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