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