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