includes/db/Database.php

   1 <?php
   2
   3 /**
   4  * @defgroup Database Database
   5  *
   6  * This file deals with database interface functions
   7  * and query specifics/optimisations.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  * @ingroup Database
  26  */
  27
  28 /**
  29  * Database abstraction object
  30  * @ingroup Database
  31  */
  32 abstract class DatabaseBase implements IDatabase {
  33         /** Number of times to re-try an operation in case of deadlock */
  34         const DEADLOCK_TRIES = 4;
  35         /** Minimum time to wait before retry, in microseconds */
  36         const DEADLOCK_DELAY_MIN = 500000;
  37         /** Maximum time to wait before retry */
  38         const DEADLOCK_DELAY_MAX = 1500000;
  39
  40         /** How long before it is worth doing a dummy query to test the connection */
  41         const PING_TTL = 1.0;
  42         const PING_QUERY = 'SELECT 1 AS ping';
  43
  44         const TINY_WRITE_SEC = .010;
  45         const SLOW_WRITE_SEC = .500;
  46         const SMALL_WRITE_ROWS = 100;
  47
  48         /** @var string SQL query */
  49         protected $mLastQuery = '';
  50         /** @var bool */
  51         protected $mDoneWrites = false;
  52         /** @var string|bool */
  53         protected $mPHPError = false;
  54         /** @var string */
  55         protected $mServer;
  56         /** @var string */
  57         protected $mUser;
  58         /** @var string */
  59         protected $mPassword;
  60         /** @var string */
  61         protected $mDBname;
  62         /** @var bool */
  63         protected $cliMode;
  64
  65         /** @var BagOStuff APC cache */
  66         protected $srvCache;
  67
  68         /** @var resource Database connection */
  69         protected $mConn = null;
  70         /** @var bool */
  71         protected $mOpened = false;
  72
  73         /** @var array[] List of (callable, method name) */
  74         protected $mTrxIdleCallbacks = [];
  75         /** @var array[] List of (callable, method name) */
  76         protected $mTrxPreCommitCallbacks = [];
  77         /** @var array[] List of (callable, method name) */
  78         protected $mTrxEndCallbacks = [];
  79         /** @var array[] Map of (name => (callable, method name)) */
  80         protected $mTrxRecurringCallbacks = [];
  81         /** @var bool Whether to suppress triggering of transaction end callbacks */
  82         protected $mTrxEndCallbacksSuppressed = false;
  83
  84         /** @var string */
  85         protected $mTablePrefix;
  86         /** @var string */
  87         protected $mSchema;
  88         /** @var integer */
  89         protected $mFlags;
  90         /** @var bool */
  91         protected $mForeign;
  92         /** @var array */
  93         protected $mLBInfo = [];
  94         /** @var bool|null */
  95         protected $mDefaultBigSelects = null;
  96         /** @var array|bool */
  97         protected $mSchemaVars = false;
  98         /** @var array */
  99         protected $mSessionVars = [];
 100         /** @var array|null */
 101         protected $preparedArgs;
 102         /** @var string|bool|null Stashed value of html_errors INI setting */
 103         protected $htmlErrors;
 104         /** @var string */
 105         protected $delimiter = ';';
 106
 107         /**
 108          * Either 1 if a transaction is active or 0 otherwise.
 109          * The other Trx fields may not be meaningfull if this is 0.
 110          *
 111          * @var int
 112          */
 113         protected $mTrxLevel = 0;
 114         /**
 115          * Either a short hexidecimal string if a transaction is active or ""
 116          *
 117          * @var string
 118          * @see DatabaseBase::mTrxLevel
 119          */
 120         protected $mTrxShortId = '';
 121         /**
 122          * The UNIX time that the transaction started. Callers can assume that if
 123          * snapshot isolation is used, then the data is *at least* up to date to that
 124          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 125          *
 126          * @var float|null
 127          * @see DatabaseBase::mTrxLevel
 128          */
 129         private $mTrxTimestamp = null;
 130         /** @var float Lag estimate at the time of BEGIN */
 131         private $mTrxReplicaLag = null;
 132         /**
 133          * Remembers the function name given for starting the most recent transaction via begin().
 134          * Used to provide additional context for error reporting.
 135          *
 136          * @var string
 137          * @see DatabaseBase::mTrxLevel
 138          */
 139         private $mTrxFname = null;
 140         /**
 141          * Record if possible write queries were done in the last transaction started
 142          *
 143          * @var bool
 144          * @see DatabaseBase::mTrxLevel
 145          */
 146         private $mTrxDoneWrites = false;
 147         /**
 148          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 149          *
 150          * @var bool
 151          * @see DatabaseBase::mTrxLevel
 152          */
 153         private $mTrxAutomatic = false;
 154         /**
 155          * Array of levels of atomicity within transactions
 156          *
 157          * @var array
 158          */
 159         private $mTrxAtomicLevels = [];
 160         /**
 161          * Record if the current transaction was started implicitly by DatabaseBase::startAtomic
 162          *
 163          * @var bool
 164          */
 165         private $mTrxAutomaticAtomic = false;
 166         /**
 167          * Track the write query callers of the current transaction
 168          *
 169          * @var string[]
 170          */
 171         private $mTrxWriteCallers = [];
 172         /**
 173          * @var float Seconds spent in write queries for the current transaction
 174          */
 175         private $mTrxWriteDuration = 0.0;
 176         /**
 177          * @var integer Number of write queries for the current transaction
 178          */
 179         private $mTrxWriteQueryCount = 0;
 180         /**
 181          * @var float Like mTrxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 182          */
 183         private $mTrxWriteAdjDuration = 0.0;
 184         /**
 185          * @var integer Number of write queries counted in mTrxWriteAdjDuration
 186          */
 187         private $mTrxWriteAdjQueryCount = 0;
 188         /**
 189          * @var float RTT time estimate
 190          */
 191         private $mRTTEstimate = 0.0;
 192
 193         /** @var array Map of (name => 1) for locks obtained via lock() */
 194         private $mNamedLocksHeld = [];
 195
 196         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 197         private $lazyMasterHandle;
 198
 199         /**
 200          * @since 1.21
 201          * @var resource File handle for upgrade
 202          */
 203         protected $fileHandle = null;
 204
 205         /**
 206          * @since 1.22
 207          * @var string[] Process cache of VIEWs names in the database
 208          */
 209         protected $allViews = null;
 210
 211         /** @var float UNIX timestamp */
 212         protected $lastPing = 0.0;
 213
 214         /** @var int[] Prior mFlags values */
 215         private $priorFlags = [];
 216
 217         /** @var Profiler */
 218         protected $profiler;
 219         /** @var TransactionProfiler */
 220         protected $trxProfiler;
 221
 222         public function getServerInfo() {
 223                 return $this->getServerVersion();
 224         }
 225
 226         /**
 227          * @return string Command delimiter used by this database engine
 228          */
 229         public function getDelimiter() {
 230                 return $this->delimiter;
 231         }
 232
 233         /**
 234          * Boolean, controls output of large amounts of debug information.
 235          * @param bool|null $debug
 236          *   - true to enable debugging
 237          *   - false to disable debugging
 238          *   - omitted or null to do nothing
 239          *
 240          * @return bool|null Previous value of the flag
 241          */
 242         public function debug( $debug = null ) {
 243                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 244         }
 245
 246         public function bufferResults( $buffer = null ) {
 247                 if ( is_null( $buffer ) ) {
 248                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 249                 } else {
 250                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 251                 }
 252         }
 253
 254         /**
 255          * Turns on (false) or off (true) the automatic generation and sending
 256          * of a "we're sorry, but there has been a database error" page on
 257          * database errors. Default is on (false). When turned off, the
 258          * code should use lastErrno() and lastError() to handle the
 259          * situation as appropriate.
 260          *
 261          * Do not use this function outside of the Database classes.
 262          *
 263          * @param null|bool $ignoreErrors
 264          * @return bool The previous value of the flag.
 265          */
 266         protected function ignoreErrors( $ignoreErrors = null ) {
 267                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 268         }
 269
 270         public function trxLevel() {
 271                 return $this->mTrxLevel;
 272         }
 273
 274         public function trxTimestamp() {
 275                 return $this->mTrxLevel ? $this->mTrxTimestamp : null;
 276         }
 277
 278         public function tablePrefix( $prefix = null ) {
 279                 return wfSetVar( $this->mTablePrefix, $prefix );
 280         }
 281
 282         public function dbSchema( $schema = null ) {
 283                 return wfSetVar( $this->mSchema, $schema );
 284         }
 285
 286         /**
 287          * Set the filehandle to copy write statements to.
 288          *
 289          * @param resource $fh File handle
 290          */
 291         public function setFileHandle( $fh ) {
 292                 $this->fileHandle = $fh;
 293         }
 294
 295         public function getLBInfo( $name = null ) {
 296                 if ( is_null( $name ) ) {
 297                         return $this->mLBInfo;
 298                 } else {
 299                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 300                                 return $this->mLBInfo[$name];
 301                         } else {
 302                                 return null;
 303                         }
 304                 }
 305         }
 306
 307         public function setLBInfo( $name, $value = null ) {
 308                 if ( is_null( $value ) ) {
 309                         $this->mLBInfo = $name;
 310                 } else {
 311                         $this->mLBInfo[$name] = $value;
 312                 }
 313         }
 314
 315         /**
 316          * Set a lazy-connecting DB handle to the master DB (for replication status purposes)
 317          *
 318          * @param IDatabase $conn
 319          * @since 1.27
 320          */
 321         public function setLazyMasterHandle( IDatabase $conn ) {
 322                 $this->lazyMasterHandle = $conn;
 323         }
 324
 325         /**
 326          * @return IDatabase|null
 327          * @see setLazyMasterHandle()
 328          * @since 1.27
 329          */
 330         public function getLazyMasterHandle() {
 331                 return $this->lazyMasterHandle;
 332         }
 333
 334         /**
 335          * @return TransactionProfiler
 336          */
 337         protected function getTransactionProfiler() {
 338                 return $this->trxProfiler;
 339         }
 340
 341         /**
 342          * @param TransactionProfiler $profiler
 343          * @since 1.27
 344          */
 345         public function setTransactionProfiler( TransactionProfiler $profiler ) {
 346                 $this->trxProfiler = $profiler;
 347         }
 348
 349         /**
 350          * Returns true if this database supports (and uses) cascading deletes
 351          *
 352          * @return bool
 353          */
 354         public function cascadingDeletes() {
 355                 return false;
 356         }
 357
 358         /**
 359          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 360          *
 361          * @return bool
 362          */
 363         public function cleanupTriggers() {
 364                 return false;
 365         }
 366
 367         /**
 368          * Returns true if this database is strict about what can be put into an IP field.
 369          * Specifically, it uses a NULL value instead of an empty string.
 370          *
 371          * @return bool
 372          */
 373         public function strictIPs() {
 374                 return false;
 375         }
 376
 377         /**
 378          * Returns true if this database uses timestamps rather than integers
 379          *
 380          * @return bool
 381          */
 382         public function realTimestamps() {
 383                 return false;
 384         }
 385
 386         public function implicitGroupby() {
 387                 return true;
 388         }
 389
 390         public function implicitOrderby() {
 391                 return true;
 392         }
 393
 394         /**
 395          * Returns true if this database can do a native search on IP columns
 396          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 397          *
 398          * @return bool
 399          */
 400         public function searchableIPs() {
 401                 return false;
 402         }
 403
 404         /**
 405          * Returns true if this database can use functional indexes
 406          *
 407          * @return bool
 408          */
 409         public function functionalIndexes() {
 410                 return false;
 411         }
 412
 413         public function lastQuery() {
 414                 return $this->mLastQuery;
 415         }
 416
 417         public function doneWrites() {
 418                 return (bool)$this->mDoneWrites;
 419         }
 420
 421         public function lastDoneWrites() {
 422                 return $this->mDoneWrites ?: false;
 423         }
 424
 425         public function writesPending() {
 426                 return $this->mTrxLevel && $this->mTrxDoneWrites;
 427         }
 428
 429         public function writesOrCallbacksPending() {
 430                 return $this->mTrxLevel && (
 431                         $this->mTrxDoneWrites || $this->mTrxIdleCallbacks || $this->mTrxPreCommitCallbacks
 432                 );
 433         }
 434
 435         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 436                 if ( !$this->mTrxLevel ) {
 437                         return false;
 438                 } elseif ( !$this->mTrxDoneWrites ) {
 439                         return 0.0;
 440                 }
 441
 442                 switch ( $type ) {
 443                         case self::ESTIMATE_DB_APPLY:
 444                                 $this->ping( $rtt );
 445                                 $rttAdjTotal = $this->mTrxWriteAdjQueryCount * $rtt;
 446                                 $applyTime = max( $this->mTrxWriteAdjDuration - $rttAdjTotal, 0 );
 447                                 // For omitted queries, make them count as something at least
 448                                 $omitted = $this->mTrxWriteQueryCount - $this->mTrxWriteAdjQueryCount;
 449                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 450
 451                                 return $applyTime;
 452                         default: // everything
 453                                 return $this->mTrxWriteDuration;
 454                 }
 455         }
 456
 457         public function pendingWriteCallers() {
 458                 return $this->mTrxLevel ? $this->mTrxWriteCallers : [];
 459         }
 460
 461         public function isOpen() {
 462                 return $this->mOpened;
 463         }
 464
 465         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 466                 if ( $remember === self::REMEMBER_PRIOR ) {
 467                         array_push( $this->priorFlags, $this->mFlags );
 468                 }
 469                 $this->mFlags |= $flag;
 470         }
 471
 472         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 473                 if ( $remember === self::REMEMBER_PRIOR ) {
 474                         array_push( $this->priorFlags, $this->mFlags );
 475                 }
 476                 $this->mFlags &= ~$flag;
 477         }
 478
 479         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 480                 if ( !$this->priorFlags ) {
 481                         return;
 482                 }
 483
 484                 if ( $state === self::RESTORE_INITIAL ) {
 485                         $this->mFlags = reset( $this->priorFlags );
 486                         $this->priorFlags = [];
 487                 } else {
 488                         $this->mFlags = array_pop( $this->priorFlags );
 489                 }
 490         }
 491
 492         public function getFlag( $flag ) {
 493                 return !!( $this->mFlags & $flag );
 494         }
 495
 496         public function getProperty( $name ) {
 497                 return $this->$name;
 498         }
 499
 500         public function getWikiID() {
 501                 if ( $this->mTablePrefix ) {
 502                         return "{$this->mDBname}-{$this->mTablePrefix}";
 503                 } else {
 504                         return $this->mDBname;
 505                 }
 506         }
 507
 508         /**
 509          * Return a path to the DBMS-specific SQL file if it exists,
 510          * otherwise default SQL file
 511          *
 512          * @param string $filename
 513          * @return string
 514          */
 515         private function getSqlFilePath( $filename ) {
 516                 global $IP;
 517                 $dbmsSpecificFilePath = "$IP/maintenance/" . $this->getType() . "/$filename";
 518                 if ( file_exists( $dbmsSpecificFilePath ) ) {
 519                         return $dbmsSpecificFilePath;
 520                 } else {
 521                         return "$IP/maintenance/$filename";
 522                 }
 523         }
 524
 525         /**
 526          * Return a path to the DBMS-specific schema file,
 527          * otherwise default to tables.sql
 528          *
 529          * @return string
 530          */
 531         public function getSchemaPath() {
 532                 return $this->getSqlFilePath( 'tables.sql' );
 533         }
 534
 535         /**
 536          * Return a path to the DBMS-specific update key file,
 537          * otherwise default to update-keys.sql
 538          *
 539          * @return string
 540          */
 541         public function getUpdateKeysPath() {
 542                 return $this->getSqlFilePath( 'update-keys.sql' );
 543         }
 544
 545         /**
 546          * Get information about an index into an object
 547          * @param string $table Table name
 548          * @param string $index Index name
 549          * @param string $fname Calling function name
 550          * @return mixed Database-specific index description class or false if the index does not exist
 551          */
 552         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 553
 554         /**
 555          * Wrapper for addslashes()
 556          *
 557          * @param string $s String to be slashed.
 558          * @return string Slashed string.
 559          */
 560         abstract function strencode( $s );
 561
 562         /**
 563          * Constructor.
 564          *
 565          * FIXME: It is possible to construct a Database object with no associated
 566          * connection object, by specifying no parameters to __construct(). This
 567          * feature is deprecated and should be removed.
 568          *
 569          * DatabaseBase subclasses should not be constructed directly in external
 570          * code. DatabaseBase::factory() should be used instead.
 571          *
 572          * @param array $params Parameters passed from DatabaseBase::factory()
 573          */
 574         function __construct( array $params ) {
 575                 global $wgDBprefix, $wgDBmwschema;
 576
 577                 $this->srvCache = ObjectCache::getLocalServerInstance( 'hash' );
 578
 579                 $server = $params['host'];
 580                 $user = $params['user'];
 581                 $password = $params['password'];
 582                 $dbName = $params['dbname'];
 583                 $flags = $params['flags'];
 584                 $tablePrefix = $params['tablePrefix'];
 585                 $schema = $params['schema'];
 586                 $foreign = $params['foreign'];
 587
 588                 $this->cliMode = isset( $params['cliMode'] )
 589                         ? $params['cliMode']
 590                         : ( PHP_SAPI === 'cli' );
 591
 592                 $this->mFlags = $flags;
 593                 if ( $this->mFlags & DBO_DEFAULT ) {
 594                         if ( $this->cliMode ) {
 595                                 $this->mFlags &= ~DBO_TRX;
 596                         } else {
 597                                 $this->mFlags |= DBO_TRX;
 598                         }
 599                 }
 600
 601                 $this->mSessionVars = $params['variables'];
 602
 603                 /** Get the default table prefix*/
 604                 if ( $tablePrefix === 'get from global' ) {
 605                         $this->mTablePrefix = $wgDBprefix;
 606                 } else {
 607                         $this->mTablePrefix = $tablePrefix;
 608                 }
 609
 610                 /** Get the database schema*/
 611                 if ( $schema === 'get from global' ) {
 612                         $this->mSchema = $wgDBmwschema;
 613                 } else {
 614                         $this->mSchema = $schema;
 615                 }
 616
 617                 $this->mForeign = $foreign;
 618
 619                 $this->profiler = isset( $params['profiler'] )
 620                         ? $params['profiler']
 621                         : Profiler::instance(); // @TODO: remove global state
 622                 $this->trxProfiler = isset( $params['trxProfiler'] )
 623                         ? $params['trxProfiler']
 624                         : new TransactionProfiler();
 625
 626                 if ( $user ) {
 627                         $this->open( $server, $user, $password, $dbName );
 628                 }
 629
 630         }
 631
 632         /**
 633          * Called by serialize. Throw an exception when DB connection is serialized.
 634          * This causes problems on some database engines because the connection is
 635          * not restored on unserialize.
 636          */
 637         public function __sleep() {
 638                 throw new MWException( 'Database serialization may cause problems, since ' .
 639                         'the connection is not restored on wakeup.' );
 640         }
 641
 642         /**
 643          * Given a DB type, construct the name of the appropriate child class of
 644          * DatabaseBase. This is designed to replace all of the manual stuff like:
 645          *    $class = 'Database' . ucfirst( strtolower( $dbType ) );
 646          * as well as validate against the canonical list of DB types we have
 647          *
 648          * This factory function is mostly useful for when you need to connect to a
 649          * database other than the MediaWiki default (such as for external auth,
 650          * an extension, et cetera). Do not use this to connect to the MediaWiki
 651          * database. Example uses in core:
 652          * @see LoadBalancer::reallyOpenConnection()
 653          * @see ForeignDBRepo::getMasterDB()
 654          * @see WebInstallerDBConnect::execute()
 655          *
 656          * @since 1.18
 657          *
 658          * @param string $dbType A possible DB type
 659          * @param array $p An array of options to pass to the constructor.
 660          *    Valid options are: host, user, password, dbname, flags, tablePrefix, schema, driver
 661          * @throws MWException If the database driver or extension cannot be found
 662          * @return DatabaseBase|null DatabaseBase subclass or null
 663          */
 664         final public static function factory( $dbType, $p = [] ) {
 665                 global $wgCommandLineMode;
 666
 667                 $canonicalDBTypes = [
 668                         'mysql' => [ 'mysqli', 'mysql' ],
 669                         'postgres' => [],
 670                         'sqlite' => [],
 671                         'oracle' => [],
 672                         'mssql' => [],
 673                 ];
 674
 675                 $driver = false;
 676                 $dbType = strtolower( $dbType );
 677                 if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
 678                         $possibleDrivers = $canonicalDBTypes[$dbType];
 679                         if ( !empty( $p['driver'] ) ) {
 680                                 if ( in_array( $p['driver'], $possibleDrivers ) ) {
 681                                         $driver = $p['driver'];
 682                                 } else {
 683                                         throw new MWException( __METHOD__ .
 684                                                 " cannot construct Database with type '$dbType' and driver '{$p['driver']}'" );
 685                                 }
 686                         } else {
 687                                 foreach ( $possibleDrivers as $posDriver ) {
 688                                         if ( extension_loaded( $posDriver ) ) {
 689                                                 $driver = $posDriver;
 690                                                 break;
 691                                         }
 692                                 }
 693                         }
 694                 } else {
 695                         $driver = $dbType;
 696                 }
 697                 if ( $driver === false ) {
 698                         throw new MWException( __METHOD__ .
 699                                 " no viable database extension found for type '$dbType'" );
 700                 }
 701
 702                 // Determine schema defaults. Currently Microsoft SQL Server uses $wgDBmwschema,
 703                 // and everything else doesn't use a schema (e.g. null)
 704                 // Although postgres and oracle support schemas, we don't use them (yet)
 705                 // to maintain backwards compatibility
 706                 $defaultSchemas = [
 707                         'mssql' => 'get from global',
 708                 ];
 709
 710                 $class = 'Database' . ucfirst( $driver );
 711                 if ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) {
 712                         // Resolve some defaults for b/c
 713                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 714                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 715                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 716                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 717                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 718                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 719                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global';
 720                         if ( !isset( $p['schema'] ) ) {
 721                                 $p['schema'] = isset( $defaultSchemas[$dbType] ) ? $defaultSchemas[$dbType] : null;
 722                         }
 723                         $p['foreign'] = isset( $p['foreign'] ) ? $p['foreign'] : false;
 724                         $p['cliMode'] = $wgCommandLineMode;
 725
 726                         return new $class( $p );
 727                 } else {
 728                         return null;
 729                 }
 730         }
 731
 732         protected function installErrorHandler() {
 733                 $this->mPHPError = false;
 734                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 735                 set_error_handler( [ $this, 'connectionErrorHandler' ] );
 736         }
 737
 738         /**
 739          * @return bool|string
 740          */
 741         protected function restoreErrorHandler() {
 742                 restore_error_handler();
 743                 if ( $this->htmlErrors !== false ) {
 744                         ini_set( 'html_errors', $this->htmlErrors );
 745                 }
 746                 if ( $this->mPHPError ) {
 747                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 748                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 749
 750                         return $error;
 751                 } else {
 752                         return false;
 753                 }
 754         }
 755
 756         /**
 757          * @param int $errno
 758          * @param string $errstr
 759          */
 760         public function connectionErrorHandler( $errno, $errstr ) {
 761                 $this->mPHPError = $errstr;
 762         }
 763
 764         /**
 765          * Create a log context to pass to wfLogDBError or other logging functions.
 766          *
 767          * @param array $extras Additional data to add to context
 768          * @return array
 769          */
 770         protected function getLogContext( array $extras = [] ) {
 771                 return array_merge(
 772                         [
 773                                 'db_server' => $this->mServer,
 774                                 'db_name' => $this->mDBname,
 775                                 'db_user' => $this->mUser,
 776                         ],
 777                         $extras
 778                 );
 779         }
 780
 781         public function close() {
 782                 if ( $this->mConn ) {
 783                         if ( $this->trxLevel() ) {
 784                                 if ( !$this->mTrxAutomatic ) {
 785                                         wfWarn( "Transaction still in progress (from {$this->mTrxFname}), " .
 786                                                 " performing implicit commit before closing connection!" );
 787                                 }
 788
 789                                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 790                         }
 791
 792                         $closed = $this->closeConnection();
 793                         $this->mConn = false;
 794                 } elseif ( $this->mTrxIdleCallbacks || $this->mTrxEndCallbacks ) { // sanity
 795                         throw new MWException( "Transaction callbacks still pending." );
 796                 } else {
 797                         $closed = true;
 798                 }
 799                 $this->mOpened = false;
 800
 801                 return $closed;
 802         }
 803
 804         /**
 805          * Make sure isOpen() returns true as a sanity check
 806          *
 807          * @throws DBUnexpectedError
 808          */
 809         protected function assertOpen() {
 810                 if ( !$this->isOpen() ) {
 811                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 812                 }
 813         }
 814
 815         /**
 816          * Closes underlying database connection
 817          * @since 1.20
 818          * @return bool Whether connection was closed successfully
 819          */
 820         abstract protected function closeConnection();
 821
 822         function reportConnectionError( $error = 'Unknown error' ) {
 823                 $myError = $this->lastError();
 824                 if ( $myError ) {
 825                         $error = $myError;
 826                 }
 827
 828                 # New method
 829                 throw new DBConnectionError( $this, $error );
 830         }
 831
 832         /**
 833          * The DBMS-dependent part of query()
 834          *
 835          * @param string $sql SQL query.
 836          * @return ResultWrapper|bool Result object to feed to fetchObject,
 837          *   fetchRow, ...; or false on failure
 838          */
 839         abstract protected function doQuery( $sql );
 840
 841         /**
 842          * Determine whether a query writes to the DB.
 843          * Should return true if unsure.
 844          *
 845          * @param string $sql
 846          * @return bool
 847          */
 848         protected function isWriteQuery( $sql ) {
 849                 return !preg_match(
 850                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 851         }
 852
 853         /**
 854          * @param $sql
 855          * @return string|null
 856          */
 857         protected function getQueryVerb( $sql ) {
 858                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
 859         }
 860
 861         /**
 862          * Determine whether a SQL statement is sensitive to isolation level.
 863          * A SQL statement is considered transactable if its result could vary
 864          * depending on the transaction isolation level. Operational commands
 865          * such as 'SET' and 'SHOW' are not considered to be transactable.
 866          *
 867          * @param string $sql
 868          * @return bool
 869          */
 870         protected function isTransactableQuery( $sql ) {
 871                 $verb = $this->getQueryVerb( $sql );
 872                 return !in_array( $verb, [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET' ], true );
 873         }
 874
 875         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
 876                 global $wgUser;
 877
 878                 $priorWritesPending = $this->writesOrCallbacksPending();
 879                 $this->mLastQuery = $sql;
 880
 881                 $isWrite = $this->isWriteQuery( $sql );
 882                 if ( $isWrite ) {
 883                         $reason = $this->getReadOnlyReason();
 884                         if ( $reason !== false ) {
 885                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
 886                         }
 887                         # Set a flag indicating that writes have been done
 888                         $this->mDoneWrites = microtime( true );
 889                 }
 890
 891                 # Add a comment for easy SHOW PROCESSLIST interpretation
 892                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 893                         $userName = $wgUser->getName();
 894                         if ( mb_strlen( $userName ) > 15 ) {
 895                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 896                         }
 897                         $userName = str_replace( '/', '', $userName );
 898                 } else {
 899                         $userName = '';
 900                 }
 901
 902                 // Add trace comment to the begin of the sql string, right after the operator.
 903                 // Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (bug 42598)
 904                 $commentedSql = preg_replace( '/\s|$/', " /* $fname $userName */ ", $sql, 1 );
 905
 906                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
 907                 if ( !$this->mTrxLevel && $this->getFlag( DBO_TRX )
 908                         && $this->isTransactableQuery( $sql )
 909                 ) {
 910                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
 911                         $this->mTrxAutomatic = true;
 912                 }
 913
 914                 # Keep track of whether the transaction has write queries pending
 915                 if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $isWrite ) {
 916                         $this->mTrxDoneWrites = true;
 917                         $this->getTransactionProfiler()->transactionWritingIn(
 918                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
 919                 }
 920
 921                 if ( $this->debug() ) {
 922                         wfDebugLog( 'queries', sprintf( "%s: %s", $this->mDBname, $commentedSql ) );
 923                 }
 924
 925                 # Avoid fatals if close() was called
 926                 $this->assertOpen();
 927
 928                 # Send the query to the server
 929                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isWrite, $fname );
 930
 931                 # Try reconnecting if the connection was lost
 932                 if ( false === $ret && $this->wasErrorReissuable() ) {
 933                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
 934                         # Stash the last error values before anything might clear them
 935                         $lastError = $this->lastError();
 936                         $lastErrno = $this->lastErrno();
 937                         # Update state tracking to reflect transaction loss due to disconnection
 938                         $this->handleTransactionLoss();
 939                         wfDebug( "Connection lost, reconnecting...\n" );
 940                         if ( $this->reconnect() ) {
 941                                 wfDebug( "Reconnected\n" );
 942                                 $msg = __METHOD__ . ": lost connection to {$this->getServer()}; reconnected";
 943                                 wfDebugLog( 'DBPerformance', "$msg:\n" . wfBacktrace( true ) );
 944
 945                                 if ( !$recoverable ) {
 946                                         # Callers may catch the exception and continue to use the DB
 947                                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname );
 948                                 } else {
 949                                         # Should be safe to silently retry the query
 950                                         $ret = $this->doProfiledQuery( $sql, $commentedSql, $isWrite, $fname );
 951                                 }
 952                         } else {
 953                                 wfDebug( "Failed\n" );
 954                         }
 955                 }
 956
 957                 if ( false === $ret ) {
 958                         # Deadlocks cause the entire transaction to abort, not just the statement.
 959                         # http://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
 960                         # https://www.postgresql.org/docs/9.1/static/explicit-locking.html
 961                         if ( $this->wasDeadlock() ) {
 962                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
 963                                         $tempIgnore = false; // not recoverable
 964                                 }
 965                                 # Update state tracking to reflect transaction loss
 966                                 $this->handleTransactionLoss();
 967                         }
 968
 969                         $this->reportQueryError(
 970                                 $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 971                 }
 972
 973                 $res = $this->resultObject( $ret );
 974
 975                 return $res;
 976         }
 977
 978         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
 979                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 980                 # generalizeSQL() will probably cut down the query to reasonable
 981                 # logging size most of the time. The substr is really just a sanity check.
 982                 if ( $isMaster ) {
 983                         $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 984                 } else {
 985                         $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 986                 }
 987
 988                 # Include query transaction state
 989                 $queryProf .= $this->mTrxShortId ? " [TRX#{$this->mTrxShortId}]" : "";
 990
 991                 $startTime = microtime( true );
 992                 $this->profiler->profileIn( $queryProf );
 993                 $ret = $this->doQuery( $commentedSql );
 994                 $this->profiler->profileOut( $queryProf );
 995                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
 996
 997                 unset( $queryProfSection ); // profile out (if set)
 998
 999                 if ( $ret !== false ) {
1000                         $this->lastPing = $startTime;
1001                         if ( $isWrite && $this->mTrxLevel ) {
1002                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime );
1003                                 $this->mTrxWriteCallers[] = $fname;
1004                         }
1005                 }
1006
1007                 if ( $sql === self::PING_QUERY ) {
1008                         $this->mRTTEstimate = $queryRuntime;
1009                 }
1010
1011                 $this->getTransactionProfiler()->recordQueryCompletion(
1012                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1013                 );
1014                 MWDebug::query( $sql, $fname, $isMaster, $queryRuntime );
1015
1016                 return $ret;
1017         }
1018
1019         /**
1020          * Update the estimated run-time of a query, not counting large row lock times
1021          *
1022          * LoadBalancer can be set to rollback transactions that will create huge replication
1023          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1024          * queries, like inserting a row can take a long time due to row locking. This method
1025          * uses some simple heuristics to discount those cases.
1026          *
1027          * @param string $sql A SQL write query
1028          * @param float $runtime Total runtime, including RTT
1029          */
1030         private function updateTrxWriteQueryTime( $sql, $runtime ) {
1031                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1032                 $indicativeOfReplicaRuntime = true;
1033                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1034                         $verb = $this->getQueryVerb( $sql );
1035                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1036                         if ( $verb === 'INSERT' ) {
1037                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1038                         } elseif ( $verb === 'REPLACE' ) {
1039                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1040                         }
1041                 }
1042
1043                 $this->mTrxWriteDuration += $runtime;
1044                 $this->mTrxWriteQueryCount += 1;
1045                 if ( $indicativeOfReplicaRuntime ) {
1046                         $this->mTrxWriteAdjDuration += $runtime;
1047                         $this->mTrxWriteAdjQueryCount += 1;
1048                 }
1049         }
1050
1051         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1052                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1053                 # Dropped connections also mean that named locks are automatically released.
1054                 # Only allow error suppression in autocommit mode or when the lost transaction
1055                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1056                 if ( $this->mNamedLocksHeld ) {
1057                         return false; // possible critical section violation
1058                 } elseif ( $sql === 'COMMIT' ) {
1059                         return !$priorWritesPending; // nothing written anyway? (T127428)
1060                 } elseif ( $sql === 'ROLLBACK' ) {
1061                         return true; // transaction lost...which is also what was requested :)
1062                 } elseif ( $this->explicitTrxActive() ) {
1063                         return false; // don't drop atomocity
1064                 } elseif ( $priorWritesPending ) {
1065                         return false; // prior writes lost from implicit transaction
1066                 }
1067
1068                 return true;
1069         }
1070
1071         private function handleTransactionLoss() {
1072                 $this->mTrxLevel = 0;
1073                 $this->mTrxIdleCallbacks = []; // bug 65263
1074                 $this->mTrxPreCommitCallbacks = []; // bug 65263
1075                 try {
1076                         // Handle callbacks in mTrxEndCallbacks
1077                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1078                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1079                         return null;
1080                 } catch ( Exception $e ) {
1081                         // Already logged; move on...
1082                         return $e;
1083                 }
1084         }
1085
1086         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1087                 if ( $this->ignoreErrors() || $tempIgnore ) {
1088                         wfDebug( "SQL ERROR (ignored): $error\n" );
1089                 } else {
1090                         $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1091                         wfLogDBError(
1092                                 "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1093                                 $this->getLogContext( [
1094                                         'method' => __METHOD__,
1095                                         'errno' => $errno,
1096                                         'error' => $error,
1097                                         'sql1line' => $sql1line,
1098                                         'fname' => $fname,
1099                                 ] )
1100                         );
1101                         wfDebug( "SQL ERROR: " . $error . "\n" );
1102                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
1103                 }
1104         }
1105
1106         /**
1107          * Intended to be compatible with the PEAR::DB wrapper functions.
1108          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
1109          *
1110          * ? = scalar value, quoted as necessary
1111          * ! = raw SQL bit (a function for instance)
1112          * & = filename; reads the file and inserts as a blob
1113          *     (we don't use this though...)
1114          *
1115          * @param string $sql
1116          * @param string $func
1117          *
1118          * @return array
1119          */
1120         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
1121                 /* MySQL doesn't support prepared statements (yet), so just
1122                  * pack up the query for reference. We'll manually replace
1123                  * the bits later.
1124                  */
1125                 return [ 'query' => $sql, 'func' => $func ];
1126         }
1127
1128         /**
1129          * Free a prepared query, generated by prepare().
1130          * @param string $prepared
1131          */
1132         protected function freePrepared( $prepared ) {
1133                 /* No-op by default */
1134         }
1135
1136         /**
1137          * Execute a prepared query with the various arguments
1138          * @param string $prepared The prepared sql
1139          * @param mixed $args Either an array here, or put scalars as varargs
1140          *
1141          * @return ResultWrapper
1142          */
1143         public function execute( $prepared, $args = null ) {
1144                 if ( !is_array( $args ) ) {
1145                         # Pull the var args
1146                         $args = func_get_args();
1147                         array_shift( $args );
1148                 }
1149
1150                 $sql = $this->fillPrepared( $prepared['query'], $args );
1151
1152                 return $this->query( $sql, $prepared['func'] );
1153         }
1154
1155         /**
1156          * For faking prepared SQL statements on DBs that don't support it directly.
1157          *
1158          * @param string $preparedQuery A 'preparable' SQL statement
1159          * @param array $args Array of Arguments to fill it with
1160          * @return string Executable SQL
1161          */
1162         public function fillPrepared( $preparedQuery, $args ) {
1163                 reset( $args );
1164                 $this->preparedArgs =& $args;
1165
1166                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
1167                         [ &$this, 'fillPreparedArg' ], $preparedQuery );
1168         }
1169
1170         /**
1171          * preg_callback func for fillPrepared()
1172          * The arguments should be in $this->preparedArgs and must not be touched
1173          * while we're doing this.
1174          *
1175          * @param array $matches
1176          * @throws DBUnexpectedError
1177          * @return string
1178          */
1179         protected function fillPreparedArg( $matches ) {
1180                 switch ( $matches[1] ) {
1181                         case '\\?':
1182                                 return '?';
1183                         case '\\!':
1184                                 return '!';
1185                         case '\\&':
1186                                 return '&';
1187                 }
1188
1189                 list( /* $n */, $arg ) = each( $this->preparedArgs );
1190
1191                 switch ( $matches[1] ) {
1192                         case '?':
1193                                 return $this->addQuotes( $arg );
1194                         case '!':
1195                                 return $arg;
1196                         case '&':
1197                                 # return $this->addQuotes( file_get_contents( $arg ) );
1198                                 throw new DBUnexpectedError(
1199                                         $this,
1200                                         '& mode is not implemented. If it\'s really needed, uncomment the line above.'
1201                                 );
1202                         default:
1203                                 throw new DBUnexpectedError(
1204                                         $this,
1205                                         'Received invalid match. This should never happen!'
1206                                 );
1207                 }
1208         }
1209
1210         public function freeResult( $res ) {
1211         }
1212
1213         public function selectField(
1214                 $table, $var, $cond = '', $fname = __METHOD__, $options = []
1215         ) {
1216                 if ( $var === '*' ) { // sanity
1217                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1218                 }
1219
1220                 if ( !is_array( $options ) ) {
1221                         $options = [ $options ];
1222                 }
1223
1224                 $options['LIMIT'] = 1;
1225
1226                 $res = $this->select( $table, $var, $cond, $fname, $options );
1227                 if ( $res === false || !$this->numRows( $res ) ) {
1228                         return false;
1229                 }
1230
1231                 $row = $this->fetchRow( $res );
1232
1233                 if ( $row !== false ) {
1234                         return reset( $row );
1235                 } else {
1236                         return false;
1237                 }
1238         }
1239
1240         public function selectFieldValues(
1241                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1242         ) {
1243                 if ( $var === '*' ) { // sanity
1244                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1245                 } elseif ( !is_string( $var ) ) { // sanity
1246                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1247                 }
1248
1249                 if ( !is_array( $options ) ) {
1250                         $options = [ $options ];
1251                 }
1252
1253                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1254                 if ( $res === false ) {
1255                         return false;
1256                 }
1257
1258                 $values = [];
1259                 foreach ( $res as $row ) {
1260                         $values[] = $row->$var;
1261                 }
1262
1263                 return $values;
1264         }
1265
1266         /**
1267          * Returns an optional USE INDEX clause to go after the table, and a
1268          * string to go at the end of the query.
1269          *
1270          * @param array $options Associative array of options to be turned into
1271          *   an SQL query, valid keys are listed in the function.
1272          * @return array
1273          * @see DatabaseBase::select()
1274          */
1275         public function makeSelectOptions( $options ) {
1276                 $preLimitTail = $postLimitTail = '';
1277                 $startOpts = '';
1278
1279                 $noKeyOptions = [];
1280
1281                 foreach ( $options as $key => $option ) {
1282                         if ( is_numeric( $key ) ) {
1283                                 $noKeyOptions[$option] = true;
1284                         }
1285                 }
1286
1287                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1288
1289                 $preLimitTail .= $this->makeOrderBy( $options );
1290
1291                 // if (isset($options['LIMIT'])) {
1292                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1293                 //              isset($options['OFFSET']) ? $options['OFFSET']
1294                 //              : false);
1295                 // }
1296
1297                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1298                         $postLimitTail .= ' FOR UPDATE';
1299                 }
1300
1301                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1302                         $postLimitTail .= ' LOCK IN SHARE MODE';
1303                 }
1304
1305                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1306                         $startOpts .= 'DISTINCT';
1307                 }
1308
1309                 # Various MySQL extensions
1310                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1311                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1312                 }
1313
1314                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1315                         $startOpts .= ' HIGH_PRIORITY';
1316                 }
1317
1318                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1319                         $startOpts .= ' SQL_BIG_RESULT';
1320                 }
1321
1322                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1323                         $startOpts .= ' SQL_BUFFER_RESULT';
1324                 }
1325
1326                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1327                         $startOpts .= ' SQL_SMALL_RESULT';
1328                 }
1329
1330                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1331                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1332                 }
1333
1334                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1335                         $startOpts .= ' SQL_CACHE';
1336                 }
1337
1338                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1339                         $startOpts .= ' SQL_NO_CACHE';
1340                 }
1341
1342                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1343                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1344                 } else {
1345                         $useIndex = '';
1346                 }
1347                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1348                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1349                 } else {
1350                         $ignoreIndex = '';
1351                 }
1352
1353                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1354         }
1355
1356         /**
1357          * Returns an optional GROUP BY with an optional HAVING
1358          *
1359          * @param array $options Associative array of options
1360          * @return string
1361          * @see DatabaseBase::select()
1362          * @since 1.21
1363          */
1364         public function makeGroupByWithHaving( $options ) {
1365                 $sql = '';
1366                 if ( isset( $options['GROUP BY'] ) ) {
1367                         $gb = is_array( $options['GROUP BY'] )
1368                                 ? implode( ',', $options['GROUP BY'] )
1369                                 : $options['GROUP BY'];
1370                         $sql .= ' GROUP BY ' . $gb;
1371                 }
1372                 if ( isset( $options['HAVING'] ) ) {
1373                         $having = is_array( $options['HAVING'] )
1374                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1375                                 : $options['HAVING'];
1376                         $sql .= ' HAVING ' . $having;
1377                 }
1378
1379                 return $sql;
1380         }
1381
1382         /**
1383          * Returns an optional ORDER BY
1384          *
1385          * @param array $options Associative array of options
1386          * @return string
1387          * @see DatabaseBase::select()
1388          * @since 1.21
1389          */
1390         public function makeOrderBy( $options ) {
1391                 if ( isset( $options['ORDER BY'] ) ) {
1392                         $ob = is_array( $options['ORDER BY'] )
1393                                 ? implode( ',', $options['ORDER BY'] )
1394                                 : $options['ORDER BY'];
1395
1396                         return ' ORDER BY ' . $ob;
1397                 }
1398
1399                 return '';
1400         }
1401
1402         // See IDatabase::select for the docs for this function
1403         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1404                 $options = [], $join_conds = [] ) {
1405                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1406
1407                 return $this->query( $sql, $fname );
1408         }
1409
1410         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1411                 $options = [], $join_conds = []
1412         ) {
1413                 if ( is_array( $vars ) ) {
1414                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1415                 }
1416
1417                 $options = (array)$options;
1418                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1419                         ? $options['USE INDEX']
1420                         : [];
1421                 $ignoreIndexes = ( isset( $options['IGNORE INDEX'] ) && is_array( $options['IGNORE INDEX'] ) )
1422                         ? $options['IGNORE INDEX']
1423                         : [];
1424
1425                 if ( is_array( $table ) ) {
1426                         $from = ' FROM ' .
1427                                 $this->tableNamesWithIndexClauseOrJOIN( $table, $useIndexes, $ignoreIndexes, $join_conds );
1428                 } elseif ( $table != '' ) {
1429                         if ( $table[0] == ' ' ) {
1430                                 $from = ' FROM ' . $table;
1431                         } else {
1432                                 $from = ' FROM ' .
1433                                         $this->tableNamesWithIndexClauseOrJOIN( [ $table ], $useIndexes, $ignoreIndexes, [] );
1434                         }
1435                 } else {
1436                         $from = '';
1437                 }
1438
1439                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1440                         $this->makeSelectOptions( $options );
1441
1442                 if ( !empty( $conds ) ) {
1443                         if ( is_array( $conds ) ) {
1444                                 $conds = $this->makeList( $conds, LIST_AND );
1445                         }
1446                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex WHERE $conds $preLimitTail";
1447                 } else {
1448                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1449                 }
1450
1451                 if ( isset( $options['LIMIT'] ) ) {
1452                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1453                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1454                 }
1455                 $sql = "$sql $postLimitTail";
1456
1457                 if ( isset( $options['EXPLAIN'] ) ) {
1458                         $sql = 'EXPLAIN ' . $sql;
1459                 }
1460
1461                 return $sql;
1462         }
1463
1464         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1465                 $options = [], $join_conds = []
1466         ) {
1467                 $options = (array)$options;
1468                 $options['LIMIT'] = 1;
1469                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1470
1471                 if ( $res === false ) {
1472                         return false;
1473                 }
1474
1475                 if ( !$this->numRows( $res ) ) {
1476                         return false;
1477                 }
1478
1479                 $obj = $this->fetchObject( $res );
1480
1481                 return $obj;
1482         }
1483
1484         public function estimateRowCount(
1485                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
1486         ) {
1487                 $rows = 0;
1488                 $res = $this->select( $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options );
1489
1490                 if ( $res ) {
1491                         $row = $this->fetchRow( $res );
1492                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1493                 }
1494
1495                 return $rows;
1496         }
1497
1498         public function selectRowCount(
1499                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1500         ) {
1501                 $rows = 0;
1502                 $sql = $this->selectSQLText( $tables, '1', $conds, $fname, $options, $join_conds );
1503                 $res = $this->query( "SELECT COUNT(*) AS rowcount FROM ($sql) tmp_count", $fname );
1504
1505                 if ( $res ) {
1506                         $row = $this->fetchRow( $res );
1507                         $rows = ( isset( $row['rowcount'] ) ) ? (int)$row['rowcount'] : 0;
1508                 }
1509
1510                 return $rows;
1511         }
1512
1513         /**
1514          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1515          * It's only slightly flawed. Don't use for anything important.
1516          *
1517          * @param string $sql A SQL Query
1518          *
1519          * @return string
1520          */
1521         protected static function generalizeSQL( $sql ) {
1522                 # This does the same as the regexp below would do, but in such a way
1523                 # as to avoid crashing php on some large strings.
1524                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1525
1526                 $sql = str_replace( "\\\\", '', $sql );
1527                 $sql = str_replace( "\\'", '', $sql );
1528                 $sql = str_replace( "\\\"", '', $sql );
1529                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1530                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1531
1532                 # All newlines, tabs, etc replaced by single space
1533                 $sql = preg_replace( '/\s+/', ' ', $sql );
1534
1535                 # All numbers => N,
1536                 # except the ones surrounded by characters, e.g. l10n
1537                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1538                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1539
1540                 return $sql;
1541         }
1542
1543         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1544                 $info = $this->fieldInfo( $table, $field );
1545
1546                 return (bool)$info;
1547         }
1548
1549         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1550                 if ( !$this->tableExists( $table ) ) {
1551                         return null;
1552                 }
1553
1554                 $info = $this->indexInfo( $table, $index, $fname );
1555                 if ( is_null( $info ) ) {
1556                         return null;
1557                 } else {
1558                         return $info !== false;
1559                 }
1560         }
1561
1562         public function tableExists( $table, $fname = __METHOD__ ) {
1563                 $table = $this->tableName( $table );
1564                 $old = $this->ignoreErrors( true );
1565                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1566                 $this->ignoreErrors( $old );
1567
1568                 return (bool)$res;
1569         }
1570
1571         public function indexUnique( $table, $index ) {
1572                 $indexInfo = $this->indexInfo( $table, $index );
1573
1574                 if ( !$indexInfo ) {
1575                         return null;
1576                 }
1577
1578                 return !$indexInfo[0]->Non_unique;
1579         }
1580
1581         /**
1582          * Helper for DatabaseBase::insert().
1583          *
1584          * @param array $options
1585          * @return string
1586          */
1587         protected function makeInsertOptions( $options ) {
1588                 return implode( ' ', $options );
1589         }
1590
1591         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1592                 # No rows to insert, easy just return now
1593                 if ( !count( $a ) ) {
1594                         return true;
1595                 }
1596
1597                 $table = $this->tableName( $table );
1598
1599                 if ( !is_array( $options ) ) {
1600                         $options = [ $options ];
1601                 }
1602
1603                 $fh = null;
1604                 if ( isset( $options['fileHandle'] ) ) {
1605                         $fh = $options['fileHandle'];
1606                 }
1607                 $options = $this->makeInsertOptions( $options );
1608
1609                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1610                         $multi = true;
1611                         $keys = array_keys( $a[0] );
1612                 } else {
1613                         $multi = false;
1614                         $keys = array_keys( $a );
1615                 }
1616
1617                 $sql = 'INSERT ' . $options .
1618                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1619
1620                 if ( $multi ) {
1621                         $first = true;
1622                         foreach ( $a as $row ) {
1623                                 if ( $first ) {
1624                                         $first = false;
1625                                 } else {
1626                                         $sql .= ',';
1627                                 }
1628                                 $sql .= '(' . $this->makeList( $row ) . ')';
1629                         }
1630                 } else {
1631                         $sql .= '(' . $this->makeList( $a ) . ')';
1632                 }
1633
1634                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1635                         return false;
1636                 } elseif ( $fh !== null ) {
1637                         return true;
1638                 }
1639
1640                 return (bool)$this->query( $sql, $fname );
1641         }
1642
1643         /**
1644          * Make UPDATE options array for DatabaseBase::makeUpdateOptions
1645          *
1646          * @param array $options
1647          * @return array
1648          */
1649         protected function makeUpdateOptionsArray( $options ) {
1650                 if ( !is_array( $options ) ) {
1651                         $options = [ $options ];
1652                 }
1653
1654                 $opts = [];
1655
1656                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1657                         $opts[] = $this->lowPriorityOption();
1658                 }
1659
1660                 if ( in_array( 'IGNORE', $options ) ) {
1661                         $opts[] = 'IGNORE';
1662                 }
1663
1664                 return $opts;
1665         }
1666
1667         /**
1668          * Make UPDATE options for the DatabaseBase::update function
1669          *
1670          * @param array $options The options passed to DatabaseBase::update
1671          * @return string
1672          */
1673         protected function makeUpdateOptions( $options ) {
1674                 $opts = $this->makeUpdateOptionsArray( $options );
1675
1676                 return implode( ' ', $opts );
1677         }
1678
1679         function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1680                 $table = $this->tableName( $table );
1681                 $opts = $this->makeUpdateOptions( $options );
1682                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1683
1684                 if ( $conds !== [] && $conds !== '*' ) {
1685                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1686                 }
1687
1688                 return $this->query( $sql, $fname );
1689         }
1690
1691         public function makeList( $a, $mode = LIST_COMMA ) {
1692                 if ( !is_array( $a ) ) {
1693                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1694                 }
1695
1696                 $first = true;
1697                 $list = '';
1698
1699                 foreach ( $a as $field => $value ) {
1700                         if ( !$first ) {
1701                                 if ( $mode == LIST_AND ) {
1702                                         $list .= ' AND ';
1703                                 } elseif ( $mode == LIST_OR ) {
1704                                         $list .= ' OR ';
1705                                 } else {
1706                                         $list .= ',';
1707                                 }
1708                         } else {
1709                                 $first = false;
1710                         }
1711
1712                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1713                                 $list .= "($value)";
1714                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1715                                 $list .= "$value";
1716                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1717                                 // Remove null from array to be handled separately if found
1718                                 $includeNull = false;
1719                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1720                                         $includeNull = true;
1721                                         unset( $value[$nullKey] );
1722                                 }
1723                                 if ( count( $value ) == 0 && !$includeNull ) {
1724                                         throw new MWException( __METHOD__ . ": empty input for field $field" );
1725                                 } elseif ( count( $value ) == 0 ) {
1726                                         // only check if $field is null
1727                                         $list .= "$field IS NULL";
1728                                 } else {
1729                                         // IN clause contains at least one valid element
1730                                         if ( $includeNull ) {
1731                                                 // Group subconditions to ensure correct precedence
1732                                                 $list .= '(';
1733                                         }
1734                                         if ( count( $value ) == 1 ) {
1735                                                 // Special-case single values, as IN isn't terribly efficient
1736                                                 // Don't necessarily assume the single key is 0; we don't
1737                                                 // enforce linear numeric ordering on other arrays here.
1738                                                 $value = array_values( $value )[0];
1739                                                 $list .= $field . " = " . $this->addQuotes( $value );
1740                                         } else {
1741                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1742                                         }
1743                                         // if null present in array, append IS NULL
1744                                         if ( $includeNull ) {
1745                                                 $list .= " OR $field IS NULL)";
1746                                         }
1747                                 }
1748                         } elseif ( $value === null ) {
1749                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1750                                         $list .= "$field IS ";
1751                                 } elseif ( $mode == LIST_SET ) {
1752                                         $list .= "$field = ";
1753                                 }
1754                                 $list .= 'NULL';
1755                         } else {
1756                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1757                                         $list .= "$field = ";
1758                                 }
1759                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1760                         }
1761                 }
1762
1763                 return $list;
1764         }
1765
1766         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1767                 $conds = [];
1768
1769                 foreach ( $data as $base => $sub ) {
1770                         if ( count( $sub ) ) {
1771                                 $conds[] = $this->makeList(
1772                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
1773                                         LIST_AND );
1774                         }
1775                 }
1776
1777                 if ( $conds ) {
1778                         return $this->makeList( $conds, LIST_OR );
1779                 } else {
1780                         // Nothing to search for...
1781                         return false;
1782                 }
1783         }
1784
1785         /**
1786          * Return aggregated value alias
1787          *
1788          * @param array $valuedata
1789          * @param string $valuename
1790          *
1791          * @return string
1792          */
1793         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1794                 return $valuename;
1795         }
1796
1797         public function bitNot( $field ) {
1798                 return "(~$field)";
1799         }
1800
1801         public function bitAnd( $fieldLeft, $fieldRight ) {
1802                 return "($fieldLeft & $fieldRight)";
1803         }
1804
1805         public function bitOr( $fieldLeft, $fieldRight ) {
1806                 return "($fieldLeft | $fieldRight)";
1807         }
1808
1809         public function buildConcat( $stringList ) {
1810                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1811         }
1812
1813         public function buildGroupConcatField(
1814                 $delim, $table, $field, $conds = '', $join_conds = []
1815         ) {
1816                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
1817
1818                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1819         }
1820
1821         /**
1822          * @param string $field Field or column to cast
1823          * @return string
1824          * @since 1.28
1825          */
1826         public function buildStringCast( $field ) {
1827                 return $field;
1828         }
1829
1830         public function selectDB( $db ) {
1831                 # Stub. Shouldn't cause serious problems if it's not overridden, but
1832                 # if your database engine supports a concept similar to MySQL's
1833                 # databases you may as well.
1834                 $this->mDBname = $db;
1835
1836                 return true;
1837         }
1838
1839         public function getDBname() {
1840                 return $this->mDBname;
1841         }
1842
1843         public function getServer() {
1844                 return $this->mServer;
1845         }
1846
1847         /**
1848          * Format a table name ready for use in constructing an SQL query
1849          *
1850          * This does two important things: it quotes the table names to clean them up,
1851          * and it adds a table prefix if only given a table name with no quotes.
1852          *
1853          * All functions of this object which require a table name call this function
1854          * themselves. Pass the canonical name to such functions. This is only needed
1855          * when calling query() directly.
1856          *
1857          * @note This function does not sanitize user input. It is not safe to use
1858          *   this function to escape user input.
1859          * @param string $name Database table name
1860          * @param string $format One of:
1861          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1862          *            so that it can be used in a query.
1863          *   raw - Do not add identifier quotes to the table name
1864          * @return string Full database name
1865          */
1866         public function tableName( $name, $format = 'quoted' ) {
1867                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables, $wgSharedSchema;
1868                 # Skip the entire process when we have a string quoted on both ends.
1869                 # Note that we check the end so that we will still quote any use of
1870                 # use of `database`.table. But won't break things if someone wants
1871                 # to query a database table with a dot in the name.
1872                 if ( $this->isQuotedIdentifier( $name ) ) {
1873                         return $name;
1874                 }
1875
1876                 # Lets test for any bits of text that should never show up in a table
1877                 # name. Basically anything like JOIN or ON which are actually part of
1878                 # SQL queries, but may end up inside of the table value to combine
1879                 # sql. Such as how the API is doing.
1880                 # Note that we use a whitespace test rather than a \b test to avoid
1881                 # any remote case where a word like on may be inside of a table name
1882                 # surrounded by symbols which may be considered word breaks.
1883                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1884                         return $name;
1885                 }
1886
1887                 # Split database and table into proper variables.
1888                 # We reverse the explode so that database.table and table both output
1889                 # the correct table.
1890                 $dbDetails = explode( '.', $name, 3 );
1891                 if ( count( $dbDetails ) == 3 ) {
1892                         list( $database, $schema, $table ) = $dbDetails;
1893                         # We don't want any prefix added in this case
1894                         $prefix = '';
1895                 } elseif ( count( $dbDetails ) == 2 ) {
1896                         list( $database, $table ) = $dbDetails;
1897                         # We don't want any prefix added in this case
1898                         # In dbs that support it, $database may actually be the schema
1899                         # but that doesn't affect any of the functionality here
1900                         $prefix = '';
1901                         $schema = null;
1902                 } else {
1903                         list( $table ) = $dbDetails;
1904                         if ( $wgSharedDB !== null # We have a shared database
1905                                 && $this->mForeign == false # We're not working on a foreign database
1906                                 && !$this->isQuotedIdentifier( $table ) # Prevent shared tables listing '`table`'
1907                                 && in_array( $table, $wgSharedTables ) # A shared table is selected
1908                         ) {
1909                                 $database = $wgSharedDB;
1910                                 $schema = $wgSharedSchema === null ? $this->mSchema : $wgSharedSchema;
1911                                 $prefix = $wgSharedPrefix === null ? $this->mTablePrefix : $wgSharedPrefix;
1912                         } else {
1913                                 $database = null;
1914                                 $schema = $this->mSchema; # Default schema
1915                                 $prefix = $this->mTablePrefix; # Default prefix
1916                         }
1917                 }
1918
1919                 # Quote $table and apply the prefix if not quoted.
1920                 # $tableName might be empty if this is called from Database::replaceVars()
1921                 $tableName = "{$prefix}{$table}";
1922                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $tableName ) && $tableName !== '' ) {
1923                         $tableName = $this->addIdentifierQuotes( $tableName );
1924                 }
1925
1926                 # Quote $schema and merge it with the table name if needed
1927                 if ( strlen( $schema ) ) {
1928                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $schema ) ) {
1929                                 $schema = $this->addIdentifierQuotes( $schema );
1930                         }
1931                         $tableName = $schema . '.' . $tableName;
1932                 }
1933
1934                 # Quote $database and merge it with the table name if needed
1935                 if ( $database !== null ) {
1936                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
1937                                 $database = $this->addIdentifierQuotes( $database );
1938                         }
1939                         $tableName = $database . '.' . $tableName;
1940                 }
1941
1942                 return $tableName;
1943         }
1944
1945         /**
1946          * Fetch a number of table names into an array
1947          * This is handy when you need to construct SQL for joins
1948          *
1949          * Example:
1950          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
1951          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1952          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1953          *
1954          * @return array
1955          */
1956         public function tableNames() {
1957                 $inArray = func_get_args();
1958                 $retVal = [];
1959
1960                 foreach ( $inArray as $name ) {
1961                         $retVal[$name] = $this->tableName( $name );
1962                 }
1963
1964                 return $retVal;
1965         }
1966
1967         /**
1968          * Fetch a number of table names into an zero-indexed numerical array
1969          * This is handy when you need to construct SQL for joins
1970          *
1971          * Example:
1972          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
1973          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1974          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1975          *
1976          * @return array
1977          */
1978         public function tableNamesN() {
1979                 $inArray = func_get_args();
1980                 $retVal = [];
1981
1982                 foreach ( $inArray as $name ) {
1983                         $retVal[] = $this->tableName( $name );
1984                 }
1985
1986                 return $retVal;
1987         }
1988
1989         /**
1990          * Get an aliased table name
1991          * e.g. tableName AS newTableName
1992          *
1993          * @param string $name Table name, see tableName()
1994          * @param string|bool $alias Alias (optional)
1995          * @return string SQL name for aliased table. Will not alias a table to its own name
1996          */
1997         public function tableNameWithAlias( $name, $alias = false ) {
1998                 if ( !$alias || $alias == $name ) {
1999                         return $this->tableName( $name );
2000                 } else {
2001                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2002                 }
2003         }
2004
2005         /**
2006          * Gets an array of aliased table names
2007          *
2008          * @param array $tables [ [alias] => table ]
2009          * @return string[] See tableNameWithAlias()
2010          */
2011         public function tableNamesWithAlias( $tables ) {
2012                 $retval = [];
2013                 foreach ( $tables as $alias => $table ) {
2014                         if ( is_numeric( $alias ) ) {
2015                                 $alias = $table;
2016                         }
2017                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2018                 }
2019
2020                 return $retval;
2021         }
2022
2023         /**
2024          * Get an aliased field name
2025          * e.g. fieldName AS newFieldName
2026          *
2027          * @param string $name Field name
2028          * @param string|bool $alias Alias (optional)
2029          * @return string SQL name for aliased field. Will not alias a field to its own name
2030          */
2031         public function fieldNameWithAlias( $name, $alias = false ) {
2032                 if ( !$alias || (string)$alias === (string)$name ) {
2033                         return $name;
2034                 } else {
2035                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2036                 }
2037         }
2038
2039         /**
2040          * Gets an array of aliased field names
2041          *
2042          * @param array $fields [ [alias] => field ]
2043          * @return string[] See fieldNameWithAlias()
2044          */
2045         public function fieldNamesWithAlias( $fields ) {
2046                 $retval = [];
2047                 foreach ( $fields as $alias => $field ) {
2048                         if ( is_numeric( $alias ) ) {
2049                                 $alias = $field;
2050                         }
2051                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2052                 }
2053
2054                 return $retval;
2055         }
2056
2057         /**
2058          * Get the aliased table name clause for a FROM clause
2059          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2060          *
2061          * @param array $tables ( [alias] => table )
2062          * @param array $use_index Same as for select()
2063          * @param array $ignore_index Same as for select()
2064          * @param array $join_conds Same as for select()
2065          * @return string
2066          */
2067         protected function tableNamesWithIndexClauseOrJOIN(
2068                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2069         ) {
2070                 $ret = [];
2071                 $retJOIN = [];
2072                 $use_index = (array)$use_index;
2073                 $ignore_index = (array)$ignore_index;
2074                 $join_conds = (array)$join_conds;
2075
2076                 foreach ( $tables as $alias => $table ) {
2077                         if ( !is_string( $alias ) ) {
2078                                 // No alias? Set it equal to the table name
2079                                 $alias = $table;
2080                         }
2081                         // Is there a JOIN clause for this table?
2082                         if ( isset( $join_conds[$alias] ) ) {
2083                                 list( $joinType, $conds ) = $join_conds[$alias];
2084                                 $tableClause = $joinType;
2085                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2086                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2087                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2088                                         if ( $use != '' ) {
2089                                                 $tableClause .= ' ' . $use;
2090                                         }
2091                                 }
2092                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2093                                         $ignore = $this->ignoreIndexClause( implode( ',', (array)$ignore_index[$alias] ) );
2094                                         if ( $ignore != '' ) {
2095                                                 $tableClause .= ' ' . $ignore;
2096                                         }
2097                                 }
2098                                 $on = $this->makeList( (array)$conds, LIST_AND );
2099                                 if ( $on != '' ) {
2100                                         $tableClause .= ' ON (' . $on . ')';
2101                                 }
2102
2103                                 $retJOIN[] = $tableClause;
2104                         } elseif ( isset( $use_index[$alias] ) ) {
2105                                 // Is there an INDEX clause for this table?
2106                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2107                                 $tableClause .= ' ' . $this->useIndexClause(
2108                                         implode( ',', (array)$use_index[$alias] )
2109                                 );
2110
2111                                 $ret[] = $tableClause;
2112                         } elseif ( isset( $ignore_index[$alias] ) ) {
2113                                 // Is there an INDEX clause for this table?
2114                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2115                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2116                                         implode( ',', (array)$ignore_index[$alias] )
2117                                 );
2118
2119                                 $ret[] = $tableClause;
2120                         } else {
2121                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2122
2123                                 $ret[] = $tableClause;
2124                         }
2125                 }
2126
2127                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2128                 $implicitJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2129                 $explicitJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2130
2131                 // Compile our final table clause
2132                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2133         }
2134
2135         /**
2136          * Get the name of an index in a given table.
2137          *
2138          * @param string $index
2139          * @return string
2140          */
2141         protected function indexName( $index ) {
2142                 // Backwards-compatibility hack
2143                 $renamed = [
2144                         'ar_usertext_timestamp' => 'usertext_timestamp',
2145                         'un_user_id' => 'user_id',
2146                         'un_user_ip' => 'user_ip',
2147                 ];
2148
2149                 if ( isset( $renamed[$index] ) ) {
2150                         return $renamed[$index];
2151                 } else {
2152                         return $index;
2153                 }
2154         }
2155
2156         public function addQuotes( $s ) {
2157                 if ( $s instanceof Blob ) {
2158                         $s = $s->fetch();
2159                 }
2160                 if ( $s === null ) {
2161                         return 'NULL';
2162                 } else {
2163                         # This will also quote numeric values. This should be harmless,
2164                         # and protects against weird problems that occur when they really
2165                         # _are_ strings such as article titles and string->number->string
2166                         # conversion is not 1:1.
2167                         return "'" . $this->strencode( $s ) . "'";
2168                 }
2169         }
2170
2171         /**
2172          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2173          * MySQL uses `backticks` while basically everything else uses double quotes.
2174          * Since MySQL is the odd one out here the double quotes are our generic
2175          * and we implement backticks in DatabaseMysql.
2176          *
2177          * @param string $s
2178          * @return string
2179          */
2180         public function addIdentifierQuotes( $s ) {
2181                 return '"' . str_replace( '"', '""', $s ) . '"';
2182         }
2183
2184         /**
2185          * Returns if the given identifier looks quoted or not according to
2186          * the database convention for quoting identifiers .
2187          *
2188          * @note Do not use this to determine if untrusted input is safe.
2189          *   A malicious user can trick this function.
2190          * @param string $name
2191          * @return bool
2192          */
2193         public function isQuotedIdentifier( $name ) {
2194                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2195         }
2196
2197         /**
2198          * @param string $s
2199          * @return string
2200          */
2201         protected function escapeLikeInternal( $s ) {
2202                 return addcslashes( $s, '\%_' );
2203         }
2204
2205         public function buildLike() {
2206                 $params = func_get_args();
2207
2208                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2209                         $params = $params[0];
2210                 }
2211
2212                 $s = '';
2213
2214                 foreach ( $params as $value ) {
2215                         if ( $value instanceof LikeMatch ) {
2216                                 $s .= $value->toString();
2217                         } else {
2218                                 $s .= $this->escapeLikeInternal( $value );
2219                         }
2220                 }
2221
2222                 return " LIKE {$this->addQuotes( $s )} ";
2223         }
2224
2225         public function anyChar() {
2226                 return new LikeMatch( '_' );
2227         }
2228
2229         public function anyString() {
2230                 return new LikeMatch( '%' );
2231         }
2232
2233         public function nextSequenceValue( $seqName ) {
2234                 return null;
2235         }
2236
2237         /**
2238          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2239          * is only needed because a) MySQL must be as efficient as possible due to
2240          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2241          * which index to pick. Anyway, other databases might have different
2242          * indexes on a given table. So don't bother overriding this unless you're
2243          * MySQL.
2244          * @param string $index
2245          * @return string
2246          */
2247         public function useIndexClause( $index ) {
2248                 return '';
2249         }
2250
2251         /**
2252          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2253          * is only needed because a) MySQL must be as efficient as possible due to
2254          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2255          * which index to pick. Anyway, other databases might have different
2256          * indexes on a given table. So don't bother overriding this unless you're
2257          * MySQL.
2258          * @param string $index
2259          * @return string
2260          */
2261         public function ignoreIndexClause( $index ) {
2262                 return '';
2263         }
2264
2265         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2266                 $quotedTable = $this->tableName( $table );
2267
2268                 if ( count( $rows ) == 0 ) {
2269                         return;
2270                 }
2271
2272                 # Single row case
2273                 if ( !is_array( reset( $rows ) ) ) {
2274                         $rows = [ $rows ];
2275                 }
2276
2277                 // @FXIME: this is not atomic, but a trx would break affectedRows()
2278                 foreach ( $rows as $row ) {
2279                         # Delete rows which collide
2280                         if ( $uniqueIndexes ) {
2281                                 $sql = "DELETE FROM $quotedTable WHERE ";
2282                                 $first = true;
2283                                 foreach ( $uniqueIndexes as $index ) {
2284                                         if ( $first ) {
2285                                                 $first = false;
2286                                                 $sql .= '( ';
2287                                         } else {
2288                                                 $sql .= ' ) OR ( ';
2289                                         }
2290                                         if ( is_array( $index ) ) {
2291                                                 $first2 = true;
2292                                                 foreach ( $index as $col ) {
2293                                                         if ( $first2 ) {
2294                                                                 $first2 = false;
2295                                                         } else {
2296                                                                 $sql .= ' AND ';
2297                                                         }
2298                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2299                                                 }
2300                                         } else {
2301                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2302                                         }
2303                                 }
2304                                 $sql .= ' )';
2305                                 $this->query( $sql, $fname );
2306                         }
2307
2308                         # Now insert the row
2309                         $this->insert( $table, $row, $fname );
2310                 }
2311         }
2312
2313         /**
2314          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2315          * statement.
2316          *
2317          * @param string $table Table name
2318          * @param array|string $rows Row(s) to insert
2319          * @param string $fname Caller function name
2320          *
2321          * @return ResultWrapper
2322          */
2323         protected function nativeReplace( $table, $rows, $fname ) {
2324                 $table = $this->tableName( $table );
2325
2326                 # Single row case
2327                 if ( !is_array( reset( $rows ) ) ) {
2328                         $rows = [ $rows ];
2329                 }
2330
2331                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2332                 $first = true;
2333
2334                 foreach ( $rows as $row ) {
2335                         if ( $first ) {
2336                                 $first = false;
2337                         } else {
2338                                 $sql .= ',';
2339                         }
2340
2341                         $sql .= '(' . $this->makeList( $row ) . ')';
2342                 }
2343
2344                 return $this->query( $sql, $fname );
2345         }
2346
2347         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2348                 $fname = __METHOD__
2349         ) {
2350                 if ( !count( $rows ) ) {
2351                         return true; // nothing to do
2352                 }
2353
2354                 if ( !is_array( reset( $rows ) ) ) {
2355                         $rows = [ $rows ];
2356                 }
2357
2358                 if ( count( $uniqueIndexes ) ) {
2359                         $clauses = []; // list WHERE clauses that each identify a single row
2360                         foreach ( $rows as $row ) {
2361                                 foreach ( $uniqueIndexes as $index ) {
2362                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2363                                         $rowKey = []; // unique key to this row
2364                                         foreach ( $index as $column ) {
2365                                                 $rowKey[$column] = $row[$column];
2366                                         }
2367                                         $clauses[] = $this->makeList( $rowKey, LIST_AND );
2368                                 }
2369                         }
2370                         $where = [ $this->makeList( $clauses, LIST_OR ) ];
2371                 } else {
2372                         $where = false;
2373                 }
2374
2375                 $useTrx = !$this->mTrxLevel;
2376                 if ( $useTrx ) {
2377                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2378                 }
2379                 try {
2380                         # Update any existing conflicting row(s)
2381                         if ( $where !== false ) {
2382                                 $ok = $this->update( $table, $set, $where, $fname );
2383                         } else {
2384                                 $ok = true;
2385                         }
2386                         # Now insert any non-conflicting row(s)
2387                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2388                 } catch ( Exception $e ) {
2389                         if ( $useTrx ) {
2390                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
2391                         }
2392                         throw $e;
2393                 }
2394                 if ( $useTrx ) {
2395                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2396                 }
2397
2398                 return $ok;
2399         }
2400
2401         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2402                 $fname = __METHOD__
2403         ) {
2404                 if ( !$conds ) {
2405                         throw new DBUnexpectedError( $this,
2406                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2407                 }
2408
2409                 $delTable = $this->tableName( $delTable );
2410                 $joinTable = $this->tableName( $joinTable );
2411                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2412                 if ( $conds != '*' ) {
2413                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2414                 }
2415                 $sql .= ')';
2416
2417                 $this->query( $sql, $fname );
2418         }
2419
2420         /**
2421          * Returns the size of a text field, or -1 for "unlimited"
2422          *
2423          * @param string $table
2424          * @param string $field
2425          * @return int
2426          */
2427         public function textFieldSize( $table, $field ) {
2428                 $table = $this->tableName( $table );
2429                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2430                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2431                 $row = $this->fetchObject( $res );
2432
2433                 $m = [];
2434
2435                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2436                         $size = $m[1];
2437                 } else {
2438                         $size = -1;
2439                 }
2440
2441                 return $size;
2442         }
2443
2444         /**
2445          * A string to insert into queries to show that they're low-priority, like
2446          * MySQL's LOW_PRIORITY. If no such feature exists, return an empty
2447          * string and nothing bad should happen.
2448          *
2449          * @return string Returns the text of the low priority option if it is
2450          *   supported, or a blank string otherwise
2451          */
2452         public function lowPriorityOption() {
2453                 return '';
2454         }
2455
2456         public function delete( $table, $conds, $fname = __METHOD__ ) {
2457                 if ( !$conds ) {
2458                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2459                 }
2460
2461                 $table = $this->tableName( $table );
2462                 $sql = "DELETE FROM $table";
2463
2464                 if ( $conds != '*' ) {
2465                         if ( is_array( $conds ) ) {
2466                                 $conds = $this->makeList( $conds, LIST_AND );
2467                         }
2468                         $sql .= ' WHERE ' . $conds;
2469                 }
2470
2471                 return $this->query( $sql, $fname );
2472         }
2473
2474         public function insertSelect(
2475                 $destTable, $srcTable, $varMap, $conds,
2476                 $fname = __METHOD__, $insertOptions = [], $selectOptions = []
2477         ) {
2478                 if ( $this->cliMode ) {
2479                         // For massive migrations with downtime, we don't want to select everything
2480                         // into memory and OOM, so do all this native on the server side if possible.
2481                         return $this->nativeInsertSelect(
2482                                 $destTable,
2483                                 $srcTable,
2484                                 $varMap,
2485                                 $conds,
2486                                 $fname,
2487                                 $insertOptions,
2488                                 $selectOptions
2489                         );
2490                 }
2491
2492                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2493                 // on only the master (without needing row-based-replication). It also makes it easy to
2494                 // know how big the INSERT is going to be.
2495                 $fields = [];
2496                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2497                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2498                 }
2499                 $selectOptions[] = 'FOR UPDATE';
2500                 $res = $this->select( $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions );
2501                 if ( !$res ) {
2502                         return false;
2503                 }
2504
2505                 $rows = [];
2506                 foreach ( $res as $row ) {
2507                         $rows[] = (array)$row;
2508                 }
2509
2510                 return $this->insert( $destTable, $rows, $fname, $insertOptions );
2511         }
2512
2513         public function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2514                 $fname = __METHOD__,
2515                 $insertOptions = [], $selectOptions = []
2516         ) {
2517                 $destTable = $this->tableName( $destTable );
2518
2519                 if ( !is_array( $insertOptions ) ) {
2520                         $insertOptions = [ $insertOptions ];
2521                 }
2522
2523                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2524
2525                 if ( !is_array( $selectOptions ) ) {
2526                         $selectOptions = [ $selectOptions ];
2527                 }
2528
2529                 list( $startOpts, $useIndex, $tailOpts, $ignoreIndex ) = $this->makeSelectOptions(
2530                         $selectOptions );
2531
2532                 if ( is_array( $srcTable ) ) {
2533                         $srcTable = implode( ',', array_map( [ &$this, 'tableName' ], $srcTable ) );
2534                 } else {
2535                         $srcTable = $this->tableName( $srcTable );
2536                 }
2537
2538                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2539                         " SELECT $startOpts " . implode( ',', $varMap ) .
2540                         " FROM $srcTable $useIndex $ignoreIndex ";
2541
2542                 if ( $conds != '*' ) {
2543                         if ( is_array( $conds ) ) {
2544                                 $conds = $this->makeList( $conds, LIST_AND );
2545                         }
2546                         $sql .= " WHERE $conds";
2547                 }
2548
2549                 $sql .= " $tailOpts";
2550
2551                 return $this->query( $sql, $fname );
2552         }
2553
2554         /**
2555          * Construct a LIMIT query with optional offset. This is used for query
2556          * pages. The SQL should be adjusted so that only the first $limit rows
2557          * are returned. If $offset is provided as well, then the first $offset
2558          * rows should be discarded, and the next $limit rows should be returned.
2559          * If the result of the query is not ordered, then the rows to be returned
2560          * are theoretically arbitrary.
2561          *
2562          * $sql is expected to be a SELECT, if that makes a difference.
2563          *
2564          * The version provided by default works in MySQL and SQLite. It will very
2565          * likely need to be overridden for most other DBMSes.
2566          *
2567          * @param string $sql SQL query we will append the limit too
2568          * @param int $limit The SQL limit
2569          * @param int|bool $offset The SQL offset (default false)
2570          * @throws DBUnexpectedError
2571          * @return string
2572          */
2573         public function limitResult( $sql, $limit, $offset = false ) {
2574                 if ( !is_numeric( $limit ) ) {
2575                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2576                 }
2577
2578                 return "$sql LIMIT "
2579                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2580                         . "{$limit} ";
2581         }
2582
2583         public function unionSupportsOrderAndLimit() {
2584                 return true; // True for almost every DB supported
2585         }
2586
2587         public function unionQueries( $sqls, $all ) {
2588                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2589
2590                 return '(' . implode( $glue, $sqls ) . ')';
2591         }
2592
2593         public function conditional( $cond, $trueVal, $falseVal ) {
2594                 if ( is_array( $cond ) ) {
2595                         $cond = $this->makeList( $cond, LIST_AND );
2596                 }
2597
2598                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2599         }
2600
2601         public function strreplace( $orig, $old, $new ) {
2602                 return "REPLACE({$orig}, {$old}, {$new})";
2603         }
2604
2605         public function getServerUptime() {
2606                 return 0;
2607         }
2608
2609         public function wasDeadlock() {
2610                 return false;
2611         }
2612
2613         public function wasLockTimeout() {
2614                 return false;
2615         }
2616
2617         public function wasErrorReissuable() {
2618                 return false;
2619         }
2620
2621         public function wasReadOnlyError() {
2622                 return false;
2623         }
2624
2625         /**
2626          * Determines if the given query error was a connection drop
2627          * STUB
2628          *
2629          * @param integer|string $errno
2630          * @return bool
2631          */
2632         public function wasConnectionError( $errno ) {
2633                 return false;
2634         }
2635
2636         /**
2637          * Perform a deadlock-prone transaction.
2638          *
2639          * This function invokes a callback function to perform a set of write
2640          * queries. If a deadlock occurs during the processing, the transaction
2641          * will be rolled back and the callback function will be called again.
2642          *
2643          * Avoid using this method outside of Job or Maintenance classes.
2644          *
2645          * Usage:
2646          *   $dbw->deadlockLoop( callback, ... );
2647          *
2648          * Extra arguments are passed through to the specified callback function.
2649          * This method requires that no transactions are already active to avoid
2650          * causing premature commits or exceptions.
2651          *
2652          * Returns whatever the callback function returned on its successful,
2653          * iteration, or false on error, for example if the retry limit was
2654          * reached.
2655          *
2656          * @return mixed
2657          * @throws DBUnexpectedError
2658          * @throws Exception
2659          */
2660         public function deadlockLoop() {
2661                 $args = func_get_args();
2662                 $function = array_shift( $args );
2663                 $tries = self::DEADLOCK_TRIES;
2664
2665                 $this->begin( __METHOD__ );
2666
2667                 $retVal = null;
2668                 /** @var Exception $e */
2669                 $e = null;
2670                 do {
2671                         try {
2672                                 $retVal = call_user_func_array( $function, $args );
2673                                 break;
2674                         } catch ( DBQueryError $e ) {
2675                                 if ( $this->wasDeadlock() ) {
2676                                         // Retry after a randomized delay
2677                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
2678                                 } else {
2679                                         // Throw the error back up
2680                                         throw $e;
2681                                 }
2682                         }
2683                 } while ( --$tries > 0 );
2684
2685                 if ( $tries <= 0 ) {
2686                         // Too many deadlocks; give up
2687                         $this->rollback( __METHOD__ );
2688                         throw $e;
2689                 } else {
2690                         $this->commit( __METHOD__ );
2691
2692                         return $retVal;
2693                 }
2694         }
2695
2696         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2697                 # Real waits are implemented in the subclass.
2698                 return 0;
2699         }
2700
2701         public function getSlavePos() {
2702                 # Stub
2703                 return false;
2704         }
2705
2706         public function getMasterPos() {
2707                 # Stub
2708                 return false;
2709         }
2710
2711         public function serverIsReadOnly() {
2712                 return false;
2713         }
2714
2715         final public function onTransactionResolution( callable $callback ) {
2716                 if ( !$this->mTrxLevel ) {
2717                         throw new DBUnexpectedError( $this, "No transaction is active." );
2718                 }
2719                 $this->mTrxEndCallbacks[] = [ $callback, wfGetCaller() ];
2720         }
2721
2722         final public function onTransactionIdle( callable $callback ) {
2723                 $this->mTrxIdleCallbacks[] = [ $callback, wfGetCaller() ];
2724                 if ( !$this->mTrxLevel ) {
2725                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
2726                 }
2727         }
2728
2729         final public function onTransactionPreCommitOrIdle( callable $callback ) {
2730                 if ( $this->mTrxLevel ) {
2731                         $this->mTrxPreCommitCallbacks[] = [ $callback, wfGetCaller() ];
2732                 } else {
2733                         // If no transaction is active, then make one for this callback
2734                         $this->startAtomic( __METHOD__ );
2735                         try {
2736                                 call_user_func( $callback );
2737                                 $this->endAtomic( __METHOD__ );
2738                         } catch ( Exception $e ) {
2739                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2740                                 throw $e;
2741                         }
2742                 }
2743         }
2744
2745         final public function setTransactionListener( $name, callable $callback = null ) {
2746                 if ( $callback ) {
2747                         $this->mTrxRecurringCallbacks[$name] = [ $callback, wfGetCaller() ];
2748                 } else {
2749                         unset( $this->mTrxRecurringCallbacks[$name] );
2750                 }
2751         }
2752
2753         /**
2754          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
2755          *
2756          * This method should not be used outside of Database/LoadBalancer
2757          *
2758          * @param bool $suppress
2759          * @since 1.28
2760          */
2761         final public function setTrxEndCallbackSuppression( $suppress ) {
2762                 $this->mTrxEndCallbacksSuppressed = $suppress;
2763         }
2764
2765         /**
2766          * Actually run and consume any "on transaction idle/resolution" callbacks.
2767          *
2768          * This method should not be used outside of Database/LoadBalancer
2769          *
2770          * @param integer $trigger IDatabase::TRIGGER_* constant
2771          * @since 1.20
2772          * @throws Exception
2773          */
2774         public function runOnTransactionIdleCallbacks( $trigger ) {
2775                 if ( $this->mTrxEndCallbacksSuppressed ) {
2776                         return;
2777                 }
2778
2779                 $autoTrx = $this->getFlag( DBO_TRX ); // automatic begin() enabled?
2780                 /** @var Exception $e */
2781                 $e = null; // first exception
2782                 do { // callbacks may add callbacks :)
2783                         $callbacks = array_merge(
2784                                 $this->mTrxIdleCallbacks,
2785                                 $this->mTrxEndCallbacks // include "transaction resolution" callbacks
2786                         );
2787                         $this->mTrxIdleCallbacks = []; // consumed (and recursion guard)
2788                         $this->mTrxEndCallbacks = []; // consumed (recursion guard)
2789                         foreach ( $callbacks as $callback ) {
2790                                 try {
2791                                         list( $phpCallback ) = $callback;
2792                                         $this->clearFlag( DBO_TRX ); // make each query its own transaction
2793                                         call_user_func_array( $phpCallback, [ $trigger ] );
2794                                         if ( $autoTrx ) {
2795                                                 $this->setFlag( DBO_TRX ); // restore automatic begin()
2796                                         } else {
2797                                                 $this->clearFlag( DBO_TRX ); // restore auto-commit
2798                                         }
2799                                 } catch ( Exception $ex ) {
2800                                         MWExceptionHandler::logException( $ex );
2801                                         $e = $e ?: $ex;
2802                                         // Some callbacks may use startAtomic/endAtomic, so make sure
2803                                         // their transactions are ended so other callbacks don't fail
2804                                         if ( $this->trxLevel() ) {
2805                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
2806                                         }
2807                                 }
2808                         }
2809                 } while ( count( $this->mTrxIdleCallbacks ) );
2810
2811                 if ( $e instanceof Exception ) {
2812                         throw $e; // re-throw any first exception
2813                 }
2814         }
2815
2816         /**
2817          * Actually run and consume any "on transaction pre-commit" callbacks.
2818          *
2819          * This method should not be used outside of Database/LoadBalancer
2820          *
2821          * @since 1.22
2822          * @throws Exception
2823          */
2824         public function runOnTransactionPreCommitCallbacks() {
2825                 $e = null; // first exception
2826                 do { // callbacks may add callbacks :)
2827                         $callbacks = $this->mTrxPreCommitCallbacks;
2828                         $this->mTrxPreCommitCallbacks = []; // consumed (and recursion guard)
2829                         foreach ( $callbacks as $callback ) {
2830                                 try {
2831                                         list( $phpCallback ) = $callback;
2832                                         call_user_func( $phpCallback );
2833                                 } catch ( Exception $ex ) {
2834                                         MWExceptionHandler::logException( $ex );
2835                                         $e = $e ?: $ex;
2836                                 }
2837                         }
2838                 } while ( count( $this->mTrxPreCommitCallbacks ) );
2839
2840                 if ( $e instanceof Exception ) {
2841                         throw $e; // re-throw any first exception
2842                 }
2843         }
2844
2845         /**
2846          * Actually run any "transaction listener" callbacks.
2847          *
2848          * This method should not be used outside of Database/LoadBalancer
2849          *
2850          * @param integer $trigger IDatabase::TRIGGER_* constant
2851          * @throws Exception
2852          * @since 1.20
2853          */
2854         public function runTransactionListenerCallbacks( $trigger ) {
2855                 if ( $this->mTrxEndCallbacksSuppressed ) {
2856                         return;
2857                 }
2858
2859                 /** @var Exception $e */
2860                 $e = null; // first exception
2861
2862                 foreach ( $this->mTrxRecurringCallbacks as $callback ) {
2863                         try {
2864                                 list( $phpCallback ) = $callback;
2865                                 $phpCallback( $trigger, $this );
2866                         } catch ( Exception $ex ) {
2867                                 MWExceptionHandler::logException( $ex );
2868                                 $e = $e ?: $ex;
2869                         }
2870                 }
2871
2872                 if ( $e instanceof Exception ) {
2873                         throw $e; // re-throw any first exception
2874                 }
2875         }
2876
2877         final public function startAtomic( $fname = __METHOD__ ) {
2878                 if ( !$this->mTrxLevel ) {
2879                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
2880                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
2881                         // in all changes being in one transaction to keep requests transactional.
2882                         if ( !$this->getFlag( DBO_TRX ) ) {
2883                                 $this->mTrxAutomaticAtomic = true;
2884                         }
2885                 }
2886
2887                 $this->mTrxAtomicLevels[] = $fname;
2888         }
2889
2890         final public function endAtomic( $fname = __METHOD__ ) {
2891                 if ( !$this->mTrxLevel ) {
2892                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
2893                 }
2894                 if ( !$this->mTrxAtomicLevels ||
2895                         array_pop( $this->mTrxAtomicLevels ) !== $fname
2896                 ) {
2897                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
2898                 }
2899
2900                 if ( !$this->mTrxAtomicLevels && $this->mTrxAutomaticAtomic ) {
2901                         $this->commit( $fname, self::FLUSHING_INTERNAL );
2902                 }
2903         }
2904
2905         final public function doAtomicSection( $fname, callable $callback ) {
2906                 $this->startAtomic( $fname );
2907                 try {
2908                         $res = call_user_func_array( $callback, [ $this, $fname ] );
2909                 } catch ( Exception $e ) {
2910                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
2911                         throw $e;
2912                 }
2913                 $this->endAtomic( $fname );
2914
2915                 return $res;
2916         }
2917
2918         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
2919                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
2920                 if ( $this->mTrxLevel ) {
2921                         if ( $this->mTrxAtomicLevels ) {
2922                                 $levels = implode( ', ', $this->mTrxAtomicLevels );
2923                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
2924                                 throw new DBUnexpectedError( $this, $msg );
2925                         } elseif ( !$this->mTrxAutomatic ) {
2926                                 $msg = "$fname: Explicit transaction already active (from {$this->mTrxFname}).";
2927                                 throw new DBUnexpectedError( $this, $msg );
2928                         } else {
2929                                 // @TODO: make this an exception at some point
2930                                 $msg = "$fname: Implicit transaction already active (from {$this->mTrxFname}).";
2931                                 wfLogDBError( $msg );
2932                                 wfWarn( $msg );
2933                                 return; // join the main transaction set
2934                         }
2935                 } elseif ( $this->getFlag( DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
2936                         // @TODO: make this an exception at some point
2937                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
2938                         wfLogDBError( $msg );
2939                         wfWarn( $msg );
2940                         return; // let any writes be in the main transaction
2941                 }
2942
2943                 // Avoid fatals if close() was called
2944                 $this->assertOpen();
2945
2946                 $this->doBegin( $fname );
2947                 $this->mTrxTimestamp = microtime( true );
2948                 $this->mTrxFname = $fname;
2949                 $this->mTrxDoneWrites = false;
2950                 $this->mTrxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
2951                 $this->mTrxAutomaticAtomic = false;
2952                 $this->mTrxAtomicLevels = [];
2953                 $this->mTrxShortId = wfRandomString( 12 );
2954                 $this->mTrxWriteDuration = 0.0;
2955                 $this->mTrxWriteQueryCount = 0;
2956                 $this->mTrxWriteAdjDuration = 0.0;
2957                 $this->mTrxWriteAdjQueryCount = 0;
2958                 $this->mTrxWriteCallers = [];
2959                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
2960                 // Get an estimate of the replica DB lag before then, treating estimate staleness
2961                 // as lag itself just to be safe
2962                 $status = $this->getApproximateLagStatus();
2963                 $this->mTrxReplicaLag = $status['lag'] + ( microtime( true ) - $status['since'] );
2964         }
2965
2966         /**
2967          * Issues the BEGIN command to the database server.
2968          *
2969          * @see DatabaseBase::begin()
2970          * @param string $fname
2971          */
2972         protected function doBegin( $fname ) {
2973                 $this->query( 'BEGIN', $fname );
2974                 $this->mTrxLevel = 1;
2975         }
2976
2977         final public function commit( $fname = __METHOD__, $flush = '' ) {
2978                 if ( $this->mTrxLevel && $this->mTrxAtomicLevels ) {
2979                         // There are still atomic sections open. This cannot be ignored
2980                         $levels = implode( ', ', $this->mTrxAtomicLevels );
2981                         throw new DBUnexpectedError(
2982                                 $this,
2983                                 "$fname: Got COMMIT while atomic sections $levels are still open."
2984                         );
2985                 }
2986
2987                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
2988                         if ( !$this->mTrxLevel ) {
2989                                 return; // nothing to do
2990                         } elseif ( !$this->mTrxAutomatic ) {
2991                                 throw new DBUnexpectedError(
2992                                         $this,
2993                                         "$fname: Flushing an explicit transaction, getting out of sync."
2994                                 );
2995                         }
2996                 } else {
2997                         if ( !$this->mTrxLevel ) {
2998                                 wfWarn( "$fname: No transaction to commit, something got out of sync." );
2999                                 return; // nothing to do
3000                         } elseif ( $this->mTrxAutomatic ) {
3001                                 // @TODO: make this an exception at some point
3002                                 $msg = "$fname: Explicit commit of implicit transaction.";
3003                                 wfLogDBError( $msg );
3004                                 wfWarn( $msg );
3005                                 return; // wait for the main transaction set commit round
3006                         }
3007                 }
3008
3009                 // Avoid fatals if close() was called
3010                 $this->assertOpen();
3011
3012                 $this->runOnTransactionPreCommitCallbacks();
3013                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3014                 $this->doCommit( $fname );
3015                 if ( $this->mTrxDoneWrites ) {
3016                         $this->mDoneWrites = microtime( true );
3017                         $this->getTransactionProfiler()->transactionWritingOut(
3018                                 $this->mServer, $this->mDBname, $this->mTrxShortId, $writeTime );
3019                 }
3020
3021                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3022                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3023         }
3024
3025         /**
3026          * Issues the COMMIT command to the database server.
3027          *
3028          * @see DatabaseBase::commit()
3029          * @param string $fname
3030          */
3031         protected function doCommit( $fname ) {
3032                 if ( $this->mTrxLevel ) {
3033                         $this->query( 'COMMIT', $fname );
3034                         $this->mTrxLevel = 0;
3035                 }
3036         }
3037
3038         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3039                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3040                         if ( !$this->mTrxLevel ) {
3041                                 return; // nothing to do
3042                         }
3043                 } else {
3044                         if ( !$this->mTrxLevel ) {
3045                                 wfWarn( "$fname: No transaction to rollback, something got out of sync." );
3046                                 return; // nothing to do
3047                         } elseif ( $this->getFlag( DBO_TRX ) ) {
3048                                 throw new DBUnexpectedError(
3049                                         $this,
3050                                         "$fname: Expected mass rollback of all peer databases (DBO_TRX set)."
3051                                 );
3052                         }
3053                 }
3054
3055                 // Avoid fatals if close() was called
3056                 $this->assertOpen();
3057
3058                 $this->doRollback( $fname );
3059                 $this->mTrxAtomicLevels = [];
3060                 if ( $this->mTrxDoneWrites ) {
3061                         $this->getTransactionProfiler()->transactionWritingOut(
3062                                 $this->mServer, $this->mDBname, $this->mTrxShortId );
3063                 }
3064
3065                 $this->mTrxIdleCallbacks = []; // clear
3066                 $this->mTrxPreCommitCallbacks = []; // clear
3067                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3068                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3069         }
3070
3071         /**
3072          * Issues the ROLLBACK command to the database server.
3073          *
3074          * @see DatabaseBase::rollback()
3075          * @param string $fname
3076          */
3077         protected function doRollback( $fname ) {
3078                 if ( $this->mTrxLevel ) {
3079                         # Disconnects cause rollback anyway, so ignore those errors
3080                         $ignoreErrors = true;
3081                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3082                         $this->mTrxLevel = 0;
3083                 }
3084         }
3085
3086         public function flushSnapshot( $fname = __METHOD__ ) {
3087                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3088                         // This only flushes transactions to clear snapshots, not to write data
3089                         throw new DBUnexpectedError(
3090                                 $this,
3091                                 "$fname: Cannot COMMIT to clear snapshot because writes are pending."
3092                         );
3093                 }
3094
3095                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3096         }
3097
3098         public function explicitTrxActive() {
3099                 return $this->mTrxLevel && ( $this->mTrxAtomicLevels || !$this->mTrxAutomatic );
3100         }
3101
3102         /**
3103          * Creates a new table with structure copied from existing table
3104          * Note that unlike most database abstraction functions, this function does not
3105          * automatically append database prefix, because it works at a lower
3106          * abstraction level.
3107          * The table names passed to this function shall not be quoted (this
3108          * function calls addIdentifierQuotes when needed).
3109          *
3110          * @param string $oldName Name of table whose structure should be copied
3111          * @param string $newName Name of table to be created
3112          * @param bool $temporary Whether the new table should be temporary
3113          * @param string $fname Calling function name
3114          * @throws MWException
3115          * @return bool True if operation was successful
3116          */
3117         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
3118                 $fname = __METHOD__
3119         ) {
3120                 throw new MWException(
3121                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
3122         }
3123
3124         function listTables( $prefix = null, $fname = __METHOD__ ) {
3125                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
3126         }
3127
3128         /**
3129          * Reset the views process cache set by listViews()
3130          * @since 1.22
3131          */
3132         final public function clearViewsCache() {
3133                 $this->allViews = null;
3134         }
3135
3136         /**
3137          * Lists all the VIEWs in the database
3138          *
3139          * For caching purposes the list of all views should be stored in
3140          * $this->allViews. The process cache can be cleared with clearViewsCache()
3141          *
3142          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
3143          * @param string $fname Name of calling function
3144          * @throws MWException
3145          * @return array
3146          * @since 1.22
3147          */
3148         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3149                 throw new MWException( 'DatabaseBase::listViews is not implemented in descendant class' );
3150         }
3151
3152         /**
3153          * Differentiates between a TABLE and a VIEW
3154          *
3155          * @param string $name Name of the database-structure to test.
3156          * @throws MWException
3157          * @return bool
3158          * @since 1.22
3159          */
3160         public function isView( $name ) {
3161                 throw new MWException( 'DatabaseBase::isView is not implemented in descendant class' );
3162         }
3163
3164         public function timestamp( $ts = 0 ) {
3165                 return wfTimestamp( TS_MW, $ts );
3166         }
3167
3168         public function timestampOrNull( $ts = null ) {
3169                 if ( is_null( $ts ) ) {
3170                         return null;
3171                 } else {
3172                         return $this->timestamp( $ts );
3173                 }
3174         }
3175
3176         /**
3177          * Take the result from a query, and wrap it in a ResultWrapper if
3178          * necessary. Boolean values are passed through as is, to indicate success
3179          * of write queries or failure.
3180          *
3181          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3182          * resource, and it was necessary to call this function to convert it to
3183          * a wrapper. Nowadays, raw database objects are never exposed to external
3184          * callers, so this is unnecessary in external code.
3185          *
3186          * @param bool|ResultWrapper|resource|object $result
3187          * @return bool|ResultWrapper
3188          */
3189         protected function resultObject( $result ) {
3190                 if ( !$result ) {
3191                         return false;
3192                 } elseif ( $result instanceof ResultWrapper ) {
3193                         return $result;
3194                 } elseif ( $result === true ) {
3195                         // Successful write query
3196                         return $result;
3197                 } else {
3198                         return new ResultWrapper( $this, $result );
3199                 }
3200         }
3201
3202         public function ping( &$rtt = null ) {
3203                 // Avoid hitting the server if it was hit recently
3204                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3205                         if ( !func_num_args() || $this->mRTTEstimate > 0 ) {
3206                                 $rtt = $this->mRTTEstimate;
3207                                 return true; // don't care about $rtt
3208                         }
3209                 }
3210
3211                 // This will reconnect if possible or return false if not
3212                 $this->clearFlag( DBO_TRX, self::REMEMBER_PRIOR );
3213                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3214                 $this->restoreFlags( self::RESTORE_PRIOR );
3215
3216                 if ( $ok ) {
3217                         $rtt = $this->mRTTEstimate;
3218                 }
3219
3220                 return $ok;
3221         }
3222
3223         /**
3224          * @return bool
3225          */
3226         protected function reconnect() {
3227                 $this->closeConnection();
3228                 $this->mOpened = false;
3229                 $this->mConn = false;
3230                 try {
3231                         $this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
3232                         $this->lastPing = microtime( true );
3233                         $ok = true;
3234                 } catch ( DBConnectionError $e ) {
3235                         $ok = false;
3236                 }
3237
3238                 return $ok;
3239         }
3240
3241         public function getSessionLagStatus() {
3242                 return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
3243         }
3244
3245         /**
3246          * Get the replica DB lag when the current transaction started
3247          *
3248          * This is useful when transactions might use snapshot isolation
3249          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3250          * is this lag plus transaction duration. If they don't, it is still
3251          * safe to be pessimistic. This returns null if there is no transaction.
3252          *
3253          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3254          * @since 1.27
3255          */
3256         public function getTransactionLagStatus() {
3257                 return $this->mTrxLevel
3258                         ? [ 'lag' => $this->mTrxReplicaLag, 'since' => $this->trxTimestamp() ]
3259                         : null;
3260         }
3261
3262         /**
3263          * Get a replica DB lag estimate for this server
3264          *
3265          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3266          * @since 1.27
3267          */
3268         public function getApproximateLagStatus() {
3269                 return [
3270                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3271                         'since' => microtime( true )
3272                 ];
3273         }
3274
3275         /**
3276          * Merge the result of getSessionLagStatus() for several DBs
3277          * using the most pessimistic values to estimate the lag of
3278          * any data derived from them in combination
3279          *
3280          * This is information is useful for caching modules
3281          *
3282          * @see WANObjectCache::set()
3283          * @see WANObjectCache::getWithSetCallback()
3284          *
3285          * @param IDatabase $db1
3286          * @param IDatabase ...
3287          * @return array Map of values:
3288          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3289          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3290          *   - pending: whether any of the DBs have uncommitted changes
3291          * @since 1.27
3292          */
3293         public static function getCacheSetOptions( IDatabase $db1 ) {
3294                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3295                 foreach ( func_get_args() as $db ) {
3296                         /** @var IDatabase $db */
3297                         $status = $db->getSessionLagStatus();
3298                         if ( $status['lag'] === false ) {
3299                                 $res['lag'] = false;
3300                         } elseif ( $res['lag'] !== false ) {
3301                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3302                         }
3303                         $res['since'] = min( $res['since'], $status['since'] );
3304                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3305                 }
3306
3307                 return $res;
3308         }
3309
3310         public function getLag() {
3311                 return 0;
3312         }
3313
3314         function maxListLen() {
3315                 return 0;
3316         }
3317
3318         public function encodeBlob( $b ) {
3319                 return $b;
3320         }
3321
3322         public function decodeBlob( $b ) {
3323                 if ( $b instanceof Blob ) {
3324                         $b = $b->fetch();
3325                 }
3326                 return $b;
3327         }
3328
3329         public function setSessionOptions( array $options ) {
3330         }
3331
3332         /**
3333          * Read and execute SQL commands from a file.
3334          *
3335          * Returns true on success, error string or exception on failure (depending
3336          * on object's error ignore settings).
3337          *
3338          * @param string $filename File name to open
3339          * @param bool|callable $lineCallback Optional function called before reading each line
3340          * @param bool|callable $resultCallback Optional function called for each MySQL result
3341          * @param bool|string $fname Calling function name or false if name should be
3342          *   generated dynamically using $filename
3343          * @param bool|callable $inputCallback Optional function called for each
3344          *   complete line sent
3345          * @throws Exception|MWException
3346          * @return bool|string
3347          */
3348         public function sourceFile(
3349                 $filename, $lineCallback = false, $resultCallback = false, $fname = false, $inputCallback = false
3350         ) {
3351                 MediaWiki\suppressWarnings();
3352                 $fp = fopen( $filename, 'r' );
3353                 MediaWiki\restoreWarnings();
3354
3355                 if ( false === $fp ) {
3356                         throw new MWException( "Could not open \"{$filename}\".\n" );
3357                 }
3358
3359                 if ( !$fname ) {
3360                         $fname = __METHOD__ . "( $filename )";
3361                 }
3362
3363                 try {
3364                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3365                 } catch ( Exception $e ) {
3366                         fclose( $fp );
3367                         throw $e;
3368                 }
3369
3370                 fclose( $fp );
3371
3372                 return $error;
3373         }
3374
3375         /**
3376          * Get the full path of a patch file. Originally based on archive()
3377          * from updaters.inc. Keep in mind this always returns a patch, as
3378          * it fails back to MySQL if no DB-specific patch can be found
3379          *
3380          * @param string $patch The name of the patch, like patch-something.sql
3381          * @return string Full path to patch file
3382          */
3383         public function patchPath( $patch ) {
3384                 global $IP;
3385
3386                 $dbType = $this->getType();
3387                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3388                         return "$IP/maintenance/$dbType/archives/$patch";
3389                 } else {
3390                         return "$IP/maintenance/archives/$patch";
3391                 }
3392         }
3393
3394         public function setSchemaVars( $vars ) {
3395                 $this->mSchemaVars = $vars;
3396         }
3397
3398         /**
3399          * Read and execute commands from an open file handle.
3400          *
3401          * Returns true on success, error string or exception on failure (depending
3402          * on object's error ignore settings).
3403          *
3404          * @param resource $fp File handle
3405          * @param bool|callable $lineCallback Optional function called before reading each query
3406          * @param bool|callable $resultCallback Optional function called for each MySQL result
3407          * @param string $fname Calling function name
3408          * @param bool|callable $inputCallback Optional function called for each complete query sent
3409          * @return bool|string
3410          */
3411         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3412                 $fname = __METHOD__, $inputCallback = false
3413         ) {
3414                 $cmd = '';
3415
3416                 while ( !feof( $fp ) ) {
3417                         if ( $lineCallback ) {
3418                                 call_user_func( $lineCallback );
3419                         }
3420
3421                         $line = trim( fgets( $fp ) );
3422
3423                         if ( $line == '' ) {
3424                                 continue;
3425                         }
3426
3427                         if ( '-' == $line[0] && '-' == $line[1] ) {
3428                                 continue;
3429                         }
3430
3431                         if ( $cmd != '' ) {
3432                                 $cmd .= ' ';
3433                         }
3434
3435                         $done = $this->streamStatementEnd( $cmd, $line );
3436
3437                         $cmd .= "$line\n";
3438
3439                         if ( $done || feof( $fp ) ) {
3440                                 $cmd = $this->replaceVars( $cmd );
3441
3442                                 if ( ( $inputCallback && call_user_func( $inputCallback, $cmd ) ) || !$inputCallback ) {
3443                                         $res = $this->query( $cmd, $fname );
3444
3445                                         if ( $resultCallback ) {
3446                                                 call_user_func( $resultCallback, $res, $this );
3447                                         }
3448
3449                                         if ( false === $res ) {
3450                                                 $err = $this->lastError();
3451
3452                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3453                                         }
3454                                 }
3455                                 $cmd = '';
3456                         }
3457                 }
3458
3459                 return true;
3460         }
3461
3462         /**
3463          * Called by sourceStream() to check if we've reached a statement end
3464          *
3465          * @param string $sql SQL assembled so far
3466          * @param string $newLine New line about to be added to $sql
3467          * @return bool Whether $newLine contains end of the statement
3468          */
3469         public function streamStatementEnd( &$sql, &$newLine ) {
3470                 if ( $this->delimiter ) {
3471                         $prev = $newLine;
3472                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3473                         if ( $newLine != $prev ) {
3474                                 return true;
3475                         }
3476                 }
3477
3478                 return false;
3479         }
3480
3481         /**
3482          * Database independent variable replacement. Replaces a set of variables
3483          * in an SQL statement with their contents as given by $this->getSchemaVars().
3484          *
3485          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3486          *
3487          * - '{$var}' should be used for text and is passed through the database's
3488          *   addQuotes method.
3489          * - `{$var}` should be used for identifiers (e.g. table and database names).
3490          *   It is passed through the database's addIdentifierQuotes method which
3491          *   can be overridden if the database uses something other than backticks.
3492          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
3493          *   database's tableName method.
3494          * - / *i* / passes the name that follows through the database's indexName method.
3495          * - In all other cases, / *$var* / is left unencoded. Except for table options,
3496          *   its use should be avoided. In 1.24 and older, string encoding was applied.
3497          *
3498          * @param string $ins SQL statement to replace variables in
3499          * @return string The new SQL statement with variables replaced
3500          */
3501         protected function replaceVars( $ins ) {
3502                 $vars = $this->getSchemaVars();
3503                 return preg_replace_callback(
3504                         '!
3505                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
3506                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
3507                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
3508                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
3509                         !x',
3510                         function ( $m ) use ( $vars ) {
3511                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
3512                                 // check for both nonexistent keys *and* the empty string.
3513                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
3514                                         if ( $m[1] === 'i' ) {
3515                                                 return $this->indexName( $m[2] );
3516                                         } else {
3517                                                 return $this->tableName( $m[2] );
3518                                         }
3519                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
3520                                         return $this->addQuotes( $vars[$m[3]] );
3521                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
3522                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
3523                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
3524                                         return $vars[$m[5]];
3525                                 } else {
3526                                         return $m[0];
3527                                 }
3528                         },
3529                         $ins
3530                 );
3531         }
3532
3533         /**
3534          * Get schema variables. If none have been set via setSchemaVars(), then
3535          * use some defaults from the current object.
3536          *
3537          * @return array
3538          */
3539         protected function getSchemaVars() {
3540                 if ( $this->mSchemaVars ) {
3541                         return $this->mSchemaVars;
3542                 } else {
3543                         return $this->getDefaultSchemaVars();
3544                 }
3545         }
3546
3547         /**
3548          * Get schema variables to use if none have been set via setSchemaVars().
3549          *
3550          * Override this in derived classes to provide variables for tables.sql
3551          * and SQL patch files.
3552          *
3553          * @return array
3554          */
3555         protected function getDefaultSchemaVars() {
3556                 return [];
3557         }
3558
3559         public function lockIsFree( $lockName, $method ) {
3560                 return true;
3561         }
3562
3563         public function lock( $lockName, $method, $timeout = 5 ) {
3564                 $this->mNamedLocksHeld[$lockName] = 1;
3565
3566                 return true;
3567         }
3568
3569         public function unlock( $lockName, $method ) {
3570                 unset( $this->mNamedLocksHeld[$lockName] );
3571
3572                 return true;
3573         }
3574
3575         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
3576                 if ( $this->writesOrCallbacksPending() ) {
3577                         // This only flushes transactions to clear snapshots, not to write data
3578                         throw new DBUnexpectedError(
3579                                 $this,
3580                                 "$fname: Cannot COMMIT to clear snapshot because writes are pending."
3581                         );
3582                 }
3583
3584                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
3585                         return null;
3586                 }
3587
3588                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
3589                         if ( $this->trxLevel() ) {
3590                                 // There is a good chance an exception was thrown, causing any early return
3591                                 // from the caller. Let any error handler get a chance to issue rollback().
3592                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
3593                                 $this->onTransactionResolution( function () use ( $lockKey, $fname ) {
3594                                         $this->unlock( $lockKey, $fname );
3595                                 } );
3596                         } else {
3597                                 $this->unlock( $lockKey, $fname );
3598                         }
3599                 } );
3600
3601                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
3602
3603                 return $unlocker;
3604         }
3605
3606         public function namedLocksEnqueue() {
3607                 return false;
3608         }
3609
3610         /**
3611          * Lock specific tables
3612          *
3613          * @param array $read Array of tables to lock for read access
3614          * @param array $write Array of tables to lock for write access
3615          * @param string $method Name of caller
3616          * @param bool $lowPriority Whether to indicate writes to be LOW PRIORITY
3617          * @return bool
3618          */
3619         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3620                 return true;
3621         }
3622
3623         /**
3624          * Unlock specific tables
3625          *
3626          * @param string $method The caller
3627          * @return bool
3628          */
3629         public function unlockTables( $method ) {
3630                 return true;
3631         }
3632
3633         /**
3634          * Delete a table
3635          * @param string $tableName
3636          * @param string $fName
3637          * @return bool|ResultWrapper
3638          * @since 1.18
3639          */
3640         public function dropTable( $tableName, $fName = __METHOD__ ) {
3641                 if ( !$this->tableExists( $tableName, $fName ) ) {
3642                         return false;
3643                 }
3644                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3645                 if ( $this->cascadingDeletes() ) {
3646                         $sql .= " CASCADE";
3647                 }
3648
3649                 return $this->query( $sql, $fName );
3650         }
3651
3652         /**
3653          * Get search engine class. All subclasses of this need to implement this
3654          * if they wish to use searching.
3655          *
3656          * @return string
3657          */
3658         public function getSearchEngine() {
3659                 return 'SearchEngineDummy';
3660         }
3661
3662         public function getInfinity() {
3663                 return 'infinity';
3664         }
3665
3666         public function encodeExpiry( $expiry ) {
3667                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3668                         ? $this->getInfinity()
3669                         : $this->timestamp( $expiry );
3670         }
3671
3672         public function decodeExpiry( $expiry, $format = TS_MW ) {
3673                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3674                         ? 'infinity'
3675                         : wfTimestamp( $format, $expiry );
3676         }
3677
3678         public function setBigSelects( $value = true ) {
3679                 // no-op
3680         }
3681
3682         public function isReadOnly() {
3683                 return ( $this->getReadOnlyReason() !== false );
3684         }
3685
3686         /**
3687          * @return string|bool Reason this DB is read-only or false if it is not
3688          */
3689         protected function getReadOnlyReason() {
3690                 $reason = $this->getLBInfo( 'readOnlyReason' );
3691
3692                 return is_string( $reason ) ? $reason : false;
3693         }
3694
3695         /**
3696          * @since 1.19
3697          * @return string
3698          */
3699         public function __toString() {
3700                 return (string)$this->mConn;
3701         }
3702
3703         /**
3704          * Run a few simple sanity checks
3705          */
3706         public function __destruct() {
3707                 if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
3708                         trigger_error( "Uncommitted DB writes (transaction from {$this->mTrxFname})." );
3709                 }
3710                 $danglingCallbacks = array_merge(
3711                         $this->mTrxIdleCallbacks,
3712                         $this->mTrxPreCommitCallbacks,
3713                         $this->mTrxEndCallbacks
3714                 );
3715                 if ( $danglingCallbacks ) {
3716                         $callers = [];
3717                         foreach ( $danglingCallbacks as $callbackInfo ) {
3718                                 $callers[] = $callbackInfo[1];
3719                         }
3720                         $callers = implode( ', ', $callers );
3721                         trigger_error( "DB transaction callbacks still pending (from $callers)." );
3722                 }
3723         }
3724 }
3725
3726 /**
3727  * @since 1.27
3728  */
3729 abstract class Database extends DatabaseBase {
3730         // B/C until nothing type hints for DatabaseBase
3731         // @TODO: finish renaming DatabaseBase => Database
3732 }