includes/db/Database.php

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