 349          *
 350          * @return bool
 351          */
 352         public function cleanupTriggers() {
 353                 return false;
 354         }
 355
 356         /**
 357          * Returns true if this database is strict about what can be put into an IP field.
 358          * Specifically, it uses a NULL value instead of an empty string.
 359          *
 360          * @return bool
 361          */
 362         public function strictIPs() {
 363                 return false;
 364         }
 365
 366         /**
 367          * Returns true if this database uses timestamps rather than integers
 368          *
 369          * @return bool
 370          */
 371         public function realTimestamps() {
 372                 return false;
 373         }
 374
 375         public function implicitGroupby() {
 376                 return true;
 377         }
 378
 379         public function implicitOrderby() {
 380                 return true;
 381         }
 382
 383         /**
 384          * Returns true if this database can do a native search on IP columns
 385          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 386          *
 387          * @return bool
 388          */
 389         public function searchableIPs() {
 390                 return false;
 391         }
 392
 393         /**
 394          * Returns true if this database can use functional indexes
 395          *
 396          * @return bool
 397          */
 398         public function functionalIndexes() {
 399                 return false;
 400         }
 401
 402         public function lastQuery() {
 403                 return $this->mLastQuery;
 404         }
 405
 406         public function doneWrites() {
 407                 return (bool)$this->mDoneWrites;
 408         }
 409
 410         public function lastDoneWrites() {
 411                 return $this->mDoneWrites ?: false;
 412         }
 413
 414         public function writesPending() {
 415                 return $this->mTrxLevel && $this->mTrxDoneWrites;
 416         }
 417
 418         public function writesOrCallbacksPending() {
 419                 return $this->mTrxLevel && (
 420                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 421                 );
 422         }
 423
 424         public function pendingWriteQueryDuration() {
 425                 return $this->mTrxLevel ? $this->mTrxWriteDuration : false;
 426         }
 427
 428         public function pendingWriteCallers() {
 429                 return $this->mTrxLevel ? $this->mTrxWriteCallers : [];
 430         }
 431
 432         public function isOpen() {
 433                 return $this->mOpened;
 434         }
 435
 436         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 437                 if ( $remember === self::REMEMBER_PRIOR ) {
 438                         array_push( $this->priorFlags, $this->mFlags );
 439                 }
 440                 $this->mFlags |= $flag;
 441         }
 442
 443         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 444                 if ( $remember === self::REMEMBER_PRIOR ) {
 445                         array_push( $this->priorFlags, $this->mFlags );
 446                 }
 447                 $this->mFlags &= ~$flag;
 448         }
 449
 450         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 451                 if ( !$this->priorFlags ) {
 452                         return;
 453                 }
 454
 455                 if ( $state === self::RESTORE_INITIAL ) {
 456                         $this->mFlags = reset( $this->priorFlags );
 457                         $this->priorFlags = [];
 458                 } else {
 459                         $this->mFlags = array_pop( $this->priorFlags );
 460                 }
 461         }
 462
 463         public function getFlag( $flag ) {
 464                 return !!( $this->mFlags & $flag );
 465         }
 466
 467         public function getProperty( $name ) {
 468                 return $this->$name;
 469         }
 470
 471         public function getWikiID() {
 472                 if ( $this->mTablePrefix ) {
 473                         return "{$this->mDBname}-{$this->mTablePrefix}";
 474                 } else {
 475                         return $this->mDBname;
 476                 }
 477         }
 478
 479         /**
 480          * Return a path to the DBMS-specific SQL file if it exists,
 481          * otherwise default SQL file
 482          *
 483          * @param string $filename
 484          * @return string
 485          */
 486         private function getSqlFilePath( $filename ) {
 487                 global $IP;
 488                 $dbmsSpecificFilePath = "$IP/maintenance/" . $this->getType() . "/$filename";
 489                 if ( file_exists( $dbmsSpecificFilePath ) ) {
 490                         return $dbmsSpecificFilePath;
 491                 } else {
 492                         return "$IP/maintenance/$filename";
 493                 }
 494         }
 495
 496         /**
 497          * Return a path to the DBMS-specific schema file,
 498          * otherwise default to tables.sql
 499          *
 500          * @return string
 501          */
 502         public function getSchemaPath() {
 503                 return $this->getSqlFilePath( 'tables.sql' );
 504         }
 505
 506         /**
 507          * Return a path to the DBMS-specific update key file,
 508          * otherwise default to update-keys.sql
 509          *
 510          * @return string
 511          */
 512         public function getUpdateKeysPath() {
 513                 return $this->getSqlFilePath( 'update-keys.sql' );
 514         }
 515
 516         /**
 517          * Get information about an index into an object
 518          * @param string $table Table name
 519          * @param string $index Index name
 520          * @param string $fname Calling function name
 521          * @return mixed Database-specific index description class or false if the index does not exist
 522          */
 523         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 524
 525         /**
 526          * Wrapper for addslashes()
 527          *
 528          * @param string $s String to be slashed.
 529          * @return string Slashed string.
 530          */
 531         abstract function strencode( $s );
 532
 533         /**
 534          * Constructor.
 535          *
 536          * FIXME: It is possible to construct a Database object with no associated
 537          * connection object, by specifying no parameters to __construct(). This
 538          * feature is deprecated and should be removed.
 539          *
 540          * DatabaseBase subclasses should not be constructed directly in external
 541          * code. DatabaseBase::factory() should be used instead.
 542          *
 543          * @param array $params Parameters passed from DatabaseBase::factory()
 544          */
 545         function __construct( array $params ) {
 546                 global $wgDBprefix, $wgDBmwschema, $wgCommandLineMode;
 547
 548                 $this->srvCache = ObjectCache::getLocalServerInstance( 'hash' );
 549
 550                 $server = $params['host'];
 551                 $user = $params['user'];
 552                 $password = $params['password'];
 553                 $dbName = $params['dbname'];
 554                 $flags = $params['flags'];
 555                 $tablePrefix = $params['tablePrefix'];
 556                 $schema = $params['schema'];
 557                 $foreign = $params['foreign'];
 558
 559                 $this->mFlags = $flags;
 560                 if ( $this->mFlags & DBO_DEFAULT ) {
 561                         if ( $wgCommandLineMode ) {
 562                                 $this->mFlags &= ~DBO_TRX;
 563                         } else {
 564                                 $this->mFlags |= DBO_TRX;
 565                         }
 566                 }
 567
 568                 $this->mSessionVars = $params['variables'];
 569
 570                 /** Get the default table prefix*/
 571                 if ( $tablePrefix === 'get from global' ) {
 572                         $this->mTablePrefix = $wgDBprefix;
 573                 } else {
 574                         $this->mTablePrefix = $tablePrefix;
 575                 }
 576
 577                 /** Get the database schema*/
 578                 if ( $schema === 'get from global' ) {
 579                         $this->mSchema = $wgDBmwschema;
 580                 } else {
 581                         $this->mSchema = $schema;
 582                 }
 583
 584                 $this->mForeign = $foreign;
 585
 586                 if ( isset( $params['trxProfiler'] ) ) {
 587                         $this->trxProfiler = $params['trxProfiler']; // override
 588                 }
 589
 590                 if ( $user ) {
 591                         $this->open( $server, $user, $password, $dbName );
 592                 }
 593         }
 594
 595         /**
 596          * Called by serialize. Throw an exception when DB connection is serialized.
 597          * This causes problems on some database engines because the connection is
 598          * not restored on unserialize.
 599          */
 600         public function __sleep() {
 601                 throw new MWException( 'Database serialization may cause problems, since ' .
 602                         'the connection is not restored on wakeup.' );
 603         }
 604
 605         /**
 606          * Given a DB type, construct the name of the appropriate child class of
 607          * DatabaseBase. This is designed to replace all of the manual stuff like:
 608          *    $class = 'Database' . ucfirst( strtolower( $dbType ) );
 609          * as well as validate against the canonical list of DB types we have
 610          *
 611          * This factory function is mostly useful for when you need to connect to a
 612          * database other than the MediaWiki default (such as for external auth,
 613          * an extension, et cetera). Do not use this to connect to the MediaWiki
 614          * database. Example uses in core:
 615          * @see LoadBalancer::reallyOpenConnection()
 616          * @see ForeignDBRepo::getMasterDB()
 617          * @see WebInstallerDBConnect::execute()
 618          *
 619          * @since 1.18
 620          *
 621          * @param string $dbType A possible DB type
 622          * @param array $p An array of options to pass to the constructor.
 623          *    Valid options are: host, user, password, dbname, flags, tablePrefix, schema, driver
 624          * @throws MWException If the database driver or extension cannot be found
 625          * @return DatabaseBase|null DatabaseBase subclass or null
 626          */
 627         final public static function factory( $dbType, $p = [] ) {
 628                 $canonicalDBTypes = [
 629                         'mysql' => [ 'mysqli', 'mysql' ],
 630                         'postgres' => [],
 631                         'sqlite' => [],
 632                         'oracle' => [],
 633                         'mssql' => [],
 634                 ];
 635
 636                 $driver = false;
 637                 $dbType = strtolower( $dbType );
 638                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 639                         $possibleDrivers = $canonicalDBTypes[$dbType];
 640                         if ( !empty( $p['driver'] ) ) {
 641                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 642                                         $driver = $p['driver'];
 643                                 } else {
 644                                         throw new MWException( __METHOD__ .
 645                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 646                                 }
 647                         } else {
 648                                 foreach ( $possibleDrivers as $posDriver ) {
 649                                         if ( extension_loaded( $posDriver ) ) {
 650                                                 $driver = $posDriver;
 651                                                 break;
 652                                         }
 653                                 }
 654                         }
 655                 } else {
 656                         $driver = $dbType;
 657                 }
 658                 if ( $driver === false ) {
 659                         throw new MWException( __METHOD__ .
 660                                 " no viable database extension found for type '$dbType'" );
 661                 }
 662
 663                 // Determine schema defaults. Currently Microsoft SQL Server uses $wgDBmwschema,
 664                 // and everything else doesn't use a schema (e.g. null)
 665                 // Although postgres and oracle support schemas, we don't use them (yet)
 666                 // to maintain backwards compatibility
 667                 $defaultSchemas = [
 668                         'mssql' => 'get from global',
 669                 ];
 670
 671                 $class = 'Database' . ucfirst( $driver );
 672                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 673                         // Resolve some defaults for b/c
 674                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 675                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 676                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 677                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 678                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 679                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 680                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global';
 681                         if ( !isset( $p['schema'] ) ) {
 682                                 $p['schema'] = isset( $defaultSchemas[$dbType] ) ? $defaultSchemas[$dbType] : null;
 683                         }
 684                         $p['foreign'] = isset( $p['foreign'] ) ? $p['foreign'] : false;
 685
 686                         return new $class( $p );
 687                 } else {
 688                         return null;
 689                 }
 690         }
 691
 692         protected function installErrorHandler() {
 693                 $this->mPHPError = false;
 694                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 695                 set_error_handler( [ $this, 'connectionErrorHandler' ] );
 696         }
 697
 698         /**
 699          * @return bool|string
 700          */
 701         protected function restoreErrorHandler() {
 702                 restore_error_handler();
 703                 if ( $this->htmlErrors !== false ) {
 704                         ini_set( 'html_errors', $this->htmlErrors );
 705                 }
 706                 if ( $this->mPHPError ) {
 707                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 708                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 709
 710                         return $error;
 711                 } else {
 712                         return false;
 713                 }
 714         }
 715
 716         /**
 717          * @param int $errno
 718          * @param string $errstr
 719          */
 720         public function connectionErrorHandler( $errno, $errstr ) {
 721                 $this->mPHPError = $errstr;
 722         }
 723
 724         /**
 725          * Create a log context to pass to wfLogDBError or other logging functions.
 726          *
 727          * @param array $extras Additional data to add to context
 728          * @return array
 729          */
 730         protected function getLogContext( array $extras = [] ) {
 731                 return array_merge(
 732                         [
 733                                 'db_server' => $this->mServer,
 734                                 'db_name' => $this->mDBname,
 735                                 'db_user' => $this->mUser,
 736                         ],
 737                         $extras
 738                 );
 739         }
 740
 741         public function close() {
 742                 if ( $this->mConn ) {
 743                         if ( $this->trxLevel() ) {
 744                                 if ( !$this->mTrxAutomatic ) {
 745                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 746                                                 " performing implicit commit before closing connection!" );
 747                                 }
 748
 749                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 750                         }
 751
 752                         $closed = $this->closeConnection();
 753                         $this->mConn = false;
 754                 } elseif ( $this->mTrxIdleCallbacks || $this->mTrxEndCallbacks ) { // sanity
 755                         throw new MWException( "Transaction callbacks still pending." );
 756                 } else {
 757                         $closed = true;
 758                 }
 759                 $this->mOpened = false;
 760
 761                 return $closed;
 762         }
 763
 764         /**
 765          * Make sure isOpen() returns true as a sanity check
 766          *
 767          * @throws DBUnexpectedError
 768          */
 769         protected function assertOpen() {
 770                 if ( !$this->isOpen() ) {
 771                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 772                 }
 773         }
 774
 775         /**
 776          * Closes underlying database connection
 777          * @since 1.20
 778          * @return bool Whether connection was closed successfully
 779          */
 780         abstract protected function closeConnection();
 781
 782         function reportConnectionError( $error = 'Unknown error' ) {
 783                 $myError = $this->lastError();
 784                 if ( $myError ) {
 785                         $error = $myError;
 786                 }
 787
 788                 # New method
 789                 throw new DBConnectionError( $this, $error );
 790         }
 791
 792         /**
 793          * The DBMS-dependent part of query()
 794          *
 795          * @param string $sql SQL query.
 796          * @return ResultWrapper|bool Result object to feed to fetchObject,
 797          *   fetchRow, ...; or false on failure
 798          */
 799         abstract protected function doQuery( $sql );
 800
 801         /**
 802          * Determine whether a query writes to the DB.
 803          * Should return true if unsure.
 804          *
 805          * @param string $sql
 806          * @return bool
 807          */
 808         protected function isWriteQuery( $sql ) {
 809                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 810         }
 811
 812         /**
 813          * Determine whether a SQL statement is sensitive to isolation level.
 814          * A SQL statement is considered transactable if its result could vary
 815          * depending on the transaction isolation level. Operational commands
 816          * such as 'SET' and 'SHOW' are not considered to be transactable.
 817          *
 818          * @param string $sql
 819          * @return bool
 820          */
 821         protected function isTransactableQuery( $sql ) {
 822                 $verb = substr( $sql, 0, strcspn( $sql, " \t\r\n" ) );
 823                 return !in_array( $verb, [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET' ] );
 824         }
 825
 826         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 827                 global $wgUser;
 828
 829                 $priorWritesPending = $this->writesOrCallbacksPending();
 830                 $this->mLastQuery = $sql;
 831
 832                 $isWrite = $this->isWriteQuery( $sql );
 833                 if ( $isWrite ) {
 834                         $reason = $this->getReadOnlyReason();
 835                         if ( $reason !== false ) {
 836                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 837                         }
 838                         # Set a flag indicating that writes have been done
 839                         $this->mDoneWrites = microtime( true );
 840                 }
 841
 842                 # Add a comment for easy SHOW PROCESSLIST interpretation
 843                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 844                         $userName = $wgUser->getName();
 845                         if ( mb_strlen( $userName ) > 15 ) {
 846                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 847                         }
 848                         $userName = str_replace( '/', '', $userName );
 849                 } else {
 850                         $userName = '';
 851                 }
 852
 853                 // Add trace comment to the begin of the sql string, right after the operator.
 854                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 855                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 856
 857                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 858                 if ( !$this->mTrxLevel && $this->getFlag( DBO_TRX )
 859                         && $this->isTransactableQuery( $sql )
 860                 ) {
 861                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
 862                         $this->mTrxAutomatic = true;
 863                 }
 864
 865                 # Keep track of whether the transaction has write queries pending
 866                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $isWrite ) {
 867                         $this->mTrxDoneWrites = true;
 868                         $this->getTransactionProfiler()->transactionWritingIn(
 869                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 870                 }
 871
 872                 if ( $this->debug() ) {
 873                         wfDebugLog( 'queries', sprintf( "%s: %s", $this->mDBname, $commentedSql ) );
 874                 }
 875
 876                 # Avoid fatals if close() was called
 877                 $this->assertOpen();
 878
 879                 # Send the query to the server
 880                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isWrite, $fname );
 881
 882                 # Try reconnecting if the connection was lost
 883                 if ( false === $ret && $this->wasErrorReissuable() ) {
 884                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
 885                         # Stash the last error values before anything might clear them
 886                         $lastError = $this->lastError();
 887                         $lastErrno = $this->lastErrno();
 888                         # Update state tracking to reflect transaction loss due to disconnection
 889                         $this->handleTransactionLoss();
 890                         wfDebug( "Connection lost, reconnecting...\n" );
 891                         if ( $this->reconnect() ) {
 892                                 wfDebug( "Reconnected\n" );
 893                                 $msg = __METHOD__ . ": lost connection to {$this->getServer()}; reconnected";
 894                                 wfDebugLog( 'DBPerformance', "$msg:\n" . wfBacktrace( true ) );
 895
 896                                 if ( !$recoverable ) {
 897                                         # Callers may catch the exception and continue to use the DB
 898                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
 899                                 } else {
 900                                         # Should be safe to silently retry the query
 901                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isWrite, $fname );
 902                                 }
 903                         } else {
 904                                 wfDebug( "Failed\n" );
 905                         }
 906                 }
 907
 908                 if ( false === $ret ) {
 909                         # Deadlocks cause the entire transaction to abort, not just the statement.
 910                         # http://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
 911                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
 912                         if ( $this->wasDeadlock() ) {
 913                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
 914                                         $tempIgnore = false; // not recoverable
 915                                 }
 916                                 # Update state tracking to reflect transaction loss
 917                                 $this->handleTransactionLoss();
 918                         }
 919
 920                         $this->reportQueryError(
 921                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 922                 }
 923
 924                 $res = $this->resultObject( $ret );
 925
 926                 return $res;
 927         }
 928
 929         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
 930                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 931                 # generalizeSQL() will probably cut down the query to reasonable
 932                 # logging size most of the time. The substr is really just a sanity check.
 933                 if ( $isMaster ) {
 934                         $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 935                 } else {
 936                         $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 937                 }
 938
 939                 # Include query transaction state
 940                 $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
 941
 942                 $profiler = Profiler::instance();
 943                 if ( !( $profiler instanceof ProfilerStub ) ) {
 944                         $queryProfSection = $profiler->scopedProfileIn( $queryProf );
 945                 }
 946
 947                 $startTime = microtime( true );
 948                 $ret = $this->doQuery( $commentedSql );
 949                 $queryRuntime = microtime( true ) - $startTime;
 950
 951                 unset( $queryProfSection ); // profile out (if set)
 952
 953                 if ( $ret !== false ) {
 954                         $this->lastPing = $startTime;
 955                         if ( $isWrite && $this->mTrxLevel ) {
 956                                 $this->mTrxWriteDuration += $queryRuntime;
 957                                 $this->mTrxWriteCallers[] = $fname;
 958                         }
 959                 }
 960
 961                 $this->getTransactionProfiler()->recordQueryCompletion(
 962                         $queryProf, $startTime, $isWrite, $this->affectedRows()
 963                 );
 964                 MWDebug::query( $sql, $fname, $isMaster, $queryRuntime );
 965
 966                 return $ret;
 967         }
 968
 969         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
 970                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
 971                 # Dropped connections also mean that named locks are automatically released.
 972                 # Only allow error suppression in autocommit mode or when the lost transaction
 973                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
 974                 if ( $this->mNamedLocksHeld ) {
 975                         return false; // possible critical section violation
 976                 } elseif ( $sql === 'COMMIT' ) {
 977                         return !$priorWritesPending; // nothing written anyway? (T127428)
 978                 } elseif ( $sql === 'ROLLBACK' ) {
 979                         return true; // transaction lost...which is also what was requested :)
 980                 } elseif ( $this->explicitTrxActive() ) {
 981                         return false; // don't drop atomocity
 982                 } elseif ( $priorWritesPending ) {
 983                         return false; // prior writes lost from implicit transaction
 984                 }
 985
 986                 return true;
 987         }
 988
 989         private function handleTransactionLoss() {
 990                 $this->mTrxLevel = 0;
 991                 $this->mTrxIdleCallbacks = []; // bug 65263
 992                 $this->mTrxPreCommitCallbacks = []; // bug 65263
 993                 try {
 994                         // Handle callbacks in mTrxEndCallbacks
 995                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
 996                         return null;
 997                 } catch ( Exception $e ) {
 998                         // Already logged; move on...
 999                         return $e;
1000                 }
1001         }
1002
1003         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1004                 if ( $this->ignoreErrors() || $tempIgnore ) {
1005                         wfDebug( "SQL ERROR (ignored): $error\n" );
1006                 } else {
1007                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1008                         wfLogDBError(
1009                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1010                                 $this->getLogContext( [
1011                                         'method' => __METHOD__,
1012                                         'errno' => $errno,
1013                                         'error' => $error,
1014                                         'sql1line' => $sql1line,
1015                                         'fname' => $fname,
1016                                 ] )
1017                         );
1018                         wfDebug( "SQL ERROR: " . $error . "\n" );
1019                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1020                 }
1021         }
1022
1023         /**
1024          * Intended to be compatible with the PEAR::DB wrapper functions.
1025          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1026          *
1027          * ? = scalar value, quoted as necessary
1028          * ! = raw SQL bit (a function for instance)
1029          * & = filename; reads the file and inserts as a blob
1030          *     (we don't use this though...)
1031          *
1032          * @param string $sql
1033          * @param string $func
1034          *
1035          * @return array
1036          */
1037         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1038                 /* MySQL doesn't support prepared statements (yet), so just
1039                  * pack up the query for reference. We'll manually replace
1040                  * the bits later.
1041                  */
1042                 return [ 'query' => $sql, 'func' => $func ];
1043         }
1044
1045         /**
1046          * Free a prepared query, generated by prepare().
1047          * @param string $prepared
1048          */
1049         protected function freePrepared( $prepared ) {
1050                 /* No-op by default */
1051         }
1052
1053         /**
1054          * Execute a prepared query with the various arguments
1055          * @param string $prepared The prepared sql
1056          * @param mixed $args Either an array here, or put scalars as varargs
1057          *
1058          * @return ResultWrapper
1059          */
1060         public function execute( $prepared, $args = null ) {
1061                 if ( !is_array( $args ) ) {
1062                         # Pull the var args
1063                         $args = func_get_args();
1064                         array_shift( $args );
1065                 }
1066
1067                 $sql = $this->fillPrepared( $prepared['query'], $args );
1068
1069                 return $this->query( $sql, $prepared['func'] );
1070         }
1071
1072         /**
1073          * For faking prepared SQL statements on DBs that don't support it directly.
1074          *
1075          * @param string $preparedQuery A 'preparable' SQL statement
1076          * @param array $args Array of Arguments to fill it with
1077          * @return string Executable SQL
1078          */
1079         public function fillPrepared( $preparedQuery, $args ) {
1080                 reset( $args );
1081                 $this->preparedArgs =& $args;
1082
1083                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1084                         [ &$this, 'fillPreparedArg' ], $preparedQuery );
1085         }
1086
1087         /**
1088          * preg_callback func for fillPrepared()
1089          * The arguments should be in $this->preparedArgs and must not be touched
1090          * while we're doing this.
1091          *
1092          * @param array $matches
1093          * @throws DBUnexpectedError
1094          * @return string
1095          */
1096         protected function fillPreparedArg( $matches ) {
1097                 switch ( $matches[1] ) {
1098                         case '\\?':
1099                                 return '?';
1100                         case '\\!':
1101                                 return '!';
1102                         case '\\&':
1103                                 return '&';
1104                 }
1105
1106                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1107
1108                 switch ( $matches[1] ) {
1109                         case '?':
1110                                 return $this->addQuotes( $arg );
1111                         case '!':
1112                                 return $arg;
1113                         case '&':
1114                                 # return $this->addQuotes( file_get_contents( $arg ) );
1115                                 throw new DBUnexpectedError(
1116                                         $this,
1117                                         '& mode is not implemented. If it\'s really needed, uncomment the line above.'
1118                                 );
1119                         default:
1120                                 throw new DBUnexpectedError(
1121                                         $this,
1122                                         'Received invalid match. This should never happen!'
1123                                 );
1124                 }
1125         }
1126
1127         public function freeResult( $res ) {
1128         }
1129
1130         public function selectField(
1131                 $table, $var, $cond = '', $fname = __METHOD__, $options = []
1132         ) {
1133                 if ( $var === '*' ) { // sanity
1134                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1135                 }
1136
1137                 if ( !is_array( $options ) ) {
1138                         $options = [ $options ];
1139                 }
1140
1141                 $options['LIMIT'] = 1;
1142
1143                 $res = $this->select( $table, $var, $cond, $fname, $options );
1144                 if ( $res === false || !$this->numRows( $res ) ) {
1145                         return false;
1146                 }
1147
1148                 $row = $this->fetchRow( $res );
1149
1150                 if ( $row !== false ) {
1151                         return reset( $row );
1152                 } else {
1153                         return false;
1154                 }
1155         }
1156
1157         public function selectFieldValues(
1158                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1159         ) {
1160                 if ( $var === '*' ) { // sanity
1161                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1162                 } elseif ( !is_string( $var ) ) { // sanity
1163                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1164                 }
1165
1166                 if ( !is_array( $options ) ) {
1167                         $options = [ $options ];
1168                 }
1169
1170                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1171                 if ( $res === false ) {
1172                         return false;
1173                 }
1174
1175                 $values = [];
1176                 foreach ( $res as $row ) {
1177                         $values[] = $row->$var;
1178                 }
1179
1180                 return $values;
1181         }
1182
1183         /**
1184          * Returns an optional USE INDEX clause to go after the table, and a
1185          * string to go at the end of the query.
1186          *
1187          * @param array $options Associative array of options to be turned into
1188          *   an SQL query, valid keys are listed in the function.
1189          * @return array
1190          * @see DatabaseBase::select()
1191          */
1192         public function makeSelectOptions( $options ) {
1193                 $preLimitTail = $postLimitTail = '';
1194                 $startOpts = '';
1195
1196                 $noKeyOptions = [];
1197
1198                 foreach ( $options as $key => $option ) {
1199                         if ( is_numeric( $key ) ) {
1200                                 $noKeyOptions[$option] = true;
1201                         }
1202                 }
1203
1204                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1205
1206                 $preLimitTail .= $this->makeOrderBy( $options );
1207
1208                 // if (isset($options['LIMIT'])) {
1209                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1210                 //              isset($options['OFFSET']) ? $options['OFFSET']
1211                 //              : false);
1212                 // }
1213
1214                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1215                         $postLimitTail .= ' FOR UPDATE';
1216                 }
1217
1218                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1219                         $postLimitTail .= ' LOCK IN SHARE MODE';
1220                 }
1221
1222                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1223                         $startOpts .= 'DISTINCT';
1224                 }
1225
1226                 # Various MySQL extensions
1227                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1228                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1229                 }
1230
1231                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1232                         $startOpts .= ' HIGH_PRIORITY';
1233                 }
1234
1235                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1236                         $startOpts .= ' SQL_BIG_RESULT';
1237                 }
1238
1239                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1240                         $startOpts .= ' SQL_BUFFER_RESULT';
1241                 }
1242
1243                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1244                         $startOpts .= ' SQL_SMALL_RESULT';
1245                 }
1246
1247                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1248                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1249                 }
1250
1251                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1252                         $startOpts .= ' SQL_CACHE';
1253                 }
1254
1255                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1256                         $startOpts .= ' SQL_NO_CACHE';
1257                 }
1258
1259                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1260                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1261                 } else {
1262                         $useIndex = '';
1263                 }
1264
1265                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail ];
1266         }
1267
1268         /**
1269          * Returns an optional GROUP BY with an optional HAVING
1270          *
1271          * @param array $options Associative array of options
1272          * @return string
1273          * @see DatabaseBase::select()
1274          * @since 1.21
1275          */
1276         public function makeGroupByWithHaving( $options ) {
1277                 $sql = '';
1278                 if ( isset( $options['GROUP BY'] ) ) {
1279                         $gb = is_array( $options['GROUP BY'] )
1280                                 ? implode( ',', $options['GROUP BY'] )
1281                                 : $options['GROUP BY'];
1282                         $sql .= ' GROUP BY ' . $gb;
1283                 }
1284                 if ( isset( $options['HAVING'] ) ) {
1285                         $having = is_array( $options['HAVING'] )
1286                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1287                                 : $options['HAVING'];
1288                         $sql .= ' HAVING ' . $having;
1289                 }
1290
1291                 return $sql;
1292         }
1293
1294         /**
1295          * Returns an optional ORDER BY
1296          *
1297          * @param array $options Associative array of options
1298          * @return string
1299          * @see DatabaseBase::select()
1300          * @since 1.21
1301          */
1302         public function makeOrderBy( $options ) {
1303                 if ( isset( $options['ORDER BY'] ) ) {
1304                         $ob = is_array( $options['ORDER BY'] )
1305                                 ? implode( ',', $options['ORDER BY'] )
1306                                 : $options['ORDER BY'];
1307
1308                         return ' ORDER BY ' . $ob;
1309                 }
1310
1311                 return '';
1312         }
1313
1314         // See IDatabase::select for the docs for this function
1315         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1316                 $options = [], $join_conds = [] ) {
1317                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1318
1319                 return $this->query( $sql, $fname );
1320         }
1321
1322         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1323                 $options = [], $join_conds = []
1324         ) {
1325                 if ( is_array( $vars ) ) {
1326                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1327                 }
1328
1329                 $options = (array)$options;
1330                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1331                         ? $options['USE INDEX']
1332                         : [];
1333
1334                 if ( is_array( $table ) ) {
1335                         $from = ' FROM ' .
1336                                 $this->tableNamesWithUseIndexOrJOIN( $table, $useIndexes, $join_conds );
1337                 } elseif ( $table != '' ) {
1338                         if ( $table[0] == ' ' ) {
1339                                 $from = ' FROM ' . $table;
1340                         } else {
1341                                 $from = ' FROM ' .
1342                                         $this->tableNamesWithUseIndexOrJOIN( [ $table ], $useIndexes, [] );
1343                         }
1344                 } else {
1345                         $from = '';
1346                 }
1347
1348                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) =
1349                         $this->makeSelectOptions( $options );
1350
1351                 if ( !empty( $conds ) ) {
1352                         if ( is_array( $conds ) ) {
1353                                 $conds = $this->makeList( $conds, LIST_AND );
1354                         }
1355                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1356                 } else {
1357                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1358                 }
1359
1360                 if ( isset( $options['LIMIT'] ) ) {
1361                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1362                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1363                 }
1364                 $sql = "$sql $postLimitTail";
1365
1366                 if ( isset( $options['EXPLAIN'] ) ) {
1367                         $sql = 'EXPLAIN ' . $sql;
1368                 }
1369
1370                 return $sql;
1371         }
1372
1373         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1374                 $options = [], $join_conds = []
1375         ) {
1376                 $options = (array)$options;
1377                 $options['LIMIT'] = 1;
1378                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1379
1380                 if ( $res === false ) {
1381                         return false;
1382                 }
1383
1384                 if ( !$this->numRows( $res ) ) {
1385                         return false;
1386                 }
1387
1388                 $obj = $this->fetchObject( $res );
1389
1390                 return $obj;
1391         }
1392
1393         public function estimateRowCount(
1394                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1395         ) {
1396                 $rows = 0;
1397                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1398
1399                 if ( $res ) {
1400                         $row = $this->fetchRow( $res );
1401                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1402                 }
1403
1404                 return $rows;
1405         }
1406
1407         public function selectRowCount(
1408                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1409         ) {
1410                 $rows = 0;
1411                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1412                 $res = $this->query( "SELECT COUNT(*) AS rowcount FROM ($sql) tmp_count", $fname );
1413
1414                 if ( $res ) {
1415                         $row = $this->fetchRow( $res );
1416                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1417                 }
1418
1419                 return $rows;
1420         }
1421
1422         /**
1423          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1424          * It's only slightly flawed. Don't use for anything important.
1425          *
1426          * @param string $sql A SQL Query
1427          *
1428          * @return string
1429          */
1430         protected static function generalizeSQL( $sql ) {
1431                 # This does the same as the regexp below would do, but in such a way
1432                 # as to avoid crashing php on some large strings.
1433                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1434
1435                 $sql = str_replace( "\\\\", '', $sql );
1436                 $sql = str_replace( "\\'", '', $sql );
1437                 $sql = str_replace( "\\\"", '', $sql );
1438                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1439                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1440
1441                 # All newlines, tabs, etc replaced by single space
1442                 $sql = preg_replace( '/\s+/', ' ', $sql );
1443
1444                 # All numbers => N,
1445                 # except the ones surrounded by characters, e.g. l10n
1446                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1447                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1448
1449                 return $sql;
1450         }
1451
1452         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1453                 $info = $this->fieldInfo( $table, $field );
1454
1455                 return (bool)$info;
1456         }
1457
1458         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1459                 if ( !$this->tableExists( $table ) ) {
1460                         return null;
1461                 }
1462
1463                 $info = $this->indexInfo( $table, $index, $fname );
1464                 if ( is_null( $info ) ) {
1465                         return null;
1466                 } else {
1467                         return $info !== false;
1468                 }
1469         }
1470
1471         public function tableExists( $table, $fname = __METHOD__ ) {
1472                 $table = $this->tableName( $table );
1473                 $old = $this->ignoreErrors( true );
1474                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1475                 $this->ignoreErrors( $old );
1476
1477                 return (bool)$res;
1478         }
1479
1480         public function indexUnique( $table, $index ) {
1481                 $indexInfo = $this->indexInfo( $table, $index );
1482
1483                 if ( !$indexInfo ) {
1484                         return null;
1485                 }
1486
1487                 return !$indexInfo[0]->Non_unique;
1488         }
1489
1490         /**
1491          * Helper for DatabaseBase::insert().
1492          *
1493          * @param array $options
1494          * @return string
1495          */
1496         protected function makeInsertOptions( $options ) {
1497                 return implode( ' ', $options );
1498         }
1499
1500         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1501                 # No rows to insert, easy just return now
1502                 if ( !count( $a ) ) {
1503                         return true;
1504                 }
1505
1506                 $table = $this->tableName( $table );
1507
1508                 if ( !is_array( $options ) ) {
1509                         $options = [ $options ];
1510                 }
1511
1512                 $fh = null;
1513                 if ( isset( $options['fileHandle'] ) ) {
1514                         $fh = $options['fileHandle'];
1515                 }
1516                 $options = $this->makeInsertOptions( $options );
1517
1518                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1519                         $multi = true;
1520                         $keys = array_keys( $a[0] );
1521                 } else {
1522                         $multi = false;
1523                         $keys = array_keys( $a );
1524                 }
1525
1526                 $sql = 'INSERT ' . $options .
1527                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1528
1529                 if ( $multi ) {
1530                         $first = true;
1531                         foreach ( $a as $row ) {
1532                                 if ( $first ) {
1533                                         $first = false;
1534                                 } else {
1535                                         $sql .= ',';
1536                                 }
1537                                 $sql .= '(' . $this->makeList( $row ) . ')';
1538                         }
1539                 } else {
1540                         $sql .= '(' . $this->makeList( $a ) . ')';
1541                 }
1542
1543                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1544                         return false;
1545                 } elseif ( $fh !== null ) {
1546                         return true;
1547                 }
1548
1549                 return (bool)$this->query( $sql, $fname );
1550         }
1551
1552         /**
1553          * Make UPDATE options array for DatabaseBase::makeUpdateOptions
1554          *
1555          * @param array $options
1556          * @return array
1557          */
1558         protected function makeUpdateOptionsArray( $options ) {
1559                 if ( !is_array( $options ) ) {
1560                         $options = [ $options ];
1561                 }
1562
1563                 $opts = [];
1564
1565                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1566                         $opts[] = $this->lowPriorityOption();
1567                 }
1568
1569                 if ( in_array( 'IGNORE', $options ) ) {
1570                         $opts[] = 'IGNORE';
1571                 }
1572
1573                 return $opts;
1574         }
1575
1576         /**
1577          * Make UPDATE options for the DatabaseBase::update function
1578          *
1579          * @param array $options The options passed to DatabaseBase::update
1580          * @return string
1581          */
1582         protected function makeUpdateOptions( $options ) {
1583                 $opts = $this->makeUpdateOptionsArray( $options );
1584
1585                 return implode( ' ', $opts );
1586         }
1587
1588         function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1589                 $table = $this->tableName( $table );
1590                 $opts = $this->makeUpdateOptions( $options );
1591                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1592
1593                 if ( $conds !== [] && $conds !== '*' ) {
1594                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1595                 }
1596
1597                 return $this->query( $sql, $fname );
1598         }
1599
1600         public function makeList( $a, $mode = LIST_COMMA ) {
1601                 if ( !is_array( $a ) ) {
1602                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1603                 }
1604
1605                 $first = true;
1606                 $list = '';
1607
1608                 foreach ( $a as $field => $value ) {
1609                         if ( !$first ) {
1610                                 if ( $mode == LIST_AND ) {
1611                                         $list .= ' AND ';
1612                                 } elseif ( $mode == LIST_OR ) {
1613                                         $list .= ' OR ';
1614                                 } else {
1615                                         $list .= ',';
1616                                 }
1617                         } else {
1618                                 $first = false;
1619                         }
1620
1621                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1622                                 $list .= "($value)";
1623                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1624                                 $list .= "$value";
1625                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1626                                 // Remove null from array to be handled separately if found
1627                                 $includeNull = false;
1628                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1629                                         $includeNull = true;
1630                                         unset( $value[$nullKey] );
1631                                 }
1632                                 if ( count( $value ) == 0 && !$includeNull ) {
1633                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1634                                 } elseif ( count( $value ) == 0 ) {
1635                                         // only check if $field is null
1636                                         $list .= "$field IS NULL";
1637                                 } else {
1638                                         // IN clause contains at least one valid element
1639                                         if ( $includeNull ) {
1640                                                 // Group subconditions to ensure correct precedence
1641                                                 $list .= '(';
1642                                         }
1643                                         if ( count( $value ) == 1 ) {
1644                                                 // Special-case single values, as IN isn't terribly efficient
1645                                                 // Don't necessarily assume the single key is 0; we don't
1646                                                 // enforce linear numeric ordering on other arrays here.
1647                                                 $value = array_values( $value )[0];
1648                                                 $list .= $field . " = " . $this->addQuotes( $value );
1649                                         } else {
1650                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1651                                         }
1652                                         // if null present in array, append IS NULL
1653                                         if ( $includeNull ) {
1654                                                 $list .= " OR $field IS NULL)";
1655                                         }
1656                                 }
1657                         } elseif ( $value === null ) {
1658                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1659                                         $list .= "$field IS ";
1660                                 } elseif ( $mode == LIST_SET ) {
1661                                         $list .= "$field = ";
1662                                 }
1663                                 $list .= 'NULL';
1664                         } else {
1665                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1666                                         $list .= "$field = ";
1667                                 }
1668                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1669                         }
1670                 }
1671
1672                 return $list;
1673         }
1674
1675         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1676                 $conds = [];
1677
1678                 foreach ( $data as $base => $sub ) {
1679                         if ( count( $sub ) ) {
1680                                 $conds[] = $this->makeList(
1681                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1682                                         LIST_AND );
1683                         }
1684                 }
1685
1686                 if ( $conds ) {
1687                         return $this->makeList( $conds, LIST_OR );
1688                 } else {
1689                         // Nothing to search for...
1690                         return false;
1691                 }
1692         }
1693
1694         /**
1695          * Return aggregated value alias
1696          *
1697          * @param array $valuedata
1698          * @param string $valuename
1699          *
1700          * @return string
1701          */
1702         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1703                 return $valuename;
1704         }
1705
1706         public function bitNot( $field ) {
1707                 return "(~$field)";
1708         }
1709
1710         public function bitAnd( $fieldLeft, $fieldRight ) {
1711                 return "($fieldLeft & $fieldRight)";
1712         }
1713
1714         public function bitOr( $fieldLeft, $fieldRight ) {
1715                 return "($fieldLeft | $fieldRight)";
1716         }
1717
1718         public function buildConcat( $stringList ) {
1719                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1720         }
1721
1722         public function buildGroupConcatField(
1723                 $delim, $table, $field, $conds = '', $join_conds = []
1724         ) {
1725                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1726
1727                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1728         }
1729
1730         public function selectDB( $db ) {
1731                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1732                 # if your database engine supports a concept similar to MySQL's
1733                 # databases you may as well.
1734                 $this->mDBname = $db;
1735
1736                 return true;
1737         }
1738
1739         public function getDBname() {
1740                 return $this->mDBname;
1741         }
1742
1743         public function getServer() {
1744                 return $this->mServer;
1745         }
1746
1747         /**
1748          * Format a table name ready for use in constructing an SQL query
1749          *
1750          * This does two important things: it quotes the table names to clean them up,
1751          * and it adds a table prefix if only given a table name with no quotes.
1752          *
1753          * All functions of this object which require a table name call this function
1754          * themselves. Pass the canonical name to such functions. This is only needed
1755          * when calling query() directly.
1756          *
1757          * @note This function does not sanitize user input. It is not safe to use
1758          *   this function to escape user input.
1759          * @param string $name Database table name
1760          * @param string $format One of:
1761          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1762          *            so that it can be used in a query.
1763          *   raw - Do not add identifier quotes to the table name
1764          * @return string Full database name
1765          */
1766         public function tableName( $name, $format = 'quoted' ) {
1767                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables, $wgSharedSchema;
1768                 # Skip the entire process when we have a string quoted on both ends.
1769                 # Note that we check the end so that we will still quote any use of
1770                 # use of `database`.table. But won't break things if someone wants
1771                 # to query a database table with a dot in the name.
1772                 if ( $this->isQuotedIdentifier( $name ) ) {
1773                         return $name;
1774                 }
1775
1776                 # Lets test for any bits of text that should never show up in a table
1777                 # name. Basically anything like JOIN or ON which are actually part of
1778                 # SQL queries, but may end up inside of the table value to combine
1779                 # sql. Such as how the API is doing.
1780                 # Note that we use a whitespace test rather than a \b test to avoid
1781                 # any remote case where a word like on may be inside of a table name
1782                 # surrounded by symbols which may be considered word breaks.
1783                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1784                         return $name;
1785                 }
1786
1787                 # Split database and table into proper variables.
1788                 # We reverse the explode so that database.table and table both output
1789                 # the correct table.
1790                 $dbDetails = explode( '.', $name, 3 );
1791                 if ( count( $dbDetails ) == 3 ) {
1792                         list( $database, $schema, $table ) = $dbDetails;
1793                         # We don't want any prefix added in this case
1794                         $prefix = '';
1795                 } elseif ( count( $dbDetails ) == 2 ) {
1796                         list( $database, $table ) = $dbDetails;
1797                         # We don't want any prefix added in this case
1798                         # In dbs that support it, $database may actually be the schema
1799                         # but that doesn't affect any of the functionality here
1800                         $prefix = '';
1801                         $schema = null;
1802                 } else {
1803                         list( $table ) = $dbDetails;
1804                         if ( $wgSharedDB !== null # We have a shared database
1805                                 && $this->mForeign == false # We're not working on a foreign database
1806                                 && !$this->isQuotedIdentifier( $table ) # Prevent shared tables listing '`table`'
1807                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
1808                         ) {
1809                                 $database = $wgSharedDB;
1810                                 $schema = $wgSharedSchema === null ? $this->mSchema : $wgSharedSchema;
1811                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
1812                         } else {
1813                                 $database = null;
1814                                 $schema = $this->mSchema; # Default schema
1815                                 $prefix = $this->mTablePrefix; # Default prefix
1816                         }
1817                 }
1818
1819                 # Quote $table and apply the prefix if not quoted.
1820                 # $tableName might be empty if this is called from Database::replaceVars()
1821                 $tableName = "{$prefix}{$table}";
1822                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) && $tableName !== '' ) {
1823                         $tableName = $this->addIdentifierQuotes( $tableName );
1824                 }
1825
1826                 # Quote $schema and merge it with the table name if needed
1827                 if ( strlen( $schema ) ) {
1828                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $schema ) ) {
1829                                 $schema = $this->addIdentifierQuotes( $schema );
1830                         }
1831                         $tableName = $schema . '.' . $tableName;
1832                 }
1833
1834                 # Quote $database and merge it with the table name if needed
1835                 if ( $database !== null ) {
1836                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
1837                                 $database = $this->addIdentifierQuotes( $database );
1838                         }
1839                         $tableName = $database . '.' . $tableName;
1840                 }
1841
1842                 return $tableName;
1843         }
1844
1845         /**
1846          * Fetch a number of table names into an array
1847          * This is handy when you need to construct SQL for joins
1848          *
1849          * Example:
1850          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
1851          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1852          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1853          *
1854          * @return array
1855          */
1856         public function tableNames() {
1857                 $inArray = func_get_args();
1858                 $retVal = [];
1859
1860                 foreach ( $inArray as $name ) {
1861                         $retVal[$name] = $this->tableName( $name );
1862                 }
1863
1864                 return $retVal;
1865         }
1866
1867         /**
1868          * Fetch a number of table names into an zero-indexed numerical array
1869          * This is handy when you need to construct SQL for joins
1870          *
1871          * Example:
1872          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
1873          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1874          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1875          *
1876          * @return array
1877          */
1878         public function tableNamesN() {
1879                 $inArray = func_get_args();
1880                 $retVal = [];
1881
1882                 foreach ( $inArray as $name ) {
1883                         $retVal[] = $this->tableName( $name );
1884                 }
1885
1886                 return $retVal;
1887         }
1888
1889         /**
1890          * Get an aliased table name
1891          * e.g. tableName AS newTableName
1892          *
1893          * @param string $name Table name, see tableName()
1894          * @param string|bool $alias Alias (optional)
1895          * @return string SQL name for aliased table. Will not alias a table to its own name
1896          */
1897         public function tableNameWithAlias( $name, $alias = false ) {
1898                 if ( !$alias || $alias == $name ) {
1899                         return $this->tableName( $name );
1900                 } else {
1901                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
1902                 }
1903         }
1904
1905         /**
1906          * Gets an array of aliased table names
1907          *
1908          * @param array $tables [ [alias] => table ]
1909          * @return string[] See tableNameWithAlias()
1910          */
1911         public function tableNamesWithAlias( $tables ) {
1912                 $retval = [];
1913                 foreach ( $tables as $alias => $table ) {
1914                         if ( is_numeric( $alias ) ) {
1915                                 $alias = $table;
1916                         }
1917                         $retval[] = $this->tableNameWithAlias( $table, $alias );
1918                 }
1919
1920                 return $retval;
1921         }
1922
1923         /**
1924          * Get an aliased field name
1925          * e.g. fieldName AS newFieldName
1926          *
1927          * @param string $name Field name
1928          * @param string|bool $alias Alias (optional)
1929          * @return string SQL name for aliased field. Will not alias a field to its own name
1930          */
1931         public function fieldNameWithAlias( $name, $alias = false ) {
1932                 if ( !$alias || (string)$alias === (string)$name ) {
1933                         return $name;
1934                 } else {
1935                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
1936                 }
1937         }
1938
1939         /**
1940          * Gets an array of aliased field names
1941          *
1942          * @param array $fields [ [alias] => field ]
1943          * @return string[] See fieldNameWithAlias()
1944          */
1945         public function fieldNamesWithAlias( $fields ) {
1946                 $retval = [];
1947                 foreach ( $fields as $alias => $field ) {
1948                         if ( is_numeric( $alias ) ) {
1949                                 $alias = $field;
1950                         }
1951                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
1952                 }
1953
1954                 return $retval;
1955         }
1956
1957         /**
1958          * Get the aliased table name clause for a FROM clause
1959          * which might have a JOIN and/or USE INDEX clause
1960          *
1961          * @param array $tables ( [alias] => table )
1962          * @param array $use_index Same as for select()
1963          * @param array $join_conds Same as for select()
1964          * @return string
1965          */
1966         protected function tableNamesWithUseIndexOrJOIN(
1967                 $tables, $use_index = [], $join_conds = []
1968         ) {
1969                 $ret = [];
1970                 $retJOIN = [];
1971                 $use_index = (array)$use_index;
1972                 $join_conds = (array)$join_conds;
1973
1974                 foreach ( $tables as $alias => $table ) {
1975                         if ( !is_string( $alias ) ) {
1976                                 // No alias? Set it equal to the table name
1977                                 $alias = $table;
1978                         }
1979                         // Is there a JOIN clause for this table?
1980                         if ( isset( $join_conds[$alias] ) ) {
1981                                 list( $joinType, $conds ) = $join_conds[$alias];
1982                                 $tableClause = $joinType;
1983                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
1984                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
1985                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
1986                                         if ( $use != '' ) {
1987                                                 $tableClause .= ' ' . $use;
1988                                         }
1989                                 }
1990                                 $on = $this->makeList( (array)$conds, LIST_AND );
1991                                 if ( $on != '' ) {
1992                                         $tableClause .= ' ON (' . $on . ')';
1993                                 }
1994
1995                                 $retJOIN[] = $tableClause;
1996                         } elseif ( isset( $use_index[$alias] ) ) {
1997                                 // Is there an INDEX clause for this table?
1998                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
1999                                 $tableClause .= ' ' . $this->useIndexClause(
2000                                         implode( ',', (array)$use_index[$alias] )
2001                                 );
2002
2003                                 $ret[] = $tableClause;
2004                         } else {
2005                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2006
2007                                 $ret[] = $tableClause;
2008                         }
2009                 }
2010
2011                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2012                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2013                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2014
2015                 // Compile our final table clause
2016                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2017         }
2018
2019         /**
2020          * Get the name of an index in a given table.
2021          *
2022          * @param string $index
2023          * @return string
2024          */
2025         protected function indexName( $index ) {
2026                 // Backwards-compatibility hack
2027                 $renamed = [
2028                         'ar_usertext_timestamp' => 'usertext_timestamp',
2029                         'un_user_id' => 'user_id',
2030                         'un_user_ip' => 'user_ip',
2031                 ];
2032
2033                 if ( isset( $renamed[$index] ) ) {
2034                         return $renamed[$index];
2035                 } else {
2036                         return $index;
2037                 }
2038         }
2039
2040         public function addQuotes( $s ) {
2041                 if ( $s instanceof Blob ) {
2042                         $s = $s->fetch();
2043                 }
2044                 if ( $s === null ) {
2045                         return 'NULL';
2046                 } else {
2047                         # This will also quote numeric values. This should be harmless,
2048                         # and protects against weird problems that occur when they really
2049                         # _are_ strings such as article titles and string->number->string
2050                         # conversion is not 1:1.
2051                         return "'" . $this->strencode( $s ) . "'";
2052                 }
2053         }
2054
2055         /**
2056          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2057          * MySQL uses `backticks` while basically everything else uses double quotes.
2058          * Since MySQL is the odd one out here the double quotes are our generic
2059          * and we implement backticks in DatabaseMysql.
2060          *
2061          * @param string $s
2062          * @return string
2063          */
2064         public function addIdentifierQuotes( $s ) {
2065                 return '"' . str_replace( '"', '""', $s ) . '"';
2066         }
2067
2068         /**
2069          * Returns if the given identifier looks quoted or not according to
2070          * the database convention for quoting identifiers .
2071          *
2072          * @note Do not use this to determine if untrusted input is safe.
2073          *   A malicious user can trick this function.
2074          * @param string $name
2075          * @return bool
2076          */
2077         public function isQuotedIdentifier( $name ) {
2078                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2079         }
2080
2081         /**
2082          * @param string $s
2083          * @return string
2084          */
2085         protected function escapeLikeInternal( $s ) {
2086                 return addcslashes( $s, '\%_' );
2087         }
2088
2089         public function buildLike() {
2090                 $params = func_get_args();
2091
2092                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2093                         $params = $params[0];
2094                 }
2095
2096                 $s = '';
2097
2098                 foreach ( $params as $value ) {
2099                         if ( $value instanceof LikeMatch ) {
2100                                 $s .= $value->toString();
2101                         } else {
2102                                 $s .= $this->escapeLikeInternal( $value );
2103                         }
2104                 }
2105
2106                 return " LIKE {$this->addQuotes( $s )} ";
2107         }
2108
2109         public function anyChar() {
2110                 return new LikeMatch( '_' );
2111         }
2112
2113         public function anyString() {
2114                 return new LikeMatch( '%' );
2115         }
2116
2117         public function nextSequenceValue( $seqName ) {
2118                 return null;
2119         }
2120
2121         /**
2122          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2123          * is only needed because a) MySQL must be as efficient as possible due to
2124          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2125          * which index to pick. Anyway, other databases might have different
2126          * indexes on a given table. So don't bother overriding this unless you're
2127          * MySQL.
2128          * @param string $index
2129          * @return string
2130          */
2131         public function useIndexClause( $index ) {
2132                 return '';
2133         }
2134
2135         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2136                 $quotedTable = $this->tableName( $table );
2137
2138                 if ( count( $rows ) == 0 ) {
2139                         return;
2140                 }
2141
2142                 # Single row case
2143                 if ( !is_array( reset( $rows ) ) ) {
2144                         $rows = [ $rows ];
2145                 }
2146
2147                 // @FXIME: this is not atomic, but a trx would break affectedRows()
2148                 foreach ( $rows as $row ) {
2149                         # Delete rows which collide
2150                         if ( $uniqueIndexes ) {
2151                                 $sql = "DELETE FROM $quotedTable WHERE ";
2152                                 $first = true;
2153                                 foreach ( $uniqueIndexes as $index ) {
2154                                         if ( $first ) {
2155                                                 $first = false;
2156                                                 $sql .= '( ';
2157                                         } else {
2158                                                 $sql .= ' ) OR ( ';
2159                                         }
2160                                         if ( is_array( $index ) ) {
2161                                                 $first2 = true;
2162                                                 foreach ( $index as $col ) {
2163                                                         if ( $first2 ) {
2164                                                                 $first2 = false;
2165                                                         } else {
2166                                                                 $sql .= ' AND ';
2167                                                         }
2168                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2169                                                 }
2170                                         } else {
2171                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2172                                         }
2173                                 }
2174                                 $sql .= ' )';
2175                                 $this->query( $sql, $fname );
2176                         }
2177
2178                         # Now insert the row
2179                         $this->insert( $table, $row, $fname );
2180                 }
2181         }
2182
2183         /**
2184          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2185          * statement.
2186          *
2187          * @param string $table Table name
2188          * @param array|string $rows Row(s) to insert
2189          * @param string $fname Caller function name
2190          *
2191          * @return ResultWrapper
2192          */
2193         protected function nativeReplace( $table, $rows, $fname ) {
2194                 $table = $this->tableName( $table );
2195
2196                 # Single row case
2197                 if ( !is_array( reset( $rows ) ) ) {
2198                         $rows = [ $rows ];
2199                 }
2200
2201                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2202                 $first = true;
2203
2204                 foreach ( $rows as $row ) {
2205                         if ( $first ) {
2206                                 $first = false;
2207                         } else {
2208                                 $sql .= ',';
2209                         }
2210
2211                         $sql .= '(' . $this->makeList( $row ) . ')';
2212                 }
2213
2214                 return $this->query( $sql, $fname );
2215         }
2216
2217         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2218                 $fname = __METHOD__
2219         ) {
2220                 if ( !count( $rows ) ) {
2221                         return true; // nothing to do
2222                 }
2223
2224                 if ( !is_array( reset( $rows ) ) ) {
2225                         $rows = [ $rows ];
2226                 }
2227
2228                 if ( count( $uniqueIndexes ) ) {
2229                         $clauses = []; // list WHERE clauses that each identify a single row
2230                         foreach ( $rows as $row ) {
2231                                 foreach ( $uniqueIndexes as $index ) {
2232                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2233                                         $rowKey = []; // unique key to this row
2234                                         foreach ( $index as $column ) {
2235                                                 $rowKey[$column] = $row[$column];
2236                                         }
2237                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2238                                 }
2239                         }
2240                         $where = [ $this->makeList( $clauses, LIST_OR ) ];
2241                 } else {
2242                         $where = false;
2243                 }
2244
2245                 $useTrx = !$this->mTrxLevel;
2246                 if ( $useTrx ) {
2247                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2248                 }
2249                 try {
2250                         # Update any existing conflicting row(s)
2251                         if ( $where !== false ) {
2252                                 $ok = $this->update( $table, $set, $where, $fname );
2253                         } else {
2254                                 $ok = true;
2255                         }
2256                         # Now insert any non-conflicting row(s)
2257                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2258                 } catch ( Exception $e ) {
2259                         if ( $useTrx ) {
2260                                 $this->rollback( $fname );
2261                         }
2262                         throw $e;
2263                 }
2264                 if ( $useTrx ) {
2265                         $this->commit( $fname, self::TRANSACTION_INTERNAL );
2266                 }
2267
2268                 return $ok;
2269         }
2270
2271         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2272                 $fname = __METHOD__
2273         ) {
2274                 if ( !$conds ) {
2275                         throw new DBUnexpectedError( $this,
2276                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2277                 }
2278
2279                 $delTable = $this->tableName( $delTable );
2280                 $joinTable = $this->tableName( $joinTable );
2281                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2282                 if ( $conds != '*' ) {
2283                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2284                 }
2285                 $sql .= ')';
2286
2287                 $this->query( $sql, $fname );
2288         }
2289
2290         /**
2291          * Returns the size of a text field, or -1 for "unlimited"
2292          *
2293          * @param string $table
2294          * @param string $field
2295          * @return int
2296          */
2297         public function textFieldSize( $table, $field ) {
2298                 $table = $this->tableName( $table );
2299                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2300                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2301                 $row = $this->fetchObject( $res );
2302
2303                 $m = [];
2304
2305                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2306                         $size = $m[1];
2307                 } else {
2308                         $size = -1;
2309                 }
2310
2311                 return $size;
2312         }
2313
2314         /**
2315          * A string to insert into queries to show that they're low-priority, like
2316          * MySQL's LOW_PRIORITY. If no such feature exists, return an empty
2317          * string and nothing bad should happen.
2318          *
2319          * @return string Returns the text of the low priority option if it is
2320          *   supported, or a blank string otherwise
2321          */
2322         public function lowPriorityOption() {
2323                 return '';
2324         }
2325
2326         public function delete( $table, $conds, $fname = __METHOD__ ) {
2327                 if ( !$conds ) {
2328                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2329                 }
2330
2331                 $table = $this->tableName( $table );
2332                 $sql = "DELETE FROM $table";
2333
2334                 if ( $conds != '*' ) {
2335                         if ( is_array( $conds ) ) {
2336                                 $conds = $this->makeList( $conds, LIST_AND );
2337                         }
2338                         $sql .= ' WHERE ' . $conds;
2339                 }
2340
2341                 return $this->query( $sql, $fname );
2342         }
2343
2344         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2345                 $fname = __METHOD__,
2346                 $insertOptions = [], $selectOptions = []
2347         ) {
2348                 $destTable = $this->tableName( $destTable );
2349
2350                 if ( !is_array( $insertOptions ) ) {
2351                         $insertOptions = [ $insertOptions ];
2352                 }
2353
2354                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2355
2356                 if ( !is_array( $selectOptions ) ) {
2357                         $selectOptions = [ $selectOptions ];
2358                 }
2359
2360                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2361
2362                 if ( is_array( $srcTable ) ) {
2363                         $srcTable = implode( ',', array_map( [ &$this, 'tableName' ], $srcTable ) );
2364                 } else {
2365                         $srcTable = $this->tableName( $srcTable );
2366                 }
2367
2368                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2369                         " SELECT $startOpts " . implode( ',', $varMap ) .
2370                         " FROM $srcTable $useIndex ";
2371
2372                 if ( $conds != '*' ) {
2373                         if ( is_array( $conds ) ) {
2374                                 $conds = $this->makeList( $conds, LIST_AND );
2375                         }
2376                         $sql .= " WHERE $conds";
2377                 }
2378
2379                 $sql .= " $tailOpts";
2380
2381                 return $this->query( $sql, $fname );
2382         }
2383
2384         /**
2385          * Construct a LIMIT query with optional offset. This is used for query
2386          * pages. The SQL should be adjusted so that only the first $limit rows
2387          * are returned. If $offset is provided as well, then the first $offset
2388          * rows should be discarded, and the next $limit rows should be returned.
2389          * If the result of the query is not ordered, then the rows to be returned
2390          * are theoretically arbitrary.
2391          *
2392          * $sql is expected to be a SELECT, if that makes a difference.
2393          *
2394          * The version provided by default works in MySQL and SQLite. It will very
2395          * likely need to be overridden for most other DBMSes.
2396          *
2397          * @param string $sql SQL query we will append the limit too
2398          * @param int $limit The SQL limit
2399          * @param int|bool $offset The SQL offset (default false)
2400          * @throws DBUnexpectedError
2401          * @return string
2402          */
2403         public function limitResult( $sql, $limit, $offset = false ) {
2404                 if ( !is_numeric( $limit ) ) {
2405                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2406                 }
2407
2408                 return "$sql LIMIT "
2409                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2410                         . "{$limit} ";
2411         }
2412
2413         public function unionSupportsOrderAndLimit() {
2414                 return true; // True for almost every DB supported
2415         }
2416
2417         public function unionQueries( $sqls, $all ) {
2418                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2419
2420                 return '(' . implode( $glue, $sqls ) . ')';
2421         }
2422
2423         public function conditional( $cond, $trueVal, $falseVal ) {
2424                 if ( is_array( $cond ) ) {
2425                         $cond = $this->makeList( $cond, LIST_AND );
2426                 }
2427
2428                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2429         }
2430
2431         public function strreplace( $orig, $old, $new ) {
2432                 return "REPLACE({$orig}, {$old}, {$new})";
2433         }
2434
2435         public function getServerUptime() {
2436                 return 0;
2437         }
2438
2439         public function wasDeadlock() {
2440                 return false;
2441         }
2442
2443         public function wasLockTimeout() {
2444                 return false;
2445         }
2446
2447         public function wasErrorReissuable() {
2448                 return false;
2449         }
2450
2451         public function wasReadOnlyError() {
2452                 return false;
2453         }
2454
2455         /**
2456          * Determines if the given query error was a connection drop
2457          * STUB
2458          *
2459          * @param integer|string $errno
2460          * @return bool
2461          */
2462         public function wasConnectionError( $errno ) {
2463                 return false;
2464         }
2465
2466         /**
2467          * Perform a deadlock-prone transaction.
2468          *
2469          * This function invokes a callback function to perform a set of write
2470          * queries. If a deadlock occurs during the processing, the transaction
2471          * will be rolled back and the callback function will be called again.
2472          *
2473          * Avoid using this method outside of Job or Maintenance classes.
2474          *
2475          * Usage:
2476          *   $dbw->deadlockLoop( callback, ... );
2477          *
2478          * Extra arguments are passed through to the specified callback function.
2479          * This method requires that no transactions are already active to avoid
2480          * causing premature commits or exceptions.
2481          *
2482          * Returns whatever the callback function returned on its successful,
2483          * iteration, or false on error, for example if the retry limit was
2484          * reached.
2485          *
2486          * @return mixed
2487          * @throws DBUnexpectedError
2488          * @throws Exception
2489          */
2490         public function deadlockLoop() {
2491                 $args = func_get_args();
2492                 $function = array_shift( $args );
2493                 $tries = self::DEADLOCK_TRIES;
2494
2495                 $this->begin( __METHOD__ );
2496
2497                 $retVal = null;
2498                 /** @var Exception $e */
2499                 $e = null;
2500                 do {
2501                         try {
2502                                 $retVal = call_user_func_array( $function, $args );
2503                                 break;
2504                         } catch ( DBQueryError $e ) {
2505                                 if ( $this->wasDeadlock() ) {
2506                                         // Retry after a randomized delay
2507                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2508                                 } else {
2509                                         // Throw the error back up
2510                                         throw $e;
2511                                 }
2512                         }
2513                 } while ( --$tries > 0 );
2514
2515                 if ( $tries <= 0 ) {
2516                         // Too many deadlocks; give up
2517                         $this->rollback( __METHOD__ );
2518                         throw $e;
2519                 } else {
2520                         $this->commit( __METHOD__ );
2521
2522                         return $retVal;
2523                 }
2524         }
2525
2526         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2527                 # Real waits are implemented in the subclass.
2528                 return 0;
2529         }
2530
2531         public function getSlavePos() {
2532                 # Stub
2533                 return false;
2534         }
2535
2536         public function getMasterPos() {
2537                 # Stub
2538                 return false;
2539         }
2540
2541         public function serverIsReadOnly() {
2542                 return false;
2543         }
2544
2545         final public function onTransactionResolution( callable $callback ) {
2546                 if ( !$this->mTrxLevel ) {
2547                         throw new DBUnexpectedError( $this, "No transaction is active." );
2548                 }
2549                 $this->mTrxEndCallbacks[] = [ $callback, wfGetCaller() ];
2550         }
2551
2552         final public function onTransactionIdle( callable $callback ) {
2553                 $this->mTrxIdleCallbacks[] = [ $callback, wfGetCaller() ];
2554                 if ( !$this->mTrxLevel ) {
2555                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2556                 }
2557         }
2558
2559         final public function onTransactionPreCommitOrIdle( callable $callback ) {
2560                 if ( $this->mTrxLevel ) {
2561                         $this->mTrxPreCommitCallbacks[] = [ $callback, wfGetCaller() ];
2562                 } else {
2563                         // If no transaction is active, then make one for this callback
2564                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
2565                         try {
2566                                 call_user_func( $callback );
2567                                 $this->commit( __METHOD__ );
2568                         } catch ( Exception $e ) {
2569                                 $this->rollback( __METHOD__ );
2570                                 throw $e;
2571                         }
2572                 }
2573         }
2574
2575         /**
2576          * Whether to disable running of post-commit callbacks
2577          *
2578          * This method should not be used outside of Database/LoadBalancer
2579          *
2580          * @param bool $suppress
2581          * @since 1.28
2582          */
2583         final public function setPostCommitCallbackSupression( $suppress ) {
2584                 $this->suppressPostCommitCallbacks = $suppress;
2585         }
2586
2587         /**
2588          * Actually run and consume any "on transaction idle/resolution" callbacks.
2589          *
2590          * This method should not be used outside of Database/LoadBalancer
2591          *
2592          * @param integer $trigger IDatabase::TRIGGER_* constant
2593          * @since 1.20
2594          * @throws Exception
2595          */
2596         public function runOnTransactionIdleCallbacks( $trigger ) {
2597                 if ( $this->suppressPostCommitCallbacks ) {
2598                         return;
2599                 }
2600
2601                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
2602                 /** @var Exception $e */
2603                 $e = null; // first exception
2604                 do { // callbacks may add callbacks :)
2605                         $callbacks = array_merge(
2606                                 $this->mTrxIdleCallbacks,
2607                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2608                         );
2609                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2610                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2611                         foreach ( $callbacks as $callback ) {
2612                                 try {
2613                                         list( $phpCallback ) = $callback;
2614                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
2615                                         call_user_func_array( $phpCallback, [ $trigger ] );
2616                                         if ( $autoTrx ) {
2617                                                 $this->setFlag( DBO_TRX ); // restore automatic begin()
2618                                         } else {
2619                                                 $this->clearFlag( DBO_TRX ); // restore auto-commit
2620                                         }
2621                                 } catch ( Exception $ex ) {
2622                                         MWExceptionHandler::logException( $ex );
2623                                         $e = $e ?: $ex;
2624                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2625                                         // their transactions are ended so other callbacks don't fail
2626                                         if ( $this->trxLevel() ) {
2627                                                 $this->rollback( __METHOD__ );
2628                                         }
2629                                 }
2630                         }
2631                 } while ( count( $this->mTrxIdleCallbacks ) );
2632
2633                 if ( $e instanceof Exception ) {
2634                         throw $e; // re-throw any first exception
2635                 }
2636         }
2637
2638         /**
2639          * Actually run and consume any "on transaction pre-commit" callbacks.
2640          *
2641          * This method should not be used outside of Database/LoadBalancer
2642          *
2643          * @since 1.22
2644          * @throws Exception
2645          */
2646         public function runOnTransactionPreCommitCallbacks() {
2647                 $e = null; // first exception
2648                 do { // callbacks may add callbacks :)
2649                         $callbacks = $this->mTrxPreCommitCallbacks;
2650                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2651                         foreach ( $callbacks as $callback ) {
2652                                 try {
2653                                         list( $phpCallback ) = $callback;
2654                                         call_user_func( $phpCallback );
2655                                 } catch ( Exception $ex ) {
2656                                         MWExceptionHandler::logException( $ex );
2657                                         $e = $e ?: $ex;
2658                                 }
2659                         }
2660                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2661
2662                 if ( $e instanceof Exception ) {
2663                         throw $e; // re-throw any first exception
2664                 }
2665         }
2666
2667         final public function startAtomic( $fname = __METHOD__ ) {
2668                 if ( !$this->mTrxLevel ) {
2669                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2670                         $this->mTrxAutomatic = true;
2671                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2672                         // in all changes being in one transaction to keep requests transactional.
2673                         if ( !$this->getFlag( DBO_TRX ) ) {
2674                                 $this->mTrxAutomaticAtomic = true;
2675                         }
2676                 }
2677
2678                 $this->mTrxAtomicLevels[] = $fname;
2679         }
2680
2681         final public function endAtomic( $fname = __METHOD__ ) {
2682                 if ( !$this->mTrxLevel ) {
2683                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2684                 }
2685                 if ( !$this->mTrxAtomicLevels ||
2686                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2687                 ) {
2688                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2689                 }
2690
2691                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2692                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2693                 }
2694         }
2695
2696         final public function doAtomicSection( $fname, callable $callback ) {
2697                 $this->startAtomic( $fname );
2698                 try {
2699                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2700                 } catch ( Exception $e ) {
2701                         $this->rollback( $fname );
2702                         throw $e;
2703                 }
2704                 $this->endAtomic( $fname );
2705
2706                 return $res;
2707         }
2708
2709         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2710                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2711                 if ( $this->mTrxLevel ) {
2712                         if ( $this->mTrxAtomicLevels ) {
2713                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2714                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2715                                 throw new DBUnexpectedError( $this, $msg );
2716                         } elseif ( !$this->mTrxAutomatic ) {
2717                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2718                                 throw new DBUnexpectedError( $this, $msg );
2719                         } else {
2720                                 // @TODO: make this an exception at some point
2721                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2722                                 wfLogDBError( $msg );
2723                                 return; // join the main transaction set
2724                         }
2725                 } elseif ( $this->getFlag( DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2726                         // @TODO: make this an exception at some point
2727                         wfLogDBError( "$fname: Implicit transaction expected (DBO_TRX set)." );
2728                         return; // let any writes be in the main transaction
2729                 }
2730
2731                 // Avoid fatals if close() was called
2732                 $this->assertOpen();
2733
2734                 $this->doBegin( $fname );
2735                 $this->mTrxTimestamp = microtime( true );
2736                 $this->mTrxFname = $fname;
2737                 $this->mTrxDoneWrites = false;
2738                 $this->mTrxAutomatic = false;
2739                 $this->mTrxAutomaticAtomic = false;
2740                 $this->mTrxAtomicLevels = [];
2741                 $this->mTrxShortId = wfRandomString( 12 );
2742                 $this->mTrxWriteDuration = 0.0;
2743                 $this->mTrxWriteCallers = [];
2744                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
2745                 // Get an estimate of the slave lag before then, treating estimate staleness
2746                 // as lag itself just to be safe
2747                 $status = $this->getApproximateLagStatus();
2748                 $this->mTrxSlaveLag = $status['lag'] + ( microtime( true ) - $status['since'] );
2749         }
2750
2751         /**
2752          * Issues the BEGIN command to the database server.
2753          *
2754          * @see DatabaseBase::begin()
2755          * @param string $fname
2756          */
2757         protected function doBegin( $fname ) {
2758                 $this->query( 'BEGIN', $fname );
2759                 $this->mTrxLevel = 1;
2760         }
2761
2762         final public function commit( $fname = __METHOD__, $flush = '' ) {
2763                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
2764                         // There are still atomic sections open. This cannot be ignored
2765                         $levels = implode( ', ', $this->mTrxAtomicLevels );
2766                         throw new DBUnexpectedError(
2767                                 $this,
2768                                 "$fname: Got COMMIT while atomic sections $levels are still open."
2769                         );
2770                 }
2771
2772                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
2773                         if ( !$this->mTrxLevel ) {
2774                                 return; // nothing to do
2775                         } elseif ( !$this->mTrxAutomatic ) {
2776                                 throw new DBUnexpectedError(
2777                                         $this,
2778                                         "$fname: Flushing an explicit transaction, getting out of sync."
2779                                 );
2780                         }
2781                 } else {
2782                         if ( !$this->mTrxLevel ) {
2783                                 wfWarn( "$fname: No transaction to commit, something got out of sync." );
2784                                 return; // nothing to do
2785                         } elseif ( $this->mTrxAutomatic ) {
2786                                 // @TODO: make this an exception at some point
2787                                 wfLogDBError( "$fname: Explicit commit of implicit transaction." );
2788                                 return; // wait for the main transaction set commit round
2789                         }
2790                 }
2791
2792                 // Avoid fatals if close() was called
2793                 $this->assertOpen();
2794
2795                 $this->runOnTransactionPreCommitCallbacks();
2796                 $writeTime = $this->pendingWriteQueryDuration();
2797                 $this->doCommit( $fname );
2798                 if ( $this->mTrxDoneWrites ) {
2799                         $this->mDoneWrites = microtime( true );
2800                         $this->getTransactionProfiler()->transactionWritingOut(
2801                                 $this->mServer, $this->mDBname, $this->mTrxShortId, $writeTime );
2802                 }
2803
2804                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
2805         }
2806
2807         /**
2808          * Issues the COMMIT command to the database server.
2809          *
2810          * @see DatabaseBase::commit()
2811          * @param string $fname
2812          */
2813         protected function doCommit( $fname ) {
2814                 if ( $this->mTrxLevel ) {
2815                         $this->query( 'COMMIT', $fname );
2816                         $this->mTrxLevel = 0;
2817                 }
2818         }
2819
2820         final public function rollback( $fname = __METHOD__, $flush = '' ) {
2821                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
2822                         if ( !$this->mTrxLevel ) {
2823                                 return; // nothing to do
2824                         }
2825                 } else {
2826                         if ( !$this->mTrxLevel ) {
2827                                 wfWarn( "$fname: No transaction to rollback, something got out of sync." );
2828                                 return; // nothing to do
2829                         } elseif ( $this->getFlag( DBO_TRX ) ) {
2830                                 throw new DBUnexpectedError(
2831                                         $this,
2832                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
2833                                 );
2834                         }
2835                 }
2836
2837                 // Avoid fatals if close() was called
2838                 $this->assertOpen();
2839
2840                 $this->doRollback( $fname );
2841                 $this->mTrxAtomicLevels = [];
2842                 if ( $this->mTrxDoneWrites ) {
2843                         $this->getTransactionProfiler()->transactionWritingOut(
2844                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
2845                 }
2846
2847                 $this->mTrxIdleCallbacks = []; // clear
2848                 $this->mTrxPreCommitCallbacks = []; // clear
2849                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
2850         }
2851
2852         /**
2853          * Issues the ROLLBACK command to the database server.
2854          *
2855          * @see DatabaseBase::rollback()
2856          * @param string $fname
2857          */
2858         protected function doRollback( $fname ) {
2859                 if ( $this->mTrxLevel ) {
2860                         # Disconnects cause rollback anyway, so ignore those errors
2861                         $ignoreErrors = true;
2862                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
2863                         $this->mTrxLevel = 0;
2864                 }
2865         }
2866
2867         public function explicitTrxActive() {
2868                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
2869         }
2870
2871         /**
2872          * Creates a new table with structure copied from existing table
2873          * Note that unlike most database abstraction functions, this function does not
2874          * automatically append database prefix, because it works at a lower
2875          * abstraction level.
2876          * The table names passed to this function shall not be quoted (this
2877          * function calls addIdentifierQuotes when needed).
2878          *
2879          * @param string $oldName Name of table whose structure should be copied
2880          * @param string $newName Name of table to be created
2881          * @param bool $temporary Whether the new table should be temporary
2882          * @param string $fname Calling function name
2883          * @throws MWException
2884          * @return bool True if operation was successful
2885          */
2886         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
2887                 $fname = __METHOD__
2888         ) {
2889                 throw new MWException(
2890                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2891         }
2892
2893         function listTables( $prefix = null, $fname = __METHOD__ ) {
2894                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2895         }
2896
2897         /**
2898          * Reset the views process cache set by listViews()
2899          * @since 1.22
2900          */
2901         final public function clearViewsCache() {
2902                 $this->allViews = null;
2903         }
2904
2905         /**
2906          * Lists all the VIEWs in the database
2907          *
2908          * For caching purposes the list of all views should be stored in
2909          * $this->allViews. The process cache can be cleared with clearViewsCache()
2910          *
2911          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
2912          * @param string $fname Name of calling function
2913          * @throws MWException
2914          * @return array
2915          * @since 1.22
2916          */
2917         public function listViews( $prefix = null, $fname = __METHOD__ ) {
2918                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
2919         }
2920
2921         /**
2922          * Differentiates between a TABLE and a VIEW
2923          *
2924          * @param string $name Name of the database-structure to test.
2925          * @throws MWException
2926          * @return bool
2927          * @since 1.22
2928          */
2929         public function isView( $name ) {
2930                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
2931         }
2932
2933         public function timestamp( $ts = 0 ) {
2934                 return wfTimestamp( TS_MW, $ts );
2935         }
2936
2937         public function timestampOrNull( $ts = null ) {
2938                 if ( is_null( $ts ) ) {
2939                         return null;
2940                 } else {
2941                         return $this->timestamp( $ts );
2942                 }
2943         }
2944
2945         /**
2946          * Take the result from a query, and wrap it in a ResultWrapper if
2947          * necessary. Boolean values are passed through as is, to indicate success
2948          * of write queries or failure.
2949          *
2950          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
2951          * resource, and it was necessary to call this function to convert it to
2952          * a wrapper. Nowadays, raw database objects are never exposed to external
2953          * callers, so this is unnecessary in external code.
2954          *
2955          * @param bool|ResultWrapper|resource|object $result
2956          * @return bool|ResultWrapper
2957          */
2958         protected function resultObject( $result ) {
2959                 if ( !$result ) {
2960                         return false;
2961                 } elseif ( $result instanceof ResultWrapper ) {
2962                         return $result;
2963                 } elseif ( $result === true ) {
2964                         // Successful write query
2965                         return $result;
2966                 } else {
2967                         return new ResultWrapper( $this, $result );
2968                 }
2969         }
2970
2971         public function ping() {
2972                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
2973                         return true;
2974                 }
2975
2976                 $ignoreErrors = true;
2977                 $this->clearFlag( DBO_TRX, self::REMEMBER_PRIOR );
2978                 // This will reconnect if possible or return false if not
2979                 $ok = (bool)$this->query( "SELECT 1 AS ping", __METHOD__, $ignoreErrors );
2980                 $this->restoreFlags( self::RESTORE_PRIOR );
2981
2982                 return $ok;
2983         }
2984
2985         /**
2986          * @return bool
2987          */
2988         protected function reconnect() {
2989                 $this->closeConnection();
2990                 $this->mOpened = false;
2991                 $this->mConn = false;
2992                 try {
2993                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
2994                         $this->lastPing = microtime( true );
2995                         $ok = true;
2996                 } catch ( DBConnectionError $e ) {
2997                         $ok = false;
2998                 }
2999
3000                 return $ok;
3001         }
3002
3003         public function getSessionLagStatus() {
3004                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3005         }
3006
3007         /**
3008          * Get the slave lag when the current transaction started
3009          *
3010          * This is useful when transactions might use snapshot isolation
3011          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3012          * is this lag plus transaction duration. If they don't, it is still
3013          * safe to be pessimistic. This returns null if there is no transaction.
3014          *
3015          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3016          * @since 1.27
3017          */
3018         public function getTransactionLagStatus() {
3019                 return $this->mTrxLevel
3020                         ? [ 'lag' => $this->mTrxSlaveLag, 'since' => $this->trxTimestamp() ]
3021                         : null;
3022         }
3023
3024         /**
3025          * Get a slave lag estimate for this server
3026          *
3027          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3028          * @since 1.27
3029          */
3030         public function getApproximateLagStatus() {
3031                 return [
3032                         'lag'   => $this->getLBInfo( 'slave' ) ? $this->getLag() : 0,
3033                         'since' => microtime( true )
3034                 ];
3035         }
3036
3037         /**
3038          * Merge the result of getSessionLagStatus() for several DBs
3039          * using the most pessimistic values to estimate the lag of
3040          * any data derived from them in combination
3041          *
3042          * This is information is useful for caching modules
3043          *
3044          * @see WANObjectCache::set()
3045          * @see WANObjectCache::getWithSetCallback()
3046          *
3047          * @param IDatabase $db1
3048          * @param IDatabase ...
3049          * @return array Map of values:
3050          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3051          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3052          *   - pending: whether any of the DBs have uncommitted changes
3053          * @since 1.27
3054          */
3055         public static function getCacheSetOptions( IDatabase $db1 ) {
3056                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3057                 foreach ( func_get_args() as $db ) {
3058                         /** @var IDatabase $db */
3059                         $status = $db->getSessionLagStatus();
3060                         if ( $status['lag'] === false ) {
3061                                 $res['lag'] = false;
3062                         } elseif ( $res['lag'] !== false ) {
3063                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3064                         }
3065                         $res['since'] = min( $res['since'], $status['since'] );
3066                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3067                 }
3068
3069                 return $res;
3070         }
3071
3072         public function getLag() {
3073                 return 0;
3074         }
3075
3076         function maxListLen() {
3077                 return 0;
3078         }
3079
3080         public function encodeBlob( $b ) {
3081                 return $b;
3082         }
3083
3084         public function decodeBlob( $b ) {
3085                 if ( $b instanceof Blob ) {
3086                         $b = $b->fetch();
3087                 }
3088                 return $b;
3089         }
3090
3091         public function setSessionOptions( array $options ) {
3092         }
3093
3094         /**
3095          * Read and execute SQL commands from a file.
3096          *
3097          * Returns true on success, error string or exception on failure (depending
3098          * on object's error ignore settings).
3099          *
3100          * @param string $filename File name to open
3101          * @param bool|callable $lineCallback Optional function called before reading each line
3102          * @param bool|callable $resultCallback Optional function called for each MySQL result
3103          * @param bool|string $fname Calling function name or false if name should be
3104          *   generated dynamically using $filename
3105          * @param bool|callable $inputCallback Optional function called for each
3106          *   complete line sent
3107          * @throws Exception|MWException
3108          * @return bool|string
3109          */
3110         public function sourceFile(
3111                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3112         ) {
3113                 MediaWiki\suppressWarnings();
3114                 $fp = fopen( $filename, 'r' );
3115                 MediaWiki\restoreWarnings();
3116
3117                 if ( false === $fp ) {
3118                         throw new MWException( "Could not open \"{$filename}\".\n" );
3119                 }
3120
3121                 if ( !$fname ) {
3122                         $fname = __METHOD__ . "( $filename )";
3123                 }
3124
3125                 try {
3126                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3127                 } catch ( Exception $e ) {
3128                         fclose( $fp );
3129                         throw $e;
3130                 }
3131
3132                 fclose( $fp );
3133
3134                 return $error;
3135         }
3136
3137         /**
3138          * Get the full path of a patch file. Originally based on archive()
3139          * from updaters.inc. Keep in mind this always returns a patch, as
3140          * it fails back to MySQL if no DB-specific patch can be found
3141          *
3142          * @param string $patch The name of the patch, like patch-something.sql
3143          * @return string Full path to patch file
3144          */
3145         public function patchPath( $patch ) {
3146                 global $IP;
3147
3148                 $dbType = $this->getType();
3149                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3150                         return "$IP/maintenance/$dbType/archives/$patch";
3151                 } else {
3152                         return "$IP/maintenance/archives/$patch";
3153                 }
3154         }
3155
3156         public function setSchemaVars( $vars ) {
3157                 $this->mSchemaVars = $vars;
3158         }
3159
3160         /**
3161          * Read and execute commands from an open file handle.
3162          *
3163          * Returns true on success, error string or exception on failure (depending
3164          * on object's error ignore settings).
3165          *
3166          * @param resource $fp File handle
3167          * @param bool|callable $lineCallback Optional function called before reading each query
3168          * @param bool|callable $resultCallback Optional function called for each MySQL result
3169          * @param string $fname Calling function name
3170          * @param bool|callable $inputCallback Optional function called for each complete query sent
3171          * @return bool|string
3172          */
3173         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3174                 $fname = __METHOD__, $inputCallback = false
3175         ) {
3176                 $cmd = '';
3177
3178                 while ( !feof( $fp ) ) {
3179                         if ( $lineCallback ) {
3180                                 call_user_func( $lineCallback );
3181                         }
3182
3183                         $line = trim( fgets( $fp ) );
3184
3185                         if ( $line == '' ) {
3186                                 continue;
3187                         }
3188
3189                         if ( '-' == $line[0] && '-' == $line[1] ) {
3190                                 continue;
3191                         }
3192
3193                         if ( $cmd != '' ) {
3194                                 $cmd .= ' ';
3195                         }
3196
3197                         $done = $this->streamStatementEnd( $cmd, $line );
3198
3199                         $cmd .= "$line\n";
3200
3201                         if ( $done || feof( $fp ) ) {
3202                                 $cmd = $this->replaceVars( $cmd );
3203
3204                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3205                                         $res = $this->query( $cmd, $fname );
3206
3207                                         if ( $resultCallback ) {
3208                                                 call_user_func( $resultCallback, $res, $this );
3209                                         }
3210
3211                                         if ( false === $res ) {
3212                                                 $err = $this->lastError();
3213
3214                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3215                                         }
3216                                 }
3217                                 $cmd = '';
3218                         }
3219                 }
3220
3221                 return true;
3222         }
3223
3224         /**
3225          * Called by sourceStream() to check if we've reached a statement end
3226          *
3227          * @param string $sql SQL assembled so far
3228          * @param string $newLine New line about to be added to $sql
3229          * @return bool Whether $newLine contains end of the statement
3230          */
3231         public function streamStatementEnd( &$sql, &$newLine ) {
3232                 if ( $this->delimiter ) {
3233                         $prev = $newLine;
3234                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3235                         if ( $newLine != $prev ) {
3236                                 return true;
3237                         }
3238                 }
3239
3240                 return false;
3241         }
3242
3243         /**
3244          * Database independent variable replacement. Replaces a set of variables
3245          * in an SQL statement with their contents as given by $this->getSchemaVars().
3246          *
3247          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3248          *
3249          * - '{$var}' should be used for text and is passed through the database's
3250          *   addQuotes method.
3251          * - `{$var}` should be used for identifiers (e.g. table and database names).
3252          *   It is passed through the database's addIdentifierQuotes method which
3253          *   can be overridden if the database uses something other than backticks.
3254          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3255          *   database's tableName method.
3256          * - / *i* / passes the name that follows through the database's indexName method.
3257          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3258          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3259          *
3260          * @param string $ins SQL statement to replace variables in
3261          * @return string The new SQL statement with variables replaced
3262          */
3263         protected function replaceVars( $ins ) {
3264                 $vars = $this->getSchemaVars();
3265                 return preg_replace_callback(
3266                         '!
3267                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3268                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3269                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3270                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3271                         !x',
3272                         function ( $m ) use ( $vars ) {
3273                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3274                                 // check for both nonexistent keys *and* the empty string.
3275                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3276                                         if ( $m[1] === 'i' ) {
3277                                                 return $this->indexName( $m[2] );
3278                                         } else {
3279                                                 return $this->tableName( $m[2] );
3280                                         }
3281                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3282                                         return $this->addQuotes( $vars[$m[3]] );
3283                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3284                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3285                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3286                                         return $vars[$m[5]];
3287                                 } else {
3288                                         return $m[0];
3289                                 }
3290                         },
3291                         $ins
3292                 );
3293         }
3294
3295         /**
3296          * Get schema variables. If none have been set via setSchemaVars(), then
3297          * use some defaults from the current object.
3298          *
3299          * @return array
3300          */
3301         protected function getSchemaVars() {
3302                 if ( $this->mSchemaVars ) {
3303                         return $this->mSchemaVars;
3304                 } else {
3305                         return $this->getDefaultSchemaVars();
3306                 }
3307         }
3308
3309         /**
3310          * Get schema variables to use if none have been set via setSchemaVars().
3311          *
3312          * Override this in derived classes to provide variables for tables.sql
3313          * and SQL patch files.
3314          *
3315          * @return array
3316          */
3317         protected function getDefaultSchemaVars() {
3318                 return [];
3319         }
3320
3321         public function lockIsFree( $lockName, $method ) {
3322                 return true;
3323         }
3324
3325         public function lock( $lockName, $method, $timeout = 5 ) {
3326                 $this->mNamedLocksHeld[$lockName] = 1;
3327
3328                 return true;
3329         }
3330
3331         public function unlock( $lockName, $method ) {
3332                 unset( $this->mNamedLocksHeld[$lockName] );
3333
3334                 return true;
3335         }
3336
3337         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3338                 if ( $this->writesOrCallbacksPending() ) {
3339                         // This only flushes transactions to clear snapshots, not to write data
3340                         throw new DBUnexpectedError(
3341                                 $this,
3342                                 "$fname: Cannot COMMIT to clear snapshot because writes are pending."
3343                         );
3344                 }
3345
3346                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3347                         return null;
3348                 }
3349
3350                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3351                         if ( $this->trxLevel() ) {
3352                                 // There is a good chance an exception was thrown, causing any early return
3353                                 // from the caller. Let any error handler get a chance to issue rollback().
3354                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3355                                 $this->onTransactionResolution( function () use ( $lockKey, $fname ) {
3356                                         $this->unlock( $lockKey, $fname );
3357                                 } );
3358                         } else {
3359                                 $this->unlock( $lockKey, $fname );
3360                         }
3361                 } );
3362
3363                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
3364
3365                 return $unlocker;
3366         }
3367
3368         public function namedLocksEnqueue() {
3369                 return false;
3370         }
3371
3372         /**
3373          * Lock specific tables
3374          *
3375          * @param array $read Array of tables to lock for read access
3376          * @param array $write Array of tables to lock for write access
3377          * @param string $method Name of caller
3378          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3379          * @return bool
3380          */
3381         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3382                 return true;
3383         }
3384
3385         /**
3386          * Unlock specific tables
3387          *
3388          * @param string $method The caller
3389          * @return bool
3390          */
3391         public function unlockTables( $method ) {
3392                 return true;
3393         }
3394
3395         /**
3396          * Delete a table
3397          * @param string $tableName
3398          * @param string $fName
3399          * @return bool|ResultWrapper
3400          * @since 1.18
3401          */
3402         public function dropTable( $tableName, $fName = __METHOD__ ) {
3403                 if ( !$this->tableExists( $tableName, $fName ) ) {
3404                         return false;
3405                 }
3406                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3407                 if ( $this->cascadingDeletes() ) {
3408                         $sql .= " CASCADE";
3409                 }
3410
3411                 return $this->query( $sql, $fName );
3412         }
3413
3414         /**
3415          * Get search engine class. All subclasses of this need to implement this
3416          * if they wish to use searching.
3417          *
3418          * @return string
3419          */
3420         public function getSearchEngine() {
3421                 return 'SearchEngineDummy';
3422         }
3423
3424         public function getInfinity() {
3425                 return 'infinity';
3426         }
3427
3428         public function encodeExpiry( $expiry ) {
3429                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3430                         ? $this->getInfinity()
3431                         : $this->timestamp( $expiry );
3432         }
3433
3434         public function decodeExpiry( $expiry, $format = TS_MW ) {
3435                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3436                         ? 'infinity'
3437                         : wfTimestamp( $format, $expiry );
3438         }
3439
3440         public function setBigSelects( $value = true ) {
3441                 // no-op
3442         }
3443
3444         public function isReadOnly() {
3445                 return ( $this->getReadOnlyReason() !== false );
3446         }
3447
3448         /**
3449          * @return string|bool Reason this DB is read-only or false if it is not
3450          */
3451         protected function getReadOnlyReason() {
3452                 $reason = $this->getLBInfo( 'readOnlyReason' );
3453
3454                 return is_string( $reason ) ? $reason : false;
3455         }
3456
3457         /**
3458          * @since 1.19
3459          * @return string
3460          */
3461         public function __toString() {
3462                 return (string)$this->mConn;
3463         }
3464
3465         /**
3466          * Run a few simple sanity checks
3467          */
3468         public function __destruct() {
3469                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3470                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3471                 }
3472                 $danglingCallbacks = array_merge(
3473                         $this->mTrxIdleCallbacks,
3474                         $this->mTrxPreCommitCallbacks,
3475                         $this->mTrxEndCallbacks
3476                 );
3477                 if ( $danglingCallbacks ) {
3478                         $callers = [];
3479                         foreach ( $danglingCallbacks as $callbackInfo ) {
3480                                 $callers[] = $callbackInfo[1];
3481                         }
3482                         $callers = implode( ', ', $callers );
3483                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
3484                 }
3485         }
3486 }
3487
3488 /**
3489  * @since 1.27
3490  */
3491 abstract class Database extends DatabaseBase {
3492         // B/C until nothing type hints for DatabaseBase
3493         // @TODO: finish renaming DatabaseBase => Database
3494 }